JP2006342748A - Control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect adhesion of water on an air flow meter even at an engine transient time and execute suitable internal combustion engine control when adhesion of water is detected. <P>SOLUTION: This control device for an internal combustion engine is provided with the air flow meter 7 provided in an intake passage of the internal combustion engine 1, a means 21 calculating an absolute value of a change speed of output value of the air flow meter 7, and a means 21 determining irregularity of the air flow meter according to comparison results of a predetermined value and the calculated absolute value of change speed. Water adhesion on the air flow meter can be detected in a state other than steady state of the engine, namely transient state. Also, when such water adhesion is detected, control is executed with using output value of the air flow meter before the detection. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a control device for an internal combustion engine, and in particular, measures the amount of air sucked into the internal combustion engine using an air flow meter for the internal combustion engine, and executes predetermined control using the value of the measured air amount. The present invention relates to a control device for an internal combustion engine.

  A hot-wire air flow meter has been put to practical use as an air flow meter for internal combustion engines, in which a heater (temperature-sensitive resistor) is controlled so that the temperature of the passing air is higher by a certain amount. Has been. That is, the current supplied to the heater is reduced when the amount of air passing through is small, the current is increased when the amount of air passing is large, and the current is supplied in an amount corresponding to the heat radiation from the heater to the air.

  By the way, some of the environmental conditions when actually mounted on a vehicle may run on a flooded road or follow a rainy day, etc., so that a large amount of rainwater may be flooded into the air cleaner. If this is done, the amount of air increases, so water may scatter and water droplets may adhere to the heater. Even at this time, if the air flow meter keeps a constant temperature, a large current flows until the water evaporates. Therefore, the air flow meter erroneously measures the amount required for the heat of vaporization, and the output of the air flow meter becomes excessive. . If engine control is performed on the basis of this output, it is of course impossible to perform desired control, which causes various problems.

  Therefore, it is desired to detect such water adhesion to the air flow meter and, if this is detected, control at least for a certain period until the water evaporates with another substitute value. As a technique for this purpose, Patent Document 1 discloses an air flow at a predetermined time in an engine steady state in which the change rate of the throttle valve opening is smaller than a predetermined value and the change rate of the engine speed is smaller than a predetermined value. It is disclosed that when the amount of change in the output value of the meter is larger than a predetermined value, it is determined that there is water adhesion. Further, it is disclosed that when this water adhesion is determined, a minimum value is selected from the air flow meter output data within a predetermined period, and the air amount is calculated based on the selected value.

Japanese Patent Laid-Open No. 7-77094

  However, in the first place, water adheres to the air flow meter because water scatters from the inner wall of the air cleaner or the intake pipe. Such water scatter causes a large change in intake air amount during sudden acceleration. It tends to occur during engine transitions. Therefore, the technique disclosed in Patent Document 1 cannot detect water adhesion during an essential engine transition, and must be said to be insufficient as a method for detecting water adhesion.

  Moreover, the technique of patent document 1 presupposes that the output rises when water adhesion occurs in the air flow meter. However, in recent years, air flow meters that can detect the flow in the reverse flow direction have appeared, and when such air flow meters are attached, the output does not necessarily increase and may decrease. Therefore, in the technique of Patent Document 1, an abnormal value that is extremely lowered is handled as the minimum value, and control may be executed using the minimum value. There is a possibility of coming.

  Therefore, the present invention has been made in view of such circumstances, and an object thereof is to provide a control device for an internal combustion engine that can detect water adhesion to an air flow meter during engine transition. Another object of the present invention is to provide a control device for an internal combustion engine that can execute suitable control of the internal combustion engine when water adhesion to the air flow meter is detected.

  In order to achieve the above object, an internal combustion engine control apparatus according to a first embodiment of the present invention calculates an absolute value of an air flow meter provided in an intake passage of an internal combustion engine and a change rate of an output value of the air flow meter. And means for determining an abnormality of the air flow meter according to a comparison result between the calculated absolute value of the change rate of the output value of the air flow meter and a predetermined value.

  An internal combustion engine control apparatus according to a second embodiment of the present invention includes an air flow meter provided in an intake passage of the internal combustion engine, a sensor whose output value changes in synchronization with a change in the output value of the air flow meter, , Based on the output value of the air flow meter, means for calculating the rate of change of the amount of air taken into the internal combustion engine, means for calculating the rate of change of the output value of the sensor, and the rate of change of the air amount, And a means for determining an abnormality of the air flow meter according to a comparison result with a change speed of an output value of the sensor. In this case, it is preferable that the sensor is a throttle opening degree sensor that detects an opening degree of a throttle valve provided in the intake passage.

  An internal combustion engine control apparatus according to a third aspect of the present invention includes an air flow meter provided in an intake passage of the internal combustion engine, means for detecting an opening of a throttle valve provided in the intake passage, Based on the output value of the air flow meter, means for calculating the rate of change of the actual value of the amount of air sucked into the internal combustion engine, and the amount of air sucked into the internal combustion engine based on the detected opening of the throttle valve And a means for determining an abnormality of the air flow meter in accordance with a comparison result between the change speed of the actual value of the air amount and the change speed of the estimated value of the air amount. It is characterized by that.

  According to the first to third embodiments of the present invention, since there are no restrictions on the operating conditions of the engine, even if the engine is not in a steady state, that is, even when the engine is in transition, water adhesion to the air flow meter and thus the air flow meter. Abnormalities can be detected. Further, according to the first embodiment of the present invention, since the abnormality of the air flow meter is determined according to the comparison result between the absolute value of the change speed of the output value of the air flow meter and the predetermined value, the flow in the reverse flow direction can be detected. In such an air flow meter, even when the output drops when water adheres, it is possible to detect an abnormality of the air flow meter. Furthermore, according to the second and third embodiments of the present invention that use the correspondence between the intake air amount and a value that changes in synchronism (typically, the opening of the throttle valve), backflow detection is possible. In addition, it is possible to suitably detect abnormalities in the air flow meter and improve detection accuracy.

  Preferably, in the first to third embodiments, when the air flow meter is determined to be abnormal, it further includes means for executing predetermined control using an output value of the air flow meter before the abnormality determination.

  Alternatively, preferably, in the first to third embodiments, when the air flow meter is determined to be abnormal, a predetermined smoothing process is performed on the output value of the air flow meter, and a value obtained thereby is used. Means for executing predetermined control.

  Alternatively, preferably, in the first to third embodiments, means for executing a predetermined control based on a value obtained by executing a predetermined smoothing process on an output value of the air flow meter, and the air flow meter Is further provided with means for changing a predetermined smoothing coefficient so that the smoothing degree in the smoothing process is increased.

  Alternatively, preferably, in the first to third embodiments, when the air flow meter is determined to be abnormal, a predetermined averaging process is performed on the output value of the air flow meter, and a value obtained thereby is used. Means for executing predetermined control.

  Alternatively, preferably, in the first to third embodiments, means for executing a predetermined control based on a value obtained by executing a predetermined averaging process on the output value of the air flow meter, and the air flow meter Is further provided with means for extending the sampling time in the averaging process.

  Alternatively, preferably, in the third embodiment, the means for calculating an estimated value of the amount of air taken into the internal combustion engine based on the detected opening of the throttle valve and the air flow meter are determined to be abnormal. Means for executing predetermined control using the estimated value of the air amount.

  According to these, even when an abnormality of the air flow meter is detected, the control of the internal combustion engine can be suitably executed using a value close to the actual air amount.

  According to the present invention, it becomes possible to detect water adhesion to the air flow meter even during engine transition, and it is possible to execute suitable control of the internal combustion engine even when water adhesion to the air flow meter is detected. Excellent effect is exhibited.

  Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 shows a schematic system of a control device for an internal combustion engine using a hot-wire air flow meter. A four-cycle four-cylinder spark ignition gasoline engine 1 is mounted on an automobile. An intake pipe 2 constituting an intake passage is connected to the engine 1, and an air cleaner 3 for filtering air taken into the engine 1 is provided at the most upstream portion of the intake pipe 2. The intake pipe 2 is provided with a throttle valve 4, and the amount of intake air taken into the cylinder by the throttle valve 4 is adjusted. Injectors (electromagnetic fuel injection valves) 5a, 5b, 5c, and 5d are arranged in the intake ports of the cylinders of the gasoline engine 1. Further, spark plugs 6a, 6b, 6c, and 6d are disposed in each cylinder in the engine 1. The present embodiment exemplifies an intake passage injection type internal combustion engine that injects fuel into the intake passage of the engine. The present invention is also applicable to so-called dual injection internal combustion engines.

  A hot-wire air flow meter 7 is disposed upstream of the throttle valve 4 in the intake pipe 2. The detail of the arrangement | positioning part of this hot wire type air flow meter 7 is shown in FIG. In FIG. 2, the intake pipe 2 extends in the horizontal direction, and a cylindrical case 7 a of a hot-wire air flow meter 7 is fitted into the front end opening of the intake pipe 2. A case 8 of the air cleaner 3 is attached to the other end opening of the case 7 a of the hot-wire air flow meter 7. In the case 8 of the air cleaner 3, an air cleaner element 3a is disposed in the horizontal direction. An air intake port 8a is formed in the case 8 of the air cleaner 3, and air is drawn into the case 8 from the air intake port 8a in the horizontal direction. The air passes through the air cleaner element 3a and enters the case 7a of the hot-wire air flow meter 7. Inhaled.

  In the case 7a of the hot-wire air flow meter 7, the body 9 is fixedly supported at the center of the case 7a by a plurality of stays 10 extending from the inner wall of the case 7a. An air passage 11 is formed in the body 9, and one end of the air passage 11 is open at the center of the upstream side of the body 9 and the other end is open at the side of the body 9. A flow rate detection element having a thermal resistor (heater) 12 and a temperature compensating resistor 13 is disposed in the air passage 11.

  FIG. 3 shows the electrical configuration of the hot-wire air flow meter 7. A bridge circuit is formed using the thermal resistor 12, the temperature compensating resistor 13, and the resistors 14, 15, and 16 described above. The power supply voltage Vcc is applied to the connection point a in this bridge circuit, and the connection point b is grounded. The power supply voltage Vcc is controlled to keep the temperature constant so that the unbalanced voltage between the connection point c and the connection point d in the bridge circuit becomes zero. That is, the current-heated thermal resistor 12 and the temperature compensating resistor 13 are placed in the air flow, and the resistor temperature changes depending on the air flow rate, but the current is controlled so as to keep this temperature constant. The current is taken out as a voltage (analog voltage).

  In this case, the temperature sensitive resistor 12 is controlled so as to be always higher than the temperature of the passing air by a certain temperature. That is, when there is little air passing through, the current (ie, voltage) supplied to the temperature sensitive resistor 12 is reduced, and when there is much air, the current (ie, voltage) is increased. It is configured to allow a current to flow by the specified amount.

  In FIG. 1, an exhaust manifold 17 is disposed in the engine 1, and an exhaust pipe 18 is connected to the exhaust manifold 17. Fuel is supplied from injectors (electromagnetic fuel injection valves) 5a, 5b, 5c, and 5d provided corresponding to each cylinder from a fuel system (not shown). Combustion air is sucked into the combustion chamber of the engine 1 through the air cleaner 3, the intake pipe 2, and the throttle valve 4. The exhaust gas after combustion is discharged to the atmosphere through an exhaust manifold 17, an exhaust pipe 18, and a catalytic converter (not shown).

  Further, the engine 1 is provided with a thermistor-type water temperature sensor 19, which detects the cooling water temperature and outputs an analog voltage (analog detection signal) corresponding to the cooling water temperature. The engine 1 is provided with a rotation sensor 20, which detects a predetermined rotation angle position of the crankshaft of the engine and outputs a pulse signal having a frequency proportional to the rotation speed. As the rotation sensor 20, for example, an ignition coil of an ignition device may be used, and an ignition pulse signal from a primary terminal of the ignition coil may be used as a rotation speed signal. Moreover, what converts a magnetic flux change into an electric signal with an electromagnetic pick-up may be used.

  An electronic control unit (hereinafter referred to as ECU) 21 for engine control is composed of a CPU, a ROM, a RAM, an interface, and the like. A starter switch 22 and a key switch 23 are connected to the ECU 21. Further, a throttle opening sensor 24 for detecting the opening of the throttle valve 4 is connected to the ECU 21, and the throttle opening sensor 24 also detects whether the throttle is fully closed. A battery 25 is connected to the starter switch 22 and the key switch 23. A water temperature sensor 19 is connected to the ECU 21, and the ECU 21 detects the cooling water temperature based on a signal from the water temperature sensor 19. A rotation sensor 20 is connected to the ECU 21, and the ECU 21 detects the rotation speed of the engine based on a signal from the rotation sensor 20. Further, the ECU 21 inputs a signal from the hot wire type air flow meter 7.

  Further, the ECU 21 basically calculates the basic fuel injection amount (basic injection pulse width) and the ignition timing based on the signals of the hot-wire air flow meter 7 and the rotation sensor 20. Then, the final injection pulse width and the ignition timing are obtained by correcting the basic fuel injection amount (basic injection pulse width) and the ignition timing by the engine cooling water temperature or the like, and thereby the injectors 5a, 5b, 5c and 5d. And the ignition timing of the spark plugs 6a, 6b, 6c, 6d are controlled.

  Next, a water adhesion detection method for an air flow meter in the control apparatus for an internal combustion engine having such a configuration and a control method when water adhesion is detected will be described.

FIG. 4 shows the change in the output value (voltage value) V of the air flow meter when such water adheres (see FIG. 4B), and the opening of the throttle valve 4 corresponding thereto (hereinafter referred to as the throttle opening). ) Changes in TH (see (a) figure). In the present embodiment, digital processing is performed, and the acquisition of the output value V of the air flow meter and each processing described later are executed every predetermined period Δt (for example, 4 ms). In the illustrated example, water adhesion occurs between the timings t = t ₀ and t = t ₋₁ . Below the _{t 0} referred to as a reference at the time. With reference to the reference time t ₀ as a boundary, timings that sequentially go back from the reference time t ₀ are t ₋₁ , t ₋₂ , t _−3, etc., and timings that are sequentially delayed from the reference time t ₀ are t ₋₁ , t _−2. , T ₋₃ ... And each timing _{t 0, t -1, t -2} , t -3 ···, t -1, t -2, t -3 V 0 the output value V of the air flow meter in · · _{·, V -1,} V- ₂ , V- ₃ ..., V- ₁ , V- ₂ , V- _3, etc.

  The illustrated example shows an acceleration time when the throttle opening TH is gradually increased as an example of an engine transition, and accordingly, the output value V of the air flow meter is increased in the direction of increasing the air amount. ing. In the middle of this, water adheres to the air flow meter, and the output value V of the air flow meter is extremely increased. This is because a large current is passed through the temperature sensitive resistor 12 in an attempt to keep the temperature sensitive resistor 12 at a constant temperature as described above. If the adhering water evaporates, it returns to the original normal state, so it can be said that such an abnormality is temporary or temporary. Control after abnormality detection described later in the present embodiment is performed only for a predetermined time until it is considered that such water evaporates. In addition, although this embodiment mainly demonstrates the water adhesion to an air flow meter, this invention is applicable with respect to abnormality in a broad sense other than the water adhesion with respect to an air flow meter.

  The RAM of the ECU 21 is provided with an address for temporarily storing a predetermined number of airflow meter output values V at each timing, and this address includes output values V from the latest output value V to a predetermined number of times before. Are stored while being updated at each timing. That is, the output value data in the address is updated every time at each timing. The number of data to be stored is, for example, 10, but can be set to an arbitrary value.

  Next, detection of water adhesion to the air flow meter will be described. In the first aspect, the ECU 21 calculates the absolute value of the change speed of the output value V of the air flow meter, and adheres water to the air flow meter according to the comparison result between the calculated absolute value of the change speed and a predetermined value ( That is, abnormal) is determined.

This will be described with reference to FIG. At each processing timing, the ECU 21 sets the air flow meter output value V _n at the time t _n (n =..., -2, -1, 0, 1, 2,...) And a predetermined period before the time t _n. For example, the air flow meter output value V _n−1 one cycle before is read from the RAM, and the difference (V _n −V _n−1 ) is calculated. Since this difference indicates the amount of change in the air flow meter output value during the period Δt, this is the rate of change in the air flow meter output value. Then, the difference or the absolute value of the change rate _| predetermined a, are stored in advance in _{ROM | V n -V n-1} | is calculated, the calculated absolute value of the change rate _| V _{n -V n-1} The value is compared with the determination threshold value Vx (> 0). The determination threshold value Vx is a value determined based on experiments and the like, and is set to a value larger than the maximum absolute value of the change rate of the air flow meter output value assumed when there is no water adhesion to the air flow meter. Is set. When the ECU 21 determines that the absolute value | V _n −V _n−1 | is greater than the determination threshold value Vx, the ECU 21 determines that there is water adhesion, and the absolute value | V _n −V _n−1 | If judged, water is judged not adhered. According to this, as shown in FIG. 4, at the timing of the reference time t ₀ , the absolute value | V ₀ −V ₋₁ | exceeds the determination threshold value Vx, and it is determined that water has adhered, for example, from the reference time t ₀ . At the previous timing, the absolute value | V ₋₁ −V ₋₂ | is equal to or less than the determination threshold Vx, and it is determined that there is no water adhesion.

According to this, in particular, the water adhesion to the air flow meter is determined according to the comparison result between the absolute value | V _n −V _n−1 | of the change rate of the output value of the air flow meter and the predetermined determination threshold value Vx. The determination condition is not limited to the steady operation of the engine, and water adhesion to the air flow meter can be detected even in a wide range of operation conditions, particularly during transient operation. Further, even in an air flow meter capable of detecting a reverse flow in which the output value of the air flow meter moves in the descending direction when water adheres, it becomes possible to suitably detect water adherence. Note that the air flow meter 7 shown in FIG.

  Hereafter, the configuration of an air flow meter capable of detecting a reverse flow applicable to the present invention will be described. The configuration of this air flow meter is the same as that disclosed in Japanese Patent No. 3475853.

  FIG. 5 shows a configuration of another flow rate detecting element that replaces the flow rate detecting element having the thermal resistor 12 and the temperature compensating resistor 13 shown in FIG. (A) is a front view, (b) is the bb sectional view taken on the line of (a). Reference numeral 301 denotes a flat substrate made of silicon having a thickness of about 0.4 mm, for example, and an insulating support film 302 made of silicon nitride or the like having a thickness of 0.5 μm is formed on the surface thereof by sputtering, vapor deposition, CVD or the like. A heating resistor 304 such as platinum having a thickness of 0.1 μm and temperature measuring resistors 306 and 307 are deposited thereon by a method such as vapor deposition or sputtering. Connection patterns 308a to 308c and 308f to 308h, which are current paths, are formed on the heating resistor 304 and the temperature measuring resistors 306 and 307 by using a method such as photoengraving, wet or dry etching. Similarly, a fluid temperature detector 305 made of a heat-sensitive resistive film such as platinum having a thickness of 0.1 μm is deposited by a method such as vapor deposition or sputtering. Lead patterns 308d and 308e, which are current paths, are formed on the fluid temperature detector 305 using a method such as photolithography, wet or dry etching. Further, an insulating protective film 303 made of, for example, silicon nitride having a thickness of 0.5 μm is formed on the heat generating resistor 304 and the temperature measuring resistors 306 and 307 by a method such as sputtering or CVD.

  The heating element 304 is connected in series and connected to electrodes 309c and 309f for electrical connection with the outside of the flow rate detection element via connection patterns 308c and 308f. The fluid temperature detection body 305 is connected to electrodes 309d and 309e for electrical connection with the outside of the flow rate detection element via lead patterns 308d and 308e. Similarly, the temperature measuring resistor 306 is connected to the electrodes 309a and 309b via the connection patterns 308a and 308b, and the temperature measuring resistor 307 is connected to the electrodes 309g and 309h via the connection patterns 308g and 308h, respectively. The protective film 303 is removed from the electrodes 309a to 309h in order to be electrically connected to the outside by a method such as wire bonding.

  Further, after forming the etching hole 312 in the protective film 311 formed on the back surface of the flat substrate 301 by a method such as photolithography, a part of the flat substrate 301 is removed by performing, for example, alkali etching or the like. By forming the cavity 314, a flow rate detection diaphragm 313 which is a flow rate detection unit is configured. The arrow A is the forward direction of the flow of air that is the fluid to be measured, and the flow rate detection diaphragm 313 is arranged to be exposed to the flow of the fluid to be measured. The size of the diaphragm 313 is 1000 μm × 2000 μm, and the thickness thereof is 1 μm at a portion where the resistors 304, 306, and 307 are not formed.

  The heating element 304 is controlled to have a resistance value such that a predetermined average temperature is obtained by a constant temperature difference driving circuit shown in FIG. The detection circuit is a bridge circuit including a fluid temperature detector 305 and a heating resistor 304. In the figure, R1, R2, R3, R4 and R5 are fixed resistors, OP1 and OP2 are operational amplifiers, TR1 and TR2 are transistors, and BATT is a power supply. The detection circuit works so as to make the potentials at points a and b in the figure substantially equal, and controls the heating current IH of the heating resistor 304. When the flow rate of the fluid to be measured increases, the amount of heat transfer from the heating element 304 to the fluid to be measured increases, so that the heating current IH when maintaining the average temperature of the heating element 4 at a predetermined value increases. On the other hand, the temperature measuring resistors 306 and 307 obtain an output corresponding to the temperature of each resistor by a circuit (not shown), and take the difference to obtain an output of the air flow meter. That is, when fluid movement occurs in the direction A, the temperature of the temperature measuring resistor 306 is lowered, and the temperature of the temperature measuring resistor 307 is not lowered as much as the temperature measuring resistor 306. FIG. 7 shows the relationship between the flow rate and the temperature of the temperature measuring resistors 306 and 307. If the difference in output corresponding to the temperature of the resistance temperature detectors 306 and 307 is the output of the air flow meter, the flow rate and the direction of the flow can be detected. In order to detect the temperature of the temperature measuring resistors 306 and 307, a method of applying a predetermined constant voltage to the temperature measuring resistors 306 and 307 or applying a predetermined constant current can be considered. In this way, it is possible to detect bidirectional flow rates of forward flow and reverse flow. Such a flow rate detection element capable of detecting a backflow is also applicable to each aspect described below.

  Next, a second aspect related to detection of water adhesion to the air flow meter will be described. In this aspect, the ECU 21 calculates the change rate of the amount of air sucked into the internal combustion engine based on the output value of the air flow meter, and calculates the output value of the throttle opening sensor 24, that is, the change rate of the throttle opening. The abnormality of the air flow meter is determined according to the comparison result between the change rate of the air amount and the change rate of the throttle opening.

  This will be described again with reference to FIG. As can be seen from the figure, the change in the throttle opening TH and the change in the output value V of the air flow meter are synchronized. When the throttle opening TH increases, the output value V of the air flow meter increases accordingly. Accordingly, there is a correlation between the amount of change and the change speed of the throttle opening TH and the output value V of the air flow meter and hence the air amount A obtained therefrom. Therefore, if the change rate of the air amount A is compared with the change rate of the opening degree of the throttle valve, it can be determined whether or not water has adhered to the air flow meter. According to this method, since the abnormality of the air flow meter is determined by comparison with another value that changes in synchronization with the change in the output value of the air flow meter, the air flow is more accurately compared with the first aspect. An abnormality of the meter can be determined. However, the other value that changes in synchronization with the change in the output value of the air flow meter is not limited to the output value of the throttle opening sensor, and may be the value of another sensor. Since the air amount A and the air flow meter output value V are in a correspondence relationship, the water adhesion of the air flow meter can also be determined by comparing the change speed of the air flow meter output value V and the change speed of the throttle opening TH. it can.

  Here, as in the case of the air flow meter output value V, the RAM of the ECU 21 is provided with an address for temporarily storing a predetermined number of throttle openings TH acquired at each processing timing. The address stores the throttle opening TH from the latest throttle opening TH up to a predetermined number of times while being updated at each timing. That is, the throttle opening data is updated every time at each timing. The number of data to be stored is, for example, 10, but can be set to an arbitrary value.

4A, the throttle opening TH at each timing t ₀ , t ₋₁ , t ₋₂ , t ₋₃ ..., T ₋₁ , t ₋₂ , t _{−3. 0} , TH- ₁ , TH- ₂ , TH- ₃ , TH- ₁ , TH- ₂ , TH- _3, etc. At each processing timing, the ECU 21 determines the throttle opening TH and the air flow meter output values TH _n and V _n at the time t _n (n =..., −2, −1, 0, 1, 2,...) The throttle opening TH and the air flow meter output values TH _n−1 and V _{n−1 of the} predetermined period before the time t _n , for example, are read from the RAM, and the air flow meter output values V _n and V _n−1 are read. after converting air amount _{a n,} the _{a n-1,} calculates a throttle opening difference _{(TH n -TH n-1)} and air amount difference _{(a n -A n-1)} . The throttle opening difference (TH _n -TH _n-1 ) and the air amount difference (A _n -A _n-1 ) are compared to determine whether the water flow adheres to the air flow meter.

Specifically, for example, the ratio R = (A _n −A _n−1 ) / (TH _n ) between the air amount difference (A _n −A _n−1 ) and the throttle opening difference (TH _n −TH _n−1 ). -THn _-1 ) is calculated, and the ratio R is compared with a predetermined value stored in advance in the ROM, that is, the determination threshold value Rx. The determination threshold value Rx is a value determined based on experiments or the like. The ECU 21 determines that there is water adhesion when it is determined that the ratio R is greater than the determination threshold value Rx, and determines that there is no water adhesion when it is determined that the ratio R is equal to or less than the determination threshold value Rx. According to this, at the timing of the reference time t ₀ , the ratio R = (A ₀ −A ₋₁ ) / (TH ₀ −TH ₋₁ ) exceeds the determination threshold value Rx, and it is determined that there is water adhesion. _At the timing one time before ₀ , the ratio R = (A ₋₁ −A ₋₂ ) / (V ₋₁ −V ₋₂ ) is equal to or less than the determination threshold Rx, and it is determined that there is no water adhesion.

Alternatively, the absolute value R ′ = | (A _n −A _n−1 ) − (V _n ) of the difference between the air amount difference (A _n −A _n−1 ) and the throttle opening difference (TH _n −TH _n−1 ). -Vn _-1 ) | may be compared with a predetermined determination threshold value Rx 'to determine the presence or absence of water adhesion. That is, when it is determined that the absolute value R ′ of the difference is larger than the determination threshold value Rx, it is determined that there is water adhesion, and when it is determined that the absolute value R ′ of the difference is equal to or less than the determination threshold value Rx, it is determined that there is no water adhesion. .

  According to the second aspect, the same effect as that of the first aspect can be obtained. The second aspect has an advantage that the detection resolution is higher than that of the first aspect.

  Next, a third aspect relating to detection of water adhesion to the air flow meter will be described. In this embodiment, the ECU 21 calculates the change rate ΔAr of the actual value Ar of the amount of air sucked into the internal combustion engine based on the output value of the air flow meter, and the throttle opening TH detected by the throttle opening sensor 24. The change rate ΔAe of the estimated value of the air amount sucked into the internal combustion engine is calculated based on the above, and the air flow is determined according to the comparison result between the change rate ΔAr of the actual value Ar of the air amount and the change rate ΔAe of the estimated value Ae. Determine water adhesion to the meter. Here, it is particularly characteristic that the change rate ΔAe of the estimated value of the air amount is calculated based on the throttle opening TH.

  The change rate ΔAe of the air amount estimated value is set in advance through experiments, simulations, and the like. FIG. 8 shows a map set in this way. The map includes a change amount of the throttle opening TH during a predetermined period (for example, one period (Δt)), that is, a change speed ΔTH of the throttle opening, and a change speed ΔAe of the estimated air amount corresponding thereto. Have been entered. Using this map, the ECU 21 determines water adhesion.

Specifically, the ECU 21 determines the throttle opening and the air flow meter output value TH _{n at} the time t _n (n =..., −2, −1, 0, 1, 2,...) At each processing timing. V _n and the throttle opening and air flow meter output values TH _n−1 and V _{n−1 one} predetermined period before the time point t _n , for example, one period before, are read from the RAM. Then, the air flow meter output values V _n and V _n−1 are converted into air amounts Ar _n and Ar _n−1 as actual values. Thereafter, a change rate ΔTH = (TH _n −TH _n−1 ) of the throttle opening and a change rate ΔAr = (Ar _n −Ar _n−1 ) of the actual value of the air amount are calculated. Then, an estimated change rate ΔAe of the air amount corresponding to the throttle opening change rate ΔTH = (TH _n −TH _n−1 ) is obtained from the map of FIG. The air flow meter is judged to adhere to water by comparing the change rate ΔAr = (Ar _n −Ar _n−1 ) of the actual value of the air amount.

Specifically, for example, the ratio RA = (Ar _n −Ar _n−1 ) between the change rate ΔAr = (Ar _n −Ar _n−1 ) of the actual value of the air amount and the change rate ΔAe of the estimated value of the air amount. ) / ΔAe is calculated, and this ratio R is compared with a predetermined value stored in the ROM in advance, that is, the determination threshold value RAx. The determination threshold RAx is a value determined based on experiments or the like. The ECU 21 determines that there is water adhesion when it is determined that the ratio RA is greater than the determination threshold value RAx, and determines that there is no water adhesion when it is determined that the ratio RA is equal to or less than the determination threshold value RAx. According to this, at the timing of the reference time t ₀ , the ratio RA = (Ar ₀ −Ar ₋₁ ) / ΔAe exceeds the determination threshold value RAx, and it is determined that water has adhered, for example, a timing one time before the reference time t _0. Then, the ratio RA = (A ₋₁ −A ₋₂ ) / ΔAe becomes equal to or less than the determination threshold value RAx, and it is determined that there is no water adhesion.

Alternatively, the absolute value RA ′ = | ΔAr−ΔAe | of the difference between the change rate ΔAr = (Ar _n −Ar _n−1 ) of the actual value of the air amount and the change rate ΔAe of the estimated value of the air amount is a predetermined determination threshold value. You may judge the presence or absence of water adhesion compared with RAx '. That is, when it is determined that the absolute value RA ′ of the difference is larger than the determination threshold value RAx, it is determined that there is water adhesion, and when it is determined that the absolute value RA ′ of the difference is equal to or less than the determination threshold value RAx, it is determined that there is no water adhesion. .

For example, the change rate ΔAe of the estimated air amount may be calculated based on the change rate ΔTH of the throttle opening and the change rate ΔNE of the engine rotation speed using the map shown in FIG. In this case, in addition to the above, at each processing timing, a step of detecting the engine rotational speed NE from the output of the rotation sensor 20 and an engine rotational speed before a predetermined period (for example, one period before) from the current engine rotational speed NE _n. NE _n−1 is subtracted to obtain a change speed ΔNE of the engine speed, and based on the change speed ΔNE of the engine speed and the change speed ΔTH of the throttle opening, the map of FIG. Determining a change rate ΔAe of the estimated value.

  Incidentally, in recent years, a system that physically models an intake system to estimate an intake air amount is also known, and an estimated air amount obtained from this system can also be used. An example of this system is described below. This system is the same as that disclosed in Japanese Patent Laid-Open No. 2002-147279.

  FIG. 10 shows one form of a calculation block for predicting the intake pressure from each actual measurement value such as the engine speed NE including the throttle opening TH, and this calculation is performed by the ECU 21. As a premise, the configuration shown in FIG. 1 includes a variable valve timing mechanism that changes the valve timing of the intake valve and the exhaust valve, and a purge system that introduces fuel vapor from the canister into the intake passage. . As shown in FIG. 10, the throttle opening TH0, the engine speed NE, and the valve timing VT are output from the electronic throttle model 51 to the TA model (throttle-air model) 52. Here, the throttle opening TH0 is a throttle opening after a predetermined time has elapsed from the present time, and is a value estimated based on the current throttle opening TH or the like.

  Further, the intake pipe predicted pressure P 0 output from the intake pipe model 53 is input to the TA model 52. The TA model 52 calculates the air flow rate QA0 passing through the throttle valve based on the throttle opening TH0, the engine rotational speed NE, the valve timing VT, and the intake pipe predicted pressure P0. The air flow rate QA0 output from the TA model 52 is added to the purge flow rate QP and input to the intake pipe model 53.

  An intake valve model 54 is set in the intake pipe model 53. By inputting the inflowing air amount (QA0, QP), the intake air after a predetermined time has elapsed from the present based on the law of conservation of mass and the law of conservation of energy. A predicted pipe pressure P0 is calculated. The intake pipe predicted pressure P0 is a pressure obtained by predicting the intake pipe pressure when the intake valve 3 is closed.

    On the other hand, the throttle opening TH, the engine speed NE, and the valve timing VT are input to the TA model 62. The TA model 62 is set under the same conditions as the TA model 52 described above.

  Further, the current intake pipe pressure P <b> 1 output from the intake pipe model 63 is input to the TA model 62. In the TA model 62, the current air flow rate QA1 passing through the throttle valve is calculated based on the throttle opening TH, the engine rotational speed NE, the valve timing VT, and the intake pipe pressure P1. The air flow rate QA1 output from the TA model 62 is added to the purge flow rate QP and input to the intake pipe model 63.

  An intake valve model 64 is set in the intake pipe model 63, and by inputting the inflowing air amount (QA1, QP), based on the gas state equation (P · V = m · R · T), The current intake pipe pressure P1 is calculated. The intake pipe model 63 is set under the same conditions as the intake pipe model 53 described above.

  The air flow rate QA1 output from the TA model 62 is input to an AFM model (air flow meter model) 71. The AFM model 71 inputs the current air flow rate QA1, and outputs an air flow rate QA2 in consideration of the detection delay of the air flow meter with respect to the air flow rate QA1. That is, the air flow rate QA2 is a value having a time delay with respect to the air flow rate QA1.

  The air flow rate QA2 is input to the intake pipe model 73. An intake valve model 74 is set in the intake pipe model 73. By inputting the inflowing air amount (QA2), the time delay is based on the gas state equation (P · V = m · R · T). Is calculated. The intake pipe model 73 is set under the same conditions as the intake pipe models 63 and 53 described above.

  On the other hand, the air flow rate QA, which is the output of the air flow meter, is input to the intake pipe model 83. An intake valve model 84 is set in the intake pipe model 83, and a time delay is calculated based on the gas equation of state (P · V = m · R · T) by the input air flow rate (QA). The included intake pipe pressure P3 is calculated. The intake pipe model 83 is set under the same conditions as the intake pipe models 73, 63, and 53 described above.

  The intake pipe pressure P3 output from the intake pipe model 83 includes a time delay similarly to the intake pipe pressure P2 output from the intake pipe model 73, and has the same response as the intake pipe pressure P2.

  Then, the intake pipe pressure P0 output from the intake pipe model 53 is added to the intake pipe pressure P3 output from the intake pipe model 83, and the intake pipe pressure P2 output from the intake pipe model 73 is subtracted. The pressure P is calculated. This predicted pressure P is a pressure obtained by correcting the difference between the intake pipe pressure P3 calculated based on the output QA of the air flow meter and the actual intake pipe pressure by the intake pipe pressures P0 and P1 taking the purge flow rate QP into consideration. Yes.

  In this case, the actual value of the air amount can be calculated from the air flow rate QA, and the estimated value of the air amount can be calculated from the air flow rate QA 1 that is the output of the AFM model 71. Therefore, by comparing the change rates of these air amounts with the above method, it is possible to suitably detect water adhesion on the air flow meter.

  The same effect as described above can be obtained by the third aspect described above. In addition, this 3rd aspect has the advantage that detection resolution is high like the 2nd aspect.

  Next, processing or control executed when water adhesion to the air flow meter is detected, that is, when the air flow meter is determined to be abnormal will be described. As described above, the attached water evaporates in a relatively short time, and the abnormality is considered to be eliminated. Therefore, the processing or control described below is assumed to be required for such water evaporation (for example, 1 second) only.

  In the case of the control device in the present embodiment, each control of the fuel injection amount, the fuel injection timing, the ignition timing, etc. is normally executed using the air amount (actual value) calculated based on the output value of the air flow meter. Is done. However, when moisture adheres to the air flow meter and an abnormal output value is obtained, control can no longer be performed depending only on that value. Therefore, in such a case, a substitute value is set and control is performed using this value.

According to the first aspect of the process or control executed when water adhesion is detected, when the ECU 21 determines that there is water adhesion to the air flow meter, the ECU 21 performs control using the normal air flow meter output value before the abnormality determination. Execute. That is, as shown in FIG. 4, when the ECU 21 determines that water adheres at the reference time t ₀ , the ECU 21 performs control using the previous air flow meter output value stored in the RAM. In this case, output values before a plurality of cycles may be used, but in this embodiment, control is performed using the output value immediately before one cycle, that is, V- ₁ . This is because the immediately preceding value is closest to the current value. Also at timings t ₁ , t ₂ , t ₃ ... After the reference time t ₀ , the output value V ₋₁ immediately before the abnormality determination is used. The output value V _-1 is not necessarily a value that accurately reflects the air amount at each timing, but is still the closest value in terms of timing and a highly reliable value. Therefore, by using such a substitute value, it becomes possible to perform control more suitable for the current situation.

Next, a 2nd aspect is demonstrated. According to the second aspect, when the ECU 21 determines that there is water adhering to the air flow meter, the ECU 21 performs a predetermined smoothing process on the air flow meter output value, and executes control using the value obtained thereby. . That is, as shown in FIG. 4, when the ECU 21 determines that water adheres at the reference time t ₀ , the current air flow meter output value V ₀ stored in the RAM and the output value V immediately before one cycle are stored. get a _-1, the output VS ₀ after moderation formula: VS ₀ = calculated from _{αV 0 + (1-α)} V -1, control of the reference time _{t 0} with the output VS ₀ after Shi this raw I do. Here, α is a smoothing coefficient, and a predetermined value less than 1 (for example, 0.4) is set. Here, although the air flow meter output value V ₀ at the reference time t ₀ is an abnormal value, it is considered that some of the air flow meter output value V ₀ includes accurate air amount information. Therefore, rather than completely ignoring, is set to be calculated from the idea of lowering the degree of influence, the output VS ₀ after moderation air flow meter output value V ₀ be included in the reference time t _0.

After the reference time t ₀ , the post-annealing output VS _n is calculated from the formula: VS _n = αV _n + (1−α) V _n−1 (n = 1, 2, 3...). Such smoothing a result of the processing, the output waveform of the reference time t ₀ after the air flow meter shown in FIG. 4 (b) becomes smoother.

By the way, there may be a case where such an annealing process has already been performed under normal control. In such a case, the ECU 21 may change the smoothing coefficient so that the degree of smoothing in the smoothing process increases when it is determined that water adheres to the air flow meter. Specifically, when the ECU 21 determines that water adheres at the reference time t ₀ , the ECU 21 reduces the influence of the air flow meter output value V ₀ at the reference time t _0, so that the expression: VS ₀ = αV ₀ + (1 -Α) Change the smoothing coefficient α at V ₋₁ to a lower value. For example, α = 0.8 is changed to α = 0.4. Thereafter, similarly, a lower value is continuously used as the annealing coefficient α. As described above, also according to the second aspect, provisional processing or control while water adhesion occurs can be suitably performed.

Next, according to the third aspect, when the ECU 21 determines that water has adhered to the air flow meter, the ECU 21 performs a predetermined averaging process on the output value of the air flow meter, and uses the value obtained thereby. Execute control. That is, as shown in FIG. 4, when the ECU 21 determines that water adheres at the reference time t ₀ , the current air flow meter output value V ₀ stored in the RAM and the air flow meter from one to a plurality of cycles before are stored. The output value, for example, the air flow meter output values V ₋₁ and V ₋₂ up to two cycles before is obtained, and the averaged output VM ₀ is calculated from the formula: VM ₀ = V ₀ + V ₋₁ + V ₋₂ / 3 Then, the control at the reference time t ₀ is performed using the averaged output VM ₀ . The reason for using the air flow meter output value V ₀ at the reference time t ₀ is the same as described above. However, this can be avoided.

Here, as in the second embodiment, there may be a case where such an averaging process has already been performed under normal control. In such a case, the ECU 21 can prolong the sampling time in the averaging process when it is determined that there is water adhesion to the air flow meter. As a result, the control can be executed using a value close to the actual air amount while reducing the influence of the abnormal value. Specifically, ECU 21, when determining the reference time t ₀ and has water adheres, for example, the sampling time 2Δt from the current t ₀ to 2 periods before and twice that of 4Derutati. As a result, the sampling data is changed from V ₀ , V ₋₁ , V ₋₂ to V ₀ , V ₋₁ , V ₋₂ , V ₋₃ , V ₋₄ , and the averaged output VM ₀ is expressed by the formula VM _0. = V ₀ + V ₋₁ + V ₋₂ + V ₋₃ + V ₋₄ / 5 Is a similar averaging process performed at baseline after t _0. As described above, also according to the third aspect, provisional processing or control while water adhesion occurs can be performed.

Next, a 3rd aspect is demonstrated. This third aspect relates to a system (FIG. 10) that can estimate the intake air amount as described later in the third aspect relating to the detection of water adhesion. According to the third aspect, the ECU 21 normally calculates an estimated value of the air amount based on the throttle opening detected by the throttle opening sensor 24. At this time, the control can be performed by associating the estimated value of the air amount with the actual value of the air amount obtained from the air flow meter or by using both of them. On the other hand, when it is determined that water has adhered to the air flow meter, the ECU 21 does not use the output value of the air flow meter, but instead executes control using only the estimated value of the air amount. That is, the ECU 21 normally performs calculations such as those shown in the block diagram of FIG. 10 to perform prediction and estimation of the air amount and the like, and when it is determined that there is water adhesion at the reference time t ₀ , Thereafter, the air amount is calculated based on the air flow rate QA0 (estimated value) passing through the throttle valve, which is the output of the TA model 52, and the control is executed based on this air amount.

  Note that air flow rate data in such a modeled system can be learned over time based on the output value of the air flow meter. In such a case, control may be performed using the air amount estimated based on the data after learning. As described above, also according to the third aspect, provisional processing or control while water adhesion occurs can be suitably performed.

However, such provisional processing or termination of the control, i.e. when the return to the normal control, the simplest, even if the time from the reference time t _0, which is measured by the timer or the like is completed, or return After exceeds a predetermined time Good. Alternatively, it may be terminated or returned when the deviation between the actual value and the estimated value of the air amount falls within a predetermined range, and according to this, the end / return timing can be determined with higher accuracy.

  In the above embodiment, the air flow meter is a hot-wire type, but the present invention is widely applicable to air flow meters other than the hot-wire type.

  The embodiment of the present invention is not limited to the above-described embodiment, and includes all modifications, applications, and equivalents included in the concept of the present invention defined by the claims. Therefore, the present invention should not be construed as being limited, and can be applied to any other technique belonging to the scope of the idea of the present invention.

It is a figure which shows the schematic system of the control apparatus of the internal combustion engine which concerns on this embodiment. It is detail drawing which shows the arrangement | positioning part of an airflow meter. It is an electric circuit diagram of an air flow meter. It is a time chart which shows the opening degree change of a throttle valve, and the change of an air flow meter output value. It is a figure which shows the structure of another flow volume detection element. It is a figure which shows the constant temperature difference drive circuit with respect to the flow volume detection element of FIG. It is a figure which shows the relationship between the flow volume obtained by the flow volume detection element of FIG. 5, and temperature sensing resistance. It is a map for calculating the change speed of the estimated value of air amount. It is another map for calculating the change rate of the estimated value of air amount. It is a block diagram of intake pressure calculation.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine 2 Intake pipe 4 Throttle valve 7 Air flow meter 12 Heat sensitive resistor 13 Temperature compensation resistor 24 Throttle opening sensor V Output value of air flow meter TH Throttle opening A Air amount Ar Actual value of air amount Ae Estimation of air amount Value ΔAr Change rate of actual value of air amount ΔAe Change rate of estimated value of air amount α Smoothing coefficient Δt Period between processing timings

Claims (10)

An air flow meter provided in the intake passage of the internal combustion engine;
Means for calculating an absolute value of a change speed of an output value of the air flow meter;
A control device for an internal combustion engine, comprising: means for determining an abnormality of the air flow meter according to a comparison result between the absolute value of the change speed of the calculated output value of the air flow meter and a predetermined value. An air flow meter provided in the intake passage of the internal combustion engine;
A sensor whose output value changes in synchronization with a change in the output value of the air flow meter;
Means for calculating the rate of change of the amount of air taken into the internal combustion engine based on the output value of the air flow meter;
Means for calculating the rate of change of the output value of the sensor;
A control apparatus for an internal combustion engine, comprising: means for determining an abnormality of the air flow meter according to a comparison result between the change rate of the air amount and the change rate of the output value of the sensor.   3. The control apparatus for an internal combustion engine according to claim 2, wherein the sensor is a throttle opening degree sensor that detects an opening degree of a throttle valve provided in the intake passage. An air flow meter provided in the intake passage of the internal combustion engine;
Means for detecting an opening of a throttle valve provided in the intake passage;
Means for calculating the rate of change of the actual value of the amount of air taken into the internal combustion engine based on the output value of the air flow meter;
Means for calculating a change rate of an estimated value of the amount of air taken into the internal combustion engine based on the detected opening of the throttle valve;
A control device for an internal combustion engine, comprising: means for determining an abnormality of the air flow meter according to a comparison result between a change rate of the actual value of the air amount and a change rate of the estimated value of the air amount.   5. The apparatus according to claim 1, further comprising a unit that executes predetermined control using an output value of the air flow meter before the abnormality determination when the air flow meter is determined to be abnormal. Control device for internal combustion engine.   When the air flow meter is determined to be abnormal, it further comprises means for executing a predetermined smoothing process on the output value of the air flow meter and executing a predetermined control using a value obtained thereby. The control device for an internal combustion engine according to any one of claims 1 to 4. Means for executing a predetermined control based on a value obtained by executing a predetermined annealing process on the output value of the air flow meter;
5. A means for changing a predetermined smoothing coefficient so as to increase a smoothing degree in the smoothing process when the air flow meter is determined to be abnormal. 5. The control apparatus of the internal combustion engine described in 1.   When it is determined that the air flow meter is abnormal, it further comprises means for executing a predetermined averaging process on the output value of the air flow meter and executing a predetermined control using a value obtained thereby. The control device for an internal combustion engine according to any one of claims 1 to 4. Means for executing a predetermined control based on a value obtained by executing a predetermined averaging process on the output value of the air flow meter;
5. The control device for an internal combustion engine according to claim 1, further comprising: means for extending a sampling time in the averaging process when the air flow meter is determined to be abnormal. Means for calculating an estimated value of the amount of air taken into the internal combustion engine based on the detected opening of the throttle valve;
The control device for an internal combustion engine according to claim 4, further comprising: a unit that performs predetermined control using the estimated value of the air amount when the air flow meter is determined to be abnormal.

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