JPS5825907B2 - Swing drive control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a drive control device for a swing drive body used in a hydraulic excavator or the like.

In conventional hydraulic excavators, it is common for the boom, arm, packet, etc. to be raised and raised and other operations and swing operations to be performed at the same time.

However, when performing such a combined operation, interference with the hydraulic pressure source tends to occur, making it impossible to perform the combined operation smoothly.

Therefore, the following swing independent drive type was proposed, which gives priority to the swing operation over other operations and is driven so as to be completely unaffected by other operations.

First of all, when the swing circuit is open, a directional control valve C is inserted in the circuit connecting the swing pump a and the swing motor b as shown in the first diagram, and the switching operation is performed by, for example, two valves. This is done by the fluid pressure of an external pilot pressure source g that acts through a joystick valve f that is equipped with a pressure reducing valve d1d and a lever e that controls the degree of pressure reduction, and by tilting the lever e of the joystick valve f. A reduced pressure fluid is obtained in one side of the pilot circuit h y t, and a pressure fluid with a higher pressure is obtained in the other, and the pressure difference between them causes the control valve C to be switched.According to this, the discharge amount of pump a is Since the speed is controlled by the directional control valve C without any control, there are drawbacks such as large power loss, generation of heat in the fluid, and poor controllability.

In addition, when the discharge amount of the swing hydraulic pump j installed in the closed hydraulic circuit is arbitrarily controlled in proportion to the pressure of the external pilot pressure source as shown in the second diagram, the discharge amount of the pump j can be precisely controlled. However, when trying to rapidly accelerate the hydraulic motor 1 and pushing the lever of the joystick valve to the maximum, the hydraulic pump d
When the discharge amount reaches its maximum and the hydraulic motor 1 reaches its maximum speed, the unnecessary amount of oil is returned to the tank via the pressure control valve, which requires a large output and has the disadvantage of generating a large amount of heat at startup. be.

Furthermore, as shown in FIG. 3, there is also known a system in which the pump discharge amount is controlled to be constant at a value proportional to the discharge pressure of the swing pump m and the external pilot pressure source n. The circuit pressure required for the supply side circuit of motor O is determined by the size of the load, the required speed, and the cutting edge speed, but the pressure can be maintained constant even if the load condition changes, and the inclination angle of the lever of joystick valve P Since it is possible to make the pressure on the pump discharge side proportional to the pressure on the pump discharge side, only torque is required, and when starting a rotation at a low speed, that is, when the pump discharge pressure is high but the flow rate may be small, the pump m has the amount necessary to maintain the pressure. This has the advantage of reducing output loss and heat generation.

However, if excavation or other work is carried out with the lever of the joystick valve p in the neutral position, the external force will cause the rotating body to rotate in the direction of rotation, resulting in a serious danger.

The cause of this is that the angle of inclination of the lever of the joystick valve p is proportional to the pump discharge pressure.In order to correct this defect, it would be possible to install a parking brake on the motor 0, but this would complicate the hydraulic circuit. This raises the problem of increased costs, and it is difficult to know when to activate the brake, resulting in operational inconvenience.

It is an object of the present invention to provide a swing drive control device that eliminates the disadvantages of the conventional example, and is equipped with a variable displacement hydraulic pump and a hydraulic motor, and a discharge amount control device provided on the hydraulic pump. In a closed hydraulic circuit that controls the discharge amount of the hydraulic pump by introducing pressure from an external pilot pressure source into the cylinder via a throttle switching valve, both the supply side and return side circuits of the closed hydraulic circuit are a first control section that is actuated by a pressure difference and two pressures from a joystick valve provided in a circuit connected to the external pilot pressure source to control the action of the external pilot pressure source; operated by a pressure difference between two pressures to select either the pressure of the external pilot pressure source or the two pressures from the joystick valve, and to cause the selected pressure to cause the throttle switching valve to perform a switching operation therebetween. The invention is characterized in that it includes a second control section that operates the control section.

The fourth embodiment of the present invention will be described with reference to the attached drawings.
In the figure, 1 is a variable displacement hydraulic pump, 2 is a hydraulic motor connected to the power shovel packet or other swinging body for rotation, and 4 and 5 are circuits connecting pump 1 and motor 2. Pump 1, motor 2, and circuits 4 and 5 constitute a closed hydraulic circuit 6.

Reference numeral 7 indicates a discharge amount control cylinder that controls the discharge amount of the pump 1, and the operation of the cylinder 7 is controlled by the throttle switching valve 8, the first control section 9, and the second control section 10.

11 is an external pilot pressure source consisting of, for example, a fixed capacity pump, and this pressure source 11 is connected to the closed hydraulic circuit 6 with a check valve 12.
, 13 and a relief valve 14, and supplies pressure fluid to the throttle switching valve 8 and first control section 9 via a pilot circuit 16. also supplies pressure fluid.

The joystick valve 17 includes, for example, two pressure reducing valves 18 and 19 and a tilting lever 20, as shown in the figure, and by tilting the tilting lever 20 left and right, each pressure reducing valve 18,
Each setting pressure of 19 is changed and an arbitrary reduced fluid pressure is taken out from each pressure reducing circuit 2L22 of joint valve 18 and 19.

The first control section 9 has one end on which the pressure of the circuit 4 of the closed hydraulic circuit 6 and the pressure from one of the pressure reducing valves 18 of the joystick valve 17 act, and the other end of which the pressure of the circuit 4 of the closed hydraulic circuit 6 acts. 5
The switching valve 23 is composed of a switching valve 23 to which the pressure from the pressure reducing valve 19 and the pressure from the other pressure reducing valve 19 act, and when the switching valve 23 slides to the left or right, the pilot circuit 16 of the pilot pressure source 11 is shut off or the direction is directed to the second control unit 10. Change and connect.

Further, the second control unit 10 includes a switching valve 28 that extracts high pressure from one of the pressure reducing circuits 2L22 from the joystick valve 17 using a shuttle valve 25, and switches from position 26 to position 27 using the high pressure. According to the switching operation, the pressure of each fluid in the pressure reducing circuit 2L22 is throttled and applied to both ends of the switching valve 8, or the pressure of the pilot circuit 16 from the first control section 9 is applied to one end of the throttle switching valve 8. At the same time, the other end is communicated with the knob 29, and the pressure of the pilot circuit 16 or the two pressures of the joystick valve 17 are selected and applied to the throttle switching valve 8.

The throttle switching valve 8 controls the pressure of the pilot circuit 16, that is, the pressure of the pilot pressure source 11, acting on the discharge amount control cylinder 7 with the pressure from the second control unit 10, but the switching valve 8 is in the neutral position 30. When it is in position 31 or 32, the pressure in the pilot circuit 16 is cut off and the discharge amount control cylinder 7 is immobilized, and when it is in position 31 or 32, the cylinder 7 is moved to the right or left, and the pump is accordingly moved. The discharge amount and discharge direction of the pilot pressure source 11 are adjusted, and at an intermediate position between the pilot pressure sources 11 and 11, the flow rate passing from the pilot pressure source 11 is throttled in accordance with the moving distance.

33 is a crossover relief device.

To explain its operation, when the lever 20 of the joystick valve 17 is not operated, the pressure of the pilot pressure source 11 is reduced by each pressure reducing valve 18, 19 to its set pressure of zero, and the pressure is applied to each pressure reducing circuit 2L22. Since this does not occur, the switching valve 28 of the second control unit 10 is not switched by the reduced pressure in the pressure reducing circuit 21 or 22 extracted via the shuttle valve 25, and its position 26 is maintained.

In addition, in this case, the switching valve 23 of the first control section 9 is configured so that a pressure difference above a certain level is generated between the supply side circuit and the return side circuit 5 of the closed hydraulic circuit 6 due to an external force acting on the hydraulic motor 2. ,
The differential pressure may cause the external pilot pressure source 11 to operate to communicate the pressure to the second control section 10, but since the switching valve 28 of the second control section 10 maintains the position 26, the pressure The pressure of the source 11 is shut off in the second control section 10.

Therefore, in this case, the pressure from the pilot circuit 16 does not act on the cylinder 7 via the throttle switching valve 8, and the cylinder 7 does not operate, so the discharge amount of the hydraulic pump 1 becomes zero and is not connected to the packet etc. The hydraulic motor 2 is in a stopped state.

Also, while the hydraulic motor 2 is stopped, even if an external force is applied to the excavator or the like in the direction of rotation, the cylinder 7 will not be activated and the flow rate in the closed hydraulic circuit 6 will not change, so there will be no accidental rotation. , the turning can be prevented without installing a parking brake or the like.

When the lever 20 of the joystick valve 17 is tilted slightly, for example, the set pressure of the pressure reducing valve 19 becomes a little higher, and the pressure reducing valve 18 reduces the pressure with the pressure remaining at zero, but in this case, the pressure is extracted via the shuttle valve 25. Since the pressure in the pressure reducing circuit 22 is small, the switching valve 28 of the second control part 10 is not moved from the position 26, and the pressure in both pressure reducing circuits 21, 22 is transferred via the second control part 10 to both ends of the throttle switching valve 8. act.

The throttle switching valve 8 slides a small amount in response to the small pressure difference between the two pressure reducing circuits 21 and 22, and a small flow rate corresponding to the sliding distance is transferred from the pilot circuit 16 to the discharge amount control cylinder 7.
Since the discharge amount of the hydraulic pump 1 can be slightly changed in response to a small tilt angle of the joystick valve 17, this is convenient for precision operations such as inching operations of a rotating structure.

Further, when the lever 20 of the joystick valve 17 is tilted greatly, for example, the set pressure reduction of the pressure reducing valve 19 increases significantly, and the pressure reducing valve 18 is in a reduced pressure state of zero pressure, but in this case, the differential pressure between the pressure reducing circuits 21 and 22 also increases. Since the pressure extracted from the shuttle valve 25 is also large, the switching valve 28 of the second control part 10 is switched to position 27, and at the same time the switching valve 23 of the first control part 9 is also switched, for example, to the left switching position. The pressure in the pilot circuit 16 acts to greatly move the throttle switching valve 8 toward the position 31, and a large flow rate flows into the cylinder 7 from the pilot circuit 16 via the switching valve 8.

In this way, the hydraulic pump 1 changes its discharge amount significantly depending on the inclination angle of the lever 20, causing the rotating structure to rapidly rotate.

Note that even if the lever 20 of the joystick valve 17 is operated greatly to increase the discharge amount of the pump 1 when the load is large, the load pressure of the supply side circuit 4 is high, so the switching valve 23 of the first control section 9 remains neutral. The pump 1 automatically enters the position or the right position and performs control according to the pressure of the closed hydraulic circuit 6, and the pump 1 does not discharge more flow than necessary into the circuit 6, resulting in less power loss and less fluid heat generation. It operates conveniently during load fluctuations and acceleration start-up.

In this way, according to the present invention, the first control section is operated by the circuit pressure of the closed hydraulic circuit and the pressure from the joystick valve, and the second control section is operated according to the pressure controlled by the joystick valve. The second control section selectively selects the pressure of the pilot circuit and the pressure from the joystick valve to act on the throttle switching valve that controls the operation of the discharge amount control cylinder. The control section performs pressure constant control that controls the pump discharge amount to keep the pressure of the closed hydraulic circuit constant, and the second control section performs pressure proportional control that controls the pump discharge amount according to the pressure from the joystick valve. , it is possible to prevent accidental rotation of the rotating body without installing special equipment, it is possible to improve safety easily and inexpensively, and it is possible to perform precise operation control such as inching operation,
There are effects such as the ability to obtain a swing drive control device with less fluid heat generation and less output loss.

[Brief explanation of the drawing]

1 to 3 are diagrams of a conventional device, and FIG. 4 is a diagram of an embodiment of the device of the present invention. 1......variable displacement hydraulic pump, 2...
......Hydraulic motor, 4,5......Circuit, 6......Closed hydraulic circuit, 7......
. . . Discharge rate control cylinder, 8 . . . Throttle switching valve, 9 . . . First control section, 10 .
. . . Second control section, 11 . . . External pilot pressure source, 17 . . . Joystick valve.

Claims (1)

[Claims] 1. Equipped with a variable displacement hydraulic pump and a hydraulic motor, and controlling the discharge amount of the hydraulic pump by introducing pressure from an external pilot pressure source into a discharge amount control cylinder provided on the hydraulic pump with a throttle switching valve. In the closed hydraulic circuit of the formula, the pressure is actuated by the pressure difference between the supply side and the return side of the closed hydraulic circuit, and two pressures from a joystick valve provided in the circuit connected to the external pilot pressure source. a first control section that controls the operation of the external pilot pressure source; and a first control section that is actuated by a pressure difference between two pressures from the joystick valve to control either the pressure of the external pilot pressure source or the two pressures from the joystick valve. A swing drive side device comprising: a second control section that selects a pressure and applies the selected pressure to the throttle switching valve to perform the switching operation thereof.