JPH10205752A - Glow plug - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a glow plug which can be manufactured at low cost by filling unsintered mixed powder into a protecting tube and at the time of start-up, a heating part can be heated smoothly by bypassing a PTC member having current control functions. SOLUTION: In the glow plug, a heating body 5 is put into a sleeve member 1 formed from dense ceramics, and filling members comprising solidified materials of mixed powder, which is not sintered are filled into the member 1 and an open end of the member 1 is sealed with a heat-resistant sealing member. The heating body 5 is connected to a battery 17 through a self current control member 8 provided in a plug body 15 and a bypass lead wire 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a glow plug used for starting a diesel engine or the like.

[0002]

2. Description of the Related Art As a conventional glow plug, a high-melting point metal such as tungsten or molybdenum is used as a heating element, and is sandwiched between silicon nitride molded bodies. A glow plug manufactured by a method of simultaneously integrating the components is known (Japanese Patent Application Laid-Open No. 6-272861, Japanese Patent Publication No. 60-194).
No. 04, etc.). For example, Japanese Unexamined Patent Application Publication No.
The ceramic heating element disclosed in Japanese Patent Laid-Open Publication No. H10-157, in which a heating resistor made of an inorganic conductive material is embedded in a silicon nitride-based sintered body, a silicon nitride-based molded body is manufactured, and the silicon nitride-based molded body is provided. On the other hand, a heating resistor made of a coiled tungsten wire and a heating resistor made of a tungsten wire forming a lead wire connected to the heating resistor are arranged, and another silicon nitride molding is sandwiched so as to sandwich the heating resistor. The bodies are stacked, pressed and fired to produce a silicon nitride sintered body.

[0003] As a self-current control type glow plug, there is one disclosed in Japanese Patent Application Laid-Open No. 7-167432. The self-current control type glow plug is capable of automatically interrupting energization of a coil after a predetermined time has elapsed. The glow plug includes a ceramic pipe fixed to a hollow body provided with a connector, and a ceramic filler filled in the pipe. It comprises a body, a coil embedded in a ceramic filler, and a PTC member connected to the coil. PTC (positive
The temperature coefficient) member cuts off the current to the coil due to a sudden increase in the resistance value at a predetermined temperature or higher, and connects the end of the coil to the connector of the connector.

[0004]

The conventional glow plug is manufactured by placing a tungsten wire in a protective tube, filling the protective tube with a filler material such as a precursor, and sintering the filler. Have been. However, refractory metals such as tungsten and molybdenum that form the heater coil are easily oxidized, and as the temperature rises, the crystal grains become larger and recrystallize at a temperature of 1100 ° C. or more, and their quality becomes brittle. It has been known. That is, when a glow plug is manufactured as in the related art, when a material filled in a protective tube is sintered at a high temperature of 1400 ° C. to 1900 ° C., a heater coil disposed in the protective tube becomes brittle, This was the main cause of disconnection of the heater coil.
Further, sintering the slurry requires an expensive sintering furnace and complicates the manufacturing process, which has been a factor in increasing the cost of the glow plug.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problem, and arrange a heating element made of a heat-resistant metal such as Ni, Co, Mo, or Cr which generates heat by energization in a sheath member. At the same time, the sheath member is filled with a first filling member made of an insulating solidified material obtained by drying and solidifying the slurry of the mixed powder to increase the density of the inside of the sheath member. The heating element is controlled by the self-current control member, and the heating element is connected to the battery by bypassing the self-current control member. Another object of the present invention is to provide a glow plug that can heat a heat generating portion without flowing a current to a self-current control member at the time of startup even if the glow plug itself is at a high temperature.

[0006] The present invention provides a sheath member made of dense heat-resistant and oxidation-resistant ceramic, inexpensive Ni, Co, M.
a heating element arranged in the sheath member made of a heat-resistant material of an alloy such as o, Cr, etc .; and a mixture made of an insulating material selected from ceramics, silicon, titanium, carbon and graphite filled in the sheath member. An insulating first filling member made of a powdery unsintered material, a heat-resistant sealing member for sealing an open end of the sheath member with a lead wire connected to the heating element extending from the sheath member; A plug body attached to an end of the sheath member; and a first terminal disposed in the insulating second filling member filled in the plug body and provided on the first lead wire and the plug body. And a self-current control member made of a material having a positive temperature coefficient of resistance connected in series.

[0007] The first filling member may include silicon nitride,
It is made of ceramics such as silica and alumina, titanium, and an insulating solidified material obtained by solidifying the slurry of the mixed powder made of carbon or graphite whose outer periphery is coated with an insulating material. That is, the mixed powder of the first filling member becomes high in temperature due to the heat generated by the heating element.
Reacts with ₂ to form a solidified material of TiN and Si ₃ N ₄ ,
The first member having a high temperature due to a high density inside the sheath member.
The filling member comes into close contact with the wall surface of the sheath member. Further, even if the mixed powder is present without solidification inside the sheath member, the mixed powder is distributed in a high-density state because the heating element does not oxidize or corrode because it is in an oxygen-free state. As a result, there is no problem in terms of heat conduction, and a favorable heat conduction state can be achieved.

The self-current control member is made of a barium titanate-based sintered body or a titanate-based sintered body whose resistance value rapidly increases at a predetermined temperature or higher.

Further, the sealing member is a first sealing member made of a glass material adjacent to the first filling member, and a liquid sealing material located at an end of the sheath member adjacent to the first sealing member. And a second sealing member.

[0010] The sheath member is formed of ceramics selected from silicon nitride, silicon carbide, sialon, and a composite thereof. N ₂ gas is sealed in the sheath member.

Further, the heating element is made of a material selected from Ni, Cr, Mo and alloys thereof. The heating element is connected to the plug body through a second lead wire.

Alternatively, according to the present invention, a first lead wire connected to one end of a heating element arranged in a sheath member made of dense ceramics is connected in series with a self-current control member made of a material having a positive temperature resistance coefficient. The bypass lead wire is directly connected to a power source, and the second lead wire connected to the other end of the heating element is related to a glow plug which is grounded.

Further, the present invention provides a sheath member made of dense ceramics, a heating element disposed in the sheath member, an insulating first filling member filled in the sheath member, and a heating element connected to the heating element. A heat-resistant sealing member for sealing the open end of the sheath member with the lead wire extended from the sheath member, a plug body attached to an end of the sheath member, and filled in the plug body. A self-current control member made of a material having a positive temperature resistance coefficient, wherein the self-current control member is disposed in an insulating second filling member and the first lead wire is connected in series to a first terminal provided on the plug body; The present invention relates to a glow plug comprising a bypass lead wire in which one lead wire is connected in series to a second terminal provided in the plug body, bypassing the self-current control member.

Further, the internal resistance of the bypass lead wire is set to be larger than the internal resistance of the self-current control member.

Further, the first terminal and the second terminal are connected to a start switch, and the start switch connects the first terminal to a battery and selectively connects the second terminal to the battery. It is configured.

The start switch is connected to an on terminal of a key switch that is turned on at the time of starting, and is configured to supply current to the heating element through the second terminal and the bypass lead when the engine is started. ing.

In the glow plug according to the present invention, as described above, the first terminal connected to the heating element through the PCT member of the self-current control member and the second terminal connected to the heating element through the bypass lead are connected to the plug body. The first terminal is connected to an ON position of a start switch, the second terminal is connected to a start position of a start switch, and the start switch is connected to a battery. Therefore, when the engine is started, the heating element is directly connected to the battery through the bypass lead wire bypassing the self-current control member, and is configured to heat the heating section of the glow plug. Even when the battery is in a high temperature state, the current from the battery is supplied to the heating element bypassing the self-current control member, and the engine can be started smoothly. After the engine is started, the heating element is connected to the battery through the self-current control member. When the engine temperature is high, the resistance of the self-current control member increases and the current supplied to the heating element decreases. , And the current is controlled.

In this glow plug, as described above, the heating element is made of a relatively inexpensive metal such as Ni, Cr, Mo, or Co, and the heating element is disposed in a sheath member serving as a protective tube. For example, ceramic, Ti, insulating carbon, and Si powder are put in a member, and N ₂ gas is sealed. Therefore, when the temperature rises due to heating by the heating element, Si and Ti react with N ₂ and are converted into Ti ₃ to Si ₃ N ₄ , and no gap is generated between the sheath member and the filling member due to TiN and volume expansion. , Heat conduction becomes good. Or,
As a filling member, insulating graphite, Si
₃ is intended to fill the powder of N _4, etc., is not performed sintering at a high temperature filler after filling the sheath, the material is inexpensive and does not require expensive sintering furnace. That is, the material of the filling member to be filled in the sheath member is not specified, and any material having heat resistance, such as powder or granules, is sufficient. In this production method, after the slurry material is injected into the sheath, the sheath is dried, and the heating coil is heated in N ₂ gas.
After being solidified, it may be sealed with a sealing member so as to obtain airtightness.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a glow plug according to the present invention will be described below with reference to the drawings. FIG. 1 is an explanatory view showing an embodiment of a glow plug according to the present invention.

This glow plug is preferably applied to a glow plug as a starting aid for a diesel engine, and has a heat generating portion 20 heated by energization. The glow plug is mainly disposed inside the sheath member 1, a plug body 15 attached to an end of the sheath member 1 as a protective tube constituting the heat generating portion 20 formed in a hollow shape from ceramics. A heating element 5 composed of a heating coil, an insulating first filling member 4 composed of a mixed powder filled in the sheath member 1, a lead wire 6 connected to the heating element 5,
The heat-resistant sealing members 2 and 3 for sealing the open ends of the sheath member 1 with the 7 extended from the sheath member 1, the plug body 15 to which the end of the sheath member 1 is fixed, and the inside of the plug body 15. A self-current control member 8 made of a material having a positive temperature coefficient of resistance arranged in the filled insulating second filling member 9 and connected in series with the lead wire 6 and the terminal 12 provided on the plug body 15. Have been. The plug main body 15 is provided with a screw portion 28 and a nut portion 29 for fixing the glow plug to the engine main body or the like. Terminals 12 and 13 are
It extends outward from the nut portion 29.

The sheath member 1 constitutes the heat generating portion 20 and has excellent heat resistance and corrosion resistance, such as silicon nitride (Si ₃ N ₄ ), silicon carbide (SiC), and sialon (Si—Al—). ON-N) and a composite thereof, and is formed of a dense ceramic having a closed end at one end and an open end at the other end.

The heating element 5 is made of a material selected from Ni, Cr, Mo, Co and alloys thereof, for example, Inconel or the like, which has excellent heat resistance and excellent oxidation resistance, and has a coil-shaped metal wire. Is formed. Ni, C
An alloy made of r, Mo, and Co has a heat resistance of about 1300 ° C., but has a relatively strong property for oxidation, and is therefore suitable for producing the heating element 5. Also, Ni,
Cr, Mo, Co, which has a property of contracting due to thermal expansion upon heating, their alloys, for example, the thermal expansion coefficient of Inconel ^{(5 × 10 - 6 / ℃} ) silicon nitride and thermal expansion coefficient (3.1 × 10 ⁻⁶ / ° C)
If the sheath member 1 is made of silicon nitride and the heating element 5 is made of a material such as Inconel, the matching between the sheath member 1 and the heating element 5 becomes good. When the heating element 5 was manufactured with a material of tungsten or its alloys, the material is very strong in the heat, like structure is not exposed to oxygen in view of the weak to oxidation, for example, encapsulating the N ₂ gas It is necessary to configure it to have such a structure.

The first filling member 4 is made of a material selected from ceramics such as silicon nitride, alumina and silicon carbide, silica (SiO ₂ ), Y ₂ O ₃ as an additive, and carbon or graphite coated with insulation. Of the mixed powder. Further, N ₂ gas is sealed in the first filling member 4 filled in the sheath member 1 in order to prevent oxidation and corrosion of the heating element 5. In this embodiment, the first filling member 4 forms a slurry by adding water or a solvent to the mixed powder, pours the slurry into the sheath member 1 on which the heating element 5 is disposed, and causes the slurry to dry and solidify. It is made of an insulating solidified material. The solidified material is the sheath member 1
The density is increased in the sheath member 1 by being fixed to the inner wall surface, but the phenomenon becomes remarkable especially in the case of a mixed powder containing Ti. Then, in a state where the solidified material is in close contact with the sheath member 1, N ₂ gas is sealed and the ends of the sheath member 1 are sealed with the sealing members 2 and 3.

The sealing members 2 and 3 are composed of a first sealing member 2 made of a glass material adjacent to the first filling member 4 and a liquid positioned at an end of the sheath member 1 adjacent to the first sealing member 2. It comprises a second sealing member 3 made of a sealing material. The first sealing member 2 is made of a heat-resistant glass material composed of SiO ₂ , Al ₂ O ₃ , and oxynitride material, and is used to improve the airtightness inside the sheath member 1 filled with the first filling member 4. I keep it. Further, in order to maintain the airtightness between the first sealing member 2 and the lead wires 6 and 7 and between the first sealing member 2 and the inner wall surface of the sheath member 1, a liquid sealing material made of a liquid material is used. 2 sealing member 3
Is filled in the end of the sheath member 1.

The first lead wire 6 connected to the heating element 5 extends from the second sealing member 3 filled at the end of the sheath member 1 and is connected to the connecting member 14. Connection member 1
4 is connected to a self-current control member 8 and to a bypass lead wire 10. Further, the self-current control member 8 is connected to a first terminal 12 provided on the plug body 15 through a lead wire 11. The bypass lead wire 10 is a line that bypasses the self-current control member 8 and is connected to a second terminal 13 provided on the plug body 15. The second lead wire 7 connected to the heating element 5 is connected to a metal plug body 15 and is grounded.

The self-current control member 8 disposed in the plug main body 15 is composed of a positive temperature coefficient member (PTC member) having a function of controlling the current to decrease when the resistance value suddenly increases above a predetermined temperature. The material is, for example, a plywood material obtained by laminating a barium titanate-based sintered body or a titanate-based sintered body. Further, the plug body 15 is filled with a second filling member 9 so as to fill the self-current control member 8. The second filling member 9
It is composed of an insulating material made of non-conductive alumina, silicon carbide, silicon nitride, and composite ceramic fibers thereof.

In this glow plug, the first terminal 12
And the second terminal 13 are connected to a start switch 27. The start switch 27 connects the first terminal 12 to the battery 17 and connects the second terminal 13 to the battery 17.
To be selectively turned on or off. The start switch 27 has a battery 17
A battery terminal 21 connected to the first terminal 12 by a line 22; an ON terminal 18 connected to the first terminal 12 by a line 22;
A start terminal 19 connected to the terminal 13 by a line 23 is provided. The start switch 27 is provided with the key switch 16.
Is connected to the battery terminal 21 and the ON terminal 18 at all times, and is connected to the start terminal 19 only at the time of starting. The battery 17 is connected to the plug body 15 of the glow plug by a line 25 and is grounded. The start switch 27 is connected to the on terminal 18 of the key switch 16 that is turned on at the time of starting, and is configured to supply current to the heating element 5 through the second terminal 13 and the bypass lead wire 10 at the time of starting the engine. .

The glow plug according to the present invention has a feature in the structure of the heat generating portion 20 heated by energization in the above configuration. The heat generating portion 20 constituting the glow plug is manufactured by sealing the end of the sheath member 1 with the unsintered mixed powder without sintering the filling member 4 filled or inserted into the sheath member 1. This prevents the heating element 5 and the lead wires 6 and 7 from deteriorating, does not require a sintering step, and is manufactured at low cost.

Further, this glow plug incorporates a self-current control member 8 of a PTC member, and when the engine is started, current is supplied to the heating element 5 through the bypass lead wire 10 bypassing the self-current control member 8. In addition, the starting at the time of starting can be reliably performed without being affected by the temperature of the area of the self-current control member 8, and a smooth starting can be ensured. Also,
When the start switch 27 is turned on, the resistance of the start terminal 19 is set to be larger than the internal resistance of the self-current control member 8. The self-current control member 8 can reach its operating temperature by the heat energy generated by the self-current control member 8 flowing through the current control member 8 and generated by the internal resistance and the heat energy generated by the heat generated by the heat generation member 20. The smooth current control function can be exhibited.

[0030]

As described above, in the glow plug according to the present invention, the filling member filled in the sheath member is not sintered at a high temperature of 1700 ° C., and the filling member is made of unsintered mixed powder. Since the heating element is not exposed to high temperature and does not deteriorate without being exposed to a high temperature, even if a sheath member made of ceramics to which a filling pressure cannot be applied is used, the bulk density can be reduced by heating the mixed powder to about 600 ° C. or more. The life can be greatly extended without disconnection of the heating element even when subjected to repeated thermal stress, and the sintering step is not required, so that the production can be performed at low cost.

Further, the glow plug can reliably supply current to the heating element through the bypass lead wire bypassing the self-current control member when the engine is started. For example, immediately after the engine is stopped, even if the glow plug is at a high temperature, the current from the battery can be supplied to the heating element by bypassing the self-current control member. When the engine is started, the heating element is reliably heated, and smooth start can be achieved.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing one embodiment of a glow plug according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Sheath member 2 1st sealing member 3 2nd sealing member 4 1st filling member 5 Heating element 6 1st lead wire 7 2nd lead wire 8 Self-current control member 9 2nd filling member 10 Bypass lead wire 11 Lead wire DESCRIPTION OF SYMBOLS 12 1st terminal 13 2nd terminal 14 Connecting member 15 Plug body 16 Key switch 17 Battery 18 ON terminal 19 Start terminal 20 Heating part 21 Battery terminal 27 Start switch

Claims (13)

[Claims] 1. A sheath member made of a dense ceramic, a heating element disposed in the sheath member made of a heat-resistant material, and ceramics, silicon, titanium, carbon, and graphite filled in the sheath member. An insulating first filling member made of a non-sintered material of a mixed powder made of an insulating material, and an opening end of the sheath member with the lead wire connected to the heating element extending from the sheath member. A heat-resistant sealing member for sealing, a plug body attached to an end of the sheath member, and the first lead wire and the plug disposed in an insulating second filling member filled in the plug body. A glow plug comprising a self-current control member made of a material having a positive temperature resistance coefficient and connected in series with a first terminal provided on the main body. 2. The glow plug according to claim 1, wherein the first filling member is made of an insulating solidified material obtained by solidifying a slurry of the mixed powder. 3. The self-current control member is made of a barium titanate-based sintered body or a titanate-based sintered body whose resistance value rapidly increases at a predetermined temperature or higher. Glow plug. 4. The glow plug according to claim 1, wherein the sheath member is formed of ceramics selected from silicon nitride, silicon carbide, sialon, and a composite thereof. 5. The heating element is made of Ni, Cr, Mo, Co.
The glow plug according to any one of claims 1 to 4, wherein the coil-shaped heat generating portion is formed from a material selected from the group consisting of alloys thereof. 6. The sealing member is a first sealing member made of a glass material adjacent to the first filling member, and a liquid sealing material located at an end of the sheath member adjacent to the first sealing member. 6. A second sealing member comprising:
The glow plug according to any one of the above. 7. The glow plug according to claim 1, wherein an N ₂ gas is sealed in the sheath member. 8. The glow plug according to claim 1, wherein the heating element is connected to the plug body through a second lead wire. 9. A first lead wire connected to one end of a heating element disposed in a sheath member made of a dense ceramic is connected in series with a self-current control member made of a material having a positive temperature resistance coefficient, and A glow plug, wherein a second lead wire directly connected to a power source and connected to the other end of the heating element is grounded. 10. A sheath member made of a dense ceramic,
A heating element disposed in the sheath member, an insulating first filling member filled in the sheath member, and a lead wire connected to the heating element extending from the sheath member; A heat-resistant sealing member for sealing an open end of the plug, a plug body attached to an end of the sheath member, an insulating second filling member filled in the plug body, and the first lead. A self-current control member made of a material having a positive temperature resistance coefficient, wherein a wire is connected in series to a first terminal provided on the plug body, and the first lead wire is connected to the plug body by bypassing the self-current control member. A glow plug comprising a bypass lead wire connected in series to the second terminal provided. 11. The internal resistance of the bypass lead is:
The glow plug according to claim 9, wherein the glow plug is set to be larger than an internal resistance of the self-current control member. 12. The first terminal and the second terminal are connected to a start switch. The start switch connects the first terminal to a battery and selectively connects the second terminal to the battery. The glow plug according to claim 10, wherein the glow plug is configured. 13. The start switch is connected to an on terminal of a key switch that is turned on at the time of starting, and is configured such that current is supplied to the heating element through the second terminal and the bypass lead when the engine is started. The glow plug according to claim 12, wherein