JPH0759902B2 - Slotter valve operating device for carburetor for internal combustion engine - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a throttle valve operating device for a carburetor of an internal combustion engine, and more particularly to a throttle valve operating device that opens and closes a throttle valve by using an oscillating cam mechanism. Regarding the device.

[Prior Art] Generally, in a throttle valve operating device of a type in which a throttle valve is opened and closed by using an oscillating cam mechanism including a throttle cam and a cam follower, the rotation angle of the throttle cam and the opening degree of the throttle valve are 1: Ideally, it should be set corresponding to 1.

For this purpose, the contour curve of the throttle cam must be greatly curved, but this causes the pressure angle formed by the throttle cam and the cam follower to become large in the vicinity of the full opening of the throttle valve. As a result, the resistance of the cam follower to swing increases, and the operability of the swing cam mechanism deteriorates.

Conventionally, from the viewpoint of safety, for example, the operability of the swing cam mechanism has been prioritized and the curve of the contour curve of the throttle cam has been made small so that the pressure angle in the vicinity of the full opening of the throttle valve becomes small. Therefore, there is a drawback that the responsiveness of the swing cam mechanism is impaired.

[Problems to be Solved by the Invention] According to the present invention, the pressure angle formed by the throttle cam and the cam follower is reduced even in the vicinity of fully open throttle valve, even if the responsiveness of the swing cam mechanism is improved. An object of the present invention is to provide a throttle valve operating device for a carburetor, which can simultaneously maintain good operability of the swing cam mechanism.

[Means for Solving Problems] The present invention is for an internal combustion engine that converts the rotation of a throttle cam into the swing of a cam follower and transmits the swing to a valve shaft of a throttle valve of a carburetor, thereby opening and closing the throttle valve. In the throttle valve operating device of the carburetor, the contact end of the cam follower to the throttle cam is made to have a thickness in the direction parallel to the rotation axis of the throttle cam, and the distance from the swing end of the cam follower to the contact end is set to be the longest. Gradually increase in the thickness direction up to the portion, and the contour curve of the throttle cam is curved in the thickness direction corresponding to the shortest portion to the longest portion of the cam follower, and the shortest portion of the cam follower is closed when the throttle valve opening is near the fully closed position. Arranged so that the longest part of the cam follower comes into contact with the throttle cam when the throttle valve opening is near full opening. It was done.

[Operation] With such a configuration of the present invention, the contour curve of the throttle cam is curved corresponding to the shortest part to the longest part of the contact end of the cam follower. Sometimes the shortest part of the cam follower comes into contact with the corresponding part, and when the throttle cam rotates from this position and the throttle valve opening is near full opening, the longest part of the cam follower is in the part of the contour curve corresponding to this. It comes in contact. Therefore, even if the contour curve of the throttle cam rises sharply when the throttle valve opening is near full opening, the pressure angle between the throttle cam and the cam follower is kept small, which improves responsiveness and operability. It

[Examples] Hereinafter, the present invention will be described based on Examples shown in the drawings.

FIG. 1 is a side view of an outboard motor three-cylinder internal combustion engine to which an embodiment of the present invention is applied. Internal combustion engine 10
Is mounted on the upper portion of an outboard motor body (not shown), has three carburetors 12, 14, 16 for each of the three cylinders, and has an intake box 18.

Reference numeral 20 is a throttle operating lever, which is composed of a pair of arms 22 and 24, and both arms 22 and 24 can swing together around a bolt 26 as a unit. A throttle cable 28 for transmitting the operation force of the operator is connected to one arm 22, and a throttle cam 32 is connected to the other arm 24 via a link 30. Reference numeral 34 is a central axis of rotation of the throttle cam 32. Throttle cam
A roller 36 as a cam follower is provided in contact with the contour curve of 32, and this roller 36 is provided at the end of the swing lever 38, and at the substantially middle portion of the lever 38, a throttle valve 40 is provided.
Is connected to the valve shaft 42. This rocking lever 38 has a valve shaft 42
Is supported so as to swing around the
The opposite end is connected to a connecting rod 44 which extends over the three vaporizers 12, 14, 16. Here, the swing lever 38 having the roller 36 is adapted to directly open and close the throttle valve of the central carburetor 14 in the figure among the three carburetors, and the swing of the swing lever 38 is caused by the connecting rod 44. The throttle valves 46, 48 of the carburetors 12, 16 at the upper and lower ends are also opened and closed via the. Reference numerals 50 and 52 are valve shafts of the respective throttle valves.

2 to 4 show in detail the swing cam mechanism constituted by the throttle cam 32 and the roller 36 as a cam follower. As shown in FIG. 2, the contour curve of the throttle cam 32 is formed asymmetrically with respect to the rotation center shaft 34, and the point indicated by reference symbol A corresponds to the vicinity of the throttle valve fully closed position, and the reference symbol B indicates. The point shown corresponds to the vicinity of the fully open position of the throttle valve. Here, the contour curve near point B is
It is formed so that it rises somewhat rapidly, and the response of the throttle valve resolution is increased.

As shown in FIG. 3, the roller 36 as a cam follower
Is rotatably supported by a shaft 54 fixed to the end of the swing lever 38, and is formed to have a thickness in the axial direction thereof, that is, in the direction parallel to the axis of the rotation center shaft 34 of the throttle cam. Has been done. The roller 36 is composed of a large-diameter portion 56 and a small-diameter portion 58 whose diameter gradually decreases from the end of the large-diameter portion 56. On the other hand, as shown in FIGS. 3 and 4, the contour curve of the throttle cam 32 is curved in the thickness direction of the roller 36. In particular, a point A, which is a point corresponding to the vicinity of the fully closed throttle valve in the contour curve, is curved toward the end portion of the small diameter portion 58 of the roller 36, and at this point A, the minimum portion of the small diameter portion 58 of the roller 36 is formed. The point B corresponding to the vicinity of the fully open position of the throttle valve corresponds to the large diameter portion 56 of the roller 36, and the large diameter portion 56 is arranged so as to contact this point B. That is, the contour shape of the throttle cam 32 is determined so that the roller 36 comes into contact with the throttle cam 32 at a position where the diameter of the roller 36 gradually increases from the point A to the point B of the throttle cam 32.

Next, the operation of the throttle valve operating device having the above configuration will be described.

The state shown by the solid line in FIG. 2 is a state near the throttle valve fully closed position, and the roller 36 is in contact with the point A of the throttle cam 32. From this state, the throttle cam 32 rotates
When the roller 36 rotates in the clockwise direction in the figure around 34, the roller 36 changes the contact position toward the point B along the contour curve of the throttle cam.
It swings around the swing center axis indicated by. Where roller 36
Is in contact with point A on the throttle cam 32,
Of the contact ends of 36, the end of the small diameter portion 58 is in contact with the point A. Since the throttle cam 32 is not flat as shown in FIGS. 3 and 4 but is curved in the thickness direction of the roller 36, it contacts the contour curve of the throttle cam 32 as the roller 36 approaches the point B of the contour curve. The position of the roller 36 gradually moves from the small diameter portion 58 to the large diameter portion 56. When the state shown by the alternate long and short dash line in FIG. 2 is reached, the roller 36 comes into contact with the point B of the contour curve of the throttle cam 32. Here, the large diameter portion 56 of the roller 36 is in contact with the point B. At this time, the pressure angle between the throttle cam 32 and the roller 36 is indicated by α in FIG. For comparison, FIG. 2 further shows the contact state with the point B when the roller 36 is formed only by the small diameter portion 58, and the throttle cam at that time is shown by a chain double-dashed line. The pressure angle is β as shown in FIG. Here, the pressure angle is an angle formed by the normal line of the contour curve of the cam and the moving direction of the cam follower at the contact point between the cam and the cam follower. Therefore, this pressure angle is smaller for smooth movement of the cam. Is good. In this way, by bringing the large diameter portion 56 of the roller 36 into contact with the point B near the throttle valve fully open position, the pressure angle α can be reduced and the cam can be operated smoothly. The force can be reduced. That is, the force acting from the throttle cam to the cam follower is the reaction force in the normal direction at the contact point (see FIG. 2).
F1 and F2), but for the cam follower to swing,
It is preferable that the components of the reaction forces F1 and F2 in the movement direction of the cam follower (X direction in FIG. 2) are large. When the small diameter portion 58 contacts the point B when the throttle valve is fully opened, and the pressure angle is large (β), the component of the reaction force in the normal direction acting on the cam follower is F1 ′ in FIG. On the contrary, when the large diameter portion 56 contacts the point B and therefore the pressure angle is small (α), it is represented by F2 ′. As is clear from FIG. 2, since F2 'is larger than F1', the cam follower can be swung with a relatively small operating force if the pressure angle is small.

Therefore, according to this embodiment, in the vicinity of the fully open position of the throttle valve, the contour curve of the throttle cam 32 is rapidly raised as shown in the drawing (the contour curve from point A to point B in FIG. Even if it is bent to improve the responsiveness of the throttle valve operation, it is possible to prevent the operation force from being extremely large.

In the above embodiment, as shown in FIG. 3, the throttle cam 32 is curved in the direction of the rotation center axis 34, and
The contact surface itself is inclined in a tapered shape, but since the shape of the roller 36 is reduced from the large diameter portion 56 toward the small diameter portion 58, this roller 36 and the throttle cam are
This is to prevent 32 from interfering with each other, and thus it is not always necessary to form the surface of the contour curve in such a taper shape.For example, a plate material having a substantially similar inclined shape may be used. Good.

Further, although the roller 36 is used as the cam follower in the above-mentioned embodiments, the present invention is not limited to this, and the contact end shape of the cam follower is substantially set to the shortest distance from the swing center C of the cam follower to the contact end. The pressure angle may be reduced by gradually increasing in the thickness direction from the portion to the longest portion.

[Effect] As described above, according to the present invention, there is an excellent effect that the response of the throttle valve operation can be improved without increasing the operation force of the throttle valve.

[Brief description of drawings]

FIG. 1 is a side view showing an embodiment of a throttle valve operating device for a carburetor for an internal combustion engine according to the present invention, and FIG. 2 is an enlarged side view showing a contact state between a throttle cam and a cam follower in the same embodiment, 3 is a plan view of FIG. 2 and FIG. 4 is a side view of FIG. 10 ... Internal combustion engine 12, 14, 16 ... Vaporizer 32 ... Throttle cam 36 ... Roller as cam follower 40 ... Throttle valve 42 ... Valve shaft 56 ... Large diameter portion 58 ... Small diameter portion

Claims (1)

[Claims] 1. A throttle cam operating device for a carburetor for an internal combustion engine, wherein a movement of a throttle cam is transmitted to a valve shaft of a throttle valve of a carburetor by swinging a cam follower, thereby opening and closing the throttle valve. Has a thickness in the direction parallel to the rotation axis of the throttle cam, and the distance from the swinging axis of the cam follower to the contact end is gradually increased in the thickness direction from the shortest portion to the longest portion, and the contour of the throttle cam is The curve is inclined in the thickness direction from the shortest part to the longest part of the cam follower, and the shortest part of the cam follower is brought into contact with the throttle cam when the throttle valve opening is close to fully closed, and the throttle valve opening is close to fully open. The carburetor throttle for the internal combustion engine arranged so that the longest part of the cam follower contacts the throttle cam when Operating device.