Hydraulic control loop of high-speed injection molding machine and control method of hydraulic control loop

Abstract

The invention relates to the technical field of hydraulic control loops, in particular to a high-speed injection molding machine hydraulic control loop and a control method thereof, and the high-speed injection molding machine hydraulic control loop comprises a first cartridge valve, a second cartridge valve, a first shuttle valve, a second shuttle valve, a first two-position three-way reversing valve, a second two-position three-way reversing valve and a two-position two-way reversing 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 a port A of a first cartridge valve, a port B of the first cartridge valve is communicated with a port P of a two-position two-way reversing valve, a port A of a second cartridge valve and a port P of a three-position four-way proportional reversing valve, and a port C of the first cartridge valve is communicated with a port A of a first shuttle valve. During use, an injection and liquid filling hydraulic control loop is optimized, the drift diameter of the second cartridge valve is small, the cost advantage is achieved, the liquid filling flow of a main pump is reduced in the liquid filling later period of the energy accumulator, overflow heating is reduced, and it is guaranteed that the injection molding machine normally operates stably and reliably.

Description

Technical Field

[0001] The present invention relates to the technical field of hydraulic control circuits, and particularly to a hydraulic control circuit for a high-speed injection molding machine and its control method. Background Art

[0002] For injection molding machines that require high-speed injection, in order to save costs or pump room space, an accumulator is generally considered as an auxiliary power source to increase the output flow of the hydraulic system. When the hydraulic circuit of an existing injection molding machine is operating and the valve is working, the hydraulic pump and the accumulator will output flow simultaneously, resulting in a large requirement for the through-hole diameter at the valve. 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 as the flow is output. In order to ensure that there is sufficient pressure and the pressure can maintain high speed throughout the injection process of the injection molding machine, therefore, higher requirements are imposed on the charging pressure ratio and working pressure of the accumulator. In order to meet the high requirements of the charging pressure ratio and working pressure of the accumulator, higher output torque and power of the motor need to be considered. Therefore, based on the characteristics of the accumulator volume and the charging pressure, in the later stage of charging, a small volume change will result in a large pressure change, and a large-displacement hydraulic pump is more likely to be overcharged, leading to overflow and heat generation, which seriously affects the normal operation of the injection molding machine when severe. Summary of the Invention

[0003] The technical problem to be solved by the present invention is: to solve the problem that in the later stage of charging of an existing accumulator, a small volume change will result in a large pressure change, and a large-displacement hydraulic pump is more likely to be overcharged, leading to overflow and heat generation, which seriously affects the normal operation of the injection molding machine. Now, a hydraulic control circuit for a high-speed injection molding machine and its control method are provided.

[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 reversing valve, and an injection cylinder, further including a first cartridge valve, a second cartridge valve, a first shuttle valve, a second shuttle valve, a first two-position three-way reversing valve, a second two-position three-way reversing valve, and a two-position two-way reversing valve;

[0005] The input end of the main pump is communicated with the hydraulic oil tank, the output end of the main pump is communicated with the port A of the first cartridge valve, the port B of the first cartridge valve is respectively communicated with the port P of the two-position two-way directional valve, the port A of the second cartridge valve and the port P of the three-position four-way proportional directional valve, the port C of the first cartridge valve is communicated with the port A of the first shuttle valve, the port P1 of the first shuttle valve is communicated with the port P of the first two-position three-way directional valve, the port P2 of the first shuttle valve is communicated with the port B of the first cartridge valve, the port A of the first two-position three-way directional valve is communicated with the port A of the first cartridge valve, the port T of the two-position two-way directional valve is communicated with the hydraulic oil tank, the port C of the second cartridge valve is communicated with the port A of the second shuttle valve, the port P1 of the second shuttle valve is communicated with the port P of the second two-position three-way directional valve, the port P2 of the second shuttle valve is communicated with the port P of the three-position four-way proportional directional valve, the port A of the second two-position three-way directional valve is communicated with the port B of the second cartridge valve, the port A of the three-position four-way proportional directional valve is communicated with the port B of the injection oil cylinder, the port B of the three-position four-way proportional directional valve is communicated with the port A of the injection oil cylinder, the port T of the three-position four-way proportional directional valve is communicated with the hydraulic oil tank, and the output end of the main pump is communicated with the clamping unit of the injection molding machine.

[0006] In some preferred embodiments, a first relief 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 between the port P and the port T of the two-position two-way directional valve.

[0008] In some preferred embodiments, a first pressure sensor is provided at the input end of the accumulator.

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

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

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

[0012] S1. When starting up, the servo motor is powered on and in a standby state;

[0013] S2. During liquid filling, start the servo motor and drive the main pump to work. The first two-position three-way directional valve is energized, the port P and the port B of the first two-position three-way directional valve are communicated, the first cartridge valve is opened, the second two-position three-way directional valve is energized, the port P and the port B of the second two-position three-way directional valve are communicated, 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. When the liquid filling is completed, both the first two-position three-way directional valve and the second two-position three-way directional valve are de-energized, both the first cartridge valve and the second cartridge valve are closed, and the servo motor is controlled to be in a standby state;

[0014] S3. During injection, start the servo motor according to the working conditions, and control the first two-position three-way directional control valve, the second two-position three-way directional control valve, and the three-position four-way proportional directional control valve to be energized or de-energized, so as to control the low-speed injection, high-speed injection, or synchronous mold clamping injection of the injection cylinder;

[0015] S4. When stopping the machine, the two-position two-way directional control valve is de-energized, and the high-pressure oil of the accumulator is unloaded to the hydraulic oil tank.

[0016] Preferably, in some embodiments, step S3 respectively includes:

[0017] When performing low-speed injection, the servo motor drives the main pump to work, the first two-position three-way directional control valve is energized, the P port and the B port of the first two-position three-way directional control valve are connected, the first cartridge valve opens, and the main pump outputs high-pressure oil. At the same time, the second two-position three-way directional control valve is de-energized, the second cartridge valve closes, and the pressure oil of the accumulator does not participate in the action. The left side of the three-position four-way proportional directional control valve is energized, and the hydraulic oil passes through the P port of the three-position four-way proportional directional control valve to the B port and reaches the B port of the injection cylinder, reaching the injection cylinder. When the injection and holding pressure action is completed, the first two-position three-way directional control valve is de-energized, the first cartridge valve closes, and the servo motor is controlled to be in a standby state;

[0018] When performing high-speed injection, the servo motor drives the main pump to work, the first two-position three-way directional control valve is energized, the P port and the B port of the first two-position three-way directional control valve are connected, the first cartridge valve opens, and the main pump outputs high-pressure oil. At the same time, the second two-position three-way directional control valve is energized, the P port and the B port of the second two-position three-way directional control valve are connected, the second cartridge valve opens, and the hydraulic oil of the main pump and the accumulator converges with each other. The hydraulic oil passes through the P port of the three-position four-way proportional directional control valve to the B port and reaches the B port of the injection cylinder, reaching the injection cylinder. When the injection and holding pressure action is completed, the first two-position three-way directional control valve and the second two-position three-way directional control valve are de-energized, the first cartridge valve and the second cartridge valve close, and the servo motor is controlled to be in a standby state;

[0019] When performing synchronous mold clamping injection, the servo motor drives the main pump to work, the first two-position three-way directional control valve is de-energized, the first cartridge valve closes, the second two-position three-way directional control valve is energized, the second cartridge valve opens, and the hydraulic oil of the accumulator passes through the P port of the three-position four-way proportional directional control valve to the B port and reaches the B port of the injection cylinder, reaching the injection cylinder. The flow rate of the main pump is delivered to the mold clamping unit of the injection molding machine, so as to realize the synchronous action of the injection cylinder and the mold clamping unit of the injection molding machine.

[0020] The beneficial effects of the present invention are as follows: When the hydraulic control circuit and its control method of a high-speed injection molding machine according to the present invention are 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 stage of the accumulator liquid filling, the liquid filling flow rate of the main pump is reduced, the overflow heat is reduced, and the normal operation of the injection molding machine is ensured to be stable and reliable. It avoids the problem that in the later stage of the existing accumulator liquid filling, a relatively small volume change will cause a relatively large pressure change, and a large-displacement hydraulic pump is more likely to be overfilled with liquid, resulting in overflow heat, which seriously affects the normal operation of the injection molding machine when severe. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0022] Figure 1 It is a schematic structural diagram of the present invention.

[0023] In the figure: 1, hydraulic oil tank; 2, servo motor; 3, main pump; 4, accumulator; 5, three-position four-way proportional reversing 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 reversing valve; 12, second two-position three-way reversing valve; 13, two-position two-way reversing valve; 14, first overflow valve; 15, second overflow valve; 16, first pressure sensor; 17, second pressure sensor. DETAILED DESCRIPTION OF THE EMBODIMENTS

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

[0025] The present invention is not limited to the following specific embodiments. Those of ordinary skill in the art can implement the present invention in other various specific embodiments according to the content disclosed in the present invention, or any simple changes or modifications made by adopting the design structure and idea of the present invention fall within the protection scope of the present invention. It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other.

[0026] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first", "second", etc. may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise specified, the meaning of "a plurality" is two or more.

[0027] In the description of the present invention, it should be noted that unless otherwise clearly specified and defined, the terms "mounted", "connected", "coupled" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood through specific circumstances.

[0028] As Figure 1 shown, a hydraulic control circuit of 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 reversing 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 reversing valve 11, a second two-position three-way reversing valve 12, and a two-position two-way reversing valve 13;

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

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

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

[0032] In this embodiment, the main pump 3 is an electronic variable pump. When the displacement of the electronic variable pump decreases, the torque requirement of the main pump 3 is reduced. Therefore, a motor with large torque and power is not required.

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

[0034] Embodiment 2

[0035] Embodiment 2 is a control method for a hydraulic control circuit of a high-speed injection injection molding machine in Embodiment 1. Specifically, it is: a control method for a hydraulic control circuit of a high-speed injection injection molding machine as described above, which includes the following steps:

[0036] S1. When starting up, the servo motor 2 is powered on and in a standby state. The first relief valve 14 limits the maximum system pressure to prevent the main pump 3 from overpressure and the servo motor 2 from overloading. The second relief valve 15 limits the maximum filling pressure.

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

[0038] S3. During injection, control the start of the servo motor 2 according to the working conditions, and control the first two-position three-way directional control valve 11, the second two-position three-way directional control valve 12, and the three-position four-way proportional directional control valve 5 to be energized or de-energized to achieve the control of low-speed injection, high-speed injection, or synchronous mold closing injection of the injection cylinder 6;

[0039] S4. When shutting down, the two-position two-way directional control valve 13 is de-energized, and the high-pressure oil in the accumulator 4 is unloaded to the hydraulic oil tank 1 to reduce safety risks.

[0040] Among them, step S3 respectively includes:

[0041] When injecting at low speed, the servo motor 2 drives the main pump 3 to work. The first two-position three-way directional control valve 11 is energized and located in the left position. The P port and B port of the first two-position three-way directional control valve 11 are connected, and the first cartridge valve 7 opens. The main pump 3 outputs high-pressure oil. At the same time, the second two-position three-way directional control valve 12 is de-energized and located in the right position. The second cartridge valve 8 is closed, and the pressure oil in the accumulator 4 does not participate in the action. The left side of the three-position four-way proportional directional control valve 5 is energized, and the hydraulic oil passes through the P port to B port of the three-position four-way proportional directional control valve 5 and reaches the B port of the injection cylinder 6, reaching the injection cylinder 6. The second pressure sensor 17 is mainly used for pressure control during injection and holding pressure. When the injection and holding pressure actions are completed, the first two-position three-way directional control valve 11 is de-energized, and the first cartridge valve 7 is closed. The servo motor 2 is controlled to be in a standby state, or the main pump 3 supplies liquid for other injection molding machine operations. Compared with the original control circuit, during low-speed injection, the accumulator 4 also needs to participate. After the injection action ends, an additional liquid filling step for the accumulator 4 is required, and the servo motor 2 also needs to be frequently started, resulting in frequent use of the accumulator 4 and reducing the life of its bladder. This solution does not require the participation of the accumulator 4, which can extend the life of the bladder of the accumulator 4. In addition, the servo motor 2 has no additional liquid filling time, increasing the cooling time of the servo motor 2;

[0042] When injecting at high speed, the servo motor 2 drives the main pump 3 to work. The first two-position three-way directional control valve 11 is energized and located in the left position. The P port and B port of the first two-position three-way directional control valve 11 are connected, and the first cartridge valve 7 opens. The main pump 3 outputs high-pressure oil. At the same time, the second two-position three-way directional control valve 12 is energized and located in the left position. The P port and B port of the second two-position three-way directional control valve 12 are connected, and the second cartridge valve 8 opens. The left side of the three-position four-way proportional directional control valve 5 is energized and located in the left position. The hydraulic oil of the main pump 3 and the accumulator 4 converges with each other. The hydraulic oil passes through the P port to the B port of the three-position four-way proportional directional control valve 5 and reaches the B port of the injection cylinder 6, reaching the injection cylinder 6. The second pressure sensor 17 is mainly used for pressure control during the injection and holding pressure processes. After the injection and holding pressure actions are completed, the first two-position three-way directional control valve 11 and the second two-position three-way directional control valve 12 are de-energized, the first cartridge valve 7 and the second cartridge valve 8 are closed, and the servo motor 2 is controlled to be in a standby state, or the main pump 3 supplies liquid for other injection molding machine actions;

[0043] When synchronously clamping and injecting, the servo motor 2 drives the main pump 3 to work. The first two-position three-way directional control 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 control valve 12 is energized and located in the left position. The second cartridge valve 8 opens. The hydraulic oil of the accumulator 4 passes through the P port to the B port of the three-position four-way proportional directional control valve 5 and reaches the B port of the injection cylinder 6, reaching the injection cylinder 6. In this circuit, the hydraulic oil for the injection action is only provided by the accumulator 4, and the flow rate of the main pump 3 is delivered to the clamping unit of the injection molding machine, thereby realizing the synchronous action of the injection cylinder 6 and the clamping unit of the injection molding machine.

[0044] Based on the inspiration of the ideal embodiments of the present invention, through the above description, relevant staff can completely make various changes and modifications without departing from the technical idea of this invention. The technical scope of this invention is not limited to the content in the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A hydraulic control circuit for a high-speed injection molding machine, comprising a hydraulic oil tank, a servo motor, a main pump, an accumulator, a three-position four-way proportional directional control 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 control valve, a second two-position three-way directional control valve, and a two-position two-way directional control valve; The input end of the main pump is communicated with the 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 control valve, the A port of the second cartridge valve, and the P port of the three-position four-way proportional directional control 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 control valve, the P2 port of the first shuttle valve is communicated with the B port of the first cartridge valve, the A port of the first two-position three-way directional control valve is communicated with the A port of the first cartridge valve, the T port of the two-position two-way directional control valve is communicated with the hydraulic oil tank, the C port of the second cartridge valve is communicated with the A port of the second shuttle valve, the P1 port of the second shuttle valve is communicated with the P port of the second two-position three-way directional control valve, the P2 port of the second shuttle valve is communicated with the P port of the three-position four-way proportional directional control valve, the A port of the second two-position three-way directional control valve is communicated with the B port of the second cartridge valve, the A port of the three-position four-way proportional directional control valve is communicated with the B port of the injection cylinder, the B port of the three-position four-way proportional directional control valve is communicated with the A oil port of the injection cylinder 6, the T port of the three-position four-way proportional directional control valve is communicated with the hydraulic oil tank, and the output end of the main pump is communicated with the clamping unit of the injection molding machine.

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

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

4. A hydraulic control circuit of a high-speed injection molding machine according to claim 1, characterized in that: A first pressure sensor is provided at the input end of the accumulator.

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

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

7. A control method for a hydraulic control circuit of a high-speed injection molding machine using the hydraulic control circuit according to any one of claims 1-6, characterized in that, It includes the following steps: S1. When starting up, the servo motor is powered on and in a standby state; S2. During liquid filling, the servo motor is started and drives the main pump to work. The first two-position three-way directional control valve is energized, the P port and the B port of the first two-position three-way directional control valve are communicated, the first cartridge valve is opened, the second two-position three-way directional control valve is energized, the P port and the B port of the second two-position three-way directional control valve are communicated, the second cartridge valve is opened, the three-position four-way proportional directional control 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. When the liquid filling is completed, both the first two-position three-way directional control valve and the second two-position three-way directional control valve are de-energized, both the first cartridge valve and the second cartridge valve are closed, and the servo motor is controlled to be in a standby state; S3. During injection, the servo motor is controlled to start according to the working conditions, and the first two-position three-way directional control valve, the second two-position three-way directional control valve, and the three-position four-way proportional directional control valve are controlled to be energized or de-energized to achieve the control of low-speed injection, high-speed injection, or synchronous clamping injection of the injection cylinder; S4. When shutting down, the two-position two-way directional control valve is de-energized, and the high-pressure oil of the accumulator is unloaded to the hydraulic oil tank.

8. The control method according to claim 7, wherein Among them, step S3 respectively includes: When injecting at low speed, the servo motor drives the main pump to work. The first two-position three-way directional control valve is energized, and the P port and B port of the first two-position three-way directional control valve are connected. The first cartridge valve opens, and the main pump outputs high-pressure oil. At the same time, the second two-position three-way directional control valve is de-energized, the second cartridge valve closes, and the pressure oil of the accumulator does not participate in the action. The left side of the three-position four-way proportional directional control valve is energized, and the hydraulic oil passes through the P port of the three-position four-way proportional directional control valve to the B port and reaches the B port of the injection cylinder. When the injection and holding pressure action is completed, the first two-position three-way directional control valve is de-energized, the first cartridge valve closes, and the servo motor is controlled to be in a standby state; When injecting at high speed, the servo motor drives the main pump to work. The first two-position three-way directional control valve is energized, and the P port and B port of the first two-position three-way directional control valve are connected. The first cartridge valve opens, and the main pump outputs high-pressure oil. At the same time, the second two-position three-way directional control valve is energized, the P port and B port of the second two-position three-way directional control valve are connected, the second cartridge valve opens, and the hydraulic oil of the main pump and the accumulator converges with each other. The hydraulic oil passes through the P port of the three-position four-way proportional directional control valve to the B port and reaches the B port of the injection cylinder. When the injection and holding pressure action is completed, the first two-position three-way directional control valve and the second two-position three-way directional control valve are de-energized, the first cartridge valve and the second cartridge valve close, and the servo motor is controlled to be in a standby state; When synchronously clamping and injecting, the servo motor drives the main pump to work. The first two-position three-way directional control valve is de-energized, the first cartridge valve closes, the second two-position three-way directional control valve is energized, the second cartridge valve opens, and the hydraulic oil of the accumulator passes through the P port of the three-position four-way proportional directional control valve to the B port and reaches the B port of the injection cylinder. When it reaches the injection cylinder, the flow rate of the main pump is delivered to the clamping unit of the injection molding machine, thereby realizing the synchronous action of the injection cylinder and the clamping unit of the injection molding machine.

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