JPH0435604B2 - - Google Patents

Description

[Detailed Description of the Invention] A. Purpose of the Invention (1) Industrial Application Field The present invention provides a camshaft in which a plurality of types of cams each having a different valve lift amount are provided on a camshaft.
An intake valve or an exhaust valve is interlocked and connected to at least one of the plurality of cam followers that respond to each of the cams, a valve spring is interposed between the intake valve or the exhaust valve and the engine body, and the cam followers are interconnected. A connection switching mechanism capable of switching between a connection state in which the connection is made and a connection release state in which the connection is released causes the plurality of cams to selectively act on the intake valve or the exhaust valve according to the connection state and the connection release state to release the intake air. The present invention relates to a valve operating device for an internal combustion engine that is provided between the plurality of cam followers to switch the valve lift amount of a valve or an exhaust valve.

(2) Conventional technology Conventionally, in such a valve train, for example,
As disclosed in Japanese Patent Publication No. 19911, it is common to use a spring having a linear load characteristic in which the spring load changes proportionally to the amount of displacement as the valve spring.

(3) Problems to be Solved by the Invention By the way, there is a valve train in which the opening timing and valve lift amount of the intake valve or exhaust valve are changed according to the operating state of the engine by switching the connection state of the cam follower. In this case, the spring load of the valve spring is set so that jumps, bounces, etc. of the intake valve or the exhaust valve do not occur during high-speed operation of the engine. However, during low-speed operation, the lift amount of the intake or exhaust valve is low, so the load on the valve spring is low, but since the load characteristics are linear, the amount of load reduction is small, and the spring load during low-speed operation may be more than necessary. It's getting bigger. Accordingly, the friction loss of the valve train is also relatively large.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a valve operating system for an internal combustion engine that reduces the spring load during low-speed operation of the engine to reduce friction loss.

B. Structure of the Invention (1) Means for Solving the Problems According to the present invention, the valve spring has a nonlinear load characteristic in which the rate of change in spring load increases as the valve lift amount in the valve opening direction increases. have

(2) Effect According to the above configuration, the spring load can be reduced during low-speed operation when the valve lift amount is reduced by the connection switching mechanism, and the spring load can be reduced during high-speed operation when the valve lift amount is increased by the connection switching mechanism. can be made larger.

(3) Embodiments Below, embodiments of the present invention will be described with reference to the drawings. First, in FIGS. 1 and 2 showing an embodiment of the present invention, a pair of intake valves 1a and 1b provided in the engine body E are shown. is 1/1 in synchronization with engine rotation.
A low-speed cam 3, 3 and a high-speed cam 5 are integrally provided on a camshaft 2 driven at a rotation ratio of 2.
Through the functions of the first, second and third rocker arms 7, 8, 9 as cam followers, which are pivotally supported by the rocker shaft 6 parallel to the camshaft 2, and the connection switching mechanism 31 provided between the rocker arms 7 to 9. Driven to open and close.

The camshaft 2 is rotatably disposed above the engine body E, and the low-speed cams 3, 3 are integrated into the camshaft 2 at positions corresponding to both the intake valves 1a, 1b. The high-speed cam 5 connects both intake valves 1a, 1
It is integrated into the camshaft 2 at a position corresponding to the position between b. Furthermore, the low-speed cam 3 has a shape suitable for low-speed operation of the engine, and has a high portion 3a that projects outward in a relatively small amount along the radial direction of the camshaft 2, and a base circle 3b. Further, the high-speed cam 5 has a shape suitable for high-speed operation of the engine, and has a shape that projects outward in the radial direction of the camshaft 2 to be larger than the high portion 3a, and is wider than the high portion 3a. It has a high portion 5a spanning a central angle range and a base circular portion 5b.

The rocker shaft 6 is fixedly arranged below the camshaft 2. A first locking arm 7, a second locking arm 8, and a third locking arm 9 are pivotally supported on the locking shaft 6 adjacent to each other.
are basically formed in the same shape. That is, the first and second rocker arms 7, 8 are connected to the intake valve 1.
Its base is swingably supported by the rock shaft 6 at positions corresponding to the intake valves 1a and 1b, respectively.
It extends to a position above 1b. Further, a cam slipper 10 that slides on the low-speed cam 3 is provided on the top of the first rocker arm 7, and a cam slipper 10 that slides on the low-speed cam 3 is provided on the top of the second rocker arm 8.
1 is provided. Further, in the first and second rocker arms 7, 8, tappet screws 12, 13 which can come into contact with the upper ends of the respective intake valves 1a, 1b are screwed so as to be able to move forward and backward at the ends located above the respective intake valves 1a, 1b. It will be worn.

On the other hand, a flange 1 is provided at the upper part of both intake valves 1a and 1b.
4, 15 are provided, and these collar parts 14,
Valve springs 16, 17 are interposed between 15 and the engine body E, and each intake valve 1a, 1b is biased in the valve opening direction, that is, upward.

The valve springs 16 and 17 are unequal pitch coil springs, and the pitch p is set to increase toward the center in the axial direction. The load characteristics of such an unequal pitch coil spring are shown by the solid line in Figure 3, and as the valve lift amount in the valve opening direction, that is, the amount of compression increases, the spring load increases, but the rate of change is becomes larger as the amount of compression increases. In other words, while an equal pitch coil spring has a linear load characteristic as shown by the chain line,
The valve springs 16, 17, which are unequal pitch coil springs, have nonlinear loading characteristics.

Referring also to FIG. 4, the third rocker arm 9
is pivotally supported on the rocker shaft 6 between the first and second rocker arms 7 and 8. This third rocker arm 9 connects both intake valves 1a, 1 from the rocker shaft 6.
A cam slipper 18 is provided on the upper part of the cam slipper 18, which extends slightly toward the b side and slides into contact with the high-speed cam 5.

A bottomed cylindrical lifter 19 is brought into contact with the lower end of the third rocker arm 9 on the front end side, and a lifter spring 20 is interposed between the lifter 19 and the engine body E. As a result, the lifter 19 resiliently pushes up the third rocker arm 9, and the third rocker arm 9 resiliently slides into contact with the high-speed cam 5.

In FIG. 5, the first rocker arm 7, the third rocker arm 9, and the third rocker arm 9 are shown.
The second rocker arms 8 are in sliding contact with each other, and a connection switching mechanism 3 is provided between each rocker arm 7 to 9.
1 is provided.

The connection switching mechanism 31 includes a first connection pin 32 that can connect the first rocker arm 7 and the third rocker arm 9, and a first connection pin 32 that can connect the third rocker arm 9 and the second rocker arm 8.
The second connecting pin 33 that comes into contact with the second connecting pin 33 and both connecting pins 3
2 and 33, and a return spring 35 that urges each connecting pin 32, 33 and stopper 34 toward the disconnection side.

The first locking arm 7 has a third locking arm 9.
A first guide hole 36 that is open toward the side and parallel to the rocker shaft 6 is bored, and the first connecting pin 32 is slidably fitted into this first guide hole 36, and the closed end of the first guide hole 36 and the first 1 connection pin 3
A hydraulic chamber 37 is defined between the two. Also the first
An oil passage 38 communicating with the hydraulic chamber 37 is bored in the rocker arm 7, and an oil passage 39 communicating with a hydraulic pressure supply source (not shown) is bored in the rocker shaft 6.
Both oil passages 37 and 38 are always in communication through a communication hole 40 formed in the side wall of the rocker shaft 6, regardless of the swinging state of the first rocker arm 7.

In the third rocker arm 9, a guide hole 41 corresponding to the first guide hole 36 is bored between both sides, and a second connecting pin 33 having a length spanning the entire length of the guide hole 41 is provided in the third rocker arm 9. It is rubbed together. Moreover, the outer diameter of the second connecting pin 33 is set to be the same as the outer diameter of the first connecting pin 32.

The second rocker arm 8 is provided with a second guide hole 42 parallel to the rocker shaft 6 and open to the third rocker arm 9 side, corresponding to the guide hole 41 . A stopper 34 is slidably fitted into the second guide hole 42, and the stopper 34 is connected to the second connecting pin 3.
Contact with 3. A shaft portion 43 is coaxially connected to the stopper 34 , and the shaft portion 43 is inserted into a guide hole 44 provided in the second rocker arm 8 at the closed end of the second guide hole 42 .

A return spring 35 is interposed between the stopper 34 and the closed end of the second guide hole 42 to surround the shaft portion 43, and the stopper 34, the second connecting pin 33, and the first connecting pin 32 are The spring 35 urges it toward the disconnection position.

Next, the operation of this embodiment will be explained. When the engine is operated at low speed, hydraulic pressure is not supplied to the hydraulic chamber 37. Therefore, in the connection switching mechanism 31, the first
and second connecting pins 32, 33 and stopper 3
4 is moved to the maximum extent toward the hydraulic chamber 37 by the return spring 35. In this state, the contact surfaces of the first and second connecting pins 32 and 33 are connected to the first rocker arm 7.
and a position corresponding to the sliding surface of the third rocker arm 9, and the second connecting pin 33 and the stopper 34.
The abutting surfaces of are located at positions corresponding to the sliding surfaces of the third rocker arm 9 and the second rocker arm 8. Therefore, the first rocker arm 7, the third rocker arm 9, and the second rocker arm 8 are in sliding contact with each other, and the first and second connecting pins 32, 33, the second connecting pin 33, and the stopper 34 are in sliding contact with each other. , relative angular displacement is possible.

When the connection switching mechanism 31 is in the disconnection position, the first and second rocker arms 7 and 8 swing in sliding contact with the low-speed cams 3 and 3 due to the rotational movement of the camshaft 2. , both intake valves 1
a and 1b are opened and closed at timing and lift amount according to the shape of the low-speed cams 3, 3. At this time, the third rocker arm 9 swings due to sliding contact with the high-speed cam 5, but the swinging action is
It has no effect on b.

During high-speed operation of the engine, hydraulic pressure is supplied to the hydraulic chamber 37. As a result, the first connecting pin 32 presses and moves the second connecting pin 33 and the stopper 34 against the spring force of the return spring 35. During this movement, the first and second rocker arms 7 and 8 come into sliding contact with the base circle 3b of the low-speed cam 3, the third rocker arm 9 comes into sliding contact with the base circle 5b of the high-speed cam 5, and the first guide hole 36 This is done when the axes of the guide hole 41 and the second guide hole 42 coincide, and the first connecting pin 32 fits into the guide hole 41 and the second connecting pin 33 fits into the second guide hole 42. match.

In this state, the first rocker arm 7, the third rocker arm 9, and the second rocker arm 8 are integrally connected. At this time, the amount of rocking of the third rocker arm 9 that is in sliding contact with the high-speed cam 5 is the largest, so the first and second rocker arms 7 and 8 rock together with the third rocker arm 9, and both intake valves 1a and 1b are It opens and closes with timing and lift amount depending on the shape of the cam 5.

In this way, the connection state of each rocker arm 7 to 9 is switched between low and high speeds of the engine, and accordingly, the intake valves 1a and 1b are opened and closed with a large lift amount at high speeds, and lifted at low speeds. It is opened and closed in small quantities. At this time, as shown in FIG. 3, the set compression amount of the valve springs 16 and 17 when the first and second rocker arms 7 and 8 are in sliding contact with the base circle 3b of the low-speed cam 3 is δo, and the set load is of
When Po, the spring load becomes P ₁ as the compression amount becomes δ ₁ at low speeds, and P ₂ as the compression amount becomes δ ₂ at high speeds. In contrast, with conventional valve springs that have linear load characteristics, the spring load at high speeds is the same value.
When P ₂ is assumed, at low speed it becomes P ₁ ', and the spring load becomes larger by ΔP than when using an unequal pitch coil spring according to the present invention.

That is, the spring loads of the valve springs 16, 17 can be made relatively small during low speed operation, and the friction loss between the low speed cams 3, 3 and the first and second rocker arms 7, 8 can be reduced. Furthermore, the width of the cam slipper 11 can also be reduced in accordance with the reduction in surface pressure.

FIG. 6 shows another embodiment of the present invention, and parts corresponding to those in the previous embodiment are given the same reference numerals.

The valve springs 16a, 17a interposed between the intake valves 1a, 1b and the engine body E have a wire diameter d.
A tapered coil spring is used in which the spring is varied along the longitudinal direction of the strands, and this embodiment can also achieve the same effects as the above-mentioned embodiment.

Further, as another embodiment of the present invention, conical coil springs as shown in FIG. 7 may be used as the valve springs 16b, 17b.

In yet another embodiment of the present invention, a valve spring formed by connecting a plurality of coil springs having different spring constants in series may be used.

Although the above embodiments have been described in relation to the intake valves 1a and 1b, the present invention can also be implemented in relation to exhaust valves. Also, the number of cam followers,
The number of intake valves or exhaust valves is not limited to those in each of the above embodiments.

C. Effects of the Invention As described above, according to the present invention, the valve spring has a nonlinear load characteristic in which the rate of change in spring load increases as the valve lift amount in the valve opening direction increases. During low-speed operation with a small valve lift, the spring load can be reduced to reduce friction loss in the valve train, and during high-speed operation with a large valve lift due to the connection switching mechanism, the spring load can be increased. Jumps and bounces of the intake valve or exhaust valve can be prevented from occurring.

[Brief explanation of drawings]

1 to 5 show an embodiment of the present invention, in which FIG. 1 is a plan view, FIG. 2 is a sectional view taken in the direction of the arrow in FIG. 1, and FIG. 3 is a load characteristic diagram of a valve spring. Figure 4 is a sectional view taken along the - line in Figure 1, and Figure 5 is a - line sectional view in Figure 2.
The enlarged line sectional views, FIGS. 6 and 7, are sectional views corresponding to FIG. 2 for showing other embodiments of the present invention, respectively. 1a, 1b...Intake valve, 2...Camshaft,
3...Low speed cam, 5...High speed cam, 7, 8,
9...Lotsuka arm as a cam follower, 1
6, 16a, 16b, 17, 17a, 17b...
Valve spring, 31... Connection switching mechanism, E... Engine body.

Claims (1)

[Claims] 1. A plurality of types of cams 3 and 5 with mutually different valve lift amounts are provided on the camshaft 2,
At least one of the plurality of cam followers 7, 8, 9 responsive to each of the cams 3, 5 has an intake valve 1a, 1b.
Alternatively, the exhaust valves are interlocked and connected, and the intake valves 1a,
1b or between the exhaust valve and the engine body E are valve springs 16, 16a, 16b, 17, 17a, 17b.
A connection switching mechanism 31 that can switch between a connection state in which the cam followers 7, 8, and 9 are connected to each other and a connection release state in which the connections are released is configured to switch between the plurality of cam followers 7, 8, and 9 according to the connection state and the connection release state. is provided between the plurality of cam followers 7, 8, and 9 in order to selectively act on the intake valves 1a, 1b or the exhaust valve to switch the valve lift amount of the intake valves 1a, 1b or the exhaust valve. In a valve train for an internal combustion engine, valve springs 16, 16a, 16b, 1
Reference numerals 7, 17a, and 17b refer to a valve train for an internal combustion engine characterized by having nonlinear load characteristics in which the rate of change in spring load increases as the valve lift amount in the valve opening direction increases.