Controller of engine and variable capacity pump

Details Controller of engine and variable capacity pump Controller of engine and variable capacity pump

1999-07-20

2000-12-19

Miller, Carl S.

Internal-combustion engines

Engine speed regulator

Having condition responsive means with engine being part of...

123357, F02B 2300

Patent

active

061615226

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

The present invention relates to a controller of an engine and a variable capacity pump which performs a pressure increase control for a hydraulic circuit, a control for increasing an engine rotational speed and a control for a pump absorption torque so as to coincide with an engine output torque when selecting a power active mode, in order to facilitate a heavy excavation at a time of operating a construction machine such as a hydraulic excavator and the like.


BACKGROUND OF THE INVENTION

A hydraulic circuit shown in FIG. 6 is employed in a conventional construction machine such as a hydraulic excavator and the like. The hydraulic circuit is provided with a variable capacity pump 11 (hereinafter, referred to as a pump 11) driven by an engine 1 and a pilot pump 81. An angle of a swash plate in the pump 11 is controlled by a servo piston 12, and an operation pressure of the servo piston 12 is controlled by a servo control valve 200. An operation portion 200a of the servo control valve 200 is connected to a neutral control valve 210 (hereinafter, refer to as an NC valve 210), a cut-off valve 220 (hereinafter, refer to as a CO valve 220) and a torque variable control valve 230 (hereinafter, refer to as a TVC valve 230) in series. A pipe passage 202 branched from a discharge pipe passage 201 of the pump 11 is connected to each of the operation portions in the CO valve 220 and the TVC valve 230. A pipe passage 222 branched from a discharge pipe passage 221 of the pilot pump 81 is connected to the operation portion 200a in the servo valve 200 via the TVC valve 230, the CO valve 220 and the NC valve 210. An engine rotation sensor 5 for detecting a rotational speed of the engine 1 is connected to a controller 240. The controller 240 is connected to the TVC valve 230.
Further, the discharge pipe passage 200 of the pump 11 is connected to a direction switch valve 250. The direction switch valve 250 is connected to a hydraulic cylinder 260 via pipe passages 251a and 251b and also connected to a jet sensor (a pressure detecting portion) 253 via a pipe passage 252. The jet sensor 253 is connected to a drain passage 254.
Still further, a discharge pipe passage 223 branched from the discharge pipe passage 221 in the pilot pump 81 is connected to a pressure proportional control valve 270 and an operation lever 271 is connected to the pressure proportional control valve 270. The pressure proportional control valve 270 is connected to an operation portion of the direction switch valve 250 via pipe passages 272a and 272b.
An operation of the controller mentioned above will be described below. The NC valve 210 receives a pressure detected by the jet sensor 253 at an operation portion in one side from a pipe passage 256 and receives a pressure detected by the drain pipe passage 254 disposed downstream the jet sensor 253 at an operation portion in the other side from a pipe passage 257, thereby being switched in accordance with a differential pressure between a front and a back of the jet sensor 253. Since all the discharge flow amount of the pump 11 is drained from the drain passage 254 to a tank 258 via the jet sensor 253 when the direction switch valve 250 becomes a neutral position shown in the drawing, a pressure downstream of the jet sensor 253 becomes high and the NC valve 210 is switched to a port position 210b. Accordingly, the servo valve 200 becomes at a port position 200c so as to move the servo piston 12 to a left side in the drawing and reduce a flow amount of the pump 11. Therefore, an energy loss at a neutral position of the direction switch valve 250 is reduced.
Next, since no oil flows in the jet sensor 253 when an operator switches the direction switch valve 250, the NC valve is switched to the port position 210a. Further, a rotational speed signal from the engine rotation sensor 5 in the engine 1 is always input to the controller 240, and a command signal is input to the operation portion 230a of the TVC valve 230 from the controller 240 in correspondence to the rotational speed sig

REFERENCES:
patent: 4773369 (1988-09-01), Kobayashi
patent: 4774921 (1988-10-01), Sakaguchi
patent: 5468126 (1995-11-01), Lukich
patent: 5878721 (1999-03-01), Nakamura

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