JPH0681921B2 - Air amount detection device for internal combustion engine - Google Patents

Description

The present invention relates to an air amount detection device for an internal combustion engine.

(Prior Art) In a fuel injection type internal combustion engine, it is important to accurately detect the amount of air taken into the engine. As a detection device, the amount of air can be directly measured by a flow sensor such as a hot wire type. There are those that are indirectly detected from the internal pressure of the intake pipe measured by the pressure sensor and the engine rotation speed.
In addition to the pressure sensor, a throttle valve opening sensor is provided to detect the air amount from the throttle valve opening and the intake pipe internal pressure (see Japanese Patent Publication No. 61-4981).

(Problems to be Solved by the Invention) However, in the detection device using the flow rate sensor and the pressure sensor as described above, the variation of the detected value due to the intake pulsation is large, and the injection of the fuel injection valve controlled based on this is large. Since the amount fluctuates, the engine torque fluctuates greatly.

Further, since the flow rate sensor and the pressure sensor are not so responsive, there is a problem that the detection error during a transition is large and the cost is high.

On the other hand, in these detection devices, since the air flow rate at the sensor position is detected, the detected value and the amount of air flowing into the cylinder do not match at the time of a transition, and especially the fuel injection valve is connected to the intake manifold collecting portion. In the internal combustion engine provided on the upstream side of the above, the amount of air passing through the fuel injection portion does not match the amount of air flowing into the cylinder, so the air-fuel ratio becomes rich or lean during acceleration or deceleration. There is a problem that it will end up.

An object of the present invention is to solve the above problems and to provide an air amount detection device having good transient response.

(Means for Solving the Problems) The present invention relates to means 1 for detecting the throttle valve opening degree as shown in FIG. 1 in an internal combustion engine in which a fuel injection portion is provided on the upstream side of a collecting portion of an intake manifold. And a means 2 for detecting the engine speed, and a steady air flow rate Q _H from both detected values.
From the steady-state air flow rate calculation means 3 and the delay coefficient calculation means 4 that similarly calculates the delay coefficient K of the air flow from the detected values, and from the steady-state air flow rate Q _H and the delay coefficient K, the following equation Qc = Qc
_{o + K (Q H -Qco)} ( although Qco is previously calculated value Qc) and the delay correcting means 5 for calculating an air flow rate Qc flowing into the cylinder, the coefficient KN and delay correcting means defined in accordance with the volume of the intake manifold From the calculated value, the following formula △ CM ＝ KN (Qc
-Qco), an addition amount calculating means 6 for calculating a predetermined addition amount ΔCM, and an air flow rate adding means for calculating the passing air flow rate Qa of the fuel injection unit by adding the steady air flow rate Q _H and the addition amount ΔCM 7 and.

(Operation) Thus, from the throttle valve opening and the engine rotational speed, without being affected by the intake pulsation, together with the air flow rate Q _H is detected accurately, throttle valve opening and the engine rotates in the air flow rate Q _H By adding the correction based on the delay coefficient K based on the speed, the air flow rate Qc to the cylinder can be accurately detected without deteriorating the responsiveness even during the transient time. Then, the passing air flow rate Qa at the fuel injection portion is also accurately detected by adding the predetermined addition amount ΔCM corresponding to the intake manifold volume to the steady-state air flow rate Q _H.

(Embodiment) FIG. 2 shows a mechanical structure of an embodiment in which the present invention is applied to a single-point injection type engine in which one fuel injection valve 12 is installed in an intake passage 11 upstream of a throttle valve 10. .

14 is a throttle valve opening sensor that detects the opening α of the throttle valve 10, 15
Is a crank angle sensor that detects the engine speed N,
These detection signals are sent to the control unit 18 together with signals from the water temperature sensor 16 for detecting the engine cooling water temperature, the intake air temperature sensor (not shown) for detecting the temperature of the intake air, the air-fuel ratio sensor 17 for detecting the air-fuel ratio, etc. Is entered.

Further, 19 is a passage that bypasses the throttle valve 10, and 20 is an idle control valve that makes the opening area Ab of the bypass passage 19 variable.

The control unit 18 is composed of a microcomputer including a CPU, a RAM, a ROM, an I / O device, etc., and has all the functions of each means 1 to 7 shown in FIG. Fuel injection control of the injection valve 12 is performed. Further, the control unit 18 drives and controls the idle control valve 20 so as to maintain a predetermined engine rotation speed during idling, for example.

Next, the contents executed in the control unit 18 will be described with reference to the flowcharts of FIGS. Note that the control according to the above flow chart shows an example applicable to both the single point injection system and the multipoint injection system in which a fuel injection valve is provided for each intake port.

FIG. 3 shows a calculation routine of the air flow rate Qc flowing into the cylinder. First, at step 10, the throttle valve opening sensor 14
The throttle valve opening area Aα is obtained from the signal α of the above by a table search. FIG. 6 shows a characteristic diagram showing the contents of the table. The opening area Aα changes in proportion to the throttle valve opening α.

In step 11, the opening area Ab of the passage 19 that bypasses the throttle valve 10 is obtained by a table search from the drive control signal (duty signal) ISCD commanding the idle control valve 20.
FIG. 7 shows a characteristic diagram showing the contents of the table. The opening degree of the idle control valve 20 increases as the duty value increases, and the opening area Ab also increases accordingly.

Then, in step 12, the total flow passage area A is calculated from the sum of the throttle valve opening area Aα and the bypass passage opening area Ab.

Next, determine the air flow rate Q _H in the steady against Soryuro area A in step 13, the engine rotational speed N of the case air flow rate Q _H is Soryuro area A from the crank angle sensor 15
It is calculated from the three-dimensional table assigned to the value A / N divided by and the engine speed N. FIG. 8 is a characteristic diagram showing the contents of the table, and the equal air flow rate line has a characteristic of increasing substantially according to A / N. This means that if the rotation speed N is constant, A / N changes according to the throttle valve opening α,
This is because the air flow rate increases as α increases.

In step 14, a delay coefficient K (K <K <in consideration of a delay until the air passing near the throttle valve 10 flows into the cylinder.
1) is obtained by a table search from the total flow passage area A and the engine rotation speed N. This search is performed by a three-dimensional table, and FIG. 9 shows a characteristic diagram showing the contents of the table. The delay coefficient K changes substantially according to the total flow passage area A.

The air flow rate Qc of the step 15 to the cylinder, the air flow rate Q _H and the delay coefficient K, is calculated by the equation _{Qc = Qco + K (Q H} -Qco). Qco is the previously calculated air flow rate Qc
In, in a steady state it is Qco = _{Q H.}

FIG. 4 shows a calculation routine of the air flow rate Qa passing through the intake passage 11 of the fuel injection valve 12.
Then, the addition amount ΔCM is obtained from the difference value ΔQc (= Qc−Qco) of the air flow rate Qc obtained by the calculation routine of FIG. 3 and the constant KN. The pressure in the intake manifold 21 changes according to the difference value ΔQc of the air flow rate Qc, that is, the increase / decrease amount of the air flow rate Qc.
The amount of addition ΔCM is calculated by multiplying the volume of the intake manifold 21 by the constant KN having a strong correlation with the air amount that changes the pressure.

Then, in step 21, the addition amount ΔCM is added to the air flow rate Q _H , and the air flow rate Qa is calculated. Air flow through the fuel injector to increase or decrease the amount of air flow Q _H and the air flow rate Qc based on
Since it is calculated back from Qa, the air flow rate Qa is the addition amount Δ corresponding to the increase / decrease in the pressure in the intake manifold 21 to the air flow rate Q _H.
Corresponds to the addition of CM.

In step 22, the air flow rate Qc is set as Qco to prepare for the next calculation. In the steady state, of course, △ CM = 0, Qa ＝ Qc ＝ Q _H
Becomes

FIG. 5 shows a calculation routine of the fuel injection amount Ti of the fuel injection valve 12. In the case of the single point injection method as shown in FIG. 2, the process goes to steps 30 to 31, and the basic fuel injection amount Tp is It is obtained by multiplying the flow rate Qa by the atmospheric pressure correction coefficient Kp, the intake air temperature correction coefficient Kt, and the constant Ka.

Further, for example, when applying to a multi-point injection method in which a fuel injection valve is installed in each intake port, go to steps 30 to 32, the basic injection amount Tp is the air flow rate Qc atmospheric pressure correction coefficient Kp, intake air temperature correction It is obtained by multiplying the coefficient Kt and the constant Ka.

Then, in step 33, each basic injection amount Tp is multiplied by various correction coefficients COEF conventionally used and the feedback correction coefficient LA from the air-fuel ratio sensor 17, and the invalid pulse width (voltage correction amount) Ts is further added to perform fuel injection. The amount Ti is required.

Each routine is executed at predetermined time intervals or in synchronization with engine rotation.

In this way, the air flow rate Q _H is calculated based on the opening α of the throttle valve 10 (and the opening of the bypass passage 19 of the throttle valve 10) and the engine rotation speed N. It is not affected by intake pulsation unlike when using a sensor, and it is possible to maintain good responsiveness during transient changes in engine operating conditions, and to obtain an accurate detected value of air flow rate Q _H. can get.

On the other hand, the air flow rate Q _H does not match the air flow rate Qc flowing into the cylinder due to the air flow delay except in the steady state, but the air flow delay corresponds to the throttle valve opening α and the engine speed N. By correcting the air flow rate Q _H by the delay coefficient K based on the α and N, the air flow rate Qc to the cylinder during the transition can be accurately obtained.

Therefore, in the case of the multi-point injection method, by calculating the fuel injection amount based on the air flow rate Qc, it becomes possible to perform accurate fuel injection control, and as a result, the fuel injection amount Ti becomes excessive during acceleration and deceleration. As described above, the proper air-fuel ratio can be maintained as in the steady state.

When showing the operating characteristics during acceleration in Figure 10, will be an air flow rate Qc of the cylinder is gradually increased while the air flow rate Q _H corresponds to the quick opening of the throttle valve 10, this time the air flow rate Q
_When fuel is injected into the intake port according to _H , the air-fuel ratio is greatly enriched (similar to the conventional example), but the air flow rate Qc
By injecting fuel according to the above, a substantially constant air-fuel ratio can be obtained.

On the other hand, in the case of the single point injection method, the fuel injection amount is calculated based on the air flow rate Qa passing through the fuel injection valve 12, and the fuel injection control is performed.
The air flow rate Qa is the intake manifold to the air flow rate Q _H
It is obtained by adding the addition amount ΔCM corresponding to the increase / decrease in the pressure inside 21.

Here, the steady-state flow rates of the air flow rates Qa, Q _H , and Qc are represented by Qa ₀ , Q
_{As H 0} and Qc ₀ (Qa ₀ = Q _{H 0} = Qc ₀ ), when Q _{H 0} becomes Q _H due to the opening operation of the throttle valve 10, Qc flowing into the cylinder from Qc _{0 as} shown in FIG. equilibrated in Q _H gradually increased, after Qa of fuel injection portion was instantaneously increased from Qa _0,
It gradually decreases and equilibrates with Q _H , but at this time, Qc increases according to the difference between Qa and Q _H. Therefore, the addition amount ΔCM calculated from the increase amount Qc of Qc is added to Q _H. By doing so, Qa can be obtained. It has been confirmed by experiments that the air flow rate Qa thus detected substantially matches the true value flow rate. Although it is also possible to calculate the Qa by adding those by a predetermined multiplying the △ Qc in this case Qc, the Q _H △ CM
In the above case where Q is added, a value with less error is obtained because Q _H is used as a reference.

Therefore, even in the case of the single point injection method, it is possible to perform accurate fuel injection control, and it is possible to always maintain an appropriate air-fuel ratio according to the air flow rate Qa during steady state, acceleration, deceleration, etc.

FIG. 12 shows the operating characteristics during acceleration.When the throttle valve 10 is rapidly opened, the air flow rate Qa passing through the fuel injection portion upstream of the throttle valve 10 temporarily increases, and then decreases, but At this time, for example, if the amount of fuel injected according to the opening α of the throttle valve 10 is injected, the air-fuel ratio becomes largely lean (conventional example), but the air flow rate Qa
By injecting fuel in accordance with the above, it is possible to suck the air-fuel mixture having a substantially constant air-fuel ratio into the cylinder.

It should be noted that in FIGS. 10 and 12, the air-fuel ratio is somewhat lean, which is an error due to an increase in the adhered fuel in the intake pipe during acceleration.

(Effect of the Invention) As described above, according to the present invention, by correcting the steady-state air flow rate calculated from the throttle valve opening degree and the engine rotation speed with the delay coefficient according to the operating state, the cylinder in the transient state can be obtained. To the fuel injection part can be accurately detected by adding a predetermined amount of addition to the air flow rate at steady state, and therefore even in the internal combustion engine of the single point injection system. The transient air-fuel ratio control can be accurately performed.

[Brief description of drawings]

FIG. 1 is a block diagram of the present invention, FIG. 2 is a mechanical block diagram showing an embodiment of the present invention, FIGS. 3 to 5 are flowcharts showing the contents of each calculation, and FIGS. 6 to 9 are the calculations. FIG. 10 is a characteristic diagram showing the contents of each table used in FIG. 10, FIGS. 10 and 12 are explanatory diagrams showing operating characteristics at the time of acceleration, and FIG. 11 is an explanatory diagram showing the relationship of each air flow rate at the time of acceleration. 1 ... Throttle valve opening detection means, 2 ... Engine rotation speed detection means, 3 ... Steady air flow rate detection means, 4 ... Delay coefficient calculation means, 5 ... Delay correction means, 6 ... Addition amount calculation means , 7
...... Air flow rate addition means.

Claims (1)

[Claims] 1. In an internal combustion engine having a fuel injection portion provided upstream of a collection portion of an intake manifold, a means for detecting a throttle valve opening, a means for detecting an engine rotation speed, and a steady detection from both detection values. air flow rate Q and a constant air flow rate calculating _{means H} calculates the, likewise delay coefficient K of the air flow from both the detection values of
A delay coefficient calculating means for calculating a steady air flow rate Q _H and the delay coefficient K with the following equation _{Qc = Qco + K (Q H} -Qco) ( provided that
Qco is the previously calculated value of Qc), the delay correction means that calculates the air flow rate Qc flowing into the cylinder, and the coefficient KN determined according to the volume of the intake manifold and the calculated value of the delay correction means. Qc-Qco) gives a predetermined addition amount ΔC
Addition amount calculation means for calculating M, and the steady air flow rate Q _H
And an air flow rate addition means for calculating the passing air flow rate Qa of the fuel injection unit by adding the addition amount ΔCM and the addition amount ΔCM.