JP2613131B2 - Output control device for hydraulic pump - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic drive device mounted on a construction machine such as a hydraulic excavator, and more particularly to a differential pressure between a discharge pressure of a hydraulic pump and a load pressure of an actuator. The present invention relates to an output control device of a hydraulic pump in a load sensing system that controls a discharge amount of the hydraulic pump such that the output value is maintained at a set value.

2. Description of the Related Art Conventionally, in a hydraulic drive device mounted on a hydraulic excavator or the like, matching between output torque of an engine and absorption torque of a variable displacement hydraulic pump (hereinafter referred to as a pump) is always maintained in an optimum state. For this reason, some systems use a combined engine / pump control system that controls the pump discharge amount in response to fluctuations in engine rotation due to pump load.

FIG. 5 shows an example of this, in which a governor motor 4 is connected via a rod 3 to a governor lever 2a of a fuel injection pump 2 attached to the engine 1, a potentiometer 5 for detecting the operating angle of the governor motor 4, and the power of the engine 1. mode
A power mode switch 9 for selecting H, S, and L, a fuel dial 8, and an electromagnetic proportional pressure control valve (hereinafter referred to as a TVC valve) 12 for controlling the discharge amount of the pump 10 are connected to the controller 6 by wiring.

A change in the engine speed due to a change in the load of the pump 10 is detected by a rotation speed sensor 7 and an output signal of the fuel dial 8 and input to the controller 6. The controller 6 calculates based on the input signal and outputs the result to the TVC valve 12 as a signal. The TVC valve 12 controls the pump discharge amount via the servo valve 11 so that the engine output torque and the pump absorption torque are calculated. We always match best.

[Problems to be Solved by the Invention] For example, excavating earth and sand using a hydraulic excavator, scooping it into a bucket, turning the upper rotating body while raising the boom, and loading the earth and sand into a dump truck, After that, the next work cycle is performed, and the required pump output is greatly different from the case of turning while lowering the boom. However, in the above-described pump output control device, the pump is controlled in accordance with the content of the single operation of each work machine or the simultaneous combined operation of two or more work machines and devices in such a series of work, and the operation amount of the operation lever. The output cannot be controlled. Therefore, there is a problem that wasteful energy is consumed depending on the operating machine / device operated.

The present invention pays attention to the above-mentioned conventional problems, and can change the pump output to an optimum state in accordance with the operating machine / device to be operated and the operation content, thereby preventing unnecessary energy consumption. It is an object to provide such an output control device for a hydraulic pump.

Means for Solving the Problems To achieve the above object, an output control device for a hydraulic pump according to the present invention controls a variable displacement hydraulic pump driven by an engine and an output of the variable displacement hydraulic pump. An electromagnetic proportional pressure control valve, a plurality of hydraulic actuators such as a boom, an arm, or a swivel driven by pressure oil discharged from the variable displacement hydraulic pump, and a pressure supplied to the plurality of hydraulic actuators from the variable displacement hydraulic pump. A plurality of directional control valves for controlling the flow of oil, and a plurality of operating levers connected to each directional control valve and switching the directional control valve, independently operating a plurality of hydraulic actuators such as a boom, an arm or a swing, Alternatively, a variable displacement hydraulic pump may have a different negative In a hydraulic pump output control device in which a load acts and a variable displacement hydraulic pump outputs different horsepower, a means for detecting an operation direction and an operation amount of an operation lever; The required output of the variable displacement hydraulic pump is determined by detecting the operation direction and the operation amount, and when the output is changed, the output is gradually changed during a predetermined time to become the predetermined output after the change. A controller that outputs a signal, and outputs a signal by changing the length for a predetermined time according to the magnitude of the output to be changed,
When the output is changed, the pressure control valve controls the output of the variable displacement hydraulic pump so as to gradually change during a predetermined time according to a command signal from the controller and to obtain the predetermined output after the change.

[Operation] According to the above configuration, means for detecting an operation direction and an operation amount of the operation lever for driving the hydraulic actuator and inputting the detected operation amount to the controller, a controller for outputting a command signal based on the detection result, and a controller A governor motor that controls the engine output based on the output signal and an electromagnetic proportional pressure control valve that controls the output of the pump are configured. Therefore, the output of the engine and the pump depends on the type of actuator operated by the operator and the combination. Can be changed.

In addition, when changing the pump output, it was made to change smoothly over a preset time,
It is possible to reduce a decrease in engine rotation due to an increase in pump output and a shock applied to an actuator, a working machine, and the like.

Embodiment An embodiment of an output control device for a hydraulic pump according to the present invention will be described below in detail with reference to the drawings.

FIG. 1 schematically shows a pump discharge volume variable circuit in a load sensing system used in a hydraulic drive device of a hydraulic excavator. A governor motor 4 is connected via a rod 3 to a governor lever 2a of a fuel injection pump 2 attached to the engine 1. Wiring of the governor motor 4 and wiring of a potentiometer 5 for detecting an operating angle of the governor motor 4 are transmitted to a controller 6. It is connected. Wirings of a rotation speed sensor 7 for detecting the engine rotation speed, a fuel dial 8 for controlling the engine rotation speed, and a power mode switch 9 for arbitrarily setting the output mode of the engine 1 are also connected to the controller 6.

As means for controlling the displacement of a pump 10 driven by the engine 1, a servo valve 11 for changing the swash plate angle is used.
And a TVC valve 12 for controlling the servo valve 11 are provided,
The solenoid of the TVC valve 12 is connected to the controller 6 via a wiring.

A boom, an arm, a work implement such as a bucket, a hydraulic actuator that drives a swing device that swings an upper swing body, and a direction switching valve 13 provided between a pump 10 are combined into one to form a circuit 14. It is connected to the pump 10.
A pilot circuit is connected to both ends of these directional control valves 13, and the other end of the pilot circuit is connected to a pilot pressure control valve (PPC valve) 16 operated by operating the operation lever 15.
It is connected to the. FIG. 1 shows a boom raising circuit 17, an arm excavation circuit 18, and a clockwise turning circuit 19 as examples of the pilot circuit. Each of these pilot circuits is provided with a pressure switch 20.
Are connected to the controller 6.

Next, the operation of the output control device of the hydraulic pump will be described. In the present embodiment, the pump output is, for example, 55 PS during turning, 75 PS when the boom and bucket are fixed and the arm is pulled forward to excavate, and the combined simultaneous operation of turning and boom raising is 85 PS. Control of pump output
This is performed by changing the signal current value sent from the controller 6 to the solenoid of the TVC valve 12 as shown in FIG. 2, and by operating the TVC valve 12 to control the servo valve 11, as shown in FIG. Thus, the pump output changes for each signal current value.

When excavation is over, earth and sand are scooped into the bucket, and when the upper revolving unit is swiveled while raising the boom to load this earth and sand into the dump truck, the pump output is 85
Requires PS. That is, 10PS for arm excavation
In this case, the pump output increase required time is set to 0.1 second.

When the dump truck completes loading the earth and sand and turns to the excavation position while lowering the boom for the next excavation, the pump output will be 55PS and the pump output will be reduced by 30PS. The time required is also 0.
It is set to 1 second. Next, the setting output when excavating the arm is 7
Since it is 5PS, it will increase by 20PS, but in this case, the required time for increasing the output is set to 0.5 seconds, and it is changed smoothly as shown in Fig. 4 to reduce the engine speed due to the increase in load. In addition, a shock caused by a sharp rise in output is prevented. In this embodiment, 55
Time required only when upgrading from PS to 75PS and 85PS
0.5 seconds, all other up and down was set to 0.1 seconds.

In this embodiment, a pressure switch is provided in the pilot circuit of the direction switching valve as means for detecting the operation direction and the operation amount of the operation lever for driving the actuator.However, the present invention is not limited to this. For example, an electric / hydraulic or mechanical detecting means can be used.

The present invention can be applied to any of a hydraulic drive device using an open center load sensing system and a hydraulic drive device using a closed center load sensing system.

[Effects of the Invention] As described above, according to the present invention, which operation lever is operated by the operator and how much is input to the controller, and the controller sends a command signal to the engine and the pump based on the detection result. Because it was configured to output,
The pump output can be changed in several stages according to the type and combination of actuators operated by the operator. Therefore, if the optimal output is set for each operation pattern, the optimal output according to the work content can be obtained each time,
Since useless use of output is prevented, an energy saving effect can be obtained.

Also, when increasing the pump output, it was made to smoothly increase over a preset time,
It is possible to alleviate a decrease in engine rotation and an impact applied to an actuator, a working machine, and the like due to an increase in pump output, thereby reducing a physical load on an operator and preventing deterioration of the machine.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a hydraulic drive device including an output control device of a hydraulic pump according to an embodiment, FIG. 2 is a diagram showing a relationship between a current value sent from a controller to a TVC valve and a pump absorption horsepower, 3 is a diagram showing the pump output according to the current value, FIG. 4 is a diagram showing a change in the pump output and a current value acting on the TVC valve, and FIG. 5 is a schematic configuration diagram of a conventional hydraulic drive device. 1 ... Engine 4 ... Governor motor 6 ... Controller 10 ... Variable displacement hydraulic pump 12 ... Electromagnetic proportional pressure control valve (TVC valve) 13 ... Direction switching valve 15 ... Operation lever 16 ... Pilot pressure control valve (PPC valve)

Claims (1)

(57) [Claims] A variable displacement hydraulic pump driven by an engine, an electromagnetic proportional pressure control valve for controlling an output of the variable displacement hydraulic pump, a boom driven by pressure oil discharged from the variable displacement hydraulic pump, A plurality of hydraulic actuators such as an arm or a swing, a plurality of directional control valves for controlling the flow of hydraulic oil supplied from the variable displacement hydraulic pump to the plurality of hydraulic actuators, and a directional control valve connected to each directional control valve; It is equipped with a plurality of operating levers for switching, and is different from a variable displacement hydraulic pump when a plurality of hydraulic actuators such as a boom, an arm, a swivel, etc. are operated independently, or when any one of a plurality of hydraulic actuators is simultaneously operated simultaneously When a load is applied, the variable displacement hydraulic pump outputs a different horsepower to the output control device of the hydraulic pump. Te, means for detecting the operation direction and the operation amount of the operating lever,
The required output of the variable displacement hydraulic pump is determined by detecting the operating direction and the operating amount of the operated operating lever out of the plurality of operating levers. A controller that outputs a signal that changes gradually and outputs a predetermined output after the change, and that outputs a signal by changing the length of a predetermined time according to the size of the output to be changed; and A pressure control valve for controlling the output of the variable displacement hydraulic pump so as to gradually change during a predetermined time according to a command signal from the controller and to obtain a predetermined output after the change. Output control device.