JPS61217624A - Self-temperature control type glow plug - Google Patents

Abstract

PURPOSE:To attempt rapid red-heating of the tip of a heater and control its peak temperature and saturation temperature appropriately by constituting as one body a rod-shaped heat generating section made of conductive ceramic material and a control section made of conduc tive material with a positive resistance temperature coefficient larger than that of the former and exposing the heat generating section to the surface of the heater. CONSTITUTION:A rod-shaped heater 11 is constituted with a heat generating section 20 made of conductive ceramic material with a small positive resistance temperature coefficient and a control section 21 made of conductive material with a positive resistance temperature coefficient that is larger than that of the heat generating section 20. When a voltage is applied to the heat generating section 20 and the control section 21, a larger voltage is applied to the heat generating section with a larger resistance than to the control section, and the heat generating section 20 has a larger electric power density relative to the control section, making the heat generating section 20 at the tip of the heater 11 generate heat rapidly. As the resistance value of the heat generating section increase with heat generation, the voltage applied between the heat generating section 20 and the control section 21 changes, and the applied voltage to the heat generating section 20 is controlled and its temperature is saturated at about 850 deg.C after it has reached a peak temperature of about 1,200 deg.C, and its overheating can be avoided.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention provides a 1sfl glow plug used for preheating the auxiliary combustion chamber or combustion chamber of a diesel engine.
In particular, the present invention relates to an improvement of a self-temperature-controlled glow plug equipped with a rod-shaped heater that exhibits a fast-heating function, improves its heat-generating characteristics, and achieves long-term afterglow.

[Conventional technology]

Generally, diesel engines have poor startability at low temperatures, so glow plugs are installed in the auxiliary combustion chamber or combustion chamber.
A method has been adopted in which a current is passed through this to generate heat, thereby raising the intake air temperature or using it as an ignition source to improve engine startability. Conventional glow plugs of this type are generally of the so-called sheath type, in which a metal sheath is filled with heat-resistant insulating powder and a coiled heating wire made of iron chromium, nickel, etc. is embedded, but other glow plugs are commonly used. As shown in Japanese Patent Application Laid-Open No. 57-41523, a ceramic heater type is also known which uses a rod-shaped heater in which a heating wire made of tungsten or the like is embedded in a ceramic material. Compared to the sheath type, which heats indirectly through heat-resistant insulating powder and a sheath, this ceramic heater type improves heat transfer efficiency and has superior heat generation characteristics, and when heated, it quickly becomes red-hot and reaches a temperature of It has been widely adopted in recent years because it can significantly improve the startup characteristics and exhibit a certain level of performance as a fast-heating type.

In addition, as a configuration that can self-control the power applied to the heating wire described above to significantly improve the heat generation characteristics and prevent overheating in the heater part, the temperature coefficient of resistance (PTC) is more positive than that of the heating wire.
A self-temperature control type glow plug made of so-called dual materials, in which a resistor made of a material with a large diameter is connected in series with a heating wire as an energizing power control element, is also disclosed in Japanese Patent Publication No. 45-11848, for example. This method has already been proposed in publications such as Japanese Patent Laid-Open Publication No. 54-109538.

[Problem that the invention seeks to solve]

However, the former ceramic heater type glow plug simply has one type of heating wire buried inside it, just like the conventional sheathed type, so there are some problems when controlling the energized power. is occurring. In other words, in order to significantly improve the temperature rise characteristics during heating in such a ceramic heater, it is necessary to flow a large current at the beginning of one energization to rapidly generate heat in the heating wire. There is a risk that the ceramic heater may be adversely affected by the high heat.
Furthermore, it may have an adverse effect on the battery and electric circuits, causing problems such as fuse breakage, and to prevent this, it is necessary to separately provide temperature control means on the circuit to the heating wire. As a result, the cost of the entire preheating device including the glow plug increases. In particular, in such a ceramic heater type, a heating wire made of tungsten or the like is buried within the ceramic heater made of silicon nitride, etc., but the temperature distribution within this heater tends to be uneven, and the heat resistance strength There were problems in terms of reliability, and there were also drawbacks such as high costs, so some kind of countermeasure was required.

Also, the latter self-temperature-controlled glow plug.

Although this method can solve the problems with the ceramic heater type described above, it not only causes some problems in terms of reliability of its control function, etc., but also has the problem of indirect interference via the ceramic material like the sheath type described above. Since it involves heating, there are also problems in terms of rapid heating, and there is still room for improvement. In other words, in this type of self-temperature control type using two types of materials, conventionally, the power control resistor was installed inside the holder with an insulating material such as water glass filled, or it was placed in series with the heat generating wire within the sheath. Generally, the structure is complicated and the assembly process is troublesome and complicated, and it is also difficult to properly utilize the control effect of using resistors. was there. Furthermore, with such a configuration, it is not possible to accelerate the temperature rise time to within, for example, 7 seconds, and with the recent market demand for a longer period of energization, so-called afterglow, after starting the engine, the temperature rise time of the wire itself becomes shorter. Deterioration is becoming a problem.

In particular, in recent years, glow plugs of this type have improved the startability of diesel engines, are more durable against high-temperature usage conditions associated with the spread of turbo engines, and have also been improved by lowering the cost of the entire preheating device. The so-called after-glow method is adopted, in which the glow plug is kept energized for a certain period of time after startup to ensure smooth and appropriate combustion within the engine, thereby reducing exhaust and noise. There are great demands for this, and moreover, it is necessary to make this afterglow hour as long as possible. In other words, even after the engine is started, the engine is too cold in cold regions, and it takes time for the engine to warm up. The above-mentioned afterglow etc. have been required because the noise is large and incomplete combustion causes problems such as exhaust and noise such as white smoke and engine stalling.

[Means for solving problems]

In order to meet the above-mentioned requirements, the self-temperature control type glow plug according to the present invention replaces the rod-shaped heater held at the tip of the hollow holder with a conductive material having a small positive temperature coefficient of resistance and having a rod-like shape as a whole. A heat generating part made of a ceramic material and a heat-resistant insulating layer formed on the outer periphery of the rear end of the heat generating part, a part of which is electrically connected to the heat generating part and has a resistance temperature higher than that of the heat generating part. The control section is made of a conductive material such as a conductive ceramic material or a metal material having a large coefficient.

[Effect]

According to the present invention, the heat generating part is integrally constituted by a rod-shaped heat generating part made of a conductive ceramic material and a control part made of a conductive material having a larger positive temperature coefficient of resistance than the heat generating part formed on the outer periphery of the rear end. is exposed on the surface of the heater, allowing the tip of the heater to quickly become red-hot and exhibiting the performance of a fast-heating type, while also appropriately controlling the peak temperature and saturation temperature due to its own temperature saturation property. It's something you get.

〔Example〕

Hereinafter, the present invention will be explained in detail using embodiments shown in the drawings.

FIGS. 1 and 2 show an embodiment of a self-temperature-controlled glow plug according to the present invention. First, the schematic structure of the self-temperature-controlled glow plug, which is generally designated by the reference numeral 10 in FIG. 2, will be briefly described. Then, this glow plug lO is equipped with a rod-shaped heater 11 whose tip side functions as a heating element, and a substantially tubular metal holder 12 that holds this heater 11 at its tip, and the rear end of this holder lz is made of synthetic resin. An external connection terminal 14 is fitted and held concentrically through an insulating bushing 13 made of material, etc.
4 is connected to an electrode rod 15, which will be described later, which is connected to the heat generating part 20 of the heater 11, via a metal conducting wire 16 such as a flexible wire. Note that 13a in the figure is integrally fitted to the outer circumference of the insulating bush 13 and buckled in the axial direction due to the high pressure applied by the rear end of the holder 12 which is swaged during assembly, thereby causing the insulating bush 13 to snap into the holder 12. It is a metal pipe that is integrated with the side with the required mechanical strength and has a structure that is not easily affected by temperature.This is a metal pipe that is made of a metal pipe that is integrated with the side with the required mechanical strength and is not susceptible to temperature effects. It can be easily understood from the fact that 17a, 17b, 17
c is an insulating ring, a fixing nut, and a nut for tightening the external lead, which are screwed onto the threaded portion on the rear end side of the external connection terminal 14, and a lead wire from a battery (not shown) is connected between the nuts 17b and 17a. By holding the external connection terminal 14 between the battery terminals, the external connection terminal 14 is electrically connected to the battery terminal. on the other hand,
The holder 12 is electrically connected to ground by having a threaded portion 12a on its outer circumference screwed into a threaded hole formed in the cylinder head of the engine, and at the same time, the holder 12 is electrically connected to the ground.
1 is disposed so that its tip protrudes into the auxiliary combustion chamber or the combustion chamber.

Here, the reason why the external connection terminal 14 is connected to the above-mentioned heater 11 using the metal conductor wire 16 is that various vibrations and tightening applied to the external connection terminal 14 may cause the heater 11 to be damaged due to mechanical external forces such as torque. This is for protection, and it is preferable to use a material that has a certain degree of flexibility as the material for the conducting wire 16. However, the configuration is not necessarily limited to this, and modifications such as omitting the metal conductive wire 16 mentioned above and forming the external connection terminal 14 and the electrode rod 15 integrally are also possible.

Now, according to the present invention, in the glow plug 10 having the above-described configuration, the rod-shaped heater 11 held at the tip of the holder 12 is formed into a rod-like shape as a whole and has a positive temperature coefficient of resistance. A heat generating part 20 made of a small conductive ceramic material is formed on the outer periphery of the rear end side of this heat generating part 20 with a heat-resistant insulating layer 22 interposed therebetween, and a part of the heat generating part 20 is electrically connected to the heat generating part 20. It is characterized in that it is constructed with a control section 21 formed of a conductive material having a larger positive temperature coefficient of resistance than the heat generating section 20.

That is, according to the present invention, the problem that the conventional glow plug lacks the function of a fast heating type because it is an internal heating type in which the heating wire is buried in a sheath or ceramic, can be solved by replacing the heating part 20 with the heater 11. The problem is solved by exposing the control unit 2 to the outer surface of the control unit 2, which has a power control function.
1 is integrated into the outer periphery of the rear end of the heat generating section 20 to provide a function as a self-temperature control type, and further improve reliability such as overall heat resistance strength. According to the rod-shaped heater 11 according to the present invention, the heat generating part 20 is exposed on the surface of the heater 11 and at the same time extends into the inside thereof, so that it can be said to be an inside/outside heat generation type compared to the conventional internal heat generation type. , the advantages will be obvious.

Here, the heat generating part 20 constituting the rod-shaped heater 11 described above
The conductive ceramic material used to form the silicon-based ceramic material is so-called fine ceramics, which are stable in performance even at high temperatures (for example, up to about 1400°C) and have excellent thermal shock resistance. Oxides etc. are preferred, such as MoSi2, WSi2, RuO
2, SiC, LaCr01, etc. can be considered, and it is sufficient to select an appropriate material from these materials.

Further, the control section 21 described above may be formed of a conductive ceramic material like the heat generating section 20 described above, or may be formed of a metal material such as W, No., Pt, It, Rh, Cr, Ta, etc. It will be easily understood that the positive temperature coefficient of resistance on the side of the heat generating part 1 is the same as that of the control part 2.
It is sufficient to select a material whose positive temperature coefficient of resistance is smaller than the positive temperature coefficient of resistance on the first side. Here, the control section 2 described above
When forming 1 from a metal material, it may be formed from an oxidizing substance, but it goes without saying that a protective film may be formed on its surface using an oxidation-resistant substance. Furthermore, this control section 21
When a metal material is used as the heat generating part 20, it is possible to make the positive temperature coefficient of resistance different from that of the heat generating part 20 to a greater extent than when a conductive ceramic material is used. It is possible to exhibit advantages such as being able to act appropriately.

Note that it is also possible to use the same conductive ceramic material as the material for forming the heat generating section 20 and the control section 21 described above. For example, when TiN is added to sialon, it becomes conductive (so-called conductive sialon).
has been confirmed, and it is known that the resistance value changes continuously by adding more than T.
It is obvious that a device with a different iN content may be used as appropriate.Furthermore, the volumes of the heat generating section 20 and the control section 21 constituting the above-mentioned rod-shaped heater 11 may be adjusted depending on the required volume. It is set appropriately according to the resistance ratio.
It is something that can be freely chosen.

Here, in the above-described rod-shaped heater 11 according to the present invention, a heat-resistant insulating layer 22 is coated on the outer periphery of the rear end of a heat generating part 20 formed in a predetermined molded state, and a control part is further coated on the outside thereof. A metal coating layer 23 is formed on the outer periphery of the rear end side of the control section 21 to be joined to the holder 12 side, and then , an electrode rod 15 is inserted into the electrode insertion hole 20a formed in the heat generating part 20H.
It is preferable to fit and insert the heat generating part 20, and to electrically connect the tip end thereof to the tip side of the heat generating part 20. In this case, the metal coating layer 23 described above is for bonding and holding the heater 11 to the holder 12 by silver brazing or the like, and has a coefficient of thermal expansion that matches that of the conductive ceramic material on the heater 11 side. It is only necessary to select the materials, and the heat-resistant insulating layer 22, the control section 21 and the metal coating layer 2 described above may be used.
As the molding method in step 3, thermal spraying, CVO, pV port, vacuum evaporation, and other known methods may be employed. Furthermore, it goes without saying that the above-described electrode rod 15 also has a coefficient of thermal expansion that matches that of the conductive ceramic material.

Note that 15a in the figure is fitted to the tip side portion of the electrode rod 15, leaving only the tip end, and the electrode rod 15 and the heat generating section 20 are connected to each other.
An insulating coating layer that insulates the rear end of the
According to this embodiment, the distal end side of the heat generating section 20 includes the external connection terminal 14, the metal conductor wire 16, and so on. And it will be connected to the positive side via the electrode rod 15. Of course, the above-mentioned control section 21 controls the metal coating layer 23 on the rear end side.
It will be easily understood that the holder 12 is electrically connected to the holder 12 through the holder 12, thereby being connected to the negative (ground) side.

Further, in this embodiment, the rod-shaped heater 11 is formed in the shape of a round rod so that its cross-sectional shape is approximately circular (the tip of the heat generating part 20 is formed as a small diameter part in order to quickly become red hot). This shows the case where the shape is formed, and this has advantages such as ease of molding and assembly to the holder 12 side. However, the present invention is not limited to this, and various shapes such as an ellipse shape and a square shape can be formed. Modifications are possible.

According to the rod-shaped heater 11 as previously described, since the heat generating portion 20 is directly exposed on the outer surface of the heater, it can exhibit its effect as a faster heating type than the conventional sheath type or ceramic heater type. It is. In particular, since the tip of the heater 11 can quickly become red hot, the startability of the engine can be greatly improved, and the output can be made appropriate and good. Although the explanation was omitted in the above-mentioned embodiment, greater durability can be expected if a protective film having oxidation resistance is formed on the outer surface of the rod-shaped heater 11 by vapor deposition or the like. It is.

When the heater 11 in which the heat generating part 20 and the control part 21 are integrally constructed as described above is used, excellent characteristics can be exhibited as the glow plug 10 shown in FIG. 3. That is, the glow plug 1 according to the present invention
According to 0, the time to reach 800℃ is 3.0 seconds, and the peak temperature is approximately 120℃ with the allowable range of 1400℃ or less.
It has been confirmed through experiments that the saturation temperature can be increased to 0°C and further to 850°C.

In the self-temperature-controlled glow plug 10 having the above configuration, from the external connection terminal 14 to the metal conductor 16 and the electrode rod 15.
When a voltage is applied to the heat generating part 20 of the heater 11 through the heat generating part 20 . Control unit 2
1, and a larger voltage is applied to the heat generating part 20 side, which has a larger resistance value, than to the control part 21 side, resulting in a relatively large power density with respect to the control part 21,
The heat generating portion 20 at the tip of the heater 11, which has excellent quick heating properties, rapidly generates heat.

Furthermore, when the control section 21 side gradually generates heat and its resistance value increases accordingly after a predetermined period of time elapses from the start of energization, the voltage applied between the heat generating section 20 and the control section 21 gradually changes, causing heat generation. By controlling the voltage applied to the part 20 side, the heat generating part 20 side reaches a peak temperature at about 1200° C. and then saturates at about 850° C., thereby preventing overheating. That is, the resistance value on the control section 21 side at this point is considerably larger than that on the heat generating section 20 side. The control function of the control unit 21 limits the voltage applied to the heat generating unit 20 to a predetermined value or less.
This can fully guarantee its durability when performing afterglow over a long period of time.

Therefore, according to the glow plug 10 having such a configuration, by using the rod-shaped heater 11 consisting of the heat generating part 20 and the control part 21 which are integrally made of conductive ceramic materials having different positive temperature coefficients of resistance,
Its self-temperature control function eliminates the need for a conventional configuration in which a control circuit or the like is attached to the circuit for the heater, which is effective in reducing the cost of the entire preheating device.

Note that the present invention is not limited to the structure of the embodiment described above, and the shape, structure, etc. of each part may be modified or changed as appropriate. For example, in the embodiment described above, when applying voltage to the heat generating part 20 and the control part 21 that constitute the rod-shaped heater 11, a case was explained in which the positive terminal was connected to the heat generating part 20 side and the negative terminal was connected to the control part 21 side. 1 The present invention is not limited to this, and as shown in FIG. Variations are possible.

〔Effect of the invention〕

As explained above, according to the self-temperature-controlled glow plug according to the present invention, the rod-shaped heater held at the tip of the holder is made entirely of a rod-shaped conductive ceramic material with a small positive temperature coefficient of resistance. A heat generating part and a conductive layer formed on the rear end side outer periphery of this heat generating part through a heat-resistant insulating layer, a part of which is electrically connected to the heat generating part, and having a larger positive temperature coefficient of resistance than the heat generating part. Although the configuration is simple and inexpensive, the heat-generating part is exposed on the outer surface of the heater. Due to the self-temperature control function of the power control control unit connected to the body weight, the tip becomes red hot more quickly and reliably than conventional types, and the function as a fast heating type can be enhanced. It also has heat resistance against corrosion, greatly improves engine startability, and greatly improves heat generation characteristics such as overshoot characteristics, making it possible to maintain long-term afterglow as a measure against engine exhaust and noise. , it is possible to demonstrate its characteristics as a glow plug, and the overall structure is simple and easy to assemble, and it has excellent heat resistance strength and durability that can withstand harsh usage conditions. It has various excellent effects.

[Brief explanation of drawings]

FIG. 1 is an enlarged side view of essential parts showing an embodiment of a self-temperature-controlled glow plug according to the present invention, FIG. 2 is a vertical sectional view of a self-temperature-controlled glow plug to which the present invention is applied, and FIG. 3 4 is a characteristic diagram showing the temperature characteristics of the rod-shaped heater which is the main part thereof, and FIG. 4 is a schematic cross-sectional view of the rod-shaped heater showing another embodiment of the present invention. 10...Fist self-temperature control type glow plug. 11・+111・Rod heater, 12111111・Hollow holder, 14・・External connection terminal, 15・Fist φ electrode rod, 15a*・・Insulating coating layer. 16... Metal conductor wire, 20-... Heat generating part, 21φ.
Φsha (for power control) control section, 22... Fengken heat-resistant insulation layer,
23...Fist/metal coating layer. Patent applicant: Automotive Equipment Co., Ltd. Agent: Masatsuna Yamakawa (and 2 others) Figure 4

Claims (4)

[Claims] (1) Equipped with a rod-shaped heater held at the tip of a hollow holder with one end protruding outside. A heat generating part formed on the outer periphery of the rear end side of the heat generating part through a heat-resistant insulating layer, a part of which is electrically connected to the heat generating part, and having a temperature coefficient of resistance more positive than that of the heat generating part. A self-temperature-controlled glow plug characterized by comprising a control section made of a large conductive material. (2) The self-temperature control type glow plug according to claim 1, wherein the control portion is formed of a conductive ceramic material having a larger positive temperature coefficient of resistance than the heat generating portion. (3) The self-temperature control type glow plug according to claim 1, wherein the control section is formed of a metal material having a larger positive temperature coefficient of resistance than the heat generating section. (4) The heat generating part and the control part that constitute the rod-shaped heater are electrically connected in series, and the external connection terminal held at the rear end of the hollow holder is connected to the heat generating part, and the control part The self-temperature-controlled glow plug according to claim 1, wherein the glow plug is connected to the holder side.