Patent Abstract:
A rotation angle sensor and a method of winding a rotation angle sensor involve a single electrical wire that is wound from a rotor transformer to a magnetic rotor. The magnetic rotor is axially spaced on a shaft from the rotor transformer. A notch is formed in a wall of a bobbin of the rotor transformer to permit the wire to pass from the rotor transformer to the magnetic rotor. The ends of the single wire are electrically connected together at a junction, and the junction is fixed to the rotor transformer with resin.

Full Description:
CROSS REFERENCE TO RELATED APPLICATION  
       [0001]     This application is based on and incorporates by reference Japanese Patent Application No. 2003-275952, which was filed on 17. Jul. 2003.  
       BACKGROUND OF THE INVENTION  
       [0002]     The present invention relates to a rotation angle sensor that includes a brushless resolver having a transformer and a magnetic rotor and to a method for winding a rotation angle sensor, and in particular, to a rotation angle sensor in which a rotor transformer winding and a magnetic rotor winding are wound with a single wire.  
         [0003]     A brushless resolver has a transformer winding such that, in addition to the rotor and stator for excitation and detection, the resolver includes a transformer for a power supply.  FIG. 5  shows an example.  
         [0004]      FIG. 5  is a cross-sectional view of the structure on the rotor of a conventional resolver. The structure of the stator is omitted.  FIG. 5  shows the rotor structure including a rotor  102  having bobbin  103  integrally formed with the rotation shaft  101  (the rotor winding is not shown in the drawing).  FIG. 5  represents an improvement over a conventional rotor transformer structure in which the bobbin  103  from is formed separately from the rotation shaft  101  and combined later. The rotor winding and rotor transformer winding are individually formed, and then combined. (e.g., see Japanese patent publication JP H10-170306). Then, the rotor winding and rotor transformer winding are connected, and the connection is performed as described below.  
         [0005]      FIGS. 6A and 6B  show a conventional connection of the rotor winding and rotor transformer winding.  FIG. 6A  shows that a rotor having a magnetic rotor winding and a rotor transformer having a rotor transformer winding are mounted on a rotation shaft.  FIG. 6B  shows a state in which the lead wires of each winding shown in  FIG. 6A  are connected.  
         [0006]     The coil bobbin  113  of the rotor transformer  112  is mounted on a winding machine (not shown in the drawing), and an electrical wire is coiled around the groove of the coil bobbin  113  for a predetermined number of times. Then the lead wire  122   a  at the starting side of the winding and the lead wire  122   b  at the ending side of the winding are temporarily fixed with an insulation tape (not shown in the drawing). Then, the lead wires  122   a ,  122   b  are led out from the winding machine.  
         [0007]     Regarding the magnetic rotor  114 , a laminated rotor core  123  is mounted on the winding machine and the electric wire is coiled for a predetermined number of times on each of many magnetic poles of the rotor core  123 . The wire may be coiled directly on each magnetic pole or indirectly via a coil bobbin. Then, the lead wire  124   a  at the start of the winding and the lead wire  124   b  at the end of the winding are temporarily fixed with insulation tape, and then led out from the winding machine.  
         [0008]     Next, a hollow rotation shaft  111  is inserted and fitted in the magnetic rotor  114  and the rotor transformer  112 . Then, as shown in  FIG. 6A , the magnetic rotor  114  and the rotor transformer  112  are positioned at predetermined locations on the rotation shaft  111 . At that time, the magnetic rotor  114  and the rotor transformer  112  are arranged so that an opening  119  of the coil bobbin  113  of the rotor transformer  112  is located on the side of the coil bobbin  113  that faces the magnetic rotor  114 .  
         [0009]     When the magnetic rotor  114  and the rotor transformer  112  are positioned properly, insulation tubes  128  are mounted on the lead wires  124   a  and  124   b . Then, the starting lead wire  124   a  and the ending lead wire  124   b  of the magnetic rotor winding  121  are led into the groove of the coil bobbin  113  via the opening  119 . Then, while taking the polarity of the magnetic rotor winding  121  and rotor transformer winding  120  into account, the lead wires  124   a  and  124   b  of the magnetic rotor winding  121  are connected to the starting lead wire  122   a  and ending lead wire  122   b  of the rotor transformer winding  120 , so that a series circuit is formed. The insulation coating of the electric wire will not be damaged by the edge of the opening  119  due to the insulation tubes  128 .  
         [0010]     In the case of  FIG. 6B , the ending lead wire  124   b  and the starting lead wire  122   a  are connected with solder  126 . Similarly, the starting lead wire  124   a  and the ending lead wire  122   b  are connected with solder  127 . The soldered connections are made along insulation tape  125 , which is attached to the surface of the rotor transformer winding  120 , and fixed with resin. This method has the following problems.  
         [0011]     Conventionally, a semi-finished product has been manufactured for each unit. That is, a semi-finished rotor component, in which the magnetic rotor winding is coiled and its lead wire is temporary fixed with tape, and a semi-finished rotor transformer component, in which the rotor transformer winding is coiled and its lead wire is temporarily fixed with tape, are individually formed. Then, an alignment process in which the rotation shaft is inserted in the components is carried out. The alignment is difficult because the finished winding may be mistakenly deformed by being pressed manually or the temporary insulation tape may detach, and the predetermined shape of the coiled winding may be destroyed.  
         [0012]     In addition, when the lead wires of the magnetic rotor winding and the lead wires of the rotor transformer are connected, the lead wires of the magnetic rotor winding are covered with insulation tubes  128  and then fed through the opening  119 . Then, the lead wires  124   a ,  124   b ,  122   a ,  122   b  are connected at two junctions, and the two junctions are placed along the rotor transformer winding via insulation tape and fixed with resin. The process is difficult to carry out in a small space, and thus, long lead wires must be employed. Unlike the winding portion, the long lead wires may generate an irregular magnetic field that has an effect on the basic magnetic field, which is based on the designated number of windings, and may create an uneven weight distribution, which may cause oscillations during the rotation. Further, the long lead wires may cause a restriction such that the interval between the rotor transformer and magnetic rotor cannot be narrowed.  
       SUMMARY OF THE INVENTION  
       [0013]     An objective of the invention is, by taking the above-mentioned problems into account, to provide a rotation angle sensor having a simple connection structure for the lead wires.  
         [0014]     The present invention is mainly characterized in that, in order to reduce the number of connections between the lead wires of the magnetic rotor winding and rotor transformer to one, both windings are formed by a continuous coiling of a single electric wire. To allow the continuous coiling, a notch, through which the wire passes, is formed on the coil bobbin of the rotor transformer.  
         [0015]     The invention is basically a rotation angle sensor characterized in that a coil bobbin of a rotor transformer, which has a notch on its side wall, and a laminated core of a magnetic rotor are arranged parallel to one another on a rotation shaft. A rotor transformer winding and a magnetic rotor winding, in which a single electric wire is continuously coiled on the coil bobbin of the rotor transformer and the laminated core of the magnetic rotor via the notch, are formed. The ends of the electric wire are connected via the notch and are fixed on the rotor transformer winding with resin.  
         [0016]     The laminated core of the magnetic rotor has a plurality of magnetic poles, and the electric wire is continuously coiled on each magnetic pole.  
         [0017]     In another aspect of the invention, the coil bobbin of the rotor transformer has annular grooves, and the grooves are arranged to accommodate the rotor transformer windings.  
         [0018]     In another aspect of the invention, edges of the walls that define the notch are coated with a resin to provide the edges with a low friction surface. The resin is one that provides low friction contact. Thus, the wire will not be damaged by contact with the edges of the walls that define the notch  
         [0019]     Therefore, in one aspect of the invention, the rotation angle sensor includes a coil bobbin of a rotor transformer, which has a notch on the side wall, and a laminated magnetic rotor core. The coil bobbin and the laminated core are located in a parallel relationship on a rotation shaft. A single electric wire is continuously coiled on the coil bobbin to form a rotor transformer. The same wire is continuously coiled on the laminated core to form a magnetic rotor winding. The wire passes from the rotary transformer to the magnetic rotor through the notch. First and second ends of the winding of the electric wire are connected through the notch and fixed on the rotor transformer winding with resin. Therefore, the rotor transformer winding and magnetic rotor winding are formed by a continuous winding of a single electric wire. In addition, only one connection is needed at only one location, allowing the length of electric wire to be shortened at only one place. Consequently, the electric effect and magnetic effect on the winding at the connection can be reduced compared to the prior art.  
         [0020]     The laminated core of the magnetic rotor has magnetic poles, and in principle, only the projected magnetic poles are coiled, allowing machine winding. In addition, for the magnetic rotor winding, when all the magnetic poles are coiled, the end of the winding is directed back to the beginning of the winding, which allows continuous coiling with a single electric wire.  
         [0021]     The coil bobbin of the rotor transformer has annular grooves, which extend at a right angle to the axis of the rotation shaft, and therefore, the rotor transformer winding which is a continuously coiled single electric wire, can be arranged in the grooves. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0022]     The accompanying figures, in which like reference numerals refer to identical or functionally similar elements throughout the separate views and which, together with the detailed description below, are incorporated in and form part of the specification, serve to further illustrate various embodiments and to explain various principles and advantages all in accordance with the present invention.  
         [0023]      FIG. 1A  is a diagrammatic side view illustrating an initial stage of the winding process of the magnetic rotor and rotor transformer of the rotation angle sensor of the present invention;  
         [0024]      FIG. 1B  is a diagrammatic side view illustrating an intermediate stage of the winding process of the magnetic rotor and rotor transformer of the rotation angle sensor of the present invention;  
         [0025]      FIG. 1C  is a diagrammatic side view illustrating a late stage of the winding process of the magnetic rotor and rotor transformer of the rotation angle sensor of the present invention;  
         [0026]      FIG. 2  is diagrammatic side view of a winding machine that uses the multi-joint robot of the present invention;  
         [0027]      FIG. 3A  is a diagrammatic side view of a further embodiment of the invention in which shield plates are fixed adjacent to the rotor transformer and the magnetic rotor;  
         [0028]      FIG. 3B  is an end view of a shield plate  52 ;  
         [0029]      FIG. 3C  is an end view of a sidewall  18  of a rotor transformer  12 .  
         [0030]      FIG. 3D  is an end view of a shield plate  51 ;  
         [0031]      FIG. 4  is a partial cross sectional view of a side wall of the bobbin showing a resin coating on the notch;  
         [0032]      FIG. 5  is a cross-sectional view of a rotor of a conventional resolver;  
         [0033]      FIG. 6A  is a diagrammatic side view illustrating an initial stage of a method of connecting lead wires of a magnetic rotor winding and a rotor transformer winding of a conventional resolver; and  
         [0034]      FIG. 6B  is a diagrammatic side view illustrating a later stage of a method of connecting lead wires of a magnetic rotor winding and a rotor transformer winding of a conventional resolver. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0035]      FIG. 1  shows an initial stage of the winding process for a magnetic rotor  14  and a rotor transformer  12  of a rotation angle sensor of the present invention.  FIG. 1A  shows a laminated core  15  of the magnetic rotor  14  and a coil bobbin  13  of the rotor transformer  12  prior to initiation of coiling.  FIG. 1B  shows the laminated core  15  of the magnetic rotor  14  and the coil bobbin  13  of the rotor transformer  12  during the coiling process, and  FIG. 1C  shows the laminated core  15  of the magnetic rotor  14  and the coil bobbin  13  of the rotor transformer  12  after the coiling is completed. The rotation angle sensor includes a stator (not shown) and the magnetic rotor  14  for excitation and detection. In addition, the rotation angle sensor includes a stator transformer (not shown) and the rotor transformer  12  for the electric supply.  
         [0036]     First, as shown in  FIG. 1A , the coil bobbin  13  of the rotor transformer  12  and the laminated core  15  of the magnetic rotor  14  are fitted to a hollow rotation shaft  11 , which is made of a metal such as an aluminum alloy. Then the coil bobbin  13  and the laminated core  15  are positioned and fixed. The coil bobbin  13  is made of a magnetic substance, an aluminum alloy, or the like. Alternatively, the coil bobbin  13  of the rotor transformer  12  can be formed on the hollow rotation shaft  11  in advance.  
         [0037]     The coil bobbin  13  of the rotor transformer  12  is arranged annularly on the surface of the rotation shaft  11  and its rim has a cross-sectional shape that resembles a squared U-shape.  
         [0038]     The U shape is, as shown in the circled window of  FIG. 1A , a bottom  16  and side walls  17  and  18 . On one side wall  18 , a notch  19  is formed to accommodate an electric wire (magnet wire). Preferably, the edges of the notch  19  are rounded or coated a resin  18   a  with a small contact resistance, for example, Teflon (trademark), to prevent damage to the insulation coating of the electric wire (See  FIG. 4 ). The notch  19  is shaped such that the magnetic flux generated due to the electric current flow in the rotor transformer winding  20  practically has no effect on a magnetic rotor winding  21 . When the coil bobbin  13  is formed by a magnetic substance, it forms a magnetic path and functions as an electromagnetic shield.  
         [0039]     The laminated core  15  is, in the case of the embodiment of  FIG. 1A , laminated with a predetermined number of silicon steel plates and fixed. The steel plates are punched in a shape that includes salient poles, or magnetic poles, and then fixed, and an insulator that also serves as a coil bobbin is mounted as required. The magnetic poles of the plates that form the laminated core  15  are skewed as shown. That is, the plates that form the laminated core  15  are slightly offset from one another to form the skewed poles as shown in  FIG. 1A .  
         [0040]     Next, the rotation shaft  11 , in which the positioning of the coil bobbin  13  of the rotor transformer  12  and the laminated core  15  of the magnetic rotor  14  is completed, is fixed on a winding machine (not shown in the drawing) and then, through a process using a multi-joint robot (not shown in the drawing) a first end  22   a  of an electric wire  22  is temporarily fixed to the coil bobbin  13  of the rotor transformer  12  with insulation tape  26 . Then, with the multi-joint robot, the rotor transformer  12  is continuously coiled with the same piece of electric wire  22 . Then the same piece of wire  22  is coiled for a predetermined number of times and fed through the notch  19  of the bobbin  13 . Then, the same piece of wire  22  is coiled on the rotor transformer  12  and then on each of the magnetic poles  23  of the laminated core  15  of the magnetic rotor  14  in one direction for a predetermined number of times.  
         [0041]     When all the magnetic poles  23  are coiled, a second end  22   b  of the electric wire  22  of the magnetic rotor winding  21  is arranged in the coil bobbin  13  through the notch  19  of the coil bobbin  13 . Insulation tape  25  is attached on the rotor transformer winding  20  so that the winding will not come off and so that solder from the next process will not fall on the electric wire and break it.  
         [0042]     The first and second ends  22   a ,  22   b  of the wire  22  are soldered together and arranged along the insulation tape  25 . Then, the solder joint is sealed with resin. The resin-sealed portion is arranged along the insulation tape, and then fixed with resin.  
         [0043]     The winding direction of the rotor transformer winding  20  and the winding direction of the magnetic rotor winding  21  are significantly different; they are essentially transverse to one another. Therefore for the winding machine, for example, a vertical multiple-joint robot  31  is used. Multiple-joint robots are commercially available from a variety of companies and, in the present invention, the robot  31  can be appropriately selected from those available based on the circumstances.  
         [0044]      FIG. 2  shows a winding machine  30  that uses the multi-joint robot  31 . In  FIG. 2 , the winding machine  30  includes the multi-joint robot  31  and a work holder  39  that are arranged on a platform  42 . The position of the multi-joint robot  31  and work holder  39  can be changed on the platform  42 .  
         [0045]     The multi-joint robot  31  of  FIG. 2  has only three axes, however, the number of axes is determined in connection with the operation of the work holder  39  and a movable tip  36 . Often, a multi-joint robot with 6 axes is employed. The electric wire  32  is led to a nozzle  37 , which is arranged on the movable tip  36  of the multi-joint robot  31  through electric wire guides  33 ,  34  and  35 , which are provided on the multi-joint robot  31 . The nozzle  37  can be either fixed or movable on the movable tip  36 . When the nozzle  37  is movable, the nozzle  37  is structured so that the installation angle of the nozzle  37  against the movable tip  36  is changed to carry out a regular winding, and it carries out the designated winding operation with an integrated motor (not shown in the drawing).  
         [0046]     The work holder  39  has a control circuit and a driving source such as a motor that moves a chuck  38  rotationally and axially.  
         [0047]     The multi-joint robot  31  and work holder  39  are connected with a cable  40 , and the required control is carried out by a controller  41 . The controller  41  includes a microcomputer that executes a program. The program includes a winding process routine. The winding process routine has a learning routine that includes a learning routine for the movable tip  36 , and in particular, it has a learning routine for the winding process of the magnetic poles of the laminated core  15  of the magnetic rotor  14 .  
         [0048]     In the winding process, the rotation shaft  11 , on which are the coil bobbin  13  of the rotor transformer  12  and the laminated core  15 , is held by the chuck  38  of the work holder  39  as shown in  FIG. 2 .  
         [0049]     On a rear side of the multi-joint robot  31 , an electric wire reel (not shown in the drawing) is provided, and the electric wire  22  sent out from the reel passes through the wire guides  33 ,  34  and  35  of the multi-joint robot  31 . Then, the wire  22  is led to the nozzle  37 , as shown. The electric wire  22  is supplied from the nozzle  37  via a tension setting mechanism (not shown in the drawing) so that the wire  22  has a constant tension.  
         [0050]     By programmatically controlling the nozzle  37  while the chuck  38  of the work holder  39  is rotation controlled so that the tension of the electric wire  32  is constant, the electric wire  22  is coiled around the coil bobbin  13 . Once the number of windings for the coil bobbin reaches a predetermined number, the multi-joint robot  31  directs the wire  22  to the magnetic rotor  14  through the notch  19 . Then, the multi-joint robot  31  continuously coils the magnetic poles of the magnetic rotor  14  using the same single electric wire  22 . Note that the wire  22  passes through the notch  19  directly to one of the nearest poles of the magnetic rotor  14  so that the insulation coating of the wire  22  is not damaged by contact with the edges of the notch  19 .  
         [0051]     The magnetic poles are coiled by moving the nozzle  37  around the magnetic poles of the laminated core  15  of the magnetic rotor  14 . The electric wire  22  sent out from the nozzle  37  is coiled from the base end (inner end) of each salient pole to the distal end, or from the distal end to the base end in a single line, and then it is coiled in a plurality of layers.  
         [0052]     When the nozzle  37  passes through the slot between the magnetic poles, it moves in a slanted state and is inclined outwards from the salient poles, so that the nozzle  37  can coil without contacting the distal ends of the magnetic poles.  
         [0053]     By moving the nozzle  37  around each magnetic pole using the multi-joint robot  31 , the angle and moving speed of the nozzle  37  can be freely adjusted depending on the rounding position. Therefore, damage to the insulation coating of the electric wire  32  is prevented, which allows multiple-layer coiling of the electric wire  32 . When the winding of the laminated core of the magnetic rotor  14  is completed, the wire  22  is lead through the notch  19  to the coil bobbin  13 , and then the winding process by the multiple-joint robot  31  is completed.  
         [0054]     Once the winding is completed, both ends  22   a ,  22   b  of the single electric wire  22  are soldered in the coil bobbin  13  in the rotor transformer  12 , and then fixed with resin.  
         [0055]     With regard to the winding of the multi-joint robot, continuous coiling of a single electric wire for the magnetic rotor winding and the rotor transformer winding with different winding directions is accomplished. In addition, it is possible to coil  3  or more windings in different directions, and they are similarly carried out.  
         [0056]     In addition, if a flyer is used instead of a multi-joint robot, the function of the work holder should be enhanced and, at a minimum, the winding direction is matched to the direction of the operation.  
         [0057]      FIGS. 3A, 3B ,  3 C and  3 D show an alternative embodiment in which shield plates  51 ,  52  provide electromagnetic shielding.  
         [0058]      FIG. 3A  shows an embodiment like that of  FIG. 2  in which a rotor transformer winding and magnetic rotor winding are made with a single electric wire in a predetermined form, and the ends are soldered and fixed with resin. In this embodiment, a first shield plate  51  is provided on the rotation shaft  11  between the rotor transformer  12  and magnetic rotor  14 , and a second shield plate  52  is provided on a side of the magnetic rotor  14  that is opposite to the shield plate  51 . Thus, the magnetic rotor  14  is located between the first and second shield plates  51 ,  52 .  
         [0059]     Using the first shield plate  51  and the second shield plate  52 , the effect of the magnetic field of the rotor transformer  12  on the magnetic rotor  14  and the effect of an external magnetic field and external noise can be practically nullified. Note that the first shield plate  51  includes a notch  53  to permit passage of the wire  22 . The position of the notch  19  of the sidewall  18  of the bobbin  13  and the notch  53  of the first shield plate are selected so that the effect of the magnetic field and noise will not be increased.  
         [0060]     The notches  19 ,  53  are located so that they do not overlap in the axial direction. That is, the angular position and length L of the notch  19  is chosen so that the notch  19  does not align in the axial direction with the notch  53 . Accordingly, there is no magnetic flux passing through both of the notches  19 ,  53 .  
         [0061]     The distance of the first shield plate  51  from the rotor transformer winding  20  and the magnetic rotor winding  21  is, in principle, determined according to electric characteristics such as the SN ratio of the magnetic rotor winding. In addition, the distance is determined by the precision of the winding machine. In  FIG. 3 , two shield plates  51 ,  52  are provided. However, the number can be increased or decreased as required. The positions of the notches of the shield plates shall be set as described above.  
         [0062]     Even when providing a shield plate, there is a single electric wire winding so that there is a single process for the electric wire. Therefore the structure is simple, manufacturing is easy and the electrical properties are improved.

Technology Classification (CPC): 6