JPH0431327Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a drive control device for a swing driving body such as a hydraulic excavator.

(Prior art) The applicant had previously developed a device of this type in the
As seen in Publication No. 58-25907, a variable displacement hydraulic pump and a hydraulic motor are provided, and pressure from an external pilot pressure source is introduced into a discharge amount control cylinder provided in the hydraulic pump through a throttle switching valve. In a closed hydraulic circuit configured to control the discharge amount of the hydraulic pump, a pressure difference between the supply side and the return side of the closed hydraulic circuit and a circuit connected to the external pilot pressure source are provided. a first control section operated by the pressure from the joystick valve to control the operation of the external pilot pressure source; A second control section for applying pressure to the throttle switching valve to perform the switching operation has been proposed.

(Problems to be solved by the invention) In the above proposal, the discharge flow rate of the variable displacement hydraulic pump can be controlled by slightly tilting the lever of the joystick valve, and by tilting the joystick valve lever greatly. It is possible to control the circuit pressure of a closed hydraulic circuit. The switching between these two controls is automatically performed by the second control section of the two-position valve, which switches depending on the balance between the pressure controlled by the joystick valve and the spring force. There is a problem in that it is not possible to arbitrarily select only one control to control the entire range of tilting operation of the joystick valve.

The present invention aims to solve these inconveniences.

(Means for Solving the Problems) In the present invention, as described above, an external pilot pressure source is introduced into the discharge amount control cylinder of a variable displacement hydraulic pump provided in a closed hydraulic circuit via a throttle switching valve. In a device in which pressure is controlled and introduced by a first control section and a second control section, the second control section
The control section is provided with a pilot pressure circuit for selecting either the pressure of the external pilot pressure source or the pressure from the joystick valve, and the pilot pressure circuit is switchably connected to the tank and the pilot pressure source. The above-mentioned problem was solved by providing a switching valve.

(Function) When the switching valve of the pilot pressure circuit for causing the second control section to perform a selective operation is in the position connected to the tank, when the joystick valve is operated, the pressure controlled thereby is transferred to the first control section. It also acts on the throttle switching valve via the second control section. At this time, the first control section operates and directs pressure from the external pilot pressure source to the second control section, but
Since the pressure in the pilot pressure circuit corresponds to the tank pressure, the second control section directs the pressure from the joystick valve to the throttle switching valve, and the external pilot pressure source via the first control section is not selected. Therefore, the throttle switching valve is operated in accordance with the lever operation angle of the joystick valve, and pressure from an external pilot pressure source is introduced into the discharge amount control cylinder via the throttle switching valve so that the cylinder is operated to a desired position. Therefore, the speed of the hydraulic motor can be controlled by causing the variable displacement hydraulic pump to discharge a discharge amount according to the operation of the joystick valve.

When the switching valve is switched so that the pilot pressure circuit to the second control section is connected to an external pilot pressure source, and the joystick valve is operated, the first control section is actuated by the pressure from the joystick valve and connects to the external pilot pressure source. pressure is guided to the second control section. The second control is moved to select the pressure from the first control with the pressure in the pilot pressure circuit, so that the external pilot pressure source pressure from the first control is routed through the second control. The throttle switching valve is operated to switch this, and this switching causes the pressure of the external pilot pressure source to be introduced into the discharge amount control cylinder, the hydraulic pump discharges fluid into the closed hydraulic circuit, and the hydraulic motor is driven. In this case, when the hydraulic motor is started and the pressure in the closed hydraulic circuit becomes equal to the pressure from the joystick valve, the first control section closes and stops guiding the pressure from the external pilot pressure source to the second control section, so that the throttle switching The valve returns to the neutral position, the discharge amount control cylinder maintains the moved position, the pressure in the closed hydraulic circuit is automatically kept constant, and the hydraulic motor can be driven with a constant torque.

The switching valve of the pilot pressure circuit can also be operated during operation of the joystick valve, and can be arbitrarily switched between discharge amount control and circuit pressure control while the hydraulic motor is being driven.

(Example) Embodiments of the present invention will be described based on the drawings.

In FIG. 1, reference numeral 1 is a variable displacement hydraulic pump, 2 is a hydraulic motor connected to rotate the bucket or other rotating body of the power shovel, and 4, 5 are
is a circuit connecting these pump 1 and motor 2, and the pump 1, motor 2, and circuits 4 and 5 form a closed hydraulic circuit 6.

Reference numeral 7 indicates a discharge amount control cylinder provided in the hydraulic pump 1 to control its discharge amount, and the operation of the control cylinder 7 is controlled by the throttle switching valve 8, the first control section 9, and the second control section 10. be done.

Reference numeral 11 denotes an external pilot pressure source consisting of, for example, a fixed capacity pump, and this pressure source 11 replenishes fluid to the closed hydraulic circuit 6 via a charge valve block 14 consisting of check valves 12a, 12b and a relief valve 13. At the same time, pressure fluid is supplied to the throttle switching valve 8, the first control section 9, and the joystick valve 16 through the pilot circuit 15, respectively.

The joystick valve 16 includes, for example, two pressure reducing valves 17 and 18 and a tilting lever 19 as shown in the figure, and by tilting the tilting lever 19 from side to side, the set pressure of each pressure reducing valve 17 and 18 can be adjusted. Any reduced fluid pressure is taken out from the pressure reducing circuits 20, 21 of each valve 17, 18 in a variable manner.

The first control section 9 includes a piston 22a on one end, on which the pressure of the circuit 4 of the closed hydraulic circuit 6 acts, and a piston 23a, on which the pressure from one of the pressure reducing valves 17 of the joystick valve 16 acts, and on the other end. , the piston 22 on which the pressure of the circuit 5 of the closed hydraulic circuit 6 acts
b and a piston 23b on which the pressure from the other pressure reducing valve 18 acts, and when the switching valve 24 slides to the left or right, the pilot circuit 15 from the pilot pressure source 11 is shut off or the second control section 1
Change direction to 0 and connect.

The second control section 10 also operates a pilot pressure circuit at positions 25 and 26 to select either the pressure from the external pilot pressure source 11 via the first control section 9 or the pressure from the joystick valve 16. The switching valve 28 is operated by the pressure from the pilot pressure circuit 27.
7 to tank 32 and external pilot pressure source 11. Second control unit 1
The secondary pressure selected by 0 is the circuit 33a, 33
b to each end of the throttle switching valve 8 for controlling its operation.

The throttle switching valve 8 controls the pressure of the pilot circuit 15 acting on the discharge amount control cylinder 7 with the pressure from the second control section 10, but when the throttle switching valve 8 is in the neutral position 34, the pilot circuit 16 to keep the discharge amount control cylinder 7 immobile, and when it is at position 35 or 36, move the cylinder 7 to the right or left, and accordingly change the discharge amount and discharge amount of the pump 1. The direction is adjusted, and at intermediate positions between the positions, the flow rate passing from the pilot pressure source 11 is throttled in accordance with the distance traveled.
37 is a crossover relief device.

The operation in the above embodiment is as follows.
First, when the hydraulic motor 2 is stopped and the lever 19 of the joystick valve 16 and the switching valve 29 are not operated, no pressure is generated in each pressure reducing circuit 20, 21, and the circuits 4, 5 of the closed hydraulic circuit 6 Since no pressure is generated in either, the first control section 9 and the second control section 10 remain in the positions shown in the first figure, and no secondary pressure is generated in the circuits 33a and 33b to the throttle switching valve 8. Therefore, in this case, the throttle switching valve 8 maintains the neutral position 34, and the pressure from the external pilot pressure source 11 does not act on the discharge amount control cylinder 7. Since the control cylinder 7 is not operated, the hydraulic pump 1 becomes zero, and the hydraulic motor 2 is not driven. In this case, even if an external force acts on the stopped hydraulic motor 2 to rotate it and pressure is generated in the closed hydraulic circuit 6, for example, in the circuit 4, the switching valve of the second control section 10 28 does not move, the throttle switching valve 8 and the discharge amount control cylinder 7 also do not move, and no flow is discharged from the hydraulic pump 1, so rotation of the hydraulic motor 2 due to external force can be prevented.

For example, when the lever 19 of the joystick valve 16 is tilted to the right in the drawing at a certain inclination angle, a pressure corresponding to the inclination angle is generated in the pressure reducing circuit 20 by the pressure reducing valve 17, and this pressure is applied to the piston 23a of the first control section 9.
It also acts on the throttle switching valve 8 via the second control section 10 and the circuit 33a. The throttle switching valve 8 moves to a position corresponding to the pressure in the circuit 33a, and the pressure from the external pilot pressure source 11 acts on the discharge amount control cylinder 7 to move it.
The hydraulic pump 1 gradually increases the flow rate delivered to the closed hydraulic circuit 6 according to the movement of the control cylinder 7, and drives the hydraulic motor 2. The control cylinder 7 stops when it moves by a distance corresponding to the movement distance of the throttle switching valve 8, so the discharge amount of the hydraulic pump 1 becomes constant. The speed of the hydraulic motor 2 can be controlled.

In the state shown in FIG. 1, when the switching valve 29 is energized to position 31 and the pressure of the external pilot pressure source 11 is introduced into the pilot pressure circuit 27, the second control section 10 is switched to position 25. After that, when the joystick valve 16 is operated to generate pressure in the pressure reducing circuit 20, the first control section 9 is switched and the pressure of the external pilot pressure source 11 is changed to the pilot circuit 1.
5 acts on the throttle switching valve 8 via the first control section 9 and the second control section 10, so the throttle switching valve 8 moves to the switching position, and the discharge amount control cylinder 7 accordingly moves to the switching position. Hydraulic pump 1 is actuated with pressure from an external pilot pressure source 11 via 8.
A flow rate is discharged from the closed hydraulic circuit 6 to, for example, the circuit 4. In this case, when the torque of the hydraulic motor 2 is large, the pressure in the circuit 4 also increases, but this pressure is guided to the piston 22a of the first control section 9, and the force due to this pressure acts on the piston 23a in the pressure reducing circuit 20. The first is that the force is equal to or greater than the force due to pressure.
The control unit 9 automatically returns to the neutral position.

As a result, the circuits 33a, 33 to the throttle switching valve 8
b is sealed and the throttle switching valve 8 is locked in its moving position, so the movement of the cylinder 7 is stopped and the discharge amount of the hydraulic pump 1 stops increasing and becomes constant. If the pressure in the circuit 4 drops, the first control section 9 opens again and introduces the pressure from the external pilot pressure source 11 into the throttle switching valve 8, so that the control cylinder 7 moves again and the hydraulic pump 1 is activated. The discharge amount increases, and as a result, the pressure in the circuit 4 becomes equal to the pressure from the pressure reduction circuit 20, and the first control section 9 closes. This operation reduces the pressure in the circuit 4 to the joystick valve 16.
The hydraulic motor 2 can be controlled to a constant pressure according to the operation, and the hydraulic motor 2 can be driven with a constant torque.

For example, a switch for controlling the switching valve 29 may be provided attached to the lever 19 of the joystick valve 16, and the switching valve 29 may be operated while the hydraulic motor 2 is being driven to switch between circuit pressure control and discharge flow rate control. It is possible.

In the previously proposed patent publication No. 58-25907, when circuit pressure control is entered, regardless of whether the drive torque of the hydraulic motor is large or small, if the torque is higher than the rotational resistance during high-speed operation, the hydraulic motor will continue to operate up to the maximum speed. The rotation speed of increases. The magnitude of the torque value controls the magnitude of the acceleration time, and in actual use, when the acceleration force is small, that is, when the torque value is small and it takes a long time to accelerate, the steady state of the hydraulic motor When the operating speed is low and the acceleration force is large, that is, when the torque value is large and the time required for acceleration is short, a control that increases the steady operating speed is required, and this cannot be met with the previous proposal. . However, in the present invention, the steady operating speed can be changed arbitrarily by switching the switching valve 29, and the controllability of the hydraulic motor 2 can be improved.

Curves A, B, and C in FIG. 2 indicate that the hydraulic motor 2 is initially driven by circuit pressure control with the switching valve 29 placed in position 31, and after a certain period of time t ₁ or t ₀ , the switching valve 24 is placed in position 30. When the angle of inclination of the lever 19 of the joystick valve 16 is small, curve A is obtained, and when the angle of inclination is large, control as shown in curves B and C is obtained. It starts with acceleration with a torque proportional to the operating inclination angle, and when it reaches a speed proportional to the operating inclination angle, it switches to discharge amount control and the hydraulic motor 2
It is possible to control the speed at a constant speed.

(Effects of the invention) As described above, according to the invention, the throttle switching valve that controls the discharge amount control cylinder of the hydraulic pump in the closed hydraulic circuit provided with the hydraulic motor is controlled by the first control unit operated by the joystick valve. and a second control section that performs pressure selection operation, by providing a pilot pressure circuit in the second control section and connecting it to the tank and an external pilot pressure source. Since the selection operation is carried out, the switching valve can be arbitrarily operated to select and drive the hydraulic motor of the closed hydraulic circuit between discharge flow rate control and circuit pressure control, regardless of the operation state of the joystick valve. The present invention has the following effects: it can improve the controllability of the hydraulic motor, and its structure is relatively simple and can be manufactured at low cost.

[Brief explanation of drawings]

FIG. 1 is a diagram of an embodiment of the present invention, and FIG. 2 is a diagram of control characteristics according to the present invention. DESCRIPTION OF SYMBOLS 1... Variable displacement hydraulic pump, 2... Hydraulic motor, 6... Closed hydraulic circuit, 7... Discharge amount control cylinder, 8... Throttle switching valve, 9... First control section, 10
... second control section, 11 ... external pilot pressure source, 16 ... joystick valve, 27 ... pilot pressure circuit, 28 ... switching valve.

Claims (1)

[Scope of utility model registration request] Equipped with a variable displacement hydraulic pump and a hydraulic motor,
A closed hydraulic circuit that controls the discharge amount of the hydraulic pump by introducing pressure from an external pilot pressure source to a discharge amount control cylinder provided in the hydraulic pump via a throttle switching valve, is connected to the supply side and the return side of the closed hydraulic circuit. a first control section that controls the action of the external pilot pressure source by being controlled by a pressure difference between both side circuits and a pressure from a joystick valve provided in a circuit connected to the external pilot pressure source; A second control section that selects either the pressure of the pilot pressure source or the pressure from the joystick valve and causes the selected pressure to act on the throttle switching valve to perform the switching operation thereof. The second control section is provided with a pilot pressure circuit for performing the selection operation, and a switching valve is provided for switchingly connecting the pilot pressure circuit to the tank and the external pilot pressure source. swing drive control device.