JPH0357861A - Intake air temperature detecting device for internal combustion engine - Google Patents

Abstract

PURPOSE:To improve the control characteristic of air-fuel ratio at the time of transient operation with an intake air temperature detected accurately in good responsiveness by correcting a detection value of the outside air temperature to estimate the intake air temperature, being based on a difference between the outside air temperature and an engine temperature, intake air flow amount and an engine speed. CONSTITUTION:An engine operative condition, which contains at least a speed of an internal combustion engine and its intake pressure, is detected by a means A, while being based on a result of this detection, a fuel supply amount is set. Here temperatures of the outside air and the engine are further detected respectively by means B, C. While a difference between the detected outside air temperature and engine temperature is calculated in a means D. On the other hand, being based on the above described engine speed and intake air pressure, an intake air amount is set in a means E. Being based on the above described temperature difference, intake air amount and the engine speed, the outside air temperature is corrected, and an intake air temperature is estimated by a means F. Thus by detecting the intake air temperature accurately in good responsiveness, the control characteristic of air-fuel ratio is improved at the time of transient operation of the internal combustion engine.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an intake air temperature detection device for an internal combustion engine that sets a fuel supply amount based on engine rotational speed and intake pressure.

Conventional technology> Some electronically controlled fuel supply systems for internal combustion engines set the basic fuel supply amount by a combination of intake pressure and engine rotation speed, but in this case, it is necessary to determine the mass flow rate of intake air. Because of this, the intake air temperature (hereinafter,
A sensor is provided to detect the intake air temperature), and air density correction is applied to the basic fuel supply amount based on this intake air temperature (see Japanese Utility Model Application Publication No. 120239/1988, etc.).

Problems to be Solved by the Invention> By the way, as described above, when detecting the intake air temperature and correcting the air density of the fuel supply amount, it is necessary to arrange the intake air temperature sensor for detecting the intake air temperature at the gathering part of the intake manifold, etc. However, when the intake air temperature changes rapidly, such as during 4i operation with large changes in the throttle valve opening TVO as shown in Figure 6, the responsiveness of the intake air temperature sensor is poor, so a good air density correction is required. Therefore, there was a problem that the air-fuel ratio controllability deteriorated.

This is because the intake air temperature in the intake manifold in the low intake air flow area increases as it receives heat from a heat source such as the engine, and in the high air flow area there is less time to receive heat, so the rise in intake air temperature is smaller than in the low air flow area. For this reason, when the engine accelerates, a difference in the intake air temperature occurs, and the intake air temperature sensor has a response delay, resulting in a large lean change. This phenomenon becomes more noticeable when the engine temperature is high and the outside air temperature is low. Furthermore, as shown in Figure 4, the temperature tends to vary depending on the intake air temperature in the intake manifold, outside air temperature, intake air amount, engine rotation speed, and load. The present invention has been made in view of the above circumstances, and provides a detection device capable of responsively and accurately detecting intake air temperature, thereby improving the fuel supply of an engine that is not equipped with a sensor that directly detects the mass flow rate of intake air. In control, the purpose is to improve air-fuel ratio controllability during engine transient operation. <Means for Solving the Problems> Therefore, as shown in FIG. 1, the present invention includes an engine operating state detection means for detecting an engine operating state including at least engine rotation speed and intake pressure. In an internal combustion engine in which the fuel supply amount is set based on the engine rotational speed and intake pressure detected by the detection means, an outside air temperature detection means for detecting outside air temperature, an engine temperature detection means for detecting the engine temperature, and each temperature difference calculation means for calculating the difference between the outside air temperature detected by the detection means and the engine temperature; and an intake air flow rate setting for setting the intake air flow rate from the engine rotational speed and intake pressure detected by the operating state detection means. and intake air temperature estimating means for estimating the intake air temperature by correcting the detected value of the outside air temperature based on the temperature difference calculated by the temperature difference calculating means, the set intake air flow rate, and the detected engine rotation speed. It is composed of the following.

<Function> According to this structure, the outside air temperature detection means detects the outside air temperature which is not easily influenced by the engine temperature, so the outside air temperature detected by the outside air temperature detection means is not affected by response delay or engine temperature. Erroneous detections due to this influence can be avoided. In addition, when the intake air of the engine is taken in from the outside air and passes through the intake passage, heat is exchanged with the engine.
The heat exchange here is approximately determined by the temperature difference between the intake air flow rate and engine temperature (particularly the wall temperature of the intake manifold) and the outside air temperature, so the engine temperature is detected by the engine temperature detection means and the detected engine temperature is A temperature difference calculation means calculates the difference between the temperature and the outside air temperature detected by the outside air temperature detection means, and an intake air flow rate setting means sets the intake air flow rate based on the intake air pressure and engine rotational speed detected by the operating state detection means. However, the intake air temperature estimating means estimates the intake air temperature from the outside air temperature by estimating the state of the heat exchange from these calculated values and set values.

Example Hereinafter, one embodiment of the present invention will be described based on the drawings.

In FIG. 2, air is taken into the engine body 1 through an air cleaner 2, an intake duct 3, a throttle chamber 4, and an intake manifold 5. As shown in FIG.

The air cleaner 2 is provided with an outside air temperature sensor 6 as an outside air temperature detection means for detecting the outside air temperature TAIR of the engine body 1. The throttle chamber 4 is provided with a throttle valve 7 that operates in conjunction with an accelerator pedal (not shown) to control the intake air flow IQ. The throttle valve 7 is provided with a potentiometer for detecting the TVO and a throttle sensor 8 including an idle switch 8A that is turned on at its idle position. The intake manifold 5 downstream of the throttle valve 7 is provided with an intake pressure sensor 9 that detects the intake pressure PB.
An electromagnetic fuel injection valve 10 is provided for each cylinder.

The fuel injection valve 10 is driven to open for a predetermined time by an injection pulse signal output from a controller 1'l having a built-in microcomputer, which will be described later, in synchronization with the ignition timing, and is driven to open for a predetermined time by a fuel pump (not shown). Fuel controlled to a predetermined pressure by a pressure regulator is injected and supplied into the intake manifold 5.

Furthermore, the cooling water temperature Tw in the cooling jacket of the engine body l
A water temperature sensor 12 is provided to detect the water temperature. Since the cooling water temperature Tw represents the engine temperature, the water temperature sensor 12 corresponds to the engine temperature detection means in this embodiment.

The control unit 11 counts the crank unit angle signal POS outputted from the crank angle sensor 15 in synchronization with engine rotation for a certain period of time, or outputs a crank reference angle signal REF (for 4 cylinders) at every predetermined crank angle position. The engine rotation speed N is calculated by measuring the period (every 180 degrees).

The control unit 1l also controls the intake pressure PB detected by the intake pressure sensor 9 and the crank angle sensor l5.
The engine rotation speed N calculated based on the detection signal from
The basic fuel injection amount (basic fuel supply amount) Tp is set based on the air density correction coefficient KTSA based on the intake air temperature TSA, and the basic fuel injection amount TP is corrected based on various operating conditions to determine the final fuel injection amount. The injection amount Ti is calculated, and an injection pulse signal having a pulse width corresponding to the fuel injection lTi is outputted to the fuel injection valve lO at a predetermined timing to intermittently supply fuel to the engine body 1.

Furthermore, the control unit 11 includes an outside temperature sensor 6.
The outside air temperature TAIR detected by
．． and a fine correction term K. which is set according to the engine rotational speed N and engine load. Temperature correction value ΔTAIR obtained by
By correcting this value, this corrected value is estimated as the true intake air temperature TSA. Here, the control unit} 11 corresponds to a temperature difference calculation means, an intake air flow rate setting means, and an intake air temperature estimation means, and as described above, the intake pressure sensor 9 and the crank angle sensor 15 correspond to an engine operating state detection means. .

Estimation of the true intake air temperature TSA will be explained with reference to the flowchart of FIG. 3.

First, in Stella 1 (indicated by S1 in the figure, the same applies hereinafter), the cooling water temperature is measured from the water temperature sensor l2. The analog signal output according to Tw is converted into a digital signal and the cooling water temperature Tw is read.

In step 2, the outside air temperature TAI is detected from the outside air temperature sensor 6.
The analog signal output according to m is converted into a digital signal and the outside air temperature TA, . Read the instantaneous value of .

In step 3, the analog signal outputted from the intake pressure sensor 9 according to the intake pressure PB is converted into a digital signal and the intake pressure PB is read.

In step 4, the engine rotational speed N is calculated as described above based on the signal from the crank angle sensor l5.

In step 5, the read cooling water temperature Tw and outside air temperature T
The temperature difference ΔT (=Tw TAIN ) between the AI and the other is calculated.

In step 6, an air amount correction coefficient K. From the map? intake air 11Q
Search for the air amount correction coefficient K0 corresponding to . In step 7, a fine correction term K8 corresponding to the engine rotation speed N and engine load is determined from a map of fine correction terms KN set in advance according to the engine rotation speed N and intake pressure PB (or the basic fuel supply amount Tp). search for.

In step 8, the temperature difference ΔT obtained in steps 5 to 7 is
and air amount correction coefficient K. The temperature correction value ΔTAIN is set by multiplying by the fine correction term KN.

In step 9, the temperature correction value ΔTAI set in step 8 is set to the outside air temperature T, detected by the outside air temperature sensor 6.
m is added, and this added value is estimated as the true intake air temperature TSA.

Air taken into the engine is taken in from outside air via an air cleaner 2, and then heat exchanged when passing through a throttle chamber 4 and an intake manifold 5 before being taken into the cylinder. Therefore, the intake air temperature TSA is related to the temperature difference between the intake manifold 5 etc. and the outside air, and as shown in FIG. If it is larger, the intake air temperature TSA will be higher,
In addition, if the amount of air flowing is small, the cost will be high. Furthermore, it changes depending on the engine rotational speed N and the engine load.

As a result, the intake manifold 5, which affects the heat exchange state,
The cooling water temperature Tw and the outside air temperature T a are representative of the temperatures such as
Temperature difference ΔT with I*, intake pressure PB and engine rotation speed N
The correction coefficient K0 obtained from the airflow MQ that can be estimated from
The true intake air temperature TSA can be estimated by correcting the outside air temperature TAIll using the fine correction term KH corresponding to the engine speed N and the engine load.

Since the outside air temperature sensor 6 is located far from the heat generating part of the engine body work, it is not easily affected by the heat generation of the engine body l, and the outside air temperature T, has a gentle temperature fluctuation, so the detection response is Gender is not an issue. In addition, the cooling water temperature Tw detected by the water temperature sensor l2 does not show a sudden temperature fluctuation that would cause a sensor response delay, and furthermore, the detection by the intake pressure sensor 9 has almost no response considering the level of the temperature sensor. I can say there is no delay.

? Therefore, the intake air temperature TSA estimated in this example has sufficient responsiveness even when the engine body l is operated transiently, and the air density of the fuel supply amount is determined using this intake air temperature TSA. If correction is performed, air-fuel ratio controllability will be improved.

When the intake air temperature TSA is estimated from the outside air temperature TA1,l as described above, the air density correction coefficient KTA is found by searching from the map shown in Fig. 5 based on this intake air temperature TSA, and the basic fuel supply ftTp is calculated from this. The fuel supply amount is set according to the mass air amount by being corrected by the air density correction coefficient KTA.

Setting of the basic fuel supply amount Tp based on the intake pressure PB and the engine rotational speed N is performed, for example, as follows.

First, based on the intake pressure PB, the basic volumetric efficiency correction coefficient K
In addition to setting PM, engine rotation speed N and intake pressure PB
Set the minute correction coefficient KFLAT from and multiply these to obtain the volumetric efficiency correction coefficient KQcvL (←K■XKFLA
? ) is calculated. Then, this volumetric efficiency correction coefficient KQc
yL, the intake pressure PB, and a constant K based on the injection characteristics of the fuel injection valve 10. 8 and the air density correction coefficient KTA, the basic fuel supply amount Tp('-KeoNX P B
X KQcvt X KTA) is calculated.

<Effects of the Invention> As explained above, according to the present invention, the intake air temperature of the engine can be detected with good response, and there is no erroneous detection due to the influence of the engine temperature. In engines where the mass flow rate of intake air cannot be directly detected by setting a prediction based on the rotation speed, the air-fuel ratio controllability during transient operation is improved by correcting the air density of the fuel supply amount based on the detected intake air temperature. can improve transient operation performance.

[Brief explanation of drawings]

Fig. 1 is a block diagram explaining the structure of the present invention, Fig. 2 is a system schematic diagram showing an embodiment of the present invention, Fig. 3 is a flowchart showing control contents of the above embodiment, and Fig. 4 is an engine diagram. FIG. 5 is a graph showing the relationship between the operating state and intake air temperature, FIG. 5 is a diagram showing a search map for the air density correction coefficient, and FIG. 6 is a diagram for explaining problems with the conventional device. 1... Engine body 6... Outside temperature sensor 8.
...Throttle sensor 9...Intake pressure sensor 1
1... Control unit 12... Water temperature sensor l5... Crank angle sensor

Claims (1)

[Claims] An engine operating state detection means is provided for detecting an engine operating state including at least an engine rotation speed and an intake pressure, and the fuel supply amount is set based on the engine rotation speed and intake pressure detected by the engine operation state detection means. In an internal combustion engine, an outside air temperature detection means for detecting outside air temperature, an engine temperature detection means for detecting engine temperature, and a temperature difference calculation means for calculating the difference between the outside air temperature detected by each detection means and the engine temperature; intake air flow rate setting means for setting an intake air flow rate based on the engine rotational speed and intake pressure detected by the operating state detection means; and a temperature difference calculated by the temperature difference calculation means, the set intake air flow rate, and detection. 1. An intake air temperature detection device for an internal combustion engine, comprising an intake air temperature estimating means for estimating an intake air temperature by correcting a detected value of outside air temperature based on the detected engine rotational speed.