Abstract:
In a linear motor comprising, a stator, a movable element, and an electromagnetic coil device for magnetizing the movable element or stator, the stator includes at least one pair of magnetic core parts, and at least two pairs of magnetic poles, the magnetic poles of each of the at least two pairs are aligned on an imaginary line perpendicular to the movable direction, magnetic polar directions of the at least two pairs adjacent to each other are opposite to each other, first one of the magnetic poles of each of the at least two pairs faces to a first side surface of the movable element, and second one of the magnetic poles of each of the at least two pairs faces to a second side surface of the movable element opposite to the first side surface in a traverse direction perpendicular to the movable direction.

Description:
BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT 
     The present invention relates to a linear motor in which a movable member is magnetically driven between magnetic poles. 
     In a prior art linear motor as disclosed by JP-A-10-174418, pairs of magnetic poles adjacent to each other are magnetized by respective electromagnetic coils. 
     OBJECT AND SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a linear motor in which a number of electromagnetic coils is minimized and a magnetic flux is effectively utilized for generating an output force. 
     According to the present invention, in a linear motor comprising, a stator, a movable element movable with respect to the stator in a movable direction, and an electromagnetic coil device for energizing at least one of the movable element and the stator to be magnetized so that a relative movement between the movable element and the stator in the movable direction is generated by a magnetic field between the movable element and the stator, the stator includes at least one pair of magnetic core parts, and at least two pairs of magnetic poles adjacent to each other in the movable direction, the magnetic poles of each of the at least two pairs are aligned on an imaginary line perpendicular to the movable direction to generate the magnetic field passing the magnetic poles of each pair through the movable element, a magnetic polar direction of one of the at least two pairs is opposite to that of another one of the at least two pairs adjacent to the one of the at least two pairs in the movable direction, first one of the magnetic poles of each of the at least two pairs faces to a first side surface of the movable element, and second one of the magnetic poles of each of the at least two pairs faces to a second side surface of the movable element opposite to the first side surface in a traverse direction perpendicular to the movable direction. 
     Since the magnetic polar direction of one of the at least two pairs is opposite to that of another one of the at least two pairs adjacent to the one of the at least two pairs in the movable direction, a size of the stator is decreased. 
     When one of the magnetic core parts forms both of the first one of the magnetic poles of the one of the at least two pairs and the second one of the magnetic poles of the another one of the at least two pairs adjacent to the one of the at least two pairs in the movable direction, and another one of the magnetic core parts forms both of the first one of the magnetic poles of the another one of the at least two pairs and the second one of the magnetic poles of the one of the at least two pairs adjacent to the another one of the at least two pairs in the movable direction, a size of the stator is minimized. When the pair of magnetic core parts is magnetized by single electromagnetic coil, a number of electromagnetic coils in the linear motor is minimized. 
     When one of the magnetic core parts forms both of the first one of the magnetic poles of the one of the at least two pairs and the first one of the magnetic poles of the another one of the at least two pairs adjacent to the one of the at least two pairs in the movable direction, and another one of the magnetic core parts forms both of the second one of the magnetic poles of the another one of the at least two pairs and the second one of the magnetic poles of the one of the at least two pairs adjacent to the another one of the at least two pairs in the movable direction, a size of the stator is minimized. When the pair of magnetic core parts is magnetized by single electromagnetic coil, a number of electromagnetic coils in the linear motor is minimized. 
     When the at least one of the movable element and the stator energized by the electromagnetic coil device has at least two parts to be magnetized respectively with a difference in energized phase between the at least two parts so that a travelling magnetic field for generating the relative movement between the movable element and the stator element in the movable direction is formed, and each of the at least two parts is magnetized by single electromagnetic coil, a number of electromagnetic coils in the linear motor is minimized. 
     When the stator includes at least two of the pairs of magnetic core parts and at least four of the pairs of magnetic poles juxtaposed with each other in the movable direction, each of the at least two pairs of magnetic core parts forms at least partially two of the at least four pairs of magnetic poles adjacent to each other in the movable direction, and a magnetic polar direction of one of the two of the at least four pairs of magnetic poles is opposite to a magnetic polar direction of another one of the two of the at least four pairs of magnetic poles, a size of the stator is minimized. When each of the at least two pairs of magnetic core parts is magnetized by single electromagnetic coil, a number of electromagnetic coils in the linear motor is minimized. 
     The movable member may include at least one of an electromagnetic coil and a permanent magnet to form pairs of magnetic poles juxtaposed with each other in the movable direction. The movable member may include pairs of high-reluctance portions and low-reluctance portions adjacent to each other in the movable direction, and the pairs of high-reluctance portions and low-reluctance portions are juxtaposed with each other in the movable direction. The movable member may be stationary while the stator is moved. The stator may be stationary while the movable member is moved. The electromagnetic coil device may energize the movable element. The electromagnetic coil device may energizes the stator. The stator may have a permanent magnet for forming therein at least one pair of magnetic poles. 
     When the linear motor is a multi-phase linear motor, a distance between a pair of magnetic poles of one of the at least two parts and a pair of magnetic poles of another one of the at least two parts adjacent to each other in the movable direction=(k*P)+(P/M), when P is a pitch of the pairs of the magnetic poles adjacent to each other in the movable direction in each of the at least two parts, k is an integral number not less than zero, and M is a number of the at least two parts energized with respective energized phases different from each other while M is an integral number not less than two. When the linear motor is a single-phase linear motor for moving or vibrating the movable member by a moving or vibrating width substantially equal to the pitch P of the pairs of the magnetic poles adjacent to each other in the movable direction, the magnetic polar direction of each of the at least two pairs of magnetic poles alternates while the magnetic polar direction of one of the at least two pairs of magnetic poles is opposite to that of another one of the at least two pairs of magnetic poles adjacent to the one of the at least two pairs of magnetic poles in the movable direction. 
     The stator or magnetic core may have an opening through which the movable member is inserted between the magnetic poles of each of the pairs in a direction perpendicular to the movable direction. A magnetic force is generated in a direction perpendicular to the movable direction and not parallel to the polar directions between the stator and the movable member, when a magnetic flux axis of the magnetic poles of at least one pair on the stator is distant away from a magnetic flux axis of the magnetic poles of at least one pair on the movable member in the direction between the magnetic poles of at least one pair on the stator. When the electromagnetic coil device has an electromagnetic coil whose circumferential part is completely surrounded by the pair of magnetic core parts as seen in the movable direction, that is, the pair of magnetic core parts extends around or over the whole outer periphery of the circumferential part of the electromagnetic coil, the electromagnetic coil is securely held or protected by the pair of magnetic core parts. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an oblique projection view showing a combination of a stator magnetic core with single electromagnetic coil and a movable member with permanent magnets in a linear motor of the invention. 
     FIG. 2 is an oblique projection view showing a part of the stator magnetic core. 
     FIG. 3 is an oblique projection view showing another part of the stator magnetic core. 
     FIG. 4 is an oblique projection view showing the stator magnetic core. 
     FIG. 5 is an oblique projection view showing a combination of the stator magnetic core with single electromagnetic coil and another movable member with electromagnetic coils in another linear motor of the invention. 
     FIG. 6 is an oblique projection view showing a combination of the stator magnetic core with single electromagnetic coil and another movable member with pairs of high-reluctance portions and low-reluctance portions in another linear motor of the invention. 
     FIG. 7 is an oblique projection view showing a combination of another stator magnetic core with a permanent magnet and the another movable member with electromagnetic coils in another linear motor of the invention. 
     FIG. 8 is an oblique projection view showing a combination of another stator magnetic core with single electromagnetic coil and another movable member with permanent magnets in a linear motor of the invention. 
     FIG. 9 is an oblique projection view showing a part of the another stator magnetic core of FIG.  8 . 
     FIG. 10 is an oblique projection view showing another part of the another stator magnetic core of FIG.  8 . 
     FIG. 11 is an oblique projection view showing the another stator magnetic core of FIG.  8 . 
     FIG. 12 is an oblique projection view showing a combination of the another stator magnetic core with single electromagnetic coil and another movable member with electromagnetic coils in a linear motor of the invention. 
     FIG. 13 is an oblique projection view showing a combination of the another stator magnetic core with single electromagnetic coil and another movable member with pairs of high-reluctance portions and low-reluctance portions in another linear motor of the invention. 
     FIG. 14 is an oblique projection view showing a combination of another stator magnetic core with a permanent magnet and the another movable member with pairs of high-reluctance portions and low-reluctance portions in another linear motor of the invention. 
     FIG. 15 is a schematic view showing a combination of single movable member, and a plurality of stators arranged in series. 
     FIG. 16 is a schematic view showing a combination of a plurality of movable members arranged in parallel, and a plurality of stators arranged in parallel. 
     FIG. 17 is a schematic view showing a combination of a plurality of movable members arranged in series, and a stator. 
     FIG. 18 is a schematic view showing a combination of a plurality of movable members arranged in parallel, and a stator. 
     FIG. 19 is an oblique projection view showing a combination of another stator magnetic core with single electromagnetic coil and another movable member with permanent magnets in another linear motor of the invention. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     As shown in FIG. 1, a linear motor has a stator  10  including a magnetic core  11  of magnetic conductivity and an electromagnetic coil  12  surrounding a part of the magnetic core  11 , and a movable member  20  supported movably with respect to the stator  10 . The magnetic core may include iron or the like. The movable member  20  has permanent magnets  21  which are juxtaposed with each other in a movable direction of the movable member  20  while polar directions  21   a  and  21   b  of the permanent magnets  21  adjacent to each other in the movable direction are opposite to each other. 
     As shown in FIG. 2, a magnetic core part  13  of the magnetic core  11  has first magnetic poles  13   a  and second magnetic poles  13   b , and as shown in FIG. 3, a magnetic core part  14  of the magnetic core  11  has first magnetic poles  14   a  and second magnetic poles  14   b . Arrows in FIGS. 2 and 3 denote flows of magnetic flux generated in the magnetic core  11  by single electromagnetic coil  12 . As shown in FIG. 4, in the assembled magnetic core  11 , a polar direction of a pair of the first magnetic poles  13   a  and the second magnetic poles  14   b  is opposite to a polar direction of a pair of the first magnetic poles  13   b  and the second magnetic poles  14   a  adjacent to the pair of the first magnetic poles  13   a  and the second magnetic poles  14   b  in the movable direction when the magnetic core  11  is magnetized by the electromagnetic coil  12 . The movable member  20  extends between the first magnetic poles  13   a  and the second magnetic poles  14   b  of each pair and between the first magnetic poles  13   b  and the second magnetic poles  14   a  of each pair so that the movable member  20  cooperates magnetically with the magnetic core  11 . A circumferential part of the electromagnetic coil  12  is surrounded by the magnetic core  11  as seen in the movable direction. 
     As shown in FIG. 5, the movable member  20  may include electromagnetic coils  22  which are juxtaposed with each other in the movable direction while polar directions of the electromagnetic coils  22  adjacent to each other in the movable direction are opposite to each other so that the movable member  20  cooperates magnetically with the magnetic core  11 . A pitch between the magnetic poles adjacent to each other in the movable member  20  is equal to a pitch between the magnetic poles adjacent to each other in the magnetic core  11 . A pole core member of high-magnetic-conductivity may be surrounded by each of the electromagnetic coils  22 . The movable member  20  may include both the electromagnetic coils  22  and the permanent magnets  21 . The electromagnetic coils  22  may overlap each other as seen in a direction perpendicular to the movable direction. The electromagnetic coils  22  may be printed coils. 
     As shown in FIG. 6, the movable member  20  may include pairs of high reluctance portions  25  and low reluctance portions  24  juxtaposed with each other in the movable direction. The permanent magnets  21  may be additionally included by the movable member  20  with the pairs of high reluctance portions  25  and low reluctance portions  24 . The high reluctance portions  25  may be formed of non-magnetically-conductive material. 
     As shown in FIG. 7, the magnetic core  11  may be magnetized by a permanent magnet  15 . A cross sectional shape of the movable member  20  may be rectangular, circular or oval. The stator  10  may be stationary while the movable member  20  is movable, and alternatively the stator  10  may be movable while the movable member  20  is stationary. 
     As shown in FIG. 8, a linear motor has the stator  10  including the magnetic core  11  of magnetic conductivity and the electromagnetic coil  12  surrounding the part of the magnetic core  11  between longitudinal ends of the magnetic core  11  so that a magnetic flux passes the longitudinal ends, and the movable member  20  supported movably with respect to the stator  10 . The magnetic core may include iron or the like. The movable member  20  has the permanent magnets  21  which are juxtaposed with each other in a movable direction of the movable member  20  and magnetically conductive areas  26  with non magnetically conductive areas  27  between the permanent magnets  21  and between the magnetically conductive areas  26  while the polar directions  21   a  and  21   b  of the permanent magnets  21  adjacent to each other in the movable direction are opposite to each other. 
     As shown in FIG. 9, the magnetic core part  13  of the magnetic core  11  has the first magnetic poles  13   a  and the second magnetic poles  13   b  , and as shown in FIG. 10, the magnetic core part  14  of the magnetic core  11  has the first magnetic poles  14   a  and the second magnetic poles  14   b  . Arrows in FIGS. 9 and 10 denote flows of magnetic flux generated in the magnetic core  11  by the electromagnetic coil  12 . As shown in FIG. 11, in the assembled magnetic core  11 , the polar direction of the pair of the first magnetic poles  13   a  and the second magnetic poles  14   b  is opposite to the polar direction of the pair of the first magnetic poles  13   b  and the second magnetic poles  14   a  adjacent to the pair of the first magnetic poles  13   a  and the second magnetic poles  14   b  in the movable direction when the magnetic core  11  is magnetized by the electromagnetic coil  12 . The movable member  20  extends between the first magnetic poles  13   a  and the second magnetic poles  14   b  of each pair and between the first magnetic poles  13   b  and the second magnetic poles  14   a  of each pair so that the movable member  20  cooperates magnetically with the magnetic core  11 . The magnetic core  11  may be magnetized by a plurality of the electromagnetic coils  12 . 
     As shown in FIG. 12, the movable member  20  may include the electromagnetic coils  22  which are juxtaposed with each other in the movable direction with the non magnetically conductive areas  27  between the magnetically conductive areas  26  while the polar directions of the electromagnetic coils  22  adjacent to each other in the movable direction are opposite to each other so that the movable member  20  cooperates magnetically with the magnetic core  11 . The magnetically conductive areas  26  as the high-magnetic-conductivity pole core members may extend into the electromagnetic coils  22  respectively. A pitch between the magnetic poles adjacent to each other in the movable member  20  is equal to a pitch between the magnetic poles adjacent to each other in the magnetic core  11 . The movable member  20  may include both the electromagnetic coils  22  and the permanent magnets  21 . The electromagnetic coils  22  may overlap each other as seen in a direction perpendicular to the movable direction. The electromagnetic coils  22  may be printed coils. 
     As shown in FIG. 13, the movable member  20  may include the pairs of the non magnetically conductive areas  27  as the high reluctance portions  25  and the magnetically conductive areas  26  as the low reluctance portions  24  juxtaposed with each other in the movable direction. The permanent magnets  21  may be additionally included by the movable member  20  with the pairs of high reluctance portions  25  and low reluctance portions  24 . 
     As shown in FIG. 14, the magnetic core  11  may be magnetized by the permanent magnet  15 . A cross sectional shape of the movable member  20  may be rectangular, circular or oval. The stator  10  may be stationary while the movable member  20  is movable, and alternatively the stator  10  may be movable while the movable member  20  is stationary. 
     When the stator is single, that is, the linear motor is a single phase linear motor so that the magnetic field is moved between the pairs of magnetic poles adjacent to each other in the movable direction, the movable member  20  is moved or reciprocates between the pairs of magnetic poles adjacent to each other in the movable direction. 
     As shown in FIGS. 15 and 16, a distance between the pair of magnetic poles of one of the stators and the pair of magnetic poles of another one of the stators  10  juxtaposed with each other in the movable direction=(k*P)+n(P/M), when P is a pitch Ps of the pairs of the magnetic poles in each of the stators and a pitch Pm of the magnetic poles of the movable member  20  adjacent to each other in the movable direction, k is an integral number not less than zero, M is a number of the stators  10  energized with respective energized phases different from each other to generate a travelling magnetic field while M is an integral number not less than two, and n is a series of integral number from 1 to M. In FIG. 15, the stators  10  are arranged in series, and in FIG. 16, the stators  10  are arranged in parallel. 
     As shown in FIGS. 17 and 18, a distance between the pair of magnetic poles of one of the movable members  20  and the pair of magnetic poles of another one of the movable members  20  juxtaposed with each other in the movable direction=(k*P)+n(P/M), when P is a pitch Ps of the pairs of the magnetic poles in the stator and a pitch Pm of the magnetic poles of the movable members  20  adjacent to each other in the movable direction, k is an integral number not less than zero, M is a number of the movable members  20  energized with respective energized phases different from each other to generate a travelling magnetic field while M is an integral number not less than two, and n is a series of integral number from 1 to M. In FIG. 17, the movable members  20  are arranged in series, and in FIG. 18, the movable members  20  are arranged in parallel. 
     The magnetic core  11  has an opening or groove extending from spaces between the magnetic poles  13   a  and  14   b  and between the magnetic poles  14   a  and  13   b  so that the movable member  20  is inserted into the spaces between the magnetic poles through the opening from an outside of the magnetic core  11  in a direction perpendicular to the movable direction of the movable member  20 . When a magnetic flux axis of the magnetic poles of on the stator  10  is distant away from a magnetic flux axis of the magnetic poles on the movable member  10  in a direction perpendicular to the movable direction and not parallel to the polar directions, a magnetic force is generated in the direction so that the magnetic flux axis of the magnetic poles of on the stator  10  and the magnetic flux axis of the magnetic poles on the movable member  10  are urged to approach each other in the direction. At least one of the pairs of magnetic poles may be energized to generate the magnetic force for supporting a force to be borne by the movable member  10  in the direction. 
     As shown in FIG. 19, the movable member  10  may be surrounded by the magnetic core  11 .