Engine with two cylinder banks each with a valve operating device enabling variation of valve timing and valve lift characteristic

Description

TECHNICAL FIELD

The present invention relates to an internal combustion engine with two cylinder banks each having a valve operating device enabling valve timing and valve lift characteristic to be varied, and in particular being capable of changing both valve timing and valve lift characteristic (working angle and valve lift) of intake and/or exhaust valves depending on engine operating conditions, and specifically to a variable valve timing and variable valve lift characteristic device applicable to a two-bank engine in which a cylinder head and intake and exhaust valves arranged in one cylinder bank and a cylinder head and intake and exhaust valves arranged in the other cylinder bank are substantially mirror-symmetrical with respect to a centerline of the two cylinder banks.

BACKGROUND ART

In recent years, there have been proposed and developed various types of variable valve timing and valve lift characteristic mechanism which variably adjust both valve timing and valve lift characteristic (working angle and valve lift) of intake and/or exhaust valves, for the purpose of improved fuel economy (low fuel consumption) and enhanced stability (stable engine operations) at low-speed light-load operation, and sufficient engine power output resulting from the enhanced charging efficiency of intake air at high-speed heavy-load operation. One such variable valve timing and variable valve lift characteristic mechanism or device has been disclosed in Japanese Patent Provisional Publication No. 55-137305 (hereinafter is referred to as JP55-137305). The variable valve timing and variable valve lift characteristic mechanism or device as disclosed in JP55-137305, includes a drive shaft rotating in synchronism with rotation of an engine crankshaft, a camshaft having cams and fitted on the outer periphery of the drive shaft to be relatively rotatable about the drive shaft, a rockable cam provided on the outer periphery of a support shaft for driving intake and exhaust valves, an eccentric cam provided eccentrically on a control shaft, and a rocker arm rotatably fitted onto the outer periphery of the eccentric cam for mechanically linking the associated cam with the rockable cam therethrough. Rotating the control shaft varies the center of oscillating motion of the rocker arm, thereby varying a valve lift characteristic of intake and/or exhaust valves.

SUMMARY OF THE INVENTION

Assuming that the variable valve timing and variable valve lift characteristic mechanism or device as disclosed in JP55-137305 is applied simply to each of two cylinder banks of a V-type engine without full deliberation upon the layout of the variable valve timing and variable valve lift characteristic mechanism or device with regard to a direction of rotation of each of the drive shafts, there is a possibility that valve lift characteristics of left and right banks differ from each other.

Accordingly, it is an object of the invention to provide an internal combustion engine with two cylinder banks each having a valve operating device enabling variations of valve timing and valve lift characteristic (working angle and valve lift), which avoids the aforementioned disadvantages.

It is another object of the invention to provide a valve operating device for an internal combustion engine with two cylinder banks each having a variable valve timing and variable valve lift characteristic mechanism in which a valve lift characteristic of a first bank of the two cylinder banks is essentially equivalent to that of the second bank during variable valve-lift control.

In order to accomplish the aforementioned and other objects of the present invention, an internal combustion engine with a crankshaft and two cylinder banks, each cylinder bank having a cylinder head and a valve operating device enabling both valve timing and valve lift characteristic to be varied, each valve operating device comprises a drive shaft installed in the cylinder head of each cylinder bank and rotating in synchronism with rotation of the crankshaft, the drive shaft having a center and an axis of rotation, an eccentric cam fixedly connected to the drive shaft so that a center of the eccentric cam is eccentric with respect to the center of the drive shaft, a rockable cam arranged to drive at least one engine valve, a power-transmission mechanism mechanically linking the eccentric cam to the rockable cam, a control mechanism provided for varying an attitude of the power-transmission mechanism, and as viewed in the same axial direction, a lifting direction of the rockable cam arranged in a first one of the two cylinder banks relative to a rotational direction of the drive shaft arranged in the first cylinder bank, and a lifting direction of the rockable cam arranged in the second cylinder bank relative to a rotational direction of the drive shaft arranged in the second cylinder bank are set to be identical to each other.

According to another aspect of the invention, an internal combustion engine with a crankshaft and two cylinder banks, each cylinder bank having a cylinder head and a valve operating device enabling both valve timing and valve lift characteristic to be varied, each valve operating device comprises a drive shaft installed in the cylinder head of each cylinder bank and rotating in synchronism with rotation of the crankshaft, the drive shaft having a center and an axis of rotation, a control shaft extending substantially parallel to the drive shaft and rotated toward and held at an angular position based on engine operating conditions, a rockable cam fitted to an outer periphery of the drive shaft so as to be relatively rotatable about the drive shaft and to drive at least one engine valve, an eccentric cam fixedly connected to the drive shaft so that a center of the eccentric cam is eccentric with respect to the center of the drive shaft, a first link member fitted to an outer periphery of the eccentric cam so as to be relatively rotatable about the eccentric cam, a control cam fixedly connected to the control shaft so that a center of the control cam is eccentric with respect to a center of the control shaft, a rocker arm whose one end is linked to a tip end of the first link member so as to be rotatable relative to the first link member, the rocker arm being fitted to an outer periphery of the control cam so as to be relatively rotatable about the control cam, a second link member linked to both the other end of the rocker arm and the rockable cam so as to be rotatable relative to both the rocker arm and the rockable cam, as viewed in the same axial direction and when using a valve stem axis of the engine valve as a reference, the valve operating device arranged in the first cylinder bank and the valve operating device arranged in the second cylinder bank are laid out substantially similarly to each other, and the rotational direction of the drive shaft arranged in the first cylinder bank and the rotational direction of the drive shaft arranged in the second cylinder bank are set to be identical to each other.

According to a further aspect of the invention, a valve operating device for a V-type internal combustion engine equipped with a crankshaft and left and right cylinder banks, each cylinder bank having a cylinder head and a variable valve timing and variable valve lift characteristic mechanism, comprises a drive shaft installed in the cylinder head of each cylinder bank and rotating in synchronism with rotation of the crankshaft, the drive shaft having a center and an axis of rotation, an eccentric cam fixedly connected to the drive shaft so that a center of the eccentric cam is eccentric with respect to the center of the drive shaft, a rockable cam arranged to drive at least one engine valve, a power-transmission mechanism mechanically linking the eccentric cam to the rockable cam, a control mechanism provided for varying an attitude of the power-transmission mechanism, and as viewed in the same axial direction, a lifting direction of the rockable cam arranged in a first one of the left and right cylinder banks relative to a rotational direction of the drive shaft arranged in the first cylinder bank, and a lifting direction of the rockable cam arranged in the second cylinder bank relative to a rotational direction of the drive shaft arranged in the second cylinder bank are set to be identical to each other, the lifting direction being defined as a direction of oscillating motion of the rockable cam from a position that the engine valve begins to lift to a position that the engine valve reaches a maximum valve-lift state in which a magnitude of valve lift of the engine valve is a maximum value.

According to a still further aspect of the invention, a valve operating device for a V-type internal combustion engine equipped with a crankshaft and two cylinder banks, each cylinder bank having a cylinder head and a variable valve timing and variable valve lift characteristic mechanism, comprises a drive shaft installed in the cylinder head of each cylinder bank and rotating in synchronism with rotation of the crankshaft, the drive shaft having a center and an axis of rotation, a control shaft extending substantially parallel to the drive shaft and rotated toward and held at an angular position based on engine operating conditions, a rockable cam fitted to an outer periphery of the drive shaft so as to be relatively rotatable about the drive shaft and to drive at least one intake valve, an eccentric cam fixedly connected to the drive shaft so that a center of the eccentric cam is eccentric with respect to the center of the drive shaft, a first link member fitted to an outer periphery of the eccentric cam so as to be relatively rotatable about the eccentric cam, a control cam fixedly connected to the control shaft so that a center of the control cam is eccentric with respect to a center of the control shaft, a rocker arm whose one end is linked to a tip end of the first link member so as to be rotatable relative to the first link member, the rocker arm being fitted to an outer periphery of the control cam so as to be relatively rotatable about the control cam, a second link member linked to both the other end of the rocker arm and the rockable cam so as to be rotatable relative to both the rocker arm and the rockable cam, as viewed in the same axial direction and when using a valve stem axis of the intake valve as a reference, the valve operating device arranged in the first cylinder bank and the valve operating device arranged in the second cylinder bank are laid out substantially congruently with each other, and the rotational direction of the drive shaft arranged in the first cylinder bank and the rotational direction of the drive shaft arranged in the second cylinder bank are set to be identical to each other.

The other objects and features of this invention will become understood from the following description with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1

is a front enlarged view illustrating the essential part of a valve operating device of a first embodiment.

FIG. 2

is a lateral cross-sectional view illustrating left-bank and right-bank cylinder heads of a two-bank internal combustion engine equipped with the valve operating device with a variable valve timing and valve lift characteristic mechanism of the first embodiment shown in FIG.

1

.

FIG. 3

is a rear view illustrating details of the valve operating device of the first embodiment applied to the two-bank engine.

FIGS. 4 and 5

are explanatory views showing dimensions of the valve operating device shown in FIG.

3

.

FIG. 6

is a lateral cross-sectional view illustrating left-bank and right-bank cylinder heads of a two-bank internal combustion engine equipped with a valve operating device with a variable valve timing and valve lift characteristic mechanism of a second embodiment.

FIG. 7

is a lateral cross-sectional view illustrating left-bank and right-bank cylinder heads of a two-bank internal combustion engine equipped with a valve operating device with a variable valve timing and valve lift characteristic mechanism of a third embodiment.

FIG. 8

is a lateral cross-sectional view illustrating left-bank and right-bank cylinder heads of a two-bank internal combustion engine equipped with a valve operating device with a variable valve timing and valve lift characteristic mechanism of a fourth embodiment.

FIG. 9

is a lateral cross-sectional view illustrating left-bank and right-bank cylinder heads of a two-bank internal combustion engine equipped with a valve operating device with a variable valve timing and valve lift characteristic mechanism of a fifth embodiment.

FIG. 10

is a partial cutaway view from the front of a V-type internal combustion engine to which the valve operating device of the fifth embodiment is applied.

FIG. 11

is a lateral cross-sectional view illustrating left-bank and right-bank cylinder heads of a two-bank internal combustion engine equipped with a valve operating device with a variable valve timing and valve lift characteristic mechanism of a sixth embodiment.

FIG. 12

is a partial cutaway view from the front of a V-type internal combustion engine to which the valve operating device of the sixth embodiment is applied.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings, particularly to

FIGS. 1 and 2

, the valve operating device of the first embodiment is exemplified as a valve operating device with a variable valve timing and valve lift characteristic mechanism for intake valves employed in a V-type double-overhead-camshaft (DOHC) combustion engine equipped with left and right cylinder banks. As seen in

FIG. 1

, the V-type engine has a cylinder head RH arranged in a right bank and a cylinder head LH arranged in a left bank. In

FIGS. 1 and 2

, although a cylinder-block mounting surface RHa of right-bank cylinder head RH and a cylinder-block mounting surface LHa of left-bank cylinder head LH are illustrated in the same plane, actually these mounting surfaces RHa and LHa are inclined to each other at a predetermined bank angle. A pair of valve operating devices are located at the respective left and right cylinder banks. Basically, the left-bank valve operating device and the right-bank valve operating device are symmetrically arranged each other. For the purpose of simplification of the disclosure, the same reference signs used to designate elements shown in the left bank will be applied to the corresponding elements shown in the right bank, and also, in case of necessity for discrimination between left and right banks, the character “L” is added to indicate component parts arranged in the left bank whereas the character “R” is added to indicate component parts arranged in the right bank. As best seen in

FIG. 2

, intake valves are toward the inside of the two banks, whereas exhaust valves are toward the outside of the two banks. An exhaust camshaft (not numbered) is provided for opening and closing exhaust valves arranged in each of the two banks. One drive shaft

11

is arranged above the intake valves and located parallel to the exhaust camshaft over a plurality of engine cylinders. The drive shaft

11

has a center C

1

and an axis of rotation. The exhaust camshaft has a camshaft sprocket (not shown) at its front end, and has a driven connection with the engine crankshaft via a crankshaft sprocket (not shown). Drive shaft

11

, arranged in each of the two banks, has a camshaft sprocket (not shown) at its front end, and has a driven connection with the crankshaft, so that the drive shaft rotates together with the exhaust camshaft via a timing chain (not shown) during rotation of the crankshaft. That is to say, the crankshaft sprocket drives the timing chain, and then the timing chain drives all of the exhaust camshafts and the drive shafts arranged in the two banks. Generally, in V-type engines, the timing belt and sprocket arrangement is symmetric. Thus, a pair of drive shafts

11

of the left and right banks rotate in the same rotational direction (as can be seen from the two clockwise arrows shown in

FIGS. 1

or

2

). Details of the valve operating device of the first embodiment are shown in FIG.

3

. The variable valve timing and valve lift characteristic mechanism of the valve operating device of the embodiment is provided for every engine cylinders of each bank.

The detailed structure of the variable valve timing and valve lift characteristic mechanism of the valve operating device of the first embodiment is hereunder described in reference to FIG.

3

. Note that

FIG. 3

shows the view from the rear end of the variable valve timing and valve lift characteristic mechanism, whereas

FIGS. 1 and 2

show the lateral cross-sectional view from the front end. Therefore, in

FIGS. 3 through 5

, drive shaft

11

rotates in the counterclockwise direction.

As shown in

FIG. 3

, a substantially cylindrical eccentric cam

12

is fixedly connected onto the outer periphery of drive shaft

11

by way of press-fitting, so that eccentric cam

12

rotates together with drive shaft

11

. The center C

2

of eccentric cam

12

and the center C

1

of drive shaft

11

are eccentric to each other by a predetermined distance. A comparatively large-diameter, main portion

13

a

of a substantially ring-shaped link (a first link member)

13

is fitted onto the outer periphery of eccentric cam

12

, so that first link member

13

is rotatable relative to eccentric cam

12

. A so-called control shaft

14

is off to the upper right of drive shaft

11

, such that control shaft

14

is located parallel to drive shaft

11

over all of engine cylinders. Control shaft

14

is driven within a predetermined angular range by means of an actuator (not shown) such as a motor, a hydraulic actuator, or the like. Control shaft

14

is rotated toward and held at a desired angular position based on engine operating conditions such as engine speed and engine load. An eccentric ring-shaped control cam

15

is fixedly connected to the outer periphery of control shaft

14

by press-fitting, so that control cam

15

rotates together with control shaft

14

. The center C

4

of control cam

15

and the center C

3

of control shaft

14

are eccentric to each other by a predetermined distance. A central main portion of a rocker arm

16

is fitted onto the outer periphery of control cam

15

, so that rocker arm

16

is rotatable relative to control cam

15

. One end

16

a

of rocker arm

16

and a tip portion

13

b

of first link member

13

are rotatably connected to each other by means of a connecting pin (or a connecting portion or a connecting pin center C

5

). The other end

16

b

of rocker arm

16

and a rockable cam

18

are mechanically linked to each other through a rod-shaped link (a second link member)

17

extending in the vertical direction (viewing FIG.

3

). One end

17

a

of second link member

17

and the other end

16

b

of rocker arm

16

are rotatably connected to each other by means of a connecting pin (or a connecting portion or a connecting pin center C

7

). The other end

17

b

of second link member

17

and the tip portion of rockable cam

18

are rotatably connected to each other by means of a connecting pin (or a connecting portion or a connecting pin center C

6

). A journal portion of drive shaft

11

and a journal portion of control shaft

14

are rotatably supported on the cylinder head (RH, LH) by means of a journal bearing bracket

8

and mounting bolts

9

.

With the previously-noted arrangement, when drive shaft

11

rotates in synchronism with rotation of the engine crankshaft, rotational motion of the center C

2

of eccentric cam

12

with respect to the center C

1

of drive shaft

11

results in a displacement of first link member

13

. Responsively to the displacement of first link member

13

, rocker arm

16

oscillates or rocks about the center C

4

of control cam

15

. That is, the center C

4

of control cam

15

serves as a center of oscillating motion of rocker arm

16

. In the same manner, rockable cam

18

oscillates or rocks through second link member

17

. At this time, the cam surface

18

c

of rockable cam

18

is in sliding-contact with the upper surface

19

b

of a valve lifter

19

a

which is located on the upper end (valve stem end) of intake valve

19

and serves as a force-transmission member, and thus the intake valve is able to close and open in synchronism with rotation of the engine crankshaft by moving up and down the valve lifter by the aid of and against the bias of a valve spring (not shown). That is to say, first link member

13

, rocker arm

16

, and second link member

17

cooperate with each other to construct a power-transmission mechanism via which eccentric cam

12

and rockable cam

18

are mechanically linked to each other.

On the other hand, when control shaft

14

is rotated or driven toward a desired angular position based on the engine operating conditions, the center C

4

of control cam

15

, i.e., the center C

4

of oscillating motion of rocker arm

16

, rotates relative to the center C

3

of control shaft

14

. As a result, the valve lift characteristic of intake valve

19

varies continuously. Concretely, the valve lift and working angle of intake valve

19

tend to increase, as the distance between the center C

4

of rocker arm

16

and the center C

1

of drive shaft

11

decreases or shortens. Conversely, the valve lift and working angle of intake valve

19

tend to decrease, as the distance between the center C

4

of rocker arm

16

and the center C

1

of drive shaft

11

increases or lengthens. That is to say, the control shaft

14

and control cam

15

cooperate with each other to construct a control mechanism capable of varying the attitude of the previously-noted power-transmission mechanism.

As discussed above, the valve operating device of the first embodiment of

FIGS. 1-3

is constructed in such a manner that rockable cam

18

having a driving connection with the intake valve is fitted onto the outer periphery of drive shaft

11

rotating in synchronism with rotation of the engine crankshaft to permit relative rotation of rockable cam

18

to drive shaft

11

. There is no deviation of the center of rotation of rockable cam

18

from the center of rotation of drive shaft

11

, thus enhancing the control accuracy of the variable valve timing and valve lift characteristic mechanism. The drive shaft also serves as a support shaft for rockable cam

18

. This contributes to reduced component parts and efficient use of a limited installation space. Additionally, three links, namely first link member

13

, rocker arm

16

, and second link member

17

, are linked to each other by way of pin-connection (that is, connecting pin portions C

5

, C

6

, and C

7

), in other words, wall contact between the respective link member and pin. Such a connecting structure (pin-connection) is superior in wear and abrasion resistance and lubricity. As viewed from one axial direction of drive shaft

11

, as shown in

FIGS. 1 and 2

, component parts (

12

,

13

,

15

-

18

) of the variable valve timing and valve lift characteristic mechanism of the valve operating device contained in the left cylinder bank and component parts (

12

,

13

,

15

through

18

) of the variable valve timing and valve lift characteristic mechanism of the valve operating device contained in the right cylinder bank are arranged or laid out substantially similarly to each other or substantially congruently with each other. On the other hand, the left-bank cylinder head and left-bank intake and exhaust valves and the right-bank cylinder head and right-bank intake and exhaust valves are substantially mirror-symmetrical with respect to a plane which is mid-way between the axes of the two drive shafts and which is perpendicular to a plane containing the axes. When using the axis of the valve stem of intake valve

19

as a reference, the left-bank valve operating device and the right-bank valve operating device are arranged in the same direction. Moreover, in both of the left and right banks, the straight line

21

passing through the center C

1

of drive shaft

11

and the center C

3

of control shaft

14

(or line segment

21

between and including drive-shaft center C

1

and control-shaft center C

3

) is set to a predetermined position that the left-bank straight line

21

L and the right-bank straight line

21

R are rotated about the respective drive shafts

11

L and

11

R in the same direction (in the same counterclockwise direction opposite to the rotational direction of drive haft

11

) by the predetermined same angle α with respect to the valve stem axis

20

(see FIG.

1

). That is, a relative phase of left-bank control shaft

14

L to drive shaft

11

L is set to be identical to a relative phase of right-bank control shaft

14

R to drive shaft

11

R. The center C

1

of drive shaft

11

is located on the valve stem axis

20

.

Referring now to

FIGS. 4 and 5

, there are shown the dimensions of the valve operating device shown in FIG.

3

and the locuses of the center C

2

of eccentric cam

12

and the connecting pin center C

5

.

As shown in

FIG. 4

, in synchronism with rotation of the engine, the center C

2

of eccentric cam

12

moves along the circle with a center which is identical to the center C

1

of drive shaft

11

. On the other hand, the length of the arm of rocker arm

16

(corresponding to the eccentric distance between the center C

4

of control cam

15

and the center C

3

of control shaft

14

), and the length of the arm of first link member

13

(corresponding to the length between the center C

2

of eccentric cam

12

and the connecting pin center C

5

) are fixed values. Under a condition in which the center C

4

of oscillating motion of rocker arm

16

is kept at the position indicated by C

4

in

FIG. 4

, in synchronism with rotation of drive shaft

11

, the center C

2

of eccentric cam

12

is movable within a specified range from the position indicated by C

2

OPEN to the position indicated by C

2

CLOSE, while the connecting pin center C

5

is movable within a specified range from the position indicated by C

5

MAX to the position indicated by C

5

S. Under such a condition, when the three points of application of force, namely the first applied-force point C

1

, the second applied-force point C

2

, and the third applied-force point C

5

, are aligned with each other, that is, the center C

2

of eccentric cam

12

is held at the position C

2

MAX and additionally the connecting pin center C

5

is held at the position C

5

MAX, the rockable cam

18

is shifted toward and held at the position corresponding to the maximum valve opening of intake valve

19

. At this time, the magnitude of valve lift of intake valve

19

is a maximum value. Suppose the center C

2

of eccentric cam

12

moves clockwise from the angular position C

2

OPEN via the angular position C

2

MAX to the angular position C

2

CLOSE. In this case, the angular position C

2

OPEN of center C

2

of eccentric cam

12

obtained at the beginning of valve-lift operation is different from the angular position C

2

CLOSE of center C

2

of eccentric cam

12

obtained at the end of valve-lift operation. On the other hand, the angular position C

5

S of connecting pin center C

5

obtained at the beginning of valve-lift operation and the angular position C

5

S of connecting pin center C

5

obtained at the end of valve-lift operation are identical to each other. As shown in

FIG. 5

, when control shaft

14

is rotated in the counterclockwise direction from the controlled phase shown in

FIG. 4

so as to vary the valve lift characteristic (working angle and valve lift) of intake valve

19

, the center C

4

of rocker arm

16

is shifted to the angular position indicated by C

4

′ and thus the dimensions of the valve operating device vary as indicated by the broken lines of FIG.

5

. That is to say, the position of connecting pin center C

5

, corresponding to the maximum valve lift of intake valve

19

, changes from the position indicated by C

5

MAX to the position indicated by C

5

MAX′. Owing to the displacement from C

5

MAX to C

5

MAX′, the position of the center C

2

of eccentric cam

12

, corresponding to the maximum valve lift, also changes from the position indicated by C

2

MAX to the position indicated by C

2

MAX′. In the same manner, the rotation angle of drive shaft

11

from the angular position (C

2

OPEN) corresponding to the beginning of valve-lift operation to the angular position (C

2

MAX) corresponding to the maximum valve lift changes from θ

1

to θ

1

′, and also the rotation angle of drive shaft

11

from the angular position (C

2

MAX) corresponding to the maximum valve lift to the angular position (C

2

CLOSE) corresponding to the end of valve-lift operation changes from θ

2

to θ

2

′. The variation (θ

1

-θ

1

′) of valve-open timing is slightly different from the variation (θ

2

-θ

2

′) of valve-closure timing. Therefore, assuming that the left-bank drive shaft and right-bank drive shaft rotate in the same rotational direction and the left-bank valve operating device and the right-bank valve operating device are arranged to be substantially mirror-symmetrical with respect to a plane which is mid-way between the axes of the two drive shafts and which is perpendicular to a plane containing the axes, in one of the two banks the position C

5

MAX of connecting pin center C

5

corresponding to the maximum valve lift of intake valve

19

, and the aforementioned rotation angles θ

1

and θ

2

of drive shaft

11

vary in the timing-advance direction. Conversely, in the other bank the position C

5

MAX of connecting pin center C

5

corresponding to the maximum valve lift of intake valve

19

, and the aforementioned rotation angles θ

1

and θ

2

of drive shaft

11

vary in the timing-retard direction. In this case, the valve lift characteristics of the left and right banks are different from each other. In contrast to the above, in the valve operating device of the shown embodiment, as viewed from the axial direction of drive shaft

11

, component parts (

12

,

13

,

15

-

18

) of the variable valve timing and valve lift characteristic mechanism of the valve operating device contained in the left bank and component parts (

12

,

13

,

15

-

18

) of the variable valve timing and valve lift characteristic mechanism of the valve operating device contained in the right bank are arranged or laid out substantially similarly to each other or substantially congruently with each other. Additionally, in both of the left and right banks, the straight line

21

passing through the center C

1

of drive shaft

11

and the center C

3

of control shaft

14

is set to the predetermined position that the left-bank straight line

21

L and the right-bank straight line

21

R are rotated about the respective drive shafts

11

L and

11

R in the same rotational direction by the predetermined same angle α with respect to the valve stem axis

20

(see FIG.

1

). Therefore, the variation of the valve lift characteristic of the left-bank valve operating device, occurring owing to a change of angular phase of left-bank control shaft

14

L, is identical to that of the right-bank valve operating device, occurring owing to the same angular phase change of right-bank control shaft

14

R as the left-bank control shaft

14

L. Thus, it is possible to provide the same valve lift characteristic over all of the engine cylinders. In other words, it is unnecessary to drive the drive shafts (

11

L,

11

R) of the two banks in opposite rotational directions. In the same manner as typical V-type engines, the drive shafts (

11

L,

11

R) of two banks can be driven in the same rotational direction by means of a timing chain, a timing belt or the like.

FIGS. 6

,

7

, and

8

, respectively show the second, third and fourth embodiments. The first, second, third, and fourth embodiments are similar to each other. Thus, the same reference signs used to designate elements shown in the first embodiment will be applied to the corresponding elements shown in each of the second, third, and fourth embodiments, for the purpose of comparison among the first, second, third and fourth embodiments.

In the valve operating device of the second embodiment shown in

FIG. 6

, in order for the degree of freedom (the variation) of the valve lift characteristic to greatly increase, as viewed in the axial direction, in each of the left and right banks, the center C

6

of the connecting pin (connecting portion) which mechanically links rockable cam

18

to second link member

17

and whose position corresponds to a state of the maximum valve lift, lies on the prolongation of the line segment (or straight line)

21

between and including the center C

1

of drive shaft

11

and the center C

3

of control shaft

14

, and laid out in the reverse side of the center C

3

of control shaft

14

, sandwiching drive-shaft center C

1

between two centers C

3

and C

6

. That is, in the maximum valve lift state, control-shaft center C

3

, drive-shaft center C

1

, and connecting pin center C

6

are aligned with each other. This enhances the degree of freedom of working-angle characteristic of the engine valve (intake valve). Furthermore, in the right bank, the straight line

21

R through drive-shaft center C

1

R and control-shaft center C

3

R is set to a predetermined position that the right-bank straight line

21

R is rotated about the drive shaft

11

R in the rotational direction opposite to the rotational direction of drive shaft

11

R by a predetermined angle α

1

with respect to the valve stem axis

20

R (see the left-hand side of FIG.

6

). Conversely, in the left bank, the straight line

21

L through drive-shaft center C

1

L and control-shaft center C

3

L is set to a predetermined position that the left-bank straight line

21

L is rotated about the drive shaft

11

L in the rotational direction of drive shaft

11

L by a predetermined angle α

2

with respect to the broken line

21

L′ rotated about the drive shaft

11

L in the rotational direction opposite to the rotational direction of drive shaft

11

L by the predetermined angle α

1

with respect to the valve stem axis

20

L (see the right-hand side of FIG.

6

). The distance between left-bank drive-shaft center C

1

L and left-bank control-shaft center C

3

L and the distance between right-bank drive-shaft center C

1

R and right-bank control-shaft center C

3

R are set to be identical to each other. Additionally, in the right bank, the straight line

21

R through connecting pin center C

6

R, drive-shaft center C

1

R and control-shaft center C

3

R is set to a predetermined position that the right-bank straight line

21

R is rotated about the drive shaft

11

R in the rotational direction opposite to the rotational direction of drive shaft

11

R by a predetermined angle α

3

with respect to a line segment

22

between and including the drive-shaft center C

1

R and a valve-lift starting point

24

R on the cam surface

18

c

of rockable cam

18

. In the same manner as right-bank control shaft

14

R, in the left bank, the straight line

21

L through connecting pin center C

6

L, drive-shaft center C

1

L and control-shaft center C

3

L is set to a predetermined position that the left-bank straight line

21

L is rotated about the drive shaft

11

L in the rotational direction of drive shaft

11

L by a predetermined angle α

2

with respect to the broken line

21

L′ rotated about the drive shaft

11

L in the rotational direction opposite to the rotational direction of drive shaft

11

L by the predetermined angle α

1

with respect to the valve stem axis

20

L. The distance between left-bank rockable-cam center C

1

L and left-bank connecting pin center C

6

L and the distance between right-bank rockable-cam center C

1

R and right-bank connecting pin center C

6

R are set to be identical to each other. That is, as compared to the right bank, the position of the center C

3

L of left-bank control shaft

14

L and the angular phase of left-bank rockable cam

18

L are set at specified positions that these are rotated about the drive shaft

11

L in the same rotational direction (the rotational direction of drive shaft

11

L) by the same angle α

2

. As a result, the variation of the valve lift characteristic of the left-bank valve operating device, occurring owing to a change of angular phase of left-bank control shaft

14

L, is identical to that of the right-bank valve operating device, occurring owing to the same angular phase change of right-bank control shaft

14

R as the left-bank control shaft

14

L. Thus, the valve operating device of the second embodiment can provide the same effect of the first embodiment. That is, it is possible to provide the same valve lift characteristic over all of the engine cylinders. Additionally, in the second embodiment, it is possible to provide a different position of the center of control shaft

14

relative to drive shaft

11

and a different initial phase of rockable cam

18

at left and right banks. Thus, it is possible to arrange or lay out the control shafts (

14

L,

14

R) and rockable cams (

18

L,

18

R) at optimal locations, considering a limited mounting space, thereby enhancing the design flexibility and the degree of freedom of layout. In more detail, assuming that the center C

3

L of left-bank control shaft

14

L is laid out in the same control-shaft center position C

3

L′(on the broken line

21

L′) as the right-bank side, the rocker arm

16

L and the substantially ring-shaped link (first link member)

13

L tend to project to the lateral sides. In such a case, there is a tendency for the left-bank rocker arm

16

L and left-bank first link member

13

L to interfere with the cylinder head. This layout is undesirable. To avoid this, in the valve operating device of the second embodiment, the center C

3

L of left-bank control shaft

14

L is laid out at the predetermined position such that the center C

3

L of left-bank control shaft

14

L is rotated about the drive shaft

11

L toward the center (see the rightmost end of

FIG. 6

) of the left-bank cylinder head by the predetermined angle α

2

in comparison with the right bank. Therefore, each of the valve operating devices of the left and right banks can be laid out within the overall width of the associated cylinder head. As a consequence, it is possible to apply or mount the variable valve operating device of the second embodiment to or on both of the left and right banks, without changing the overall width of the cylinder head.

A line denoted by reference sign

30

in

FIG. 6

indicates a horizontal plane

30

corresponding to the overall height of the right-bank variable valve timing and valve lift characteristic mechanism, on the assumption that the variable valve operating device of the second embodiment is practically applied to an intake-valve side of a V-type internal combustion engine. As can be seen from the level of the horizontal plane

30

corresponding to the overall height of the right-bank variable valve timing and valve lift characteristic mechanism, the overall height of the right-bank valve operating device is dimensioned to be lower than that of the left-bank valve operating device. As viewed from a reduced overall height, in the right-bank valve operating device, in order to reduce the overall height, the center of right-bank control shaft

14

R is set at the position that the control-shaft center C

3

R is greatly rotated about the drive shaft

11

R toward the center of the right-bank cylinder head by the predetermined angle α

1

with regard to the valve stem axis

20

R. To realize this, regarding right-bank rockable cam

18

R, the angle α

3

between the connecting pin center C

6

R shifted to the position corresponding to the maximum valve lift and the valve-lift starting point

24

R of rockable cam

18

is set to be relatively remarkably greater than that of the left bank. For this reason, regarding right-bank rockable cam

18

R, its cam lobe

28

to which the connecting pin portion C

6

R is linked, is large-sized in comparison with the left-bank rockable cam

18

L. In case that the variable valve operating device of the second embodiment is applied to an intake valve side of a V-type transverse internal combustion engine of a front-engine, front-drive (FF) vehicle, by applying the right-bank variable valve operating device (the left-hand side of

FIG. 6

) of a relatively lower overall height to a front bank, it is possible to relatively reduce the overall height of the front portion of the vehicle. This is useful or effective or favorable to a hood line (e.g. , a properly slanted hood).

Referring now to

FIG. 7

, there is shown the valve operating device of the third embodiment. The fundamental structure of the valve operating device of the third embodiment is similar to that of the first embodiment shown in

FIGS. 1 through 5

. The third embodiment is slightly different from the first embodiment, in that the inclination angle α of straight line

21

to valve stem axis

20

is set to 0° (see FIG.

7

). In other words, as viewed from the axial direction of drive shaft

11

, in both the left and right banks the drive-shaft center C

1

and the control-shaft center C

3

are aligned with the valve stem axis

20

. According to the structure of the valve operating device of the third embodiment, component parts (containing rockable cam

18

L) of the left-bank valve operating device and component parts (containing rockable cam

18

R) of the right-bank valve operating device can be communized with each other. Additionally, the left-bank drive shaft

11

L, left-bank control shaft

14

L, left-bank journal bearing bracket

8

L and bolts

9

L and the right-bank drive shaft

11

R, right-bank control shaft

14

R, right-bank journal bearing bracket

8

R and bolts

9

R are mirror-symmetrical with respect to a plane which is mid-way between the axes of the two drive shafts and which is perpendicular to a plane containing the axes. This facilitates the engine design and manufacture of the variable valve operating device.

Referring now to

FIG. 8

, there is shown the valve operating device of the fourth embodiment. The fundamental structure of the valve operating device of the fourth embodiment is similar to that of the second embodiment shown in FIG.

6

. In the fourth embodiment, the left-bank drive shaft

11

L and left-bank control shaft

14

L, and the right-bank drive shaft

11

R and right-bank control shaft

14

R are also laid out to be mirror-symmetrical with respect to a plane which is mid-way between the axes of the two drive shafts and which is perpendicular to a plane containing the axes. In addition to the above, in the valve operating device of the fourth embodiment, in the right bank, the straight line

21

R through drive-shaft center C

1

R and control-shaft center C

3

R is set to a predetermined position that the right-bank straight line

21

R is rotated about the drive shaft

11

R in the rotational direction opposite to the rotational direction of drive shaft

11

R by a predetermined angle β

1

with respect to the valve stem axis

20

R. On the other hand, in the left bank, the straight line

21

L through drive-shaft center C

1

L and control-shaft center C

3

L is set to a predetermined position that the left-bank straight line

21

L is rotated about the drive shaft

11

L in the rotational direction of drive shaft

11

L by a predetermined angle β

2

with respect to the broken line

21

L′ rotated about the drive shaft

11

L in the rotational direction opposite to the rotational direction of drive shaft

11

L by the predetermined angle β

1

with respect to the valve stem axis

20

L. The predetermined angle β

2

is set to be two times greater than the predetermined angle

31

. Thus, the angle between valve stem axis

20

L and broken line

21

L′ is equal to the predetermined angle β

1

, while the angle between valve stem axis

20

L and left-bank straight line

21

L is also equal to the predetermined angle β

1

, because of β

2

=

2

β

1

. As can be appreciated from the above, the center C

3

L of left-bank control shaft

14

L is set to the predetermined position that the left-bank control-shaft center C

3

L is rotated by the same predetermined angle β

1

with respect to the valve stem axis

20

L in the opposite rotational direction (corresponding to the rotational direction of drive shaft

11

) as compared to the right-bank control shaft

14

R. The distance between left-bank drive-shaft center C

1

L and left-bank control-shaft center C

3

L is designed to be equal to the distance between right-bank drive-shaft center C

1

R and right-bank control-shaft center C

3

R. Additionally, in the right bank, the straight line

23

through the center C

1

R of oscillating motion of rockable cam

18

R and the center C

6

R of connecting pin linking rockable cam

18

R to second link member

17

R therevia is set to a predetermined position that the right-bank straight line

23

is offset from a line segment

22

between and including the center C

1

R of oscillating motion of rockable cam

18

and a valve-lift starting point

24

R on the cam surface of rockable cam

18

R in the rotational direction opposite to the rotational direction of drive shaft

11

R by a predetermined angle β

3

. On the other hand, in the same manner as right-bank control shaft

14

R, in the left bank, the straight line

23

through the center C

1

L of oscillating motion of rockable cam

18

L and the connecting pin center C

6

L is set to a predetermined position that the left-bank straight line

23

is rotated about the drive shaft

11

L in the rotational direction of drive shaft

11

L by a predetermined angle β

2

with respect to the broken line

21

L′ being offset from the valve stem axis

20

L in the rotational direction opposite to the rotational direction of drive shaft

11

L by the predetermined angle β

3

. The distance between the center C

1

L of oscillating motion of left-bank rockable cam

18

L and left-bank connecting pin center C

6

L is designed to be equal to the distance between the center C

1

R of oscillating motion of right-bank rockable cam

18

R and right-bank connecting pin center C

6

R. That is, in the same manner as the second embodiment, in the valve operating device of the fourth embodiment, as compared to the right bank, the position of the center C

3

L of left-bank control shaft

14

L and the angular phase of left-bank rockable cam

18

L are set at specified positions that these are rotated about the drive shaft

11

L in the same rotational direction (the rotational direction of drive shaft

11

L) by the same angle β

2

. As a result of this, the variation of the valve lift characteristic of the left-bank valve operating device, occurring owing to a change of angular phase of left-bank control shaft

14

L, is identical to that of the right-bank valve operating device, occurring owing to the same angular phase change of right-bank control shaft

14

R as the left-bank control shaft

14

L. Thus, the valve operating device of the fourth embodiment can provide the same effect of the second embodiment, that is, it is possible to provide the same valve lift characteristic over all of the engine cylinders. Additionally, in the fourth embodiment, the left-bank drive shaft

11

L and left-bank control shaft

14

L are mirror-symmetrical with respect to a plane which is mid-way between the axes of the two drive shafts and which is perpendicular to a plane containing the axes. Thus, the layout of the inside half of the left-bank cylinder head LH being toward the inside of the V-type engine and mounting thereon the left-bank variable valve operating device and the layout of the inside half of the right-bank cylinder head RH being toward the inside of the V-type engine and mounting thereon the right-bank variable valve operating device can be designed to be symmetrical with each other. This facilitates the engine design and manufacture of the variable valve operating device. According to the structure of the valve operating device of the fourth embodiment, mounting parts (containing journal bearing bracket

8

L, mounting bolts

9

L and the like) on the left-bank cylinder head as well as component parts of the left-bank valve operating device, and mounting parts (containing journal bearing bracket

8

R, mounting bolts

9

R and the like) on the right-bank cylinder head as well as component parts of the right-bank valve operating device can be communized with each other. In aforementioned first, second, and fourth embodiments, control-shaft center C

3

and connecting pin center C

6

are arranged to be opposite to each other with respect to valve stem axis

20

used as a reference. The opposite layout of control-shaft center C

3

and connecting pin center C

6

with respect to valve stem axis

20

is superior to the other layout that the control-shaft center C

3

and the connecting pin center C

6

are both located in the same side of valve stem axis

20

, from the viewpoint of enhanced bearing strength, the enhanced degree of freedom of layout, enhanced design flexibility and the enhanced reliability and durability of the valve operating device.

Referring now to

FIGS. 9 and 10

, there is shown the valve operating device of the fifth embodiment. In

FIG. 9

, a cylinder-block mounting surface RHa of right-bank cylinder head RH and a cylinder-block mounting surface LHa of left-bank cylinder head LH are illustrated in the same plane, however, as can be seen from the partial cutaway view of the V-type engine of

FIG. 10

, these mounting surfaces RHa and LHa are actually inclined to each other at a predetermined bank angle. In the fifth embodiment of

FIGS. 9 and 10

, as viewed from the front of the V-type engine in the same axial direction of left-bank and right-bank drive shafts

11

L and

11

R, the left-bank and right-bank valve operating devices are laid our or arranged to be substantially mirror-symmetrical with respect to a bank centerline (i.e., a centerline of the two banks)

32

. In the fifth embodiment shown in

FIGS. 9 and 10

, elements or component parts denoted by reference signs

111

R,

111

L,

112

,

113

,

113

b

,

114

R,

114

L,

115

,

116

,

117

,

118

,

119

R,

119

L, and

119

a

respectively mean almost equivalent to elements or component parts denoted by reference signs

11

R,

11

L,

12

,

13

,

13

b

,

14

R,

14

L,

15

,

16

,

17

,

18

,

19

R,

19

L, and l

9

a

shown in the first, second, third and fourth embodiments. Detailed description of elements

111

R,

111

L,

112

,

113

,

113

b

,

114

R,

114

L,

115

,

116

,

117

,

118

,

119

R,

119

L, and

119

a

will be omitted because the above description thereon seems to be self-explanatory. On V-type internal combustion engines, the left and right banks are inclined to the outside at a predetermined bank angle. In take valves

119

of an induction system are arranged to be toward the inside of the two banks with respect to a cylinder axis

33

of each of the two banks. Exhaust valves

62

of an exhaust system are arranged to be toward the outside of the two banks with respect to the cylinder axis

33

of each of the two banks. Therefore, the upper surface of a rocker cover

68

is laid out to be substantially parallel to the lower surface of the hood. The space above a valve lifter

60

of exhaust valve

62

located at the outside of each bank, is relatively wider than the space above a valve lifter

119

a

of intake valve

119

located at the inside of each bank. Therefore, in the fifth embodiment, almost all of component parts of the intake-valve operating device which variably controls valve timing and valve lift characteristic (working angle and valve lift) of intake valve

119

, are located outside of the cylinder axis

33

, that is, outside of each of the two banks. As a result of this, the overall height of the engine can be effectively reduced, thus ensuring easy mounting of the two-bank engine in the engine room. To be concrete, in the variable valve operating device of the fifth embodiment, the drive shaft

111

rotating in synchronism with rotation of the engine crankshaft, the eccentric cam

112

provided eccentrically to drive shaft

111

, the substantially ring-shaped link (first link member)

113

fitted onto eccentric cam

112

to permit relative rotation of first link member

113

to eccentric cam

112

, the control shaft

114

located substantially parallel to drive shaft

111

and rotated to and held at a desired angular position based on engine operating conditions, the control cam

115

provided eccentrically to control shaft

114

, the rocker arm

116

fitted onto control cam

115

to permit relative rotation of rocker arm

116

to control cam

115

and linked at one end to the tip end

113

b

of first link member

113

, are all laid out at the outside of each of the banks with respect to a plug post

66

which extends along the cylinder axis

33

as viewed in the axial direction. On the other hand, of component parts of the variable valve operating device, the rockable cam

118

opening and closing the associated intake valve

119

, is located above the intake valve

119

, that is, at the inside of each of the banks. On the other hand, the rod-shaped link (second link member)

117

, which is linked to each of rocker arm

116

and rockable cam

118

to permit relative rotation of second link member

117

to each of rocker arm

116

and rockable cam

118

, is laid out in such a manner as to extend over both the outside of each of the banks (i.e., the exhaust valve side) and the inside of each of the banks (i.e., the intake valve side). That is, the rod-shaped link (second link member)

117

extends from the exhaust valve side to the intake valve side in a manner so as to cross the cylinder axis

33

. The previously-noted drive shaft

111

has a rotary cam

58

fixedly connected thereto or integrally formed therewith, for opening and closing the exhaust valve

62

via the valve lifter

60

. In other words, drive shaft

111

also serves as the camshaft for exhaust valve

62

. Thus, the valve operating device of the fifth embodiment shown in

FIGS. 10 and 11

is simple in structure. Drive shaft

111

is rotatably supported by means of a lower journal bearing bracket

56

a

and a semi-circular camshaft journal bearing portion (not numbered) of the cylinder head (RH, LH). On the other hand, control shaft

114

is rotatably supported by means of the lower journal bearing bracket

56

a

and an upper journal bearing bracket

56

b

serving as a bearing cap. Journal bearing brackets

56

a

and

56

b

are fixedly connected to or mounted on the cylinder head (RH, LH) by means of common bolts

56

c

, thereby enabling a more simple structure of the variable valve operating device. In order to be able to install substantially ring-shaped link (first link member)

113

on eccentric cam

112

from the rear of the engine, the substantially ring-shaped link is formed as a half-split structure, namely upper and lower halves

113

b

and

113

a

which are fixedly connected to the outer periphery of eccentric cam

112

by bolts

64

, while sandwiching the eccentric cam between them. Rocker cam

118

is oscillatingly or rockably fitted onto a support shaft

52

. Support shaft

52

is supported on the cylinder head (RH. LH) via a bracket

50

, so that the support shaft extends parallel to drive shaft

111

in the cylinder-row direction. The working principle of the variable valve operating device of each of the banks is essentially identical to that of the first embodiment shown in

FIGS. 4 and 5

. That is, when control shaft

114

is rotated or driven such that the maximum valve lift is reduced, the position of the center C

2

MAX of eccentric cam

112

, corresponding to the maximum valve lift of intake valve

119

, changes in the timing-retard direction or in the timing-advance direction. As discussed above, in the valve operating device of the fifth embodiment of

FIGS. 9 and 10

, the left-bank and right-bank valve operating devices are substantially symmetrical with each other with respect to the bank centerline

32

. Assuming that the rotational direction of left-bank drive shaft

111

L and the rotational direction of right-bank drive shaft

111

R are identical to each other, in a first bank of the two banks the position of the center C

2

MAX of eccentric cam

112

, corresponding to the maximum valve lift, tends to change in the timing-advance direction, whereas in the second bank the position of the center C

2

MAX of eccentric cam

112

, corresponding to the maximum valve lift, tends to change in the timing-retard direction. In this case, valve lift characteristics of the left and right banks undesirably differ from each other. For the reasons set forth above, in the fifth embodiment, the drive shafts (

11

L,

111

R) of the left and right banks are driven in the opposite rotational directions, as viewed in the same axial direction. As can be seen from the diagrams shown in

FIGS. 9 and 10

, the rotational direction of right-bank drive shaft

111

R is set to be the counterclockwise direction, whereas the rotational direction of left-bank drive shaft

111

L is set to be the clockwise direction. The rotational direction of right-bank control shaft

114

R, decreasing the valve lift, is set to be the clockwise direction, while the rotational direction of left-bank control shaft

114

L, decreasing the valve lift, is set to be the counterclockwise direction. In other words, as viewed from the back side of

FIGS. 9 and 10

, the right-bank valve operating device is essentially identical to the left-bank valve operating device in layout, and additionally the rotational direction of right-bank drive shaft

111

R is set to be identical to that of left-bank drive shaft

111

L and the rotational direction of right-bank control shaft

114

R is set to be identical to that of left-bank control shaft

114

L. Therefore, in the same manner as the cylinder head (RH, LH) and intake (

119

R,

119

L) and exhaust valves (

62

R,

62

L), the left-bank and right-bank valve operating devices are mirror-symmetrical with respect to the bank centerline

32

, and additionally the valve lift characteristic of the left-bank valve operating device is identical to that of the right-bank valve operating device. This avoids an undesirable situation that the eccentric-cam center C

2

MAX of the first bank, corresponding to the maximum valve lift, changes in the phase-advance direction, whereas the eccentric-cam center C

2

MAX of the second bank, corresponding to the maximum valve lift, changes in the phase-retard direction.

Hereinafter described in detail in reference to

FIG. 10

is the concrete structure needed to rotate left-bank and right-bank drive shafts

111

L and

111

R in the opposite rotational directions.

A crank sprocket

70

is fixedly mounted on one end of the engine crankshaft (not shown). Crank sprocket

70

rotates together with the crankshaft in the clockwise direction (viewing FIG.

10

). A timing chain

72

is wound on all of the crank sprocket

70

, a first sprocket

74

located in the left bank, and a second sprocket

76

located in the right bank. Second sprocket

76

is often called as an “idler sprocket”. Thus, first and second sprockets

74

and

76

rotate in the same rotational direction. Owing to setting of the number of teeth among crank sprocket

70

, and first and second sprockets

74

and

76

, the rotational speed of each of first and second sprockets

74

and

76

is reduced to one-half the rotational speed of crank sprocket

70

. As can be seen from the right-hand side of

FIG. 10

, first sprocket

74

is fixed to one end of left-bank drive shaft

11

L, so that the first sprocket rotates together with the left-bank drive shaft. Thus, left-bank drive shaft

111

L rotates in the same direction (the clockwise direction as viewed from the partial cutaway view of

FIG. 10

) as the crankshaft at one-half the rotational speed of the crankshaft. As can be seen from the left-hand side of

FIG. 10

, a first reverse-rotational pulley

78

and a second reverse-rotational pulley

80

are provided in the right bank. First and second reverse-rotational pulleys

78

and

80

are two meshing gears with the same number of teeth, and therefore the first and second reverse-rotational pulleys rotate in the opposite directions at the same rotational speed. First reverse-rotational pulley

78

is coaxially arranged with and fixedly mounted on second sprocket

76

, so that first reverse-rotational pulley

78

rotates together with second sprocket

76

. On the other hand, second reverse-rotational pulley

80

is fixedly mounted on one end of right-bank drive shaft

111

R, so that second reverse-rotational pulley

80

rotates together with right-bank drive shaft

111

R. Thus, right-bank drive shaft

11

R rotates in the opposite direction (the counterclockwise direction as viewed from the partial cutaway view of

FIG. 10

) at one-half the rotational speed of the crankshaft. As discussed above, the chain-drive structure for the left-bank and right-bank drive shafts is simple, however, it is possible to rotate left-bank and right-bank drive shafts

111

L and

111

R in the opposite directions at the same rotational speed.

Referring now to

FIGS. 11 and 12

, there is shown the valve operating device of the sixth embodiment. The concrete structure and fundamental working principle of the valve operating device of the sixth embodiment are essentially identical to those of the first embodiment. Therefore, the same reference signs used to designate elements shown in the first embodiment will be applied to the corresponding elements shown in the sixth embodiment, for the purpose of comparison between the first and sixth embodiments.

In the sixth embodiment, although in

FIG. 11

a cylinder-block mounting surface RHa of right-bank cylinder head RH and a cylinder-block mounting surface LHa of left-bank cylinder head LH are illustrated in the same plane, these mounting surfaces RHa and LHa are actually inclined to each other at a predetermined bank angle (see FIG.

12

). In each of left-bank and right-bank cylinder heads (LH, RH), intake valves

19

are arranged to be toward the inside of the two banks, whereas exhaust valves

62

are arranged to be toward the outside of the two banks. A camshaft

35

is located above exhaust valve

62

for opening and closing the exhaust valve via valve lifter

60

. Camshaft

35

is rotatably supported on each of the cylinder heads (RH, LH) by means of a camshaft journal bearing bracket

36

serving as a bearing cap and a semi-circular camshaft journal bearing portion (not numbered) of the cylinder head (RH, LH). Camshaft journal bearing bracket

36

and the semi-circular camshaft journal bearing portion of the cylinder head (RH, LH) are fixedly connected to each other by mounting bolts

37

, while sandwiching camshaft

35

between them and permitting rotational motion of the camshaft. In the same manner as the fifth embodiment of

FIGS. 9 and 10

, as viewed in the same axial direction of left-bank and right-bank drive shafts

11

L and

11

R, in the sixth embodiment the left-bank and right-bank valve operating devices are laid out to be substantially mirror-symmetrical with respect to a bank centerline

32

. Additionally, the rotational directions of left-bank and right-bank drive shafts

11

L and

11

R are set so that drive shafts

11

L and

11

R rotate in the opposite directions. Furthermore, the rotational directions of left-bank and right-bank control shafts

14

L and

14

R are set so that control shafts

14

L and

14

R rotate in the opposite directions. Therefore, it is possible to equally set intake-valve lift characteristics of the left and right banks, so that the variation of the valve lift characteristic of the left-bank valve operating device, occurring owing to a change of angular phase of left-bank control shaft

14

L, is identical to that of the right-bank valve operating device, occurring owing to the same angular phase change of right-bank control shaft

14

R as the left-bank control shaft

14

L. In the sixth embodiment, all of component parts of the intake-valve operating device which variably controls valve timing and valve lift characteristic (working angle and valve lift) of intake valve

19

, are located inside of the cylinder axis

33

, that is, inside of each of the two banks. As compared to the valve operating device of the fifth embodiment of

FIGS. 9 and 10

in which second link member

117

of the variable valve operating device extends from the exhaust valve side to the intake valve side and crosses the cylinder axis

33

, the valve operating device of the sixth embodiment of

FIGS. 11 and 12

is inferior to that of the fifth embodiment from the viewpoint of the reduced overall height of the engine. However, in the sixth embodiment, there is no need to lay out the second link member of the variable valve operating device from the exhaust valve side to the intake valve side. Therefore, the valve operating device of the sixth embodiment is very simple in structure.

Hereunder described in detail in reference to

FIG. 12

is the concrete structure needed to rotate left-bank and right-bank drive shafts

11

L and

11

R in the opposite rotational directions.

Timing chain

72

is wound on all of crank sprocket

70

, a right-bank cam sprocket

84

R, and a left-bank cam sprocket

84

L. Owing to setting of the number of teeth among crank sprocket

70

, and right-bank and left-bank cam sprockets

84

R and

84

L, the rotational speed of each of right-bank and left-bank cam sprockets

84

R and

84

L is reduced to one-half the rotational speed of crank sprocket

70

. Additionally, right-bank and left-bank cam sprockets

84

R and

84

L rotate in the same direction as crank sprocket

70

. A pair of meshing gears, namely a first gear

86

and a second gear

88

, are provided in each of the left and right banks. The meshing gear pair (

86

,

88

) has the same number of teeth, and therefore first and second gears

86

and

88

rotate in the opposite directions at the same rotational speed. First gear

86

of each bank is coaxially arranged with and fixedly mounted on cam sprocket

84

, so that first gear

86

rotates together with cam sprocket

84

. In the right bank, right-bank cam sprocket

84

R is fixedly mounted on one end of the drive shaft

11

R of the intake valve side, while right-bank second gear

88

R is fixedly mounted on one end of the camshaft

35

R of the exhaust valve side. Therefore, right-bank drive shaft

11

R rotates in the same direction as the crankshaft at one-half the rotational speed of the crankshaft. Right-bank, exhaust-valve camshaft

35

R rotates in the opposite direction at one-half the rotational speed of the crankshaft. On the other hand, in the left bank, left-bank cam sprocket

84

L is fixedly mounted on one end of the camshaft

35

L of the exhaust valve side. The second gear

88

L is fixedly mounted on one end of the drive shaft

11

L of the intake valve side. Therefore, left-bank drive shaft

11

L rotates in the direction opposite to the rotational direction of the crankshaft at one-half the rotational speed of the crankshaft. Left-bank, exhaust-valve camshaft

35

L rotates in the same direction as the crankshaft at one-half the rotational speed of the crankshaft. The structure of the valve operating device of the sixth embodiment of

FIGS. 11 and 12

does not require idler pulley (second sprocket) used in the fifth embodiment of

FIGS. 9 and 10

. Though the valve operating device of the sixth embodiment is very simple in structure, it is possible to rotate left-bank and right-bank drive shafts

11

L and

11

R in the opposite directions at the same rotational speed and also to rotate left-bank and right-bank exhaust-valve camshafts

35

L and

35

R in the opposite directions at the same rotational speed.

For the purpose of simplification of the disclosure,

FIGS. 1 and 2

(first embodiment),

FIG. 6

(second embodiment),

FIG. 7

(third embodiment),

FIG. 8

(fourth embodiment),

FIGS. 9 and 10

(fifth embodiment), and

FIGS. 11 and 12

(sixth embodiment) show only the particular phase corresponding to the maximum valve lift. Actually, in the same manner as typical multiple cylinder engines, the timing at which the intake valve reaches the maximum valve lift is set to be different for every engine cylinder, and thus each cylinder experiences in turn the maximum valve lift. In other words, the intake valves of a plurality of engine cylinders never reach their maximum valve lift points at the same time.

In the shown embodiments, although a valve-operating device equipped with a variable valve timing and valve lift characteristic mechanism is used for only intake valves employed in a V-type combustion engine for the sake of illustrative simplicity, it will be appreciated that the valve-operating device of the invention may be applied to exhaust valves usually arranged toward the outside of each of left and right cylinder banks of a V-type engine.

In the shown embodiments, although a valve-operating device of the present invention is exemplified in a V-type combustion engine with two banks and a variable valve timing and valve lift characteristic mechanism, the device of the invention may be applied to the other two-bank engine such as a horizontally opposed cylinder engine containing a typical flat four cylinder engine, a flat six cylinder engine or the like.

As will be appreciated from the above, there are at least two features being common to all of the shown embodiments. First, as viewed in the same axial direction, the lifting direction of left-bank rockable cam

18

L relative to the rotational direction of left-bank drive shaft

11

L and the lifting direction of right-bank rockable cam

18

R relative to the rotational direction of right-bank drive shaft

11

R are set to be identical to each other. The lifting direction is defined as a direction of oscillating motion of rockable cam

18

from a position that the valve begins to lift to a position that the valve reaches the maximum valve lift, or as a direction of oscillating motion of rockable cam

18

from the position that the valve reaches the maximum valve lift to a position that the valve re-seats and thus the lifting action of the valve ends. Thus, it is possible to substantially equally set valve lift characteristics of left and right banks, in such a manner that the valve lift characteristic (working angle and valve lift) of the left bank is substantially identical to that of the right bank. Secondly, as viewed in the same axial direction, the rotational direction of left-bank control shaft

14

L relative to the rotational direction of left-bank drive shaft

11

L and the rotational direction of right-bank control shaft

14

R relative to the rotational direction of right-bank drive shaft

11

R are set to be identical to each other. Thus, it is possible to substantially equally set intake-valve lift characteristics of the left and right banks, so that the variation of the valve lift characteristic of the left-bank valve operating device, occurring owing to a change of angular phase of left-bank control shaft

14

L, is substantially identical to that of the right-bank valve operating device, occurring owing to the same angular phase change of right-bank control shaft

14

R as the left-bank control shaft

14

L.

The entire contents of Japanese Patent Application No. P2000-250838 (filed Aug. 22, 2000) is incorporated herein by reference.

While the foregoing is a description of the preferred embodiments carried out the invention, it will be understood that the invention is not limited to the particular embodiments shown and described herein, but that various changes and modifications may be made without departing from the scope or spirit of this invention as defined by the following claims.

Claims

1. An internal combustion engine with a crankshaft and two cylinder banks, each cylinder bank having a cylinder head and a valve operating device enabling both valve timing and valve lift characteristic to be varied, each valve operating device comprising:a drive shaft installed in the cylinder head of each cylinder bank and rotating in synchronism with rotation of the crankshaft, the drive shaft having a center and an axis of rotation; an eccentric cam fixedly connected to the drive shaft so that a center of the eccentric cam is eccentric with respect to the center of the drive shaft; a rockable cam arranged to drive at least one engine valve; a power-transmission mechanism mechanically linking the eccentric cam to the rockable cam; a control mechanism provided for varying an attitude of the power-transmission mechanism; and as viewed in the same axial direction, a lifting direction of the rockable cam arranged in a first one of the two cylinder banks relative to a rotational direction of the drive shaft arranged in the first cylinder bank, and a lifting direction of the rockable cam arranged in the second cylinder bank relative to a rotational direction of the drive shaft arranged in the second cylinder bank are set to be identical to each other.
2. The internal combustion engine as claimed in claim 1, wherein:the power-transmission mechanism comprises a first link member fitted to an outer periphery of the eccentric cam so as to be relatively rotatable about the eccentric cam, a rocker arm whose one end is linked to a tip end of the first link member so as to be rotatable relative to the first link member, and a second link member linked to both the other end of the rocker arm and the rockable cam so as to be rotatable relative to both the rocker arm and the rockable cam; the control mechanism comprises a control shaft extending substantially parallel to the drive shaft and rotated toward and held at an angular position based on engine operating conditions, and a control cam fixedly connected to the control shaft so that a center of the control cam is eccentric with respect to a center of the control shaft; and the rocker arm is fitted to an outer periphery of the control cam so as to be relatively rotatable about the control cam.
3. The internal combustion engine as claimed in claim 2, wherein:as viewed in the same axial direction, a rotational direction of the control shaft arranged in the first cylinder bank relative to the rotational direction of the drive shaft arranged in the first cylinder bank, and a rotational direction of the control shaft arranged in the second cylinder bank relative to the rotational direction of the drive shaft arranged in the second cylinder bank are set to be identical to each other.
4. The internal combustion engine as claimed in claim 1, wherein:as viewed in the same axial direction and when using a valve stem axis of the engine valve as a reference, the valve operating device arranged in the first cylinder bank and the valve operating device arranged in the second cylinder bank are laid out substantially similarly to each other; and the rotational direction of the drive shaft arranged in the first cylinder bank and the rotational direction of the drive shaft arranged in the second cylinder bank are set to be identical to each other.
5. An internal combustion engine with a crankshaft and two cylinder banks, each cylinder bank having a cylinder head and a valve operating device enabling both valve timing and valve lift characteristic to be varied, each valve operating device comprising:a drive shaft installed in the cylinder head of each cylinder bank and rotating in synchronism with rotation of the crankshaft, the drive shaft having a center and an axis of rotation; a control shaft extending substantially parallel to the drive shaft and rotated toward and held at an angular position based on engine operating conditions; a rockable cam fitted to an outer periphery of the drive shaft so as to be relatively rotatable about the drive shaft and to drive at least one engine valve; an eccentric cam fixedly connected to the drive shaft so that a center of the eccentric cam is eccentric with respect to the center of the drive shaft; a first link member fitted to an outer periphery of the eccentric cam so as to be relatively rotatable about the eccentric cam; a control cam fixedly connected to the control shaft so that a center of the control cam is eccentric with respect to a center of the control shaft; a rocker arm whose one end is linked to a tip end of the first link member so as to be rotatable relative to the first link member, the rocker arm being fitted to an outer periphery of the control cam so as to be relatively rotatable about the control cam; a second link member linked to both the other end of the rocker arm and the rockable cam so as to be rotatable relative to both the rocker arm and the rockable cam; as viewed in the same axial direction and when using a valve stem axis of the engine valve as a reference, the valve operating device arranged in the first cylinder bank and the valve operating device arranged in the second cylinder bank are laid out substantially similarly to each other; and the rotational direction of the drive shaft arranged in the first cylinder bank and the rotational direction of the drive shaft arranged in the second cylinder bank are set to be identical to each other.
6. The internal combustion engine as claimed in claim 5, wherein:a straight line through the center of the drive shaft arranged in the first cylinder bank and a center of the control shaft arranged in the first cylinder bank is set to a predetermined position that the straight line is rotated about the drive shaft arranged in the first cylinder bank in a rotational direction by an angle with respect to the valve stem axis of the engine valve arranged in the first cylinder bank; and a straight line through the center of the drive shaft arranged in the second cylinder bank and a center of the control shaft arranged in the second cylinder bank is set to a predetermined position that the straight line is rotated about the drive shaft arranged in the second cylinder bank in the same rotational direction by the same angle with respect to the valve stem axis of the engine valve arranged in the second cylinder bank.
7. The internal combustion engine as claimed in claim 5, wherein:a distance between the center of the drive shaft arranged in the first cylinder bank and a center of the control shaft arranged in the first cylinder bank and a distance between the center of the drive shaft arranged in the second cylinder bank and a center of the control shaft arranged in the second cylinder bank are set to be identical to each other; a distance between the center of the drive shaft arranged in the first cylinder bank and a center of a connecting portion between the rockable cam and the second link member both arranged in the first cylinder bank and conditioned in a maximum valve-lift state in which a magnitude of valve lift of the engine valve is a maximum value, and a distance between the center of the drive shaft arranged in the second cylinder bank and a center of a connecting portion between the rockable cam and the second link member both arranged in the second cylinder bank and conditioned in the maximum valve-lift state are set to be identical to each other; as compared to the first cylinder bank, the center of the control shaft arranged in the second cylinder bank is set to a predetermined position that the center of the control shaft arranged in the second cylinder bank is rotated about the drive shaft arranged in the second cylinder bank in a predetermined rotational direction by a predetermined angle α2 with respect to the valve stem axis of the engine valve arranged in the second cylinder bank; and as compared to the first cylinder bank, the center of the connecting portion arranged in the second cylinder bank is set to a predetermined position that the center of the connecting portion arranged in the second cylinder bank is rotated about the drive shaft arranged in the second cylinder bank in the same predetermined rotational direction as the center of the control shaft arranged in the second cylinder bank by the same predetermined angle α2 as the center of the control shaft arranged in the second cylinder bank with respect to a line segment between and including a center of oscillating motion and a valve-lift starting point of the rockable cam arranged in the second cylinder bank.
8. The internal combustion engine as claimed in claim 5, wherein:in each of the two cylinder banks, a center of a connecting portion between the rockable cam and the second link member conditioned in a maximum valve-lift state in which a magnitude of valve lift of the engine valve is a maximum value, is laid out to lie on a prolongation of the straight line through the center of the drive shaft and a center of the control shaft.
9. The internal combustion engine as claimed in claim 5, wherein:in each bank of the two cylinder banks, the center of the drive shaft and a center of the control shaft are aligned with the valve stem axis of the engine valve.
10. The internal combustion engine as claimed in claim 7, wherein:the center of the control shaft arranged in the first cylinder bank is set to a predetermined position that the center of the control shaft arranged in the first cylinder bank is rotated about the drive shaft arranged in the first cylinder bank in a predetermined rotational direction by a predetermined angle β1 with respect to the valve stem axis of the engine valve arranged in the first cylinder bank; and the center of the control shaft arranged in the second cylinder bank is set to a predetermined position that the center of the control shaft arranged in the second cylinder bank is rotated about the drive shaft arranged in the second cylinder bank in a rotational direction opposite to the predetermined rotational direction of the control shaft arranged in the first cylinder bank by the same predetermined angle β1 as the center of the control shaft arranged in the first cylinder bank with respect to the valve stem axis of the engine valve arranged in the second cylinder bank.
11. The internal combustion engine as claimed in claim 5, wherein:in at least one of the two cylinder banks, as viewed in an axial direction, a center of a connecting portion between the rockable cam and the second link member both conditioned in the maximum valve-lift state are laid out in a reverse side of a center of the control shaft with respect to the valve stem axis of the engine valve.
12. The internal combustion engine as claimed in claim 5, wherein:in at least one of the two cylinder banks, the center of the control shaft is laid out to be toward a center of the cylinder head with respect to the valve stem axis of the engine valve.
13. The internal combustion engine as claimed in claim 12, wherein:the valve operating device of the internal combustion engine with the crankshaft and the two cylinder banks comprises an intake valve operating device of a V-type transverse internal combustion engine; the center of the control shaft arranged in a front cylinder bank of the two cylinder banks is laid out to be toward the center of the cylinder head with respect to the valve stem axis of the intake valve.
14. The internal combustion engine as claimed in claim 1, wherein:as viewed in the same axial direction, the valve operating device arranged in the first cylinder bank and the valve operating device arranged in the second cylinder bank are laid out to be substantially mirror-symmetrical with respect to a bank centerline; the rotational direction of the drive shaft arranged in the first cylinder bank and the rotational direction of the drive shaft arranged in the second cylinder bank are set to be opposite to each other.
15. The internal combustion engine as claimed in claim 1, wherein:an intake valve of each of the two cylinder banks is arranged to be toward an inside of the cylinder bank, and an exhaust valve of each of the two cylinder banks is arranged to be toward an outside of the cylinder bank; the rockable cam, which drives the intake valve, is arranged to be toward the inside of the cylinder bank, and the drive shaft is arranged to be toward the outside of the cylinder bank; and the power-transmission mechanism is laid out to extend from the outside of the cylinder bank to the inside of the cylinder bank.
16. The internal combustion engine as claimed in claim 15, further comprising:a first sprocket and a second sprocket, both rotating in the same rotational direction as the crankshaft; a first reverse-rotational gear and a second reverse-rotational gear, both in meshed-engagement with each other and rotating in opposite rotational directions; wherein the first sprocket is fixed to the drive shaft arranged in one of the two cylinder banks, the first reverse-rotational gear is fixed to the second sprocket, and the second reverse-rotational gear is fixed to the drive shaft arranged in the other cylinder bank.
17. A valve operating device for a V-type internal combustion engine equipped with a crankshaft and left and right cylinder banks, each cylinder bank having a cylinder head and a variable valve timing and variable valve lift characteristic mechanism, comprising:a drive shaft installed in the cylinder head of each cylinder bank and rotating in synchronism with rotation of the crankshaft, the drive shaft having a center and an axis of rotation; an eccentric cam fixedly connected to the drive shaft so that a center of the eccentric cam is eccentric with respect to the center of the drive shaft; a rockable cam arranged to drive at least one engine valve; a power-transmission mechanism mechanically linking the eccentric cam to the rockable cam; a control mechanism provided for varying an attitude of the power-transmission mechanism; and as viewed in the same axial direction, a lifting direction of the rockable cam arranged in a first one of the left and right cylinder banks relative to a rotational direction of the drive shaft arranged in the first cylinder bank, and a lifting direction of the rockable cam arranged in the second cylinder bank relative to a rotational direction of the drive shaft arranged in the second cylinder bank are set to be identical to each other, the lifting direction being defined as a direction of oscillating motion of the rockable cam from a position that the engine valve begins to lift to a position that the engine valve reaches a maximum valve-lift state in which a magnitude of valve lift of the engine valve is a maximum value.
18. The valve operating device as claimed in claim 17, wherein:the power-transmission mechanism comprises a first link member fitted to an outer periphery of the eccentric cam so as to be relatively rotatable about the eccentric cam, a rocker arm whose one end is linked to a tip end of the first link member so as to be rotatable relative to the first link member, and a second link member linked to both the other end of the rocker arm and the rockable cam so as to be rotatable relative to both the rocker arm and the rockable cam; the control mechanism comprises a control shaft extending substantially parallel to the drive shaft and rotated toward and held at an angular position based on engine operating conditions, and a control cam fixedly connected to the control shaft so that a center of the control cam is eccentric with respect to a center of the control shaft; and the rocker arm is fitted to an outer periphery of the control cam so as to be relatively rotatable about the control cam.
19. The valve operating device as claimed in claim 18, wherein:as viewed in the same axial direction, a rotational direction of the control shaft arranged in the first cylinder bank relative to the rotational direction of the drive shaft arranged in the first cylinder bank, and a rotational direction of the control shaft arranged in the second cylinder bank relative to the rotational direction of the drive shaft arranged in the second cylinder bank are set to be identical to each other.
20. The valve operating device as claimed in claim 17, wherein:as viewed in the same axial direction and when using a valve stem axis of the engine valve as a reference, the valve operating device arranged in the first cylinder bank and the valve operating device arranged in the second cylinder bank are laid out substantially congruently with each other; and the rotational direction of the drive shaft arranged in the first cylinder bank and the rotational direction of the drive shaft arranged in the second cylinder bank are set to be identical to each other.
21. A valve operating device for a V-type internal combustion engine equipped with a crankshaft and two cylinder banks, each cylinder bank having a cylinder head and a variable valve timing and variable valve lift characteristic mechanism, comprising:a drive shaft installed in the cylinder head of each cylinder bank and rotating in synchronism with rotation of the crankshaft, the drive shaft having a center and an axis of rotation; a control shaft extending substantially parallel to the drive shaft and rotated toward and held at an angular position based on engine operating conditions; a rockable cam fitted to an outer periphery of the drive shaft so as to be relatively rotatable about the drive shaft and to drive at least one intake valve; an eccentric cam fixedly connected to the drive shaft so that a center of the eccentric cam is eccentric with respect to the center of the drive shaft; a first link member fitted to an outer periphery of the eccentric cam so as to be relatively rotatable about the eccentric cam; a control cam fixedly connected to the control shaft so that a center of the control cam is eccentric with respect to a center of the control shaft; a rocker arm whose one end is linked to a tip end of the first link member so as to be rotatable relative to the first link member, the rocker arm being fitted to an outer periphery of the control cam so as to be relatively rotatable about the control cam; a second link member linked to both the other end of the rocker arm and the rockable cam so as to be rotatable relative to both the rocker arm and the rockable cam; as viewed in the same axial direction and when using a valve stem axis of the intake valve as a reference, the valve operating device arranged in the first cylinder bank and the valve operating device arranged in the second cylinder bank are laid out substantially congruently with each other; and the rotational direction of the drive shaft arranged in the first cylinder bank and the rotational direction of the drive shaft arranged in the second cylinder bank are set to be identical to each other.
22. The valve operating device as claimed in claim 21, wherein:a straight line through the center of the drive shaft arranged in the first cylinder bank and a center of the control shaft arranged in the first cylinder bank is set to a predetermined position that the straight line is rotated about the drive shaft arranged in the first cylinder bank in a rotational direction by an angle with respect to the valve stem axis of the intake valve arranged in the first cylinder bank; and a straight line through the center of the drive shaft arranged in the second cylinder bank and a center of the control shaft arranged in the second cylinder bank is set to a predetermined position that the straight line is rotated about the drive shaft arranged in the second cylinder bank in the same rotational direction by the same angle with respect to the valve stem axis of the intake valve arranged in the second cylinder bank.
23. The valve operating device as claimed in claim 21, wherein:a distance between the center of the drive shaft arranged in the first cylinder bank and a center of the control shaft arranged in the first cylinder bank and a distance between the center of the drive shaft arranged in the second cylinder bank and a center of the control shaft arranged in the second cylinder bank are set to be identical to each other; a distance between the center of the drive shaft arranged in the first cylinder bank and a center of a connecting portion between the rockable cam and the second link member both arranged in the first cylinder bank and conditioned in a maximum valve-lift state in which a magnitude of valve lift of the intake valve is a maximum value, and a distance between the center of the drive shaft arranged in the second cylinder bank and a center of a connecting portion between the rockable cam and the second link member both arranged in the second cylinder bank and conditioned in the maximum valve-lift state are set to be identical to each other; as compared to the first cylinder bank, the center of the control shaft arranged in the second cylinder bank is set to a predetermined position that the center of the control shaft arranged in the second cylinder bank is rotated about the drive shaft arranged in the second cylinder bank in a predetermined rotational direction by a predetermined angle α2 with respect to the valve stem axis of the intake valve arranged in the second cylinder bank; and as compared to the first cylinder bank, the center of the connecting portion arranged in the second cylinder bank is set to a predetermined position that the center of the connecting portion arranged in the second cylinder bank is rotated about the drive shaft arranged in the second cylinder bank in the same predetermined rotational direction as the center of the control shaft arranged in the second cylinder bank by the same predetermined angle α2 as the center of the control shaft arranged in the second cylinder bank with respect to a line segment between and including a center of oscillating motion and a valve-lift starting point of the rockable cam arranged in the second cylinder bank.
24. The valve operating device as claimed in claim 21, wherein:in each of the two cylinder banks, a center of a connecting portion between the rockable cam and the second link member conditioned in a maximum valve-lift state in which a magnitude of valve lift of the intake valve is a maximum value, is laid out to lie on a prolongation of the straight line through the center of the drive shaft and a center of the control shaft.
25. The valve operating device as claimed in claim 21, wherein:in each bank of the two cylinder banks, the center of the drive shaft and a center of the control shaft are aligned with the valve stem axis of the intake valve.
26. The valve operating device as claimed in claim 23, wherein:the center of the control shaft arranged in the first cylinder bank is set to a predetermined position that the center of the control shaft arranged in the first cylinder bank is rotated about the drive shaft arranged in the first cylinder bank in a predetermined rotational direction by a predetermined angle β1 with respect to the valve stem axis of the intake valve arranged in the first cylinder bank; and the center of the control shaft arranged in the second cylinder bank is set to a predetermined position that the center of the control shaft arranged in the second cylinder bank is rotated about the drive shaft arranged in the second cylinder bank in a rotational direction opposite to the predetermined rotational direction of the control shaft arranged in the first cylinder bank by the same predetermined angle β1 as the center of the control shaft arranged in the first cylinder bank with respect to the valve stem axis of the intake valve arranged in the second cylinder bank.
27. The valve operating device as claimed in claim 21, wherein:in at least one of the two cylinder banks, as viewed in an axial direction, a center of a connecting portion between the rockable cam and the second link member both conditioned in the maximum valve-lift state are laid out in a reverse side of a center of the control shaft with respect to the valve stem axis of the intake valve.
28. The valve operating device as claimed in claim 21, wherein:in at least one of the two cylinder banks, the center of the control shaft is laid out to be toward a center of the cylinder head with respect to the valve stem axis of the intake valve.
29. The valve operating device as claimed in claim 28, wherein:the valve operating device of the V-type internal combustion engine with the crankshaft and the left and right cylinder banks comprises an intake valve operating device of a V-type transverse internal combustion engine; the center of the control shaft arranged in a front cylinder bank of the two cylinder banks is laid out to be toward the center of the cylinder head with respect to the valve stem axis of the intake valve.
30. The valve operating device as claimed in claim 17, wherein:as viewed in the same axial direction, the valve operating device arranged in the first cylinder bank and the valve operating device arranged in the second cylinder bank are laid out to be substantially mirror-symmetrical with respect to a bank centerline; the rotational direction of the drive shaft arranged in the first cylinder bank and the rotational direction of the drive shaft arranged in the second cylinder bank are set to be opposite to each other.
31. The valve operating device as claimed in claim 17, wherein:an intake valve of each of the two cylinder banks is arranged to be toward an inside of the cylinder bank, and an exhaust valve of each of the two cylinder banks is arranged to be toward an outside of the cylinder bank; the rockable cam, which drives the intake valve, is arranged to be toward the inside of the cylinder bank, and the drive shaft is arranged to be toward the outside of the cylinder bank; and the power-transmission mechanism is laid out to extend from the outside of the cylinder bank to the inside of the cylinder bank.
32. The valve operating device as claimed in claim 31, further comprising:a first sprocket and a second sprocket, both rotating in the same rotational direction as the crankshaft; a first reverse-rotational gear and a second reverse-rotational gear, both in meshed-engagement with each other and rotating in opposite rotational directions; wherein the first sprocket is fixed to the drive shaft arranged in one of the left and right cylinder banks, the first reverse-rotational gear is fixed to the second sprocket, and the second reverse-rotational gear is fixed to the drive shaft arranged in the other cylinder bank.
33. The valve operating device as claimed in claim 32, wherein:the drive shaft has a rotary cam and also serves as a camshaft for the exhaust valve for opening and closing the exhaust valve.

Priority Claims (1)

Number	Date	Country	Kind
2000-250838	Aug 2000	JP

US Referenced Citations (7)

Number	Name	Date	Kind
5423295	Murata et al.	Jun 1995	A
5429079	Murata et al.	Jul 1995	A
5988125	Hara et al.	Nov 1999	A
6019076	Pierik et al.	Feb 2000	A
6123053	Hara et al.	Sep 2000	A
6260523	Nakamura et al.	Jul 2001	B1
6311659	Pierik	Nov 2001	B1

Foreign Referenced Citations (1)

Number	Date	Country
55-137305	Oct 1980	JP

Engine with two cylinder banks each with a valve operating device enabling variation of valve timing and valve lift characteristic

Information

Patent Number

Date Filed

Date Issued

Inventors

Original Assignees

Examiners

Agents

CPC

US Classifications

Field of Search

US

International Classifications

Term Extension

Abstract

Description

Claims

Priority Claims (1)

US Referenced Citations (7)

Foreign Referenced Citations (1)