JPH06254934A - Oil quantity control device for injection molding machine - Google Patents

Abstract

PURPOSE:To mold efficiently even when a molding condition of an injection molding machine is changed. CONSTITUTION:A plurality of pumps 10, 12, and 14 are integrally connected to a motor 18. At a discharging pipeline 42 of the first pump 10, a first change- over valve 26 is provided. At a discharging pipeline 44 of the second pump 12, a second change-over valve 28 is provided. At a discharging pipeline 46 of the third pump 14, a third change-over valve 30 is provided. One port of each of the change-over valves is connected to a return line 58. The discharging pipelines of the pumps are connected to a discharging line 56. A pressure sensor 38 is provided for detecting the pressure of the discharging line 56 and outputting a signal. A control device 40 is provided for inputting the signal from the pressure sensor. The control device designates change-over positions of the change-over valves dependent on measured pressure from the pressure sensor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oil quantity control device for an injection molding machine.

[0002]

2. Description of the Related Art As a conventional oil amount control device for an injection molding machine, there is one disclosed in Japanese Patent Publication No. 59-35771. In the hydraulic control device shown therein, a plurality of fixed discharge type pumps are independently driven by the same number of motors. As the motor, a motor having a power commensurate with the maximum power consumption of the corresponding pump (power at maximum pressure) is used. As a result, even if the pump requires the maximum power consumption, the motor does not suffer a failure such as burnout.

[0003]

However, the above-described conventional oil amount control device for an injection molding machine has a problem that the motor cannot fully exhibit its capabilities. That is, except when the pump is driven at the maximum discharge pressure, the motor capacity has a margin, but in reality, the hydraulic pump is driven at the maximum discharge pressure during the entire injection molding process (injection process). Since the time ratio (such as) is relatively small, it means that the motor is not fully performing. In addition, in injection molding, there is a method in which injection is performed at a low injection pressure (low-pressure injection) in order to mold a product with a small internal strain, but in such a case,
Since the injection cylinder is driven with a small pump discharge pressure even in the injection process, the capacity of the motor is not effectively used in almost all processes.
In order to solve such a problem, the oil chamber of the injection cylinder is concentrically divided into a plurality of parts, and when performing normal injection molding, by supplying hydraulic pressure to all the oil chambers, The injection cylinder is driven at a certain speed, and when low-pressure injection molding is performed, the hydraulic pressure is supplied only to a predetermined part of the oil chambers, and the predetermined speed (speed during normal molding) There are some that enable low-pressure injection at higher speeds, but the structure of the injection cylinder is complicated to enable low-pressure injection, and the control of the hydraulic circuit is also complicated, making the device expensive. Become. The present invention aims to solve such problems.

[0004]

According to the present invention, when a plurality of pumps are driven by one motor, the pumps are controlled so that the discharge flow rate with respect to the discharge pressure is maximized within the range of the motor capacity. This solves the above problem. That is, the oil amount control device for an injection molding machine according to the present invention includes a plurality of fixed discharge pumps (10, 12, 14) constituting a hydraulic source of the injection molding machine, and a discharge side pipe (4).
2, 44, 46) and a pressure sensor (38) for detecting the pressure of the hydraulic oil discharged to the discharge pipe line (56), and a switching valve provided in the discharge side pipes (42, 44, 46), respectively. (26, 28, 30) and discharge side piping (42, 44,
The check valve ((20, 22, 24)) and the pressure sensor (3) which are respectively arranged at positions closer to the discharge conduit (56) than the positions where the switching valves (26, 28, 30) of (46) are arranged.
8) Depending on the magnitude of the signal output from the pump (1
0, 12, 14) and a controller (40) for controlling the discharge side pipes (42, 44, 46) and the return side pipes. It is configured so that it can be switched to either one of a no-load position that communicates with (58) and a load position that shuts off between these (58).
2, 24) are the corresponding discharge side pipes (42, 44, 4).
The fixed discharge pump (10, 12, 14) is intended for the arrangement in which the flow from 6) to the discharge pipe line (56) is permitted, but the flow in the opposite direction is not permitted.
Are three or more in number and have different discharge amounts, and are configured to be integrally driven by one motor (18).
8) has a fixed discharge pump (10, 12,
14) is less than half of the power when it is driven at a predetermined maximum pressure.
0) is provided with a number of setting sections corresponding to all combinations of pumps (10, 12, 14), and the setting sections have a set pressure and a combination of pumps to be brought into a load state corresponding to the set pressure. Can be set respectively, and the controller (4
0) selects the set pressure corresponding to the measured pressure so that the corresponding one of the switching valves (26, 28, 30) is located on the load position side, and the non-corresponding one is located on the non-load position side. It is located at. The reference numerals in parentheses indicate the corresponding members of the embodiment.

[0005]

When the motor is rotated, a plurality of pumps are driven simultaneously. When no signal is output from the controller (before the molding process starts), the corresponding switching valve is
Each is in a de-energized state, and therefore each pump is in an unloaded state. That is, the discharge amount of each pump is returned to the tank through each switching valve and the return pipe line. When the molding process of the injection molding machine is started, the pressure in the discharge conduit also changes depending on the process. The pressure sensor detects the pressure in the discharge conduit and outputs it to the controller. The controller is
It is determined which of the stored plurality of pressure set values corresponds to the measured pressure, and the excitation / non-excitation of the plurality of switching valves is instructed according to the determination result. As a result, only the pump corresponding to the excited switching valve is in the loaded state, the other pumps remain in the unloaded state,
A predetermined process is executed. In this way, the controller selects the pump to be loaded in accordance with the pressure of the discharge conduit for each process. For example, when low-pressure injection is required, the molding process is started after the relief valve on the injection cylinder side is set to a predetermined low pressure. As a result, the pump to be put in the load state is selected in accordance with the injection cylinder pressure of the low pressure injection, so that the injection is performed at a higher speed than in the case of the normal injection pressure.

[0006]

EXAMPLE FIG. 1 shows an example of the present invention. In the hydraulic circuit of the injection molding machine, three pumps 10, 1 with different discharge amounts are provided.
2 and 14 are provided. The first pump 10 has the smallest discharge amount, the third pump 14 has the largest discharge amount, and the second pump 12 has an intermediate discharge amount (however, the discharge amount ratio of the three pumps is 1 + second <third Relationship). Each pump 10, 12 and 14 has one drive shaft 1
6 are connected to each other. One end of the drive shaft 16 is connected to the motor 18. That is, the three pumps 10, 12, and 14 are driven by the single motor 18 via the drive shaft 16. The suction ports of the pumps 10, 12, and 14 are in communication with the tank 60 via the suction side pipes 50. First
The discharge port of the pump 10 is connected to the discharge pipe line 56 via the first discharge side pipe 42 and the first check valve 20.
Similarly, the discharge port of the second pump 12 is the second discharge side pipe 44.
And the discharge line 56 via the second check valve 22, and the discharge port of the third pump 14 is connected to the discharge line 56 via the third discharge side pipe 46 and the third check valve 24.
It is connected to the. The discharge conduit 56 is connected to a hydraulic circuit on the actuator side (not shown). Return oil from the hydraulic circuit on the actuator side returns to the tank 60 via the return pipe line 58.
The first discharge side pipe 42 branches from this to the return pipe line 5
8 is provided with a first branch pipe 48, and a first switching valve 26 is provided in the middle of the first branch pipe 48. The first switching valve 26 is a two-position electromagnetic switching valve, and connects the first discharge side pipe 42 and the return pipe 58 at the symbol position shown (when the solenoid is not excited) (that is, the first switching valve 26). The pump 10 is in an unloaded state, and at the symbol position opposite to the illustrated position (when the solenoid is excited), the first discharge side pipe 42 and the return pipe line 58 are shut off (that is, the first pump 10 is It becomes a load state). Similarly second
The discharge side pipe 44 is provided with a second branch pipe 52 which branches from this and communicates with the return pipe line 58.
The second switching valve 28 is provided in the middle of the branch pipe 52, and the third discharge pipe 46 is provided with a third branch pipe 54 that branches from this and communicates with the return pipe 58. , The relief valve 3 is provided in the middle of the third branch pipe 54.
4 are provided. The vent circuit of the relief valve 34 is provided with the third switching valve 30. Switching valves 28 and 3
0 is also a two-position electromagnetic switching valve, and communicates the corresponding discharge side pipe with the return conduit 58 at the symbol position shown in the figure (the corresponding pump is in an unloaded state). Further, at the symbol position opposite to the illustrated position, the corresponding discharge side pipe and the return pipe 58 are shut off (the corresponding pump is in a load state). The discharge pipe line 56 is provided with a relief valve 36 for setting the maximum pressure of the circuit. The relief valve 36 is designed to prevent the discharge pipe 56 from rising above a set pressure. The discharge pipe 56 is provided with a pressure sensor 38 that detects the pressure of the discharge pipe 56. Further, a controller 40 for inputting the pressure signal from now on is provided. The controller 40 can control the solenoids of the switching valves 26, 28, and 30. In the case of this embodiment, the controller 40 is
Six set pressures are set corresponding to all combinations of three pumps, and the first switching valve 26 is excited / the second switching valve 2 in order from the highest set pressure.
8 and the third switching valve 30 are de-energized, the second switching valve 28 is energized, the first switching valve 26 and the third switching valve 30 are de-energized, the third switching valve 30 is energized, the first switching valve 26 and the second switching valve 30. The switching valve 28 is de-energized, the first switching valve 26 and the second switching valve 28 are energized, the third switching valve 30 is de-energized, the first switching valve 26 and the third switching valve 30 are energized, and the second switching valve 28 is energized. De-energized, second switching valve 28
And so that the third switching valve 30 is energized and the first switching valve 26 is de-energized, and when the set pressure is less than or equal to each switching valve 2
All 6, 28, and 30 are adapted to be excited. As a result, the combination of no-load driving and load driving of the three pumps is determined. For the six set pressures, these values are determined so that the motor 18 does not have power exceeding the limit in comparison with the above combinations, but has power as large as possible.

Next, the operation of this embodiment will be described. Rotating the motor 18 drives the three pumps 10, 12 and 14 simultaneously. When no signal is output from the controller 40 (the state before the start of the molding process), 3
The three switching valves 26, 28 and 30 are each in the de-energized state shown and therefore the three pumps 10, 12,
Nos. 14 and 14 are in an unloaded state. That is, the discharge amounts of the pumps 10, 12, and 14 are as follows: the first branch pipe 48 and the first switching valve 26, the second switching valve 28 and the second branch pipe 52, the third branch pipe 54 and the relief valve 34, and It returns to the tank 60 through the return line 58. When the molding process of the injection molding machine is started, the actuator driven according to the process changes, and the driving force for driving these also changes, so the pressure of the discharge conduit 56 also changes. The pressure sensor 38 detects the pressure in the discharge conduit 56 and outputs it to the controller 40. The controller 40 determines which of the six stored pressure set values corresponds to the measured pressure, and determines the three switching valves 26, 2 according to the determination result.
8 and 30 are respectively instructed to be energized / de-energized (for example, only the first switching valve 26 is energized, and the second switching valve 28 and the third switching valve 30 are each de-energized). This allows
Only the first pump 10 corresponding to the excited first switching valve 26 is in the loaded state, the second pump 12 and the third pump 14 remain in the unloaded state, and the predetermined process is executed. In this way, the controller 40 selects the pump to be put in the loaded state according to the pressure of the discharge pipe line 56 corresponding to the process. For example, when low-pressure injection is required, the molding process is started after the relief valve on the injection cylinder side (not shown) is set to a predetermined low pressure. As a result, the pump to be put in the load state is selected in accordance with the injection cylinder pressure of the low pressure injection, so that the injection is performed at a higher speed than in the case of the normal injection pressure.

Although three pumps 10, 12, and 14 are used as hydraulic pressure sources in the above description of the embodiment, the number of pumps may be three or more, and other numbers may be used. The discharge amounts of the three pumps 10, 12, and 14 are different from each other, and the sum of the discharge amounts of any two pumps is not equal to the discharge amount of the other pump. However, by doing this, the total discharge amount for each combination will be different,
Fine control can be performed. When the number of pumps is two, the number of combinations of pumps is small, and therefore the detailed control as described above cannot be expected and the present invention cannot be implemented.

[0009]

As described above, according to the present invention,
Within the range of the allowable power of the motor, the plurality of pumps can be controlled to discharge the maximum total discharge amount in accordance with the discharge pressure required for each molding process. Therefore, the device can be driven most efficiently under various molding conditions. By limiting the power of the motor to less than half of the power when the fixed discharge pump is driven at a predetermined maximum pressure, the electric system can be made to have a small power capacity. And the equipment cost of the factory can be reduced.

[Brief description of drawings]

FIG. 1 is a diagram showing an oil amount control device of an injection molding machine to which the device of the present invention is applied.

[Explanation of symbols]

 10 First Pump 12 Second Pump 14 Third Pump 18 Motor 20, 22, 24 Check Valve 26, 28, 30 Switching Valve 38 Pressure Sensor 40 Controller 42, 44, 46 Discharge Side Pipe 56 Discharge Pipeline 58 Return Pipeline

Claims (1)

[Claims] 1. A plurality of fixed discharge pumps (10, 12, 14) constituting a hydraulic pressure source of an injection molding machine, and a discharge pipe (56) through the discharge side pipes (42, 44, 46).
Pressure sensor (3
8), switching valves (26, 28, 30) provided on the discharge side pipes (42, 44, 46), respectively, and switching valves (26, 28, 30) for the discharge side pipes (42, 44, 46). Check valves ((20, 22, 24) respectively arranged at positions on the discharge pipe line (56) side of the positions at which
A controller (4) for controlling the pumps (10, 12, 14) according to the magnitude of the signal output from the pressure sensor (38).
0), and a switching valve (26, 28, 30)
Is switched to either one of a no-load position where the discharge side pipes (42, 44, 46) and the return side pipe line (58) communicate with each other, and a load position where the discharge side pipes (42, 44, 46) communicate with each other. And each check valve ((20, 22, 24) has a corresponding discharge side pipe (4
2, 44, 46) to the discharge pipe line (56) but does not allow flow in the opposite direction. In the oil quantity control device of the injection molding machine, the fixed discharge pump ( 10, 12 and 14) are three or more in number, have different discharge amounts, and are configured to be integrally driven by one motor (18). (18) is a fixed discharge pump (1
(0, 12, 14) is less than half the power when it is driven at a predetermined maximum pressure. The controller (40) includes a pump (10, 12, 14).
The number of setting sections corresponding to all the combinations of (1) and (2) is set, and the setting section and the combination of pumps to be brought into a load state corresponding to the set pressure can be set respectively. , Select a set pressure corresponding to the measured pressure, and place the corresponding one of the switching valves (26, 28, 30) on the load position side, and place the other one on the no-load position side. Oil amount control device for injection molding machine.