JPH0670403B2 - 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 therefore, the value also varies depending on the position of the fuel injection valve. However, there is a problem that the air-fuel ratio becomes rich or lean during acceleration or deceleration.

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

(Means for Solving Problems) The present invention is, as shown in FIG. 1, a means 1 for detecting a throttle valve opening, a means 2 for detecting an engine rotation speed, and a steady air from both detected values. From the constant air flow rate calculation means 3 for calculating the flow rate QH, the delay coefficient calculation means 4 for similarly calculating the delay coefficient K of the air flow from the detected values, and the constant air flow rate QH and the delay coefficient K, the following equation Qc = Qco + K ( QH-Qco) (where Qco is Q
Air flow rate Qc flowing into the cylinder according to the previous calculation value of c)
And the correction means 5 for calculating

(Operation) Therefore, the air flow rate QH is accurately detected from the throttle valve opening α and the engine rotation speed N without being affected by the intake pulsation, and the throttle valve opening α and the engine are set to the air flow rate QH. By adding the correction by the delay coefficient K based on the rotation speed N, the air flow rate Qc to the cylinder can be accurately detected without deteriorating the responsiveness even during the transient state.

(Embodiment) FIG. 2 shows a fuel injection valve for each intake port 10 according to the present invention.
11 shows a mechanical structure of an embodiment applied to a multipoint injection type engine in which 11 is installed.

Reference numeral 12 is a throttle valve opening sensor that detects the opening α of the throttle valve 14 in the intake passage 13, reference numeral 15 is a crank angle sensor that detects the engine rotation speed N, and these detection signals are water temperature sensors 16 that detect the engine cooling water temperature. A signal 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, and the like are input to the control unit 18.

Further, 19 is a passage that bypasses the throttle valve 14, 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 the respective means 1 to 4 shown in FIG. The fuel injection control of the injection valve 11 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.

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 12
The throttle valve opening area Aα is obtained from the signal α of the above by a table search. FIG. 5 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 bypassing the throttle valve 14 is obtained by a table search from the drive control signal (duty signal) ISCD commanding the idle control valve 20.
FIG. 6 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, in step 13, the steady air flow rate QH with respect to the total flow passage area A is obtained. In this case, the air flow rate QH is a value A / the total flow passage area A divided by the engine rotation speed N from the crank angle sensor 15. It is obtained from a three-dimensional table assigned to N and engine speed N. FIG. 7 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 is because if the rotation speed N is constant, the A / N changes according to the throttle valve opening α, and 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 14 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. 8 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 QH and delay coefficient _{K, Qc = Qc 0 + K} (QH-Qc 0)
It is calculated by the formula. Qc ₀ is the previously calculated air flow rate Qc
So, in the steady state, Qc ₀ = QH.

FIG. 4 shows a calculation routine of the fuel injection amount Ti of the fuel injection valve 11. In step 20, the basic injection amount Tp is the air flow rate Qc, the atmospheric pressure correction coefficient Kp, the intake temperature correction coefficient Kt and the constant.
It is calculated by multiplying Ka.

Then, in step 21, the basic injection amount Tp is multiplied by various correction factors COEF conventionally used and the feedback correction factor LA from the air-fuel ratio sensor 17, and the invalid pulse width (voltage correction amount) Ts is added to add the fuel injection 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 QH is calculated based on the opening degree α of the throttle valve 14 (and the opening degree of the bypass passage 19 of the throttle valve 14) and the engine rotation speed N. It is not affected by the intake pulsation unlike the case of using, and it can maintain good responsiveness during transient changes in the engine operating conditions, and an accurate detection value of the air flow rate QH can be obtained. .

On the other hand, the air flow rate QH does not match the air flow rate Qc flowing into the cylinder due to the air flow delay except in the steady state,
Since the delay of the air flow corresponds to the throttle valve opening α and the engine rotation speed N, the air flow rate QH is corrected by the delay coefficient K based on the α and N, so that the air flow to the cylinder during the transition is increased. The flow rate Qc is accurately calculated.

Therefore, by calculating the fuel injection amount based on the air flow rate Qc thus detected, it is possible to prevent the fuel injection amount Ti from the fuel injection valve 11 from becoming excessive or insufficient even during acceleration or deceleration. Instead, it becomes possible to perform fuel injection control according to the air flow rate Qc, and as a result, the proper air-fuel ratio can be maintained during acceleration and deceleration, as in the steady state.

Fig. 9 shows the operating characteristics during acceleration. The air flow rate QH corresponds to the rapid opening of the throttle valve 14, while the air flow rate to the cylinder is increased.
Qc will gradually increase. At this time, if fuel is injected into the intake port according to the air flow rate QH, the air-fuel ratio will be greatly enriched (similar to the conventional example), but the fuel will be increased according to the air flow rate Qc. By injecting, an almost constant air-fuel ratio can be obtained. In this case, the air-fuel ratio will be somewhat lean, which is an error due to the buildup of deposited fuel in the intake pipe during acceleration.

The ignition timing of the engine may be controlled on the basis of the air flow rate Qc, which makes it possible to control the optimal ignition timing even during a transition.

As described above, according to the present invention, the steady air flow rate is accurately detected from the throttle valve opening degree and the engine rotation speed, and this is corrected with the delay coefficient according to the operating state. By doing so, the air flow rate to the cylinder at the time of transition can be accurately detected, so that accurate air-fuel ratio control can always be performed.

[Brief description of drawings]

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 and 4 are flow charts showing the contents of respective calculations, and FIGS. FIG. 9 is a characteristic diagram showing the contents of each table used in FIG. 9, and FIG. 9 is an explanatory diagram showing operating characteristics during 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 ... Correction means.

Claims (1)

[Claims] 1. A means for detecting a throttle valve opening, a means for detecting an engine rotation speed, and a steady air flow rate QH from both detected values.
From the steady air flow rate calculation means, the delay coefficient calculation means that similarly calculates the delay coefficient K of the air flow from the detected values, and from the steady air flow rate QH and the delay coefficient K, the following equation Qc = Qco +
An air amount detecting device for an internal combustion engine, comprising: a correction unit that calculates an air flow rate Qc flowing into a cylinder based on K (QH-Qco) (where Qco is a previously calculated value of Qc).