WO2018084083A1

WO2018084083A1 - Heater and glow plug with same

Info

Publication number: WO2018084083A1
Application number: PCT/JP2017/038910
Authority: WO
Inventors: 貴史宮口
Original assignee: 京セラ株式会社
Priority date: 2016-11-04
Filing date: 2017-10-27
Publication date: 2018-05-11
Also published as: JP6817325B2; JPWO2018084083A1

Abstract

This heater is provided with a rod-shaped ceramic body and a heat generating resistor which is located inside the ceramic body. The ceramic body is provided with: a circular solid cylindrical first portion having a longitudinal direction; and a second portion adjacent to the first portion in the longitudinal direction and tapered in the direction away from the first portion. A plurality of grooves are provided in the surface of the second portion. The plurality of grooves are formed such that one end of each of the plurality of grooves is located at the boundary between the first portion and the second portion and extends and tilts relative to the radial direction of the ceramic body when viewed in the longitudinal direction.

Description

Heater and glow plug equipped with the same

The present disclosure is, for example, for a heater for ignition or flame detection in a combustion-type in-vehicle heating device, a heater for ignition of various combustion devices such as a petroleum fan heater, a heater for a glow plug of a diesel engine, and various sensors such as an oxygen sensor. In particular, the present invention relates to a heater used for a heater or a heater for heating a measuring instrument, and a glow plug including the heater.

As a heater, for example, a ceramic heater described in Japanese Patent Application Laid-Open No. 2008-288110 (hereinafter referred to as Patent Document 1) is known. The ceramic heater described in Patent Document 1 includes a rod-shaped base and a resistor provided inside the base. The base has a portion having a constant diameter and a portion that narrows toward the tip. Generally, cutting is used for processing the surface shape of the substrate. In the cutting process, there was a tendency for grooves to remain along the circumferential direction on the surface of the processed substrate.

A heater according to an aspect of the present disclosure includes a rod-shaped ceramic body and a heating resistor positioned inside the ceramic body, and the ceramic body includes a columnar first portion having a length direction and the first portion. It has a second portion that is adjacent to the first portion in the lengthwise direction and becomes thinner as it gets away from the first portion, and a plurality of grooves are provided on the surface of the second portion, One end of each of the plurality of grooves is located at a boundary between the first portion and the second portion, and extends in an inclined manner with respect to the radial direction of the ceramic body as viewed from the length direction.

It is sectional drawing which shows an example of a heater. (A) is the enlarged view which shows the vicinity of the 1st part among the heaters shown in FIG. 1, (b) is the side view which looked at the 1st part from the length direction. (A) is the enlarged view which shows the vicinity of the 1st part among the examples according to a heater, (b) is the side view which looked at the 1st part from the length direction. It is the side view which looked at the 1st part among other examples of a heater from the length direction. It is the side view which looked at the 1st part among other examples of a heater from the length direction. It is the side view which looked at the 1st part among other examples of a heater from the length direction. It is sectional drawing which shows an example of a glow plug.

As shown in FIG. 1, the heater 1 includes a ceramic body 2, a heating resistor 3 located inside the ceramic body 2, and leads 4 connected to the heating resistor 3 and drawn to the surface of the ceramic body 2. It has.

The ceramic body 2 in the heater 1 is formed in a rod shape having a longitudinal direction, for example. A heating resistor 3 and leads 4 are embedded in the ceramic body 2. Here, the ceramic body 2 includes ceramics. Thereby, it becomes possible to provide the heater 1 with high reliability at the time of rapid temperature rise. Examples of the ceramic include electrically insulating ceramics such as oxide ceramics, nitride ceramics, and carbide ceramics. In particular, the ceramic body 2 may include silicon nitride ceramics. This is because silicon nitride ceramics is superior in terms of strength, toughness, insulating properties, and heat resistance.

The ceramic body 2 having a silicon nitride ceramic is, for example, 3 to 12% by mass of a rare earth such as Y ₂ O ₃ , Yb ₂ O ₃ or Er ₂ O ₃ as a sintering aid with respect to silicon nitride as a main component. Element oxide, 0.5 to 3% by mass of Al ₂ O ₃ and SiO ₂ are mixed so that the amount of SiO ₂ contained in the sintered body is 1.5 to 5% by mass, and formed into a predetermined shape. Thereafter, it can be obtained by hot press firing at 1650 to 1780 ° C. The length of the ceramic body 2 is set to 20 to 50 mm, for example, and the diameter of the ceramic body 2 is set to 3 to 5 mm, for example.

In the case of using those having a silicon nitride ceramic as the ceramic body 2 can be prepared by mixing the MoSiO ₂ or WSi _2, etc., may be dispersed. In this case, the thermal expansion coefficient of the silicon nitride ceramic that is the base material can be brought close to the thermal expansion coefficient of the heating resistor 3, and the durability of the heater 1 can be improved.

The heating resistor 3 is provided inside the ceramic body 2. The heating resistor 3 is embedded in the tip side (one end side) of the ceramic body 2. The heating resistor 3 is a member that generates heat when an electric current flows. The heating resistor 3 has a parallel portion extending along the longitudinal direction of the ceramic body 2 and a folded portion connecting them. As a material for forming the heating resistor 3, a material mainly composed of carbide, nitride, silicide or the like such as W, Mo or Ti can be used. In the case where the ceramic body 2 includes silicon nitride ceramics, tungsten carbide (WC) is the heating resistor 3 among the above materials in that the difference in coefficient of thermal expansion from the ceramic body 2 is small and the heat resistance is high. It is excellent as a material.

Furthermore, when the ceramic body 2 includes silicon nitride ceramics, the heating resistor 3 is mainly composed of WC of an inorganic conductor, and the content of silicon nitride added thereto is 20% by mass or more. Good. For example, in the ceramic body 2 having silicon nitride ceramics, the conductor component that becomes the heating resistor 3 has a larger coefficient of thermal expansion than that of silicon nitride, and therefore is usually in a state where tensile stress is applied. On the other hand, by adding silicon nitride to the heating resistor 3, the thermal expansion coefficient is brought close to that of the ceramic body 2, and the stress due to the difference between the thermal expansion coefficients when the heater 1 is heated and lowered is alleviated. can do.

Further, when the content of silicon nitride contained in the heating resistor 3 is 40% by mass or less, the variation in the resistance value of the heating resistor 3 can be reduced. Therefore, the content of silicon nitride contained in the heating resistor 3 may be 20 to 40% by mass. Further, as a similar additive to the

heating resistor

3, 4 to 12% by mass of boron nitride can be added instead of silicon nitride. The heating resistor 3 can have a total length of 3 to 15 mm and a cross-sectional area of 0.15 to 0.8 mm ² .

The lead 4 is a member for electrically connecting the heating resistor 3 and an external power source. The lead 4 is connected to the heating resistor 3 and pulled out to the surface of the ceramic body 2. Specifically, leads 4 are joined to both ends of the heating resistor 3. One lead 4 has one end connected to one end of the heating resistor 3 and the other end closer to the rear end of the ceramic body 2. The other lead 4 has one end connected to the other end of the heating resistor 3 and the other end led from the rear end of the ceramic body 2.

The lead 4 is formed using the same material as the heating resistor 3, for example. The lead 4 has a lower resistance per unit length by making the cross-sectional area larger than that of the heating resistor 3 or by making the content of the forming material of the ceramic body 2 smaller than that of the heating resistor 3. ing. The lead 4 may be mainly composed of WC, which is an inorganic conductor, and silicon nitride may be added to the lead 4 so that the content is 15% by mass or more. As the content of silicon nitride increases, the thermal expansion coefficient of the lead 4 can be made closer to the thermal expansion coefficient of silicon nitride constituting the ceramic body 2. Further, when the content of silicon nitride is 40% by mass or less, the resistance value of the lead 4 is lowered and stabilized. Accordingly, the silicon nitride content may be 15 to 40% by mass.

Here, in the heater 1 of the present embodiment, as shown in FIG. 2, a rod-shaped ceramic body 2 and a heating resistor 3 embedded on the tip side of the ceramic body 2 are provided. The first portion 21 has a columnar shape having a length direction, and the second portion 22 is adjacent to the first portion 21 in the length direction and becomes thinner as the distance from the first portion 21 increases. The second portion 22 is provided with a plurality of grooves 23 on the surface, and one end of each of the plurality of grooves 23 is located at the boundary between the first portion 21 and the second portion 22. The plurality of grooves 23 extend obliquely with respect to the radial direction of the ceramic body 2 when viewed from the end face, in other words, when viewed from the length direction. More specifically, each groove 23 is linear, and is inclined from both the length direction of the ceramic body 2 and the boundary between the first portion 21 and the second portion 22.

Thus, the groove 23 extends with an inclination with respect to the length direction in which the ceramic body 2 thermally expands greatly under a heat cycle. Thereby, compared with the case where a groove | channel is along the circumferential direction, the thermal stress to generate | occur | produce can be disperse | distributed other than the boundary of the 1st part 21 and the 2nd part 22. FIG. Moreover, compared with the case where the groove | channel 23 is extended in the length direction, the possibility that a thermal stress may concentrate on the center of the front-end | tip of the ceramic body 2 can be reduced. As a result, the risk of cracks and the like occurring in the ceramic body 2 can be reduced.

Hereinafter, a method of forming the grooves 23 so as to extend with an inclination with respect to the radial direction of the ceramic body 2 will be described.

First, while the ceramic body 2 is rotated, the rotated blade of NC processing (numerical control machining) is moved three-dimensionally. At this time, the rotational speed of the ceramic body 2 is set to 1/10 or less of the rotational speed of the rotary blade for NC machining, and the groove 23 is set not in the length direction but in the circumferential direction. Further, in this state, the rotary shaft of the NC machining rotary blade is tilted so that the axis of rotation does not intersect the axis of rotation of the ceramic body 2. In this way, the heater 1 shown in FIGS. 2 and 3 can be manufactured.

Further, when the heater 1 shown in FIG. 4 is manufactured, the ceramic body 2 is moved while gradually moving the position where the rotary blade contacts the ceramic body 2 toward the center of the ceramic body 2 in accordance with the direction of the groove 23. Rotate.

5 and 6, when the blade is moved from the center of the ceramic body 2 to the outer peripheral side during NC machining, the axis of rotation of the ceramic body 2 and the axis of the rotary blade The projection angle may be changed.

When the length of the ceramic body 2 is 26.5 mm, for example, the length of the second portion 22 can be set to 1 mm, for example. The depth of the groove 23 can be set to 5 μm, for example. The length of the groove 23 can be set to 100 μm or more, for example.

Further, as shown in FIG. 3, the plurality of grooves 23 may extend in a curved shape. Thereby, it can reduce that a thermal stress concentrates on a specific site | part. As a result, the risk of cracks and the like occurring in the ceramic body 2 can be reduced.

Further, the second portion 22 may have a dome shape. Thereby, since the diameter of the 2nd part 22 changes gradually, a possibility that a thermal stress may concentrate locally on the 2nd part 22 can be reduced.

Further, as shown in FIG. 4, the plurality of grooves 23 may be spirally distributed throughout the second portion 22. Thereby, compared with the case where there exists the area | region where the groove | channel 23 exists, and the area | region which does not exist, a possibility that a thermal stress may concentrate locally on the 2nd part 22 can be reduced. Moreover, since the groove 23 is spiral, the bias of thermal stress in the circumferential direction of the second portion 22 can be reduced. As shown in FIG. 4, one groove 23 may be provided from the boundary between the first portion 21 and the second portion 22 to the center of the second portion, or a plurality of grooves 23 may be intermittently formed. By being provided, it may be provided from the boundary between the first portion 21 and the second portion 22 to the center of the second portion.

Further, as shown in FIG. 5, each of the plurality of grooves 23 may extend in an S shape. By extending the groove 23 in an S shape, the groove 23 has a plurality of arc-shaped portions that are convex in different directions. Therefore, compared with the case where the groove 23 has a shape having one arc-shaped portion, the thermal stress can be dispersed in various directions.

Further, as shown in FIG. 6, each of the plurality of grooves 23 passes through the center of the second portion 22 from the boundary between the first portion 21 and the second portion 22 and again, the first portion 21 and the second portion. The shape extending to the boundary with 22 may be S-shaped. In this case, since the plurality of grooves 23 can be arranged with high symmetry, it is possible to reduce the possibility of thermal stress being concentrated locally.

As shown in FIG. 7, the glow plug 10 includes the above-described heater 1 and a cylindrical metal cylinder 5 attached so as to cover a part (the rear end side) of the heater 1. In addition, an electrode fitting 6 that is disposed inside the metal tube 5 and is attached to the rear end of the heater 1 is provided. According to the glow plug 10, since the heater 1 described above is used, durability is improved.

The metal cylinder 5 is a member for holding the ceramic body 2. The metal cylinder 5 is a cylindrical member and is attached so as to surround the rear end side of the ceramic body 2. That is, the rod-shaped ceramic body 2 is inserted inside the cylindrical metal tube 5. The metal cylinder 5 is provided on the side surface on the rear end side of the ceramic body 2 and is electrically connected to a portion where the lead 4 is exposed. The metal cylinder 5 includes, for example, stainless steel or iron (Fe) -nickel (Ni) -cobalt (Co) alloy.

The metal cylinder 5 and the ceramic body 2 are joined by a brazing material. The brazing material is provided between the metal cylinder 5 and the ceramic body 2 so as to surround the rear end side of the ceramic body 2. By providing this brazing material, the metal cylinder 5 and the lead 4 are electrically connected.

As the brazing material, silver (Ag) -copper (Cu) brazing, Ag brazing, Cu brazing or the like containing 5 to 20% by mass of a glass component can be used. Since the glass component has good wettability with the ceramic of the ceramic body 2 and has a large coefficient of friction, the bonding strength between the brazing material and the ceramic body 2 or the bonding strength between the brazing material and the metal cylinder 5 can be improved.

The electrode fitting 6 is located inside the metal cylinder 5 and attached to the rear end of the ceramic body 2 so as to be electrically connected to the lead 4. Various types of electrode fittings 6 can be used. However, in the example shown in FIG. 12, the cap part attached to cover the rear end of the ceramic body 2 including the lead 4 and the external connection electrode are electrically connected. It is the structure by which the coil-shaped part connected electrically is connected by the linear part. The electrode fitting 6 is held away from the inner peripheral surface of the metal cylinder 5 so as not to cause a short circuit with the metal cylinder 5.

The electrode fitting 6 is a metal wire having a coil-shaped portion provided for stress relaxation in connection with an external power source. The electrode fitting 6 is electrically connected to the lead 4 and is electrically connected to an external power source. By applying a voltage between the metal cylinder 5 and the electrode fitting 6 by an external power source, a current can be passed through the heating resistor 3 via the metal cylinder 5 and the electrode fitting 6. The electrode fitting 6 has nickel or stainless steel, for example. The heater 1 can be formed by, for example, an injection molding method using a die having the shape of the heating resistor 3, the lead 4, and the ceramic body 2 configured as described above.

1: Heater 2: Ceramic body 21: First portion 22: Second portion 23: Groove 3: Heating resistor 4: Lead 5: Metal cylinder 6: Electrode fitting 10: Glow plug

Claims

A rod-shaped ceramic body; and a heating resistor positioned inside the ceramic body, the ceramic body having a columnar first portion having a length direction and the first portion in the length direction. Having a second portion that is adjacent and narrows away from the first portion;
A plurality of grooves are provided on the surface of the second portion,
The plurality of grooves, one end of which is located at the boundary between the first part and the second part, and which extends at an angle with respect to the radial direction of the ceramic body as viewed from the length direction .
The heater according to claim 1, wherein the plurality of grooves extend in a curved shape.
The heater according to claim 1 or 2, wherein the second portion has a dome shape.
The heater according to any one of claims 1 to 3, wherein the plurality of grooves are spirally distributed over the entire second portion as viewed from the length direction.
The heater according to any one of claims 1 to 4, wherein each of the plurality of grooves extends in an S shape.
A glow plug comprising the heater according to any one of claims 1 to 5 and a metal cylinder attached so as to cover a part of the ceramic body.