JPH04292552A - Device for detecting intake air quantity of engine - Google Patents

Abstract

PURPOSE:To provide a device for detecting intake air quantity of an engine, which can obtain the accurate absolute value output, at a relatively low cost. CONSTITUTION:The output of an absolute output type sensor 1 is taken into an A/D converting unit 3 through an input unit 2, and is converted to the digital output to be an output value Q on the basis of the reference voltage generated by a reference voltage source 4. When an engine stop judging unit 11 detects the stop condition of an engine, the output value Q at this stage is held as Q-stop by a stop time holding unit 12. A deviation output unit 13 obtains a deviation Q between the R-stop, which is previously set as an ideal value of the Q-stop by a reference value holding unit 14, and a real Q-stop. A subtraction unit 15 corrects the output value Q with the deviation Q and eliminates the offset component of an error to obtain a correction value QQ, and this correction value QQ is given to a fuel injection quantity computing unit 5.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine intake air amount detection device, and more particularly to an intake air amount detection device using an absolute output type intake air amount detection sensor.

0002

[Background Art] The intake air amount of the engine is a very important parameter when performing electronic engine control, and in order to perform appropriate fuel injection control, it is necessary to detect the intake air amount with high accuracy. . Engine intake air amount detection devices include absolute output type devices that use air flow meters such as hot wires, hot resistors, and pressure sensors as intake air amount sensors, and devices that use vane type air flow meters as intake air amount sensors. It is classified as a relative output type device. For example, Japanese Unexamined Patent Publication No. 12843/1984 discloses an absolute output type intake air amount detection device using a hot wire.

0003

[Problems to be Solved by the Invention] The above-mentioned relative output type device has the advantage that absolute errors are canceled out because the detected value is determined as a relative value, but since it uses a vane type air flow meter, The disadvantages are that the pressure loss is large, the response is slow, and the degree of freedom in the layout of the intake system is reduced. On the other hand, an absolute output type device has the advantage of eliminating these drawbacks, but has a major problem in that the detected value is determined as an absolute value, so an absolute error is included in the detected value. In order to obtain more accurate absolute value output, sensors, A/D
It is necessary to improve the accuracy of each signal processing circuit such as the converter and its reference voltage source, resulting in a significant increase in cost.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an engine intake air amount detection device that can ensure accurate absolute value output at a relatively low cost.

[0005]

[Means for Solving the Problems] (1) The first invention of the present application provides an intake air amount detection device for an engine, which includes an absolute output type intake air amount detection sensor and a detection means for detecting a predetermined operating state of the engine. means for storing a reference value preset as an ideal output value of the sensor in this predetermined operating state; and means for storing a deviation between the actual output value of the sensor in this predetermined operating state and the stored reference value. This includes means for determining the deviation, and means for correcting the actual output value of the sensor based on this deviation.

(2) The second invention of the present application is an engine intake air amount detection device, which includes an absolute output type intake air amount detection sensor, a detection means for detecting a predetermined operating state of the engine, and a detection means for detecting a predetermined operating state of the engine. means for storing a first reference value preset as an ideal output value of the sensor in the current state; and causing the sensor to perform a test operation of outputting a predetermined test output value regardless of the actual intake air amount. means for storing a second reference value preset as an ideal value of the test output value; an actual output value of the sensor in the aforementioned predetermined operating state; and an actual output value of the sensor during the test operation. and means for correcting the actual output value of the sensor based on the first reference value and the second reference value.

[0007]

[Function] (1) In the intake air amount detection device according to the first invention of the present application, a predetermined operating state of the engine, such as when the engine is stopped, is detected. Then, the deviation between the actual output value of the sensor when the engine is stopped and a preset reference value is determined. If a correct sensor output value with no error is set as a reference value when the engine is stopped, the determined deviation will be a value indicating an offset component that causes an error. Therefore, by correcting the actual output value of the sensor based on this deviation, it is possible to obtain a detected value with the offset component of the error removed.

(2) In the intake air amount detection device according to the second invention of the present application, like the first invention described above, a predetermined operating state such as when the engine is stopped is detected, and when the engine is stopped, the sensor The actual output value is determined. Furthermore, the sensor is caused to perform a test operation and output a predetermined test output value regardless of the actual amount of intake air. In this way, the actual output value of the sensor is corrected based on the actual output value of the sensor when the engine is stopped, the actual output value of the sensor during test operation, and the reference value set in advance for each. be exposed. Since the linear conversion correction is performed based on four values, it is possible to obtain a detected value from which both the offset component of the error and the proportional component of the error are removed.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained below based on illustrative embodiments. FIG. 1 is a block diagram showing the basic configuration of an intake air amount detection device according to an embodiment of the first invention of the present application. The sensor 1 is an absolute output type intake air amount sensor such as a hot wire, hot resistor, or pressure sensor. Input section 2
consists of circuits such as noise filters, and sensor 1
The detected value is extracted as an electrical signal. The extracted electrical signal is subjected to analog/digital conversion in the A/D converter 3. This conversion is performed based on the reference voltage value generated in the reference voltage source 4. In this way, the output value of the sensor is converted into digital data and then input to the fuel injection amount calculation section 5. The fuel injection amount calculation unit 5 calculates the fuel injection amount based on the input data.

The above is the basic configuration of a system using a conventional absolute output type engine intake air amount detection device. However, the output value Q of the A/D converter 3 generally includes an error. This error is due to the characteristics of the circuits that constitute the sensor 1, input section 2, and A/D conversion section 3, and in particular, the reference voltage generated by the reference voltage source 4 contains a large error. There are many things.

The intake air amount detection device of the present invention corrects the output value Q including such an error to obtain a correction value QQ from which the error is removed. For this purpose, the following components are provided: an engine stop determination section 11, a stop state holding section 12, a deviation output section 13, a reference value holding section 14, and a subtractor 15. The engine stop determination unit 11 has a function of determining whether the engine is stopped based on a signal given from the outside. In this embodiment, a signal RPM indicating the engine rotational speed is input, and it is determined that the engine has stopped when the RPM becomes less than or equal to a predetermined threshold value. The stop state holding unit 12 always receives the output value Q of the A/D converter 3, and stores the input output value Q at the time when a signal indicating the engine stop state is given from the engine stop judgment unit 11. It has the function of holding. Here, the output value held when the engine is stopped will be expressed as Qstop. This held value Qstop is given to the deviation output section 13. The deviation output unit 13 is given a predetermined reference value Rstop from the reference value holding unit 14 . Reference value holding unit 14
holds a preset reference value Rstop. This reference value Rstop is determined by the A/D when the engine stops when the entire device is an ideal device with no errors.
This value is set in advance as a value corresponding to the output value Q to be output from the converter 3. When the deviation output unit 13 receives a signal indicating the stopped state of the engine from the engine stop determination unit 11, the deviation output unit 13 outputs the held value Qstop held by the stop state holding unit 12 and the reference value held by the reference value holding unit 14. Find the deviation ΔQ between Rstop and output it. The subtracter 15 calculates a deviation from the output value Q of the A/D converter 3.
Subtract the deviation ΔQ output by 3 and use the result as the correction value QQ
It is given to the fuel injection amount calculation unit 5 as a value.

The basic configuration of this device has been explained above, but
Next, the principle of correction by this device will be explained using the graph of FIG. 2. The graph in FIG. 2(a) is a graph showing the relationship between the intake air amount and the sensor output value in an ideal case (that is, when this device does not include any errors). With absolute output type intake air flow rate sensors such as hot wires, hot resistors, and pressure sensors, as shown in this graph, even when the intake air flow rate is 0, the sensor output value does not become 0, but reaches a predetermined value. An output value Rstop is obtained. In other words, even when the engine is stopped, the sensor outputs the predetermined output value Rstop. The reference value held by the reference value holding unit 14 is exactly this output value R.
This corresponds to stop. That is, sensor 1,
If the input section 2, A/D conversion section 3, and reference voltage source 4 are ideal and do not contain any errors, the ideal output value Q that should be obtained from the A/D conversion section 3 when the engine is stopped is corresponds to the value. However, in reality, it is inevitable that errors will occur as described above, and the correct output value will be different from the actual output value. The graph in FIG. 2(b) is a graph showing the relationship between the correct output value and the actual output value. In an ideal device that does not include errors, the correct output value and the actual output value will always be the same value over the entire range, as shown in graph A in the figure. However, in reality, as shown in graph B, the actual output value Q does not match graph A and contains an error. Here, if the correct output value when the engine is stopped is Rstop, the actual output value Qstop is greater than that by the deviation ΔQ. Therefore, if a correction value QQ obtained by subtracting the deviation ΔQ is used instead of the actual output value Q, a value with less error can be used. That is, graph C is used instead of graph B, and values closer to the correct graph A can be obtained. In other words, the offset component of the error can be removed.

The apparatus shown in FIG. 1 performs correction based on this principle. That is, the engine stop determination unit 1
1, when it is determined that the engine has stopped, the output value Q of the sensor at that time is held as a holding value Qstop by the stop holding unit 12, and the deviation output unit 13 sets the holding value Qstop as the holding value Qstop. The deviation ΔQ from the reference value Rstop is determined by the following calculation: ΔQ = Qstop − Rstop. The subtracter 15 performs the calculation QQ = Q - ΔQ on the output value Q to obtain a correction value QQ, and provides this to the fuel injection amount calculation section 5 . In this way, even after the engine is started, correction using the same deviation ΔQ is performed. The deviation ΔQ is
Since it is updated every time the engine is stopped, it is possible to always perform correction using the latest deviation.

Next, an embodiment of the intake air amount detection device according to the second invention of the present application will be described with reference to FIG. In the embodiment of FIG. 3, the same components as in the embodiment of FIG. 1 are designated by the same reference numerals. That is, the detected value of the sensor 1 is taken out as an electrical signal by the input section 2, and
The /D conversion section 3 digitizes the reference voltage given from the reference voltage source 4 and outputs an output value Q to be given to the fuel injection amount calculation section 5. In order to correct this output value Q, each component includes an engine stop judgment section 11, a stop holding section 12, a test control section 21, a test holding section 22, a correction section 23, and reference value holding sections 14 and 24. has been established.

As described above, the engine stop determination unit 11 receives the signal RPM indicating the engine rotational speed, and determines that the engine has stopped when the RPM becomes equal to or less than a predetermined threshold value. Further, the stop state holding unit 12 always inputs the output value Q of the A/D converter 3, and when a signal indicating the engine stop state is given from the engine stop determination unit 11,
It has a function of holding the input output value Q as a holding value Qstop. The reference value holding unit 14 holds a preset reference value Rstop. As mentioned above, this reference value Rstop is a value corresponding to the output value Q that should be output from the A/D converter 3 when the engine is stopped when the entire device is an ideal device that does not include errors. This is set in advance. A feature of the second invention of the present application is that a test control section 21 is further provided to cause the sensor 1 to execute a test operation. This test operation is performed when the engine is stopped. The test control unit 21 issues a command to the sensor 1 to execute a test operation when a signal indicating the engine stop state is output from the engine stop determination unit 11. The sensor 1 is designed so that it can perform a test operation when receiving such a command. This test operation is an operation that outputs a predetermined test output value regardless of the actual amount of intake air. Although any value may be output as the test output value, in order to perform optimal correction, it is preferable to output an output value corresponding to the full range of the sensor as the test output value. In this embodiment, during a test operation, the power supply voltage supplied to the sensor 1 is output as is as a test output value.Hereinafter, the output value Q of the A/D converter 3 during this test operation will be described. The output value will be expressed as Qfull. The test holding unit 22 always receives the output value Q of the A/D converter 3, and when a signal indicating execution of the test operation is given from the test control unit 21, the value of the input output value Q is held as a value. It has a function to hold as Qfull. On the other hand, the reference value holding unit 24 holds a preset reference value Rfull. This reference value Rful
l is preset as a value corresponding to the output value Q that should be output from the A/D converter 3 during test operation if the entire device is an ideal device without errors. The correction unit 23 stores the holding value Qstop held in the stop holding unit 12, the holding value Qfull held in the testing holding unit 22, the reference value Rstop held in the reference value holding unit 14, and the reference value holding unit 14. Based on the four values of the reference value Rfull held in the unit 24, A/
A correction is made to the output value Q of the D converter 3, and the result is given to the fuel injection amount calculation section 5 as a correction value QQ.

The basic configuration of this device has been explained above, but
Next, the principle of correction by this device will be explained using the graph of FIG. 4. The graph in FIG. 4 is a graph showing the relationship between correct output values and actual output values. In an ideal device that does not include errors, the correct output value and the actual output value will always be the same value over the entire range, as shown in graph A in the figure. However, in reality, as shown in graph B, the actual output value Q does not match graph A and contains an error. Here, if the correct output value when the engine is stopped is Rstop, then the actual output value Qstop
p is larger than that by the deviation ΔQ1. Also,
The correct output value when sensor 1 performs the test operation is R
If it is full, the actual output value Qfull is smaller by the deviation ΔQ2. Therefore,
Match 2 points PA1 and PB1, 2 points PA2 and PB2
Graph B can be made to match graph A by performing a linear transformation so that they match.

The apparatus shown in FIG. 3 performs correction based on this principle. That is, the engine stop determination unit 1
1, when it is determined that the engine has stopped, the stop state holding unit 12 holds the output value Q of the sensor at that time as a held value Qstop. Subsequently, the test control unit 21 outputs an instruction to perform a test operation, and the test holding unit 22 sets the output value Q during the test to the held value Qfull.
is retained as. The correction unit 23 has a holding value Qstop,
Qfull, and reference values Rstop, Rfull, for the output value Q, α = (Qfull-Qstop)/(Rful
l-Rstop)QQ= (Q-Qstop
+ α·Rstop) / α is performed to obtain a correction value QQ, which is provided to the fuel injection amount calculation unit 5. In the embodiment shown in FIG. 1 described above, only the offset component of the error was removed, but in the embodiment shown in FIG. 3, not only the offset component but also the proportional component can be removed. Another advantage is that a span check over the full range of the sensor 1 can be performed at the same time, providing a sensor self-diagnosis function.

Although the present invention has been described above based on two embodiments, the present invention is not limited to these embodiments only, and can be implemented in various other forms. For example, in the above embodiment, the output when the engine is stopped is compared with the reference value, but it is not necessarily limited to when the engine is stopped, but when the engine is in a predetermined operation, such as when the engine is in an idling state. What is necessary is to compare the output when in the state with the reference value. Also,
In the second embodiment described above, the output corresponding to the full range of sensor 1 was used as the output during the test operation, but the output corresponding to 90% of the full range, or 50% of the full range was used.
An output corresponding to %, etc. may also be used.

[0019]

[Effects of the Invention] As described above, according to the engine intake air amount detection device according to the present invention, since the predetermined output value of the sensor is corrected by comparing it with a reference value, it is possible to obtain accurate information at a relatively low cost. Absolute value output can be obtained.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the basic configuration of an intake air amount detection device according to an embodiment of the first invention of the present application.

FIG. 2 is a graph for explaining the principle of correction processing performed by the apparatus shown in FIG. 1;

FIG. 3 is a block diagram showing the basic configuration of an intake air amount detection device according to an embodiment of the second invention of the present application.

FIG. 4 is a graph for explaining the principle of correction processing performed by the apparatus shown in FIG. 3;

[Explanation of symbols]

1...Sensor 2...Input section 3...A/D conversion section 4...Reference voltage source 5...Fuel injection amount calculation section 11...Engine stop judgment unit 12...Holding part when stopped 13... Deviation output section 14...Reference value holding unit 15...Subtractor 21...Test control section 22...Test holding part 23...Correction section 24...Reference value holding unit

Claims (2)

[Claims] 1. An absolute output type intake air amount detection sensor, a detection means for detecting a predetermined operating state of the engine, and a reference value preset as an ideal output value of the sensor in the predetermined operating state. means for storing, means for determining a deviation between the actual output value of the sensor and the reference value in the predetermined operating state, and means for correcting the actual output value of the sensor based on the deviation. An engine intake air amount detection device comprising: 2. An absolute output type intake air amount detection sensor, a detection means for detecting a predetermined operating state of the engine, and a first output value preset as an ideal output value of the sensor in the predetermined operating state. means for storing a reference value; means for causing the sensor to perform a test operation to output a predetermined test output value regardless of the actual intake air amount; Second
means for storing a reference value of the sensor, an actual output value of the sensor in the predetermined operating state, an actual output value of the sensor during the test operation, the first reference value, and the second reference value; An intake air amount detection device for an engine, comprising: a reference value; and means for correcting the actual output value of the sensor based on the reference value.