Abstract:
A wire winding device which uses a large-sized supply bobbin, which has a large capacity and a large diameter, to highly precisely suppress a variation in tension which variation occurs when a coil is formed by winding a wire material at high speed with the wire material aligned with a winding frame. Rotation (the number of rotation, and timing) of the supply bobbin relative to rotation of the coil is controlled based on the difference between the amount of take-up of the wire material taken up on the winding frame side and the amount of pay-out of the wire material paid out from the supply bobbin, and the control is performed such that the amount of the take-up and the amount of the pay-out agree with each other every moment. This can highly precisely suppress a variation in tension even if there are large differences between inertia of and the diameters of the coil and the supply bobbin.

Description:
CROSS-REFERENCED TO RELATED APPLICATION 
     This application is a National Stage entry of International Application No. PCT/JP2009/059948, filed on Jun. 1, 2009, which claims priority to Japanese Patent Application 2008-168503, filed Jun. 27, 2008. The disclosure of the prior application is herby incorporated in its entirety by reference. 
     TECHNICAL FIELD 
     The present invention relates to a wire winding device for producing a coil by winding a wire material, which is supplied from a supply bobbin, on a winding frame while applying tension to the wire material. 
     BACKGROUND ART 
     For example, for use in a DC brushless motor, a stator has been adopted, which is constructed by assembling a substantially T-shaped core in an annular form, having an arcuate yoke section and pole sections that extend diametrically to an inner side thereof from the yoke section. 
     This type of stator is manufactured by clamping and rotating the yoke section of the core about a spindle shaft, and while a wire material, which is supplied from a supply bobbin, is guided by a nozzle, and by being reciprocally operated in an axial direction (spindle shaft direction) of the pole sections (winding frame), a multi-layered winding coil is produced on the pole sections. 
     Generally, the wire winding device for producing the coil is equipped with a supply bobbin that supplies the wire material, a coil producing section that produces the coil by winding the wire material on the winding frame (core), and a tensioning mechanism arranged between the supply bobbin and the coil producing section for alleviating variations in tension that occur upon winding the wire material on the winding frame. 
     When the wire material is wound on the winding frame, because the wire material becomes stretched if the tension is too high, or slacking occurs if the tension is too low, it is essential that the tension be maintained at an appropriate value. 
     As a tensioning mechanism, there has been adopted a mechanism that absorbs tension variations using a spring or a damper, or a mechanism in which the wire material is wound on a brake roller, which adjusts the braking force of the brake roller responsive to a tension that is estimated from the wire material length, or the like. 
     However, with such a tensioning mechanism using a spring or a damper, because the tension adjustment range is determined arbitrarily by the spring constant, the capability to suppress tension variations is low. On the other hand, with the brake roller mechanism, because the wire material is made to intersect and is trained around the roller multiple times, when the supply bobbin is replaced, time is required for resetting and performing maintenance thereon. 
     In Japanese Laid-Open Patent Publication No. 11-222357, there is disclosed a wire winding device comprising a spool (wire material source) that feeds out a wire material, a spindle that retains a winding frame on which the wire material is wound, a spindle motor for rotatably driving the spindle, a detecting means for detecting a supply amount of the wire material to the winding frame, and a control means for controlling the feed-out speed of the wire material from the wire material source so that the supply amount of the wire material to the winding frame, which is detected by the detecting means, and the wire material feed-out amount agree with each other. 
     With the technique disclosed in Japanese Laid-Open Patent Publication No. 11-222357, by means of a feed-out motor arranged at the spool, a tensioning mechanism can be simplified, which alleviates variations in tension by controlling the feed-out amount of the wire material. Even without using a tensioning mechanism such as a brake roller mechanism, variations in tension can be suppressed reliably. 
     SUMMARY OF INVENTION 
     In the foregoing manner, in order to improve manufacturing capacity, development of techniques have progressed, by which variations in tension that occur when the wire material is wound on the winding frame are controlled, and the wire material is wound onto the winding frame at a high speed. 
     Incidentally, in order to improve manufacturability for producing a coil, an improvement is considered in which, by using a large capacity supply bobbin having a large amount of wire material wound thereon, the time required for maintenance (setup time) can be shortened. 
     However, in the case that a large capacity bobbin is used, tension variations tend to increase, caused by an increase in the inertia and difference in diameter of the supply bobbin and the winding frame (the core, bobbin, wound coil, etc.). 
     The present invention, taking into consideration these types of problems, has the object of providing a wire winding device, which is capable of controlling with high accuracy variations in tension that occur when a coil is formed by winding a wire material at high speeds while the wire material is arrayed on a winding frame, using a large scale, large capacity and large diameter supply bobbin. 
     A wire winding device according to the present invention comprises a bobbin rotating mechanism for rotating a supply bobbin that supplies a wire material, a coil rotating mechanism for winding the wire material supplied from the supply bobbin via a nozzle while the wire material is arrayed on a winding frame to thereby produce a coil, and a controller for controlling the rotational speed of the bobbin rotating mechanism and the coil rotating mechanism. The controller comprises a coil rotational speed setting unit for setting a coil rotational speed of a constant velocity, a bobbin rotational speed target value calculating unit for calculating a bobbin rotational speed target value based on the coil rotational speed, the coil diameter and the supply bobbin diameter, a winding take-up amount calculating unit for calculating a winding take-up amount of the wire material that is wound on the winding frame as the coil, from an actual rotational speed of the coil and the coil diameter, a feed-out amount calculating unit for calculating a feed-out amount of the wire material that is fed from the supply bobbin, from an actual rotational speed of the supply bobbin and the bobbin diameter, and timing setting means for setting a timing at which rotation of the bobbin rotating mechanism is started at the bobbin rotational speed target value, based on a feed-out delay time of the supply bobbin, which is calculated from the calculated winding take-up amount and the calculated feed-out amount. 
     According to the present invention, based on a difference between the winding take-up amount of the wire material, which is taken up on the side of the winding frame, and the feed-out amount of the wire material, which is fed out from the supply bobbin, rotation of the supply bobbin with respect to rotation of the coil is controlled so that the winding take-up amount and the feed-out amount are kept in agreement moment by moment, such that, even if the inertia and diameter of the coil and the supply bobbin differ greatly from each other, variations in tension can be suppressed highly accurately. 
     For example, the rotational speed of the coil is fixed at a value on the order of 1000 rpm, and the rotational speed of the bobbin is maintained within a range of 1/10 to 1/20 thereof (coil rotational speed&gt;&gt;bobbin rotational speed). According to the present invention, the coil can be produced within a short time while variations in tension are suppressed with high accuracy. 
     In this case, the controller calculates a bobbin rotational speed target value for each of respective layers, corresponding to a number of layers of the coil that is wound on the winding frame, and sets a timing for starting rotation of the bobbin or for switching the rotational speed for the respective layers. If carried out in this manner, in a regular winding coil, responsive to the winding layers (number of coil layers), because control is performed corresponding to the outer diameter of the coil becoming larger and as the winding take-up amount per each turn of the coil increases, and so that the actual rotational speed of the bobbin becomes greater, variations in tension can be suppressed with higher accuracy. 
     Further, preferably, a tensioning mechanism is provided over which the wire material is trained, for alleviating variations in tension that occur when the wire material is wound on the winding frame, the tensioning mechanism being disposed in a wire material feed-out path between the supply bobbin and the winding frame. Because the difference between the winding take-up amount of the wire material by the coil (coil take-up amount) and the feed-out amount of the wire material from the bobbin (bobbin feed-out amount) is made small, the displacement amount of the pulley of the tensioning mechanism also becomes small, whereby the tensioning mechanism can be simplified and made smaller in scale. As a result, adoption of a large scale and complex mechanism using a brake roller mechanism for suppressing tension variations is unnecessary, and, for example, only a tensioning mechanism formed by means of a linear tensioner, which is simple in structure, can be utilized. 
     In this case, in the event that a tensioning mechanism in the form of a linear tensioner is provided, the controller may further comprise a bobbin rotational speed target value correcting unit for calculating a next bobbin rotational speed target value, based on a shift amount in position of the linear tensioner and a total feed-out amount of the wire material at a present time of winding, such that a total feed-out amount error, defined as a deviation between a coil winding take-up amount and a bobbin feed-out amount at a next time of winding, vanishes. As a result, cumulative winding deviations in a single coil can be eliminated. 
     According to the wire winding device of the present invention, at a large scale, using a large capacity and large diameter supply bobbin, variations in tension that occur when a coil is formed by winding a wire material at high speeds while the wire material is arrayed on a winding frame can be suppressed highly accurately. 
     Further, because the rotational speed on the side of the coil that takes up the wire material is set as a constant rotational speed, the time required to manufacture the coil can be shortened. 
     Furthermore, because the mechanism for guiding the wire material from the supply bobbin to the winding frame is simplified, maintainability thereof is improved. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a side view of a wire winding device according to an embodiment of the present invention; 
         FIG. 2  is an exploded perspective view of a coil; 
         FIG. 3  is a perspective view of the coil; 
         FIG. 4  is a functional block diagram of a controller of the wire winding device; 
         FIG. 5  is a flowchart in which operations of the controller of the wire winding device are explained; 
         FIG. 6A  is an explanatory drawing of the relationship of the bobbin rotational speed target value and an actual bobbin rotational speed, with respect to start of rotation timing of the bobbin according to a comparative example; 
         FIG. 6B  is an explanatory drawing of the relationship of the bobbin rotational speed target value and an actual bobbin rotational speed, with respect to start of rotation timing of the bobbin according to the present embodiment; 
         FIG. 7A  is an explanatory drawing showing a difference in a coil winding take-up amount and a bobbin feed-out amount according to a comparative example; 
         FIG. 7B  is an explanatory drawing showing a difference in a coil winding take-up amount and a bobbin feed-out amount according to the present embodiment; 
         FIG. 8  is an explanatory drawing of a positional deviation amount of a tensioning mechanism; and 
         FIG. 9  is an explanatory drawing showing elimination of a difference in a total coil winding take-up amount and a total bobbin feed-out amount. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     An embodiment of the wire winding device according to the present invention shall be presented below and explained with reference to the accompanying  FIGS. 1 through 8 . 
     As shown in  FIG. 1 , a wire winding device  10  according to the present embodiment includes a supply bobbin  14  for supplying (feeding out) a wire material  12  (conductive wire) that is wound thereon, a coil producing section  20  for producing a coil  18  by winding the supplied wire material  12  on a winding frame  30 , a tensioning mechanism  22  disposed between the supply bobbin  14  and the coil producing section  20  for alleviating variations in tension that occur upon winding of the wire material  12 , and a controller  23  for carrying out overall control of the wire winding device  10 . The wire material  12  is a copper wire having, for example, an enamel or a polyurethane covering layer. 
     As shown in  FIGS. 2 and 3 , the coil  18  includes a stacked steel plate (core)  24  made up from a plurality of roughly T-shaped steel plates, which are punched out by a press and caulked together in an integral manner, insulators  26 ,  28  that insulate the stacked steel plate  24 , the wire material  12 , which is wound around the stacked steel plate  24  via the insulators  26 ,  28 , and metallic terminals  33 ,  34 . The insulators  26 ,  28  are formed, for example, from PPS (polyphenylene sulfide), and include a winding frame (coil winding member)  30  ( 30 A,  30 B) over which the wire material  12  is wound. The insulators  26 ,  28  are joined together by respective overlapping portions thereof, so that the stacked steel plate  24  and the wire material  12  are electrically insulated from each other. 
     A winding-start end part  12   a  of the wire material  12  is caulked onto the terminal  33  and cut, thereby fixing the end part  12   a  to the terminal  33 , whereas a winding-finish end part  12   b  of the wire material  12  is caulked onto the terminal  34  and cut, thereby fixing the end part  12   b  to the terminal  34 . 
     Returning to  FIG. 1 , the coil producing section  20  includes a clamp jig  40  for rotatably retaining the stacked steel plate  24  on which the insulators  26 ,  28  are mounted, a spindle  42  that rotates the clamp jig  40 , a nozzle  44  that stabilizes the supply direction of the wire material  12 , and an orthogonal shaft robot  46  that adjusts the position in the vertical direction (the direction of arrow A) of the nozzle  44 , and arrays the wire material  12  in a plurality of layers. The spindle  42  is supported axially on a motor (spindle motor)  48  (coil rotating mechanism) and is rotated at a constant speed under a rotary action of the spindle motor  48 . The orthogonal shaft robot  46  is capable of being operated at high speeds by a linear motor. 
     A tension measuring unit  49 , which measures the tension of the wire material  12 , is disposed between the coil producing section  20  and the tensioning mechanism  22 . Tension measurements therefrom are supplied in real time to the controller  23 . 
     The supply bobbin  14  is supported axially and disposed in the interior of an openable/closable box  50  for carrying out supply of the wire material  12  through a plurality of compartment interior pulleys  52 . The supply bobbin  14  is supported axially on the shaft of a bobbin motor  15  (bobbin rotating mechanism), the rotational speed of which is capable of being adjusted under the control of the controller  23 . 
     The tensioning mechanism  22  is constituted from pulleys  56 ,  62 ,  64 ,  68  and a tension roller  70 , respective axes of which are disposed in parallel on a base plate  60  arranged on an upper portion of the box  50 , and a linear motor  76  that serves as a linear tensioner disposed on a rear surface of the base plate  60 . 
     The tension roller  70  is connected to the linear motor  76  through a slit  80  that is provided in a horizontal direction on the base plate  60 , and is axially supported rotatably by the linear motor  76 . The linear motor  76  moves the tension roller  70  horizontally (in the direction of arrow B). 
     The wire material  12 , which is fed out from the box  50 , after passing over the pulleys  56 ,  62 ,  64 ,  68  and being trained around the tension roller  70 , passes through the nozzle  44  and is drawn out to the coil producing section  20 . 
     As a result of the tension roller  70  being moved horizontally (in the direction of arrow B) by the controller  23  via the linear motor  76 , the tension imposed with respect to the wire material  12  is adjusted. 
     Next, an explanation shall be given concerning a procedure for training the wire material  12  in the wire winding device  10  constructed as described above. 
     First, the controller  23  drives the linear motor  76  and moves the tension roller  70  horizontally along the slit  80  to a standby position (origin point) at the left end (tension measuring unit  49  side) thereof. 
     Next, the wire material  12  is pulled out from the supply bobbin  14  and the wire material  12  is trained over the illustrated path with respect to the pulley  56  of the base plate  60  via the compartment interior pulleys  52 ,  52 ,  52 . 
     Furthermore, from the pulley  56 , the wire material  12  is wound over the illustrated path with respect to the tension roller  70  via the pulleys  62 ,  64 ,  68 . 
     The wire material  12  is drawn out further from the tension roller  70  via the tension measuring unit  49  and up to the coil producing section  20 , where the wire material  12  is stopped at the winding frame  30 . Pulling out and threading of the wire material  12  in this manner may be carried out automatically by an automated machine, or may be performed manually. 
     Next, the tension roller  70  is moved by the linear motor  76  to a substantially intermediate position of the slit  80 . Consequently, the tension roller  70  is moved to an active side from the standby position, whereby tension is applied to the wire material  12 . As a result of the tension roller  70  being arranged at a substantially intermediate position of the slit  80 , the tension adjusting allowance with respect to the wire material  12  can be made larger. 
     In the foregoing manner, the wire material  12  is trained in a state of having a predetermined tension from the supply bobbin  14  up to the stacked steel plate  24  (winding frame  30 ). 
     Next, the winding process is initiated. When rotation of the bobbin motor  15  is started, the wire material  12  is fed out from the supply bobbin  14 , whereas the spindle  42  of the coil producing section  20  is rotated by the spindle motor  48 , whereupon the wire material  12  is taken up and wound onto the winding frame  30  (see  FIG. 2 ), thereby producing the coil  18 . At this time, in the tensioning mechanism  22 , the linear motor  76  is subjected to feedback control (PID control) in real time under operation of the controller  23 , so that the tension of the wire material  12  is maintained at a suitable value, and the tension that is measured by the tension measuring unit  49  acquires a suitable tension value. 
     The structure and operation of the controller  23  that effects the wire winding process shall be explained below. 
     First, explanations shall be made concerning the structure and basic operations of the controller  23 . The controller  23  is constituted by a computer and a digital signal processor (DSP), etc. Based on various inputs thereto, by execution of programs in a CPU, which are stored in a memory such as a ROM or the like, the controller  23  operates as a function realizing unit (function realizing means) for implementing various functions. 
     As shown in  FIG. 4 , in the present embodiment, the controller  23  functions as an arithmetic processing unit  100 , a coil rotational speed controller  102  that receives coil (winding frame or core) rotation commands from the arithmetic processing unit  100 , a bobbin rotational speed controller  104  that receives bobbin rotation commands (rotational speed and timing) from the arithmetic processing unit  100 , and a tension controller  106  that receives timing commands (origin, layer switching) from the arithmetic processing unit  100 . 
     The coil rotational speed controller  102  receives a coil rotation command from the arithmetic processing unit  100 , and by rotating the spindle motor  48  at a coil rotational target value Nctar (in the present embodiment, a constant value of 1000 rpm for example), rotates the winding frame  30  to thereby produce the coil  18 . 
     An encoder  108  is provided on the spindle motor  48 . By supplying the coil actual rotational speed Nce, which is detected by the encoder  108 , to the coil rotational speed controller  102 , the coil rotational speed controller  102  performs a feedback control such that the coil actual rotational speed Nce of the spindle motor  48  is maintained at the coil rotational speed target value Nctar. The coil actual rotational speed Nce also is supplied to the arithmetic processing unit  100 . Further, in actual practice, the coil actual rotational speed Nce is calculated on the basis of pulses from the encoder  108 , which are counted by the coil rotational speed controller  102  and the arithmetic processing unit  100 . 
     On the other hand, the bobbin rotational speed controller  104  receives a bobbin rotation command (rotational speed and timing) from the arithmetic processing unit  100 , and more specifically, receives from the arithmetic processing unit  100  a bobbin rotational speed target value Nbtar, which differs for each layer of the coil  18 , together with a switching timing therefor, and rotates the bobbin motor  15 . 
     An encoder  110  is provided on the bobbin motor  15 . By supplying the bobbin actual rotational speed Nbe, which is detected by the encoder  110 , to the bobbin rotational speed controller  104 , the bobbin rotational speed controller  104  performs a feedback control such that the bobbin actual rotational speed Nbe of the bobbin motor  15  is maintained at the bobbin rotational speed target value Nbtar. The bobbin actual rotational speed Nbe also is supplied to the arithmetic processing unit  100 . Further, in actual practice, the bobbin actual rotational speed Nbe is calculated on the basis of pulses from the encoder  110 , which are counted by the bobbin rotational speed controller  104  and the arithmetic processing unit  100 . 
     The bobbin outside diameter φD (see  FIG. 1 ) of the supply bobbin  14  becomes reduced upon feed-out of the wire material  12  from the supply bobbin  14 . The bobbin outside diameter φD is detected (measured) by a proximity sensor  112 , which is arranged in the vicinity of the supply bobbin  14 , and is supplied to the arithmetic processing unit  100 . 
     Because the bobbin outside diameter φD is extremely large compared with the outside diameter φd of the coil  18 , during formation of a single coil  18  (wire material multi-layer arrayed coil), the bobbin outside diameter φD may be considered as a constant (φD=constant). 
     In  FIG. 4 , a tension (stress) detection value Tf [N], which is measured by the tension measuring unit  49 , is supplied to the tension controller  106 . The tension controller  106 , responsive to a layer switching (switching of winding layers of the coil  18 ) timing command from the arithmetic processing unit  100 , drives the linear motor  76 , moves the tension roller  70 , and performs tension feedback control, such that the tension detection value Tf coincides with a tension target value Tftar, which is a suitable value (predetermined value) regardless of layer switching. 
     Next, an explanation shall be made with reference to the flowchart of  FIG. 5  concerning detailed operations of the controller  23 , which is constructed and operates basically as described above. 
     In step S 1 , the arithmetic processing unit  100  of the controller  23  receives a winding start command from a non-illustrated upper level apparatus or an input device. In step S 2 , the arithmetic processing unit  100  sends commands to perform initial settings in the coil rotational speed controller  102 , the bobbin rotational speed controller  104 , and the tension controller  106 . 
     By the initial settings made in step S 2 , in the coil rotational speed controller  102 , the coil rotational speed target value Nctar is set in an internal setting memory thereof, and in the tension controller  106 , the tension target value Tftar is set in an internal setting memory thereof. The initial value of the bobbin rotational speed target value Nbtar (bobbin rotational speed target value Nbtar for a first layer of the coil  18 ) is set in a setting memory of the bobbin rotational speed controller  104  from the arithmetic processing unit  100 . 
     In this case, the bobbin rotational speed target value Nbtar is calculated in the arithmetic processing unit  100  from the coil rotational speed target value Nctar, and from a ratio between the outer diameter φd (first layer), which is a circular diameter converted value of the outer circumferential (rectangular) length of the winding frame  30 , which is stored beforehand, and the bobbin outer diameter φD, which is measured by the proximity sensor  112  (Nbtar=Nctar×φd/φD). 
     Before describing the processes of step S 3  and thereafter, in order that the significance of the method according to the present embodiment is well understood, explanations shall be made concerning main features (characteristics) of the process by the flowchart of  FIG. 5 , while also describing disadvantages that result in a process according to a comparative example. 
       FIG. 6A  shows the relationship of the bobbin rotational speed value Nb [rpm] and passage of time according to a comparative example. On the time axis, one graduation interval thereof corresponds to one second [s]. 
     At time Tc 1 , when the command value of the bobbin rotational speed target value Nbtar is output to the bobbin motor  15 , due to the inertia of the supply bobbin  14 , the bobbin actual rotational speed Nbe rises in rotational speed while being delayed along an S-shaped curve, until at time tc 1 , the bobbin rotational speed target value Nbtar and the bobbin actual rotational speed Nbe coincide with each other. 
     On the other hand, at time Tc 1 , although the command value of the coil rotational speed target value Nctar is output simultaneously to the spindle motor  48 , because the inertia of the spindle  42  is small, roughly from time Tc 1 , the coil actual rotational speed Nce coincides with the coil rotational speed target value Nctar (refer to the upper side in  FIG. 6A ). 
     The interval from time Tc 1  to time Tc 2  represents a time over which the winding of the first layer (bottommost layer) of the coil  18  is wound on the winding frame  30 . 
     Similarly, when the second layer bobbin rotational speed target value Nbtar of the coil  18  is output at time Tc 2  (as shown in  FIG. 6A , the second layer bobbin rotational speed target value Nbtar increases corresponding to a portion by which the winding take-up amount increases per fixed unit of time as the outside diameter φd of the coil  18  becomes greater), in this case as well, due to the inertia of the supply bobbin  14 , the bobbin actual rotational speed Nbe rises in rotational speed while being delayed along an S-shaped curve, at time tc 2 , the bobbin rotational speed target value Nbtar and the bobbin actual rotational speed Nbe coincide with each other. 
     Henceforth, transitions are carried out similarly until reaching a winding termination time Tc 7  of the sixth layer, which is the outermost layer of a single coil  18 . 
     In this case, according to the comparative example shown in  FIG. 7A , as indicated by the relationship between the feed-out amount Lr of the wire material  12  from the supply bobbin  14  and the winding take-up amount Lw on the winding frame  30 , the feed-out amount Lr [m] from the supply bobbin  14  with respect to the winding take-up amount Lw [m] of the coil  18  becomes the same value at a point in time after passage of a delay time Δtd {i.e., a delay time of (rotation of) the bobbin shaft with respect to (rotation of) the coil shaft, also referred to simply as a bobbin shaft delay time}. 
     However, with the wire winding plan according to the comparative example shown in  FIGS. 6A and 7A , in order to perform rotational control on the spindle motor  48  and the bobbin motor  15 , because the difference in inertia and the difference in outer diameters φd, φD of the coil  18  and the supply bobbin  14  are large, an excessive load is imposed on the tensioning mechanism. More specifically, the tensioning mechanism is required to incorporate therein a non-illustrated brake roller or the like, and thus becomes larger in scale and more complex in structure. 
     The processing that was described above provides an explanation of processing by the comparative example and the disadvantages thereof. 
     In the processing of the comparative example, the inventors of the present application considered the fact that the delay time Δtd pertaining to the difference ΔL between the winding take-up amount Lw of the coil  18  and the feed-out amount Lr of the supply bobbin  14  shown in  FIG. 7A  corresponds to the integral value of the portion shown in hatching in  FIG. 6A , formed by the bobbin rotational speed target value Nbtar, which is a stepwise command, and the bobbin actual rotational speed Nbe, which is in the form of an S-shaped curve. 
     Consequently, according to the present embodiment, as shown in  FIG. 6B , at a time Tot that arises before the rotation start time Tc 1  of the spindle motor  48 , the first layer bobbin rotational speed target value Nbtar command is sent from the bobbin rotational speed controller  104  to the bobbin motor  15 . 
     The first layer rotation start time Tc 1 ′ of the bobbin motor  15 , which arises before the rotation start time Tc 1  of the spindle motor  48  (bearing in mind that this time is the same as the time shown in  FIG. 6A ), can be determined by the following equation (1), taking into consideration the time tc 1  shown in  FIG. 6A , at which the first layer bobbin rotational speed target value Nbtar and the first layer actual rotational speed Nbe coincide with each other.
 
 Tc 1′= Tc 1−Δ td≈Tc 1−( tc 1− Tc 1)/2  (1)
 
     Similarly, it is understood that the command time Tc 2 ′ of the second layer bobbin rotational speed target value Nbtar can be determined from the following equation (2). 
     
       
         
           
             
               
                 
                   
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     In general, after the second layer, it is understood that the command time Tcn′ of the nth layer bobbin rotational speed target value Nbtar can be determined from the following equation (3). 
     
       
         
           
             
               
                 
                   
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                   ) 
                 
               
             
           
         
       
     
     In the above equation (3), the value of n is such that n≧2. 
     In this manner, in the wire winding step at the next time, at each of the layers of the coil  18 , by controlling the rotation start time of the bobbin motor  15  so as to occur earlier by a time that is approximately ½ of the bobbin delay time Δtd {i.e., for the first layer, a time of Δtd/2, and for the second and subsequent layers, a time calculated by the above equation (3), which in addition to the time Δtd/2, further takes into consideration a delay time caused by inertia of the supply bobbin  14 , based on the difference in rotational speeds between the inner layer (a previously wound layer) and the outer layer (a layer to be wound from now)}, as shown in  FIG. 7B , the winding take-up amount Lw of the coil  18  at each of the winding start times Tc 1 , and Tc 2 ′ through Tc 6 ′, from the first layer winding start time Tc 1  of the coil  18  of the spindle motor  48  to the sixth layer winding start time Tc 6 ′ of the coil  18 , and the feed-out amount Lr of the supply bobbin  14  can be made to coincide substantially with each other moment by moment. 
     Owing thereto, according to the present embodiment, the tensioning mechanism  22  having a simple structure that does not utilize a braking roller or the like can be adopted, in which the linear motor  76  and the tension roller  70  shown in  FIG. 1  are used. 
     The time Tc 1 ′ that arises before the rotation start time Tc 1  of the spindle motor  48  depends on the delay time Δtd. Because this delay time Δtd depends on the bobbin rotational speed Nb and the inertia of the supply bobbin  14 , a chart (table, map) of times Tc 1 ′ is created, in which the bobbin rotational speed Nb and the bobbin outside diameter φD are taken as variables, and the delay time Δtd is defined as a function thereof {Δtd=f(Nb, φD)}. The chart (table, map) is stored beforehand in a memory (ROM) of the arithmetic processing unit  100 . 
     As shown in  FIG. 7B , although by carrying out the winding take-up and feed-out control according to the novel plan described above, the difference ΔL (see  FIG. 7A ) between the winding take-up amount Lw and the feed-out amount Lr can be eliminated, even if the winding take-up and feed-out control according to the novel plan is performed, a total feed-out amount error ΔLt [m], defined as a differential between the winding take-up amount Lw and the feed-out amount Lr after the time Tc 7 ′ in  FIG. 7B  when the control is terminated, is generated. Next, a plan for zeroing out (eliminating) such a total feed-out amount error ΔLt shall be described. 
     As shown in  FIG. 8 , it is understood that the total feed-out amount error ΔLt [m] is two times the shift amount x in position from a reference position X 0  in the direction of the arrow B of the tension roller  70 .
 
Δ Lt= 2× x   (4)
 
     The shift amount x in position is generated by the tensioning mechanism  22  for the purpose of applying a suitable tension to the wire material  12 , and in general, zeroing out the same is extremely difficult in terms of cost. 
     Consequently, for zeroing out the total feed-out amount error ΔLt [m] while the shift amount x in position is permitted, a variable (changeable) bobbin rotational speed target value Nbtar is corrected at a next time of winding. Since the coil rotational speed Nc of the spindle motor  48  is constant, the coil rotational speed Nc is not corrected. 
     In this case, a feed-out amount correction coefficient K′ at a next time of winding is calculated from a present feed-out amount correction coefficient K, according to the following equation (5).
 
 K′=K ×(Δ Lt−L )/ L   (5)
 
     where 
     K′: a feed-out amount correction coefficient at a next time of winding 
     K: a feed-out amount correction coefficient at a present time of winding 
     ΔLt: a total feed-out amount error at a present time of winding 
     L: a reference total feed-out amount 
     Using the feed-out amount correction coefficient K′, the next bobbin rotational frequency target value Nbtar′ can be corrected with respect to the present bobbin rotational frequency target value Nbtar, according to the following equation (6). 
     
       
         
           
             
               
                 
                   
                     Nbtar 
                     ′ 
                   
                   = 
                   
                     
                       Nbtar 
                       × 
                       
                         K 
                         ′ 
                       
                     
                     = 
                     
                       Nbtar 
                       × 
                       K 
                       × 
                       
                         
                           ( 
                           
                             
                               Δ 
                               ⁢ 
                               
                                   
                               
                               ⁢ 
                               Lt 
                             
                             - 
                             L 
                           
                           ) 
                         
                         / 
                         L 
                       
                     
                   
                 
               
               
                 
                   ( 
                   6 
                   ) 
                 
               
             
           
         
       
     
     Herein, the reference total feed-out amount L can be calculated from the following equation (7).
 
 L=ΣπD×Nbe×Δt   (7)
 
     The range of the summation Σ is a range from the winding start time t=0 to the winding time tend, over which the feed-out length is calculated per each control processing time interval Δt. The winding time tend is the time it takes to wind a single coil  18  (i.e., the time interval from time Tc 1 ′ to time Tc 7 ′ shown in  FIG. 6B ), and the number of calculation times is tend/Δt. 
     In equation (7), π is a circle ratio, D is the bobbin outer diameter, and Nbe is the bobbin actual rotational speed. Δt is a control processing time interval, such that when a sequencer using a ladder program is modeled and described, Δt corresponds to a so-called ladder execution interval. For example, Δt may be selected so that Δt=0.004 [s]. 
     In this manner, when at the next time, the bobbin rotational speed target value Nbtar′ is corrected, as shown in  FIG. 9 , the total feed-out amount error ΔLt between the winding take-up amount Lw (actual line) of the coil  18  and the feed-out amount Lr (dashed line) of the supply bobbin  14  can be reduced substantially to zero. 
     The above explanations are of essential features of a process according to the flowchart, which shall now be described in further detail, and which is shown in  FIG. 4  pertaining to the present embodiment, in which explanations have been made in contrast to disadvantages of a process according to a comparative example. 
     Henceforth, in step S 3 , by initiating rotation of the bobbin motor  15  in accordance with an initial value of the bobbin rotational speed target value Nbtar, which was set in step S 2 , rotation of the supply bobbin  14  is started (also referred to as start of bobbin shaft rotation). 
     Next, simultaneously with the process of step S 3  (i.e., at the time of start of bobbin shaft rotation), in step S 4 , the arithmetic processing unit  100  initiates, by means of a timer  101  (timer section for determining output times of second and subsequent layer bobbin rotational speed target value Nbtar commands), a timing for the purpose of determining output times Tcn′ {the above-mentioned equation (3)} of commands for the bobbin rotational speed target value Nbtar for second and subsequent layers, in order to wind n layers (where n is of values from 2 to 6) of the coil  18 . 
     Further, simultaneously with the process of step S 3  (i.e., at the time of start of bobbin shaft rotation), in step S 5 , a bobbin rotational speed command value Nbcom is calculated by means of the bobbin rotational speed target value Nbtar and a so-called S-shaped curve acceleration/deceleration control for absorbing the bobbin shaft inertia, and rotation control is initiated. By carrying out control in accordance with the bobbin rotational speed command value Nbcom, as shown in  FIG. 6B , the bobbin rotational speed command value Nbcom becomes substantially equivalent to the bobbin actual rotational speed Nbe. 
     Further, simultaneously with the process of step S 3 , in step S 6 , starting of rotation of the spindle motor  48  is placed on standby (also referred to as placing on standby the start of rotation of the coil shaft, or coil shaft rotation standby). The coil shaft rotation start standby time is equivalent to the bobbin delay time Δtd=Tcl−Tcl′ (see  FIGS. 6A and 7A ). 
     Next, in step S 7 , rotation of the spindle motor  48  is initiated (also referred to as start of coil shaft rotation) at time Tc 1  (see  FIG. 6B ) after passage of the bobbin delay time Δtd according to the timer  101 , whereupon winding of the wire material  12  of the first layer of the coil  18  on the winding frame  30  is started. 
     Next, in step S 8 , a judgment is made as to whether timekeeping by the timer  101 , until the output time Tcn′ of the bobbin rotational speed target value command Nbtar of the second and subsequent layers, is completed. In the case that such timekeeping is not completed, in step S 9 , the arithmetic processing unit  100  advances (counts up) the count of a winding number counter  103  (counter) from the coil actual rotational speed Nce (in effect, pulses) output from the encoder  108 . 
     Next, in step S 10 , from the count value of the winding number counter  103 , it is determined whether or not the winding number has increased. Such increments in the winding number are recorded beforehand as a table or a map in the coil rotational speed controller  102  and in the arithmetic processing unit  100 . The arithmetic processing unit  100  makes such determinations with reference to the table (map) in which until the number of windings of the coil shaft is y1 times, a first layer is determined, until the number of windings of the coil shaft is y2 times, a second layer is determined, . . . , and until the number of windings of the coil shaft is yn times, an nth layer is determined. 
     Next, in step S 11 , it is determined whether or not the count value of the winding number counter  103  is equivalent to one coil  18 , or more specifically, whether the count value has obtained a value indicative of completion of one workpiece. 
     If a value indicative of completion of one workpiece has not been reached, then step S 8  is returned to. When the timing by the timer  101  reaches the output time Tcn′ of commands for the second and subsequent layer bobbin rotational speed target value Nbtar (determined by equation (3) above), then in step S 12 , commands for the second and subsequent layer bobbin rotational speed target values Nbtar are output, whereupon the bobbin motor  15  is rotated through the bobbin rotational speed controller  104 . 
     In step S 9 , furthermore, the winding number counter  103  is incremented (counted up), and in step S 10 , when it is determined that the winding number has increased, then in step S 13 , the layer number n is incremented by one layer (n←n+1). Then, in step S 14 , similar to step S 5 , a bobbin rotational speed command value Nbcom is calculated by means of the bobbin rotational speed target value Nbtar and a so-called S-shaped curve acceleration/deceleration control for absorbing the bobbin shaft inertia, and rotation control, i.e., in this case, a rotation control for the second and subsequent layers, is initiated. 
     Control is repeated in the foregoing manner, and in step S 11 , when the count number of the winding number counter  103  reaches a value indicative of completion of one workpiece, then in step S 15 , the bobbin diameter φD is measured by the proximity sensor  112 , and with reference to the table, a rotation start time Tcn′ of the bobbin motor  15  for the first layer, for producing a next new coil  18 , is calculated and stored in memory, which is then read out at step S 3  upon receipt of a winding start command, from step S 1  in the next cycle. 
     Further, in step S 16 , the feed-out amount correction coefficient K′ at a next time of winding is calculated by the aforementioned equation (5) from the present feed-out amount correction coefficient K. Using the calculated feed-out amount correction coefficient K′, a next bobbin rotational speed target value Nbtar′ is corrected and calculated by the aforementioned equation (6) with respect to the present bobbin rotational speed target value Nbtar, which, in step S 2  of the next cycle, is set in the setting memory of the bobbin rotational speed controller  104 . 
     Moreover, when rotation of the bobbin shaft (bobbin motor  15  and the supply bobbin  14 ) is started in step S 3 , operation of the tensioning mechanism  22  is initiated in step S 21  by a start command from the arithmetic processing unit  100 , whereupon the tension roller  70  is subjected to a PID feedback control through the linear motor  76 , such that the tension value Tf measured by the tension measuring unit  49  is maintained at a suitable value (i.e., the tension target value Tftar). Concerning operation of the tensioning mechanism  22 , when winding of one coil  18  is completed (i.e., upon conclusion of step S 11 ), a stop command is output with respect to the tension controller  106  from the arithmetic processing unit  100 , whereupon, in step S 22 , the tension controller  106  halts operation of the linear motor  76  that governs the tensioning mechanism  22 . 
     As described above, the aforementioned wire winding device  10  according to the present embodiment is equipped with the bobbin motor  15  as a bobbin rotating mechanism, which rotates the supply bobbin  14  that supplies the wire material  12 , the spindle motor  48  as a coil rotating mechanism, which produces the coil  18  by winding the wire material  12  supplied from the supply bobbin  14  while arraying the wire material  12  on the winding frame  30  via the nozzle  44 , and the controller  23  for controlling rotational speeds Nb, Nc of the bobbin motor  15  and the spindle motor  48 . 
     The controller  23  comprises the coil rotational speed controller  102  as a coil rotational speed setting unit for setting the constant speed coil rotational speed target value Nctar, the arithmetic processing unit  100  as a bobbin rotational speed target value calculating unit for calculating the bobbin rotational speed target value Nbtar based on the coil rotational speed target value Nctar, the coil diameter φd, and the supply bobbin diameter φD, the arithmetic processing unit  100  as a winding take-up amount calculating unit for calculating a winding take-up amount Lw of the wire material  12 , which is wound up on the winding frame  30  as a coil  18 , from the coil actual winding speed Nce of the coil  18  and the coil diameter φD, the arithmetic processing unit  100  as a feed-out amount calculating unit for calculating a feed-out amount Lr of the wire material  12 , which is fed out from the supply bobbin  14 , from the bobbin actual rotational speed Nbe from the bobbin motor  15  that rotates the supply bobbin  14  and from the bobbin diameter φD, and the arithmetic processing unit  100  as a timing setting means for setting, in the bobbin motor  15  via the bobbin rotational speed controller  104 , a timing (Tc 1 ′, Tc 2 ′, . . . , Tc 6 ′ shown in  FIG. 6B ) at which rotation of the bobbin motor  15  is started at the bobbin rotational speed target value Nbtar, based on a feed-out delay time Δtd of the supply bobbin  14 , which is calculated from the calculated winding take-up amount Lw and the calculated feed-out amount Lr. 
     More specifically, based on the difference between the winding take-up amount Lw of the wire material  12 , which is taken up on the side of the winding frame  30 , and the feed-out amount Lr of the wire material  12 , which is fed out from the supply bobbin  14 , because the rotation (rotational speed, timing of change of the rotational speed) of the supply bobbin  14  with respect to rotation of the coil  18  is controlled such that the winding take-up amount Lw of the wire material  12  of the coil  18  and the feed-out amount Lr of the wire material  12  of the supply bobbin  14  are kept in agreement moment by moment, even in the case that the inertia and diameter of the coil  18  and the supply bobbin  14  differ greatly, variations in tension can be suppressed with high accuracy. 
     For example, the rotational speed of the coil is fixed at a value on the order of 1000 rpm, and the rotational speed of the bobbin is maintained within a range of 1/10 to 1/20 thereof (coil rotational speed&gt;&gt;bobbin rotational speed). According to the present invention, the coil  18  having the multi-layered wire material  12  can be produced (mass produced) within a short time while variations in tension are suppressed with high accuracy. 
     In this case, the controller  23  calculates a bobbin rotational speed target value Nbtar for each of respective layers, corresponding to a number of layers of the coil  18  that is wound on the winding frame  30 , and sets a timing for starting rotation of the bobbin, or for switching the rotational speed for the respective layers. When carried out in this manner, in a regular winding coil such as the coil  18 , responsive to the winding layers (number of layers of the coil  18 ), because control is performed corresponding to the outer diameter φd of the coil  18  becoming larger and as the winding take-up amount per each turn of the coil  18  increases, and so that the actual rotational speed Nbe of the bobbin becomes greater, variations in tension can be suppressed with higher accuracy. 
     Further, the tensioning mechanism  22  is provided over which the wire material  12  is trained, for alleviating variations in tension that occur when the wire material  12  is wound on the winding frame  30 , the tensioning mechanism  22  being disposed in a wire material feed-out path between the supply bobbin  14  and the winding frame  30 . However, according to the present embodiment, because the difference between the winding take-up amount (coil take-up amount) Lw of the wire material  12  by the coil  18  and the feed-out amount (bobbin feed-out amount) Lr of the wire material  12  from the supply bobbin  14  is made small, the displacement amount x of the tension roller  70  that is a pulley of the tensioning mechanism  22  also is made small, whereby the tensioning mechanism  22  can be simplified and made smaller in scale. As a result, adoption of a large scale and complex mechanism using a brake roller mechanism for suppressing tension variations is unnecessary, and, for example, only the tensioning mechanism  22 , which is formed by means of a linear tensioner made up of the linear motor  76  according to the present embodiment, which is simple in structure, can be utilized. 
     In this case, by equipping the arithmetic processing unit  100  of the controller  23  further with a bobbin rotational speed target value correcting section for calculating a next bobbin rotational speed target value Nbtar′ based on a shift amount x in position of the linear motor  76  and a standard total feed-out length L, which is a total feed-out amount of the wire material at a present time of winding, such that a total feed-out amount error ΔLt, defined as a deviation between a coil winding take-up amount Lw and a bobbin feed-out amount Lr at a next time of winding, vanishes, the total feed-out amount error ΔLt, which represents the cumulative winding deviation in a single coil, can be eliminated. 
     The wire winding device according to the present invention is not limited to the above-described embodiment, and it is a matter of course that various other structures could be adopted without deviating from the essence and scope of the invention.