JP2023097560A - High frequency heating coil and coil spring molding device - Google Patents

Abstract

To provide a high frequency heating coil which can improve the carburization property without reducing the feeding speed of a steel wire material and simply expanding and increasing the heating coil.SOLUTION: There is provided a high frequency heating coil which performs high frequency heating by making a steel wire material inserted from a coil inlet pass therethrough. A double coil part 48 made of a closely wound inner coil part 41 and a closely wound or coarsely wound outer coil part 43 arranged on the outer side of the inner coil part 41 is provided on the coil inlet side. A closely wound single coil part 45 having the larger outer diameter than the outer diameter of the inner coil part 41 is provided so as to be adjacent to a coil outlet side of the double coil part 48. A coarsely wound coil part 46 which is coarsely wound and has the larger outer diameter than the outer diameter of the single coil part is extended to the coil outlet adjacently to the coil outlet side of the single coil part 45.SELECTED DRAWING: Figure 2

Description

The present invention relates to a high-frequency heating coil and a spring forming apparatus for heating a steel wire with high-frequency waves, and in particular, by shortening the time required to reach the maximum temperature, the holding time at the maximum temperature is extended to improve carburization. Regarding technology.

For example, in the manufacturing process of a coil spring, a steel wire rod is hot-coiled in a state of being heated to an austenite region by a high-frequency heating coil, and then quenched and tempered. In such a process, when the steel wire is heated and held, the steel wire is sometimes brought into contact with a hydrocarbon-based gas to carburize the steel wire.

For example, in the high-frequency hot coiling technology disclosed in Patent Document 1, a carbon-enriched layer having a uniform thickness is formed on the steel wire surface by carburizing by supplying a hydrocarbon-based gas during heating of the steel wire. Here, the depth of the C-enriched layer is affected by the heating temperature and time. If the heating time is too short, the carburization will not progress and the desired depth of the carburized layer cannot be obtained. On the other hand, the higher the heating temperature, the higher the carburizing property, but the larger the crystal grain size, so the heating temperature is preferably 1000° C. or higher and 1100° C. or lower, or 1000° C. or higher and 1050° C. or lower.

Japanese Patent No. 6251830

Conventionally, it has been necessary to slow down the feed rate of the steel wire rod in order to uniformly obtain a desired carburized layer depth. The slower the steel wire feeding speed, the longer the contact time between the steel wire and the hydrocarbon-based gas, and the longer the diffusion time of C, so that the carburization property is improved, but the productivity is impaired.

Therefore, it is preferable to obtain a desired carburized layer depth without lowering the steel wire rod feeding speed. There was a problem that a uniform carburized layer could not be obtained over the circumference. Further, in hot coiling, if the heating area is expanded, the steel wire will buckle and the shape will vary, so the coil length is limited to 350 mm or less.

The present invention has been made in view of the above circumstances, and a high-frequency heating coil that can improve carburization properties without lowering the feed rate of steel wire rods and without simply expanding or adding more heating coils. and to provide a spring forming apparatus.

The present invention relates to a high-frequency heating coil for high-frequency heating by passing a steel wire rod inserted from a coil inlet inside, wherein a densely-wound inner coil portion and a densely-wound inner coil portion disposed outside the inner coil portion are provided on the coil inlet side. A multiple coil portion consisting of an outer coil portion of winding or coarse winding is provided, and a close winding single coil portion having an outer diameter larger than the outer diameter of the inner coil portion is provided adjacent to the coil exit side of the multiple coil portion. is provided adjacent to the coil outlet side of the single coil portion, and a coarsely wound coil portion having an outer diameter larger than the outer diameter of the single coil portion is extended to the coil outlet. A high frequency heating coil.

According to the present invention, since the multiple coil portion including the densely wound inner coil portion and the densely wound or coarsely wound outer coil portion disposed outside the inner coil portion is provided on the coil inlet side, the multiple coil portion is provided. In the coil section, the steel wire can be rapidly heated to the austenitic region with a short feeding distance. Then, the rapidly heated portion of the steel wire reaches the single coil portion. Since the single coil portion has an outer diameter larger than that of the inner coil portion, the magnetic flux density at the position through which the steel wire passes is reduced, thereby suppressing the heat generation of the steel wire. As a result, the rapidly heated portion of the steel wire entering the single coil portion is kept in a heat-retaining state in which the temperature in the austenite region is maintained.

Furthermore, the portion of the steel wire material kept in a heat-insulating state reaches the rough-wound coil portion. Since the coarsely wound coil portion has an outer diameter larger than that of the single coil portion and is loosely wound, the magnetic flux density at the position through which the steel wire passes is further reduced, further suppressing the heat generation of the steel wire. As a result, the temperature of the austenite region is maintained in the heat-insulating portion of the steel wire rod that has entered the rough-wound coil portion. Therefore, carburization can be performed in a long portion of the high-frequency heating coil.

Note that "closely wound" refers to the case where the gap between the high-frequency heating coil wires that do not contain an insulating coating is 2 mm or less, and "coarse winding" means the gap between the high-frequency heating coil wires that do not contain the insulating coating. is greater than 2 mm.

Here, in the above configuration, the single coil portion can also be extended to the coil exit side. Even in such a configuration, the effect of the single coil is maintained up to the coil exit, so carburizing can be performed in the long portion of the high-frequency heating coil.

In the present invention, the multiple coil is a double coil, the ends of the inner coil portion and the outer coil portion on the coil inlet side are connected by a connecting piece, and the first terminal is connected to the coil outlet side end of the outer coil. can be fixed, and a second terminal can be fixed to the end of the coarsely wound coil portion on the coil outlet side.

In this case, the second terminal extends in a direction orthogonal to the end surface of the rough coil portion, and the first terminal extends in a direction substantially parallel to the second terminal and orthogonal to the end surface of the outer coil portion. an axial terminal portion extending from the end of the lateral terminal portion in the axial direction of the outer coil portion; and an end portion of the axial terminal portion toward the second terminal side It is preferable to comprise an extending vertical terminal portion and a second horizontal terminal portion extending from an end portion of the vertical terminal portion in the same direction and parallel to the second terminal. With this configuration, the second terminal and the second horizontal terminal are arranged in parallel and close to each other, making it easy to connect these terminals to the power supply device.

Also, the multiple coil portion preferably has a length of ⅓ or less of the total length of the high-frequency heating coil. That is, since the carburizing treatment can be performed on a portion of the length of 2/3 or more of the total length of the high-frequency heating coil, the carburizing property can be improved without extending the high-frequency heating coil. As a result, the total length of the high-frequency heating coil can be reduced to 350 mm or less.

Next, the present invention includes a feed roller for continuously supplying a steel wire, a coiling section for forming the steel wire into a coil, and a steel wire that is continuously supplied from the rear after being coiled for a predetermined number of turns. A high-frequency heating coil having the above-described configuration, which includes a cutting means for separating the steel wire and a heating means provided between the feed roller and the coiling portion, the heating means having the above-described configuration in which the steel wire passes through the inside of the heating means. and a hydrocarbon supply means for creating a hydrocarbon-based gas atmosphere in a portion through which the steel wire passes.

According to such a coil spring forming apparatus, the steel wire is rapidly heated to the austenitic region in the heating means and then carburized by the hydrocarbon gas within a sufficient heat retention period. Carburization can be enhanced without degradation and without simple extension or addition of heating coils.

ADVANTAGE OF THE INVENTION According to the present invention, a high-frequency heating coil and a spring forming apparatus are provided that can improve the carburization property without lowering the feeding speed of the steel wire and without simply expanding or adding more heating coils. be.

It is a side view which shows the spring forming apparatus of embodiment of this invention. (A) is a side view showing a high-frequency heating coil according to an embodiment of the present invention, and (B) is a side sectional view thereof. (A) is a side view showing a high-frequency heating coil of a reference example of the present invention, and (B) is a side sectional view thereof. 4 is a graph showing the relationship between the distance of the steel wire from the coil inlet and the temperature of the steel wire.

1. Configuration of Spring Forming Apparatus As shown in FIG. 1, the spring forming apparatus 1 includes a feed roller 10 for continuously supplying the steel wire M and a coiling section 20 for forming the steel wire M into a coil shape. there is The coiling unit 20 includes a wire guide 21 for guiding the steel wire M supplied by the feed roller 10 to an appropriate position, and a wire guide 21 for processing the steel wire M supplied via the wire guide 21 into a coil shape. A coiling tool 22 consisting of a coiling pin (or coiling roller) 22a and a pitch tool (not shown) for pitching are provided.

In addition, the spring forming apparatus 1 includes a cutting means 30 having a cutting blade 30a and an inner die 30b for separating the steel wire M continuously supplied from the rear after coiling a predetermined number of turns, A high-frequency heating coil 40 that heats the steel wire M between the coiling tools 22 is provided.

Near the middle between the high-frequency heating coil 40 and the feed roller 10, a hydrocarbon-based gas supply unit (hydrocarbon-based gas supply means) 50 is arranged to create a hydrocarbon-based gas atmosphere in the area through which the steel wire M passes. A surrounding member 51 made of, for example, ceramics is disposed inside the high-frequency heating coil 40, and a hydrocarbon-based gas is supplied into the surrounding member 51 from a hydrocarbon-based gas supply unit 50 so that the steel wire M passes through. ing.

2. Configuration of High-Frequency Heating Coil A high-frequency heating coil 40 according to an embodiment of the present invention will be described with reference to FIG. In addition, in FIG. 2, the left side is the coil inlet and the right side is the coil outlet. The high-frequency heating coil 40 is composed of various coil portions having uniform coil wire diameters and different pitches and outer diameters.

A tightly wound inner coil portion 41 is disposed on the coil inlet side, and the inner coil portion 41 extends three and a half turns toward the coil outlet. One end of a connecting piece 42 protruding radially outward is fixed to the end face of the inner coil portion 41 on the coil entrance side, and the end face of the coarsely wound outer coil portion 43 is fixed to the other end of the connecting piece 42 . It is

The inner diameter of the outer coil portion 43 is larger than the outer diameter of the inner coil portion 41 , so a gap is formed between the inner coil portion 41 and the outer coil portion 43 . The outer coil portion 43 extends two turns toward the coil outlet. A double coil portion (multiple coil portion) 48 is composed of the outer coil portion 43 and the inner coil portion 41 .

A first terminal 44 is fixed to the end face of the outer coil portion 43 on the coil outlet side. The first terminal 44 includes a first lateral terminal portion 44a extending to the depth side perpendicular to the plane of the drawing, an axial terminal portion 44b extending axially from the end of the first lateral terminal portion 44a, A vertical terminal portion 44c extending downward from an end portion of the axial terminal portion 44b, and a second horizontal terminal portion 44d extending from an end portion of the vertical terminal portion 44c to the depth side orthogonal to the plane of the drawing. consists of

A close-wound single coil portion 45 extends three turns from the end of the inner coil portion 41 on the coil exit side toward the coil exit side. The outer diameter of the single coil portion 45 is larger than the outer diameter of the inner coil portion 41 and smaller than the outer diameter of the outer coil portion 43 .

From the end of the single coil portion 45 on the coil exit side, the rough coil portion 46 extends by one turn toward the coil exit side. The outer diameter of the coarse coil portion 46 is approximately the same as the outer diameter of the outer coil portion 43 , but the pitch is approximately 2.5 times the pitch of the outer coil portion 43 . A second terminal 47 is fixed to the end of the coarsely wound coil portion 46 and extends to the far side perpendicular to the plane of the drawing. A power supply is connected to the first and second terminals 44 and 47 .

3. Operation of Spring Forming Apparatus The steel wire M is fed into the enclosing member 51 by the feed roller 10 and passes through the enclosing member 51 . At that time, the steel wire M is heated by the high-frequency heating coil 40 . In the high-frequency heating coil 40, when a high-frequency alternating current is supplied to the first and second terminals 44 and 47, an alternating magnetic flux is generated inside the terminals 44 and 47, and Joule heat due to the eddy current is generated in the conductor to be heated. Occur.

In the high-frequency heating coil 40 configured as described above, since the double coil portion 48 consisting of the inner coil portion 41 and the outer coil portion 43 is provided on the coil entrance side, a high-density alternating magnetic flux passes through the inner side. As a result, the steel wire M passing through the high-frequency heating coil 40 is rapidly heated and reaches a temperature in the austenite region within, for example, 2.5 seconds.

The portion of the steel wire M that has been heated to the temperature in the austenite region then enters the single coil portion 45 . Since the single coil portion 45 has an outer diameter larger than that of the inner coil portion 41, the magnetic flux density at the position through which the steel wire M passes is reduced, and the heat generation of the steel wire M is suppressed. As a result, the steel wire rod M entering the single coil portion 45 is in a heat retaining state in which the temperature in the austenite region is maintained.

Then, the portion of the steel wire M that has maintained the temperature in the austenite region enters the rough-wound coil portion 46 . Since the coarsely wound coil portion 46 has a larger outer diameter and pitch than the single coil portion 45, the magnetic flux density at the position where the steel wire M passes is further reduced, and the heat generation of the steel wire M is suppressed, so that the austenite region is formed. temperature is maintained.

The portion of the steel wire M that maintains the temperature in the austenite region is carburized in contact with the hydrocarbon-based gas supplied from the hydrocarbon-based gas supply section 50 into the enclosing member 51 . Then, the portion concerned is supplied to the coiling section 20 via the wire guide 21 . In the coiling section 20, the steel wire M passed through the wire guide 21 is brought into contact with the coiling pin 22a and bent with a predetermined curvature, and further brought into contact with the downstream coiling pin 22a and bent with a predetermined curvature. Then, the pitch tool is brought into contact with the steel wire M to impart a pitch so as to form a desired coil shape. When the desired number of turns is reached, the cutting edge 30a of the cutting means 30 shears the steel wire M from the straight portion of the inner mold 30b to separate the spring-shaped steel wire M from the steel wire M supplied from the rear. .

In the high-frequency heating coil 40 configured as described above, the temperature rise region due to the double coil portion 48 is short, and the heat retention region formed by the single coil portion 45 and the coarsely wound coil portion 46 is long. , it can be in contact with a hydrocarbon-based gas for a long time and undergo sufficient carburization. Therefore, the carburization property can be improved without lowering the feeding speed of the steel wire M and without simply extending or adding the high-frequency heating coil 40 .

Particularly in the above-described embodiment, the second terminal 47 is fixed to the end of the rough-wound coil portion 46, and the second horizontal terminal portion 44d is arranged in close proximity to the second terminal 47 and extending in the same direction. can be easily connected to the power supply.

4. Modifications The present invention is not limited to the above embodiments, and various modifications are possible as follows.

(1) The single coil portion 45 can be extended to the coil outlet without providing the rough coil portion 46 .

(2) The outer coil portion 43 may be tightly wound. As a result, it is possible to further shorten the temperature rising region by the double coil portion 48 and extend the heat retaining region.

(3) The double coil section 48 may be a multiple coil section in which the double coil section 48 is stacked three times. This also makes it possible to further shorten the temperature rising region by the multiple coil portion and extend the heat retaining region.
(4) The heating coil may be formed as a continuous coil without providing connecting pieces or terminals.

5. REFERENCE EXAMPLE Next, a high-frequency heating coil manufactured as a trial in the process of completing the high-frequency heating coil 40 of the present invention will be described.

FIG. 3 is a side view (A) and a cross-sectional view (B) showing a high-frequency heating coil 60 of a reference example. A close-wound single coil portion 61 is arranged on the coil entrance side of the high-frequency heating coil 60 . The single coil portion 61 extends for seven and a half turns toward the coil outlet. A connecting piece 62 protruding radially outward is fixed to the end of the single coil portion 61 on the coil outlet side, and the end of the rough winding coil portion 63 is fixed to the end of the connecting piece 62 .

The coarsely wound coil portion 63 has the same pitch and outer diameter as those of the coarsely wound coil portion 46 of the above-described embodiment, and extends three turns to the coil outlet. A terminal 64 is fixed to the end of the coarsely wound coil portion 63 . A terminal 65 is also fixed to the end of the single coil portion 61 on the coil inlet side. By supplying a high-frequency alternating current to the terminals 64 and 65, an alternating magnetic flux passes inside.

In the high-frequency heating coil 60 configured as described above, it seems that the steel wire M can be rapidly heated in the single coil portion 61 and kept warm in the coarsely wound coil portion 63 . However, according to the study of the present inventor, as shown in the following performance test, it has been found that the high-frequency heating coil 60 is not sufficiently carburized.

6. Performance test (1) Steel wire temperature distribution A conventional high-frequency heating coil (conventional example) consisting only of a close-wound coil portion, a high-frequency heating coil 60 (reference example) shown in FIG. 3, and a high-frequency heating coil 40 ( Inventive Example) was attached to the spring forming apparatus 1 shown in FIG. The results are shown in FIG.

FIG. 4 shows the temperature distribution of the steel wire from the coil inlet. In a conventional high-frequency heating coil consisting only of a close-wound coil portion, the temperature reaches 1000 ° C. at a position 100 mm from the coil inlet, but in the reference example, the temperature reaches 1000 ° C. has reached

(2) Carburizing test The above three types of high-frequency heating coils were attached to the spring forming apparatus 1 shown in Fig. 1, and coil springs were formed under the following conditions.
Coil wire diameter: 4.1 mm Heating temperature: 1050°C Feeding speed: Faster than before Spring index: 6

When the state of carburization was investigated in the cross section of the formed coil spring, carburization was confirmed in 100% of the peripheral portion of the cross section in the invention example. At this time, the carburizing depth was 30 to 40 μm and the carbon concentration was 0.7 to 1.0% by mass. Moreover, the region with a carbon concentration of 0.8% by mass or more was 97% around the cross section.

On the other hand, in the conventional example, carburization was confirmed in 70 to 80% of the circumference of the cross section, and in the reference example, carburization was confirmed in 78% of the circumference of the cross section. Therefore, in the conventional example and the reference example, carburization was not sufficient at a higher feed rate than in the conventional example, and the feed rate had to be reduced to the conventional level. Thus, in the present invention, it was confirmed that carburization was reliably performed even when the steel wire rod was fed at a higher speed than in the prior art.

INDUSTRIAL APPLICABILITY The present invention enables reliable carburization without lowering the production speed and without simply extending or increasing the number of heating coils. , agricultural machinery, etc., and can be used in the industry of coil springs used in all technical fields.

DESCRIPTION OF SYMBOLS 10... Feed roller 20... Coiling part 21... Wire guide 22... Coiling tool 22a... Coiling pin 30... Cutting means 30a... Cutting blade 30b... Inner mold 40, 60... High-frequency heating coil 41... Inner coil portion 42 Connecting piece 43 Outer coil portion 44 First terminal 44a First lateral terminal portion 44b Axial terminal portion 44c Vertical terminal portion 44d Second lateral Directional terminal portion 45 Single coil portion 46 Rough coil portion 47 Second terminal 48 Double coil portion (multiple coil portion) 50 Hydrocarbon gas supply portion (hydrocarbon gas supply Means), 51... Surrounding member, W... Steel wire rod.

Claims (7)

In a high-frequency heating coil for high-frequency heating by passing a steel wire inserted from a coil inlet inside, a densely wound inner coil portion and a densely wound or coarsely wound coil disposed outside the inner coil portion are provided on the coil inlet side. and a close-wound single coil portion having an outer diameter larger than that of the inner coil portion is provided adjacent to the coil exit side of the multiple coil portion, and the 1. A high-frequency heating coil comprising: a coarsely wound coil portion having an outer diameter larger than the outer diameter of the single coil portion adjacent to a coil outlet side of a single coil portion and extending to the coil outlet. The multiple coil portion is a double coil portion, the ends of the inner coil portion and the outer coil portion on the coil inlet side are connected with a connecting piece, and the end portion of the outer coil on the coil outlet side is provided with a first coil. 2. The high-frequency heating coil according to claim 1, wherein a terminal is fixed, and a second terminal is fixed to an end portion of the rough-wound coil portion on the coil outlet side. The second terminal extends in a direction perpendicular to the end face of the rough coil portion, and the first terminal extends in a direction substantially parallel to the second terminal and perpendicular to the end face of the outer coil portion. a first lateral terminal portion extending from an end of the lateral terminal portion in an axial direction of the outer coil portion; and an end portion of the axial terminal portion extending from the second terminal portion. and a second horizontal terminal portion extending in the same direction and parallel to the second terminal from an end of the vertical terminal portion. The high frequency heating coil according to claim 2. In a high-frequency heating coil for high-frequency heating by passing a steel wire inserted from a coil inlet inside, a densely wound inner coil portion and a densely wound or coarsely wound coil disposed outside the inner coil portion are provided on the coil inlet side. and a closely wound single coil portion having an outer diameter larger than the outer diameter of the inner coil portion adjacent to the coil exit side of the multiple coil portion and extending to the coil exit. A high-frequency heating coil characterized by being extended. The high-frequency heating coil according to any one of claims 1 to 4, wherein the multiple coil portion has a length of ⅓ or less of the total length of the high-frequency heating coil. The high-frequency heating coil according to any one of claims 1 to 5, wherein the total length is 350 mm or less. A feed roller for continuously supplying the steel wire, a coiling section for forming the steel wire into a coil, and a steel wire for separating the steel wire continuously supplied from the rear after coiling the steel wire for a predetermined number of turns. and a heating means provided between the feed roller and the coiling section,
The heating means comprises the high-frequency heating coil according to any one of claims 1 to 6, through which the steel wire passes, and a hydrocarbon supply means for creating a hydrocarbon-based gas atmosphere in the place through which the steel wire passes. Coil spring forming equipment.

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