JPS624543B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel injection device, and more particularly to a fuel injection device that corrects differences in the amount of injected fuel resulting from differences in the characteristics of fuel injection valves.

In known fuel injection valves used in electronically controlled fuel injection devices for internal combustion engines, the amount of injected fuel depends on the area of the nozzle hole, the energization time of the coil that lifts the seat of the valve body, and the length of the nozzle hole. It is mainly determined by the fuel pressure before and after and the pressure difference between the outside air. However, the response of the valve body of the fuel injector to the electric pulse that energizes the coil varies depending on the individual fuel injector, so even if an electric pulse of the same pulse width is applied, the response of the valve body of the fuel injector to the electric pulse that energizes the coil varies depending on the This results in a difference in the amount of fuel injected. In particular, this difference in the amount of injected fuel has a greater effect as the pulse time width of the electric pulse is shorter, that is, the smaller the desired amount of injected fuel is, increasing the error in the amount of injected fuel.

By the way, when we investigated the correlation between the operation of the fuel injection valve and the amount of injected fuel, we found that if the nozzle hole area and other factors are the same, the amount of injected fuel is determined by the amount of time the coil is energized to lift the valve body, and the amount of time the valve body lifts. It was found that it was a function of the time taken to complete the operation. That is,
This relationship can be roughly expressed by the following relational expression.

q=Q・(t _i +a−bT _p )...(1) In equation (1), q is the amount of injected fuel, Q is the fuel flow rate per unit time when the fuel injection valve continues to open, t _i is the pulse time width of the electric pulse applied to the coil of the fuel injection valve as shown in FIG. 1a, T
_p is the time required for the valve body of the injector to finish lifting in response to the application of an electric pulse as shown in FIG. 1b, and its value varies depending on the characteristics of each fuel injector.
a and b are constants. Here, the pulse time width t _i is further set as follows.

t _i =t _p +a'+bT _p (2) In equation (2), t _p is a pulse time width determined by the outputs of various sensors that detect the operating state of the internal combustion engine, and a' is a constant. Note that for a certain fuel injection valve, a'=0 [mSec] and b=0.5. (2) to (1)
Substituting it into the equation and rearranging it, we get q=Q・(t _p +a″) ……(3).In equation (3), a″ is a constant of a″=a+a′.In equation (3), Since T _p is not included, it can be seen that by setting the pulse time width t _i of the electric pulse as shown in equation (2), it is possible to absorb the variation in the amount of injected fuel due to the delay in the lift operation of the valve body of the injector. In other words, Detects the operating status of the internal combustion engine using various sensors,
The pulse time width corresponding to (t _p +a') is calculated from the output, and the pulse time width corresponding to bT _p is added to this, and this time (t _p +a' + bT _p ) is calculated as the pulse time width t _i. In this way, variations due to delays in the operation of the injection valves can be absorbed.

If we further examine in detail the interrelationships between the electric pulse, the valve body lift operation, and the current flowing through the coil of the injection valve, we will find the relationship shown in FIG. 1. When an electric pulse with a pulse duration t _i as shown in Fig. 1a is applied to the coil of the injector, the lift of the valve body of the injector ends with a delay of T _p as shown in Fig. 1b. . Further, the valve body closes with a delay of _Tc after the electric pulse disappears. As mentioned above, this valve body lift operation differs depending on the individual variations of the injection valves, for example, as shown by the broken line. The current flowing through the coil of the injection valve becomes as shown in Figure 1c due to the influence of inductance, but the first drop (singular point) in the middle of the rise of the current waveform is the lift operation of the valve body shown in Figure 1b. Match at the end. Therefore, find the time width T _p from the current waveform flowing through this coil, or
Alternatively, by directly detecting the end of lift operation to find the time width T _p and then calculating the pulse time width t _i from the above calculation formula, it is possible to obtain an injected fuel amount that is not affected by variations in individual injection valves. Become.

The present invention has been made in view of the above points, and
It is an object of the present invention to provide a fuel injection device that corrects the energization time of the injector coil using the time width from the start of energization of the electric pulse applied to the injector coil to the end of the lift operation of the valve body as a correction factor.

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 2 is a block diagram showing a schematic configuration of the present invention. In the figure, reference numeral 10 denotes an internal combustion engine, and the operating state of the internal combustion engine 10 is detected by a group of various sensors 20. Based on this output, an injection pulse width calculation circuit 30 calculates the pulse time width (t _p +
a′). 40 is an injection pulse width correction circuit which is a feature of the present invention, and calculates the time T _p until the end of the valve body lift operation described above, and calculates the pulse time width (t _p +
a') to obtain a pulse time width of t _i =(t _p +a' + bT _p ). Reference numeral 50 denotes an electromagnetic injection valve that injects fuel in an amount corresponding to an electric pulse having a time width t _i from the correction circuit 40 . Note that the internal combustion engine 10,
Sensor group 20, arithmetic circuit 30, and fuel injection valve 5
Since 0 may be a known one, a detailed explanation of the configuration will be omitted.

FIG. 3 is a schematic electrical circuit diagram showing a specific example of the injection pulse width correction circuit 40. The configuration and operation of the circuit shown in FIG. 3 will be explained below with reference to the waveforms of each part shown in FIG. In FIG. 3, as described above, the injection pulse width calculation circuit 30 operates the engine 10 based on the output from the sensor group 20 that detects the operating state of the internal combustion engine 10.
It outputs a pulse with a pulse time width (t _p +a') that is compatible with the operating condition of the engine and synchronized with the engine rotation. In response to the output from the arithmetic circuit 30, the timer circuit 41 activates the constant voltage circuit 4 for a certain period (for example, 1.5 to 2 mSec).
2 is activated to output a constant voltage lower than the power supply voltage V _B to its output terminal (ouT), and after a certain period of time has elapsed, the power supply voltage V _B is output. Reference numeral 43 denotes a pulse width correction unit, which is provided as many as the number of injection valves required by the internal combustion engine 10, but only one is shown in the figure for the sake of simplicity.

On the other hand, the output end of the arithmetic circuit 30 is also connected to a pulse width t _i arithmetic circuit 44 . In response to the rise of the pulse with a time width (t _p +a') from the arithmetic circuit 30, the output of the pulse width t _i arithmetic circuit 44 connected to the base of the transistor Tr1 becomes high level, making the transistor Tr1 conductive. . When the transistor Tr1 becomes conductive, current flows from the constant voltage circuit 42 to the coil 51 of the corresponding injection valve 50 through the resistors R1 and R2, causing the injection valve 50 to open. The voltage across the resistor R1 is applied to the input terminal of the differential operational amplifier Q1, and a voltage having a waveform corresponding to the current flowing through the coil 51 as shown in FIG. 4a is obtained at the output terminal A of the differential operational amplifier Q1. The output voltage of the operational amplifier Q1 passes through a differentiator circuit composed of a capacitor C and a resistor R3. Therefore B
The voltage at the point has a waveform that falls at the time width T _p as shown in FIG. 4b. This waveform is amplified by amplifier Q2 and applied to the reset input terminal R of flip-flop circuit Q3 of gate circuit 45. Note that the amplifier Q2 may be provided with hysteresis characteristics such as a Schmitt circuit. An operational amplifier Q is connected to the set input terminal S of the flip-flop circuit Q3.
Since the output terminal of the flip-flop circuit Q3 is connected to the output terminal Q of the flip-flop circuit Q3 (that is, the point C), it becomes high level when the output voltage of the operational amplifier Q1 rises, and becomes low level when the output voltage of the amplifier Q2 falls. In this way, a pulse as shown in FIG. 4c is generated with a pulse time width T _p from the rising point of the pulse t _p to the first drop point (singular point) G of the injector drive current. The AND gate Q4 of the gate circuit 45 receives the clock pulse from the clock pulse generating circuit 46, which oscillates at a predetermined frequency, such as a crystal oscillator, only when the output terminal Q of the flip-flop circuit Q3 is at a high level, that is, the pulse time width _Tp. Allow only the interval to pass. Therefore, the voltage at point D of the frequency divider circuit 48 which divides the output of the AND gate Q4 becomes as shown in FIG. 4d. Note that the clock pulse of the clock pulse generating circuit 46 serves as a reference for measuring the time width T _p and its frequency is determined with the required minimum measurement accuracy. The clock pulse at point D that occurs during the time width T _p is counted by the pulse width T _p counter 47, and its contents expressed in binary numbers are preset by the pulse width t _i arithmetic circuit 44 consisting of the aforementioned preset counter. Added to the set data input terminal. The time width (t
_p + a') falls, the pulse width t _i calculation circuit 44 counts down from the preset data value given from the pulse width T _p counter 47 every time it receives a clock pulse from the clock pulse generation circuit 46. do. Note that the frequency dividing circuit 48 divides the frequency of the clock of the clock pulse generating circuit 46 according to the constant b of the above-mentioned calculation formulas (1) and (2).
In this embodiment, a 1/2 frequency divider circuit is used with b=0.5, but it is necessary to appropriately change the frequency division ratio depending on the value of b. When the pulse width t _i arithmetic circuit 44 counts down to zero, the voltage at the output terminal E becomes the fourth
As shown in Figure e, the level becomes low and the transistor
Make Tr1 non-conductive. In this way, the injection valve 5
0 coil 51 is energized for a period of t _i =(t _p +a'+bT _p ), and even if the lift operation end time T _p of the valve body differs for each injection valve, the energization time of the electric pulse is appropriate for each injection valve. By calculating t _i , the influence of variations in the injection valves 50 can be absorbed, and an accurate amount of fuel can be injected and supplied to the engine.

Next, FIG. 5 shows another embodiment for detecting the time T _p until the end of the lift operation of the valve body of the injection valve. As is clear from the figure, an acceleration sensor (G sensor) 52 is attached to a known fuel injection valve. When the electric pulse is applied and the lift of the valve body (needle) 53 is completed, the impact that hits the stopper 54 causes the piezoelectric element 55, the weight 56, and the spring 5 to
7. Utilizes the fact that a large output voltage is generated in the piezoelectric element 55 of the G sensor 52 constituted by the terminal 58. In this case, it is desirable that the piezoelectric element 55 be arranged so that vibrations of the needle 53 in the lift direction can be detected efficiently.

In this embodiment, a pulse width correction section 43 is provided for each fuel injection valve, but for example, an operational amplifier Q1, resistors R1 and R2, and a transistor Tr.
1 is provided for each injection valve, and the other parts are common,
A separate selector circuit may be used to select input/output signals.

As described above, according to the present invention, it is possible to reduce the variation in the amount of injected fuel caused by differences in the individual characteristics of the injection valve, and even when the valve opening time of the injection valve is short, which is particularly affected by the variation, This has the excellent effect of providing an appropriate amount of injected fuel.

[Brief explanation of the drawing]

FIG. 1 is a waveform diagram showing the operating characteristics of the injection valve. FIG. 2 is a block diagram showing a schematic configuration of the fuel injection device of the present invention. FIG. 3 is a schematic electrical circuit diagram showing an embodiment of the main part of the device according to the present invention. FIG. 4 is a waveform diagram of each part of the circuit shown in FIG. 3. FIG. 5 is a longitudinal sectional view showing another embodiment of the device of the present invention. 20... Sensor group, 30... Injection pulse width calculation circuit, 44... Pulse width t _i calculation circuit, 45...
Gate circuit, 46... clock pulse generation circuit,
47... Pulse width T _p counter, 50... Fuel injection valve, 52... G sensor.

Claims (1)

[Scope of Claims] 1. A fuel injection device including an electromagnetic fuel injection valve that is driven to open by the application of an electric pulse, which includes a detection device that detects the end of lift operation of the valve body of the injection valve. The fuel injection device is characterized in that the pulse time width of the electrical pulse is corrected based on the time from the start of application of the electrical pulse to the end of lift operation of the valve body. 2. In the device according to claim 1,
A fuel injection device characterized in that the detection device detects the end of lift operation of the valve body by detecting a singular point in a current waveform flowing through an electromagnetic coil of the injection valve. 3. In the device according to claim 1,
The fuel injection device is characterized in that the detection device includes an acceleration sensor that detects an impact that occurs when the lift operation of the valve body ends.