阅读说明：本技术 一种双向制动液压机及其工作方法 (Bidirectional braking hydraulic machine and working method thereof ) 是由 张昌松 杨官琳 王楚 王世元 魏立柱 王如鹏 高晓阳 陈飞昌 于 2021-07-29 设计创作，主要内容包括：本发明公开了一种双向制动液压机及其工作方法,包括油箱出油口连接油泵输入端；液动换向阀和第一电磁换向阀均为三位四通阀,第一电磁换向阀中位时其第一和第二油口连接液动换向阀,第三油口连接油箱,第四油口连接油泵输出端；液动换向阀中位时其第一油口连接油箱,第二油口连接溢流阀进油口,第三油口连接油泵输出端第四油口连接两个液压缸的无杆腔,第五油口分为两路,一路依次连接节流阀与两个液压缸的有杆腔,节流阀并联有第二电磁换向阀,另一路连接有溢流阀；溢流阀出油口分别连接有第三电磁换向阀进油口和油箱,第三电磁换向阀出油口连接油箱。实现了双向的压制成型,提高成型件质量与生产效率,极大的降低生产成本。(The invention discloses a bidirectional braking hydraulic machine and a working method thereof, wherein an oil outlet of an oil tank is connected with an input end of an oil pump; the hydraulic reversing valve and the first electromagnetic reversing valve are both three-position four-way valves, a first oil port and a second oil port of the first electromagnetic reversing valve are connected with the hydraulic reversing valve when the first electromagnetic reversing valve is in a middle position, a third oil port is connected with an oil tank, and a fourth oil port is connected with the output end of an oil pump; when the hydraulic reversing valve is in the middle position, a first oil port is connected with an oil tank, a second oil port is connected with an oil inlet of an overflow valve, a third oil port is connected with an output end of an oil pump, a fourth oil port is connected with rodless cavities of two hydraulic cylinders, a fifth oil port is divided into two paths, one path of the fifth oil port is sequentially connected with a throttle valve and rod cavities of the two hydraulic cylinders, the throttle valve is connected with a second electromagnetic reversing valve in parallel, and the other path of the throttle valve is connected with the overflow valve; the oil outlet of the overflow valve is respectively connected with an oil inlet of a third electromagnetic directional valve and an oil tank, and the oil outlet of the third electromagnetic directional valve is connected with the oil tank. The two-way press forming is realized, the quality and the production efficiency of the formed part are improved, and the production cost is greatly reduced.)

1. A bidirectional braking hydraulic machine is characterized by comprising an oil tank (1), an oil pump (3), a hydraulic reversing valve (5), a first electromagnetic reversing valve (6), an overflow valve (21), a first hydraulic cylinder (9) and a second hydraulic cylinder (14);

the oil outlet of the oil tank (1) is connected with the input end of the oil pump (3); the hydraulic reversing valve (5) and the first electromagnetic reversing valve (6) are both three-position four-way valves, a first oil port and a second oil port of the first electromagnetic reversing valve (6) are connected with the hydraulic reversing valve (5) when the first electromagnetic reversing valve (6) is in a middle position, a third oil port is connected with an oil inlet of the oil tank (1), and a fourth oil port is connected with an output end of the oil pump (3); when the hydraulic reversing valve (5) is in a middle position, a first oil port is connected with an oil inlet of an oil tank (1), a second oil port is connected with an oil inlet of an overflow valve (21), a third oil port is connected with a fourth oil port at the output end of an oil pump (3) and is connected with rodless cavities of a first hydraulic cylinder (9) and a second hydraulic cylinder (14), a fifth oil port is divided into two paths, one path is sequentially connected with a throttle valve (17) and rod cavities of the first hydraulic cylinder (9) and the second hydraulic cylinder (14), the throttle valve (17) is connected with a second electromagnetic reversing valve (18) in parallel, and the other path is connected with the overflow valve (21); an oil outlet of the overflow valve (21) is respectively connected with an oil inlet of a third electromagnetic directional valve (22) and an oil inlet of the oil tank (1), and an oil outlet of the third electromagnetic directional valve (22) is connected with an oil inlet of the oil tank (1).

2. The two-way hydraulic brake machine according to claim 1, wherein an accumulator (15) is connected between the fourth port of the hydraulically operated directional control valve (5) and the rodless chambers of the first hydraulic cylinder (9) and the second hydraulic cylinder (14).

3. A two-way brake hydraulic machine according to claim 1, characterised in that the rodless chambers of the first (9) and second (14) hydraulic cylinders are connected with electrical contact forcers (23).

4. The two-way brake hydraulic machine according to claim 1, characterized in that a pressure relay (16) is arranged between the fourth oil port of the hydraulic reversing valve (5) and the rodless cavities of the first hydraulic cylinder (9) and the second hydraulic cylinder (14), and the output end of the pressure relay (16) is electrically connected with the third electromagnetic reversing valve (22).

5. A two-way brake hydraulic machine according to claim 4, characterised in that the pressure relay (16) output is connected to a time relay input, the time relay output being electrically connected to the first electromagnetic directional valve (6).

6. The hydraulic two-way brake machine according to claim 1, characterized in that the first hydraulic cylinder (9) and the second hydraulic cylinder (14) are provided with displacement sensors (10), and the output ends of the displacement sensors (10) are electrically connected with the first electromagnetic directional valve (6) and the second electromagnetic directional valve (18).

7. A two-way brake hydraulic machine according to claim 1, characterised in that the oil pump (3) is a pressure-limited variable vane pump.

8. A working method of a hydraulic machine according to any one of claims 1 to 7, characterized by comprising the following steps:

and (3) idle stroke pressing stage: the left side of the first electromagnetic directional valve (6) is electrified, the valve core moves to the right, and the left position enters a working state; hydraulic oil pumped by the oil pump (3) reaches the hydraulic reversing valve (5) through the first electromagnetic reversing valve (6), so that a valve core of the hydraulic reversing valve (5) moves to the right, and the left position enters a working position; then hydraulic oil pumped out by the oil pump (3) flows into rodless cavities of the first hydraulic cylinder (9) and the second hydraulic cylinder (14) through the hydraulic reversing valve (5) and the first electromagnetic reversing valve (6), and the first hydraulic cylinder (9) and the second hydraulic cylinder (14) perform clamping action; hydraulic oil in rod cavities of the first hydraulic cylinder (9) and the second hydraulic cylinder (14) passes through the hydraulic reversing valve (5), and the hydraulic oil is converged with oil pumped out by the oil pump (3) and flows into rodless cavities of the first hydraulic cylinder (9) and the second hydraulic cylinder (14) together;

a pressing stage: after the first hydraulic cylinder (9) and the second hydraulic cylinder (14) contact a workpiece, the left side of the second electromagnetic directional valve (18) is electrified, the valve core moves to the right, the left position enters a working state, hydraulic oil pumped out by the oil pump (3) flows into rodless cavities of the first hydraulic cylinder (9) and the second hydraulic cylinder (14) through the hydraulic directional valve (5) and the throttle valve (17), the first hydraulic cylinder (9) and the second hydraulic cylinder (14) are slowly pushed, and the hydraulic oil in the rod cavity returns to the oil tank (1) through the hydraulic directional valve (5) and the overflow valve (21);

and (3) pressure maintaining stage: the hydraulic cylinder is continuously pressurized, the work is further increased, the left side of the third electromagnetic directional valve (22) is electrified, the valve core moves to the right, the left position enters a working position, and hydraulic oil pumped out by the oil pump (3) returns to the oil tank (1) through the overflow valve (21) and the third electromagnetic directional valve (22);

and (3) fast backing stage: the left side of the first electromagnetic directional valve (6) is powered off, the right side is powered on, the valve core moves leftwards, the right position enters a working state, hydraulic oil pumped out by the oil pump (3) reaches the hydraulic directional valve (5) through the first electromagnetic directional valve (6), the valve core of the hydraulic directional valve (5) moves leftwards, and the right position enters the working position. Hydraulic oil pumped by the oil pump (3) flows into rod cavities of the first hydraulic cylinder (9) and the second hydraulic cylinder (14) through the hydraulic reversing valve (5), the first hydraulic cylinder (9) and the second hydraulic cylinder (14) do separation movement, and the hydraulic oil without the rod cavities flows back to the oil tank (1) through the hydraulic reversing valve (5);

a motion stopping stage: the first hydraulic cylinder (9) and the second hydraulic cylinder (14) return to original positions, the right side of the first electromagnetic directional valve (6) is powered off, and the valve core returns to a normal position, namely a neutral position; the hydraulic oil can not pass through the first electromagnetic directional valve (6), so that the hydraulic directional valve (5) returns to a normal position, namely a neutral position; the oil pump (3) is unloaded through the middle position of the hydraulic reversing valve (5) to complete a working cycle.

9. Method according to claim 8, characterized in that during the depression phase, when the hydraulic oil pressure reaches the set value of the pressure relay (16), a pressure holding phase is performed, the accumulator (15) being opened for pressure holding.

10. A method for operating a two-way brake hydraulic machine, according to claim 9, characterized in that the pressure relay (16) sends a signal to the time relay when the hydraulic oil pressure reaches the set value of the pressure relay (16), and after a time delay set by the time relay, the signal is sent to the first electromagnetic directional valve (6) for the fast-reversing phase.

Technical Field

The invention belongs to the field of hydraulic machines, and relates to a bidirectional braking hydraulic machine and a working method thereof.

Background

Powder press forming processes associated with hydraulic presses, with metal powders, ceramic powders, and cermet batch powders being the most common. The powder pressing forming process is one dry pressing forming process, which includes setting powder material into mold and pressing with hydraulic press to form. The most key of the powder compression molding process is a hydraulic machine, an aging one-way hydraulic machine is mostly adopted at present, and the traditional hydraulic machine is used for unidirectionally compressing and molding powder through a single hydraulic cylinder; the unidirectional pressing scheme can lead to uneven density of the formed part certainly, the formed part close to the pressing movable rod has high density, the formed part far away from the pressing movable rod has low density, and the formed part is obvious in layering.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provides a bidirectional braking hydraulic machine and a working method thereof, so that bidirectional compression molding is realized, the quality and the production efficiency of a molded part are improved, and the production cost is greatly reduced.

In order to achieve the purpose, the invention adopts the following technical scheme to realize the purpose:

a bidirectional braking hydraulic machine comprises an oil tank, an oil pump, a hydraulic reversing valve, a first electromagnetic reversing valve, an overflow valve, a first hydraulic cylinder and a second hydraulic cylinder;

the oil outlet of the oil tank is connected with the input end of the oil pump; the hydraulic reversing valve and the first electromagnetic reversing valve are both three-position four-way valves, a first oil port and a second oil port of the first electromagnetic reversing valve are connected with the hydraulic reversing valve when the first electromagnetic reversing valve is in a middle position, a third oil port is connected with an oil inlet of an oil tank, and a fourth oil port is connected with an output end of an oil pump; when the hydraulic reversing valve is in the middle position, a first oil port of the hydraulic reversing valve is connected with an oil inlet of an oil tank, a second oil port of the hydraulic reversing valve is connected with an oil inlet of an overflow valve, a third oil port of the hydraulic reversing valve is connected with an output end of an oil pump, a fourth oil port of the hydraulic reversing valve is connected with rodless cavities of a first hydraulic cylinder and a second hydraulic cylinder, a fifth oil port is divided into two paths, one path of the fifth oil port is sequentially connected with a throttle valve and rod cavities of the first hydraulic cylinder and the second hydraulic cylinder, the throttle valve is connected with a second electromagnetic reversing valve in parallel, and the other path of the throttle valve is connected with the overflow valve; the oil outlet of the overflow valve is respectively connected with an oil inlet of a third electromagnetic directional valve and an oil inlet of an oil tank, and the oil outlet of the third electromagnetic directional valve is connected with the oil inlet of the oil tank.

Preferably, an energy accumulator is connected between the fourth oil port of the hydraulic reversing valve and the rodless cavities of the first hydraulic cylinder and the second hydraulic cylinder.

Preferably, the rodless cavities of the first hydraulic cylinder and the second hydraulic cylinder are connected with electric contact type pressure devices.

Preferably, a pressure relay is arranged between the fourth oil port of the hydraulic reversing valve and the rodless cavity of the first hydraulic cylinder and the rodless cavity of the second hydraulic cylinder, and the output end of the pressure relay is electrically connected with the third electromagnetic reversing valve.

Furthermore, the output end of the pressure relay is connected with the input end of a time relay, and the output end of the time relay is electrically connected with the first electromagnetic directional valve.

Preferably, displacement sensors are arranged on the first hydraulic cylinder and the second hydraulic cylinder, and the output ends of the displacement sensors are electrically connected with the first electromagnetic directional valve and the second electromagnetic directional valve.

Preferably, the oil pump is a pressure-limiting variable vane pump.

A working method of the hydraulic machine comprises the following processes:

and (3) idle stroke pressing stage: the left side of the first electromagnetic directional valve is electrified, the valve core moves to the right, and the left position enters a working state; hydraulic oil pumped out by the oil pump reaches the hydraulic reversing valve through the first electromagnetic reversing valve, so that a valve core of the hydraulic reversing valve moves to the right, and the left enters a working position; then hydraulic oil pumped out by the oil pump flows into the rodless cavities of the first hydraulic cylinder and the second hydraulic cylinder through the hydraulic reversing valve and the first electromagnetic reversing valve, and the first hydraulic cylinder and the second hydraulic cylinder perform clamping action; hydraulic oil in the rod cavities of the first hydraulic cylinder and the second hydraulic cylinder passes through the hydraulic reversing valve, and the hydraulic oil and oil pumped out by the oil pump are converged and flow into the rodless cavities of the first hydraulic cylinder and the second hydraulic cylinder together;

a pressing stage: after the first hydraulic cylinder and the second hydraulic cylinder contact a workpiece, the left side of the second electromagnetic directional valve is electrified, the valve core moves rightwards, the left position enters a working state, hydraulic oil pumped out by the oil pump flows into rodless cavities of the first hydraulic cylinder and the second hydraulic cylinder through the hydraulic directional valve and the throttle valve, the first hydraulic cylinder and the second hydraulic cylinder are slowly pushed, and the hydraulic oil in the rod cavity returns to an oil tank through the hydraulic directional valve and the overflow valve;

and (3) pressure maintaining stage: the hydraulic cylinder is continuously pressurized, the work is further increased, the left side of the third electromagnetic directional valve is electrified, the valve core moves to the right, the left position enters a work position, and hydraulic oil pumped out by the oil pump returns to the oil tank through the overflow valve and the third electromagnetic directional valve;

and (3) fast backing stage: the left side of the first electromagnetic reversing valve is powered off, the right side of the first electromagnetic reversing valve is powered on, the valve core moves leftwards, the right position of the first electromagnetic reversing valve enters a working state, hydraulic oil pumped out by the oil pump reaches the hydraulic reversing valve through the first electromagnetic reversing valve, the valve core of the hydraulic reversing valve moves leftwards, and the right position of the hydraulic reversing valve enters the working position. Hydraulic oil pumped out by the oil pump flows into rod cavities of the first hydraulic cylinder and the second hydraulic cylinder through the hydraulic reversing valve, the first hydraulic cylinder and the second hydraulic cylinder do separation movement, and the hydraulic oil without the rod cavities flows back to the oil tank through the hydraulic reversing valve;

a motion stopping stage: the first hydraulic cylinder and the second hydraulic cylinder return to original positions, the right side of the first electromagnetic directional valve is powered off, and the valve core returns to a normal position, namely a neutral position; the hydraulic oil can not pass through the first electromagnetic directional valve, so that the hydraulic directional valve returns to a normal position, namely a neutral position; the oil pump is unloaded through the middle position of the hydraulic reversing valve to complete a working cycle.

Preferably, during the pressing-down stage, when the hydraulic oil pressure reaches the set value of the pressure relay, the pressure maintaining stage is performed, and the energy accumulator is opened to maintain the pressure.

Further, when the hydraulic oil pressure reaches the set value of the pressure relay, the pressure relay sends a signal to the time relay, and when the signal is delayed by the set time of the time relay, the signal is sent to the first electromagnetic directional valve to carry out the quick-backing stage.

Compared with the prior art, the invention has the following beneficial effects:

the hydraulic cylinder with bidirectional braking is an electro-hydraulic reversing valve which is formed by adding a hydraulic cylinder with the same cylinder diameter and the same stroke and adopting a first electromagnetic reversing valve and a hydraulic reversing valve under the condition that only one hydraulic cylinder is used originally, so that bidirectional compression molding is realized, and the working efficiency and the working precision of the whole hydraulic press system are improved. The two-way press forming ensures the uniformity of the density of the formed part and meets the requirement of the movement of press forming after the double cylinders are quickly close to the formed part.

Furthermore, the energy accumulator can supplement pressure to the hydraulic cylinder, the energy accumulator can improve the pressure value of the hydraulic machine in a pressure maintaining state, and the powder compression molding effect is improved.

Furthermore, the electric contact type pressure gauge can detect the pressure of the hydraulic cylinder, and the safety factor is improved.

Furthermore, after 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 directional valve to enable the third electromagnetic directional valve to change the position of the third electromagnetic directional valve, pressure maintaining is conducted, and automatic switching from a pressing-down stage to a pressure maintaining stage is achieved.

Furthermore, the pressure relay can send a signal to the time relay, and after the preset pressing time is reached, the time relay can send an electric signal to control the first electromagnetic directional valve to change the position for fast moving, so that the automatic switching from the pressure maintaining stage to the fast moving stage is realized.

Further, after the hydraulic cylinder contacts the workpiece, the pressure of the hydraulic cylinder is increased, the movement of the movable rod is reduced, or the pressing is finished, and the movable rod returns to the original position, the displacement sensor can control the first electromagnetic directional valve or the second electromagnetic directional valve to change the position, so that the switching of the working stage is realized.

Drawings

FIG. 1 is a schematic diagram of a two-way brake hydraulic machine of the present invention.

Wherein: 1-an oil tank; 2-an oil filter; 3-an oil pump; 4-a first one-way valve; 5-a hydraulically operated directional control valve; 6-a first electromagnetic directional valve; 7-a first one-way throttle valve; 8-a second one-way throttle valve; 9 a first hydraulic cylinder; 10-a first displacement sensor; 11-right chopping block; 12-left chopping block; 13-a second displacement sensor; 14-a second hydraulic cylinder; 15-an accumulator; 16-a pressure relay; 17-a throttle valve; 18-a second electromagnetic directional valve; 19-a second one-way valve; 20-a third one-way valve; 21-relief valve; 22-a third electromagnetic directional valve; 23-electrical contact type forcer.

Detailed Description

The invention is described in further detail below with reference to the accompanying drawings:

as shown in FIG. 1, the bidirectional braking hydraulic machine comprises a power element, an execution element, a control element, an auxiliary element and a working medium. Wherein the power element is an oil pump 3; the execution elements are 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 comprises a one-way valve and a reversing valve, the pressure control element comprises a pressure relay 16, an energy accumulator 15 and an overflow valve 21, and the flow control element comprises a throttle valve and a one-way throttle valve; the auxiliary elements comprise an oil filter 2, an oil tank 1, a first displacement sensor 10, a second first displacement sensor 13, a hydraulic line and an electric contact type pressure device 23; the working medium is hydraulic oil.

The oil tank 1 is an auxiliary element, is a container for storing hydraulic oil of the whole hydraulic press system, comprises an oil inlet and an oil outlet, is filled with the hydraulic oil, the oil inlet of the oil tank 1 is connected with a hydraulic reversing valve, a first electromagnetic reversing valve, an overflow valve 21 and a third electromagnetic reversing valve 22, and the oil outlet is externally connected with an oil filter 2.

The oil filter 2 is an auxiliary element of the hydraulic oil filtering device, is filtering equipment for filtering hydraulic oil and provides a hydraulic machine with the function of filtering the hydraulic oil, and an oil inlet of the oil filter 2 is connected with the oil tank 1, and an oil outlet of the oil filter 2 is connected with the oil pump 3.

The oil pump 3 is a power element, and the oil pump 3 of the embodiment adopts a pressure-limiting variable vane pump which is an energy conversion device and converts mechanical energy of a driving motor into pressure energy of hydraulic oil so as to meet the requirement of the hydraulic machine for driving an external load. The oil inlet of the pressure-limiting variable vane pump is connected with an oil filter 2, hydraulic oil of an oil tank 1 filtered by the oil filter 2 is sucked in during operation, the hydraulic oil is pressurized and output through mechanical energy, and the oil outlet is connected with a first one-way valve 4 and a first electromagnetic reversing valve 6.

The one-way valve is a direction control element of the invention, fluid can only flow along the water inlet, but the medium at the water outlet can not flow back, and the one-way valve is a valve body which can prevent hydraulic oil from flowing back into the pressure-limiting variable vane pump in a static state.

The first electromagnetic directional valve 6 is a direction control element, the first electromagnetic directional valve 6 is a three-position four-way valve, the valve has three working position states and four oil ports, and different working states can be replaced to meet different hydraulic loop requirements after receiving an electric signal, so that the output of the hydraulic cylinder is influenced. In the middle position of the three-position four-way electromagnetic directional valve, a first oil port and a second oil port are respectively connected with a first one-way throttle valve 7 and a second one-way throttle valve 8 and then communicated with the hydraulic directional valve 5, a third oil port is connected with an oil inlet of an oil tank 1, and a fourth oil port is connected with a pressure limiting variable vane pump.

The hydraulic change valve 5 is a direction control element, and the hydraulic change valve 5 is a three-position four-way valve which is a change valve operated by pilot fluid pressure. The hydraulic reversing valve 5 has three working position states and five oil ports, a first oil port is connected with the oil tank 1 when in a middle position, a second oil port is connected with a third check valve 20 of an oil inlet of the overflow valve 21 and a pipeline middle point of the overflow valve 21, the third oil port is connected with a first check valve 4 of an oil outlet of the pressure-limiting variable vane pump, a fourth oil port is connected with rod cavities of the first hydraulic cylinder 9 and the second hydraulic cylinder 14, and a fifth oil port is connected with a pipeline node of a third check valve 20, a throttle valve 17 and a second check valve 19 which are connected with an oil inlet of the overflow valve 21 and a pressure relay 16.

An oil outlet of the overflow valve 21 is respectively connected with an oil inlet of a third electromagnetic directional valve 22 and an oil inlet of the oil tank 1, and an oil outlet of the second two-way third electromagnetic directional valve 22 is connected with an oil inlet of the oil tank 1.

The hydraulic reversing valve 5 of the flow valve and the first electromagnetic reversing valve 6 jointly form an electro-hydraulic reversing valve of the hydraulic press system, and the requirements of hydraulic loops under different requirements are met.

The first hydraulic cylinder 9 and the second hydraulic cylinder 14 are executing elements of the invention, and can convert hydraulic energy into mechanical energy and perform linear reciprocating motion (or swinging motion), the first hydraulic cylinder 9 and the second hydraulic cylinder 14 are both internally provided with a movable rod, the movable rod divides an inner cavity of the hydraulic cylinder into a rod cavity and a rodless cavity, and one ends of the two movable rods extending out of the hydraulic cylinders are respectively a right chopping block 11 and a left chopping block 12. The rod cavities of the two hydraulic cylinders are connected with the hydraulic reversing valve 5, the oil passages connected with the rodless cavities are divided into three, the first path is communicated with the fifth oil port of the hydraulic reversing valve 5 after being sequentially communicated with the pressure relay 16 and the second one-way valve 19, the second path is communicated with the fifth oil port of the hydraulic reversing valve 5 after being sequentially communicated with the energy accumulator 15 and the throttle valve 17, the second electromagnetic reversing valve 18 with two positions and two ways is connected to the throttle valve 17 in parallel, and the third path is communicated with the electric contact type pressure gauge 23. And the first hydraulic cylinder 9 and the second hydraulic cylinder 14 are also connected with a first displacement sensor 10 and a second displacement sensor 13, respectively.

The hydraulic oil is the working medium of the invention and runs through the whole system.

The working stroke of the hydraulic machine can be divided into five stages: the method comprises an idle stroke pressing stage, a pressure maintaining stage, a fast withdrawing stage and a motion stopping stage.

And (4) a lost motion pressing stage. After the start button is pressed, the left side of the first electromagnetic directional valve 6 is electrified, the valve core moves to the right, and the left position enters a working state. The hydraulic oil pumped by the oil pump 3 passes through the oil filter 2 and the first electromagnetic directional valve 6 to reach the hydraulic directional valve 5, so that the valve core of the hydraulic directional valve 5 moves to the right, and the left position enters the working position. Then, the hydraulic oil pumped out by the oil pump 3 flows into the rodless cavities 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, the movable rod is pushed to perform clamping action, the left cutting board 11 moves to the right, and the right cutting board 12 moves to the left. The hydraulic oil in the rod cavity passes through the hydraulic reversing valve 5, and the external load is small, so that the working pressure of the pipeline is small, the overflow valve 21 cannot be opened, and the hydraulic oil can only pass through the third one-way valve 20 and is converged with the oil pumped out by the oil pump 3 to flow into the rodless cavity together. At the moment, the hydraulic cylinder is in a differential connection mode and is in a fast-forward idle stroke pressing state.

And (5) a pressing-down stage. After the left cutting board 11 and the right cutting board 12 contact the workpiece, the pressure of the hydraulic cylinder increases, the motion of the movable rod slows down, the displacement sensor 10 sends an electric signal to the second electromagnetic directional valve 18, the left side of the second electromagnetic directional valve 18 is electrified, the valve core moves to the right, the left position enters a working state, hydraulic oil pumped out by the oil pump 3 flows into rodless cavities 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 directional valve 5 and the throttle valve 17, and the movable rod is slowly pushed. The hydraulic oil in the rod cavity passes through the hydraulic reversing valve 5, and at this stage, the movable rod is required to be pushed by the hydraulic oil to pass through the throttle valve 17, so that the flow rate of the hydraulic oil is reduced, the oil pressure is increased, the oil pressure of the pipeline is equal to the set oil pressure of the overflow valve 21, the overflow valve 21 is opened, and the hydraulic oil flows back to the oil tank 1. The mode of rodless cavity oil inlet connection is adopted at the moment.

And (5) a pressure maintaining stage. The hydraulic cylinder is continuously pressurized, the system pressure is further increased, when the set value of the pressure relay 16 is reached, the pressure relay 16 sends an electric signal to the third electromagnetic directional valve 22 and the time relay, the left side of the third electromagnetic directional valve 22 is electrified, the valve core moves to the right, the left position enters a working position, and hydraulic oil pumped out by the oil pump 3 flows back to the oil tank through the oil filter 2, the first one-way valve 4, the overflow valve 21 and the third electromagnetic directional valve 22. The accumulator 15 maintains pressure by detecting the oil pressures of the first hydraulic cylinder 9 and the second hydraulic cylinder 14 by the electric contact type pressure gauge 23. At this time, the connecting mode of unloading and pressure maintaining is adopted.

And (5) a fast-backing stage. The pressure relay 16 sends an electric signal to the time relay, the electric signal is sent to the first electromagnetic directional valve 6 after the time relay delays, the left side of the first electromagnetic directional valve 6 is powered off, the right side of the first electromagnetic directional valve is powered on, the valve core moves to the left, the right position of the valve core enters a working state, hydraulic oil pumped out by the oil pump 3 passes through the oil filter 2, the first electromagnetic directional valve 6 reaches the hydraulic directional valve 5, and the valve core of the hydraulic directional valve 5 moves to the left and the right position of the valve core enters the working position. The hydraulic oil pumped by the oil pump 3 flows into the rod cavity through the oil filter 2 and the hydraulic reversing valve 5 to push the movable rods to do separation movement, and the hydraulic oil in the rodless cavity flows back to the oil tank 25 through the hydraulic reversing valve 5. At the moment, the rod cavity is in an oil inlet connection mode, the system pressure is low, the output flow of the variable pump is large, and the movable rod returns quickly.

And a motion stop stage. The movable rod returns to the original position, the displacement sensor 13 sends an electric signal, the right side of the first electromagnetic directional valve 6 is powered off, the valve core returns to the normal position, namely the middle position, the hydraulic oil cannot pass through the first electromagnetic directional valve 6, the hydraulic directional valve 5 is powered off and returns to the normal position, namely the middle position, and the oil pump 3 unloads through the middle position of the hydraulic directional valve 5 to complete a work cycle.

The hydraulic machine only needs to set threshold values in advance in the displacement sensor 10, the pressure relay 16 and the time relay when working, and the automatic working process of the hydraulic machine can be realized through pure hardware.

The above-mentioned contents are only for illustrating the technical idea of the present invention, and the protection scope of the present invention is not limited thereby, and any modification made on the basis of the technical idea of the present invention falls within the protection scope of the claims of the present invention.