CN110219843B - A pumpless hydraulic loading and positioning device - Google Patents

Abstract

The invention discloses a pumpless hydraulic loading and positioning device, which belongs to the field of hydraulic loading equipment. The device includes: a linear drive, a loading hydraulic cylinder, a pressure-bearing cylinder, a retraction mechanism and a processor; the output end of the linear drive is provided with a piston push rod; the loading hydraulic cylinder includes a cylinder block, a piston rod and a displacement sensor; the pressure-bearing cylinder has a storage Oil chamber, one end of the oil storage chamber is provided with a piston hole for the piston push rod of the linear drive to enter, and the other end is communicated with the high pressure chamber of the loading hydraulic cylinder through the first hydraulic pipeline; the retraction mechanism includes a gas-hydraulic pressure conversion cylinder and a gas pressure source , the hydraulic chamber of the gas-hydraulic pressure conversion cylinder is connected to the low-pressure chamber of the loading hydraulic cylinder through the second hydraulic pipeline; the air-pressure chamber of the gas-liquid pressure conversion cylinder is connected to the air pressure source; the processor is connected to the displacement sensor and the linear driver to carry out the displacement of the piston rod. Closed-loop control. The invention does not need a hydraulic pump station, reduces the energy loss of the loading system, avoids the noise of the hydraulic pump station, and can accurately position the piston rod.

Description

A pumpless hydraulic loading and positioning device

technical field

The invention belongs to the field of hydraulic loading equipment, and more particularly relates to a pumpless hydraulic loading and positioning device, which is especially suitable for the situation where high precision is required for the displacement of the piston of the loading hydraulic cylinder, which can work not only in the loading mode but also in the loading mode. in positioning mode.

Background technique

The hydraulic loading device can complete the load simulation and performance evaluation of the key bearing components of large equipment (such as ship main propulsion shafting and steering gear, etc.) under experimental conditions. It is of great significance for optimizing structural design, saving development time, reducing experimental cost and improving equipment reliability.

The traditional hydraulic loading device mainly uses the valve-controlled hydraulic cylinder as the actuator, and adjusts the opening of the servo valve to change the oil pressure inside the loading hydraulic cylinder, so as to obtain the desired loading force of the system. Due to the influence of the throttling loss of the hydraulic valve itself, the energy utilization rate of the loading device is very low, and the hydraulic oil is prone to overheating, which reduces the stability and control accuracy of the system. Moreover, most of them use the hydraulic pump station as the power source, and realize the retraction of the loading hydraulic cylinder piston by controlling the opening and closing of a large number of electro-hydraulic servo valves. The noise generated by the hydraulic pump station used in the method will hinder the work of the on-site operators, and at the same time, the hydraulic pump station occupies a large space, which affects the utilization efficiency of the equipment.

SUMMARY OF THE INVENTION

In view of the above defects or improvement needs of the prior art, the present invention provides a pumpless hydraulic loading and positioning device, the purpose of which is to use a linear drive as a pressure source to drive a loading cylinder to load, and use a pneumatic source as a pressure source. Drive the loading cylinder to retreat, so as to realize the driving and retraction of the loading cylinder piston without using the hydraulic pump station, effectively reduce the energy loss of the loading system, and avoid the noise generated by the operation of the hydraulic pump station; at the same time, through the displacement sensor, The processor and linear driver perform displacement closed-loop control to achieve precise positioning of the loading cylinder piston and improve control accuracy.

In order to achieve the above object, according to one aspect of the present invention, a pumpless hydraulic loading and positioning device is provided, comprising: a linear drive, a loading hydraulic cylinder, a pressure bearing cylinder, a first hydraulic pipeline, a second hydraulic pipeline, fallback mechanisms and processors;

The output end of the linear drive has a piston push rod;

The loading hydraulic cylinder includes a cylinder block, a piston rod and a displacement sensor. The piston rod divides the cylinder block into a high-pressure chamber and a low-pressure chamber; the displacement sensor is used to measure the position of the piston rod.

The pressure-bearing cylinder has an oil storage chamber, one end of the oil storage chamber is provided with a piston hole for the entry of the piston push rod of the linear drive, and the other end is communicated with the high-pressure chamber of the loading hydraulic cylinder through the first hydraulic pipeline;

The retraction mechanism includes a gas-liquid pressure conversion cylinder and an air pressure source; a gas-liquid pressure conversion piston is arranged inside the gas-liquid pressure conversion cylinder, and the gas-liquid pressure conversion piston separates the gas-liquid pressure conversion cylinder into a hydraulic chamber and an air pressure chamber; the gas-liquid pressure conversion piston The hydraulic chamber of the cylinder is connected to the low pressure chamber of the loading hydraulic cylinder through the second hydraulic pipeline; the air pressure chamber of the gas-hydraulic pressure conversion cylinder is connected to the air pressure source;

The processor connects the displacement sensor and the linear driver to perform closed-loop control on the displacement of the piston rod according to the displacement signal fed back by the displacement sensor.

Further, the cross-sectional area of the hydraulic chamber of the air-to-hydraulic pressure conversion cylinder is not greater than the cross-sectional area of the air pressure chamber.

Further, the cross-sectional area of the hydraulic chamber is smaller than the cross-sectional area of the air pressure chamber; the gas-liquid pressure conversion piston includes a hydraulic chamber plug body and an air pressure chamber plug body that are fixed to each other, the hydraulic chamber plug body is located in the hydraulic chamber, and the air pressure chamber plug body is located in the air pressure chamber. The cross-sectional shape and size of the plug body of the hydraulic chamber are the same as the cross-section of the hydraulic chamber, and the cross-sectional shape and size of the plug body of the air pressure chamber are the same as the cross-section of the air pressure chamber.

Further, it includes a plurality of loading hydraulic cylinders, a first hydraulic pipeline and a second hydraulic pipeline with an equal number and a one-to-one correspondence; each loading hydraulic cylinder is connected in parallel through its corresponding first hydraulic pipeline and second hydraulic pipeline Enter between the pressure-bearing cylinder and the gas-hydraulic pressure conversion cylinder.

Further, each first hydraulic pipeline is provided with a pressure gauge, a first cut-off valve and a pressure sensor; the processor is connected to the pressure sensor to perform closed-loop control on the pressure of the first hydraulic pipeline according to the pressure signal fed back by the pressure sensor .

Further, each first hydraulic pipeline merges into the first hydraulic manifold, and is connected to the oil storage chamber through the first hydraulic manifold; each second hydraulic pipeline merges into the second hydraulic manifold, and is connected to the hydraulic chamber through the second hydraulic manifold; The first hydraulic main pipe and the second hydraulic main pipe are respectively provided with pressure gauges, and the second hydraulic main pipe is also provided with a second stop valve.

Further, it is characterized in that it also includes an oil storage cylinder, and the oil storage cylinder is connected to the oil inlet of the pressure-bearing cylinder.

Further, the oil outlet of the pressure-bearing cylinder is provided with a relief valve.

Another object of the present invention is to use a linear actuator as a pressure source to drive the loading cylinder to load, and use a pneumatic source as a pressure source to drive the loading cylinder to retreat, so as to realize the driving of the loading cylinder piston without using a hydraulic pump station It can effectively reduce the energy loss of the loading system and avoid the noise generated by the operation of the hydraulic pump station.

In order to achieve the above object, according to another aspect of the present invention, a pumpless hydraulic loading device is provided, comprising: a linear drive, a loading hydraulic cylinder, a pressure bearing cylinder, a first hydraulic pipeline, a second hydraulic pipeline and a return withdrawal agency;

The output end of the linear drive has a piston push rod;

The loading hydraulic cylinder includes a cylinder body and a piston rod, and the piston rod divides the cylinder body into a high-pressure chamber and a low-pressure chamber;

The pressure-bearing cylinder has an oil storage chamber, one end of the oil storage chamber is provided with a piston hole for the entry of the piston push rod of the linear drive, and the other end is communicated with the high-pressure chamber of the loading hydraulic cylinder through the first hydraulic pipeline;

The retraction mechanism includes a gas-liquid pressure conversion cylinder and an air pressure source; a gas-liquid pressure conversion piston is arranged inside the gas-liquid pressure conversion cylinder, and the gas-liquid pressure conversion piston separates the gas-liquid pressure conversion cylinder into a hydraulic chamber and an air pressure chamber; the gas-liquid pressure conversion piston The hydraulic chamber of the cylinder is connected to the low pressure chamber of the loading hydraulic cylinder through the second hydraulic pipeline; the air pressure chamber of the gas-liquid pressure conversion cylinder is connected to the air pressure source.

Further, the cross-sectional area of the hydraulic chamber of the gas-liquid pressure conversion cylinder is not greater than the cross-sectional area of the air pressure chamber; wherein, when the cross-sectional area of the hydraulic chamber is smaller than the cross-sectional area of the air pressure chamber:

The gas-liquid pressure conversion piston includes a hydraulic cavity plug body and an air pressure cavity plug body that are fixed to each other, the hydraulic cavity plug body is located in the hydraulic cavity, and the air pressure cavity plug body is located in the air pressure cavity; The cross-section is the same, and the cross-sectional shape and size of the plug body of the air pressure chamber are the same as the cross-section of the air pressure chamber.

In general, compared with the prior art, the above technical solutions conceived by the present invention can achieve the following beneficial effects:

1) The linear driver and pressure-bearing cylinder are used as pressure amplifying elements to drive the movement of the loading hydraulic cylinder, and at the same time, the pressure source is used to drive the loading hydraulic cylinder to reset, which avoids the problem of noise easily generated by traditional valve-controlled electro-hydraulic loading devices such as hydraulic pump stations; The processor, displacement sensor and linear drive device form a displacement closed-loop feedback control module, which uses the data fed back by the displacement sensor to adjust the displacement of the piston push rod of the linear drive device in real time, so as to realize real-time adjustment and precise positioning of the displacement of the loading hydraulic cylinder piston. High reliability.

2) Since there is almost no throttling loss in the hydraulic circuit of the present invention, the loss in the energy transmission process mainly comes from mechanical transmission, which has higher energy efficiency compared with the traditional valve-controlled electro-hydraulic loading device;

3) The retraction mechanism of the present invention utilizes the compressibility of the gas, and can be freely compressed when the loading hydraulic cylinder performs the loading work without interfering with its normal operation; and when it needs to be reset, it can be directly pushed by the energy stored due to the gas compression. The reset of the loading hydraulic cylinder not only eliminates the need to use a hydraulic pump station, but also saves energy and improves the space utilization of the loading device;

4) The present invention can support the parallel connection of multiple loading hydraulic cylinders. By controlling the opening and closing of each first stop valve, different loading hydraulic cylinders can be connected to the oil circuit, and the parallel loading hydraulic cylinders can be controlled independently or in parallel. flexible;

5) The present invention can form a pressure closed-loop feedback control mechanism through a processor, a pressure sensor and a linear drive device, and use the data fed back by the pressure sensor to adjust the displacement of the piston push rod of the linear drive device in real time, thereby realizing real-time adjustment and precise control of the loading force. , with extremely high reliability.

Description of drawings

1 is a system schematic diagram of a pumpless hydraulic loading device according to a preferred embodiment of the present invention;

FIG. 2 is a schematic diagram of the connection between the linear driver and the pressure-bearing cylinder in FIG. 1;

Fig. 3 is the cross-sectional structural schematic diagram of the pressure-bearing cylinder in Fig. 1;

Fig. 4 is the sectional structure diagram of the loading hydraulic cylinder in Fig. 1;

Fig. 5 is the sectional structure diagram of the gas-hydraulic pressure conversion cylinder in Fig. 1;

6 is a schematic cross-sectional structural diagram of a gas-hydraulic pressure conversion cylinder according to a second embodiment of the present invention.

Throughout the drawings, the same reference numbers are used to refer to the same elements or structures, wherein:

1-Linear drive, 2-Oil accumulator, 3-Pressure cylinder, 4-Pressure gauge, 5-First stop valve, 6-Pressure sensor, 7-Displacement sensor, 8-Load hydraulic cylinder, 9-Retraction mechanism, 10-Pneumatic-hydraulic pressure conversion cylinder, 11-Air pressure source, 12-Third globe valve, 13-Relief valve, 14-Oil injection control valve group, 15-Pressure cylinder oil outlet, 16-Pressure cylinder front end cover, 17-Oil storage chamber, 18-Back end cover of pressure cylinder, 19-Piston push rod, 20-Electric cylinder, 21-Reducer, 22-Servo motor, 23-Shaft seal block, 24-Oil inlet, 25- Overflow port connector, 26-oil outlet connector, 27-high pressure chamber, 28-piston rod, 29-low pressure chamber, 30-hydraulic chamber, 31-air-hydraulic pressure conversion piston, 32-air pressure chamber, 33-first hydraulic pipe Road, 34-second hydraulic pipeline, 35-second stop valve.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

The principle of the present invention is to adjust the pressure inside the container by forcibly changing the volume of hydraulic oil in the closed container. The present invention uses the inverse relationship between the above-mentioned liquid pressure and volume to achieve the purpose of loading. The specific method is: the piston push rod 19 of the linear actuator 1 enters the inside of the pressure-bearing cylinder 3 through the sealing ring, and the volume of the enclosed oil inside the pressure-bearing cylinder 3 is changed by the expansion and contraction of the piston push rod 19. According to the inverse relationship between the oil pressure and the volume The desired loading pressure is generated, and the piston rod 28 of the loading hydraulic cylinder 8 is pushed to output the specified loading force.

As shown in FIG. 1 , the pumpless hydraulic loading device according to the preferred embodiment of the present invention includes: a linear drive 1, an oil accumulator 2, a pressure bearing cylinder 3, a pressure gauge 4, a stop valve 5, a pressure sensor 6, a displacement sensor 7, a loading Hydraulic cylinder 8, retraction mechanism 9, pneumatic-hydraulic pressure conversion cylinder 10, pneumatic source 11, third stop valve 12, relief valve 13, oil injection control valve group 14, first hydraulic pipeline 33, second hydraulic pipeline 34 and the second shut-off valve 35 .

Wherein, the linear actuator 1 is connected to the pressure-bearing cylinder 3, and the oil storage cylinder 2 is used to inject oil into the pressure-bearing cylinder 3 through an oil filling pipeline, and a third shut-off valve 12 is arranged on the oil filling pipeline. The relief valve 13 is connected to the pressure cylinder 3 and the oil accumulator 2. The oil accumulator 2 is driven by gas to inject oil. The oil injection control valve group 14 includes two solenoid valves and a manual valve, which are used to electrically or manually control the gas to the piston of the oil accumulator 2. Apply pressure to realize oil injection. The air source of the oil storage cylinder 2 is omitted in the figure, and the conventional pressurized air source can be used. Two ends of the loading hydraulic cylinder 8 are respectively connected to the pressure bearing cylinder 3 and the left end of the retracting mechanism 9 through a first hydraulic pipeline 33 and a second hydraulic pipeline 34 . The right end of the retracting mechanism 9 is connected to an air pressure source 11 .

Preferably, the gas pressure source 11 may be an industrial gas cylinder, an ideal gas source or an accumulator, so as to provide stable gas pressure and use the gas compression characteristics to store energy during the loading process. The air supply method similar to that used by the oil accumulator 2 can also be directly used, and the air supply is directly performed during the reset.

Referring to FIGS. 1 to 5 , the linear actuator 1 of this embodiment includes a piston push rod 19 , an electric cylinder 20 , a reducer 21 and a servo motor 22 . The piston push rod 19 is a built-in component of the electric cylinder 20, and the electric cylinder 20 can be directly purchased as an existing product. Using the servo motor 22 can precisely control the feed amount of the piston push rod 19 , so as to precisely control the hydraulic pressure and the loading force of the loading hydraulic cylinder 8 and the position of the piston rod 28 . In other embodiments, the piston push rod 19 can be mounted on any linear feed mechanism for driving, for example, mounted on the mover of the ball screw. Pressurize and release pressure. The loading hydraulic cylinder 8 includes a cylinder block and a piston rod 28 , and the piston rod 28 divides the cylinder block into a high pressure chamber 27 and a low pressure chamber 29 , as shown in FIG. 4 .

The pressure bearing cylinder 3 has an oil storage chamber 17, and one end of the oil storage chamber 17 is provided with a piston hole for the entry of the piston push rod 19 of the linear drive 1, and the piston push rod 19 is connected to the pressure bearing cylinder through the shaft seal block 23 in a shaft seal manner. The rear end cover 18 is sealed and connected and can freely reciprocate in the axial direction. The other end of the oil storage chamber 17 is communicated with the high pressure chamber 27 of the loading hydraulic cylinder 8 through the first hydraulic pipeline 33 . The pressure cylinder 3 further includes an oil outlet 15 of the pressure cylinder, a front end cover 16 of the pressure cylinder, an oil inlet 24 , an overflow joint 25 and an oil outlet 26 . The oil outlet 15 of the pressure-bearing cylinder is connected to the first hydraulic pipeline 33 through the oil outlet joint 26 , and is connected to the relief valve 13 through the overflow port joint 25 . The oil storage chamber 17 is connected to the oil inlet pipeline and the oil storage cylinder 2 through the oil inlet 24 .

The retraction mechanism 9 includes a gas-hydraulic pressure conversion cylinder 10 and a gas pressure source 11 . The gas-liquid pressure conversion cylinder 10 is provided with a gas-liquid pressure conversion piston 31 , and the gas-liquid pressure conversion piston 31 divides the gas-liquid pressure conversion cylinder 11 into a hydraulic chamber 30 and an air pressure chamber 32 . The hydraulic chamber 30 of the gas-hydraulic pressure conversion cylinder 10 is connected to the low-pressure chamber 29 of the loading hydraulic cylinder 8 through a second hydraulic pipeline 34 . The air pressure chamber 32 of the air-liquid pressure conversion cylinder 10 is connected to the air pressure source 11, and the air pressure source 11 is used to provide stable air pressure.

Preferably, the cross-sectional area of the hydraulic chamber 30 is smaller than the cross-sectional area of the air pressure chamber 32 in order to increase the pressure in the hydraulic chamber 30 so that a larger restoring force can be provided by the air pressure source 11 with lower pressure. Specifically, as shown in FIG. 5 , the gas-liquid pressure conversion piston 31 includes a hydraulic chamber plug body and an air pressure chamber plug body fixedly connected to each other, the hydraulic chamber plug body is located in the hydraulic chamber 30 , and the air pressure chamber plug body is located in the air pressure chamber 32 . The cross-sectional shape and size of the plug body of the hydraulic chamber are the same as the cross-section of the hydraulic chamber 30 , and the cross-sectional shape and size of the plug body of the air pressure chamber are the same as the cross-section of the air pressure chamber 32 . The ratio of the hydraulic chamber 30 to the air pressure chamber 32 determines the pressure conversion multiple.

Preferably, in this embodiment, a multi-cylinder parallel and independent control scheme is adopted. Specifically, as shown in FIG. 1 , in this embodiment, a plurality of loading hydraulic cylinders 8 , first hydraulic pipelines 33 and second hydraulic pipelines 34 are provided in an equal number and in one-to-one correspondence; The first hydraulic pipeline 33 and the second hydraulic pipeline 34 are connected in parallel between the pressure bearing cylinder 3 and the gas-hydraulic pressure conversion cylinder 10 . Each first hydraulic pipeline 33 is provided with a pressure gauge 4 , a first shut-off valve 5 and a pressure sensor 6 . Each first hydraulic pipeline 33 merges into the first hydraulic manifold and is connected to the oil storage chamber 17 through the first hydraulic manifold; each second hydraulic pipeline 34 merges into the second hydraulic manifold and is connected to the hydraulic chamber 30 through the second hydraulic manifold ; The first hydraulic main pipe and the second hydraulic main pipe are respectively provided with pressure gauges 4, and the second hydraulic main pipe is also provided with a second stop valve 35. Each loading hydraulic cylinder 8 is provided with a displacement sensor 7 for measuring the position of the piston rod 8 . The processor (not shown) connects the displacement sensor 7 and the linear drive 1 to form a closed-loop feedback control mechanism for displacement, which is used to precisely control the feed amount of the piston push rod 19 in the linear drive 1, thereby accurately controlling the piston rod of the hydraulic cylinder 8 28 position for precise positioning. The processor (not shown) is connected with the pressure sensor 6 and the linear drive 1 to form a pressure closed-loop feedback control mechanism, which is used to precisely control the feed amount of the piston push rod 19 in the linear drive 1, so as to precisely control the loading force of the loading hydraulic cylinder 8 .

Hereinafter, the working process and working principle of this embodiment will be introduced by taking the used air pressure source 11 as an industrial gas cylinder as an example:

Before loading, it is necessary to inject oil into the pressure-bearing cylinder 3. Open the manual valve or solenoid valve of the oil injection control valve group 14 and the third stop valve 12 on the oil injection pipeline, and use the air pressure to push the piston in the oil storage cylinder 2 to inject the oil into the oil storage chamber 17 of the pressure cylinder 3 . When the loading pressure of the pressure-bearing cylinder 3 is too high, the overflow valve 13 is opened for overflow and connected to the accumulator cylinder 2 to prevent the linear actuator 1 from being overloaded. After filling the oil, close the third stop valve 12 .

When loading, according to the actual work requirements, open the second cut-off valve 35 and any first cut-off valve 5, and then start the servo motor 22 to control the piston push rod 19 of the electric cylinder 1 to generate a specified displacement, thereby forcibly changing the pressure-bearing cylinder 3 The internal oil volume of the oil storage chamber 17 changes its internal pressure. During loading, the servo motor 22 rotates forward, the piston push rod 19 extends, and the high pressure oil in the pressure bearing cylinder 3 is injected into the high pressure chamber 27 of the corresponding loading hydraulic cylinder 8 to push the piston rod 28 to generate the corresponding loading force. At this time, the gas in the gas pressure chamber 32 of the gas-liquid pressure conversion cylinder 10 is compressed back into the industrial gas cylinder. In addition, the movement of the piston rod 28 can be made more stable due to the reaction force of the compressed gas.

Preferably, the present invention can work both in the positioning mode and in the loading mode:

For the positioning working mode, during the loading process, the control amount input to the electric cylinder 1 can be corrected through the feedback signal of the displacement sensor 7, so as to realize the precise control of the displacement of the piston rod 28 of the loading hydraulic cylinder 8;

For the loading working mode, during the loading process, the control amount input to the electric cylinder 1 can be corrected through the feedback signal of the pressure sensor 6 to achieve precise control of the loading force of the piston rod 28 of the loading hydraulic cylinder 8 .

The present invention can keep the loading pressure unchanged after reaching a certain level. The specific operation is as follows: after loading the specified force, the servo motor 22 can be turned off or suspended, and the first cut-off valve 5 and the second cut-off valve 35 can be closed. At this time, the electric cylinder 1 has no input, the piston push rod 19 does not act, and the oil in the high pressure chamber 27 of the loading hydraulic cylinder 8 is isolated from the outside world and maintains a constant pressure.

After the loading, the piston rod of the loading hydraulic cylinder 8 is retracted by using the principle of gas compressibility. Specifically, after the loading is completed, the first cut-off valve 5 and the second cut-off valve 35 are opened, the processor controls the servo motor 22 to reverse, drives the piston push rod 19 of the electric cylinder 1 to retreat, and the oil in the inner cavity of the pressure-bearing cylinder 3 recovers. Initial pressure before loading. At the same time, the hydraulic chamber 30 of the gas-liquid pressure conversion cylinder 10 is depressurized, and the gas in the industrial gas cylinder is recharged into the air pressure chamber of the gas-hydraulic pressure conversion cylinder 10, pushing the gas-liquid pressure conversion piston 31 to return to its initial position, and simultaneously pushing the hydraulic pressure The oil in the cavity 30 is injected into the low pressure cavity 29 of the loading hydraulic cylinder 8 through the second hydraulic pipeline 34, and pushes the piston push rod 19 of the loading hydraulic cylinder 8 to return to the initial position.

Those skilled in the art can easily understand that the above are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention, etc., All should be included within the protection scope of the present invention.

Claims (10)

1. A pumpless hydraulic loading and positioning device, characterized in that it comprises: a linear drive (1), a loading hydraulic cylinder (8), a pressure-bearing cylinder (3), a first hydraulic pipeline (33), a second hydraulic Hydraulic pipeline (34), retraction mechanism (9) and processor; The output end of the linear drive (1) has a piston push rod (19); The loading hydraulic cylinder (8) includes a cylinder block, a piston rod (28) and a displacement sensor (7). The piston rod (28) divides the cylinder block into a high pressure chamber (27) and a low pressure chamber (29); the displacement sensor (7) uses To measure the position of the piston rod (28); The pressure bearing cylinder (3) has an oil storage chamber (17), one end of the oil storage chamber (17) is provided with a piston hole for the entry of the piston push rod (19) of the linear drive (1), and the other end passes through the first hydraulic pipeline (33) communicate with the high pressure chamber (27) of the loading hydraulic cylinder (8); The retraction mechanism (9) includes a gas-hydraulic pressure conversion cylinder (10) and an air pressure source (11); the gas-liquid pressure conversion cylinder (10) is provided with a gas-liquid pressure conversion piston (31), and the gas-liquid pressure conversion piston (31) The gas-hydraulic pressure conversion cylinder (10) is divided into a hydraulic chamber (30) and an air pressure chamber (32); the hydraulic chamber (30) of the gas-hydraulic pressure conversion cylinder (10) is connected to the loading hydraulic cylinder through a second hydraulic pipeline (34) The low pressure chamber (29) of (8); the air pressure chamber (32) of the gas-liquid pressure conversion cylinder (10) is connected to the air pressure source (11); The processor is connected with the displacement sensor (7) and the linear drive (1) to perform closed-loop control on the displacement of the piston rod (28) according to the displacement signal fed back by the displacement sensor (7). 2. A pumpless hydraulic loading and positioning device according to claim 1, characterized in that the cross-sectional area of the hydraulic chamber (30) of the gas-hydraulic pressure conversion cylinder (10) is not greater than the cross-sectional area of the pneumatic chamber (32). area. 3. A pumpless hydraulic loading and positioning device according to claim 2, characterized in that the cross-sectional area of the hydraulic chamber (30) is smaller than the cross-sectional area of the air pressure chamber (32); the gas-hydraulic pressure conversion piston (31) The hydraulic chamber plug body and the air pressure chamber plug body are fixedly connected to each other, the hydraulic chamber plug body is located in the hydraulic chamber (30), and the air pressure chamber plug body is located in the air pressure chamber (32); The cross section of (30) is the same, and the cross-sectional shape and size of the air pressure chamber plug body are the same as the cross section of the air pressure chamber (32). 4. A pumpless hydraulic loading and positioning device according to any one of claims 1 to 3, characterized in that it comprises a plurality of loading hydraulic cylinders (8), a first hydraulic pipe, an equal number and a one-to-one correspondence. circuit (33) and second hydraulic pipeline (34); each loading hydraulic cylinder (8) is connected in parallel to the pressure-bearing cylinder (3) through its corresponding first hydraulic pipeline (33) and second hydraulic pipeline (34) ) and the gas-hydraulic pressure conversion cylinder (10). 5. The pumpless hydraulic loading and positioning device according to claim 4, wherein each first hydraulic pipeline (33) is provided with a pressure gauge (4), a first shut-off valve (5) ) and a pressure sensor (6); the processor is connected to the pressure sensor (6) to perform closed-loop control on the pressure of the first hydraulic pipeline (33) according to the pressure signal fed back by the pressure sensor (6). 6. The pumpless hydraulic loading and positioning device according to claim 5, characterized in that each first hydraulic pipeline (33) merges into the first hydraulic manifold, and is connected to the oil storage chamber through the first hydraulic manifold (17); each second hydraulic pipeline (34) merges into the second hydraulic manifold, and is connected to the hydraulic chamber (30) through the second hydraulic manifold; pressure gauges (4) are respectively provided on the first hydraulic manifold and the second hydraulic manifold ), and a second shut-off valve (35) is also provided on the second hydraulic main pipe. 7. A pumpless hydraulic loading and positioning device according to any one of claims 1 to 3, characterized in that it further comprises an oil storage cylinder (2), the oil storage cylinder (2) being connected to the pressure bearing cylinder (3) imported oil. 8 . The pumpless hydraulic loading and positioning device according to claim 1 , wherein a relief valve ( 13 ) is provided at the oil outlet of the pressure bearing cylinder ( 3 ). 9 . 9. A pumpless hydraulic loading device, characterized by comprising: a linear drive (1), a loading hydraulic cylinder (8), a pressure bearing cylinder (3), a first hydraulic pipeline (33), a second hydraulic pipeline road (34) and retraction mechanism (9); The output end of the linear drive (1) has a piston push rod (19); The loading hydraulic cylinder (8) includes a cylinder body and a piston rod (28), and the piston rod (28) divides the cylinder body into a high pressure chamber (27) and a low pressure chamber (29); The pressure bearing cylinder (3) has an oil storage chamber (17), one end of the oil storage chamber (17) is provided with a piston hole for the entry of the piston push rod (19) of the linear drive (1), and the other end passes through the first hydraulic pipeline (33) communicate with the high pressure chamber (27) of the loading hydraulic cylinder (8); The retraction mechanism (9) includes a gas-hydraulic pressure conversion cylinder (10) and an air pressure source (11); the gas-liquid pressure conversion cylinder (10) is provided with a gas-liquid pressure conversion piston (31), and the gas-liquid pressure conversion piston (31) The gas-hydraulic pressure conversion cylinder (10) is divided into a hydraulic chamber (30) and an air pressure chamber (32); the hydraulic chamber (30) of the gas-hydraulic pressure conversion cylinder (10) is connected to the loading hydraulic cylinder through a second hydraulic pipeline (34) The low pressure chamber (29) of (8); the air pressure chamber (32) of the gas-liquid pressure conversion cylinder (10) is connected to the air pressure source (11). 10. A pumpless hydraulic loading device according to claim 9, characterized in that the cross-sectional area of the hydraulic chamber (30) of the gas-hydraulic pressure conversion cylinder (10) is not greater than the cross-sectional area of the air pressure chamber (32); Wherein, when the cross-sectional area of the hydraulic chamber (30) is smaller than the cross-sectional area of the air pressure chamber (32): The gas-liquid pressure conversion piston (31) includes a hydraulic chamber plug body and an air pressure chamber plug body that are fixed to each other, the hydraulic chamber plug body is located in the hydraulic chamber (30), and the air pressure chamber plug body is located in the air pressure chamber (32); the hydraulic chamber plug body is located in the air pressure chamber (32). The cross-sectional shape and size of the body are the same as those of the hydraulic chamber (30), and the cross-sectional shape and size of the plug body of the air pressure chamber are the same as those of the air pressure chamber (32).

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