Pumps – Condition responsive control of drive transmission or pump... – Adjustable cam or linkage
Patent
1991-10-17
1993-03-02
Smith, Leonard E.
Pumps
Condition responsive control of drive transmission or pump...
Adjustable cam or linkage
F04B 4908
Patent
active
051904454
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present, invention relates to a variable capacity pump controller for a hydraulically driven wheel adapted for controlling a variable capacity hydraulic pump adapted for increasing, and decreasing an rpm of an engine of a vehicle in accordance with a driving load in an industrial vehicle such as a shovel loader using a static hydraulic driving system.
DESCRIPTION OF THE PRIOR ART
FIGS. 6 and 8 are views explaining systems of a conventional variable capacity pump controller of hydraulically driven wheel.
In FIG. 7, a variable capacity control cylinder C for controlling a variable capacity hydraulic pump P (hereinafter referred to as variable pump) has a pilot circuit a provided with a throttle valve b wherein the operation speed of the pump capacity control cylinder C can be changed at the same speed in both directions to increase and reduce the pump capacity. Designated at E is an engine, A is a control pump, V is a control valve, K is a charge circuit, M is a motor and S is a main circuit.
In FIG. 8, a pilot circuit a includes a one way throttle valve d composed of a throttle valve d.sub.1 and a check valve d.sub.2 in which a pressurized oil flows through the check valve d.sub.2 in the direction to increase the pump capacity while pressurized oil flows through the throttle valve d.sub.1, in the direction to decrease the capacity whereby travelling performance and stability of the vehicle are made compatible with each other by increasing the acceleration at the time of accelerating the speed of the vehicle and decreasing the deceleration rate at the time of reducing the speed.
In the conventional variable capacity pump controller of hydraulically driven wheel as illustrated in FIG. 7 and 8, the acceleration and deceleration of the vehicle are regulated and the operational instability at the time of switching to forward or backward motion and varying an rpm of the engine are improved by controlling the operation speed of the pump capacity control cylinder C having the throttle valve b or one way throttle valve d in the pilot circuit thereof.
The conventional variable capacity pump controller operates effectively in a normal travelling state but has the following problem in an excavating and loading operation by the shovel loader and the like. That is, when the vehicle carries out the excavation and loading operations, the driving load increases sharply. At this time, the variable pump P tends to pull back the pump capacity control cylinder C in the direction to reduce the pump capacity due to the increase of the oil under pressure in the main circuit S. However, an amount, of oil to be escaped from the control cylinder C is limited due to the presence of the throttle valve b or d.sub.1 in the pilot circuit a whereby the reducing speed of the pump capacity is reduced and a torque of the variable pump P to be applied to the engine is increased, which causes the problem of decreasing the rpm of the engine. As a result, there were other problems in that the loading efficiency is decreased and the engine stops since an excessive torque is applied to the engine in case that the pressurized oil is used for controlling the variable pump and performing the excavating and loading operations.
It is therefore an object of the present invention to solve the problems of the conventional variable capacity pump controller of hydraulically driven wheel and to provide a conventional variable capacity pump controller of hydraulically driven wheel capable of speeding up the reducing speed of the pump capacity and preventing the excessive torque to the engine.
SUMMARY OF THE INVENTION
To achieve the above object, the present invention is to provide a variable capacity pump controller in a hydraulically driven vehicle equipped with a variable capacity hydraulic pump, the controller includes variable throttle devices which are disposed in pilot circuits of a pump capacity control cylinder for an industrial vehicle such as a shovel loader using a static hydraulic driving system. In a hydraulically
REFERENCES:
patent: 4216656 (1980-08-01), Hamma
Kabushiki Kaisha Komatsu Seisakusho
Komatsu Mec Kabushiki Kaisha
Smith Leonard E.
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