JPH06339838A - Contact detector - Google Patents

Abstract

PURPOSE:To accurately detect contact between a detecting object and a detecting member by arranging a means to set a sampling period so as to synchronize with the detecting result while detecting rotational time per unit rotation or the number of revolutions per unit time of the detecting object. CONSTITUTION:A sampling means 21 samples an elastic wave signal from an elastic wave detecting means 18 so as to correspond to an angle phase of a detecting member 16, and a contact judging means 22 detects continuously the elastic wave signal corresponding to this angle phase over plural rotations of a detecting object 9, and judges contact between the detecting object 9 and the detecting member 16. In this way, even if a change in the number of revolutions per unit time of the detecting object 9 or rotation of the detection object 9 is not carried out according to the preset number of revolutions, since the sampling means 21 samples accurately the elastic wave signal from the elastic wave detecting means 18 so as to correspond to the angle phase of the detecting object 9, contact between the detecting object 9 and the detecting member 16 can be detected reliably.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contact detecting device used in a grinding machine for detecting the surface position of a grinding wheel during truing or grinding.

[0002]

2. Description of the Related Art Conventionally, in a grinding machine, an AE (Acoustic Emission) sensor is used as a contact detection device for detecting the position of the grinding surface of a grinding wheel during tooling or grinding. A contact detection device using this AE sensor is equipped with a detection pin incorporating the AE sensor on a fixed part such as a headstock, and the grindstone is moved forward in the same manner as when grinding or truing to grind a rotating grinding wheel. The surface is brought into contact with the detection pin, the elastic wave generated at the detection pin at this time is detected by the AE sensor, and the contact of the grinding wheel is determined from the level of the signal output from the AE sensor. The surface position of the grinding wheel is detected from the position of the grinding wheel head at the time of determination.

[0003]

In order to detect the grindstone surface position during this grinding, the same conditions as during grinding are used.
This is done by rotating the grinding wheel and injecting coolant.
Therefore, the coolant ejected from the nozzle is applied to the detection pin, an elastic wave is generated in the detection pin due to the collision pressure of the coolant, and when the elastic wave is detected by the AE sensor, it is erroneously determined as contact with the grinding wheel. There was a case.

Therefore, conventionally, a method of detecting the surface position of the grindstone by stopping the supply of the coolant has been adopted. However, even if such a method is taken, if the coolant remaining in the pipe and nozzle drops onto the grinding wheel and circulates along with the grinding wheel and collides with the detection pin, the elastic waves generated at this time cause contact with the grinding wheel. Was sometimes falsely detected. Therefore, conventionally, the contact of the grindstone is detected after the coolant remaining in the pipe and the nozzle is removed by air. For this reason, a preparation time (about 30 seconds) is required until the contact detection of the grindstone is required, the detection cycle time becomes long, and the grinding cycle or the truing cycle is affected. In order to solve this, the elastic wave generated in the AE sensor is sampled in synchronization with the rotation of the grinding wheel, for example, 256 times for each rotation of the grinding wheel, so that the surface of the grinding wheel has 256 angular phases. We devised a method to detect contact between the grinding wheel and the detection pin by detecting that elastic waves are continuously generated at the same position (angle phase) of the grinding wheel. However, in order to synchronize the sampling with the rotation of the grinding wheel, the sampling period must be set according to the rotation time per rotation of the grinding wheel.
Rotation time per revolution of the grinding wheel, i.e., the rotational speed per unit of the grinding wheel time is suitably changed by the operator based on the accuracy and the like which are required to the workpiece, of how to configure because not constant Problem has occurred. Furthermore,
Even if the number of revolutions per unit time to be set is known and the sampling cycle is adjusted corresponding to this, the grinding wheel is driven by the inverter motor, so it is affected by the mass of the grinding wheel, friction of each member, etc. There was a problem in that sampling could not be performed in synchronization with the rotation of the grinding wheel if the sampling cycle was adjusted based on the set rotation speed without rotating at the set rotation speed.

The present invention is intended to solve the above-described problems, and the contact between the grinding wheel and the AE sensor can be made even if the rotation speed per unit time is changed or the grinding wheel does not rotate according to the set rotation speed. An object of the present invention is to provide a contact detection device that can reliably detect

[0006]

A detection member 16 with which a rotating detection object 9 contacts, and the detection member 1 when the detection object 9 contacts the detection member 16 while rotating.
6, an elastic wave detecting means 18 for detecting an elastic wave generated and outputting an elastic wave signal, and a sampling means 21 for sampling the elastic wave signal from the elastic wave detecting means 18 at a set cycle. The rotation detection member 38 for detecting the rotation time per rotation or the number of rotations per unit time of the detected object 9 and the rotation time per rotation or the number of rotations per unit time detected by the rotation detection member 38. Based on the sampling period setting means 21a for setting the sampling interval of the sampling means 21, and a contact for judging the contact between the detected object 9 and the detection member 16 based on the elastic wave signal sampled by the sampling means 21. And a determination means 22, wherein the sampling period setting means 21a is used to measure the rotation time per rotation of the detected object 9 or The elastic wave detecting means is set so that the sampling means 21 corresponds to the angular phase of the member 16 to be detected by setting the sampling means 21 with a sampling period of a predetermined fraction of one rotation based on the number of rotations per unit time. Sampling the elastic wave signal from 18,
The contact determination means 22 determines that the detected object 9 is in contact with the detection member 16 by detecting the elastic wave signal corresponding to this angular phase continuously over a plurality of rotations of the detected object. And

[0007]

With the above construction, the detection member 1 is brought into contact with the rotating detection object 9 such as a grinding wheel or the like and the coolant impact.
The elastic wave generated at 6 is detected by the elastic wave detecting means 18 and output as an elastic wave signal. On the other hand, the rotation detection member 38 detects the rotation time per rotation of the detection target member 9 or the rotation speed of the detection target object 9 per unit time. Then, the sampling cycle of the sampling means 21 is set to the rotation time per rotation of the detected object 9 based on the rotation time per rotation detected by the rotation detection member 38 by the sampling cycle setting means 21a or the number of rotations per unit time. It is set to a predetermined value of 1 /. Thereby, the sampling means 2
The elastic wave signal from the elastic wave detecting means 18 is sampled so that 1 corresponds to the angular phase of the detected member 16, and the contact judging means 22 outputs the elastic wave signal corresponding to this angular phase to the plurality of detected objects 9. It is determined that the detected object 9 and the detection member 16 are in contact with each other by continuously detecting the rotation of the detection object 9. As described above, the sampling unit 21 accurately corresponds to the angular phase of the detected object 9 even if the rotational speed of the detected object 9 per unit time is changed and the detected object 9 does not rotate at the set rotational speed. Since the elastic wave signal from the elastic wave detecting means 18 is sampled, the contact between the detected object 9 and the detecting member 16 can be surely detected.

[0008]

Embodiments of the present invention will be described below with reference to FIGS. FIG. 1 is an overall configuration diagram of a contact detection device according to the present invention, and FIG. 2 is a schematic plan view of a grinding machine to which the contact detection device of the present invention is applied.

First, the structure of the grinder will be described with reference to FIG. The grinding machine 1 has a bed 2, and a work table 3 is installed on the bed 2 so as to be movable in the Z-axis direction. The work table 3 is rotated by a servo motor 4 and the servo motor 4. Lead screw (not shown)
Is moved in the Z-axis direction by.

A headstock 5 and a tailstock 6 are installed on the work table 3 so as to face each other on the left and right. Between the headstock 5 and the tailstock 6, a headstock 5a of the headstock 5 is provided. Both ends of the workpiece W are supported by the chuck 5b provided and the center 6a provided on the tailstock 6.

In FIG. 2, the grindstone base 7 is installed on the bed 2 so as to be movable in the X-axis direction perpendicular to the moving direction of the workpiece table 3, and is fixed to the bed 2 by the servomotor 8 and the servomotor. It is moved in the X-axis direction by a feed screw (not shown) rotated by the motor 8. The encoder 14 attached to the servomotor 8 is configured to detect the position (or movement amount) of the grinding wheel base 7 from the number of rotations thereof. An inverter motor 30 is attached to the grindstone base 7,
A grinding wheel 9 for grinding the workpiece W is attached, and the driving force of the inverter motor 30 is
Is transmitted from the pulley 32 attached to the pulley 36 to the pulley 36 on the grinding wheel 9 side via the belt 34, and the grinding wheel 9 is rotated. This grinding wheel 9 has a grinding wheel cover 10
And a coolant nozzle 11 is arranged on the exposed side facing the work table 3,
The coolant nozzle 11 is connected to the coolant supply pipe 12. A truing device 15 is attached to the headstock 5 so as to face the grindstone base 7.

Next, the mechanism for detecting the rotation time per rotation of the grinding wheel 9 of this embodiment will be described. A rotation detection sensor 38 is attached to the side of the pulley 36 on the grinding wheel 9 side shown in FIG. A signal generator 40 for generating an optical signal is attached to a side portion of the pulley 36 as shown in FIG. 1, which schematically shows the pulley 36 in FIG. The rotation of 36 causes the signal generator 40 to pass in front of the rotation detection sensor 38, and counts pulse signals until the signal generator 40 passes in front of the rotation detection sensor 38 again, and this count value is the grinding wheel. The rotation time per rotation of 9 is output from the rotation detection sensor 38.

Next, a mechanical mechanism for detecting the grinding surface position of the grinding wheel 9 of this embodiment will be described. As shown in FIG. 2, the detection pin 16 is attached to detect the surface position of the grinding wheel 9, and the detection pin 16 is, as shown in FIG. It is fixed at 5. In addition, this detection pin 16
An AE sensor 18 for detecting elastic waves generated at the time of contact with the surface of the grindstone and by the collision of the coolant is attached integrally therewith.

Here, the principle of the contact detection device of this embodiment detecting contact with the grindstone based on the output of the AE sensor 18 will be described with reference to FIG. In the contact detection device of this embodiment, the output from the AE sensor 18 is synchronized with the rotation of the grinding wheel 9 to perform sampling. Here, 1 of the grinding wheel 9
Sampling is performed 128 times for each rotation. That is, the grinding wheel 9
Sampling is performed in a sampling cycle in which the rotation time per one rotation is divided into 128 times. As a result, the outer peripheral surface of the grinding wheel 9 is sampled by being divided into angular phases of 360 ° / 128 = 2.8125 °, and the AE sensor 1 corresponding to the angular phase of every 2.8125 ° of the grinding wheel 9.
8 outputs are obtained. The outer peripheral surface of the grinding wheel 9 has small irregularities, and when the convex portion comes into contact with the detection pin 16, a contact signal of the AE sensor 18 is generated. The contact signal corresponding to the convex portion is the grinding wheel 9 No matter how many times it is rotated, it will occur at the same angular phase. On the other hand, it is very unlikely that the signals generated by the collision of the coolant with the detection pin 16 are generated in the same angular phase. Therefore, in the contact detection device of this embodiment, AEs sampled so as to correspond to substantially the same angular phase over a plurality of rotations, that is, the same angular phase.
When the output of the sensor 18 is continuously generated over a plurality of rotations, it is determined that the contact is made. On the other hand, the elastic wave generated in the AE sensor 18 regardless of the angular phase is generated by the impact of the coolant. It is determined that the noise is generated.

Further, the configuration of the contact detection device will be described with reference to FIG. In FIG. 1, the contact detection device is a rectangular wave generation circuit 20 that shapes each elastic wave signal having a predetermined level or higher detected by the AE sensor 18 into a rectangular wave and outputs a rectangular wave signal corresponding to the duration of the elastic wave. And a sampling circuit 21 for sampling and outputting the rectangular wave signal 128 times per one rotation of the grinding wheel in synchronization with the rotation of the grinding wheel, and the rectangular wave signal sampled by the sampling circuit 21 is taken in to obtain the above continuity. The signal processing circuit 22 performs a determination process for determining whether or not the grinding wheel 9 and the detection pin 16 are in contact with each other, and a rotation speed calculation process for calculating the rotation speed of the grinding wheel 9.

The rectangular wave generation circuit 20 includes a high-pass filter 20a for extracting only the elastic wave component from the detection signal output from the AE sensor 18, and the high-pass filter 20a.
Circuit 20b for full-wave rectifying the elastic wave signal passing through
And a smoothing circuit 20c for smoothing this rectified signal, and the smoothed signal and the reference signal are compared, and while the level of the smoothed signal exceeds the reference signal level, the output is set to the high level and the elasticity is set. And a comparator 20d that outputs a rectangular wave signal according to the wave signal.

The sampling circuit 21 passes the rectangular wave signal from the rectangular wave generation circuit 20 to the signal processing circuit 22 each time a sampling pulse is applied to the gate circuit 2.
1c, a sampling pulse generating circuit 21b for applying a sampling pulse to the gate circuit 21c so as to sample 128 times during one rotation of the grinding wheel 9, and a sampling cycle of the sampling pulse generating circuit 21b The setting time is set to 1/128 of the rotation time per one rotation of the grinding wheel 9 so as to be synchronized with, and the sampling device is configured to correspond to each angular phase of 128 grinding wheel outer peripheral surfaces. There is.

The signal processing circuit 22 is the sampling circuit 2
The interface 22a receives the rectangular wave signal of the rectangular wave generation circuit 20 sampled by 1, the interface 22d receives the rotation signal of the grinding wheel 9 from the rotation detection sensor 38, the CPU 22b, and the memory 22c. The CPU 22b performs a contact determination process of determining whether or not the grinding wheel 9 and the detection pin 16 are in contact with each other based on a rectangular wave signal corresponding to each angular phase of the outer peripheral surface of the grinding wheel 9 fetched through the interface 22a, and In order to synchronize the sampling cycle of the sampling circuit 21 with the rotation of the grinding wheel 9, based on the rotation time per rotation of several grinding wheels 9 taken in through the interface 22d, the average of the grinding wheel 9 per rotation is determined. Rotation time calculation processing for calculating the rotation time is performed.

The memory 22c stores control information for the contact determination process and the rotation time calculation process of the CPU 22b, and stores data processed by the CPU 22b (rectangular wave signal of the rectangular wave generation circuit 20). It is stored in the form of the mask shown in FIG. This mask conceptually explains the data based on the rectangular wave signal stored in the memory 22c, and the vertical columns indicate the number of rotations of the grinding wheel 9 acquired by the horizontal column. The column of indicates the order of sampling data in the rotation. In other words, the sampling number (hereinafter referred to as a sampling number) in the horizontal column represents the correspondence between the grindstone outer circumference (angle phase) and the sampled number, and, for example, “1”, “2” in the horizontal column, “3” indicates the angular phase of the grinding wheel 9 “0 ° to 2.8125 °” and “2.812”, respectively.
5 ° to 5.625 ° "," 5.625 ° to 8.4375.
Represents the output (square wave signal) of the AE sensor 18 at "°". In addition, here, "1" in the column means that the sampled rectangular wave signal is treated as the state of "H",
In addition, “0” indicates that the sampled rectangular wave signal is “L”.
It is treated as the state of.

Next, referring to FIG. 1, the AE sensor 18
The processing of the elastic wave generated in the above will be described in detail. The projection on the outer peripheral surface of the grinding wheel 9 comes into contact with the detection pin 16, or the coolant that rotates around the grinding wheel 9 is detected by the detection pin 16
When applied to the outer peripheral surface of the grindstone, an elastic wave corresponding to the spraying force of the coolant is generated on the detection pin 16, and the elastic wave is detected by the AE sensor 18. The elastic wave signal output from the AE sensor 18 is a rectangular wave generation circuit 20.
When input to the high-pass filter 20a, the elastic wave signal S1 having a waveform as shown in FIG. 3A is extracted from the high-pass filter 20a and output to the rectifier circuit 20b.

In the rectifier circuit 20b, the elastic wave signal S1 is full-wave rectified into the waveform shown in FIG. 3B and output to the smoothing circuit 20c. The smoothing circuit 20c outputs the signal S2 having the waveform shown in FIG. 3C by smoothing the full-wave rectified waveform shown in FIG. When the smoothed signal S2 is input to the comparator 20d, the comparator 20d compares the smoothed signal S2 with the reference signal Vref, and the output is set to the H level while the smoothed signal S2 exceeds the reference signal Vref. To do. As a result, the rectangular wave signal S3 having a width corresponding to the duration of the elastic wave signal as shown by the solid line in FIG.
Is generated.

On the other hand, when the sampling pulse of the sampling pulse generating circuit 21b set to 1/128 of the rotation time per rotation of the grinding wheel 9 is applied to the gate circuit 21c as described above, the gate circuit 21c becomes The rectangular wave signal S3 from the rectangular wave generation circuit 20 is applied to the interface 22a of the signal processing circuit 22 using a gate.
Then, the rectangular wave signal is applied to the CPU 22b via the interface 22a. The contact determination process based on the rectangular wave signal S3 by the CPU 22b will be described in detail later.

Next, with reference to FIG. 1 and FIG. 2 and FIG. 5, which is a flow chart showing the processing of this position detection, for the outline of the position detection operation of the surface of the grindstone by the contact detection apparatus of the present embodiment configured as described above. And explain. When the position of the grindstone surface corresponding to the grinding surface of the grinding wheel 9 with respect to the workpiece W or the truing device 15 is detected during grinding or truing (determination step 1 is Yes), a position detection cycle starts (step 2). First, the workpiece table 3 is moved in the Z-axis direction by the servo motor 4, and the detection pin 16 is positioned at a position directly facing the grinding wheel 9. In this state, the grinding wheel 9 is rotated by the inverter motor 30 in the same manner as during truing or grinding. Next, the process proceeds to step 3, and in order to synchronize the sampling cycle of the sampling circuit 21 with the rotation of the grinding wheel 9, first, a plurality of rotation times per one rotation of the grinding wheel 9 are measured, and then this measurement is performed. An average rotation time per one rotation is calculated based on the rotation time per one rotation, and a sampling cycle in which the average rotation time per one rotation is 1/128 is set. Then, the process proceeds to step 4 to start the contact detection process. Here, first, the servomotor 8 is driven to move the grindstone base 7 toward the detection pin 16 side in a stepwise manner. When it is detected that the outer peripheral surface of the grinding wheel 9 contacts the detection pin 16, the advance of the grinding wheel base 7 is stopped and the position at this time is detected by the encoder 14 attached to the servo motor 8. Then, the grindstone base 7 is moved backward by fast forward.

Regarding the processing of measuring the rotation time per one rotation of the grinding wheel 9 and setting the sampling period in the sampling circuit 21 in the above step 3, the flowchart of FIG. 6 showing the processing of this step 3 in detail and FIG. 1 and A description will be given with reference to FIG.

The inverter motor 30 is driven to drive the grinding wheel 9
When the pulley 36 is rotated, the signal generator 40 attached to the pulley 36 passes in front of the rotation detection sensor 38 as shown in FIG. At each passage of the signal generator 40, the rotation detecting sensor 38 determines the rotation time per rotation of the grinding wheel 9 in the interface 22 in step 11.
It is transmitted to the CPU 22b via d. It is judged in the next judgment step 13 whether or not the reception of the rotation time is repeated p times, for example, 5 times, and if it is repeated p times (Yes in the judgment step 13), in the next step 14, p times are repeated. Calculate the average rotation time. Next, in step 15, C
The PU 22b uses the calculated average rotation time to calculate the 128
The fractional time is set in the setter 21a. Then, the setter 21a determines the cycle of the sampling pulse generation of the sampling pulse generation circuit 21b based on the set time.
By adjusting the rotation time of the grinding wheel 9 to 1/128, the sampling cycle is set to be synchronized with the rotation of the grinding wheel 9. As a result, the elastic wave from the detection pin 16 is sampled 128 times per revolution of the grinding wheel 9.

Next, regarding the contact detection processing between the grinding wheel 9 and the detection pin 16 based on the elastic wave from the AE sensor 18 in step 4 of the flowchart shown in FIG.
This process will be described in detail with reference to the flowchart of FIG. 7 and FIGS. 1 and 2.

First, in step 21, a predetermined number of forward command pulses are applied to the servo motor 8 to advance the grindstone base 7 toward the detection pin 16 by one step (1 pitch). The grinding wheel 9 is configured to rotate 16 times when the grinding wheel base 7 advances by one pitch. At this time, the CPU 22b
In step 22, the number of revolutions of the grindstone, that is, a variable m representing the number of revolutions in 16 revolutions is initialized to 1, and further, in step 23, a variable n representing how many times the revolution of the grindstone is sampled is set to 1. Initialize to. In this state, the process proceeds to step 24, and the process of the first sampled elastic wave signal (hereinafter referred to as data) from the detection pin 16 in the first rotation is started.

When the first sampled signal of the first rotation is applied to the CPU 22b, the CPU 22b
The presence or absence of the E signal, that is, the presence or absence of the rectangular wave signal S3 from the rectangular wave generation circuit 20 is determined (decision step 25).
If there is no AE signal, the decision step 25 is N
Then, the process proceeds to step 29. In step 29, "0" without the AE signal is stored in the first position of the first rotation in the mask of the memory shown in FIG. On the other hand, A
If there is an E signal, the judgment step 25 becomes Yes, and the routine proceeds to the next judgment step 26. In the judgment step 26, it is judged whether or not the rotation of the grinding wheel 9 is the first rotation. Here, since it is the first rotation, the determination step 26 is Yes.
Then, the process proceeds to step 28. In step 28, "1" with the AE signal is stored in the first position of the first rotation in the mask shown in FIG.

Next, in a judgment step 30, it is judged whether or not one rotation of the grinding wheel 9, that is, 128 pieces of data have been processed. Here, since the processing of the first sampled data has been performed, the determination result is No, and the process proceeds to step 31. In step 31, 1 is added to the variable n representing the number of samplings to make it "2", and the process returns to step 24 to process the second sampled data. Repeat the processing from the judgment step 25 onwards to 1
When the processing is completed up to the 28th sampled data, the judgment step 30 becomes Yes, and the judgment in the next judgment step 32 is performed.

In the judgment step 32, it is judged whether or not the data of 16 revolutions of the grinding wheel 9 has been processed. That is, as described above, the grinding wheel 9 is configured to rotate 16 times when the grinding wheel base 7 advances by one pitch, and thus it is determined whether or not this rotation is completed. Here, the grinding wheel 9
Since it is the first rotation of No., the determination step 32 becomes No and the process proceeds to step 33. In step 33, 1 is added to the variable m representing the number of revolutions to set it to “2”, and the process returns to step 23 and n representing the sampled number of the data is set to 1 again, and the first sampled data of the second revolution is set. The process of is started.

In the judgment step 25, the CPU 22b judges again whether or not the AE signal is present. Here, if there is no AE signal, the process proceeds to step 29 and "0" without an AE signal is stored in the first position of the second rotation in the mask of the memory. On the other hand, if there is an AE signal, judgment step 2
Go to 6. In the judgment step 26, the rotation of the grinding wheel 9 is 1
It is determined whether the rotation is the second rotation, but since it is the second rotation here, the determination step 26 becomes No and the process proceeds to the determination step 27.
At decision step 27, a decision is made as to the connectivity with the data sampled during the previous rotation (m-1). That is, in the previous rotation (m-1), n-1, n, n
It is determined whether or not "1" with the AE signal is stored in any of the masks of the + 1st sampled data.

This determination will be described in detail with reference to FIG. For example, when storing the third sampled data (with AE signal) of the second rotation in the third position of the second rotation of the mask, n-1 of the previous rotation (here, the first rotation) , N, n + 1th sampled data (here, the second, third, and fourth sampled data) is stored in one of the masks.
Determine if is placed. Here, since “1” is placed in the second sampled data corresponding to n−1, this determination step 27 becomes Yes, and the process proceeds to step 28, and the third step of this second rotation is performed. Place "1" at the position corresponding to the sampled data.
Further, when the AE signal is included in the fifth sampled data in the second rotation, the fifth data corresponding to n in the first rotation is obtained.
Since "1" is placed in the data sampled the second time, "1" is placed in the position of the mask corresponding to the data sampled fifth in the second rotation. Similarly, in the 7th sampled data of the 2nd rotation, A
If there is an E signal, the eighth rotation corresponding to n + 1 of the first rotation
Since "1" is placed in the data sampled the second time, "1" is placed in the position of the mask corresponding to the data sampled seventh in the second rotation. On the other hand,
AE is applied to the 10th sampled data of the second rotation.
If there is a signal, since the “0” is placed in all of the 9th, 10th and 11th sampled data corresponding to n−1, n, n + 1 of the first rotation, the judgment step 27 If No, the process moves to step 29 and the mask 2
At the position corresponding to the 10th sampled data of the rotation, "0" is placed in spite of the AE signal.

By repeating the above-mentioned processing for 16 revolutions of the grinding wheel 9, a mask of sampled data as shown in FIG. 4 is completed. As a result, the judgment step 32 becomes Yes.
Therefore, the process proceeds to the judgment step 34. In decision step 34, the final rotation of the mask of data shown in FIG.
The presence or absence of contact is determined by whether or not there is "1" in any of the 1st to 128th rotations. Here, if there is no "1" at the 16th rotation, the determination step 34 becomes No and the process returns to step 21 to add one pulse to the servo motor 8 to move the grinding wheel head 7 to the detection pin 16 side by one pitch. After advancing, it progresses to step 22 and advances the process of the said contact determination. On the other hand, if there is "1" at the 16th rotation, the judgment step 34 becomes Yes and the routine proceeds to step 35,
Send a contact signal ON to the numerical controller. Thereby, the numerical controller determines the position of the grindstone surface based on the output of the encoder 14 attached to the servomotor 8.

Since the outer peripheral surface of the grinding wheel 9 has small irregularities, a contact signal (AE signal) is generated when the convex portion comes into contact with the detection pin 16, and the AE corresponding to this convex portion.
The signal is generated with the same angular phase each time the grinding wheel 9 rotates. However, since the grinding wheel 9 has a slight rotation irregularity and the rotation of the grinding wheel 9 and the sampling cycle are not completely synchronized, it is not possible to sample the AE signals generated at the same angular phase with the same number. That is, when the rotation time per one rotation of the grinding wheel 9 tends to be short, the same A as the third sample of the first rotation is sampled.
The E signal will be sampled at the third to fourth positions in the second rotation, and will be sampled at the fourth to fifth positions in the third rotation. Therefore, in the contact detection device of the present embodiment, the AE signal is acquired by performing sampling so as to substantially correspond to the angular phase of the grinding wheel 9, and the A
As shown in FIG. 4, from the first rotation of the grinding wheel 9, the E signal is sequentially checked for continuity with the AE signal acquired during the previous rotation, and the continuity with the AE signal during the previous rotation is confirmed. If there is, it is stored in the memory 22c as "1". Then, when the data in this memory occurs for 16 rotations in an angular phase having continuity, that is, when "1" is placed in any of the 1st to 128th rotations in the final 16th rotation. It is determined that the grinding wheel 9 has come into contact with the detection pin 16. That is, in the mask shown in FIG. 4, the third sampled data indicates that the detection pin 16 contacts the grinding wheel 9.

Further, in this embodiment, the elastic wave of the detection pin generated by the contact of the grindstone and the collision of the coolant is detected by the AE sensor 18, and the elastic wave signal output from the AE sensor is equal to or higher than a predetermined level. The vehicle 9 is sampled 128 times per rotation and taken into the signal processing circuit 22. In this signal processing circuit 22, it is judged whether or not an elastic wave signal is generated continuously, and when this state is confirmed. It is determined that the grinding wheel 9 has come into contact with the detection pin 16. That is, as described above, the contact signal generated when the convex portion on the outer peripheral surface of the grinding wheel 9 comes into contact with the detection pin 16 is generated at substantially the same angular phase each time the grinding wheel 9 rotates. On the other hand, the signals generated by the coolant impinging on the detection pin 16 are very unlikely to be generated in the same angular phase. Therefore, even if the coolant hits the detection pin 16 and an elastic wave is generated at the time of detecting the position of the surface of the grindstone, erroneous detection of the grindstone contact due to this will not occur, and the contact with the grindstone can be reliably detected. You can Along with this, it is possible to detect contact with the grindstone under the same conditions as when grinding while ejecting the coolant, and stop the coolant as in the past to eliminate residual coolant in the pipe and nozzle by air. No cycles required,
The detection cycle time can be shortened.

The grinding machine is used by appropriately changing the number of revolutions per revolution of the grinding wheel based on the precision required for the workpiece, and the grinding wheel is set to a predetermined number of revolutions due to its mass and the like. It does not rotate and uneven rotation occurs. In the present embodiment, even if the rotation speed of the grinding wheel 9 is arbitrarily set, or if the grinding wheel 9 does not rotate at the set rotation speed and uneven rotation occurs, the rotation of the grinding wheel 9 and the sampling cycle Since the rotation speed of the grinding wheel 9 is detected and the sampling cycle of the sampling pulse generation circuit 21b is set in synchronization with the rotation speed of the grinding wheel 9, the output from the AE sensor 18 is synchronized with the rotation of the grinding wheel 9. Can be sampled.

In the above embodiment, the CPU
22b calculates the average rotation time required for one rotation of the grinding wheel 9 from the pulse of the rotation detection sensor 38, and sets the sampling cycle of the sampling pulse generation circuit 21b based on this time. Instead, the rotation detection is performed. The average number of revolutions of the grinding wheel 9 per unit time is calculated based on the plurality of revolutions per unit time from the sensor 38, and the sampling cycle of the sampling pulse generation circuit 21b is determined based on the average number of revolutions. It is also preferable to set. Further, in the above-described embodiment, since there is uneven rotation of the grinding wheel 9, when there is a contact signal at the nth rotation of m rotations, m-1
The method of determining "1" when any of the n-1, n, and n + 1 rotations is "1" has been described, but if the rotation unevenness of the grinding wheel is small, the applicant or the earlier application has been filed. As shown in Japanese Patent Application No. 4-261630, 256 samples are repeated 16 times, and when the elastic wave signal is continuous in the data sampled with the same number, it is possible to determine that the whetstone is in contact. Is.

Further, in the above-mentioned embodiment, the grinding wheel 9 was rotated 16 times when the grinding wheel head was moved forward by one pitch, and sampling was performed 128 times during this one rotation, but these values may be changed appropriately. It is possible. Further, in the above-described embodiment, the contact detection of the grinding wheel has been described as an example, but the contact detection device of the present invention can also be applied to the contact detection of an object to be detected other than the grinding stone.

[0039]

According to the present invention, in the contact detection device for detecting the contact of the grinding wheel by sampling the output from the AE sensor in synchronism with the rotation of the grinding wheel, the rotation time or unit of one rotation of the grinding wheel Since the number of revolutions per hour is detected and the sampling cycle is set to synchronize with this, even if the number of revolutions per unit time of the grinding wheel is set arbitrarily, the grinding wheel will rotate at the set number of revolutions. Even without the contact, it is possible to accurately detect the contact of the grindstone.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of a contact detection device according to an embodiment of the present invention.

FIG. 2 is a schematic plan view of a grinding machine provided with the contact detection device of the present invention.

FIG. 3 is a waveform diagram showing output waveforms at various parts of the contact detection device shown in FIG.

FIG. 4 is an explanatory diagram showing an example of storage of sampled data used for contact determination in a memory in the present embodiment.

FIG. 5 is a flowchart showing the entire processing of contact determination in the present embodiment.

6 is a flowchart showing a rotation speed measurement and sampling period setting process of the flowchart shown in FIG.

7 is a flowchart showing a contact detection process of the flowchart shown in FIG.

[Explanation of symbols]

 1 Grinding Machine 7 Grinding Wheel Stand 9 Grinding Wheel 11 Coolant Nozzle 16 Detection Pin 18 AE Sensor 20 Square Wave Generation Circuit 21 Sampling Circuit 21a Setting Device 22 Signal Processing Circuit 38 Rotation Detection Sensor 40 Signal Generator

[Procedure amendment]

[Submission date] August 19, 1993

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 2

[Correction method] Change

[Correction content]

[Fig. 2]

Claims (1)

[Claims] 1. A detection member with which a rotating detection object contacts, and an elastic wave signal generated by detecting an elastic wave generated in the detection member when the detection object rotates and contacts the detection member, and outputs an elastic wave signal. An elastic wave detecting means for outputting and a sampling means for sampling the elastic wave signal from the elastic wave detecting means at a set cycle are provided, and the rotation time per rotation of the detected object or the number of rotations per unit time. A rotation detection unit that detects the rotation speed, a sampling period setting unit that sets the sampling period of the sampling unit based on the rotation time per rotation detected by the rotation detection unit or the number of rotations per unit time, A contact determination unit that determines contact between the object to be detected and the detection member based on the elastic wave signal sampled by the sampling unit; The ring cycle setting means sets the sampling means to a sampling cycle of a predetermined fraction of one rotation based on the measured rotation time per rotation of the object to be detected or the number of rotations per unit time. Sample the elastic wave signal from the elastic wave detecting means so as to correspond to the angular phase of the detected member, and the contact determining means outputs the elastic wave signal corresponding to this angular phase over a plurality of rotations of the detected object. A contact detection device, characterized in that it is judged as contact between a detected object and a detection member by detecting with continuity.