JPH0568602B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a valve operating system for an engine that can change the lift amount and opening period of intake and exhaust valves according to operating conditions.

(Prior art) When setting the operating characteristics of the engine's intake and exhaust valves, at low speeds, combustion stability and fuel efficiency are improved by suppressing exhaust blow-back and intake air blow-through during the valve overlap period, etc. Therefore, it is desirable to make the valve lift amount and the valve opening period relatively small, and at high speeds, it is desirable to increase the valve lift amount and the valve opening period in order to improve the output.

In order to satisfy these requirements, a valve train is equipped with multiple cams of different shapes, a valve is selectively linked to one of these cams, and the linkage is switched depending on the operating state. This type of valve train is known in the past, and is disclosed in, for example, Japanese Utility Model Application Publication No. 182205/1983. This device has two cams, a low-speed type and a high-speed type, and one Rocker arm for one valve, and the cam side part of the Rocker arm is used as a selector mechanism to switch the linkage between each cam and the valve. It is formed into a bifurcated shape with one end serving as a contact portion for the low-speed cam, and the other end is equipped with a slidable high-speed cam contact member and a stopper to prevent the sliding. This stopper is operated by an actuator such as a hydraulic cylinder via an interlocking mechanism. By controlling the actuator according to the operating condition, the high-speed cam abutting member moves loose at low speeds and the operation of the high-speed cam is not transmitted to the valve, and the valve is operated by the low-speed cam, and at high speeds Sliding of the cam abutting member is prevented so that the operation of the high-speed cam is transmitted to the valve.

However, this device requires a large number of members for constructing the above-mentioned high-speed cam contact member, stopper, actuator, interlocking mechanism, etc., making the structure complicated. In addition, these members are installed on the Rockscar arm, increasing the overall weight of the Rockscar arm.Moreover, since the high-speed cam contact member and stopper are installed at the end of the Rockscar arm, which is far from the Rockscar shaft, the moment of inertia of the Rockscar arm becomes large. As a result, so-called valve jumping tends to occur during high-speed rotation, and this causes the problem of lowering the engine speed limit.

(Object of the Invention) In view of these circumstances, the present invention simplifies the structure for changing the valve lift characteristics by switching the linkage between the cam and the valve, and also reduces the inertia of the Rocker arm compared to conventional devices of this type. An object of the present invention is to provide an engine valve train that can reduce the moment and increase the engine speed limit.

(Structure of the Invention) The present invention provides a plurality of cams with different shapes, selectively links the valve to one of the cams, and switches the linkage depending on the operating state, thereby controlling the lift amount or opening of the valve. In an engine valve operating system that changes at least one of the periods, the rocker arm that contacts the plurality of cams and the valves is divided into an arm that contacts some of the cams and an arm that has a portion that contacts the valves. divide,
Both arms are supported so as to be movable relative to each other around the rocker shaft, and a plunger is arranged on the outer periphery of the rocker shaft to be able to slide freely relative to the rocker shaft and to be operated according to the operating condition. A locking piece is provided that moves between a locking position where both arms are locked and connected to each other and a locking release position where both arms are unlocked as the arm slides.

In other words, when both arms are locked and connected, both arms swing together as a part of the cam rotates, so that the operation of this part of the cam is transmitted to the valve. When both arms are unlocked, both arms swing independently of each other, so that the operation of some of the cams is not transmitted to the valve, and the valve is operated by the other cam. In particular, the plunger for engaging and disengaging both arms as described above is arranged on the outer periphery of the rocker shaft, thereby reducing the distance between the rocker shaft and the plunger.

(Embodiment) FIGS. 1 to 5 show an embodiment in which the device of the present invention is applied to the intake valves of an engine having two intake valves per cylinder. In these figures, 1 is the cylinder, 2a, 2
b is an intake valve installed in the cylinder 1, and illustration of the exhaust valve and its drive system is omitted. A plurality of cams with different shapes are provided for the intake valves 2a and 2b, and in this embodiment, three cams are provided, consisting of high-speed cams 3a and 3b of the same shape on both sides and a low-speed cam 4 in the center. is arranged on the camshaft 5. The above high-speed cams 3a, 3b
The cam noses of the high-speed cams 3a and 3b are formed to be larger than the cam nose of the low-speed cam 4. The high-speed cams 3a, 3b and the low-speed cam 4 may be cams that differ in at least one of the valve lift amount and the valve opening period, and therefore have different cam nose heights and formation ranges ( (including similar shapes), or may be different from either one of these.

These cams 3a, 3b, 4 and the intake valve 2
a, 2b, and the Rotzker arm 6
The first arm 7 has a pair of left and right arm portions 7a, 7b that contact the high-speed cams 3a, 3b and are connected to each other via an upper connecting portion 7c, and a first arm 7 that abuts both the intake valves 2a, 2b. A second unit integrally equipped with contact portions 8a, 8b and a contact portion 8c to the low-speed cam 4.
The second arm 8 is arranged between both arm parts 7a and 7b of the first arm 7. Both arms 7 and 8 are supported around a rocker shaft 9 so as to be movable relative to each other.

Both arms 7 and 8 are adapted to be engaged and disengaged from each other depending on the operating state by a plunger 11 disposed on the outer periphery of the rocker shaft 9. Specifically, this engagement and disengagement mechanism is constructed as follows. has been done. That is, the plunger 11 is slidably fitted to the outer periphery of the rocker shaft 9, and a locking piece 12 having an arc-shaped cross section along the rocker shaft 9 is coupled to the plunger 11. On the other hand, the arm portion 7 on one side of the first arm 7
An arc-shaped engagement recess 13 corresponding to the locking piece 12 is formed on the inner circumferential surface of the portion of the second arm 8 supported on the rocker shaft 9 in b, and the inner circumferential surface of the portion of the second arm 8 supported on the rocker shaft 9 is formed. An engagement recess 14 corresponding to the locking piece 12 is also provided on the circumferential surface.
is partially formed. The locking piece 12 of the plunger 11 is always engaged with the engagement recess 13 of the first arm 7 and rotates together with the first arm 7, and the plunger 11 moves in the axial direction of the rocker shaft 9. Plunger 1 according to
1 moves to the left in FIG. 4, the locking piece 12 also engages with the engaging recess 14 of the second arm 8, and becomes the locking position where both arms 7 and 8 are locked and connected to each other. (state shown), when the plunger 11 moves to the right in FIG. It is arranged to be displaced to the stop release position.

The position of the locking piece 12 and the engaging recesses 13, 14 relative to the rocker shaft 9 is determined by the position of the cam 3a,
3b, 4 and the intake valves 2a, 2b. In other words, as shown in the figure, the cams 3a, 3b, 4 and the intake valves 2a, 2b
are arranged below both ends of the rocker arm 6, it is better to position the locking piece 12 above the rocker shaft 9. In other words, by doing this, the surface pressure applied to the locking piece 12 is reduced, and wear of the locking piece 12 can be prevented.

The outer end of the plunger 11 is fitted into a hydraulic actuator 15 annularly provided around the rocker shaft 9, and the plunger 11
A return spring 16 is disposed between the middle part of and the side surface of the first arm 7, and a control valve 18 is provided in an oil passage 17 between the actuator 15 and an oil pump (not shown). This control valve 18 is controlled by a control circuit 20 that receives an engine rotational speed signal 19 and the like. Then, depending on the operating condition, for example, at high speeds above a predetermined rotation speed, oil is supplied to the actuator 15 to operate the plunger 11 toward the locking position, and at low speeds below a predetermined rotation speed, oil is relieved from the actuator 15. As a result, the plunger 11 is operated by the return spring 16 toward the unlocked position. The operation of the plunger 11 may be controlled depending on the engine speed and load depending on the operating state.

Note that 21 is an adjuster for adjusting valve clearance provided at the end of the second arm 8 corresponding to the intake valves 2a and 2b. Further, 22 is a cylinder head.

According to this valve train, when the engine is running at high speed, the plunger 11 is operated to the locking position, and both arms 7 and 8 are locked to each other by the locking piece 12.
This prevents the relative movement of both arms 7 and 8. Therefore, when the first arm 7 is pushed by the cam noses of the high-speed type cams 3a and 3b and swings, the second arm 8 moves to the low-speed type. The first one is spaced apart from cam 4.
High-speed cams 3a and 3b swing together with the arm 7.
The intake valves 2a and 2b are operated in accordance with the rotation of the intake valves 2a and 2b. On the other hand, at low speeds, the plunger 11 is operated to the unlocking position and the locking piece 12 is disengaged from the second arm 8, allowing relative movement of both arms 7 and 8. ,3b
The swinging of the first arm 7 due to the rotation of the second arm 8
The second
The swinging of the arm 8 operates the intake valves 2a and 2b. In this way, the valve lift characteristics can be changed to suit the operating conditions.

In particular, the Rotzker arm 6 is the first arm 7.
and a second arm 8, and by engaging and disengaging both arms 7 and 8, the cam 3a,
3b, 4 and the intake valves 2a, 2b is disposed on the outer periphery of the rocker shaft 9, and the distance from the rocker shaft 9 to the plunger 11 is small. The moment of inertia is reduced compared to the case where the cam-side end of the rocker arm is equipped with a linkage switching member like the conventional device shown. Furthermore, the actuator 15 for operating the plunger 11 is provided outside the rocker arm 6, and the overall weight of the rocker arm 6 can be reduced compared to the conventional device, so that the moment of inertia can also be reduced. Therefore, even during high-speed rotation, so-called valve jumping (a phenomenon in which the rocker arm and valve float off the cam due to inertia during operation) can be prevented. Furthermore, since the plunger 11 can be directly connected to the actuator 15, there is no need to provide an interlocking mechanism such as a rod or lever between the plunger 11 and the actuator 15.

In the above embodiment, the high-speed cams 3a, 3a and 3b on both sides of the intake valves 2a, 2b per cylinder are
3b and the central low-speed cam 4 are arranged, but one high-speed cam and one low-speed cam may be arranged. In this case, the first arm 7 of the rocker arm 6 is The design may be changed to a shape that contacts one high-speed cam. In addition, in the above embodiment, 1
Although the invention is applied to an engine having two intake valves 2a and 2b per cylinder, it is of course possible to apply the invention to one intake valve by changing the shape of the second arm 8. Furthermore, the device of the present invention may be applied to an exhaust valve, or to both an intake valve and an exhaust valve.

(Effects of the Invention) As described above, the present invention divides a rocker arm that contacts a plurality of cams and valves of different shapes into an arm that contacts some of the cams and an arm that has a portion that contacts the valve. By engaging and disengaging these two arms, the linkage between the cam and the valve is switched, and a plunger equipped with a locking piece that engages and disengages both arms is arranged on the outer periphery of the rocker shaft. Therefore, the valve lift characteristics can be changed with a simple structure, and the moment of inertia of the Rocker arm can be reduced, preventing valve jumping at high speeds and increasing the engine speed limit. .

[Brief explanation of the drawing]

FIG. 1 is a plan view showing an embodiment of the device of the present invention;
Figure 2 is a sectional view taken along the - line in Figure 1, and Figure 3 is a cross-sectional view of Figure 1.
4 is a vertical sectional front view at the rocker shaft position, and FIG. 5 is an exploded perspective view of the main parts. 2a, 2b... Intake valve, 3a, 3b, 4... Multiple cams with different shapes, 6... Rocker arm,
7, 8...Each divided arm, 9...Rocker shaft, 11...Plunger, 12...Locking piece.

Claims (1)

[Claims] 1. By providing a plurality of cams with different shapes, selectively linking the valve to one of the cams, and switching the linkage depending on the operating condition, at least one of the valve lift amount or the valve opening period can be changed. In the valve train of the engine,
The rocker arm that contacts the plurality of cams and valves is divided into an arm that contacts some of the cams and an arm that has a portion that contacts the valve, and both arms are supported for relative movement around the rocker shaft. , a plunger is disposed on the outer periphery of the rocker shaft, and is slidable with respect to the rocker shaft and is operated according to the operating state,
This plunger is provided with a locking piece that moves between a locking position where the two arms are mutually locked and connected and a locking release position where both arms are unlocked as the plunger slides. Characteristic engine valve gear.