JPH01297550A - Method of discriminating activity of oxygen concentration sensor - Google Patents

Abstract

PURPOSE:To exactly discriminate the state of an oxygen concn. sensor and to provide the improvement in the exhaust gas characteristics and fuel ratio of an engine, etc., by regulating a battery element terminal voltage, oxygen pump element voltage and heating element heater resistance value in such a manner that all these values are respectively within prescribed ranges. CONSTITUTION:A sensor body 20 has nearly a cubic shape and consists of a solid electrolytic material having oxygen ion conductivity (for example, zirconium dioxide). The body 20 is formed with 1st and 2nd wall parts 21, 22 in parallel with each other and a gas diffusion chamber 23 is delineated in both wall parts 21, 22. This diffusion chamber 23 is communicated with a discharge pipe via an introducing hole 24 and an exhaust gas is introduced through the hole 24 therein. A gas reference chamber 26 is formed between the wall part 21 and an outside wall part 25 formed to the wall part 21 side. Electrode pairs 27a, 27b on one side consisting of platinum are provided opposite to each other to both side faces of the wall part 21 to form a radio wave element 28 and the electrodes 29a, 29b on the other side are similarly provided to both side faces of the wall part 22 to form an oxygen pump 30. A heater 31 which accelerates the activity of the elements 28 and 39 by heating the same is provided to the outside wall part 25.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a method for determining the activity of an oxygen concentration sensor that detects the oxygen concentration of exhaust gas from an internal combustion engine, and particularly relates to a method for determining the activity of an oxygen concentration sensor that detects the oxygen concentration of exhaust gas from an internal combustion engine. The present invention relates to a method for determining the activity of an oxygen concentration sensor.

(Prior art) Conventionally, in order to improve the exhaust characteristics and fuel efficiency of internal combustion engines, the oxygen concentration of exhaust gas is detected, and the air-fuel ratio (hereinafter referred to as A technique for feedback-controlling the "supply air-fuel ratio" (referred to as "supply air-fuel ratio") to a target air-fuel ratio is well known, and in this case, as an oxygen concentration sensor for detecting the oxygen concentration in exhaust gas, a A so-called proportional type is known.

In addition, the output characteristics of this type of oxygen concentration sensor depend on temperature, and in order to accurately detect oxygen concentration, the sensor must be activated, that is, the sensor body must be at a temperature higher than a predetermined temperature.
(Since it is necessary that the air-fuel ratio is maintained, various methods have been proposed for determining this activation in order to start feedback control of the supply air-fuel ratio early, especially immediately after startup. This conventional activation determination method determines that the oxygen concentration sensor is in an activated state when the terminal voltage of the battery element is within a predetermined range.

(Problem to be Solved by the Invention) However, the conventional determination method described in -■- may determine that the oxygen concentration sensor is in an active state even though the temperature is low, resulting in incorrect detection results immediately after startup. Since feedback control of the supplied air-fuel ratio is performed based on this, there is a problem in that exhaust characteristics, fuel efficiency, etc. at this time deteriorate.

That is, in this type of oxygen concentration sensor, the battery element f and the oxygen pump element P are arranged separated by a gas diffusion chamber into which exhaust gas is introduced, and the exhaust gas in the gas diffusion chamber has a heat insulating effect. In addition, since the oxygen ion conductive solid electrolyte material (e.g. Z ro 2) that integrally constitutes the battery element and oxygen pump element has low thermal conductivity, the temperature of the battery element is lower than that of the oxygen pump element. may not match that of In particular, since the oxygen pump element is exposed to the exhaust gas, when the temperature of the exhaust gas is low, such as when the engine is under low load conditions, the temperature of the oxygen pump element is significantly lower than that of the battery element. This also applies to the case where the heater is provided on the battery element side.

On the other hand, the conventional determination method is configured to determine activation based only on the terminal voltage of the battery element.
When only the temperature of the oxygen pump element is low as in the series of cases, it is erroneously determined that the oxygen pump element is in the active state, resulting in the problem described in item I.

In this case, it is conceivable to install temperature sensors for each of the battery element and oxygen pump element, but there is no sensor that can withstand high temperatures to detect the extremely high temperature of these elements, and there is no temperature sensor located far from the element. If a sensor is provided, it is still not possible to accurately determine Δill of the element 411 degrees, and the above-mentioned problem cannot be solved.

The present invention has been made in order to solve the drawbacks of the conventional techniques described in I-I, and it is possible to accurately determine the activation state, thereby improving the exhaust characteristics and fuel efficiency of the engine immediately after starting. The purpose of this invention is to provide a method for determining the activity of an oxygen concentration sensor.

(Means for Solving the Problems) In order to achieve the above object 1, the present invention is arranged in the exhaust system of an internal combustion engine, and each consists of an oxygen ion conductive solid electrolyte material and an m pole sandwiching the solid electrolyte material for gas diffusion. An oxygen concentration detection element having an oxygen pump element and a battery element forming a restricted region, and the 'l'i! of the oxygen pump element. In a method for determining the activity of an oxygen concentration sensor, the method includes a pump current supply means for supplying a pump current between electrodes, and a heating element that heats the oxygen concentration detection element in accordance with a heater current supplied from the heater current supply means. Recorded battery cell element voltage,
When the terminal voltage of the oxygen pump element 111j and the heater resistance value of the heating element are all within respective predetermined ranges, it is determined that the oxygen purulence sensor 111j is activated.

(Example) An example of the present invention will be described below with reference to the drawings.

FIG. 1 is an overall configuration diagram of a fuel supply control device including an oxygen concentration sensor to which the discrimination method of the present invention is applied. In the figure, reference numeral 1 denotes an oxygen concentration sensor (hereinafter referred to as [02 sensor J), which is attached to the exhaust gas W3 of the internal combustion engine 2. 02
The sensor l has a configuration described below, detects the oxygen concentration of the exhaust gas, and supplies a signal corresponding to the detected value to the electronic control unit (hereinafter referred to as rECUJ) 4. 0
A three-way catalyst 5 is installed in the exhaust pipe 3 on the downstream side of the 2 sensor 1, and purifies components such as 1-(C, Go, NOx, etc.) in the exhaust gas.

The engine 2 is, for example, a four-cylinder, four-cycle engine, and intake air is supplied through an air cleaner 6 and an intake pipe 7.

The air cleaner 6 has an intake 1H (T^) sensor 8 (
-J is detected, the intake air temperature T^ is detected, and a corresponding electric signal is supplied to the ECU 4.

A throttle valve 9 is arranged in the middle of the intake pipe 7. A throttle valve opening (OT11) sensor lO is connected to the throttle valve 9, and the opening OT of the throttle valve 9 is detected.
It outputs an electric signal according to I+ and supplies it to IECU4.

The fuel injection valve 11 is located between the engine 2 and the throttle valve 9.
Each injector 11 is provided for each cylinder a little upstream of an intake valve (not shown) in the intake pipe 7, and each injection valve 11 is connected to a fuel pump (not shown) and electrically connected to E C:tJ4. The valve opening time of fuel injection is controlled by the signal from the ECU 4.

On the other hand, immediately downstream of the throttle valve 9, a tracheal absolute pressure (1) sensor 12 is provided, which supplies an electric signal corresponding to the intake pipe absolute pressure I)B to the ECIJ4.

The temperature of the engine cooling water installed in the main body of engine 2 (
Tw) The sensor 13 consists of a thermistor, etc., and detects the engine cooling water temperature 'I''W and sends a corresponding electrical signal to the IE C
Supply to U4. Engine speed (Ne) sensor 14
is attached around the camshaft or crankshaft (not shown) of the engine 2. The engine rotation speed sensor 14 outputs a pulse (hereinafter referred to as r i' D C signal pulse J) at a predetermined crank angle position every 180 degree rotation of the crankshaft of the engine 2, and supplies it to the ECU 4.

FIG. 2 shows the configuration of the sensor body 20 of the 02 sensor I.

The sensor main body 20 has a substantially cubic shape and is made of an oxygen ion conductive solid electrolyte material (for example, ZrOz (zirconium dioxide)). First and second wall portions 21 and 22 are formed in the sensor body 20 so as to extend downward from each other, and a gas diffusion chamber (gas diffusion restricted area) 23 is defined between the two wall portions 21 and 22. . The gas diffusion chamber 23 communicates with the exhaust pipe 3 through an introduction hole 24, and exhaust gas is introduced through the introduction hole 24. Further, a gas reference chamber 26 is formed between the first wall portion 21 and an outer wall portion 25 formed on the wall portion 21 side, and air is introduced into the gas reference chamber 26.

One pair of electrodes 27a and 27b made of PL (platinum) are provided on both sides of the first wall portion 21 so as to face each other to form a battery element 28; Similarly, the other pair of electrodes 29a and 29b are provided on both sides of the oxygen pump element 22 to form an oxygen pump element 3°. On the other hand, the outer wall portion 25 includes an electronic device 28 and an oxygen pump device 30.
A heater (heating element) 31 is provided to heat and promote activation of the .

FIG. 3 is a diagram showing the circuit configuration of an air-fuel ratio control device consisting of 02 sensor l, 1ζCU4, etc.

1); Of the electrodes j, the inner electrodes 27b and 29b, that is, the electrode on the gas diffusion chamber 23 side, are grounded, and the outer electrode 27a of the battery element 28 is connected to the inverting input terminal of the differential amplifier circuit 32. has been done. The differential amplifier circuit 32 is
Together with the base 71+1 voltage source 33 connected to its non-inverting input end and the switch 34 connected to its output end, it constitutes a current supply circuit (pump current supply means) 35 for the 02 sensor I.

0; 1 group 7111 voltage source 33 group rll! Voltage Vs
o is set to the voltage (for example, 0.4V) that occurs in the battery element 28 when the supplied air-fuel ratio is equal to the stoichiometric mixture ratio.

The switch 34 is connected to the outer electrode 29a of the oxygen pump element 30 via a current detection resistor 36.

In addition, 111jl! L! The current supply circuit 35 and the current detection lft resistor 36 are incorporated into the ■ζCU4.

The voltage across the current detection resistor 36 is l', CU
The signal is supplied to the 4th A/D converter of 4. In addition, each terminal voltage VS, VP of the battery element 28 and the oxygen pump element 30
The applied voltage Vo and current amount 1++ of the heater 31 are sequentially applied to the A/D converter 40 by the multiplexer 402.
3. Furthermore, an intake temperature sensor 8, a throttle valve opening sensor 10. The respective output signals from the intake pipe absolute pressure sensor 12 and the engine coolant temperature sensor 13 are corrected to a predetermined voltage level by a level conversion circuit 404, and then sequentially sent to an A/D converter 406 by a multiplexer 405.
supplied to

A/D converters 401, 403 and 406 sequentially convert the supplied analog signals into digital signals and send them to the central processing unit (hereinafter referred to as [CPUJ]) via a data bus 407.
) 408.

The output signal from the engine speed sensor 14 is converted into a waveform ql by a waveform path I09, and then is supplied to CI) tJ408 as an i'DC signal pulse, and is also supplied to the counter O. The counter old 0 measures the time interval from the previous input of the C signal pulse of the engine rotation speed sensor 14 to the current input, and its a1 value Mc3 is proportional to the reciprocal of the engine rotation speed Ne. .Counter/110 supplies this counted value Me to c+->u4os via data bus 407.

The CPU 108 further transfers a read-only memory (hereinafter referred to as FROM J) 411 via a data bus 407;
Random access memory (hereinafter referred to as “R to MJ”) 41
2 and drive circuits 3 to 415. ROM
4+1 temporarily stores the calculation results in CPU U2O5, ROM4+1 is the control program executed by CI) U/108, and the fuel injection time 'I'' of the fuel injection valve 11.
It stores maps, etc. for calculating OUT.

The CPU 2O5 determines the on/off state of the heater 31, the applied voltage Vu, and the on/off state of the switch 31 of the current supply circuit 35 according to the control program shown in FIG. 4, which will be described later, and is stored in the ROM 411. A drive signal is supplied to the heater 31 and the switch 34 via the drive circuit 413 and the old circuit 4.

Further, the CPU 2 O 5 determines the engine operating state such as the feedback operating range based on the various engine parameter signals described in 01j including the detection signal of the 02 sensor l, and injects fuel according to the control program (not shown) according to the engine operating state. Fuel injection time of valve 11 Too
r is calculated and a drive signal based on the calculation result is sent to the drive circuit 4.
+5 to the fuel injection valve 11. Thereby, during feedback operation of the lever engine 2, the supplied air-fuel ratio is feedback-controlled to the target air-fuel ratio.

Next, the operation of the air-fuel ratio control device having the above configuration will be explained.

First, the function of the 02 sensor l will be explained. As the engine 2 operates, exhaust gas flows into the gas diffusion chamber 23 through the introduction hole 24.
When the outside air is introduced into the air, a difference in oxygen concentration occurs between the inside of the gas diffusion chamber 23 and the inside of the gas reference chamber 26 into which outside air is introduced.

When the battery element 28 is in an active state, the '[I electrode 27 a r 27
A voltage Vs is generated during the period b, and this voltage Vs is supplied to the inverting input terminal of the differential amplifier circuit 32. As mentioned above, the reference voltage V supplied to the non-inverting input terminal of the differential amplifier circuit 32
s.

is the battery element 2 when the supplied air-fuel ratio is equal to the stoichiometric mixture ratio.
The voltage Vs generated at 8 is set to Vs.

Therefore, when the supplied air-fuel ratio is on the lean side, the voltage Vs of the battery element 28 becomes smaller than the reference voltage Vso, so that the output level of the differential amplifier circuit 32 becomes a positive level, and this positive level voltage is applied to the switch 34. The current is applied to the oxygen pump element 30 via the current detection resistor 36. By applying this positive level voltage, when the oxygen pump element 30 is in the active state, oxygen in the gas diffusion chamber 23 is ionized and released through the electrode 29b, the second wall 22, and the electrode 29a. , 02 The pump current is pumped to the outside of the sensor I, and the pump current is pumped from the electrode 29a to @l
flows towards i429 b.

On the other hand, when the supplied air-fuel ratio is on the rich side, the voltage Vs of the battery element 28 becomes thicker than the base 1111 voltage Vso, and the output level of the differential amplifier circuit 32 becomes a negative level. 02 Oxygen outside the sensor 1 passes through the oxygen pump element 'F30 to the gas diffusion chamber 23.
The pump current flows from electrode 29b toward current 29a. Further, when the supplied air-fuel ratio is equal to the stoichiometric mixture ratio, the voltage Vs of the battery element 28 becomes equal to the reference voltage Vso, so the output level of the differential amplifier circuit 32 becomes O, and oxygen is not pumped out or pumped in. , so no pump current flows.

As described below, oxygen is pumped out and pumped in so that the oxygen concentration in the gas diffusion chamber 23 is constant, and the pump current flows, so this pump current value IP is on the lean side and on the lean side of the supplied air-fuel ratio. On the rich side, it becomes proportional to the oxygen concentration of the exhaust gas.

This pump current value 1r is supplied to the ECU 4 as the detection signal Y) of the 02 sensor 1, as described above, due to the voltage drop appearing across the current detection resistor 36.

FIG. 4 shows a flowchart of a program for determining activation of the 02 sensor l according to the present invention.

First, it is determined whether the engine rotation speed Ne is equal to or higher than a predetermined rotation speed Nex (for example, 400 rpm) (step 41). If the answer is negative (No), it is determined that the engine 2 is cranking, and a heater current supply stop command is issued to maintain the heater 31 in an inoperative state (step 42).

This is because the heater element (not shown) of the heater 31 is often cold when the engine 2 is cranking, and this prevents cracks from occurring due to a sudden rise in temperature of the heater element when electricity is applied in this state. It's for a reason.

Next, step 43 generates a pump current supply stop command.
), that is, the switch 34 of the current supply circuit 35 is turned off (opened).
state so that the pump current does not flow, then 02
It is determined that the sensor l is in an inactive state (step 44).
, 02, the program is terminated without performing feedback control according to the detection signal of the sensor l.

The answer to step 41 is i′r constant (Yes), that is, Ne
When Ne1 is satisfied, it is determined whether a predetermined period of time (for example, 5 seconds) has elapsed after the condition was satisfied (step 45). 0 if this answer is negative (NO)
Execute step 42 and subsequent steps in 1j to end this program. This prevents the heater 31 from being energized when the engine rotation is still unstable.

0; The answer to Step 45 of j is affirmative (Yes), that is, Ne
When the predetermined time L1 has elapsed after ≧Ncl is established, a heater current supply command is generated based on the applied voltage Vu calculated by the CPU 2 O 5 to put the heater 31 into an operating state (step 46).

Next, the resistance value Ro of the heater 31 is greater than or equal to the first predetermined value r (for example, 3Ω), and the second predetermined value Ru l 2
(for example, 8Ω) or less (step 47). This resistance value 11 is the applied voltage V of the heater 31
It is calculated from u and the current amount 1u. If the answer to step 47 is negative (No), that is, R11<R1111 or Ru>
When R old 2 is established and the heater element is in a low temperature state or a high temperature state, 0; step 43 and subsequent steps in j are executed and the program is terminated. This can prevent decomposition of ZrO2 and deterioration of the oxygen pump element 30 due to the flow of pump current when the oxygen pump element 30 is at a low temperature, for example.

The answer to step 47 is affirmative (Yes), that is, R111.
When 1≦l≦R1+12 is established and therefore the heater element is not in the low 41 state or high temperature state, a pump current supply command is generated (step 48), that is, the switch 34 of the current supply circuit 35 is turned on (closed). state so that the pump current can flow.

Next, it is determined whether the terminal voltage Vs of the battery element J'28, the terminal voltage Vp of the oxygen pump IAI' 30, and the resistance value Ru of the heater 31 are within respective predetermined ranges. That is, whether the terminal voltage Vs of the battery element 28 is less than the first predetermined value Vst (for example, 250 mV) or less than the second predetermined value VS2 (for example, 650 rnV) (step 49); Terminal voltage V of oxygen pump element 30
Whether P is greater than or equal to the first predetermined value VPI (e.g. -2V) and less than or equal to the second predetermined value V2 (e.g. 2V) (step 50) and the resistance value R++ of the heater 31 is 01
The third predetermined value RI is greater than the first predetermined value RI
121 (for example, 5.0Ω) and less than a fourth predetermined value RI+22 (for example, 6.2Ω), which is smaller than the second predetermined value I7112 (step 51).

As is clear from the above, the resistance value of the heater 31 is 11
The predetermined range is 0; it is narrower than the range set in step 47, and is set to a value indicated when the heater 31 is at an appropriate temperature. In addition, the battery element 28 and the oxygen pump element 30
The above-mentioned predetermined range of the terminal voltages VS and VP indicates that the oxygen concentration in the gas diffusion chamber 23 is close to the acid IA concentration corresponding to the stoichiometric mixing ratio, and therefore the output of the 02 sensor l is stable and the oxygen It is set to a value that indicates when the concentration can be accurately detected.

Either the answer to step 49 or 50 is negative (No
), that is, Vs (Vs+ or VS>VS2 or VP<
When either VPI or V P > V P 2 holds true, the oxygen concentration in the gas diffusion chamber 23 does not show a value close to the oxygen concentration corresponding to the stoichiometric mixing ratio, that is, a value on the lean side or rich side. It is determined that the output of the 02 sensor 1 is not stable, and the program is terminated at step 44 indicated by I'+ij. Further, when the answer to step 51 is negative (No), the heater 3
Similarly, if the temperature in step 1 is not stable, perform step 4.
Execute step 4 to end this program. The resistance value R of the heater 31 reflects the temperature of the old battery element 28 and the oxygen pump element 30, and the output of the 02 sensor l is affected by the 1llllt degree change in these elements. Fluctuations in the output of the 02 sensor l due to this influence can be prevented.

1) All answers to steps 4 to 51 in 1j are t1 constant (
Yes), that is, the terminal voltage Vs of the battery element 28.

If the terminal voltage VP of the oxygen pump element Y30 and the resistance value 1<11 of the heater 31 are all within the respective predetermined ranges described above, it is determined that the 02 sensor I is in the active state.Step 52 ), when the engine 2 is in the feedback operation fl region, feedback control of the supply air-fuel ratio is performed according to the detection signal of the 02 sensor l, and this program ends.As described above, the battery element 28 and the oxygen pump element T -30 is in a high temperature state and the oxygen concentration in the gas diffusion chamber 23 shows a value close to the oxygen concentration corresponding to the stoichiometric mixing ratio, by determining that the 02 sensor l is in the active state, It is possible to accurately determine the state in which the output is stable and the oxygen concentration can be accurately detected, and based on the determination result, feedback control of the supplied air-fuel ratio can be performed based on the detection signal S'f of the 02 sensor l. It is possible to improve the exhaust characteristics and fuel efficiency of the engine.

Further, even if the heater 31 is installed at a different position from that of this embodiment, the same effect as described above can be obtained.

(Effects of the Invention) As described in detail hereinafter, according to the present invention, the active state of the oxygen concentration sensor, that is, the state in which the oxygen concentration sensor can accurately and stably detect the oxygen concentration of exhaust gas, can be accurately determined. I can do it,
Therefore, it is possible to improve the engine exhaust characteristics and fuel efficiency immediately after starting the engine.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention, in which Fig. 1 is an overall diagram of the obstetric supply control device, Fig. 2 is a perspective view showing the sensor body of the 02 sensor, and Fig. 3 is a diagram of the air-fuel ratio control device. FIG. 4 is a flowchart of a subroutine for determining the activity of the 02 sensor according to the present invention.]...02 sensor (oxygen concentration sensor), 2...internal combustion engine, 3... - Exhaust pipe, 4... Electronic control unit I- (ECU) (heater current supply means), 21.
22... 1st. Second wall (solid electrolyte material), 23.
...Gas diffusion chamber (gas diffusion restricted area), 27a, 27b. 29a, 291)...electrode, 28...battery element, 3o
. . . Oxygen pump element, 31 . . . Heater (heating element), 35 . . . Current supply circuit (pump current supply means). Applicant Ki111 Giken Kogyo Co., Ltd.

Claims (1)

[Claims] 1. An oxygen concentration detection element disposed in the exhaust system of an internal combustion engine, each comprising an oxygen ion conductive solid electrolyte material and electrodes sandwiching the same, and forming a gas diffusion restricted area, an oxygen concentration detection element and an oxygen concentration detection element; Determining the activity of an oxygen concentration sensor comprising a pump current supply means for supplying a pump current between electrodes of an oxygen pump element, and a heating element that heats the oxygen concentration detection element according to the heater current supplied from the heater current supply means. The method is characterized in that it is determined that the oxygen concentration sensor is activated when a terminal voltage of the battery element, a terminal voltage of the oxygen pump element, and a heater resistance value of the heating element are all within respective predetermined ranges. A method for determining the activity of an oxygen concentration sensor.