JP6243252B2 - Induction heating method - Google Patents

Description

  The present invention relates to induction heating for heating a flat or curved plate surface of a box or a vehicle body formed of a conductive metal plate to dry the surface coating or preheating a mold. Regarding the method.

  Drying of a box made of a conductive metal plate or the surface of a vehicle body with a spray gun applied to the surface of the vehicle body with an industrial robot burns the painted box body or body with gas or heavy oil. In general, it is carried out by heating in a heated Yamagata furnace.

  In the method of heating a box or car body with a Yamagata furnace, not only the heating efficiency is low, but also the temperature distribution in the furnace becomes non-uniform, resulting in uneven heating of the box and car body. There was a problem that it had to be dried.

  On the other hand, a wide range can be heated with high efficiency by using a method in which an induction current is supplied to a box or a vehicle body made of a metal plate in a non-contact manner by an induction heating coil. In order to induction-heat an object to be heated, such as a box formed of a metal plate or a vehicle body, an induction heating coil configured in a flat plate shape by winding a coil conductor in a spiral shape on a plane is used. Used. Since such a flat induction heating coil is formed by winding a coil conductor in a spiral shape, a portion that does not allow magnetic flux to pass through is generated at the center, so that the flat induction heating coil is induction heated by the flat induction heating coil. The region (region where the induction current flows) becomes a donut shape, and the entire planar region of the induction heating coil cannot be heated uniformly.

  For this reason, when heating a metal plate of a wide area using such a flat induction heating coil, as shown in Patent Document 1 and Patent Document 2, the induction heating coil is used as a drive device for an industrial robot or the like. It is mounted, and the induction heating coil is moved along the surface of the vehicle body or the mold by this driving device, and the entire surface of the vehicle body or the mold is scanned to uniformly heat the whole.

  However, in such a method of inductively heating the metal plate while moving the induction heating coil, when the induction heating coil is moved to the dark clouds, a temperature difference occurs between a place where the heating amount is large and a place where the heating amount is small depending on the place of the metal plate. There is a problem that drying unevenness occurs, and therefore, the drying time of the coating becomes long, or the coating becomes too high in temperature and the paint is carbonized (overbaked).

JP 2011-069500 A JP 2010-284714 A

  In order to solve the above-described problems, the present invention induction-heats a metal plate while moving along a flat induction heating coil on the surface of a metal plate having a large area, particularly a coated metal plate. In this case, it is an object of the present invention to provide an induction heating method for a metal plate that can heat the entire metal plate more uniformly and thereby can dry the coating uniformly.

  In order to solve the above-mentioned problems, the invention of claim 1 is characterized in that an induction heating coil configured by winding a coil conductor in a spiral shape on a flat surface and mounting it on a flat plate is attached to a driving device for moving the coil. The induction heating coil is moved along the surface of the metal plate to be heated having a larger area than the coil by a driving device, and the entire heating area of the metal plate is scanned to inductively heat the metal plate. In the induction heating method described above, when the induction heating coil is moved while being moved away from the metal plate to be heated while the metal plate is induction heated, the induction heating coil is changed when the induction heating coil is moved. The heating current supplied to the heating coil is stopped.

  According to the second aspect of the present invention, an induction heating coil configured by winding a coil conductor in a spiral shape on a flat surface is mounted on a driving device for moving the coil heating coil, and the induction heating coil is mounted by the driving device. In the induction heating method in which the coil is moved along the surface of the metal plate to be heated having a larger area than the coil, and the entire heating region of the metal plate is scanned to inductively heat the metal plate. When induction heating the metal plate while moving the induction heating coil away from the metal plate to be heated, the heating area by the induction heating coil does not protrude from the end of the heated metal plate. It is characterized by induction heating.

  According to a third aspect of the present invention, an induction heating coil comprising a coil conductor wound in a spiral shape on a plane and mounted in a flat plate shape is mounted on a driving device for moving the coil heating coil, and the induction heating coil is used to move the induction heating coil. In the induction heating method in which the coil is moved along the surface of the metal plate to be heated having a larger area than the coil, and the entire heating region of the metal plate is scanned to inductively heat the metal plate. When induction heating the metal plate while moving the induction heating coil away from the metal plate to be heated, the induction heating coil is inclined at a predetermined angle with respect to the surface of the metal plate to be heated. It is characterized by moving in parallel.

  According to the first aspect of the present invention, the supply of the heating current to the induction heating coil is stopped while the movement line of the induction heating coil is changed from the heated movement line to another newly heated movement line. During this time, induction heating of the metal plate is stopped. Therefore, since the overlapping of the heating area | region in the metal plate by the induction heating coil at the time of switching of a movement line can be eliminated, the heating temperature of a metal plate can be equalized over the whole region. For this reason, if the coating applied to the metal plate is to be dried, the coating can be dried uniformly, unevenness in the finish of the coating can be reduced, and the quality of the coating can be improved.

  According to the invention of claim 2, since the heating is performed by moving the induction heating coil so that the planar area of the induction heating coil does not deviate from the end of the metal plate to be heated, the projected planar area of the induction heating coil is heated. Since it is possible to prevent local heating of the end of the metal plate caused by concentration of the induced current flowing in the metal plate at the end when it goes out of the end of the target metal plate, the heating temperature of the entire metal plate Can be made more uniform.

  According to the invention of claim 3, when the metal plate is heated while moving the induction heating coil, the metal plate moves while being inclined at a predetermined angle with respect to the plane of the metal plate that heats the plate-like induction heating coil. Thereby, the area of the heating area | region on the metal plate by an induction heating coil can be narrowed. For this reason, for example, when the temperature distribution of the target metal plate heated once is measured by a thermography device and the low temperature portion is reheated, the heating is limited to the low temperature region. This is effective in making the temperature of the entire metal plate uniform.

It is a block diagram of the induction heating apparatus of the Example which applied the method of this invention to the drying of the coating of the vehicle body of a motor vehicle. The structure of the induction heating coil used for this invention is shown, (a) is a top view, (b) is a front view. It is a figure which shows the shape of the heating area | region by the induction heating coil in this invention. It is explanatory drawing of the reciprocation of the induction heating coil of this invention. It is explanatory drawing of the heating method of this invention, (a) is a figure which shows the state which the induction heating coil shifted | deviated outside from the edge of the metal plate to be heated, (b) shows the heating area | region of the metal plate at this time FIG. It is explanatory drawing of the method of inclining and heating the induction heating coil of this invention. It is a figure which shows the shape of the heating area | region at the time of inclining and heating the induction heating coil of this invention. It is a figure which shows the relationship between drying (baking) temperature and drying (baking) time in the case of performing dry baking of the coating of a metal plate.

  Embodiments of the present invention will be described with reference to the embodiments shown in the drawings.

  FIG. 1 shows an induction heating apparatus for drying a paint of an automobile body formed of a metal plate, to which the method of the present invention is applied.

  In the induction heating apparatus shown in FIG. 1, reference numeral 1 denotes an induction heating coil, which is attached to a driving measure 2 constituted by an industrial robot or the like for movement. Reference numeral 5 denotes a vehicle body that is induction-heated by the induction heating coil 1.

  The vehicle body 5 is formed of a conductive metal plate such as a steel plate, and is already electrodeposited on the surface in the previous step, and a coating film is formed thereon. In order to dry this coating film, the vehicle body 5 is induction-heated using the induction heating coil 1.

  As shown in FIG. 2, the induction heating coil 1 supports a coil 12 in which a coil conductor 11 is spirally wound on a plane and is formed into a flat plate shape by a support substrate 13 formed of an insulating heat-resistant material. Configured.

  As shown in FIG. 2A, the coil 12 has a circular planar shape and is supported by a square support substrate 13. For this reason, the outer shape of the induction heating coil 1 has a flat plate shape in which the planar shape is substantially square and the thickness is approximately the sum of the thickness of the coil conductor 11 and the thickness of the support substrate 13. When a high-frequency heating current is supplied to the induction heating coil 1 from a high-frequency power source (not shown), an eddy current induced in the metal plate by applying a high-frequency magnetic flux generated by the induction heating coil 1 to the conductive metal plate 51. As a result, the metal plate generates heat and is heated. The shape of the region where the metal plate is heated (the region where the heating current flows) is similar to the planar shape of the induction heating coil 1 wound in a spiral shape, and becomes a donut shape as indicated by H in FIG. A region N that is not heated is generated in the central portion. The surface area of the vehicle body 5 to be heated is larger than the planar area that is the heating area of the induction heating coil 1.

  Therefore, when the entire vehicle body 5 is heated by the induction heating coil 1 as described above, the induction heating coil 1 is separated from the surface of the vehicle body 5 by the drive device 2 as shown in FIG. By moving along, it is necessary to scan the entire vehicle body 5 by the induction heating coil 1.

  Thus, in the process of heating the vehicle body 5 while reciprocatingly moving the induction heating coil 1 along the surface of the vehicle body 5, the temperature and temperature distribution of the surface of the vehicle body 5 are measured by the thermography device 3. According to the measurement result of the surface temperature distribution of the vehicle body 5 by the thermography device 3, the magnitude of the high-frequency current supplied to the induction heating coil 1 by a control device (not shown), the moving speed and position of the induction heating coil 1 by the drive device 2, The surface temperature of the vehicle body 5 can be controlled to a desired temperature by controlling the distance from the surface, the number of reciprocating movements, and the like.

  A specific example of scanning of the vehicle body 5 to be heated by the induction heating coil 1 is shown in FIG.

  Here, the metal plate 51 forming the vehicle body 5 and the like is shown as a simple rectangle for the sake of simplicity. The induction heating coil 1 supplied with the high-frequency heating current is first driven from the scanning start end S1 at the upper left corner of the metal plate 51 toward the end E1 by the driving device 2 not shown in FIG. Moved in a straight line. Note that the induction heating coil 1 may reciprocate a plurality of times on the forward movement line O1 from the start end S1 to the end end E1 so that the surface temperature of the vehicle body 5 becomes a predetermined temperature. The induction heating coil 1 that has reached the terminal end E1 is moved from here to the starting end S2 on the return movement line B1, and is moved toward the terminal end E2 on the forward movement line B1. Subsequently, the induction heating coil 1 is moved to the start end S2 on the forward movement line O2, moved to the terminal end E2 on the forward movement line O2, and further moved from the terminal end E2 to the start end S3 of the return movement line B2. It is moved to the terminal end E3 on the return path movement line B2.

  In this way, if the induction heating coil 1 is reciprocated on the metal plate 51 with a predetermined interval by the driving device 2 and the entire metal plate 51 is scanned, the entire metal plate 51 can be induction-heated. it can.

  However, for example, when the induction heating coil 1 is moved from the terminal end E1 to the start end S2, the position of the return line from the end position of the forward path line or the position of the start of the return line from the position of the return line end position. When moving the induction heating coil 1 to the induction heating coil 1, if the heating current is supplied to the induction heating coil 1, the heating area on the metal plate 51 is overlapped by the induction heating coil 1 in the moving process.

  Such an overlapping portion of the heating region of the metal plate 51 generates a large amount of heat, and becomes a higher temperature than a portion where there is no overlapping. For this reason, a high temperature part (heating part) arises partially in the both ends of the metal plate 51, and distribution of the heating temperature of the metal plate 51 becomes non-uniform | heterogenous.

  For this reason, in Example 1, when the induction heating coil 1 is reciprocated to inductively heat the metal plate 51, the induction heating coil 1 is moved from the end position of the forward movement line to the start position of the return movement line, or the return path. In the process of moving from the terminal position of the moving line to the starting position of the forward moving line, the supply of the heating current to the induction heating coil 1 is stopped.

  As a result, when the induction heating coil moves on the forward path line and on the return path line, the heating current is supplied to the induction heating coil 1, so that the metal plate 51 is heated on this movement line. However, when the induction heating coil 1 changes the movement line, for example, from the start of the transition from the end position E1 to the start position S2 until the start position S2 is reached, the heating current is stopped. For this reason, induction heating by the induction heating coil 1 is not performed, so that there is no occurrence of overlapping portions of the heating regions in the transition path of the induction heating coil 1. Therefore, overheating in the part which moves the reciprocation line of the metal plate 51 is prevented, and the metal plate 51 can be heated so that the whole has a uniform temperature distribution.

  Next, a second embodiment of the present invention will be described.

  In the process of reciprocating the induction heating coil 1 and induction heating the metal plate 51, if no particular restriction is imposed, the projection plane area of the induction heating coil 1 is the metal plate to be heated as shown in FIG. In some cases, it may be moved to a position protruding to the outside of the end of 51. In such a case, a part of the current induced in the metal plate 51 by the induction heating coil 1 is concentrated on the end of the metal plate 51. Thus, when concentration of the induced current of the metal plate 51 at the end portion occurs, the end portion of the metal plate 51 is heated from the other portion.

  In this case, the shape of the heating region H of the metal plate 51 by the induction heating coil 1 is formed by winding the induction heating coil 1 in a spiral shape so that the induction heating coil 1 protrudes from the half metal plate 51. Is substantially semicircular as shown in FIG. A portion Ha that is in contact with the edge of the metal plate 51 in the heating region H is a portion that is heated by the concentration of the induced current and has a higher temperature than the other portions.

  Therefore, when the induction heating coil 1 is moved to a position protruding beyond the end of the metal plate 51 to be heated in this way, the end portion of the metal plate 51 becomes partially hot, and the temperature distribution of the metal plate 51 is increased. Becomes non-uniform.

  In order to prevent the end of the metal plate 51 from being heated, in the second embodiment, the induction heating coil 1 reciprocates to scan along the surface of the metal plate 51 to be heated to guide the metal plate 41. When heating, as shown in FIG. 4, the end of the heating region H does not protrude from the end of the metal plate 51 at the start end positions S 1, S 2, S 3 and the end position of the moving line of the induction heating coil 1. Thus, the movement of the induction heating coil 1 is controlled by the drive device 2.

  As described above, since the end of the heating area H moves so as not to protrude from the end of the metal plate 51 to be heated, the end of the metal plate 51 can be prevented from being heated. The entire plate 51 can be heated to a uniform temperature.

  In the third embodiment of the heating method according to the present invention to be described next, when the heating of the entire induction heating coil 1 of the metal plate 51 to be heated is once finished, the temperature distribution on the surface of the metal plate 51 is measured by the thermography device. This is a method for making the temperature distribution uniform by correcting and heating the low temperature part when there is temperature irregularity that is measured and lower than the specified temperature.

  In such a case, instead of moving the induction heating coil 1 parallel to the surface of the metal plate 51 to be heated, as shown in FIG. 6, it is directed toward the metal plate 51 in the moving direction indicated by the arrow. Then, heating is performed by moving at a predetermined angle Θ.

  Thus, inclining the induction heating coil 1 by the predetermined angle Θ with respect to the metal plate 51 can be easily performed by adjusting the mounting angle to the driving device 2 that drives the induction heating coil 1. Further, when an industrial robot is used for the driving device 2, the inclination angle of the induction heating coil 1 can be easily adjusted by adjusting the angle of the holding arm that holds the induction heating coil 1.

  When the induction heating coil 1 is tilted with respect to the metal plate 51 in the moving direction (arrow direction) and the metal plate 51 is heated, the heating region of the metal plate 51 by the induction heating coil 1 (region where the induction current flows) is increased. The shape can be similar to a crescent moon whose width is narrowed in the moving direction of the induction heating coil 1 as indicated by H in FIG.

  The size of the heating region H can be reduced as the inclination angle of the induction heating coil 1 is increased, and the direction in which the width of the region is narrowed is determined by the direction of the inclination. It is possible to adjust the size of the heating region to some extent by adjusting.

  In accordance with the region where the heating temperature of the metal plate 51 is low, if this region is adjusted and heated by limiting the inclination angle of the induction heating coil 1, the accuracy of correcting the temperature of the metal plate 51 can be improved. Can do. For this reason, according to the shape of the area | region where the heating temperature of the metal plate 51 is low, the inclination direction and angle of the induction heating coil 1 are adjusted, the shape of the heating area | region by this induction heating coil 1 is adjusted, When the low temperature region is scanned by the induction heating coil 1, the temperature of the low temperature region can be accurately heated to the temperature of the peripheral region, and the temperature distribution of the metal plate 51 can be made more uniform. Can do.

  As described above, according to the present invention, the entire area of the metal plate 51 to be heated is scanned by reciprocating the induction heating coil 1 supplied with the high-frequency current on the metal plate 51 having a larger area. Thus, the metal plate 51 can be efficiently heated to a uniform temperature.

  For this reason, when this invention is used for the heating for drying of the coating of a metal plate, the heating temperature of a metal plate can be contained in the range of 145-165 degreeC.

  By the way, according to the conventional heating method using the Yamagata furnace, the heating temperature of the metal plate can only be within the range of 135 to 165 ° C. due to the heating temperature difference between the ceiling and the bottom in the furnace.

  FIG. 8 is a drying characteristic diagram showing the relationship between baking temperature (drying temperature) -baking time (drying time) in the case of painting with a general water-based paint. The polygonal frame A in this figure is the allowable range of the drying temperature and drying time.

  As can be understood from this, if the drying temperature is high, the drying time may be short, and if the drying temperature is low, the drying time needs to be long. When the drying (baking) time is less than the permissible range at a low drying (baking) temperature range, the drying (baking) is insufficient and the coating strength is insufficient.

  In addition, if the drying (baking) temperature is higher and the drying (baking) time exceeds an allowable range, the coating is overbaked and yellowed.

  When heating a metal plate for coating drying with a conventional Yamagata furnace, since the heating temperature range is large, the drying process is performed in the region indicated by T in the characteristic diagram of FIG. is there.

  On the other hand, according to the present invention, since the metal plate is heated by induction heating, not only can the heating be performed efficiently, but also the heating temperature range can be accurately set within a narrow range of 148 to 165 ° C. For this reason, according to the present invention, the drying process can be performed in the region indicated by P in FIG. 8, so that the drying process time can be remarkably shortened as compared with the prior art.

  In the above description, heating of an automobile body has been described. However, the present invention can also be used for heating in the case of preheating a casting mold made of a conductive metal.

1: Induction heating coil 2: Drive device (industrial robot)
3: Thermography device 5: Conductive metal plate (vehicle body)

Claims (2)

The coil conductors wound spirally in a plane with the induction heating coil configured in a plate shape, it is attached to a driving device for moving it by the drive unit, the induction heating coil, from the induction heating coil In the induction heating method in which the metal plate is inductively heated by moving along the surface of the metal plate to be heated having a large area and scanning the entire heating region of the metal plate, the induction heating coil is When changing the moving line of the induction heating coil when induction heating the metal plate while moving away from the metal plate to be heated, the heating current supplied to the induction heating coil is stopped. Induction heating method. The coil conductors wound spirally in a plane with the induction heating coil configured in a plate shape, it is attached to a driving device for moving it by the drive unit, the induction heating coil, from the induction heating coil In the induction heating method in which the metal plate is moved by being moved along the surface of the metal plate to be heated having a large area and the entire heating region of the metal plate is scanned to heat the metal plate, the induction heating coil is heated. When the metal plate is induction heated while moving away from the target metal plate, the induction heating coil is moved in parallel at a predetermined angle with respect to the surface of the metal plate to be heated. An induction heating method characterized by the above.

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