JP5557488B2 - Ceramic glow plug - Google Patents

Description

  The present invention relates to a ceramic glow plug used for an internal combustion engine such as an automobile diesel engine.

  Conventionally, ceramic glow plugs have been used to promote startup of internal combustion engines such as automobile diesel engines. As such a ceramic glow plug, the front end side protrudes from the front end portion of the housing and the rear end side is accommodated in the housing in a cylindrical housing provided with a screw portion for engine attachment on the outer peripheral surface. A structure in which a ceramic heater is supported is known.

  In the above ceramic glow plug, the ceramic heater includes a ceramic base, a heating element embedded in the ceramic base, a pair of lead portions electrically connected to the heating body, and a lead portion. A device having a first electrode extraction portion and a second electrode extraction portion that are electrically connected and extend to the outer periphery of a ceramic substrate is known. And the thing of the structure which makes a metal outer cylinder and a metal ring fit in the part of the 1st electrode extraction part and the 2nd electrode extraction part, respectively, and performs an electrical connection is known.

  As a method for attaching the metal outer cylinder and the metal ring to the ceramic heater, a cylindrical ceramic heater is press-fitted into the metal outer cylinder and the metal ring, and the metal outer cylinder and the metal ring are tightly fitted to the outer peripheral surface of the ceramic heater. A method of attaching an outer cylinder and a metal ring is known. At this time, it is known that a softer metal layer than the metal outer cylinder and the metal ring is provided between the ceramic heater and the metal outer cylinder and the metal ring (the inner peripheral surface of the metal outer cylinder and the metal ring). (For example, refer to Patent Document 1.)

JP 2003-56848 A

  In the above-described conventional glow plug, the metal outer cylinder is configured to be relatively thick, for example, about several millimeters, and thus is configured from a material having a low hardness, such as SUS430 (200 to 230 Hv). On the other hand, the metal ring has a relatively thin wall thickness of, for example, 1 mm or less, and is therefore made of a material having high hardness, such as SUS630 (360 to 430 Hv). For this reason, the metal ring has a problem that the load at the time of press-fitting becomes large, making it difficult to manufacture and possibly causing damage during the manufacturing, resulting in poor productivity.

  Moreover, about a metal outer cylinder, the metal layer is provided only in a part of inner peripheral surface. For this reason, a level | step difference is formed between the part in which the metal layer is formed, and the part in which it is not formed, There exists a problem that a fitting area with a ceramic heater reduces and fitting force tends to become inadequate.

  The present invention has been made to solve the above problems. The present invention is intended to provide a ceramic glow plug that can improve the productivity as compared with the prior art and can secure a fitting force between a metal outer cylinder and a ceramic heater.

The ceramic glow plug according to the present invention includes a ceramic base made of an insulating ceramic having a rod shape along an axis, a heating element embedded in the ceramic base, and an electrical connection between the heating base and the ceramic base. A ceramic heater comprising a pair of connected lead portions, and a first electrode extraction portion and a second electrode extraction portion that are electrically connected to the pair of lead portions and extend to the outer periphery of the ceramic base, A metal outer cylinder fitted to the outer periphery of the ceramic heater by press- fitting and electrically connected via the first electrode take-out portion and the first metal layer, and an outer periphery of the ceramic heater, after the metal outer cylinder fitted by press fitting on the end side, and a metal ring which is electrically connected through the second electrode extraction portion and the second metal layer, fitted to the rear end side of the metal ring A central shaft formed of a conductor and formed into a rod shape, and the front end side of the ceramic heater protrudes from the front end of the ceramic heater, and the rear end side of the ceramic heater is placed inside through the metal outer cylinder. A ceramic glow plug having a holding housing, wherein the metal outer cylinder is less hard than the metal ring, and the first metal layer is formed on a part of an inner peripheral surface of the metal outer cylinder. It is formed and is thinner than the second metal layer.

  In the ceramic glow plug of the present invention having the above-described configuration, the metal outer cylinder is smaller in hardness than the metal ring, and the first metal layer formed between the first electrode take-out portion and the metal outer cylinder is the second electrode. The thickness is thinner than the second metal layer formed between the take-out portion and the metal ring. As described above, the first metal layer formed between the first electrode extraction portion and the metal outer cylinder is formed by forming a portion where the first metal layer is formed and a first metal layer by reducing the thickness. It is possible to reduce the level difference of the part that is not made, to suppress the reduction of the fitting area with the ceramic heater, and to secure the fitting force. Further, by increasing the thickness of the second metal layer formed between the second electrode lead-out portion and the metal ring, the action of the second metal layer as a buffer layer is increased, and the metal ring is engaged during fitting. It is possible to reduce the load applied to the. Thus, the fitting process can be easily performed, and the productivity can be improved.

  In the ceramic glow plug of the present invention, the first metal layer may be formed on a part of the inner peripheral surface of the metal outer cylinder. As a result, the amount of material necessary for forming the first metal layer can be reduced.

  On the other hand, in the ceramic glow plug of the present invention, the second metal layer can be formed on the entire inner peripheral surface of the metal ring. As a result, even when the middle shaft is press-fitted and fixed to the rear end side of the metal ring, the second metal layer is interposed between the metal ring and the middle shaft so that the second metal layer is buffered. Can be used as a layer.

  Moreover, the ceramic glow plug of the present invention can be suitably used when the thickness of the metal outer cylinder is thicker than the thickness of the metal ring. Furthermore, in the ceramic glow plug of the present invention, the first metal layer and the second metal layer can be made of silver. Thus, by using silver as a constituent material of the first metal layer and the second metal layer, the manufacturing cost can be reduced as compared with the case where gold is used, for example.

  According to the present invention, it is possible to provide a ceramic glow plug that can improve productivity as compared with the conventional art and can secure a fitting force between the metal outer cylinder and the ceramic heater.

1 is a longitudinal sectional view showing an overall schematic configuration of a ceramic glow plug according to an embodiment of the present invention. The perspective view which shows the principal part structure of the ceramic glow plug of FIG. The longitudinal cross-sectional view which expands and shows the metal outer cylinder of the ceramic glow plug of FIG.

  Embodiments of the present invention will be described below with reference to the drawings. 1 to 3 show a configuration of a ceramic glow plug 100 according to an embodiment of the present invention. FIG. 1 is a longitudinal sectional view showing an overall schematic configuration of the ceramic glow plug 100, and FIG. FIG. 3 is an enlarged longitudinal sectional view showing a metal outer cylinder of a ceramic glow plug. Note that the vertical direction in the drawing is the axis AX direction, the lower part is the front end, and the upper part is the rear end.

  As shown in FIG. 1, the ceramic glow plug 100 is configured by combining a housing 10, a center shaft 20, a ceramic heater 30, a metal ring 40, a pin terminal 50, and a metal outer cylinder 60.

  The housing 10 is made of, for example, carbon steel (S45C or the like) and has a cylindrical shape having an inner hole 101 through which the inside of the housing 10 passes along the axis AX. A diesel engine (not shown) is provided on the outer peripheral surface. ) Is formed by rolling or cutting.

  The rear end portion 103 of the housing 10 is formed with a tool engaging portion 104 for engaging a tool such as a hexagon wrench or a plug wrench when the housing 10 is attached to the diesel engine. In addition, a tapered portion 105 that expands the inner hole 101 toward the rear end side and a large-diameter hole 106 that is further adjacent to the rear end side of the tapered portion 105 are formed on the inner peripheral side of the rear end portion 103. ing.

  The metal outer cylinder 60 is made of a metal (SUS430 (melting point: 1480 to 1508 ° C.) in this embodiment) having high heat resistance and relatively low hardness (for example, about 200 to 230 Hv). This metal outer cylinder 60 has a bowl-shaped part (large cylindrical part 601), and has a substantially cylindrical shape with an inner hole 602 formed on its inner periphery. The ceramic heater 30 is held by being press-fitted into the inner hole 602.

  The metal outer cylinder 60 includes a relatively thin small cylindrical portion 603 on the front end side, a taper 604 that expands toward the rear end adjacent to the rear end side of the small cylindrical portion 603, and a small cylindrical portion following the taper 604. A large cylindrical portion 601 having a larger diameter than 603 and having substantially the same outer diameter as the front end portion of the housing 10, and an engagement cylindrical portion 605 having a smaller diameter than the large cylindrical portion 601 at the rear end side of the large cylindrical portion 601. It has a formed configuration. When the glow plug 100 is attached to a diesel engine (not shown), the taper 604 plays a role as a seal for ensuring airtightness with the combustion chamber. As shown in an enlarged view in FIG. 3, a part of the inner peripheral surface of the metal outer cylinder 60 (in this embodiment, a region extending from the rear end of the metal outer cylinder 60 to the inner peripheral portion of the taper 604) One metal layer 61 is formed. The first metal layer 61 is made of a metal (Ag in this embodiment) that is softer than the constituent material of the metal outer cylinder 60 (SUS430 in this embodiment), and has a thickness that is smaller than that of the second metal layer 41 described later. It is thinned. In addition, the thickness of each part of the metal outer cylinder 60 is about several millimeters (the range of 3.3-5.1 mm in this embodiment).

  The middle shaft 20 is made of a conductive metal and has a rod shape. The tip end portion of the middle shaft 20 is formed with a tip small-diameter portion 201 so as to be fitted to the metal ring 40, while the rear end portion 202 is formed with a smaller diameter than other portions because the pin terminal 50 is attached.

The metal ring 40 has a cylindrical shape and is thinner than the metal outer cylinder 60 described above (thickness is about 1 mm or less (in this embodiment, 0.59 mm)). For this reason, the metal ring 40 has a higher tensile strength (for example, 1310 N / mm ² or more) and a higher hardness (for example, about 360 to 430 Hv) than the metal outer cylinder 60 (tensile strength 500 to 620 N / mm ² ) described above. (SUS630 in this embodiment). The inner diameter of the metal ring 40 is substantially the same as the outer diameter of each of the rear end portion 301 of the ceramic heater 30 and the tip small diameter portion 201 of the center shaft 20. On the other hand, the outer diameter of the metal ring 40 is set to be substantially the same as the outer diameter of the portion adjacent to the rear end side from the tip small diameter portion 201 of the middle shaft 20.

  A second metal layer 41 is formed on the inner peripheral surface of the metal ring 40 over the entire surface. The second metal layer 41 is made of a metal (Ag in the present embodiment) that is softer than the constituent material of the metal ring 40 (SUS630 in the present embodiment), and is thicker than the first metal layer 61 described above. Yes. The first metal layer 61 is preferably 0.3 to 0.8 μm thick, and the second metal layer 41 is preferably 0.9 to 1.3 μm thick. In the present embodiment, the first metal layer 61 has a thickness of 0.7 μm, and the second metal layer 41 has a thickness of 1.0 μm.

  The ceramic heater 30 is configured such that a heating element 32 made of a conductive ceramic and a pair of lead portions 33 and 33 are embedded in a ceramic base 31 formed in a rod shape from an insulating ceramic (silicon nitride, alumina, etc.). ing. The heating element 32 positioned inside the ceramic heater 30 is formed in a U shape with conductive ceramic. Further, the two lead portions 33 extending rearward from the respective base ends of the heating element 32 are similarly formed from a conductive ceramic.

  One of the lead portions 33 (the right lead portion 33 in FIG. 1) has a second electrode that extends in the radial direction perpendicular to the axis AX at the rear end portion 301 of the heater 30 and is exposed on the surface of the ceramic substrate 31. A portion 34 is provided. The second electrode extraction portion 34 is electrically connected to the metal ring 40. The other lead portion 33 (the left lead portion 33 in FIG. 1) extends in the radial direction perpendicular to the axis AX and is exposed on the surface of the ceramic base 31 on the tip side from the second electrode lead-out portion 34 described above. A first electrode take-out portion 35 is provided. The first electrode extraction portion 35 is electrically connected to the metal outer cylinder 60.

  Next, a process for press-fitting the heater 30 into the metal outer cylinder 60 and the metal ring 40 when the ceramic glow plug 100 is manufactured will be described.

  The metal ring 40 can be manufactured by cutting the pipe material of SUS630 and preparing a predetermined cylindrical shape, and then forming the second metal layer 41 having a predetermined thickness by barrel plating. Similarly, the metal outer cylinder 60 is formed by cutting or cutting a SUS430 pipe material into a predetermined shape and forming a first metal layer 61 having a predetermined thickness by partial plating (electrolytic plating) on a predetermined portion of the inner peripheral surface thereof. Can be manufactured.

  In the press-fitting process, first, the ceramic heater 30 is inserted (press-fitted) into the metal ring 40 to be integrated. The ceramic heater 30 integrated with the metal ring 40 is further inserted (press-fitted) into the metal outer cylinder 60 to produce an integrated object 110 shown in FIG. Further, the central shaft 20 is press-fitted into the integrated metal ring 40 and laser welding is carried out to produce a heater / medium shaft integrated body.

  In the process of press-fitting the ceramic heater 30, the second metal layer 41 having a large thickness is formed on the metal ring 40 made of a material having a small thickness and a large hardness. A high buffering effect is exhibited, the load applied during press-fitting can be reduced, and the press-fitting step can be easily performed.

  On the other hand, a first metal layer 61 having a small thickness is formed on a metal outer cylinder 60 made of a material that is thicker and less hard than the metal ring 40. Although the buffering action of the thin first metal layer 61 is low, the metal outer tube 60 is made of a material having a low hardness, so that the load during press-fitting does not become so high that press-fitting becomes difficult. And since the thickness of the 1st metal layer 61 is thin, the level | step difference of the formation site | part of the 1st metal layer 61 and a non-formation site | part decreases, and the fall of the fitting force after press injection can be suppressed.

  After assembling the ceramic heater 30, the metal ring 40, the metal outer cylinder 60, and the middle shaft 20 as described above, the housing 10 is put on these assemblies and the metal outer cylinder 60 and the welded portion 12 (see FIG. 1). The ceramic glow plug 100 is completed by inserting the O-ring 111 and the insulating bush 112 and caulking and fixing the pin terminal 50 to the rear end 202 of the middle shaft 20 protruding from the rear end 103 of the housing 10. .

  In the ceramic glow plug 100 having the above-described configuration, as shown in FIG. 1, the tip of the ceramic heater 30 protrudes from the tip of the metal outer cylinder 60. Then, the ceramic glow plug 100 is inserted into a plug mounting hole of a diesel engine (not shown), and the screw portion 102 is fastened to the mounting screw of the diesel engine to bring the taper 604 into contact with the diesel engine, thereby ensuring airtightness. In this state, the heater 30 is attached to the internal combustion engine so that the front end side is located in the combustion chamber, and the diesel engine is started by energizing the heater 30 through the pin terminal 50, the middle shaft 20, and the metal ring 40 to generate heat. Assist.

  In the above, the present invention has been described with reference to the embodiment. However, the present invention is not limited to the above-described embodiment and the like, and it is needless to say that the present invention can be appropriately modified and applied without departing from the gist thereof.

  DESCRIPTION OF SYMBOLS 10 ... Housing, 20 ... Middle shaft, 30 ... Ceramic heater, 31 ... Ceramic base, 32 ... Heat generating body, 33 ... Lead part, 34 ... Second electrode taking-out part, 35 ... First electrode taking-out 40 ... Metal ring 41 ... Second metal layer 50 ... Pin terminal 60 ... Metal outer cylinder 61 ... First metal layer 100 ... Ceramic glow plug

Claims (4)

A ceramic base made of an insulating ceramic in the form of a rod along the axis, a heating element embedded in the ceramic base, and a pair of lead portions embedded in the ceramic base and electrically connected to the heating element; A ceramic heater provided with a first electrode extraction portion and a second electrode extraction portion that are electrically connected to the pair of lead portions and extend to the outer periphery of the ceramic base,
A metal outer cylinder that is fitted to the outer periphery of the ceramic heater by press fitting, and is electrically connected to the first electrode take-out portion via the first metal layer;
Of the outer periphery of the ceramic heater, a metal ring that is fitted to the rear end side from the metal outer cylinder by press fitting, and is electrically connected via the second electrode extraction portion and the second metal layer,
A center shaft having a tip portion fitted on the rear end side of the metal ring, made of a conductor and formed in a rod shape,
A ceramic glow plug including a housing that protrudes from a front end of the ceramic heater from a front end of the ceramic heater and holds a rear end side of the ceramic heater through the metal outer cylinder;
The metal outer cylinder has a lower hardness than the metal ring, and the first metal layer is formed on a part of the inner peripheral surface of the metal outer cylinder and is thinner than the second metal layer. A ceramic glow plug characterized by that. The ceramic glow plug according to claim 1,
The ceramic glow plug, wherein the second metal layer is formed on the entire inner peripheral surface of the metal ring. The ceramic glow plug according to claim 1 or 2,
The ceramic glow plug characterized in that a thickness of the metal outer cylinder is larger than a thickness of the metal ring. The ceramic glow plug according to any one of claims 1 to 3,
The ceramic glow plug, wherein the first metal layer and the second metal layer are made of silver.

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