JPS634009B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for correcting the fuel injection amount at the time of starting an internal combustion engine having an electronic fuel injection device in accordance with the state of the engine.

The conventional components of electronic fuel injection systems related to starting are a water temperature sensor that detects the temperature of the internal combustion engine's cooling water, a starter SW signal to determine the starting state, and a system that atomizes the fuel. It consists of an injector, a delivery pipe that supplies fuel to the injector, a fuel pump, and a control circuit that determines the internal combustion engine's rotation speed, cooling water temperature, etc. In the above configuration, when the internal combustion engine is started, if the output of the water temperature sensor that detects the cooling water temperature is below a certain temperature (for example, 35 degrees Celsius), additional auxiliary fuel for starting is supplied only for a certain period of time. This is how it works.

That is, when considering the fuel required for starting, the following phenomenon occurs, and it becomes necessary to correct the starting fuel. First, when the chemical equivalence ratio (λ) of fuel and air near the spark plug is close to 1, both ignition performance and combustion speed should be the fastest, but when the internal combustion engine is started and has not been sufficiently warmed up, the supplied fuel is Since it adheres to the intake pipe and the combustion chamber wall, a large amount is supplied in anticipation of this amount. The amount of these deposits varies depending on the distillation curve of the fuel and the temperature of the internal combustion engine. Once the engine has started, the amount of fuel that has adhered to the intake pipe and the combustion chamber wall is sequentially supplied to the combustion chamber, so it is only necessary to supply approximately λ≈1 fuel from the injector. Therefore, when the engine is restarted after it has been warmed up, the fuel on the intake pipe wall is already saturated, so there is no need to correct the starting fuel. Therefore, a water temperature sensor was used to prevent the supply of auxiliary starting fuel at temperatures above approximately 35°C.

However, if the internal combustion engine is stopped and left unattended after it has been completely warmed up, heat from high-temperature parts such as the cylinder block and combustion head is transferred by thermal conduction and heats the intake pipe. For this reason, the cooling water temperature rises for 10 to 15 minutes after the engine stops, and remains at a high temperature for the next 40 to 70 minutes. During this high temperature state, the fuel adhering to the wall of the intake pipe evaporates and expands in volume, and the amount that overflows from the intake pipe is adsorbed onto activated carbon or the like.

Therefore, if the engine is started approximately 40 minutes after the engine has been stopped, the cooling water temperature will be in the high temperature range, and no auxiliary starting fuel will be supplied. However, since no fuel adheres to the intake pipe wall, there is a problem that if only fuel with λ≒1 is supplied, a large proportion of fuel will adhere to the intake pipe, resulting in an overly lean mixture that cannot be ignited for a while. Ta.

In order to solve the above problems, the present invention has a water temperature detection means for detecting the temperature of the cooling water of the engine and a wall temperature detection means for detecting the temperature of the intake pipe wall of the engine. The maximum temperature of the intake pipe wall detected during the period up to engine startup is stored, and when the engine is started, if the cooling water temperature is below a predetermined value, and when the cooling water temperature is above the predetermined value and If the maximum value of the memorized intake pipe wall temperature is within a predetermined range, the amount of starting fuel will be corrected to increase the amount of starting fuel. The object of the present invention is to provide a starting correction method for an electronic fuel injection system that can achieve stable and reliable starting.

An embodiment of the present invention will be described below with reference to the drawings. In Fig. 1, 1 is a control circuit that calculates the fuel injection amount according to operating conditions, and includes a cooling water temperature sensor 2, which serves as a water temperature detection means for detecting the engine cooling water temperature, and an engine intake pipe wall. A signal from a wall temperature memory circuit 4 that stores the peak value of a signal from a wall temperature sensor 3, which is a wall temperature detection means attached to the wall temperature sensor 3, is input to calculate starting auxiliary fuel. The configuration is such that the necessary signals are supplied to the injector 5 for use. In addition, in this block diagram, the arithmetic configuration other than for starting is in the arithmetic circuit block 10.
3 as a representative, and disclosure of the specific configuration is omitted. In this case, if the signal from the cooling water temperature sensor 2 input to the control circuit 1 is below a predetermined temperature (e.g., 35°C or less), and if the signal from the wall temperature memory circuit 4 is above a predetermined temperature (e.g., 85°C or more), If the signal from the cooling water temperature sensor 2 is at a predetermined temperature or higher (for example, 35° C. or higher), logic is set up so that a starting auxiliary fuel command signal can pass through the signal line 110. Here, the above-mentioned specific temperatures (35° C., 85° C.) are values based on experience determined by the engine structure, characteristics, etc., and can be arbitrarily selected within a range that does not impair engine performance.

Block 6 is a circuit block that generates a starter starting signal when the starter switch is activated. The reset circuit 7 clears the memory of the temperature memory circuit 4 immediately after the completion of starting the starter and maintains the temperature in a predetermined state, and resets the memory of the temperature memory circuit 4 upon receiving the male signal of the ignition switch 8, that is, the engine stop signal. Operation (i.e. wall temperature signal detection operation)
It is configured to start. Of course, in the above embodiment, the memory operation of the temperature memory circuit 4 is stopped after the engine is started, but since the intake pipe is cooled by the intake air while the engine is running, the temperature does not rise much, so the memory is cleared. There is actually no problem even if the memory operation is performed as it is afterwards.

In addition, in the control circuit 1, a comparator 10
1 receives the wall temperature signal stored in the temperature storage circuit 4 and determines that the maximum wall temperature (peak value) is a predetermined value (for example, 85
℃) or more, an L level signal is generated, and when it is lower than that, an H level signal is generated. Further, the comparator 102 receives the input cooling water temperature signal and determines that the cooling water temperature is a predetermined value (for example, 35
℃) or more, an L level signal is generated, and when it is lower than that, an H level signal is generated. The time limit circuit 103 is a circuit that receives a starter start signal and generates a drive signal for a predetermined period of time determined by the operating state of the engine. Drive circuit 104
The injector 5 is driven in accordance with an input drive signal (for example, a current signal), and is composed of, for example, a transistor amplifier circuit. Further, the transistor 108 restricts the passage of current from the signal line 110 to the drive circuit 104, and is connected to the invert gate 105, the NAND gate 106, and
Controlled by the logic output of NOR gate 107.

Note that power is supplied to the control circuit 1 via the ignition switch 8, but the temperature storage circuit 4 and the reset circuit 7 are supplied with power via the ignition switch 8.
The configuration is such that power is supplied directly without going through the.

FIG. 2 shows details of the wall temperature memory circuit 4.
In the case where a thermistor is used as the wall temperature sensor 3, it is connected in series with a resistor 41, and its divided voltage is inputted to the negative input terminal of the differential amplifier circuit 4a. The resistor 44 and the resistor 45 are connected in series and connected to the positive input terminal of the differential amplifier circuit 4a to adjust the bias. The configuration is such that the amplification degree of this circuit is adjusted by a resistor 43 and a resistor 42. Reference numeral 4b denotes a comparator, which is configured to switch between two inputs using two contacts of an electric switch 4c operated by the output of the comparator.
The output of the differential amplifier circuit 4a is connected to the neutral terminal of the electric switch 4c, and is connected to the negative input terminal of the comparator 4b to charge the capacitor 47 when the output of the comparator 4b is at H level. When the output of the comparator 4b is at L level, the output of the differential amplifier circuit 4a is connected to the positive input terminal of the comparator 4b and charges the capacitor 46. 4
Signal terminals 8 and 49 connect the output terminal side of the capacitor 46 to the control circuit 1 and the reset circuit 7, respectively.

In the above configuration, when the internal combustion engine is running, the air-fuel mixture constantly flows in the intake pipe and is cooled, so the resistance of the wall temperature sensor (thermistor) 3 is large, and the resistance of the differential amplifier 4a is large. Since the negative input voltage is large, the output voltage of the differential amplifier 4a is at a relatively low level.

When the internal combustion engine stops, the temperature storage circuit 4 starts storing data, and the intake pipe is heated by heat conduction from the cylinder block, etc., and the resistance of the wall temperature sensor (thermistor) 3 decreases, and the resistance of the differential amplifier 4a decreases. The negative input voltage gradually decreases, and the output voltage of the differential amplifier 4a increases accordingly. When the output of the comparator 4b is at H level, the output of the differential amplifier 4a is connected to the negative input terminal of the comparator 4b via the electric switch 4c, so that the capacitor 47 is charged until it becomes equal to the output voltage. When the terminal voltage of the capacitor 47 becomes higher than the voltage of the capacitor 45, the comparator 4b switches to the L level, and the switch 4
The output of the differential amplifier 4a is connected to the positive input terminal of the comparator 4b by switching the capacitor 4.
Charge 6. When the terminal voltage of the capacitor 46 becomes higher than the terminal voltage of the capacitor 47, the comparator 4b becomes H level, and the switch 4c is turned over to return to the original state. Thereafter, while the output voltage of the differential amplifier 4a increases, the capacitors 46 and 47 are alternately charged and become equal to the output voltage of the differential amplifier 4a.

Next, when the temperature stops rising and begins to cool down, the output voltage of the differential amplifier 4a begins to decrease. When the output voltage of the differential amplifier 4a decreases, the capacitor starts discharging, but when the terminal voltage of the capacitor 47 becomes lower than the terminal voltage of the capacitor 46, the comparator 4b is held at H level, so the switch 4c The terminal voltage of the capacitor 46 remains connected to the negative input terminal of the capacitor 46, and the terminal voltage of the capacitor 46 remains at the peak voltage.

Next, when restarting the internal combustion engine, if the signal from the cooling water temperature sensor 2 is below the set value, the output of the comparator 102 becomes H level and turns off the transistor 108, so the current signal is driven from the signal line 110. input to the circuit 104,
Eventually, the control circuit 1 outputs a starting correction fuel signal to the injector 5 to start the engine in the conventional manner. On the other hand, when the signal from the cooling water temperature sensor 2 is equal to or higher than the set value, the comparator 102 outputs an L level and opens the NAND gate 106. At that time, the comparator 101 receives the wall temperature signal of the wall temperature memory circuit 4 which stores the peak value of the output of the wall temperature sensor 3, and if the value is less than the set value, the comparator 101 outputs the H level, so the NAND The output of gate 106 becomes L level, and therefore the output of NOR gate 107 becomes H level, turning transistor 108 ON. Therefore, the signal line 110 is short-circuited to ground, and a signal instructing corrected fuel for starting is not transmitted to the drive circuit 104, and as a result, starting fuel is not supplied from the injector. That is, when the cooling water temperature is high but the intake pipe temperature is not so high, for example, when the atmosphere is low in winter and the operating time is short, or when the time from when the engine is stopped to when it is restarted is short. etc.

On the other hand, if the signal of the cooling water temperature sensor 2 is above the set value and the output of the wall temperature memory circuit 4 is above the set value, both the comparators 101 and 102 output L level, and the NOR gate 107 outputs L level. Since the transistor 108 is turned off, a command signal for starting correction fuel is transmitted to the drive circuit 104 to drive the injector 5 to facilitate starting at high temperatures. As a result, even if a portion of the fuel is taken away by the dry intake pipe wall, the air-fuel mixture with λ≒1 is quickly supplied to the vicinity of the spark plug, resulting in good starting performance even when restarting at a high temperature. be able to.

Further, the signal terminals 48 and 49 are configured to be received by elements with extremely high input impedance such as field effect transistors, and after the engine is started, the capacitor 46 is short-circuited by the reset circuit 7 to eliminate the stored voltage value and return to a predetermined state. It will be retained. Then, when the engine stops, the wall temperature memorization operation starts again.

In addition, in the above-mentioned embodiment, the case where a starting auxiliary injector is provided as the injector 5 has been described as an example, but in the present invention, the main injector of the fuel injection system is used as the injector 5 without using an auxiliary injector, It may be incorporated as a start-up increasing system in this system.

Further, in the above embodiment, an electrical peak hold circuit was used as a means for storing the temperature peak of the intake pipe wall, but a configuration may also be adopted in which the temperature peak is detected using a mechanical storage function of the detection section. . In addition, in the case of a system in which fuel control is performed using a microcomputer, the temperature signal of the tube wall is exchanged from analog to digital, read into a register in the computer, and constantly sampled and compared, and the higher temperature signal is stored in the register. It is also possible to have a configuration in which the information is stored in advance and read out at the time of initial setting at startup.

As described above, in the present invention, the peak value of the intake pipe wall temperature while the internal combustion engine is stopped is stored, and both this peak temperature value and the temperature of the cooling water are stored when the internal combustion engine is started. Since the starting fuel is corrected by detecting and estimating the adhesion state of fuel on the intake pipe wall, the system is configured to correct the starting fuel. An excellent effect of starting performance can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention.
FIG. 2 is an electrical wiring diagram showing details of the temperature storage circuit in FIG. 1. DESCRIPTION OF SYMBOLS 1... Control circuit, 2... Cooling water temperature sensor forming water temperature detection means, 3... Intake pipe wall temperature sensor forming wall temperature detection means, 4... Temperature storage circuit, 5... Injector, 7
...Reset circuit.

Claims (1)

[Claims] 1. In an electronic fuel injection system that controls fuel injection time according to the operating conditions of an internal combustion engine, a water temperature detection means for detecting the engine cooling water temperature and a wall temperature detection means for detecting the temperature of the intake pipe wall of the engine are provided. The maximum temperature of the intake pipe wall detected by this wall temperature detection means during the period from immediately after the engine stops until the engine is started is stored, and when the engine is started, the cooling water temperature is below a predetermined value. and when the coolant temperature is equal to or higher than the predetermined value and the stored maximum value of the temperature of the intake pipe wall is within a predetermined range, an increase in fuel is corrected. How to correct the start of the injection system.