JP3218136B2 - Whetstone peripheral surface condition determination device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for determining whether or not the condition of the peripheral surface of a grinding wheel is normal.

[0002]

2. Description of the Related Art A method of shaping a cylindrical grindstone peripheral surface with a dresser while checking the peripheral surface condition of the grindstone is disclosed in Japanese Unexamined Patent Publication No.
It is disclosed in Japanese Patent Publication No. 3-265106. In this publication, the determination of the peripheral surface state of the grindstone is performed by an ultrasonic sensor that detects an ultrasonic vibration generated during dressing of the grindstone by a dresser, and a comparing unit that compares an output level of the ultrasonic sensor with a predetermined threshold level. And determination means for determining the state of the grinding wheel peripheral surface from the result of the comparison means. The diameter of the cross section of the cylindrical grinding wheel is constant, and the peripheral speed on the peripheral surface of the grinding wheel is constant since the grinding wheel is rotated at a constant speed. If it is the normal condition of the peripheral surface of the grindstone without dents,
At the time of dressing, an ultrasonic vibration proportional to the constant peripheral speed is generated, and the output of the ultrasonic sensor due to the ultrasonic vibration is also substantially constant over the entire peripheral surface of the grindstone. The threshold level is set lower than the fixed value by a predetermined level. The comparing means compares the threshold level with the actual output of the ultrasonic sensor. If the output of the ultrasonic sensor exceeds the threshold level over the entire area of the grindstone peripheral surface, the determination means determines that the state of the peripheral surface of the grindstone is a normal peripheral surface without depression. When there is a depression on the peripheral surface of the grindstone, the output of the ultrasonic sensor decreases at the depression and falls below the threshold level. In this case, it is determined by the determining means that the dent is formed. Then, the dressing is repeated until it is determined by the determining means that the peripheral surface has no depression.

[0003]

When dressing a conical whetstone, the peripheral speed of the peripheral surface of the whetstone increases as the diameter of the cross section of the conical whetstone increases. And the output level of the ultrasonic sensor increases linearly. in this way,
With a conical grinding wheel, the output of the ultrasonic sensor changes even in a normal peripheral surface state without depression, so even when compared with the ultrasonic sensor output using a constant threshold level as described in the above publication, Judgment is not possible. For example, if the threshold level is set to a level lower than the threshold by a predetermined amount based on the ultrasonic sensor output generated when shaping a portion having a small cross section diameter, the ultrasonic sensor generated when shaping a portion having a large cross section diameter is set as a threshold level. This is because the output exceeds the threshold level even if there is a depression. Further, when a level lower by a predetermined amount than the ultrasonic sensor output generated at the time of shaping a portion having a large cross-sectional diameter is set as a threshold level, an ultrasonic sensor generated at the time of shaping a portion having a small cross-sectional diameter is set. This is because the output falls below the threshold level even if there is no depression. Since the dent cannot be detected as described above, if the dent is to be completely eliminated, the peripheral surface of the grindstone will be cut too much more than necessary, and if the amount of cutting is suppressed, the dent will remain due to insufficient cutting.

[0004]

SUMMARY OF THE INVENTION The gist of the present invention is to determine whether or not a grindstone having a shape of a rotating body and having a cross section whose diameter changes along a rotation axis has a normal peripheral surface state. In a device for determining the peripheral surface condition of a grindstone, a dresser, moving means for relatively moving the dresser in the direction of the rotation axis of the grindstone along the regular peripheral surface shape of the grindstone, the dresser and the peripheral surface of the grindstone An ultrasonic sensor that detects ultrasonic vibration generated due to the contact of the grinding wheel, and a threshold that changes according to the diameter of the cross-section of the grinding wheel as the contact portion between the dresser and the grinding wheel moves in the direction of the rotation axis of the grinding wheel. A threshold level supplying means for supplying a level, a comparing means for comparing the output from the ultrasonic sensor with a threshold level corresponding to the contact portion, and determining whether or not the peripheral surface state of the grindstone is normal based on the comparison result. Judgment In circumference determination device of the grinding wheel, characterized in that it comprises a determination means that, the. In the invention according to claim 2, the threshold level supply means sets a normal output level in a normal peripheral surface state in advance based on an actual output of the ultrasonic sensor when the dresser moves along a regular peripheral surface shape of the grindstone. It is characterized in that a level lower than this normal output level by a predetermined amount is supplied as a threshold level.

[0005]

According to the first aspect of the present invention, the ultrasonic sensor detects ultrasonic vibration generated due to the contact between the dresser and the peripheral surface of the grindstone, and the contact portion between the dresser and the grindstone moves in the rotation axis direction of the grindstone. A threshold level that varies according to the diameter of the cross-section of the grinding wheel is supplied, and the output from the ultrasonic sensor is compared with a threshold level corresponding to the contact portion. Is determined to be normal. As described above, the threshold level is supplied according to the diameter of the cross section of the grindstone. Therefore, even if the diameter of the cross section changes, the condition of the peripheral surface of the grindstone can be correctly determined. According to the second aspect of the present invention, a normal output level is obtained in advance based on the actual output of the ultrasonic sensor, and a level lower than the normal output level by a predetermined amount is supplied as a threshold level. Thus, an appropriate threshold level can be supplied even to a grinding wheel having a rotating body shape.

[0006]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram illustrating a configuration of a peripheral surface state determination device for a grinding stone. A grindstone peripheral surface state determination device includes a dresser 1 and a dresser moving mechanism 2 for relatively moving the dresser 1 in the rotational axis direction of the grindstone along the regular peripheral shape of the grindstone.
(Moving means), an AE sensor 3 (ultrasonic sensor) for detecting ultrasonic vibration generated due to the contact between the dresser 1 and the peripheral surface of the grinding wheel, and an amplifier circuit for amplifying a detection signal from the AE sensor 3 A rectifying / smoothing circuit 5 for rectifying and smoothing the amplified signal; a contact detecting circuit 6 for detecting contact between the grinding wheel and the dresser 1 from the rectified / smoothed signal; and a threshold level supply circuit 7 for supplying a threshold level. (Threshold level supply means), a level comparison circuit 8 (comparison means) for outputting a high-level comparison signal when the output from the AE sensor 3 is equal to or higher than the threshold level, and a high-level input signal from the level comparison circuit 8. A time measuring circuit 9 for measuring the duration of the comparison signal, and outputting an end signal when the duration measured by the time measuring circuit 9 is longer than a predetermined time. That time comparison circuit 10 (determination means)
And a control circuit 11 for driving the dresser moving mechanism 2 as described above until receiving the end signal from the time comparing circuit 10.
And

FIG. 2 is an explanatory view for explaining a method of dressing the grindstone 20 by the dresser 1 of the apparatus for determining the peripheral surface condition of the grindstone. The dresser 1 includes a housing 40,
AE sensor 3 housed in housing 40, dresser shaft 41 protruding from housing 40, dresser shaft 4
1 and a disk-shaped grinding portion 42 fixed to the first grinding portion 42. The grinding wheel 20 has a conical shape (rotating body shape), and its peripheral surface has a CBN (Cubic Boron N).
Abrasive grains such as nitride and diamond are fixed. The angle formed between the peripheral surface of the grindstone 20 and the rotating shaft 20a is represented by θ in the figure. As shown in FIG. 2, the dresser moving mechanism 2 moves the dresser 1 close to the grindstone 20 to some extent while the dresser shaft 41 is at an angle θ with the rotation shaft 20a, and then moves in the a, b, c, and d directions. The cycle consisting of the movement of is repeated. First, the dresser 1 is fed by a predetermined amount in the direction a (a direction orthogonal to the peripheral surface of the grindstone 20 and approaching the grindstone 20). Next, in the direction b parallel to the circumferential surface of the grindstone 20, it is sent at a constant speed from the tip of the grindstone 20 toward the base end. When it reaches the base end of the grindstone 20, it is sent in the direction c opposite to the direction a. Send in the reverse d direction. Feeding in direction a is 1 more than feeding in direction c.
Since the size is larger by μm, the dresser 1 and the grindstone 20 come into contact during the repetition of the above cycle, and the dressing is executed. Then, after the contact, the peripheral surface of the grindstone 20 is dressed 1 μm deep in one cycle (the cycle after the contact is referred to as a dressing cycle in the following description). At the time of this dressing, the grindstone 20 is rotated at a high speed about the rotating shaft 20a, and the grinding unit 42 is also rotated at a low speed.

With reference to FIG. 1, the operation of the apparatus for judging the peripheral surface condition of a grindstone of the present invention will be described in detail. FIG. 3 (a)
When the dressing cycle is started by the contact between the dresser 1 and the grindstone 20 as shown in FIG. 1, the AE sensor 3 detects the ultrasonic vibration generated by the contact as shown in FIG.
This detection signal is amplified and rectified and smoothed. The rectified and smoothed signal is input to the contact detection circuit 6. If the contact detection circuit 6 determines that the signal is equal to or higher than the contact determination level, the contact signal is input to the control circuit 11. The control circuit 11 responds to the contact signal.
Outputs a command signal for commanding the threshold level setting to the threshold level supply circuit 7. In response to this command signal, the threshold level supply circuit 7 receives a rectified and smoothed signal from the rectifying and smoothing circuit 5 and sets a threshold level to be described later based on the signal. FIG. 3B shows a rectified smoothed signal when dressing is being performed as shown in FIG.
Is indicated by a solid line. The signal thus rectified and smoothed is substantially proportional to the diameter D of the cross section of the grinding stone 20 at the contact portion. As described above, the threshold level supply circuit 7 sets the threshold level indicated by the dotted line in FIG. 3B in accordance with the change of the rectified smoothed signal according to the diameter D of the cross section. Although there are various methods for setting the threshold level, in this embodiment, the input rectified and smoothed signal is stored many times at predetermined time intervals, and the normal output level I is obtained from the stored value by the well-known least square method.
L (indicated by a dashed line) is calculated, and a level several dB lower than the normal output level IL is set to a threshold level TL.
Set as The threshold level TL thus set is a linear function corresponding to the diameter D of the cross section at the contact portion of the grinding wheel 20. This threshold level TL is equal to 1 (time elapsed from the start of the movement of the dresser 1 in the b direction).
It is stored in the threshold level supply circuit 7 as a next function.

When the above-mentioned dressing cycle is repeated and four cycles are completed from the first contact, the fifth cycle of dressing is started. At this time, the control circuit 11 instructs the level comparison circuit 8 to perform a level comparison. The rectified and smoothed signal generated by the contact is input to the level comparison circuit 8 and a threshold level TL corresponding to the elapsed time from the start of the movement of the dresser 1 in the direction b from the threshold level supply circuit 7 (that is, the Whetstone 2
A threshold level corresponding to a cross-sectional diameter D of 0 is input. FIG. 3C shows that during the period when the dresser 1 is moving in the direction b, the level comparing circuit 8 switches to the time measuring circuit 9.
3 shows the comparison signal output. This comparison signal is integrated by the next time measurement circuit 9 only for the output time of the high-level comparison signal, and an integrated time signal is output. This integrated time signal is input to the time comparison circuit 10 to determine whether or not it is equal to or longer than a predetermined time T. Here, the predetermined time T is a time shorter than the time obtained by dividing the moving distance of the grinding wheel 20 on the peripheral surface by the feed speed of the dresser 1 in the direction b, by an allowable error.

Therefore, when the dressing is completed in a normal peripheral state where there is no dent in the peripheral surface of the grindstone 20 and no chipping of the tip of the grindstone as shown in FIG. 3A, the comparison signal as shown in FIG. Is high level for a predetermined time T or more.
At this time, the time comparison circuit 10 outputs an end signal (a determination signal that the peripheral surface state is normal) to the control circuit 11. When this end signal is input to the control circuit 11, the control circuit 11
Stops the dresser moving mechanism 2.

When there is a depression on the peripheral surface of the grindstone 20 as shown in FIG.
The rectified and smoothed signal shown in (b) is input to the level comparison circuit 8. Since the rectified and smoothed signal corresponding to the depression is lower than the threshold level TL, the level comparison circuit 8 outputs a low-level comparison signal during the period corresponding to the depression as shown in FIG. For this reason, the integration time of the high level of the comparison signal in the time comparison circuit 10 is the predetermined time T.
The time comparison circuit 10 determines that the time is less than
1 is output as a dressing continuation signal (a determination signal indicating that the peripheral surface state is not normal). Upon receiving the dressing continuation signal, the control circuit 11 drives the dresser moving mechanism 2 to continue the dressing cycle.

When the tip of the grindstone 20 is chipped as shown in FIG. 5A, the dresser 1 cannot contact the tip of the grindstone, and the integrated time signal is smaller than the predetermined time T by that time. In this case, as shown in FIG. 5B, a rectified smoothed signal that should be output at the beginning of the dressing is not output.
Since the rectified and smoothed signal at the beginning of the dressing corresponding to the tip missing is smaller than the threshold level TL, the level comparison circuit 8 outputs the low-level comparison signal to the next time measuring circuit 9 during the period corresponding to the tip missing. Since the time measurement circuit 9 integrates only the output time of the high-level comparison signal, the output time of the low-level comparison signal corresponding to the above-mentioned lack of the tip is not integrated, and as shown in FIG. The time corresponding to the chip is shorter than that of the whetstone having no chip, and the time comparison circuit 10 determines that the time is smaller than the predetermined time T, and the time comparison circuit 10 outputs a dressing continuation signal to the control circuit 11. You.
In this embodiment, since the quality of the peripheral surface state of the grindstone 20 is determined by comparing the integration time of the high-level comparison signal with the predetermined time T, it is not possible to distinguish between the hollow and the chipped end. In the case of a chipped end, the chipped end is not eliminated even if dressing is repeated. Therefore, the control circuit 11
It is preferable to stop the dresser moving mechanism 2 after performing a predetermined number of dressing cycles.

The present invention is not limited to the above-described embodiment, and various modes are possible. For example, instead of determining the threshold level based on the actual sensor output as in the above embodiment, the threshold level supply circuit may store a threshold level that changes linearly with time as a map. . Also in this case, the threshold level changes linearly according to the grindstone cross-sectional diameter at the contact portion. The threshold level supply circuit may store the threshold level as a linear function of the position of the dresser. In this case, a dresser position detecting means is required, and a dresser position signal must be supplied to a threshold level supply circuit in a dressing cycle. The grindstone does not need to have a conical shape, and may have another rotating body shape. Also, the determination means does not measure the output time of the high level of the comparison signal, but monitors the comparison signal at a predetermined time, and determines that the peripheral surface state is not normal if the comparison signal is at least once at the low level. Is also good. Further, the determination means may distinguish between the hollow and the missing end based on the time when the low level of the comparison signal appears.

[0014]

As described above, the apparatus for determining the peripheral surface condition of a grinding wheel according to the first aspect uses the threshold level that varies according to the diameter of the cross section of the grinding wheel, so that the rotating body whose cross sectional diameter changes is used. It is possible to accurately determine the state of the peripheral surface of the shaped grindstone, for example, the presence or absence of a depression. According to the second aspect, it is possible to easily set an appropriate threshold level based on the actual output of the ultrasonic sensor.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a basic configuration of the present invention.

FIG. 2 is a side view for explaining a movement trajectory when dressing a conical grindstone.

3A and 3B are diagrams for explaining a case of dressing a normal conical grinding wheel, and FIG. 3A is a diagram illustrating a positional relationship between the grinding wheel and a dresser. (B) is a diagram showing a relationship between a rectified smoothed signal and a threshold level. (C) is a diagram showing a comparison signal.

FIG. 4 is a view for explaining a case of dressing a conical whetstone 20 having a depression on a peripheral surface, and (a).
It is a figure which shows the positional relationship between the grindstone with a hollow and a dresser. (B) is a diagram showing the relationship between the rectified smoothed signal and its threshold level. (C) is a diagram showing a comparison signal.

5A and 5B are diagrams illustrating a case of dressing a conical grindstone having a chip at a tip, and FIG. 5A is a diagram illustrating a positional relationship between a grindstone having a chipped tip and a dresser. (B) is a diagram showing the relationship between the rectified smoothed signal and its threshold level. (C) is a diagram showing a comparison signal.

[Explanation of symbols]

Reference Signs List 1 dresser 2 dresser moving mechanism (moving means) 3 AE sensor (ultrasonic sensor) 7 threshold level supply circuit (threshold level supply means) 8 level comparison circuit (comparison means) 10 time comparison circuit (judgment means) 11 control circuit 20 grinding wheel 20a Rotary axis

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Yutaka Shiki 3-13-26 Yayumicho, Higashimatsuyama-shi, Saitama Prefecture Zexel Higashimatsuyama Plant (56) References JP-A-63-265106 (JP, A) ( 58) Field surveyed (Int. Cl. ⁷ , DB name) B24B 53/00

Claims (2)

(57) [Claims] An apparatus for determining the peripheral surface condition of a grindstone, which determines whether or not a grindstone having a shape of a rotating body and having a diameter of a transverse section changing along a rotation axis has a normal peripheral surface condition,
(A) a dresser, (b) a moving means for relatively moving the dresser in the direction of the rotational axis of the grindstone along the regular peripheral shape of the grindstone, and (c) accompanying the contact between the dresser and the peripheral surface of the grindstone. An ultrasonic sensor for detecting ultrasonic vibration generated by
(D) threshold level supply means for supplying a threshold level that changes in accordance with the diameter of the cross section of the grindstone at the contact portion as the contact portion between the dresser and the grindstone moves in the rotation axis direction of the grindstone; (E) comparing means for comparing the output from the ultrasonic sensor with the threshold level, and (f) determining means for determining whether or not the peripheral surface state of the grindstone is normal based on the comparison result. A device for determining the condition of the peripheral surface of a grindstone. The threshold level supply means determines in advance a normal output level in a normal peripheral surface state based on an actual output of the ultrasonic sensor when the dresser moves along a regular peripheral surface shape of the grindstone. 2. The apparatus according to claim 1, wherein a level lower than the normal output level by a predetermined amount is supplied as a threshold level.