GB2291127A

GB2291127A - Exhaust gas recirculation valve mounting

Info

Publication number: GB2291127A
Application number: GB9514152A
Authority: GB
Inventors: Bruno Hezel; Andreas-Bernd Rosenbusch
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1994-07-13
Filing date: 1995-07-11
Publication date: 1996-01-17
Anticipated expiration: 2015-07-11
Also published as: ITMI951371A1; ITMI951371A0; DE4424644C1; DE4424644C5; GB2291127B; FR2722532B1; IT1277189B1; JPH0861160A; GB9514152D0; KR100378453B1; FR2722532A1

Description

Exhaust-gas recirculation valve The invention relates to an exhaust-gas

recirculation valve in accordance with the

precharacterizing clause of Claim 1.

Prior art

The use of exhaust-gas recirculation valves in motor vehicles, especially in motor vehicles which employ a diesel engine an the internal combustion engine, in known. These valves serve for the addition of exhaust gas from the internal combustion engine to the intake air of the internal combustion engine in order in this way to reduce the oxygen content of the intake air. An a result, it in possible to achieve a reduction in the nitrogen oxides formed during the combustion process and the pollutant emissions of the motor vehicle are thus reduced. It in, however, disadvantageous in the case of the known exhaust-gas recirculation valves that the recirculated exhaust gas has temperatures of about 4000C and that the intake duct carrying the intake air to the internal combustion engine must be composed of a heatresistant material. Castings are generally used for this purpose. However, these are relatively complicated to manufacture since a different shape of intake duct is necessary for each type of internal combustion engine. An a result, there is additional expense associated with the production of intake ducts from metal castings. Because of the high temperature in exhaust-gas recirculation, the use of plastic mouldings for the intake ducts, which are simple and economical to produce, was not possible.

2 Advantages of the invention In contrast, the exhaust-gas recirculation valve according to the Invention with the features mentioned In Claim 1 offers the advantage that the use of inexpensive 5 plastic parts ia possible when employing exhaust-gas recirculation. By virtue of the fact that the valve sleeve of the exhaust-gas recirculation valve in assigned means which permit cooling of the valve sleeve, especially In the region of contact between the valve sleeve and the intake duct, this particularly critical region can be cooled down to such an extent that the use of plastic becomes possible. An a result, the intake ducts can be manufactured in a simple manner an plastic mouldings, making it considerably simpler to use them in a very wide variety of different geometries on the different types of internal combustion engine.

In an advantageous development of the invention, it in envisaged that, outside the Intake duct, the valve sleeve should be surrounded by a flange of good thermal conductivity which serves an a means for fastening the valve sleeve to the Intake duct. This advantageously makes it possible to transfer the heat carried along with the exhaust gas to the flange via the valve sleeve, allowing It to be dissipated there over a large area by radiation. This prevents the plastic parts of the intake duct from being subjected to a high temperature since this has already been lowered to below a critical value by the heat radiation.

In a further advantageous development of the invention, it is envisaged that, on the intake side, the valve sleeve should have at least one air-guide element, which causes a deflection of a partial air stream of the intake air to an area of contact between the valve sleeve and the intake duct. This additionally effects cooling of the critical region of contact between the valve sleeve subjected to the hot exhaust gas and the intake duct, and excess heat energy which has not been radiated by the fastening flange is absorbed by the partial air stream and can be dissipated by the valve sleeve. Exceeding of a critical temperature f or the plastic material of the intake duct in thus reliably prevented.

Further advantageous developments of the 5 invention emerge from the remaining features mentioned in the subclaims.

Drawing The invention in explained in greater detail below in exemplary embodiments, with reference to the associated drawings. In the drawings:

Figure 1 shows, schematically, an overview of an internal combustion engine with exhaust gas recirculation; Figure 2 shown a sectional representation of an exhaustgas recirculation valve in a first embodiment -and Figure 3 shows a sectional representation of an exhaustgas recirculation valve in another embodiment.

Description of the exemplary embodiments

Figure 1 shows, schematically, the mode of operation of an exhaust-gas recirculation valve 10. A cylinder chamber 12 of an internal combustion engine in shown. The cylinder chamber 12 is connected, on the one hand, to an intake duct 14 and, on the other hand, to an exhaust duct 16. The intake duct 14 and the exhaust duct 16 are connected to the cylinder chamber 12 in a generally known manner by valves 18. A bypass 20 leads from the exhaust duct 16 to the intake duct 14. Arranged in this bypass 20 is the exhaust-gas recirculation valve 10, which can thus open and close the connection between the bypass 20 and the exhaust duct 14. The exhaust-gas recirculation valve 10 is controlled by way of a pilot valve 22 which connects a vacuum source 24 to an operating means 26 of the exhaust-gas recirculation valve 10. The pilot valve 22 is controlled by a control unit 28 connected to an injection pump 30 and an accelerator pedal 32 of the motor vehicle (not shown). During the operation of the internal combustion engine, fresh air In drawn In via the intake duct 14 and fuel is injected Into It. When the valve 18 In open, this air f lows into the cylinder chamber. There, the universally known combustion process takes place and, as a result of this process, the exhaust gas in expelled via the exhaust duct 16 when the second valve 18 In open.

Particularly in the case of diesel engines, the exhaust gases from combustion contain a component of nitrogen oxides NO,, and these lead to pollution of the environment. Some of the exhaust gas is passed via the bypass 20 to the exhaust-gas recirculation valve 10, the is exhaust gas here having a temperature of about 4000C. Depending on the engine management and the operating state of the motor vehicle, for example the engine speed, the coolant temperature, the boost pressure, the control unit 28 supplies a switching pulse for the pilot valve 22, which thus actuates the operating means 26 of the exhaust-gas recirculation valve 10. An a result, the exhaust-gas recirculation valve 10 opens and establishes a connection between the bypass 20 and the intake duct 14, allowing a part-stream of the exhaust gas to be mixed in with the fresh air via the bypass 20. This reduces the oxygen content of the fresh air and a smaller quantity of nitrogen oxide in thus formed In the combustion processes. Pollution of the environment is thus reduced.

Figure 2 shown a sectional representation of an exhaust-gas recirculation valve 10. The exhaust-gas recirculation valve has a valve sleeve 34 which passes through a wall region 36 of the intake duct 14. The wall region 36 can be an integral part of the intake duct 14 but can also be f Itted into an Intake duct 14 as a separate sleeve. In this case, a fresh-air-side region 38 and an engine- side region 40 of the intake duct 14 would adjoin the wall region, here denoted by 36, on both sides.

The valve sleeve 34 has a section 42 of larger diameter and a section 34 of smaller diameter, which merge Into one another by way of an annular step 46. The wall region 36 forms a stub 48 through which the valve sleeve 34 in passed. Section 42 of the valve sleeve 34 in 5 surrounded by a flange 50 which is fastened to the stud 48. The flange 50 thus holds the valve sleeve 34 in a fixed position. A large contact area 52 In formed between the valve sleeve 34, especially section 42, and the flange 50 and this surface on the one hand ensures 10 sufficient positional fixing of the valve sleeve 34 and on the other hand a large heat transfer surface. The flange 50 is composed of a material of good thermal conductivity, f or example aluminium, and has a large-area annular shoulder 51. Between section 42 and the stub 48 15 there is only a relatively small contact area 54 and the heat transfer surface available here In thus not large. An inside diameter of the stub 48 in larger than an outside diameter of the section 44 of smaller diameter of the valve sleeve 34, an annular chamber 56 thus being 20 formed in the region of the stub 48. The annular chamber 56 is connected to the intake duct 14. Arranged on the !=er wall of the stub 48 In an air guide element 58 designed as a blade 60. The blade 60 here surrounds the valve sleeve 34 In its section 44 at least an far an an axial line 62 of the valve sleeve 34. The blade 60 is designed to give optimum flow. The blade 60 extends approximately parallel to an axial line 64 of the intake duct 14 and ends approximately in the region of the axial line 62 on the stub 48. In this arrangement, the blade 60 forms a deflection surface 66. By means of the blade 60 and its deflection surface 66, a partial air stream, here denoted by the arrows 68, from the fresh air passing through the intake duct 14 is guided into the annular chamber 56. The partial air stream 68 flown around 35 section 44 of the valve sleeve 34 and then reemerges from the annular chamber 56 into the intake duct 14. The bypass 20 shown in Figure 1 can be connected to the valve sleeve 34 at the flange end. At the end where the intake duct 14 is situated, the valve sleeve 34 is closed by a valve ring 70, which in connected by way of a valve rod 72 to a diaphragm 74 of a pressure capsule 76. The pressure capsule 6 here forms the operating means 26 shown in Figure 1. The diaphragm 74 can be moved axially counter to the force of a spring 78. The spring 78 is supported on a diaphragm cover 80. The valve rod 72 is connected to a diaphragm plate 82 which carries the diaphragm 74. The valve rod 72 is supported by a bush 84 and is guided in a sealed and movable manner in the latter.

The exhaust-gas circulation valve 10 shown in Figure 2 performs the following function:

During the operation of the internal combustion engine (not shown), the valve sleeve 34 is supplied is continuously, via the bypass 20, with exhaust gas, which has a temperature of about 4000C. If exhaust gas is to be added to the fresh air flowing In the intake duct 14, the pressure capsule 76 In connected to the vacuum source 24 and the diaphragm 74 in thus moved counter to the force of the spring 78. At the came time, the valve ring 70 opens and a connection thus arises between the valve sleeve 44 and the intake duct 14. In accordance with the degree of opening andlor duration of opening of the valve ring 70, a particular, selectable quantity of exhaust gas can be added to the fresh air. When the pressure capsule 76 in separated from the vacuum source 24, the spring 78 presses the diaphragm 74 in the axial direction and the valve ring 70 thus closes the valve sleeve 34 again.

The exhaust gas, which ia at a temperature of about 4000C, releases a large part of its heat energy to the valve sleeve 34. Via the contact area 52, a large part of the heat in transferred to the flange 50. This has a large radiating area, allowing the valve sleeve 34 to remove heat energy continuously from the exhaust gas.

The partial air stream 68, which has a lower temperature, namely the temperature of the fresh air, is furthermore guided around section 44 of the valve sleeve 34, with the result that the said section removes a large part of the remaining residual heat of the valve sleeve 34. The valve 7 sleeve 34, In thereby cooled down, particularly in its contact area 54 with the wall section 36 composed of plastic, to such an extent that the valve sleeve there has a temperature which lies below a critical temperature, In particular below a melting point of the plastic used. Despite the hot exhaust gas, the wall section 36 or the entire exhaust duct 14 can thus he manufactured from a plastic moulding, which can be produced economically, without the occurrence of any deformations and hence impairment of the exhaust-gas recirculation valve 10.

Figure 3 shown an exhaust-gas recirculation valve 10 in a further variant embodiment. Parts which are the same an in Figure 2 are provided with the same reference numerals and are not explained again here. in the exemplary embodiment shown here, the air-gulde element 58 is formed by a sleeve-shaped extension 86 of the stub 48, the said extension surrounding section 44 of the valve sleeve 34. An annular space 88 In formed between the extension 86 and the valve sleeve 34. The annular space 88 in connected to the intake duct 14 by means of at least one through opening 90. In this arrangement, at least one through opening 90 points in the direction of region 38 and at least one through opening 90 In the direction of region 40 of the intake duct 14.

The exhaust-gas recirculation valve 10 shown in Figure 3 operates in the same way as that in Figure 2 and is not explained again here. Additional cooling by the partial air stream 68 is here provided In addition to the cooling by means of the flange 50 likewise explained with reference to Figure 2, being provided in such a way that the partial air stream enters the annular space 88 through the through opening 90 pointing in the direction of region 38 of the Intake duct 14. There, the partial air stream 68 flows around section 44 of the valve sleeve 34 and thus cools it down further. The partial air stream 68 reemerges into the intake duct 14 through the through opening 90 pointing in the direction of region 40. overall, it is thereby possible to lower the temperature - a - of the valve sleeve 34 In the critical area of contact between the valve sleeve 34 and the wall region 36 to such an extent that thermal damage to the plastic does not occur.

The invention in not limited to the exemplary embodiments shown. Thus any desired shape of the air guide elements 58 which diverts a partial air stream 68 from the overall fresh air stream and uses it to cool the transitional zone between the valve sleeve 34 and the wall region 36 is conceivable. In particular, these can be any desired integrally formed features on the inner wall of the wall region 36 in the region of the stub 48. The provision of the flange 50 or an arrangement corresponding to this can be an additional or exclusive is feature, on the one hand having such a large contact area with the valve sleeve 34 and on the other hand such a large radiating area that sufficiently great heat removal from the exhaust gas can take place.

Claims

Patent claims

1. Exhaust-gas recirculation valve with a valve sleeve which in arranged in an exhaust duct and carries exhaust gas, characterized in that the valve sleeve (34) is assigned =cans which permit cooling of the valve sleeve (34), especially In a region of contact between the valve sleeve (34) and t he intake duct (14).

2. Exhaust-gas recirculation valve according to Claim 1, characterized in that the valve sleeve (34) is surrounded outside the intake duct (14) with a flange (50) of good thermal conductivity which serves an a means for fastening the valve sleeve (34) to the intake duct (14).

3. Exhaust-gas recirculation valve according to one of the preceding claims, characterized in that the flange (50) and the valve sleeve (34) have only a small contact area (54) with the intake duct (14).

4. Exhaust-gas recirculation valve according to one of the preceding claims, characterized in that the flange (50) has a large-area annular shoulder (51) serving an a radiating area.

5. Exhaust-gas recirculation valve according to one of the preceding claims, characterized in that, at the intake end, the valve sleeve (34) has at least one air guide element (58), which causes deflection of a partial air stream (68) to the contact area (54) between the valve sleeve (34) and the intake duct (14).

6. Exhaust-gas recirculation valve according to Claim 5, characterized in that the air-guide element (58) is a blade (60) which points towards the intake-air flow and surrounds the valve sleeve (34) at least in the form of a semicircle.

7. Exhaust-gas recirculation valve accordingto Claim 6, characterized in that the blade (60) has a shape which In optimized In terms of flow.

8. Exhaust-gas recirculation valve according to either of Claims 6 and 7, characterized in that the blade (60) has a deflection surface (66) for the partial air stream (68).

9. Exhaust-gas recirculation valve according to one of Claims 1 to 5, characterized in that the air-guide element (58) in formed by an extension (86) of a wall 10 region (36) of the intake duct (14).

10. Exhaust-gas recirculation valve according to Claim 9, characterized In that the extension (86) surrounds the valve sleeve (34) and forms an annular space (88) which in connected to the Intake duct (14) by 15 means of at least one through opening (90).

11. Exhaust-gas recirculation valve according to one of the preceding claims, characterized In that, in the axial direction, the valve sleeve (34) has a section (44) of smaller diameter which passes through the wall region (36) of the intake duct (14).

12. Exhaust-gas recirculation valve according to Claim 11, characterized in that the wall region (36) forms a stub (48) which has a larger inside diameter than an outside diameter of the section (44) of the valve 25 sleeve (34).

13. Exhaust-gas recirculation valve according to Claim 11 and 12, characterized In that an annular chamber (56) which is connected to the intake duct (14) is formed between the stub (48) and the section (44).

14. An exhaust-gas recirculation valve substantially as herein described with reference to Figures 1 and 2, or Figures 1 and 3, of the accompanying drawings.