JPH02104941A - Device for controlling fuel injection of diesel engine - Google Patents

Abstract

PURPOSE:To restrain the lowering of torque or the increase of smoke at the time of the maximum injection quantity by correcting a fundamental injection starting timing based on the learned correcting quantity at the time of idling even in an operating condition other than the idling time. CONSTITUTION:A fundamental injecting term Avm and a fundamental injection starting timing Itm which are common to the whole cylinders are calculated by means 23, 24 in accordance with an accelerator pedal opening Acc and an engine speed N by sensors 21, 22. At the time of idling judged by a means 26, a feedback correcting quantity is learned by a means 25 so as t make engine speed for each cylinder 25 a predetermined target engine speed NM, and each fundamental injection starting timing Itm is corrected by this leaned feedback correcting quantity DELTAAvi even in an operating condition other than the idling time, to calculate a determined injecting term Avt and a determined injection starting timing Iti by a means 27. Thereby, the increase in idling noise or misfire at the time of flow temperature can be prevented, while suppressing the discharge of smoke at the time of injecting the maximum injection quantity.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a fuel injection control device for a diesel engine.

(Prior Art) Conventionally, some diesel engines for automobiles electronically control fuel injection 1 and the like on a cylinder-by-cylinder basis in order to suppress vibrations during idling and the like.

Such a control device calculates a feedback correction amount for the valve closing period based on the deviation between the idle rotation speed detected for each cylinder and the target rotation speed so that the idle rotation speed becomes a predetermined target rotation speed, In addition to controlling the idle speed for each cylinder, there are systems that learn this feedback correction amount and correct variations in the fuel injection amount for each cylinder even under uncontrolled operation conditions other than when idling (for example, Japanese Patent Application Laid-Open No. 1983-1999). (See Publication No. 32254).

(Problem to be solved by the invention) Furthermore, diesel Ia that controls the fuel injection amount for each cylinder
In a combustion engine, if the opening pressure of the injection nozzle facing the combustion chamber changes due to changes over time, misfires may occur, resulting in an increase in white smoke or knocking noise (combustion noise).

However, in the past, the correction amount for each cylinder was reflected in the injection start timing, so for example, if the nozzle opening pressure decreases when the valve closing start timing of a certain cylinder is advanced, the needle valve is adjusted earlier by that amount. Since lift is started, the needle valve in this state both starts and ends earlier (t 177 ). As a result, fuel is injected earlier in that cylinder, so the combustion sound becomes louder as the combustion condition improves. On the other hand, if the nozzle opening pressure increases when the valve closing start timing is delayed, both the lift start (t I77 ) and the end will be delayed, making misfires more likely to occur.

In addition, conventionally, the correction amount for each cylinder at idle is only reflected during no-load operation, which makes it impossible to prevent torque reduction and smoke increase at maximum injection amount due to variations in fuel injection amount for each cylinder. Ta.

The present invention has been made in view of these conventional problems, and an object of the present invention is to provide a device that controls the fuel injection start timing until the maximum injection amount by using the cylinder-specific correction amount learned during idling. do.

(Means for Solving the Problems) The present invention includes a fuel injection pump (see FIG. 2) whose fuel injection start timing and injection start timing are variably controlled, and as shown in FIG. A sensor that detects the operating state quantity of the engine (for example, a sensor 21 that detects the accelerator valve opening (Ace) as an amount equivalent to the engine load, and a sensor 22 that detects the engine rotation speed (N)), and the sensor detection value ( Ace and N), the basic fuel injection period (Avm) and basic injection start timing (I
ts), and means 25 for determining whether or not the engine is idling, and a means 25 for determining whether the engine is running at idle so that the number of engine revolutions for each cylinder becomes a predetermined target rotation speed (NM) at idle. A means 26 for learning the feedback correction amount for each cylinder, and this learned feedback correction even under operating conditions other than idling! (Δ
Means 27 is provided for calculating the determined injection period (Avt) and determined injection start timing (Iti) by correcting the basic injection start timing (Itl) at Avi).

(Function) According to the present invention, by changing the fuel injection start timing, the needle valve starts earlier or later.
As a result, the idle rotation speed for each cylinder converges to the target rotation speed. In this case, if the nozzle valve opening pressure changes, the start of the needle valve 7F will be affected and become earlier or slower by the change in valve opening pressure, but the timing at which the needle valve 7F ends will be affected. As a result, the same amount of fuel is supplied to all cylinders, the torque becomes uniform among the cylinders, and engine vibration is suppressed.

By learning this feedback correction amount during idling and controlling the injection start timing for each cylinder until the maximum injection amount, it is possible to eliminate variations in the maximum injection amount that occur in some cylinders in the smoke emission region and improve the overall cylinder efficiency. Control the amount of smoke.

(Example) The present invention will be described in detail below based on the accompanying drawings.

In the tIIJ2 diagram, 1 is the pump housing, 2 and 3
are a low-pressure 'm feed pump and a high-pressure side plunger pump driven by a drive shaft 4; fuel sucked by the feed pump 2 from a fuel inlet (not shown) is supplied to the feed pump chamber 5 in the housing 1;
It is sent to the plunger pump 3 via a suction passage 6 that opens to the plunger pump 3.

The plunger 7 of the plunger pump 3 has suction grooves 8 of the same number as the shillings of the engine formed at the tip, and a 7-eighth cam 9 having the same number of cam ridges at the other end.
The eighth cam 9 rotates together with the drive shaft 4 and reciprocates by a predetermined cam lift, passing over the rows 211 disposed on the roller ring 10.

Therefore, the plunger 7 reciprocates while rotating, and the fuel sucked into the plunger chamber 12 from the suction groove 8 due to this rotational reciprocating motion is delivered from a distribution boat for each cylinder (not shown) that communicates with the plunger chamber 12. It passes through the pulp and is pumped to the injection nozzle facing the combustion chamber.

In order to control the fuel injection timing and injection amount, a fuel return passage 13 is formed that communicates the feed pump chamber 5 and the plunger chamber 12, and a fast-response type solenoid valve 14 is provided in the middle of this fuel return passage 13. is interposed.

This electromagnetic valve 14 opens the plunger chamber 12 when the valve is opened, and is closed for a predetermined period during the discharge stroke of the plunger pump 3 according to the operating conditions of the engine by a drive pulse.

Fuel injection is started by closing the solenoid valve 14 during the compression stroke of the planter 7, and injection ends by opening the solenoid valve 14. Therefore, depending on the closing timing of the solenoid valve 14, the fuel injection start timing can be changed. The injection amount is controlled according to the valve closing period.

If the electromagnetic valve 14 is opened briefly during the compression stroke of the plunger 7, pilot injection can be performed prior to main injection of fuel.

On the other hand, a device that controls the electromagnetic valve 14 includes a sensor 17 that detects engine operating parameters, a control unit 19 that processes these detection signals, and an electromagnetic valve drive circuit 16.

FIG. 13 shows details of the control unit 19, which includes input/output circuits (Ilo) 41. ROM42°RAM43
．． It is composed of a microcomputer consisting of a CPU 44, and has the functions of each means 23 to 28 shown in FIG.

The input/output circuit 41 includes one reference pulse 31 per revolution of the injection pump, 36 scale pulses 32 per revolution, and an accelerator pulse as an amount equivalent to the engine load, in order to detect the basic value of the operating state quantity of the engine. In addition to the sensor 33 that detects the valve opening degree, the sensors that detect other operating conditions (fuel temperature sensor 34, water temperature sensor 3
5. Idle switch 36. Signals from a sensor 37 that detects the actual opening start timing and closing period of the electromagnetic valve 14 and a sensor 38 that detects the actual injection start timing are input, respectively.

The CPU 44 searches for information from the input/output circuit 41 according to the program stored in the ROM 42, performs various arithmetic processing, and generates data (
(valve closing timing and valve closing period) are set in the input/output circuit 41.

Note that the RAM 43 is used to temporarily save data related to arithmetic processing by the CPU 44. Input/output circuit 4
1, a drive pulse for the solenoid valve 14 is output based on the data output from the CPU 44.

Next, the operation of the CPU 44 will be explained based on chart 70 in FIG.

In step 50, it is determined whether the idle state is stable. This is determined based on whether the idle rotation speed and the difference between the idle rotation speeds for each cylinder are equal to or less than a set value. if,
If it is determined in step 50 that the idle state is stable, in step 57 the feedback correction amount ΔAvi of the basic injection amount for each cylinder at that time is learned, and in step 58
The value of ΔAvi is stored in memory.

If it is determined in step 50 that the idle is not in a stable state, step 51 indicates 8! The engine rotation speed N and the accelerator opening degree Ace are read, and it is determined in step 52 whether or not the amount is greater than the idle injection amount. For example, the characteristics shown in FIG. 5 are stored in the ROM 42, and the characteristics are Calculate the correction coefficient K.

In step 53, for example, the characteristics shown in FIGS. 6 and 7 are stored in the ROM.
42, and determines the basic injection period Avm and the basic injection start timing Its.

In step 54, the cylinder-by-cylinder learning correction amount ΔAvi stored in step 58 is read out, and in step 55, the basic injection jlAvm and the cylinder-by-cylinder learning correction amount ΔAvi with the correction coefficient K in red are added to determine the determined injection period Avi. At the same time, the basic injection start time ■ts and the generous learning correction amount ΔAvi multiplied by the correction coefficient K are added to obtain the determined injection start time Iti, and in step 56, the determined injection period A is determined.
y and the determined injection start timing It are stored in a predetermined address of the RAM 41, and the process ends.

To explain this with reference to FIG. 8, the drive pulse for opening the solenoid valve 14 is different from the basic injection period and basic injection start timing corresponding to the engine conditions.For example, if the nozzle opening pressure is high, When the separate learning correction amount ΔAvi becomes positive, the rise of the drive pulse is accelerated and the correction is made so that the start of the nozzle needle valve is not delayed. On the other hand, if the nozzle valve opening pressure decreases, the cylinder-specific learning correction lΔAvi becomes negative, thereby delaying the rise of the drive pulse and correcting the nozzle needle so that it does not start too early.

When the nozzle valve opening pressure changes, the start of the needle valve 7F will be affected and the start of the needle valve 7F will be earlier (or later) by the change in valve opening pressure. It is unaffected by changes in valve pressure, resulting in the same amount of fuel being supplied to all cylinders, equalizing torque between cylinders and suppressing engine vibration.

Even if an air-fuel mixture so rich as to exceed the smoke limit is supplied to any one airflow due to variations in the maximum injection amount in a high load range, the overall amount of smoke increases. However, by learning this feedback correction amount during idle and learning and correcting the injection start timing for each cylinder up to the maximum injection amount, the variation in maximum injection amount that occurs in some cylinders in the smoke emission region can be eliminated. This suppresses the amount of smoke in the cylinder as a whole. Note that if the shape of the seven-eighth cam 9 is formed so that the oil feeding rate is always constant, it is not necessary to correct the basic injection amount in step 55.

FIG. 9 shows details of a control unit 19 showing another embodiment, which is provided with an air-fuel ratio sensor 39 attached to the exhaust manifold gathering part, detects the excess air ratio of each cylinder, and changes the fuel injection start timing. It is.

Step 55, as shown in the 70-chart in FIG.
Now, add the basic injection period AVM to the correction amount ΔAvi for each cylinder multiplied by the correction coefficient K, and then add the correction amount ΔAvp according to the air-fuel ratio for each cylinder to obtain the determined injection period Avi. The determined injection start timing Iti is obtained by adding It- and the cylinder-by-cylinder correction amount ΔAvi multiplied by the correction coefficient K, and further adding the correction amount ΔItAF according to the cylinder-by-cylinder air-fuel ratio.

Figure 11 shows a map for determining the target air-fuel ratio λ@ap using the rotation speed and accelerator opening as parameters, and based on the difference between the value λ-aρ determined in this way and the actual air-fuel ratio λt, tI
The injection amount correction amount ΔAV is determined from the maps of pi 12 and 13.
F and the injection timing correction amount ΔAvi are respectively determined.

According to this example, the injection period and injection start timing are controlled for each cylinder along with learning correction during idling so as not to exceed a predetermined excess air ratio, thereby suppressing variations in the maximum injection amount even more accurately in the high load range. However, the amount of smoke from the cylinder as a whole can be suppressed.

(Effects of the Invention) As described above, according to the present invention, since the feedback correction amount for each cylinder learned during idling is reflected in the injection start timing, the nozzle opening pressure is In addition to preventing an increase in idle noise and misfires at low temperatures due to changes in the actual injection timing due to changes in the actual injection timing, it is also possible to suppress smoke emissions when injecting the maximum injection amount.

[Brief explanation of the drawing]

Fig. 1 is a diagram corresponding to the claims of the present invention, Fig. 2 is a sectional view of an injection pump according to an embodiment, Fig. WIJ3 is a block diagram of the control unit, Fig. 4 is a 7a-chart explaining control operation, and Fig. 5 8 through 8 are characteristic diagrams showing the contents of each component used in the control operation. FIG. 9 is a block diagram of a control unit showing another embodiment, FIG. 10 is a flowchart explaining the control operation, and FIGS. 11 to 13 are characteristic diagrams showing the contents of each part used in the control operation. . 1...Pump housing, 3...Plunger pump, 7...Plantsya, 9...7 Acecam, 12.
...Plunger chamber, 13...Fuel return passage, 14...
- Solenoid valve, 16... Solenoid valve drive circuit, 19... Control unit, 21... Accelerator opening sensor, 2
2... Rotation speed sensor, 23... Basic injection period calculation means, 24... Basic injection start time calculation means, 25...
Idle time determination means, 26... Cylinder-specific correction amount learning means, 27... Injection period correction means, 31... IJ77 lens pulse generation means, 32... Scale pulse generation means, 41... Input/output Circuit, 42・ROM, 43・RA
M, 44・CPU.

Claims (1)

[Claims] It is equipped with a fuel injection pump whose fuel injection start timing and injection end timing are variably controlled, and a sensor that detects the operating state of the engine, and a basic fuel injection period common to all cylinders and a basic fuel injection period that is common to all cylinders according to the sensor detection value. A means for calculating each injection start timing, a means for determining whether or not it is idling, and a feedback correction amount required so that the engine rotation speed for each cylinder becomes a predetermined target rotation speed during idling are learned. A fuel injection control device for a diesel engine, comprising means for correcting the basic injection start timing based on the learning correction amount even under operating conditions other than idling.