Claims
- 1. A system for controlling a clutch for a motor vehicle having vehicle speed detecting means for producing a vehicle speed signal dependent on vehicle speed, wherein the clutch is engaged for locking-up the clutch when said vehicle is accelerated up to a first reference speed , the system comprising:
- first detecting means for detecting release of an accelerator pedal of the vehicle and for producing a release signal;
- second detecting means for detecting acceleration of the vehicle during existence of the release signal and for producing an acceleration signal when an increment of change of the vehicle speed represented by said vehicle speed signal is larger than a predetermined value;
- third detecting means for detecting downhill acceleration and for producing a downhill acceleration signal when the vehicle is accelerated at least up to a second reference speed, which is set lower than the first reference speed, during existence of the acceleration signal; and
- engaging means responsive to the downhill acceleration signal for locking-up the clutch.
- 2. The system according to claim 1 wherein the clutch is an electromagnetic clutch.
- 3. The system according to claim 2, wherein the engaging means responsive to said downhill acceleration signal is for controlling current passing through a coil of the electromagnetic clutch.
- 4. The system according to claim 1 wherein
- said second detecting means includes means for determining said increment of change of the vehicle speed as the difference between the present vehicle speed and an acceleration start vehicle speed.
- 5. The system according to claim 4, further comprising
- means for setting the acceleration start vehicle speed to present value of the vehicle speed when the accelerator pedal is released during deceleration of the vehicle, and when the accelerator is depressed.
- 6. The system according to claim 4, wherein
- said engaging means is responsive to said downhill acceleration signal for locking-up said clutch above said second reference speed with said accelerator pedal released.
Priority Claims (1)
| Number |
Date |
Country |
Kind |
| 61-083121 |
Apr 1986 |
JPX |
|
BACKGROUND OF THE INVENTION
This application is a continuation of our co-pending application Ser. No. 035,557 filed April 7, 1987 now abandoned.
The present invention relates to a system for controlling a clutch for an automatic transmission of a motor vehicle.
An automobile provided with a continuously variable belt-drive transmission with an electromagnetic clutch is disclosed in EP-A No. 151038. The electromagnetic clutch of the transmission is controlled by a control system to provide various operational modes such as a starting mode of a vehicle, reverse excitatior mode, drag mode, and mode of lock-up engagement. One of the modes is selected in accordance with a position of a selector lever and driving conditions to control the electromagnetic clutch.
In the above-described control system, a clutch engaging vehicle speed at which the clutch is engaged is set at a relatively high speed so as to enhance coasting of the vehicle. Accordingly, when the vehicle coasts down a hill at a speed lower than the clutch engaging speed, the vehicle may be acclerated in spite of releasing the accelerator pedal.
Such an acceleration of the vehicle moring downhill critical in ordinary conditions. However, for example, on snowy downhill travel it is desirable for the clutch to be engaged in a low vehicle speed range to effect the engine braking without coasting. Since the clutch engaging vehicle speed is set at a high speed in the convention system, the vehicle is accelerated up to the high speed without engine braking.
Japanese Patent Laid Open 60-157930 proposes a control system wherein once the vehicle speed reaches a speed for the engagement of the clutch during the release of the accelerator pedal (this means coasting downhill), the clutch engaging vehicle speed at which the clutch is engaged is changed to a lower speed. Thus, engine braking is effective at low vehicle speed.
However, in such a system, when the vehicle is acclerated after starting of the vehicle without depressing the accelerator pedal, the clutch is not engaged until the normal high speed. Thus, the vehicle may be accelerated up to the high speed.
The object of the present invention is to provide a system for controlling an electromagnetic clutch wherein sufficient engine braking effect can be achieved during downhil driving even at low vehicle speed.
The other objects and features of this invention will become understood from the following description with reference to the accompanying drawings.
US Referenced Citations (2)
| Number |
Name |
Date |
Kind |
| 4675817 |
Sakakiyama et al. |
Jun 1987 |
|
| 4680712 |
Sakakiyama et al. |
Jul 1987 |
|
Foreign Referenced Citations (4)
| Number |
Date |
Country |
| 151038 |
Aug 1985 |
EPX |
| 57-15024 |
Jan 1982 |
JPX |
| 60-157930 |
Aug 1985 |
JPX |
| 61-84422 |
Apr 1986 |
JPX |
Continuations (1)
|
Number |
Date |
Country |
| Parent |
35557 |
Apr 1987 |
|
Patent Grant
4911275
