Patent Publication Number: US-2016241108-A1

Title: Brushless wiper motor

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     Applicant hereby claims foreign priority benefits under U.S.C. §119 from International Patent Application Serial No. PCT/JP2013/075712 filed on Sep. 24, 2013, the content of which is incorporated by reference herein. 
    
    
     TECHNICAL FIELD 
     The present invention relates to a brushless wiper motor for driving a wiper member which wipes a windshield to remove extraneous matters which is in contact with the windshield. 
     BACKGROUND 
     Conventionally, a wiper apparatus for wiping a windshield to remove rain water, dust and the like on the windshield is installed on a vehicle such as automotive vehicle or the like. The wiper apparatus is provided with: a wiper member which performs swinging movement on the windshield; and a wiper motor for swinging the wiper member. When an operator turns on a wiper switch provided in the vehicle room, the wiper motor drives the wiper member, thereby causing the wiper member to carry out reciprocal wiping operations on the windshield to wipe a windshield to remove extraneous matters on the windshield. 
     As one example of the wiper motor to be used in this wiper apparatus, a technique described in Japanese Patent Application Laid-Open Publication No. 2009-225520 (FIG. 1) has been known. The electric motor (wiper motor) described in Japanese Patent Application Laid-Open Publication No. 2009-225520 (FIG. 1) is provided with a motor unit having an armature shaft (rotating shaft), and a commutator is integrally formed on the armature shaft. A pair of brushes is in sliding contact with the commutator, the wiper motor described in Japanese Patent Application Laid-Open Publication No. 2009-225520 (FIG. 1) is composed of a wiper motor with brushes. The motor unit is connected to a speed reduction mechanism unit, and a speed reducer having a worm and a worm wheel is housed in a gear case (gear housing) of the speed reduction mechanism unit. 
     Furthermore, a control board is housed in the gear case, and a first magnetic sensor and a second magnetic sensor are installed on the control board. Furthermore, the first magnetic sensor is used for detecting a change in the magnetic pole of a ring-shaped magnet secured to the armature shaft, thereby detecting the rotation number of the armature shaft. On the other hand, the second magnetic sensor is used for detecting a change in the magnetic pole of a sensor magnet secured to a rotation center portion of the worm wheel, thereby detecting the rotation position of the output shaft. 
     In such a wiper motor with brushes, output limitations, such as reduction in output of the wiper motor or the like, tends to be imposed on the basis of increase in temperature of the brushes, and this causes the operation of the wiper motor to become unstable. Furthermore, since sliding sound of the brushes to the commutator is comparatively great, it is necessary to install a soundproof measure on a high-class vehicle or the like in which a high degree of quietness. In addition, since electronic parts such as capacitor, choke coil or the like for removing brush noise need to be installed in the vicinity of each brush, there is a limitation in downsizing of the wiper motor, this resulting in a reduction in mountability of a small-size vehicle such as light vehicle or the like. 
     Therefore, in order to solve these problems, a brushless wiper motor which is not provided with brushes has been proposed as a motor to be applied to a vehicle. Japanese Patent Application Laid-Open Publication No. H06-105521 (FIG. 1) discloses one example of a motor composed without using brushes (brushless motor). The brushless motor disclosed in Japanese Patent Application Laid-Open Publication No. H06-105521 (FIG. 1) is a so-called inner rotor-type brushless motor, and a stator on which a stator winding wire (coil) is wound is installed on the inner circumference of a housing, with a rotor having a main magnet (permanent magnet) being rotatably installed in the stator. Furthermore, a sub-magnet for use in detecting the rotation position of the rotor relative to the stator is installed on the rotating shaft fixed on the rotation center of the rotor, and the sub-magnet faces each of Hall elements of motor boards secured to an end bracket. Thus, by successively switching a driving current to a stator coil on the basis of an electric signal from each of the Hall elements, the rotor is rotated. 
     SUMMARY 
     However, in a case where the brushless motor disclosed in Japanese Patent Application Laid-Open Publication No. H06-105521 (FIG. 1) is simply applied in place of the motor unit (with brushes) disclosed in Japanese Patent Application Laid-Open Publication No. 2009-225520 (FIG. 1), since a thickness dimension Japanese Patent Application Laid-Open Publication No. 2009-225520 (FIG. 1) on the periphery of the brush unit along the axial direction of the rotating shaft and a thickness dimension Japanese Patent Application Laid-Open Publication No. H06-105521 (FIG. 1) on the periphery of the sub-magnet along the axial direction of the rotating shaft are substantially the same thickness dimension, with the result that it is difficult to further reduce the size of the wiper motor. Therefore, in order to further miniaturize the wiper motor, it has been required to basically reconsider the structure of the brushless wiper motor and the structure of the control board housed in a gear housing. 
     An object of the present invention is to provide a brushless wiper motor in which a sensor for detecting the rotation position of the rotor relative to the stator is installed on a control board which is housed in the gear housing so that the size thereof is improved. 
     According to an aspect of the present invention, there is provided a brushless wiper motor for driving a wiper member which wipes a windshield to remove extraneous matters which is in contact with the windshield, the brushless wiper motor comprising: a stator around which coils are wound; a rotor provided with a permanent magnet and a rotating shaft; an output shaft for externally outputting a rotation of the rotating shaft; a gear housing for rotatably supporting the output shaft; a control board installed in the gear housing; a first magnet integrally formed on an extended portion of the rotating shaft in the gear housing, and used for detecting a rotation position of the rotating shaft relative to the stator; a first sensor installed on the control board so as to face the first magnet, and adapted to generate an electric signal in response to the relative rotation of the first magnet; a second magnet integrally formed on the extended portion of the rotating shaft in the gear housing, and used for detecting a rotation number of the rotating shaft; a second sensor installed on the control board so as to face the second magnet, and adapted to generate an electric signal in response to the relative rotation of the second magnet; a third magnet integrally formed on the extended portion of the rotating shaft in the gear housing and used for detecting the rotation position of the output shaft relative to the gear housing; and a third sensor installed on the control board so as to face the third magnet, and adapted to generate an electric signal in response to the relative rotation of the third magnet. 
     In the brushless wiper motor according to the present invention, the first magnet and the second magnet are formed of a common magnet and the first sensor and the second sensor are formed of a common sensor. 
     In the brushless wiper motor according to the present invention, the permanent magnet, first and second magnets are magnetized such that polarities are alternately aligned toward a circumferential direction of the rotating shaft, with the polarity of the permanent magnet and the polarities of the first and second magnets being matched in an axial direction of the rotating shaft. 
     In the brushless wiper motor according to the present invention, the number of poles of the first and second magnets is equal to an integral multiple of the number of poles of the permanent magnet. 
     In another aspect of the present invention, there is provided a brushless wiper motor for driving a wiper member for wiping a windshield to remove extraneous matters which is in contact with the windshield, the brushless wiper motor comprising: a stator around which coils are wound; a rotor provided with a permanent magnet and a rotating shaft; an output shaft for externally outputting a rotation of the rotating shaft; a gear housing for rotatably supporting the output shaft; a control board installed in the gear housing; a first magnet integrally formed on an extended portion of the output shaft in the gear housing and used for detecting a rotation position of the rotating shaft relative to the stator; a first sensor which is installed on the control board so as to face the first magnet and adapted to generate an electric signal in response to the relative rotation of the first magnet; a second magnet which is integrally formed on the extended portion of the output shaft in the gear housing and used for detecting a rotation number of the rotating shaft; a second sensor which is installed on the control board so as to face the second magnet and adapted to generate an electric signal in response to the relative rotation of the second magnet; a third magnet which is integrally formed on an extended portion of the rotating shaft in the gear housing and used for detecting the rotation position of the output shaft relative to the gear housing; and a third sensor which is installed on the control board so as to face the third magnet and adapted to generate an electric signal in response to the relative rotation of the third magnet. 
     According to the brushless wiper motor of the present invention, a first magnet is installed on an extended portion in the gear housing of the rotating shaft, and a first sensor is installed on a control board inside the gear housing so as to face the first magnet so that the rotation position of the rotating shaft relative to the stator, that is, the rotation position of the rotor relative to the stator, is detected by the first sensor. Thus, the first sensor for detecting the rotation position of the rotor, the second sensor for detecting the rotation number of the rotating shaft and the third sensor for detecting the rotation position of the output shaft relative to the gear housing can be concentrated and formed on the control board. Therefore, since it is no longer required to install the first sensor close to the rotor of the brushless wiper motor, the dimension along the axial direction of the rotating shaft of the brushless wiper motor can be shortened and further downsized. 
     According to the brushless wiper motor of the present invention, the first magnet and the second magnet can be formed by a commonly-used magnet and the first sensor and the second sensor can be formed as a commonly-used sensor, and in this case, by cutting the number of the magnets and the number of the sensors, it is possible to achieve a low cost and light-weight of the brushless wiper motor. 
     According to the brushless wiper motor of the present invention, the permanent magnet, the first and second magnets are respectively magnetized so as to alternately align the polarities toward the circumferential direction of the rotating shaft, and the polarity of the permanent magnet and the polarities of the first and second magnets can be matched toward the axial direction of the rotating shaft; thus, in this case, the detection of the rotation position of the rotor relative to the stator and the rotor control on the basis of this detection can be simplified. 
     According to the brushless wiper motor of the present invention, the number of poles of the first and second magnets can be set to an integral multiple of the number of poles of the permanent magnet, and in this case, the detection precision of the rotation position of the rotor relative to the stator can be improved so that the control of the rotor can be carried out with higher precision. 
     According to the brushless wiper motor of the present invention, a first magnet, a second magnet, and a third magnet are formed on the extended portion of the output shaft in the gear housing, and a first sensor, a second sensor and a third sensor can be installed on a control board so as to face these first magnet, second magnet and third magnet. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a view showing a wiper apparatus mounted on a vehicle, and provided with a wiper motor according to the present invention; 
         FIG. 2  is an outside view showing the wiper motor of  FIG. 1 ; 
         FIG. 3  is a bottom view showing the wiper motor with a gear cover being detached from a gear housing; 
         FIG. 4  is an explanatory view explaining detailed structures of a rotor and a rotating shaft; 
         FIG. 5A  is a cross-sectional view taken along a line A-A of  FIG. 4 ; 
         FIG. 5B  is a cross-sectional view taken along a line B-B of  FIG. 4 ; 
         FIG. 5C  is a cross-sectional view showing a modified example of a magnet for the rotating shaft; 
         FIG. 6  is a block diagram explaining an electric system of the wiper motor; 
         FIG. 7  is pulse waveform diagrams showing an output state of an electric signal from each of Hall ICs; 
         FIG. 8  is a bottom view corresponding to  FIG. 3  of the wiper motor according to a second embodiment; 
         FIG. 9  is a block diagram explaining an electric system of the wiper motor of  FIG. 8 ; 
         FIG. 10  shows pulse waveform diagrams showing an output state of an electric signal from each of Hall ICs and MR sensors; 
         FIG. 11  is a bottom view corresponding to  FIG. 3  of a wiper motor according to a third embodiment; 
         FIG. 12  is a block diagram explaining an electric system of the wiper motor of  FIG. 11 ; 
         FIG. 13  is a view corresponding to  FIG. 4  of a wiper motor according to a fourth embodiment; 
         FIG. 14A  is a cross-sectional view taken along a line D-D of  FIG. 13 ; 
         FIG. 14B  is a cross-sectional view taken along a line E-E of  FIG. 13 ; and 
         FIG. 14C  is a cross-sectional view showing a modified example of a magnet for the rotating shaft. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, the first embodiment of the present invention will be described in detail with reference to the accompanying drawings. 
       FIG. 1  is a view showing a wiper apparatus mounted on a vehicle and provided with a wiper motor according to the present invention,  FIG. 2  is an outside view showing the wiper motor of  FIG. 1 ,  FIG. 3  is a bottom view showing a gear housing with a gear cover being detached from a gear housing,  FIG. 4  is an explanatory view explaining detailed structures of a rotor and a rotating shaft,  FIG. 5A  is a cross-sectional view taken along a line A-A of  FIG. 4 ,  FIG. 5B  is a cross-sectional view taken along a line B-B of  FIG. 4 ,  FIG. 5C  is a cross-sectional view showing a modified example of a magnet for the rotating shaft, and  FIG. 6  is a block diagram explaining an electric system of the wiper motor. 
     As shown in  FIG. 1 , a vehicle  10 , such as an automotive vehicle or the like, is provided with a front glass  11  serving as a windshield, and a wiper apparatus  12  is mounted on the vehicle  10 , and close to the front glass  11 . Furthermore, the wiper apparatus  12  is operated by on-operating a wiper switch (not shown) in a vehicle room so as to wipe a front glass  11  to remove extraneous matters which is in contact with the front glass  11 . 
     The wiper apparatus  12  has: a wiper motor (brushless wiper motor)  20 ; a power transmission mechanism  14  for transmitting swinging movements of the wiper motor  20  to each of pivot axes  13   a  and  13   b ; and a pair of wiper members  15   a  and  15   b  having: base end sides which are secured to the pivot axes  13   a  and  13   b ; and tip end sides which carry out reciprocal wiping operations on the front glass  11  by the swinging movements of the pivot axes  13   a  and  13   b . The wiper members  15   a  and  15   b  are installed so as to correspond to the driver&#39;s side and the passenger&#39;s side, and the wiper members  15   a  and  15   b  are respectively composed of: wiper arms  16   a  and  16   b ; and wiper blades  17   a  and  17   b  which are attached to the wiper arms  16   a  and  16   b.    
     Thus, by driving and rotating the wiper motor  20 , the swinging movements of the wiper motor  20  are transmitted to the pivot axes  13   a  and  13   b  via the power transmission mechanism  14 , thereby carrying out swinging movements of the pivot axes  13   a  and  13   b . In this manner, the driving force of the wiper motor  20  is transmitted to the wiper members  15   a  and  15   b  so that the wiper blades  17   a  and  17   b  wipe the wiping ranges  11   a  and  11   b  of the front glass  11  to remove extraneous matters which is in contact with the wiping ranges  11   a  and  11   b  of the front glass  11 . 
     As shown in  FIGS. 2 and 3 , the wiper motor  20  has: a motor unit  30 ; and a speed reduction mechanism unit  40 . The motor unit  30  has a yoke  31  which is formed into a bottomed cylinder shape by carrying out a press machining process or the like on a steel plate, and a stator  32  formed into an annular shape is secured in the yoke  31 . As shown in  FIG. 6 , on the stator  32 , coils  32   a ,  32   b  and  32   c  of U-phase, V-phase and W-phase (three phases) are wound around in the winding form of star connection. 
     As shown in  FIG. 3 , a rotor  33  is rotatably installed in the stator  32  with a predetermined gap (air gap). As shown in  FIG. 4 , the rotor  33  is formed of a plurality of stacked steel plates into a substantially column shape. In the rotor  33 , as indicated by a shaded portion in  FIG. 5A , a plurality of plate-shaped permanent magnets  33   a  (six poles in this embodiment) are embedded in a manner so as to extend in their axial direction, and the permanent magnets  33   a  are installed with equal intervals (60° interval) so that their polarities are alternately arranged in the circumferential direction of the rotor  33 . In this manner, the wiper motor  20  is composed of a brushless wiper motor having an IPM (Interior Permanent Magnet) structure in which the permanent magnets  33   a  are embedded inside the rotor  33 . However, not limited to the brushless wiper motor of the IPM structure, the present invention may be applied to a brushless motor of an SPM (Surface Permanent Magnet) structure in which a plurality of permanent magnets are attached to the outer peripheral surface of the rotor. With respect to the SPM structure, a detailed explanation will be given in a fourth embodiment which will be described later. 
     A rotating shaft  33   b  is secured so as to extend through the rotation center of the rotor  33 . The base end (upper side in  FIG. 3 ) of the rotating shaft  33   b  is rotatably supported by a bearing (not shown) formed on the bottom portion of the yoke  31 , and the tip (lower side in  FIG. 3 ) of the rotating shaft  33   b  extends to the inside of a gear housing  41  forming the speed reduction mechanism unit  40 . An extended portion of the rotating shaft  33   b  in the gear housing  41 , that is, the tip portion and the substantially center portion of the rotating shaft  33   b  located inside the gear housing  41 , are rotatably supported by bearings (not shown) installed in the gear housing  41 . 
     A worm  51  forming a speed reduction mechanism  50  is integrally installed on the tip side of the rotating shaft  33   b . Furthermore, the rotating shaft  33   b  has a portion positioned between the worm  51  of and the rotor  33  and close to the worm  51 , an annular magnet  34  for the rotating shaft is integrally installed on this portion of the rotating shaft  33   b . The magnet  34  for the rotating shaft is formed on the extended portion of the rotating shaft  33   b  in the gear housing  41 , and provided with a plurality of permanent magnets  34   a  (see a shaded portion in the figure) whose N-poles and S-poles are alternately arranged along the circumferential direction of the rotating shaft  33   b . The permanent magnets  34   a , which have the number of poles of 6 in the same manner as that of the permanent magnets  33   a  inside the rotor  33 , as shown in  FIG. 5B , are installed along the circumferential direction of the magnet  34  for the rotating shaft with mutually equal intervals (60° interval). In this case, the magnet  34  for the rotating shaft forms a first magnet and a second magnet in the present invention. That is, in this embodiment, the first magnet and the second magnet are formed by a commonly-used magnet  34  for the rotating shaft. 
     In addition to utilization for detecting the rotation number of the rotating shaft  33   b  (function as the second magnet in the present invention), the magnet  34  for the rotating shaft is also used for detecting the rotation position of the rotor  33  relative to the stator  32  via the rotating shaft  33   b  (function as the first magnet in the present invention). Therefore, as shown in  FIGS. 5A and 5B , in order to allow the rotation position of the rotating shaft  33   b  relative to the stator  32  and the rotation position of the rotor  33  relative to the stator  32  to have the same positional relationship toward the rotation direction, the polarities of the permanent magnets  33   a  (rotor  33  side) and the polarities of the permanent magnets  34   a  (rotating shaft-use magnet  34  side) are made to be matched toward the axial direction of the rotating shaft  33   b . In other words, for example, the magnet  34  for the rotating shaft is secured to the rotating shaft  33   b  so as to allow the S-poles of the permanent magnets  33   a  and  34   a  to be located at positions each having 30° relative to a reference position C. By making the polarities matched with each other in this manner, upon detecting the rotation position of the rotor  33 , it is possible to omit a correcting operation for correcting a phase offset of polarities, etc., and consequently to avoid complicated control operations of the wiper motor  20 . 
     Additionally, the number of poles of the permanent magnets  34   a  of the magnet  34  for the rotating shaft may not be set to the same number of poles (6 poles) as the number of poles of the permanent magnets  33   a  of the rotor  33  as shown in  FIG. 5B , the permanent magnets  34   a  may be set to 12 poles (double the number of poles of the permanent magnets  33   a ), for example, as shown in  FIG. 5C . In short, it is only necessary to make appearing timings of the permanent magnets  33   a  and the permanent magnets  34   a  synchronized with each other so that the number of poles of the permanent magnets  34   a  may be set to an integer multiple (1 fold, 2 folds, 3 folds, 4 folds, etc.) of the number of poles of the permanent magnets  33   a . By increasing the number of poles of the permanent magnets  34   a  to  2  folds or more of the number of poles of the permanent magnets  33   a , an electric signal (pulse signal) from each of Hall ICs  65   a  to  65   c  for the rotating shaft (see  FIG. 3 ) for use in detecting a change in polarities of the permanent magnets  34   a  can be finely divided. Thus, the detection precision of the rotation position of the rotor  33  relative to the stator  32  can be improved, and the control operations of the rotor  33  can be carried out more precisely. 
     As shown in  FIGS. 2 and 3 , the speed reduction mechanism unit  40  is provided with the gear housing  41  made of aluminum, and a gear cover  42  made of plastic material for shielding an opening  41   a  (front side in  FIG. 3 ) of the gear housing  41 . In the gear housing  41 , the yoke  31  is secured with a fastening member (fixing screw or the like), not shown, and the motor unit  30  and the speed reduction mechanism unit  40  are thus integrally combined with each other and assembled so that the worm  51  formed in the rotating shaft  33   b  and the magnet  34  for the rotating shaft are disposed inside the gear housing  41 . 
     Inside the gear housing  41 , a worm wheel  52  (not shown in detail) is rotatably installed. The worm wheel  52  is formed into a disc shape by using resin material such as for example POM (polyacetal) plastic or the like, and gear teeth  52   a  (not shown in detail) are formed on its outer peripheral portion. The worm  51  is engaged with the gear teeth  52   a  of the worm wheel  52  so that the worm wheel  52  forms the speed reduction mechanism  50  together with the worm  51 . 
     To the rotation center of the worm wheel  52 , the base end of the output shaft  52   b  is secured, and the output shaft  52   b  is rotatably supported by a boss portion  41   b  of the gear housing  41  via a bearing (not shown). The tip end of the output shaft  52   b  extends to the outside of the gear housing  41 , and to the tip portion of the output shaft  52   b , the power transmission mechanism  14  is secured as shown in  FIG. 1 . Thus, the rotation number of the rotating shaft  33   b  is reduced via the worm  51  and the worm wheel  52  (speed reduction mechanism  50 ), and the output speed-reduced to have a high torque is released to the power transmission mechanism  14  via the output shaft  52   b.    
     As shown in  FIG. 3 , on the rotation center of the worm wheel  52 , a magnet  53  for the output shaft (third magnet) having an annular shape is installed, and the corresponding magnet  53  for the output shaft is integrally secured to the output shaft  52   b  so as to surround the periphery of the base end of the output shaft  52   b . That is, the magnet  53  for the output shaft is integrally attached to an extended portion of the output shaft  52   b  in the inside of the gear housing  41 . However, the magnet  53  for the output shaft may be directly secured to the output shaft  52   b  which extends through the worm wheel  52 . 
     The magnet  53  for the output shaft has its range having substantially 270° along the circumferential direction magnetized to have the S-pole, with the other range having substantially 90° magnetized to have the N-pole. In this case, the magnet  53  for the output shaft forms the third magnet in the present invention, and the corresponding magnet  53  for the output shaft is used for detecting the rotation position of the output shaft  52   b  relative to the gear housing  41 . 
     The opening  41   a  of the gear housing  41  is formed so as to house constituent members, such as the worm wheel  52  or the like, inside the gear housing  41 , and the opening  41   a  is shielded by the gear cover  42 , as shown in  FIG. 2 . A sealing member (not shown) is installed between the gear housing  41  and the gear cover  42 , and with this configuration, it is possible to prevent rain water or the like from entering the inside of the speed reduction mechanism unit  40  via a gap between the gear housing  41  and the gear cover  42 . A control board  60  is attached to the inside of the gear cover  42 , as shown in  FIGS. 2 and 3 ; thus, an external power source  64  and a wiper switch  67  (see  FIG. 6 ) are electrically connected to the control board  60  via an external connector (not shown) of the vehicle  10  which is connected to a connector connection unit (not shown) formed on the gear cover  42 . 
     The control board  60  is installed in the gear housing  41 , and as shown in  FIG. 6 , an inverter circuit  61 , a control circuit  62  and a PWM signal generating circuit  63  are assembled on the control board  60 . To the inverter circuit  61 , the external power source  64 , such as an onboard battery or the like, to be mounted on the vehicle  10  is electrically connected, and coils  32   a ,  32   b  and  32   c  forming U-phase, V-phase and W-phase are electrically connected. The inverter circuit  61  is provided with a plurality of switching elements composed of semiconductor elements, such as FETs or the like, and these switching elements are constituted by three positive-electrode side switching elements (not shown) which are respectively connected to the positive electrodes of the external power source  64  and correspond to the U-phase, V-phase and W-phase, and three negative-electrode side switching elements (not shown) which are respectively connected to the negative electrodes of the external power source  64  and correspond to the U-phase, V-phase and W-phase. 
     The control circuit  62  is electrically connected to the inverter circuit  61  so as to perform ON/OFF control of the switching elements installed on the inverter circuit  61 . In this case, the control circuit  62  is constituted by known microcomputers provided with CPUs, RAMs, ROMs or the like (not shown). 
     The PWM signal generating circuit  63  is designed to determine a duty ratio for intermittently ON/OFF controlling the switching elements of the inverter circuit  61 , and to output a resulting duty ratio signal to the control circuit  62 . Thus, the ratio at which the switching elements of the inverter circuit  61  are separately turned on is adjusted, and the size of a driving current to be supplied to each of the coils  32   a ,  32   b  and  32   c  is subsequently controlled. 
     The control board  60  is further provided with three Hall ICs (U-phase, V-phase, W-phase)  65   a ,  65   b  and  65   c  for the rotating shaft and two Hall ICs (A-phase and B-phase)  66   a  and  66   b  for the output shaft. Each of the Hall ICs  65   a  to  65   c , as well as  66   a  and  66   b , has the same configuration as each other, and is designed to carry out switching operations depending on changes in polarities (change from the N-pole to the S-pole or change from the S-pole to the N-pole) so as to generate a pulse signal (rectangular waveform signal)(see  FIG. 7 ). That is, the Hall ICs  65   a  to  65   c , as well as  66   a  and  66   b , are allowed to form non-contact type sensors to be used in combination with magnets. 
     As shown in  FIG. 3 , the Hall ICs  65   a  to  65   c  for the rotating shaft are installed on the control board  60  so as to face the magnets  34  for the rotating shaft. More specifically, the Hall ICs  65   a  to  65   c  for the rotating shaft are aligned with equal intervals and installed on the control board  60  so as to face the outer peripheral surface (side face) of the magnets  34  for the rotating shaft. Thus, the Hall ICs  65   a  to  65   c  for the rotating shaft are allowed to successively generate pulse signals (electric signals) with predetermined phase differences in response to the rotation of the magnets  34  for the rotating shaft (see  FIG. 7 ). 
     In this case, the Hall ICs  65   a  to  65   c  for the rotating shaft form the first sensor and the second sensor in the present invention. In other words, in this embodiment, the first sensor and the second sensor are formed by using commonly-used Hall ICs  65   a  to  65   c  for the rotating shaft. Additionally, in order to detect the rotation position of the rotor  33  relative to the stator  32 , all the U-phase, V-phase and W-phase corresponding to the outputs of the Hall ICs  65   a  to  65   c  for the rotating shaft are used (function as the first sensor of the present invention). On the other hand, in order to detect the rotation number of the rotating shaft  33   b , at least two (U-phase and V-phase or U-phase and W-phase or V-phase and W-phase) of the U-phase, V-phase and W-phase corresponding to the outputs of the Hall ICs  65   a  to  65   c  for the rotating shaft are used (function as the second sensor of the present invention). 
     As shown in  FIG. 3 , the Hall ICs  66   a  and  66   b  for the output shaft are installed on the control board  60  so as to face the magnets  53  for the output shaft. More specifically, the Hall ICs  66   a  and  66   b  for the output shaft are installed on the control board  60  so as to face the upper surface (annular surface) of the magnet  53  for the output shaft, and so as to have predetermined intervals (substantially 90° interval) along the circumferential direction of the magnet  53  for the output shaft. Thus, the Hall ICs  66   a  and  66   b  for the output shaft are allowed to successively generate pulse signals (electric signals) with predetermined phase differences in response to the rotation of the magnet  53  for the output shaft (see  FIG. 7 ). In this case, the Hall ICs  66   a  and  66   b  for the output shaft form the third sensor in the present invention. 
     As shown in  FIG. 6 , the wiper switch  67  installed in the vehicle room of the vehicle  10  is electrically connected to the control circuit  62  so that the operation signal of the wiper switch  67  is inputted to the control circuit  62 . In this case, the operation signal for the wiper switch  67  differs depending on the operation state of the wiper switch  67  by the operator, a high-speed wiping operation signal (High), a low-speed wiping operation signal (Low), an intermittent wiping operation signal (Int) are listed as one example. 
     Next, an operation of the wiper motor  20  constructed as described above will be described in detail with reference to the drawings.  FIG. 7  is pulse waveform diagrams showing an output state of an electric signal from each of Hall ICs. 
     “U-phase pulse” of  FIG. 7  indicates an output waveform of the Hall IC  65   a  for the rotating shaft, “V-phase pulse” indicates an output waveform of the Hall IC  65   b  for the rotating shaft, and “W-phase pulse” indicates an output waveform of the Hall IC  65   c  for the rotating shaft. Furthermore, “A phase pulse” indicates an output waveform of the Hall IC  66   a  for the output shaft, and “B phase pulse” indicates an output waveform of the Hall IC  66   b  for the output shaft. Furthermore, reference numeral “H” of  FIG. 7  represents a state in which the Hall IC is operated to be switched ON, and reference numeral “L” represents a state in which the Hall IC is operated to be switched OFF. 
     When the wiper switch  67  is operated by the operator so that the wiper motor  20  is driven to rotate (0 sec), a driving current is successively supplied to the coils  32   a ,  32   b  and  32   c  wound around the stator  32  from the external power source  64  via the inverter circuit  61 . Thus, the rotor  33  is rotated at a predetermined rotation number so that the wiper blades  17   a  and  17   b  start to carry out wiping operations (see  FIG. 1 ) from the lower reversing position (step position) toward the upper reversing position. In this case, the rotation number of the rotor  33 , that is, the wiping speed of the wiper blades  17   a  and  17   b , is determined by the operation signal (“High”, “Low”, or “Int”) from the wiper switch  67 . 
     When the wiper motor  20  is driven to rotate so that the rotor  33  is allowed to rotate relative to the stator  32 , pulse signals having a predetermined phase difference and comparatively short intervals are successively outputted from the Hall ICs  65   a  to  65   c  for the rotating shaft in response to the rotation of the rotor  33  (0 sec and so on). Furthermore, the appearance timings and the number of occurrences of these pulse signals composed of U-phase, V-phase and W-phase are inputted to the control circuit  62  and are also stored therein. On the basis of the pulse signals (three), the control circuit  62  ON/OFF controls the switching elements installed in the inverter circuit  61 , while detecting the rotation positions relative to the stator  32  of the rotor  33 , so that the wiper motor  20  is driven to rotate. Furthermore, the control circuit  62  detects the rotation number of the rotating shaft  33   b  on the basis of two pulse signals so that the wiper motor  20  is driven to rotate so as to have the rotation number in accordance with the operation signal from the wiper switch  67 . 
     When the wiper motor  20  is driven to rotate and the worm wheel  52  and the output shaft  52   b  are consequently rotated, pulse signals having a predetermined phase difference and comparatively long intervals are successively outputted from the Hall ICs  66   a  and  66   b  for the output shaft in response to the rotation of the worm wheel  52  (output shaft  52   b ) (0 sec and so on). Furthermore, the appearing timings and the number of occurrences of these pulse signals composed of A-phase and B-phase are respectively inputted to the control circuit  62  and are also stored therein. On the basis of the pulse signals, the control circuit  62  detects the rotation positions of the output shaft  52   b  relative to the gear housing  41 , so that the positions of the wiper blades  17   a  and  17   b  relative to the front glass  11  are thus detected. Furthermore, the control circuit  62  ON/OFF controls the switching elements installed in the inverter circuit  61  so as to drive the wiper motor  20  to rotate so that the wiper blades  17   a  and  17   b  are allowed to stop at predetermined positions and to carry out reversing operations on the front glass  11 . 
     In this case, as shown in  FIG. 7 , each of the wiper blades  17   a  and  17   b  is designed to make one reciprocal movement on the front glass  11  between 0 sec and 2.0 sec. That is, from 0 sec to 1.0 sec, each of the wiper blades  17   a  and  17   b  is moved toward the upper reversing position, and at the time point of 1.0 sec, the wiper motor  20  is reversely operated from a forward driving process to a backward driving process so that each of the wiper blades  17   a  and  17   b  is thereafter moved toward the lower reversing position between 1.0 sec and 2.0 sec. Therefore, as shown by an arrow indicating the reversing position, the pulse signals are placed on the right and left sides of the drawing symmetrically in a mirror image, with the corresponding time point (point of 1.0 sec) serving as a border. 
     As described above in detail, according to the wiper motor  20  of the first embodiment, the magnet  34  for the rotating shaft (first magnet, second magnet) is installed on the extended portion of the rotating shaft  33   b  in the gear housing  41 , and the Hall ICs  65   a  to  65   c  for the rotating shaft (first sensor, second sensor) are formed on the control board  60  inside the gear housing  41  so as to face the magnet  34  for the rotating shaft. The Hall ICs  65   a  to  65   c  for the rotating shaft are adapted to detect the rotation position of the rotating shaft  33   b  relative to the stator  32 , that is, the rotation position of the rotor  33  relative to the stator  32 , and the Hall ICs  65   a  to  65   c  for the rotating shaft are adapted to detect the rotation number of the rotating shaft  33   b.    
     With this arrangement, the Hall ICs  65   a  to  65   c  for the rotating shaft (compatibly used) for detecting the rotation position of the rotor  33  and the rotation number of the rotating shaft  33   b  and the Hall ICs  66   a  and  66   b  for the output shaft for detecting the rotation position of the output shaft  52   b  relative to the gear housing  41  can be concentrated and formed on the control board  60 . Therefore, since it is unnecessary to install a sensor (first sensor in the present invention) for detecting the rotation position of the rotor  33  at a portion of the wiper motor  20  close to the rotor  33 , the dimension of the wiper motor  20  along the axial direction of the rotating shaft  33   b  can be shortened, and further downsized. 
     Furthermore, according to the wiper motor  20  of the first embodiment, since the magnet and the sensor (first magnet/first sensor) for detecting the rotation position of the rotor  33  and the magnet and the sensor (second magnet/second sensor) for detecting the rotation number of the rotating shaft  33   b  are formed in a manner so as to be commonly shared by the Hall ICs  65   a  to  65   c  for the rotating shaft and the magnet  34  for the rotating shaft, the number of the magnets and the number of the sensors can be reduced so that the low cost and light-weight of the wiper motor  20  can be realized. 
     Furthermore, according to the wiper motor  20  of the first embodiment, since the permanent magnets  33   a  of the rotor  33  and the permanent magnets  34   a  of the magnet  34  for the rotating shaft are magnetized so as to allow its polarities to be alternately aligned toward the circumferential direction of the rotating shaft  33   b , with the polarities of the permanent magnets  33   a  and the polarities of the permanent magnets  34   a  being matched toward the axial direction of the rotating shaft  33   b , the detection of the rotation position of the rotor  33  relative to the stator  32  and the control of the rotor  33  on the basis of this detection can be simplified. 
     Next, the second embodiment of the present invention will be described with reference to the accompanying drawings. In addition, elements the same in function as those of the above-explained first embodiment are denoted by the same reference numbers as those of the first embodiment, the detail description of those elements are omitted here. 
       FIG. 8  is a bottom view corresponding to  FIG. 3  of the wiper motor according to a second embodiment,  FIG. 9  is a block diagram explaining an electric system of the wiper motor of  FIG. 8 , and  FIG. 10  shows pulse waveform diagrams showing an output state of an electric signal from each of Hall ICs and MR sensors. 
     The wiper motor according to the second embodiment differs from the wiper motor according to the first embodiment in that the shape of the third magnet and the function of the third sensor differ from those of the first embodiment. 
     As shown in  FIG. 8 , a magnet  71  for the output shaft (third magnet) having a tablet shape is attached to the extended portion of the output shaft  52   b  in the gear housing  41  via the worm wheel  52 , and the magnet  71  for the output shaft is rotated integrally with the output shaft  52   b . The magnet  71  for the output shaft has its range with substantially 180° being magnetized to the S-pole, with the other range having substantially 180° being magnetized to the N-pole. 
     An MR sensor (third sensor)  72  made of a magnetic resistance element is attached to a portion of the control board  60  facing the magnet  71  for the output shaft. As shown in  FIG. 9 , the MR sensor  72  is electrically connected to the control circuit  62  so that an output voltage corresponding to an electric signal from the MR sensor  72  is inputted to the control circuit  62 . The MR sensor  72  has its resistance value changed in response to a change in the magnetic flux due to the rotation of the magnet  71  for the output shaft facing the corresponding MR sensor  72 ; thus, as shown in  FIG. 10 , the output voltage (0 to 500 mV) is adapted to change substantially linearly. More specifically, the MR sensor  72  is set so as to have its output voltage maximized at the point of time of 1.0 sec corresponding to the reversing position of each of the wiper blades  17   a  and  17   b . Thus, the rotation position (absolute position) of the output shaft  52   b  relative to the gear housing  41  can be detected. 
     In the wiper motor  70  according to the second embodiment constructed as described above, the same functions and effects as those of the first embodiment can be obtained. In addition to this, in the second embodiment, the magnet  71  for the output shaft is formed into a tablet shape so as to achieve further small size and light-weight in comparison with the magnet  53  for the output shaft of the first embodiment. Furthermore, since the third sensor can be configured by using the single MR sensor  72 , a packaging process of electronic parts including the MR sensor  72  on the control board  60  can be simplified. Furthermore, since the MR sensor  72  detects the absolute position of the output shaft  52   b  relative to the gear housing  41 , it is possible to omit computing processes for use in detecting positions in the control circuit  62 . 
     Next, the third embodiment of the present invention will be described with reference to the accompanying drawings. In addition, elements the same in function as those of the above-explained first embodiment are denoted by the same reference numbers as those of the first embodiment, the detail description of those elements are omitted here. 
       FIG. 11  is a bottom view corresponding to  FIG. 3  of a wiper motor according to a third embodiment, and  FIG. 12  is a block diagram explaining an electric system of the wiper motor of  FIG. 11 . 
     The wiper motor according to the third embodiment differs from the wiper motor  20  according to the first embodiment in that the first magnet, the second magnet, and the third magnets are formed of a commonly-used magnet, and the first sensor, the second sensor, and the third sensor are formed of a commonly-used sensor. 
     As shown in  FIG. 11 , a magnet  81  for the output shaft (first magnet, second magnet and third magnet) having a tablet shape is attached to the extended portion of the output shaft  52   b  in the gear housing  41  via the worm wheel  52 , the magnet  81  for the output shaft is rotated integrally with the output shaft  52   b . The magnet  81  for the output shaft has its range with substantially 180° along the circumferential direction being magnetized to the S-pole, with the other range having substantially 180° being magnetized to the N-pole. 
     A magnet-type rotary encoder  82  (first sensor, second sensor, third sensor) capable of outputting pulse signals (three types) corresponding to U-phase, V-phase and W-phase which are spuriously obtained in response to the rotation of the output shaft  52   b  and an electric signal the same as that of the MR sensor  72  (see  FIG. 8 ) in accordance with the second embodiment is installed on a portion of the control board  60  facing the magnet  81  for the output shaft. As shown in  FIG. 12 , the rotary encoder  82  is electrically connected to the control circuit  62 , and a pulse signal and an output voltage corresponding to the electric signals from the rotary encoder  82  are inputted to the control circuit  62 . 
     In this case, the electric signal from the rotary encoder  82  is an electric signal the same as that of  FIG. 10 . Furthermore, although the rotation state (the rotation number and the rotation position) of the rotating shaft  33   b  is not directly detected in the wiper motor  80  according to the third embodiment in the same manner as those of the first embodiment and the second embodiment, on the basis of the pulse signals (three types) corresponding to U-phase, V-phase and W-phase spuriously obtained by the rotation of the worm wheel  52 , the rotation state of the rotating shaft  33   b  is estimated by the control circuit  62 . 
     In the wiper motor  80  according to the third embodiment constructed as described above, the same functions and effects as those of the first embodiment can be obtained. In addition to this, in the third embodiment, since only the single magnet  81  for the output shaft and the single rotary encoder  82  are installed, it is possible to achieve further small size and light-weight of the wiper motor  80 . Furthermore, the control logic of the wiper motor  80  can be further simplified. 
     Next, the fourth embodiment of the present invention will be described with reference to the accompanying drawings. In addition, elements the same in function as those of the above-explained first embodiment are denoted by the same reference numbers as those of the first embodiment, the detail description of those elements are omitted here. 
       FIG. 13  is a view corresponding to  FIG. 4  of a wiper motor according to a fourth embodiment,  FIG. 14A  is a cross-sectional view taken along a line D-D of  FIG. 13 ,  FIG. 14B  is a cross-sectional view taken along a line E-E of  FIG. 13 , and  FIG. 14C  is a cross-sectional view showing a modified example of a magnet for the rotating shaft. 
     As shown in  FIGS. 13-14C , the fourth embodiment differs from the third embodiment in that a rotor  90  and a magnet  100  for the rotating shaft differ in structure from those of the third embodiment, and a radial bearing  110  is fixed between the rotor  90  of the rotating shaft  33   b  and the magnet  100  for the rotating shaft. 
     A rotor  90  is formed into a substantially column shape by carrying out cutting work or the like on a round rod, and is pressed and fixed in the rotating shaft  33   b  so as to integrally rotate. A cylindrical permanent magnet (ring magnet)  91  is attached to the outer peripheral surface of the rotor  90 . That is, in the fourth embodiment, an SPM (Surface Permanent Magnet) structure is used in the rotor  90 . In this case, since the permanent magnet  91  is formed into a ring magnet and allowed to cover all the circumference of the rotor  90 , more poles can be installed in comparison with the first embodiment. Therefore, the fourth embodiment makes it possible to improve the degree of freedom in designing, that is, to suitably correspond to the variation of motor specifications. 
     Additionally, the rotor  90  is formed into the substantially column shaped by cutting work of a round rod and shown in the above description; however, in the same manner as that of the first embodiment, the rotor may be formed of a plurality of stacked steel plates into a substantially column shape. 
     A permanent magnet  91  is formed of a plurality of magnetic poles which is alternately magnetized along the circumferential direction (6 poles in this embodiment), and the rotor  90  and the permanent magnet  91  are firmly fixed to each other with an adhesive or the like. Furthermore, as shown in  FIG. 13 , a skew SK which is tilted toward the axial direction of the rotor  90  is formed in the permanent magnet  91  so that by this arrangement, the occurrence of a failure such as a cogging torque, a torque ripple or the like can be suppressed. In this case, as the permanent magnet  91 , a permanent magnet of a so-called segment type (divided type), which is divided into a plurality of portions in the circumferential direction, may be used. In this case, in order to prevent dropping off (separation) from the rotor  90 , as shown in  FIGS. 5B and 5C , it is preferable to cover the circumference of each permanent magnet with a cylindrical cover. 
     In the same manner as that of the permanent magnet  91  fixed to the rotor  90 , a magnet  100  for the rotating shaft is formed of a permanent magnet (ring magnet) having a cylindrical shape. The magnet  100  for the rotating shaft is formed of a plurality of magnetic poles which is alternately magnetized along the circumferential direction, and it has six magnetic poles in the same manner as that of the permanent magnet  91 . However, no skew SK as that of the permanent magnet  91  is formed in the magnet  100  for the rotating shaft. In this case, since the magnet  100  for the rotating shaft is formed as a ring magnet, many poles can be formed in the same manner as that of the permanent magnet  91  so that more precise detailed control operations can be carried out. 
     An attaching cylinder  101  for use in attaching the magnet  100  to the rotating shaft  33   b  is installed between an inner peripheral portion of the magnet  100  and an outer peripheral portion of the rotating shaft  33   b . The attaching cylinder  101  is formed by, for example, a pipe member (not shown in detail) made of brass, and is swaged and fixed to a fixing concave portion (not shown) formed on the periphery of the rotating shaft  33   b  with the magnet  100  attached to the rotating shaft. 
     In this case, the magnet  100  for the rotating shaft constitutes the first magnet and the second magnet of the present invention. In the same manner as that of the permanent magnet  91 , a so-called “segment type (divided type) permanent magnet”, which is divided into a plurality of portions in the circumferential direction, may be used as the magnet  100  for the rotating shaft. In this case, in order to prevent the magnet from dropping off (or being separated) from the attaching cylinder  101 , as shown in  FIGS. 5B and 5C , it is preferable to cover the circumference of each permanent magnet with a cylindrical cover. Furthermore, the magnet  100  for the rotating shaft may have twelve poles (two times the pole number of the permanent magnet  91 ) as shown in  FIG. 14C . 
     A ball bearing composed of an inner race, an outer race and a plurality of steel balls is used as a radial bearing  110  shown in  FIG. 13 . Furthermore, although it is not shown in drawings in detail, the radial bearing  110  is fixed between the rotor  90  and the magnet  100  for the rotating shaft by press fitting of the rotating shaft  33   b  into the inner race of the radial bearing  110 . On the other hand, the outer race of the radial bearing  110  is fixed to a predetermined portion of the gear housing  41  (see  FIGS. 2 and 3 ) by a stopper member (not shown). In this manner, the radial bearing  110  rotatably supports the rotating shaft  33   b , and prevents the rotating shaft  33   b  from moving toward the axial direction. Therefore, it is unnecessary to install thrust bearings or the like on the both sides in the axial direction of the rotating shaft  33   b , thereby making it possible to reduce the number of parts and consequently to greatly reduce the sliding loss of the rotating shaft  33   b.    
     In the fourth embodiment described above, the same functions and effects as those of the first embodiment can be obtained. 
     The present invention is not intended to be limited by the above-mentioned embodiments, and it is needless to say that various modifications may be made therein within a scope not departing from the gist of the present invention. For example, in a manner different from the above-mentioned embodiments, the first magnet, the second magnet and the third magnet of the present invention may be prepared as different members without being prepared as commonly shared members. In a manner different from the above-mentioned embodiments, the first sensor, the second sensor and the third sensor of the present invention may also be prepared as different members without being prepared as commonly shared members. Furthermore, not limited to the front glass  11 , the wiper apparatus  12  may be used for wiping rear glass (not shown). Furthermore, the wiper apparatus  12  has a structure in which as shown in  FIG. 1 , wiper arms  16   a  and  16   b  are coupled to the output shaft  52   b  via the power transmitting mechanism  14 ; however, it may have a structure in which the wiper arms are directly coupled to the output shaft. Although the wiper apparatus  12  shown in  FIG. 1  has a structure in which the two wiper arms  16   a  and  16   b  are driven by the single wiper motor  20 , it may have a structure in which the two wiper arms are driven by respectively individual wiper motors. Furthermore, the number of coils to be wound around the stator  32  and the number of permanent magnets to be installed in the rotors  33  and  90  may be altered on demand. Furthermore, not limited to a brushless wiper motor of an inner rotor type in which the rotors  33  and  90  are rotatably installed in the stator  32 , the present invention may be applied to a brushless wiper motor of an outer rotor type in which the rotor is placed outside the stator. Although a configuration is shown in which the radial bearing  110  is attached to the rotating shaft  33   b  to which the rotor  90  is fixed, which relates to the fourth embodiment, the radial bearing  110  may be attached to the rotating shaft  33   b  (see  FIG. 4 ) to which the rotor  33  is fixed, which relates to the first embodiment. 
     The brushless wiper motor is used for driving a wiper member forming a wiper apparatus installed in a vehicle, such as an automotive vehicle, so as to wipe a windshield. 
     While the present disclosure has been illustrated and described with respect to a particular embodiment thereof, it should be appreciated by those of ordinary skill in the art that various modifications to this disclosure may be made without departing from the spirit and scope of the present disclosure.