JP2000225542A - Screw hole inspecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a screw hole inspecting device which can decide on success or failure of a screw hole accurately and efficiently by using a gage and air. SOLUTION: In a screw hole inspecting device provided with a gage main unit 12 having an external thread part 11 capable of insertion along a thread groove of a screw hole which must be inspected, a groove 20 is formed in an external peripheral part in the axial direction intermediate part of the external thread part 11 of the gage main unit 12. The groove 20 is continued in a peripheral direction of the gage main unit 12. An air jet nozzle 21 and air supply hole 22 are formed in the gage main unit 12. The air jet nozzle 21 is opened in the groove 20. The air supply hole 22 is connected to an air supply source supplying air of prescribed pressure and a back pressure sensor for detecting a back pressure of supply air.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a screw hole inspection apparatus suitable for use in judging whether or not the diameter of a screw hole is within a predetermined tolerance.

[0002]

2. Description of the Related Art For example, in a work (work) in which a plurality of screw holes are machined such as an engine cylinder block and the screw holes are required to have relatively high accuracy, each of the machined screw holes is machined. It is an important inspection item to determine whether the inner diameter or the like is within a predetermined tolerance. Conventionally, in an inspection process for determining a screw hole, an operator inspects the screw holes one by one using a jig called a screw gauge.
The screw holes may be through holes or non-through holes. 7A is a through hole, and FIG.
The screw hole 1 shown in (B) is an example of a non-through hole.

Conventionally, two different sizes of thread gauges have been used to determine the acceptability of a single screw hole 1. That is, as shown in FIG. 7 (A), the outer diameter of the screw hole 1 to be inspected is slightly smaller than the diameter of the thread hole 1 as shown in FIG. 7 (C). The "stop gauge 2b" whose outer diameter is slightly larger than that is used.

Here, if the diameter of the screw hole 1 is within a predetermined tolerance, as shown in FIG.
a can be inserted into the screw hole 1, and the stop gauge 2b cannot be inserted into the screw hole 1 as shown in FIG. In other words, if the gauge 2a cannot be inserted into the screw hole 1, it is determined that the hole diameter is small, and if the stop gauge 2b can be inserted into the screw hole 1, it is determined that the hole diameter is large. Either case is rejected.

[0005]

As described above, conventionally, two types of gauges 2a, 2a,
Since the gauges 2b are required, the handling of the gauges 2a and 2b becomes complicated. In particular, when there are a plurality of screw hole sizes to be inspected, the number of gauges becomes extremely large, such as the necessity of multiple gauges, and the time required for the inspection becomes long. In addition, the inspection result may be affected by the skill of the worker.

Therefore, the present inventors opened an air ejection hole on the side surface of the screw gauge, and inserted the screw gauge into the screw hole. A device for determining whether a screw hole is acceptable by flowing the air into a gap between the gauge and the outer surface and detecting the back pressure of the air was considered. That is, if the screw hole is within a predetermined tolerance, the amount of air that escapes from between the inner surface of the screw hole and the outer surface of the screw gauge is regulated,
It utilizes the fact that back pressure exceeding a certain value is generated.

However, according to the study of the present inventors,
It was found that the mere opening of the air ejection hole on the side surface of the screw gauge caused a large variation in the back pressure, and it was not always possible to make an accurate pass / fail judgment due to differences in the skill levels of the workers. The cause was thought to be that the contact condition between the screw gauge and the inner surface of the screw hole slightly changed for each screw hole, and the air outlet cross-section was partially blocked, and the air flow path cross-sectional area was reduced. And, as a result, back pressure. Incidentally, in order to efficiently determine the acceptability of a large number of screw holes in a short time, it is desirable to automate the inspection using a robot or the like.However, it is difficult to automate the screw hole inspection from the above-mentioned circumstances. there were.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a screw hole inspection apparatus capable of accurately and efficiently judging the acceptability of a screw hole using a gauge and air.

[0009]

To achieve the above object, a screw hole inspection apparatus according to the present invention is configured as described in claim 1. In this screw hole inspection device, a male screw portion of a gauge body is inserted into a screw hole to be inspected, and compressed air having a predetermined pressure is supplied from an air supply source to the air supply hole. The air supplied to the air supply hole is blown out from the air outlet of the gauge body, and is diffused along the groove in the circumferential direction of the gauge body, and is blown out between the outer surface of the male screw part of the gauge body and the inner surface of the screw hole. I do.

Here, if the diameter of the screw hole is within a predetermined tolerance, the amount of air escaping from between the inner surface of the screw hole and the outer surface of the male thread portion of the screw gauge is regulated, so that a certain value or more is obtained. Back pressure occurs. This back pressure is detected by back pressure detecting means connected to the air supply hole, and if a back pressure exceeding a predetermined value is detected, it is determined that the test is passed.

As the air referred to in this specification, general-purpose compressed air which can be easily used in a factory, such as a so-called factory air, is suitable. However, in some cases, an inert gas other than air, such as nitrogen, is also included. It is a concept. Air supply pressure is
For the reasons described below, around ² kgf / cm ²
It is recommended that the pressure be 1 kgf / cm ² or more and less than 3 kgf / cm ² .

In the screw hole inspection apparatus according to the present invention, the air supplied from the air supply source to the air supply hole diffuses in the circumferential direction of the gauge body along the groove and blows out toward the inner surface of the screw hole. A stable back pressure is generated without being substantially affected by the state of contact between the main body and the inner surface of the screw hole.

In the screw hole inspection apparatus according to the present invention, a torque sensor may be added to the gauge main body to detect a screwing torque when the gauge main body is inserted into the screw hole. In this case, when a torque exceeding a predetermined value is detected, or when the male screw portion cannot be inserted into the screw hole, it is determined to be “small hole diameter (fail)”. By doing so, it is also possible to find screw holes with incompletely processed screw grooves, in addition to screw holes with “small hole diameter”.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A screw hole inspection apparatus 10 according to one embodiment of the present invention will be described below with reference to FIGS. The screw hole inspection device 10 shown in FIG. 2 includes a gauge main body 12 having a male screw portion 11 having a pitch that can be inserted along the screw groove 1a of the screw hole 1 to be inspected. The male screw portion 11 is provided at the tip of the shaft 13. The shaft 13 is provided, for example, in a rotation mechanism 15 having a torque sensor 14, and can be rotated by, for example, a servomotor or the like. In addition,
The gauge body 12 may be a manual type in which an operator who inspects the screw hole 1 rotates the shaft 13 by hand.

As shown in FIG. 1, the gauge body 12 has a ring-shaped groove 20 formed in the outer peripheral portion of the externally threaded portion 11 at the axially intermediate portion, and an air outlet 21 communicating with the groove 20. ing. The groove 20 is continuous in the circumferential direction of the gauge body 12. In the case of the illustrated example, the cross section of the groove 20 along the axial direction is semicircular.

The air outlet 21 is open at a plurality of positions in the groove 20. These air outlets 21 are preferably opened at equal intervals in the circumferential direction of the gauge main body 12 as a preferred form, and in the illustrated example, are opened at two positions at 180 ° intervals in the circumferential direction of the gauge main body 12. Let me. An example of the inner diameter of the air outlet 21 is φ2.0 mm.

The air outlet 21 communicates with an air supply hole 22 formed in the gauge body 12. As shown in FIG. 2, the air supply hole 22 passes through the shaft 13 and communicates with the air supply pipe 30. The air supply pipe 30 is provided with a throttle 31
, A regulator 32, a filter 33 and the like, and connected to a compressed air supply source 34 such as factory air. The air supply source 34 generates, for example, a pressure of 2 kgf / cm ² or more at a gauge pressure, and can supply the air adjusted to a predetermined pressure (eg, 2 kgf / cm ² at a gauge pressure) by the regulator 32 to the air supply hole 22. It has become.

A back pressure sensor 40 is provided in the middle of the air supply pipe 30.
, A supply pressure sensor 41 is provided. Back pressure sensor 4
0 is provided on the downstream side of the throttle unit 31 and the supply pressure sensor 41
Is provided on the upstream side of the throttle unit 31. The supply pressure sensor 41 has a function of monitoring the pressure so that the air supply pressure becomes, for example, 2 kgf / cm ² . The back pressure sensor 40 functioning as a back pressure detecting means has a function of detecting a pressure between the throttle section 31 and the air supply hole 22, that is, a back pressure of the air. The back pressure sensor 40 and the torque sensor 14 are electrically connected to an information processing device 43 such as a personal computer via an analog / digital converter 42.

Next, the operation of the screw hole inspection device 10 having the above configuration will be described. The distal end of the male screw portion 11 of the gauge body 12 is opposed to the screw hole 1 to be inspected, and the male screw portion 11 is inserted into the screw hole 1 by rotating the shaft 13. At this time, the external thread 11 is detected by the torque sensor 14.
When the torque exceeding a predetermined value is detected, or when the male screw portion 11 cannot be inserted into the screw hole 1, it is determined that the hole diameter is small (fail). The pass / fail judgment based on the detected torque value may be performed by an operator, but may be automatically performed by the information processing device 43. By using such a torque sensor 14, it is possible to find a screw hole in which the machining of the screw groove 1a is incomplete, such as a case where the screw hole 1 is "small hole diameter".

The male screw portion 11 is inserted into the screw hole 1, and compressed air is supplied from the air supply source 34 to the air supply hole 22 through the regulator 32 and the throttle portion 31. That is, the air sent from the air supply source 34 is supplied to the regulator 3
2, the pressure is reduced to a predetermined pressure (for example, 2 kgf / cm ² ), and is supplied to the air supply hole 22 through the throttle unit 31.
The air supplied to the air supply hole 22 is ejected from the air ejection port 21 and diffuses in the circumferential direction of the gauge body 12 along the groove 20 and is ejected between the male screw portion 11 and the inner surface of the screw hole 1. .

Here, if the hole diameter of the screw hole 1 is within a predetermined tolerance, the inner surface of the screw hole 1 and the male screw portion 11 are inserted in a state where the male screw portion 11 is inserted until it is completely hidden in the screw hole 1. The amount of air escaping to the outside from between the outer surface and the outside surface is regulated, thereby generating a back pressure exceeding a certain level.
This back pressure is detected by the back pressure sensor 40, and when a back pressure exceeding a predetermined value is detected, it is determined that the screw hole diameter is within a predetermined tolerance.

In this embodiment, since the air supplied to the air supply hole 22 spreads in the circumferential direction of the gauge body 12 along the groove 20 and blows out from the circumferential portion of the groove 20 toward the inner surface of the screw hole 1, A stable back pressure is generated without being affected by the state of contact between the male screw portion 11 and the inner surface of the screw hole 1.

FIG. 3 shows that the air supply pressure of test pieces having screw holes of various sizes (hole diameters) is 2 kgf /
The results obtained by measuring and organizing the relationship between the hole diameter and the back pressure in the case of cm ² are shown. As can be seen from this figure, if the hole diameter was in the range from the reference value D to around +0.072 mm, the back pressure could be maintained at about 2 kgf / cm ² , but immediately before the hole diameter exceeded the tolerance (+0.15 mm). The back pressure has been significantly reduced. In this case, for example, when the back pressure is 1.5
If it is not less than kgf / cm ^2, it can be determined that the hole diameter is within the tolerance.

FIG. 4 shows the effect of the air supply pressure on the back pressure by three types of air supply pressures (1, ² , 3 kgf / cm ² ).
It is the result of having investigated about. Two types of screw holes, a through hole and a non-through hole, were compared. Here, when the air supply pressure was 2 kgf / cm ² , stable back pressure was detected in both the through holes and the non-through holes. At 3 kgf / cm ² ,
In particular, the degree of influence in the case of a non-through hole is large, and accurate determination is difficult. From FIG. 4, it is expected that when the pressure is less than 1 kgf / cm ² , the variation ΔP / 3σ of the back pressure is considerably deteriorated in the case of the non-through hole. For these reasons, the air supply pressure is set at 1 kgf / c around ² kgf / cm ^2.
It is recommended that it is not less than m ^{2 and} less than 3 kgf / cm ² .

FIG. 5 shows six types of gauges (A) to
Regarding (F), the back pressure was measured for two types of screw holes (through hole and non-through hole) in the case where the cutting fluid did not adhere (dry) and in the case where the cutting fluid adhered (wet). , The result of measuring the probability of occurrence of erroneous detection. The air supply pressure was 2 kgf / cm ^2, and each measurement was performed 10 times. The measurement position is at the center of the screw hole depth.

In FIG. 5, (A),
(B) and (C) are gauges (without grooves) each having the shape shown in FIG. 6 (A), and the length L of the male screw portion 50 is 10 m.
m, the hole diameter d of the air ejection port 51 is φ1.5 mm,
φ2.0 mm and φ2.5 mm. (D) in FIG. 5 is a short type in which the length L of the male screw portion 50 is 5 mm.

(E) in FIG. 5 shows a measurement result of one embodiment of the present invention (the gauge body 12 having the groove 20). (F) in FIG. 5 is a gauge (without grooves) in which a counterbore 52 having an inner diameter of 4 mm is formed in the air ejection port 51 as shown in FIG. 6 (B). As can be seen from these measurement results, the above embodiment (gauge body 12 having groove 20)
It was confirmed that, regardless of whether the threaded hole was a through hole or a non-through hole, the probability of erroneous detection was extremely lower than that of any other gauge, regardless of the presence or absence of cutting fluid (dry or wet).

In carrying out the present invention, it goes without saying that the constituent elements of the present invention, such as the gauge body, the male screw portion, the groove, the air outlet, and the air supply hole, can be variously changed as necessary. No. Further, even if the gauge body 12 is manually inserted into the screw hole 1 without providing the torque sensor 14 and the rotation mechanism 15 described in the above embodiment, the intended object of the present invention can be achieved. is there.

[0029]

According to the screw hole inspection apparatus of the present invention, the back pressure of the air blown out from the air outlet of the gauge body depends on the contact state between the gauge body and the inner surface of the screw hole. Can be avoided and a back pressure corresponding to the screw hole diameter can be generated, so that the acceptability of the screw hole can be accurately determined. Moreover, according to the present invention, it is not necessary to use two types of conventional gauges, such as a "street gauge" and a "stop gauge", and it is possible to judge the quality of a screw hole using one type of gauge body. can do.
If the gauge body is mounted on a robot arm or the like and teaching is performed in advance on the positions of the screw holes and the like, it is possible to cope with automation of the inspection of the screw holes of a workpiece having a large number of screw holes.

[Brief description of the drawings]

FIG. 1 is a side view of a gauge body showing one embodiment of the present invention.

FIG. 2 is a schematic diagram of a screw hole inspection device having the gauge body shown in FIG. 1;

FIG. 3 is a diagram showing a relationship between a screw hole diameter and a back pressure.

FIG. 4 Variations in three types of air pressure and back pressure ΔP / 3σ
FIG.

FIG. 5 is a diagram showing the relationship between the shape of the gauge body and the probability of erroneous detection.

FIG. 6 is a sectional view showing a comparative example of the gauge body.

FIG. 7 is a sectional view showing a conventional thread gauge.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Screw hole 1a ... Screw groove 10 ... Screw hole inspection device 11 ... Male screw part 12 ... Gauge body 14 ... Torque sensor 20 ... Groove 21 ... Air ejection port 22 ... Air supply hole 34 ... Air supply source 40 ... Back pressure sensor ( Back pressure detecting means)

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Kazuhiro Katagiri, 130 Rokujizo, Ritto-cho, Kurita-gun, Shiga Prefecture Mitsubishi Heavy Industries, Ltd. F-term in Kyoto Seiki Mfg. Co., Ltd. (Reference) 2F062 AA36 BB03 BC61 CC27 EE09 EE62 FF13 FF17 GG29 GG46 GG81 3C029 BB04 EE02 3C038 AA01 BC01 BC02 CA06 EA02

Claims (1)

[Claims] An air supply source for supplying air having a predetermined pressure and a back pressure detecting means for detecting a back pressure of the supply air. A screw hole inspection device provided with a gauge body to be connected, a groove formed in an outer peripheral portion of an axially intermediate portion of the male thread portion of the gauge body, and a groove provided in a circumferential direction of the gauge body; An air ejection port formed in the main body and opening into the groove; and an air supply hole communicating with the air ejection port and connected to the air supply source and the back pressure detecting means. Screw hole inspection device.