JPH10325368A - Egr gas cooling device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable promoting warming-up during warming-up an engine. SOLUTION: In an EGR gas cooling device of this type, an EGR cooler 10 adopting engine cooling water to coolant is arranged on the ways of EGR passages 9a, 9b, 9c. An exhaust passage 15 leading to an exhaust passage 7 of an engine 1 is connected to the EGR passages 9b, 9c in the downstream of the EGR cooler 10. A changeover means 14 is arranged for changing over the EGR passage 9c in the downstream of the connection part with the exhaust passage 15.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an EGR for an engine.
The present invention relates to an EGR gas cooling device incorporated in a device.

[0002]

2. Description of the Related Art It is generally known to perform EGR in order to reduce NOx in exhaust gas from an engine.
There is known an EGR gas cooling device that lowers the temperature of the GR gas, improves the gas density, and enhances the NOx reduction effect.

As disclosed in Japanese Patent Application Laid-Open No. Hei 7-180620, this device has an EGR cooler that uses engine cooling water as a refrigerant in the middle of an EGR passage, and provides an EGR cooler between the EGR gas and the engine cooling water. By performing heat exchange at
This is to lower the gas temperature. On the other hand, the engine cooling water whose temperature has been increased by heat exchange is preferably passed through a heater heat exchanger. As a result, the amount of heat obtained by the cooling water can be used for heating the vehicle interior. Further, when this is performed during the engine warm-up operation, the water temperature can be raised in a short time by using the high heat of the exhaust gas, the warm-up of the engine is promoted, and the heating start timing is advanced.

[0004]

By the way, in the apparatus disclosed in the above publication, when the water temperature is to be raised by the heat of the EGR gas, the EGR must be executed without fail. On the other hand, if EGR is performed at a low engine temperature, a large amount of white smoke is generated due to unstable combustion state,
Misfire may cause engine stall. For this reason, there is a problem that EGR cannot be performed during the warm-up operation, and consequently heating of the cooling water cannot be performed.

[0005]

An EGR gas cooling device according to the present invention has an EGR cooler that uses engine cooling water as a refrigerant in the middle of an EGR passage, and the EGR cooler is provided in the EGR passage downstream of the EGR cooler. An exhaust passage leading to an exhaust passage of the engine is connected, and switching means for switching between the EGR passage and the exhaust passage downstream of the connection portion is provided.

According to this configuration, by selecting the exhaust passage by the switching means, the EGR gas after passing through the EGR cooler is discharged to the exhaust passage, and the EGR can be stopped while heating the cooling water. Thereby, the above problem can be solved.

Here, it is preferable that the switching means closes the EGR passage downstream of the connection portion and opens the exhaust passage during an engine warm-up operation. Further, it is preferable that the EGR cooler is disposed in the middle of a cooling water passage for circulating engine cooling water, and a heat exchanger for a heater is provided in the cooling water passage downstream of the EGR cooler.

[0008]

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a block diagram showing an EGR gas cooling apparatus according to the present invention, which is applied to a turbocharged engine. That is, the engine 1 has an intake path 4 composed of an intake pipe 2 and an intake manifold 3, and an exhaust path 7 composed of an exhaust manifold 5 and an exhaust pipe 6. The intake path 4 and the exhaust path 7 are formed by a turbocharger 8. The exhaust gas of the engine 1 drives the turbine 8a and the compressor 8b to perform supercharging.

As a configuration for performing EGR, the exhaust manifold 5 and the intake manifold 3 are connected by EGR pipes 9a, 9b, 9c forming an EGR passage. That is, EG
The R passage extracts a part of the exhaust gas (EGR gas) from the exhaust passage 7 at a position on the upstream side of the turbine 8a and returns it to the intake passage 4 at a position on the downstream side of the compressor 8b, as indicated by the solid line arrow. The fuel is re-burned within 1.

An EGR cooler 10 is provided between the first EGR pipe 9a and the second EGR pipe 9b to cool the EGR gas flowing through the EGR pipes 9a, 9b, 9c. The EGR cooler 10 uses engine cooling water as a refrigerant, that is, introduces cooling water from a cooling water pipe 11a, performs heat exchange between the cooling water and the EGR gas inside, and then cools the cooling water to a cooling water pipe 11b. Is derived.

The cooling water pipe 11b is connected to a heater core 12 as a heat exchanger for the heater, so that the cooling water after the heat exchange is used as a heat source for heating the vehicle interior. The heater core 12 and the engine 1 are connected by a cooling water pipe 11c, and a water pump 13 provided in the engine 1 circulates cooling water in the water pipes 11a. I have. Here, the cooling water pipes 11a, 11b, 11c form a cooling water passage.

Here, an electromagnetic switching valve 14 of three types is interposed between the EGR pipes 9b and 9c, and a return pipe 15 as an exhaust passage extends from the electromagnetic switching valve 14. That is, at a position downstream of the EGR cooler 10, the EGR
An exhaust passage (return pipe 15) is connected to the passage, and an electromagnetic switching valve 14 as switching means is provided at the connection part thereof, and the switching means is an EGR passage (EGR pipe 9c) downstream of the connection part.
And the exhaust passage (return pipe 15). The return pipe 15 is connected to the exhaust path 7 downstream of the turbine 8a. The electromagnetic switching valve 14 performs a switching operation in response to a control signal from a controller 16 such as an ECU serving as a control unit. That is, when it is switched to one, EGR
The return pipe 15 is closed by communicating the pipes 9b and 9c, and when switched to the other, the EGR pipe 9b and the return pipe 15 are connected to close the EGR pipe 9c. The controller 16
The engine speed, engine load, cooling water temperature, and the like are read from various sensors (not shown), and engine control is performed based on these signal values, and switching control of the electromagnetic switching valve 14 is performed. In the intake manifold 3, a flow control valve 17 is provided at the outlet of the EGR pipe 9c. The flow control valve 17 also receives a control signal from the controller 16 and is controlled to a predetermined opening corresponding to the engine operating state. A predetermined amount of EGR gas is supplied to the intake side.

Next, the operation of the present embodiment will be described. First, during normal engine operation, that is, when the cooling water temperature Tw exceeds a predetermined value (for example, Tw> 0 ° C.), the electromagnetic switching valve 14
The return pipe 15 is closed by communicating the GR pipes 9b and 9c, and the EG is closed.
R control can be executed. At this time, the flow control valve 17
The opening is controlled to a predetermined value so that the GR amount becomes optimal. On the other hand, E
The GR gas is cooled by the cooling water when passing through the EGR cooler 10, thereby lowering the gas temperature and increasing the NOx reduction effect.

On the other hand, when the engine is warming up immediately after a cold start or the like, that is, when the cooling water temperature Tw falls below a predetermined value (for example, Tw ≦ 0 ° C.), the electromagnetic switching valve 1
4 communicates the EGR pipe 9b and the return pipe 15 with the EGR pipe 9c.
To make EGR control impossible. And EG
The EGR gas after passing through the R cooler 10 is returned to the exhaust path 7 through the return pipe 15. Since EGR is not performed during the engine warm-up operation, generation of white smoke due to unstable combustion state and engine stall due to misfire can be prevented.

At this time, in the EGR cooler 10, the EGR gas actively heats the cooling water to raise the temperature. Thereby, warm-up is promoted, the engine warm-up time is reduced, and the start time of heating using the heater core 12 can be advanced. As described above, in the present device, the warm-up can be promoted without performing the EGR during the engine warm-up operation, and the problems of the conventional device can be solved at once.

Here, in this apparatus, since the EGR gas is taken out on the upstream side of the turbine 8a, the relatively high pressure EG
R gas can be taken out, and a sufficient amount of EGR gas flowing through the EGR cooler 10 can be secured. When the present device is applied to an engine without the turbocharger 8, a fixed or variable exhaust throttle may be provided between the connection of the EGR pipe 9a and the connection of the return pipe 15.

Here, even during the warm-up operation, when the engine load exceeds a predetermined value (for example, L ≧ 20%), the EGR pipes 9b and 9c are connected and the return pipe is connected similarly to the normal operation. 15 may be blocked. At this time, even if EGR is performed, combustion failure or the like does not occur, so that communication between the EGR pipes 9b and 9c is possible. Further, in the state of the warm-up operation, a part of the exhaust gas is bypassed between the upstream side and the downstream side of the turbine 8a, and the rotation of the turbine 8a is suppressed from increasing, which hinders the boost pressure. This can be prevented by setting the state during normal operation, and a sufficient boost can be achieved.

Even during normal operation, the EGR pipe 9
b and the return pipe 15 to communicate with each other to cut off the EGR pipe 9c,
The EGR pipes 9a and 9b and the return pipe 15 are used as an exhaust bypass passage, and can be used for suppressing an increase in the supercharging pressure. In this case, the electromagnetic switching valve 14 is used as a wastegate valve, so that a separate wastegate valve is not required, and the cost can be reduced by reducing the number of parts. In this case, EGR cannot be executed,
Since such an exhaust bypass control is generally performed when the engine is in a non-EGR region where the engine is operated at a high load and a high speed, there is no particular problem.

Next, another embodiment will be described. In the embodiment shown in FIG. 2, the EGR pipe 9b and the return pipe 15 are branched and connected to the EGR pipe 9b, and the switching means is EG.
It comprises a flow control valve 18 having a variable restrictor provided in the middle of the R pipe 9c, and a two-way solenoid valve 19 provided in the middle of the return pipe 15. The flow rate control valve 18 and the electromagnetic opening / closing valve 19 are controlled by the controller 16 for opening control and opening / closing control, respectively. Therefore, the flow control valve 18
Is a predetermined opening degree and the electromagnetic opening / closing valve 19 is closed.
When the R control is executed and the opening degree of the flow control valve 18 is set to zero and the electromagnetic opening / closing valve 19 is opened, the warm-up can be promoted without performing the EGR. Here, since the valve provided on the EGR pipe 9c is not an electromagnetic on-off valve but a flow control valve 18, the flow control valve 17 of the above-described embodiment is used in common to prevent an increase in the number of valves. Further, according to the present embodiment, the valve structure is simplified as compared with the case where the three-system electromagnetic switching valve 14 of the above-described embodiment is used, and good sealing performance can be obtained at low cost.

Various other embodiments of the present invention are conceivable.

[0022]

According to the present invention, it is possible to promote the warm-up during the engine warm-up operation, and to achieve an excellent effect that the heating start timing is advanced.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an EGR gas cooling device according to the present invention.

FIG. 2 is a configuration diagram showing another embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 engine 7 exhaust path 9a, 9b, 9c EGR pipe 10 EGR cooler 11a, 11b, 11c cooling water pipe 12 heater core 14 electromagnetic switching valve 15 return pipe

Claims (3)

[Claims] 1. An EGR cooler that uses engine cooling water as a refrigerant is provided in the middle of an EGR passage, and an exhaust passage leading to an exhaust passage of an engine is connected to the EGR passage downstream of the EGR cooler. An EGR gas cooling device comprising: a switching unit that switches between the EGR passage and the exhaust passage downstream of a connection portion. 2. The EGR gas cooling device according to claim 1, wherein said switching means closes an EGR passage downstream of said connection portion and opens said exhaust passage during engine warm-up operation. 3. The EGR cooler is disposed in the middle of a cooling water passage through which engine cooling water flows, and a heat exchanger for a heater is provided in the cooling water passage downstream of the EGR cooler. 2. The EGR gas cooling device according to 2.