JP2003232774A - Gas concentration detecting apparatus for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately detect the concentration of NOx in which a NOx detection value of a gas concentration sensor is not affected by the amount of production of ammonia. <P>SOLUTION: A detection value of a sensor cell 130 immediately before exhaust gases introduced to the concentration sensor 100 turn to a rich atmosphere is held with a period, as a mask period, in which the exhaust gases turn to a lean atmosphere from the rich atmosphere, in other words, a pump cell current Ip changes to the positive (+) side from the negative (-) side after the exhaust gases turn to the rich atmosphere from the lean atmosphere, in other words, the pump cell current Ip changes from [mA] side to the negative (-) side. By this, it is possible to eliminate the effects of the amount of production of ammonia on a detection value of a sensor cell current Is corresponding to the NOx in the gas concentration of the exhaust gases introduced to the gas concentration sensor 100 and accurately detect the concentration of the NOx. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas concentration detecting device for an internal combustion engine, which detects the concentration of a specific gas component in exhaust gas of the internal combustion engine based on a detection value from a composite type gas concentration sensor.

[0002]

2. Description of the Related Art Conventionally, as a prior art document relating to a gas concentration detecting device for an internal combustion engine, Japanese Patent Laid-Open No. 11-27127 is known.
The one disclosed in Japanese Patent Publication No. 2 is known. This type uses a composite gas concentration sensor to detect the NOx (nitrogen oxide) concentration during lean combustion and to detect NOx (nitrogen oxide) concentration during lean combustion in air-fuel ratio control in which rich combustion is temporarily performed during lean combustion. A technique for performing lean combustion and rich combustion at an appropriate time by detecting the oxygen (O2) concentration is disclosed.

[0003]

By the way, in the case of lean combustion of an internal combustion engine, for example, in the case of a three-way catalyst that purifies the exhaust gas, the purification rate for NOx decreases, so the three-way catalyst passes through the three-way catalyst. The exhaust gas contains NOx. Here, the gas concentration sensor discharges oxygen from the exhaust gas as the gas to be detected introduced into the chamber,
The NOx concentration as a specific gas component is detected.

At this time, the exhaust gas introduced into the chamber is changed from a lean atmosphere to a rich atmosphere exceeding stoichiometry (theoretical air-fuel ratio). By changing the exhaust gas introduced into this chamber to a rich atmosphere,
Ammonia (NH3) will be produced. Then, in the gas concentration sensor, a value due to the amount of generated ammonia is added to the detected value of NOx, which causes a problem that the NOx concentration in the exhaust gas cannot be accurately detected.

Therefore, the present invention has been made to solve the above problems, and NOx by a gas concentration sensor is used.
The detected value of is not affected by the amount of ammonia produced,
An object of the present invention is to provide a gas concentration detection device for an internal combustion engine that can accurately detect NOx concentration.

[0006]

According to a gas concentration detecting device for an internal combustion engine of claim 1, the upstream side of at least one exhaust gas purification means arranged to purify exhaust gas in an exhaust passage of the internal combustion engine. Or a pump cell arranged on the downstream side,
During the period when the exhaust gas introduced into the gas concentration sensor having at least the sensor cell and the monitor cell changes from the lean atmosphere to the rich atmosphere, the detection by the gas concentration detecting means is stopped, the detection value is a mask, and the detection value immediately before the rich atmosphere At least one of the holds is executed. As a result, the influence of other components during the above period on the detection value of the sensor cell according to the concentration of the specific gas component in the exhaust gas introduced into the gas concentration sensor is eliminated, and the concentration of the specific gas component is accurately detected. It

In the gas concentration detecting means in the gas concentration detecting device for the internal combustion engine according to the second aspect, the held detection value is maintained during the period when the exhaust gas introduced into the gas concentration sensor changes from the lean atmosphere to the rich atmosphere. The output or estimated value is output or the output function is stopped. Thereby, the influence of other components during the above period on the detection value of the sensor cell according to the concentration of the specific gas component in the exhaust gas introduced into the gas concentration sensor is eliminated, and the concentration of the specific gas component is appropriately output. It

According to the third aspect of the gas concentration detecting device for the internal combustion engine, the gas concentration detecting device is arranged on the upstream side or the downstream side of at least one exhaust gas purification means arranged to purify the exhaust gas in the exhaust passage of the internal combustion engine. The exhaust gas introduced into the gas concentration sensor having at least the pump cell, the sensor cell and the monitor cell is changed from the lean atmosphere to the rich atmosphere for a predetermined period, and then the detection by the gas concentration detecting means is stopped.
At least one of the detection value held just before the mask and the rich atmosphere is held. As a result, the response delay of the gas concentration sensor is compensated, and the influence of other components after the lapse of the predetermined period on the detection value of the sensor cell according to the concentration of the specific gas component in the exhaust gas introduced into the gas concentration sensor is eliminated. Thus, the concentration of the specific gas component is accurately detected.

In the gas concentration detecting means in the gas concentration detecting device for the internal combustion engine according to the fourth aspect, the exhaust gas introduced into the gas concentration sensor is held after the lapse of a predetermined period from the lean atmosphere to the rich atmosphere. The detected value is output or the predicted value output is estimated, or the output function is stopped. As a result, the influence of other components after the lapse of the predetermined period on the detection value of the sensor cell according to the concentration of the specific gas component in the exhaust gas introduced into the gas concentration sensor is eliminated, and the concentration of the specific gas component is suitable. Is output.

In the gas concentration detecting means in the gas concentration detecting device for the internal combustion engine according to the fifth aspect, when the exhaust gas introduced into the gas concentration sensor changes from the rich atmosphere to the lean atmosphere, the detection is stopped or the detected value is changed. The hold state of the mask or the detection value is released, and the state is switched to the normal detection state. As a result, the influence of other components on the detection value of the sensor cell corresponding to the concentration of the specific gas component in the exhaust gas introduced into the gas concentration sensor is eliminated, and the concentration of the specific gas component is accurately detected.

In the gas concentration detecting means in the gas concentration detecting device for an internal combustion engine according to the sixth aspect, the detection is stopped or the detection is stopped after a lapse of a predetermined period after the exhaust gas introduced into the gas concentration sensor changes from the rich atmosphere to the lean atmosphere. The hold state of the mask to the value or the detected value is released, and the state is switched to the normal detection state. As a result, the influence of other components on the detection value of the sensor cell corresponding to the concentration of the specific gas component in the exhaust gas introduced into the gas concentration sensor is eliminated, and the concentration of the specific gas component is accurately detected.

In the gas concentration detecting means in the gas concentration detecting device for an internal combustion engine according to claim 7, the exhaust gas introduced into the gas concentration sensor is switched from a lean atmosphere to a rich atmosphere or from a rich atmosphere to a lean atmosphere. Is determined according to the output from the pump cell. As a result, the influence of other components on the detection value of the sensor cell corresponding to the concentration of the specific gas component in the exhaust gas introduced into the gas concentration sensor is eliminated, and the concentration of the specific gas component is accurately detected.

In the gas concentration detecting apparatus for an internal combustion engine according to claim 8, the gas concentration sensor has a λ cell in addition to the pump cell, the sensor cell and the monitor cell, and the exhaust gas introduced into the gas concentration sensor by this λ cell The oxygen concentration of is accurately detected. As a result, the influence of other components on the detection value of the sensor cell corresponding to the concentration of the specific gas component in the exhaust gas introduced into the gas concentration sensor is eliminated, and the concentration of the specific gas component is accurately detected.

In the gas concentration detecting means in the gas concentration detecting device for an internal combustion engine according to claim 9, the exhaust gas introduced into the gas concentration sensor is switched from a lean atmosphere to a rich atmosphere or from a rich atmosphere to a lean atmosphere. Is determined according to the output from the λ cell. This allows
The influence of other components on the detection value of the sensor cell according to the concentration of the specific gas component in the exhaust gas introduced into the gas concentration sensor is eliminated, and the concentration of the specific gas component is accurately detected.

According to the gas concentration detecting device for an internal combustion engine of claim 10, the gas concentration detecting device is arranged upstream or downstream of at least one exhaust gas purification means arranged to purify exhaust gas in the exhaust passage of the internal combustion engine. After a lapse of a predetermined period from the output start time of the sensor cell for the exhaust gas introduced into the gas concentration sensor having at least the pump cell, the sensor cell and the monitor cell, the predetermined period according to the operating condition of the internal combustion engine is set, and during the predetermined period Then, at least one of the detection by the gas concentration detection means is stopped, the detection value is masked, and the detection value immediately before is held. This eliminates the influence of other components during the above-mentioned predetermined period on the detection value of the sensor cell according to the concentration of the specific gas component in the exhaust gas introduced into the gas concentration sensor, and accurately detects the concentration of the specific gas component. To be done.

In the gas concentration detecting means in the gas concentration detecting device for an internal combustion engine according to the eleventh aspect, after a predetermined period has elapsed from the output start time of the sensor cell for the exhaust gas introduced into the gas concentration sensor, the operating condition of the internal combustion engine is met. During the predetermined period, the held detection value is output or the estimated prediction value is output or the output function is stopped. This eliminates the influence of other components during the above-mentioned predetermined period on the detection value of the sensor cell according to the concentration of the specific gas component in the exhaust gas introduced into the gas concentration sensor, and outputs the concentration of the specific gas component appropriately. To be done.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below based on Examples.

<First Embodiment> FIG. 1 is a schematic configuration diagram showing an internal combustion engine and its peripheral equipment to which a gas concentration detecting apparatus for an internal combustion engine according to a first embodiment of the present invention is applied.

In FIG. 1, an internal combustion engine 1 is constructed as a 4-cylinder 4-cycle spark ignition type, and its intake air passes from an upstream side through an air cleaner 2, an intake passage 3, a throttle valve 4, a surge tank 5 and an intake manifold 6. Then, it is mixed with the fuel injected from the injector (fuel injection valve) 7 in the intake manifold 6, and distributed and supplied to each cylinder as a mixture having a predetermined air-fuel ratio. Further, an igniter 9 directly connected to an ignition plug 8 provided in each cylinder of the internal combustion engine 1 includes an ECU (Electronic Contr.
The ignition signal is input from the electronic control unit 30), and the air-fuel mixture in each cylinder is burned at a predetermined timing by the spark ignition of the spark plug 8. Then, the exhaust gas after combustion is exhausted to the exhaust manifold 11 and the exhaust passage 12.
CO (carbon monoxide) which is a harmful component in the three-way catalyst 13 which is provided in the exhaust passage 12 and carries catalyst components such as platinum and rhodium and additives such as cerium and lanthanum.
HC (hydrocarbons) and the like are purified, and N which is a harmful component in the NOx storage reduction catalyst 14 provided on the downstream side thereof is further purified.
Ox is purified and discharged into the atmosphere.

An air flow meter 21 is provided in the intake passage 3 on the downstream side of the air cleaner 2, and the air flow meter 21 detects the intake air amount QA passing through the air cleaner 2 per unit time. Further, the throttle valve 4 is provided with a throttle opening sensor 22. The throttle opening sensor 22 detects an analog signal corresponding to the throttle opening TA, and the throttle valve 4 is almost fully closed. It is detected by an on / off signal from an idle switch (not shown). An intake pressure sensor 23 is provided in the surge tank 5,
The intake pressure PM is detected by the intake pressure sensor 23. Further, a water temperature sensor 24 is provided in the cylinder block of the internal combustion engine 1.
Is provided, and the coolant temperature THW of the internal combustion engine 1 is detected by the coolant temperature sensor 24.

A crank angle sensor 25 is provided in the internal combustion engine 1, and the crank angle sensor 25 detects the engine speed NE of the internal combustion engine 1. Furthermore, the exhaust passage 1
A linear voltage signal VO corresponding to the air-fuel ratio λ of the exhaust gas discharged from the internal combustion engine 1 is provided on the upstream side of the two-way three-way catalyst 13.
An air-fuel ratio sensor 26 that outputs X1 is provided. Further, between the three-way catalyst 13 and the NOx storage reduction catalyst 14 in the exhaust passage 12, there is provided an oxygen sensor 27 for detecting lean-to-rich or rich-to-lean reversal of the exhaust gas. Further, a NOx sensor 28 that detects NOx in the exhaust gas that has passed through the NOx storage / reduction catalyst 14 is disposed downstream of the NOx storage / reduction catalyst 14 in the exhaust passage 12. Further, the NOx storage reduction catalyst 14 is provided with an exhaust temperature sensor 29 for detecting the exhaust temperature THG of the exhaust gas in the NOx storage reduction catalyst 14.

ECU 3 for controlling the operating state of internal combustion engine 1
0 is an R that stores a CPU as a central processing unit that executes various known arithmetic processes, a control program, and a control map.
An OM, a RAM for storing various data, a B / U (backup) RAM, etc. are mainly configured as a logical operation circuit,
It is connected via a bus to an input port for inputting detection signals from various sensors and an output port for outputting control signals to various actuators. Further, the ECU 30
Is provided with a control circuit 200 for controlling a gas concentration sensor 100 described later and its peripheral circuits.

The intake air amount QA from the air flow meter 21, the throttle opening TA from the throttle opening sensor 22, the intake pressure PM from the intake pressure sensor 23, the water temperature sensor 24 from the water temperature sensor 24 are input to the ECU 30 via the input port. Cooling water temperature THW, engine speed N from crank angle sensor 25
Various sensor signals such as E are input, the fuel injection amount TAU, the ignition timing Ig, and the like are calculated based on them, and control signals are output to the injector 7, the igniter 9, and the like through the output port.

Further, the air-fuel ratio of the air-fuel mixture based on the exhaust gas is determined by the voltage signal VOX1 from the air-fuel ratio sensor 26 input to the ECU 30. And ECU3
Voltage signal VOX2 from the oxygen sensor 27 input to 0
Detects when the exhaust gas reverses from lean to rich or from rich to lean. Further, the ECU 30
The oxygen concentration and the NOx concentration in the exhaust gas are detected by the output signal from the NOx sensor 28 input to the control circuit 200.

Next, FIG. 2 showing an outline of a gas concentration detecting apparatus for an internal combustion engine according to a first embodiment of the present invention,
Description will be made with reference to the configuration diagrams of FIGS. 3 and 4. The gas concentration detection device of the present embodiment uses a limiting current type gas concentration sensor to detect the oxygen concentration in the exhaust gas from the internal combustion engine 1 which is the gas to be detected, and also the NOx concentration as the concentration of the specific gas component. To detect.

First, the structure of the gas concentration sensor 100 constituting the NOx sensor 28 will be described with reference to FIGS. 2 and 3.

As shown in FIG. 2, the gas concentration sensor 100
Is a three-cell structure having a pump cell 110, a monitor cell 120, and a sensor cell 130, and is embodied as a so-called composite gas sensor capable of simultaneously detecting the oxygen concentration and NOx concentration in exhaust gas. 2 (a)
2 is a cross-sectional view showing the structure of the tip of the sensor element, and FIG.
2B is a sectional view taken along the line AA of FIG.

As shown in FIG. 2, the gas concentration sensor 100
In the above, solid electrolytes (solid electrolyte elements) 141 and 142 made of an oxygen ion conductive material are formed in a plate shape and are vertically stacked at a predetermined interval via a spacer 143 made of an insulating material such as alumina. Of these, a pinhole 141a is formed in the solid electrolyte 141, and exhaust gas around the gas concentration sensor 100 is introduced into the first chamber 144 via the pinhole 141a. The first chamber 144 communicates with the second chamber 146 via the throttle portion 145. 147 is a porous diffusion layer.

The solid electrolyte 142 includes a first chamber 14
4 is provided so as to face No. 4, oxygen in the exhaust gas introduced into the first chamber 144 by the pump cell 110 is discharged or pumped, and at this time, the oxygen concentration in the exhaust gas is increased. To be detected.
Here, the pump cell 110 is formed with a pair of electrodes 111 and 112 with the solid electrolyte 142 sandwiched therebetween. Of these electrodes, the electrode 111 on the first chamber 144 side is a NOx inert electrode (an electrode that does not easily decompose NOx gas). Has been formed.
Oxygen existing in the first chamber 144 is decomposed by the pump cell 110 and the atmosphere passage 15 is generated from the electrode 112.
It is discharged to the 0 side.

Further, the solid electrolyte 141 is provided with a monitor cell 120 and a sensor cell 130 so as to face the second chamber 146. From the monitor cell 120, a current output is generated according to the electromotive force or the voltage application according to the excess oxygen concentration in the second chamber 146. Also,
The sensor cell 130 detects the NOx concentration in the gas that has passed through the pump cell 110.

In particular, as shown in FIG. 2 (b), the monitor cell 1 is placed at the same position in the exhaust gas flow direction.
20 and the sensor cell 130 are arranged in parallel, and the electrodes on the atmosphere passage 148 side of these cells 120 and 130 are formed as the common electrode 122. That is, the monitor cell 120 is composed of the solid electrolyte 141 and the electrode 121 and the common electrode 122 that are opposed to each other with the solid electrolyte 141 interposed therebetween, and the sensor cell 130 is the solid electrolyte 141 and the electrode 131 and the common electrode 122 that are also opposed to each other with the solid electrolyte 141 interposed therebetween.
Consists of. The electrode 121 of the monitor cell 120 (the electrode on the second chamber 146 side) is A that is inert to NOx gas.
While the electrode 131 of the sensor cell 130 (the electrode on the second chamber 146 side) is formed of a noble metal such as u-Pt, it is formed of a noble metal such as Pt that is active in NOx gas.

Further, FIG. 3A is a sectional view of the electrodes of the monitor cell 120 and the sensor cell 130 as seen from the second chamber 146 side, and FIG. 3B shows the electrodes of these cells in the atmosphere passage 148 side. It is sectional drawing seen from. However, the electrodes of the monitor cell 120 and the sensor cell 130 are as shown in FIG.
As shown in (a), instead of being arranged in parallel along the flow direction of the exhaust gas, they may be arranged front and back (that is, left and right in FIG. 3A) in the flow direction of the exhaust gas. For example, the monitor cell 120 may be arranged on the upstream side (left side in FIG. 3A) and the sensor cell 130 may be arranged on the downstream side (right side in FIG. 3A).

As shown in FIG. 2A, an insulating layer 149 is provided on the lower surface of the solid electrolyte 142, and the insulating layer 149 forms an atmosphere passage 150. A heater 151 for heating the entire sensor is embedded in the insulating layer 149. And the pump cell 11
In order to activate the entire sensor including 0, the monitor cell 120, and the sensor cell 130, the heater 151 generates heat energy by external power supply.

In the gas concentration sensor 100 having the above structure, the exhaust gas is the porous diffusion layer 147 and the pinhole 14.
It is introduced into the first chamber 144 through 1a. When this exhaust gas passes near the pump cell 110, a decomposition reaction is caused by applying a voltage between the electrodes 111 and 112 of the pump cell 110, and the first chamber 1
Oxygen is discharged or pumped through the pump cell 110 depending on the oxygen concentration in 44. At this time, since the electrode 111 on the side of the first chamber 144 is a NOx inert electrode, NOx in the exhaust gas is not decomposed in the pump cell 110, and only oxygen is decomposed and discharged into the atmosphere passage 150. Then, the oxygen concentration contained in the exhaust gas is detected by the pump cell current Ip flowing through the pump cell 110.

After that, the exhaust gas passing near the pump cell 110 flows into the second chamber 146, and the monitor cell 120 produces an output according to the concentration of excess oxygen in the gas. The output of the monitor cell 120 is the monitor cell 12
When a predetermined voltage is applied between the zero electrodes 121 and 122, the monitor cell current Im is detected. Further, when a predetermined voltage is applied between the electrodes 131 and 122 of the sensor cell 130, NOx in the gas is reduced and decomposed, and oxygen generated at this time is discharged to the atmosphere passage 148. At this time, the NOx concentration contained in the exhaust gas is detected by the sensor cell current Is flowing through the sensor cell 130.

Next, the electrical construction of the gas concentration detecting apparatus for an internal combustion engine of this embodiment will be described with reference to FIG. Although FIG. 4 shows a gas concentration detecting device using the gas concentration sensor 100 shown in FIGS. 2 and 3, the electrode arrangements of the monitor cell 120 and the sensor cell 130 are shown side by side for convenience.

In FIG. 4, the control circuit 2 in the ECU 30
Reference numeral 00 is a well-known microcomputer including a CPU, an A / D converter, a D / A converter, an I / O port, etc., and is a pump cell 110 and a monitor cell 1.
The voltage applied to 20 and the sensor cell 130 is appropriately output from the D / A converter (D / A0 to D / A2). Further, the control circuit 200 has terminals Vc, Ve, Vd, Vb, Vg, and Vh for measuring currents flowing through the pump cell 110, the monitor cell 120, and the sensor cell 130.
Are input from the A / D converters (A / D0 to A / D5). Then, in the control circuit 200, the detected values of the oxygen concentration and NOx concentration in the exhaust gas based on the current measured by the pump cell 110 and the sensor cell 130 are the ECU 3 values.
It is output to 0.

When the control circuit 200 and its peripheral circuits are arranged near the gas concentration sensor 100 and away from the ECU 30, the detected values of the oxygen concentration and NOx concentration in the exhaust gas are controlled. It is output from the circuit 200 to the ECU 30 side via a D / A converter or communication.

For details of the circuit configuration, one electrode 112 of the pump cell 110 is connected to the reference power source 201.
And the reference voltage Va is applied by the operational amplifier 202,
The command voltage Vb from the control circuit 200 is applied to the other electrode 111 via the operational amplifier 203 and the current detection resistor 204.
Is applied. When a current flows through the pump cell 110 according to the oxygen concentration in the exhaust gas when the command voltage Vb is applied, this current is detected by the current detection resistor 204.
That is, both terminal voltages Vb and Vd of the current detection resistor 204 are taken into the control circuit 200, and the pump cell current Ip is calculated from these voltages Vb and Vd.

Further, the monitor cell 120 and the sensor cell 1
The reference voltage Vf is applied to the common electrode 122 of 30 by the reference power supply 205 and the operational amplifier 206, and the common electrode 1
The sensor cell electrode 131 different from 22 is connected to the control circuit 20 via the operational amplifier 207 and the current detection resistor 208.
A command voltage Vg from 0 is applied. When a current flows through the sensor cell 130 according to the NOx concentration in the exhaust gas when the command voltage Vg is applied, this current is detected by the current detection resistor 20.
Detected by 8. That is, both terminal voltages Vg and Vh of the current detection resistor 208 are taken into the control circuit 200, and the sensor cell current Is is calculated from these voltages Vg and Vh.

An LPF (low-pass filter) 2 is attached to the monitor cell electrode 121, which is different from the common electrode 122.
The command voltage Vc from the control circuit 200 is applied via the 09, the operational amplifier 210, and the current detection resistor 211. When a current flows through the monitor cell 120 according to the NOx concentration in the exhaust gas when the command voltage Vc is applied, this current is detected by the current detection resistor 211. That is, both terminal voltages Vc and Ve of the current detection resistor 211 are taken into the control circuit 200, and the monitor cell current I is obtained by these voltages Vc and Ve.
m is calculated. The LPF 209 is realized by, for example, a primary filter including a resistor and a capacitor.

Further, in this embodiment, the element impedance is detected by using the sweep method for the monitor cell 120. That is, when the impedance of the monitor cell 120 is detected, the control circuit 200 instantaneously switches the monitor cell applied voltage (command voltage Vc) to at least one of the positive side and the negative side. This applied voltage is applied to the monitor cell 120 while being sine-wave tuned by the LPF 209. The frequency of the AC voltage is 1
0 [kHz] or more is desirable, and the time constant of the LPF 209 is set to about 5 [μsec]. Then, the element impedance of the monitor cell 120 is calculated from the voltage change amount and the current change amount at this time.

Further, the monitor cell 120 and the sensor cell 1
In No. 30, since one electrode is formed as the common electrode 122, the advantage that the drive circuit on the reference voltage side can be reduced and the number of lead wires taken out from the gas concentration sensor 100 can be reduced. Further, since the monitor cell 120 and the sensor cell 130 are formed adjacent to each other with the same solid electrolyte 141, a current may flow to the adjacent electrode during the sweep, which may deteriorate the impedance detection accuracy, but the common electrode 122. Since the electrode is provided, one of the electrodes has the same potential, and this influence is reduced.

By the way, in the monitor cell 120, only a current of about several μA flows when detecting the residual oxygen, whereas several m when sweeping for impedance detection.
A current of about A] flows. If currents of different orders are detected by the same detection resistor, overrange or detection accuracy deteriorates. Therefore, in this embodiment, the current detection resistance is switched between when the monitor cell 120 detects residual oxygen and when it detects impedance.

Specifically, another current detection resistor 212 and a switch circuit 213 (for example, a semiconductor switch) are provided in parallel with the current detection resistor 211. And
The switch circuit 213 is configured to be turned on / off by the output from the I / O port of the control circuit 200. In this case, at the time of normal gas concentration detection, the switch circuit 213 is turned off (opened), and the monitor cell current Im is detected by the resistance of several hundred [kΩ] by the current detection resistance 211. On the other hand, when detecting impedance,
The switch circuit 213 is turned on (closed), and the monitor cell current Im is detected by the resistance of several hundred [Ω] by the current detection resistances 211 and 212.

The control command value Duty is output from the I / O port by the CPU in the control circuit 200.
The OSFET driver 251 is driven. At this time, M
The power supplied from the power supply 253 (for example, a battery power supply) to the heater 151 is PWM-controlled by the OSFET 252.

Next, the gas concentration sensor 100 in the CPU in the control circuit 200 used in the gas concentration detecting device for the internal combustion engine according to the first example of the embodiment of the present invention.
Sensor cell current I which is the output from the sensor cell 130 of
An explanation will be given with reference to FIG. 6 based on the flowchart of FIG. 5 showing the mask control processing procedure for s. Here, FIG. 6 shows the sensor cell current Is [nA] and the pump cell current Ip [m] according to the gas concentration [ppm] in the process of FIG.
It is a time chart which shows the transition state of [A]. It should be noted that this mask control routine is repeatedly executed by the CPU at every predetermined time after the control circuit 200 is powered on.

In FIG. 5, in step S101, the sensor cell current Is corresponding to the gas concentration of the exhaust gas introduced into the gas concentration sensor 100 is detected. Next, in step S102, the pump cell current Ip, which is the output from the pump cell 110, is detected. Next step S1
03, the pump cell current Ip is 0 (zero) [m
It is determined whether it is less than A].

Here, as shown in FIG. 6, the timing at which NOx at the gas concentration starts to be detected as the sensor cell current Is (time t01 in FIG. 6) is the timing at which the exhaust gas becomes stoichiometric from the lean atmosphere. The pump cell current Ip becomes 0 [mA] from the positive (+) side until then. Further, the timing at which the influence of ammonia on the NOx at the gas concentration begins to appear (at time t shown in FIG. 6)
02) is the timing at which the exhaust gas changes from stoichiometric to a rich atmosphere, and the pump cell current Ip goes from 0 [mA] to the negative (-) side. The timing at which the influence of ammonia on the detected value of the sensor cell current Is corresponding to NOx in the gas concentration disappears (time t03 shown in FIG. 6) is the timing at which the exhaust gas changes from the rich atmosphere to the lean atmosphere, and the pump cell The current Ip goes from the negative (−) side to the positive (+) side.

Therefore, the determination condition of step S103 is satisfied, that is, the pump cell current Ip at which the influence of ammonia appears on the detected value of the sensor cell current Is corresponding to NOx in the gas concentration is less than 0 [mA] (see FIG. 6). At times t02 to t03 shown in the drawing, the process proceeds to step S104, the sensor cell current Is is masked, and this routine ends. On the other hand, when the determination condition of step S103 is not satisfied, that is, when the pump cell current Ip is as large as 0 [mA] or more, it is determined that there is no influence of ammonia on the detected value of the sensor cell current Is corresponding to NOx in the gas concentration.
This routine ends without doing anything.

As for the sensor cell current Is in the mask period, as shown in FIG. 6, the detection value at time t02 may be held (held) as it is, and the detection value is ignored as 0 [nA] when the detection is stopped. Alternatively, the detected value may be gradually decreased from time t02.

As described above, the gas concentration detecting apparatus for the internal combustion engine of this embodiment has the pump cell 110 for discharging or pumping oxygen in the gas to be detected introduced into the first chamber 144,
A sensor cell 130 that detects the NOx concentration as a specific gas component from the gas that has passed through the pump cell 110;
A composite gas concentration sensor 100 that has at least a monitor cell 120 that detects the residual oxygen concentration in the second chamber 146, and that keeps each cell in an active state based on the element resistance of the solid electrolyte that forms each cell; A NOx storage reduction catalyst 14 as an exhaust gas purification means for purifying exhaust gas from the internal combustion engine 1, which is disposed in the exhaust passage 12 of the engine 1;
A gas concentration detecting means for detecting the sensor cell current Is flowing in the sensor cell 130 of the gas concentration sensor 100 arranged on the downstream side of the NOx storage reduction catalyst 14 and sequentially detecting the NOx concentration in the exhaust gas from the detected value is achieved. ECU3
The control circuit 200 holds the detection value by the sensor cell 130 immediately before the rich atmosphere during the period when the exhaust gas introduced into the gas concentration sensor 100 changes from the lean atmosphere to the rich atmosphere. It is a thing.

Further, in the control circuit 200 in the ECU 30 which achieves the gas concentration detecting means of the gas concentration detecting device for the internal combustion engine of the present embodiment, the exhaust gas introduced into the gas concentration sensor 100 changes from a lean atmosphere to a rich atmosphere. During the period, the detected value by the held sensor cell 130 is output.

Then, in the control circuit 200 in the ECU 30 which achieves the gas concentration detecting means of the gas concentration detecting device for the internal combustion engine of this embodiment, the exhaust gas introduced into the gas concentration sensor 100 changes from a rich atmosphere to a lean atmosphere. In this case, the hold state of the detection value by the sensor cell 130 is released and the detection state is switched to the normal detection state.

Further, the control circuit 200 in the ECU 30 which realizes the gas concentration detecting means of the gas concentration detecting device for the internal combustion engine of this embodiment changes the lean gas of the exhaust gas introduced into the gas concentration sensor 100 from the rich atmosphere to the rich atmosphere. The switching or switching from the rich atmosphere to the lean atmosphere is determined according to the pump cell current Ip output from the pump cell 110.

That is, the exhaust gas introduced into the gas concentration sensor 100 is from a lean atmosphere to a rich atmosphere, that is, the pump cell current Ip is from 0 [mA] to the negative (-) side,
After that, the exhaust gas is detected from the rich atmosphere to the lean atmosphere, that is, the period until the pump cell current Ip is changed from the negative (−) side to the positive (+) side is a mask period and is detected by the sensor cell 130 immediately before the rich atmosphere. The value is held and the detected value is output. As a result, it is possible to eliminate the influence of the ammonia generation component on the detection value of the sensor cell current Is according to NOx in the gas concentration of the exhaust gas introduced into the gas concentration sensor 100,
The NOx concentration can be accurately detected.

By the way, in the above embodiment, when the exhaust gas introduced into the gas concentration sensor 100 changes from the lean atmosphere to the rich atmosphere, the detection value by the sensor cell 130 is immediately held, and the held detection value is output. Then, when the rich atmosphere is changed to the lean atmosphere, the hold state of the detection value by the sensor cell 130 is immediately released and switched to the normal detection state. However, the present invention is not limited to this. However, if there is a response delay in the output from the gas concentration sensor 100, it is possible to deal with it by providing a time lag of a predetermined period.

Such a gas concentration detecting apparatus for an internal combustion engine has a pump cell 110 for discharging or pumping oxygen in the gas to be detected introduced into the first chamber 144, and a gas after passing through the pump cell 110 as a specific gas component. Sensor cell 130 for detecting the NOx concentration in the second chamber and the monitor cell 120 for detecting the residual oxygen concentration in the second chamber 146.
And a composite gas concentration sensor 100 that holds each cell in an active state based on the element resistance of the solid electrolyte that forms each cell, and is disposed in the exhaust passage 12 of the internal combustion engine 1. NOx storage reduction catalyst 14 as an exhaust purification means for purifying the exhaust gas from No. 1, and a gas concentration sensor 10 arranged downstream of the NOx storage reduction catalyst 14.
A control circuit 200 in the ECU 30 that achieves a gas concentration detection unit that detects the sensor cell current Is flowing in the zero sensor cell 130 and sequentially detects the NOx concentration in the exhaust gas from the detected value. The value detected by the sensor cell 130 immediately before the exhaust gas introduced into the gas concentration sensor 100 is changed from the lean atmosphere to the rich atmosphere and the pump cell current Ip becomes the negative (−) side, and after a predetermined period has elapsed and the mask period is immediately before the rich atmosphere. In addition, the control circuit 200 in the ECU 30 that holds the gas concentration sensor 10
The exhaust gas introduced to 0 changes from the rich atmosphere to the lean atmosphere and outputs the held detection value after a lapse of a predetermined period, and the control circuit 200 in the ECU 30 that achieves the gas concentration detecting means After the exhaust gas introduced into the gas concentration sensor 100 has changed from the rich atmosphere to the lean atmosphere for a predetermined period of time, the hold state of the detection value by the sensor cell 130 in the mask period is released and switched to the normal detection state. The same actions and effects as those of the above-mentioned embodiment can be expected.

7 and 8 show the first embodiment of the present invention.
A first modified example of the mask control processing procedure for the sensor cell current Is output from the sensor cell 130 of the gas concentration sensor 100 in the CPU in the control circuit 200 used in the gas concentration detection apparatus for the internal combustion engine according to the embodiment. FIG. 9 is a flowchart showing the above and will be described with reference to FIG. Here, FIG. 9 is a time chart showing a transition state of the sensor cell current Is [nA] and the pump cell current Ip [mA] according to the gas concentration [ppm] in the processes of FIGS. 7 and 8. It should be noted that this mask control routine is repeatedly executed by the CPU at every predetermined time after the control circuit 200 is powered on.

In FIG. 7, step S201 to step S204 correspond to step S101 to step S104 in the above-described embodiment, and therefore detailed description thereof will be omitted. Here, after the sensor cell current Is is masked in step S204, the process proceeds to step S204, a gas concentration estimating process described below is executed, and the present routine is ended. On the other hand, the determination condition of step S203 is not satisfied, that is, the pump cell current Ip is 0.
When it is as large as [mA] or more and there is no influence of ammonia on the detected value of the sensor cell current Is corresponding to NOx in the gas concentration, this routine is ended.

In the gas concentration estimating process shown in FIG. 8, in step S301, the estimated value decreasing speed is the engine rotation speed N.
It is calculated based on a three-dimensional map using E and intake pressure PM as parameters. It should be noted that, as shown on the right side of FIG. 8, this estimated value decrease speed is set with the engine speed NE as a parameter 2
It may be calculated based on a two-dimensional map having the dimension map and the intake pressure PM as parameters. Next, the process proceeds to step S302, and the estimated value decrease speed correction value is calculated according to the elapsed time of the gas concentration estimation process. Next, the process proceeds to step S303, and the value obtained by subtracting the value obtained by multiplying the estimated value decrease speed by the estimated value decrease speed correction value from the previous value is updated as the estimated value in the gas concentration estimation process. As a result, in the present modification, the sensor cell current Is in the mask period is as shown in FIG.
As shown in, the estimated value gradually decreases from time t12. In the present modification, the exhaust gas is in a rich atmosphere to a lean atmosphere, that is, a period until the pump cell current Ip changes from the negative (−) side to the positive (+) side is a mask period (time t12 to t13 shown in FIG. 9). ) Further, a predetermined mask extension period (time t13 to t14 shown in FIG. 9) is set in advance to mask the detection value by the sensor cell 130. Therefore, it is possible to eliminate the influence of the ammonia generation component on the detected value of the sensor cell current Is corresponding to NOx in the gas concentration of the exhaust gas introduced into the gas concentration sensor 100,
The NOx concentration can be accurately detected.

As described above, in the control circuit 200 in the ECU 30 which achieves the gas concentration detecting means of the gas concentration detecting device for the internal combustion engine of the present modification, the exhaust gas introduced into the gas concentration sensor 100 is changed from the lean atmosphere to the rich atmosphere. In such a period, the estimated value is output as the estimated value. That is, the exhaust gas introduced into the gas concentration sensor 100 changes from a lean atmosphere to a rich atmosphere, that is,
The pump cell current Ip changes from 0 [mA] to the negative (−) side, and thereafter, the exhaust gas from the rich atmosphere to the lean atmosphere, that is, the pump cell current Ip changes from the negative (−) side to the positive (+) side. In the mask period as a period, the sensor cell current Is is gradually reduced by the estimated value.
As a result, it is possible to eliminate the influence of the ammonia generation component on the detection value of the sensor cell current Is corresponding to NOx in the gas concentration of the exhaust gas introduced into the gas concentration sensor 100, and it is possible to accurately detect the NOx concentration. it can.

FIG. 10 shows the gas concentration sensor 10 in the CPU in the control circuit 200 used in the gas concentration detecting apparatus for the internal combustion engine according to the first embodiment of the present invention.
It is a flowchart which shows the 2nd modification of the process procedure of the mask control with respect to the sensor cell current Is which is the output from the sensor cell 130 of 0, and is demonstrated with reference to FIG. 11, FIG. 12 and FIG. Here, FIG. 11 and FIG.
Mask timing α, mask release timing β
Is a map for setting each of the above according to operating conditions. Further, FIG. 13 shows the gas concentration [ppm] in the process of FIG.
5 is a time chart showing transition states of the sensor cell current Is [nA], the NOx purge request flag, and the NOx purge counter CNOXCNT according to the above. It should be noted that this mask control routine is repeatedly executed by the CPU at every predetermined time after the control circuit 200 is powered on.

In FIG. 10, in step S401,
The engine speed NE and the intake pressure PM of the internal combustion engine 1 are read as operating conditions. Next, in step S402,
The mask timing α and the mask release timing β are set by the maps of FIGS. 11 and 12. Note that the map shown in FIG. 11 sets the mask timing α at a timing at which the influence of ammonia appears on the detected value of the sensor cell current Is corresponding to NOx in the gas concentration, and the mask shown in FIG. Timing β is set to a timing at which the influence of ammonia on the detected value of the sensor cell current Is corresponding to NOx in the gas concentration disappears. Then, as shown in FIGS. 11 and 12, both the mask timing α and the mask release timing β have characteristics that become smaller as the operating condition changes from low load to high load.

Next, the routine proceeds to step S403, where NOx
It is determined whether there is a purge request. The determination condition of step S403 is satisfied, that is, the NOx purge request flag is “1.
(Requested) "(after time t21 shown in FIG. 13) NOx
When there is a purge request for the NOx purge counter CNOXCNT, the process proceeds to step S404.
1 ”is incremented.

Then, the process proceeds to step S405, where α≤C
It is determined whether the inequality NOXCNT ≦ β holds.
When the determination condition of step S405 is satisfied, that is, when the NOx purge counter CNOXCNT is between the mask timing α and the mask release timing β, it is determined that the mask period is set (time t22 to t23 in FIG. 13) and step S4 is performed.
Then, the flow shifts to 06, the sensor cell current Is is masked, and this routine is finished.

On the other hand, when the determination condition of step S403 is not satisfied, that is, when the NOx purge request flag is "0 (no request)" and there is no purge request for NOx,
The determination condition of step S405 is not satisfied, that is, NOx
When the purge counter CNOXCNT is not between the mask timing α and the mask release timing β, it is determined that there is no influence of ammonia on the detected value of the sensor cell current Is corresponding to NOx in the gas concentration, and this routine is ended without doing anything. .

As described above, the gas concentration detecting apparatus for the internal combustion engine according to the present modification includes the pump cell 110 for discharging or pumping oxygen in the gas to be detected introduced into the first chamber 144,
A sensor cell 130 that detects the NOx concentration as a specific gas component from the gas that has passed through the pump cell 110;
A composite gas concentration sensor 100 that has at least a monitor cell 120 that detects the residual oxygen concentration in the second chamber 146, and that keeps each cell in an active state based on the element resistance of the solid electrolyte that forms each cell; A NOx storage reduction catalyst 14 as an exhaust gas purification means for purifying exhaust gas from the internal combustion engine 1, which is disposed in the exhaust passage 12 of the engine 1;
A gas concentration detecting means for detecting the sensor cell current Is flowing in the sensor cell 130 of the gas concentration sensor 100 arranged on the downstream side of the NOx storage reduction catalyst 14 and sequentially detecting the NOx concentration in the exhaust gas from the detected value is achieved. ECU3
The control circuit 200 includes a control circuit 200 in which the engine speed NE and the intake pressure PM of the internal combustion engine 1 are increased after a predetermined period has elapsed from the output start time of the sensor cell 130 for the exhaust gas introduced into the gas concentration sensor 100. The NOx purge counter CNOXCNT corresponding to the (operating condition) sets a predetermined period from the mask timing α to the mask release timing β, and the NOx purge counter C is set during the predetermined period.
The value detected by the sensor cell 130 immediately before NOXCNT coincides with the mask timing α is held, and the control circuit 200 in the ECU 30 that achieves the gas concentration detection means outputs the held detection value after a predetermined period has elapsed. It is what is output.

That is, the output value from the sensor cell 130 of the gas concentration sensor 100 is the value detected by the sensor cell 130 immediately before during a predetermined period from the mask timing α to the mask release timing β which is preset according to the operating conditions. The held detection value is output and output after a lapse of a predetermined period. As a result, it is possible to eliminate the influence of the ammonia generation component on the detection value of the sensor cell current Is corresponding to NOx in the gas concentration of the exhaust gas introduced into the gas concentration sensor 100, and it is possible to accurately detect the NOx concentration. it can.

FIG. 14 shows the gas concentration sensor 10 in the CPU in the control circuit 200 used in the gas concentration detecting apparatus for the internal combustion engine according to the first example of the embodiment of the present invention.
8 is a flowchart showing a third modified example of the processing procedure of the mask control for the sensor cell current Is output from the sensor cell 130 of 0, and FIG.
2. And, it demonstrates with reference to FIG. Here, FIG.
5 is a time chart showing transition states of the sensor cell current Is [nA], the NOx purge request flag, and the NOx purge counter CNOXCNT according to the gas concentration [ppm] in the process of FIG. It should be noted that this mask control routine is repeatedly executed by the CPU at every predetermined time after the control circuit 200 is powered on.

In FIG. 14, step S501 to step S506 correspond to step S401 to step S406 in the above-described modification, and therefore detailed description thereof will be omitted. Here, after the sensor cell current Is is masked in step S506, the process proceeds to step S507, the above-described gas concentration estimation process shown in FIG. 8 is executed, and this routine ends. On the other hand, when the determination condition of step S503 is not satisfied, that is, when the NOx purge request flag is "0 (no request)" and there is no purge request for NOx, and the determination condition of step S505 is not satisfied, that is, NOx. Purge counter CNOXCN
When T is not between the mask timing α and the mask release timing β, it is determined that there is no influence of ammonia on the detected value of the sensor cell current Is corresponding to NOx in the gas concentration, and this routine is ended without doing anything.

As described above, the control circuit 200 in the ECU 30 which achieves the gas concentration detecting means of the gas concentration detecting device for the internal combustion engine of the present modified example has the estimated value as the estimated value after the elapse of the predetermined period. Is output. In this modification, the NOx purge counter CNOXCN is used.
T is set between the mask timing α and the mask release timing β (time t32 to t33 shown in FIG. 15), and further, a predetermined mask extension period (time t33 to t34 shown in FIG. 15) is set in advance to be detected by the sensor cell 130. The value is masked. Therefore, it is possible to eliminate the influence of the ammonia generation component on the detected value of the sensor cell current Is corresponding to NOx in the gas concentration of the exhaust gas introduced into the gas concentration sensor 100, and it is possible to accurately detect the NOx concentration. .

<Embodiment 2> FIG. 16 is a block diagram showing the structure of a gas concentration sensor 100 'used in a gas concentration detecting apparatus for an internal combustion engine according to a second embodiment of the present invention. The gas concentration sensor 100 'according to the present embodiment is different from the gas concentration sensor 100 according to the first embodiment described above only in that a λ cell 180 is additionally formed. Since it is the same as FIGS. 2, 3 and 4 showing the configuration diagram of the first embodiment, detailed description thereof will be omitted. Also, regarding an internal combustion engine and its peripheral equipment to which the gas concentration detecting device for an internal combustion engine according to the second example of the embodiment of the present invention is applied, FIG. 1 showing a schematic configuration diagram of the above-mentioned first example The same is true and detailed description thereof is omitted.

As shown in FIG. 16, in the gas concentration sensor 100 'of this embodiment, in order to output the electromotive force according to the oxygen concentration in the first chamber 144 to the upper solid electrolyte 141 near the pump cell 110. Λ cell 1
80 is provided. Then, the voltmeter 181 causes λ
The electromotive force of the cell 180 is measured, and the measured value is taken in by the control circuit 200.

Next, the gas concentration sensor 10 in the CPU in the control circuit 200 used in the gas concentration detecting device for the internal combustion engine according to the second example of the embodiment of the present invention.
A description will be given with reference to FIG. 18 based on the flowchart of FIG. 17 showing the mask control processing procedure for the sensor cell current Is output from the 0 ′ sensor cell 130. Here, FIG. 18 shows the gas concentration [pp
7 is a time chart showing transition states of the sensor cell current Is [nA] and the λ cell voltage Vp [V] according to m].
It should be noted that this mask control routine is repeatedly executed by the CPU at every predetermined time after the control circuit 200 is powered on.

In FIG. 17, in step S601,
The sensor cell current Is corresponding to the gas concentration of the exhaust gas introduced into the gas concentration sensor 100 is detected. Next, in step S602, the λ cell voltage Vp output from the λ cell 180 is detected. Next, proceeding to step S603, it is determined whether the λ cell voltage Vp is 0.45 [V] or higher. Here, as shown in FIG. 18, during the period in which the λ cell voltage Vp is 0.45 [V] or more, the influence of ammonia begins to appear on the detected value of the sensor cell current Is corresponding to NOx in the gas concentration. This coincides with the period when the influence of ammonia disappears from the timing.

Therefore, the determination condition of step S603 is satisfied, that is, the λ cell voltage Vp at which the influence of ammonia appears on the detected value of the sensor cell current Is corresponding to NOx in the gas concentration is 0.45 [V] or more ( At time t42 to t43 shown in FIG. 18, the process proceeds to step S604, the sensor cell current Is is masked, and this routine is finished. On the other hand, when the determination condition of step S603 is not satisfied, that is, when the λ cell voltage Vp is smaller than 0.45 [V], it is considered that there is no influence of ammonia on the detected value of the sensor cell current Is corresponding to NOx in the gas concentration. , This routine ends without doing anything.

As described above, the gas concentration sensor 100 'of the gas concentration detecting apparatus for the internal combustion engine of this embodiment further outputs λ that outputs an electromotive force according to the oxygen concentration in the first chamber 144.
It has a cell 180. Further, the control circuit 200 in the ECU 30 that achieves the gas concentration detecting means of the gas concentration detecting device for the internal combustion engine according to the present embodiment includes the gas concentration sensor 10
The switching from the lean atmosphere to the rich atmosphere or the switching from the rich atmosphere to the lean atmosphere of the exhaust gas introduced into 0'is determined based on the output from the λ cell 180.

That is, as a period in which the influence of ammonia generation appears on the detected value of the sensor cell current Is corresponding to NOx in the gas concentration of the exhaust gas introduced into the gas concentration sensor 100, the lean atmosphere of the exhaust gas changes to the rich atmosphere. The switching to or the switching from the rich atmosphere to the lean atmosphere is detected by the output of the λ cell 180.
That is, the λ cell voltage Vp detected by the λ cell 180 is 0.
Since the period of 45 [V] or more corresponds to the switching of the exhaust gas from the lean atmosphere to the rich atmosphere to the switching from the rich atmosphere to the lean atmosphere, the λ cell voltage Vp is set as the mask period. Is 0.45
The value detected by the sensor cell 130 immediately before the voltage becomes equal to or higher than [V] is held. As a result, NOx in the gas concentration of the exhaust gas introduced into the gas concentration sensor 100 'is increased.
It is possible to eliminate the influence of the ammonia generation component on the detected value of the sensor cell current Is depending on the above, and it is possible to accurately detect the NOx concentration.

By the way, in the above-mentioned embodiment and modification, the NO concentration sensor 100 is provided downstream of the NOx storage reduction catalyst 14 arranged in the exhaust passage 12 of the internal combustion engine 1.
Although the x sensor 28 is provided, the present invention is not limited to this, and the NOx sensor 28 is provided upstream of the NOx storage reduction catalyst 14, and the oxygen sensor 27 is provided as the NOx storage reduction. It may be arranged on the downstream side of the catalyst 14. In this case, NO with the NOx sensor 28
Although the NOx concentration after passing through the x storage reduction catalyst 14 cannot be detected, the NOx concentration in the exhaust gas flowing into the NOx storage reduction catalyst 14 is detected to accumulate the NOx storage amount in the NOx storage reduction catalyst 14. By estimating, the NOx reduction control for the NOx storage reduction catalyst 14 can be executed.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an internal combustion engine and its peripheral equipment to which a gas concentration detecting device for an internal combustion engine according to first and second examples of an embodiment of the present invention is applied.

FIG. 2 is a configuration diagram showing a structure of a gas concentration sensor that constitutes a NOx sensor in a gas concentration detection device for an internal combustion engine according to a first example of an embodiment of the present invention.

FIG. 3 is a configuration diagram showing a structure of the gas concentration sensor of FIG.

FIG. 4 is a circuit diagram showing an electrical configuration of a gas concentration detecting device for an internal combustion engine according to a first example of an embodiment of the present invention.

FIG. 5 is a flowchart showing a mask control processing procedure in the CPU in the control circuit used in the gas concentration detection apparatus for the internal combustion engine according to the first example of the embodiment of the present invention.

FIG. 6 is a time chart showing transition states of various control amounts corresponding to the processing of FIG.

FIG. 7 is a first modification of the mask control processing procedure in the CPU in the control circuit used in the gas concentration detection apparatus for the internal combustion engine according to the first example of the embodiment of the present invention. It is a flowchart shown.

8 is a flowchart showing a gas concentration estimation process in the mask control of FIG.

FIG. 9 is a time chart showing transition states of various control amounts corresponding to the processes of FIGS. 7 and 8.

FIG. 10 is a second modification of the mask control processing procedure in the CPU in the control circuit used in the gas concentration detection apparatus for the internal combustion engine according to the first example of the embodiment of the present invention. It is a flowchart shown.

FIG. 11 is a map for setting the mask timing in FIG. 10 according to operating conditions.

FIG. 12 is a map for setting the mask release timing in FIG. 10 according to operating conditions.

13 is a time chart showing transition states of various controlled variables corresponding to the processing of FIG.

FIG. 14 is a third modification of the mask control processing procedure in the CPU in the control circuit used in the gas concentration detection apparatus for the internal combustion engine according to the first example of the embodiment of the present invention. It is a flowchart shown.

15 is a time chart showing transition states of various controlled variables corresponding to the processing of FIG.

FIG. 16 is a configuration diagram showing a structure of a gas concentration sensor that constitutes a NOx sensor in a gas concentration detection device for an internal combustion engine according to a second example of the embodiment of the present invention.

FIG. 17 is a flowchart showing a mask control processing procedure in the CPU in the control circuit used in the gas concentration detection apparatus for the internal combustion engine according to the second example of the embodiment of the present invention.

FIG. 18 is a time chart showing transition states of various controlled variables corresponding to the processing of FIG.

[Explanation of symbols]

1 Internal combustion engine 14 NOx storage reduction catalyst 28 NOx sensor 30 ECU (electronic control unit) 100,100 'gas concentration sensor 110 pump cells 120 monitor cells 130 sensor cells 144 First chamber 146 Second chamber 180 lambda cell 200 control circuit

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) F02D 45/00 368 G01N 27/46 327N G01N 27/416 327A 327E 327G 327R 331

Claims (11)

[Claims] 1. A pump cell for discharging or pumping oxygen in a gas to be detected introduced into a chamber, a sensor cell for detecting a concentration of a specific gas component from the gas after passing through the pump cell, and a residual oxygen concentration in the chamber. A gas concentration sensor of a composite type for holding each cell in an active state based on the element resistance of the solid electrolyte forming each cell, and a monitor cell for detecting At least one exhaust gas purification means for purifying exhaust gas from the internal combustion engine, and a current flowing through the sensor cell of the gas concentration sensor arranged on the upstream side or the downstream side of the exhaust gas purification means is detected, and from the detected value Gas concentration detecting means for sequentially detecting the concentration of a specific gas component in the exhaust gas, wherein the gas concentration detecting means is introduced into the gas concentration sensor. The internal combustion engine is characterized in that detection is stopped during a period in which the generated exhaust gas changes from a lean atmosphere to a rich atmosphere, and at least one of a detection value is masked and a detection value immediately before a rich atmosphere is held. Gas concentration detector. 2. The gas concentration detecting means outputs the held detection value or outputs the estimated prediction value or stops the output function during the period. Gas concentration detector for internal combustion engine. 3. A pump cell for discharging or pumping oxygen in the gas to be detected introduced into the chamber, a sensor cell for detecting the concentration of a specific gas component from the gas after passing through the pump cell, and a residual oxygen concentration in the chamber. A gas concentration sensor of a composite type for holding each cell in an active state based on the element resistance of the solid electrolyte forming each cell, and a monitor cell for detecting At least one exhaust gas purification means for purifying exhaust gas from the internal combustion engine, and a current flowing through the sensor cell of the gas concentration sensor arranged on the upstream side or the downstream side of the exhaust gas purification means is detected, and from the detected value Gas concentration detecting means for sequentially detecting the concentration of a specific gas component in the exhaust gas, wherein the gas concentration detecting means is introduced into the gas concentration sensor. The exhaust gas is changed from the lean atmosphere to the rich atmosphere, and after a lapse of a predetermined period of time, detection is stopped, and at least one of the detection value is masked and the detection value immediately before the rich atmosphere is held is performed. For detecting gas concentration in internal combustion engine. 4. The gas concentration detecting means outputs the held detection value or outputs the estimated prediction value or stops the output function after the lapse of the predetermined period. A gas concentration detection device for an internal combustion engine according to item 1. 5. The gas concentration detection means, when the exhaust gas introduced into the gas concentration sensor changes from a rich atmosphere to a lean atmosphere, stops detection or masks the detected value or holds the detected value. The gas concentration detecting device for an internal combustion engine according to claim 1 or 3, wherein the gas concentration detecting device is released and switched to a normal detection state. 6. The gas concentration detecting means stops the detection or masks the detection value or a detection value after the elapse of a predetermined period after the exhaust gas introduced into the gas concentration sensor changes from a rich atmosphere to a lean atmosphere. 4. The gas concentration detecting device for an internal combustion engine according to claim 1, wherein the hold state is released and the normal detection state is switched to. 7. The gas concentration detecting means switches the exhaust gas introduced into the gas concentration sensor from a lean atmosphere to a rich atmosphere or from a rich atmosphere to a lean atmosphere according to an output from the pump cell. The gas concentration detecting device for an internal combustion engine according to any one of claims 1 to 6, wherein the gas concentration detecting device according to any one of claims 1 to 6 is used. 8. The gas concentration sensor further comprises a λ cell that outputs an electromotive force according to the oxygen concentration in the chamber.
5. A gas concentration detecting device for an internal combustion engine according to claim 3. 9. The gas concentration detecting means uses the output from the λ cell to switch the exhaust gas introduced into the gas concentration sensor from a lean atmosphere to a rich atmosphere or from a rich atmosphere to a lean atmosphere. The gas concentration detecting device for an internal combustion engine according to claim 8, wherein the determination is made according to the determination. 10. A pump cell for discharging or pumping oxygen in a gas to be detected introduced into a chamber, a sensor cell for detecting a concentration of a specific gas component from the gas after passing through the pump cell, and a residual oxygen concentration in the chamber. A gas concentration sensor of a composite type for holding each cell in an active state based on the element resistance of the solid electrolyte forming each cell, and a monitor cell for detecting At least one exhaust gas purification means for purifying exhaust gas from the internal combustion engine, and a current flowing through the sensor cell of the gas concentration sensor arranged on the upstream side or the downstream side of the exhaust gas purification means is detected, and from the detected value Gas concentration detecting means for sequentially detecting the concentration of a specific gas component in the exhaust gas, wherein the gas concentration detecting means is connected to the gas concentration sensor. After a lapse of a predetermined period from the output start time of the sensor cell for the entered exhaust gas, a predetermined period according to the operating conditions of the internal combustion engine is set, during the predetermined period, the detection is stopped, the detection value is masked, A gas concentration detecting device for an internal combustion engine, wherein at least one of the detection values immediately before a predetermined period is held. 11. The gas concentration detecting means outputs the held detection value or outputs the estimated prediction value or stops the output function during the predetermined period. A gas concentration detection device for an internal combustion engine as described above.