JP2001173448A - Fuel injection control device - Google Patents

Abstract

(57) Abstract: In an engine fuel injection control device provided with an EGR control mechanism and a variable displacement turbocharger, the drivability at the time of acceleration in a low load and low speed range is improved. When an operating state of an engine shifts to an acceleration operation, a turbine nozzle of a turbocharger is once fully opened regardless of EGR control if the engine is in a low rotation speed / low load range, and then a normal nozzle is used. Return to control.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a fuel injection control device, and more particularly to a fuel injection control device for an engine having an EGR (exhaust gas recirculation amount) control mechanism and a variable displacement turbocharger.

[0002]

2. Description of the Related Art FIG. 2 shows a conventional example of a fuel injection control device for an engine provided with an EGR control mechanism and a variable displacement turbocharger, and particularly shows a common rail type fuel injection control device.

[0003] First, the structure will be described. Fuel sucked from a fuel tank 2 by a feed pump (not shown) is sent to a fuel supply pump 4 through a fuel pipe 3. The fuel supply pump 4 is, for example, a plunger-type variable displacement high-pressure pump driven by the engine 1, and a pump driving cam driven by the output of the engine 1 and a plunger ( The fuel is pumped to the common rail 6 through the fuel pipe 5.

[0004] The amount of fuel discharged by the fuel supply pump 4 is controlled by adjusting it on the suction side or the discharge side. The fuel stored in the common rail 6 in an accumulated pressure state
The fuel is supplied from the common rail 6 directly or through a short fuel supply pipe 7 to a plurality of (four in the illustrated example) injectors 8 corresponding to the cylinders according to the type of the engine 1. It is injected into the combustion chamber.

The injector 8 generally includes a needle valve that can reciprocate in the injector body, and an injection hole that opens when the needle valve is lifted to inject fuel into a combustion chamber (not shown). The needle is provided by a balance between a pressing force based on the pressure in the pressure control chamber to which the fuel pressure from the fuel supply pipe 7 is supplied, a lifting force based on the fuel pressure acting on the tapered surface of the needle valve, and a return force of the return spring. The valve lift is controlled.

The pressure in the pressure control chamber is controlled by a controller (E
The control can be performed by supplying a control current from the CU) 10 to a solenoid provided in the injector 8 through a control line 13 to open and close an on-off valve provided in a discharge path of the pressure control chamber.

The controller 10 has an engine speed Ne detected by an engine speed sensor (not shown) and an engine load such as an accelerator pedal depression amount Ac detected by an accelerator pedal depression sensor (not shown). Is input. Further, the common rail pressure Pr detected by the common rail pressure sensor is input to the controller 10 via the signal line 12.

Other input signals to the controller 10 include a temperature upper Te detected by the cooling water temperature sensor and the atmospheric temperature sensor and the like, and pressure information Pe about the engine 1 detected by the atmospheric pressure sensor and the pressure sensor in the intake pipe. Alternatively, there are signals from an engine cylinder discrimination sensor, a top dead center detection sensor, and various sensors for detecting the operating state of the engine.

Further, since the output of a diesel engine is smaller than that of a gasoline engine at the same displacement, the engine is designed to improve the engine output during high-speed rotation and high-load operation without reducing the displacement. In general, supercharging of intake air into the air is performed.

In this supercharging control, the turbine 18 is driven by using the energy contained in the exhaust gas of the engine flowing in the exhaust pipe 16, and the compressor 18 disposed in the intake pipe 17 is driven by the turbine 18. This is performed by a turbocharger 15 as a supercharger. The intake air is compressed in the compressor 19, and the intake efficiency of the intake air supplied into the combustion chamber is increased.

The turbocharger 15 is of a variable displacement type, and the throttle amount of the turbine nozzle (not shown) (the area of the turbine nozzle between the variable vanes) is controlled by the controller 10. . An EGR (exhaust gas recirculation) passage 20 for recirculating a part of the exhaust gas to the intake pipe 17 is connected between the intake pipe 17 and the exhaust pipe 16 of the engine 1 in order to reduce NOx. I have. In the middle of the EGR passage 20, an EGR valve 21 for controlling the amount of exhaust gas to open and close the EGR passage 20 to recirculate is provided.

The valve lift position for determining the valve opening of the EGR valve 21 is determined, for example, by the controller 10 using a pressure adjusting valve (EVR).
V) changes the load of the vacuum pump as a vacuum source to EGR.
It is controlled by controlling the rate introduced into the valve 21. Next, the controller 10 in the fuel injection control device shown in FIG. 2 with reference to the flowchart shown in FIG.
The operation of will be described.

First, when the engine 1 is started and the mode is shifted from the start mode to the normal mode, the accelerator opening Ac and the engine speed Ne are read into the controller 10 (step S1). Thereafter, each injector 8 is set in accordance with the detected engine speed Ne and the accelerator depression amount Ac based on the map data 31 prepared in advance.
From the total fuel injection amount Qt to be injected in one fuel injection
Is obtained (step S2).

[0014] Diesel engines tend to generate combustion noise due to fuel ignition delay, especially in low-speed and low-load operating conditions such as idling operating conditions. As means for reducing the combustion noise, it has been found effective to perform pilot injection in which part of the total fuel injection amount in the combustion cycle is injected prior to the main injection.

Therefore, based on the engine speed Ne and the total fuel injection amount Qt obtained in step S2, a pilot to be injected from the injector 8 prior to the main injection based on map data 32 prepared in advance. The fuel injection amount Qp is obtained (step S3).

Based on the engine speed Ne and the pilot fuel injection amount Qp obtained in step S3, based on the map data 33 prepared in advance, the pilot control from the pilot injection end timing to the main injection start timing is performed.
The main injection time interval Int is determined (step S
4).

The pilot-main injection interval Int is controlled so as to be constant at the crank angle so as to become shorter as the operating state of the engine, that is, as the engine rotational speed or the fuel injection amount (engine load) becomes larger. However, in Japanese Patent Application Laid-Open No. H10-205383, in order to avoid fluctuations in fuel injection pressure at the start of main injection and to suppress engine rotation fluctuations, especially in an idling operation state, the main injection start timing is changed from the pilot injection end timing to the main injection start timing. It is proposed to make the pilot-main injection time interval Int up to a constant.

Further, the fuel injection timing Ti and the common rail pressure Pr are calculated from the engine speed Ne and the total fuel injection amount Qt obtained in step S2 based on map data 34 to 36 prepared in advance. The exhaust gas recirculation amount EGR is obtained (steps S5, S6 and S
7).

The map data 36 is shown in FIG. Here, the main fuel injection timing is obtained as the fuel injection timing Ti, and the pilot injection timing is calculated from the pilot fuel injection amount Qp obtained in step S3 and the pilot-main injection time interval Int obtained in step S4. However, the fuel injection timing Ti may be the pilot injection timing, and the pilot fuel injection amount Qp
The main injection timing may be obtained from the pilot-main injection time interval Int.

The fuel injection timing Ti,
Pilot fuel injection amount Qp and exhaust gas recirculation amount EGR
Is further corrected according to the temperature information Te about the engine detected by the cooling water temperature sensor, the atmospheric temperature sensor, and the like, and the pressure information Pe about the engine detected by the atmospheric pressure sensor, the intake pipe pressure sensor, and the like (step S8).

Thereafter, the throttle amount of the turbine nozzle of the variable capacity turbocharger 15 is calculated based on the map data 37 (this is also shown in FIG. 5) (step S9).

[0022]

In such a conventional fuel injection control device, when calculating the EGR amount in step S7, as shown in FIG. 4, the engine speed Ne and the fuel injection amount Qt are both low. The controller 10 controls the opening degree of the EGR valve 21 to increase in such a manner that the EGR amount increases.

At this time, in order to maximize the EGR amount, it is necessary to restrict the nozzle of the turbine 18 to the maximum and to suppress the exhaust gas emission as much as possible. However, in this case, there is a problem that the pumping loss due to the difficulty in flowing the exhaust gas during the acceleration operation increases, the engine speed increases slowly, and the drivability (acceleration performance) deteriorates.

Accordingly, an object of the present invention is to improve the drivability during acceleration in a low load and low speed range in a fuel injection control device for an engine provided with an EGR control mechanism and a variable displacement turbocharger.

[0025]

In order to achieve the above-mentioned target low, the fuel injection control device according to the present invention is a fuel injection control device for an engine having an EGR control mechanism and a variable displacement turbocharger. Means for detecting the engine speed, means for detecting the engine load, and, when it is determined from the engine load that the engine is in an accelerating operation state, if the engine speed and the load are both less than predetermined values, the turbocharger is provided. Means for fully opening the turbine nozzle for a predetermined time and thereafter controlling the throttle of the nozzle.

That is, according to the present invention, when the engine is running at a low speed and a low load, the EGR amount is controlled to the maximum amount as described with reference to FIG. 4 and the turbine nozzle of the variable turbocharger is throttled to the maximum. At this time, if the accelerated operation state is detected, the turbine nozzle is once fully opened for a predetermined time corresponding to, for example, the mechanical reaction time, and thereafter the turbine nozzle is controlled as usual.

In this manner, in the low rotation speed and low load range, the pumping loss obtained by making the exhaust gas easier to flow is reduced as compared with the boost pressure reduction caused by opening the turbine nozzle. The engine speed increases quickly and the drivability is improved.

This seems to sacrifice the turbo function, but it can also be said that attention was paid to the fact that the turbo function was not originally large in such a low rotation speed and low load region. The control means can determine that the vehicle is in the acceleration operation state when the change amount of the fuel injection amount per unit time exceeds a predetermined value.

Further, the means for detecting the engine load can use an accelerator pedal depression amount sensor.

[0030]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a fuel injection control device according to the present invention will be described below with reference to the flowchart of FIG. The configuration of this embodiment can be the same as that of the conventional example shown in FIG. 2, and therefore, FIG. 2 is also referred to.

First, steps S1 to S9 in FIG.
Are performed in the same manner as steps S1 to S9 of the conventional example shown in FIG. Therefore, their description is omitted. Next, in order to determine whether or not the vehicle has shifted to the acceleration operation state, the deviation ΔQt between the previous total fuel injection amount Qt (I-1) and the current total fuel injection amount Qt (I) (or the total fuel injection amount It is determined whether or not the amount of change in the amount Qt per unit time has exceeded a predetermined value Qac corresponding to the acceleration operation of the engine 1 (step S1).
0).

If the deviation ΔQt exceeds the value Qac, it is determined that the engine has shifted to the acceleration operation. The determination of the acceleration operation state may be made based on the accelerator depression amount Ac itself. If it is determined in step S10 that the engine has shifted to the acceleration operation, the acceleration correction flag Iv is set to "
It is determined whether it is "0" (step S11).

If it is determined that the flag Iv is "0", that is, it is determined that the acceleration correction of the turbine 18 has not yet been performed in spite of the acceleration operation state, the acceleration correction of the turbine 18 is executed ( Step S12). That is, since the variable-capacity turbocharger 5 has just been shifted to the acceleration operation state, and is in the low-rotation / low-load region (shaded region) as shown in FIG. As described above, the amount is controlled to the maximum amount from the relationship with the EGR amount (see FIG. 4).

Therefore, when the engine 1 is in such a low rotation speed / low load region, the controller 10 once controls the turbine nozzle to a fully open state regardless of the map data 31 to 36 of the turbocharger 15, Flag Iv "
1 "is set (step S12).

In this way, the turbo function seems to be impaired especially in the low rotation / low load region, but the turbo function in the low rotation / low load region is originally lower than that in the medium rotation / middle load region. Therefore, even if a slight turbo function is sacrificed, since the exhaust gas easily flows out from the exhaust pipe 16, it is more advantageous that the pumping loss is reduced.

Accordingly, the engine speed rapidly increases with a decrease in pumping loss, so that drivability (acceleration performance) is improved. After executing step S12, the program returns to step S1 in the execution cycle and executes steps S1 to S8 as described above.
The current value of the total fuel injection amount Qt, the pilot fuel injection amount Qp, the injection interval Int, the injection timing Ti, the common rail pressure Pr, and the EGR amount is calculated based on the map data 31 to 36, respectively.

In step S9, the current throttle amount VNT of the turbine nozzle is similarly calculated based on the map data 37 (see FIG. 5). The aperture amount is increased in accordance with the data 37.

In step S10, when the acceleration is no longer determined, the acceleration correction flag Iv is reset to "0". Note that, in step S12, the flag Iv
Is set to "1", a "NO" determination is made in step S11 in the next program execution cycle.
The time for fully opening the turbine nozzle is only the execution cycle of this program, but there is no problem if the turbine nozzle can react mechanically even in such a short time.

Accordingly, if the execution cycle of the program is so short that the turbine nozzle cannot react mechanically, the time of step S12 may be extended to cope therewith.

[0040]

As described above, according to the fuel injection control apparatus of the present invention, when the operating state of the engine shifts to the acceleration operation, if the engine is in the low rotation speed / low load range, regardless of the EGR control. , The turbine nozzle of the turbocharger is once fully opened, and then returned to normal nozzle control.This improves pumping loss in low-load and low-speed ranges, resulting in a rapid rise in engine speed. And drivability becomes good.

[Brief description of the drawings]

FIG. 1 is a flowchart illustrating the operation of a fuel injection control device according to the present invention.

FIG. 2 is a block diagram showing a configuration example of a common rail fuel injection control device according to the present invention and a conventional example.

FIG. 3 is a flowchart showing the operation of the conventional example.

FIG. 4 is a graph showing a relationship between an engine speed and a fuel injection amount used in the present invention and a conventional example, using an EGR amount as a parameter.

FIG. 5 is a graph showing the relationship between the engine speed and the fuel injection amount used in the present invention and the conventional example, using the throttle amount of the turbine nozzle as a parameter.

[Explanation of symbols]

 Reference Signs List 1 engine 4 fuel supply pump 6 common rail 7 fuel supply pipe 8 injector 10 arithmetic unit 15 variable capacity turbocharger 16 exhaust pipe 17 intake pipe 18 turbine 19 compressor 20 EGR passage 21 EGR valve 31-37 map data Ne engine rotation Ac accelerator pedal Step amount Pr Common rail pressure Qt Total fuel injection amount Qp Pilot fuel injection amount Int Pilot-main injection time interval Ti Fuel injection timing Qac Judgment value of acceleration operation for total fuel injection amount Show.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02D 21/08 311 F02D 23/00 J 23/00 23/02 F 23/02 41/02 380D 41/02 380 380E 41/04 375 41/04 375 41/10 351 41/10 351 45/00 314E 45/00 314 364K 364 F02M 25/07 530Z F02M 25/07 530 570F 570 570J 570P F02B 37/12 301NF Reference) 3G005 DA02 EA04 EA15 EA16 FA04 GA04 GD02 GD13 GD17 GE06 GE09 HA12 JA01 JA02 JA39 JA42 JB02 3G062 AA01 AA05 BA00 BA05 CA04 EA04 GA04 GA05 GA06 GA15 GA21 3G084 AA01 BA08 BA20 CA04 DA05 EB02 FA02 A03 FA10 EA01 FA03 FA25 GA05 GA12 GA17 HA15X HB01Z HF09Z 3G301 HA02 HA11 HA13 JA01 JA03 KA08 KA12 KA 24 LA00 MA11 MA18 MA23 MA27 MA28 NA06 NA08 NE01 NE23 PA17Z PB03Z PD15Z PE01Z PF03Z

Claims (4)

[Claims] 1. An EGR control mechanism and a variable capacity turbocharger.
A means for detecting an engine speed, a means for detecting an engine load, and determining that the engine is in an accelerating operation state based on the engine load. Means for fully opening the turbine nozzle of the turbocharger for a predetermined time if the load is equal to or less than a predetermined value, and thereafter controlling the throttle of the nozzle. 2. The system according to claim 1, wherein the control means determines that the vehicle is in the acceleration operation state when the change amount of the fuel injection amount per unit time exceeds a predetermined value. Fuel injection control device. 3. The fuel injection control device according to claim 1, wherein the predetermined time is a mechanically responsive time of the turbine nozzle. 4. The fuel injection control device according to claim 1, wherein the means for detecting the engine load is an accelerator pedal depression amount sensor.