JPS6311310Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to an electronically controlled fuel injection system for an internal combustion engine using a thermal linear intake air flowmeter.

As a conventional electronically controlled fuel injection device of this type, there is, for example, one shown in the configuration diagram of FIG. First, the configuration will be explained. Intake air pipe 1
The hot wire resistance (hereinafter simply referred to as hot wire) R _H of the hot linear intake air flow meter 2 installed inside the air, the temperature compensation resistance R ₁ , and the resistances R ₂ and R ₃ outside the intake air pipe 1 are connected in a loop. The connection point between the two resistors R ₂ and R ₃ is grounded, and the connection point 4 between the hot wire R _H and the temperature compensation resistor R ₁ facing the ground point 3 is connected to the collector of the power transistor T. do. In addition, the connection point 5 between the temperature compensation resistor R ₁ and the resistor R ₂ is connected to the input side of the differential amplifier 7, and the hot wire R _H and the resistor
The connection point 6 with R ₃ is connected to the input side of the differential amplifier 7, and the output side of the differential amplifier 7 is connected to the base of the transistor T. A voltage V _B from a battery (not shown) is applied to the emitter of the transistor T to form a bridge circuit,
A thermal linear intake air flow meter 2 is constructed. The air flow rate measurement value of the thermal linear intake air flow meter 2 is output from the connection point 6 through the output end 8.

Next, the effect will be explained. The resistance value of the hot wire R _H provided in the intake air pipe 1 of the above-mentioned thermal linear intake air flowmeter 2 is determined by the operation of the power transistor T and the differential amplifier 7 so that there is no air flow inside the intake air pipe 1. When the hot wire R _H is cooled by the intake air flow flowing through the intake air pipe 1, the power transistor _T and the differential The amplifier 7 automatically increases the bridge current, raises the temperature of the hot wire R _H , and returns the low resistance value of the hot wire R _H to the above-mentioned predetermined value. Then, the current flowing through the hot wire R _H at that time is detected at the connection point 6, and is outputted from the output end 8 as a measured value of the intake air flow rate. Figure 2 shows the characteristics of the intake air flow rate and the thermal linear intake air flow meter output, that is, the intake air flow rate measurement value Q. Based on the rotational speed measurement value N, the basic fuel injection amount Q _P is determined by the following equation and limits the mixture ratio of the internal combustion engine.

Q _P = KQ/N (where K is a constant) However, in such conventional electronically controlled fuel injection systems, the control configuration did not have an auxiliary mixture ratio control function when the battery voltage decreased. When the battery voltage decreases, the output of the thermal linear intake air flowmeter also decreases, and in the low flow region, the output saturates, causing the fuel injection pulse to become a constant value, making it impossible to control the mixture ratio. It was hot.

This invention was made by focusing on the above conventional problems, and in addition to the thermal linear intake air flow meter and crank angle sensor, it also includes a battery voltage sensor, a throttle valve opening sensor, and the crank angle sensor. A fuel injection amount calculation and control unit is provided in which a data table of internal combustion engine rotational speed signals, throttle valve opening signals, and fuel injection amounts is stored, and the fuel injection amount calculation and control unit is equipped with the thermal linear intake air flow meter and the fuel injection amount calculation and control unit. By connecting each sensor, when the battery voltage drops, the calculation of the fuel injection pulse based on the output of the thermal linear intake air flow meter, that is, the intake air flow measurement value, is stopped, and the above rotation speed signal and throttle valve The purpose of this invention is to solve the above problems by switching to the table pull-up of the data table based on the opening signal, and generating and outputting a fuel injection pulse using the table pull-up. be.

This invention will be explained below based on the drawings. FIG. 3 is a block diagram of an embodiment of this invention, and FIG. 4 is a diagram of an embodiment of a basic fuel injection amount table. In addition, in each figure including FIG. 1, the same or equivalent parts are given the same reference numerals. First, the configuration will be explained. Only the configuration added to the configuration shown in FIG. 1 will be described as follows. 9 is a crank angle sensor, 10 is a battery voltage sensor, 11
12 is a throttle valve opening sensor, 12 is an internal combustion engine, and 13 is a fuel injection amount calculation control unit.
The throttle valve opening sensor 11 is inserted between the intake air pipe 1 and the internal combustion engine 12, and is connected to a fuel injection amount calculation control unit 13. In addition, the thermal linear intake air flow meter 2
The output terminal 8, crank angle sensor 9, and battery voltage sensor 10 are also connected to a fuel injection amount calculation and control unit 13, and the required fuel injection pulses are sent from the fuel injection amount calculation and control unit 13 to a fuel pump (not shown). It is configured to output to

The fuel injection amount calculation control unit 13 is composed of a known microcomputer consisting of, for example, a CPU, RAM, ROM, I/O, etc., and has a memory in which a basic fuel injection amount table as shown in FIG. 4 is stored in advance. It has built-in means.

Next, the effect will be explained.

In normal times, that is, when the battery voltage is higher than a predetermined value, the fuel injection amount calculation control unit 13
calculates the fuel injection amount based on the intake air flow rate detected by the thermal linear intake air flow meter 2 and the rotational speed of the internal combustion engine 12 detected by the crank angle sensor 9. Specifically, for example, the above formula Q _P =K
Calculate the basic fuel injection amount Q _P by (Q/N),
The actual fuel injection amount is determined by adding corrections based on engine temperature, etc.

In addition, the fuel injection amount calculation control unit 13 inputs the signal from the battery voltage sensor 10 and detects that the battery voltage has fallen below a predetermined value (a value that may cause the output of the thermal linear intake air flow meter 2 to become saturated). If detected, the normal control calculation as described above is switched to the low voltage control calculation.

This control calculation at the time of low voltage is performed according to the rotational speed of the internal combustion engine 12 detected by the above-mentioned crank angle sensor 9 and the throttle valve opening detected by the throttle valve opening sensor 11. The corresponding basic fuel injection amount is read out by table lookup from a storage means that stores a basic fuel injection amount table in advance as shown in FIG. This determines the fuel injection amount.

As explained above, according to this idea,
The battery voltage is detected, and if the voltage falls below a predetermined value, a table is created based on the throttle valve opening detected by the throttle valve opening sensor instead of the thermal linear intake air flowmeter and the internal combustion engine rotation speed. Since the fuel injection amount is determined by looking up the fuel injection amount, it is possible to perform proper mixture ratio control even when the battery voltage decreases.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram of a conventional example, Fig. 2 is a characteristic diagram of intake air flow rate and thermal linear intake air flow meter output,
FIG. 3 is a block diagram of an embodiment of this invention, and FIG. 4 is a diagram of an embodiment of a basic fuel injection amount table. Explanation of symbols, 1... Intake air pipe, 2... Thermal linear intake air flow meter, 3... Earth point, 4, 5, 6...
... Connection point, 7 ... Differential amplifier, 8 ... Output end, 9
... Crank angle sensor, 10 ... Battery voltage sensor, 11 ... Throttle valve opening sensor, 1
2...Internal combustion engine, 13...Fuel injection amount calculation control unit, R _H ...Hot wire, _R1 ...Temperature compensation resistor, _R2 ,
R ₃ ...Resistance.

Claims (1)

[Scope of utility model registration request] In an electronically controlled fuel injection system for an internal combustion engine, there is a thermal linear intake air flow meter that detects the intake air flow rate of the engine, a rotation speed detection means that detects the engine rotation speed, and an opening degree that detects the opening degree of the throttle valve. a detection means, a voltage detection means for detecting the battery voltage, a storage means for pre-memorizing the fuel injection amount according to the engine speed and the opening degree of the throttle valve, and the above-mentioned thermal linear intake air in normal times. The fuel injection amount is calculated based on the intake air flow rate detected by the flow meter and the rotational speed detected by the rotational speed detection means, and when the battery voltage detected by the voltage detection means falls below a predetermined value, calculation means for setting a fuel injection amount based on a value read from the storage means in accordance with the rotation speed detected by the rotation speed detection means and the throttle valve opening detected by the opening detection means; electronically controlled fuel injection system.