JPS6156959A - Linear air/fuel ratio detector - Google Patents

Abstract

PURPOSE:To measure the air/fuel ratio accurately, by determining the difference between the first current value from a measuring circuit with respect to the air/ fuel ratio before the alteration and the second current value from the measuring circuit with respect to the air/fuel ratio after the alteration with a linear air/fuel (A/F) sensor. CONSTITUTION:A linear air/fuel ratio A/F sensor 9 which is interposed in an exhaust tube 7 of the engine for a vehicle is made up of an oxygen partial pressure ratio detection cell 20, an oxygen pump cell 21 and a diffusion clearance 29 as slit about 0.1mm. wide between the cells 20 and 21. Electrodes 30 and 30' are attached to the clearance 29 side surface of the cell 21 and the downstream side surface of an exhaust pipe 7 respectively. Moreover, electrodes 31 and 31' are attached to the upstream side surface of the exhaust pipe 7 of the cell 20 and the clearance 29 side surface respectively. When the electrodes 30 and 30' are controlled so that the electromotive force Vs detected between the electrodes 31 and 31' will become constant, for example, at 40mV, it is possible to obtain a characteristic of having the pump current Ip zero in the theoretical air/ fuel ratio. Therefore, the characteristic of the current Ip being zero also can be obtained in the theoretical air/fuel ratio by controlling the current so that the electromotive force Vs will become constant, for example, at 200mV.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention relates to a linear air-fuel ratio (Δ/F) detection device iP/, and in particular, a two-element type detection cell standard suitable for use in vehicle engines. and 1, relates to an air-fuel ratio detection device 1d using an oxygen pump type lean sensor that uses a lean gas atmosphere.

[Conventional technology]

Conventionally, a linear air-fuel ratio (A
/F) sensor is proposed by JIM, and this linear A/F sensor is made of zirconia (Z r O2).
An oxygen partial pressure ratio detection cell composed of an oxygen ion permeable solid electrolyte consisting of the like, an oxygen pump cell also composed of an oxygen ion permeable solid electrolyte, and a zero ．． +
It is formed from a diffusion gap (slit) of about mn+ (see Fig. 4).

Then, the diffusion gap side surface of the oxygen pump cell and 4I+
Electrodes made of platinum or the like are attached to the surface of the downstream side of the trachea, and at the electrode on the diffusion gap side, the following reaction of the first equation takes place, and at the electrode on the downstream side of the exhaust pipe, the following reaction occurs: The reaction of Eq.

(1/2)02+2e-→02-...(1)02
-→(1/2)02 +2e-...(2):+
FLlrElt11! , 1%-1= 7kfl*
%1mff1lhti'ffi""1"JN, one electrode made of platinum or the like is also provided on the surface of the gap side, respectively.

If the pump current Ip flowing between the electrodes is controlled so that the electromotive force Vs detected between the electrodes becomes constant at around 1 (for example, 4. (LmV)) indicated by the symbol I in FIG. 1556, a V-shaped characteristic in which the pump current Tp becomes zero at an ideal air-fuel ratio (stoichiometry) is obtained.

Then, if the pump current T11 is controlled so that the electromotive force Vs becomes constant around the symbol ■ in FIG. 5 (for example, 20 (1 mV)), as shown by the chain line in FIG. Pump current Tp at air-fuel ratio (stoichiometry)
A Z-shaped material property in which the is zero is obtained.

[Problem that the invention seeks to solve]

However, in such a conventional linear air-fuel ratio detection device, when the pump current ■p is controlled so that the electromotive force \lS of the oxygen partial pressure ratio detection cell of the linear A/F sensor becomes a small value, is pump current-air combustibility f1: is\ll
In terms of time characteristics, the air-fuel ratio and the pump current Tp do not correspond one-to-one; in other words, as shown by the symbols (', , r) in FIG. Since the two air-fuel ratios correspond to the rich side air-fuel ratio A/F (R) and the lean side air-fuel ratio A/F (L, ), there is a problem that the air-fuel ratio cannot be uniquely determined. Therefore, it is not possible to distinguish between the lean side and the rich side.

On the other hand, when the pump current 1p is controlled so that the electromotive force Vs of the oxygen partial pressure ratio detection cell of the linear A/F sensor becomes a large value, the pump current-air-fuel ratio characteristic becomes Z-shaped, Although it is possible to determine whether it is on the lean side or the rich side within a limited range, there is a problem that extreme lean cannot be distinguished from rich.

Furthermore, due to the Z-shaped material, it is not possible to use the linear A/F sensor for a long time on the rich side due to durability problems, and it is undesirable to flow a large current even on the lean side.

The present invention aims to solve these problems, and aims to provide a linear air-fuel ratio detection device that can accurately detect the air-fuel ratio from the lean side to the rich side. do.

[Means for solving problems]

Therefore, the linear air-fuel ratio detection device Fl of the present invention includes an air-fuel ratio adjusting means capable of adjusting the relationship between the fuel filtj and the air supplied to the engine, and 4j1 from 11 introduces the slit into the slit
1 is equipped with a sensor body with a dedicated gap for
An oxygen partial pressure ratio detection cell made of an oxygen ion permeable solid electrolyte for permeating and introducing oxygen ions into the slit from the exhaust gas side, forming the wall of the sensor body;
1) An electromotive force detection circuit for detecting the voltage between the slit-side electrode and the slit-side electrode attached to the introduction oxygen partial pressure ratio detection cell, and -1; the wall of the sensor body; Oxygen □ is formed and the oxygen ions are discharged from the slit.
A discharge oxygen pump cell made of an ion-permeable solid electrolyte was attached to the discharge oxygen pump cell in order to set the detection voltage from the electromotive force detection circuit to the set voltage. It is equipped with an adjustment circuit that adjusts the voltage applied between the L slit side electrode and the discharge side electrode, and a measurement circuit that measures the current flowing between these electrodes, which is adjusted by the air-fuel ratio adjustment means. an air-fuel ratio changing means capable of changing the air-fuel ratio; a first current value from the measuring circuit;
: Changes made by the arrangement fuel ratio changing means! a second current value from the measuring circuit for the subsequent air-fuel ratio;
- An air-fuel ratio measuring means for measuring the air-fuel ratio of the air-fuel mixture supplied to the engine is provided.

[Effect]

In the linear air-fuel ratio detection device of the present invention described in 1-1, the adjustment circuit and the measuring circuit adjust the detected voltage from the electromotive force detection circuit at the air-fuel ratio before change to the set voltage. At the same time as measuring the first current value when the air-fuel ratio is changed by the air-fuel ratio changing means, the second current value is measured when the detection voltage is adjusted so as to obtain the air-fuel ratio after changing by the air-fuel ratio changing means. 1 and 2 of the air-fuel mixture supplied to the engine. The air-fuel ratio is measured by an air-fuel ratio measuring means.

〔Example〕

Hereinafter, embodiments of the present invention will be explained with reference to the drawings.
1 to 6 show a linear air-fuel ratio detection device as an embodiment of the present invention, and FIG.
- Chart, Figure 2 is a graph to explain its action, Figure tlS3 is its overall configuration diagram, Figure 4 is its linear A
The schematic diagram showing the /F sensor and FIGS. 5 and 6 are graphs for explaining its operation.

As shown in FIGS. 3 to 6, intake air from an air cleaner 1 is supplied to a combustion chamber (not shown) of an engine body 6 through an intake pipe 5, and exhaust air from the combustion chamber passes through a catalyst 10. It is opened to the atmosphere through an exhaust pipe 7 provided therein.

Then, inhale *;1! ? A control device (computer) 11 serving as an air-fuel ratio changing means and an air-fuel ratio measuring means is provided to control the air-fuel ratio adjusting means for supplying the air-fuel ratio to the This control device 11 includes an intake air temperature sensor 39 that detects intake air temperature.
Inlet valve opening sensor 4 for detecting the opening degree of the valve 15. Air 70-sensor 8 for detecting airflow
．． Linear Δ/l・゛sensor 9. The water temperature sensor for detecting the engine cooling water temperature is connected to the tour 12, the engine rotation speed sensor 13 for detecting the engine rotation speed, the crank angle sensor 14 for detecting the crank angle, and the voltmeter 28' for converting the pump current. Each sensor 3.4. ．． 8,9.12～
In response to the detection signal from 14, a control signal is output to the fuel supply device 2 in order to achieve a desired air-fuel ratio.

Further, the control device 11 appropriately outputs a control signal via a DA converter or the like so that the voltage value of the reference voltage power source 26 can be changed to a predetermined value.

Note that the voltmeter 28' may be omitted and an A-r) converter may be provided as appropriate.

As shown in FIG. 4, the linear A/F sensor 9 is installed in the grip/trachea 7 of a vehicle engine, and is made of an oxygen ion permeable solid electrolyte made of zirconia (7,rO2) or the like. The oxygen partial pressure ratio detection cell 20 and the oxygen pump cell 21 which are also made of an oxygen ion permeable solid electrolyte, and the 0.0. It is formed from two diffusion gaps as slits of the order of Imn+ -8 = (G, late rate-determining body).

Electrodes 30 made of platinum or the like are placed on the surface of the oxygen pump cell 21 on the diffusion gap 29 side and on the downstream surface of the gripping trachea 7.
At the electrode 30 on the side of the diffusion gap 29, a reaction according to the following first formula is carried out, and at the electrode 30' on the downstream side of the exhaust pipe 7, a reaction according to the following second formula is carried out. It will be done.

(1/2) ()2 +'2e-→02-...
(1)02-→(1/2)02+2e-...(2) Electrodes 31, 31' made of platinum or the like are also provided on the upstream surface of the exhaust pipe 7 of the oxygen partial pressure ratio detection cell 20 and the surface on the diffusion gap 29 side. Each is attached.

Electromotive force ■s detected between the electrodes 31 and 31'
is around the area indicated by the symbol I in FIG. 5 (for example, 40 mV
When the pump current rp flowing between the electrodes 0 and 30 is controlled, the pump current Tp becomes zero at the ideal air-fuel ratio (stoichiometry), as shown by the chain line in Figure 6. ■Provides shapeability.

Then, the electromotive force Vs is indicated by the symbol "(=
If the pump current p is controlled so that it remains constant near I (for example, 200 mV), the pump current p will decrease to 1p at the ideal air-fuel ratio (stoichiometry), as shown by the broken line in Figure 6.
A Z-shaped material property in which the is zero is obtained.

- The linear A/F (02) sensor 9 described in is the next product! l
It operates on the l+ principle.

(1) When the device is placed in the exhaust gas flow and the oxygen pump cell 21 is energized, 02 gas is ionized on the device electrode surface, 02- ions are moved from the negative electrode to the positive electrode, and are released as 02 gas from the positive electrode.

(2) At this time, due to the decrease in 02ff in the slit, a difference occurs between the 02 partial pressure PA in the current 32 and the 02 partial pressure Ps in the slit. Based on the formula, the electromotive force Vs:, ”′”t
″.

Vs=(R,T/4F)fn(PA/Ps)...
(3) (3) If the pump current I is supplied so as to keep this electromotive force Vs constant, the pump current 1p1. t#ff
It is proportional to 02 minutes P^ of current.

Tp=(4F/RT)Qll-exp((4P/It
T)V! +llll-... (4) Only 17,'": Component environmental temperature F; 7 Arade constant [<; Space constant Q; Constant determined by element shape Note that the symbol 22 in Fig. 4 is resistance): i , 23 is J'l
i Amplifier, 24 capacitor, which constitutes the power detection circuit,
25 is a transistor constituting an adjustment circuit, 27 is a pump cell power supply, 28 is a resistor, 32 is a current at 11, 33 is an inorganic heat-resistant adhesive layer, and CI is an fl'1 circuit consisting of an amplifier 23 and a capacitor 24. are shown respectively.

Additionally, a ceramic heater (not shown) is provided to control the element environmental temperature to a predetermined value.

The near air-fuel ratio detection device as an embodiment of the present invention is constructed as described above, and is shown in FIG.
, 1, while the reference voltage \'ref is fixed at a low set voltage Vref that allows the shapeability to be obtained, the pump current 1 pl is measured by the voltmeter 28' (or In step a1), two air-fuel ratios A/F(R,) and A/F(R,) corresponding to points A and B in FIG. 2 are detected based on this pump current Iρ1. F('i-+) is calculated (converted) (step a2).

Immediately after step a2 is completed, a control signal is sent from the control device 11 to the fuel supply device 2 to change the amount of fuel supplied from the fuel supply device 2 to the intake pipe 5 (step Q2
').

It is determined whether the fuel injection amount was increased last time (step 83), and if the fuel injection amount was decreased last time,
To increase the current fuel injection amount, select NO from step a3.
Step a4 is reached via the route, and the current fuel injection amount is increased by a predetermined amount (this amount is set to an amount that can sufficiently distinguish changes in pump current corresponding to changes in the air-fuel ratio, which will be described later).

With this increase in the fuel injection amount, the air-fuel ratio is changed from the air-fuel ratio before the change to the air-fuel ratio after the change, and the pump current tp'' at this time is detected (step a5).

Next, the pump currents Tpl and pl of the first air-fuel ratio A/F,
Difference Δ1 between air-fuel ratio A/F2 of S2 and pump current ■p'
=lp' rp+l is calculated, and it is determined whether this difference Δ is larger than zero (step n6).

When the difference Δ is smaller than zero, it is determined that the pump current Δ(■5) which is the difference between point B and point B' shown in FIG. 2 has been detected, that is, the pump current Tl at point B'
It is determined that l3 is detected, and the air-fuel ratio is on the lean side, and A of A/F (R) and A/F (L) is detected.
/F(1-) is determined (step a7).

Further, when the difference A is larger than zero, it is determined that the pump current J(R) of the difference between the point A and the point A' shown in FIG. 2 has been detected, that is, the pump current Tp2 at the point A'
is determined to be detected, and the air-fuel ratio is on the rich side, and if A/F(R) of A/F(T?) and A/F(T, ) is detected, the air-fuel ratio is 1. 'l is determined (step a8)
.

If the fuel injection amount was increased last time, in order to reduce the current fuel injection amount, the process goes from step a3 to step a9 via the YES route, and the current fuel injection amount is set to a predetermined value, which will be described later. It is set to a value that allows sufficient discrimination of changes in pump current corresponding to changes in air-fuel ratio. )reduce weight.

As the fuel injection amount decreases, the air-fuel ratio is changed from the air-fuel ratio before the change to the air-fuel ratio after the change, and the pump current Il)'' at this time is detected (step a10).

Next, the pump current Tpl of the first air-fuel ratio A/F +
The difference ΔI=Tp″−Tp+l between the pump current Tp″ and the air-fuel ratio A/F2 of tIS2 is calculated, and it is determined whether this difference Δ is larger than zero (step a11).

If the difference Δ is larger than zero, it is determined that a pump current Δ(I,) of the difference between point B and point B'' shown in FIG. 2 has been detected, that is, at point Fl''. It is determined that the pump current 11) is detected, and the air-fuel ratio is on the lean side and is A/F (L) of A/F (R,) and A/F (L). One to be judged! (Step a12).

Further, when the difference Δ is smaller than zero, it is determined that the pump current Δ(R) of the difference between point A and point A″ shown in FIG. 2 has been detected, that is, the pump current at point A″ is 11
5 is detected, the air-fuel ratio is on the rich side, and A/F (R) and A/F (T, , ) are detected.
It is determined that the A/F(R) of
13).

By alternately repeating increases and decreases in the fuel injection amount, the air-fuel ratio is prevented from changing significantly from the desired air-fuel ratio.

In this way, the air-fuel ratio can be determined, and the air-fuel ratio can be detected in the entire range from the lean side to the rich side.

Note that the current air-fuel ratio may be detected accurately by performing the same operation as step a2 between step a5 and step a6 and between step alO and step all.

Further, the control device 11 constituting the air-fuel ratio changing means sends information to the fuel injection device 2 serving as the air-fuel ratio adjusting means.
The control signal that is set to 1 may be as follows.

(1) When the fuel injection device 2 is configured with an injector or the like, it is determined whether the fuel injection is on the rich side or the lean side every predetermined number of times, that is, periodically increases or decreases, and based on this, Measure the air/fuel ratio. This makes it possible to prevent large fluctuations in the air-fuel ratio.

(2) By determining that the vehicle engine is on the rich side when accelerating, and determining that it is on the lean side when decelerating, and controlling the amount of fuel injected from the fuel injection device 2 in advance.'' - Determination in Power Distribution Item 1 and measurement is prohibited to prevent lean spikes and rich spikes from occurring during over-deceleration.

Such an air-fuel ratio adjustment device for an engine equipped with a linear air-fuel ratio detection device uses feedback control to adjust the amount of fuel supplied from the fuel supply device 2 so that an arbitrary air-fuel ratio of stoichiometry or higher is achieved. This allows you to perform feedback control to keep the air-fuel ratio on the lean side to select fuel economy and exhaust gas preferences, or to perform feedback control to keep the air-fuel ratio on the lean side at all times while performing high-load sudden changes. During acceleration, rich-side feedback control is performed to select output and drivability.

Note that even if a choke valve or the like is provided as an air-fuel ratio adjustment means to reduce the amount of air instead of increasing it, the air-fuel ratio (the ratio of the amount of fuel to the amount of air) can be adjusted by -1° C. It may be configured so that.

〔Effect of the invention〕

As described in detail below, according to the linear air-fuel ratio detection device of the present invention, if the fuel supplied to the engine (4) is
an air-fuel ratio adjusting means capable of adjusting the ratio between l and the air amount;
] A sensor body is provided with an exhaust gas introduction gap for introducing reconnaissance from the air loss system of the engine into the surin 1, and a part 11.1 of the sensor body is formed to introduce oxygen into the slit from the exhaust gas side. an oxygen partial pressure ratio detection cell made of an oxygen ion-permeable solid electrolyte that permeates and introduces ions;
An electromotive force detection circuit for detecting the voltage between the electrode on the slit side and the electrode on the exhaust gas side attached to the oxygen partial pressure ratio detection cell for introduction, and the wall part of the sensor main body are formed. A discharge oxygen pump cell made of an oxygen ion-permeable solid electrolyte that permeates and discharges oxygen ions, and the above-mentioned tools attached to the discharge oxygen pump cell in order to set the detection voltage from the electromotive force detection circuit to the set voltage. It is equipped with an adjustment circuit that adjusts the voltage applied between the F-side electrode and the discharge-side electrode, and a measurement circuit that measures the current flowing between these electrodes, and the air-fuel ratio adjusted by the air-fuel ratio adjustment means. an air-fuel ratio changing means capable of changing the wind ratio; The air-fuel ratio is clamped with a simple structure including an air-fuel ratio measuring means that receives the second current value from the measuring circuit and measures the air-fuel ratio of the air-fuel mixture supplied to the engine. It has the advantage of being able to detect the air-fuel ratio in the entire range from the lean side to the rich side by receiving exhaust gas from the engine.

[Brief explanation of drawings]

1 to 6 show a linear air-fuel ratio detection system as an embodiment of the present invention, and FIG.
-Chart, Figure 2 is a graph to explain its action, Figure 3 is its overall configuration diagram, Figure 4 is its linear A/F
The schematic diagram showing the sensor, FIGS. 5 and 6, are graphs for explaining its operation. 1. Air cleaner, 2. Air-fuel ratio adjustment means Ml control system (supply device, 3. Intake air temperature sensor, 4. Throttle position sensor, 5. IIl & trachea, 6.
Engine body, 7. Air exhaust pipe, 8. Air 70-sensor, 9. Linear A/F sensor, 10. Catalyst, 11.
Air-fuel ratio change - control device 6 (computer) that also serves as F stage and air-fuel ratio measuring means, 12... water temperature sensor, 13... engine rotational speed change, 14... crank angle sensor;
15... Throttle valve, 20... Oxygen partial pressure ratio detection cell,
21...Oxygen pump cell, 22...Resistor, 23...Amplifier constituting the electromotive force detection circuit, 24...Capacitor,
25...Transistor that constitutes the adjustment circuit, 26...Power source for reference voltage, 27...Power source for pump cell, 28...Resistor, 28'...Voltmeter that forms the measuring circuit, two...As slit Diffusion gap (diffusion barrier), 30.
30', 31.31'... Electrode, 32... Exhaust gas flow, 33... Inorganic heat-resistant adhesive layer, C1... Integral circuit. Agent Patent Attorney Yoshihiko Iinuma Figure 2 Air Fuel Ratio (A/F) ◆ Figure 3

Claims (1)

[Claims] The sensor body includes an air-fuel ratio adjusting means that can adjust the ratio between the amount of fuel and the amount of air supplied to the engine, and a sensor body that has an exhaust gas introduction gap that introduces exhaust gas from the exhaust system of the engine into the slit. An oxygen partial pressure ratio detection cell for introduction made of an oxygen ion permeable solid electrolyte that forms the wall of the sensor body and permeates oxygen ions into the slit from the exhaust gas side, and an oxygen partial pressure ratio detection cell for introduction that is attached to the introduction oxygen partial pressure ratio detection cell. An electromotive force detection circuit that detects the voltage between the slit side electrode and the exhaust gas side electrode, and an oxygen ion permeable solid electrolyte that forms the wall of the sensor body and permeates and discharges oxygen ions from the slit. Adjusting the voltage applied between the discharge oxygen pump cell and the discharge side electrode and the slit-side electrode attached to the discharge oxygen pump cell so that the detected voltage from the electromotive force detection circuit is a set voltage. an air-fuel ratio changing means that includes an adjustment circuit and a measuring circuit that measures the current flowing between these electrodes, and is capable of changing the air-fuel ratio adjusted by the air-fuel ratio adjusting means; and the measuring circuit for the air-fuel ratio before the change. and a second current value from the measuring circuit for the changed air-fuel ratio changed by the air-fuel ratio changing means, and measure the air-fuel ratio of the air-fuel mixture supplied to the engine. What is claimed is: 1. A linear air-fuel ratio detection device, characterized in that it is provided with air-fuel ratio measuring means.