JP2015202508A - Brazing method and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a brazing method and device which reduces consumption amount of energy by miniaturizing the device, suppresses temperature fluctuation in a workpiece, brings a part to be brazed into a temperature region to be aimed, performs the brazing and improves productivity.SOLUTION: In a brazing method, upon the heating of a workpiece by means of a high-frequency induction heating coil, the workpiece is heated at a high speed and power supply to a coil is stopped at such a time point that a predetermined time elapses or the workpiece arrives at a predetermined temperature since the heating of the workpiece to the coil is started, inactive gas is blown against the workpiece to cool the workpiece at least while the power supply is stopped and the power supply is again performed after the predetermined time elapses since the power supply is stopped. According to such a configuration, the temperature equalization of the workpiece is facilitated, all of parts to be brazed in the workpiece can be brought into a temperature region to be aimed in a short time and high productivity can be provided.

Description

  The present invention relates to a brazing method and apparatus that are suitable for brazing between metal parts such as heat exchangers of automobiles and refrigeration and air-conditioning equipment, and that uniformly heat a workpiece in a short time and perform brazing efficiently. .

  Heat exchangers for automobiles and refrigeration air conditioners are manufactured by assembling and brazing parts made of aluminum or stainless steel. As a conventional brazing apparatus used in the brazing process, there is an apparatus that continuously conveys a plurality of workpieces by a conveyor and sequentially brazes in a large electric furnace (for example, see Patent Document 1). FIG. 7 shows an example of a conventional brazing apparatus that sequentially brazes in a large electric furnace.

  In FIG. 7, reference numeral 101 denotes an inlet portion, and a workpiece 102 is input from the inlet portion 101 and is continuously conveyed downstream (right side in the drawing) by a conveyor 103. Reference numeral 104 denotes a heating unit, and the workpiece 102 conveyed through the muffle (heating passage) 105 is heated to about 600 ° C. by the heating source 106 and brazed. Reference numeral 107 denotes a cooling unit, and the work 102 conveyed is cooled by a cooling fan 108. In 109, a workpiece whose cooling is completed is taken out at the outlet. Nitrogen gas is supplied in the apparatus in order to obtain a low oxygen state.

  Moreover, as a conventional brazing apparatus used in the brazing process, there is an apparatus that transports a workpiece alone and brazes it by induction heating using a coil (see, for example, Patent Documents 2 and 3). 8 and 9 show an example of a conventional brazing apparatus that performs brazing by induction heating.

  In FIG. 8, reference numeral 110 denotes a container, and the workpiece 111 is handled by a transfer device not shown in the drawing and set on a stage 112 in the container 110. Reference numeral 113 denotes a coil attached to the matching unit 114, and the work 111 is brazed by induction heating of the induction heating coil 113. Similarly to the case of FIG. 7, this apparatus is also supplied with nitrogen gas in order to bring the inside of the container 110 into a low oxygen state.

  FIG. 9 shows the correlation between the control for induction heating and the temperature of the brazing part. At all locations where the workpiece is brazed, the temperature reached must be within the range from the lower limit temperature T1 at which the brazing material melts to the upper limit temperature T2 at which the brazing material melts but the base material does not melt. There is.

  When the high-frequency current I1 is passed through the coil until time t1, the temperature at the highest point of the brazing point rises to a temperature exceeding T1. Next, when the high-frequency current is lowered to I2 and flowed until time t2 in order to eliminate overshoot, the temperature at the highest point of the brazing point is lower than the upper limit reference T2, and the temperature at the lowest point of the brazing point exceeds the lower limit reference T1 To rise.

  Further, as a method of repeatedly heating a workpiece in a short time, there is a method of repeatedly performing induction heating while continuously conveying the workpiece (see, for example, Patent Document 4). FIG. 10 shows a change in temperature between the steel surface and the center when the steel is subjected to continuous heat treatment by induction heating.

  In FIG. 10, the vertical axis represents temperature and the horizontal axis represents time. The workpiece passes near the induction heating coil Ln placed in the feed passage. In this figure, ln is the coil length, dn is the coil interval, Pn is the power density applied to the coil, A is the surface temperature, and B is the center temperature.

  This figure shows the case where the steel material is heated four times and quenched as a whole. During repeated heating, the temperatures of the surface A and the central portion B approach each other and become equalized.

JP 2007-78328 A Japanese Patent Laid-Open No. 5-15969 Japanese Patent No. 2600465 Japanese Patent Publication No.59-13567

  As shown in FIG. 7, the conventional brazing apparatus secures production capacity by simultaneously processing the workpiece 102 while continuously conveying it on the conveyor 103. However, in the case of such an apparatus, the furnace length becomes several tens of meters, for example, and a large amount of electricity and supply of nitrogen gas are required, which has a problem of consuming a lot of energy.

  In another conventional brazing apparatus, as shown in FIG. 8, a workpiece 111 is set on a stage 112 as a single unit, and an electric current is passed through an induction heating coil 113 as shown in FIG. . In the case of such an apparatus, the apparatus is small in size and consumes little energy, but the induction heating method of this example has a drawback that temperature variation due to the location of the workpiece tends to occur due to variations in the generated magnetic field.

  Therefore, in the case of the induction heating method, the current value is suppressed so that the temperature variation does not increase in order to put the entire brazed part in the target temperature range, and the temperature is equalized by heat conduction from the high temperature part to the low temperature part of the workpiece. It was necessary to raise the temperature of the workpiece slowly while letting it go. As a result, there was a problem that productivity did not increase. This temperature variation is a phenomenon in which the temperature near the coil, for example, the temperature on the side surface of the workpiece is high, but the temperature far from the coil, for example, the temperature at the center of the workpiece is low.

  In another conventional brazing apparatus, as shown in FIG. 10, the induction heating is repeatedly performed while the workpiece is continuously conveyed. However, in the case of such an apparatus, a plurality of coils are required, and there is a problem that the equipment is expensive. As another method, there is a method of fixing a work and repeating a similar thermal cycle with a single coil, but it has a problem that it takes time for cooling and productivity does not increase.

  The present invention solves the above-described conventional problems, downsizing a device for brazing a workpiece such as a heat exchanger, reducing energy consumption, suppressing temperature variation of the workpiece, and all brazing portions. It is an object of the present invention to provide a highly productive brazing method and apparatus capable of entering a target temperature range in a short time.

  In order to achieve the above object, the brazing method and apparatus of the present invention rapidly heats a workpiece when the workpiece is heated by a high frequency induction heating coil, and a certain time has elapsed since the heating of the workpiece was started. Stop energization of the coil at the time or when the temperature reaches a predetermined temperature, and at least while the energization is stopped, blow the inert gas onto the work piece to cool it, and after a certain time has passed since the energization was stopped Energize the coil again.

  With this configuration, the temperature variation of the workpiece can be suppressed, and all the brazed portions in the workpiece can be put in a target temperature range in a short time, and high productivity can be obtained.

  As described above, according to the brazing method and apparatus of the present invention, the amount of energy consumed is kept low, the temperature variation in the workpiece is suppressed, and the brazed portion is placed in the target temperature range in a short time. Productivity.

The figure which shows the brazing apparatus in Embodiment 1 of this invention. The figure showing the correlation of control and the temperature of a brazing part in Embodiment 1 of this invention The figure showing the correlation of the temperature of the control and brazing part in Embodiment 2 of this invention The figure showing the correlation of the temperature of control and brazing part in Embodiment 3 of this invention The figure showing the correlation of the temperature of the control and brazing part in Embodiment 4 of this invention The figure which shows the brazing apparatus in Embodiment 5 of this invention. The figure which shows the conventional brazing apparatus The figure which shows the conventional brazing apparatus The figure showing the correlation between the control and the temperature of the brazing part in the conventional brazing device The figure showing the temperature of the steel material surface and the center part in the conventional brazing device

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
1 and 2 show a brazing apparatus according to Embodiment 1 of the present invention.

  In FIG. 1, reference numeral 1 denotes a workpiece, which is sandwiched by a jig 2. The workpiece 1 set on the jig 2 is handled in the container 3 by a transfer device not shown in the drawing, and is set on the stage 4 with the periphery surrounded by the induction heating coil 5. And nitrogen gas is supplied in the container 3 in order to make it a low oxygen state.

  The induction heating coil 5 is electrically connected to the power supply unit 6, and the output of the high frequency power supply 7 is controlled to a value suitable for brazing operation by the control device 9 based on an instruction from the control circuit 8. Supplied.

  Here, when the workpiece 1 is heated by the induction heating coil 5, the temperature of the side surface portion of the workpiece 1 close to the coil increases due to the feature of induction heating. As a result, the highest temperature of the workpiece 1 tends to appear on the side surface.

  Therefore, in the present invention, the blow nozzle 11 is disposed at a position where nitrogen gas for cooling can be sprayed onto the side surface of the work 1 in order to equalize the work 1. The cooling is performed by giving an instruction to the pneumatic valve 12 from the control circuit 8.

  FIG. 2 shows the correlation between the control at the time of performing induction heating and the temperature of the brazing part in the first embodiment of the present invention.

  For all locations where the workpiece is brazed, the temperature reached is within a range from a lower limit temperature T1 at which the brazing material melts to an upper limit temperature T2 at which the brazing material melts but the base material does not melt. There is a need.

  When the high-frequency current I1 is passed through the coil until time t1, the temperature at the highest point of the brazing point rises to the vicinity of T2. At this time, if the value of the high-frequency current I1 is increased, the difference between the highest point temperature and the lowest point temperature of the brazed portion increases, but the value of the high-frequency current I1 is increased so that the highest point temperature rises quickly.

  Next, when the high-frequency current is turned off and the cooling nitrogen gas 10 is blown onto the side surface of the work 1 until time t2, the highest temperature of the brazed portion is radiated to the outside air and the heat to the low temperature part. It goes down by conduction. On the other hand, the temperature at the lowest point of the brazing point rises because the amount of heat transferred from the high temperature portion exceeds the amount of heat released to the outside, and as a result, the temperature difference between the highest point and the lowest point is reduced. This heat radiation to the outside is efficiently performed because the highest temperature is in the vicinity of T2 and in a high temperature region.

  At this time, the temperature of the high temperature portion decreases only by turning off the high frequency current, but the cooling is accelerated by blowing the nitrogen gas 10 for cooling on the side surface of the work 1, and the temperature difference between the highest point and the lowest point is rapid. Will be shrunk.

  Next, when the high-frequency current I1 is allowed to flow until time t3, the temperature of the highest point of the brazing point is equal to or lower than the upper limit reference T2, and the temperature of the lowest point of the brazing point increases until it exceeds the lower limit reference T1.

  According to such a configuration, when the workpiece is heated by the high frequency induction heating coil, the workpiece is rapidly heated, and when a certain time has elapsed since the heating of the workpiece is started, the coil is stopped from being energized. While the operation is stopped, the workpiece is cooled by blowing an inert gas, and the coil is energized again after a predetermined time has elapsed since the energization was stopped. Thereby, the temperature variation in a workpiece | work can be suppressed and productivity can be improved by putting a brazing part in the temperature range which aims at a short time.

  Conventionally, the value of the high-frequency current has been suppressed in order to suppress the temperature variation in the workpiece, but this method can increase the value of the high-frequency current while suppressing the temperature variation. It is possible to improve the sex.

  In this embodiment, while the energization to the coil is stopped, the workpiece is cooled by blowing an inert gas. However, if there is a margin for raising the temperature of the workpiece, the coil is energized. Alternatively, an inert gas may be sprayed onto the workpiece.

  In the present embodiment, the coil is energized again after a predetermined time has elapsed since the energization was stopped, but the temperature of the workpiece is measured by a temperature measuring instrument such as a radiation thermometer, and a predetermined reference value is obtained. It is also possible to energize the coil again when it falls below.

(Embodiment 2)
FIG. 3 shows the correlation between the control when performing induction heating and the temperature of the brazing part in the second embodiment of the present invention. The configuration of the apparatus is the same as in FIG.

  When the high-frequency current I1 is passed through the coil until time t1, the temperature at the highest point of the brazing point rises to the vicinity of T2. At this time, if the value of the high-frequency current I1 is increased, the difference between the highest point temperature and the lowest point temperature of the brazed portion increases, but the value of the high-frequency current I1 is increased so that the highest point temperature rises quickly.

  Next, when the high-frequency current is turned off until time t2, the temperature at the highest point of the brazing point is lowered by heat radiation to the outside air by blowing nitrogen gas and heat conduction to the low temperature part. On the other hand, the temperature at the lowest point of the brazing point increases because the heat transfer amount from the high temperature part exceeds the heat radiation amount to the outside, and as a result, the temperature difference between the highest point and the lowest point is reduced. This heat radiation to the outside is efficiently performed because the highest temperature is in the vicinity of T2 and in a high temperature region.

  Next, when the high-frequency current I1 is again supplied to the coil until time t3, the temperature at the highest point of the brazing point rises again to the vicinity of T2. Next, when the high-frequency current is turned off until time t4, the temperature difference between the highest point and the lowest point of the brazing point is reduced as in the case where the high-frequency current is turned off until time t2. Next, when the high-frequency current I1 is supplied until time t5, the highest point temperature of the brazed portion is lower than the upper limit reference T2, and the lowest point temperature is increased until it exceeds the lower limit reference T1.

  By increasing the number of times of turning off by one as compared with the first embodiment, the temperature variation can be further suppressed, and this is an effective method in brazing where temperature uniformity is required at a higher level. In the present embodiment, the number of times of turning off is set to 2, but the number of times may be increased as appropriate.

(Embodiment 3)
FIG. 4 shows the correlation between the control at the time of performing induction heating and the temperature of the brazing part in the third embodiment of the present invention. The configuration of the apparatus is the same as in FIG.

  In the third embodiment, the high-frequency current at the time of re-energization after turning off the high-frequency current is set to be equal to or less than that of the previous energization. That is, the high frequency currents I1, I2, and I3 have the following relationship.

I1 ≧ I2 ≧ I3
According to the third embodiment, it is possible to prevent an increase in temperature variation between the highest point and the lowest point during the temperature increase due to re-energization, and increase the productivity by putting the brazed portion in a target temperature range in a short time. Can do.

(Embodiment 4)
FIG. 5 shows the correlation between the control at the time of performing induction heating and the temperature of the brazing part in the fourth embodiment. The configuration of the apparatus is the same as in FIG.

  In the fourth embodiment, the time for re-energization after turning off the high-frequency current is set to be equal to or less than that for the previous energization. That is, the following relationships exist between the times t1, t2, t3, t4, and t5.

t1 ≧ (t3-t2) ≧ (t5-t4)
According to the fourth embodiment, it is possible to prevent an increase in temperature variation between the highest point and the lowest point during the temperature increase due to re-energization, and increase the productivity by putting the brazed portion in a target temperature range in a short time. Can do.

(Embodiment 5)
FIG. 6 shows a brazing apparatus according to the fifth embodiment.

  Since steps 1 to 12 in FIG. 6 are the same as those in the first embodiment, description thereof is omitted. Reference numerals 13 and 14 denote radiation thermometers. The radiation thermometer 13 measures the temperature at the center of the side surface of the workpiece 1, and the radiation thermometer 14 measures the temperature near the jig 2 on the side surface of the workpiece 1. When the jig 2 is less likely to be induction-heated than the work 1 and the temperature tends to be lower than that of the work 1, the heat of the work 1 is taken away by the jig, and the temperature near the jig is lower than the central portion of the side surface.

  The control circuit 8 can take in the temperature measurement results of the radiation thermometers 13 and 14 and compare the difference with a reference value to determine the degree of temperature uniformity.

  The correlation between the current during induction heating and the temperature of the brazing part is the same as that shown in FIG. 2 of the first embodiment. However, in this sixth embodiment, the time t2 at which energization is started again is determined as the radiation. Determined by the measured values of the thermometers 13 and 14. Specifically, the difference between the radiation thermometers 13 and 14 is always confirmed, and the time when the timing becomes smaller than a predetermined reference value is set as time t2, and the energization is started again.

  When the temperature variation in the workpiece can be measured with a radiation thermometer, the temperature control can be controlled according to the workpiece variation by confirming the progress of temperature equalization based on the measurement result and determining the timing to start energization again. Therefore, productivity can be improved comprehensively.

  The present invention is not limited to a heat exchanger and can be applied to brazing between various metal parts, and can reduce the consumption energy with a small facility and uniformly heat a workpiece in a short time. .

DESCRIPTION OF SYMBOLS 1 Work 2 Jig 3,110 Container 4,112 Stage 5 Induction heating coil 6 Power supply part 7 High frequency power supply 8 Control circuit 9 Control apparatus 10 Nitrogen gas 11 for cooling Blow nozzle 12 Pneumatic valve 13, 14 Radiation thermometer 102 Workpiece 103 Conveyor 106 Heating source 111 Work 113 Induction heating coil Ln Induction heating coil

Claims (7)

In a brazing method using a high frequency induction heating coil,
When a certain time has elapsed since the heating by the high-frequency induction heating coil for the workpiece was started, or when the workpiece reached a predetermined temperature,
To stop energizing the high frequency induction heating coil,
At least while energization is stopped, the work is blown with an inert gas to cool the work, and after a certain period of time has elapsed after stopping energization, the energization of the high-frequency induction heating coil is performed again.
A brazing method characterized by. The brazing method according to claim 1, wherein the operation of energizing the high-frequency induction heating coil is performed twice or more again. The brazing method according to claim 2, wherein at the time of re-energization, the current is made equal to or less than that immediately before energization. The brazing method according to claim 2, wherein the energization time is set to be equal to or less than the energization immediately before the energization. When the temperature of the workpiece is measured at two or more locations and the energization is stopped, the energization is performed again when the temperature difference becomes a predetermined reference value or less.
The brazing method as described in any one of Claims 1-4. A container that contains a workpiece and is filled with an inert gas;
A high-frequency induction heating coil that is supported inside the container and induction-heats the workpiece;
A jig that is disposed inside the container and holds the workpiece;
A blow nozzle for jetting inert gas;
Control means for controlling the operation of the high frequency induction heating coil, the flow of inert gas and the operation of the blow nozzle,
Blowing the inert gas ejected from the blow nozzle to the workpiece while at least energizing the high-frequency induction heating coil is stopped by the control means;
Brazing device characterized by. It further comprises two or more temperature measuring instruments for measuring the temperature of the workpiece,
While the energization to the high-frequency induction heating coil is stopped, when the temperature difference measured by the temperature measuring instrument becomes a predetermined value or less, energize again.
The brazing apparatus according to claim 6.

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