JPH05256181A - Thermal intake air amount detector - Google Patents

Abstract

(57) [Summary] [Object] The present invention relates to a thermal type intake air amount detection device, and an object thereof is to detect an accurate intake air amount regardless of operating states with different average flow rates, and to reduce the map capacity. And [Structure] Internal combustion engine M1 detected by a thermal flow rate detector M2
The detected value of the intake air is corrected by the flow rate correction means M3 to obtain the intake air amount used for calculating the fuel injection amount. In the corrected flow rate map M4, the difference between the true intake air amount and the detection value of the thermal type flow rate detector is set as the corrected flow rate, and the pulsation rate, which is the ratio between the pulsation width and the average flow rate, and the engine speed are stored in advance as parameters. is doing. The flow rate correction means M3 reads the corrected flow rate from the corrected flow rate map using the pulsation rate of the detected value and the engine speed during engine operation, and adds and corrects the detected value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal type intake air amount detecting device for detecting an intake air amount using a thermal type flow rate detector.

[0002]

2. Description of the Related Art Conventionally, for detecting the intake air amount of an internal combustion engine, current control is performed so that a heating wire disposed in an intake passage has a constant temperature, and the intake air amount is detected from the supplied current amount. There is a thermal type intake air amount detecting device using a thermal type flow rate detector.

As such a thermal type intake air amount detecting device, as described in Japanese Patent Publication No. 59-17371, a correction value is obtained based on the pulsation width of the detected air amount and the engine speed, and this correction is performed. There is one that adds a value to the detected air amount to correct the detected air amount.

[0004]

However, even when the exhaust gas recirculation device (EGR) is inhaling the exhaust gas into the intake system, or when the vehicle is traveling at a high altitude, the throttle opening is the same. If the intake air volume decreases,
To obtain the same intake air amount, the throttle opening becomes large, and the pressure wave easily propagates to the detector, so the pulsation width also becomes large. Therefore, even when the pulsation width is the same, there are operating states in which the average flow rate is different, and in such operating states with different average flow rates, the required correction amount also differs, and based on the pulsation width and the number of revolutions as in the past, There is a problem that an accurate intake air amount cannot be obtained with the correction value.

The present invention has been made in view of the above points,
By adding and correcting the detected value with the correction flow rate according to the pulsation rate and the engine speed, it is possible to detect the accurate intake air amount regardless of the operating state where the average flow rate is different, and the thermal type intake that requires a small map capacity. An object is to provide an air amount detection device.

[0006]

FIG. 1 shows the principle of the present invention.

In the figure, the detected value of the intake air of the internal combustion engine M1 detected by the thermal type flow rate detector M2 is corrected by the flow rate correction means M3 to obtain the intake air amount used for calculating the fuel injection amount.

The correction flow rate map M4 uses the difference between the true intake air amount and the detection value of the thermal type flow rate detector as the correction flow rate, and sets the pulsation rate, which is the ratio between the pulsation width and the average flow rate, and the engine speed as parameters. Is stored in advance.

The flow rate correcting means M3 reads the corrected flow rate from the corrected flow rate map using the pulsation rate of the detected value and the engine speed during engine operation, and adds and corrects the detected value.

[0010]

In the present invention, the pulsation rate and the engine speed are used to find the correction flow rate stored in advance in the map M4, and the detection value of the detector M2 is added and corrected. In such correction, the average flow rate changes. However, the average flow rate does not need to be added as a parameter for referencing the map because it is not affected, and the capacity of the map M4 is small, and the average flow rate is different at the same pulsation width and the same rotation speed. Even with this, the accurate intake air amount is detected.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 2 is a block diagram of an embodiment of an internal combustion engine to which the present invention is applied. The present embodiment is an example in which a four-cylinder, four-cycle spark ignition type internal combustion engine (engine) is applied as the internal combustion engine 32, and is controlled by a microcomputer 21 described later.

In FIG. 2, a surge tank 24 is provided downstream of the air cleaner 22 via a throttle valve 23. An intake air temperature sensor 25 that detects the intake air temperature is attached near the air cleaner 22, and an idle switch 26 that is turned on when the throttle valve 23 is fully closed is attached to the throttle valve 23.
Further, a hot wire type air flow meter 27 is provided on the upstream side of the throttle valve 23 to detect the flow rate of the intake air from the current value required to maintain the hot wire 27a disposed in the intake passage at a constant temperature.

A bypass passage 28 that bypasses the throttle valve 23 and connects the upstream side and the downstream side of the throttle valve 23 is provided.
Idle speed control valve (ISCV) 29 whose degree of valve opening is controlled by a solenoid in the middle of
Is installed. By controlling the valve opening degree by controlling the duty ratio of the current flowing through the ISCV 29, and by adjusting the amount of air flowing through the bypass passage 28, the idling speed is controlled to the target speed. The surge tank 24 includes the intake manifold 30 and the intake port 3.
It communicates with the combustion chamber 33 of the engine 32 via 1. A fuel injection valve 10 is provided for each cylinder so that a part of the fuel injection valve 10 projects into the intake manifold 30, and the fuel 17 is injected into the air flow passing through the intake manifold 30 by the fuel injection valve 10.

The combustion chamber 33 is connected to a catalyst device 36 via an exhaust port 34 and an exhaust manifold 35. Further, 37 is a spark plug, which is provided so as to partially project into the combustion chamber 33. Further, 38 is a piston, which reciprocates vertically in the drawing.

The igniter 39 generates a high voltage and the distributor 40 distributes and supplies the high voltage to the ignition plug 37 of each cylinder. The rotation angle sensor 41 detects the rotation of the shaft of the distributor 40 and detects, for example, 30 °.
The engine rotation signal for each CA is sent to the microcomputer 21.
Output to.

A water temperature sensor 42 is provided so as to penetrate the engine block 43 and partially project into the water jacket, and detects the water temperature of the engine cooling water and outputs a water temperature sensor signal. Further, 44 is an oxygen concentration detection sensor (O ₂ sensor), which is arranged so that a part thereof projects through the exhaust manifold 35 and detects the oxygen concentration in the exhaust gas before entering the catalyst device 36.

Further, an exhaust manifold 35 on the upstream side of the O ₂ sensor 44 and an intake manifold 30 on the downstream side of the throttle valve 23 are connected by a return passage 45, and in the middle of the return passage 45, an EG is provided.
R cooler 46 and EGR valve (hereinafter referred to as EGRV)
47 are provided respectively.

The EGR cooler 46 is for lowering the temperature of the exhaust gas flowing through the recirculation passage 45. Also, EG
The RV 47 has a structure in which a rotor 47a of a step motor rotates in response to a control signal from a microcomputer 21 described later to open and close a valve 47b.

A fuel temperature sensor 48 is provided below the fuel tank 16 to measure the temperature of the fuel 17. The vapor passage 4 is provided above the fuel tank 16.
9 is provided, and the vapor passage 49 is provided with a vapor flow meter 50.
It is connected to the canister 51 via.

The vapor generated in the fuel tank 16 flows into the canister 51 after its flow rate is measured by the vapor flow meter 50. The vapor flowmeter 50 has a rotating portion 52 attached thereto in response to the flow rate of vapor, and a signal rotor (not shown) is attached to the rotating portion 52.

Reference numeral 53 denotes a vapor flow sensor, which is provided in the housing portion of the vapor flow meter 50, and which rotates the rotary portion 5.
When the signal rotor of No. 2 crosses the vapor flow rate sensor 53, it becomes a high voltage, and when it separates, it becomes a low voltage (that is,
A vapor flow rate detection signal, which becomes a high voltage once for each rotation of the rotating unit 52, is generated and sent to the microcomputer 21.

On the other hand, the vapor adsorbed by the canister 51 passes through the purge passage 54 and the intake manifold 30.
Inhaled into. Since the purge passage 54 is provided with an orifice (not shown), the intake manifold 30
The negative pressure of is not directly applied to the fuel tank 16. A purge control valve 55 provided in the middle of the purge passage 54 adjusts the valve opening degree by adjusting the current flowing through the solenoid, and adjusts the purge flow rate flowing through the purge passage 54.

The microcomputer 21 for controlling the operation of each section of the present embodiment having such a configuration has a hardware configuration as shown in FIG. 2, those parts which are the same as those corresponding parts in FIG. 2 are designated by the same reference numerals, and a description thereof will be omitted. In FIG. 3, the microcomputer 21 is a central processing unit (M
PU) 60, read only memory (ROM) 61 storing a processing program, random access memory (RAM) 62 used as a work area, backup RAM 63 that retains data even after the engine is stopped, MP
It has a clock generator 64 for supplying the master clock to the U60, and these are connected to each other via a bidirectional bus line 65, and also connected to the input / output port 66, the input port 67, and the output ports 68 to 72, respectively. It is configured.

Further, the microcomputer 21 uses the hot wire type air flow meter 27 taken out via the buffer 74.
Intake air amount detection signal from the intake air temperature sensor 25, the intake air temperature sensor 25 from the intake air temperature sensor 25, and the water temperature sensor signal (TH
W) and the fuel temperature detection signal from the fuel temperature sensor 48 taken out via the buffer 77 are selectively output by the multiplexer 78, converted into a digital signal by the A / D converter 79, and then input / output port 66. Through the bus line 65
It is configured to be sent to.

Thus, each input detection signal of the multiplexer 78 is sequentially selected and output from the multiplexer 78 under the control of the MPU 60, converted into a digital signal by the A / D converter 79, and then stored in the RAM 62. .. Therefore, the MPU 60, the multiplexer 78, the A / D converter 79, and the input / output port 66 act as sampling means for sampling the detection signals from the fuel temperature sensor 48 and the like at predetermined time intervals. In addition, the microcomputer 21
Is a buffer 8 for the oxygen concentration detection signal from the O ₂ sensor 44.
It is input to the comparator 81 via 0, and the waveform is shaped here and supplied to the input port 67.
2, the detection signals from the rotation angle sensor 41 and the vapor flow rate sensor 53 are waveform-shaped, and the output signal of the idle switch 26 that has passed through a buffer (not shown) is supplied to the input port 67.

Further, the microcomputer 21 has drive circuits 83 to 87, supplies a signal from the output port 68 to the igniter 39 via the drive circuit 83, and has a down counter for the signal from the output port 69. Is supplied to the fuel injection valve 10 via the drive circuit 84
The signal from 0 is supplied to the ISCV 29 via the drive circuit 85, and the output signal of the output port 71 is supplied to the drive circuit 86.
It is configured to be supplied to the purge control valve 55 via. Further, the output signal of the output port 72 is supplied to the EGRV 47 through the drive circuit 87 to control the opening / closing thereof.

4 and 5 are flow charts of the air flow meter reading process and the intake air amount calculating process.

The air flow meter reading process shown in FIG. 4 is, for example, an interrupt process every 4 msec. Step S10
Then, set the output signal voltage of the hot wire air flow meter 27 to A /
It is digitized by the D converter 79, the instantaneous flow rate G is calculated by referring to the map shown in FIG. 6 with this digital value (V), and the processing is ended.

The intake air amount calculation process shown in FIG. 5 is part of the main routine. In step S20, the average flow rate GA ₀ is calculated from the instantaneous flow rate G within the predetermined time. In step S22, the pulsation rate, which is the difference between the maximum value and the minimum value of the instantaneous flow rate G within the predetermined time, is divided by the average flow rate GA ₀ to calculate the pulsation rate.

In the next step S24, the pulsation rate and the rotation speed N
The corrected flow rate (air flow rate per unit time) is calculated from E by referring to the map shown in FIG. 7. FIG. 7 described above shows a map of the corrected flow rate at an arbitrary rotation speed.

By the way, as shown in FIG. 8 (A), the correction flow rate (g / g) required in accordance with the pulsation width at any rotation speed.
s) is EGR with low atmospheric pressure or EGRV 47 opened
There is a difference between the case where the average flow rate is small in the presence state and the like and the case where the atmospheric pressure is high or the average flow rate is large in the state without EGR with the EGRV 47 closed.

Further, as shown in FIG. 8 (B), the correction rate (%) required according to the pulsation width at an arbitrary number of revolutions differs depending on whether the average flow rate is small or high. Further, as shown in FIG. 8 (C), the correction rate (%) required according to the pulsation rate at any rotation speed is different when the average flow rate is small and when the average flow rate is high.

On the other hand, as shown in FIG. 7, the correction flow rate (g / s) required according to the pulsation rate at any rotation speed.
Is the same even if the average flow rate is different due to the difference in atmospheric pressure. Therefore, the corrected flow rate calculated from the map of FIG. 7 according to the rotational speed NE and the pulsation rate has the same value even if the average flow rate changes at the same pulsation width and the same rotational speed.

After executing step S24,
In step 26, the corrected average flow rate GA ₀ is added to the corrected flow rate (g / s) calculated from the map of FIG. 7 to calculate the corrected average flow rate GA. Next, in step S27, the corrected average flow rate GA is divided by the engine speed NE to calculate the intake air amount GN per engine revolution. After this, the process proceeds to step S28,
The smoothed value GNSM of the intake air amount is calculated by the following formula.

GNSM _i = GNSM _i-1 + (GN-GNSM _i-1 ) / n However, each of GNSM _i and GNSM _i-1 is the previous smoothed value and n is the smoothing coefficient.

Next, in step S30, the smoothed value GNSM of the intake air amount is multiplied by the conversion factor KINJ for converting the fuel injection amount determined for each engine and various correction factors to obtain the basic injection amount TP.
Is calculated, and in step S32, various increases are added to the basic injection amount TP for correction, the fuel injection amount TAU is calculated, and the process ends.

The corrected flow rate obtained from the rotation speed and the pulsation width using a map adapted without EGR assuming that the average flow rate does not change is the average flow rate with the same pulsation width and the same rotation speed in the state with EGR. When the correction of the state in which the air-fuel ratio decreases is performed, the air-fuel ratio A / F deviates from the stoichiometric air-fuel ratio as the intake air amount GN increases as shown by the solid line in FIG. When the correction is performed with the correction flow rate (g / s) obtained by referring to the map of FIG. 9, the air-fuel ratio A for any intake air amount GN as shown by the broken line in FIG.
/ F can be the stoichiometric air-fuel ratio.

[0038]

As described above, according to the thermal type intake air amount detecting device of the present invention, an accurate intake air amount can be detected irrespective of the operating state in which the average flow rate is different, and the map capacity can be small. It is extremely useful in practice.

[Brief description of drawings]

FIG. 1 is a principle diagram of the present invention.

FIG. 2 is a configuration diagram of an embodiment of the present invention.

FIG. 3 is a block diagram of a microcomputer.

FIG. 4 is a flowchart of an air flow meter reading process.

FIG. 5 is a flowchart of an intake air amount calculation process.

FIG. 6 is a diagram showing a map of an instantaneous flow rate.

FIG. 7 is a diagram showing a map of a corrected flow rate.

FIG. 8 is a diagram showing a map of a required correction flow rate or a required correction rate.

FIG. 9 is a diagram showing an air-fuel ratio characteristic.

[Explanation of symbols]

 M1 Internal combustion engine M2 Thermal flow rate detector M3 Flow rate correction means M4 Flow rate correction map 27 Hot wire type air flow meter 47 EGRV

Claims (1)

[Claims] Claim: What is claimed is: 1. A thermal intake air amount detection device for correcting an intake air detection value of an internal combustion engine detected by a thermal flow rate detector to obtain an intake air amount used for calculating a fuel injection amount, comprising: The difference between the flow rate and the detection value of the thermal type flow rate detector is used as the correction flow rate, and the correction flow rate map stored in advance with the pulsation rate, which is the ratio of the pulsation width to the average flow rate, and the engine speed as parameters, and during engine operation. A thermal intake air amount detection device, comprising: a flow rate correction unit that reads the corrected flow rate from the corrected flow rate map by using the pulsation rate of the detected value and the engine speed and adds and corrects the detected value.