Abstract:
In a joint driving apparatus, a linear motor includes at least one stator part, a movable element, and an electromagentic coil device for energizing the stator part to generate a magnetic field, the stator part includes pairs of magnetic poles, the pairs are adjacent to each other in each of the stator parts, the magnetic poles of each of the pairs face into each other through the movable element to generate a magnetic field passing the magnetic poles through the movable element, and 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 when the stator part is magnetized.

Description:
BACKGROUND OF THE INVENTION AND RELATED STATEMENT  
         [0001]    The present invention relates to a joint driving apparatus for generating a relative movement between first and second members on a joint.  
           [0002]    In a prior art joint driving apparatus, a rotational motor is used to generate a relative movement between first and second members on a joint. In another prior art joint driving apparatus, a linear motor is used to generate the relative movement between first and second members on the joint, and a stator structure of the linear motor is similar to that of the rotational motor.  
         OBJECT AND SUMMARY OF THE INVENTION  
         [0003]    An object of the present invention is to provide a joint driving apparatus for generating a relative movement between first and second members on a joint, by which apparatus a magnetic flux is effectively utilized to generate a force for urging the first and second members with respect to each other.  
           [0004]    According to the invention, in a joint driving apparatus for generating a relative movement between first and second members on a joint, comprising, a linear motor including at least one stator part fixed to another one of the first and second members, a movable element movable with respect to the stator part in a movable direction and connected to the one of the first and second members to be moved with respect to the another one of the first and second members, and an electromagnetic coil device for energizing the stator part to be magnetized so that a magnetic field for urging the movable element in the movable direction with respect to the stator part is generated, the stator part includes at least two pairs of magnetic poles, the at least two pairs are adjacent to each other in the movable direction, the magnetic poles of each of the at least two pairs face to each other through the movable element in a traverse direction perpendicular to the movable direction to generate the magnetic field passing the magnetic poles through the movable element, and 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 when the stator part is magnetized.  
           [0005]    Since the magnetic poles of each of the at least two pairs face to each other through the movable element in a traverse direction perpendicular to the movable direction to generate the magnetic field passing the magnetic poles through the movable element, and 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 when the stator part is magnetized, a magnetic flux is effectively utilized to generate a force for urging the first and second members with respect to each other.  
           [0006]    The joint driving apparatus may further comprise a sensor for generating a signal corresponding to an actual movement of the movable element with respect to the stator part, wherein the electromagnetic coil device controls a change in energized phase of the stator part on the basis of a comparison between the signal and an instructed movement of the movable element with respect to the stator parts to form a closed-loop control system. The electromagnetic coil device may control a change in energized phase of the stator part on the basis of an instructed movement of the movable element with respect to the stator part to form an open-loop control system. An actual movement of the movable element with respect to the stator part may be estimated from a voltage induced in the electro-magnetic coil device by the actual movement of the movable element or from an electric current flowing through the electromagnetic coil device.  
           [0007]    When the apparatus comprises at least two of the stator parts, the electromagnetic coil device energizes the at least two stator parts respectively to be magnetized with a difference in energized phase between the at least two stator parts so that a travelling magnetic field for urging the movable element in the movable direction is generated by a cooperation between the at least two stator parts, P is a pitch of the pairs of the magnetic poles adjacent to each other in the movable direction in each of the stator parts, k is an integral number not less than zero, and M is a number of the stator parts energized with respective energized phases different from each other while M is an integral number not less than two, a distance between the pair of magnetic poles of one of the stator parts and the pair of magnetic poles of another one of the stator parts adjacent to each other in the movable direction=(k*P)+(P/M).  
           [0008]    The joint driving apparatus may further comprise an elastic member a part of which is connected to one of the first and second members, wherein the movable element is connected to another part of the elastic member to drive the one of the first and second members through the elastic member with respect to the another one of the first and second members. The apparatus may comprise a plurality of pairs of the elastic members and linear motors while the relative movement between the first and second members is performed along each of directions different from each other by respective one of the pairs of the elastic members and linear motors. The apparatus may comprise a plurality of the elastic members while the relative movement between the first and second members is performed along each of directions different from each other by respective one of the elastic members connected selectively to the linear motor. The joint driving apparatus may further comprise a dust cover covering a portion of the movable element projecting from the stator parts. The joint driving apparatus may further comprise a cooling device for cooling the linear motor. The joint driving apparatus may further comprise a switching device for switching, between a battery and an outer electric power source, an electric power supply source for supplying an electric power to the linear motor. The joint driving may further comprise a spring member for urging the movable element with respect to the another one of the first and second members in the movable direction. The elastic member may include a spring for connecting elastically between the movable element and the one of the first and second members. The elastic member may include a rubber for connecting elastically between the movable element and the one of the first and second members.  
           [0009]    When first one of the magnetic poles of each of the at least two pairs faces to a first side surface of the movable element, 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 the traverse direction, a magnetic polar direction between the first one of the magnetic poles of one of the at least two pairs and the second one of the magnetic poles of the one of the at least two pairs is opposite to a magnetic polar direction between the first one of the magnetic poles of another 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, and the at least two pairs is magnetized by single electromagnetic coil, a number of electromagnetic coils for the linear motor is minimized.  
           [0010]    When first one of the magnetic poles of each of the at least two pairs faces to a first side surface of the movable element, 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 the traverse direction, the stator part has a magnetic core and the electromagnetic coil device has an electromagnetic coil surrounding an intermediate portion of the magnetic core between longitudinal ends of the magnetic core to generate a magnetic field passing the longitudinal ends of the magnetic core so that the at least two pairs of magnetic poles are energized by the electromagnetic coil, and one of the longitudinal ends of the magnetic core 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 while another one of the longitudinal ends of the magnetic core 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, a size of the magnetic core is minimized.  
           [0011]    When the apparatus comprises at least two of the stator parts energized respectively to be magnetized with a difference in energized phase between the at least two stator parts so that a travelling magnetic field for urging the movable element in the movable direction is generated by a cooperation between the at least two stator parts, and each of the stator parts is magnetized by single electromagnetic coil, a number of electromagnetic coils for the linear motor is minimized.  
           [0012]    When the apparatus comprises at least two of the stator parts energized respectively to be magnetized with a difference in energized phase between the at least two stator parts so that a travelling magnetic field for urging the movable element in the movable direction is generated by a cooperation between the at least two stator parts, and the at least two pairs of magnetic poles in one of the stator parts is energized by single electromagnetic coil and the at least two pairs of magnetic poles in another one of the stator parts is energized by another single electromagnetic coil, a number of electromagnetic coils for the linear motor is minimized. When the stator part is magnetized by single electromagnetic coil, a number of electromagnetic coils for the linear motor is minimized. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    [0013]FIG. 1 is a schematic view showing a joint driving apparatus including a linear motor of the invention.  
         [0014]    [0014]FIG. 2 a  is a block diagram showing a control system of the joint driving apparatus.  
         [0015]    [0015]FIG. 2 b  is a block diagram showing another control system of the joint driving apparatus.  
         [0016]    [0016]FIG. 3 a  is a block diagram showing another control system of the joint driving apparatus.  
         [0017]    [0017]FIG. 3 b  is a block diagram showing another control system of the joint driving apparatus.  
         [0018]    [0018]FIG. 4 is a schematic view showing another joint driving apparatus including a linear motor of the invention.  
         [0019]    [0019]FIG. 5 is a schematic view showing another joint driving apparatus including a linear motor of the invention.  
         [0020]    [0020]FIG. 6 a  is a schematic oblique projection view showing a stator drive unit of a linear motor of the invention.  
         [0021]    [0021]FIG. 6 b  is a schematic oblique projection view showing another stator drive unit of a linear motor of the invention.  
         [0022]    [0022]FIG. 7 a  is a schematic oblique projection view showing a magnetic core unit of a linear motor of the invention.  
         [0023]    [0023]FIG. 7 b  is a schematic oblique projection view showing a magnetic core assembly of a linear motor of the invention.  
         [0024]    [0024]FIG. 8 a  is a schematic oblique projection view showing an outer shape of a linear motor of the invention.  
         [0025]    [0025]FIG. 8 b  is a schematic oblique projection view showing an outer shape of another linear motor of the invention.  
         [0026]    [0026]FIG. 8 c  is a schematic oblique projection view showing an outer shape of another linear motor of the invention.  
         [0027]    [0027]FIG. 9 is a schematic oblique projection view showing stator parts of the invention arranged in series and a movable element driven on the stator parts.  
         [0028]    [0028]FIG. 10 is a schematic oblique projection view showing stator parts of the invention arranged in parallel and a movable element driven on the stator parts.  
         [0029]    [0029]FIG. 11 is a schematic oblique projection view showing another movable element of the invention.  
         [0030]    [0030]FIG. 12 is a schematic view showing another movable element of the invention, and a stator usable therefor.  
         [0031]    [0031]FIG. 13 is a partially cross-sectional view showing another linear motor of the invention.  
         [0032]    [0032]FIG. 14 is a diagram showing a relation ship between input instruction pulses, a proceeding of movable element, and electric current phases for energizing stator parts respectively, in a two-phases linear motor.  
         [0033]    [0033]FIG. 15 is a diagram showing another relation ship between input instruction pulses, a proceeding of movable element, and electric current phases for energizing stator parts respectively, in the two-phases linear motor.  
         [0034]    [0034]FIG. 16 is a diagram showing another relation ship between input instruction pulses, a proceeding of movable element, and electric current phases for energizing stator parts respectively, in the two-phases linear motor.  
         [0035]    [0035]FIG. 17 is a schematic view showing another joint driving apparatus including a linear motor of the invention. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0036]    As shown in FIG. 1, a linear motor  101  has a controller  102 , an electric driver  103 , a battery  104 , an electric source line  105 , a connector  106 , a swingable joint  108 , first and second members  109  and  110  swingable with respect to each other on the joint  106 , an elastic member  107  of spring or rubber whose one end is connected to a movable element through the connector  106 , whose another end is connected to the second member  110  and which has an elastic characteristic for movement similar to muscle, and another elastic member  111  of spring or rubber whose one end is connected to the first member, whose another end is connected to the second member  110  and which has an elastic characteristic for movement similar to muscle.  
         [0037]    An electric power may be supplied to the linear motor  101  from either the battery  104  or electric source line  105 . At least one of the battery  104  and electric source line  105  may be detachable. A spring  120  may be arranged between the first member  109  and the movable element as a damper. As shown in FIG. 17, the linear motor  101  may has a cooling device  121  and/or a dust cover  122  for covering a portion of the movable element projecting from a stator. The cooling device  121  may be a motor drive fan or cooling fin.  
         [0038]    As shown in FIG. 2 a , a closed-loop control system may be formed by a sensor  123  for measuring the relative movement of the movable member and the stator and/or a positional relationship between magnetic poles on the movable member and magnetic poles on the stator, the controller  102  receiving signals from the sensor  123  and the power driver  103 .  
         [0039]    As shown in FIG. 2 b , an open-loop control system may be formed by the linear motor  101 , the controller  102  and the power driver  103 .  
         [0040]    As shown in FIG. 3 a , the power driver  103  may be controlled on the basis of the positional relationship between magnetic poles on the movable member and magnetic poles on the stator estimated in the controller  102  from an induced voltage E 0  generated by the linear motor  101 .  
         [0041]    As shown in FIG. 3 b , the power driver  103  may be controlled on the basis of the positional relationship between magnetic poles on the movable member and magnetic poles on the stator estimated in the controller  102  from the induced voltage E 0  calculated from a voltage and a measured electric current supplied to the linear motor  101 .  
         [0042]    As shown in FIG. 4, a relative movement between the first and second members may be brought about by a pair of the linear motors  101 . As shown in FIG. 5, the linear motors  101  may be selectively connected to one of the elastic members  107   a  and  107   b  to drive the second member  110  in either direction.  
         [0043]    As shown in FIGS. 6 a  and  6   b , a first magnetic core  51  forms a first pair of magnetic poles  11   a  and  21   b , and a second magnetic core  52  forms a second pair of magnetic poles  12   b  and  22   a . A (2n−1)th magnetic core has the first pair of magnetic poles  11   a  and  21   b  and a (2n)th magnetic core has the second pair of magnetic poles  12   b  and  22   a  when n=1, 2, 3, - - - . The first magnetic core  51  and second magnetic core  52  are surrounded by a single electromagnetic coil  4 . A movable member  6  including pairs of magnetic poles whose pitch Pm is equal to a pitch Ps between the first magnetic cores  51  and  52  adjacent to each other in a movable direction of the movable member  6  is movable in a gap  8  between the magnetic poles  11   a  and  21   b  of the first magnetic core  51  and between the magnetic poles  12   b  and  22   a  of the second magnetic core  52 . The magnetic poles of the movable member  6  are formed by permanent magnets, electromagnetic coils and/or differences in magnetic conductivity relative to the magnetic cores along the movable direction. Magnetic polar directions of the first and second magnetic cores  51  and  52  adjacent to each other in the movable direction are opposite to each other.  
         [0044]    As shown in FIGS. 7 a  and  7   b , since a drawing force between the movable member  6  and the magnetic poles  11   a  and  22   a  is substantially equal to a drawing force between the movable member  6  and the magnetic poles  21   b  and  12   b , a drawing force between the movable member  6  and the magnetic cores  51  and  52  is decreased. The magnetic cores  51  and  52  may be formed by a stack of steel plates.  
         [0045]    As shown in FIGS. 8 a ,  8   b  and  8   c , a stator  3  including the magnetic cores  51  and  52  and the electromagnetic coil  4  may be contained by various shape molded plastic. The movable member  6  may be rectangular or cylindrical as shown in FIG. 12.  
         [0046]    As shown in FIG. 9, the stator  3  has stator parts A and B arranged in series each of which stator parts includes the magnetic cores  51  and  52  and the electromagnetic coil  4  and which are energized to be magnetized respectively with a difference in energized phase between the stator parts A and B so that a travelling magnetic field for urging the movable element  6  in the movable direction is generated by a cooperation between the stator parts A and B. As shown in FIGS.  14 - 16 , the difference in energized phase between the stator parts A and B is π/2 when the linear motor is a two phase linear motor. As shown in FIG. 15, an electric current supplied to each of the stator parts A and B may be changed along a sine curve. As shown in FIG. 16, the electric current supplied to each of the stator parts A and B may changed by changing a pulse width of voltage or current to be supplied.  
         [0047]    As shown in FIG. 10, the stator parts A and B may be arranged in parallel, and the movable members  6  may be arranged in parallel. The movable members  6  arranged in parallel may be one-piece. As a matter of course, the linear motor may be three, four or five phase linear motor.  
         [0048]    A distance between the pair of magnetic poles of one of the stator parts and the pair of magnetic poles of another one of the stator parts adjacent to each other in the movable direction=(k*P)+(P/M), when P is a pitch Ps of the pairs of the magnetic poles of the stator parts A and B adjacent to each other in the movable direction in each of the stator parts and a pitch Pm of the magnetic poles of the movable member  6  adjacent to each other in the movable direction, k is an integral number not less than zero, and M is a number of the stator parts energized with respective energized phases different from each other while M is an integral number not less than two.  
         [0049]    As shown in FIG. 11, the movable member  6  may have a base band  16  and magnetically conductive protrusions  13  to change a reluctance between the movable member  6  and the magnetic cores  51  and  52  in a longitudinal direction of the movable member  6 . The magnetically conductive protrusions  13  may be magnetized by permanent magnets on the movable member  6 . The base band  16  may be non-magnetically permeable.  
         [0050]    As shown in FIG. 12, the movable member  6  may be formed by a rod  35 , high-magnetic-conductivity large diameter rings  36  and low-magnetic-conductivity small diameter rings  37 . The rings  36  may include permanent magnets. Surfaces of the magnetic cores  51  and  52  are curved along outer surfaces of the high-magnetic-conductivity large diameter rings  36 .  
         [0051]    As shown in FIG. 13, the magnetic cores  51  and  52  may have slide supports  14 , and the movable member  6  may have a slider  15  which can slide on the slide supports  14  with low friction.