JPH0735747B2 - 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. Some of them are detected, and some are indirectly detected from the intake pipe internal pressure measured by the pressure sensor and the engine speed. In addition to the pressure sensor, a throttle valve opening sensor or the like is provided to detect the air amount based on the throttle valve opening and the engine speed (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.

In addition, boost control that avoids the rise of negative pressure in the intake manifold during engine deceleration and suppresses the generation of CO and HC, and bypasses the throttle valve during deceleration to guide air to the intake manifold to suppress oil return. In an internal combustion engine equipped with a valve (manifold negative pressure control valve), air flows regardless of the throttle valve when the boost control valve is opened. The values will not match.

The present invention aims to solve such problems.

That is, the present invention has been made to improve the measurement accuracy in the means for detecting the air amount based on the throttle valve opening and the engine rotation speed.

(Means for Solving Problems) According to the present invention, as shown in FIG. 1, in an internal combustion engine provided with a boost control valve 3 that bypasses the throttle valve 1 at the time of deceleration and guides air to the intake manifold 2, The boost control valve includes a speed detecting unit 4, a throttle valve opening detecting unit 5, and an air flow rate calculating unit 6 calculating an intake air flow rate based on the throttle valve opening and the rotation speed. Means 7 for determining the open / closed state of No. 3 and means 8 for outputting a predetermined flow rate value regardless of the calculation result of the intake air flow rate when the valve is opened are provided.

(Operation) Therefore, since the air flow rate is calculated from the throttle valve opening α and the engine rotation speed N, the flow rate can be accurately detected without being influenced by the intake pulsation of the internal combustion engine. In this case, instead of directly determining the air flow rate from α and N, the flow passage area A determined from α is divided by N and set as a parameter, and the air flow rate is calculated based on this and N. Then, the number of data in the calculation table and the like can be small, and matching becomes easy.

Further, when the boost control valve is opened, air flows by bypassing the throttle valve, but the air flow rate can be obtained by setting this flow rate value in advance.

(Embodiment) FIG. 2 shows a fuel injection valve for each intake port 23 according to the present invention.
22 shows a mechanical configuration of an embodiment applied to a multipoint injection type engine in which 22 is installed.

Reference numeral 24 is a throttle valve opening sensor that detects the opening α of the throttle valve 20 in the intake passage 21, 25 is a crank angle sensor that detects the engine rotation speed N, and these detection signals are water temperature sensors that detect the engine cooling water temperature. 26, signals from an intake air temperature sensor (not shown) that detects the temperature of intake air, an air-fuel ratio sensor 27 that detects an air-fuel ratio, etc. are input to the control unit 28.

Further, 29 is a passage that bypasses the throttle valve 20, and 30 is an idle control valve that makes the opening of the bypass passage 29 variable.

Further, 31 is a boost control valve, and in order to prevent the negative pressure in the intake manifold 32 from becoming excessive during engine deceleration, when the negative pressure in the intake manifold 32 reaches a set value, the valve element 33 causes the spring 34 to move. The boost passage 35 is opened against this, and air is introduced into the intake manifold 32 from upstream of the throttle valve 20 through the boost passage 35.

The control unit 28 is composed of a microcomputer including a CPU, a RAM, a ROM, an I / O device, etc., has all the functions of each means shown in FIG. 1, detects the amount of air, and injects fuel. The fuel injection amount control via 22 is performed. The control unit 28 also controls the idle control valve so as to maintain a predetermined engine rotation speed during idle operation, for example.
Drive and control 30.

Next, the contents executed in the control unit 28 will be described with reference to the flow charts shown in FIG.

FIG. 3 shows a calculation routine of the air flow rate Qc flowing into the engine cylinder. First, at step 50, the flow passage area of the intake passage 21 near the throttle valve 20 is searched by a table search from the signal α of the throttle valve opening sensor 24. Aα is required. FIG. 4 shows a characteristic diagram showing the contents of the table.

In step 51, the flow passage area Ab of the bypass passage 29 is obtained by a table search from the drive control signal (duty signal) ISCD commanding the idle control valve 30. FIG. 5 shows a characteristic diagram showing the contents of the table.

Then, in step 52, the total flow passage area A is calculated from the sum of Aα and Ab.

Next, in step 53, the steady-state basic air flow rate QH ₀ corresponding to the total flow path area A is obtained. In this case, QH ₀
Is obtained from a two-dimensional table that is pre-assigned with a value A / N obtained by dividing the total flow passage area A by the rotational speed N from the crank angle sensor 25 as a parameter. The basic air flow rate Q
H ₀ is a linearization of the air flow rate QH during steady state.
So that the steady amount of air flow QH determined at step 54 by multiplying the correction coefficient KFLAT this QH _0. FIGS. 6 and 7 show examples of the contents of the two-dimensional table that gives QH ₀ and KFLAT.

After the steady-state air flow rate QH is obtained in this way,
In the next step 55, the delay coefficient K ₂ (K ₂
<1) is obtained by searching a three-dimensional table using the total flow passage area A and the rotation speed N as parameters. 8th
A characteristic diagram showing the contents of the table is shown in the figure.

Then, in step 56, the air flow rate Qc to the cylinder is obtained from the above QH and K ₂ . That is, in this case Qc = Qco
+ K ₂ (QH-Qco). However, Qco is the previously calculated value of the air flow rate Qc, and Qc = QH in the steady state.

By the way, the boost control valve 31 opens when the negative pressure in the intake manifold 32 reaches a set value.
Qcmin may be determined according to the engine speed N, for example.

Therefore, in step 57, a preset air flow rate Qcmin is obtained from the rotation speed N, and in step 58, this Qcmin is compared with the air flow rate Qc to determine whether or not the boost control valve 31 is opened. .

Then, when the air flow rate Qc is larger than Qcmin and the boost control valve 31 is closed, Qc is directly adopted as the flow rate value in step 59, while when Qc is smaller than Qcmin, it is determined that the boost control valve 31 is open. In step 60, Qcmin is adopted as the flow rate value. In this way, the setting of Qcmin is the aim of the present invention. This is because the BCV itself has the function that the boost pressure does not fall below the set value due to the BCV, and one cylinder per cylinder depending on the manifold pressure. This is an application of the property that the intake air amount Qc is determined as follows.

Qc = η × PM / RT M × Vcyl Qc; Intake air amount per cylinder per stroke η; Volume efficiency PM; Manifold pressure R; Gas constant TM; Gas temperature Vcyl; Volume per cylinder That is, compensated by BCV Qc depending on the set value of PM
The lower limit of is determined.

FIG. 9 shows a flow rate characteristic of the boost control valve 31. The boost control valve 31 has an ON-OFF characteristic with a predetermined boost pressure as a boundary, and the flow rate is set so as not to fall below the predetermined boost pressure.

After obtaining the air flow rate Qc to the cylinder in this way,
The fuel injection amount Ti of the fuel injection valve 22 is determined based on this Qc, and the fuel injection control is performed based on this Ti.

In this way, the air flow rate Qc is calculated based on the throttle valve opening α (and the opening of the bypass passage 29) and the engine rotation speed N, so that it is possible to use a hot wire type flow sensor or pressure sensor. Therefore, the accurate intake air amount of the internal combustion engine can be detected without being affected by the intake pulsation.

Further, during deceleration when the boost control valve 31 opens, air flows by bypassing the throttle valve 20. In this case, the air flow rate Qc (Qcmin) corresponding to the engine rotation speed N.
Therefore, an accurate air flow rate value can be obtained even during deceleration.

Therefore, by calculating the fuel injection amount based on the air flow rate Qc detected in this way, it becomes possible to perform accurate fuel control, thereby maintaining the appropriate air-fuel ratio during acceleration and deceleration as in steady state. As a result, it becomes possible to remarkably improve the driving performance and the exhaust performance of an automobile engine whose operating condition changes frequently.

In the present embodiment, Qcmin may be assigned to the rotation speed N, or Qcmin may be a constant for simplification of control.

(Effects of the Invention) As described above, according to the present invention, the intake air amount is obtained from the throttle valve opening degree and the engine rotation speed, so that an accurate air amount that is not affected by the intake pulsation of the internal combustion engine can be obtained. .

Further, since the predetermined flow rate value is adopted when the boost control valve is opened, it is possible to accurately detect the air amount even during deceleration.

[Brief description of drawings]

FIG. 1 is a block diagram of the present invention, FIG. 2 is a mechanical block diagram of one embodiment of the present invention, FIG. 3 is a flow chart showing the contents of arithmetic processing of the above embodiment, and FIGS. FIG. 9 is a characteristic diagram showing the contents of the table used in the process of the arithmetic processing, and FIG. 9 is a graph showing the flow rate characteristic of the boost control valve. 1 ... Throttle valve, 2 ... Intake manifold, 3 ... Boost control valve, 4 ... Engine speed detection means,
5: throttle valve opening detection means, 6: air flow rate calculation means,
7: open / close state determination means, 8: predetermined flow rate value output means.

Claims (1)

[Claims] 1. An internal combustion engine having a boost control valve for controlling an intake manifold pressure so as not to fall below the set value by bypassing a throttle valve to introduce air into the intake manifold when the intake manifold pressure falls below the set pressure. In the above, the boost control is provided with a means for detecting an engine rotation speed, a means for detecting a throttle valve opening, and an air flow rate calculating means for calculating an intake air flow rate based on the throttle valve opening and the rotation speed. A means for determining the open / closed state of the valve from a calculation value corresponding to the intake air amount of the calculation means, and a predetermined flow rate value regardless of the calculation result of the intake air flow rate when the determination means determines that the valve is open. An air amount detecting device for an internal combustion engine, comprising: an output unit.