A hydraulic control circuit for a high-speed injection molding machine and a control method thereof

Abstract

The application relates to the technical field of hydraulic control circuits, in particular to a high-speed injection injection molding machine hydraulic control circuit and a control method thereof, which further comprises a first cartridge valve, a second cartridge valve, a first shuttle valve, a second shuttle valve, a first two-position three-way directional valve, a second two-position three-way directional valve and a two-position two-way directional valve; the input end of a main pump is communicated with a hydraulic oil tank, the output end of the main pump is communicated with the A port of the first cartridge valve, the B port of the first cartridge valve is respectively communicated with the P port of the two-position two-way directional valve, the A port of the second cartridge valve and the P port of a three-position four-way proportional directional valve, the C port of the first cartridge valve is communicated with the A port of the first shuttle valve, the P1 port of the first shuttle valve is communicated with the P port of the first two-position three-way directional valve, in use, the injection and liquid filling hydraulic control circuits are optimized, the second cartridge valve has a small diameter and has a cost advantage, in the later period of energy accumulator liquid filling, the liquid filling flow of the main pump is reduced, overflow heating is reduced, and the normal operation of the injection molding machine is ensured to be stable and reliable.

Description

Technical Field

[0001] This invention relates to the field of hydraulic control circuit technology, and in particular to a hydraulic control circuit and control method for a high-speed injection molding machine. Background Technology

[0002] For injection molding machines requiring high-speed injection, accumulators are often used as auxiliary power sources to increase the output flow of the hydraulic system in order to save costs or pump room space. In existing injection molding machine hydraulic circuits, when valves are operating, both the hydraulic pump and the accumulator output flow simultaneously, resulting in a large valve diameter requirement. Due to the different characteristics of the accumulator and the hydraulic pump, the output flow and pressure of the hydraulic pump can be continuous and stable, but the accumulator continuously decreases with the output flow. To ensure sufficient pressure throughout the injection process and maintain high speed, the accumulator's filling pressure ratio and operating pressure are required to be high. To meet these high requirements, the motor's output torque and power need to be considered higher. Therefore, based on the characteristics of the accumulator's volume and filling pressure, a small volume change in the later stages of filling can produce a large pressure change. Large-displacement hydraulic pumps are prone to overfilling, leading to overflow and heat generation, which can severely affect the normal operation of the injection molding machine. Summary of the Invention

[0003] The technical problem to be solved by the present invention is: in order to solve the problem that in the later stage of filling of existing accumulators, a small volume change will produce a large pressure change, and large displacement hydraulic pumps are prone to overfilling, resulting in overflow and heat generation, which in severe cases affects the normal operation of injection molding machines. The present invention provides a hydraulic control circuit and control method for high-speed injection molding machines.

[0004] The technical solution adopted by the present invention to solve its technical problem is: a hydraulic control circuit for a high-speed injection molding machine, including a hydraulic oil tank, a servo motor, a main pump, an accumulator, a three-position four-way proportional directional valve and an injection cylinder, and also including a first cartridge valve, a second cartridge valve, a first shuttle valve, a second shuttle valve, a first two-position three-way directional valve, a second two-position three-way directional valve and a two-position two-way directional valve;

[0005] The input end of the main pump is connected to the hydraulic oil tank, and the output end of the main pump is connected to port A of the first cartridge valve. Port B of the first cartridge valve is connected to port P of the two-position two-way directional valve, port A of the second cartridge valve, and port P of the three-position four-way proportional directional valve. Port C of the first cartridge valve is connected to port A of the first shuttle valve. Port P1 of the first shuttle valve is connected to port P of the first two-position three-way directional valve. Port P2 of the first shuttle valve is connected to port B of the first cartridge valve. Port A of the first two-position three-way directional valve is connected to port A of the first cartridge valve. Port T of the two-position two-way directional valve is connected to the hydraulic oil tank. The system is connected to the hydraulic tank. The C port of the second cartridge valve is connected to the A port of the second shuttle valve. The P1 port of the second shuttle valve is connected to the P port of the second two-position three-way directional valve. The P2 port of the second shuttle valve is connected to the P port of the three-position four-way proportional directional valve. The A port of the second two-position three-way directional valve is connected to the B port of the second cartridge valve. The A port of the three-position four-way proportional directional valve is connected to the B port of the injection cylinder. The B port of the three-position four-way proportional directional valve is connected to the A port of the injection cylinder. The T port of the three-position four-way proportional directional valve is connected to the hydraulic tank. The output end of the main pump is connected to the injection molding machine's mold clamping unit.

[0006] In some preferred embodiments, a first overflow valve is connected in parallel between the output end and the input end of the main pump.

[0007] In some preferred embodiments, a second relief valve is connected in parallel to the P port and T port of the two-position two-way reversing valve.

[0008] In some preferred embodiments, a first pressure sensor is provided on the input terminal of the energy storage device.

[0009] In some preferred embodiments, a second pressure sensor is provided at the B port end of the injection cylinder.

[0010] In some preferred embodiments, the main pump is a variable pump.

[0011] A control method for a high-speed injection molding machine hydraulic control circuit as described above includes the following steps:

[0012] S1. When powered on, the servo motor is powered on and in standby mode;

[0013] S2. During filling, the servo motor is started and the main pump is driven to work. The first two-position three-way directional valve is energized, and the P port and B port of the first two-position three-way directional valve are connected. The first cartridge valve is opened. The second two-position three-way directional valve is energized, and the P port and B port of the second two-position three-way directional valve are connected. The second cartridge valve is opened. The three-position four-way proportional directional valve is in the middle position. The main pump fills the accumulator with hydraulic oil through the first cartridge valve and the second cartridge valve. After filling is completed, the first two-position three-way directional valve and the second two-position three-way directional valve are de-energized. The first cartridge valve and the second cartridge valve are closed. The servo motor is put into standby mode.

[0014] S3. During injection, the servo motor is started according to the working conditions, and the first two-position three-way reversing valve, the second two-position three-way reversing valve and the three-position four-way proportional reversing valve are energized or de-energized to realize the control of the injection cylinder for low-speed injection, high-speed injection or synchronous mold closing injection.

[0015] S4. When the machine stops, the two-position two-way directional valve loses power, and the high-pressure oil in the accumulator is unloaded to the hydraulic oil tank.

[0016] In some preferred embodiments, step S3 includes:

[0017] During low-speed injection, the servo motor drives the main pump, energizes the first and second position three-way directional valves, connects the P and B ports of the first and second position three-way directional valves, opens the first cartridge valve, and the main pump outputs high-pressure oil. At the same time, the second and second position three-way directional valves are de-energized, the second cartridge valve is closed, the accumulator pressure oil does not participate in the action, the left side of the three-position four-way proportional directional valve is energized, and the hydraulic oil flows through the P port of the three-position four-way proportional directional valve to the B port and reaches the B port of the injection cylinder. When the injection and pressure holding action is completed, the first and second position three-way directional valves are de-energized, the first cartridge valve is closed, and the control servo motor is in standby mode.

[0018] During high-speed injection, the servo motor drives the main pump, energizes the first and second position three-way directional valves, connects the P and B ports of the first and second position three-way directional valves, opens the first cartridge valve, and the main pump outputs high-pressure oil. At the same time, the second and second position three-way directional valves are energized, connect the P and B ports of the second and second cartridge valves, and open the second cartridge valve. The hydraulic oil from the main pump and the accumulator flows into each other. The hydraulic oil flows through the P port of the three-position four-way proportional directional valve to the B port and reaches the B port of the injection cylinder. After the injection and pressure holding action is completed, the first and second position three-way directional valves and the second and second position three-way directional valves are de-energized, the first and second cartridge valves are closed, and the control servo motor is in standby mode.

[0019] During synchronous injection molding, the servo motor drives the main pump, the first two-position three-way directional valve is de-energized, the first cartridge valve is closed, the second two-position three-way directional valve is energized, the second cartridge valve is opened, and the hydraulic oil from the accumulator flows through the P port of the three-position four-way proportional directional valve to the B port and reaches the B port of the injection cylinder. The flow rate of the main pump is delivered to the injection molding machine's mold closing unit, thereby realizing the synchronous operation of the injection cylinder and the injection molding machine's mold closing unit.

[0020] The beneficial effects of this invention are as follows: When using the hydraulic control circuit and control method of the high-speed injection molding machine, this invention optimizes the injection and filling hydraulic control circuit. The second cartridge valve has a small diameter, which has a cost advantage. In the later stage of accumulator filling, the main pump filling flow rate is reduced, which reduces overflow heat generation and ensures the normal, stable and reliable operation of the injection molding machine. This avoids the problem that in the later stage of existing accumulator filling, a small volume change will produce a large pressure change, and the large displacement hydraulic pump is prone to overfilling, resulting in overflow heat generation, which in severe cases affects the normal operation of the injection molding machine. Attached Figure Description

[0021] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0022] Figure 1 This is a schematic diagram of the structure of the present invention.

[0023] In the diagram: 1. Hydraulic oil tank, 2. Servo motor, 3. Main pump, 4. Accumulator, 5. Three-position four-way proportional directional valve, 6. Injection cylinder, 7. First cartridge valve, 8. Second cartridge valve, 9. First shuttle valve, 10. Second shuttle valve, 11. First two-position three-way directional valve, 12. Second two-position three-way directional valve, 13. Two-position two-way directional valve, 14. First relief valve, 15. Second relief valve, 16. First pressure sensor, 17. Second pressure sensor. Detailed Implementation

[0024] The present invention will be further described in detail below with reference to the embodiments:

[0025] This invention is not limited to the specific embodiments listed below. Those skilled in the art can implement this invention using various other specific embodiments based on the content disclosed herein. Any modifications or alterations made to the design structure and concept of this invention fall within the protection scope of this invention. It should be noted that, unless otherwise specified, the embodiments and features described in this invention can be combined with each other.

[0026] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0027] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0028] like Figure 1 As shown, a hydraulic control circuit for a high-speed injection molding machine includes a hydraulic oil tank 1, a servo motor 2, a main pump 3, an accumulator 4, a three-position four-way proportional directional valve 5, an injection cylinder 6, a first cartridge valve 7, a second cartridge valve 8, a first shuttle valve 9, a second shuttle valve 10, a first two-position three-way directional valve 11, a second two-position three-way directional valve 12, and a two-position two-way directional valve 13.

[0029] The input end of the main pump 3 is connected to the hydraulic oil tank 1, and the output end of the main pump 3 is connected to port A of the first cartridge valve 7. Port B of the first cartridge valve 7 is connected to port P of the two-position two-way directional valve 13, port A of the second cartridge valve 8, and port P of the three-position four-way proportional directional valve 5. Port C of the first cartridge valve 7 is connected to port A of the first shuttle valve 9. Port P1 of the first shuttle valve 9 is connected to port P of the first two-position three-way directional valve 11. Port P2 of the first shuttle valve 9 is connected to port B of the first cartridge valve 7. Port A of the first two-position three-way directional valve 11 is connected to port A of the first cartridge valve 7. Port T of the two-position two-way directional valve 13 is connected to the hydraulic oil tank 1. The system is connected to the hydraulic tank 1. The C port of the second cartridge valve 8 is connected to the A port of the second shuttle valve 10. The P1 port of the second shuttle valve 10 is connected to the P port of the second two-position three-way directional valve 12. The P2 port of the second shuttle valve 10 is connected to the P port of the three-position four-way proportional directional valve 5. The A port of the second two-position three-way directional valve 12 is connected to the B port of the second cartridge valve 8. The A port of the three-position four-way proportional directional valve 5 is connected to the B port of the injection cylinder 6. The B port of the three-position four-way proportional directional valve 5 is connected to the A port of the injection cylinder 6. The T port of the three-position four-way proportional directional valve 5 is connected to the hydraulic tank 1. The output end of the main pump 3 is connected to the injection molding machine mold closing unit.

[0030] A first relief valve 14 is connected in parallel between the output and input ends of the main pump 3, and a second relief valve 15 is connected in parallel between the P port and the T port of the two-position two-way directional valve 13.

[0031] A first pressure sensor 16 is installed on the input end of the accumulator 4, and a second pressure sensor 17 is installed on the B port end of the injection cylinder 6.

[0032] In this embodiment, the main pump 3 is an electronic variable pump. The displacement of the electronic variable pump is reduced, which reduces the torque requirement of the main pump 3. Therefore, there is no need for a motor with high torque and power.

[0033] The first two-position three-way directional valve 11, the second two-position three-way directional valve 12, the two-position two-way directional valve 13, and the three-position four-way proportional directional valve 5 are all solenoid directional valves.

[0034] Example 2

[0035] Example 2 describes a control method using the hydraulic control circuit of a high-speed injection molding machine as described in Example 1. Specifically, it includes the following steps:

[0036] S1. When the machine is powered on, the servo motor 2 is powered on and in standby mode. The first overflow valve 14 limits the maximum system pressure to prevent the main pump 3 from being over-pressurized and the servo motor 2 from being overloaded. The second overflow valve 15 limits the maximum filling pressure.

[0037] S2. During filling, the servo motor 2 is started and the main pump 3 is driven to work. The main pump 3 draws hydraulic oil from the hydraulic oil tank 1 and pumps it into the filling system. The first two-position three-way directional valve 11 is energized and is in the left position. The P port and B port of the first two-position three-way directional valve 11 are connected, and the first cartridge valve 7 is opened. The second two-position three-way directional valve 12 is energized and is in the left position. The P port and B port of the second two-position three-way directional valve 12 are connected. The two cartridge valves 8 are open, the three-position four-way proportional directional valve 5 is in the middle position, the main pump 3 pumps hydraulic oil through the first cartridge valve 7 from port A to port B and the second cartridge valve 8 from port A to port B and fills the accumulator 4 with liquid. When the set filling pressure is reached, the filling is completed. The first two-position three-way directional valve 11 and the second two-position three-way directional valve 12 are both de-energized, the first cartridge valve 7 and the second cartridge valve 8 are both closed, the control servo motor 2 is in standby state, or the main pump 3 supplies liquid for other injection molding machine operations.

[0038] S3. During injection, the servo motor 2 is started according to the working conditions, and the first two-position three-way reversing valve 11, the second two-position three-way reversing valve 12 and the three-position four-way proportional reversing valve 5 are energized or de-energized to realize the control of the injection cylinder 6 for low-speed injection, high-speed injection or synchronous mold closing injection.

[0039] S4. When the machine stops, the two-position two-way directional valve 13 is de-energized, and the high-pressure oil of the accumulator 4 is unloaded to the hydraulic oil tank 1, reducing safety risks.

[0040] Step S3 includes the following:

[0041] During low-speed injection, servo motor 2 drives main pump 3, energizing the first two-position three-way directional valve 11. The first two-position three-way directional valve 11 is in the left position, with its P and B ports connected. The first cartridge valve 7 opens, and main pump 3 outputs high-pressure oil. Simultaneously, the second two-position three-way directional valve 12 is de-energized and is in the right position. The second cartridge valve 8 closes, and the pressure oil from accumulator 4 does not participate in the operation. The left side of the three-position four-way proportional directional valve 5 is energized, and hydraulic oil flows through the P port of the three-position four-way proportional directional valve 5 to the B port and reaches the injection cylinder 6 at the B port. The second pressure sensor 17 primarily... For pressure control during injection and holding pressure, after the injection and holding pressure action is completed, the first and second position three-way reversing valve 11 is de-energized, the first cartridge valve 7 is closed, and the servo motor 2 is put into standby state, or the main pump 3 supplies liquid for other injection molding machine actions. Compared with the original control circuit, when the injection is low speed, the accumulator 4 also needs to participate. After the injection action is completed, an additional liquid filling step is required for the accumulator 4, and the servo motor 2 also needs to be started frequently, causing the accumulator 4 to be used frequently and reducing its bladder life. This solution does not require the participation of the accumulator 4, which can extend the accumulator 4 bladder life. In addition, the servo motor 2 has no extra liquid filling time, which increases the cooling time of the servo motor 2.

[0042] During high-speed injection, servo motor 2 drives main pump 3, energizing the first two-position three-way directional valve 11. The first two-position three-way directional valve 11 is in the left position, with its P and B ports connected. The first cartridge valve 7 opens, and main pump 3 outputs high-pressure oil. Simultaneously, the second two-position three-way directional valve 12 is energized, is in the left position, with its P and B ports connected. The second cartridge valve 8 opens, and the left side of the three-position four-way proportional directional valve 5 is energized. When valve 5 is in the left position, the hydraulic oil of the main pump 3 and accumulator 4 flows into each other. The hydraulic oil flows through port P of the three-position four-way proportional directional valve 5 to port B and reaches port B of the injection cylinder 6. The second pressure sensor 17 is mainly used for pressure control during the injection and holding process. When the injection and holding action is completed, the first two-position three-way directional valve 11 and the second two-position three-way directional valve 12 are de-energized, the first cartridge valve 7 and the second cartridge valve 8 are closed, and the control servo motor 2 is in standby mode, or the main pump 3 supplies liquid for other injection molding machine actions.

[0043] When synchronous injection occurs, the servo motor 2 drives the main pump 3 to work, the first two-position three-way directional valve 11 is de-energized and located in the right position, the first cartridge valve 7 is closed, and the hydraulic oil of the main pump 3 does not enter the injection circuit. The second two-position three-way directional valve 12 is energized and located in the left position, the second cartridge valve 8 is opened, and the hydraulic oil of the accumulator 4 passes through the three-position four-way proportional directional valve 5P port to port B and reaches the injection cylinder 6B port. In this circuit, the hydraulic oil for the injection action is only provided by the accumulator 4, and the flow of the main pump 3 is delivered to the injection molding machine's mold closing unit, thereby realizing the synchronous action of the injection cylinder 6 and the injection molding machine's mold closing unit.

[0044] The above description, based on the preferred embodiments of the present invention, provides inspiration. Those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification but must be determined according to the claims.

Claims

1. A hydraulic control circuit for a high-speed injection molding machine, comprising a hydraulic tank, a servo motor, a main pump, an accumulator, a three-position four-way proportional directional valve, and an injection cylinder, characterized in that: It also includes a first cartridge valve, a second cartridge valve, a first shuttle valve, a second shuttle valve, a first two-position three-way directional valve, a second two-position three-way directional valve, and a two-position two-way directional valve; The input end of the main pump is connected to the hydraulic oil tank, and the output end of the main pump is connected to port A of the first cartridge valve. Port B of the first cartridge valve is connected to port P of the two-position two-way directional valve, port A of the second cartridge valve, and port P of the three-position four-way proportional directional valve. Port C of the first cartridge valve is connected to port A of the first shuttle valve. Port P1 of the first shuttle valve is connected to port P of the first two-position three-way directional valve. Port P2 of the first shuttle valve is connected to port B of the first cartridge valve. Port A of the first two-position three-way directional valve is connected to port A of the first cartridge valve. Port T of the two-position two-way directional valve is connected to the hydraulic oil tank. The C port of the second cartridge valve is connected to the A port of the second shuttle valve, the P1 port of the second shuttle valve is connected to the P port of the second two-position three-way directional valve, the P2 port of the second shuttle valve is connected to the P port of the three-position four-way proportional directional valve, the A port of the second two-position three-way directional valve is connected to the B port of the second cartridge valve, the A port of the three-position four-way proportional directional valve is connected to the B port of the injection cylinder, the B port of the three-position four-way proportional directional valve is connected to the A port of the injection cylinder (6), the T port of the three-position four-way proportional directional valve is connected to the hydraulic oil tank, and the output end of the main pump is connected to the injection molding machine mold closing unit. When filling, the servo motor is started and the main pump is driven to work. The main pump draws hydraulic oil from the hydraulic oil tank (1) and pumps it into the filling system. The first two-position three-way directional valve is energized and is in the left position. The P port and B port of the first two-position three-way directional valve are connected. The first cartridge valve is opened. The second two-position three-way directional valve is energized and is in the left position. The P port and B port of the second two-position three-way directional valve are connected. The second cartridge valve is opened. The three-position four-way proportional directional valve is in the middle position. The main pump (3) fills the accumulator with hydraulic oil through the first cartridge valve A port to B port and the second cartridge valve A port to B port. When the set filling pressure is reached, the filling is completed. The first two-position three-way directional valve and the second two-position three-way directional valve are de-energized. The first cartridge valve and the second cartridge valve are closed. The servo motor is controlled to be in standby mode, or the main pump supplies liquid for other injection molding machine actions. During injection, the servo motor is started according to the working conditions, and the first two-position three-way reversing valve, the second two-position three-way reversing valve, and the three-position four-way proportional reversing valve are energized or de-energized to control the injection cylinder for low-speed injection, high-speed injection, or synchronous mold-closing injection. The second cartridge valve is commonly used in the later stage of accumulator filling, reducing the main pump filling flow rate and reducing overflow heat generation.

2. The hydraulic control circuit for a high-speed injection molding machine according to claim 1, characterized in that: A first overflow valve is connected in parallel between the output and input ends of the main pump.

3. The hydraulic control circuit for a high-speed injection molding machine according to claim 1, characterized in that: A second relief valve is connected in parallel to the P port and T port of the two-position two-way reversing valve.

4. The hydraulic control circuit for a high-speed injection molding machine according to claim 1, characterized in that: A first pressure sensor is installed on the input terminal of the accumulator.

5. The hydraulic control circuit for a high-speed injection molding machine according to claim 1, characterized in that: A second pressure sensor is installed at port B of the injection cylinder.

6. The hydraulic control circuit for a high-speed injection molding machine according to claim 1, characterized in that: The main pump is a variable displacement pump.

7. A control method for a high-speed injection molding machine hydraulic control circuit as described in any one of claims 1-6, characterized in that, Includes the following steps: S1. When powered on, the servo motor is powered on and in standby mode; S2. During filling, the servo motor is started and the main pump is driven to work. The first two-position three-way directional valve is energized, and the P port and B port of the first two-position three-way directional valve are connected. The first cartridge valve is opened. The second two-position three-way directional valve is energized, and the P port and B port of the second two-position three-way directional valve are connected. The second cartridge valve is opened. The three-position four-way proportional directional valve is in the middle position. The main pump fills the accumulator with hydraulic oil through the first cartridge valve and the second cartridge valve. After filling is completed, the first two-position three-way directional valve and the second two-position three-way directional valve are de-energized. The first cartridge valve and the second cartridge valve are closed. The servo motor is put into standby mode. S3. During injection, the servo motor is started according to the working conditions, and the first two-position three-way reversing valve, the second two-position three-way reversing valve and the three-position four-way proportional reversing valve are energized or de-energized to realize the control of the injection cylinder for low-speed injection, high-speed injection or synchronous mold closing injection. S4. When the machine stops, the two-position two-way directional valve loses power, and the high-pressure oil in the accumulator is unloaded to the hydraulic oil tank.

8. The control method according to claim 7, characterized in that, Step S3 includes the following: During low-speed injection, the servo motor drives the main pump, energizes the first and second position three-way directional valves, connects the P and B ports of the first and second position three-way directional valves, opens the first cartridge valve, and the main pump outputs high-pressure oil. At the same time, the second and second position three-way directional valves are de-energized, the second cartridge valve is closed, the accumulator pressure oil does not participate in the action, the left side of the three-position four-way proportional directional valve is energized, and the hydraulic oil flows through the P port of the three-position four-way proportional directional valve to the B port and reaches the B port of the injection cylinder. When the injection and pressure holding action is completed, the first and second position three-way directional valves are de-energized, the first cartridge valve is closed, and the control servo motor is in standby mode. During high-speed injection, the servo motor drives the main pump, energizes the first and second position three-way directional valves, connects the P and B ports of the first and second position three-way directional valves, opens the first cartridge valve, and the main pump outputs high-pressure oil. At the same time, the second and second position three-way directional valves are energized, connect the P and B ports of the second and second cartridge valves, and open the second cartridge valve. The hydraulic oil from the main pump and the accumulator flows into each other. The hydraulic oil flows through the P port of the three-position four-way proportional directional valve to the B port and reaches the B port of the injection cylinder. After the injection and pressure holding action is completed, the first and second position three-way directional valves and the second and second position three-way directional valves are de-energized, the first and second cartridge valves are closed, and the control servo motor is in standby mode. During synchronous injection molding, the servo motor drives the main pump, the first two-position three-way directional valve is de-energized, the first cartridge valve is closed, the second two-position three-way directional valve is energized, the second cartridge valve is opened, and the hydraulic oil from the accumulator flows through the P port of the three-position four-way proportional directional valve to the B port and reaches the B port of the injection cylinder. The flow rate of the main pump is delivered to the injection molding machine's mold closing unit, thereby realizing the synchronous operation of the injection cylinder and the injection molding machine's mold closing unit.

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