Valve assembly and method of producing a valve assembly

Abstract

A valve assembly comprises a housing 12 having a bore 14, a valve member located within the bore and moveable relative to the housing between open and closed positions, wherein the valve member is sec

Description

Valve assembly and method of producing a valve assembly TECHNICAL FIELD This disclosure relates to valve assemblies and methods for manufacturing valve assemblies. BACKGROUND OF THE INVENTION It is known to control the passage of exhaust gases from internal combustion engines with a valve assembly or valve block having a valve member which operates via rotation of a spindle. Such valve assemblies are used in exhaust brakes, thermal management systems, waste heat recovery systems, exhaust gas recirculation (EGR) and EGR bypass valves, for example. Conventionally, such spindles are rotatably mounted in one or more bushes, which are pre-formed and pressed into a pre-formed aperture in the valve assembly or valve block (typically, a cast body). In order to prevent movement of a bush under operational loads, the bush will be pinned in the housing (e.g. using a retaining pin). The conventional methods of spindle mounting requires machining of the apertures into which the bushes are to be press-fitted. The location and orientation of the bushes is critical to correct operation of the valve. Hence, such valves may be prone to leakage without a low tolerance on the correction location and orientation of the valve. In worst cases, scrap levels are high if the machining is not precise or if there are problems in setting the bush in position, e.g. if the retaining pin becomes dislodged. Moreover, in extreme circumstances, there is a risk of engine fire if the bush becomes loose and dislodged in use. An object of the invention is to provide an improved method for mounting a valve member in a valve or valve block. SUMMARY OF THE INVENTION According to the first aspect of the disclosure, there is provided a valve assembly comprising a housing, the housing having a bore, wherein a valve member is located within the bore and is moveable relative to the housing between an open position and a closed position; wherein the valve member is secured to a rotatable spindle; wherein the spindle is mounted in a bush; and wherein the bush is an integral mounting in the housing. The phrase ‘integral mounting’ is intended to mean that the bush is integrally mounted in the housing; that is to say, the skilled person would be able to see that the bush had been integrally mounted in the housing during formation of the housing. Such an arrangement is advantageous in that it overcomes the need to post-process a pre-produced valve housing in order to machine in place apertures or recesses for receiving a bush for the spindle. In exemplary embodiments, the housing comprises a first material and the bush comprises a second material, and wherein the second material has a composition which is different to the composition of the first material. Integrally forming the bush with the housing may obviate the need to provide a secondary step for securing the bush relative to the housing. That is to say, an integral bond may exist between the first and second materials, suitable to avoid the need for a pinning operation (of the kind required in known valve assemblies). Hence, such an integrally mounted bush may overcome a number of risks associate with the prior art, such as leakage and fire risk. In exemplary embodiments, the second material is bonded with the first material (e.g. the skilled person would be able to see that the bush had bonded with the material of the housing during formation of the housing). In exemplary embodiments, the first material is a metallic material, e.g. a form of cast iron. In exemplary embodiments, the second material is a metallic material, e.g. an alloy composition, such as an alloy composition from the niresist range or the nitronic range. In exemplary embodiments, the housing is a casting (i.e. formed by a casting process). The casting process helps to advantageously bond the second material with the first material. In exemplary embodiments, the second material has a matrix which is at least partially diffused with the first material, e.g. in a zone at the interface between the outer surface of the bush and the housing. In exemplary embodiments, the housing is a casting and the bush has been integrally located in the housing during casting of the housing. In exemplary embodiments, the valve assembly includes first and second integrally mounted bushes, arranged opposite one another, and wherein one end of the spindle extends into in the first integrally mounted bush and an opposite end of the spindle extends into the second integrally mounted bush; wherein the second integrally mounted is an open bush, such that said opposite end of the spindle extends out of the body of the valve assembly and is connected to a lever which is movable for rotating the spindle in the first and second integrally mounted bushes. According to another aspect of the disclosure, there is provided a method of manufacturing a valve assembly, wherein the method involves a casting process using a mould to produce a body having a bore for directing fluid through the body; and wherein the method involves integrally locating a bush in the body at a predetermined position and orientation in association with the bore during the casting process. In exemplary embodiments, the bush is to serve as a bearing for receiving a rotatable valve spindle for a valve member intended to be operable within the bore between an open and closed position. In exemplary embodiments, the bush is formed from a slug of material, which is placed into the mould for the body. In exemplary embodiments, the body comprises a first material and the bush comprises a second material, and wherein the second material has a composition which is different to the composition of the first material. In exemplary embodiments, the method involves flowing the first material in a molten state around the slug in the mould, and materially coupling the first and second materials (i.e. for preventing the bush slug from moving under normal machining and operational loading conditions). In exemplary embodiments, the material coupling is the result of diffusion between material of the bush slug and the molten first material. Put another way, in exemplary embodiments, fixation of the bush relative to the body is via a material diffusion between the first and second materials during the casting process. In exemplary embodiments, the second material has a matrix which is at least partially diffused with the first material during the casting process, e.g. wherein a degree of diffusion takes place in a zone at the interface between the outer surface of the bush and the material of the housing. In exemplary embodiments, the bush slug is of solid form prior to casting. In exemplary embodiments, the bush slug has opposing ends, wherein one end is orientated to face the bore of the valve assembly, in use. In exemplary embodiments, the bush slug has a longitudinal axis and is generally circular or elliptical in cross-section, or is of a polygonal cross section. In exemplary embodiments, the bush slug has a nominal diameter in the region Smm to 40mm, e.g. 8mm to 36mm. In exemplary embodiments, the bush slug has an outer surface extending between the opposing ends; and wherein the outer surface includes one or more recesses or grooves and / or one or more flat surfaces or other such form of keyway for creating interdigitation of the first material with the bush slug during casting. In exemplary embodiments, after the casting process, the bush slug is finished in order to form a bush to be used as a bearing for a rotatable spindle, e.g. via drilling and reaming operation. In exemplary embodiments, the bush has an internal surface having a surface finish in the range 120 to 900 RMS. In exemplary embodiments, the method involves integrally locating first and second bushes in the body, with the first bush arranged opposite the second bush so as to define a spindle axis, for receiving a rotatable valve spindle therebetween. In exemplary embodiments, the second bush is an open bush, wherein said opposite end of the spindle may extend out of the body of the valve assembly for connection to a lever movable for rotating the spindle in the first and second bushes. In exemplary embodiments, the first material is a metallic material, e.g. suitable for forming a cast iron body. In exemplary embodiments, the second material is a metallic material; optionally, an alloy composition; further optionally, an alloy composition from the niresist range or the nitronic range. In exemplary embodiments, the or each bush slug has an outer surface which is intended to be bonded with the material of the body during the casting process, and wherein a flux is applied to said outer surface, for creating an exothermic reaction during the casting process; optionally, wherein the flux is in the form of a paste. In exemplary embodiments, the flux is a thermite composition; optionally, wherein the composition of the flux is formulated to ignite on contact with the molten first material In exemplary embodiments, the flux comprises a composition of aluminium powder and iron oxide particles. BRIEF DESCRIPTION OF THE DRAWINGS Aspects and features of the disclosure are set forth in the following description, with reference to the accompanying drawings, in which: Fig. 1 is a schematic cross-sectional view of part of a conventional valve assembly for rotationally mounting a butterfly valve member in a bore of the valve body; Fig.2 is a schematic cross-sectional view of part of a valve assembly in accordance with an exemplary aspect this disclosure immediately after a casting operation; Fig.3 is similar to Fig.2, showing the valve assembly of Fig.2 after a finishing operation; Fig. 4 shows a first embodiment of a bush slug for use in the production of a valve assembly in accordance with Figs. 2 and 3; Fig. 5 shows a second embodiment of a bush slug for use in the production of a valve assembly in accordance with Figs. 2 and 3; Fig.6 shows bushes projecting from the valve body prior to a finishing operation, in accordance with an exemplary method of the disclosure; Fig.7 is a first non-exhaustive table of materials suitable for forming a bush slug for use in valve assemblies of this disclosure; and Fig.8 is a second non-exhaustive table of materials suitable for forming a bush slug for use in valve assemblies of this disclosure. DESCRIPTION OF EMBODIMENTS Referring firstly to Fig. 1, part of a conventional valve assembly is indicated at 1, having a cast body 2 with a bore 4. Opposing bushes 6a,6b have been pressed into respective apertures 5 that have been pre-formed in the body 2. The bushes 6a,6b are intended for locating a spindle (not shown), for operation of a valve member (not shown) to be positioned in the bore 4, such that the valve member is operable between an open and closed position within the bore 4 via rotation of the spindle. In the illustrated embodiment of Fig.1, bush 6a is a closed bush for receiving one end of a spindle, whereas bush 6b is an open bush, such that an opposite end of the spindle may extend through the bush 6b (e.g. so as to extend out of the body 2, for connection to a lever movable for rotation of the spindle). It will be understood that machining of the apertures 5 and the formation and finishing of the 6a,6b needs to be precise, to ensure suitable location of the bushes 6a,6b in the apertures 5. Moreover, in order to prevent movement of the 6a,6b relative to the body 2 under operational loads, the bushes 6a,6b have to be secured in place by a respective retaining pin 7. It will be understood that the manufacture of the valve assembly is therefore complex. Figs. 2 to 4 relate to an alternative valve assembly in accordance with this disclosure. In Figs. 2 and 3, part of the valve assembly is indicated at 10, having a cast body 12 with a bore 14. Fig.2 shows the valve assembly 10 immediately after the casting process, wherein the body 12 has been cast in a mould (not shown). The body 12 is configured to define bore 14 for use in directing fluid through the body 12. In accordance with an exemplary method of this disclosure, opposing bushes 16a,16b have been integrally located in the body 12 at a predetermined position and orientation in association with the bore 14 during the casting process. For example, the bore 14 may define a fluid flow path having an axis A, and the bushes 16a,16b define a spindle axis B which is orientated orthogonal to the axis A. Moreover, each bush 16a,16b may have an open end 18 which is arranged to face into the bore 14. The bushes 16a,16b are intended for locating a spindle (not shown), for operation of a valve member (not shown) to be positioned in the bore 14 and be operable between an open and closed position within the bore 14 via rotation of the spindle. In the illustrated embodiment of Figs. 2 and 3, bush 16a is a closed bush for receiving one end of a spindle, whereas bush 16b is an open bush, such that an opposite end of the spindle may extend through the bush 16b (e.g. so as to extend out of the body 12, for connection to a lever, not shown, movable for rotation of the spindle). The body 14 is formed from a first material and the bushes 16a,16b are formed from a second material. The second material has a composition which is different to the composition of the first material. As can be seen from Fig. 2, each bush is formed from a slug 20 of the second material. Each slug is placed into the mould (not shown) for the body at a predetermined position and orientation, in order to provide the arrangement as shown in Figs. 2 and 3, i.e. wherein the bushes 16a,16b define a spindle axis. An exemplary method of this disclosure involves flowing the first material around the bush slugs 20 in the mould and using the casting process to promote a material coupling between the first and second materials, i.e. for preventing the bush slug from moving under normal machining and operational loading conditions. For example, during the casting process, the temperature of the poured casting material may melt or soften the outer surface of the bush slug, thereby allowing diffusion between the first and second materials, leading to fusion of the first and second materials under cooling. Hence, in exemplary embodiments, the second material has a matrix which is at least partially diffused with the first material during the casting process, e.g. wherein a degree of diffusion takes place in a zone at least at the interface between the outer surface of the bush and the material of the housing. In exemplary embodiments, dependent on the material of the body and the or each bush slug, it is likely that the casting process will need to take place at temperatures in the region of 600C or higher, in order to obtain suitable bonding between the first and second materials. In exemplary embodiments, the first material is a metallic composition, for example an iron alloy composition, which may include spheroidal graphite. In exemplary embodiments, body is a cast iron component, which may comprise with spheroidal graphite (EN-GJS) according to German Standard (DIN) EN 1563 (an iron-C cast material). However, it should be understood that other materials may be suitable. An example is Ausferritic Ductile Iron (as defined by DIN EN 1564.). In exemplary embodiments, the second material is a metallic composition, for example an alloy composition. It has been found that bush slug materials in the niresist range (see Fig. 7) and the nitronic range (see Fig. 8) provide good bonding performance. However, it should be understood that other materials may be suitable. It will be understood that the or each bush slug 20 has an outer surface which is intended to be bonded with the material of the body 12 during the casting process. In exemplary embodiments, a flux is applied to said outer surface, for creating an exothermic reaction during the casting process, in order to promote fusion between the first and second materials (i.e. the material of the body 12 and bush slug 20). Such technology is known from other industries (for diffusion bonding of two metallic materials), such as in the joining of rail steel. In exemplary embodiments, the flux is a thermite composition, typically in the form of a paste, which is applied to the outer surface of the bush slug. The composition of the flux can be configured to ignite on contact with the poured, molten first material, thereby increasing the local temperature at the critical interface of the first and second materials, thereby promoting an improved (metallurgical) bond. A suitable flux may comprise a composition of aluminium powder and iron oxide particles, for example. Fig. 3 shows the arrangement of Fig.2 after a subsequent finishing operation, in which each diffused bush slug 20 is finished in order to form a bush to be used as a bearing for a rotatable spindle, e.g. via drilling and reaming operation. In exemplary embodiments, the bush has an internal surface having a surface finish in the range 120 to 900 RMS. Surface finishes in this range have been found to maintain durability targets for ‘bush to spindle wear’ and end of life valve leakage performance. Fig.4 shows an embodiment of an advantageous bush slug 120 for use in the method of this disclosure. The bush slug is of a solid, generally cylindrical form, which is circular in cross-section. Bush slug 120 includes at least one recess or groove 122 (which may be of various sizes, configuration and location), for enhancing fusion with the first material of the body 12 during the casting process. Fig.5 shows an embodiment of an advantageous bush slug 220 for use in the method of this disclosure. The bush slug 220 is similar to the bush slug 120, but includes at least one flat surface 224 on its outer perimeter, for enhancing fusion with the first material of the body 12 during the casting process. The cross-section of the slugs 120, 220 may be of other shape, e.g. elliptical or polygonal shape such as a square, pentagon, hexagon etc. (regular or irregular). In exemplary embodiments, each bush slug may include one or more recesses or grooves and / or one or more flat surfaces of the kind described in relation to Figs. 4 and 5. In exemplary embodiments, the body of each bush slug has a nominal diameter in the region 5mm to 40mm, e.g. 8mm to 36mm, depending on the size of the spindle / flow capacity of the valve. In exemplary embodiments, the body of each bush slug has a nominal length in the region 40mm to 50mm for the bottom slugs (i.e. the blind bushes), and in the region , e.g. 60 to 90mm for the top slugs (i.e. the ‘through’ bushes). Again, sizes will be dependent upon the size of the spindle / flow capacity of the valve. It will be understood that the bush slugs 20,120,220 will be supported at the correction location and orientation relative to the mould for the body 112 using conventional core techniques. Typically, the bush slugs 20,120,220 will have a free end intended to project away from the intended location of the bore of the body 12, prior to casting. Example free ends are indicated 126,226 in Figures 4 and 5, respectively. The projecting free ends are provided for engagement with an associated core of the mould, in order to facilitate correct location and orientation of the slugs 20,120,220. The ends 126,226 may include an undercut 128,228 or other such formation to facilitate simple engagement with a core of the mould. Conventional core techniques can allow the bush slugs to positioned at the correct location and orientation with accuracy below 0.1mm, which significantly reduces the risk of scrap and / or leakage associated with mis-location or disturbance of bushes in conventional valve assemblies of the type discussed above. Fig.6 shows an example view of how the free end 126,226 of such a bush slug 120,220 may project from the body 12 of the valve assembly 10 after casting. It may be desirable to remove the free ends 126,226 (e.g. by a machining operation) prior to installation of the valve assembly 10. It should be noted that the bush slugs shown in Fig.6 are schematic only and are not intended to be definitive in terms of their respective shapes. Valve assemblies and methods of producing valve assemblies in accordance with this invention are less complex to produce. Valve assemblies in accordance with this disclosure are ideally suited for use in controlling the passage of exhaust gases from internal combustion engines. Such valve assemblies may be used in exhaust brakes, thermal management systems, waste heat recovery systems, exhaust gas recirculation (EGR) and EGR bypass valves, for example.

Claims

Claims 1. A method of manufacturing a valve assembly of the kind having a valve body with a fluid bore intended for receiving a valve member; wherein the method involves using a mould to produce a cast body having a bore for directing fluid through the body; and wherein the method involves providing the cast body with an integrally located bush at a predetermined position and orientation in association with the bore, to serve as a bearing for receiving a rotatable valve spindle for a valve member intended to be operable within the bore between an open and closed position.

2. The method of claim 1, wherein the bush is formed from a slug of material, which is placed into the mould for the body; wherein the body is formed from a first material and the slug comprises a second material; wherein the second material has a composition which is different to the composition of the first material; and wherein the method involves flowing the first material in a molten state around the slug in the mould, and materially coupling the first and second materials.

3. The method of claim 2, wherein said material coupling is the result of diffusion between material of the slug and the molten first material. 4, The method according to any of claims 1 to 3, wherein the method involves integrally locating first and second bushes in the body, with the first bush arranged opposite the second bush so as to define a spindle axis, for receiving a rotatable valve spindle therebetween.

5. The method of any of claims 2 to 4, wherein, after the casting process, the or each slug is finished, optionally, via a drilling and reaming operation, in order to define a bush to serve as a bearing for receiving a rotatable valve spindle for a valve member intended to be operable within the bore between an open and closed position; optionally, wherein the or each bush has an internal surface having a surface finish in the range 120 to 900 RMS.

6. The method of any of claims 2 to 5, wherein the bush slug is of solid form prior to casting; optionally, of circular, elliptical or polygonal cross section.

7. The method of any of claims 2 to 6, wherein the or each bush slug has a nominal diameter in the region 5mm to 40mm.

8. The method of any of claims 2 to 7, wherein the or each bush slug has an outer surface extending between the opposing ends; and wherein the outer surface includes one or more recesses or grooves and / or one or more flat surfaces prior to casting.

9. The method of any of claims 2 to 8, wherein the first material is a metallic material suitable for forming a cast iron body; and wherein the second material is a metallic material; optionally, an alloy composition from the niresist range or the nitronic range.

10. The method of any of claims 2 to 8, wherein the second material is a metallic material in the form of an alloy composition from the niresist range or the nitronic range. 11.The method of any of claims 2 to 10, wherein the or each bush slug has an outer surface which is intended to be bonded with the material of the body during the casting process, and wherein a flux is applied to said outer surface, for creating an exothermic reaction during the casting process; optionally, wherein the flux is in the form of a paste.

12. The method of claim 11, wherein the flux is a thermite composition; optionally, wherein the composition of the flux is formulated to ignite on contact with the molten first material 13. The method of claim 11 or claim 12, wherein the flux comprises a composition of aluminium powder and iron oxide particles.

14. A valve assembly comprising a housing, the housing having a bore, wherein a valve member is located within the bore and is moveable relative to the housing between an open position and a closed position; wherein the valve member is secured to a rotatable spindle; wherein the spindle is rotatably mounted in a bush; and wherein the bush is an integral mounting in the housing.

15. The valve assembly of claim 14, wherein the housing comprises a first material and the bush comprises a second material, and wherein the second material has a composition which is different to the composition of the first material, and is bonded with the first material.

16. The valve assembly of claim 15, wherein the second material has a matrix which is at least partially diffused with the first material, e.g. in a zone at the interface between the outer surface of the bush and the housing. 17.The valve assembly of claim 15 or claim 16, wherein the first material is a metallic material (e.g. a form of cast iron), and wherein the second material is a metallic material (e.g. an alloy composition in the niresist range or the nitronic range).

18. The valve member of any of claims 14 to 16 wherein the housing is a casting and the bush has been integrally located in the housing during casting of the housing.

19. The valve assembly of any of claims 14 to 18, wherein the bush has an internal surface having a surface finish in the range 120 to 900 RMS.

20. The valve assembly of any of claims 14 to 19, wherein the valve assembly includes first and second integrally mounted bushes, arranged opposite one another, and wherein one end of the spindle extends into in the first integrally mounted bush and an opposite end of the spindle extends into the second integrally mounted bush; wherein the second integrally mounted is an open bush, such that said opposite end of the spindle extends out of the body of the valve assembly and is connected to a lever which is movable for rotating the spindle in the first and second integrally mounted bushes. Claims 1. A method of manufacturing a valve assembly of the kind having a valve body with a fluid bore intended for receiving a valve member; wherein the method involves using a mould to produce a cast body via a casting process, the cast body having a bore for directing fluid through the body; wherein the method involves providing the cast body with an integrally located bush at a predetermined position and orientation in association with the bore, to serve as a bearing for receiving a rotatable valve spindle for a valve member intended to be operable within the bore between an open and closed position; wherein the bush is formed from a slug of material, which is placed into the mould for the body; wherein the body is formed from a first material and the slug comprises a second material; wherein the second material has a composition which is different to the composition of the first material; and wherein the method involves flowing the first material in a molten state around the slug in the mould, and materially coupling the first and second materials during the casting process.

2. The method of claim 1, wherein said material coupling is the result of diffusion between material of the slug and the molten first material.

3. The method according to claim 1 or claim 2, wherein the method involves integrally locating first and second bushes in the body, with the first bush arranged opposite the second bush so as to define a spindle axis, for receiving a rotatable valve spindle therebetween.

4. The method of any preceding claim, wherein the or each integrally located bush is formed from the slug of material via a finishing operation after the casting process.

5. The method of claim 4, wherein the finishing operation is a drilling and reaming operation.

6. The method of claim 4 or claim 5, wherein the or each bush has an internal surface having a surface finish in the range 120 to 900 RMS.

7. The method of any preceding claim, wherein the bush slug is of solid form prior to casting; optionally, of circular, elliptical or polygonal cross section.

8. The method of any preceding claim, wherein the or each bush slug has a nominal diameter in the region 5 mm to 40 mm.

9. The method of any of any preceding claim, wherein the or each bush slug has an outer surface extending between the opposing ends; and wherein the outer surface includes one or more recesses or grooves and / or one or more flat surfaces prior to casting.

10. The method of any of any preceding claim, wherein the first material is a metallic material suitable for forming a cast iron body; and wherein the second material is a metallic material; optionally, an alloy composition from the niresist range or the nitronic range.

11. The method of any of any preceding claim, wherein the second material is a metallic material in the form of an alloy composition from the niresist range or the nitronic range.

12. The method of any of any preceding claim, wherein the or each bush slug has an outer surface which is intended to be bonded with the material of the body during the casting process, and wherein a flux is applied to said outer surface, for creating an exothermic reaction during the casting process; optionally, wherein the flux is in the form of a paste.

13. The method of claim 12, wherein the flux is a thermite composition; optionally, wherein the composition of the flux is formulated to ignite on contact with the molten first material 14. The method of claim 12 or claim 13, wherein the flux comprises a composition of aluminium powder and iron oxide particles.

15. A valve assembly comprising a housing, the housing having a bore, wherein a valve member is located within the bore and is moveable relative to the housing between an open position and a closed position; wherein the valve member is secured to a rotatable spindle; wherein the spindle is rotatably mounted in a bush; wherein the housing is a cast body; wherein the housing comprises a first material and the bush comprises a second material, and wherein the second material has a composition which is different to the composition of the first material; and wherein the first material is located around the second material, and has been bonded with the second material during casting of the cast body such that the bush is an integral mounting in the housing.

16. The valve assembly of claim 15, wherein the second material has a matrix which is at least partially diffused with the first material, e.g. in a zone at the interface between the outer surface of the bush and the housing. 17.The valve assembly of claim 15 or claim 16, wherein the first material is a metallic material (e.g. a form of cast iron), and wherein the second material is a metallic material (e.g. an alloy composition in the niresist range or the nitronic range).

18. The valve assembly of any of claims 15 to 17, wherein the bush has an internal surface having a surface finish in the range 120 to 900 RMS.

19. The valve assembly of any of claims 15 to 18, wherein the valve assembly includes first and second integrally mounted bushes, arranged opposite one another, and wherein one end of the spindle extends into in the first integrally mounted bush and an opposite end of the spindle extends into the second integrally mounted bush; wherein the second integrally mounted is an open bush, such that said opposite end of the spindle extends out of the body of the valve assembly and is connected to a lever which is movable for rotating the spindle in the first and second integrally mounted bushes.

Images