JP5190740B2 - Induction heating device - Google Patents

Description

  The present invention relates to a method of soaking an object to be heated in induction heating.

  In the case where a single object to be heated is induction-heated with a tunnel-type coil, the following three methods are mainly conceivable as a method corresponding to a plurality of objects to be heated with one coil.

  As a first method, a coil having an overall length matching the length of the object to be heated is manufactured and used for each length of the object to be heated.

  As a second method, a method of providing a tap in the middle of the solenoid coil is conceivable (Patent Document 1).

  As a third method, there is a method of arranging a conductive material on the coil end face (Patent Document 2).

  JP 2002-141165 A   JP 2005-063753 A

  When a single object to be heated is induction-heated by a tunnel-type coil (circular, square or elliptical coil, regardless of the coil axis direction, horizontal and vertical coils), the conventional method will be described later. There was a problem.

Hereinafter, a detailed description will be given of the conventional method.
In the tunnel type coil, heat outflow from the opening portions at both ends and overheating of the end portions due to magnetic flux concentration become problems.
FIG. 6 shows an example of the coil position and the heat generation energy of the object to be heated. In the figure, the object to be heated is arranged at the center of the coil so that the dimensions of h1 and h2 are equal. In FIG. 6A, the heat generation energy distribution in the axial direction of the object to be heated is larger at the end than in the center of the object to be heated.

  The magnitude of the heat generation at this end is determined by the distance from the coil end to the heated object end, h1 (= h2) in the figure. If h1 is large, the heat generation energy at the end portion is increased, and if h1 is small, the heat generation energy at the end portion is decreased. FIG. 6B shows an example where h1 is large, and FIG. 6C shows an example where h1 is small.

  FIG. 7 shows ideal heating of an object to be heated in the conventional method. FIG. 7A shows a state where h1 (= h2) is appropriately selected and the heat generation energy at the end of the object to be heated is slightly larger than that at the center.

  FIG. 7B shows the loss energy of the object to be heated. Loss energy is heat energy lost from the object to be heated. Since the end of the coil is open, the loss energy is increased at the end.

  The temperature of the object to be heated rises due to the difference between the heat generation energy and the loss energy. The energy that contributes to this temperature rise is termed temperature rising energy. When soaking in the conventional method, it is necessary to make the temperature rising energy in the coil axis direction of the object to be heated equal. FIG. 7C shows that the temperature rising energy, which is the difference between the heat generation energy and the loss energy, is constant in the coil axis direction.

  In order to obtain the state of FIG. 7C, it is necessary to compensate for the loss energy from the coil opening shown in FIG. For this reason, in the conventional method, it is necessary to obtain the distribution of heat generation energy shown in FIG. 7A, and each method is devised.

  In the first conventional method described above, the coil length is changed to correspond to the length of the object to be heated. If an appropriate coil length cannot be obtained, that is, if the length of the object to be heated is short relative to the coil length, the end is overheated. If the length of the object to be heated is too long, the end is heated. It becomes insufficient. This is as shown in FIGS. 6B and 6C. Therefore, this method requires a plurality of coils when there are many types of heated object lengths to be heated.

  In the second conventional method described above, the same coil is used to correspond to the length of the object to be heated, but the coil length is changed using a tap. Changing the tap changes the inductance value of the heating coil, which may be undesirable in terms of control depending on the type of induction heating power source that energizes the coil. In this method, every time the object to be heated has a different length, a tap switching operation is required.

  In the third conventional method described above, in order to cope with the length of the object to be heated, the conductive material is disposed near the end of the coil to prevent overheating of the end of the object to be heated. ) To heat the heat distribution.

  As described above, in the conventional method, when the object to be heated is single-heated, the heat generation energy in the axial direction needs to have a distribution as shown in FIG.

  In an induction heating apparatus that heats a single object to be heated using a tunnel type coil, the axial center of the object to be heated is located in the direction of the first terminal of the coil from the center in the length direction of the tunnel type coil. It stops at the shifted first position, preheats for a first predetermined time, and then moves the object to be heated. The center of the object in the axial direction is the center in the length direction of the tunnel coil. The temperature deviation in the axial direction of the object to be heated due to the preceding heating after stationary at the second position shifted in the second terminal direction different from the first terminal of the coil, followed by the second predetermined time. Is compensated by subsequent heating, and the temperature distribution in the axial direction of the object to be heated is made uniform.

  In the present invention, in order to uniformly heat the object to be heated, even if the heat generation in the length direction of the object to be heated is temporarily nonuniform, the position of the object to be heated in the coil axis direction is appropriately changed. The temperature is compensated by heating, and finally the temperature distribution in the axial direction of the object to be heated is made uniform.

  By using the present invention, in the case where a single object to be heated is induction-heated with a tunnel coil, the heat uniformity in the length direction of the object to be heated can be improved.

  Further, even when the length of the object to be heated is different in one tunnel type coil, the heat uniformity in the length direction of the object to be heated can be improved.

Inductive heating method for tunnel type coil of the present invention (first embodiment) Heat generation energy distribution when the object to be heated of the present invention is arranged on the right side (Part 1) Heat generation energy distribution when the object to be heated of the present invention is arranged on the left side (Part 2) 2 and 3 of the present invention combined heat energy Distribution of heat generation energy of the heated object of the present invention (first embodiment) Example of coil length of tunnel type coil and heat distribution of heated object in conventional example Soaking materials to be heated in the conventional example

Mode for carrying out the invention

  Hereinafter, the best mode for carrying out the present invention will be described. FIG. 2 shows an example of heat generation in the coil axis direction when the length of the object to be heated is shorter than the coil length. The object to be heated 1 is arranged on the right side of the coil 2. Since the heat generation energy is non-uniform, if it is heated as it is, it will be in a state with a temperature difference in the axial direction.

  The example of FIG. 3 is obtained by changing the position of the object to be heated in the coil axis direction from the state of FIG. It can be seen that the object to be heated 1 is located on the left side with respect to the coil 2 and has a heat generation distribution opposite to that shown in FIG.

  Here, FIG. 4 shows an average of the heating in the states of FIGS. The solid line in FIG. 4 has the same shape as the heat generation distribution in FIG. 7A described by the conventional method. The heat generation distribution in FIG. 4 is obtained by heating the article 1 to be heated at the position of FIG. 2 and then heating at the position of FIG. 3 (or heating at the position of FIG. 3 and then heating at the position of FIG. 2). be able to. As shown in FIG. 7, if a heat generation distribution that compensates for loss energy can be obtained, the temperature of the object to be heated can be equalized.

  As can be seen from this example, if the coil axial position of the object to be heated is appropriately changed, the temperature distribution in the axial direction becomes constant.

  Further, in this method, even if the length of the object to be heated changes, the temperature of the object to be heated can be equalized by appropriately changing the position.

  FIG. 1 shows an induction heating method for heating an object 1 to be heated, for example, a metal, using an induction heating device 5 having a tunnel type coil 2, and shows Example 1 of the present invention. 3 is a power controller such as an inverter for controlling the power of the coil 2, and 4 is a feed control device for the heated object 1 such as a pusher.

  A two-position control method will be described. When the heated object 1 is fed into the coil 2 from the carry-in end of the coil 2 by the pusher 4, and the rear end 11 of the heated object 1 reaches the vicinity of the rear end portion 21 of the coil 2, the feed control of the pusher 4 stops. Then, the preceding power control of the converter 3 is started from a predetermined position for a predetermined preceding heating time, and a predetermined preceding power control is performed for a predetermined preceding heating time. An example of the heat generation distribution by this preheating is as shown in FIG.

  After performing predetermined power control for a predetermined preceding heating time, the pusher 4 moves the article 1 to be heated to the vicinity of the front end 22 of the coil 2. When the front end 12 of the article to be heated 1 reaches the vicinity of the front end 22 of the coil 2, it stops at a predetermined position and performs subsequent power control for a predetermined subsequent heating time. An example of the heat generation distribution by the subsequent heating is as shown in FIG.

  Therefore, the heat generation distribution in the axial direction of the object to be heated is averaged, and a combined heat generation distribution as shown by the solid line in FIG. 4 can be obtained.

  Although the two-position control method for changing the position of the object to be heated once has been described, the power control is performed by changing the position of the object to be heated N times (N = 1, 2, 3,..., N is a natural number). A method of providing a heating time to make the temperature distribution in the axial direction of the object to be heated uniform is also conceivable. The direction of position movement N times does not matter.

  The pusher feed control has been considered to move the object to be heated at a high feed rate that can ignore the feed time compared to the time to stop and heat up until now. Control the heated object toward the coil unloading end at an arbitrary speed, and control the distribution of heating during stoppage and heating during movement to equalize the temperature distribution in the coil axis direction of the heated object A way to do this is also conceivable.

  FIG. 5 shows how the distribution of heat generation energy of the object to be heated in the two-position control system changes corresponding to the position of the object to be heated. The distances from the coil end of the heated object when the heated object is at the right position are h11 and h12, and the distances from the coil end of the heated object when at the left position are h21 and h22. In this case, although it does not exist as an operation mode, when it is in the middle, distances h31 and h32 from the coil end of the object to be heated are h31 = h32.

  In the two-position control, it is not necessary that h11 = h22 and h12 = h21. In the middle of heating, temperature non-uniformity occurs in the coil axis direction. Therefore, the distribution of loss energy in the axial direction is different from that in FIG. 7B due to the influence of heat conduction in the object to be heated. As a result, the heat energy distribution synthesized for soaking the temperature is as shown in FIG. ) Distribution is different.

When the object to be heated is an iron cylindrical billet material and heated from room temperature to around 1200 ° C with two-position control, the dimensions from the coil end are approximately the following values, so that the temperature in the axial direction is equalized: Can be planned.
h12 = 0 to -d / 2
h21 = d / 3 to d
(D is the diameter of the object to be heated, and the negative value of h12 indicates that the rear end of the object to be heated 1 protrudes from the coil 2.)

Industrial applicability

  Applicable to metal heating devices.

DESCRIPTION OF SYMBOLS 1 Heated object 2 Heating coil 3 Power controller 4 Feed control apparatus 5 Induction heating apparatus 11 Heated object rear end 12 Heated object front end 21 Coil rear end 22 Coil front end

Claims (1)

In an induction heating apparatus for heating a single object to be heated using a tunnel type coil composed of a circular, square or elliptical coil, the axial center of the object to be heated is the length direction of the tunnel type coil coil. It stops at the first position shifted in the direction of the first terminal of one of the coils from the center, preheats for a first predetermined time, and then moves the object to be heated in the axial direction of the object to be heated. The center is stationary at the second position shifted in the second terminal direction different from the first terminal of the coil from the center in the length direction of the tunnel type coil, and then heated for a second predetermined time, An induction heating method characterized in that a temperature deviation in the axial direction of a superheated material is made uniform by compensating a temperature deviation in the axial direction of the heated material due to preceding heating by subsequent heating .

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