Throttle valve control device for an internal combustion engine

Abstract

A motor-driven throttle valve control device has a throttle shaft and a coupling lever rotatably provided on the shaft, both being coupled by a spring. A default spring energizes the coupling lever toward a position of the default opening of the throttle valve. The throttle shaft rotates separately from the coupling lever in the direction of the full open throttle valve from a point at which the coupling lever comes into contact with a stopper defining the default position and, together with the coupling lever, in the full close direction of the throttle valve from the point. Thereby, the throttle valve can be kept at the default position by the default spring through the coupling lever when a motor driving the throttle valve is not powered.

Description

BACKGROUND OF THE INVENTION[0001]The present invention relates to a throttle valve control device for an internal combustion engine, and more particularly to a throttle valve control device with a motor-driven throttle valve.[0002]A conventional throttle valve control device is disclosed in JP-A-63-150449 (1988), and U.S. Pat. Nos. 4,947,815 and 4,735,179 (the last one being owned by the same assignee as this application).[0003]As discussed in the above documents, one of the most important things in a throttle valve device driven by an actuator, such as a DC motor or a step motor, is that the minimum safety can be secured even against a fault in the actuator.[0004]With the aforesaid “minimum safety”, the following is meant; i.e., even in the event of occurrence of a fault in a throttle valve actuator, an engine can produce torque of a certain magnitude, whereby an automobile can travel at a predetermined speed, e.g. 30 km / h or so, to reach a nearby repair shop. According to circumst...

AI Technical Summary

Benefits of technology

[0022]An object of the present invention is to provide a motor-driven throttle valve control device for an internal combustion engine, in which torque required to be produced by a throttle valve motor can be reduced by reducing torque for making the closing operation of a throttle valve starting from the position defined by a default stopper, whereby the throttle valve motor can be miniaturized and hence the electrical load against the engine is reduced.

[0024]According to the present invention, a return spring serves to put back a throttle valve to a default position, at which the aforesaid minimum safety can be secured. When the throttle valve moves in the closing direction from the default position, it is operably separated from the return spring and moves against force caused by a separately provided spring (default spring).

Problems solved by technology

In such a case, a throttle valve is rapidly returned by a return spring to a full close position or an idle position, with the result that a traveling automobile is decelerated drastically.

Then, after the throttle valve is returned to the full close position, the automobile can no longer continue to travel at a desirable speed, because the engine can not produce sufficient torque with such opening of the throttle valve.

If the throttle valve is allowed to stand at the full close position for a long period of time after the engine stops, combustion products, such as tar and carbon, accumulate and adhere between the throttle valve and an inner wall of an intake pipe so that the throttle valve is fixed to the inner wall and experiences difficulty in being opened again by the torque of the driving motor.

With such a rotational speed of the engine, however, an automobile can never travel at the speed of 30 km / h, for example.

Under the condition of the limp-home travel, the opening of the throttle valve is maintained at a value to attain the aforesaid minimum safety, but the opening can be no longer adjusted, even if an acceleration pedal is operated.

Namely, the engine gets into a runaway condition.

Of course, if a throttle valve motor operates normally, the default stopper is unnecessary and awkward, because desirably the motor can control the opening of a throttle valve without any limitation between the position defined by the full close stopper and the full open position, in proportion to the depression amount of an acceleration pedal.

Images