JP2002038998A - Diesel engine fuel injection system - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To accurately correct variations in fuel injection amount during pilot injection. In a diesel engine fuel injection device that performs pilot injection, fuel injection during one cycle is divided into a plurality of substantially equal injections during idle operation every predetermined period, and rotation of each cylinder is substantially reduced. The fuel injection amount for each cylinder is controlled to increase or decrease so as to match, and the pilot fuel injection amount is determined for each cylinder based on the fuel injection amount for each cylinder at this time. As a result, variations in the pilot fuel injection amount during idle operation are accurately corrected, and noise and vibration characteristics can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art As a fuel injection nozzle of a fuel injection device for a diesel engine, a needle valve constantly urged in a valve closing direction by a return spring is operated by a pressure difference between a fuel chamber and a back pressure chamber. 2. Description of the Related Art A configuration in which the pressure in a pressure chamber is controlled using an actuator such as a solenoid valve has been widely known (see JP-A-10-18934).

In such a fuel injection nozzle, variations in the seat diameter on which the needle valve is seated and changes with time, variations in the springs of the return spring and the solenoid valve and deterioration with time, variations in the lift amount of the solenoid valve, etc. Due to the many factors described above, the fuel injection amount for each cylinder during the equal energization time varies for each cylinder or changes over time. That is, even if the energization time of each solenoid valve corresponding to each cylinder is fixed, the fuel injection amount for each cylinder may vary for each cylinder or change over time.

To cope with such a variation in the fuel injection amount, Japanese Patent Laid-Open Publication No. Hei 6-101532 discloses
Focusing on the fact that the non-uniform rotation of each cylinder during idling operation is caused by the variation of the fuel injection amount, the fuel injection amount of the fuel injection nozzle for each cylinder is controlled so that the non-uniform rotation during idling operation is eliminated. Is disclosed, and the fuel injection amount of the fuel injection nozzle in an operation state other than the idle operation is corrected based on the result.

[0005]

However, the fuel injection amount determined according to the energization time of the solenoid valve includes an error, and this error is proportional to the energization time of the solenoid valve as shown in FIG. Not in a relationship.

Therefore, in the fuel injection amount correction method disclosed in Japanese Patent Application Laid-Open No. 6-101532, the fuel injection amount at the time of idling can be accurately corrected, but the other conditions that the energization time of the solenoid valve is different from that at the time of idling. For example, there is a problem that the fuel injection amount cannot be corrected in a high load region where the fuel injection amount is large, a medium to high rotation region where the pressure in the common rail is higher than idle, and a pilot injection where the fuel injection amount is very small.

[0007] The present invention has been made in view of the above problems, and in particular, noise and vibration during idling, HC
It is an object of the present invention to provide a fuel injection device for a diesel engine that accurately corrects a variation in pilot injection amount during idling operation, which greatly affects exhaust emission such as.

[0008]

According to a first aspect of the present invention, there is provided a fuel injection device for a diesel engine for performing a pilot injection, wherein a plurality of fuel injections during one cycle are performed at substantially equal intervals during idle operation every predetermined period. The injection is divided into injections, and the fuel injection amount of each cylinder is controlled to increase or decrease so that the rotation of each cylinder is substantially matched, and the pilot fuel injection amount is determined for each cylinder based on the fuel injection amount of each cylinder at this time. It is characterized by: Thus, the pilot fuel injection amount is corrected based on the fuel injection amount of each cylinder in a fuel injection state in which the rotation between the cylinders is uniform and close to the pilot fuel injection amount.

According to a second aspect of the present invention, in the first aspect of the present invention, the division of the fuel injection is performed such that one fuel injection amount is substantially equal to the pilot fuel injection amount. Features.

According to a third aspect of the present invention, in the first aspect of the present invention, a difference between a fuel injection amount for each cylinder and an average value thereof when the increase / decrease control is performed is used as a correction amount for each cylinder. It is characterized in that the calculated pilot fuel injection amount is corrected for each cylinder based on the correction amount. As a result, the pilot fuel injection amount during the idling operation is accurately aligned for each cylinder.

According to a fourth aspect of the present invention, in the first aspect of the present invention, a fuel injection amount for each cylinder when the increase / decrease control is performed or an amount obtained by subtracting a certain amount from the fuel injection amount. The pilot fuel injection amount is set for each cylinder. As a result, the pilot fuel injection amount during the idling operation is accurately aligned for each cylinder, and the ratio between the pilot fuel injection amount and the main fuel injection amount is also accurately aligned.

According to a fifth aspect of the present invention, in the first aspect of the present invention, the predetermined period is a period in which a vehicle on which the diesel engine is mounted travels a predetermined distance. As a result, the pilot fuel injection amount is corrected according to the temporal change of the fuel injection device.

According to a sixth aspect of the present invention, in the first aspect, the predetermined period is a period in which the diesel engine rotates a predetermined number of times.

According to a seventh aspect of the present invention, in the first aspect, the predetermined period is a period in which fuel injection is executed a predetermined number of times.

According to an eighth aspect of the present invention, in the first aspect, the predetermined period is a period in which a product of a coefficient determined according to the fuel injection pressure and the number of times of injection reaches a predetermined value. Features. The fuel injection amount changes with the aging of the fuel injection device. Thus, the pilot fuel injection amount is corrected according to the degree of the temporal change of the fuel injection device.

[0016]

According to the present invention, the pilot fuel injection amount is corrected based on the fuel injection amount of each cylinder in the fuel injection state in which the rotation between the cylinders is uniform and close to the pilot fuel injection amount. In addition, the variation in the pilot fuel injection amount is accurately corrected, and the noise and vibration characteristics during the idling operation can be effectively improved.

Further, according to the third or fourth aspect of the present invention, the pilot fuel injection amount during idle operation is
Since the cylinders are accurately aligned for each cylinder, noise and vibration characteristics during idle operation can be more effectively improved.

Further, when the correction amount of the pilot fuel injection amount is detected, since the fuel injection is divided into a plurality of times, the fuel injection state becomes different from the normal state, and the emission of HC or the like is temporarily stopped during that time. Although the combustion noise may increase and the combustion noise may change to give the driver a sense of incongruity, the correction amount may be changed according to the degree of the temporal change of the fuel injection device as in the invention of claims 5 to 8. , The frequency of detecting the correction amount can be reduced to the minimum necessary.

[0019]

FIG. 1 shows the overall configuration of a diesel engine fuel injection device according to the present invention.

This fuel injection device mainly comprises a fuel tank 2
1, a low-pressure fuel supply passage 22, a supply pump 24, a high-pressure fuel supply passage 25, a common rail (accumulation chamber) 26, and a fuel injection nozzle 1 provided for each cylinder. Passage 25
, The high-pressure fuel in the common rail 26 is distributed to the fuel injection nozzles 1 for the number of cylinders.

The fuel injection nozzle 1 has a nozzle holder 15
And a needle valve 4 for opening and closing the nozzle 13 at the tip of the nozzle body 3
A piston 7 connected to the base end of the needle valve 4 via an intermediate member 6, a return spring 14 for urging the needle valve 4 through the intermediate member 6 in the valve closing direction, and a solenoid 10a
And an electromagnetic valve 10 as an actuator having a valve element 10b. The fuel is supplied to a fuel chamber 5 surrounding the tip of the needle valve 4 through a fuel passage 2, and the back pressure is A chamber 8 is defined, and the back pressure chamber 8 communicates with the fuel passage 2 via a charging orifice 9. The back pressure chamber 8 is connected to the low pressure chamber 1 through the discharge orifice 11.
The discharge orifice 11 is connected to the solenoid valve 1.
The zero valve element 10b opens and closes. The fuel passage 2 is connected to a common rail 26, and the low-pressure chamber 12 is opened to the fuel tank 21 via the drain passage 16.

In the fuel injection nozzle 1 of this embodiment, the diameter of the piston 7 is larger than the diameter of the needle valve 4. Therefore, even when the needle valve 4 is lifted, the pressure of the needle valve 4 with respect to the fuel chamber 5 is maintained. The pressure receiving area of the piston 7 with respect to the back pressure chamber 8 is larger than the area. Also, the return spring 14
Is provided mainly for seating the needle valve 4 on the nozzle seat portion 17 and closing the injection port 13 when the engine is stopped.

Here, the basic operation of the fuel injection nozzle 1 will be described. When the solenoid valve 10 is in the OFF state, the high pressure fuel of the common rail 26 is guided to both the fuel chamber 5 and the back pressure chamber 8. Since the pressure receiving area of the piston 7 is larger than the pressure receiving area of the needle valve 4, the needle valve 4 is in a seated state.

On the other hand, when the solenoid valve 10 is turned on and the discharge orifice 11 is opened, the pressure in the back pressure chamber 8 decreases, and the needle valve 4 starts to lift. As a result, the needle valve 4 is separated from the nozzle seat portion 17, and fuel is injected from the injection port 13 at the front end.

The fuel injection device further includes a common rail 2 for adjusting the pressure of the fuel supplied to the fuel injection nozzle 1.
A return passage 23 and a pressure control valve 31 are provided so as to return the high-pressure fuel discharged from the supply pump 24 to the low-pressure side in order to control the fuel pressure Pr in the fuel pump 6.

The pressure control valve 31 changes the valve opening timing of the return passage 23 during the discharge stroke of the supply pump 24 in accordance with a signal from the control unit 41, and adjusts the amount of fuel discharged to the common rail 26. The fuel pressure Pr is variably controlled. The fuel injection rate of the fuel injection nozzle 1 changes depending on the fuel pressure Pr, and the higher the fuel pressure Pr, the higher the fuel injection rate.

The control unit 41 includes a signal from the pressure sensor 32 for detecting the fuel pressure Pr, an accelerator opening sensor 33, a crank angle sensor 34 (for detecting the engine speed Ne and the crank angle), and a cylinder discrimination sensor 35. (Generating a cylinder discrimination signal) and a signal from the water temperature sensor 36 are input.

The control unit 41 calculates a target fuel injection amount and a target pressure of the common rail 26 according to the engine speed Ne and the engine load (accelerator opening).
The fuel pressure Pr in the common rail 26 is feedback-controlled through the pressure control valve 31 so that the fuel pressure Pr detected by the pressure sensor 32 matches the target pressure. Further, in addition to controlling the ON time of the solenoid valve 10 in accordance with the calculated target fuel injection amount, control for correcting a pilot fuel injection amount described later is executed as necessary.

As shown in FIG. 2, the diesel engine of this embodiment performs a so-called pilot injection for injecting a small amount of fuel prior to the main injection.

Here, the correction of the pilot fuel injection amount will be described.

First, the fuel injection during one cycle of all the cylinders during the idling operation at predetermined intervals is divided into several times as shown in FIG. 3 for a predetermined time, and the fuel injection amount of each time becomes equal. Set as follows. FIG. 3 is an example of a case where the image is equally divided into four times.

At this time, if there is a variation in the actual fuel injection amount for each cylinder, the rotation of each cylinder becomes non-uniform as shown in FIG. In this case, the rotation of each cylinder is obtained by measuring each rotation measurement period indicated by A, B, C, and D in FIG. 4, that is, during a predetermined crank angle, and calculating an average value, as shown in FIG. Then, the fuel injection amount for each cylinder is increased or decreased so that the rotational speeds of the cylinders are equal to each other.
That is, the energization time of the solenoid valve 10 corresponding to the target fuel injection amount is corrected for each cylinder so that the rotation of each cylinder becomes uniform. Here, the rotation speed of each cylinder may be determined as the maximum value of each rotation measurement period. FIGS. 4 and 5 show an example of a four-cylinder diesel engine.

The solenoid valve 10 corrected for each cylinder
The correction amount P is calculated for each cylinder using the current supply time as a control parameter, and the current supply time of each solenoid valve 10 of each cylinder at the time of pilot injection is corrected by the correction value P.

FIG. 6 is a flowchart relating to the correction of the pilot fuel injection amount described above.

In step 11, it is determined whether or not it is time to detect the correction amount P. If so, in step 12, whether or not the engine is currently idling and the engine has been warmed up is determined. If it is determined that the engine is idling and after warming up, the process proceeds to step S13.

The reason why the above control parameters are detected after warming-up is that when the engine is cold, the friction of the engine is large and the fuel injection is divided into several injections. Per fuel injection amount,
This is because the difference from the pilot fuel injection amount becomes large, and the detection accuracy of the correction amount P cannot be ensured.

Next, in step 13, the fuel injection is performed a predetermined number of times and the fuel injection amount of each time is made equal, that is, the energization time of each solenoid valve 10 in each time is made equal. At this time, the rotation speed of each cylinder is measured.

In step 15, it is determined whether or not the variation width of the rotational speed between the cylinders is equal to or greater than a predetermined value. For example, it is determined whether or not the difference in rotation speed between the cylinder having the minimum rotation speed and the cylinder having the maximum rotation speed is equal to or greater than a predetermined value.

If it is determined that the variation range of the rotational speed is equal to or greater than the predetermined value and the rotational speed between the cylinders is determined to be non-uniform, step 1 is executed.
In the cylinders having higher rotations than the average value of all cylinders, the fuel injection amount is reduced by shortening the energization time of the solenoid valve 10 per one fuel injection, and conversely, the rotation of the cylinders is higher than the average value of all cylinders. In a low cylinder, the amount of fuel injection is increased by increasing the energizing time of the solenoid valve 10 per fuel injection. Here, the average value of all the cylinders is an average value of the respective rotation speeds measured during the rotation measurement periods A, B, C, and D (see FIG. 4).

When the rotation among the cylinders becomes uniform, at step 17, the energizing time of the solenoid valve 10 of each cylinder at this time is set as a control parameter for each cylinder, and the average energizing time of the solenoid valve is
That is, the difference between the average energization time of the solenoid valve per one fuel injection and the control parameter in each cylinder in the state where the rotation between the cylinders is uniform is calculated for each cylinder, and the correction amount P is calculated. It is stored in the control unit 41, and returns to the normal injection consisting of the pilot injection and the main injection in step 18.

Until the next correction amount P is detected, the solenoid valve energizing time during pilot injection is corrected for each cylinder based on the correction amount P calculated for each cylinder.

In step 11, when the correction amount P is detected, the integrated value of the engine speed is set to a predetermined value when the vehicle travel distance exceeds a predetermined value with reference to the previous control parameter detection. It is assumed that the determination is made on the basis of any one of the time when the number of fuel injections exceeds the predetermined value and the time when the number of times of fuel injection by the fuel injection nozzle exceeds a predetermined value.

As described above, the fuel injection is divided into several injections, the fuel injection amount of each injection is made equal, and the correction value P is calculated with the fuel injection amount per injection approaching the pilot fuel injection amount. Therefore, during idle operation, the pilot fuel injection amount can be accurately corrected for each cylinder, and the pilot fuel injection amount between each cylinder becomes uniform.
Noise and vibration characteristics during idle operation can be effectively improved.

The division of the number of times of fuel injection is desirably set so that the amount of fuel injected at one time approaches the pilot fuel injection amount as much as possible.

In the first embodiment, instead of using the energizing time of the solenoid valve 10 for each cylinder as a control parameter, the fuel injection nozzle of each cylinder in a state where rotation between cylinders is uniform is used. May be used.

Next, a second embodiment of the present invention will be described with reference to the flowchart of FIG. The second embodiment is different from the first embodiment in that when each fuel injection is divided into several injections, the fuel injection amount of each injection is made substantially equal to the pilot fuel injection amount. Only two points, that is, either the energization time of each solenoid valve 10 per one fuel injection or the time obtained by uniformly adding or subtracting a predetermined value from these energization times as the correction amount for each cylinder, are used. The first mentioned above
This is different from the embodiment.

That is, steps 23 and 27 corresponding to steps 13 and 17 in FIG.
Are different from those of the first embodiment described above.

That is, in step 23, the number of fuel injections is set so that the fuel injection amount of each time becomes as close as possible to the pilot fuel injection amount.

In step 27, the control unit 41 determines which one of the control parameters, the energizing time of each solenoid valve 10 per fuel injection, and the correction value obtained by uniformly adding or subtracting a predetermined value from these energizing times. Is stored as the correction amount Q.

Until the next correction amount is detected, the value of the correction value Q itself is changed to the value of each solenoid valve 1 at the time of pilot injection.
Used as 0 energizing time.

In the second embodiment, the ratio between the pilot fuel injection amount and the main fuel injection amount during the idling operation can be accurately set for each cylinder.

When the variation in friction among the engines is small, the pilot fuel injection amount itself as well as the pilot fuel injection ratio between the pilot fuel injection amount and the main fuel injection amount during idling is compared with the first embodiment. More accurate correction can be made.

Therefore, it is sufficient to determine which of the first and second embodiments is to be applied according to the friction variation of each engine during the idling operation.

In the second embodiment, at step 27, either the commanded injection amount per fuel injection or a correction value obtained by uniformly adding or subtracting a predetermined value from the commanded injection amount is set in the control unit. 41, and stores the correction amount R until the next detection of the correction amount.
It is also possible to control each solenoid valve 10 at the time of pilot injection with the value itself.

Next, a third embodiment of the present invention will be described with reference to the flowchart of FIG. The third embodiment differs from the first embodiment only in the method of determining the correction amount detection time, that is, only in step 31 corresponding to step 11 in FIG.

That is, in step 31, the product of the number of times of fuel injection and the coefficient K determined as shown in FIG. 9 by the fuel pressure Pr in the common rail 26 indicating the pressure of the fuel supplied to the fuel injection nozzle 1 at that time. Is greater than a predetermined value, the correction amount P of the pilot fuel injection amount during idling operation
Is detected.

The change in the fuel injection amount due to the aging of the fuel injection nozzle 1 is mainly due to the change in the diameter of the nozzle seat 17 due to the wear or deformation of the nozzle seat 17.
In addition, in response to the fact that the wear and deformation increase as the fuel pressure Pr in the common rail 26 increases, as shown in FIG. 9, the coefficient K is set to increase as the fuel pressure Pr increases. ing.

According to the third embodiment, it is possible to predict the time at which the degree of change over time of the fuel injection amount of the fuel injection nozzle 1 becomes large, so that the correction amount P of the fuel injection amount can be detected. The frequency of the operation can be reduced to a necessary minimum.

When the correction amount is detected,
Since the fuel injection is divided into a plurality of times, the fuel injection state becomes unusual, the emission of HC and the like increases during that time, and the combustion noise changes to give the driver an uncomfortable feeling. According to the third embodiment, the frequency can be reduced.

[Brief description of the drawings]

FIG. 1 is a configuration explanatory view of an entire fuel injection device showing a first embodiment according to the present invention.

FIG. 2 is an explanatory diagram showing a fuel injection pattern in a normal idle state.

FIG. 3 is an explanatory diagram showing a fuel injection pattern when detecting a correction amount for correcting a pilot fuel injection amount.

FIG. 4 is an explanatory diagram showing the rotation state of the engine when the rotation of each cylinder varies.

FIG. 5 is an explanatory diagram showing a rotation state of an engine when rotation of each cylinder is uniform.

FIG. 6 is a flowchart illustrating a routine for detecting a correction amount in the first embodiment.

FIG. 7 is a flowchart illustrating a routine for detecting a correction amount according to the second embodiment.

FIG. 8 is a flowchart illustrating a routine for detecting a correction amount according to the third embodiment.

FIG. 9 is a correlation diagram between a fuel pressure Pr and a weight coefficient K for the fuel pressure Pr.

FIG. 10 is a correlation diagram showing an error of a fuel injection amount with respect to an energization time of a solenoid valve.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Fuel injection nozzle 4 ... Needle valve 8 ... Back pressure chamber 10 ... Solenoid valve 13 ... Fuel injection hole

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02M 47/02 F02M 47/02 F-term (Reference) 3G066 AA07 AB02 AC09 BA22 BA26 CC06U CE22 DA01 DA09 DB04 DB07 DC04 DC05 DC09 DC14 DC18 3G301 HA02 JA15 JA17 JA26 JA37 KA05 KA07 LB11 LC01 MA11 MA23 NA01 NA06 NC01 NE01 NE06 PB03A PB08A PE01A PE03A PE05A PE08A PF03A

Claims (8)

[Claims] In a fuel injection device for a diesel engine that performs pilot injection, during idle operation every predetermined period, fuel injection in one cycle is divided into a plurality of substantially equal injections, and rotation for each cylinder is performed. A fuel injection device for a diesel engine, wherein a fuel injection amount for each cylinder is controlled to increase or decrease so as to substantially match each other, and a pilot fuel injection amount is determined for each cylinder based on the fuel injection amount for each cylinder at this time. 2. The fuel injection device for a diesel engine according to claim 1, wherein the division of the fuel injection is performed such that a single fuel injection amount is substantially equal to a pilot fuel injection amount. 3. A difference between a fuel injection amount for each cylinder and an average value when the increase / decrease control is performed is calculated as a correction amount for each cylinder, and a pilot fuel injection amount for each cylinder is calculated based on the correction amount. The fuel injection device for a diesel engine according to claim 1, wherein 4. A pilot fuel injection amount for each cylinder, wherein a fuel injection amount for each cylinder when the increase / decrease control is performed or an amount obtained by subtracting a fixed amount from these fuel injection amounts is set. 2. The fuel injection device for a diesel engine according to 1. 5. The diesel engine fuel injection device according to claim 1, wherein the predetermined period is a period in which a vehicle on which the diesel engine is mounted travels a predetermined distance. 6. The diesel engine fuel injection device according to claim 1, wherein the predetermined period is a period in which the diesel engine rotates a predetermined number of times. 7. The fuel injection device for a diesel engine according to claim 1, wherein the predetermined period is a period in which fuel injection is performed a predetermined number of times. 8. The fuel injection device for a diesel engine according to claim 1, wherein the predetermined period is a period in which a product of a coefficient determined according to a fuel injection pressure and the number of times of injection reaches a predetermined value.