JP2775828B2 - Variable valve drive for engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a valve drive device capable of changing the opening / closing timing and lift amount of an intake / exhaust valve of an engine according to an operating state.

<Related Art> In an engine, the optimal opening / closing timing of the intake / exhaust valve differs between low-speed operation and high-speed operation. In general,
It is preferable to make the exhaust start timing earlier and the intake closing timing later during high-speed operation than during low-speed operation. Therefore, the profile of the cam that controls the opening and closing of the intake and exhaust valves should be appropriately determined depending on whether the high-speed engine is a low-speed engine.

However, automobile engines are used over a wide range from low speed to high speed, and the selection of the cam profile for driving the intake and exhaust valves must be compromised in consideration of the advantages and disadvantages of low speed cams and high speed cams. Was done under.

<Problems to be Solved by the Invention> In general, when a high-speed cam is used, idle stability is poor, output torque in a low-medium-speed region is reduced, and the cam is not suitable for ordinary city driving. There is a problem that the exhaust gas deteriorates due to an increase in the overlap angle.

Conversely, when a low-speed cam is used, there is a problem that the high-speed spread is insufficient, lacking a sporty feeling, and the maximum speed is reduced.

The present invention has been made in view of the above situation,
It is an object of the present invention to provide a valve drive device for an engine that includes both a low-speed cam and a high-speed cam, and can selectively use them according to operating conditions.

<Means for Solving the Problems> A variable valve drive device for an engine according to the present invention that achieves the above object provides a low-speed cam that provides a valve motion suitable for low-speed operation and a valve-type cam suitable for high-speed operation. A high-speed cam, a first rocker arm driven by the low-speed cam and directly pressing the valve, a second rocker arm driven by the high-speed cam and pressing the valve via the first rocker arm, A driving device for preventing pressing of the second rocker arm against the first rocker arm during operation, the driving device being provided on a pivot shaft of the second rocker arm and capable of moving the pivot shaft in and out. It can be switched between a normal state and a protruding fixed state.

<Operation> During low-speed operation, the pivot shaft of the hitting device is in a retractable state, the swing of the second rocker arm does not affect the swing of the first rocker arm, and the first rocker arm does not rotate. It is driven by a low-speed cam to open and close the valve.

On the other hand, at the time of high-speed operation, the pivot shaft is in the protruding and fixed state, the second rocker arm presses the first rocker arm by its swing, and both swing as one, and the first rocker arm is substantially moved. It is driven by a high-speed cam to open and close the valve.

<Example> Hereinafter, an example of the present invention will be specifically described with reference to the drawings.

FIG. 1 is a sectional view of a main part of the first embodiment of the present invention (I in FIG. 2).
FIG. 2 is a plan view thereof. In the drawings, 1 is an intake or exhaust valve, 2 is a valve spring, and 4 is a cam shaft.

The distal end of the first rocker arm 5 is divided into a T-shape, and a pressing portion 5a extending forward and a driving portion extending on both sides, respectively.
5b. Each drive unit 5b is in contact with the valve 1, and the first rocker arm 5 swings via the roller receiving unit 9 by the low-speed cam 7 to open and close the two valves 1 at the same time. On the other hand, the pressing portion 5a is in contact with the spring receiver 51 to prevent the rocker arm 5 from rising.

Further, second rocker arms 6 are disposed on both sides of the first rocker arm 5, respectively, and their tip portions 6a are mounted on the drive unit 5b of the first rocker arm 5, respectively. These second rocker arms 6 are engaged with the high-speed cam 8 via slipper receiving portions 6b which make sliding contact.

Here, the low-speed cam 7 refers to a cam that gives an optimal valve opening / closing timing and a lift amount at the time of low-speed operation of the engine. Gives a cam. FIG. 3 shows an example of these. Fig. 3 (a)
The high-speed cam 8 is represented by a solid line in FIG. 4, and the profile of the low-speed cam 7 is small as represented by a broken line. Therefore, as shown in FIG. 3B showing the cam lift amounts, the cam lift of the high-speed cam 8
8a is always larger than the cam lift 7a of the low-speed cam 7 and includes the cam lift 7a. As a result, the swing amount of the second rocker arm 6 becomes larger than the swing amount of the first rocker arm 5.

A drive pin 11 is attached to the swinging end of the first rocker arm 5 driven by the low-speed cam 7 so that the amount of protrusion can be adjusted by a nut 12.
Is in contact with the rear end face of the stem.

On the other hand, a driving device 13 is provided on the pivot support portion of the second rocker arm 6. Thus, the driving device 13 fixes the pivot shaft 53 to the cylinder head 54 so as to be slidable or protruding in the protruding and retracting direction. That is, when the pivot shaft 53 that supports the second rocker arm 6 can move in and out, it does not function as a fulcrum. Accordingly, in this case, even if the second rocker arm 6 is driven by the high-speed cam 8, the swing of the first rocker arm 5 is not affected, and as a result, the first rocker arm 5 is driven at a low speed which is the original driving cam. The two valves 1 are opened and closed by being driven by the mold cam 7. On the other hand, when the pivot shaft 53 is fixed, the second rocker arm 6 is swung by the high-speed cam 8 and its tip 6a presses the driving portion 5b of the first rocker arm 5, and as a result, the first rocker arm 5 swings integrally with the second rocker arm 6 and the first rocker arm 5
Is driven by the high-speed cam 8 to open and close the valve 1.

FIG. 4 is a sectional view of the pivot support. As shown in FIG. 4, the pivot shaft 53 has a spherical support portion 53 at its tip.
A hexagonal hole 53b into which a tool such as a hexagonal wrench can be inserted is formed in the top surface thereof. A screw is formed on the outer periphery of the pivot shaft 53, and a sleeve 55 is screwed onto the pivot shaft 53 so that the axial position can be adjusted, and is fixed with a lock nut 56.

On the other hand, a bush 57 is fitted to the cylinder head 54,
The pivot shaft 53 is slidably inserted through a sleeve 55, and the pivot shaft 53 is urged upward by a spring 58. Notch 54 in cylinder head 54
a is provided, from which the stopper 16 of the driving device 13
Is arranged. In the stopper 16, the arc-shaped space 29 is formed slightly larger than the outer diameter of the sleeve 55, and the interval between the two legs is set smaller than the outer diameter of the sleeve 55.

Therefore, when the stopper 16 is advanced and inserted below the sleeve 55, the pivot shaft 53 is fixed in a protruding state, and the pivot shaft 53 is prevented from being immersed. On the other hand, if the stopper 16 is moved backward to position the sleeve 55 in the arc-shaped space 29, the pivot shaft 53 can slide up and down in the up and down direction, and the function as a fulcrum is lost.

Here, a hydraulic actuator is used. However, the device shown in FIG. 5 is used to obtain the timing for operating the stopper 16. FIG. 5 is a view corresponding to the VV cross section of FIG. 2, but as shown in FIG.
A timing cam 42 is projected from the camshaft 4 and a timing follower 41 is brought into contact with the cam 42 so that the timing plate 37 is disengaged from the piston 22 at a required timing.

FIG. 6 is a plan view of a main part of a second embodiment of the present invention. In the above-described first embodiment, the actuator 15 is provided on each of the two pivot shafts 53. As shown in FIG. 6, this embodiment provides two arc-shaped spaces 29 in the stopper 16 and This is driven by a single actuator 15. Thereby, the number of actuators 15 can be reduced.

7 and 8 show a third embodiment of the present invention. FIG. 7 is a cross-sectional view of a main part thereof, and FIG. 8 is a side view showing an expanded view of the punching device.

This third embodiment is a modification of the first embodiment described above.
The difference is that the stopper 16 is not directly driven by the actuator 15 but via a link mechanism to improve the efficiency of the arrangement space. That is, as shown in FIGS. 7 and 8, a link 61 bent in an L-shape is pivotally attached to the cylinder head 54 by a pin 62, and one end of the link 61 is connected to the stopper 16. On the other hand, the other end is connected to the actuator 15. Therefore, the movement of the actuator 15 causes the link 61 to swing, and the swing movement of the link 61 causes the stopper 16 to move forward and backward.

Here, as in the first and third embodiments described above,
If the punching device 13 is provided on the cylinder head 54 side without being provided on the rocker arm 6, there is an advantage that the weight of the rocker arm can be reduced.

When the rocker arms 5 and 6 are driven by the cams 7 and 8, there are a roller type that makes rolling contact at a contact portion between the two and a slipper type that makes sliding contact. Comparing the roller type and the slipper type, first, regarding the wear, the roller type is excellent in the low speed region of the engine rotation, and the slipper type is excellent in the high speed region. In terms of cam friction, the roller type is excellent in the low-speed range, and there is no significant difference between the two in the high-speed range. In addition, the slipper type is advantageous in cost.

Therefore, in the present invention, as in the first and third embodiments, the contact between the first rocker arm 5 functioning in the low-speed region and the low-speed cam 7 is of the roller type, and the second rocker arm 5 functioning in the high-speed region. If the contact between the rocker arm 6 and the high-speed cam 8 is made to be a slipper type, the advantages of both can be used.

FIG. 9 is a graph conceptually showing a change in camshaft driving torque with respect to the engine speed. As described above, by using the roller type in the low-speed region and using the slipper type in the high-speed region, good characteristics can be obtained over the entire range from the low-speed region to the high-speed region as shown by the broken line in FIG.

In the present invention, the present invention is not necessarily limited to this. In some cases, both the rocker arms 5 and 6 may be of a roller type, and conversely, both may be of a slipper type.

 Next, adjustment of the valve clearance will be described.

In the valve driving device according to the present invention, when adjusting the valve clearance, for example,
It is assumed that the valve clearance of the low-speed first rocker arm 5 is adjusted to a predetermined value in a state where the high-speed second rocker arm 6 is hit from the high-speed type. Then, in this case,
Next, even if the valve clearance is adjusted while the second rocker arm 6 is operated, the valve clearance does not exceed the previously adjusted value. That is, a state occurs in which the adjustment of the valve clearance for the second rocker arm 6 cannot be substantially performed.

Then, when adjusting the valve clearance, first, the valve clearance is adjusted to the first adjustment state by the ramming device 13 with the second rocker arm 6 operating. This adjustment is performed, for example, in the first embodiment,
The screwing position with respect to the pivot shaft 53 to change the pivot shaft 53
This is done by changing the amount of protrusion. Next, the second rocker arm 6 is set in the hit state, and the valve clearance is set to the second position.
Adjust to the adjustment value of. This adjustment is performed on the first rocker arm 5.
This is performed by changing the amount of protrusion of the drive pin 11. here,
The first adjustment value is set to be larger than the second adjustment value, for example, about 0.25 mm and about 0.15 mm, respectively. In order to make these adjustment values different, the high-speed cam 8 is more
Lamp height needs to be increased.

By adjusting in this manner, it is possible to always obtain an appropriate valve clearance when driven by either the low-speed cam 7 or the high-speed cam 8.

In the above-described embodiment, the case of one valve and two valves has been described, but the number of valves to which the present invention can be applied is not limited to this.

Further, in the above-described embodiment, the stopper 16 is moved and retracted at an appropriate timing by an actuator as the punching device 13, but the punching device according to the present invention is not limited to this, and may correspond to, for example, a cylinder. Alternatively, the plunger may be fixed by enclosing the pressurized oil in an object and released by the pressurized oil.

<Effects of the Invention> As described above in detail with the embodiments, according to the present invention, both the low-speed cam and the high-speed cam are provided, and they are selectively used depending on the driving situation. Good engine performance can be obtained over the entire region.

In addition, since the high-speed second rocker arm presses the low-speed first rocker arm to obtain an integral movement of both, even if an error occurs in both rocker arms due to, for example, abrasion, the valve clearance of both rocker arms is obtained. Can be easily eliminated by individually adjusting.

Further, since the punching device is provided on the pivot shaft of the second rocker arm, the weight of the rocker arm can be reduced.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part of the first embodiment of the present invention (I in FIG. 2).
FIG. 2 is a plan view of the same, FIG. 3 is an explanatory view of a low-speed cam and a high-speed cam, FIG. 4 is a cross-sectional view of a pivot support portion, and FIG. V sectional view, FIG. 6 is a plan view of main parts of a second embodiment of the present invention, FIG. 7 is a cross sectional view of main parts of a third embodiment of the present invention, and FIG. FIG. 9 is a graph conceptually showing a change in camshaft driving torque with respect to the engine speed. In the drawings, 1 ... valve, 4 ... cam shaft, 5 ... first rocker arm, 6 ... second rocker arm, 7 ... low speed cam, 8 ... high speed cam, 13 ... , 53 ... The pivot axis.

Claims (2)

(57) [Claims] 1. A low-speed cam for providing a valve motion suitable for low-speed operation, a high-speed cam for providing a valve motion suitable for high-speed operation, and a first rocker arm driven by the low-speed cam and directly pressing a valve. A second rocker arm driven by the high-speed cam and pressing the valve via the first rocker arm; and a hitting device for preventing the second rocker arm from pressing against the first rocker arm during low-speed operation. The lashing device is provided on a pivot shaft of the second rocker arm, and is capable of switching the pivot shaft between a retractable state and a protruding fixed state. Variable valve drive. 2. A contact portion between the low-speed cam and the first rocker arm is a roller type, and a contact portion between the high-speed cam and the second rocker arm is a slipper type. The variable valve driving device for an engine according to item (1).