JPS6254972B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electronically controlled fuel injection device that intermittently injects fuel into an internal combustion engine in synchronization with the engine rotation, and particularly to one that prevents fluctuations in the engine rotation speed in the low rotation range. It depends.

Electronically controlled fuel injection devices that intermittently supply fuel are known to calculate the fuel supply amount each time in synchronization with engine rotation, and are classified as follows depending on the operating parameters used for the calculation. In other words, one uses the speed density method, which calculates based on intake pipe pressure and rotational speed, one uses the throttle speed method, which calculates based on throttle opening and rotational speed, and one uses mass flow, which calculates based on intake air flow rate and rotational speed. It uses a method.

When the engine is in the low speed, low load range and the throttle is fully closed or at a nearly constant low opening, the intake pipe pressure changes only depending on the engine speed, but the response is relatively small due to the volume of the intake system. slow. On the other hand, the response of the rotational speed due to changes in external load, which is a disturbance, depends on the inertia factors of the engine and drive system, and is relatively fast. Therefore, when there is a change in external load due to disturbance, the response of the rotational speed is fast, but the response of the intake pipe pressure or the intake air flow rate upstream of the throttle, which is dependent on it, is slow. The fuel supply system has the disadvantage that the metering becomes irregular temporarily. In particular, in the mass flow method, which calculates the intake air flow rate signal with the rotational speed signal and determines the amount of fuel supplied each time, large rotational fluctuations known as surging at low rotational speeds will directly affect the metering and cause misfires. Even after the load changes due to disturbances have ceased, disturbances in fuel metering may promote or persist rotational fluctuations, and in the case of internal combustion engines for vehicles, the rotational speed may fluctuate periodically at a rate of several hertz. This has the serious drawback of causing vehicle vibration called surging. In particular, when the engine is idling while the vehicle is stopped, the engine rotation speed may increase.
Since the speed is low at around 700 rpm, this vibration causes discomfort to vehicle occupants.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems, and aims to provide an electronically controlled fuel injection device that can reduce surging rotation fluctuations caused by load changes due to disturbances.

To achieve the above object, the electronically controlled fuel injection system of the present invention, as shown in FIG. a fuel amount calculation means for calculating an amount of fuel to be supplied to the engine according to the load detected by the load detection means and the rotational speed detected by the speed detection means; an injection means for injecting the amount of fuel into the engine; and a speed change calculation means for calculating an increase or decrease in the rotational speed detected by the speed detection means as a ratio of a rotational speed change amount at that time to the rotational speed at that time. and determining means for determining whether the increase or decrease in rotational speed calculated by the speed change calculating means is equal to or greater than a predetermined value corresponding to surging rotational fluctuations in the low speed and low load region of the engine; If an increase or decrease in the rotation speed is determined to be greater than or equal to the value, the rotation speed change is reduced in accordance with the direction of the increase or decrease in the rotation speed relative to the amount of fuel that should be calculated based on the load and the rotation speed. and a correction means for causing the fuel amount calculation means to correct and calculate the amount of fuel increased or decreased in the direction.

It goes without saying that the present invention can be realized using analog or digital circuits, but an embodiment using a microcomputer, which has begun to be used to control internal combustion engines due to recent dramatic developments and cost reductions, will be described below. .

The embodiment shown in FIG. 1 shows the configuration of a 6-cylinder engine, where 1 is the engine body, 2 is a load detection means, and is a known air amount sensor that detects the intake air flow rate of the engine. It has a dam plate 3 whose opening degree changes, and a potentiometer 4 converts the change in the opening degree into an electrical quantity and sends the signal to a microcomputer 5. 6 is a rotation sensor, which is a magnetic body 61 that rotates at 1/2 the speed of the engine crankshaft, that is, rotates once for every 2 revolutions of the crankshaft;
62 and 63 are built-in. The magnetic bodies 61 and 62 have one tooth, and the magnetic body 63 has 12 teeth equally spaced, and the induced electromotive force generated when the teeth pass from the electromagnetic pickups 64, 65, and 66 provided on each is generated. It detects and sends a signal to the microcomputer 5. Fuel in the fuel tank 7 is supplied under pressure to a distributor 9 by a fuel pump 8. Fuel is sent from the distributor to the fuel injection valve 10 attached to the intake pipe position of each cylinder, and the solenoid 11 built into the injection valve 10 is energized by the electric signal from the microcomputer, lifting the needle valve 12 and injecting fuel. do. Here, 13 is an electric resistance that keeps the pressure of the pressurized fuel constant and a pressure regulator 14 that is useful for stabilizing the operation of the injection valve 10. 15 is an air purifier, 1
6 is a throttle valve, and 17 is an accelerator pedal.

FIG. 2 is a block diagram for explaining the microcomputer 5 in detail. In the figure, 500 is a microprocessor unit that interrupts and calculates the fuel injection amount. Reference numeral 501 denotes an interrupt command unit that commands the microprocessor unit 500 to perform interrupt processing for calculating the fuel injection amount based on rotation angle signals obtained from the electromagnetic pickups 64, 65, and 66 of the rotation sensor 6. 500. Also, the interrupt command unit 501 is a unit 506 which will be described later.
It also outputs a timing signal that controls when to start operation. 502 similarly receives the rotation angle signal of the rotation sensor 6, and the microprocessor unit 50
This is a rotation speed counter unit that calculates the engine rotation speed by counting the period of a predetermined rotation angle based on a clock signal of a predetermined frequency starting from zero. 50
A digital signal processing unit 7 sequentially reads signals from the starter switch 20 and signals from other operating state detectors (not shown) into the microprocessor unit 500 in accordance with control signals from the microprocessor unit 500. Reference numeral 503 is an A-D conversion processing unit including an analog multiplexer, which includes an air amount sensor 2, a water temperature sensor 18, and an intake air temperature sensor 19 (not shown).
The microprocessor unit 500 has the function of converting each signal from analog to digital and sequentially reading it into the microprocessor unit 500. Output information from each of these units 501, 502, 503 is transmitted to microprocessor unit 500 through common path 510. 504 stores a control program for the microprocessor unit 500 and also controls each unit 501, 50.
The memory unit has a function of storing output information from the microprocessor unit 500, and information is transmitted through the coyon path 510. 505 is a fuel injection time control counter unit including a register, which is composed of two down counters having the same function, and each outputs a binary signal representing the opening time of the fuel injection valve 10 calculated by the microprocessor unit 500, that is, the fuel injection amount. It is converted into a pulse signal having a pulse time width that gives the opening time of the fuel injection valve 10. 506 is a power amplifier that amplifies the pulse signal from this counter unit 505 and supplies it to the fuel injection valve.
Two are provided correspondingly.

As shown in FIG. 3A, the waveform obtained by shaping the output of the electromagnetic pickup 61 of the rotation sensor 6 outputs a signal once every two revolutions of the engine crankshaft at a position an angle θ before the crank angle from 0°. The waveform obtained by shaping the output of the electromagnetic pickup 62 is expressed by the crank angle with respect to A, as shown in Figure 3B.
A similar signal is output only once every two rotations of the crankshaft with a 360° delay. As shown in Fig. 3C, the waveform obtained by shaping the output of the electromagnetic pickup 63 is such that the number of angle signals equal to the number of cylinders per revolution of the crankshaft is distributed at equal intervals. It is configured to output six angle signals every 60 degrees.

The interrupt command unit 501 divides the frequency of the signal C by 6, and divides the calculation of the fuel injection amount every 360 degrees in synchronization with the 6th c signal after the signals A and B are output, as shown in FIG. 3D. Outputs the input command signal D.

FIG. 4 shows a schematic flowchart of the microprocessor unit 500, and the functions of the microprocessor unit 500 will be explained based on this flowchart. When the engine is started, the calculation of the mail routine starts at the start of the first step 1001. In the second step 1002, A-
Engine water temperature from D conversion processing unit 503,
At the same time as reading a digital value corresponding to the intake air temperature, a correction ratio for the fuel injection amount corresponding to this digital value is calculated and stored in the memory unit 504. Normally, the processing of this main routine is executed repeatedly.

When the interrupt command signal shown in FIG. 3D is input from the interrupt command unit 501, the microprocessor unit 500 immediately interrupts the main routine processing even if it is in the process of processing the main routine and returns to step 100.
The process moves on to the interrupt handling routine.

In this case, steps 1101 to 11
Step 02 takes in the signal Ni representing the engine rotational speed from the rotational speed counter unit 502 and the rotational speed signal (Ni-1) captured in the previous interrupt calculation and stored in the memory unit 504, and in step 1103 ΔN=(Ni-1). ) - (Ni) to find the amount of change in rotational speed ΔN, and ΔN
is divided by the rotational speed signal Ni to obtain the rotational change rate ΔN/
Find Ni. This step 1102, 1103
constitutes the speed change calculation means in FIG. Next, in steps 1104 and 1105, the rotation rate of change ΔN/Ni is set to predetermined values A and -B (where A>0, B>
0) to determine the size. This step 110
4,1105 constitutes the discriminating means in FIG. next,
Proceed to steps 1106, 1107, and 1108 to obtain the rotational speed signal used to calculate the basic injection amount.
Find Ni′. In other words, when ΔN/Ni≧A
Find Ni′ by the calculation Ni′=Ni _-1 +αc×Ni (however, αc>0), and when ΔN/Ni≦−B,
Ni′=Ni _-1 −α _D ×Ni, −B<ΔN/Ni<
When A, find Ni′=Ni. This step 11
06, 1108 constitutes the correction means in FIG. Next, in step 1109, the signal data Q representing the intake air amount from the A-D conversion unit 503 is fetched, and in step 1110, the intake air amount signal Q and the rotation signal are input.
Execute the calculation (division) Q/Ni′ by Ni′ and calculate the amount of fuel required for each injection (that is, the corresponding injection time).
Find tP). This step 1110 constitutes the fuel amount calculation means in FIG. Next step 1111
Then, the fuel injection amount correction ratio obtained in the main routine is read out from the memory unit 504 and correction calculation is performed. Next, in step 1112, the corrected and calculated fuel injection amount data is set in the register of the counter unit 505 for fuel injection time control, and in step 1113, the Ni data is stored in the memory unit 50.
Memory within 4. Next, the process advances to step 1114 to return to the main routine. When returning to the main routine, the process returns to the processing step at which it was interrupted due to interrupt processing. Microprocessor unit 500
The general function of is as above.

According to the inventor's experiments, the crankshaft
Idling (Ni =
If surging rotational fluctuations occur near 700rpm), ΔN/Ni = ±100rpm/700rpm = about ±0.14, but even if sudden acceleration/deceleration occurs while driving (for example, Ni = 200rpm), ΔN/Ni = ±30rpm/200rpm = ±
It has been confirmed that it is only about 0.015. Therefore, by setting the reference values A and B in steps 1104 and 1105 described above to, for example, about 0.1, it is possible to reliably determine whether so-called surging rotational fluctuations are occurring at low loads and low speeds.

As shown in FIG. 5, the counter unit 505 is a register 50 into which data representing the fuel injection amount from the microprocessor unit 500 is input.
51 and two registers 5051 provided corresponding to the two groups #1 and #2 of the fuel injection valves 10 as described above, into which the temporarily held data, that is, the digital binary signal representing the fuel injection amount is input. It consists of down counters 5052, 5053 and two flip-flops 5054, 5055 which are connected to these down counters 5052, 5053 and output injection pulse signals for a period from the start of fuel injection to the end of fuel injection. The operation start point of the down counter 5052, which counts the injection time of the first group #1 of the injection valves 10, is generated by the interrupt command unit 501, as shown in FIG. This is the time when the E signal is input, which is out of phase with D by 60 degrees in terms of crank angle and is output only once every two revolutions of the crankshaft. Further, a digital signal representing the fuel injection amount is input to the down counter 5052 from the register 5051 immediately before the E signal is input.

The down counter 5052 counts down this digital signal using a clock signal of a predetermined period from the time when the angle signal E is input to determine the fuel injection time. The flip-flop 5054 outputs the injection pulse signal G as shown in G in FIG. Output. This pulse signal G is amplified by one of the amplifiers 5061 of the power amplifier 506 and then supplied to the first group #1 of the injection valves 10 to perform injection supply once every two rotations of the crankshaft. Regarding the other group #2 of the injection valves 10, the down counter 5053 is activated at the moment when the angle signal F shown in FIG. However, the flip-flop 5055 and the power amplifier 5062 operate in the same manner as in the case of #1, and the fuel is injected and supplied from the injection valve of the #2 group once every two revolutions of the crankshaft, with a 360° shift from that of #1.

For example, if the rotation speed is detected when the rotation speed temporarily decreases due to a disturbance,
This decreased rotational speed signal Ni (broken line A in Figure 7)
If the amount of fuel is calculated by dividing the intake air amount signal Q, which hardly changes, by Q/Ni, the amount of fuel injected (broken line in FIG. 7B) increases. This amount of fuel burns after injection and increases the output torque of the engine, so the rotational speed increases again (Figure 7A
dashed line). Conversely, when the rotational speed increases, the rotational speed is detected, and the calculated amount of fuel is then injected to the decreasing side, but this amount of fuel is burned and the output torque decreases, so the speed decreases again. . Such a large increase or decrease in rotational speed is caused by a time delay in the intake and compression of fuel between the time when the rotational speed is detected and the time when the amount of fuel calculated based on it is actually combusted to produce output torque. This occurs periodically because of the

Therefore, as in the above embodiment, step 110
Only when it is determined in Step 4, 1105 that the rotational speed has changed by a predetermined value or more, the rotational speed used to calculate the fuel amount is corrected in Steps 1106 and 1107, thereby effectively changing the fuel amount calculated in Step 1110. By correcting the rotational speed, it is possible to prevent large fluctuations in the rotational speed. For example, when the rotational speed decreases, step 1104
If it is determined in step 1106 that the change from the previous rotational speed is greater than or equal to a predetermined value in the decreasing direction, the current and previous rotational speeds Ni, Ni _-1 (solid line A in Fig. 7) are determined in step 1106.
A larger rotational speed Ni' is calculated using
is forced to be calculated on the decreasing side. As a result, the output torque of the engine is reduced at the time when this amount of fuel is combusted, thereby preventing the rotational speed from increasing significantly (solid line A in FIG. 7).

In the embodiment described above, an example has been described in which the basic injection amount is calculated using the intake air amount signal and the rotational speed signal. In the method using the speed signal, by correcting the rotational speed signal in the same way, it is possible to obtain the same effect of preventing the metering during transients in the low speed and low load range and the resulting rotational fluctuations. Of course.

Further, although the above embodiment has been described with respect to a six-cylinder engine, it is of course applicable to engines having other numbers of cylinders.

Furthermore, although this embodiment uses a pressurized injection device with one injector installed in each cylinder, it is also possible to use a type in which one injector supplies fuel to two or more cylinders. Of course.

As described above, in the present invention, in a fuel injection device that intermittently supplies fuel, when the increase/decrease in rotational speed becomes larger than a predetermined value, the amount of fuel exceeds the normal amount of fuel calculated from the load and rotational speed. Since the fuel amount is corrected to increase or decrease in the direction corresponding to the direction of increase or decrease in rotational speed, it prevents disturbances in metering caused by temporary rotational fluctuations due to disturbances in the engine's low speed and low load range. In the case of periodic rotation fluctuations or vehicle engines, this has an excellent effect of preventing vehicle vibration.

In particular, the magnitude of the increase or decrease in rotational speed is determined by the ratio of the amount of change in rotational speed to the rotational speed at that time,
In other words, by calculating it as a speed change rate, the surging rotational fluctuation occurs at low rotational speeds and the difference in rotational speed is relatively large, so the calculated speed change rate also differs from normal engine acceleration at a relatively high rotational speed. It is significantly larger than that during deceleration, and as a result, there is also the effect that surging rotational fluctuations can be easily distinguished from rotational fluctuations during normal acceleration and deceleration.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a block diagram of the microcomputer shown in FIG. 1, FIG. 3 is a schematic output waveform diagram of each part of FIG. 5 is a block diagram of the counter unit shown in FIG. 2, FIG. 6 is a block diagram showing the configuration of the present invention, and FIG. 7 is an explanation of the operation of the present invention. It is a schematic variation characteristic diagram used. 2...Air amount sensor serving as load detection means, 6...
...Rotation sensor serving as speed detection means 10...Fuel injection amount serving as injection means 5...Fuel amount calculation means 1
110, speed change calculation means 1103, determination means 1
104, 1105, correction means 1106, 1107
microcomputers including;

Claims (1)

[Scope of Claims] 1. Load detection means for detecting the load of the engine, speed detection means for detecting the rotational speed of the engine, and the load detected by the load detection means and the speed detected by the speed detection means. a fuel amount calculation means for calculating an amount of fuel to be supplied to the engine according to the rotational speed; an injection means for injecting the fuel amount calculated by the fuel amount calculation means to the engine; and a speed detection means. a speed change calculating means for calculating an increase or decrease in the rotational speed using the rotational speed detected by the means as a ratio of the amount of change in the rotational speed at that time to the rotational speed at that time; a determining means for determining whether the increase or decrease in rotational speed is greater than or equal to a predetermined value that is set in advance in accordance with surging rotational fluctuations in a low speed and low load region of the engine; only when it is determined that the amount of fuel is increased or decreased in the direction corresponding to the direction of increase or decrease in the rotational speed than the amount of fuel that should be calculated based on the load and the rotational speed. An electronically controlled fuel injection device comprising: a correction means for calculating a correction. 2. The correction means corrects the current rotational speed detected by the speed detection means using the previous rotational speed, and causes the fuel amount calculation means to calculate the fuel amount using the corrected rotational speed. An electronically controlled fuel injection device according to claim 1. 3. The load detecting means detects an intake air amount as the load of the engine, and the fuel amount calculating means calculates the fuel amount by dividing the intake air amount by the rotational speed. The electronically controlled fuel injection device according to either item 1 or 2.