Differential hydraulic circuit of sewing machine and control method

Abstract

The invention belongs to the technical field of hydraulic control of non-ferrous metal strip finishing equipment, and particularly discloses a differential hydraulic circuit of a sewing machine and a control method of the differential hydraulic circuit of the sewing machine. The differential control valve set comprises a piston cavity oil inlet two-way cartridge valve, a piston cavity oil return two-way cartridge valve, a piston rod cavity oil inlet two-way cartridge valve, a piston rod cavity oil return two-way cartridge valve, a piston cavity control electromagnetic directional valve, a rod cavity control electromagnetic directional valve and an unloading control electromagnetic directional valve, wherein the piston cavity control electromagnetic directional valve and the rod cavity control electromagnetic directional valve are used for logic control. The piston cavity oil inlet two-way cartridge valve and the piston rod cavity oil inlet two-way cartridge valve are controlled to be opened at the same time, the piston cavity oil return two-way cartridge valve and the piston rod cavity oil return two-way cartridge valve are controlled to be closed at the same time, pressure oil enters two cavities of the sewing oil cylinder at the same time, and due to the area difference of the two cavities, the pressure oil in the piston rod cavity returns to the piston cavity; and rapid die assembly can be realized without selecting a too large hydraulic pump and a motor with relatively high power, so that the acquisition cost and the use cost of an enterprise are reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of hydraulic control of nonferrous metal strip finishing equipment, and specifically discloses a differential hydraulic circuit of a stitching machine and a control method. Background Art

[0002] The finishing equipment for non-ferrous metal strips includes stretching and straightening units, cleaning units, etc. The production line is long, and the initial threading is troublesome, time-consuming and labor-intensive. To avoid repeated threading, a stitching machine stitching scheme is currently commonly used. After the previous roll of strip completes the production process, the tail of the previous roll of strip is stitched together with the head of the next roll of strip, thereby achieving smooth threading of the next roll of strip to improve production efficiency. Usually, the stitching function of the stitching machine is completed by two hydraulic cylinders, and its working process includes fast mold closing, slow mold closing, pressure holding, return and other actions. Because the two stitching cylinders have large cylinder diameters, a large flow rate is required for fast mold closing, which requires a large flow hydraulic pump and a large power drive motor to achieve, and the purchase cost and use cost are high. Summary of the invention

[0003] In order to solve the problems in the background technology, the present invention discloses a differential hydraulic circuit and control method for a sewing machine, including a pump station and a differential control valve group. When working, the oil inlet two-way cartridge valves of the piston chamber and the piston rod chamber are opened at the same time, and the oil return two-way cartridge valves of the piston chamber and the piston rod chamber are closed at the same time, and the pressure oil enters the two chambers of the sewing cylinder at the same time. The pressure difference between the piston chamber and the piston rod chamber is used to return the pressure oil in the piston rod chamber to the piston chamber. When realizing rapid mold closing, there is no need to select a too large hydraulic pump and a high-power motor to realize rapid mold closing, thereby reducing enterprise costs.

[0004] In order to achieve the above-mentioned invention object, the present invention adopts the following technical solutions: A differential hydraulic circuit of a sewing machine comprises a pump station and a sewing oil cylinder, and also comprises a differential control valve group, wherein the differential control valve group comprises a piston chamber oil inlet two-way cartridge valve, a piston chamber oil return two-way cartridge valve, a piston rod chamber oil inlet two-way cartridge valve and a piston rod chamber oil return two-way cartridge valve, wherein the B ports of the piston chamber oil inlet two-way cartridge valve and the piston rod chamber oil inlet two-way cartridge valve are respectively connected to the pump station P port, and the B ports of the piston chamber oil return two-way cartridge valve and the piston rod chamber oil return two-way cartridge valve are respectively connected to the pump station T port; The A port of the piston chamber oil inlet two-way cartridge valve is respectively connected to the piston chamber of the sewing cylinder, the A port of the piston chamber oil return two-way cartridge valve and the A port of the unloading control electromagnetic reversing valve, the B port of the piston chamber oil inlet two-way cartridge valve is also connected to the P port of the plug chamber control electromagnetic reversing valve through the shuttle valve in its cover plate, the A port of the plug chamber control electromagnetic reversing valve is connected to the valve core upper chamber of the piston chamber oil inlet two-way cartridge valve, the B port of the plug chamber control electromagnetic reversing valve is connected to the valve core upper chamber of the piston chamber oil return two-way cartridge valve, and the T ports of the plug chamber control electromagnetic reversing valve and the unloading control electromagnetic reversing valve are respectively connected to the B port of the piston chamber oil return two-way cartridge valve; The A port of the two-way cartridge valve for oil inlet to the piston rod chamber is respectively connected to the piston rod chamber of the sewing oil cylinder and the A port of the two-way cartridge valve for oil return from the piston rod chamber. The B port of the two-way cartridge valve for oil inlet to the piston rod chamber is also connected to the P port of the rod chamber control electromagnetic reversing valve through the shuttle valve in its cover plate. The A port of the rod chamber control electromagnetic reversing valve is connected to the upper cavity of the valve core of the two-way cartridge valve for oil inlet to the piston rod chamber. The B port of the rod chamber control electromagnetic reversing valve is connected to the upper cavity of the valve core of the two-way cartridge valve for oil return from the piston rod chamber. The T port of the rod chamber control electromagnetic reversing valve is connected to the T port of the pump station. Plug cavity pressure measuring joints and pressure relays are arranged at intervals on the pipeline adjacent to the sewing cylinder piston cavity, and a rod cavity pressure measuring joint is arranged on the pipeline adjacent to the sewing cylinder piston rod cavity. The pressure relay is used for real-time monitoring of the mold clamping pressure, and the plug cavity pressure measuring joint and the rod cavity pressure measuring joint are respectively used for connecting pressure gauges to detect the pressure of the sewing cylinder piston cavity or the sewing cylinder piston rod cavity.

[0005] Furthermore, the differential hydraulic circuit of the sewing machine is provided with a throttle at port A of the unloading control electromagnetic reversing valve.

[0006] A method for controlling a differential hydraulic circuit of a sewing machine, using the differential hydraulic circuit of the sewing machine to control the rapid clamping of a sewing cylinder, specifically comprises the following steps: The electromagnetic reversing valves are not energized, the piston chamber oil inlet two-way cartridge valve and the piston rod chamber oil inlet two-way cartridge valve are both in a closed state, and the sewing cylinder does not move; The a-end electromagnet of the plug cavity control solenoid reversing valve and the rod cavity control solenoid reversing valve are energized at the same time, the piston cavity oil return two-way cartridge valve is closed, the piston cavity oil inlet two-way cartridge valve is opened, and the pressure oil enters the piston cavity of the sewing oil cylinder through the piston cavity oil inlet two-way cartridge valve. At the same time, the piston rod cavity oil return two-way cartridge valve is closed, the piston rod cavity oil inlet two-way cartridge valve is opened, and the pressure oil enters the piston rod cavity of the sewing oil cylinder through the piston rod cavity oil inlet two-way cartridge valve. The piston cavity and piston rod cavity oil are combined to push the sewing oil cylinder piston up, and the sewing oil cylinder is quickly molded; The rod chamber control electromagnetic reversing valve is powered off, the piston rod chamber oil inlet two-way cartridge valve is closed, and the piston rod chamber oil return two-way cartridge valve is opened. The oil in the piston rod chamber returns to the oil tank of the pump station through the piston rod chamber oil return two-way cartridge valve. The plug chamber control electromagnetic reversing valve remains powered on, and the pressure oil enters the piston chamber of the sewing cylinder through the piston chamber oil inlet two-way cartridge valve, and the sewing cylinder closes the mold slowly; The pressure relay sends a mold closing signal, the plug cavity control electromagnetic reversing valve is powered off and in the middle position, the piston cavity oil inlet two-way cartridge valve and the piston cavity oil return two-way cartridge valve are closed, and the sewing machine is in the pressure holding position; The unloading control electromagnetic reversing valve is energized and the sewing machine is depressurized; The pressure relay sends a pressure relief completion signal, the B-end solenoid of the plug chamber control solenoid reversing valve and the rod chamber control solenoid reversing valve are energized at the same time, the piston rod chamber oil inlet two-way cartridge valve opens, and the piston rod chamber oil return two-way cartridge valve is closed, and the pressure oil enters the piston rod chamber of the stitching cylinder through the piston rod chamber oil inlet two-way cartridge valve. At the same time, the piston chamber oil return two-way cartridge valve opens, and the piston chamber oil inlet two-way cartridge valve is closed, and the piston chamber oil returns to the oil tank of the pump station through the piston chamber oil return two-way cartridge valve, and the stitching cylinder returns.

[0007] Compared with the prior art, the present invention has the following beneficial effects: The differential hydraulic circuit of a sewing machine disclosed in the present invention comprises a pump station and a differential control valve group, wherein the differential control valve group comprises a piston chamber oil inlet two-way cartridge valve, a piston chamber oil return two-way cartridge valve, a piston rod chamber oil inlet two-way cartridge valve, a piston rod chamber oil return two-way cartridge valve, a plug chamber control electromagnetic reversing valve and a rod chamber control electromagnetic reversing valve for logic control, and an unloading control electromagnetic reversing valve for unloading. During rapid mold closing, the piston chamber oil inlet two-way cartridge valve and the piston rod chamber oil inlet two-way cartridge valve are opened at the same time, the piston chamber oil return two-way cartridge valve and the piston rod chamber oil return two-way cartridge valve are closed at the same time, and the pressure oil enters the two chambers of the sewing oil cylinder at the same time. Due to the difference in area between the two chambers, the pressure oil in the piston rod chamber returns to the piston chamber, thereby realizing rapid mold closing of the sewing oil cylinder, and rapid mold closing can be realized without selecting a too large hydraulic pump and a high-power motor, thereby reducing the purchase cost and use cost of the enterprise. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 It is a schematic diagram of a differential hydraulic circuit of a sewing machine of the present invention; In the above figure: 1- pump station; 2- piston chamber oil inlet two-way cartridge valve; 3- piston chamber oil return two-way cartridge valve; 4- piston rod chamber oil inlet two-way cartridge valve; 5- piston rod chamber oil return two-way cartridge valve; 6- plug chamber control solenoid reversing valve; 7- rod chamber control solenoid reversing valve; 8- unloading control solenoid reversing valve; 9- rod chamber pressure measuring joint; 10- plug chamber pressure measuring joint; 11- pressure relay; 12- sewing cylinder. DETAILED DESCRIPTION

[0009] In order to better understand the present invention, the content of the present invention is further clearly set forth in conjunction with the embodiments below, but the protection content of the present invention is not limited to the following embodiments. In the following description, a large number of specific details are provided in order to provide a more thorough understanding of the present invention. However, it is obvious to those skilled in the art that the present invention can be implemented without one or more of these details.

[0010] Combined with Figure 1, the differential hydraulic circuit of a sewing machine of the present invention is described in detail, including a pump station 1 and a sewing oil cylinder 12, and also including a differential control valve group. Because the flow rate of the sewing machine 12 is relatively large, the present invention adopts a two-way cartridge valve integrated control circuit, and the differential control valve group includes a piston chamber oil inlet two-way cartridge valve 2, a piston chamber oil return two-way cartridge valve 3, a piston rod chamber oil inlet two-way cartridge valve 4 and a piston rod chamber oil return two-way cartridge valve 5. The B ports of the piston chamber oil inlet two-way cartridge valve 2 and the piston rod chamber oil inlet two-way cartridge valve 4 are respectively connected to the P port of the pump station 1, and the B ports of the piston chamber oil return two-way cartridge valve 3 and the piston rod chamber oil return two-way cartridge valve 5 are respectively connected to the T port of the pump station 1; The A port of the piston chamber oil inlet two-way cartridge valve 2 is respectively connected to the piston chamber of the sewing cylinder 12, the A port of the piston chamber oil return two-way cartridge valve 3 and the A port of the unloading control electromagnetic reversing valve 8, the B port of the piston chamber oil inlet two-way cartridge valve 2 is also connected to the P port of the plug chamber control electromagnetic reversing valve 6 through the shuttle valve in its cover plate, the A port of the plug chamber control electromagnetic reversing valve 6 is connected to the valve core upper chamber of the piston chamber oil inlet two-way cartridge valve 2, the B port of the plug chamber control electromagnetic reversing valve 6 is connected to the valve core upper chamber of the piston chamber oil return two-way cartridge valve 3, and the T ports of the plug chamber control electromagnetic reversing valve 6 and the unloading control electromagnetic reversing valve 8 are respectively connected to the B port of the piston chamber oil return two-way cartridge valve 3; It should be noted here that: when the plug cavity controlled electromagnetic reversing valve 6 is not energized, the valve is in the middle position, the pressure oil port P of the plug cavity controlled electromagnetic reversing valve 6 is connected with the port A and the port B, and the return oil port T is blocked. At this time, the pressure oil of the port A of the plug cavity controlled electromagnetic reversing valve 6 acts on the upper end of the valve core of the piston cavity oil inlet two-way cartridge valve 2, and the pressure oil of the port B of the plug cavity controlled electromagnetic reversing valve 6 acts on the upper end of the valve core of the piston cavity oil return two-way cartridge valve 3. The piston cavity oil inlet two-way cartridge valve 2 and The piston chamber oil return two-way cartridge valve 3 is in a closed state; when the a-end electromagnet of the plug chamber control electromagnetic reversing valve 6 is energized, the electromagnetic valve is in the left position, the pressure oil P port of the plug chamber control electromagnetic reversing valve 6 is connected to the B port, and the A port is connected to the oil return T port; when the b-end electromagnet of the plug chamber control electromagnetic reversing valve 6 is energized, the electromagnetic valve is in the right position, the pressure oil P port of the plug chamber control electromagnetic reversing valve 6 is connected to the A port, and the B port of the plug chamber control electromagnetic reversing valve 6 is connected to the oil return T port; The A port of the piston rod chamber oil inlet two-way cartridge valve 4 is respectively connected to the piston rod chamber of the sewing cylinder 12 and the A port of the piston rod chamber oil return two-way cartridge valve 5, the B port of the piston rod chamber oil inlet two-way cartridge valve 4 is also connected to the P port of the rod chamber control electromagnetic reversing valve 7 through the shuttle valve in its cover plate, the A port of the rod chamber control electromagnetic reversing valve 7 is connected to the valve core upper cavity of the piston rod chamber oil inlet two-way cartridge valve 4, the B port of the rod chamber control electromagnetic reversing valve 7 is connected to the valve core upper cavity of the piston rod chamber oil return two-way cartridge valve 5, and the T port of the rod chamber control electromagnetic reversing valve 7 is connected to the T port of the pump station 1; It should be noted here that: when the electromagnet of the rod chamber control electromagnetic reversing valve 7 is not energized, the electromagnetic valve is in the right position, the pressure oil P port of the rod chamber control electromagnetic reversing valve 7 is connected to the A port, and the B port of the rod chamber control electromagnetic reversing valve 7 is connected to the return oil T port; when the electromagnet of the rod chamber control electromagnetic reversing valve 7 is energized, the electromagnetic valve is in the left position, the pressure oil P port of the rod chamber control electromagnetic reversing valve 7 is connected to the B port, and the A port of the rod chamber control electromagnetic reversing valve 7 is connected to the return oil T port; A plug cavity pressure measuring joint 10 and a pressure relay 11 are arranged at intervals on the pipeline adjacent to the piston cavity of the sewing oil cylinder 12, and a rod cavity pressure measuring joint 9 is arranged on the pipeline adjacent to the piston rod cavity of the sewing oil cylinder 12. The pressure relay 11 is used for real-time monitoring of the mold clamping pressure, and the plug cavity pressure measuring joint 10 and the rod cavity pressure measuring joint 9 are respectively used for connecting pressure gauges to detect the pressure of the piston cavity of the sewing oil cylinder 12 or the piston rod cavity of the sewing oil cylinder 12.

[0011] As an optional design, the differential hydraulic circuit of the sewing machine is preferably provided with a throttle at port A of the unloading control electromagnetic reversing valve 8 to prevent impact, vibration and noise caused by excessive pressure relief.

[0012] A method for controlling a differential hydraulic circuit of a sewing machine, using the differential hydraulic circuit of the sewing machine to control the rapid mold closing of the sewing cylinder 12, specifically comprising the following steps: The electromagnetic reversing valves are not energized, the piston chamber oil inlet two-way cartridge valve 2 and the piston rod chamber oil inlet two-way cartridge valve 4 are both in a closed state, and the sewing cylinder 12 is not in action; The a-end electromagnet of the plug cavity control electromagnetic reversing valve 6 and the rod cavity control electromagnetic reversing valve 7 are energized at the same time, the piston cavity oil return two-way cartridge valve 3 is closed, the piston cavity oil inlet two-way cartridge valve 2 is opened, and the pressure oil enters the piston cavity of the sewing oil cylinder 12 through the piston cavity oil inlet two-way cartridge valve 2. At the same time, the piston rod cavity oil return two-way cartridge valve 5 is closed, the piston rod cavity oil inlet two-way cartridge valve 4 is opened, and the pressure oil enters the piston rod cavity of the sewing oil cylinder 12 through the piston rod cavity oil inlet two-way cartridge valve 4. The piston cavity and piston rod cavity oil are combined to push the piston of the sewing oil cylinder 12 to rise, and the sewing oil cylinder 12 is quickly molded; The rod chamber control electromagnetic reversing valve 7 is powered off, the piston rod chamber oil inlet two-way cartridge valve 4 is closed, and the piston rod chamber oil return two-way cartridge valve 5 is opened. The oil in the piston rod chamber returns to the oil tank of the pump station 1 through the piston rod chamber oil return two-way cartridge valve 5. The plug chamber control electromagnetic reversing valve 6 remains powered on. The pressure oil enters the piston chamber of the sewing cylinder 12 through the piston chamber oil inlet two-way cartridge valve 2, and the sewing cylinder 12 closes the mold slowly. The pressure relay 11 sends a mold closing signal, the plug cavity control electromagnetic reversing valve 6 is powered off and in the middle position of the valve, the piston cavity oil inlet two-way cartridge valve 2 and the piston cavity oil return two-way cartridge valve 3 are closed, and the sewing machine is in the pressure holding position; The unloading control electromagnetic reversing valve 8 is energized, and the sewing machine is depressurized; The pressure relay 11 sends a pressure relief completion signal, the B-end electromagnet of the plug chamber control solenoid reversing valve 6 and the rod chamber control solenoid reversing valve 7 are energized at the same time, the piston rod chamber oil inlet two-way cartridge valve 4 is opened, and the piston rod chamber oil return two-way cartridge valve 5 is closed, and the pressure oil enters the piston rod chamber of the stitching cylinder 12 through the piston rod chamber oil inlet two-way cartridge valve 4. At the same time, the piston chamber oil return two-way cartridge valve 3 is opened, and the piston chamber oil inlet two-way cartridge valve 2 is closed, and the piston chamber oil returns to the oil tank of the pump station 1 through the piston chamber oil return two-way cartridge valve 3, and the stitching cylinder 12 returns.

[0013] The working process of the differential hydraulic circuit of the sewing machine of the present invention is as follows: The pressure oil port P and the return oil port T of the pump station 1 are connected to the differential control valve group through pipelines. The pressure oil enters the differential control valve group and acts on the B port of the piston chamber oil inlet two-way cartridge valve 2 and the B port of the piston rod chamber oil inlet two-way cartridge valve 4. When the solenoid reversing valves are not energized, the pressure oil reaches the P port of the plug chamber control solenoid reversing valve 6 and the rod chamber control solenoid reversing valve 7 through the shuttle valves in the cover plates of the piston chamber oil inlet two-way cartridge valve 2 and the piston rod chamber oil inlet two-way cartridge valve 4. Then the pressure oil acts on the upper ends of the valve cores of the piston chamber oil inlet two-way cartridge valve 2 and the piston rod chamber oil inlet two-way cartridge valve 4 through the solenoid reversing valve, so that the piston chamber oil inlet two-way cartridge valve 2 and the piston rod chamber oil inlet two-way cartridge valve 4 are both in a closed state, and the sewing cylinder 12 does not move. The purpose of the shuttle valves in the cover plates of the piston chamber oil inlet two-way cartridge valve 2 and the piston rod chamber oil inlet two-way cartridge valve 4 is to ensure that the cartridge valves are closed reliably. When the a-end electromagnet (YV1a) of the piston chamber control solenoid reversing valve 6 and the rod chamber control solenoid reversing valve 7 (YV2) are energized at the same time, the pressure oil acts on the upper end of the valve core of the piston chamber oil return two-way cartridge valve 3 through the solenoid valve YV1, so that the piston chamber oil return two-way cartridge valve 3 is closed, and the upper end of the valve core of the piston chamber oil inlet two-way cartridge valve 2 is in the oil return state. The pressure oil opens the valve core of the piston chamber oil inlet two-way cartridge valve 2 through the B port of the piston chamber oil inlet two-way cartridge valve 2 to reach the A port and then enter The piston chamber of the sewing oil cylinder 12, at the same time, after YV2 is energized, the piston rod chamber oil return two-way cartridge valve 5 is closed, and the piston rod chamber oil inlet two-way cartridge valve 4 is opened. The pressure oil enters the piston rod chamber of the sewing oil cylinder 12 through the piston rod chamber oil inlet two-way cartridge valve 4. Because the piston chamber area is larger than the piston rod chamber area, the thrust generated by the piston chamber oil pressure is greater than the piston rod chamber oil pressure thrust. In this way, the piston chamber and piston rod chamber oil liquids merge together to push the piston of the sewing oil cylinder 12 to rise, and the sewing oil cylinder 12 is quickly molded; When approaching the mold closing position, the proximity switch installed on the equipment sends a signal to cut off the power of the rod chamber control electromagnetic reversing valve 7, close the piston rod chamber oil inlet two-way cartridge valve 4, open the piston rod chamber oil return two-way cartridge valve 5, and the oil in the piston rod chamber returns to the oil tank of the pump station 1 through the piston rod chamber oil return two-way cartridge valve 5. The plug chamber control electromagnetic reversing valve 6 remains powered on, and the pressure oil continues to enter the piston chamber of the sewing cylinder 12 through the piston chamber oil inlet two-way cartridge valve 2, and the sewing cylinder 12 slowly closes the mold; The pressure relay 11 monitors the mold closing pressure in real time. When the pressure stops increasing, it indicates that the mold is in place. The pressure relay 11 sends a mold closing signal, and the plug cavity control electromagnetic reversing valve 6 (YV1) is powered off and in the middle position of the valve. The pressure oil acts on the valve cores of the piston cavity oil inlet two-way cartridge valve 2 and the piston cavity oil return two-way cartridge valve 3 through the electromagnetic valve YV1, respectively, so that the piston cavity oil inlet two-way cartridge valve 2 and the piston cavity oil return two-way cartridge valve 3 are closed, and the plug cavity pressure oil is sealed inside, and the sewing machine is in the pressure holding position; When the set pressure holding time is reached, the unloading control electromagnetic reversing valve 8 (YV3) is energized and the sewing machine is depressurized; When the pressure relay 11 detects the set pressure relief completion signal, the pressure relay 11 sends a pressure relief completion signal, the b-end electromagnet (YV1b) of the plug chamber control solenoid reversing valve 6 and the rod chamber control solenoid reversing valve 7 are energized at the same time, the piston rod chamber oil inlet two-way cartridge valve 4 is opened, and the piston rod chamber oil return two-way cartridge valve 5 is closed, and the pressure oil enters the piston rod chamber of the stitching cylinder 12 through the piston rod chamber oil inlet two-way cartridge valve 4. At the same time, the piston chamber oil return two-way cartridge valve 3 is opened, and the piston chamber oil inlet two-way cartridge valve 2 is closed, and the piston chamber oil returns to the oil tank of the pump station 1 through the piston chamber oil return two-way cartridge valve 3, and the stitching cylinder 12 returns.

[0014] In order to clearly show the relationship between the on-off status of the electromagnetic reversing valve solenoid and the various actions of the oil cylinder, the following table is used to briefly express it:

[0015] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Other modifications or equivalent substitutions made to the technical solution of the present invention by ordinary technicians in the field should be included in the scope of the claims of the present invention as long as they do not depart from the spirit and scope of the technical solution of the present invention.

Claims

1. A differential hydraulic circuit for a sewing machine, comprising a pump station and a sewing cylinder, characterized in that: It also includes a differential control valve group, which includes a piston chamber oil inlet two-way cartridge valve, a piston chamber oil return two-way cartridge valve, a piston rod chamber oil inlet two-way cartridge valve and a piston rod chamber oil return two-way cartridge valve, the B ports of the piston chamber oil inlet two-way cartridge valve and the piston rod chamber oil inlet two-way cartridge valve are respectively connected to the pump station P port, and the piston chamber oil return two-way cartridge valve and the piston rod chamber oil return two-way cartridge valve B ports are respectively connected to the pump station T port; The A port of the piston chamber oil inlet two-way cartridge valve is respectively connected to the piston chamber of the sewing cylinder, the A port of the piston chamber oil return two-way cartridge valve and the A port of the unloading control electromagnetic reversing valve, the B port of the piston chamber oil inlet two-way cartridge valve is also connected to the P port of the plug chamber control electromagnetic reversing valve through the shuttle valve in its cover plate, the A port of the plug chamber control electromagnetic reversing valve is connected to the valve core upper chamber of the piston chamber oil inlet two-way cartridge valve, the B port of the plug chamber control electromagnetic reversing valve is connected to the valve core upper chamber of the piston chamber oil return two-way cartridge valve, and the T ports of the plug chamber control electromagnetic reversing valve and the unloading control electromagnetic reversing valve are respectively connected to the B port of the piston chamber oil return two-way cartridge valve; The A port of the two-way cartridge valve for oil inlet to the piston rod chamber is respectively connected to the piston rod chamber of the sewing oil cylinder and the A port of the two-way cartridge valve for oil return from the piston rod chamber. The B port of the two-way cartridge valve for oil inlet to the piston rod chamber is also connected to the P port of the rod chamber control electromagnetic reversing valve through the shuttle valve in its cover plate. The A port of the rod chamber control electromagnetic reversing valve is connected to the upper cavity of the valve core of the two-way cartridge valve for oil inlet to the piston rod chamber. The B port of the rod chamber control electromagnetic reversing valve is connected to the upper cavity of the valve core of the two-way cartridge valve for oil return from the piston rod chamber. The T port of the rod chamber control electromagnetic reversing valve is connected to the T port of the pump station. Plug cavity pressure measuring joints and pressure relays are arranged at intervals on the pipeline adjacent to the sewing cylinder piston cavity, and a rod cavity pressure measuring joint is arranged on the pipeline adjacent to the sewing cylinder piston rod cavity. The pressure relay is used for real-time monitoring of the mold clamping pressure, and the plug cavity pressure measuring joint and the rod cavity pressure measuring joint are respectively used for connecting pressure gauges to detect the pressure of the sewing cylinder piston cavity or the sewing cylinder piston rod cavity.

2. The differential hydraulic circuit of a sewing machine according to claim 1, characterized in that: A throttle is provided at port A of the unloading control electromagnetic reversing valve.

3. A differential hydraulic circuit control method for a sewing machine, characterized in that: The method of controlling the rapid mold closing of the sewing cylinder by using the differential hydraulic circuit of the sewing machine according to claim 1 or 2 specifically comprises the following steps: The electromagnetic reversing valves are not energized, the piston chamber oil inlet two-way cartridge valve and the piston rod chamber oil inlet two-way cartridge valve are both in a closed state, and the sewing cylinder does not move; The a-end electromagnet of the plug cavity control solenoid reversing valve and the rod cavity control solenoid reversing valve are energized at the same time, the piston cavity oil return two-way cartridge valve is closed, the piston cavity oil inlet two-way cartridge valve is opened, and the pressure oil enters the piston cavity of the sewing oil cylinder through the piston cavity oil inlet two-way cartridge valve. At the same time, the piston rod cavity oil return two-way cartridge valve is closed, the piston rod cavity oil inlet two-way cartridge valve is opened, and the pressure oil enters the piston rod cavity of the sewing oil cylinder through the piston rod cavity oil inlet two-way cartridge valve. The piston cavity and piston rod cavity oil are combined to push the sewing oil cylinder piston up, and the sewing oil cylinder is quickly molded; The rod chamber control electromagnetic reversing valve is powered off, the piston rod chamber oil inlet two-way cartridge valve is closed, and the piston rod chamber oil return two-way cartridge valve is opened. The oil in the piston rod chamber returns to the oil tank of the pump station through the piston rod chamber oil return two-way cartridge valve. The plug chamber control electromagnetic reversing valve remains powered on, and the pressure oil enters the piston chamber of the sewing cylinder through the piston chamber oil inlet two-way cartridge valve, and the sewing cylinder closes the mold slowly; The pressure relay sends a mold closing signal, the plug cavity control electromagnetic reversing valve is powered off and in the middle position, the piston cavity oil inlet two-way cartridge valve and the piston cavity oil return two-way cartridge valve are closed, and the sewing machine is in the pressure holding position; The unloading control electromagnetic reversing valve is energized and the sewing machine is depressurized; The pressure relay sends a pressure relief completion signal, the B-end solenoid of the plug chamber control solenoid reversing valve and the rod chamber control solenoid reversing valve are energized at the same time, the piston rod chamber oil inlet two-way cartridge valve opens, and the piston rod chamber oil return two-way cartridge valve is closed, and the pressure oil enters the piston rod chamber of the stitching cylinder through the piston rod chamber oil inlet two-way cartridge valve. At the same time, the piston chamber oil return two-way cartridge valve opens, and the piston chamber oil inlet two-way cartridge valve is closed, and the piston chamber oil returns to the oil tank of the pump station through the piston chamber oil return two-way cartridge valve, and the stitching cylinder returns.

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