JP3458475B2 - Engine air-fuel ratio control device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air-fuel ratio control system for an engine, which performs an air-fuel ratio feedback control using an oxygen concentration sensor having an oxygen pump element made of an oxygen ion conductive solid electrolyte member.

[0002]

2. Description of the Related Art Conventionally, it has been generally practiced to detect the oxygen concentration in exhaust gas corresponding to the air-fuel ratio of an air-fuel mixture and perform feedback control of the air-fuel ratio accordingly. Various sensors for detecting the oxygen concentration in exhaust gas are known, but as an oxygen concentration sensor suitable for performing feedback control while changing the air-fuel ratio according to the operating state in a lean burn engine, For example, there is one disclosed in JP-A-62-76446.

This oxygen concentration sensor has a pair of oxygen ion conductive solid electrolyte members, one of which functions as an oxygen pump element and the other of which functions as an oxygen concentration ratio measuring battery element, and these functions are utilized. The sensor circuit is configured so that an output proportional to the oxygen concentration in the exhaust gas can be obtained, and a heater for heating the element to a predetermined temperature is provided.

In such an oxygen concentration sensor, the oxygen pump element performs an oxygen pump action of taking in oxygen from the space on one side and sending out oxygen to the space on the other side in response to the energization of the element, and the oxygen pump element has a predetermined function. Activation temperature of (7
When it reaches 50 to 850 ° C), it exerts a regular pumping action. However, when the element temperature is low (600 °
When less than about C) is energized, oxygen is deprived from the element itself, and, for example, when ZrO ₂ (zirconium dioxide) is used as the solid electrolyte member, O ₂ is depleted and Zr is depleted.
Causes a so-called blackening phenomenon, which causes deterioration of the device.

Therefore, in the oxygen concentration sensor control method disclosed in the above publication, energization of the oxygen pump element is prohibited for a predetermined time from the start of the current supply to the heater until the element temperature rises sufficiently. By doing so, deterioration of the element due to the blackening phenomenon is prevented.

[0006]

In the case where the energization of the oxygen pump element is prohibited until the element temperature rises sufficiently as described above, the energization is prohibited in consideration of variations in the element temperature rise time due to various operating environment conditions. Need to set the time. That is, the element temperature rise time up to the predetermined temperature changes depending on the outside air temperature, the battery voltage, etc., for example, when the outside air temperature is low, or the battery voltage drops due to the use of another electric device, and the current supply to the heater When the amount decreases, the temperature rise time of the element is long. Therefore, even in such a case, the energization prohibition time is set to be considerably long, for example, about 100 seconds, so that the energization to the oxygen pump element is prohibited until the element temperature rises sufficiently.

However, if the energization prohibition time is set to be long in this way, when the inspection of the air-fuel ratio feedback control system or the like that requires detection by the oxygen concentration sensor is performed at the inspection site of a factory or the like, the time Loss occurs, which becomes an obstacle in the inspection process.

More specifically, in the inspection process in the factory, usually, a roller running test is carried out on a test running roller for a predetermined time in a predetermined running pattern, followed by the air-fuel ratio feedback control system and the like. The temperature of the element is raised to some extent during the roller running test by performing the above inspection, but the time required for this roller running test is about 60 to 90 seconds, whereas the above energization prohibition is prohibited. The time is longer than this. Therefore, a waiting time occurs after the roller running test is completed until the oxygen concentration sensor can detect (the inspection of the air-fuel ratio feedback control system and the like can be performed), resulting in a time loss in the inspection process, There is a problem that work does not flow smoothly.

In view of the above circumstances, the present invention provides an air-fuel ratio feedback control using an oxygen concentration sensor having an oxygen pump element, and prevents deterioration of the oxygen pump element while inspecting at an inspection site. It is an object of the present invention to provide an engine air-fuel ratio control device capable of preventing a time loss from occurring and smoothing the flow of an inspection process.

In particular, it is usually necessary to set the energization prohibition period for the pump element to be long in anticipation of large fluctuations in operating environment conditions. It is intended to improve the work efficiency of the inspection by paying attention to the fact that the variation in the use environment condition is relatively small and the deterioration can be avoided even when the energization prohibition period is shorter than usual.

[0011]

The invention according to claim 1 is
An oxygen concentration sensor having an oxygen pump element made of an oxygen ion conductive solid electrolyte member for detecting the oxygen concentration in the exhaust gas of an engine, and means for receiving the output of the oxygen concentration sensor and performing feedback control of the air-fuel ratio. In the air-fuel ratio control device for the engine, which includes means for prohibiting the energization of the oxygen pump element until a preset energization prohibition time has elapsed after the engine is started, a predetermined inspection process at the inspection place is determined. The determination means and the energization prohibition time changing means for shortening the energization prohibition time when it is determined that the inspection step is performed are provided.

According to a second aspect of the present invention, in the apparatus according to the first aspect, the oxygen concentration sensor has a pair of oxygen ion conductive solid electrolyte members, and the pair of oxygen ion conductive solid electrolyte members. One of them is configured to function as an oxygen pump element and the other functions as an oxygen concentration ratio measuring battery element, and is heated by the heating means from the time of engine start.

The invention according to claim 3 is the invention according to claim 1 or 2.
In the apparatus described in (1), the inspection step determined by the determination means is such that the vehicle travels on the test travel roller for a predetermined time in a predetermined travel pattern.

According to a fourth aspect of the present invention, in the apparatus according to any one of the first to third aspects, the operating state of the air-fuel ratio feedback control system is checked in the inspection step, and the operating state is output to the monitor means. The operating state output means is provided.

According to a fifth aspect of the present invention, in the apparatus according to any one of the first to fourth aspects, when the inspection step is determined by the determination means, the energization prohibition time changing means shortens the energization prohibition. The air-fuel ratio means for setting the air-fuel ratio to the stoichiometric air-fuel ratio is provided from the time elapsed until the time corresponding to the normal energization prohibition time elapses.

According to a sixth aspect of the present invention, in the device according to any one of the first to fifth aspects, the determining means is one element for determining whether or not the test terminal is turned on. Is.

[0017]

According to the first aspect of the present invention, the oxygen pump element of the oxygen concentration sensor is prohibited from being energized during the energization prohibition time, thereby preventing deterioration of the oxygen pump element.
After the passage of the energization prohibition time, the oxygen pump element is energized, and the oxygen concentration in the exhaust gas is detected accordingly. Then, in normal times, the energization prohibition time is set to be relatively long in anticipation of large fluctuations in the usage environment conditions, while the energization prohibition time is shortened in the inspection process at the inspection site where the fluctuations in the usage environment conditions are small. As a result, while the function of preventing the deterioration of the element is maintained, the time when the detection by the oxygen concentration sensor and the inspection based on the oxygen concentration sensor are possible is advanced.

According to the second aspect of the present invention, the oxygen concentration sensor detects the oxygen concentration by utilizing the functions of the oxygen pump element and the oxygen concentration ratio measuring battery element formed by the pair of oxygen ion conductive solid electrolyte members. Like this,
The heating means heats the engine from the start, but as described above, by setting the energization prohibition time according to the normal time and the inspection process, deterioration of the element is prevented and oxygen is not detected in the inspection process. The detection by the concentration sensor and the inspection based on it can be advanced.

According to the third aspect of the present invention, the oxygen concentration sensor is heated during the traveling test on the test traveling roller, and the energization prohibition time shortened by the energization prohibition time changing means elapses. , Detectable state.

According to the fourth aspect of the present invention, if the oxygen concentration sensor becomes detectable after the shortened energization prohibition time has passed in the inspection process, the operating state of the air-fuel ratio feedback control system is monitored. The output to the means enables the confirmation of the operating state.

According to the fifth aspect of the present invention, in the inspection step, during the period from the passage of the energization inhibition time shortened by the energization inhibition time changing means to the passage of the time corresponding to the normal energization inhibition time. Even if the oxygen concentration sensor has not completely risen to the activation temperature, the oxygen concentration can be properly detected.

According to the sixth aspect of the present invention, by determining whether or not the test terminal is turned on, it can be reliably determined that a predetermined inspection should be performed in the inspection step.

[0023]

Embodiments of the present invention will be described with reference to the drawings.
FIG. 1 schematically shows an apparatus according to an embodiment of the present invention. In this figure, an intake port 3 and an exhaust port 4 are opened in a combustion chamber 2 of each cylinder of an engine 1, and ports 3 and 4 are provided.
An intake valve 5 and an exhaust valve 6 are provided at the same time, and an ignition plug 7 is provided.

An intake passage 8 communicating with the intake port 3 is provided with an air flow sensor 10 for detecting an intake flow rate and a throttle valve 11 which operates in response to an accelerator operation, and a fuel is provided near the intake port 3 of each cylinder. A fuel injection valve 12 for injecting and supplying is provided. on the other hand,
An oxygen concentration sensor 15 that detects the air-fuel ratio of the air-fuel mixture by detecting the oxygen concentration in the exhaust gas is provided in the exhaust passage 13 that communicates with the exhaust port 4.

The oxygen concentration sensor 15 includes an oxygen concentration detecting element portion 16 and a heater 17 for heating the element portion.
And a heater circuit 19 for energizing the element unit 16 and outputting a detection signal, and a heater circuit 19 for energizing the heater 17, and the element unit 16 includes an oxygen ion conductive solid. An oxygen pump element made of an electrolyte member is included.

The structure of the oxygen concentration sensor 15 will be described with reference to FIG. 2. The oxygen concentration detecting element portion 16 has a pair of elements 21 and 22 made of an oxygen ion conductive solid electrolyte member such as zirconia. . Both elements 21,
One of the electrodes 22 functions as an oxygen concentration ratio measuring battery 21, and the other functions as an element oxygen pump element 22, and electrode layers 21a, 21b, 22a, 22 are provided on both side surfaces of each element.
b is formed. A diffusion chamber 24 for introducing exhaust gas from the exhaust passage through the diffusion layer 23 at a constant diffusion rate is formed between the two elements 21 and 22, and one side of the oxygen concentration ratio measuring battery element 21 is formed. , A comparative oxygen concentration chamber 2 kept at a constant oxygen concentration (for example, an oxygen concentration similar to the atmosphere)
5 is formed. Further, the sensor circuit 18 connected to the element section 16 includes an operational amplifier 26, a resistor 27, and the like.

The oxygen concentration sensor 15 specifically detects the oxygen concentration in the exhaust gas as follows.

That is, when the oxygen ion conductive solid electrolyte members constituting the above-mentioned elements 21 and 22 are arranged between two chambers having different oxygen partial pressures, oxygen corresponding to the ratio of the oxygen partial pressures of the both chambers is used. Ions move inside the element to generate electromotive force and function as a battery, and when a voltage is applied between both electrodes, it functions as an oxygen pump that takes in oxygen from one side and releases oxygen to the other side. .

Therefore, the element 21 located between the comparative oxygen concentration chamber 25 and the diffusion chamber 24 functions as an oxygen battery, and the other element 22 functions as an oxygen pump. When the amount of oxygen in the exhaust gas in the diffusion chamber 24 increases, oxygen is pumped out of the diffusion chamber 24 by the oxygen pump element 22, and when the oxygen in the exhaust gas in the diffusion chamber 24 becomes insufficient, the oxygen pump element 22 causes Oxygen is taken into the diffusion chamber 24 from the outside so that the inside of the diffusion chamber 24 is kept in a state corresponding to the stoichiometric air-fuel ratio. The voltage applied to the pump element 22 is adjusted, and accordingly, an output corresponding to the current flowing through the oxygen pump element 22 is taken out from the resistor 27.

With this structure, an output proportional to the oxygen concentration in the exhaust gas (air-fuel ratio of the air-fuel mixture) can be obtained.

The heater circuit 19 for the heater 17 that heats the element portion 16 has resistors 28, 2 as shown in FIG.
It is composed of a bridge circuit including 9 and 30, a transistor 31, an operational amplifier 32, etc.
Heat to 50-850 ° C). The heater 17 is heated by energizing the heater circuit 19 when the engine is started.

Further, in FIG. 1, the oxygen concentration sensor 15 is connected to a control unit (ECU) 40. The control unit is composed of a microcomputer or the like, outputs an energization control signal to the sensor circuit 18 of the oxygen concentration sensor 15 and inputs an oxygen concentration detection signal from the sensor circuit 18, and further, the air flow sensor 10 and the engine speed. A signal from the rotation speed sensor 35 or the like for detecting the fuel injection is input and a fuel injection control signal is output to the fuel injection valve 12.

Reference numeral 36 is a monitor device provided at an inspection site such as a factory, which is connected to a control unit at a predetermined inspection time. 37 is the control unit 4
It is a test terminal connected to 0 and is turned on at the time of a predetermined inspection.

FIG. 4 shows a functional configuration of the control unit 40. As shown in this figure, the control unit 40 includes an energization prohibition time setting means 41 and a determination means 4
2, the energization prohibition time changing unit 43, the energization control unit 44, the fuel injection amount control unit 45, the air-fuel ratio setting unit 46, and the operating state output unit 47.

The energization prohibition time setting means 41 starts the energization of the heater (at the time of starting) and the oxygen concentration sensor 15
In order to prohibit energization up to a predetermined activation temperature, a normal time energization prohibition time Tb is set. The energization prohibition time Tb set here is a time sufficient to surely heat the oxygen concentration sensor 15 to a predetermined activation temperature even if there are variations in temperature rise due to various factors. It is set to about 100 seconds.

The determination means 42 determines a predetermined inspection process in a factory (inspection site). In this embodiment, the roller running test is determined by the processing shown in the flow chart described later, and the test is performed. The terminal 37 is determined to be on. Further, the energization prohibition time changing means 4
3 is adapted to set an energization inhibition time Ta for inspection (for example, about 65 seconds) shorter than the energization inhibition time Tb for normal time when the inspection process is determined by the determination means 42. There is.

The energization control means 44 uses the energization prohibition time T
The oxygen concentration sensor 15 is operated until a or Tb elapses.
The sensor circuit 18 is prohibited from being energized, and the sensor circuit 18 is energized when the energization prohibition time has elapsed.

The fuel injection amount control means 45 calculates the basic injection amount according to the outputs of the air flow sensor 10 and the engine speed sensor 35, and compares the output of the oxygen concentration sensor 15 with the target air-fuel ratio. A feedback correction amount corresponding thereto is calculated, a final injection amount is calculated based on the basic injection amount, the feedback correction amount, and various other correction amounts, and a control signal corresponding to the final injection amount is output to the fuel injection valve 12. Has become.

The air-fuel ratio setting means 46 sets the air-fuel ratio according to the operating condition, such as setting a target air-fuel ratio that is larger than the theoretical air-fuel ratio in a predetermined lean burn operation region. When determined, the air-fuel ratio is set to the stoichiometric air-fuel ratio regardless of the operating state, etc., from the time when the inspection energization prohibition time Ta elapses to the time when the normal time energization prohibition time Tb elapses. Has become.

The operating state output means 47 indicates the operating state of the feedback control system of the fuel injection amount control means 45 when the test terminal 37 is turned on during the inspection in the inspection process. The signal is output to the external monitor device 36, for example, a signal according to the feedback correction amount is output.

FIG. 5 and FIG. 6 are flowcharts of the control performed by the above control in the inspection process in the factory.

When the control shown in this flow chart is started, first in step S1, the flags Xpmd and Xpmdp for determining the roller running test, the timer Cp for determining the elapsed time after starting, the timer Cm for determining the roller running test elapsed time, and the sensor. Initialize the energization flag Xponl and the factory energization flag Xponr to "0".

Next, in step S2, the start determination flag X
It is determined whether st is "1". This start judgment flag X
st is set to "1" when the engine is stopped and is started at "0" by a start determination process (not shown). When the flag Xst becomes "1", the timers Cp and Cm are incremented (step S3).

Subsequently, it is checked whether or not the current vehicle speed Vs [i] is greater than 0 and the previous vehicle speed Vs [i-1] is 0, that is, whether or not it is the time to start traveling (step S4). ,
At the start of traveling, the timer Cm is reset to "0". Therefore, the timer Cm measures the time from the start of traveling.

Subsequently, it is determined whether both conditions that the timer Cm is equal to the first roller traveling determination value A1 and that the vehicle speed Vs is equal to the first roller traveling determination value V1 are satisfied ( If the determination is YES in step S6), the flag XPmdp is set to "1" (step S7). Further, the timer Cm sets the second roller traveling determination value A2.
And the vehicle speed Vs is equal to the second roller traveling determination value V
It is determined whether or not the conditions that the flag Xpmdp is equal to 2 and the flag Xpmdp are "1" are satisfied (step S8),
If the determination is YES, the flag XPmd is set to "1" (step S9).

The processing of these steps S6 to S9 is to check whether or not the roller running test is being performed in the factory. In other words, in the roller running test, the vehicle is run on a running test row or the like according to a predetermined running pattern as shown in FIG. 6, for example.
The first checkpoint (time A
1, vehicle speed V1) and second checkpoint (time A2,
The vehicle speed V2) is set, and it is checked whether or not the time from the start of traveling and the vehicle speed match the above check points. If the flag XPmd becomes "1" by these processes, it means that the roller running test is in progress.

Then, the flag Xpmd is "1", the test terminal flag Xtest indicating that the test terminal is turned on is "1", and the timer Cp is energized for inspection. It is determined whether or not each condition that the prohibition time Ta is longer than or equal to is satisfied (step S10),
If the determination is YES, the factory energizing flag Xponr
Is set to "1" (step S11). That is, when the roller running test is being performed in the factory and the test terminal is on, if the elapsed time from the start exceeds the energization prohibition time Ta for inspection, energization should be permitted. The flag Xponr is set to "1".

Subsequently, it is determined whether or not the timer Cp is longer than the energization prohibition time Tb for normal time (step S1).
2) When the determination is YES, that is, when the elapsed time from the start exceeds the energization prohibition time Tb for normal time, the sensor energization flag Xponl is set to "1" to allow the energization unconditionally. (Step S13).

Next, it is determined whether the factory energizing flag Xponr is "1" or the sensor energizing flag Xponl is "1" (step S14). If the flags Xponr and Xponl are both "0", the energization of the sensor circuit of the oxygen concentration sensor 15 is prohibited (step S15), and if the flag Xponr or Xponl is "1", the oxygen is discharged. The sensor circuit of the concentration sensor 15 is energized (step S16).

Next, it is determined whether or not a predetermined lean burn condition, for example, a condition that the cooling water temperature is equal to or higher than a predetermined value and the operating state is in a predetermined lean burn operation region is satisfied (step S17). If this determination is YES,
Further, it is determined whether or not the sensor energization flag Xponl is "1" (step S18). When the lean burn condition is satisfied and the sensor energization flag Xponl is "1", the lean burn flag Xlean is set to "1", and when the lean burn condition is not satisfied or the lean burn flag Xlean is "0". In the case of Lean Burn Flag X
Set lean to "0".

Next, the air-fuel ratio of the air-fuel mixture is set according to the operating condition and the lean burn flag Xlean. In other words, in the lean burn area, lean burn flag X
When lean is "1", the target air-fuel ratio for feedback control is set to a value larger than the theoretical air-fuel ratio, and
When the lean burn flag Xlean is "0" in the feedback control region (including the lean burn region), the target air-fuel ratio is set to the theoretical air-fuel ratio.

According to such a device of the present invention, current is supplied to the heater 17 of the oxygen concentration sensor 15 when the engine is started, but the sensor circuit 18 of the oxygen concentration sensor 15 is supplied until the energization prohibition time elapses. By prohibiting the energization of the oxygen pump element 21, it is possible to prevent a situation in which a current flows through the oxygen pump element 21 while the temperature is low and blackening occurs. Then, after the passage of the energization prohibition time, the sensor circuit 18 is energized to detect the oxygen concentration in the exhaust gas by the oxygen concentration sensor 15, and the air-fuel ratio feedback control is performed according to the output.

In such control, a relatively long energization prohibition time Tb of about 100 seconds is set during normal operation in which the fluctuations in the operating environment conditions are large, so that the outside air temperature is lowered and the current is supplied to the heater. Even when the element temperature rises slowly due to a decrease in the amount or the like, the energization is prohibited until the temperature of the oxygen pump element 21 surely rises to the activation temperature.

On the other hand, during the inspection process in the factory, specifically, when the test terminal is ON during the roller running test, a relatively short energization prohibition time Ta for inspection of about 65 seconds is set. When this time Ta elapses, detection by the oxygen concentration sensor 15 and feedback control of the air-fuel ratio according to the detection are performed, and the operating state of the air-fuel ratio feedback control system and the like are inspected. That is, the timing of the inspection that requires detection by the oxygen concentration sensor 15 is advanced. In particular, by performing such processing in the roller running test process, the above inspection can be performed during the roller running test time, and time loss is prevented.

Even if the energization prohibition time Ta for inspection is shortened as described above, in the inspection process in the factory where the variation of the operating environment condition is small, during this time Ta, the temperature of the oxygen pump element is at least black. Since the temperature rises to a temperature (about 600 ° C. or higher) at which the cooling can be avoided, the element is not deteriorated.

In this inspection process, the element temperature of the oxygen concentration sensor 15 is completely activated during the period from the passage of the energization inhibition time for inspection to the passage of the energization inhibition time for normal operation. Although there is a possibility that the temperature has not risen to the temperature, the air-fuel ratio set for feedback control is set to the stoichiometric air-fuel ratio during this period, so that the detection by the oxygen concentration sensor 15 and the control based on it are satisfactory. Done.

This will be specifically described with reference to FIG.
In the normal state where the element temperature of the oxygen concentration sensor 15 reaches the activation temperature, its output changes at a predetermined rate of change according to the air-fuel ratio (solid line in FIG. 7), while the element of the oxygen concentration sensor 15 When the temperature does not reach the activation temperature, the rate of change in the output according to the air-fuel ratio becomes smaller than in the normal state (broken line in FIG. 7), so an error occurs in the detected value as the air-fuel ratio becomes leaner. However, the detected value of the theoretical air-fuel ratio is the same as in the normal state.

Therefore, during the period from the passage of the inspection energization prohibition time Ta to the passage of the normal time energization prohibition time Tb, the stoichiometric air-fuel ratio is detected and feedback control is performed. Even if the element temperature does not reach the activation temperature, the detection and the control according to the detection are accurately performed. Then, in the inspection process, even if the stoichiometric air-fuel ratio is set in this way, it is possible to inspect the operating state of the feedback control system and the like.

If the oxygen concentration sensor 15 becomes detectable after the passage of the current-carrying prohibition time in the inspection process, the operating state of the air-fuel ratio feedback control system is set to the factory, provided that the test terminal is on. Is output to the monitor device 36 installed in the. For example, in the feedback control system, the feedback correction amount is calculated based on the comparison between the output of the oxygen concentration sensor 15 and the target value (target air-fuel ratio), the monitor signal is created based on the feedback correction amount, and the monitor device 36 is generated. Is output. As a result, the operator can check the operating state of the feedback control system, inspect it, and so on.

In the above embodiment, the energization prohibition time Ta for the normal time is elapsed after the energization prohibition time Ta for the inspection has elapsed.
The air-fuel ratio is set to the stoichiometric air-fuel ratio until the time elapses, but in relation to the operating environment conditions in the inspection process,
If the element temperature of the oxygen concentration sensor 15 surely reaches the activation temperature by the time the inspection energization prohibition time Ta elapses, the air-fuel ratio is changed from the time when the inspection energization prohibition time Ta elapses. It may be set to lean.

Besides, the structure of the oxygen concentration sensor and the configuration of the control system may be changed without departing from the gist of the present invention.

[0062]

As described above, the present invention is provided with an oxygen concentration sensor having an oxygen pump element composed of an oxygen ion conductive solid electrolyte member, and the oxygen pump element is supplied to the oxygen pump element until the energization inhibition time elapses after the engine is started. In devices that prohibit energization, the energization prohibition time is set to be relatively long in anticipation of large fluctuations in the operating environment conditions during normal operation, while the energization prohibition time is used in inspection processes at inspection sites where fluctuations in the operating environment conditions are small. I am trying to shorten. For this reason,
While surely preventing the situation where the oxygen pump element is energized when the temperature is low and the element deteriorates, it is possible to eliminate or reduce the time loss in the inspection process, improve the inspection work efficiency, and perform the inspection. The process flow can be made smooth.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an air-fuel ratio control device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a structure of an oxygen concentration sensor.

FIG. 3 is a circuit diagram showing a heater circuit of an oxygen concentration sensor.

FIG. 4 is a functional block diagram of a control system.

FIG. 5 is a flowchart of control.

FIG. 6 is a flowchart following the flowchart of FIG.

FIG. 7 is a diagram showing output characteristics of an oxygen concentration sensor.

[Explanation of symbols]

15 Oxygen concentration sensor 17 heater 21 Oxygen pump element 22 Battery element for oxygen concentration ratio measurement 40 control unit 41 Energization prohibition period setting means 42 Judgment means 43 Means to change energization prohibited period

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI G01M 17/007 G01M 17/00 A (58) Fields investigated (Int.Cl. ⁷ , DB name) G01N 27/419 F02D 41 / 14 310 F02D 45/00 368 G01M 15/00 G01M 17/007

Claims (6)

(57) [Claims] 1. An oxygen concentration sensor having an oxygen pump element made of an oxygen ion conductive solid electrolyte member for detecting the oxygen concentration in the exhaust gas of an engine, and an output of this oxygen concentration sensor to obtain an air-fuel ratio In an air-fuel ratio control device for an engine, which is provided with means for performing feedback control and means for prohibiting energization to the oxygen pump element until a preset energization prohibition time elapses after the engine is started, a predetermined value at an inspection site is set. An air-fuel ratio of an engine, comprising: a determination unit that determines an inspection process; and an energization prohibition time change unit that shortens the energization prohibition time when the determination process determines that the inspection process is performed. Control device. 2. The oxygen concentration sensor has a pair of oxygen ion conductive solid electrolyte members, one of the pair of oxygen ion conductive solid electrolyte members is an oxygen pump element, and the other is an oxygen concentration ratio measurement. 2. The air-fuel ratio control device for an engine according to claim 1, wherein the air-fuel ratio control device for an engine is configured to function as a battery element for a vehicle, and is heated by the heating means from the time when the engine is started. 3. The inspection process determined by the determination means is for causing the vehicle to travel on a test travel roller in a predetermined travel pattern for a predetermined time. Engine air-fuel ratio control device. 4. The operating state output means for checking the operating state of the air-fuel ratio feedback control system in the inspection step and outputting the operating state to the monitoring means is provided. The air-fuel ratio control device for the engine according to. 5. When the inspection step is determined by the determination means, from the passage of the energization inhibition time shortened by the energization inhibition time changing means to the passage of a time corresponding to the normal energization inhibition time. The air-fuel ratio control device for an engine according to any one of claims 1 to 4, further comprising air-fuel ratio setting means for setting the air-fuel ratio to a stoichiometric air-fuel ratio. 6. The air-fuel ratio control of an engine according to claim 1, wherein the determination means uses one element for determination as to whether or not a test terminal is turned on. apparatus.