JPH0874532A - Valve train for internal combustion engine - Google Patents

Abstract

(57) [Summary] [Purpose] To improve the degree of freedom in setting the valve lift characteristics of low-speed cams and high-speed cams, as well as to increase the strength of camshafts and to make them easily mountable on engines. A low-speed cam 5 and a high-speed cam 6 for opening the intake valve 4 are provided on the outer periphery of the camshaft 1, and a wedge-shaped follower member is provided between the high-speed cam 6 and the outer pad 10 of the valve lifter 9. 12 is provided so as to be movable back and forth, and the valve lift characteristics are changed by switching between the cams 5 and 6 according to the engine speed.
When the follower member 12 moves backward, the tip portion 12b is fitted and slid into the recess 11 of the valve lifter 9 by the biasing means 17 so that the tip portion 12b is quickly separated from the outer peripheral surface 6a of the high speed cam 6 to be in a non-contact state. .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve operating system for an internal combustion engine capable of variably controlling the opening / closing timing and the opening amount of an intake valve or an exhaust valve according to the engine operating condition.

[0002]

2. Description of the Related Art Conventionally, in an internal combustion engine for an automobile, an intake valve or an exhaust valve is selected depending on an operating state in order to achieve both fuel consumption at low and medium speeds and improvement of output torque at high speeds. It is known that the lift characteristic is made different, and a valve operating device capable of controlling the opening / closing timing and the opening amount of the intake / exhaust valve by this is provided (see US Pat. No. 4,205,634).

In this structure, a low speed cam and a high speed cam having different profiles for integrally opening an intake valve against the spring force of a valve spring are provided integrally on the outer periphery of a cam shaft which is rotationally driven by a crankshaft. In addition, a direct-acting valve lifter or rocker arm that is a transmission member that transmits the lift of each cam to the intake valve is provided at the upper end of the valve stem of the intake valve. In addition, a wedge-shaped follower member is movable back and forth along the diametrical direction of the valve lifter between the outer peripheral surface of one high speed cam disposed between the pair of low speed cams and the upper end surface of the valve lifter. It is provided in. The follower member has a base end portion which is moved forward and backward by a drive mechanism through a slide guide member provided on the rocker cover, and a tip end portion of the high speed cam which is constantly operated by a spring force of a torsion spring. It makes elastic contact with the outer peripheral surface.

When the engine is running at low speed, the follower member is held in the retracted position by the drive mechanism, and a gap is formed between the lower surface of the tip of the follower member and the upper end surface of the valve lifter. At the same time, the outer peripheral surfaces of the low speed cams contact the upper end surface of the valve lifter. Therefore, the intake valve opens and closes according to the small valve lift characteristic of the low speed cam via the valve lifter.

On the other hand, when shifting from the low speed range to the high speed range, the follower member moves forward by the drive mechanism, and the upper and lower surfaces of the tip end contact the outer peripheral surface of the high speed cam and the upper end surface of the valve lifter, respectively. The contact state between the low speed cam and the upper end surface of the valve lifter is released. That is, the contact between the low speed cam and the valve lifter is released by the wall thickness of the follower member, while the contact between the high speed cam and the valve lifter is switched. Therefore, the intake valve opens and closes according to the large valve lift characteristic of the high speed cam transmitted to the valve lifter.

As a result, the fuel consumption and the output torque can be improved according to the engine operating condition.

[0007]

However, in the conventional valve operating system described above, the upper surface of the tip of the wedge-shaped follower member is always elastically contacted with the outer peripheral surface of the high speed cam by the spring force of the torsion spring. It has become. In other words, the tip portion of the follower member at the time of maximum retreat is in a position where it comes into contact with the outer peripheral surface of the high speed cam, and is always placed in a position within the motion range of the high speed cam.

Therefore, the size of the gap between the high speed cam and the valve lifter at the time of maximum retreat is naturally limited. Therefore, the valve lift difference between the low speed cam and the high speed cam is inevitably restricted and cannot be set sufficiently large. As a result, the opening / closing timing of the intake valve, the phase difference, and the lift amount cannot be changed significantly, and it becomes difficult to sufficiently exert the above-described engine performance according to the engine operating state.

Moreover, as described above, since the tip portion is located between the high speed cam and the valve lifter even when the follower portion is fully retracted, the high speed cam is considered in consideration of the thickness of the tip portion. The difference in diameter between the base circles of the low speed cam must be set large. That is, the base circle diameter of the high speed cam must be set sufficiently smaller than that of the low speed cam. As a result, the shaft diameter of the camshaft is unavoidably small, and therefore the strength of the camshaft is not only lowered, but on the contrary, the base circle diameter of the low speed cam must be made sufficiently large, so that the existing Mounting on an internal combustion engine becomes difficult.

[0010]

The present invention has been devised in view of the above problems of the prior art. The invention of claim 1 is directed to a camshaft which is rotationally driven by a crankshaft of an engine, and the camshaft. Is provided on the outer periphery of the intake / exhaust valve, and is interposed between the intake / exhaust valve and the high / low speed cam, and at least a pair of high / low speed cams for opening the intake / exhaust valve against the spring force of the valve spring. Is provided in a gap between the transmission member for transmitting the lift of each cam to the intake / exhaust valve and the high-speed cam and the transmission member, and transmits the cam lift of the high-speed cam when advancing. A follower member that transmits to the intake / exhaust valve via a member, an urging means that separates at least the tip of the follower member from the high speed cam when the follower member is retracted, and the follower part according to the engine operating state,
It is characterized in that it is provided with a drive mechanism for moving back and forth.

According to a second aspect of the present invention, a recess is formed at the upper end of the transmission member so that the tip end of the follower member fits in and slides, and the bottom surface of the recess is tapered so that the outer end side is lower. Alternatively, it is characterized by being formed in an arc shape.

The invention of claim 3 is characterized in that a lever member for transmitting the driving force from the drive mechanism to the follower member is rotatably provided between the follower member and the drive mechanism.

[0013]

According to the first aspect of the present invention, the follower portion is moved back and forth between the high speed cam and the transmission member according to the engine operating state, so that the valve lift characteristics of the intake and exhaust valves can be switched between large and small. Needless to say, the tip end of the follower member at the time of maximum retraction can be separated from the high speed cam to be in a non-contact state, and can be sufficiently retracted to the outside of the movement range of the high speed cam. Therefore, it is possible to improve the degree of freedom in setting the valve lift characteristics of the low speed cam and the high speed cam.

According to the second aspect of the present invention, since the tip end of the follower member moves backward while sliding on the tapered or arcuate bottom surface in the recess of the upper end of the transmission member, the follower member can be slightly moved backward. It is possible to greatly separate from the high speed cam by the amount. Therefore, the operation response of the drive mechanism is improved.

According to the third aspect of the present invention, the linear driving force of the drive mechanism is converted into rotational movement by the lever member and transmitted to the follower member, so that the drive stroke of the drive mechanism is reduced and the drive mechanism is reduced. Can be miniaturized.

[0016]

1 and 2 show a first embodiment in which a valve operating system according to the present invention is applied to the intake side of a multi-cylinder internal combustion engine.

That is, in FIG. 1, reference numeral 1 denotes a cam shaft whose journal portion 1a is supported by the upper end portion of a cylinder head 2 via a cam bracket 3 and which is rotationally driven by a crank shaft (not shown), and 4 denotes intake air in the cylinder head 2. There are two intake valves per cylinder that open and close each open end of the port.

The camshaft 1 is provided between a pair of low speed cams 5 and 5 arranged at an outer peripheral surface position corresponding to substantially the center of the valve stem 4a of the intake valve 4, and between the low speed cams 5 and 5. One arranged high-speed cam 6 is integrally provided. The low speed cams 5 and 5 are set to have the same cam profile such that the outer peripheral surfaces 5a and 5a have a small valve lift characteristic as indicated by X in FIG.

On the other hand, the high-speed cam 6 has a cam profile whose outer peripheral surface 6a is smaller than that of the low-speed cams 5 and 5, but when the follower member 12 is advanced, which will be described later, Y in FIG.
The profile is set so as to have a large valve lift characteristic, as shown in. The high speed cam 6 is
The width W is set to be larger than that of the low speed cams 5 and 5.

The intake valve 4 is biased in the closing direction by the spring force of a valve spring 8 elastically held by a cotter 7 fixed to the stem end of the valve stem 4a, and abuts on each stem end. Opening operation is performed against the spring force of the valve springs 8 and 8 by the high and low speed cams 5, 5 and 6 via a pair of direct acting type valve lifters 9 and 9 which are transmission members.

Both of the valve lifters 9 are formed in a substantially cylindrical shape with a lid, are provided with a guide hole 2a formed in an upper end portion of the cylinder head 2 slidably in the vertical direction, and have a circular upper wall 9a. A disc-shaped outer pad 10 made of a wear resistant material is fitted and fixed in a circular groove formed on the upper surface of the. Further, the rising outer peripheral wall 9b of the upper wall 9a is formed with an engaging groove 9c into which a tip portion 12b of a follower member 12 described later is engaged, while the upper surface of the outer pad 10 is continuous with the engaging groove 9c. The recessed portion 11 is formed along the diametrical direction. As shown in FIGS. 1 and 4, the recess 11 has a bottom surface 11a formed in a taper step shape from a position opposite to the engagement groove 9c in the engagement groove 9c direction, and has a flat high step surface 11b and a low step step. The surface 11c is continuously connected by a gently sloping surface 11d.

The follower member 12 includes the outer pad 10 and the high speed cam 6 as shown in FIGS. 1, 2 and 7.
Is provided so as to be able to advance and retreat in a gap S between the outer end side and a base portion 12a on the outer end side, which is rotatably supported by a lower end portion 13b of a lever member 13 described later via a pivot shaft 14 and has a tip end edge of a circle. An arcuately chamfered inner end 12b on the inner end side is slidably guided while being fitted into the engaging groove 9c and the recess 11. The tip portion 12b is constantly urged by the lever member 13 toward the bottom surface 11a of the recess 11.

As shown in FIGS. 1 and 5, the lever member 13 is rotatably supported by a pin 15 inserted through a cylindrical portion 13b provided at the upper end of the main body 13a, and has a cylindrical shape. Protrusion 13 provided on the lower end side of the portion 13b
While c is pressed by the plunger 16 and is urged to rotate in the clockwise direction in FIG. 1, an inclined projection 13d integrally provided on the upper surface of the cylindrical portion 13c is pressed by a drive mechanism 18 described later. It is designed to be rotated counterclockwise. Further, at the lower end portion of the main body 13a, holding pieces 13f, 13f, through which the pivot shaft 14 is inserted and supported, and which hold the base portion 12a of the follower member 12, are integrally provided. The plunger 16 is slidably held in a bottomed tubular member 16a fixed in a support hole on the side of the cam bracket 3, and a coil spring 16b in the tubular member 16a.
The spring force urges the front of the projection 13c. Further, a urging means 17 for urging the tip portion 12b of the follower member 12 downward is provided on the lower portion of the main body 13a.

The biasing means 17 is mounted on the bottom of the sliding hole 13e and a biasing plunger 17a slidably provided in a slidable hole 13e formed on one side of the lower portion of the main body 13a. And a coil spring 17b for pushing the urging plunger 17a in the advancing direction. The urging plunger 17a includes an inner rising surface 12 of the follower member base 12a.
By pressing c, the tip portion 12b is rotationally biased toward the concave portion 11 side.

The drive mechanism 18 is a cylinder 1 formed at the upper end of the cam bracket 3 as shown in FIGS.
A piston 20 that slides inside 9 and a hydraulic circuit that supplies and discharges hydraulic pressure to and from a pressure receiving chamber 21 formed at the bottom of the cylinder 19 are provided. The piston 20 advances by the hydraulic pressure in the pressure receiving chamber 21 and presses the tip of the protrusion 13d. The hydraulic circuit includes a hydraulic passage 22 having a downstream portion 22a formed in the cam bracket 3, and the hydraulic passage 22.
An oil pump 23 provided at the upstream end of the oil pump 23, and a three-way electromagnetic switching valve 25 provided at the downstream side of the oil pump 23 for switching between the hydraulic passage 22 and the drain passage 24. This electromagnetic switching valve 25 is switched and operated by an ON-OFF signal output from a controller 26 with a built-in microcomputer. This controller 26 operates as a crank angle sensor, an air flow meter, a throttle opening sensor, a water temperature sensor, etc. (not shown). The current engine operating state is detected based on the information signal from each sensor, and the operation of the electromagnetic switching valve 25 is controlled mainly according to the engine speed.

The operation of this embodiment will be described below.
First, at the time of high engine speed, an ON signal is output from the controller 26 to the electromagnetic switching valve 25, so that the drain passage 24
Is closed, the upstream and downstream of the hydraulic passage 22 are communicated with each other, and the working hydraulic pressure is supplied into the pressure receiving chamber 21 to become a high pressure.
Therefore, as shown in FIG. 6, the protrusion 13d of the lever member 13 is pressed as the piston 20 advances, so that the lever member 13 rotates counterclockwise around the pivot 15 against the spring force of the coil spring 16b of the plunger 16. Turn to. Therefore, the follower member 12 advances and moves in the gap S through the pin 14, and the tip portion 12 b is the high step surface 1 of the recess 11.
1b and the outer peripheral surface 6a of the cam 6 for high speed. Therefore, the intake valve 4 is opened and closed according to the large valve lift characteristic shown by Y in FIG. 3, and as a result, the intake charging efficiency is improved and a high output torque can be obtained.

In the follower member 12, since the tip end portion 12b is urged to rotate downward (clockwise) by the spring force of the coil spring 17b of the urging plunger 17a, the lower surface 12d is engaged during the forward movement. The bottom surface of the groove 9c and the bottom surface 11a of the recess 11 are brought into sliding contact with each other to move.

On the other hand, for low and medium engine speed, the controller 2
Since an OFF signal is output from 6 to the electromagnetic switching valve 25,
The drain passage 24 is opened, and the upstream and downstream communication of the hydraulic passage 22 is cut off. Therefore, the hydraulic oil pumped from the oil pump 23 and the hydraulic oil in the pressure receiving chamber 21 are returned from the drain passage 24 into the oil pan 27, and the pressure receiving chamber 21
The inside becomes low pressure. Therefore, as shown in FIG. 1, the lever member 13 rotates clockwise around the pivot 15 by the pressing force of the plunger 16 to move the follower member 12 to the maximum retracted position shown. Therefore, the outer peripheral surfaces 5a and 5a of the low speed cams 5 and 5 come into contact with both upper surfaces of the outer pads 10 and 10 of the valve lifters 9 and 9, whereby the intake valves 4 and 4 are small as shown by X in FIG. It opens and closes according to the valve lift characteristics.

As a result, as shown in FIG. 3, the overlap with the exhaust valve is reduced, and the residual gas in the combustion chamber can be reduced, so that the combustion is improved and the fuel consumption is improved. Moreover, since the closing timing of the intake valves 4 and 4 can be brought close to the bottom dead center, the intake charging efficiency is improved and the torque can be improved.

Here, the follower portion 12 is rotationally biased by the biasing plunger 17a in the clockwise direction, so that the lower surface 12d of the tip portion 12b slides on the high step surface 11b and the low step surface 11a of the recess 11. Engagement groove 9c while touching
Move backward to the bottom position of. That is, when the tip portion 12b moves from the high step surface 11b to the low step surface 11a, the upper surface 12e of the tip portion 12b immediately separates from the outer peripheral surface 6a of the high speed cam 6 and becomes a non-contact state. It is always in a non-contact state during the backward movement and at the maximum backward movement position. Therefore, the tip portion 12b has the high-speed cam 6
Quickly and fully retreat out of range. For this reason,
A large gap S is formed between the recess bottom surface 11a and the outer peripheral surface 6a of the high speed cam 6 instead of the upper surface 12e of the tip portion 12b. Therefore, the shape of the outer peripheral surface 6a of the high-speed cam 6 can be set larger by the amount of the large gap S.

As a result, the degree of freedom in setting the valve lift characteristics of the low speed cam 5 and the high speed cam 6 can be improved. That is, it is possible to greatly change the opening / closing timing of the intake valves 4, 4, the valve lift phase difference, and the valve lift amount. Therefore, the above-mentioned engine performance according to the engine speed can be further exerted.

Moreover, when the follower member 12 is fully retracted, the tip portion 12b is located away from the high speed cam 6 as described above, and when the valve lift phase by the low speed cam 5 and the high speed cam 6 changes, As shown in FIG. 3, it is possible to increase the cam lift difference corresponding to the maximum valve lift difference L generated near the bottom dead center. Therefore, it is not necessary to set a large difference in diameter between the base circles of the low speed cam 5 and the high speed cam 6, and it is possible to set the difference as small as possible. As a result, the shaft diameter of the camshaft 1 can be increased, the strength of the camshaft 1 can be improved, and conversely, the base circle diameter of the low speed cam 5 can be reduced, so that the existing engine can be used. The mountability of is also improved.

Further, when the follower member 12 is retracted,
Since the tip portion 12b descends toward the bottom surface 11a of the recess 11, the follower member 12 can be largely separated from the high speed cam 6 with a small amount of backward movement.
Therefore, the amount of rotation of the lever member 13 can be reduced, and the operation response of the drive mechanism 18 is also improved.

Further, the follower member 12 is replaced with the lever member 13
The linear movement of the piston 20 of the drive mechanism 18 is caused by the rotation of the lever member 13.
Is converted into rotational movement by the lever member 13
Since the pivot point is located near the upper end, the turning stroke on the lower end side becomes large even with a small amount of turning, so that the moving stroke of the piston 20 can also be made small. As a result, the driving load of the drive mechanism 18 can be reduced, and the drive mechanism 18 can be reduced in size and weight.

Furthermore, the drive mechanism 1 is attached to the cam bracket 3.
Since a part of 8, the follower member, the lever member 13 and the like can be integrally assembled and sub-assembled, the assemblability to the cylinder head 2 is improved.

Furthermore, since the follower member 12 is constantly engaged in the engagement groove 9c, the follower member 12 functions as a detent for the valve lifters 9 and 9 when the cams 5 and 6 are switched. Therefore, the occurrence of malfunction is prevented.

Further, the bottom surface 11a of the recess is a high level step surface 11
Since b is flat, the follower member tip 12
b can be stably supported, and the tip end portion 12b can be smoothly moved back and forth due to the gently sloping surface 11d.

FIGS. 8 and 9 show a second embodiment of the present invention, in which the upper wall 29a is formed in a spherical shape without providing an outer pad on the upper surface of each valve lifter 29, and the upper wall 2 is formed.
9a, the tip portion 12b of the follower member 12 in the diametrical direction of the upper surface.
Is formed with a concave portion 11 having an arcuate bottom surface 11a that engages and slides.

Therefore, also in this embodiment, the bottom surface 11a of the recess 11 causes the follower member 12 to be steeply inclined in the backward direction as shown by the arrow, so that the backward movement amount can be further reduced. Further, the follower member 12 can function as a rotation stopper for each valve lifter 29, and the number of parts can be reduced because the outer pad is eliminated.

FIG. 10 shows a third embodiment of the present invention, in which the engaging groove 9c and the recess 11 of the first embodiment are omitted. Therefore, the difference in diameter between the base circles of the low-speed cam 5 and the high-speed cam 6 must be set to be slightly larger than that in the first embodiment, but the existing valve lifter 9 can be used. In terms of advantages.

FIG. 11 shows a fourth embodiment in which a rocker arm 31 whose one end is swingably supported by a rocker shaft 30 is used as the transmission member instead of the valve lifter. In this case, the rocker arm 31 is used. Since the upper surface of the slipper 32 provided on the upper surface of the is formed in an arc shape, the backward movement amount of the follower member 12 can be reduced. The other structure is similar to that of the first embodiment.

FIG. 12 shows a fifth embodiment of the present invention, in which the urging means 17 is arranged in the direction opposite to that of each of the above-described embodiments and the tip portion 1 of the follower member 12 has the basic construction of the third embodiment.
2b urges the high speed cam 6 to rotate, while the base 12a
Rising surface 12c and the lower end inclined surface 1 of the lever member 13
It is configured as a stopper 33 that regulates the upward rotation position of the tip portion 12b by 3g. As a result, the downward biasing force of the follower member 12 with respect to the valve lifter 9 is avoided, so that the spring force of the valve spring 8 is not offset, and a decrease in the spring force of the valve spring 8 can be prevented. Further, the stopper 33 ensures the non-contact state between the tip portion 12b and the high speed cam 6 during the backward movement.

The present invention is not limited to the configuration of the above-described embodiment, but the structure of the transmission member may be further modified, and the drive mechanism 18 may be constituted by an electromagnetic actuator or the like. . Further, it can be applied not only to the intake side but also to the exhaust side or both.

[0044]

As is clear from the above description, according to the present invention, at least when the follower member moves backward, the biasing means separates the tip end portion of the follower member from the high speed cam so that the high speed cam. Since it is moved out of the range of motion, a large gap can be secured between the transmission member and the high speed cam. Therefore, the outer peripheral surface shape of the high speed cam can be set large, and the degree of freedom in setting the valve lift characteristics of the low speed cam and the high speed cam can be improved. As a result, the opening / closing timing of the intake / exhaust valves, the valve lift phase difference, and the lift amount can be significantly changed, and the engine performance can be further improved according to the engine operating state.

Moreover, since the follower member can be quickly moved out of the movement range of the high speed cam by the recess formed on the upper surface of the transmission member, the diameter of the base circle of the high speed cam can be increased accordingly. Becomes possible,
As a result, the difference in the base circle diameter between the cams can be reduced. Therefore, the shaft diameter of the camshaft can be increased, the strength of the camshaft can be increased, and the mountability on the existing engine can be improved.

Further, as described above, since the follower member can be lowered into the concave portion and can be largely separated from the high speed cam, the driving amount of the driving mechanism can be reduced, whereby the driving mechanism can be driven. The operation response is also good.

Further, since the driving force of the driving mechanism is converted into rotational movement by the lever member and transmitted to the follower member, the driving load of the driving mechanism can be reduced and the driving mechanism can be downsized.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part showing a first embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a valve lift characteristic diagram of the intake valve according to the present embodiment.

FIG. 4 is a perspective view showing a valve lifter used in this embodiment.

FIG. 5 is a perspective view showing a lever member used in this embodiment.

FIG. 6 is a cross-sectional view of a main part showing the operation of this embodiment.

7 is a partial cross-sectional view seen from the direction of arrow B in FIG.

FIG. 8 is a sectional view of a main part showing a second embodiment of the present invention.

FIG. 9 is a perspective view showing a valve lifter used in this embodiment.

FIG. 10 is a cross-sectional view of the essential parts showing the third embodiment of the present invention.

FIG. 11 is a cross-sectional view of the essential parts showing the fourth embodiment of the present invention.

FIG. 12 is a cross-sectional view of essential parts showing a fifth embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Cam shaft 4 ... Intake valve 5 ... Low speed cam 6 ... High speed cam 8 ... Valve spring 9,29 ... Valve lifter (transmission member) 10 ... Outer pad 11 ... Recessed portion 11a ... Bottom surface 13 ... Lever member 12 ... Follower member 12b … Tip S… Gap

Claims (3)

[Claims] 1. A camshaft rotatably driven by a crankshaft of an engine, and at least a pair of high and low speed motors provided on the outer periphery of the camshaft to open an intake / exhaust valve against the spring force of a valve spring. A cam, a transmission member interposed between the intake / exhaust valve and the high / low speed cam for transmitting the lift of each cam to the intake / exhaust valve, and between the high speed cam and the transmission member. A follower member that is installed in the gap between the two to move forward and backward and that transmits the cam lift of the high-speed cam to the intake and exhaust valves via the transmission member at the time of advancing, and at least the tip of the follower member when the follower member retracts. A valve operating system for an internal combustion engine, comprising: an urging means for separating the cam from the cam; and a drive mechanism for moving the follower part forward and backward according to an engine operating state. 2. A recess is formed at the upper end of the transmission member, into which the tip end of the follower member is fitted and slides, and the bottom surface of the recess is formed in a tapered shape or an arc shape whose outer end side is lower. The valve operating system for an internal combustion engine according to claim 1, wherein: 3. Between the follower member and the drive mechanism,
2. A valve operating system for an internal combustion engine according to claim 1, wherein a lever member for transmitting the driving force from the driving mechanism to the follower member is rotatably provided.