阅读说明：本技术 一种板材拉伸机的液压系统和控制方法以及板材拉伸机 (Hydraulic system and control method of plate stretching machine and plate stretching machine ) 是由 刘杰 郭星良 丘铭军 吴伟 彭立广 于 2020-12-03 设计创作，主要内容包括：本发明属于板材拉伸机技术领域,具体提供了一种板材拉伸机的液压系统和控制方法以及板材拉伸机,该系统包括第一逻辑阀、第二逻辑阀、第三逻辑阀、第四逻辑阀、比例溢流逻辑阀、比例溢流阀、溢流阀、卸荷逻辑阀、换向阀、I侧拉伸缸、II侧拉伸缸、I侧操作缸和II侧操作缸。本发明解决了现有技术中没有一种既能实现不同拉伸工况下两侧负载压力设定相同又能保证低故障率且卸荷平稳的多缸同步加载卸荷液压系统的问题。本发明实现同步加载和精确设定两侧拉伸力,拉伸结束后实现平稳卸荷,具有高效节能、性能可靠、故障率以及成本低的特点。(The invention belongs to the technical field of plate stretching machines, and particularly provides a hydraulic system and a control method of a plate stretching machine and the plate stretching machine. The invention solves the problem that the prior art does not have a multi-cylinder synchronous loading and unloading hydraulic system which can realize the same load pressure settings at two sides under different stretching working conditions and can ensure low failure rate and stable unloading. The invention realizes synchronous loading and accurate setting of stretching force at two sides, realizes stable unloading after stretching is finished, and has the characteristics of high efficiency, energy saving, reliable performance, failure rate and low cost.)

1. The utility model provides a hydraulic system of panel stretcher which characterized in that: the hydraulic control system comprises a first logic valve (1), a second logic valve (2), a third logic valve (3), a fourth logic valve (4), a proportional overflow logic valve (6), a proportional overflow valve (9), an I-side stretching cylinder (10), an II-side stretching cylinder (11), an I-side operating cylinder (12) and an II-side operating cylinder (13), wherein an oil port of the I-side stretching cylinder (10) is connected with an oil inlet of the first logic valve (1), and an oil outlet of the first logic valve (1) is connected with an oil inlet of the proportional overflow logic valve (6) and an oil inlet of the proportional overflow valve (9) in parallel; an oil port of a stretching cavity of the I-side operating cylinder (12) is connected with an oil inlet of a third logic valve (3), and an oil outlet of the third logic valve (3) is connected with an oil inlet of a proportional overflow logic valve (6) and an oil inlet of a proportional overflow valve (9) in parallel; an oil port of the II side stretching cylinder (11) is connected with an oil inlet of the second logic valve (2), and an oil outlet of the second logic valve (2) is connected with an oil inlet of the proportional overflow logic valve (6) and an oil inlet of the proportional overflow valve (9) in parallel; an oil port of a stretching cavity of the II-side operating cylinder (13) is connected with an oil inlet of a fourth logic valve (4), and an oil outlet of the fourth logic valve (4) is connected with an oil inlet of a proportional overflow logic valve (6) and an oil inlet of a proportional overflow valve (9) in parallel; the oil outlet of the first logic valve (1) is connected with the oil outlet of the second logic valve (2), the oil outlet of the third logic valve (3) and the oil outlet of the fourth logic valve (4) in parallel; an oil outlet of the proportional overflow logic valve (6) is connected with a main oil return port, an oil inlet of the proportional overflow valve (9) is connected with an oil inlet and a control oil port of the proportional overflow logic valve (6) in parallel, and an oil outlet of the proportional overflow valve (9) is connected with a main oil drain pipe.

2. The hydraulic system of a sheet stretching machine of claim 1, wherein: the oil inlet of the overflow valve (8) is connected with the oil inlet and the control oil port of the proportional overflow logic valve (6) in parallel, and the oil outlet of the overflow valve (8) is connected with the main oil drain pipe.

3. The hydraulic system of a sheet stretching machine of claim 2, wherein: the oil inlet of the unloading logic valve (5) is connected with the oil outlet of the first logic valve (1), the oil outlet of the second logic valve (2), the oil outlet of the third logic valve (3) and the oil outlet of the fourth logic valve (4) in parallel, and the oil outlet of the unloading logic valve (5) is connected with the main oil return port.

4. The hydraulic system of a sheet stretching machine of claim 3, wherein: the unloading logic valve is characterized by further comprising a reversing valve (7), an oil inlet of the reversing valve (7) is connected with an oil inlet of the unloading logic valve (5), an oil outlet of the reversing valve (7) is connected with a control oil port of the unloading logic valve (5), and an oil return port of the reversing valve (7) is connected with a main oil drainage pipe.

5. The hydraulic system of a sheet stretching machine of claim 4, wherein: and displacement sensors are connected to the I side stretching cylinder (10), the II side stretching cylinder (11), the I side operating cylinder (12) and the II side operating cylinder (13).

6. The hydraulic system of a sheet stretching machine of claim 5, wherein: an oil outlet of the first logic valve (1) is connected with a control oil port of the first logic valve (1), an oil outlet of the second logic valve (2) is connected with a control oil port of the second logic valve (2), an oil outlet of the third logic valve (3) is connected with a control oil port of the third logic valve (3), and an oil outlet of the fourth logic valve (4) is connected with a control oil port of the fourth logic valve (4).

7. The hydraulic system of a sheet stretching machine of claim 6, wherein: the first logic valve (1), the second logic valve (2), the third logic valve (3) and the fourth logic valve (4) are all one-way cartridge logic valves.

8. A method for controlling a hydraulic system of a plate stretching machine according to any one of claims 1-7, characterized in that: the method comprises the following steps:

under the stretching working condition of the I-side stretching cylinder (10) and the II-side stretching cylinder (11), setting a given signal of a proportional overflow valve (9) according to plates of different specifications and different alloys, and enabling the I-side stretching cylinder (10) and the II-side stretching cylinder (11) to be symmetrically loaded due to the matched use of a first logic valve (1) and a second logic valve (2); after the stretching is finished, the stretching cylinder (10) at the I side and the stretching cylinder (11) at the II side are unloaded synchronously;

under the stretching working condition of the I side operating cylinder (12) and the II side operating cylinder (13), setting a given signal of the proportional overflow valve (9) according to plates of different specifications and different alloys, and enabling the I side operating cylinder (12) and the II side operating cylinder (13) to be symmetrically loaded due to the cooperation of the third logic valve (3) and the fourth logic valve (4); after the stretching is finished, the I side operating cylinder (12) and the II side operating cylinder (13) are unloaded synchronously;

under the combined stretching working condition, setting a given signal of a proportional overflow valve (9) according to plates of different specifications and different alloys, and enabling an I-side stretching cylinder (10), an II-side stretching cylinder (11), an I-side operating cylinder (12) and an II-side operating cylinder (13) to stretch simultaneously by using a first logic valve (1), a second logic valve (2), a third logic valve (3) and a fourth logic valve (4) in a matched manner; after the stretching is finished, the I side stretching cylinder (10), the II side stretching cylinder (11), the I side operating cylinder (12) and the II side operating cylinder (13) are unloaded synchronously.

9. A panel stretcher, characterized by comprising a hydraulic system according to any one of claims 1-7.

Technical Field

The invention belongs to the technical field of plate stretching machines, and particularly relates to a hydraulic system of a plate stretching machine, a control method and the plate stretching machine.

Background

The large-sized plate stretcher is mainly used for pre-stretching aluminum and aluminum alloy plates, and stress of the aluminum and aluminum alloy plates is eliminated according to a certain stretching rate. At present, the stretching heads of large-scale plate stretchers in China are composed of two sets of main stretching cylinder devices, which are symmetrically arranged on two sides of the stretching heads and used for stretching plates and moving stretching chucks in no-load mode. In the stretching process, when the unbalance loading of the main stretching cylinders on two sides of the stretching chuck exceeds the set working pressure or the unloading of other multi-cylinders on two sides is inconsistent after stretching is finished, a series of problems such as large system pressure fluctuation, abnormal equipment sound, forward twisting, pipeline vibration and the like occur, and the phenomena of plate cracking, overlarge stretching rate, unstable retraction rate and the like are caused in serious conditions, so that the plate quality is seriously influenced.

The conventional solution is that electromagnetic proportional overflow valves are respectively arranged in parallel in main stretching cylinder loops on two sides, so that the use requirement can be basically met, but because the characteristics of the two proportional valves are different, the set pressures on the two sides cannot be ensured to be completely consistent when the same signal is given, and the overflow valves on the two sides need to work frequently, so that the heat productivity of the system is large; meanwhile, after the stretching is finished, due to the fact that unloading pressure curves of the main stretching cylinders on the two sides are not consistent, when the plate drives the stretching chuck to retreat, asynchronous actions occur, and the phenomenon of serious shaking of equipment occurs; in addition, the main stretching cylinder and the operation cylinder are adopted for combined stretching during the stretching of the large-tonnage thick plate, and in order to ensure that the total stretching forces on two sides are close to consistency, electromagnetic proportional overflow valves are required to be respectively arranged in parallel in control loops of the operation cylinders on the two sides, so that the cost is high, and the electrical control is complicated. In view of the defects of the synchronous loading and unloading control system for the main stretching cylinder and the operating cylinder during stretching and combined stretching of the main stretching cylinder, a multi-cylinder synchronous loading and unloading hydraulic system which can realize the same setting of load pressure on two sides under different stretching working conditions and can ensure low failure rate and stable unloading is urgently needed.

Disclosure of Invention

The invention provides a hydraulic system and a control method of a plate stretcher and the plate stretcher, and aims to solve the problem that no multi-cylinder synchronous loading and unloading hydraulic system which can realize the same setting of load pressures on two sides under different stretching working conditions and can ensure low failure rate and stable unloading exists in the prior art.

Therefore, the invention provides a hydraulic system of a plate stretching machine, which comprises a first logic valve, a second logic valve, a third logic valve, a fourth logic valve, a proportional overflow valve, an I-side stretching cylinder, an II-side stretching cylinder, an I-side operating cylinder and an II-side operating cylinder, wherein an oil port of the I-side stretching cylinder is connected with an oil inlet of the first logic valve, and an oil outlet of the first logic valve is connected with an oil inlet of the proportional overflow logic valve and an oil inlet of the proportional overflow valve in parallel; an oil port of a stretching cavity of the I-side operating cylinder is connected with an oil inlet of a third logic valve, and an oil outlet of the third logic valve is connected with an oil inlet of a proportional overflow logic valve and an oil inlet of a proportional overflow valve in parallel; an oil port of the II side stretching cylinder is connected with an oil inlet of a second logic valve, and an oil outlet of the second logic valve is connected with an oil inlet of the proportional overflow logic valve and an oil inlet of the proportional overflow valve in parallel; an oil port of a stretching cavity of the II-side operating cylinder is connected with an oil inlet of a fourth logic valve, and an oil outlet of the fourth logic valve is connected with an oil inlet of the proportional overflow logic valve and an oil inlet of the proportional overflow valve in parallel; the oil outlet of the first logic valve is connected with the oil outlet of the second logic valve, the oil outlet of the third logic valve and the oil outlet of the fourth logic valve in parallel; an oil outlet of the proportional overflow logic valve is connected with a main oil return port, an oil inlet of the proportional overflow valve is connected with an oil inlet and a control oil port of the proportional overflow logic valve in parallel, and an oil outlet of the proportional overflow valve is connected with a main oil drainage pipe.

The hydraulic system of the plate stretching machine preferably comprises an overflow valve, wherein an oil inlet of the overflow valve is connected with an oil inlet and a control oil port of a proportional overflow logic valve in parallel, and an oil outlet of the overflow valve is connected with a main oil drain pipe.

As the optimal technical scheme of the hydraulic system of the plate stretching machine, the hydraulic system further comprises an unloading logic valve, an oil inlet of the unloading logic valve is connected with an oil outlet of the first logic valve, an oil outlet of the second logic valve, an oil outlet of the third logic valve and an oil outlet of the fourth logic valve in parallel, and an oil outlet of the unloading logic valve is connected with a main oil return port.

As the optimal technical scheme of the hydraulic system of the plate stretcher, the hydraulic system further comprises a reversing valve, wherein an oil inlet of the reversing valve is connected with an oil inlet of the unloading logic valve, an oil outlet of the reversing valve is connected with a control oil port of the unloading logic valve, and an oil return port of the reversing valve is connected with a main oil drain pipe.

As a preferable technical scheme of the hydraulic system of the plate stretcher, displacement sensors are connected to the side I stretching cylinder, the side II stretching cylinder, the side I operating cylinder and the side II operating cylinder.

As a preferred technical scheme of the hydraulic system of the plate stretching machine, an oil outlet of the first logic valve is connected with a control oil port of the first logic valve, an oil outlet of the second logic valve is connected with a control oil port of the second logic valve, an oil outlet of the third logic valve is connected with a control oil port of the third logic valve, and an oil outlet of the fourth logic valve is connected with a control oil port of the fourth logic valve.

As a preferable technical scheme of the hydraulic system of the plate material stretching machine, the first logic valve, the second logic valve, the third logic valve and the fourth logic valve are all one-way cartridge logic valves.

A method of controlling a hydraulic system of a sheet material stretching machine as set forth in any of the above aspects, comprising the steps of:

under the stretching working condition of the stretching cylinder at the I side and the stretching cylinder at the II side, setting a given signal of a proportional overflow valve according to plates of different specifications and different alloys, and enabling the stretching cylinder at the I side and the stretching cylinder at the II side to be symmetrically loaded by matching a first logic valve and a second logic valve; after the stretching is finished, synchronously unloading the stretching cylinder at the I side and the stretching cylinder at the II side;

under the stretching working condition of the I side operating cylinder and the II side operating cylinder, setting a given signal of a proportional overflow valve according to plates of different specifications and different alloys, and enabling the I side operating cylinder and the II side operating cylinder to be symmetrically loaded by using a third logic valve and a fourth logic valve in a matched manner; after the stretching is finished, synchronously unloading the I side operating cylinder and the II side operating cylinder;

under the combined stretching working condition, setting a given signal of a proportional overflow valve according to plates of different specifications and different alloys, and enabling an I-side stretching cylinder, an II-side stretching cylinder, an I-side operating cylinder and an II-side operating cylinder to simultaneously stretch by matching a first logic valve, a second logic valve, a third logic valve and a fourth logic valve; and after the stretching is finished, synchronously unloading the stretching cylinder at the I side, the stretching cylinder at the II side, the operating cylinder at the I side and the operating cylinder at the II side.

A sheet stretcher comprising a hydraulic system as described in any of the above aspects.

The invention has the beneficial effects that: according to the hydraulic system and the control method of the plate stretcher and the plate stretcher, when the stretching cylinders on two sides and the operating cylinders (the stretching cylinder on the I side, the stretching cylinder on the II side, the operating cylinder on the I side and the operating cylinder on the II side) work, a main oil path realizes synchronous loading and accurate setting of stretching forces on two sides through a proportional overflow valve, and stable unloading is realized after stretching is finished; compared with the traditional proportional unloading loop formed by a plurality of proportional overflow valves, the hydraulic system of the plate stretcher formed by the single proportional overflow valve has the advantages of high efficiency, energy conservation, reliable performance, low failure rate, low cost and the like.

Drawings

The present invention will be described in further detail below with reference to the accompanying drawings.

Fig. 1 is a schematic representation of the hydraulic system of a sheet-material stretching machine.

Description of reference numerals: 1. a first logic valve; 2. a second logic valve; 3. a third logic valve; 4. a fourth logic valve; 5. an unloading logic valve; 6. a proportional overflow logic valve; 7. a diverter valve; 8. an overflow valve; 9. a proportional relief valve; 10. i, stretching a cylinder on the side; 11. II, stretching the cylinder at the side; 12. an I-side operating cylinder; 13. the II side operates the cylinder.

Detailed Description

Example 1:

as shown in fig. 1, a hydraulic system of a plate stretching machine includes a first logic valve 1, a second logic valve 2, a third logic valve 3, a fourth logic valve 4, a proportional overflow logic valve 6, a proportional overflow valve 9, an I-side stretching cylinder 10, an II-side stretching cylinder 11, an I-side operating cylinder 12 and an II-side operating cylinder 13, an oil port of the I-side stretching cylinder 10 is connected to an oil inlet of the first logic valve 1, and an oil outlet of the first logic valve 1 is connected in parallel to an oil inlet of the proportional overflow logic valve 6 and an oil inlet of the proportional overflow valve 9; an oil port of a stretching cavity of the I-side operating cylinder 12 is connected with an oil inlet of a third logic valve 3, and an oil outlet of the third logic valve 3 is connected with an oil inlet of a proportional overflow logic valve 6 and an oil inlet of a proportional overflow valve 9 in parallel; an oil port of the II side stretching cylinder 11 is connected with an oil inlet of the second logic valve 2, and an oil outlet of the second logic valve 2 is connected with an oil inlet of the proportional overflow logic valve 6 and an oil inlet of the proportional overflow valve 9 in parallel; an oil port of a stretching cavity of the II-side operating cylinder 13 is connected with an oil inlet of the fourth logic valve 4, and an oil outlet of the fourth logic valve 4 is connected with an oil inlet of the proportional overflow logic valve 6 and an oil inlet of the proportional overflow valve 9 in parallel; the oil outlet of the first logic valve 1 is connected with the oil outlet of the second logic valve 2, the oil outlet of the third logic valve 3 and the oil outlet of the fourth logic valve 4 in parallel; an oil outlet of the proportional overflow logic valve 6 is connected with a main oil return port, an oil inlet of the proportional overflow valve 9 is connected with an oil inlet and a control oil port of the proportional overflow logic valve 6 in parallel, and an oil outlet of the proportional overflow valve 9 is connected with a main oil drain pipe.

When the two-side stretching cylinder and the operation cylinder (the I-side stretching cylinder 10, the II-side stretching cylinder 11, the I-side operation cylinder 12 and the II-side operation cylinder 13) work, the main oil circuit only needs one proportional overflow valve 9 to realize synchronous loading and accurately set two-side stretching force, and stable unloading is realized after stretching is finished, and a hydraulic system of the sheet material stretcher consisting of the proportional overflow valve 9 and the proportional overflow logic valve 6 has the advantages of small impact and accurate control; compared with the traditional proportional unloading loop formed by a plurality of proportional overflow valves, the hydraulic system of the plate stretcher formed by the single proportional overflow valve has the advantages of simple structure, high efficiency, energy conservation, reliable performance, low failure rate and low cost, and solves the problems of high cost, low efficiency and inconsistent pressures at two sides when the load working pressure and the unloading pressure are synchronously set under different stretching working conditions in the current domestic large plate stretcher system.

Example 2:

on the basis of the embodiment 1, the system further comprises an overflow valve 8, wherein an oil inlet of the overflow valve 8 is connected with an oil inlet and a control oil port of the proportional overflow logic valve 6 in parallel, and an oil outlet of the overflow valve 8 is connected with a main oil drain pipe. When overpressure occurs to the pipeline, the overflow valve 8 performs overflow protection on the pipeline, and stability and safety of the hydraulic system are improved.

Further, the oil inlet of the unloading logic valve 5 is connected with the oil outlet of the first logic valve 1, the oil outlet of the second logic valve 2, the oil outlet of the third logic valve 3 and the oil outlet of the fourth logic valve 4 in parallel, and the oil outlet of the unloading logic valve 5 is connected with the main oil return port. When the proportional overflow valve 9 fails or the pressures of the main stretching cylinders and the operating cylinders (the I side stretching cylinder 10, the II side stretching cylinder 11, the I side operating cylinder 12 and the II side operating cylinder 13) on two sides are unloaded to a low-pressure working condition, the quick and stable unloading of the main stretching cylinders and the operating cylinders on two sides can be realized through the unloading logic valve 5.

Furthermore, the unloading logic valve further comprises a reversing valve 7, an oil inlet of the reversing valve 7 is connected with an oil inlet of the unloading logic valve 5, an oil outlet of the reversing valve 7 is connected with a control oil port of the unloading logic valve 5, and an oil return port of the reversing valve 7 is connected with a main oil drain pipe. When the proportional overflow valve 9 fails and the main stretching cylinders on the two sides are overhauled, the reversing valve 7 controls the unloading logic valve 5 to realize quick unloading to zero pressure, and safe return and overhaul of the main stretching cylinders on the two sides are realized.

Further, the reversing valve 7 is an electromagnetic reversing valve. The electromagnetic directional valve has accurate action, high automation degree and stable and reliable work.

Further, displacement sensors are connected to the I-side stretching cylinder 10, the II-side stretching cylinder 11, the I-side operating cylinder 12, and the II-side operating cylinder 13. The displacement sensor can perform accurate positioning when the stretching cylinder and the operation cylinder are stretched, so that the setting signal of the proportional overflow valve 9 is more accurate, and the automation and the accuracy are high.

Further, an oil outlet of the first logic valve 1 is connected with a control oil port of the first logic valve 1, an oil outlet of the second logic valve 2 is connected with a control oil port of the second logic valve 2, an oil outlet of the third logic valve 3 is connected with a control oil port of the third logic valve 3, and an oil outlet of the fourth logic valve 4 is connected with a control oil port of the fourth logic valve 4. The connection mode ensures that under the stretching working condition of the stretching cylinder 10 at the I side and the stretching cylinder 11 at the II side, the synchronous unloading of the stretching cylinder 10 at the I side and the synchronous unloading of the stretching cylinder 11 at the II side are accurately realized after the stretching of the I side is finished; under the stretching working condition of the I side operating cylinder 12 and the II side operating cylinder 13, the synchronous unloading of the I side operating cylinder 12 and the II side operating cylinder 13 is accurately realized after the stretching is finished; under the combined stretching working condition, synchronous unloading of the stretching cylinder 10 at the I side, the stretching cylinder 11 at the II side, the operating cylinder 12 at the I side and the operating cylinder 13 at the II side is accurately realized after stretching is finished.

Further, the first logic valve 1, the second logic valve 2, the third logic valve 3 and the fourth logic valve 4 are all one-way cartridge logic valves. Ensures that the oil in the pipe flows along the designated direction, prevents the oil from flowing back, and improves the working efficiency and the use safety. For the stretching cylinders and the operation cylinders for driving stretching machines with different specifications, only a logic valve matched with the flow is required to be replaced, stable unloading can be realized for plates with different specifications and different working conditions through a proportional overflow valve, and the control system has strong adaptability.

Example 3:

on the basis of embodiment 2, a method for controlling a hydraulic system of a plate stretching machine comprises the following steps:

under the stretching working condition of the I side stretching cylinder 10 and the II side stretching cylinder 11, setting a given signal of the proportional overflow valve 9 according to plates of different specifications and different alloys, and enabling the I side stretching cylinder 10 and the II side stretching cylinder 11 to be symmetrically loaded by using the first logic valve 1 and the second logic valve 2 in a matched mode; after the stretching is finished, the stretching cylinder 10 at the I side and the stretching cylinder 11 at the II side are unloaded synchronously;

under the stretching working condition of the I side operating cylinder 12 and the II side operating cylinder 13, setting a given signal of the proportional overflow valve 9 according to plates of different specifications and different alloys, and enabling the I side operating cylinder 12 and the II side operating cylinder 13 to be symmetrically loaded by using the third logic valve 3 and the fourth logic valve 4 in a matched manner; after the stretching is finished, the I side operating cylinder 12 and the II side operating cylinder 13 are unloaded synchronously;

under the combined stretching working condition, setting a given signal of the proportional overflow valve 9 according to plates of different specifications and different alloys, and enabling the first logic valve 1, the second logic valve 2, the third logic valve 3 and the fourth logic valve 4 to be matched for use so as to simultaneously stretch the I-side stretching cylinder 10, the II-side stretching cylinder 11, the I-side operating cylinder 12 and the II-side operating cylinder 13; after the stretching is finished, the I side stretching cylinder 10, the II side stretching cylinder 11, the I side operating cylinder 12 and the II side operating cylinder 13 are unloaded synchronously.

Furthermore, when the I side stretching cylinder 10 main oil circuit and the II side stretching cylinder 11 main oil circuit which are provided with displacement sensors work in the stretching cylinders at two sides (the I side stretching cylinder 10 and the II side stretching cylinder 11), primary synchronization is realized through a servo variable pump, and high-precision synchronous stretching of the stretching cylinders is realized through an oil supplementing high-frequency response servo valve; working pressure of a proportional overflow valve 9 is set through a computer (the computer is the prior control technology, the control technology of calculation is not described in detail, and setting given signals for the proportional flow valve 9 can be set through the computer), unbalance loading overpressure of any one side of a stretching cylinder is unloaded through the proportional overflow valve 9, pressure drop of a high-frequency response servo valve inlet and outlet valve of the stretching cylinders at two sides is guaranteed to be stable, and accurate oil supplement is realized; when the displacement sensors of the stretching cylinders on the two sides detect the position difference of the stretching cylinders on the two sides, a valve control compensation control loop (the valve control compensation control loop is the prior art, and the detailed description of the specific loop is not provided herein) automatically selects a high-frequency response servo valve corresponding to the stretching cylinder on the one side with less output displacement to carry out oil supplementing control, controls the positions of the stretching cylinders on the two sides within a set value, and realizes the accurate synchronization of the stretching cylinders on the two sides; when the high-frequency-response servo valve of the stretching cylinder on one side replenishes oil, the high-frequency-response servo valve of the stretching cylinder on the other side stops working; after the stretching is finished, a slope curve of a proportional overflow valve 9 is given through a computer, the stretching cylinders on two sides are synchronously and stably unloaded through logic circuits, the logic circuits are a first logic valve 1, a second logic valve 2, a third logic valve 3 and a fourth logic valve 4, the logic valve with any side pressure higher than the proportional set pressure is opened, and the outlets of the other three logic valves control a high-pressure oil pressure dead cover plate, so that the stable and synchronous unloading of the stretching cylinders on two sides and the operating cylinder is realized.

Example 4:

on the basis of embodiment 3, in a hydraulic system of a plate stretching machine, an oil port a1 of an I-side stretching cylinder 10 is connected with an oil inlet a of a first logic valve 1, and an oil outlet B of the first logic valve 1 is connected in parallel with an oil inlet a of an unloading logic valve 5, an oil inlet a of a proportional overflow logic valve 6, an oil inlet of an overflow valve 8 and an oil inlet of a proportional overflow valve 9; a stretching cavity oil port B1 of the I-side operating cylinder 12 is connected with an oil inlet A of a third logic valve 3, and an oil outlet B of the third logic valve 3 is connected with an oil inlet A of an unloading logic valve 5, an oil inlet A of a proportional overflow logic valve 6, an oil inlet of an overflow valve 8 and an oil inlet of a proportional overflow valve 9 in parallel; an oil port A2 of the II side stretching cylinder 11 is connected with an oil inlet A of the second logic valve 2, and an oil outlet B of the second logic valve 2 is connected with an oil inlet A of the unloading logic valve 5, an oil inlet A of the proportional overflow logic valve 6, an oil inlet of the overflow valve 8 and an oil inlet of the proportional overflow valve 9 in parallel; a stretching cavity oil port B2 of the II side operating cylinder 13 is connected with an oil inlet A of a fourth logic valve 4, and an oil outlet B of the fourth logic valve 4 is connected with an oil inlet A of an unloading logic valve 5, an oil inlet A of a proportional overflow logic valve 6, an oil inlet of an overflow valve 8 and an oil inlet of a proportional overflow valve 9 in parallel; an oil outlet B of the first logic valve 1 is connected with an oil outlet B of the third logic valve 3 and an oil outlet B of the fourth logic valve 4 in parallel, and an oil outlet B of the second logic valve 2 is connected with an oil outlet B of the third logic valve 3 and an oil outlet B of the fourth logic valve 4 in parallel; an oil outlet B of the first logic valve 1 is connected with a control oil port of the first logic valve 1, an oil outlet B of the second logic valve 2 is connected with a control oil port of the second logic valve 2, an oil outlet B of the third logic valve 3 is connected with a control oil port of the third logic valve 3, and an oil outlet B of the fourth logic valve 4 is connected with a control oil port of the fourth logic valve 4; an oil outlet B of the proportional overflow logic valve 6 and an oil outlet B of the unloading logic valve 5 are connected with a main oil return port T0 in parallel, an oil inlet of the proportional overflow valve 9 and an oil inlet of the overflow valve 8 are connected with a control oil port of the proportional overflow logic valve 6 in parallel, an oil inlet P of the reversing valve 7 is connected with an oil inlet A of the unloading logic valve 5, an oil outlet A of the reversing valve 7 is connected with a control oil port of the unloading logic valve 5, and an oil return port T of the reversing valve 7, an oil outlet of the overflow valve 8 and an oil outlet of the proportional overflow valve 9 are connected with a main oil drain.

When the stretching or unloading work of the stretching cylinder 10 at the I side, the stretching cylinder 11 at the II side, the operating cylinder 12 at the I side and the operating cylinder 13 at the II side starts, the synchronous loading and unloading of the stretching cylinder 10 at the I side and the stretching cylinder 11 at the II side can be realized by different signals of the overflow valve 9 with a given proportion through the main oil circuit, the synchronous loading and unloading of the operating cylinder 12 at the I side and the operating cylinder 13 at the II side can be realized, when the combined stretching working condition is realized, the symmetrical synchronous loading and unloading of the stretching cylinder and the operating cylinder at two sides can be realized by different signals of the overflow valve 9 with a given proportion through the main oil circuit, the quick constant pressure overflow protection is realized when the overpressure occurs in the stretching cylinder and the operating cylinder at two sides, and the; the return chamber C1 of the I-side operating cylinder 12 ensures the return stroke of the I-side stretching cylinder 10, and the return chamber C2 of the II-side operating cylinder 13 ensures the return stroke of the II-side stretching cylinder 11.

Example 5:

the plate stretching machine comprises the hydraulic system of the plate stretching machine in the scheme.

In the description of the present invention, it should be understood that if there is an orientation or positional relationship indicated by the terms "oil inlet", "oil outlet", etc., it is based on the orientation or positional relationship shown in the drawings, and it is not intended to indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore the terms describing the positional relationship in the drawings are for illustrative purposes only and are not to be construed as limiting the present patent.

The above examples are merely illustrative of the present invention and should not be construed as limiting the scope of the invention, which is intended to be covered by the claims and any design similar or equivalent to the scope of the invention.