JPS60184911A - Valve lift changer - Google Patents

Abstract

PURPOSE:To stabilize the run of an engine and improve its fuel efficiency at the low revolution speed and enhance the output power of the engine at the high revolution speed, by making a pivot movable depending on the running condition of the engine so that the position of a rocker arm supported by the pivot is displaced away from a cam at the low revolution speed and toward the cam at the high revolution speed. CONSTITUTION:In the slow run of an engine, a support 8 is rotated clockwise in the recess 7 of a cylinder head 6, through the action of a lever 10 and a shaft 9, by that of an actuator 11 which is performed according to a revolution sensor 12. As a result, a rocker arm 2 is displaced away from a valve 3 relative to a cam 5 so that the position of the rocker arm supported by a pivot 4 secured on the support 8 is located more distantly from the cam 5. For that reason, the motion of the valve 3 is reduced together with the swing of the rocker arm 2 caused by the rotation of the cam 5, to shorten the period of opening and closing of the valve to prevent the blow-by and blowoff of the intake and exhaust of the engine in its slow run. The stability of the run of the engine and its fuel efficiency are thus improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a variable valve lift g, position that varies the lift amount of a valve in a valve train of an internal combustion engine, and in particular, a method for changing the lever ratio of a rocker arm depending on operating conditions to change the valve lift amount. Concerning what you do.

In general, valve timing in the valve train of an internal combustion engine is determined by adjusting the opening angle of the intake valve and the exhaust valve in order to reduce and stabilize losses such as intake air blow-through and exhaust blow-through when low-speed performance is important. . On the other hand, when high-speed performance is important, in order to improve intake inertia and exhaust efficiency and increase volumetric efficiency, the opening angle of the intake valve and the closing angle of the exhaust valve are set farther from top dead center and overlap with the valve operating angle. It is desirable to increase .

Incidentally, conventionally, the cam lift, phase, valve clearance, etc., which determine such valve timing, are generally fixedly set to one of the above-mentioned low speed or high speed. Therefore, there has been a problem in that it is not possible to obtain optimal valve timing in both low-speed and high-speed operating regions.

In view of these circumstances, the present invention makes the valve lift variable depending on the operating conditions, and optimally controls the overlap area at low and high speeds, that is, the lift amount when the intake valve and exhaust valve overlap, thereby improving the output and An object of the present invention is to provide a variable valve lift device that improves fuel efficiency, etc.

For this purpose, the device according to the present invention, in the 01-IC rocker arm type valve train, changes the valve lift amount and the overlap area by shifting the position of the fulcrum at one end of the self-adjusting arm and changing the lever ratio. By rotating the pivot that supports the side of the rocker arm opposite to the valve depending on the operating conditions, the pivot supports one end of the rocker arm, and at low speeds, the rocker arm lever ratio is reduced to improve the valve lift amount and overlap. The area is reduced, and at high speeds, the rocker arm lever ratio is increased to increase the overlap area.

Incidentally, as a prior art related to the present invention, for example,
-173120, in which the intermediate support position of the rocker arm is changed to make the valve lift variable. However, in this prior art, the valve lift is adjusted for each engine when a cam is shared among various engines, and this is completely different from the method of the present invention in which the valve lift is made variable depending on the operating conditions.

Hereinafter, one embodiment of the present invention will be specifically described with reference to the drawings. In FIGS. 1 and 2, reference numeral 1 denotes an OHC type valve mechanism, in which intake and exhaust valves 3 are brought into contact with one end of a rocker arm 2, and the other end is freely supported by a pivot 4. The rotation of a cam 5 provided at the middle of the rocker arm 2 causes the rocker arm 2 to swing up and down about the pivots I to 4 as fulcrums, thereby moving the valve 3 and opening and closing the valve. On the other hand, a semicircular indentation 7 is formed on the side of the cylinder head 6 at the location of the pivot 4, and the pivot 4 is fixed to a support 8 that fits into this indentation 7 to rotate in the same semicircular shape. The pivot 4 is rotated around an axis 9, which is the center of rotation of the support 8, and is supported at each rotational position. As an operating system for rotating the pivot 4 and the support 8, a hydraulic actuator 11 is attached to a lever 10 from the shaft 9. For example, a control device 13 is controlled by a signal of the engine rotation speed from a rotation sensor 12. The actuator 11 is operated through the recess 7, and supports 8 are provided at both left and right ends of the recess 7.
Stoppers 14 and 15 are provided to restrict the rotation of.

With this configuration, when the engine is running at low speed, the rotation sensor 12 causes the actuator 11 to operate, and the pivot 4 and the support 8 are rotated clockwise as shown by the solid line in FIG. As a result, the rocker arm 2 moves to the side of the cam 5 opposite to the valve 3, and the supporting position of the arm 2 by the pivot 4 moves away from the cam 5.

Therefore, the rocker arm 2 swings due to the rotation of the cam 5, and the movement of the valve 3 becomes smaller, thereby shortening the valve opening/closing time.

That is, in this case, if the distance from the pivot 4 of the rocker arm 2 to the cam 5 is al, the distance to the valve 3 is al, and the lift m of the cam 5 is 11, then the lift ItAz of the valve 3 is jlt = (al /a1) A1 and f=,ru. Here, the lever ratio of rocker arm 2 (a.

/a1) is small, the lift 1 kAz of the valve 3 is also small as mentioned above, and the overlap area (area surrounded by a, b, c) is small as shown by the solid line in FIG.

Next, in the case of high speed, the rotation sensor 12 operates the actuator 11 to rotate the pivot 4 together with the support 8 in the counterclockwise direction as indicated by the two-dot chain line in FIG. Then, rocker arm 2 moves to the cam 5 side and pivots 4.
The supporting position of the rocker arm 2 approaches the cam 5, and the amount of lift of the valve 3 due to the rotation of the cam 5 increases.

That is, if the distance from the fulcrum of the pivot 4 to the cam 5 and valve 3 in this case is al' + al', the lever ratio of the rocker arm 2 is (a2' / a1')
Therefore, the valve lift fizz' is 12'='
(al'/ai')jlt. Here, since the lever ratio (82'/al') of the rocker arm 2 is larger than (a2/al) in the case of low speed mentioned above, the valve lift amount 12' is also larger than 12 ((ax'/at')-(az/at))A
t increases, the valve lifts of the intake and exhaust valves become as shown by the broken lines in FIG. 3, and the pallet overlap area S also increases.

As is clear from the above description, according to the present invention, OHC
In the case where a type-moveable horizontal movement mechanism 1 supports one end of a rocker arm 2 with a pivot 4, and a cam 5 is located in the middle and a valve 3 is located at the other end, the supporting position of the rocker arm 2 by the pivot 4 is changed at low speed or high speed. By doing so, at low speed A-
The variation area is small, and at high speeds it can be changed to become larger, making it optimal for each operating condition.

Therefore, blow-by or blow-out of intake and exhaust gas during low-speed operation is prevented, improving stability and fuel efficiency, and improving output during high-speed operation. Also, in this method, the rocker arm 2
A large load is applied to the pivot 4 that supports the side opposite to the valve, but since the pivot 4 is attached to a semicircular rotatable support 8, the rocker arm 2 is moved at each rotational position of the pivot 4. One end can be firmly supported, and the pivot 4 can be easily rotated.

Note that the present invention is not limited to the above-mentioned embodiments, and various embodiments are possible, such as one in which the support body 8 is directly operated by the actuator 11.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the apparatus according to the present invention, FIG. 2 is a sectional view taken along the line 1--2 in FIG. 1, and FIG. 3 is a diagram without valve timing. DESCRIPTION OF SYMBOLS 1... Valve train mechanism, 2... Rocker arm, 3... Valve, 4... Pivot, 5... Cam, 6... Cylinder head, 7... Hollow, 8... Support Body, 9...
・Shaft, 1o lever, 11...actuator, 12・
...Rotation sensor, 13...Control device, 14.15...
・Stopper. Patent applicant: Fuji Heavy Industries Co., Ltd. Attorney: Nobuo Kobashi, Jundo Patent attorney: Susumu Murai

Claims (1)

[Claims] In an OHC type valve train in which one end of a rocker arm is supported by a pivot, a cam is provided in the middle of the rocker arm, and a valve is provided at the other end, the pivot is configured to move depending on operating conditions, and the pivot is configured to move the rocker arm according to operating conditions. A variable valve lift device characterized by shifting the support position away from the cam at low speeds and closer to the cam at high speeds.