JPH11248156A - Glow device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a practical glow device having a combustion ion detecting function. SOLUTION: An end of the energizing heat generator 12 of a glow plug 1 is always conducted to one pole of a power source 3 by a first feeder 21. The other end of the energizing heat generator 12 is brought into a continuity with or interrupted from the other pole of the power source 3 by a second feeder 22 provided with a switch 4. A glow plug includes a first electrode 51 making a continuity with the energizing heat generator 12 integrally with the low plug 1, a second electrode 52 connected to the other pole of the power source 3 through a detecting wire 6 and a current detecting means 7 for detecting the current supplied to the detecting wire 6. Thus, the power source 3 and the glow plug 1 serve to operate a glow and detect ions, so that an ion current can be detected without turning on or off the switch 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a glow device for an internal combustion engine, and more particularly to a glow device having a function of detecting combustion ions generated during combustion.

[0002]

2. Description of the Related Art In a glow apparatus for an internal combustion engine, a glow plug containing a heater is provided on a chamber wall of a combustion chamber.

On the other hand, in a combustion control system for an internal combustion engine, various techniques for measuring a combustion state have been proposed.
Among them, utilizing the fact that combustion ions are generated at the time of combustion and the combustion flame shows conductivity according to the concentration of combustion ions, for example, a detection plug having a pair of electrodes is prepared. At the same time, the state of combustion is measured by applying a voltage between the electrodes provided on the chamber wall of the combustion chamber and detecting a current (ion current) flowing according to the concentration of the combustion ions.

[0004]

The above-mentioned combustion state measurement technique requires electrodes for detection and a circuit for applying a voltage to the electrodes. However, if these are separately provided in an internal combustion engine, the structure becomes complicated. Therefore, an increase in the number of manufacturing processes and costs is inevitable.

Accordingly, an object of the present invention is to provide a practical glow device in which a part of a glow plug and a circuit is also used as a structure for detecting a combustion state.

[0006]

According to the first aspect of the present invention, a glow plug in which an electric heating element is embedded in an insulator is provided on a wall of a combustion chamber of an internal combustion engine. A first power supply line constantly connects one end of the current-carrying heating element and one pole of the power supply, and a second power supply line provided with a switch conducts or connects the other end of the current-carrying heating element and the other pole of the power supply. Let me shut off. The first and second electrodes are provided integrally with the glow plug so as to be exposed to the atmosphere of the combustion chamber. The first electrode is electrically connected to the electric heating element or the first power supply line. The second electrode is connected to the other pole of the power supply via the detection line. A current detecting means for detecting a current flowing through the detection line is provided.

When the switch is turned on, one of the poles of the power supply
A current flows through a path for glow operation, that is, a first power supply line, a power supply heating element, a second power supply line, and the other pole of the power supply. The current flows through the power supply heating element, ignites an air-fuel mixture in the combustion chamber, and a combustion flame is generated. Occur.

The combustion flame exhibits conductivity due to the combustion ions, and is separate from the above-described path, from one pole of the power supply to the first power supply line (or the first power supply line to the current-carrying heating element) to the first and second power supply lines. A current flows through a path for detection operation, namely, the electrode, the detection line, and the other electrode of the power supply. At this time, the current flowing through the current line is only the ion current flowing according to the combustion ion concentration, and the current detecting means can detect a minute ion current with high detection accuracy. Even if the switch is turned off and the current stops flowing through the glow operation path, the ion current flows through the detection operation path. Thus, regardless of whether the glow operation is being performed, the combustion state can always be detected based on the ion current.

In addition, the power supply is used for both glow operation and detection operation. In addition, the glow plug and the electrode for detection operation are integrated, and there is no need to change the design of the combustion chamber and the like.
The glow device has an extremely practical ion current detecting function.

According to the second aspect of the present invention, the first electrode is embedded in the insulator at a position close to the current-carrying heating element, and a part of the first electrode is exposed from the surface of the insulator. It is arranged on the surface of the body at a position close to the energized heating element. As described above, by bringing both electrodes close to the current-carrying heating element, the effect of deposit on the conductance between both electrodes can be reduced due to the deposit burning-off action of the glow plug at the time of switch-on.

[0011] In the invention according to claim 3, the first electrode is
By adopting a configuration in which the first power supply line is drawn out of the connection portion with the current-carrying heating element, a voltage drop in a path from one pole of the power supply to the first electrode can be small, and both switches can be turned on even when the switch is turned on. The voltage applied between the electrodes is increased, and the detection sensitivity of the ion current can be increased to about the same level as when the switch is turned off.

According to a fourth aspect of the present invention, there is provided a judging means for judging the combustion state by comparing the current detected by the current detecting means with a preset combustion judgment reference value. The above-described combustion determination reference value is set when the switch is turned on and when the switch is turned off.

Thus, even when the voltage applied to both electrodes is different between when the switch is turned on and when the switch is turned off and the detected current is different, the same determination result can be obtained regarding the combustion state.

According to the fifth aspect of the present invention, by providing a high-pass filter for removing the DC component from the current detection signal in the current detection means, it is possible to prevent the zero point of the ion current from rising due to the deposit.

According to the sixth aspect of the present invention, by providing another power supply having a polarity opposite to that of the power supply in the middle of the detection line, the voltage applied between both electrodes is increased by the voltage of the other power supply, and the ion current is detected. Sensitivity can be further increased.

According to the present invention, the difference between the detected currents is determined in advance by the current detection means for detecting the current of the detection line and another current detection means for detecting the current of the first power supply line. A detection abnormality judging means for judging that the current is abnormal when the current value is larger than the reference value is provided.

When the switch is off, the current flows only through the detection path. If a leak current or noise is mixed in the path, a difference occurs in the current flowing between the first power supply line and the detection line, and the difference increases as the leak current or the like increases. Thus, by comparing the difference between the detection currents of the two current detection means with the abnormality determination reference value, the presence or absence of abnormality in the current detection is known.

[0018]

(First Embodiment) FIG. 1 shows a first embodiment of a glow apparatus according to the present invention. The glow device includes a glow plug 1 and its peripheral circuits 3, 4, and the like. The glow plug 1 has a chamber wall W of the combustion chamber B.
And a cylindrical housing 13 screwed to the chamber wall W and a rod-shaped heater 1a held coaxially and protruding toward the combustion chamber B side.

The heater 1a has a substantially U-shaped current-carrying heating element 12 embedded at the tip of an insulator 11, and the insulator 11 is made of an insulating ceramic such as Si ₃ N ₄ .
The heating element 12 is made of, for example, the insulating ceramic and M
A mixture with a conductive ceramic such as oO ₂ is used.

Leads 211 and 221 are connected to both ends 121 and 122 of the electric heating element 12, respectively. Lead ends of the leads 211 and 221 communicate with terminals 15 and 16 protruding from the upper end surface of the housing 13, respectively. . The lead 211 is made of a metal having a high melting point, such as tungsten, at least in a portion on the side of the heating element 12 where the temperature becomes high.

A first terminal 15 connected to one end 121 of the current-carrying heating element 12 is connected to a positive electrode of a DC power supply 3 such as a vehicle-mounted battery through a conductor 212. Lead 211,
A first power supply line 21 is formed by the conductor 212, and the conduction between the one end 121 of the electric heating element 12 and the positive electrode of the power supply 3 is always maintained. On the other hand, the second terminal 16 connected to the other end 122 of the current-carrying heating element 12 is connected to one contact 41 of the relay 4 which is a switch by a conducting wire 222. The negative electrode of the power supply 3 and the other contact 42 of the relay 4 are grounded. The second power supply line 22 is configured by the lead 221 and the conductive wire 222,
The other end 122 of the electric heating element 12 and the negative electrode of the power supply 3 are electrically connected or disconnected. The relay 4 is energized and turned on by the solenoid 43 from a control unit (not shown) for controlling the combustion of the internal combustion engine, thereby energizing the energizing heating element 12 from the power source 3 and heating the heater 1a to heat the air-fuel mixture in the combustion chamber B. Is set to ignite.

On the heating element 12, a projection 51 is formed in the middle of the curved portion so as to be exposed from the insulator 11.
Electrode 51. A second electrode 52 is provided on the outer peripheral surface of the heater 1a. The second electrode 52 is formed by forming a conductive material into a sleeve shape and fitted to the heater 1a, and covers the heater 1a except for the distal end. Second electrode 5
2 is insulated from the housing 13 grounded via the chamber wall W of the combustion chamber B by the insulating member 14 provided between the housing 13 and the heating element 12.

The second electrode 52 is connected to a third
And the third terminal 17 is connected to the ground by a conducting wire 62 provided with a detection resistor 71. The lead 61 and the conductor 62 constitute the detection line 6.

A voltage drop occurs in the detection resistor 71 in proportion to the current flowing through the detection line 6, and the voltage between both ends of the detection resistor 71 is input to the operational amplifier 72. The operational amplifier 72 outputs a detection voltage proportional to the current flowing through the detection line 6, and the detection resistor 71 and the operational amplifier 72 constitute the current detecting means 7.

A combustion state determination circuit 8 is provided as a combustion state determination means by using a detection voltage from the operational amplifier 72 as an input. The combustion state determination circuit 8 is configured by a comparator or the like having the detection voltage as one input and compares the detection voltage with a reference voltage having the detection voltage therein.
It is possible to determine whether or not a combustion determination reference value according to the reference voltage has been exceeded, or to measure the time when the value has been exceeded. The measurement result is output to the control unit and used for combustion control.

The operation of the glow apparatus will be described. The control unit turns on the relay 4 at a predetermined timing, energizes the energizing heating element 12 to cause the heater 1a to glow red, thereby igniting the air-fuel mixture in the combustion chamber B and generating a combustion flame.

The measurement of the combustion state will be described. FIG. 2 is a schematic equivalent circuit of the glow device when the relay 4 is turned on.
FIG. 3 is a schematic equivalent circuit when the relay 4 is off.

When the relay 4 is turned on, the positive electrode of the power supply 3 to the first power supply line 21 to the energizing heating element 12 to the first and second electrodes 51,
Current flows through a path for glow operation from 52 to the second power supply line 22 to the negative electrode of the power supply 3, and the first electrode 51 is substantially connected to the resistance value of the half of the one end 121 side of the heating element 12 and the other end. 12
It is a potential divided by the resistance value of the two half parts. In the illustrated example, the first electrode 51 is formed in the middle of the current-carrying heating element 12.
1 is about 6 V, and about 6 V is applied between both electrodes 51 and 52.
Is applied.

When the relay 4 is off, no current flows through the glow operation path. If the power supply 3 is 12 V, the potential of the first electrode 51 is about 12 V.
A voltage of about 12 V is applied between 1, 52. That is, regardless of whether the relay 4 is on or off, both electrodes 5
A voltage is applied between 1 and 52.

The combustion flame exhibits conductivity using the combustion ions as a carrier, and regardless of whether the relay 4 is on or off, the positive electrode of the power supply 3 to the first power supply line 21 to the one end 121 side half of the heating element 12. ~ First and second electrodes 51 and 52
A current flows through a detection operation path from the detection line 6 to the negative electrode of the power supply 3, and the operational amplifier 72 outputs a detection voltage proportional to the current.

The detected current does not include the glow current flowing through the heating element 12 when the relay 4 is turned on, but only the ion current flowing according to the concentration of the combustion ions. it can. Since the combustion ion concentration changes according to the size of combustion and the in-cylinder pressure, the combustion state determination circuit 8 determines the combustion state by using the output voltage of the operational amplifier 72 as an input.

FIG. 4 shows the change with time of the ion current from ignition (start of combustion) to end of combustion during normal combustion.
The solid line is when the relay 4 is off, and the broken line is when the relay 4 is on. After ignition, the ionic current increases with the expansion of the combustion, and decreases through a peak with the decay of the combustion scale and the decrease of the in-cylinder pressure. The reason why the current value is higher when the relay 4 is off is because the voltage applied between the electrodes 51 and 52 is different between when the relay 4 is on and when the relay 4 is off as described above.

The combustion state determination circuit 8 determines whether or not the detected current exceeds a predetermined combustion determination reference value, measures the profile of the chronological change of the ion current based on the timing of the detection, and determines whether or not there is combustion, ignition timing, and blowing. Judge the disappearance. For example, if there is combustion, a predetermined timing (crank angle)
In, binary output is performed according to the magnitude of the detected current and the combustion determination reference value.

As described above, according to the configuration of the present invention, the combustion state can always be measured based on the ion current regardless of whether the relay 4 is on or off (regardless of whether the glow operation is being performed).

The power supply may be an alternating current instead of a direct current. In this case, the ion current is extracted by removing the current component due to the capacitance between the electrodes 51 and 52 from the detected current.

The detection resistor 71 is used for detecting the ion current.
However, a magnetic field formed around the detection line 6 when a current flows through the detection line 6 may be detected.

(Second Embodiment) FIG. 5 shows a second embodiment of the present invention. In the figure, the portions denoted by the same reference numerals as those in FIG. 1 perform substantially the same operation, and therefore, the description will be focused on the differences from the first embodiment.

This embodiment is different from the first embodiment in that another power source 3a is provided between the connection point between the negative input terminal of the detection resistor 71 and the operational amplifier 72 and the ground. The other power supply 3 a is a DC power supply. The negative electrode is connected to the detection resistor 71, the positive electrode is grounded, and a voltage having a polarity opposite to that of the power supply 3 is applied to the second electrode 52.

With this arrangement, a voltage higher than that of the first embodiment by a voltage of another power source 3a is applied between the electrodes 51 and 52 both when the relay 4 is turned on and when the relay 4 is turned off. Is done. Therefore, a larger detection current can be obtained,
The S / N can be improved, and the ion current detection sensitivity can be increased.

(Third Embodiment) FIG. 6 shows a third embodiment of the present invention. In the figure, the portions denoted by the same reference numerals as those in FIG. 1 perform substantially the same operation, and therefore, the description will be focused on the differences from the first embodiment.

In the present embodiment, in the configuration of the first embodiment, another detection resistor 71a is provided in the middle of the first power supply line 21. Another detection resistor 71a has a resistance value of the detection resistor 7
Same as 1. An operational amplifier 72a is provided with a voltage between both ends of another detection resistor 71a as an input, and detects an electric current flowing through another detection resistor 71a. Another detection resistor 71a and the operational amplifier 72a constitute another current detection means 7a.

An operational amplifier 91 is provided which receives the output voltage of the operational amplifier 72a and the output voltage of the operational amplifier 72 as inputs, and outputs a voltage signal proportional to the difference voltage between the outputs of the operational amplifiers 72 and 72a. I have.

This output voltage is input to an abnormality judging circuit 92 constituting the detection abnormality judging means 9 together with the operational amplifier 91. The abnormality determination circuit 92 is composed of a comparator or the like that uses the output voltage of the operational amplifier 91 as one input, and performs a binary determination by comparing the output voltage with a predetermined reference voltage when the relay 4 is off. The reference voltage is the two detection resistors 71,
This corresponds to an abnormality determination reference value for determining whether or not the difference between the detected currents at 71a is larger than a value that can be regarded as abnormal.

When the relay 4 is turned off, the positive electrode of the power supply 3 to another detection resistor 71a to the first power supply line 21 to the power supply heating element 12
A current flows through a path from the half on one end 121 side to the first and second electrodes 51 and 52, the detection resistor 71, and the negative electrode of the power supply 3, and ideally the current value is the same in each part of the path. Therefore, the voltage between both ends of both detection resistors 71 and 71a having the same resistance value is equal. Therefore, the operational amplifiers 72 and 72a output the same voltage, the signal input from the operational amplifier 91 to the abnormality determination circuit 92 is 0, and the difference between the detection currents of the two detection resistors 71 and 71a is smaller than the abnormality determination reference value.

On the other hand, if a current leaks or noise is mixed in the current path, a difference occurs between the output voltages of the operational amplifiers 72 and 72a. When the difference between the detection currents of the two detection resistors 71 and 71a exceeds the abnormality determination reference value, the abnormality determination circuit 92 determines that the ion current may be erroneously detected due to a current leak or the like, and issues an alarm to the control unit. Emits a signal. Accordingly, the control unit stops the combustion control based on the detection of the ion current, thereby preventing the appropriate combustion control from being performed.

The features of this embodiment can be applied not only to the configuration of the first embodiment but also to the configuration of the second embodiment.

In each of the above embodiments, the applied voltage between the two electrodes is different between when the relay is turned on and when the relay is turned off, as described above. The detected current at the time is smaller than the detected current when the relay 4 is off (see FIG. 4).

Therefore, the combustion state determination circuit 8 is configured so that a relay state signal for informing whether the relay 4 is on or off is input from the control unit to the combustion state determination circuit 8.
The combustion state may be detected according to the state of the relay 4.

FIG. 7 shows an example of the determination of the combustion state corresponding to the state of the relay 4. In step S101, the on / off state of the relay 4 is determined from the relay state signal input from the control unit. If the relay 4 is off, the process proceeds to step S102, where the detected current is compared with a combustion determination reference value 1 for turning off the relay 4, and if the relay 4 is on, the process proceeds to step S103, and the detected current is compared with the combustion determination value for turning on the relay 4. Compare with the criterion value 2. In both Steps S102 and S103, if the detected current is smaller than the combustion determination reference value, it is determined that combustion is not occurring (Step S1O4), and if the detected current is larger than the combustion determination reference value, it is determined that combustion is in progress (Step S1O4). S1O5).

The switching of the combustion determination reference value is performed by a logic circuit or the like. Alternatively, the combustion state determination circuit 8 may be constituted by a microcomputer, and the switching of the combustion determination reference value and the determination of the combustion state shown in FIG. 7 may be executed on software.

The reference values for both combustion determinations are set as follows. When the relay 4 is on, a current flows through the heating element 12, and the applied voltage between the electrodes 51 and 52 is divided by the resistance value of one half of the heating element 12 and the resistance value of the other half of the other end. Since the voltage is reduced, a value obtained by multiplying the reduction ratio by the combustion determination reference value 1 for turning off the relay 4 is set to be the combustion determination reference value 2 for turning on the relay 4.

Instead of switching the combustion determination reference value as described above, the output difference of the operational amplifier 72 when the relay 4 is turned on and when the relay 4 is turned off may be reduced. For example, the first electrode 51 is formed closer to one end 121 side than the middle position of the current-carrying heating element 12 to increase the voltage between both electrodes when the relay 4 is turned on, and to increase the voltage between both electrodes when the relay 4 is turned off. Can be reduced. Alternatively, the first electrode 51 is connected to the lead 21
It may be withdrawn from the middle of 1.

Further, as shown in FIG.
The first electrode 51 a may be extended from the connection portion with the energized power generator 12, and the tip 511 may be exposed from the hemispherical top surface of the insulator 11. In this case, the manufacturing is facilitated by integrating the lead 211 and the first electrode 51a, and the two electrodes 51 are turned on and off when the relay 4 is turned on and off.
The voltage between a and 52 can be substantially the same.

However, when the ignition timing is measured by detecting the timing at which the ion current reaches a predetermined ignition determination reference value, as shown in FIG. It is better to use As shown in FIG.
This is because the ignition current gradually rises at the time of ignition, and if there is a difference in the detected currents, the ignition determination time will be greatly different.

Alternatively, instead of a single operational amplifier 72, two operational amplifiers having different amplification factors are used, and the operational amplifier to which the detection voltage from the detection resistor 71 is input is switched between when the relay 4 is turned on and when the relay 4 is turned off. Then, the amplification factor of the operational amplifier for turning off the relay 4 is set to the amplification factor obtained by multiplying the amplification factor of the operational amplifier for turning on the relay 4 by the above-mentioned reduction ratio. If the combustion ion concentrations are equal, both operational amplifiers have the same size. An output voltage may be obtained.

In each of the above embodiments, the high-pass filter 73 is provided after the operational amplifier 72 as shown in FIG.
May be provided. According to FIG.
When the relay 4 is turned on (when the glow plug is activated), even if the deposit adheres to the surface of the heater 1a, the deposit is burned off by the heating of the heater 1a, and the ion current is accurately detected (FIG. 11). (A)). However, if the deposit adheres to the surface of the heater 1a when the relay 4 is turned off, parasitic conductance due to the deposit occurs between the two electrodes 51 and 52 (or 51a and 52), thereby increasing the ion current detection error (FIG. 11 ( b)) There is a possibility.

By providing the high-pass filter 73, even if the above-mentioned parasitic conductance occurs, the DC component is removed from the detection current, and the effect of the deposit can be reduced (FIG. 11C).

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a first glow device of the present invention.

FIG. 2 is a schematic equivalent circuit diagram of a main part of a first glow device of the present invention.

FIG. 3 is another schematic equivalent circuit diagram of a main part of the first glow device of the present invention.

FIG. 4 is a graph illustrating the operation of the first glow device of the present invention.

FIG. 5 is a configuration diagram of a second glow device of the present invention.

FIG. 6 is a configuration diagram of a third glow device of the present invention.

FIG. 7 is a flowchart illustrating a fourth glow apparatus of the present invention.

FIG. 8 is a sectional view of a glow plug of a fifth glow device of the present invention.

FIG. 9 is a graph illustrating a sixth glow device of the present invention.

FIG. 10 is a main part circuit diagram of a seventh glow device of the present invention.

FIG. 11 (a). (B), (c) is a flowchart explaining the operation of the seventh glow device of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Glow plug 1a Heater 11 Insulator 12 Electric heating element 121 One end 122 Other end 21, 22 Power supply line 3 Power supply 3a Another power supply 4 Relay (switch) 51, 52, 51a Electrode 6 Detection line 7 Current detection means 71 Detection resistance 72 Operational amplifier 73 High pass filter 7a Separate current detection means 8 Combustion state determination circuit (combustion state determination means) 9 Detection abnormality determination means 91 Operational amplifier 92 Abnormality determination circuit B Combustion chamber W Room wall

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Michihiro Wakimoto, 14 Iwatani, Shimowakaku-cho, Nishio-shi, Aichi Prefecture Inside Japan Automotive Parts Research Institute (72) Inventor Atsushi Kurano 1-1-1, Showa-cho, Kariya-shi, Aichi Share Inside the company DENSO

Claims (7)

[Claims] A glow plug in which an electric heating element is embedded in an insulator is provided on a chamber wall of a combustion chamber of an internal combustion engine, and a voltage is applied from a power supply to the electric heating element through first and second power supply lines. In the glow apparatus which ignites the air-fuel mixture in the combustion chamber, one end of the energizing heating element and one pole of the power supply are always brought into conduction by the first power supply line.
A pair of electrodes provided integrally with the glow plug exposed to the atmosphere of the combustion chamber by providing a switch in the power supply line to conduct or cut off the other end of the heating element and the other electrode of the power supply. A second electrode connected to the other electrode of the power supply via a first electrode and a detection line, which are electrically connected to the current-carrying heating element or the first power supply line, and a current detection means for detecting a current flowing through the detection line A glow device comprising: 2. The glow apparatus according to claim 1, wherein the first electrode is embedded in the insulator at a position adjacent to the current-carrying heating element, and a part of the first electrode is exposed from the surface of the insulator. A glow device in which an electrode is arranged on a surface of an insulator at a position close to the electric heating element. 3. The glow device according to claim 1, wherein the first electrode is configured such that the first power supply line is led out from a connection portion with the current-carrying heating element. 4. The glow device according to claim 1, further comprising: a combustion state determination unit that determines a combustion state by comparing a current detected by the current detection unit with a preset combustion determination reference value. A glow device in which the combustion determination reference value is set when the switch is turned on and when the switch is turned off. 5. The glow device according to claim 1, wherein the current detection means includes a high-pass filter for removing a DC component from a current detection signal. 6. The glow apparatus according to claim 1, wherein another power supply having a polarity opposite to that of the power supply is provided in the middle of the detection line. 7. The glow device according to claim 1, wherein another current detecting means for detecting a current flowing through the first power supply line and a difference between the currents detected by the two current detecting means are determined in advance. A glow device comprising: a detection abnormality determining means for determining an abnormal current detection when the value is larger than a set abnormality determination reference value.