Patent Publication Number: US-2022239189-A1

Title: Motor for Electric Cylinder and Encoder for Motor

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an electric cylinder and, more particularly, to a motor for an electric cylinder and an encoder for the motor. 
     2. Description of the Related Art 
     Conventional electric cylinders or slide devices are widely used in industrial machines and generally employ a motor to drive a rotating shaft (screw shaft), so that the load end can move linearly. The general electric cylinder mainly includes a linear track, a sliding unit arranged on the linear track, and a motor. The sliding unit is provided with a rotating shaft which is connected with a spindle of the motor through a coupling. When the motor drives the rotating shaft to rotate through the coupling, the sliding unit can reciprocate relative to the linear track along a longitudinal direction, so that the carrier mounted on the sliding unit will be driven to move linearly. However, in long-term use, the coupling is prone to damage or loosening. In addition, the arrangement of the coupling will cause the electric cylinder to have a longer longitudinal length and a larger volume, which cannot effectively save space to achieve the purpose of light weight. 
     To mitigate the above-mentioned problems caused by the use of the coupling to connect the rotating shaft, a hollow motor without a spindle is designed. The hollow motor includes a housing, a hollow rotor housed in the housing, a magnet coupled to the rotor, a stator coil, and an encoder. The rotating shaft of the electric cylinder can be directly engaged in the hollow rotor, so the use of the coupling can be omitted. When the rotor of the hollow motor rotates, the rotating shaft is driven, so that the sliding unit can reciprocate relative to the linear track along the longitudinal direction. Since the hollow motor does not have a spindle, the longitudinal length of the electric cylinder can he educed, thereby reducing the volume of the electric cylinder. However, the completion of magnetic pole angle alignment is achieved after the hollow motor and the rotating shaft are assembled. When the components of the hollow motor are damaged or the magnets are demagnetized, the assembly step of replacing the hollow motor is quite complicated. Generally, the customer cannot replace it by himself, and the entire electric cylinder needs to be sent hack to the factory for repair, which is time-consuming. Specifically, after the hollow motor and the rotating shaft are assembled, the magnetic pole phase of the rotor magnet needs to be aligned with the stator coil first. This alignment operation is generally to send power to the stator coil, so that the rotor rotates to an initial position relative to the stator coil and then stops to complete the alignment. In addition, the magnetic pole position of the encoder magnet of the encoder also needs to complete the alignment operation with the magnetic sensor of the encoder. However, in the operation of adjusting the magnetic pole position of the encoder magnet, in addition to power transmission to the stator coil, it is more necessary to manually adjust the magnetic pole position of the encoder magnet relative to the magnetic sensor, which is very tedious and time-consuming in the alignment adjustment operation. 
     Thus, an objective of the present invention is to provide a motor for an electric cylinder, which is a hollow motor without a spindle and has a hollow rotor that can be connected to a rotating shaft of the electric cylinder. The design effect of the motor on the structure is to allow the manufacturer to complete the alignment of the magnetic pole phase of the rotor magnet with the stator coil in the factory, and also to complete the alignment of the magnetic pole position of the encoder magnet with the magnetic sensor of the encoder. Thus, the magnetic pole alignment problems of the rotor magnet and the encoder magnet are avoided when the motor of the electric cylinder is replaced by the customer, so that the customer can quickly, conveniently and accurately conduct motor replacement and assembly, and the competitiveness of the electric cylinder is improved. 
     To achieve this and other objectives, a motor according to an embodiment of the present invention is applicable to an electric cylinder including a rotating shaft which extends along a longitudinal direction and has a motor-side shaft portion provided with a shaft coupling portion and a shaft fixing portion spaced from the shaft coupling portion. The motor comprises a motor body, an encoder, a rotor coupling portion, and an encoder fixing portion. The motor body includes a housing, a rotor contained in the housing, a stator coil, a rotor magnet. The rotor has a shaft hole extending in the longitudinal direction through which the motor-side shaft portion extends. The rotor magnet is coupled to the rotor and has at least one pair of magnetic poles. The rotor is rotatable about a central axis of the rotating shaft relative to the stator coil. The encoder is installed on the motor body and includes a fixing ring, a magnet holder combined with the fixing ring, an encoder magnet, and a magnetic sensor. The motor-side shaft portion of rotating shaft extends through the fixing ring. The encoder magnet is mounted on the magnet holder and has at least one pair of magnetic poles. The magnetic sensor and the encoder magnet are spaced and opposed in the longitudinal direction. The magnet holder is rotatable relative to the fixing ring. The rotor coupling portion is provided in the rotor and aligned with the shaft coupling portion. The rotor coupling portion and the shaft coupling portion are coupled by a coupling member. The encoder fixing portion is provided in the fixing ring and aligned with the shaft fixing portion. The encoder fixing portion and the shaft fixing portion are fixed together by a fixing member. 
     In a preferred form, the shaft fixing portion is a first keyway provided in an outer circumference of the rotating shaft and extending in the longitudinal direction. The fixing ring has a through-hole extending in the longitudinal direction. The encoder fixing portion is a recess provided in a hole wall of the through-hole and extending in the longitudinal direction. The fixing member is a first key engaged in the keyway and the recess. 
     In a preferred form, the shaft coupling portion is a second keyway provided in the outer circumference of the rotating shaft and extending in the longitudinal direction. The rotor coupling portion is a groove provided in a hole wall of the shaft hole and extending in the longitudinal direction. The coupling member is a second key engaged in the second keyway and the groove. 
     In a preferred form, the shaft coupling portion includes two notches spaced in the longitudinal direction and opposite to each other in a circumferential direction of the rotating shaft. The rotor coupling portion includes two notches respectively located at two ends of the rotor and opposite to each other in a circumferential direction of the rotor. The two notches in the rotor respectively correspond to the two slots of the rotating shaft. The coupling member includes two sets of a combination of a fixing piece and two screws. The fixing piece abuts against one of the two slots, and the two screws extend through the fixing piece and are locked into one of the two notches of the rotor. 
     In a preferred form, the magnet holder includes a body portion and a positioning portion protruding outward from an inner side of the body portion. The encoder magnet is mounted on the body portion. The positioning portion is combined in the through-hole of the fixing ring. The magnet holder is fixed to the fixing ring by a positioning member extending through a positioning hole in the fixing ring and pressing against the positioning portion. 
     An encoder according to an embodiment of the present invention is applicable to a motor connected with a rotating shaft. The encoder is adapted for detecting rotation of the rotating shaft. The encoder comprises a fixing ring fixed on the rotating shaft, a magnet holder combined with the fixing ring, an encoder magnet, and a magnetic sensor. The encoder magnet is installed on the magnet holder and has at least one pair of magnetic poles. The magnetic sensor is spaced from and opposite to the encoder magnet in the longitudinal direction. The magnet holder is rotatable relative to the fixing ring to adjust magnetic pole positions of the encoder magnet relative to the magnetic sensor. 
     In a preferred form, the fixing ring has a through-hole extending in the longitudinal direction, and the rotating shaft extends through the through-hole. 
     The present invention will become clearer in light of the following detailed description of illustrative embodiments of this invention described in connection with the drawings. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       The illustrative embodiments may best be described by reference to the accompanying drawings where: 
         FIG. 1  is a schematic cross-sectional view of a motor in accordance with a first embodiment of the present invention applied to an electric cylinder. 
         FIG. 2  shows a partially exploded view of the electric cylinder of  FIG. 1 , 
         FIG. 3  shows a partially exploded view of an encoder of  FIG. 1 . 
         FIG. 4  shows a schematic view of assembling a motor body and a rotating shaft of  FIG. 2  together. 
         FIG. 5  is a schematic cross-sectional view of a motor in accordance with a second embodiment of the present invention applied to an electric cylinder. 
         FIG. 6  shows a partially exploded view of the electric cylinder of  FIG. 5 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A motor  10  according to a first embodiment of the present invention is shown in  FIGS. 1 through 4  of the drawings and is applied to an electric cylinder  112 . The electric cylinder  12  includes a linear track  14 , a sliding unit  16 , a rotating shaft  18 , a motor body  20 , and an encoder  22 . The linear track  14  extends along a longitudinal direction (X). The sliding unit  16  is mounted on the linear track  14 . The rotating shaft  18  includes a sliding-side shaft portion  24  combined with the sliding unit  16  and a motor-side shaft portion  26  combined with the motor body  20 . When the motor  10  is running, the rotating shaft  18  is driven to drive the sliding unit  16  to reciprocate relative to the linear track  14  in the longitudinal direction (X). Since the structures of the linear track  14  and the sliding unit  16  are well known to those skilled in the art, they will not be described in detail here. 
     The motor-side shaft portion  26  extends outside the sliding unit  16  and is provided with a shaft coupling portion  28  and a shaft fixing portion  30 . The shaft coupling portion  28  is located between the sliding-side shall portion  24  and the shaft fixing portion  30  in the longitudinal direction (X). In a feasible embodiment, the shaft coupling portion  28  and the shaft fixing portion  30  may be respectively constituted by at least one keyway or at least one slot. In this embodiment, the shaft fixing portion  30  is a first keyway  30   a  provided in an outer circumference of the rotating shaft  18 , and the shaft coupling portion  28  is a second keyway  28   a  provided in the outer circumference of the rotating shaft  18 , The two keyways  28   a  and  30   a  extend in a direction parallel to the central axis of the rotating shaft  18  and are aligned in the longitudinal direction, that is, the keyways  28   a,    30   a  have no angular offset in the circumference direction of the rotating shaft  18 . In a feasible embodiment, the keyways  28   a,    30   a  are offset by an angle (for example, 90 or 180 degrees) about the rotating shaft  18 . However, the keyways  28   a,    30   a  are preferably arranged to be aligned in the longitudinal direction, which is advantageous for making the shaft coupling portion  28  and the shaft fixing portion  30  on the rotating shaft  18 . 
     The motor  10  of the present invention includes the motor body  20  and the encoder  22 . The motor body  20  includes a housing  32 , a rotor  34  received in the housing  32 , a stator coil  36 , a rotor magnet  38  coupled to the rotor  34 , and a rear cover  40 . A bearing  41  is provided on an inner periphery of the rear cover  40 . The rotor  34  has a shaft hole  42  extending in the longitudinal direction through which the motor-side shaft portion  26  extends. The rotor  34  is provided with a rotor coupling portion  44 . In a feasible embodiment, the rotor coupling portion  44  is formed by at least one groove or at least one recess. In this embodiment, the rotor coupling portion  44  is a groove  44   a  provided in the hole wall of the shaft hole  42  and extending in the longitudinal direction. By aligning the rotor coupling portion  44  with the shaft coupling portion  28  and inserting a coupling member  46  such as a key (second key) into the shaft coupling portion  28  (second keyway  28   a ) and the rotor coupling portion  44  (groove  44   a ) to form a limit, the rotor coupling portion  44  will be combined and fixed with the shaft coupling portion  28 , so that the rotor  34  and the rotating shaft  18  can rotate together about the central axis of the rotating shaft  18 . In addition, a limiting member  47  such as a set screw extends through the rotor  34  and abuts against the coupling member  46  to limit the movement of the rotor  34  relative to the rotating shaft  18  in the longitudinal direction. The stator coil  36  is coupled to an inner peripheral wall of the housing  32 . 
     The rotor magnet  38  is combined with the outer periphery of the rotor  34  and has a plurality of pairs of magnetic poles (N pole and S pole). When the stator coil  36  is energized, the rotor  34  and the rotating shaft  18  together rotate an angle relative to the stator coil  36 . 
     The encoder  22  is installed on the motor body  20  to detect the rotation number, rotation direction, and rotation angle of the rotating shaft  18 . The encoder  22  includes a fixing ring  48 , a magnet holder  50 , an encoder magnet  52  and a magnetic sensor  54 . In this embodiment, the fixing ring  48  has a through-hole  56  extending in the longitudinal direction through which an outer end  57  of the motor-side shaft portion  26  extends. The outer end  57  has a smaller outer diameter and extends out of the housing  32  of the motor body  20 , and the shaft fixing portion  30  is provided in the outer end  57 . At least one encoder fixing portion  58  is provided in the fixing ring  48 . In a feasible embodiment, the encoder fixing portion  58  is formed by at least one groove or at least one recess. In this embodiment, the encoder fixing portion  58  is a recess  58   a  provided in the hole wall of the through-hole  56  and extending in the longitudinal direction. By aligning the encoder fixing portion  58  with the shaft fixing portion  30  and inserting a fixing member  60  such as a key (first key) into the shaft fixing portion  30  (first keyway  30   a ) and the encoder fixing portion  58  (recess  58   a ) to form a limit, the encoder fixing portion  58  can be combined and fixed with the shaft fixing portion  30 , so that the encoder magnet  52  and the rotating shaft  18  can rotate together about the central axis of the rotating shaft  18 . In addition, a limiting member  61  such as a set screw passes through the fixing ring  48  and abuts against the fixing member  60  to restrict the movement of the fixing ring  48  relative to the rotating shaft  18  in the longitudinal direction. 
     The magnet holder  50  is rotatably combined with the fixing ring  48 . In this embodiment, the magnet holder  50  includes a body portion  62 , a positioning portion  64  protruding outward from an inner side of the body portion  62 , and an abutting portion  66  located between the body portion  62  and the positioning portion  64 . The body portion  62  and the positioning portion  64  are respectively provided with first and second recesses  68  and  70  separated by the abutting portion  66 . The encoder magnet  52  is installed in the first recess  68  of the main body  62 . The positioning portion  64  is inserted into the through-hole  56  of the fixing ring  48 , and the outer end  57  of the motor-side shaft portion  26  is inserted into the second recess  70  and abuts against the abutting portion  66 . In this embodiment, a positioning member  72  such as a set screw passes through a positioning hole  74  provided in the fixing ring  48  and abuts against the positioning portion  64 , so that the magnet holder  50  can be fixed to the fixing ring  48 . When the positioning member  72  is loosened, the magnet holder  50  can be rotated relative to the fixing ring  48  to adjust the magnetic pole position of the encoder magnet  52 . In this embodiment, the magnetic sensor  54  is mounted on a circuit board  76  which is fixed to the rear cover  40  of the motor body  20  through two supporting posts  78 . The magnetic sensor  54  and the encoder magnet  52  are spaced and opposed in the longitudinal direction. When the encoder magnet  52  rotates, the magnetic sensor  54  can sense the encoder magnet  52 . When the magnet holder  50  rotates an angle relative to the fixing ring  48 , the magnetic pole position of the encoder magnet  52  relative to the magnetic sensor  54  will be adjusted. 
     With regard to the assembly of the motor  10  and the rotating shaft  18  of the present invention, the motor-side shaft portion  26  first extends through the shaft hole  42  of the rotor  34 , and the shaft coupling portion  28  of the rotating shaft  18  is aligned with the rotor coupling portion  44  of the rotor  34 . The rotor coupling portion  44  and the shaft coupling portion  28  are coupled by the coupling member  46 , so that a first corresponding position between the rotor  34  and the rotating shaft  18  is fixed. Next, the housing  32  containing the stator coil  36  is installed around the outer circumference of the rotor  34  and fixed to an end cover  84  of the electric cylinder  12  (see  FIG. 4 ). Then, the fixing ring  48  combined with the magnet holder  50  is installed on the motor-side shaft portion  26 , and the encoder fixing portion  58  is aligned with the shaft fixing portion  30 . The encoder fixing portion  58  and the shaft fixing portion  30  are combined by the fixing member  60 , so that a second corresponding position between the fixing ring  48  and the rotating shaft  18  is fixed. Finally, the circuit board  76  of the encoder  22  is mounted on the motor housing  32  by the support posts  78 . After the motor  10  and the rotating shaft  18  are assembled, a power supply can be sent to the stator coil  36  to make the rotor  34  relative to the stator coil  36  rotate to a position and then stop to complete the alignment of the magnetic pole phase of the rotor magnet  38  with the stator coil  36 . Next, the magnet holder  50  is rotated to adjust the position of the magnet holder  50  relative to the fixing ring  48  such that the magnetic pole position of the encoder magnet  52  is aligned with the magnetic sensor  54 . Then, the magnet holder  50  is fixedly combined with the fixing ring  48  by the positioning member  72 , so that the magnetic pole position of the encoder magnet  52  relative to the magnetic sensor  54  will not change. After the motor  10  assembled on the rotating shaft  18  completes the alignment procedure described above, the motor  10  can be operated to drive the rotating shaft  18  of the electric cylinder  12  to rotate, and the encoder  22  can detect the rotation of the rotating shaft  18 . 
     The structure of the motor  10  of the present invention has an advanced feature that is not available in the prior art. This feature allows manufacturers with assembly expertise to first complete the alignment of the magnetic pole phase of the rotor magnet  38  with the stator coil  36  in the factory, and also complete the alignment of the magnetic pole position of the encoder magnet  52  with the magnetic sensor  54  of the encoder  22 , so that the customers can quickly and easily complete the replacement of the motor  10 , without the need to send the entire electric cylinder back to the factory for repair. Specifically, after the motor  10  that has completed the magnetic pole position alignment procedure is detached from the rotating shaft  18 , if the rotor  34  of the motor  10  is then assembled on another rotating shaft  18  according to the first corresponding position between the rotor  34  and the rotating shaft  18  with the encoder  22  of the motor  10  assembled on the another rotating shaft  18  according to the second corresponding position between the fixing ring  48  and the rotating shaft  18 , the magnetic pole phase of the rotor magnet  38  and the magnetic pole position of the encoder magnet  52  will not be changed. Accordingly, when the customer needs to replace the motor  10  because the motor  10  is damaged or the magnet is demagnetized, the manufacturer can provide the motor  10  that has completed the alignment procedure in the factory to the customer. Then, the customer only needs to connect the rotor coupling portion  44  (groove  44   a ) of the rotor  34  of the motor  10  with the shaft coupling portion  28  (second keyway  28   a ) of the rotating shaft  18  at the customer side by the coupling member (second key)  46 , and to connect the encoder fixing portion  58  (the recess  58   a ) of the fixing ring  48  with the shaft fixing portion  30  (first keyway  30   a ) of the rotating shaft  18  by the fixing member (first key)  60 , so that the replacement of the motor  10  can be completed without the magnetic pole alignment problems of the rotor magnet  38  and the encoder magnet  52  on the customer side. 
       FIG. 5  and  FIG. 6  show a motor  10  according to a second embodiment of the present invention. In this embodiment, the shaft coupling portion  28  on the motor-side shaft portion  26  includes two slots  28   b  spaced in the longitudinal direction and opposite in the circumferential direction of the rotating shaft  18 . The rotor coupling portion  44  on the rotor  34  includes two notches  44   b  respectively located at two ends of the rotor  34  and opposite to each other in the circumferential direction of the rotor  34 . The coupling member  46  includes two sets of a combination of a fixing piece  80  and two screws  82 . After the motor-side shaft portion  26  passes through the shaft hole  42  of the rotor  34 , the notches  44   b  of the rotor  34  can respectively correspond to the slots  28   b  of the motor-side shaft portion  26 . Then the two fixing pieces  80  are used to abut against the two slots  28   b  (shaft coupling portion  28 ) respectively, and the screws  82  extend through the fixing piece  80  and are locked into the two notches  44   b  (rotor coupling portion  44 ) of the rotor  34  to combine the motor-side shaft portion  26  and the rotor  34 . Thus, the rotor  34  and the rotating shaft  18  can rotate together about the central axis of the rotating shaft  18 , and the movement of the rotor  34  relative to the rotating shaft  18  in the longitudinal direction can be restricted. In this embodiment, the shaft fixing portion  30 , the encoder fixing portion  58 , and the fixing member  60  have the same structure as the shaft fixing portion  30 , the encoder fixing portion  58  and the fixing member  60  in the first embodiment, wherein the first keyway  30   a  constituting the shaft fixing portion  30  and the two slots  28   b  constituting the shaft coupling portion  28  have a preset relative positional relationship, for example, the first keyway  30   a  and one of the slots  28   b  are aligned in the longitudinal direction. It should be noted that the shaft fixing portion  30 , the encoder fixing portion  58  and the fixing member  60  in this embodiment can also be configured to have the same structure as the shaft coupling portion  28 , the rotor coupling portion  44  and the coupling member  46  in this embodiment. 
     The scope of the invention is to be indicated by the appended claims, rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are intended to be embraced therein. 
     
       
         
           
               
             
               
                   
               
               
                 REFERENCE SIGNS LIST 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                   
                 10 motor 
                 12 electric cylinder 
               
               
                   
                 14 linear track 
                 16 sliding unit 
               
               
                   
                 18 rotating shaft 
                 20 motor body 
               
               
                   
                 22 encoder 
                 24 sliding-side shaft portion 
               
               
                   
                 26 motor-side shaft portion 
                 28 shaft coupling portion 
               
               
                   
                 28a second keyway 
                 28b slot 
               
               
                   
                 30 shaft fixing portion 
                 30a first keyway 
               
               
                   
                 32 housing 
                 34 rotor 
               
               
                   
                 36 stator coil 
                 38 rotor magnet 
               
               
                   
                 40 rear cover 
                 41 bearing 
               
               
                   
                 42 shaft hole 
                 44 rotor coupling portion 
               
               
                   
                 44a groove 
                 44b notch 
               
               
                   
                 46 coupling member 
                 47 limiting member 
               
               
                   
                 48 fixing ring 
                 50 magnet holder 
               
               
                   
                 52 encoder magnet 
                 54 magnetic sensor 
               
               
                   
                 56 through-hole 
                 57 outer end 
               
               
                   
                 58 encoder fixing portion 
                 58a recess 
               
               
                   
                 60 fixing member 
                 61 limiting member 
               
               
                   
                 62 body portion 
                 64 positioning portion 
               
               
                   
                 66 abutting portion 
                 68 first recess 
               
               
                   
                 70 second recess 
                 72 positioning member 
               
               
                   
                 74 positioning hole 
                 76 circuit board 
               
               
                   
                 78 supporting post 
                 80 fixing piece 
               
               
                   
                 82 screw 
                 84 end cover