HK1079035B - Apparatus and method for heating works - Google Patents

Description

Workpiece heating device and workpiece heating method

Technical Field

The invention relates to a workpiece heating device and a workpiece heating method, which can uniformly heat workpieces with large sizes and complex shapes and can prevent overburning and crucible burning phenomena.

Background

Since it is difficult to finely adjust the temperature when high-frequency induction heating is used, it has been conventionally used only for heating small-sized workpieces one by one or heating workpieces having a uniform shape such as pipes.

However, since the high-frequency induction heating heats the workpiece itself, when a coated product treated with the powder coating material is baked by the high-frequency induction heating, the coating material on the side in contact with the workpiece is heated, and thus the coating film is firmly fixed to the workpiece. In addition, there is an advantage that oil and the like can be dissipated without degreasing treatment, and since heating from the outside is not required, a dome drying (dome) device is not required.

In view of these advantages, the present applicant has developed a workpiece heating apparatus using high-frequency induction heating, and disclosed the contents thereof in patent documents 1 and 2.

Patent document 1: JP Kokai No. 2002-126584

Patent document 2: JP Kokai No. 2003-10737

With the workpiece heating apparatuses disclosed in patent documents 1 and 2, even if the number of workpieces is large, uniform heating can be performed when the workpiece size is small. However, when the size of the workpiece is large, the workpiece coil must be increased to increase the output power in order to heat the entire workpiece at one time. Further, if there is only one output source and the shape of the workpiece is not uniform like a pipe, there is a disadvantage that the heating temperature is likely to vary.

In view of the above-described problems, it is an object of the present invention to provide a workpiece heating apparatus and a workpiece heating method, which can process workpieces of various sizes and shapes in a plurality of consecutive ways and therefore have high versatility.

Disclosure of Invention

A first aspect of the invention relates to a workpiece heating apparatus provided with a plurality of high-frequency induction heating sections including a pair of workpiece coils disposed opposite to each other; a distance adjusting mechanism for adjusting a distance between each of the work coils and the work positioned between the pair of work coils; and an output power adjusting mechanism for adjusting the high-frequency output power of the workpiece coil.

A second aspect of the present invention relates to a workpiece heating method using the workpiece heating apparatus according to the first aspect of the present invention, wherein the workpiece is heated while being continuously conveyed between a pair of workpiece coils of the high-frequency induction heating section.

A third aspect of the present invention relates to a workpiece heating method according to the second aspect of the present invention, wherein a heating state of a plurality of portions of a workpiece is analyzed in advance for the workpiece, the workpiece is made to be in a state of being uniformly heatable based on the analysis result, information on a distance between each of workpiece coils and the workpiece and information on an output power of the workpiece coils are obtained for each of the workpiece coils, and the workpiece is heated while adjusting the distance between each of the workpiece coils and the workpiece and the output power of the workpiece coils based on the obtained information.

A fourth aspect of the present invention is a workpiece heating method according to the second or third aspect, wherein a thermometer for measuring the temperature of the workpiece is provided in the high-frequency induction heating unit, and the distance and/or the high-frequency output are adjusted based on temperature information from the thermometer.

If the workpiece heating apparatus and the workpiece heating method of the present invention are employed, even in the case where a plurality of workpieces are intended to be continuously processed, the heating uniformity can be achieved by controlling the shape and position of the workpiece coil in accordance with the size and shape of the workpiece (W).

If the work heating apparatus and the work heating method of the present invention are used for the baking treatment (post-treatment) of the powder coated piece, the degreasing treatment is not required and the heating is not performed from the outside, and thus, the drying dome (dome) device is not required.

In particular, even when the coating film is thin as in the case of electrostatic coating, a good product can be produced. The shape and position of the workpiece coil can be controlled according to the size and shape of the workpiece (W), thereby achieving the purpose of uniform heating.

Drawings

Fig. 1 is a perspective view of a workpiece heating apparatus according to a first embodiment of the present invention;

fig. 2 is a partially cut-away perspective view of a high-frequency inductive heating portion of the workpiece heating apparatus of fig. 1;

FIG. 3 is a perspective view of a workpiece coil of the workpiece heating apparatus of FIG. 1;

fig. 4 is a sectional view of the high-frequency inductive heating portion of fig. 2;

fig. 5 is a perspective view of a driving part of the high-frequency inductive heating part of fig. 2;

fig. 6 is an explanatory view of a moving state of the high-frequency inductive heating portion of fig. 2;

fig. 7 is an explanatory view of a method of suspending a workpiece by the workpiece hanger of fig. 1;

FIG. 8 is a diagram illustrating a control system of the workpiece heating apparatus of FIG. 1;

fig. 9 is an explanatory view of a workpiece heating method using the workpiece heating apparatus of fig. 1;

FIG. 10 is an enlarged view taken along the line of FIG. 9;

FIG. 11 is a plan view of FIG. 9;

fig. 12 is a perspective view of a high-frequency guiding heating portion of a second embodiment of the present invention.

Description of the reference numerals

Reference numeral 1 denotes a workpiece heating device;

reference numeral 3 denotes a high-frequency induction heating section;

reference numerals 5, 7 denote workpiece coils;

reference numeral 9 denotes a copper pipe;

reference numeral 11 denotes a spiral portion;

reference numeral 13 denotes a bottom;

reference numeral 15 denotes an active electrically-powered cooling hose;

reference numerals 17, 19 denote coil housings;

reference numeral 21 denotes a top surface;

reference numeral 23 denotes a side face;

reference numeral 25 denotes a back face;

reference numerals 27, 29 denote contact prevention covers;

reference numerals 31, 33, 35 denote separators;

reference numerals 37, 39 denote nuts;

reference numerals 41, 43 denote openings;

reference numerals 45, 47 denote sliders;

reference numerals 51, 53 denote guide rails;

reference numeral 59 denotes an opening and closing motor;

reference numeral 60 denotes a belt;

reference numeral 61 denotes an opening and closing screw;

reference numeral 63 denotes a bearing;

reference numeral 65 denotes a support body;

reference numeral 67 denotes a nut;

reference numeral 69 denotes a center moving motor;

reference numeral 70 denotes a device mounting base;

reference numeral 71 denotes a moving screw;

reference numeral 73 denotes a high-frequency power supply;

reference numeral 75 denotes a radiation thermometer;

reference numeral 77 denotes a workpiece hanger;

reference numeral 79 denotes a stay;

reference numeral 81 denotes an arm mounting lever;

reference numeral 83 denotes a boom;

reference numerals 85, 87 denote hook portions;

reference numeral 89 denotes a small attachment (tag);

reference numeral 91 denotes a control section;

reference numeral 101 denotes a high-frequency induction heating portion;

reference numerals 103, 105 denote workpiece coils;

reference numeral W denotes a workpiece.

Detailed Description

A workpiece heating apparatus 1 according to a first embodiment of the present invention will be described with reference to fig. 1 to 12.

Reference numeral 3 denotes a high-frequency induction heating unit, and the high-frequency induction heating unit 3 includes a pair of workpiece coils 5 and 7 provided to face each other.

As shown in fig. 2 and 3, the pair of work coils 5 and 7 are formed by two spiral portions formed by winding one copper pipe 9 made of a conductive material. Since eddy currents cancel each other at the middle portion of the spiral portion, the output power is reduced, and the spiral coil (P) is narrower than the peripheral portion.

The two spiral portions constituting the work coils 5 and 7 are connected by the intermediate portion, and both end portions of the work coil are cut off and removed to connect by the active electric cooling hose 15.

If formed as described above, the workpiece coils 5 and 7 are connected by one active electric cooling hose 15 as shown in fig. 2, and therefore, the present invention is used in a case where the receiving space is small.

The active electric cooling hose 15 is composed of a flexible water hose 16, and a flexible copper stranded wire 18 for high-frequency current coupling wound around the water hose 16 in a spiral shape. Then, the work coils 5 and 7 are integrally connected to a current circuit through the flow path of the cooling water. Further, since the active electric-conduction cooling hose 15 is formed of a flexible member as described above, the work coils 5 and 7 move in a direction of approaching or separating from each other.

Reference numerals 17 and 19 denote a pair of long coil cases, and the coil cases 17 and 19 are disposed so as to face each other. The work coils 5 and 7 are accommodated in the coil housings 17 and 19 in a vertically standing posture.

The top 21, side 23 and back 25 of the coil housing 17, 19 are made of copper plates for high-frequency shielding. In addition, the mutually opposed front faces are covered with contact prevention covers (ケミット plates) 27, 29 so as to prevent contact between the workpiece coils 5, 7 and the workpiece (W).

At the bottom of the front face of the coil housings 17, 19, inverted U-shaped partition bodies 31, 33, 35 are provided. The spacer bodies 31, 33, 35 are each made of a copper plate in order to achieve high-frequency shielding. The left end of the spacer 31 is fixed to the coil case 17, and the right end of the spacer 33 is fixed to the coil case 19. The partition body 35 slidably engages with the partition bodies 31, 33.

The partition bodies 31, 33, and 35 can shield a driving portion such as a motor 59 described later from a high frequency.

Plate-shaped nuts 37 and 39 are provided below the spacer bodies 31 and 33, respectively. The nut 37 is fixed at its bottom end to the coil case 17 and at its side to the spacer body 31. The nut 39 is fixed at its bottom end to the coil case 19 and at its side to the partition body 33.

The nuts 37, 39 are configured to have an opposite thread relationship.

Between the partitions 31, 33 and the nuts 37, 39, openings 41, 43 are formed, respectively, for the passage of the active electrically-powered cooling hose 15.

Sliders 45 and 47 are attached to the bottom surfaces of the coil housings 17 and 19, respectively. Reference numeral 49 denotes a device mounting base, and guide rails 51 and 53 are attached to the device mounting base 49. The guide rails 51 and 53 are slidably engaged with sliders 45 and 47, respectively.

Reference numeral 59 denotes an opening/closing motor, and an opening/closing screw 61 is connected to the opening/closing motor 59 via a belt 60. The opening/closing screw 61 is screwed to the nuts 37 and 39.

If the opening-closing motor 59 is driven, the integrated assembly formed by the coil housing 17 (including the contact preventing cover 27), the diaphragm 31 and the workpiece coil 5, and the integrated assembly formed by the coil housing 19 (including the contact preventing cover 29), the diaphragm 33 and the workpiece coil 7 move in directions to approach or separate from each other. Thus, the distance (D) between the workpiece coils 5, 7 is changed.

Reference numeral 65 denotes a rectangular support member, and one end of the support member 65 is bent downward and vertically. The opening/closing motor 59 and the bearing 63 of the opening/closing screw 61 are fixed to the support body 65. A nut 67 is formed at the bent portion of the support body 65.

Reference numeral 69 denotes a center moving motor, and the center moving motor 69 is fixed to the apparatus mounting base 47. A moving screw 71 is connected to the center moving motor 69, and the moving screw 71 is screwed to the nut 67.

When the center moving motor 69 is driven, the support 65 moves, and the bearing 63, the opening/closing screw 61, and the opening/closing motor 59 also move simultaneously with the support 65, thereby moving the coil housings 17 and 19 in the arrow direction shown in fig. 4 while keeping the distance (D) between the work coils 5 and 7 constant. I.e. the centre line (C) between the work piece coils 5, 7 is moved.

The two opening and closing motors 59 and the center moving motor 69 are driven independently of each other, whereby the distance (D) between the work coils 5, 7, the shortest distance (D (r)) between the work (W) and the work coil 5, and the shortest distance (D (1)) between the work coil 7 can be changed.

Fig. 6(1) shows a state in which the opening/closing motor 59 is driven and the distance between the workpiece coils 5 and 7 is increased. Fig. 6(2) shows a state in which the center shift motor 69 is further driven thereafter.

The distances (D1) and (D2) between the workpiece coils 5, 7 of fig. 6(1) and (2) are the same, and the center line (C2) of fig. 6(2) is located on the right side with respect to the center line (C1) of fig. 6 (1).

Both ends of the copper pipe 9 of the workpiece coils 5 and 7 constituting the high-frequency induction heating unit 3 are galvanically coupled to a commercial high-frequency power supply 73, which will be described later. A cooling water circulation unit not shown is also connected to the high-frequency power supply 73.

In the workpiece heating apparatus 1, three high-frequency induction heating sections 3 having the above-described configuration are provided, and for the sake of distinction, they are referred to as No.1 coil, No.2 coil, and No.3 coil, respectively, in order from the left.

Between the respective workpiece coils 5 and 7 of the No.1 coil, No.2 coil, No.3 coil are conveyance paths that convey the workpiece (W).

Reference numeral 75 denotes a radiation thermometer of a non-contact type, and the radiation thermometer 75 is disposed between the No.2 coil and the No.3 coil.

As is known from the above, the distance adjusting mechanism is constituted by an opening and closing movement mechanism of the work coils 5, 7 including the opening and closing motor 59, the opening and closing screw 61, and the nut 37, 39, and an integral horizontal movement mechanism of the work coils 5, 7 including the center movement motor 69, the movement screw 71, the support body 65, and the nut 67. The output adjustment mechanism includes a high frequency power supply 73.

Reference numeral 77 denotes a work hanger 77, and the work hanger 77 is designed so as to be suitable for the shape of the work (W) and the number of the work (W) to be hung. In the work hanger 77, square tubular stays 79 made of a conductive member (copper) are provided at a constant pitch, and arm attachment rods 81 are fixed to the stays 79 at a constant pitch in the vertical direction.

Reference numerals 83 and 84 denote U-shaped arms, and are attached to both sides of the arm attachment rod 81 one at a time.

As shown in fig. 7, the tip of the arm 83 is provided with pyramid-shaped hook portions 85, 87. Holes 88 are formed in the top portions of both sides of the workpiece W, respectively. By passing the booms 83, 84 through this hole 88, the workpiece (W) is suspended from the workpiece hanger 77.

The workpiece hanger 77 is configured to be conveyable by a hanger conveyance mechanism as shown in patent documents 1 and 2.

The control system is described below with reference to fig. 8.

Reference numeral 89 denotes a small attachment (tag) as a rewritable data recording medium, and the small attachment (tag)89 is detachably attached to an attachment portion 90 provided on the stay 79 of the work hanger 77. In the small attachment (tag)89, the model of the workpiece (W) is recorded.

Reference numeral 91 denotes a control unit (controller), and the high-frequency power supplies 73 corresponding to the No.1 coil, the No.2 coil, and the No.3 coil are connected to the control unit 91. Further, a driving power source, not shown, of the opening and closing motor 59 and the center moving motor 69 is connected. In addition, a radiation thermometer 75 is also connected.

The control unit 91 is provided with a reading unit (not shown) for reading data of the small accessory (tag) 89.

When the control section 91 reads the model of the workpiece (W) from the small attachment (tag)89, the output information of the high-frequency power source 73 corresponding to the No.1 coil, the No.2 coil and the No.3 coil corresponding to the workpiece (W) is read out from the data file obtained in advance, and the drive information of the on-off motor 59 and the center-moving motor 69 is controlled accordingly.

In addition, if temperature information from the radiation thermometer 75 is obtained, the high frequency output of the No.3 coil is adjusted in accordance with this.

A method of using the above-described workpiece heating apparatus 1 will be described below.

First, before actually heating the workpiece (W), thermometers such as thermocouples are provided at a plurality of locations on the workpiece (W) having the same shape as the workpiece (W), and then the workpiece is transported to the workpiece heating apparatus 1, and the heating state of each location is analyzed.

Based on the result, the distance between the workpiece coils 5, 7, the distance between the workpiece (W) and the workpiece coil 5, the distance between the workpiece (W) and the workpiece coil 7, and the output are appropriately set for each of nos. 1 to 3 of the high-frequency induction heating section 3 so as to form a state of uniformly heating the workpiece (W).

The basic guideline of the adjustment utilizes the following point of view.

(1) The temperature of the workpiece (W) can be increased in accordance with the decreasing distance (D) between the workpiece coils 5, 7 and/or the increasing degree of the high-frequency output, whereas the temperature of the workpiece (W) can be decreased in accordance with the increasing distance (D) and/or the decreasing degree of the high-frequency output.

(2) By adjusting the shortest distances (d (r), d (1)) between the workpiece coils 5, 7 and the respective portions of the workpiece (W) which are opposed to each other, even in the case of a curved member (shaped member) such as a rail grid, the temperature difference between the respective portions can be reduced.

In addition, if the conveying speed of the workpiece (W) is reduced, the temperature of the workpiece (W) can be increased, and if the speed is conversely increased, the temperature of the workpiece (W) can be decreased.

Actually, as the work (W), a horizontally long guide grid (uncoated, 4 mm in plate thickness and 1000 mm in horizontal length (T)) shown in fig. 1, 9 to 11 was used, and a plurality of works (W) were suspended on the work hanger 77 as shown in fig. 1. At this time, the distance (G) between the right and left adjacent workpieces (W) is 100 mm. The workpieces having the same size (the length (L) in the conveying direction is 300 mm) of the coils nos. 1 to 3 are used side by side at intervals of 300 mm each time.

By providing thermocouples at the positions a, B, and C of the workpiece (W), the workpiece is continuously conveyed in the direction of the arrows in fig. 1 and 11 while changing the distance (D) of the workpiece coil to various degrees and changing the condition of high-frequency output. Further, the heating state (maximum temperature) of each part after the workpiece (W) is discharged from the high-frequency induction heating unit 3 is analyzed.

In addition, when only one workpiece (W) is suspended from the workpiece hanger 77, the temperature changes from when a plurality of workpieces (W) are suspended. In the above test case, a plurality of workpieces (W) are suspended according to actual operations, and the temperature is measured for each test workpiece.

The measurement results are as follows.

Table 1 conveyance speed: 0.8 m/min

	No.1	No.2	No.3
				D (millimeter)	185	Left side is the same	Left side is the same
d (r) (mm)	55	Left side is the same	Left side is the same
				d (l) (mm)	55	Left side is the same	Left side is the same
High frequency output (kW)	30	Left side is the same	Left side is the same

d (r) represents the shortest distance between the workpiece (W) and the workpiece coil 7, and d (l) represents the shortest distance between the workpiece (W) and the workpiece coil 5.

TABLE 2 Cross flow

Inlet average temperature: 165 ℃, mean average temperature: 213 ℃, exit average temperature: at a temperature of 178 c,

temperature difference between inlet and center: 48 ℃, temperature difference between center and outlet: 35 deg.C

From the above table, it is known that the "inlet" temperature is 48 ℃ lower than the "intermediate" temperature and the "outlet" temperature is 35 ℃ lower than the "intermediate" temperature. It is also known that the temperature difference between "A" and "B" is 4 ℃ at the inlet side, 14 ℃ at the middle part, and 15 ℃ at the outlet side.

Based on a plurality of test results including the above, the following matters were confirmed.

(1) The temperature of the inlet is 40-50 ℃ lower than that of the middle, and the temperature of the outlet is 30-40 ℃ lower than that of the middle.

(2) In the case where the "workpiece" (W) is a curved member such as a rail grid, the maximum temperature difference may be in the range of 10 to 20 degrees centigrade depending on the distance between each of the portions a, B, and C and the workpiece coils 5 and 7.

If the heating temperature varies from one part of the workpiece (W) to another, uneven baking occurs, and the strength of the coating film decreases.

In order to make the heating temperature uniform, the following measures are taken for the above confirmation.

(1) A plurality of high-frequency induction heating sections 3 are provided.

(2) On the inlet side and outlet side, where the temperature is lower, the distance (D) between the workpiece coils 5, 7 is reduced and/or the high-frequency output power is increased.

(3) The distance between the workpiece coils 5 and 7 facing each other and each part of the workpiece is adjusted according to the shape of the rail grid.

Specifically, the adjustment was performed in the following manner.

TABLE 3

Under the above conditions, the positions of the No.1 coil and the No.3 coil move halfway.

That is, the opening/closing motor 59 and the center moving motor 69 are driven so that the position conditions described in the lower column of the approach distance x are satisfied before the workpiece W enters x (200 mm) from the head direction, the position conditions described in the lower column of the approach distance y are satisfied before the workpiece W enters y (650 mm), and the position conditions described in the lower column of the approach distance x are satisfied when the workpiece W passes y.

The output of No.3 is further finely adjusted based on the temperature information from the radiation thermometer 75, whereby an appropriate final temperature is obtained.

Fig. 12 shows a second embodiment.

Reference numeral 101 denotes a high-frequency induction heating section, and the high-frequency induction heating section 101 is characterized in that a pair of workpiece coils 103 and 105 are provided to be opposed to each other in the vertical direction. The workpiece (W) is box-shaped with an open top as viewed in a cross-sectional view in the conveying direction of the inside of the ball. In the workpiece (W) having such a shape, it is necessary to surely perform vertical temperature control so as to uniformly heat the workpiece, and therefore, the workpiece coils 103 and 105 are provided vertically and the distance from the workpiece in the height direction is adjusted.

Although the embodiments of the present invention have been described above, the specific structure of the present invention is not limited to the embodiments, and is included in the present invention even if there are design changes without departing from the scope of the present invention.

For example, in the first embodiment, the distance between the workpiece coils and the high-frequency output are controlled based on the information obtained in advance in principle, but thermometers may be provided at a plurality of locations and may be controlled gradually based on the temperature information from the thermometers.

Further, a thermometer may be provided on the output side of the high-frequency induction heating unit, and the temperature information may be used as quality evaluation information of the heated product.

Claims (7)

1. A workpiece heating apparatus, characterized in that:

the device is provided with a plurality of high-frequency induction heating parts, and the high-frequency induction heating parts also comprise a plurality of high-frequency induction heating units,

a pair of work coils disposed opposite to each other;

a distance adjusting mechanism that adjusts a distance between each of the work coils and a workpiece, the workpiece being located between the pair of work coils;

an output power adjusting mechanism for independently adjusting the high-frequency output power of the workpiece coil;

the distance adjusting means can change the distance setting between the workpiece and each of the workpiece coils in accordance with the entering distance of each of the conveyed workpieces into the apparatus.

2. The workpiece heating apparatus according to claim 1, wherein the distance adjusting mechanism comprises:

a changing mechanism including an opening/closing motor and a center moving motor, the opening/closing motor being driven to move the pair of work coils in directions to approach or separate from each other, and the center moving motor being driven to move a center line between the pair of work coils while a distance between the pair of work coils is kept constant;

and a moving mechanism for integrally moving the pair of workpiece coils.

3. A workpiece heating apparatus according to claim 1 or 2, wherein each of the high-frequency induction heating sections further comprises a control section that controls the distance adjusting mechanism and the output power adjusting mechanism, and the control section independently controls the distance adjusting mechanism and the output power adjusting mechanism based on information acquired in advance.

4. The workpiece heating apparatus according to claim 3, further comprising a thermometer disposed between the workpiece coils of the adjacent high-frequency induction heating units and measuring a temperature of the workpiece, wherein the control unit finely adjusts a distance and/or a high-frequency output power of the high-frequency induction heating unit on a front side in the conveying direction based on the temperature information.

5. A workpiece heating method using the workpiece heating apparatus according to claim 1, characterized in that: the work is heated while continuously conveying a plurality of works.

6. A workpiece heating method using the workpiece heating apparatus according to claim 3, characterized in that: the heating state of each high-frequency induction heating unit is analyzed in advance using a workpiece, and based on the analysis result, distance information between the workpiece coil of each high-frequency induction heating unit and the workpiece and output power information of the workpiece coil are obtained so that the workpiece can be uniformly heated.

7. A workpiece heating method using the workpiece heating apparatus according to claim 4, characterized in that: the distance and/or the high-frequency output power on the front side in the conveying direction are/is finely adjusted based on temperature information from a thermometer that measures the temperature of the workpiece, the thermometer being disposed between the workpiece coils of adjacent high-frequency induction heating sections.