JPH0579367A - Starting time fuel supply device for internal combustion engine - Google Patents

Abstract

(57) [Summary] [Purpose] The purpose is to improve the cold startability of the engine. [Structure] Determine whether the engine is cranking (S
1), if cranking, water temperature T, alcohol concentration C
Also, the cranking rotation speed N _K is read (S2), and it is determined whether or not the cold start valve is ON based on the water temperature T and the alcohol concentration C (S3). When it is ON, the cranking rotation speed N _K and the set value N _K are set. A comparison is made with ₀ (S5), and when N _K ≦ N ₀ , the injection amount of the main fuel injection valve is set to increase at the beginning of injection and then to decrease in a short time (S7). As a result, even when the cranking rotation is low, the overrich in the cylinder can be prevented and the engine can be reliably started.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel supply device for starting an internal combustion engine which uses a mixed fuel in which alcohol and gasoline are mixed at an arbitrary ratio, and more particularly to a technique for improving startability.

[0002]

2. Description of the Related Art Conventionally, in an internal combustion engine which uses a mixed fuel in which alcohol (mainly methanol) and gasoline are mixed at an arbitrary ratio, each cylinder is provided in an intake passage of the engine for the purpose of improving startability. In addition to a normal fuel injection valve (here, a main fuel injection valve), a cold start valve (C
It is known that a single auxiliary fuel injection valve called SV) for cold starting is provided (Japanese Patent Laid-Open No. 1-22).
62337).

The cold start valve for low temperature starting is ON / OFF controlled according to the engine cooling water temperature representative of the engine temperature and the alcohol concentration when the engine is started, and the cooling water temperature is below a predetermined value and the alcohol concentration is below a predetermined value. At the above time, ON control is performed to inject fuel, thereby increasing the fuel injection amount at the time of engine low temperature start and improving startability.

In an internal combustion engine equipped with such a cold start valve, the fuel injection amount of the main fuel injection valve at the time of starting the engine depends on whether the cold start valve is ON or OFF as shown in the flowchart of FIG. The injection characteristics of the main fuel injection valve are set differently, and the injection characteristics of the main fuel injection valve at the time of engine start set in FIG. 8 are shown by a solid line. Fig. 8 shows the case of gasoline only and the case of M85 (mixed fuel of alcohol 85% and gasoline 15%). In the case of gasoline, CSV is OFF regardless of the cooling water temperature, and in the case of M85, the cooling water temperature is Is reduced in a region in which CSV is equal to or less than a predetermined value and is turned on.

[0005]

By the way, the cranking rotation at the time of starting the engine depends on the charging state of the battery and the like, and it takes time to start when the battery voltage is low and the cranking rotation speed is low. As described above, in spite of the fact that the time until the engine is started differs depending on the cranking rotation speed, conventionally, the injection amount at the time of starting the main fuel injection valve does not depend on the cranking rotation speed as described above. It is designed to supply a fixed amount for a long time (about 10 seconds). For this reason, when the cranking rotation speed, which requires a long time before starting, is low, there is a problem that fuel is accumulated and the cylinder is likely to overrich due to incomplete combustion, which induces irregular combustion and deteriorates startability.

The present invention has been made in view of the above circumstances. By appropriately setting the fuel injection amount of the main fuel injection valve in accordance with the cranking rotation condition, the irregular combustion due to the overrich in the cylinder is prevented. An object of the present invention is to provide a starting-time fuel supply device for an internal combustion engine, which can surely improve engine startability.

[0007]

Therefore, as shown in FIG. 1, the starting fuel supply system for an internal combustion engine according to the present invention can use a mixed fuel in which gasoline and alcohol are mixed at an arbitrary ratio. In an internal combustion engine having an auxiliary fuel injection valve for starting in the engine intake passage upstream of the main fuel injection valve, a cranking rotation speed detection means, an alcohol concentration detection means, an engine temperature detection means, and Determination means for determining whether or not to operate the auxiliary fuel injection valve based on both detection values from the alcohol concentration detection means and the engine temperature detection means, and the determination means determines whether or not the auxiliary fuel injection valve is activated. When the detected value of the cranking rotation speed detection means is less than or equal to the set value, the fuel injection amount from the main fuel injection valve is set to the fuel injection amount when the cranking rotation speed is higher than the set value. It was constructed with a starting initially increasing correction and then a short time and the fuel injection amount setting means for setting a fuel injection amount to decrease correction.

[0008]

In this structure, when the cranking rotation speed is low at the low temperature start when the mixed fuel having the alcohol concentration of the predetermined value or more is used and the auxiliary fuel injection valve is operated, the fuel injection amount from the main fuel injection valve is By increasing the amount in comparison with the conventional amount at the beginning of the injection, the fuel is prevented from leaking gas from the piston ring, the cylinder pressure is increased, and the vaporization is promoted. After that, by rapidly reducing the amount to a smaller amount than the conventional amount in a short time, it is possible to prevent irregular combustion without overrich, and to reliably start the engine.

[0009]

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 a system configuration of an embodiment of the present invention, in addition to a normal main fuel injection valve 3 being provided for each cylinder in an intake passage 2 of an engine 1, the main fuel injection valve 3 is also provided.
A cold start valve (CSV) 4 is provided as an auxiliary fuel injection valve at a collecting portion (collector portion) on the upstream side of the. The cold start valve 4 is controlled to be turned on and off, and is turned on when the engine cooling water temperature is equal to or lower than a predetermined value and the alcohol concentration of the fuel is equal to or higher than a predetermined value as in the conventional case.
The fuel is injected and supplied, and when the engine cooling water temperature is higher than a predetermined value or the alcohol concentration of the fuel is lower than a predetermined value, O
It doesn't work as FF.

The control unit 5 has a built-in microcomputer, a starter switch 6, a water temperature sensor 7 as an engine temperature detecting means, an electrode as an alcohol concentration detecting means or an alcohol concentration sensor 8 such as a capacitance type.
And the detection signals output from the crank angle sensor 9 as the cranking rotation speed detecting means for detecting the cranking rotation speed of the engine are input, and as shown in the flowchart of FIG. 3, based on these detection signals, a cold start is performed. While controlling ON-OFF of the valve 4,
The fuel injection amount of the main fuel injection valve 3 when the engine is started is appropriately set.

That is, the control unit 5 determines whether or not to operate the cold start valve 4 based on both detection values from the alcohol concentration sensor 8 and the crank angle sensor 9, and the determination means performs a cold start. When it is determined that the valve 4 is operating and the detected value of the crank angle sensor 9 is less than or equal to the set value, the fuel injection amount from the main fuel injection valve 3 is compared with the fuel injection amount when the cranking rotation speed is higher than the set value. It corresponds to a fuel injection amount setting means for setting the fuel injection amount so that the fuel injection amount is corrected at the initial stage of fuel injection start and then the fuel injection amount is corrected at a short time, and these functions are provided by software as shown in the flowchart of FIG. There is.

Next, the setting operation of the fuel injection of the main fuel injection valve at the time of starting the engine of this embodiment will be explained based on the flow chart of FIG. First, in step 1 (denoted as S1 in the drawing, the same applies hereinafter), it is determined based on an ON / OFF signal from the starter switch 6 whether or not the engine is cranking. If cranking (YE
S), the process proceeds to step 2, and if the cranking is not in progress (NO), the routine ends.

In step 2, the cooling water temperature T, the alcohol concentration C and the cranking rotation speed N _K are read based on the outputs from the water temperature sesan 7, the alcohol concentration sensor 8 and the crank angle sensor 9. In Step 3, Step 2
Based on the cooling water temperature T and the alcohol concentration C read in step 3, it is determined whether or not the cold start valve (CSV) is turned on. Here, if the alcohol concentration C is equal to or higher than a predetermined value and the water temperature T is equal to or lower than a predetermined value (for example, M ₀ is T ₀ in FIG. 8), the CSV is turned on. Where CSV
When is determined to be OFF, the process proceeds to step 4 and CSVO
The main fuel injection amount at FF is set. This setting is the same as the conventional one. On the other hand, when it is determined that the CSV is ON, the process proceeds to step 5.

In step 5, the data read in step 2
Cranking rotation speed N_KAnd set value N₀Compare with
_K> N₀If so, go to step 6 and click at CSV ON.
Set the main fuel injection amount when the ranking rotation speed is high.
To do. The setting in step 6 is the same as the conventional one.
Fuel is injected and supplied for a fixed amount of time. On the other hand, N_K≦ N ₀
If so, the process proceeds to step 7, and the characteristic feature of this embodiment, CS
Main fuel injection when cranking speed is low at VON
Set the target. That is, as shown in FIG.
Injection amount Q when the cranking speed set by is high
₁For a predetermined time t from the start of injection₁(About 1-2 seconds)
Increase the injection quantity Q₂Fuel injection at the specified time
Interval t₂Injection amount Q during (about 2-3 seconds)₃Sharply reduce to
To set.

When the cold start valve is ON and the cranking rotation speed is low and the main fuel injection amount is set as described above, gas leakage from the piston ring is prevented by the fuel due to the increase in the amount of injection at the beginning of injection, and the in-cylinder pressure is reduced. Increased vaporization is promoted. Then, after that, by suddenly reducing the amount to a smaller amount than before, overrich can be prevented and irregular combustion can be suppressed, so that the engine can be started more reliably than before. The low temperature startability can be improved.

Here, the period t ₁ and the ratio (Q
₂ / Q ₁ ), the time t _{2 of} reduction and the ratio (Q ₃ / Q ₁ ) are set as shown in FIGS. 5 and 6 according to the alcohol concentration and the cooling water temperature. That is, the increase period t ₁ and the decrease time t ₂
Is set to be smaller as the alcohol concentration is higher and the cooling water temperature is lower as shown in FIG. This is because the higher the alcohol concentration, the larger the fuel injection amount, and the poorer the startability due to the wetting of the spark plug.Therefore, by shortening the fuel increase period and rapidly reducing the fuel injection amount to reduce the injection amount, Even if it hits, it is sure to start. Further, when the water temperature is high, even if the injection amount is large, it is easily vaporized, so that even if the increase period t ₁ or the decrease time t ₂ is lengthened, the influence of the wetting of the spark plug is small and the engine can be started easily.
On the other hand, the increase rate (Q ₂ / Q ₁ ) and the decrease rate (Q ₃ /
As shown in FIG. 6, Q ₁ ) is related to the increasing ratio (Q ₂ / Q ₁ ) as the alcohol concentration is higher and the cooling water temperature is lower,
The weight reduction ratio (Q ₃ / Q ₁ ) is set to be smaller as the alcohol concentration is higher and the cooling water temperature is lower. This is because when the alcohol concentration is high, the injection amount is increased in a short time to prevent the gas from leaking from the piston ring due to the fuel and raise the temperature by increasing the cylinder pressure to promote the vaporization of the fuel. Since the higher the value is, the higher the increasing rate is, the smaller the injection amount thereafter is set to prevent the ignition plug from getting wet.

[0017]

As described above, according to the present invention, when the cranking rotation speed is low when the auxiliary fuel injection valve for starting is operated, the injection amount of the main fuel injection valve is set to the initial injection start. The engine is configured to increase the amount and then decrease the amount in a short time.Therefore, it is possible to suppress the irregular combustion due to the overrich state at the time of low cranking rotation, which takes a long time to start, and it is possible to reliably start the engine. It is possible to improve the property.

[Brief description of drawings]

FIG. 1 is a block diagram illustrating a configuration of the present invention.

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

FIG. 3 is a flowchart for explaining the operation of the above embodiment.

FIG. 4 is a diagram showing an injection characteristic of the main fuel injection amount at the time of engine start in the embodiment.

FIG. 5 is a characteristic diagram of the amount increasing time and the amount decreasing time according to the alcohol concentration and the cooling water temperature in the above embodiment.

FIG. 6 is a characteristic diagram of an increase ratio and a decrease ratio according to the alcohol concentration and the cooling water temperature in the above embodiment.

FIG. 7 is a flowchart for setting a main fuel injection amount of a conventional device.

FIG. 8 is a main fuel injection amount characteristic diagram according to alcohol concentration and cooling water temperature of a conventional device.

[Explanation of symbols]

 1 engine 2 intake passage 3 main fuel injection valve 4 cold start valve (auxiliary fuel injection valve) 5 control unit 6 starter switch 7 water temperature sensor 8 alcohol concentration sensor 9 crank angle sensor

Claims (1)

[Claims] 1. An internal combustion engine which can use a mixed fuel in which gasoline and alcohol are mixed at an arbitrary ratio, and which is provided with an auxiliary fuel injection valve for starting in an engine intake passage upstream of a main fuel injection valve. In, cranking rotation speed detection means, alcohol concentration detection means, engine temperature detection means,
A determination unit that determines whether to operate the auxiliary fuel injection valve based on both detection values from the alcohol concentration detection unit and the engine temperature detection unit; and when the determination unit determines that the auxiliary fuel injection valve is operating. When the detected value of the cranking rotation speed detection means is less than or equal to a set value, the fuel injection amount from the main fuel injection valve is set at the initial stage of fuel injection with respect to the fuel injection amount when the cranking rotation speed is higher than the set value. An internal combustion engine starting fuel supply device, comprising: a fuel injection amount setting means for setting a fuel injection amount so as to perform an increase correction and then a decrease correction in a short time.