Motor vehicles – Power – Including traction motor of kind driven by noncompressible...
Patent
1992-11-17
1994-01-11
Camby, Richard M.
Motor vehicles
Power
Including traction motor of kind driven by noncompressible...
60391, 60388, B60K 1700
Patent
active
052772691
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an engine revolution speed control device which is used for a hydraulically driven vehicle such as a wheel type hydraulic shovel or the like.
BACKGROUND ART
Before the present applicant, for example in Japanese Patent Laying-Open Publication Serial No.3-135844, has proposed the following type of hydraulically driven vehicle has been proposed. With this hydraulically driven vehicle, when the vehicle movement is accelerated, along with increasing the revolution speed of the engine according to the amount by which the vehicle driving pedal (accelerator pedal) is stepped upon, the flow supply of hydraulic fluid to the hydraulic motor for vehicle movement is also increased. Further, when the driving pedal is released so as to initiate deceleration action, from the point of view of preventing cavitation, along with performing controlled slowing down by which the engine revolution speed is gradually dropped according to the passage of time without directly reducing the engine revolution speed to the idling revolution speed even when the driving pedal is released, also slow return control is performed by which the control valve for vehicle movement is gradually returned to its neutral position.
However, if the above described controlled slowing down is always permitted, various problems arise during specific operations. Application Serial No. 2-185876, has proposed a hydraulically driven vehicle in which the engine revolution speed can be increased and decreased according to the amount by which a vehicle driving pedal is stepped upon, not only during vehicle movement but also while performing work such as excavation or the like. However if during reduction of vehicle moving speed as described above controlled slowing down is performed, then the controlled slowing down will also undesirably always be in operation during working when the engine revolution speed is adjusted by the use of the vehicle driving pedal, and this will give rise to the problem of bad operational feeling. the vehicle driving pedal although he has no plans to move the vehicle away from rest, may even for only an instant slightly depress the vehicle driving pedal, so that the engine revolution speed is slightly increased, and the control valve for vehicle movement also slightly opens. At this time, if the above described controlled slowing down control and also slow return control are performed, pressurized hydraulic fluid may be supplied from the control valve to the hydraulic motor.
DISCLOSURE OF INVENTION
The objective of the present invention is to provide an engine revolution speed control device for a hydraulically driven vehicle so constructed that, in specific operational circumstances, when speed reduction action is performed by use of the vehicle driving pedal, controlled slowing down of the engine revolution speed is prohibited.
(1) The present invention is applied to an engine revolution speed control device for a hydraulically driven vehicle, comprising: a hydraulic pump which is driven by an engine; a hydraulic motor for vehicle movement which is driven by oil expelled from said hydraulic pump during vehicle movement; an actuator for working which is driven by the oil expelled from said hydraulic pump during the working state; a vehicle driving pedal which during vehicle movement controls vehicle speed according to its amount of operation; a means for speed reduction decision which makes a decision as to whether the amount by which said vehicle driving pedal is depressed is being reduced; and a means for revolution speed control, which performs: a first type of engine revolution speed control by increasing or decreasing the revolution speed of said engine according to the amount by which said vehicle driving pedal is depressed; and a second type of engine revolution speed control by reducing the revolution speed of said engine while delaying its reduction amount, when it is decided that the amount by which said vehicle driving pedal is depressed is decreasing.
And the above d
REFERENCES:
patent: 4542802 (1985-09-01), Garvey et al.
patent: 4704866 (1987-11-01), Myers
patent: 4759185 (1988-07-01), McConnell et al.
Asano Kazuo
Hosono Junichi
Ichimura Kazuhiro
Kihara Mitsuo
Tamura Seiji
Camby Richard M.
Hitachi Construction Machinery Co. Ltd.
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