Embedded rotor motor for Cartesian robots

Abstract

The present invention provides an embedded rotor motor for a rectangular coordinate robot. It solves the existing technical problems. The embedded rotor motor of the rectangular coordinate robot includes a housing with an axial cavity, wherein a stator and a rotor with a rotating shaft are respectively arranged in the axial cavity, wherein the rotor is formed by axially docking a plurality of rotor monoliths through an axial positioning structure, wherein a plurality of magnetic steel slots are provided on the rotor monolith, wherein the magnetic steel slots are arranged in a ring shape on the rotor monolith, and the extension lines of the magnetic steel slots in the long axis direction intersect with the center of the circle of the rotor monolith, and a winding slot is also provided between two adjacent magnetic steel slots, and the winding slot is polygonal. The present invention has the advantages of small error in the gap between the magnetic steel and the stator, and high efficiency in using the magnetic steel.

Description

Technical Field

[0001] The invention belongs to the technical field of motors, and in particular relates to an embedded rotor motor of a rectangular coordinate robot. Background Art

[0002] The coordinate robot is a multi-purpose manipulator that can realize automatic control, reprogrammable, multi-degree-of-freedom, and the degrees of freedom of motion are built into a spatial right-angle relationship. Its working behavior is mainly through completing linear motion along the X, Y, and Z axes. Different design requirements are required for coordinate robots for different applications, such as selecting different transmission methods according to the requirements for accuracy and speed, selecting different clamping equipment fixtures, claws, mounting brackets, etc. for the end working head according to specific process requirements, and design selections for teaching programming, coordinate positioning, visual recognition and other working modes, so that it can meet the application requirements of different fields and different working conditions. Most of the magnets in the existing motors for rectangular coordinate robots are attached to the circumferential outer side of the rotor segment. The external attachment method causes a gap error between the magnet and the stator, and one piece of magnet corresponds to only one coil, which is inefficient.

[0003] In response to this problem, people have also conducted exploration and research in long-term production and life practices. For example, a Chinese invention patent discloses a fixing mechanism for the magnetic steel of an inner rotor motor [application number: CN201420188020.1], including a rotor body, a magnetic steel fixing groove formed on the rotor body, and a magnetic steel arranged in the magnetic steel fixing groove, characterized in that an inner clamping plate for fixing is arranged at both ends of the rotor body and the magnetic steel, an outer clamping plate is arranged outside the inner clamping plate, and the edge of the inner clamping plate has a flange, and the flange is blocked on the outer wall of the magnetic steel. The magnetic steel fixing groove can be a straight groove, which is easy to process and labor-saving. The magnetic steel is arranged on the straight groove. The magnetic steel can be a square magnetic steel, which is cheap and low in cost. An inner clamping plate and an outer clamping plate are respectively arranged on both ends of the rotor body and the magnetic steel, and the magnetic steel is placed flat in the magnetic steel fixing groove of the rotor body according to the polarity requirements, and the magnetic steel and the rotor body are fixed by the inner clamping plate and the outer clamping plate.

[0004] The above solution improves some of the problems of the prior art to a certain extent. However, the solution still has at least the following defects: the error of the gap between the magnetic steel and the stator is large, and the use efficiency of the magnetic steel is low. Summary of the invention

[0005] The object of the present invention is to provide an embedded rotor motor for a rectangular coordinate robot with small error and high magnetic steel utilization efficiency in view of the above problems.

[0006] To achieve the above-mentioned purpose, the present invention adopts the following technical solutions: the embedded rotor motor of the rectangular coordinate robot includes a housing with an axial cavity, wherein the axial cavity is respectively provided with a stator and a rotor with a rotating shaft, characterized in that the rotor is formed by axially docking a plurality of rotor monoliths through an axial positioning structure, a plurality of magnetic steel slots are opened on the rotor monolith, the magnetic steel slots are arranged in a ring shape on the rotor monolith, and the extension lines of the magnetic steel slots in the long axis direction intersect with the center of the circle of the rotor monolith, and a winding slot is also provided between two adjacent magnetic steel slots, and the winding slot is polygonal. Magnetic steel slots are provided on both sides of the winding slot, so that the magnetic steel wound in the winding slot can correspond to at least two coils, thereby improving the utilization rate of the magnetic steel, and the polygonal winding slot can make the cross section of the wire group more flat after winding, and avoid the rotor rotating and causing the coil to deviate; and the magnetic steel is provided in the magnetic steel slot on the rotor monolith, so that the gap between the magnetic steel and the stator is more stable, effectively reducing the error.

[0007] In the above-mentioned embedded rotor motor of the rectangular coordinate robot, the axial positioning structure includes a plurality of docking pin holes opened on the rotor monolith, the docking pin holes are arranged in annular intervals on the rotor monolith, and the docking pin holes and magnetic steel slots between two rotor monoliths that are butted against each other are connected, and a plug-in fastening component is arranged in the docking pin holes. The installation and positioning between the rotor monoliths are achieved through the docking pin holes, and the combination of the rotor monoliths is convenient.

[0008] In the above-mentioned embedded rotor motor of the rectangular coordinate robot, the plug-in fastening assembly includes a first positioning pin and a second positioning pin, the first positioning pin and the second positioning pin are plugged into each other, and a plug hole for the second positioning pin to pass through is provided in the middle of the first positioning pin, and a locking structure is also provided between the first positioning pin and the docking pin hole. When the rotor monoliths are docked, the circumferential and axial fixation of the rotor monolithic assembly can be achieved by inserting the first positioning pin and the second positioning pin on both sides respectively.

[0009] In the above-mentioned embedded rotor motor of the rectangular coordinate robot, the locking structure includes a plurality of positioning bodies arranged on the circumferential outer side of the first positioning pin, the positioning bodies are arranged at intervals in the axial direction of the first positioning pin, the positioning bodies are connected to the telescopic grooves on the side of the first positioning pin through elastic components, and the rotor is provided with a plurality of positioning slots arranged corresponding to the first positioning pin. The positioning bodies on the first positioning pin and the positioning slots in the rotor can realize the axial positioning of the first positioning pin in the docking pin hole, thereby improving the axial and circumferential stability of the first positioning body in the docking pin hole.

[0010] In the above-mentioned embedded rotor motor of the rectangular coordinate robot, the elastic component includes a plurality of spring bodies arranged in the telescopic slot, the two ends of the spring body are respectively connected to the bottom of the telescopic slot and the spring seat arranged on the bottom side of the positioning body, the spring seat is provided with a spring hole, the spring body is at least partially located in the spring hole, and the spring body is arranged in a ring shape on the spring seat. The positioning body is connected to the telescopic slot through the spring body, so that the positioning body can have elasticity, which not only allows the first positioning pin to be inserted into the docking pin hole more smoothly, but also allows the locking effect between the positioning body and the positioning slot to be better.

[0011] In the above-mentioned embedded rotor motor of the rectangular coordinate robot, a one-way engaging structure is further provided between the first positioning pin and the second positioning pin, and the one-way engaging structure includes a plurality of conical card bodies arranged on the circumferential outer side of the second positioning pin, and a conical card slot corresponding to the conical card body is provided in the insertion hole, and the conical card slot is arranged at an angle, and the conical card body is made of elastic plastic. The second positioning pin is positioned in the insertion hole by the conical card body and the conical card slot, which can improve the stability of the second positioning pin when plugged into the first positioning pin, and the conical card slot is arranged at an angle so that the second positioning pin cannot be pulled out axially after being inserted, and the structure is more reliable.

[0012] In the above-mentioned embedded rotor motor of the rectangular coordinate robot, the end of the first positioning pin away from the second positioning pin and the end of the second positioning pin away from the first positioning pin are respectively provided with limiting steps, and the two sides of the rotor are provided with accommodating grooves with a groove depth equal to the thickness of the limiting steps. After the first positioning pin and the second positioning pin are plugged in, the limiting steps at the ends will be embedded in the accommodating grooves, so that the end faces of the two ends of the rotor can be smoothed.

[0013] In the above-mentioned embedded rotor motor of the rectangular coordinate robot, the rotating shaft is hollow, the rear end of the housing is provided with a heat dissipation cover, a heat dissipation fan is provided in the heat dissipation cover, the heat dissipation fan is plugged with the rear end of the rotating shaft through a hollow connecting shaft, and the connecting shaft is connected with the middle of the rotating shaft, a dust screen is provided at the rear end of the heat dissipation cover, and the connecting shaft is detachably connected with the rotating shaft through a plug-in structure. The rotating shaft is hollow, and when the heat dissipation fan rotates through the rotating shaft, air convection can be generated between the rotating shaft and the heat dissipation cover, thereby reducing the temperature in the shaft cavity.

[0014] In the above-mentioned embedded rotor motor of the rectangular coordinate robot, the plug-in structure includes a plurality of strip convex ribs arranged on the circumferential outer side of the connecting shaft, a strip groove arranged corresponding to the strip convex ribs is arranged in the rotating shaft, a plurality of positioning convex parts are also arranged on the outer side of the strip convex ribs, a plurality of positioning concave parts arranged corresponding to the positioning convex parts are arranged in the strip grooves, and the positioning convex parts and the positioning concave parts are arranged axially at intervals. The positioning convex parts and the positioning concave parts can realize the axial positioning between the connecting shaft and the rotating shaft, and the strip convex ribs and the strip grooves can realize the circumferential positioning between the connecting shaft and the rotating shaft, so that the cooling fan and the rotating shaft can be installed by inserting the connecting shaft into the rotating shaft, which is convenient to install and has a reliable structure.

[0015] In the above-mentioned embedded rotor motor of the rectangular coordinate robot, the housing is further provided with a heat dissipation cylinder located on the circumferential outer side of the stator, the heat dissipation cylinder is provided with a heat dissipation layer made of graphite material, and the heat dissipation cylinder is provided with a plurality of strip heat dissipation grooves on the circumferential outer side. The heat dissipation layer made of graphite material and the strip heat dissipation grooves on the circumferential outer side of the heat dissipation cylinder can effectively conduct heat in the shaft cavity, thereby extending the service life of the motor.

[0016] Compared with the existing technology, the advantages of the embedded rotor motor of the rectangular coordinate robot are: reasonable design, magnetic steel grooves are arranged on both sides of the winding groove, so that the coil wound in the winding groove can correspond to at least two coils, the magnetic steel is used efficiently, and the magnetic steel is embedded, with a small gap error. In addition, the cooling fan and the hollow shaft can also improve the heat dissipation effect of the motor. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a cross-sectional view of a junction provided by the present invention;

[0018] Figure 2 It is a schematic diagram of the structure of a rotor monolith provided by the present invention;

[0019] Figure 3 is a structural cross-sectional view of a rotor provided by the present invention;

[0020] Figure 4 It is a schematic diagram of the structure after the first positioning pin and the second positioning pin provided by the present invention are connected to each other;

[0021] Figure 5 It is a structural schematic diagram of the bottom surface of the spring seat provided by the present invention;

[0022] Figure 6 is a cross-sectional view of the connecting shaft and the rotating shaft provided by the present invention after being connected;

[0023] Figure 7 is a schematic diagram of another viewing angle after the connecting shaft provided by the present invention is connected to the rotating shaft;

[0024] In the figure, the shaft cavity 1, the housing 2, the stator 3, the shaft 4, the rotor 5, the rotor single piece 6, the magnetic steel slot 7, the winding slot 8, the docking pin hole 9, the first positioning pin 10, the second positioning pin 12, the socket 13, the positioning body 14, the telescopic slot 15, the positioning card slot 16, the spring body 17, the spring seat 18, the spring hole 19, the conical card body 20, the conical bayonet 21, the limiting step 22, the accommodating groove 23, the heat dissipation cover 24, the heat dissipation fan 25, the connecting shaft 26, the dustproof net 27, the strip convex rib 28, the strip groove 29, the positioning protrusion 30, the positioning recess 31, the heat dissipation cylinder 32, the heat dissipation layer 33, and the strip heat dissipation groove 34. DETAILED DESCRIPTION

[0025] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0026] like Figure 1-7 As shown, the embedded rotor motor of the rectangular coordinate robot includes a housing 2 with an axial cavity 1, in which a stator 3 and a rotor 5 with a rotating shaft 4 are respectively arranged, and the rotor 5 is formed by axially docking a plurality of rotor monoliths 6 through an axial positioning structure, and a plurality of magnetic steel slots 7 are opened on the rotor monolith 6, and the magnetic steel slots 7 are arranged in a ring shape on the rotor monolith 6, and the extension lines of the magnetic steel slots 7 in the long axis direction intersect with the center of the rotor monolith 6, and a winding slot 8 is further provided between two adjacent magnetic steel slots 7, and the winding slot 8 is polygonal.

[0027] Magnetic steel slots 7 are provided on both sides of the winding slot 8, so that the magnetic steel wound in the winding slot 8 can correspond to at least two coils, thereby improving the utilization rate of the magnetic steel, and the polygonal winding slot 8 can make the cross-section of the wire group smoother after winding, thereby preventing the rotor 5 from rotating and causing the coil to deviate; and the magnetic steel is arranged in the magnetic steel slot 7 on the rotor single piece 6, so that the gap between the magnetic steel and the stator 3 is more stable, effectively reducing the error.

[0028] The axial positioning structure includes a plurality of docking pin holes 9 provided on the rotor monolith 6. The docking pin holes 9 are arranged in a ring-shaped interval on the rotor monolith 6, and the docking pin holes 9 and the magnetic steel slots 7 between two rotor monoliths 6 that are butted against each other are connected. A plug-in fastening assembly is provided in the docking pin holes 9. The installation and positioning between the rotor monoliths 6 are realized through the docking pin holes 9, and the assembly of the rotor monoliths 6 is convenient.

[0029] Preferably, the plug-in fastening assembly includes a first positioning pin 10 and a second positioning pin 12. The first positioning pin 10 and the second positioning pin 12 are plugged into each other, and a hole 13 for the second positioning pin 12 to pass through is opened in the middle of the first positioning pin 10. A locking structure is also provided between the first positioning pin 10 and the docking pin hole 9. When the rotor single piece 6 is docked, the circumferential and axial fixation of the rotor single piece 6 assembly can be achieved by respectively inserting the first positioning pin 10 and the second positioning pin 12 on both sides.

[0030] The locking structure includes a plurality of positioning bodies 14 arranged on the circumferential outer side of the first positioning pin 10, the positioning bodies 14 are arranged at intervals in the axial direction of the first positioning pin 10, the positioning bodies 14 are connected to the telescopic groove 15 on the side of the first positioning pin 10 through an elastic component, and a plurality of positioning slots 16 corresponding to the first positioning pin 10 are provided in the rotor 5. The first positioning pin 10 can be axially positioned in the docking pin hole 9 through the positioning bodies on the first positioning pin 10 and the positioning slots 16 in the rotor, thereby improving the axial and circumferential stability of the first positioning body 14 in the docking pin hole 9. The elastic component includes a plurality of spring bodies 17 arranged in the telescopic groove 15, and the two ends of the spring body 17 are respectively connected to the bottom of the telescopic groove 15 and a spring seat 18 arranged on the bottom side of the positioning body 14. A spring hole 19 is opened on the spring seat 18. The spring body 17 is at least partially located in the spring hole 19, and the spring body 17 is arranged in a ring shape on the spring seat 18. The positioning body 14 is connected to the telescopic groove 15 through the spring body 17, so that the positioning body 14 can have elasticity, which not only allows the first positioning pin 10 to be inserted into the docking pin hole 9 more smoothly, but also allows the locking effect between the positioning body 14 and the positioning slot 16 to be better.

[0031] Furthermore, a one-way snap-fit ​​structure is provided between the first positioning pin 10 and the second positioning pin 12, and the one-way snap-fit ​​structure includes a plurality of conical card bodies 20 arranged on the circumferential outside of the second positioning pin 12, and a conical snap-fit ​​21 corresponding to the conical card body 20 is provided in the insertion hole 13, and the conical snap-fit ​​21 is inclined, and the conical card body 20 is made of elastic plastic.

[0032] The second positioning pin 12 is positioned in the insertion hole 13 by means of the conical card body 20 and the conical bayonet 21, which can improve the stability of the second positioning pin 12 when plugged into the first positioning pin 10, and the conical bayonet 21 is tilted so that the second positioning pin 12 cannot be axially pulled out after insertion, and the structure is more reliable.

[0033] One end of the first positioning pin away from the second positioning pin 12 and one end of the second positioning pin 12 away from the first positioning pin 10 are respectively provided with a limiting step 22, and both sides of the rotor 5 are provided with a receiving groove 23 with a groove depth the same as the thickness of the limiting step 22. After the first positioning pin 10 and the second positioning pin 12 are plugged in, the limiting step 22 at the end will be embedded in the receiving groove 23, so that the end faces of the two ends of the rotor 5 can be smoothed.

[0034] Furthermore, the rotating shaft 4 is hollow, and a heat dissipation cover 24 is provided at the rear end of the casing 2. A heat dissipation fan 25 is provided in the heat dissipation cover 24. The heat dissipation fan 25 is plugged into the rear end of the rotating shaft 4 through a hollow connecting shaft 26, and the connecting shaft 26 is connected to the middle part of the rotating shaft 4. A dustproof net 27 is provided at the rear end of the heat dissipation cover 24, and the connecting shaft 26 is detachably connected to the rotating shaft 4 through a plug-in structure. The rotating shaft 4 is hollow. When the heat dissipation fan 25 rotates through the rotating shaft 4, air convection can be generated between the rotating shaft 4 and the heat dissipation cover 24, thereby reducing the temperature in the shaft cavity 1.

[0035] The plug-in structure includes a plurality of strip convex ribs 28 arranged on the circumferential outer side of the connecting shaft 26, a strip groove 29 arranged corresponding to the strip convex rib 28 is arranged in the rotating shaft 4, a plurality of positioning convex portions 30 are also arranged on the outer side of the strip convex rib 28, a plurality of positioning recesses 31 arranged corresponding to the positioning convex portions 30 are arranged in the strip groove 29, and the positioning convex portions 30 and the positioning recesses 31 are arranged axially at intervals, the positioning convex portions 30 and the positioning recesses 31 can realize the axial positioning between the connecting shaft 26 and the rotating shaft 4, the strip convex rib 28 and the strip groove 29 can realize the circumferential positioning between the connecting shaft 26 and the rotating shaft 4, so that the connecting shaft 26 can be inserted into the rotating shaft 4 to realize the installation of the cooling fan 25 and the rotating shaft 4, the installation is convenient and the structure is reliable.

[0036] In addition, a heat dissipation cylinder 32 is provided in the casing 2 and is located on the circumferential outer side of the stator 3. A heat dissipation layer 33 made of graphite material is provided in the heat dissipation cylinder 32, and a plurality of strip heat dissipation grooves 34 are provided on the circumferential outer side of the heat dissipation cylinder 32. The heat dissipation layer 33 made of graphite material and the strip heat dissipation grooves 34 on the circumferential outer side of the heat dissipation cylinder 32 can effectively dissipate the heat in the shaft cavity 1, thereby extending the service life of the motor.

[0037] The specific embodiments described herein are merely examples of the spirit of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in similar ways, but they will not deviate from the spirit of the present invention or exceed the scope defined by the appended claims.

[0038] Although the present invention uses more terms such as shaft cavity 1, housing 2, stator 3, rotating shaft 4, rotor 5, rotor monolith 6, magnetic steel slot 7, winding slot 8, docking pin hole 9, first positioning pin 10, second positioning pin 12, plug hole 13, positioning body 14, telescopic slot 15, positioning slot 16, spring body 17, spring seat 18, spring hole 19, conical card body 20, conical bayonet 21, limiting step 22, accommodating slot 23, heat dissipation cover 24, heat dissipation fan 25, connecting shaft 26, dustproof net 27, strip convex rib 28, strip slot 29, positioning convex part 30, positioning concave part 31, heat dissipation cylinder 32, heat dissipation layer 33, strip heat dissipation slot 34, etc., it does not exclude the possibility of using other terms. The use of these terms is only for the purpose of more conveniently describing and explaining the essence of the present invention; interpreting them as any additional restrictions is contrary to the spirit of the present invention.

Claims

1. An embedded rotor motor for a rectangular coordinate robot, comprising a housing (2) having an axial cavity (1), wherein a stator (3) and a rotor (5) having a rotating shaft (4) passing through the axial cavity (1) are respectively arranged, wherein: The rotor (5) is formed by axially butting a plurality of rotor monoliths (6) via an axial positioning structure. A plurality of magnetic steel slots (7) are provided on the rotor monolith (6). The magnetic steel slots (7) are arranged in a ring shape on the rotor monolith (6), and the extension lines of the magnetic steel slots (7) in the long axis direction intersect with the center of the rotor monolith (6). A winding slot (8) is provided between two adjacent magnetic steel slots (7), and the winding slot (8) is polygonal. The axial positioning structure comprises a plurality of docking pin holes (9) provided on the rotor single piece (6), wherein the docking pin holes (9) are arranged in an annular manner on the rotor single piece (6), and the docking pin holes (9) between two rotor single pieces (6) that are butted against each other are connected to the magnetic steel grooves (7), and a plug-in fastening assembly is provided in the docking pin holes (9); The housing (2) is further provided with a heat dissipation cylinder (32) located on the circumferential outer side of the stator (3), the heat dissipation cylinder (32) is provided with a heat dissipation layer (33) made of graphite material, and the circumferential outer side of the heat dissipation cylinder (32) is provided with a plurality of strip-shaped heat dissipation grooves (34); The plug-in fastening assembly comprises a first positioning pin (10) and a second positioning pin (12). The first positioning pin (10) and the second positioning pin (12) are plugged into each other, and a plug hole (13) is provided in the middle of the first positioning pin (10) for the second positioning pin (12) to pass through. A locking structure is also provided between the first positioning pin (10) and the docking pin hole (9).

2. The embedded rotor motor of the rectangular coordinate robot according to claim 1, characterized in that: The locking structure comprises a plurality of positioning bodies (14) arranged on the circumferential outer side of the first positioning pin (10), the positioning bodies (14) being arranged at intervals in the axial direction of the first positioning pin (10), the positioning bodies (14) being connected to the telescopic grooves (15) on the side of the first positioning pin (10) through elastic components, and a plurality of positioning slots (16) corresponding to the first positioning pin (10) are provided in the rotor (5).

3. The embedded rotor motor of the rectangular coordinate robot according to claim 2, characterized in that: The elastic component comprises a plurality of spring bodies (17) arranged in the telescopic groove (15), the two ends of the spring body (17) being respectively connected to the bottom of the telescopic groove (15) and a spring seat (18) arranged on the bottom side of the positioning body (14), a spring hole (19) being formed on the spring seat (18), the spring body (17) being at least partially located in the spring hole (19), and the spring body (17) being arranged in a ring shape on the spring seat (18).

4. The embedded rotor motor of the rectangular coordinate robot according to claim 2, characterized in that: A one-way snap-fit ​​structure is also provided between the first positioning pin (10) and the second positioning pin (12), the one-way snap-fit ​​structure comprising a plurality of conical snap-fit ​​bodies (20) arranged on the circumferential outer side of the second positioning pin (12), a conical snap-fit ​​socket (21) corresponding to the conical snap-fit ​​body (20) is provided in the insertion hole (13), and the conical snap-fit ​​socket (21) is inclined, and the conical snap-fit ​​body (20) is made of elastic plastic.

5. The embedded rotor motor of the rectangular coordinate robot according to claim 2, characterized in that: An end of the first positioning pin away from the second positioning pin (12) and an end of the second positioning pin (12) away from the first positioning pin (10) are respectively provided with a limiting step (22), and two sides of the rotor (5) are provided with a receiving groove (23) with a groove depth equal to the thickness of the limiting step (22).

6. The embedded rotor motor of the rectangular coordinate robot according to claim 1, characterized in that: The rotating shaft (4) is hollow, a heat dissipation cover (24) is provided at the rear end of the housing (2), a heat dissipation fan (25) is provided in the heat dissipation cover (24), the heat dissipation fan (25) is plugged into the rear end of the rotating shaft (4) through a hollow connecting shaft (26), and the connecting shaft (26) is connected to the middle part of the rotating shaft (4), a dustproof net (27) is provided at the rear end of the heat dissipation cover (24), and the connecting shaft (26) is detachably connected to the rotating shaft (4) through a plug-in structure.

7. The embedded rotor motor of the rectangular coordinate robot according to claim 6, characterized in that: The plug-in structure comprises a plurality of strip convex ribs (28) arranged on the circumferential outer side of the connecting shaft (26); a strip groove (29) arranged corresponding to the strip convex ribs (28) is arranged in the rotating shaft (4); a plurality of positioning convex portions (30) are also arranged on the outer side of the strip convex ribs (28); a plurality of positioning concave portions (31) are arranged corresponding to the positioning convex portions (30) in the strip groove (29); and the positioning convex portions (30) and the positioning concave portions (31) are arranged axially at intervals.

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