JP2003222048A - Multi-cylinder diesel engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multi-cylinder diesel engine for suppressing emission. <P>SOLUTION: The multi-cylinder diesel engine is provided with an injector 3 for feeding fuel by pilot injection to a combustion chamber according to a current application condition, a means for controlling an EGR rate in sucked air, and a controller 7 for controlling the condition for applying current to the injector 3 according to the EGR rate and the operating conditions by using the flow rate control means. The controller 7 corrects the timing for applying current to the injector 3 of each cylinder on the basis of the EGR rate, so that the combustion starting timing of fuel fed by pilot injection, which is different from each other between cylinders, is unified at a crank angle. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-cylinder diesel engine, and more particularly to an improvement of a multi-cylinder diesel engine that performs pilot injection of fuel.

[0002]

2. Description of the Related Art As a technique for detecting the combustion state of an internal combustion engine and controlling the air-fuel mixture according to the combustion state, Japanese Patent Laid-Open No. 6-1
There is a technique described in No. 01518.

This is to detect the fluctuation in the rotation of the internal combustion engine by a combustion state detecting means such as a knock sensor and correct the air-fuel mixture to improve the combustion state when the combustion state is not proper.

[0004]

However, in this prior art, the combustion state is detected by the combustion state detecting means to correct the air-fuel mixture, and the combustion start timing in each cylinder is determined. There is no disclosure of improving the combustion state by detecting and correcting. Therefore, there is a problem that the combustion start timing (ignition timing) in each cylinder varies, and the equivalence ratio of the fuel differs among the cylinders, resulting in deterioration of exhaust emission and deterioration of noise and vibration. .

The present invention has been made in order to solve the above problems of the present situation, and an object thereof is to provide a multi-cylinder diesel engine in which the ignition timing with respect to the crank angle is the same in all cylinders. .

[0006]

A first aspect of the present invention is an injector for pilot-injecting fuel into a combustion chamber on the basis of an energization condition, and means for controlling an EGR amount recirculated into intake air.
In a multi-cylinder diesel engine equipped with a controller that controls the energization condition to the injector according to the EGR amount and the operating condition by using the flow rate control means, the controller starts combustion of pilot-injected fuel different for each cylinder. EG so that the timing is the same in crank angle
The timing of energizing the injector of each cylinder is corrected based on the R ratio.

A second aspect of the present invention is the fuel cell system according to the first aspect, further comprising a pressure sensor for detecting a fuel combustion start timing in the combustion chamber, wherein the controller receives a signal from the pressure sensor and injects each cylinder. The ignition delay period from the start of energization to the start of combustion is calculated for each EGR rate, and the timing of starting energization of the injector of each cylinder is corrected based on the difference between the detected ignition delay period and the target ignition delay period.

[0008]

According to the first aspect of the invention, the timing of energizing the injectors is corrected based on the EGR rate so that the combustion start timing of the pilot injected fuel in each cylinder is the same in crank angle. The combustion start timing is the same with respect to the crank angle, and the combustion state in all the cylinders can be made equal and good. Therefore, it is possible to suppress the deterioration of exhaust emission and the deterioration of noise / vibration due to the difference in the equivalence ratio of the fuel between the cylinders, and it is possible to improve the output because the smoke performance is improved.

A second invention is provided with a pressure sensor for detecting a fuel combustion start timing in the combustion chamber, and the controller is
The signal from the pressure sensor is input, and the ignition delay period from the start of power supply to the injector of each cylinder to the start of combustion is set to EGR.
The timing for starting the energization to the injector of each cylinder is corrected based on the difference between the detected ignition delay period and the target ignition delay period, which is calculated for each rate, so that the combustion start timing can be accurately controlled.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION An example of the structure of a four-cylinder diesel engine to which the fuel injection device of the present invention is applied is shown in FIGS. 1 and 2.

In the figure, 1 is a cylinder block, 2 is a cylinder head, 3 is an injector for injecting pilot fuel and main fuel into a combustion chamber, 4 is a common rail for accumulating high-pressure fuel and supplying high-pressure fuel to the injector 3, Reference numeral 5 denotes a supply pump that feeds high-pressure fuel to the common rail 4, and reference numeral 6 denotes a piezoelectric knock sensor that detects pressure fluctuations in the cylinder.

An ECU (controller) 7 for controlling the operation of the diesel engine as shown in FIG. 3 is installed.
The ECU 7 outputs the output of the knock sensor (pressure sensor) 6,
An output signal of an EGR control valve (flow rate control means) opening degree (not shown) for detecting an EGR (exhaust gas recirculation) rate in the air-fuel mixture is input. Further, in order to detect the operating state, the ECU 7 is input with the depression amount (or throttle valve opening) of an accelerator pedal (not shown), the crank angle detected by the angle sensor, the engine speed etc. by the rotation sensor.

The ECU 7 serves as a basis for fuel injection output to the injector 3 by calculating the EGR rate in the air-fuel mixture from, for example, the accelerator pedal depression amount and the opening degree of the EGR control valve, the operating state of which is detected. Correct the energization conditions (time, period). Also, the heat quantity and pressure in the cylinder are calculated from the fuel injection quantity, the accelerator pedal depression quantity, and the crank angle.

Further, the ECU 7 of the present invention includes a knock sensor 6
The timing for energizing the injector 3 is corrected so that the combustion start timing of the pilot fuel, which is different from each cylinder and is detected from the output of the above, becomes the same at the crank angle based on the EGR rate.

As will be described later, the combustion start timing is different between the cylinders even if electricity is applied at the same timing at the crank angle due to a difference in the characteristics of the combustion chamber and the like, which causes deterioration of exhaust emission and deterioration of vibration and noise. Invite.

The injector 3 and the supply pump 5
Is controlled by the output signal of the ECU 7.

The ECU 7 stores the difference between the measured pilot fuel injection amount characteristic of the injector 3 and the target characteristic (or median value characteristic). This information is represented by an energization time map as shown in FIG. 4, and in FIG. 4, the minimum energization time (MDP; Minimum Driving Pulses).
(e) shows the ignition delay from the time when the fuel injection signal to the injector 3 is transmitted until the fuel actually starts combustion, and the slope of the curve shows the sensitivity of the fuel injection amount to the energization time. . This characteristic is stored for each common rail pressure.

FIG. 5 is a timing chart showing the crank angle from the power supply command to the injector 3 output from the ECU 7 in one cylinder to the actual injection and ignition of pilot fuel.

Crank angle α advanced from top dead center TDC
At 1, the energization signal to the injector 3 is output, but the actual injection of pilot fuel is delayed by the angle α2 after the angle α1.
Is jetted at. Ignition of the fuel is further delayed, starting at angle α3 after TDC. This ignition delay, that is, the minimum energization time MDP is mainly due to the delay from the transmission of the energization signal to the injector 3 to the fuel injection and the EGR rate.

As shown in FIG. 5, when the fuel is ignited, heat is generated in the cylinder, the pressure in the cylinder rises due to the rise of the piston, and the pressure is decreasing past TDC. The internal pressure also rises sharply due to combustion.

As described above, the fuel injection timing and the combustion start timing in the cylinder are delayed from the start of energization of the injector 3, but the delay amount is different for each cylinder, that is, the equivalence ratio is different. Therefore, deterioration of exhaust emission and deterioration of noise and vibration will occur.

Therefore, according to the present invention, the knock sensor 6 detects the combustion start timing of each cylinder, and the combustion start timing of the pilot-injected fuel is set to the same crank angle between the cylinders according to the EGR rate. The above problem is solved by correcting the delay of the combustion start timing with respect to the target. Next, the outline of the present invention will be described with reference to FIGS.

The combustion start time delay (ignition delay) is EG
A change occurs depending on the R rate. Generally, as shown in FIG. 6, even if the energization start timing is the same, the ignition delay is small under operating conditions with a low EGR rate, and the ignition delay is large under operating conditions with a high EGR rate. Furthermore, because it changes depending on the combustion chamber specifications such as compression ratio, swirl ratio, filling efficiency, injection rate,
Even if the EGR rate is the same, as shown in FIG. 7, the ignition delay differs for each cylinder having different specifications of the combustion chamber, and the difference from the target with respect to the target ignition delay changes for each cylinder.

FIG. 8 is a graph in which the ignition delay of each cylinder for the target ignition delay characteristic shown in FIG. 7 is replaced with a pulse adjustment amount corresponding to the crank angle. The adjustment amount is made smaller than the target value, in other words, the energization start is accelerated and the target combustion start timing is corrected. On the other hand, when the ignition delay with respect to the target ignition delay characteristic is small, the pulse adjustment amount is set large and the ignition delay is corrected so as to match the target ignition delay characteristic. FIG. 9 shows the ignition delay of each cylinder after the above-mentioned correction. The characteristic of the ignition delay, which largely varies from the target ignition delay characteristic shown in FIG. 7, is corrected by the target ignition delay. It shows that the delay characteristics are adjusted in the vicinity.

The flow charts shown in FIGS. 10 to 12 are for explaining the control contents executed by the ECU 7.

FIG. 10 shows an example of storing the calculated pulse adjustment amount for the EGR rate for each cylinder as a map value. In steps 1 to 4, the minimum energization time MDP for each EGR rate in each cylinder described later is mapped.
In step 5, the difference between the target minimum energization time (target ignition delay characteristic) and the minimum energization time MDP is calculated for each cylinder and for each EGR rate, and the pulse adjustment amount is calculated based on this difference.
The map diagram as shown in (3) is stored for each cylinder. In addition,
As the ignition delay target characteristic, the ignition delay characteristic with respect to the EGR rate is detected from a large number of manufactured engine cylinders, and the median value of the detected plurality of characteristics is stored in advance as the target characteristic.

FIG. 11 is a flow chart for calculating the pulse adjustment amount of each cylinder from step 11 to step 14 shown in FIG. First, in step 11, it is determined whether or not the operation range is such that the ignition delay characteristic can be corrected and controlled. For example, it is determined that correction is possible if the operating region is the operating region in which pilot injection is performed. Step 1 if possible
If not possible, the control is terminated.

In step 12, the EGR rate is calculated using the map stored in advance from the operating region. The ignition delay amount Pilot Q when there is no ignition delay at the time of pilot injection at the EGR rate calculated in step 13 is set to 0 (zero).
Set to. In other words, the pulse adjustment amount Pulse without pulse adjustment during pilot injection at the calculated EGR rate
Set Pilot to 0.

In step 14, the ignition delay amount Pilot
A new ignition delay amount Pilo by adding a constant value ΔQ to Q
Set as t Q. Or pulse adjustment amount Pulse
A constant value ΔP is added to Pilot to set as a new pulse adjustment amount Pulse Pilot.

Next, using the output signal from the knock sensor 6, it is determined whether combustion has started (step 1
5). When combustion starts, go to step 16,
If not started, the process returns to step 14 and the ignition delay amount Pilot Q or the pulse adjustment amount Pulse P
The setting of ilot is repeated until combustion starts.

Subsequently, in step 16, the calculated EG
The calculated pulse adjustment amount Pulse Pilot is set as the minimum energization time MDP to the injector 3 at the R rate.

At step 17, the process proceeds to the setting of the minimum energization time at the next EGR rate. In other words, the predetermined value ΔEGR is added to the EGR rate EGR, and the added value is again calculated.
Set as GR. In step 18, it is determined whether or not the newly set EGR rate EGR is less than or equal to the upper limit EGR rate. If it is less than the above, the process proceeds to step 19, and if it is greater, the control ends.

The control contents of the following steps 19 to 22 are the same as those of steps 13 to 16, and the description thereof will be omitted.

After setting the minimum energization time MDP in step 22, the process returns to step 17 and shifts to the setting of the minimum energization time MDP at the next EGR rate. Hereinafter, the above control content is repeated.

By such control, the minimum energization time of each cylinder at each EGR rate is set.

FIG. 12 is a flow chart for explaining the control contents for correcting the energization start timing of the injector using the pulse adjustment amount map set in FIG. First, in step 31, fuel injection characteristics (fuel injection timing and its period) are calculated from the engine operating conditions. Continued Step 32
Then, the energization condition (energization timing and its period) to the injector 3 is calculated based on the fuel injection characteristics. In step 33, the pulse adjustment amount is calculated from the above-mentioned map from the operating condition (for example, EGR rate). In step 34, the pulse adjustment amount calculated in step 33 is added to the energization timing calculated in step 32 to determine the final energization timing. In the following step 35, an instruction for fuel injection is output to the injector 3 under energization conditions including the final energization timing.

As described above, in the present invention, the minimum energization time MDP (ignition delay) for each cylinder is detected using the knock sensor 6 for each EGR rate during pilot injection, and compared with the target value, and based on the difference between them. By calculating the pulse adjustment amount and correcting the energization timing for each cylinder, the ignition timing (combustion start timing) with respect to the crank angle of each cylinder will be accurately the same, and the combustion state will be equal in all cylinders. It is possible to suppress the deterioration of exhaust emission and the deterioration of noise and vibration due to the difference in the equivalence ratio of fuel between the cylinders, and it is possible to improve the output because the smoke performance is improved.

The present invention is not limited to the above-mentioned embodiments, and it is obvious that various modifications can be made within the scope of the technical idea of the present invention.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an outline of a four-cylinder diesel engine to which the present invention is applied.

FIG. 2 is a configuration diagram showing an outline of a fuel injection device of the same.

FIG. 3 is a configuration diagram showing an outline of an ECU 7.

FIG. 4 is a diagram showing an example of an energization time map.

FIG. 5 is a timing chart showing a combustion state of fuel.

FIG. 6 is a timing chart showing the difference in fuel combustion state depending on the EGR rate.

FIG. 7 is a diagram for explaining variations in ignition delay due to EGR rate for each cylinder.

FIG. 8 is a diagram for explaining variations in pulse adjustment amount depending on the EGR rate for each cylinder.

FIG. 9 is a diagram showing an ignition delay when the present invention is used.

FIG. 10 is a flowchart for storing a pulse adjustment amount with respect to an EGR rate for each cylinder as a map.

FIG. 11 is a flowchart for calculating a pulse adjustment amount for each cylinder.

FIG. 12 is a flowchart for correcting the energization start timing of the injector using a map of pulse adjustment amount.

[Explanation of symbols]

1 cylinder block 2 cylinder head 3 injectors 4 common rail 5 supply pumps 6 knock sensor 7 ECU

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) F02D 41/14 330 F02D 41/14 330B 41/38 41/38 B 41/40 41/40 D N 45 / 00 368 45/00 368S F02M 25/07 570 F02M 25/07 570J F Term (reference) 3G062 AA01 AA03 BA05 FA13 GA04 GA06 GA18 GA21 3G084 AA01 AA03 BA15 BA20 DA02 DA10 DA39 EA04 EB08 EC03 FA10 FA21 A02 FA37 FA37 FA37 FA37 FA37 FA37 FA37 FA37 FA37 FA37 FA37 FA09 FA37 FA37 FA37 FA37 FA37 FA09 FA37 FA09 FA37 FA37 FA37 FA09 FA37 FA09 FA38 FA09 FA38 AA08 AA13 AA17 AB03 BB06 BB13 BB15 DC09 DE03S DE09S EA16 EC08 EC09 FA14 FA18 FA24 HA06Z HC01Z HC05Z HE01Z HE03Z 3G301 HA02 HA04 HA07 HA13 JA02 JA24 JA25 JA26 LB12 PC01 PZB01Z01 PE01 P01 P01 P01 P01 P01 P01 P01 P01 P01 P01 P01 P01 P01 P01 P01 P01 P01 PZN

Claims (2)

[Claims] 1. An injector for pilot-injecting fuel into a combustion chamber based on an energization condition, a means for controlling an EGR amount recirculated into intake air, and an injector according to the EGR amount and an operating condition by using this flow rate control means. In a multi-cylinder diesel engine including a controller for controlling the energization conditions of the cylinders, the controller controls the cylinders based on the EGR rate so that the combustion start timings of the pilot-injected fuels are different for each cylinder at the same crank angle. A multi-cylinder diesel engine characterized by correcting the timing of energization of the injector. 2. A pressure sensor for detecting a fuel combustion start timing in a combustion chamber, wherein the controller inputs a signal from the pressure sensor and ignites from the start of energization of an injector of each cylinder to the start of combustion. The delay time is calculated for each EGR rate, and the timing of starting energization of the injector of each cylinder is corrected based on the difference between the detected ignition delay time and the target ignition delay time. Cylinder diesel engine.