Internal-combustion engines – Engine speed regulator – Open loop condition responsive
Reexamination Certificate
1999-08-04
2001-04-03
Argenbright, Tony M. (Department: 3747)
Internal-combustion engines
Engine speed regulator
Open loop condition responsive
C123S399000
Reexamination Certificate
active
06209518
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an internal combustion engine equipped with an electronically controlled throttle system opened and closed by an actuator in order to accomplish a target position of the throttle valve disposed in an intake system and, particularly, to fail-safe control technology at a time when the sensors constituting the system become abnormal.
2. Related Art of the Invention
There has been proposed an electronically-controlled throttle system for electronically controlling the position of the throttle valve to obtain a target air quantity based on the position of the accelerator (depressed amount of the accelerator pedal) or on the position of the accelerator and the engine rotation speed (see Japanese Unexamined Patent Publication No. 7-180570).
Among such electronically controlled throttle systems, in case the drive system fails to operate, those (fully electronically-controlled throttle systems) without a limp-home mechanism for mechanically linking the throttle valve by the accelerator operation through a wire employ the below-mentioned system.
That is, provision is made of two accelerator position sensors and two throttle position sensors. As for the position of the accelerator, the smaller value is selected between the two detection values (to prevent the output from becoming excessive). As for the position of the throttle valve, the detection value of the main throttle position is used and, depending upon the cases, the larger value is selected between the two detection values (selecting the larger value effects the correction toward the decreasing side due to the feedback control, and prevents the excessive output).
In case one of the two accelerator position sensors or one of the two throttle position sensors fails to operate, the output from the actuator is stopped, and the throttle valve is linked between two springs (return spring and default spring) and is held at a predetermined default position at which these springs are balanced, in order to maintain a so-called limp-home state (low-speed fail-safe operation of a minimum compensation capable of traveling with the minimum output). In case the one sensor fails to operate, if the throttle valve position is controlled using the remaining sensor, there may take place acceleration or deceleration due to the unintended opening/closing operation of the throttle valve in case the remaining sensor also fails to operate.
According to the fail-safe system in the above-mentioned fully electronically-controlled throttle system, however, if the one sensor fails to operate, the throttle valve is forcibly maintained the fail-safe position at least at that moment without utilizing the value detected by the remaining normal sensor, causing such an inconvenience that the travelling can only be performed at, for example, 40 kilometers/hour at the fastest.
Besides, among the parts constituting the electronically-controlled throttle system, the accelerator position sensor and the throttle position sensor are likely to fail to operate. It has, therefore, been demanded to guarantee traveling performance of some degree at a time of single-failure of these sensors.
The present invention was accomplished by giving attention to the above-mentioned problem inherent in the prior art, and has an object of controlling the operation at a desired speed (fail-safe control in case of single-failure=limp-home control) by using a value detected by the remaining sensor (at a time of single-failure of the sensor) if the remaining sensor is normal, while maintaining a low-speed fail-safe operation of the minimum compensation.
Another object of the invention is to smoothly take over the single-failure fail-safe control operation when the single-failure occurs in the sensor.
SUMMARY OF THE INVENTION
A first method of fail-safe controlling an electronically-controlled throttle-type internal combustion engine of the present invention comprises the steps of;
setting a target position of a throttle valve disposed in an intake system depending upon engine operation conditions inclusive of a position of an accelerator detected by one accelerator position sensor selected from two accelerator position sensors equipped to the engine;
operating the throttle valve to be opened and closed by an actuator so that a position of the throttle valve detected by one throttle position sensor selected from two throttle position sensors equipped to the engine reaches the target position;
when either one of the two accelerator position sensors or either one of the two throttle position sensors fails to operate, executing a first fail-safe control operation for controlling the position of the throttle valve by basically using a value detected by the remaining sensor; and
in a state where one sensor fails to operate between the two accelerator position sensors or one sensor fails to operate between the two throttle position sensors, interrupting the first fail-safe control operation and, instead, executing a second fail-safe control operation to hold the throttle valve at a predetermined position when an operation for decelerating the engine is detected by a sensor in a system separate from the sensors.
A first apparatus for fail-safe controlling an electronically-controlled throttle-type internal combustion engine of the present invention comprises:
two accelerator position sensors for detecting a position of the accelerator;
a target position setting device for setting a target position of a throttle valve disposed in an intake system depending upon engine operation conditions inclusive of the position of the accelerator detected by one accelerator position sensor selected from the two accelerator position sensors;
two throttle position sensors for detecting a position of the throttle valve;
a throttle valve drive device for opening and closing the throttle valve using an actuator, so that the position of the throttle valve detected by one throttle position sensor selected from the two throttle position sensors reaches the target position;
a first fail-safe device which, when either one of the two accelerator position sensors or either one of the two throttle position sensors fails to operate, controls the position of the throttle valve using a value detected by the remaining sensor; and
a second fail-safe device which, in a state where one sensor fails to operate between the two accelerator position sensors or one sensor fails to operate between the two throttle position sensors, interrupts the operation of the first fail-safe device and holds the throttle valve at a predetermined position when an operation for decelerating the engine is detected by a sensor in a system separate from the sensors.
According to the thus constituted first method or the first apparatus for fail-safe controlling an electronically-controlled throttle-type internal combustion engine of the present invention, when either one of the two accelerator position sensors or either one of the two throttle position sensors fails to operate, the throttle valve is usually controlled to acquire a desired target position depending upon the position of the accelerator based on a value detected by the remaining sensor to travel at a desired speed.
When the engine is decelerated by the will of the driver, on the other hand, the deceleration operation is detected by a sensor of a separate system and the throttle valve is held at a predetermined position (default position), in order to assure a double guarantee by using the sensor in the separate system in the case of a single-failure. That is, even if the remaining sensor may fail to operate, the deceleration operation makes it possible to maintain the limp-home control operation of the minimum compensation, preventing the occurrence of undesired acceleration or deceleration.
It is further allowable to use an idle switch as a sensor in the separate system, so that the deceleration operation of the engine may be detected on condition that the idling state of the engine is detected by the
Iriyama Masahiro
Machida Kenichi
Nozaki Mikio
Argenbright Tony M.
McDermott & Will & Emery
Unisia Jecs Corporation
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