JP2527625Y2 - Engine exhaust recirculation system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) The present invention relates to an exhaust gas recirculation device for an engine provided with an intercooler.

(Prior Art) Conventionally, in an engine, a supercharger is provided downstream of a throttle body in an intake passage, and supercharged air by the supercharger is cooled by an intercooler. It is known as disclosed in JP-A-51121. In addition, a bypass passage that bypasses the supercharger and the intercooler is provided, and the bypass valve interposed in the bypass passage supplies intake air through the bypass passage in a low-load-side non-supercharging region or the like according to an operation state. I have to.

In addition, it is preferable to supply the intake air by bypassing the intercooler, particularly at a low load, in that the intake air temperature can be increased to improve the combustion, and the fuel efficiency and emission can be improved.

(Problems to be Solved by the Invention) However, a bypass passage that bypasses the intercooler as described above is provided, and the supply of the intake air passing through the intercooler and the supply of the bypass intake air are performed according to the operation state. However, there is a problem in securing the sealing performance at the joint between the bypass passage and the intake passage.

That is, since it is difficult to integrally form the connection between the intake passage and the bypass passage downstream of the intercooler, a connection structure using a flange is adopted. Due to the large temperature difference, poor sealing is likely to occur due to the thermal deformation, and when the internal pressure increases due to the supercharging pressure, air may leak from this joint. In other words, when the engine is sufficiently warmed up and the temperature is rising, the ambient temperature of the engine also rises, and the intake air supplied through the bypass passage becomes relatively high in temperature. There is a considerable temperature difference from the temperature of the intake air that has been cooled through, and when the temperature is suddenly changed by the switching, a seal failure is likely to occur.

In view of the above circumstances, the present invention utilizes a mechanism that recirculates a part of the exhaust gas to the intake passage to ensure the sealing performance at the junction between the intake passage and the bypass passage downstream of the intercooler. It is an object of the present invention to provide an exhaust gas recirculation device.

(Means for Solving the Problems) In order to achieve the above object, the exhaust gas recirculation device of the present invention includes an intercooler for cooling intake air in an intake passage, and a bypass passage for bypassing the intercooler. An EGR valve that supplies intake air by bypassing the intercooler and that is provided in the middle of an EGR passage that recirculates part of exhaust gas to the intake passage is provided between the intake passage downstream of the intercooler and the bypass. It is arranged and arranged in the vicinity of the junction with the passage.

(Operation and Effect) In the exhaust gas recirculation device for an engine as described above, the EGR valve interposed in the EGR passage is disposed near the junction of the intake passage and the bypass passage downstream of the intercooler. The exhaust gas passes through the EGR passage,
Since the temperature of the valve is high and maintains a substantially constant temperature, the junction of the bypass passage and the intake passage can be maintained at a constant temperature by the heat radiation of the EGR valve. In the junction between the intake passage and the bypass passage, even if the temperature of the intake air passing therethrough changes due to the switching of the bypass passage, thermal deformation based on this temperature difference is prevented, and good sealing performance at the joint is provided. And secure reliability.

(Embodiment) Hereinafter, an embodiment of the present invention will be described with reference to the drawings. First
FIG. 2 shows a plan structure of a V-type engine provided with an exhaust gas recirculation device of one embodiment, FIG. 2 shows a front structure, and FIG. 3 shows a side structure. The left side of FIG. 1 is the front of the engine, and the left and right toward the front indicate the left and right directions of the engine.

The engine body 1 is a V-type 6 cylinder, and cylinder heads 3, 3 are fastened to the left and right upper portions of the cylinder block 2 in an inclined state, respectively, to form a left bank 1A and a right bank 1B, and left and right banks 1A, 1B. Are each provided with three cylinders C (see FIG. 3). And left and right bank 1A, 1
In the space between B, a Richolm type supercharger 4 is arranged in the direction of the crankshaft, and is fixed to the upper center of the cylinder block 2.

Above the left and right banks 1A, 1B, surge tanks 5, 6 extending in the direction of the crankshaft, respectively, are provided. On the inner side surfaces of the left and right surge tanks 5 and 6, branch pipes forming independent intake passages connected to the cylinders C of the banks 1A and 1B, respectively.
At the front ends of the left and right surge tanks 5 and 6, communication pipes 9 and 10 forming a communication path with an intercooler 12 described later extend forward. In addition, an injector mounting hole 11a is provided at a distal end of each of the branch pipes 7 and 8 to each cylinder C, and an injector 1 for fuel injection is provided.
1 (see FIG. 3) is provided.

An intercooler 12 is disposed in the upper front of the engine 1 in a direction perpendicular to the crankshaft. The intercooler 12 has two cooling units 12 corresponding to the left and right banks 1A and 1B.
a, 12b (air cooling fins), which are arranged substantially symmetrically with respect to the engine center. A common inlet pipe 15 is provided at the upper center, and outlet pipes 1 are provided at both left and right ends.
6 and 17 are provided, and the air from the inlet pipe 15 is cooled by the left and right cooling units 12a,
It cools through 12b and flows out of the left and right outlet pipes 16,17.
The inlet pipe 15 is connected to a discharge pipe 18 provided forward from an upper portion of the supercharger 4.

The supercharger 4 is provided with a pulley 4b projecting forward of a main body portion 4a extending in the longitudinal direction. The pulley 4b is driven by a belt pulled from a crank pulley (not shown) of the engine 1 and is driven by the pulley 4b. The air from the inlet 19 at the end is compressed inside and discharged forward from the upper discharge pipe 18.
The throttle body 20 on the upstream side of the intake is connected to the inlet 19 at the rear end.

An air bypass valve 22 is provided on the upper surface of the inlet portion 19 of the turbocharger 4. An inflow portion 22a at one end of the air bypass valve 22 is communicated directly downstream of the throttle body 20, and an outflow portion at the other end. 22b is communicated with the discharge pipe 18 of the supercharger 4 via a bypass passage pipe 23, and an intermediate portion thereof is opened and closed. Further, the air bypass valve 22 and the discharge pipe 18
The intercooler bypass passage pipes 24 and 25 that constitute a bypass passage that bypasses the intercooler 12 are connected from both sides to the bypass passage pipe 23 that connects the intercooler 12 and the downstream side of the intercooler bypass passage pipes 24 and 25. An intercooler bypass valve 26 is provided in the discharge pipe 18. An actuator 27 for opening and closing the intercooler bypass valve 26 is connected.

The intercooler bypass passage pipes 24 and 25 are integrally connected to the bypass passage pipe 23 from both sides, and the distal ends are directed toward the intercooler-side communication pipes 9 and 10 formed integrally with the left and right surge tanks 5 and 6. Each extends diagonally forward. The distal end flanges 24a, 25a of the bypass passage pipes 24, 25 are connected from above to connecting parts 9a, 10a that branch off from the lower ends of the communication pipes 9, 10 and rise from above. And bypasses the intercooler 12 and is connected to an intake passage downstream of the intercooler 12.

The outlet pipes 16, 17 at both ends of the intercooler 12 are bolted to rigids via joints 28 made of thick rubber, respectively, to the communication pipes 9, 10 of the left and right surge tanks 5, 6. , 6 and a bracket (not shown) separately fixed below. Then, a duct 31 is provided to cover the front surface of the intercooler 12 and opens at a position of the vehicle body grill 30 beyond the radiator 29 located in front, and a film-shaped rubber seal bolted to the inner surface of the rear end of the duct 31 is provided. By 32
The gap between the duct 31 and the intercooler 12 is sealed.

In addition, connecting portions 9a, 10 between the front flange portions 24a, 25a of the intercooler bypass passage tubes 24, 25 on both sides formed integrally with the bypass passage tube 23 and the intercooler-side communication sides 9, 10 are provided.
The joint with a is bolted via a thick rubber joint 33, and is connected so as to be able to absorb a slight displacement. The connecting portions of the bypass passage pipe 23 with the air bypass valve 22 and the discharge pipe 18 at the front and rear ends thereof are provided in a seal structure in which an O-ring 34 is interposed to absorb a dimensional error in manufacturing in the axial direction. Like that.

On the other hand, an EGR pipe 36 that constitutes an EGR passage that recirculates a part of exhaust gas from an exhaust passage (not shown) to an intake passage is provided. The downstream end of this EGR pipe 36 is intercooler 1
2 These are connected to EGR inlets 37, 37 opened to the communication pipes 9, 10 upstream of the left and right surge tanks 5, 6 downstream of the surge tanks 5, 6, respectively, and recirculate exhaust gas from these portions. Also, the above EGR pipe 3
6 has an EGR valve that adjusts the recirculation timing and amount on the way
The EGR valve 38 is provided at the junction between the distal end portions of the intercooler bypass passage tubes 24, 25 and the connection portions 9a, 10a of the intercooler-side communication tubes 9, 10, that is, the bypass passage and the intake passage. Is provided at a position near the front of the junction. Then, the heat of the EGR valve 38 heats the joint.

By supplying EGR gas upstream of the left and right surge tanks 5 and 6 through the EGR introduction port 37, the mixture with the intake air is enhanced and the mixture is introduced into the engine.

The air bypass valve 22 is constituted by a diaphragm-type pressure responsive valve, and opens when the engine load is low, gradually closes when the supercharging pressure becomes a predetermined value or more, and fully closes when the load increases. The intercooler bypass valve 26 is also opened / closed by an actuator 27 constituted by a diaphragm-type pressure-responsive valve, and is opened at a low load.
Then, the air bypass valve 22 starts closing from a lower load side, and is fully closed when it enters the supercharging region. As a result, in the non-supercharged region, intake is performed by bypassing the supercharger 4, and an increase in pressure loss is prevented. In particular, in the low load region, the intake air is bypassed through the intercooler 12.

Therefore, at a low load, the supercharger 4 is stopped, the drive loss is reduced, the pressure loss is reduced by the air bypass, and the intake air is not cooled by bypassing the intercooler 12. The intake air temperature increases,
With improved atomization and better combustion,
Fuel economy and emissions (HC) are improved. On the other hand, when the load is high, the intercooler valve 26 is fully closed, and the intake air discharged from the supercharger 4 and sufficiently cooled by the intercooler 12 is supplied to the engine, thereby preventing abnormal combustion. Reliability is ensured.

The intercooler bypass passage pipes 24 and 25 are EGR
At the upstream side of the inlet 37, the communication pipes 9,1 for the surge tanks 5,6
By being connected to 0, the EGR gas does not flow backward to the supercharger 4 via the intercooler bypass passage tubes 24 and 25.

On the other hand, with the opening operation according to the operation state of the EGR valve 38, the exhaust gas having a high temperature flows through the EGR pipe 36,
The GR valve 38 receives the heat of the exhaust gas and has its temperature increased. The EGR valve 38 is disposed near the junction of the distal end flange 25a of the intercooler bypass passage pipe 25 and the communication pipe 10, and the junction is heated to a constant temperature by heat radiation, and Low-temperature intake air passing through the intercooler 12 passing through the joint and the intercooler bypass passage pipe
Reduces the amount of thermal deformation corresponding to the temperature change at the time of switching to high-temperature intake air that has passed through 25, maintains the sealability of this part in a good state, and causes leakage of intake air even when supercharging pressure acts Is prevented.

Further, since the EGR valve 38 is disposed behind the intercooler 12 with respect to the traveling direction of the vehicle, a part of the traveling wind that cools the intercooler 12 hits, and the EGR valve 38 becomes extremely hot. Can be prevented.

In the above-described embodiment, an example in which one EGR valve 38 is provided is shown. However, an EGR valve may be provided for each of the left and right banks 1A and 1B, and may be installed near the left and right joints. Good.

[Brief description of the drawings]

FIG. 1 is a plan view of an engine having an exhaust gas recirculation device according to an embodiment of the present invention, FIG. 2 is a front view thereof, and FIG. 3 is a side view thereof. 1 ... Engine, 4 ... Supercharger, 5,6 ... Surge tank, 9,10 ... Communication pipe, 9a, 10a ... Connection, 12 ... Intercooler, 24,25 ... Intercooler bypass Passage pipe (bypass passage), 24a, 25a …… Flange, 36 …… EGR
Pipe (EGR passage), 37 ... EGR inlet, 38 ... EGR valve.

Claims (1)

(57) [Scope of request for utility model registration] 1. An engine in which an intercooler for cooling intake air is provided in an intake passage, and a bypass passage for bypassing the intercooler is provided to supply intake air by bypassing the intercooler according to an operation state. An EGR valve interposed in the middle of an EGR passage that recirculates part of exhaust gas to the intake passage is disposed near a junction of the intake passage and the bypass passage downstream of the intercooler. Engine exhaust recirculation system.