JP2013198188A - Brushless motor and wiper device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a brushless motor which does not require a special position detection sensor for detecting the rotational position of the rotor.SOLUTION: A brushless motor 19 including a stator 21 for forming a rotating magnetic field when currents are supplied to armature coils 21a, 21b, 21c, and a rotor 22 having a permanent magnet 22b and being rotated by the rotating magnetic field is further provided with a drive unit 33 for controlling the number of revolution of the rotor 22 by performing field-weakening control, and a drive unit 33 for estimating the rotational position of the rotor 22 based on the voltages induced in the armature coils 21a, 21b, 21c when controlling the number of revolution of the rotor 22 by performing field-weakening control.

Description

  The present invention relates to a brushless motor and a wiper device having a rotor with a permanent magnet and a stator provided with an armature coil.

  2. Description of the Related Art Conventionally, as a motor capable of switching the rotational speed of a rotor, for example, a wiper motor such as an automobile is known. The wiper motor can switch the rotation speed between a low speed and a high speed by a driver's switching operation. Examples of such wiper motors capable of speed switching are described in Patent Documents 1 and 2.

  A wiper motor described in Patent Document 1 includes a case, a magnet housed in the case, an armature that is rotatably provided inside the case, a coil wound around the shaft, and a shaft that rotates integrally with the armature And a commutator provided on the shaft, and a high-speed operation brush and a low-speed operation brush that are in contact with the commutator. When the driver operates the wiper switch to the low speed driving side, a current flows through the low speed driving brush and the shaft rotates at a low speed. On the other hand, when the driver operates the wiper switch to the high speed driving side, a current flows through the high speed driving brush and the shaft rotates at high speed.

  By the way, a wiper motor having a brush has noise caused by the brush such as a problem that a motor output is limited due to a rise in the temperature of the brush, a problem that a space for arranging the brush is necessary, and a sliding sound of the brush. I have problems that occur.

  On the other hand, the motor described in Patent Document 2 is fixed to the inner surface of the yoke housing, and is arranged in an annular stator around which a plurality of windings are wound, and is rotatably disposed inside the stator, and has a rotating shaft. And a magnet provided on the rotating shaft. In the motor described in Patent Document 2, excitation currents having different phases are supplied to a plurality of windings to generate a rotating magnetic field, and the rotor rotates. Since the motor described in Patent Document 2 has no brush, there is no problem specific to a motor with a brush.

JP 2007-202391 A JP 2010-93977 A

  However, in a brushless motor as described in Patent Document 2, a dedicated position detection sensor, for example, a Hall IC, a ring magnet, etc. must be provided to detect the rotational position of the rotor, and the number of parts is reduced. There was a problem that the cost increased due to the increase.

  An object of the present invention is to provide a brushless motor and a wiper device that do not require a dedicated position detection sensor to detect the rotational position of a rotor.

  The brushless motor of the present invention is a brushless motor including a stator that forms a rotating magnetic field when current is supplied to an armature coil, and a rotor that has a permanent magnet and rotates by the rotating magnetic field. A first rotation speed control unit that controls the rotation speed of the rotor by performing field control, and occurs in the armature coil when the first rotation speed control section performs field weakening control and controls the rotation speed of the rotor. And a rotational position estimating unit that estimates the rotational position of the rotor based on the induced voltage.

  In the brushless motor of the present invention, a speed reduction mechanism is provided in a power transmission path for transmitting the power of the rotor to the operating member, and the speed reduction mechanism is configured to decelerate the output rotation speed with respect to the input rotation speed. It is characterized by.

  In the brushless motor of the present invention, the speed reduction mechanism has an output shaft that is decelerated with respect to the input rotational speed, and an output shaft sensor that detects at least one of the rotational speed and the absolute position of the output shaft is provided. The rotational position estimating unit performs control to estimate the rotational position of the rotor based on the rotational speed of the output shaft detected by the output shaft sensor.

  The brushless motor of the present invention includes a rotation direction control unit that rotates the rotor forward and backward by switching the direction of the current flowing through the armature coil.

  The brushless motor of the present invention is provided with a control board having the first rotation speed control unit and the rotation position estimation unit, and the speed reduction mechanism and the control board are accommodated in a common housing. Features.

  The wiper device of the present invention is characterized in that the rotor of any brushless motor according to the present invention is connected to a wiper arm, which is an operation member for wiping the glass of the vehicle, so that power can be transmitted.

  The wiper device of the present invention has a low-speed wiping mode for operating the wiper arm at a predetermined low speed as a mode for controlling the wiping operation of the wiper arm, and a high-speed wiping mode for operating the wiper arm at a higher speed than the low-speed wiping mode. When the high-speed wiping mode is selected when the characteristics of the brushless motor can obtain the rotation speed and torque of the rotor required in the low-speed wiping mode, the first rotation The number control unit performs control to obtain the rotational speed and torque of the rotor required in the high-speed wiping mode by increasing the rotational speed of the rotor by performing the field weakening control.

  In the wiper device according to the present invention, the brushless motor has a function of switching between an on state in which current is passed through the armature coil and an off state in which current is not passed through the armature coil, A second rotational speed control unit having a function of controlling the rotational speed of the rotor by controlling a duty ratio that is a ratio, and the second rotational speed control unit further includes the low-speed wiping mode. When is selected, it has a function of controlling the rotational speed of the rotor by controlling the duty ratio without performing the field weakening control.

  The wiper device of the present invention includes a sensor magnet that rotates integrally with the rotor, and a switching element that outputs an on / off signal according to a change in magnetic pole of the sensor magnet when the rotor rotates. The rotational speed control unit performs control to detect the rotational speed of the rotor based on an on / off signal of the switching element when performing the field weakening control, and sets an energization timing to the armature coil in an electrical angle. It has a function of controlling the rotational speed of the rotor by advancing by 30 degrees.

  According to the present invention (Claim 1), the rotational position of the rotor can be estimated based on the induced voltage generated in the armature coil when the field-weakening control is performed to control the rotational speed of the rotor. Therefore, it is not necessary to provide a dedicated sensor for detecting the rotational position of the rotor, and the number of parts and the manufacturing cost of the brushless motor can be reduced.

  According to the present invention (Claim 2), in addition to performing field-weakening control to control the rotational speed of the rotor, the speed reduction ratio of the speed reduction mechanism can be set.

  According to the present invention (Claim 3), the rotational position of the rotor can be estimated based on the rotational speed of the output shaft.

  According to the present invention (Claim 4), the rotor can be rotated forward and backward by switching the direction of the current flowing through the armature coil.

  According to the present invention (Claim 5), since the speed reduction mechanism and the control board are accommodated in a common housing, the brushless motor can be reduced in size, and the layout property when the brushless motor is attached to an object. Will improve.

  According to the present invention (Claim 6), the power of the rotor of the brushless motor is transmitted to the wiper arm, and the wiper arm is operated to wipe the glass of the vehicle.

  According to the present invention (Claim 7), when the motor characteristic corresponding to the low speed wiping mode is set, the brushless motor performs field weakening control to increase the rotation speed of the rotor. The required rotor speed and torque can be obtained. Therefore, the power consumption of the brushless motor can be reduced and the motor efficiency can be improved.

  According to the present invention (Claim 8), when the low-speed wiping mode is selected, the rotational speed of the rotor can be controlled by controlling the duty ratio without performing the field weakening control.

  According to the present invention (Claim 9), when field-weakening control is performed, the rotational speed of the rotor is detected based on the ON / OFF signal of the switching element, and the energization timing to the armature coil is set to 30 degrees in electrical angle. The rotation speed of the rotor can be controlled by advancing the angle.

It is the schematic which shows the example which applied the brushless motor of this invention to the wiper apparatus of the vehicle. It is an external view which shows the brushless motor of this invention. It is a brushless motor of the present invention, and is a bottom view in a state where an under cover is removed. It is a schematic diagram which shows the control system of the brushless motor of this invention. It is a diagram which shows an example of the characteristic of the brushless motor of this invention.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. The vehicle 10 shown in FIG. 1 has a windshield 11. The vehicle 10 also has a wiper device 12 that wipes the windshield 11. The wiper device 12 includes a wiper arm 14 that swings about a pivot shaft 13 and a wiper arm 16 that swings about a pivot shaft 15. A wiper blade 17 is attached to the free end of the wiper arm 14, and a wiper blade 18 is attached to the free end of the wiper arm 16. The wiper device 12 has a brushless motor 19 as a power source for driving the wiper arms 14 and 16. The power of the brushless motor 19 is individually transmitted to the wiper arms 14 and 16 via a power transmission mechanism 20 configured by levers, links and the like.

  The brushless motor 19 is configured as shown in FIGS. 2, 3, and 4. As an example of the brushless motor 19 in this embodiment, a three-phase four-pole motor is used. The brushless motor 19 has a stator 21 and a rotor 22. The brushless motor 19 has a bottomed cylindrical case 23, and a stator 21 is fixedly provided on the inner periphery of the case 23. As shown in FIG. 4, the stator 21 has armature coils 21 a, 21 b, and 21 c of three phases, specifically, U phase, V phase, and W phase. As shown in FIG. 3, the rotor 22 is provided inside the stator 21. The rotor 22 has a rotating shaft 22a and a four-pole permanent magnet 22b attached to the rotating shaft 22a. For convenience, the rotating shaft 22a is omitted in FIG. A plurality of bearings (not shown) are provided in the case 23, and the rotating shaft 22a is rotatably supported by the plurality of bearings.

  The brushless motor 19 has a hollow frame 24, and the frame 24 and the case 23 are fixed by a fastening member (not shown). The rotation shaft 22 a has a half in the length direction arranged inside the case 23 and the other half in the frame 24. A worm 22c is formed on the outer periphery of a portion of the rotating shaft 22a disposed in the frame 24. A worm wheel 25 is provided in the frame 24. A gear 25a is formed on the outer periphery of the worm wheel 25, and the gear 25a and the worm 22c are engaged with each other. Further, a sensor magnet 38 is attached to a portion of the rotating shaft 22a disposed in the frame 24. The sensor magnet 38 rotates integrally with the rotation shaft 22a. The sensor magnet 38 is magnetized so that N poles and S poles are alternately arranged along the circumferential direction of the rotating shaft 22a.

  The worm wheel 25 is configured to rotate integrally with the output shaft 26. The worm 22c and the gear 25a constitute the speed reduction mechanism 27 in the present embodiment. The reduction ratio of the reduction mechanism 27 is such that the rotational speed of the output shaft 26 is lower than the rotational speed of the rotor 22 when the power of the rotor 22 is transmitted to the output shaft 26. Further, in FIG. 2, a shaft hole (not shown) is provided in the upper part of the frame 24. The end of the output shaft 26 opposite to the end to which the worm wheel 25 is fixed is exposed to the outside via the shaft hole of the frame 24. A power transmission mechanism 20 is connected to a portion of the output shaft 26 exposed to the outside of the frame 24 as shown in FIG.

  An opening 24a is provided in a portion of the frame 24 opposite to the shaft hole. The opening 24 a is formed for attaching the worm wheel 25 and the like inside the frame 24. An under cover 28 is provided to close the opening 24a. The under cover 28 has a tray shape, and a control board 29 is provided in a space surrounded by the under cover 28 and the frame 24. FIG. 2 shows an example in which the control board 29 is attached to the under cover 28.

  A drive device 33 for controlling the brushless motor 19 is provided on the control board 29 as shown in FIG. The drive device 33 includes an inverter circuit 30 that controls energization of the armature coils 21a, 21b, and 21c. The inverter circuit 30 is connected to a terminal (not shown). The frame 24 is provided with a connector (not shown). By attaching a socket (not shown) of an electric wire connected to the external power supply 31 to the connector, the external power supply 31 and the inverter circuit 30 are connected. Connected. The external power supply 31 is a battery or a capacitor mounted on the vehicle 10.

  The inverter circuit 30 includes a switching element 30a that connects and disconnects the external power supply 31 and the armature coils 21a, 21b, and 21c. The switching element 30a is configured by a semiconductor element such as an FET, for example. More specifically, three positive-side switching elements connected to the positive electrode of the external power supply 31 corresponding to the U phase, V phase, and W phase, and corresponding to the U phase, V phase, and W phase, the external power supply 3 switching elements connected to the negative electrode side of 31. Further, a control circuit (controller) 32 having a function of switching on and off of the switching element 30a is connected to the inverter circuit 30.

  The control circuit 32 is a known microcomputer provided with a CPU, RAM, ROM and the like. The driving device 33 includes a PWM signal generation circuit 34, and the signal of the PWM signal generation circuit 34 is configured to be input to the control circuit 32. The control circuit 32 outputs a drive signal for controlling the three negative-side switching elements, and a PWM signal is superimposed on the drive signal. That is, the three negative-side switching elements are driven by PWM control and are intermittently turned on in each conduction section. The current values supplied to the armature coils 21a, 21b, and 21c are controlled by controlling the rate at which the three negative-side switching elements are individually turned on, that is, the duty ratio. . Further, the control circuit 32 stores data, a program, and the like for control executed when the brushless motor 19 is started. The time when the brushless motor 19 is started is an initial stage when the brushless motor 19 is stopped.

  Furthermore, an induced voltage detector 35 is connected to the unconnected end of each armature coil 21a, 21b, 21c. The induced voltage detector 35 is a sensor that detects an induced voltage generated in each armature coil 21 a, 21 b, 21 c as the rotor 22 rotates, and a detection signal of the induced voltage detector 35 is input to the control circuit 32. . The control circuit 32 performs processing for estimating the rotation position (phase in the rotation direction) of the rotor 22 based on the detection signal input from the induced voltage detection unit 35.

  Further, the brushless motor 19 according to the present embodiment controls the switching of the switching element 30a to be turned on and off, and reverses the direction of energization to the armature coils 21a, 21b, and 21c, thereby rotating the rotor 22 forward and backward. It is possible. When the switching element 30a is turned on, the external power supply 31 and each armature coil 21a, 21b, 21c are connected, and when the switching element 30a is turned off, the external power supply 31 and each armature coil 21a, 21b, 21c Is cut off.

  Furthermore, an output shaft sensor 36 that detects at least one of the rotational speed and the absolute position of the output shaft 26 is provided inside the frame 24. The absolute position means the rotation angle of the output shaft 26 with respect to the reference position. The reference position may be set at an arbitrary position within the range of 360 degrees. The detection signal of the output shaft sensor 36 is input to the control circuit 32. Further, a Hall IC 39 is attached to the control board 29. The Hall IC 39 is fixed facing the sensor magnet 38 in a non-contact manner. The Hall IC 39 performs a switching operation by a change in the magnetic pole of the sensor magnet 38 as the rotor 22 rotates, and generates a switching signal (ON / OFF signal). The control circuit 32 can detect the rotational speed (rotational speed) of the rotor 22 based on the switching signal of the Hall IC 39. Further, a wiper switch 37 is provided in the interior of the vehicle 10, and an operation signal of the wiper switch 37 is input to the control circuit 32.

  In the wiper device 12, the wiping speed of the wiper arms 14 and 16 can be switched based on conditions such as rainfall and snowfall. For example, when the amount of rainfall and the amount of snowfall are small, the driver can select the low speed wiping mode in which the wiper switch 37 is operated at a predetermined low speed by operating the wiper switch 37. On the other hand, when the amount of rainfall and snowfall is large, the driver can operate the wiper switch 37 to select the high speed wiping mode in which the wiper arms 14 and 16 are operated at a higher speed than the low speed. For this reason, the control circuit 32 stores in advance patterns, data, arithmetic expressions, and the like for controlling the switching element 30a for the low speed wiping mode and the high speed wiping mode.

  Control of the brushless motor 19 in this embodiment will be described. When the wiper switch 37 is operated and the low speed mode is selected, the detection signal of the induced voltage detection unit 35 is input to the control circuit 32. The control circuit 32 estimates the rotational position (angle in the rotational direction) of the rotor 22 based on the detection signal of the induced voltage detector 35 and performs energization control based on the rotational position of the rotor 22. That is, the positive-side switching elements of each phase are sequentially turned on by 120 degrees in electrical angle, and the negative-side switching elements of phases different from the positive-side switching elements are sequentially turned on by 120 degrees in electrical angle. The energization of the child coils 21a, 21b, and 21c is switched to commutate the phase current.

  When the above control is repeated, a rotating magnetic field is formed by the stator 21 and the rotor 22 rotates. Further, the brushless motor 19 has a characteristic that the rotational speed increases as the current value increases. Furthermore, the brushless motor 19 has a characteristic that the torque decreases as the rotational speed increases. When the low-speed wiping mode is selected, the actual rotational speed of the rotor 22 can be brought close to the required rotational speed by controlling the duty ratio without performing the field weakening control.

  On the other hand, when the high-speed wiping mode is selected, the low-speed wiping mode is selected for the energization timing of the armature coils 21a, 21b, and 21c without changing the current value supplied to the armature coils 21a, 21b, and 21c. Field-weakening control with a leading phase as compared with In the field weakening control, the energization timing to the armature coils 21a, 21b, and 21c is advanced by 30 degrees in electrical angle compared to when the low speed wiping mode is selected. The field weakening control is control for weakening the magnetic field formed by supplying current to the armature coils 21a, 21b, and 21c as much as possible. When this field weakening control is performed, the counter electromotive force generated in the armature coils 21a, 21b, and 21c is reduced, and the rotational speed of the rotor 22 is increased.

  FIG. 5 is a diagram showing the characteristics of the brushless motor 19. In FIG. 5, the rotation speed of the brushless motor 19 is shown on the vertical axis, and the torque of the brushless motor 19 is shown on the horizontal axis. Moreover, the broken line shown in FIG. 5 is an example of the low speed characteristic corresponding to the low speed wiping mode, and the solid line shown in FIG. 5 is an example of the high speed characteristic corresponding to the high speed wiping mode.

  The brushless motor 19 of the present embodiment has a setting characteristic at a position indicated by a solid line, for example, so that the rotation speed and torque corresponding to the low speed characteristic of FIG. 5 can be obtained when setting the rating. . For this reason, when the low-speed wiping mode is selected by operating the wiper switch 37, the required rotation speed and torque can be obtained within the range of the set characteristics or less.

  On the other hand, when the high-speed wiping mode is selected by operating the wiper switch 37 and the required torque and rotation speed exceed the setting characteristics, the control circuit 32 executes the field weakening control to thereby set the setting characteristics. A range of rotational speed and torque exceeding can be obtained. As a result, the characteristics of the brushless motor 19 are apparently equivalent to being at the position indicated by the two-dot chain line. The fact that the torque can be increased by increasing the rotational speed of the brushless motor 19 without changing the current value means that the torque constant becomes relatively large. In other words, the brushless motor 19 of this embodiment can generate as high torque as possible with less power consumption, and the motor efficiency is improved.

  Generally, a wiper device for a vehicle is used more frequently in the low-speed wiping mode than in the high-speed wiping mode. For this reason, when the brushless motor 19 of this embodiment is used for the wiper apparatus 12, the effect of reducing power consumption is large when the low-speed wiping mode is selected. Further, the brushless motor 19 of the present embodiment does not need to be rated based on the high-speed wiping mode in design, and the physique of the brushless motor 19 can be made as small as possible.

  Further, the brushless motor 19 of the present embodiment can estimate the rotational position of the rotor 22 based on the detection signal of the induced voltage detector 35 when performing field weakening control. Furthermore, the rotational position of the rotor 22 can be estimated based on the detection signal of the output shaft sensor 36 and the reduction ratio of the speed reduction mechanism 27 instead of the detection signal of the induced voltage detection unit 35. Thus, the brushless motor 19 of this embodiment can estimate the rotational position of the rotor 22 using the induced voltage detection unit 35 and the output shaft sensor 36 that are provided in advance. That is, the brushless motor 19 of this embodiment has a sensorless structure that does not require a dedicated sensor for detecting the rotational position of the rotor 22. Therefore, the number of parts and the manufacturing cost of the brushless motor 19 can be reduced.

  Further, the brushless motor 19 according to the present embodiment can obtain the rotation speed and torque corresponding to the high speed characteristics by performing field weakening control, and is provided with a speed reduction mechanism 27. Therefore, the brushless motor 19 can set the reduction ratio of the reduction mechanism 27 so as to have characteristics suitable for the operating conditions of the wiper arms 14 and 16 of the wiper device 12, that is, the rotation speed and torque. The reduction ratio of the speed reduction mechanism 27 is a value obtained by dividing the rotation speed of the output shaft 26 by the rotation speed of the rotor 22, and the rotation speed of the output shaft 26 decreases as the speed reduction ratio of the speed reduction mechanism 27 increases.

  Furthermore, the brushless motor 19 of the present embodiment can optimize the advance angle control when the brushless motor 19 is rotating forward and backward based on the estimation result of the rotational position of the rotor 22. Furthermore, since the brushless motor 19 of this embodiment is not provided with a brush, a commutator (commutator), etc., friction torque is not generated by sliding between the brush and the commutator, and a reduction in motor efficiency can be prevented. Furthermore, the brushless motor 19 of this embodiment can also prevent the occurrence of noise due to the presence of the brush.

  Furthermore, the brushless motor 19 of the present embodiment has a structure in which the control board 29 and the speed reduction mechanism 27 are both disposed in a space surrounded by the frame 24 and the under cover 28, that is, an electromechanical integrated structure. Therefore, the entire brushless motor 19 can be configured in a compact manner, and the layout when the brushless motor 19 is attached to the vehicle body is improved.

  Furthermore, in the brushless motor 19 of the present embodiment, when the field weakening control is performed, the control circuit 32 performs control to detect the rotation speed of the rotor 22 based on the on / off signal of the Hall IC 39, and the armature coil. It has a function of controlling the number of rotations of the rotor 22 by advancing the energization timing of 21a, 21b, and 21c by 30 electrical degrees.

  Here, the correspondence relationship between the configuration described in the present embodiment and the configuration of the present invention will be described. The drive device 33 having the control circuit 32 includes the first rotation speed control unit and the second rotation speed control unit of the present invention. The frame 24 and the under cover 28 correspond to the housing of the present invention, the windshield 11 corresponds to the glass of the present invention, and the wiper arms 14 and 16 correspond to the main body. The Hall IC 39 corresponds to the operation member of the invention and the switching element of the invention. Furthermore, the characteristics represented by the rotation speed and torque in FIG. 5 correspond to the characteristics of the brushless motor in the present invention.

  It goes without saying that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention. For example, the wiper device 12 is not limited to the windshield 11 and may wipe the rear glass. 1 has the wiper arms 14 and 16 coupled to the output shaft 26 via the power transmission mechanism 20, but may have a structure in which the wiper arm is directly coupled to the output shaft. Further, the wiper device 12 shown in FIG. 1 has a configuration in which the two wiper arms 14 and 16 are driven by a single brushless motor 19, but the two wiper arms are each driven by a separate brushless motor. Also good. Further, the brushless motor of this embodiment may be an IPM (Interior Permanent Magnet) type motor having a structure in which a permanent magnet is embedded in an iron core. Furthermore, the mode selected by the wiper switch is not limited to two types of the low-speed wiping mode and the high-speed wiping mode, and there may be three or more types. Furthermore, the number of armature coils and the number of permanent magnets can be arbitrarily changed.

  Furthermore, the brushless motor of the present invention can be applied to either an inner rotor type brushless motor in which a rotor is arranged inside a stator or an outer rotor type brushless motor in which a rotor is arranged outside a stator. Furthermore, the brushless motor of the present embodiment is used as a power source for operating doors, roofs, glass and other operating members in a convenient comfort system device provided in a vehicle, for example, a power slide door device, a sunroof device, a power window device, etc. It can also be used.

DESCRIPTION OF SYMBOLS 10 Vehicle 11 Windshield 12 Wiper apparatus 13,15 Pivot shaft 14,16 Wiper arm 17,18 Wiper blade 19 Brushless motor 20 Power transmission mechanism 21 Stator 21a, 21b, 21c Armature coil 22 Rotor 22a Rotating shaft 22b Permanent magnet 22c Worm 23 Case 24 Frame 24a Opening 25 Worm wheel 25a Gear 26 Output shaft 27 Deceleration mechanism 28 Undercover 29 Control board 30 Inverter circuit 30a Switching element 31 External power supply 32 Control circuit 33 Drive device 34 PWM signal generation circuit 35 Induced voltage detection unit 36 Output Axis sensor 37 Wiper switch 38 Sensor magnet 39 Hall IC

Claims (9)

A brushless motor comprising a stator that supplies a current to an armature coil to form a rotating magnetic field, and a rotor that has a permanent magnet and rotates by the rotating magnetic field,
A first rotational speed control unit that performs field weakening control to control the rotational speed of the rotor;
A rotational position estimating unit for estimating a rotational position of the rotor based on an induced voltage generated in the armature coil when the first rotational speed control unit performs field weakening control to control the rotational speed of the rotor; A brushless motor characterized by comprising.   2. The brushless motor according to claim 1, wherein a speed reduction mechanism is provided in a power transmission path for transmitting the power of the rotor to the operation member, and the speed reduction mechanism decelerates the output rotation speed with respect to the input rotation speed. A brushless motor characterized by being configured. 3. The brushless motor according to claim 2, wherein the speed reduction mechanism includes an output shaft that is decelerated with respect to the input rotational speed, and an output shaft sensor that detects at least one of a rotational speed and an absolute position of the output shaft is provided. And
The brushless motor, wherein the rotational position estimating unit performs control to estimate a rotational position of the rotor based on a rotational speed of the output shaft detected by the output shaft sensor.   4. The brushless motor according to claim 1, further comprising a rotation direction control unit that rotates the rotor forward and backward by switching a direction of a current flowing through the armature coil. Brushless motor.   4. The brushless motor according to claim 2, wherein a control board having the first rotation speed control unit and the rotation position estimation unit is provided, and the speed reduction mechanism and the control board are accommodated in a common housing. A brushless motor characterized by   6. The wiper device according to claim 1, wherein the rotor of the brushless motor is connected to a wiper arm, which is an operation member for wiping the glass of the vehicle, so that power can be transmitted. The wiper device according to claim 6, wherein a mode for controlling the wiping operation of the wiper arm includes a low speed wiping mode for operating the wiper arm at a predetermined low speed, and a high speed for operating the wiper arm at a higher speed than the low speed wiping mode. A wiping mode,
When the high-speed wiping mode is selected when the characteristics of the brushless motor can obtain the rotation speed and torque of the rotor required in the low-speed wiping mode, the first rotation speed control unit is A wiper device that performs control to obtain the rotational speed and torque of the rotor required in the high-speed wiping mode by increasing the rotational speed of the rotor by performing the field weakening control.   8. The wiper device according to claim 7, wherein the brushless motor causes a current to flow through the armature coil without performing a field weakening control and a function of switching between an on state in which current flows through the armature coil and an off state in which current is not passed through the armature coil. A second rotational speed control unit having a function of controlling the rotational speed of the rotor by controlling a duty ratio which is an ON ratio, and the second rotational speed control unit further includes the low speed control unit. A wiper device having a function of controlling the number of rotations of the rotor by controlling the duty ratio without performing the field weakening control when a wiping mode is selected. The wiper device according to claim 6, comprising: a sensor magnet that rotates integrally with the rotor; and a switching element that outputs an on / off signal according to a change in the magnetic pole of the sensor magnet when the rotor rotates.
The first rotational speed control unit performs control to detect the rotational speed of the rotor based on an on / off signal of the switching element when performing the field-weakening control, and sets an energization timing to the armature coil. A wiper device having a function of controlling the rotational speed of the rotor by advancing the electrical angle by 30 degrees.

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