A hydraulic control system for injection molding machine

Abstract

The invention discloses a hydraulic control system for an injection molding machine, comprising an oil tank, an energy unit and an execution unit, wherein the energy unit comprises a servo driver, a servo motor and a bidirectional closed pump, the oil tank supplies oil to the bidirectional closed pump, the servo motor is driven by the servo driver, the bidirectional closed pump is driven by the servo motor, the oil inlet end of the bidirectional closed pump is connected to the oil return end of the execution unit through a first working oil circuit, and the oil outlet end of the bidirectional closed pump is connected to the oil inlet end of the execution unit through a second working oil circuit. The advantages are simple structure, precision, high efficiency and energy saving.

Description

Technical Field

[0001] The invention relates to a hydraulic system, in particular to a hydraulic control system for an injection molding machine. Background Art

[0002] The hydraulic control system of the injection molding machine is an important part of the injection molding machine. For example, in the control of injection, sol, mold opening and closing, and ejection of the injection molding machine, the conventional use is as follows Figure 1 The form shown is mainly composed of energy unit A1, control and regulation unit A2, execution unit A3, auxiliary unit and working medium. Energy unit A1 is usually composed of servo driver A10, servo motor A9 and metering pump A8, and its function is to convert the mechanical energy provided by servo motor A9 into pressure energy of liquid; control and regulation unit A2 is mainly composed of various valves, and its function is to control and regulate the pressure, flow and direction of liquid; execution unit A3 generally refers to hydraulic cylinder or hydraulic motor, and its function is to convert the pressure energy of liquid into mechanical energy, and drive the load to do linear reciprocating motion or rotary motion; auxiliary unit generally includes oil tank A7, oil filter A4, cooler A5, pressure sensor A11, pressure gauge A6, liquid level gauge A12, oil pipe and joints, etc.; working medium generally refers to hydraulic oil, which is responsible for energy transmission in hydraulic system.

[0003] The working principle of the above hydraulic control system is as follows: after the metering pump A8 is driven by the servo motor A9 to rotate, it absorbs oil from the oil tank A7. The oil enters the metering pump A8 through the oil filter A4, and then the oil is output from the metering pump A8 into the pipeline to reach the reversing valve A13. After the left or right end of the reversing valve A13 is powered, the oil enters the actuator A3 through the B port or the C port, driving the actuator A3 to perform linear reciprocating motion or rotary motion.

[0004] Due to the existence of the control and adjustment unit 2, the oil circuit design of the above-mentioned hydraulic control system is usually more complicated. The more complicated the oil circuit is, the greater the pressure loss is. The greater the pressure loss is, the lower the efficiency of the entire system is and the higher the energy consumption is. In addition, when the execution unit 3 starts to run, since it is difficult to synchronize the metering pump 8 and the reversing valve 13, the existence of the time difference will cause the starting shock. When the metering pump 8 and each valve are closed and the execution unit 3 stops, the existence of inertia will cause the stopping shock, and the stopping positioning of the execution unit 3 is inaccurate. Similarly, when the reversing valve 13 in the control and adjustment unit 2 is reversed to drive the execution unit 3 to move in the opposite direction, due to the existence of the inertia of the execution unit 3, the shock during reversal is large and difficult to eliminate. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a precise, efficient and energy-saving hydraulic control system for an injection molding machine.

[0006] The technical solution adopted by the present invention to solve the above technical problems is:

[0007] A hydraulic control system for an injection molding machine comprises an oil tank, an energy unit and an execution unit, wherein the energy unit comprises a servo drive, a servo motor and a bidirectional closed pump, the oil tank replenishes oil for the bidirectional closed pump, the servo motor is driven by the servo drive, the bidirectional closed pump is driven by the servo motor, the oil inlet end of the bidirectional closed pump is connected to the oil return end of the execution unit via a first working oil circuit, and the oil outlet end of the bidirectional closed pump is connected to the oil inlet end of the execution unit via a second working oil circuit.

[0008] A pressure sensor is provided on the first working oil circuit and the second working oil circuit respectively, and the pressure sensor is connected to the servo driver by electrical signals. The two pressure sensors are used to respectively collect the oil pressure of the first working oil circuit and the second working oil circuit, and the collected oil pressure is fed back to the servo driver. The servo motor feeds back the current speed information to the servo driver through the encoder, and the servo driver feeds back the received information to the controller on the injection molding machine, compares it with the value set in the controller, and adjusts the output value of the servo driver to the servo motor accordingly, so as to realize dynamic control of the servo motor speed and realize accurate closed-loop control of pressure and flow.

[0009] It also includes an oil replenishment unit, the oil replenishment unit includes an oil replenishment valve group and an oil replenishment power group, the oil replenishment power group includes an oil replenishment pump and a three-phase asynchronous motor for driving the oil replenishment pump, and the oil replenishment valve group includes a first overflow valve, a second overflow valve, a third overflow valve, a flushing valve, a first check valve and a second check valve;

[0010] The two oil inlet ends of the flushing valve are connected to the first working oil circuit and the second working oil circuit respectively, the oil outlet end of the flushing valve is connected to the oil inlet end of the first overflow valve, and the oil return end of the first overflow valve is connected to the oil tank;

[0011] The oil inlet end of the second overflow valve is connected to the first working oil circuit, the oil inlet end of the third overflow valve is connected to the second working oil circuit, the oil return end of the second overflow valve is connected to the second working oil circuit, the oil return end of the third overflow valve is connected to the first working oil circuit, the oil outlet end of the first check valve is connected to the first working oil circuit, the oil outlet end of the second check valve is connected to the second working oil circuit, the common oil circuit formed by the oil inlet ends of the first check valve and the second check valve is connected to the oil outlet end of the oil replenishment pump, and the oil inlet end of the oil replenishment pump is connected to the oil tank;

[0012] The common oil circuit formed by connecting the oil inlet ends of the first check valve and the second check valve is connected to the oil tank through the fourth overflow valve, the common oil circuit formed by connecting the oil inlet ends of the first check valve and the second check valve is connected to the oil inlet end of the fourth overflow valve, and the oil return end of the fourth overflow valve is connected to the oil tank. The above structure can effectively solve the oil leakage and oil heating problems that occur during the operation of the entire hydraulic system, ensuring the stable operation of the entire hydraulic system.

[0013] An oil suction filter is arranged between the oil inlet end of the oil replenishment pump and the oil tank, the first port of the oil suction filter is connected to the oil tank, and the second port of the oil suction filter is connected to the oil inlet end of the oil replenishment pump. The oil suction filter is arranged here, and the pollutants remaining in the oil tank can be filtered out by the oil suction filter to protect the oil replenishment pump.

[0014] The oil outlet of the oil replenishment pump is provided with a high-pressure filter, the first port of the high-pressure filter is connected to the oil outlet of the oil replenishment pump, and the common oil path formed by connecting the oil inlet of the fourth overflow valve, the first check valve and the second check valve is respectively connected to the second port of the high-pressure filter. The high-pressure filter is provided here to prevent pollutants from entering the entire hydraulic system, effectively control the pollution concentration of the hydraulic system, and protect important components such as the two-way closed pump.

[0015] The oil return ends of the first overflow valve and the fourth overflow valve are connected to the oil tank through a cooler, and the oil return ends of the first overflow valve and the fourth overflow valve are respectively connected to the first port of the cooler, and the second port of the cooler is connected to the oil tank. The cooler is used to cool the hot oil flushed back from the first working oil circuit or the second working oil circuit. The hot oil is cooled by the cooler to become cold oil and enters the oil tank for recycling, thereby effectively controlling the heating of the entire system during operation and ensuring the stable and efficient operation of the entire system.

[0016] The oil drain port of the bidirectional closed pump is connected to the oil tank, so that the leaked hot oil can be cooled in the oil tank and then recycled.

[0017] The flushing valve is a three-position three-way valve with a simple structure and convenient control.

[0018] The execution unit is an equal-area double-rod oil cylinder. The execution unit uses an equal-area double-rod oil cylinder to achieve the same oil inlet and outlet flow rates and realize the circulation work of the closed system.

[0019] The execution unit is a bidirectional rotating hydraulic motor. The execution unit uses a hydraulic motor to achieve the same oil inlet and outlet flow rates, thereby achieving the circulation work of the closed system.

[0020] The oil drain port of the bidirectional rotary hydraulic motor is connected to the oil tank, so that the leaked hot oil can be cooled in the oil tank and then recycled.

[0021] Compared with the prior art, the advantages of the present invention are: simple structure, the oil inlet end of the two-way closed pump is directly connected to the oil return end of the execution unit through the first working oil circuit, the oil outlet end of the two-way closed pump is directly connected to the oil inlet end of the execution unit through the second working oil circuit, the forward and reverse rotation of the two-way closed pump is controlled by the servo driver and the servo motor to drive the execution unit to perform reciprocating or two-way rotation movement, and the control and adjustment device in the conventional hydraulic system is omitted. Therefore, firstly, the problem of the starting impact of the execution unit caused by the asynchronous opening of the pump valve does not exist; secondly, the layout of the pipeline is simplified, making the overall structure compact and saving space; the servo The motor drives the bidirectional closed pump to output hydraulic oil to drive the actuator to move, which is basically equivalent to the servo motor directly driving the actuator. The starting, braking and reversing of the actuator are all controlled and adjusted by the servo driver and servo motor. The action response is faster (about 80% higher than the traditional technology) and the position control is more precise (up to about 80% higher than the traditional technology). It avoids the hydraulic shock and energy loss caused by the traditional hydraulic system that achieves reversing and speed regulation through control and adjustment devices. It is more precise, efficient and energy-saving. It can also be used in situations where multiple actions work synchronously in the injection molding machine, thereby effectively improving production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is the schematic diagram of the hydraulic system used for mold opening and closing control of a traditional injection molding machine;

[0023] Figure 2 This is a schematic diagram of the first embodiment of the present invention;

[0024] Figure 3 This is a schematic diagram of the second embodiment of the present invention. DETAILED DESCRIPTION

[0025] The present invention is further described in detail below with reference to the accompanying drawings.

[0026] Embodiment 1: Figure 1As shown, a hydraulic control system for an injection molding machine includes an oil tank 1, an energy unit and an execution unit 5. The energy unit includes a servo driver 2, a servo motor 3 and a bidirectional closed pump 4. The oil tank 1 replenishes oil to the bidirectional closed pump 4. The servo motor 3 is driven by the servo driver 2. The bidirectional closed pump 4 is driven by the servo motor 3. The oil inlet end of the bidirectional closed pump 4 is connected to the oil return end of the execution unit 5 through a first working oil circuit D, and the oil outlet end of the bidirectional closed pump 4 is connected to the oil inlet end of the execution unit 5 through a second working oil circuit E.

[0027] In this specific embodiment, a pressure sensor 6 is provided on the first working oil circuit D and the second working oil circuit E, respectively, and the pressure sensor 6 is electrically connected to the servo driver 2. The two pressure sensors 6 are used to respectively collect the oil pressure of the first working oil circuit D and the second working oil circuit E, and the collected oil pressure is fed back to the servo driver 2. The servo motor 3 feeds back the current speed information to the servo driver 2 through the encoder. The servo driver 2 feeds back the received information to the controller on the injection molding machine, compares it with the value set in the controller, and adjusts the output value of the servo driver 2 to the servo motor 3 accordingly, so as to realize the dynamic control of the speed of the servo motor 3 and realize the precise closed-loop control of the pressure and flow.

[0028] In this specific embodiment, an oil replenishment unit is also included, the oil replenishment unit includes an oil replenishment valve group and an oil replenishment power group, the oil replenishment power group includes an oil replenishment pump 7 and a three-phase asynchronous motor 8 for driving the oil replenishment pump 7, and the oil replenishment valve group includes a first overflow valve 9, a second overflow valve 10, a third overflow valve 11, a flushing valve 12, a first check valve 13 and a second check valve 14;

[0029] The two oil inlet ends of the flushing valve 12 are connected to the first working oil circuit D and the second working oil circuit E respectively, the oil outlet end of the flushing valve 12 is connected to the oil inlet end of the first overflow valve 9, and the oil return end of the first overflow valve 9 is connected to the oil tank 1;

[0030] The oil inlet end of the second relief valve 10 is connected to the first working oil circuit D, the oil inlet end of the third relief valve 11 is connected to the second working oil circuit E, the oil return end of the second relief valve 10 is connected to the second working oil circuit D, the oil return end of the third relief valve 11 is connected to the first working oil circuit E, the oil outlet end of the first check valve 13 is connected to the first working oil circuit D, the oil outlet end of the second check valve is connected to the second working oil circuit E, the common oil circuit formed by the oil inlet ends of the first check valve 13 and the second check valve 14 is connected to the oil outlet end of the oil replenishment pump 7, and the oil inlet end of the oil replenishment pump 7 is connected to the oil tank 1;

[0031] The common oil circuit formed by connecting the oil inlet ends of the first check valve 13 and the second check valve 14 is connected to the oil tank 1 through the fourth relief valve 15, and the common oil circuit formed by connecting the oil inlet ends of the first check valve 13 and the second check valve 14 is connected to the oil inlet end of the fourth relief valve 15, and the oil return end of the fourth relief valve 15 is connected to the oil tank 1. The above structure can effectively solve the oil leakage and oil heating problems of the entire hydraulic system during operation, ensuring the stable operation of the entire hydraulic system.

[0032] In this specific embodiment, an oil suction filter 16 is provided between the oil inlet end of the oil replenishment pump 7 and the oil tank 1, a first port of the oil suction filter 16 is connected to the oil tank 1, and a second port of the oil suction filter 16 is connected to the oil inlet end of the oil replenishment pump 7. The oil suction filter 16 is provided here, and the pollutants remaining in the oil tank 1 can be filtered out by the oil suction filter 16, so as to protect the oil replenishment pump 7.

[0033] In this specific embodiment, a high-pressure filter 17 is provided at the oil outlet of the oil replenishment pump 7, a first port of the high-pressure filter 17 is connected to the oil outlet of the oil replenishment pump 7, and a common oil path formed by connecting the oil inlet of the fourth relief valve 15, the first check valve 13, and the oil inlet of the second check valve 14 is respectively connected to the second port of the high-pressure filter 17. The high-pressure filter 17 is provided here, and the high-pressure filter 17 can prevent pollutants from entering the entire hydraulic system, effectively control the pollution concentration of the hydraulic system, and protect important components such as the two-way closed pump 4.

[0034] In this specific embodiment, the return oil ends of the first relief valve 9 and the fourth relief valve 15 are connected to the oil tank 1 through a cooler 18. The return oil ends of the first relief valve 9 and the fourth relief valve 15 are respectively connected to the first port of the cooler 18, and the second port of the cooler 18 is connected to the oil tank 1. The cooler 18 is used to cool the hot oil flushed back from the first working oil circuit D or the second working oil circuit E. The hot oil is cooled by the cooler 18 to become cold oil and enters the oil tank 1 for recycling, thereby effectively controlling the heating of the entire system during operation and ensuring the stable and efficient operation of the entire system.

[0035] In this specific embodiment, the oil drain port of the bidirectional closed pump 4 is connected to the oil tank 1. The leaked hot oil can be cooled in the oil tank 1 and then recycled.

[0036] In this specific embodiment, the flushing valve 12 is a three-position three-way valve with a simple structure and convenient control.

[0037] In this specific embodiment, the execution unit 5 is an equal-area double-rod oil cylinder. The execution unit 5 uses an equal-area double-rod oil cylinder to achieve the same oil inlet and outlet flow rates and realize the circulation work of the closed system.

[0038] Among them, the servo motor 3 drives the two-way closed pump 4 to work in forward and reverse directions respectively to control the oil pressure and flow; the two-way closed pump 4 can rotate in forward and reverse directions and can work normally; the two pressure sensors 6 are responsible for collecting the oil pressure of the two working oil circuits and feeding it back to the servo driver 2; the first one-way valve 13 and the second one-way valve 14 are used for one-way oil passage to prevent the oil from backflowing back to the replenishment pump 7 when replenishing oil; the second relief valve 10 and the third relief valve 11 are used to prevent the first working oil circuit D and the second working oil circuit E from overloading the pressure and limit the maximum pressure during operation. The first relief valve 9 mainly plays the role of maintaining the replenishment pressure, and the fourth relief valve 15 plays the role of limiting the pressure of the replenishment pump 7; When there is a pressure difference between the first working oil circuit D and the second working oil circuit E, the flushing valve 12 is opened by high pressure, and the oil of the oil replenishing pump 7 is replenished into the working oil circuit with lower oil pressure, and then returns to the oil tank 1 through the flushing valve 12 and the first overflow valve 9. Since the oil replenishing pump 7 replenishes filtered cold oil and flushes back hot oil, this circulation process can filter and cool the oil in the working oil circuit; the oil replenishing pump 7 is a quantitative pump driven by a three-phase asynchronous motor 8; the cooler 18 cools the hot oil flushed back from the first working oil circuit D and the second working oil circuit E; the oil tank 1 is used to provide cold oil to the oil replenishing pump 7 and the two-way closed pump 4 and collect the hot oil returned from the working oil circuit.

[0039] The working principle is as follows: assuming that when the servo motor 3 drives the bidirectional closed pump 4 to rotate forward, the first working oil circuit D is a high-pressure oil circuit, and the second working oil circuit E is a low-pressure oil circuit, then the two pressure sensors 6 feed back the current pressure information to the servo driver 2, and the servo motor 3 feeds back the current speed information to the servo driver 2 through the encoder, and the servo driver 2 feeds back the received information to the controller on the injection molding machine, compares it with the value given in the controller, and adjusts the output value of the servo driver 2 to the servo motor 3 accordingly, dynamically controls the servo motor 3, and realizes precise closed-loop control of pressure and flow; when the actuator needs to be reversed, the servo motor 3 drives the bidirectional closed pump 4 to reverse, the first working oil circuit D is a low-pressure oil circuit, and the second working oil circuit E is a high-pressure oil circuit, and the two pressure sensors 6 feed back the current pressure information to the servo driver 2, and the servo motor 3 feeds back the current speed information to the servo driver 2 through the encoder, and the servo driver 2 feeds back the received information to the controller on the injection molding machine, and compares it with the value given in the controller, and adjusts the output value of the servo driver 2 to the servo motor 3 accordingly, dynamically controls the servo motor 3, and realizes precise closed-loop control of pressure and flow.

[0040] After the energy unit and the oil replenishment unit are started, the bidirectional closed pump 4 directly drives the equal-area double-rod oil cylinder to work forward or backward, and a pressure difference is generated between the first working oil circuit D and the second working oil circuit E. The flushing valve 12 is opened by the oil pressure on the high-pressure side of the working oil circuit. The oil of the oil replenishment pump 7 is first filtered by the high-pressure filter 17, and then replenished into the low-pressure working oil circuit through the one-way valve connected to the low-pressure working oil circuit. The excess oil flows back to the oil tank 1 through the flushing valve 12, the first overflow valve 9, and the cooler 18. The excess oil provided by the oil replenishment unit will flow back to the oil tank 1 through the fourth overflow valve 15 and the cooler 18. When the first working oil circuit D or the second working oil circuit E is overpressured, the oil pressure on the overpressure side will open the second overflow valve 10 or the third overflow valve 11, and the overflowed oil will flow into the low-pressure side to prevent the system from overloading.

[0041] Embodiment 2: Figure 2 As shown, other parts are the same as those of the first embodiment, except that the execution unit 5 is a bidirectional rotating hydraulic motor. The execution unit 5 uses a hydraulic motor to achieve the same oil inlet and outlet flow rates, thereby achieving the circulation of the closed system.

[0042] In this specific embodiment, the oil drain port of the bidirectional rotary hydraulic motor is connected to the oil tank 1. The leaked hot oil can be cooled in the oil tank 1 and then recycled.

[0043] After the energy unit and the oil replenishment unit are started, the bidirectional closed pump 4 directly drives the bidirectional rotary hydraulic motor to work forward or reverse, and a pressure difference is generated between the first working oil circuit D and the second working oil circuit E. The flushing valve 12 is opened by the oil pressure on the high-pressure side of the working oil circuit. The oil of the oil replenishment pump 7 is first filtered by the high-pressure filter 17, and then replenished into the low-pressure working oil circuit through the one-way valve connected to the low-pressure working oil circuit. The excess oil flows back to the oil tank 1 through the flushing valve 12, the first overflow valve 9, and the cooler 18. The excess oil provided by the oil replenishment unit will flow back to the oil tank 1 through the fourth overflow valve 15 and the cooler 18. When the first working oil circuit D or the second working oil circuit E is overpressured, the oil pressure on the overpressure side will open the second overflow valve 10 or the third overflow valve 11, and the overflowed oil will flow into the low-pressure side to prevent the system from overloading.

Claims

1. A hydraulic control system for an injection molding machine, comprising an oil tank, an energy unit and an execution unit, characterized in that The energy unit includes a servo drive, a servo motor and a bidirectional closed pump, the oil tank replenishes oil for the bidirectional closed pump, the servo motor is driven by the servo drive, the bidirectional closed pump is driven by the servo motor, the oil inlet end of the bidirectional closed pump is connected to the oil return end of the execution unit through a first working oil circuit, and the oil outlet end of the bidirectional closed pump is connected to the oil inlet end of the execution unit through a second working oil circuit; It also includes an oil replenishment unit, the oil replenishment unit includes an oil replenishment valve group and an oil replenishment power group, the oil replenishment power group includes an oil replenishment pump and a three-phase asynchronous motor for driving the oil replenishment pump, and the oil replenishment valve group includes a first overflow valve, a second overflow valve, a third overflow valve, a flushing valve, a first check valve and a second check valve; The two oil inlet ends of the flushing valve are connected to the first working oil circuit and the second working oil circuit respectively, the oil outlet end of the flushing valve is connected to the oil inlet end of the first overflow valve, and the oil return end of the first overflow valve is connected to the oil tank; The oil inlet end of the second overflow valve is connected to the first working oil circuit, the oil inlet end of the third overflow valve is connected to the second working oil circuit, the oil return end of the second overflow valve is connected to the second working oil circuit, the oil return end of the third overflow valve is connected to the first working oil circuit, the oil outlet end of the first check valve is connected to the first working oil circuit, the oil outlet end of the second check valve is connected to the second working oil circuit, the common oil circuit formed by the oil inlet ends of the first check valve and the second check valve is connected to the oil outlet end of the oil replenishment pump, and the oil inlet end of the oil replenishment pump is connected to the oil tank; The common oil circuit formed by the oil inlet ends of the first one-way valve and the second one-way valve is connected to the oil tank through the fourth overflow valve, the common oil circuit formed by the oil inlet ends of the first one-way valve and the second one-way valve is connected to the oil inlet end of the fourth overflow valve, and the oil return end of the fourth overflow valve is connected to the oil tank; An oil suction filter is provided between the oil inlet end of the oil replenishment pump and the oil tank, a first port of the oil suction filter is connected to the oil tank, and a second port of the oil suction filter is connected to the oil inlet end of the oil replenishment pump; The oil drain port of the bidirectional closed pump is connected to the oil tank.

2. A hydraulic control system for an injection molding machine as claimed in claim 1, characterized in that The first working oil circuit and the second working oil circuit are respectively provided with a pressure sensor, and the pressure sensor is electrically connected to the servo driver.

3. A hydraulic control system for an injection molding machine as claimed in claim 1, characterized in that The oil outlet end of the oil replenishment pump is provided with a high-pressure filter, the first port of the high-pressure filter is connected to the oil outlet end of the oil replenishment pump, and the common oil circuit formed by connecting the oil inlet end of the fourth overflow valve, the first check valve and the oil inlet end of the second check valve is respectively connected to the second port of the high-pressure filter.

4. A hydraulic control system for an injection molding machine as claimed in claim 1, characterized in that The oil return ends of the first overflow valve and the fourth overflow valve are connected to the oil tank through a cooler, and the oil return ends of the first overflow valve and the fourth overflow valve are respectively connected to the first port of the cooler, and the second port of the cooler is connected to the oil tank.

5. A hydraulic control system for an injection molding machine as claimed in claim 1, characterized in that The execution unit is an equal-area double-rod oil cylinder.

6. A hydraulic control system for an injection molding machine as claimed in claim 1, characterized in that The execution unit is a bidirectional rotating hydraulic motor.

7. A hydraulic control system for an injection molding machine as claimed in claim 6, characterized in that The oil drain port of the bidirectional rotating hydraulic motor is connected to the oil tank.

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