Patent Description:
Conventionally, a shaft-like body has been subjected to traverse hardening by induction heating to increase a fatigue strength of the shaft-like body. "Traverse hardening" as used herein means performing hardening while moving a coil member or the like with respect to a shaft-like body in an axial direction of the shaft-like body.

In induction heating, a shaft-like body is inserted into a primary coil member formed in a solenoidal shape, and a high-frequency current is caused to flow in the primary coil member to heat the shaft-like body using induction heating. In induction heating, a shaft-like body is more efficiently heated as a distance between the shaft-like body and the primary coil member becomes smaller. Therefore, when a shaft-like body includes a main body part and a small diameter part provided in the main body part and having a smaller diameter than the main body part, there is a problem that the small diameter part is not easily heated compared to the main body part.

In regard to this problem, a traverse hardening device including a secondary coil member that has an outer diameter smaller than an inner diameter of a primary coil member on an inner side of the primary coil member has been proposed (see Patent Documents <NUM> to <NUM>, for example). The secondary coil member is formed in an O-shape or a C-shape. In the proposed device using the secondary coil, since a distance between a shaft-like body and a coil member close to the shaft-like body does not change as much between the main body part and the small diameter part, the main body part and the small diameter part can be heated equally.

In these traverse hardening devices, since a plurality of coil members are concentrically disposed, distances between the shaft-like body and the coil members close to the shaft-like body are uniform in a circumferential direction. Since a coil member having a large number of turns and satisfactory current efficiency can be used, a shaft-like body can be heated uniformly and efficiently with a small amount of current.

<CIT> and <CIT> disclose induction coils.

However, when a secondary coil formed in an O shape or a C shape is utilized as in the related art described above, it is not possible to freely dispose or take a second coil in or outside of a gap between a primary coil and a shaft-like body (particularly, small diameter part) while the primary coil is traversing relative to the shaft-like body (that is, during traverse hardening). In order to realize this, it is necessary to introduce a complicated mechanism into a traverse hardening device. Thus, this leads to an increase in development costs and the like.

For this reason, in the related art, there has been a demand for the development of a traverse hardening device capable of hardening a shaft-like body having a form in which a diameter changes along an axis with a relatively simple constitution.

The present invention was made in view of the above circumstances, and an object thereof is to provide a traverse hardening device capable of hardening a shaft-like body having a form in which a diameter changes along an axis with a relatively simple constitution, and a traverse hardening method which can be realized using the traverse hardening device.

The present invention is as described in the attached claims, to solve the above-described problems and achieve the object.

According to each of the above aspects of the present invention, it is possible to provide a traverse hardening device capable of hardening a shaft-like body having a form in which a diameter changes along an axis with a relatively simple constitution, and a traverse hardening method which can be realized using the traverse hardening device.

First, a shaft-like body <NUM> which is a body to be heated will be described with reference to <FIG> and <FIG>. As shown in <FIG> and <FIG>, the shaft-like body <NUM> includes a small diameter part <NUM> provided on an intermediate section of a main body part <NUM> in an axis C direction and the main body part <NUM>. The main body part <NUM> and the small diameter part <NUM> are each formed in a columnar shape and an axis of the small diameter part <NUM> coincides with an axis C of the main body part <NUM>.

In the following description, a portion of the main body part <NUM> disposed on one side D1 in the axis C direction with respect to the small diameter part <NUM> is referred to as a "first main body part 52A". A portion of the main body part <NUM> disposed on the other side D2 in the axis C direction with respect to the small diameter part <NUM> is referred to as a "second main body part 52B".

The first main body part 52A, the small diameter part <NUM>, and the second main body part 52B are each formed in a columnar shape and are disposed on a common axis C. An outer diameter of the small diameter part <NUM> is smaller than outer diameters of the first main body part 52A and the second main body part 52B.

In order to transform a metal structure of a hardened place of the shaft-like body <NUM> into austenite as described above, normally, it is necessary to heat the shaft-like body <NUM> to a temperature of an Ac1 point or higher which exceeds <NUM>. A primary coil <NUM> as shown in <FIG> is generally utilized for heating the shaft-like body <NUM>. The primary coil <NUM> is a coil having a solenoidal shape and is formed of a strand of a coil wound in a spiral shape. If the primary coil <NUM> is caused to traverse in the axis C direction so that the shaft-like body <NUM> passes inside the primary coil <NUM> in a radial direction while causing a high-frequency electric current to flow through the primary coil <NUM>, eddy currents sequentially occur on a surface of the shaft-like body <NUM> due to an electromagnetic induction phenomenon. As a result, the surface of the shaft-like body <NUM> is heated through heat generation according to a Joule's law.

In order to induce an eddy current on a surface of the shaft-like body <NUM> which can be heated to a high temperature of an Ac1 point or higher, it is necessary to cause a large current to flow through the primary coil <NUM> as well. For example, when a large current is caused to flow through a one-turn coil, the power efficiency decreases and the coil also easily overheats. For this reason, generally, as in the primary coil <NUM> shown in <FIG>, measures are taken to reduce an electric current value per coil by utilizing a coil which is wound a plurality of times in a spiral shape having a form in which the coil is wound along a surface of the shaft-like body <NUM>. The reason why the coil is wound in the spiral shape having the form in which the coil is wound along the surface of the shaft-like body <NUM> is that, if a distance between the coil and the shaft-like body <NUM> increases, an influence of a change in magnetic flux density caused due to the coil on the shaft-like body <NUM> is reduced.

Here, for example, as shown in <FIG>, when the primary coil <NUM> reaches a position corresponding to an upper end portion of the small diameter part <NUM> (an end portion on the one side D1 in the axis C direction), an upper end portion of the primary coil <NUM> comes close to a corner portion <NUM> which is a place in which a diameter starts to change from the first main body part 52A toward the small diameter part <NUM>. At this time, due to the skin effect, a magnetic flux is concentrated at the corner portion <NUM> close to the upper end portion of the primary coil <NUM>. On the other hand, when the small diameter part <NUM> is heated, a distance between the primary coil <NUM> and the shaft-like body <NUM> is maximized. Thus, it is necessary to increase an amplitude value of a high-frequency electric current flowing through the primary coil <NUM>. As a result, when the primary coil <NUM> reaches the position shown in <FIG>, the corner portion <NUM> at which a magnetic flux is concentrated overheats to a high temperature which exceeds a target temperature.

Such an overheating phenomenon of the corner portion <NUM> can also occur in a corner portion <NUM> which is a place in which a diameter starts to change from the second main body part 52B toward the small diameter part <NUM>.

The inventors of the present invention have studied a method for minimizing an overheating phenomenon occurring in the corner portions <NUM> and <NUM> as described above using a secondary coil. As a result, in order to minimize the overheating phenomenon, it became clear that a very complicated mechanical mechanism in which a secondary coil can be freely disposed or removed in or from a gap between the primary coil <NUM> and the shaft-like body <NUM> (the small diameter part <NUM>) needed to be introduced into a traverse hardening device.

Thus, the inventors of the present invention have diligently studied a measure capable of hardening a shaft-like body having a form in which a diameter changes along an axis with a relatively simple constitution. As a result, for example, it was found that, by employing a coil wound a plurality of times in the shape as shown in <FIG> as a primary coil <NUM>, it is possible to minimize an overheating phenomenon occurring in the corner portions <NUM> and <NUM> without using a secondary coil or the like.

As shown in <FIG>, when a horizontal axis represents a radial direction of the primary coil <NUM> and a vertical axis represents a direction orthogonal to the radial direction in a plane orthogonal to a circumferential direction of the primary coil <NUM>, a cross-sectional image of the primary coil <NUM> which appears in the plane appears in a form of segmentations by a matrix of <NUM> pieces vertically×<NUM> pieces horizontally.

If the primary coil <NUM> having such a cross-sectional shape is utilized, as shown in <FIG>, when the primary coil <NUM> reaches a position corresponding to the upper end portion of the small diameter part <NUM>, it is possible to keep the upper end portion of the primary coil <NUM> away from the corner portion <NUM>. As a result, since it is possible to minimize the concentration of a magnetic flux on the corner portion <NUM>, it is possible to minimize an overheating phenomenon occurring in the corner portion <NUM>. Similarly, it is also possible to minimize an overheating phenomenon occurring in the corner portion <NUM>.

On the other hand, if the primary coil <NUM> having such a cross-sectional shape is utilized, a distance between the shaft-like body <NUM> and the primary coil <NUM> increases. Thus, there is a concern that it will be difficult to induce an eddy current required for performing heating to a target temperature on a surface of the shaft-like body <NUM>. However, as a result of the analysis by the inventors of the present invention, it was confirmed that an eddy current necessary and sufficient for performing heating to the target temperature can be induced on the surface of the shaft-like body <NUM> (the analysis result will be described later).

The present invention has been completed on the basis of the above findings and an embodiment of the present invention will be described in detail below with reference to the drawings.

<FIG> is a schematic side view showing a partial cutout portion of a traverse hardening device <NUM> according to the embodiment. As shown in <FIG>, the traverse hardening device <NUM> is a device for performing traverse hardening on the shaft-like body <NUM> such as an axle for a railroad vehicle using a high-frequency electric current.

The shaft-like body <NUM> includes the main body part <NUM>, and the small diameter part <NUM> provided on the intermediate section of the main body part <NUM> in the axis C direction. The main body part <NUM> and the small diameter part <NUM> are each formed in a columnar shape and the axis of the small diameter part <NUM> coincides with the axis C of the main body part <NUM>.

In the following description, a portion of the main body part <NUM> disposed on the one side D1 in the axis C direction with respect to the small diameter part <NUM> is referred to as the "first main body part 52A". A portion of the main body part <NUM> disposed on the other side D2 in the axis C direction with respect to the small diameter part <NUM> is referred to as the "second main body part 52B".

The first main body part 52A, the small diameter part <NUM>, and the second main body part 52B are each formed in a columnar shape and are disposed on the common axis C. The outer diameter of the small diameter part <NUM> is smaller than the outer diameters of the first main body part 52A and the second main body part 52B.

The shaft-like body <NUM> is formed of a conductive material such as carbon steel, low alloy steel containing not less than <NUM>% by weight of iron (Fe), and the like which have ferrite.

The traverse hardening device <NUM> includes a support member <NUM>, a primary coil <NUM>, a current transformer <NUM> (electric current supply device), a cooling ring <NUM>, a pump <NUM> (cooling liquid supply device), uniaxial actuators (<NUM>, <NUM>, <NUM>), and a control device <NUM>.

As shown in <FIG>, the support member <NUM> includes a lower center <NUM> and an upper center <NUM>. The lower center <NUM> supports the second main body part 52B of the shaft-like body <NUM> from below the second main body part 52B. The upper center <NUM> supports the first main body part 52A of the shaft-like body <NUM> from above the first main body part 52A. The lower center <NUM> and the upper center <NUM> support the shaft-like body <NUM> so that the axis C is directed in an upward/downward direction, the one side D1 in the axis C direction is directed upward, and the other side D2 is directed downward.

The primary coil <NUM> is a coil which has an inner diameter larger than the outer diameter of the main body part <NUM> and has a solenoidal shape. As shown in <FIG>, a cross-sectional image of the primary coil <NUM> which appears in the plane appears in a form of segmentations by a matrix of <NUM> pieces vertically×<NUM> pieces horizontally when a horizontal axis represents a radial direction of the primary coil <NUM> in a plane orthogonal to the circumferential direction of the primary coil <NUM> and a vertical axis represents a direction orthogonal to the radial direction thereof. That is to say, on the right side of the paper surface of the axis C of <FIG>, a cross-sectional image of the primary coil <NUM> appears in a form of segmentations by a matrix of <NUM> pieces vertically×<NUM> pieces horizontally. Similarly, on the left side of the paper surface of the axis C of <FIG>, a cross-sectional image of the primary coil <NUM> appears in a form of segmentations by a matrix of <NUM> pieces vertically×<NUM> pieces horizontally.

<FIG> shows an example of the primary coil <NUM> having the cross-sectional shape as described above. <FIG> is a perspective view of the primary coil <NUM>. The primary coil <NUM> shown in <FIG> can be manufactured through the following procedure.

The primary coil <NUM> shown in <FIG> can be prepared through the procedure as described above. In the embodiment, an outer diameter of the primary coil <NUM> means an outer diameter of the outer upper stage portion <NUM> and the outer lower stage portion <NUM> and an inner diameter of the primary coil <NUM> means an inner diameter of the inner lower stage portion <NUM> and the inner upper stage portion <NUM>.

Referring to <FIG> again, description will be provided below continuously.

The respective end portions (the first extraction end portion <NUM> and the second extraction end portion <NUM>) of the primary coil <NUM> are electrically and mechanically connected to the current transformer <NUM>. The current transformer <NUM> is an electric current supply device which supplies a high-frequency electric current to the primary coil <NUM> under the control of the control device <NUM>. That is to say, a high-frequency electric current flows between the first extraction end portion <NUM> and the second extraction end portion <NUM> of the primary coil <NUM>.

The cooling ring <NUM> is a solenoidal shape member having an inner diameter larger than the outer diameter of the main body part <NUM>. An internal space 36a is formed in the cooling ring <NUM>. A plurality of nozzles 36b communicating with the internal space 36a are formed in an inner circumferential surface of the cooling ring <NUM> so as to be away from each other in the circumferential direction. The shaft-like body <NUM> is coaxially inserted inside the cooling ring <NUM> in the radial direction. The cooling ring <NUM> is disposed closer to the other side D2 in the axis C direction than the primary coil <NUM>.

The pump <NUM> is joined to the cooling ring <NUM> via a water supply pipe 37a. The pump <NUM> is a cooling liquid supply device which supplies a cooling liquid L such as water into the internal space 36a of the cooling ring <NUM> via the water supply pipe 37a under the control of the control device <NUM>. The cooling liquid L supplied into the internal space 36a of the cooling ring <NUM> is ejected toward an outer circumferential surface of the shaft-like body <NUM> through the plurality of nozzles 36b to cool the shaft-like body <NUM>.

The primary coil <NUM>, the current transformer <NUM>, the cooling ring <NUM>, and the pump <NUM> are fixed to a support plate <NUM>. Pinions 39a are formed on the support plate <NUM>. A motor <NUM> configured to drive the pinions 39a is attached to the support plate <NUM>.

The pinions 39a of the support plate <NUM> meshes with a rack <NUM>. If the motor <NUM> is driven, the pinions 39a rotates forward or backward. Thus, the support plate <NUM> traverses upward or downward (that is, in the axis C direction) with respect to the rack <NUM>.

The rack <NUM> may be a ball screw. In this case, the plurality of pinions 39a may be disposed to have the ball screw disposed therebetween.

The support plate <NUM> having the pinions 39a described above, the motor <NUM>, and the rack <NUM> are mechanical elements constituting an example of the uniaxial actuators of the present invention. That is to say, each of the uniaxial actuators composed of these mechanical elements is configured to enable positioning of the primary coil <NUM> in the axis C direction which supporting the primary coil <NUM> and the cooling ring <NUM> so that the shaft-like body <NUM> passes inside the primary coil <NUM> and the cooling ring <NUM> in the radial direction and the primary coil <NUM> is disposed on the one side D1 in the axis C direction with respect to the cooling ring <NUM>.

The control device <NUM> includes an arithmetic circuit (not shown) and a memory (not shown). The memory has a control program or the like for driving the arithmetic circuit stored therein. The control device <NUM> is connected to the current transformer <NUM>, the pump <NUM>, and the motor <NUM> (the mechanical element of the uniaxial actuator) and synchronously controls these operations in accordance with the control program.

A traverse hardening method realized using the traverse hardening device <NUM> configured as described above will be described below with reference to <FIG>. The traverse hardening method according to the embodiment has, as a basic process, a preparatory process (first step) and a hardening process (second step).

In the preparatory process, the shaft-like body <NUM> which is a body to be heated and the traverse hardening device <NUM> including the above constitution are prepared. Moreover, the upper center <NUM> supports an end surface of the first main body part 52A on an upper side (the one side D1 in the axis C direction) so that the axis C of the shaft-like body <NUM> is perpendicular to a horizontal plane and the lower center <NUM> supports an end surface of the second main body part 52B on a lower side (the other side D2 in the axis C direction) (refer to <FIG>). In this case, the one side D1 (upper side) in the axis C direction is a direction in which the primary coil <NUM> and the cooling ring <NUM> moves forward.

In the hardening process, first, the control device <NUM> of the traverse hardening device <NUM> performs, as an initial setting process, a process for traversing the primary coil <NUM> to an initial position (traverse start position) set in advance in the axis C direction and making the primary coil <NUM> stand by.

To be specific, as shown in <FIG>, as an initial setting process, the control device <NUM> controls the motor <NUM> of the uniaxial actuator so that the primary coil <NUM> stands by at a traverse start position set at a position corresponding to a lower end portion of the second main body part 52B. The traverse start position of the primary coil <NUM> may be set to a position corresponding to the lower end portion of the second main body part 52B. Alternatively, the traverse start position of the primary coil <NUM> may be set to a position which is away by a distance shorter than a coil width of the primary coil <NUM> in a direction orthogonal to the radial direction from the lower end portion of the second main body part 52B further to the other side D2 (lower side) in the axis C direction. In other words, the traverse start position may be set to a position in which the entire shaft-like body <NUM> can be subjected to induction heating through traversing (upward movement) of the primary coil <NUM>.

As described above, the uniaxial actuator including the support plate <NUM>, the motor <NUM>, and the rack <NUM> is configured to enable positioning of the primary coil <NUM> in the axis C direction while supporting the primary coil <NUM> and the cooling ring <NUM> so that the shaft-like body <NUM> passes coaxially inside the primary coil <NUM> and the cooling ring <NUM> in the radial direction and the primary coil <NUM> is disposed on the one side D1 (upper side) in the axis C direction with respect to the cooling ring <NUM>. For this reason, when the uniaxial actuator composed of these mechanical elements is controlled, it is possible to traverse the primary coil <NUM> to the traverse start position and make the primary coil <NUM> stand by in a state in which the primary coil <NUM> is disposed on the upper side (forward movement direction side) with respect to the cooling ring <NUM>.

Subsequently, after the completion of the initial setting process as described above, as shown in <FIG>, the control device <NUM> controls the motor <NUM> of the uniaxial actuator so that the primary coil <NUM> traverses (moves upward) from the traverse start position toward the one side D1 (forward movement direction side) in the axis C direction. At this time, the cooling ring <NUM> also moves upward together with the primary coil <NUM> while a state in which the primary coil <NUM> is disposed on the upper side (forward movement direction side) with respect to the cooling ring <NUM> is being maintained. The control device <NUM> synchronously controls the current transformer <NUM>, the pump <NUM>, and the motor <NUM> of the uniaxial actuator so that a high-frequency electric current is supplied to the primary coil <NUM> and the cooling liquid L is supplied to the cooling ring <NUM> while the primary coil <NUM> and the cooling ring <NUM> are traversing in a forward movement direction.

In this way, the current transformer <NUM>, the pump <NUM>, and the motor <NUM> of the uniaxial actuator are synchronously controlled. Thus, it is possible to move upward the primary coil <NUM> and the cooling ring <NUM> in the forward movement direction so that the shaft-like body <NUM> (second main body part 52B) passes inside the primary coil <NUM> and the cooling ring <NUM> in the radial direction while a high-frequency electric current is being supplied to the primary coil <NUM> and the cooling liquid L is being supplied to the cooling ring <NUM> in a state in which the primary coil <NUM> is disposed on the forward movement direction side with respect to the cooling ring <NUM>.

When the primary coil <NUM> moves upward in the axis C direction while receiving the supply of a high-frequency electric current, the second main body part 52B is subjected to continuous induction heating in the axis C direction and a metal structure of a surface of the second main body part 52B transforms into austenite. At this time, since the cooling ring <NUM> also moves upward in the form in which the cooling ring <NUM> follows the primary coil <NUM>, immediately after the second main body part 52B is subjected to induction heating, the second main body part 52B is continuously cooled in the axis C direction through the injection of the cooling liquid L from the cooling ring <NUM>. As a result, the metal structure of the surface of the second main body part 52B transforms from the austenite into hard martensite. In this way, as the primary coil <NUM> and the cooling ring <NUM> move upward, the second main body part 52B is seamlessly hardened.

After the primary coil <NUM> has passed through the second main body part 52B, the primary coil <NUM> then continues to move upward toward the forward movement direction side so that the small diameter part <NUM> of the shaft-like body <NUM> passes inside the primary coil <NUM> in the radial direction. Thus, following the second main body part 52B, the small diameter part <NUM> is subjected to continuous induction heating in the axis C direction and the metal structure of the surface of the small diameter part <NUM> transforms into austenite. When the small diameter part <NUM> is heated, a distance between the primary coil <NUM> and the shaft-like body <NUM> is maximized. Thus, the control device <NUM> controls the current transformer <NUM> so that an amplitude value of a high-frequency electric current flowing through the primary coil <NUM> increases.

While the primary coil <NUM> is passing through the small diameter part <NUM>, the cooling ring <NUM> also moves upward in the form in which the cooling ring <NUM> follows the primary coil <NUM>. For this reason, immediately after the small diameter part <NUM> is subjected to induction heating, the small diameter part <NUM> is continuously cooled in the axis C direction through the injection of the cooling liquid L from the cooling ring <NUM>. As a result, the metal structure of the surface of the small diameter part <NUM> transforms from the austenite into hard martensite. In this way, as the primary coil <NUM> and the cooling ring <NUM> move upward, the small diameter part <NUM> is seamlessly hardened following the second main body part 52B.

<FIG> shows a state in which the primary coil <NUM> has reached a position corresponding to the lower end portion of the small diameter part <NUM>. Reference numeral <NUM> indicates a corner portion which is a place in which a diameter starts to change from the second main body part 52B toward the small diameter part <NUM>. As shown in <FIG>, when the primary coil <NUM> has reached the position corresponding to the lower end portion of the small diameter part <NUM>, it is possible to keep the lower end portion of the primary coil <NUM> away from the corner portion <NUM> of the shaft-like body <NUM>. As a result, since it is possible to minimize the concentration of a magnetic flux on the corner portion <NUM>, it is also possible to minimize an overheating phenomenon occurring at the corner portion <NUM>.

<FIG> shows a state in which the primary coil <NUM> has reached a position corresponding to the upper end portion of the small diameter part <NUM>. Reference numeral <NUM> indicates a corner portion which is a place in which a diameter starts to change from the first main body part 52A toward the small diameter part <NUM>. As shown in <FIG>, when the primary coil <NUM> has reached the position corresponding to the upper end portion of the small diameter part <NUM>, it is possible to keep the upper end portion of the primary coil <NUM> away from the corner portion <NUM> of the shaft-like body <NUM>. As a result, since it is possible to minimize the concentration of a magnetic flux on the corner portion <NUM>, it is also possible to minimize an overheating phenomenon occurring at the corner portion <NUM>.

After the primary coil <NUM> has passed through the small diameter part <NUM>, the primary coil <NUM> then continues to move upward toward the forward movement direction so that the first main body part 52A of the shaft-like body <NUM> passes inside the primary coil <NUM> in the radial direction. Thus, following the small diameter part <NUM>, the first main body part 52A is subjected to continuous induction heating in the axis C direction and the metal structure of the surface of the first main body part 52A transforms into austenite. When the first main body part 52A is heated, a distance between the primary coil <NUM> and the shaft-like body <NUM> returns to a minimum, the control device <NUM> controls the current transformer <NUM> so that an amplitude value of a high-frequency electric current flowing through the primary coil <NUM> returns to the original value.

While the primary coil <NUM> is passing through the first main body part 52A, the cooling ring <NUM> also moves upward following the primary coil <NUM>. For this reason, immediately after the first main body part 52A has been subjected to induction heating, the first main body part 52A is continuously cooled in the axis C direction through the injection of the cooling liquid L from the cooling ring <NUM>. As a result, the metal structure of the surface of the first main body part 52A transforms from the austenite into hard martensite. In this way, as the primary coil <NUM> and the cooling ring <NUM> move upward, the first main body part 52A is seamlessly hardened following the small diameter part <NUM>.

Also, as shown in <FIG>, finally, the control device <NUM> controls the motor <NUM> of the uniaxial actuator so that the primary coil <NUM> moves upward to a traverse stop position set to a position away from the first main body part 52A to the one side D1 in the axis C direction and the primary coil <NUM> stops at the traverse stop position. The control device <NUM> stops the supply of a high-frequency electric current when the primary coil <NUM> exceeds an upper end of the first main body part 52A. On the other hand, the current transformer <NUM> and the pump <NUM> are synchronously controlled together with the uniaxial actuator so that the cooling liquid L is continuously supplied to the cooling ring <NUM> until the primary coil <NUM> stops at the traverse stop position.

Through the process as described above, when the primary coil <NUM> has reached the traverse stop position, the entire shaft-like body <NUM> has been hardened.

As described above, according to the embodiment, when the primary coil <NUM> having a specific cross-sectional shape is utilized, it is possible to minimize an overheating phenomenon occurring at the corner portion <NUM> and the corner portion <NUM> of the shaft-like body <NUM> without utilizing a secondary coil or the like. That is to say, according to the embodiment, it is possible to provide the traverse hardening device <NUM> capable of hardening the shaft-like body <NUM> having a shape in which an outer diameter changes along the axis with a relatively simple constitution and the traverse hardening method which can be realized using the traverse hardening device <NUM>.

Although the embodiment of the present invention has been described above, the present invention is not limited to the embodiment described above and various modifications can be provided within the scope of the attached claims.

For example, in the embodiment, the shaft-like body <NUM> may not be disposed so that the axis C is disposed in the upward/downward direction (vertical direction) and the axis C may be disposed to be inclined with respect to the upward/downward direction. In this case, the primary coil <NUM> and the cooling ring <NUM> traverse to be inclined in the upward/downward direction.

Although the shaft-like body <NUM> is assumed to be an axle for a railroad vehicle, the shaft-like body <NUM> may be another shaft-like body such as a ball screw.

<FIG> shows the results of simulation analysis of a surface temperature distribution of the shaft-like body <NUM> when the shaft-like body <NUM> is subjected to induction heating using the primary coil <NUM> (refer to <FIG>) having a general cross-sectional shape. <FIG> shows only the analysis result of the right half of a vertical cross-sectional view of the shaft-like body <NUM> with respect to the axis C.

In this simulation, the outer diameter of the main body part <NUM> (the first main body part 52A, the second main body part 52B) was set to <NUM> and the outer diameter (minimum diameter) of the small diameter part <NUM> was set to <NUM>. Furthermore, a material of the shaft-like body <NUM> was set to carbon steel. A frequency of a high-frequency electric current flowing through the primary coil <NUM> was set to <NUM>. A frequency at the time of heating the small diameter part <NUM> and a frequency at the time of heating the main body part <NUM> are the same.

Also, when the primary coil <NUM> was caused to traverse from the other side D2 (lower side) toward the one side D1 (upper side) of the shaft-like body <NUM> in the axis C direction while a high-frequency electric current was being supplied to the primary coil <NUM>, the shaft-like body <NUM> was subjected to continuous induction heating in the axis C direction. <FIG> shows the analysis result of a maximum value of a surface temperature distribution of the shaft-like body <NUM> when the shaft-like body <NUM> is subjected to heating required for performing hardening up to a certain depth through traverse hardening.

<FIG> shows the results of simulation analysis of a surface temperature distribution of the shaft-like body <NUM> when the shaft-like body <NUM> is subjected to induction heating using the primary coil <NUM> of the embodiment (that is, using the traverse hardening device <NUM> in the embodiment described above). <FIG> shows only the analysis result of the right half of the vertical cross-sectional view of the shaft-like body <NUM> with respect to the axis C.

Also in this simulation, the outer diameter of the main body part <NUM> (the first main body part 52A, the second main body part 52B) was set to <NUM> and the outer diameter (minimum diameter) of the small diameter part <NUM> was set to <NUM>. Furthermore, a material of the shaft-like body <NUM> was set to carbon steel. A frequency of a high-frequency electric current flowing through the primary coil <NUM> was set to <NUM>.

Also, when the primary coil <NUM> was caused to traverse from the other side D2 (lower side) toward the one side D1 (upper side) of the shaft-like body <NUM> in the axis C direction while a high-frequency electric current was being supplied to the primary coil <NUM>, the shaft-like body <NUM> was subjected to continuous induction heating in the axis C direction. <FIG> shows the analysis result of the surface temperature distribution of the shaft-like body <NUM> when the shaft-like body <NUM> is subjected to heating required for performing hardening up to a certain depth through traverse hardening.

As shown in <FIG>, it was found that, when the shaft-like body <NUM> was subjected to induction heating using the primary coil <NUM> having a general cross-sectional shape (in the case of a comparative example), the small diameter part <NUM> is heated to <NUM> or higher from the surface to a region having a depth of about <NUM> and a maximum value of the surface temperature distribution is <NUM>.

On the other hand, as shown in <FIG>, it was found that, when the shaft-like body <NUM> is subjected to induction heating using the primary coil <NUM> in the embodiment (that is, using the traverse hardening device <NUM> and the traverse hardening method in the embodiment described above) (in the case of the example of the present invention), the small diameter part <NUM> is heated to <NUM> or higher from the surface to a region having a depth of about <NUM> and a maximum value of the surface temperature distribution is <NUM>.

From the analysis result as described above, as compared with the comparative example, according to the example of the present invention, it was confirmed that the entire shaft state <NUM> can be heated at a high temperature of <NUM> or higher in a deeper region from the surface and the shaft-like body <NUM> can be sufficiently heated and hardened as much as needed with a relatively simple constitution. Furthermore, as compared with the comparative example, according to the example of the present invention, it was confirmed that it is possible to minimize an overheating phenomenon by reducing a maximum value of a surface temperature of the shaft-like body <NUM>.

In the embodiment described above, in the plane orthogonal to the circumferential direction of the primary coil <NUM>, when a horizontal axis represents the radial direction of the primary coil <NUM> and a vertical axis represents the direction orthogonal to the radial direction, a case in which the cross-sectional image of the primary coil <NUM> which appears on the plane appears in a form of segmentations by a matrix of <NUM> pieces vertically×<NUM> pieces horizontally is illustrated. The cross-sectional shape of the primary coil of the present invention is not limited thereto and the cross-sectional image of the primary coil which appears on the plane may appear in a form of segmentations by a matrix of m pieces vertically×n pieces horizontally (m and n are each an integer of <NUM> or more than <NUM>).

For example, as shown in <FIG>, the cross-sectional image of the primary coil which appears on the plane may appear in a form of segmentations by a matrix of <NUM> pieces vertically×<NUM> pieces horizontally. Alternatively, as shown in <FIG>, the cross-sectional image of the primary coil which appears on the plane may appear in a form of segmentations by a matrix of <NUM> pieces vertically×<NUM> piece horizontally. Alternatively, as shown in <FIG>, the cross-sectional image of the primary coil which appears on the plane may appear in a form of segmentations by a matrix of <NUM> pieces vertically×<NUM> pieces horizontally.

Claim 1:
A traverse hardening device which performs traverse hardening on a shaft-like body which has a main body part, and a small diameter part provided in an intermediate section of the main body part in an axial direction and having an outer diameter smaller than that of the main body part, comprising:
a primary coil having an inner diameter larger than an outer diameter of the main body part and having a solenoidal shape;
an electric current supply device which supplies a high-frequency electric current to the primary coil;
a uniaxial actuator configured to enable positioning of the primary coil in the axial direction while supporting the primary coil so that the shaft-like body passes inside the primary coil in a radial direction; and
a control device which controls the electric current supply device and the uniaxial actuator,
wherein, when a horizontal axis represents a radial direction of the primary coil and a vertical axis represents a direction orthogonal to the radial direction in a plane orthogonal to a circumferential direction of the primary coil, a cross-sectional image of the primary coil which appears on the plane appears in a form of segmentations by a matrix of m pieces vertically×n pieces horizontally, wherein m and n are each an integer of <NUM> or more than <NUM>.