Interrelated power delivery controls – including engine control – Transmission control – With clutch control
Reexamination Certificate
2000-07-10
2002-03-19
Bonck, Rodney H. (Department: 3681)
Interrelated power delivery controls, including engine control
Transmission control
With clutch control
C477S093000, C477S171000
Reexamination Certificate
active
06358182
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a driving force control unit for a vehicle, which is capable of switching driving force to be transmitted to driving wheels in accordance with depression of the brake pedal.
BACKGROUND OF THE INVENTION
In the prior art, there is known a vehicle in which driving force is transmitted to the driving wheels when the transmission is selected to a running range and the vehicle is in idling condition at a certain or lower vehicle speed including the condition that the vehicle stops. Such driving force is called “creep force”, by which unintentional backward displacement of the vehicle on a slope is restricted or an improvement is made on the run at a traffic jam. In this conventional vehicle, creep force is generated even when the brake pedal is depressed in the idling condition at the certain or lower vehicle speed. To this end, there is a drawback in that such a vehicle requires strong brake pedal depression for stopping, compared to a vehicle without generating creep force. Further, since the creep force generated by the rotation of the engine is forcibly restricted by braking force, the vehicle is susceptible to vibrations or noise.
In order to solve this problem, Japanese Patent Publication No. 1-244930 (i.e., Japanese Patent Application No. 63-71520) discloses a control unit for a vehicular automatic clutch, which is applied to a control system for generating low dragging torque (creep force) when the transmission is selected to a running range and the vehicle moves at an extremely low speed. The control unit makes creep force lower at a depression of the brake pedal than at a release of the brake pedal. According to this disclosure, creep force is changed by the depression of the brake pedal from a high state (strong creep condition) to a low state (weak creep condition) so that the aforementioned problems, such as the strong brake pedal depression requirement and the vibrations during stops of the vehicle can be eliminated.
In Japanese Patent Publication No. 9-202159 (i.e., Japanese Patent Application No. 8-12457), there is disclosed a vehicle with a starting clutch, in which the starting clutch is half engaged so as to apply the vehicle with driving force (creep force) when the transmission is selected to a running range and the vehicle moves at an extremely low speed. In this vehicle, engaging state of the starting clutch is controlled in response to a braking operation of the driver so that driving force is made lower (in the weak creep condition) at a depression of the brake pedal than at a release of the brake pedal.
However, when creep force is decreased from the strong creep condition to the weak creep condition in accordance with depression of the brake pedal, driving force to be transmitted to the driving wheels lowers. The driver recognizes the reduction of the driving force as braking force. Therefore, if the brake pedal is depressed when the vehicle moves at a certain or lower vehicle speed with the engine being in idling condition, the vehicle receives braking force by the reduction of creep force as well as by the depression of the brake pedal. As a result, the driver feels unintentional deceleration of the vehicle.
Especially in the prior art vehicle, the difference of the creep force (difference of the driving force values) between the strong creep condition and the weak creep condition is set greater, in order to achieve various purposes such as restriction of the vehicle in the strong creep condition from unintentional backward displacement on a slope, noise reduction of the vehicle in the weak creep condition upon depression of the brake pedal, and the like. For this reason, when the driver depresses the brake pedal, he receives unintentional strong deceleration, which is more than the actual brake pedal depression and is recognized as an awkward feel.
SUMMARY OF THE INVENTION
With the foregoing drawback of the prior art in view, the present invention seeks to provide a driving force control unit for a vehicle, which prevents the driver's unintentional strong deceleration feel.
According to the present invention, there is provided a driving force control unit for a vehicle, which allows transmission of driving force from a driving motor to driving wheels irrespective of releasing an accelerator pedal at a certain or lower vehicle speed when a transmission is selected to a running range, and which switches the magnitude of the driving force while the accelerator pedal is released at a vehicle speed no more than the certain vehicle speed between a greater condition and a smaller condition in accordance with depression of a brake pedal so that the driving force is made lower at a depression of the brake pedal than at a release of the brake pedal, wherein the driving force value in said greater condition at a certain or lower vehicle speed is changed according to the vehicle speed, and the change of the driving force value is characterized in that the driving force value becomes smaller as reaching from the vehicle speed at the maximum driving force value to said certain vehicle speed, and further switching said driving force, before stopping the vehicle, from said greater condition to said smaller condition is permitted merely in the vicinity of said certain vehicle speed.
Also, there is provided a driving force control unit for a vehicle, which allows transmission of driving force from a driving motor to driving wheels irrespective of releasing an accelerator pedal at a certain or lower vehicle speed when a transmission is selected to a running range, and which switches the magnitude of the driving force while the accelerator pedal is released at a vehicle speed no more than the certain vehicle speed between a greater condition and a smaller condition in accordance with depression of a brake pedal so that the driving force is made lower at a depression of the brake pedal than at a release of the brake pedal, wherein the driving force control unit further comprises means for changing the driving force value in said greater condition at a certain or lower vehicle speed so that the driving force value is changed according to the vehicle speed, the change of the driving force value being characterized in that the driving force value becomes smaller as reaching from the vehicle speed at the maximum driving force value to said certain vehicle speed, and switching said driving force, before stopping the vehicle, from said greater condition to said smaller condition being permitted merely in the vicinity of said certain vehicle speed.
In such driving force control units, reduction of the driving force upon depressing the brake pedal is carried out only when the difference between the driving force values before and after decreasing the driving force becomes smaller.
Here, the term “a certain vehicle speed” indicates a vehicle speed just before the vehicle stops. Therefore, if a certain vehicle speed is 5 km/h as an example shown in the preferred embodiments and examples, the vehicle speed range “at a certain or lower vehicle speed” includes vehicle speeds from 0 km/h (when the vehicle stops) to 5 km/h.
Meanwhile, the “smaller condition” indicates a weak creep condition. However, the “smaller condition” includes not only a case that the absolute value of the driving force generated by the driving motor is made smaller, but also a case that the driving force to be transmitted to the driving wheels becomes zero by completely reducing the engaging force of a hydraulically engaging element such as a starting clutch.
The “vehicle speed” in the wording “changed according to the vehicle speed” includes vehicle speed itself and its equivalent parameters. For example, as shown in the preferred embodiments and examples, if the vehicle speed and the speed ratio of the starting clutch (speed ratio between the input and output sides of the starting clutch) are in corresponding relation, the driving force may be changed in accordance with the speed ratio. This is also included in the case “changed according to the vehicl
Bonck Rodney H.
Honda Giken Kogyo Kabushiki Kaisha
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