JP2016143625A - Ceramic heater and glow plug - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ceramic heater which allows for long term use of a mold used in the injection molding of a ceramic heater.SOLUTION: A ceramic heater 800 includes: a substrate 810; a heating part 833 including a front end 832, and a pair of legs 834a,b extending from the front end 832 toward rear end; and conductive parts 836a,b connected with the legs 834a,b and extending to the rear end side. A ratio S1/S2 of a smallest cross-sectional area S1 of the heating part 833 to a cross-sectional area S2 of the legs 834a,b is 0.4 or less. The heating part 833 includes convex parts 8341-8351 provided with a cross-sectional area smaller than the legs 834a,b on the legs 834a,b. The convex parts 8341-8351 are disposed at positions farther from other legs 834a,b than a part closest thereto.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a ceramic heater used for a glow plug or the like.

  A ceramic heater used for a glow plug has a rod-like form in which a ceramic resistor made of a conductive ceramic is embedded in a ceramic base made of an insulating ceramic. The ceramic resistor is arranged in a form extending along the direction of the axis of the heater body on the rear side of the first resistor part arranged at the tip of the heater body, and the tip part is the first resistor. It has a pair of second resistor parts made of ceramic with lower resistivity while being bonded to both ends in the energization direction of the body part (Patent Document 1). This ceramic resistor is formed by injection molding.

JP 2003-22889 A International Publication No. 2008/123296 Pamphlet JP 2006-35630 A

  In the injection molding, after the filling material reaches the inside of the injection space inside the mold, the pressure of the filling material in the injection space rapidly increases until the injection of the filling material is stopped. As a result, the high-pressure filling material may enter the mating surfaces of the molds and become burrs. The filling material for the ceramic resistor includes a material having high hardness such as tungsten carbide. When these materials having high hardness repeatedly enter the mating surfaces of the molds, the mating surfaces of the molds are worn, gaps between the molds increase, and burrs are more likely to occur. As a result, in the injection molding of the ceramic resistor, the mold cannot be used earlier than in the resin injection molding.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.

(1) According to one form of this invention, a ceramic heater is provided. The ceramic heater includes: a base made of insulating ceramic; a heat generating part made of conductive ceramic and embedded in the base; a front end located at a front end of the heat generating part; and from the front end A heat generating portion comprising a pair of legs extending toward the rear end; and a conductive ceramic different from the conductive ceramic of the heat generating portion, embedded in the base, and each of the legs A pair of conductive portions that are connected and extend toward the rear end side while maintaining a substantially constant cross-sectional area. The ratio S1 / S2 of the cross-sectional area S1 of the portion having the smallest cross-sectional area of the heat generating portion to the cross-sectional area S2 of the leg portion is 0.4 or less. The heat generating part includes a convex part provided on the leg part with a cross-sectional area smaller than the cross-sectional area of the leg part in the direction from the front end to the rear end. The part where the convex part is arranged is provided at a position farther from the other leg part than the part closest to the other leg part in the part of the leg part where the convex part is provided. It has been.
According to such an aspect, when the heat generating portion is injection-molded, the filling material can be further filled into the convex portion even after the filling material has spread over the leg portion and the connection portion. For this reason, after the filling material reaches the legs and the connecting portion, the degree of the pressure rise of the filling material until the injection of the filling material is stopped is reduced as compared with the aspect without the protrusion. be able to. Therefore, there is a high possibility that the generation of burrs in the heat generating portion can be prevented. As a result, the wear of the gap between the molds can be reduced. Furthermore, the convex part is a part of the leg part provided with the convex part, and is provided at a position farther from the other leg part than the part closest to the other leg part. There is a low possibility that the heat generating portion made of ceramic is short-circuited by the convex portion.

(2) In the ceramic heater of the above aspect, the convex portion is provided at a position not on a line segment connecting the shortest distances of the leg portions in an arbitrary cross section perpendicular to the extending direction of the pair of leg portions. It can be set as the aspect currently provided. The part on the line connecting the axis of each leg is the innermost part of each leg of the heat generating part, and the part where the current density is highest in each cross section when the heat generating part is energized. There is a high possibility. In the said aspect, since the convex part is provided in the position which is not on the said line segment which connects the axis line of each leg part, the risk of such abnormal heat generation is low.

(3) In the ceramic heater of the above aspect, the convex portion may be provided in a portion other than the portion having the smallest cross-sectional area in the heat generating portion. In such an aspect, during operation of the ceramic heater, the direction in which the current flows is the highest in the portion where the cross-sectional area is minimum. In the said aspect, since the convex part is provided in parts other than the part where cross-sectional area is the minimum among heat generating parts, possibility that abnormal heat generation of a convex part can be prevented is high.

(4) In the ceramic heater of the above aspect, the convex portion may be provided at a connection portion between the leg portion and the conductive portion, and may be in contact with the conductive portion. If it is set as such an aspect, a convex part does not protrude in the external shape of the member by the electroconductive ceramic comprised by a heat-emitting part and an electroconductive part. For this reason, the possibility that the convex portion adversely affects other surrounding members is low.

(5) In the ceramic heater of the above aspect, the convex portion includes a first portion and a second portion having a cross-sectional area larger than that of the first portion along a direction away from the leg portion. It can be set as an aspect. If it is such an aspect, when the heat generating part is injection-molded, the first part is sized so that the convex part is not filled with the filling material before the filling material reaches the leg part and the connection part. A cross-sectional area can be set. And about 2nd part, after filling material spreads to a leg part and a connection part, time until a convex part is filled with filling material is compared with the timing accuracy at the time of stopping injection of filling material. The cross-sectional area and volume can be set to be sufficient. For this reason, the extent of the pressure rise of the filling material after the filling material has spread over the leg portion and the connecting portion can be more effectively mitigated as compared with an aspect without the above configuration.

(6) In the ceramic heater according to the above aspect, the heat generating portion may include the same number of convex portions on each leg portion. With such an aspect, when the heat generating part is injection-molded, the degree of pressure increase is evenly reduced for the pair of leg parts, as compared with an aspect in which each leg part has a different number of convex parts. Can do.

(7) In the ceramic heater of the above aspect, the heat generating portion may be provided on the leg portions, and the convex portions may be provided at the same position in a direction in which the pair of leg portions extend. it can. If it is set as such an aspect, when an exothermic part is injection-molded, the grade of a pressure rise can be relieve | moderated more equally about a pair of leg part.

(8) According to another aspect of the present invention, a glow plug including the ceramic heater of the above aspect is provided.

  The present invention can be realized in various forms other than the ceramic heater and the glow plug. For example, a ceramic heater manufacturing method, a glow plug manufacturing method, a manufacturing apparatus for realizing the manufacturing method, a computer program for controlling the manufacturing apparatus, a non-temporary recording medium on which the computer program is recorded, and the like are realized. Can do.

3 is an explanatory view showing a partial cross section of the glow plug 10. FIG. It is explanatory drawing which shows the ceramic heater 800. FIG. It is a top view which shows the process at the time of forming the heating resistor 830 by the injection molding method. It is explanatory drawing which shows the 1st aspect C4p of the space | gap part C4 comprised by the metal mold | die D1 and auxiliary metal mold | die D2a, D2b. It is explanatory drawing which shows the 2nd aspect C4q of the space | gap part C4 comprised with the metal mold | die D1 and auxiliary metal mold | die D2a, D2b. It is explanatory drawing which shows the 3rd aspect C4r of the space | gap part C4 comprised with the metal mold | die D1 and auxiliary metal mold | die D2a, D2b. It is explanatory drawing which shows the 4th aspect C4s of the space | gap part C4 comprised by the metal mold | die D1 and auxiliary metal mold | die D2a, D2b. It is sectional drawing of the ceramic heater 800 in the EE cross section in FIG. It is sectional drawing of the ceramic heater 800 in the FF cross section in FIG. It is sectional drawing which shows the modification of a 1st form. It is sectional drawing which shows the modification of a 1st form. It is sectional drawing which shows the modification of a 1st form. It is sectional drawing which shows the modification of a 1st form. It is a figure which shows the modification of the metal mold | die D1 and the heat-emitting part 833. FIG. It is a figure which shows the modification of the metal mold | die D1 and the heat-emitting part 833. FIG. It is a figure which shows the modification of the metal mold | die D1 and the heat-emitting part 833. FIG. It is a figure which shows the modification of the metal mold | die D1 and the heat-emitting part 833. FIG. It is a figure which shows the modification of the metal mold | die D1 and the heat-emitting part 833. FIG.

A. Embodiment:
A1. Glow plug configuration:
FIG. 1 is an explanatory view showing a partial cross section of the glow plug 10. In FIG. 1, the outer shape of the glow plug 10 is illustrated on the right side of the drawing with the central axis SC of the glow plug 10 as a boundary, and the cross-sectional shape of the glow plug 10 is illustrated on the left side of the drawing. In the description of the present embodiment, the lower side of the glow plug 10 in FIG. 1 is referred to as “front end side” or “front”, and the upper side of FIG. 1 is referred to as “rear end side” or “rear”.

  FIG. 1 shows an X axis, a Y axis, and a Z axis as three space axes orthogonal to each other. Of the X-axis directions along the X-axis, the X-axis + direction is a positive direction, and the X-axis-direction is a negative direction. Of the Y-axis directions along the Y-axis, the Y-axis + direction is a positive direction, and the Y-axis-direction is a negative direction. Among the Z-axis directions along the Z-axis, the Z-axis + direction is a positive direction, and the Z-axis-direction is a negative direction. In the present embodiment, the Z axis is an axis along the central axis SC, the Z axis + direction is the rear end side (rear), and the Z axis − direction is the front end side (front). The XYZ axes in FIG. 1 correspond to the XYZ axes in the other drawings.

  The glow plug 10 includes a ceramic heater 800 that generates heat, and functions as a heat source that assists ignition when starting the internal combustion engine 90 such as a diesel engine. In addition to the ceramic heater 800, the glow plug 10 includes a middle shaft 200, a metal shell 500, and an outer cylinder 700. The central axis SC of the glow plug 10 is also the central axis of each member constituting the glow plug 10.

  The middle shaft 200 of the glow plug 10 is a metal body having conductivity. The middle shaft 200 has a cylindrical shape extending around the central axis SC. The middle shaft 200 receives power from the outside of the glow plug 10 via the terminal 100 on the rear end side of the middle shaft 200. In another embodiment, the middle shaft 200 may receive power supply directly from the outside of the glow plug 10 on the rear end side of the middle shaft 200. The middle shaft 200 relays electric power supplied from the outside of the glow plug 10 to the ceramic heater 800 on the front end side.

  In the present embodiment, the middle shaft 200 is electrically connected to the ceramic heater 800 via the ring 600 on the distal end side of the middle shaft 200. In another embodiment, the middle shaft 200 may be directly connected to the ceramic heater 800 on the tip side of the middle shaft 200.

  The metal shell 500 of the glow plug 10 is a metal body having conductivity. The metal shell 500 has a cylindrical shape extending around the central axis SC. The metal shell 500 includes a shaft hole 510, a tool engaging portion 520, and a male screw portion 540.

  The shaft hole 510 of the metal shell 500 is a through hole extending around the central axis SC. The inner diameter of the shaft hole 510 is larger than the outer shape of the middle shaft 200. Inside the shaft hole 510, the middle shaft 200 is positioned on the central axis SC, and a gap that electrically insulates the shaft hole 510 and the middle shaft 200 is formed between the shaft hole 510 and the middle shaft 200. In the present embodiment, the middle shaft 200 is attached to the rear end side of the shaft hole 510 via the cylindrical insulating member 300 and the annular insulating member 400.

  The tool engaging portion 520 of the metal shell 500 is configured to be able to engage with a tool (not shown) used for attaching and removing the glow plug 10 to and from the internal combustion engine 90. The male thread portion 540 of the metal shell 500 is configured to be fixed to the internal combustion engine 90 by fitting with a female thread formed in the internal combustion engine 90.

  The outer cylinder 700 of the glow plug 10 is made of a conductive metal. The outer cylinder 700 has a cylindrical shape extending about the central axis SC. The outer cylinder 700 includes a shaft hole 710 that holds the ceramic heater 800. The rear end side of the outer cylinder 700 is welded to the front end side of the metal shell 500. The ceramic heater 800 protrudes from the front end side of the outer cylinder 700.

  The ceramic heater 800 of the glow plug 10 is a heating element (heating device) made of a ceramic composition. The ceramic heater 800 includes a base 810 and a heating resistor 830.

  The base 810 of the ceramic heater 800 is made of an insulating ceramic that is a ceramic material having an electrical insulating property. A heating resistor 830 is embedded in the base 810. The base 810 supports the heating resistor 830. The base 810 electrically insulates the heating resistor 830 from the outside of the glow plug 10 and transmits heat of the heating resistor 830 to the outside of the glow plug 10.

In the present embodiment, the ceramic material forming the base 810 is mainly composed of silicon nitride (Si ₃ N ₄ ). In another embodiment, of the silicon nitride (Si ₃ N ₄ ) forming the substrate 810, at least part of silicon (Si) is replaced with aluminum (Al) and at least part of nitrogen (N) is oxygen ( O) may be substituted. The ceramic material forming the base 810 may contain a rare earth oxide (for example, ytterbium (Yb) oxide, erbium (Er) oxide, etc.) and a chromium (Cr) silicide as a sintering aid. Good.

  The heating resistor 830 of the ceramic heater 800 is a conductive ceramic made of a conductive ceramic material. The heating resistor 830 generates heat when energized. In the present embodiment, the heating resistor 830 is a member molded by an injection molding method.

In the present embodiment, the ceramic material forming the heating resistor 830 is mainly composed of tungsten carbide (WC). In this embodiment, the ceramic material contains silicon nitride (Si ₃ N ₄ ) in addition to tungsten carbide. The ceramic material contains 55 to 70 mass% tungsten carbide and 28 to 35 mass% silicon nitride, and the remaining 2 to 10 mass% is erbium oxide (Er ₂ O ₃ ) and silicon oxide (SiO ₂ ). It may contain. In other embodiments, the ceramic material may be a composition consisting primarily of molybdenum disilicide (MoSi ₂ ).

A2. Configuration of ceramic heater:
FIG. 2 is an explanatory view showing the ceramic heater 800. In FIG. 2, the heating resistor 830 when the ceramic heater 800 is viewed in the Y-axis-direction is shown together with the outline of the base 810, and the region corresponding to the base 810 is hatched.

  The heating resistor 830 of the ceramic heater 800 includes a heating part 833, a pair of conductive parts 836, and two terminal parts 838.

  The heat generating portion 833 is located on the front end side (front) with respect to the pair of conductive portions 836. The heat generating portion 833 includes a front end portion 832 and a pair of leg portions 834. The front end portion 832 is provided at the front end of the heat generating portion 833. The front end portion 832 has a linear shape obtained by folding a circular cylinder having a constant cross-sectional area into an arc shape. The front end portion 832 electrically connects the pair of leg portions 834 at the front end.

  The pair of leg portions 834 extends from the front end portion 832 toward the rear end side (Z axis + direction side). The pair of leg portions 834 includes a leg portion 834a and a leg portion 834b. The leg portion 834a extends linearly toward the rear end side on the X axis + direction side of the front end portion 832. The leg portion 834b extends linearly toward the rear end side on the X-axis-direction side of the front end portion 832. In the present embodiment, the leg portion 834a and the leg portion 834b are substantially parallel to each other. In the description of the present embodiment, the symbol “834” is used when the leg portion 834a and the leg portion 834b are collectively referred to.

  The leg 834a is provided with a portion on the front end side narrower than a portion on the rear end side. Leg 834a has the same cross-sectional area as front end 832 at its front end. The outer contour of the leg portion 834a matches the outer contour of the front end portion 832 at the front end of the leg portion 834a. And the leg part 834a has the same cross-sectional area as the electroconductive part 836a in the thickest part. The outer contour of the leg portion 834a matches the outer contour of the conductive portion 836a at the rear end of the leg portion 834a. The leg portion 834b has the same configuration as the leg portion 834a with respect to the front end portion 832 and the conductive portion 836b. In the description of the present embodiment, the symbol “834” is used when the leg portion 834a and the leg portion 834b are collectively referred to.

  The conductive ceramic constituting the heat generating portion 833 (the front end portion 832 and the leg portions 834a and b) has a higher resistivity than the conductive ceramic constituting the conductive portion 836. The size of the cross section of the heat generating portion 833 in the cross section perpendicular to the direction in which the heat generating portion 833 extends is equal to or smaller than the size of the cross section of each conductive portion 836 in the cross section perpendicular to the direction in which each conductive portion 836 extends (FIG. 2). reference). For this reason, the electrical resistance of the front end portion 832 and the leg portion 834 is larger than the conductive portion 836. In the present embodiment, the heating resistor 830 generates heat around the leg portion 834 by energization, and the leg portion 834 has the highest temperature among the heating resistor 830.

  The pair of conductive portions 836 extends from each of the pair of leg portions 834 to the rear end side (Z axis + direction side). The pair of conductive portions 836 includes a conductive portion 836a and a conductive portion 836b. The conductive portion 836a extends linearly from the leg portion 834a toward the rear end side while maintaining a substantially constant cross-sectional area. The conductive portion 836b extends linearly from the leg portion 834b to the rear end side while maintaining a constant cross-sectional area. In the present embodiment, the conductive portion 836a and the conductive portion 836b are substantially parallel to each other. In the description of this embodiment, the reference numeral “836” is used when the conductive portion 836a and the conductive portion 836b are collectively referred to. The conductive portion 836 is made of a conductive ceramic different from the conductive ceramic of the heat generating portion 833, more specifically, a conductive ceramic having a resistivity lower than that of the conductive ceramic of the heat generating portion 833.

  The two terminal portions 838 protrude from each of the pair of conductive portions 836 and are exposed on the surface of the base 810. The two terminal portions 838 include a terminal portion 838a and a terminal portion 838b. The terminal portion 838a is formed on the rear end side of the conductive portion 836a and protrudes from the conductive portion 836a in the X axis + direction. The terminal portion 838b is formed on the rear end side of the conductive portion 836b and protrudes in the X-axis direction from the conductive portion 836b. In the present embodiment, the terminal portion 838b is located on the distal end side with respect to the terminal portion 838a. In the present embodiment, in a state where the ceramic heater 800 is assembled to the metal shell 500, the terminal portion 838 a is in contact with the ring 600 and is electrically connected to the middle shaft 200 via the ring 600. The terminal portion 838b is electrically connected to the outer cylinder 700. In the description of the present embodiment, the symbol “838” is used when the terminal portion 838a and the terminal portion 838b are collectively referred to.

A3. Manufacturing method of heating resistor:
FIG. 3 is a plan view showing a process when the heating resistor 830 is formed by an injection molding method. The heating resistor 830 is generated by an injection molding method as described above. In FIG. 3, the hatched portion is a mold D1. The mold D1 is provided with a gap C having a shape corresponding to the heating resistor 830 and injection paths I1 and I2 for injecting ceramic into the gap C. The injection path I1 is connected to the front end of the portion corresponding to the front end 832 in the gap C. The injection path I2 is connected to the rear end of the portion corresponding to the pair of conductive portions 836 in the gap C. The mold D1 that forms the gap C is divided into two in a direction perpendicular to the paper surface on a surface substantially coinciding with the paper surface of FIG. At the time of injection molding, the pair of molds D1 are fitted in a direction perpendicular to the paper surface of FIG. FIG. 3 shows a state in which the heating resistor 830 is molded in the mold D1. Further, in order to facilitate understanding of the technique, auxiliary structures such as a vent hole and a cooling water channel provided in the mold D1 are omitted in FIG.

  When the heating resistor 830 is formed, first, the heating part 833 is formed. When the heat generating portion 833 is formed, the auxiliary dies D2a and D2b are disposed in portions corresponding to the pair of conductive portions 836a and 836b in the gap C of the die D1, respectively. As a result, in the gap C4 corresponding to the heat generating part 833 in the gap C of the mold D1, the gap part C6a corresponding to the conductive parts 836a and b and the terminal parts 838a and b in the gap C of the mold D1. C6b is sealed. The shapes of the front ends of the auxiliary molds D2a and D2b define the shapes of the rear ends of the pair of leg portions 834.

  In this state, the pair of molds D1 are fitted in a direction perpendicular to the paper surface of FIG. 3 and clamped, and a raw material containing conductive ceramic for forming the heat generating portion 833 is injected from the injection path I1. . Then, the raw material is injected into the gap portion C4 of the mold D1 corresponding to the heat generating portion 833, and the heat generating portion 833 is formed. At that time, the conductive ceramic injected from the injection path I1 is not injected into the gap portions C6a and C6b of the mold D1 corresponding to the conductive portions 836a and b and the terminal portions 838a and b.

  Thereafter, the auxiliary molds D2a and D2b are removed from the mold D1. And a pair of metal mold | die D1 is fitted again and it clamps, and the raw material containing the conductive ceramic for comprising the electroconductive parts 836a and 836b from the injection path I2 is inject | emitted. Then, the raw material is injected into the gap portions C6a and C6b of the mold D1 corresponding to the conductive portions 836a and b and the terminal portions 838a and b, thereby forming the conductive portions 836a and 836b. At this time, the front ends of the conductive portions 836a and 836b are formed without gaps on the rear end surface of the heat generating portion 833 that has already been formed.

  Thereafter, the heat generating resistor 830 including portions corresponding to the heat generating portion 833 and the conductive portions 836a and 836b is taken out from the mold D1, embedded in the base 810, and subjected to pressure firing to complete the ceramic heater 800. Thereafter, the ceramic heater 800 is combined with the central shaft 200, the metal shell 500, the outer cylinder 700, etc., and the glow plug 10 is completed.

  In the present specification, in order to reduce the complexity of the description, the “heating resistor 830”, “heating unit 833”, “conducting part” is also used for the heating resistor 830 before firing and the intermediate product thereof. 836a, 836b "may be used to indicate the finished product.

  The volume of the gap portion C4 corresponding to the heat generating portion 833 is smaller than the volume of the gap portions C6a and C6b corresponding to the conductive portions 836a and b and the terminal portions 838a and b. For this reason, when the raw material is further injected into the gap after the raw material has spread into the gap, the pressure in the gap portion C4 is more likely to rise than the gap portions C6a and C6b. Therefore, an event in which the pressure of the filling material in the injection space suddenly increases after the raw material reaches the gap and until the injection of the raw material is stopped is more likely to occur particularly in the molding of the heat generating portion 833. .

A4. Heating resistor and void embodiment:
(1) First aspect:
FIG. 4 is an explanatory diagram showing a first mode C4p of the gap C4 formed by the mold D1 and the auxiliary molds D2a and D2b. The heat generating portion 833 formed by the first aspect C4p of the gap portion C4 is referred to as a heat generating portion 833p. A plan view of the gap C4p is shown on the left side of FIG. A cross-sectional view taken along the line AA in the plan view of the gap C4p is shown on the right side of FIG. In order to facilitate understanding of the technique, FIG. 4 shows only the structure of the gap portion C4p and the intermediate product corresponding to the heat generating portion 833p disposed in the gap portion C4p, and the mold D1 and the auxiliary molds D2a and D2b. Illustration is omitted. The same applies to FIGS. 5 to 7 described later.

  The gap portion C4p for forming the heat generating portion 833p includes a gap portion C42 for forming the front end portion 832, a gap portion C44a, b for forming the leg portions 834a, b, and a gap portion C441a, b. . The gap portion C42 has a gap having a shape obtained by bending the cylinder 180 degrees. The gap portion C44a includes a columnar gap having a larger diameter than the gap portion C42. The columnar gap of the gap portion C44a is connected to one rear end of the gap portion C42 via a gap having a taper. The rear end of the columnar gap of the gap portion C44a is defined by a plane C44af that intersects the central axis SC at a predetermined angle (for example, 30 degrees here). In the first aspect, the thickest part of the gap part C44a and the gap part C42 have a circular cross section. However, the thickest portion of the gap portion C44a and the gap portion C42 may have other cross-sectional shapes.

  The gap portion C44b is configured similarly to the gap portion C44a. That is, the gap C44b has a shape that is a mirror image of the gap C44a across a plane defined by the central axis SC and the Y axis.

  The gap portions C441a and b are connected to the gap portions C44a and b for forming the leg portions 834a and b, respectively. The gap portion C441a is arranged so as to protrude to the opposite side of the central axis SC with respect to the gap portion C44a. The gap portion C441b is arranged so as to protrude to the opposite side of the central axis SC with respect to the gap portion C44b.

  As a result, the portion where the convex portion 8341a of the heat generating portion 833 is formed is part of the leg portion 834a where the convex portion 8341a is provided, than the portion 834na closest to the other leg portion 834b. , A position far from the other leg portion 834b. Similarly, the portion where the convex portion 8341b is disposed is also from the other leg portion 834a rather than the portion 834nb closest to the other leg portion 834a in the part of the leg portion 834b where the convex portion 8341b is provided. It is a distant position.

  The convex portions 8341a and b are located at positions not on the line segment Ls connecting the shortest distances of the leg portions 834a and b in any cross section perpendicular to the Z-axis direction in which the pair of leg portions 834a and b extend. Is provided.

  The portion on the line segment Ls connecting the shortest distances of the leg portions 834a and b is highly likely to be the innermost portion of the leg portions 834a and b of the heating resistor 830. Such a portion is a portion having the highest current density in each cross section when the heating resistor 830 is energized. If the convex portions 8341a and b are provided in such a portion, the convex portions 8341a and b may generate abnormal heat. However, in the first aspect, since the convex portions 8341a and b are provided at positions not on the line segment connecting the axes of the leg portions 834a and b, the risk of such abnormal heat generation is low. .

  The void portions C441a and b of the mold D1 are voids each having a substantially rectangular parallelepiped internal space whose longitudinal direction is parallel to the central axis SC. The cross-sectional areas of the gap portions C441a and b are smaller than the cross-sectional areas of the gap portions C44a and b for forming the leg portions 834a and b (see the right side in FIG. 4). As a result, the cross-sectional areas of the convex portions 8341a and b formed by the gap portions C441a and b are smaller than the cross-sectional areas of the leg portions 834a and b. In addition, each cross-sectional area of the additional void portion (C441a, b) of the mold when referring to the size relationship, and each cross-sectional area of the void portion (C44a, b) for forming the functional component is the central axis. The maximum cross-sectional area among the cross-sectional areas in an arbitrary cross section perpendicular to the SC is taken. The same applies to the cross-sectional areas of the convex portions (8341a, b) and the leg portions (834a, b) of the heat generating portion 833 when referring to the magnitude relationship.

  Further, the cross-sectional area of the substantially rectangular opening Co1a, which is the connecting portion between the gap portion C44a and the gap portion C441a, is smaller than the cross-sectional area in the cross section perpendicular to the central axis SC of the gap portion C44a. Similarly, the cross-sectional area of the substantially rectangular opening Co1b, which is the connecting portion between the gap portion C44b and the gap portion C441b, is also smaller than the cross-sectional area in the cross section perpendicular to the central axis SC of the gap portion C44b. By adopting such a configuration, at the time of injection molding, the gap portion C44a, b having a large cross-sectional area is filled with the raw material first, and then the gap portion passing through the connection portion (opening) Co1a, b having a small cross-sectional area. The raw material is injected into C441a and b.

  Since the gap portion C4p for molding the heat generating portion 833p has the above-described configuration, at the time of injection molding, the gap portion C42 for molding the front end portion 832 is first filled with the raw material, and then the leg portion 834a. , B are filled with raw materials in the gap portions C44a, b. Thereafter, the control unit that controls the injection molding causes the injection unit that is injecting the raw material to stop the injection.

  The injection of the raw material is preferably stopped after the gap portions C42, C44a, b are completely filled with the raw material. There is a time delay from the completion of the filling of the raw material into the gap portion C42 and the gap portions C44a and b to the stop of injection. Therefore, after the gap portions C42, C44a, b are completely filled with the raw material, until the injection is stopped, the raw material is injected into the gap portions C441a, b through the connection portion with the gap portion C44a, b. Is done.

  For this reason, according to the first aspect, the gap portions C42, C44a, b are completely formed in comparison with the aspect in which the additional gap portions C441a, b not provided for molding the functional component in the mold are not provided. It is possible to reduce the degree of pressure increase in the gap C after the raw material is filled. As a result, it is possible to reduce a possibility that the raw material ceramic enters the joint of the pair of molds D1 that are clamped and used, and wears the joint surface of the mold D1. Therefore, the mold D1 can be used without causing burrs on the joint surface over a long period of time.

  Further, since the gap portion C4p for forming the heat generating portion 833p has the above-described configuration, the gap portions C441a, b are formed on the leg portions 834a, b of the heat generating portion 833p formed by the gap portion C4p. Convex portions 8341a and b are provided as corresponding configurations. As described above, the convex portions 8341a and 8b are located farther from the other leg portion 834 than the portion 834 closest to the other leg portion 834 in a part of the leg portion 834 in which they are provided. Provided. Therefore, the shortest distance between the leg portion 834a and the convex portion 8341a extending substantially parallel to each other in the Z-axis + direction and the leg portion 834b and the convex portion 8341b is reduced by forming the convex portions 8341a and b. Never become. Therefore, when the glow plug 10 incorporating the heating resistor 830 is used, the leg portion 834a and the convex portion 8341a and the leg portion 834b and the convex portion 8341b are short-circuited without the front end portion 832. Less likely.

(2) Second aspect:
FIG. 5 is an explanatory view showing a second mode C4q of the gap C4 composed of the mold D1 and the auxiliary molds D2a and D2b. The heat generating portion 833 formed by the second aspect C4q of the gap portion C4 is referred to as a heat generating portion 833q. A plan view of the gap C4q is shown in the upper part of FIG. A cross-sectional view taken along the line BB in the plan view of the gap C4q is shown in the lower part of FIG.

  A gap portion C4q for forming the heat generating portion 833q includes a gap portion C42 for forming the front end portion 832, a gap portion C44a, b for forming the leg portions 834a, b, and a gap portion C442a, b. . In the gap portion C4q of the second aspect, the configurations of the gap portion C42 and the gap portions C44a and b are the same as the gap portion C4p of the first aspect.

  In the gap portion C4q of the second mode, the gap portions C442a and b are connected to the gap portions C44a and b for forming the leg portions 834a and b, respectively. The gap portion C442a is arranged so as to protrude in the Z axis + direction from the inclined rear end face of the gap portion C44a. The gap portion C442b is arranged so as to protrude in the Z axis + direction from the inclined rear end face of the gap portion C44b. The gap portions C442a and b do not protrude toward the central axis SC.

  As a result, the portion where the convex portion 8342a of the heat generating portion 833 is arranged is part of the leg portion 834a where the convex portion 8342a is provided, than the portion 834na closest to the other leg portion 834b. , A position far from the other leg portion 834b. The portion where the convex portion 8342b is disposed is located at a position farther from the other leg portion 834a than the portion 834nb closest to the other leg portion 834a in a part of the leg portion 834b provided with the convex portion 8342b. is there.

  And the convex parts 8342a, b are in positions not on the line segment Ls connecting the shortest distances of the leg parts 834a, b in any cross section perpendicular to the Z-axis direction in which the pair of leg parts 834a, b extends. Is provided. By setting it as such an aspect, the risk that the convex parts 8342a and b generate abnormal heat can be reduced.

  The gap portion C442b has a parallelogram section having a long side parallel to the inclined rear end face of the gap portion C44b and a short side parallel to the central axis SC, and has a shape having a thickness in the Y-axis direction. It is a void having. The cross-sectional area of the gap portion C442b is smaller than each cross-sectional area of the gap portion C44b (see the lower part of FIG. 5). Note that the cross-sectional areas of the gap portions C442a and b when referring to the magnitude relationship are the maximum cross-sectional areas among the cross-sectional areas in arbitrary cross sections perpendicular to the central axis SC of the gap portions.

  In addition, the cross-sectional area of the substantially rectangular opening Co2b, which is the connecting portion between the gap portion C44b and the gap portion C442b, is smaller than the cross-sectional area in the cross section perpendicular to the central axis SC of the gap portion C44b. By adopting such a configuration, at the time of injection molding, the raw material is first filled into the gap portion C44b having a large cross-sectional area, and then, the raw material is passed through the connection portion (opening) Co2b having a small cross-sectional area to the raw material in the gap portion C442a. Will be injected.

  The gap portion C442a is configured similarly to the gap portion C442b. That is, the gap portion C442a has a shape that is a mirror image of the gap portion C442b across a plane defined by the central axis SC and the Y axis.

  Since the gap portion C4q for molding the heat generating portion 833p has the above-described configuration, at the time of injection molding, first, the gap portion C42 for molding the front end portion 832 and the legs 834a, b are formed. The raw material is filled in the gap portions C44a and b. Thereafter, the raw materials are injected in the order of the gap portions C442a and b. For this reason, compared with the mode in which the gap portions C442a and b are not provided in the mold, the raw material ceramic may enter the joint of the pair of molds D1, and the bonding surface of the mold D1 may be worn. Can be reduced. Therefore, the mold D1 can be used without causing burrs on the joint surface over a long period of time.

  Further, since the gap portion C4q has the above-described configuration, on the leg portions 834a, b of the heat generating portion 833q formed by the gap portion C4q, a convex portion 8342a, as a configuration corresponding to the gap portion C442a, b. b is provided. As described above, the convex portions 8342a and b are located at a position farther from the other leg portion 834 than the portion 834 closest to the other leg portion 834 in a part of the leg portion 834 provided with the convex portions 8342a and b. Provided. For this reason, the shortest distance between the leg portion 834a and the convex portion 8342a extending substantially parallel to each other in the Z-axis + direction and the leg portion 834b and the convex portion 8342b is reduced by forming the convex portions 8342a and b. Never become. Therefore, when the glow plug 10 is used, there is a low possibility that the leg portion 834a and the convex portion 8341a and the leg portion 834b and the convex portion 8341b are short-circuited.

  In addition, after the heat generating portion 833q is formed in the gap portion C4q, conductive portions 836a and b are formed on the rear end sides of the leg portions 834a and b (see FIG. 3). That is, the convex portions 8342a and b of the heat generating portion 833q are provided at a connection portion between the leg portion 834 and the conductive portion 836. For this reason, the convex parts 8342a and b come into contact with the conductive parts 836a and b, respectively, and are embedded in the conductive parts 836a and b. Therefore, according to the 2nd aspect, an unnecessary convex part is not formed in exothermic resistor 830 as a finished product. For this reason, the heating resistor 830 can be formed small.

(3) Third aspect:
FIG. 6 is an explanatory diagram showing a third mode C4r of the gap C4 formed by the mold D1 and the auxiliary molds D2a and D2b. The heat generating portion 833 formed by the third aspect C4r of the gap portion C4 is referred to as a heat generating portion 833r. A plan view of the gap C4r is shown on the left side of FIG. A cross-sectional view of the C-C cross section in the plan view of the gap C4r is shown on the right side of FIG.

  In the gap portion C4r of the third aspect, gap portions C443a and b443b are further added to the gap portion C4p of the first aspect. Other configurations of the gap portion C4r of the third aspect are the same as those of the gap portion C4p of the first aspect.

  In the gap portion C4r of the third aspect, the gap portions C443a, b are connected to the gap portions C441a, b, respectively. The gap portion C443a is disposed so as to protrude in the X axis + direction from the end surface in the X axis + direction of the gap portion C441a. The gap portion C443b is arranged so as to protrude in the X-axis direction from the end surface in the X-axis direction of the gap portion C441b.

  The space portion C443b is a space having a rectangular parallelepiped shape with a thickness in the Y-axis direction larger than that of the space portion C441b. The cross-sectional area of the gap portion C443b is larger than the cross-sectional area of the gap portion C441b (see the right side of FIG. 6). The cross-sectional areas of the gap portions C443a, b and the gap portions C441a, b are the maximum cross-sectional areas of the cross-sectional areas in the cross section perpendicular to the direction away from the gap portions C44a, b.

  As a result of the gap portion C441b and the gap portion C443b having the above-described configuration, the convex portion 8350b provided on the leg portion 834 has a cross-sectional area larger than the base portion 8346b and the base portion 8346b along the direction away from the leg portion 834b. A large tip portion 8347b.

  In addition, the cross-sectional area of the substantially rectangular opening Co3b, which is a connection portion between the gap portion C441b and the gap portion C443b, is the same as the cross-sectional area of the substantially rectangular opening Co1b that is a connection portion between the gap portion C44b and the gap portion C441b. By adopting such a configuration, at the time of injection molding, the raw material is first filled into the gap portion C44b having a large cross-sectional area, and then the raw material is passed through the connection portion (opening) Co1b having a small cross-sectional area to the raw material in the gap portion C441b. Injected. Thereafter, the raw material is injected into the gap portion C443b through the connection portion (opening) Co3b.

  In other words, the gap portion C441b (the base 8346b of the convex portion 8350b) has such a size that the gap portion C441b is not filled with the filling material before the raw material reaches the leg portion 834b when the heating resistor 830 is injection molded. In addition, the cross-sectional area can be set. And about the space | gap part C443b (front-end | tip part 8347b of the convex part 8350b), after a raw material reaches | attains the leg part 834b, the time until the space | gap part C441b and C443b are filled with a raw material is when stopping injection | pouring of a raw material The cross-sectional area and volume can be set to be sufficient for the timing accuracy.

  The gap portion C443a is configured similarly to the gap portion C443b. That is, the gap C443a has a shape that is a mirror image of the gap C443b across a plane defined by the central axis SC and the Y axis.

  In the gap portion C4r of the third aspect, gap portions C443a, b are further added to the gap portion C4p of the first aspect. For this reason, the following effects are acquired. That is, during injection molding, after the gap portion C42 and the gap portions C44a and b are filled with the raw material, the gap portion C441a and b and the gap portions C443a and b are filled with the raw material until the gap portion C4r is filled with the raw material. In the first embodiment, the time required for is longer than the time required until the gap portion C4p and the gap portions C44a and b are filled with the raw material and then the gap portion C4p is filled with the raw material. For this reason, compared with a 1st aspect, possibility that the ceramic of a raw material penetrate | invades into the joint of a pair of metal mold | die D1 and wears the joining surface of metal mold | die D1 can be reduced more.

  In addition, since the gap portion C4r for forming the heat generating portion 833r has the above-described configuration, the leg portions 834a, b of the heat generating portion 833r correspond to the gap portions C441a, b and the gap portions C443a, b. Constituent portions 8350a, b each having tip portions 8347a, b having a larger cross-sectional area than the base portions 8346a, b are provided. The convex portions 8350a and 8b are also provided at a position farther from the other leg portion 834 than a portion 834 closest to the other leg portion 834 in a part of the leg portion 834 on which the convex portions 8350a and b are provided. That is, the convex portions 8350a and b do not protrude toward the central axis SC. For this reason, the shortest distance between the leg part 834a and the convex part 8350a and the leg part 834b and the convex part 8350b is not reduced by forming the convex parts 8350a and b. Therefore, when the glow plug 10 is used, there is a low possibility that the leg portion 834a and the convex portion 8350a and the leg portion 834b and the convex portion 8350b are short-circuited.

  Note that the base portions 8346a, b of the third aspect correspond to the “first portion” in the “means for solving the problem”, and the tip portions 8347a, b correspond to the “second portion”.

(4) Fourth aspect:
FIG. 7 is an explanatory view showing a fourth mode C4s of the gap C4 composed of the mold D1 and the auxiliary molds D2a and D2b. The heat generating portion 833 formed by the fourth aspect C4s of the gap portion C4 is referred to as a heat generating portion 833s. A plan view of the gap C4s is shown in the upper part of FIG. A sectional view taken along the line DD in the plan view of the gap C4s is shown in the lower part of FIG.

  In the gap portion C4s of the fourth aspect, gap portions C444a and b are further added to the gap portion C4q of the second aspect. Other configurations of the gap portion C4s of the third aspect are the same as those of the gap portion C4q of the first aspect.

  In the gap portion C4s of the fourth aspect, the gap portions C444a and b are connected to the gap portions C442a and b, respectively. The gap portion C444a is located on the rear end side (Z axis + direction) of the gap portion C442a. The gap portion C444b is located on the rear end side (Z axis + direction) of the gap portion C442b.

  The gap portion C444b has a parallelogram section having a long side parallel to the inclined rear end face of the gap portion C44b and a short side parallel to the central axis SC, and has a shape having a thickness in the Y-axis direction. It is a void having. The thickness of the gap portion C444b in the Y-axis direction is larger than the thickness of the gap portion C442b in the Y-axis direction. The volume of the gap portion C444b is larger than the volume of the gap portion C442b.

  The cross-sectional area of the gap portion C444b is larger than the cross-sectional area of the gap portion C442b (see the lower part of FIG. 7). In addition, each cross-sectional area of the space | gap part C444b and the space | gap part C442b is each largest cross-sectional area among the cross-sectional areas in a cross section perpendicular | vertical to the direction away from the space | gap part C44b (namely, direction perpendicular | vertical to the rear end surface of the space | gap part C44b). .

  As a result of the gap portion C442b and the gap portion C444b having the above-described configuration, the convex portion 8351b includes a base portion 8348b and a tip portion 8349b having a larger cross-sectional area than the base portion 8348b along the direction away from the leg portion 834b. Prepare.

  In addition, the cross-sectional area of the substantially rectangular opening Co4b, which is the connection portion between the gap portion C442b and the gap portion C444b, is the same as the cross-sectional area of the substantially rectangular opening Co2b that is the connection portion between the gap portion C44b and the gap portion C442b. By adopting such a configuration, at the time of injection molding, the raw material is first filled into the gap portion C44b having a large cross-sectional area, and then the raw material is passed through the connecting portion (opening) Co2b having a small cross-sectional area to the gap portion C442b. Injected. Thereafter, the raw material is injected into the gap portion C444b through the connection portion (opening) Co4b.

  The gap portion C444a is configured similarly to the gap portion C444b. That is, the gap portion C444a has a shape that is a mirror image of the gap portion C444b with a plane defined by the central axis SC and the Y axis interposed therebetween.

  In the gap portion C4s of the fourth aspect, gap portions C444a and b are further added to the gap portion C4q of the second aspect. For this reason, the following effects are acquired. That is, during the injection molding, after the raw material is filled in the gap portion C42 and the gap portions C44a and b, the time required for the entire gap portion C4s to be filled with the raw material is the gap portion C42 and the gap portion in the second aspect. After C44a and b are filled with the raw material, it is longer than the time required for the gap portion C4q to be filled with the raw material. For this reason, compared with a 2nd aspect, possibility that the ceramic of a raw material penetrate | invades into the joint of a pair of metal mold | die D1 and wears the joining surface of metal mold | die D1 can be reduced more.

  Further, since the gap portion C4s for forming the heat generating portion 833s has the above-described configuration, the leg portions 834a, b of the heat generating portion 833s correspond to the gap portions C442a, b and the gap portions C444a, b. Constituent portions 8351a and b each having tip portions 8349a and b having a larger cross-sectional area than the base portions 8348a and b are provided. The convex portions 8351a and b are also provided at a position farther from the other leg portion 834 than a portion 834 closest to the other leg portion 834 in a part of the leg portion 834 on which the convex portions 8351a and b are provided. That is, the convex portions 8351a and b do not protrude toward the central axis SC. For this reason, the shortest distance between the leg part 834a and the convex part 8351a and the leg part 834b and the convex part 8351b is not reduced by forming the convex parts 8351a and b. Therefore, when the glow plug 10 is used, there is a low possibility that the leg portion 834a and the convex portion 8351a and the leg portion 834b and the convex portion 8351b are short-circuited.

  In addition, after the heat generating portion 833s is formed in the gap portion C4s, conductive portions 836a and b are formed on the rear end sides of the leg portions 834a and b (see FIG. 3). For this reason, the convex portions 8351a and b are embedded in the conductive portions 836a and b. Therefore, according to the 4th aspect, an unnecessary convex part is not formed in the exothermic resistor 830 as a finished product. For this reason, useless portions that are not related to performance are not formed in the heating resistor 830.

  The base portions 8348a, b of the fourth aspect correspond to the “first portion” in the “means for solving the problem”, and the tip portions 8349a, b correspond to the “second portion”.

B. Example:
B1. Mold durability test:
About the said 1st-4th aspect, as Example 1-4, respectively, the test goods of metal mold | die D1 and D2 which satisfy | fill the following conditions are created, and it repeats by injection molding on the same conditions as the time of product manufacture. Went. Further, as Comparative Example 1, the gap portion C4 includes a gap portion C42 and a gap portion C44a, b that are gaps for molding the functional component of the heating resistor 830, and the gap portions C441a, b to C444a, b, etc. A mold without additional voids was prepared.

Maximum dimension in the Z-axis direction of the gap portion C4 of each aspect: 6 mm.
Maximum thickness in the Y-axis direction of the gap portions C44a and b of each aspect: 1 mm.

Dimension in the Z-axis direction of the gap portions C441a and b of the first aspect: 1.5 mm.
Dimension in the X-axis direction of the gap portions C441a and b of the first aspect: 0.30 mm.
Dimension in the Y-axis direction of the gap portions C441a and b of the first aspect: 0.05 mm.

Dimension in the Z-axis direction of the gap portions C442a and b of the second aspect: 0.60 mm.
Note that the gap portion C4q of the second aspect includes gap portions C442a, C442a, C442a, C442a, Cb measured in the direction perpendicular to the end surfaces from the inclined end surfaces C44af, bf of the gap portions C44a, b on the side where the gap portions C442a, b are provided. The dimension of b is provided to be 0.30 mm.
Dimension in the X-axis direction of the gap portions C442a and b of the second aspect: 1.50 mm.
Dimension in the Y-axis direction of the gap portions C442a and b of the second aspect: 0.05 mm.

Dimension in the Z-axis direction of the gap portions C441a and b of the third aspect: 1.5 mm.
Dimension in the X-axis direction of the gap portions C441a and b of the third aspect: 0.30 mm.
Dimension in the Y-axis direction of the gap portions C441a and b of the third aspect: 0.05 mm.
Dimension in the Z-axis direction of the gap portions C443a, b of the third aspect: 1.5 mm.
Dimension in the X-axis direction of the gap portions C443a, b of the third aspect: 0.30 mm.
Dimension in the Y-axis direction of the gap portions C443a, b of the third aspect: 0.10 mm.

Dimension in the Z-axis direction of the gap portions C442a, b of the fourth aspect: 0.60 mm.
Note that the gap portion C4s of the fourth aspect includes gap portions C442a, C442a, C442a, C442a, Cb measured in the direction perpendicular to the end surfaces from the inclined end surfaces C44af, bf of the gap portions C44a, b on the side where the gap portions C442a, b are provided. The dimension of b is provided to be 0.30 mm.
Dimension in the X-axis direction of the gap portions C442a and b of the fourth aspect: 1.50 mm.
Dimension in the Y-axis direction of the gap portions C442a and b of the fourth aspect: 0.05 mm.
Dimension in the Z-axis direction of the gap portions C444a and b of the fourth aspect: 0.60 mm.
Note that the gap portion C4s of the fourth mode includes gap portions C444a, C444a, C44a, C44a, measured in the direction perpendicular to the end faces from the inclined end surfaces C44af, bf of the gap portions C44a, b on the side where the gap portions C442a, b are provided. It is provided so that the dimension to the front-end | tip part of b may be 0.60 mm.
Dimension in the X-axis direction of the gap portions C444a and b of the fourth aspect: 1.50 mm.
Dimension in the Y-axis direction of the gap portions C444a and b of the fourth aspect: 0.10 mm.

  Whether or not a burr having a width of 0.1 mm or more is generated at a position Pb (see FIG. 5) inside the front end portion 832 where the burr is most likely to occur in the heat generating portion 833 was confirmed every 10,000 injection moldings. The width of the burr was defined as the distance from the contour line of the front end 832 to the farthest point of the burr measured along the Y-axis direction. The results are shown in Table 1.

  From Table 1, in Comparative Example 1 having no additional void portion, burrs having a width of 0.1 mm or more occurred in the 30000th injection molding. On the other hand, in Example 1 (first mode, see FIG. 4) and Example 2 (second mode, see FIG. 5), a burr with a width of 0.1 mm or more occurs in the 40000th injection molding. In the 50,000th injection molding, burrs having a width of 0.1 mm or more were generated. In Example 3 (third mode, see FIG. 6), burrs having a width of 0.1 mm or more were not generated in the 50,000th injection molding, and burrs having a width of 0.1 mm or more were generated in the 60000th injection molding. It was. In Example 4 (fourth aspect, see FIG. 7), no burr having a width of 0.1 mm or more was generated in the 60000th injection molding, and burr having a width of 0.1 mm or more was generated in the 70000th injection molding. It was.

  From the comparison between Examples 1 to 4 and Comparative Example 1, in addition to the gap for molding the functional component of the heating resistor 830, providing an additional gap contributes to improving the durability of the mold. I understand. Further, from the comparison between Example 1 and Example 3 and the comparison between Example 2 and Example 4, when providing an additional gap, the gap portion C441a, b, C442a, b having a small cross-sectional area is provided at the end. It can be seen that providing the larger void portions C443a, b, C444a, b further improves the durability of the mold.

B2. Burr size measurement test:
For the second mode (see FIG. 5), the configuration of the legs 834a and b is variously changed to create a test product, and the injection molding pressure is set to 20 MPa higher than the actual product setting. Then, injection molding was performed. In the test product, the cross-sectional area S1 of the front end portion 832 of the heat generating portion 833 was 0.16 mm ² . Moreover, the cross-sectional area S2 of each leg part 834 was 0.75 mm < ² >. The cross-sectional area S1 of the front end portion 832 is obtained by measuring the size of the cross section in the direction perpendicular to the direction in which the front end portion 832 extends at two or more sites of the front end portion 832 and calculating the average value thereof. To do.

  FIG. 8 is a cross-sectional view of the ceramic heater 800 taken along the line EE in FIG. FIG. 8 is a cross-sectional view of the ceramic heater 800, and thus the base 810 is shown in the drawing. Each of the EE cross sections shows a cross section of two portions of the front end portion 832 that are a part of the front end portion 832 and extend parallel to the central axis. As described above, the front end portion 832 has a constant cross-sectional area. Let S1 be the average value of the cross-sectional areas of the two portions of the front end portion 832.

  The dividing line of the mold D1 when the heating resistor 830 is formed coincides with a line connecting the centers of two circular cross sections of the front end portion 832 having a circular cross section. For this reason, the burr B is generated on a line connecting the centers of the two circles of the front end portion 832. The dimension of the burr B is represented by LB.

  FIG. 9 is a cross-sectional view of the ceramic heater 800 taken along the line FF in FIG. In the EE cross section, the cross sections of the thickest portions of the leg portion 834a and the leg portion 834b appear. Let S2 be the cross-sectional area of the thickest part of the leg part 834a and the leg part 834b. As described above, the leg portions 834a, b are provided with a thicker portion on the rear end side than a portion on the front end side, and the outer contour of the legs 834a, b is that of the conductive portions 836a, b at the rear ends of the leg portions 834a, b. It matches each outer contour. The conductive portions 836a and 8b extend linearly while maintaining a constant cross-sectional area. For this reason, in this embodiment, the cross-sectional area S2 of the thickest part of leg part 834a, b is equal to the cross-sectional area of electroconductive part 836a, b.

  In this test, for the second mode (see FIG. 5), the cross-sectional area S1 of the front end portion 832 and the cross-sectional areas S2 of the thickest portions of the leg portion 834a and the leg portion 834b are variously changed. 8 was created. And the mold D1 which does not provide the space | gap part C442a, b with respect to each Example was prepared, and the comparative examples 2-5 were created. And the dimension LB of the burr | flash B was measured about each Example and the comparative example. The method for measuring the dimension LB of the burr B is the same as the method described in the mold durability test. The results are shown in Table 2.

  In Table 2, it is shown in the “additional gap” column whether or not there is an additional gap portion that is not a gap for molding the functional component. In addition, a ratio S1 / S2 of the size S1 of the cross-sectional area of the front end 832 to the cross-sectional area S2 of the thickest part of the legs 834a and b is shown. The cross-sectional area ratio S1 / S2 is an index of the resistance (hardness of flow) of the raw material in the gap portion C42 for molding the front end portion 832 with respect to the size of the gap portions C44a, b for molding the leg portions 834a, b. It is. The raw material is injected from the narrow gap portion C42 side and supplied to the thick gap portions C44a and b via the gap portion C42. When the cross-sectional area ratio S1 / S2 is small, the raw material is injected at a higher pressure so that the entire gap can be filled in a short time while passing the raw material through the narrow gap portion C42. Therefore, when the cross-sectional area ratio S1 / S2 is small, burrs are likely to occur at the front end portion 832 formed by the gap portion C42.

  From the comparison between Example 5 and Comparative Example 2, in the aspect in which S1 / S2 is 0.12, the size of the burr was reduced by 41% by providing the gap portions C442a and b (see FIG. 5). I understand. From the comparison between Example 6 and Comparative Example 3, it can be seen that, in the aspect in which S1 / S2 is 0.21, the size of the burr is reduced by 53% by providing the gap portions C442a and b. From the comparison between Example 7 and Comparative Example 4, it can be seen that, in the aspect in which S1 / S2 is 0.40, the size of the burr is reduced by 38% by providing the gap portions C442a and b. From the comparison between Example 8 and Comparative Example 5, it can be seen that, in the aspect where S1 / S2 is 0.45, the size of the burr is reduced by 25% by providing the gap portions C442a and b.

  From the above results, in the aspect in which the ratio S1 / S2 of the cross-sectional area of the front end 832 to the cross-sectional area of the legs 834a and 8b is 0.40 or less, in addition to the gap for forming the functional component of the heating resistor It can be seen that providing additional voids is effective in reducing burrs. In addition, in an aspect in which the cross-sectional area ratio S1 / S2 is 0.21 or less, it is more effective for reducing burrs to provide an additional space in addition to the space for molding the functional component of the heating resistor. I understand that.

C. Other forms:
C1. Modification of the first embodiment:
FIG. 10 is a cross-sectional view showing a modification of the first embodiment. In the first embodiment, the gaps C441a, b of the mold D1 (that is, the protrusions 8341a, b of the heat generating part 833p) are on one side with respect to the dividing line PL of the mold D1 (see FIG. 4). See right). However, the additional void portion (that is, the convex portion of the heat generating portion) may be provided in a range including the dividing line PL of the mold D1. For example, as shown in FIG. 10, the additional gap portion C441c (that is, the convex portion 8341c of the heat generating portion 833) may be provided symmetrically about the dividing line PL of the mold D1.

  FIG. 11 is a cross-sectional view showing a modification of the first embodiment. In the first embodiment, the cavity C441a, b (that is, the convex portion 8341a, b of the heat generating portion 833p) of the mold D1 has a substantially rectangular parallelepiped shape having a rectangular cross section (see FIG. 4). However, the additional void portion may be provided in other shapes. For example, the additional gap portion (that is, the convex portion of the heat generating portion) may be provided such that the thickness in the Y-axis direction decreases as the distance from the leg portions 834a and 8b increases. For example, as shown in FIG. 11, the additional gap portion C441d (that is, the convex portion 8341d of the heat generating portion 833) may have a substantially triangular cross section in a cross section perpendicular to the Z axis.

  FIG. 12 is a cross-sectional view showing a modification of the first embodiment. Further, for example, as shown in FIG. 12, the additional gap portion C441e (that is, the convex portion 8341e of the heat generating portion 833) is provided such that the thickness in the Y-axis direction increases as the distance from the leg portions 834a and b increases. It may be.

  FIG. 13 is a cross-sectional view showing a modification of the first embodiment. In the first embodiment, the gap portions C441a and b of the mold D1 are provided in a range including the rear ends (ends in the Z axis + direction) of the gap portions C44a and b (see the left side in FIG. 4). . That is, the convex portions 8341a and b of the heat generating portion 833p are provided at the rear ends (ends in the Z axis + direction) of the leg portions 834a and b. However, the additional gap portion (that is, the convex portion of the heat generating portion) may be provided in another part of the gap portions C44a and b. That is, the convex portions 8341a and b of the heat generating portion 833p may be provided at other portions of the leg portions 834a and b.

  For example, as shown in FIG. 13, the additional gap portions C441f, g may be provided at positions separated from the rear ends of the gap portions C44a, b by a predetermined distance. That is, the convex portions 8341f and g of the heat generating portion 833 may be provided at a position away from the rear ends of the leg portions 834a and b by a predetermined distance.

  However, it is preferable that the convex portion is provided in a portion other than the portion (the front end portion 832 in the above embodiment) having the smallest cross-sectional area in the heat generating portion. During the operation of the ceramic heater, the temperature is highest in the portion where the cross-sectional area is minimum in the direction in which the current flows. In the said aspect, since the convex part is provided in site | parts other than such a part, the abnormal heat generation of a convex part can be prevented.

C2. Other variations:
FIG. 14 is a view showing a modification of the mold D1 and the heat generating portion 833. As shown in FIG. A plan view of the mold D1 and the heat generating portion 833 is shown in the upper part of FIG. A cross-sectional view of the GG cross section in the plan view of the mold D1 and the heat generating portion 833 is shown in the lower part of FIG. In the above embodiment, the legs 834a and 8b are provided such that the rear end portion is thicker than the front end portion. Then, the outer contours of the leg portions 834a and b coincide with the outer contour of the front end portion 832 at the front ends of the leg portions 834a and b, respectively. The outer contours of the leg portions 834a and b coincide with the outer contours of the conductive portions 836a and b at the rear front ends of the leg portions 834a and b, respectively (see FIGS. 4 to 7).

  However, as shown in FIG. 14, the cross-sectional area of the leg portions 834 a and b may be a constant value equal to the cross-sectional area of the front end portion 832. Further, the additional gap portions C442c, d of the mold D1 may have the same width as the width of the gap portions C44a, b in the Y-axis direction. That is, the convex portions 8342c and d of the heat generating portion 833 may be exposed on both the outer side and the inner side in the Y-axis direction of the leg portions 834a and b. In the modification of FIG. 14, the gap portions C442c, d (that is, the convex portions 8342c, d of the heat generating portion 833) are provided in a range including the dividing line PL of the mold D1 in the Y-axis direction. (See the lower part of FIG. 14).

  FIG. 15 is a view showing a modification of the mold D1 and the heat generating portion 833. As shown in FIG. The additional gap portions C442e and f of the mold D1 may have a width narrower than the width of the gap portions C44a and b in the Y-axis direction. In other words, the protrusions 8342c, d of the heat generating portion 833 may be exposed to neither the outside nor the inside in the Y-axis direction of the leg portions 834a, b.

  FIG. 16 is a view showing a modified example of the mold D1 and the heat generating portion 833. As shown in FIG. The additional gap portions C442g, h of the mold D1 may have a width narrower than the width of the gap portions C44a, b in the Y-axis direction. And as shown in FIG. 16, the convex parts 8342g and h of the heat generating part 833 may be exposed to the outside of the leg parts 834a and b in the Y-axis direction inside and outside. The protrusions 8342g and h of the heat generating portion 833 may be exposed to the inside of the legs 834a and 8b in the Y-axis direction.

  In the fourth embodiment, the gap portion C442a and the gap portion C444a (that is, the base portion 8348a and the tip portion 8349a of the convex portion 8351a) have the same width in the Y-axis direction (see FIG. 7). Further, the gap portion C442b and the gap portion C444b (that is, the base portion 8348b and the tip portion 8349b of the convex portion 8351b of the heat generating portion 833) have the same width. However, an additional gap connected to the gap for molding the functional component of the heating resistor 830 (that is, the base of the convex portion of the heating portion) and an additional gap connected to the additional gap. The gap (that is, the tip portion of the convex portion of the heat generating portion) may have a different width in the Y-axis direction.

  FIG. 17 is a view showing a modified example of the mold D1 and the heat generating portion 833. For example, as shown in FIG. 17, the additional gap connected to the gap for molding the functional component of the heating resistor 830 (that is, the base of the convex portion of the heating portion) You may have a width | variety narrower than the additional space | gap (namely, front-end | tip part of the convex part of a heat generating part) further connected to the additional space | gap.

  FIG. 18 is a view showing a modification of the mold D1 and the heat generating portion 833. As shown in FIG. For example, as shown in FIG. 18, the additional gap connected to the gap for molding the functional component of the heating resistor 830 (that is, the base of the convex portion of the heating portion) You may have a width | variety wider than the additional space | gap (namely, front-end | tip part of the convex part of a heat generating part) further connected to the additional space | gap.

  Further, as shown in FIG. 18, the additional gap may be provided only in one of the pair of gap portions C44a and b. That is, the convex part may be provided in only one of the leg parts 834a and b.

C3. Other:
(1) In the above embodiment, the front end 832 has a constant cross-sectional area. However, the front end portion of the heat generating portion may have an aspect in which the cross-sectional area in the cross section perpendicular to the direction in which the front end portion extends is not constant in the direction in which the front end portion extends. In such an aspect, in the evaluation of the cross-sectional area ratio S1 / S2, the cross-sectional area S1 of the front end portion of the heat generating portion is the smallest cross-sectional area among the cross-sectional areas in an arbitrary cross section perpendicular to the direction in which the front end portion extends. . The cross-sectional area ratio S1 / S2 is an index of the resistance (hardness of flow) of the raw material in the gap portion C42 for molding the front end portion 832 with respect to the size of the gap portions C44a, b for molding the leg portions 834a, b. This is because.

(2) In the first and third embodiments, the gap portions C441a and 443a are arranged so as to protrude on the opposite side of the central axis SC with respect to the gap portion C44a (see FIGS. 4 and 4). 6). Further, the gap portions C441b and C443b are arranged so as to protrude on the opposite side to the central axis SC with respect to the gap portion C44b. In other words, the convex portions 8341a and 8350a are arranged so as to protrude on the opposite side to the central axis SC with respect to the leg portion 834a. Further, the convex portions 8341b and 8350b are arranged so as to protrude on the opposite side to the central axis SC with respect to the leg portion 834b.

  In the second and fourth aspects, the gap portions C442a and C444a are arranged so as to protrude in the Z axis + direction from the inclined rear end face of the gap portion C44a (see FIGS. 5 and 7). . The gap portions C442b and C444b are arranged so as to protrude in the Z axis + direction from the inclined rear end face of the gap portion C44b. In other words, the convex portions 8342a and 8351a are arranged so as to protrude in the Z-axis + direction from the inclined rear end surface of the leg portion 834a. Further, the convex portions 8342b and 8351b are arranged so as to protrude in the Z axis + direction from the inclined rear end surface of the leg portion 834b.

  However, the additional void portion, in other words, the convex portion provided on the leg portion can be provided in another manner. However, it is preferable that the part where the convex part is arranged is a position farther from the other leg part than the part closest to the other leg part in the part of the leg part provided with the convex part. . In addition, "the place where the convex part is arranged is a position farther from the other leg part than the part closest to the other leg part in a part of the leg part provided with the convex part." Means that an arbitrary part of the convex part is provided farther from the other leg part than a part of the leg part provided with the convex part closest to the other leg part. To do. The parameters set when providing the convex portion in this way include the position where the convex portion is provided and the shape of the convex portion. If it is set as such an aspect, the possibility that the heat-emitting part comprised with the electroconductive ceramic will short-circuit with a convex part is low.

(3) In the above-described embodiment, one gap portion constituting the convex portion is provided in each of the leg portions 834a and b. However, two or more convex portions can be provided on each leg portion. In such an aspect, it is preferable to provide the same number of convex portions on each leg portion. If it is set as such an aspect, when an exothermic part is injection-molded, the grade of a pressure rise can be relieve | moderated more uniformly about a pair of leg part.

  Moreover, it is more preferable that each leg part is provided with a convex part at the same position in the direction in which the leg part extends. If it is set as such an aspect, when an exothermic part is injection-molded, the grade of a pressure rise can be relieve | moderated more equally about a pair of leg part.

(4) In the said embodiment, the convex parts 8341-8349 are provided in the leg part 834 (refer FIGS. 4-7, FIGS. 13-18). However, the convex portion can be provided on the front end portion 832 or the conductive portion 836. However, it is desirable that the heating resistor 830 is provided in a portion other than the portion having the smallest cross-sectional area.

DESCRIPTION OF SYMBOLS 10 ... Glow plug 90 ... Internal combustion engine 100 ... Terminal 200 ... Middle shaft 300 ... Insulating member 400 ... Insulating member 500 ... Main metal fitting 510 ... Shaft hole 520 ... Tool engaging part 540 ... Male thread part 600 ... Ring 700 ... Outer cylinder 710 ... Shaft hole 800 ... Ceramic heater 810 ... Substrate 830 ... Heat generating resistor 832 ... Front end 833 ... Heat generating part 833p to 833s ... Heat generating part 834a, b ... Leg part 836a, b ... Conducting part 838 ... Terminal part 838a, b ... Terminal part 8341a to 8341f ... convex part 8342a to 8342c ... convex part 8346a, b ... base part 8347a, b ... tip part 8348a, b ... base part 8349a, b ... tip part 8350a, b ... convex part 8351a, b ... convex part B ... burr C ... Cavity C4 ... Cavity C4p to C4s ... First to fourth aspects of Cavity C4 C42 ... Cavity C44a, b ... gap portion C441a-C441f ... gap portion C442a, b ... gap portion C443a, b ... gap portion C444a, b ... gap portion Co1a, b ... opening Co2a, b ... opening Co3a, b ... opening Co4a, b ... opening C442c to C442e: Cavity part C6a, b ... Cavity part D1 ... Die D2a, b ... Auxiliary mold I1 ... Injection path I2 ... Injection path LB ... Burr dimension PL ... Die dividing line Pb ... Burr measurement location SC ... Center axis

Claims (8)

A base made of insulating ceramic;
A heat generating part made of conductive ceramic and embedded in the substrate,
A front end located at the front end of the heat generating portion;
A heating part comprising a pair of legs extending from the front end toward the rear end,
The heat generating portion is made of a conductive ceramic different from the conductive ceramic, is embedded in the base, and is connected to the leg portions and extends toward the rear end side while maintaining a substantially constant cross-sectional area. A pair of conductive parts;
A ceramic heater comprising:
The ratio S1 / S2 of the cross-sectional area S1 of the portion having the smallest cross-sectional area of the heat generating portion to the cross-sectional area S2 of the leg portion is 0.4 or less,
The heat generating part includes a convex part provided on the leg part with a cross-sectional area smaller than the cross-sectional area of the leg part in the direction from the front end to the rear end,
The part where the convex part is arranged is provided at a position farther from the other leg part than the part closest to the other leg part in the part of the leg part where the convex part is provided. A ceramic heater. The ceramic heater according to claim 1,
The said convex part is a ceramic heater provided in the position which is not on the line segment which connects the shortest distance of each said leg part in the arbitrary cross sections perpendicular | vertical to the direction where a pair of said leg part is extended. The ceramic heater according to claim 1 or 2,
The convex portion is a ceramic heater provided in a portion other than a portion having a minimum cross-sectional area in the heat generating portion. The ceramic heater according to claim 3,
The said convex part is a ceramic heater which is provided in the connection part of the said leg part and the said electroconductive part, and is contacting the said electroconductive part. The ceramic heater according to any one of claims 1 to 4,
The convex portion includes a first portion and a second portion having a cross-sectional area larger than that of the first portion along a direction away from the leg portion. The ceramic heater according to any one of claims 1 to 5,
The heat generating portion is a ceramic heater provided with the same number of convex portions on each leg portion. The ceramic heater according to claim 6,
The said heat-emitting part is a ceramic heater which is provided on the said each leg part, Comprising: The said convex part is provided in the same position about the direction where a pair of said leg part is extended.   A glow plug comprising the ceramic heater according to any one of claims 1 to 7.

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