JPH0735753B2 - 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 a 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 intake pipe pressure or 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, in an internal combustion engine in which a flow velocity control means such as a movable blade or a swirl control valve is provided on the downstream side of the throttle valve in order to improve the combustibility by promoting the intake air flow in the cylinder in the low load operation range. Since the effective flow path area and the air amount to the cylinder vary depending on the operating position of the flow velocity control means, the correct air amount cannot always be obtained by the method of calculating based on the throttle valve opening.

The present invention has an object to solve such conventional problems.

(Means for Solving Problems) For this reason, in the present invention, as shown in FIG. 1, the engine cylinder 103 is provided in the middle of the engine intake passage 101 so as to be located downstream of the throttle valve 102. On the premise of an internal combustion engine equipped with a flow velocity control means 104 for variably controlling the intake flow velocity, a means 105 for detecting the engine speed N, a means 106 for detecting the opening α of the throttle valve 102, and the throttle valve opening. The air amount table 107 having the degree α and the rotation speed N as parameters is searched, and an air amount calculation means 108 for providing the intake air amount QH is provided. Corresponding to the above, a plurality is provided. A plurality of tables may be provided for the rotation speed N with the division result A / N and the operating position of the flow velocity control means as parameters.

(Operation) In the above configuration, since the air amount QH is calculated from the opening α of the throttle valve 102 and the engine rotation speed N, accurate flow rate detection that is not affected by intake air pulsation of the internal combustion engine can be performed.

Further, since a plurality of air amount tables 107 correspond to the operating position of the flow velocity control means 104, an accurate air amount value corresponding to the operating position can be obtained.

(Embodiment) Next, an embodiment of the present invention will be described with reference to the accompanying drawings. It should be noted that the present invention is basically based on the detection of the air amount in the steady operating state, but in the embodiment, the steady air amount is corrected to finally obtain an appropriate air amount even in the transient operating state. We will show what we have done to get the quantity.

In FIG. 2A, 10 is a throttle valve provided in the middle of the engine intake passage 11, and 12 is an electromagnetic fuel injection valve provided on the upstream side thereof. This is a so-called single-point injection type (hereinafter referred to as “SPI type”) fuel supply device, and the injection fuel from the electromagnetic fuel injection valve 12 is introduced together with the intake air through the intake branch pipe 21 into each multi-cylinder internal combustion engine. Distribution and supply to cylinders.

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

Reference numeral 19 is a bypass passage formed so as to bypass the throttle valve 10, and 20 is an idle control valve for varying the opening degree of the bypass passage 19.

Further, 22 is a swirl control valve as a flow velocity control means interposed in the intake branch pipe 21 so as to be located near the inlet of the intake port 23 for each cylinder, and 24 is a drive device thereof. Although not shown in detail, the drive device 24 includes, for example, a diaphragm device connected to the swirl control valve 22 and an electromagnetic valve for selectively supplying the intake pipe negative pressure or the atmospheric pressure as the operating negative pressure to the diaphragm device. Based on a command from the control unit 18, the swirl control valve 22 is driven to either the open or closed position.

As illustrated in FIG. 2B, the swirl control valve 22 itself has a notch 22b formed in a part of a disc-shaped valve body 22a that rotates in the same manner as the throttle valve 10. By concentrating the intake air flow into the cutout portion 22b, the flow speed of the intake air flowing into the engine cylinder is increased.

The control unit 18 is composed of a microcomputer including a CPU, a RAM, a ROM, an I / O device, and the like, has all the functions of each means 105 to 108 shown in FIG. 1, and detects the air amount. The fuel injection amount control via the fuel injection valve 12 is performed. The control unit 18 drives and controls the idle control valve 20 so as to maintain a predetermined engine rotation speed during idle operation, for example, and a low load operation region determined based on the opening degree of the throttle valve 10 and the fuel injection amount. In order to increase the intake flow velocity, the swirl control valve 22 is closed via the drive device 24.

Next, the contents executed in the control unit 18 will be described with reference to the flow charts shown in FIG.

FIG. 3 shows a calculation routine of the air amount Qc flowing into the engine cylinder. First, at step 301, the flow passage area of the intake passage 11 near the throttle valve 10 is searched by a table search from the signal α of the throttle valve opening sensor 14. Aα is required. FIG. 6 shows a characteristic diagram showing the contents of the table. Generally, Aα is geometrically determined according to the throttle valve opening α.

In step 302, the flow passage area Ab of the bypass passage 19 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 of the idle control valve 20 increases as the duty value increases, and the flow path area Ab also increases accordingly.

Then, in step 303, the total flow passage area A is calculated from the sum of Aα and Ab.

Next, in step 304, the steady basic air amount QHo with respect to the total flow passage area A is obtained. In this case, QHo uses the total flow passage area A as the rotational speed N from the crank angle sensor 15.
The value A / N divided by is assigned in advance as a parameter 2
Calculated from the dimension table. The basic air amount QHo is
It is a linearized version of the air quantity QH at a constant time, and the steady-state air quantity QH is obtained by multiplying this by a correction coefficient KFLAT, which will be described later. FIG. 8 shows an example of the contents of the two-dimensional table that gives this QHo.

Then, basically, the air amount QH is obtained by multiplying the basic air amount QHo by the correction coefficient KFLAT as described above, but the total flow passage area A is determined by the swirl control valve 22.
Since it is affected by the open / close position of the swirl control valve, in the next step 305, the swirl control valve 22 (“SC
(Abbreviated as "V") determines whether it is an open position or a closed position, and proceeds to step 306 for searching the KFLAT1 table or step 307 for searching the KFLAT2 table, respectively, according to the judgment result. That is, in this case, since the swirl control valve 22 is controlled to two positions of open and closed, two correction tables KFLAT1 and KFLAT2 are provided, and when the swirl control valve 22 is open, respectively. Appropriate correction factor depending on when closed
By giving KFLAT and multiplying this by QHo as shown in step 308, the steady-state air amount QH is obtained. The KFLAT1 or KFLAT2 table has the contents as shown in FIG. 9, for example, and constitutes a three-dimensional table in which KFLAT is given with QHo and the rotation speed N as parameters. Also swirl control valve
The determination of the open / closed position of 22 is performed by monitoring the throttle valve opening degree, the fuel injection amount value, and the like that serve as a reference for the position control.

After the steady-state air amount QH is obtained in this manner, in the next step 309, a delay coefficient K ₂ (K ₂ ) that takes into account the delay until the air passing near the throttle valve 10 flows into the cylinder.
<K ₁ ) is obtained by searching a three-dimensional table using the total flow passage area A and the rotation speed N as parameters. 10th
A characteristic diagram showing the contents of the table is shown in the figure. It should be noted that a plurality of tables for giving the delay coefficient K ₂ may be provided depending on the position of the swirl control valve 22.

Then, in step 310, the air amount 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 amount Qc, and Qco = QH in the steady state.

By the way, a so-called multipoint injection system (hereinafter referred to as "MPI
Method)), the above-mentioned Qc indicates the air amount at the fuel injection portion as it is, but in the SPI method of this embodiment, a pressure change occurs in the intake branch pipe 21 in a transient operating state such as acceleration. , The amount of air at the fuel injection site (hereinafter “Qainj”
There is a slight difference between the flow rate Qc and the flow rate Qc just before the cylinder.

FIG. 4 is a routine for compensating for such an air amount deviation. Since Qainj corresponds to Qc to which the air amount ΔCm for the pressure change is added, first, at step 401, ΔCm = K Calculate ΔCm by calculating ₁ (Qc-Qco), and then by calculating Qainj = Qc + ΔCm in step 402.
Seeking Qainj. Note that K ₁ is a constant determined according to the volume of the passage portion of the intake branch pipe 21, and Qco is the previous value of Qc. Then, in step 403, the current Q is prepared for the next process.
Substitute c for Qco, and this ends the routine.

In this way, after the air amount Qainj at the fuel injection portion in the SPI method is obtained, the fuel injection amount Ti is determined by the routine shown in FIG. This routine is SP
It is configured so as to be compatible with both the I and MPI types, and therefore, which of the injection methods is first determined in step 501.

In the case of SPI, the process proceeds to step 502, and is calculated as the air flow rate necessary for the calculation of the basic injection amount Tp by the processing shown in FIG.
If Qainj is adopted and MPI is used, proceed to step 503,
Qc obtained in the process of FIG. 3 is adopted. That is, Tp = Qainj
-The basic injection amount Tp is obtained based on the calculation formula of Ka-Kt-Kp or Tp = Qc-Ka-Kt-Kp. However, in the above equation, Ka is a constant, Kt is an intake air temperature correction coefficient, and Kp is an atmospheric pressure correction coefficient.

Then, after the basic injection amount Tp is obtained in this manner, the fuel injection amount Ti is calculated in step 504 based on the arithmetic expression of Ti = Tp · COEF · LA + Ts. However, in the above equation, COEF is the sum of various correction coefficients, LA is the air-fuel ratio feedback correction coefficient determined based on the signal from the air-fuel ratio sensor 17, and Ts is the compensation amount of the invalid pulse width of the electromagnetic fuel injection valve 12. Yes, all are the same as those conventionally used.

The above routines are periodically executed at predetermined time intervals or in synchronization with engine rotation.

In this way, the air amount QH is calculated based on the throttle valve opening α (and the opening of the bypass passage 19) 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.

On the other hand, the air amount QH does not always match the air amount Qc flowing into the cylinder due to the air flow delay or the like except in the steady state, but the air flow delay depends on the throttle valve opening α and the rotation speed N. Therefore, by correcting the air amount QH by the delay coefficient K ₂ based on α and N, the air amount Qc or Qainj at the time of transition such as acceleration can be more accurately obtained.

Further, the value of the air amount QH, which is the basis of the calculation of Qc or Qainj, is designed to compensate for the influence of the operation of the swirl control valve 22 by obtaining from a plurality of tables according to the operating position, so the swirl A correct air amount value can be obtained regardless of the operation of the control valve 22.

Therefore, by calculating the fuel injection amount based on the air amount Qc detected in this way, the fuel injection amount Ti from the fuel injection valve 12 becomes excessive or insufficient even during acceleration or deceleration. The fuel injection control according to the air amount Qc can be performed without the need to do so, and as a result, the proper air-fuel ratio can be maintained during acceleration and deceleration as in the steady state, so the operating state changes frequently. Even in the above, it becomes possible to remarkably improve the driving performance. The ignition timing of the engine may be controlled on the basis of the air amount Qc or Qainj, and in this way, the optimum ignition timing can be obtained over the entire operating range.

Next, FIG. 11 shows another embodiment relating to the arithmetic processing for obtaining QH. In the process of FIG. 3, two tables of the correction coefficient KFLAT, which form a part of the air amount table, are provided according to the open / close position of the swirl control valve 22, whereas in this embodiment, the opening / closing is performed at the beginning of the process. A difference is that position determination is performed, and a QHo ₁ table and a QHo ₂ table that give the basic air amount QHo corresponding to the opening / closing position are selected according to the determination result. In this embodiment, the number of tables is relatively large, but since the QHo itself can be appropriately set according to the open / close position of the swirl control valve 22, the control accuracy can be further improved.

In each of the above embodiments, the basic air amount QHo is set by linearizing the steady air amount QH and is multiplied by the correction coefficient KFLAT to calculate the steady air amount QH under operating conditions. Alternatively, a plurality of three-dimensional tables that directly give QH using A / N and N as parameters may be provided depending on the open / close position of the swirl control valve 22. However, QH
In terms of control accuracy, it is desirable to secure a data length of at least about 2 bytes as the data of, but when the three-dimensional table is configured to directly add this as described above, The search process becomes slightly complicated. On the other hand, in each embodiment, QHo as a basic value for QH is given in a two-dimensional table, and its correction coefficient KFLAT is a three-dimensional table,
Since it is sufficient to add the data as 1-byte data, each processing content can be made relatively simple. In this case, instead of directly calculating QH from α and N, a value obtained by dividing the flow passage area A of the intake passage determined by α by N is set as a parameter, that is, A having a relatively small variation range. Since the contribution of N to QH was reflected in advance,
The air amount table for giving QH on the basis of this and N requires a smaller number of set data than the conventional one, and therefore, the labor required for matching or the like is reduced.

(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, in an internal combustion engine provided with a flow velocity control means such as a swirl control valve on the downstream side of the throttle valve, the operating position thereof affects the air amount detection. Since a plurality of air amount tables are selectively used, it is possible to accurately detect the air amount regardless of the operating position of the flow velocity control means.

[Brief description of drawings]

FIG. 1 is a block diagram of the present invention. 2A is a mechanical configuration diagram of an embodiment of the present invention, and FIG. 2B is a sectional view taken along line AA of FIG. 3 to 5 are flow charts showing the contents of the arithmetic processing of the above embodiment, and FIGS. 6 to 10 are characteristic line diagrams showing the contents of the table used in the process of the arithmetic processing. FIG. 11 is a flowchart showing a part of the arithmetic processing contents of another embodiment of the present invention. 101 ... Engine intake passage, 102 ... Throttle valve, 103 ... Engine cylinder, 104 ... Flow velocity control means, 105 ... Engine rotation speed detection means 105, 106 ... Throttle valve opening detection means, 107 ... Air Volume table, 108 ... Air volume calculation means.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiromichi Miwa 2 Takaracho, Kanagawa-ku, Yokohama-shi, Kanagawa Nissan Motor Co., Ltd. (56) Reference JP-A-59-150943 (JP, A)

Claims (1)

[Claims] 1. An internal combustion engine having a flow velocity control means for variably controlling the flow velocity of intake air to an engine cylinder in the middle of an intake passage downstream of an intake throttle valve. A means for detecting the opening degree, and an air quantity calculating means for searching the air quantity table group having the throttle valve opening degree, the rotation speed, and the operating position of the flow velocity control means as parameters to give the intake air quantity. An air amount detection device for an internal combustion engine, comprising: