JPH05133270A - Air quantity detecting device for engine - Google Patents

Abstract

PURPOSE:To improve the accuracy of detecting the air quantity and reduce the manhours for development. CONSTITUTION:An air flow meter 1 for producing output in answer to the air quantity in the upstream of a throttle valve, a means 2 for calculating the pressure in an intake pipe based on the output of the air flow meter 1 and the calculated value of previous intake air flow into a cylinder, a means 3 for calculating the rate of intake air flowing into the cylinder based on at least the pressure in the intake pipe and the value equivalent to the throttle valve opening, and a means 4 for calculating the intake air flow flowing into the cylinder based on the rate of intake air and the pressure in the intake air pipe, are provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine air amount detecting device.

[0002]

2. Description of the Related Art In a fuel injection type engine in which an air flow meter is provided in an intake passage upstream of a throttle valve, a weighted average and other corrections are made to a basic injection pulse width obtained from the output (intake air amount) of the air flow meter and the engine speed. There is a method in which the injection pulse width corresponding to the cylinder intake air amount is obtained and the fuel injection amount of the fuel injector is controlled based on this.

Due to pressure changes in the intake manifold,
Since there is a difference between the output of the air flow meter and the intake air amount of the cylinder, it is possible to predict the cylinder intake air amount by performing each correction such as weighted average and inject the fuel according to the predicted air amount. (See Japanese Patent Application Laid-Open No. 2-156117, etc.).

[0004]

However, in order to improve each performance of the engine, intake and exhaust valve lift, a variable valve that changes the timing, a compression ratio variable device that changes the compression ratio, and a swirling flow are added to the intake air. Some engines are equipped with variable elements such as a swirl valve, but in such an engine, a sudden change in the intake air amount due to a sudden change in the ratio of fresh air flowing into the cylinder when switching the variable elements is monitored. It is not possible, even if each correction such as weighted average is performed as described above,
A gap may occur between the cylinder intake air amount and the predicted air amount, and an air-fuel ratio error remains.

Further, such a correction logic needs to be adapted in an actual machine, which causes a problem that the man-hours for development are large.

The present invention aims to solve such problems.

[0007]

A first aspect of the present invention is, as shown in FIG. 1, an air flow meter 1 that outputs according to the amount of air upstream of a throttle valve, the output of this air flow meter 1 and the previous cylinder intake air. Means 2 for calculating the intake pipe internal pressure based on the calculated value, means 3 for calculating the ratio of fresh air flowing into the cylinder based on at least the intake pipe internal pressure or the throttle valve opening equivalent value, and the fresh air ratio And means 4 for calculating the cylinder intake air amount based on the intake pipe internal pressure.

In the second aspect of the invention, as shown in FIG. 2, the fresh air ratio calculating means 3 swirls intake and exhaust valves, a variable valve for changing the timing, a variable compression ratio device for changing the compression ratio, and intake air. It has a plurality of calculation units 5 and 6 according to the states of variable elements such as swirl valves that provide flow, and means 7 for selecting these calculation units 5 and 6 according to the states of the variable elements.

[0009]

[Function] Although there is a time lag between the air flow meter output and the cylinder intake air amount during transient operation, etc., the cylinder fresh air determined by the intake pipe internal pressure, intake pipe internal pressure, etc. according to the air flow meter output and the cylinder intake air amount Since the cylinder intake air amount is determined separately based on the ratio, the fresh air ratio, and the intake pipe internal pressure, an accurate cylinder intake air amount value can be obtained and matching with the engine can be easily performed.

[0010] On the other hand, a plurality of fresh air is provided for the equipment of variable elements such as lift of intake and exhaust valves, variable valve for changing timing, variable compression ratio device for changing compression ratio, and swirl valve for giving swirl flow to intake air. Since the ratio calculator calculates the fresh air ratio in each state according to the state of the variable element, the cylinder intake air amount can be accurately obtained even when the variable element is switched.

[0011]

Embodiments of the present invention will be described below with reference to the drawings.

As shown in FIG. 3, the air taken into the intake passage 21 from the air cleaner 20 is mixed with the fuel injected from the fuel injector 23 provided in the intake port 22,
It is guided to the cylinder 24 of the engine.

The gas that burns in the cylinder 24 with the help of ignition sparks performs the work of pushing down the piston, and the burned gas after the work passes through the exhaust passage 25 and contains harmful three components (CO, HC, NOx). Purifying catalytic converter 26
Be led to.

When the accelerator pedal is depressed, the throttle valve 27 interlocking with the accelerator pedal is opened, and the amount of air flowing into the cylinder 24 increases. This change in the amount of air changes the signal of the hot-wire type air flow meter 28 provided upstream of the throttle valve 27.

Since the sensor portion of the air flow meter 28 is cooled as the amount of air increases, a current is supplied to the sensor portion so that its temperature becomes constant, which is converted into a voltage value and output as an air amount signal. It

The control unit 30 including a microcomputer has the functions of the intake pipe internal pressure calculating means, the fresh air ratio calculating means, and the cylinder intake air amount calculating means.
An air flow meter 28, a throttle valve opening sensor 31 that detects the opening of the throttle valve 27, a crank angle sensor 32 that outputs a predetermined signal in synchronization with the crankshaft, a water temperature sensor 33 that detects the cooling water temperature, and an empty space of the exhaust passage 25. A signal from the fuel ratio sensor 34 or the like is input, the control unit 30 calculates the cylinder intake air amount based on the signal from the air flow meter 28, and determines the fuel injection amount from the fuel injector 23.

Next, the calculation contents of the cylinder intake air amount will be described with reference to the flowchart of FIG. This routine is repeatedly performed at regular intervals (for example, 4 ms).

First, in step 101, the signal from the air flow meter 28 is A / D converted, and a certain process (called linearization process) is performed so that the A / D converted value is proportional to the air amount, and is linearized. Set the value to Qshw. Table characteristics for linearization are shown in FIG.

This linearized air amount Qshw becomes the basic value of the flow rate of the air flow meter portion, but in step 102, the response delay of the air flow meter itself is taken into consideration and a correction relating to this is performed.

Recently, in order to improve the durability of the air flow meter and to reduce the cost thereof, the air flow meter has been moved to the one having a sensor section in which a heating element is provided around a bobbin-shaped ceramic. Since the heat capacity causes a delay as shown in FIG. 6, this is dealt with (see Japanese Patent Application No. 2-15784).

In step 103, correction for intake pulsation and the like is performed by the following equation (1).

Qth = Qd × Ktrm (1) Ktrm is a coefficient for correcting an error of the air amount for each engine condition, and trm means trimming. The trimming coefficient Ktrm is obtained from a map allocated by the engine speed N and the α-N flow rate Qho as a throttle valve opening equivalent value as shown in FIG. Note that Qho is a known air flow rate in the steady state of the throttle valve portion, which is determined by the throttle valve opening TVO and the engine speed N.

Next, at step 104, the intake pipe internal pressure (manifold pressure) is calculated by the following equations (2) and (3) on the basis of the air flow meter air amount Qth (after correction) and the previously calculated cylinder intake air amount old Qc. ) Calculate Pm.

Cm = Old Cm + Qth · Δt−Old Qc · N · K1 (2) Pm = Cm / Vm (3) where Cm; Manifold air amount Δt; Calculation interval K1; Unit matching constant (cylinder Vm; Manifold volume Air flow meter air amount Qth (after correction) and cylinder intake air amount The manifold air amount Cm is calculated using the equation of the physical model according to the old Qc, and the intake pipe internal pressure Pm is calculated from the volume ratio. Since it is obtained, accurate Pm can be obtained without newly providing an intake pipe internal pressure sensor or the like.

The intake pipe internal pressure Pm takes an atmospheric pressure equivalent value as an initial value when the engine is started.

In step 105, the intake pipe internal pressure Pm
Then, the ratio η of fresh air flowing into the cylinder is calculated in accordance with.

This is obtained from the maps defined as shown in FIGS. In this case, η is obtained from the boost Pm of the entire engine performance and the intake air amount Q by the following equation (4), and an η map is created by calculation.

Η = 2Q760 / VeN (760-Pm) (4) where Ve; engine displacement This fresh air ratio η is the α-N flow rate as a value equivalent to the throttle valve opening. It can also be calculated using Qho. Further, the η map may be created with Pm as the atmospheric pressure ratio.

In the high engine speed region, η has a width according to the intake pulsation and the like as shown in FIG. Note that FIG. 9 shows a characteristic diagram at the engine speed shown by the broken line in FIG.

Then, in step 106, the intake pipe internal pressure P
The cylinder intake air amount Qc is calculated by the following equation (5) from m, the fresh air ratio η, and the cylinder volume Vc.

Qc = VcηPm (5) The cylinder intake air amount equivalent pulse width Avtp of the fuel injector 23 is obtained by multiplying the cylinder intake air amount Qc by the injection valve characteristic coefficient K (step 107). .. Based on this Avtp, the final injection pulse width of the fuel injector 23 is determined and fuel injection is performed.

Note that the pulse width is converted first,
Each calculation may be performed with a pulse width equivalent value.

Thus, the air flow rate of the air flow meter,
Since the intake pipe internal pressure is calculated based on the cylinder intake air amount, the cylinder fresh air ratio is calculated based on the intake pipe internal pressure, etc., and the cylinder intake air amount is calculated based on the fresh air ratio and the intake pipe internal pressure according to the physical model formulas. A highly accurate cylinder intake air amount value can be obtained.

Further, in this case, since the specifications of the cylinder volume, the number of cylinders, the manifold volume, the engine displacement, etc., may be set, it is not necessary to adapt the actual machine, and the number of matching steps can be greatly reduced.

Here, FIG. 10 shows a time chart during transition (at engine start-up). The intake pipe internal pressure Pm decreases from the initial atmospheric pressure, and at this time, the air amount Qth of the air flow meter rises with a certain delay. On the other hand, the cylinder intake air amount Qc decreases in accordance with the intake pipe internal pressure Pm as measured, and later coincides.

FIG. 11 shows an embodiment of the second aspect of the invention, in which intake and exhaust valves are lifted, a variable valve for changing the timing, a compression ratio variable device for changing the compression ratio, and a swirl valve for giving a swirling flow to the intake air. Applies to engines equipped with variable elements such as.

When such a variable element is provided, the rate η of fresh air in the cylinder changes depending on the state of the variable element. Therefore, a plurality of η maps corresponding to the state are provided and the fresh air rate η is obtained from the corresponding map. Of.

In FIG. 11, a variable valve provided with first and second cams (first cam has a large lift and second cam has a small lift as shown in FIG. 12) for changing the intake and exhaust valve lifts. Explaining the case, in steps 201 to 204, after the intake pipe internal pressure Pm is calculated based on the corrected air amount Qth of the air flow meter and the cylinder intake air amount old Qc, step 2
In 05, it is determined whether or not the drive is performed by the first cam, and Yes
If s, in step 207, η corresponding to the first cam
A map (Tη1 map) is selected, and the fresh air ratio η is calculated from the Tη1 map. On the other hand, if NO in step 205, the η map (Tη2 map) corresponding to the second cam is selected in step 209, and the fresh air ratio η is calculated from the Tη2 map.

In steps 206 and 208, the delay time is set for the cam switching, and when the cam is switched, the corresponding η map is selected after the cam is surely switched, and the fresh air ratio η is calculated.

In step 210, the cylinder intake air amount Q
c. In step 211, the cylinder intake air amount equivalent pulse width Avtp is determined.

13 and 14 show examples of the Tη1 map and Tη2 map. Of course, these maps are also created by calculation as in FIG.

In this way, the cylinder intake air amount Q
Even when the cam changes suddenly when c changes, the cylinder intake air amount Qc can be accurately monitored as shown in FIG. 15, that is, accurate fuel injection control can be ensured even during the transient operation in which the cam is changed. It is possible to reliably prevent the exhaust emission from deteriorating due to the air-fuel ratio A / F entering the misfire zone or becoming rich.

[0043]

According to the first aspect of the present invention, the intake pipe internal pressure according to the output of the air flow meter and the cylinder intake air amount, the fresh air ratio of the cylinder determined by the intake pipe internal pressure, the fresh air ratio, and the cylinder intake air according to the intake pipe internal pressure. Since the amount is calculated separately, it is not necessary to newly install a detection device such as an intake pipe internal pressure sensor, and it is possible to obtain an accurate cylinder intake air amount value without incurring cost increase, and a large matching man-hour. Can be reduced to

A second invention is a lift of intake and exhaust valves,
In an engine equipped with variable elements such as variable valves that change timing, the fresh air ratio in the relevant state is calculated according to the state of the variable element, so it is possible to respond to sudden changes in the fresh air ratio when switching the variable elements, and with high accuracy. The cylinder intake air amount can be obtained.

[Brief description of drawings]

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

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

FIG. 3 is a system diagram of an example.

FIG. 4 is a flowchart of calculation.

FIG. 5 is a characteristic diagram of a linearization process of an air flow meter output.

FIG. 6 is a characteristic diagram showing a delay of an air flow meter output.

FIG. 7 is a characteristic diagram of error correction data output from an air flow meter.

FIG. 8 is a characteristic diagram showing a data map of a fresh air ratio.

FIG. 9 is a partial characteristic diagram thereof.

FIG. 10 is a waveform diagram for explaining the operation.

FIG. 11 is a flowchart of another embodiment.

FIG. 12 is a lift characteristic diagram of a cam.

FIG. 13 is a characteristic diagram showing a data map of a fresh air ratio.

FIG. 14 is a characteristic diagram showing a data map of a fresh air ratio.

FIG. 15 is a waveform diagram for explaining the operation.

[Explanation of symbols]

 21 Intake passage 24 Cylinder 27 Throttle valve 28 Air flow meter 30 Control unit 31 Throttle valve opening sensor 32 Crank angle sensor 33 Water temperature sensor

Claims (2)

[Claims] 1. An air flow meter that outputs according to the amount of air upstream of a throttle valve, a means for calculating the intake pipe internal pressure based on the output of this air flow meter and the previous cylinder intake air amount calculation value, and at least this intake air Means for calculating the ratio of the fresh air flowing into the cylinder based on the pipe internal pressure or the throttle valve opening equivalent value, and means for calculating the cylinder intake air amount based on the fresh air ratio and the intake pipe internal pressure are provided. Engine air amount detection device. 2. The fresh air ratio calculation means includes variable elements such as intake and exhaust valve lifts, variable valves that change timing, variable compression ratio devices that change compression ratios, and swirl valves that give swirl flow to intake air. The air amount detection device for an engine according to claim 1, further comprising a plurality of calculation units according to a state, and a unit for selecting the calculation units according to a state of the variable element.