High-stability motor

Abstract

The invention relates to the technical field of motors, and discloses a high-stability motor, which comprises a casing, an output shaft is rotatably connected in the casing, the two ends of the output shaft are a first end and a second end respectively, and a connecting piece is arranged at the position, close to the first end, in the casing; the stop assembly comprises a stop piece and a gasket, the stop piece is arranged in the machine shell, the first end abuts against the stop piece, the gasket is arranged on the outer side of the output shaft in a sleeving mode, the gasket is arranged on the side, away from the first end, of the connecting piece in a spaced mode, and the distance that the gasket can move towards the connecting piece is the stop distance. When the output shaft axially moves towards the connecting piece by the stopping distance, the gasket abuts against the connecting piece, the situation that the output shaft abrades through a machine shell is effectively prevented, the working stability of the output shaft is improved, and the overall service life is prolonged.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electric machines, and particularly relates to a high-stability electric machine. BACKGROUND

[0002] The electric machine is internally provided with a stator assembly and a rotor assembly, a rotating magnetic field is generated through an energized coil and acts on a permanent magnet, so as to drive the output shaft to rotate and output power. When the electric machine is working, the output shaft will move axially. In order to stabilize the position of the output shaft, a stopper is usually installed at the end position of the output shaft inside the electric machine, so as to limit the position of the output shaft. However, after the electric machine is used for a long time, the stopper is easy to be worn. At this time, the output shaft is easy to move axially frequently when rotating to output power, and the stability of the output shaft to output power is poor, which causes obvious noise in the electric machine, affects the use experience, and even the output shaft can wear through the stopper, which damages the structure of the electric machine. Therefore, there is an urgent need for an electric machine with higher use stability. SUMMARY

[0003] The present application aims to provide a high-stability electric machine to solve one or more technical problems in the prior art, at least to provide a beneficial choice or create conditions.

[0004] The solution of the present application to solve the technical problem is:

[0005] The high-stability electric machine comprises a machine shell, an output shaft is rotatably connected inside the machine shell, two ends of the output shaft are a first end and a second end respectively, a connecting piece is arranged at a position close to the first end in the machine shell; a stopper assembly comprises a stopper piece and a gasket, the stopper piece is arranged in the machine shell, the first end abuts against the stopper piece, the gasket is sleeved outside the output shaft, the gasket is arranged at a side of the connecting piece away from the first end, a movable distance of the gasket towards the connecting piece is a stop distance, when the output shaft moves axially towards the connecting piece by the stop distance, the gasket abuts against the connecting piece.

[0006] The technical scheme has at least the following beneficial effects: the output shaft can rotate relative to the shell, the first end of the output shaft is located in the shell, and the stopper plate abuts against the first end, thereby stabilizing the position of the output shaft, the second end of the output shaft extends out of the shell to output power externally, when the output shaft rotates for a long time or is subjected to an axial impact force, the wear of the stopper plate gradually increases, when the output shaft moves along the direction close to the stopper plate by a displacement amount of the stop distance, the gasket arranged outside the output shaft abuts against the connecting piece arranged in the motor, thereby further limiting the position of the output shaft, at this time, the abutment of the gasket and the connecting piece forms a support point, and the abutment of the first end and the stopper plate forms another support point, the axial limiting of the output shaft is increased, the output shaft is effectively prevented from being worn through the shell, the stability of the output shaft in operation is improved, and the service life of the whole is prolonged.

[0007] As a further improvement of the above technical scheme, the gasket is provided with a through hole through which the output shaft passes, and the gasket is provided with protrusions on both sides of the through hole, and the two protrusions abut against the outside of the output shaft. During assembly, the output shaft passes through the through hole of the gasket, and the protrusions on both sides of the through hole of the gasket abut against the outside of the output shaft, at this time, the gasket and the output shaft can be clamped with each other, the gasket is conveniently fixed relative to the output shaft, the overall assembly efficiency is improved, and during operation, the output shaft rotates at high speed, the gasket only abuts against the output shaft at the two protrusion positions, the contact area is small, the gasket does not rotate synchronously with the output shaft, the wear of the end surface of the gasket is reduced, and the service life of the gasket is improved.

[0008] As a further improvement of the above technical scheme, the stopper assembly comprises an elastic member arranged between the gasket and the connecting piece, and the elastic member can provide elastic resistance when the output shaft moves axially towards the connecting piece. When the output shaft moves towards the direction close to the stopper plate, the output shaft drives the gasket to move close to the connecting piece, at this time, the elastic member is elastically compressed, the elastic resistance of the elastic member can reduce the pressure of the output shaft on the stopper plate, thereby reducing the wear of the stopper plate and prolonging the service life of the stopper plate, when the output shaft is subjected to a large axial stress, the elastic compression of the gasket to the elastic member reaches the end of the stroke, and the gasket abuts against the connecting piece through the elastic member.

[0009] As a further improvement of the above technical solution, the fixed ring is connected in the shell, the fixed ring is opposite to the side of the gasket away from the elastic member, the first gap is formed between the inner side of the fixed ring and the outer side of the output shaft, the tapered section is formed on the position of the output shaft outer side close to the first end, the outer diameter of the tapered section gradually decreases towards the first end, the second gap is formed between the two protrusions and the tapered section, and the tapered section can be opposite to the two protrusions when the output shaft moves axially towards the connecting piece. When the stopper piece is not worn or less worn, the displacement of the output shaft to the stopper piece is less, at this time the second gap is still present between the tapered section and the two protrusions, and the output shaft and the two protrusions are not in contact, which can further reduce the friction of the gasket and prolong the service life of the gasket. When the output shaft is subjected to a larger stress along the axial direction or the stopper piece is worn, the displacement of the output shaft to the stopper piece is larger, at this time the larger part of the outer diameter of the tapered section is opposite to the two protrusions, the elastic member is elastically deformed through the gasket, thereby preventing the continuous wear of the output shaft to the stopper piece, and further prolonging the service life of the stopper piece. When the stress transmitted by the output shaft along the axial direction is reduced or disappears, the elastic member pushes the gasket away from the connecting piece, and the gasket is limited by the fixed ring, so that the first end is away from the stopper piece, preventing continuous wear of the stopper piece, and the elastic member provides elastic resistance to the tapered section through the gasket, so that the output shaft can dynamically adjust its position according to the axial stress received, and the continuous wear of the first end to the stopper piece is ingeniously reduced.

[0010] As a further improvement of the above technical solution, the elastic member is a wave-shaped gasket. The wave-shaped gasket occupies less space along the axial direction, making the overall structure more compact, and can provide greater elastic force to the gasket to better withstand the axial pressure of the output shaft.

[0011] As a further improvement of the above technical solution, the stopper assembly further comprises a fixed sheet between the stopper sheet and the inner side of the shell. The fixed sheet is used to further shield the shell, preventing the output shaft from damaging the shell directly after wearing through the stopper sheet, and improving the stability of the overall structure.

[0012] As a further improvement of the above technical solution, the stop sheet is provided with a slot hole, the slot hole extends along the radial direction of the stop sheet, a plurality of slot holes are arranged around the center of the stop sheet, the plurality of slot holes separate the middle part of the stop sheet into a plurality of stop parts, and the top side of the fixed sheet is provided with a clearance groove corresponding to the position of the plurality of stop parts. The plurality of slot holes separate the middle part of the stop sheet into a plurality of stop parts with elastic deformation capability, at this time the first end abuts against the plurality of stop parts, when the output shaft transmits axial pressure to the plurality of stop parts, the plurality of stop parts elastically deform, and the clearance groove on the top side of the fixed sheet can provide clearance space for the elastic deformation of the plurality of stop parts, so that the elastic deformation of the plurality of stop parts can effectively reduce the wear of the first end on the stop sheet, and the elastic member provides elastic axial force to the conical section through the gasket, thereby enhancing the dynamic adjustment effect of the output shaft when subjected to axial pressure, thereby further prolonging the service life of the entire stop assembly and improving the stability of the output power of the output shaft.

[0013] As a further improvement of the above technical solution, the end face of the first end is arc-shaped. The arc-shaped end face can be closer to the plurality of stop parts located at the center of the stop sheet when abutting against the plurality of stop parts, thereby facilitating the improvement of the elastic deformation capability of the plurality of stop parts when subjected to pressure, thereby better offsetting the axial stress of the output shaft.

[0014] As a further improvement of the above technical solution, the connecting piece is a bearing connected between the first end and the shell, and when the output shaft moves axially towards the connecting piece by the stop distance, the gasket abuts against the inner ring of the bearing. The bearing is connected between the end of the output shaft and the shell, which can stabilize the position of the output shaft in the shell, and when the output shaft moves axially towards the connecting piece by a displacement amount of the stop distance, the gasket abuts against the inner ring of the bearing to limit the position of the output shaft.

[0015] As a further improvement of the above technical solution, the shell is detachably connected with an end cover corresponding to the position of the first end, and the stop sheet is located between the first end and the end cover. The shell is provided with an end cover at the position of the first end of the output shaft, which facilitates the disassembly and maintenance of the end cover and improves the convenience of disassembly and replacement of the stop assembly during maintenance. BRIEF DESCRIPTION OF DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly described below. Obviously, the described drawings are only a part of the embodiments of the present application, and other design schemes and drawings can be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0017] Figure 1 It is the overall front view of the present application.

[0018] Figure 2 is Figure 1 A-A position cross-sectional structure schematic view.

[0019] Figure 3 is Figure 2 B part local enlarged schematic view.

[0020] Figure 4 is the gasket of the present application.

[0021] Figure 5 is the stopper of the present application.

[0022] In the drawings: 100 - casing, 110 - output shaft, 111 - conical section, 120 - connecting piece, 130 - end cover, 210 - stopper, 211 - slot hole, 212 - stopper, 220 - gasket, 221 - protrusion, 230 - elastic piece, 240 - fixing ring, 250 - fixing piece, 251 - avoiding slot. DETAILED DESCRIPTION

[0023] The concept, specific structure and generated technical effects of the present application will be described clearly and completely in combination with the embodiments and drawings, so as to fully understand the purpose, features and effects of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all the embodiments, and other embodiments obtained by those skilled in the art based on the embodiments of the present application without creative labor are within the protection scope of the present application. In addition, all the connection relationships mentioned in the text do not mean that the components are directly connected, but that a more optimal connection structure can be composed by adding or reducing connecting auxiliary components according to the specific implementation situation. The technical features in the present application can be combined interactively without mutual contradiction and conflict.

[0024] Referring to Figures 1 to 3The utility model provides a high stability motor, including casing 100 and stop component, wherein, the inside rotation of casing 100 is connected with output shaft 110, and the both ends of output shaft 110 are first end and second end respectively, of course, the inside of casing 100 is provided with stator assembly and rotor assembly, and output shaft 110 is located in rotor assembly, and the inside of casing 100 is provided with connecting piece 120 near first end, stop component includes stop sheet 210 and gasket 220, stop sheet 210 is arranged in casing 100, and first end is abutted on stop sheet 210, and gasket 220 is sleeved on the outside of output shaft 110, and gasket 220 is spaced apart and is arranged on the side of connecting piece 120 away from first end, with the movable distance of gasket 220 towards connecting piece 120 as stop distance, when output shaft 110 moves axially towards connecting piece 120 by stop distance, gasket 220 is pressed against connecting piece 120.

[0025] In the high stability motor, output shaft 110 can rotate relative to casing 100, and the first end thereof is located in casing 100, and the first end is abutted on stop sheet 210, so as to stabilize the position of output shaft 110, and the second end thereof extends out of casing 100 to output power outward, when output shaft 110 rotates for a long time, is subjected to axial impact force and the like, the abrasion of stop sheet 210 is gradually increased, when output shaft 110 moves by the displacement amount of stop distance along the direction close to stop sheet 210, gasket 220 sleeved on the outside of output shaft 110 is pressed against connecting piece 120 installed in the motor, so as to further limit the position of output shaft 110, at this time, a support point is formed by the abutment of gasket 220 and connecting piece 120, and another support point is formed by the abutment of the first end and stop sheet 210, by increasing the axial limiting of output shaft 110, the abrasion of output shaft 110 through casing 100 is effectively prevented, the stability of output shaft 110 in work is improved, and the service life of the whole is prolonged.

[0026] When gasket 220 is sleeved on the outside of output shaft 110, it can be in close fitting mode, but gasket 220 is easy to be abraded at this time, or gasket 220 is connected to the outside of output shaft 110 in clearance fitting mode, but gasket 220 is easy to fall off during assembly, so assembly is difficult, therefore, as shown in the utility model, Figure 4As shown, in the embodiment, the gasket 220 is provided with a through hole for the output shaft 110 to pass through, and the gasket 220 is provided with protrusions 221 on both sides of the through hole, and the two protrusions 221 abut the outside of the output shaft 110. During assembly, the output shaft 110 passes through the through hole of the gasket 220, and the protrusions 221 on both sides of the through hole of the gasket 220 abut the outside of the output shaft 110. At this time, the gasket 220 and the output shaft 110 can be clamped with each other, which facilitates the relative fixation of the gasket 220 on the output shaft 110, improves the overall assembly efficiency, and during work, the output shaft 110 rotates at high speed. Since the gasket 220 only abuts the output shaft 110 at the positions of the two protrusions 221, the contact area is small, so that the gasket 220 does not rotate synchronously with the output shaft 110, reducing the wear of the end surface of the gasket 220 and improving the service life of the gasket 220.

[0027] In the above embodiment, the gasket 220 directly abuts the connecting piece 120 when abutting the connecting piece 120, and in the embodiment, the stop component includes an elastic member 230, the elastic member 230 is arranged between the gasket 220 and the connecting piece 120, and the elastic member 230 can provide elastic resistance when the output shaft 110 moves axially towards the connecting piece 120. When the output shaft 110 moves towards the direction close to the stop piece 210, the output shaft 110 drives the gasket 220 to move close to the connecting piece 120, at this time, the elastic member 230 is elastically compressed, and the elastic resistance of the elastic member 230 can reduce the pressure of the output shaft 110 on the stop piece 210, thereby reducing the wear of the stop piece 210 and prolonging the service life of the stop piece 210. When the output shaft 110 is subjected to a large axial stress, the gasket 220 will drive the elastic compression of the elastic member 230 to the end of the stroke, so that the gasket 220 abuts the connecting piece 120 through the elastic member 230.

[0028] Since the elastic member 230 is arranged between the gasket 220 and the connecting piece 120, the movable distance of the gasket 220 towards the connecting piece 120 is the compressible distance of the elastic member 230, which is the stop distance. When the gasket 220 moves the stop distance, the gasket 220 abuts the connecting piece 120 through the elastic member 230.

[0029] In order to make the two protrusions 221 can be separated from the tapered section 111, further reduce the wear of the gasket 220, in the embodiment, the housing 100 is connected with a fixed ring 240, the fixed ring 240 is opposite to the gasket 220 away from the elastic member 230 side, the inside of the fixed ring 240 and the outside of the output shaft 110 form a first gap, the output shaft 110 outside near the first end of the position forms a tapered section 111, the outer diameter of the tapered section 111 gradually reduces towards the first end, two protrusions 221 and the tapered section 111 form a second gap, the output shaft 110 towards the connecting piece 120 axial movement, the tapered section 111 can be opposite to the two protrusions 221. When the stop piece 210 is not worn or less wear, the displacement of the output shaft 110 to the stop piece 210 is less, at this time the tapered section 111 and the two protrusions 221 still have a second gap, the output shaft 110 and the two protrusions 221 are not in contact state, can further reduce the friction of the gasket 220, prolong the service life of the gasket 220, when the output shaft 110 along the axial stress is larger or the stop piece 210 appears larger wear, the displacement of the output shaft 110 to the stop piece 210 is larger, at this time the larger part of the outer diameter of the tapered section 111 is opposite to the two protrusions 221, the elastic member 230 is deformed by the gasket 220, so as to block the continuous wear of the output shaft 110 to the stop piece 210, further prolong the service life of the stop piece 210, when the stress transmitted by the output shaft 110 along the axial direction is reduced or disappears, the elastic member 230 will push the gasket 220 away from the connecting piece 120, and the gasket 220 is blocked by the fixed ring 240, so as to limit the gasket 220, so that the first end is away from the stop piece 210, preventing continuous wear of the stop piece 210, and the elastic member 230 provides elastic resistance to the tapered section 111 through the gasket 220, so that the output shaft 110 can dynamically adjust its position according to the axial stress, ingeniously reducing the continuous wear of the first end to the stop piece 210.

[0030] The elastic member 230 can adopt spring, rubber and other elastic structure, and in the embodiment, the elastic member 230 is a wave-shaped gasket 220. The wave-shaped gasket 220 occupies less space along the axial direction, so that the overall structure is more compact, and can provide larger elastic force to the gasket 220, better bearing the axial pressure of the output shaft 110.

[0031] After a long time of use, the stop piece 210 is easy to be worn through, in order to better protect the housing 100, in the embodiment, the stop piece assembly further comprises a fixed sheet 250, the fixed sheet 250 is located between the stop piece 210 and the inside of the housing 100. The fixed sheet 250 is used for further shielding the housing 100, preventing the output shaft 110 from directly damaging the housing 100 after the stop piece 210 is worn through, improving the stability of the overall structure.

[0032] In practical applications, the friction coefficient between the stop sheet 210 and the output shaft 110 is less than the friction coefficient between the fixing sheet 250 and the output shaft 110, and the rigidity of the fixing sheet 250 is greater than the rigidity of the fixing sheet 250. The setting of the stop sheet 210 and the fixing sheet 250 can significantly reduce the friction noise, reduce the wear and improve the system reliability while ensuring the axial constraint function. Preferably, the stop sheet 210 is one of graphite, PET or PEEK, and the fixing sheet 250 is stainless steel. Taking the stop sheet 210 as PEEK and the fixing sheet 250 as stainless steel as an example. The self-lubricating property of PEEK makes its friction coefficient with the output shaft 110 much lower than the friction between metals (the output shaft 110 and stainless steel), PEEK is a high polymer material, which can effectively suppress high-frequency vibration and avoid the peculiar "whistling" noise of metal friction. In addition, PEEK has high mechanical strength and remains stable at high temperatures. The fixing sheet 250 provides rigid support to protect the casing 100. Stainless steel has high rigidity, which prevents PEEK from being deformed or crushed under axial impact, and avoids direct wear of the end cover 130 of the output shaft 110 after PEEK failure.

[0033] In the above embodiment, the stop sheet 210 always rigidly blocks the output shaft 110, and in order to improve the overall performance, the stop sheet 210 can be flexibly blocked, specifically, as shown in Figure 5 The slot holes 211 are provided on the stop sheet 210, the slot holes 211 extend along the radial direction of the stop sheet 210, a plurality of slot holes 211 are provided around the center of the stop sheet 210, the plurality of slot holes 211 separate the middle part of the stop sheet 210 to form a plurality of stop portions 212, and the top side of the fixing sheet 250 is provided with a plurality of avoiding grooves 251 corresponding to the positions of the plurality of stop portions 212. For example, the number of slot holes 211 can be between three and six, and at this time, the corresponding stop portions 212 are also formed between three and six. The plurality of slot holes 211 separate the middle part of the stop sheet 210 to form a plurality of stop portions 212 with certain elastic deformation capacity, and the first end abuts against the plurality of stop portions 212. When the output shaft 110 transmits axial pressure to the plurality of stop portions 212, the plurality of stop portions 212 elastically deform, and the avoiding grooves 251 on the top side of the fixing sheet 250 can provide avoiding space for the elastic deformation of the plurality of stop portions 212. Thus, the elastic deformation of the plurality of stop portions 212 can effectively reduce the wear of the first end to the stop sheet 210, and the elastic axial force provided by the elastic member 230 to the conical section 111 through the gasket 220 can enhance the dynamic adjustment effect of the output shaft 110 when subjected to axial pressure, thereby further prolonging the service life of the entire stop assembly and improving the stability of the output power of the output shaft 110.

[0034] In some embodiments, the end face of the first end is arc-shaped. The arc-shaped end face is closer to the center of the stopper sheet 210 when abutting against the plurality of stoppers 212, which helps to improve the elastic deformation capability of the plurality of stoppers 212 when under pressure, thereby better offsetting the axial stress on the output shaft 110.

[0035] The connecting member 120 can be a structural member fixed in the casing 100. In the present embodiment, the connecting member 120 is a bearing connected between the first end and the casing 100. When the output shaft 110 moves axially towards the connecting member 120 by the stop distance, the washer 220 abuts against the inner ring of the bearing. The bearing is connected between the end of the output shaft 110 and the casing 100, which stabilizes the position of the output shaft 110 in the casing 100. When the output shaft 110 moves axially towards the connecting member 120 by the displacement amount of the stop distance, the washer 220 abuts against the inner ring of the bearing to limit the position of the output shaft 110.

[0036] In some embodiments, the casing 100 is detachably connected with an end cover 130 corresponding to the position of the first end, and the stopper sheet 210 is located between the first end and the end cover 130. The casing 100 is provided with the end cover 130 at the first end position of the output shaft 110, which facilitates the disassembly and maintenance of the end cover 130 and improves the convenience of disassembly and replacement of the stopper assembly during maintenance.

[0037] The preferred embodiments of the present application are specifically described above, but the present application is not limited to the embodiments. Those skilled in the art can make various equivalent modifications or replacements without departing from the spirit of the present application, and these equivalent modifications or replacements are all included in the scope defined by the claims of the present application.

Claims

1. A high stability electric machine characterized by: The utility model provides a motor, including: A casing (100) is internally rotatably connected with an output shaft (110), both ends of the output shaft (110) are a first end and a second end respectively, and the casing (100) is provided with a connecting piece (120) in the position close to the first end in the casing (100); A stopper assembly includes a stopper sheet (210) and a gasket (220), the stopper sheet (210) is arranged in the casing (100), the first end abuts against the stopper sheet (210), and the gasket (220) is sleeved outside the output shaft (110); the gasket (220) is arranged at the side, away from the first end, of the connecting piece (120) at intervals, the movable distance of the gasket (220) towards the connecting piece (120) is a stop distance, and when the output shaft (110) moves axially towards the connecting piece (120) by the stop distance, the gasket (220) abuts against the connecting piece (120).

2. A high stability electric machine according to claim 1, characterized in that: The gasket (220) is provided with a through hole for the output shaft (110) to pass through, and the gasket (220) is provided with protrusions (221) at the positions on both sides of the through hole, and the two protrusions (221) abut against the outside of the output shaft (110).

3. A high stability electric machine according to claim 2, characterized in that: The stopper assembly includes an elastic member (230), the elastic member (230) is arranged between the gasket (220) and the connecting piece (120), and the elastic member (230) can provide elastic resistance when the output shaft (110) moves axially towards the connecting piece (120).

4. A high stability electric machine according to claim 3, characterized in that: The casing (100) is connected with a fixing ring (240) therein, the fixing ring (240) abuts against the side, away from the elastic member (230), of the gasket (220), a first gap is formed between the inside of the fixing ring (240) and the outside of the output shaft (110), a tapered section (111) is formed at the position, close to the first end, of the outside of the output shaft (110), the outer diameter of the tapered section (111) gradually decreases towards the first end, a second gap is formed between the two protrusions (221) and the tapered section (111), and the tapered section (111) can abut against the two protrusions (221) when the output shaft (110) moves axially towards the connecting piece (120).

5. A high stability electric machine according to claim 3, characterized in that: The elastic member (230) is a wave-shaped gasket (220).

6. A high stability electric machine according to claim 1, characterized in that: The stopper assembly further includes a fixing sheet (250), and the fixing sheet (250) is located between the stopper sheet (210) and the inside of the casing (100).

7. A high stability electric machine according to claim 6, characterized in that: The stopper sheet (210) is provided with a slot hole (211), the slot hole (211) extends along the radial direction of the stopper sheet (210), a plurality of slot holes (211) are arranged around the center of the stopper sheet (210), a plurality of stopper portions (212) are formed in the middle part of the stopper sheet (210) by the plurality of slot holes (211), and the top side of the fixing sheet (250) is provided with a avoiding slot (251) corresponding to the positions of the plurality of stopper portions (212).

8. A high stability electric machine according to claim 1, characterized in that: The end face of the first end is in the shape of a circular arc.

9. A high stability electric machine according to claim 1, characterized in that: The connecting piece (120) is a bearing connected between the first end and the casing (100), and when the output shaft (110) moves axially towards the connecting piece (120) by the stop distance, the gasket (220) presses against the inner ring of the bearing.

10. A high stability electric machine according to claim 1, characterized in that: The casing (100) is detachably connected with an end cover (130) corresponding to the position of the first end, and the stop piece (210) is located between the first end and the end cover (130).

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