Variable valve apparatus of internal combustion engine and method of varying the open-close characteristic of an engine valve

Information

  • Patent Grant
  • 6415753
  • Patent Number
    6,415,753
  • Date Filed
    Monday, August 7, 2000
    24 years ago
  • Date Issued
    Tuesday, July 9, 2002
    22 years ago
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)
Number Name Date Kind
5048474 Matayoshi Sep 1991 A
5381764 Fukuma Jan 1995 A
5924397 Moriya et al. Jul 1999 A
6135078 Doi Oct 2000 A
Foreign Referenced Citations (1)
Number Date Country
A 4-187807 Jul 1992 JP