JPH019002Y2 - - Google Patents

Description

[Detailed description of the invention] [Field of industrial application] The present invention is a magnetic rod-like member that has a stepped portion with a diameter larger than the diameter of the rod portion in the transition area from the rod portion to the flange portion before and after surface hardening treatment. The present invention relates to a coil device for measuring a hardened surface layer of a flanged magnetic rod-shaped member, which measures the inductance of a flanged magnetic bar member and determines the thickness of the hardened surface layer from a change in the value of the inductance.

[Conventional technology]

Such a rod-shaped member, such as a rear axle, is provided with a stepped portion in the transition area from the rod portion to the flange portion for support by a bearing.

Such a rear axle may be surface hardened by an induction hardening method or the like, or the surface hardening layer may be insufficiently formed particularly in this step area due to skin effect, etc. It is necessary to know whether the thickness of the hardened layer is sufficient.

In FIG. 1, a rear axle 1 used for transmitting torque from a differential to the rear wheels has a bar section 2 and a flange section 3, in the transition area from the bar section 2 to the flange section 3 there is a bar. There is a step 4 having a larger diameter than the section 2, on which, for example, the inner ring of the axle support bearing is fitted. A hardened surface layer 5 is formed on the rear axle 1 in an area including the rod portion 2 and the stepped portion 4 by induction hardening or the like.

As shown in FIGS. 1 and 2, the device for measuring the thickness of this hardened layer consists of a Bakelite winding frame 10 that is fitted into the range of the bar portion 2 and step portion 4 of the rear axle 1, and this winding frame. 10 and an annular air-core coil 11 wound around the coil 10. This winding frame 10 is
It consists of annular end plates 12 and 13 and a cylindrical piece 14 whose inner peripheral surface corresponds to the contours of the range of the bar part 2 and step part 4 of the rear axle 1. The step is indicated at 15. Since the thickness of the cylindrical piece 14 is constant, the inner peripheral surface of the air-core coil 11 also has a step corresponding to the step 4. air core coil 11
By connecting an impedance measuring device to and measuring the inductance (impedance) of the air-core coil 11 before and after the formation of the hardened layer 5,
The thickness of this hardened layer 5 can be measured. However, since leakage magnetic flux 16 occurs that passes through the flange portion 3 without passing through the hardened layer 5 of the stepped portion 4, the measurement accuracy is insufficient.

In order to deal with this, the applicant proposed that an annular magnetic body 17 having a U-shaped cross section be fitted into the winding frame 10, covering both end faces and the outer periphery of the air-core coil 11, as shown in FIG. As a result, leakage magnetic flux to the flange portion 3 is eliminated, and most of the magnetic flux 18 now passes through the bar portion 2 and the hardened layer 5 of the step portion 4, but a shunt magnetic flux 19 is generated that passes through the outer peripheral portion of the magnetic body 17. It was found that the measurement accuracy was still insufficient because it did not pass through the hardened layer 5.

[The problem that the idea aims to solve]

An object of the present invention is to provide a coil device for measuring a hardened layer with a simple configuration and improved measurement accuracy.

[Means to solve the problem]

Therefore, according to the present invention, there is provided an annular air-core coil having an inner circumferential surface corresponding to the contours of the rod portion and the stepped portion of the rod-shaped member, and two mutually parallel annular coils provided on both end surfaces of the annular air-core coil. It is equipped with a magnetic plate.

[Effect of idea]

Thus, according to the present invention, the inner circumferential surface of the annular chamber air-core coil also has a step corresponding to the step of the rod-shaped member, so that the distance between the inner circumferential surface of the air-core coil and the outer circumferential surface of the rod-like member is Uniformity is maintained both in the area of the part and in the area of the step, improving measurement accuracy. Furthermore, almost all of the magnetic flux generated by the air-core coil passes through the magnetic plate and enters the hardened layer in the area of the step and rod portions at almost right angles, causing leakage to the flange portion as in the prior art shown in Figure 1. Since no magnetic flux is generated or no shunt magnetic flux is generated that passes through the outer peripheral portion of the magnetic material as in the prior art shown in FIG. 3, measurement accuracy can be significantly improved.

〔Example〕

An embodiment of the present invention will be explained with reference to FIG.
Parts corresponding to those in FIGS. 1 to 3 are given the same reference numerals. According to the present invention, the air-core coil 11
Annular magnetic plates 20 and 21 are inserted between both end surfaces of the winding frame 10 and both end plates 12 and 13 of the winding frame 10 in parallel with each other. Therefore, the magnetic flux generated by the air-core coil 11 is transmitted from both magnetic plates 20, 21 to the hardened layer 5 in the area of the bar portion 2 and step portion 4 of the rear axle 1.
There is no leakage to the flange portion 3 through the magnetic flux, and no shunt magnetic flux as shown in FIG. 3 is generated, thus improving measurement accuracy.

Note that the air-core coil 11 is connected to a DC power source 26 via a variable resistor 25. air core coil 11
One end is connected to the excitation oscillator 28 via a capacitor 27 as a filter, and the excitation oscillator 2
8 is further connected to the other end of the air-core coil 11 via a resistor 29. In this way, a DC bias is applied to the air-core coil 11, and the inductance generated in the air-core coil 11 in relation to the thickness of the hardened layer 5 appears as a voltage change across the resistor 29, and the voltage change is caused by the AC amplifier 30, rectifier 31, and DC amplifier. 32 and is displayed on the indicator 33.

As shown in FIG. 5, by providing radial slits 41 in each of the magnetic plates 20 and 21, it is possible to prevent eddy currents from being generated concentrically therein due to changes in magnetic flux passing through the magnetic plates 20 and 21. It can be prevented.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of a conventional measuring coil device taken along the central axis, Figure 2 is an enlarged cross-sectional view of the main part of Figure 1, and Figure 3 corresponds to Figure 1 of another conventional coil device. FIG. 4 is a sectional view of a coil device according to the present invention and a connection diagram of an inductance measuring device connected thereto, and FIG. 5 is a perspective view of another embodiment. 1... Rod-shaped member (rear axle), 2... Rod portion, 3
... Flange portion, 4 ... Step portion, 5 ... Hardened surface layer, 11 ... Air-core coil, 20, 21 ... Annular magnetic plate.

Claims (1)

[Scope of utility model registration request] Measure the inductance before and after surface hardening treatment of a magnetic rod-like member that has a stepped portion with a diameter larger than the diameter of the rod portion in the transition range from the rod portion to the flange portion, and from the change in inductance value, determine the surface hardening layer. The coil device for determining the thickness includes a toroidal air-core coil having an inner circumferential surface corresponding to the outline of the bar portion and step portion of a rod-shaped member, and two mutually parallel air-core coils provided on both end surfaces of the toroidal air-core coil, respectively. 1. A coil device for measuring a hardened surface layer of a flanged magnetic rod-like member, characterized in that it is equipped with an annular magnetic plate.