Information
-
Patent Grant
-
6415753
-
Patent Number
6,415,753
-
Date Filed
Monday, August 7, 200024 years ago
-
Date Issued
Tuesday, July 9, 200222 years ago
-
Inventors
-
Original Assignees
-
Examiners
- Denion; Thomas
- Corrigan; Jaime
Agents
-
CPC
-
US Classifications
Field of Search
US
- 123 9018
- 123 9012
- 123 9015
- 123 9017
- 123 9019
- 123 9031
- 074 568 R
- 073 116
- 073 1172
-
International Classifications
-
Abstract
A variable valve apparatus of an internal combustion engine is capable of realizing more precise valve characteristic control by reducing the error in-detection of the amount of movement of a camshaft caused by a difference in the rate of thermal expansion. The variable valve apparatus has a camshaft that is supported so as to be rotatable and slidable in a direction of an axis thereof and that has three-dimensional cams whose cam profile continuously changes in the direction of the axis. The apparatus also has an actuator for moving the camshaft in the direction of its axis. The apparatus further has a camshaft position sensor provided in a cylinder head, a detected portion provided in the camshaft, and a camshaft movement amount detection portion for detecting the amount of movement of the camshaft in the direction of the axis. The camshaft movement amount detection portion is provided near a camshaft reference position.
Description
INCORPORATION BY REFERENCE
The disclosure of Japanese Patent Application No. 11-237511 filed on Aug. 24, 1999 including the specification, drawings and abstract is incorporated herein by reference in its entirety.
BACKGROUND OF THE INVENTION
1. Field of Invention
The invention relates to a variable valve apparatus of an internal combustion engine that varies the open-close characteristic of an engine valve by moving a three-dimensional cam in the direction of an axis of the cam, the cam having a cam profile that continuously changes in the direction of the cam axis and a method of varying the open-close characteristic of an engine valve.
2. Description of Related Art
A known variable valve apparatus of an internal combustion engine employing a three-dimensional cam is described in, for example, U.S. Pat. No. 5,924,397. A construction of a detection portion provided in the apparatus for detecting the amount of movement of the camshaft in a direction of an axis thereof is illustrated in
FIGS. 5A and 5B
.
FIG. 5A
is a view of the detection portion taken in a direction of the axis of the camshaft.
FIG. 5B
is a side view of the detection portion taken in a direction indicated by an arrow B in FIG.
5
A.
As shown in
FIGS. 5A and 5B
, an engine camshaft
22
provided with a three-dimensional cam has a pair of detected portions
74
for reference extending linearly in the direction of the axis of the camshaft
22
, and a movement amount detected portion
75
for amount of movement extending helically in the direction of the axis. An electromagnetic pickup
76
that generates pulses corresponding to passage of the detected portions
74
,
75
is secured to a body of the engine (cylinder head) in the vicinity of the camshaft
22
. When the camshaft
22
, which is rotated in a direction C in the drawings, is moved in either direction of the axis (leftward or rightward in FIG.
5
B), the generation timing of pulses generated by the electromagnetic pickup
76
corresponding to the reference detected portions
74
does not change whereas the generation timing of pulses corresponding to the movement amount detected portion
75
changes. Based on these pulse generation timings, the apparatus accurately detects the amount of movement of the cam (three-dimensional cam). Therefore, precise cam position control (i.e., precise valve characteristic control) can be performed.
In variable valve apparatus employing three-dimensional cams, it is a normal practice to set a camshaft reference position as a positioning reference in the direction of the axis of a camshaft for mounting the camshaft to a cylinder head, or as a detection reference for detecting the amount of movement of the camshaft during operation. This camshaft reference position is also referred to when the electromagnetic pickup
76
and other members are secured to predetermined positions on the cylinder head.
If a base member (cylinder head) to which the electromagnetic pickup
76
is secured and the camshaft where the movement amount detected portion
75
and the like are provided are made of different materials; for example, the cylinder head is formed as a cast aluminum alloy and the camshaft is formed from iron, an increase in the engine temperature causes, in some cases, a positional deviation due to the different rates of thermal expansion of the materials. In such a case, the precision in detecting the amount of movement of the camshaft may decrease, and the control precision related to the valve characteristics determined by the three-dimensional cam, such as the valve-opening angle and the valve lift, may also decrease.
More specifically, even if, during the assembly of the engine, the position of the electromagnetic pickup
76
and the positions of the reference detected portions
74
and the movement amount detected portion
75
are initially adjusted (initialized) based on the camshaft reference position, and the reference position regarding the detection of the amount of movement of the camshaft is initialized, it is difficult to prevent the initialized positions from deviating with increases in the engine temperature, due to different rates of thermal expansion. If detection related to the amount of movement of the camshaft is performed while such a positional deviation exists, there is a possibility that precise control of the valve characteristics through the use of the three-dimensional cam becomes difficult. This possibility is particularly great if the deviation is great.
SUMMARY OF THE INVENTION
Accordingly, a variable valve apparatus of an internal combustion engine according to various exemplary embodiments of the invention is capable of realizing more precise valve characteristic control by reducing the error in detection of the amount of movement of a camshaft caused by a difference in the rate of thermal expansion.
The variable valve apparatus of an internal combustion engine for varying an open-close characteristic of an engine valve according to various exemplary embodiments of the invention includes a camshaft that has a plurality of three-dimensional cams whose cam profile continuously changes in a direction of a cam axis and that is supported so as to be rotatable and slidable in the direction of the cam axis relative to a body of the internal combustion engine. The apparatus also includes a movement mechanism that moves the camshaft in a direction of an axis of the camshaft, a camshaft position marker provided in the camshaft, and a camshaft movement amount detector that is provided in the body of the internal combustion engine and that detects the camshaft position marker and detects an amount of movement of the camshaft in the direction of the axis of the camshaft. The camshaft position marker and the camshaft movement amount detector are provided near a reference position that is provided at a predetermined position in a direction of a length of the camshaft.
Therefore, even if the engine body, where the camshaft movement amount detector is provided, and the camshaft, where the camshaft position marker is provided, are made of different materials and therefore have different rates of thermal expansion, the variable valve apparatus is able to reduce the error in detection of the amount of movement of the camshaft caused by the different rates of thermal expansion.
In the variable valve apparatus according to various exemplary embodiments of the invention, the reference position may be provided near a central portion of the camshaft.
The provision of the camshaft movement amount detector near a central portion of the camshaft reduces the distance from the movement amount detector to a farthest three-dimensional cam. Therefore, it becomes possible to reduce the deviation from the initialized position of the movement amount detection means, the deviation being caused by thermal expansion of the camshaft, and to reduce the variation in the amounts of control achieved by the three-dimensional cams in the valve characteristic control.
BRIEF DESCRIPTION OF THE DRAWINGS
Various exemplary embodiments of the invention will be described with reference to the accompanying drawings, wherein like numerals are used to represent like elements and wherein:
FIG. 1
is an illustration of a construction of a first embodiment of the variable valve apparatus according to the invention;
FIG. 2
is a hydraulic circuit diagram, illustrating a construction of a hydraulic actuator;
FIG. 3
is a sectional view illustrating a construction of a camshaft movement amount detection portion;
FIG. 4
is a partial sectional side view illustrating a construction of a side portion of a second embodiment of the variable valve apparatus according to the invention;
FIG. 5A
is a sectional view illustrating a construction of a camshaft movement amount detection portion of a related-art variable valve apparatus; and
FIG. 5B
is a side view illustrating the construction of the camshaft movement amount detection portion of FIG.
5
A.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
Various exemplary embodiments of the variable valve apparatus according to the invention will be described hereinafter with reference to the accompanying drawings.
FIG. 1
is a partial sectional side view of a construction of a first embodiment of the invention. A variable valve apparatus of the embodiment includes a camshaft
22
provided with three-dimensional cams
25
and a spline gear
26
, a hydraulic actuator
30
for moving the camshaft
22
in the directions of the camshaft axis, and a movement amount detection portion
50
for detecting the amount of movement of the camshaft
22
.
The camshaft
22
is supported by a bearing portion of a cylinder head
6
that forms an internal combustion engine body, in such a manner that the camshaft
22
is rotatable and movable in the directions of the axis of the camshaft
22
. The camshaft
22
is rotated by an output shaft (not shown) of the engine. The cam profile of each three-dimensional cam
25
continuously changes in a direction of the camshaft axis from a cam profile that provides a large valve lift (or a large valve-opening angle) and that is suitable to high-speed/high-load operation of the engine to a cam profile that provides a small valve lift (or a small valve-opening angle) and that is suitable to low-speed/low-load operation (see FIG.
1
). The cam profile surface of each three-dimensional cam
25
is shaped so that the amount of valve lift increases at the side of the hydraulic actuator
30
and decreases at the side of the spline gear
26
. Therefore, the camshaft
22
is constantly urged in the direction indicated by arrow F
2
away from the hydraulic actuator
30
toward the spline gear
26
by forces from valve springs
41
of engine valves
40
(only one engine valve is shown in
FIG. 1
for clarity) that are pressed by the three-dimensional cams
25
.
The engine valves
40
are driven in the opening and closing directions based on pressurization by the three-dimensional cams
25
. As the camshaft
22
is slid in a direction of the camshaft axis, the cam profile of a portion of each three-dimensional cam
25
that contacts the corresponding engine valve
40
changes. Therefore, the valve characteristics of the engine valves
40
, such as the valve lift and the valve-opening angle can be varied.
The spline gear
26
is bolted to a distal end of the camshaft
22
as part of a rotating mechanism
10
. Due to the spline gear
26
, the camshaft
22
can be rotated together with a sprocket
11
even when the camshaft
22
is slid in a direction of the camshaft axis. More specifically, the spline gear
26
is movable, that is, the camshaft
22
is movable, in the directions of the axis of the camshaft
22
, along splines
12
formed in an inner peripheral surface of the sprocket
11
. The sprocket
11
has, on its outer peripheral surface, outer teeth
11
a
that are engaged with a timing chain (not shown). The chain transmits torque from a crankshaft (not shown) to the sprocket
11
and the camshaft
22
. The sprocket
11
is provided with a cover
13
that is a member for restricting movement of the camshaft
22
in a direction indicated by the arrow F
2
in FIG.
1
.
A base end portion of the camshaft
22
(the right-side end portion in
FIG. 1
) is bolted to an inner ring of a bearing
27
. An outer ring of the bearing
27
is secured to a rod
32
by a nut
28
. Thus, the camshaft
22
and the rod
32
are interconnected so that the camshaft
22
and the rod
32
are rotatable relative to each other and are slidable together as one piece in the directions of the camshaft axis indicated by the arrows F
1
and F
2
.
The hydraulic actuator
30
is disposed at the distal end portion of the camshaft
22
as shown in
FIGS. 1 and 2
. The hydraulic actuator
30
is provided for moving the camshaft
22
in the directions of the camshaft axis via the rod
32
. The hydraulic actuator
30
includes a piston
31
and a case
33
secured to the cylinder head
6
.
The rod
32
is secured at one end to the piston
31
. The case
33
defines therein a cylindrically shaped cylinder
36
. The piston
31
is housed in the cylinder
36
in such a manner that the piston
31
is slidable in the directions of the camshaft axis. Thus, the piston
31
, the rod
32
and the camshaft
22
are slidable together as one piece in the directions of the camshaft axis.
The internal space of the cylinder
36
is divided into two hydraulic chambers
34
,
35
by the piston
31
. Operating fluid is charged into the hydraulic chambers
34
,
35
to actuate the hydraulic actuator
30
. Used as the operating fluid may be a portion of lubricating fluid for various portions of the engine. Fluid passages
64
,
65
are connected to the hydraulic chambers
34
,
35
, respectively, to supply the operating fluid to and discharge it from the hydraulic chambers
34
,
35
. The fluid passages
64
,
65
are connected at other ends thereof to a fluid pressure control valve
66
as shown in FIG.
2
.
The fluid pressure control valve
66
is an electromagnetic direction changeover valve that is duty-controlled by an electronic control unit (ECU)
55
. In addition to the fluid passages
64
,
65
, two fluid passages
62
,
63
are connected to the fluid pressure control valve
66
. The fluid passage
62
has in its partway a pump
67
that pumps the operating fluid from a pan
61
storing the operating fluid and that pressurizes and ejects the operating fluid. That is, the fluid passage
62
is a passage for supplying the operating fluid to the fluid pressure control valve
66
. The fluid passage
63
is a passage for discharging the operating fluid into the oil
61
. The fluid passages
62
-
65
may be formed in the cylinder head
6
or a cylinder block (not shown) that form the engine body.
The fluid pressure control valve
66
is controlled so as to selectively establish communication between the fluid passages
64
,
65
connected to the hydraulic chambers
34
,
35
of the hydraulic actuator
30
and the operating fluid supplying passage
62
and the operating fluid discharging passage
63
(two combinations) or to block the communication (balancing state). When the fluid pressure control valve
66
is in either one of the communicating states, the operating fluid is supplied from the pump
67
to one of the hydraulic chambers
34
,
35
, and is discharged from the other one of the hydraulic chambers
34
,
35
to the pan
61
. When the fluid pressure control valve
66
is in the blocking (balancing) state, the pressure of the operating fluid in the hydraulic chambers
34
,
35
is maintained. Thus, the fluid pressure control valve
66
adjusts the pressure of the operating fluid in the hydraulic chambers
34
,
35
by controlling the amounts of the operating fluid supplied and discharged.
The hydraulic actuator
30
operates based on the control of the pressure of the operating fluid in the hydraulic chambers
34
,
35
. For example, if the operating fluid pressure in the hydraulic chamber
34
is made higher than the pressure in the hydraulic chamber
35
, the piston
31
receives a force based on the operating fluid pressure difference across the piston
31
such that the piston
31
moves together with the rod
32
and the camshaft
22
in a direction indicated by the arrow F
1
in FIG.
1
. As a result, the cam profile of a portion of each three-dimensional cam
25
that contacts the corresponding engine valve
40
changes to a cam profile that provides an increased valve lift (or an increased valve-opening angle). Conversely, if the operating fluid pressure in the hydraulic chamber
34
is made lower than the pressure in the hydraulic chamber
35
, the piston
31
moves together with the rod
32
and the camshaft
22
in a direction indicated by the arrow F
2
in FIG.
1
. As a result, the cam profile of a portion of each three-dimensional cam
25
that contacts the corresponding engine valve
40
changes to a cam profile that provides a decreased valve lift (or a decreased valve-opening angle). Thus, the valve characteristics of the engine valves
40
can be changed.
The camshaft
22
has a detected portion
52
that is used to detect the amount of movement of the camshaft
22
in the directions of the camshaft axis, at a position between the distal end (left-side end in
FIG. 1
) of the camshaft
22
and the three-dimensional cam
25
that is disposed nearest to the distal end among all the three-dimensional cam
25
. The detected portion
52
is provided with a pair of protruded movement amount detected portions
52
a
for the amount of movement (see FIG.
3
). The movement amount detected portions
52
a
are made of a magnetic material. The movement amount detected portions
52
a
extend helically in the directions of the axis of the camshaft
22
. A camshaft position sensor
51
formed by an electromagnetic pickup is provided at such a position on the engine body, for example, on the cylinder head
6
, that the camshaft position sensor
51
faces the detected portion
52
.
Since the movement amount detected portions
52
a
extend helically in the direction of the axis of the camshaft
22
, pulse signals (currents) induced in the camshaft position sensor
51
when the movement amount detected portions
52
a
pass by the sensor
51
during rotation of the camshaft
22
shift in phase relative to an output signal (reference pulse signal) from, for example, a crank angle sensor provided on a crankshaft that is an output shaft of the engine, by a shift amount corresponding to the amount of movement of the camshaft
22
in the direction of the camshaft axis. Therefore, by monitoring the phase difference between the pulse signals, the amount of movement of the camshaft
22
can be detected at any time.
Therefore, to control the valve characteristics of the engine valves
40
, the operational condition of the engine is detected from output signals of various sensors
53
(FIG.
2
), such as the crank angle sensor, a pressure sensor for detecting the pressure of intake air introduced into the engine, etc., and, on the basis of the operational condition, calculates a target position of the camshaft
22
in the direction of the camshaft axis at which a suitable valve characteristic will be obtained. Furthermore, the apparatus detects the actual position of the camshaft
22
in the direction of the camshaft axis by referring to the output signal of the camshaft position sensor
51
as well. Then, based on comparison between the target position and the actual position of the camshaft
22
in the direction of the camshaft axis, the ECU
55
feedback-controls the fluid pressure control valve
66
.
In a conventional apparatus that changes the valve characteristics (the valve lift, the valve-opening angle, etc.) of engine valves by changing the cam profile by sliding a camshaft from the reference position in a direction of the axis of the camshaft, an error regarding the reference position of the camshaft in the direction of the cam axis will cause an error regarding the site in each three-dimensional cam where the cam contacts the corresponding engine valve, thereby making it impossible to achieve a desired valve characteristic. Therefore, during assembly and operation, the precision of the reference position of the camshaft in the direction of the cam axis is an important factor that affects the performance of the apparatus.
Therefore, the variable valve apparatus according to various exemplary embodiments of the invention secures a positional precision by setting a position where the spline gear
26
disposed at the distal end of the camshaft
22
contacts the cover
13
of the sprocket
11
, as a reference position P
0
of the camshaft
22
in the direction of the camshaft axis. For example, the initial positioning (initialization) of the camshaft position sensor
51
and the detected portion
52
, that is, the initialization of the detection reference position Ps for detecting the amount of movement of the camshaft
22
in the direction of the cam axis, is performed based on the reference position P
0
of the camshaft
22
.
However, even if the detection reference position Ps is initialized based on the reference position P
0
, a positional deviation can occur. If the cylinder head
6
and the camshaft
22
are formed from different materials, for example, if the cylinder head
6
is formed as a cast aluminum alloy and the camshaft
22
is formed from iron, the relative positional relationship between the camshaft position sensor
51
and the detected portion
52
changes with increases in the temperature of the engine, due to the different thermal expansion rates of the materials (e.g., aluminum has a greater linear expansion rate than iron). Thus, a deviation αPs occurs to the initialized detection reference position Ps.
In the variable valve apparatus the embodiment shown in
FIG. 1
, however, the camshaft movement amount detection portion
50
, having the camshaft position sensor
51
and the detected portion
52
, is provided near the reference position P
0
of the camshaft
22
, so that the deviation ΔPs of the detection reference position Ps caused by different rates of thermal expansion as mentioned above is minimized. More specifically, with reference to the reference position P
0
, the positional deviation caused by the different thermal expansion rates of the cylinder head
6
and the camshaft
22
increases with increases in distance from the reference position P
0
. Therefore, the provision of the camshaft movement amount detection portion
50
near the reference position P
0
minimizes the effect of the deviation caused by thermal expansion.
Thus, the variable valve apparatus of the embodiment shown in
FIG. 1
minimizes the error deviation APs of the detection reference position Ps caused by the difference in thermal expansion between the cylinder head
6
and the camshaft
22
since the camshaft movement amount detection portion
50
is provided near the reference position P
0
of the camshaft
22
. Therefore, the apparatus is able to perform precise valve characteristic control with a minimized error in detection of the amount of movement of the camshaft.
Although in the foregoing embodiment, the reference position P
0
of the camshaft
22
is set on the contact surface of the cover
13
that contacts the spline gear
26
, that is, at a position at which the camshaft
22
is restricted from moving in the direction of the arrow F
2
in
FIG. 2
, it should be appreciated that the reference position P
0
may be set at a position where the camshaft
22
is restricted from moving in the direction of the arrow F
1
in
FIG. 1
, as indicated by P
0
′ in FIG.
1
.
A second embodiment of the variable valve apparatus of the invention will be described with reference to FIG.
4
.
The variable valve apparatus of the second embodiment differs from the variable valve apparatus of the first embodiment shown in
FIG. 1
in the position of the camshaft movement amount detection portion
50
. More specifically, in the variable valve apparatus of the second embodiment shown in
FIG. 4
, a detected portion
52
forming the camshaft movement amount detection portion
50
is provided in a central portion of the camshaft
22
. A camshaft position sensor
51
is secured to a predetermined position (not shown) on a cylinder head
6
so as to face the detected portion
52
.
The provision of the camshaft movement amount detection portion
50
in a central portion of the camshaft
22
reduces the distance from the detection portion
50
to a three-dimensional cam
25
that is farthest from the detection portion
50
, that is, the greatest one of the distances to the three-dimensional cams
25
. Therefore, even though the camshaft
22
thermally expands due to increases of in the temperature of the engine, variations in the amounts of control of the valve characteristics achieved by the three-dimensional cams
25
can be reduced. More specifically, when the camshaft
22
thermally expands as described above, the error of the detected value of the amount of movement of the camshaft
22
from the actual position of a three-dimensional cam
25
becomes greater if the cam
25
is farther from the camshaft movement amount detection portion
50
. However, since the camshaft movement amount detection portion
50
is provided in a central portion of the camshaft
22
, the distance from the detection portion
50
to a farthest three-dimensional cam is reduced, for example, to about half the distance to a farthest three-dimensional cam in the case where a camshaft movement amount detection portion
50
is provided at an end of the camshaft
22
. Thus, the effect of thermal expansion of the camshaft
22
is significantly reduced in this embodiment.
In the second embodiment, the reference position of the camshaft
22
may also be set near the camshaft movement amount detection portion
50
, that is, near a central portion of the camshaft
22
. In that case, it becomes possible to reduce both the deviation from the initialized position of the movement amount detection means caused by thermal expansion of the camshaft and the variation in the amounts of control achieved by the three-dimensional cams
25
in the valve characteristic control.
In the foregoing embodiments, the actuator for moving the camshaft
22
in the directions of the axis thereof is not limited to the hydraulic actuator
30
operated based on hydraulic pressure, but may also be a different type of actuator, for example, a mechanical or a pneumatic actuator.
Furthermore, the camshaft movement amount detection portion
50
is not limited to a detection portion that includes a camshaft position sensor
51
formed by an electromagnetic pickup and a detected portion
52
having a pair of protruded movement amount detected portions
52
a
extending helically in the directions of the cam axis. For example, the camshaft position sensor may be formed by a photo-sensor or a distance sensor. The detected portion may have only one movement amount detected portion that is protruded and helically extends.
While the invention has been described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed embodiments or constructions. On the contrary, the invention is intended to cover various modifications and equivalent arrangements. In addition, while the various elements of the invention are shown in various combinations and configurations, which are exemplary, other combinations and configurations, including more, less or only a single embodiment, are also within the spirit and scope of the invention.
Claims
- 1. A variable valve apparatus of an internal combustion engine that varies an open-close characteristic of an engine valve, the apparatus comprising:a camshaft that has a plurality of three-dimensional cams whose cam profile continuously changes in a direction of a camshaft axis and that is supported so as to be rotatable and slidable in the direction of the camshaft axis relative to a body of the internal combustion engine; a rotating mechanism that rotates the camshaft about the camshaft axis; a movement mechanism that moves the camshaft in the direction of the camshaft axis; a camshaft position marker provided in the camshaft; and a camshaft movement amount detector that is provided in the body of the internal combustion engine and that detects the camshaft position marker and detects an amount of movement of the camshaft in the direction of the camshaft axis, wherein the camshaft position marker and the camshaft movement amount detector are provided at a detection reference position, the detection reference position based on a camshaft reference position that is provided at a predetermined initial position in which movement of the camshaft toward the rotating mechanism along the camshaft axis is physically restrained by the rotating mechanism, the detection reference position being established to minimize or reduce deviations in a relative axial position of the camshaft position marker and the camshaft movement amount detector due to differences in thermal expansion rates of the camshaft and the body of the internal combustion engine where the camshaft movement amount detector is provided.
- 2. A variable valve apparatus according to claim 1, further comprising a restrictor that is provided at a side of an end portion of the camshaft and that restricts a movement of the camshaft in the direction of the camshaft axis, wherein the movement mechanism is provided at a side of another end portion of the camshaft, and the reference position is a position at which the camshaft contacts the restrictor.
- 3. A variable valve apparatus according to claim 1, wherein the detection reference position is near a central portion of the camshaft.
- 4. A method of varying the open-close characteristic of an engine valve of a variable valve apparatus of an internal combustion engine having a camshaft that has a plurality of three-dimensional cams whose cam profile continuously changes in a direction of a camshaft axis and that is supported so as to be rotatable and slidable in the direction of the camshaft axis relative to a body of the internal combustion engine; a rotating mechanism that rotates the camshaft about the camshaft axis; a camshaft position marker provided in the camshaft; and a camshaft movement amount detector that is provided in the body of the internal combustion engine, wherein the camshaft position marker and the camshaft movement amount detector are provided at a detection reference position, the detection reference position based on a camshaft reference position that is provided at a predetermined initial position in which movement of the camshaft toward the rotating mechanism along the camshaft axis is physically restrained by the rotating mechanism, the detection reference position being established to minimize or reduce deviations in a relative axial position of the camshaft position marker and the camshaft movement amount detector due to differences in thermal expansion rates of the camshaft and the body of the internal combustion engine where the camshaft movement amount detector is provided; the method comprising:moving the camshaft in the direction of the of the camshaft axis; and detecting the camshaft position marker and an amount of movement of the camshaft in the direction of the camshaft axis.
- 5. A method according to claim 4, further comprising:providing a restrictor at a side of an end portion of the camshaft and that restricts a movement of the camshaft in the direction of the camshaft axis, wherein the reference position at which the camshaft contacts the restrictor.
- 6. A method according to claim 4, wherein the detection reference position is near a central portion of the camshaft.
- 7. A variable valve apparatus of an internal combustion engine that varies an open-close characteristic of an engine valve, the apparatus comprising:a camshaft that has a plurality of three-dimensional cams whose cam profile continuously changes in a direction of a camshaft axis and that is supported so as to be rotatable and slidable in the direction of the camshaft axis relative to a body of the internal combustion engine; rotating means for rotating the camshaft about the camshaft axis; movement means for moving the camshaft in the direction of the camshaft axis; a camshaft position marker provided in the camshaft; and camshaft movement amount detecting means provided in the body of the internal combustion engine for detecting the camshaft position marker and detecting an amount of movement of the camshaft in the direction of the camshaft axis, wherein the camshaft position marker and the camshaft movement amount detector are provided at a detection reference position, the detection reference position based on a camshaft reference position that is provided at a predetermined initial position in movement of the camshaft toward the rotating means along the camshaft axis is physically restrained by the rotating means, the detection reference position being established to minimize or reduce deviations in a relative axial position of the camshaft position marker and the camshaft movement amount detector due to differences in thermal expansion rates of the camshaft and the body of the internal combustion engine where the camshaft movement amount detector is provided.
- 8. A variable valve apparatus according to claim 7, further comprising a restriction member provided at a side of an end portion of the camshaft for restricting a movement of the camshaft in the direction of the camshaft axis, wherein the movement means is provided at a side of another end portion of the camshaft, and the reference position is a position at which the camshaft contacts the restriction member.
- 9. A variable valve apparatus according to claim 7, wherein the detection reference position is near a central portion of the camshaft.
Priority Claims (1)
Number |
Date |
Country |
Kind |
11-237511 |
Aug 1999 |
JP |
|
US Referenced Citations (4)
Foreign Referenced Citations (1)
Number |
Date |
Country |
A 4-187807 |
Jul 1992 |
JP |