JP6283768B2 - Glow plug - Google Patents

Description

  The present invention is a glow plug provided with a heater pin, wherein the heater pin is formed of a metal cover that accommodates a heater cartridge made of ceramic, and is welded to a front region of the tubular main body. The region has a connector for power supply, in which case the electrical connection to earth is made via a metal cover and a tubular body, and the power supply starts from the connector and connects the center electrode And the center electrode is insulated and accommodated in the tubular body.

  Many examples of such glow plugs are already known, and in particular, the connection between the power supply of the ceramic heater cartridge and the center electrode is threaded in a metal spring formed by a connection line extending from the heater ceramic. Glow plugs obtained by screwing a rod with attachment are known. Such an arrangement is held in position via insulating powder contained in a metal cover that is pushed into the tubular body of the plug. Electrical contact and position retention is obtained by compressing the insulating powder around the threaded part.

  The object of the present invention is to reduce the manufacturing costs and material costs for glow plugs by reducing the number of parts involved in the design of the glow plug and the manufacturing stage, so that the compressed insulating powder inside the glow plug Is to simplify the manufacture and structure of the glow plug.

  For the sake of brevity, the orientation concept “front” / “back” is typically used in various drawings, where the front or left side of the drawing is on the heater cartridge side of the glow plug. The rear side or the right side corresponds to the connecting pipe side of the glow plug.

For this reason, an object of the present invention is to provide an electrical connection between a rear bottom wall of a heater cartridge having an input contact and a front end of a center electrode in a glow plug of the type defined as described above. ,
A conductive connecting member;
A conductive cylindrical head fixed to the front side of the center electrode and provided with a support collar for supporting on the back side;
An electrically insulating sleeve surrounding the front section of the head across the collar and partially surrounding the connecting member;
In this case, the tubular main body has a recess at its front end, the recess forms a support shoulder, and the support shoulder houses a centering and insulating disk for insulation, in this case The brim has a smaller cross-section than the recess to abut the shoulder;
The lower unit composed of the connecting member and the head is compressed in the axial direction between the power supply contact on the bottom wall of the heater cartridge and the support shoulder of the tubular body. At this time, the connecting member is Thus, it is in close contact with the input contact, and is in close contact with the front end portion of the head on the back side, and the collar of the head is in close contact with the support portion via an insulating disk.
It is characterized by that.

  The glow plug according to the invention has a particularly simple structure that avoids the use of insulating powder surrounding the connecting member between the heater cartridge and the center electrode, thereby simplifying and ensuring the manufacture. An effective and economical glow plug is obtained.

  According to a preferred feature, the connecting member is made of graphite.

  The connecting member made of graphite guarantees perfect electrical properties between the center electrode or the front end of the center electrode and the rear side of the heater cartridge in the area of the power supply contact or input contact of the heating resistor electrical circuit. obtain.

  According to another preferred feature, the head is a conductive cylinder made of metal, which cylinder is divided into a front section and a rear section by a collar.

  According to another preferred feature, the cross section of the collar is frustoconical. With such a frustoconical cross section of the collar, it is possible to distribute the force well on the large support surface consisting of the support shoulder of the recess formed in the cylindrical body, so that the heater cartridge and the center electrode can be distributed. The total compressive force that guarantees electrical wiring between them is limited to the area located between the rear side of the heater cartridge and the head, and this force acts on the center electrode to deform the center electrode within the tubular body. It does not cause a short circuit with the earth to which the tubular body is connected.

  According to another preferred feature, the heater cartridge is configured to be retracted relative to the base of the cover of the heater pins to form a chamber that at least partly houses the connection member and partly the head. In this case, these two components are surrounded by an insulating sleeve.

  Such a chamber composed of a thick part consisting of the base part in the metal cover can form a hollow chamber or at least a main part of the chamber, and a heater in the hollow chamber or the main part of the chamber. A connecting member compressed between the rear side of the cartridge and the central electrode, ie an extension of the central electrode consisting of a head which is itself supported by a supporting shoulder in the recess, is accommodated. As a result, the depth of the concave portion can be reduced. In this case, the mechanical strength of the tubular main body does not decrease, and the thickness of the material of the tubular main body does not need to be increased.

  According to another preferred feature, the insulating disk has a through hole, which is clearly smaller than the rear section of the head or the cross section of the center electrode.

  The size of the through hole of the insulating disk is based on the elastic deformation of the rear section of the head located behind the collar, and based on the slight stress absorbed by the insulating disk under normal conditions, the center electrode or its Accurate centering of the extension can be ensured.

  According to another preferred feature, the insulating sleeve engages at least partly in the chamber of the metal cover, so that between the rear side of the heater cartridge and the front end comprising the head with the central electrode attached. A perfect centering of the electrical connection members is guaranteed.

The subject of the present invention is also a method for producing the glow plug as defined above. This manufacturing method is
A tubular body having a recess is manufactured, and the recess forms a support shoulder at the front end of the tubular body.
Apply the insulating disk to the support shoulder in the recess,
The head is fixed in advance to the center electrode, the center electrode is attached by pushing the head into the insulating disk and centering the center electrode in the tubular body to apply the collar of the head to the disk,
Apply the insulating sleeve to the front section of the head,
The connecting member is inserted into the insulating sleeve by causing the front side of the connecting member to protrude in a natural manner and bringing the rear side of the connecting member into contact with the front section of the head
A heater pin pre-assembled to the insulating sleeve is mounted so that the front side of the intermediate member is at least generally in contact with the rear side of the heater cartridge in the heater cartridge chamber, in which case the geometric parameters of the various components are A free space remains between the back side of the base part and the front side of the tubular body,
Compressing the heater pin and the tubular body in an axial direction in order to bring the metal cover of the heater cartridge and the opposite sides of the tubular body close to each other and at least substantially in contact with each other to join by welding;
Complete the assembly by attaching an insulating bushing seal and finally a connector to the rear end of the center electrode, during which a sealing and electrical insulation between the connector and the tubular body is established;
It is characterized by that.

  According to another preferred feature, the welding of the base part and the tubular body is carried out by means of a laser, in particular by a rotational movement about the axis of the plug. The laser welding process enables particularly effective, close and rapid welding.

  According to another preferred feature, the assembly of the front side of the glow plug takes place in a vertically oriented tubular body, in which case the front end of the tubular body is directed upwards and thus assembled. The lower unit is used to assemble the seal, insulating sleeve and connector to the rear end of the center electrode, in particular by edge bending, but the axis extends vertically but the rear end of the tubular body and the rear end of the center electrode. It is rotated around so that the part faces upward.

  When assembling the front section of the glow plug in the vertical direction, especially when assembling the rear section of the glow plug, the assembled lower unit corresponding to the front section of the glow plug is rotated and then the rear section of the glow plug. In particular, it is important to assemble these connectors together to assemble the connector, that is, apply a predetermined compressive force to the connector toward the tubular body and assemble to the rear end by edge bending. It is. The rear end of this center electrode is knurled or roughened or provided with a thread in a suitable manner, so that this rear end absorbs forces.

  The glow plug according to the invention is therefore particularly simple, effective and economical as a whole on the basis of its structure and also on its manufacturing method.

1 is an overall view of a glow plug according to the present invention. A special structure of the front and rear ends of the glow plug is shown. It is sectional drawing which decomposed | disassembled partially of the front-end part of the glow plug cut along the axis line xx. It is sectional drawing and the partial exploded view of the rear-end part of the glow plug cut along the axis line xx. It is an axial sectional view of the front end portion of the glow plug shown in FIG. 2A. It is an axial sectional view of the front end portion of the glow plug in a state where it is joined without pressure before welding. It is a figure which shows the various steps of joining of the glow plug shown in FIG. It is a figure which shows the various steps of joining of the glow plug shown in FIG.

  The present invention will now be described in detail with reference to an embodiment of the glow plug shown in the accompanying drawings.

  The glow plug which is the object of the present invention shown in FIG. 1 is composed of a tube-shaped main body 1, which has a heater pin 2 on the front AV and a rear end portion 110 (AR). The connector 3 is supported, whereby the glow plug can be connected to a special connection member (not shown) of each automobile manufacturer.

  The heater pin 2 is connected to the ground via an electrical connection with the metal cover 21. In this case, the tubular main body 1 itself is in contact with the ground of the on-vehicle power supply network of the vehicle. Supply is performed via a connector 3, and this connector 3 is connected to an in-vehicle power supply network via a control device (not shown), and this control device is connected via a center electrode 7 penetrating the main body 1. The power supply to the heater pin 2 is controlled.

  The detailed structure of the glow plug according to the present invention will be described with reference to the detailed drawings shown in FIGS. 2A, 2B and 3, and the assembly method will be described with reference to FIG. 4 and its partial views 4A and 4B.

  2A and 3, the front side of the glow plug is composed of a heater pin 2, and the heater pin 2 is assembled to the tubular main body 1 along the axis xx of the glow plug.

  The heater pin 2 is composed of a cylindrical metal cover 21. The metal cover 21 houses a ceramic heater cartridge 22. The heater cartridge 22 has a heating resistor 231 and a ground contact on its peripheral surface. 232 and a current circuit 23 having an input contact 233 on the bottom wall 24 or on the rear side thereof. The rear side 24 of the heater cartridge 22 is configured to recede in relation to the rear end portions of the metal cover 21 and the base portion 26 by forming the chamber 25.

  The contact 232 and the metal cover 21 are connected by soldering, pushing, shrink fitting, or a combination of pushing and shrink fitting. This connection has the reference 201. This connection preferably relates to the entire outer peripheral surface of the heater cartridge 22 and the entire inner peripheral surface of the cylindrical section of the metal cover 21.

  The metal cover 21 having a cylindrical shape ends on the back side with a base portion 26 forming a conical seal portion 27, and the conical seal portion 27 is used to support the glow plug with the cylinder head of the internal combustion engine. In this case, the front end portion formed by the heater pin 2 enters the combustion chamber of the engine cylinder.

  The current circuit 23 is in contact with the metal cover 21 by grounding via the contact 232, and the input contact 233 penetrates the tubular main body 1 based on the conductive joint made of the connection member 4 and is connected to the connector 3. The connecting member 4 is partly housed in an insulating sleeve 5, which also houses a front section 61 of the head 6, which has a tubular shape. It passes through the main body 1 and is fixed to the center electrode 7.

  2A and 3, the head 6 fixed to the front end 71 of the center electrode 7 via the weld seam 202 is a cylindrical portion having a frustoconical collar 62, for example. 62 separates its front section 61 from its rear section 63, which is welded to the front side 71 of the center electrode 7 via a weld seam 202.

  The insulating sleeve 5 fixes the wiring path in the base portion 26 of the metal cover 21 and insulates this wiring path. The insulating sleeve 5 covers the front section 61 of the head 6 and accommodates a cylindrical connecting member 4, and the connecting member 4 is made of a conductive cylindrical element made of graphite. This element is in electrical contact with the rear side 24 of the heater cartridge 22.

  Since the length L of the sleeve 5 is shorter than the sum of the length 11 of the connection member 4 and the length 12 of the front section 61 of the head 6, the connection member of the joint formed by the sleeve 5 and the front end portion 61. 4 protrudes from the front region of the insulating sleeve 5 when this joint is compressed during operation and assembly of the glow plug.

  The connecting member 4 is compressed at room temperature by maintaining its front side 41 in contact with the rear side 24 and its rear side 42 in contact with the front region of the head 6, thereby allowing the engine or hot when cold. Despite the dimensional variations caused by various expansions of the cover 21, the tubular body 1 and the central electrode 7 under the influence of the temperature fluctuations of the glow plug and its surroundings in the engine, the electrical wiring is guaranteed in hot conditions. The

  The front end 101 of the tubular body 1 has a recess 102, which forms a shoulder 103 and accommodates an insulating disk 104, which insulates the center electrode 7 from conductive. In this case, the rear section 63 is centered within the insulating disk 104 and is attached to the tubular body 1. In general, it is engaged in the insulating disk 104 in order to be kept electrically insulated. The size of the opening 1041 of the insulating disk 104 is adjusted to the size of the rear section 63 of the head or the center electrode 7. That is, the opening 1041 of the insulating disk 104 is in a position where the center electrode 7 is centered directly or indirectly, i.e. at a position clearly spaced from the inner contour of the tubular body 1 to avoid any short circuit. It is slightly tightened to keep it well. By slightly tightening the rear section 63 of the head 6 with the opening 1041, combined with the crimping of the disk 104 due to the approach of the rear side of the collar 62 and the support portion 103 of the tubular body 1, It is ensured that no wear of the rear side 42 of the connecting member 4 due to the radial movement of the front end 61 of 6 occurs.

  According to FIG. 3, in the assembled state, a frustoconical collar 62 whose cross-section is significantly smaller than the recess 102 is supported on the insulating disc 104 in order to avoid any contact risk, in this case, It does not come into contact with the wall portion of the recess 102. The base portion 26 is welded to the front region 101 of the tubular main body 1 via the weld seam 203, whereby a hollow chamber having a chamber 25 and a recess 102 is formed, and in this hollow chamber, the connection member 4 and The lower unit composed of the head 6 is accommodated, and the front section 61 of this lower unit partially engages with the insulating sleeve 5 that accommodates the connecting member 4.

  The lower unit includes an insulating disk 104 in the recess 102 between the rear side 24, particularly between the power supply contact 233 of the heater ceramic 22 and the support shoulder 103, by the connecting member 4 and the front end 61 and the collar 62 of the head 6. Compressed by As a result, pressure is applied only to the head 6 to be transmitted to the support shoulder 103, whereas the central electrode 7 is not exposed to this force, but deforms and contacts the tubular body 1 There is no sex. In consideration of the high power to be transmitted, the input contact 233 of the ceramic cartridge 22 and the front end portion 61 of the head 6 have a surface treatment or a surface coating. The disposed material or materials reduce electrical resistance, increase wear resistance, and prevent any oxidation that increases power consumption.

  According to FIG. 2B, in the rear AR, the glow plug has a connector 3, which is connected to the central electrode 7 for supplying electricity to the glow plug.

  On the rear side AR, the tubular body 1 having a screw thread 105 on the outside and a tool accommodating portion 106 for screwing into the cylinder head of the internal combustion engine has a rear recess 107, An insulating bush 9 for centering and electrically insulating the rear end 72 of the center electrode 7 is accommodated with a seal 8 interposed between the electrode 7 and the inner chamber of the tubular body 1. The annular intermediate chamber is closed to ensure the sealability of the entire front section of the plug.

  The connector 3 secured to the rear end 72 of the center electrode 7 accommodates the knurled or threaded rear end 72 of the center electrode 7 and the edge bend 204 (FIG. 1). In order to ensure the assembled state, the collar 31 is provided on the outer side and the sleeve 32 is provided on the front side.

  The rear end portion 33 of the connector 3 accommodates a connection member suitable for each automobile manufacturer. In general, the connection members are different for each automobile manufacturer, but all these special connectors (not shown) can be adapted to the end 33.

  The assembly of the glow plug is performed as shown in parts 4A and 4B in FIG.

  According to an embodiment of this assembly method, for assembling and in particular fitting the components, the process preferably comprises a vertically oriented glow plug or at least a prefabricated lower unit 180 in the glow plug axis xx. Inverted (FIG. 4A, steps E1-E7), whereby the rear AR of the glow plug is directed upward for assembly (FIG. 4B, steps E8-E10).

  The various assembly steps shown schematically are denoted E1 to E10.

  Prior to the assembly stage described below, the heater pins 2 are assembled by soldering or by pushing the heater cartridge 22 into the metal cover 21.

  The indentation is done in an offline or inline automatic form, by indentation, shrink fit, or by a combination of indentation and shrink fit.

  In the case of soldering, this assembly is done off-line by soldering a set of parts that are carried out in a furnace at high temperatures that cannot be obtained on the production line.

  The assembly of the front region of the glow plug (FIG. 4A) starts from the machined tubular body 1 (E1), inserts the insulating disk 104 (E2), and then the central electrode 7 to which the head 6 has been welded beforehand. Is introduced into the recess 102 on the upper side of the insulating disk 104 and through the insulating disk 104 (E3). The head 6 and the center electrode 7 are joined in a suitable manner by laser welding with rotational movement. Based on the very large length diversity of the center electrode 7 with respect to the length of the plug manufactured according to the manufacturer's requirements, this weld seam is preferably performed off-line.

  The insulating disk 104 has a cross-section corresponding to the cross-section of the recess 102 in a relatively precise manner, in a preferred form, for precise positioning of the insulating disk and then for precise positioning of the center electrode 7. ing.

  Next, the insulating sleeve 5 is disposed so as to surround the front end portion 61 of the head 6 (step E4), and then the intermediate member 4 is inserted into the insulating sleeve 5 (E5). The insulating sleeve 5 has an inner diameter that is matched to the inner diameter of the front section 61 of the head 6 to ensure accurate centering.

  The outer diameter of the connecting member 4 made of graphite corresponds more precisely to the inner diameter of the insulating sleeve 5 in order to ensure positioning with minimal play.

  The projection on the front side 41 of the connecting member made of graphite 4 has a surplus length associated with the front end of the insulating sleeve, preferably made of ceramic, which surpasses the connecting member made of graphite 4. This is indispensable for crimping the back side 24 of the ceramic heater cartridge 22, particularly the power supply contact 233.

  The compressive force applied to the base portion 26 in the direction of the tubular body 1 by supporting the collar 62 of the head 6 with the insulating disk 104 is obtained by welding the base portion 26 to the front end portion 101 of the tubular body 1 after assembly. It is a compressive force that is sustained.

  In this way, the connecting member 4 made of graphite is finally compressed. The compressibility varies depending on the force produced by the extension / relaxation of the assembled part, which is exposed to the temperature change experienced by the glow plug during operation. The compressive force applied to the connecting member 4 and the head 6 is generated on the one hand on the rear side 24 of the heater cartridge 22 and on the other hand on the support shoulder 103 of the tubular body 1. This final compression can absorb the expansion and contraction caused by plug temperature fluctuations to ensure a sustained electrical connection independent of temperature fluctuations in these parts.

  In step (E6), the arrangement obtained by the heater pins 2 is superimposed.

  After the heater pin 2 is inserted, an intermediate space (i) remains between the front region 111 of the tubular body 1 and the rear side 28 of the base portion 26 of the heater pin 2. This arrangement is compressed in the direction of the axis xx in order to bring the surfaces closer together, the base part 26 is welded to the tubular body 1 (E7), so that after the arrangement is kept in a compressed state, the heater pins Electrical contact between 2 and the center electrode 7 is obtained.

  The lower unit obtained after welding with the weld seam 203 obtained at the end of step (E7) is sturdy. The lower unit is rotated 180 ° so that the rear side is turned up (FIG. 4B) and reaches the position of step (E8). At this stage, the seal 8 and then the insulating bush 9 are installed (stage E9).

  The connector 3 is assembled to the rear end 72 of the center electrode 7, the connector 3 is compressed by the force F in the direction of the tubular body 1 (FIG. 2B), and the sleeve 32 is compressed at the knurled end 72. As a result, the edge bend 204 (stage E10) of the connector 3 is obtained (FIG. 1).

DESCRIPTION OF SYMBOLS 1 Tubular main body 2 Heater pin 3 Connector 4 Connection member 5 Insulation sleeve 6 Head 7 Center electrode 8 Seal 9 Insulation bush 21 Metal cover, cover 22 Heater cartridge 24 Back side 25 Chamber 26 Base part 28 Back side connection plane 41 Front side 42 Rear side 61 Front section 62 Brim, support collar 63 Rear section 71 Front end 72 Rear end 101 Front end, front area 102 Recess 103 Support shoulder 104 Insulating disk, disk 110 Rear end, rear area 111 Front connection plane 204 Edge Bending 233 Input contact, power supply contact 1041 Through hole E1-E10 Stage i Free space or play

Claims (10)

A glow plug provided with a heater pin (2), wherein the heater pin (2) is formed of a metal cover (21) for housing a heater cartridge (22) made of ceramic, and the metal cover (21) is a tube. Welded to the front region (101) of the tubular body (1), the rear region (110) of the tubular body (1) supports the connector (3) for power supply, Electrical connection with earth is made through the metal cover (21) and the tubular body (1), and the power supply starts from the connector (3) through the center electrode (7). In the type in which the central electrode (7) is insulated and accommodated in the tubular body (1),
An electrical connection between a rear side (24) of the heater cartridge ( 22 ) with an input contact (233) and a front end (71) of the central electrode (7);
A conductive connecting member (4);
A conductive cylindrical head (6) fixed to the front region (71) of the central electrode (7) and provided with a support collar (62);
An electrically insulating sleeve (5) surrounding the front section (61) of the head (6) beyond the collar (62) and partially surrounding the connecting member (4); And
The tubular body (1) has a recess (102) at its front end (101), the recess (102) forms a support shoulder (103), and the support shoulder (103) It contains an insulating disk (104) for centering and electrical insulation, and the collar (62) is smaller in cross-section than the recess (102) for contacting the support shoulder (103) Have
The lower unit composed of the connection member (4) and the head (6) includes the input contact (233), the rear side (24) of the heater cartridge (2), and the tubular body (1). The connecting member (4) is compressed to the input contact (233) by the front side (41) thereof, and the connecting member (4) is compressed. The back side (42) of the head (6) is crimped to the front end (61), and the collar (62) of the head (6) is supported by the insulating disk (104). Crimped to the shoulder (103),
A glow plug characterized by that.   The glow plug according to claim 1, characterized in that the connecting member (4) is made of graphite, is electrically conductive and can be deformed under pressure. The head (6) is a conductive cylinder made of metal, and the cylinder is divided into a front section (61) and a rear section (63) by the collar (62). The glow plug according to claim 1 or 2.   A glow plug according to claim 1, characterized in that the collar (62) has a frustoconical cross section. In order to form at least partly the connecting member (4) and partly the chamber (25) for accommodating the head (6), the heater cartridge (22) is connected to the metal cover (21) of the heater pin (2). ) In the axial direction relative to the base part (26), wherein the two components (4, 6) are surrounded by the insulating sleeve (5). The glow plug according to claim 1.   The insulating disk (104) has a through-hole (1041), which in order to obtain a play-free arrangement, the cross section of the rear section (63) of the head (6) or Glow plug according to claim 1, characterized in that it is slightly smaller than the cross section of the central electrode (7). Glow plug according to claim 5 , characterized in that the insulating sleeve (5) is at least partially engaged in the chamber (25) of the metal cover (21). In the method for manufacturing the glow plug according to any one of claims 1 to 7,
A tubular body (1) having a recess (102) is manufactured, and the recess (102) forms a support shoulder (103) at the front end (101) of the tubular body (1) (E1),
Applying an insulating disk (104) to the support shoulder (103) in the recess (102) (E2);
A head (6) is fixed in advance to the center electrode (7), and the head (6) is attached to the insulating disk (104) in order to apply the collar (62) of the head (6) to the disk (104). Attaching (E3) the center electrode (7) by pushing in and centering the center electrode (7) within the tubular body (1);
An insulating sleeve (5) is applied to the front section (61) of the head (6) (E4);
By projecting the front side (41) of the connection member (4) in a natural manner and bringing the rear side (42) of the connection member (4) into contact with the front section (61) of the head (6), Inserting the connecting member (4) into the insulating sleeve (5) (E5);
The heater pin (2) assembled in advance to the insulating sleeve (5) is connected to the front side (41) of the intermediate member (4) in the chamber (25) of the heater cartridge (22). Mounting (E6) in at least approximately contact with the rear side (24), in which case the geometric parameters of the various components are determined by the connection plane (28) behind the base (26) of the heater pin (2). And a free space or play (i) remains between the connection plane (111) on the front side of the tubular body (1),
The metal cover (21) of the heater cartridge (22) and the connecting planes (28) and (111) facing each other of the tubular body (1) are brought close to each other and at least substantially in contact with each other and joined by welding. For this purpose, the heater pin (2) and the tubular body (1) are compressed in the axial direction,
The seal (8), the insulating bush (9), and the connector (3) are assembled to the rear end (72) of the center electrode (7), while the connector (3) and the tubular body (1) Establishing a sealing property between
The assembly is completed by attaching the connector (3) to the rear end (72) of the central electrode (7), during which the connection between the connector (3) and the tubular body (1) Establish sealability,
A method for manufacturing a glow plug, characterized in that   9. Method according to claim 8, characterized in that the base part (26) and the tubular body (1) are welded by means of a laser, in particular by rotating the two components synchronously. The assembly (E1 to E7) of the front region of the glow plug is performed on the vertically oriented tubular body (1) (axis line xx), and at this time, the front end portion of the tubular body (1) ( 101) facing upward,
In order to assemble the lower unit thus assembled, the connector (3) to the rear end (72) of the central electrode (7), in particular by edge bending (204), the axis (xx) is always It extends in the vertical direction but is rotated so that the rear end portion (110) of the tubular body (1) and the rear end portion (72) of the central electrode (7) face upward. The method of claim 8, characterized in that:

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