JPH058278A - Hydraulic oil temperature control method for hydraulic system for injection molding machine - Google Patents

Abstract

(57) [Summary] (Correction) [Purpose] To lower the temperature of hydraulic oil in the tank when the actuator 2 does not operate. [Structure] When the temperature of the hydraulic oil in the tank rises when the actuator 2 does not operate and the return oil is not discharged, the temperature of the hydraulic oil is detected by the temperature sensor 35, and the detected temperature is input to the controller 30. , Compare with the set value.
A command is issued from the controller 30 to the variable discharge amount control valve 31, the electromagnetic relief valve 33, and the cooling water control valve 34 in accordance with the temperature range of the set value to efficiently cool the hydraulic oil.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic system for an injection molding machine, and more particularly to a hydraulic oil temperature control method using a variable discharge pump as a drive source.

[0002]

2. Description of the Related Art A conventional example is shown in FIG. As shown in FIG. 2, the hydraulic oil in the oil tank 6 is sucked into the variable discharge pump 1 from the pipe 11 through the suction filter 5, becomes high-pressure oil, and is discharged to the pipe 12a. Is controlled to be sent to the actuator 2 from the conduit 12b.

Return oil from the actuator 2 is returned to the pipeline 23.
The return oil sent from a to the heat exchanger 3 through the line filter 4 and the pipe line 23b is cooled by the pipe line 2
It is piped so as to return to the tank 6 through 3c. In addition,
The return oil circuit 2 of the actuator 2 through the pipelines 23a and 23b
3 is formed.

On the other hand, the case drain conduit 24a from the variable discharge pump 1 is branched into a conduit 24b and a conduit 24c from the middle, and the case drain circuit 24 of the variable discharge pump 1 is connected to the conduits 24a, 24b and 24c. Is formed. Pipeline 24
c is through the check valve 8 and through the conduit 23d, and the conduit 2
Piped to reach 3b. Check valve 8
Is attached so that the oil flows only from the case drain circuit 24 to the return oil circuit 23. Further, the pipe line 24b is arranged so as to communicate with the oil tank 6 from the pipe line 24d via the pressure release valve 9. This pressure release valve 9 is less than the operating pressure of the check valve 8 when the return oil from the actuator 2 is not discharged within the range of the allowable pressure of the case drain of the variable discharge pump 1. It is set to open at high pressure.

[0005]

However, the heat exchanger 3
When the actuator 2 does not operate, the hydraulic oil flowing through the valve uses a case drain of the variable discharge pump 1 so that the hydraulic oil has a very small flow amount, and therefore the heat exchange efficiency in the heat exchanger 3 is deteriorated. Stable temperature control was difficult. The present invention has been made in view of such problems, and an object thereof is to enable easy temperature control without providing a new device.

[0006]

In order to solve such a problem, according to the present invention, a variable discharge pump as a hydraulic source for driving an actuator and a return oil circuit of the actuator for intermittently discharging hydraulic oil are provided. The heat exchanger connected to cool the hydraulic oil and discharges it to the oil tank, the relief valve provided on the way from the discharge side of the variable discharge pump to the return oil circuit, and the discharge amount of the variable discharge pump A variable discharge pump control valve for controlling, a cooling water control valve for controlling the amount of cooling water used for cooling the working oil flowing through the heat exchanger, and a temperature sensor installed in an oil tank are provided, and The temperature sensor detects the temperature of the hydraulic oil in the oil tank, and when the temperature of the hydraulic oil exceeds a predetermined temperature set value, the variable discharge pump control is performed according to the detection signal of the temperature sensor. The flow rate command value, also, the pressure command value to the relief valve, further, the opening command value to cooling water control valve to output respectively.

[0007]

[Operation] If the temperature of the hydraulic oil in the tank rises when the actuator does not operate and the return oil is not discharged, the temperature of the hydraulic oil is detected by the temperature sensor, the detected temperature is input to the controller, and the set value is set. Compare with. When there is a temperature difference between the measured temperature and the set temperature, the controller issues a command to the variable discharge control valve, the electromagnetic relief valve, and the electromagnetic switching valve for cooling water according to the temperature difference. Therefore, a self-circulating flow of hydraulic oil is formed, and the temperature of hydraulic oil can be easily lowered.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described in detail below with reference to FIG. In the figure, the same parts as those in FIG.

The hydraulic system 40 of the injection molding machine according to the present invention
Is a variable discharge pump 1, an actuator 2, a heat exchanger 3, a controller 30, a variable discharge pump control valve 3
1, a switching valve 32, an electromagnetic relief valve 33, a cooling water electromagnetic switching valve 34, and a temperature sensor 35.

The hydraulic oil in the oil tank 6 is sucked into the variable discharge pump 1 from the pipe 11 via the suction filter 5, becomes high-pressure oil and is discharged to the pipe 12a, and the pressure is reduced by the electromagnetic relief valve 33. Controlled high pressure oil is pipe 12b
From the actuator to the actuator 2. When the discharge pressure becomes higher than the set pressure, the heat is removed from the heat exchanger 3 from the pipe 23d through the electromagnetic relief valve 33.
Sent to. The return oil from the actuator 2 is returned to the pipeline 23.
The return oil sent from a to the heat exchanger 3 through the line filter 4 and the line 23b is cooled by the line 2
It is piped so as to return to the tank 6 through 3c. In addition,
The return oil circuit 2 of the actuator 2 through the pipelines 23a and 23b
3 is formed.

Reference numeral 35 denotes a temperature sensor, which is a tank 6
Controller 30 which detects the temperature of the hydraulic oil in the
The control valve 31 for the variable discharge pump, the electromagnetic relief valve 33, and the electromagnetic switching valve 34 for the cooling water are respectively controlled via the.

Reference numeral 30 denotes a controller, to which the temperature setting value of the hydraulic oil in the tank 6, the flow rate setting value of the variable discharge pump control valve 31, and the pressure setting value of the electromagnetic relief valve 33 are input. .. When the temperature of the hydraulic oil in the tank 6 reaches the set temperature during normal operation, for example, 40 ° C. or higher, the variable discharge pump control valve 31 and the electromagnetic valve are controlled according to the rising temperature range detected by the temperature sensor 35. The relief valve 33 and the electromagnetic switching valve for cooling water 34 are operated to lower the temperature of the hydraulic oil in the tank 6 to the set temperature.

Reference numeral 31 is a control valve for the variable discharge pump, and when the temperature of the hydraulic oil in the tank 6 rises, the electromagnetic switching valve 31a is excited by the command from the controller 30 and moves to the right, so that the cylinder 31b. The pressure oil that was inside the piston head side of the
c stretches. Therefore, the discharge valve is rotated in the opening direction to discharge a large amount of high pressure oil from the variable discharge pump 1.

Reference numeral 34 is an electromagnetic switching valve for cooling water, and when the temperature of the working oil in the tank 6 rises, an electromagnetic switching valve for cooling water 34 is instructed by a command from the controller 30.
Is excited and pushed down to form a cooling water passage, which is used to cool the hydraulic oil whose temperature has risen.

Reference numeral 33 is an electromagnetic relief valve, and when the temperature of the hydraulic oil in the tank 6 rises, the temperature sensor 35 detects the temperature of the hydraulic oil, and when the temperature exceeds a preset temperature set in the controller 30 in advance. , A signal is output so as to reach the preset pressure command value of the electromagnetic relief valve 33,
High pressure oil from the variable discharge pump 1 is an electromagnetic relief valve 33.
Is sent to the heat exchanger 3 via. The pressure command value is usually set low to prevent energy loss and heat generation.

The operation of the present invention thus constructed will be described. The injection molding machine has an actuator 2 driven by hydraulic pressure, such as a mold clamping cylinder, an injection cylinder, an oil motor for screw rotation, and the variable discharge pump 1.
The pressure oil discharged from is operated by being sent to the actuator 2 via the switching valve 32, and normally repeats the main cycle of mold closing → injection filling → screw rotation → mold opening. During this time, the actuator 2 operates only during its role and discharges a relatively large amount of return oil.

In particular, when the actuator 2 is not operating as in the present invention and therefore the return oil is not discharged (that is, the switching valve 32 is demagnetized), the tank 6 is kept under this condition. When the detected temperature of the hydraulic oil by the temperature sensor 35 provided in the controller 30 rises above the set value input to the controller 30, the flow rate to the variable discharge pump control valve 31 is increased according to the measured temperature and the set temperature difference. The command value is output,
Tank 6 → Variable discharge pump 1 → Electromagnetic relief valve 33
→ The self-circulation flow rate that circulates between the heat exchanger 3 and the tank 6 increases. At this time, since the electromagnetic relief valve 33 is controlled to have a low pressure, the working oil is smoothly circulated to the heat exchanger 3.

The temperature of the cooling water used for cooling the working oil flowing in the heat exchanger 3 exceeds the preset normal temperature detected by the temperature sensor 35 in response to a command from the controller 30. And the electromagnetic switching valve 34 for cooling water are switched, and water is passed through the heat exchanger 3 to cool the working oil.

As described above, when the return oil from the actuator 2 is discharged, a relatively large amount of the return oil can be efficiently cooled, but the self-circulating flow described above is formed even when the actuator 2 is not operating. Thus, the amount of hydraulic oil can be secured, and the temperature of the hydraulic oil in the tank 6 can be efficiently cooled.

[0020]

As is apparent from the above description, in the present invention, the variable discharge pump as a hydraulic source for driving the actuator and the return oil circuit of the actuator for intermittently discharging the hydraulic oil are connected. A heat exchanger that cools working oil and discharges it to an oil tank, a relief valve provided on the way from the discharge side of the variable discharge pump to the return oil circuit, and the discharge amount of the variable discharge pump are controlled. A variable discharge pump control valve, a cooling water control valve for controlling the amount of cooling water used for cooling the working oil flowing through the heat exchanger, and a temperature sensor installed in an oil tank are provided.
When the temperature of the hydraulic oil in the oil tank is detected by the temperature sensor and the temperature of the hydraulic oil exceeds a predetermined temperature set value, the control valve for the variable discharge pump is controlled by the temperature sensor according to the detection signal of the temperature sensor. By outputting the flow rate command value, the pressure command value to the relief valve, and the open command value to the cooling water control valve, respectively, it is possible to respond to the temperature difference between the measured temperature of the hydraulic oil and the set temperature. Since the circulation amount of hydraulic oil can be controlled freely, efficient cooling can be performed in a short time.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a hydraulic device of an injection molding machine according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a hydraulic device of a conventional injection molding machine.

[Explanation of symbols]

 1 Variable Discharge Pump 2 Actuator 3 Heat Exchanger 4 Line Filter 6 Oil Tank 30 Controller 31 Variable Discharge Pump Control Valve 32 Switching Valve 33 Electromagnetic Relief Valve 34 Cooling Water Solenoid Switching Valve 35 Temperature Sensor

Claims (1)

Claim: What is claimed is: 1. A variable discharge pump as a hydraulic source for driving an actuator and a return oil circuit of the actuator for intermittently discharging hydraulic oil, which is connected to a cooling oil and cooled to discharge it to an oil tank. A heat exchanger, a relief valve provided between the discharge side of the variable discharge pump and the return oil circuit, a variable discharge pump control valve for controlling the discharge amount of the variable discharge pump, and A cooling water control valve for controlling the amount of cooling water used for cooling the working oil flowing through the heat exchanger and a temperature sensor installed in the oil tank are provided, and the temperature sensor controls the temperature of the working oil in the oil tank. Detect
When the temperature of the hydraulic oil exceeds a predetermined temperature set value,
According to the detection signal of the temperature sensor, the flow rate command value is output to the variable discharge pump control valve, the pressure command value is output to the relief valve, and the open command value is output to the cooling water control valve. A method for controlling a hydraulic oil temperature of a hydraulic device for an injection molding machine, comprising: