Patent Application
20160234885
The present invention relates to an induction heating coil, an induction heating device, and a heating method.
When performing a heat treatment on a stepped workpiece having a relatively thick portion and a relatively thin portion provided on one or both sides of the thick portion, the workpiece is typically heated in a furnace from the viewpoint of uniform heating, but induction heating methods have also been proposed (see, e.g., Patent document 1).
An induction heating coil disclosed in Patent document 1 is configured to inductively heat a double-side-stepped workpiece having a large-diameter shaft portion and small-diameter shaft portions provided on both axial sides of the large-diameter shaft portion. This induction heating coil is configured such that a conductor extends parallel with an outer line of a cross section, including its center axis, of a workpiece, and generates a magnetic flux when supplied with high-frequency power. The workpiece is inductively heated receiving the magnetic flux generated by the induction heating coil while being rotated about its center axis.
Patent Document 1: JPH5-33496U
In induction heating, the heating efficiency lowers as the gap between an induction heating coil and a workpiece increases. In contrast, in the induction heating coil disclosed in Patent Document 1, since it is formed by the conductor extending parallel with the outer line of the cross section, including the center axis, of the workpiece, the gap between itself and the workpiece can be made small and the workpiece can be set in and removed easily.
However, in the induction heating coil disclosed in Patent Document 1, a magnetic field that is formed around itself cannot be adjusted locally and hence it is difficult to adjust the temperatures of individual portions of the workpiece heated so as to obtain a uniform or desired temperature.
The present invention has been made in view of the above circumstances, and it is an object thereof to provide an induction heating coil, an induction heating device, and a heating method that can be suitably used for heat treatment of a double-side-stepped workpiece having a relatively thick portion and relatively thin portions provided on both sides thereof.
According to an aspect of the present invention, an induction heating coil includes a primary coil to which electric power is supplied, and a ring-shaped secondary coil forming a closed circuit. The primary coil includes a base-side portion that covers an outer periphery of the secondary coil and a distal-side portion extending from the base-side portion in a center axis direction of the secondary coil in a state in which the base-side portion covers the secondary coil, and an opening width of the base-side portion is greater than an opening width of the distal-side portion. The secondary coil is provided such that the secondary coil is removable inserted into the primary coil from the base-side portion of the primary coil.
According to another aspect of the present invention, an induction heating device includes the induction heating coil described above, a power source unit configured to supply the electric power to the primary coil of the induction heating coil, a workpiece supporting portion configured to support a workpiece and to move the workpiece relative to the primary coil to insert the workpiece into the primary coil from the base-side portion of the primary coil, and a secondary coil supporting portion configured to support the secondary coil of the induction heating coil and to move the secondary coil relative to the primary coil to insert the secondary coil into the primary coil from the base-side portion of the primary coil.
According to another aspect of the present invention, a heating method is provided to heat a workpiece having a relatively thick portion and relatively thin portions provided on both sides of the thick portion using the induction heating coil described above. The heating method includes inserting the workpiece into the primary coil of the induction heating coil from the base-side portion of the primary coil such that one of the thin portions of the workpiece is accommodated in the distal-side portion of the primary coil and such that the thick portion and the other thin portion of the workpiece are accommodated in the base-side portion of the primary coil, inserting the secondary coil of the induction heating coil into the primary coil from the base-side portion of the primary coil such that the secondary coil is arranged between the base-side portion of the primary coil and the thin portion of the workpiece that is accommodated in the base-side portion, and supplying the electric power to the primary coil to inductively heat the workpiece.
According to the invention, in induction heating a double-side-stepped workpiece, the gap between the induction heating coil and the workpiece can be made small over the entire workpiece because one thin portion of the workpiece is accommodated in the distal-side portion of the primary coil that has a relatively small opening width, the thick portion and the other thin portion of the workpiece are accommodated in the base-side portion of the primary coil that has a relatively large opening width, and the secondary coil is arranged between the base-side portion of the primary coil and the thin portion of the workpiece that is accommodated in the base-side portion. As a result, the workpiece can be heated uniformly and efficiently in its entirety.
In the invention, a double-side-stepped workpiece can be set in and removed from the induction heating coil by inserting or removing the workpiece and the secondary coil from the base-side portion of the primary coil that has a relatively large opening width. Therefore, the double-side-stepped workpiece can be set in and removed from the induction heating coil easily though the device configuration is simple.
In the invention, the secondary coil that forms a closed circuit can be replaced relatively easily. Therefore, the magnetic field that is formed around the secondary coil can be adjusted locally by replacing the secondary coil. As a result, the heating temperature of the thin portion of the workpiece that is accommodated in the secondary coil can be adjusted relatively easily
A heating device 1 is configured to inductively heat a workpiece 2, and includes an induction heating coil 3 having a primary coil 4 and a secondary coil 5, a power source unit 6 for supplying AC power to the primary coil 4, a workpiece supporting portion 7, and a secondary coil supporting portion 9.
The workpiece 2 is a double-side-stepped workpiece having a relatively thick portion and relatively thin portions provided on both sides of the thick portion. In the illustrated example, the workpiece 2 is substantially cylindrical as a whole, and has a large-diameter shaft portion 20 and small-diameter shaft portions 21, 22 provided on both axial sides of the large-diameter shaft portion 20. The small-diameter shaft portion 21 is longer than the other small-diameter shaft portion 22. The workpiece 2 is not limited to the one shown in the drawing, and may be, for example, a substantially prism-shaped workpiece.
The workpiece supporting portion 7 includes a first rod 70 and a second rod 71 which hold the workpiece 2 between them in their axial direction by pushing end surfaces of the two respective small-diameter shaft portions 21, 22, a first rod supporting portion 72 and a second rod supporting portion 73 which support the pair of rods 70, 71, respectively, and a drive unit 74 for moving the pair of rod supporting portions 72, 73 forward and backward in the axial direction. The drive unit 74 is an appropriate rectilinear mechanism using a ball screw, a cylinder/piston, or the like. The workpiece supporting portion 7 may be provided with a rotation mechanism for rotating, if necessary, the pair of rods 70, 71 about the axis in induction heating the workpiece 2 so that the pair of rods 70, 71 are rotated to rotate the workpiece 2 held between them.
The primary coil 4 is has a substantially cylindrical shape as a whole, and is configured to accommodate the workpiece 2. The primary coil 4 is configured such that its opening width is greater on the distal end side than the base end side. In the illustrated example, the primary coil 4 is substantially cylindrical as a whole, and is divided into a first heating portion 40 and a second heating portion 41 (arranged in this order from the tip side) so as to conform to the outer circumferential surfaces of the longer, small-diameter shaft portion 21 and the large-diameter shaft portion 20 of the workpiece 2, whereby its inner diameter (opening width) increases stepwise in the above arrangement direction. The first heating portion 40 is configured to accommodate the longer, small-diameter shaft portion 21 of the workpiece 2, and the second heating portion 41 is configured to accommodate the large-diameter shaft portion 20 and the shorter, small-diameter shaft portion 22. The primary coil 4 need not always be substantially cylindrical. For example, in a case in which the workpiece 2 has a prism shape, the primary coil 4 may be provided in a substantially polygonal-tube-shaped so as to conform to the outer shape of the workpiece 2.
The primary coil 4 is a solenoid coil, and is formed integrally by winding a single, conductive tubular material at winding diameters and intervals that are suitable for the first heating portion 40 and the second heating portion 41, respectively. Two end portions of the primary coil 4 are fastened to respective terminals 44 which are connected to the power source unit 6. A coolant such as water circulates through the tubular material of the primary coil 4, and the two end portions, fastened to respective terminals 44, of the primary coil 4 are provided with respective connectors 45 which are connected to a coolant supply unit (not shown).
The terminals 44 are fixed to, for example, a device stage (not shown) and their positions are thereby fixed. The primary coil 4 is supported by the terminals 44 and is thereby set coaxial with the first rod 70 and the second rod 71 of the workpiece supporting portion 7 and the workpiece 2 which is held between the pair of rods 70, 71.
As described later in detail, the secondary coil 5 is configured to accommodate the shorter, small-diameter shaft portion 22 of the workpiece 2 and to be inserted into and removed from the second heating portion 41 of the primary coil 4. In the illustrated example, as in the case of the primary coil 4, the secondary coil 5 is formed by a conductive tubular material, a coolant such as water circulates through the tubular material of the secondary coil 5, and the secondary coil 5 is provided with connectors 55 which are connected to the coolant supply unit (not shown).
The secondary coil supporting portion 9 has plural shafts 90 which are erected from the second rod supporting portion 73 substantially parallel with the second rod 71 of the workpiece supporting portion 7.
The secondary coil 5 is supported by the plural shafts 90 so as to be coaxial with the first rod 70 and the second rod 71 of the workpiece supporting portion 7 and the workpiece 2 which is held between the pair of rods 70, 71. By suitably adjusting the lengths of the plural shafts 90, the secondary coil 5 is placed at such a position as to accommodate the shorter, small-diameter shaft portion 22 of the workpiece 2 held between the pair of rods 70, 71. Even in the case where the workpiece supporting portion 7 is provided with a rotation mechanism for rotating the pair of rods 70, 71 about the axis and the pair of rods 70, 71 are rotated by this mechanism, the secondary coil 5 is not rotated but fixed to the second rod supporting portion 73 via the plural shafts 90.
As the first rod 70 and the second rod 71 of the workpiece supporting portion 7 are moved by the drive unit 74, the workpiece 2 held between the pair of rods 70, 71 is inserted into the primary coil 4 from the side of the second heating portion 41 of the primary coil 4 with its longer, small-diameter shaft portion 21 directed to the destination. The longer, small-diameter shaft portion 21 of the workpiece 2 is accommodated in the first heating portion 40, and the large-diameter shaft portion 20 and the shorter, small-diameter shaft portion 22 is accommodated in the second heating portion 41 of the primary coil 4.
As the first rod 70 and the second rod 71 of the workpiece supporting portion 7 are moved, the secondary coil 5 which is fixed to the second rod supporting portion 73 via the secondary coil supporting portion 9 is also inserted into the primary coil 4 and comes to be placed between the second heating portion 41 of the primary coil 4 and the shorter, small-diameter shaft portion 22 of the workpiece 2.
The secondary coil 5 has a ring-like shape that is divided at one position in the circumferential direction, and forms a closed circuit circulating alongside the outer circumference and the inner circumference. In the illustrated example, the secondary coil 5 is formed in a substantially circular ring shape so as to extend parallel with the outer circumferential surface of the shorter, small-diameter shaft portion 22 and the inner circumferences of the second heating portion 41 of the primary coil 4. The secondary coil 5 need not always have a substantially circular ring shape. For example, in a case in which the workpiece 2 has a prism shap, the secondary coil 5 may be provided in a rectangular ring shape so as to conform to the outer shape of the workpiece 2.
When AC power (current I1) is supplied to the primary coil 4 from the power source unit 6 in a state in which the secondary coil 5 is accommodated in the second heating portion 41 of the primary coil 4, the secondary coil 5 receives a magnetic flux generated by the second heating portion 41 of the power-supplied primary coil 4, as a result of which an electromotive force develops in the secondary coil 5 and an induction current I2 flows through the secondary coil 5 so as to circulate through its outer circumferential portion and inner circumferential portion because of the skin effect. In the inner circumferential portion, the induction current I2 flows in the same circumferential direction as the current I1 flowing through the second heating portion 41. Therefore, inside the secondary coil 5, the magnetic flux generated by the second heating portion 41 of the power-supplied primary coil 4 is added to a magnetic flux generated by the secondary coil 5. This increases the efficiency of heating of the shorter, small-diameter shaft portion 22 of the workpiece 2 that is accommodated in the secondary coil 5.
When AC power is supplied to the primary coil 4 from the power supply unit 6, the first heating portion 40 and the second heating portion 41 of the power-supplied primary coil 4 generate fluxes φ1 and φ2, respectively.
The longer, small-diameter shaft portion 21 of the workpiece 2 that is accommodated in the first heating portion 40 of the primary coil 4 is inductively heated by receiving the magnetic flux φ1 generated by the first heating portion 40.
The large-diameter shaft portion 20 of the workpiece 2 that is accommodated in the second heating portion 41 is inductively heated by receiving the magnetic flux 42 generated by the second heating portion 41.
The secondary coil 5 accommodated in the second heating portion 41 of the primary coil 4 receives the magnetic flux φ2 generated by the second heating portion 41 and an electromotive force develops in the secondary coil 5, whereby an induction current flows through the secondary coil 5. The secondary coil 5 generates a magnetic flux φ3 because of this induction current.
The shorter, small-diameter shaft portion 22 of the workpiece 2 that is accommodated in the secondary coil 5 is inductively heated receiving, mainly, the magnetic flux φ3 generated by the secondary coil 5.
After completion of the heating treatment on the workpiece 2, the first rod 70 and the second rod 71 of the workpiece supporting portion 7 are moved by the driving unit 74 and the workpiece 2 which is held between the pair of rods 70, 71 and the secondary coil 5 which is fixed to the second rod supporting portion 73 via the secondary coil supporting portion 9 are removed from the side of the second heating portion 41 of the primary coil 4.
The heating device 1 is to heat the workpiece 2 by induction heating in the above-described manner and, in general, requires a smaller installation space than heating furnaces. This makes it possible to incorporate the heating device 1 in a processing line of the workpiece 2 and perform heat treatment on the workpiece 2 in the processing line. Furthermore, plural heating devices 1 can be installed in a processing line of the workpiece 2. Still further, orientation of installation of the heating device 1 can be selected as appropriate according to a processing line of the workpiece 2 from vertical orientation in which the pair of rods 70, 71 of the workpiece supporting portion 7 extend vertically, horizontal orientation in which the pair of rods 70, 71 of the workpiece supporting portion 7 extend horizontally, and other kinds of orientation. In this manner, the heat treatment efficiency of the workpiece 2 can be made higher than in batch processes using a heating furnace.
According to the heating device 1, the gap between the workpiece 2 and the induction heating coil 3 can be made small over the entire heating device 1 because the longer, small-diameter shaft portion 21 of the workpiece 2 is accommodated in the first heating portion of the primary coil 4 that has a relatively small opening width, the large-diameter shaft portion 20 and the shorter, small-diameter shaft portion 22 of the workpiece 2 are accommodated in the second heating portion 41 of the primary coil 4 that has a relatively large opening width, and the secondary coil 5 is placed between the shorter, small-diameter shaft portion 22 and the second heating portion 41 of the primary coil 4. As a result, the workpiece 2 can be heated uniformly and efficiently in its entirety.
In the heating device 1, the workpiece 2 can be set in and removed from the induction heating coil 3 by inserting or removing the workpiece 2 and the secondary coil 5 from the side of the second heating portion 41 of the primary coil 4 that has a relatively large opening width. Therefore, the workpiece 2 can be set in and removed from the induction heating coil 3 easily though the device configuration is simple.
Further, according to the heating device 1, the workpiece 2 and the secondary coil 5 forming a closed circuit are moved, and the position of the primary coil 4 to which electric power is supplied can be fixed, whereby the power supply path can be maintained easily and the device configuration can be made even simpler. The entire workpiece 2 can also be heated uniformly by a configuration in which two coils are provided so as to accommodate the two respective parts, extending in the axial direction and bounded at the large-diameter shaft portion 20, of the workpiece 2 and are supplied with power independently. However, this configuration requires two power source units and at least one of the coils needs to be moved together with the associated power source unit. In contrast, the heating device 1 requires the only one power source unit and the positions of the power source unit and the primary coil 4 can be fixed, which is advantageous in terms of the equipment cost.
In the heating device 1, the secondary coil 5 that forms a closed circuit can be replaced relatively easily. Therefore, the magnetic field that is formed around the secondary coil 5 can be adjusted by replacing the secondary coil 5. As a result, the heating temperature of the shorter, small-diameter shaft portion 22 of the workpiece 2 that is accommodated in the secondary coil 5 can be adjusted relatively easily and the temperature distribution of the entire workpiece 2, for example, can be increased in uniformity.
Still further, in the heating device 1, the primary coil 4 is a solenoid coil. Therefore, the magnetic field that is formed around the first heating portion 40 can be adjusted by adjusting the wiring interval of the first heating portion 40 of the primary coil 4. As a result, the heating temperature of the longer, small-diameter shaft portion 21 of the workpiece 2 that is accommodated in the first heating portion 40 can be adjusted relatively easily and the heating temperature of the entire workpiece 2, for example, can be increased in uniformity.
While the primary coil 4 has been described as having a substantially cylindrical shape as a whole in the heating device 1 described above, the primary coil merely needs to have a base-side portion that covers the outer periphery of the secondary coil 5 and a distal-side portion extending the base-side portion in the center axis direction of the secondary coil 5 in a state in which the base-side portion covers the secondary coil, and to make the opening width of the base-side portion greater than the opening width of the distal-side portion so that the secondary coil 5 can be inserted into and removed from the primary coil from the base-side portion. For example, as shown in
The second coil 205 shown in
When the primary coil 4 is supplied with power, an electromotive force develops in the secondary coil 5 and an induction current I2 flows through the secondary coil 5 so as to circulate through its outer conductor portion 250 and inner conductor portion 251. In the inner conductor portion 251, the induction current I2 flows in the same circumferential direction as a current I1 flowing through the second heating portion 41. Therefore, inside the secondary coil 205, a magnetic flux generated by the second heating portion 41 of the primary coil 4 is added to a magnetic flux generated by the secondary coil 205. As a result, like the secondary coil 5 shown in
Like the secondary coil 205 shown in
The second heating portion 41, in which the secondary coil 305 is to be inserted, of the primary coil 4 corresponds to the outer conductor portion 350, elongated in the axial direction, of the secondary coil 305 and is elongated in the axial direction by increasing the number of turns so as to be able to accommodate the outer conductor portion 350.
As the number of turns of the second heating portion 41 of the primary coil 4 is made larger, the magnetic flux generated by the second heating portion 41 is increased. The amount of induction current flowing through the inner conductor portion 351 of the secondary coil 305 can be increased by receiving the increased magnetic flux fully by the outer conductor portion 350 of the secondary coil 305. As a result, the heating efficiency of the shorter, small-diameter shaft portion 22 of the workpiece 2 that is accommodated in the secondary coil 305 can be made even higher.
Since in this manner the amount of induction current flowing through the inner conductor portion 351 of the secondary coil 305 can be adjusted by adjusting the number of turns of the second heating portion 41 of the primary coil 4, as shown in
Like the secondary coil 205 shown in
The secondary coil 405 also has a core member 453 for adjusting the expanse of a magnetic flux generated by the secondary coil 405. The core member 453 is interposed between the outer conductor portion 450 and the inner conductor portion 451. By adjusting the expanse of a magnetic flux generated by the secondary coil 405 by means of the core member 453, the magnetic flux generated by the secondary coil 405 can be caused to cross a local portion of the workpiece 2 in a concentrated manner and can increase the heating efficiency there.
The shape of the core member 453 can be changed in a various manner according to a shape of the workpiece 2 and desired heating temperature distribution of the workpiece 2. In the example of
Test Examples will be described below.
First, in Test Example 1, in induction heating of a double-side-stepped workpiece using an induction heating coil having a primary coil and a secondary coil, a distribution of current flowing through the workpiece was analyzed by a simulation. It was assumed that the workpiece had the same structure as the workpiece 2 shown in
As shown in
Next, Test Examples 2 to 4 will be described in which induction heating heat treatment was performed on a workpiece having the same structure as the workpiece 2 shown in
Supply power: 50 kW
Frequency: 3 kHz
Power supply time: 40 sec
In Test Example 2, a primary coil of an induction heating coil for induction heating the workpiece had the same structure as the primary coil 4 shown in
In Test Example 3, a primary coil had the same structure as the primary coil 4 shown in
In Test Example 4, a primary coil had the same structure as the primary coil 4 shown in
Surface temperatures of the large-diameter shaft portion (20), longer, small-diameter shaft portion (21), and the shorter, small-diameter shaft portion (22) of the workpiece were measured immediately after execution of heating treatment in each of Examples experiments 2-4. Measurement results are as follows:
From the above results, it has been confirmed that the heating efficiency of the shorter, small-diameter shaft portion can be increased by accommodating the shorter, small-diameter shaft portion (22), forming a relatively large gap with the primary coil, of the workpiece and induction heating it via the secondary coil and that the heating efficiency of the shorter, small-diameter shaft portion can be increased further by increasing the number of turns of the heating portion of the primary coil that accommodates the secondary coil. It has also been confirmed that heating efficiency that is equivalent to heating efficiency of a case using a core member can be obtained without a core member by elongating the outer conductor portion of the secondary coil according to increase in the number of turns of the heating portion of the primary coil that accommodates the secondary coil.
The present invention can provide an induction heating coil, an induction heating device, and a heating method that can be suitably used for heat treatment of a double-side-stepped workpiece having a relatively thick portion and relatively thin portions provided on both sides thereof.
While the present invention has been described in detail with reference to certain embodiments thereof, those skilled in the art will understand that various changes and modifications may be made therein without departing from the spirit and scope of the invention. The present application is based on Japanese Patent Application No. 2013-191778 filed on Sep. 17, 2013, the content of which is incorporated herein by reference.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2013-191778 | Sep 2013 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2014/074536 | 9/17/2014 | WO | 00 |
