A liquid-cooled cable plug and a liquid-cooled cable

Abstract

The present invention discloses a liquid-cooled cable plug and a liquid-cooled cable. The liquid-cooled cable plug includes two conductive pins, two liquid-cooled cables and a pin connector, and the pin connector includes a housing; the liquid-cooled cable includes a coaxial outer tube, an inner tube and a flexible wire located in the inner tube, the housing includes two liquid-cooling cavities, the housing includes two pin holes and two cable holes; the rear part of the conductive pin includes a crimping part and a connecting part, the rear end of the conductive pin includes a stepped hole, and the front part of the connecting part includes a radial through hole communicating with the large hole of the stepped hole; the conductive pin is inserted into the liquid-cooling cavity from the pin hole, and the liquid-cooled cable is inserted into the liquid-cooling cavity from the cable hole; the flexible wire of the liquid-cooled cable is inserted into the small hole of the stepped hole and crimped with the crimping part of the conductive pin; the inner tube of the liquid-cooled cable is sleeved on the rear part of the connecting part. The conductive pin of the present invention has a simple structure, is convenient for manufacturing and assembly, and has good cooling effects for both the conductive pin and the liquid-cooled cable, and both can be fully dissipated of heat.

Description

Technical Field

[0001] The present invention relates to electric vehicle charging equipment, and particularly to a liquid-cooled cable plug and a liquid-cooled cable. Background Art

[0002] With the popularization of electric vehicles, charging equipment is increasingly widely used. The heat generated during the charging process limits the charging speed. The slow charging speed and the heavy and inconvenient charging operation have become an important factor restricting the rapid development of electric vehicles. Although traditional liquid-cooled charging technologies can achieve high-power charging, they generally have obvious limitations.

[0003] A liquid-cooled cable for a new energy electric vehicle charging socket with the patent number CN202020124091.0 includes a socket housing, two liquid-cooled jacks DC+ and DC- arranged in the socket housing, and several signal lines. It also includes two liquid-cooled electrodes for connecting to the DC+ and DC- poles of the vehicle-mounted battery pack, and two liquid-cooled cables respectively connected between the DC+ liquid-cooled jack and the DC+ liquid-cooled electrode, and between the DC- liquid-cooled jack and the DC- liquid-cooled electrode. The liquid-cooled cable includes a flexible wire for conducting electricity, a coolant inner channel and a coolant outer channel for cooling the flexible wire; one end of the coolant inner channel and the coolant outer channel connected to the liquid-cooled electrode is respectively communicated with the liquid inlet and the liquid outlet, and the end connected to the liquid-cooled jack is communicated with the communication cavity. Without increasing the diameter of the existing cable, the current carried by the charging cable is increased from the existing 250A to 600A, and the temperature rise of the charging cable can be ensured within a controllable range. At the same time, it meets the user's requirements for the charging time of electric vehicles. However, the liquid-cooled jack of this utility model includes an inner cavity and an outer cavity, with a complex structure and a relatively large manufacturing difficulty; the heat dissipation performance of the crown spring is not good enough. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a liquid-cooled cable plug with relatively small manufacturing difficulty and good heat dissipation performance.

[0005] Another technical problem to be solved by the present invention is to provide a liquid-cooled cable that matches the above liquid-cooled cable plug.

[0006] To solve the above technical problems, the technical solution adopted by the present invention is a liquid-cooled cable plug, which includes at least one conductive pin, a liquid-cooled cable corresponding to the conductive pin, and a pin connector. The pin connector includes a housing; the liquid-cooled cable includes a coaxial outer tube, an inner tube, and a flexible wire located in the inner tube. The gap between the outer tube and the inner tube is the first liquid flow channel, and the gap between the inner tube and the flexible wire is the second liquid flow channel; the housing includes a liquid-cooled cavity corresponding to the conductive pin. The front end of the housing in the liquid-cooled cavity includes a pin hole corresponding to the conductive pin, and the rear end of the housing in the liquid-cooled cavity includes a cable hole corresponding to the liquid-cooled cable; the rear part of the conductive pin includes a crimping part and a connecting part. The connecting part is located behind the crimping part, and the diameter of the connecting part is larger than that of the crimping part; the rear end of the conductive pin includes a stepped hole. The small hole of the stepped hole passes through the crimping part, and the large hole of the stepped hole is located in the connecting part. The front part of the connecting part includes a radial through hole communicating with the large hole; the rear end of the conductive pin is inserted into the liquid-cooled cavity from the pin hole, and the front end of the liquid-cooled cable is inserted into the liquid-cooled cavity from the cable hole; the front end of the flexible wire of the liquid-cooled cable is inserted into the small hole of the stepped hole and crimped with the crimping part of the conductive pin; the front end of the inner tube of the liquid-cooled cable is sleeved on the rear part of the connecting part, and the second liquid flow channel is communicated with the first liquid flow channel through the radial through hole and the liquid-cooled cavity.

[0007] For the above-mentioned liquid-cooled cable plug, the housing includes a main body, a front end cover, and a rear end cover. The front end cover is fixed to the front end of the main body, and the rear end cover is fixed to the rear end of the main body; the front end cover includes the above-mentioned pin hole, and the rear end cover includes the above-mentioned cable hole; the pin connector includes a connection component corresponding to the conductive pin. The connection component includes a limit bracket. The limit bracket includes a sleeve. The inner hole of the liquid-cooled cavity in the main body is a stepped hole with a smaller front diameter and a larger rear diameter. The sleeve of the limit bracket is arranged in the large hole of the corresponding stepped hole of the liquid-cooled cavity; the front end face of the sleeve abuts against the step of the stepped hole of the main body, and the rear end face of the sleeve abuts against the front end face of the outer tube of the liquid-cooled cable.

[0008] For the above-mentioned liquid-cooled cable plug, the sleeve is a cage grid structure, and the limit bracket includes a plurality of flow guiding strips. The front ends of the flow guiding strips are fixed to the rear end of the inner wall of the sleeve. The plurality of flow guiding strips are arranged separately along the circumferential direction of the sleeve, and the main body parts of the flow guiding strips are inserted into the gap between the outer tube and the inner tube of the liquid-cooled cable.

[0009] For the above-mentioned liquid-cooled cable plug, the connection component includes a pipe clamp. The front end of the inner tube includes a flared mouth. The flared mouth at the front end of the inner tube is sleeved on the rear end of the connecting part of the conductive pin; the pipe clamp is sleeved on the flared mouth of the inner tube.

[0010] For the liquid-cooled cable plug described above, the front end cover is fixed to the body by screws. The middle part of the conductive pin includes a flange. The back of the flange of the conductive pin abuts against the front end cover. The journal behind the flange of the conductive pin and the corresponding pin hole are sealed by a first sealing ring. The rear part of the front end cover includes a positioning sleeve corresponding to the liquid-cooling cavity. The positioning sleeve of the front end cover is inserted into the small hole of the stepped hole of the corresponding liquid-cooling cavity and is sealed with the small hole of the stepped hole of the corresponding liquid-cooling cavity by a second sealing ring. The connecting component includes a cable sealing ring, a sealing sleeve and a flange. The sealing sleeve is inserted into the large hole of the stepped hole of the corresponding liquid-cooling cavity. The outer tube of the liquid-cooled cable passes through the inner hole of the sealing sleeve. The flange of the cable sealing ring is clamped between the front end face of the rear end cover and the rear end face of the body.

[0011] For the liquid-cooled cable plug described above, the rear end cover includes a rear plate and an annular side plate. The rear end of the annular side plate is connected to the rear plate. The annular side plate is sleeved on the outer periphery of the rear end of the body. The outer periphery of the rear end of the body includes a plurality of buckles. The annular side plate includes a plurality of buckle holes. The rear end cover is clamped to the body through the buckles and the buckle holes.

[0012] A liquid-cooled cable includes an outer tube, an inner tube and a flexible wire. The flexible wire is arranged in the inner tube. The outer tube, the inner tube and the flexible wire are coaxial. The gap between the outer tube and the inner tube is the first liquid flow channel. The gap between the inner tube and the flexible wire is the second liquid flow channel.

[0013] For the liquid-cooled cable described above, a plurality of radially connecting rib bars are included between the inner tube and the outer tube.

[0014] For the liquid-cooled cable described above, it includes a spiral support bar or a corrugated pipe. The spiral support bar or the corrugated pipe is arranged on the outer surface of the flexible wire.

[0015] The conductive pin of the present invention has a simple structure, is convenient for manufacturing and assembly, and has good cooling effects for both the conductive pin and the liquid-cooled cable, and can achieve sufficient heat dissipation. Description of the Drawings

[0016] The present invention will be further described in detail below in conjunction with the drawings and specific embodiments.

[0017] Figure 1 is a perspective view of the liquid-cooled cable plug according to an embodiment of the present invention.

[0018] Figure 2 is an exploded view of the liquid-cooled cable plug according to an embodiment of the present invention.

[0019] Figure 3 is a cross-sectional view of the liquid-cooled cable plug according to an embodiment of the present invention.

[0020] Figure 4 is a perspective view of the conductive pin according to an embodiment of the present invention.

[0021] Figure 5It is a perspective view of the limit bracket in the embodiment of the present invention.

[0022] Figure 6 It is an axial sectional view of the liquid-cooled cable in the embodiment of the present invention.

[0023] Figure 7 It is a transverse sectional view of the liquid-cooled cable in the embodiment of the present invention.

[0024] Figure 8 It is a perspective view of the liquid-cooled cable in the embodiment of the present invention. Detailed implementation manners

[0025] The structure of the liquid-cooled cable plug in the embodiment of the present invention is as Figures 1 to 8 shown, including two conductive pins 100, two liquid-cooled cables 200 and a pin connector 300. The liquid-cooled cable plug in the embodiment of the present invention has two conductive pins 100, a positive pole and a negative pole, and corresponding two liquid-cooled cables 200, which can form a complete power transmission line. Although the liquid-cooled cable plug in the embodiment of the present invention shows a double-plug structure of a complete power transmission line, any one of the plugs can be an independent liquid-cooled cable plug.

[0026] The liquid-cooled cable 200 is composed of an insulating sleeve and a flexible wire. The insulating sleeve includes a coaxial outer tube 51 and an inner tube 52. The flexible wire 53 is arranged in the inner tube 52 of the insulating sleeve, and the outer tube 51, the inner tube 52 and the flexible wire 53 are coaxial. The gap between the outer tube 51 and the inner tube 52 is the first liquid flow channel 54, and the gap between the inner tube 52 and the flexible wire 53 is the second liquid flow channel 55. There are 4 radial connecting ribs 56 in the first liquid flow channel 54, that is, between the inner tube 52 and the outer tube 51, to keep the first liquid flow channel 54 unobstructed. A spiral support bar or a corrugated pipe (not shown in the figure) is wound around the outer surface of the flexible wire 53 to make the second liquid flow channel 55 unobstructed. The radial connecting ribs 56 and the spiral support bar or the corrugated pipe enable the liquid-cooled cable 200 to have good bending and compressive properties. The radial connecting ribs 56 combine the outer tube 51 and the inner tube 52 into an integral insulating sleeve, and the insulating sleeve can be mass-produced by a die extrusion process to reduce the cost of the cable.

[0027] The plastic housing of the pin connector 300 includes a body 10, a front end cover 20 and a rear end cover 30. The front end cover 20 is fixed to the front end of the body 10, and the rear end cover 30 is fixed to the rear end of the body 10. There are two liquid-cooled cavities M in the housing. The two ends of the two inner holes 11 of the body 10 are sealed by the front end cover 20 and the rear end cover 30 to form two liquid-cooled cavities M. The inner holes 11 of the liquid-cooled cavities M in the body 10 are stepped holes that are smaller in the front and larger in the rear. The front end cover 20 has two pin holes 21, and the rear end cover 30 has two cable holes 31.

[0028] The front part of the conductive pin 100 has a conductive pin 41, the middle part has a flange 42, and the rear part successively includes a crimping part 43 and a connecting part 44. The diameter of the connecting part 44 is larger than that of the crimping part 43. There is an axial stepped hole 45 at the rear end of the conductive pin 100. The large hole 451 of the stepped hole 45 is located in the connecting part 44, and the small hole 452 of the stepped hole passes through the crimping part 43. There is a radial through hole 46 communicating with the large hole 451 at the front part of the connecting part 44.

[0029] The rear end of the conductive pin 100 is inserted into the liquid cooling cavity M from the pin hole 21 of the front end cover 20, and the front end of the liquid cooling cable 200 is inserted into the liquid cooling cavity M from the cable hole 31. The front end of the flexible wire 53 of the liquid cooling cable 200 is inserted into the small hole of the stepped hole and crimped with the crimping part 43 of the conductive pin 100.

[0030] There is a flared mouth 521 at the front end of the inner tube 52. The flared mouth 521 at the front end of the inner tube 52 is sleeved on the rear end of the connecting part 44 of the conductive pin 100. The pipe clamp 57 is sleeved on the flared mouth 521 of the inner tube 52 to fix the inner tube 52 to the connecting part 44 of the conductive pin 100.

[0031] The second liquid flow channel 55 communicates with the liquid cooling cavity M through the radial through hole 46, and the liquid cooling cavity M communicates with the first liquid flow channel 54.

[0032] The front end cover 20 is fixed on the body 10 by screws (not shown in the figure). The rear end face of the flange 52 in the middle of the conductive pin 100 abuts against the front end cover 20. The journal behind the flange 52 in the middle of the conductive pin 100 and the corresponding pin hole 21 are sealed by a first sealing ring 22. There are two positioning sleeves 23 corresponding to the liquid cooling cavity M at the rear part of the front end cover 20. The positioning sleeve 23 of the front end cover 20 is inserted into the small hole 111 of the stepped hole of the corresponding liquid cooling cavity M and sealed with the small hole 111 of the stepped hole of the corresponding liquid cooling cavity M by a second sealing ring 24.

[0033] The pin connector 300 includes a connection component corresponding to the liquid cooling cavity M, and the connection component includes a limit bracket 13 and a cable sealing ring 32.

[0034] The cable sealing ring 32 includes a sealing sleeve 321 and a flange 322. The sealing sleeve 321 is inserted into the large hole 112 of the stepped hole of the corresponding liquid cooling cavity M, and the outer tube 51 of the liquid cooling cable 200 passes through the inner hole of the sealing sleeve 321. The flange 322 of the cable sealing ring 32 is clamped between the front end face of the rear end cover 30 and the rear end face of the body 10.

[0035] The rear end cover 30 includes a rear plate 33 and an annular side plate 34, and the rear end of the annular side plate 34 is connected to the rear plate 33. The annular side plate 34 is sleeved on the outer periphery of the rear end of the body 10, and there are a plurality of buckles 12 on the outer periphery of the rear end of the body 10. The annular side plate 34 has a plurality of corresponding buckle holes 35, and the rear end cover 30 is snap-connected to the body 10 through the buckles 12 and the buckle holes 35.

[0036] The limit bracket 13 includes a sleeve 131 and a plurality of flow guiding strips 132. The sleeve of the limit bracket 13 is arranged in the large hole 112 of the stepped hole of the corresponding liquid cooling cavity M. The front end face of the sleeve 131 abuts against the step 113 in the middle of the stepped hole of the body 10, and the rear end face of the sleeve 131 abuts against the front end face of the outer tube 51 of the liquid cooling cable 200.

[0037] The sleeve 131 is of a squirrel cage grid structure. The front ends of the flow guiding strips 132 are fixed to the rear end of the inner wall of the sleeve 131. The plurality of flow guiding strips 132 are arranged separately along the circumferential direction of the sleeve 131. The main parts of the flow guiding strips 132 are inserted into the gap between the outer tube 51 and the inner tube 52 of the liquid cooling cable 200 to play a role in supporting the pipe wall.

[0038] As Figure 3 shown, a large amount of heat is generated during the contact conduction of the conductive plug 100. Whether the heat generated by the conductive plug 100 can be taken away in time limits the improvement of the charging power. The heat generation of the conductive plug 100 is most concentrated at the crimping part 43. The coolant in the second liquid flow channel enters the large hole 451 of the stepped hole 45 of the conductive plug 100, and then enters the liquid cooling cavity M through the radial through hole 46. The circulating coolant fully contacts the rear part of the conductive plug 100 in the liquid cooling cavity M and takes away a large amount of heat, so that the conductive plug 100 can be fully cooled. Under the fluid pressure provided by the cold source liquid pump, the coolant flows out of the liquid cooling cavity M, enters the liquid cooling cable 200, and returns to the cold source along the first liquid flow channel 54 of the liquid cooling cable 200. The conductive plug 100, the two liquid cooling cables 200 and the plug connector 300 cooperate with the cold source to form a complete coolant circulation system, and all can be fully cooled.

[0039] The assembly process of the liquid-cooled cable plug in the embodiment of the present invention is as follows: The rear part of the conductive pin 100 penetrates into the pin hole 21 of the front end cover 20, and on the other side, the liquid-cooled cable 200 sequentially passes through the rear end cover 30, the cable sealing ring 32, the limiting bracket 13, and the body 10. According to the assembly requirements, the lengths of the outer tube 51, the inner tube 52, and the flexible wire 53 of the cable 100 are cut into a stepped shape, with the flexible wire 53 being the longest, the inner tube 52 being the second longest, and the outer tube 51 being the shortest. The front end of the flexible wire 53 is inserted into the small hole of the stepped hole of the conductive pin 100 and is to be crimped with the crimping part 43 of the conductive pin 100. The connecting part 44 of the electrical pin 100 is inserted into the flared opening 521 at the front end of the inner tube 52 of the liquid-cooled cable 200. The flared opening 521 at the front end of the inner tube 52 is locked with an annular pipe clamp 57. Then, a tool is used to crimp the crimping part 43 of the conductive pin 100 with the front end of the flexible wire 53.

[0040] After the locking of the front end of the inner tube 52 of the liquid-cooled cable 200 and the crimping of the front end of the flexible wire 53 are completed, multiple flow guiding strips 132 of the limiting bracket 13 are inserted into the first liquid flow channel 54 at the end of the outer tube 51. The length of the liquid-cooled cable 200 is arranged, and the front end cover 20 and the rear end cover 30 are assembled to both ends of the body 10, completing the assembly of the liquid-cooled cable plug in the embodiment of the present invention. Among them, the fixing method of the sealing cover 7 to the body 10 can be screw connection, ultrasonic welding, or glue bonding.

[0041] The liquid-cooled cable plug in the above embodiments of the present invention has the following characteristics:

[0042] 1) The conductive pin structure of the present invention is simple, facilitating manufacturing and assembly. The cooling effects of the conductive pin and the liquid-cooled cable are good, and both can be fully cooled.

[0043] 2) The liquid-cooled cable has two concentric flow channels, and the flexible wire is included in the inner flow channel. The two layers of flow channels are adjacent radially. The flow directions of the coolant in the two layers of flow channels are opposite.

[0044] 3) There are support ribs between the inner tube and the outer tube of the liquid-cooled cable, and the support ribs and the outer wall of the flow channel can be formed by die extrusion. The support ribs have two functions. One is that the outer walls of the inner flow channel and the outer flow channel are connected into a whole through the ribs, and the other is that the ribs play a good role in supporting and maintaining the shape of the outer wall of the flow channel.

[0045] 4) The liquid-cooled cavity of the pin connector and the liquid-cooled cable form an independent liquid-cooled circulation loop. The fluid in the inner flow channel of the liquid-cooled cable comes from the cold source, flows into the liquid-cooled cavity of the pin connector through the radial through hole at the rear of the conductive pin, and then flows back to the cold source along the outer flow channel of the liquid-cooled cable. The flexible wire is completely immersed in the coolant in the inner flow channel, and has a good heat dissipation effect.

[0046] 5) The wire crimping of the conductive pin is separated from the coolant diversion area, and the crimping part of the conductive pin and the wire is before the diversion area, without affecting the flow of the coolant through the cavity and the radial through holes at the rear of the conductive pin. Moreover, the outer diameter of the flexible wire is smaller than the inner diameter of the large hole of the stepped hole at the rear of the conductive pin, and the front end of the inner tube of the liquid-cooled cable includes a flared mouth, which is convenient for connecting the liquid-cooled cable to the conductive pin.

[0047] 6) The inner hole of the liquid-cooled cavity of the pin connector is a stepped hole, and there is a limiting step in the middle of the stepped hole. The sleeve of the limiting bracket is arranged between the limiting step and the front end face of the outer tube of the liquid-cooled cable, so as to form a firm and stable liquid-cooled connector module.

[0048] The flexible wire of the liquid-cooled cable is immersed in the fluid of the inner flow channel, and a spiral support bar or a metal bellows is wound around the conductor periphery, so that the liquid-cooled cable has good bending and compressive resistance performance and ensures the smoothness of the inner flow channel.

Claims

1. A liquid-cooled cable plug, comprising at least one conductive pin and a liquid-cooled cable corresponding to the conductive pin, characterized in that, It includes a pin connector, and the pin connector includes a housing; the liquid-cooled cable includes a coaxial outer tube, an inner tube, and a flexible wire located in the inner tube. The gap between the outer tube and the inner tube is the first liquid flow channel, and the gap between the inner tube and the flexible wire is the second liquid flow channel; the housing includes a liquid-cooled cavity corresponding to the conductive pin. The housing includes a pin hole corresponding to the conductive pin at the front end of the liquid-cooled cavity, and the housing includes a cable hole corresponding to the liquid-cooled cable at the rear end of the liquid-cooled cavity; the rear part of the conductive pin includes a crimping part and a connecting part. The connecting part is located behind the crimping part, and the diameter of the connecting part is larger than that of the crimping part; the rear end of the conductive pin includes a stepped hole. The small hole of the stepped hole passes through the crimping part, and the large hole of the stepped hole is located in the connecting part. The front part of the connecting part includes a radial through hole communicating with the large hole; the rear end of the conductive pin is inserted into the liquid-cooled cavity from the pin hole, and the front end of the liquid-cooled cable is inserted into the liquid-cooled cavity from the cable hole; the front end of the flexible wire of the liquid-cooled cable is inserted into the small hole of the stepped hole and crimped with the crimping part of the conductive pin; the front end of the inner tube of the liquid-cooled cable is sleeved on the rear part of the connecting part, and the second liquid flow channel communicates with the first liquid flow channel through the radial through hole and the liquid-cooled cavity; the housing includes a main body, a front end cover, and a rear end cover. The front end cover is fixed to the front end of the main body, and the rear end cover is fixed to the rear end of the main body; the front end cover includes the said pin hole, and the rear end cover includes the said cable hole; the pin connector includes a connection assembly corresponding to the conductive pin. The connection assembly includes a limit bracket. The limit bracket includes a sleeve. The inner hole of the liquid-cooled cavity in the main body is a stepped hole with a smaller front and a larger rear. The sleeve of the limit bracket is arranged in the large hole of the corresponding stepped hole of the liquid-cooled cavity; the front end face of the sleeve abuts against the step of the stepped hole of the main body, and the rear end face of the sleeve abuts against the front end face of the outer tube of the liquid-cooled cable.

2. The liquid-cooled cable plug according to claim 1, wherein, The sleeve is of a squirrel-cage grid structure. The limit bracket includes a plurality of guide bars. The front ends of the guide bars are fixed to the rear end of the inner wall of the sleeve. The plurality of guide bars are arranged separately along the circumferential direction of the sleeve. The main part of the guide bar is inserted into the gap between the outer tube and the inner tube of the liquid-cooled cable.

3. The liquid-cooled cable plug according to claim 1, characterized in that, The connection assembly includes a pipe clamp. The front end of the inner tube includes a flared mouth. The flared mouth at the front end of the inner tube is sleeved on the rear end of the connecting part of the conductive pin; the pipe clamp is sleeved on the flared mouth of the inner tube.

4. The liquid-cooled cable plug according to claim 1, characterized in that, The front end cover is fixed to the main body by screws. The middle part of the conductive pin includes a flange. The back of the flange of the conductive pin abuts against the front end cover. The journal behind the flange of the conductive pin and the corresponding pin hole are sealed by a first sealing ring; the rear part of the front end cover includes a positioning sleeve corresponding to the liquid-cooled cavity. The positioning sleeve of the front end cover is inserted into the small hole of the corresponding stepped hole of the liquid-cooled cavity and is sealed with the small hole of the corresponding stepped hole of the liquid-cooled cavity by a second sealing ring; the connection assembly includes a cable sealing ring. The cable sealing ring seals the sleeve and the flange; the sealing sleeve is inserted into the large hole of the corresponding stepped hole of the liquid-cooled cavity, and the outer tube of the liquid-cooled cable passes through the inner hole of the sealing sleeve; the flange of the cable sealing ring is clamped between the front end face of the rear end cover and the rear end face of the main body.

5. The liquid-cooled cable plug according to claim 1, characterized in that, The rear end cover includes a rear plate and an annular side plate. The rear end of the annular side plate is connected to the rear plate; the annular side plate is sleeved on the outer periphery of the rear end of the main body. The outer periphery of the rear end of the main body includes a plurality of buckles, and the annular side plate includes a plurality of buckle holes. The rear end cover is clamped with the main body through the buckles and the buckle holes.

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