JP5844621B2 - Method for manufacturing ceramic heater, method for manufacturing glow plug, ceramic heater and glow plug - Google Patents

Description

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

  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 is held in a mold, and an insulating ceramic powder is produced. 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

However, in the manufacturing method described in Patent Document 1, a current-carrying part molded body that becomes a heating resistor is prepared in advance, and then the current-carrying part molded body is placed on the inner surface of the first mold member for base molding. Since it arrange | positions so that the surface of one side may contact | connect, it will be easy to produce the error in alignment in this arrangement | positioning. In addition, in the molded part for the current-carrying part, the shape of the U-shaped bent-back part serving as the heat-generating part and the lead part extending in the axial direction are easily broken before firing. For this reason, it is difficult to arrange the molded part for the current-carrying part on the inner surface of the first mold member for molding the base body without being deformed and without being displaced.
Following this, the substrate mixture is filled in the cavity formed between the second mold member for substrate molding disposed on the other side and the surface on the other side of the molded part for the current-carrying part. Thus, the first base molded body is molded. At this time, the current-carrying part molded body disposed on the first mold member is not necessarily in close contact with the first mold member, and part of the current-carrying part molded body, in particular, the U-shape. The bent-back portion may be arranged so as to be lifted from the first mold member. When the base mixture is filled in such a state, the current-carrying part molded body and the first base body molded body are molded with the bent-back portion being biased.
In this way, use is made of a position shift between the current-carrying part molded body and the first base body molded body, deformation of the current-carrying part molded body, deviation of the bent portion of the current-carrying part molded body, etc. Even if the ceramic heater is formed, the heat generation performance of the heat generating resistor may be reduced, or the insulation performance of the insulating base may be reduced, and the original performance of the ceramic heater may not be exhibited.

  The present invention has been made in view of the current 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 high reliability. An object of the present invention is to provide a method for producing a glow plug having a ceramic heater, a ceramic heater, and a glow plug having the 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. A first molded body molding step for molding one molded body, a resistor molding step for molding an unfired heating resistor that includes conductive ceramic powder and becomes the heating resistor by firing, and a second insulating ceramic And a second molded body molding step that forms a second molded body that includes the powder powder and that becomes the remainder of the insulating base body by firing, wherein the resistor molding step is performed when the unfired heating resistor is molded. Using the first molded body as a part of the resistor molding die, the unfired heating resistor is molded integrally with the first molded body by an injection molding method, and the second molded body molding step includes: The second molded body is used as a part of a second molded body molding die when the second molded body is molded, and the second molded body is used as the first molded body and the unsintered heating resistor. The ceramic heater is formed integrally with the unsintered heating resistor, and the first molded body molding step is a method of manufacturing a ceramic heater in which a recess suitable for the form of the unsintered heating resistor is formed in the first molded body. .

  In this ceramic heater manufacturing method, in the first molded body molding step, a first molded body that becomes a part of the insulating substrate is molded in advance by firing, and in the resistor molding step, a heat generating resistor is not formed that becomes a heating resistor by firing. The first molded body is used as a part of the resistor mold when the fired heating resistor is molded. Furthermore, in the second molded body molding step, the first molded body and the unfired heating resistor are used as a part of the second molded body molding die when the second molded body that becomes the remaining portion of the insulating substrate is molded by firing. . Thereby, the unsintered heating resistor is molded on the basis of the first molded body, and further, the second molded body is molded on the basis of the first molded body and the unsintered heating resistor. For this reason, misalignment is unlikely to occur among the first molded body, the unfired heating resistor, and the second molded body. In addition, since the first molded body is molded first, and the unfired heating resistor is molded using this first molded body as a part of the resistor molding die, the shape of the unfired heating resistor is not deformed. There is no problem. Moreover, since the unsintered heating resistor is formed integrally with the first molded body, there is no problem that the unsintered heating resistor floats from the mold. Accordingly, it is possible to manufacture a highly reliable ceramic heater that is less likely to cause a decrease in heat generation performance and a decrease in insulation performance as compared with a conventional manufacturing method.

In addition, in the resistor molding step, the unsintered heating resistor is molded by the injection molding method using the first molded body as a part of the resistor molding die. It is not necessary to produce a part of the mold (part corresponding to the first molded body).
For this reason, a ceramic heater can be manufactured easily and inexpensively compared with the above-mentioned prior art.
Furthermore, in this method for manufacturing a ceramic heater, in the first molded body molding step, a concave portion suitable for the form of the unfired heating resistor is formed in the first molded body. Thereby, in a resistor shaping | molding process, a non-baking exothermic resistor can be shape | molded using the recessed part of this 1st molded object for a part of resistor shaping | molding die. For this reason, the unsintered heating resistor can be reliably integrated with the first molded body, and the misalignment between the unsintered heating resistor and the first molded body is less likely to occur. Therefore, it is possible to manufacture a ceramic heater that is less susceptible to performance degradation and has high reliability.

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.

The molding method of the first molded body molded in the first molded body molding step and the second molded body molded in the second molded body molding step may be an injection molding method, or other methods such as a powder press A method such as slip casting may be used.
Moreover, the 1st insulating ceramic powder which comprises a 1st molded object, and the 2nd insulating ceramic powder which comprises a 2nd molded object may use the same powder, and use the powder from which a manufacturing method and a component differ. May be.

  Furthermore, in the above-described method for manufacturing a ceramic heater, the resistor molding step is performed by placing the conductive ceramic powder in the resistor cavity formed by the resistor mold from the base end to the tip. It is preferable to use a method for manufacturing a ceramic heater in which the unheated heating resistor is formed by injecting a heating element mixture.

  The injected heating element mixture has a high temperature immediately after injection, but becomes relatively low after moving through the resistor cavity. On the other hand, in the resistor cavity formed by the resistor mold, the first molded body constitutes a part in addition to the mold. Therefore, in the first molded body molded in the first molded body molding process, in the subsequent resistor molding process, a part of the surface may be melted by the high-temperature heating element mixture. It becomes prominent near the exit. By the way, when a part of the surface of the first molded body is melted, the first insulating ceramic powder forming the first molded body is formed into a film shape (whisker-like in cross section) in the molded unfired heating resistor. May get involved. As a result, a film-like insulating ceramic portion in which the insulating ceramic extends in a film shape can be formed in the heating resistor of the fired ceramic heater. This film-like insulating ceramic part has no risk of lowering the insulating performance of the ceramic heater. However, when the film-like insulating ceramic part is formed in the heat generating part including the bent back part, there is a possibility that the heat generating performance of the ceramic heater is affected.

  On the other hand, in this ceramic heater manufacturing method, the heating element mixture is injected into the resistor cavity from the proximal end to the distal end. As a result, among the unfired heat generating resistors, the heating element mixture is relatively low in the vicinity of the bent portion before firing (hereinafter referred to as the unfired bent portion), so that the surface of the first molded body is hardly melted. In addition, the first insulating ceramic powder is not easily wound into a film shape in the unfired bent-back portion. Accordingly, it is possible to suppress a decrease in the heat generation performance of the ceramic heater after firing.

  Furthermore, in the method for manufacturing a ceramic heater described above, the first molded body molding step includes a resistor side mold that forms a joint surface with the unfired heating resistor on the first molded body, The first molded body is molded using an outer mold that forms a part of the outer peripheral surface of the insulating base body by firing of one molded body, and the resistor molding step is performed. With the first molded body disposed in the outer mold, the outer mold and the first molded body are used as a part of the resistor molding mold to mold the unfired heating resistor, In the second molded body molding step, the unfired heating resistor and the first molded body integrated with the unfired heating resistor are disposed in the outer mold, and the outer mold, the first molded body, and the An unsintered heating resistor is used as a part of the second molded body mold, and the second component is formed. May the method for producing a ceramic heater molding the body.

  In this ceramic heater manufacturing method, the outer mold is used in any of the first molded body molding process, the resistor molding process, and the second molded body molding process. Thus, after the first molded body is molded, the unfired heating resistor and the second molded body can be molded without exchanging the outer mold, so that there is no displacement due to mold replacement. In addition, the number of man-hours required for die replacement can be reduced, and the number of required dies can be reduced, so that the ceramic heater can be manufactured easily and inexpensively.

  Furthermore, in the method for manufacturing a ceramic heater described above, the first molded body molding step is performed by molding the first molded body by an injection molding method, and the second molded body molding step is performed by an injection molding method. A method of manufacturing a ceramic heater for forming the second molded body is preferable.

  In this ceramic heater manufacturing method, in addition to the unfired heating resistor, the first molded body and the second molded body are also molded by the injection molding method. For this reason, the injection molding method is used for all of the first molded body, the unsintered heating resistor, and the second molded body, so that manufacturing facilities can be shared and costs can be reduced.

  Furthermore, in the above-described method for manufacturing a ceramic heater, the second molded body molding step includes a second molded body cavity formed by the second molded body molding die, from the base end to the tip. A method of manufacturing a ceramic heater for injecting a mixture for a second substrate containing the second insulating ceramic powder to form the second molded body is preferable.

As described above, in the resistor molding step, a part of the surface of the first molded body may be melted by the high-temperature heating element mixture. On the other hand, in the second molded body molding step, since the high-temperature mixture for the second substrate is injected, a part of the surfaces of the first molded body and the unfired heating resistor may be melted by the second substrate mixture. is there. Also in this case, if this occurs in the vicinity of the unfired bent-back portion, the performance of the heat-generating resistor after firing may be deteriorated.
Therefore, in this ceramic heater manufacturing method, in the second molded body molding step, the second molded body is injected into the second molded body cavity from the base end to the distal end, and the second molded body is injected. Is molded. Thereby, in the second molded body molding step, it is possible to reduce the possibility that the unfired bent-back portion of the unfired heating resistor and the surface of the first molded body in the vicinity thereof will melt due to the high temperature mixture for the second substrate. . Accordingly, it is possible to suppress a decrease in the performance of the ceramic heater after firing.

  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 glow plug manufacturing method, since the glow plug is manufactured using the ceramic heater having high reliability and good characteristics obtained in the heater manufacturing process, good characteristics can be obtained even in the glow plug. .

  Another aspect is a ceramic heater, which is an insulating base made of an insulating ceramic and having a shape extending along an axis, and a heating resistor embedded in the insulating base and made of a conductive ceramic. A heating element that is disposed in the distal end portion of the insulating substrate and has a U-shape with the bent-back portion facing the distal end of the axial direction along the axis, and generates heat when energized, and the axial line extends from both ends of the heating portion. A heating resistor having a lead portion extending in a proximal direction opposite to the tip direction, the lead portion of the heating resistor from the insulating base in contact with the insulating ceramic. Is a ceramic heater having a film-like insulating ceramic portion extending like a film in the lead portion.

A ceramic heater having a film-like insulating ceramic part in a lead part is formed by pre-molding a first molded body containing an insulating ceramic powder in a molding process before firing, and then contacting the conductive ceramic powder. It is manufactured by injection-molding an unfired heating resistor containing
On the other hand, in the case of forming in the reverse order to the heater adopting this forming order, that is, when forming the first formed body after forming the non-fired heating resistor as in the conventional case, in the lead portion. The film-like insulating ceramic part is not formed. In this case, a part of the surface of the unfired heating resistor melts into the first molded body, so that a film-like conductive ceramic portion is formed in a portion of the insulating base corresponding to the first molded body. .
Accordingly, the heater having the film-like insulating ceramic part is obtained by molding the first molded body in advance and then molding the unfired heating resistor. As described above, by adopting this molding sequence, the performance is improved. A good and reliable ceramic heater can be obtained.

  Another aspect is a glow plug including the ceramic heater described above.

  This glow plug is provided with a highly reliable ceramic heater, and the glow plug itself can be highly reliable.

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 explanatory drawing explaining the 1st molded object formation process among the manufacturing methods of the ceramic heater which concerns on embodiment. It is explanatory drawing explaining a resistor shaping | molding process among the manufacturing methods of the ceramic heater which concerns on 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 a longitudinal cross-sectional view of the ceramic heater before baking which concerns on embodiment. It is a cross-sectional view of the ceramic heater according to the embodiment.

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 distal end 2s (left side of FIGS. 2 and 3) from a base end 2k (right side of FIGS. 2 and 3; upper side in FIG. 1) along the axis AX. It has a cylindrical shape extending to the lower side in FIG. 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 each extended toward the outer side of the parallel direction HH which orthogonally crosses the axial direction HJ seeing from the axis line AX and the lead parts 14 and 15 are arranged in parallel (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 (see FIGS. 4 to 6).
First, a 1st molded object shaping | molding process is demonstrated with reference to FIG. In this step, the first molded body 35 that becomes a part of the insulating substrate 10 is molded by firing using the resistor side mold 30 and the outer mold 31.

Among these, the outer die 31 arranged below in FIG. 4 has an outer peripheral surface 39 (lower side in FIG. 4) of the first molded body 35 that becomes a part of the outer peripheral surface 10g of the insulating base 10 by firing. This is a mold to be formed.
On the other hand, the resistor-side mold 30 disposed in the upper side in FIG. 4 is a portion on one side (of the heating resistor 11 shown in FIG. 3) of the unfired heating resistor 44 that becomes the heating resistor 11 by firing. This is a mold for forming a recess 38 in the first molded body 35 that conforms to the outline of the lower half portion).
The resistor side mold 30 has a convex portion corresponding to the shape of the concave portion 38.

  Then, by combining the resistor side mold 30 and the outer mold 31, a first molded body cavity CA is formed between the two molds 30 and 31. Further, in the outer die 31, the front end GS (left side in FIG. 4) of the first molded body cavity CA is filled with a filling port 32, a gate 34, and a first base mixture described below. An injection path SA is formed as a passage for KK1.

  Next, using an injection device (not shown), the first base mixture KK1 mixed with the first insulating ceramic powder (mainly silicon nitride ceramic powder) and the first binder is heated to form a fluid, and then the filling port Injection from 32 toward the first molded object cavity CA. In this way, by injection molding, the first base mixture KK1 is injected and filled into the first molded body cavity CA from the front end CAS to the base end CAK, so that the concave portion 38 and the semicylindrical shape are formed. A first molded body 35 having an outer peripheral surface 39 is molded. At this time, the first molded body runner 33 is formed in the injection path SA from the filling port 32 to the gate 34 together with the molding of the first molded body 35.

Next, the resistor molding step will be described with reference to FIG. In this step, first, the first molded body 35 molded in the previous first molded body molding step is left inside the outer mold 31, while the resistor molding mold is replaced with the resistor side mold 30. 40 is used. In FIG. 5, the resistor molding die 40 arranged on the upper side is a mold that forms an outer shape on the other side of the unfired heating resistor 44 (a schematic upper half of the heating resistor 11 shown in FIG. 3). .
And while combining this resistor shaping | molding die 40 and the outer side die 31, and using the 1st molded object 35 shape | molded previously as a part of resistor shaping | molding die, the recessed part formed in the 1st molded object 35 A resistor cavity CB is formed between the resistor 38 and the resistor molding die 40. Further, in the resistor molding die 40, the base end side GK (right side in FIG. 5) of the resistor cavity CB is filled with a filling port 41, a gate 43, and a heating element mixture described below. An injection path SB serving as a path for KH is formed.

  Next, using an injection device (not shown), the heating element mixture KH in which the conductive ceramic powder (silicon nitride ceramic powder containing tungsten carbide powder as a conductive component) and the second binder are mixed is heated to obtain a fluid. Above, it injects from the filling port 41 toward the resistor cavity CB. In this way, the heating element mixture KH is injected and filled into the resistor cavity CB from the base end CBK toward the tip CBS by the injection molding method, and the unsintered heating resistor 44 is first molded. Molded integrally with the body 35. In addition to the molding of the unfired heating resistor 44, a resistor runner 42 is formed in the injection path SB from the filling port 41 to the gate 43.

  As a result, the non-fired heating resistor 44 is substantially half-filled (lower side in FIG. 5) in the first molded body 35, and the rest (upper side in FIG. 5) is exposed and protrudes from the first molded body 35. It is molded into the shape. The unfired heating resistor 44 has unfired lead portions 53 and 54 that become the lead portions 14 and 15 when fired, and the tip side GS becomes the bent portion 13 of the heating resistor 11 when fired. An unfired bent-back portion 45 is provided. A part of the surface of the first molded body 35 used as a part of the resistor molding die is melted in the unfired heating resistor 44 by the high temperature heating element mixture KH. The first insulating ceramic powder that forms the molded body 35 may be wound in a film shape (whisker shape in cross section). For this reason, in the heating resistor 11 of the ceramic heater 2 after firing, a film-like insulating ceramic portion 70 in which the insulating ceramic extends from the insulating base 10 in a film shape may be formed (see FIG. 8). . However, in the present embodiment, the heating element mixture KH is injected into the resistor cavity CB from the base end CBK toward the tip CBS. Therefore, of the unfired heating resistor 44 before firing, In the vicinity of the unfired bent-back portion 45 on the tip side GS, the heating element mixture KH becomes relatively low in temperature. For this reason, compared with the lead portions 14 and 15 in the heat generating resistor 11 after firing, the above-described film-like insulating ceramic portion 70 is not easily formed in the heat generating portion 12 including the bent-back portion 13.

  Thereafter, in the runner removal process, the resistor runner 42 and the first molded body runner 33 are removed from the portions of the gate 43 and the gate 34 before the next second molded body molding process.

Next, a 2nd molded object shaping | molding process is demonstrated with reference to FIG. In this step, first, the second molded body mold 60 is replaced with the resistor molding mold 40 while the first molded body 35 and the unfired heating resistor 44 integrated with each other are left in the outer mold 31. Use. In FIG. 6, the second molded body mold 60 disposed on the upper side is a mold that forms the outer peripheral surface of the second molded body 64 that becomes the remaining part of the insulating base 10 after firing.
The second molded body mold 60 and the outer mold 31 are combined, and the previously molded first molded body 35 and the unfired heating resistor 44 are used as a part of the second molded body mold. The second molded body cavity CC is formed between the first molded body 35 and the unfired heating resistor 44 and the second molded body mold 60. Further, in the second molded body mold 60, the filling port 61, the gate 63, and the first described below are connected to the base end side GK (right side in FIG. 6) of the second molded body cavity CC. An injection path SC is formed as a passage for the two-substrate mixture KK2.

  Next, using a not-shown injection device, the second base mixture KK2 mixed with the second insulating ceramic powder (mainly silicon nitride ceramic powder) and the third binder is heated to form a fluid, and then the filling port From 61, it inject | emits toward the cavity CC for 2nd molded objects. In this way, by injection molding, the second base mixture KK2 is injected and filled into the second molded body cavity CC from the base end CCK to the front end CCS, and the second molded body 64 is filled with the second molded body 64. 1 The molded body 35 and the unfired heating resistor 44 are molded integrally. In addition to the molding of the second molded body 64, a second molded body runner 62 is formed in the injection path SC from the filling port 61 to the gate 63. 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.

  Thereafter, the integrally molded product 65 (see FIG. 7) composed of the first molded body 35, the unfired heating resistor 44 and the second molded body 64, from which the second molded body runner 62 has been removed, is fired by a known firing process. Thus, the ceramic heater 2 is manufactured.

  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 a ceramic heater according to the present embodiment, the first molded body 35 is formed in advance in the first molded body molding step, and the unfired heating resistor 44 is formed in the resistor molding step. The first molded body 35 is used as a part of the resistor molding die when molding. Further, in the second molded body molding step, the first molded body 35 and the unfired heating resistor 44 are used as a part of the second molded body molding die when the second molded body 64 is molded. Thereby, the unsintered heating resistor 44 is molded with the first molded body 35 as a reference, and the second molded body 64 is molded with the first molded body 35 and the unsintered heating resistor 44 as a reference. For this reason, misalignment is unlikely to occur among the first molded body 35, the unfired heating resistor 44, and the second molded body 64. Further, since the first molded body 35 is first molded, and the unfired heating resistor 44 is molded using the first molded body 35 as a part of the resistor molding die, the unfired heating resistor 44 is disposed. There will be no problem of losing shape. Further, since the unsintered heating resistor 44 is formed integrally with the first molded body 35, there is no problem that the unsintered heating resistor 44 floats from the mold. Therefore, it is possible to manufacture a highly reliable ceramic heater 2 that is less likely to cause a decrease in heat generation performance and a decrease in insulation performance as compared with a conventional manufacturing method.

In addition, in the present embodiment, in the resistor molding step, the unsintered heating resistor 44 is molded by the injection molding method using the first molded body 35 as a part of the resistor molding die. It is not necessary to produce a part of the mold of the resistor 44 (part corresponding to the first molded body 35).
For this reason, a ceramic heater can be manufactured easily and inexpensively compared with the above-mentioned prior art.

  Further, in the present embodiment, in the first molded body molding step, the first molded body 35 is formed with the concave portion 38 that matches the form of the unfired heating resistor 44. Thus, in the resistor molding step, the unfired heating resistor 44 can be molded using the recess 38 of the first molded body 35 in a part of the resistor molding die. For this reason, the unsintered heating resistor 44 can be reliably integrated with the first molded body 35, and the misalignment between the unsintered heating resistor 44 and the first molded body 35 is less likely to occur. Accordingly, it is possible to manufacture the ceramic heater 2 which is less likely to cause the performance degradation and has high reliability.

A film-like insulating ceramic portion 70 in which an insulating ceramic extends in a film shape may be formed in the heating resistor 11 of the ceramic heater 2 after firing. Although this film-like insulating ceramic part 70 has no risk of lowering the insulation performance of the ceramic heater 2, when the film-like insulating ceramic part 70 is formed in the heat generating part 12 including the bent-back part 13, There is a possibility of affecting the heat generation performance of the ceramic heater 2.
On the other hand, in the present embodiment, in the resistor molding step, the heating element mixture KH is injected from the base end CBK toward the tip CBS into the resistor cavity CB formed by the resistor mold. The non-fired heating resistor 44 is formed.
As a result, in the vicinity of the unfired bent-back portion 45 of the unfired heating resistor 44, the heating element mixture KH has a relatively low temperature. It is difficult for the first insulating ceramic powder to be wound into a film. Accordingly, it is possible to suppress a decrease in the heat generation performance of the ceramic heater 2 after firing.

  In the present embodiment, the outer mold 31 is used in any of the first molded body molding process, the resistor molding process, and the second molded body molding process. Thereby, after the first molded body 35 is molded, the non-fired heating resistor 44 and the second molded body 64 can be molded without replacing the outer mold 31, so that there is no displacement due to mold replacement. . Moreover, since the man-hour required for die replacement can be reduced and the required die can be reduced, the ceramic heater 2 can be manufactured easily and inexpensively.

  In the present embodiment, in addition to the unfired heating resistor 44, the first molded body 35 and the second molded body 64 are also molded by the injection molding method. For this reason, the injection molding method is used for all of the first molded body 35, the unfired heating resistor 44, and the second molded body 64, so that manufacturing facilities can be shared and costs can be reduced.

  In the present embodiment, in the second molded body molding step, in the second molded body cavity CC formed by the second molded body molding die, the mixture for the second substrate from the base end CCK toward the distal end CCS. The second molded body 64 is molded by injecting KK2. For this reason, in the second molded body molding step, the surface of the unsintered bent portion 45 of the unsintered heating resistor 44 and the surface of the first molded body 35 in the vicinity thereof is melted by the high temperature mixture KK2 for the second substrate. The fear can be reduced. Accordingly, it is possible to suppress a decrease in performance of the ceramic heater 2 after firing.

  Further, in the production direction of the glow plug 1 according to the present embodiment, since the ceramic heater 2 having high characteristics and high reliability manufactured in the heater manufacturing process can be used, the glow plug 1 also has good characteristics. Can be obtained.

The ceramic heater 2 having the film-like insulating ceramic portion 70 in the lead portions 14 and 15 is formed so that the first molded body 35 containing the insulating ceramic powder is formed in advance in the forming process before firing, and then comes into contact therewith. In addition, the non-fired heating resistor 44 containing conductive ceramic powder is manufactured by injection molding.
And in the ceramic heater 2 of this embodiment which employ | adopted this shaping | molding order, the reliable ceramic heater 2 with favorable performance is obtained compared with the conventional heater shape | molded in the reverse order.

  In addition, since the glow plug 1 according to the present embodiment includes such a highly reliable ceramic heater 2, the glow plug 1 itself can also have high reliability.

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 base 10 is a cylindrical shape. Or having a large diameter portion.
In the above-described embodiment, in addition to the unfired heating resistor 44, the first molded body 35 and the second molded body 64 are molded by the injection molding method, but the first molded body 35 and the second molded body 64 As the molding method, a molding method other than an injection molding method such as powder pressing or slip casting 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 Insulation base 10k (Insulation base) base 10s (Insulation base) tip 10g Insulation base Surface HJ Axis direction HS Tip direction HK Base end direction HH Parallel direction GS Tip side GK Base end side 11 Heating resistor 12 Heating portion 13 Bending portion 14, 15 Lead portion 18, 19 Electrode portion 30 Resistor side mold 31 Outer die Mold 33 First molded body runner 34 Gate 35 First molded body CA First molded body cavity CAS (of the first molded body cavity) Tip CAK (of the first molded body cavity) 38 Recessed portion 39 First molded body Body outer peripheral surface KK1 First substrate mixture 40 Resistor molding die 42 Resistor runner 43 Gate 44 Unsintered heating resistor 45 Unsintered bent portion C Resistor cavity CBS (resistor cavity) tip CBK (resistor cavity) proximal KH heating element mixture 64 second molded body CC second molded body cavity CCS (second molded body cavity) Tip CCK Base end KK2 (for second molded body cavity) Mixture 65 for second substrate 65 Molded body 70 Film-like insulating ceramic part

Claims (8)

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 molding step, which includes a first insulating ceramic powder and molds a first molded body that becomes a part of the insulating base by firing;
A resistor forming step of forming a non-fired heating resistor comprising the conductive ceramic powder and becoming the heating resistor by firing;
A second molded body molding step that includes a second insulating ceramic powder and molds a second molded body that becomes the remainder of the insulating substrate by firing,
The resistor molding step is
Using the first molded body as a part of the resistor molding die when molding the unfired heating resistor, the unsintered heating resistor is molded integrally with the first molded body by an injection molding method. And
The second molded body molding step includes
Using the first molded body and the unfired heating resistor as a part of the second molded body mold when molding the second molded body, the second molded body and the first molded body and Molded integrally with the unfired heating resistor ,
The first molded body molding step includes:
A method for manufacturing a ceramic heater, wherein the first molded body is formed with a recess adapted to the form of the unfired heating resistor . It is a manufacturing method of the ceramic heater according to claim 1 ,
The resistor molding step includes
A ceramic for forming the unfired heating resistor by injecting a mixture for the heating element containing the conductive ceramic powder from the base end to the tip end in the resistor cavity formed by the resistor molding die. A method for manufacturing a heater. A method of manufacturing a ceramic heater according to claim 1 or 2 ,
The first molded body molding step includes:
A resistor side mold for forming a bonding surface with the unfired heating resistor on the first molded body;
Of the first molded body, the first molded body is molded using an outer mold that forms a part of the outer peripheral surface of the insulating substrate by firing,
The resistor molding step includes
With the molded first molded body arranged in the outer mold, the unfired heating resistor is molded using the outer mold and the first molded body as a part of the resistor mold. And
The second molded body molding step includes:
The outer mold, the first molded body, and the unfired heating resistor are placed in the second mold in a state where the unfired heating resistor and the first molded body integrated with the unfired heating resistor are arranged in the outer mold. A method for manufacturing a ceramic heater, which is used as a part of a molded body molding die to mold the second molded body. It is a manufacturing method of the ceramic heater as described in any one of Claims 1-3 ,
The first molded body molding step includes:
The first molded body is molded by an injection molding method,
The second molded body molding step includes:
A method for manufacturing a ceramic heater, wherein the second molded body is formed by an injection molding method. It is a manufacturing method of the ceramic heater of Claim 4 , Comprising:
The second molded body molding step includes:
The second base mixture containing the second insulating ceramic powder is injected from the base end to the tip end in the second compact cavity formed by the second compact, and the second base A method for manufacturing a ceramic heater for forming a molded body. 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
The heater manufacturing process which manufactures the said ceramic heater by the manufacturing method of the ceramic heater as described in any one of Claims 1-5 ,
A plug assembly process for assembling the glow plug using the ceramic heater;
A method for manufacturing a glow plug comprising: 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 the proximal direction opposite to the distal end direction in the axial direction,
The lead portion of the heating resistor is
A ceramic heater having a film-like insulating ceramic portion in which the insulating ceramic extends in a film shape in the lead portion from an insulating base in contact therewith. A glow plug comprising the ceramic heater according to claim 7 .

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