JP2013105684A - Method for manufacturing ceramic heater and method for manufacturing glow plug - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a ceramic heater with good durability having an insulation base and a heating element resistor embedded in the insulation base, and a method for manufacturing a glow plug having the ceramic heater.SOLUTION: A method comprises: a semi-molded body forming step of forming a first molded body 30 serving as a part of an insulation base 10 by baking and the semi-molded body 34 having an unbaked heating element resistor 33 serving as a heating element resistor 11 by baking; and a second molded body forming step of molding a second molded body 35 integrally with the semi-molded body 34, serving as a residue of the insulation base 10 by baking. A part of an unbaked bent-back part 32 of the unbaked heating element resistor 33 is embedded in the first molded body 30, while the residue projects from the first molded body 30. In the semi-molded body forming step, the semi-molded body 34 is formed so that a rear side height HH2 projecting from the first molded body 30 is lower than a rear side depth HD2 embedded in the first molded body 30, at least at a rear side boundary 57 between the unbaked bent-back part 32 and a molded body rear side part 55.

Description

  The present invention relates to a method for manufacturing a ceramic heater including an insulating base made of an insulating ceramic, and a heating resistor embedded in the insulating base and made of a conductive ceramic, and a method for manufacturing a glow plug having a ceramic heater.

  Conventionally, various methods have been proposed as a method of manufacturing a ceramic heater including an insulating base made of an insulating ceramic and a heating resistor made of a conductive ceramic embedded in the insulating base. For example, in Patent Document 1, a process for producing a current-carrying part molded body using a mixture for a current-carrying part containing a conductive ceramic powder and a binder, and the current-carrying part molded body are held in a mold to produce an insulating ceramic powder. And filling the substrate mixture containing the binder into the above-mentioned mold to produce an element molded body in which the molded part for the current-carrying part is covered with the substrate mixture, and firing the element molded body. A manufacturing method is provided. First, when producing an element molded body, a current-carrying part molded body is first molded using a pair of opposed molds. Thereafter, the current-carrying part molded body is disposed on the inner surface of the first mold member for base molding so that the surface on one side thereof is in contact therewith. Subsequently, the substrate mixture is filled between the inner surface (cavity) of the second mold member for molding the substrate disposed on the other side and the other surface of the molded part for the current-carrying part, thereby insulating substrate. A molded body (hereinafter referred to as a first base molded body) to be a part of (a half of) is injection molded. Next, the first mold member for base molding is replaced with a third mold member for base molding, and the inner surface of the third mold member, the surface on one side of the molded part for the current-carrying part, and the first A procedure is disclosed in which an element molded body is obtained by injecting a substrate mixture into a space (cavity) composed of a single substrate molded body.

WO2009 / 057596

  In the manufacturing method described in Patent Document 1, an element molded body is obtained after molding a current-carrying part molded body that becomes a heating resistor by firing, and a first base body molded body that becomes a part of an insulating substrate by firing. In this case, in order to form a molded body (hereinafter referred to as a second base molded body) that becomes the remainder of the insulating base body by firing, the base mixture is injected toward the distal end direction or the proximal end direction. Then, the injected base mixture moves to the distal end side or the base end side while being in contact with the current-carrying part molded body and the first base body molded body, and the U-shaped bending of the current-carrying part molded body is performed. It reaches the return section and proceeds over this.

  However, as shown in FIG. 13, the shape of the portion 93 protruding from the first base molded body 90 in the bent-back portion 91 of the current-carrying part molded body 92 is semicircular in cross section, At the boundary with the one-base molded body 90, the angle formed by the protruding portion 93 and the first base-molded body 90 is 90 degrees. For this reason, before the substrate mixture which has progressed gets over the bent-back portion 91 of the current-carrying part molded body 92 or after it gets over, the first substrate-formed body 90 and the second substrate-formed body 94 in the vicinity of the bent-back portion 91. In some cases, the interface 95 does not sufficiently adhere to each other with the void 96 formed. For this reason, among the insulating bases of the ceramic heater that has been fired, in the vicinity of the bent portion of the heating resistor, as shown in FIG. 14, at the interface between the first base body and the second base body before firing. There was a possibility that gaps extending like slits or gaps arranged in a row were formed at the site, and the durability of the ceramic heater deteriorated.

  The present invention has been made in view of the present situation, and includes an insulating base made of an insulating ceramic, and a heat generating resistor made of a conductive ceramic embedded in the insulating base, and having a good durability. It is an object of the present invention to provide a method for manufacturing a heater and a method for manufacturing a glow plug having such a ceramic heater.

  The aspect includes an insulating base made of an insulating ceramic and having a shape extending along the axis, and a heating resistor embedded in the insulating base and made of a conductive ceramic, which is disposed in the tip of the insulating base. A U-shape with the bent back portion facing the tip direction in the axial direction along the axis, the heat generating portion that generates heat by energization, and the tip direction in the axial direction from both ends of the heat generating portion. Is a heat generating resistor having a lead portion extending in the opposite proximal direction, and a method for manufacturing a ceramic heater, comprising a first insulating ceramic powder and becoming a part of the insulating substrate by firing. 1. An unfired heat generating part including a green body and an unfired heat generating part that includes the conductive ceramic powder and becomes the heat generating part when fired, and includes an unfired bent part that becomes the bent back part when fired And a semi-molded body molding step for molding a half-molded body having an unfired heating resistor that becomes the above-described heating resistor by firing, and an injection molding method toward the distal direction or the proximal direction. A second molded body molding step of injecting a mixture for the second substrate containing two insulating ceramic powders and molding the second molded body that becomes the remainder of the insulating substrate by firing integrally with the semi-molded body; The semi-molded body includes at least the unsintered bent portion of the unsintered heat generating portion of the unsintered heat generating resistor over the entire extending direction thereof, and a part of the unsintered heat-generating part is in the first molded body. On the other hand, the remaining portion has a shape protruding from the first molded body, and is located on the inner side in the radial direction of bending than the unfired bent-back portion of the first molded body of the semi-molded body. The part to be used is the inner part of the molded body, and the unfired A portion located on the outer side in the radial direction from the turnover portion is a molded body outer portion, and the second base body injected in the second molded body molding step of the molded body inner portion and the molded body outer portion. The part that the mixture reaches first is the front side of the molded body, the part that the mixture for the second substrate reaches after the unfired bent part is the rear side of the molded body, and the unfired bent part and the molded body At the rear boundary with the rear side portion, the depth buried in the first molded body of the unfired bent-back portion is the rear side depth, and the protruding height protruding from the first molded body is the rear side height. In this case, the half-molded body molding step is a method for manufacturing a ceramic heater for molding the half-molded body in a form in which at least the rear side height is smaller than the rear side depth.

  In this method of manufacturing a ceramic heater, after forming a semi-molded body in the semi-molded body molding step, in the second molded body molding step, the mixture for the second substrate containing the second insulating ceramic powder is changed in the distal direction or the base. Inject toward the end. Then, the injected mixture for the second substrate moves to the front end side or the base end side while in contact with the semi-molded body, reaches the unfired bent-back portion of the semi-molded body, and proceeds over this. The mixture for the second substrate cools slightly during the movement, but the adhesion decreases slightly with this. In addition, when comparing before and after overcoming the unfired bent-back portion, the mixture for the second base turns around and comes into close contact after overcoming, and pressure is not easily applied. For this reason, the condition after overcoming the unfired bent-back portion is likely to be a condition in which the second base mixture is less likely to adhere.

  Therefore, in this manufacturing method, in the semi-molded body molding step, the semi-molded body is molded into a form in which at least the rear side height is smaller than the rear side depth. Thereby, in the second molded body molding step, when the mixture for the second substrate gets over the unfired bent-back portion, in the vicinity of the boundary between the molded body rear side portion of the first molded body and the unfired bent-back portion. The first molded body and the second molded body can be brought into close contact with each other and can be integrated with no gap therebetween. For this reason, in the insulating base body of the ceramic heater after firing, in the vicinity of the bent portion of the heating resistor, a gap is formed at the interface between the first molded body and the second molded body. Formation of voids and voids arranged in a row is suppressed, and a highly durable ceramic heater can be manufactured.

Examples of the “ceramic heater” include a ceramic heater used for a glow plug and a ceramic heater used for heating a sensor portion of a gas sensor.
In addition, examples of the form of the “insulating base body having a shape extending along the axis” include polygonal column shapes such as a columnar shape, an elliptical column shape, a long columnar shape, and a quadrangular column. However, it may have a constricted part or a large diameter part.

In addition, the molding method of the first molded body of the half-molded body and the unheated heating resistor molded in the semi-molded body molding step may be an injection molding method, or other methods such as powder press, slip Casting or the like may be used.
Further, among the semi-molded bodies, the molding order of the first molded body and the unsintered heating resistor may be that the first molded body is molded first, and then the unsintered heating resistor is molded. Conversely, the unfired heating resistor may be molded first, and then the first molded body may be molded.
In addition, the first insulating ceramic powder constituting the first molded body and the second insulating ceramic powder constituting the second molded body of the semi-molded body may be the same powder, You may use the powder from which a component differs.

  Further, in the above-described method for manufacturing a ceramic heater, the second molded body molding step includes injecting the second substrate mixture toward the distal end through the base end of the semi-molded body, and It is good to use the manufacturing method of the ceramic heater which shape | molds 2 molded object.

  In the second molded body molding step, the mixture for the second substrate that has been heated to a high temperature is injected, so that the first molded body of the semi-molded body and the unfired heating resistance are brought into contact with the semi-molded body. Part of the body surface may melt. In particular, if this occurs in the vicinity of the unfired bent-back portion of the unfired heating resistor, the performance of the fired heating resistor may be degraded. On the other hand, the injected second substrate mixture moves a relatively long distance in the axial direction. For this reason, the mixture for the second substrate, which was at a high temperature immediately after the injection, is slightly cooled during this movement and becomes a lower temperature than immediately after the injection.

  Therefore, in this ceramic heater manufacturing method, in the second molded body molding step, the second base mixture is injected toward the distal end through the proximal end of the semi-molded body. Thereby, since the mixture for the second substrate becomes relatively low temperature at the tip side, the unfired bent-back portion of the unfired heating resistor and the surface of the first formed body in the vicinity thereof melt out of the semi-formed body. The fear can be reduced. Accordingly, it is possible to suppress a decrease in the performance of the ceramic heater after firing.

  Furthermore, in the method for manufacturing the ceramic heater described above, the depth of the unfired bent-back portion embedded in the first molded body at the front boundary between the unfired bent-back portion and the molded body front side portion. Is the front depth, and the protruding height protruding from the first molded body is the front height, the half molded body molding step is to form the half molded body in a form in which the front side height is smaller than the front side depth. A method of manufacturing a ceramic heater to be molded is preferable.

  In this method of manufacturing a ceramic heater, in the semi-molded body molding step, the semi-molded body is molded into a form in which the front side height is smaller than the front side depth among the unfired bent-back portions. By making the front side height smaller than the front side depth, the injected second substrate mixture can more easily get over the unfired bent-back portion in the second molded body forming step. For this reason, it is possible to further suppress the formation of a gap at the interface between the first molded body and the second molded body adjacent to each other in the vicinity of the unfired bent-back portion, and it is possible to manufacture a more durable ceramic heater.

Another aspect is an insulating base made of an insulating ceramic and having a shape extending along the axis, and a heating resistor embedded in the insulating base and made of a conductive ceramic, and is formed in the tip of the insulating base. A U-shape which is arranged and has a U-shape with a bent-back portion facing the tip direction in the axial direction along the axis, and the tip direction in the axial direction from both ends of the heat generation portion and the heat generation portion A glow plug manufacturing method comprising a glow plug ceramic heater comprising: a heating resistor having a lead portion extending in a direction opposite to the base end of the glow plug, wherein the ceramic heater is manufactured according to any one of the above The method includes a heater manufacturing process for manufacturing the ceramic heater, and a plug assembly process for assembling the glow plug using the ceramic heater. It is a Ropuragu method of manufacturing.

  In this blow plug manufacturing method, since the glow plug is manufactured using the highly durable ceramic heater obtained in the heater manufacturing process, the durability of the glow plug can be increased.

It is a longitudinal cross-sectional view of the glow plug which concerns on embodiment. It is a longitudinal cross-sectional view of the ceramic heater which concerns on embodiment. It is the longitudinal cross-sectional view seen from the direction orthogonal to FIG. 2 of the ceramic heater which concerns on embodiment. It is a perspective view of the front-end | tip part among the semi-molded bodies shape | molded by the semi-molded body shaping | molding process according to embodiment. It is explanatory drawing explaining the shaping | molding procedure of a 1st molded object among the semi-molded object shaping | molding processes of the manufacturing method of the ceramic heater which concerns on embodiment. It is explanatory drawing explaining the shaping | molding procedure of a non-baking exothermic resistor among the semi-molded body shaping | molding processes of the manufacturing method of the ceramic heater which concerns on embodiment. It is a longitudinal cross-sectional view of the front-end | tip part among the semi-molded bodies shape | molded by the semi-molded body shaping | molding process according to embodiment. 1 is a perspective view including a longitudinal section of a semi-molded product according to an embodiment. It is explanatory drawing explaining the 2nd molded object formation process among the manufacturing methods of the ceramic heater which concerns on embodiment. It is explanatory drawing explaining progress of the mixture for 2nd base | substrates in the 2nd molded object formation process among the manufacturing methods of the ceramic heater which concerns on embodiment. It is a longitudinal cross-sectional view of the ceramic heater before baking which concerns on embodiment. It is a longitudinal cross-sectional view of the front-end | tip part among the ceramic heaters before baking which concerns on embodiment. FIG. 6 is a perspective view including a longitudinal section of a current-carrying part molded body and a first base body molded body according to a conventional technique. It is a longitudinal cross-sectional view of the ceramic heater which concerns on a prior art.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a longitudinal sectional view of a glow plug 1 using a ceramic heater 2 according to the present embodiment.
As shown in FIG. 1, the glow plug 1 according to the present embodiment includes a ceramic heater 2 that generates heat by energization in the tip end direction HS (downward in FIG. 1) in the axial direction HJ along the axis AX.
In addition, it has a cylindrical metal shell 3 that holds the proximal end portion of the ceramic heater 2.
The metal shell 3 is composed of a heater holding member 4 that holds the ceramic heater 2 and is located in the distal direction HS of the metal shell 3 and a metal shell body 5 that is located in the proximal direction HK of the heater holding member 4. .
Among these, the metal shell main body 5 has a cylindrical shape extending from the base end portion 5k to the tip end portion 5s along the axis AX. A tool engagement portion 5 e having a hexagonal cross-sectional shape is formed at the base end portion 5 k of the metal shell main body 5. Further, in the metal shell body 5, a mounting screw portion 5 f is formed on the outer periphery on the tip side of the tool engaging portion 5 e.

  Inside the metal shell body 5, a rod-shaped metal terminal shaft 6 for supplying electric power to the ceramic heater 2 from the base end direction HK is electrically insulated from the metal shell body 5 via an insulating bush 7. It is arranged in the state.

  The heater holding member 4 has a cylindrical shape, and a base end portion 4 k is welded to a tip end portion 5 s of the metal shell main body 5. The heater holding member 4 is inserted and fixed at the base end side portion of the ceramic heater 2 described above. Specifically, the ceramic heater 2 is press-fitted into and held by the heater holding member 4 such that the distal end portion 2s and the base end portion 2k protrude from the heater holding member 4, respectively.

The base end portion 6k of the metal terminal shaft 6 inserted through the metal shell main body 5 is disposed so as to protrude from the metal shell main body 5 in the base end direction HK. A terminal fitting 8 is attached to the base end 6k via the insulating bush 7 described above.
On the other hand, the tip portion 6s of the metal terminal shaft 6 is inserted into a cylindrical connection ring 9 and welded thereto. The connecting ring 9 is press-fitted with the base end 2k of the ceramic heater 2 on the other side, and one electrode portion 18 (not shown in FIG. 1; see FIG. 2) provided on the base end 2k, It is electrically connected to the connection ring 9. Thereby, one electrode part 18 of the ceramic heater 2 and the metal terminal shaft 6 are electrically connected. The other electrode portion 19 (not shown in FIG. 1; see FIG. 2) of the ceramic heater 2 is electrically connected to the heater holding member 4 that holds the ceramic heater 2, and thus the metal shell 3. .

Next, the ceramic heater 2 according to this embodiment will be described. 2 and 3 are longitudinal sectional views of the ceramic heater 2.
As shown in FIGS. 2 and 3, the ceramic heater 2 has a columnar shape extending from the base end 2k to the front end 2s along the axis AX. The ceramic heater 2 is formed by embedding a heating resistor 11 that generates heat when energized in an insulating substrate 10 whose outer shape is cylindrical.

  Of these, the insulating base 10 is made of an insulating ceramic (specifically, a silicon nitride ceramic). The insulating base 10 extends in the axis AX direction from a base end 10 k corresponding to the base end 2 k of the ceramic heater 2 to a tip 10 s corresponding to the tip 2 s of the ceramic heater 2. The tip 2s has a rounded chamfer at the cylindrical corner.

  The heat generating resistor 11 embedded in the insulating base 10 is integrally formed of a heat generating portion 12 and a pair of lead portions 14 and 15 connected to the heat generating portion 12. The heating resistor 11 is made of a conductive ceramic (specifically, a silicon nitride ceramic containing tungsten carbide as a conductive component).

Among them, the heat generating portion 12 is disposed in the distal end portion 10s of the insulating base 10, and has a U-shape in which the bent-back portion 13 is directed toward the distal end direction HS in the axial direction HJ along the axis AX. It becomes a part to do.
The pair of lead portions 14 and 15 extend in parallel with each other from both ends 12a and 12b of the heat generating portion 12 toward the proximal direction HK opposite to the distal direction HS in the axial direction HJ.
One lead portion 14 of the heating resistor 11 is located in the vicinity of the base end portion 10 k of the insulating base 10, is exposed to the outer peripheral surface 10 g of the insulating base 10, and has an electrode portion 18 electrically connected to the connection ring 9. Have. The other lead portion 15 has an electrode portion 19 that is located slightly in the tip direction HS from the electrode portion 18, is exposed on the outer peripheral surface 10 g of the insulating base 10, and is electrically connected to the heater holding member 4. ing. Moreover, the electrode parts 18 and 19 are extended toward the outer side of the arrangement direction HN in which the lead parts 14 and 15 are arranged in a direction orthogonal to the axial direction HJ when viewed from the axis AX (see FIG. 2). In addition, in FIG. 3 seen from the direction orthogonal to FIG. 2, description of the electrode parts 18 and 19 is abbreviate | omitted.

Next, a method for manufacturing the ceramic heater 2 and the glow plug 1 according to this embodiment will be described.
First, the semi-molded body molding process will be described with reference to FIGS. FIG. 4 is a perspective view of the tip portion of the half-molded body 34 molded in the half-molded body molding step. In this step, a semi-molded body 34 having a first molded body 30 that becomes a part of the insulating substrate 10 by firing and an unfired heating resistor 33 that becomes the heating resistor 11 by firing is molded. Among these, the 1st molded object 30 consists of the 1st base material mixture KK1 which mixed the 1st insulating ceramic powder (mainly silicon nitride ceramic powder) and the 1st binder. The non-fired heating resistor 33 is composed of a heating element mixture KH in which conductive ceramic powder (silicon nitride ceramic powder containing tungsten carbide powder as a conductive component) and a second binder are mixed.

  The non-fired heating resistor 33 includes an unfired heat generating portion 31 that becomes the heat generating portion 12 by firing, and unfired lead portions 36 and 37 that extend from both ends of the unfired heat generating portion 31 and become the lead portions 14 and 15 after firing. . Among these, the unfired heat generating portion 31 includes an unfired bent-back portion 32 that becomes the bent-back portion 13 by firing. In addition, the unfired bent-back portion 32 has a U shape along the extending direction HE.

  Next, in the semi-molded body molding step, the molding procedure of the first molded body 30 and the unfired heating resistor 33 will be described. First, as shown in FIG. 5, the cavity CA is formed between the two molds 40, 41 by combining the two molds 40, 41 for molding the first molded body 30 up and down. Further, in the lower mold 41, the front end GS of the cavity CA is formed with a filling port 42, a gate 43, and an injection path SA that connects these and serves as a passage for the first substrate mixture KK1. . Next, using a not-shown injection device, the first substrate mixture KK1 is heated to form a fluid, and then injected from the filling port 42 toward the cavity CA. Thus, the 1st molded object 30 is shape | molded by the injection molding method.

  Next, as shown in FIG. 6, the first molded body 30 is used as a part of the mold while the first molded body 30 is left in the lower mold 41, while the upper mold 40 is not fired. It replaces | exchanges for another metal mold | die 44 provided with the recessed part corresponding to the form of the upper side of the heating resistor 33. FIG. Thereby, a cavity CB is formed between the first molded body 30 and the mold 44. Further, in the upper mold 44, the base end side GK of the cavity CB is formed with a filling port 45, a gate 46, and an injection path SB that connects these and serves as a passage for the heating element mixture KH. Next, using a not-shown injection device, the heating element mixture KH is heated to form a fluid, and then injected from the filling port 45 toward the cavity CB. In this manner, the non-fired heating resistor 33 is molded integrally with the first molded body 30 by the injection molding method to form the semi-molded body 34.

FIG. 7 is a longitudinal sectional view of the tip portion of the semi-molded product 34. FIG. 8 is a perspective view including this cross section. Here, the unfired bent-back portion 32 of the unfired heat generating portion 31 is partially embedded in the first molded body 30 over the entire extending direction HE, while the remaining portion protrudes from the first molded body 30. It is in form. And the site | part located in the inner side RI (right side in FIG. 7) of the radial direction HR of bending back from the unfired bending-back part 32 among the 1st molded objects 30 is the outer side of the molded body inner part 52 and radial direction HR. When the portion located on the RO (left side in FIG. 7) is the molded body outer portion 55, the molded body inner portion 52 is injected in the second molded body molding step (described later). (To be described later) becomes the molded body front side portion 52 that reaches first. Further, the outer side portion 55 of the molded body becomes the rear side portion 55 of the molded body that is reached after the second base mixture KK2 gets over the unfired bent-back portion 32 in the second molded body molding step. Here, in the unfired bent-back portion 32, the depth buried in the first molded body 30 is defined as the front depth at the front boundary 54 (inner boundary) with the molded body front side portion 52 (molded body inner portion). Let HD1 and the protrusion height which protruded from the 1st molded object 30 be front side height HH1. In addition, at the rear boundary 57 (outer boundary) with the rear side portion 55 (outer portion of the molded body), the depth buried in the first molded body 30 is defined as the rear depth HD2 and the first molded body 30. Let the protrusion height which protruded from the back side height HH2 be. At this time, the semi-molded body 34 has a front height HH1 smaller than the front depth HD1 and a rear height HH2 smaller than the rear depth HD2. Further, the rear height HH2 is smaller than the front height HH1.

Next, a 2nd molded object shaping | molding process is demonstrated with reference to FIGS. In this step, the second molded body 35 that becomes the remainder of the insulating base 10 by firing is molded integrally with the above-described semi-molded body 34. The second compact 35 is made of a second base mixture KK2 in which a second insulating ceramic powder (mainly silicon nitride ceramic powder) and a third binder are mixed.
In the present embodiment, the first substrate mixture KK1 and the second substrate mixture KK2 are composed of insulating ceramic powder and binder having the same components. That is, the first insulating ceramic powder and the second insulating ceramic powder, and the first binder and the third binder are composed of the same components.

  First, as shown in FIG. 9, the half-molded body 34 is placed on the lower mold 41 and is combined with the upper mold 47 for molding the second molded body. As a result, a cavity CC is formed between the half-molded body 34 and the mold 47. In addition, in the upper die 47, the base end side GK of the cavity CC is formed with a filling port 48, a gate 49, and an injection path SC that connects these and serves as a passage for the second substrate mixture KK2. . Next, using a not-shown injection device, the second substrate mixture KK2 is heated to form a fluid, and then injected from the filling port 48 toward the cavity CC.

  Then, as shown in FIG. 10, the injected second substrate mixture KK2 moves to the tip side GS while in contact with the semi-formed body 34, and reaches the unfired bent-back portion 32 of the semi-formed body 34. Furthermore, it gets over this and advances to the front end side GS. At that time, the semi-molded body 34 has a configuration in which the front height HH1 is smaller than the front depth HD1 and the rear height HH2 is smaller than the rear depth HD2 in the unfired bent-back portion 32. ing. For this reason, the mixture KK2 for the second substrate can easily get over the unfired bent-back portion 32, and when it gets over, the molded body rear side portion 55 of the first molded body 30 and the unfired bent-back portion 32 In the vicinity of the boundary, the first molded body 30 and the second molded body 35 can be in close contact with each other. Thus, the cavity CC is filled with the second base mixture KK2, and the second molded body 35 is molded integrally with the semi-molded body 34 to form an integrally molded product 60 as shown in FIGS. In the integrally molded product 60, the first molded body 30 and the second molded body 35 are in close contact with each other at their interfaces 61 and 62 and integrated.

  Then, the ceramic heater 2 is manufactured by baking the integrally molded product 60 which consists of the semi-molded body 34 and the 2nd molded object 35 by a well-known baking process.

  Further, separately from the ceramic heater 2, members (heater holding member 4, metal shell body 5, metal terminal shaft 6, etc.) constituting the glow plug 1 shown in FIG. 1 are prepared. Then, the glow plug 1 is completed by assembling these members by a known plug manufacturing process.

  As described above, in the method for manufacturing the ceramic heater 2 according to the present embodiment, in the semi-molded body molding step, the semi-molded body 34 is molded in a form in which the rear side height HH2 is smaller than the rear side depth HD2. . In the second molded body molding step, the second base mixture KK2 is injected toward the distal direction HS or the proximal direction HK. Then, the injected second substrate mixture KK2 moves to the front end side GS or the base end side GK while being in contact with the semi-formed body 34, and reaches the unfired bent-back portion 32 of the semi-formed body 34. Go ahead and proceed.

  Here, since the semi-molded body 34 is molded in a form in which the rear height HH2 is smaller than the rear depth HD2, the second base mixture KK2 to be the second molded body 35 is converted into a semi-molded body. 34, the first molded body 30 and the second molded body 35 are located in the vicinity of the boundary between the molded body rear side portion 55 of the first molded body 30 and the unfired bent-back section 32. And can be integrated with each other. For this reason, in the fired ceramic heater 2, there are gaps at the interfaces 61 and 62 between the first molded body 30 and the second molded body 35 in the vicinity of the bent-back portion 13 of the heating resistor 11 in the insulating substrate 10. The formation of slit-like voids and voids arranged in a row due to this was suppressed, and a highly durable ceramic heater 2 could be manufactured.

  In the present embodiment, after the semi-molded body 34 is molded in the semi-molded body molding step, the second base body passes through the base end 34K of the semi-molded body 34 and toward the tip 34S in the second molded body molding step. The mixture KK2 is injected. Then, the injected second substrate mixture KK2 moves in a relatively long distance in the axial direction HJ while being in contact with the semi-formed body 34. Then, the second substrate mixture KK2 slightly cooled during this movement reaches the unfired bent-back portion 32 of the semi-molded body 34 on the tip side GS.

  For this reason, according to the manufacturing method of the present embodiment, the second base mixture KK2 becomes relatively low temperature at the distal end side GS, and therefore, the unfired bending resistance of the unfired heating resistor 33 in the semi-formed body 34 is reduced. The possibility that the surface of the part 32 and the first molded body 30 in the vicinity thereof melts can be reduced. Accordingly, it is possible to suppress a decrease in performance of the ceramic heater 2 after firing.

In the present embodiment, in the semi-molded body molding step, the semi-molded body 34 is molded into a form in which the front height HH1 is smaller than the front depth HD1 in the unfired bent-back portion 32. Thereby, the mixture KK2 for the second base injected in the second molded body forming step can more easily get over the unfired bent-back portion 32. For this reason, it is possible to further suppress the generation of gaps at the interfaces 61 and 62 between the first molded body 30 and the second molded body 35 adjacent to each other in the vicinity of the unfired bent-back portion 32, and manufacture a ceramic heater 2 having higher durability. it can.
In the semi-molded body molding step, it is preferable to mold the semi-molded body 34 in a form in which the rear side height HH2 is equal to or smaller than the front side height HH1 in the unfired bent-back portion 32. By molding in this way, the first molded body 30 and the second molded body 35 that are less likely to adhere to the rear side than the front side can be brought into close contact with each other also on the rear side.

  Further, in the method for manufacturing the glow plug 1 according to the present embodiment, poor bonding at the interfaces 61 and 62 between the first molded body 30 and the second molded body 35 manufactured in the heater manufacturing process is unlikely to occur, and the durability is high. Since the high ceramic heater 2 can be used, the glow plug 1 can also have high durability.

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 it is needless to say that the present invention can be appropriately modified and applied without departing from the gist thereof. .
For example, in the above-described embodiment, the outer shape of the ceramic heater 2 and the insulating substrate 10 is a cylindrical shape. However, in addition to this, an elliptical column shape, a long column shape, a polygonal column shape such as a quadrangular column, or the like may be used. Or having a large diameter portion.
In the above-described embodiment, in addition to the second molded body 35, the first molded body 30 and the unfired heating resistor 33 of the semi-molded body 34 are molded by the injection molding method. As a molding method of the molded body 30 and the unfired heating resistor 33, a molding technique other than an injection molding method such as powder pressing or slip casting may be used.
In the above-described embodiment, in the semi-molded body molding step, the first molded body 30 is first molded, and then the unfired heating resistor 33 is molded integrally with the first molded body 30 to perform the semi-molding. A body 34 was formed. However, conversely, the unfired heating resistor 33 is first molded with a mold, transferred to another mold, and then integrally molded with the unfired heating resistor 33 in the first molding. A procedure for forming the body 30 and forming the semi-formed body 34 may be used.
In the above-described embodiment, the first base mixture KK1 and the second base mixture KK2 are both composed of the same insulating ceramic powder (mainly silicon nitride ceramic powder) and binder. However, as the insulating ceramic powder to be used, the same powder may be used, or powders having different manufacturing methods and components may be used.

AX Axis 1 Glow plug 2 Ceramic heater 2k (Ceramic heater) base end 2s (Ceramic heater) tip 10 Insulating base 10k (Insulating base) base 10s (Insulating base) tip HJ Axial direction HS Tip Direction HK Base end direction HN Alignment direction 11 Heating resistor 12 Heating part 13 Bending part 14, 15 Lead part 30 First molded body 31 Unsintered heating part 32 Unsintered bending part 33 Unsintered heating resistor 34 Semi-molded body 34K (Semi-molded body) Base end 34S (Semi-molded body) Tip 35 Second molded body HE Extension direction KK1 First substrate mixture KK2 Second substrate mixture KH Heating body mixture GK Base end side GS Tip side HR Radial direction RI (in the direction of bending) Inner RO (in the radial direction) Outer side 52 in the radial direction Inner part of the molded body (front side of the molded body)
54 Inner boundary (front boundary)
55 Molded body outer side (molded body rear side)
57 Outer boundary (rear boundary)
HH1 Front height HD1 Front depth HH2 Rear height HD2 Rear depth 60 Integral molded product

Claims (4)

An insulating base made of an insulating ceramic and having a shape extending along an axis;
A heating resistor embedded in the insulating substrate and made of a conductive ceramic,
A heating part that is disposed in the distal end portion of the insulating base and has a U-shape with the bent-back portion facing the distal end direction in the axial direction along the axis, and generates heat when energized; and
A heating resistor having a lead portion extending from both ends of the heat generating portion toward a base end direction opposite to the distal end direction in the axial direction,
A first molded body containing a first insulating ceramic powder and becoming a part of the insulating substrate by firing; and
An unsintered heat generating part that includes conductive ceramic powder and becomes the heat generating part when fired, and has an unsintered heat generating part including an unfired bent back part that becomes the bent back part when fired. A half-molded body molding step of molding a half-molded body having an unfired heating resistor to be a body,
By injection molding, the second base body containing the second insulating ceramic powder is injected toward the distal end direction or the base end direction, and the second molded body that becomes the remainder of the insulating base body by firing is obtained. A second molded body molding step of molding integrally with the semi-molded body,
The semi-molded body is
Among the unsintered heating resistors, at least the unsintered bent portion of the unsintered heating unit extends over the entire extending direction.
While a part is embedded in the first molded body,
The remaining portion has a form protruding from the first molded body,
Of the first molded body of the semi-molded body,
The part located inside the radial direction of bending than the unfired bending-back part is a molded body inner part,
A portion located outside the unfired bent-back portion in the radial direction is an outer portion of the molded body,
Of the molded body inner part and the molded body outer part,
In the second molded body molding step, the portion where the injected second base mixture reaches first is the front side of the molded body,
The portion that the mixture for the second substrate reaches after getting over the unfired bent-back portion is the rear side of the molded body,
At the rear boundary of the unfired bent-back portion and the rear side portion of the molded body, the depth buried in the first molded body of the unfired bent-back portion is defined as the rear depth, the first molded body. When the protruding height protruding from the rear side is
The semi-molded body molding step
A method for manufacturing a ceramic heater, wherein the semi-molded body is formed in a form in which at least the rear side height is smaller than the rear side depth. It is a manufacturing method of the ceramic heater according to claim 1,
The second molded body molding step includes:
A method for manufacturing a ceramic heater, wherein the second molded body is molded by injecting the second substrate mixture through the base end of the semi-molded body toward the distal end. A method of manufacturing a ceramic heater according to claim 1 or 2,
At the front boundary between the unfired bent-back portion and the front side portion of the molded body, the depth buried in the first molded body of the unfired bent-back portion protruded from the first molded body. When the protruding height is the front height,
The semi-molded body molding step includes:
A method of manufacturing a ceramic heater, wherein the semi-molded body is formed in a form in which the front height is smaller than the front depth. An insulating base made of an insulating ceramic and having a shape extending along an axis;
A heating resistor embedded in the insulating substrate and made of a conductive ceramic,
A heating part that is disposed in the distal end portion of the insulating base and has a U-shape with the bent-back portion facing the distal end direction in the axial direction along the axis, and generates heat when energized; and
A method of manufacturing a glow plug having a ceramic heater for a glow plug, comprising: a heating resistor having a lead portion extending from both ends of the heat generating portion toward a base end direction opposite to the distal end direction in the axial direction. Because
A heater manufacturing process for manufacturing the ceramic heater by the method for manufacturing a ceramic heater according to any one of claims 1 to 3,
A plug assembly process for assembling the glow plug using the ceramic heater;
A method for manufacturing a glow plug comprising:

Images