JPH10110951A - Glow plug and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable an ion current to be detected under a superior precision without having any problem of deposition of carbon, a superior durability to be realized and also an easy manufacturing to be carried out. SOLUTION: A glow plug comprised of a housing 4 and a main body 10 supported within the housing is constructed such that the main body 10 is comprised of a rod-like insulator member 11, a pair of lead wires 21, 22 arranged within the rod-like insulator member, electrically connected to an electrical energized heating member 2 and to its both ends and fed out of the plug, and an ion sensing electrode 3 electrically insulated from the electrical energized heat generating member 2 so as to detect an ionized state in the flame. The ion sensing electrode 3 is arranged within a groove 150 formed at an outer circumferential part of the rod-like insulator 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a glow plug for promoting ignition and combustion of fuel, and a method for manufacturing the same.

[0002]

2. Description of the Related Art In recent years, in gasoline engines and diesel engines, it has been demanded to further reduce exhaust gas and smoke from the viewpoint of environmental protection. And
To meet these demands, various types of engine improvement and post-treatment (catalyst purification, etc.) have been studied to reduce exhaust gas, improve fuel and lubricating oil properties, and improve various engine combustion control systems.

Further, in recent engine combustion control systems, it is required to detect the combustion state of the engine, and it is necessary to detect the combustion state of the engine by detecting the in-cylinder pressure, combustion light, ion current, and the like. Are being considered. In particular, detecting the combustion state of an engine using an ion current is considered to be extremely useful because the chemical reaction accompanying the combustion can be directly observed, and various ion current detection methods have been proposed.

For example, Japanese Patent Application Laid-Open No. 7-259597 discloses a sleeve-shaped ion detection electrode insulated from a fuel injection nozzle and a cylinder head of an engine at a mounting seat of the fuel injection nozzle. Discloses a method for detecting an ionic current associated with fuel combustion by connecting to a detection circuit. U.S. Pat. No. 4,739,731 discloses an ion current detection sensor using a ceramic glow plug.

In these techniques, a conductive layer made of platinum is attached to the surface of a heater (electric heating element) of a glow plug, and this conductive layer is insulated from a combustion chamber and a glow plug mounting bracket. Then, an ion current measuring power supply (250 V DC) is applied to the conductive layer from the outside to detect an ion current accompanying fuel combustion.

[0006]

However, all of the above-mentioned prior arts have the following problems. That is, in the former technique (Japanese Patent Application Laid-Open No. 7-259597), in order to detect an ion current, a sleeve-like ion detection electrode that is insulated from other parts must be provided. In addition, complicated work is required in the processing. Therefore, there is a problem that the ion detection electrode has a very expensive configuration. Further, there is a shortcoming that the carbon between the fuel injection nozzle and the ion detection electrode and between the ion detection electrode and the cylinder head are short-circuited by carbon generated in the combustion chamber, so that the fuel cell cannot be used at an early stage.

The latter technique (US Pat. No. 4,734,734)
No. 9,731), there is a disadvantage that the structure is complicated because the ion detecting electrode is provided separately from the current-carrying heating element and both are connected to different power sources. In addition, since a large amount of expensive noble metal such as platinum is required in order to secure the heat resistance and wear resistance of the ion detection electrode, there is a disadvantage that the glow plug itself becomes very expensive.

The present invention has been made in view of the above problems, has no problem of carbon adhesion, can accurately detect an ion current, has excellent durability, and is easy to manufacture. It seeks to provide a way.

[0009]

According to a first aspect of the present invention, there is provided a glow plug comprising a housing and a main body supported in the housing, wherein the main body is provided in a rod-shaped insulator and inside the rod-shaped insulator. A pair of lead wires electrically connected to both ends of the energizing heating element and both ends of the energizing heating element and led out of the rod-shaped insulator, and provided along the axial direction at the outer peripheral portion of the rod-shaped insulator; The glow plug is characterized in that the glow plug is provided with an ion detection electrode for detecting a state of ionization in the flame, which is disposed inside the groove so as to be electrically insulated from the electric heating element.

What is most notable in the present invention is that a current-carrying heating element and a lead wire are disposed inside the rod-shaped insulator, and an ion-exchanger is formed inside a groove provided on the outer periphery of the rod-shaped insulator. That is, a detection electrode is provided.

[0011] In providing the energizing heating element and the lead wires inside the rod-shaped insulator, as described later, for example, screen printing is performed on the surface of a formed body (green sheet) of a ceramic material for forming the rod-shaped insulator. An electric heating element and a lead wire made of a conductive material are printed in a desired shape by pad printing, hot stamping, or the like, and then the formed body is wound around a separately manufactured center shaft, and then fired (Embodiment 1) , FIG. 3). Alternatively, there is a laminating method in which a grooved upper sheet is laminated on the formed body on which the above-mentioned energized heating elements are formed. (Refer to Embodiment 3 and FIG. 9). As a result, a bar-shaped insulator containing the printed heating element and the lead wire can be obtained.

On the other hand, regarding the arrangement of the ion detection electrode, a groove is formed in the outer periphery of the rod-shaped insulator in advance in the axial direction, and before or after the firing, the rod-shaped ion detection electrode is inserted in the groove. Arrange and fix the electrodes.

[0013] The glow plug of the present invention generates heat by passing an electric current through the above-mentioned current-carrying heating element, and the heating promotes ignition and combustion in the combustion chamber. Further, the ion detection electrode detects the state of ionization in the combustion flame. That is, at the time of detecting the ion current, the ion detection electrode and the inner wall (cylinder head) of the combustion chamber adjacent thereto are
Two electrodes are formed for capturing positive ions and negative ions during fuel combustion that exist between the two.

Thus, the ion current can be detected with high accuracy, and the information can be effectively used for combustion control. In addition, since the glow plug is provided with the original function of heating the combustion chamber (glow function) and the function of detecting the ion current, the structure can be made compact and inexpensive.

Further, since the current-carrying heating element is buried inside the rod-shaped insulator, there is no corrosion by the combustion flame,
It is possible to exhibit high heat generation performance over a long period of time without causing a decrease in resistance value and a change in heat generation characteristics, and has excellent durability. That is, since the heating element is not consumed by oxidation, its cross-sectional area is kept constant,
There is no change in the resistance value. In addition, it is possible to avoid problems such as breakage of the current-carrying heating element due to thermal shock or the like in the combustion chamber. Further, since the ion detecting electrode may be disposed in the above-described groove of the rod-shaped insulator, the manufacture of the glow plug is easy.

In addition, carbon may adhere to the surface of the ion detection electrode as the fuel burns, and the deposited carbon is used to heat the current-carrying heating element (for example, glow operation when the engine is started at a low temperature). ). Therefore, the ion current can be accurately detected over a long period of time.

Further, the glow plug of the present invention has a simple structure because the current-generating heating element, the lead wire and the electrode for ion detection are integrally provided inside the rod-shaped insulator. Therefore, according to the present invention, it is possible to provide a glow plug which has no problem of carbon adhesion, can accurately detect an ion current, has excellent durability, and is easy to manufacture.

Next, as in the second aspect of the present invention, an insulating coating material is filled on the ion detecting electrode provided in the groove so as to cover the ion detecting electrode. Is preferred. In this case, the ion detection electrode can be easily fixed to the rod-shaped insulator. As the insulating covering material, for example, an electrically insulating ceramic material is used.

Next, as in the third aspect of the present invention, it is preferable that the electric heating elements and the lead wires are formed by printing on the inner surface of the insulating substrate. In this case, it is easy to manufacture because the energizing heating element and the lead wires are printed and formed on a sheet-like insulating substrate in advance and wound around a center shaft. The current-carrying heating elements and lead wires are 0.005
The glow plug can be disposed in the glow plug in a thin layer state of about 0.02 mm, and the glow plug becomes compact.

Next, it is preferable that the tip of the ion detecting electrode is exposed at the tip of the rod-shaped insulator so as to be exposed to the flame. In this case, the response and detection accuracy (S /
N ratio) can be obtained. Next, according to a fifth aspect of the present invention, the ion detecting electrode is formed of MoSi ₂ , WC,
It can be made of one or more conductive ceramic materials of TiN. In this case, the heat resistance is improved, and the coefficient of expansion with the insulator can be easily adjusted and combined, so that the effect of improving the thermal shock resistance can be obtained.

Next, as in the sixth aspect of the present invention, the ion detection electrode can be made of one or more of W, Mo, and Ti refractory metals. In this case, since the material can be used in the form of a line or a plate, the material, processing,
The effect of cost reduction regarding assembly is obtained.

Next, one or more of Pt, Ir, Rh, Ru and Pd may be provided on the exposed portion of the ion detecting electrode exposed from the rod-shaped insulator. Is preferably provided. In this case,
The effect of improving the wear resistance and oxidation resistance of the detection electrode is obtained. Next, it is preferable that the tip of the rod-shaped insulator has a hemispherical shape. In this case, by removing the sharp edge of the rod-shaped insulator, the turbulence of the combustion flame flow near the ion detector is suppressed, the detection performance is stabilized, and the concentration of thermal stress is suppressed, and the thermal shock resistance is reduced. Is improved.

Next, as in the ninth aspect of the present invention, the first aspect
In manufacturing the glow plug of the present invention, the energizing heating element and the lead wires are formed on the surface of the formed body of the insulating substrate made of an electrically insulating ceramic material by printing, and then the electrical insulating material is formed on the printed surface of the insulating substrate. The insulating substrate is wrapped around the outer periphery of the center shaft, and a groove is formed along the axial direction between both ends of the insulating substrate in the winding direction and the center shaft. ,
There is a method for manufacturing a glow plug, wherein the ion detecting electrodes are arranged inside the outer groove, and then the electrodes are heated to bake the center shaft and the insulating substrate.

In this case, when the insulating substrate is fired,
The width of the substrate is reduced, and the ion detection electrode can be more firmly joined to the substrate. In addition, a glow plug having the effects described in claim 1 can be easily manufactured.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1 A glow plug according to an embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIGS. The glow plug of this embodiment is a ceramic glow plug used as a start-up assist device for a diesel engine. The glow plug 1 of this example is
As shown in FIG. 1, the apparatus comprises a main body 10 and a housing 4 on which the main body 10 is mounted. The main body 10 includes a rod-shaped insulator 11.
A current-carrying heating element 2 printed on one end of the rod-shaped insulator 11 and electrically connected to both ends of the current-carrying heating element 2 and led out to the other end of the rod-shaped insulator; Similarly, it has a pair of lead wires 21 and 22 formed by printing.

The state of ionization in the flame, which is electrically insulated from the electric heating element 2 and is disposed inside a groove 150 provided along the axial direction on the outer periphery of the rod-shaped insulator 11, Electrode 3 for detecting ions
Having.

As shown in FIGS. 1 and 2, the main body 10 is provided within a metal housing 4 in a metal annular support 4.
1 and is fixed. The one lead wire 21 of the current-carrying heating element 2 rises inside the rod-shaped insulator 11 and is electrically connected to the internal lead wire 231 via a conductive terminal portion 23 provided on the side surface of the main body 10. It is connected.
The other lead wire 22 is electrically connected to the housing 4 via the annular support 41. The upper end of the ion detection electrode 3 is electrically connected to the internal lead 33 via a conductive terminal 31 provided on the upper end of the rod-shaped insulator 11.

On the other hand, the housing 4 is
2, and has a protective cylinder 42 at the upper part as shown in FIG. Further, the housing 4 has a male screw portion 43 for mounting to the cylinder head 45 of the engine. A rubber bush 4 is provided at the upper opening of the protection cylinder 42.
21 are fitted. External lead wires 233 and 333 are inserted through the rubber bush 421, and these are connected to the internal lead wires 231 and 33 via connection terminals 232 and 332, respectively. Therefore, the external lead wire 233 is electrically connected to one end of the heating element 2, and the external lead wire 333 is electrically connected to the ion detecting electrode 3.

The other end of the heating element 2 is electrically connected to the housing 4 via the annular support 41 as described above (FIG. 1). The distal end (lower end) of the main body 10 is formed in a hemispherical shape as shown in FIG. 1, and the distal end 30 of the ion detection electrode 3 is exposed.

Next, a method for manufacturing the glow plug body 10 will be described with reference to FIG. First, raw materials composed of a ceramic material, a resin binder and the like are mixed to form a thin sheet 15 (FIG. 3A). Next, the conductive heating element portion 20 is printed and formed on the surface of the sheet 15 by screen printing using a conductive paste for the conductive heating element. Similarly, the lead wire portions 210 and 220 are formed by printing (FIG. 3B).

Further, on the back surface of the sheet 15, a terminal portion (not shown) is formed by printing with a conductive paste so as to be electrically connected to the lead wire portion 210. Next, a coating material including a ceramic material and a resin binder is coated and printed on the front surface side of the sheet 15. This is to eliminate the step between the print-formed portion such as the energized heating element portion 20 and the sheet surface and to flatten it, and to improve the adhesion between the sheet 15 and the center shaft 13 during the next winding.

On the other hand, a cylindrical central shaft 13 made of the same material as the sheet 15 is prepared. Then, the center shaft 13 is placed on the surface of the sheet 15 on which the energized heating elements 20 and the like are formed, and the sheet 15 is wound around the center shaft 13 (see FIG. 3).
(C)). At this time, as shown in FIG. 3C, an axial groove 150 is formed between the center shaft 13 and both end surfaces 152 and 153 in the winding direction of the sheet 15.

The groove 150 can be formed by previously reducing the width of the sheet 15 so that a gap is formed between both end surfaces 152 and 153. Or,
After the end surfaces 152 and 153 are brought into contact, one end surface is cut along the axial direction to a small width, and a groove is formed between the two.

Next, as shown in FIG.
A columnar ion detection electrode 3 is put into the inside, and an insulating coating material 19 made of a ceramic material is further filled thereon. Next, degreasing is performed by preheating, and main heating is performed, so that the sheet 15 made of a ceramic material and the center shaft 13 are formed.
Are fired integrally. At this time, seat 15, center shaft 1
In No. 3, due to firing shrinkage, both are strongly adhered to each other. The groove 150 of the ion detecting electrode 3 is narrowed by the above-described firing shrinkage, and is firmly fixed in the groove 150.

Next, as shown in FIG.
3 is plated with Cu and then with Ni. Next, an internal lead wire 231 (FIG. 1) is attached to the terminal portion 23 by brazing, and the surface thereof is plated with Ni. Also,
The tip of the rod-shaped insulator 11 is ground into a spherical state as shown in FIG. Thus, the glow plug main body 10 shown in FIG. 1 is obtained.

Next, with respect to the glow plug body 10,
For example, the center shaft 13 has an outer diameter of 2.9.
mm. The sheet 15 has a thickness of 0.8 m.
m, width 11.5 mm, length 54 mm. The outer diameter at the time of winding was 4.5 mm, and the diameter of the ion detecting electrode 3 inserted into the groove 150 was 0.7 mm. The width of the groove 150 was 0.8 mm.

The material of the center shaft 13 is Si ₃ N ₄
(Silicon nitride) powder 63% (weight ratio), MoSi ₂ (molybdenum disilicide) powder 18%, Y ₂ O ₃ (yttria) powder 4%, Al ₂ O ₃ (alumina) powder 3%
12% composite binder containing paraffin wax as a main component
Were used in a mixture. The material of the sheet 15 is Si
₃ N ₄ (silicon nitride) powder 70% (weight ratio) and MoSi
₂ (Molybdenum disilicide) powder 20% and paraffin WA
It was mixed with 10% of a composite binder containing X as a main component.

As the material of the electric heating element portion 20, a conductive paste made of W (tungsten) and Re (rhenium) was used. Also, the lead wire portions 210, 2
20, a W (tungsten) paste was used as the conductive paste on which the terminal portions 23 were formed by printing. The material of the ion detecting electrode is made of MoSi ₂ (molybdenum disilicide). The insulating coating material 19 filled in the groove 150 is composed of 63% of Si ₃ N ₄ (silicon nitride) powder and M
oSi ₂ (molybdenum disilicide) powder 18% and Y ₂ O ₃
A ceramic material composed of a mixture of 4% (yttria) powder, 3% Al ₂ O ₃ (alumina) powder, and 12% of a composite binder containing paraffin WAX as a main component was used.

Next, the above-mentioned wound material (FIG. 3D) is fired at 1700 to 1800 ° C. in an argon or nitrogen atmosphere.
Performed for 4 hours. By this baking, the outer diameter of the wound material (rod-shaped insulator) shrunk from 4.5 mm to 3.6 mm, and the ion detection electrode shrunk from 0.7 mm to 0.6 mm. Further, the surface of the exposed portion 30 (FIG. 1) at the tip of the ion detecting electrode 3 was coated with Pt.

Next, as shown in FIG. 4, the glow plug 1 composed of the main body 10 and the housing 4 is formed by screwing the male thread of the housing 4 into the cylinder head 45 of the engine as shown in FIG. Mounting.
As a result, the glow plug body 10 is mounted in a state where the tip of the glow plug body 10 projects into the swirl chamber 451 which is a part of the combustion chamber of the cylinder head 45. Reference numeral 457 indicates a main combustion chamber,
458 is a piston, and 459 is a fuel injection nozzle.

The glow plug 1 is connected to a glow plug operation circuit as shown in FIG. That is, the lead wire 21 at one end of the electric heating element 2 is connected to the external lead wire 23.
3, glow relay 53, and 12 volt battery 54
Is connected to a metal cylinder head 45 via a. Further, via the cylinder head 45, the housing 4, the annular support 41, and the lead wire 22 (FIG. 1) of the main body 10,
It is connected to the other end of the electric heating element 2. Thus, a circuit for heating the energizing heating element 2 is formed.

The external lead wire 333 of the ion detecting electrode 3 is connected to the ion current detecting resistor 521 and the DC power supply 51.
Is connected to the cylinder head 45 via the. Also,
The ionic current detecting resistor 521 is provided with a potentiometer 522 for detecting an ionic current.
(Electronic control device) 52. In addition, ECU
The glow relay 53, the engine coolant temperature sensor 525, and the engine speed sensor 526 are connected to 52.

When using the glow plug 1 shown in FIG.
The glow relay 53 is turned on by U52. Therefore, the path between the battery 54 and the heating element 2 of the glow plug is closed, and the heating element 2 of the glow plug body 10 is closed.
Is energized and generates heat. Therefore, the glow plug 1 is in a heating state, the vortex chamber 451 is heated, and the ignition temperature rises. Therefore, every time fuel is injected from the fuel injection nozzle 459, the fuel is ignited, the piston 458 is operated, and the engine is driven.

On the other hand, when the fuel is burning, ions are generated as described above, and the ion current is detected by the ion detection electrode 3, the ion current detection resistor 521, and the potentiometer 522. That is, the glow plug body 1
A voltage is applied between the ion detection electrode 3 and the cylinder head 45 by a DC power supply 51 of 12 volts.

Therefore, with the generation of active ions in the combustion flame zone in the swirl chamber 451, an ion current flows through a current path including the ion current detecting resistor 521. The ion current detecting resistor 521 has a resistance of about 500 kΩ, and the ion current flowing therethrough is detected by the potentiometer 522 as a potential difference between both ends.

Here, the principle of detecting the ion current will be briefly described. The fuel injected from the fuel injection nozzle 459 is supplied to the swirl chamber 45.
When the fuel is burned in step 1, a large amount of ionized positive ions and negative ions are generated in the combustion flame zone. At this time, since a battery voltage is applied between the ion detecting electrode 3 and the cylinder head 45 facing the ion detecting electrode 3, negative ions are captured by the ion detecting electrode 3 and positive ions are captured by the cylinder head 45. Ions are captured. As a result, the above-described current path is formed, and the ion current flowing through this current path is
1 is detected as a potential difference between both ends.

On the other hand, the ECU 52 has a CPU, ROM, R
A well-known microcomputer including an AM and an input / output circuit and an A / D converter (both are not shown) are mainly configured to input a detection signal detected by the potentiometer 522. A detection signal of a water temperature sensor 525 for detecting the temperature of the engine cooling water and a detection signal of a rotation speed sensor 526 for detecting the engine speed according to the engine crank angle are input to the ECU 52. Detects the water temperature Tw and the engine speed Ne based on each detection signal.

When the diesel engine is started at a low temperature, the ECU 52 heats the current-carrying heating element 2 of the glow plug 1 to promote ignition and combustion of the fuel. Immediately after the start of the diesel engine, the ion current is detected. Note that, at the beginning of the engine start, the glow relay 53 is in an on state, and the energized heating element 2 is maintained in a heated state.

The on / off switching process of the glow relay 53 will be described below with reference to the flowchart of FIG. FIG. 5 is executed by interruption processing for a predetermined time. First, when the process of FIG.
First, at step 11, it is determined whether or not the engine has been warmed up and the glow relay 53 is off. At the beginning of the engine start, a negative determination is made in step 11, and the ECU 52 reads the water temperature Tw and the engine speed Ne in the subsequent step 12.

Thereafter, in step 13, it is determined whether or not the water temperature Tw is equal to or higher than a predetermined warm-up completion temperature (60 ° C. in the present embodiment), and in step 14, the engine speed Ne is increased to a predetermined speed ( In the present embodiment, 2000 rpm
m) It is determined whether or not it has reached or exceeded. If a negative determination is made in both steps 13 and 14 at this time, it is considered that the warm-up of the engine has not been completed, and it is determined that heating by the current-carrying heating element 2 of the glow plug is necessary, and the process proceeds to step 15.

If any of steps 13 and 14 is affirmatively determined, it is considered that the warm-up of the engine is completed or that the heating by the glow plug 1 is not necessary, and step 1 is performed.
Proceed to 6.

When the operation proceeds to step 15, the glow relay 53 is kept on. In this state, the ignition and combustion of the fuel are continued by the heating action of the glow plug 1. When the process proceeds to step 16, the ECU 52
Turns off the glow relay 53.

Next, FIG. 6A is a current waveform diagram when an ion current generated during fuel combustion is observed using an oscilloscope. In the figure, the fuel injection timing (compression T
Immediately after DC), a waveform in which the voltage sharply rises is an ion current waveform due to fuel combustion, and point A corresponds to a combustion start position, that is, an ignition timing. Also, two peaks are observed in the ion current waveform. That is, in the early stage of combustion, the first peak B1 is observed by the active ions in the diffusion flame zone,
In the latter half of the combustion, the secondary
Mountain B2 is observed.

In this case, the ECU 52 detects the actual ignition timing from the first peak B1 of the ion current waveform,
Feedback control of the ignition timing is performed so as to eliminate the difference between the detected actual ignition timing and the target ignition timing. Further, the ECU 52 detects a combustion state such as abnormal combustion or misfire from the second peak B2 of the ion current waveform, and reflects the detection result in the fuel injection control. By reflecting the ion current in the fuel injection control of the engine in this way, it is possible to control the operating state of the engine finely.

Next, the ion detecting electrode 3 of the glow plug
When carbon (soot) generated by fuel combustion adheres, that is, when smoke is generated, as shown in FIG. 6 (B), the ion current is low before the fuel injection timing and rises thereafter. The phenomenon of going out occurs (compare (A) and (B) in FIG. 6). It should be noted that Ith in FIG. 6 (A) represents a determination level (threshold) of the peak value for determining whether or not the glow relay 53 is ON by determining the smoldering state. Therefore, when such a smoldering phenomenon occurs, the glow relay 53 is turned on and the heating element 2 is turned on.
Is heated to burn off the attached carbon.

FIG. 7 is a flow chart in which the carbon burn-off operation is performed by the ECU 52 in the circuit of FIG. That is, when the glow relay 53 is in the off state in step 21 of FIG.
In, it is determined whether or not the abnormal ion current (FIG. 6B) as described above is detected at the fuel injection timing. If not,
Proceeding to step 24, the glow relay 53 remains off. On the other hand, when an abnormal ion current is detected, the process proceeds to step 23, where the glow relay 53 is turned on, and the heating element 2 of the glow plug is heated to burn out carbon.

As described above, in the glow plug of this embodiment, the ion detecting electrode 3 is disposed inside the groove 150 of the rod-shaped insulator 11, and the electric heating element 2 and the lead wire are disposed inside the rod-shaped insulator 11. 21 and 22 are provided, and these are integrally formed. Therefore, the glow operation (heating operation) by the electric heating element 2 and the ion current detection by the ion detection electrode 3 can be achieved by one glow plug. Further, even when carbon adheres to the ion detecting electrode 3, the carbon is burned off by heating the energizing heating element 2 near the ion detecting electrode 3 so that the ion detecting electrode 3 is in a normal state. Can be returned to. Therefore, the ion current can be detected with high accuracy.

Further, the heating element 2, the lead wire 21,
Since the print 22 is formed by printing, its thickness is small, and the glow plug body can be made compact. Further, since the rod-shaped insulator 11, the electric heating element 2, the lead wires 21, 22 and the ion detecting electrode 3 are integrally formed, the configuration is simple. Further, since the electric heating element 2 and the lead wires 21 and 22 and the ion detection electrode 3 are provided inside the rod-shaped insulator 11, there is no corrosion such as oxidation due to combustion gas and the durability is excellent.

As shown in FIG. 3, the glow plug main body 10 of the present embodiment is formed by printing a heating element and a lead wire on an insulating sheet 15 and placing a central shaft 13 thereon and winding it. The electrode 3 for ion detection is arranged in the groove 150 formed at that time, and is then fired. Therefore, manufacture of the glow plug body is easy.
Further, since the tip of the rod-shaped insulator 11 has a hemispherical shape, it is possible to absorb a thermal shock in the combustion chamber.

The tip portion 30 of the ion detecting electrode 3
Is exposed so as to come into contact with the combustion gas (FIG. 1), and the exposed portion is coated with a noble metal such as Pt. Therefore, the generation of an insulator on the surface of the electrode for ion detection due to oxidation or the like is suppressed, the conductivity of the electrode or the initial resistance value is secured, and there is an effect of preventing deterioration of detection accuracy.

The rod-shaped insulator may be made of Al ₂ O ₃ or Si-Al-ON (Sialon) in addition to Si ₃ N ₄ . The conductive paste for printing and forming the heating element is W, Mo, Re, W or the like.
/ Mo, WC, WC / Re or W / Re and a paste composed of a resin.

Embodiment 2 As shown in FIG. 8, the present embodiment is a modification of the glow plug operation circuit (FIG. 4) of Embodiment 1, in which a battery 54 and a DC power supply 51 of Embodiment 1 are connected. One battery 55
Only in place. Note that a constant current and constant voltage circuit 524 can be interposed between the ion current detection resistor 521 and the battery 55. In this case, there are effects of simplifying the circuit configuration and reducing costs.

The other points are the same as in the first embodiment. Also in this example, the same effect as in the first embodiment can be obtained. In particular, in this example, by interposing the constant current / constant voltage circuit 524, even with one battery, the fluctuation of the voltage applied to the ion electrode caused at the time of heat generation of the glow plug can be prevented, and the stable detection performance can be maintained. The effect described above can be obtained.

Embodiment 3 In this embodiment, as shown in FIG. 9, the glow plug main body 10 is made of a laminated body. In this example, an upper sheet 16 (FIG. 9) made of the same material as that of the center shaft 13 is laminated on the sheet 15 (FIG. 3) on which the energized heating elements 20 and the like shown in the first embodiment are printed. . Upper sheet 1
6 has a groove 160 in which the ion detection electrode 3 is provided. The plate-like ion detection electrode 3 is inserted into the groove 160,
Further, the insulating coating material 19 is filled in the same manner as in the first embodiment.
After that, heating and firing or hot pressing are performed in the same manner as in the first embodiment.

As a result, as shown in FIG. 9, the energizing heating element 2 and the lead wires (not shown) are arranged between the rod-shaped insulators made of the electrically insulating sheets 15 and 16, and the ion detection is performed in the groove 160. Glow plug body 10 provided with electrodes for use
Is obtained. In this example, since the lamination method is used, manufacturing is simpler. Then, the desired shape is obtained by cutting (grinding). Other configurations are the same as those of the first embodiment, and the same effects as those of the first embodiment can be obtained.

[Brief description of the drawings]

1A is a cross-sectional view of a glow plug main body according to a first embodiment; FIG. 1B is a cross-sectional view taken along line AA of FIG.

FIG. 2 is an overall explanatory diagram of a glow plug according to the first embodiment.

FIG. 3 is an explanatory diagram of a method for manufacturing a glow plug body according to the first embodiment.

FIG. 4 is a glow plug operation circuit diagram according to the first embodiment.

FIG. 5 is a flowchart of the glow plug operation system according to the first embodiment when the glow plug is started.

FIG. 6 is a diagram showing (A) an ion current at the time of normal operation and (B) an ion current at the time of smoking in the first embodiment.

FIG. 7 is a flowchart of smoldering determination in the first embodiment.

FIG. 8 is a glow plug operation circuit diagram according to a second embodiment.

FIG. 9 is a sectional view of a glow plug body according to a third embodiment.

[Explanation of Codes] . . Glow plug, 10. . . Body, 11. . . 12. rod-shaped insulator; . . Center axis, 15. . . Sheet, 150, 160. . . Groove, 2. . . Current-carrying heating element, 21, 22,. . . Lead wire, 3. . . 3. electrode for ion detection, . . Housing, 45. . . Cylinder head, 451. . . Swirl chamber,

Claims (10)

[Claims] 1. A glow plug comprising a housing and a main body supported in the housing, wherein the main body comprises:
A rod-shaped insulator, a pair of lead wires provided inside the rod-shaped insulator, electrically connected to both ends of the energized heating element, and led out of the rod-shaped insulator; An ion detector for detecting the state of ionization in a flame, which is disposed in a groove provided along the axial direction on the outer periphery of the rod-shaped insulator and is electrically insulated from the current-carrying heating element. A glow plug comprising an electrode. 2. The glow according to claim 1, wherein an insulating coating material is filled on the ion detection electrode provided in the groove so as to cover the ion detection electrode. plug. 3. The glow plug according to claim 1, wherein the electric heating element and the lead wire are formed by printing. 4. The method according to claim 1, wherein:
A glow plug, wherein a tip of the ion detection electrode is exposed at a tip of the rod-shaped insulator so as to be exposed to the flame. 5. The method according to claim 1, wherein:
The ion detection electrode is made of MoSi ₂ , WC or TiN.
A glow plug characterized by being made of one or more kinds of conductive ceramic materials. 6. The method according to claim 1, wherein:
The ion detection electrode is one or two of W, Mo, and Ti.
A glow plug characterized by being made of at least one kind of high melting point metal. 7. The method according to claim 4, wherein
One or two of Pt, Ir, Rh, Ru, and Pd are provided on the exposed portion of the ion detection electrode exposed from the rod-shaped insulator.
A glow plug comprising at least one kind of noble metal. 8. The method according to claim 1, wherein:
The tip portion of the rod-shaped insulator has a hemispherical shape. 9. The method of manufacturing the glow plug according to claim 1, wherein the energizing heating element and the lead wire are formed by printing on the surface of an insulating substrate formed of an electrically insulating ceramic material. On the forming surface, a formation form of a middle shaft made of an electrically insulating ceramic material is placed, and the insulating substrate is wound around the outer periphery of the middle shaft, and axially between both ends in the winding direction of the insulating substrate and the middle shaft. A method for manufacturing a glow plug, comprising: forming a groove along the groove; then, arranging the ion detection electrode in the groove; and heating the electrode and firing the center shaft and the insulating substrate. 10. The method according to claim 9, wherein an ion detecting electrode is disposed in the groove, and an insulating coating material is filled in the groove so as to cover the ion detecting electrode, and thereafter, the heating and firing are performed. A glow plug, characterized in that: