JPH0643050A - Load-torque measuring apparatus for stepping motor - Google Patents

Abstract

PURPOSE:To make it possible to measure the load torque under the mounted state by driving a stepping motor in actual measurement, and measuring the actual load torque based on the frequency when step-out is generated and the frequency versus pull-out torque characteristic. CONSTITUTION:A switch 9 is connected to a terminal S2. A stepping motor 1 is coupled to an actual-machine mechanism part 2 through a coupling 3. A frequency undergoes slow-up control based on a control signal from a (slow-up- and-down) stepping controller 5. Thus, the motor 1 is driven by a motor driver 4. When the number of rotation is gradually increased, the motor 1 steps out at a certain frequency, and the step-out 6 is detected. When the motor 1 steps out at a point on a reference pull-out-torque curve, the detected step-out signal (a) is sent from a step-out detecting part 6 into a load-torque measuring part 10B. The slow-up frequency at this time is latched. The pull-out torque at the frequency is sent into an output device 11 as the load torque based on the detected step-out signal and the reference curve data from a pull-out-curve processing and memory part 10A with the load-torque measuring part 10B.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a load torque measuring device for a stepping motor, and more particularly to a load torque measuring device for a stepping motor capable of measuring an actual load torque in a mounted state of the stepping motor.

[0002]

2. Description of the Related Art Since stepping motors can digitally control rotational positions (angles) and rotational speeds with pulses with high precision and can use microcomputers, they are used as mechanism drive sources in a very wide range of fields today. There is. For example, FDDs, HDDs, printers, electronic typewriters, which have rapidly developed in recent years and whose market is expanding,
Its use is rapidly expanding in office automation equipment such as facsimiles, PPC copiers, recorder plotters, and FA equipment such as industrial robots. Despite the importance of measuring and controlling the load torque on the motor shaft in the development, manufacturing, and quality control of these stepping motor-equipped devices, it has been extremely difficult to perform such measurement with high accuracy. This is because, for example, when a spur gear reduction mechanism is used in the mechanism section after the motor, if the meshing state of the pinion gear attached to the motor output shaft and the first stage gear meshing with this gear is made shallow, the load torque is 100 (g- This is because the torque fluctuates greatly such that the torque is deep (cm) and 300 (g-cm). Further, the meshing of the other reduction gears is a variable factor although the influence of the meshing of the reduction gears decreases as the distance from the first stage increases. In addition, there is a problem that the load torque may vary greatly depending on the roundness (eccentricity) of the mechanical parts, the accuracy of the distance between the shafts, the assembly accuracy such as the parallelism in mechanical assembly, the tension of the timing belt and the wire, etc. Because.

Conventionally, as a method of measuring the magnitude of the torque generated in such a stepping motor (the magnitude of the torque required by the load for the motor), the shape of the motor is the same as that of the actually used motor, and a coil, a magnet or the like is used. There is a method in which a dummy motor that does not exist is attached to the system to be measured (mechanical part), a torque gauge is connected to the motor output shaft provided on the motor pinion via a collet chuck, etc., and the motor is rotated manually for measurement. is there. In addition, a motor with the same specifications as the stepping motor that is actually used has a specially manufactured motor that has a torque measurement axis on the side opposite to the output shaft, and is mounted on the mechanism to measure the torque of the collet chuck of the torque gauge. There is also a method of measuring by connecting to an axis. Furthermore, attach a pulley to the motor output shaft, pull the thread wound around the pulley to pull the pulley radius r (cm), and the spring force F.
There is a method of obtaining the load torque T (g-cm) from (g) as T = F × r. There is also a method of using a torque meter that utilizes the current / torque characteristics of a DC motor, or inserting a torque gauge between the motor and the load.

[0004]

As described above, various methods have been conventionally used to measure the torque of the motor, but it is difficult to measure the accuracy with satisfactory results. That is, it is difficult to give an arbitrary rotation speed to the load by the method using the dummy motor or the method using the pulley and the spring back, and in the former method, the load torque caused by the side load due to the inclination of the torque gauge is affected. The increase is unavoidable, and the latter method also makes it difficult to attach the pulleys stably, and the side load effect is also unavoidable. Also, in the method that uses a motor with the same specifications as the stepping motor that is actually used, since the rotor of the motor has a magnet, the holding torque (detent torque) of the magnet must be included in the measurement. Rotation generates electricity in the stator coil, and this generated current causes dynamic braking (brake torque), and the inclination of the torque gauge becomes the side load of the motor bearing, which increases the load torque from the actual value, so accurate measurement is possible. Is impossible. Further, in the method of utilizing the current / torque characteristics of the DC motor, it is necessary to remove the motor each time measurement is performed. In addition, since the load torque changes subtly due to the engagement of the pinion and gear when installing the motor, it is necessary to know how much torque the motor actually generates in the assembled actual machine. I can't.

As described above, with the conventional load torque measuring method, it is impossible to measure the torque generated from the motor with high accuracy in a state where the motor and the load are assembled. In other words, we want to know what the load torque is due to variations in the meshing of the first-stage gear with the motor pinion of each motor used in mass production and the tension of the motor timing pulley and timing belt. There was no choice but to analogize the torque. Therefore, it is not possible to know the difference between the maximum torque generated by the motor and the load torque, and the torque margin.In mass production, voltage fluctuation test, temperature test, aging test, printing test, etc. The reality is that the product is shipped after checking the reliability. For example, when the mechanical part does not move, whether the cause is the designer's torque margin is insufficient, the assembly adjustment is defective at the manufacturing site, etc. I had to spend a lot of time investigating the defective parts.

Therefore, an object of the present invention is to measure a load torque for a stepping motor capable of measuring a load torque in a state where the stepping motor itself is mounted on an actual machine mechanism part in which a stepping motor and a load are coupled to each other. To provide a device.

[0007]

In order to solve the above-mentioned problems, a load torque measuring device for a stepping motor according to the present invention changes the frequency of a drive signal supplied to a stepping motor to be measured of a predetermined standard from a low frequency to a high frequency. A reference characteristic indicating the relationship between the drive frequency and the pull-out torque for a stepping motor that is substantially the same as the predetermined standard, based on the step-out frequency when the stepping motor is driven while changing the frequency. With reference to, the measured stepping motor load torque is configured to be measured.

[0008]

According to the present invention, the frequency vs. pullout torque characteristic of the stepping motor is obtained by measuring in advance, and the stepping motor is driven from a low frequency to a high frequency during actual measurement, and the frequency at the time of out-of-step and the frequency vs. pullout torque. The actual load torque can be measured based on the characteristics.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings. FIG. 1 is a configuration block diagram showing an embodiment of a load torque measuring device for a stepping motor according to the present invention. Normally, when the load torque applied to the motor shaft is gradually increased while the stepping motor is rotating at a certain frequency, the motor cannot rotate at a certain load torque value, resulting in loss of synchronization. This phenomenon is called "step-out", and the limit maximum torque generated just before step-out is called pull-out torque. The present invention measures the load torque by utilizing the fact that the load torque of the stepping motor is stepped out when it coincides with the pullout of the rotating motor. It has been confirmed that the frequency-dependent drooping-out torque characteristic has a variation of about ± 10% for the PM type stepping motor and about ± 5% for the HB type stepping motor.
On the other hand, the load torque has a much larger variation of ± 100% due to the variation in how the stepping motor is assembled and the mechanism adjustment. By utilizing this, it becomes possible to utilize the frequency-to-pullout torque characteristic.

FIG. 2 shows an example of frequency versus pullout torque characteristics of the stepping motor. F on the horizontal axis
Represents the frequency (PPS) of the drive signal to the motor, and T on the vertical axis represents torque (g-cm). T0 is the pull-out curve, and the pull-out torque value corresponding point P1 at frequency 100 (PPS), frequency 200 (PPS), 300 (PP
S), 400 (PPS), 500 (PPS) and 600
Pull-out torque corresponding points P2, P in (PPS)
3, P4, P5 and P6, and further, the maximum continuous response frequency f _0max under no load: 700 (PPS) corresponding point P
After 7 is obtained by measurement, these points are connected by interpolation processing. Further, Ti is a pull-in torque curve showing the maximum torque that can be used when starting and stopping the motor, and the maximum no-load self-starting frequency f _imax is 300.
(PPS). From this curve, it can be seen that the motor cannot be started or stopped unless it is at or below the maximum self-starting frequency f _imax .

In FIG. 1, in order to facilitate understanding, the mechanical connection between the stepping motor, the reference load torque generator and the actual machine mechanism will be explained by taking a switch as an example. The changeover switch 9 switches the measurement function. The stepping motor 1 is connected to the terminal S1 side to obtain the frequency-to-pullout torque characteristic, and then the changeover switch 9 is connected to the S2 side to measure the load torque of the actual machine. First, the changeover switch 9 is connected to the S1 side, and the stepping motor 1 is connected to the reference load torque generator 7 via the coupling 8. As the reference load torque generator 7, a torque meter manufactured by Vibrac, Inc. in the United States can be used, which enables measurement with an accuracy of ± 0.5% of the full scale of load torque. The motor driver 4 receives the slow-up / down control signal from the stepping motor controller 5, and supplies a drive signal to the stepping motor 1 to cause the stepping motor 1 to perform the mode control. The frequency of the drive signal is changed stepwise by the control signal from the stepping motor controller 5. The stepping motor 1 is connected to a step-out detection unit 6 for detecting a step-out, and receives the load torque from the reference load torque generator 7 and the frequency data of the drive signal (frequency monitor signal from the stepping motor controller 5). Utilizing this, pull-out torque points P1 to P7 at each frequency as shown in FIG. 2 are measured. These data are input to the pull-out torque curve processing storage unit 10A, the reference pull-out torque curve is obtained by performing an appropriate interpolation process between the pull-out torque points, and is stored. The reference pullout torque curve may be individually measured, manually created, and stored instead of being automated as described above.

The load torque of the motor output shaft of the stepping motor mounted on the mechanism of the actual machine is measured as follows. The stepping motor 1 has the same specifications as the stepping motor used to obtain the pullout torque curve described above. The motor driving conditions are also the same as those used when measuring the reference pullout torque. The changeover switch 9 is connected to the terminal S2 side, and the stepping motor 1 is coupled to the actual machine mechanism section 2 via the coupling 3. When the frequency is slowed up by the control signal from the stepping motor controller 5 and the motor driver 4 drives the stepping motor 1 to gradually increase its rotation speed, the stepping motor is stepped out at a certain frequency. This step out
It is detected by the step-out detection unit 6. Here, if the stepping motor loses step at the point Pm on the reference pullout torque curve shown in FIG. 2, the step-out detection signal from the step-out detection unit 6 is sent to the load torque measurement processing unit 10B. The slow-up frequency fm (PPS) at this time is latched. The load torque measurement processing unit 10B, based on the step-out detection signal (latched frequency) and the reference pullout torque curve data from the pullout torque curve processing storage unit 10A, the pullout torque Tm (g at the frequency fm (PPS). Cm) as the load torque TL to the output device 11 such as a display or a printer.

For example, a motor having a pull-out torque curve characteristic as shown in FIG. 2 is mounted in the paper feed drive section of the printer, and 100 (PP) with a margin for starting is provided.
In S), the rotation is started and slow-up control is performed so that the frequency is gradually increased. At this time, if it becomes impossible to rotate at 550 (PPD) and loses step, it becomes 550 (PPS).
The pullout torque in Fig. 2 is 350 (g-c
Therefore, the load torque can be determined to be 350 (g-cm).

The out-of-step detection in the out-of-step detection unit 6 in FIG.
(1) Method of visually confirming the rotation state of the motor output shaft,
(2) A reflection type rotation detection method in which a mark having a reflecting material is attached to the motor output shaft, and a rotation state is detected by reflection from this mark, (3) a rotation detection method in which a back electromotive force generated in a motor coil is monitored, 4) This can be performed by using a motor coil current detection method or the like that detects that the level of the current flowing through the motor coil suddenly increases during step-out. By the way, the load of the stepping motor has a load inertia in addition to the load torque. Acceleration torque is required to accelerate the load inertia. This acceleration torque is generated as a measurement error amount according to the present invention. The acceleration torque Ta is generally represented by the following equation. Ta = [(J _R + J _L ) · 2π · (f2 −f1)] / n
Here _{θ · t ACC (g-cm} ), J R: rotor inertia of the motor (g over cm-S ²⁾ J _L: load inertia (g over cm over S ²⁾ (f2 -f1): low frequency f1 ( Frequency change from PPS) to high frequency f2 (PPS), nθ: number of one rotation step of stepping motor (step
s / rev), t _ACC : Time (sec) required for (f2-f1). For example, when the general size is Φ55 × L25 and the step angle is 7.5 ° / step, the rotor inertia J _R is J _R = 40 × 10 ^-3 (g-cm-s ² ), (f2-f1) Is 100 (PPS) and t _ACC is 1 (se
c), nθ is 48, load inertia J _L is the same as J _R 40
If x10 ^-3 (g-cm-s2), the acceleration torque Ta
Is Ta = (80 × 10 ⁻³ × 2π × 100) / 48 × 1, that is, Ta is approximately 1.0 (g-cm),
If a slow-up with 100 (PPS) change per second is performed, the acceleration torque error is 1.0 (g-cm) and 0.3 (%) with respect to the load torque of 350 (g-cm). Can be ignored. Further, the pullout torque curve of the stepping motor changes somewhat due to the temperature rise of the motor, but there is no problem if the measurement according to the present invention is carried out in a short time such as within 2 minutes. The time required for the temperature rise of the stepping motor to be saturated is about 1 hour. Further, by storing change data of the motor temperature rise and the pullout torque curve, it becomes possible to accurately measure the load torque in consideration of the temperature rise. It is also possible to make the motor temperature rise and the change of the torque curve data processing by a computer, and perform automatic torque curve correction while measuring the motor temperature.

FIG. 3 shows an example of measuring the load torque of a stepping motor attached to the transmission section of a facsimile as a specific application example of the present invention. A motor pinion gear 34 is attached to the output shaft of the stepping motor 33. After that, the gears 35, 36 and 37 decelerate and the gear 38 accelerates to rotate the transmission platen roller 32. The platen roller 32 is under pressure F so as to be pressed against the contact image sensor 31. A document (not shown) is inserted between the platen roller 32 and the image sensor 31, and the document is read by the image sensor 31 and transmitted as image data. The load torque of the stepping motor 33 depends on the precision of the gears at each stage and the meshing state, the parallelism of all the shaft columns from the motor shaft, and the platen roller 32.
Roundness, the pressure F with the contact image sensor 31, the friction coefficient between the platen roller 32 and the contact image sensor 31 when there is no paper, the original paper and the contact image sensor 31.
The factor is the coefficient of friction with. In particular, the meshing state of the motor pinion gear 34 and the first-stage gear 35 greatly affects the load torque.

As shown in FIG. 3, the frequency vs. pullout torque characteristic of the mounted motor is shown in FIG. When the mounted motor was started at 50 (PPS) and the frequency was slowed up, step out at 500 (PPS). Therefore, referring to FIG. 4, frequency 500 (PPS)
It can be seen that the load torque is 135 (g-cm) because the pull-out torque in (1) is 135 (g-cm).

The measurement of the load torque by the rotation limit method of the stepping motor in the present invention described above is performed through the following procedure. First, specify the drive system (excitation circuit configuration, drive voltage, excitation mode) of the stepping motor,
Accurately define the "frequency vs. pullout torque curve" of the target motor with a measuring machine. Next, about 10 points of pull-out torque for the frequency including the highest continuous response frequency are input to this "frequency vs. pull-out torque curve", and these 10 points are interpolated to generate a continuous curve. Enter the lower limit NG with the cursor. Next, the motor with pinion is set in the mechanism. When the measurement starts, the frequency cursor is moved, the step-out is detected by the above-mentioned method, the step-out frequency is held, and the intersection of the step-out frequency and the torque curve is processed as the load torque. Print out GO / NG and possibly load torque values. Here, it should be noted that the "f-To characteristic" changes due to the temperature rise (for example, within 2 minutes), so that the measurement should be performed in a short time. Further, the frequency slow-up is set to Δf / Δt where the acceleration torque can be ignored. The stepping motor used to define the “frequency vs. pullout torque curve” and the stepping motor set in the measured mechanism can be used separately. Therefore, once the “frequency vs. pullout torque curve” is defined for the same type of motor, thereafter, by directly measuring the step-out frequency of the motor with respect to a large number of measurement targets, the mechanical unit connected to the motor is measured. It is possible to measure the load torque of the.

Next, a method for measuring the load torque applied to the output shaft of the stepping motor by changing the pullout torque curve by changing the drive voltage of the motor will be described. Figure 5 shows size Φ4
2 x L22, step angle 7.5 ° / STEP, coil resistance 7
0 (Ω / phase) PM type stepping motor with a rated voltage of 12V is unipolar driven and 12V, 24 with 2-2 phase excitation.
It is a change graph of a pullout torque curve when V and 36V and a motor drive voltage are changed. FIG. 6 is an arrangement of FIG. 5, showing the input P (W / phase) when the motor is stationary.
Is a drive voltage V (v) and a coil resistance R (Ω / phase), and P = V ² / R is calculated. In the present invention, similarly to the above-mentioned invention, the curve of FIG. 6 is stored and stored in the processing storage unit, and interpolation processing is performed for an intermediate frequency 150 (PPS) of 100 to 200 (PPS). Now, attach the measured stepping motor to the actual machine mechanism part, and
00 (PPS), 2-2 phase excitation, 36 (v) drives the motor, and when the motor is driving and rotating the load, the voltage is gradually decreased to P = 4 (W / phase). If the motor goes out of step with a drive voltage of 16.7 (v) corresponding to
Since the pullout torque at 200 (PPS) at 4 (W / phase) is 300 (g-cm), it can be seen that the load torque is 300 (g-cm). In the above invention, the motor load torque is measured using the drive frequency as a factor, but in the present invention, the motor shaft load torque is measured using the motor drive voltage as a factor. The configuration of the step-out detection unit, the reference load torque generator, the load torque measurement processing unit, etc.
The same as the above invention.

Next, the third invention for obtaining the load torque from the self-starting frequency under load will be described. The results of various experiments,
Load self-starting frequency fs (PPS), fs (PPS)
The pull-out torque T0 (g over cm), a rotor inertia of the stepping motor J _R (g over cm over s ²⁾ in,
If the load inertia is J _L (g-cm-s ² ), the number of rotation steps of the motor is nθ (REV / STEPS), and the constant in unipolar drive 2-two phase excitation is β, the load torque TL
It was found that (g-cm) is as shown in the following formula. TL = the To - in _{[(J R + J L)} × 2π × fs 2] / (nθ × β) (1 type) The results of the experiment, beta was found to be good to put a 2.3. The method of acquiring the pullout torque curve is as described above. In the case of the motor drive voltage fixed type, the self-starting frequency is gradually increased to obtain the step out frequency fs (P
The load torque can be measured by automatically calculating using (Formula 1) from PS). In the variable motor drive voltage type described in the second aspect of the invention, the self-starting frequency under load is fixed, the motor drive voltage is gradually reduced to reduce the pullout torque, and the step out frequency fs (PPS) is reduced. From (1), the load torque can be measured automatically.

[0020]

As described above, the load torque measuring device for a stepping motor according to the present invention is obtained by previously measuring the frequency-pullout torque characteristic of the stepping motor, and drives the motor from low frequency to high frequency during actual measurement. ,
The actual load torque can be measured based on the frequency when the step-out occurs and the frequency-pullout torque characteristic. As a result, at each stage from the development stage of the stepping motor application device to the mass production, it is possible to objectively grasp the characteristics of the load mechanism section of the motor and the quality of the coupling state between the load mechanism section and the motor. .

[Brief description of drawings]

FIG. 1 is a configuration block diagram showing an embodiment of a load torque measuring device for a stepping motor according to the present invention.

FIG. 2 is a diagram showing frequency-pullout torque characteristics for explaining the measurement principle of the load torque measuring device for a stepping motor according to the present invention.

FIG. 3 is a configuration diagram of a stepping motor attached to a facsimile transmission unit as a specific application example of the present invention.

4 is a frequency vs. pullout torque characteristic diagram obtained for the example of FIG. 3. FIG.

FIG. 5 is a diagram showing changes in the pullout torque curve when the motor drive voltage is changed to explain another embodiment of the load torque measuring device for a stepping motor according to the present invention.

FIG. 6 is a diagram showing an arrangement of FIG. 5 and showing a relationship between input and torque with a frequency as a parameter.

[Explanation of symbols]

1 Stepping motor 2 Actual machine mechanism section 3, 8 Coupling 4 Motor driver 5 Stepping controller 6 Step-out detection section 7 Reference load torque generator 9 Changeover switch 10A Pullout torque curve processing storage section 10B Load torque measurement processing section 11 Output device 31 Close contact Image sensor 32 Platen roller for transmission 33 Stepping motor 34 Motor pinion gear 35-38 Gear 39 Shaft column

Claims (2)

[Claims] 1. A step-out frequency when a step-out of the stepping motor is detected by driving by changing the frequency of a drive signal supplied to a stepping motor to be measured of a predetermined standard from a low frequency to a high frequency. On the basis of the stepping motor load torque measurement, the stepping motor load torque is measured with reference to a reference characteristic indicating the relationship between the drive frequency and the pullout torque for the stepping motor substantially the same as the predetermined standard. apparatus. 2. A memory that stores a reference characteristic indicating a relationship between a drive frequency and a pullout torque for a stepping motor of a predetermined standard, and a drive applied to a stepping motor to be measured that is substantially the same as the predetermined standard. Frequency control means for sequentially increasing the frequency of the signal from a low frequency to a high frequency, step-out detection means for detecting step-out of the measured stepping motor, and the frequency based on the frequency of the drive signal at the time of step-out detection A load torque measuring device for a stepping motor, comprising: load torque output means for outputting a load torque by referring to the reference characteristic stored in a memory.