The present invention relates to a fuel supply cut control device for use in an internal combustion engine.
In order to improve a specific fuel consumption, a fuel supply cut control device is known in which the supply of fuel is stopped when the engine is decelerated. In such a device, the supply of fuel is stopped as soon as the decelerating operation is started, and the supply of fuel is started again when the engine speed is reduced below a predetermined fixed speed (hereinafter referred to as a resume speed). After this, when the engine is decelerated again after the engine speed is increased beyond a predetermined fixed speed (hereinafter referred to as a cut speed), the supply of fuel is stopped again until the engine speed is reduced below the resume speed. In such a fuel supply cut control device, in order to further improve a specific fuel consumption, it is necessary to reduce the resume speed and the cut speed as much as possible. However, if the resume speed and the cut speed are reduced, when the engine speed is reduced below the resume speed and then the supply of fuel is stopped, or when the decelerating operation of the engine is started under an operating state wherein the engine speed is slightly higher than the cut speed, and then the supply of fuel is stopped, a large torque fluctuation which provides a shock for a vehicle occurs. As a result, the drivability of a vehicle deteriorates. Therefore, in a conventional fuel supply cut control device, it is difficult to reduce the resume speed and the cut speed.