JPH0312206B2 - - Google Patents

Description

[Detailed Description of the Invention] A. Purpose of the Invention (1) Industrial Field of Application The present invention is directed to integrating a pair of intake valves or exhaust valves provided in the engine body with a camshaft that rotates according to the operating state of the engine. The present invention relates to a valve operating system for an internal combustion engine in which the cam is interlocked with a plurality of valve drive members to open and close the valve.

(2) Prior art In such a valve train, the valve diameter and valve lift amount are set at high speed so that the horsepower does not decrease due to inflow resistance when the amount of air-fuel mixture necessary to output the maximum horsepower is sucked in. It is common to set this as a priority.

By the way, if the intake valve is driven with the same valve timing and the same lift amount from low speed range to high speed range, the intake amount will differ depending on each rotation speed, so
The air-fuel mixture inflow speed into the combustion chamber is different. That is, at low speeds, the air-fuel mixture inflow speed decreases, the turbulence of the air-fuel mixture within the combustion chamber becomes small, and the combustion speed also slows down. For this reason, fuel consumption increases due to a decrease in combustion efficiency, and the knocking limit decreases due to a decrease in combustion speed.

Therefore, in order to solve this problem, a part of the intake valve or exhaust valve is closed and paused during low-speed operation, and both intake valves or exhaust valves are opened and closed during high-speed operation. It is disclosed in Publication No. 59-226216.

(3) Problems to be Solved by the Invention In the above-mentioned conventional technology, valve train control is performed separately for low speed and high speed. However, if the valve train is controlled by dividing the operating range more finely, It will be possible to improve engine output and reduce fuel consumption.

Furthermore, in the above-mentioned conventional technology, the intake valve, which is inactive during low-speed operation, may remain inactive for a long period of time depending on the operating conditions. If the intake valve remains inactive for a long period of time, carbon produced by combustion will accumulate between the intake valve and the valve seat, causing the intake valve to stick to the valve seat. For this reason, when shifting to high-speed operation and opening the valve, the intake valve is forcibly peeled off from the valve seat, resulting in a sealing problem between the intake valve and the valve seat. Also,
When the intake valve is closed and at rest, fuel pools and
The mixture concentration may become rich when opening and closing.

The present invention was made in view of the above circumstances, and aims to improve engine output and reduce fuel consumption by performing valve train control in three regions: low speed, medium speed, and high speed, and also prevents valve deactivation. An object of the present invention is to provide a valve train for an internal combustion engine that solves the problems associated with this.

B. Structure of the Invention (1) Means for Solving the Problems According to the present invention, the camshaft is provided with two low-speed cams and a high-speed cam, which slide into contact with one of the low-speed cams, and a first valve driving member connected to one intake valve or exhaust valve; a second valve driving member slidingly contacting the other low speed cam and connected to the other intake valve or exhaust valve; and the high speed cam. and a third valve driving member that is in sliding contact with the third valve driving member are arranged adjacent to each other, and between the mutually adjacent valve driving members, connection switching means capable of switching connection and disconnection between the two valve driving members are arranged so that they can operate independently of each other. Each is provided separately.

(2) Operation When the engine is operating at low speed, the valve driving members are disconnected from each other, and each intake valve or exhaust valve opens and closes at a timing and lift amount depending on the shape of the corresponding low-speed cam. Further, when the engine is operating at medium speed, one of the connection switching means is connected, and both intake valves or exhaust valves are opened and closed at a timing and lift amount corresponding to the medium speed operation. Further, when the engine is operating at high speed, all valve drive members are connected, and both intake valves or exhaust valves are opened and closed at timing and lift amount depending on the shape of the high speed cam.

(3) Embodiment Hereinafter, embodiments of the present invention will be explained 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 are installed in the engine body of an internal combustion engine. are arranged, and these intake valves 1a and 1b are rotated by 1/2 in synchronization with the rotation of the engine.
A first low-speed cam 3 and a second low-speed cam 4 are integrally provided on a camshaft 2 driven at a rotation ratio of
It is driven to open and close by the functions of the high-speed cam 5 and first, second, and third rocker arms 7, 8, and 9 that are pivotally supported by a rocker shaft 6 that is parallel to the camshaft 2.

The camshaft 2 is rotatably disposed above the engine body, and the second low-speed cam 4 is connected to both intake valves 1.
Camshaft 2 at a position corresponding to the middle of a and 1b.
is provided integrally with the Further, the first low-speed cam 3 and the high-speed cam 5 are integrally provided on the camshaft 2 on both sides of the second low-speed cam 4. Moreover, the second
The low-speed cam 4 is formed smaller than the first low-speed cam 3, and the high part 3a of the first low-speed cam 3 is smaller than the first low-speed cam 3.
It has a high portion 4a which has a smaller protrusion amount and a narrower center angle range than the other. The first and second low-speed cams 3 and 4 are each set to an optimal shape depending on the required characteristics during low-speed operation of the engine.
The opening lift amount of the valve is a very small amount of about 1mm, and the valve 1
to the extent that air intake through b is substantially blocked;
It is also possible to make the high portion 4a of the second low speed cam 4 lower.

On the other hand, the high-speed cam 5 has a shape suitable for high-speed operation of the engine, and has a higher protrusion amount than the higher part 3a of the first low-speed cam 3 and has a wider center angle range. It has 5a.

The rocker shaft 6 is fixedly arranged below the camshaft 2. This rocker shaft 6 includes a first rocker arm 7 as a first valve driving member corresponding to the first low speed cam 3, and a second rocker arm 8 as a second valve driving member corresponding to the second low speed cam 4. A third rocker arm 9 as a third valve drive member corresponding to the high-speed cam 5 is pivoted adjacent to each other, and a cam slipper in sliding contact with each cam 3, 4, 5 is provided on the upper part of each rocker arm 7, 8, 9. 7
a, 8a, and 9a are provided. Further, the first and second rocker arms 7 and 8 extend above the intake valves 1a and 1b, and have intake valves 1a and 1b at their tips.
Tappet screws 12 and 13 that can come into contact with the upper end of the holder are screwed so that they can move forward and backward.

On the other hand, the upper part of the intake valves 1a and 1b has a flange 14,
15, and valve springs 16, 17 surrounding the intake valves 1a, 1b are interposed between the flanges 14, 15 and the engine body. These valve springs 16 and 17 bias the intake valves 1a and 1b upward, that is, in the valve closing direction.

In FIG. 3, a bottomed cylindrical lifter 1 is provided on the lower surface of the end of the third rocker arm 9 as a pressing means.
9 is in contact with the lifter 19, and the lifter 19 is urged upward by a lifter spring 20, which has a relatively weak spring force and is interposed between the lifter 19 and the engine main body. As a result, the cam slipper 9a of the third rocker arm 9
It slides elastically into contact with the

In FIG. 4, the first and second rocker arms 7, 8 are in sliding contact with each other, allowing relative angular displacement, and both rocker arms 7, 8
A first connection switching means 21 that can switch between a state in which the first and second rocker arms 7 and 8 are integrally connected
provided in between. The second and third rocker arms 8 and 9 are also in sliding contact with each other, allowing relative angular displacement between the two rocker arms 8 and 9.
A second connection switching means 22 is provided between the second and third rocker arms 8 and 9, which can switch between the state in which the two rocker arms 9 are integrally connected.

The first and second connection switching means 21 and 22 basically have the same configuration, and will be described below.
Only the configuration of the first connection switching means 21 will be described in detail, and a detailed explanation of the second connection switching means 22 will be omitted.

The first connection switching means 21 includes a piston 23 that is movable between a position where the first and second rocker arms 7 and 8 are connected and a position where the connection is released.
A stopper 24 that restricts the movement of the piston 23
and a spring 25 that biases the stopper 24 to move the piston 23 toward the disconnection position.

The second locking arm 8 has a first locking arm 7.
While opening towards the side, the lock shaft 6
A first guide hole 26 parallel to the first guide hole 26 is bored, and a small diameter portion 28 is provided at the closed end side of the first guide hole 26 via a stepped portion 27. First guide hole 26
A piston 23 is slidably engaged with the piston 23 , and a hydraulic chamber 29 is defined between the piston 23 and the closed end of the first guide hole 26 .

An oil passage 30 communicating with the hydraulic chamber 29 is bored in the second rocker arm 8, and an oil passage 31 communicating with a hydraulic pressure supply source (not shown) is bored in the rocker shaft 6. Further, both oil passages 30 and 31 are connected to each other via a communication hole 32 bored in the side wall of the rock shaft 6.
Communication is always maintained regardless of the swinging state of the first rocker arm 8.

The first rocker arm 7 has a second guide hole 35 opened toward the second rocker arm 8 side corresponding to the first guide hole 26.
A disc-shaped stopper 24 is slid into the guide hole 35 . A regulating step 3 is provided on the closed end side of the second guide hole 35.
A small diameter portion 37 is provided through the hole 6, and an insertion hole 38 coaxial with the small diameter portion 37 is bored at the closed end. Moreover, a guide rod 39 coaxially and integrally provided with the stopper 24 is inserted into the insertion hole 38. Furthermore, a coiled spring 25 surrounding the guide rod 39 is interposed between the stopper 24 and the closed end of the second guide hole 35 .

The length of the piston 23 in the axial direction is such that when one end comes into contact with the stepped portion 27, the other end is located between the first and second rocker arms 7 and 8, and the stopper 24 is placed against the regulating step 36. The setting is such that one end remains in the first guide hole 26 when the second guide hole 35 is entered until the contact is made.

The oil passages 31 in the first and second connection switching means 21 and 22 are isolated from each other by a steel ball 33 that is press-fitted and fixed into the rocker shaft 6.
1 and 22 can perform switching operations independently of each other.

Next, the operation of this embodiment will be explained. When the engine is operated at low speed, the first and second connection switching means 21 and 22 are operated to the disconnection side, as shown in FIG. That is, when the hydraulic pressure in the hydraulic chamber 29 is released, the stopper 24 is moved toward the second rocker arm 8 by the spring force of the spring 25, and the piston 23 is retreated until it comes into contact with the stepped portion 27. In this state, the contact surfaces of the piston 23 and the stopper 24 are the sliding surfaces of the first and second rocker arms 7, 8, and the second and third rocker arms 8, 9.
Therefore, the first, second, and third rocker arms 7, 8, and 9 are in sliding contact with each other and are capable of relative angular displacement.

In such a disconnected state, the swinging motion of the third rocker arm 9 does not affect the first and second rocker arms 7 and 8, and the first rocker arm 7 is connected to the first low-speed cam 3. The second rocker arm 8 swings according to the sliding contact, and the second rocker arm 8 is connected to the second low-speed cam 4.
It oscillates in response to sliding contact with. Therefore, one intake valve 1a is driven to open and close by the first rocker arm 7, and the other intake valve 1b is driven to open and close by the second rocker arm 8. At this time, the third Rotsuka arm 9
Since the lifter spring 20 is only in sliding contact with the high-speed cam 5 due to the relatively weak spring force of the lifter spring 20, the friction loss in the valve train can be suppressed to a low level.

In this way, when the engine is operating at low speed, one intake valve 1a opens and closes at a timing and lift amount that corresponds to the shape of the first low-speed cam 3, and the other intake valve 1b operates according to the shape of the second low-speed cam 4. It opens and closes at the timing and lift amount depending on the situation. Therefore, an air-fuel mixture inflow speed suitable for low-speed operation can be obtained, and it is possible to reduce fuel consumption and prevent knocking. Moreover, since the shapes of the low-speed cams 3 and 4 are different, the turbulence of the air-fuel mixture in the combustion chamber is increased, which also makes it possible to reduce fuel consumption. Furthermore, since both intake valves 1a and 1b do not stop, deterioration of sealing performance due to carbon adhesion can be prevented, and fuel accumulation can also be prevented.

When the engine is operating at medium speed, the first connection switching means 21
As a result, as shown in FIG. 5, the first and second rocker arms 7, 8 are connected, and the second and third rocker arms 8, 9 remain disconnected.
That is, by supplying hydraulic pressure to the hydraulic chamber 29 of the first connection switching means 21, the piston 23 fits into the second guide hole 35 while pressing the stopper 24 against the spring force of the spring 25, and presses the stopper 24. 24
is pressed against the regulating step portion 36. In this state, the first
The second rocker arms 7 and 8 are prevented from relative rotation and swing together.

Therefore, both intake valves 1a and 1b are opened and closed at timing and lift amount according to the shape of the first low-speed cam 3. As a result, an air-fuel mixture inflow speed suitable for medium-speed operation can be obtained, and fuel consumption can be reduced.

During high-speed operation of the engine, the second connection switching means 22 connects the second and third rocker arms 8, 9, as shown in FIG. That is, the second
By supplying hydraulic pressure to the hydraulic chamber 29 of the connection switching means 22, the second and third rocker arms 8, 9
Concatenate. At this time, the connection between the first and second rocker arms 7 and 8 by the first connection switching means 21 is maintained, so that all the rocker arms 7,
8 and 9 are oscillated by the high speed cam 5. As a result, both intake valves 1a and 1b open and close at timing and lift amount depending on the shape of the high-speed cam 5, and high output and high torque can be obtained by improving intake efficiency.

FIG. 7 shows another embodiment of the present invention, in which a low speed cam 3 having the same shape as the low speed cam 3 and a high speed cam 5 are arranged on both sides of the low speed cam 3.

In this embodiment, when the engine is operating at low speed, all rocker arms 7, 8, and 9 are disconnected, and both intake valves 1a, 1b are operated at the same timing and lift amount according to the shape of each low-speed cam 3, 3. Opens and closes. Also, during medium speed operation, the first and third rocker arms 7 and 9 are connected, and one intake valve 1a opens and closes with timing and lift amount depending on the shape of the high speed cam 5, while the other intake valve 1a Valve 1
b, it opens and closes at a timing and lift amount depending on the shape of the low-speed cam 3. Furthermore, during high-speed operation, all the rocker arms 7, 8, and 9 are connected, and both intake valves 1a, 1b are opened and closed at timing and lift amount according to the shape of the high-speed cam 5.

Although the above embodiment has been described in relation to a pair of intake valves 1a and 1b, the present invention can also be implemented in relation to a pair of exhaust valves.

C Effects of the Invention As described above, according to the present invention, the camshaft is provided with two low-speed cams and a high-speed cam, which are in sliding contact with one of the low-speed cams and one of the intake valves or exhaust valves. a first valve driving member connected to the cam, a second valve driving member slidingly connected to the other low-speed cam and connected to the other intake valve or exhaust valve, and a third valve driving member slidingly connected to the high-speed cam.
Since the valve driving members are arranged adjacent to each other and the connection and disconnection of the adjacent valve driving members can be independently switched, a mixture inflow speed suitable for low speed, medium speed and high speed operation can be obtained. It is possible to reduce fuel consumption at medium speeds and increase output at high speeds.
Furthermore, since the valve does not stop during operation of the engine, deterioration of sealing performance due to carbon adhesion can be prevented, and furthermore, fuel accumulation can be prevented from occurring.

[Brief explanation of the drawing]

1 to 6 show an embodiment of the present invention, in which FIG. 1 is a longitudinal side view and a sectional view taken along the line - in FIG. 2, FIG. 2 is a plan view of FIG. 1, Figure 3 is a cross-sectional view taken along the line - - in Figure 2, Figure 4 is a cross-sectional view taken along the line - Figure 1 when each rocker arm is disconnected, and Figure 5 is a cross-sectional view taken when the first and second rocker arms are connected. 4 is a cross-sectional view corresponding to FIG. 4, FIG. 6 is a cross-sectional view corresponding to FIG. 4 when the first, second, and third rocker arms are connected, and FIG. 7 is a second view of another embodiment of the present invention. FIG. 1a, 1b...Intake valve, 2...Camshaft,
3, 4...Low speed cam, 5...High speed cam, 7...
...first rocker arm as a first valve driving member, 8
... a second rocker arm as a second valve driving member,
9... Third rocker arm as third valve driving member, 19... Lifter as pressing means, 21, 2
2...Connection switching means.

Claims (1)

[Scope of Claims] 1 A pair of intake valves or exhaust valves provided in the engine body are interlocked with a cam integrated with a camshaft that rotates depending on the operating state of the engine via a plurality of valve drive members. In a valve train for an internal combustion engine that operates to open and close a valve, the camshaft is provided with two low-speed cams and a high-speed cam, and is in sliding contact with one of the low-speed cams and one of the intake valves. Alternatively, a first valve driving member connected to the exhaust valve, a second valve driving member slidingly contacting the other low-speed cam and connected to the other intake valve or exhaust valve, and a second valve driving member slidingly contacting the high-speed cam. Three valve drive members are arranged adjacent to each other, and connection switching means capable of switching connection and disconnection between the two valve drive members are respectively provided so as to be able to operate independently of each other. A valve train for an internal combustion engine characterized by: 2. The valve train for an internal combustion engine according to claim 1, wherein the one low-speed cam has a smaller shape than the other low-speed cam. 3. The valve train for an internal combustion engine according to claim 1 or 2, wherein a pressing means for elastically biasing the high-speed cam is brought into contact with the third valve driving member. Device.