JPS637322B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a conical surface inspection apparatus for a circular member, and more particularly to an improved conical surface inspection method and apparatus that can optically and automatically inspect a conical surface in a non-contact manner.

BACKGROUND ART Circular members are used in various industrial fields for sealing and many other purposes, and are made of various materials such as elastic materials such as rubber or plastics. This type of circular member has a conical surface that forms a sealing part, etc., and defects in this conical surface can cause a big problem, and even in the past, there has been a demand for a method to precisely inspect defects in this conical surface. It had been.

For example, as is well known, various seal members are used in hydraulic or hydraulic equipment, and in particular, ring-shaped or cup-shaped circular seal members are used for pistons that slide within cylinders. The sealing element forms the most important functional component for pressure transmission. Therefore, the conical sealing surface of the circular sealing member must be machined with high precision, and surface defects can cause pressure leaks, reduced durability, and damage to the sealing member, so it must be processed with high precision before being incorporated into equipment. Its quality must be thoroughly inspected.

As the aforementioned circular seal member, the rubber cup in the brake cylinder of automobiles is well known, and it forms an important functional part that converts the driver's brake pedal force into hydraulic pressure and applies braking force to the wheels. Good quality and high durability are required because deterioration in quality has a major impact on the braking function of automobiles. Therefore, all cups for automobiles, etc. must be inspected before they are assembled into brake cylinders to reliably detect even minute surface defects, and such cups must be removed as defective products.

Defects in conventional circular seal members are mainly detected by visual inspection, and in the case of the cups and the like described above, visual inspection is performed on all units, which has the disadvantage of requiring a large number of inspectors. Furthermore, visual inspection has the disadvantage that there are large variations in inspection accuracy due to individual differences or fatigue levels, and that it is not possible to automatically and effectively inspect a large number of seal members.

The present invention was made in view of the above-mentioned conventional problems, and its purpose is to perform automatic non-contact optical inspection of a circular member made of a soft material such as rubber, without mechanically deforming it. It is an object of the present invention to provide an improved conical surface inspection method and apparatus that can reliably inspect even the smallest defects and eliminate them as defective products.

In order to achieve the above objective, a rotating table is used to place and rotate a circular member, and a scanning control is performed on the conical surface of the circular member at a scanning speed that is sufficiently faster than the rotational speed of the rotating table, approximately parallel to the rotation axis of the rotating table. a polarized scanning light source that emits inspection light, a photoelectric detector that receives specularly reflected light from a conical surface and converts it into an electrical signal, and a photoelectric detector that continuously transmits the electrical signal of the photoelectric detector during at least one revolution of the turntable. a defect detection circuit that detects a defect by diffused reflection generated from a defect on a processed conical surface, and the defect detection circuit includes a comparison circuit that performs a difference operation to compare an output of a photoelectric detector and a floating threshold value obtained based on the output. a delay attenuation circuit that delays the output of the photoelectric detector for a predetermined time and attenuates it to a predetermined level; a sample-and-hold circuit that samples and holds this delayed and attenuated signal and outputs it to the comparator as a floating threshold signal, and the floating threshold of the sample-and-hold circuit is set while the comparator outputs the defect detection signal. It is characterized by being able to optically inspect conical surfaces in a non-contact manner.

Preferred embodiments of the present invention will be described below based on the drawings.

FIG. 1 shows an automobile cup as a preferred example of a circular member used for inspecting surface defects in the present invention, and this circular seal member 10 is made of soft rubber and is axially It has a symmetrical shape and is inserted into an automobile brake cylinder so that its outer circumferential surface acts as a conical sealing surface. The sealing member 10 in FIG. 1 has four main sealing parts, namely, a conical sealing surface 10a, 10b consisting of two truncated conical surfaces that contact the cylinder, and an outer periphery forming the ridge of both sealing surfaces 10a, 10b. 10c and a ring-shaped machined surface 10d on the upper surface of the sealing member 10. In the following example, a method and apparatus for inspecting the two truncated conical sealing surfaces 10a and 10b for surface defects will be described. .

FIG. 2 shows a preferred embodiment of the seal surface inspection device according to the present invention, in which the circular seal member 10 is placed on a rotary table 12, and the seal member 10 is placed on a rotary table 12.
The shaft 100 of the rotary table 12 and the rotary table shaft 200 of the rotary table 12 are positioned substantially on the same axis. A bevel gear 16 is fixed to the rotary table shaft 14 of the rotary table 12, and by meshing and coupling the small bevel gear 20 fixed to the motor 18 and the bevel gear 16, the bevel gear 16 is rotated by the rotation of the motor 18. The stand 12, ie, the circular seal member 10, is rotated in the direction of arrow A.
An encoder 22 is fixed to the lower end of the rotary table shaft 14, and the rotational position and angle of the sealing member 10 are electrically detected as a rotational angle signal, and this signal is supplied to a defect detection circuit 24.

A polarized scanning light source 26 is provided near the sealing member 10, and the polarized scanning light source 26 is connected to the laser 2.
8, a gas laser 28 such as a helium neon laser emits a thin light beam with good monochromaticity and directivity, and the thin light beam is sent through a prism system 30 to an optical deflector 32. The optical deflector 32 has a mirror that vibrates according to its own vibration period or a mirror that deflects light in synchronization with a light flow signal supplied from the outside, and in the embodiment, can deflect light over a wide angle. A galvanometer mirror is used. The deflection plane of the optical deflector 32 is set along the rotation axis 200 of the rotary table 12, and as a result, the optical deflector 32
The polarized light reflected from the beam advances toward the rotation axis 200, and furthermore, this polarized light is reflected by the arrows B and C of the optical deflector 32.
Scanning control is performed according to the vibrations of the Of course, the scanning speed of the optical deflector 32 due to the mirror vibration is set to be sufficiently faster than the rotational speed of the rotary table 12. The polarized scanning light source 26 further includes a projection lens 34 , and the fan-shaped polarized light is converted by the projection lens 34 into parallel light rays along the scanning plane, and the parallel light rays are transmitted to the conical seal of the sealing member 10 . The surfaces 10a and 10b are scanned and irradiated. That is, the light beam scanned in parallel by the light projecting lens 34 can eliminate variations in inspection sensitivity caused by the type or eccentricity of the sealing member 10, and since the light beam is focused, Detection resolution can be significantly improved.

The parallel light beam from the polarized scanning light source 26 is reflected by both conical seal surfaces 10a and 10b of the seal member 10, received by photodetectors 36 and 38, and converted into electrical signals. Both photoelectric detectors 36 and 38 are provided at positions to receive specularly reflected light when there are no defects on the surfaces of both conical seal surfaces 10a and 10b, and the detection electric signals of both detectors 36 and 38 are sent to the defect detection circuit 24. Supplied.

Inspection information from the above-mentioned rotary table 12, polarized scanning light source 26, and photoelectric detectors 36, 38 is supplied to the defect detection circuit 24, and this information is continuously processed during at least one revolution of the rotary table 12, Defects are detected by diffused reflection caused by defects on the seal surfaces 10a and 10b, and a sorting mechanism 40 is driven by the output of the defect detection circuit 24, and seal members 10 taken out from the rotary table 12 are classified as non-defective products depending on whether the conical seal surfaces are good or bad. and are sorted out as defective products. Furthermore,
The output of the defect detection circuit 24 is supplied to the supply mechanism 42, and the next circular seal member 10 to be inspected is transferred to the rotating table 12.
A control action is taken to supply the

A preferred embodiment of the present invention has the above configuration,
The effect will be explained below.

In this embodiment, the inspection of one seal member 10 is completed by one rotation of the rotary table 12, and then the next seal member 10 is placed on the rotary table 12 by the supply mechanism 42. At this time, the axis 100 of the seal member 10 is set at a position that almost coincides with the rotation axis 200 of the rotary table 12, but even if there is a slight deviation between the two axes 100, 200, in the present invention, the deflection scanning light source 26 The parallel line of irradiation from the irradiation area has an irradiation area that fully covers the conical sealing surfaces 10a, 10b that need to be inspected, and both conical sealing surfaces 10a,
Even if the specularly reflected light from 10b changes slightly in its position, it is received by the photoelectric detectors 36 and 38, which have a sufficiently large area for these specularly reflected lights, so that the deviation of the axes 100 and 200 can be inspected. It does not significantly affect performance.

After the seal member 10 is placed on the rotary table 12,
The rotary table 12 is driven to rotate at a constant speed by the motor 18, and at the same time, the conical seal surfaces 10a and 10b are irradiated with finely focused scanning light from the polarized scanning light source 26 at a scanning speed greater than the rotational speed of the rotary table 12. .

In FIG. 3, the conical sealing surfaces 10a, 1 of the sealing member 10 are
0b is shown being scanned over its entire surface, and by rotating the sealing member 10 in the direction of the arrow A and reciprocating scanning movement D of the irradiation light, a light spot trajectory indicated by 300 is obtained, and the rotary table 12 The entire conical sealing surface 10a, 10b can be scanned during one rotation of the conical sealing surface 10a, 10b. Although the light spot locus 300 in FIG. 3 is shown roughly to simplify the explanation, in reality, the deflection speed of the deflection scanning light source 26 is set to be larger than the rotation speed of the rotary table 12. The light spot trajectory 300 draws an extremely dense trajectory.

As shown in FIG. 1, the irradiated light from the projection lens 34 is reflected from both conical seal surfaces 10a, 10b and advances to the photoelectric detectors 36, 38 as specularly reflected lights 400a and 400b. The specularly reflected lights 400a and 400b in FIG.
b indicates the reflected light from a normal surface with no defects, and if there are defects or other defects on both conical seal surfaces 10a and 10b, the reflected light will be diffusely reflected, and as a result, photoelectric detection will occur when scanning the defective part. Vessels 36, 38
It is understood that the detected signal value of is significantly reduced. Therefore, by detecting the fluctuation of this output signal with the defect detection circuit 24, it is possible to inspect the quality of the seal member 10.

FIG. 4 shows the output waveform of the photoelectric detector 36 during one scanning cycle of the irradiated light, and as is clear from _FIG . Complete the scanning of the conical seal surface 10a in the range up to t ₂ , and further scan the conical seal surface 10b by scanning downward,
The lowest scanning position is reached at time T/2, from which a reverse scan is performed, the conical seal surface 10b is scanned again, and then the conical seal surface 10a is scanned from bottom to top from time _t3 to _t4 . One scan is completed at time T.

FIGS. 4B and 4C show the electrical output signals of the photodetector 36, B when the conical sealing surface 10a has a normal planar state, and C when the conical sealing surface 10a has a normal planar state.
The case where a has a defect is shown. As is clear from FIG. 4B, at times t ₁ to _{t 2} and t ₃ to _{t 4} , an almost constant detection signal is obtained from the photoelectric detector 36, although there is some fluctuation, and the specularly reflected light is stabilized. Therefore, it can be determined that there are no defects within this scanning area.On the other hand, in Figure 4C, there is a part where the electrical output signal decreases significantly as a result of diffuse reflection due to surface defects, and from this, it can be determined that there is no defect in this scanning area. Seal surface 10a
It can be determined that there are surface defects such as scratches.

In the above manner, the photoelectric detector 36 or 3
If the electrical detection signals from 8 are continuously processed during one rotation of the rotary table 12, the conical seal surfaces 10a and 10b
Defects can be detected over the entire surface, but
Due to uneven reflectance depending on the location of the conical seal surfaces 10a and 10b, eccentricity between the seal member 10 and the rotary table 12, and other causes, a large signal value may occur even though there are no surface defects during one rotation of the rotary table 12. Variations may occur. FIG. 5A shows a case in which periodic fluctuations occur during one revolution of the turntable 12 due to the various causes described above, and for signals containing such large fluctuations, a conventional general defect detection circuit 24 is used. Correct test results cannot be obtained by comparison using fixed threshold values. That is, FIG. 5B shows a state in which the fixed threshold value V _H is applied to all detection signals during one revolution of the rotary plate, and if the fixed threshold value V _H is increased to a certain extent to prevent noise mixing, FIG.
There are cases where a signal is determined to be a defective signal even though it is a normal portion, and it is difficult to use such a fixed threshold value comparison type defect detection circuit in the present invention.

For this reason, a floating threshold type circuit has been proposed as another conventional defect detection method, and as shown in FIG. 6A, there is a corresponding slight delay with respect to the detection signal value shown by the solid line. Set a floating threshold indicated by a broken line with
It consists of a circuit configuration that outputs the discrimination signal shown in Figure B. According to this floating threshold method, it is possible to eliminate the influence of periodic detection signal value fluctuations shown in FIG. There were drawbacks such as the inability to detect defects at the scanning start point or end point of the sealing surface 10a.

From the above, in the embodiment of the present invention, the defect detection circuit 24 shown in FIG. 7 is used, and the conventional floating threshold method is further improved to provide a circuit that can reliably detect surface defects like the present invention. providing.

Although FIG. 7 shows the processing circuit on the photoelectric detector 36 side, the photoelectric detector 38 side also consists of the same processing circuit. The photoelectric detector 36 includes a photodiode, etc., and converts the specularly reflected light 400a from the conical seal surface 10a into an electrical signal with an amount of electricity corresponding to the amount of received light, and the output thereof is supplied to the positive input terminal of the comparator 44. and the other is converted into a floating threshold and supplied to the negative input terminal of the comparator 44. That is, the output of the photoelectric detector 36 is delayed by a predetermined amount in the delay circuit 46, and the output is attenuated by the attenuator 48. As a result, the output of the attenuator 48 can reduce fluctuations in the specularly reflected light from the normal surface, while providing sufficiently detectable signal change characteristics for the diffusely reflected light from the defective surface. A bias voltage from a bias voltage generator 52 is added to the output of the attenuator 48 by an adder 50, and this bias voltage is set to a voltage value slightly larger than the dark voltage of the photoelectric detector 36. As a result, Adder 50 outputs a floating threshold. A characteristic feature of this embodiment is that the floating threshold value of the adder 50 is supplied to the comparator 44 via the sample and hold circuit 54, and the hold input of the sample and hold circuit 54 is supplied to the comparator 44. The floating threshold output from the sample and hold circuit 54 is held at the threshold when the defect detection signal is output from the comparator 44, and when the detection signal from the comparator 44 disappears. The hold action of the sample and hold circuit 54 is released again, and the floating threshold value from the adder 50 can be output to the comparator 44 as is.

Defect detection on the photoelectric detector 36 side is performed as described above, and the output of the comparator 44 is further electrically processed and converted into a signal for determining the quality of the seal member. The operation will be explained below with reference to the waveform diagram in FIG.

FIG. 8A shows both inputs of comparator 44, with the solid line showing the positive input provided directly from photodetector 36 and the dashed line showing the floating threshold input provided from sample and hold circuit 54. Further, FIG. 8B shows the output of the comparator 44, in which a "1" signal is output when the surface of the conical sealing surface 10a is normal, and a "0" signal is output when the surface is defective.

In the initial state up to time t ₁ when the surface condition of the conical seal surface 10a is detected, the specularly reflected light 400a is not supplied to the photoelectric detection section 36, so the output of the comparator 44 becomes "0", and at this time, the sample and hold circuit 54 is in a hold mode and holds the previous floating threshold. From time t ₁ to conical seal surface 1
When the optical scanning of 0a is started and the specularly reflected light is received by the photoelectric detector 36, its output increases, and when the output of the photoelectric detector 36 becomes higher than the threshold value held in the sample hold circuit 54, the comparator 44 It is inverted and outputs a "1" signal. As a result, the hold of the sample and hold circuit 54 is released, and its output, the floating threshold, delays the output voltage of the photoelectric detector 36 and outputs a further attenuated voltage.
If there is a defect on the surface, when the optical scanning reaches the defective portion, the amount of light received by the photoelectric detector 36 decreases rapidly, and as a result, the detection output also decreases rapidly. Then, at time _t5 , the output of the comparator 44 is "0"
Then, a defect detection signal is output, and at this moment, the sample and hold circuit 54 is held again, so that the floating threshold voltage at this time can be held. Then, when the optical scanning passes through the defect and the amount of received light returns to normal, the output of the photoelectric detector 36 becomes higher than the output of the sample and hold circuit 54 again, and the time
At _t6 , the comparator 44 is inverted and the sample and hold circuit 54 returns to the tracking mode again. Therefore, the output value of the sample and hold circuit 54 is held during the period t ₅ to _{t 6} during which the defective part is scanned, and it is possible to ensure that the defect signal is reduced or not detected at both ends of the scanning area as in the conventional case. can be prevented. A similar sample and hold action is performed at times _t3 to _t4 when the conical seal surface 10a is scanned from bottom to top, and the above-described hold action of the sample and hold circuit 54 is performed at times _t7 to _t8 .

As described above, according to this embodiment, it is possible to eliminate the drawbacks of the conventional floating threshold method, and to adjust the optimal comparison threshold by adding changes in the amount of reflected light. This makes it possible to solve the problem of indistinguishability in the parts.

In FIG. 7, the defect detection signal of comparator 44 is supplied to one input of gate 56 for digital processing and is ANDed with the clock pulse of clock oscillator 58 supplied to the other input of gate 56. gate 5 of the half period of the deflection scan
The floating pulse passing through the first counter 60
is counted. The count value of the first counter 60 is reset every half period of the deflection scan by the output of the polarization control circuit 62 of the optical deflector 32, and as a result,
The count value of the first counter 60 decreases as the defect detection time increases within a half period of the scanning period, and thereby the size of the defect can be detected as a digital value.

At the same time, the output of the comparator 44 is directly counted by the second counter 64. The second counter 64 is also reset by the output of the deflection control circuit 62 every half period of the deflection scan. Both counters 60, 6
The output of No. 4 is supplied directly and via an OR gate 66 to an arithmetic unit 68, which processes the counts from both counters 60 and 64 during one revolution of the turntable 12. Therefore, the arithmetic unit 68 compares the counted value of the first counter 60 detected every half cycle with the previous counted value, and detects a surface defect by a sudden change in the counted value based on the difference between the two. For defects that are long in the direction perpendicular to the deflection scanning direction, the second counter 64
Defects can be determined based on the counted value from .
That is, the variation in the count value of the first counter 60 detects a long defective part in the deflection scanning direction as a variation in the count value.
Although the fluctuation of the counted value of the counter 60 is small, the presence or absence of a defect can be detected every half cycle from the second counter 64, and if this continues for a predetermined period, the arithmetic unit 68 outputs a defect signal. Can be done. The second counter 64 outputs a count value of 2 or more when there is at least one defect in each half cycle,
For this purpose, the OR gate 66 uses the second counter 64
The Q outputs of 2 bits or more are ORed,
When there is at least one defect, the OR gate 66 outputs a defective signal to the arithmetic unit 68, and the arithmetic unit 6
8 calculates this across the rotational direction of the turntable 12 to identify defects.

As described above, the quality determination signal of the defect detection circuit 24 is transmitted directly to the sealing member 10 by means of a display lamp or the like.
The quality of the seal members can be determined, and defective seal members can be removed by the sorting mechanism 40.

In the above embodiments, the circular member was described as a circular seal member, but the present invention is also applicable to circular members such as rubber plugs or rubber rings having a conical surface on the outer periphery.

As explained above, according to the present invention, the conical surface of a circular member is automatically inspected optically in a non-contact manner,
It eliminates the variations in conventional visual inspection and allows a large number of circular parts to be uniformly inspected fully automatically.
It becomes possible to significantly improve inspection efficiency.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a preferred example of a circular member to be inspected according to the present invention, FIG. 2 is a schematic configuration diagram showing a preferred embodiment of a conical surface inspection device according to the present invention, and FIG. is an explanatory diagram showing the deflection scanning state of the conical surface in Fig. 2, Fig. 4 is a waveform diagram showing the photoelectric conversion action in Fig. 2, and Figs. 5 and 6 show problems with the conventional photoelectric conversion action. FIG. 7 is a circuit diagram showing a specific example of the defect detection circuit used in the embodiment of FIG. 2, and FIG. 8 is a waveform diagram showing the defect detection operation of FIG. 7. 10... Circular seal member, 10a, 10b...
Conical seal surface, 12... Turntable, 24... Defect detection circuit, 26... Deflected scanning light source, 36, 38...
Photoelectric detector, 40... sorting mechanism.

Claims (1)

[Scope of Claims] 1. A rotary table on which a circular member is placed and rotated, and a conical surface of the circular member is scan-controlled almost parallel to the rotation axis of the rotary table at a scanning speed sufficiently faster than the rotational speed of the rotary table. A polarized scanning light source that irradiates inspection light, a photoelectric detector that receives specularly reflected light from a conical surface and converts it into an electrical signal, and the electrical signal of the photoelectric detector is continuously processed during at least one rotation of the rotary table. a defect detection circuit that detects a defect by diffused reflection generated from a defect on a conical surface, and the defect detection circuit includes a comparator that performs a difference operation to compare an output of a photoelectric detector and a floating threshold value obtained based on the output. and a floating threshold circuit that forms a floating threshold according to the output of the photoelectric detector, the floating threshold circuit delaying the output of the photoelectric detector for a predetermined time and attenuating it to a predetermined level; a sample-and-hold circuit that samples and holds the delayed and attenuated signal and outputs it to the comparator as a floating threshold signal, and the floating threshold of the sample-and-hold circuit is held while the comparator outputs the defect detection signal. A conical surface inspection device for a circular member, characterized in that the conical surface can be optically inspected in a non-contact manner.