JP5918452B2 - Diesel engine preheating plug with cylindrical electrode - Google Patents

Description

The present invention
-A metal cylinder with one end ending with a ceramic glow rod and the other end with a connecting piece;
-A glow rod containing a heating conductor incorporated in the ceramic of the heating cartridge;
A diesel engine preheat plug comprising an insulated electrode penetrating the tubular body and electrically connecting a heating cartridge and a connecting piece which is insulated and held in the end of the tubular body itself; About.

  There are several products of the preheat plug of the type defined above.

  According to a known embodiment, the preheating plug is composed of a metal cylinder whose one end constitutes a glow rod and whose other end comprises a connection piece. Near this end, the metal body is externally threaded to be screwed into the cylinder head of the heat engine, and at the other end is a cone for positioning the glow rod in the combustion chamber in this way. including.

  Internally, the plug includes a central electrode in the form of a metal rod that passes through the cylindrical body. One end of the bar is connected to the connecting piece, and the other end, which is threaded, is connected to the end of the spirally wound electrical connecting wire by screwing. The electrical connection wire is integrated with the ceramic by brazing. This brazing also ensures that electricity is supplied by one end of a metal filament built into the heated ceramic. The other end of the metal filament is connected to a metal protective tube to the glow rod by a second brazing for ground electrical return. The assembly of components is maintained in place by insulating powder compacted in a protective tube. Electrical contact and in-situ maintenance is obtained by compaction of this tube assembly / insulating powder around the threaded portion, ie, the helical winding and the threaded portion of the central electrode. The center electrode itself is kept in an insulating state in the protective tube by the compacted insulating powder and sealing material.

  This known preheating plug has the disadvantages that it is manufactured with a relatively large number of components and requires complex assembly by compacting the insulating powder, so that eventually the preheating plug with ceramic glow rods Is expensive.

  The present invention simplifies the construction and fabrication of preheat plugs, reduces their manufacturing costs, and effectively resists expansion and contraction stresses, or vibrations and shocks under the influence of intense temperature changes experienced by the plugs. The object is to produce a preheat plug with a ceramic glow rod of simple design.

For this purpose, the present invention is a preheating plug of the type defined above,
The electrode has at least one cylindrical end with an inner diameter of a circular cross section;
-The rear end of the cartridge is followed by a neck with an oval insulating head with a contact boss connected to the heating conductor of the cartridge,
-The largest cross-section of the head perpendicular to the axis of the plug has a substantially elliptical shape with a major axis larger than the inner diameter and a minor axis smaller than the inner diameter, the circumference of this almost elliptical section being the cylindrical end of the circular section; Smaller than the inner circumference of the part,
-For a preheating plug, characterized in that the contact boss is located at at least one of the vertices of the major axis of this largest elliptical cross section.

  This assembly between the heating cartridge and the front end of the electrode is based on the electrical parameters of these two elements whatever the changes in physical parameters and environmental developments (temperature changes, vibrations, shocks) created by the action of the preheating plug. Ensure the effectiveness and permanence of contact.

  Installing the electrode end at the end of the heating cartridge is a very simple task that is very quick and does not involve extraneous elements such as material supply.

  The robustness of the contact, which is achieved by the selection of the nearly elliptical major and minor axes of the cross section of the head and the size of the inner diameter of the cylindrical end of the electrode, is the effectiveness and durability of the electrical contact as well as its function. Ensure effectiveness and avoid any wasted consumption of energy.

  According to another preferred feature, the connection device constituted by the neck and the head is integrally formed on the extension of the rear end of the ceramic cartridge and of the same material as the cartridge, and the contact boss is formed by the head and neck. Via an electrical connection to the heating conductor of the cartridge.

  Fabricating the connecting device integrally with the heating cartridge facilitates manufacturing and assembly at the same time while ensuring the reliability of the connection realized by the connecting device within the cylindrical front end of the electrode.

  According to another preferred feature, the head includes a contact boss at each apex of the oval substantially elliptical maximum cross section. Duplicating this contact boss further guarantees the reliability and effectiveness of the current passing through the heating conductor.

  According to another preferred feature, the second end of the electrode has a cylindrical shape which constitutes a coupling device in the form of a clamp for receiving the bar of the connecting piece.

  The connection realized by this means at the rear end of the electrode after installation of the tubular body makes assembly easy and simple.

  According to another preferred feature, the connection device in the form of a clamp has a constriction. This shape of the coupling device simplifies the introduction of the connecting piece rod into the rear end of the electrode.

  Particularly preferably, the connecting device in the form of a clamping tool is constituted by a tongue piece. This implementation shape further simplifies assembly while ensuring the effectiveness and permanence of electrical contact.

  Finally, according to another preferred feature, the rear end of the metal cylinder includes a countersink for receiving the outer surface of the insulating sleeve, the inner surface receiving the sleeve of the connecting piece. This connection to the rear end of the preheating plug ensures simultaneously the insulation and airtightness of the plug.

According to another feature, the present invention provides:
-Incorporating a contact boss connected to the heating conductor of the cartridge and making a heating cartridge with a connecting device consisting of a head connected by a neck to the end of the cartridge;
-Assembling the heating cartridge into a metal envelope, then compressing the front end of the cylindrical electrode to the head, compressing the end, engaging the head and then loosening its compression to finally tighten the head;
-Next, weld the front end to the thick cradle with the weld and install the tubular body;
-Subsequently, the end sleeve is press-fitted into the countersink at the cylindrical end, then the sleeve of the connecting piece is pressed into the end sleeve and at the same time the rod is press-fitted into the coupling device at the rear end of the electrode. Engaged,
-Also covers the preheated plug manufacturing method defined above, which consists of fixing the end sleeve by fitting the lip of the tubular body.

  This process is particularly simple because of the very simple structure of the electrode, which is at least partly or otherwise entirely cylindrical.

  The invention will be described in more detail below with the aid of an embodiment of a preheating plug for a diesel engine schematically represented in the accompanying drawings.

It is an axial sectional view of the main elements of the preheating plug. FIG. 4 is a detailed view of a conductive path supplied to a heating element. FIG. 6 is an enlarged axial cross-sectional view of the connection between the connecting device of the heating cartridge and the cylindrical front end of the electrode. FIG. 5 is a cross-sectional view of the head of the connection device, with a plane perpendicular to the axial direction and passing through the maximum cross section. It is sectional drawing of the cylindrical edge part of the circular cross section of an electrode. It is sectional drawing in the level of the cylindrical front end of the electrode compressed for the head and head installation of a heating cartridge. Fig. 4 shows the connection made between the head of the heating cartridge and the cylindrical front end of the electrode. FIG. 6 is an axial cross-sectional view of an embodiment of the rear end of the electrode. It is sectional drawing of the rear end of the electrode which receives the spindle of the connection piece which is not cut | disconnected. FIG. 5 is a cross-sectional view of the coupling device at the rear end of the electrode engaged with the spindle of the connecting piece.

  By convention, the orientation concept “front” / “rear” is used in various figures to simplify the description, the front or left side of the figure corresponds to the glow rod side of the plug, and the rear Or the right side corresponds to the connection piece side of the preheating plug.

  According to FIG. 1, the partially represented preheating plug is composed of a cylindrical body 1 with an axis xx in which one end 11 is connected to a ceramic glow rod 2 and the other end 12 is connected to a connection piece 3.

  The plug is fixed in place in the engine cylinder head by screwing the thread groove 13 and the heating cartridge 22 protrudes from the cone 26 so that the glow rod 2 is stretched in the combustion chamber for preheating. Will come out. The cone 26 ensures centering and bearing tightness in the cylinder head.

  The glow rod 2 functions as a heating resistor connected to the ground by the support of the cone 26 in the cylinder head and simultaneously by the metal envelope, while the metal envelope itself is connected to the body 1 and the ground in the cylinder head. They are electrically connected by a screw groove 13 screwed to each other. The other end of the glow rod 2 is connected to the mounted electric circuit by a conductive path “+” via the connection device 4, the electrode 5 passing through the body 1, and the connection piece 3.

  The connecting piece 3 is connected to an on-board electric circuit (not shown) by a preheating control device (not shown). It is a generally known means that does not require detailed description or special indication.

  The glow rod 2 comprises a finger-shaped metal envelope 21 that houses a ceramic heating cartridge 22 that incorporates a heating conductor by the Joule effect. At the level of the heating cartridge 22, the thin metal envelope 21 ends with a thick cradle 24 that forms a sealed cone 26.

  The electrode 5 has a cylindrical front end 51 having a circular cross section for receiving the connection device 4 of the cartridge 22, and a rear end 54 having a connecting device 6 for the connection piece 3.

  The conductive path supplied to the heating cartridge 22 constituted by the connecting device 4, the electrode 5, the connecting device and the connecting piece 3 is by the connecting device 4 at the front end and by the insulating end sleeve 7 that receives the connecting piece 3 at the rear end. The glow rod 2 and the metal envelope 21 of the cylindrical body 1 are electrically insulated and positioned.

  The tubular body 1 is externally provided with a thread groove 13 for screwing into the heat engine, and its rear end 12 is in the form of a hexagonal nut, for example, by screwing / unscrewing the preheating plug in the engine. A tool slot 15 is included. The tubular body 1 is welded to the metal envelope 24 of the glow rod 2 by the welding portion 16.

  The rear end 12 of the cylindrical body 1 includes a countersink 17 that receives the sleeve 31 of the connecting piece 3 with an insulating end sleeve 7 interposed between the sleeve 31 and a knurled surface or grooved surface. The assembly is performed by tightening, and the fixing is performed by deformation of the lip 18 along the countersink 17.

  FIG. 2 shows the two cylindrical ends 51, 54 of the electrode 5 connected to the cartridge 22 and the connecting piece 3 by connecting means 4 and 6 described in detail below.

  FIGS. 3 to 5B show an oval and curved profile in the direction of the axis xx, which is performed by the connecting device 4 to the rear end 27 of the cartridge 22 and gives an oval or substantially elliptical (FIG. 4A) cross section. The cartridge 22 / electrode 5 connection consisting of a neck 41 terminated by a contact head 42, having a generally frustoconical end face, facilitates engagement within a cylindrical end 51 of circular cross section.

  The head 42 is made of an insulating material like the neck 41, preferably the same material as the ceramic of the cartridge 22, and is made in one piece. The head 42 includes an electrical contact boss 43 located on the major axis zz of the substantially elliptical cross section of the head and protruding from the profile of this cross section.

  The connecting device 4 may be a part added by brazing to the ceramic, or may be a shape processed by grinding of the ceramic.

4A and 4B, the diameter D, which is the diameter of the cross section between the cross section of the circular cylindrical end portion 51 having the inner diameter D ₁ and the vertices S ₁ and S ₂ of the curved portion of the head 42 (FIG. 3). ₂ can be compared with the difference D ₂ > D ₁ . In practice and very simply, the head is symmetrical with respect to the axis xx, which is the axis of the cylindrical end 51 of the electrode 5 and the head 42 of the cartridge 22 which is also installed in an aligned position. It has an oval shape with _two vertices S ₁ and S ₂ . The head 42 has a maximum cross section passing through the _two vertices S ₁ and S ₂ and perpendicular to the orientation axis xx. This cross section has a substantially elliptical rounded shape, and therefore has a major axis D ₂ and a minor axis D _{3 in} the geometric sense of the term (axis D ₂ is the orientation axis zz (FIG. There in the direction of 4A), and minor axis _{D 3} is the alignment axis yy or perpendicular direction).

The major axis D ₂ is larger than the inner diameter D ₁ of the cylindrical end 51, and the minor axis D ₃ is smaller than the inner diameter of the cylindrical end 51.

At least one of the vertices (S ₁ or S ₂ ) is occupied by a contact boss 43 that preferably overhangs the so-called contour surface of the head 42. Both vertices S ₁ , S ₂ may each be occupied by a contact boss. The contact boss 43 is electrically connected to the heating conductor of the heating cartridge 22. The long axis D ₂ takes into account the height of the contact boss 43.

According to FIGS. 4A and 4B, the elastic deformation of the laterally squeezed end 51 (along the orientation selected in the figure) allows the head 42 to engage within the cylindrical end 51 and In addition, the axes D ₂ and D ₃ are substantially elliptical in this section so that the end 51 can be sandwiched along the major axis D ₂ (zz) between the vertices S ₁ and S ₂ by elastic return to the circular cross-sectional shape. The circumference is selected to be smaller than the inner circumference (Π ^* D ₁ ) of the cylindrical end 51 having a circular cross section.

According to FIG. 5A, the installation compresses the end 51 in the transverse direction of the long axis of the head 42 so that the deformed ellipse of the circle of the end 51 of the electrode 5 can receive the head 42 by the contact boss 43. (FF). Next, the compression (FF) is relaxed so that the end 51 elastically recovers the natural circular cross section, and the head 42 and its contact boss 43 are brought to the apex S by a constant and final force PP. _1, compressed at the level of _{S 2.}

The oval or egg shape of the head 42 not only facilitates the installation of the head in the cylindrical end 51 and good electrical contact by clamping performed by the cylindrical end 51, but this shape is also cylindrical. Insufficient alignment (angle α) between the axis xx of the end 51 and the axis x ₁ x ₁ of the misaligned cartridge 22 or head 42, as well as changes in some physical parameters or exposure of the preheat plug. It also makes it possible to absorb the possible sliding caused by the effects of vibrations or shocks that can be made.

  FIGS. 6 to 7B show the connection of the electrode 5 / connecting piece 3 at the cylindrical rear end 54 of the electrode 5 in the shape of a clamp constituting the connecting device 6. FIG. The clamping tool 6 has a narrowed portion 61 having a smaller cross section than the cross section of the bar 34 of the connection piece 3. The clamp 6 can be further divided longitudinally into elastic tongues 62 to facilitate clamping as shown in the cross-sectional view of FIG. 7B.

The preheat plug manufacturing method described above is
Incorporating the contact boss 43 connected to the heating conductor of the cartridge 22 and making the heating cartridge 22 with the connecting device 4 comprising the head 42 connected to the end 27 of the cartridge 22 by the neck 41;
Assemble the heating cartridge 22 into the metal envelope 21, then connect the front end 51 of the cylindrical electrode 5 to the head 42, compress the end 41, engage the head 42 and then connect the head 42 finally Loosen its compression to tighten (this assembly may take place prior to installation of the heating cartridge 22 into the metal envelope 21);
-Next, the front end 11 is welded to the thick cradle 24 by the weld 16 to install the tubular body 1;
-Subsequently, the end sleeve 7 is press-fitted and installed in the countersink 17 at the cylindrical end,
The sleeve 31 of the connecting piece 3 is then pressed into the end sleeve 7 and at the same time the rod 34 is press-fitted into the coupling device 6 at the rear end 54 of the electrode 5,
Finally, the lip 18 located at the rear end 12 of the tubular body 1 is lowered with respect to the insulating sleeve 7.

DESCRIPTION OF SYMBOLS 1 Cylindrical body 11 Front end 12 Rear end 13 External thread groove 15 Tool insertion port 16 Thick cradle and welded part of tubular body 17 Countersink 18 Lip 2 Glow rod 21 Metal envelope 22 Heating cartridge 24 Thick cradle 26 Sealing cone 27 Rear end 3 Connection piece 31 Sleeve 32 Flange 33 Spindle / connection leg 34 Rod 4 Connection device 41 Neck 42 Head 43 Contact boss 5 Electrode 51 Front end 52 Receiving part 54 Rear end / knurled rear end 55 Electrode and connection wire Welded part 6 coupling device 61 constricted part 62 tongue piece 7 insulating end sleeve 71 outer surface 72 inner surface xx axis of plug yy direction of short axis of maximum cross section of head 42 zz direction of long axis of maximum cross section of head 42 D ₂ head end 5 substantially of generally elliptical cross section of the elliptical cross-section long axis D ₃ head of minor axis D ₁ electrode 5 1 diameter S ₁ , S ₂ apex FF compressive stress PP tightening stress

Claims (8)

A metal cylinder (1) having one end (11) ending with a ceramic glow rod (2) and the other end (12) having a connecting piece (3);
Said glow rod (2) containing a heating conductor incorporated in the ceramic of the heating cartridge (22);
-The connecting piece (3) which is insulated and penetrates the tubular body (1) and which is insulated and held within the end of the heating cartridge (22) and the tubular body (1) A preheating plug including an electrode (5) for electrically connecting
- having the electrode (5) is, at least one end of the cylindrical inner diameter _{(D 1)} of circular cross section (51),
An egg-shaped insulating head (42) with at least one contact boss "+" (43) connected to the heating conductor of the cartridge (22) at the rear end (27) of the cartridge (22); Followed by a neck (41) with
- maximum section perpendicular the head to the axis (xx) of the plug (42) is, the inner diameter _{(D 1)} larger major axis than _{(D 2)} and the inner diameter _{(D 1)} less short axis than (D ₃₎ with has a generally oval, periphery of the substantially elliptical cross section, the inner periphery of the cylindrical end portion of circular cross-section ^{(51) (Π * D 1} ) less than,
A preheating plug, characterized in that the contact boss “+” (43) is located at at least one of the vertices (S ₁ , S ₂ ) of the major axis (D ₂ ) of this largest elliptical cross section.   A connecting device (4) constituted by the neck (41) and the head (42) is integrally formed on the extension line of the rear end (27) of the ceramic cartridge (22) and with the same material as the cartridge. The contact boss (43) is connected by an electrical connection to a heating conductor of the cartridge (22) via the head (42) and the neck (41). Preheat plug as described in. Said head (42), characterized in that it comprises a substantially each vertex of the largest cross-section of elliptical oval (S _{1, S 2)} to contact the boss (43), the glow plug according to claim 1.   The second end of the electrode (5) has a cylindrical shape (54) constituting a connecting device (6) in the shape of a clamp for receiving the rod (34) of the connection piece (3). The preheating plug according to claim 1.   Preheating plug according to claim 4, characterized in that the coupling device (6) in the form of a clamp has a constriction (61).   Preheating plug according to claim 4, characterized in that the coupling device (6) in the form of a clamping tool comprises a tongue piece (62).   The rear end (15) of the metal cylindrical body (1) has a countersunk hole (61) for receiving the outer surface (71) of the insulating sleeve (7), the inner surface (62) receiving the sleeve (31) of the connecting piece (3). 17) Preheating plug according to claim 1, characterized in that it includes a lip (18) for securing the insulating sleeve (7). A connecting device comprising a head (42) which incorporates a contact boss (43) connected to the heating conductor of the cartridge (22) and is connected to the end (27) of the cartridge (22) by a neck (41) 4) to produce the heating cartridge (22)
-Assembling the heating cartridge (22) into a metal envelope (21), then compressing the front end (51) of the cylindrical electrode (5) to the head (42) and the end (41); ) And then loosen the compression so that the head (42) is finally tightened, and this assembly is also performed before the heating cartridge (22) is installed in the metal envelope (21). Can be done,
-Next, weld the front end (11) to the thick cradle (24) by the weld (16) to install the tubular body (1);
-Subsequently, the end sleeve (7) is press-fitted into the countersunk hole (17) at the cylindrical end,
The sleeve (31) of the connecting piece (3) is then in the end sleeve (7) and at the same time the rod (34) is in the coupling device (6) at the rear end (54) of the electrode (5). Press fit and engage,
A method for producing a preheating plug according to any one of claims 1 to 7, characterized in that it comprises subsequently lowering the lip (18) with respect to the insulating sleeve (7).

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