Double-speed hydraulic motor control oil way and method for injection molding material storage action

Abstract

The invention discloses a double-speed hydraulic motor control oil way and method for injection molding material storage action, and relates to the technical field of injection molding machines. The double-speed hydraulic motor control oil way and method are mainly characterized in that a two-position four-way electromagnetic valve is in a first conduction state after being initially powered off, and a one-way variable hydraulic motor is in a default large-displacement gear; the preset-pressure high-pressure oil stored by the energy accumulator is used for carrying out auxiliary supply of gear switching oil pressure; real-time material storage peak pressure is detected through a pressure sensor, and when the peak pressure is smaller than preset switching small-displacement pressure, the two-position four-way electromagnetic valve is controlled to be electrified and switched to be in a second conduction state through a switching instruction, and the one-way variable hydraulic motor is switched to be in a small-displacement gear; the real-time material storage peak pressure is detected through the pressure sensor, and when the peak pressure is larger than the preset switching large-displacement pressure, the two-position four-way electromagnetic valve is controlled to be switched to be in the first conduction state through the switching instruction in a power-off mode, and the one-way variable hydraulic motor is switched to be in the large-displacement gear. The speed mode of the oil motor is automatically switched according to the feedback information.

Description

Technical Field

[0001] The invention relates to the technical field of injection molding machines, and in particular to a dual-speed hydraulic motor control oil circuit and method for injection molding material storage action. Background Art

[0002] In the operation of the injection molding machine, the accumulator action is indeed a key link, responsible for conveying the raw materials from the hopper to the injection molding machine screw for plasticization. The traditional accumulator action drive system usually adopts a fixed displacement hydraulic motor. This drive mode has some limitations in different working stages (such as high-speed accumulator and low-speed high torque), resulting in high energy consumption and large mechanical wear. In the high-speed accumulator stage, the fixed-displacement hydraulic motor needs to provide a higher speed, but the load at this time is relatively low, resulting in energy waste, and the screw speed is high, resulting in large mechanical wear. In the low-speed and high-torque stage, the fixed-displacement hydraulic motor needs to provide a large torque, but due to the fixed displacement, the system pressure is high, resulting in energy loss. At the same time, the high system pressure causes the hydraulic components and mechanical parts to be subjected to greater stress, which accelerates wear. In addition, the fixed-displacement hydraulic motor has a slow response speed and is difficult to quickly adapt to different work requirements.

[0003] Then, when the hydraulic motor itself has an optimal efficiency range and its comprehensive efficiency shows a parabolic change with the increase of pressure, if the hydraulic motor can switch the displacement mode and adjust the load pressure according to actual needs, the hydraulic motor can maintain a high overall working efficiency and reduce energy consumption. For example, when using PP material, if the speed of the fixed displacement hydraulic motor is 100rpm, then at this time, due to the low load, it can be switched to a small displacement mode to increase the system pressure and fall into the optimal efficiency range. In the small displacement mode, if the customer uses PE material, the speed of the fixed displacement hydraulic motor is still 100rpm, then at this time there may be a situation where the system pressure is too high, resulting in insufficient motor torque. At this time, if it can be switched to a large displacement mode in time, sufficient torque can be provided to reduce the system pressure so that the hydraulic motor is still in the optimal efficiency range. Summary of the invention

[0004] In order to solve the problems existing in the material storage action of the existing injection molding machine, the present invention proposes a dual-speed hydraulic motor control oil circuit for injection molding material storage action, which controls the oil circuit conduction direction of the two-position four-way solenoid valve based on a pressure sensor, and in the control oil circuit:

[0005] The high-pressure oil is stored by the accumulator, and the high-pressure oil of preset pressure is supplied to the first oil inlet of the two-position four-way solenoid valve, the second variable oil port of the two-position four-way solenoid valve is connected to the first oil inlet of the switching chamber of the one-way variable hydraulic motor, the third variable oil port of the two-position four-way solenoid valve is connected to the second oil inlet of the switching chamber of the one-way variable hydraulic motor, and the fourth oil outlet of the two-position four-way solenoid valve is connected to the control oil circuit tank;

[0006] The gear switching of the one-way variable hydraulic motor is performed based on the storage peak pressure obtained by the pressure sensor. In the large displacement gear, when the peak pressure is less than the preset switching small displacement pressure, the two-position four-way solenoid valve is changed from the first conduction state to the second conduction state, and switched to the small displacement gear; in the small displacement gear, when the peak pressure is greater than the preset switching large displacement pressure, the two-position four-way solenoid valve is changed from the second conduction state to the first conduction state, and switched to the large displacement gear;

[0007] The oil supply port of the one-way variable hydraulic motor is connected to the hydraulic oil pumped into the driving oil circuit by the oil pump, and the oil outlet of the one-way variable hydraulic motor is connected to the driving oil circuit tank.

[0008] Furthermore, when the two-position four-way solenoid valve is in the de-energized state, it is in the first conduction state, the first oil inlet and the second variable oil port are connected, the third variable oil port and the fourth oil outlet are connected, and the unidirectional variable hydraulic motor is in the large displacement gear; when the two-position four-way solenoid valve is in the energized state, it is in the second conduction state, the first oil inlet and the third variable oil port are connected, the second variable oil port and the fourth oil outlet are connected, and the unidirectional variable hydraulic motor is in the small displacement gear.

[0009] Furthermore, when the two-position four-way solenoid valve is energized, the hydraulic oil in the control oil circuit tank is transported into the second oil inlet of the one-way variable hydraulic motor switching chamber via the accumulator, the passage between the first oil inlet of the two-position four-way solenoid valve and the third variable oil port, to assist in the supply of gear switching oil pressure.

[0010] Furthermore, when the two-position four-way solenoid valve is converted to a de-energized state, the hydraulic oil between the third variable oil port of the two-position four-way solenoid valve and the second oil inlet of the one-way variable hydraulic motor switching chamber returns to the control oil circuit tank via the passage between the third variable oil port and the fourth oil outlet of the two-position four-way solenoid valve.

[0011] Furthermore, when the two-position four-way solenoid valve loses power, the hydraulic oil in the control oil circuit tank is transported into the first oil inlet of the switching chamber of the one-way variable hydraulic motor via the accumulator, the passage between the first oil inlet and the second variable oil port of the two-position four-way solenoid valve, to assist in the supply of gear switching oil pressure.

[0012] Furthermore, when the two-position four-way solenoid valve is converted to an energized state, the hydraulic oil between the second variable oil port of the two-position four-way solenoid valve and the first oil inlet of the switching chamber of the one-way variable hydraulic motor returns to the control oil circuit tank via the passage between the second variable oil port and the fourth oil outlet of the two-position four-way solenoid valve.

[0013] Furthermore, when the oil supply pressure of the driving oil circuit connected to the oil supply port of the one-way variable hydraulic motor is greater than the preset pressure, the accumulator stops supplying oil, and the oil supply of the driving oil circuit is used to supply the oil pressure for gear switching.

[0014] The present invention also proposes a dual-speed hydraulic motor control method for injection molding material storage action, comprising the steps of:

[0015] S1: Start to execute the injection molding material storage action. The two-position four-way solenoid valve is initially de-energized and in the first conduction state. The one-way variable hydraulic motor is in the default large displacement gear. The preset pressure high-pressure oil stored in the accumulator is used to assist in the supply of gear switching oil pressure.

[0016] S2: Detect the real-time storage peak pressure through the pressure sensor, and enter the next step when the peak pressure is less than the preset switching small displacement pressure;

[0017] S3: The two-position four-way solenoid valve is energized and switched to the second conduction state through the switching command, and the one-way variable hydraulic motor is switched to the small displacement gear;

[0018] S4: Detect the real-time storage peak pressure through the pressure sensor, and enter the next step when the peak pressure is greater than the preset switching large displacement pressure;

[0019] S5: Through the switching command, the two-position four-way solenoid valve is controlled to switch from power failure to the first conduction state, and the one-way variable hydraulic motor is switched to the large displacement gear and returns to step S2.

[0020] Furthermore, the entire control process also includes the following steps:

[0021] Determine whether the oil supply pressure of the drive oil circuit connected to the oil supply port of the unidirectional variable hydraulic motor is greater than the preset pressure. If so, the accumulator stops supplying oil, and the drive oil circuit supplies oil to supply the gear switching oil pressure and ends. If not, continue to cycle through steps S2 to S5.

[0022] Furthermore, in the steps S3 and S5, the oil supply of the driving oil circuit is adjusted by controlling the rotation speed of the motor and the pump through the PLC to meet the oil supply demand of each displacement gear when the screw speed is constant.

[0023] Compared with the prior art, the present invention has at least the following beneficial effects:

[0024] (1) The dual-speed hydraulic motor control oil circuit and method for injection molding material storage action described in the present invention monitors the running status of the material storage shaft in real time through a sensor, and feeds back the data to the control system. The control system automatically switches the large and small displacement modes of the hydraulic motor according to the feedback information, and synchronously adjusts the motor speed to ensure that the comprehensive efficiency of the oil motor is minimized;

[0025] (2) When the oil supply pressure in the driving oil circuit is insufficient, the accumulator is used to assist the one-way variable hydraulic motor in shifting oil pressure, thereby helping the system to respond to shifting faster and improving the working efficiency of the motor;

[0026] (3) When high speed or high torque is not required, the system automatically switches to low speed mode to reduce unnecessary energy consumption and achieve energy saving. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is an oil circuit diagram of a dual-speed hydraulic motor control oil circuit used for injection molding storage action;

[0028] Figure 2 A step diagram of a dual-speed hydraulic motor control method for injection molding storage action;

[0029] Figure 3 It is a schematic diagram of hydraulic oil flow in the first conduction state;

[0030] Figure 4 It is a schematic diagram of the hydraulic oil flow in the second conduction state. DETAILED DESCRIPTION

[0031] The following are specific embodiments of the present invention and the accompanying drawings to further describe the technical solution of the present invention, but the present invention is not limited to these embodiments.

[0032] Embodiment 1

[0033] In view of the problem that fixed-displacement motors are mostly used in current material storage actions, resulting in poor working efficiency and limited speed, and unable to provide higher speeds, the present invention proposes to use a unidirectional variable hydraulic motor to control the material storage action under automatic gear switching. However, unidirectional variable hydraulic motors usually switch gears based on the oil pressure of the drive oil circuit, which results in a long waiting time to achieve gear switching before the oil pressure of the drive oil circuit rises, which affects both the wear of the equipment and the quality of the injection molded products. Therefore, in order to be able to perform the gear shifting operation normally before the oil pressure of the drive oil circuit meets the gear shifting demand pressure when using a unidirectional hydraulic motor to switch gears, Figure 1As shown, the present invention proposes a dual-speed hydraulic motor control oil circuit for injection molding material storage action, which controls the oil circuit conduction direction of a two-position four-way solenoid valve based on a pressure sensor, wherein:

[0034] High-pressure oil is stored through an accumulator (F6), and high-pressure oil of preset pressure is supplied to a first oil inlet of a two-position four-way solenoid valve (V81); a second variable oil port of the two-position four-way solenoid valve (V81) is connected to a first oil inlet (MAX) of a switching chamber of a one-way variable hydraulic motor (HM1); a third variable oil port of the two-position four-way solenoid valve (V81) is connected to a second oil inlet of the switching chamber of the one-way variable hydraulic motor (HM1); and a fourth oil outlet of the two-position four-way solenoid valve (V81) is connected to a control oil circuit tank;

[0035] The gear of the one-way variable hydraulic motor (HM1) is switched based on the storage peak pressure obtained by the pressure sensor (P / U). In the large displacement gear, when the peak pressure is less than the preset small displacement switching pressure, the two-position four-way solenoid valve (V81) changes from the first conduction state to the second conduction state, and switches to the small displacement gear; in the small displacement gear, when the peak pressure is greater than the preset large displacement switching pressure, the two-position four-way solenoid valve (V81) changes from the second conduction state to the first conduction state, and switches to the large displacement gear;

[0036] The oil supply port of the one-way variable hydraulic motor (HM1) is connected to the hydraulic oil pumped into the driving oil circuit (P) by the oil pump (P1), and the oil outlet of the one-way variable hydraulic motor is connected to the driving oil circuit tank.

[0037] The oil supply of the driving oil circuit (P) is driven by the motor (M1) to pump oil from the driving oil circuit tank. The motor (M1) and the oil pump (P1) are electrically connected, the oil inlet of the oil pump (P1) is connected to the driving oil circuit tank, the oil outlet of the oil pump (P1) outputs hydraulic oil to the driving oil circuit (P), and supplies oil to the accumulator (F6) through the one-way valve (V80) when the system is idle. The pressure sensor (P / U) is also connected to the driving oil circuit (P) for pressure monitoring, and the monitoring data is fed back to the PLC, which adjusts the speed of the motor (M1) and the conduction state of the two-position four-way solenoid valve (V81) ( Figure 1 The solid line in the middle is the drive oil circuit, and the dotted line is the control oil circuit).

[0038] To facilitate the understanding of the scheme of the present invention, this embodiment first analyzes and explains the oil circuit conduction direction under different oil circuit states. Before the oil supply pressure of the driving oil circuit connected to the oil supply port of the unidirectional variable hydraulic motor reaches the preset pressure, we switch the different conduction states of the two-position four-way solenoid valve to provide auxiliary supply of gear switching oil pressure for the unidirectional variable hydraulic motor.

[0039] The two-position four-way solenoid valve has two conduction states, corresponding to different gear modes of the one-way variable hydraulic motor. In the first conduction state, the two-position four-way solenoid valve loses power, the valve is reset under the action of the spring, the first oil inlet and the second variable oil port are connected, the third variable oil port and the fourth oil outlet are connected, and the one-way variable hydraulic motor is in a large displacement gear; in the second conduction state, the two-position four-way solenoid valve is energized, the valve compresses the spring under the electromagnetic force, the first oil inlet and the third variable oil port are connected, the second variable oil port and the fourth oil outlet are connected, and the one-way variable hydraulic motor is in a small displacement gear. Among them:

[0040] In the first conduction state, if Figure 3 As shown in the figure (the flow path marked by arrow 1 is the flow direction of the control oil circuit), the high-pressure oil stored in the accumulator is supplied to the first oil inlet of the switching chamber of the one-way variable hydraulic motor through the passage between the first oil inlet and the second variable oil port of the two-position four-way solenoid valve, and finally flows to the control oil circuit tank. At this time, the one-way variable hydraulic motor is in the large displacement gear state under the combined effect of the spring return elastic force inside the switching chamber itself and the pressure supplied from the first oil inlet.

[0041] After the first conduction state is changed to the second conduction state, Figure 4 As shown (the flow path marked by arrow 1 is the flow direction of the control oil circuit), the high-pressure oil stored in the accumulator is supplied with pressure to the second oil inlet of the switching chamber of the one-way variable hydraulic motor through the passage between the first oil inlet of the two-position four-way solenoid valve and the third variable oil port, and finally flows to the control oil circuit tank. Under the action of the pressure supplied from the second oil inlet, the one-way variable hydraulic motor resists the restoring elastic force of the internal spring of the switching chamber itself, compresses it, and thus changes the internal passage of the one-way variable hydraulic motor, and then switches to a small displacement gear state. At the same time, the hydraulic oil ( Figure 4 At this time, the oil can return to the control oil circuit tank through the passage between the second variable oil port and the fourth oil outlet of the two-position four-way solenoid valve.

[0042] Correspondingly, after the second conduction state is changed to the first conduction state, the hydraulic oil ( Figure 3 The oil path portion marked by arrow 2) can be returned to the control oil circuit tank through the passage between the third variable oil port and the fourth oil outlet of the two-position four-way solenoid valve.

[0043] By switching the conduction state of the above-mentioned two-position four-way solenoid valve, it is possible to actively assist in switching the gears of the unidirectional variable hydraulic motor based on the detection of the storage peak pressure by the pressure sensor before the oil pressure in the driving oil circuit reaches the preset pressure, through the high-pressure oil stored in the accumulator, thereby improving the efficiency of the gear switching and avoiding the problems of equipment wear and injection molded part quality deviation caused by gear switching lag due to insufficient oil pressure in the driving oil circuit.

[0044] When the oil pressure in the drive oil circuit meets the requirements of the one-way variable hydraulic motor, the oil supply from the drive oil circuit is used to supply the oil pressure for gear switching. At this time, the accumulator stops supplying oil and converts the energy in the system into compressed energy for subsequent use.

[0045] Based on the above description of the oil circuit, this embodiment then explains the specific use steps of the control oil circuit proposed by the present invention by way of method steps. Figure 2 As shown, the control method includes the following logical steps:

[0046] S1: Start to execute the injection molding material storage action. The two-position four-way solenoid valve is initially de-energized and in the first conduction state. The one-way variable hydraulic motor is in the default large displacement gear. The preset pressure high-pressure oil stored in the accumulator is used to assist in the supply of gear switching oil pressure.

[0047] S2: Detect the real-time storage peak pressure through the pressure sensor, and enter the next step when the peak pressure is less than the preset switching small displacement pressure;

[0048] S3: The two-position four-way solenoid valve is energized and switched to the second conduction state through the switching command, and the one-way variable hydraulic motor is switched to the small displacement gear;

[0049] S4: Detect the real-time storage peak pressure through the pressure sensor, and enter the next step when the peak pressure is greater than the preset switching large displacement pressure;

[0050] S5: Through the switching command, the two-position four-way solenoid valve is controlled to switch from power failure to the first conduction state, and the one-way variable hydraulic motor is switched to the large displacement gear and returns to step S2.

[0051] In the process of executing the above steps, the oil pressure of the driving oil circuit is also monitored in real time. Based on the detection result of the driving oil circuit oil pressure, it is determined whether the driving oil circuit oil supply pressure connected to the oil supply port of the unidirectional variable hydraulic motor is greater than the preset pressure. If so, the accumulator stops supplying oil, and the driving oil circuit supplies oil to supply the gear switching oil pressure and ends. If not, continue to execute steps S2 to S5 in a loop.

[0052] Of course, in order to keep the screw speed constant during the gear switching process, it is also necessary to synchronously adjust the oil supply of the drive oil circuit. Here, the present invention adjusts the oil supply of the drive oil circuit by controlling the speed of the motor and the pump through PLC to meet the oil supply requirements of each displacement gear when the screw speed is constant.

[0053] In summary, the dual-speed hydraulic motor control oil circuit and method for injection molding material storage action described in the present invention monitors the operating status of the material storage shaft in real time through sensors, and feeds back the data to the control system. The control system automatically switches the large and small displacement modes of the hydraulic motor according to the feedback information, and synchronously adjusts the motor speed to ensure that the overall efficiency of the oil motor is minimized.

[0054] When the oil supply pressure of the driving oil circuit is insufficient, the accumulator can assist the one-way variable hydraulic motor in shifting oil pressure, thereby helping the system to respond to shifting faster and improving the working efficiency of the motor. When high speed or high torque is not required, the system automatically switches to low speed mode, reducing unnecessary energy consumption and achieving energy saving.

[0055] It should be noted that all directional indications in the embodiments of the present invention (such as up, down, left, right, front, back, etc.) are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0056] In addition, in the present invention, descriptions such as "first", "second", "one", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0057] In the present invention, unless otherwise clearly specified and limited, the terms "connection", "fixation", etc. should be understood in a broad sense. For example, "fixation" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0058] In addition, the technical solutions between the various embodiments of the present invention can be combined with each other, but it must be based on the fact that ordinary technicians in the field can implement it. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

Claims

1. A dual-speed hydraulic motor control oil circuit for injection molding storage action, characterized in that: The oil circuit conduction direction of the two-position four-way solenoid valve is controlled based on the pressure sensor, in the control oil circuit: The high-pressure oil is stored by the accumulator, and the high-pressure oil of preset pressure is supplied to the first oil inlet of the two-position four-way solenoid valve, the second variable oil port of the two-position four-way solenoid valve is connected to the first oil inlet of the switching chamber of the one-way variable hydraulic motor, the third variable oil port of the two-position four-way solenoid valve is connected to the second oil inlet of the switching chamber of the one-way variable hydraulic motor, and the fourth oil outlet of the two-position four-way solenoid valve is connected to the control oil circuit tank; The gear position of the one-way variable hydraulic motor is switched based on the storage peak pressure obtained by the pressure sensor. In the large displacement gear, when the peak pressure is less than the preset small displacement switching pressure, the two-position four-way solenoid valve is changed from the first conduction state to the second conduction state, and switched to the small displacement gear; In the small displacement gear, when the peak pressure is greater than the preset large displacement switching pressure, the two-position four-way solenoid valve changes from the second conduction state to the first conduction state, switching to the large displacement gear; The oil supply port of the one-way variable hydraulic motor is connected to the hydraulic oil pumped into the driving oil circuit by the oil pump, and the oil outlet of the one-way variable hydraulic motor is connected to the driving oil circuit tank.

2. A dual-speed hydraulic motor control oil circuit for injection molding storage action as claimed in claim 1, characterized in that: The two-position four-way solenoid valve is in the first conduction state when it is de-energized, with conduction between the first oil inlet and the second variable oil port, conduction between the third variable oil port and the fourth oil outlet, and the unidirectional variable hydraulic motor is in the large-displacement gear; the two-position four-way solenoid valve is in the second conduction state when it is energized, with conduction between the first oil inlet and the third variable oil port, conduction between the second variable oil port and the fourth oil outlet, and the unidirectional variable hydraulic motor is in the small-displacement gear.

3. A dual-speed hydraulic motor control oil circuit for injection molding material storage action as claimed in claim 2, characterized in that: When the two-position four-way solenoid valve is energized, the hydraulic oil in the control oil circuit tank is transported into the second oil inlet of the switching chamber of the one-way variable hydraulic motor through the accumulator, the passage between the first oil inlet of the two-position four-way solenoid valve and the third variable oil port, to assist in the supply of gear switching oil pressure.

4. A dual-speed hydraulic motor control oil circuit for injection molding material storage action as claimed in claim 3, characterized in that: When the two-position four-way solenoid valve is converted to a de-energized state, the hydraulic oil between the third variable oil port of the two-position four-way solenoid valve and the second oil inlet of the switching chamber of the one-way variable hydraulic motor returns to the control oil circuit tank via the passage between the third variable oil port and the fourth oil outlet of the two-position four-way solenoid valve.

5. A dual-speed hydraulic motor control oil circuit for injection molding material storage action as claimed in claim 2, characterized in that: When the two-position four-way solenoid valve loses power, the hydraulic oil in the control oil circuit tank is transported into the first oil inlet of the switching chamber of the one-way variable hydraulic motor through the accumulator, the passage between the first oil inlet and the second variable oil port of the two-position four-way solenoid valve, to assist in the supply of gear switching oil pressure.

6. A dual-speed hydraulic motor control oil circuit for injection molding material storage action as claimed in claim 5, characterized in that: When the two-position four-way solenoid valve is converted to the energized state, the hydraulic oil between the second variable oil port of the two-position four-way solenoid valve and the first oil inlet of the switching chamber of the one-way variable hydraulic motor returns to the control oil circuit tank via the passage between the second variable oil port and the fourth oil outlet of the two-position four-way solenoid valve.

7. A dual-speed hydraulic motor control oil circuit for injection molding material storage action as claimed in claim 1, characterized in that: When the oil supply pressure of the drive oil circuit connected to the oil supply port of the one-way variable hydraulic motor is greater than the preset pressure, the accumulator stops supplying oil, and the drive oil circuit supplies oil for the gear shifting oil pressure.

8. A control method for the oil circuit control according to any one of claims 1 to 7, characterized in that: Includes steps: S1: Start to execute the injection molding material storage action. The two-position four-way solenoid valve is initially de-energized and in the first conduction state. The one-way variable hydraulic motor is in the default large displacement gear. The preset pressure high-pressure oil stored in the accumulator is used to assist in the supply of gear switching oil pressure. S2: Detect the real-time storage peak pressure through the pressure sensor, and enter the next step when the peak pressure is less than the preset switching small displacement pressure; S3: The two-position four-way solenoid valve is energized and switched to the second conduction state through the switching command, and the one-way variable hydraulic motor is switched to the small displacement gear; S4: Detect the real-time storage peak pressure through the pressure sensor, and enter the next step when the peak pressure is greater than the preset switching large displacement pressure; S5: Through the switching command, the two-position four-way solenoid valve is controlled to switch from power failure to the first conduction state, and the one-way variable hydraulic motor is switched to the large displacement gear and returns to step S2.

9. The oil circuit control method according to claim 8, characterized in that: The entire control process also includes the following steps: Determine whether the oil supply pressure of the drive oil circuit connected to the oil supply port of the unidirectional variable hydraulic motor is greater than the preset pressure. If so, the accumulator stops supplying oil, and the drive oil circuit supplies oil to supply the gear switching oil pressure and ends. If not, continue to cycle through steps S2 to S5.

10. The oil circuit control method according to claim 8, characterized in that: In the steps S3 and S5, the speed of the motor and the pump is controlled by the PLC to adjust the oil supply of the driving oil circuit to meet the oil supply requirements of each displacement gear when the screw speed is constant.

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