JP4991613B2 - Steel workpiece inspection equipment - Google Patents

Description

  The present invention relates to a steel workpiece inspection apparatus for generating an eddy current in a steel workpiece and measuring a change in a magnetic field generated by the eddy current.

  When steel workpieces such as gears are manufactured, it is inspected whether these steel workpieces have a predetermined strength. It is desirable to use a non-destructive inspection method for inspecting such a final product without destroying the steel workpiece.

As a non-destructive inspection method, an inspection apparatus has been proposed in which an eddy current is generated in a steel workpiece and a change in a magnetic field generated by the eddy current is measured (see, for example, Patent Document 1).
JP 2004-108873 A (FIG. 2)

Patent document 1 is demonstrated based on the following figure.
FIG. 12 is a diagram for explaining the basic principle of the prior art, in which an excitation coil 102 and a detection coil 103 are wound around a cylindrical workpiece 101. Then, an AC voltage (excitation voltage) is applied to the excitation coil 102 from the AC power source 104. Then, an eddy current is generated on the surface layer of the cylindrical workpiece 101. This eddy current generates an alternating current in the detection coil 103. The voltage (detection voltage) of the generated alternating current is measured by the measuring device 105.

  According to this measurement, if the voltage of the alternating current generated in the detection coil 103 is measured, the strength of the cylindrical workpiece 101 can be measured, and the strength of the workpiece can be measured quickly.

  By the way, when such a measurement is performed manually, the problem described in the next figure arises.

  FIG. 13 is a diagram for explaining a problem in the prior art. The distance from the tooth tip 108L on the left side of the gear 107 (L is a subscript indicating the left side) to the excitation and detection coils 102 and 103 is L1, and the gear 107 When the distance from the right tooth tip 108R (R is a suffix indicating the right side) to the excitation and detection coils 102 and 103 is L2, and the strength of the gear 107 is manually measured, L1 and L2 are the same distance. It may not be. If the distance between L1 and L2 is different, an error may occur in the measurement result.

In addition, it is considered that further errors can occur when the gear 107 is tilted.
Therefore, the inventors conducted an experiment on an error caused by the inclination of the gear 107. The voltage detected from the detection coil 103 at that time was measured while changing the angle (insertion angle) facing the excitation and detection coils 102 and 103 using the same gear 107.

FIG. 14 is a graph for explaining the relationship between the insertion angle of the gear and the voltage measurement value. The horizontal axis indicates the gear insertion angle, and the vertical axis indicates the voltage measurement value.
In P1 where the voltage measurement value was the highest, the voltage was 1600 mV, and in P2 where the voltage measurement value was the lowest, the voltage was 400 mV. It was found that by changing the insertion angle of the gear, the difference in the voltage measurement value was up to 4 times.

Different voltage measurements result in different measurement results for the same workpiece.
It is desired to provide a steel workpiece inspection apparatus that has no error in measurement results even when measured manually, that is, has high reliability.

  This invention makes it a subject to provide the inspection apparatus of the steel workpiece | work with high reliability.

The invention according to claim 1 is an excitation coil that is supported by an iron core and is placed in the vicinity of the steel workpiece and generates eddy current in the steel workpiece, and is placed in the vicinity of the steel workpiece that is supported by the iron core. In a steel workpiece inspection device comprising a detection coil for measuring a change in magnetic field generated by the eddy current,
This inspection device is an inspection device that includes a contact member that extends from the iron core and has a tip that contacts the steel workpiece and makes the distance from the steel workpiece to the detection coil constant .
The steel workpiece is a gear that has been vacuum carburized,
The abutting member includes a sphere to be brought into contact with the workpiece, and a support portion that connects the sphere to the iron core, and is provided in at least two in the tooth width direction of the gear,
At the tip of the iron core, a plurality of female screw holes configured in a female screw shape are provided,
At the tip of the support portion, a male screw portion configured in a male screw shape is provided,
The male screw portion is screwed into any female screw hole among the plurality of female screw holes .

The invention according to claim 2 is characterized in that the shape of the detection coil is a columnar shape, and the axis of the detection coil is disposed along the tooth bottom of the gear .

The invention which concerns on Claim 3 acquires the detection information from a detection coil, converts the carburizing depth into a carburized depth conversion device, and compares the obtained carburized depth with an acceptable reference depth to determine pass / fail. And a pass / fail display unit that displays pass / fail based on the obtained pass / fail judgment .

The invention according to claim 4 is a work support shaft for supporting the steel work, an index motor for rotating the work support at a constant pitch, and a cylinder unit for moving the steel work toward the detection coil. The index motor and the control unit for controlling the cylinder unit are provided .

  In the invention which concerns on Claim 1, the contact member which makes the distance from steel workpieces to a detection coil constant is provided. When the contact member contacts the steel workpiece, the distance from the steel workpiece to the detection coil can be made constant. There is no error in the measurement results because the distance is constant. That is, it can be said to be a highly reliable steel workpiece inspection device.

In addition, in the invention according to claim 1 , the contact member includes a sphere that is brought into contact with the workpiece and a support portion that connects the sphere to the iron core. The contact member is constituted by the sphere and the support portion. It is advantageous that the contact member can be manufactured with a small number of parts.

Further, in the invention according to claim 1 , the steel workpiece is a gear. The contact member can be brought into contact between adjacent tooth surfaces of the gear. By making a contact member contact between a tooth surface and a tooth surface, it can be made to contact 2 points | pieces with one contact member. By contacting the two points, the distance from the gear to the detection coil can be further stabilized.

In addition, in the invention according to claim 1 , the gear is subjected to vacuum carburization. The carburized depth of the vacuum carburized gear is the thinnest at the root portion. If the tooth bottom with the smallest carburization depth is measured, it can be determined whether or not the gear has a predetermined strength. That is, only the tooth bottom needs to be inspected, and the measurement time can be shortened.

Furthermore, in the invention according to claim 1 , at least two contact members are provided in the tooth width direction of the gear. By bringing two or more contact members into contact with the gear, the distance from the gear to the detection coil can be further stabilized. The reliability of the inspection device is further increased.

In addition, in the invention according to claim 1 , the contact member is provided on the iron core so as to be movable in the tooth width direction of the gear. The abutting member can be moved in the tooth width direction of the gear. The abutting member can be moved according to the size of the gear. It is beneficial to measure various gears with one inspection device.

The best mode for carrying out the present invention will be described below with reference to the accompanying drawings. The drawings are viewed in the direction of the reference numerals.
FIG. 1 is a principle diagram of a bottom carburization depth measuring device suitable for using the steel workpiece inspection device of the present invention. A bottom carburizing depth measuring device 10 includes a base 11 and the base 11. The rail 12 is provided at the center of the upper surface of the rail 12 and extends left and right in the figure, the slider 13 mounted on the rail 12 so as to be movable left and right, and supported by the slider 13 vertically and rotatably via a bearing 14. A work support shaft 16 that supports a steel work 15 such as a gear, an index motor 17 that is built in the slider 13 and rotates the work support shaft 16 at a constant pitch, and is placed on the base 11 along the rail 12. A cylinder unit 18 that reciprocates, a control unit 19 that controls the cylinder unit 18 and the index motor 17, and a bracket that extends upward from one end (left side in the figure) of the base 11. 21, a U-shaped iron core 23 attached to the upper portion of the bracket 21 with bolts 22, 22, and a detection coil support 24 supported by the iron core 23 and extending toward the steel workpiece 15. , Support members 25 and 25 arranged from the tip of the iron core 23 toward the steel workpiece 15, and contact members 28 and 28 composed of spheres 26 and 26 such as steel balls (details will be described later), and the tip of the iron core 23 Excitation coils 29, 29 wound around the coil, an AC power supply 31 for applying an AC voltage to the excitation coils 29, 29, and a detection coil 33 embedded in a resin body 32 provided at the tip of the detection coil support 24. And a carburization depth conversion device 35 that acquires detection information from the detection coil 33 and converts it to carburization depth, and a pass / fail determination unit 36 that compares the obtained carburization depth with an acceptable reference depth and determines pass / fail. , Go / No Go Based on the constant, pass, and acceptance display unit 37 for displaying the failure consists.

  Here, the steel workpiece inspection device 40 includes a resin body 32, a detection coil 33, excitation coils 29 and 29, an AC power supply 31, contact members 28 and 28, and a carburization depth conversion device 35. The

FIG. 2 is a front view of a steel workpiece inspection apparatus. The detection coil support 24 is fixed to the iron core 23 with screws 41 so as to be slidable in the horizontal direction. The support portion 25 includes a conical portion 42 and a base portion 43.
When the abutting member 28 is movably provided, it is desirable that the base 43 is formed in a hexagonal shape so that the abutting member 28 can be easily removed using a spanner or the like.

  FIG. 3 is a cross-sectional view taken along the line 3 in FIG. 2, and the detection coil 33 is supported by the detection coil support 24 via a resin body 32 such as nylon having a triangular cross section that is rich in insulation. Since the resin body 32 has a triangular cross section, the detection coil 33 can be brought close to the tooth bottom 44 when a gear is used for the steel workpiece 15.

  In addition, when a gear that has been subjected to vacuum carburization treatment is used for the steel workpiece 15, the gear carburization depth is the thinnest at the root portion 44. If the bottom of the carburized depth is measured, it can be known whether the gear has a predetermined strength. That is, only the tooth bottom needs to be inspected, and the measurement time can be shortened.

  FIG. 4 is a cross-sectional view taken along the line 4 in FIG. 2. The spherical diameter of the sphere 26 passes between the adjacent tooth tips 48 and the tooth tips 48, but before reaching the tooth bottom 44, The outer diameter is set in contact with the surface. That is, since the contact points 51 and 51 are in contact with each other, the positions of the sphere 26 in the horizontal direction and the vertical direction in the figure are defined. At the same time, the center of the sphere 26 coincides with the center of the tooth bottom 44.

  As a result, the distance of the detection coil 33 (FIG. 3) from the tooth bottom 44 and the distance of the excitation coils 29 and 29 (FIG. 2) can be made constant. There is no error in the measurement results because the distance is constant. That is, it can be said to be a highly reliable steel workpiece inspection device.

  Furthermore, when a gear is used for the steel workpiece 15, the contact member 28 can be brought into contact between the tooth surfaces 49 adjacent to each other of the gear. By contacting the contact member 28 between the tooth surface 49 and the tooth surface 49, it is possible to make contact with two points with one contact member. By contacting the two points, the distance from the gear to the detection coil can be further stabilized.

  FIG. 5 is an enlarged cross-sectional view of part 5 of FIG. 2, and as shown in FIG. The The male screw portion 46 is screwed into a female screw hole 47 provided at the tip of the iron core 23.

  The abutting member 28 includes a sphere 26 that is brought into contact with the steel workpiece 15 and a support portion 25 that connects the sphere 26 to the iron core 23. The contact member 28 is configured by the sphere 26 and the support portion 25. It is advantageous that the abutting member 28 can be manufactured with a small number of parts.

  (B) is a sectional view taken along the line bb of (a), and, for example, three female screw holes 47 are provided at the tip of the iron core 23. One female screw hole 47 is selected from these female screw holes 47 according to the size of the workpiece to be measured, and the abutting member 28 (FIG. 4) can be screwed together.

  By the way, it is necessary to memorize | store the conversion table which converts X voltage obtained by the measurement into the carburizing depth in the carburizing depth conversion apparatus 35 demonstrated in FIG. Therefore, using the root carburization depth measuring device 10 of FIG. 1, the frequency was set to 1 kHz, and the “X voltage” of the vacuum carburized gear was measured. This measurement corresponds to a nondestructive inspection.

  Next, this gear was cut and the cut surface was polished, and then the “carburizing depth” was measured. This measurement corresponds to destructive inspection.

FIG. 6 is a graph showing the hardness obtained by the measurement.
First, when the frequency was set to 1 kHz using the tooth bottom carburizing depth measuring device 10 and the “X voltage” of the gear that had been vacuum carburized was measured, the X voltage was −67 mV. Next, it cut | disconnected, polished the cut surface, and set this cut surface as a measuring object, the Vickers hardness (Hv) was measured with the micro Vickers hardness meter to 1.0 mm every 0.1 mm from the surface.

  FIG. 6 is a graph showing the hardness obtained by the measurement, and (a) is a graph in which raw data is plotted on a graph in which the horizontal axis is the depth from the surface and the vertical axis is the Vickers hardness. It is.

By the way, in this type of gear, a required specification such as “the depth of ◯ mm from the surface and the Rockwell C scale hardness is 50 or more” is often issued. The Rockwell C scale hardness 50 corresponds to Vickers hardness (Hv) 513 according to the conversion table.
Therefore, a plurality of points plotted in (a) are connected by a smooth curve.

  As a result, the graph shown in (b) is obtained. Therefore, a horizontal line is drawn from 513 on the vertical axis, the vertical line is dropped from where it intersects the curve, and the distance at which this vertical line intersects the horizontal axis is read. The distance from the surface was 0.64 mm.

FIG. 7 is a correlation diagram between the X voltage and the carburization depth. In the graph in which the horizontal axis represents the carburization depth (corresponding to the distance from the surface) and the vertical axis represents the X voltage, one piece of data (0.64 mm) is shown. , −67 mV) is plotted with ●.
Twenty-one samples obtained by changing the carburizing conditions were prepared, and the carburizing depth and the X voltage were determined for these samples by following the procedures in FIGS. 6 (a) and 6 (b). Twenty-one samples were circled and plotted on a graph.

One ● and 21 ○ are distributed along a straight line going down to the right. If the X voltage on the vertical axis is obtained by measurement, the carburization depth corresponding to the obtained X voltage can be obtained from this correlation diagram.
Although the detailed calculation method is omitted, the correlation coefficient (r ² ) in this dispersion was 0.92.

  As is clear from the above description, the present invention is also characterized by the following points. That is, as described in FIGS. 6A and 6B, the hardness and depth obtained are obtained by connecting the points obtained by plotting the hardness obtained by measurement from the surface of the gear toward the center. Get from the curve. Since the curve is obtained by connecting the points, the number of measurement points can be set small, the measurement time can be shortened, and the measurement cost can be reduced.

  Further, the carburization depth is determined based on quantitative data of hardness obtained in FIG. That is, as described with reference to FIG. 6, the hardness data by the destructive inspection and the X voltage by the nondestructive inspection are matched. Thereafter, the X voltage is obtained by nondestructive inspection, and converted to the carburization depth based on FIG. Despite the non-destructive inspection, since it is supported by the destructive inspection, the reliability of the carburization depth obtained by the non-destructive inspection is dramatically increased.

Next, for the purpose of specifying a suitable frequency, the frequency is changed from 700 Hz to 4 kHz, 22 samples are prepared for each frequency, a correlation diagram similar to FIG. 7 is created, and a correlation coefficient is obtained. It was. The result is shown in the following figure.
FIG. 8 is a graph showing the relationship between the frequency and the correlation coefficient. The maximum is 1 kHz, and the correlation coefficient is small above 2 kHz. On the other hand, at 700-1 kHz, the change is small.
In order to examine the carburizing depth of the tooth bottom of the vacuum carburized gear, it has been found that the frequency is desirably set in the range of 700 to 1 kHz.

Next, the operation of the steel workpiece inspection apparatus having the above-described configuration will be described by taking a case where a gear is used for the steel workpiece as an example.
FIG. 9 is a diagram for explaining the operation of the contact member according to the present invention. As shown in FIG. 9A, the contact member 28 is disposed so as to contact both ends of the gear 53. When the size of the gear 53 to be measured changes, the contact member 28 is turned to remove the contact member 28 from the female screw hole 47.

  Next, as shown in (b), the female screw hole 47 is selected so that the contact member 28 is arranged at both ends of the gear 54 according to the size of the gear 54 having a different size, and the female screw hole 47 is applied to the selected female screw hole 47. The member 28 is screwed.

  The abutting member 28 can be moved in the tooth width direction of the gear 54. The abutting member 28 can be moved in accordance with the size of the gear 54. It is beneficial to measure various gears with one inspection device.

  In addition, when two contact members 28 are provided in the tooth width direction of the gear 54, the distance from the gear 54 to the detection coil 33 is further stabilized by bringing the two contact members 28, 28 into contact with the gear 54. be able to. The reliability of the inspection device is further increased.

  When the position of the contact member 28 is determined, the strength of the gear 54 is measured. The method for measuring the strength of the gear will be described in the next figure.

  FIG. 10 is a diagram for explaining the operation of the steel workpiece inspection apparatus according to the present invention. As shown in FIG. 10 (a), the gear 54 is advanced to the stationary detection coil 33 as shown by the arrow (1). As shown in (b), an arbitrary tooth bottom 44 is caused to face the detection coil 33, the carburization depth of the tooth bottom 44 is detected, and whether the carburization depth is acceptable or not is determined. When finished, the gear 54 is moved backward as indicated by the arrow (2).

  Next, as shown in (c), the gear 54 is rotated by one pitch (one tooth) (arrow (3)). Then, as shown in (d), the adjacent tooth bottom 44 faces the detection coil 33. Thereafter, the process returns to (a) and continues. This continuing operation will be described again in the flow.

  FIG. 11 is a preferred work flow diagram using the steel workpiece inspection apparatus of the present invention, and the acceptance reference depth Ds is determined by a step number (hereinafter abbreviated as ST) 01. For example, the acceptance reference depth Ds is 0.5 mm. This 0.5 mm is input to the pass / fail judgment unit 36 in FIG.

  In ST02, the number N of gear teeth to be measured is input to the control unit 19 in FIG. In order to monitor the number of measurements, first, the number n is set to 1 (ST03). Next, the abutting member 28 is positioned as shown in FIG. 9 (ST04).

  When the position of the abutting member 28 is determined, the gear is advanced in the manner of FIG. 10A (ST05). In the manner shown in FIG. 10B, the X voltage of the tooth bottom is measured (ST06). The X voltage is converted into the carburization depth Da by the carburization depth conversion device 35 in FIG. 1 (ST07). The pass / fail judgment unit 36 in FIG. 1 checks whether or not the carburized depth Da obtained by the measurement is larger than the acceptance reference depth Ds (ST08). If YES, “pass” is displayed (ST09). Next, the gear is moved backward as indicated by an arrow (2) in FIG. 8B (ST10).

  Here, the number of measurements is examined (ST11). N is 1 for the first time. For example, if the number N of gear teeth is 40, since n <N, NO is advanced and 1 is added to n (ST12). Then, as shown in FIG. 10C, the gear is rotated by one tooth (ST13). Then, the carburization depth of the tooth bottom is measured again from ST05.

  If the carburization depth Da is lower than the acceptance standard depth Ds in ST08, NO is advanced and a failure display is performed (ST14). If it fails, the measurement for this gear can be terminated at this point.

  If the number of measurements n reaches the number of teeth N in ST11, the total number of tooth bottoms has been inspected, so that measurement completion is displayed and the measurement is terminated (ST15).

  The steel workpiece inspection apparatus of the present invention may measure the carburization depth with an apparatus or tool other than the root carburization depth measurement apparatus 10 shown in FIG. In short, as long as the carburization depth of the tooth base can be measured nondestructively, the form and type of the measuring device are not limited.

  The present invention is suitable for a technique for measuring the carburization depth of a gear that has been vacuum carburized.

It is a principle figure of the bottom carburization depth measuring device suitable for using the inspection device of the steel work of the present invention. It is a front view of the inspection apparatus of steel workpieces. FIG. 3 is a cross-sectional view taken along a line 3 in FIG. 2. FIG. 3 is a cross-sectional view taken along line 4 of FIG. 2. FIG. 5 is an enlarged cross-sectional view of part 5 of FIG. 2. It is a graph showing the hardness obtained by measurement. It is a correlation diagram of X voltage and carburizing depth. It is a graph which shows the relationship between a frequency and a correlation coefficient. It is action | operation explanatory drawing of the contact member which concerns on this invention. It is operation | movement explanatory drawing of the inspection apparatus of the steel workpiece which concerns on this invention. It is a suitable work flowchart using the inspection apparatus of the steel workpiece of this invention. It is a figure explaining the basic principle of the prior art. It is a figure explaining the problem of the prior art. It is a figure explaining the graph which shows the relationship between the insertion angle of a gearwheel, and a voltage measurement value.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Dental carburization depth measuring apparatus, 15 ... Steel workpiece, 16 ... Work spindle, 17 ... Index motor, 18 ... Cylinder unit, 19 ... Control part, 23 ... Iron core, 25 ... Support part, 26 ... Sphere 28 ... Abutting member, 29 ... Excitation coil, 33 ... Detection coil, 35 ... Carburization depth converting device, 36 ... Pass / fail judgment unit, 37 ... Pass / fail display unit, 40 ... Steel workpiece inspection device, 46 ... Male screw portion, 47 ... Female screw hole, 53, 54 ... Gear.

Claims (4)

An exciting coil that is supported by an iron core and is placed in the vicinity of the steel workpiece and generates an eddy current in the steel workpiece; and a magnetic field that is supported by the iron core and is placed in the vicinity of the steel workpiece and generated by the eddy current. In a steel workpiece inspection device comprising a detection coil for measuring changes in
This inspection device is an inspection device that includes a contact member that extends from the iron core and has a tip that contacts the steel workpiece and makes the distance from the steel workpiece to the detection coil constant .
The steel workpiece is a gear that has been vacuum carburized,
The abutting member includes a sphere to be brought into contact with the workpiece, and a support portion that connects the sphere to the iron core, and is provided in at least two in the tooth width direction of the gear,
At the tip of the iron core, a plurality of female screw holes configured in a female screw shape are provided,
At the tip of the support portion, a male screw portion configured in a male screw shape is provided,
An inspection apparatus for a steel workpiece , wherein the male screw portion is screwed into an arbitrary female screw hole among the plurality of female screw holes . 2. The steel workpiece inspection apparatus according to claim 1 , wherein the shape of the detection coil is a cylindrical shape, and an axis of the detection coil is disposed along a tooth bottom of the gear . Carburization depth conversion device that acquires detection information from the detection coil and converts it to carburization depth, a pass / fail determination unit that determines the pass / fail by comparing the obtained carburization depth with an acceptable reference depth, and the obtained pass / fail determination The steel workpiece inspection device according to claim 1, further comprising: a pass / fail display unit that displays pass / fail based on the above. Work support shaft for supporting the steel work, an index motor for rotating the work support at a constant pitch, a cylinder unit for moving the steel work toward the detection coil, and these index motor and cylinder unit The steel workpiece inspection apparatus according to claim 3, further comprising a control unit that controls the workpiece.

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