JPS60150470A - Exhaust gas recirculation of diesel engine - Google Patents

Abstract

PURPOSE:To reduce concentration of NOX in exhaust gas by controlling the exhaust gas recirculation under idling with correspondence to the engine temperature variation. CONSTITUTION:Under idling of engine, it will proceed to step 17. In step 19, reduction DELTAE of exhaust gas recirculation under idling is determined with correspondence to the count C. In step 20, pulse signals having duty ratio Eout predetermined on the basis of exhaust gas recirculation Ei is provided to a negative pressure regulation valve. Consequently, concentration of NOX in exhaust gas under idling can be reduced effectively.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for controlling gas recirculation in a diesel engine used in vehicles such as automobiles.

Behind the excuse... In diesel engines used in vehicles such as automatic cars,
It has already been proposed to perform exhaust gas recirculation to reduce the NoXItl level in IJI gas. In order to avoid the generation of black smoke, it is necessary to replace part of the excess intake air drawn into the engine combustion chamber with exhaust gas at a flow rate that is appropriate to the operating status of the diesel engine. However, if exhaust gas recirculation is performed even at low temperatures, harmful components such as sulfur oxides in the exhaust gas recirculated to the engine intake system will cause severe corrosion and wear of the Diegel engine components. , so-called low-temperature corrosion occurs, reducing the durability of the diesel engine. For this reason, engine temperature decreases due to less combustion fuel during idling operation, especially when exhaust gas recirculation is constantly performed.
There is a risk that low-temperature corrosion as described above will occur.

In view of the above-mentioned problems, Japanese Patent Application No. 58-920, filed by the same applicant as the present applicant, proposes that during idling, exhaust gas recirculation is performed only for a predetermined period of time from the start of idling.
It has already been proposed in No. 98 and Japanese Patent Application No. 58-20846.

Tokorogu, the exhaust gas recirculation flow rate during non-oil operation is always constant.
In order to avoid the occurrence of low 1f# corrosion, the degree of NoxilJtl in the exhaust gas during idling operation is reduced as much as possible. It is preferable to set C according to the poetic changes.

In the previously proposed exhaust gas recirculation control method for Diegel engines, the exhaust gas recirculation flow rate and the exhaust gas recirculation range between 0.' -(There are some settings, but in these, lj
The gas recirculation flow rate is once i) during idle operation.
It is constant from the start of JJI gas recirculation until the end of P1 circulation, and therefore, excessive IJI gas recirculation is performed near the end, or on the contrary, if the flow rate is still small. Even though it is possible to carry out exhaust gas recirculation, exhaust gas recirculation may end.

Purpose of Defense The present invention appropriately controls the exhaust gas recirculation flow rate during fiddle operation in accordance with the humidity change over time of a diesel engine during idle operation, thereby avoiding the occurrence of low-temperature corrosion. The object of the present invention is to provide an exhaust gas recirculation control method for a diesel engine that further reduces NOXIIIJI (ε) in exhaust gas during engine operation.

According to the present invention, during idle operation, IJi gas recirculation is carried out for a predetermined period of time from the start of idle operation, and the exhaust gas recirculation flow +1i is used during idle operation. The IC flow rate is reduced over time at the IC flow reduction rate, which is determined according to the engine operating state before the condition occurs.
During operations other than idle operation, 1) 1-gas gas recirculation is performed at a flow rate that is determined at any time depending on the operating state of the Diegel engine at that time.The 1-no-1-gas gas recirculation of the Diegel engine is characterized by the following: This is achieved through control methods.

Effect of explanation According to the exhaust gas recirculation control method according to the present invention, during idling operation, the exhaust gas recirculation flow rate is changed over a period of time at a "C predetermined flow reduction time" according to the engine operating state before the idling operation state. f during idling compared to when the exhaust gas recirculation flow rate is constant.
J[Gas recirculation time to 1/low temperature corrosion? This allows for an effective reduction in the amount of NOxl in the exhaust gas during idling.

The engine temperature at the start of idle operation is determined by the operating state of the Diegel engine before that, and the engine temperature is higher than when the Diegel engine is operated at a high load (J), which is the opposite. When the diesel engine is operated at C with a low Ω load,
How long does it take for the diesel engine to maintain a warm stone to allow exhaust gas recirculation without causing low-temperature corrosion? 1 detention (longer when being driven)

Therefore, the exhaust gas recirculation time during idling operation is longer when the f easel engine is under high load (Ic) before entering the no-idle operating state;
When the Igel engine is operated at low load, it is short...9
It would be nice if it was determined. That is, when the γ evil engine is being operated with a load greater than a predetermined value, the counter is incremented by 1, and when the diesel engine is not being operated with a load greater than a predetermined value, the counter is decreased. Callan 1
The reduction rate of the exhaust gas recirculation flow rate during idling operation may be determined according to the counter value of the counter, and the exhaust gas recirculation time may be changed accordingly.

DESCRIPTION OF EMBODIMENTS The present invention will now be described in detail with reference to embodiments with reference to the accompanying drawings.

FIG. 1 shows one embodiment of an exhaust gas recirculation device implementing the exhaust gas recirculation control method according to the present invention. In the figure, -U, 1) shows a diesel engine having a piston 3 slidably received in a cylinder bore 2 and a combustion chamber 4 defined above the piston. It also has a swirl chamber 5 communicating with the combustion chamber 4, into which liquid fuel is injected and supplied from a fuel injection nozzle (not shown).

The diesel engine 1 sucks air into the combustion chamber 4 through the intake manifold 6 and the intake bows 1 to 7, and from the combustion chamber 4 through the +j+ air boat 8 (Ill to the exhaust manifold 9).
-C begins to expel gas. Intake bow 1 to 7
The IJ1 and IJ1 air ports 8 are each opened and closed by poppet valves, and in the figure, only the 17) air I11 valve is indicated by the reference numeral 10.

11 indicates 1) 1 gas re-%'l ring control valve. J
Ji gas recirculation control valve No. 11 J robot 13 and exit 1
” Right Cushing 12 with 14 and 1 to Bow 1, and the person [
13 is connected by conduit 15 to 1-1 air gas take-off bow 1-16 formed in air manifold 9,
Exhaust gas injection boat shaped like 1 in air manifold 6'
18.

Jj) The air gas recirculation control valve 11 is located inside the casing 12.
It has one element, which is drivingly connected to the DAI A7 noram device 23 by the 5↑L1 lead 22,
A negative moon is introduced into the die A7 nonme chamber 2G provided on one side of the noram 25 (not shown) and is driven to the left by the spring force of the earth contraction coil spring 26 to the valve seat. 2
When the valves 1 to 21 are closed and negative pressure is introduced into the noram chamber 26 of the die A7, the compression coil moves to the right in the figure against the spring force of the spring 27. When driven, the valve seat 20 creates a valve boat 21 that responds to the amount of negative pressure.

The tire flamm chamber 26 is connected by a conduit 28 to the negative pressure output ports 1 to 30 of the M11 regulating valve 29.

The negative f1 regulating valve 29 is supplied with negative pressure by passing the negative pressure conduit 33 to the negative pressure input capos 1 to 31, and controls the negative L at -. The pressure is adjusted according to the control signal, and the negative pressure is output from the negative pressure output capos 1 to 30.

The control 11 device 40 includes a general micro convenience store counter and an up/down counter. information on the rotation speed of the diesel engine 1 from the rotation speed sensor 42, and information on the power at which the diesel engine 1 is operated from idle to zero from the idle switch 43. , water temperature sensor 44
From i Koi-111 machine 1 rule 1 cold u1 water temperature 1ill
In addition, the control data related to the optimal 1-1-1 gas circulation flow MIEr according to the fuel injection amount and rotational speed of the engine 1 are input manually during idling operation. Store the optimal exhaust gas recirculation flow rate [1] and the control related to the flow rate reduction ΔF.
According to the control data and the information from each of the above-mentioned hints, the present invention implements the recirculation control method shown in FIG. A signal is output to a negative pressure 2-yen regulating valve 29.

Incidentally, the fuel injection sensor 41 controls the fuel injection/l;
(b) detecting the displacement of a fuel supply amount control element such as a spill ring, or (6) detecting the accelerator pedal 6-.

[Next] Please refer to the file coach 1- shown in Figure 2 on p. a
Lc book to light J, ru + Jl ki 1 ■ J circulation system ti
ll ij method σ) The implementation procedure will be explained below.

The first one is fuel I @ River M Shin I
Information is input from J41, rotation speed sensor 42, idle switch 43, and water temperature 44.

In step 2, it is determined whether the idle switch 4; 3 is in an on state. Idle switch 4
When the idle switch 43 is not on, that is, when the engine 1 is in negative operation, the process proceeds to step 3. On the other hand, when the idle switch 43 is on, the knockdown engine 1 is in idle operation. When it's being done, it's Stetsuno 17
'\move on.

In step 3, it is determined whether flag 1-a is 1 or not. On the other hand, Nora Soge 1-a-1 (
If so, proceed to step 51\, and if the flag Fa is not 1, proceed to step 4.

In step 4, flag switching is performed to change the flag E2a to 1.

In step 5, it is determined whether the flag [[1 is O'c or not. Flag F11' = 0''
When C' is present, the process proceeds to step 7, whereas when the flag Fb is not equal to O, the process proceeds to step 6.

In step 6, flag switching is performed to set flag Fb to O.

The water temperature in the hot water tank 7 is detected by the inner tube 44, and it is determined whether the temperature of the cold IJ water in the diesel engine 1 is higher than a predetermined temperature, for example, 60°C. If it is 1u or more than the predetermined value, step 81\
On the other hand, if the water temperature of J1 (cool) is less than the predetermined 1+ri or -1-'C', the process proceeds to step 13.

In step 8, it is detected by the rotation speed sensor 1 42 that the rotation speed of the diesel engine 1 is a predetermined value of 1+Q, for example 2.
A determination is made as to whether or not it is 00 Orpm or more. When the engine speed is above the predetermined value, the process proceeds to step 9, whereas when the engine speed is not above the predetermined value, the process proceeds to step 14.

In step 9, the amount of fuel per stroke for the diesel engine 1 detected by the fuel injection amount sensor/11 is determined.
! It is determined whether the l injection amount is greater than or equal to a predetermined value. - The amount of fuel injection #4 per stroke is a predetermined value, for example 20+
If the fuel injection amount per stroke is not greater than 11111', the process proceeds to step 10, whereas if the fuel injection amount per stroke is not greater than the predetermined value, the process proceeds to step 14.

In step 10, the counter of the counter (1fIC
is moved up by one. After step 10, proceed to step 11.

In step 11 lA, control 11 data corresponding to the fuel injection amount per stroke detected by the fuel injection amount sensor 1) 41 and the rotation speed detected by the rotation speed sensor 42 is searched. A determination of the exhaust gas recirculation flow rate Er is made on the basis of the data. Exhaust gas recirculation flow rate E
From the basic concept of diesel engine exhaust gas recirculation, which is to replace a portion of the surplus intake air in the engine combustion chamber with exhaust gas, r is an increase in the amount of fuel injection, which means an increase in the t5 engine load. It also decreases as the number of engine rotations increases. After step 11, the process advances to step 12.

In step 12, a control signal based on the exhaust gas recirculation flow IEr determined in step 11, that is, a pulse signal with a predetermined duty ratio of 1:out, is output to the negative pressure control valve 29.

When the I-1 pressure control valve 29 is given the pulse signal, it outputs a negative pressure corresponding to the fuel per culm of the diesel engine 1 and the rotational speed when the pulse signal is applied. -h
30, and this negative pressure drives the 1st air scum III circulation control valve '1. Therefore, at this time, during 4-way operation other than 1-way operation, the fuel injection rate per culm (m) is determined at any time according to the engine speed (
Exhaust gas recirculation takes place.

S) The next knob 12 is reset.

In step 13, C is the counter of the counter (reflection 0 is 0
To be made into.

At Stella f'l/I, the counter 1 direction C of the counter is cranked by one. After Stella f14, proceed to Stella f1.

(S) At corner 15, the counter's 1 count is determined (whether C is smaller than 0, I, or not).

If C is exceeded, proceed to step 16;
<If it is not 0, proceed to step 11.

In step '1G, the counter (direction C) is set to O. After step 1G, the process advances to step 11.

In step 17, it is determined whether there is one flag l"a. If the flag Fa=1, the process proceeds to step '18; on the other hand, if the flag Fa=1, the process proceeds to step '24. .

In step 18, it is determined whether the flag Fb is 1 or not. When the flag Fb is equal to 1, the process proceeds to step 21, whereas when the flag Fb is not 1, the process proceeds to step 19.

In step 19, C is the counter (il') of the counter.
The reduction mΔE of the exhaust gas recirculation flow during idling operation is determined according to iC, and the flag Fb is set to 1.
The flag is switched to Counter C and reduction m△
The relationship with E is, for example, as shown in Figure 3.
Until the counter value C of the counter reaches the first predetermined value C×, it is not related to the increase in the counter value C (the reduction amount △E is a constant maximum of 111 [F, and the counter value is the first predetermined value C×
When the value is greater than or equal to Cx and less than the second predetermined value Cy, the counter (the reduction amount △1 ball decreases in inverse proportion to the increase in the number of DCs), and when the counter value C is greater than or equal to the second predetermined value Cy, the counter Regardless of the increase in the counter value C, the reduction amount ΔF becomes a constant minimum value.
After E is determined, the counter value of the counter is set to 0. After step 19, the process advances to step 20.

In step 20, a pulse signal with a predetermined duty ratio Eou1 based on the lc exhaust gas recirculation flow @I3i is output to the negative Jl regulating valve 29.

9. The control valve 29 is supplied with the AI pulse signal to adjust the negative pressure according to the 1) gas recirculation flow ff1Ei, that is, the JJI gas recirculation flow suspension value during noidle operation. - output to the output baud 1 to 30, and to this negative pressure the exhaust gas recirculation control valve 19 is activated. Exhaust gas recirculation takes place at the initial flow rate set. Step 20 is followed by a reset.

In step 21, the duty ratio EO(1) of the pulse signal that has been output to the negative pressure regulating valve 29 until now is reduced by the reduction amount ΔF() determined in step 19. .

In step 22, it is determined whether the D:L--eye ratio Fout of the pulse signal reduced in step 21 is smaller than O. When the duty ratio of the pulse signal Eout<Q, the process proceeds to step 23;
If the duty ratio of the pulse signal is not [ouL·guO, the process advances to step 25.

In step 23, flag switching is performed to set the flag Fa to O. At Slack/23, the process proceeds to step 24.

In step 24, the pulse signal A]-T ratio E
out is set to O. That is, the A-off signal is output. When the negative pressure regulating valve 29 is given the A-f signal, it no longer outputs substantial negative pressure to the negative pressure output port 3o.
As a result, the 1/1 fucus recirculation control valve 11 is closed, and exhaust gas recirculation is stopped. Next to step 23, replay 1 is performed.

By performing control according to the above-mentioned frame D-11-, the counter (11C) indicates that the diesel engine 1 is operated at a rotational speed higher than a predetermined value and fuel injection per culm is performed. It is counted up only when the number of fleas is above a predetermined value, and at other times it is counted down to 1. Therefore, the amount of reduction in the exhaust gas %1i recirculation flow rate during idling operation determined according to this counter 110C is △E In this case, the tee pill engine 1 is operated at high speed and high negative direction before idling operation, that is, the engine temperature rarely becomes high, and the diesel engine 1 is operated at low speed and low load In other words, when the engine temperature becomes low, the amount of 11M increases.

By determining the amount of reduction in the recirculation flow rate of hydrogen gas in this way, as shown in FIG. When the engine is operated in a high negative direction, the reduction rate of the exhaust gas recirculation flow rate is small, and accordingly, the exhaust gas recirculation time becomes longer. In addition, NO x IIJi in the exhaust gas generated during idling operation can be effectively reduced within a range that does not cause low-temperature corrosion.

In addition, in this embodiment, during the warm-up process when the temperature of the cooling water of the first stage is below a predetermined temperature, step 1 is
3. By setting the counter C to 0, no exhaust gas recirculation takes place during the warm-up process, especially during idling operation.

In the flowchart shown in FIG. 2, the initial value Ei of the exhaust gas recirculation flow rate during idling operation is kept constant, but as shown in FIGS. 5 to 7, the initial value E1 may be determined according to the counter value of the counter.

In this case, as shown in FIGS. 6 and 7, the initial value Ei of the exhaust gas recirculation flow rate is set to As a result, the degree of Noxa in the exhaust gas during idling operation can be reduced even more effectively within the range C that does not cause low-temperature corrosion.

FIG. 8 shows the main parts of another example of a control device for carrying out the exhaust gas recirculation control method according to the present invention. In this embodiment, when the C flag "b" is 1 in step 18 and after step 19, the process proceeds to step 26. In step 26, the idle operation state 43 is After the diesel engine 1 enters the on state, it is determined in the converter 751 whether a predetermined time T has elapsed since the diesel engine 1 entered the idle operating state.The diesel engine 1 enters the idle operating state. i.e. for a predetermined period of time 1 from the start of idling operation.
If the predetermined time period (3) has not elapsed yet, the process proceeds to step 20, whereas after the predetermined time (2) has elapsed since the start of idling, the process proceeds to step 21.

Therefore, in this embodiment, as shown in FIG. 9, the exhaust gas recirculation flow m is maintained at the initial value without being reduced until a predetermined period of time has elapsed from the start of the nodule operation. , after a predetermined period of time has elapsed since the start of idling, the counter decreases with the passage of time at a predetermined reduction rate according to the counter mc.

In the embodiment shown in FIGS. 8 and 9, the initial value of the exhaust gas recirculation flow rate during idle operation is constant, but the initial value 11a is the same as that in FIGS. 10 and 11. As shown in FIG.
Variable settings may be made in the same manner as in the embodiments shown in FIGS. 7 to 7.

Further, during idling operation, the time T for maintaining the exhaust gas recirculation flow rate at the initial value may be variably set according to the counter value C of the counter, as shown in FIGS. 12 to 14. .

In this case, the exhaust gas recirculation time 1'' is
As shown in Figure 4, the counter la of the J counter
The longer C can be set, that is, the higher the engine temperature is.

Although the present invention has been described in detail with respect to specific embodiments above, the present invention is not limited thereto, and various embodiments are possible within the scope of the present invention. This will be clear to those skilled in the art.

[Brief explanation of the drawing]

Fig. 1 shows a schematic configuration diagram of one embodiment of an exhaust gas recirculation device implementing the exhaust gas recirculation control method according to the present invention, and Fig. 2 shows an implementation of the exhaust gas recirculation control method according to the present invention. Figure 3 is a flowchart showing the procedure; Figure 3 is a graph showing the relationship between the counter value and the reduction in the exhaust gas recirculation flow rate during idle operation; Figure 4 is shown in Figure 2; FIG. 5 is a graph showing the change over time in the exhaust gas recirculation flow rate during idling operation in the embodiment, and FIG. Figure 6 is a graph showing the relationship between the counter value of the counter and the exhaust gas recirculation flow rate that increases during idling operation. Fig. 8 is a flowchart showing another embodiment of the implementation procedure of the exhaust gas recirculation control method according to the present invention with respect to its recesses. , FIG. 9 is a graph showing the change over time in the exhaust gas recirculation flow rate during idling operation in the IC embodiment shown in FIG. 8, and FIG. Still another example of the implementation procedure is not shown for its main parts.
T-1-1 FIG. 11 is a graph shown in FIG. 10 and shows the change over time in the exhaust gas recirculation flow rate during idling operation in the IC embodiment, and FIG. 12 is the exhaust gas recirculation control according to the present invention. Another embodiment of the implementation procedure of the method will be explained with reference to its main parts. Figure 13 is a graph showing the relationship between the counter value of the counter and the exhaust gas recirculation time, and Figure 14 is a graph showing the relationship between the counter value of the counter and the exhaust gas recirculation time. 12 is a graph showing the change over time in the exhaust gas recirculation flow rate during idling operation in the embodiment shown in FIG. 12. 1...Diesel engine, 2...Cylinder boyz3.
・・Viston, 4・Combustion chamber, 5・Swirl chamber, 6・
...Intake manifold, 7...Intake bow 1~,8...
・Exhaust port 1~ 9...Exhaust manifold, 9...Poppet valve, 11
...Exhaust gas recirculation control valve, 12...Casing,
13...Entrance boat, 14...Exit boat, 15.
··conduit. 16... Exhaust gas extraction boat, 17... Conduit, 1
8...' Exhaust gas injection boat, 19... Valve element, 2
0... Valve seat portion, 21... Valve boat, 22... Valve rod 1~. 23...Diaphragm device, 24...Casing, 25...Diaphragm, 26...Die 17
Fram chamber, 27... Compression coil spring, 28... Conduit, 29... Negative pressure regulating valve, 30... Negative pressure output capo-1~
, 31...Negative pressure input boat, 32゛...Negative pressure pump,
33... Conduit, 40... Control device. 41... fuel injection sensor υ, 42... rotation speed sensor. 43...Idle switch, 44...Water temperature switch Special n Applicant 1- Yota Automobile Co., Ltd. Agent
Person Patent Attorney Masaki AkashiFigure 3Figure 4Figure 6Figure 7Counter value C-O time□Figure 8Figure 9Figure 11Figure U Time- Figure 10Figure 12

Claims (1)

[Claims] During idle operation, exhaust gas is recirculated for a predetermined period of time from the start of idle operation, and the exhaust gas recirculation flow rate is
/ The flow rate is reduced over time at a flow reduction rate determined according to the engine operating state before entering the idle operating state, and during operations other than idling, the flow rate is determined as needed according to the diesel engine operating state at that time. (A method for controlling exhaust gas recirculation in a diesel engine, characterized by performing exhaust gas recirculation.