Measuring and testing – Simulating operating condition – Marine
Reexamination Certificate
2000-03-22
2001-08-21
Raevis, Robert (Department: 2856)
Measuring and testing
Simulating operating condition
Marine
Reexamination Certificate
active
06276197
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of specifying a partially engaged clutch stroke position for a vehicle fitted with an automatic clutch or the like and further relates to a method of diagnosing abnormalities in determination of the partially engaged clutch stroke position.
2. Description of the Related Art
In conventional vehicles with automatic clutch, an actuator is combined with a friction clutch, allowing the clutch to engage and disengage automatically.
In the engaging process of a friction clutch by automatic control, a disengaged clutch plate is first moved towards an engine flywheel rapidly while varying a clutch stroke position until a clutch face meets a flywheel surface, and then the clutch plate has to be moved slowly transmitting power to the flywheel with slip. Finally, the clutch plate is stopped to move, and the clutch is engaged completely without slip.
Therefore, it is necessary to specify the clutch stroke position at which the clutch face meets the flywheel surface and use this position as information in order to perform the automatic control in a satisfactory manner.
In this particular specification, “partially engaged clutch stroke position” means the position at which the clutch face meets the flywheel surface to start the power transmission with slip.
However, a friction clutch is subject to wear during use, and a partially engaged clutch stroke positions changes little by little.
Further, it exerts a deleterious effect on control if sensor faults and other factors cause a partially engaged clutch stroke position to become removed from the actual partially engaged clutch position.
SUMMARY OF THE INVENTION
An object of the present invention is to always specify a partially engaged clutch stroke position which changes with wearing of a friction clutch, whereby fine engagement control in partially engaged position determination is continuously enabled regardless of wearing of the clutch.
Another object of the present invention is to diagnose abnormalities in a determination process for a partially engaged clutch stroke position.
The present invention provides a method of specifying a partially engaged clutch stroke position for a friction clutch engaged and disengaged by a clutch actuator under automatic control or by driver's manual operation, comprising determining an initial partially engaged clutch stroke position and an initial clutch stroke position at which fluid pressure in the clutch actuator reaches a prescribed value, so as to obtain a difference between the initial partially engaged clutch stroke position and initial clutch stroke position attaining the prescribed fluid pressure value prior to initiation of automatic clutch control, detecting a current clutch stroke position at which the fluid pressure in the clutch actuator reaches the prescribed value while the automatic control is being performed, calculating a value by adding the difference to the detected current clutch stroke position, and using the value as a current partially engaged stroke position of the clutch in the automatic control operation.
As the fluid pressure in the clutch actuator rises, a clutch plate is moved in a disengaging direction so that it leaves from a flywheel of an engine. The initial partially engaged clutch stroke position may be determined when a vehicle is assembled in a factory. The initial clutch stroke position may also be determined immediately upon completion of vehicle assembling. The difference between the initial partially engaged clutch stroke position and initial clutch stroke position does not change in spite of wearing of the friction clutch. On the other hand, both of the partially engaged clutch stroke position and clutch stroke position attaining the predetermined fluid pressure changes with the wearing of the clutch. Therefore, by calculating the sum of the above mentioned difference and a current clutch stroke position attaining the predetermined fluid pressure value, it is possible to obtain a current partially engaged clutch stroke position.
All of the clutch stroke positions may be determined according to output voltages from a clutch stroke sensor. The predetermined value of fluid pressure may be a value which causes a clutch plate to start disengaging from a flywheel of an engine.
According to another aspect of the present invention, there is provided a method of diagnosing abnormalities in determining a partially engaged clutch stroke position of a friction clutch comprising determining an initial partially engaged clutch stroke position and an initial clutch stroke position at which fluid pressure in a clutch actuator used to disengage the friction clutch under automatic control reaches a prescribed value, so as to determine a difference between the two clutch stroke positions prior to initiation of operation of the automatic control, and determining an automatic clutch system to be abnormal when the determined difference does not fall within a predetermined range. This abnormality diagnosis may be performed before a vehicle is marketed. The initial partially engaged clutch stroke position may be determined based on an output voltage from a clutch stroke sensor. If the clutch stroke sensor malfunctions and does not provide an accurate value, the difference between the determined two clutch stroke positions may have an abnormal value.
According to still another aspect of the present invention, there is provided a method of diagnosing abnormalities in an automatic clutch control for a vehicle equipped with a friction clutch comprising the steps of sensing a partially engaged clutch stroke position, sensing a clutch stroke position at which fluid pressure in a clutch actuator used to disengage the friction clutch under automatic control reaches a prescribed value, calculating a difference between the two clutch stroke positions, and determining occurrence of abnormalities if the calculated difference does not fall within a predertermined range. This abnormality diagnosis may be performed while a vehicle is running.
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Copy of the May 7, 2001 European Search Report (representing a concise explanation where non-English language information is cited).
Arai Hiroyuki
Hayashi Masahiko
Imai Junichi
Kobayashi Kazuhiko
Isuzu Motors Limited
Rader & Fishman & Grauer, PLLC
Raevis Robert
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