Motor vehicles – Having four wheels driven – Including pump and fluid motor – or generator and electric...
Reexamination Certificate
2000-05-11
2001-11-27
Johnson, Brian L. (Department: 3618)
Motor vehicles
Having four wheels driven
Including pump and fluid motor, or generator and electric...
C475S005000, C475S002000
Reexamination Certificate
active
06321865
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a front-and-rear wheel drive vehicle in which one of pairs of front and rear wheels is driven by an engine, while the other pair is driven by start assisting motors.
2. Description of the Related Art
The applicant of this patent application has already proposed a front-and-rear wheel drive vehicle as described above in which when the front wheels slip when they are driven by the engine to start the vehicle, the start assisting motors are driven and the dog clutch provided between the motors and the rear wheels is engaged so as to drive the rear wheels to thereby provide a four-wheel drive condition (refer to Japanese Patent Application No.Hei.9-79348).
When a front-and-rear wheel drive vehicle such as described above starts by driving the front wheels with the engine, since the rear wheels follow by virtue of friction force received from the road surface, the movable dog (a dog connected to the rear wheels and motors) of the dog clutch disposed between the motors and rear wheels rotates and there is generated a relative rotation between the stationary dog (a dog fixed to the casing of the transmission) and the movable dog. Even if the dog clutch is tried to be engaged in this state, since the movable dog is repelled by the stationary dog, it is difficult to have a smooth engagement. Conventionally, to cope with this, the motors are driven idly prior to the engagement of the dog clutch to stop thereby the rotation of the movable dog which is rotated by the rear wheels, and then the two dogs are engaged together in a state in which the relative rotation between the stationary and movable dogs is eliminated or reduced.
However, it was difficult to stop the movable dog by running the motors idly, and it was not possible to avoid an engagement shock that is produced when the dog clutch is engaged.
In general, since there are provided on the vehicle wheel speed sensors for detecting the wheel speeds of the rear wheels, the revolution speed of the movable dog can be computed based on the wheel speeds so detected by the sensors. Therefore, if the motors are driven at a speed corresponding to the detected wheel speed of the rear wheels, it is possible to stop the rotation of the movable dog to have a smooth engagement of the dog clutch. However, in order to perform a feedback control so that the motors run at a predetermined motor rotation number, a motor rotation number sensor is required to detect the speed of the motor, and this leads to an increase in cost. It is, therefore, desirable to prevent the engagement shock of the dog clutch without provision of motor rotation number sensors.
SUMMARY OF THE INVENTION
The present invention was made in view of the aforesaid situation, and an object thereof is to enable a smooth engagement of the dog clutch without provision of any special motor rotation number sensor.
With a view to attaining the aforesaid object, according to a first feature of the invention, there is provided a front-and-rear wheel drive vehicle comprising an engine for driving one of pairs of front wheels and rear wheels, motors for driving the other pair of the pairs of front wheels and rear wheels, a dog clutch (a jaw clutch) disposed between the other pair of the pairs of front wheels and rear wheels and said motors and a control means for controlling the motor rotation numbers and the engagement of the dog clutch wherein when a vehicle starts, the dog clutch is engaged to allow the motor to drive the other pair of wheels to render assistance in starting, and wherein the assistance in starting is stopped when the vehicle speed reaches a predetermined value. Further, there are provided wheel speed sensors for detecting wheel speeds of the other pair of wheels and a motor rotation number estimating means for estimating the motor rotation numbers from the current and duty value (Duty) of the motors, wherein the control means engages the dog clutch after the control means controls the motor rotation numbers such that motor rotation numbers estimated with the motor rotation number estimating means coincide with motor rotation numbers corresponding to wheel speeds detected with the wheel speed sensors.
According to the above construction, when the starting assist by the motors is attempted in starting the vehicle by engaging the dog clutch, since the dog clutch is engaged after the control means controls the motor rotation numbers such that motor rotation numbers estimated with the motor rotation number estimating means coincide with motor rotation numbers corresponding to wheel speeds detected with the wheel speed sensors, it is possible to eliminate a relative rotation between the teeth of the respective dogs which are being brought into mesh engagement with each other to thereby have a smooth engagement of the dogs. Moreover, since the motor rotation numbers needed to control the motors so as to have such a smooth engagement are estimated from the current and duty value of the motors without using any special motor rotation number sensor, it is possible to avoid an increase in the number of components involved and cost. In particular, since the wheel speed sensors generally provided on the vehicle for the anti-lock braking system and the traction control system can be used as the wheel speed sensors for this purpose, there is no risk of increasing the number of components involved and production cost.
REFERENCES:
patent: 4635743 (1987-01-01), Riehl
patent: 5509491 (1996-04-01), Hall, III
patent: 6024182 (2000-02-01), Hamada et al.
patent: 6053833 (2000-04-01), Masaki
patent: 6105704 (2000-08-01), Hamada et al.
patent: 6125953 (2000-10-01), Arai et al.
patent: 8-175209 (1996-07-01), None
patent: 9-79348 (1997-03-01), None
Kuribayashi Takashi
Matsuo Hiroyuki
Honda Giken Kogyo Kabushiki Kaisha
Johnson Brian L.
Luby Matthew
Sughrue Mion Zinn Macpeak & Seas, PLLC
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