JP6041745B2 - Manufacturing method and manufacturing apparatus for composite structure - Google Patents

Description

  The present invention relates to a manufacturing method and a manufacturing apparatus for a composite structure.

  Automotive exterior parts such as automobile fenders and roofs are generally formed of a metal plate such as steel. In order to improve the fuel efficiency and reduce the production cost, it is considered that the metal plate is formed thin and light.

  However, since the required rigidity may not be obtained if the metal plate is thinned, a resin-made rib material as a reinforcing member is a composite structure provided on one surface of the metal plate as a member to be reinforced. Therefore, it is conceivable to ensure rigidity.

  As a manufacturing method of the composite structure, conventionally, a metal plate heated by a heating device is transported to a rib forming pressing device by a transport robot, and in the rib forming pressing device, molten resin is discharged to form a rib material, A method of forming the composite structure by pressing the rib material against the surface of the metal plate with a pressing roller is known (for example, see Patent Document 1).

JP 2011-16275 A

  However, in the conventional manufacturing method, the rib material formed from a molten resin is pressed against the metal plate by the pressing roller to form the composite structure. Depending on the shape of the rib material, the rib material is molded. As the mechanism becomes complicated, the rib material needs to be cooled and solidified, resulting in a disadvantage that the formation speed of the composite is lowered. Further, the conventional manufacturing method has a problem that the temperature of the heated metal plate is lowered during the transfer by the transfer robot, and the welding failure of the rib material may occur.

  Therefore, it is conceivable to heat a reinforcing member made of a preformed thermoplastic resin molded body to a temperature equal to or higher than the softening temperature of the thermoplastic resin and weld it to the metal plate. Then, as a method of heating the reinforcing member to a temperature equal to or higher than the softening temperature, a magnetic material is contained in the thermoplastic resin of the reinforcing member, and the magnetic material is induction heated by an induction heating coil. It is conceivable that the temperature of the reinforcing member is increased by conducting heat to the thermoplastic resin.

  However, if the reinforcing member is heated to a temperature equal to or higher than the softening temperature of the thermoplastic resin by the induction heating, the induction heating coil may be lengthened and a high voltage is required.

  Then, an object of this invention is to provide the manufacturing method and manufacturing apparatus of a composite structure which can heat a reinforcement member so that welding is possible, without using a high voltage.

To achieve the above object, the present invention, the reinforcing member to a method of manufacturing a composite structure comprising on one side of the reinforcing member, Ri Do a thermoplastic resin containing a magnetic material, a long body reinforcement Heating the reinforcing member to a temperature range higher than the softening temperature of the thermoplastic resin and lower than the deterioration temperature by inductively heating the magnetic body with a plurality of induction heating means connected in parallel with each other. And a step of welding the reinforcing member heated to the temperature range to one surface of the member to be reinforced.

In the production method of the present invention, first, made of a thermoplastic resin containing a magnetic material elements, after supplying the reinforcing member is a long body, by induction heating of the magnetic body with a plurality of induction heating means, the The magnetic material is thermally conducted to the thermoplastic resin, and the reinforcing member is heated to a temperature range not lower than the softening temperature and lower than the deterioration temperature of the thermoplastic resin. Next, a composite structure can be obtained by welding the reinforcing member heated to the temperature range to one surface of the member to be reinforced.

  According to the manufacturing method of the present invention, since the plurality of induction heating means are connected in parallel to each other, it is possible to prevent the total value of the inductances of the plurality of induction heating means from increasing. Accordingly, since the voltage applied to the plurality of induction heating means can be reduced, the reinforcing member is heated to a temperature range higher than the softening temperature of the thermoplastic resin and lower than the deterioration temperature without using a high voltage. Can be welded.

  In the production method of the present invention, it is preferable that the plurality of induction heating means have different heating rates. By combining a plurality of induction heating means having different heating rates, the heating rate in each of the low temperature region and the high temperature region can be controlled when the reinforcing member is heated.

  Further, in the manufacturing method of the present invention, the plurality of induction heating means can be configured such that the temperature rising rate is smaller on the supply side of the reinforcing member and the temperature raising rate is higher on the discharge side. In this case, first, the reinforcing member is heated to a temperature region below the softening temperature of the thermoplastic resin at a low temperature increase rate on the supply side and close to the softening temperature, and then the reinforcing member is discharged from the supply side to the discharge side. Next, on the discharge side, the reinforcing member is heated to a temperature range higher than the softening temperature of the thermoplastic resin and lower than the deterioration temperature at a high temperature rising rate. Since the reinforcing member can be preheated to a temperature range close to the softening temperature on the supply side at a small temperature increase rate and then heated to the temperature range on the discharge side at a large temperature increase rate, the heating time in the high temperature range Can be shortened. Moreover, since a large amount of reinforcing members can be heated together on the discharge side, it is suitable for batch processing of reinforcing members having a predetermined length.

  By the way, in the manufacturing method of the present invention, since the reinforcing member is heated by conducting heat from the magnetic body to the thermoplastic resin, if the heating rate of the discharge-side induction heating means is too high, Even after the reinforcing member is discharged from the induction heating means on the discharge side, the thermoplastic resin may be heated to reach a deterioration temperature, and the reinforcing member may be deteriorated.

  Therefore, in the manufacturing method of the present invention, the plurality of induction heating means can be configured such that the temperature rise rate is larger on the supply side of the reinforcing member and the temperature rise rate is lower on the discharge side. In this case, first, the reinforcing member is heated to a temperature range below the softening temperature of the thermoplastic resin at a high temperature rising rate and close to the softening temperature, and then the reinforcing member is moved from the supply side to the discharge side. Next, the reinforcing member is heated to a temperature range not lower than the softening temperature and lower than the deterioration temperature of the thermoplastic resin at a low temperature rising rate. Since heating is performed at a small temperature increase rate on the discharge side of the reinforcing member, the heating can be reliably controlled by the temperature range.

In order to achieve the above object, the present invention is Ri Do a thermoplastic resin containing a magnetic material, an apparatus for producing a composite structure comprising a reinforcing member which is elongate body on one side of the reinforcement member A supply means for supplying the reinforcing member; a plurality of induction heating means connected in parallel to each other for induction heating the reinforcing member to a temperature range not lower than the softening temperature of the thermoplastic resin and lower than the deterioration temperature; and the temperature range. And welding means for welding the reinforcing member heated to one surface of the member to be reinforced.

In the manufacturing apparatus of the present invention, first, made of a thermoplastic resin containing a Ri磁 material elements by the feed means, after supplying the reinforcing member is a long body, induction heating magnetic body by a plurality of induction heating means To do. Thereby, heat conduction is performed from the magnetic body to the thermoplastic resin, and the reinforcing member is heated to a temperature range higher than the softening temperature of the thermoplastic resin and lower than the deterioration temperature. Next, a composite structure can be obtained by welding the reinforcing member heated to the temperature range by the welding means to one surface of the member to be reinforced.

  According to the manufacturing apparatus of the present invention, since the plurality of induction heating means are connected in parallel to each other, it is possible to prevent the total value of the inductances of the plurality of induction heating means from increasing. Accordingly, since the voltage applied to the plurality of induction heating means can be reduced, the reinforcing member is heated to a temperature range higher than the softening temperature of the thermoplastic resin and lower than the deterioration temperature without using a high voltage. Can be welded.

  In the manufacturing apparatus of the present invention, it is preferable that the plurality of induction heating means have different magnetic flux densities. By combining a plurality of induction heating means having different heating rates with different magnetic flux densities, the heating rate in each of the low temperature region and the high temperature region can be controlled when the reinforcing member is heated.

  In the manufacturing apparatus of the present invention, the plurality of induction heating means may be provided so that the magnetic flux density is smaller on the supply side of the reinforcing member and the magnetic flux density is larger on the discharge side. In this case, first, the reinforcing member was heated to a temperature range close to the softening temperature below the softening temperature of the thermoplastic resin at a low heating rate by induction heating means having a small magnetic flux density provided on the supply side. Later, the reinforcing member is moved from the supply side to the discharge side. Next, the reinforcing member heated by the supply-side induction heating means is heated at a high temperature increase rate by the induction heating means provided on the discharge side and having a magnetic flux density larger than that of the supply-side induction heating means. To a temperature range above the softening temperature and below the degradation temperature. Since the reinforcing member can be preheated to a temperature range close to the softening temperature on the supply side at a small temperature increase rate and then heated to the temperature range on the discharge side at a large temperature increase rate, the heating time in the high temperature range Can be shortened. Moreover, since a large amount of reinforcing members can be heated together on the discharge side, it is suitable for batch processing of reinforcing members having a predetermined length.

  In the manufacturing apparatus of the present invention, the plurality of induction heating means may be provided such that the magnetic flux density is larger on the supply side of the reinforcing member and the magnetic flux density is smaller on the discharge side. In this case, first, after the reinforcing member is heated to a temperature range close to the softening temperature below the softening temperature of the thermoplastic resin at a large heating rate by the induction heating means having a large magnetic flux density provided on the supply side. The reinforcing member is moved from the supply side to the discharge side. Next, the reinforcing member heated by the induction heating means on the supply side is provided at the discharge side with a magnetic flux density smaller than that of the supply side, and the softening temperature of the thermoplastic resin is equal to or higher than the softening temperature of the thermoplastic resin. And it heats to the temperature range below the deterioration temperature. On the discharge side, the reinforcing member is heated to the induction heating means having a low magnetic flux density at a lower temperature increase rate, so that the reinforcing member can be reliably controlled and heated by the temperature range.

The side view which shows the structure of the composite structure manufacturing apparatus of embodiment of this invention. The schematic diagram which shows the 1st example of arrangement | positioning of the induction heating coil in the composite structure manufacturing apparatus of embodiment of this invention. The schematic diagram which shows the 2nd example of arrangement | positioning of the induction heating coil in the composite structure manufacturing apparatus of embodiment of this invention.

  Next, embodiments of the present invention will be described in more detail with reference to the accompanying drawings.

  The composite structure manufacturing apparatus 1 of the present embodiment shown in FIG. 1 welds a reinforcing member P made of a thermoplastic resin to one surface of a metal plate M made of steel having a thickness of 0.7 mm, for example, used for an automobile exterior part. It is an apparatus for manufacturing the composite structure reinforced by this. The metal plate M corresponds to a member to be reinforced in the present invention. It is also possible to use a resin plate instead of the metal plate M as the member to be reinforced.

  The reinforcing member P is formed of a long molded body made of a thermoplastic resin containing a magnetic body. As the magnetic body, for example, a fibrous body made of ferrite SUS, steel, soft iron, steel, nickel, etc., having a diameter of 80 to 150 μm and a length of 1 to 3 mm can be used. As the thermoplastic resin, for example, a styrene elastomer can be used. The reinforcing member P contains the magnetic body in a range of 30 to 60% by mass with respect to the thermoplastic resin, and the magnetic body is dispersed in the thermoplastic resin.

  The composite structure manufacturing apparatus 1 draws out the reinforcing member P of the elongated molded body wound around the bobbin B through the relay roller R, and pulls out the reinforcing member P in order from the start end side toward the end side. The metal plate M is reinforced by welding to one surface of the metal plate M placed on J. The composite structure manufacturing apparatus 1 is accommodated in the housing 2 and can be moved to an arbitrary position above the metal plate M by a robot (not shown). The housing 2 is provided with a supply port 2a for supplying the reinforcing member P to the inside and a discharge port 2b for discharging the reinforcing member P.

  The composite structure manufacturing apparatus 1 includes a pair of feed rollers 3 that sequentially pull out the reinforcing member P wound around the bobbin B and continuously supply it into the housing 2 from the side closer to the supply port 2a to the side farther from the supply port 2a. An induction heater 4 that heats the member P so as to be welded by induction heating, a cutter 5 that cuts the reinforcing member P at a predetermined position, and a reinforcing member P that is provided at the bottom of the housing 2 and is discharged from the outlet 2b. And a pressure roller 6 that is welded by pressing the metal plate M against the metal plate M. Moreover, the composite structure manufacturing apparatus 1 includes an atmospheric plasma cleaner 7 that is provided at the bottom of the casing 2 below the induction heater 4 and degreases and cleans the surface of the metal plate M.

  The induction heater 4 can heat the reinforcing member P so that it can be welded by inductively heating the magnetic body contained in the reinforcing member P to cause heat conduction from the magnetic body to the thermoplastic resin. The induction heater 4 includes a plurality of induction heating coils connected in parallel to a power source (not shown). In the present embodiment, the first induction heating coil 4a provided on the supply side of the reinforcing member P, and the reinforcing member And a second induction heating coil 4b provided on the P discharge side. The first induction heating coil 4a can heat the reinforcing member P at a higher temperature increase rate than the second induction heating coil by providing a magnetic flux density larger than that of the second induction heating coil 4b. The first induction heating coil 4a can be set to a magnetic flux density larger than that of the second coil 4b, for example, by increasing the number of turns in the coil unit length or shortening the coil length. In addition, although this embodiment demonstrates the case where two induction heating coils 4a and 4b are used, the number will not be limited if it is plurality.

  Next, the manufacturing method of the composite structure by the composite structure manufacturing apparatus 1 is demonstrated. First, the reinforcing member P of the long molded body wound around the bobbin B is pulled out by the feed roller 3 through the relay roller R, and the first induction heating coil 4a and the second induction heating coil of the induction heater 4 are extracted. Continuous supply to the inside of 4b.

  Next, the reinforcing member P is heated by the induction heater 4 so as to be welded. First, by inductively heating the magnetic body with the first induction heating coil 4a, the reinforcing member P is brought to the softening temperature below the softening temperature of the thermoplastic resin at a first heating rate of 350 ° C./second, for example. Heat to a near temperature range.

  Next, after the reinforcing member P moves from the supply side to the discharge side, the magnetic body is induction-heated by the second induction heating coil 4b, whereby the reinforcing member P is heated at a second temperature of, for example, 200 ° C./second. The thermoplastic resin is heated at a speed to a temperature range not lower than the softening temperature of the thermoplastic resin and lower than the deterioration temperature, thereby enabling welding. Here, the second temperature increase rate is set to be smaller than the first temperature increase rate.

  Next, after discharging the reinforcing member P heated so as to be welded by the induction heater 4 from the second induction heating coil 4a, the metal plate M depressurized and cleaned by the atmospheric plasma cleaner 7 and the pressing rollers 6, 6 Supply during. At this time, by reducing the angle sent between the metal plate M and the pressing roller 6, the stress generated by the bending of the angle in the reinforcing member P can be reduced.

  Next, the reinforcing member P heated so as to be welded is pressed against the surface of the metal plate M by the pressing roller 6. At this time, since the reinforcing member P is in a weldable state, the reinforcing member P can be welded to the metal plate M without heating the metal plate M.

  Then, when the length of the reinforcing member P welded to the metal plate M approaches a predetermined length to be reinforced of the metal plate M, the supply of the reinforcing member P is stopped by cutting the reinforcing member P with the cutter 5. To do. Further, the cut reinforcing member P is pressed by the pressing rollers 6 and 6 and welded to the metal plate M up to the end of the reinforcing member P, whereby the metal plate M is reinforced by the reinforcing member P having a predetermined length. A structure can be obtained.

  The composite structure manufacturing apparatus 1 performs the above operation while moving in the width direction of the metal plate M while moving from the start end side to the end side of the reinforcing member P of the elongated shaped body via a robot (not shown). Repeat.

  According to the composite structure manufacturing apparatus 1 of the present embodiment, since the two induction heating coils 4a and 4b are connected to the power supply in parallel with each other, the two induction heating coils 4a and 4b are connected in series with each other. Compared with the case where it is, the total value of an inductance can be made small. Thereby, since the voltage applied to the two induction heating coils 4a and 4b can be reduced, the reinforcing member P is made to be not less than the softening temperature of the thermoplastic resin and less than the deterioration temperature without using a high voltage as the power source. Heating to a temperature range enables welding.

  In the composite structure manufacturing apparatus 1 of the present embodiment, the reinforcing member P made of a long shaped body is heated so as to be welded, and then the reinforcing member P is made to have a predetermined length in the step of welding to the metal plate M. Although it cut | disconnects, you may make it weld to the metal plate M by heating so that the reinforcement member P which consists of a molded object previously cut | disconnected by predetermined length so that welding is possible.

  Moreover, in the composite structure manufacturing apparatus 1 of this embodiment, when the reinforcement member P is heated by combining a plurality of induction heating coils 4a and 4b having different magnetic flux densities and different heating rates, the low temperature region and the high temperature are increased. The temperature increase rate in each region can be controlled. The specific method will be described below.

  First, the case where the three induction heating coils 8a, 8b, and 8c are provided so that the magnetic flux density is larger on the supply side of the reinforcing member P and the magnetic flux density is smaller on the discharge side will be described with reference to FIG. .

  As shown in FIG. 2 (a), in the composite structure manufacturing apparatus 1 of the present embodiment, the first induction heating coil 8a, the second induction heating coil 8b, and the reinforcement member P are sequentially supplied from the supply side to the discharge side. A third induction heating coil 8c is provided, and each induction heating coil 8a, 8b, 8c is connected to the power source 9 in parallel with each other. Each induction heating coil 8a, 8b, 8c has the same wire diameter, coil radius, and number of turns in the coil unit length, and only the coil length is different. Each induction heating coil 8a, 8b, 8c has a magnetic flux density that is larger on the supply side of the reinforcing member P and smaller on the discharge side because the coil lengths Aa, Ab, Ac are Aa <Ab <Ac. .

  The reinforcing member P is sequentially heated by the induction heating coils 8a, 8b, and 8c while moving from the supply side to the discharge side. FIG. 2B shows the temperatures of the thermoplastic resin and the magnetic body constituting the reinforcing member P at this time. The temperature of the thermoplastic resin can be regarded as the temperature of the reinforcing member P.

  Immediately before supplying the reinforcing member P to the first induction heating coil 8a, the temperature of the thermoplastic resin and the temperature of the magnetic body are both the temperature To.

  Next, the reinforcing member P is supplied to the first induction heating coil 8a and discharged. As a result, the magnetic body is induction-heated by the first induction heating coil 8a and the temperature is raised to the temperature Tma. Heat is conducted from the magnetic body to the thermoplastic resin, and the thermoplastic resin is raised to the temperature Tra. To do.

  Next, the reinforcing member P is supplied to the second induction heating coil 8b and discharged. As a result, the magnetic body is induction-heated by the second induction heating coil 8b and the temperature is raised to the temperature Tmb. Heat is conducted from the magnetic body to the thermoplastic resin, and the thermoplastic resin is heated to the temperature Trb. To do. At this time, the second induction heating coil 8b is provided with a magnetic flux density smaller than that of the first induction heating coil 8a, and thus has a heating rate lower than that of the first induction heating coil 8a. The temperature Trb can be controlled to a temperature range lower than the softening temperature Ts and close to the softening temperature Ts.

  Next, the reinforcing member P is supplied to the third induction heating coil 8c and discharged. As a result, the magnetic body is inductively heated by the third induction heating coil 8c and the temperature is raised to the temperature Tmc. Heat is conducted from the magnetic body to the thermoplastic resin, and the thermoplastic resin is heated to the temperature Trc. To do. At this time, the third induction heating coil 8c is provided with a magnetic flux density smaller than that of the second induction heating coil 8b, and thus has a temperature increase rate smaller than that of the second induction heating coil 8b. The temperature Trc of the plastic resin can be reliably controlled to be within the temperature range of the softening temperature Ts of the thermoplastic resin and the deterioration temperature Td.

  Next, the case where the three induction heating coils 8a, 8b, and 8c are provided so that the magnetic flux density is smaller on the supply side of the reinforcing member P and the magnetic flux density is larger on the discharge side will be described with reference to FIG. To do.

  As shown in FIG. 3A, in the composite structure manufacturing apparatus 1 of the present embodiment, the first induction heating coil 8a, the second induction heating coil 8b, and the third induction heating coil 8c have a diameter of a conducting wire. The number of turns in the coil radius and the coil unit length is the same, and only the coil length is different. Each induction heating coil 8a, 8b, 8c has a magnetic flux density that is smaller on the supply side of the reinforcing member P and larger on the discharge side because the coil lengths Aa, Ab, Ac are Aa> Ab> Ac. .

  The reinforcing member P is sequentially heated by the induction heating coils 8a, 8b, and 8c while moving from the supply side to the discharge side. FIG. 3B shows the temperatures of the thermoplastic resin and the magnetic body constituting the reinforcing member P at this time.

  Immediately before supplying the reinforcing member P to the first induction heating coil 8a, the temperature of the thermoplastic resin and the temperature of the magnetic body are both the temperature To.

  Next, the reinforcing member P is supplied to the first induction heating coil 8a and discharged. As a result, the magnetic body is induction-heated by the first induction heating coil 8a and the temperature is raised to the temperature Tma. Heat is conducted from the magnetic body to the thermoplastic resin, and the thermoplastic resin is raised to the temperature Tra. To do.

  Next, the reinforcing member P is supplied to the second induction heating coil 8b and discharged. As a result, the magnetic body is induction-heated by the second induction heating coil 8b and the temperature is raised to the temperature Tmb. Heat is conducted from the magnetic body to the thermoplastic resin, and the thermoplastic resin is heated to the temperature Trb. To do. At this time, the second induction heating coil 8b is provided with a magnetic flux density larger than that of the first induction heating coil 8a, so that the second induction heating coil 8b has a higher heating rate than the first induction heating coil 8a. The temperature Trb can be rapidly raised to a temperature range close to the softening temperature Ts below the softening temperature Ts.

  Next, the reinforcing member P is supplied to the third induction heating coil 8c and discharged. As a result, the magnetic body is inductively heated by the third induction heating coil 8c and the temperature is raised to the temperature Tmc. Heat is conducted from the magnetic body to the thermoplastic resin, and the thermoplastic resin is heated to the temperature Trc. To do. At this time, the third induction heating coil 8c is provided with a higher magnetic flux density than the second induction heating coil 8b, and thus has a higher heating rate than the second induction heating coil 8b. The temperature Trc of the plastic resin can be further rapidly increased to a temperature range of the softening temperature Ts of the thermoplastic resin and the deterioration temperature Td. Thereby, the heating time of the reinforcing member P by the third induction heating coil 8c can be shortened in a high temperature region near the softening temperature Ts of the thermoplastic resin.

DESCRIPTION OF SYMBOLS 1 ... Composite structure manufacturing apparatus, 3 ... Supply means (feed roller), 4a, 4b, 8a, 8b, 8c ... Induction heating means (induction heating coil), 6 ... Welding means (pressing roller), M ... Metal plate (Reinforced member), P: Reinforcing member, Td: Deterioration temperature of thermoplastic resin, Ts: Softening temperature of thermoplastic resin.

Claims (8)

A method of manufacturing a composite structure including a reinforcing member on one side of a member to be reinforced,
Ri Do a thermoplastic resin containing a magnetic material, and supplying a reinforcing member is a long body,
Heating the reinforcing member to a temperature range higher than the softening temperature of the thermoplastic resin and lower than the deterioration temperature by induction heating the magnetic body with a plurality of induction heating means connected in parallel to each other;
And a step of welding the reinforcing member heated to the temperature range to one surface of the member to be reinforced. In the manufacturing method of the composite structure of Claim 1 ,
The method for manufacturing a composite structure, wherein the plurality of induction heating means have different heating rates. In the manufacturing method of the composite structure of Claim 2 ,
The method of manufacturing a composite structure, wherein the plurality of induction heating means has a temperature rising rate that is smaller on a supply side of the reinforcing member and a temperature rising rate is higher on a discharge side. In the manufacturing method of the composite structure of Claim 2 ,
The method of manufacturing a composite structure, wherein the plurality of induction heating means has a temperature rising rate larger toward a supply side of the reinforcing member and a temperature rising rate lower toward a discharge side. An apparatus for manufacturing a composite structure including a reinforcing member on one surface of a member to be reinforced,
Ri Do a thermoplastic resin containing a magnetic material, a supply means for supplying a reinforcing member is a long body,
A plurality of induction heating means connected in parallel to each other and inductively heating the magnetic body to heat the reinforcing member to a temperature range not lower than the softening temperature of the thermoplastic resin and lower than the deterioration temperature;
An apparatus for manufacturing a composite structure, comprising: welding means for welding the reinforcing member heated to the temperature range to one surface of the member to be reinforced. In the manufacturing apparatus of the composite structure according to claim 5 ,
The apparatus for manufacturing a composite structure, wherein the plurality of induction heating means have different magnetic flux densities. In the composite structure manufacturing apparatus according to claim 6 ,
The apparatus for manufacturing a composite structure, wherein the plurality of induction heating means are provided such that a magnetic flux density is smaller on a supply side of the reinforcing member and a magnetic flux density is larger on a discharge side. In the composite structure manufacturing apparatus according to claim 6 ,
The apparatus for manufacturing a composite structure, wherein the plurality of induction heating means are provided such that a magnetic flux density is larger on a supply side of the reinforcing member and a magnetic flux density is smaller on a discharge side.

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