Device and method for assembling piston pin hole bushing

Abstract

The invention relates to a device and method for assembling a piston pin hole bushing, and relates to the field of mechanical manufacturing. The device and method are used for assembling a bushing on a pin hole of an engine piston, and include a mounting seat, a fixing device, a bushing clamping device and an angle positioning device. The mounting seat includes a base and a support body a and a support body b respectively fixed at two ends of the base, and the fixing device includes a clamping cylinder and a top plate; the piston is placed between the support body a and the support body b, and the two end faces of the piston are respectively in contact with the support body a and the support body b; the bushing clamping device includes a clamp and a moving device, the moving device is fixed on the support body a, and the clamp is connected to the moving device; the angle positioning device includes an angle positioning rod, a limit adjustment sleeve and a limit pin; the invention can achieve higher assembly efficiency and better assembly quality when assembling bushings with an interference amount of ≥0.1, and lower defective product rate under the same conditions, and the overall structure is simple, safe and reliable.

Description

Technical Field

[0001] The invention relates to the field of mechanical manufacturing, and in particular to a piston pin hole bushing assembly device and a bushing assembly method. Background Art

[0002] In order to improve the bearing capacity of the piston pin hole and prevent the pin hole from cracking, the industry usually embeds copper bushings in the piston pin hole. At present, the assembly of the piston pin hole bushing of the internal combustion engine usually adopts the solution of cold installation or a combination of hot and cold installation. For pure manual assembly, there are problems of large assembly position error and low assembly efficiency; and for the automatic assembly fixture method used in the industry, during the assembly process, the frozen bushing must be manually installed on the assembly fixture before assembly can be carried out. During the process of manual contact with the frozen bushing for installation, the bushing will absorb heat and expand, causing the assembly gap to decrease rapidly. This method has the problem of assembly jamming and scrapping for bushings with relatively large interference. If the assembly gap is too small and the assembly tool is forced in, the matching surface of the bushing and the pin hole will be scratched, causing the bushing to fail when the engine is running. Summary of the invention

[0003] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a piston pin hole bushing device and a method for assembling a bushing, which can achieve higher assembly efficiency, better assembly quality and lower defective rate under the same conditions when assembling a bushing with an interference fit ≥0.1.

[0004] The object of the present invention is achieved through the following technical solutions: a piston pin hole bushing assembly device, used for assembling a bushing on a pin hole on an engine piston, wherein one end of the piston is provided with a countersunk inner cavity, the countersunk inner cavity is symmetrical along the axial direction of the piston, and the pin hole penetrates the countersunk inner cavity along a direction perpendicular to the axial direction of the piston, comprising a mounting seat, a fixing device, a bushing clamping device and an angle positioning device; wherein:

[0005] The mounting seat comprises a base and a support body a and a support body b respectively fixed at two ends of the base, the fixing device comprises a clamping cylinder and a top plate, the clamping cylinder is fixed to one end of the support body b, the top plate is located at the other end of the support body b and is connected to the output shaft of the clamping cylinder; the piston is placed between the support body a and the support body b, and the two end faces of the piston are respectively in contact with the support body a and the support body b; the bushing clamping device comprises a fixture and a moving device, the moving device is fixed on the support body a, and the fixture is connected to the moving device; the angle positioning device comprises an angle positioning rod, a limit adjustment sleeve and a limit pin, one end of the limit adjustment sleeve passes through the support body a and is fixedly connected to the support body; the other end of the limit adjustment sleeve is provided with a limit hole; one end of the angle positioning rod passes through the limit adjustment sleeve and is placed in the inner cavity of the countersunk head and is in contact with the inner wall of the inner cavity of the countersunk head, and the shape of one end of the angle limiting rod matches the shape of the inner cavity of the countersunk head; the other end of the angle positioning rod is provided with a strip hole, and the limit pin passes through the limit hole and is connected to the strip hole.

[0006] Preferably, the moving device includes a linear rail bracket, a linear guide rail, a slider and a circumferential limit fork, the linear rail bracket is "L"-shaped, a right-angle plate of the linear rail bracket is fixedly connected to the support body a; the linear guide rail is fixedly connected to another right-angle plate of the linear rail bracket, the slider is placed in the linear guide rail and movably connected to the linear guide rail; one end of the circumferential limit fork is fixedly connected to the slider; one end of the clamp is placed in the fork mouth of the circumferential limit fork and is detachably connected to the circumferential limit fork.

[0007] Preferably, the installation direction of the circumferential limit fork is perpendicular to the installation direction of the linear guide rail; the axial direction of the clamp is perpendicular to the plane formed by the circumferential limit fork and the linear guide rail.

[0008] Preferably, it also includes a stop seat, the diameter of the outer surface of the stop seat matches the diameter of the cavity opening of the countersunk inner cavity; a threaded rod is provided on one end face of the stop seat, a through hole and an external thread are provided in the axial direction of the threaded rod, and the stop seat is fixedly connected to the support body a through the threaded rod; one end face of the stop seat is in contact with one end of the limit adjustment sleeve; the angle limit rod passes through the through hole.

[0009] Preferably, the angle positioning rod, the limit adjustment sleeve, the piston, the output shaft of the clamping cylinder, and the stop seat are all collinear in the axial direction; the axial direction of the clamp is perpendicular to the axial direction of the piston.

[0010] Preferably, the clamp includes a clamping body, a connecting rod, a power bolt, two support frames and two claw pieces, the clamp is a "Z"-shaped structure including an active edge, a connecting edge and a driven edge, one end of the connecting edge is movably connected to the support frame, and the active edge is movably connected to one end of the connecting rod; the connecting rod is placed in the clamping body, a stepped through hole is provided along the axis of the power bolt, a connecting pin is provided between the connecting rod and the power bolt, one end of the connecting pin passes through the small-diameter hole of the stepped through hole and fits with the step of the stepped through hole, and the other end of the connecting pin is fixedly connected to the other end of the connecting rod; one end of the power bolt is placed inside the clamping body and movably connected to the clamping body; the support frame is fixedly connected to the clamping body.

[0011] A method for assembling a bushing of a piston pin hole bushing device, characterized in that it comprises the following steps:

[0012] S1: Use a fixture to clamp the bushing;

[0013] S11: Rotate and retract the power bolt to drive the connecting rod to retract, so that the active side of the clip moves with the connecting rod, thereby causing the passive side of the clip to contract inward;

[0014] S12: Rotate and advance the power bolt to drive the connecting rod forward, so that the active side of the clip moves with the connecting rod, so that the driven side of the clip passes through the inner hole of the bushing and clamps the bushing, and the clamp clamps the bushing;

[0015] S2: Place the bushing and the clamp into liquid nitrogen and freeze for a sufficient time;

[0016] S3: clamping piston;

[0017] S31: The piston is installed on the outer side of the stop seat, pushing the angle positioning rod to move so that one end of the angle positioning rod matches the countersunk inner cavity of the piston;

[0018] S32: Start the clamping cylinder to make the top plate press against the other end of the piston, thereby clamping the piston;

[0019] S4: lining assembly;

[0020] S41: Take the bushing and the fixture out of the liquid nitrogen together, and quickly connect the fixture to the fork of the circumferential limit fork; use the chamfer on the end face of the bushing to fit the bushing into the piston pin hole and make it fit with the angle positioning rod; thereby achieving axial positioning of the bushing;

[0021] S42: According to the actual position of the fixture, the axial limit fork automatically follows the position of the fixture on the guide rail through the slider, ensuring the smooth installation action while controlling the rotation angle of the fixture to achieve accurate installation of the angle;

[0022] S5: When the bushing absorbs heat and expands, the fixture withdraws from the inner hole of the bushing, and the outer wall of the bushing is tightly attached to the inner wall of the piston pin hole.

[0023] The present invention has the following advantages:

[0024] 1. The assembly process of the present invention allows the bushing and the fixture to be assembled together and frozen, and does not contact with other objects to absorb heat before assembly. The air retention time is short, the bushing absorbs less heat and is less likely to expand, which is more conducive to assembly;

[0025] 2. The assembly device of the present invention has simple and flexible clamping operation, especially the clamping and loosening action is fast, and the bushing can be quickly assembled and unassembled, so the assembly time is extremely short, the efficiency is high, and the liquid nitrogen loss is low; when the assembly is abnormal and the bushing has not expanded to tighten the pin hole, there is enough time to take out the bushing again, thereby avoiding the scrapping of the piston and bushing;

[0026] 3. The assembly device of the present invention has high bushing assembly position accuracy, and can better meet the assembly requirements of pistons with complex countersunk inner cavity shapes;

[0027] 4. The assembly process method of the present invention can effectively avoid the problem of bushing jamming and scrapping when assembling a bushing with an interference ratio of ≥0.1 because the assembly speed is faster, the bushing absorbs less heat and expands less, and the actual assembly clearance is larger; under the condition of the same interference ratio, it is more advantageous in avoiding scratches on the matching surfaces of the bushing and the pin hole caused by assembly; therefore, under the same conditions, the assembly process method of the present invention has a lower bushing assembly defective rate, and is therefore more advantageous;

[0028] 5. The assembly process of the present invention can realize the assembly of the piston and the bushing at room temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a structural schematic diagram of a piston pin hole bushing assembly device;

[0030] Figure 2 It is a schematic diagram of the clamp structure in the present invention;

[0031] Figure 3 This is a schematic diagram of the piston structure in the present invention;

[0032] Figure 4 It is an exploded view of the present invention;

[0033] In the figure: 1-angle positioning rod; 2-limit adjustment sleeve; 3-limit pin; 4-support body a; 5-stop seat; 6-line rail bracket; 7-bushing; 8-linear guide; 9-slider; 10-circumferential limit block; 11-clamp; 1101-claw; 1102-support frame; 1103-clamping body; 1104-connecting rod; 1105-connecting pin; 1106-power bolt; 1107-suspension screw; 12-piston; 13-base; 14-top plate; 15-support body b; 16-clamping cylinder. DETAILED DESCRIPTION

[0034] The present invention is further described below in conjunction with the accompanying drawings, but the protection scope of the present invention is not limited to the following description.

[0035] like Figure 1-Figure 4 As shown, a piston pin hole bushing assembly device is used to assemble a bushing 7 on a pin hole on an engine piston 12, wherein one end of the piston 12 is provided with a countersunk cavity, the countersunk cavity is symmetrical along the axial direction of the piston 12, and the pin hole passes through the countersunk cavity along a direction perpendicular to the axial direction of the piston 12, comprising a mounting seat, a fixing device, a bushing 7 clamping device and an angle positioning device; wherein:

[0036] The mounting seat includes a base 13 and a support body a4 and a support body b15 respectively fixed at both ends of the base 13; the fixing device includes a clamping cylinder 16 and a top plate 14; the clamping cylinder 16 is fixed to one end of the support body b15; the top plate 14 is located at the other end of the support body b15 and is connected to the output shaft of the clamping cylinder 16; the piston 12 is placed between the support body a4 and the support body b15, and the two end faces of the piston 12 are respectively in contact with the support body a4 and the support body b15; the bushing 7 clamping device includes a fixture 11 and a moving device, and the moving device is fixed to the Fixed on the support body a4, the clamp 11 is connected to the moving device; the angle positioning device includes an angle positioning rod 1, a limit adjustment sleeve 2 and a limit pin 3, one end of the limit adjustment sleeve 2 passes through the support body a4 and is fixedly connected to the support body; the other end of the limit adjustment sleeve 2 is provided with a limit hole; one end of the angle positioning rod 1 passes through the limit adjustment sleeve 2 and is placed in the countersunk cavity and is attached to the inner wall of the countersunk cavity, and the shape of one end of the angle limit rod matches the shape of the countersunk cavity; the other end of the angle positioning rod 1 is provided with a strip hole, and the limit pin 3 passes through the limit hole and is connected to the strip hole.

[0037] Preferably, the moving device includes a linear rail bracket 6, a linear guide rail 8, a slider 9 and a circumferential limit fork 10, the linear rail bracket 6 is "L"-shaped, a right-angle plate of the linear rail bracket 6 is fixedly connected to the support body a4; the linear guide rail 8 is fixedly connected to another right-angle plate of the linear rail bracket 6, the slider 9 is placed in the linear guide rail 8 and is movably connected to the linear guide rail 8; one end of the circumferential limit fork 10 is fixedly connected to the slider 9; one end of the clamp 11 is placed in the fork mouth of the circumferential limit fork 10 and is detachably connected to the circumferential limit fork 10.

[0038] Preferably, the installation direction of the circumferential limit fork 10 is perpendicular to the installation direction of the linear guide rail 8 ; the axial direction of the clamp 11 is perpendicular to the plane formed by the circumferential limit fork 10 and the linear guide rail 8 .

[0039] Preferably, it also includes a stop seat 5, the diameter of the outer surface of the stop seat 5 matches the diameter of the cavity opening of the countersunk cavity; a threaded rod is provided on one end face of the stop seat 5, a through hole and an external thread are provided in the axial direction of the threaded rod, and the stop seat 5 is fixedly connected to the support body a4 through the threaded rod; one end face of the stop seat 5 is in contact with one end of the limit adjustment sleeve 2; the angle limit rod passes through the through hole.

[0040] Preferably, the angle positioning rod 1 , the limit adjustment sleeve 2 , the piston 12 , the output shaft of the clamping cylinder 16 , and the stop seat 5 are all collinear in the axial direction; the axial direction of the clamp 11 is perpendicular to the axial direction of the piston 12 .

[0041] Preferably, the clamp 11 includes a clamping body 1103, a connecting rod 1104, a power bolt 1106, two support frames 1102 and two claws 1101, the clamp is a "Z"-shaped structure including an active edge, a connecting edge and a driven edge, one end of the connecting edge is movably connected to the support frame 1102, and the active edge is movably connected to one end of the connecting rod 1104; the connecting rod 1104 is placed in the clamping body 1103, and the power bolt 1106 is provided along the axis. There is a stepped through hole, and a connecting pin 1105 is provided between the connecting rod 1104 and the power bolt 1106. One end of the connecting pin 1105 passes through the small-diameter hole of the stepped through hole and fits with the step of the stepped through hole, and the other end of the connecting pin is fixedly connected to the other end of the connecting rod 1104; one end of the power bolt 1106 is placed inside the clamping body 1103 and is movably connected to the clamping body 1103; the support frame 1102 is fixedly connected to the clamping body 1103.

[0042] Preferably, the clamping body 1103 is a "T"-shaped column including a head and a tail, the head is provided with a countersunk hole along the axis, the tail is provided with a through hole along the axis, and the support frame 1102 is placed in the countersunk hole; the tail is provided with an internal thread at the very end, and the power bolt 1106 is provided with an external thread, and the power bolt 1106 is movably connected to the clamp through thread matching.

[0043] Preferably, the outer diameter of the head and the bushing 7 are slightly smaller than the inner diameter of the bushing 7 .

[0044] Preferably, a positioning boss is provided on the connecting surface between the head and the tail, and the positioning boss is located outside the head; the height of the positioning boss matches the thickness of the bushing 7.

[0045] Preferably, the active edge of the claw piece 1101 is provided on a bar through hole, and a through hole is provided on the other end of the connecting rod 1104. The axial direction of the through hole is perpendicular to the axial direction of the connecting rod 1104, and the active edge is connected to the connecting rod 1104 through a pin shaft passing through the through hole and the bar through hole.

[0046] Preferably, the connection between the connecting edge of the claw piece 1101 and the support frame 1102 is located at the turning point from the active edge to the connecting edge; the support frame 1102 and the clamping body 1103 are fixedly connected by screws.

[0047] Preferably, when the claw piece 1101 is opened, the driven edge can fit with an end surface of the bushing 7 , so that the driven edge cooperates with the positioning boss to lock the bushing 7 .

[0048] Preferably, in order to make it easier for the claw piece 1101 to lock the bushing 7, the contact surface between the driven edge and the bushing 7 has a certain inclination.

[0049] Preferably, it also includes a hanging bolt 1107, one end of which is placed in the large-diameter hole of the stepped through hole and fixedly connected by a thread; the other end of the hanging bolt 1107 is connected to the circumferential limit fork 10.

[0050] Preferably, the central axes of the connecting rod 1104, the clamping body 1103, and the power bolt 1106 are all on the same straight line.

[0051] Preferably, the two claw pieces 1101 are spatially symmetrical about the central axis of the clamping body 1103 .

[0052] Preferably, one end of the support body b15 is fixedly connected to the base 13; the other end of the support body b15 is provided with a through hole, the clamping cylinder 16 is fixed to one end of the support body b15 by bolts, and the output shaft of the clamping cylinder 16 passes through the through hole and is coaxially connected to the top plate 14.

[0053] Preferably, one end of the support body a4 is fixedly connected to the base 13; the other end of the support body is fixedly connected to the moving device.

[0054] A method for assembling a piston pin hole bushing device and assembling a bushing 7, characterized in that it comprises the following steps:

[0055] S1: Clamp the bushing 7 using the clamp 11;

[0056] S11: Rotate and retract the power bolt 1106 to drive the connecting rod 1104 to retract, so that the active edge of the clip moves along with the connecting rod 1104, thereby causing the passive edge of the clip to contract inwardly;

[0057] S12: Rotate and advance the power bolt 1106 to drive the connecting rod 1104 forward, so that the active side of the clip moves along with the connecting rod 1104, so that the passive side of the clip passes through the inner hole of the bushing 7 to clamp the bushing 7, and the clamp 11 clamps the bushing 7;

[0058] S2: Put the bushing 7 and the clamp 11 into liquid nitrogen and freeze them for a sufficient time;

[0059] S3: clamping piston 12;

[0060] S31: The piston 12 is installed on the outer surface of the stop seat 5, pushing the angle positioning rod 1 to move so that one end of the angle positioning rod 1 matches the countersunk inner cavity of the piston 12;

[0061] S32: Start the clamping cylinder 16 to make the top plate 14 press against the other end of the piston 12, thereby clamping the piston 12;

[0062] S4: Bushing 7 assembly;

[0063] S41: Take out the bushing 7 and the fixture 11 from the liquid nitrogen, and quickly connect the fixture 11 to the fork of the circumferential limit fork 10; use the chamfer on the end surface of the bushing 7 to install the bushing 7 into the pin hole of the piston 12 and make it fit with the angle positioning rod 1; thereby achieving the axial positioning of the bushing 7;

[0064] S42: According to the actual position of the fixture 11, the axial limit fork automatically follows the position of the fixture 11 on the guide rail through the slider 9, ensuring that the loading action is carried out smoothly and controlling the rotation angle of the fixture 11, thereby achieving accurate installation of the angle;

[0065] S5: When the bushing 7 absorbs heat and expands, the clamp 11 withdraws from the inner hole of the bushing 7, and the outer wall of the bushing 7 is tightly attached to the inner wall of the pin hole of the piston 12.

Claims

1. A piston pin hole bushing assembly device, used for assembling a bushing (7) on a pin hole on an engine piston (12), wherein one end of the piston (12) is provided with a countersunk inner cavity, the countersunk inner cavity is symmetrical along the axial direction of the piston (12), and the pin hole penetrates the countersunk inner cavity in a direction perpendicular to the axial direction of the piston (12). Features: It comprises a mounting seat, a fixing device, a bushing (7), a clamping device and an angle positioning device; wherein: The mounting seat comprises a base (13) and a support body a (4) and a support body b (15) respectively fixed to two ends of the base (13); the fixing device comprises a clamping cylinder (16) and a top plate (14); the clamping cylinder (16) is fixed to one end of the support body b (15); the top plate (14) is located at the other end of the support body b (15) and is connected to the output shaft of the clamping cylinder (16); the piston (12) is placed between the support body a (4) and the support body b (15); the two end surfaces of the piston (12) are respectively in contact with the support body a (4) and the support body b (15); the bushing (7) clamping device comprises a clamp (11) and a moving device; the moving device is fixed to the support body a (4); the clamp (11) ) is connected to the moving device; the angle positioning device comprises an angle positioning rod (1), a limit adjustment sleeve (2) and a limit pin (3); one end of the limit adjustment sleeve (2) passes through the support body a (4) and is fixedly connected to the support body; the other end of the limit adjustment sleeve (2) is provided with a limit hole; one end of the angle positioning rod (1) passes through the limit adjustment sleeve (2) and is placed in the countersunk cavity and abuts against the inner wall of the countersunk cavity, and the shape of one end of the angle limiting rod matches the shape of the countersunk cavity; the other end of the angle positioning rod (1) is provided with a strip hole, and the limit pin (3) passes through the limit hole and is connected to the strip hole. The bushing (7) and the clamp (11) are placed in liquid nitrogen for a sufficient period of time. The clamp (11) comprises a clamping body (1103), a connecting rod (1 104), a power bolt (1106), two support frames (1102) and two claw pieces (1101), and the clamping piece is a "Z"-shaped structure including an active edge, a connecting edge and a driven edge, one end of the connecting edge is movably connected to the support frame (1102), and the active edge is movably connected to one end of a connecting rod (1104); the connecting rod (1104) is placed in a clamping body (1103), a stepped through hole is provided along the axis of the power bolt (1106), a connecting pin (1105) is provided between the connecting rod (1104) and the power bolt (1106), one end of the connecting pin (1105) passes through the small-diameter hole of the stepped through hole and fits with the step of the stepped through hole, and the other end of the connecting pin is fixed to the connecting rod (1104) ) is fixedly connected to the other end of the support body a (4); one end of the power bolt (1106) is placed inside the clamping body (1103) and is movably connected to the clamping body (1103); the support frame (1102) is fixedly connected to the clamping body (1103); the moving device comprises a linear rail bracket (6), a linear guide rail (8), a slider (9) and a circumferential limit fork (10); the linear rail bracket (6) is "L"-shaped; a right-angle plate of the linear rail bracket (6) is fixedly connected to the support body a (4); the linear guide rail (8) is fixedly connected to another right-angle plate of the linear rail bracket (6); the slider (9) is placed inside the linear guide rail (8) and is movably connected to the linear guide rail (8); one end of the circumferential limit fork (10) is fixedly connected to the slider (9);One end of the clamp (11) is placed in the fork of the circumferential limit fork (10) and is detachably connected to the circumferential limit fork (10); it also includes a stopper seat (5), the diameter of the outer side surface of the stopper seat (5) matches the diameter of the cavity opening of the countersunk inner cavity; a threaded rod is provided on one end surface of the stopper seat (5), a through hole and an external thread are provided in the axial direction of the threaded rod, and the stopper seat (5) is fixedly connected to the support body a (4) through the threaded rod; one end surface of the stopper seat (5) is in contact with one end of the limit adjustment sleeve (2); the angle limit rod passes through the through hole. ; 2. A piston pin hole bushing assembly device according to claim 1, Features: The installation direction of the circumferential limit fork (10) is perpendicular to the installation direction of the linear guide rail (8); and the axial direction of the clamp (11) is perpendicular to the plane formed by the circumferential limit fork (10) and the linear guide rail (8).

3. A piston pin hole bushing assembly device according to claim 1, Features: The angle positioning rod (1), the limit adjustment sleeve (2), the piston (12), the output shaft of the clamping cylinder (16), and the stop seat (5) are all collinear in the axial direction; the axial direction of the clamp (11) is perpendicular to the axial direction of the piston (12).

4. A method for assembling a bushing (7) of a piston pin hole bushing device according to any one of claims 1 to 3, Features: The following steps are involved: S1: Clamp the bushing (7) using a clamp (11); S2: Put the bushing (7) and the clamp (11) into liquid nitrogen and freeze them for a sufficient time; S3: clamping piston (12); S4: Bushing (7) assembly; S5: When the bushing (7) absorbs heat and expands, the clamp (11) is withdrawn from the inner hole of the bushing (7), and the outer wall of the bushing (7) is closely attached to the inner wall of the pin hole of the piston (12).

5. A method for assembling a bushing (7) according to claim 4, Features: The specific steps of S1 are as follows: S11: rotating and retracting the power bolt (1106), driving the connecting rod (1104) to retract, causing the active edge of the clip to move along with the connecting rod (1104), thereby causing the passive edge of the clip to contract inwardly; S12: Rotate and advance the power bolt (1106), drive the connecting rod (1104) forward, and make the active side of the clamp follow the movement of the connecting rod (1104), so that the passive side of the clamp passes through the inner hole of the bushing (7) to clamp the bushing (7), and complete the clamping of the bushing (7) by the clamp (11).

6. A method for assembling a bushing (7) according to claim 4, Features: The specific steps of S3 are as follows: S31: The piston (12) is mounted on the outer surface of the stop seat (5) to push the angle positioning rod (1) to move so that one end of the angle positioning rod (1) matches the countersunk inner cavity of the piston (12); S32: Start the clamping cylinder (16) so that the top plate (14) presses against the other end of the piston (12), thereby clamping the piston (12).

7. A method for assembling a bushing (7) according to claim 4, Features: The specific steps of S4 are as follows: S41: The bushing (7) and the fixture (11) are taken out of the liquid nitrogen together, and the fixture (11) is quickly connected to the fork of the circumferential limit fork (10); the chamfer on the end surface of the bushing (7) is used to install the bushing (7) into the pin hole of the piston (12) and make it fit with the angle positioning rod (1); thereby achieving axial positioning of the bushing (7); S42: According to the actual position of the clamp (11), the axial limit fork automatically follows the position of the clamp (11) on the guide rail through the slider (9), thereby ensuring that the loading action is carried out smoothly and controlling the rotation angle of the clamp (11), thereby achieving accurate installation of the angle.

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