JPH0278721A - Valve gear of internal combustion engine - Google Patents

Abstract

PURPOSE:To maintain the relative position of both free and drive rocker arms constant for always smoothly changing over a connecting means by causing the abutting portion of the drive rocker arm to slidably contact a protrusion when the free rocker arm slidably contacts a circular base of a cam. CONSTITUTION:Intake valves 1a, 1b as a pair of engine valves provided on an engine body E are opened and closed by low and high speed cams 3, 5 provided on a cam shaft 2, first and second drive rocker arms 7, 8 and a free rocker arm 9 pivotably supported by a rocker shaft 6 parallel to the cam shaft 2. Then, the cam shaft 2 is provided integrally with circular protrusions 4 corresponding to base edges 3b, 5b of the respective cams 3, 5 so that the intake valve 1b is held closed in the low speed running. On the upper portion of the second drive rocker arm 8 is provided an abutting portion 11 for abutting against the protrusion 4.

Description

Detailed Description of the Invention A6 Object of the Invention (1) Industrial Application Field The present invention is directed to a cam that is integrated into a camshaft that is rotationally driven in synchronization with the rotation of an engine, and a cam that is attached with a spring in the valve closing direction. a drive rocker arm that comes into contact with the energized engine valve; a free rocker arm that slides against the cam and is disposed adjacent to the drive rocker arm while being able to be free with respect to the engine valve; and a position that connects both rocker arms. and a connecting means having a connecting piston that is movable between positions where the connection is released.

(2) Prior Art Conventionally, such a valve train has been developed, for example, in Japanese Patent Application Laid-Open No. 59-372.
It is known from Publication No. 23.

(3) Problems to be Solved by the Invention In the above-mentioned conventional device, the spring that exerts the spring force in the direction of bringing the drive rocker arm into contact with the engine valve and in the direction of sliding the free rocker arm against the cam is attached to the drive rocker arm. and a free rocker arm. However, switching between the connected state and the disconnected state of both rocker arms by the connecting means is only possible when the engine valve is in the closed state, that is, when the free rocker arm is in sliding contact with the inside of the base of the cam and the relative position of the rocker arms is constant. However, in the conventional method described above, it is difficult to ensure that the relative position of the drive rocker arm to the free rocker arm remains constant even if the free rocker arm is in sliding contact with the inside of the base of the cam. be. In other words, when switching the connection state by the connection means, it cannot be said that the axes of the holes drilled in both rocker arms to fit the connection pistons can be reliably aligned with each other when the engine valve is in the closed state. It may become unsmooth.

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a valve train for an internal combustion engine in which switching operation by a connecting means can always be performed smoothly.

B0 Structure of the Invention (1) Means for Solving the Problems According to the present invention, the camshaft is integrally provided with a circularly formed protuberance centered on the axis of the camshaft, and the drive rocker arm is is provided with an abutting portion that slides into contact with the raised portion.

(2) Effect According to the above configuration, when the free rocker arm is in sliding contact with the inside of the base of the cam, the abutment part of the drive rocker arm is kept in sliding contact with the raised part, so that the drive rocker arm and the free rocker arm can be moved relative to each other. The position can be a constant position.

(3) Embodiment Hereinafter, an embodiment of the present invention will be explained with reference to the drawings. First, in FIGS. A low-speed cam 3 and a high-speed cam 5 are integrally provided on the camshaft 2 and are driven at a rotation ratio of A in synchronization with the rotation of the camshaft 2. , 1. It is opened and closed by the action of the second drive rocker arms 7, 8 and the free rocker arm 9.

Further, the engine body E is provided with exhaust valves (not shown) as a pair of engine valves, and these exhaust valves are also opened and closed in the same manner as the intake valves 1a and lb described above.

The camshaft 2 is rotatably disposed above the engine body E, and the low-speed cam 3 is integrally provided on the camshaft 2 at a position corresponding to one intake valve 1a. Also, the high speed cam 5 has both intake valves 1a.

It is integrally provided on the camshaft 2 at a position corresponding to between lbs. Moreover, the high-speed cam 5 has a shape suitable for high-speed operation of the engine, and has a shape in which the high portion 5a protrudes outward in the radial direction of the camshaft 2 from the inside of the base 5b. The low-speed cam 3 has a shape suitable for low-speed operation of the engine, and the amount of protrusion of the high portion 3a of the camshaft 2 radially outward from the base interior 3b and the central angle range are determined by the high-speed cam 5. It is formed smaller than the higher part 5a of. Further, at a position corresponding to the other intake valve 1b, the camshaft 2 is provided with a circular shape corresponding to the base interiors 3b and 5b of the low-speed cam 3 and the high-speed cam 5, with the axis of the camshaft 2 as the center. A formed protuberance 4 is integrally provided, and this protuberance 4 serves to keep the intake valve lb closed during low-speed operation.

The rocker shaft 6 is fixedly arranged below the camshaft 2. This rocker shaft 6 has a first and a second
A drive rocker arm 7.8 and a free rocker arm 9 are respectively pivoted, the first and second drive rocker arms 7.
．． 8 are basically formed in the same shape. That is, the first
and the second driving rocker arm 7.8, the intake valves 1a, l.
At a position corresponding to b, its base is pivotally supported by the rocker shaft 6 and extends to a position above each intake valve 1a, lb. Further, a cam slipper 10 that slides on the low-speed cam 3 is provided at the top of the first drive rocker arm 7, and a contact portion 11 that can come into contact with the raised portion 4 is provided at the top of the second drive rocker arm 8. In the first and second drive rocker arms 7.8, a tappet screw 12.13 that can abut the upper end of each intake valve 1a, lb is screwed so as to be able to move forward and backward at the end located above each intake valve 1a, lb. It will be worn.

On the other hand, flange portions 14 and 15 are provided at the upper portions of both intake valves 1a and lb. These flanges 14, 15 and the engine body E
and a valve spring 16.1 surrounding the intake valves 1a and Ib.
7 is interposed, and each intake valve 1a, lb is biased toward the valve closing direction, that is, upward, by a valve spring 16, 17.

Referring also to FIG. 3, the free rocker arm 9 has a first
and a second drive rocker arm 7.8 on the rocker shaft 6. This free rocker arm 9 extends from the rocker shaft 6 to both intake valves Ia.

1b side, and a high-speed cam 5 is mounted on the upper part.
A cam slipper 18 is provided which slides into contact with the cam slipper 18.

Further, a bottomed cylindrical lid 19 is in contact with the lower surface of the end of the free rocker arm 9, and this lifter 19 is interposed between the engine body E and is biased upward by a lid spring 20. . As a result, the cam slipper 18 of the free rocker arm 9 is always in sliding contact with the high-speed cam 5.

In FIG. 4, first and second drive rocker arms 7.
8 and the free rocker arms 9 are in sliding contact with each other, and a connecting means 21 that can switch between a state that allows relative angular displacement thereof and a state that connects each rocker arm 7 to 9 integrally connects each rocker arm. ? , 8. 9.

The connecting means 21 has a first connecting piston 22 movable between a position where the first driving rocker arm 7 and the free rocker arm 9 are connected and a position where the connection is released, and a position where the free rocker arm 9 and the second driving rocker arm 8 are connected. and a second connecting piston 23 movable between positions for releasing the connection, and first and second connecting pistons 22 .
A stopper 24 that restricts movement of the first and second
A spring 25 is provided which biases the stopper 24 to move the coupling piston 22, 23 toward the disengagement position.

The first driving rocker arm 7 has a first guide hole 26 with a bottom that opens toward the free rocker arm 9 and is parallel to the rocker shaft 6. The first guide hole 26 has a closed end. A small diameter R28 is provided via the stepped portion 27. The first connecting piston 22 is located in the first guide hole 26.
are slid together, thereby defining a hydraulic chamber 29 between the first connecting piston 22 and the closed end of the first guide hole 26.

See you in 111j! An oil passage 30 communicating with the hydraulic chamber 29 is bored in the dynamic rocker arm 7, and an oil passage 31 communicating with a hydraulic pressure supply source (not shown) is bored in the rocker shaft 6. Furthermore, both oil passages 30 and 31 are always in communication through a communication hole 32 formed in the side wall of the rocker shaft 6, regardless of the swinging state of the first drive rocker arm 7.

The axial length of the first connecting piston 22 is such that, when its lower end contacts the stepped portion 27, the other end does not protrude toward the free rocker arm 9 side from the side surface of the first drive rocker arm 7 facing the free rocker arm 9 side. It is set as follows. Further, a spring 33 having a smaller spring force than the spring 25 is interposed between the closed end of the first guide hole 26 and the first connecting piston 22.

A guide hole 34 corresponding to the first large guide 26 of the first driving rocker arm 7 is bored in the free rocker arm 9 between both sides, and the guide hole 34 has a length corresponding to the entire length of the guide hole 34. The second connecting piston 23 having a diameter is slidably connected thereto.

Moreover, the outer diameter of the second connecting piston 23 is set to be the same as that of the first connecting piston 22.

The second driving rocker arm 8 is provided with a bottomed second guide hole 35 that is open toward the free rocker arm 9 side and corresponds to the guide hole 34 . The stopper 24 is slid together. A small diameter portion 37 is provided on the closed end side of the second guide hole 35 via a regulating step portion 36 . Further, in the second drive rocker arm 8, an insertion hole 38 that passes through the closed end of the second guide hole 35 is provided in the second guide hole 35.
The stopper 24 is drilled concentrically and with a small diameter.
A small-diameter guide rod 39 that is integrally and concentrically provided is inserted into the insertion hole 38. Further, 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 .

Next, the operation of this embodiment will be explained. When the engine is operating at low speed, no hydraulic pressure is supplied to the hydraulic chamber 29 of the coupling means 21, and the stopper 24 is pressed toward the free rocker arm 9 by the spring 25, so that the first coupling The piston 22 has moved via the second connecting piston 23 until it comes into contact with the stepped portion 27 .

In this state, the contact surfaces of the first and second connecting pistons 22 and 23 are in positions corresponding to the sliding surfaces of the first driving rocker arm 7 and the free rocker arm 9, and the contact surfaces of the second connecting piston 23 and the stopper 24 are in positions corresponding to the sliding surfaces of the first driving rocker arm 7 and the free rocker arm 9. The contact surfaces are located at positions corresponding to the sliding contact surfaces of the free rocker arm 9 and the second vL movable rocker arm 8. Therefore, each rocker arm 7, 8.
9 are in sliding contact with each other, and the first and second connecting pistons 22, 23, the second connecting piston 23, and the stopper 24 are in sliding contact with each other, respectively, so that relative angular displacement is possible.

When the coupling means 21 is in the disconnected state, the rotation of the camshaft 2 causes the first drive rocker arm 7 to
swings in response to sliding contact with the low-speed cam 3, and one intake valve 1a is opened and closed by retarding its opening timing, advancing its closing timing, and reducing its lift amount. On the other hand, the second drive rocker arm 8 does not swing because the raised portion 4 is circular, and the other intake valve 1b remains closed.

At this time, the free rocker arm 9 swings due to sliding contact with the high-speed cam 5, but the swinging action is similar to that of both intake valves 1a, lb.
has no effect on the operation.

In this way, when the engine is operating at low speed, only one intake valve 1a is opened or closed, thereby reducing fuel consumption and improving idling characteristics.

During high-speed operation of the engine, hydraulic pressure is supplied to the hydraulic chamber 29 of the coupling hand rlt21. As a result, as shown in FIG. 5, the first connecting piston 22 moves toward the free rocker arm 9 against the spring force of the spring 25, and the second connecting piston 23 is pushed by the first connecting piston 22 and moves toward the free rocker arm 9. Move to the 2-drive rocker arm 8 side. As a result, the first and second connecting pistons 22,23 move until the stopper 24 comes into contact with the regulation Jt portion 36, the first driving rocker arm 7 and the free rocker arm 9 are connected by the first connecting piston 22, and the first driving rocker arm 7 and the free rocker arm 9 are connected. A two-coupling piston 23 connects the free rocker arm 9 and the second drive rocker arm 8.

In this way, when each rocker arm 7.8.9 is interconnected by the coupling means 21, the high speed cam 5
The first and second drive rocker arms 7.8 swivel together with the free rocker arm 9, since the free rocker arm 9 that is in sliding contact with the free rocker arm 9 has the greatest amount of swivel. Therefore, both intake valves 1a and 1b are opened and closed with their opening timings advanced, their closing timings delayed, and their lift amounts increased.

When switching between the connected state and the uncoupled state by the connecting means 21, when the free rocker arm 9 is in sliding contact with the high-speed cam 50 base interior 5b, the second
The driving rocker arm 8 is in sliding contact with the raised portion 4, and the first
The drive rocker arm 7 is in sliding contact with the base interior 3b of the low-speed cam 3. Therefore, when the intake valves 1a and lb are in the closed state, the first guide hole 2 in the connecting means 21
6. The axes of the guide hole 34 and the second guide hole 35 are aligned, so that the first and second connecting pistons 22
．． 23 can be smoothly connected and uncoupled, and the switching operation of the connecting means 21 can be performed smoothly.

The effect of improving the output of the engine due to the function of the connecting means 21 as described above is illustrated by curve A in FIG. 6. On the other hand, curve B shows a conventional internal combustion engine in which the engine valve does not stop operating when the engine is running at low speed; Conventional one (Japanese Unexamined Patent Publication No. 59-37223
It is clear that the configuration of this embodiment improves the output over a wide range from low speed ranges to high speed ranges.

In the above embodiment, the protrusion 4 in sliding contact with the second drive rocker arm 8 was explained as being completely circular, but the square cam 3.5
A protrusion may be formed on the protruding portion 4 at a position corresponding to the high portion 3a, 5a of the intake valve 1a, lb to operate the intake valve 1a, lb in the valve opening direction to the extent that the intake valve 1b is considered to be in a substantially closed state.

Further, in the above description, the portions related to the intake valves 1a and 1b have been described, but the pair of exhaust valves are also operated in the same manner as the intake valves.

C0 Effects of the Invention As described above, according to the present invention, the camshaft is integrally provided with a raised portion formed in a circular shape centered on the axis of the camshaft, and the drive rocker arm is provided with a sliding portion on the raised portion. Since an abutting portion is provided, when the free rocker arm is in sliding contact with the inside of the base of the cam, the driving rocker arm can be slid against the raised portion to ensure that the relative position of both rocker arms is constant, thereby facilitating the switching operation of the coupling means. It can be done.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention, and FIG. 1 is a plan view, FIG. 2 is a sectional view taken along the line ■-■ in FIG. Figure 4 is IV-IV of Figure 2.
A line sectional view, FIG. 5 is a sectional view corresponding to FIG. 4 during high-speed operation, and FIG. 6 is a diagram showing the output characteristics of the engine. la, lb...Intake valve as engine valve, 2...Camshaft, 4...Protuberance, 5...Cam, 8...Drive rocker arm, 9...Free rocker arm, 21...
・Connection means, 23...connection piston

Claims (1)

[Claims] A cam that is integrated into a camshaft that is rotationally driven in synchronization with the rotation of the engine, a drive rocker arm that comes into contact with the engine valve that is spring-biased in the valve-closing direction, and a drive rocker arm that is free from the engine valve. an internal combustion engine, comprising: a free rocker arm disposed adjacent to a drive rocker arm in sliding contact with said cam; and coupling means having a coupling piston movable between a position for coupling and a position for disengaging the rocker arms; In the valve train, the camshaft is integrally provided with a raised part formed in a circular shape centered on the axis of the camshaft, and the drive rocker arm is provided with an abutment part that slides into contact with the raised part. Features of internal combustion engine valve gear.