JPH0617628A - Variable valve timing device of engine - Google Patents

Abstract

PURPOSE:To obtain a variable valve timing device of an engine which is capable of simultaneously and continuously changing the valve opening angle, the valve lift amount, and the phase of the cam relative to the cam shaft. CONSTITUTION:A variable valve timing device is provided with a cam 2 in a relatively rotatable and eccentric manner relative to a cam shaft 1, and at the same time, provided with an intermediate member 3 to execute the relative rotation of the cam 2 around the cam shaft 1, and an oscillating arm 6 which is energized in the direction facing toward the cam by a spring 8, and is constantly abutted the cam 2. The relative rotation of the cam 2 around the cam shaft 1 by the intermediate member 3 allows the continuous change of the phase of the cam 2 relative to the cam shaft 1 and the relative position of the cam 2 to the valve.

Description

Detailed Description of the Invention

[0001]

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

[0002]

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

For example, Japanese Patent Application Laid-Open No. 59-1 filed by the present applicant
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. Disclosed is a valve timing control device for an engine, which includes a rotating member that has a hole and is rotatably supported around a cam shaft, and an operating device that rotates the rotating member according to an operating state of the engine. There is.

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 operating under a high load and a high rotation, so that the tappet and the valve stem are separated from each other. There is no slippage between them, and during low speed rotation, the rotating member is rotated from the standard position, causing slippage between the tappet and the valve stem, which causes a gap between low speed rotation and high speed rotation. The valve timing can be changed with.

Further, in the valve timing variable device disclosed in Japanese Patent Laid-Open No. 3-115714, a low speed cam and a high speed cam are arranged side by side on a cam shaft, and both the low speed cam and the valve are associated with each other. A matching main rocker arm and a sub-rocker arm that engages only with the high-speed cam are 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 the interlocked state or the non-interlocked state by engaging and disengaging the pins.When the engine is operating at high speed, the main and sub rocker arms are coupled by the pins. The valve is driven by a high-speed cam, and when the engine is operating at low speed, the main,
The sub rocker arm is in a non-interlocking state, and the valve is driven by the low speed cam.

[0006]

By the way, in the former structure, that is, the structure disclosed in Japanese Patent Laid-Open No. 59-188014, slippage occurs between the tappet and the valve stem during high-speed rotation of an engine having a high valve operating speed. Wears the valve stem and tappet less, and when the engine runs at low speed, the valve operating speed is low even if slippage occurs between the tappet and the valve stem, so wear on the valve stem and tappet also decreases. That is, it has an excellent effect.

However, in this configuration, the valve timing can only be delayed by the slip between the tappet and the valve stem, and for example, the advance timing of the valve opening timing and the retard timing of the valve closing timing are simultaneously performed. Since it is impossible in principle to expand the valve opening angle, it was difficult to meet the purpose of significantly improving the maximum output in the high load and high rotation range.

On the other hand, in the latter structure, that is, in the structure disclosed in Japanese Patent Laid-Open No. 3-115714, it is possible to independently select the valve lift characteristics which are adapted to the low speed region and the high speed region of the engine. However, not only the number of parts increases and a special camshaft and a complicated oil passage are required, but the main and sub rocker arms can be connected between the linked state and the non-linked state. There is a risk of impact when switching, and there is a problem in the durability of the pin because the engagement / disengagement pin is subjected to shear stress.

Further, in the high load and high rotation range, not only the valve opening angle and the valve lift amount are increased more than in the light load range, but also the region of the valve closing side is expanded more than that of the opening side in order to fill the intake air. It is known to be advantageous in increasing efficiency, but it is not possible to change such valve lift characteristics continuously from the light load region to the high rotation and high load region by the conventional configuration. It was a thing.

In view of the above problems, the present invention provides a variable valve timing device for an engine capable of simultaneously and continuously changing the valve opening angle, the valve lift amount, and the phase of the cam relative to the camshaft. To aim.

[0011]

In a valve timing varying device for an engine according to the present invention, a cam is provided so as to be rotatable relative to a cam shaft, and the cam is relatively rotatable around the cam shaft. It is characterized in that it is provided with a variable mechanism for making it move, and a swinging arm which is urged by the urging means in the direction toward the cam and is always in contact with the cam. Then, by relatively rotating the cam around the cam shaft by the variable mechanism,
The phase of the cam with respect to the cam shaft and the relative position of the cam with respect to the valve are configured to be continuously changed,
The swing arm has a function of transmitting the valve opening / closing driving force from the cam to the valve by swinging the swing arm.

According to one aspect of the present invention, the cam is provided eccentrically with respect to the cam shaft, and the variable mechanism is provided between the cam shaft and the cam. And an actuator that rotates around a cam shaft, and the intermediate member is
The cam is rotatably rotatably supported by the cam shut.

[0013]

According to the present invention, the cam provided so as to be rotatable relative to the cam shaft, and the phase of the cam relative to the cam shaft by rotating the cam relatively around the cam shaft, By providing the variable mechanism capable of continuously changing the relative position of the cam with respect to the valve and the swing arm interposed between the cam and the valve, the cam relative to the cam shaft of the cam depending on the operating state of the engine. The effect that not only the phase can be continuously changed, but also the valve opening angle and lift amount of the cam can be continuously changed at the same time with high reliability. There is.

[0014]

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

FIG. 1 is a diagram showing the basic construction of a valve timing varying device for an engine according to the present invention. In addition, FIG. 1 is a sectional view taken along line II-II of FIG.
Shown as a cross-section along line II. Also, FIG.
FIG. 3 is a sectional view taken along line III-III in FIG.

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

The cam 2 is provided with a center hole 2a which is a circular hole centering on the rotation axis L2, and the cam shaft 1 penetrates through the center hole 2a. The cam shaft 1 and the cam 2 maintain a mutual positional relationship by an intermediate member 3 interposed therebetween.

The intermediate member 3 is rotatably provided around the rotation axis L1 of the cam shaft 1 while being rotatably supported by the cam shaft 1 in such a manner that the cam shaft 1 is rotatably passed through the intermediate member 3. It has a cylindrical portion 3a which fits in the center hole 2a of the cam 2, and the cylindrical portion 3a causes the cam 2 to move along its axis L.
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 circumference except the portion where the cylindrical portion 3a of the intermediate member 3 is fitted. Also, the camshaft 1
An external gear 1a that is internally meshed with the internal gear 2b of the cam 2 is formed on the outer peripheral surface of, and both gears 1a and 2b constitute a differential gear mechanism. Further, the gear ratio between the external gear 1a of the camshaft 1 and the internal gear 2b of the cam 2 is set to 1: 2, so that the camshaft 1 and the cam 2 have a reduction ratio of 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 which is rotationally driven via the timing pulley and the like.

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

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, and an outer peripheral surface of the shaft 4 is provided.
An external gear 4a that meshes 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. 4, the intermediate member 3 is rotated.
Is rotated about the cam shaft 1 while still supporting the cam 2, and accordingly, the cam 2 is rotated relative to the cam shaft 1 to change the phase of the cam 2 with respect to the cam shaft 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 cam shaft 1, and the relative position of the cam 2 with respect 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 valve which is opened and closed by the cam 2 and the cam 2, and the lash adjuster is further provided. 5, a swinging 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.

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

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

Now, as shown in FIG. 1, the cam 2
Of the cam shaft 1 and the intermediate member rotating shaft 4 on the plane including the axes L1 and L4 of the intermediate shaft, and the contact surface 6a above the swinging arm 6 of the cam 2. It is assumed that the valve is in a closed state by coming into contact with the equal-diameter cylindrical surface portion of the cam surface 2c. Then, the swing arm 6 is
It is assumed that the lower contact surface 6b is set to contact the top surface 5a of the lash adjuster 5.

From this state, when the cam shaft 1 rotates clockwise in FIG. 1, the cam 2 rotates clockwise at a rotation speed of 1/2 of the cam shaft 1 and moves to the position indicated by the chain line (valve). (Maximum lift position) of the rocking arm 6 and the rocking arm 6 is rocked greatly downward from the horizontal state to the state shown by the chain line.

By the swinging of the swinging arm 6, the lash adjuster 5 is pushed downward by the distance H1. Therefore, the valve is opened with a lift curve as shown by the curve A in FIG. The valve is closed by turning in the direction. The valve lift characteristics in this case 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 around the cam shaft 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 cam shaft 1 is advanced. The swing arm 6 biased by the spring 8 toward the cam surface 2c is rotated clockwise, and with this rotation, the swing arm 6 contacts 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 the 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 to the position shown in FIG.
When the cam 2 is rotated in the clockwise direction, the cam 2 rotates in the clockwise direction to the position indicated by the chain line (the maximum lift position of the valve), and the swing arm 6 swings counterclockwise accordingly. It is moved to the position shown by the chain line.

In this case, the contact position of the swing arm 6 with respect to the top surface 5a of the lash adjuster 5 when the valve is closed is, as shown in FIG. 4, a point on the arc surface 6c as described above. Since it is in P2, even if the swing arm 6 is swung counterclockwise from this state, the contact position of the swing arm 6 with respect to the top surface 5a of the lash adjuster 5 is an arc surface.
It is apparent that the cam 2 does not act on the lash adjuster 5 in the initial stage of the swing on the 6c from the point P2 to the point P1. Similarly, even when the valve is closed, in the section from the point P1 to the point P2, the contact position of the rocking member 6 with respect to the top surface 5a of the lash adjuster 5 is:
The cam 2 does not act on the lash adjuster 5.

Further, 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 the case of FIG. 1, the lash adjuster 5 is pushed downward. The distance H2 is the distance H1 in FIG.
Will be smaller than. Therefore, in this case, FIG.
As shown by the curve B in FIG. 3, the characteristic is that the valve opens late and the valve closes faster than the curve A, and the valve lift characteristic changes from the small opening angle to the 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. The shape is deviated in the angular direction). Therefore, if the valve lift characteristic of the intake valve in the light load range of the engine is set as shown by curve B and the valve lift characteristic of the intake valve in the high load and high rotation range is set as shown by curve A, high load and high rotation speed In the region, the ideal valve lift characteristic that the tendency of the intake valve to close late becomes remarkable, and the intake charging efficiency can be improved to that extent.
Moreover, in the configuration shown in FIGS. 1 to 4, by rotating the intermediate member rotating shaft 4 by the actuator, it is possible to continuously change the characteristics from the characteristic of the curve B to the characteristic of the curve A. There are advantages.

The shapes of curves A and B in FIG. 5 and the lift amount are as follows: 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. 2 and the lash adjuster 5 relative positions with respect to both, and the like.

From the above description, the structure and operation of the valve timing varying device for an engine according to the present invention has been clarified. Next, only the structure of the swing arm 6 of the above device is slightly modified and applied to the engine. An example of the case will be described based on FIGS. 6 and 7. In FIGS. 6 and 7, members having the same functions as those shown in FIGS. 1 to 4 are designated by the same reference numerals.

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

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

In the configuration shown in FIGS. 6 and 7, the swing arm 6 is provided 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 pair of members 6B, 6A, 6A, 6B is fixed to each other with a predetermined interval therebetween, which is a difference from the configuration shown in FIGS. 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 contacts the cam 2 and the cylinder head 10, so that the member 6A always contacts the cam 2.

[Brief description of drawings]

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

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

FIG. 3 is a sectional view taken along line III-III in FIG.

FIG. 4 is a cross-sectional view showing a state in which the intermediate member is rotated from the state of FIG.

FIG. 5 is a diagram showing valve lift characteristics.

6 is a diagram showing a configuration of an embodiment of the present invention as a sectional view taken along line VI-VI of FIG.

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

[Explanation of symbols]

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

Claims (2)

[Claims] 1. A camshaft that is rotationally driven in synchronization with rotation of a crankshaft of an engine, a cam that is rotatable relative to the camshaft, and a cam that is relatively rotatable around the camshaft. A variable mechanism that can continuously change the phase of the cam with respect to the cam shaft and the relative position of the cam with respect to the valve by rotating, and is provided so as to be swingable around an axis parallel to the cam shaft. And a swinging arm that is biased by the biasing means in the direction toward the cam and is always in contact with the cam and is swung, and the swinging arm that transmits the valve opening / closing driving force from the cam to the valve by the swinging. A variable valve timing device for an engine, characterized by being provided. 2. The intermediate member, wherein the cam is provided eccentrically with respect to the cam shaft, and the variable mechanism is axially supported by the cam shaft in a state in which the cam is rotatably axially supported, and the intermediate member. The valve timing varying device for an engine according to claim 1, further comprising: an actuator that rotates a member around the cam shaft together with the cam.