JPS627943A - Exhaust reflux device of diesel engine - Google Patents

Abstract

PURPOSE:To prevent worsening of combustion during warming-up and decrease of an intake air amount after warming-up, by a method wherein reflux of high temperature EGR gas through a first EGR passage and reflux of low temperature EGR gas through a second EGR passage are effected according to an operating condition and a warming-up condition. CONSTITUTION:First and second EGR passage 21 and 22, through which a suction passage 2 and an exhaust passage 4 located down a line from a suction throttle valve 6 are intercommunicated, are formed. A first EGR control valve 24 is located in the first EGR passage 21, and a second EGR control valve 26 and a cooler 27, cooling reflux exhaust, are located in the second EGR passage 22. Meanwhile, a load sensor 18 and a rotation sensor 19, both detecting an operating condition, and a water temperature sensor 38, detecting a warming-up condition, are provided, and based on the detecting values thereof, a control circuit 39 controls the openings of the throttle valve 6 and the first and second EGR control valves 24 and 26. This performs reflux of high temperature EGR gas through the first EGR passage 21 as it is during warming-up, and effects reflux of EGR gas cooled through the second EGR passage 22 during normal operation after warming-up.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an exhaust gas recirculation device for a diesel engine.

(Prior art) Exhaust recirculation equipment (which recirculates part of the exhaust gas into intake air to suppress combustion in order to reduce NOV emitted from an engine)
In order to improve the exhaust composition without impairing engine drivability, the flow rate of the recirculated exhaust gas (EGR gas) must be adjusted appropriately according to the operating conditions. need to be controlled.

Figure 11 shows an example of an exhaust recirculation device installed in a conventional diesel engine (see Japanese Utility Model Application Publication No. 1987-75942), in which 1 is an air cleaner, 2 is an intake passage, 3 is an engine body, 4 is an exhaust passage, Reference numeral 5 indicates an EGR passage that communicates the intake passage 2 and the exhaust passage 4. The intake passage 2 has a throttle valve 6 upstream of the opening of the EGR passage 5, and an EGR control valve is provided in the middle of the EGR passage 5. Each valve bong is interposed.

The throttle valve 6 is driven by a Guyafram device 8, and a negative pressure source (vacuum pump,
When negative pressure from a vacuum tank, etc.) 10 is applied, the chamber is placed in a predetermined half-open position, and when the pressure chamber 9 is opened to the atmosphere, it is placed in a fully open position. Switching between negative pressure and atmospheric pressure at this time is performed via a three-way solenoid valve 12 that responds to a signal from a control circuit 11.

The EGR control valve 7 is driven by the second Guyar 7 ram device 13, and when the negative pressure from the negative pressure source 10 directly acts on the pressure chamber 14, the EGR control valve 7 is brought to the fully open position, and the negative pressure is reduced (by the orifice 15). When the pressure chamber 14 is opened to the atmosphere, it becomes a fully closed position. This switching between negative pressure, reduced pressure, and atmospheric pressure for the mackerel is performed by second and third three-way solenoid valves 16 and 17 that respond to signals from the control circuit 11. However, three-way solenoid valves 1, 2, 16. : Each motor is energized.
When the power is turned OFF, the baud)N and shoulder are connected, and when the power is turned off, the baud)N and n are connected.

The control circuit 11 detects the load condition of the engine via a load sensor 18 that follows a control lever of a fuel injection pump (not shown) and the rotational speed of the engine via a rotation sensor 19, and detects the engine rotation speed according to the operating condition. E
G Rlfx amount and EGR rate, the three-way solenoid valve 12. :16,1.7 is driven.

For example, in a low-speed, low-load range where a relatively high rate of exhaust gas recirculation is required, the throttle valve (3) is controlled so that it is in the half-open position, and the GR control valve (1) is in the fully open position. 6
A large amount of EG Rff gas is refluxed by the negative pressure generated on the downstream side.

In the partial load range, from this state, the throttle valve 6 is set to the fully open position to cancel the generation of suction negative pressure, and when the load or rotational speed increases to a certain extent, tsG+<control valve 7 is set to the half open position and EG
Decrease Rffx by an odd amount.

Furthermore, in high load ranges and high rotation ranges where the load and rotational speed are large, the EGR is activated to maintain high output from the engine.
Control valve 7 is fully opened to stop exhaust gas recirculation.

In this way, appropriate exhaust gas recirculation is performed depending on the operating state of the engine. Furthermore, Figure 12 shows the three-way solenoid valve 1.
2.16. Throttle valve 6, EGR by control operation of L'l'
The relationship between the opening degree of the control valve 7 and the EGR rate is shown.

(Problem to be Solved by the Invention) However, in such a single-flow exhaust gas recirculation system, the high temperature EGR gas is introduced into the intake air, so the temperature of the intake air increases. Since the actual amount of intake air decreases, smoke and particulates tend to increase and fuel efficiency deteriorates. In addition, since the density of the EGRff gas is low to high, sufficient EQ is required in areas where a large amount of EGR is desired.
A large amount of R was not secured, which made it difficult to effectively suppress No.

Therefore, to solve this problem, the E recirculated into the intake air
One possibility is to cool the GR4, but this will cause the following problems if the engine is not warmed up enough.

For example, in direct-injection diesel engines, when warm-up is insufficient, such as immediately after startup, recirculating an appropriate amount of high-temperature EGR gas stabilizes combustion and reduces unburned HC. If the low-temperature EGR4 gas is refluxed, it will actually worsen combustion.

The present invention aims to solve these problems, α-4=, by cooling the EGRff according to the operating conditions of the engine.

(Means for Solving the Problems) This invention provides an intake throttle valve opening in the middle of the intake passage A, as shown in the ftSi diagram, and connects the intake passage A and the exhaust passage C downstream of the throttle valve opening. 1st communication. A cooler that forms passage water in the second EGR passage and cools the first EGR passage water 1 to the EGR control valve, the second EGR passage water 1 to the second EGR control valve, and the recirculated exhaust gas. On the other hand, means for detecting the operating state of the engine includes a means for detecting a warm-up state, a means for detecting the warm-up state, a means for detecting the warm-up state, and a means for detecting the throttle valve port based on these detected values. The second EGR control valve is provided with a control means for controlling the opening degree of 1.

(Function) Therefore, during warm-up, the first EGR passage has water and the EGR
By guiding the Rff gas, the high temperature EGR and f gas are directly refluxed, thereby preventing deterioration of combustion during warm-up.

On the other hand, during normal operation after warming up, the second EGr (EGR1j') with a cooler installed (by guiding the EGR1j' through the passage H,
This cools the EGR and ff spaces, thereby avoiding a decrease in the amount of intake air and ensuring an appropriate amount of EGR and ff spaces.

(Example) Embodiments of the present invention will be described below based on the drawings.

In Fig. 2, 1 is an air cleaner, 2 is an intake passage, and 3 is an air cleaner.
is the engine body, 4 is the exhaust passage (exhaust manifold),
20 is a turbocharger, and an intake throttle valve 6 driven by a seven-diameter ram device 8 is interposed in an intake passage 2 upstream of the turbocharger 20.

The exhaust passage 4 is connected to the intake passage (intake manifold) 2 via the first and second EGR passages 21 and 22 by the turbocharger 20'' water flow, and the first EGR passage 21 is connected to the intake passage 2 driven by the diaphragm device 23. A first EGR control well 24 is provided.

In addition, the second EGR passage 22 includes a dial diaphragm device 2.
A second EGR control well 26 driven by EGR control well 5 is interposed, and a multi-tube cooler 27, for example, is interposed therebetween.

Cooling water is circulated inside the cooler 27 by a pump from an engine radiator (not shown) through piping 28 and 29, and the EGR water is circulated from the exhaust passage 4 through the second EGR passage 22.
It is designed to cool R gas.

10 is a negative pressure source consisting of a vacuum pump, etc., 12.30
, 31. ．． 32 is a three-way solenoid valve, three-way solenoid valve 12.30
．． Reference numeral 32 communicates the boat l and the shoulder when the power is ON, and transfers the negative pressure from the negative pressure source 10 to each of the diamond 7 ram devices 8 and 23.
, 25 into the pressure chambers 9, 33, and 34, the throttle valve 6 is half-opened, and the EGR control wells 24 and 26 are fully opened. On the other hand, energized O
FF time boat! and n to communicate with each other to form pressure chambers 9 and 3.
3 and 34 to the atmosphere via the chair 35, fully open the throttle valve 6, and fully close the EGR control valves 24 and 26.

In addition, the three-way solenoid valve 31 closes the boat l when the energization is ON, but communicates the boats β and n when the energization is OFF, and introduces atmospheric air from the air cleaner 1 side into the pressure chamber 34 via the orifice 15. When the solenoid valve 32 is ON, the negative pressure introduced into the pressure chamber 34 is reduced, and the EGR control well 26 is half-opened.

On the other hand, the fuel injection pump 36 includes a load sensor 18 and a crank pulley portion 37 as means for detecting the operating state of the engine.
A rotation sensor 19 and a water temperature sensor 38 for detecting engine cooling water temperature as means for detecting the warm-up state of the engine are provided, and these detection signals are sent to a control circuit (control means).
Sent to 39th.

Then, the control circuit 39 controls each of the three-way solenoid valves 12, 30,
31.32 is controlled ON-OFF.

Specifically, during operation after the end of warm-up when the detected value of the water temperature sensor 38 is higher than a predetermined value, the throttle valve 6 is closed depending on the operating state.
and the first and second EGR control wells 24 and 26 in Figures 3 and 4.
Turn on the three-way solenoid valves 12, 30, 31, and 32 to control the opening degrees shown in stages A, B, , C, and D in the figure.
-0-FI-, do.

On the other hand, during warm-up when the detected value of the water temperature sensor 38 is lower than a predetermined value, the throttle valve 6 and the first and second E
G R control valve 24.26 in Figure 3, Figure 5, E, F
Three-way solenoid valve 12.3 ? , 31.32 is turned OFF.

Incidentally, when the detected value of the water temperature sensor 38 is extremely low, regardless of the above conditions, the three-way solenoid valve 12.3 (1, '31.32 is QFFed so as to be in the 1) stage in Fig. 3. Figure 6 shows the control flow based on water temperature.When water temperature T is lower than TI (low temperature set value),
Proceeding from Sl to S2, the D stage is selected, and the water temperature T h
When fT is higher than , and lower than T2 (warm-up set value) (well, S + -S 3 to S.

In step S5, stages E and F are selected depending on the operating condition, and when the water temperature is higher than TfJtT2, stages A, B, C, and I' are selected in accordance with the operating condition in step S5.

With this configuration, during warm-up when the engine cooling water temperature is lower than a predetermined value, the EGR control valve 26 of the second EGR passage 22 is kept fully closed, and the throttle valve 6 and the first EGR control valve 26 are kept fully closed.
The EGR control valve 24 in the passage 21 is activated (see FIGS. 3 and 5). For example, during warm-up idling (E stage), the three-way solenoid valve 12°30 is turned on, and the throttle valve 6
is half open, and the first EGR control valve 24 is fully opened. Furthermore, when the load and rotational speed increase somewhat in this state (F stage), the three-way solenoid valve 12 is turned off and the throttle valve 6 is fully opened.

As a result, the first EGR passage 21 is opened during warm-up, and an amount of EGR corresponding to the operating state is discharged from the first EGR passage 21.
R4 gas is introduced into the intake passage 2.

Therefore, the temperature of the intake air is raised by the high-temperature EGR and f gas, reducing NOx during warm-up operation and achieving stable combustion.

In addition, during warm-up, the ignition delay period of the fuel increases due to the low compression end temperature, and its fluctuations are large, so diesel knock is likely to occur. By heating the intake air, diesel knock can be prevented at low temperatures.

Furthermore, white smoke may be generated due to fuel adhering to the low-temperature combustion chamber wall immediately after startup, but the high-temperature EGRtJ'' gas accelerates the evaporation of the adhering fuel.
White smoke decreases.

On the other hand, when the engine cooling water temperature exceeds a predetermined value and warm-up is completed, the EGR control valve 24 of the first EGR passage 21 is kept fully closed, and the throttle valve 6 and the EGR control valve 26 of the second EGR passage 22 are driven. (See Figures 3 and 4). For example, in the low speed and low load range (A stage), the three-way solenoid valve 12.
31 and 32 are turned on, throttle valve 6 is half open, and the second EGR
Control valve 26 is fully opened. In addition, when entering the partial load range from this state, the three-way solenoid valve 1
2 is turned off and the throttle valve 6 is fully opened (B stage).
Furthermore, the three-way solenoid valve 31 is turned off, and the second EGR control well 26 is half-opened (C stage).

As a result, during normal operation after warming up, the second EGR passage 2
2 is opened, and an amount of EGR gas corresponding to the operating condition is supplied to the intake passage 2 through the second EGR passage 22 in which a cooler 27 is interposed.
The first introduction can be completed.

Therefore, the intake passage 2 is filled with low-temperature glue/GR, which is cooled by the cooling water in the cooler 27. Since the intake air is introduced, the temperature of the intake air does not increase, and a predetermined intake air filling rate can be maintained. In addition, lowering the temperature increases the EGR)
Even in the area where R is performed, the appropriate amount of EGR according to the driving condition
ffs reflux can be done.

As a result, it is possible to prevent an increase in smoke and vapor and to reduce fuel consumption, and it is also possible to sufficiently reduce NOx.

In addition, in the high load range and high rotation range, the throttle valve 6 is fully opened, the first and second EGR control'' + P24-in 26 are fully closed (D stage), and the EGR is stopped. EGR is similarly stopped when the engine load or rotational speed becomes high, or even when the engine cooling water temperature is extremely low. Figures 7 to 10 show other embodiments of the present invention. By way of example, in addition to the control mode 1 of the above embodiment, the first and second F!: G R control valves 24.
are opened at the same time, and the high temperature EG is discharged from the first EGR passage 21.
The low-temperature EG and Rff gases cooled from the second r': GR passage 22 are made to flow at a high speed at the same time.

Even in the low speed and low load range after the end of the warm-up period, it is possible to introduce more E
At this time, the throttle valve 6 is half-opened and the first and second EGR control valves 24 and 26 are fully opened, as shown in stage 2 in Figs. 7 and 8, to recirculate a large amount of EGR and fs. I'm trying to do that.

During idling, the temperature level inside the combustion chamber is relatively low, so the high temperature EGRf is generated along with the low temperature EGRW gas.
Even if F gas is introduced, it will not affect the intake air filling rate by +2, and by introducing high temperature gas, the temperature level in the combustion chamber will increase to a certain extent, so combustion will become stable. While NOx is sufficiently reduced,
It is possible to reduce l-IC and reduce noise during idling.

・However, each stage ■, ■, v, vr, ■, ■ corresponds to ASB, C, E, F, D in FIG. 3, respectively.

In addition, in the low speed and low load range after warming up, control may be performed to the ■ stage as shown in FIG.

(Effects of the Invention) As described above, according to the present invention, high temperature F:
The low-temperature EG is passed from the second EGR passage through the cooler. , f gas is recirculated, it is possible to reduce NOx, white smoke, particulates, and diesel knock during warm-up, and to reduce NOx while suppressing increases in fuel consumption, smoke, and particulates after warm-up.

[Brief explanation of drawings]

Fig. 1 is an hVI diagram of the present invention, Fig. 2 is a configuration diagram showing an embodiment of the invention, Figs. 3 to 5 are tables and diagrams showing its control mode, and Fig. 6 is its control. A flowchart showing the operation, FIGS. 7 to 10 are tables and diagrams of control modes showing other embodiments of the present invention, and FIGS. 11 and 12 are schematic configuration diagrams showing conventional examples and their control. This is the mode table. 2... Intake passage, 4... Exhaust path, 6... Throttle valve, 18... Load sensor, 19... Rotation sensor, 21
... 1st EGR trace, 22... 20th EGR
Passage, 24...first EGR control valve, 26...second
EGR control valve, 27... Cooler, 38... Water temperature sensor, 39... Control circuit. Go to small・\Turn around the side O

Claims (1)

[Claims] An intake throttle valve is interposed in the middle of the intake passage, and first and second EGs communicate the intake passage downstream of the throttle valve and the exhaust passage.
An R passage is formed, and the first EGR passage is provided with a first EGR control valve, and the second EGR passage is provided with a second EGR control valve and a cooler that cools the recirculated exhaust gas. means for detecting a warm-up state; and means for detecting a warm-up state; and a means for detecting a warm-up state;
1. An exhaust gas recirculation device for a diesel engine, comprising a control means for controlling the opening degree of an R control valve.