JPH0686842B2 - 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 fluctuation of the detection value is large due to the intake pulsation, and the injection of the fuel injection valve controlled based on the fluctuation Since the amount fluctuates, the engine torque fluctuates greatly.

Further, in the case of directly determining the air amount from the throttle valve opening degree and the rotation speed, a three-dimensional table (or map) that gives the air amount using each detected value as a parameter is formed in the storage circuit. However, since the amount of air changes in characteristics depending on the rotational speed, the total amount of air amount data that makes up the table becomes enormous, and for this reason, matching when actually applied to an internal combustion engine is performed. You have to spend a lot of money on. Of course, if the number of data is reduced, it is possible to solve the problems of the storage capacity of the table and the matching man-hour to some extent, but in that case, the resolution of the air amount value is lowered, and as a result, the air-fuel ratio control The accuracy will be reduced.

The present invention aims to solve these conventional problems.

(Means for Solving the Problems) In order to achieve the above object, first, as a first invention, means 101 for detecting an engine rotation speed N as shown in FIG.
Means 103 for detecting the opening α of the throttle valve 102, flow passage area calculating means 105 for calculating the passage area A of the engine intake passage 104 based on the throttle opening α, and the passage area A Is divided by the rotation speed N, and an air amount calculation means 107 for calculating the intake air amount QH by searching a table in which the intake air amount QH is assigned with the division value A / N and the rotation speed N as parameters. And.

In addition, as a second invention, for example, as an internal combustion engine equipped with a bypass passage 108 that bypasses the throttle valve 102 for controlling the idle rotation speed and a bypass control valve 109 that variably controls the opening thereof, In addition to the first aspect of the invention, means 110 for detecting the opening degree β of the bypass passage 108 bypassing the throttle valve 102 is provided as shown by an imaginary line in the figure, and the throttle valve opening degree α and the bypass passage opening degree are provided. The flow passage area calculation means 1 calculates the flow passage area A of the intake passage 104 based on β
Make up 05.

(Operation) In the above configuration, the air flow rate QH is calculated from the opening degree α of the throttle valve 102 and the engine rotation speed N, so that the accurate flow rate detection that is not affected by the intake air pulsation of the internal combustion engine can be performed. Moreover,
Instead of directly obtaining QH from α and N, the flow passage area A of the intake passage 104, which is determined from α, is set as a parameter, that is, for A having a relatively small variation range. Since the contribution of N to QH has been reflected, the number of set data is smaller than before when forming a three-dimensional table that assigns QH based on this and N. Therefore, the time and effort required for matching, etc. And the cost is reduced.

Further, according to the second aspect of the invention, in the engine having the bypass passage 108, it is possible to detect the air amount more accurately.

(Embodiment) Next, an embodiment of the contents including the first invention and the second invention will be described with reference to the accompanying drawings. Note that the present invention is basically based on the detection of the air flow rate in a steady operating state, but in the embodiment, the steady air amount is corrected to finally obtain an appropriate air amount even in a transient operating state. It is shown that the flow rate is obtained.

In FIG. 2, 10 is a throttle valve provided in the middle of the engine intake passage 11, and 12 is an electromagnetic fuel injection valve provided upstream of the throttle valve. 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.

Further, 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.

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 105 to 107 shown in FIG. The fuel injection amount control via the injection valve 12 is performed. Further, the control unit 18 is, for example, an idle control valve so as to maintain a predetermined engine speed during idle operation.
Drive control of 20.

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 flow rate 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 drive control signal (duty signal) ISCD commanding the idle control valve 20 or a table search. Fig. 7 shows a characteristic diagram showing the table contents.
The opening degree of 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-state air flow rate QH for the total flow passage area A is obtained. In this case, QH is the rotational speed N from the crank angle sensor 15 and the value A / N obtained by dividing A by N. It is obtained from a three-dimensional table that is assigned in advance as a parameter. FIG. 8 shows an example of the contents of this three-dimensional table. In this case, since the rotational speed N is reflected in the total flow passage area A, when the air flow rate is directly calculated from A (or α) and N In comparison with the above, the number of data to be prepared on the storage device in order to secure the same resolution becomes smaller.

In step 305, a delay coefficient K (K <K <considering the delay until the air passing near the throttle valve 10 flows into the cylinder.
1) is obtained by searching a three-dimensional table having the total flow passage area A and the rotation speed N as parameters. FIG. 9 shows a characteristic diagram showing the contents of the table. The delay coefficient K changes substantially in correlation with the total flow passage area A.

Then, in step 306, the air flow rate Qc to the cylinder is obtained from the above QH and K. That is, in this case Qc = Qco
+ K (QH-Qco). However, Qco is the previously calculated value of the air flow rate 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 flow rate 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 air flow rate at the fuel injection site (hereinafter referred to as "Qain
j)) and the flow rate Qc just before the cylinder may be slightly deviated.

FIG. 4 is a routine for compensating for the deviation of the air flow rate. Since Qainj corresponds to Qc to which the air amount ΔCm for the pressure change is added, the first step is
At 401, ΔCm is calculated by calculating ΔCm = K1 (Qc−Qco), and then at step 402, by calculating Qainj = Qc + ΔCm.
Seeking Qainj. Note that K1 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 flow rate Qainj at the fuel injection portion in the SPI method is obtained, the fuel injection amount Ti is determined by Sutin shown in FIG. This routine is
It is configured to support both SPI and MPI,
Therefore, first of all, the injection method is 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 flow rate 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 flow rate QH does not always match the air flow rate 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 flow rate QH by the delay coefficient K based on α and N, the air flow rate Qc or Qainj in the transition such as acceleration can be more accurately obtained (see FIG. 10).

Therefore, by calculating the fuel injection amount based on the air flow rate Qc thus detected, the fuel injection amount Ti from the fuel injection valve 12 becomes excessive or insufficient even during acceleration or deceleration. It is possible to control the fuel injection according to the air flow rate Qc and maintain the proper air-fuel ratio during acceleration and deceleration as in the steady state. Can significantly improve its driving performance. The ignition timing of the engine may be controlled on the basis of the air flow rate 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. Instead of using the A / N as it is, first, in steps 1101 to 1102, a table search is performed for the signal QHo linearized with respect to the A / N (see FIG. 12), and then in step 1103. The correction coefficient KFLAT is searched in the table (see FIG. 13), and these are multiplied in the next step 1104 to obtain QH.

The data of QH requires a data length of about 2 bytes for control accuracy. In the first embodiment, this is given by a three-dimensional table (see FIG. 8), whereas in this embodiment, QH data is added. Assign QHo as a basic value in a two-dimensional table,
Furthermore, the correction coefficient KFLAT is a three-dimensional table,
Since it is sufficient to add this as 1-byte data, there are advantages that the processing is simplified as a whole and the operation speed is further improved.

As described above, according to the present invention, the air flow rate is obtained from the throttle valve opening and the engine rotation speed, so that an accurate air flow rate that is not affected by the intake pulsation of the internal combustion engine can be obtained. Further, since the air flow rate is obtained from a table in which the air flow rate is assigned with the engine speed as a parameter, which is obtained by dividing the flow passage area of the intake passage represented by the throttle valve opening by the engine speed, the air flow rate is relatively small. An accurate air flow rate value can be obtained with a small amount of data processing, so that the storage capacity of the control system can be saved, or the number of matching man-hours for each engine type can be reduced.

[Brief description of drawings]

FIG. 1 is a block diagram of the present invention. FIG. 2 is a mechanical block diagram of an embodiment of the present invention, FIGS. 3 to 5 are flow charts showing the contents of the arithmetic processing of the embodiment, and FIGS. 6 to 9 are the steps of the arithmetic processing. FIG. 10 is a characteristic diagram showing the contents of the table used in FIG. 10, and FIG. 10 is an explanatory diagram showing the relationship between the engine operating state and the calculated air flow rate value according to the above embodiment. FIG. 11 is a flow chart showing the contents of arithmetic processing of another embodiment of the present invention,
FIG. 13 and FIG. 13 are characteristic diagrams showing the contents of the table used in the process of the arithmetic processing. 101 ... Engine rotation speed detection means, 102 ... Throttle valve, 103 ...
... Throttle valve opening detection means, 104 ... intake passage, 105 ... flow passage area calculation means, 106 ... division means, 107 ... air amount calculation means, 108 ... bypass passage, 109 ... bypass control valve, 11
0: Bypass passage opening detection means.

Claims (2)

[Claims] 1. A means for detecting an engine rotational speed, a means for detecting a throttle valve opening, and a flow passage area calculating means for calculating a flow passage area of an engine intake passage based on the throttle valve opening. It has a division means for dividing the flow path area by the rotation speed, and an air amount calculation means for calculating a suction air amount by searching a table in which the intake air amount is assigned using the division value and the rotation speed as parameters. An air amount detection device for an internal combustion engine. 2. A means for detecting an engine speed, a means for detecting a throttle valve opening, a means for detecting an opening of a bypass passage bypassing the throttle valve, the throttle valve opening and the bypass passage opening. The flow passage area calculating means for calculating the flow passage area of the intake passage based on the above, the dividing means for dividing this flow passage area by the rotation speed, and the intake air amount are assigned with the division value and the rotation speed as parameters. An air amount detecting device for an internal combustion engine, comprising: an air amount calculating means for searching a table to calculate an intake air amount.