阅读说明：本技术 一种油量高精度检测的闭式调压油箱 (Closed pressure regulating oil tank for high-precision detection of oil quantity ) 是由 杨亚楠 颜培男 王树新 *** 王延辉 刘玉红 于 2019-10-23 设计创作，主要内容包括：本发明公开一种油量高精度检测的闭式调压油箱,包括油箱主体单元与气压调节单元；所述油箱主体单元包括油箱前端盖、油箱筒壁、密封活塞体、油箱后端盖和行程位移传感器；所述气压调节单元包括：压力传感器、气泵、气路单向阀和气路电磁阀；油箱前端盖、油箱筒壁和油箱后端盖构成油箱的封闭内腔,并采用拉紧杆将油箱主体单元拉紧固定；油箱前端盖上开有进排油孔；油箱后端盖上开有油箱进排气孔；进排油孔能够连接至液压系统,进排气孔连接至气压调节单元；密封活塞体设置于封闭内腔内并将封闭内腔分为油液侧和气体侧；压力传感器安装在油箱后端盖的螺纹孔内；气泵与气路电磁阀通过螺钉固定在油箱后端盖外侧。本发明结构紧凑、集成度高、质量轻。(The invention discloses a closed pressure regulating oil tank for high-precision oil quantity detection, which comprises an oil tank main body unit and an air pressure regulating unit; the oil tank main body unit comprises an oil tank front end cover, an oil tank cylinder wall, a sealing piston body, an oil tank rear end cover and a stroke displacement sensor; the air pressure adjusting unit includes: the air pump is connected with the air passage one-way valve; the front end cover of the oil tank, the wall of the oil tank wall and the rear end cover of the oil tank form a closed inner cavity of the oil tank, and the main body unit of the oil tank is tensioned and fixed by adopting a tensioning rod; an oil inlet and outlet hole is formed in the front end cover of the oil tank; an oil tank air inlet and outlet hole is formed in the rear end cover of the oil tank; the oil inlet and outlet holes can be connected to a hydraulic system, and the air inlet and outlet holes are connected to the air pressure adjusting unit; the sealing piston body is arranged in the sealing inner cavity and divides the sealing inner cavity into an oil side and a gas side; the pressure sensor is arranged in a threaded hole of the rear end cover of the oil tank; the air pump and the air path electromagnetic valve are fixed on the outer side of the rear end cover of the oil tank through screws. The invention has compact structure, high integration level and light weight.)

1. A closed pressure regulating oil tank for high-precision detection of oil mass is characterized by comprising an oil tank main body unit and an air pressure regulating unit; the oil tank main body unit comprises an oil tank front end cover (1), an oil tank cylinder wall (4), a sealing piston body (6), an oil tank rear end cover (12) and a stroke displacement sensor (15); the air pressure adjusting unit includes: a pressure sensor (17), an air pump (18), an air path one-way valve (19) and an air path electromagnetic valve (20);

the front end cover (1), the cylinder wall (4) and the rear end cover (12) of the oil tank form a closed inner cavity of the oil tank, and the main body unit of the oil tank is tensioned and fixed by a tensioning rod (5); an oil inlet and outlet hole (2) is formed in the front end cover (1) of the oil tank; an oil tank air inlet and outlet hole (14) is formed in the rear end cover (12) of the oil tank; the oil inlet and outlet holes (2) can be connected to a hydraulic system, and the air inlet and outlet holes (14) are connected to an air pressure adjusting unit; the sealing piston body (6) is arranged in the closed inner cavity and divides the closed inner cavity into an oil side and a gas side; the sealing piston body (6) can move along the axis of the oil tank cylinder wall (4) in the closed inner cavity; the middle part of the rear end cover (12) of the oil tank is connected with the stroke displacement sensor (15) through a mounting hole, a telescopic rod extending into the closed inner cavity is arranged in the stroke displacement sensor (15), and the tail end of the telescopic rod is connected with the center of the sealing piston body (6);

the pressure sensor (17) is arranged in a threaded hole of the rear end cover (12) of the oil tank; the air pump (18) and the air path electromagnetic valve (20) are fixed on the outer side of the oil tank rear end cover (12) through screws; the pressure sensor (17) is used for detecting the internal pressure of the oil tank; the air pump (18) is used for pressurizing the oil tank and increasing the gas side pressure of the oil tank in the oil discharge stage; the air path one-way valve (19) is arranged between the air pump (18) and the air path electromagnetic valve (20); the gas path one-way valve (19) is used for preventing gas in the oil tank from reversely flowing through the second port of the gas path electromagnetic valve (20); the gas circuit electromagnetic valve (20) is a two-position three-way electromagnetic valve, a first port of the gas circuit electromagnetic valve (20) is connected with a gas inlet and outlet hole (14) in a rear end cover of the oil tank, a second port is connected with a one-way valve (19), a third port is directly communicated with the external environment, the gas circuit is used for conducting a gas pump (18) and a gas side pipeline of the oil tank in an oil discharging stage of the oil tank, and the gas circuit is used for communicating the external environment and the gas side of the oil tank in an oil inlet.

2. The closed type pressure regulating oil tank for detecting the oil quantity with high precision according to claim 1 is characterized in that a side wall which is in clearance fit with the oil tank cylinder wall (4) is arranged on the sealing piston body (6), three grooves are arranged on the contact surface of the side wall and the oil tank cylinder wall (4), and a double-acting polyester surface preloading sealing ring (11) is arranged in the middle groove; a first guide ring (9) and a second guide ring (10) are respectively arranged in the grooves at the two sides; the first guide ring (9) and the second guide ring (10) realize the low-resistance sliding of the sealing piston body (6) in the oil tank cylinder wall (4) along the axial direction.

3. The closed type pressure regulating oil tank capable of detecting the oil quantity with high precision as claimed in claim 2 is characterized in that the double-acting polyester surface preloading sealing ring (11) realizes bidirectional dynamic sealing between the oil tank cylinder wall (4) and the sealing piston body (6).

4. The closed type pressure regulating oil tank for detecting the oil quantity with high precision according to claim 1 is characterized in that an exhaust hole (7) is formed in the sealing piston body (6); an exhaust valve (8) is arranged in the exhaust hole (7); residual gas on the oil liquid side of the oil tank can be discharged by opening the exhaust valve (8).

5. The closed pressure-regulating oil tank for detecting the oil quantity with high precision as claimed in claim 1 is characterized in that a mounting end face of the stroke displacement sensor (15) is provided with a groove, an O-shaped ring (16) is arranged in the groove, and the groove and a mounting hole in the center of a rear end cover (12) of the oil tank form an end face seal; the stroke displacement sensor (15) is fixed at a central mounting hole of the rear end cover (12) of the oil tank by a screw; the displacement L of the telescopic rod of the stroke displacement sensor (15) can be detected to obtain the displacement of the sealing piston (6) and the volume change of oil in the oil tank.

6. Closed type pressure regulating oil tank for detecting oil quantity with high precision according to claim 1 or 5, characterized in that the linear error of the stroke displacement sensor (15) is +/-0.25%, and the measurement resolution is less than 0.1 μm.

7. The closed pressure-regulating oil tank with high-precision oil quantity detection according to claim 1, characterized in that when the oil tank is in an oil discharge working stage, the air pump (18) is powered on and started, the air path solenoid valve (20) is in a state that the first port is communicated with the second port and the third port is cut off, the air pump (18) is communicated with a pipeline on the gas side of the oil tank, gas is pressurized by the air pump (18) and then enters the gas side of the oil tank through the air path check valve (19) and the air path solenoid valve (20), and the pressure of the oil tank is increased; under the action of the pressure at the gas side of the oil tank, the sealing piston body (6) overcomes the friction force between the sealing piston body and the cylinder wall (4) of the oil tank and moves forwards to the oil tank along the axis of the cylinder wall of the oil tankThe end cover (1) moves, and oil enters a hydraulic system through the oil inlet and outlet hole (2) of the oil tank; the telescopic rod of the stroke displacement sensor (15) fixedly connected on the sealing piston body (6) is gradually extended, and the displacement extension L of the telescopic rod of the stroke displacement sensor (15) ₁The product of the internal diameter and the cross section area S of the cylinder wall (4) of the oil tank is the volume V reduced by the oil in the oil tank ₁；

When the oil tank is in an oil inlet working stage, the gas circuit electromagnetic valve (20) is electrified, the first port and the third port of the gas circuit electromagnetic valve (20) are communicated, the second port is closed, the gas side of the oil tank is communicated with the external environment atmosphere, and the pressure of the oil tank is equal to the ambient pressure; oil from a hydraulic system enters the oil side of the oil tank through the oil inlet and outlet holes (2) of the oil tank, and the oil simultaneously pushes the sealing piston body (6) to gradually move towards the rear end cover (12) of the oil tank along the axis of the cylinder wall of the oil tank; the telescopic rod of the stroke displacement sensor (15) fixedly connected on the sealing piston body (6) is gradually contracted at the same time, and the displacement reduction L of the telescopic rod of the stroke displacement sensor (15) ₂The product of the volume V and the cross section S of the inner diameter of the wall of the cylinder is the volume V added to the oil in the oil tank ₂。

8. The closed pressure-regulating oil tank for detecting the oil quantity with high precision as claimed in claim 1 is characterized in that the oil tank cylinder wall (4) is manufactured by adopting a cold-drawing honing process; the dimensional accuracy of the inner wall of the oil tank cylinder wall (4) is higher than IT9 level, and the roughness Ra of the inner surface is less than 0.4 mu m.

Technical Field

The invention belongs to the field of unmanned aircraft integrated hydraulic systems, and particularly relates to a closed pressure regulating oil tank for high-precision oil quantity detection.

Background

Unmanned vehicles generally refer to unmanned mobile platforms that navigate in the air, underwater. Compared with a manned aircraft, the unmanned aircraft has stronger maneuvering capability and can perform high-difficulty maneuvering actions such as rolling, transversely turning, pitching adjustment and the like. In order to ensure that an integrated hydraulic system of the unmanned aircraft can obtain continuous oil and liquid supply when the unmanned aircraft executes high-difficulty maneuvering actions, a closed oil tank, namely a scheme of isolating oil in the oil tank from the external environment atmosphere, becomes one of available schemes of the integrated hydraulic system of the unmanned aircraft.

Currently, the isolation of oil from the outside atmosphere in a closed oil tank includes a metal folding bellows, a rubber bellows, and the like. In the oil volume change process, the folding corrugations and the rubber bellows are not uniformly deformed and show strong nonlinear rules, the oil tank adopting the isolation mode increases the difficulty of accurate detection of the oil volume, the volume change of the measured oil volume cannot be accurately obtained through direct and indirect means, and only the oil volume can be roughly estimated. Some students have proposed the technical scheme that the piston is used for isolating oil from the environment, and meanwhile, the stay wire type displacement sensor is used for detecting the displacement of the piston in the cylinder barrel so as to measure the volume of the oil. However, the current scheme has significant defects in various aspects of structural design, detection principle and manufacturing process, for example, the problem of frictional resistance between the piston of the oil tank and the inner wall of the cylinder barrel is not considered, so that the closed oil tank in the scheme cannot actively provide oil outlet pressure for a hydraulic system, and when oil returns to the oil tank, work is required to be done to push the piston to move; the measuring method of the length of the thread rope adopted by the stay wire type displacement sensor is not strictly linear, and the measurement of the volume of the oil still has obvious errors; the cylinder barrel of the oil tank is too heavy, and the extremely harsh requirement of the unmanned aircraft on the load quality cannot be met.

Therefore, the novel closed oil tank has the advantages of compact and simple structure, light weight, capability of realizing high-precision detection on the volume of oil and very necessary requirement for adjusting the pressure of oil discharge and oil inlet. The method has an important effect on improving the performance level of the integrated hydraulic system of the unmanned aircraft.

Disclosure of Invention

The invention aims to overcome the defects in the prior art and provide a closed pressure regulating oil tank for high-precision detection of oil quantity; the invention can be integrated in hydraulic systems of small and medium unmanned aircrafts in the air and underwater, and realizes the continuous oil supply for the unmanned aircrafts under the postures of inclination, overturning and the like. The invention adopts a clearance fit structure of the cylinder wall and the piston and a high-precision stroke displacement sensor to realize the accurate detection of the volume change of the oil in the oil tank. The invention realizes the regulation of the oil tank pressure in the oil inlet and oil discharge stages by changing the air pressure mode of the oil tank. The invention adopts the cold-drawing honing process to realize the lightweight forming manufacture of the wall of the oil tank cylinder.

The purpose of the invention is realized by the following technical scheme:

a closed pressure regulating oil tank for high-precision detection of oil quantity comprises an oil tank main body unit and an air pressure regulating unit; the oil tank main body unit comprises an oil tank front end cover, an oil tank cylinder wall, a sealing piston body, an oil tank rear end cover and a stroke displacement sensor; the air pressure adjusting unit includes: the air pump is connected with the air passage one-way valve;

the front end cover of the oil tank, the wall of the oil tank wall and the rear end cover of the oil tank form a closed inner cavity of the oil tank, and the main body unit of the oil tank is tensioned and fixed by adopting a tensioning rod; an oil inlet and outlet hole is formed in the front end cover of the oil tank; an oil tank air inlet and outlet hole is formed in the rear end cover of the oil tank; the oil inlet and outlet holes can be connected to a hydraulic system, and the air inlet and outlet holes are connected to the air pressure adjusting unit; the sealing piston body is arranged in the sealing inner cavity and divides the sealing inner cavity into an oil side and a gas side; the sealing piston body can move along the axis of the wall of the oil tank cylinder in the closed inner cavity; the middle part of the rear end cover of the oil tank is connected with the stroke displacement sensor through a mounting hole, a telescopic rod extending into the closed inner cavity is arranged in the stroke displacement sensor, and the tail end of the telescopic rod is connected with the center of the sealing piston body;

the pressure sensor is arranged in a threaded hole of the rear end cover of the oil tank; the air pump and the air path electromagnetic valve are fixed on the outer side of the rear end cover of the oil tank through screws; the pressure sensor is used for detecting the internal pressure of the oil tank; the air pump is used for increasing the gas side pressure of the oil tank in the oil discharge stage; the air path one-way valve is arranged between the air pump and the air path electromagnetic valve; the gas path one-way valve is used for preventing gas in the oil tank from reversely flowing through the second port of the gas path electromagnetic valve; the gas circuit electromagnetic valve is a two-position three-way electromagnetic valve, a first port of the gas circuit electromagnetic valve is connected with a gas inlet and outlet hole on a rear end cover of the oil tank, a second port of the gas circuit electromagnetic valve is connected with the one-way valve, and a third port of the gas circuit electromagnetic valve is directly communicated with the external environment. The oil pump is used for communicating the air pump with the oil tank gas side pipeline in the oil discharging stage of the oil tank, and the oil inlet stage of the oil tank is used for communicating the external environment with the oil tank gas side.

Furthermore, a side wall in clearance fit with the cylinder wall of the oil tank is arranged on the sealing piston body, three grooves are arranged on the contact surface of the side wall and the cylinder wall of the oil tank, and a double-acting polyester surface preloading sealing ring is arranged in the middle groove; a first guide ring and a second guide ring are respectively arranged in the grooves at the two sides; the first guide ring and the second guide ring realize low-resistance sliding of the sealing piston body in the wall of the oil tank along the axial direction.

Furthermore, the double-acting polyester surface preloading sealing ring realizes bidirectional dynamic sealing between the cylinder wall of the oil tank and the sealing piston body.

Further, an exhaust hole is formed in the sealing piston body; an exhaust valve is arranged in the exhaust hole; residual gas on the oil liquid side of the oil tank can be discharged by opening the exhaust valve.

Furthermore, a groove is formed in the mounting end face of the stroke displacement sensor, an O-shaped ring is arranged in the groove, and the groove and the mounting hole in the center of the rear end cover of the oil tank form end face seal; the stroke displacement sensor is fixed at a central mounting hole of the rear end cover of the oil tank by a screw; the displacement L of the telescopic rod of the stroke displacement sensor can be detected to obtain the displacement of the sealing piston and the volume change of oil in the oil tank.

Further, the linear error of the stroke displacement sensor is +/-0.25%, and the measurement resolution is less than 0.1 mu m.

Further, when the oil tank is in an oil discharge working stage, the air pump is electrified and started, the air path electromagnetic valve is in a state that the first port is communicated with the second port and the third port is cut off, the air pump is communicated with the air side pipeline of the oil tank, air enters the air side of the oil tank through the air path one-way valve and the air path electromagnetic valve after being pressurized by the air pump, and the pressure of the oil tank is increased; under the action of the pressure at the gas side of the oil tank, the sealing piston body overcomes the friction force between the sealing piston body and the cylinder wall of the oil tank and moves towards the front end cover of the oil tank along the axis of the cylinder wall of the oil tank, and oil enters a hydraulic system through an oil inlet and outlet hole of the oil tank; the telescopic rod of the stroke displacement sensor fixedly connected on the sealing piston body is gradually extended, and the telescopic rod of the stroke displacement sensor is extended by displacement ₁The product of the volume and the inner diameter cross-sectional area S of the cylinder wall of the oil tank is the volume V reduced by the oil in the oil tank ₁；

When the oil tank is in an oil inlet working stage, the gas circuit electromagnetic valve is electrified, the first port and the third port of the gas circuit electromagnetic valve are communicated, the second port is closed, the gas side of the oil tank is communicated with the external environment atmosphere, and the pressure of the oil tank is equal to the ambient pressure; oil from a hydraulic system enters the oil side of the oil tank through the oil inlet and outlet holes of the oil tank, and the oil simultaneously pushes the sealing piston body to gradually move towards the rear end cover of the oil tank along the axis of the cylinder wall of the oil tank; the telescopic rod of the stroke displacement sensor fixedly connected on the sealing piston body simultaneously and gradually contracts, and the displacement reduction amount L of the telescopic rod of the stroke displacement sensor ₂The product of the volume V and the cross section S of the inner diameter of the wall of the cylinder is the volume V added to the oil in the oil tank ₂。

Further, the wall of the oil tank is manufactured by adopting a cold-drawing honing process; the dimensional accuracy of the inner wall of the cylinder wall of the oil tank is higher than IT9 level, and the roughness Ra of the inner surface is less than 0.4 μm.

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

1. the invention forms an oil tank closed inner cavity by an oil tank front end cover, an oil tank cylinder wall, an oil tank rear end cover and a sealing piston body to form a closed oil tank, and hydraulic oil in the oil liquid side of the oil tank is not contacted with external environment gas. The closed oil tank can be integrated into an unmanned aircraft hydraulic system in the air and under water, oil can be supplied to the hydraulic system when the unmanned aircraft is in an inclined posture and an overturning posture, and the problems that an oil interface of an open oil tank shakes in the inclined posture and the overturning posture, oil is mixed with air, and oil cannot be supplied continuously are solved.

2. The invention adopts the air pressure adjusting unit to adjust the oil tank pressure of the oil tank in the oil inlet and oil discharge stages. In the oil discharge stage, the oil discharge pressure of the oil tank is increased by increasing the gas side pressure of the oil tank, so that the oil supply pressure of the unmanned aircraft hydraulic system is ensured; in the oil inlet stage, the low-load oil inlet of the oil tank is realized by keeping the pressure of the gas side of the oil tank balanced with the pressure of the external environment.

3. The invention adopts a clearance fit structure of the cylinder wall of the oil tank and the sealing piston body and a high-precision stroke displacement sensor to realize the accurate detection of the oil quantity of the closed oil tank. The linear error of the stroke displacement sensor used by the invention can be controlled within +/-0.25%, the measurement resolution is less than 0.1 mu m, and the temperature drift phenomenon is almost avoided. The sealing piston body is in clearance fit with the wall of the oil tank cylinder, and the contact degree between the rotation axis of the sealing piston body and the displacement direction is high. The volume change of oil in the oil tank is the product of the displacement of the piston body and the inner diameter sectional area of the wall of the oil tank cylinder. The detection error of the oil volume can be controlled within +/-0.25%, and the measurement resolution is less than S multiplied by 10 ^-7ml (S is the cross section area of the inner diameter of the cylinder wall of the oil tank and is unit cm) ²)。

4. The wall of the oil tank is manufactured by adopting a cold-drawing honing process. Compared with a turning processing mode, the inner diameter of the cylinder wall of the oil tank formed by adopting a cold-drawing honing process has high dimensional accuracy, and reaches IT9 level; the inner surface of the cylinder wall is smooth, and the roughness Ra is less than 0.4 mu m; the hardness of the inner surface of the cylinder wall is high, and the abrasion resistance is strong. By adopting the cold-drawing honing process, the sliding friction force between the sealing piston body and the oil tank cylinder wall can be obviously reduced, the low-resistance smooth movement of the sealing piston body in the oil tank cylinder wall is realized, the sealing effect between the double-acting polyester surface preloading sealing ring and the oil tank cylinder wall is improved, and the leakage and mixing of media on the oil side and the gas side can be effectively prevented. In addition, the wall of the oil tank cylinder made by cold-drawing honing is small in thickness and small in length-diameter ratio, so that light-weight forming manufacturing is realized, the method is suitable for batch production, and the processing cost is low.

5. And a double-acting polyester surface preloading sealing ring is adopted between the sealing piston body and the wall of the oil tank to realize dynamic sealing. The double-acting polyester surface preloading sealing ring has the characteristics of uniform sealing contact pressure, high sealing pressure, allowance for larger radial deflection, groove size error and the like. The dynamic sealing structure can have a reliable bidirectional dynamic sealing effect, and the problem of trace leakage caused by uneven wear and deterioration damage of the conventional O-shaped ring dynamic seal is avoided.

6. The invention has the advantages of simple structure, high reliability, long service life and low manufacturing cost, and the hydraulic and gas circuit valves are mature products.

7. The invention has compact design, high integration level and light weight, and is suitable for being integrated and used in hundreds kilogram-level small and medium-sized unmanned aircrafts.

Drawings

FIG. 1 is a schematic structural view of the present invention;

FIG. 2 is a functional diagram of the present invention;

Detailed Description

The invention is described in further detail below with reference to the figures and specific examples. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

As shown in fig. 1 and 2, the invention provides a closed type pressure regulating oil tank for detecting oil quantity with high precision. Mainly comprises an oil tank main body unit and an air pressure adjusting unit. As shown in fig. 1. The fuel tank main body unit includes: the oil tank comprises an oil tank front end cover 1, an oil tank oil inlet and outlet hole 2, an O-shaped ring 3, an oil tank cylinder wall 4, a tension rod 5, a sealing piston body 6, an exhaust valve hole 7, an exhaust valve 8, a first guide ring 9, a second guide ring 10, a double-acting polyester surface preloading sealing ring 11, an oil tank rear end cover 12, an O-shaped ring 13, an oil tank air inlet and outlet hole 14, a stroke displacement sensor 15 and a sealing O-shaped ring 16. The air pressure regulating unit comprises a pressure sensor 17, an air pump 18, an air path one-way valve 19 and an air path electromagnetic valve 20.

The oil tank front end cover 1, the oil tank cylinder wall 4 and the oil tank rear end cover 12 form an oil tank closed inner cavity, and the oil tank front end cover 1, the oil tank cylinder wall 4 and the oil tank rear end cover 12 are fixedly pulled by a tensioning rod 5. An oil inlet and outlet hole 2 is arranged on the front end cover 1 of the oil tank. An oil tank air inlet and outlet hole 14 is arranged on the oil tank rear end cover 12. The oil inlet and outlet holes 2 are connected to a hydraulic system, and the air inlet and outlet holes 14 are connected to an air pressure adjusting unit.

The oil tank cylinder wall 4 is manufactured by adopting a cold-drawing honing process. Compared with a turning processing mode, the inner diameter size precision of the oil tank cylinder wall 4 formed by adopting a cold-drawing honing process is high and reaches IT9 level; the inner surface of the cylinder wall 4 is smooth, and the roughness Ra is less than 0.4 mu m; the inner surface of the cylinder wall 4 has high hardness and strong abrasion resistance. By adopting the cold-drawing honing process, the sliding friction force between the sealing piston body 6 and the oil tank cylinder wall 4 can be obviously reduced, and the sealing effect between the double-acting polyester surface preloading sealing ring 11 and the oil tank cylinder wall 4 is improved. In addition, the wall of the oil tank cylinder made by cold-drawing honing is small in thickness and small in length-diameter ratio, so that light-weight forming manufacturing is realized, the method is suitable for batch production, and the processing cost is low.

The oil tank adopts sealed piston body 6 to keep apart oil liquid side and gaseous side of oil tank. The grooves on the two sides of the sealing piston body 6 are internally provided with a first guide ring 9 and a second guide ring 10, and the middle groove is provided with a double-acting polyester surface preloading sealing ring. The sealing piston body 6 is in clearance fit with the oil tank cylinder wall 4, and the first guide ring 9 and the second guide ring 10 realize low-resistance sliding of the sealing piston in the oil tank cylinder wall along the axial direction. The double-acting polyester surface preloading sealing ring 11 realizes the dynamic sealing between the oil tank cylinder wall 4 and the sealing piston body 6. The double-acting polyester surface preloading sealing ring 11 has the characteristics of small friction coefficient, uniform sealing contact pressure, high sealing pressure, allowance of larger radial deflection, groove size error and the like.

The sealing piston body 6 is provided with an exhaust hole 7. The exhaust valve 8 is arranged at the position of the exhaust hole 7 corresponding to the sealing piston body 6. And the opening of the exhaust valve can be used for exhausting residual gas on the oil liquid side of the oil tank.

A groove is reserved on the installation end face of the stroke displacement sensor 15, an O-shaped ring 16 is arranged in the groove, and the groove and the installation hole in the center of the oil tank rear end cover 12 form end face sealing. The stroke displacement sensor 15 is fixed at a central mounting hole of the oil tank rear end cover 12 by a screw. The tail end of the telescopic rod of the stroke displacement sensor 15 is provided with an external thread, and the tail end of the telescopic rod is fixedly connected with the threaded hole at the center of the sealing piston body 6. The sealing piston body 6 drives the telescopic rod of the stroke displacement sensor 15 to move along the axis of the cylinder wall of the oil tank in the moving process. The displacement of the sealing piston body 6 and the volume change of oil in the oil tank can be obtained by detecting the displacement L of the telescopic rod of the stroke displacement sensor 15.

The stroke displacement sensor 15 has the advantages of high resolution, good repeatability, no sliding contact, long service life and the like. The linearity error can be controlled within plus or minus 0.25%, the measurement resolution is less than 0.1 μm, and the temperature drift phenomenon is almost avoided. The high-precision detection of the oil volume of the oil tank can be realized.

The air pressure sensor 17 is mounted in a threaded hole of the rear end cover 12 of the oil tank. The air pump 18 and the air path electromagnetic valve 20 are fixed on the outer side of the rear end cover of the oil tank through screws. The air pressure sensor 17 is used for detecting the air pressure inside the oil tank. The air pump 18 is used to increase the tank gas side pressure during the drain phase. The air passage check valve 19 is used for preventing the air in the oil tank from reversely flowing through the second port B of the air passage solenoid valve 20. The gas path electromagnetic valve 20 is a two-position three-way electromagnetic valve, in the oil tank oil discharging stage, a first port A and a second port B of the gas path electromagnetic valve 20 are communicated and used for conducting the gas pump 18 and a gas side pipeline of the oil tank, and a third port C of the gas path electromagnetic valve 20 is cut off; in the oil inlet stage of the oil tank, the first port a and the third port C of the gas path electromagnetic valve 20 are communicated for communicating the external environment and the gas side of the oil tank, and the second port B of the gas path electromagnetic valve 20 is cut off.

The outlet of the air pump 18 is connected with the second port B of the air path electromagnetic valve 20 through a one-way valve 19. The first port A of the air path electromagnetic valve 20 is connected with an air inlet and outlet hole 14 on the rear end cover of the oil tank. The third port C of the gas circuit solenoid valve 20 is directly connected to the external environment.

The installation process of the invention is as follows:

1. the grooves on the two sides of the sealing piston body 6 are respectively provided with a first guide ring 9 and a second guide ring 10, and the middle groove is provided with a double-acting polyester surface preloading sealing ring 11. The exhaust valve 8 is installed at the exhaust hole 7 thread of the sealing piston body 6.

2. An O-shaped ring 3 is arranged in a groove of the front end cover 1 of the oil tank, and the front end cover 1 of the oil tank is arranged at the port of the wall 4 of the oil tank.

3. Keeping the rotation axis of the cylinder wall of the oil tank vertical and the downward placing position of the front end cover 1 of the oil tank. And injecting quantitative hydraulic oil into the oil side of the oil tank through the oil inlet and outlet holes 2. The sealing piston body 6 is inserted into the tank cylinder wall 4 from the port of the other side of the tank cylinder wall. And applying external force to slowly and stably push the piston body 6 towards the oil tank front end cover 1. The oil side residual air is discharged from the exhaust valve 8. When a small amount of hydraulic oil flows out of the exhaust valve 8, the exhaust valve 8 is screwed closed. At the moment, the oil side of the oil tank finishes exhausting and sealing.

4. An O-shaped ring 16 is arranged in a groove of the mounting end face of the stroke displacement sensor 15 and forms end face seal with a mounting hole at the center of the oil tank rear end cover 12, and the stroke displacement sensor 15 is fixed with the oil tank rear end cover 11 through screws. The tail end of the telescopic rod of the stroke displacement sensor 15 is fixedly connected in a threaded mounting hole in the center of the sealing piston body 6.

5. An O-shaped ring 13 is arranged in a groove of the oil tank rear end cover 12 and is installed at the port of the oil tank cylinder wall 4. And adjusting the installation phase of the front end cover 1 of the oil tank and the rear end cover 12 of the oil tank to align the outer edge radial holes of the end covers. The tensioning rod 5 penetrates through radial holes in the outer edges of the front end cover 1 and the rear end cover 12 of the oil tank, and two ends of the tensioning rod 5 are screwed and fixed by nuts.

6. The air pressure sensor 17 is installed in a threaded hole at the rear end cover 12 of the oil tank, and the air pump 18 and the air path electromagnetic valve 20 are fixed on the outer side of the rear end cover 12 of the oil tank through screws. A first port A of the air path electromagnetic valve 20 is connected with an oil tank air inlet and outlet hole 14 on the oil tank rear end cover 12 through a rigid air pipe; the second port B is connected with the check valve 19 and the air pump 18 in series; the third port C is directly connected to the external environment.

The assembled tank is completed as shown in fig. 1.

The working process of the invention is as follows:

1. as shown in fig. 2, when the oil tank is in the oil discharge working stage, the air pump 18 is powered on and started, the air path solenoid valve 20 is in a state that the first port a is communicated with the second port B, the third port C is cut off, air enters the air side of the oil tank through the air path check valve 19 and the air path solenoid valve 20 after being pressurized by the air pump, and the pressure of the oil tank is increased. Under the action of the pressure at the gas side of the oil tank, the sealing piston body 6 overcomes the friction force between the sealing piston body and the cylinder wall 4 of the oil tank and moves towards the front end cover 1 of the oil tank along the axis of the cylinder wall 4 of the oil tank, and oil enters and is discharged through the oil tankThe oil hole 2 enters a hydraulic system. The telescopic rod of the stroke displacement sensor 15 fixedly connected on the sealing piston body is gradually extended at the same time, and the telescopic rod displacement extension L of the stroke displacement sensor 15 ₁The product of the oil volume and the cross section S of the inner diameter of the cylinder wall 4 of the oil tank is the volume V reduced by the oil liquid of the oil tank ₁。

2. When the oil tank is in an oil inlet working stage, the gas circuit electromagnetic valve 20 is powered on, the first port A and the third port C of the gas circuit electromagnetic valve are communicated, the second port B is cut off, the gas side of the oil tank is communicated with the external environment, and the pressure of the oil tank is equal to the ambient air pressure. Oil from a hydraulic system enters the oil side of the oil tank through the oil inlet and outlet holes 2 of the oil tank, and the oil simultaneously pushes the sealing piston body 6 to gradually move towards the rear end cover 12 of the oil tank along the axis of the cylinder wall 4 of the oil tank. The telescopic rod of the stroke displacement sensor 15 fixedly connected on the sealing piston body is gradually contracted at the same time, and the displacement reduction L of the telescopic rod of the stroke displacement sensor 15 is ₂The product of the volume V and the inner diameter cross section area S of the cylinder wall 4 of the oil tank is the volume V added to the oil in the oil tank ₂。

The present invention is not limited to the above-described embodiments. The foregoing description of the specific embodiments is intended to describe and illustrate the technical solutions of the present invention, and the above specific embodiments are merely illustrative and not restrictive. Those skilled in the art can make many changes and modifications to the invention without departing from the spirit and scope of the invention as defined in the appended claims.