JP2000321229A - Coking sensor for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the subject coking sensor capable of accurately detecting the coking quantity on the inner surface of a pipe even during the operation of an internal combustion engine. SOLUTION: A coking sensor 10 for an internal combustion engine for detecting the coking quantity on the inner surface of the exhaust pipe 2 used in the inernal combustion engine 1 is equipped with a plurality of electrodes 13, 13 provided in the exhaust pipe 2 in mutually opposed relationship and coated with an insulating material, and a sensor circuit for detecting coking quantity on the basis of the parameter showing a change of at least one of the resistance value Rs and electrostatic capacity Cs between a plurality of the electrodes 13, 13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coking sensor for an internal combustion engine for detecting a coking amount (amount of soot accumulation) on an inner surface of a pipe used in the internal combustion engine.

[0002]

2. Description of the Related Art In an internal combustion engine, when fuel is burned, soot contained in exhaust gas adheres to an inner surface of an exhaust pipe or the like. This soot is burned by the heat of the exhaust gas when the exhaust gas is at a predetermined temperature or higher, but when the temperature of the exhaust gas is low, for example, immediately after a cold start of the internal combustion engine, the soot does not burn and the exhaust gas Adheres and deposits on the inner surface of the tube.
When the internal combustion engine is repeatedly started in such a state, soot adheres and accumulates on the three-way catalyst provided in the exhaust pipe, and the performance of the three-way catalyst is reduced, or the exhaust resistance in the exhaust pipe and the three-way catalyst increases. Or become. In addition, if the exhaust pipe is provided with a hydrocarbon adsorber for adsorbing unburned component hydrocarbons contained in the exhaust gas, the soot will clog the pores of the adsorbent zeolite, deteriorating it. May be caused. For this reason, in order to burn the deposited and deposited soot, the internal combustion engine is controlled so that the temperature of the hydrocarbon adsorbing device is increased, or the degree of deterioration of the zeolite of the hydrocarbon adsorbing device is indirectly determined. It is necessary to detect the amount of coking on the inner surface of the exhaust pipe in order to notify the driver of the status of soot accumulation in the exhaust pipe.

As a method of detecting the coking amount in the exhaust pipe, for example, while the internal combustion engine is stopped,
2. Description of the Related Art A method is known in which an exhaust pipe is removed from an internal combustion engine and the weight of the exhaust pipe is directly measured to detect a coking amount from a weight difference from before use.

[0004]

In the above-described method for detecting the amount of coking, it is possible to accurately detect the amount of coking, but at the time of detection, the exhaust pipe is removed from the internal combustion engine as described above. It is not only time-consuming, but also impossible to detect the coking amount during operation of the internal combustion engine.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and is intended for an internal combustion engine capable of accurately detecting the amount of coking on the inner surface of a pipe even during the operation of the internal combustion engine. It is an object of the present invention to provide a caulking sensor.

[0006]

In order to achieve this object, the invention according to claim 1 of the present application is directed to a pipe (exhaust gas) used in an internal combustion engine (an internal combustion engine 1 in the embodiment (hereinafter, the same applies in this section)). A coking sensor 10 for an internal combustion engine for detecting a coking amount on an inner surface of a pipe 2), which is provided in a pipe (exhaust pipe 2) so as to face each other and whose surface is coated with an insulating material. Multiple electrodes 1
3, 13 and a resistance value R between the plurality of electrodes 13, 13
a caulking detecting means (sensor circuit 15) for detecting a coking amount based on a parameter representing at least one change of the capacitance s and the capacitance Cs.

According to this caulking sensor, soot adheres and deposits on the electrodes provided in the tube so as to face each other and the surface of which is coated with an insulating material. Since the resistance value and the capacitance between the electrodes change, it is possible to detect the coking amount in the tube by using a parameter representing at least one of the change in the resistance value and the capacitance between the electrodes. In other words, soot adheres and accumulates on both the inner surface of the tube and the electrode with almost the same tendency. Therefore, the amount of coking on the inner surface of the tube is accurately detected by detecting the amount of coking of the electrode by the coking detecting means based on the above parameters. Can be detected. Further, unlike the conventional detection method of directly measuring the weight of the pipe, the amount of coking in the pipe can be detected easily and during operation of the internal combustion engine without removing the pipe from the internal combustion engine or the like. In addition, since the surface of each electrode is covered with an insulating material, short-circuiting between the electrodes due to soot attached and deposited between the electrodes does not occur.

According to a second aspect of the present invention, in the caulking sensor 10 of the first aspect, the parameter is a plurality of electrodes 1.
The voltage Vs is generated between the plurality of electrodes 13 when a predetermined DC voltage is applied between the electrodes 3 and 13.

According to this caulking sensor, the voltage generated between the electrodes when the predetermined DC voltage is applied between the electrodes reflects the change in the resistance value between the electrodes in a favorable manner. Therefore, the coking amount on the inner surface of the tube can be detected satisfactorily by using the voltage generated between the electrodes by the application as a parameter.

According to a third aspect of the present invention, in the caulking sensor of the first aspect, a signal having an oscillation frequency fosc corresponding to at least one of a resistance value Rs and a capacitance Cs between the plurality of electrodes 13 is output. An oscillator 19 is further provided, wherein the parameter is an oscillation frequency fos of the oscillator 19.
c.

According to this caulking sensor, the signal of the oscillation frequency output from the oscillator in accordance with at least one of the resistance value between the electrodes and the capacitance is a change in at least one of the resistance value between the electrodes and the capacitance. Reflect well. That is, the oscillation frequency corresponding to the resistance value between the electrodes and the capacitance respectively appropriately reflects the change in the resistance value between the electrodes and the capacitance. Therefore, by using the oscillation frequency as a parameter, the amount of coking on the inner surface of the tube can be detected satisfactorily.

According to a fourth aspect of the present invention, in the caulking sensor 10 of the first aspect, the parameter is a plurality of electrodes 1.
It is characterized by being at least one of a convergence voltage Vsat and a convergence time Trise when the voltage Vs generated between the plurality of electrodes 13 and 13 converges when a pulsed voltage Vin is applied between the electrodes 3 and 13.

In this specification, the convergence voltage is
When a voltage generated between the electrodes converges to a constant value when a pulsed voltage is applied between the electrodes, the voltage of that value means the voltage of the value.On the other hand, the convergence time is a voltage generated between the electrodes by the application. , A rise time until a predetermined ratio with respect to the convergence voltage is reached.

According to this caulking sensor, when a pulse-like voltage (hereinafter, referred to as “pulse voltage” in the present specification) is applied between the electrodes, the voltage generated between the electrodes is:
The convergence converges to a predetermined value, and the convergence voltage and convergence time at which the convergence reflects the change in the resistance value and the capacitance between the electrodes well. Therefore, by using at least one of the convergence voltage and the convergence time as a parameter, the coking amount on the inner surface of the tube can be detected satisfactorily.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows a schematic configuration of a state in which a caulking sensor for an internal combustion engine according to an embodiment of the present invention is incorporated in an exhaust pipe. As shown in the figure, an exhaust pipe 2 for discharging exhaust gas to the outside is connected to the internal combustion engine 1 via an exhaust manifold (not shown). A three-way catalyst 3 is provided in the middle of the exhaust pipe 2, and a hydrocarbon adsorbing device for adsorbing hydrocarbons, which are unburned components in the exhaust gas, downstream of the three-way catalyst 3. 4 are provided. Also, the exhaust pipe 2
On the upstream side of the hydrocarbon adsorbing device 4,
Is provided with a caulking sensor 10 for detecting the amount of caulking on the inner surface of the coke. The caulking sensor 10 and the internal combustion engine 1 are electrically connected to the ECU 11,
The ECU 11 notifies the driver of the detection result of the caulking sensor 10 and controls the internal combustion engine 1.

The three-way catalyst 3 itself is heated by the heat of the exhaust gas, and is activated at a predetermined temperature (for example, 300 ° C.) or higher, so that harmful substances (hydrocarbons) in the exhaust gas discharged from the internal combustion engine 1 are obtained. , Carbon monoxide and nitrogen compounds) by oxidation and reduction. However, the three-way catalyst 3 is not activated for about 30 to 40 seconds after the cold start of the internal combustion engine 1. Therefore, in order to prevent hydrocarbons, which are unburned components, of the harmful substances from being discharged to the outside, the hydrocarbons that have passed through the three-way catalyst 3 are adsorbed by the hydrocarbon adsorbing device 4.

The hydrocarbon adsorbing device 4 has a zeolite 12 as a hydrocarbon adsorbent provided along the outflow direction of the exhaust gas. The zeolite 12 has a large number of pores (not shown) on the surface, and adsorbs hydrocarbons by allowing hydrocarbon molecules to enter these pores. Note that, when the zeolite 12 is heated to a predetermined temperature or higher (for example, 100 to 250 ° C.) by the exhaust gas, the hydrocarbon once adsorbed is desorbed.

As shown in FIG. 2, the caulking sensor 10
Are arranged at a predetermined interval so as to face each other.
It includes a pair of electrodes 13, an electrode support 14 for supporting these electrodes 13, 13, and a sensor circuit 15 (caulking detecting means, see FIG. 4) built in the electrode support 14. Each electrode 13 is made of, for example, a copper alloy plate or the like having conductivity and heat resistance, and its surface is covered with an insulating material (not shown).

Further, the pair of electrodes 13, 13 is
As shown in FIG. In this case, the opposing portions of the electrodes 13 are formed in a comb-tooth shape, and are engaged with each other and at a predetermined interval.
It is arranged on a substrate (not shown) made of an insulating material having heat resistance. In the case where such comb-shaped electrodes 13 are formed, a rectangular metal plate is fixed on the substrate, a gap 13a shown in FIG. 3 is formed by etching, and then the surface of the metal plate is formed. May be coated with an insulating material. By such a manufacturing method,
The comb-shaped electrodes 13, 13 can be produced very easily.

The electrode support 14 is entirely made of a material having heat resistance, and as shown in FIG.
, A cylindrical supporting portion 14b protruding from the upper surface of the main body portion 14a and fixing and supporting the electrodes 13, 13 at lower ends thereof, and projecting from a lower surface of the main body portion 14a. The terminal of the sensor circuit 15 is connected to the ECU 11
And a columnar connecting portion 14c having a connecting port (not shown) for electrically connecting the connecting portion 14c. The two electrodes 13, 13 supported by the support portion 14b are connected to the support portion 14b.
As shown in FIG. 4, it is electrically connected to the sensor circuit 15 in the main body portion 14a by two connection wires 16 and 16 passed through the inside of the body portion 14b.

The sensor circuit 15 has a pair of input terminals 17, 17 and output terminals 18, 18, respectively.
Each input terminal 17 and output terminal 18 are connected to the ECU 11
Is electrically connected to The sensor circuit 15 outputs an electric signal of a parameter described later indicating a change in at least one of the resistance value and the capacitance between the electrodes 13 by applying a predetermined voltage described later to the input terminals 17, 17. Output is made from the output terminal 18.

The caulking sensor 1 configured as described above
Numeral 0 is attached to the exhaust pipe 2 so that the electrodes 13 and 13 and the support portion 14b are inserted into the exhaust pipe 2.

FIG. 5A shows an equivalent circuit of the caulking sensor 10. When a predetermined voltage is applied to the input terminals 17, 17 shown in the figure, the resistance value Rs and the capacitance Cs between the electrodes 13, 13 vary according to the amount of caulk deposited and deposited on the surface of the electrode 13. It changes as shown in FIG. That is, the resistance value Rs gradually decreases as the coking amount of the electrode 13 increases, and the resistance value Rs falls within the predetermined range Mr.
Within the predetermined range Mr, and gradually falls again when the predetermined range Mr is exceeded. On the other hand, the capacitance Cs
Gradually increases as the amount of coking increases, greatly increases within a predetermined range Mc, and gradually increases again beyond the predetermined range Mc.

It should be noted that the caulking sensor 10 is
The resistance value Rs and the capacitance Cs between 3 and 13 are configured to be much larger than the resistance value Rh of the harness in the sensor circuit 15 and the parasitic capacitance Cp due to the harness. Therefore, the resistance value Rs between the electrodes 13
The capacitance Cs changes according to the coking amount of the electrodes 13 without being affected by the resistance value Rh and the parasitic capacitance Cp.

According to the caulking sensor 10 configured as described above, the electrodes 13 and 13 are provided in the exhaust pipe 2 so as to face each other and the surfaces of which are covered with an insulating material.
Then, when the soot is deposited and deposited, the resistance value Rs and the capacitance Cs between the electrodes 13 and 13 are changed according to the amount of the deposited and deposited soot. This makes it possible to detect the coking amount in the exhaust pipe 2 by using a parameter representing at least one of the change in the resistance value Rs and the capacitance Cs between the electrodes 13 and 13. That is, the soot adheres and accumulates on the inner surface of the exhaust pipe 2 and on both of the electrodes 13 and 13 with almost the same tendency. Therefore, the coking amount of the electrodes 13 and 13 is determined based on the above-described parameters.
Thus, the amount of coking in the exhaust pipe 2 can be accurately detected. When the caulking sensor 10 is provided at a position close to the hydrocarbon adsorbing device 4 as in the embodiment, it is possible to indirectly determine the deterioration of the zeolite 12 of the hydrocarbon adsorbing device 4. .

Further, unlike the conventional detection method in which the weight of the exhaust pipe 2 is directly measured, the amount of coking in the exhaust pipe 2 can be easily determined during the operation of the internal combustion engine 1 without removing the exhaust pipe 2 from the internal combustion engine 1. Can be detected. Furthermore, since the surface of each electrode 13 is covered with an insulating material, short-circuiting between the electrodes 13 and 13 due to soot attached and deposited between the electrodes 13 and 13 can be reliably prevented.

As shown in FIG. 5B, the predetermined ranges Mr and Mc of the coking amounts of the resistance Rs and the capacitance Cs between the electrodes 13 and 13 which greatly change according to the coking amount are as follows. However, they do not coincide with each other, but partially overlap. Therefore, electrode 1
By detecting the coking amount using both the resistance value Rs and the capacitance value Cs between the resistance values 3 and 13, the resistance value Rs
The coking amount can be accurately detected over a wide range as compared with the case where only one of s and the capacitance Cs is used for detection.

Next, referring to FIG. 6 to FIG.
A description will be given of a case where the change in the resistance value Rs and the capacitance Cs between 13 are detected by various parameters.
In the following description, the case where the voltage between the electrodes, the oscillation frequency of the oscillator, and the convergence voltage and the convergence time between the electrodes are used as parameters will be sequentially described.

[0029] When the voltage between the electrodes was set Parameters Figure 6 (a) shows an equivalent circuit diagram of a coking sensor 10 when applying a predetermined DC voltage between the electrodes 13 and 13 schematically. In this case, the electrodes 13 and 13 function as resistors, and the resistor Ri is a resistor in the sensor circuit 15 connected in series to the electrodes 13 and 13. In such a circuit, the electrodes 13, 13 are connected via the input terminals 17, 17.
When a predetermined DC voltage is applied to the
The voltage Vs generated between the electrodes 3 and 13 decreases as the amount of coking deposited and deposited on the surfaces of the electrodes 13 and 13 increases. Specifically, as shown in FIG. 6B, the voltage Vs gradually decreases as the coking amount of the electrodes 13 and 13 increases, greatly decreases within a predetermined range Mr, and further decreases the predetermined range Mr. When it exceeds, it gradually decreases again.

That is, the predetermined DC voltage is applied to the electrode 13,
The change in the voltage Vs generated between the electrodes 13 and 13 by applying the voltage between the electrodes 13 substantially matches the change in the resistance Rs between the electrodes 13 and 13 and reflects the resistance Rs well.
Therefore, by using the voltage Vs generated between the electrodes 13 and 13 by the application as a parameter, the coking amount on the inner surface of the exhaust pipe 2 can be detected satisfactorily.

The oscillation frequency of the oscillator is defined as a parameter.
If the view. 7 (a) shows an equivalent circuit diagram of a coking sensor 10 when incorporating the oscillator 19 to the sensor circuit 15 is schematically shown. The oscillator 19 outputs a signal having an oscillation frequency fosc corresponding to the capacitance Cs between the electrodes 13 and 13 to the output terminal 1.
8 and 18. In such a circuit, the oscillation frequency fosc by the oscillator 19
Increases as the amount of caulk deposited and deposited on the surfaces of the electrodes 13 and 13 increases. More specifically, as shown in FIG. 7B, the oscillation frequency fosc
13 gradually increases as the amount of coking increases,
It greatly increases within a predetermined range Mc, and further increases within the predetermined range M
When it exceeds c, it gradually increases again.

That is, the change in the oscillation frequency fosc output by the oscillator 19 substantially matches the change in the capacitance Cs between the electrodes 13 and 13 and reflects the capacitance Cs well. Therefore, by using the oscillation frequency fosc as a parameter, the coking amount on the inner surface of the exhaust pipe 2 can be detected satisfactorily.

The oscillator 19 has electrodes 13, 13
It is not limited to the one that outputs a signal of the oscillation frequency according to the capacitance Cs between the electrodes 13, 13, instead of or together with this signal.
May be configured to output a signal having an oscillation frequency corresponding to In this case, the change of the oscillation frequency is
13 substantially matches the change in the resistance Rs between
s is favorably reflected. As a result, the amount of coking on the inner surface of the exhaust pipe 2 can be detected even better. Note that the oscillator is connected to the outside of the sensor circuit 15, for example, the ECU 1
1 may be provided.

The convergence voltage and convergence time between the electrodes are set as parameters.
Figure 8 case of a meter (a) is an equivalent circuit diagram of a coking sensor 10 when applying a predetermined rectangular pulse voltage Vin between the electrodes 13 and 13 schematically. In such a circuit,
When the predetermined pulse voltage Vin is applied between the electrodes 13 and 13 via the input terminals 17 and 17, the voltage between the electrodes 13 and 13 is changed according to the amount of coking deposited and deposited on the surfaces of the electrodes 13 and 13. As a result, a voltage Vs converging to a predetermined value is generated. The convergence voltage Vsat of this voltage Vs decreases as the coking amount of the electrodes 13 increases. Specifically, as shown in FIG. 9, the convergence voltage Vsat gradually decreases as the coking amount of the electrodes 13 and 13 increases, greatly decreases within a predetermined range Mr, and further exceeds the predetermined range Mr. It gradually drops again. On the other hand, the convergence time Trise increases as the coking amount of the electrodes 13 increases. Specifically, the convergence time Trise is, as shown in FIG.
Gradually increases as the amount of coking increases, greatly increases within a predetermined range Mc, and gradually increases again beyond the predetermined range Mc.

That is, the predetermined pulse voltage is applied to the electrode 1
The change in the convergence voltage Vsat and the convergence time Trise when the voltage Vs generated between the electrodes 13 and 13 converges when applied to the electrodes 3 and 13 is determined by the resistance value Rs between the electrodes 13 and 13.
And the change of the capacitance Cs substantially coincides with each other, and the resistance Rs and the capacitance Cs are well reflected.
Therefore, the convergence voltage Vsat and the convergence time Tr
By using at least one of the parameters as a parameter, the coking amount on the inner surface of the exhaust pipe 2 can be detected satisfactorily.

The present invention is not limited to the above-described embodiment, but can be implemented in various modes. For example, three or more electrodes of the caulking sensor may be configured. In this case, the coking amount of the electrode is
Detection can be performed more accurately, and as a result, the amount of coking on the inner surface of the exhaust pipe can be detected more accurately.
Further, in the embodiment, the case where the caulking sensor is provided in the exhaust pipe has been described. However, the present invention is not limited to this, and it is naturally possible to provide the caulking sensor in a pipe such as an EGR pipe to which soot may adhere. Also in this case, the amount of coking adhered and deposited on the inner surface of the pipe can be accurately detected. Further, the detailed configuration of the caulking sensor shown in the embodiment is merely an example, and can be appropriately changed within the scope of the present invention.

[0037]

As described above in detail, the caulking sensor for an internal combustion engine according to the present invention has an effect that the coking amount on the inner surface of the pipe can be accurately detected even during the operation of the internal combustion engine. Having.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a schematic configuration of a state in which a caulking sensor according to an embodiment of the present invention is incorporated in an exhaust pipe.

FIGS. 2A and 2B are diagrams showing a caulking sensor, FIG. 2A is a perspective view showing an appearance of the sensor, and FIG. 2B is a perspective view showing an appearance of an electrode.

FIG. 3 is a perspective view showing the appearance of a comb-shaped electrode having a different shape from the electrode of FIG. 2;

FIG. 4 is a block diagram showing a caulking sensor.

5 (a) is an equivalent circuit diagram of a caulking sensor, and FIG. 5 (b) is a graph showing the relationship between the amount of coking deposited in an exhaust pipe and the resistance and capacitance between electrodes.

FIG. 6 is a diagram illustrating a case where a predetermined DC voltage is applied between electrodes and a voltage generated between the electrodes is used as a parameter;
(A) is a schematic equivalent circuit diagram of a caulking sensor,
(B) is a graph showing the relationship between the amount of coking deposited in the exhaust pipe and the voltage generated between the electrodes.

FIGS. 7A and 7B are diagrams illustrating a case where an oscillator frequency signal is output by an oscillator and the oscillation frequency is used as a parameter; FIG. 7A is a schematic equivalent circuit diagram of a caulking sensor;
(B) is a graph showing the relationship between the amount of coking deposited in the exhaust pipe and the oscillation frequency.

8A and 8B are diagrams illustrating a case where a pulse voltage is applied between electrodes and a convergence voltage and a convergence time when a voltage generated between the electrodes converges are used as parameters; FIG. 8A is a schematic diagram of a caulking sensor; FIG. 4B is an equivalent circuit diagram, and FIG. 4B is a waveform diagram showing a relationship between a pulse voltage and a corresponding convergence voltage and convergence time.

FIG. 9 is a graph showing a relationship between a coking deposition amount in an exhaust pipe and a convergence voltage and a convergence time when a pulse voltage is applied between electrodes.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Exhaust pipe 10 Caulking sensor 13 Electrode 15 Sensor circuit (caulking detecting means) 19 Oscillator

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Yuji Yasui 1-4-1 Chuo, Wako-shi, Saitama F-term in Honda R & D Co., Ltd. 2F063 AA16 BA30 BD17 DA02 DA05 FA10 HA03 HA14 LA04 2G060 AA03 AE20 AE40 AF07 AF10 AG08 AG10 AG11 HA01 HA03 HC13 3G090 EA01

Claims (4)

[Claims] 1. A coking sensor for an internal combustion engine for detecting a coking amount on an inner surface of a pipe used in an internal combustion engine, wherein the coking sensor is provided in the pipe so as to face each other, and a surface is coated with an insulating material. And a caulking detecting means for detecting the coking amount by a parameter representing at least one of a change in a resistance value and a capacitance between the plurality of electrodes. Caulking sensor for engines. 2. The internal combustion engine according to claim 1, wherein the parameter is a voltage generated between the plurality of electrodes when a predetermined DC voltage is applied between the plurality of electrodes. Caulking sensor. 3. An oscillator for outputting a signal having an oscillation frequency according to at least one of a resistance value and a capacitance between the plurality of electrodes, wherein the parameter is the oscillation frequency of the oscillator. The caulking sensor for an internal combustion engine according to claim 1. 4. The method according to claim 1, wherein the parameter is at least one of a convergence voltage and a convergence time when a voltage generated between the plurality of electrodes converges when a pulsed voltage is applied between the plurality of electrodes. The caulking sensor for an internal combustion engine according to claim 1.