JP2001193706A - Hydraulic circuit for hydraulic driving device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten the rising time of discharge pressure of a pump unit after switching from a stop state to a driving state, when a plurality of pump units are used as an oil pressure supply source, and a method for appropriately driving or stopping some of the pump units depending on operational conditions is adopted. SOLUTION: The plural pump units are used as the oil pressure supply source. Each pump unit is constituted of a motor and a plurality of hydraulic pumps. A constantly driven hydraulic pump PF11 among the hydraulic pumps is provided with a branch portion on its discharge side, and a pilot line connection pipe 30 is connected to the branch portion. The pilot line connection pipe 30 is connected to a pilot pressure supply line of hydraulic pumps PF21, PF22, PF24 belonging to other pump unit PF2X and a pressure supply line of hydraulic pump PF31, PF32, PF34 belonging to other pump unit PF3X. Thereby, even if the other pump units PF2X, PF3X are in a stop state, the pilot pressure for operation is constantly supplied to each of the hydraulic pumps.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic drive device using a plurality of pump units in combination as a hydraulic supply source, and more particularly to a configuration of a pilot pressure supply line for operating a hydraulic pump belonging to each pump unit. .

[0002]

2. Description of the Related Art In a hydraulic drive device such as an injection molding machine, a hydraulic drive mechanism is used for operating parts such as an injection plunger, a screw for measuring a raw material, and a mechanism for opening and closing a mold.
The hydraulic supply source of each hydraulic drive mechanism is usually constituted by a plurality of pump units, and these pump units are used in a state where they are connected to each other on the discharge side.
Each pump unit includes one electric motor and one or more hydraulic pumps driven by the electric motor.

[0003] The amount of oil to be supplied to the hydraulic supply line fluctuates in response to changes in operating conditions such as injection conditions. For this reason, conventionally, a relief valve and a proportional solenoid valve are provided in this order on the downstream side of the above-mentioned connecting portion, and the amount of oil supplied to the hydraulic supply line is controlled using the proportional solenoid valve, and excess hydraulic oil is relieved. It was returned to the tank via a valve.

On the other hand, Japanese Patent Application Laid-Open No. 5-338000 proposes an operation method for stopping the operation of some pump units in accordance with set operation conditions for the purpose of energy saving. ing. That is, according to this operation method, a combination of necessary hydraulic pumps is selected according to set operation conditions (for example, injection speed), and as a result, a pump that is not used at all during one injection cycle is selected. When a unit appears, the operation of the pump unit, and therefore the motor driving it, is stopped.

The above operation method will be further described with reference to FIGS.

FIG. 3 is an example of a hydraulic supply line having a plurality of actuators. In this example, three pump units (PF1X, PF2
X, PF3X), and each pump unit has one motor (motor 1, motor 2, motor 3)
And three hydraulic pumps (PF11, PF12, PF14; PF21, PF2) driven by this motor.
2, PF24; PF31, PF32, PF34).

The three hydraulic pumps belonging to each pump unit have different discharge capacities, and the large capacity hydraulic pumps (PF14, PF24, PF34) are different from the small capacity hydraulic pumps (PF11, PF21, PF31). Medium capacity hydraulic pumps (PF12, PF22,
PF32) are small capacity hydraulic pumps (PF11, PF2).
1, PF31).

Thus, for example, in a PF1X pump unit, PF11, PF12, PF12 + PF
11, PF14, PF14 + PF11, PF14 + PF
A combination of seven types of hydraulic pumps, 12, and PF14 + PF12 + PF11, is possible. From the minimum discharge capacity (when only the small-capacity hydraulic pump PF11 is used) to the maximum discharge capacity (all three hydraulic pumps are used) ), The discharge capacity can be adjusted in seven stages.

FIG. 4 shows the configuration of the pump drive hydraulic circuit 1 in FIG. The pump drive hydraulic circuits 2 and 3 have the same configuration.

In FIG. 4, for example, the combination of hydraulic pumps “PF12 + P
When "F11" is selected, the solenoid valves 11 and 12 are excited, and the solenoid valve 14 is demagnetized. As a result, the hydraulic oil discharged from the hydraulic pumps PF11 and PF12 becomes the electromagnetic valves 11 and 12 respectively.
To the actuator (FIG. 3) via the direction / flow / pressure control circuit. On the other hand, the hydraulic pump PF1
The hydraulic oil discharged from 4 is unloaded via the electromagnetic valve 14 and returned to the tank.

In the hydraulic supply line having the above configuration, a required combination of hydraulic pumps is selected based on set operating conditions, and then a pump unit corresponding to the selected combination of hydraulic pumps is provided. Selected. As a result, when none of the hydraulic pumps belonging to a certain pump unit is used during one injection cycle, the operation of the motor for driving the pump unit is stopped.

(Problems of the conventional operation control method) When the operation control method of repeating the driving and stopping of the pump unit based on the set operation conditions is adopted in the injection molding machine as described above, It turns out that a problem arises. That is, when the pump unit is switched from the stop state to the drive state, even if a drive command is transmitted to the drive motor of the pump unit, the hydraulic oil actually discharged from the pump unit reaches a predetermined pressure and flow rate. There is a large time delay before reaching.

The reason will be described by taking the case of a vane pump as an example.

FIG. 5 is a sectional view of the vane pump. The vane pump includes a cam ring 55, a rotor 51 rotating in the cam ring 55, and side plates 57 fixed to both side surfaces of the cam ring 55.

On the inner peripheral surface of the cam ring 55, two large arc portions 55a and two small arc portions 55b are respectively formed symmetrically. A large number of grooves 52 are radially formed on the outer periphery of the rotor 51, and vanes (blades) 53 are inserted into these grooves 52 in a state in which the vanes 53 can freely advance and retreat. As the rotor 51 rotates, the vane 53 jumps out due to centrifugal force, and the tip of the vane 53 comes into contact with the inner peripheral surface of the cam ring 55 and slides.

In the side plate 57, two suction ports 58 are formed symmetrically in the vicinity of a boundary portion (when viewed clockwise) from the small arc portion 55b of the cam ring 55 to the large arc portion 55a, and the large arc portion 55a is formed. Two discharge ports 59 are also provided symmetrically in the vicinity of the boundary part where the discharge port moves to the small arc portion 55b. A suction line 61 is connected to the suction port 58, and a discharge line 62 is connected to the discharge port 59.

With the rotation of the rotor 51, the vanes 53,
The volume of the small section surrounded by the rotor 51, the cam ring 55, and the side plate 57 expands and contracts. As a result, the hydraulic oil flows from the suction line 61 to the suction port 58.
, And is sucked into the above-mentioned small section, and sent out to the discharge line 62 through the discharge port 59.

Since the pressure in the pump acts on the tip of the vane 53, a force for pushing the vane 53 into the groove 52 is generated. To counter this force, a back pressure (pilot pressure) is applied to the base end of the vane 53 as follows. That is, the ring-shaped back pressure supply path 5 is provided inside the rotor 51.
4 are formed, and the back pressure supply path 54 is connected to the discharge line 62 via the pilot line 65. Each groove 5
The back of 2 opens into this back pressure supply path 54. In this way, a back pressure is applied to the base end of the vane 53 so as to oppose the pressure acting on the tip of the vane 53, whereby the vane 53
Is made to fly outward by centrifugal force.

In the above vane pump, when the operation of the vane pump is started, the pilot line 6
Since the pressure in the inside 5 is low, the vane 53 does not reliably jump out, so that it takes time until the pressure and flow rate on the discharge side line 62 side reach predetermined values.

Also, in the case of a swash plate (or swash shaft) piston pump, pilot pressure for controlling the inclination of the swash plate (or cylinder block) is not generated at the start of operation. In addition, the discharge flow rate becomes unstable.

[0021]

SUMMARY OF THE INVENTION The present invention relates to a hydraulic drive system using a plurality of pump units as a hydraulic supply source as described above. The object of the present invention is to speed up the rise of the discharge pressure of the pump unit switched from the stopped state to the driving state when such a method is employed. ,
Thereby, the hydraulic drive device connected to the hydraulic supply source is reliably operated.

[0022]

The hydraulic circuit of the hydraulic drive system according to the present invention is provided with a plurality of sets of pump units each including one electric motor and one or more hydraulic pumps driven by the electric motor. Depending on the operating conditions
Some of the hydraulic pumps are constantly used in the hydraulic circuit of the hydraulic drive device that switches the supply flow rate of hydraulic oil by operating some of the pump units and stopping other pump units. A branch is provided on at least one discharge side of the hydraulic pump, and a pilot pressure supply line of a hydraulic pump belonging to another pump unit is connected to the branch.

According to the hydraulic circuit of the hydraulic drive device of the present invention, the pilot pressure supply line of each hydraulic pump is maintained at a predetermined pressure while the hydraulic circuit is operating. Therefore, when the drive command is sent to the electric motor of the pump unit that is stopped, the hydraulic pump belonging to the pump unit can quickly reach the predetermined discharge pressure and discharge flow rate.

That is, according to the hydraulic circuit of the hydraulic drive device of the present invention, when the pump unit is switched from the stopped state to the driven state, the discharge pressure and the discharge flow rate rise quickly.

In the above-described hydraulic circuit, when there is no hydraulic pump that is constantly used, a branch is provided on the discharge side of the most frequently used hydraulic pump among all the hydraulic pumps. Section is connected to a pilot pressure supply line of a hydraulic pump belonging to another pump unit.

[0026]

FIG. 1 shows an example of a hydraulic circuit of an injection molding machine according to the present invention.

This hydraulic circuit has a plurality of actuators and three sets of pump units (PF
1X, PF2X, PF3X). Each pump unit has one motor (motor 1, motor 2, motor 3) and three hydraulic pumps (PF11, PF11,
PF12, PF14; PF21, PF22, PF24;
PF31, PF32, PF34).
In the figure, the configuration of the hydraulic circuit excluding the portion of the pilot line connection pipe 30 is the same as that of FIG. 3 described earlier in the section of "Prior Art", and therefore the description thereof is omitted.

In this example, a branch portion is provided on the discharge side of the small-capacity hydraulic pump PF11 belonging to the pump unit PF1X, and the pilot line connection pipe 30 is connected thereto. The pilot line connection pipe 30 is connected to each hydraulic pump (P) belonging to another pump unit (PF2X, PF3X).
F21, PF22, PF24; PF31, PF32, P
F34) is connected to a pilot pressure supply line (not shown).

It should be noted that another hydraulic pump (PF1) belonging to the same pump unit PF1X as the above-described hydraulic pump PF1
2, PF13) does not need to connect the pilot line connection pipe 30. If the motor 1 belonging to the pump unit PF1X is in a driving state, the hydraulic pump (PF1X
2, PF13) is in the unloaded state, the pilot pressure is maintained in each pilot pressure supply line.

As described above, the pilot line connection piping 3
0, while the hydraulic pump PF11 is in use, the other pump units (PF2X, PF3
The pilot pressure is also maintained in the pilot pressure supply line of the hydraulic pump belonging to X). Therefore, when a drive signal is sent to the drive motor of another stopped pump unit, the hydraulic pump belonging to that pump unit quickly reaches the predetermined discharge pressure and discharge flow rate.

That is, according to the hydraulic circuit of the injection molding machine, when the pump unit is switched from the stopped state to the driven state, the discharge pressure and the discharge flow rate can be quickly raised.

FIG. 2 shows an example in which the present invention is applied to a swash plate type piston pump.

In FIG. 2, a variable displacement pump unit PF11 includes a motor M1, a swash plate type piston pump 3 (main body), an operation actuator 4, a safety valve 6, a proportional electromagnetic three-way control valve 5, a control amplifier device 9, and the like. It is composed of The other variable displacement pump unit PF12 has the same configuration as the variable displacement pump unit PF11.

The swash plate type piston pump 3 is connected to the motor M1 (or M2) via the drive shaft 2. The swash plate type piston pump 3 is provided with an operation actuator 4 for changing a tilt angle of a swash plate (not shown) incorporated therein to control a discharge flow rate. The operation actuator 4 has an oil chamber one of which is partitioned by a piston, and the piston of the piston is controlled by a balance between a hydraulic pressure supplied to an oil chamber behind the piston and a reaction force of a spring disposed in front of the piston. The position moves, and the discharge flow rate of the swash plate type piston pump 3 is controlled. When the hydraulic pressure in the oil chamber is increased to advance the piston, the discharge flow rate decreases.
Reducing the oil pressure in the oil chamber and retracting the piston increases the discharge flow rate. The displacement (position of the piston) of the operation actuator 4 is detected by the displacement detector 7 and sent to the control amplifier device 9.

The hydraulic oil introduced from the branch provided in the discharge line 18 of the swash plate type piston pump 3 is supplied into the oil chamber of the operation actuator 4 via the proportional electromagnetic three-way control valve 5 and the safety valve 6. You. A pressure sensor 8 is arranged between the branch and the proportional electromagnetic three-way control valve 5.
This pressure sensor 8 detects the pressure of the discharge line 18.

In a normal state, the safety valve 6 communicates between the outlet port of the proportional electromagnetic three-way control valve 5 and the oil chamber of the operation actuator 4. When the pressure in the discharge line 18 becomes excessive, the supply of hydraulic oil from the proportional electromagnetic three-way control valve 5 to the operation actuator 4 is cut off, and the hydraulic oil is supplied directly from the discharge line 18 to the operation actuator 4. And the discharge amount of the swash plate type piston pump 3 is reduced.

The control amplifier device 9 has three amplifiers: a first amplifier 9a, a second amplifier 9b, and an output amplifier 9c. A set value of discharge pressure (set pressure 17) is input to the first amplifier 9a, and a set value (set flow rate) of discharge flow is input to the second amplifier 9b. The output side of the output amplifier 9c is connected to the solenoid 15 of the proportional electromagnetic three-way control valve 5. The control amplifier device 9 controls the amount of displacement of the operation actuator 4 by controlling the opening of the proportional electromagnetic three-way control valve 5 based on the output of the pressure sensor 8 and the output of the displacement detector 7, whereby The discharge pressure and the discharge flow rate of the variable displacement pump unit PF11 (or PF21) are controlled.

When the present invention is applied to a hydraulic supply line provided with a plurality of sets of variable displacement pump units as described above, the pilot line connection pipe 30 is branched from the discharge line of one of the variable displacement pump units PF11. The pilot line connection pipe 30 is connected to the pilot pressure supply line of the operating actuator 4 of the other variable displacement pump unit PF21.

As described above, the pilot line connection piping 30
When the motor M2 is stopped and the variable displacement pump unit PF21 is in the stopped state,
A pilot pressure is applied to the operation actuator 4 for driving the swash plate in the swash plate type piston pump 3. Therefore, when the motor M2 is switched from the stopped state to the driven state, the discharge flow rate does not become unstable.

[0040]

According to the hydraulic circuit of the hydraulic drive system of the present invention, when the pump unit is switched from the stop state to the drive state, the discharge pressure and the discharge flow rate rise quickly and do not become unstable. .

[Brief description of the drawings]

FIG. 1 is a diagram showing an example in which the present invention is applied to a hydraulic supply line of an injection molding machine.

FIG. 2 is a diagram showing an example in which the present invention is applied to a pump unit using a swash plate type piston pump.

FIG. 3 is a diagram showing an example of a hydraulic supply line of a conventional injection molding machine.

FIG. 4 is a diagram showing a configuration of a pump drive hydraulic circuit in FIG. 3;

FIG. 5 is a diagram showing a structure of a vane pump.

[Explanation of symbols]

 M1, M2: motor, 2: drive shaft, 3: swash plate type piston pump (main body), 4: actuator for operation, 5: proportional three-way electromagnetic control valve, 6: Safety valve, 7: Displacement detector, 8: Pressure sensor, 9: Control amplifier, 9a: First amplifier, 9b: Second amplifier, 9c: Output amplifier, 15. ··· Solenoid, 16: set flow rate, 17: set pressure, 18: discharge line, 19: pilot pressure supply line, 30: pilot line connection pipe 30

Claims (2)

[Claims] An electric motor and a plurality of pump units each including one or a plurality of hydraulic pumps driven by the electric motor are provided, and some of the pump units are provided according to set operating conditions. In the hydraulic circuit of the hydraulic drive device that switches the supply flow rate of the hydraulic oil by operating the other pump unit and stopping other pump units, at least one of the hydraulic pumps that are constantly used among all the hydraulic pumps A hydraulic circuit for a hydraulic drive device, characterized in that a branch portion is provided on the discharge side of a hydraulic pump, and a pilot pressure supply line of a hydraulic pump belonging to another pump unit is connected to the branch portion. 2. A plurality of pump units each including one motor and one or more hydraulic pumps driven by the motor, and some of the pump units are selected according to set operating conditions. In the hydraulic circuit of the hydraulic drive unit that switches the supply flow rate of hydraulic oil by operating the other pump unit and stopping other pump units, branches to the discharge side of the most frequently used hydraulic pump among all hydraulic pumps A hydraulic circuit for a hydraulic drive device, wherein a pilot pressure supply line of a hydraulic pump belonging to another pump unit is connected to the branch portion.