JPS62119450A - Decision on characteristic of exhaust density detector - Google Patents

Abstract

PURPOSE:To judge an exhaust concentration detector accurately without erroneous diagnosis, by determining the ratio of time until a change in the actual concentration is detected after it shifts from a low to high to time until a change in the actual concentration is detected after it shifts to a low from high value. CONSTITUTION:A mixed gas supply tester 15 forcibly changes the air/fuel ratio of a mixed gas to be supplied into an engine to a specified value on the lean side from a specified value on the rich side and measures the elapse time TRL -- how long it takes for the output voltage V02 of an O2 sensor 13 to come down to a reference value Vref. It also forcibly changes the air/fuel ratio to a specified value on the rich side from a specified value on the lean side and measures the elapse time TLR -- how long it taken for the output voltage V02 of the sensor 13 to go up to the reference value Vref. Then, the ratio K=TLR /TRL is determined. When the response ratio K is within a specified range, the O2 sensor is determined to be acceptable but when it is outside the specified range, it is determined to be rejectable.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for determining the characteristics of an exhaust gas concentration detector that is placed in the exhaust system of an internal combustion engine and detects the concentration of components in exhaust gas.

(Prior Art and its Problems) Conventionally, an exhaust concentration detector (hereinafter referred to as " The air-fuel ratio of the air-fuel mixture supplied to the engine is set by correcting the air-fuel ratio of the air-fuel mixture supplied to the engine by adjusting the air-fuel ratio of the air-fuel mixture supplied to the engine. An air-fuel ratio feedback control device that controls the stoichiometric mixture ratio at which the maximum conversion efficiency of the three-way catalyst can be obtained is generally used (Japanese Patent Application Laid-Open No. 2003-130013).
No. 7633).

The 02 sensor used in such devices uses zirconium oxide or the like as a sensor element, and the amount of oxygen ions passing through the zirconium oxide is determined by the difference between the oxygen partial pressure in the atmosphere and the oxygen partial pressure in the exhaust gas. The oxygen concentration in the exhaust gas is detected by changing the output voltage of the 02 sensor in response to this change.

If the 02 sensor used in the air-fuel ratio feedhack control device described above is defective, the air-fuel ratio of the air-fuel mixture supplied to the engine will exhibit an abnormal value, making proper engine control impossible.

For this reason, conventional methods have mainly been used to determine that the 02 sensor is defective when the output voltage value of the 02 sensor is out of the range defined by the maximum and minimum values that can occur during normal operation, and the method of determining that the 02 sensor is defective. 0 when the so-called 02 sensor reversal, in which the level changes from the rich side to the lean side or vice versa, does not occur for a predetermined time or more based on a predetermined reference value.
The quality of the 02 sensor was determined by the method of determining that the 02 sensor was defective.

However, in the former method, as long as the output voltage level of the O2 sensor remains within the range between the maximum value and the minimum value, the O2 sensor outputs an output that biases the output voltage toward either the rich side or the lean side. The 02 sensor is not determined to be defective even when the 02 sensor has such characteristics, and if the 02 sensor with such characteristics is used, the air-fuel ratio of the air-fuel mixture will shift to the lean side or rich side. Similarly, in the latter method, as long as the output reversal of the 02 sensor occurs within the predetermined time period, it is not possible to determine whether the 02 sensor has an output characteristic biased towards the rich side or the lean side as described above.

Conventionally, in general, the 02 sensor determined to be a good product by the above-mentioned method is installed in the engine exhaust system on the vehicle mass production line, and then the finished vehicle is actually driven and the harmful components in the exhaust gas are tested using the so-called 10-mode test method. However, as a result of this test, it was determined that the engine using the 02 sensor, which was once determined to be good as described above, does not meet the requirements for the required HC regulation value or NOx regulation value in exhaust gas. In such cases, it is necessary to replace the 02 sensor, which requires a great deal of time and effort.

(Object of the Invention) The present invention has been made to solve the above-mentioned problems, and the purpose of the present invention is to provide a method for determining the characteristics of an exhaust gas concentration detector that can accurately determine the characteristics of the 02 sensor without misdiagnosis. It is about providing.

(Summary of the Invention) According to the present invention, the actual concentration of exhaust components supplied to an exhaust concentration detector disposed in the exhaust system of an internal combustion engine is lower than a predetermined concentration of components. a first time period from when the concentration changes from a low value to a high value until the change is detected by the exhaust gas concentration detector; and when the actual concentration changes from a value higher than the predetermined component concentration to a value lower than the predetermined component concentration. The ratio between the time and the second time until the change is detected by the exhaust gas concentration detector is determined, and the ratio of the first
A method for determining characteristics of an exhaust gas concentration detector is provided, which determines whether or not the exhaust gas concentration detector is a good product based on a ratio between a time period of 1 and a second time period.

(Embodiments of the Invention) A method for determining characteristics of an 02 sensor according to the present invention will be described below with reference to the drawings.

FIG. 1 is a configuration diagram showing an example of a fuel supply control device for an internal combustion engine using a 02 sensor, and the reference numeral 1 is, for example, a 4
A cylinder internal combustion engine is shown, and an intake pipe 2 is connected to the engine 1. A throttle body 3 is provided in the middle of the intake pipe 2, and a throttle valve 3' is provided inside. Throttle valve opening degree (θTH) for throttle valve 3°
The sensor 4 is connected to convert the valve opening of the throttle valve 3'' into an electrical signal, and an electronic control unit (hereinafter rEcU)
J) 5.

A fuel injection valve 6 is provided in the intake pipe 2 between the engine 1 and the throttle body 3 for each cylinder, slightly upstream of the intake valve (not shown) of each cylinder.

The fuel injection valve 6 is connected to a fuel pump (not shown) and electrically connected to the ECU 3, and the opening time of the fuel injection valve 6 is controlled by a signal from the ECU 3.

On the other hand, an absolute pressure (PBA) sensor 8 is provided downstream of the throttle valve 3° of the throttle body 3 via a pipe 7, and the absolute pressure signal converted into an electrical signal by the absolute pressure sensor 8 is It is sent to the ECU 3.

The engine cooling water temperature sensor (rT) is installed on the engine 1 body.
The Tw sensor 9 is made of a thermistor or the like, and is inserted into the circumferential wall of the engine cylinder filled with cooling water, and supplies its detected water temperature signal to the ECU 3. An engine rotation speed sensor (hereinafter referred to as "rNe sensor") 10 is attached around the camshaft or crankshaft (not shown) of the engine, and the Ne sensor 10 rotates at a predetermined crank angle position every 180° rotation of the engine crankshaft. , that is, the top dead center (TDC) at the start of the intake stroke of each cylinder.
), a crank angle position signal (hereinafter referred to as "rTDC signal") is generated at a crank angle position before a predetermined crank angle.
This TDC signal is sent to the ECU 3.

A three-way catalyst 12 is disposed in the exhaust pipe 11 of the engine 1 to purify HC, Go, and NOx components in the exhaust gas. Upstream of this three-way catalyst 12, an O2 sensor (exhaust gas concentration detector) 13 is inserted into the exhaust pipe 11. The detected value VO2 of the 02 sensor 13 is a large value when the oxygen concentration in the exhaust gas is low, and a small value when the oxygen concentration is high, and the detected value Vo2 and the reference value Vref, which will be detailed later, are
(FIG. 3) A deviation signal is sent to the ECU 3.

Furthermore, other parameter sensors 14 such as an atmospheric pressure sensor are connected to the ECU 3, and the other parameter sensors 14 supply their detected value signals to the ECU 3.

The ECU 3 includes an input circuit 5a having functions such as shaping input signal waveforms from various sensors, correcting voltage levels to predetermined levels, and converting analog signal values into digital signal values.
Central processing circuit (hereinafter referred to as rCPUJ) 5b, C
It is comprised of a storage means 5c for storing various calculation programs and calculation results executed by the PU 5b, an output circuit 5d for supplying a drive signal to the fuel injection valve 6, and the like.

Every time the TDC signal is input, the CPU 5b calculates the fuel injection time Tout of the fuel injection valve 6 given by the following equation based on the engine parameter signals from the various sensors described above supplied via the input circuit 5a. .

Touv=Ti xKo2 XK1 +2...
(1) Here, Ti indicates the basic fuel injection time of the fuel injection valve 6, and this basic injection time is, for example, the absolute pressure in the intake pipe PBA.
and the engine rotational speed Ne from the storage means 5C. Ko2 is an 02 feedback correction coefficient which will be described later. K1 and K2 are a correction coefficient and a correction variable respectively calculated according to various engine parameter signals, and are set to required values to optimize fuel consumption characteristics, exhaust gas characteristics, etc. according to engine operating conditions. Ru.

The above-mentioned 02 feedback correction coefficient KO2 has a value set according to the output of the 02 sensor 13 shown in FIG. 1 in the air-fuel ratio feedback region of the engine, and is multiplied by the above-mentioned basic injection time Ti to correct it. The resulting injection time Touv is controlled to a stoichiometric mixture ratio (for example, 14.7) at which the air-fuel ratio of the air-fuel mixture supplied to the engine 1 maximizes the conversion efficiency of the three-way catalyst 12. Specifically, in the CPU 5 b, the output value (voltage value) representing the oxygen concentration of the 02 sensor 13 is set to a predetermined reference value (for example, 0.59
volt), and when the output value changes from the rich side to the lean side or vice versa with respect to the predetermined reference value, the first correction value Pi is added or subtracted to the correction coefficient Ko2 for each change (P-term control). , as long as the output value of the 02 sensor 13 remains on the lean side or rich side with respect to the predetermined reference value, the second correction value Δk is set to the correction coefficient KO2 every time a predetermined period of time elapses, for example, every time the TDC signal generates a predetermined number of pulses. is adjusted (one term control).

FIG. 2 is a block diagram of a response ratio (K) measuring device that implements the characteristic determination method of the present invention for the 02 sensor used in the fuel supply control device of an internal combustion engine, etc., as described above. The 02 sensor 13 used for measurement is attached to the exhaust system of the internal combustion engine 1 to which it is applied. The air-fuel mixture supply test device 15 changes the air-fuel ratio of the air-fuel mixture supplied to the engine 1 from a predetermined value on the rich side (for example, 13.1) to a predetermined value on the lean side (for example, 16.1) or to a predetermined lean side. A certain period of time (for example, 2 seconds) from the value to the predetermined value on the rich side.
It is forcibly switched as the time passes. 02 sensor 13
A response ratio (K) measuring device 16 is connected to the output side of the 0
The response ratio K of the two sensors 13 is measured.

As shown in FIG. 3, this response ratio includes, for example, when the air-fuel mixture supply test device 15 forcibly changes the air-fuel ratio of the air-fuel mixture supplied to the engine from a predetermined value on the rich side to a predetermined value on the lean side. From the time when the change is made (FIG. 3, 11), a change in the air-fuel ratio to the lean side is detected by the output of the 02 sensor 13, that is, the output voltage Vo2 of the sensor 13 decreases to the predetermined reference value Vref. (e.g. 0.59 volts)
The elapsed time TRL up to the point in time (L2) and the point in time (t3) when the air-fuel ratio is forcibly changed from the predetermined value on the lean side to the predetermined value on the rich side by the air-fuel mixture supply test device 15.
) to the point in time when a change in the air-fuel ratio toward the rich side is detected by the output of the 02 sensor 13, that is, the point in time when the output voltage Vo2 of the sensor 13 rises to the reference value Vref (t
4) is the ratio TL R/TRL to the elapsed time TLR until 4), and when this response ratio is larger than 1, the time for the O2 sensor 13 to determine the air-fuel ratio of the air-fuel mixture as lean is longer. On the other hand, when the sensor 1 is smaller than 1,
3 indicates that the time required to determine the air-fuel ratio to be rich is longer. Therefore, this response ratio K is within a predetermined range (KL
~KH), it is determined that the O2 sensor is a good product, and if it is outside this range, it is determined that it is a defective product.

FIG. 4 is a diagram illustrating a method of setting the predetermined range for the response ratio. 02 in the air-fuel ratio feedback control method
When the response ratio K of the sensor is greater than 1, when the mixture at the stoichiometric mixture ratio is supplied to the engine, the mixture is determined to be lean and the air-fuel ratio is controlled to the rich side.On the other hand, when the response ratio K is less than 1 On the contrary, it is controlled to the lean side.

As is generally known, when the air-fuel mixture is rich, the amount of Co and HC in the exhaust gas increases, while when the air-fuel mixture is lean, there is a lot of NOx. The upper limit of the predetermined range for the ratio is determined by exhaust gas regulations.

Similarly, the lower limit of the value KH (Fig. 4 (a)) corresponding to the regulation target value (maximum allowable value) (g/km) of HC is NO.
The value KL (FIG. 4(b)) corresponding to the regulation target value (maximum target value) (g/km) of x is set respectively. Therefore, when using the 02 sensor in which the response ratio K reaches the upper limit value KH, even if the stoichiometric mixture is supplied to the engine, the feedback control action described above will result in Co, HC in the shaded area A shown in Fig. 4(a). When using the 02 sensor, which also increases above the lower limit value KL, the NOx emissions increase beyond the regulatory target value in the shaded area B shown in Figure (b). do.

Therefore, the 02 sensor whose response ratio K is within the range KL-KH that satisfies all regulation target values of Co, HC, and NOx is considered to be a good product.

Curves I and II in FIG. 4 (al (bl) show changes in Co, HC, and NOx emissions with changes in values.

(Effects of the Invention) As explained above, according to the method for determining characteristics of an exhaust concentration detector of the present invention, the actual concentration of exhaust components supplied to the exhaust concentration detector arranged in the exhaust system of an internal combustion engine can be determined. a first time period from when the change occurs from a value lower than a predetermined component concentration to a value higher than the predetermined component concentration until the change is detected by the exhaust gas concentration detector; and the actual concentration is higher than the predetermined component concentration. The ratio of the second time from the time when the value changes to a lower value until the change is detected by the exhaust gas concentration detector is determined, and the ratio between the first time and the second time thus determined is determined. Since it is determined whether the exhaust gas concentration detector is a good product or not, it is possible to accurately determine the characteristics of the 02 sensor without misdiagnosis, and it is possible to accurately determine the characteristics of the 02 sensor after it is installed in a finished vehicle.
There is almost no need to replace sensors, making it possible to significantly save time and labor.

[Brief explanation of drawings]

Fig. 1 is an overall configuration diagram of a fuel supply control device as an example of the use of an O2 sensor, Fig. 2 is a block diagram showing a response ratio measuring device for carrying out the method of the present invention, and Fig. 3 is a diagram showing a fuel supply control device as an example of the use of an O2 sensor. FIG. 4 is a timing chart showing the relationship between the change in the air-fuel ratio of the air-fuel mixture and the change in the output voltage of the 02 sensor, and FIG. 4 is a graph showing the relationship between the exhaust gas component emission amount and the response ratio. 1... Internal combustion engine, 12... Three-way catalyst, 13...
・02 sensor, 15...Mixture supply test device, 16
...Response ratio (K) measuring device.

Claims (1)

[Claims] 1. From the time when the actual concentration of the exhaust components supplied to the exhaust concentration detector arranged in the exhaust system of the internal combustion engine changes from a value lower than a predetermined component concentration to a value higher than the predetermined component concentration, the exhaust concentration detector detects the change. a first time until is detected;
Determine the ratio to a second time from the time when the actual concentration changes from a value higher than the predetermined component concentration to a value lower than the predetermined component concentration until the change is detected by the exhaust gas concentration detector, and A method for determining characteristics of an exhaust gas concentration detector, in which it is determined whether or not the exhaust gas concentration detector is a good product based on a ratio between a first time and a second time.