JPS62291458A - Exhaust gas recirculation control device for diesel engine - Google Patents

Abstract

PURPOSE:To prevent production of an adverse influence due to disorder control of an EGR amount during transient running, by a method wherein, from the change width per a unit hour of a detecting injection amount instruction value, a transient correction time is calculated, and during transient running, the EGR amount is controlled to a minimum value during the transient correction time. CONSTITUTION:During running of a diesel engine 10 having an EGR valve 32 controlling an EGR amount depending upon a control negative pressure applied on a diaphragm chamber 32A, a rotation speed NE of an engine, detected by an NE sensor 52, and an injection amount instruction value Q are first read in an ECU 36. Based on the number NE of revolutions of an engine and the injection amount instruction value Q, a fundamental RGR amount is calculated, and based on the fundamental EGR amount, a negative pressure switching valve 38 is controlled so as to control the opening of the EGR valve 32. From the change width per a unit hour of the injection amount instruction value Q, a transient correction time is calculated. During transient running of an engine 10, the EGR is controlled to a minimum value during the calculated transient correction time.

Description

[Detailed description of the invention]

3. Detailed description of the invention

[Industrial Application Field] The present invention relates to an exhaust gas recirculation control device for a diesel engine, and in particular, an exhaust gas recirculation control device for a diesel engine suitable for use in an electronically controlled diesel engine.
2Il device improvement. [Prior Art] In diesel engines, one way to reduce NOx in exhaust gas is to recirculate a portion of the inert exhaust gas to the intake system and mix the exhaust gas into the intake air. Exhaust gas recirculation (hereinafter referred to as EGR) devices are used to lower the maximum temperature during combustion and reduce the generation of NOx. For example, Japanese Patent Application Laid-open No. 5
There is one proposed in No. 9-215954. This is an EGR control method between diesel lines that detects the load and intake pressure, determines the basic EGR II according to the detected load, and corrects the EGR interval according to the detected decrease in intake pressure. . In this control method, by reducing and correcting EGRfa according to the load condition during transient periods, even if the intake air pressure relative to the engine load is reduced due to intake throttling or high-altitude driving, white smoke is generated, especially in high-load operating ranges. Or you can prevent companies from emitting black smoke.

[Problems to be solved by the invention]

By the way, the proposed EGR! II l! 11
A turbocharger 2 as shown in Fig. 2 will be described below.
When used in a diesel engine equipped with No. 4, it is thought that the generation of white smoke due to transient supercharging delay of the turbocharger 24 can be suppressed to some extent. However, when controlling the EGR valve 32 for controlling EGRffl as shown in FIG. Since the change in EGRffi is rapid, a slight change in EGR negative pressure will cause EGRff
i changes greatly, and the EGRf cannot be fully controlled.
There was a risk that the fi would go awry. If control goes out of order and EGRfl becomes excessive, problems such as misfire, reduced acceleration, and deterioration of drivability will occur, and if EGRI is insufficient, NOx
Sometimes it increases. Also, normally EGRffl is determined by the passage resistance of the EGR valve body and E
It is determined by the differential pressure between the upstream and downstream of the GR valve, but the EGR
As the passage resistance of the valve changes, the differential pressure also changes. That is, if the passage resistance is large, the differential pressure will be small, and if the passage resistance is small, the differential pressure will be large. In this way, since the differential pressure is determined by the passage resistance, the EGR negative pressure and EaRt
The characteristics between ih and ih are as shown in FIG. 5, for example. Therefore, on the low-flow tail side of EGRI where the EGR negative pressure is small, there is a problem that a slight change in the differential pressure may cause the EGRild to go out of order as much as in the case where the EGR negative pressure changes. It was. In addition, as a technique related to the present invention, for example,
162048, there is a technique for determining engine acceleration based on the output of a position detection device of a fuel control member, and for stopping EGR when the determining means determines sudden acceleration. This technology indirectly reads changes in injection amount based on changes in accelerator opening. However, with this technology, the range of change in injection amount relative to the range of change in accelerator opening varies depending on the engine speed, so it is necessary to change the sudden acceleration judgment level for each engine speed, which requires complicated control. It was. Furthermore, since the change in the injection amount is indirectly read, a delay in control is unavoidable.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned conventional problems, and is directed to EGR during transient operation of a diesel engine.
It is an object of the present invention to provide an exhaust gas recirculation control device for a diesel engine that can minimize the negative effects caused by miscontrol of ffl, and can therefore reliably prevent deterioration in drivability and increase in NOx. .

[Means to solve the problem]

The present invention provides exhaust gas recirculation (EG) for diesel engines.
R) In the control device, as shown in FIG. 1, the control device includes means for detecting the engine rotational speed NE and injection amount command value Q of the diesel engine, and means for detecting the detected engine rotational speed NE and injection amount command value Q. Value Qk: Based on basic EG
means for controlling EGRm of the diesel engine to Rf &; means for calculating a transient correction time from a variation width per unit time of the detected injection base command value Q; and a means for calculating a transient correction time during transient operation of the diesel engine; Said EGR
Control Ea to the minimum value. The above object has been achieved by providing means.

[Operation 1] In the present invention, in an exhaust gas recirculation (EGR) control device for a diesel engine, the engine rotation speed NE
and injection tJJD command value Q, and detect the detected engine rotational speed NE and injection maximum command value Q1. :Based basic EG
EGRω of the diesel engine is controlled to Rffl, a transient correction time is calculated from the range of change per time of the detected injection D'J ffi command command value, and during the transient operation of the diesel engine, during the calculated transient correction time, The EGRm
is controlled to the minimum value. Therefore, it is possible to minimize the adverse effects of EGRfffi control error during transient operation of the diesel engine, and to reliably prevent misfires, acceleration reduction, drivability deterioration, and NOx increase due to EGRff error. Can be done. That is, if the present invention is implemented, when the diesel engine is operated transiently, for example, the more rapidly the diesel engine is accelerated, the longer the transient correction time will be, the longer the time for fixing the minimum EGR value will be, and the less EGRm will be controlled. Problems due to deviations in the engine are eliminated, and during steady operation after the transient operation period, it is possible to return to the original EGR control with stable combustion, making it possible to perform accurate EGR control. . Further, according to the present invention, the above-mentioned Japanese Patent Application Laid-Open No. 60-162048
In the prior art disclosed in 2003, the change in injection amount was read indirectly from the change in the accelerator opening to determine the change in the injection amount, but in the present invention, the change in the injection amount is read directly from the change in the command value for the injection rA. There is. Therefore, generation of black smoke due to variations in the accelerator opening degree can be prevented, and since control can be performed directly using the command value of the injection tAffl without involving the accelerator opening degree, time delays in control can be prevented. Note that when controlling the EGR amount to the minimum value according to the present invention, the EGR amount can also be made zero by shutting off the EGR valve. [Example] Exhaust gas recirculation (E
(GR) An embodiment of the control device will be described in detail below. This embodiment is an EGR control device installed in a diesel engine 10 as shown in FIG. This diesel engine 10 is configured such that liquid fuel for the diesel engine is injected and supplied to its combustion chamber from a fuel injection valve 14. This diesel engine 10 also includes an intake boat (not shown) that opens into the combustion chamber and an exhaust port (not shown).
The intake boat has an intake manifold 16.
is connected, and an exhaust manifold 18 is connected to the exhaust port. An intake pipe 20 is connected to the upstream side of the aeration manifold 16, and an exhaust pipe 22 is connected to the downstream side of the exhaust manifold 18. A turbocharger 24 is disposed midway between the intake pipe 20 and the exhaust pipe 22 to compress the intake air flowing through the intake pipe 20 using the pressure of the exhaust gas flowing through the exhaust pipe 22. The fuel injection valve 14 is connected to a fuel injection pump 28 by a fuel vibrator 26, and the fuel injection pump 28 supplies liquid fuel at a predetermined pressure in a flow m measured according to the engine load. The fuel injection pump 28 includes, for example, an adjuster lever 28 that rotates in motion with an accelerator pedal (not shown).
A1129 Spill ring (not shown) driven by a governor etc. to control the fuel injection amount according to the engine rotation speed, and a timer piston 28 to control the fuel injection timing.
B1 Idle up mechanism 28 for controlling idle up when cold or when the air conditioner is turned on, for example C1 Supercharged fuel increase mechanism with altitude compensation (hereinafter referred to as BAC8) for increasing supercharged fuel according to intake pressure ) 28D, which is a fuel injection pump known per se, which controls the fuel injection j depending on the position of the spill ring. The exhaust manifold 18 has an exhaust gas intake boat 18.
In addition, the intake manifold 16 is provided with an exhaust gas injection boat (not shown), and the exhaust gas intake port 18A is connected to the exhaust gas injection boat via an EGR passage 30 and an EGR valve 32. It is connected. The EGR valve 32 is adapted to control the flow area of the EGR passage 30 in response to a control negative pressure applied to its diaphragm chamber 32A. The diaphragm 'J32A is a temperature-sensing negative pressure switching valve (hereinafter referred to as BVSV) 34 that opens and closes in response to engine temperature, and a negative pressure switching valve that is turned on and off by the output of an electronic control unit (hereinafter referred to as ECtJ) 36. (hereinafter referred to as VSv) 38 and is connected to the EVRV 40. This EVRV 40 is also connected to a vacuum pump 44 provided in the diesel engine 10 via a constant pressure valve (hereinafter referred to as CPV) 42 for supplying constant negative pressure. Therefore, the opening degree of the EGR valve 32 is
VSV38 is interrupted by the output of CLi2.6, and EC
It is controlled according to the control negative pressure adjusted by EVRV40 by the internal output of U36. The constant negative pressure of the CPV42 output is the same as that of the BAC328D.
is also supplied. Further, the output of the VSV 38 is also supplied to the idle up mechanism 28C. The fuel injection pump 28 includes an accelerator opening sensor 46 for detecting the opening of the adjuster lever 28A, and a reference position @ for detecting that the rotation angle of the engine is at a reference position, for example, top dead center. A sensor 48 (hereinafter referred to as TDC) is provided. Further, the fuel injection pump 28 is equipped with a timer piston 2 according to the output of the ECU 36.
A timer control valve (hereinafter referred to as TCV) 50 is provided to control the injection timing by hydraulically controlling the position of 8B. The engine rotation speed (NE) is input to the ECU 36 from an engine rotation speed (NE) sensor 52 . The effects of the embodiment will be explained below. The EGR control device shown in FIG. 2 is controlled by a control procedure as shown in FIG. 3, which is stored in the ECU 36. That is, the flowchart shown in (A) of the figure is a routine that interrupts every 50 milliseconds, and this 50 milliseconds corresponds to the reference time ΔT when determining the range of change in injection ωQv per unit time. When this routine is interrupted, first step 1 is executed.
At step 10, it is determined whether the constant EA for determining the transient correction time is zero. When the determination result is negative, in step 120, 1 is subtracted from the constant EA for determining the transient correction time, and a new constant EA is set. Next, the process proceeds to step 130, and also when the determination result in step 110 is positive, the process proceeds to step 130. In step 130, the injection amount command value (in the case of the embodiment Qt
in) and the injection tAffl command value Qrinα left in the previous routine. Next, in step 140, the variation width ΔQrin of the injection amount command value is calculated using the following equation (1). Δ Qt i lo = Qr i lo − Q
f inc ... (1) Then, a constant EA' is calculated from the calculated variation width ΔQfin of the injection amount command value using the relationship as shown in FIG. 4 (as shown in the figure, in the case of the example, The constant EA' is 20 when the variation width ΔQrin is 20u3/str, and str represents one stroke of the engine). Next, in step 150, the larger of the constants EA1EA' is newly set to the constant fitEA. Then, in step 160, the injection amount command value Qti
Put n in Qrinc and leave it there. Next, the EGR control routine shown in FIG. 3(B) will be explained. In this routine, first, step 1
At 70, the engine speed NE and injection command value Qrin
etc. Next, in step 180, the basic E is determined from the read engine speed NE, injection value Qrin, etc.
Calculate the GR amount. Next, in step 190, it is determined whether or not the constant EA is zero, and when the determination result is negative, that is, when it is determined that the transition is occurring, the process proceeds to step 200, where the minimum value of EGRfl is set by the ECU 3.
Set to output port 6. The signal set to this output port is input to the EVRV 40 to control the negative pressure to the EGR valve 32. Note that the minimum value of EGRJn at this time is the minimum value determined from the viewpoint of preventing emissions and black smoke in the exhaust gas discharged from the diesel engine according to the embodiment. Further, step 205 within the broken line indicated by the symbol A in FIG. 3(B) can be executed instead of step 200, and a signal that makes EGRfa zero can be set at the output port. 10,000, when the determination result in step 190 is positive, it is determined that the diesel engine is in steady operation, and the process proceeds to step 210;
Set the basic EGRfit to the output port. According to this embodiment, EGRfa can be maintained at the minimum value or zero for 50 milliseconds x 20 = 1 second during a transient period such as when the injection amount command value 0rin changes by 20 u''/str within 50 milliseconds. In the 11th embodiment, the constant EA was calculated using a routine that interrupts every <50 milliseconds as shown in FIG. 3(A). The interrupt time is not limited to 50 milliseconds, and interrupts can be made at other times.Also, by using the constant EA obtained in Figure (A), the flowchart shown in Figure (B) can be created. ECU36 in control procedure
However, the EGRffi according to the present invention
The control procedure used for the GR control system is shown in (A) and (B) in the same figure.
) It is clear that the control is not limited to the one shown in () and can be controlled by other procedures. Further, in the above embodiments, the present invention is applied to an electronically controlled diesel engine as shown in FIG. 2, but the electronic control device and diesel engine to which the present invention is applied are limited to these. It is clear that the present invention can be applied to other diesel engines equipped with other electronic control devices. Effects of the Invention As described above, according to the present invention, the adverse effects of EGRffi control errors during transient operation of a diesel engine can be minimized as much as possible. Therefore, it is possible to prevent the effects caused by such variations, such as misfires, reduced acceleration, deterioration of drivability, increase in NOx, and generation of black smoke.Furthermore, after the transient operation period has passed, combustion is stabilized as it should be. Since exhaust gas recirculation control can be performed, excellent effects such as accurate exhaust gas recirculation control as a whole can be obtained.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the gist of the present invention;
The figure is a plan view including a partial block diagram showing the configuration of an embodiment of the exhaust gas recirculation control device for a diesel engine according to the present invention, and FIGS. 3(A) and 3(B) show the operation of the embodiment. FIG. 4 is a flowchart showing the 50 millisecond interrupt routine and the exhaust gas recirculation routine to explain the fuel injection routine used in the routine. FIG. 5 is a diagram showing an example of the relationship between the constant of the 8 bus command value and the transient correction time. DESCRIPTION OF SYMBOLS 10...Diesel engine, 30...EGR passage, 32...EGR valve, 36...ECUl 52...NE sensor.

Claims (1)

[Claims] (1) means for detecting the engine rotational speed and injection amount command value of a diesel engine; means for calculating the transient correction time from the range of change per unit time of the detected injection amount command value; An exhaust gas recirculation control device for a diesel engine, comprising: means for controlling the exhaust gas recirculation value.