JPS5862552A - Performance measuring apparatus for air-fuel ratio - Google Patents

Abstract

PURPOSE:To measure the performance of a sensor on the condition similar to that when the sensor is used by varying the air-fuel ratio of a mixed gas fed to a combustion gas generator cyclically. CONSTITUTION:A mixed gas is fed to a combustion gas generator 8 by way of an air feed pipeline 1a having reducing valves 2 and 3 and a solenoid valve 17 and a propane gas feed pipeline 1b having reducing valves 4 and 5 and a solenoid valve 7. A square wave oscillator is used for the signal generator 18, which controls the opening or closing of the valves 7 and 17 through a solenoid valve driving circuit 13. According to the closing and opening of the valves 7 and 17, and air-fuel ratio of the mixed gas to be fed to the generator 8 varies in a square wave. Outputs of an air-fuel sensor 9 and the signal generator 18 are inputted into a waveform processor 19 to be processed over many cycles.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a performance measuring device for an air-fuel ratio sensor (such as an oxygen sensor) used for air-fuel ratio control of an internal combustion engine.

As a conventional air-fuel ratio performance measuring device, there is a powerful one as shown in FIG. 1, for example.

This is a device that burns a mixture of propane gas and air and uses the combustion gas to measure the performance of a single air-fuel ratio sensor, and consists of the following parts.

That is, 1a is an air supply pipe having a pressure reducing valve 2.6 and a solenoid valve 6, 1b is a propane gas supply pipe having a pressure reducing valve 4.5 and a solenoid valve 7, 8 is a burner which is a combustion gas generator, 9 1 is an air-fuel ratio sensor to be measured, 10 is a thermal lightning pair for measuring exhaust temperature, 11 is an ignition device, 12 is a gas sampling pipe for an analyzer, 1
6 is a solenoid valve drive 1j31 path, 14 is a step voltage generator, 15 is a response characteristic measuring device, and 16 is a recording device.

When measuring the performance of the air-fuel ratio sensor using this device, the air-fuel ratio of the mixed gas supplied to the burner 8 is controlled as follows. 1. First, adjust the basic supply amount of air and nopan gas using the pressure reducing valve 2.4 to determine the base air-fuel ratio. The base air-fuel ratio is set to 1, IJ, 7ch (rich) or 1in (lean). By adjusting kjP6 and opening the solenoid valve 6, air is added to the mixed gas and the air-fuel ratio can be brought to a lean state. In other words, turn on the solenoid valve 6 -)
By switching from ol' F or 011' I- to ON, the air-fuel ratio of the mixed gas changes from lean to rich to rich.
It changes in a lean and step-like manner. Step voltage generator (
When a step voltage is generated at step 14 (change the voltage stepwise using a manual switch), and is converted into power that can operate the solenoid valve 6 by the solenoid valve drive circuit 13 and transmitted, the solenoid valve 6 changes from ON to 0FF4 or OFF'- +ON operation,
An output voltage is generated in the air-fuel ratio sensor 9 in response to this change in the state of the combustion gas from lean to rich or from rich to lean.

FIGS. 2(a) and 2(b) show the step voltage and the waveform of the air-fuel ratio sensor output voltage in response thereto. The response characteristic measuring device 15 inputs the air-fuel ratio sensor output voltage and the step voltage, and calculates the response time from a certain reference value of the air-fuel ratio sensor output voltage to another reference value (1. and 1f in FIG. 2). ) to measure. The response characteristic measuring device 15 also measures the upper and lower peak values of the air-fuel ratio sensor output voltage, that is, the rich side output and the rich side output.

Solenoid valve 6 (D ON -+ OF F, OF]!'-
+ON (D t'h The operation is based on a manual signal and has no periodicity, and the interval between each operation is several tens of seconds or more. In measurement with this device, each operation is performed only once.

This device is used, for example, to test the performance of air-fuel ratio sensors at the time of factory shipment, and the rich side output is below a certain test standard value, and the lean side output is above a certain test standard value.1. The conditions for the performance test are that 1 (is below a certain test standard value) and 1 (is below a certain test standard value).

However, the air-fuel ratio changes from rich to lean and lean to rich in this device are changes from one static state to another static force state, and the air-fuel ratio repeats pulsating changes due to feedback control by the air-fuel ratio sensor. Even if you use this device to measure the rich side output, lean side output, Ill, and L(), the condition will be very different from the one at 11 o'clock.
The measured value is an accurate reflection of the control performance with the sensor installed on the 111 cars, especially the exhaust gas during pattern running such as 107-7. There is also large variation in the measured values of tr and tl. For this reason, measurements made by the Jonin device could only be used to identify extremely defective products, and the only way to evaluate control performance with the sensor mounted on a vehicle was through actual vehicle driving tests.

In view of the above points, the present invention provides an air-fuel ratio sensor that can obtain measurement results that have a good correlation with the amount of exhaust gas during pattern driving with a single air-fuel ratio sensor, and that can evaluate performance in use without conducting actual vehicle driving tests. The purpose is to provide a performance measurement device.

In order to achieve the above object, the present invention controls the air-fuel ratio of the mixed gas supplied to the combustion gas generator using an air-fuel ratio change signal with a waveform that changes periodically, and simulates the air-fuel ratio in the state when the sensor is used. A waveform processing device calculates the difference between the rising slope and falling slope of the output waveform in response to the periodic air-fuel ratio changes of the air-fuel ratio sensor to be measured, which is placed in the combustion gas produced by the combustion gas generator. It is calculated and displayed using the following formula.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 6 is a schematic diagram showing an embodiment of the present invention, in which the same reference numerals as in FIG. 1 indicate corresponding parts, and the explanation thereof will be omitted.

This device is similar to the conventional example shown in FIG.
By adjusting the basic supply amount of propane gas on air to set a base air-fuel ratio (rich), air can be added to it using the pressure reducing valve 6 and the solenoid valve 17 to create a lean state. The solenoid valve 17 and the solenoid valve drive circuit 16 constitute an air-fuel ratio control device. As the solenoid valve 17, tens to hundreds of 112
If you use a device that can open and close at a high rate of 1 degree and adjust the air flow rate continuously by changing the duty ratio, the air flow rate can be adjusted to 11 degrees in response to any waveform other than a rectangular wave. It is also possible to control the solenoid valve 17 in the first
As a valve similar to the solenoid valve 6 shown in the figure, a case will be described in which the air flow: □;• is changed in a rectangular wave shape.

A1: A square wave oscillator is used as the generator 18, and 0.
The rectangular wave-like air-fuel ratio change range, which occurs every 6 to 5 seconds, is applied to the solenoid valve drive circuit 13 and converted into power for driving the solenoid valve 17, and the solenoid valve 17 is opened and closed by this signal.

As a result, the air flow rate passing through the electromagnetic valve 17 changes in a rectangular wave pattern, and therefore the air-fuel ratio of the mixed gas supplied to the burner 8, which is a combustion gas generating device, also changes in a rectangular wave pattern from rich to lean and lean to lean. The air-fuel ratio change width is set between A/F=0.5 and 2 with the stoichiometric air-fuel ratio as the center.

As a result of the above, the periodic change in the air-fuel ratio approximates the state when the air-fuel ratio sensor is in use.

In response to this air-fuel ratio change, the output voltage generated by the air-fuel ratio sensor 9 to be measured placed in the combustion gas of the burner 8 and the rectangular wave signal of the signal generator 18 are input to the waveform processing device 19.
Waveform processing is performed over multiple cycles. If necessary, the sensor output and the exhaust temperature measured by the thermocouple 10 are recorded by the recording device 16.

The solenoid valve 7 is kept fully closed during the measurement. The 1L solenoid valve 7 and the pressure reducing valve 5 are used to accelerate warming up at the start of work or to create an extremely rich condition. ℃), and the exhaust temperature is 650 to 700.
Set the amount of gas flow port so that the Q value remains at a predetermined value during ℃.

The waveform processing device 19 is composed of a digital computer or the like. Next, the waveform processing method will be explained with reference to FIG.

The maximum value of the air-fuel ratio sensor output voltage [Fig. 4 (1+)] corresponding to one period (i IIN) of the rectangular wave signal [Fig. 4 (a)] is set as 100 coefficient output, the minimum value as 0% output, and The time from the moment when the wave signal changes from the lean side to the rich side until the sensor output reaches 50% is '11.', and the time when the sensor output is 50% or more (1) The rising slope (i bin θ17) and the falling slope (i'-1 an O) are measured by waveform processing.

This (111, (1) is the slope at a predetermined reference value between the upper doveak values of the sensor output, or the average slope divided by the response time from the predetermined reference value to another predetermined reference value. The single waveform processing device 19 calculates this T.
Average the values of old ゛, Or, ()'' over multiple periods ``
11. The values of (il and
)) That is, the difference between the slope and the falling slope and the upper and lower peak values are displayed.

According to this device, the air-fuel ratio of the mixed gas supplied to the combustion gas generator changes periodically, approximating the state when the sensor is used. The values of T11, RT, Gr, G, . . . dG accurately reflect the control performance of the air-fuel ratio sensor when mounted on the vehicle. Figure 5 shows the relationship between the d(i value (msec/V)) measured by this device and the NOx emissions (g/km) during pattern running, and it is clear that there is a good correlation between the two. This means that in the air-fuel ratio control of a vehicle engine, if the falling slope of the sensor response waveform is large (the d() value is large) compared to the rising slope of the sensor response waveform, the air-fuel ratio is controlled to the lean side. Emission NO.
x amount increases, and conversely, the falling slope is small (dG value is small)
If so, this is because the air-fuel ratio is controlled to the rich side and the amount of exhaust NOx decreases, and this relationship between the dG value and the amount of exhaust gas was confirmed for the first time from the measurement results using this device.

By using this relationship, it is possible to immediately determine from the dG value whether the air-fuel ratio sensor to be measured has control performance that complies with exhaust gas regulations. Note that Tr', RT, and upper and lower peak values are used to discover abnormal sensors in performance tests.

This device can obtain measurement results that reflect the dynamic characteristics of the sensor by taking just one period of the response waveform to periodic changes in the air-fuel ratio, but by taking the average value over multiple periods, the variation in measured values can be reduced. can do.

Although the above embodiment describes the case where the air-fuel ratio is changed in the form of a rectangular wave, similar effects can be obtained by using a triangular wave, trapezoidal wave, sine wave, etc. other than the rectangular wave as the air-fuel ratio change signal. In addition, if an air-fuel ratio sensor with known characteristics is used as a master sensor and the air-fuel ratio of the mixed gas is changed quasi-periodically by feedback-controlling the air-fuel ratio of the mixed gas using the output signal of this master sensor, it is possible to change the air-fuel ratio when using the sensor. 4. The performance of the air-fuel ratio sensor to be measured can be measured under conditions closer to the actual state.The air-fuel ratio sensors that can be measured by this device include an luconia-based oxygen sensor, a titania-based oxygen sensor, and a cobalt oxide-based oxygen sensor. There are other oxygen sensors, such as '1: and carbon oxide sensors.

As is clear from the above description, the air-fuel ratio sensor performance measuring device according to the present invention has a good correlation between the output waveform of the air-fuel ratio sensor that responds to periodic air-fuel ratio changes and the amount of exhaust gas of the vehicle during pattern driving. Since the measurement results can be obtained, it is possible to accurately evaluate the control performance of the air-fuel ratio sensor installed in the vehicle without conducting actual vehicle driving tests, and is useful for performance inspections at the time of factory shipment or performance evaluation of prototypes. It has great benefits when used for.

[Brief explanation of drawings]

Figure 1 is a schematic diagram of a conventional example of an air-fuel ratio sensor performance measurement device.
Fig. 2 is a diagram of the air-fuel ratio change signal and the output waveform of the air-fuel ratio sensor, Fig. 3 is a schematic diagram showing an embodiment of the present invention, and Fig. 4 is a diagram of the air-fuel ratio change signal and the output waveform of the air-fuel ratio sensor. FIG. 5 is a diagram showing the relationship between the dG value measured by this device and the amount of NoX discharged during pattern running. 1a... Air supply pipe 1b... Propane gas, gas supply pipe 8... Burner 9, which is a combustion gas generator... Air-fuel ratio sensor to be measured 16... Solenoid valve drive circuit 17... Solenoid valve 18, which is an air-fuel ratio control device... Rectangular wave oscillator 19, which is a signal generator...Waveform processing device Patent attorney Junnosuke Nakamura Daiichi Kyōjiki 1 Main job: vJ ・ ・ ・ ・ ・・ ・

Claims (1)

[Scope of Claims] (1) A device for measuring the performance of a single air-fuel ratio sensor using combustion gas, comprising: a combustion gas generator; a signal generator that generates an air-fuel ratio change signal with a periodically changing waveform; ,
Air-fuel ratio control I devices for controlling the air-fuel ratio of the mixed gas supplied to the combustion gas generation device according to the air-fuel ratio change signal generated by the signal generation device, arranged in the combustion gas from the combustion gas generation device 6 a waveform processing device that inputs the output voltage of the air-fuel ratio sensor to be measured and the air-fuel ratio change signal to calculate and display the difference between the rising slope and the falling slope of the emerging waveform of the air-fuel ratio sensor; An air-fuel ratio sensor performance measuring device characterized by comprising: (2) The waveform processing device controls the air-fuel ratio sensor output waveform)
1. The air-fuel ratio sensor performance measuring device according to claim 1, wherein the difference between the rising slope and the falling slope is calculated by averaging over multiple periods. (5) The waveform processing device calculates the difference between the rising slope and the falling slope at a predetermined reference value between the upper and lower peak values of the air-fuel ratio sensor output waveform, or the difference between the rising slope and the falling slope at a predetermined reference value between the upper and lower peak values. The air-fuel ratio sensor performance measuring device according to claim (1), characterized in that the difference between the average rising slope and falling slope calculated from the response time to the reference value is calculated.