JPH01155051A - Fuel controller for diesel engine - Google Patents

Abstract

PURPOSE:To prevent preignition from occurring as well as to check any drop in combustion efficiency by performing such control as delaying the timing of pilot injection to the main injection according to an exhaust gas recirculation rate detected. CONSTITUTION:In a Diesel engine which is provided with an exhaust gas recirculation system while constituted so as to perform pilot injection before doing the main injection of fuel, there is provided with a control means which delays only injection timing for the pilot injection but makes it for the main injection so as not to be delayed, with the increase of an EGR rate of the exhaust gas recirculation system. In brief, an EGR correction value is operated at an electronic control unit 19 by a detected value of an oxygen sensor 45 installed in a suction passage 41, thereby controlling actuation of a control rack in a fuel injection pump P. With this constitution, since the injection timing of the pilot injection is delayed with the increase of the EGR rate, even if an intake temperature goes up, premature ignition is prevented from occurring owing to the exhaust gas recirculation system.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a fuel control device for a diesel engine that is configured to perform injection from a pyrower 1 before main injection of fuel.

(Prior Art) In general, in a diesel engine that uses compression ignition, an ignition delay may occur when the injected fuel is under conditions that make it relatively difficult to ignite, and this causes explosive combustion, causing combustion noise and NOx in the exhaust gas may increase.

As a means to suppress such combustion noise and NOx, it is known to pilot inject a small amount of fuel prior to main injection and use this as a spark for combustion of the main injected fuel (for example, Japanese Patent Laid-Open No. 59 (Refer to Publication No.-165856).

Additionally, in order to further reduce NOx, in addition to the pilot injection described above, an EGR (exhaust gas recirculation) device is installed to recirculate the exhaust gas to the intake side, thereby lowering the combustion temperature and reducing the generation of NOx. Engines that are suppressed are also known.

However, in the case of a engine equipped with such an EGR device, as the FGR rate increases, the intake air temperature increases, so the timing of ignition due to the injection from the pylon 1 becomes earlier, resulting in so-called premature ignition. This allows reverse 1~
There is a problem in that it tends to cause leakage. Also, when FGR is performed, combustion in the engine becomes slow combustion, so
In particular, if the injection timing of the main injection is late, the timing of the combustion center due to the injection will be moved back to a greater extent than usual, and this will cause the disadvantage of lowering the combustion efficiency.

(Object of the Invention) In view of the above circumstances, the present invention has been made to prevent over-ignition caused by EGR and improve combustion efficiency in a diesel engine equipped with an EGR device and configured to perform pilot injection before main fuel injection. Fuel r that can suppress the decline
1 control device.

(Structure of the Invention) The present invention provides a diesel engine equipped with an EGR device that recirculates a portion of exhaust gas to the intake side and configured to perform pilot injection before main injection of fuel. As the EGR rate increases, only the injection timing of the pilot injection is delayed, and the injection timing of the main injection is controlled so as not to be delayed.

According to such a configuration, the injection timing of the pilot injection is retarded as the EGR rate increases, so that premature ignition due to the upper temperature range of the intake air is prevented. On the other hand, since the timing of main injection is not delayed, a decrease in combustion efficiency is suppressed.

(Embodiment) FIGS. 1(a) and 1(b) show a diesel engine according to an embodiment of the present invention, and this diesel engine is equipped with a morning type fuel as shown in FIG. Injection pump P
is provided.

In the figure, a camshaft 1 is rotationally driven by the driving force of a crankshaft of an engine, and a cam 3 for driving a plunger 2 is provided on the camshaft 1. On the other hand, the plunger t2 is supported in the housing 4 so as to be movable in the axial direction, and a tappet roller 5 is attached below the plunger t2 in sliding contact with the cam 3, and is urged downward by a spring 24. It becomes. Therefore, due to the rotation of the camshaft 1 and the cam 3, the plunger 2 is reciprocated in a downward direction.

A center hole 2a is provided at the center of the plunger 2 and extends in the axial direction to its upper end, and this center hole 2a communicates with a fuel pumping chamber 4a formed above. A fuel intake groove 6, a first glue portion 7, and a second lead 8, which communicate with the center hole 2a, are formed on the outer peripheral surface of the plunger 2. , 8 have a shape in which the upper edges thereof are inclined with respect to the outer peripheral surface of the plunger 2.

On the other hand, a control sleeve 9, a cam disk 10, a control sleeve 11, and a control sleeve 12 are fitted around the plunger 2 from the outside in order from below, and a cam disk 13 is fitted on the outer peripheral surface of the control sleeve 12. It is fitted. moreover,"
The control sleeve 12 is provided with a fuel boat 12a corresponding to the fuel intake groove 6 and the first lead 7, and the control sleeve 11 is provided with a cutoff boat 11a/% corresponding to the second lead 8. and
Fuel for injection is supplied into the fuel pumping chamber 4a above the plunger 2 through the fuel intake groove 6 and the center hole 2a of the fuel boat 12a.

The control sleeve 9 is movable only in the axial direction relative to the plunger 2 (actually, the plunger 2 moves), and has a cap-shaped disk 2 on its outer peripheral surface.
The lower end of the disk 25 is fixed, and the tenth end surface of the disk 25 engages with a control rack 14 provided within the housing 4. The horizontal movement of the control rack 14 causes the disk 25, control sleeve 9, and plunger 2 to rotate together.

The cam disc 10 is rotatable relative to the plunger v2, and the control sleeve 11 is rotatable and movable in the axial direction relative to the plunger 2. A wavy cam 10a is formed on the upper surface of the cam disk 10,
The control sleeve 11 is placed on the upper surface of this cam 10a.
A part of the lower surface of the cam disc 10 is in contact with the cam disc 10.
Control racks 15 and 16 are engaged with the outer peripheral surfaces of the control sleeves 11 and 11, respectively.

Therefore, the horizontal movement of the control rack 16 causes the control sleeve 11 to rotate, and the horizontal movement of the control rack 15 causes the cam disc 10 to rotate, thereby causing the control sleeve 1 to rotate.
1 moves in the axial direction (vertical direction).

The controller 1 to the roll sleeve 12 are supported from below by a spring 18 and are movable only in the axial direction relative to the plunger 2. The cam disc 13 is
A cam 13a similar to the cam 10a is formed on its lower surface, and a portion of the upper surface of the control sleeve 12 is in contact with this cam 13a. This cam disc 1
The outer peripheral surface of 3 is engaged with the control rack 17,
This horizontal movement of the turn rack 17 causes the cam disk 13 to rotate, thereby causing the control sleeve 12 to move axially relative to the plunger 2.

Further, above the plunger 2, a delivery valve 2 is provided.
6, a spring 27, a delivery valve holder 28, etc. are provided, and the delivery valve holder 28 is provided with a fuel delivery port 28a communicating with the fuel pressure delivery chamber 4a.

On the other hand, each of the control racks 14 to 17 is provided with a position sensor (not shown), and the output of this position sensor is input to the ECU 19 shown in FIGS. 1(a) and 1(b). Conversely, the drive control of each of the control racks 14 to 17 is performed by control signals output from the ECU 19.

Furthermore, this engine is provided with an EGR device that recirculates part of the exhaust gas to the intake side, and as shown in FIG. an EGR passage 43 communicating with the exhaust passage 42;
and an EGR valve 44. The above intake passage 41
is provided with a CO2 sensor 45, and this CO2 sensor 4
In addition to 5, detected values of the position sensor, accelerator sensor 20 (FIG. 1(a)), engine water temperature sensor 21, engine speed sensor 22, etc. are input to the FCU 19.
: In response to these input values, the ECU 19 controls the operation of each rack 14 to 17 and the FOR valve 44.
Opening/closing control.

In such a structure, the plunger 2 is driven up and down by the rotation of the camshaft 1. First, when the plunger 2 descends and its intake groove 6 matches the fuel port portion 12a, the fuel port 12a Fuel is sucked into the center hole 2a from the center hole 2a. Then, the plunger 2 rises again from the bottom dead center, and the lower edge of the intake groove 6 touches the fuel port 12.
When located above the upper edge of the plunger 2, the center hole 2a of the plunger 2 is blocked from the outside, so that fuel is forced to be delivered from the fuel delivery chamber 4a to the engine cylinder through the delivery port 28a (pilot injection The start of the).

Further, the plunger 2 continues to rise, and when the second glue portion 8 reaches the cut-off boat 11a of the control sleeve 11, the two become in communication, and the fuel escapes to the outside from the cut-off boat 11a. Pumping is interrupted (end of pilot injection).

Furthermore, when the plunger 2 is moved once and the position of the second glue portion 8 is shifted from the cut-off boat 11a, both are cut off.
Pressure feeding of fuel is started again (start of main injection). Then, the first lead 7 rises to the position of the fuel port 12a and communicates with the fuel port 12a, so that the fuel is sent back from the fuel port 12a, and the pressure feeding is stopped again (the end of the main injection ). Therefore, each time the plunger 2 performs one upward movement, the pilot injection and main injection as shown by solid lines 30 in FIGS. 3(a) to 3(d) are repeated.

Moreover, in this structure, the timing and injection amount of the pilot injection and main injection are changed by the operation of the control racks 14 to 17.

Specifically, when the disk 13, control sleeve 9, and plunger 2 are rotated by the control rack 14, the upper edges of both leads 7.8 are formed to be inclined with respect to the plunger 2. Therefore, by the rotation of this plunger 2, each boat 11a
, 12a, the opening area of the portions 7 and 8 changes. For example, if the plunger 2 is rotated so that this opening area becomes larger, the pilot injection J
5 and the end timing of the main injection amount become earlier, thereby the injection amount of both injections decreases (see the two-dot chain line 31 in Fig. 3(a)), and conversely, the plunger 2 is rotated so that the above opening area becomes smaller. In this case, the end timing of the pilot injection and the main injection is delayed, thereby increasing the injection amount of both injections (see the broken line 32 in FIG. 3(a)).

Next, when the cam disc 10 is rotated by the control rack 15, the control sleeve 11 moves up and down due to this rotation, and its cut-off port 11
a will move up and down with respect to the plunger 2. When the cut-off port 11a is set above the plunger 2, the end timing of the pilot injection and the start timing of the main injection are delayed, thereby increasing the amount of injection by the pilot injection and increasing the amount by the main injection. The injection amount decreases (see broken line 33 in FIG. 3(b)). Conversely, when the cutoff port 11a is lowered relative to the plunger 2, the end timing of the pilot injection and the start timing of the main injection become earlier, thereby reducing the amount of injection from the pylon 1 and the main injection. The injection INl increases (see the two-dot chain line 34 in FIG. 3(b)).

Furthermore, when the control sleeve 11 is rotated by the roll rack 16, the cut-off port 11a and the plunger 2 rotate relative to each other, thereby causing the second glue corresponding to the cut-off port 11a to rotate. The opening area of part 8 will change. Therefore, when the control sleeve 11 is rotated so that this opening area becomes larger, the end timing of the pilot injection becomes earlier, and as a result, only the amount of injection caused by the pilot injection decreases. (See dot-dashed line 35), and conversely, if the 1-1 call sleeve 11 is rotated so that the above-mentioned opening area becomes smaller, the end timing of the pilot injection will be delayed, and as a result, only the injection amount due to the pilot injection will be (See the broken line 36 in FIG. 3(C)).

Roughly speaking, when the cam disc 13 is rotated by the roll rack 17, the control sleeve 12 moves up and down due to this rotation, and its fuel port 12a is connected to the fuel intake groove 6 and the first port 7 of the plunger 2. It goes up and down with respect to both.

Therefore, if this fuel port 12a is set at 14 degrees with respect to the plunger 2, the start timing of pilot injection and the end timing of main injection will be delayed, and as a result, the injection amount by pilot injection will decrease, and the injection amount by main injection will be delayed. The amount increases (see dashed line 37 in FIG. 3(d)).

Conversely, when the cut-off port 11a is lowered relative to the plunger 2, the start timing of pilot injection and the end timing of main injection become earlier, thereby increasing the injection amount 9A1 due to pilot injection and increasing the amount due to main injection. The injection amount decreases ((d) in the same figure)
(See chain double-dashed line 38).

That is, in this fuel injection pump P, the control sleeve 11.12 is rotated and axially moved relative to the plunger 2 by the operation of the control rack 14-17, and the combination of these movements causes pilot injection and The timing and amount of main injection can be changed as appropriate. For example, if you want to change only the injection timing of the pilot injection, you can change the injection timing of the pilot injection and the end timing of the main injection by operating the control rack 17 (Fig. 3(d)), and also change the injection timing of the pilot injection and the end timing of the main injection. The control rack 14 is operated so that the amount of change in the end timing becomes O (Fig. 3(a)).
) Furthermore, the control rack 16 may be operated to change the end timing of the pilot injection, thereby adjusting the injection amount of the pilot injection.

As shown in FIGS. 1(a) and 1(b) above, the operation control of these control racks 14 to 17 and the EGR valve 4
The opening/closing control of No. 4 is performed by the ECU 19, but here, as a feature of the present invention, in addition to the operating state detected by the accelerator sensor 20, etc., the EGR control by the EGR device
The injection timings of pilot injection and main injection are controlled according to the R rate.

The fuel control operation actually performed by this ECU 19 is as follows:
This will be explained based on the flowcharts of FIGS. 4 and 5.

In FIG. 4, first, the driving state detected by the accelerator sensor 20 etc. is read (step S1).
, Then, the basic M A P IIJ all is started (step S2).Here, first, the above step S1 is started.
Based on the operating conditions read in, the pilot injection timing is set to ignite near compression top dead center, taking into account the time from injection to ignition, and the main injection is started at the same time as the ignition. Set the main injection timing.

In this way, the injection timing and injection amount of pilot injection and main injection are determined, and the output values to each rack 14 to 17 are calculated accordingly, that is, the output of the pump actuator is calculated (step $3), and further,
Step S3 according to the EGR rate by the EGR device.
The control value calculated in step S4 is corrected.

This correction routine is shown in the flowchart of FIG. In the figure, first, the operating state is read (step 551), and it is determined whether the current state is in the range where EGR is performed (step 552). If it is in the EGR region, the EGR valve 44 is operated to be in the ON state (step 853), and the CO of the intake air is
Step S54> to measure the concentration, an EGR correction value is calculated from the EGR rate obtained thereby (Step 555).

This correction value is set based on the graph in FIG. 6(a). That is, as the EGR rate increases, the injection timing of pilot injection is retarded (broken line 61a), and conversely, the injection timing of main injection is advanced (solid line 62a).
). Therefore, the relationship between the actual injection timing of pilot injection and main injection and the EGR rate is as shown by the broken line 61b and the solid line 62b in FIG. 6(b), respectively. Then, the correction values set in this way are converted into output values for each rack 14 to 17 (step 856) L/
After that, the process returns to the main routine shown in FIG. on the other hand,
If the operating state is not in the EGR region in step S52, the EGR valve 44 is turned off (step 857), and no EGR correction is performed.

After returning to the main routine, the control values set and corrected as described above are transferred to each control rack 14~
At the same time, each rack position is read (step S6), and the output of the control value is continued until the predetermined rack position is reached (step S5).
7).

As described above, in this device, in step S4, the injection timing of the pilot injection is retarded in accordance with EGR''J1 by the EGR device, so that when the intake air temperature rises due to EGR, the timing of the pilot injection is too early due to the pilot injection. It is possible to prevent ignition from occurring.Furthermore, combustion in the engine becomes slow combustion due to this EGR, but by advancing the main injection timing according to the EGR rate as in this embodiment, the main It is possible to actively advance the timing of the combustion center due to injection, thereby suppressing reduction in combustion efficiency due to EGR.

Note that if it is difficult to actively advance the injection timing of the main injection in this way, the dashed line 71 in FIG.
Even if the injection gFl amount of the pilot injection is increased as the EGR rate increases as shown in , and the injection amount of the main injection is decreased as shown by the solid line 72 in the same figure, the premix amount until ignition is increases, so the combustion center of the main injection can be advanced in the same way as above. Of course, both the timing of the main injection and the injection amount of both injections may be changed, and in the present invention, the timing of the main injection need not be delayed at least.

Further, although this embodiment shows a case where the pilot injection and the main injection are performed using a single fuel injection pump P, the present invention is not limited to this, and the pilot injection and the main injection are performed separately using two systems of fuel injection means. It can also be applied to equipment used for

(Effect of the invention) As described above, the present invention provides the following advantages in a diesel engine:
As the EGR rate increases with the EGR device, only the injection timing of the pilot fuel injection is delayed, so even if the intake air temperature reaches 100 degrees due to FGR, this prevents premature ignition due to the pyrower 1 jet. This can be prevented from occurring. Furthermore, since the injection timing of the main injection is not delayed, the retreat of the combustion center of the main injection based on EGR is suppressed, and a decrease in combustion efficiency is reduced.

[Brief explanation of the drawing]

FIG. 1 (a>(b) is a structural diagram showing a diesel engine according to an embodiment of the present invention and the input/output of ECtJ in the engine, FIG. 2 is a sectional view of a fuel injection pump installed in the engine, and FIG. 3(a) to (d) are graphs showing the timing and amount of main injection and pilot injection adjusted by the operation of each three 1, and FIGS. 4 and 5 are flowcharts showing the control operation of the ECU. 1~
, Figure 6(a) is a graph showing the relationship between the FGR rate and injection timing correction amount, Figure 6(b) is a graph showing the relationship between the EGR rate and injection timing, and Figure 7 is a graph showing the relationship between the EGR rate and injection amount. It is a graph showing the relationship between. P... Fuel injection pump, 19... ECU (control means), 43... FOR passage, 44... EGR valve, 4
5...CO2 sensor. Patent applicant Mazda Co., Ltd. Representative Patent attorney Etsushi Kogane
Patent Attorney Chief 1) Masamukai Patent Attorney
Sheet Metal Genjin (b) Unknown Figure 3 (a) (b) (C) G (d) '-37TDC Chapter 6 (a) (b) Figure 7

Claims (3)

[Claims] 1. In a diesel engine that is equipped with an EGR device that recirculates a portion of exhaust gas to the intake side and is configured to perform pilot injection before main injection of fuel, as the EGR rate increases due to the EGR device, the pilot injection 1. A fuel control device for a diesel engine, comprising a control means for controlling only the injection timing of injection so as not to delay the injection timing of main injection. 2. 2. The fuel control device for a diesel engine according to claim 1, further comprising control means for delaying the injection timing of the pilot injection and advancing the injection timing of the main injection as the EGR rate increases. 3. Claim 1, characterized by comprising a control means for delaying the injection timing of the pilot injection, increasing the injection amount of the pilot injection, and decreasing the injection amount of the main injection as the EGR rate increases. Or the fuel control device for a diesel engine according to item 2.