JPH0515141U - Brushless motor - Google Patents

Abstract

(57) [Abstract] [Purpose] The rotor yoke is plastically deformed to eliminate the imbalance of the magnetic attraction force. [Structure] In a brushless motor having a freely rotatable rotor yoke 2, a rotor magnet 6 provided on the rotor yoke, and a stator coil 24 facing the magnet in plan view, the amount of unbalance of magnetic attraction force distortion of a rotor 30 is measured. Then, based on this measured value, the rotor yoke 2
Is plastically deformed, thereby eliminating the imbalance of the distortion of the magnetic attraction force and suppressing the runout of the rotor.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a brushless motor, and more particularly to a brushless motor capable of canceling the imbalance of magnetic attraction force distortion.

[0002]

[Prior Art]

 Generally, motors used in video cameras, word processors and the like are required to be small and lightweight, and for example, capstan motors of video cameras employ flat brushless motors as shown in FIG. 12, for example. For example, in this brushless motor, a rotor magnet 4 and a stator coil 6 provided on a disk-shaped rotor yoke 2 are provided so as to face each other in a plane, and a base end of a capstan shaft 8 that is mounted upright at the center of the rotor yoke 2. The part is rotatably supported by a bearing holder 14 via an upper bearing 10 and a lower bearing 12. To fix the brushless motor to the device side, the bearing holder 14 is solidified to the device side.

By the way, based on the recent demand for further reduction in size and weight of small motors, the cantilever support structure shown in FIG. 12 is changed from the cantilever support structure of the capstan shaft shown in FIG. 12 to the both-end support structure shown in FIG. This has led to the development of motors that shorten the overall length of the motor and contribute to making it thinner. The brushless motor shown in FIG. 13 is shown upside down with respect to the motor shown in FIG. This brushless motor has a disk-shaped rotor yoke 2 having a capstan shaft 8 attached to the center thereof, and a ring-shaped rotor magnet 4 in which N and S poles are alternately arranged on the peripheral edge of the lower surface of the rotor yoke 2. Is provided. The upper and lower ends of the shaft 8 are rotatably supported by a long bearing holder 20 whose one side is open via a ball bearing 16 and an oilless bearing 18, respectively. The mounting plate 22 at the base end of the bearing holder 20 is attached to a stator yoke 24 having a stator coil 6 by screws or the like, as shown in FIG.

[0004]

[Problems to be solved by the device]

 By the way, the brushless motor shown in FIG. 13 can be made thinner than the motor shown in FIG. 12, but this reduces the air gap between the magnet and the coil, thus reducing the magnetic attraction of the rotor. The force increases, and the force due to the variation in the magnetic attraction force of the rotor acts on the stator yoke surface and the capstan shaft 8, and the shaft runout and the shaft diameter due to the tilting of the bearing holder due to the distortion of the stator yoke plate are reduced. This also helps reduce the shaft rigidity and causes shaft runout. For example, if the entire motor makes one revolution, it will run out by several microns. When the capstan shaft swings in this way, the tape travels unevenly, and as a result, wow and flutter deteriorates. In addition, there is a case where mechanical distortion occurs in the shaft or the like due to the imbalance of the magnetic attraction force. The variation in the magnetic attraction force as described above is caused by the shaft center of the capstan shaft 8 as shown in FIG. 26 and the magnet center 28 of the rotor magnet 4 having the radius r, when there is a coaxial deviation of a distance Δr, even if the attraction force F1 on the right side and the attraction force F2 on the left side are equal, a difference in moment occurs and It causes variations in power. This phenomenon similarly occurs even if the distance Δr = 0, if there is unevenness in the magnet material due to coaxial deviation of the magnetizing yoke or uneven distribution of magnet powder during magnet molding.

Further, as another cause of the variation of the magnetic attraction force, as shown in FIG. 16, the capstan shaft 8 and the rotor yoke 2 are not attached at right angles, and the distance Δg between the magnet surface and the stator yoke 24 is increased. If the runout occurs, the left and right gaps g of the rotor magnet 4 are different, and the attraction force is inversely proportional to the square of the gap, so that a difference occurs between the attraction forces F1 and F2. In order to suppress the variation in the magnetic attraction force described above, it is possible to increase the rigidity of each part and to improve the accuracy of parts and assembly. However, if the rigidity of each part is increased, the motor itself It will be impossible to achieve smaller size and lighter weight, and in terms of accuracy improvement, it will have to be increased by almost 3 times from the current accuracy, which is practically impossible. The present invention has been devised in order to effectively solve the above problems. An object of the present invention is to provide a brushless motor in which the imbalance of magnetic attraction force distortion is corrected by plastically deforming the rotor yoke.

[0006]

[Means for Solving the Problems]

 In order to solve the above problems, the present invention provides a brushless motor having a rotor magnet provided on a peripheral portion of a rotatable rotor yoke, and a stator coil provided so as to face the rotor magnet in a plane. The rotor yoke is deformed in order to eliminate the imbalance of the magnetic attraction force distortion of the magnet.

[0007]

[Action]

 Since the present invention is configured as described above, when there is variation in the magnetic attraction force, the rotor yoke with the smaller attraction force is deformed to reduce the gap with the stator coil at this location, and the rotor yoke Try to balance the entire magnetic attraction around the axis of. As a result, the fluctuation of the shaft itself is suppressed, uneven running of the tape is eliminated, and deterioration of wow and flutter is prevented.

[0008]

【Example】

 An embodiment of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a sectional view of a rotor deformed to eliminate the imbalance of magnetic attraction force distortion, and FIG. 2 is a sectional view of the rotor before deformation. The same parts as those of the apparatus shown in FIG. 11 are designated by the same reference numerals. The rotor 30 is mainly composed of a rotor yoke 2 formed in a disk shape and a ring-shaped rotor magnet 6 in which N and S poles are alternately arranged on the peripheral portion of the rotor yoke 2. A long shaft 8 such as a capstan shaft is provided in the section. The rotor 30 configured as described above is assembled as shown in FIG. 13 after the rotor yoke 2 is deformed at, for example, the bent portion A in order to eliminate the imbalance of the magnetic attraction force distortion. In order to perform the above-mentioned deformation operation of the rotor yoke, the unbalance amount of the magnetic attraction force strain of the rotor 30 is measured, and the deformation operation is performed based on the measured value. The suction force balance measurement / correction device will be described first. FIG. 3 is a schematic perspective view showing the measurement / correction device, and FIG. 4 is an explanatory view for explaining the outline of the components of the measurement / correction device shown in FIG.

As shown in the drawing, the measurement correction device 32 includes a magnetic attraction force measurement unit 34 for measuring the degree of imbalance of the magnetic attraction force strain of the rotor 30, and the above-mentioned measurement unit 34 based on the measurement value by the unit 34. The rotor 30 is mainly configured by a correction unit 36 that actually deforms, and the entire apparatus except the correction press 38 of the correction unit 36 is housed in a rectangular casing 40. As shown in FIG. 5, the magnetic attraction force measuring unit 34 has a shaft insertion hole 42 that rotatably supports the shaft 8 of the rotor 30 by rotatably supporting the shaft 8 of the rotor 30. It has a dummy stator 44. Around the periphery of the shaft insertion hole 42, a plurality of strain gauges 46, for example, four magnetoresistive elements as shown in FIG. 7 are arranged at equal angles along the circumferential direction. Therefore, it is possible to detect the fluctuation of the magnetic attraction force due to the rotation of the rotor 30. The output from each strain gauge 46 is input to, for example, a strain gauge amplifier 48 having a noise cut filter, and the output of this amplifier 48 is input to, for example, an A / D converter 52 of a personal computer 50. (See Figure 4).

Further, as a mechanism for rotating and driving the rotor 30 at the time of setting, three rollers 56 with a belt 54 interposed are provided on a side portion of the rotor 30, and one roller 56 a among them is , Is configured to be rotationally driven by a measuring step motor 58 which is brought into contact with the step motor driver 57 (see FIG. 4). Therefore, by bringing the belt 54 into contact with the side portion of the rotor 30 and moving the belt, the rotor 30 is rotated. In the present embodiment, the rotor 30 is set to rotate once by adding 200 pulses to the step motor 58 as described later. The dummy stator 44 is connected to a base 60 located below the dummy stator 44 via a connecting shaft 61, and the base 60 is like a plurality of springs having guide pins 62 inserted through the center thereof. It is elastically supported by the elastic member 64 on the apparatus main body side, that is, with respect to a fixing die fixing portion to be described later, and has a floating structure that functions at the time of correction. In the vicinity of the central portions of the dummy stator 44 and the base 60, insertion holes 65 and 67 are formed, respectively, through which a correction movable pin and a rotor yoke fixing pin, which will be described later, are inserted in a loosely fitted state.

On the other hand, the correction unit 34 is provided above the apparatus main body and below the correction press 38 for supporting the upper portion of the rotor 30 and the rotor 30 and the magnetic attraction force measurement unit 34. It is mainly composed of a correction mold 66 as shown in FIG. The correction press 38 is connected to an air unit 68 and can be moved up and down by the air pressure from this (see FIG. 4). The correction mold 66 is mainly composed of a correction mold fixing portion 70 having a hole 69 in the center thereof, and a correction mold movable portion 72 arranged substantially in parallel therewith. There is. An adjusting screw 76 connected to the correcting step motor 74 is screwed to one end of the correcting mold moving part 72, and the adjusting screw 76 can be rotated forward and backward. Thus, the correction mold movable part 72 can be moved up and down with the end P as a fulcrum to change the inclination angle. This angle adjustment is performed by a drive signal from the step motor drive 57 (see FIG. 4) to which the correction step motor 74 is connected.

Then, on the upper surface of the correction mold fixing portion 70, for example, three (only one in FIG. 7) rotor yoke fixing pins 78 are provided upright, and each of these is fixed. The pin 78 passes through the center hole 80 of the correction mold movable part 72 and the insertion holes 65 and 67 provided in the dummy status 44 and the base 60, and the pin 78 and the lower end of the correction press 38. The rotor 30 is sandwiched and fixed between them.

Further, one correction movable pin 82 is provided upright at a portion located on the adjustment screw 76 side from the center of the correction mold movable portion 72, and this pin 82 is also provided. The dummy stator 44 and the insertion holes 65 and 67 provided in the base 60 are penetrated, and the tip end of the correction movable pin 82 is increased by increasing the inclination angle of the movable portion 72 so that the rotor yoke 72 of the rotor 30. It is configured so that it can come into contact with and be plastically deformed by a predetermined amount. At this time, a recess 84 is formed at the lower end of the correction press 38 to allow plastic deformation of the rotor yoke. In the illustrated example, the correction mold movable portion 72 is described with a considerably steep inclination angle for the sake of description, but in reality, the inclination angle is about 0.1 degree at the maximum. That is, the vertical movement of the correction movable pin 82 is very small, about 0.1 mm. Further, the movable portion 72 is also provided with an insertion hole (not shown) through which the guide pin 62 is inserted, and the lower end portion thereof is fixed to the correction mold fixing portion 70. As shown in FIG. 4, the step motor driver 57 and the air unit 68 are operated by the control signal from the I / O unit of the personal computer 50, and the processing contents of the personal computer 50 are controlled by the monitor 86. It is ready to be monitored.

Next, the measurement correction operation of the magnetic attraction force balance of the rotor will be described using the measurement correction apparatus configured as described above. First, the operation of measuring the distortion of the magnetic attraction force of the rotor 30 will be described with reference to the flowcharts shown in FIGS. 5 and 8. The uncorrected rotor 30 formed as shown in FIG. 2 is installed on the dummy stator 44 of the magnetic attraction force measurement unit 34. Then, starting from the pulse number N = 1 (S1), the measuring step motor 58 is driven by gradually increasing the pulse number to gradually rotate the rotor 30 by the belt 54 every one pulse (S2). The magnetic attraction force at this time is always detected by the strain gauge 46 (S3), and this detection is performed until N = 200 pulses, that is, until the rotor 30 makes one rotation, and the measurement step motor 58 is used. The data of 200 points is taken in while rotating (S4).

Then, based on this detection result, the personal computer 50 obtains the imbalance or distortion amount of the magnetic attraction force of 360 degrees, and obtains the direction to be corrected (S5). Specifically, for example, the above measurement result is obtained as a magnetic attraction force with respect to the rotor rotation angle θ as shown in FIG. 9, and this is shown in FIG. 10 when the center of rotation of the rotor is represented as the origin. The amount to be corrected and its direction are represented by the centroid in FIG. 10, that is, the center of gravity Q, and this value is calculated. Then, in S6, the phase lag due to the nozzle cut filter used in the distortion gauge amplifier 48 is corrected and the measurement operation is completed. The amplitude H of the measured quantity in FIGS. 9 and 10 indicates noise. When the measurement operation is completed in this way, the operation proceeds to the deformation correction operation. This modification operation is performed by the modification die 66 shown in FIG. First, in S1 of the flowchart shown in FIG. 11, when the measurement operation of the magnetic attraction force strain unbalance amount is completed as described above, it is determined in S2 whether the unbalance amount is within a predetermined allowable range. Is judged, and if it is within the allowable range, GO judgment is made and the rotor is sent to the next assembly process without being modified.

Further, when the unbalance amount requires deformation correction outside the predetermined allowable range, it is determined how many times the rotor has already undergone deformation correction, and for example, the rotor has already been subjected to deformation correction five times. In some cases, the rotor is discarded as defective. If the number of deformation corrections received is zero or less than four, the process moves to S3 to drive the measurement step motor 58 to rotate the rotor 30 by the desired angle based on the measurement result. And install the rotor in the correction position. Then, in S4, the correction movable pin 82 is moved up in accordance with the predetermined correction amount to deform the rotor yoke 2 by a predetermined amount. Specifically, the adjustment screw 76 is rotated by sending the number of pulses corresponding to the correction amount to the correction step motor 74, whereby the correction mold movable part 72 is tilted by a predetermined angle. Due to this inclination, the correction movable pin 82 of the correction mold movable portion 72 rises, and the rotor yoke 2 is plastically deformed by a predetermined amount as described above. In this case, the rotor 30 is securely sandwiched and fixed between the correction press 38 and the rotor yoke fixing pin 78 provided upright on the repairing die fixing portion 70. Further, when the correction press 38 is lowered and the rotor 30 is fixed, the dummy stator 44 receives a pressing force, but the stator 44, together with the base 60, becomes a floating structure by the elastic member 64. Because it is done, it is possible to sink downward, and there will be no problem.

Further, when the amount of movement of the correction movable pin 82 is obtained, the amount of plastic deformation of the rotor yoke is not stable due to subtle undulations on the surface of the spring back, and therefore the actual correction from the data values before and after the correction is performed. A learning function (S5) for obtaining the correlation between the deformation amount and the movement amount of the movable pin 82 and obtaining the movement amount of the movable pin to be sent out from this correlation is operated. Based on the movement amount thus obtained, the correction movable pin 82 is lifted and the correction deformation is performed (S6). Then, in this modified and deformed rotor 30, the imbalance amount of the magnetic attraction force is measured again using the magnetic attraction force measurement unit 34 in S1, and the above-mentioned correction operation is repeated up to 5 times. Will be done. In this way, the plastically deformed rotor as shown in FIG. 1 is completed, and this is assembled as shown in FIG. 13 to complete the brushless motor.

As described above, the amount of unbalance of the magnetic attraction force of the rotor 30 is measured, and the rotor yoke 2 is plastically deformed based on the measured value. Therefore, it is possible to improve the magnetic accuracy without improving the component accuracy and the assembly accuracy. It is possible to eliminate the distortion of the suction force. Specifically, as a result of this embodiment, the motor runout can be suppressed to about 1/5 of that of the conventional device, and the process defect rate is significantly increased from about 80% to about 0.5%. It has become possible to improve. In the above embodiment, the number of correction deformations was set to 5 at maximum, but it is not limited to this. Further, in the present embodiment, the measurement operation and the correction deformation operation are performed in one station, but they may be performed in another station.

[0019]

[Effect of the device]

 As described above, according to the present invention, the following excellent operational effects can be exhibited. Since the rotor yoke is plastically deformed according to the amount of unbalance of the magnetic attraction force, it is possible to eliminate the unbalance of the magnetic attraction force distortion without improving the component accuracy and the assembly accuracy. It is possible to suppress the occurrence of mechanical strain on the shaft and the like. Therefore, shaft runout of the motor can be significantly suppressed, and wow and flutter can be improved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a modified rotor for use in a brushless motor according to the present invention.

FIG. 2 is a cross-sectional view showing a rotor before correction.

FIG. 3 is a schematic perspective view showing a measurement correction device.

FIG. 4 is an explanatory diagram for explaining an outline of a measurement correction device.

FIG. 5 is a schematic perspective view showing a magnetic attraction force measurement unit.

FIG. 6 is a plan view showing a strain gauge.

FIG. 7 is a schematic cross-sectional view showing a correction mold.

FIG. 8 is a flowchart when measuring a magnetic attraction force.

FIG. 9 is a relationship diagram showing a relationship between a rotor rotation angle and a measured amount.

FIG. 10 is a diagram showing a graph showing a measured amount around a rotation center.

FIG. 11 is a flowchart when performing modification correction.

FIG. 12 is a partial cross-sectional view showing a general brushless motor.

FIG. 13 is an assembly diagram showing assembly of a capstan motor as a brushless motor.

FIG. 14 is a perspective view showing the attachment of the stator yoke and the bearing holder of the capstan motor.

FIG. 15 is an explanatory diagram for explaining an imbalance of the attraction force due to coaxial displacement of the rotor.

FIG. 16 is an explanatory diagram for explaining imbalance of suction force due to surface wobbling of a rotor.

[Explanation of symbols]

2 ... Rotor yoke, 4 ... Rotor magnet, 6 ... Stator coil, 8 ... Shaft, 16 ... Ball bearing, 1
8 ... Oilless bearing, 20 ... Bearing holder,
24 ... Stator yoke, 30 ... Rotor, 34 ... Magnetic attraction force measurement unit, 36 ... Correction unit, 38 ... Correction press, 44 ... Dummy stator, 46 ... Strain gauge, 58 ...
Measuring step motor, 66 ... Correction mold, 70 ... Correction mold fixed part, 72 ... Correction mold movable part, 76 ... Adjustment screw, 78 ... Rotor yoke fixing pin, 82 ... Correction movable pin.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Susumu Masuda 3-12 Moriya-cho, Kanagawa-ku, Yokohama-shi Kanagawa Japan Victor Company of Japan, Ltd.

Claims (1)

[Scope of utility model registration request] 1. In a brushless motor having a rotor magnet provided on a rotatable rotor yoke and a stator coil provided so as to face the rotor magnet in a plane, unbalance of magnetic attraction force distortion of the rotor magnet is eliminated. A brushless motor, characterized in that the rotor yoke is deformed in order to do so.