JPH0230945A - Internal combustion engine - Google Patents

Abstract

PURPOSE:To prevent the precision deterioration due to the aging change of an intake air flow meter by setting the opening of an air flow control valve to the preset opening at the time of idling and calibrating the air flow meter with the intake air flow determined from the engine rotating speed as a reference. CONSTITUTION:The flow signal is outputted from a flow converter 6 in response to the output signal of the sensor section 5 of a hot-wire air flow meter detecting the flow in an intake passage 2, a fuel injection valve 7 is controlled by the signal from a fuel injection quantity setter 10 at the time of its operation to hold the engine rotating speed at the fixed value. The second flow signal Mj is determined by a flow converting device 13 based on output signals of a throttle valve opening setter 9 and an engine rotating speed detector 11, the verification curve for converting the output signal of the sensor section 5 of the flow converter 6 into the flow signal is calibrated by a verification curve calibrating circuit 14 based on the flow signal Mj.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an air flow meter that detects the intake air amount of an internal combustion engine. The present invention relates to an internal combustion engine equipped with an air flow meter suitable for dealing with changes in output over time caused by

[Conventional technology]

As the performance of internal combustion engines increases and exhaust gas regulations become stricter, the intake air flow rate value, which is part of the combustion control device, is required to have higher accuracy and durability so that precise air-fuel ratio control can be performed. However, in order to realize this, for example, in the case of a hot wire type air flowmeter, dust and the like that adhere to the hot wire become a problem.

A hot wire air flow meter places an electrically heated heating resistor in the air flow, and changes the amount of heat dissipated due to changes in air flow rate. Because it has a low resistance, the flow rate is detected by capturing the change in voltage across the resistor, which causes a change in the amount of heat generated. Generally, the resistance value (in other words, the temperature) of the heating resistor
The circuit is constructed to keep the value constant. The heating element is a wire or foil made of platinum, nickel, etc. whose resistance value has good temperature dependence.

The film is used as the main body of the heating resistor, and is formed either alone or by winding it around a bobbin of ceramics, glass, polyimide resin, etc., or bonding it to a substrate. In this specification, heating elements are collectively referred to as hot wire elements or hot wires.

When the intake air contains dust, it adheres to the hot wire, changing the heat transfer coefficient of the two heating resistors to the air, and changing the cooling characteristics of the resistor. As a result, even if the flow rate is constant, the voltage across the resistor to keep the resistance value of the heating resistor constant, that is, the output value as a sensor, changes, so the pre-given sensor output and flow rate verification curve If the flow rate is determined by , as dust adheres to the flow rate, it will change over time, resulting in poor flow rate measurement precision and air-fuel ratio control precision.

As a countermeasure, for example, as shown in Japanese Patent Laid-Open No. 54-76182, there is a method of heating a hot wire above the normal operating temperature to burn off the attached dust, and
As shown in Japanese Patent Publication No. 190624, a method of placing an obstacle upstream of the hot wire to reduce the number of dust particles directly attached to the hot wire has been studied.

[Problem to be solved by the invention]

In the method of heating a hot wire above the normal operating temperature and burning the attached dust, the silicon compounds contained in the dust particles melt and vitrify on the heated hot wire.
The radiation characteristics of the heat rays change due to stronger adhesion to the heat rays, and the method of placing obstacles upstream of the heat rays to reduce the number of dust particles directly adhering to the heat rays, Because of this, a hot wire is placed in its wake, which has the disadvantage of adding noise to the output signal, and is not very effective as a countermeasure against aging of hot wire air flowmeters. There was a problem.

SUMMARY OF THE INVENTION An object of the present invention is to provide an internal combustion engine that can improve the above-mentioned drawbacks, compensate for aging of the air flow meter, and perform highly accurate air-fuel ratio control.

[Means to solve the problem]

The above problem consists of a sensor that generates a signal corresponding to the intake air flow rate of an internal combustion engine, and a first sensor that inputs the signal and calculates the intake air flow rate based on a predetermined first flow rate conversion function.
Based on the air flow rate calculation means and a second flow rate conversion function that indicates the relationship between the rotational speed of the internal combustion engine and the intake air flow rate with the opening degree of the air flow control valve that controls the intake air flow rate set to a predetermined opening degree. a second air flow rate calculation means for calculating an intake air flow rate from the rotational speed of the internal combustion engine; and a calibration means for calibrating the first flow rate conversion function based on the intake air flow rate calculated by the second air flow rate calculation means. This is achieved by mounting an internal combustion engine air flow meter equipped with , on the internal combustion engine.

Further, the second air flow rate calculation means calculates the relationship between the outside temperature, atmospheric pressure, the rotational speed of the internal combustion engine, and the intake air flow rate with the opening degree of the air control valve that controls the intake air flow rate set to a predetermined opening degree. The internal combustion engine air flow meter may be used as an internal combustion engine air flow meter that calculates the intake air flow rate from outside temperature, atmospheric pressure, and the rotational speed of the internal combustion engine based on a second flow rate conversion function that indicates When the device to be set is idling, it is fully opened by the action of a spring provided on the air flow control valve, and a wire connected to the air flow control valve via a pulley is connected to the accelerator pedal to operate the accelerator pedal. The wire of the device configured to adjust the opening degree of the air flow control valve is cut in the middle and connected with a shape memory alloy, and the shape memory alloy is controlled to adjust the air flow control valve during idling. It may also be an internal combustion engine air flow meter that opens fully.

[Effect]

a first air flow rate calculation means that calculates an intake air amount based on a first flow rate conversion function based on an output signal from a sensor section of the hot wire air flow meter; and a throttle valve opening whose opening is set in advance and the rotation of the internal combustion engine. second air flow rate calculation means for calculating an intake air amount based on a second flow rate conversion function from a number; and calibration for calibrating the first flow rate conversion function based on the intake air flow rate calculated by the second air flow rate calculation means. The first flow rate conversion function is successively calibrated by the calibration means when the hot wire air flowmeter changes over time due to dust or the like contained in the intake air and exceeds a permissible value. As a result, the intake air flow rate can be accurately measured even if the hot wire air flow meter itself changes over time.

Further, the first air flow rate calculation means inputs a signal corresponding to the intake air flow rate from the sensor and calculates the intake air flow rate based on the first flow rate conversion function, and the second air flow rate calculation means calculates the intake air flow rate based on the first flow rate conversion function.
The calibration means calculates the intake air flow rate based on the conversion function by inputting the rotation speed of the internal combustion engine while setting the opening degree of the air flow control valve to a predetermined angle, and calculates the intake air flow rate based on the conversion function to the second flow +1. The first flow rate conversion function of the first air flow rate calculation means can be calibrated based on the intake air flow rate calculated by the means. In addition, the second air flow rate calculating means improves calculation accuracy by adding outside temperature and atmospheric pressure in addition to the rotational speed of the internal combustion engine as parameters for calculating the flow rate.

In addition, in order to set the opening degree of the air flow control valve to be fully open when idling, a shape memory alloy is installed in the middle of the wire that opens and closes the air flow control valve. It is fully opened by applying a control current to the shape memory alloy.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 4.

FIG. 1 shows parts constituting an air intake path of an internal combustion engine, a hot wire air flow meter, and a calibration device. External air flows in from the intake section 1, passes through the flow path 2, and is supplied to the intake chamber 3 of the engine. Between the intake section 1 and the intake chamber 3 of the engine, there is a throttle valve 4 for controlling the amount of intake air, and upstream thereof is a sensor section 5 of a hot-wire air flow meter, for example, as shown in Japanese Patent Application No. 148128/1983. The fuel injection valve 7 is installed protruding into the flow path 2, and downstream of the throttle valve is a fuel injection valve 7 as shown in Japanese Patent Application No. 63-3737, for example.

Normally, the flow rate flowing through the flow path 2 is determined as a flow rate signal by passing an output signal from the sensor unit 5 of the hot wire air flowmeter through a converter 6 having a memory. Note that a verification curve g for converting an output signal into a flow rate signal is stored inside the converter 6.

Next, the mode of operation of the calibration device 8 will be explained. This device 8 is
When the change over time of the hot wire air flow meter exceeds the allowable value, that is, when the traveling distance exceeds the set value, or the flow rate determined from the throttle valve opening θ0 and the engine rotation speed NJ is determined by the sensor 5. When the difference in flow rate exceeds the set value, the system is activated automatically or manually when idling or driving. Once the calibration device 8 is in operation.

First, the opening degree of the throttle valve 4 is determined by the valve opening setting device 9.
It is set to 00 by the signal from . Next, while 00 remains fixed, the fuel injection amount is set to G based on the signal from the fuel injection amount setting device 10.
i is set. As a result, the output of the engine rotation speed detector 11 becomes a constant rotation speed Nt. This rotation speed Ni
When signals of outside air temperature To and atmospheric pressure Pa are input from a temperature and pressure lancer 12 provided separately from the converter 13, a flow rate MJ corresponding to the above setting state is determined.

However, the conversion device 13 has built-in data in its memory that represents the relationship between the engine rotational speed N, the standard outside temperature Ts, the standard atmospheric pressure Ps, and the flow kM when the opening degree of the throttle valve 4 is Oo. The signal of the flow ftHvti obtained in this way is sent to the calibration curve calibration circuit 14, and together with the output signal (3a) from the sensor unit 5 of the hot-wire air flowmeter obtained separately, a pair of calibration signals are sent to the test curve calibration circuit 14. Create data. By repeating the above procedure n times while changing the fuel injection MGJ and finding the relationship between the flow rate signal MJ and the sensor output signal 87, the verification curve g is recalibrated, and a new verification curve is generated at the converter 6. and the operation of the calibration device 8 is completed.

Next, the flow rate conversion and verification curve calibration flow will be explained with reference to FIG.

Conversion device 13 and test curve calibration circuit 14 in FIGS. 2 and 1
3 is a flowchart showing the software of the microcomputer in FIG.

It was previously entered in step 21. Standard temperature Ts
, from the experimental data of the engine rotation speed N1 at standard atmospheric pressure Ps and the flow rate fa (J=1p 2+...M) at that time, f=f (N
) is calculated using the least squares method. In step 22, J=O is set, and in step 23, data necessary for calculating the current flow rate is input. In step 24, the flow rate MJ in the standard state when the engine speed is NJ is determined from MJ=f(NJ), and further in step 25, it is determined by correcting the flow rate MNJ and M- at the temperature To. Then, in step 26, MJ and the sensor output signal e are stored as a set of data.

In step 27, the above steps 23 to 26 are repeated until the number of engine rotational speed data j max. This data (MJ, ea) (j = 1 + 2
,...j wax), in step 28, the flow i
The relationship M,=g(e) between M and the sensor output signal e is determined by the least squares method. As a result, a new verification curve showing the relationship between the sensor output signal value and the intake air amount is completed.

Based on this new verification curve, the sensor output signal e determines the intake air flow rate, and based on this value, the fuel supply of the fuel injection device is controlled. This allows for highly accurate air-fuel ratio control. The above test can be performed in a short time, so the test may be performed by determining when the angle θ0 is reached during driving, or the database may be based on the throttle valve angle θ0, engine speed N, and flow rate M.
1 may be stored in memory as a map and tested.

Note that depending on the accuracy required for flow rate measurement, atmospheric pressure Po
The calibration device can be simplified by keeping Po constant and removing Po from the equation f used to determine the flow rate. Further, the formula f may be determined in the factory during engine production, or may be determined using the output signal of the sensor 5 at the initial stage when the internal combustion engine is completed and operated.

FIG. 3 shows a device for setting the throttle valve opening to 00 (fully open). Normally, the throttle valve 4 is kept fully open by the force of the spring 21 when the engine is idling, since no tension is applied to the wire 20. However, when the calibration bag @8 is activated, the shape memory alloy 22 that constitutes a part of the wire 20 is heated and contracted by electricity, so tension acts on the wire 20, which overcomes the force of the spring 21 and opens the throttle valve. , the opening degree is fixed at 00 (fully open) with the stopper 23. Inside 24 is an accelerator pedal.

In FIG. 4, the opening degree of the throttle valve is controlled by an electric motor. 31 is an electric motor, and 32 is a reduction gear. In this case, the opening degree of the throttle valve can be easily set by setting the rotation angle of the electric motor.

In addition, as a method for calibrating a hot wire air flow meter, it is possible to prepare a separate hot wire flowmeter for calibration or to provide a Pitot tube flowmeter separately from the hot wire, but in either case, a dual device is required. It turns out.

On the other hand, the present invention is superior in that calibration can be performed by only making some improvements to the equipment originally installed around the engine. Further, by using a hot wire air flow meter, it is possible to eliminate the need for an 02 sensor that measures 02 in the exhaust gas.

〔Effect of the invention〕

According to the present invention, the intake air flow meter measured at the same time is calibrated based on the intake air flow rate determined from the rotational speed of the internal combustion engine by setting the opening degree of the air flow rate control valve at a predetermined opening degree during idling. It is possible to prevent accuracy deterioration due to aging of the intake air flow meter. Therefore, accurate air-fuel ratio control can be performed.

Furthermore, by adding external temperature and atmospheric pressure to the rotational speed of the internal combustion engine as parameters, the accuracy of calibration is improved. Further, by using a shape memory alloy to maintain the opening degree of the air flow position needle control valve at a predetermined opening degree during acid ringing, the opening degree can be maintained at a predetermined opening degree with a simple device.

[Brief explanation of the drawing]

Fig. 1 shows an embodiment of the present invention, and Fig. 2 shows a block diagram of an air intake passage of an internal combustion engine, a block diagram of a fuel injection device, a hot wire air flow meter, and a calibration device, and Fig. 2 shows a flow rate conversion and verification curve. The calibration flowchart, FIGS. 3 and 4, are general views showing the throttle valve opening degree setting device in FIG. 1. DESCRIPTION OF SYMBOLS 1... Intake part, 2... Flow path, 3... Suction chamber of engine, 4... Throttle valve, 6... Flow rate converter, 7... Fuel injection valve, 8... Calibration device. S 2 mouths

Claims (1)

[Scope of Claims] 1. A first air flow rate calculation means that includes a sensor that generates a signal corresponding to the intake air flow rate of the internal combustion engine, a flow rate conversion function that converts the signal into an intake air flow rate value, and at least a second air flow rate calculation means that calculates an intake air flow rate value from the opening degree of an air flow control valve that controls the air flow rate and the rotational speed of the internal combustion engine; and a fuel injection device that injects fuel into a passage through which the intake air passes. calibrating the flow rate conversion function based on the intake air flow rate value calculated by the second air flow rate calculation means, and calibrating the flow rate conversion function based on the intake air flow rate value calculated by the first air flow rate calculation means. An internal combustion engine characterized in that air-fuel ratio control is performed by controlling the fuel injection device. 2. A sensor that generates a signal corresponding to the intake air flow rate of the internal combustion engine, a first air flow rate calculation means that includes a built-in flow rate conversion function that converts the signal into an intake air flow rate value, and an air sensor that controls at least the intake air flow rate. a second air flow rate calculation means for calculating an intake air flow rate value from the opening degree of the flow rate control valve and the rotational speed of the internal combustion engine, and based on the intake air flow rate value calculated by the second air flow rate calculation means. An internal combustion engine equipped with an internal combustion engine air flow meter, characterized in that the flow rate conversion function is successively calibrated. 3. A sensor that generates a signal corresponding to the intake air flow rate of the internal combustion engine; a first air flow rate calculation means that inputs the signal and calculates the intake air flow rate based on a predetermined first flow rate conversion function; Based on the second flow rate conversion function that indicates the relationship between the rotation speed of the internal combustion engine and the intake air flow rate with the opening degree of the air flow rate control valve that controls the flow rate set to a predetermined opening degree, the intake air is calculated based on the rotation speed of the internal combustion engine. An internal combustion engine air flow meter comprising: a second air flow rate calculation means for calculating a flow rate; and a calibration means for calibrating the first flow rate conversion function based on the intake air flow rate calculated by the second air flow rate calculation means. . 4. The second air flow rate calculation means calculates the relationship between the outside temperature, atmospheric pressure, the rotational speed of the internal combustion engine, and the intake air flow rate with the opening degree of the air control valve that controls the intake air flow rate set to a predetermined opening degree. 4. The internal combustion engine air flow meter according to claim 3, wherein the intake air flow rate is calculated from outside air temperature, atmospheric pressure, and the rotational speed of the internal combustion engine based on the second flow rate conversion function. 5. A device for setting the opening degree of the air flow control valve to full open is connected to the air flow control valve via a pulley and is fully closed by the action of a spring provided on the air flow control valve when idling. A device configured to connect a wire to an accelerator pedal and adjust the opening degree of the air flow control valve by operating the accelerator pedal, cut the middle of the wire and connect it with a shape memory alloy, and The internal combustion engine air flow meter according to claim 3, wherein the air flow control valve is fully opened by controlling the shape memory alloy. 6. When the difference between the intake air flow rate value calculated by the first air flow rate calculation means 1 and the intake air flow rate value calculated by the second air flow rate calculation means exceeds a permissible value, the first 4. The internal combustion engine air flow meter of claim 3, wherein the internal combustion engine air flow meter calibrates a flow rate conversion function.