A bidirectional brake hydraulic press and its working method

Abstract

The invention discloses a bidirectional brake hydraulic machine and a working method thereof, comprising: an oil tank outlet connected to an oil pump input end; a hydraulic reversing valve and a first electromagnetic reversing valve are both three-position four-way valves; when the first electromagnetic reversing valve is in the middle position, its first and second oil ports are connected to the hydraulic reversing valve, the third oil port is connected to the oil tank, and the fourth oil port is connected to the oil pump output end; when the hydraulic reversing valve is in the middle position, its first oil port is connected to the oil tank, the second oil port is connected to the overflow valve inlet, the third oil port is connected to the oil pump output end, and the fourth oil port is connected to the rodless chambers of two hydraulic cylinders; the fifth oil port is divided into two paths, one path is connected to the throttle valve and the rod chambers of the two hydraulic cylinders in sequence, the throttle valve is connected in parallel with the second electromagnetic reversing valve, and the other path is connected with the overflow valve; the overflow valve outlet is respectively connected to the third electromagnetic reversing valve inlet and the oil tank, and the third electromagnetic reversing valve outlet is connected to the oil tank. Bidirectional pressing and forming is realized, the quality and production efficiency of the formed parts are improved, and the production cost is greatly reduced.

Description

Technical Field

[0001] The invention belongs to the field of hydraulic presses and relates to a bidirectional braking hydraulic press and a working method thereof. Background Art

[0002] Powder pressing molding process related to hydraulic press, among which metal powder, ceramic powder and metal-ceramic mixed powder are the most common. Powder pressing molding process belongs to dry pressing molding process technology, which generally puts powdered raw materials into the mold, and then uses the hydraulic press to output mechanical force to press and mold. The most critical part of the powder pressing molding process is the hydraulic press. Most of them are aging one-way hydraulic presses. Traditional hydraulic presses use a single hydraulic cylinder to press and mold powder in one direction; the one-way pressing scheme will definitely lead to uneven density of the molded parts. The density of the molded parts near the pressing movable rod is high, and the density is low far away from the pressing movable rod. The stratification is more obvious, especially when pressing ceramic powder. The stratification caused by this molding method will directly cause the molded parts to have faults, cracks, and severe deformation during the ceramic firing process, thereby causing the molded parts to become scrapped. In addition, the consumption of expensive ceramic powder raw materials and certain metal powder raw materials is a huge expense, so it is particularly important to improve the hydraulic press that provides mechanical force. Summary of the invention

[0003] The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art and provide a bidirectional brake hydraulic press and a working method thereof, so as to realize bidirectional pressing and forming, improve the quality of formed parts and production efficiency, and greatly reduce production costs.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions:

[0005] A bidirectional brake hydraulic machine comprises an oil tank, an oil pump, a hydraulic reversing valve, a first electromagnetic reversing valve, a relief valve, a first hydraulic cylinder and a second hydraulic cylinder;

[0006] The oil outlet of the oil tank is connected to the oil pump input end; the hydraulic reversing valve and the first solenoid reversing valve are both three-position four-way valves. When the first solenoid reversing valve is in the middle position, its first and second oil ports are connected to the hydraulic reversing valve, the third oil port is connected to the oil inlet of the oil tank, and the fourth oil port is connected to the oil pump output end; when the hydraulic reversing valve is in the middle position, its first oil port is connected to the oil inlet of the oil tank, the second oil port is connected to the oil inlet of the overflow valve, and the third oil port is connected to the oil pump output end. The fourth oil port is connected to the rodless chamber of the first hydraulic cylinder and the second hydraulic cylinder, and the fifth oil port is divided into two paths, one path is connected to the throttle valve and the rod chamber of the first hydraulic cylinder and the second hydraulic cylinder in sequence, the throttle valve is connected in parallel with the second solenoid reversing valve, and the other path is connected with the overflow valve; the overflow valve outlet is respectively connected to the third solenoid reversing valve inlet and the oil tank inlet, and the third solenoid reversing valve outlet is connected to the oil tank inlet.

[0007] Preferably, an accumulator is connected between the fourth oil port of the hydraulic reversing valve and the rodless chambers of the first hydraulic cylinder and the second hydraulic cylinder.

[0008] Preferably, the rodless chambers of the first hydraulic cylinder and the second hydraulic cylinder are connected with electric contact pressers.

[0009] Preferably, a pressure relay is provided between the fourth oil port of the hydraulic reversing valve and the rodless chambers of the first hydraulic cylinder and the second hydraulic cylinder, and the output end of the pressure relay is electrically connected to the third electromagnetic reversing valve.

[0010] Furthermore, the output end of the pressure relay is connected to the input end of the time relay, and the output end of the time relay is electrically connected to the first electromagnetic reversing valve.

[0011] Preferably, the first hydraulic cylinder and the second hydraulic cylinder are both provided with displacement sensors, and output ends of the displacement sensors are electrically connected to the first electromagnetic reversing valve and the second electromagnetic reversing valve.

[0012] Preferably, the oil pump adopts a pressure-limited variable displacement vane pump.

[0013] A working method of the hydraulic press based on any one of the above items, comprising the following process:

[0014] Idle stroke downward pressure stage: the left side of the first solenoid reversing valve is energized, the valve core moves to the right, and the left position enters the working state; the hydraulic oil pumped out by the oil pump passes through the first solenoid reversing valve to the hydraulic reversing valve, causing the valve core of the hydraulic reversing valve to move to the right, and the left position enters the working position; then the hydraulic oil pumped out by the oil pump passes through the hydraulic reversing valve and the first solenoid reversing valve and flows into the rodless chambers of the first hydraulic cylinder and the second hydraulic cylinder, and the first hydraulic cylinder and the second hydraulic cylinder perform a clamping action; the hydraulic oil in the rod chambers of the first hydraulic cylinder and the second hydraulic cylinder passes through the hydraulic reversing valve, and the hydraulic oil and the oil pumped out by the oil pump merge and flow into the rodless chambers of the first hydraulic cylinder and the second hydraulic cylinder;

[0015] Pressing stage: After the first hydraulic cylinder and the second hydraulic cylinder contact the workpiece, the left side of the second electromagnetic reversing valve is energized, the valve core moves right, and the left position enters the working state. The hydraulic oil pumped out by the oil pump flows into the rodless chamber of the first hydraulic cylinder and the second hydraulic cylinder through the hydraulic reversing valve and the throttle valve. The first hydraulic cylinder and the second hydraulic cylinder are slowly pushed forward, and the hydraulic oil in the rod chamber passes through the hydraulic reversing valve and the overflow valve and returns to the oil tank;

[0016] Pressure holding stage: The hydraulic cylinder is continuously pressurized, the work is further increased, the left side of the third electromagnetic reversing valve is energized, the valve core moves right, the left position enters the working position, and the hydraulic oil pumped out by the oil pump passes through the overflow valve and the third electromagnetic reversing valve and returns to the oil tank;

[0017] Fast rewind stage: the left side of the first electromagnetic reversing valve is powered off, the right side is powered on, the valve core moves to the left, the right position enters the working state, the hydraulic oil pumped out by the oil pump passes through the first electromagnetic reversing valve to the hydraulic reversing valve, causing the valve core of the hydraulic reversing valve to move to the left, and the right position enters the working position. The hydraulic oil pumped out by the oil pump passes through the hydraulic reversing valve and flows into the rod chambers of the first hydraulic cylinder and the second hydraulic cylinder. The first hydraulic cylinder and the second hydraulic cylinder perform separation movement, and the hydraulic oil in the rodless chamber flows back to the oil tank through the hydraulic reversing valve;

[0018] Movement stop stage: the first hydraulic cylinder and the second hydraulic cylinder return to their original positions, the right side of the first solenoid reversing valve is powered off, and the valve core returns to its normal position, i.e., the middle position; the hydraulic oil cannot pass through the first solenoid reversing valve, causing the hydraulic reversing valve to return to its normal position, i.e., the middle position; the oil pump unloads through the middle position of the hydraulic reversing valve to complete a working cycle.

[0019] Preferably, during the pressing stage, when the hydraulic oil pressure reaches the set value of the pressure relay, the pressure maintaining stage is carried out, and the accumulator is opened to maintain the pressure.

[0020] Furthermore, when the hydraulic oil pressure reaches the set value of the pressure relay, the pressure relay sends a signal to the time relay. After the signal is delayed by the time relay setting time, it is sent to the first electromagnetic reversing valve to enter the fast reversing stage.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The bidirectional hydraulic cylinder used in the present invention is a hydraulic cylinder with the same cylinder diameter and the same stroke as the original one. The electro-hydraulic reversing valve composed of the first electromagnetic reversing valve and the hydraulic reversing valve realizes bidirectional pressing and molding, and improves the working efficiency and working accuracy of the entire hydraulic press system. Bidirectional pressing and molding ensures the uniform density of the molded parts, and realizes the movement requirement of the double cylinders to quickly approach the molded parts for pressing and molding.

[0023] Furthermore, the accumulator can supplement the pressure of the hydraulic cylinder, and the accumulator can increase the pressure value of the hydraulic press in the pressure-maintaining state, thereby improving the powder pressing and molding effect.

[0024] Furthermore, the electric contact pressure sensor can perform pressure detection on the hydraulic cylinder to improve the safety factor.

[0025] Furthermore, when the pressure of the hydraulic cylinder reaches the preset value of the pressure relay, the pressure relay can send a signal to the third electromagnetic reversing valve to change its position and maintain the pressure, thereby realizing automatic switching from the downward pressure to the pressure-maintaining stage.

[0026] Furthermore, the pressure relay can send a signal to the time relay. When the preset pressing time is reached, the time relay will send an electrical signal to control the first electromagnetic reversing valve to change position and perform fast retreat, thereby realizing automatic switching from pressure maintenance to fast retreat stage.

[0027] Furthermore, when the hydraulic cylinder contacts the workpiece, the hydraulic cylinder pressure increases, the movement of the movable rod slows down, or when the pressing is completed and the movable rod returns to its original position, the displacement sensor can control the first electromagnetic reversing valve or the second electromagnetic reversing valve to switch positions to achieve switching of working stages. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is the principle diagram of the bidirectional brake hydraulic press of the present invention.

[0029] Among them: 1-oil tank; 2-oil filter; 3-oil pump; 4-first one-way valve; 5-hydraulic reversing valve; 6-first solenoid reversing valve; 7-first one-way throttle valve; 8-second one-way throttle valve; 9-first hydraulic cylinder; 10-first displacement sensor; 11-right anvil; 12-left anvil; 13-second displacement sensor; 14-second hydraulic cylinder; 15-accumulator; 16-pressure relay; 17-throttle valve; 18-second solenoid reversing valve; 19-second one-way valve; 20-third one-way valve; 21-overflow valve; 22-third solenoid reversing valve; 23-electric contact pressure device. DETAILED DESCRIPTION

[0030] The present invention is further described in detail below in conjunction with the accompanying drawings:

[0031] like Figure 1 As shown, the bidirectional brake hydraulic machine of the present invention includes a power element, an actuator, a control element, an auxiliary element and a working medium. The power element is an oil pump 3; the actuator is a first hydraulic cylinder 9 and a second hydraulic cylinder 14; the control element is divided into a direction control element, a pressure control element and a flow control element. The direction control element includes a one-way valve and a reversing valve, the pressure control element includes a pressure relay 16, an accumulator 15 and a relief valve 21, and the flow control element includes a throttle valve and a one-way throttle valve; the auxiliary elements include an oil filter 2, an oil tank 1, a first displacement sensor 10, a second first displacement sensor 13, a hydraulic pipeline and an electric contact pressure device 23; the working medium is hydraulic oil.

[0032] The oil tank 1 is an auxiliary component. It is a container for storing the hydraulic oil of the entire hydraulic press system. It includes two through holes, an oil inlet and an oil outlet, which are filled with hydraulic oil. The oil inlet of the oil tank 1 is connected to the hydraulic reversing valve, the first solenoid reversing valve, the overflow valve 21 and the third solenoid reversing valve 22, and the oil outlet is externally connected to the oil filter 2.

[0033] The oil filter 2 is an auxiliary component of the invention. It is a filtering device for filtering hydraulic oil and provides the function of filtering hydraulic oil for the hydraulic press. The oil inlet of the oil filter 2 is connected to the oil tank 1, and the oil outlet is connected to the oil pump 3.

[0034] The oil pump 3 is a power element. In this embodiment, the oil pump 3 adopts a pressure-limited variable vane pump, which is an energy conversion device that converts the mechanical energy of the driving motor into the pressure energy of the hydraulic oil to meet the needs of the hydraulic press to drive the external load. The oil inlet of the pressure-limited variable vane pump is connected to the oil filter 2. When working, it sucks the hydraulic oil from the oil tank 1 filtered by the oil filter 2, and outputs the hydraulic oil through mechanical energy pressure. The oil outlet is connected to the first check valve 4 and the first electromagnetic reversing valve 6.

[0035] The one-way valve is a directional control element of the invention. The fluid can only flow along the water inlet, but the medium at the water outlet cannot flow back into the valve body. The one-way valve prevents the hydraulic oil from flowing back into the pressure-limiting variable vane pump when static.

[0036] The first electromagnetic reversing valve 6 is a direction control element. The first electromagnetic reversing valve 6 is a three-position four-way valve, which means that the valve has three working positions and four oil ports. After receiving the electrical signal, different working states can be changed to meet different hydraulic circuit requirements, thereby affecting the output of the hydraulic cylinder. In this invention, when the three-position four-way electromagnetic reversing valve is in the middle position, the first and second oil ports are respectively connected to the first one-way throttle valve 7 and the second one-way throttle valve 8, and then connected to the hydraulic reversing valve 5, the third oil port is connected to the oil inlet of the oil tank 1, and the fourth oil port is connected to the pressure-limiting variable vane pump.

[0037] The hydraulic reversing valve 5 is a directional control element. The hydraulic reversing valve 5 is a three-position four-way valve. It is a reversing valve operated by pilot fluid pressure. The hydraulic reversing valve 5 has three working positions and five oil ports. In the middle position, the first oil port is connected to the oil tank 1, the second oil port is connected to the pipeline middle point of the third check valve 20 and the overflow valve 21 at the oil inlet of the overflow valve 21, the third oil port is connected to the first check valve 4 at the oil outlet of the pressure-limiting variable vane pump, the fourth oil port is connected to the rod chamber of the first hydraulic cylinder 9 and the second hydraulic cylinder 14, and the fifth oil port is connected to the pipeline node of the third check valve 20 connected to the oil inlet of the overflow valve 21, the throttle valve 17 and the second check valve 19 connected to the pressure relay 16.

[0038] The oil outlet of the overflow valve 21 is connected to the oil inlet of the third electromagnetic reversing valve 22 and the oil inlet of the oil tank 1 respectively, and the oil outlet of the two-position two-way third electromagnetic reversing valve 22 is connected to the oil inlet of the oil tank 1.

[0039] The hydraulic reversing valve 5 and the first electromagnetic reversing valve 6 together constitute the electro-hydraulic reversing valve of the hydraulic press system, which meets the requirements of the hydraulic circuit under different needs.

[0040] The first hydraulic cylinder 9 and the second hydraulic cylinder 14 are the actuators of the invention, which can convert hydraulic energy into mechanical energy and perform linear reciprocating motion (or swinging motion). A movable rod is arranged in each of the first hydraulic cylinder 9 and the second hydraulic cylinder 14, and the movable rod divides the inner cavity of the hydraulic cylinder into a rod cavity and a rodless cavity. The ends of the two movable rods extending out of the hydraulic cylinder are respectively the right anvil 11 and the left anvil 12. The rod cavity of the two hydraulic cylinders is connected to the hydraulic reversing valve 5, and the oil circuit connected to the rodless cavity is divided into three. The first circuit is connected to the pressure relay 16 and the second one-way valve 19 in sequence and then communicates with the fifth oil port of the hydraulic reversing valve 5. The second circuit is connected to the accumulator 15 and the throttle valve 17 in sequence and then communicates with the fifth oil port of the hydraulic reversing valve 5. A two-position two-way second electromagnetic reversing valve 18 is connected in parallel to the throttle valve 17, and the third circuit is connected to the electric contact pressure device 23. The first hydraulic cylinder 9 and the second hydraulic cylinder 14 are also connected to the first displacement sensor 10 and the second displacement sensor 13 respectively.

[0041] Hydraulic oil is the working medium of the invention and runs through the entire system.

[0042] The working stroke of the hydraulic press can be divided into five stages: idle pressure stage, pressure stage, pressure holding stage, fast retraction stage, and movement stop stage.

[0043] Idle stroke downward pressure stage. After pressing the start button, the left side of the first electromagnetic reversing valve 6 is energized, the valve core moves to the right, and the left position enters the working state. The hydraulic oil pumped out by the oil pump 3 passes through the oil filter 2 and the first electromagnetic reversing valve 6 to the hydraulic reversing valve 5, causing the valve core of the hydraulic reversing valve 5 to move to the right, and the left position enters the working position. Subsequently, the hydraulic oil pumped out by the oil pump 3 flows into the rodless chamber of the first hydraulic cylinder 9 and the second hydraulic cylinder 14 through the oil filter 2, the first one-way valve 4, the hydraulic reversing valve 5 and the first electromagnetic reversing valve 6, pushing the movable rod to perform a clamping action, the left anvil 11 moves to the right, and the right anvil 12 moves to the left. The hydraulic oil in the rod chamber passes through the hydraulic reversing valve 5. Due to the small external load and the low working pressure of the pipeline, the overflow valve 21 cannot be opened, and the hydraulic oil can only pass through the third one-way valve 20 and merge with the oil pumped out by the oil pump 3 to flow into the rodless chamber together. At this time, it is a differential connection mode, and the hydraulic cylinder is in a fast-forward idle stroke downward pressure state.

[0044] Downward pressure stage. After the left anvil 11 and the right anvil 12 contact the workpiece, the pressure in the hydraulic cylinder increases, the movement of the movable rod slows down, and the displacement sensor 10 sends an electrical signal to the second electromagnetic reversing valve 18. The left side of the second electromagnetic reversing valve 18 is energized, the valve core moves to the right, and the left position enters the working state. The hydraulic oil pumped out by the oil pump 3 flows into the rodless chamber of the first hydraulic cylinder 9 and the second hydraulic cylinder 14 through the oil filter 2, the first one-way valve 4, the hydraulic reversing valve 5, and the throttle valve 17, and slowly pushes the movable rod. The hydraulic oil in the rod chamber passes through the hydraulic reversing valve 5. Since the hydraulic oil at this stage not only needs to push the movable rod but also passes through the throttle valve 17, the flow rate of the hydraulic oil decreases, the oil pressure increases, and at this time the pipeline oil pressure is equal to the oil pressure set by the overflow valve 21. The overflow valve 21 opens, and the hydraulic oil flows back to the oil tank 1. This is the rodless chamber oil inlet connection mode.

[0045] Pressure maintenance stage. The hydraulic cylinder is continuously pressurized, and the system pressure further increases. When it reaches the set value of the pressure relay 16, the pressure relay 16 sends an electrical signal to the third electromagnetic reversing valve 22 and the time relay, and the left side of the third electromagnetic reversing valve 22 is energized, the valve core moves to the right, and the left position enters the working position. The hydraulic oil pumped out by the oil pump 3 flows back to the oil tank through the oil filter 2, the first non-return valve 4, the overflow valve 21 and the third electromagnetic reversing valve 22. The oil pressure of the first hydraulic cylinder 9 and the second hydraulic cylinder 14 is detected by the electric contact pressure device 23, and the accumulator 15 maintains the pressure. At this time, it is a load-unloading pressure-maintaining connection mode.

[0046] Fast rewind stage. The pressure relay 16 sends an electrical signal to the time relay, which is delayed by the time relay, and then sends an electrical signal to the first electromagnetic reversing valve 6. The left side of the first electromagnetic reversing valve 6 is powered off, and the right side is powered on. The valve core moves to the left, and the right position enters the working state. The hydraulic oil pumped out by the oil pump 3 passes through the oil filter 2, and the first electromagnetic reversing valve 6 reaches the hydraulic reversing valve 5, so that the valve core of the hydraulic reversing valve 5 moves to the left, and the right position enters the working position. The hydraulic oil pumped out by the oil pump 3 flows into the rod chamber through the oil filter 2 and the hydraulic reversing valve 5, pushing the movable rod to separate, and the hydraulic oil in the rodless chamber flows back to the oil tank 25 through the hydraulic reversing valve 5. At this time, it is a rod chamber oil inlet connection mode, the system pressure is low, the variable pump output flow is large, and the movable rod retracts quickly.

[0047] Movement stop stage. The movable rod returns to the original position, the displacement sensor 13 sends an electrical signal, the right side of the first electromagnetic reversing valve 6 is powered off, the valve core returns to the normal position, i.e., the middle position, and the hydraulic oil cannot pass through the first electromagnetic reversing valve 6, causing the hydraulic reversing valve 5 to be powered off and return to the normal position, i.e., the middle position, and the oil pump 3 is unloaded through the hydraulic reversing valve 5 in the middle position, completing a working cycle.

[0048] The operation of the hydraulic press only requires setting thresholds in advance in the displacement sensor 10, the pressure relay 16 and the time relay, so that the automatic operation process of the hydraulic press can be realized through pure hardware.

[0049] The above contents are only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A working method of a bidirectional brake hydraulic press, characterized in that: The bidirectional brake hydraulic machine comprises an oil tank (1), an oil pump (3), a hydraulic reversing valve (5), a first electromagnetic reversing valve (6), a relief valve (21), a first hydraulic cylinder (9) and a second hydraulic cylinder (14); The oil outlet of the oil tank (1) is connected to the input end of the oil pump (3); the hydraulic reversing valve (5) is a three-position five-way valve, the first solenoid reversing valve (6) is a three-position four-way valve, and when the first solenoid reversing valve (6) is in a neutral position, its first and second oil ports are connected to the hydraulic reversing valve (5), the third oil port is connected to the oil inlet of the oil tank (1), and the fourth oil port is connected to the output end of the oil pump (3); when the hydraulic reversing valve (5) is in a neutral position, its first oil port is connected to the oil inlet of the oil tank (1), the second oil port is connected to the oil inlet of the overflow valve (21), the third oil port is connected to the output end of the oil pump (3), and the fourth oil port is connected to the output end of the oil pump (3). The fourth oil port is connected to the rod chambers of the first hydraulic cylinder (9) and the second hydraulic cylinder (14); the fifth oil port is divided into two paths, one path is connected to the throttle valve (17) and the rodless chambers of the first hydraulic cylinder (9) and the second hydraulic cylinder (14) in sequence, the throttle valve (17) is connected in parallel with the second electromagnetic reversing valve (18), and the other path is connected to the overflow valve (21); the oil outlet of the overflow valve (21) is respectively connected to the oil inlet of the third electromagnetic reversing valve (22) and the oil inlet of the oil tank (1), and the oil outlet of the third electromagnetic reversing valve (22) is connected to the oil inlet of the oil tank (1); The working method includes the following processes: In the idle stroke downward pressure stage: the left side of the first electromagnetic reversing valve (6) is energized, the valve core moves rightward, and the left position enters the working state; the hydraulic oil pumped out by the oil pump (3) passes through the first electromagnetic reversing valve (6) to reach the hydraulic reversing valve (5), causing the valve core of the hydraulic reversing valve (5) to move rightward, and the left position enters the working state; then, when the hydraulic oil pumped out by the oil pump (3) passes through the hydraulic reversing valve (5) and the first electromagnetic reversing valve (6) and flows into the rodless chamber of the first hydraulic cylinder (9) and the second hydraulic cylinder (14), the first hydraulic cylinder (9) and the second hydraulic cylinder (14) perform a clamping action; the hydraulic oil in the rod chamber of the first hydraulic cylinder (9) and the second hydraulic cylinder (14) passes through the hydraulic reversing valve (5), and the hydraulic oil and the oil pumped out by the oil pump (3) merge and flow into the rodless chamber of the first hydraulic cylinder (9) and the second hydraulic cylinder (14); Pressing down stage: after the first hydraulic cylinder (9) and the second hydraulic cylinder (14) contact the workpiece, the left side of the second electromagnetic reversing valve (18) is energized, the valve core moves to the right, and the left position enters the working state. The hydraulic oil pumped out by the oil pump (3) flows into the rodless chamber of the first hydraulic cylinder (9) and the second hydraulic cylinder (14) through the hydraulic reversing valve (5) and the throttle valve (17). The first hydraulic cylinder (9) and the second hydraulic cylinder (14) are slowly pushed forward, and the hydraulic oil in the rod chamber passes through the hydraulic reversing valve (5) and the overflow valve (21) and returns to the oil tank (1); Pressure-maintaining stage: the hydraulic cylinder is continuously pressurized, the work is further increased, the left side of the third electromagnetic reversing valve (22) is energized, the valve core moves rightward, the left position enters the working position, and the hydraulic oil pumped out by the oil pump (3) passes through the overflow valve (21) and the third electromagnetic reversing valve (22) and returns to the oil tank (1); Fast rewind stage: the left side of the first electromagnetic reversing valve (6) is powered off, the right side is powered on, the valve core moves to the left, the right position enters the working state, the hydraulic oil pumped out by the oil pump (3) passes through the first electromagnetic reversing valve (6) to the hydraulic reversing valve (5), causing the valve core of the hydraulic reversing valve (5) to move to the left, and the right position enters the working state; the hydraulic oil pumped out by the oil pump (3) passes through the hydraulic reversing valve (5) and flows into the rod chambers of the first hydraulic cylinder (9) and the second hydraulic cylinder (14), the first hydraulic cylinder (9) and the second hydraulic cylinder (14) perform separation movement, and the hydraulic oil in the rodless chamber flows back to the oil tank (1) through the hydraulic reversing valve (5); Movement stop stage: the first hydraulic cylinder (9) and the second hydraulic cylinder (14) return to their original positions, the right side of the first electromagnetic reversing valve (6) is powered off, and the valve core returns to its normal position, i.e., the middle position; the hydraulic oil cannot pass through the first electromagnetic reversing valve (6), causing the hydraulic reversing valve (5) to return to its normal position, i.e., the middle position; the oil pump (3) is unloaded through the hydraulic reversing valve (5) at the middle position, completing a working cycle.

2. The working method of the bidirectional brake hydraulic machine according to claim 1, characterized in that: An accumulator (15) is connected between the fifth oil port of the hydraulic reversing valve (5) and the rodless chambers of the first hydraulic cylinder (9) and the second hydraulic cylinder (14).

3. The working method of the bidirectional brake hydraulic machine according to claim 1, characterized in that: The rodless chambers of the first hydraulic cylinder (9) and the second hydraulic cylinder (14) are connected to an electric contact type presser (23).

4. The working method of the bidirectional brake hydraulic machine according to claim 1, characterized in that: A pressure relay (16) is provided between the fifth oil port of the hydraulic reversing valve (5) and the rodless chambers of the first hydraulic cylinder (9) and the second hydraulic cylinder (14), and an output end of the pressure relay (16) is electrically connected to the third electromagnetic reversing valve (22).

5. The working method of the bidirectional brake hydraulic machine according to claim 4, characterized in that: The output end of the pressure relay (16) is connected to the input end of the time relay, and the output end of the time relay is electrically connected to the first electromagnetic reversing valve (6).

6. The working method of the bidirectional brake hydraulic machine according to claim 1, characterized in that: The first hydraulic cylinder (9) and the second hydraulic cylinder (14) are both provided with a displacement sensor (10), and the output end of the displacement sensor (10) is electrically connected to the first electromagnetic reversing valve (6) and the second electromagnetic reversing valve (18).

7. The working method of the bidirectional brake hydraulic machine according to claim 1, characterized in that: The oil pump (3) adopts a pressure-limiting variable displacement vane pump.

8. The working method of the bidirectional brake hydraulic machine according to claim 1, characterized in that: During the pressing stage, when the hydraulic oil pressure reaches the set value of the pressure relay (16), the pressure maintaining stage is carried out and the accumulator (15) is opened to maintain the pressure.

9. The working method of the bidirectional brake hydraulic machine according to claim 8, characterized in that: When the hydraulic oil pressure reaches the set value of the pressure relay (16), the pressure relay (16) sends a signal to the time relay. After the signal is delayed by the time delay set by the time relay, it is sent to the first electromagnetic reversing valve (6) to enter the fast reversing stage.

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