JPH06109565A - Apparatus and method for cogging torque of motor - Google Patents

Abstract

PURPOSE:To easily obtain a T-.theta. characteristic measured with high accuracy with being less influenced by a coupling loss by a method wherein a torque is converted to a linear force and further converted to an electric signal by means of a weight sensor to detect a relative position between a stator and a rotor. CONSTITUTION:An axle 2 of a motor 1 to be measured is attached to a chucking device 4 so that the calibration of two load cells 7 is carried out. A string 8 is fitted to the two cells 7, wound on a pulley 3 and pulled to the opposite sides. An output of a dynamic strain measuring device 9 is be operated by a computer 10 through an A/D board and the result is printed out by a printer 11. In response to the instruction from the computer 10, the axle 2 is slowly rotated by a belt-driving device 6. A relative position at that time between the rotor and the stator is detected by means of an encoder 5 to be sent to the computer 10 as a position information. Indication values of the measuring device 9 in accordance with predetermined positions are inputted to the computer so that a cogging torque T is determined. Then, the axle 2 of the rotor is rotated by one revolution, thereby obtaining a T-.theta. characteristic.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cogging torque measuring apparatus and method for a motor, and more particularly to measuring the direction and magnitude of the cogging torque at an arbitrary relative position between a rotor and a stator of the motor over the entire circumference of the motor. An apparatus and a method.

[0002]

2. Description of the Related Art Three typical examples of conventional devices for measuring the cogging torque of a motor will be described below.

FIG. 11 is a side view for explaining an example of the first measuring device of the conventional examples. In FIG. 11, a torque gauge 21 is attached to the shaft 2 of the rotor of the measured motor 1. The measurement is performed by the shaft 2 of the rotor of the measured motor 1.
The torque gauge 21 is rotated while maintaining a high coaxiality, and the maximum value of the cogging torque is read.

As a problem of the measuring device shown in FIG. 11,
First, without actually angle theta ₂ which the axis 2 is rotated in the measured motor rotor coincides with the angle theta ₁ which rotates the torque gauge, the measured motor rotor and the relative positions of the stator theta cogging torque T That is, the T-θ characteristic showing the relationship with is not obtained. Secondly, when rotating the torque gauge 21,
It is difficult to rotate the motor to be measured 1 while maintaining a high degree of coaxiality with respect to the rotor shaft 2. If the degree of coaxiality cannot be maintained, a large lateral pressure is applied to the rotor shaft 2, resulting in a large gap between the shaft and the bearing. Friction force (coupling loss) occurs, and an accurate value cannot be obtained. Thirdly, this measuring device cannot measure the state in which the direction of the force of the cogging torque is reversed.

FIG. 12 shows a second measuring device of a conventional example, and FIG. 13 is a graph showing a measurement result by the second measuring device of the conventional example. In FIG. 12, a known pulley 22 whose rotation angle can be read is attached to the shaft 2 of the rotor of the measured motor 1. The cogging torque is measured by applying a weight 23 to the pulley 22. In this measuring device, the influence of static friction torque between the shaft of the motor to be measured and the bearing is large, and the weight 23 is increased to measure a balanced position, and the weight is decreased to measure. Then the measurement results are different. The graph showing the relationship between the balanced position and the load (weight of weight) shown in FIG. 13 cannot be said to be the T-θ characteristic of the measured motor.

14 to 18 show a third example of the conventional measuring apparatus. FIG. 14 particularly shows the overall structure of the measuring apparatus. In FIG. 14, the shaft 2 of the rotor of the motor 1 to be measured is connected to a commercially available torque meter 26 by a coupling 24. The torque meter 26 is an encoder 3
A drive motor 29 to which 0 is connected is connected by a coupling 28.

FIG. 15 is a side view showing the internal structure of the torque meter 26. In FIG. 15, a torque transmission shaft 31 is provided between the load side shaft 25 and the drive side shaft 27 of the torque meter 26.
Are connected by. The torque is obtained from the twist angle of the torque transmission shaft 31. The torque is obtained by detecting the positions of the gear 32a provided on the load side shaft 25 and the gear 32b provided on the drive side shaft 27 by the sensors 33a and 33b, respectively, and detecting the phase difference. Required from.

Next, a procedure for obtaining the T-θ characteristic showing the relationship between the cogging torque T and the relative position θ between the rotor and the stator of the motor to be measured will be described using the measuring apparatus of FIG.

First, the drive motor 29 is started by a command from the computer 10, such as a personal computer. The driving force of the drive motor 29 is transmitted to the shaft 2 of the rotor of the measured motor 1 through the coupling 28, the torque meter 26, and the coupling 24, and the shaft 2 rotates slowly. During rotation, the relative position of the rotor and the stator is detected by the encoder 30 and sent to the computer 10 as position information. Further, during rotation, the computer 10 captures the output signals of the sensors 33a and 33b at each preset position,
Calculate cogging torque. As described above, the cogging torque T at 360 ° (entire circumference) is measured while rotating the rotor shaft 2 of the measured motor 1.

In the measuring apparatus shown in FIG. 14, the coupling loss between the rotor shaft 2 of the measured motor 1 and the load side shaft 25 of the torque meter 26 has a great influence on the measurement. This state will be described with reference to FIGS.

FIG. 16 shows the rotor shaft 2 of the motor 1 to be measured.
6 shows a state in which the coaxiality between the torque meter 26 and the load-side shaft 25 is not maintained. FIG. 17 shows a state in which the motor to be measured 1 is tilted and attached. In both cases of FIG. 16 and FIG. 17, a large lateral pressure or frictional force is applied to the shaft 2 of the rotor of the measured motor 1, and accurate measurement cannot be performed.

FIG. 18 shows the rotor shaft 2 of the motor 1 to be measured.
The state in which the torque meter 26 is attached to the load side shaft 25 in a state of being strongly pushed or pulled is shown. In this case, a large frictional force is always applied and accurate measurement cannot be performed. The coupling loss other than that shown in FIGS. 16 to 18 may be bending of the shaft of the measuring device or the motor to be measured. Strictly speaking, since all axes have bends, there is no center line of rotation where the measuring instrument side and the measured motor match.
Since it tries to rotate it forcibly, lateral pressure is applied to the shaft of the measuring device or the motor to be measured.

FIG. 19 is a diagram showing an ideal T-θ characteristic. However, when measured in the states shown in FIGS. 16 to 18, the T-θ characteristic diagrams shown in FIGS. 20 and 21 are obtained. FIG. 20 is an example of a T-θ characteristic diagram in which the result of cogging torque is placed on a large undulation. Such a characteristic diagram is likely to occur mainly in the states shown in FIGS. 16 and 17. Figure 2
3 shows an example of a T-θ characteristic diagram on which irregular noise is added. Such a characteristic diagram occurs in any of the cases of FIGS.

In addition to FIG. 16 to FIG. 18, T that always rides on a large frictional force due to coupling loss due to various factors.
A T-θ characteristic obtained by combining the T-θ characteristic diagram shown in FIG. 20 with the T-θ characteristic diagram shown in FIG. 20 and the T-θ characteristic diagram showing a large swell shown in FIG. 20. It becomes a figure.

In all of the conventional measuring devices, the motor to be measured is fixed for measurement.

[0016]

As described above,
With the conventional measuring device (or measuring method), even if the T-θ characteristic is not obtained, or even if the T-θ characteristic is obtained, if the measurement is performed while keeping the coaxiality strictly, the influence of the coupling loss will occur. However, there was a problem that the measurement accuracy was not obtained.

Therefore, an object of the present invention is to provide a cogging torque measuring apparatus and method which can reduce the influence of coupling loss, can be easily measured with a simple structure, and can obtain a T-θ characteristic with high measurement accuracy. To provide.

[0018]

In order to achieve the above-mentioned object, the measuring device of the present invention has the following means. That is, an arm or pulley having a known distance and radius from the center of the rotating shaft is attached to the stator of the motor to be measured, and force converting means for converting a torque, which is a rotating force, into a linear force, and the arm or the pulley are prevented from slipping. A force transmitting means for transmitting the force for attaching the string to the load sensor, a force detecting means for converting the force transmitted from the string into an electric signal by the load sensor, a rotor holding means for holding the rotor of the motor to be measured, It has a rotating means for rotating the rotor holding means, and a relative position detecting means represented by an encoder for detecting a relative position of the stator and the rotor during rotation of the rotor of the motor to be measured by the rotating means.

Further, the measuring method of the present invention has the following measuring steps. That is, the rotor of the motor to be measured is held and rotated, and the relative position of the stator with respect to the rotor is detected. The relative position of the rotor and the stator is generated by the arm or pulley attached to the stator of the motor to be measured. The cogging torque T is converted into a distance F from the rotation axis or a radius r and a force F, and the force is transmitted to the two load sensors in a state where they are attracted by a string with equal force. The direction and magnitude of the torque are calculated by the calculation process from the difference, the cogging torque at an arbitrary relative position between the rotor and the stator is measured, and the rotor is rotated while performing the above measurement to measure the motor under test. Measurement of cogging torque at arbitrary relative position between rotor and stator and measurement of cogging torque of motor under test in specified angle range T-θ characteristic measurement A step of T-theta characteristic measuring See full 360 ° circumference of the cogging torque of the measured motor.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will now be described with reference to the drawings. Before entering specific examples, the structural features of the measuring apparatus of the present invention will be summarized and listed below.

(1) Cogging torque T of the motor to be measured
Is converted into a force F exerted on the arm or pulley having a known radius r from the center of the rotor rotation axis, and the force F is attached to the arm or pulley so that the force F does not slip.
It is configured to transmit to one load sensor.

(2) Tensions Fa and Fb of equal force are applied to the two load sensors in advance, and these are used as the reference (bias point) of the operation.

(3) The direction and magnitude of the force F are, as shown below, the forces Fa ₁ and Fb ₁ applied to the two load sensors.
Calculated from the difference of. Power orientation: Fa ₁ -Fb ₁ sign (+ or -) is determined in a. Magnitude of force: Calculated as the absolute value of Fa ₁ −Fb ₁ .

(4) From the force F obtained in (3) above, the cogging torque T is obtained by the following equation. T = F · r (1)

(5) The influence of coupling loss generated in the conventional measuring device is reduced. More specifically, (a) the forces due to the positional deviation (shown in FIGS. 5 to 7) and other disturbances are simultaneously applied to the two load sensors to cancel each other. (B) Since the error of the measurement value with respect to the positional deviation (shown in FIGS. 5 and 6) occurs in proportion to the cosine (cosine) of the trigonometric function, the influence of the error is small even if there is a relatively large positional deviation. . (C) In the conventional measuring device, even if the coaxiality is slightly misaligned, the metals are pressed against each other and a large coupling loss occurs. However, in the present invention, since it is attached by a string, there is a degree of freedom and a positional deviation. Also, there is little coupling loss.

(6) This is a method of detecting the cogging torque by the arm or pulley attached to the stator of the motor to be measured (the method of detecting the torque from the stator has not been heretofore available). The stator is provided with a portion for positioning and a screw hole or a hole or a protruding portion for mounting, and a screw hole, a hole, a protruding portion or the like that also has a role of mounting and positioning, so that the arm or the It is convenient to position and install the pulley.

(7) Since the shaft of the rotor of the motor to be measured is held, high coaxial accuracy with the measuring device can be easily obtained.

(8) In the T-θ characteristic measurement in which the cogging torque of the measured motor over the entire circumference of 360 ° is measured, since the rotor shaft of the measured motor is rotated, the measurement can be performed with high coaxial accuracy and rotation. The shaft runout at the time can be suppressed.

An embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 is a perspective view showing the overall construction of the cogging torque measuring device of the present invention. A pulley 3 is attached to the stator of the measured motor 1. Further, the shaft 2 of the rotor of the measured motor 1 is held tightly by the chucking device rotor (holding means) 4 without play. An encoder (relative position detecting means) 5 is attached to the chucking device 4 so as to detect the relative position between the rotor and the stator of the motor to be measured. The detected position signal is sent to the computer 10.

In the measuring apparatus of the embodiment shown in FIG. 1,
Measurement is performed by rotating the rotor of the motor to be measured around the rotor rotation axis with the motor to be measured 1 in an axially downward posture (vertical orientation). This posture is preferable because the influence of gravity due to the imbalance of the stator of the motor to be measured can be reduced, but the present invention is not limited to this posture, and if necessary, an axial or lateral posture can be used. It is also possible to make measurements.

Further, in FIG. 1, a belt driving device 6 is shown as an example of a driving device (rotating means) for rotating the rotor of the motor to be measured. As such a driving device, it is desired that the motor under test is not subjected to impact or vibration, there is little uneven rotation, and there is no backlash. In addition, as a driving method, not only an external driving device that provides rotation from outside the chucking device but also a method in which the chucking device itself has a driving source and is directly driven may be used.

In FIG. 1, a load sensor (force detecting means)
As one example of the above, the one using the load cell 7 is shown. Then, as the load sensor, one having a small movable distance of the sensor movable portion is desired. Specific load sensors include strain gauges, pressure-voltage transducers that are piezoelectric elements, strain gauges, and the like.

Further, in FIG. 1, two load cells 7 are provided.
As an example of the string (force transmitting means) 8 which is attached so as to attract each other, a thin metal wire is shown. This string is desired to be flexible and less elastic.

The measuring procedure of the cogging torque measuring device of the present invention thus constructed will be described below. First, the pulley 3 is attached to the stator of the measured motor 1 to be measured.
An example of a method of attaching the pulley 3 to the stator of the motor to be measured 1 with high coaxial accuracy with respect to the center of the rotating shaft will be described with reference to FIGS. 2 and 3.

FIG. 2 is a perspective view showing how the measured motor 1 is mounted for driving a mechanism typified by audio equipment. When mounting the motor 1 on the mounting plate 14 on the mechanical side, the protrusion 12 of the stator of the motor is fitted into the hole 15 of the mounting plate 14 for positioning, and the screw 17 is attached to the clearance hole 16 of the mounting plate and the motor. The fastening plate 14 is fixed through the screw holes 13. For this reason, the protrusion 12 is
In contrast, it has a high coaxial precision d and a high dimensional precision D. On the other hand, the measuring device also has a high dimensional accuracy E on the mounting plate 14.
When the motor 1 is attached, the hole 15 is provided so that a high coaxial precision e can be secured.

FIG. 3 is a side view showing how the pulley 3 is attached to the motor 1 to be measured. The pulley 3 is positioned by fitting the protrusion 12 of the motor 1 to be measured into the hole 18.
Insert the screw 17 into the clearance hole 19 of the pulley and the screw hole 13 of the motor.
It is fixed by tightening through. Hole in pulley 18
Is made with high dimensional accuracy G and high coaxial accuracy g. Therefore, a high coaxial accuracy can be easily obtained with respect to the center of the rotation axis simply by fitting and mounting the measured protrusion 13 and the hole 18 of the pulley.

Next, the shaft 2 of the motor to be measured 1 is attached to the chucking device 4. Then, the two load cells in the cogging torque measuring device are calibrated.

FIG. 4 shows an example of a method of calibrating the load cell and the dynamic strain measuring instrument. This is the weight 20 on the load cell 7.
It is a method of hanging and calibrating. A commercially available load cell is connected to a dynamic strain measuring instrument to operate. For each load cell, the dynamic strain measuring instrument must be calibrated by making corrections and adjustments.

After the calibration is completed, as shown in FIG.
Attach the string 8 to the two load cells 7a and 7b, and
Wrap this string 8 around and pull it to both sides so that the string 8 and the pulley 3 do not slip. The magnitudes of the forces Fa and Fb that pull the string (wire) to both sides are set to about half the rated load of the load cell. The forces Fa and Fb must be equal in magnitude. The forces Fa and Fb having the same magnitude serve as the base points (bias points) of the operations of the load cells 7a and 7b. The load cell 7a,
For 7b, it is necessary to select one having a rated load that is at least twice the absolute value of the force applied during measurement.

In FIG. 1, the output of the dynamic strain measuring device 8 is taken into the computer 10 via the A / D board, and after being processed by the computer 10, the result is output by the printer 11.

Next, a method of calculating the cogging torque T at an arbitrary relative position θ between the rotor and the stator of the motor to be measured will be described with reference to FIG. When the radius of the pulley 3 attached to the stator of the motor 1 to be measured is r and the force applied to the pulley 3 is F, the cogging torque T is obtained by the following equation. T = F · r (1)

Using the load cells 7a and 7b and the dynamic strain measuring instruments 9a and 9b shown in FIG. 6, the direction and magnitude of the force F of the equation (1) can be obtained as follows.

Assuming that the force magnitude indicating value by the dynamic strain measuring device 9a is Fa ₁ and the force magnitude indicating value by the dynamic strain measuring device 9b is Fb ₁ , Fa ₁ −Fb ₁ > 0. (2) If so,
Force is the direction from the load cell 7b to load cell _{7a, Fb 1 -Fa 1> 0} ······ (3) if,
The direction of force is from load cell 7a to load cell 7
It can be determined that the direction is toward b. The magnitude of the force F is the absolute value of the difference between Fa ₁ and Fb ₁ F = | Fa ₁ −Fb ₁ | (4) From the force F calculated as described above, the cogging torque T at an arbitrary position of the motor can be obtained by the equation (1).

On the other hand, in FIG. 1, the relative position of the rotor and the stator of the measured motor 1 is indicated by the rotation angle θ by the encoder 5. The relationship between the rotation angle and the cogging torque T, that is, the T-θ characteristic showing the state of the cogging torque T over the entire circumference of 360 ° of the measured motor is determined as follows.

(1) By a command from the computer 10,
The drive device (belt drive device 6 in the embodiment of FIG. 1) is activated.

(2) The belt driving device 6 slowly rotates the shaft 2 of the rotor of the motor to be measured 1, and the relative position of the rotor and the stator at that time is detected by the encoder 5.
It is sent to the computer 10 as position information.

Dynamic strain measuring device 9 for each preset position
The indicated value of is taken into the computer 10 and the cogging torque T is obtained.

As described above, the T-θ characteristic can be obtained by rotating the rotor shaft 2 of the motor to be measured once. In order to obtain a more accurate value of the T-θ characteristic, the data of the number of rotations of the measured motor may be acquired, the arithmetic processing may be performed, and the averaged T-θ characteristic may be calculated.

Next, how the measured cogging torque value is affected by the coupling position accuracy in the embodiment described with reference to FIGS. 1 to 6 will be described with reference to FIGS.

As shown in FIG. 7, considering the case where the measured motor is radially deviated from the normal position by an angle α, the force applied to the load cell 7 is defined as Fα ₁ .
If the detected force is Fα ₂ , then Fα ₂ = Fα ₁ · cosα ··· (5), and a cosα-fold error occurs. However, looking at the relationship between the error and the deviation angle (angle α), there is an error of 3% and 14.0.
7 °, 5% error 18.19 °, 10% error 2
It is 5.84 °, and it can be seen that even if the coupling position accuracy is considerably poor, the influence on the measured value is small.

As shown in FIG. 8, considering a case where the motor to be measured is deviated in the vertical direction (vertical direction) by an angle β with respect to the normal position, in this case as well, the same as in the above case. Has little effect. Further, as shown in FIG. 9, when the motor under measurement is tilted by an angle γ with respect to the vertical axis, the influence is similarly small.

What must be particularly noted in this embodiment is that the motor to be measured does not oscillate at an angle δ, as shown in FIG. The reason is that, in the state shown in FIGS. 7 to 9, even if the coupling positions are slightly deviated, the same force is applied to the two load cells 7, so that they are canceled out in the calculation, and there is an influence when the force F is obtained. On the other hand, in the case of FIG. 10, the string 8 is pulled in various directions due to the axial runout, which affects the measurement of the force F.

[0054]

As is apparent from the above description, the present invention has various effects as described below.

(1) Cogging torque T of the motor to be measured
Is converted to a force F applied to an arm or pulley having a known radius r from the center of the rotation axis of the rotor.
(A) Coupling loss is small because the method of transmitting the load to the two load sensors is carried out by a string attached to the arm or pulley. (B) The allowable range of the mounting position of the measured motor is large. (C) The error of the measured value is small and high accuracy can be obtained.

(2) Since the method of calculating the cogging torque T from the difference between the two load sensors is adopted, (a) the force due to the positional displacement and the disturbance is canceled to reduce the influence on the measurement. (B) Not only the magnitude of the cogging torque T but also the direction of force can be known.

(3) Since the arm or pulley is attached to the stator of the motor to be measured and the rotor shaft is held and rotated, (a) it is not necessary to rotate the laterally long device side, Can be downsized. (B) It is possible to measure the cogging torque over the entire circumference of 360 ° of the measured motor. (C) Since the stator is provided with a portion for positioning and mounting, positioning and mounting of the arm or pulley can be facilitated. (D) Since the rotor shaft of the motor to be measured is held, high coaxial accuracy with the measuring device can be easily obtained, and shaft runout during rotation can be suppressed.

[Brief description of drawings]

FIG. 1 is a schematic perspective view showing an entire cogging torque measuring device of the present invention.

FIG. 2 is a perspective view showing how the measured motor is mounted on the mechanical side.

FIG. 3 is a side view showing how a pulley is attached to a motor to be measured.

FIG. 4 is a side view showing an example of a calibration method of the load cell and the dynamic strain measuring instrument of FIG. 1.

5 is a plan view showing a state in which a force is applied to obtain a base point of operation of the load cell of FIG. 1. FIG.

6 is a schematic configuration diagram showing a part of the measuring device of FIG. 1 that measures the force generated in the stator of the motor to be measured.

FIG. 7 is a plan view for explaining the influence of the displacement of the measured motor in the radial direction on the measurement.

FIG. 8 is a side view for explaining the influence of vertical displacement of the motor under measurement on the measurement.

FIG. 9 is a side view for explaining the influence of the inclination of the measured motor installation on the measurement.

FIG. 10 is a side view for explaining the influence of shaft runout of the measured motor on measurement.

FIG. 11 is a side view showing a first example of a conventional cogging torque measuring device.

FIG. 12 is a perspective view showing a second example of a conventional cogging torque measuring device.

FIG. 13 is a graph showing the measurement results obtained by the measuring device of FIG.

FIG. 14 is a schematic diagram showing an overall configuration of a third example of a conventional cogging torque measuring device.

FIG. 15 is a side view showing the internal structure of the torque meter used in the measuring device of FIG.

16 is a side view for explaining the influence of the positional deviation in the measurement device of FIG. 14 on the measurement.

17 is a side view for explaining the influence of the positional deviation in the measurement device of FIG. 14 on the measurement.

FIG. 18 is a side view for explaining the influence of the positional deviation in the measurement device of FIG. 14 on the measurement.

FIG. 19 is a graph showing an ideal T-θ characteristic.

FIG. 20 is a graph showing an example of T-θ characteristics affected by coupling loss.

FIG. 21 is a graph showing another example of the T-θ characteristic affected by the coupling loss.

[Explanation of symbols]

 1 Motor to be Measured 2 Rotor Shaft of Motor to be Measured 3, 22 Pulley 4 Chucking Device 5, 30 Encoder 6 Drive Device 7, 7a, 7b Load Cell 8 String 9, 9a, 9b Dynamic Strain Measuring Device 10 Computer 11 Printer 12, Projection of stator of motor to be measured 13 Screw hole of stator of motor to be measured 14 Mechanical mounting plate 15 Mounting plate hole 16 Mounting plate clearance hole 17 Screw 18 Pulley hole 19 Pulley clearance hole 20 23 Weight 21 Torque Gauge 24, 28 Coupling 25 Torque meter load side shaft 26 Torque meter 27 Torque meter drive side shaft 29 Drive motor 31 Torque meter torque transmission shaft 32a Gear wheel provided on torque meter load side shaft 32b Torque meter drive side Gears 33a, 33b provided on the shaft Sensor

Claims (14)

[Claims] 1. A rotor holding means for holding a rotor of a motor, a rotating means for rotating the rotor holding means, and a relative position detecting means for detecting a relative position between the stator and the rotor during rotation of the rotor of the motor by the rotating means. And force converting means for converting the cogging torque, which is a rotational force, into a linear force,
A cogging torque measuring device for a motor, comprising: a force transmitting means for transmitting the force converted by the force converting means; and a force detecting means for detecting the force. 2. The cogging torque measuring device according to claim 1, wherein the rotor of the motor is arranged vertically. 3. The cogging torque measuring device according to claim 1, wherein the rotor holding means is a chucking device, the rotating means is a belt device for rotating the chucking device, and the relative position detecting means is the chucking device. An encoder rotated by the belt device at the same time as the king device, the force converting means being a pulley or an arm attached to a stator of a motor, and the force transmitting means being attached to a string or an arm wound around the pulley. A cogging torque measuring device comprising a string. 4. A cogging torque measuring device according to claim 3, wherein the force detecting means comprises a load sensor and a dynamic strain measuring device for detecting a dynamic strain of the load sensor. 5. The cogging torque measuring device according to claim 4, wherein the load sensor is a load cell. 6. The cogging torque measuring device according to claim 5, wherein the load cell is a strain gauge, a piezoelectric element, or a strain gauge. 7. The cogging torque measuring device according to claim 3, wherein the arm or pulley which is the force converting means is utilized by utilizing a protrusion, a hole, a screw hole or the like provided on the stator of the motor to be measured. A cogging torque measuring device characterized in that positioning is performed with high coaxial accuracy with respect to a shaft, and a stator of a motor to be measured is attached. 8. A method for measuring a cogging torque of a motor to be measured, which comprises two components, a rotor and a stator,
The cogging torque, which is a rotational force, is taken out from the stator of the motor to be measured by the force converting means, and is transmitted to the force detecting means by the force transmitting means to be detected, and the rotor, which is the other component of the motor to be measured, is held by the holding means. The cogging torque measuring method is characterized in that the relative position between the rotor and the stator is changed while being held by the rotating means, and the changed relative position is detected by the relative position detecting means. 9. The cogging torque measuring device according to claim 8, wherein the force converting means converts the cogging torque, which is a rotational force, into a linear force by means of an arm or pulley attached to a stator of the motor to be measured. A cogging torque measuring method, which is performed by converting the distance or radius from the center of the rotating shaft and the force applied to a string attached so as not to slip on an arm or a pulley. 10. The cogging torque measuring method according to claim 8, wherein the force detection is performed by two load sensors, and the direction and magnitude of the force are determined based on the difference between the forces detected by the two load sensors. The cogging torque measuring method is characterized by calculating the torque and the direction and magnitude of the torque. 11. The cogging torque measuring method according to claim 10, wherein when the force is detected from the two load sensors,
A cogging torque measuring method, characterized in that equal forces are applied to two load sensors in advance. 12. The cogging torque measuring method according to claim 8, wherein the rotor is rotated at least by a certain angle, and the relative position θ between the rotor and the stator detected by the relative position detecting means, and the force F detected by the force detecting means. A cogging torque measuring method, characterized in that a T-θ characteristic is obtained from a torque T calculated by a product of a distance from a center of a rotation axis or a radius r. 13. The cogging torque measuring method according to claim 12, wherein the stator is rotated by 360 °. 14. The cogging torque measuring method according to claim 12, wherein the stator is rotated by 360 ° or more and an average value at each position is calculated to obtain a more accurate T-θ characteristic. Method.