JPH1089224A - Glow plug - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a glow plug to prevent the occurrence of a problem on adhesion of carbon, detect an ion current with high precision, and have excellent durability. SOLUTION: A body 10 comprises an insulation body 11; an energization heat generating body 2 and a pair of lead wires 21 and 22, which are arranged at the internal part thereof; and an electrode 3 for detecting ion. The electrode 3 for detecting ion is electrically connected to the middle of the energization heat generating body 2 and its tip end is exposed from the insulation body 11 in a manner to be exposed to flame. The tip 30 of the electrode 3 for detecting ion is arranged in a position spaced away by 2mm or more from the tip part 411 of a housing 4. Further, provided electric resistance of the whole of the energization heat generating body 2 is R(Ω), electric resistance from the plus end of the energization heat generation body 2 to the tip 30 of the electrode 3 for detecting ion is B(Ω), a relation of B(Ω)>=R(Ω)/3 is pereferably established.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a glow plug for promoting ignition and combustion of fuel.

[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, and has as its object to provide a glow plug which has no problem of carbon adhesion, can accurately detect an ion current, and has excellent durability. .

[0009]

According to a first aspect of the present invention, there is provided a glow plug including a housing and a main body supported in the housing, wherein the main body includes an insulator, and an electric heating element provided inside the insulator. A pair of lead wires electrically connected to both ends of the energized heating element and led out of the insulator; and a state of ionization in the flame, disposed inside the insulator. The electrode is electrically connected to the middle of the heating element, and the tip of the electrode is exposed from the insulator so as to be exposed to the flame. And
The glow plug is characterized in that a tip of the ion detection electrode is arranged at a position separated from the tip of the housing by 2 mm or more.

What is most notable in the present invention is that the electric heating element and the ion detection electrode are disposed inside the insulator, and the tip of the ion detection electrode is
That is, it is arranged at a position separated from the tip of the housing by 2 mm or more.

In order to dispose the heating element and the electrode for ion detection in the insulator, for example, as shown in FIG. Embedded in a ceramic powder, and integrally molded. Alternatively, the current-carrying heating element and the electrode for ion detection are interposed between two separate insulators separately manufactured in advance. These insulator molded products or the integrally molded product of the electric heating element and the ion detection electrode are produced by, for example, injection molding these materials.

Further, the current-carrying heating element and the electrode for ion detection may be provided by printing inside the insulator. As an example of such a print formation, for example, two formed bodies (green sheets) of a ceramic material for forming an insulator are prepared, and screen printing, pad printing, hot stamping, etc. are formed on the surface of one of the formed bodies. The printing is performed by printing a current-carrying heating element made of a conductive material, a lead wire thereof, and an electrode for ion detection in a desired shape.

Next, another formed body is laminated so as to cover the printing section, and then fired. Here, the current-carrying heating element, the lead wire, and the ion detection electrode may be printed and laminated on two or more generators. Alternatively, the heating element and the electrode for ion detection may be printed on separate formed bodies, and may be electrically connected during lamination or after firing. As a result, an insulator containing the printed heating element, lead wire, and ion detection electrode is obtained.

Next, the operation and effect of the present invention will be described.
First, 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 to the ion detection electrode form two electrodes between the two for capturing the positive ions and the negative ions during fuel combustion. Form.

As a result, the ion current can be accurately detected, 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.

In the present invention, the tip of the ion detecting electrode is separated from the tip of the housing by 2 mm or more. Therefore, even if carbon is deposited on the surface of the glow plug main body, the ion current can be reliably detected. That is, as shown in FIG. 10, which will be described later, the distance (L,
If FIG. 2) is less than 2 mm, the shorter the distance, the lower the ion output detection rate. On the other hand, in the present invention in which the distance is 2 mm or more, the ion output can be reliably detected.

The reason is considered as follows. When the distance (L) from the tip of the ion detection electrode to the tip of the housing is less than 2 mm, if carbon deposits on the glow plug body, the insulation resistance between the ion detection electrode and the housing decreases. Since it is large and close to a short circuit, it is difficult to detect the ion current. In contrast,
In the present invention, since the distance (L) is 2 mm or more, even if carbon is deposited on the main body of the glow plug, a decrease in insulation resistance is small and a short circuit does not occur. In addition, even if the insulation resistance is reduced by use for a long time, the carbon can be burned off by heat generated by energizing the energizing heating element described later. Therefore, the glow plug of the present invention can reliably detect the ion current.

Further, the glow plug of the present invention has a simple structure because the above-mentioned heating element, lead wires and nine poles for ion detection are integrally provided inside the 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, and has excellent durability.

Next, as in the second aspect of the present invention, the electric resistance of the whole energized heating element is R (Ω), and the electric resistance from the plus end of the energized heating element to the tip of the ion detecting electrode is defined as R (Ω). When B (Ω) is satisfied, it is preferable that B (Ω) ≧ R (Ω) / 3. In this case, even if carbon accumulates on the glow plug main body and the state is close to the above-mentioned short circuit, an appropriate current can be supplied to the circuit of the heating element, the ion detection electrode, and the attached carbon. Therefore, carbon can be burned off by the heat generated by the current flowing in this circuit. Further, after the short-circuit state is eliminated, a current flows through the current-carrying heating element, and carbon loss is promoted.

When the electric resistance B (Ω) is very large, the resistance of the circuit of the heating element, the ion detecting electrode, and the attached carbon becomes large. In this case, even if the attached carbon is present, a substantially normal current flows through the entire heating element, and the attached carbon can be burned off by the heat generated by the heating element. Therefore, the heat generating function inherent in the glow plug can be always exerted, and the carbon deposited on the glow plug body can be easily burned off.

Further, the electric resistances R (Ω) and B (Ω)
In order to make B (Ω) ≧ R (Ω) / 3,
This can be performed by changing the materials of the current-carrying heating element and the electrode for ion detection, or the thickness, thickness, length, and the like of the current-carrying path. For example, the means for changing the material can be achieved by adjusting the mixing ratio of the conductive ceramic powder and the insulating ceramic powder as the raw materials. Also,
The means for changing the length of the current-carrying path can be achieved by changing the connection position of the ion detection electrode to the current-carrying heating element.

[0022]

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 FIG. 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, it comprises a main body 10 and a housing 4 on which the main body 10 is mounted. The main body 10 includes an insulator 11
And a current-carrying heating element 2 provided inside the insulator 11;
It has a pair of lead wires 21 and 22 that are electrically connected to both ends of the current-carrying heating element 2 and led out to the other end of the insulator.

Further, there is provided an ion detection electrode 3 disposed inside the insulator 11 for detecting the state of ionization in the flame. The ion detecting electrode 3 is electrically connected to the middle of the current-carrying heating element 2 and its tip 30 is exposed from the insulator 11 so as to be exposed to the flame.

As shown in FIGS. 1 and 2, the tip 30 of the ion detecting electrode 3 is disposed at a position at least 2 mm away from the tip 411 of the housing. Further, in this example, the electric resistance value of the entire heating element 2 is represented by R
(Ω), when the electrical resistance from the positive end 210 of the current-carrying heating element 2 to the tip of the ion detecting electrode 3 is B (Ω),
The configuration is such that B (Ω) ≧ R (Ω) / 3.

As shown in FIGS. 1 and 3, the main body 10 is fixed in a metal housing 4 via a metal annular support 41. Then, one lead wire 21 of the current-carrying heating element 2 rises inside the insulator 11 and is electrically connected to the internal lead wire 231 via a conductive terminal portion 23 provided on a side surface of the main body 10. Have been.
Further, the other lead wire 22 is electrically connected to the internal lead wire 33 via a conductive terminal 31 provided at the upper end of the insulator 11. Note that the external lead wire 231 is
It is commonly used as a lead wire for the electric heating element 2 and the ion detection electrode 3.

On the other hand, the housing 4 is
1, 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.

Accordingly, the external lead wire 233 is electrically connected to one end of the current-carrying heating element 2, and the external lead wire 333 is electrically connected to the other end of the current-carrying heating element 2. Also, the main body 1
As shown in FIG. 1, the leading end (lower end) of 0 is formed in a hemispherical shape, and the leading end 30 of the ion detection electrode 3 is exposed.

Next, in manufacturing the glow plug body 10, first, as shown in FIG.
And an electrode 3 for ion detection are prepared.
This integrally molded article 29 is manufactured by injection molding or press molding using ceramic powder for the electric heating element 2 and the ion detection electrode 3. And this one-piece molding 29
Are buried in the insulator 11 and are integrally formed by hot pressing. Prior to the embedding, the lead wires 21 and 22 are connected. Thereby, the glow plug main body 10 is obtained.

The heating element 2, the ion detecting electrode 3, and the insulator 11 were made of an insulating ceramic and a conductive ceramic. And the mixing ratio of the insulating ceramic particles and the conductive ceramic particles,
The physical characteristics such as the coefficient of linear expansion and the electrical resistance of the heating element 2, the ion detection electrode 3, and the insulator 11 were adjusted by adjusting the particle size.

In this example, silicon nitride (Si ₃ N ₄ ) was used as the insulating ceramic, and molybdenum silicide (MoSi ₂ ) was used as the conductive ceramic. In addition, AlO ₃ , BN, AlN, or the like can be used as the insulating ceramic. Further, as the conductive ceramic, Mo ₅ Si ₃ , WC, TiN or the like can be used.

The above-described electric resistance R in this embodiment is
(Ω) and B (Ω) were adjusted by changing the connection position of the ion detection electrode 3 while maintaining the value of the distance L at 2 mm or more. That is, the relationship of B (Ω) ≧ R (Ω) / 3 was realized by adjusting the length of current.

Next, as shown in FIG. 5, the glow plug 1 constituted by 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, a glow relay 53, 531 and a 12 volt battery 54 are connected to an external lead wire 333. Further, the external lead wire 333 is
3, and through the lead wire 22 (FIG. 1) in 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 ion detecting electrode 3 is connected to the cylinder head 45 via the external lead wire 233, the ion relay 530, the ion current detecting resistor 521, and the DC power supply 51.
It is connected to the. Further, the ion current detecting resistor 5
Reference numeral 21 denotes a potentiometer 522 for detecting an ion current.
Which is connected to an ECU (electronic control unit) 52. The glow relays 53 and 531, the ion relay 530, the engine coolant temperature sensor 525, and the engine speed sensor 526 are connected to the ECU 52.

When using the glow plug 1 shown in FIG.
By U52, the ion relay 530 is turned off, and the glow relays 53 and 531 are turned on. 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 energized to generate heat. Therefore, the glow plug 1 is in a heating state, the vortex chamber 451 is heated, and the ignition temperature rises. Therefore,
Each 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, so that the glow relays 53, 5
31 is turned off, the ion relay 530 is turned on, and the ion current is detected by the ion detection electrode 3, the ion current detection resistor 521, and the potentiometer 522. That is, a voltage is applied between the ion detection electrode 3 of the glow plug main body 10 and the cylinder head 45 by the DC power supply 51 of 12 volts.

Then, 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 the 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 relays 53 and 531 are in an on state, and the energizing heating element 2 is maintained in a heated state.

The on / off switching process of the glow relays 53, 531 will be described below with reference to the flowchart of FIG. FIG. 6 is executed by interruption processing for a predetermined time. First, when the processing in FIG.
U52 first determines whether or not the glow relays 53 and 531 are off after the engine warm-up is completed in step S11. Step 1 at the beginning of engine start
1 is negatively determined, and the ECU 52 reads the water temperature Tw and the engine speed Ne in the following 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 has been completed or that the heating by the glow plug 1 is not necessary.
Proceed to 6.

When the operation proceeds to step 15, the glow relays 53 and 531 are kept on. In this state, the ignition and combustion of the fuel are continued by the heating action of the glow plug 1. Also, if you proceed to step 16,
The ECU 52 turns off the glow relays 53 and 531. Then, the ion relay 530 is turned on to detect the ion current.

Next, FIG. 7A is a current waveform diagram when the ionic 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.

In the present embodiment, as described above, the tip 30 of the ion detecting electrode 3 and the tip 4
11 is 2 mm or more. Therefore, carbon (soot) generated by fuel combustion in the glow plug body
Even if is deposited, the ion current can be reliably detected.

However, carbon (soot) generated by fuel combustion is applied to the ion detecting electrode 3 of the glow plug.
In the state in which is adhered, that is, when smoldering occurs, FIG.
As shown in FIG. 7B, a phenomenon occurs in which the ion current is low before the fuel injection timing and increases thereafter (compare FIGS. 7A and 7B). It should be noted that Ith in FIG. 7B represents a peak value determination level (threshold value) for determining whether the glow relays 53 and 531 are on by determining the smoldering state. Therefore, when such a smoking phenomenon occurs, the glow relays 53 and 531 are used.
Is turned on, the heating element 2 is heated, and the above attached carbon is burned off.

FIG. 8 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 relays 53 and 531 are in the off state in step 21 of FIG. 7, it is determined in step 22 whether the abnormal ion current (FIG. 7B) as described above is detected at the fuel injection timing. If no, the process proceeds to step 25 and the glow relays 53, 53
1 remains off.

On the other hand, when an abnormal ion current is detected, the routine proceeds to step 23, where the ion relay 530 is turned off.
Next, in step 24, the glow relays 53 and 531 are turned on to heat the energizing heating element 2 of the glow plug to burn off carbon.

What is important here is, as shown in FIG. 2, the electric resistance R (Ω) of the entire heating element 2 and the distance from the plus end 210 of the heating element 2 to the tip 30 of the ion detecting electrode 3. Is the electrical resistance B (Ω) of B (Ω) ≧ R
(Ω) / 3. Therefore, even if carbon is deposited on the glow plug main body 10 and the state between the ion detection electrode 3 and the housing 4 is almost short-circuited, an appropriate current flows.

That is, when carbon is deposited on the glow plug main body 10 and the state becomes close to a short circuit, an appropriate current flows from the current-carrying heating element to the circuit of the path of the ion detection electrode and the attached carbon. it can. Therefore, carbon can be burned off by the heat generated by the current flowing through the circuit. Further, after the short-circuit state is eliminated, a current flows through the current-carrying heating element, and the burning of carbon is further promoted.

When the electric resistance B (Ω) is very large, the resistance of the circuit of the heating element, the electrode for ion detection, and the attached carbon becomes large. In this case, even if the attached carbon is present, a substantially normal current flows through the entire heating element, and the attached carbon can be burned off by the heat generated by the heating element.

As described above, in the glow plug of this embodiment, the heating element 2, the lead wires 21 and 22, and the ion detection electrode 3 are provided inside the insulator 11, and these are integrally formed. It is configured. 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. Also, the glow plug becomes compact.

Further, even when carbon adheres to the surface of the ion detecting electrode 3 and the glow plug, the carbon is burned off by heating the current-carrying heating element 2 as described above, and the ion detecting electrode 3 is further restored to normal. State. Therefore, the ion current can be detected with high accuracy.

The heating element 2, the lead wires 21,
2. Since the ion detection electrode 3 is provided inside the insulator 11, there is no corrosion such as oxidation due to combustion gas, and the durability is excellent. Further, since the tip of the insulator 11 has a hemispherical shape, it is possible to absorb a thermal shock in the combustion chamber.

Further, the tip portion 30 of the ion detecting electrode 3
Are exposed to come into contact with the combustion gas (Fig. 1). In addition, as shown in FIG.
1 may be disposed at the tip (downstream). In this case, ion currents in all directions in the combustion chamber can be detected with high accuracy.

Embodiment 2 In this embodiment, as shown in FIG. 10, the distance L between the tip 30 of the ion detecting electrode 3 and the tip 411 of the housing 4 for the glow plug body 10 shown in Embodiment 1 is shown. The following shows a specific example of a test for a correlation between the ion output and the detection rate. In manufacturing the glow plug main body 10, various integrally molded articles 29 in which the ion detection electrodes 3 are arranged at positions corresponding to the distance L are previously produced by injection molding (FIG. 4). Next, the integrally molded article 29 is embedded in the ceramic powder and hot-pressed, so that the insulator 1 is formed.
An insulator 11 having an electric heating element 2 and an ion detection electrode 3 built therein is manufactured. In this way, various glow plugs having different distances L are manufactured and prepared.

The detection rate of the ion output was defined as follows. That is, if the ion current is continuously sampled during the operation of the engine, the peak value H of the ion waveform shown in FIG. 7 is not constant, but varies due to combustion, a decrease in output due to carbon adhesion, and the like. Therefore, the average value h of the peak value H during operation for a fixed time and under a constant condition is obtained, and a case where the peak value is 0.3 times or more of the average value h is regarded as good detection accuracy. The occurrence rate of 0.3 times or more was defined as the ion output detection rate. The test was conducted on a 4-cylinder 2
Using a 2,000 cc diesel engine, the operation of depositing carbon on the glow plug body was first performed, and then
The state of ion detection was investigated.

The carbon deposition operation was carried out by operating the above engine at 800 rpm with no load for 2 minutes and then operating at 4000 rpm with no load for 2 minutes as one cycle, and performing 30 cycles of this. Further, the measurement of the ion detection state was performed by performing the above-described cycle for another 10 cycles and detecting the ion current during that cycle.

FIG. 10 shows the measurement results. In the figure, the horizontal axis represents the distance L (mm), and the vertical axis represents the ion output detection rate (%). As is known from the figure, when the distance L is 2 mm or more, the detection rate of the ion output becomes 100%. On the other hand, when the distance L is less than 2 mm, the detection rate becomes smaller as the L becomes smaller. Recognize.

Embodiment 3 In this embodiment, as shown in Table 1, with respect to the glow plug body 10 shown in Embodiment 1, the total electric resistance R (Ω) (FIG. 2) The relationship between the electrical resistance B (Ω) from the plus end 210 of the current-carrying heating element 2 to the tip 30 of the ion detection electrode 3 (FIG. 2) was changed and tested. The electric resistance B (Ω) was changed by changing the arrangement position of the ion detection electrode 3 in the integrally molded product of the current-carrying heating element 2 and the ion detection electrode 3 as in the second embodiment.

As shown in Table 1, eight kinds of glow plugs (all of which have a constant total electrical resistance R (Ω) and varied values of B (Ω) as shown in Table 1 were tested. Sample Nos. C1 to C3, E1 to E5) were prepared.
The manufacturing method, structure, and others of the glow plug are the same as those of the first embodiment.

In the durability test, a four-cylinder diesel engine was used. Then, when the engine is stopped, energization of the energizing heating element 2 is started, and after 2 minutes, the energization is stopped.
On the other hand, the engine is started 5 seconds after the start of the energization, immediately after starting, is operated at no load 800 rpm for 1 minute, then is operated at no load 4000 rpm for 2 minutes, then is operated at no load 800 rpm for 1 minute, and is stopped. The cycle from the start of energization to the energizing heating element 2 to the stop of the engine was defined as one cycle, and this cycle was performed for 500 cycles.

Table 1 shows the test results. As is known from Table 1, when B (Ω) <R (Ω) / 3 (C1 to C3)
In each case, the fuse was blown out early. In this case, a short circuit occurs between the tip 30 of the ion detection electrode 3 and the tip 411 of the housing 4, and a short circuit is formed between the tip and the positive lead wire. This indicates that a current large enough to blow the fuse has flowed since the power was supplied. On the other hand, B (Ω)
When ≧ R (Ω) / 3 (E1 to E5), no abnormality occurred during the 500 cycles of the test.

[0066]

[Table 1]

Fourth Embodiment As shown in FIG. 11, this embodiment is a modification of the glow plug operation circuit (FIG. 5) of the first embodiment.
Battery 54 and DC power supply 51 are connected to one battery 5
Only 5 is replaced. Further, another glow relay 53, 5311 is newly provided in a circuit between the external lead wire 333 of the glow plug and the battery 55. 2
The three glow relays 53, 531 and 531 are simultaneously operated, and are configured to be always on or both off. 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, the interposition of the constant current / constant voltage circuit 524 prevents fluctuations in the voltage applied to the ion detection electrode caused when the glow plug generates heat even with a single battery, thereby achieving stable detection performance. The effect that it can be maintained can be obtained.

[Brief description of the drawings]

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

FIG. 2 shows electric resistances R (Ω) and B in the first embodiment.
FIG.

FIG. 3 is an overall explanatory diagram of a glow plug according to the first embodiment.

FIG. 4 is an explanatory diagram of a method for manufacturing a glow plug body according to the first embodiment.

FIG. 5 is a glow plug operation circuit diagram according to the first embodiment.

FIG. 6 is a flowchart of the glow plug operation system according to the first embodiment when the glow plug is started.

FIGS. 7A and 7B are diagrams 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. 8 is a flowchart of smoldering determination in the first embodiment.

FIG. 9 is an explanatory view showing an example in which the position of an ion detection electrode is changed in the first embodiment.

FIG. 10 is an explanatory diagram illustrating a relationship between a distance L and a detection rate of an ion output in the second embodiment.

FIG. 11 is a glow plug operation circuit diagram according to a fourth embodiment.

[Explanation of symbols]

 1. . . Glow plug, 10. . . Body, 11. . . Insulator, 2. . . Current-carrying heating element, 21, 22,. . . Lead wire, 210. . . Plus end, 220. . . Minus end, 3. . . 3. electrode for ion detection, . . Housing, 45. . . Cylinder head, 451. . . Swirl chamber,

Claims (2)

[Claims] 1. A glow plug comprising a housing and a main body supported in the housing, wherein the main body comprises:
An insulator, a current-carrying heating element provided inside the insulator, and a pair of lead wires electrically connected to both ends of the current-carrying heating element and led out of the insulator; An ion detection electrode for detecting the state of ionization in the flame is provided inside, and the ion detection electrode is electrically connected to the middle of the current-carrying heating element. The tip is exposed from the insulator so as to be exposed to the flame, and the tip of the ion detection electrode is arranged at a position at least 2 mm away from the tip of the housing. And glow plug. 2. The method according to claim 1, wherein the electric resistance of the entire energizing heating element is R (Ω), and the electric resistance from a positive end of the energizing heating element to the tip of the ion detection electrode is B.
A glow plug characterized in that, when (Ω), B (Ω) ≧ R (Ω) / 3.