WO2016140032A1

WO2016140032A1 - Method for determining conditions of motor driving mechanism

Info

Publication number: WO2016140032A1
Application number: PCT/JP2016/054041
Authority: WO
Inventors: 宮嵜克則
Original assignee: 株式会社ブレイド
Priority date: 2015-03-02
Filing date: 2016-02-11
Publication date: 2016-09-09

Abstract

[Problem] To immediately determine, online, how satisfactory are the processing conditions of a motor-driven mechanism such as a motor-driven spin riveting mechanism for performing spin riveting, and remove faulty components in advance. [Solution] The following process is performed using a computer 9. The drive current waveform of an AC drive motor is detected, and for every predetermined cycle of the detected drive current waveform, an equivalent sine waveform having an area identical to the waveform area in the cycle is obtained. The waveform of a difference between the equivalent sine waveform and the driving current waveform for each of the predetermined cycles is calculated. A change in the centroid position of the waveform of the difference for each of the predetermined cycles is detected. How satisfactory the processing conditions are is determined on the basis of the change in the centroid position.

Description

Motor drive mechanism status determination method

The present invention relates to a state determination method for a motor drive mechanism, and more particularly to a state determination method that can be suitably used for determining the machining state of a motor drive spin caulking mechanism.

FIG. 16 shows an example of the caulking portion of the component. The caulking pin 6 is passed through the

resin plates

11 and 12 stacked one above the other, and both ends of the caulking pin 6 are expanded and collapsed into an arc cross-sectional shape via the

metal washers

13 and 14. Thus, both

resin plates

11 and 12 are coupled. An example of a motor-driven spin caulking mechanism that performs such caulking is shown in FIG. In FIG. 17, the spin caulking mechanism has a main shaft 1 in a vertical posture, and the main shaft 1 is rotationally driven with a base end (upper end) connected to a drive motor 2.

The main shaft 1 has a sleeve portion 3 for holding the main shaft 1 coupled to a hydraulic device 4, and a constant pressing pressure is applied to the main shaft 1 during caulking. On the tip (lower end) surface of the main shaft 1, a processing pin 5 protrudes obliquely inward and downward around the rotation axis Ax of the main shaft 1, and the outer peripheral portion of the tip is pre-shaped into a flat cylindrical shape in advance. The crimping pin 6 is in pressure contact with the upper surface of one end 61 (FIG. 18). In this way, by rotating the machining pin 5 around the rotation axis Ax of the main shaft 1 while pressing the tip of the machining pin 5 against one end of the caulking pin 6, one end of the caulking pin 6 is expanded and collapsed into the arc cross-sectional shape as described above. To do.

In Patent Document 1, in the internal thread tapping process, the fluctuation of the driving current of the motor is set as the actual machining load curve in synchronization with the progress of the internal thread tapping process, and the actual machining load curve, the standard load curve, the upper limit load curve, the lower limit load An abnormality monitoring method for determining deterioration of a tap by comparing with each load curve is disclosed.

JP 2002-239838 A

Conventionally, in spin caulking, processing is performed by empirically setting the pressing force and pressing speed of the processing pin 5, the lower limit of lowering at the time of pressing, and the like. Machining conditions change due to variations in positioning. For this reason, defects such as bending (FIG. 19 (1)) and bending (FIG. 19 (2)) or cracking at the end of the processing pin 6 (FIG. 19 (3)) occur in the mass production process. was there. However, these defects are often difficult to find by visual inspection after processing because they are invisible or fine, and often cause defects after the parts are assembled.

Therefore, the present invention solves such a problem, and it is possible to immediately determine whether the output side mechanical condition of a motor drive mechanism such as a motor drive spin caulking mechanism that performs spin caulking processing is good or bad on-line, and to detect defective parts. It is an object of the present invention to provide a method for determining the state of a motor drive mechanism that can eliminate the above in advance.

In order to solve the above-described problem, in the motor drive mechanism status determination method according to the first aspect of the present invention, a step of detecting a drive current waveform of an AC drive motor and a predetermined cycle of the detected drive current waveform are included in the cycle. Obtaining an equivalent sine waveform having an area equal to that of the waveform area, calculating a waveform of a difference between each absolute value of the drive current waveform and the equivalent sine waveform for each predetermined cycle, and the step for each predetermined cycle Determining the mechanical condition on the output side of the AC drive motor from the transition of the difference waveform.

According to the first aspect of the present invention, the mechanical condition on the output side of the AC drive motor can be determined from the transition of the difference between the drive current waveform and the equivalent sine waveform for each predetermined cycle. It is possible to immediately determine online and eliminate defective parts in advance.

In the motor drive mechanism status determination method of the second aspect of the invention, the transition of the difference waveform is detected by a change in the centroid position of the difference waveform.

In the situation determination method of the motor drive mechanism according to the third aspect of the present invention, the transition of the difference waveform is obtained by multiplying the amplitude value at each time of the equivalent sine wave by the positive amplitude value of the difference waveform at the time. As the amplitude moment value, the amplitude moment value is detected by a change in the amplitude moment integrated value obtained by integrating the amplitude moment value within a range in which the amplitude value of the waveform of the difference is positive within the predetermined cycle.

In the motor drive mechanism status determination method of the fourth aspect of the invention, the difference waveform transition is a unit obtained by dividing the amplitude moment integrated value by the total area value of the difference waveform in the range in which the amplitude value is positive. Detection is based on the relative behavior of the amplitude moment integrated value with respect to the amplitude moment integrated value.

In the motor drive mechanism status determination method according to the fifth aspect of the invention, the relative behavior is an average of the difference of the amplitude moment integrated value with respect to the unit amplitude moment integrated value. Here, “average” includes, in addition to the average value, the height from the zero point of a straight line obtained by linearly approximating the time-varying portion of the difference of the integrated amplitude moment value with respect to the unit amplitude moment integrated value.

In the sixth aspect of the present invention, the relative behavior is the degree of inclination of a straight line obtained by linearly approximating a time-change portion of the difference between the integrated amplitude moment value and the integrated amplitude moment value.

In the seventh aspect of the invention, the transition of the difference waveform is detected by at least the depression angle of the positive apex at which the amplitude moment integrated value changes.

In the motor drive mechanism status determination method according to the eighth aspect of the invention, the mechanical status is a quality of machining using a machining tool driven by the AC drive motor.

In the motor drive mechanism status determination device of the ninth aspect of the invention, the means for detecting the drive current waveform of the AC drive motor has an area equal to the waveform area in the cycle for each predetermined cycle of the detected drive current waveform. Means for obtaining an equivalent sine waveform; means for calculating a waveform of a difference between the absolute values of the drive current waveform and the equivalent sine waveform for each predetermined cycle; and the alternating current from a transition of the waveform of the difference for each predetermined cycle. Means for determining a mechanical condition on the output side of the drive motor.

As described above, according to the method for determining the state of the motor drive mechanism of the present invention, it is immediately determined online whether the mechanical state on the output side of the motor drive mechanism such as the motor drive spin caulking mechanism that performs spin caulking is good or not. Thus, defective parts can be eliminated in advance.

It is a schematic block diagram of the motor drive mechanism which implements the method of this invention in 1st Embodiment of this invention. It is a figure which shows the time-dependent change of the waveform of a motor drive current. FIG. 3 is an enlarged view of a part A and a part B in FIG. 2. It is a figure which shows the time-dependent change of the drive current waveform of a half cycle, the waveform of an equivalent sine wave, and the waveform of a difference. It is a figure which shows the time-dependent change of the centroid of the difference waveform for every half cycle over a free running area | region, a tool contact area | region, and a crimping process area | region. It is a scatter diagram of centroids. It is a determination figure which shows the change range of the x-axis direction of a centroid, and a y-axis direction. It is a figure which shows the time-dependent change of the centroid of the difference waveform for every half cycle over a free running area | region, a tool contact area | region, and a crimping process area | region. It is a scatter diagram of centroids. It is a determination figure which shows the change range of the x-axis direction of a centroid, and a y-axis direction. It is a figure which shows the time-dependent change of the drive current waveform of a half cycle, the waveform of an equivalent sine wave, and the waveform of a difference in 2nd Embodiment of this invention. It is a figure which shows the change of unit amplitude moment integrated value AMis and amplitude moment integrated value AMi for every half cycle when processing is performed favorably. It is a figure which shows the change of unit amplitude moment integrated value AMis and amplitude moment integrated value AMi for every half cycle when a process is not performed favorably. It is a figure which shows the other example of the change of unit amplitude moment integrated value AMis and amplitude moment integrated value AMi for every half cycle when a process is not performed favorably. It is a figure which shows the enlarged waveform of the top part which fluctuates in saw shape of amplitude moment integrated value AMi for every half cycle. It is sectional drawing of a component crimping part. It is a schematic block diagram of the conventional motor drive mechanism. It is a partial cross section enlarged side view of a processing pin press-contact part. It is an enlarged side view of a caulking pin.

(First embodiment)
FIG. 1 shows an apparatus configuration for carrying out the method of the present invention. In FIG. 1, the spin caulking mechanism to which the method of the present invention is applied has the same structure as the conventional one already described. That is, the spin caulking mechanism includes a main shaft 1 in a vertical posture, and the main shaft 1 is rotationally driven with a base end (upper end) connected to a three-phase AC drive motor 2. The main shaft 1 is connected to a hydraulic device 4 with a sleeve 3 that rotatably holds the main shaft 1, and a constant pressing pressure is applied to the main shaft 1 during caulking. On the tip (lower end) surface of the main shaft 1, a processing pin 5 protrudes obliquely inward and downward around the rotation axis Ax of the main shaft 1, and the outer peripheral portion of the tip is pre-shaped into a flat cylindrical shape in advance. The crimping pin 6 is in pressure contact with the upper surface of one end 61.

And in this embodiment, the clamp meter 7 is installed in one phase of the three-phase power line of the drive motor 2 of such a spin caulking mechanism, and the drive current of the drive motor 2 is detected. The detected drive current is input to the computer 9 via the A / D conversion circuit 8.

FIG. 2 shows an example of the detected drive current Id. In FIG. 2, an X area indicates an idle running area where the machining pin 5 has not yet contacted the caulking pin 6, a Y area indicates a tool contact area where the machining pin 5 starts to contact the caulking pin 6, and a Z area indicates pressure contact. The crimping process area | region where one end of the crimping pin 6 is diameter-expanded by the processed pin 5 is shown, respectively.

Also in the idling region X, as shown in FIG. 3 (1), which is an enlargement of the portion A in FIG. Is observed. The waveform distortion of the drive current Id is as shown in FIG. 3 (2), which is an enlargement of the portion B in FIG. 2, due to the fact that the machining resistance gradually increases in the process of shifting from the tool contact area Y to the crimping area Z. It gradually increases and the peak value (size) of the current Id also increases.

In the present embodiment, the waveform distortion of the drive current Id of the drive motor 2 is separated into a time axis (x axis) direction indicating the degree of caulking processing and a current axis (y axis) direction indicating the caulking processing force. Think about it. For this purpose, as shown in FIG. 4, the difference between the waveform of the half cycle drive current Id and the waveform of the equivalent sine wave Se is calculated. Here, the equivalent sine wave Se is a sine wave having the same pitch and the same area as the waveform of the drive current Id. Note that the half cycle is determined in consideration of the number of detected samples of the drive current Id and the processing speed of the computer 9, and in this embodiment, about 500 data pieces sufficient for analysis are obtained for each half cycle waveform. The following processing is performed within the computer 9 by sampling within seconds.

4 is a difference waveform (hereinafter referred to as a difference waveform) Dw obtained by subtracting the waveform (absolute value) of the equivalent sine wave Se from the waveform (absolute value) of the drive current Id in a half cycle. . The difference waveform Dw changes in magnitude and positive / negative depending on the waveform distortion of the drive current Id. Therefore, in the computer 9, the centroids fcp and fcm are calculated for the positive difference waveforms Dw1 and Dw2 and the negative difference waveforms Dw3 and Dw4. The x-coordinates of the centroids fcp and fcm are positive when they are located on the left side of FIG. 4 from the center line lc of the equivalent sine wave Se. Further, the y-coordinates of the centroids fcp and fcm are located on the upper side of FIG. 4 with respect to the line in which the waveform of the drive current Id matches the waveform of the equivalent sine wave Se and the difference waveform Dw is zero. The case is positive. In this figure, for easy understanding, the amplitude of the difference waveform Dw is drawn larger than the actual size.

In the present embodiment, the calculation of the centroids fcp and fcm of the difference waveform Dw for each half cycle described above is performed using the drive current Id obtained in all the regions of the idle region X, the tool contact region Y, and the crimping region Z. Perform on the waveform. An example is shown in FIG. As apparent from FIG. 5, not only in the crimping region (Z region) but also in the idle region (X region), the x-coordinate and y-coordinate of the centroid change with time due to the waveform distortion of the drive current Id. .

Therefore, in the computer 9, a scatter plot of centroids fcp and fcm as shown in FIG. 6 is drawn. The scatter diagram is a plot of centroids fcp and fcm for each half cycle in the free-running region X and the crimping region Z with the horizontal axis as the x-axis and the vertical axis as the y-axis. The centroids in the free running region are fcp0 and fcm0. 6 (1) to 6 (4) are scatter plots in which the crimping region Z is divided into four in the time axis direction and the positions of the centroids fcp and fcm are plotted in each of the divided regions Z1 to Z4.

Next, in the computer 9, a new origin On is set in the scatter diagram in order to determine whether the caulking process is good or bad. This origin On is, for example, the average value of the x and y coordinates of the centroids fcp0 and fcm0 in the free running region X. Then, the values of the x-coordinate and y-coordinate of the centroids fcp and fcm obtained in the respective divided areas Z1 to Z4 of the caulking process are converted into those for the new origin On.

Subsequently, in the computer 9, a determination diagram for determining whether the caulking process is good or bad is created as shown in FIG. Here, FIG. 7A is a determination diagram showing a change range in the x-axis direction of the centroids fcp and fcm in each of the divided regions Z1 to Z4 (change range of the x coordinate with respect to the new origin On). FIG. 7B is a determination diagram showing a change range in the y-axis direction of the centroids fcp and fcm in each of the divided regions Z1 to Z4 (change range of the y coordinate with respect to the new origin On). In FIG. 7, the centroid fcm of the negative difference waveform Dw is inverted between positive and negative for easy comparison.

In the example shown in FIG. 7, the centroids fcp and fcm are sufficiently separated from the zero axis in both the x-axis direction and the y-axis direction. This indicates that the caulking processing degree and processing force are sufficient, and in such a case, no defect occurs in the caulking pin 6 that is spin caulked.

On the other hand, when there is a time change of the centroids fcp and fcm as shown in FIG. 8 in the idle running region X, the tool contact region Y, and the crimping region Z, the crimping region Z is divided into four in the time axis direction. A scatter diagram of the change in the centroid position of each of the divided regions Z1 to Z4 is as shown in FIG. In this case, the determination diagram for determining whether or not the caulking process is good is as shown in FIG.

In the example shown in FIG. 10, the centroids fcp and fcm are sufficiently separated from the zero axis in the y-axis direction (FIG. 10 (2)) in each of the divided regions Z1 to Z4, but the x-axis direction (FIG. 10 (1) ) Shows that the change range of the centroid fcp is in the vicinity of the zero axis in the divided areas Z1 and Z2, indicating that the degree of caulking is not sufficient. Therefore, in this case, there is a possibility that a defect is generated in the caulking pin 6 to be spin caulked.

As described above, according to this embodiment, by confirming the range of change in the x-axis direction and the y-axis direction of the centroid position of the difference waveform between the drive current waveform of the drive motor and the equivalent sine waveform, the quality of spin caulking is determined. Can be determined immediately online, and defective parts can be reliably eliminated.

(Second Embodiment)
In the present embodiment, the computer 9 (see FIG. 1) determines whether or not the spin caulking process is good or not based on the change of the amplitude moment value described below, instead of the change of the centroid position of the first embodiment.

FIG. 11 shows a half-cycle waveform of the drive current Id of the drive motor 2 (see FIG. 1), similar to FIG. 4 described in the first embodiment. In the present embodiment, for the waveform Dw of the difference obtained by subtracting the waveform (absolute value) of the equivalent sine wave Se from the waveform of the drive current Id (absolute value), the amplitude value Dw (n) of the waveform Dw at each sample time tn is Let Dw (n) · Se (n) multiplied by the amplitude value Se (n) of the equivalent sine wave Se at the sample time tn be the amplitude moment value at each sample time tn.

Then, the amplitude moment values Dw (n) · Se (n) are integrated in the time ranges T1 and T2 in which the amplitude value of the difference waveform Dw is positive in the half cycle, and the integrated value is amplitude in the half cycle. The moment integrated value AMi is used. Subsequently, the unit amplitude amplitude integrated value AMis (= Dw (n) · Se () is obtained by dividing the amplitude moment integrated value AMi by the total area St of the difference waveforms Dw1 and Dw2 whose amplitude value is positive in the half cycle. n) / St). Here, the reason why the amplitude moment value Dw (n) · Se (n) is calculated is that the portion having a larger current value is considered to have a larger influence on the machining. The reason for integrating only in the time ranges T1 and T2 is that the portion where the drive current waveform is larger than the equivalent sine wave is considered to contribute more to machining.

FIG. 12 shows an example of changes in unit amplitude moment integrated value AMis and amplitude moment integrated value AMi for each half cycle obtained in this way. Note that the circles attached to the unit amplitude moment integrated value AMis and the amplitude moment integrated value AMi in FIG. 12 indicate the midpoints of the up and down fluctuations, and are attached to indicate the standard of the change. According to FIG. 12, the unit amplitude moment integrated value AMis maintains a substantially constant value. Therefore, a graph AMg in which the amplitude moment integrated value AMi is drawn in a bar graph shape for each half cycle with reference to the unit amplitude moment integrated value AMis is shown in the lower half of FIG.

The average value AMgv of the graph AMgv is calculated, and then the approximate straight line Lx of the changing part of the graph AMg is drawn by the least square method or the like. Then, the first determination is performed as follows based on the degree of change (inclination) of the approximate straight line Lx. Note that the height from the zero point of the approximate straight line Lx may be used instead of the average value.

The above average value AMgv is positive and large, and the closer the approximate straight line Lx is to the horizontal, the better the processing is performed. In this respect, in the state shown in FIG. 2, since the average value AMgv is positive and large, and the inclination of the approximate straight line Lx is almost horizontal, the processing level is high and the processing is performed well.

On the other hand, as shown in FIG. 13, when the graph AMg is inverted from the positive side to the negative side in the middle, the average value AMgv becomes positive and small or negative, and the slope of the approximate straight line Lx is horizontal. Inclined far away from. This indicates that the machining is not performed well, and there is a possibility that a defect is caused in a component to be subjected to spin caulking due to the cross section of the machining portion being deformed to a drum shape.

Furthermore, as shown in FIG. 14, when the graph AMg is consistently negative, the average value AMgv is negative. Therefore, even if the inclination of the approximate straight line Lx is almost horizontal, it indicates that the processing is not performed well.

In the present embodiment, the following second determination is further performed in addition to the first determination. That is, the depression angle θ of the positive apex is detected for the enlarged waveform (FIG. 15) of the apex portion that fluctuates in a saw-like manner in the integrated amplitude moment value AMi for each half cycle. In FIG. 15, points a and b indicate vertices with a large depression angle θ, and points c and d indicate vertices with a small depression angle θ. The depression angle θ calculates, for example, the number of vertices in the uppermost angle area in three stages and the number of vertices in the intermediate angle area. Then, as shown in the following formula (1), the ratio Rmx of the number of vertices in the highest angle region with respect to the total number Na of vertices and the number of vertices in the intermediate angle region with respect to the total number Na of vertices The ratio Rmm multiplied by ½ is added to obtain the R value. This R value is an index indicating the stability of processing. Therefore, when the R value is large, it is determined that the processing has been performed stably, and when the R value is small, it is determined that the processing has not been performed stably. If the processing is not stable, there is a possibility that a problem is caused in a component to be subjected to spin caulking. Note that the depression angle θ may be detected not only on the positive vertex but also on the negative vertex.
R = Rmx + 1/2 · Rmm (1)

In this way, in the present embodiment, by performing the second determination in addition to the first determination, the parts that have failed during processing are more reliably excluded. In addition, the threshold value for determining the quality of the processing described above is determined by design by trial on site.

In each of the above-described embodiments, the case of determining the quality of spin-caulking is described. However, the present invention is not limited to the determination of quality of spin-caulking, and is widely applied to the quality of machining using a machining tool driven by an AC drive motor. can do. Furthermore, the scope of application of the present invention is not only the judgment of the quality of machining, but also the wear damage of thrust bearings that receive caulking load and rotary bearings that receive machining pins, due to changes in centroid position during idle running and tool contact. Presence / absence can also be detected and can be widely used for the purpose of determining the mechanical condition on the output side of the drive motor.

DESCRIPTION OF SYMBOLS 1 ... Main shaft, 2 ... Drive motor, 3 ... Sleeve, 4 ... Hydraulic device, 5 ... Processing pin, 6 ... Caulking pin, 7 ... Clamp meter, 8 ... A / D conversion circuit, 9 ... Computer.

Claims

Detecting a drive current waveform of an AC drive motor; obtaining an equivalent sine waveform having an area equal to a waveform area in the cycle for each predetermined cycle of the detected drive current waveform; and Calculating a waveform of a difference between each absolute value of the drive current waveform and the equivalent sine waveform; determining a mechanical condition on the output side of the AC drive motor from a transition of the waveform of the difference for each predetermined cycle; A method for determining the status of a motor drive mechanism comprising:
The motor drive mechanism status determination method according to claim 1, wherein transition of the difference waveform is detected by a change in a centroid position of the difference waveform.
Transition of the waveform of the difference is obtained by multiplying the amplitude value at each time of the equivalent sine wave by the positive amplitude value of the waveform of the difference at the time as an amplitude moment value, and the amplitude moment value is within the predetermined cycle. The motor drive mechanism status determination method according to claim 1, wherein the detection is performed by a change in an amplitude moment integrated value integrated within a range in which the amplitude value of the waveform of the difference is positive.
Relative behavior of the amplitude moment integrated value with respect to a unit amplitude moment integrated value obtained by dividing the transition of the difference waveform by the amplitude moment integrated value by the total area value of the difference waveform in the range where the amplitude value is positive The method for determining the state of the motor drive mechanism according to claim 3, which is detected at step (1).
The motor drive mechanism status determination method according to claim 4, wherein the relative behavior is an average of a difference of the amplitude moment integrated value with respect to the unit amplitude moment integrated value.
6. The motor drive mechanism according to claim 4, wherein the relative behavior is a degree of a slope of a straight line obtained by linearly approximating a time-changing portion of a difference of the amplitude moment integrated value with respect to the unit amplitude moment integrated value. Situation judgment method.
The motor drive mechanism status determination method according to any one of claims 3 to 6, wherein a transition of the waveform of the difference is detected by at least a depression angle of a positive apex at which the amplitude moment integrated value changes.
The motor drive mechanism status determination method according to claim 1, wherein the mechanical status is quality of machining using a machining tool driven by the AC drive motor.
Means for detecting a drive current waveform of an AC drive motor; means for obtaining an equivalent sine waveform having an area equal to a waveform area in the cycle for each predetermined cycle of the detected drive current waveform; and Means for calculating a waveform of a difference between the absolute values of the drive current waveform and the equivalent sine waveform; and means for determining a mechanical condition on the output side of the AC drive motor from a transition of the waveform of the difference for each predetermined cycle; The state determination apparatus of a motor drive mechanism provided with these.