JPS599739B2 - Engine electronic fuel injection system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electronic fuel injection system for an engine, and particularly to fuel increase correction control thereof.

Generally, as shown in FIG. 1, the amount of intake air detected by an air flow meter 2 installed in the intake passage 1 and the engine rotation speed detected by the ignition device 3 of the engine E are input as basic signals to the computer 4. The valve opening time of the fuel injection nozzles 5, . Electronic fuel injection systems for engines of this type are well known.

The computer 4 basically consists of a basic pulse setting circuit T and a correction increase circuit 8, and the basic pulse setting circuit 7 sets a basic pulse τ0 having a time interval according to the intake air amount and the engine rotation speed, Cooling water temperature signal p
Then, a required correction PALNU Δτ is added to the idle signal q to increase the amount of fuel.

By the way, the above-mentioned cooling water temperature signal p detects the cooling water temperature of the engine E with a thermistor, and using the resistance change of the therminuta, is inputted to the correction increase circuit 8 as a signal in which the voltage decreases in response to the rise in the cooling water temperature. The correction increase circuit 8 performs a so-called warm-up increase at an increase ratio inversely proportional to the rise in cooling water temperature, as shown by curve A in FIG.

Conventionally, the idle signal q is input to the intake passage 1.
An idle switch on signal was used to detect that the throttle valve 9 of the engine was in a fully closed state, and the input voltage was constant, so the increase ratio was also constant.

Conventionally, there are two ways to increase the amount of fuel at idle using the idle signal q, depending on the input method of the idle signal.
As shown by the dotted line B in Fig. 2, there is a method in which the idle signal q is input regardless of the cooling water temperature and the amount is increased by adding it to the warm-up amount A, and as shown in the two-dot chain line C in Fig. 2, the cooling water is increased. A method is known in which the idle signal q is input only when the water temperature is 80° C. or higher, so that the warm-up increase and the idle increase do not overlap.

However, the actual fuel demand line when the engine is left to warm up, that is, during warm-up operation with the throttle valve 9 closed, is as shown by solid line D in Figure 2, when the cooling water temperature is 20°C or lower. Sometimes it matches the warm-up increase line A, and when the cooling water temperature is 8000 or higher, it matches the idle increase line B and C, but in the intermediate temperature range,
There is a tendency for the fuel to deviate from both the warm-up fuel increase line A and the idle fuel increase line B. In the former method, the excess fuel places an excessive burden on the exhaust gas purification catalyst installed in the engine's exhaust system, causing the catalyst to overflow. A force that causes a decline in performance,
In the latter method, there is a fuel shortage in the above intermediate temperature range,
There were problems such as engine stalling.

This problem is due to the following reasons.

In other words, the fuel is generally corrected in the direction of increased force as the cooling water temperature falls, but at the same time, in order to ensure engine stability, the throttle opening at idle is corrected in the direction of opening force as the cooling water temperature falls. I have to.

Therefore, in places where the cooling water temperature is extremely low, even if the engine is running at idle, if you look at the engine itself, the throttle opening will be relatively open compared to the idle opening when the engine has warmed up, and it will no longer be idle. Therefore, performing idle correction in this state would naturally deviate from the requirements.

As the cooling water temperature rises, the throttle opening gradually decreases, so it becomes necessary to perform idle correction accordingly.

Therefore, the present invention provides an electronic fuel injection device that is capable of performing idle correction and increase in fuel amount in accordance with the fuel demand line when the engine is left to warm up, in other words, in an intermediate temperature range before warm-up is completed. The basic purpose is to

For this reason, the present invention corrects the fuel injection amount determined by the intake air amount according to the engine cooling water temperature, so that the lower the temperature is, the more the fuel injection amount is corrected, and the more the temperature is lower, the more the fuel injection amount is adjusted to be zero when the temperature is higher than the first temperature. In addition to the above correction when the engine is idle,
In an electronic fuel injection device for an engine equipped with a correction increase circuit that performs idle correction to further increase the fuel injection amount, the idle correction amount is set to a temperature at which the engine cooling water temperature is lower than the first temperature. When , it is zero, and the second
A control circuit is provided that increases the cooling water temperature as the cooling water temperature rises above the first temperature, and remains approximately constant above the first temperature. Its basic feature is that it can be controlled.

Hereinafter, the present invention will be described in more detail with reference to the illustrated embodiments.

In FIG. 3, reference numeral 8 denotes a correction increase circuit for a computer (see FIG. 1) having an input terminal 8a for the cooling water temperature signal P and an input terminal 8b for the idle signal Q as described above, 10 a battery power supply, and 11 a key switch. , 12 is a control circuit for the cooling water temperature signal P (hereinafter referred to as a warm-up signal control circuit).

), 13 is a control circuit for the idle signal Q (hereinafter referred to as an idle signal control circuit).

). The warm-up signal control circuit 12 includes a voltage dividing circuit 16 in which a fixed resistor 14 and a negative characteristic thermistor 15 for detecting the engine cooling water temperature are connected in series to the power supply 10 via the key switch 11; It consists of an emitter follower type transistor 17 that takes out the voltage Vr divided by the voltage dividing circuit 16, and the voltage Vr taken out by the transistor 17 is sent to the warm-up increase terminal 8a of the correction increase circuit 8 through the fixed resistor 18. Enter.

That is, the voltage Vr of the cooling water temperature signal P input to the warm-up increase terminal 8a is controlled by the therminutor 15 with negative characteristics, and as the cooling water temperature rises, the resistance of the therminutor 15 decreases, so that the cooling water temperature rises. As explained in Fig. 2, the increase ratio decreases as the cooling water temperature rises, and becomes 1 (the increase is zero) at 80°C (first temperature) or higher. A warm-up increase line A can be provided.

First, the idle signal control circuit 13 is directly connected to the power supply 10.
Another voltage divider circuit 21 divides the power supply voltage at a constant ratio using two fixed resistors 19 and 20, and the reference voltage Vo given by the voltage divider circuit 21 is used as one input, and the other input is the Let the voltage Vr be the cooling water temperature signal P taken out by the transistor 17, and both voltages Vo, V
A subtraction circuit 22 that amplifies the differential voltage (vo-vr) of r by a predetermined amplification factor k, a diode 23 that is connected to the output side of the subtraction circuit 22 and turns off when the output is negative, and a diode 23 and an idler. It consists of an idle switch 24 connected between the fuel increasing terminal 8b and turned on when the throttle valve is fully closed.

The above reference voltage Vo is the cooling water temperature at which the engine fuel demand line D starts to deviate from the warm-up increase line A. Specifically, the cooling water temperature signal P when the cooling water temperature is about 20° C. (second temperature)
The fixed resistor 19 is set so that the voltage Vr (20°C) is the value of
．． Set a value of 20.

Further, the amplification rate k of the subtraction circuit 22 is determined when the cooling water temperature is approximately 80°C.
Each fixed resistor 2 5 ,
2 6 , 2 5', 2 6' resistance value R1,
R2 may be set appropriately.

That is, fixed resistance 2 5 . When the resistance value of the fixed resistors 2 6 and 2 6' is R2, the amplification factor k is given by (R2/Rl).

Therefore, the idle signal Q given by the idle signal control circuit 13 indicates that the cooling water temperature is the second temperature (20°C
) or below, the voltage value is zero, and when the cooling water temperature exceeds the second temperature, the voltage value increases almost in proportion to the increase in the cooling water temperature, and the water temperature correction ratio is 1 (when the cooling water temperature is 80°C (first
warm-up is completed (for example, when the cooling water temperature reaches 80℃).
℃ or higher), it becomes constant.

In other words, when the cooling water temperature is at or above the second temperature and is at idle, an idle increase is started that is superimposed on the warm-up increase, and since the idle increase ratio is approximately proportional to the coolant temperature, the corrective increase is made in line with the engine's fuel demand line. A line is obtained.

The set coolant temperature at which the idle correction is started in the above embodiment may be arbitrarily selected depending on the type of engine and the like.

As is clear from the detailed explanation above, the present invention controls the idle correction of a computer that controls the fuel injection amount according to the engine cooling water temperature, and the idle correction is performed when the cooling water temperature is adjusted to a second level. When the temperature is below
When the cooling water temperature is higher than a second temperature, the idle correction amount is increased commensurate with the cooling water temperature, and the idle correction amount is kept substantially constant at a temperature higher than the first temperature. The present invention provides a type fuel injection device.

According to the electronic fuel injection device for an engine according to the present invention,
Since it is possible to obtain a fuel correction increase characteristic that matches the fuel requirement characteristic when the engine is idling, it is possible to obtain an advantage that appropriate fuel control can be performed without causing excess or deficiency of fuel.

[Brief explanation of the drawing]

Figure 1 is a schematic explanatory diagram of the engine's electronic fuel injection system;
FIG. 2 is a graph showing a fuel correction increase line, and FIG. 3 is a circuit diagram of a signal control circuit according to an embodiment of the present invention. 2...Air flow meter, 3...Ignition device, 4...Computer, 5...
, 5... Fuel injection nozzle, 7... Basic pulse setting circuit, 8... Correction increase circuit, 12...
... Warm-up signal control circuit, 13 ... Idle signal control circuit, 21 ... Voltage dividing circuit, 22 ...
...Subtraction circuit, 23...Diode, 24
...Idle switch.

Claims (1)

[Scope of Claims] 1. The fuel injection amount determined by the intake air amount is corrected in the direction of increasing the fuel injection amount as the temperature becomes lower, depending on the engine cooling water temperature, and becomes zero at a first temperature or higher. In addition, in an electronic fuel injection device for an engine equipped with a correction increase circuit that performs idle correction to further increase the fuel injection amount in addition to the above-mentioned correction when the engine is idling, the above-mentioned idle correction amount is adjusted depending on the engine cooling water temperature. 1st above
When the temperature is below the second temperature, which is lower than the temperature of
An engine electronic fuel injection device characterized by comprising a control circuit that maintains a substantially constant temperature above a first temperature. 2. In the electronic fuel injection system for an engine according to claim 1, the temperature of the cooling water is controlled by the first partial pressure circuit that provides a threshold voltage corresponding to the second water temperature and the thermistor that detects the temperature of the cooling water. a second voltage divider circuit that provides a voltage that decreases as the voltage increases; a subtraction circuit that amplifies the difference between the voltages provided by the first and second voltage divider circuits at a predetermined amplification rate; and an output of the subtraction circuit. 1. An electronic fuel injection device for an engine, characterized in that a control circuit includes a rectifying element that becomes non-conducting when is negative, and an idle switch. 3. In the electronic fuel injection system for an engine according to claim 2, the thermistor is shared by a control circuit that controls the input voltage for warm-up increase and a control circuit that controls the input voltage for idle increase. An electronic fuel injection device for an engine, characterized in that it is configured to: