JPH0778375B2 - Fuel injection control device for diesel engine - Google Patents

Description

The present invention relates to a fuel injection control device for a diesel engine.

(Prior Art) Conventionally, in a diesel engine for an automobile, etc., there is one that electronically controls a fuel injection amount and the like for each cylinder in order to suppress vibration during idling.

As such a control device, the feedback correction amount of the valve opening engine is obtained based on the deviation between the idle speed detected for each cylinder and the target speed so that the idle speed becomes a predetermined target speed. There has been a technique in which the idle speed control is performed for each cylinder, and the feedback correction amount is learned to correct the variation in the fuel injection amount among cylinders even under no-load operating conditions other than during idle (for example, JP-A-62-32254). (See the official gazette).

(Problems to be Solved by the Invention) In such a diesel engine that controls the fuel injection amount for each cylinder, if the valve opening pressure of the injection nozzle facing the combustion chamber changes over time and changes, misfire is caused and whitening occurs. Smoke may increase or knocking sound (combustion sound) may increase.

When the valve opening pressure (spring set load, etc.) of the injection nozzle decreases, the fuel injection starts earlier than in the normal state, and when the valve opening pressure increases, the fuel injection timing tends to be delayed. . However, the conventional correction of the fuel injection amount is
It is controlled by adjusting the injection end timing while keeping the injection start timing unchanged.

For example, when the rotational speed of a certain cylinder is higher than the target during idling and the fuel injection amount of the cylinder is reduced and corrected, the injection end timing is advanced. At this time, if the valve opening pressure of the injection nozzle is lowered due to deterioration, the fuel injection start timing of that cylinder is earlier than that of the other cylinders.
Even if the end time is advanced, this point is not corrected, and thus combustion noise still tends to be large.

Further, when the rotational speed is lower than the target and the fuel injection amount is corrected to increase, if the valve opening pressure is high, the injection start timing is delayed compared to the other cylinders, and the end timing is also delayed. The low rotation speed of the cylinder reflects instability of combustion, and no matter how much the injection amount is increased, the improvement effect of combustion is low unless the injection timing is advanced. Further, in such a cylinder having a high valve opening pressure, since the injection timing is always delayed, deterioration of combustion and misfire are likely to occur when the engine is at a low temperature.

On the other hand, conventionally, the cylinder-by-cylinder correction amount at idle is reflected only during no-load operation, so that the variation in fuel injection amount by cylinder causes a torque decrease at the maximum injection amount,
Sometimes smoke increased.

The present invention has been proposed to solve such a problem, and improves the combustion and reduces noise by feedback controlling the combustion injection start timing and the injection period for each cylinder during idle operation. The purpose of this study is to reliably prevent the occurrence of smoke by reflecting the results of learning at times other than idle operation.

(Means for Solving the Problems) As shown in the first drawing, the present invention is directed to a fuel injection pump in which the injection start timing and the injection end timing of fuel are variably controlled, and a sensor for detecting an operating state quantity of an engine (for example, Sensor that detects the accelerator pedal opening corresponding to the engine load
21, a sensor 22) for detecting the engine speed, and means 24, 23 for calculating a basic injection start timing and a basic injection period of fuel common to all cylinders from the fuel injection pump in accordance with the sensor detection value. Means 25 for determining whether or not the engine is idle, and for each cylinder when idle, when the engine speed is higher than a predetermined target engine speed, the fuel injection start timing of that cylinder is delayed from the basic injection start timing. Together with the injection period shorter than the basic injection period,
Similarly, when it is low, the feedback control means 28 for correcting the injection start timing earlier than the basic injection start timing and correcting the injection period to be longer than the basic injection period, and the feedback correction amount for these basic injection start timing and injection period are learned. Means 26 and means 27 for correcting the basic injection start timing and the basic injection period of the corresponding cylinder on the basis of this learning correction amount even under operating conditions other than idling.

(Operation) In the present invention, the feedback control for each cylinder during idling is performed by adjusting the injection start timing at the same time as the fuel injection period.

When the feedback speed is higher than the target,
The fuel injection amount is reduced, but at the same time, the valve opening pressure of the needle valve of the fuel injection nozzle is low, and it is judged that the injection start timing is too early,
The injection amount is reduced by delaying the injection start timing and shortening the fuel injection period. As a result, the rotation speed is controlled so as to match the target value, the fuel injection start timing of the cylinder becomes appropriate, and combustion noise can be prevented from increasing.

When the fed back rotation speed is lower than the target, the fuel injection amount is increased, but at the same time, it is determined that the valve opening pressure of the injection nozzle is high and the injection start timing is delayed, and the injection start timing is advanced. Increase fuel injection amount. Therefore, this not only controls the rotational speed so as to match the target value, but also reliably prevents misfire due to the delay of the injection timing such as when the engine temperature is low.

On the other hand, based on the learning value of the feedback correction amount at the time of idling, even during the operation other than idling, by correcting the fuel injection start timing and the injection amount for each cylinder, it is possible to eliminate the variation in the fuel injection for each cylinder, It is possible to accurately suppress the amount of smoke generated at the time of maximum injection in the entire cylinder.

(Embodiment) An embodiment of the present invention will be described below with reference to the accompanying drawings.

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

The plunger 7 of the plunger pump 3 has the same number of suction grooves 8 as the cylinders of the engine at the tip and a face cam 9 having the same number of cam peaks at the other end. While rotating, it goes over the roller 11 arranged on the roller ring 10 and reciprocates by a predetermined cam lift.

Therefore, the plunger 7 reciprocates while rotating, and the fuel sucked into the plunger chamber 12 from the suction groove 8 in association with this rotational reciprocating motion is delivered from the unillustrated distribution port of each cylinder communicating with the plunger chamber 12. It is pumped through a valve to an injection nozzle facing the combustion chamber.

A fuel return passage 13 that connects the feed pump chamber 5 and the plunger chamber 12 is formed in order to control the fuel injection timing and injection amount, and a high-speed response solenoid valve 14 is formed in the middle of the fuel return passage 13. Is intervening.

The solenoid valve 14 opens the plunger chamber 12 when the valve is opened, and is closed by a drive pulse in a predetermined cycle in the discharge stroke of the plunger pump 3 according to the operating conditions of the engine.

The injection of fuel is started by closing the solenoid valve 14 during the compression stroke of the plunger 7, and the injection is ended by opening the solenoid valve 14. Therefore, the opening timing of the solenoid valve 14 causes the fuel injection start timing to The injection amount is controlled according to the valve closing period. During the compression stroke of the plunger 7, the solenoid valve 14
If the valve is opened once, pilot injection can be performed prior to the main injection of fuel.

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

FIG. 3 shows the details of the control unit 19, which is composed of a microcomputer composed of input / output circuits (I / O) 41, ROM 42, RAM 43, and CPU 44, and each means 23 shown in FIG.
It has ~ 28 functions.

In the input / output circuit 41, one reference pulse 31 per revolution of the injection pump and 36 scale pulses 32 per revolution of the injection pump are detected in order to detect the basic value of the operating state quantity of the engine.
Not only the sensor 33 that detects the accelerator pedal opening as an amount equivalent to the engine load, but also sensors that detect other operating conditions (fuel temperature sensor 34, water temperature sensor 35, idle switch 36, solenoid valve 14 actual closing start Signals from a sensor 37 that detects the timing and the valve closing period and a sensor 38) that detects the actual injection start timing are input.

The CPU44 takes in information from the input / output circuit 41 according to the program stored in the ROM42, performs various arithmetic processing, and outputs data (valve closing timing and valve closing period) for controlling the solenoid valve 14 to the input / output circuit. Set to 41. RAM43 is CPU
It is used to temporarily save the data related to 44 arithmetic processes. The input / output circuit 41 outputs a drive pulse for the solenoid valve 14 based on the data output from the CPU 44.

Next, the operation of the CPU 44 will be described based on the flowchart of FIG.

In step 50, it is determined whether the engine is in the idle stable state.
This is determined by whether or not the difference between the idle speed and the idle speed for each cylinder is less than or equal to a set value. If it is determined in step 50 that the engine is in the idle stable state, the feedback correction amount ΔAvi of the basic injection amount for each cylinder at that time is learned in step 57, and the value of ΔAvi is stored in the memory in step 58.

If it is determined in step 50 that the engine is not in the stable idle state, the engine speed N and the accelerator opening Acc are read in step 51, and it is determined in step 52 whether or not the amount is greater than the idle injection amount. The characteristics shown in are stored in the ROM 42, and the correction coefficient K is calculated by a calculation formula or a map.
To calculate.

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

In step 54, the learning correction amount for each cylinder ΔAvi stored in step 58 is read out, and in step 55, the basic injection amount Av _M
And the learning correction amount for each cylinder ΔAvi multiplied by the correction coefficient K are added to obtain the determined injection period Avi, and the basic injection start timing Itm and the learning correction amount for each cylinder ΔAvi multiplied by the correction coefficient K are added. Then, the determined injection start timing Iti is obtained, and the determined injection period Av and the determined injection start timing It are RA in step 56.
Store in the specified address of M41 and finish.

Explaining this with reference to FIG. 8, the drive pulse for opening the solenoid valve 14 is different for each cylinder when the nozzle opening pressure is high with respect to the basic injection period and the basic injection start timing corresponding to various conditions of the engine. The learning correction amount ΔAvi becomes positive and the rising of the drive pulse is accelerated to correct the start of the needle valve lift of the nozzle without delay, while when the nozzle opening pressure decreases, the learning correction amount for each cylinder ΔAvi becomes negative. Therefore, the rise of the drive pulse is delayed, and the needle valve lift of the nozzle is corrected so as not to start too early.

When the fed-back idle speed is higher than the target, the fuel injection amount of the cylinder is reduced, but at the same time, the valve opening pressure of the needle valve of the fuel injection nozzle is low, and it is judged that the injection start timing is too early. The injection start timing is delayed from the fuel injection start timing, and the fuel injection period is corrected to be shorter than the basic fuel injection period. As a result, the idle speed of the cylinder is controlled so as to match the target value, the fuel injection start timing becomes appropriate, and combustion noise can be prevented from increasing.

Further, when the idle speed is lower than the target, the fuel injection amount is increased, but at the same time, the valve opening pressure of the injection nozzle is high,
It is determined that the injection start timing is delayed, and the injection start timing is made earlier than the basic fuel injection start timing and the fuel injection period is made longer than the basic fuel injection period. Therefore, this not only controls the rotational speed so as to match the target value, but also reliably prevents misfire due to the delay of the injection timing such as when the engine temperature is low.

When the nozzle valve opening pressure changes, the start of the needle valve lift is affected and becomes faster or slower by the amount of valve opening pressure change.However, regarding when the needle valve lift ends, the nozzle valve opening pressure changes. Is not affected by. As a result, the same amount of fuel is supplied to all the cylinders, the torque becomes uniform among the cylinders, and engine vibration is suppressed.

Even if a mixture that is rich enough to exceed the smoke limit is supplied to any one of the cylinders due to variations in the maximum injection amount in the high load range, the overall smoke amount increases. However, by learning the feedback correction amount at the time of idling and learning-correcting the injection start timing for each cylinder up to the maximum injection amount, the variation in the maximum injection amount that occurs in some cylinders in the smoke discharge region is eliminated. Suppress the amount of smoke as a whole. Incidentally, if the shape of the face cam 9 is formed so as to always have an equal oil feeding rate, 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, in which an air-fuel ratio sensor 39 attached to an exhaust manifold collecting portion is provided to detect an excess air ratio of each cylinder and change a fuel injection start timing. Is.

As shown in the flowchart in FIG. 10, in step 55, the correction coefficient K is added to the correction amount ΔAvi for each cylinder during the basic injection period Av _M.
And then add the correction amount ΔAv _F according to the cylinder-by-cylinder air-fuel ratio to obtain the determined injection period Avi, and
Correction coefficient K for basic injection start timing Itm and correction amount ΔAvi for each cylinder
Then, the determined injection start timing Iti is obtained by adding the value obtained by multiplying by, and further adding the correction amount ΔIt _AF according to the cylinder-by-cylinder air-fuel ratio.

FIG. 11 shows a map for obtaining the target air-fuel ratio λmap using the rotation speed and the accelerator opening as parameters. Based on the difference between the value λmap and the actual air-fuel ratio λt determined in this way, FIG.
The injection amount correction amount ΔAv _F and the injection timing correction amount Δ
It is designed to ask for each Avi.

According to this example, the control of the injection period and the injection start timing for each cylinder is performed together with the learning correction at the time of idling so that the predetermined excess air ratio is not exceeded, so that the variation in the maximum injection amount in the high load range is suppressed more accurately. However, the amount of smoke in the entire cylinder is suppressed.

As described above, according to the present invention, the feedback control for each cylinder at the time of idling is performed by adjusting the injection start timing at the same time as the fuel injection period, and when the rotation speed is higher than the target, the fuel injection is performed. Although the amount is reduced, at the same time, the valve opening pressure of the needle valve of the fuel injection nozzle is low, it is judged that the injection start timing is too early, and the injection amount is reduced by delaying the injection start timing and shortening the fuel injection period. As a result, the engine speed is controlled to match the target value, the fuel injection start timing for that cylinder is also optimized, and the increase in combustion noise during idling can be prevented, while when the engine speed is lower than the target, Although the injection amount is increased, at the same time, it is determined that the valve opening pressure of the injection nozzle is high and the injection start timing is delayed, so the injection start timing is advanced and the fuel injection period is lengthened. As a result, not only is the rotational speed controlled to match the target value, but it is possible to reliably prevent misfire due to a delay in the injection timing, such as when the engine temperature is low. Further, based on the learning value of the feedback correction amount at the time of idling, the fuel injection start timing and the injection amount are corrected for each cylinder even during the operation other than the idling, so that the variation of the fuel injection for each cylinder is eliminated, As a whole, the amount of smoke generated at the time of maximum fuel injection can be accurately suppressed.

[Brief description of drawings]

1 is a sectional view of an injection pump according to an embodiment of the present invention, FIG. 3 is a block diagram of a control unit, FIG. 4 is a flow chart for explaining a control operation, and FIGS. FIG. 8 is a characteristic diagram showing the content of each value used in the control operation. FIG. 9 is a block diagram of a control unit showing another embodiment, FIG. 10 is a flow chart for explaining the control operation, and FIGS. 11 to 13 are characteristic diagrams showing the contents of each value used in the control operation. is there. 1 ... Pump housing, 3 ... Plunger pump, 7
...... Plunger, 9 ...... Face cam, 12 ...... Plunger chamber, 13 ...... Fuel return passage, 14 ...... Solenoid valve, 16 ...... Solenoid valve drive circuit, 19 ...... Control unit, 21 ...... Accelerator position sensor , 22 ... rotation speed sensor, 23 ... basic injection period calculation means, 24 ... basic injection start timing calculation means, 25 ...
… Idle judgment means, 26 …… Cylinder correction amount learning means,
27 ... Injection period correction means, 31 ... Reference pulse generation means, 32 ... Scale pulse generation means, 41 ... Input / output circuit, 42 ... ROM, 43 ... RAM, 44 ... CPU.

Claims (1)

[Claims] 1. A fuel injection pump in which fuel injection start timing and injection end timing are variably controlled, a sensor for detecting an engine operating state amount, and all cylinders from the fuel injection pump according to the sensor detection value. A means for calculating a common fuel basic injection start timing and a common injection engine, a means for determining whether or not the engine is idling, and an engine speed higher than a predetermined target speed for each cylinder at the time of idling. When the fuel injection start timing of the cylinder is delayed from the basic injection start timing and the injection period is shorter than the basic injection period, when it is also low, the injection start timing is advanced from the basic injection start timing and the injection period is shorter than the basic injection period. Feedback control means for making corrections to increase the length and feedback compensation for these basic injection start timing and injection period A means for learning the amount, and means for correcting the basic injection start timing and the basic injection period of the corresponding cylinder based on the learning correction amount even under operating conditions other than idling, are provided for the diesel engine. Fuel injection control device.