JP2009236770A - Workpiece strength measuring method and measuring device therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology capable of reducing a failure rate of a measuring mechanism for measuring strength of a workpiece subjected to surface processing, elongating a lifetime, and measuring precisely in each measurement. <P>SOLUTION: A gear 15 is advanced or retreated by a slide mechanism 20 relative to a fixed measuring mechanism 29. Since the measuring mechanism 29 is not vibrated by movement, a stable state can be kept, and the failure rate can be reduced. The workpiece is advanced or retreated relative to the fixed measuring mechanism. Since the measuring mechanism is fixed and is not vibrated, the failure rate of the measuring mechanism can be reduced. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a workpiece strength measurement technique for measuring the strength of a surface-treated workpiece.

The strength of the surface-treated workpiece is measured by either a destructive inspection method or a nondestructive inspection method.
Many strength measurement techniques using nondestructive inspection methods have been proposed (see, for example, Patent Document 1).
JP 2006-349055 A (Claim 1)

  Claim 1 of Patent Document 1 states that “the gear is vacuum carburized so that the surface carbon concentration in the smooth surface portion is 0.6 mass% or more, and the effective hardened layer depth of the surface portion is D (mm). The gear is characterized in that, prior to the vacuum carburization, the surface including the stress concentration portion located in the vicinity of the tooth root is chamfered with D ± 0.25 (mm). ” It is disclosed that the gear is subjected to vacuum carburization.

As described above, since the gear is an important mechanical element, it is necessary to measure the strength by sampling inspection or 100% inspection, and a nondestructive inspection method using eddy current has been put into practical use for this measurement (for example, , See Patent Document 2).
JP 2004-108873 A (FIG. 2)

Patent document 2 is demonstrated based on the following figure.
FIG. 11 is a diagram for explaining the basic principle of the prior art. As shown in FIG. 11A, 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. The correlation between the excitation voltage and the detection voltage will be described with reference to (c).

(C) is a graph in which the horizontal axis is the time axis and the vertical axis is the voltage. When the sine wave V1 is an excitation voltage curve, the detected voltage is represented by the sine wave V2. The phase difference between the sine wave V1 and the sine wave V2 is defined as Φ.
In (b), the X value represented by cosΦ has a good correlation with the carburization depth, and the Y value represented by sinΦ has a good correlation with the surface hardness.

  As the carburization depth and surface hardness change, the size of Φ and the height of V2 change. Therefore, by determining cosΦ and sinΦ by measurement, the carburization depth and surface hardness at that time can be specified. Since this is a non-destructive inspection, it is suitable for measuring the strength of gears.

  By the way, in claim 2 of Patent Document 2, “... The detection coil and the excitation coil are integrally formed as a detection coil body, and the detection coil body is moved in the axial direction of the axial measurement target. There is a description of the detection signal obtained from the detection coil of the detection coil body at each position, and it is disclosed that the measurement mechanism as the detection coil body is moved.

When measuring all the mass-produced products such as gears, it is necessary to repeatedly move the measuring mechanism many times.
However, the measurement mechanism is made up of precision parts such as a detection coil, and the measurement mechanism breaks down and its life is shortened by repeatedly applying vibration and the like due to movement.
Therefore, it is required to reduce the failure rate of the measurement mechanism. Furthermore, it is necessary to measure precisely every measurement.

  An object of the present invention is to provide a technique capable of reducing the failure rate of a measuring mechanism that measures the strength of a surface-treated workpiece, extending the life, and measuring accurately every measurement.

  The invention according to claim 1 is a workpiece strength measurement method for measuring the strength of a workpiece subjected to surface treatment with a measurement mechanism, wherein the measurement mechanism is fixed, and the workpiece is moved forward and backward with respect to the measurement mechanism. And

  The invention according to claim 2 is characterized in that the workpiece is a gear.

  The invention according to claim 3 is characterized in that the tooth bottom of the gear is measured by the measuring mechanism.

  The invention according to claim 4 is characterized in that the surface treatment is a vacuum carburizing treatment.

  In the invention which concerns on Claim 5, in the workpiece | work intensity | strength measuring apparatus which measures the intensity | strength of the workpiece | work in which the surface treatment is performed, this workpiece | work intensity | strength measuring apparatus is fixed to this base | substrate, and measures the intensity | strength of a workpiece | work. It is characterized by comprising a measuring mechanism, a slider that is slidably provided on the base toward the measuring mechanism, and on which a work is placed, and a slide mechanism that moves the slider back and forth.

  The invention according to claim 6 is characterized in that the workpiece is a gear.

  According to the first aspect of the present invention, the measurement mechanism is fixed, and the workpiece is advanced and retracted relative to the measurement mechanism. Since the measurement mechanism is fixed and does not vibrate, the failure rate of the measurement mechanism can be reduced.

  In the invention which concerns on Claim 2, a workpiece | work is a gearwheel. Although it is said that it is difficult to measure the strength of a gear, according to the present invention, the strength of a gear can be measured by nondestructive inspection.

  According to a third aspect of the invention, the tooth bottom of the gear is measured by the measurement mechanism. Although it is said that it is difficult to measure the strength of the root, according to the present invention, it is possible to measure the strength of the root by nondestructive inspection.

  In the invention which concerns on Claim 4, surface treatment is a vacuum carburizing process. It is said that the vacuum carburizing process is more likely to vary than the gas carburizing process. According to the present invention, it is possible to accurately measure the strength of a workpiece by vacuum carburization.

  In the invention according to claim 5, the workpiece strength measuring device includes a measuring mechanism fixed to the base for measuring the strength of the workpiece, a slider provided on the base so as to be slidable toward the measuring mechanism, And a slide mechanism for moving the slider back and forth. Since the measurement mechanism is fixed and does not vibrate, the failure rate of the measurement mechanism can be reduced.

  In the invention which concerns on Claim 6, a workpiece | work is a gearwheel. Although it is said that it is difficult to measure the strength of a gear, according to the present invention, the strength of a gear can be measured by nondestructive inspection.

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 workpiece strength measuring apparatus suitable for the workpiece strength measuring method of the present invention. A workpiece strength measuring apparatus 10 is provided at the center of an upper surface of the base 11 and the base 11 and extends to the left and right in the figure. A rail 12, a slider 13 mounted on the rail 12 so as to be movable left and right, and a workpiece (hereinafter referred to as “surface treatment”) supported on the slider 13 in a vertical direction and rotatably via a bearing 14. (Referred to as a gear) 15) a gear support shaft 16 that supports 15; an index motor 17 built in the slider 13 that rotates the gear support shaft 16 at a constant pitch; and a slider 13 that is mounted on the base 11 and reciprocates along the rail 12 The cylinder unit 18 to be moved, the control unit 19 for controlling the cylinder unit 18 and the index motor 17, and the control unit 19 and the cylinder unit 18 are configured. A slide mechanism 20 for moving the slider 13 forward and backward, a bracket 21 extending upward from one end (left side in the figure) of the base 11, and a U-shape attached to the upper portion of the bracket 21 with bolts 22 and 22 An iron core 23, a detection coil support 24 supported by the iron core 23 and extending toward the gear 15, steel balls 25 and 25 extending from the tip of the iron core 23 toward the gear 15, and iron An excitation coil 26, 26 wound around the tip of the core 23, an AC power supply 27 for applying an AC voltage to these excitation coils 26, 26, a detection coil 28 provided at the tip of the detection coil support 24, A measuring mechanism 29 configured by an iron core 23, a detection coil support 24, steel balls 25 and 25, excitation coils 26 and 26, an AC power supply 27, and a detection coil 28, and measuring the strength (carburization depth) of the gear, and detection The carburization depth conversion device 30 that acquires the detection information from the il 28 and converts it to the carburization depth, the pass / fail determination unit 31 that determines the pass / fail by comparing the obtained carburization depth with the acceptance reference depth, and the obtained Based on the pass / fail judgment, the pass / fail display unit 32 displays pass / fail.

The surface treatment applied to the workpiece is not limited to vacuum carburizing treatment, but carburizing treatment such as gas carburizing, liquid carburizing and solid carburizing, or induction hardening, flame hardening, electrolytic hardening, plasma surface hardening, electron beam hardening and laser. Quenching such as quenching, surface treatment using heat treatment atmosphere such as N ₂ base atmosphere heat treatment and vacuum heat treatment, or nitriding such as gas nitriding method, salt bath nitriding method, gas soft nitriding method and ion nitriding method, or Sulfurizing treatment, such as sulfurization treatment, molten salt sulfiding method and gas nitrosulphurizing method, or metal infiltration method, boride treatment, ion implantation method, vapor deposition treatment method, coating treatment method, etc. There is no limitation on the type as long as it is a treatment for reinforcing the surface of the metal member.

  The measurement mechanism 29 is fixed to the base 11 via the bracket 21 and does not vibrate. The gear 15 is advanced and retracted toward the measurement mechanism 29 via the slider 13 to perform measurement.

  FIG. 2 is an enlarged view of the main part of FIG. 1, and the detection coil support 24 is fixed to the iron core 23 with screws 33 so as to be slidable in the horizontal direction. Further, the steel ball 25 is fixed to the iron core 23 via a conical part 34 and a cylindrical part 35.

  FIG. 3 is a cross-sectional view taken along the line 3 in FIG. 2, and the detection coil 28 is supported by the detection coil support 24 via a resin body 36 such as nylon having a triangular cross section that is rich in insulation. Since the resin body 36 has a triangular cross section, the detection coil 28 can be brought close to the tooth bottom 37 of the gear 15. In addition, the tooth bottom 37 can be measured.

4 is a cross-sectional view taken along the line 4 of FIG. 2, and the diameter of the steel ball 25 passes between the adjacent tooth tips 38 and the tooth tips 38, but before reaching the tooth bottom 37, the tooth portions 39, It is set to an outer diameter that contacts the surface of 39. That is, since it is in contact with the contact points 41, 41, the positions of the steel balls 25 in the horizontal direction and the vertical direction in the figure are defined. In addition, the center of the steel ball 25 coincides with the center of the tooth bottom 37.
As a result, the distance of the detection coil 28 from the tooth bottom 37 and the distance of the excitation coils 26 and 26 (FIG. 2) can be made constant. As a result, measurement reliability can be increased.

By the way, it is necessary to memorize | store the conversion table which converts the X voltage obtained by the measurement into the carburization depth in the carburization depth conversion apparatus 30 demonstrated in FIG. Therefore, using the workpiece strength measuring apparatus 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, after cutting this gear and polishing the cut surface, the "hardness" was measured and the "carburization depth" was determined. This measurement corresponds to destructive inspection.

FIG. 5 is a graph showing the hardness obtained by the measurement.
First, the work strength measuring apparatus 10 was used to set the frequency to 1 kHz, and when the “X voltage” of the vacuum carburized gear 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. 5 is a graph showing the hardness obtained by the measurement. (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. 6 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. 5 (a) and 5 (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. 5A and 5B, 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 the quantitative data of hardness obtained in FIG. That is, as described with reference to FIG. 5, 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. 6 is created, and a correlation coefficient is obtained. It was. The result is shown in the following figure.
FIG. 7 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 workpiece strength measuring apparatus 10 having the above configuration will be described.
FIG. 8 is an explanatory diagram of the operation of the workpiece strength measuring device. As shown in FIG. 8A, the gear 15 is advanced to the stationary detection coil 28 as shown by an arrow (1). As shown in (b), an arbitrary tooth bottom 37 is made to face the detection coil 28, the carburization depth of the tooth base 37 is detected, and whether the carburization depth is acceptable or not is determined. When finished, the gear 15 is moved backward as indicated by the arrow (2).

  Next, as shown in (c), the gear 15 is rotated by one pitch (one tooth) (arrow (3)). Then, as shown in (d), the adjacent tooth root 37 faces the inspection coil 28. Thereafter, the process returns to (a) and continues. This continuing operation will be described again in the flow.

FIG. 9 is a work flow chart suitable for the work strength measurement method of the present invention, and the acceptance reference depth range Ds is defined by a step number (hereinafter abbreviated as ST) 01. For example, the acceptance standard depth range Ds is 0.5 mm to 0.8 mm. This 0.5 mm to 0.8 mm is input to the pass / fail determination unit 31 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).

  The gear is moved forward in the manner of FIG. 8A (ST04). In the manner shown in FIG. 8B, the X voltage of the tooth bottom is measured (ST05). The X voltage is converted into the carburization depth Da by the carburization depth conversion device 30 in FIG. 1 (ST06). The pass / fail determination unit 31 of FIG. 1 checks whether or not the carburized depth Da obtained by the measurement is within the acceptable reference depth range Ds (ST07). If YES, “pass” is displayed (ST08). Next, the gear is moved backward as indicated by the arrow (2) in FIG. 8B (ST09).

  Here, the number of measurements is examined (ST10). N is 1 for the first time. For example, if the number of gear teeth N is 40, since n <N, NO is advanced and 1 is added to n (ST11). Then, as shown in FIG. 8C, the gear is rotated by one tooth (ST12). Then, the carburization depth of the tooth bottom is measured again from ST04.

  If the carburizing depth Da is not within the acceptance standard depth range Ds in ST07, NO is advanced and a failure display is performed (ST13). 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 ST10, the total number of tooth bottoms has been inspected, so that measurement completion is displayed and the measurement is terminated (ST14).

FIG. 10 is a comparative explanatory view of the operation of the workpiece strength measuring device. In the comparative example shown in FIG. 10A, the measuring mechanism 112 is advanced and retracted as shown by the arrow (4) with respect to the fixed gear 111. FIG. Since the measurement mechanism 112 includes precision parts such as the detection coil 113, the measurement mechanism is liable to fail due to vibrations caused by repetitive movement and the life is shortened.
In the embodiment shown in (b), the gear 15 is moved forward and backward by the slide mechanism 20 as shown by the arrow (5) with respect to the fixed measuring mechanism 29. Since there is no vibration due to the movement of the measuring mechanism 29, a stable state can be maintained and the failure rate can be reduced. Further, the gear 15 is not affected at all even if it moves while being supported. As a result, it is possible to measure accurately every measurement.

  The workpiece is not limited to a gear, and any type may be used as long as it is a general mechanical member such as a shaft, an engine piston, etc., and is made of steel that can be surface-treated.

  The present invention is suitable for a technique for measuring the strength of a surface-treated workpiece.

It is a principle figure of the workpiece | work intensity | strength measuring apparatus suitable for the workpiece | work intensity | strength measuring method of this invention. It is a principal part enlarged view of FIG. 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. 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 operation | movement explanatory drawing of a workpiece | work intensity | strength measuring apparatus. It is a work flow figure suitable for the work strength measuring method of the present invention. It is comparison explanatory drawing of an effect | action of a workpiece | work intensity | strength measuring apparatus. It is a figure explaining the basic principle of the prior art.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Work intensity | strength measuring apparatus, 11 ... Base, 13 ... Slider, 15 ... Workpiece (gear), 20 ... Slide mechanism, 29 ... Measuring mechanism, 30 ... Carburizing depth conversion apparatus, 31 ... Pass / fail judgment part, 37 ... Teeth Bottom, Ds ... Acceptance standard depth, Da ... Carburization depth obtained by measurement.

Claims (6)

In the workpiece strength measurement method that measures the strength of the workpiece that has been surface-treated with a measurement mechanism,
A workpiece strength measuring method, wherein the measuring mechanism is fixed and the workpiece is advanced and retracted relative to the measuring mechanism.   The work strength measuring method according to claim 1, wherein the work is a gear.   The workpiece strength measuring method according to claim 2, wherein the tooth bottom of the gear is measured by the measuring mechanism.   4. The work strength measuring method according to claim 1, wherein the surface treatment is a vacuum carburizing treatment. In a workpiece strength measuring device that measures the strength of a workpiece that has been surface-treated,
The work strength measuring device includes a base, a measurement mechanism that is fixed to the base and measures the strength of the work, a slider that is slidably provided on the base toward the measurement mechanism, and places the work on the base. A work strength measuring device comprising a slide mechanism for moving the slider back and forth.   The work strength measuring apparatus according to claim 5, wherein the work is a gear.

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