JPH0828320A - Fuel supply control device for internal combustion engine at starting - Google Patents

Abstract

PURPOSE:To improve characteristics of exhaust by estimating a fuel amount remaining in an internal combustion engine at starting,and correcting the fuel supply rate. CONSTITUTION:When electromotive force VO2, of an oxygen sensor 19 is within a specified range at the time of starting, it is judged not to be activated, while when the force is out of the specified range, it is judged to be activated. In the case that it is activated, a decreasing correction factor K of a reference fuel supply rate TCS is set according to a water temperature, such that it is incrased as the time is short from lowering of an engine 11 to re-starting, cylinder residual fuel exists, and a water temperature is low. A fuel supply rate at the starting time TCS is set by multiplying TCS by K.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for controlling the fuel supply amount at the time of starting an internal combustion engine, and more particularly to a technique for estimating the fuel amount remaining in the engine at the time of starting and correcting the fuel supply amount. Regarding

[0002]

2. Description of the Related Art In an internal combustion engine in which the fuel supply amount is electronically controlled, the startability is improved by increasing the fuel supply amount at the time of start-up to increase the mixture ratio.
In this case, the fuel increase correction coefficient is set to be larger as the engine temperature is lower and the atomization of the fuel is lower and the temperature is lower.

For this reason, in general, a water temperature sensor or the like is used to detect the engine temperature state, and a larger amount of fuel increase correction at startup is set as the temperature gets lower.

[0004]

However, in the general fuel increase correction method at the time of starting based on only the engine temperature as described above, the engine is stopped before the engine temperature has risen sufficiently and then restarted immediately thereafter. In the case of a start-up, the liquid fuel (so-called wall-flow fuel) adhering to the wall of the intake passage flows into the cylinder and restarts when it remains.
The increase correction corresponding to the normal cold start is performed without considering the residual fuel, the air-fuel ratio becomes excessively rich, and the exhaust property deteriorates.
The emission amount of was sometimes increased.

For this reason, there is a system in which the elapsed time from the stop of the engine to the restart is measured, and when the elapsed time is short, the fuel supply amount at the restart is reduced and corrected.
This can prevent the air-fuel ratio from becoming rich due to the residual wall-flow fuel in the cylinder. However, this method has problems that the control software becomes complicated, a large amount of ROM and RAM is required, and a timer must be used.

The present invention has been made in view of the above conventional problems, and estimates the residual fuel state at the time of restart based on the output state of the existing oxygen sensor, and thereby supplies the fuel at the time of restart. It is an object of the present invention to provide a starting fuel supply control device for an internal combustion engine, which is configured to perform an increase correction control of the amount.

[0007]

Therefore, as shown in FIG. 1, the starting fuel supply control device for an internal combustion engine according to the present invention, as shown in FIG. 1, supplies the air-fuel mixture supplied to the engine through detection of the oxygen concentration in the exhaust gas. In an internal combustion engine starting fuel supply control device having an oxygen sensor for detecting the air-fuel ratio, an activity determining means for determining the activity of the oxygen sensor at the time of engine startup by the electromotive force of the oxygen sensor, When it is determined that the oxygen sensor has a high activity, a start-time fuel supply amount correction unit that corrects the fuel supply amount at the time of starting is reduced compared to when the oxygen sensor is determined to have a low activity. Characterize.

The activity determining means is not activated, for example, when the electromotive force of the oxygen sensor is settled within a predetermined range, and is smaller than the predetermined range in accordance with the change in the air-fuel ratio. When it changes to the large side, it is determined to be activated. Further, the engine temperature detection means is included, and the basic value of the fuel supply amount at the time of starting is set to be larger as the engine temperature at the time of starting is lower. When it is determined that the temperature is low, the reduction correction amount may be set larger as the engine temperature is lower.

[0009]

When the engine is restarted in a short time after being stopped, the amount of wall-flow fuel remaining in the cylinder is large, but the oxygen sensor is activated by heating by exhaust gas. When the oxygen sensor is activated, the electromotive force is large when rich, and swings slightly when lean, but when not activated,
It is settled in the middle value at both rich and lean. Therefore, it is determined whether or not the oxygen sensor is activated based on the electromotive force of the oxygen sensor, and when it is not activated, the fuel supply amount is set to be increased in proportion to the normal low temperature start. If so, it is determined that the elapsed time from the stop to the restart is short, and therefore the residual fuel amount in the cylinder is large, and the fuel supply amount is reduced and corrected accordingly.

Specifically, it is determined that the electromotive force is not activated when the electromotive force falls within a predetermined range according to the characteristics of the oxygen sensor, and is activated when the electromotive force changes to a larger side or a smaller side than the predetermined range. can do. In addition, the fuel supply amount at the time of starting is basically set to be larger when the temperature is low, at which fuel vaporization is low. By setting the reduction correction amount to be large on the basis of the determination that the amount is large, it is possible to obtain a total fuel supply amount that is sufficient.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In FIG. 2 showing the configuration of an embodiment, an intake air flow rate Q is controlled in an intake passage 12 of an engine 11 in conjunction with an air flow meter 13 as an intake air flow rate detecting means for detecting the intake air flow rate Q and an accelerator pedal. A throttle valve 14 is provided, and an electromagnetic fuel injection valve 15 as fuel supply means is provided for each cylinder in the downstream manifold portion.

The fuel injection valve 15 is opened and driven by an injection pulse signal from a control unit 16 having a built-in microcomputer, and is fuel-fed by a fuel pump (not shown) to be injected and supplied at a predetermined pressure by a pressure regulator. . Further, a water temperature sensor 17 for detecting the cooling water temperature Tw in the cooling jacket of the engine 11 is provided, and an oxygen sensor 19 for detecting the air-fuel ratio of the intake air-fuel mixture by detecting the oxygen concentration in the exhaust gas of the exhaust passage 18. Oxidation of CO and HC in the exhaust gas and N
The three-way catalyst 20 for purifying performing the reduction of O _X is provided.

A crank angle sensor 21 is built in the distributor (not shown), and the control unit 16 counts a crank unit angle signal output from the crank angle sensor 21 in synchronization with the engine rotation for a certain period of time. Alternatively, the engine rotation speed N is detected by measuring the cycle of the crank reference angle signal. In addition to the above signals, signals from the ignition switch 22 and the start switch 23 are also input to the control unit 16, which are used for fuel supply control at the time of starting, which will be described later.

Next, the fuel supply control routine at the time of starting according to the present invention by the control unit 16 will be described with reference to the flowchart of FIG. In step 1, it is determined whether or not the ignition switch is turned on to determine whether or not the engine is starting. If it is determined to be on, the process proceeds to step 2. In step 2, the electromotive force VO ₂ of the oxygen sensor 19 is read.

In step 3, it is determined whether the electromotive force VO ₂ is within a predetermined range, for example, 200 mmV to 400 mmV, and it is determined whether the oxygen sensor 19 is activated. Here, when the oxygen sensor heated by the exhaust gas heat is kept at a high temperature for a short time until the engine is restarted after the engine is stopped, the sensor element is kept in the active state. At this time, as shown in FIG. The electromotive force VO ₂ deviates to a larger side or a smaller side than the predetermined range according to rich / lean, but when the oxygen sensor is cooled and has a low temperature for a sufficiently long time from the engine stop to the restart, the sensor is detected. The element is not activated, and as shown in the figure, the electromotive force remains within the predetermined range (200 mmV to 400 mmV) due to the rich / lean change of the air-fuel ratio. Therefore, by judging the presence or absence of such activation,
After the engine is stopped, the time elapsed until the engine is restarted can be estimated, and the presence or absence of residual fuel in the cylinder at the time of restarting can be determined by this.

When it is determined in step 3 that the electromotive force is within the predetermined range and the oxygen sensor 19 is not activated, it is determined that the engine has started normally after a sufficient time has elapsed since the engine was stopped. After the restart flag F is set to 0 in step 4, the process proceeds to step 6, but when it is determined that the electromotive force is out of the predetermined range and the oxygen sensor 19 is activated, the elapsed time after the engine is stopped It is determined that the engine is restarting for a short time, the process proceeds to step 5, the restart flag F is set to 1, and then the process proceeds to step 6.

In step 6, the start switch 23 is turned on, that is, waits until it is started, and after it is turned on, the process proceeds to step 7. In step 7, the restart flag F
When the engine restarts in a short time after the engine is stopped, which is 1, the process proceeds to step 8, and the fuel supply amount at the time of restart is considered in consideration of the fuel remaining in the cylinder due to the previous operation. The weight reduction correction coefficient K for weight reduction correction is set according to the water temperature at restart. Here, as the engine temperature at restart is lower, the amount of wall flow fuel when the engine is stopped is larger, and the amount of evaporation from after stop to restart is also smaller, so the amount of residual fuel in the cylinder is larger. Therefore, the weight reduction correction coefficient K is set to a small value (a large weight reduction rate) correspondingly.

Further, at the time of normal starting when the value of the restart flag F is 0, the time from stop to restart is sufficiently long, the residual fuel amount in the cylinder is vaporized and almost disappears through the intake system. Since it can be estimated that the amount of residual fuel is reduced, the amount of reduction correction based on the residual fuel amount is not performed. Therefore, the process proceeds to step 9, and the reduction correction coefficient K is set to 1. In step 10, the basic fuel supply amount TCS ₀ at the time of starting is calculated. This TCS
For example, ₀ is set by increasing the fuel vaporization property as the water temperature is lower, because the fuel vaporization property is lower.

In step 11, the basic fuel supply amount TC
S ₀ is multiplied by the reduction correction coefficient K to set the fuel supply amount TCS at the time of starting. The amount T set in this way
The fuel of CS is injected and supplied from the fuel injection valve 15. By doing this, when the engine is stopped before the engine temperature has risen completely and restarted immediately thereafter, even if the fuel from the previous operation remains in the cylinder, Since the amount of fuel supply is reduced to match the amount of residual fuel, the total amount of newly injected fuel and the fuel remaining in the cylinders can be set to a sufficient amount, and the air-fuel ratio can be adjusted. It is possible to suppress the deterioration of the exhaust property due to the excessive enrichment of the exhaust gas, especially the increase of the HC emission amount.

[0020]

As described above, according to the present invention, a complicated software or an existing oxygen sensor can be operated based on the electromotive force characteristics, specifically whether or not the electromotive force is within a predetermined range. Without the need of a timer, etc., the elapsed time from engine stop to restart, and hence the presence or absence of fuel remaining in the cylinder, can be estimated, and if it is estimated that fuel remains in the cylinder Since the fuel supply amount at the time of restart is corrected to be reduced, it is possible to prevent the air-fuel ratio from becoming excessively rich at the time of restart, and it is possible to prevent an increase in the exhaust property, particularly the HC emission amount.

Further, when the basic fuel supply amount at the time of starting is set to be large as the temperature is low when the fuel vaporization is low, and the elapsed time from engine stop to restart when the oxygen sensor is activated is short, the cylinder is operated at a lower temperature. Since there is a large amount of residual fuel in the inside, by setting a large reduction correction amount, it is possible to obtain a total fuel supply amount that is sufficient.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration and functions of the present invention.

FIG. 2 is a diagram showing a system configuration of an embodiment of the present invention.

FIG. 3 is a flowchart showing a fuel supply control routine at the time of starting according to the embodiment.

FIG. 4 is an electromotive force characteristic diagram of the oxygen sensor.

[Explanation of symbols]

 11 Engine 15 Fuel injection valve 16 Control unit 17 Water temperature sensor 19 Oxygen sensor 23 Start switch

Claims (3)

[Claims] 1. A start-up fuel supply control apparatus for an internal combustion engine, comprising an oxygen sensor for detecting an air-fuel ratio of an air-fuel mixture supplied to the engine through detection of an oxygen concentration in exhaust gas, wherein the oxygen is provided at the time of starting the engine. Activity determining means for determining the activity of the sensor based on the electromotive force of the oxygen sensor; and when the activity of the oxygen sensor is determined to be high, the fuel supply at the time of starting is determined to be lower than when the activity of the oxygen sensor is determined to be low. A starting-time fuel supply control device for an internal combustion engine, comprising: a starting-time fuel supply amount correcting means for correcting the amount to be reduced. 2. The activity determining means is not activated when the electromotive force of the oxygen sensor is within a predetermined range, and is smaller and larger than the predetermined range depending on the change in the air-fuel ratio. The startup fuel supply control device for an internal combustion engine according to claim 1, wherein it is determined that the fuel supply is activated when it changes to and. 3. An engine temperature detecting means is included, and the basic value of the fuel supply amount at the time of starting is set to be larger as the engine temperature at the time of starting is lower, and the starting time fuel supply amount correcting means is an oxygen sensor. 3. The startup fuel supply control device for an internal combustion engine according to claim 1 or 2, wherein when it is determined that the activity is low, the reduction correction amount is set to be larger as the engine temperature is lower. .