JPS61217627A - 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 saturated temperature appropriately by providing the tip side and the rear end side of the outer peripheral section of a heat resistant insulating body with a conductive heat generating section and a conductive control section with different positive resistance temperature coefficients and exposing the heat generating section to the surface of the heater. CONSTITUTION:A rod-shpaed heater 11 is constituted with a heat generating section 20 formed on the outer peripheral section of the tip side of an heat resistant insulation body 22 and made of conductive material and a control section 21 that is formed on the outer peripheral section on the rear end side of the heat resistant insulation body 22 and connected to the heat generating section 20 electrically and made of conductive material with a positive resistance temperature coefficient larger that of the heat generating section 20. A voltage is applied from an outside connection terminal 14 to the heat generating section 20 and control section 21 of the heater 11. Then, a larger voltage is applied to the heat generating section 20 with a larger resistance value than to that of the control section 21, and the heat generating section at the tip of the heater 11 generates heat rapidly. As the resistance of the control section 21 increases with its heat generation, the voltage applied to the heat generating section 20 and the control section 21 changes and the applied voltage to the heat generating section is controlled, so that its temperature is saturated at about 850 deg.C after after it has reached its peak temperature of about 1,200 deg.C and its overheating can be avoided.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a glow plug used for preheating the auxiliary combustion chamber or combustion chamber of a diesel engine, and particularly to a glow plug that exhibits a function as a fast heating type. The present invention relates to an improvement of a self-temperature-controlled glow plug equipped with a rod-shaped heater that improves heat generation 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 resistor made of a material with a large diameter is connected in series with the heating wire within the glow plug as an energization power control element. Self-temperature control glow plugs made of so-called dual materials have already been proposed, for example, in Japanese Patent Publication No. 45-11648 and Japanese Patent Application Laid-open 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 initial stage of 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 are also problems in terms of reliability and high cost, and some countermeasures are 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. However, the structure is complex and the assembly work 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, for example, 7 seconds or less, and with the recent market demand for a longer period of energization, so-called afterglow, after starting the engine, the wire itself is Deterioration is becoming a problem.

Especially with these types of glow plugs these days.

Improved startability of diesel engines, durability against high operating conditions due to the spread of turbo engines, and reduction in the cost of the entire preheating device, as well as the ability to keep the glow plug energized for a certain period of time after the engine has started. There is a strong demand for the adoption of the so-called after-groove method, which ensures smooth and appropriate combustion within the engine by maintaining the It is necessary to make each 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 holder with a conductive material with a small positive resistance temperature coefficient formed on the outer periphery of the heat-resistant insulator on the tip side. a heat generating part made of a conductive material, and electrically connected to the heat generating part on the outer periphery of the rear end side of the heat-resistant insulator, and made of a conductive material having a larger positive temperature coefficient of resistance than the heat generating part. The control section is constructed by forming a control section.

[Effect]

According to the present invention, there is provided a heat generating part and a control part made of conductive materials having different positive temperature coefficients of resistance, which are arranged in parallel on the front end side and the rear end side of the outer peripheral part of the heat-resistant insulator, and the heat generating part is located on the surface of the heater. Because it is exposed, the tip of the heater can quickly become red hot, exhibiting the performance of a fast heating type, and its own temperature saturation property allows it to appropriately control the peak temperature and saturation temperature. .

〔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 10 includes 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 12 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 connected to a heat generating section 20 of the heater 11, which will be described later, via a metal conductor 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 screwed onto the threaded portion on the rear end side of the external connection terminal 14, a fixing nut, and a nut for tightening the external lead, which is used to tighten lead wires from a battery (not shown) (17b, 17c). This external connection terminal 14 is electrically connected to the battery terminal by sandwiching it between the two terminals. 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 with the tip thereof protruding 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 lO having the above-described configuration, the rod-shaped heater 11 held at the tip of the holder 12 is connected to the #thermal insulating body 2 as shown in FIG.
A heat generating part 20 made of a conductive material such as a conductive ceramic material or a metal material having a small positive temperature coefficient of resistance is formed on the outer peripheral part of the front end of the heat-resistant insulator 22, and a heat generating part is formed on the outer peripheral part of the rear end of the heat-resistant insulator 22. 20 and a control section 21 formed of a conductive material such as a conductive ceramic material or a metal material having a larger positive temperature coefficient of resistance than the heat generating section 20. It is characterized by the fact that it is made to do so.

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 provided integrally with the heat generating part 20 to have a function as a self-temperature control type, and furthermore, the reliability such as the heat resistance strength of the whole can be improved. According to the rod-shaped heater 11 according to the present invention, since the first heat generating part 20 is provided exposed on the outer surface of the heater 11, it can be said to be a surface heat generating type compared to the conventional internal heat generating type, and its advantages are as follows. It should be obvious.

Here, the heat-resistant insulator 22 constituting the rod-shaped heater 11 described above is formed into a rod-shape from a heat-resistant insulating material such as silicon nitride (Si2N) or asbestos.
In addition, the conductive ceramic material that forms the heat generating part 20 and the control part 21 formed at the front and rear ends of the outer periphery has stable performance even under high temperature conditions (for example, up to about 1400 degrees Celsius). It has excellent thermal shock resistance, etc.
It is preferable to use non-oxide materials such as silicon-based materials, which are so-called fine ceramics, and have electrical conductivity.

For example, MoSi2, WSiz, RuO2, SiC
, LaCr01, etc., and may be appropriately selected from these materials. However, the heat generating section 20 and the control section 21 are not limited to the above-mentioned conductive ceramic materials, and are made of, for example, W, No., Pt, It, Rh,
It is easily understood that it may be formed of a metal material such as Cr, 〒A, etc.; the point is that the positive temperature coefficient of resistance on the side of the heat generating part 20 is smaller than the positive temperature coefficient of resistance on the side of the control part zl. All you need to do is to choose a material that will. Here, when the heat generating section 20 and the control section 21 described above are formed of a metal material, they may be formed of an oxidation-resistant material, but a protective film may be formed on the surface thereof using an oxidation-resistant material. Of course. Furthermore, in this way, the heat generating part 20 or the control part 2
When either one of 1 is formed using a metal material, it is possible to make the positive temperature coefficient of resistance between the two 1 more different than when both are made of conductive ceramic material. It is possible to bring about advantages such as being able to apply control effects more 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 heaters with different iN content may be used as appropriate.Furthermore, this rod-shaped heater 1
The volumes of the heat generating part 2G and the control part 21 constituting the heat generating part 1 are appropriately set according to the required resistance ratio, and can be freely selected.

Here, the rod-shaped heater 11 according to the present invention described above has a heat-generating portion 20 and a control portion 21 coated on the outer peripheral tip and rear end of a heat-resistant insulator 22 formed in advance in a rod shape,
The insulator 22 is connected in series at approximately the center of the insulator 22 to form an integrated state.
It is preferable to form a metal coating layer 23 to be bonded to the side, and to electrically connect the tip of the electrode rod 15 inserted into the electrode insertion hole 22a formed in the insulator 22 to the heat generating part 20. . In this case, the metal coating layer 23 described above is applied to the heater 11 with respect to the holder 12.
Silver brazing is used to join and hold the parts, and the material should be selected to have a coefficient of thermal expansion that matches the conductive ceramic material and heat-resistant insulating material on the heater 11 side. Control section 21 and metal coating layer 23
The molding method may be thermal spraying, CVO, PV deposition, vacuum evaporation, or other known methods. here.

It goes without saying that the above-mentioned electrode rod 15 should also have a coefficient of thermal expansion matched to that of a conductive ceramic material, a heat-resistant insulating material, or the like.

According to the above-described configuration, the tip of the heat generating section 20 is connected to the external connection terminal 14 and the metal conductor wire 16 in this embodiment.
, and to the positive side via the electrode rod 15. Of course, it will be easily understood that the above-mentioned control section 21 is electrically connected to the holder 12 side via the metal coating layer 23 on the rear end side, and thereby connected to the negative (ground) side.

Further, in this embodiment, the rod-shaped heater 11 is formed into a round rod shape with a substantially circular cross-sectional shape. However, it is of course not limited to this, and various modifications such as an elliptical shape and a angular shape are possible.

According to the above-mentioned rod-shaped heater 11, since the heat generating part 20 is directly exposed on the outer surface of the heater, it can exhibit its effect as a faster heating type compared to the conventional sheath type or ceramic heater type. be. 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.

As described above, the heater 11 has the heat generating section 20 and the control section 21 integrated with each other via the heat-resistant insulator 22.
When used, it is possible to exhibit excellent characteristics as a glow plug lO as shown in FIG. That is, according to the glow plug IO according to the present invention, the time to reach 900°C is 3.0 seconds, the peak temperature is approximately 1200°C with the allowable range of 1400°C or less, and the saturation temperature is 850°C.
It has been confirmed through experiments that the temperature can be reduced to ℃.

In the self-temperature-controlled glow plug 1O with the above configuration, from the external connection terminal 14 to the metal conductor 16, 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 , and further to the control part 21 side through the heat generating part 20 , in the initial stage of energization, the applied voltage is the same as that of the heat generating part 20 . Control part 2
The voltage is divided at a resistance ratio of 1, and a larger voltage is applied to the heat generating part 20 side having a large resistance value than that to the control part zl 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 1O having such a configuration, the rod-shaped glow plug 10 is composed of a heat generating part 20 and a control part 21 which are integrally made of conductive ceramic materials having different positive temperature coefficients of resistance through a heat-resistant insulator 22. By using heater 11.

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 above-mentioned embodiment, when applying voltage to the heat generating part 20 and the control part 21 that constitute the rod-shaped heater 11, the positive terminal was connected between the control parts 21 and the negative terminal was connected to the heat generating part 20 side. However, the present invention is not limited to this, and the connections may be made in the opposite direction, and various modifications can be made to the shape and structure of the rod-shaped heater 11 and the connection structure of the electrodes.

For example, in FIG. 4, a round bar is used as the heat-resistant insulator 22, and the heat-generating part 20 and the control part 21 are continuously formed on the outer periphery, and a heat-resistant insulating layer 30 is formed on the outer periphery.
Forming an electrode lead layer 31 from the heat generating part 20 via the
A case is shown in which this is connected to the holder 12, and the electrode rod 15 is connected to the rear end of the control section 21.

Further, FIG. 5 shows a case in which the heat generating part 20 and the control part 21 are formed by extending to the front and rear end faces of the heat-resistant insulator 2z, and the heat generating part 20 side is connected to the holder via the electrode lead calendar 31. The control unit 21 is connected to the electrode rod 15 on the 12th side, similar to the embodiment shown in FIG.

Furthermore, in FIG. 6, a heat-resistant and insulating cylindrical body 40 is used as a base for forming the heat generating part 20 and the W control part 21. control section 2
1, and the heating element 20 and the control body 21 are connected in series at the outer circumference of the cylinder 40, while maintaining an insulated state at the inner circumference. In this embodiment, the tip of the electrode rod 15 is connected to the inner end of the heat generating part 20 within the cylindrical body 40, and the cylindrical body 4
The electrode lead layer 42 drawn out from the inner end of the control section 21 to the outer periphery m via the heat-resistant insulating layer 41 in the holder 1
This shows the case where the connection is made in two directions. According to such a configuration, it is possible to take a larger resistance value between the heat generating part 20 and the control part 21 compared to the above-mentioned embodiment, so the degree of freedom in design is increased, and the characteristics are further improved. It is possible to obtain excellent glow plugs in the market, and the benefits are significant.

[Effects of the Invention] As explained above, according to the self-temperature control type glow plug according to the present invention, the rod-shaped heater held at the tip of the holder is connected to the positive electrode formed on the outer circumference of the tip side of the heat-resistant insulator. A heat generating part made of a conductive material with a small temperature coefficient of resistance and a temperature coefficient of resistance more positive than that of the heat generating part is formed on the outer periphery of the rear end side of the heat-resistant insulator and electrically connected to the heat generating part. Although the construction is simple and inexpensive, the heat generating part is exposed on the outer surface of the heater, and the power control control unit is integrally connected to the control part made of a large conductive material. Due to the self-temperature control effect of the
Achieves faster and more reliable tip heating compared to conventional types, enhances its functionality as a rapid heating type, and has heat resistance against high-temperature operating conditions, and also significantly improves engine startability. At the same time, the heat generation characteristics such as overshoot characteristics have been greatly improved, enabling long-term after-glow as a countermeasure for engine exhaust and noise, making it possible to demonstrate the performance as a glow plug, and further improving the overall performance. It has various excellent effects such as a simple structure, ease of assembly, and excellent heat-resistant strength and durability that can sufficiently withstand harsh usage conditions.

[Brief explanation of the drawing]

FIG. 1 is an enlarged cross-sectional view of essential parts showing one embodiment of a self-temperature-controlled glow plug according to the present invention, FIG. 2 is a vertical cross-sectional view of a self-temperature-controlled glow plug to which the present invention is applied, and FIG. 3 1 is a characteristic diagram showing the temperature characteristics of the rod-shaped heater which is the main part thereof, and FIGS. 4 to 6 are enlarged sectional views of the main part showing other embodiments of the present invention. lO...Self-temperature control type glow plug. 11...Rod-shaped heater, 12-Fist φ hollow holder,
14 Fist...External connection terminal, 15...Fist/electrode rod, 16
---Metal conductor wire, 20---Heating part, 21--
(For power control) Control unit, 22...Heat-resistant insulator, 2
3... Φ metal coating layer, 30, 42... Φ... electrode lead layer, 31.41... heat-resistant insulating layer, 40...
...Heat-resistant insulating cylindrical body.

Claims (13)

[Claims] (1) Equipped with a rod-shaped heater held at the tip of a hollow holder with one end protruding outside, this rod-shaped heater has a positive temperature coefficient of resistance formed on the outer periphery of the heat-resistant insulator on the tip side. A heat generating part made of a small conductive material, and a conductive material having a larger positive temperature coefficient of resistance than the heat generating part, which is electrically connected to the heat generating part on the outer periphery of the rear end side of the heat-resistant insulator. A self-temperature-controlled glow plug characterized by comprising a control section made of a material. (2) The self-temperature-controlled glow plug according to claim 1, wherein the heat generating portion is formed of a conductive ceramic material having a smaller positive temperature coefficient of resistance than the control portion. (3) The self-temperature-controlled glow plug according to claim 1, wherein the heat generating portion is formed of a metal material having a smaller positive temperature coefficient of resistance than the control portion. (4) The self-temperature control type glow plug according to claim 1, wherein the control section is formed of a conductive ceramic material having a larger positive temperature coefficient of resistance than the heat generating section. (5) 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. (6) The heat generating part and the control part that constitute the rod-shaped heater are electrically connected in series, and the electrode rod 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. (7) The heat generating part and the control part constituting the rod-shaped heater are electrically connected in series, and the electrode rod held at the rear end of the hollow holder is connected to the control part, and the heat generating part The self-temperature-controlled glow plug according to claim 1, wherein the glow plug is connected to the holder side. (8) A rod-shaped heater is provided which is held at the tip of the hollow holder with one end protruding outside, and this rod-shaped heater includes the outer periphery on the tip side of the heat-resistant insulating cylinder, the end surface on the tip side, and the inner periphery thereof. a heat generating part made of a conductive material with a small positive temperature coefficient of resistance formed on the cylindrical body, and electrically connected to the heat generating part on the rear end side outer peripheral part, the rear end side end surface and the inner peripheral part of the cylinder. and a control section made of a conductive material having a larger positive temperature coefficient of resistance than the heat generating section, and the heat generating section and the control section are in an insulated state at the inner circumferential portion of the cylindrical body. A self-temperature-controlled glow plug. (9) The self-temperature-controlled glow plug according to claim 8, wherein the heat generating portion is formed of a conductive ceramic material having a smaller positive temperature coefficient of resistance than the control portion. (10) The self-temperature-controlled glow plug according to claim 8, wherein the heat generating portion is formed of a metal material having a smaller positive temperature coefficient of resistance than the control portion. (11) The self-temperature control type glow plug according to claim 8, wherein the control section is formed of a conductive ceramic material having a larger positive temperature coefficient of resistance than the heat generating section. (12) The self-temperature control type glow plug according to claim 8, wherein the control section is formed of a metal material having a larger positive temperature coefficient of resistance than the heat generating section. (13) The heat generating part and the control part that constitute the rod-shaped heater are electrically connected in series, and the electrode rod 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 8, characterized in that the glow plug is connected to the holder side.