Engine

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an engine. Particularly, an improvement of an engine including a crankshaft having first and second journals disposed at opposite ends of the crankshaft. An engine block has a crankcase with a first bearing to support the first journal on one sidewall and an opening is provided in the other sidewall to facilitate assembly of the crankshaft. A case cover is coupled to the crankcase by a plurality of bolts to close the opening.

2. Description of the Related Art

Such an engine is known, as disclosed, for example, in Japanese Utility Model Publication No.3-49996.

In order to define a position for coupling the crankcase and the case cover to each other in the engine, it is conventional practice to fit knock pins into at least two positioning bores which open into joint faces of the crankcase and the case cover. The two knock pins are disposed on opposite sides of the axis of the crankshaft. The knock pins are used exclusively to define the position for coupling the crankcase and the case cover to each other.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide an engine which is constructed with a durability in such a manner that at least two knock pins fit into the crankcase and the case cover over their joint faces not only define the position for coupling of the crankcase and the case cover to each other, as in the conventional engine described above, but also increase the rigidity of the case cover.

To achieve the above object, according to a first aspect and feature of the present invention, there is provided an engine including a crankshaft having first and second journals disposed at opposite ends thereof. An engine block has a crankcase with a first bearing that supports the first journal on one sidewall and an opening is provided in the other sidewall to facilitate assembly of the crankshaft. A case cover is coupled to the crankcase by a plurality of bolts to close the opening. A second bearing is also provided to support the second journal, wherein at least two knock pins are fitted into the crankcase and the case cover over their joint faces at locations closer to a cylinder bore in the engine block than the second bearing.

The first and second bearings correspond to first and second bearing bushes in an embodiment of the present invention, which will be described hereinafter. With the above arrangement, when an explosion load is applied from the crankshaft to the case cover during an explosion stroke of the engine, a tensile stress is generated on the case cover over a wide area between the second bearing and the two knock pins. At this point, the case cover, which has a strong resistance to the tensile stress, can exhibit a high rigidity. Therefore, the two knock pins define the position for coupling the crankcase and the case cover to each other, and moreover increase the rigidity of the case cover. Thus, it is possible to increase the supporting strength for the crankshaft while reducing the weight of the case cover.

According to a second aspect and feature of the present invention, in addition to the first feature, the two knock pins are substantially equidistantly positioned on opposite sides of a plane that includes an axis of a cylinder bore and an axis of the crankshaft.

With the above arrangement, it is possible to equalize the shearing load applied to each knock pin and disperse the tensile stress in the case cover, thereby enhancing the durability of the knock pins and the case cover.

According to a third aspect and feature of the present invention, in addition to the first or second features, one of the knock pins is hollow. An oil passage in the engine block and an oil passage in the case cover communicate with each other through a hole in the hollow knock pin.

With the above arrangement, one of the hollow knock pins has a function of permitting communication between the oil passage in the engine block and the oil passage in the case cover. Therefore, the oil passages and the knock pin can be disposed coaxially, and thus, the disposition of the oil passage and the knock pin in the narrow joint faces can be achieved easily.

According to a fourth aspect and feature of the present invention, in addition to any of the first to third features, the knock pins are press-fit into one of the crankcase and the case cover.

With the above arrangement, a fitting gap for the knock pins is provided only between each knock pin and the other of the crankcase and the case cover. Therefore, it is possible to limit dislocation between the joint faces of the crankcase and the case cover due to the relatively small fitting gap, which enhances the coupling accuracy.

The above and other objects, features and advantages of the invention will become apparent from the following description taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1

is a side view of an outboard engine system including an engine according to the present invention;

FIG. 2

is a cross-sectional view of the engine mounted in the engine casing;

FIG. 3

is an enlarged view of the engine illustrated in

FIG. 2

;

FIG. 4

is a top view of the engine illustrated in

FIG. 3

as taken in the direction of an arrow

4

;

FIG. 5

is a cross-sectional view taken along section line

5

—

5

in

FIG. 4

; and

FIG. 6

is a cross-sectional view taken along section line

6

—

6

in FIG.

4

.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to

FIG. 1

, an outboard engine system O includes a stern bracket

1

clamped at a transom T of a hull. A vertically extending casing

3

that swings in a lateral direction relative to the hull is connected to the stern bracket

1

through a swivel shaft

2

. An engine E is mounted at an upper portion of the casing

3

and an engine cover

4

is coupled to the casing

3

to cover the engine E. Power output from a crankshaft

5

of the engine E is transmitted to a propeller shaft

8

supported at a lower portion of the casing

3

through a drive shaft

6

disposed in the casing

3

and a bevel gear transmitting device

7

capable of switching-over the forward and rearward movements from each other, thereby driving a propeller

9

mounted at a rear end of the propeller shaft

8

.

Referring to

FIGS. 2 and 3

, the engine E is mounted in the casing

3

in an attitude in which the crankshaft

5

has been turned vertically and a cylinder block

11

has been turned rearwards of the hull. The engine E includes an engine block

12

with a crankcase

10

and the cylinder block

11

formed integrally with each other. Two upper and lower cylinder bores

13

,

13

having axes turned horizontally are provided in the cylinder block

11

.

The crankcase

10

has a closed bottom wall and an upper wall provided having an opening

14

for assembling the crankshaft

5

. A case cover

15

is coupled to the crankcase

10

to cover the opening

14

. Its coupling structure will be described below.

First and second bearing bores

20

and

21

are provided in the bottom wall of the crankcase

10

and the case cover

15

. A lower first journal

25

and an upper second journal

26

of the crankshaft

5

are carried by first and second bearing bushes

22

and

23

which are fitted in the bearing bores

20

and

21

, respectively. Pistons

27

,

27

reciprocally movable in the cylinder bores

13

,

13

are connected to the crankshaft

5

through connecting rods

28

,

28

, respectively.

Each connecting rod

28

,

28

has a larger end of a split structure, and a working bore

10

a

is provided in a sidewall of the crankcase

10

opposite to the cylinder bores

13

,

13

for assembling the connecting rods

28

,

28

. The working bore

10

a

is closed by a side lid

10

b.

The structure of coupling the crankcase

10

and the case cover

15

will be described with reference to

FIGS. 4

to

6

.

The crankcase

10

and the case cover

15

are each provided with a pair of positioning bores

32

and

33

;

34

and

35

, respectively, which open into a joint face

30

,

31

thereof. The positioning bores

32

,

33

,

34

and

35

are disposed at locations closer to the cylinder block

11

than the second bearing bush

23

and spaced equidistantly on opposite sides of a plane P including an axis Y of the crankshaft

5

and axes X of the cylinder bores

13

,

13

. Halves of a pair of knock pins

36

and

37

are press-fit into the positioning bores

32

and

33

in the crankcase

10

, and the positioning bores

34

and

35

in the case cover

15

are fit over the other halves of the knock pins

36

and

37

, respectively. Thus, the joint positions of the crankcase

10

and the case cover

15

are defined to coaxially arrange the first and second bearing bushes

22

and

23

.

A plurality of threaded bores

38

are provided in the crankcase

10

and open into the joint face

30

to surround the opening

14

. A corresponding number of bolt-insertion bores

39

are provided in the case cover

15

. Thus, the crankcase

10

and the case cover

15

are coupled to each other by threadedly fitting bolts

40

through the bolt-insertion bores

39

into the threaded bores

38

and then tightening the bolts

40

. A liquid packing is then applied to at least one of the joint faces

30

and

31

of the crankcase

10

and the case cover

15

.

One of the knock pins

36

is hollow such that a hole

36

a

in the hollow knock pin

36

is connected at one end thereof to an oil passage

42

defined in the cylinder block

11

and at the other end to an oil passage

43

defined in the case cover

15

. Therefore, both of the oil passages

42

and

43

communicate with each other through the hole

36

a

in the knock pin

36

. The oil passage

42

in the cylinder block

11

communicates with a lubrication bore (not shown) in the first bearing bush

22

, while the oil passage

43

in the case cover

15

communicates with a lubrication bore (not shown) in the second bearing bush

23

.

A working bore

43

a

of the oil passage

43

opens into one side of the case cover

15

, as shown in

FIGS. 4 and 5

. A hydraulic pressure sensor

46

is threadedly mounted in the working bore

43

a

to detect a pressure discharged from an oil pump

53

through the oil passage

43

. With such a structure, it is not necessary to especially provide an exclusive bore for mounting the hydraulic pressure sensor

46

in the case cover

15

, thereby leading to a reduction in cost. In this case, the disposition of the hydraulic pressure sensor

46

, with a tip end turned laterally and rearwards of the outboard engine system O, decreases the overhanging of the hydraulic pressure sensor

46

in an outward direction of the engine block

12

, which avoids increasing the size of the engine cover

4

.

Referring again to

FIG. 3

, a valve operating camshaft

48

is disposed parallel relative to the crankshaft

5

and is carried in the cylinder head

16

coupled to a rear end of the cylinder block

11

. Driving and driven pulleys

50

and

51

are secured to the crankshaft

5

and the camshaft

48

above the cylinder head

16

and the case cover

15

, respectively, and a timing belt

52

is reeved around the driving and driven pulleys

50

and

51

, so that the crankshaft

5

drives the camshaft

48

at a reduction ratio of ½.

The oil pump

53

is mounted at a lower rear portion of the cylinder block

11

and driven by the camshaft

48

. The oil pump

53

pumps oil from an oil pan

54

(see

FIG. 2

) coupled to a lower portion of the engine block

12

and accommodated in the casing

3

to supply the oil to the oil passages

42

and

43

and other portions, thereby lubricating the first and second bearing bushes

22

and

23

and the like. The oil, which has finished the lubrication of the various portions, is passed through the lower portion of the crankcase

10

back to the oil pan

54

.

As shown in

FIGS. 2

to

4

, a large number of mounting bosses are projectingly provided on an outer surface of the case cover

15

. A recoiled starting device

58

is bolted to mounting bosses

55

a

to

55

c

disposed at apexes of a triangle at locations farthest from the crankshaft

5

. In the present embodiment, a measure is taken so that the parts or components can be used commonly in any outboard engine system having a specification of 6 volts or 12 volts in power-generating and charging systems. For example, in the specification of 12 volts, a circular annular multi-pole power generating coil C (see

FIG. 2

) is secured by a bolt

59

to bosses

56

a

to

56

c

disposed at apexes of a triangle at locations closest to the crankshaft

5

. In the specification of 6 volts, a semicircular igniting power coil is bolted at its opposite ends to bosses

57

a

and

57

b

disposed at intermediate locations, and semicircular charging coil is bolted at its opposite ends to bosses

57

c

and

57

d.

Referring to

FIG. 4

, reference character U designates an igniting CDI device mounted on the side lid

10

b

and a boss formed on the case cover

15

. Reference character S is a starting motor, and R is a regulator rectifier for a power supply, both of which are mounted on an upper wall of the engine block

12

.

The operation of the engine E will be described below.

The bearing bore

20

for mounting of the first bearing bush

22

to support the first journal

25

of the crankshaft

5

is provided in the engine block

12

, and the bearing bore

21

for mounting of the second bearing bush

23

to support the second journal

26

of the crankshaft

5

is provided in the case cover

15

. Therefore, it is not necessary to machine the two members while in a coupled state in order to form the bearing bores

20

and

21

as is common in conventional engines. Thus, a step of coupling the two members to each other and a step of separating them from each other is not required, which reduces the manufacturing cost, but also permits replacement of either the engine block

12

and the case cover

15

, leading to an enhanced interchangeability of parts.

Moreover, the supplying of a lubricating oil to the second journal

26

of the crankshaft

5

is conducted from the oil pump

53

through the oil passages

42

and

43

provided in the engine block

12

and the case cover

15

. Therefore, it is not necessary to define an oil passage for lubricating the second journal

26

in the crankshaft

5

, which also simplifies the structure or the oil passage in the crankshaft

5

.

In addition, the halves of the knock pins

36

and

37

are fit on the positioning bores

32

,

33

,

34

and

35

which open into the joint faces

30

and

31

of the crankcase

10

having the first bearing bush

22

and the case cover

15

having the second bearing bush

23

. Also, the crankcase

10

and the case cover

15

are coupled to each other by the plurality of bolts

40

. Therefore, in a state in which the first and second bearing bushes

22

and

23

have been positioned accurately on the same axis, the crankcase

10

and the case cover

15

can be firmly coupled to each other, and the first and second journals

25

and

26

of the crankshaft

5

can be properly supported by the first and second bearing bushes

22

and

23

.

Accordingly, when an explosion load is applied from the pistons

27

,

27

to the crankshaft

5

through the connecting rods

28

,

28

during an explosion stroke of the engine E, a shearing load is applied to the joint faces

30

and

31

of the crankcase

10

and the case cover

15

. However, a shearing stress generated on the knock pins

36

and

37

and a frictional force applied to the joint faces

30

and

31

by the plurality of bolts

40

resists the shearing load.

Furthermore, because the pair of knock pins

36

and

37

are positioned closer to the cylinder block

11

than the second bearing bushes

23

, when the explosion load is applied from the crankshaft

5

to the case cover

15

, a tensile stress is generated in a wide area between the second bearing bushes

23

and the pair of knock pins

36

and

37

. Therefore, because the case cover

15

is strongly resistant to the tensile stress, the case cover

15

exhibits a high rigidity in cooperation with the dispersion of the tensile stress.

In this way, the pair of knock pins

36

and

37

define the position for coupling of the crankcase

10

and the case cover

15

to each other, but also contribute to increasing the rigidity of the case cover

15

. Therefore, it is possible to increase the supporting strength of the crankshaft

5

, reduce the weight of the case cover

15

, and decrease the number of bolts

40

used.

In addition, the knock pins

36

and

37

are positioned equidistantly on opposite sides of the plane P including the axis of the crankshaft

5

and the axes X of the cylinder bores

13

,

13

. Therefore, it is possible to effectively provide the equalization of the shearing load applied to both of the knock pins

36

and

37

and disperse the tensile stress generated on the case cover

15

, thereby enhancing the durability of the knock pins

36

and

37

and the case cover

15

.

Further, one knock pin

36

has a function of permitting communication between the oil passage

42

in the cylinder block

11

and the oil passage

43

in the case cover

15

. Hence, the oil passage

42

and the knock pin

36

can be disposed coaxially, and as a result, the disposition of the oil passage

42

and the knock pin

36

in the narrow joint faces

30

and

31

can be easily achieved.

Yet further, the knock pins

36

and

37

are press-fit in the positioning bores

33

,

33

in the crankcase

10

, and hence, a fitting gap for the knock pins

36

and

37

may be provided only between the knock pins

36

and

37

and the positioning bores

34

and

35

in the case cover

15

. Therefore, dislocation between the joint faces

30

and

31

of the crankcase

10

and the case cover

15

due to the fitting gap for the knock pins

36

and

37

can be minimized, wherein the accuracy of coupling the crankcase

10

and the case cover

15

is increased.

Although the preferred embodiment of the present invention has been described above in detail, it will be understood that the present invention is not limited to the above-described embodiment, and various modifications may be made without departing from the spirit and scope of the invention defined in claims. For example, three or more knock pins may be disposed at locations closer to the cylinder block than the second bearing bushes

23

. In addition, the knock pins

36

and

37

may be press-fit into the positioning bores

34

and

35

in the case cover

15

.

Number	Date	Country
61-23851	Feb 1986	JP
3-49996	Oct 1991	JP

Information

Patent Number

Date Filed

Date Issued

Inventors

Original Assignees

Examiners

Agents

CPC

US Classifications

Field of Search

US

International Classifications

Abstract

Description

Claims

Priority Claims (1)

Foreign Referenced Citations (2)