JP3330640B2 - Variable engine valve timing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable valve timing device for an engine that changes the opening and closing timing of intake and exhaust valves.

[0002]

2. Description of the Related Art In general, suction in an automobile engine,
Since it is preferable that the opening / closing timing of the exhaust valve be changed according to the operating state of the engine, various valve timing variable devices have been conventionally proposed.

[0003] For example, Japanese Patent Application Laid-Open No.
Japanese Patent No. 88014 discloses a tappet having a pressure receiving portion for receiving a force from a cam surface of a camshaft and a pressing portion for transmitting a force from the cam surface to a valve stem, and a fitting for slidably fitting the tappet. An engine valve timing control device is disclosed which includes a rotating member having a hole and rotatably supported around a camshaft, and an operating device for rotating the rotating member according to an operating state of the engine. I have.

In this device, the rotating member is held at a reference position where the sliding direction of the tappet and the moving direction of the valve coincide with each other at least when the engine is under a high load and a high speed, so that the tappet and the valve stem are separated. No slippage occurs between the tappet and the valve stem at the time of low-speed rotation, so that the rotation member is rotated from the reference position, thereby causing a slip between the tappet and the valve stem. , So that the valve timing can be changed.

In the variable valve timing apparatus disclosed in Japanese Patent Application Laid-Open No. Hei 3-115714, a low-speed cam and a high-speed cam are provided side by side on a camshaft, and both the low-speed cam and the valve are engaged. The main rocker arm and the auxiliary rocker arm that engages only with the high-speed cam are provided adjacent to each other so as to be swingable on the rocker shaft, and can move in the axial direction of the rocker shaft by hydraulic pressure. A switching mechanism is provided which can selectively switch the main and sub rocker arms to an interlocking state or a non-interlocking state by engaging and disengaging a pin. When the engine is running at high speed, the main and sub rocker arms are connected by the pins. The valve is driven by the high-speed cam, and the main and
The sub rocker arm is set in a non-interlocked state, and the valve is driven by the low speed cam.

[0006]

By the way, in the former, that is, in the structure disclosed in Japanese Patent Application Laid-Open No. 59-188014, when the engine with a high valve operating speed rotates at high speed, a slip occurs between the tappet and the valve stem. The wear of the valve stem and tappet is reduced, and when the engine is running at a low speed, even if the tappet and the valve stem are slipped, the wear of the valve stem and tappet is also reduced due to the low valve operating speed. It has an excellent effect.

However, in this configuration, only the valve timing can be delayed by the slip between the tappet and the valve stem. For example, the advance of the valve opening timing and the delay of the valve closing timing are simultaneously performed. Since it is theoretically impossible to extend the valve opening angle, it has been difficult to increase the maximum output in a high-load and high-speed range.

On the other hand, the latter, that is, the structure disclosed in Japanese Patent Application Laid-Open No. HEI 3-115714, makes it possible to independently select valve lift characteristics suitable for the low rotation range and the high rotation range of the engine. Although it is possible to improve the performance of, the number of parts increases and not only requires a special camshaft and complicated oil passage, but also the main and sub rocker arms can be switched between the interlocked state and the non-interlocked state. There is a possibility that an impact may occur when switching, and there is a problem in durability of the pin because a shearing stress acts on the pin for disengagement.

Further, in the high-load and high-speed range, not only the valve opening angle and the valve lift amount are simply increased than in the light-load range, but the region on the closed side of the valve is enlarged more than the open side. Although it is known to be advantageous in increasing the efficiency, it is not possible to continuously change such valve lift characteristics from a light load region toward a high rotation and high load region by a conventional configuration. Was something.

In view of the above problems, the present invention provides a variable valve timing device for an engine that can simultaneously and continuously change a valve opening angle, a valve lift, and a phase of a cam with respect to a camshaft. Aim.

[0011]

SUMMARY OF THE INVENTION
The variable valve timing device is used for the engine crankshaft.
The engine is driven in synchronization with the rotation of the
A camshaft pivotally supported by a cylinder head, and the cam
It is provided so as to be rotatable relative to the shaft and
A cam provided eccentrically with respect to the camshaft;
Relative rotation of the cam about the camshaft
The cam phase with respect to the cam shaft and the cam phase
The position of the system relative to the valve can be changed continuously.
Swinging around an axis parallel to the camshaft.
Movably provided and facing the cam by a biasing means
Direction, and is always in contact with the cam and is swung.
The valve opening / closing driving force from the cam is
Valve arm of an engine comprising
An imming variable device, wherein the variable mechanism comprises the cam
Can be turned on the camshaft while being rotatably supported
An intermediate member pivotally supported by the arm, and the intermediate member
Actuator to rotate around said camshaft
And the intermediate member is biased with the camshaft.
The cam is rotatably supported around a centered position.
A shaft supporting portion, and the cam has an inner portion concentric with the shaft supporting portion.
The internal gear is provided on the camshaft.
Is provided with an external gear that meshes with.

[0012]

According to the present invention, the cam provided so as to be rotatable relative to the camshaft, and by rotating this cam relatively around the camshaft, the phase of the cam with respect to the camshaft is improved. By providing a variable mechanism that can continuously change the relative position of the cam with respect to the valve, and a swing arm interposed between the cam and the valve, the cam with respect to the camshaft can be adjusted according to the operating state of the engine. The effect of being able to obtain a highly reliable variable valve timing device that can not only continuously change the phase but also simultaneously change the valve opening angle and lift amount of the cam at the same time. There is.

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing a basic configuration of a variable valve timing device for an engine according to the present invention. FIG. 1 is a sectional view taken along line II-II of FIG.
It is shown as a cross-sectional view along the -I line. FIG. 3 is a sectional view taken along the line III-III in FIG.

1 to 3, a camshaft 1 driven to rotate in synchronization with the rotation of a crankshaft of an engine.
Is rotatably supported by a cylinder head of the engine. A cam 2 having a rotation axis L2 parallel to the rotation axis L1 and separated by a predetermined distance D is provided on the camshaft 1 with respect to the camshaft 1. Eccentrically provided.

The cam 2 has a center hole 2a formed of a circular hole centered on the rotation axis L2, and the camshaft 1 passes through the center hole 2a. The camshaft 1 and the cam 2 maintain a mutual positional relationship by an intermediate member 3 interposed therebetween.

The intermediate member 3 is supported by the camshaft 1 in a manner that the camshaft 1 is rotatably penetrated, and is rotatably provided around the rotation axis L1 of the camshaft 1. 2 is provided with a cylindrical portion 3a that fits into the center hole 2a.
It is rotatably supported around 2.

On the inner peripheral surface of the center hole 2a of the cam 2, an internal gear 2b is formed over the entire periphery except for the portion where the cylindrical portion 3a of the intermediate member 3 is fitted. Also, camshaft 1
An external gear 1a internally meshing with the internal gear 2b of the cam 2 is formed on the outer peripheral surface of the cam 2, and the two gears 1a and 2b constitute a differential gear mechanism. Further, since the ratio of the number of teeth between the external gear 1a of the camshaft 1 and the internal gear 2b of the cam 2 is set to 1: 2, the reduction ratio of the camshaft 1 and the cam 2 is set to 2. It also constitutes a speed reduction mechanism. Therefore, the cam pulley attached to one end of the camshaft 1 is formed to have the same diameter as the crank pulley of the crankshaft that is driven to rotate via this and the timing belt.

The intermediate member 3 is integrally provided with a plate portion 3b projecting from the camshaft 1 on the side opposite to the rotation axis L2 side of the cam 2. This plate portion 3b is
Is provided with an end surface that forms an arc surface centered on the rotation axis L1 of the first gear, and the external gear 3c is formed along this end surface.

In order to rotate the intermediate member 3, a shaft 4 having a rotation axis L4 parallel to the rotation axes L1 and L2 is provided.
An external gear 4a meshing with the external gear 3c of the intermediate member 3 is formed. The shaft 4 is rotated by an actuator such as a step motor, and when the shaft 4 is rotated, as shown in FIG.
Is rotated about the camshaft 1 while the cam 2 is supported, and accordingly, the cam 2 is rotated relatively to the camshaft 1 to change the phase of the cam 2 with respect to the camshaft 1. At the same time, the rotation axis L2 of the cam 2 moves up and down on an arc centered on the rotation axis L1 of the camshaft 1, so that the relative position of the cam 2 to the valve is also changed.

On the other hand, a bucket-type lash adjuster (HLA) 5 having a flat top surface 5a is provided between the cam 2 and a valve which is opened and closed by the cam 2. The lash adjuster is further provided with a lash adjuster. A swing arm 6 that swings by the cam 2 and transmits the driving force from the cam 2 to the valve via the lash adjuster 5 is provided between the swing arm 6 and the swing arm 5.

The swing arm 6 is fixed to a shaft 7 having a rotation axis L7 parallel to the rotation axis L1 of the camshaft 1 and is swingably provided.
Is provided with a flat contact surface 6a always in contact with the cam surface 2c of the cam 2 on the upper surface side, and a gentle curved contact surface 6b always in contact with the top surface 5a of the lash adjuster 5 on the lower surface side. 1, and is urged by the spring 8 in a clockwise direction in FIG. 1, that is, a direction in which the cam 2 is pressed against the cam surface 2c. The swing arm 6 has an arc surface 6c around the rotation axis L7 of the shaft 7 around the shaft 7, and the arc surface 6c is provided with the lash adjuster 5
Is formed so as to be continuous with the contact surface 6b with the top surface 5a at the point P1.

Next, the operation of the apparatus shown in FIGS. 1 to 4 will be described.

Now, as shown in FIG.
Is present on a plane including the axes L1 and L4 of the camshaft 1 and the shaft 4 for rotating the intermediate member, and the contact surface 6a above the swing arm 6 is It is assumed that the valve is in a closed state in contact with the cylindrical portion of the cam surface 2c having the same diameter. And the swing arm 6
The lower contact surface 6b is set so as to contact the top surface 5a of the lash adjuster 5.

When the camshaft 1 rotates clockwise in FIG. 1 from this state, the cam 2 rotates clockwise at half the rotation speed of the camshaft 1 and moves to the position indicated by the chain line (the valve). (The maximum lift position), the swing arm 6 is swung largely clockwise downward from the horizontal state to the state shown by the chain line.

Since the lash adjuster 5 is pushed downward by the distance H1 by the swing of the swing arm 6, the valve is opened with a lift curve as shown by a curve A in FIG. The valve is closed by turning in the direction. In this case, the valve lift characteristics are a large valve opening angle and a large lift amount.

Next, the intermediate member rotating shaft 4 is rotated clockwise from the state shown in FIG. 1 and the intermediate member 3 is rotated counterclockwise about the camshaft 1 as shown in FIG. As described above, the rotation axis L2 of the cam 2 moves upward together with the cam 2, and the phase of the cam 2 with respect to the camshaft 1 is advanced. Then, the swing arm 6 urged toward the cam surface 2c by the spring 8 is rotated clockwise. With this rotation, the swing arm 6 comes into contact with the lash adjuster 5 when the valve is closed. The surface moves from the surface 6b through the point P1 to the arc surface 6c, and at a point P2 on the arc surface 6c, the top surface of the lash adjuster 5
It comes into contact with 5a.

Next, from this state, the camshaft 1 is moved from FIG.
Is rotated clockwise, the cam 2 rotates clockwise to reach the position shown by the dashed line (maximum lift position of the valve), whereby the swing arm 6 swings counterclockwise. It is moved to the position indicated by the dashed line.

In this case, when the swing arm 6 abuts on the top surface 5a of the lash adjuster 5 when the valve is closed, as shown in FIG. In this state, even if the swing arm 6 is swung counterclockwise from this state, the contact position of the swing arm 6 with the top surface 5a of the lash adjuster 5 is changed to an arc surface.
It is clear that the cam 2 does not act on the lash adjuster 5 at the beginning of the swing from the point P2 to the point P1 on 6c. Similarly, even when the valve is closed, the cam 2 does not act on the lash adjuster 5 in a section where the contact position of the swing arm 6 with the top surface 5a of the lash adjuster 5 from the point P1 to the point P2. become.

In this case, since the distance between the cam surface 2a of the cam 2 and the top surface 5a of the lash adjuster 5 is larger than that in FIG. 1, the lash adjuster 5 is pushed down. The distance H2 is the distance H1 in FIG.
Will be smaller than Therefore, in this case, FIG.
As shown by the curve B, the valve has a characteristic of late opening and early closing compared to the curve A, and the valve lift characteristic changes from a small valve opening angle to a small lift amount.

Further, in the state shown in FIG. 4, the phase of the cam 2 with respect to the camshaft 1 is advanced more than in the state shown in FIG. (Angular direction). Therefore, if the valve lift characteristic of the intake valve in the light load region of the engine is set as shown by the curve B and the valve lift characteristic of the intake valve in the high load and high rotation region is set as shown by the curve A, the high load and high rotation In the range, the intake valve has an ideal valve lift characteristic in which the tendency of late closing of the intake valve becomes remarkable, and the charging efficiency of the intake air can be increased accordingly.
In addition, in the configuration shown in FIGS. 1 to 4, the characteristic change can be continuously achieved from the characteristic of the curve B to the characteristic of the curve A by rotating the intermediate member rotating shaft 4 by the actuator. There are advantages that can be done.

The shapes of the curves A and B and the lift amount in FIG. 5 correspond to the profile of the cam surface of the cam 2, the profile of the contact surface 6b of the swing arm 6, and the cam of the shaft 7 which is the swing center. It can be arbitrarily set depending on the relative position and the like with respect to both the lash adjuster 2 and the lash adjuster 5.

From the above description, the structure and operation of the variable valve timing device of the engine according to the present invention have been clarified. Next, only the structure of the swing arm 6 of the above device was slightly modified and applied to the engine. An embodiment in such a case will be described with reference to FIGS. In FIGS. 6 and 7, members having the same functions as the members shown in FIGS. 1 to 4 are denoted by the same reference numerals.

An intake camshaft 1 is rotatably supported on the cylinder head 10, and an intake valve driving cam 2 is mounted on the camshaft 1 in the same manner as in FIGS.

A pair of intake valves 11 driven by the cam 2 are slidably supported by a valve guide 12, urged upward by a valve spring 13 in the drawing, that is, in the valve closing direction. The swing arm 6 and the lash adjuster 5 are provided between the swing arm 6 and the intake valve 11.

In the configuration shown in FIGS. 6 and 7, the swing arm 6 is used to reduce the overall height.
Is a member 6A having a contact surface 6a for the cam 2.
And a pair of members 6B, 6B provided with a contact surface 6b for the lash adjuster 5, and a shaft 7 rotatably supported by a cylinder head 10 is provided with the members 6B, 6A, 6B are different from the configurations shown in FIGS. 1 to 4 in that they are fixed to each other with a predetermined space therebetween. And in the configuration shown in FIGS. 6 and 7,
The spring 8 is contracted between the tip of the member 6A of the swing arm 6 that comes into contact with the cam 2 and the cylinder head 10, so that the member 6A always comes into contact with the cam 2.

[Brief description of the drawings]

FIG. 1 is a diagram showing a basic configuration of a variable valve timing device for an engine according to the present invention as a cross-sectional view taken along line II of FIG. 2;

FIG. 2 is a sectional view taken along the line II-II in FIG.

FIG. 3 is a sectional view taken along the line III-III of FIG. 2;

FIG. 4 is a sectional view showing a state in which the intermediate member is rotated from the state shown in FIG. 1;

FIG. 5 is a diagram showing valve lift characteristics.

FIG. 6 is a diagram showing the configuration of the embodiment of the present invention as a cross-sectional view along the line VI-VI in FIG. 7;

FIG. 7 is a cross-sectional side view of the device of FIG.

[Explanation of symbols]

 Reference Signs List 1 camshaft 2 cam 3 intermediate member 4 intermediate member rotating shaft 5 lash adjuster 6 swing arm 7 swing arm shaft 8 spring 10 cylinder head 11 intake valve

Claims (1)

(57) [Claims] (1) The rotation of a crankshaft of an engine is synchronized with the rotation of the engine.
As well as the engine cylinder head
A camshaft that is pivotally supported on the camshaft, and that is provided so as to be rotatable relative to the camshaft.
A cam provided eccentrically to the camshaft
And rotating the cam relatively around the camshaft.
By this, the phase of the cam with respect to the camshaft,
Can continuously change the position of the cam relative to the valve
A variable mechanism and a swingable mechanism about an axis parallel to the camshaft.
And is urged by the urging means in a direction toward the cam.
The cam is always in contact with the cam and is rocked.
The valve opening / closing drive force from the cam is transmitted to the valve.
A variable valve timing device for an engine having a swing arm.
In the state where the variable mechanism rotatably supports the cam,
An intermediate member pivotally supported by the camshaft,
Turning the intermediate member together with the cam around the camshaft
An actuator that rotates the cam shaft in a position eccentric to the camshaft.
The cam has a shaft supporting portion rotatably supporting the cam, and the cam is provided with an internal gear coaxial with the shaft supporting portion .
It is, in the camshaft external gear meshing with the internal gear
Variable valve timing equipment for engines equipped with
Place.