Pumps – Condition responsive control of pump drive motor – Plural pumps having separate drive motors – supply sources,...
Reexamination Certificate
2001-01-05
2003-10-28
Robinson, Daniel (Department: 3746)
Pumps
Condition responsive control of pump drive motor
Plural pumps having separate drive motors, supply sources,...
Reexamination Certificate
active
06638022
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a hybrid vehicle constructed so that running drive can be effected by transmitting engine output through a gear-change mechanism to the vehicle and running drive is also possible by means of a drive motor that is arranged in parallel with the engine, so that, in prescribed operating conditions, the engine may be temporarily stopped and running drive may be performed by driving the vehicle by means of the drive motor.
BACKGROUND OF THE INVENTION
Efforts are being made to put into practice hybrid vehicles wherein running can be performed using engine drive and electric motor drive in combination, with the object of improving engine fuel consumption etc. Such a hybrid vehicle is disclosed for example in Laid-open Japanese Patent Application Number H. 11-132321. This vehicle comprises an engine, a first motor generator connected to the engine crankshaft, a belt type infinitely variable gear-change mechanism connected to the engine output shaft through a torque converter, and a second motor generator connected to a power transmission system on the output side of this infinitely variable gear-change mechanism. This vehicle is arranged such that ordinary running is performed by converting the gear ratio of the engine driving force in the infinitely variable gear-change mechanism before transmitting it to the vehicle wheels; when the vehicle is temporarily stopped, the engine is also temporarily stopped; and when subsequently the vehicle is made to move off, the vehicle wheels are driven by a second motor generator. It should be noted that, when the vehicle is thus made to move off again, the engine is restarted by the first motor generator, and after the vehicle has moved off a changeover is effected to running using engine drive.
If the engine is thus stopped when the vehicle is temporarily stopped, hydraulic pump drive by the engine is also stopped, causing the hydraulic pressure of the infinitely variable gear-change mechanism to be lost. Accordingly, a second hydraulic pump is provided that is driven by an electric motor and when the engine is stopped a prescribed hydraulic pressure is generated by driving the second hydraulic pump by means of this electric motor so as to prepare for the next move-off in a condition with the gear ratio set to the maximum (LOW) to enable motive force transmission, by supplying this prescribed hydraulic pressure to the output pulley cylinder chamber of the infinitely variable gear-change mechanism. In this way, in a hybrid vehicle as described above, an improvement is sought to be achieved in respect of fuel costs by stopping the engine when the vehicle is temporarily stopped, and an improvement in respect of fuel costs is sought to be achieved by driving the vehicle wheels using the second motor generator on moving off.
Consideration has also been given, with the object of further improving the fuel consumption, to stopping the engine and performing running using the electric motor drive also when the vehicle is running at comparatively high speed. If in this case the conventional hybrid vehicle control described above is employed without modification, the following problems arise.
Conventionally, when the engine was stopped in a condition where the vehicle was temporarily stopped, it was arranged for the clutch, which is provided in the power transmission system, to be prepared for the next move-off by being in an engaged condition, by hydraulic fluid pressure supplied from the second hydraulic fluid pump during the engine stoppage. However, if the clutch is put in engaged condition when the engine is stopped during running, the problem arises that the gear-change mechanism and the torque converter are rotated by the driving force from the vehicle wheels, generating entrainment torque, necessitating additional driving torque from the electric motor, thereby lowering the drive efficiency.
Also, conventionally, the arrangement was such that, when the engine was stopped on temporary stoppage of the vehicle, the next move-off was prepared for in a condition with transmission of motive force being made possible by setting the gear ratio to the maximum (LOW), by supplying hydraulic fluid, supplied from the second hydraulic fluid pump, to the output pulley cylinder chamber of the infinitely variable gear-change mechanism. However, there was the problem that, if the engine was stopped during running and running drive effected using the electric motor, since control was performed such as to make the gear ratio the maximum (LOW), on return from electric motor drive to engine drive during running, since the gear ratio was the maximum (LOW) for the current vehicle speed, the engine speed had to be raised unnecessarily, impairing fuel consumption and drivability.
Accordingly, the present applicants gave consideration to performing gear ratio control such that the gear ratio of the infinitely variable gear-change mechanism should have a value corresponding to the current operating condition, by using hydraulic pressure obtained by driving the second hydraulic pump by the electric motor when running was performed with the engine stopped.
However, when the engine is temporarily stopped as described above, for reasons relating to battery capacity etc it is demanded to make the electric power consumption of the electric motor that drives the second hydraulic pump as small as possible; also, the delivery capacity of the second hydraulic pump is made as small as possible and the hydraulic pressure for gear ratio control is also made as low as possible. However, when gear-change control is performed using such a miniaturized second hydraulic pump, there is the problem that the rate at which gear change can be achieved is limited; for example in the case of sudden braking action whilst running, resulting in abrupt deceleration and stopping, gear change control in a manner such as to track this cannot be achieved i.e. gear change control displays a time-lag.
Specifically, for example, in a case where brake action is performed when running at comparatively high speed in a condition with the gear ratio close to the minimum (TOP), causing abrupt deceleration and stopping the vehicle, gear-change control is demanded whereby the gear ratio can be changed to the maximum (LOW) in the short time that elapses before the vehicle is thus abruptly stopped. However, since, as described above, the rate of gear-change that is achievable is reduced by miniaturizing the second hydraulic pump, the condition is generated that the gear ratio is left at an intermediate value, since the gear ratio has not been able to return to the maximum (LOW) by the time the vehicle has stopped, owing to the gear-change control lag.
In this situation, typically control is effected such that the engine is stopped when the vehicle is stopped, with the object of improving the fuel consumption; consequently, when the vehicle stops, the engine is stopped and the gear ratio remains at an intermediate gear ratio; thus, there is the problem that when the engine is started and the vehicle moves off moving-off control must be effected from an intermediate gear ratio, with the consequence that sufficient moving-off driving force is not obtained. Also, if, in order to obtain sufficient driving force, the gear ratio is returned to the maximum (LOW) before moving-off control is exercised, there is the problem that moving off is delayed, impairing drivability.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a hybrid vehicle control device constructed such that fuel consumption and running performance are not impaired even when performing running drive wherein the engine is stopped and an electric motor is used during running at comparatively high speed.
A further object of the present invention is to provide a hybrid vehicle control device constructed such that it can cope with such gear-change requests even when abrupt gear-change requests are generated by for example abrupt deceleration during running with the engine stopped.
Yet a fur
Hasebe Tetsuya
Ibaraki Shigeru
Kishida Makoto
Shimabukuro Eijirou
Shirasaka Takuya
Arent Fox Kintner & Plotkin & Kahn, PLLC
Honda Giken Kogyo Kabushiki Kaisha
Robinson Daniel
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