JPH0126426Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a hydraulic circuit for an injection molding machine that takes energy saving into consideration.

Generally, when controlling large flow rate hydraulic pressure in a hydraulic system with a variable displacement pump, since there is no large flow rate variable displacement pump, two or three small flow rate variable displacement pumps are connected in series to control the large flow rate. It is occurring.
However, it has the drawbacks of complicated control and high cost.

In addition, in the hydraulic circuit of a conventional injection molding machine equipped with a mechanism that generates a large flow rate by connecting a variable displacement pump as described above, an expensive proportional Solenoid relief valve C
This was one of the major causes of high costs, as it was necessary to install a screw to control the back pressure of the screw resin pressure.

The present invention was developed in view of these points, and its purpose is to combine a variable displacement pump and a constant displacement pump to achieve the same effect as the conventional two-way variable displacement pump. The purpose of this invention is to provide a circuit that enables the function of the hydraulic circuit of a conventional injection molding machine and eliminates one expensive proportional electromagnetic relief valve from the hydraulic circuit of a conventional injection molding machine.

Hereinafter, the present invention will be explained with reference to the embodiment shown in FIG. 2. 1 is a motor, 2 is a constant displacement pump, and 3 is a variable displacement pump. A capacity pump 3 is connected in series. 4 is a strainer, and 5 is an oil tank. The discharge line 6 of the constant displacement pump 2 is connected to a 4-port switching valve 10 (pressure port block) that controls an actuator 9, which will be described later, via a check valve 7 and a proportional electromagnetic flow rate adjustment valve 8 that sets the required flow rate. It is connected to the P port line 11.

Further, a separately provided 4-port switching valve 13 is connected to the T-port line 12 of the 4-port switching valve 10 to control back pressure in the plasticizing process of the injection molding machine.
A vent line 15 of the B port 14 of the four-port switching valve 13 is connected to the P port line 11 of the four-port switching valve 10 via a throttle valve 16. Furthermore, the T port line 17 of the 4-port switching valve 10
A proportional electromagnetic relief valve 18 is connected to. In addition, a 4-port switching valve 20 (open center) is provided in the branch line 19 provided between the constant displacement pump 2 and the check valve 7, and is activated during on-loading. The hydraulic oil discharged from the four-port switching valve 20 is connected to be returned to the oil tank 5 from the open center thereof.

Here, the actuator 9 is composed of a hydraulic pump 31 and a slew 32 and an injection cylinder 33 of an injection molding machine that are operated by the drive of the pump.
In addition, the injection cylinders 33 are connected to the B ports 35 by piping, respectively.

Further, a discharge line 21 of the variable displacement pump 3 is connected between the check valve 7 and the proportional electromagnetic flow rate regulating valve 8. Also, the branch line 22 of the discharge line 21
A 4-port throttle switching valve 24 is provided as a load pressure detection valve via a control valve 23 connected to the variable displacement pump 3, and one branched vent line 2 of a relief valve 25 as a safety valve is connected to the 4-port switching valve 24.
6 and connect the other vent line 27 to the vent line 15 of the 4-port switching valve 13 described above.
It is connected to.

In the hydraulic circuit of the injection molding machine constructed as described above, as an example, the maximum discharge amount of the variable displacement pump 3 is
65/M, the maximum discharge amount of constant volume pump 2 is 60/M.
To explain the operating state in the case of M, if the set value of the proportional electromagnetic flow rate adjustment valve 8 is in the range of 0 to 65/M, the 4-port switching valve 20 is de-energized and the discharge amount is controlled only by the variable displacement pump 3. Control. Also, if the set value of the proportional solenoid flow rate adjustment valve 8 is 65/M or more,
The 4-port switching valve 20 is automatically determined by the microcomputer.
is energized to control the total discharge amount of the pumps 2 and 3 with respect to the required flow rate in both the constant displacement pump 2 and the variable displacement pump 3. (See Figure 3) If the setting value of the proportional electromagnetic flow rate adjustment valve 8 is 80/M,
20/M for variable displacement pump 3, and 20/M for constant displacement pump 2.
60/M, and can exhibit the same effect as conventional variable displacement pumps that are connected in two series.

Furthermore, by energizing the screw charge side of the 4-port switching valve 10 and energizing the 4-port switching valve 13 at the same time, the screw drive pressure is automatically controlled to the load pressure + 2 kg/cm ² and no upper limit regulation is required. The screw back pressure can be controlled by a proportional solenoid relief valve 18.

In this way, the present invention connects a constant displacement pump 2 and a variable displacement pump 3 to be driven by the same motor 1, and connects the discharge line 6 of the constant displacement pump 2 to the check valve 7 and the proportional electromagnetic flow rate adjustment valve 8. The 4-port switching valve 10 is connected to the P port line 11 of the 4-port switching valve 10 that controls the actuator 9 via the
Another 4-port switching valve 13 is connected to the T port line 12 of
and connect the vent line 15 of the B port 14 of the 4-port switching valve 13 to the 4-port switching valve 1.
0 to the P port line 11, and further connect the proportional electromagnetic relief valve 18 to the T port line 17 of the 4-port switching valve 13, and connect the 4-port to the branch line 19 between the constant displacement pump 2 and the check valve 7. The switching valve 20 is connected, and the discharge line 21 of the variable displacement pump 3 is connected to the connection line between the check valve 7 and the proportional electromagnetic flow rate adjustment valve 8, and the discharge line 2
A 4-port switching valve 24 is connected to the variable displacement pump 3 to the branch line 22 of 1, and one vent line 26 branched from the relief valve 25 is connected to the 4-port switching valve 24, and the other vent line 27 This is a hydraulic circuit for an injection molding machine characterized by a configuration in which the 4-port switching valve 13 is connected to the vent line 15 of the above-mentioned 4-port switching valve 13, so it is the same as the conventional variable displacement pump connected in two series with simple control and low cost. It is possible to achieve the following effects. Furthermore, the present invention makes it possible to remove one expensive proportional electromagnetic relief valve from the hydraulic circuit of a conventional injection molding machine, thereby reducing costs.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing a hydraulic circuit of a conventional injection molding machine, and FIG. 2 is a circuit diagram showing an embodiment of the present invention.
FIG. 3 is an explanatory diagram showing the relationship between the pump discharge amount and the flow rate setting value. 1... Motor, 2... Constant displacement pump, 3... Variable capacity pump, 6... Discharge line, 7... Check valve, 8... Proportional electromagnetic flow rate adjustment valve, 9... Actuator, 10... 4 Port switching valve, 11...P port line, 12...T port line, 13...4
Port switching valve, 14...B port, 15...Vent line, 17...T port line, 18...Proportional electromagnetic relief valve, 20...4 port switching valve, 2
1...Discharge line, 22...Relief valve, 26...
...Bent line, 27...Bent line.

Claims (1)

[Scope of utility model registration request] A constant displacement pump 2 and a variable displacement pump 3 are connected in series so as to be driven by the same motor 1, and the discharge line 6 of the constant displacement pump 2 is connected to an actuator 9 via a check valve 7 and a proportional electromagnetic flow rate adjustment valve 8. It is connected to the P port line 11 of the 4 port switching valve 10 to be controlled, and the T port line 1 of the 4 port switching valve 10 is connected to the P port line 11 of the 4 port switching valve 10 to be controlled.
2 is connected to another 4-port switching valve 13, and the 4-port switching valve 13 is connected to
Connect the vent line 15 of the B port 14 of the port switching valve 13 to the P port line 11 of the 4-port switching valve 10, and further connect the proportional electromagnetic relief valve 18 to the T port line 17 of the 4-port switching valve 13, A 4-port switching valve 20 is connected to the branch line 19 between the constant volume pump 2 and the check valve 7,
Furthermore, the discharge line 21 of the variable displacement pump 3 is connected to the connection line between the check valve 7 and the proportional electromagnetic flow rate adjustment valve 8, and the variable displacement pump 3 is connected to the branch line 22 of the discharge line 21 to form a 4-port configuration. A configuration in which a switching valve 24 is provided, and one vent line 26 branched from a relief valve 25 is connected to the 4-port switching valve 24, and the other vent line 27 is connected to the vent line 15 of the 4-port switching valve 13 described above. A hydraulic circuit for an injection molding machine featuring: