JP4464252B2 - Filtration member, method for producing the filtration member, and apparatus for producing the filtration member - Google Patents

Description

  The present invention relates to a filtration member formed in a cylindrical body having stitches in which a plurality of layers forming a plurality of layers overlap each other in a radial direction, such as a wound filter constituting an inflator filter in an airbag device, and the filtration The present invention relates to a method for manufacturing a member and an apparatus for manufacturing the filter member.

  2. Description of the Related Art Conventionally, an air bag apparatus that inflates a bag by instantaneously releasing gas with rapid deceleration due to a collision or the like is mounted on the vehicle. The airbag device includes an inflator that has a function of instantaneously releasing a gas in response to the operation thereof, and a bag that is inflated by the gas released from the inflator to protect an occupant. The inflator is provided with an igniter and a gas generating agent that generates gas by explosively burning with the heat of the igniter, and a gas or liquid having a residue at a high temperature generated by the combustion of the gas generating agent. An air bag inflator filter for filtering and cooling is provided as a filtering member. This air bag inflator filter is usually a wound type in which irregular wires such as metal round wires or square wires (hereinafter referred to as “element wires”) are wound in a plurality of layers and knitted into a cylindrical body having stitches. A filter is adopted. In other words, this wire-wound filter is configured to function as a filtering member when gas or liquid passes through a mesh gap formed by winding an element wire into a cylindrical body.

  In this type of wire-wound filter, in order to prevent gas or liquid from passing through the stitches and expanding and impact force, the stitch shape is lost and the filtration performance is changed. The overlapping portions of the strands forming the stitches after the strands are wound are joined. In particular, in an air bag inflator filter used as a filtering member in an air bag, a very high temperature gas passes, and thus it is necessary to provide a strong bonding strength. Therefore, recently, as a manufacturing method for improving the bonding strength by the required performance of the airbag inflator filter, for example, a manufacturing method of an airbag inflator filter described in Patent Document 1 (hereinafter referred to as “conventional manufacturing method”). ) Has been proposed.

That is, in the conventional manufacturing method, an electric furnace is used to sinter the wound filter, and the wound filter is sintered in the electric furnace at a high temperature of about 1150 ° C. for about 60 minutes. Thus, the overlapping portions of the strands are joined. The inside of the electric furnace is filled with an atmosphere gas (inert gas) such as nitrogen gas kept at a high temperature of about 1150 ° C. during the sintering process, and after the sintering process, the wound filter is attached to the furnace. The temperature is lowered to about room temperature for cooling inside.
JP 2001-171472 A (paragraph number [0025], FIG. 4)

  By the way, in the electric furnace used by the conventional manufacturing method, there existed the actual condition that it took 1 hour or more to raise the temperature in this electric furnace from normal temperature to the high temperature of 1150 degreeC. Therefore, even when the wire wound filter is not produced, the electric furnace cannot be stopped (that is, the temperature inside the electric furnace cannot be lowered), and the electric furnace has to be continuously operated all day. Further, in the conventional manufacturing method, the wire-wound filter has to be held in the electric furnace for a long time (about 60 minutes) for the sintering process for joining the strands. Accordingly, there is a problem in that the production efficiency is poor when the production method of sintering a wound filter using an electric furnace is performed.

  On the other hand, the manufacturing method in which the overlapping portions of the strands in the wire wound filter are melted and joined using a resistance welding machine (for example, an electrical resistance welding machine) regardless of the manufacturing method using the electric furnace as described above. A method is also conceivable. However, in this manufacturing method using a resistance welder, there are a large number of portions that need to be joined in the wound filter, and thus it takes a lot of time to manufacture the wound filter. There was a problem.

  The present invention has been made in view of such circumstances. The purpose is to provide a filtration member that can be manufactured at low cost by efficiently joining the overlapping portions of the strands in a tubular body having a stitch by overlapping the strands forming a plurality of layers in the radial direction, It is providing the manufacturing method of a filtration member, and the manufacturing apparatus of this filtration member.

In order to achieve the above object, the invention according to claim 1 is the method of manufacturing a filtration member formed in a cylindrical body having a stitch by overlapping the strands forming a plurality of layers in the radial direction. Among the outermost layer and a layer adjacent to the outermost layer on the radially inner side at least when the strands of the specific layer are joined together by high frequency induction heating, the heating period spent on the induction heating The temperature of the strand in the specific layer is lower than the melting point of the strand and has a soaking period that is maintained at a temperature equal to or higher than a predetermined target induction heating temperature , and within the heating period, the specific layer A first heating period in which the temperature of the element wire is raised to the Curie temperature of the element wire, and the strand in the specific layer at a heating rate faster than the heating rate of the element wire in the first heating period The temperature of the wire Curie It is summarized in that comprising further a second heating period for heating up the target induction heating temperature from degrees.

  The gist of the invention according to claim 2 is that, in the method for manufacturing a filtration member according to claim 1, the target induction heating temperature is set to a temperature of 80% or more of the absolute temperature at the melting point of the strand. Yes.

Invention of Claim 3 is a manufacturing method of the filtration member of Claim 1 or Claim 2, After the temperature of the strand in the said specific layer is made into the said target induction heating temperature in the said soaking | uniform-heating period. The elapsed time is to satisfy the following formula.

t ≧ (4 / (C1 × P × b ² × n)) ^2.5 × T × exp (2.5 × C2 / T)
However, T: target induction heating temperature, t: elapsed time, P: contact pressure, b: wire between the contact width, n: number of the joint portion of the strand between, C1, C2 are engaged Number

Invention of Claim 4 is a manufacturing method of the filtration member as described in any one of Claims 1-3 . WHEREIN: When joining the strands in the said specific layer by high frequency induction heating, the said The gist is to regulate the deformation of the tubular body in a direction along the axial direction of the tubular body until a predetermined threshold time elapses from the start of the heating period.

The gist of the invention described in claim 5 is that it is manufactured by the method for manufacturing a filtration member according to any one of claims 1 to 4 .
The invention according to claim 6 is an apparatus for manufacturing a filtration member formed in a cylindrical body having a stitch by overlapping strands forming a plurality of layers in a radial direction, and the outermost layer and the outermost layer among the plurality of layers A high-frequency induction heating device that joins the wires of a specific layer including at least a layer adjacent on the radially inner side by high-frequency induction heating, the high-frequency induction heating device being an induction heating object Induction heating means arranged so as to surround the outer peripheral surface of the cylindrical body, and control means for controlling the power supplied to the induction heating means, the control means within the heating period spent on the induction heating Output to the induction heating means so as to form a soaking period in which the temperature of the wire in the specific layer is lower than the melting point of the wire and is equal to or higher than a predetermined target induction heating temperature. To do Controls, the control unit, in the heating period, the a first heating period for the temperature of the strand at a particular layer is heated to the Curie temperature of the wire, the element in the first heating period And a second temperature raising period in which the temperature of the wire in the specific layer is raised from the Curie temperature of the wire to the target induction heating temperature at a heating rate faster than the heating rate of the wire. The gist is to control the power output to the induction heating means .

The gist of the invention according to claim 7 is that the target induction heating temperature is set to a temperature of 80% or more of the absolute temperature at the melting point of the strand in the filter member manufacturing apparatus according to claim 6. Yes.

The invention according to claim 8 is the apparatus for manufacturing a filtration member according to claim 6 or claim 7 , wherein the soaking period is after the wire temperature in the specific layer is set to the target induction heating temperature. The elapsed time is to satisfy the following formula.

t ≧ (4 / (C1 × P × b ² × n)) ^2.5 × T × exp (2.5 × C2 / T)
However, T: target induction heating temperature, t: elapsed time, P: contact pressure, b: wire between the contact width, n: number of the joint portion of the strand between, C1, C2 are engaged Number

Invention of claim 9, apparatus for manufacturing a filtering member as claimed in any one of claims 6 to claim 8, the wires each other in the particular layer in joining by high-frequency induction heating, the Deformation restricting means for restricting deformation of the tubular body in a direction along the axial direction of the tubular body by pressing the tubular body from a direction along the axial direction of the tubular body, and the control means, The gist is that the cylindrical body is pressed in the direction along the axial direction of the cylindrical body by the deformation restricting means until a predetermined threshold time elapses from the start of the heating period.

  ADVANTAGE OF THE INVENTION According to this invention, it can manufacture at low cost by joining the overlapping part of the said strands in the cylindrical body which has the stitches by overlapping the strands which make multiple layers in radial direction efficiently.

  Hereinafter, an embodiment in which the present invention is embodied in a filter for an airbag inflator installed in an inflator of an airbag apparatus, a method for manufacturing the filter, and an apparatus for manufacturing the filter will be described with reference to FIGS.

  As shown in FIG. 1, an igniter 11 that performs ignition based on an operation signal from a sensor (not shown) is provided at a central portion of an inflator 10 of an airbag device (not shown) in the present embodiment, and the igniter 11. A flammable auxiliary combustor 12 is provided to assist the generation of heat by ignition. A chamber portion 13 is provided on the outer periphery of the igniter 11 and the auxiliary combustor 12 so that heat generated by the igniter 11 and the auxiliary combustor 12 flows. In addition, a gas generating agent 14 is provided in the chamber 13, and the gas generating agent 14 explosively burns by the heat generated by the operation of the igniter 11 and the auxiliary combustor 12 to generate a large amount of gas. The gas is supplied together with the inflator 10 to a bag (not shown) provided in the airbag device.

  In the inflator 10, an airbag inflator filter (hereinafter referred to as “filter”) 15, which is a filtering member, is disposed so as to surround the chamber portion 13. The filter 15 functions as a cooling member that cools the high-temperature gas generated by the explosive combustion of the gas generating agent 14 and supplies the bag to the bag, and filters the residue contained in the gas into the bag. It has a function as a filtration member for supplying gas.

As shown in FIG. 2, the filter 15 is wound around a cylindrical bobbin (not shown) serving as a shaft member with a deformed wire (hereinafter referred to as “element wire”) 16 such as a metal square wire or a round wire. After forming the stitches, the bobbin is pulled out to form a hollow cylinder. That is, the filter 15 is formed in a cylindrical body having stitches in which the strands 16 forming a plurality of layers in the radial direction overlap each other. In the present embodiment, as an example, an iron wire material containing iron as a main component is used as an element wire 16, and the element wire 16 is wound around the outer peripheral surface of the bobbin 500 times (the number of turns: 500). A winding type filter 15 having a hollow cylindrical shape with an inner diameter of 46 mm is illustrated. Moreover, the strand 16 is a square wire, the horizontal width is 0.35 mm, and the vertical width is 0.6 mm (that is, the strand cross-sectional area is 0.2 mm ² ). The resistivity ρ of the iron wire at normal temperature (approximately 20 ° C.) is 20 × 10 ⁻⁸ Ω · m, and the relative permeability μr is 30. The resistivity ρ of the iron wire at 1100 ° C. is 120 × 10 ⁻⁸ Ω · m, and the relative permeability μr is 1.

  Therefore, in this filter 15, when a large amount of high-temperature gas generated by explosive combustion of the gas generating agent 14 passes through the gap formed by winding the metal wire 16, It is possible to cool the gas or filter the residue contained in the gas. Further, as shown in FIG. 2, the winding interval of the strands 16 at the time of winding is the pitch H, the winding angle between the strands 16 crossing each other to form a stitch is the crossing angle θ, and the bobbin axis of the strands 16 A winding width with respect to the direction is referred to as a winding width L, and a portion where the intersecting strands 16 come into contact with each other is referred to as a contact portion S.

Next, the manufacturing method of the filter 15 which is a filtration member is demonstrated.
First, the metal strand 16 is applied with a predetermined tension and is wound around the outer peripheral surface of the bobbin by cross winding to form a stitch. As a winding method, there are a method of winding the wire 16 to be wound in the winding width L direction, a method of winding the strand 16 while moving the shaft portion of the bobbin in the winding width L direction, and the like. The stitches of the filter 15 are calculated by calculating the pitch H, the winding width L, the crossing angle θ, and the like of the strands 16 and manufacturing them with the calculated values. Various stitches are formed according to the demands of various filtration functions.

  Subsequently, at the end of winding of the element wire 16, the winding end end 17 of the element wire 16 is fixed (joined) by welding, caulking or the like while a predetermined tension is still applied to the element wire 16. And the filter 15 before heat processing of a cylindrical body is obtained by extracting the bobbin which is a shaft member. Thereafter, the filter 15 is induction-heated by high-frequency induction heating in order to join the contact portions S of the strands 16 that intersect in a radial direction by forming a plurality of layers by winding.

Next, the manufacturing apparatus of the filter 15 in this embodiment is demonstrated below based on FIGS.
As shown in FIG. 3, the filter 15 manufacturing apparatus (hereinafter abbreviated as “manufacturing apparatus”) M in this embodiment includes a wire winding portion (not shown) that forms the filter 15 before heat treatment, and the filter And a high-frequency induction heating device 18 for induction heating 15, and the high-frequency induction heating device 18 is provided with a case main body 19 extending in the left-right direction in FIG. An opening / closing door 20 a for inserting the filter 15 into the case body 19 is provided on one end side in the longitudinal direction of the case body 19 (left end side in FIG. 3). On the other hand, an opening / closing door 20b for carrying the filter 15 in the case body 19 out of the case body 19 is provided on the other end side in the longitudinal direction of the case body 19 (right end side in FIG. 3). . Incidentally, the inside of the case main body 19 is filled with a nitrogen atmosphere gas, and the opening / closing door 20a opens and closes only when the filter 15 is inserted into the case main body 19, and the opening / closing door 20b is opened from the inside of the case main body 19. Only when unloading 15 is opened and closed. That is, since each opening / closing door 20a, 20b is in a closed state except when the filter 15 is loaded and unloaded, the nitrogen atmosphere gas flows out of the case body 19 through the opening / closing door 20a, 20b. It has become difficult. Further, purge chambers (not shown) communicating with the inside of the case body 19 when the open / close doors 20a and 20b are opened are provided at both ends in the longitudinal direction of the case body 19, respectively. A nitrogen atmosphere gas is always supplied into each purge chamber.

  An endless belt conveyor 21 is disposed below the case body 19 along the longitudinal direction of the case body 19, and the filter 15 is mounted on the transport surface 21 a of the belt conveyor 21. It is supposed to be placed. As shown by arrows in FIG. 3, the belt conveyor 21 has one side (left side in FIG. 3) on the upstream side in the transport direction and the other side (right side in FIG. 3) on the downstream side in the transport direction. Yes. That is, the filter 15 conveyed from one side is put into the case main body 19 via the opening / closing door 20a, and is conveyed in the case main body 19 in the direction indicated by the arrow. And the filter 15 conveyed in the case main body 19 to the other side edge part is carried out to the said case main body 19 through the said opening-and-closing door 20b. In the present embodiment, the filter 15 is intermittently inserted into the case body 19 from the opening / closing door 20a, so that the belt conveyor 21 intermittently places each filter 15 on the transport surface 21a. It is designed to be driven in a state where it is mounted on.

  An induction heating coil (induction heating means) 22 is disposed on one side of the case body 19 at a position above the conveying surface 21 a of the belt conveyor 21. An elevator (hydraulic cylinder or the like) having a mounting plate 23A movable in the vertical direction in FIG. 3 at a position immediately below the induction heating coil 22 and below the conveying surface 21a of the belt conveyor 21. ) 23 is provided. As shown in FIG. 4, the induction heating coil 22 is formed in a spiral shape, and a high-frequency current flows in a predetermined direction (the direction indicated by the solid line arrow in FIG. 4). Then, when such a high frequency current flows, an alternating magnetic flux is generated inside the induction heating coil 22 (indicated by a broken arrow in FIG. 4).

  Here, when the filter 15, which is an induction heating object, is disposed at a position inside the induction heating coil 22 by driving the elevator 23, the outer peripheral surface 15 a of the filter 15 is surrounded by the induction heating coil 22. Thus, the alternating magnetic flux enters the filter 15. Therefore, an eddy current flows in the filter 15 so as to cancel the alternating magnetic flux entering the filter 15, and the filter 15 generates heat due to the eddy current loss and the hysteresis loss based on the eddy current. As a result, the specific layer (the main layer) including the outermost layer (outermost layer in the radial direction) 24 closest to the induction heating coil 22 in the filter 15 and the layer adjacent to the outermost layer 24 in the radial direction inside by the heat generation. In the embodiment, the contact portions S of the strands 16 in the layer including a position approximately 2 mm away from the outer peripheral surface 15a of the filter 15 with respect to the radially inner side are joined.

  Incidentally, the current density of the eddy current flowing through the filter 15 when a high-frequency current is passed through the induction heating coil 22 is maximized in the outermost layer 24 of the induction heating coil 22 and gradually decreases as it progresses radially inward of the filter 15. It has properties. That is, in the high frequency induction heating, the outermost layer 24 of the filter 15 is easily heated by the so-called skin effect, and is gradually less likely to be heated toward the radially inner side. However, in the present embodiment, the outermost layer 24 of the filter 15 is in contact with the nitrogen atmosphere gas in the case body 19, and the nitrogen atmosphere gas is induction heated by high frequency induction heating (particularly the outermost layer 24). Is sufficiently lower than the temperature of Therefore, the temperature of the filter 15 that is induction-heated is slightly lowered by heat exchange with the nitrogen atmosphere gas in the outermost layer 24, and on the other hand, the portion located radially inward from the outermost layer 24 (from the outermost layer 24 to the radial direction). The heating temperature is high at a position approximately 0.5 mm away from the inside.

  The elevator 23 has a placement plate 23A at a stage before the filter 15 put into the case body 19 from the opening / closing door 20a is conveyed by the belt conveyor 21 to a position directly above the placement plate 23A in the elevator 23. Is waiting at a position below the conveying surface 21a of the belt conveyor 21. On the other hand, when the filter 15 is conveyed by the belt conveyor 21 to a position directly above the mounting plate 23A in the elevator 23, the elevator 23 is placed on the mounting surface 23a constituted by the upper surface of the mounting plate 23A. With the filter 15 mounted, the mounting plate 23A is raised to move the filter 15 upward. And the elevator 23 raises the said mounting plate 23A, when the mounting plate 23A raises to the height position where the filter 15 mounted on the mounting surface 23a is arrange | positioned inside the induction heating coil 22. FIG. It is supposed to stop. The belt conveyor 21 of the present embodiment is driven for transport when the filter 15 transported to a position directly above the elevator 23 (that is, a position directly below the induction heating coil 22) is detected by a sensor (not shown). Is temporarily stopped. In addition, when the ascent plate 23A stops rising, the plate 15 rotates together with the filter 15 in the direction indicated by the arrow Q in FIG. 4 in a state where the filter 15 is disposed inside the induction heating coil 22. ing. And when the induction heating to the filter 15 is complete | finished, the said mounting plate 23A stops the rotation.

  The elevator 23 is placed so that the filter 15 is moved downward after the contact portion S between the strands 16 of the specific layer is joined by induction heating by the induction heating coil 22 by high frequency induction heating. The plate 23A is lowered. When the filter 15 is transferred from the placement surface 23a of the placement plate 23A onto the transport surface 21a of the belt conveyor 21 again, the belt conveyor 21 resumes its drive and causes the filter 15 to move for a predetermined time. It is conveyed toward the opening / closing door 20b on the other side (approximately 6 minutes in this embodiment). In the middle of this conveyance, normal temperature nitrogen atmosphere gas is sprayed on the filter 15 on the conveyance surface 21a (that is, a cooling process is performed). Therefore, the filter 15 is sufficiently cooled when it is carried out of the case body 19 from the open / close door 20b, and can be prevented from being oxidized by oxygen contained in the outside air. .

  In the case main body 19, a pressing machine 25 having a weight member 25A formed in a disc shape with ceramic is provided above the induction heating coil 22 so as to move the weight member 25A in the vertical direction in FIG. ing. The weight member 25A is formed as a pressing surface 25a whose one surface (the lower side surface in FIG. 3) is flat, and the pressing surface 25a is placed on the elevator 23 as the weight member 25A moves downward. The filter 15 placed on the placement surface 23a of the plate 23A can be pressed from above. In the present embodiment, when the pressing surface 25 a presses the filter 15 on the placement surface 23 a based on the downward movement of the weight member 25 </ b> A, the pressing machine 25 follows the axial direction of the filter (tubular body) 15. The filter 15 is pressed with a load of approximately 1 kilogram from the direction.

  Incidentally, the filter 15 heated by induction by the induction heating coil 22 has a temperature difference between the radially outer side and the radially inner side as described above. Therefore, the filter 15 tends to be deformed in a direction along the axial direction of the filter 15 (vertical direction in FIG. 4) when induction-heated. However, when induction heating is performed by the induction heating coil 22, the lower portion of the filter 15 is in contact with the placement surface 23 a of the placement plate 23 </ b> A in the elevator 23, and the upper portion in the axial direction is a weight member in the pressing device 25. It will be pressed by the pressing surface 25a of 25A, and the deformation | transformation to the said axial direction is controlled. That is, in this embodiment, as a deformation restricting means for restricting deformation of the pressing machine 25 in the direction along the axial direction by pressing the filter (tubular body) 15 from the direction along the axial direction of the filter 15. It is supposed to function.

Next, the control structure in the high frequency induction heating apparatus 18 of this embodiment is demonstrated below based on FIG.
As shown in FIG. 5, the high-frequency induction heating device 18 according to the present embodiment is provided with a control unit 26 for controlling the amount of power output to the induction heating coil 22 (that is, the amount of current to be fed). . The control unit 26 includes a CPU (control means) 26a, and a ROM 26b and a RAM 26c are connected to the CPU 26a. The ROM 26b stores and manages the amount of power output to the induction heating coil 22, a control program for controlling the belt conveyor 21, and the like. The RAM 26c stores various information (such as the amount of power output to the induction heating coil 22) that can be appropriately rewritten while the high frequency induction heating device 18 is in operation. And CPU26a performs the electric energy control output to the induction heating coil 22 based on the said control program, drive control of the belt conveyor 21, the elevator 23, and the pressing machine 25, and the opening / closing control of each said opening / closing door 20a, 20b. It is like that. The ROM 26b stores in advance an induction heating pattern for induction heating of the filter 15, and the CPU 26a controls the amount of power output to the induction heating coil 22 based on the induction heating pattern. . In addition, an operation unit 27 is connected to the control unit 26, and the target induction heating temperature T of the filter 15 that is induction-heated by high-frequency induction heating based on the operation content of the operation unit 27 (see FIG. 6A). Etc. can be set.

  Here, as described above, the main component of the wire 16 constituting the filter 15 is iron, and the melting point of this iron is about 1530 ° C. Therefore, in the case where the filter 15 is induction-heated by high-frequency induction heating, when the heating temperature of the filter 15 becomes 1530 ° C. or higher, the strand 16 is melted and consequently melted. There is a possibility. Therefore, it is desirable that the target induction heating temperature T is less than 1530 ° C., which is the melting point of iron.

  Further, in induction heating by high frequency induction heating, an elapsed time for induction heating of the filter 15 at the target induction heating temperature T is set corresponding to the target induction heating temperature T. That is, when the target induction heating temperature T is a relatively high temperature, the elapsed time is set to a relatively short time, whereas when the target induction heating temperature T is a relatively low temperature, the elapsed time is set. The time is set to a relatively long time. Here, when the target induction heating temperature T is set too low in relation to the melting point of the wire 16, the elapsed time required for joining the contact portions S of the wires 16 in the filter 15 is joined. It will be very long. Therefore, in order to shorten the elapsed time, the target induction heating temperature T is preferably set to 80% (about 1170 ° C.) or more of the absolute temperature at the melting point of the strand 16. Incidentally, the target induction heating temperature T in this embodiment is set to 1300 ° C.

In the present embodiment, the target induction heating temperature T and the elapsed time are set to satisfy the following conditional expression (1).
t ≧ (4 / (C1 × P × b ² × n)) ^2.5 × T × exp (2.5 × C2 / T) (1)
Where T: target induction heating temperature, t: elapsed time, P: contact surface pressure between the wires 16 in the specific layer, b: contact width between the wires 16 in the specific layer, n: wires 16 in the specific layer In the present embodiment, the manufacturing apparatus M (case body 19) is filled with a nitrogen atmosphere gas (that is, because it is a nitrogen atmosphere). C1 = 6.06 × 10 ⁹ and C2 = 25061 are set.

  Further, as described above, the induction heating pattern is set and stored in the ROM 26b. In this induction heating pattern, as shown in FIG. 6A, a heating period K that is spent for induction heating of the filter 15 is set. Within this heating period K, the temperature of the wire 16 (shown as “outside” in FIG. 6A) in the specific layer of the filter 15 is increased to the target induction heating temperature (1300 ° C.) T. A period A and a soaking period B in which the temperature is lower than the melting point and the temperature is equal to or higher than the target induction heating temperature T are provided.

  Here, the Curie temperature of iron (element wire 16) is approximately 770 ° C., and when the Curie temperature is exceeded, the permeability of the iron greatly changes. Incidentally, when the temperature of the filter 15 that does not exceed the Curie temperature is rapidly raised, the current transmission depth during induction heating becomes shallow, and more current flows through the outermost layer 24 of the filter 15. become. If it becomes so, the temperature increase rate of the outermost layer 24 of the filter 15 will become very fast, and as a result, the strand 16 which comprises the said outermost layer 24 may melt | fuse out exceeding melting | fusing point. Therefore, in the temperature raising period A of the present embodiment, the temperature of the strand 16 in the specific layer of the filter 15 is raised relatively slowly until it reaches the Curie temperature. On the other hand, when the temperature of the strand 16 in the specific layer exceeds the Curie temperature, the rate of temperature increase is relatively faster than before.

  That is, the temperature raising period A includes a first temperature raising period A1 in which the temperature of the strand 16 in the specific layer is gradually raised to the Curie temperature, and a wire 16 in the specific layer in the first temperature raising period A1. The temperature of the wire 16 in the specific layer is distinguished from a second temperature increase period A2 in which the temperature of the wire 16 in the specific layer is increased from the Curie temperature to the target induction heating temperature T at a rate higher than the rate of temperature increase. Incidentally, in the first heating period A1, 14 kW of power is output to the induction heating coil 22 for 6.0 seconds, and in the second heating period A2, 24 kW of power is output to the induction heating coil 22 in 2.6 seconds. Is output. Further, “(s)” shown in FIG. 6A is an abbreviation for “Second (second)”.

  In the soaking period B, the temperature of the wire 16 in the specific layer of the filter 15 is about 1530 ° C. which is the melting point of the wire 16 (1430 ° C. which is 100 ° C. lower than 1530 ° C. in this embodiment). Also, the temperature is maintained at a temperature lower than the target induction heating temperature T. The metal molecules are diffused by the wires 16 forming the filter 15 during the soaking period B, and the contact portions S of the wires 16 in the specific layer are sufficiently diffused. Are to be joined. Incidentally, in the soaking period B, 13 kW of power is output to the induction heating coil 22 in 6.4 seconds. That is, in the present embodiment, the elapsed time t is set to 6.4 seconds. When the soaking period B (heating period K) ends, the output of power to the induction heating coil 22 is stopped, and the filter 15 is naturally cooled.

  Further, FIG. 6A shows temperature changes at a plurality of positions of the filter 15. That is, in the innermost layer of the filter 15 (indicated as “inside” in FIG. 6A) that is farthest from the induction heating coil 22, the rate of temperature rise is the slowest, and induction heating by the induction heating coil 22 starts. After that, the temperature is gradually raised and reaches approximately 500 ° C. after 60 seconds. Further, in the intermediate layer (shown as “middle side” in FIG. 6A) between the inner peripheral surface and the outer peripheral surface 15 a of the filter 15, the temperature increase rate is faster than the radially inner position, The maximum temperature (approximately 650 ° C.) is reached 20 seconds after the induction heating by the induction heating coil 22 is started, and then the temperature gradually decreases to approximately 550 ° C. In the specific layer, the rate of temperature increase is the fastest, and after about 8 seconds from the start of induction heating by the induction heating coil 22, the target induction heating temperature T is reached, and after the soaking period B ends, the temperature rises. It gradually decreases. And 45 seconds after the soaking period B ends, the temperature at the radially outer position decreases to approximately 500 ° C. Finally, on the outer peripheral surface 15a of the filter 15, the temperature change is substantially the same as the temperature change of the specific layer. However, as described above, the temperature on the outer peripheral surface 15a of the filter 15 is somewhat lower as a whole than the specific layer.

  In addition, the ROM 26b has the weight member 25A of the pressing machine 25 to press the filter 15 from the direction along the axial direction of the filter 15 from the start of the heating period K to the end of the heating period K. A threshold time longer than the period K (25 seconds in this embodiment) is set and stored. Therefore, when induction heating the filter 15, the CPU 26 a uses the pressing surface 25 a of the weight member 25 </ b> A to press the filter 15 until 10 seconds (25 seconds after the heating period K starts) after the soaking period B ends. Are pressed in a direction along the axial direction of the filter 15. Therefore, the filter 15 is well regulated from being deformed in the axial direction based on induction heating.

Next, the filter 15 after induction heating with the induction heating pattern of this embodiment will be described.
When induction heating is performed by the induction heating pattern, as shown in FIG. 6B, bonding at the contact portion S between the strands 16 at a position approximately 0.35 mm away from the outer peripheral surface 15a of the filter 15 radially inward. The strength is approximately 15 N / winding, and the bonding strength gradually increases as the distance from the outer peripheral surface 15a further toward the inside in the radial direction. The bonding strength becomes strongest at a position approximately 0.7 mm away radially inward from the outer peripheral surface 15a of the filter 15 (bonding strength = about 31 N / winding). become weak. And finally, when it is 2 mm or more away from the outer peripheral surface 15a of the filter 15 (that is, when it is radially inward of the specific layer), the bonding strength is substantially 0 (zero) N / wind. That is, the contact part S of the strand 16 in the specific layer is securely bonded. In addition, in FIG.6 (b), the measured value of the said joint strength at the time of induction heating with the induction heating pattern of this embodiment is illustrated with a broken line, and the analysis value by computer simulation is illustrated with the continuous line. The measured value and the analysis value are almost the same.

Next, a case where the filter 15 is induction-heated with an induction heating pattern that does not include the soaking period B within the heating period K will be described as a comparative example.
In the induction heating pattern of the comparative example, as shown in FIG. 7A, the temperature raising period A3 in which the temperature of the wire 16 in the specific layer of the filter 15 is raised to the target induction heating temperature (approximately 1300 ° C.) T. Is provided. Incidentally, the temperature raising period A3 (heating period K) is set to about 4 seconds. When induction heating is performed using such an induction heating pattern of the comparative example, as shown in FIG. 7B, the strands 16 at a position approximately 0.35 mm away from the outer peripheral surface 15 a of the filter 15 radially inward. The joint strength at the contact portion S is about 4.8 N / wind.

  Further, the bonding strength of the contact portion S gradually increases as it moves away from the outer peripheral surface 15a of the filter 15 toward the radially inner side, and is strongest at a position approximately 0.5 mm away from the outer peripheral surface 15a radially inward. It will be about 2N / wind. Thus, in the induction heating pattern of the comparative example, even if the bonding strength is the strongest, it is about 5.2 N / turn, and the bonding strength is only about one-sixth that when the induction heating pattern of this embodiment is induction heated. Can't get. In addition, when induction heating is performed with the induction heating pattern of the present embodiment, the contact portion S from the outer peripheral surface 15a to a position 2 mm away from the outer peripheral surface is joined, but when induction heating is performed with the induction heating pattern of the comparative example Only the contact portion S up to a position 1.5 mm away from the outer peripheral surface 15a radially inward is joined. The reason is that when induction heating is performed using the induction heating pattern of the comparative example, since the soaking period B is not provided, there is almost no time for metal molecules to be sufficiently diffused when the strands 16 are joined together. It is. That is, in the induction heating pattern of the present embodiment, since the soaking period B is provided, the strands 16 are bonded to each other after the metal molecules are sufficiently diffused, and as a result, very strong bonding is performed. Strength can be obtained.

  Next, the process of induction heating the filter 15 by the high frequency induction heating device 18 of the present embodiment will be described below. When the filter 15 is not disposed at a position inside the induction heating coil 22, it is assumed that no electric power is output to the induction heating coil 22.

  First, when the filter 15 before heat treatment is conveyed from one side of the belt conveyor 21 into the purge chamber, the open / close door 20a that has been closed is opened, and then the filter 15 is put into the case main body 19. Then, the open / close door 20a in the open state is closed. Then, when the filter 15 is conveyed to a position directly below the induction heating coil 22, the belt conveyor 21 is temporarily stopped and the elevator 23 raises the placement plate 23A. Then, the filter 15 is delivered and placed on the placement surface 23 a of the placement plate 23 </ b> A in the elevator 23 from the transport surface 21 a of the belt conveyor 21. As the mounting plate 23A is raised, the filter 15 placed on the placement surface 23a is positioned inside the induction heating coil 22 (that is, the outer peripheral surface 15a of the filter 15 is surrounded by the induction heating coil 22). When the elevator 23 is raised to the height position), the elevator 23 stops raising the placement plate 23A. Then, the mounting plate 23A starts to rotate together with the filter 15, and the weight member 25A of the pressing machine 25 moves downward and comes into contact with the filter 15 from above, and the weight member 25A reaches the filter 15 via the pressing surface 25a. Start pressing.

  Next, electric power is output to the induction heating coil 22, and the filter 15 is induction heated. That is, the heating period K is started. First, in the first temperature raising period A1, 14 kW of power is output to the induction heating coil 22 and the filter 15 is heated. Then, when 6.0 seconds have elapsed after the first temperature raising period A1 is started and the temperature of the wire 16 in the specific layer of the filter 15 reaches the Curie temperature (approximately 770 ° C.), the second temperature raising period. A2 is started. Then, 24 kW of electric power is output to the induction heating coil 22, and the wire 16 in the specific layer is heated at a temperature increase rate faster than the temperature increase rate in the first temperature increase period A1. Then, after 2.6 seconds have elapsed from the start of the second temperature raising period A2, when the temperature of the wire 16 in the specific layer reaches the target induction heating temperature (1300 ° C.) T, the soaking period B is Be started.

  Then, 13 kW of electric power is output to the induction heating coil 22 and held so that the temperature of the strand 16 in the specific layer does not become lower than the target induction heating temperature T. At this time, metal atoms are diffused from the strands 16 forming the filter 15. Therefore, the contact portion S between the strands 16 in the specific layer obtains a sufficiently strong bonding strength (approximately 31 N / winding), and the contact portion S of the specific layer (from the outer peripheral surface 15a of the filter 15 radially inward). The contact portion S) up to a position 2 mm away is joined (see FIG. 6A). Then, when 6.4 seconds elapse after the soaking period B is started, the soaking period B ends. Incidentally, the weight member 25 </ b> A of the pressing machine 25 presses the filter 15 in the direction along the axial direction of the filter 15 through the pressing surface 25 a until 10 seconds elapse after the soaking period B ends. When 10 seconds elapse after the soaking period B ends, the weight member 25A stops pressing the filter 15.

  Then, when the soaking period B ends, the power output to the induction heating coil 22 is stopped. Therefore, the filter 15 is naturally cooled without being induction-heated. Then, the filter 15 is cooled centering on the specific layer having the highest temperature. That is, part of the heat of the specific layer moves to the outer peripheral surface 15a of the filter 15 and is radiated from the outer peripheral surface 15a. Further, most of the heat of the specific layer moves further radially inward and is dissipated from the inner peripheral surface. Therefore, as the soaking period B ends and the time elapses, the temperature of the specific layer gradually decreases, while the temperature radially inward from the specific layer gradually increases (see FIG. 6A). .

  Further, when the press on the filter 15 by the weight member 25A is stopped, the elevator 23 lowers the placement plate 23A in a state where the filter 15 is placed on the placement surface 23a, and the filter 15 is lowered to the belt. It is delivered and placed on the transport surface 21 a of the conveyor 21. Then, the belt conveyor 21 is driven again, and the filter 15 placed on the transport surface 21a is transported toward the other side (right side in FIG. 3). That is, the filter 15 is transported from the position immediately below the induction heating coil 22 toward the open / close door 20b over approximately 6 minutes. Incidentally, the filter 15 is further cooled by the nitrogen atmosphere gas sprayed when it is conveyed by the belt conveyor 21. When the filter 15 is transported to the other end of the case body 19, the opening / closing door 20b opens and is carried out of the case body 19 (the purge chamber) via the opening / closing door 20b. Thereafter, the opening / closing door 20b is closed, and the belt conveyor 21 conveys the filter 15 in the purge chamber further to the other side.

Therefore, in this embodiment, the following effects can be obtained.
(1) In the induction heating pattern of the above-described embodiment, the temperature of the strand 16 in the specific layer of the filter 15 is maintained at the target induction heating temperature (1300 ° C.) T or higher within the heating period K for induction heating of the filter 15. Soaking period B is provided. Moreover, since the strand 16 is formed from iron, metal molecules (iron molecules) are sufficiently diffused during the soaking period B from the strand 16 in the specific layer. Thus, since the contact part S of the strands 16 in the specific layer is joined in a state where the metal molecules are sufficiently diffused, the joining strength in the contact part S is induction heating that does not form the soaking period B. It becomes very strong compared to the case of induction heating with a pattern. Moreover, since the heat generated in the specific layer of the filter 15 by induction heating also enters the radial inner side of the specific layer, it is also joined at the contact portion S on the radial inner side. Accordingly, the contact portions S (the overlapping portions of the strands 16) of the strands 16 in the filter (tubular body) 15 having a stitch formed by overlapping the strands 16 forming a plurality of layers in the radial direction can be efficiently joined. Thus, the filter 15 can be manufactured at a low cost.

  (2) The target induction heating temperature T is generally set to 1300 ° C. (a temperature of 80% or more of the absolute temperature at the melting point of the strand 16) higher than the temperature (1100 to 1200 ° C.) for sintering in an electric furnace or the like. ing. Therefore, the contact portions S of the strands 16 in the specific layer of the filter 15 are joined in a very short time (15 seconds in total including the first temperature increase period A1, the second temperature increase period A2, and the soaking period B). be able to. Moreover, since the target induction heating temperature T is set lower than the melting point (1530 ° C.) of the strand 16, the filter 15 (the strand 16) is partially dissolved when heated. Can be suppressed satisfactorily.

  (3) The elapsed time t after the temperature of the strand 16 in the specific layer of the filter 15 is set to the target induction heating temperature (1300 ° C.) T is set so as to satisfy the conditional expression (1). Therefore, in the soaking period B, the contact part S of the strands 16 in the specific layer of the filter 15 can be reliably joined.

  (4) In the induction heating pattern of the present embodiment, the first heating period A1 in which the temperature of the wire 16 in the specific layer of the filter 15 is raised to the Curie temperature (770 ° C.), and the wire 16 in the specific layer. And a second temperature raising period A2 for raising the temperature from the Curie temperature to the target induction heating temperature (1300 ° C.) T. If the wire 16 in the specific layer is heated at the same temperature increase rate as the wire 16 in the specific layer in the second temperature increase period A2 during the first temperature increase period A1, the filter 15 The current flowing in the filter 15 concentrates on the outermost layer 24, and only the vicinity of the outermost layer 24 is heated. As a result, the temperature of the strand 16 of the outermost layer 24 may exceed the melting point. However, in the first temperature increase period A1, the temperature of the strands 16 in the specific layer is increased at a temperature increase rate slower than the temperature increase rate of the strands 16 in the specific layer in the second temperature increase period A2. The temperature of the strand 16 of the outermost layer 24 does not exceed the melting point during the temperature raising period A1, and the strand 16 can be prevented from being melted.

  (5) When the filter (tubular body) 15 is induction-heated, the filter 15 is pressed by a pressing machine (deformation restricting means) 25 from the direction along the axial direction of the filter 15. At that time, the weight member 25A of the pressing machine 25 moves the filter 15 along the axial direction of the filter 15 through the pressing surface 25a until the threshold time (10 seconds) elapses from the end of the soaking period B. Press in the direction. Therefore, the filter 15 can satisfactorily regulate deformation based on a temperature difference in the radial direction when induction heating is performed by the induction heating coil (induction heating means) 22.

The present embodiment may be changed to another embodiment (another example) as follows.
-In the said embodiment, if the threshold time for canceling the press state of the filter 15 by the pressing machine 25 during the heating period K after the end of the soaking period B is longer than the set time of the heating period K, It may be set to an arbitrary time (for example, 20 seconds). Moreover, the threshold time may be set to the same time (15 seconds) as the set time of the heating period K. Even when configured in this way, during the heating period K, during the first temperature raising period A1, the second temperature raising period A2, and the soaking period B, the filter 15 is caused by the weight member 25A of the pressing machine 25 to It is pressed in the direction along the axial direction of the filter 15. Therefore, the deformation of the filter 15 in the axial direction can be effectively suppressed as compared with the case where the pressing machine 25 is not provided.

  In the embodiment, when the filter 15 is induction-heated, the elevator 23 (mounting plate 23A) presses the filter 15 in the direction along the axial direction of the filter 15 (upward in FIG. 4). Also good. That is, the elevator 23 may function as a deformation restricting unit. Further, the pressing machine 25 may have an arrangement configuration in which the weight member 25 </ b> A comes into contact with the filter 15 when the elevator 23 raises the filter 15 to a position inside the induction heating coil 22. When configured in this manner, the pressing machine 25 can press the filter 15 in a direction along the axial direction of the filter 15 without operating (moving) the weight member 25A.

  -In the said embodiment, the press machine 25 presets the distance dimension between the mounting surface 23a of the mounting plate 23A in the case of carrying out the induction heating of the filter 15, and the pressing surface 25a of the weight member 25A, You may make it press the said filter 15 when the said distance dimension is longer than the height direction dimension (winding width L) of the filter 15 used as induction heating object.

In the embodiment, the cooling of the filter 15 after the heating period K is not natural cooling but may be forcibly cooled using, for example, a fan.
In the embodiment, the weight member 25A of the pressing machine 25 is an arbitrary member other than iron as long as it is a member that does not affect the filter 15 by melting during induction heating (that is, a member that is difficult to be induction heated). May be.

  In the embodiment, the temperature increase period A is distinguished into the first temperature increase period A1 and the second temperature increase period A2 depending on the temperature increase rate of the strand 16 in the specific layer of the filter 15, but the target Until the induction heating temperature T is reached (that is, during the temperature increase period A), the temperature increase rate of the wire 16 in the specific layer may be changed to a constant temperature increase rate. In this case, in the temperature raising period A, it is desirable to set the temperature raising rate of the wire 16 in the specific layer in the first temperature raising period A1 in order to suppress the melting of the wire 16 in the specific layer.

In the embodiment, the elapsed time t may be set to an arbitrary time (for example, 15 seconds) as long as the conditional expression (1) is satisfied.
In the above embodiment, the target induction heating temperature T is lower than the melting point (approximately 1530 ° C.) of the strand 16 and not less than 80% of the absolute temperature (approximately 1170 ° C.) at the melting point of the strand 16. Any temperature (for example, 1400 ° C.) may be used. However, it is desirable to change the elapsed time t so as to satisfy the conditional expression (1) according to the target induction heating temperature T.

  In the embodiment, the CPU 26a controls the amount of power output to the induction heating coil 22 during the soaking period B, but the power may be intermittently output to the induction heating coil 22. That is, the CPU 26a may perform switching control. In this case, as shown in FIG. 8A, the temperature of the wire 16 in the specific layer during the soaking period B increases or decreases rapidly according to switching control (ON / OFF switching control). To do. When the filter 15 is induction-heated with the induction heating pattern shown in FIG. 8A, as shown in FIG. 8B, the element at a position approximately 0.35 mm away from the outer peripheral surface 15a of the filter 15 radially inward. The joint strength at the contact portion S between the wires 16 is approximately 8 N / wind. The bonding strength gradually increases as the distance further inward in the radial direction, and reaches the strongest value (approximately 16 N / turn) at a position approximately 0.7 mm away from the outer peripheral surface 15a. Further, the bonding strength gradually decreases with increasing distance to the inner side in the radial direction, and becomes 0 (zero) N / winding when the distance from the outer peripheral surface 15a by 2 mm or more to the inner side in the radial direction. Even in this case, the bonding strength between the strands 16 in the specific layer of the filter 15 is sufficiently higher than that in the comparative example (see FIG. 7B). In addition, the target induction heating temperature T in Fig.8 (a) is set to 1200 degreeC.

  In the above embodiment, the case main body 19 is mixed with nitrogen atmosphere gas which is inert gas, but other inert gas (for example, argon gas) may be mixed.

-In the said embodiment, although the strand 16 is an iron wire, arbitrary wires (for example, stainless steel wire) may be sufficient.
-In the said embodiment, when the filter 15 was arrange | positioned in the position used as the inner side of the induction heating coil 22, the induction heating coil was arrange | positioned also in the position used as the inner side of the said filter 15 It may be a configuration. When configured in this way, the filter 15 is also induction-heated from the induction heating coil arranged inside thereof, so that the contact portion S between the strands 16 is joined also inside the filter 15. Become.

Sectional drawing of an inflator. The perspective view of a filter, and its partially enlarged view. The schematic sectional drawing of a high frequency induction heating apparatus. The perspective view of an induction heating coil. The block diagram which shows the control structure of a high frequency induction heating apparatus. (A) is a graph which shows the induction heating pattern of this embodiment, (b) is a graph which shows the relationship between the distance from the outer peripheral surface of a filter, and the joint strength of the contact part in strands. (A) is a graph which shows the induction heating pattern of a comparative example, (b) is a graph which shows the relationship between the distance from the outer peripheral surface of a filter, and the joint strength of the contact part in strands. (A) is a graph which shows the induction heating pattern of another example, (b) is a graph which shows the relationship between the distance from the outer peripheral surface of a filter, and the joint strength of the contact part in strands.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 15 ... Filter (Air bag inflator filter, cylindrical body, filtration member), 15a ... Outer peripheral surface, 16 ... Elementary wire, 18 ... High frequency induction heating apparatus, 22 ... Induction heating coil (induction heating means), 24 ... Outermost layer 25 ... Pressing machine (deformation restricting means), 26a ... CPU (control means), A1 ... first temperature raising period, A2 ... second temperature raising period, B ... soaking period, K ... heating period, M ... filtering member Manufacturing apparatus, T ... target induction heating temperature, t ... elapsed time.

Claims (9)

In the manufacturing method of the filtration member formed in the cylindrical body having the stitches overlapping the strands forming a plurality of layers in the radial direction,
A heating period spent for induction heating when the strands of a specific layer including at least the outermost layer and a layer adjacent to the outermost layer on the radially inner side among the plurality of layers are joined by high-frequency induction heating. It has a soaking period in which the temperature of the strand in the specific layer is lower than the melting point of the strand and is maintained at a temperature equal to or higher than a predetermined target induction heating temperature .
Within the heating period, a first temperature raising period in which the temperature of the strand in the specific layer is raised to the Curie temperature of the strand, and a temperature rise rate faster than the temperature raising rate of the strand in the first temperature raising period. The manufacturing method of the filtration member further provided with the 2nd temperature rising period which heats up the temperature of the strand in the said specific layer from the Curie temperature of the said strand to the said target induction heating temperature with a temperature rate . The said target induction heating temperature is a manufacturing method of the filtration member of Claim 1 set to the temperature of 80% or more of the absolute temperature in melting | fusing point of the said strand. 3. The filtration according to claim 1 , wherein, in the soaking period, an elapsed time after the wire temperature in the specific layer is set to the target induction heating temperature satisfies the following expression. Manufacturing method of member.
t ≧ (4 / (C1 × P × b ² × n)) ^2.5 × T × exp (2.5 × C2 / T)
Where T: target induction heating temperature, t: elapsed time, P: contact surface pressure, b: contact width between strands, n: number of joints between strands, C1, C2 are coefficients When joining the strands in the specific layer by high-frequency induction heating, a predetermined threshold time from the start of the heating period that the cylindrical body is deformed in a direction along the axial direction of the cylindrical body. The manufacturing method of the filtration member as described in any one of Claims 1-3 which regulates until it passes. The filtration member manufactured with the manufacturing method of the filtration member as described in any one of Claims 1-4 . In the manufacturing apparatus of the filtration member formed in the cylindrical body having the stitches by overlapping the strands forming a plurality of layers in the radial direction,
A high-frequency induction heating apparatus that joins the strands of a specific layer including at least the outermost layer of the plurality of layers and a layer adjacent to the outermost layer radially inward by high-frequency induction heating; The heating device includes induction heating means disposed so as to surround an outer peripheral surface of the cylindrical body that is an induction heating object, and control means that controls electric power supplied to the induction heating means. Is a soaking period in which the temperature of the wire in the specific layer is lower than the melting point of the wire and is equal to or higher than a predetermined target induction heating temperature within the heating period spent for the induction heating. Controlling the power output to the induction heating means to be formed ,
The control means includes a first temperature raising period for raising the temperature of the strand in the specific layer to the Curie temperature of the strand during the heating period, and a temperature rise of the strand in the first temperature raising period. The induction heating means so as to form a second temperature raising period in which the temperature of the wire in the specific layer is raised from the Curie temperature of the wire to the target induction heating temperature at a temperature raising rate faster than a speed. The manufacturing apparatus of the filtration member which controls the electric power output to the . The said induction heating temperature is a manufacturing apparatus of the filtration member of Claim 6 set to the temperature of 80% or more of the absolute temperature in melting | fusing point of the said strand. The soaking period is elapsed time from the temperature of the wire in the specific layer is between the target induction heating temperature, filtered according to claim 6 or claim 7, characterized in that it satisfies the following equation Manufacturing equipment for members.
t ≧ (4 / (C1 × P × b ² × n)) ^2.5 × T × exp (2.5 × C2 / T) where T: target induction heating temperature, t: elapsed time, P: contact surface Pressure, b: contact width between strands, n: number of joints between strands, C1 and C2 are coefficients When joining the strands in the specific layer by high frequency induction heating, the cylindrical body is deformed in a direction along the axial direction of the cylindrical body by pressing from the direction along the axial direction of the cylindrical body. Further comprising a deformation restricting means for restricting
The control means according to claim 6 to claim to be pressed in a direction along the tubular body in the axial direction of the tubular body by the deformation restricting means to a threshold time predetermined from the start of the heating period has elapsed The manufacturing apparatus of the filtration member as described in any one of 8 .

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