JPH03121230A - Fuel supply device for internal combustion engine - Google Patents

Abstract

PURPOSE:To secure constantly desirable operability by providing a means for setting the recovery engine speed for resuming fuel supply low at the time of high alcohol concn. compared to the time of high gasoline concn. in mixed fuel when the engine cooling water temperature or the like is over the specified value. CONSTITUTION:A device for supplying an engine with gasoline-alcohol mixed fuel is provided with a means B for stopping the operation of a means A for supplying fuel when the actual engine speed is over the cut engine speed at the time of decelerating operation, and a means C for resuming the operation of the means A when the actual engine speed is lowered down to the recovery engine speed. In such constitution, the one fuel concn. in the mixed fuel is detected at a means D. The temperature such as the engine cooling water temperature is detected at a means E. When the cooling water temperature or the like is over the specified value, for instance, a means E sets the recovery engine speed in such a way as to be lowered at the time of high alcohol concn. compared to the time of high gasoline concn.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a fuel supply device for an internal combustion engine that uses a mixed fuel of alcohol such as methanol and gasoline, and particularly relates to a technology for improving fuel efficiency during deceleration operation. .

<Prior Art> Conventional examples of this type of fuel supply device for an internal combustion engine include the following.

That is, after calculating the basic injection amount from, for example, the engine rotational speed and the intake air flow rate (engine load), the basic injection amount is corrected based on the cooling water temperature and the like to calculate the fuel injection amount. Then, an injection pulse signal corresponding to the calculated fuel injection amount is output to the fuel injection valve to supply fuel to the engine.

In addition, when the engine rotation speed exceeds the cut rotation speed during deceleration operation (for example, when the idle switch is turned on), the fuel supply to the engine is stopped (hereinafter referred to as fuel cut), and the engine rotation speed is reduced to the recovery rotation speed. At times, the fuel supply to the engine is restarted to reduce fuel consumption.

Here, the cut rotational speed and the recovery rotational speed are set to decrease as the cooling water temperature increases.

(Problem to be solved by the invention) By the way, the lean limit of the air-fuel ratio at which engine combustion is stable is:
As shown in FIG.
°C) or higher, the methanol concentration is high, making it lean compared to gasoline, and when the cooling water temperature is below a predetermined value, the methanol concentration is high, making it lean compared to gasoline.

However, in the past, the recovery rotational speed in particular was changed depending only on the cooling water temperature, so when the cooling water temperature was higher than a predetermined value, the higher the methanol concentration, the greater the fuel savings. However, there is a problem in that the reduction in fuel consumption is constant and the fuel efficiency cannot be improved sufficiently.

Further, when the cooling water temperature is lower than a predetermined value, the lean limit is low and the higher the alcohol concentration, the worse the alcohol vaporization characteristics are, resulting in a problem that the drivability is deteriorated.

The present invention has been made in view of the above-mentioned circumstances, and it is an object of the present invention to provide a fuel supply device for an internal combustion engine that takes the above-mentioned characteristics into account and can improve fuel efficiency while maintaining good engine drivability during recovery. With the goal.

Means for Solving the Problems> For this reason, the present invention, as shown in FIG. a fuel supply stop means B that stops the fuel supply operation to the fuel supply means when the rotation speed is equal to or higher than the cut rotation speed; and a fuel supply stop means B that stops the fuel supply operation of the fuel supply means A when the actual engine rotation speed has decreased to a recovery rotation speed. fuel supply restart means C for restarting;
a fuel concentration detection means for detecting the concentration of one of the fuels in the mixed fuel; a temperature detection means E for detecting the engine cooling water temperature or a state related thereto;
When the cooling water temperature or related conditions are above a predetermined value, the recovery rotation speed is set to be lower when using high concentration alcohol than when using high concentration gasoline, and when the coolant temperature or related conditions are below the predetermined value. A recovery rotation speed setting means F is provided for setting the recovery rotation speed higher when using high concentration alcohol than when using high concentration gasoline.

<Operation> In this way, by changing the recovery rotation speed in accordance with the lean limit, fuel efficiency can be greatly reduced while maintaining good engine operability regardless of the alcohol concentration and cooling water temperature. I tried to improve it.

<Example> An example of the present invention will be described below based on FIGS. 2 to 7.

In FIG. 2, a microcomputer 1 detects an air-fuel ratio based on an intake air flow rate signal from an air flow meter 2, an engine rotational speed signal from a rotational speed sensor 3, and an oxygen concentration in the exhaust gas, which is installed in an exhaust passage. the oxygen concentration signal from the oxygen sensor 4, the alcohol concentration signal from the alcohol concentration sensor 5 as a fuel concentration detection means installed in the fuel supply passage, and the water temperature as a temperature detection means for detecting the engine cooling water temperature. A cooling water temperature detection signal from the sensor 6 and an on/off signal from the idle switch 7, which is turned on when the intake throttle valve is fully closed, are input.

The microcomputer 1 includes l10IA and CPt.
It is configured with a JIB, a ROMIC, and a RAMID, and calculates the fuel injection amount based on the signals from the various sensors, etc. An injection pulse signal is output to the injection valve 8.

Here, the microcomputer 1 constitutes a fuel supply stop means, a fuel supply restart means, and a recovery rotational speed setting means.

Next, the operation will be explained according to the flowcharts of FIGS. 3 and 4.

First, to explain normal fuel injection control, the basic injection amount T, (=KQ/N; K is constant), and
Various correction coefficients mainly based on the cooling water temperature, an air-fuel ratio feedback correction coefficient α based on the air-fuel ratio detected by the oxygen sensor 4, a methanol correction coefficient K based on the methanol concentration detected by the alcohol concentration sensor 5, a correction coefficient T based on the battery voltage, and After calculating the fuel injection amount T, (-T
, x COE F X αX Katc + Ts).

Then, an injection pulse signal corresponding to the calculated fuel injection 1tTt is output to the fuel injection valve 8 to supply mixed fuel to the engine.

During such fuel injection control, a routine shown in the flowchart of FIG. 3 is executed.

At Sl, the on/off signal from the idle switch 7 is read.

In S2, it is determined whether the idle switch 7 is turned on, and if YES, that is, when deceleration operation has started, S
If the answer is NO in step 2, the routine is ended.

In S3, the methanol concentration in the mixed fuel detected by the alcohol concentration sensor 5 and the cooling water temperature detected by the water temperature sensor 6 are read.

In S4, the cut rotation speed N is searched from the map based on the detected methanol concentration and cooling water temperature. As shown in FIG. 5, this cutting rotation speed Nc is set to decrease as the cooling water temperature increases. In addition, the cutting rotation speed N is as shown in FIG.
In the low temperature range where the cooling water temperature is less than a predetermined value (for example, 20°C), the methanol concentration is set to be high (it increases as the temperature increases), and in the high temperature range where the cooling water temperature exceeds the predetermined value, the methanol concentration decreases as the temperature increases. It is set.

In S5, the recovery rotation speed N is searched from the map based on the detected methanol concentration and cooling water temperature. As shown in FIG. 5, this recovery rotational speed NR is set to decrease as the cooling water temperature increases. In addition, the recovery rotational speed NR is set to a predetermined value (
For example, in a low temperature range of cooling water temperature below 20°C, the methanol concentration is set to increase as the methanol concentration increases, and in a high temperature range of cooling water temperature above a predetermined value, the methanol concentration is set to decrease as the methanol concentration increases. There is.

Note that the predetermined value may be changed depending on the methanol concentration.

In S6, the actual engine rotation speed N detected by the rotation speed sensor 3 is read.

In S7, it is determined whether the cut flag is 1 or not, and YES is determined.
When , that is, when fuel is being cut, the process proceeds to S13, and when NO, that is, when fuel is not being cut, the process proceeds to S8.

In S8, it is determined whether the actual engine rotational speed N is equal to or higher than the cut rotational speed NR. If YES, the process proceeds to S9, and if NO, the routine is ended without performing a fuel cut.

In S9, the output of the injection pulse signal to the fuel injection valve 8 is stopped and fuel cut is started.

In S10, the cut flag is set to 1.

At 311, a clamp value α of the air-fuel ratio feedback correction coefficient is determined based on the detected alcohol concentration and cooling water temperature. Search from the map. This clamp value α. is set in consideration of drivability such as misfires and shocks when fuel supply is resumed, and as shown in Figure 6, it is set to decrease as the methanol concentration increases, and the cooling water temperature also increases. It is set to decrease as the height increases. Also, the clamp value α. is set smaller than l.

In S12, the air-fuel ratio feedback correction coefficient α is set to the clamp α. to keep it fixed.

In 313, it is determined whether the actual engine rotation speed N has decreased below the recovery rotation speed Nu. If YES, the process proceeds to 315, and if NO, the routine ends to continue the fuel cut.

In S14, the cut flag is set to zero.

In S15, an injection pulse signal is output to the fuel injection valve 8 to restart fuel supply. At this time, the clamp value α is used to calculate the fuel injection amount. is used.

In step 316, the set rotation speed for feedback clamp release is searched from the map based on the detected methanol concentration and cooling water temperature. As shown in FIG. 7, this set rotation speed is set to decrease as the methanol concentration increases and also as the cooling water temperature increases. Note that instead of this set rotation speed, a time period for returning to feedback control may be set depending on the cooling water temperature and methanol concentration.

In S17, it is determined whether the engine rotation speed has exceeded the set rotation speed from the time when fuel supply is resumed, and YES is determined.
If so, proceed to S18, and if NO, set the clamp value α.

The routine is terminated so that it remains fixed.

31B, the clamp value α. is released from being held fixed, and air-fuel ratio feedbank control is started based on the detected value of the oxygen sensor 4.

Next, air-fuel ratio feedback control will be explained according to the flowchart of FIG.

In S21, the engine cooling water temperature reaches a predetermined temperature (for example, 40'
C) Determine whether or not the above is true. If YES, proceed to S22; if NO, terminate the routine.

The predetermined temperature is set to decrease as the alcohol concentration increases.

In step 322, it is determined whether the idle switch 7 is on or not. If YES, the process advances to step S23, and if NO, the process proceeds to step S25.
Proceed to.

In S23, it is determined whether or not fuel is currently being cut, and the answer is YES.
If so, the process proceeds to 324, and if NO, the process proceeds to S25.

In S24, the air-fuel ratio feedback correction coefficient is set to 31.
Clamp value α searched at 1. to keep it fixed.

In step 325, it is determined whether or not it is a rich clamp time such as in a high-load operation region, and if YES, the process advances to S26, and if NO, the process advances to S27.

In S26, a clamp value α1 is set to clamp the air-fuel ratio to a richer side than the stoichiometric air-fuel ratio.

In S27, the air-fuel ratio feedback correction coefficient α is changed based on the oxygen concentration in the exhaust gas detected by the oxygen sensor 4 (from the actual air-fuel ratio) so that the air-fuel ratio becomes the stoichiometric air-fuel ratio (λ=1). Set.

α, α set in this way. , α1 are used to calculate the fuel injection amount in the normal fuel injection control.

As explained above, when the cooling water temperature is above a predetermined value, the cut rotation speed and the recovery rotation speed are set to be lower than when using gasoline as the methanol concentration increases, thereby reducing fuel consumption during deceleration operation. can be greatly improved. At this time, as the methanol concentration increases, the lean limit at which combustion is stabilized shifts to the lean side as shown in Figure 8, so even if the recovery rotation speed is lowered, driveability when resuming fuel supply can be maintained. Can be maintained. Also, when the cooling water temperature is below a predetermined value, the methanol concentration is high (as the methanol concentration increases, the cut rotation speed and recovery rotation speed are set to be higher than when using gasoline, so vaporization occurs in this cooling water temperature range). Even if the lean limit shifts to the richer side than when using gasoline (see Figure 8) as the methanol concentration increases due to deterioration of the characteristics, combustion can be maintained well when fuel supply is resumed, thereby maintaining good drivability. can.

Also, the clamp value α during fuel cut. is set so that the air-fuel ratio becomes leaner (α) becomes smaller () as either the cooling water temperature or the methanol concentration increases, so the air-fuel ratio when fuel supply is restarted is set to the lean limit. The exhaust characteristics can be improved, and fuel efficiency can also be improved.

Furthermore, since the set rotational speed for returning to air-fuel ratio feedback control is set to decrease as either the cooling water temperature or the methanol concentration increases, the clamp value α. Even if the air-fuel ratio is changed to the lean side depending on the cooling water temperature and the methanol concentration, the air-fuel ratio feedback control starts early in response to this change, and the air-fuel ratio can be brought closer to the stoichiometric air-fuel ratio.

<Effects of the Invention> As explained above, the present invention sets the recovery rotation speed so that when the cooling water temperature or related conditions are above a predetermined value, the recovery rotation speed decreases as the alcohol concentration increases compared to when using gasoline. However, when the cooling water temperature or related conditions are below a predetermined value, the recovery rotation speed is set so that it becomes higher as the alcohol concentration increases compared to when using gasoline. Regardless of the situation, fuel efficiency can be greatly improved while maintaining good engine drivability.

[Brief explanation of drawings]

Fig. 1 is a claim correspondence diagram of the present invention, Fig. 2 is a configuration diagram showing an embodiment of the present invention, Fig. 3 is a flowchart of the same as above,
Figures 4 to 7 are diagrams for explaining the same effect as above, and Figure 8
The figure is a diagram for explaining the conventional drawbacks and the same effects.

Claims (1)

[Claims] A fuel supply stop means that supplies a mixed fuel of gasoline and alcohol to the engine, and stops the fuel supply operation of the fuel supply means when the actual engine rotation speed is higher than the cut rotation speed during deceleration operation. , a fuel supply restart means for restarting the fuel supply operation of the fuel supply means when the actual engine rotation speed decreases to the recovery rotation speed, wherein the fuel concentration of one of the mixed fuels is reduced. a fuel concentration detection means for detecting engine cooling water temperature or a state related thereto; and a temperature detection means for detecting engine cooling water temperature or a state related thereto; recovery rotation speed setting means for setting the recovery rotation speed to be lower than that for high concentration gasoline when the cooling water temperature or related conditions are lower than a predetermined value; A fuel supply device for an internal combustion engine, comprising: