JPH0136905Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a high-frequency heating coil used for heating when surface hardening or tempering a member.

(Prior art) When heating the surface of a non-rotating member using a high-frequency induction heating coil for hardening or tempering, the shape of the heating coil according to the shape of the member, the required hardening specifications, the amount of heating power, etc. Due to these factors, the heating effect due to the magnetic flux generated from the high-frequency heating coil may be greater in only certain portions of the member than in other portions. In such a heating state, for example, in the case of heating for the purpose of quenching, quenching cracks may occur during rapid cooling, or even if quenching cracks do not occur, stress concentration may occur in the part concerned.
There is a risk of causing a breakage accident in the next step, such as polishing the hardened peripheral surface, and it is not possible to form a uniform hardened layer over the entire surface of the member. Furthermore, in the case of heating for the purpose of tempering, for example, non-uniform tempering results in portions where the heating effect is large having a lower hardness than other portions. Therefore, if the heating effect due to the magnetic flux generated from the heating coil is greater in a predetermined portion than in other portions, it is necessary to gradually reduce the heating effect of the magnetic flux acting on the predetermined portion.

In addition, contrary to the above, even though the heated surface is uniformly heated by the heating coil over the entire surface, there are cases where it is desired to keep the heating temperature lower in only a certain part than other parts for special reasons. It is also necessary to gradually reduce the heating effect of the magnetic flux acting on the predetermined portion.

The conventional means to meet the above requirements is Utility Model Application Publication No. 1973-32311 (Registration No. 801721)
As shown in FIG. 2, which refers to the attached drawings, there is a gap between the portion A on the circumferential surface of the heated member W1 where the heating effect is to be reduced and the inner circumferential wall of the heating coil C' that faces the portion A. A U-shaped magnetic body M is interposed, the base surface direction of the magnetic body M is opposite to the part A, and the heating coil C' is enclosed between the sides, and the magnetic flux generated from the heating coil C' is transferred to the coil. The structure is such that it is guided in the direction of the outer circumference of the area, and does not act in the direction of part A.

(Problems existing in the prior art) However, there are cases where the above-described conventional means cannot be applied.

An example of this is the case where a pin portion of a crankshaft is heated in a non-rotating state. This will be explained with reference to FIG.

In FIG. 3, the shaft portion S, which is the heated portion of the member W2, is sandwiched between the crank arms R, R. r on the half-circumference side that corresponds to the base direction of
Since mechanical strength is particularly required for this part, it is required to form a hardened layer shown as h including up to the crank arm R, and it is also required to temper the formed hardened layer. In the split-type heating coil C' used to meet this requirement, the semicircular heating conductor c1' facing the half circumference of the side shaft in the proximal direction of the crank arm R has a large protrusion B that stands out on both widthwise edges of the inner circumferential wall. A semicircular arc heating conductor c2 having a cross-sectional shape and facing half the circumference of the side shaft in the distal direction of the crank arm R.
has a cross-sectional shape with small, inconspicuous protrusions b on both edges in the width direction of the inner circumferential wall. In the figure, P is a silicon steel plate for guiding magnetic flux.

However, the hardened layer pattern (of course, the same applies to the tempering heating pattern) formed when using the above-mentioned split coil C' is such that only the central part of the half circumference of the shaft portion S facing the heating conductor c1' is formed as H. There is a tendency to cause overheating that shows stipples.

Even if we try to apply conventional means for the purpose of reducing the heating effect of this H portion, it is difficult to attach the magnetic material M to the heating conductor c1' having the cross-sectional shape with the large protrusion B, and even if we try to attach it forcibly. , the heating effect of the shaft portion S facing the base of the magnetic body M is gradually reduced over the entire length of the shaft and both r portions along the axis line by a predetermined width.

Since the conventional means are rejected for the above-mentioned reasons, if the large protrusion B is formed small so as not to cause overheating H, the heating to the r part will not be sufficient.
It was not possible to obtain the required hardened layer pattern h, and a solution was needed.

(Purpose of the invention) The present invention is applicable not only to the above-mentioned cases, but also to cases where it is necessary to reduce the heating effect of the magnetic flux generated from the heating coil in a predetermined part compared to other parts, and in cases where conventional means cannot solve the problem. It is an object of the present invention to provide a high frequency heating coil that can be gradually reduced in a limited manner.

(Structure of the invention) The structure of the invention is such that when the surface of a member is heated by magnetic flux generated from a heating coil wound with a predetermined gap, the heating effect on a predetermined part of the member is gradually reduced compared to other parts. The high frequency heating coil is characterized in that the heating coil is formed by embedding pure iron in a position facing the predetermined portion of the inner circumferential wall of the heating conductor so as to expose it from the circumferential wall.

The reason why pure iron is embedded in a predetermined part of the component in this invention is that pure iron has lower conductivity than a coil conductor normally made of copper material, and self-heating due to current is higher than that of other iron alloys or other metals. This is because it has various properties such as a low melting point and a relatively high melting point that can sufficiently withstand the radiant heat from the heated surface that rises to around 1000°C.

(Function of the invention) The present invention shows that the current flowing through the inner circumferential surface of the heating conductor tends to flow to both sides of the heating conductor, avoiding the pure iron, which has lower conductivity than the copper material. The magnetic flux generated from the heating conductor is distributed to both sides, and has the effect of reducing the amount of magnetic flux directed toward the heated surface facing the pure iron.

(Example) An example in which the present invention is applied to a high-frequency heating coil used for heating a crankshaft will be described in detail below with reference to FIGS. 1a to 1c.

In FIG. 1a, C is a high-frequency heating coil according to the present invention, which is attached to the shaft portion S of the crankshaft W.
This coil is similar to known split coils in that semicircular arc-shaped heating conductors c1 and c2, which can face the semicircular surface with a predetermined gap between them, are constructed so as to be able to come into contact with and separate from them. In addition, it is usual that the heating conductors c1 and c2 are each equipped with laminated silicon steel plates shown as P at multiple locations, and configured to guide magnetic flux in the direction of the shaft S to improve heating efficiency. .

The main point of the present invention in the above-mentioned high-frequency heating coil C is that in FIG. 1a, it is hidden behind the large protrusion B facing the connecting portion r to be heated and cannot be seen directly, so it is indicated by a broken line in FIG. 1a. In FIG. 1b, which is a sectional view taken along the line X--X, pure iron, which can be seen directly, is shown as F in the actual implementation, and is arranged at the center of the semicircular arc of the heating conductor c1. The shaft portion S, which the semicircular arc center portion of the heating conductor c1 faces, is a portion that is overheated as described above. The above pure iron F consists of a head part f1 and a leg part f2, and a heating conductor c
The legs f2 are fitted into the holes made in the heating conductor c1 so that the head f1 is exposed on the surface of the valley sandwiched between the protrusions B and B formed on both ends of the inner circumferential wall of the heating conductor c1. embedded.

By heating the non-rotating shaft portion S using the high-frequency heating coil C having the above configuration, quenching heating or tempering heating can be performed to obtain the ideal quenching pattern h shown in FIG. 1c, The occurrence of overheating H as shown in FIG. 3 is avoided.

In the above embodiment, two pieces of pure iron F are arranged in the central part of the semicircular arc of the heating conductor c1, but the number of pieces of pure iron F arranged can be increased or decreased depending on the size of the angle range in which overheating H occurs in the shaft portion S. be done.

(Other Embodiments) The present invention is effective even when applied to a member that cannot be rotated and heated and has a small hole such as an oil hole in the heated surface. That is, if there is a small hole, the edges of the small hole will overheat due to the edge effect during heating, leading to quench cracking in that part. In this case, if the conventional means shown in FIG.
This occurs over the entire length of the member along the axial direction.

However, in the present invention, the leg part f2 of pure iron F having the head f1 having a slightly larger area than the area of the small hole is embedded in the wall surface of the high-frequency heating coil C facing the small hole. The heating effect is gradually reduced only in the vicinity of the edge of the small hole, thereby avoiding overheating of the edge of the small hole and eliminating the risk of quench cracking, and achieving uniform heating of other parts other than the vicinity of the edge of the small hole.

Furthermore, the present invention is useful not only when a part of the surface to be heated is particularly overheated and the overheating is to be avoided, but also when a hardened layer is used for specific reasons such as applying special additional processing to a predetermined part after quenching. This is applied when it is desired to avoid the formation of , and when heating is required that does not raise the temperature of only the relevant part to the quenching temperature.

(Effect of the invention) By implementing the invention, it becomes possible not only to reduce the heating effect on the overheated portion of the heating surface of the member and achieve uniform heating, but also to achieve uniform heating on a predetermined portion of the heating surface of the member... It is also possible to control the heating effect to a low level only in the range where the heating effect is desired, and the application range is wide, not limited to the above embodiments, and it is prized because it brings about extremely remarkable effects.

[Brief explanation of drawings]

Figure 1a is a front view of one implementation of the present invention, Figure 1b
1A is a sectional view taken along the line X-X in FIG. 1A, FIG. 1C is a cross-sectional front view of a member showing the effect of the present invention, FIG. 2 is a perspective view showing a conventional heating effect reduction means, and FIG. 3 is a conventional heating effect reduction means. It is a cross-sectional front view showing a case that cannot be solved by means. C... High frequency heating coil, W... Member, F...
Pure iron, c1, c2...Coil conductor.

Claims (1)

[Scope of utility model registration request] When the surface of a member is heated by magnetic flux generated from a heating coil wound at a predetermined interval, the heating coil is used to reduce the heating effect on a predetermined portion of the member relative to other portions. A high-frequency heating coil characterized by having pure iron buried in a position facing the part so as to be exposed from the surrounding wall.