JPS5832936A - Measuring device of fuel injection quantity - Google Patents

Abstract

PURPOSE:To make the capacity of an ROM small by looking at the constitution of the axes of ordinate and abscissa of a data table again. CONSTITUTION:The axes of ordinate and abscissa on a data table 6B forming a microcomputer memory part are constituted taking a function of a product of fuel injection time and the number of revolutions of an engine and the said number of revolutions as parameters. Accordingly, a characteristic curve representing a fuel injection quantity is distributred over the entire region of the data table 6B, enabling the rate of utilization to be raised, and the number of memories required to ensure the same reading accuracy as the conventional one is reduced allowing the capacity of an ROM to be made small.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel injection amount measuring device for an internal combustion engine using a microcomputer.

For example, when determining the fuel injection amount per unit time for each cylinder of a diesel engine, focusing on the fact that the fuel injection amount is a correlation function between the engine rotation speed and the fuel injection period, conventional methods were used as shown in Figure 1. It was measured using a microcomputer.

(For example, Japanese Patent Application No. 56-45649) The period during which the fuel injection valve is open is defined as the movement (lift) of the needle valve.
is determined by a sensor 1 (such as a piezoelectric element) that detects the pulse, and is shaped into a rectangular pulse corresponding to the valve opening time by a waveform processing circuit 2.

This pulse width is counted as 1 from clock oscillator 4 by counter →
The fuel injection time T is measured by counting based on the output pulse.

On the other hand, a speed calculation circuit 8 measures the number of pulses per unit time to generate pulses corresponding to the rotational speed of the engine rotational speed sensor 7 (crank angle sensor), and calculates the rotational speed -
N (r# I)t m ) is determined. Then, input the signals of the injection time T and rotational speed N to the interface 5.
．． 9 to the CPU of microprocessor 6 (
Central processing circuit) 6AK input.

On the other hand, when the fuel injection amount Q per unit time is calculated from the fuel injection time T and the rotational speed N, a correlation as shown in FIG. 2, for example, is obtained.

This shows the fuel injection amount of a diesel engine, but even if the engine speed changes greatly, the fuel injection time determined by the crank angle does not change that much, so the absolute fuel injection time T depends on the rotational speed. As the speed increases, the amount decreases, and eventually the fuel injection amount per unit time has such a hyperbolic characteristic.

Therefore, if the fuel injection time T and the rotational speed N are stored in advance as parameters in the ROM (read-only memory) 6B of the microprocessor 6, by reading T and N via the interfaces 5 and 9 mentioned above, Therefore, the fuel injection amount Q can be determined.

However, if a data table is formed based on a simple correlation between the injection time T and the engine speed N, it is difficult to read the data and ensure sufficient accuracy on the axis of the injection time T. Since the lattice points of 1" rotation speed to high rotation, speed 1"": cannot be covered 1, a large amount of memory must be used, and therefore a large capacity ROM is required.
is necessary.

However, as can be seen from Figure 2, even with such a large-capacity ROM, the data distribution range that is actually used is only a small part of the whole, and the remaining area shown by diagonal lines is It would be a complete waste.

In this case, even if the number of lattice points on the T-axis indicating the injection time is reduced in order to reduce the memory capacity and the readout accuracy is made rougher, the proportion of the data distribution area actually used will not change, and in any case the memory The utilization rate is low.

In order to solve this problem, the present invention changes the data processing that is stored in the memory, that is, the engine rotation speed N is displayed as a parameter on the vertical axis instead of the fuel injection time T.
and a function of the injection time T, for example, N, T, or N@T, thereby reducing the unused data distribution range in the data table as much as possible. shall be.

Embodiments of the present invention will be described below based on the drawings.

First, FIGS. 3 and 4 show the correlation of fuel injection tQ with the vertical axis representing the function (product) of fuel injection time T and rotational speed N and the horizontal axis representing rotational speed N.

Figure 3 shows the product of rotational speed N and injection time T, that is, N-
T is the parameter on the vertical axis, and in FIG. 4, the injection time is further multiplied by T, and N-de is the parameter on the vertical axis.

In this way, the curve showing the equal fuel injection characteristics will be
The table data distribution range becomes larger because it is more linear than in the figure and the distribution width in the vertical axis direction is also expanded.
゛For this reason, even if the number of grid points in the vertical axis direction is reduced, the data reading accuracy will be higher than in Figure 2, and in the end the RO
A small capacity M can be used.

In order to read out the data stored in the data table (ROM) 6B in this way, a program for the arithmetic operation of the CPU 6A of the microprocessor 6 is set as shown in FIG.

First, the fuel injection time T is read, and then the rotational speed N is read.

Then, Tx'N is calculated from T and N, and based on T-N and N, the fuel injection amount Q is read out by table lookup in the ROM 6B.

Then, the read Q is outputted and the operation routine ends. A concrete block circuit of this is shown in FIG. 6, and the difference from FIG. 1 is that the output of the counter 3 for detecting the fuel injection time T and the speed for detecting the engine rotational speed N A function generator 10 is provided which multiplies N and T based on the output of the calculation circuit 8, and this output N@
T and the output N of the speed calculation circuit 8 are input to the microprocessor 6 and a table lookup is performed.

Next, FIG. 7 shows the fuel injection time T and engine rotation speed N.
The relationship between the The fuel injection amount Q is determined based on the relationship between α(Q) and N·(T −To) and N (a constant used as a parameter).

In this case, regardless of the engine speed N, N・(T−T
o) has a nearly constant value α0, the fuel injection amount Q is set to N
・Can be approximately determined as a function of (TTo),
This eliminates the need for a data table and saves ROM6B'
Further miniaturization is possible.

FIG. 8 shows the force J representing the calculation flowchart in the microprocessor 6 in this case. After reading the fuel injection time T and the rotational speed N, the calculation of N・(T − To ) is performed. The fuel injection amount Q is calculated as Q=f(N・(
'r - T, )) is obtained as a function and this Q is output. However, as can be seen in Fig. 7, the parameter N.
- It is clear that Q may be read by table lookup based on (TTo) and N.

Note that the present invention is not limited to simply calculating the fuel injection amount island, but also calculates the fuel injection time T and rotational speed N, for example, as shown in FIG.
It is also possible to store the control target value of exhaust gas recirculation control, etc. in a χ data table using the function N-T and the rotational speed N as parameters on the vertical and horizontal axes. In addition, as a reference example for reducing the capacity of the ROM, in FIG. 10 and below, there is a fuel injection amount characteristic curve Qn when the fuel injection time T and the rotation speed N are taken as parameters on the vertical axis and the horizontal axis. only part,
This example shows how to create separate lookup tables and read data from each table as needed.

As shown in FIG. 10, fuel injection time Tl * Tl
*Separately divided tables Q+ -C20-Qs and Q4 are created using T3 as a boundary.

Then, this is read out by the microprocessor 6 using an arithmetic program as shown in FIG. 11 to determine the fuel injection amount Q.

That is, the rotational speed N and the fuel injection time T are read, and the magnitude of T and TI is first determined. If T<T1,
The data in this area is read based on the data T and N of the table q which is stored, and the fuel injection amount Q is output.

If T < T, then the magnitude of T and Tt k is determined. At this time, if T is smaller than T, then f
r < 4) Since TI≦T≦T holds true, Q can be read by looking up the data in table q.

Also, if T≦T, then the magnitude of T and T is determined, and if T is smaller than T, then T
Since 15T≦T3, data is read from the table false, and if VCT is not smaller than Ts, data from the table is read.

In this way, even ROMs of substantially small capacity can be read with the same accuracy. .

FIG. 12 is a block circuit diagram for realizing the same function as the arithmetic operation shown in FIG. 11 without using a microcomputer.

The output of the counter 3 which counts the injection time T is D7.
A converter 11 converts it into an analog/4G value, and comparators 12 to 14 compare the output 1 with set values TI, T, , T, and the like.

Comparator 12 outputs an H level signal S when T≦T, similarly, comparator 13 outputs an H level signal S3 when T≦T, and comparator 14 outputs an H level signal S3 when T≦T. Mine sometimes outputs an H level signal Ss.

On the other hand, the conversion values N')-T' of the rotational speed and injection time from the engine speed calculation circuit 8 are input to the function generators 24, 25, 26, and 27, respectively, as shown in FIG. The values corresponding to the table Qt*Qs*Qs, Q4 are output.

The outputs Q of these function generators 24 to 27 are selectively outputted to the injection amount output circuit 28 by analog switches 20, 21, 22, and 23.

The analog switches 20 to 23 are operated as shown in FIG. 13 according to the value of the injection period by the NOT circuits 15, 17, 19 and the AND circuit 1 to 18.

That is, the first analog switch 20 is turned on when the output S1 of the comparator 12 is at H level (T≦T), and the function generator 24 outputs the fuel corresponding to the table Q based on N and T at that time. It outputs the injection amount Q,
Hereinafter, according to FIG. 13, T, (T≦T, the function generator 25, T!<T≦1゛3, the function generator 26, and T, <T, the function Equipment 7
The output Q is output based on the analog switches 21, 22, and 23 being turned on, respectively.

As explained above, the present invention creates a data table that is a microcomputer storage part, and uses functions such as the product of fuel injection time and engine rotational speed, and the engine rotational speed as parameters, and the vertical and horizontal axes of the data table. As a result, the characteristic curve of the fuel injection amount is distributed over the entire data table, which increases the table utilization rate and ultimately reduces the memory required to ensure the same reading accuracy as before. The number of ROMs is reduced, the capacity of the ROM can be reduced, and the costs associated with this can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a conventional device, and FIG. 2 is a fuel injection amount characteristic diagram using fuel injection time and engine rotational speed as parameters. Figures 3 and 4 are fuel injection amount characteristic diagrams according to the present invention, where Figure 3 is the product of the fuel injection time and rotational speed, and Figure 4 is the product of the square of the fuel injection time and the rotational speed. are respectively shown as parameters on the vertical axis. FIG. 5 is a flowchart showing the arithmetic program of the microcomputer, and FIG. 6 is a circuit block diagram for performing the same functions as in FIG. FIG. 7 is another fuel injection amount characteristic diagram of the present invention, in which the product of the rotational speed and the fuel injection time minus a constant is taken as a parameter on the vertical axis. FIG. 8 is a flowchart showing the calculation program of the microcomputer, and FIG. 9 is a control characteristic diagram of the exhaust gas recirculation rate expressed using the same parameters as in FIG. 7. 10 to 13 show reference examples of the present invention,
FIG. 10 is a fuel injection amount characteristic diagram, FIG. 11 is a flowchart showing the calculation program of the microcomputer, FIG. 12 is a block circuit diagram, and FIG. 13 is an explanatory diagram showing the operating status of the block circuit. 1... Lift sensor, 3... Counter, 5, 9...
・Interface, 6...Microprocessor, 6
A...CPU, 6B...ROMJ7...Engine rotation speed sensor, 10.L.Function generator,

Claims (1)

[Claims] means for detecting injection time from a lift period of a fuel injector; means for detecting engine rotation speed; and fuel injection converted in advance based on at least the product of engine rotation speed and injection time, and the correlation with engine rotation speed. 1. A fuel injection amount measuring device comprising: means for storing quantity characteristics; and means for converting a signal from the rain detecting means in correspondence with a parameter of the storing means and then reading the stored data.