JPH0823284B2 - Valve train for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A. Purpose of the Invention (1) Field of Industrial Application The present invention can be free to a drive cam follower that is interlocked with and connected to an intake valve or an exhaust valve, and an intake valve or an exhaust valve. The free cam follower and the free cam follower are arranged adjacent to each other so as to be actuated in different modes depending on the rotation of the cam shaft, and a connection switching mechanism capable of mutual connection and disconnection is provided between the cam followers. The present invention relates to a valve train of an internal combustion engine that is elastically biased toward a shaft.

(2) Conventional Technology Conventionally, such a valve operating system has been disclosed in, for example, Japanese Patent Laid-Open No. 61-19911.
As disclosed in the publication, a spring is contracted between a lifter abutting against the free cam follower and the engine body, and the spring force of the spring elastically biases the free cam follower toward the camshaft.

(3) Problems to be Solved by the Invention By the way, when the cam followers are connected by the connection switching mechanism, it is possible to slightly swing the free cam followers so as to allow a slight dimensional tolerance. Moreover, it is desirable to set the set load of the spring small.
However, in order to prevent the overstroke of the connecting pin when the connection fails, it is necessary to sufficiently increase the compression load of the spring, and it is difficult to satisfy these contradictory requirements. Therefore, there is also one in which a spring having a relatively large spring constant and a spring having a relatively small spring constant are connected in series to elastically urge the free cam follower.

Further, in the above-mentioned conventional one, the spring is interposed between the engine body and the free cam follower, and the engine body needs a space for receiving the spring, so that the degree of freedom in arrangement is narrowed. Further, if the spring is expanded and contracted with respect to the full stroke of the cam that swings the free cam follower, friction is increased due to useless work, which becomes an obstacle in improving output and fuel saving.

The present invention has been made in view of such circumstances,
An object of the present invention is to provide a valve train for an internal combustion engine that solves the above problems by using a single spring.

B. Configuration of the Invention (1) Means for Solving the Problems According to the present invention, the drive cam follower is opposed to the free cam follower with an interval slightly larger than the relative actuation amount difference between the drive cam follower and the free cam follower. In order to do so, the arm part that extends to the free cam follower side is integrally provided,
A spring for elastically urging the free cam follower toward the camshaft is interposed between the widthwise center of the free cam follower along the axis of the camshaft and the arm.

(2) Operation According to the above configuration, it is not necessary to secure a space for receiving the spring in the engine body, and the degree of freedom in arrangement is increased. In addition, since the free cam follower limits the amount of movement by the arm, it is possible to prevent overstroke of the connecting pin even if the spring load is relatively small, and it is possible to reduce friction loss by reducing the spring load. Becomes Furthermore, since a single spring is used, it is possible to reduce the number of parts compared to the one using two springs, and the spring force acts on the center portion in the width direction of the free cam follower. Tilt is avoided.

(3) Embodiment Hereinafter, one embodiment of the present invention will be described with reference to the drawings. First, in FIG. 1 and FIG. 2, a pair of intake valves 1, 1 provided in an engine main body E includes a crankshaft of the engine. 1/2
Low speed cam 3, high speed cam 4 and low speed cam 3 that are integrally provided on the cam shaft 2 that is rotationally driven at a reduction ratio of
A first rocker arm 6 as a drive cam follower pivotally supported by a rocker shaft 5 parallel to the camshaft 2, a second rocker arm 7 as a free cam follower and a third rocker arm 8 as a drive cam follower, and first and second rocker arms. It is driven to open and close by the connection switching mechanisms 9a and 9b provided between 6, 7 and the second and third rocker arms 7 and 8.

The cam shaft 2 is rotatably disposed above the engine body E, and the low speed cam 3, the high speed cam 4 and the low speed cam 3 are integrated in the cam shaft 2 so as to be adjacent to each other in the axial direction. . The low speed cams 3, 3 are formed such that the protrusion amount and center angle range of the high-order portion 3a thereof are smaller than that of the high speed cam 4.

The rocker shaft 5 is fixedly arranged below the cam shaft 2. On the rocker shaft 5, a first rocker arm 6 having a cam slipper 10 slidingly contacting the low speed cam 3 at the upper portion, a second rocker arm 7 having a cam slipper 11 slidingly contacting the high speed cam 4 at the upper portion, and a low speed cam A third rocker arm 8 having a cam slipper 12 slidably contacting the upper portion 3 is pivotally supported adjacent to each other in the axial direction of the rocker shaft 5.

Intake valves 1,1 are interlocked and connected to the first and third rocker arms 6,8. That is, each intake valve 1, 1 has a valve spring 14 interposed between the flange 13 provided at the upper end of the intake valve 1, 1 and the engine body E.
Is urged in the valve closing direction, that is, upward by
Tappet screws 15 that come into contact with the upper ends of the intake valves 1, 1 are respectively screwed to the tips of the first and third rocker arms 6, 8 so as to be able to move forward and backward.

Referring also to FIG. 3, the first rocker arm 6 includes
The arm portion 16 facing the second rocker arm 7 below is the second
It extends to the rocker arm 7 side and is integrally provided. The arm 16
The cushioning material 17 is fixed on the upper surface of the
The distance d between the second rocker arm 7 and the second rocker arm 7 is set to be slightly larger than the relative lift difference between the first and second rocker arms 6 and 7. Moreover, a bottomed hole 18 is provided through the cushioning material 17 at a portion of the upper surface of the arm portion 16 corresponding to the widthwise central portion of the second rocker arm 7 along the axis of the camshaft 2. A bottomed hole 19 corresponding to the bottomed hole 18 is provided on the lower surface of the center portion of the width direction 7.
A coil-shaped spring 20 is contracted between the arm portion 16 and the second rocker arm 7 so as to fit both ends in the bottomed holes 18 and 19.
Due to the spring force of the spring 20, the second rocker arm 7 is elastically urged in the direction in which the cam slipper 11 is always in sliding contact with the high speed cam 4.

The connection switching mechanism 9a includes the first and second rocker arms 6,7.
A connecting pin 22a movable between a position for connecting the two and a position for releasing the connected state, a stopper 23a for restricting the movement of the connecting pin 22a, and a stopper 23a for moving the connecting pin 22a to the connection releasing side. And a return spring 24a for urging.

The second rocker arm 7 is provided with a bottomed first guide hole 25a that is open toward the first rocker arm 6 side and is parallel to the rocker shaft 5. The first guide hole 2
A small diameter portion 27a is provided on the closed end side of 5a via a step portion 26a. A connecting pin 22a is slidably fitted in the first guide hole 25a, and a hydraulic chamber 28a is defined between the connecting pin 22a and the closed end of the first guide hole 25a.

Corresponding to the first guide hole 25a, a bottomed second guide hole 29a opened to the side of the second rocker arm 7 is formed in the first rocker arm 6 in parallel with the rocker shaft 5. A disk-shaped stopper 23a is slidably fitted in the hole 29a. A small diameter portion 31a is provided on the closed end side of the second guide hole 29a via a regulation step portion 30a, and a small diameter portion 31a is provided at the closed end.
An insertion hole 32a coaxial with the above is formed. Moreover, the guide rod 33a provided coaxially and integrally with the stopper 23a is inserted into the insertion hole 32a. Further, between the stopper 23a and the closed end of the second guide hole 29a, a coil-shaped return spring 24a surrounding the guide rod 33a.
Is interposed.

The axial length of the connecting pin 22a is such that the other end is located between the first and second rocker arms 6 and 7 when one end contacts the stepped portion 26a, and the stopper 23a is provided on the regulation stepped portion 30a. It is set so that one end remains in the first guide hole 25a when entering the second guide hole 29a until it abuts.

On the other hand, in the rocker shaft 5, two oil passages 34a and 34b are defined by a partition wall 35 extending in the axial direction,
Hydraulic pressure is supplied to these oil passages 34a and 34b from a hydraulic pressure supply source (not shown). Moreover, the one oil passage 34a always communicates with the hydraulic chamber 28a regardless of the swinging state of the second rocker arm 7.

The connection switching mechanism 9b provided between the second and third rocker arms 7 and 8 has a connection pin 22b, a stopper 23b and a return spring 24b, and is basically configured the same as the connection switching mechanism 9a. Although detailed description is omitted, the hydraulic chamber 28b of the connection switching mechanism 9b communicates with the oil passage 34b in the rocker shaft 5 regardless of the swinging state of the second rocker arm 7.

Next, the operation of this embodiment will be described. During low speed operation of the engine, hydraulic pressure is not supplied to both oil passages 34a and 34b, and the connection switching mechanisms 9a and 9b are in the connection released state. Therefore, the first and third rocker arms 6 and 8 are rockably driven by the low speed cams 3 and 3, and both intake valves 1 and 1 are opened and closed at the timing and lift amount according to the shape of the low speed cams 3 and 3. .

During medium speed operation of the engine, hydraulic pressure is supplied only to one oil passage 34a, and in the one connection switching mechanism 9a, the connection pin 22a moves to the first rocker arm 6 side against the spring force of the return spring 24a. The 1st and 2nd rocker arms 6 and 7 are connected. Also, the other connection switching mechanism 9b is in the connection release state,
The second and third rocker arms 7 and 8 are not connected. In this state, one intake valve 1 is driven by the high speed cam 4, and the other intake valve 1 is opened and closed by the low speed cam 3.

Further, during high-speed operation of the engine, hydraulic pressure is supplied to both oil passages 34a, 34b, both connection switching mechanisms 9a, 9b are connected together, and the first and second rocker arms 6, 7 are connected, as well as the second and third rocker arms 6, 7. The rocker arms 7 and 8 are connected to each other. As a result, both intake valves 1, 1 are opened and closed by the second rocker arm 7 which is rockably driven by the high speed cam 4, and operate at timing and lift amount according to the shape of the high speed cam 4.

In such a valve operating device, the spring 20 that biases the second rocker arm 7 in the direction of sliding contact with the high-speed cam 4 can regulate the swinging motion of the second rocker arm 7 by the arm portion 16, thereby connecting pins 22a, 22b. The overstroke can be prevented, and it is sufficient to manage so as to have a relatively small set load. Therefore, the friction loss between the cam slipper 11 and the high speed cam 4 can be made relatively small. Moreover, the collision noise and damage due to the collision between the second rocker arm 7 and the arm portion 16 can be dealt with by providing the cushioning material 17 on the upper surface of the arm portion 16.

Further, since only one spring 20 is provided between the arm portion 16 and the second rocker arm 7, it is possible to contribute to the reduction of the number of parts, and the engine body E needs a space for receiving the spring 20. Therefore, the degree of freedom in arrangement can be made relatively large.

Moreover, since the spring force of the spring 20 acts on the central portion in the width direction of the second rocker arm 7 along the axis of the camshaft 2, the inclination of the second rocker arm 7 is avoided, and the connection switching mechanisms 9a, 9a and 9b are provided.
In b, the engagement / disengagement operation of the connecting pins 22a, 22b can be made smooth. Although the valve operating device for the intake valve 1 has been described, the present invention is also applicable to an exhaust valve operating device.

C. Effects of the Invention As described above, according to the present invention, the drive cam follower extends toward the free cam follower side so as to face the free cam follower with a gap slightly larger than the relative operation amount difference between the drive cam follower and the free cam follower. Since the arm portion is integrally provided, and a spring for elastically urging the free cam follower toward the camshaft side is interposed between the arm portion and the widthwise central portion of the free cam follower along the axis of the camshaft. , The space for receiving the spring on the engine body side is unnecessary, the degree of freedom in arrangement can be made relatively large, and the load of the spring can be set relatively small to reduce the friction loss. Since one spring is used, the number of parts can be reduced, and the spring force acts on the center portion of the free cam follower in the width direction to reduce the inclination of the free cam follower. And avoid, it may facilitate the operation of connection switching mechanism.

[Brief description of drawings]

1 is a plan view, FIG. 2 is a cross-sectional view taken along line II-II of FIG. 1, and FIG.
It is the III-III sectional view taken on the line of FIG. 1 ... Intake valve, 2 ... Cam shaft, 6 ... First rocker arm as drive cam follower, 7 ... Second rocker arm as free cam follower, 9a, 9b ... Connection switching mechanism, 16 ... Arm, 20 ...... Spring

Claims (1)

[Claims] 1. A drive cam follower that is interlocked with and connected to an intake valve or an exhaust valve and a free cam follower that can be free with respect to the intake valve or the exhaust valve can operate in mutually different modes depending on the rotation of a camshaft. In the valve train of the internal combustion engine, the free cam follower is elastically urged toward the camshaft, and the drive cam follower is provided between the cam followers. Is integrally provided with an arm portion extending toward the free cam follower side so as to face the free cam follower with an interval slightly larger than the relative actuation amount difference between the drive cam follower and the free cam follower. A spring for elastically biasing the free cam follower toward the camshaft between the widthwise central portion and the arm portion. A valve gear of an internal combustion engine, characterized in that interposed.