CN107664078B

CN107664078B - EGR device for internal combustion engine

Info

Publication number: CN107664078B
Application number: CN201710623029.9A
Authority: CN
Inventors: 三好一也; 桥本惠太
Original assignee: Honda Motor Co Ltd
Current assignee: Honda Motor Co Ltd
Priority date: 2016-07-29
Filing date: 2017-07-27
Publication date: 2020-01-17
Anticipated expiration: 2037-07-27
Also published as: DE102017213101B4; DE102017213101A1; US20180030876A1; JP6387379B2; JP2018017210A; CN107664078A

Abstract

The invention provides an EGR apparatus for an internal combustion engine, which allows easy removal of an EGR valve even when the EGR valve is disposed adjacent to a turbocharger. The EGR device includes: a first connecting tube portion (41b) that extends from a compressor of a super supercharger and has a first annular shoulder surface (41c) at a base end thereof; an EGR valve (65) fixedly attached to a portion of the engine; a joint member (71) that includes a flange (71a) attached to the EGR valve (65) and a second connecting pipe portion (71b) that is opposite to the first connecting pipe portion in a coaxial relationship, a base end of the second connecting pipe portion being provided with a second annular shoulder surface (71 c); and a flexible tube member (72) having a first end fitted to the first connecting tube portion and a second end fitted to the second connecting tube portion. The distance (L2) between the two annular shoulder surfaces is greater than the length (L1) of the flexible tube member by a predetermined distance.

Description

EGR device for internal combustion engine

Technical Field

The present invention relates to an EGR (exhaust gas recirculation) apparatus for an internal combustion engine equipped with a super supercharger such as a turbocharger.

Background

In known EGR devices for internal combustion engines, the EGR device is attached to a cylinder bank end of a cylinder head and internally defines a portion of an exhaust passage extending from an exhaust system. An upstream end of the exhaust passage is connected to a converging portion of the exhaust manifold via an exhaust introduction pipe, and a downstream end of the exhaust passage is connected to an intake passage of the intake manifold via an exhaust injection pipe. See, for example, JP 2000-87807A.

Engines are often equipped with super-superchargers, such as turbochargers, to improve fuel economy. Turbochargers supply compressed air into the combustion chambers of an engine such that volumetric efficiency is improved and a high engine input can be obtained for a given engine displacement of the engine. In an engine equipped with a turbocharger, a high-pressure EGR device that recirculates high-pressure exhaust gas in an upstream portion of an exhaust system to intake air at high pressure and a low-pressure EGR device that recirculates low-pressure exhaust gas in a downstream portion of the exhaust system to intake air at negative pressure are employed simultaneously. Therefore, the structures of the intake system and the exhaust system tend to be highly complicated due to the presence of these EGR devices. To allow for a compact design of the intake and exhaust systems, at least one of the EGR valves is typically placed adjacent to the turbocharger.

When the EGR valve is positioned adjacent to the turbocharger, it is difficult to remove the EGR valve for maintenance because the associated piping and other components come together around the turbocharger. It is often necessary to remove the turbocharger itself to remove or replace the EGR valve.

Disclosure of Invention

The present invention has been made in view of these problems of the prior art, and a primary object of the present invention is to provide an EGR apparatus that allows easy removal of an EGR valve even when the EGR valve is disposed adjacent to a super supercharger.

In order to achieve such an object, the present invention provides an EGR apparatus for a multi-cylinder engine equipped with a super supercharger (41) for returning a part of exhaust gas discharged from an exhaust system of the engine to an intake system of the engine, comprising: a first connecting tube portion (41b) that extends from a compressor of the super supercharger and has a first annular shoulder surface (41c) at a base end thereof; an EGR valve (65) fixedly attached to a portion of the engine; a joint member (71) including a flange (71a) attached to the EGR valve (65) and a second connecting pipe portion (71b) defining a passage communicating with an inlet end of the EGR valve and opposing the first connecting pipe portion in a coaxial relationship, a base end of the second connecting pipe portion being provided with a second annular shoulder surface (71 c); and a flexible tube member (72) having a first end fitted to the first connecting tube portion and a second end fitted to the second connecting tube portion; wherein a distance (L2) between the two annular shoulder surfaces is greater than a length (L1) of the flexible tube member by a predetermined distance.

According to this arrangement, the EGR valve can be removed without having to remove any major components such as the supercharger by moving the joint member (optionally together with the flexible tube member) axially away from the EGR valve. The joint member is allowed to move axially until both ends of the flexible pipe member abut the respective annular shoulder surfaces.

In a preferred embodiment of the invention, the super charger consists of a turbocharger comprising a turbine for powering the compressor and attached to a part of the engine such that the compressor protrudes from an exhaust side portion of the engine beyond a cylinder bank end of the engine, and the first connecting tube portion (41b), the EGR valve (65), the flexible tube member (72) and the second connecting tube portion (71b) extend from the compressor along the cylinder bank end of the engine.

Thus, the EGR device can be mounted in a highly compact manner in a region adjacent to the body of the engine.

The EGR device may further include an upstream EGR tube assembly (62-64) communicating a portion of the exhaust system to an inlet end of the EGR valve, the upstream EGR tube assembly (62-64) including a portion extending generally vertically along the bank end of the engine toward a downstream portion of the exhaust system of the engine.

This also contributes to a compact arrangement of the EGR device.

Preferably, an exhaust gas purification device is positioned on an exhaust gas side of the engine below the turbine, and an upstream end of the upstream EGR pipe assembly is connected to a downstream portion of the exhaust gas purification device.

Thus, low-pressure exhaust gas having a relatively low temperature is returned to the intake system of the engine and mixed with intake air under negative pressure. The exhaust gas contains moisture of a certain acidity, but the acidity of the exhaust gas is reduced by the catalytic converter before returning to the intake system. Thus, thermal degradation of the flexible pipe member may be minimized.

According to a preferred embodiment of the present invention, between the engine and the exhaust gas purification apparatus, the upstream EGR pipe assembly extends from an upstream end thereof generally upward along the bank end portion of the engine toward the intake side of the engine, and then turns back toward the exhaust side of the engine and is connected to the inlet end of the EGR valve.

This also contributes to a compact arrangement of the EGR device.

The upstream EGR tube assembly may include an EGR cooler (63).

Thus, the EGR cooler may reduce the temperature of the exhaust gas guided to the flexible pipe member, so that thermal degradation of the flexible pipe member may be minimized.

The upstream EGR tube assembly may include a rigid tube member (64) connected between the EGR cooler and the EGR valve.

The rigid tube member may be fixedly attached to a suitable portion of the engine such that the EGR valve (at the downstream end of the rigid tube member) and the EGR cooler (at the upstream end of the rigid tube member) may be fixedly secured to the engine in a highly stable manner without the need for additional brackets.

In a particularly preferred embodiment of the present invention, a plurality of bolts (81, 82) are passed through a flange (64b) provided at the downstream end of the rigid pipe member of the upstream EGR pipe assembly, the EGR valve (65), and the joint member (71) to fasten these components to each other.

Thus, the EGR valve and the joint member can be fixed to the rigid pipe member fastened to the upstream EGR pipe assembly in a simple and stable manner.

Preferably, the bolts comprise at least one pair of stud bolts each having a base end screwed into one of the flange (64b) of the rigid pipe member and the flange (71a) of the joint member and a free end having a threaded portion to which a nut (83) is fastened.

Thus, the rigid pipe member, the EGR valve, and the joint member can be assembled together with the aid of the stud bolts in proper alignment with each other, so that the assembly work can be facilitated. Typically, shims need to be placed between the various interfaces, but this arrangement allows the assembly process to be performed in a highly efficient manner.

Typically, the free end of each stud is provided with a tool engagement feature (81 a). Thus, each stud may be easily installed and removed by engaging a suitable tool with the tool engagement feature.

Alternatively or additionally, the threaded portion on the free end of each stud bolt may be provided with a length that is at least twice the thickness of the nut. Thus, by screwing on the additional nut (84) until the additional nut abuts the original nut (double nut arrangement), the stud bolt can be unscrewed from the flange of the rigid pipe member or the flange of the joint member (as the case may be) by engaging the original nut with a suitable tool.

In a preferred embodiment of the present invention, a first shim (68) is interposed between the flange of the rigid tube member of the upstream EGR tube assembly and the EGR valve, and a second shim (69) is interposed between the EGR valve and the joint member, and wherein the distance (L2) between the two annular shoulder surfaces is greater than the length (L1) of the flexible tube member by at least the combined thickness of the two shims in an unused state.

According to this arrangement, it is possible to create appropriate spaces between the flange of the rigid pipe member of the upstream EGR pipe assembly and the EGR valve and between the EGR valve and the joint member, so that replacement of the EGR valve can be achieved without causing any difficulty.

Each end of the flexible pipe member may be secured to a corresponding connecting pipe portion with a hose clip.

Thereby, the flexible tube member can be mounted in a simple and economical manner.

Drawings

FIG. 1 is a plan view of an engine of a motor vehicle equipped with an EGR device embodying the present invention;

FIG. 2 is a block diagram of an intake system and an exhaust system of the engine;

fig. 3 is a partial perspective view of the low-pressure EGR apparatus shown in fig. 2;

FIG. 4 is a partial cross-sectional view of a portion of the low-pressure EGR device;

fig. 5 is an exploded perspective view of a part of the low-pressure EGR device; and

fig. 6 is a view similar to fig. 4 when the low-pressure EGR device is detached.

Detailed Description

Embodiments of the present invention will be described below with reference to the accompanying drawings. An engine 4 constituted by an inline four-cylinder diesel engine is located in an engine room 3 formed in a front portion of a vehicle body 2 of the motor vehicle 1.

The engine 4 is laterally installed in the engine room 3, and is slightly offset in the right direction. The engine 4 is supported by the vehicle body 2 via an engine bracket (not shown in the drawings) with a slight backward tilt. The transmission system is connected to the lower side of the left end portion of the engine 4. A pair of front side frames 6 (only one of which is shown in fig. 1) extend along both sides of the engine room 3, and a pair of damper seats 7 are located on both sides of a rear end portion of the engine room 3.

The rectangular battery 8 is located inside the left damper base 7, and the long side of the battery 8 extends in the front-rear direction. An ECU unit 9 for controlling various portions of the vehicle 1 is provided immediately in front of the battery 8, and an air cleaner 10 is located immediately in front of the ECU unit 9. A relay box 11 elongated in the front-rear direction is located outside the battery 8.

A front bulkhead (not shown in the drawings) that supports a radiator (not shown in the drawings) is provided in a front end portion of the engine room 3. The cover member 12 is located at the top of the forward bulkhead. The engine 4 is provided with an intake/exhaust system 18, which is composed of an intake system 20 for supplying air to the engine 4 and an exhaust system 30 for discharging exhaust gas from the engine 4. The exhaust system 30 is provided with a turbocharger 40, which is powered by the flow of exhaust gas and compresses the intake air supplied to the engine 4. The high-pressure EGR device 50 is provided in a downstream portion of the turbocharger 40, and the low-pressure EGR device 60 is provided in an upstream portion of the turbocharger 40, both for returning a controlled amount of exhaust gas to the intake system 20.

Fig. 2 is a block diagram illustrating the overall structure of intake/exhaust system 18. In the intake system 20, air drawn from the atmosphere is introduced into the first intake passage 21 via the intake inlet 21a, and then is guided to the throttle valve 23 via the air cleaner 10 and the second intake passage 22. Then, after being compressed by the compressor 41 of the turbocharger 40, the intake air is forwarded to the intercooler 25 via the third intake passage 24, and to the intake manifold 29 via the fourth intake passage 26, the intake valve 27, and the fifth intake passage 28.

In the exhaust system 30, the exhaust gas collected from the engine 4 by the exhaust manifold 31 is forwarded to the turbine 42 of the turbocharger 40, and is discharged to the atmosphere via the first exhaust pipe 32, the catalytic converter 33, the DPF 34, and the second exhaust pipe 35. The high-pressure EGR device 50 includes, in order from the exhaust system 30 side, a first high-pressure EGR pipe 51 directly connected to the exhaust manifold 31; a high-pressure EGR valve 52; and a second high-pressure EGR pipe 53 connected to the downstream side of the intake valve 27. The low-pressure EGR device 60 includes, in order from the exhaust system 30 side, an EGR filter device 61 connected to the DPF 34, a first low-pressure EGR pipe 62, a low-pressure EGR cooler 63, a second low-pressure EGR pipe 64, a low-pressure EGR valve 65, and a third low-pressure EGR pipe 66 connected to the downstream side of the throttle valve 23.

The throttle valve 23 controls the intake air amount and the intake air pressure of the intake air supplied into the cylinders of the engine 4. The intake valve 27 is configured to selectively reduce the intake air amount by narrowing the intake passage at the valve body to raise the temperature of the exhaust gas when regeneration of the DPF by burning off Particulate Matter (PM) collected by the DPF 34 is required, and otherwise to remain fully open.

The first low-pressure EGR pipe 62, the low-pressure EGR cooler 63, and the second low-pressure EGR pipe 64 on the upstream side of the low-pressure EGR valve 65 may be collectively referred to as an upstream EGR pipe assembly. In the illustrated embodiment, the second low pressure EGR tube 64 forms a portion of an upstream EGR tube assembly.

Referring again to fig. 1, the exhaust port of the engine 4 is provided on the front side of the engine 4. An exhaust gas convergence pipe 36 is attached to a planar mounting surface defined on the front side of the engine 4 and communicates with the exhaust manifold 31, which in the illustrated embodiment is internally defined in a cylinder head of the engine 4. The exhaust manifold may also be provided separately from the engine and attached to the front side of the engine 4. The outlet end of the exhaust gas collecting pipe 36 is located on the left end side of the engine 4, and is fitted with a turbine 42 of a turbocharger 40.

The turbine 42 is located on the front side of the exhaust convergence pipe 36, and is provided with a turbine housing and a turbine wheel rotatably supported by the turbine housing about a rotation center line extending in the lateral direction of the vehicle body. The turbine housing defines a turbine inlet extending circumferentially along a tangential direction of the turbine housing and a turbine inlet extending axially in a rightward direction from a central portion of the turbine housing. The turbine inlet is connected to the outlet end of the exhaust gas converging tube 36, and the turbine outlet is connected to the first exhaust pipe 32, the first exhaust pipe 32 being connected to the right side wall of the turbine housing.

The first exhaust pipe 32 is bent downward as it extends rightward, and is connected to an upper portion of the catalytic converter 33, and the catalytic converter 33 is disposed in a forwardly-spaced relationship below the turbine 42 to the exhaust side (front side) of the engine 4. The catalytic converter 33 removes HC, CO, and NOx from the exhaust gas. A DPF 34 (fig. 2) for trapping particulates from the exhaust gas is disposed below the catalytic converter 33. A second exhaust pipe 35 (fig. 2) is connected to the lower side of the DPF 34 and extends in the rearward direction under the engine 4. The second exhaust pipe 35 also extends under the floor to the rear end portion of the vehicle.

The air cleaner 10 is connected to a downstream end of the first air-intake duct 21 (fig. 2) such that air drawn into the engine room 3 via the front grill is forwarded to the air cleaner 10 via the air-intake inlet 21 a. An intake air outlet is formed at the right side of the air cleaner 10, and is connected to the upstream end of the second intake duct 22. The downstream end of the second intake passage 22 is connected to the left end of a throttle valve 23, and the interior of the throttle valve 23 defines a laterally extending intake passage.

The compressor 41 of the turbocharger 40 is located between the throttle valve 23 and the turbine 42 so as to be coaxial with the turbine 42, and protrudes beyond the left end of the engine 4. The compressor 41 includes a compressor housing 41a (fig. 4) and a compressor wheel rotatably supported by the compressor housing 41a about a transversely extending rotational centerline. The compressor housing 41a is provided with a compressor inlet provided at the center on the left side wall of the compressor housing 41a, and a low-pressure EGR introduction port is opened and protruded from the rear side of the peripheral wall of the compressor housing 41 a. The compressor housing 41a is further provided with a compressor outlet that extends tangentially from a lower portion of the outer peripheral wall of the compressor housing 41 a. The compressor inlet is connected to the intake passage of the throttle valve 23, and the low-pressure EGR introduction port is connected to the EGR gas passage of the low-pressure EGR device 60. The compressor outlet is connected to the intake passage of the third intake duct 24, which is connected to the lower wall of the compressor housing 41 a.

The turbocharger 40 is provided with a drive shaft 40a (fig. 2) that connects the turbine wheel on the exhaust system 30 side to the compressor wheel on the intake system 20 side. The rotational power of the turbine wheel is transmitted to the compressor wheel via the drive shaft 40 a. Thus, the turbocharger 40 compresses the intake air supplied from the throttle valve 23 and the exhaust gas supplied from the low-pressure EGR device 60, and transfers the mixture to the engine 4 at a pressure higher than atmospheric pressure.

The third gas intake duct 24 connected to the lower portion of the outer periphery of the compressor 41 is connected to an intercooler 25 (fig. 2) located below the cover member 12. A fourth intake duct 26 (fig. 2) passes behind the engine 4 via an intercooler 25, and is connected to an intake manifold 29 (fig. 2) attached to the rear side of the engine 4.

The first high-pressure EGR pipe 51 of the high-pressure EGR device 50 is connected to the right end of the exhaust gas collecting pipe 36, and receives exhaust gas from the exhaust gas collecting pipe 36. The high-pressure EGR valve 52 is attached to the front side of the cylinder head, and the rear end of the first high-pressure EGR pipe 51 is attached to the front end of the high-pressure EGR valve 52. In the cylinder head of the engine 4, an upstream side passage portion of the second high-pressure EGR pipe 53 (fig. 2) that communicates with the EGR passage of the high-pressure EGR valve 52 is formed to extend in the front-rear direction. A downstream-side passage portion of the second high-pressure EGR pipe 53, which is connected to the back surface of the engine 4, is connected to an intake air introduction portion of the intake manifold 29, and returns the exhaust gas that has passed through the high-pressure EGR valve 52 to the intake system 20. The downstream-side passage portion of the second high-pressure EGR pipe 53 may be connected to a portion other than the intake manifold 29 as long as it is on the downstream side of the compressor 41 in the intake system 20 and on the upstream side of the intake air introduction portion.

As shown in fig. 3, the vertically extending first low-pressure EGR pipe 62 includes a first upstream flange 62a that is provided at the lower end of the first low-pressure EGR pipe 62 and is fastened to the lower end of the DPF 34 with bolts; and a first downstream flange 62b provided at an upper end of the first low-pressure EGR pipe 62. The first low-pressure EGR pipe 62 extends rightward from the first upstream flange 62a, and then curves upward before extending obliquely upward and rearward to extend along the right side of the DPF 34. The first upstream flange 62a faces generally leftward, and the first downstream flange 62b faces obliquely upward and rearward. The lower portion of the vertical cross section of the first low-pressure EGR pipe 62 is formed as a flexible pipe or a bellows pipe 62 c. Therefore, the first upstream flange 62a and the first downstream flange 62b can be displaced relative to each other, and stress concentration in the first low-pressure EGR pipe 62 due to thermal expansion of the exhaust system 30 can be avoided.

The EGR filter device 61 is composed of a metal mesh interposed between the first upstream flange 62a of the first low-pressure EGR pipe 62 and the connecting flange (not shown in the figure) of the DPF 34. The EGR filter device 61 captures debris of the DPF 34 and other metal pieces that may be introduced into the first low-pressure EGR tube 62.

The low-pressure EGR cooler 63 is provided with a rectangular cooler main body portion 63a having a laterally elongated cross section and a front-rear dimension smaller than a vertical dimension. The right end portion of the cooler main body portion 63a is integrally provided with an upstream side connecting pipe portion 63b extending rearward and forward, and the left end portion of the cooler main body portion 63a is integrally provided with a downstream side connecting pipe portion 63c extending to the front. The connection flanges are integrally formed at the free end of the upstream-side connection pipe portion 63b and the free end of the downstream-side connection pipe portion 63c, respectively. The cooler main body portion 63a is provided with a plurality of mounts 63d for attachment to the engine 4. The cooler main body portion 63a is located between the engine 4 and the catalytic converter 33, and the catalytic converter 33 is separated from the front side of the engine 4 and attached to the front side of the engine 4 via a mount 63d and associated bolts. The cooler main body portion 63a is configured to circulate cooling water inside, and cool the exhaust gas by heat exchange between the cooling water flowing through the cooler main body portion 63a and the exhaust gas.

The second low-pressure EGR pipe 64 is made of a rigid pipe member, and includes a second upstream flange 64a that is located at a lower end of the second low-pressure EGR pipe 64 and is fastened to the downstream-side connection pipe portion 63c of the low-pressure EGR cooler 63 by means of bolts; and a second downstream flange 64b located at the upper end of the second low-pressure EGR pipe 64. The second low-pressure EGR pipe 64 extends forward from the second upstream flange 64a, and then extends along a curved path in the upward and leftward directions toward the left end side of the engine 4. The second low-pressure EGR pipe 64 is bent again along the left end side of the engine 4 in the rearward direction (toward the intake side). The second low-pressure EGR pipe 64 then bends upward and forward (toward the exhaust side), forming a U-turn. In other words, the downstream portion of the second low-pressure EGR pipe 64 extends rearward along the end of the cylinder bank of the engine toward the intake side of the engine, and then turns back toward the exhaust side of the engine. The second low-pressure EGR pipe 64 is made of metal, and therefore has high rigidity (as opposed to a flexible pipe). A connection 64d for attachment to the engine 4 is provided at an appropriate position of the second low-pressure EGR pipe 64. The second low-pressure EGR pipe 64 is fixed to the engine 4 via a pipe tie 64e (which is attached to the left end face of the engine 4) by fastening the connector 64d to the pipe tie 64e with bolts.

Fig. 4 is a longitudinal sectional view of the third low-pressure EGR pipe 66 and the EGR valve 65, which form a key part of the low-pressure EGR device 60, and fig. 5 is an exploded perspective view of the third low-pressure EGR pipe 66 and associated components. As shown in fig. 3 and 4, the compressor connecting pipe portion 41b extends rearward from the rear surface of the rear wall portion of the compressor housing 41a of the compressor 41. The base end of the compressor connecting pipe portion 41b is formed with a rearward facing annular shoulder surface 41 c. In the illustrated embodiment, the annular shoulder surface 41c projects rearward from the peripheral surface of the rear wall portion of the compressor housing 41a by a predetermined distance, but may also be defined by a portion of the surface of the rear wall portion itself around the compressor connecting pipe portion 41 b.

The third low-pressure EGR pipe 66 includes: a joint member 71 on the downstream side of the low-pressure EGR valve 65; a flexible tube member 72; and a pair of hose clips 73 provided on both axial ends of the flexible pipe member 72. As shown in fig. 4 and 5, the joint member 71 includes a joint flange portion 71a and a joint connection pipe portion 71b, which extends forward toward the free end of the compressor connection pipe portion 41 b. The joint connection pipe portion 71b is provided with an annular shoulder surface 71c which faces forward so as to face the annular shoulder surface 41c in a coaxial relationship. In the illustrated embodiment, the annular shoulder surface 71c projects forwardly a predetermined distance from the forwardly facing surface of the joint flange portion 71a, but may be defined by a portion of the forwardly facing surface of the joint flange portion 71a around the joint connection pipe portion 71 b. The joint flange portion 71a is provided with three bolt holes 70, one at the center of the upper portion of the joint flange portion 71a and two at the lower side portions of the joint flange portion 71 a.

The low-pressure EGR valve 65 includes: a valve housing 65a defining a low-pressure EGR passage extending in the front-rear direction; and a disc-shaped butterfly valve 65d rotatably supported in the valve housing 65a for opening and closing the low-pressure EGR passage defined in the valve housing 65 a. The valve housing 65a has both axial ends defining mating faces facing in the front-rear direction and parallel to each other. Three bolt holes 65b extending in the axial direction penetrate through each thick-walled portion 65c formed at regular angular intervals on the outer peripheral portion of the valve housing 65a such that the three bolt holes 65b are aligned with the corresponding bolt holes 70 of the joint flange portion 71 a.

The second downstream flange 64b of the second low-pressure EGR pipe 64 is opposed to the compressor connecting pipe portion 41b in a coaxial relationship from the rear and at a certain distance. The second downstream flange 64b is provided with three bolt holes 64c, one at the center of the upper portion and two on the lower side portions of the second downstream flange 64 b. One of the shaft end surfaces (rear shaft end surface) of the valve housing 65a is connected to the second downstream flange 64b of the second low-pressure EGR pipe 64 via the first gasket 68, and the other shaft end surface (front shaft end surface) of the valve housing 65a is connected to the joint flange portion 71a of the joint member 71.

The bolt holes 70 of the joint flange portion 71a are constituted by female screw holes that pass through the joint flange portion 71 a. A bolt 82 having a threaded portion at one end and a hexagonal head at the other end passes through one of the bolt holes 64c (lower right bolt hole 64c) of the second downstream flange 64b and the corresponding bolt hole 65b formed in the thick-walled portion 65c of the valve housing 65a, and is screwed into the corresponding bolt hole 70 of the joint flange portion 71 a. A stud bolt 81 (bolt) having a threaded portion at one end is passed through each of the remaining two bolt holes 64c (the upper bolt hole 64c and the lower left bolt hole 64c) and the corresponding bolt hole 65b formed in the rear wall portion 65c of the valve housing 65a, and is screwed into the corresponding bolt hole 70 of the joint flange portion 71 a. A nut 83 is screwed to the threaded portion of each stud bolt 82 projecting rearward from the second downstream flange 64 b.

Therefore, the second downstream flange 64b of the second low pressure EGR pipe 64, the low pressure EGR valve 65, and the joint flange portion 71a of the joint member 71 are fastened together, and the first gasket 68 and the second gasket 69 are placed in the interface between these three components. Thereby, the fastener composed of the bolt 82, the stud bolt 81, and the nut 83 detachably connects the second low-pressure EGR pipe 64, the low-pressure EGR valve 65, and the joint member 71 to each other.

When the second downstream flange 64b and the low-pressure EGR valve 65 are jointly fastened to the joint flange portion 71a, the length of the threaded portion of each stud bolt 81 that protrudes from the outer (rear) surface of the second downstream flange 64b is at least twice the thickness of the nut 83, so that an additional nut 84 (indicated by a broken line) other than the nut 83 can be screwed onto the protruding portion of the stud bolt 81. A tool engagement feature 81a for engaging a tool is formed at the free end of the stud 81. In the illustrated embodiment, the tool engagement features 81a are formed as protrusions having a hexagonal cross-section. Alternatively, the tool engagement feature 81a may consist of a protrusion having any other non-circular cross-section, or a non-circular recess, as long as it can be used to rotate the stud 81 about its central axis.

The flexible tube member 72 is made of an elastic material such as synthetic rubber, natural rubber, and elastomers (such as urethane rubber and silicone rubber), and is elastically deformable in the lateral and axial directions. The flexible pipe member 72 is provided between the joint member 71 and the compressor 41, and has an upstream-side end portion 72a fitted on the joint connection pipe portion 71b and a downstream-side end portion 72b fitted on the compressor connection pipe portion 41 b. A pair of annular projections 72c are formed on the outer peripheral surfaces of the upstream-side end portion 72a and the downstream-side end portion 72b of the flexible pipe member 72, respectively, for preventing axial misalignment of the hose clip 73. Each pair of annular projections 72c are spaced apart from each other by a distance slightly larger than the width of the hose clip 73.

Each of the hose clips 73 may be constituted by a known hose clip, and the circumference thereof may be adjusted, for example, by using a fastening structure (not shown) such as a screw. The hose clip 73 clamps the upstream-side end portion 72a and the downstream-side end portion 72b of the flexible pipe member 72 to the compressor connecting pipe portion 41b and the joint connecting pipe portion 71b, respectively, to achieve airtight connection at these two components.

When the exhaust gas flows through the low-pressure EGR device 60, the second low-pressure EGR pipe 64 and the low-pressure EGR valve 65 are heated, and thermally expand. The flexible tube member 72 absorbs expansion and contraction of these members and prevents stress concentration due to thermal expansion.

Specifically, in a state where the low-pressure EGR device 60 is not at a high temperature (a state where maintenance work can be performed), the length L1 of the flexible pipe member 72 is shorter than the distance L2 between the annular shoulder surface 41c on the compressor 41 side and the annular shoulder surface 71c on the joint member 71 side, which are opposed to each other. Thus, the axial end surface of the flexible tube member 72 is spaced from the corresponding annular shoulder surfaces 41c and 71c by the combined gap G. In the illustrated example, the corresponding end of the flexible tube member 72 abuts the annular shoulder surface 71c such that a space L3 (L2-L1) is created between the annular shoulder surface 41c and the front end face of the flexible tube member 72.

The size L3 of the gap G is selected so that both the first and

second shims

68 and 69 in an unused state (not yet compressed) can be inserted between the low-pressure EGR valve 65 and the second low-pressure EGR pipe 64 and between the low-pressure EGR valve 65 and the joint member 71, respectively. More specifically, if the thickness of the first shim 68 is t1 and the thickness of the second shim 68 is t2, the dimension L3 is greater than the sum of these thicknesses by a predetermined margin α corresponding to the combined amount of compression of the two shims 68 and 69 (L3> t1+ t2+ α). The thickness of the gasket in the unused state is made up of the thickness of the beads and the warpage of the gasket. Therefore, when the stud bolt 81 and the bolt 82 are not tightened, and the hose clip 73 for the flexible pipe member 72 is loosened, the two

washers

68 and 69 may be inserted between the low-pressure EGR valve 65 and the second low-pressure EGR pipe 64 and between the low-pressure EGR valve 65 and the joint member 71, respectively.

The following describes an assembly process for the low-pressure EGR device 60.

As shown in fig. 3, when the low-pressure EGR device 60 is installed, the low-pressure EGR cooler 63 to which the first low-pressure EGR pipe 62 is connected is attached to the engine 4 via a mount 63 d. Next, the second upstream flange 64a of the second low-pressure EGR pipe 64 is connected to the downstream-side connecting pipe portion 63c of the low-pressure EGR cooler 63, and the second low-pressure EGR pipe 64 is attached to the engine 4 via the connection 64 d. Since the second low-pressure EGR pipe 64 is fixed to the engine 4, its support rigidity is high and the two stud bolts 81 are also held in a stable condition. As shown in fig. 5, the two stud bolts 81 are fastened to the joint member 71 in advance such that the two stud bolts 81 extend rearward from the joint flange portion 71a of the joint member 71.

Thereafter, the two stud bolts 81 are passed through the through holes of the second spacer 69 to temporarily assemble the first spacer 68 to the joint member 71. Subsequently, the two stud bolts 81 are inserted into the bolt holes 65b of the low-pressure EGR valve 65 to temporarily assemble the low-pressure EGR valve 65 to the joint member 71. Because the two stud bolts 81 are provided in the upper and lower left portions of the second upstream flange 64a, the position of the low-pressure EGR valve 65 in the direction perpendicular to the axis of the joint member 71 is correctly determined.

Thereafter, the two stud bolts 81 are passed through the through holes of the first spacer 68 to temporarily assemble the second spacer 69 to the joint member 71. Therefore, the first gasket 68, the low-pressure EGR valve 65, the second gasket 69, and the joint member 71 are in the temporarily assembled state, so that the relative positions in the direction perpendicular to the axis are correctly determined in a stable manner. Subsequently, while holding the assembly together, the two stud bolts 81 are passed into the bolt holes 64c of the second low-pressure EGR pipe 64, and the two nuts 83 are screwed onto the stud bolts 81, so that the assembly is pressed against the second downstream flange 64 b. Only the nut 83 is now loosely tightened. In this state, the low-pressure EGR valve 65 and the joint member 71 are suspended by the second low-pressure EGR pipe 64 via the stud bolts 81 under stable conditions. Thereafter, threaded bolts 82 having hexagonal heads are passed through the bolt holes of these members from behind, and screwed into the bolt holes 70 of the joint member 71. The two nuts 83 and the bolt 82 having the hexagonal head are successively tightened so that the second low-pressure EGR pipe 64, the low-pressure EGR valve 65, and the joint member 71 are finally assembled together.

Thereafter, as shown in fig. 3 and 4, the upstream-side end portion 72a of the flexible pipe member 72 from which the hose clip 73 is released is fitted onto the joint connecting pipe portion 71b, and the corresponding shaft end of the flexible pipe member 72 is brought into contact with the annular shoulder surface 71 c. The hose clip 73 is tightened at this position, so that the flexible pipe member 72 is connected to the joint connecting pipe portion 71b in an airtight manner.

Thereafter, in order to assemble the turbocharger 40 to the engine 4, the compressor connection pipe portion 41b is inserted into the downstream side end portion 72b of the flexible pipe member 72, and the turbocharger 40 is fixedly attached to the engine 4 in place. Accordingly, a gap G having a dimension L3 is created between the annular shoulder surface 41c and the front end surface of the joint member 71. Finally, the hose clip 73 on the downstream side is tightened, thereby connecting the downstream-side end portion 72b of the flexible pipe member 72 to the compressor connecting pipe portion 41b in an airtight manner. This ends the assembly of the low-pressure EGR device 60 to the engine 4.

Thereafter, the catalytic converter 33 and the DPF 34 are connected to the downstream side of the turbine 42. This can be achieved without being hindered by the low-pressure EGR device 60. Further, a first upstream flange 62a of the first low-pressure EGR pipe 62 is connected to the lower end of the DPF 34. Because the lower portion of the first low-pressure EGR pipe 62 is configured as the bellows 62c, stress concentration in the first low-pressure EGR pipe 62 due to thermal expansion of the exhaust system 30 can be avoided.

The following describes a disassembly process of the low-pressure EGR device 60 for maintenance and other purposes.

First, as shown in fig. 4 and 5, the hose clip 73 on the downstream side is loosened, and the two nuts 83 and the bolt 82 are loosened. Therefore, the joint member 71 and the flexible pipe member 72 can be moved toward the compressor 41 side so that the gap G is created. Subsequently, the bolt 82 is pulled out rearward. The studs 81 are each loosened by engaging the tool engagement features 81a with a suitable tool and pulled rearwardly. If any stud bolt 81 is securely received in the threaded hole of the joint flange portion 71a so as not to rotate, an additional nut 84 may be screwed onto the stud bolt 81 in addition to the original nut 83, so that the two

nuts

83 and 84 are locked to the stud bolt 81. The original nut 83 may then be engaged by a wrench or any suitable tool and rotated in a counterclockwise direction. Because the effective diameter of the nut 83 is greater than the effective diameter of the tool engagement feature 81a, greater torque can be applied to the stud 81.

Once the stud bolts 81 and the bolts 82 are removed, the low-pressure EGR valve 65 may be removed by sliding it upward or leftward. If high frictional resistance is encountered while sliding the low-pressure EGR valve 65 upward or leftward, the joint member 71 and the flexible pipe member 72 may be moved until the flexible pipe member 72 abuts against the annular shoulder surface 41 c. Therefore, the distance between the second downstream flange 64b and the joint member 71 is increased, so that the low-pressure EGR valve 65 can be slid off relatively easily. Therefore, the subsequent work of reinstalling the low-pressure EGR valve 65 or installing a new low-pressure EGR valve 65 can be facilitated.

As described above, the dimension L3 of the gap G is selected so that the first and

second shims

68 and 69 in the unused state can be inserted between the low-pressure EGR valve 65 and the second low-pressure EGR pipe 64 and between the low-pressure EGR valve 65 and the joint member 71, respectively. More specifically, as shown in fig. 6, with the low pressure EGR valve 65 installed at a specified position, a clearance t3 that is greater than the thickness of the first gasket 68 in the unused state is created between the low pressure EGR valve 65 and the second low pressure EGR pipe 64, and a clearance t4 that is greater than the thickness of the second gasket 69 in the unused state is created between the low pressure EGR valve 65 and the joint member 71. Therefore, the first and

second shims

68 and 69 can be installed in the specified positions without any difficulty after the installation of the low-pressure EGR valve 65. Thereafter, the remaining components of the low-pressure EGR valve 65 and associated components are assembled by reversing the disassembly sequence previously described.

According to the low-pressure EGR device 60 configured as described above, the following advantages can be obtained. As shown in fig. 4, the inlet end of the low-pressure EGR valve 65 is detachably connected to the second downstream flange 64b of the second low-pressure EGR pipe 64, and the free end of the compressor connecting pipe portion 41b is detachably connected to the outlet end of the low-pressure EGR valve 65. The flexible pipe member 72 connected to the compressor connecting pipe portion 41b and the joint connecting pipe portion 71b by means of the hose clip 73 has a length L1 smaller than the distance L2 between the annular shoulder surface 41c and the annular shoulder surface 71 c. Thus, a gap G is created between the flexible tube member 72 and the annular shoulder surface 41 c. Therefore, the flexible tube member 72 and the joint member 71 can be axially moved toward the compressor 41 side until the flexible tube member 72 abuts against the annular shoulder surface 41c, so that the low-pressure EGR valve 65 can be easily removed without removing the compressor 41.

As shown in fig. 1, 3, and 4, the compressor 41 is provided to protrude beyond the left end of the engine 4, and the second downstream flange 64b of the second low-pressure EGR pipe 64, the low-pressure EGR valve 65, the joint connection pipe portion 71b, the flexible pipe member 72, and the compressor connection pipe portion 41b are arranged in the front-rear direction along the left side of the engine 4. Therefore, the low-pressure EGR device 60 can be arranged adjacent to the engine 4 in a compact manner.

As shown in fig. 2 and 3, the first upstream flange 62a of the first low-pressure EGR pipe 62 is connected to a portion of the exhaust system 30 on the downstream side of the catalytic converter 33, and the compressor connecting pipe portion 41b is connected to the upstream side of the compressor 41. Therefore, the exhaust gas contains moisture having a certain acidity, but the acidity of the exhaust gas becomes weaker as the exhaust gas passes through the catalytic converter 33 before the exhaust gas is recirculated to the intake air of the intake system 20 via the low-pressure EGR device 60 at negative pressure. Therefore, deterioration of the flexible pipe member 72, which may be caused by acidity, can be minimized.

As shown in fig. 3, the low-pressure EGR device 60 includes a low-pressure EGR cooler 63 that is fixedly attached to the engine 4 and is disposed between the engine 4 and the catalytic converter 33. In view of the flow of exhaust gas, the low-pressure EGR cooler 63 is provided with an intermediate portion of the exhaust path, or between the first low-pressure EGR pipe 62 and the second low-pressure EGR pipe 64. The low-pressure EGR device 60 extends from the first upstream flange 62a to the left side of the engine 4 through the space defined between the engine 4 and the catalytic converter 33. The low-pressure EGR apparatus 60 then extends along the left side of the engine, toward the intake side of the engine 4, and curves upward to bend back toward the exhaust side of the engine 4. Accordingly, the temperature of the exhaust gas flowing through the flexible pipe member 72 decreases as the exhaust gas flows along the path, such that thermal degradation of the flexible pipe member 72 is minimized. Also, the low-pressure EGR device 60 can be provided in a highly compact manner by utilizing the space defined between the engine 4 and the catalytic converter 33.

The second low-pressure EGR pipe 64 that connects the low-pressure EGR cooler 63 to the low-pressure EGR valve 65 is made of a rigid member, and is fixed to the engine 4. Therefore, the support rigidity of the second low-pressure EGR pipe 64 is very high. This facilitates the work of installing and removing the low-pressure EGR valve 65, and also eliminates the need to remove or install the low-pressure EGR cooler 63 when removing the low-pressure EGR valve 65, so that the work involved in removing and filling the cooling water of the low-pressure EGR cooler 63 can be eliminated.

As shown in fig. 4 and 5, as fastening means for detachably fastening the second low-pressure EGR pipe 64, the low-pressure EGR valve 65, and the joint member 71 having the joint connection pipe portion 71b, at least one stud bolt 81 (more preferably, at least two stud bolts) each penetrating the EGR valve 65 with its base end screwed into the joint member 71 is used. The free end of the stud 81 is provided with a threaded position and a nut 83 is screwed on this threaded position. Therefore, the low-pressure EGR valve 65 and the joint member 71 can be temporarily assembled to the second low-pressure EGR pipe 64 using the stud bolts 81, so that the assembly of the low-pressure EGR device 60 is facilitated. In the illustrated embodiment, two stud bolts 81 are used as the fastening means. Therefore, the relative position of the low-pressure EGR valve 65 with respect to the joint member 71 in the direction perpendicular to the joint member 71 is correctly determined, while the EGR valve 65 and the joint member 71 are temporarily assembled, so that the assembly of the low-pressure EGR device 60 is even further facilitated.

In the illustrated embodiment, the base end of each stud bolt 81 is screwed into the joint flange portion 71a of the joint member 71, but may also be screwed or otherwise detachably fastened to the second downstream flange 64b of the second low-pressure EGR pipe 64.

As shown in fig. 4, each stud 81 has a tool engagement feature 81a at the free end. Further, the stud bolts 81 protrude from the second downstream flange 64b by more than twice the thickness of the nuts 83 in the assembled state, so that additional nuts 84 can be screwed onto the free ends of the stud bolts 81. Therefore, even when the stud bolts 81 are securely received in the threaded holes 70 of the joint flange portion 71a, the stud bolts 81 can be unscrewed from the threaded holes 70 by applying a loosening torque to the additional nuts 84 with an appropriate tool. Since the additional nut 84 has a relatively large diameter, a large loosening torque can be applied to the stud bolt 81.

As shown in fig. 4 and 6, the dimension L3 of the clearance G in the axial direction of the flexible pipe member 72 is selected so that the first gasket 68 and the second gasket 69 in the unused state can fit into the clearance between the low pressure EGR valve 65 and the second low pressure EGR pipe 64 and the clearance between the low pressure EGR valve 65 and the joint member 71, respectively. More specifically, when the flexible pipe member 72 is moved leftward until the corresponding end of the flexible pipe member 72 abuts against the annular shoulder surface 41c, the clearance (t3) created between the low-pressure EGR valve 65 and the second low-pressure EGR pipe 64 and the clearance (t4) created between the low-pressure EGR valve 65 and the joint member 71 are larger than the thicknesses of the first shim 68 and the second shim 69 in the unused state. Therefore, the removal and reinstallation of the low-pressure EGR valve 65 can be easily achieved.

Although the present invention has been described in terms of its preferred embodiments, it will be apparent to those skilled in the art that various changes and modifications are possible without departing from the spirit of the invention. For example, the invention applies to automotive diesel engines, but may also be applied to gasoline engines, and may also be applied to engines for other applications, such as rail and other ground transportation vehicles, boats and aircraft.

Further, in the above embodiment, the engine 4 is mounted transversely on the motor vehicle 1, but may be mounted longitudinally. The exhaust side of the engine may also be disposed on the opposite side of the engine without departing from the spirit of the present invention. In the above embodiment, the EGR device is applied to the low-pressure EGR device 60, but may be applied to the high-pressure EGR device 50. In the above embodiments, the turbocharger 40 may be replaced with a super charger, which may be powered by the output of an electric motor or engine. In the above embodiment, the compressor connecting pipe portion 41b is formed integrally with the compressor housing 41a, but may be formed separately from the compressor housing 41a and coupled to the compressor housing 41 a. In the above embodiment, two stud bolts 81 are implanted in the joint member 71, but one or three or more stud bolts 81 may also be used, and the stud bolts 81 may also be implanted to the second low-pressure EGR piping system 64. Alternatively, it is also possible to remove all the stud bolts 81 and use only ordinary bolts.

In the above embodiment, the stud bolt 81 and the ordinary bolt 82 pass through the valve housing 65a of the low-pressure EGR valve 65, and the second low-pressure EGR pipe 64, the low-pressure EGR valve 65, and the joint member 71 are fastened together by the nut 83. However, the fastening means for fastening the second low-pressure EGR pipe 64 and the low-pressure EGR valve 65 to each other and the fastening means for fastening the low-pressure EGR valve 65 and the joint member 71 to each other may be provided separately.

Alternatively, the fastening member may use a fastener other than a bolt and a nut. In the above embodiment, the gap G is formed between the annular shoulder surface 41c and the flexible pipe member 72, but it may be formed between the annular shoulder surface 71c and the corresponding end of the flexible pipe member 72. Also, the compressor connecting tube portion 41b and the fitting connecting tube portion 71b may not be perfectly aligned in a coaxial relationship, and/or the flexible tube member 72 may be bent or otherwise curved.

Claims

1. An EGR apparatus for a multi-cylinder engine equipped with a super charger for returning a portion of exhaust gas discharged from an exhaust system of the engine to an intake system of the engine, comprising:

a first connecting pipe portion extending from a compressor of the super supercharger and having a first annular shoulder surface at a base end thereof;

an EGR valve fixedly attached to a portion of the engine;

a joint member including a flange attached to the EGR valve and a second connecting pipe portion defining a passage communicating with the inlet end of the EGR valve and opposing the first connecting pipe portion in a coaxial relationship, the second connecting pipe portion being provided at a base end thereof with a second annular shoulder surface; and

a flexible pipe member having a first end fitted to the first connecting pipe portion and a second end fitted to the second connecting pipe portion;

wherein a distance between the first and second annular shoulder surfaces is greater than a length of the flexible pipe member by a predetermined distance.

2. The EGR apparatus of claim 1, wherein the super-supercharger is comprised of a turbocharger that includes a turbine to power the compressor and that is attached to a portion of the engine such that the compressor protrudes from an exhaust-side portion of the engine beyond a cylinder bank end of the engine; and the first connecting pipe portion, the EGR valve, the flexible pipe member, and the second connecting pipe portion extend from the compressor along the cylinder bank end of the engine.

3. The EGR apparatus of claim 2, further comprising an upstream EGR tube assembly communicating a portion of the exhaust system to the inlet end of the EGR valve, the upstream EGR tube assembly including a portion extending generally vertically along the cylinder bank end of the engine toward a downstream portion of the exhaust system of the engine.

4. The EGR apparatus according to claim 3, wherein an exhaust gas purification apparatus is located on an exhaust gas side of the engine below the turbine, and an upstream end of the upstream EGR pipe assembly is connected to a downstream portion of the exhaust gas purification apparatus.

5. The EGR apparatus according to claim 4, wherein the upstream EGR pipe assembly extends from an upstream end thereof generally upward along the bank end of the engine toward an intake side of the engine, then turns back toward the exhaust side of the engine and is connected to the inlet end of the EGR valve, between the engine and the exhaust gas purification apparatus.

6. The EGR device of claim 5, wherein the upstream EGR tube assembly comprises an EGR cooler.

7. The EGR apparatus of claim 6, wherein the upstream EGR tube assembly comprises a rigid tube member connected between the EGR cooler and the EGR valve.

8. The EGR apparatus according to claim 7, wherein a plurality of bolts pass through a flange provided on a downstream end of the rigid pipe member of the upstream EGR pipe assembly, the EGR valve, and the joint member to fasten these components to each other.

9. The EGR apparatus according to claim 8, wherein the bolts include at least a pair of stud bolts each having a base end screwed into one of the flange of the rigid pipe member and the flange of the joint member and a free end having a threaded portion to which a nut is fastened.

10. The EGR apparatus of claim 9, wherein the free end of each stud bolt is provided with a tool engagement feature.

11. The EGR apparatus of claim 9, wherein the threaded portion on the free end of each stud bolt is provided with a length that is at least twice a nut thickness.

12. The EGR apparatus of claim 9, wherein a first shim is interposed between the flange of the rigid tube member of the upstream EGR tube assembly and the EGR valve, and a second shim is interposed between the EGR valve and the joint member; and wherein the distance between the first and second annular shoulder surfaces is greater than the length of the flexible pipe member by at least the combined thickness of the first and second shims in an unused state.

13. The EGR apparatus according to claim 9, wherein each end of the flexible pipe member is fastened to the corresponding connecting pipe portion with a hose clip.