CN108562419B - Free piston buffer gear - Google Patents

Free piston buffer gear Download PDF

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Publication number
CN108562419B
CN108562419B CN201711373527.9A CN201711373527A CN108562419B CN 108562419 B CN108562419 B CN 108562419B CN 201711373527 A CN201711373527 A CN 201711373527A CN 108562419 B CN108562419 B CN 108562419B
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free piston
ring
bottom plate
buffer
inner sleeve
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CN201711373527.9A
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CN108562419A (en
Inventor
李辰
陈星�
王玉东
宋可清
马雁捷
谌君谋
张冰冰
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China Academy of Aerospace Aerodynamics CAAA
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China Academy of Aerospace Aerodynamics CAAA
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    • GPHYSICS
    • G01MEASURING; TESTING
    • G01MTESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G01M9/00Aerodynamic testing; Arrangements in or on wind tunnels
    • G01M9/02Wind tunnels
    • G01M9/04Details

Abstract

The invention relates to a free piston buffer mechanism, which comprises an installation bottom plate, an inner sleeve, a one-way valve, a spring, a buffer rubber slide block and a tail end limiting ring, wherein the installation bottom plate is provided with a first end and a second end; the mounting bottom plate is mounted at the tail end of the wind tunnel compression pipe and used for positioning and mounting other buffer mechanism components; after the free piston collides with the free piston buffer mechanism, the rubber slide block moves backwards, the spring is compressed to provide buffer force, meanwhile, the cavity B is reduced, the pressure in the cavity B rises, and the gas in the cavity B provides buffer force. The invention realizes the effective buffering of the free piston with high speed at the tail end in the free piston shock tunnel, eliminates the influence of the pressure change of the inner cavity at the tail end of the compression pipe on the buffering effect, has compact structure and can improve the safety of the operation of the wind tunnel.

Description

Free piston buffer gear
Technical Field
The invention relates to a free piston buffer mechanism, which is applied to an environment needing to buffer the high-speed impact action of the tail end of a free piston in a free piston shock tunnel and belongs to the field of buffer mechanisms.
Background
In the free piston shock wave wind tunnel, a free piston running at high speed in a compression pipe is a core component of a wind tunnel driving section and is used for forward compression to generate high-temperature high-pressure gas meeting the test requirements. However, the free piston, which runs at a high speed, tends to have a high speed when moving to the end of the compression tube, so that a direct collision occurs in a state of a high pressure at the end of the compression tube. If the speed is not enough when the piston runs to the tail end of the compression pipe for the first time, the piston rebounds under the action of the high pressure at the front end of the piston, after rebounding for a certain distance, the front pressure of the piston is rapidly reduced to a very low state, the piston is accelerated again by the pressure at the rear end, the pressure at the front end of the piston is very low at the moment, and gas flows into components such as a downstream shock tube, a test section and the like, the pressure cannot be increased again, so that the piston can move to the tail end of the compression pipe at a high speed to generate rebound collision.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide a free piston buffer mechanism which has sufficient and stable buffer effect on a piston, prevents the free piston or a film clamping mechanism structure at the tail end from being damaged by collision and ensures the safe operation of a free piston shock tunnel.
The purpose of the invention is realized by the following technical scheme:
the utility model provides a free piston buffer gear, free piston removes in the compression pipe which characterized in that: comprises a mounting bottom plate, an inner sleeve, a one-way valve, a spring and a buffer rubber slide block;
the bottom plate is of a circular ring structure and is fixed at the tail end of the compression pipe;
the inner sleeve is vertical to the bottom plate, and the rear section of the side wall is provided with a one-way valve;
the buffer rubber slide block and the sleeved spring are sleeved outside the inner sleeve, and the spring is arranged between the buffer rubber slide block and the bottom plate;
the outer wall of the inner sleeve, the inner wall of the pipe diameter, the rear end face of the buffer rubber slide block and the front end face of the mounting bottom plate form a closed space; when the gas pressure in the inner sleeve is higher than the gas pressure in the closed space, the gas can enter the closed space through the one-way valve; the free piston runs to the rear end of the compression pipe at a certain speed and collides with the buffer rubber slide block.
Preferably, the buffer rubber slide block further comprises an end limiting ring for limiting the axial position of the buffer rubber slide block.
Preferably, the inner wall surface of the buffer rubber slider and the outer wall surface of the inner sleeve form a sliding friction pair, and a gap is reserved between the outer wall surface and the inner wall surface of the compression pipe.
Preferably, the buffer rubber slide block comprises a chassis and a rubber block; the chassis comprises a bottom ring, a side wall and a rubber block fixing ring, wherein the bottom ring is a circular ring, the side wall is a cylinder, the bottom ring is vertically arranged at the bottom end of the side wall, the rubber block fixing ring is of a circular ring structure and is arranged at the middle rear part of the side wall, and the outer diameter of the rubber block fixing ring is smaller than that of the bottom ring; the rubber block is arranged on the bottom ring, outside the side wall and forms a cylinder shape with the chassis.
Preferably, the free piston moves axially in the compression tube and the free piston cushioning mechanism is mounted coaxially with the compression tube.
Preferably, the outer ring side of the upper surface of the mounting bottom plate is provided with a mounting spigot which is matched and fixed with a spigot at the tail end of the compression pipe; the inner side of the inner ring of the upper surface is provided with a positioning spigot installation inner sleeve.
Preferably, the spring is a large-diameter cylindrical spiral spring or a disc spring.
Preferably, the spring is a disc spring, and a plurality of vent holes are arranged on the reed.
Preferably, the mounting base plate is clamped between the end of the compression tube and the diaphragm clamping means.
Preferably, the inner diameters of the mounting bottom plate and the inner sleeve are the same and are not smaller than the inner diameter of the shock tube.
Compared with the prior art, the invention has the following advantages:
(1) the free piston buffer mechanism solves the problem that the high-pressure air buffer effect is influenced by the change of the tail end pressure of the compression pipe under two collision modes of direct collision and rebound collision of the free piston. Utilize three kinds of combination buffering forms of rubber backing ring buffering, high-pressure gas ring chamber buffering, major diameter spring buffering, provide high-efficient, stable cushioning effect, guaranteed that free piston can not take place structural damage when the terminal higher speed striking.
(2) The invention utilizes the comprehensive superposition of the buffering force provided by the spring and the buffering force provided by the gas in the cavity to provide the buffering force which is close to linear with the displacement of the slide block, thereby ensuring the stable increase of the total buffering force.
(3) The invention realizes effective buffering of the free piston still having high speed at the tail end in the free piston shock tunnel, eliminates the influence of the pressure change of the inner cavity at the tail end of the compression pipe on the buffering action, has compact structure and can improve the safety of the operation of the tunnel.
Drawings
FIG. 1 is a schematic structural view of a free piston cushioning mechanism of the present invention;
FIG. 2 is a schematic diagram of the free piston cushioning mechanism of the present invention after impact;
FIG. 3 is a schematic view of the free piston cushioning mechanism of the present invention installed;
FIG. 4 is a schematic structural view of a buffer rubber slide block;
FIG. 5 is a schematic diagram of a variation curve of the damping force according to the present invention.
Detailed Description
The invention will be described in further detail with reference to the accompanying drawings and specific embodiments.
Referring to fig. 3, the wind tunnel body includes a compression tube 8 and a shock tube 11, and the membrane 10 is held between the compression tube 8 and the shock tube 11 by a clamping mechanism. The free piston 7 is arranged in the compression pipe 8 and can freely move to the tail end of the compression pipe 8 along the axial direction, and if the speed of the free piston 7 is still high when the free piston runs to the tail end of the compression pipe 8, the free piston 7 can directly collide with a clamping mechanism of the diaphragm 10 to cause damage. Therefore, the invention adds a free piston buffer mechanism 9 which is arranged at the tail section of the compression pipe 8 and the front part of the clamping mechanism of the diaphragm 10.
With reference to fig. 1, the free piston buffering mechanism suitable for buffering the impact action of the motion tail end of the free piston in the free piston shock tunnel comprises an installation bottom plate 1, an inner sleeve 2, a one-way valve 3, a spring 4, a buffering rubber slide block 5 and a tail end limiting ring 6. The free piston 7 moves axially in the compression tube 8, the piston axis coincides with the compression tube, and the damping mechanism is mounted coaxially with the compression tube 8. The schematic diagram after the collision is seen in fig. 2.
The mounting bottom plate 1 is of a circular ring structure, the inner diameter of the mounting bottom plate is the same as the ventilation diameter of the membrane clamping mechanism and is not smaller than the inner diameter of the shock tube 11, and the mounting bottom plate 1 is clamped between the tail end of the compression tube 8 and the membrane 10 clamping mechanism; the upper surface of the mounting base plate 1 is provided with a mounting spigot which is matched and fixed with a spigot at the tail end of the compression pipe 8, and the coincidence of the axis of the mounting base plate 1 and the axis of the compression pipe 8 is ensured. The left side of the mounting bottom plate is provided with a diaphragm 10, and the right side is provided with a positioning spigot and other structures for positioning and mounting the inner sleeve 2.
The inner sleeve 2 is of a long cylindrical structure. Is installed on the installation bottom plate 1 through the positioning spigot of the installation bottom plate 1. The inner diameter of the inner sleeve is the same as the ventilation diameter of the film clamping mechanism and is used for leading out test airflow. The outer diameter is matched with the buffer rubber slide block 5 to provide movement restriction of the rubber slide block. The front end of the inner sleeve is provided with threads for mounting the tail end limiting ring 6.
The non-return valve 3 is mounted in the rear wall of the inner sleeve in the radial direction of the latter. The rear end face of the buffer rubber slide block (5), the front end face of the mounting base plate 1, the outer wall face of the inner sleeve 2 and the inner wall face of the compression pipe 8 form a closed annular cavity B. The inner space of the inner sleeve 2 is communicated with the end space of the compression pipe and is a cavity A. The direction of the air flow passage of the one-way valve is the direction from the inner surface to the outer surface of the inner sleeve, and when the piston compresses the gas at the tail end of the compression pipe to cause the pressure of the inner cavity of the inner sleeve, namely the cavity A to rise, a part of high-pressure gas flows into the outer cavity of the inner sleeve, namely the cavity B from the cavity A through the one-way valve to form buffer gas. When the diaphragm clamped behind the mounting bottom plate is broken, particularly when secondary impact occurs after the piston rebounds, the pressure of the cavity A is greatly reduced, high-pressure gas sealed in the cavity B is blocked by the one-way valve and cannot be discharged quickly, and the pressure of buffer gas, namely the stability of the buffer performance of the buffer mechanism, is ensured.
The spring 4 is sleeved between the inner wall surface of the compression pipe and the outer wall surface of the inner sleeve and is a large-diameter cylindrical spiral spring, a disc spring and the like. In the case of a disc spring, enough vent holes need to be arranged on the reed, so that the space of the cavity B is not separated. The spring is sleeved outside the inner sleeve and is positioned and restrained by the inner wall surface of the compression pipe. The spring is used for keeping the buffer rubber slide block at the front part of the inner sleeve when no impact occurs and providing a part of buffer acting force when the collision occurs.
Referring to fig. 4, the buffer rubber slide block 5 is a middle hardness rubber block 5.2 which is annularly die-cast on the chassis 5.1. The chassis 5.1 includes that end ring, lateral wall and the solid fixed ring of block rubber, and the end ring is the ring, and the lateral wall is the drum, and the end ring sets up the bottom at the lateral wall perpendicularly, and the solid fixed ring of block rubber sets up the well rear portion at the lateral wall for the ring structure, and the solid fixed ring's of block rubber external diameter is less than the external diameter of end ring. The rubber block 5.2 is arranged on the bottom ring, outside the side wall, and forms a cylinder with the chassis 5.1.
The inner wall surface of the side wall of the chassis 5.1 and the outer wall surface of the inner sleeve 2 form a sliding friction pair, and a certain gap is formed between the outer wall surface and the inner wall surface of the compression pipe. The buffer rubber slide block 5 is used for buffering the impact generated by the contact of the piston with the buffer mechanism and providing partial buffer action.
The tail end limiting ring 6 is an internal thread circular ring, is screwed on a thread pair on the outer wall of the front end of the inner sleeve and is used for limiting the axial movement of the buffer rubber slide block and cannot be separated from the inner sleeve.
After the wind tunnel test is started, the free piston moves backwards to compress the gas in the compression pipe 8, so that the pressure in the cavity A is rapidly increased, a part of high-pressure gas flows into the cavity B from the cavity A through the one-way valve, the pressure in the cavity B is increased, and the pressure reaches the highest value equivalent to the pressure in the cavity A. When the pressure in the cavity A is rapidly reduced after the diaphragm 10 is broken, and the free piston 7 collides with the free piston buffer mechanism 9, the rubber slide block 5 moves backwards, the spring is compressed to provide buffer force, meanwhile, the cavity B is reduced, the pressure in the cavity B is increased, and the gas in the cavity B provides buffer force.
With reference to fig. 5, the horizontal axis represents the displacement of the rubber slider 5, the vertical axis F represents the magnitude of the damping force, wherein the curve 1 represents the damping force provided by the spring, the curve 3 represents the damping force provided by the gas in the cavity B, and the curve 2 represents the total damping force provided by the spring and the gas in the cavity B, and the total damping force provided steadily increases as the displacement of the rubber slider 5 increases. It can be seen from this figure that the spring does not provide sufficient cushioning force to the compression end, but the compressed gas provides greater cushioning force, ensuring an overall cushioning effect.
The invention is suitable for the end buffering of a heavy piston with large diameter, and the buffering force provided by compressed gas can reach 7 x 10 at most6N。
The above description is only for the best mode of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention.
Those skilled in the art will appreciate that the invention may be practiced without these specific details.

Claims (10)

1. A free piston cushioning mechanism, a free piston (7) moving within a compression tube (8), characterized by: comprises a mounting bottom plate (1), an inner sleeve (2), a one-way valve (3), a spring (4) and a buffer rubber slide block (5);
the bottom plate (1) is of a circular ring structure and is fixed at the tail end of the compression pipe (8);
the inner sleeve (2) is vertical to the bottom plate (1), and the rear section of the side wall is provided with a one-way valve (3);
the buffering rubber sliding block (5) and the sleeving spring (4) are sleeved outside the inner sleeve (2), and the spring (4) is arranged between the buffering rubber sliding block (5) and the bottom plate (1);
the outer wall of the inner sleeve (2), the pipe diameter inner wall of the compression pipe, the rear end face of the buffer rubber slide block (5) and the front end face of the mounting bottom plate (1) form a closed space; when the gas pressure in the inner sleeve (2) is higher than the gas pressure in the closed space, gas can enter the closed space through the one-way valve (3); the free piston (7) runs to the rear end of the compression pipe (8) at a certain speed to collide with the buffer rubber slide block (5).
2. The free piston cushioning mechanism of claim 1, wherein: the buffer rubber slide block structure further comprises a tail end limiting ring (6) for limiting the axial position of the buffer rubber slide block (5).
3. The free piston cushioning mechanism of claim 1 or 2, wherein: the inner wall surface of the buffer rubber slide block (5) and the outer wall surface of the inner sleeve (2) form a sliding friction pair, and a gap is reserved between the outer wall surface of the buffer rubber slide block (5) and the inner wall surface of the compression pipe.
4. The free piston cushioning mechanism of claim 1 or 2, wherein: the buffer rubber sliding block (5) comprises a chassis (5.1) and a rubber block (5.2); the chassis (5.1) comprises a bottom ring, a side wall and a rubber block fixing ring, wherein the bottom ring is a circular ring, the side wall of the chassis is a cylinder, the bottom ring is vertically arranged at the bottom end of the side wall of the chassis, the rubber block fixing ring is of a circular ring structure and is arranged at the middle rear part of the side wall of the chassis, and the outer diameter of the rubber block fixing ring is smaller than that of the bottom ring; the rubber block (5.2) is arranged on the bottom ring, and the side wall of the chassis and the chassis (5.1) form a cylinder shape.
5. The free piston cushioning mechanism of claim 1 or 2, wherein: the free piston (7) moves in the compression pipe (8) along the axial direction, and the free piston buffer mechanism is coaxially arranged with the compression pipe (8).
6. The free piston cushioning mechanism of claim 1 or 2, wherein: an installation seam allowance is arranged on the outer ring side of the upper surface of the installation bottom plate (1) and is matched and fixed with a seam allowance at the tail end of the compression pipe (8); and a positioning spigot mounting inner sleeve (2) is arranged on the inner ring side of the upper surface of the mounting bottom plate.
7. The free piston cushioning mechanism of claim 1 or 2, wherein: the spring (4) is a large-diameter cylindrical spiral spring or a disc spring.
8. The free piston cushioning mechanism of claim 1 or 2, wherein: the spring (4) is a disc spring, and a plurality of vent holes are formed in the reed.
9. The free piston cushioning mechanism of claim 1 or 2, wherein: the mounting base plate (1) is clamped between the tail end of the compression pipe (8) and the diaphragm (10) clamping mechanism when applied to the wind tunnel.
10. The free piston cushioning mechanism of claim 1 or 2, wherein: the inner diameters of the mounting bottom plate (1) and the inner sleeve (2) are the same and are not smaller than the inner diameter of the shock tube (11).
CN201711373527.9A 2017-12-19 2017-12-19 Free piston buffer gear Active CN108562419B (en)

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Application Number Priority Date Filing Date Title
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CN108562419B true CN108562419B (en) 2020-05-12

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Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113029507B (en) * 2021-03-23 2022-07-05 中国空气动力研究与发展中心超高速空气动力研究所 Device and method for measuring speed of tail end of piston compression pipe
CN114235326A (en) * 2021-11-30 2022-03-25 中国航天空气动力技术研究院 Free piston shock tunnel quality buffer mechanism

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1993001393A1 (en) * 1991-07-10 1993-01-21 Wbm Pty. Ltd. Piston motion control in free piston driver
JPH07159278A (en) * 1993-12-07 1995-06-23 Mitsubishi Heavy Ind Ltd Impact wind tunnel
JP2000275136A (en) * 1999-03-26 2000-10-06 Mitsubishi Heavy Ind Ltd Circulation-type wind tunnel for experiment
CN105683611A (en) * 2013-11-08 2016-06-15 Kyb株式会社 Shock absorber device
CN106763413A (en) * 2016-12-21 2017-05-31 中国航天空气动力技术研究院 A kind of free-piston two-stage buffering stop stop mechanism
CN106840579A (en) * 2016-12-07 2017-06-13 中国航天空气动力技术研究院 A kind of variable cross-section weight piston compressor

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1993001393A1 (en) * 1991-07-10 1993-01-21 Wbm Pty. Ltd. Piston motion control in free piston driver
JPH07159278A (en) * 1993-12-07 1995-06-23 Mitsubishi Heavy Ind Ltd Impact wind tunnel
JP2000275136A (en) * 1999-03-26 2000-10-06 Mitsubishi Heavy Ind Ltd Circulation-type wind tunnel for experiment
CN105683611A (en) * 2013-11-08 2016-06-15 Kyb株式会社 Shock absorber device
CN106840579A (en) * 2016-12-07 2017-06-13 中国航天空气动力技术研究院 A kind of variable cross-section weight piston compressor
CN106763413A (en) * 2016-12-21 2017-05-31 中国航天空气动力技术研究院 A kind of free-piston two-stage buffering stop stop mechanism

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