JPH08261071A - Egr device for diesel engine - Google Patents

Abstract

PURPOSE: To prevent cooling water from cumulating in a cooler at the time of engine stop so as to prevent corrosion of the cooler by connecting the cooler for cooling reflux exhaust gas and a reserve tank to each other through a drain pipe, and interposing the drain valve for opening the flow passage of the drain pipe at the time of engine stop. CONSTITUTION: In the reflux (EGR) range of a diesel engine 1, a part of exhaust gas G discharged passing an exhaust passage 3 is refluxed in an intake passage. At this time, cooling water W in a reserve tank 11 is led in a cooler 13 mounted in an EGR pipe 5 by a water pump 19 through a cooling water leading-in pipe 15, cooling water W is circulated from a cooling water leading-out pipe 17 to the reserve tank 11 through a condenser 21, and exhaust gas G passing the EGR pipe 5 is cooled. When a pump 19 is stopped and then circulation of cooling water W is stopped, a drain valve 47 is opened, and cooling water W remained in a tube and a core bottom part 31' is discharged to the tank 11 through the drain pipe 45.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an EGR device for a diesel engine.

[0002]

2. Description of the Related Art In order to reduce nitrogen oxides (NO _x ) generated during combustion of a diesel engine, an EGR device has been known which recirculates a part of exhaust gas to the intake side (EGR). Nitrogen oxides are formed by the reaction of oxygen and nitrogen in the air under high-temperature exhaust gas, so this EGR device lowers the combustion temperature by exhaust gas recirculation and suppresses the generation of nitrogen oxides. In this EGR device, the lower the temperature of the exhaust gas recirculated to the intake side,
It has been experimentally revealed that the generation of nitrogen oxides during combustion is reduced.

Therefore, these days, as shown in FIG. 2, an intake passage (not shown) and an exhaust passage 3 of the diesel engine 1 are provided.
There is known an EGR device 9 in which a water-cooling type cooling device 7 is attached to an EGR pipe 5 connected between and. The cooling device 7
Is a reserve tank 11 arranged separately from the reserve tank of the engine cooling system, and a cooler 13 attached to the EGR pipe 5.
Are connected by a cooling water inlet pipe 15 and a cooling water outlet pipe 17 to form a cooling water passage, and the reserve tank 1 is provided in this cooling water passage.
The cooling water W in 1 is circulated by the water pump 19, and the cooling water W that has cooled the exhaust gas G by the cooler 13 is cooled by the radiator 21 mounted on the cooling water outlet pipe 17 and returns to the reserve tank 11. It is like this.

FIG. 3 shows a conventional example of the cooler 13, which is equipped with the EGR via the flange 23.
A large number of plate fins 27 and a plurality of flat tubes 2 that are stacked in a tubular container 25 made of metal connected to the tube 5.
9 has a structure in which a core 31 composed of 9 is mounted.
Then, as shown in FIGS. 3 and 4, the cooling water W introduced from the cooling water introduction pipe 15 flows down the tube 29 and is inverted at the core bottom portion 31 ′, and then passes through another tube 29 again to cool the cooling water. The exhaust gas G is introduced from the outlet pipe 17 to the radiator 21, and the exhaust gas G flowing into the EGR pipe 5 from the exhaust passage 3 is cooled by the cooling water W flowing through the tube 29 when passing through the core 31. Becomes

Therefore, according to the EGR device 9, since the exhaust gas G cooled by the cooling device 7 is recirculated to the intake passage, the combustion temperature is lowered and the generation of nitrogen oxides is suppressed.

[0006]

However, in the cooling device 7, since the water pump 19 is stopped with the stop of the diesel engine 1 and the circulation of the cooling water W is stopped,
When the diesel engine 1 stops, the tube 29 may be corroded by the condensed water generated by cooling the EGR gas during long-term use.

If the tube 29 is damaged, the cooling water W leaks into the diesel engine 1 (in the cylinder) and the diesel engine 1 deteriorates. In the worst case, there is a risk of engine damage due to a water hammer. It was
The present invention has been devised in view of such circumstances, and when cooling the exhaust gas with a water-cooled cooler mounted on the EGR pipe, even if corrosion of the cooler due to condensed water in the EGR pipe occurs, the engine stops. An object of the present invention is to provide an EGR device for a diesel engine in which cooling water is prevented from entering the inside of the engine.

[0008]

In order to achieve such an object, the invention according to claim 1 provides an EGR pipe connected between an intake passage and an exhaust passage of a diesel engine.
A cooler for cooling the exhaust gas flowing back to the intake passage via the R pipe is installed, the cooler and the reserve tank are connected by the cooling water introduction pipe and the cooling water discharge pipe, and the cooling water discharge pipe is connected to the cooling water. EGR of diesel engine equipped with radiator
In the device, the cooler and the reserve tank are connected by a drain pipe, and the drain pipe is equipped with a drain valve that opens a flow path of the drain pipe when the engine is stopped.

The invention according to claim 2 is based on claim 1.
In the diesel engine EGR device described above, the reserve tank is arranged separately from the reserve tank of the engine cooling system connected to the radiator, and the invention according to claim 3 is characterized in that the reserve tank is , A reserve tank for an engine cooling system connected to a radiator.

[0010]

According to the inventions according to each claim, the cooling water in the reserve tank is introduced into the cooler through the cooling water introducing pipe,
It circulates from the cooling water outlet pipe to the reserve tank through the radiator.

Then, the cooling water introduced into the cooler is EG
The exhaust gas passing through the R pipe is cooled, and the cooling water is cooled by the radiator. Also, when the water pump stops and the circulation of cooling water stops with the stop of the diesel engine, the drain valve opens the flow path of the drain pipe, so the cooling water remaining in the cooler is reserved via the drain pipe to the reserve tank. Will be discharged to.

When the diesel engine is driven again, the drain valve closes the drain pipe.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. Incidentally, the same parts as those of the conventional example shown in FIG.

FIG. 1 shows the EGR according to claim 1 and claim 2.
An embodiment of the device is shown, in which 33 is an EGR valve mounted on the EGR pipe 5, and the EGR valve 33 is the EGR pipe 5.
It is mounted near the connecting portion between the exhaust passage 3 and the exhaust passage 3. This E
The GR valve 33 opens and closes the flow path of the EGR pipe 5 by driving the actuator 37 in response to a command from the control unit 35. As in the conventional case, the control unit 35 includes a rotation sensor 39 mounted on the diesel engine 1. A signal from the rack sensor 43 mounted on the fuel injection pump 41 is input. Then, the control unit 35 drives the actuator 37 in a predetermined EGR region of the diesel engine 1 based on the signals from both the sensors 39 and 43 to open the flow path of the EGR pipe 5. ing.

The drain pipe 4 is provided between the core bottom 31 'of the cooler 13 mounted on the EGR pipe 5 and the reserve tank 11.
5 are connected. A drain valve 47 controlled by the control unit 35 is attached to the drain pipe 45, and the control unit 35 controls the diesel engine 1 based on the signals from the rotation sensor 39 and the rack sensor 43 described above. When stopped, drain valve 47
Command to the actuator 49 that drives the drain pipe 4
The flow channel 5 is opened.

Since the EGR device 51 according to the present embodiment is constructed in this way, the EGR valve 33 causes the passage of the EGR pipe 5 to flow in the EGR region of the diesel engine 1 under the control of the control unit 35 in a predetermined EGR region. Since it is opened, part of the exhaust gas G discharged through the exhaust passage 3 is returned to the intake passage via the EGR pipe 5. Then, at this time, the cooling water W in the reserve tank 11 is introduced into the cooler 13 attached to the EGR pipe 5 through the cooling water introduction pipe 15 by the water pump 19, and the heat is radiated from the cooling water discharge pipe 17. It circulates to the reserve tank 11 through the container 21,
The cooling water W introduced into the cooler 13 cools the exhaust gas G passing through the EGR pipe 5. Then, the cooling water W is cooled by the radiator 13.

With the stop of the diesel engine 1,
When the water pump 19 is stopped and the circulation of the cooling water W is stopped, the control unit 35 operates the drain valve 47 to open the flow path of the drain pipe 45, so that the cooling water W remaining on the tube 29 or the core bottom portion 31 'is formed. Will be discharged to the reserve tank 11 via the drain pipe 45. Then, when the diesel engine 1 is driven again, the EGR is restarted and the control unit 35 closes the drain valve 47 of the drain pipe 45.

As described above, in this embodiment, the core bottom 31 'of the cooler 13 mounted on the EGR pipe 5 and the reserve tank 1 are provided.
1 is connected to the drain pipe 45, and
Since the drain valve 47 that opens the flow path when the diesel engine 1 is stopped is attached, the cooling water W does not accumulate in the tube 29 of the cooler 13 even when the diesel engine 1 stops.

Therefore, according to this embodiment, even if the tube 29 is corroded by the condensed water generated by cooling the EGR gas, the diesel engine 1 is stopped while the engine is stopped.
Since the cooling water W does not enter the inside, it is possible to prevent deterioration of the diesel engine 1 and engine destruction due to water hammer.

In the above embodiment, the reserve tank 11 and the water pump 19 are installed separately from the reserve tank and the water pump of the engine cooling system, and the reserve tank 11 and the core bottom 31 'of the cooler 13 are drained. Tube 45
However, the reserve tank 11 and the water pump 19 may be replaced with a reserve tank and a water pump for an engine cooling system connected to a radiator, as in the inventions according to claims 1 and 3. Of course.

Although not shown, this embodiment can also achieve the intended purpose as in the case of the above embodiment.

[0022]

As described above, according to the inventions according to the claims, even if the diesel engine is stopped, the cooling water is not accumulated in the cooler mounted on the EGR pipe. Even if the cooler corrodes due to the condensed water generated by cooling the engine, the cooling water will not enter the diesel engine when the engine is stopped, and it is possible to prevent deterioration of the diesel engine and engine damage due to water hammer. It was

[Brief description of drawings]

FIG. 1 is a schematic view of an embodiment of an EGR device according to claims 1 and 2.

FIG. 2 is a schematic diagram of a conventional EGR device.

FIG. 3 is a partially cutaway side view of a conventional cooler mounted on an EGR pipe.

FIG. 4 is a front view of the main part of the core.

[Explanation of symbols]

 1 Diesel Engine 3 Exhaust Passage 5 EGR Pipe 11 Reserve Tank 13 Cooler 15 Cooling Water Inlet Pipe 17 Cooling Water Outlet Pipe 19 Water Pump 21 Radiator 33 EGR Valve 35 Control Unit 45 Drain Pipe 47 Drain Valve 51 EGR Device G Exhaust Gas W Cooling water

Front Page Continuation (72) Inventor Konobu Hirata, 1-chome, Ichi-chome, Ageo-shi, Saitama, Nissan Nissan Diesel Industry Co., Ltd.

Claims (3)

[Claims] 1. An EGR pipe connected between an intake passage and an exhaust passage of a diesel engine is equipped with a cooler for cooling exhaust gas flowing back to the intake passage via the EGR pipe,
In the EGR device of a diesel engine in which the cooling device and the reserve tank are connected by a cooling water introduction pipe and a cooling water discharge pipe, and a cooling water radiator is attached to the cooling water discharge pipe, the cooling device and the reserve tank are provided. EGR of a diesel engine, characterized in that the drainage pipes are connected with a drainage pipe, and the drainage pipe is equipped with a drainage valve that opens the flow path of the drainage pipe when the engine is stopped.
apparatus. 2. The EGR device for a diesel engine according to claim 1, wherein the reserve tank is arranged separately from the reserve tank of the engine cooling system connected to the radiator. 3. The EGR device for a diesel engine according to claim 1, wherein the reserve tank is a reserve tank for an engine cooling system connected to a radiator.