JP6512848B2 - Ceramic heater and glow plug - Google Patents

Description

  The present invention relates to a ceramic heater used for glow plugs and the like.

  The ceramic heater used for the glow plug has a rod-like form in which a ceramic resistor made of conductive ceramic is embedded in a ceramic base made of insulating ceramic. Then, the ceramic resistor is disposed to extend along the direction of the axis of the heater body on the rear side of the first resistor portion disposed at the tip of the heater body, and the tip is the first resistor. The body portion has a pair of second resistor portions that are respectively joined to both end portions in the current-carrying direction and are made of ceramic having a lower resistivity (Patent Document 1). The ceramic resistor is formed by injection molding.

JP 2003-22889 A WO 2008/123296 pamphlet JP 2006-35630 A

  In injection molding, the pressure of the filling material in the injection space rapidly increases until the injection of the filling material is stopped after the filling material has spread in the injection space inside the mold. As a result, the high-pressure filling material may intrude into the mating surfaces of the mold and become burrs. In addition, filling materials for ceramic resistors include materials with high hardness such as tungsten carbide. The material having high hardness repeatedly intrudes into the mating surfaces of the dies, which abrades the mating surfaces of the dies, increases the gap between the dies, and easily causes burrs. As a result, in injection molding of the ceramic resistor, the mold can not be used earlier than injection molding of resin.

The present invention has been made to solve at least a part of the above-described problems, and can be realized as the following modes or application examples.
A substrate made of insulating ceramic,
A heat generating portion made of conductive ceramic and embedded in the substrate,
A front end portion located at the front end of the heat generating portion;
A heat generating portion 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 legs and extends while maintaining a substantially constant cross-sectional area toward the rear end side A pair of conductive parts,
A ceramic heater comprising
Ratio S1 / S2 with respect to the cross-sectional area S2 of the said leg part of the cross-sectional area S1 of the part with the smallest cross-sectional area among the said heat-emitting part is 0.4 or less,
The heat generating portion includes, on the leg, a convex portion provided with a cross-sectional area smaller than a cross-sectional area of the leg in a direction from the front end to the rear end.
The convex portion is
The leg portion protrudes to the side opposite to the central axis of the ceramic heater,
It is provided in a part other than the part where the cross-sectional area is the smallest among the heat generating parts,
The portion where the convex portion is disposed is provided at a position farther from the other leg portion than the portion closest to the other leg portion among the portions of the leg portion in which the convex portion is provided. The ceramic heater has been

(1) According to one aspect of the present invention, a ceramic heater is provided. The ceramic heater comprises: a base made of an insulating ceramic; a heat generating part made of a conductive ceramic and embedded in the base; a front end located at the front end of the heat generating part; from the front end A heat generating portion comprising a pair of legs extending toward the rear end side; and a conductive ceramic different from the conductive ceramic of the heat generating portion, embedded in the base and respectively embedded in the legs And a pair of conductive portions connected and extending while maintaining a substantially constant cross-sectional area toward the rear end side. Ratio S1 / S2 with respect to the cross-sectional area S2 of the said leg part of the cross-sectional area S1 of the part with the smallest cross-sectional area among the said heat-emitting part is 0.4 or less. The heat generating portion includes, on the leg portion, a convex portion provided with a cross-sectional area smaller than the cross-sectional area of the leg portion in the direction from the front end to the rear end. The portion where the convex portion is disposed is provided at a position farther from the other leg portion than the portion closest to the other leg portion among the portions of the leg portion in which the convex portion is provided. It is done.
According to such an aspect, when injection molding of the heat-generating portion, the filling material can be further filled in the convex portion even after the filling material has spread to the legs and the connection portion. For this reason, after filling material has spread to the legs and the connection part, the degree of pressure increase of the filling material before the injection material of the filling material is stopped is alleviated compared to the embodiment without the protrusion be able to. Therefore, there is a high possibility that generation of burrs in the heat generating portion can be prevented. In addition, as a result, it is possible to reduce the wear of the gap between the dies. Furthermore, since the projection is a part of the leg provided with the projection and is provided at a position farther from the other leg than the part closest to the other leg, the conductive portion is conductive. There is a low possibility that the heat generating portion made of ceramic will be short-circuited by the convex portion.

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

(3) In the ceramic heater according to the above aspect, the convex portion may be provided at a portion other than the portion where the cross-sectional area of the heat generating portion is the smallest. In such an embodiment, during operation of the ceramic heater, the highest temperature is reached in the portion where the cross-sectional area is the smallest in the direction in which the current flows. In the above-mentioned mode, since a convex part is provided in parts other than a portion which has the smallest cross-sectional area among heating parts, possibility that abnormal heat generation of a convex part can be prevented is high.

(4) In the ceramic heater according to 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. According to such an aspect, the convex portion does not protrude to the outer shape of the member made of the conductive ceramic including the heat generating portion and the conductive portion. For this reason, the projections are unlikely to adversely affect the other surrounding members.

(5) In the ceramic heater according to the above aspect, the convex portion includes a first portion and a second portion having a larger cross-sectional area than the first portion along a direction away from the leg portion. It can be an aspect. According to such an aspect, in the first portion, when injection molding of the heat-generating portion, the protrusion is not filled with the filling material before the filling material reaches the legs and the connection portion. The cross-sectional area can be set. Then, for the second part, after the filling material has spread to the legs and the connection part, the time until the convex part is filled with the filling material is for the accuracy of the timing when stopping the injection of the filling material. The cross-sectional area and volume can be set to be sufficient. Therefore, the degree of pressure increase of the filling material after the filling material has spread to the legs and the connection can be alleviated more effectively as compared with the embodiment without the above configuration.

(6) In the ceramic heater according to the above aspect, the heat generating portion may be configured to include the same number of convex portions on each of the leg portions. According to such an aspect, the degree of pressure increase is mitigated equally for the pair of legs when injection molding the heat-generating portion, as compared to the aspect in which each leg has a different number of projections. Can.

(7) In the ceramic heater according to the above aspect, the heat generating portion may include the convex portion at the same position on each of the leg portions in the direction in which the pair of leg portions extend. it can. According to such an aspect, when injection molding the heat generating portion, the degree of pressure increase can be mitigated more evenly for the pair of legs.

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

  The present invention can also be realized in various forms other than ceramic heaters and glow plugs. For example, a method of manufacturing a ceramic heater, a method of manufacturing a glow plug, a manufacturing apparatus for realizing the manufacturing method, a computer program for controlling the manufacturing apparatus, and a nontemporary recording medium recording the computer program Can.

FIG. 2 is an explanatory view showing a partial cross section of the glow plug 10; It is an explanatory view showing a ceramic heater 800. 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 1st aspect C4p of the cavity part C4 comprised with the metal mold | die D1 and auxiliary | assistant metal mold | die D2a, D2b. It is explanatory drawing which shows 2nd aspect C4q of the cavity part C4 comprised with the metal mold | die D1 and auxiliary | assistant metal mold | die D2a, D2b. It is explanatory drawing which shows 3rd aspect C4r of the cavity part C4 comprised with the metal mold | die D1 and auxiliary | assistant metal mold | die D2a, D2b. It is explanatory drawing which shows 4th aspect C4s of the cavity part C4 comprised with the metal mold | die D1 and auxiliary | assistant 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. 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 “tip side” or “front”, and the upper side of FIG. 1 is referred to as “rear end” or “rear”.

  FIG. 1 shows the X axis, the Y axis, and the Z axis as three space axes orthogonal to one another. 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. Of 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 figures.

  The glow plug 10 includes a ceramic heater 800 for generating heat and functions as a heat source for assisting ignition at the start of the internal combustion engine 90 including a diesel engine. The glow plug 10 includes, in addition to the ceramic heater 800, an inner 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 central axis 200 of the glow plug 10 is a metal body having conductivity. The central shaft 200 has a cylindrical shape extending around the central axis SC. The center shaft 200 receives power feeding from the outside of the glow plug 10 via the terminal 100 on the rear end side of the center shaft 200. In another embodiment, the center shaft 200 may receive power directly from the outside of the glow plug 10 on the rear end side of the center shaft 200. The center shaft 200 relays the power supplied from the outside of the glow plug 10 to the ceramic heater 800 on the tip side.

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

  The metal shell 500 of the glow plug 10 is a conductive metal body. The metal shell 500 has a tubular shape extending around the central axis SC. The metal shell 500 includes an axial hole 510, a tool engagement portion 520, and an external thread portion 540.

  The axial 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 diameter of the middle shaft 200. Inside the shaft hole 510, the middle shaft 200 is positioned on the central axis SC, and a space is formed between the shaft hole 510 and the middle shaft 200 to electrically insulate the shaft hole 510 from the middle shaft 200. In the present embodiment, the center 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 engagement portion 520 of the metal shell 500 is configured to be engageable with a tool (not shown) used for attaching and detaching the glow plug 10 to the internal combustion engine 90. The male screw portion 540 of the metal shell 500 is configured to be fixable to the internal combustion engine 90 by being fitted to a female screw 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 tubular shape extending around the central axis SC. The outer cylinder 700 is provided with an axial hole 710 for holding 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 heat generating element (heat generating 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 which is a ceramic material having electrical insulation. A heat generating resistor 830 is embedded in the base 810. The substrate 810 supports the heating resistor 830. The base 810 electrically insulates the heating resistor 830 from the outside of the glow plug 10 and transfers the heat of the heating resistor 830 to the outside of the glow plug 10.

In the present embodiment, the ceramic material forming the substrate 810 is mainly made of silicon nitride (Si ₃ N ₄ ). In another embodiment, at least a portion of silicon (Si) of the silicon nitride (Si ₃ N ₄ ) forming the substrate 810 is replaced with aluminum (Al), and at least a portion of nitrogen (N) is oxygen ( O) may be substituted. The ceramic material forming the substrate 810 may contain a rare earth oxide (eg, ytterbium (Yb) oxide, erbium (Er) oxide, etc.) and a silicide of chromium (Cr) 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 mainly comprises tungsten carbide (WC). In the present embodiment, the ceramic material contains silicon nitride (Si ₃ N ₄ ) in addition to tungsten carbide. The ceramic material contains 55 to 70% by weight of tungsten carbide and 28 to 35% by weight of silicon nitride, and the remaining 2 to 10% by weight of erbium oxide (Er ₂ O ₃ ) and silicon oxide (SiO ₂ ) May be contained. In another embodiment, 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 a ceramic heater 800. As shown in FIG. 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 portion 833, a pair of conductive portions 836, and two terminal portions 838.

  The heat generating portion 833 is located on the front end side (front side) 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 in which a cylinder having a constant cross-sectional area is folded in an arc shape. The front end 832 electrically connects the pair of legs 834 at the front end.

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

  The leg portion 834a is provided such that a portion on the front end side is thinner than a portion on the rear end side. The leg 834 a has the same cross-sectional area at its front end as the front end 832. The outer contour of the leg 834a coincides with the outer contour of the front end 832 at the front end of the leg 834a. The leg 834a has the same cross-sectional area as the conductive portion 836a at the thickest portion. The outer contour of the leg 834a matches the outer contour of the conductive portion 836a at the rear end of the leg 834a. The leg 834 b also has the same configuration as the leg 834 a with respect to the front end 832 and the conductive portion 836 b. In the description of the present embodiment, when the leg 834a and the leg 834b are collectively referred to, the symbol "834" is used.

  The conductive ceramic forming the heat generating portion 833 (the front end portion 832 and the legs 834 a and b) has a higher resistivity than the conductive ceramic forming the conductive portion 836. The size of the cross section of the heat generating portion 833 in the cross section perpendicular to the extending direction of the heat generating portion 833 is equal to or less than the size of the cross section of each conductive portion 836 in the cross section perpendicular to the extending direction of each conductive portion 836 (FIG. 2) reference). Therefore, the electrical resistance of the front end portion 832 and the leg portion 834 is larger than that of the conductive portion 836. In the present embodiment, the heating resistor 830 generates heat centering on the leg 834 by energization, and the leg 834 has the highest temperature of the heating resistor 830.

  The pair of conductive portions 836 extend from each of the pair of legs 834 to the rear end side (the 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 834a to the rear end side while maintaining a substantially constant cross-sectional area. The conductive portion 836b extends linearly from the leg 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 the present embodiment, when the conductive portion 836a and the conductive portion 836b are collectively referred to, the symbol "836" is used. 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 in the X axis + direction from the conductive portion 836a. The terminal portion 838 b is formed on the rear end side of the conductive portion 836 b and protrudes from the conductive portion 836 b in the negative X-axis direction. In the present embodiment, the terminal portion 838 b is located on the tip side of the terminal portion 838 a. In the present embodiment, in the state where the ceramic heater 800 is assembled to the metal shell 500, the terminal portion 838a is in contact with the ring 600 and is electrically connected to the middle shaft 200 via the ring 600. Terminal portion 838 b is electrically connected to outer cylinder 700. In the description of the present embodiment, when the terminal portion 838a and the terminal portion 838b are collectively referred to, the symbol “838” is used.

A3. Manufacturing method of heating resistor:
FIG. 3 is a plan view showing the process of forming the heating resistor 830 by the injection molding method. The heating resistor 830 is produced by injection molding as described above. In FIG. 3, the hatched portion is a mold D1. The mold D1 is provided with a space C having a shape corresponding to the heating resistor 830, and injection paths I1 and I2 for injecting the ceramic into the space C. The injection path I 1 is connected to the front end of the portion of the air gap C corresponding to the front end portion 832. The injection path I2 is connected to the rear end of the portion of the air gap C corresponding to the pair of conductive portions 836. The mold D1 forming the air gap C is divided into two in a direction perpendicular to the paper surface in a plane substantially coinciding with the paper surface of FIG. The pair of molds D1 are used in injection molding in such a manner that they are fitted in a direction perpendicular to the paper surface of FIG. 3, clamped, and used. Note that FIG. 3 shows a state in which the heating resistor 830 is formed in the mold D1. Further, in order to facilitate understanding of the technology, in FIG. 3, auxiliary configurations such as a gas venting hole and a cooling water channel provided in the mold D1 are omitted.

  When forming the heating resistor 830, first, the heating portion 833 is formed. When the heat generating portion 833 is formed, the auxiliary molds D2a and D2b are respectively disposed in portions corresponding to the pair of conductive portions 836a and 836b in the space C of the mold D1. As a result, with respect to the void portion C4 corresponding to the heat generating portion 833 in the void C of the mold D1, void portions C6a, C corresponding to the conductive portions 836a, b and the terminal portions 838a, b in the void 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 is fitted in a direction perpendicular to the sheet of FIG. 3 and clamped, and a raw material including a conductive ceramic for forming the heat generating portion 833 is injected from the injection path I1. . Then, the raw material is injected into the void portion C4 of the mold D1 corresponding to the heat generating portion 833, and the heat generating portion 833 is formed. At this time, the conductive ceramic ejected from the injection path I1 is not injected into the void 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. Then, the pair of molds D1 is again fitted and clamped, and a raw material including a conductive ceramic for forming the conductive portions 836a and 836b is injected from the injection path I2. Then, the raw material is injected into the void portions C6a and C6b of the mold D1 corresponding to the conductive portions 836a and b and the terminal portions 838a and b, and the conductive portions 836a and 836b are formed. At that time, the front ends of the conductive portions 836a and 836b are formed without a gap on the rear end surface of the heat generating portion 833 which has already been formed.

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

  In the present specification, in order to reduce the complexity of the description, “heat generating resistor 830”, “heat generating portion 833”, and “conductive portion” are also used for the heat generating resistor 830 before firing and the intermediate product of its component parts. The names of finished products, such as 836a, 836b, etc., may be used to indicate.

  The volume of the void portion C4 corresponding to the heat generating portion 833 is smaller than the volume of the void 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 void after the raw material has spread in the void, the pressure in the void portion C4 is likely to increase more than the void portions C6a and C6b. Therefore, after the raw material reaches the space, the phenomenon in which the pressure of the filling material in the injection space rapidly increases is more likely to occur particularly in the formation of the heat generating portion 833 until the injection of the raw material is stopped. .

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

  A void portion C4p for molding the heat generating portion 833p includes a void portion C42 for molding the front end portion 832, void portions C44a and b for molding the leg portions 834a and b, and void portions C441a and b. . The void portion C 42 has a void having a shape obtained by curving the cylinder 180 degrees. The void portion C44a includes a cylindrical void having a larger diameter than the void portion C42. The cylindrical void of the void portion C44a is connected to one rear end of the void portion C42 through a tapered void. The rear end of the cylindrical gap of the gap portion C44a is defined by a plane C44af which intersects at a predetermined angle (for example, 30 degrees here) with respect to the central axis SC. In the first embodiment, the thickest portion of the void portion C44a and the void portion C42 have a circular cross section. However, the thickest portion of the void portion C44a and the void portion C42 may have other cross-sectional shapes.

  The void portion C44b is also configured in the same manner as the void portion C44a. That is, the void portion C44b has a shape that is in a mirror image relationship with the void portion C44a across the plane defined by the central axis SC and the Y axis.

  The void portions C 441 a and b are connected to void portions C 44 a and b for forming the leg portions 834 a and b, respectively. The void portion C441a is arranged to protrude to the opposite side of the central axis SC with respect to the void portion C44a. The void portion C441b is disposed to protrude to the side opposite to the central axis SC with respect to the void portion C44b.

  As a result, the portion where the convex portion 8341a of the heat generating portion 833 is disposed is a portion of the leg portion 834a in which the convex portion 8341a is provided, rather than the portion 834na closest to the other leg portion 834b. , And the other leg 834b. Similarly, in the portion where the convex portion 8341b is disposed, from the other leg 834a than the portion 834nb closest to the other leg 834a among the portions of the leg 834b in which the convex 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. It is provided.

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

  The void portions C 441 a, b of the mold D 1 are voids having a substantially rectangular parallelepiped internal space whose longitudinal direction is parallel to the central axis SC. The cross-sectional areas of the void portions C 441 a, b are smaller than the cross-sectional areas of the void portions C 44 a, b for forming the leg portions 834 a, b (see the right side of FIG. 4). As a result, the cross-sectional areas of the convex portions 8341 a and b formed by the void portions C 441 a and b are smaller than the cross-sectional areas of the leg portions 834 a and b. In addition, each cross-sectional area of the additional space | gap part (C441a, b) of the metal mold | die in the case of referring to magnitude relation, and each cross-sectional area of the space | gap part (C44a, b) for forming a functional component is a central axis The largest cross-sectional area among cross-sectional areas in any cross section perpendicular to SC. The same applies to the cross-sectional areas of the convex portion (8341a, b) and the leg portion (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 a connection portion between the gap portion C44a and the gap portion C441a is smaller than the cross-sectional area in a 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 connection portion of the gap portion C44b and the gap portion C441b is smaller than the cross-sectional area in the cross section perpendicular to the central axis SC of the gap portion C44b. With such a configuration, at the time of injection molding, the void portions C44a and B having a large cross-sectional area are first filled with the raw material, and then the void portions are obtained through connection portions (openings) Co1a and B having a small cross-sectional area. The raw material is injected into C441a and b.

  Since the void portion C4p for molding the heat generating portion 833p has the configuration as described above, at the time of injection molding, the void portion C42 for molding the front end portion 832 is first filled with the raw material, and then the leg portion 834a The raw material is filled in the void portions C 44 a and b for forming B and b. Thereafter, the control unit performing control of the injection molding causes the injection unit injecting the raw material to stop the injection.

  It is preferable to stop the injection of the raw material after the void portions C42, C44a and b are completely filled with the raw material. And, from the completion of the filling of the raw material in the void portion C42 and in the void portions C44a and b, a time delay occurs from the termination of the injection. Therefore, after the gap portions C42, C44a, b are completely filled with the material, the material is injected into the gap portions C441a, b through the connecting portion with the gap portions C44a, b until the injection is stopped. Be done.

  For this reason, according to the first aspect, compared with the aspect in which the additional void portion C 441 a, b which is not for molding the functional part in the mold is not provided, the void portions C 42, C 44 a, b are completely The degree of pressure rise in the space C can be reduced after the raw material is filled. As a result, it is possible to reduce the possibility that the raw material ceramic will intrude into the joint of the pair of molds D1 which are used after being clamped and wear the joint surface of the mold D1. Therefore, the mold D1 can be used without causing burrs in the joint surface for a long time.

  In addition, since the void portion C4p for molding the heat generating portion 833p has the above-described configuration, the leg portions 834a and b of the heat generating portion 833p molded by the void portion C4p have the void portions C441a and b. The convex portions 8341 a and b are provided as a corresponding configuration. The convex portions 8341 a, b are located farther from the other leg 834 than the portion 834 closest to the other leg 834 among the portions of the legs 834 where they are provided, as described above. Provided. Therefore, the shortest distance between the leg 834a and the projection 8341a extending substantially parallel to each other in the Z-axis + direction, and the leg 834b and the projection 8341b is reduced by forming the projections 8341a and 8341b. It will never be. Therefore, when the glow plug 10 in which the heating resistor 830 is incorporated is used, the leg 834a and the projection 8341a, and the leg 834b and the projection 8341b are short-circuited without passing through the front end 832. The possibility is low.

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

  An air gap C4q for forming the heat generating portion 833q includes an air gap C42 for forming the front end 832, air gaps C44a and B for forming the legs 834a and b, and air gaps C442a and b. . In the void portion C4q of the second aspect, the configurations of the void portion C42 and the void portions C44a and C44b are the same as the void portion C4p of the first aspect.

  In the void portion C4q of the second embodiment, the void portions C442a and B are connected to void portions C44a and b for forming the leg portions 834a and b, respectively. The void portion C 442 a is arranged to protrude in the Z-axis + direction from the inclined rear end face of the void portion C 44 a. The void portion C 442 b is disposed so as to protrude in the Z-axis + direction from the inclined rear end face of the void portion C 44 b. The void portions C 442 a 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 to be formed is located is more than the portion 834na closest to the other leg 834b among the portions of the leg 834a in which the convex portion 8342a is provided. , And the other leg 834b. The portion where the convex portion 8342b is arranged is located at a position farther from the other leg 834a than the portion 834nb closest to the other leg 834a among the portions of the leg 834b in which the convex 8342b is provided. is there.

  Then, the convex portions 8342a, b are not located on the line segment Ls connecting the shortest distances of the leg portions 834a, b in an arbitrary cross section perpendicular to the Z-axis direction in which the pair of leg portions 834a, b extend. It is provided. By adopting such an aspect, the risk that the convex portions 8342 a and 8 b abnormally heat can be reduced.

  The void portion C 442b has a parallelogram cross section having a long side parallel to the inclined rear end face of the void portion C 44b 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 which it has. The cross-sectional area of the void portion C 442b is smaller than the cross-sectional area of the void portion C 44b (see the lower part of FIG. 5). In addition, each cross-sectional area of space | gap part C442a, b at the time of referring magnitude relation is taken as the largest cross-sectional area in the cross-sectional area in arbitrary cross sections perpendicular | vertical to central axis SC of each space | gap part.

  In addition, the cross-sectional area of the substantially rectangular opening Co2b which is the connection 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. With such a configuration, at the time of injection molding, the void portion C44b having a large cross-sectional area is first filled with the raw material, and then the raw material is introduced to the void portion C442a through the connecting portion (opening) Co2b having a small cross-sectional area. It will be injected.

  The void portion C 442a is also configured in the same manner as the void portion C 442b. That is, the void portion C 442a has a shape that has a mirror image relationship with the void portion C 442b across the plane defined by the central axis SC and the Y axis.

  Since the void portion C4q for molding the heat generating portion 833p has the above-described configuration, at the time of injection molding, the void portion C42 for molding the front end portion 832 and the legs 834a and b are first molded. The raw material is filled in the void portions C 44 a and b. Thereafter, the raw material is injected in the order of the void portions C 442 a and b. For this reason, compared with the aspect in which the void portions C 442 a and b are not provided in the mold, the raw material ceramic may intrude into the joint of the pair of molds D1 and wear the bonding surface of the molds D1. Can be reduced. Therefore, the mold D1 can be used without causing burrs in the joint surface for a long time.

  Further, since the void portion C4q has the configuration as described above, the convex portion 8342a, as a configuration corresponding to the void portion C442a, b on the leg portions 834a, b of the heat generating portion 833q formed by the void portion C4q. b is provided. The convex portions 8342a, b are located farther from the other leg 834 than the portion 834 closest to the other leg 834 among the portions of the legs 834 where they are provided, as described above. Provided. Therefore, the shortest distance between the leg 834a and the projection 8342a extending substantially parallel to each other in the Z-axis + direction, and the leg 834b and the projection 8342b is reduced by forming the projections 8342a and b. It will never be. Therefore, when the glow plug 10 is used, there is a low possibility that the leg 834a and the projection 8341a, and the leg 834b and the projection 8341b are short-circuited.

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

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

  In the void portion C4r of the third aspect, void portions C443a and B are further added to the void portion C4p of the first aspect. The other configuration of the void portion C4r of the third aspect is the same as the void portion C4p of the first aspect.

  In the void portion C4r of the third aspect, the void portions C443a and B are connected to the void portions C441a and b, respectively. The void portion C443a is disposed so as to protrude in the X axis + direction from the end face of the void portion C 441 a in the X axis + direction. The void portion C 443 b is disposed so as to protrude in the X axis − direction from the end face of the void portion C 441 b in the X axis direction.

  The void portion C443b is a void having a rectangular parallelepiped shape having a greater thickness in the Y-axis direction than the void portion C441b. The cross-sectional area of the void portion C443b is larger than the cross-sectional area of the void portion C441b (see the right side of FIG. 6). The cross-sectional area of each of the void portions C443a and b and the void portions C441a and b is the maximum cross-sectional area in the cross section perpendicular to the direction away from the void portions C44a and B.

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

  Further, the cross-sectional area of the substantially rectangular opening Co3b which is a connection portion between the void portion C441b and the void portion C443b is the same as the cross-sectional area of a substantially rectangular opening Co1b which is a connection portion of the void portion C44b and the void portion C441b. With such a configuration, at the time of injection molding, the void portion C44b having a large cross-sectional area is first filled with the raw material, and then the raw material is applied to the void portion C441b through the connecting portion (opening) Co1b having a small cross-sectional area. Be injected. Thereafter, the raw material is injected into the void portion C443b through the connection portion (opening) Co3b.

  In other words, for the void portion C441b (the base 8346b of the convex portion 8350b), when injection molding of the heating resistor 830, the void portion C441b is not filled with the filling material before the raw material reaches the leg portion 834b. And the cross-sectional area can be set. Then, with regard to the void portion C443b (the tip portion 8347b of the convex portion 8350b), after stopping the injection of the raw material, the time until the void portions C441b and C443b are filled with the raw material after the raw material reaches the leg 834b The cross-sectional area and volume can be set to be sufficient for the accuracy of the timing.

  The void portion C443a is also configured similarly to the void portion C443b. That is, the void portion C443a has a shape that is in a mirror image relationship with the void portion C443b across the plane defined by the central axis SC and the Y axis.

  In the void portion C4r of the third aspect, void portions C443a and B are further added to the void portion C4p of the first aspect. For this reason, the following effects can be obtained. That is, until the void portions C 441 and C 44 a and b are filled with the raw material during injection molding, the void portions C 441 a and b and the void portions C 443 a and b are filled with the raw material and the void portion C 4 r is filled with the raw material In the first embodiment, the time required to complete is longer than the time required to fill the entire void portion C4p after the void portion C42 and the void portions C44a and b are filled with the feedstock. For this reason, compared with the first aspect, the possibility that the raw material ceramic intrudes at the joint of the pair of molds D1 and abrades the bonding surface of the mold D1 can be further reduced.

  Further, since the void portion C4r for molding the heat generating portion 833r has the above-described configuration, the leg portions 834a and b of the heat producing portion 833r correspond to the void portions C441a and b and the void portions C443a and b. As a configuration to be provided, convex portions 8350a, b are respectively provided with tip portions 8347a, b having larger cross-sectional areas as compared with the base portions 8346a, b. The protrusions 8350a and 8350b are also provided at positions farther from the other leg 834 than the portion 834 closest to the other leg 834 among the parts of the legs 834 in which they are provided. That is, the convex portions 8350a, b do not project toward the central axis SC. Therefore, the shortest distance between the leg 834a and the projection 8350a, and the leg 834b and the projection 8350b is not reduced by forming the projections 8350a and 8350b. Therefore, when the glow plug 10 is used, there is a low possibility that the leg 834a and the projection 8350a, and the leg 834b and the projection 8350b are short-circuited.

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

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

  In the void portion C4s of the fourth aspect, void portions C444a and B are further added to the void portion C4q of the second aspect. The other configuration of the void portion C4s of the third aspect is the same as the void portion C4q of the first aspect.

  In the void portion C4s of the fourth aspect, the void portions C444a and B are connected to the void portions C442a and B, respectively. The void portion C 444 a is located on the rear end side (Z-axis + direction) of the void portion C 442 a. The void portion C444b is located on the rear end side (Z-axis + direction) of the void portion C442b.

  The void portion C444b has a parallelogram cross section having a long side parallel to the inclined rear end face of the void 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 which it has. The thickness of the void portion C444b in the Y-axis direction is larger than the thickness in the Y-axis direction of the void portion C442b. The volume of the void portion C 444 b is larger than the volume of the void portion C 442 b.

  The cross-sectional area of the void portion C 444 b is larger than the cross-sectional area of the void portion C 442 b (see the lower part of FIG. 7). The cross-sectional areas of the void portion C 444 b and the void portion C 442 b are the maximum cross-sectional areas of the cross sections perpendicular to the direction away from the void portion C 44 b (that is, the direction perpendicular to the rear end face of the void portion C 44 b). .

  As a result of the void portion C 442 b and the void portion C 444 b having the configuration as described above, the convex portion 8351 b extends in the direction away from the leg portion 834 b from the base 8348 b and the tip portion 8349 b having a larger cross-sectional area than the base 8348 b. Prepare.

  Further, the cross-sectional area of the substantially rectangular opening Co4b which is a connection portion between the void portion C442b and the void portion C444b is the same as the cross-sectional area of a substantially rectangular opening Co2b which is a connection portion of the void portion C44b and the void portion C442b. With such a configuration, at the time of injection molding, the void portion C44b having a large cross-sectional area is first filled with the raw material, and then the raw material is applied to the void portion C442b through the connecting portion (opening) Co2b having a small cross-sectional area. Be injected. Thereafter, the raw material is injected into the void portion C 444 b through the connection portion (opening) Co 4 b.

  The void portion C444a is also configured in the same manner as the void portion C444b. That is, the void portion C444a has a shape that is in a mirror image relationship with the void portion C444b, sandwiching a plane defined by the central axis SC and the Y axis.

  In the void portion C4s of the fourth aspect, void portions C444a and B are further added to the void portion C4q of the second aspect. For this reason, the following effects can be obtained. That is, in the second embodiment, the time required for the raw material to be filled in the entire void portion C4s after the void portion C42 and the void portions C44a and B are filled with the raw material in injection molding, the void portion C42 and the void portion After C44a and b are filled with the raw material, it takes longer than the time required for the void portion C4q to be filled with the raw material. For this reason, compared with the second aspect, the possibility that the raw material ceramic intrudes at the joint of the pair of molds D1 and abrades the bonding surface of the mold D1 can be further reduced.

  Further, since the void portion C4s for forming the heat generating portion 833s has the above-described configuration, the leg portions 834a and b of the heat generating portion 833s correspond to the void portions C 442a and b and the void portions C444a and b. As a configuration to be provided, convex portions 8351a, b are provided which are provided with tip portions 8349a, b having larger cross-sectional areas as compared with the base portions 8348a, b. The projections 8351 a and b are also provided at a position farther from the other leg 834 than the portion 834 closest to the other leg 834 among the parts of the legs 834 in which they are provided. That is, the convex portions 8351a and b do not protrude toward the central axis SC. Therefore, the shortest distance between the leg 834a and the projection 8351a, and the leg 834b and the projection 8351b is not reduced by forming the projections 8351a and 8351b. Therefore, when the glow plug 10 is used, the possibility that the leg 834a and the projection 8351a, and the leg 834b and the projection 8351b are short-circuited is low.

  In addition, after the heat generating portion 833s is formed in the void portion C4s, conductive portions 836a and 836b are formed on the rear end sides of the leg portions 834a and b (see FIG. 3). Therefore, the convex portions 8351a and b are embedded in the conductive portions 836a and b. Therefore, according to the fourth aspect, unnecessary convex portions are not formed in the heating resistor 830 as a finished product. Therefore, no useless portion having no relation to the performance is formed in the heating resistor 830.

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

B. Example:
B1. Mold endurance test:
About the said 1st-4th aspect, the test article of metal mold | die D1 and D2 which satisfy the following conditions is created as Example 1-4, respectively, It repeats under the same conditions as the time of product manufacture, and injection molding Did. Further, as Comparative Example 1, the void portion C4 is provided with a void portion C42 and a void portion C44a, b, which are voids for molding the functional component of the heating resistor 830, such as void portions C441a, b to C444a, b, etc. A mold was prepared without an additional void.

Maximum dimension in the Z-axis direction of the void portion C4 of each embodiment: 6 mm.
Maximum thickness in the Y-axis direction of the void portions C 44 a and b in each embodiment: 1 mm.

Dimension in the Z-axis direction of the void portions C 441 a and b of the first aspect: 1.5 mm.
Dimension in the X-axis direction of the void portion C 441 a, b of the first aspect: 0.30 mm.
Dimension in the Y-axis direction of the void portion C 441 a, b of the first aspect: 0.05 mm.

Dimension in the Z-axis direction of the void portion C 442 a, b of the second embodiment: 0.60 mm.
The void portion C4q of the second embodiment is a void portion C442a measured in the direction perpendicular to the end faces C44af and bf of the void portions C44a and B on the side where the void portions C442a and b are provided. It is provided so that the dimension of b may be 0.30 mm.
Dimension in the X-axis direction of the void portion C 442 a, b of the second embodiment: 1.50 mm.
Dimension in the Y-axis direction of the void portion C 442 a, b of the second embodiment: 0.05 mm.

Dimension in the Z-axis direction of the void portions C 441 a and b of the third aspect: 1.5 mm.
Dimension in the X-axis direction of the void portions C 441 a and b of the third aspect: 0.30 mm.
Dimension in the Y-axis direction of the void portion C 441 a, b of the third aspect: 0.05 mm.
Dimension in the Z-axis direction of the void portion C443a, b of the third aspect: 1.5 mm.
Dimension in the X-axis direction of the void portion C443a, b of the third aspect: 0.30 mm.
Dimension in the Y-axis direction of the void portion C443a, b of the third aspect: 0.10 mm.

Dimension in the Z-axis direction of the void portion C 442 a, b of the fourth embodiment: 0.60 mm.
The void portion C4s of the fourth embodiment is a void portion C442a, which is measured in a direction perpendicular to the end faces C44af and bf of the void portions C44a and B on the side where the void portions C442a and b are provided. It is provided so that the dimension of b may be 0.30 mm.
Dimension in the X-axis direction of the void portion C 442 a, b of the fourth embodiment: 1.50 mm.
Dimension in the Y-axis direction of the void portion C 442 a, b of the fourth embodiment: 0.05 mm.
Dimension in the Z-axis direction of the void portion C444a, b of the fourth embodiment: 0.60 mm.
The void portion C4s of the fourth embodiment is a void portion C444a measured in the direction perpendicular to each end face from the inclined end faces C44af and bf of the void portions C44a and C on the side where the void portions C442a and b are provided. The dimension to the tip of b is set to 0.60 mm.
Dimension in the X-axis direction of the void portion C 444 a, b of the fourth embodiment: 1.50 mm.
Dimension in the Y-axis direction of the void portion C 444 a, b of the fourth aspect: 0.10 mm.

  Whether or not burrs having a width of 0.1 mm or more were generated at positions Pb (see FIG. 5) on the inner side of the front end portion 832 where burrs are most likely to be generated in the heat generation portion 833 was confirmed every injection molding 10000 times. The width of the burr was the distance from the contour of the front end portion 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 were generated in the 30,000th injection molding. On the other hand, in Example 1 (first aspect, see FIG. 4) and Example 2 (second aspect, see FIG. 5), burrs having a width of 0.1 mm or more occur in the 40000th injection molding. In the 50000th injection molding, burrs having a width of 0.1 mm or more were generated. In Example 3 (third embodiment, see FIG. 6), no burr of 0.1 mm or more in width occurs in the 50000th injection molding, and a burr of 0.1 mm or more in width occurs in the 60000th injection molding. The In Example 4 (fourth embodiment, see FIG. 7), no burr of 0.1 mm or more in width occurs in the 60,000th injection molding, and a burr of 0.1 mm or more in width occurs in the 70000th injection molding. The

  From the comparison of Examples 1 to 4 and Comparative Example 1, providing an additional void in addition to the void for molding the functional component of the heating resistor 830 contributes to the improvement of 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 additional air gaps, the gaps C441a, b and C 442a, b with small cross-sectional areas are further included. It can be seen that providing the void portions C 443 a, b, C 444 a, b having a larger volume further improves the durability of the mold.

B2. Measurement test of the size of the burr:
Regarding the second aspect (see FIG. 5), the configuration of the legs 834a, b is variously changed to create a test article, and the pressure of injection molding is set to be 20 MPa higher than the setting at the time of production of the actual product. The 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 . The cross-sectional area S2 of each leg 834 was 0.75 mm ² . The cross-sectional area S1 of the front end 832 is obtained by measuring the size of the cross section in the direction perpendicular to the direction in which the front end 832 extends at two or more portions of the front end 832 and calculating the average value thereof. Do.

  FIG. 8 is a cross-sectional view of the ceramic heater 800 taken along the line E-E in FIG. FIG. 8 is a cross-sectional view of the ceramic heater 800, so the substrate 810 is shown in the figure. In the E-E cross section, cross sections of two parts of the front end 832, which are each a part of the front end 832 and extend parallel to the central axis, appear. As mentioned above, the front end 832 has a constant cross-sectional area. The average value of the sizes of the cross-sectional areas of the two portions of the front end portion 832 is S1.

  The dividing line of the mold D1 at the time of molding the heating resistor 830 coincides with the line connecting the centers of two circular cross sections of the front end portion 832 having a circular cross section. For this reason, the burrs B occur on the line connecting the centers of the two circles at the front end portion 832. The dimensions of the burr B are denoted by LB.

  FIG. 9 is a cross-sectional view of the ceramic heater 800 in the F-F cross section in FIG. A cross section of the thickest portion of the leg 834 a and the leg 834 b appears in the EE cross section. The cross-sectional area of the thickest portion of the leg 834a and the leg 834b is S2. As described above, the leg portions 834a and b are provided such that the rear end portion is thicker than the front end portion, and the outer contour thereof is the same as that of the conductive portions 836a and b at the rear end of the leg portions 834a and b. Match the outer contour respectively. The conductive portions 836a and 836b extend linearly while maintaining a constant cross-sectional area. For this reason, in the present embodiment, the cross-sectional area S2 of the thickest portion of the leg portions 834a, b is equal to the cross-sectional area of the conductive portions 836a, b.

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

  In Table 2, it is indicated in the "Additional void" column whether or not there is an additional void portion which is not a void for molding a functional part. Further, a ratio S1 / S2 of the size S1 of the cross-sectional area of the front end portion 832 to the cross-sectional area S2 of the thickest portion of the leg portions 834a, b is shown. The cross-sectional area ratio S1 / S2 is an index of the resistance (flow difficulty) of the raw material in the void portion C42 for molding the front end portion 832 with respect to the size of the void portions C44a and b for molding the leg portions 834a and b. It is. The raw material is injected from the thin void portion C42 side, and is supplied to the wide void portions C44a and C4b via the void portion C42. When the cross-sectional area ratio S1 / S2 is small, the raw material is injected at a higher pressure in order to be able to fill the entire space in a short time while passing the raw material through the narrow space portion C42. Therefore, when the cross-sectional area ratio S1 / S2 is small, burrs easily occur in the front end portion 832 formed by the void portion C42.

  From the comparison between Example 5 and Comparative Example 2, in the embodiment in which S1 / S2 is 0.12, the size of the burr is reduced by 41% by providing the void portions C 442 a and b (see FIG. 5). I understand. From the comparison between Example 6 and Comparative Example 3, it is understood that the size of the burr is reduced by 53% by providing the void portions C 442 a and b in the embodiment in which S1 / S2 is 0.21. From the comparison between Example 7 and Comparative Example 4, it is understood that the size of the burr is reduced by 38% by providing the void portions C 442 a and b when the S1 / S2 is 0.40. From the comparison between Example 8 and Comparative Example 5, it is understood that the size of the burr is reduced by 25% by providing the void portions C 442 a and b in the embodiment in which S1 / S2 is 0.45.

  From the above results, when the ratio S1 / S2 of the cross-sectional area of the front end 832 to the cross-sectional area of the legs 834a, b is 0.40 or less, in addition to the air gap for molding the functional component of the heating resistor Providing additional air gaps proves to be effective in reducing burrs. Further, in the aspect that the cross-sectional area ratio S1 / S2 is 0.21 or less, it is more effective to reduce burrs by providing an additional void in addition to the void 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 void portions C 441 a, b of the mold D 1 (that is, the convex portions 8341 a, b of the heat generating portion 833 p) are on one side with respect to the parting line PL of the mold D 1 (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 parting line PL of the mold D1. For example, as shown in FIG. 10, the additional air 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 void portions C441a, b of the mold D1 (that is, the convex portions 8341a, b of the heat generating portion 833p) have a substantially rectangular parallelepiped shape having a rectangular cross section (see FIG. 4). However, additional void portions may be provided in other shapes. For example, the additional void portion (that is, the convex portion of the heat generating portion) may be provided such that the thickness in the Y-axis direction decreases with distance from the leg portions 834a and 834b. For example, as shown in FIG. 11, the additional void portion C 441 d (that is, the convex portion 8341 d of the heat generating portion 833) can 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. Also, for example, as shown in FIG. 12, an additional void portion C 441 e (ie, the convex portion 8341 e of the heat generating portion 833) is provided such that the thickness in the Y axis direction increases with distance from the leg portions 834 a and b. It may be

  FIG. 13 is a cross-sectional view showing a modification of the first embodiment. In the first embodiment, the void portions C 441 a and b of the mold D 1 are provided in a range including the rear ends (the ends in the Z-axis + direction) of the void portions C 44 a and b (see the left side of FIG. 4). . That is, the convex portions 8341a, b of the heat generating portion 833p are provided at the rear ends (ends in the Z-axis + direction) of the leg portions 834a, b. However, additional air gap portions (i.e., the convex portions of the heat generating portion) may be provided at other portions of the air gap portions C44a and C4. That is, the convex portions 8341 a, b of the heat generating portion 833 p may be provided at other portions of the leg portions 834 a, b.

  For example, as shown in FIG. 13, the additional void portions C 441 f and g may be provided at a predetermined distance from the rear ends of the void portions C 44 a and b. That is, the convex portions 8341 f and g of the heat generating portion 833 may be provided at positions separated from the rear ends of the leg portions 834 a and b by a predetermined distance.

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

C2. Other variants:
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 taken along the line GG 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 leg portions 834a and b are provided such that the rear end portion is thicker than the front end portion. The outer contours of the legs 834a and b coincide with the outer contour of the front end 832 at the front ends of the legs 834a and b, respectively. The outer contours of the leg portions 834a, b coincide with the outer contours of the conductive portions 836a, b at the rear front end of the leg portions 834a, b (see FIGS. 4 to 7).

  However, as shown in FIG. 14, the cross-sectional areas of the legs 834 a, b may be constant values equal to the cross-sectional area of the front end 832. Further, the additional void portions C 442 c and d of the mold D 1 may have the same width as the void portions C 44 a and b in the Y-axis direction. That is, the convex portions 8342 c, d of the heat generating portion 833 may be exposed to both the outer side and the inner side of the leg portions 834 a, b in the Y axis direction. In the modification of FIG. 14, the void portions C 442 c, d (ie, the convex portions 8342 c, d of the heat generating portion 833) are provided in a range including the parting 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 void portion C 442 e, f of the mold D 1 may have a narrower width than the void portion C 44 a, b in the Y-axis direction. That is, the convex portions 8342 c and d of the heat generating portion 833 may not be exposed to either the outer side or the inner side in the Y-axis direction of the leg portions 834 a and b.

  FIG. 16 is a view showing a modification of the mold D1 and the heat generating portion 833. As shown in FIG. The additional void portion C 442 g, h of the mold D 1 may have a narrower width than the void portion C 44 a, b in the Y-axis direction. Then, as shown in FIG. 16, the convex portions 8342 g and h of the heat generating portion 833 may be exposed to the outside of the inside and the outside of the leg portions 834 a and b in the Y-axis direction. The convex portions 8342 g and h of the heat generating portion 833 may be exposed to the inner side of the inner and outer sides in the Y-axis direction of the leg portions 834 a and b.

  In the fourth embodiment, the void portion C 442 a and the void portion C 444 a (that is, the base 8348 a and the tip portion 8349 a of the convex portion 8351 a) have the same width in the Y-axis direction (see FIG. 7). Further, the void portion C 442 b and the void portion C 444 b (that is, the base 8348 b and the tip portion 8349 b of the convex portion 8351 b of the heat generating portion 833) have the same width. However, the additional air gap connected to the air gap for molding the functional component of the heating resistor 830 (that is, the base of the protrusion of the heat generating portion) and the additional air gap further connected to the additional air gap The gap (i.e., the tip of the protrusion of the heat generating portion) may have a different width in the Y-axis direction.

  FIG. 17 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. 17, the additional air gap (that is, the base of the convex portion of the heat generating portion) connected to the air gap for molding the functional component of heat generating resistor 830 is The width may be narrower than the additional air gap (i.e., the tip portion of the protrusion of the heat generating portion) further connected to the additional air 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 air gap (that is, the base of the convex portion of the heat generating portion) connected to the air gap for molding the functional component of heat generating resistor 830 is The width may be wider than the additional air gap (i.e., the tip portion of the convex portion of the heat generating portion) further connected to the additional air gap.

  Further, as shown in FIG. 18, the additional air gap may be provided only in one of the pair of air gap portions C44a and C44b. That is, the convex portion may be provided on only one of the leg portions 834a and 834b.

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

(2) In the first and third embodiments, the void portions C441a and 443a are arranged to protrude to the side opposite to the central axis SC with respect to the void portion C44a (FIG. 4 and FIG. 4). 6). In addition, the void portions C441b and C443b are disposed so as to protrude to the side opposite to the central axis SC with respect to the void portion C44b. In other words, the convex portions 8341a and 8350a are arranged to protrude to the side opposite to the central axis SC with respect to the leg portion 834a. In addition, the convex portions 8341 b and 8350 b are disposed so as to project to the side opposite to the central axis SC with respect to the leg portion 834 b.

  In the second and fourth embodiments, the void portions C 442 a and C 444 a are arranged to protrude in the Z-axis + direction from the inclined rear end face of the void portion C 44 a (see FIGS. 5 and 7). . The void portions C 442 b and C 444 b are arranged to project in the Z-axis + direction from the inclined rear end face of the void portion C 44 b. In other words, the convex portions 8342a and 8351a are disposed so as to project in the Z-axis + direction from the inclined rear end surface of the leg portion 834a. Further, the convex portions 8342 b and 8351 b are disposed so as to protrude in the Z-axis + direction from the inclined rear end surface of the leg portion 834 b.

  However, the additional air gaps, in other words the projections provided on the legs, can also be provided in other ways. However, it is preferable that the location where the convex portion is disposed is a position farther from the other leg than the portion closest to the other leg among the portions of the legs where the convex is provided. . Note that "the location where the convex portion is disposed is a position farther from the other leg portion than the portion closest to the other leg portion among the portions where the convex portion is provided" Means that any part of the convex part is provided to be farther from the other leg than the part closest to the other leg among the parts of the legs provided with the convex part Do. The parameters set when providing such a protrusion include the position where the protrusion is provided and the shape of the protrusion. In such an embodiment, there is a low possibility that the heat generating portion made of the conductive ceramic will be short-circuited by the convex portion.

(3) In the above-described embodiment, the gap portions constituting the convex portion are provided one by one in the leg portions 834 a and b. However, two or more convex portions can be provided on each leg. In such an embodiment, it is preferable to provide the same number of projections on each leg. According to such an aspect, when injection molding the heat generating portion, the degree of pressure increase can be mitigated more evenly for the pair of legs.

  Further, each leg is more preferably provided with a projection at the same position in the direction in which the leg extends. According to such an aspect, when injection molding the heat generating portion, the degree of pressure increase can be mitigated more evenly for the pair of legs.

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

10: glow plug 90: internal combustion engine 100: terminal 200: central shaft 300: insulating member 400: insulating member 500: main metal fitting 510: axial hole 520: tool engagement portion 540: external thread portion 600: ring 700: outer cylinder 710 ... Axial hole 800: Ceramic heater 810: Base body 830: Heating resistor 832: Front end portion 833: Heating portion 833p to 833s: Heating portion 834a, b: Leg portion 836a, b: Conductive portion 838: Terminal portion 838a, b: Terminal portion 8341a to 8341f: convex portion 8342a to 8342c: convex portion 8346a, b: base portion 8347a, b: tip portion 8348a, b: base portion 8349a, b: tip portion 8350a, b: convex portion 8351a, b: convex portion B: burr C Void C4 Void portion C4p to C4s First to fourth aspects of void portion C4 C42 Void portion C44a, b: void portion C441a to C441f: void portion C442a, b: void portion C443a, b: void portion C444a, b: void portion Co1a, b: opening Co2a, b: opening Co3a, b: opening Co4a, b: opening C442c to C442e: Void portion C6a, b: Void portion D1: Mold D2a, b: Auxiliary mold I1: Injection path I2: Injection path LB: Size of burr PL: Parting line of mold Pb: Location where burr is to be measured SC: Central axis

Claims (6)

A substrate made of insulating ceramic,
A heat generating portion made of conductive ceramic and embedded in the substrate,
A front end portion located at the front end of the heat generating portion;
A heat generating portion 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 legs and extends while maintaining a substantially constant cross-sectional area toward the rear end side A pair of conductive parts,
A ceramic heater comprising
Ratio S1 / S2 with respect to the cross-sectional area S2 of the said leg part of the cross-sectional area S1 of the part with the smallest cross-sectional area among the said heat-emitting part is 0.4 or less,
The heat generating portion includes, on the leg, a convex portion provided with a cross-sectional area smaller than a cross-sectional area of the leg in a direction from the front end to the rear end.
The convex portion is
The leg portion protrudes to the side opposite to the central axis of the ceramic heater,
It is provided in a part other than the part where the cross-sectional area is the smallest among the heat generating parts,
The portion where the convex portion is disposed is provided at a position farther from the other leg portion than the portion closest to the other leg portion among the portions of the leg portion in which the convex portion is provided. The ceramic heater has been The ceramic heater according to claim 1, wherein
The ceramic heater, wherein the convex portion is provided at a position not on a line segment connecting the shortest distances of the legs in an arbitrary cross section perpendicular to a direction in which the pair of legs extend. The ceramic heater according to claim 1 or 2 , wherein
The ceramic heater, wherein the protrusion includes a first portion and a second portion having a larger cross-sectional area than the first portion along a direction away from the leg. The ceramic heater according to any one of claims 1 to 3, wherein
The ceramic heater, wherein the heat generating portion includes the same number of convex portions on each of the leg portions. The ceramic heater according to claim 4,
The ceramic heater, wherein the heat generating portion includes the convex portion at the same position on each of the legs and in a direction in which the pair of legs extend.   A glow plug comprising the ceramic heater according to any one of claims 1 to 5.

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