JP3361841B2 - Diesel engine with exhaust gas recirculation device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diesel engine equipped with an exhaust gas recirculation device for recirculating a part of exhaust gas to the intake side.

[0002]

2. Description of the Related Art In a diesel engine, an exhaust gas recirculation passage branched from the middle of the exhaust passage is provided to mix exhaust gas with intake air to reduce NO _X , and this exhaust gas recirculation passage is connected to the intake side. The exhaust gas is recirculated to the intake side due to the engine back pressure.

In the above diesel engine equipped with an exhaust gas recirculation device, a backwashable soot trap is provided in the middle of the exhaust gas recirculation passage in order to remove the soot and dust contained in the recirculation gas. This soot trap removes soot and dust contained in the recirculation gas flowing in the exhaust gas recirculation passage by adhering it to, for example, a ceramic filter. Also, in order to remove the soot and dust adhering to the filter, it is possible to perform so-called backwashing in which cleaning air is blown to the filter from the direction opposite to the flow direction of the reflux gas and the cleaning air is discharged from the exhaust passage to the outside of the engine. There is.

[0004]

When the soot trap is backwashed during the operation of the engine, the wash air is jetted in the direction opposite to the flow direction of the recirculation gas, and the jet air pressure thereof is propagated to the exhaust pipe. There is a problem that the engine back pressure increases and the engine speed decreases. In particular, when the load is low and the recirculation rate is large, fluctuations in the rotation speed are large, and when the fluctuations in the rotation speed are unfavorable, such as in a generator engine, this is a serious problem.

Further, at the time of starting the operation of the engine or the start of exhaust gas recirculation, the temperature of the exhaust gas recirculation passage and the soot trap is low, so that the recirculation gas condenses to generate strongly acidic condensed water, which causes the pipe and engine to It shortens the life.

An object of the present invention is to provide a diesel engine equipped with an exhaust gas recirculation device that can solve the above-mentioned conventional problems.

[0007]

It is an the matter onset bright features [SUMMARY OF] includes an exhaust passage, an exhaust gas recirculation passage branched from the exhaust passage part of the exhaust gas in order to recirculate to the intake side, the recirculating gas A soot trap that can be backwashed in the middle of the exhaust gas recirculation passage to remove soot and dust contained in the exhaust gas, a back pressure control valve that is provided in the middle of the exhaust passage to adjust the engine back pressure, and the soot trap. And a control device for controlling the opening of the back pressure adjusting valve so that the backwash air pressure is released during the backwash.

[0008] a temperature detecting means for detecting the temperature of the exhaust gas recirculation passage of that, a bypass passage for connecting the intermediate portion of the exhaust gas recirculation passage and an exhaust passage, an intake side and the bypass path side flow recirculated gas preferably comprises a selectively switchable changeover valve, the flow of the recirculation gas corresponding to the temperature of the exhaust gas recirculation passage is a control device for operating controls cut switched so switching valve on the intake side and a bypass road in .

[0009]

According to the above-mentioned structure of the present invention, when backwashing the filter of the soot trap, the backwash air pressure can be released to the outside of the engine by adjusting the opening of the back pressure control valve.
It is possible to prevent the engine back pressure from rising.

According to the above preferred construction, in the range where the temperature in the exhaust gas recirculation passage is low and the recirculation gas is condensed, the recirculation gas containing strongly acidic condensed water is discharged from the bypass passage to the outside of the engine through the exhaust passage, The recirculation gas can be recirculated to the intake side in a range where the temperature in the exhaust gas recirculation passage is high and condensation of the recirculation gas does not occur.

[0011]

EXAMPLES Hereinafter, with reference to FIGS describing the present matter onset Ming embodiment.

A multi-cylinder diesel engine 1 shown in FIG. 1 includes an engine body 2, an intake manifold 9 connected to an intake port of the engine body 2, and an exhaust turbocharger 4 connected to the intake manifold 9. The compressor 4b, the intake pipe 8 connected to the compressor 4b, the filter 16 provided at the inlet of the intake pipe 8, and the exhaust manifold 3 connected to the exhaust port of the engine body 2
A turbine 4a of the exhaust turbocharger 4 connected to the exhaust manifold 3, an exhaust pipe 5 connected to the turbine 4a, and a first back pressure control valve 6 provided in the middle of the exhaust pipe 5. And an exhaust economizer 10 provided at the outlet of the exhaust pipe 5. In the exhaust pipe 5, a bypass pipe 51 that connects the upstream side and the downstream side of the first back pressure adjusting valve 6 is provided.
A second back pressure adjusting valve 52 constituted by an electromagnetic opening / closing valve is provided in the middle of.

In order to recirculate a part of the exhaust gas flowing through the exhaust pipe 5 to the intake side, an exhaust gas recirculation pipe 7 branches from the exhaust pipe 5, and the exhaust gas recirculation pipe 7 is connected to the intake pipe 8. ing. In the middle of the exhaust gas recirculation pipe 7, a soot trap 1 for removing soot and dust contained in the recirculation gas.
1, a heater 12 for heating the reflux gas for purifying the reflux gas by the oxidation catalyst, an oxidation catalyst 13 for purifying the reflux gas,
A cooler 14 for cooling the reflux gas and a valve 15 for controlling the reflux rate are provided.

The soot trap 11 is shown in FIG.
As shown in FIG. 2, the exhaust gas recirculation pipe 7 has a pair of passages 11a and 11b, and ceramic filters 18 and 19 are provided in the passages 11a and 11b. As shown by A and B, soot and dust contained in the reflux gas flowing through the passages 11a and 11b are attached. The ceramic filters 18, 19
Downstream, the air injection devices 22 and 23 for injecting the cleaning air into the passages 11a and 11b, and the passages 11a and 1b.
Electromagnetic valves 20 and 21 for opening and closing 1b are provided. The air injection devices 22 and 23 are composed of, for example, a high pressure air source and an air ejection nozzle opened and closed by a solenoid valve.
Normally, both electromagnetic on-off valves 20 and 21 are opened as shown in (1) of FIG. 2, and reflux gas flows through both passages 11a and 11b. When cleaning one ceramic filter 19,
As shown in (2) of FIG. 2, the electromagnetic valve 21 downstream of the one ceramic filter 19 is closed, and the reflux gas is allowed to flow only through the one passage 11a. As shown, one air injection device 2
The cleaning air from 3 is blown onto the filter 19 from the direction opposite to the flow direction of the reflux gas to remove the soot and dust adhering to the filter 19. When cleaning the other ceramic filter 18, the other electromagnetic valve 20 is closed, and the cleaning air is blown from the other air injection device 22 to the filter 18 from the direction opposite to the flow direction of the reflux gas.

A control device 60 for controlling the opening of the second back pressure adjusting valve 52 is provided so that the engine back pressure is released when the soot trap 11 is backwashed. The control device 60 is composed of, for example, a microcomputer, is connected to the air injection devices 22 and 23 of the soot trap 11, the solenoid valves 20 and 21, the second back pressure adjusting valve 52, and the operation panel outside the drawing, and is reverse from the operation panel. When the washing start signal is input, the soot trap 11 is backwashed according to the time chart shown in FIG. 3 and the opening / closing control of the second back pressure adjusting valve 52 is performed. That is, first, the second back pressure adjusting valve 5
2 open and a pair of solenoid valves 2 of the soot trap 11
After closing one of 0 and 21 and opening and closing it, one of the pair of air injection devices 22 and 23 is turned on for a certain period of time to perform backwashing, and after the jet air pressure escapes to the outside of the engine, the second back pressure adjustment is performed. The valve 52 is closed and one of the solenoid valves 20, 21 is opened.

According to the above configuration, the backwash air pressure is released when backwashing the filters 18 and 19 of the soot trap 11, so that the engine back pressure which is conventionally increased as shown by the broken line in FIG. As shown by the solid line, there can be almost no fluctuation. As a result, in the conventional case, the engine speed that decreases as shown by the broken line in FIG. 3 can be maintained constant as shown by the solid line.

[0017] It should be noted that the present matter onset Akira is not limited to the embodiments described above. For example, FIG. 4 shows a first modification of the above embodiment. The difference from the above embodiment is that instead of the bypass pipe 51 connecting the upstream side and the downstream side of the first back pressure adjusting valve 6 in the exhaust pipe 5, the downstream side of the first back pressure adjusting valve 6 in the exhaust pipe 5 is replaced. A bypass pipe 71 connecting the exhaust gas recirculation pipe 7 and the exhaust gas recirculation pipe 7 is provided, and a second back pressure adjusting valve 52 configured by an electromagnetic opening / closing valve is provided in the middle of the bypass pipe 71.
Others are the same as the above-mentioned embodiment, and the same portions are denoted by the same reference numerals. FIG. 5 shows a second modification of the above embodiment. The difference from the above-mentioned embodiment is that the bypass pipe 51 and the second back pressure adjusting valve 52 are not provided, and the opening degree of the first back pressure adjusting valve 6 is reversed by the control device 60 when the soot trap is backwashed. It is controlled to release the wash air pressure. Others are the same as the above-mentioned embodiment, and the same portions are denoted by the same reference numerals.

[0018] In the following, this matter onset Ming good with reference to FIGS. 6 to 8
An example of a better configuration will be described.

A multi-cylinder diesel engine 1 shown in FIG. 1 includes an engine body 2, an intake manifold 9 connected to an intake port of the engine body 2, and an exhaust turbocharger 4 connected to the intake manifold 9. The compressor 4b, the intake pipe 8 connected to the compressor 4b, the filter 16 provided at the inlet of the intake pipe 8, and the exhaust manifold 3 connected to the exhaust port of the engine body 2
A turbine 4a of the exhaust turbocharger 4 connected to the exhaust manifold 3, an exhaust pipe 5 connected to the turbine 4a, and a back pressure control valve 6 provided in the middle of the exhaust pipe 5. An exhaust economizer 10 provided at the outlet of the exhaust pipe 5 is provided.

In order to recirculate a part of the exhaust gas flowing through the exhaust pipe 5 to the intake side, an exhaust gas recirculation pipe 7 branches from the exhaust pipe 5, and the exhaust gas recirculation pipe 7 is connected to the intake pipe 8. ing. A temperature detection sensor 31 for detecting the temperature in the exhaust gas recirculation passage 7 is provided in the middle of the exhaust gas recirculation pipe 7.
A soot trap 11 for removing soot and dust contained in the recirculation gas, a cooler 14 for cooling the recirculation gas, and a solenoid valve-type recirculation rate control valve 15 for controlling the exhaust gas flow rate to the intake pipe 8 are provided. Has been. A solenoid valve type flow control valve 32 is provided on the water supply side of the cooler 14.

A bypass pipe 36 is provided which connects between the cooler 14 and the recirculation rate control valve 15 in the middle of the exhaust gas recirculation pipe 7 and the upstream side of the exhaust economizer 10 in the exhaust pipe 5. . A solenoid valve type three-way switching valve 35 capable of selectively switching the flow of the recirculation gas between the intake side and the bypass pipe 36 side is provided at the connection portion between the exhaust gas recirculation pipe 7 and the bypass pipe 36.

The temperature detecting sensor 31, the reflux rate control valve 15, the flow rate control valve 32, and the switching valve 35.
And the load detection sensor 34 of the engine 1 are connected to the control device 33. The control device 33 is composed of, for example, a microcomputer.

The control procedure by the control device 33 will be described with reference to the flowchart shown in FIG. 7 and the time chart shown in FIG.

At the time of starting the engine 1, the flow control valve 3
2, the flow rate of the cooler 14 is maximized, the recirculation gas is caused to flow to the bypass pipe 36 by the switching valve 35, and the recirculation rate of the exhaust gas is minimized by the recirculation rate control valve 15 (step 1). Next, detection of the reflux gas temperature by the temperature detection sensor 31 is started (step 2). Next, it is judged whether or not the detected temperature is equal to or lower than the generation temperature of condensed water (step 3). If the reflux gas temperature is equal to or lower than the condensate water generation temperature, the flow rate of the cooler 14 is minimized, the exhaust gas recirculation rate is maximized, and the process returns to step 2 (step 4). As a result, the temperature of the recirculation gas is increased following the temperature increase of the engine exhaust gas, and the temperature increase is promoted.
Next, if the reflux gas temperature exceeds the condensate water generation temperature, the flow rate of the cooler 14 is maximized and the switching valve 35 allows the reflux gas to flow to the intake side (step 5). Thereafter, the recirculation rate control valve 15 is controlled according to the load detected by the load detection sensor 34, and the recirculation rate of the exhaust gas is controlled as in the conventional case. The recirculation rate control valve 15 may be controlled not only according to the engine load but also according to other factors such as humidity.

According to the above configuration, in the range where the temperature in the exhaust gas recirculation passage is low and the recirculation gas is condensed, the recirculation gas containing strongly acidic condensed water is discharged from the bypass pipe 36 to the outside of the engine through the exhaust pipe 6. As long as the temperature in the exhaust gas recirculation passage is high and the condensation of the recirculation gas does not occur, the recirculation gas can be recirculated to the intake side. This can prevent the reflux gas containing the strongly acidic condensed water from shortening the life of the pipe or the engine.

[0026] It should be noted that the preferred configuration of the Akira this matter onset is not limited to the embodiments described above. For example, in place of the bypass pipe 36 that connects the exhaust gas recirculation pipe 7 and the downstream side of the exhaust economizer 10 in the exhaust pipe 5, as shown by the phantom line in FIG. A bypass pipe 36 ′ that connects to the downstream side of the exhaust economizer 10 may be provided to eliminate the pressure loss of the recirculation gas by the exhaust economizer 10 and accelerate the temperature rise of the recirculation gas.

[0027]

According to the present matter onset light according to the present invention, never engine speed drops by performing cleaning of the soot trap during engine operation.

According to the present matter onset Ming preferred configuration, it is possible to prevent the reflux gas containing strongly acidic condensate will shorten the life of the pipes and institutions.

[Brief description of drawings]

FIG. 1 is a diagram illustrating the configuration of this matter onset Ming Example

FIG. 2 is an explanatory diagram of a soot trap configuration according to an embodiment of the present invention.

[Figure 3] this matter onset Akira embodiment time chart for describing control of

[4] Configuration diagram of the matter onset Ming first modification

FIG. 5 is a diagram illustrating the configuration of this matter onset Akira of the first modification

[6] diagram illustrating the configuration of an embodiment of the present matter onset Akira preferred arrangement

FIG. 7 is a flowchart of an embodiment of the present matter onset Akira preferred arrangement

[8] this matter onset Ming preferred configuration embodiment time chart for describing control of the

[Explanation of symbols]

5 exhaust pipe 6 1st back pressure control valve 7 Exhaust gas recirculation pipe 8 intake pipe 11 suit trap 31 Temperature sensor 33 Control device 35 Switching valve 36 Bypass pipe 52 Second back pressure control valve 60 control device

─────────────────────────────────────────────────── ───Continued from the front page (56) References JP-A-4-17711 (JP, A) JP-A-4-31613 (JP, A) Fukuihei 2-46058 (JP, U) (58) Field (Int.Cl. ⁷ , DB name) F02M 25/07 580 F02M 25/07 570 F02D 9/04

Claims (2)

(57) [Claims] 1. An exhaust passage, an exhaust gas recirculation passage branched from the exhaust passage for recirculating a part of exhaust gas to an intake side, and an exhaust gas recirculation passage for removing soot and dust contained in the recirculation gas. A soot trap that can be backwashed, a backpressure control valve that is provided in the middle of the exhaust passage to adjust the engine backpressure, and a backpressure that allows backwash air pressure to escape when backwashing the soot trap. A diesel engine with an exhaust gas recirculation device, comprising: a control device that controls the opening of a control valve. 2. A temperature detection means for detecting the temperature of the exhaust gas recirculation passage of that, the bypass passage and the intake side and the bypass flow of recirculated gas connecting the intermediate portion of the exhaust gas recirculation passage and an exhaust passage claims comprising: a switching valve switchable selectively to the roadside, the flow of the recirculation gas corresponding to the temperature of the exhaust gas recirculation passage is a control device for operating controls cut switched so switching valve on the intake side and a bypass road Item 1. A diesel engine with an exhaust gas recirculation device according to Item 1 .