JPH01321370A - Fuel consumption level measuring apparatus for internal combustion engine - Google Patents

Abstract

PURPOSE:To enable indirect measurement from a flow rate of air intake and an air/fuel ratio by delaying a reading timing of a flow rate data according to a delay time of the detection of the air/fuel ratio from an exhaust composition from the detection of the flow rate of the intake air of an internal combustion engine. CONSTITUTION:A flow rate of an intake air is detected with an air flowmeter 27 disposed on the upstream side of an intake path 24 of an internal combustion engine 21. An air/fuel ratio is detected with an air/fuel ratio sensor 30 disposed on the downstream side of an exhaust path 24 of the engine 21. In a control unit 31, the current air/fuel ratio is determined from a detection signal of the sensor 30 with an air/fuel ratio computing section 32 and a fuel consumption per unit time is computed with a fuel consumption level computing section 33 based on the air/fuel ratio thus obtained and the flow rate of the intake air detected with the flowmeter 27. In addition, a time corresponding to a delay time of the detection of the air/fuel ratio from the detection of the flow rate of the intake air is applied to an arithmetic section 33 with a delay time setting section 35 to delay the reading of the intake air flow rate data accordingly thereby computing a fuel consumption level by the set delay time using previous data.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a fuel consumption measuring device that indirectly measures the fuel consumption of an internal combustion engine from an intake air flow rate and an air-fuel ratio.

Conventional technology For example, as a type of display device for the driver of a car,
There are devices that display fuel consumption per unit time that changes from moment to moment and the distance that can be traveled with remaining fuel based on this (for example, Japanese Patent Application Laid-Open No. 60-50420, Japanese Patent Application Laid-Open No. 60-60
-143720, etc.).

In this type, a fuel flow meter is interposed in the middle of the fuel pipe to measure the amount of fuel consumed, so that the amount of fuel consumed can be directly measured.

Problems to be Solved by the Invention However, this conventional fuel consumption measuring device has the disadvantage that the cost of parts increases due to the addition of a new fuel flow meter. Furthermore, in an internal combustion engine equipped with a fuel injection valve, only a portion of the fuel supplied to the fuel injection valve is actually injected, and excess fuel is returned to the fuel tank, making measurement using a fuel flowmeter difficult.

Means for Solving the Problems Therefore, in the present invention, the fuel consumption amount is determined indirectly from the intake air flow type and the air-fuel ratio. That is,
The fuel consumption measuring device for an internal combustion engine according to the present invention includes a first
As shown in the figure, there is a means 1 for detecting the intake air flow rate of an internal combustion engine, a means 2 for detecting the air-fuel ratio from the exhaust composition, and a delay time of the air-fuel ratio detection with respect to the intake air flow rate detection.
Means 3 for delaying the timing of reading intake air flow rate data
and means 4 for calculating the fuel consumption based on the detected air-fuel ratio and the intake air flow rate detected earlier by the delay time.
It is composed of:

The air-fuel ratio detected from the exhaust composition of an internal combustion engine is the weight ratio of the amount of air actually involved in combustion and the amount of supplied fuel, so if this and the intake air flow rate per unit time are known,
You can know the amount of fuel consumed per unit time. That is, assuming that the air-fuel ratio is R1 and the intake air flow rate (g/sea) is A, the fuel consumption amount F (g/5ec) is basically determined by the following equation.

F=A/R Here, the air-fuel ratio is detected in the exhaust system of the engine, and the response of the sensor itself is also lower than that of the sensor for detecting the intake air flow rate, so its detection lags behind the detection of the intake air flow rate. It includes time. In other words, while the intake air flow rate is detected immediately before combustion, the air-fuel ratio is detected a considerable amount of time after combustion.

In the above configuration, the fuel consumption amount is calculated based on the air-fuel ratio detected at a certain moment and the intake air flow rate detected earlier by the delay time, taking this delay time into account. Therefore, even during transient operation, the influence of the delay time is eliminated.

Embodiment FIG. 2 shows the mechanical configuration of an embodiment of the present invention.

In the figure, 21 is an internal combustion engine equipped with a fuel injection valve 22 at each intake port, 23 is an intake passage connected to this internal combustion engine 21, and 24 is an exhaust passage similarly connected to the internal combustion engine 2I.

The intake passage 23 has a throttle valve 25 and an air cleaner 26 upstream thereof. And air cleaner 2
An air flow meter 27 for detecting the intake air flow rate is disposed further upstream of the air flowmeter 6 . As the air flow meter 27, one that can measure mass flow rate, such as a hot wire flow meter, is used.

Further, a catalytic converter 28 and a muffler 29 are interposed in the exhaust passage 24. And the above muffler 29
An air-fuel ratio sensor 30 is disposed downstream of the air-fuel ratio sensor 30 . As the air-fuel ratio sensor 30, a wide-range air-fuel ratio sensor is used that utilizes the fact that the pumping current 1p changes depending on the air-fuel ratio depending on the exhaust composition (see FIG. 3).

In addition to the downstream position of the muffler 29 (position D), the air-fuel ratio sensor 30 can be installed slightly downstream of the exhaust boat (position A) or slightly downstream of the catalytic converter 28, as shown by the broken line. It is also possible to select the upstream side (position B) or between the catalytic converter 28 and the muffler 29 (position C).

Reference numeral 31 indicates a control unit that calculates the amount of fuel consumed, controls the injection amount of the fuel injection valve 22, and the like.

This control unit 3■ includes CPU, ROM, R
It is composed of a microcomputer consisting of an AM, an interface, etc., and functionally includes an air-fuel ratio calculation section 32, a fuel consumption calculation section 33, an operating condition detection section 34, a delay time setting section 35, and an output as shown in the figure. 36.

That is, the air-fuel ratio sensor 30 is
The air-fuel ratio at that time is determined from the detection signal. In addition, the fuel consumption calculation unit 33 calculates the fuel consumption per unit time based on this air-fuel ratio and the intake air flow rate detected by the air flow meter 27 using the above-mentioned calculation formula, and outputs the fuel consumption amount from the output unit 36. Output as a quantity. Here, an appropriate delay time T is given to the fuel consumption amount calculation section 33 by the delay time setting section 35, and the reading of the intake air flow rate data in the fuel consumption amount calculation section 33 is delayed by that amount. That is, the fuel consumption amount is calculated using the intake air flow rate data before the delay time T set by the delay time setting section 35.

The delay time T described above corresponds to the delay time of air-fuel ratio detection with respect to intake air flow rate detection, and is variably set according to the operating conditions detected by the operating condition detection section 34.

That is, the air flow meter 27 is located upstream of the internal combustion engine 21 and detects the intake air flow rate before it flows into the combustion chamber. Furthermore, the sensor itself has very high responsiveness to changes in intake air flow rate. Therefore, the detection delay is usually less than 1xs and can be almost ignored.

On the other hand, the air-fuel ratio sensor 30 is located downstream of the internal combustion engine 2I and detects the air-fuel ratio based on the composition of the exhaust after combustion. The time required for exhaust gas to flow from the combustion chamber to the air-fuel ratio sensor 30 always exists as a mechanical delay time To (see FIG. 4). Incidentally, FIG. 4 shows how the detection signal changes when the actual air-fuel ratio is suddenly changed. Then, this delay time To is determined by the air-fuel ratio sensor 30.
The delay time varies greatly depending on the mounting position of the air-fuel ratio sensor 30, and as shown in FIG. 5, the delay time TD, ~'rod at each position A-D described above becomes larger as the air-fuel ratio sensor 30 is located downstream. Further, as a characteristic of the sensor itself, the delay time T9° (see FIG. 4) required for the detection signal level to change by 90% is generally 50 degrees or more and cannot be ignored.

Therefore, in the above configuration, the delay time T is To+T s. I am trying to eliminate that influence by giving it a close-up.

FIG. 6 shows the flow of processing for setting a specific delay time T. First, the detection signal Q of the air flow meter 27 is read as a signal indicating the operating condition (step 1).

Next, based on the value of Q, the mechanical delay time TD
Perform a table lookup (Step 2). In other words, since the delay time To depends on the exhaust flow velocity, it has a unique relationship with the air flow rate. Therefore, the delay time T follows the characteristics shown in FIG. is determined. Furthermore, this characteristic is
It will be different if the layout of the exhaust system is different, but since the change mainly depends on the volume of the exhaust flow path from the internal combustion engine 21 to the air-fuel ratio sensor 30, it is necessary to define a correction coefficient corresponding to the volume of the exhaust flow path. Even if the exhaust system layout changes, the appropriate delay time To can be determined simply by manually inputting data on the exhaust flow path volume.

Next, the delay time T, which depends on the characteristics of the sensor.

is looked up in a table based on the value of Q (step 3). This delay time T. It is also affected by the exhaust flow velocity, and has a relationship with the detection signal Q of the air flow meter 27 as shown in FIG. And finally T = T o +
Ts. Then, the delay time T is determined (step 4).

In addition, engine speed, intake pipe pressure, exhaust pressure, etc. can be used as engine operating conditions, or exhaust flow rate (
(flow velocity) may be directly detected.

Further, even if the delay time T is fixedly set to an appropriate value without being changed depending on the engine operating conditions as described above, sufficiently good fuel consumption can be measured.

Figure 9 shows the results of an experiment in which fuel consumption was measured using the above-mentioned example device.
(Constant Volume Sample
ng) shows the fuel consumption determined from the exhaust gas analysis values (co, Co, IC) by the device. The two are in good agreement, which means that the device of the present invention performs measurements with sufficiently high accuracy even during transient times. Note that the time difference between the two is due to the response speed of the comparative example being about 1 second slower.

Effects of the Invention As is clear from the above explanation, the fuel consumption measuring device for an internal combustion engine according to the present invention can indirectly measure the fuel consumption from the intake air flow rate and the air-fuel ratio. There is no need to provide a fuel flow meter inside. Therefore, the piping does not become complicated in an internal combustion engine equipped with a fuel injection valve, and it can be easily applied to an engine using LPG fuel.

[Brief explanation of the drawing]

Fig. 1 is a claim correspondence diagram showing the configuration of the present invention, Fig. 2 is a configuration explanatory diagram showing an embodiment of the invention, Fig. 3 is a characteristic diagram showing the output characteristics of the air-fuel ratio sensor, and Fig. 4 is a diagram showing the air-fuel ratio sensor. Figure 5 is a characteristic diagram showing the response characteristics of the fuel ratio sensor; Figure 5 is a characteristic diagram showing the response characteristics when the air-fuel ratio sensor is installed at different positions;
The figure is a flowchart showing the flow of processing when setting the delay time T, Figure 7 is a characteristic diagram showing the relationship between the air flow rate signal Q and the delay time To, and Figure 8 is the air flow rate signal Q and the delay time. FIG. 9 is a characteristic diagram showing the relationship with T8°, and FIG. 9 is a characteristic diagram showing changes in fuel consumption measured by the measuring device according to the present invention. DESCRIPTION OF SYMBOLS 1... Intake air flow rate detection means, 2... Air-fuel ratio detection means, 3... Delay means, 4... Calculation means. Figure 1 Figure 3 Air-fuel ratio 512 Figure 4 Figure 5 Figure 1 = Figure 6 Figure 7 Figure 8 aQa Time (sec)

Claims (1)

[Claims] (1) A means for detecting the intake air flow rate of the internal combustion engine, a means for detecting the air-fuel ratio from the exhaust composition, and a delay in the reading timing of the intake air flow rate data according to the delay time of the air-fuel ratio detection with respect to the intake air flow rate detection. and means for calculating fuel consumption based on the detected air-fuel ratio and the intake air flow rate detected earlier by the delay time.