Electric machine and method for assembling electric machine
By forming an accurate contact surface between the stator frame and the stator of the motor and using bolt connections, the vibration problems caused by position deviation of the motor parts are solved, and the simplified assembly and performance improvement of the motor is achieved.
Patent Information
- Application Number
- CN202410992068.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2023-07-25
- Filing Date
- 2024-07-23
- Publication Date
- 2025-02-28
AI Technical Summary
During the motor manufacturing process, small deviations in the size or position of the motor components may lead to a significant impact on the characteristics and performance of the motor, resulting in vibration problems.
By machining the stator frame and the stator, the first contact surface of the intermediate plate and the second contact surface of the stator form close contact at a precise predetermined position, and a solid connection between the stator and the stator is achieved by bolts passing through the drilled and threaded holes between the stator frame and the stator.
This method simplifies the assembly process of the motor and reduces vibrations during use, especially during the start and shutdown phases by providing a solid connection.
Smart Images
Figure CN119543491A_ABST
Abstract
Description
Field of the Invention
[0001] The invention relates to an electric machine and a method for assembling an electric machine. Background Art
[0002] In the manufacture of industrial electric motors, the motor components are usually manufactured separately and first assembled into several individual sub-entities, forming the structural base units of the motor. These structural base units include, for example, stator and rotor assemblies, and stator frames. These individual sub-entities are then assembled into the final motor unit during the later steps of the manufacturing process. The final motor assembly is usually performed using shrink fit connections and mechanical connector elements between the sub-entities, so that the receiving points for the mechanical connector elements need to be prepared and carefully positioned at the corresponding connection surfaces of each sub-entity to be assembled.
[0003] The challenge involving electric motors is that even very small deviations in the size or mutual position of the components of the motor can have a significant effect on the characteristics and performance of the motor. If the components of the motor are not securely attached together in exactly the right mutual position, problems in the form of vibrations can occur. Summary of the invention
[0004] The object of the present invention is to solve the above mentioned disadvantages and to provide a solution which simplifies the assembly of the electric machine and provides a secure connection between the stator and the stator frame. These objects are achieved by a method according to independent claim 1 and an electric machine according to independent claim 5.
[0005] By machining the stator frame so that a hole is drilled through the intermediate plate at a precise predetermined position of each first contact surface of the intermediate plate, and machining the stator by preparing a threaded hole at a precise predetermined position of each second contact surface provided on a beam of the stator, and then inserting the stator into the stator frame, the stator frame and the stator can be separately machined to conveniently provide a strong connection between the stator and the stator frame.
[0006] Preferred embodiments of the invention are disclosed in the dependent claims. BRIEF DESCRIPTION OF THE DRAWINGS
[0007] In the following, the present invention will be described in more detail by way of examples and with reference to the accompanying drawings, in which
[0008] Figure 1 An embodiment of a motor is shown diagonally from above.
[0009] Figure 2 The diagram shows a diagonal view from above. Figure 1 The stator core of the motor,
[0010] Figure 3 The diagram shows the Figure 1The cross section of the motor,
[0011] Figure 4 Pictured Figure 2 A partial view of the stator core.
[0012] Figure 5 The diagram shows a diagonal view from above. Figure 1 Details of the motor,
[0013] Figure 6 The diagram shows the attachment to the processing station as seen directly from the side. Figure 1 The stator frame of the motor, and
[0014] Figure 7 The diagram shows the attachment to the processing station as seen directly from the side. Figure 2 stator core. DETAILED DESCRIPTION
[0015] Figure 1 An embodiment of an electric machine 1 is illustrated, in which the rotor included in the electric machine assembly has been faded and represented only in dotted lines in order to more clearly illustrate the other structural units of the electric machine. As shown in this example, the electric machine 1 includes a stator 2, which is operatively connected to a rotor 3 to provide torque to the rotor 3, in other words, so that during operation, a magnetic field is generated in the stator 2 to generate torque to the axis of the rotor 3 and rotate the rotor 3. The rotor 3 in the example is arranged inside the stator 2 to be coaxial with the stator 2, and it can represent, for example, any rotor structure known from the prior art. The electric machine 1 also includes a stator frame 5 surrounding the stator 2, wherein the stator frame 5 is provided at the bottom of the stator 2. Figure 1 In the example of the motor 1, the stator frame 5 comprises two intermediate plates 6 having coaxially aligned openings 7 for receiving the stator 2. The intermediate plates in this example are arranged between the frame end shields 101, 102 and extend in a substantially perpendicular direction relative to the longitudinal direction of the stator 2 and the rotor 3. In other embodiments of the motor 1, the number and position of the intermediate plates 6 may also deviate from Figure 1 , so that a plurality of intermediate plates 6 may also be included in the structure.
[0016] To further illustrate the structure of the stator 2, Figure 2 The diagram shows the motor separated from the rest of the structure. Figure 1 The stator core assembly of the electric machine 1 in FIG. As shown in this example, the outer periphery of the stator 2, which corresponds to the circumference of the cylindrical stator 2 in this example, has beams 4 extending in the longitudinal direction of the stator 2. The beams 4 can be used, for example, to hold together the layers forming the core of the stator 2 and to provide additional rigidity to the stator structure, and the number of beams and their positioning at the outer periphery of the stator 2 can deviate from those in other embodiments of the electric machine 1. Figure 2 .
[0017] In order to further illustrate the structure of the stator frame 5 and the mutual arrangement of the stator 2 and the stator frame, Figure 3 Pictured Figure 1 A cross-section of an electric machine 1 in a direction perpendicular to the longitudinal direction of the stator 2. As can be clearly seen in the present example, at least two intermediate plates 6 of the stator frame comprise a first contact surface 9 facing a central axis 8, said central axis 8 being located in the middle of the stator frame 5 and being oriented in the longitudinal direction of the frame such that the first contact surfaces 9 together define a circle having a first radius 10. In other words, said first contact surface 9 at each intermediate plate 6 is formed as a curved surface following the curvature of a circle having the first radius 10 and a central axis 8, the central axis 8 being shared between the first contact surfaces 9 of adjacent intermediate plates 6. Figure 3 In the example of , some first contact surfaces 9 are provided on protrusions 20 extending toward the center of the opening 7 at each opening 7, in other words, the protrusions 20 extend from the periphery of the opening 7, and the first contact surfaces 9 are provided on the surface of the protrusions 20 facing the center of the opening 7. Preferably, at least one first contact surface 9 is arranged in this way.
[0018] like Figure 3 As shown in the example of FIG. 4 , the first contact surface 9 forms a close contact with the corresponding second contact surface 11 provided on the beam 4. In more detail, in Figure 3 The second contact surface 11 in the example is provided on a surface of the beam 4 radially away from the stator 2, together defining a circle with a second radius 12 slightly smaller than the first radius 10, so that a close contact can be formed between the first contact surface 9 and the corresponding second contact surface 11. In some embodiments of the electric machine 1, the first contact surface 9 can be connected to the corresponding second contact surface 11 by shrink fit, wherein the contact between the first contact surface 9 and the second contact surface 11 can be formed under the condition that the stator frame 5 at least in the vicinity of the first contact surface 9 is heated to an elevated temperature. Therefore, the shrink fit connection is formed due to the shrinkage of the intermediate plate 6 and the circle defined by the first contact surface 9 tightly around the stator 2 in connection with the cooling.
[0019] To further illustrate the arrangement of the second contact surface 11 at the stator 2, Figure 4 Graphics Figure 2 A partial view of the stator 2. As shown in this figure, in the stator 2, according to Figure 2 and Figure 4In the example of the motor 1 , the second contact surface 11 is provided to a contact plate 19 on the beam 4. More precisely, the contact plate 19 is provided on a surface of the beam 4 facing away from the stator 2 in the radial direction, so that the second contact surface 11 is formed on the outer surface of the contact plate 19, thereby rising from the surface level of the beam 4. Using the arrangement as described above, the shape and size of the second contact surface 11 can be adjusted by affecting only the contact plate 19, without affecting the beam 4. The contact plate 19 can include, for example, a steel plate with a rigid structure so as to resist any deformation caused by forces applied to the stator-stator frame contact interface, for example during use of the motor 1. In other embodiments of the motor 1, only one or some of the second contact surfaces 11 may be provided to the contact plate 19, or the second contact surface 11 may be omitted completely, so that the second contact surface 11 is provided directly on the beam 4.
[0020] exist Figure 4 In the example of , some of the second contact surfaces 11 have flanges 23 for inhibiting the movement of the stator 2 beyond the predetermined position through the opening 7. More specifically, each of the second contact surfaces 11 provided on the contact plate 19 near the rear end of the stator 2 has a flange 23 extending away from the stator 2 in the radial direction of the stator 2, so that when the stator 2 moves through the opening 7 until the predetermined position, the flange 23 contacts the intermediate plate 6. By the arrangement as described above, the flange 23 can be used as an auxiliary surface for correctly positioning the stator 2 relative to the stator core 5 in the axial direction of the stator 2.
[0021] like Figure 3 As is clearly shown by the example of , the motor 1 has a bolt 13 extending through the intermediate plate 6 between the outside of the stator frame 5 and the opening 7. More precisely, the motor 1 has a bore extending through the outer surface of the stator frame 5 and the intermediate plate 6 in a direction substantially perpendicular to the central axis 8, and the bolt 13 is provided to the bore. The bolt 13 extends at a precise predetermined position of each first contact surface 9, in other words, so that the bolt 13 extends to the opening 7 at the precise predetermined position and engages with a threaded hole 14 provided to the precise predetermined position of each second contact surface 11. In other words, the threaded hole 14 is provided at a position that completely matches the corresponding bore position of the stator frame 5, so that a continuous, uninterrupted channel is created for the bolt 13 extending through the stator frame 5 to the stator 2.
[0022] The bores of the stator frame 5 may not have threads, so that the bolts 13 are only threadedly connected to the threaded holes 14 provided to the second contact surface 11. Each bolt 13 may also have a bolt head 103 that engages with the opening area of the corresponding bore of the stator frame 5, so that the bolts 13 can be tensioned between the stator 2 and the stator frame 5. By the arrangement described, the stator 2 can be close to the stator frame 5 at each pair of the first contact surface 9 and the second contact surface 11, so that the forces applied to the stator frame contact interface during use of the motor 1 are carried by the bolts 13 and by the friction between the first contact surface 9 and the second contact surface 11. Therefore, the arrangement can be used to provide support for the forces affecting the stator-stator frame contact interface in the radial and tangential directions of the central axis 8, rather than for example, using a non-tensioning connecting pin to prevent axial movement of the stator relative to the frame and preventing radial movement of the stator by a shrink fit connection. Therefore, vibrations of the motor 1 during use, especially during the start-up and shutdown phases of the motor operation, can be effectively weakened.
[0023] exist Figure 3 In the example of the motor 1, the motor 1 has two bolts 13 extending through the intermediate plate 6 of each first contact surface 9 and engaging with corresponding two threaded holes 14 provided to the second contact surface 11 at precisely predetermined positions. In other words, in the example described, two bolts 13 are arranged into corresponding two parallel bores extending at each pair of first contact surface 9 and second contact surface 11 of the stator-stator frame contact interface and engage with corresponding two threaded holes 14 which together with the bore create a continuous, uninterrupted passage for the bolts 13. The number of bolts 13 may be based on, for example, the tensioning force required in each application or structure of the motor 1 and may deviate from the described example in other embodiments of the motor 1. Preferably, at least two bolts 13 are provided to each first contact surface 9. The bores of the stator frame 5 may also have the following features: Figure 3 The countersunk or groove-shaped immersed section 104 shown in the example of FIG. 5 is provided so that the bolt 13 can be completely embedded in the outer periphery of the stator frame 5 .
[0024] By means of the described arrangement of the stator frame contact interface, in other words by means of the arrangement of the bolts 13 extending between the intermediate plates 6 of the stator and the beams 4 of the stator, the distance between the intermediate plates 6 can be set independently of the length of the stator 2 in the axial direction. More precisely, in the described arrangement, the distance between the outermost intermediate plates 6 can also be set smaller than the stator length 2, in contrast to conventional motor structures, in which the contact interface is formed between the intermediate plates and the end rings of the stator. This in turn allows the same stator frame design to be used for various stator structures with different outer dimensions, thereby eliminating the need to modify the stator frame structure for each use case of the motor 1. For example, in Figure 1In the example of FIG. 2 , the two intermediate plates 6 are located at a distance 22 from one another that is smaller than the length of the stator 2 .
[0025] exist Figure 3 In the example of FIG. 1 , each intermediate plate 6 comprises four first contact surfaces 9, and the bolts 13 at two of these first contact surfaces 9 extend horizontally from above into the threaded holes 14 of the second contact surfaces 11 at an angle 21 of 20-25 degrees, preferably about 22 degrees. In other words, the two first contact surfaces 9 are located on opposite sides of the central axis 8, and the two first contact surfaces 9 are provided with protrusions 20 having an extension similar to that of the corresponding bolts 13 in the example, so that the bolts 13 at these contact surfaces are connected to the threaded holes 14 of the second contact surfaces 11. Figure 3 The horizontal direction indicated by the dashed line forms an angle of about 22 degrees. In this case, the horizontal direction refers to the direction perceived at the installation location of the motor 1. In other embodiments of the motor 1, the angle 21 can also be set to be greater than Figure 3 The angle shown in the example is small and can be set based on, for example, the number of poles of the motor.
[0026] At the same time, in the example described, two further first contact surfaces 9 are located directly above and below the stator 2. By means of the described arrangement, an optimal distribution of forces affecting the stator frame contact interface can be achieved between the four contact points between the stator 2 and the stator frame 5, and vibrations of the motor 1 during use, in particular during the start-up and shutdown phases of motor operation, can be further suppressed. The arrangement and number of contact points between the stator 2 and the stator frame 5 may be based on the stator frame, for example, on an estimated maximum loading condition of the motor 1 in each application, so that the number of first contact surfaces at each intermediate plate 6 is preferably at least four, and the bolts 1 at the two contact surfaces form an angle 21 of 20-25 degrees with the horizontal direction. The first contact surface 9 and the second contact surface 11 may be oriented relative to the bolt 13 so that the bolt 13 forms an approximately right angle with the corresponding contact surface.
[0027] Figure 5 according to Figure 1 The example of illustrates the details of the motor. In this example, the stator 2 also includes a guide pin 17 extending radially outward from the stator 2, and the stator frame 5 also includes a centering fork 18 opening in the direction of the center axis 8. With the described arrangement, the stator fork 18 can be used to receive the guide pin 17 when the stator 2 is received in the stator frame 5 during the assembly stage of the motor 1, thereby guiding the stator 2 to the correct angular position relative to the stator frame 5. In other words, the guide pin 17 and the centering fork 18 in the described example are positioned relative to each other so that when the guide pin 17 is received into the stator fork 18, the correct angular position of the stator 2 is obtained. Figure 5In the example of FIG. 1 , in which the stator 2 is presented in the final position in which the stator 2 is mounted within the stator frame 5 , the guide pin 17 extends through the slit formed between the two branches of the centering fork 18 .
[0028] according to Figure 1 For example, the motor 1 can be assembled by first separately machining the stator 2 and the stator frame 5. In the assembly method of the motor 1, the stator frame 5 is machined using a machining station 15, which supports the stator frame 5 during machining, such as Figure 6 The machining of the stator frame 5 comprises, in a first stage, machining first contact surfaces 9 of at least two intermediate plates 6 facing the central axis 8, so that the first contact surfaces 9 jointly define a circle having a first radius 10 at each intermediate plate 6, as described above with reference to Figure 3 In practice, the machining of the first contact surface 9 can be performed by, for example, precisely positioning the stator frame 5 in a vertical position on a rotating support or spindle 105 of the machining station 15, so that the axis of rotation of the spindle 105 corresponds to the central axis 8 defined by the first contact surface 9 after machining. Then, for example, by utilizing the rotational movement of the stator frame 5 precisely positioned and attached to the spindle 105, a machining tool placed in the opening 7 of the intermediate plate 6 can be used to remove material from the intermediate plate 6, thereby obtaining the first contact surface 9 with the first radius 10 and the central axis 8.
[0029] In a second stage of machining of the stator frame 5, which may be carried out before or after the first stage described above, holes are drilled through the stator frame 5 at the exact predetermined position of each first contact surface 9 through at least two intermediate plates 6 between the exterior of the stator frame 5 and the opening 7. By using the machining station 15, possibly without moving the stator frame on the machining station between the first and second stages, the exact predetermined position can be obtained by, for example, placing a drilling tool 106 with a drilling head in the machining station 15 at a position which exactly corresponds to the desired position of the hole to be drilled in the direction of the center axis 8, as Figure 6 This is schematically shown in the example of Figure 6 , the position of the intermediate plate 6 is indicated by a dotted line. The placement of the drilling tool 106 may be performed based on, for example, a known position of the spindle 105 and the stator frame 5 placed on the spindle 105. The stator frame 5 may then be rotated relative to the drilling head to obtain the correct angular position of each hole to be drilled, in other words a position along the circumference of a circle having a first radius 10.
[0030] according to Figure 2 In the example of FIG. 1 , the machining of the stator 2 is performed using a machining station 16 that supports the stator 2 during machining, such as Figure 7The machining of the stator 2 comprises, in a first stage, machining the second contact surfaces 11 of the stator 2 provided on the beam 4 so that the second contact surfaces 11 together define a circle having a second radius 12, as described above with reference to Figure 3 For example, Figure 2 and 7 The beam 4 shown extends in the longitudinal direction at the outer periphery of the stator 2. In practice, the machining of the second contact surface 11 can be performed, for example, by precisely positioning the stator 2 in a vertical position on a rotating support or spindle 107 of the machining station 16, so that the axis of rotation of the spindle 107 corresponds to the central axis 108 defined by the second contact surface 11 after machining. Then, for example, by taking advantage of the rotational movement of the stator 2 precisely positioned and attached to the spindle 107, a machining tool placed outside the stator 2 can be used to cut the second contact surface 11 from the beam 4, such as Figure 1 In the case shown in the example of , or material is removed from a contact plate 19 provided on the beam 4, thereby obtaining a second contact surface 11 with a second radius 12. In an embodiment using a contact plate 19, the contact plate 19 can be provided on the beam 4 by welding before machining the second contact surface 11.
[0031] In a second stage of machining of the stator 2, which may be carried out before or after the first stage described above, threaded holes 14 are prepared at precisely predetermined positions of each second contact surface 11. The preparation of the threaded holes 14 may be performed by a single drilling step, in which the holes and the threads are provided simultaneously, or by separate steps of first preparing unthreaded holes and then providing the unthreaded holes with threads. By using a machining station 16, possibly without moving the stator on the machining station between the first and second stages, the precise predetermined positions may be obtained by, for example, placing a drilling tool 109 with a drilling head in the machining station 16 at a position that precisely corresponds to the desired position of the threaded holes 14 in the direction of the center axis 108, as Figure 7 The placement of the drilling tool 109 can be performed based on, for example, the known position of the spindle 107 and the stator 2 placed on the spindle 107. The stator 2 can then be rotated relative to the drilling head to obtain the correct angular position of each threaded hole 14. In some variations of the method of assembling the electric motor 1, the processing station 15 for processing the stator frame 5 can also be used to process the stator 2, so that a separate processing station 16 is not required to process the stator 2.
[0032] After processing, the stator 2 is inserted into the stator frame 5 through the opening 7 to a position where the first contact surface 9 of the intermediate plate 6 and the corresponding second contact surface 11 of the stator 2 are in close contact. Figure 1An example of a method for assembling an electric motor 1 is provided. In practice, the insertion may be performed by, for example, lowering the stator 2 in a vertical position from above to the stator frame 5 so that the opening 7 is positioned to open upward for receiving the stator 2. Then, the intimate contact is formed as a first contact surface 9 defining a circle with a first radius 10 and a corresponding second contact surface 11 defining a circle with a second radius 12 are positioned to face each other, the first radius 10 being slightly larger than the second radius 12. In some variations of the method, the method may further include heating the stator frame 5 before inserting the stator 2 into the stator frame 5, thereby forming intimate contact by creating a shrink fit between the first contact surface 9 and the corresponding second contact surface 11.
[0033] In the electric machine 1 according to embodiments 1 to 7, in which the stator 2 has a guide pin 17 and the stator frame 5 has a centering fork 18, inserting the stator 2 into the stator frame 5 may further comprise the step of guiding the guide pin 17 to the centering fork 18. By means of said arrangement, the guide pin 17 and the centering fork 18 may be used to position the stator 2 relative to the stator frame 5 to ensure the correct angular position of said components around the central axis 8. Similarly, in embodiments of the electric machine 1 in which at least one second contact surface 11 has a Figure 4 The flange 23 can be used to position the stator 2 relative to the stator frame 5 in the axial direction of the stator 2 .
[0034] When the stator 2 and the stator frame 5 are positioned to the correct mutual position, assembly of the electric machine 1 is continued by providing bolts 13 to extend through the drilled holes provided to the stator frame 5 and threadedly engage with the threaded holes 14 provided to the stator 2. More precisely, the bolts 13 may be inserted into holes drilled through the stator frame 5 from the outside of the frame so that the threaded end of the bolts 13 engages with the threads provided to the threaded holes 14, and the other end of the bolts 13 may have a bolt head 103 that engages with the open area of the drilled hole of the stator frame 5. At this point, the bolts 13 may be tightened to provide the desired level of compressive force for the stator-stator frame contact interface, locking the stator 2 and the stator frame 5 together to withstand the axial and torsional loads applied to the stator 2 and the stator frame.
[0035] It should be understood that the above description and the accompanying drawings are only intended to illustrate the present invention. It will be apparent to those skilled in the art that the present invention can be varied and modified without departing from the scope of the present invention.
Claims
1. A method for assembling an electric motor, characterized in that: The method comprises: Processing the stator frame having at least two intermediate plates with openings using a processing station supporting the stator frame during processing, the processing of the stator frame comprising: In a first stage, first contact surfaces of the at least two intermediate plates facing the central axis are machined, the first contact surfaces jointly defining a circle having a first radius at each intermediate plate, and in a second stage, before or after the first stage, drilling the stator frame through the at least two intermediate plates between the exterior of the stator frame and the opening at a precisely predetermined location of each of the first contact surfaces, The stator is machined using a machining station that supports the stator during machining, the machining of the stator comprising: In a first stage, second contact surfaces of the stator are machined, the second contact surfaces being provided on beams extending in a longitudinal direction at an outer periphery of the stator such that the second contact surfaces together define a circle having a second radius, and In a second stage, before or after said first stage, threaded holes are prepared at precisely predetermined positions of each of said second contact surfaces, inserting the stator through the opening into the stator frame to a position where a close contact is formed between the first contact surfaces of the at least two intermediate plates and the corresponding second contact surfaces of the stator, and A bolt is provided to extend through the bore provided to the stator frame and threadingly engage the threaded hole provided to the stator.
2. The method according to claim 1, characterized in that The method further comprises: The stator frame is heated before inserting the stator into the stator frame to form the intimate contact by creating a shrink fit between the first contact surfaces of the at least two intermediate plates and the corresponding second contact surfaces of the stator.
3. The method according to claim 1, characterized in that Inserting the stator into the stator frame includes guiding a guide pin extending radially outward from the stator to a centering fork provided to the stator frame and opening in the direction of the central axis.
4. The method according to claim 1, characterized in that: The method further comprises: Before machining the second contact surface, a contact plate is welded on the beam to provide the second contact surface.
5. A motor, characterized in that: The motor comprises: a stator having an outer periphery provided with beams extending in the longitudinal direction of the stator, and A stator frame surrounds the stator, the stator frame comprising at least two intermediate plates, the at least two intermediate plates having openings for receiving the stator, wherein The at least two intermediate plates comprise first contact surfaces facing the central axis, the first contact surfaces jointly defining a circle having a first radius at each intermediate plate and forming an intimate contact with corresponding second contact surfaces provided on the beam, the second contact surfaces jointly defining a circle having a second radius, and The motor is provided with a bolt extending through the at least two intermediate plates between the outside of the stator frame and the opening at a precisely predetermined position of each first contact surface and engaging with a threaded hole provided to a precisely predetermined position of each second contact surface.
6. The motor according to claim 5, characterized in that At least one of the first contact surfaces is provided on a protrusion which extends at each of the openings towards the centre of the opening, and At least one of the second contact surfaces is provided to a contact plate, which is provided on the beam.
7. The motor according to claim 5, characterized in that The first contact surface is connected to the corresponding second contact surface by shrink fitting.
8. The motor according to claim 5, characterized in that Each of the at least two intermediate plates comprises at least four contact surfaces, and The bolts at two of the at least four contact surfaces extend from above to the threaded hole of the second contact surface at an angle of 20 to 25 degrees from the horizontal direction.
9. The motor according to claim 5, characterized in that The motor is provided with at least two bolts extending through the at least two intermediate plates at each of the first contact surfaces and engaging with corresponding at least two threaded holes provided to precisely predetermined positions on each of the second contact surfaces.
10. The motor according to claim 5, characterized in that The stator further includes a guide pin extending radially outward from the stator, and The stator frame further comprises a centering fork which is open in the direction of the center axis for receiving the guide pin when the stator is received in the stator frame.
11. The motor according to claim 5, characterized in that The distance between the at least two intermediate plates is smaller than the length of the stator.
12. The motor according to claim 5, characterized in that At least one of the second contact surfaces is provided with a flange protruding outwardly from the second contact surface for inhibiting movement of the stator through the opening beyond a predetermined position.