JPS6276452A - Oxygen concentration detection device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

Blood Loss n1 The present invention relates to an oxygen concentration detection device for detecting oxygen concentration in gas such as engine exhaust gas. 1) For the purpose of gas purification and fuel efficiency improvement of the internal combustion engine, the oxygen concentration in the exhaust gas is detected, and the air-fuel ratio of the mixture supplied to the engine is set to the target air-fuel ratio according to the detection result. There is an air-fuel ratio control device that performs feedback control 211. There is an oxygen concentration detection device used in such an air-fuel ratio control device that generates an output proportional to the oxygen concentration in the gas to be measured (Japanese Patent Laid-Open No. 153155/1983). In such an oxygen concentration detection device 43, a pair of flat plate f
An oxygen concentration detector is provided that monitors the ionically conductive solid IA electrolyte material. The solid electrolyte material is placed in the gas to be measured, and electrodes are formed on each side of the solid electrolyte material, and the solid electrolyte materials are arranged in parallel so as to face each other with a predetermined gap in between. It is located. One side of solid electrolyte 71 material is oxygen 1? As a pump element, the other acts as a lightning pond element for determining the oxygen permeability ratio ml. When a current is supplied between the electrodes of the oxygen pump element so that the electrode on the gap side becomes the negative electrode in the gas to be measured, the oxygen gas in the gap gas is ionized on the negative electrode side of the oxygen pump cord, and the oxygen pump It moves within the element f toward the positive electrode surface and is released from the positive electrode surface as oxygen gas. At this point, due to the decrease in oxygen gas in the gap, the gas in the gap and the gas in the gap are reduced. Since there is a difference in oxygen concentration between the gas outside the element and the gas outside the element, if the pump current value supplied to the B element pump element is changed so as to keep the voltage at a constant value, the pump current 1iCi at a constant temperature will be It is almost linearly proportional to the acid^ concentration. Furthermore, by keeping the supply ratio rXj to the oxygen pump element constant, a voltage approximately proportional to the oxygen concentration in the gas to be measured is generated between the electrodes of the battery element. In such an oxygen concentration detection device, when an excessive current is supplied to the oxygen pump element, a blackening phenomenon occurs in which oxygen is taken away from the solid electrolyte material. For example, when ZrO2 (zirconium dioxide) is used as the solid electrolytic material, excessive current supply to the oxygen pump cord decomposes M element O2 from ZrO2 and deposits zirconium Zr. This blackening causes rapid deterioration of the oxygen pump element and deteriorates its performance as an oxygen concentration detector, so the value of the current supplied to the oxygen pump element should be smaller than the value in the area where the blackening phenomenon occurs. There must be. Figure 1 shows the oxygen concentration and the pump current fif supplied to the oxygen pump cord, using the voltage Vs generated in the battery element as a parameter.
The relationship characteristics with fIp and the area where the blackening phenomenon occurs are shown, and the boundary line with the area where the blackening phenomenon occurs is a linear function characteristic as shown in h), which is a one-man characteristic with the voltage Vs as a parameter. Further, in an oxygen concentration detection device, a heater is usually provided to heat the oxygen concentration detector, that is, the oxygen pump element and the battery element. This is because the temperature of the oxygen concentration detector is set to a predetermined hot water temperature (for example, 650℃) by the heat generated by the heater.
℃), the oxygen concentration detector will not become active and voltage will not be applied to the battery element.

[This is because J hardly occurs, so output characteristics proportional to yarn resistance density cannot be obtained. However, in an oxygen concentration detection device that outputs a current proportional to oxygen concentration, when the oxygen concentration detector is in an inactive state, current is supplied to the battery element in order to raise the output voltage to a predetermined constant value. The problem is that since the means operates to increase the current value supplied to the oxygen pump element, the current value supplied to the oxygen pump element may exceed the blackning phenomenon occurrence limit 116, causing the blackning phenomenon to occur. was there. In addition, in the oxygen concentration proportional voltage output type oxygen concentration detection device, when the oxygen concentration detector is in an inactive concave state, it is determined that the air-fuel ratio is leaner than the target air-fuel ratio from the voltage between the electrodes of the battery element. The air-fuel ratio of the determined C-supply air is controlled in the rich direction. However, as the air-fuel ratio becomes richer, the blackening phenomenon occurrence boundary value becomes smaller, and the supply current value to the anti-Δ pump element is constant, so when the air-fuel ratio is controlled in the rich direction, the supply current value to the oxygen pump element decreases. There has been a problem in that the blackening phenomenon may occur when the amount exceeds the threshold value for the occurrence of the blackning phenomenon. fl Toyotan] Therefore, an object of the present invention is to provide an oxygen concentration detection device that can prevent the blackening phenomenon when the oxygen concentration detector is inactive. The oxygen concentration detection device of the present invention supplies a minute current between the electrodes of the battery element, detects the internal resistance value of the battery element from the voltage between the electrodes of the battery element that helps supply the minute current, and detects the internal resistance value of the battery element. IR"fl is used to supply a current for oxygen concentration detection between the electrodes of the oxygen pump element when the current is less than a reference value. Hereinafter, embodiments of the present invention will be described with reference to the drawings. Figure 2 shows an air-fuel ratio control device using an oxygen concentration proportional voltage output type oxygen concentration detection device. M-element CJ consisting of an oxygen pump element 1 and a battery cable 2 in the form of an element
The degree detector is disposed within the exhaust pipe (not shown). The main body of the oxygen pump element 1 and the battery element 2 is made of an oxygen ion conductive solid electrolyte material, and a gap 3 is formed between one end thereof, and the other end thereof is connected to each other via a spacer 4. Further, rectangular electrode plates 5 to 8 made of porous heat-resistant metal are provided on the front and back surfaces of one end of the oxygen pump element 1 and the battery element 2, and the lead wires 5a of the electrode plates 5 to 8 are provided on the other end surface. 8a are formed. A constant current circuit 1 is connected between the electrode plates 5 and 6 of the oxygen pump cord 1.
A constant current is supplied from 1. The constant current circuit 11 is a sink type circuit, and the operational amplifier 12. It consists of an NPNI transistor 13 and resistors 15 to 17. operational amplifier 12
The output terminal of is connected to the bases of transistors 1 to 13 via a resistor 15. Further, the emitters of transistors 1 to 13 are grounded through a resistor 16 and connected to the inverse Iλ input terminal of the operational amplifier 12 through a resistor 17. 1-ransistor 13
The collector of l'l' is the inner electrode plate 6 of l pump element 1.
[This is connected via the lead wire 6a, and the external
A voltage V[1 is supplied to the M bar 5 via a lead wire 5a. On the other hand, the inner electrode plate 7 of the battery cord 2 is grounded via the lead wire 7a, and the outer electrode plate 8 is connected to the operational amplifier 26 via the lead wire 8a. It is connected to a non-inverting amplifier 30 consisting of resistors 27-29. The output terminal of the non-inverting amplifier 30 is connected to the Vs'- input terminal of the air-fuel ratio control circuit 31. D is connected to the Ic control output terminal of the air-fuel ratio control circuit 31.
/A converter 32 is connected, and D/A converter 32 generates a voltage according to I+ value command data output from the Ic control output terminal of air-fuel ratio control circuit 31. D/A strange 1! l!
! The output terminal of 2; 32 is connected to an integrating circuit 34 via a voltage follower circuit 33 consisting of an operational amplifier. The integrating circuit 34 is made up of resistors 35, 36 and a capacitor 37, and its output voltage is supplied to the non-inverting input terminal of the operational amplifier 12. The air-fuel ratio control circuit 31 preferably includes a microcomputer, and in addition to the above-mentioned Ic output terminal and Vs-input terminal,
It has an S output end and a Δ/F drive end. A constant current circuit 40 is connected to the Is output terminal via a buffer 139. The buffer 39 generates a low level signal in response to the minute current supply command output from the Is output, and generates a high level signal when the minute current supply command is stopped. The constant current circuit 40 is a PNPt-run raster 41. It consists of a resistor 42 and a Zener diode 43, a voltage V[+ is supplied to the emitter of the transistor 41 via the resistor 42, and the collector is connected to the lead wire 8a of the electrode plate 8 of the battery cord 2 as a constant current output. ing. The base of the transistor 41 is connected to the outputs 9'jl: of the three buffers, and the Zener diode 43 is connected between the base and one end of the resistor 42. The drive unit A2 is connected to a solenoid valve 44 for adjusting secondary air supply. Electromagnetic?/I
4 communicates with the intake passage downstream of the engine's carburetor throttle valve J-
It is provided in the intake secondary air supply passage. Note that a heater 38 is provided in parallel with the sea urchin oxygen pump element 1 and the battery cord 2 shown in FIG. Heater 3
8 generates heat by a heater current supplied from a current supply circuit (not shown) when the engine is in operation, heating the oxygen pump cord 1 and the battery element 2. In this configuration, when the IP value command data is output from the 10 output terminal of the air-fuel ratio control circuit 31 to the D/A converter 32 after the activation of the oxygen pump element 1 and the battery cable 2 is completed, the D/A converter 32 The I p lfi command data is converted into voltage by the A converter 32 , and the converted voltage is supplied to the integration circuit 34 via the voltage follower circuit 33 . Integrating circuit 34
The output voltage of resistor 35.36 gradually increases due to the integration time constant due to resistor 35.36 and capacitor 37.
11 voltage of the above converted voltage is reached. This minute y]
-'The city voltage is equal to the voltage V r' + A amplifier 1
2 non-inverting inputs O;, i. '4A quasi-voltage V
r+ supply 11! Oxygen pump to I/electrode plates 5, 6 of element 1
The pump current flowing between the terminals 1 and 1 is detected by the voltage at the terminal of the resistor 16, and the voltage at the terminal 1h is supplied to the inverting input terminal of the operational amplifier 12 via the resistor IA 17.
'h pressure is the base (voltage 11TVr+, when the rise is small (,1
Since the output level of the operational amplifier 12 becomes high level and the current at the base of the transistor 13 increases, the pump current lρ increases, and when the voltage Vr1 becomes higher than the voltage Vr1, the output voltage of the transistor 13 increases. The output level of 12 becomes a very low level, and the pump ih flow decreases while avoiding a decrease in the base current of transistor 13. This operation is repeated at high speed, so the pump current 1p becomes a constant current value according to the reference voltage Vr+. On the other hand, a voltage VS is generated between the electrode plates 7 and 8 of the battery element 2, and the voltage Vs is supplied to the non-inverting amplifier 30, which amplifies the voltage Vs and detects the degree of oxygen cJ. It is supplied as an output to the Vs-input terminal of the air-fuel ratio control circuit 31.
Created by J.J. The air-fuel ratio 11 sin circuit 31 is shown in FIG.
Step 51) First, it is determined whether the flag FIG indicating the ON state of the ignition switch (not shown) is equal to 1". If F+c=O, it is determined whether the ignition switch has been switched from ON to ON. (Step 52) If the ignition switch is on, set flag F+c to "1" (Step 53), and generate a minute current supply command (Step 54)
. As a result, the buffer 39 supplies a low level signal to the constant current circuit 40, transistors 1 to 41 become active, and the constant current circuit 40 sends a predetermined value 11 between the electrode plates 7 and 8 of the battery element 2. A small current is supplied. Next, read the output voltage Vs- of the non-inverting amplifier 30 (step 55
>, the read output voltage Vs- is divided by the minute current value 11, and the calculated value is set as the battery resistance 11fjR+o (step 56). The battery resistance value Rho is activated 1i'v
; Determine whether it is greater than the value R1 (step 57
). If R+ o > R+, the oxygen pump cord 1 and the battery element 2 are inactive and there is a possibility of blackening occurring, and the internal time counter △ of the air-fuel ratio control circuit 31 is set as 61 hours. Sera T1 (~ and start Down 61 teaching (step 58). Meanwhile, R+0
If ≦R+, it is determined from the 51 value of the time counter Δ whether the state has continued for more than time T1 (step 59
). For example, the time T1 is set to be smaller as the engine cold water temperature is higher, smaller as the intake air temperature is higher, or set to be more discreet as the time elapsed after starting the engine is shorter. R+o≦
If the R1 state continues for more than time T1, it is assumed that the activation of the oxygen pump element 1 and the battery element 2 has been completed, and the flag Fo2 for determining activation is set to ``1'' indicating completion of activation (Step 60). , step 61) to stop the generation of the minute current supply command in order to stop the supply of minute current between the electrode plates 7.8 of the battery element 2; step 61); The contents of the Iρ value command γ-ri are set in order to supply a pump current of (step 62
). And Tsunoden) 1. : Read VS- (
In step 63), it is determined whether the voltage Vs- that has been inserted is older than the reference voltage J1vr2 corresponding to the target air-fuel ratio (step 64). Since the output voltage V3- increases as the air-fuel ratio of the supplied air-fuel mixture becomes richer, Vs->
If it is VF6, the air-fuel ratio of the air-fuel mixture supplied to the engine is rich, and the air-fuel ratio control circuit 31 opens the solenoid valve 44 to supply secondary air to the corn gin (step 65). If Vs-≦r2, it is assumed that the air-fuel ratio is lean, and the air-fuel ratio control circuit 31 stops driving the solenoid valve 44 to open, and the supply of secondary air to the engine is stopped (step 66). Also, in step 57, R+o>
If it is determined that F+c is 1, then step 58 is executed ((then step 66 is executed to stop the supply of secondary air to the engine. Since this has already been determined, it is determined whether the activation determination flag Fo2 is equal to "1" (step 67). If FO2 = 0, it has not been determined that it is activated, so step 54 is executed. , FO2-1, the activation is completed and step 63 is executed immediately.Furthermore, the flag F+c and FO2 are set to "o" when the power is turned on.
Figure 5 shows an air-fuel ratio control device using the oxygen concentration proportional current output type oxygen concentration detection device according to the present invention.In this device, the device shown in FIG. Identical parts are indicated by the same reference numerals, and electrode plates 5 and 6 of the oxygen pump element 1
A current is supplied between them by a current supply circuit 45. The current supply circuit 45 is an A Bearsive 46. Consists of NPNI transistor 48 and resistor 47.49. Nine outputs of the operational amplifier 46 are connected to the base of a transistor 48 via a resistor 47. Further, the emitter of the transistor 48 is grounded via four resistors. A resistor 49 corresponds to the pump current value rp flowing between the electrode plates 5 and 6 of the oxygen pump element 1.
The terminal voltage is supplied to the Ip input terminal of the control circuit 31 as the pump current value 1p. 1 to the collectors of the transistors 48 are connected to the inner electrode plate 6 of the oxygen pump element 1 via the lead wire 6a,
A voltage VO is supplied to the outer electrode plate 5 via a lead wire 5a. Also, non-anti-Chumu j (1 width 2;
30's output Oη: is connected to the inverting input Qi; of the operational amplifier 46. Other +j+1 configurations are shown in Figure 2.
It is similar to this device. In this configuration, when the Vs value command data is output from the Ic output terminal of the air-fuel ratio control circuit 31 to the D/Δ converter 32, the Vs value command f- is controlled by the D/Δ converter 32. It is converted to voltage Vc, and its r[,! The I control voltage VC is supplied to the integrating circuit 34 via the low voltage lower circuit 33. The output voltage of the integrating circuit 34 gradually rises due to the integration time constant of the resistor 35, 36 and the capacitor 37, and reaches the divided voltage of the control voltage VC by the resistor 35, 36. This divided voltage is supplied to the non-inverting input terminal of the operational amplifier 46 as a reference voltage Vr3.At this time, since the voltage level at the inverting input terminal of the operational amplifier 46 is smaller than the reference voltage Vr3, The output level becomes a high level and the transistors 1 to 48 are turned on. A voltage Vs is generated between the two electrode plates 7.8, and the voltage Vs is supplied to a non-inverting amplifier 30. The non-inverting amplifier 30 amplifies the voltage VS and supplies it to the inverting input terminal of the operational amplifier 46. When the voltage Vs rises, the output voltage Vs- of the non-inverting amplifier 30 also rises.When the output voltage Vs- exceeds the reference voltage Vr3, the output level of the operational amplifier 46 is inverted to a low level, and the transistor 48 is turned off.Transistor 48 is turned off, the pump current decreases, so the voltage Vs generated between the electrode plates 7 and 8 of the battery cord 2 decreases, and the voltage Vs- supplied from the non-inverting amplifier 30 to the inverting input terminal of the A-bearing 46 also decreases. When the voltage Vs' falls below the reference voltage Vr3, the output level of the A passive 46 becomes high again, increasing the pump current.This operation is repeated at high speed, so the voltage Vs is controlled to a constant value. The voltage corresponds to I+r+ expressed by the S supply command data.The pump current value I flowing between the electrode plates 5 and 6 of the oxygen pump cable 1 when the reference voltage VI"3 is supplied to the operational amplifier 4G.
p is detected by the terminal voltage of the resistor 49, and the terminal voltage is supplied to the IP input terminal of the air-fuel ratio control circuit 31. The air-fuel ratio control circuit 31 operates at predetermined intervals as shown in FIG. The air-fuel ratio control circuit 31 performs steps 51 to 6 as in the case of the oxygen concentration proportional voltage output type shown in FIG.
2 and to supply the pump current ■5lll'
The contents of the 1 command data are set as 11 (step 62a).
. Then, the voltage voltage current value 1p of the four resistors *η1
It is determined whether or not the read pump current value 1p is smaller than a reference value [r corresponding to the target air-fuel ratio (step 64a). Ir〈Ir
If so, assuming that the air-fuel ratio of the air-fuel mixture supplied to the engine is rich, the air-fuel ratio control circuit 31 operates the solenoid valve 44 to supply secondary air to the engine (step 65). If IP≧lr, the air-fuel ratio is lean, and the air-fuel ratio control circuit 31 stops driving the 11;1 valve of the solenoid valve 44.1-S, the supply of secondary air to the engine is stopped at t": (Step 6G).In this way, in the oxygen concentration detector 2t of the present invention,
Engine starting +1. When the heater 38 is supplied with the heater upstream to the inactive state of the oxygen pump element 1 and the battery element 2 of 'l, the oxygen pump elements 1 and ? In the li, Yasukko 2 is heated by the light from the heater 38 (oxygen bomb).
And the eaves of the battery cord 2 rises. At this time, the internal resistance 1i [i Rt o of the battery cord 2 gradually decreases as the heating progresses, as shown in FIG. 7 FJ. When the internal resistance value Rho reaches the activation value R1 determined in advance based on experimental results etc., activation of the oxygen pump cord 1 and the battery element 2 is completed, and after a further time T1 has elapsed, the oxygen pump cable 1 and the battery element 2 are activated. The pump cord 1 is supplied with a pump upstream for oxygen concentration detection. As described above, in the oxygen ci degree detection device of the present invention, the occurrence of rib blackning can be reliably prevented.
A minute current is supplied between the electrodes of the battery element, and the internal resistance of the battery element (1 is detected from the voltage between the electrodes of the battery element of the minute current supply 1.1, and the internal resistance value is 3;' , !
i'; When the oxygen concentration detector is in an inactive state, the oxygen concentration detector is cut off and the supply upstream of the pump for detecting the oxygen concentration is stopped using a minute current, so there is no blackening when the sensor is inactive. This makes it possible to prevent the phenomenon from occurring.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the oxygen pump current characteristics and the blackening phenomenon occurrence area, Fig. 2 is a circuit diagram showing an embodiment of the present invention, and Fig. 3 shows the configuration of an oxygen concentration detector.゛Perspective view. Figure 4 is a flow diagram showing the movement of the air-fuel ratio control circuit in the device shown in Figure 2. Figure 4 shows the battery element voltage vs. pump resistance characteristic. FIG. 5 is a circuit diagram showing another embodiment of the present invention, FIG. 6 is a flow diagram showing the dynamics of the air-fuel ratio control circuit in the device shown in FIG. 5, and FIG. 7 is a diagram showing the boundaries. FIG. 3 is a diagram showing changes in internal resistance value of a battery element upon activation. Explanation of symbols of main parts 1...Oxygen pump element 2...'1゛u bend 2Ruko 3...Gap section 4...Sube (Y 5 or 8... Electrode plate 11, 40... Constant upstream circuit 30... Non-inverting amplifier 44... Magnetic valve 45 at °:1... ...Current supply circuit applicant Honda Motor Co., Ltd. agent But I'l!

Claims (1)

[Claims] A pair of oxygen ion conductive solid electrolyte materials disposed in a gas to be measured, a pair of electrodes formed on each of the solid electrolyte materials, and the pair of solid electrolyte materials facing each other with a predetermined gap interposed therebetween. an oxygen concentration detector arranged in such a manner that one of the pair of solid electrolyte materials acts as an oxygen pump element and the other acts as a battery element for measuring oxygen concentration ratio; and a current supply that supplies current between the electrodes of the oxygen pump element. an oxygen concentration detection device that uses a voltage between the electrodes of the battery element or a current value flowing between the electrodes of the oxygen pump element as an oxygen concentration detection value, the current supply means includes a voltage between the electrodes of the battery element; A minute current is supplied between them, and the internal resistance value of the battery element is detected from the voltage between the electrodes of the battery element when the minute current is supplied, and when the internal resistance value is less than a reference value, a current for oxygen concentration detection is detected. is supplied between the electrodes of the oxygen pump element.