Hydraulic circuit control device of construction machinery

Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Construction or agricultural-type vehicle

Reexamination Certificate

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Details

C033S037000, C033S0010DD, C180S053400

Reexamination Certificate

active

06430490

ABSTRACT:

TECHNICAL FIELD
The present invention relates to a hydraulic circuit control system for a construction machine in which an operating system of the construction machine, particularly a control lever device, comprises a joystick device of the type generating an electrical operational signal (electric signal) depending on an input amount upon shift of a control lever, and a flow control valve is controlled with the operational signal for controlling the operation of an actuator.
BACKGROUND ART
In recent construction machines, particularly in those machines that are employed for various kinds of works because of convenience in use as represented by hydraulic excavators, operability has become increasingly valued in making the machines adaptable for a variety of usages. Stated otherwise, taking a hydraulic excavator as an example, the machine must be able to operate a working device as intended by an operator over a wide range from work in which primary importance is put on the amount of work carried out by the machine, e.g., excavation, to work in which fine adjustment is required in operation, e.g., leveling. To that end, it has been proposed to employ a hydraulic circuit control system in which a control lever device comprises an electric joystick for generating an electrical operational signal depending on an input amount upon shift a control lever, and the operational signal is electrically processed to control a flow control valve with a processed signal. Several known examples of such a control system are as follows.
(1) Japanese Patent No. 2509311 entitled “Working Device Control Method for Construction Machine”
This publication discloses a working device control method for a construction machine comprising a hydraulic control valve (operational valve), which is operated through a controller upon manipulation of an electrical lever, and a pump varying device. Modulation control is performed to absorb shocks caused upon operation of the operational valve and the pump varying device by setting a modulation pattern for rise/fall of a circuit pressure and increase/decrease of a pump delivery rate upon operation of the operational valve to restrict a maximum operating speed of the operational valve (maximum change rate of an operational signal) so that a rate of the rise/fall of the circuit pressure and increase/decrease of the pump delivery rate is gradually changed in multiple stages with a working time, and by operating the operational valve and the pump varying device so as not to move faster than the speeds set by the modulation pattern when the circuit pressure rises and falls at a constant rate with a working time. Furthermore, a cavitation is prevented from occurring upon operation of the pump varying device. This publication also discloses that a plurality of modulation patterns for the operational valve are prepared and one of the patterns is set depending on the working condition automatically or manually with selection by an operator.
(2) JP,B 7-107279 entitled “Working Device Control Method for Construction Machine”
This publication discloses an improvement of the modulation control in the above-mentioned (1). At the time when an electrical lever is manipulated from a shift position on the side in one direction toward the side in an opposite direction in a continuous manner and an operational signal from the electrical lever enters the opposite direction side beyond a dead zone corresponding to a neutral position, the modulation pattern having been effective so far is released and another modulation pattern for the opposite direction side is made effective. The operation of a working device and an operating feeling in the lever-reversed operation are thereby matched with each other.
(3) JP,A 10-37247 entitled “Operation Control Device and Operation Control method”
This publication discloses a hydraulic circuit controller for controlling the operation of a working device of a construction machine through a flow control valve, wherein a maximum change rate of an operational signal for the flow control valve is restrained to be not larger than a setting value, and the operation of the working device is controlled by changing the setting value depending on an input amount upon shift of a control lever.
Meanwhile, there is also known a hydraulic circuit control system in which an actuator speed is controlled by controlling a delivery rate of a hydraulic pump with an operational signal instead of controlling a flow control valve with the operational signal, and a maximum operating speed of a pump displacement varying mechanism is restrained. Several examples of such a hydraulic circuit control system are as follows.
(4) JP,B 62-13542 entitled “Controller for Hydraulic Circuit”
This publication discloses a hydraulic circuit controller for a closed circuit system wherein an actuator speed is controlled to a speed instructed by an operating device by controlling a delivery rate of a hydraulic pump (position of a pump displacement varying mechanism). When an operating speed of the pump displacement varying mechanism is restrained to be not larger a setting maximum speed, the setting maximum speed is changed depending on an input amount upon shift of a control lever, thereby controlling acceleration/deceleration of an actuator.
(5) JP,B 62-39295 entitled “Control System for Hydraulic Circuit Apparatus”
This publication discloses that the controller of the above-mentioned (4) is modified so as to detect a condition of the operating device (control lever) instructing the operation to be stopped or made in the reversed direction, and to set the setting maximum speed larger than that in acceleration.
DISCLOSURE OF INVENTION
The above-described prior art however has the following problems.
First problem: The setting value for restricting the maximum operating speed of the operational valve (flow control valve) (i.e., the maximum change rate of the operational signal) is not set corresponding to individual operating status, i.e., acceleration, deceleration/stop, and lever-reversed condition. Therefore, the operational valve cannot be always controlled at an optimum maximum change rate adapted for the operating status of a construction machine.
Second problem: In the lever-reversed operation, the dead zone in the vicinity of a neutral position of the flow control valve is not appropriately handled or not handled at all. When quickly reversing the control lever, therefore, the actuator undergoes a shock or stalls in the vicinity of the neutral position, causing the operator to feel a pause in the operation.
Third problem: Since the maximum change speed of the operational valve is just restrained to the fixed modulation pattern regardless of the input amount upon shift of the control lever, an appropriate acceleration/deceleration feeling corresponding to the lever shift amount cannot be provided.
More specifically, in Japanese Patent No. 2509311 and JP,B 7-107279, the modulation patterns are set for the maximum operating speed of the operational valve in acceleration and deceleration/stop, and in the lever-reversed operation, the maximum operating speed of the operational valve is restricted in accordance with the modulation pattern for deceleration/stop. However, the lever reversing is performed when it is required to quickly change the moving direction of the working device in the case of, e.g., dropping mud from a bucket, bumping a boom against a vertical surface, or avoiding a risk, and a rapid response is demanded until the working device changes the moving direction. Accordingly, restricting the maximum operating speed of the operational valve in the lever-reversed operation in accordance with the modulation pattern for deceleration/stop cannot be the as providing an optimum maximum operating speed for the lever-reversed operation, and hence cannot change the moving direction of the working device with a good response (first problem).
Also, according to JP,B 7-107279, as soon as the operational signal indicates a reversed direction, the modulation control performed so far is ce

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