WO2014048285A1 - Vent structure for clutched device - Google Patents

Abstract

A clutched device, for example a decoupler, may be provided with a vent structure that opens into a cavity of the clutched device to permit at least partial equalization of pressure between the cavity and the ambient environment of the clutched device, while inhibiting ingress of contaminants into the cavity. The vent structure may have one or more of a mechanical one-way valve, a semi- permeable membrane or a passageway with a circuitous path. Uni Ref.: OP130923

Description

Title: VENT STRUCTURE FOR CLUTCHED DEVICE CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of United States Provisional Patent Application Serial Number 61/705,485 filed September 25, 2012, the contents of which are incorporated herein by reference.

FIELD

[0002] The present application relates to clutched devices, particularly decouplers, especially for use in vehicles.

BACKGROUND

[0003] Clutched devices are used in a variety of applications to disengage two moving elements, for example a pulley from a shaft. One example of a clutched device in the automobile industry is a decoupler, which may be used in connection with vehicular engines and belt-driven accessories such as alternators. Decouplers are used to reduce the transmission of torsional vibrations from a decoupler input member to a decoupler output member. For example, a decoupler may be used to inhibit torsional vibrations from an engine crankshaft to an accessory drive belt, or from an accessory drive belt to an input shaft of a belt-driven accessory such as an alternator. Additionally, decouplers typically include a clutch, such as, for example, a wrap spring clutch, that permits the decoupler output member to overrun the input member when needed. The decoupler is typically sealed to the outside environment to prevent ingress of contaminants (such as moisture and debris) that would reduce effectiveness and life of the decoupler components. However, the action of the decoupler components, such as an isolation spring and the aforementioned clutch, generates heat, which increases pressure inside the OAD pulley, which can cause damage to the components and reduce the effective life of the components. Additionally, if lubricant is used in the decoupler (e.g. to lubricate the clutch), the increased pressure may result in the forcing out of the lubricant from the chamber in the decoupler in which it resides.

[0004] Thus, there is a need for a clutched device, such as a decoupler, in which this problem is at least partially addressed.

SUMMARY [0005] There is provided a clutched device, comprising a first clutch member, a second clutch member wherein a cavity is provided between the first and second clutched members, a clutching structure provided in the cavity that acts between the first and second clutch members and positionable in an engagement position wherein the clutching member operatively connects the first clutched member to the second clutch member, and positionable in a disengagement position wherein the clutching member operatively disconnects the first clutch member from the second clutch member; and a vent structure that opens into the cavity and that permits at least partial equalization of pressure between the cavity and the ambient environment of the clutched device, while inhibiting ingress of contaminants into the cavity.

[0006] The vent structure may include a seal with an aperture that opens as a result of a higher pressure in the cavity than exists in the ambient environment and that closes when the pressure in the cavity is substantially the same as the pressure in the ambient environment. The vent structure may include a membrane that permits the flow-through of gas between the cavity and the ambient environment. The membrane may be configured to inhibit water flow into the cavity. The membrane may have a one-way permeability to water, and may be arranged to permit water to flow through the membrane out of the cavity but to inhibit the flow of water through the membrane into the cavity. The membrane may be configured to inhibit lubricant flow therethrough out of the cavity. The membrane is configured to inhibit ingress of contaminants into the cavity. The membrane may be configured to have a relatively lower permeability to the passage of oxygen therethrough into the cavity but and a relatively higher permeability to the passage of oxygen therethrough out of the cavity.

[0007] The vent structure may include an aperture that passes between the cavity and the ambient environment, wherein the aperture is sized to permit the flow therethrough of gases but to inhibit the flow therethrough of contaminants when the clutched device, particularly the second clutched member, is mounted to an engine block or installed in an accessory. A portion of the aperture may be a groove that extends along an exterior surface of the clutched device and that forms a closed channel when the clutched device is mounted to the engine block or installed in the accessory. The aperture may have an aperture wall that includes an oleophilic coating thereon to inhibit the flow of lubricant through the aperture.

[0008] The vent structure may be configured to inhibit egress of lubricant out of the cavity. The vent structure may be configured to inhibit ingress of water into the cavity. The vent structure may be configured to facilitate egress of water out of the cavity.

[0009] The first clutched member may be a pulley. The second clutched member may be a hub or shaft. The clutching structure may be a wrap spring clutch, for example a helical spring (e.g. a wrap spring). The clutched device may further comprise an isolator or isolation spring that acts between the first and second clutched members to accommodate oscillations in the speed of a drive belt relative to the hub or shaft. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] A detailed description will now be provided by way of example only with reference to the attached drawings, in which:

[0011] Figure 1 is an end view of an engine that includes a vented clutched device, which is a decoupler;

[0012] Figure 2A is a magnified sectional view of a first configuration of the vented decoupler with a vent in an end cap thereof;

[0013] Figure 2B is an exploded perspective view of the decoupler shown in Figure 1 ;

[0014] Figure 3A is a top view of a first embodiment of a mechanical oneway vent for an end cap of a decoupler in which a flexible seal is fixed on an upper surface of a backing plate of the end cap;

[0015] Figure 3B is a bottom view of the end cap depicted in Figure 3A;

[0016] Figure 3C is a sectional view through A-A of the end cap depicted in Figure 3A;

[0017] Figure 3D depicts the end cap of Figure 3C under pressure from gases and vapor in the decoupler;

[0018] Figure 3E is a perspective view of the end cap of Figure 3A under pressure from gases and vapor in the decoupler;

[0019] Figure 4A is a perspective view of a second embodiment of a mechanical one-way vent for an end cap of a decoupler in which a flexible seal is fixed on an upper surface of a backing plate of the end cap;

[0020] Figure 4B is a bottom view of the end cap depicted in Figure 4A;

[0021] Figure 4C is a sectional view through B-B of the end cap depicted in Figure 4A; [0022] Figure 4D depicts the end cap of Figure 4C under pressure from gases and vapor in the decoupler;

[0023] Figure 4E is a view of the end cap of Figure 4A under pressure from gases and vapor in the decoupler;

[0024] Figure 5A is a top view of a third embodiment of a mechanical oneway vent for an end cap of a decoupler in which a flexible seal is fixed on an upper surface of a backing plate of the end cap;

[0025] Figure 5B is a sectional view of the end cap depicted in Figure 5A;

[0026] Figure 5C depicts the end cap of Figure 5B under pressure from gases and vapor in the decoupler;

[0027] Figure 5D is a perspective view of the end cap of Figure 5A under pressure from gases and vapor in the decoupler;

[0028] Figure 6A is an exploded perspective view of a fourth embodiment of a mechanical one-way vent for an end cap of a decoupler in which a valve label is fixed on an upper surface of a backing plate of the end cap nested in an aperture in a cover seal covering the backing plate;

[0029] Figure 6B is a sectional view of the end cap depicted in Figure 6A having the valve label nested in the aperture in the cover seal;

[0030] Figure 6C depicts the end cap of Figure 6B under pressure from gases and vapor in the decoupler;

[0031] Figure 6D is a perspective view of the end cap of Figure 6A under pressure from gases and vapor in the decoupler;

[0032] Figure 7 is an exploded plan perspective view of a first embodiment of a membrane vent for an end cap of a decoupler in which a semi-permeable membrane is fixed on an upper surface of a backing plate of the end cap nested in an aperture in a cover seal covering the backing plate; [0033] Figure 8 is a side cross-sectional view of a second embodiment of a membrane vent for an end cap of a decoupler in which a snap-in vent with a semi-permeable membrane is housed in a housing inserted through an aperture in the end cap;

[0034] Figure 9 a perspective view of the decoupler shown in Figure 1 , with a passageway in a side of the hub shown in Figure 2A;

[0035] Figure 10A is a perspective view of the decoupler shown in Figure 1 , with a passageway in an end of the hub shown in Figure 2A;

[0036] Figure 10B is a perspective view of an accessory on which the decoupler shown in Figure 10A is mounted; and,

[0037] Figure 1 1 is a sectional view of a decoupler showing a protrusion on a bearing to provide a vent passageway between the bearing and a bearing race of an automobile accessory after installation of the decoupler in the accessory.

DETAILED DESCRIPTION

[0038] In this specification and in the claims, the use of the article "a", "an", or "the" in reference to an item is not intended to exclude the possibility of including a plurality of the item in some embodiments. It will be apparent to one skilled in the art in at least some instances in this specification and the attached claims that it would be possible to include a plurality of the item in at least some embodiments.

[0039] Reference is made to Figure 1 , which shows an engine 10 for a vehicle. The engine 10 includes a crankshaft 12 which drives an endless drive element, which may be, for example, a belt 14. Via the belt 14, the engine 10 drives a plurality of accessories 16 (shown in dashed outlines), such as an alternator and a compressor. Each accessory 16 includes an input drive shaft 15 with a pulley 13 thereon, which is driven by the belt 14. A decoupler 20 is provided instead of a pulley, between the belt 14 and the input shaft 15 of any one or more of the belt driven accessories 16. The decoupler 20 transfers torque between the belt 14 and the shaft 15 but automatically decouples the shaft 15 from the belt 14 when the belt 14 decelerates relative to the shaft 15. Additionally, the decoupler 20 allows the speed of the belt 14 to oscillate relative to the shaft 15. Thus, oscillations in the belt speed that are the result of oscillations in the speed of the crankshaft (an inherent property of internal combustion piston engines), are reduced by the decoupler 20, and as a result, the stresses that would otherwise be incurred by the shaft 15 and the component 16 are reduced.

[0040] Reference is made to Figure 2a, which shows a sectional view of the decoupler 20. The decoupler 20 includes a hub 22, a pulley 24, a bearing 26, an isolation spring 28, a carrier 30, a wrap spring clutch 32 and an end cap 34 (Figure 3).

[0041] The hub 22 may be adapted to mount to the shaft 15 in any suitable way. For example, the hub 22 may have a shaft-mounting aperture 36 therethrough that defines a rotational axis A for the decoupler 20. The shaft mounting aperture 36 may be configured to snugly receive the end of the shaft 15. A shaft-mounting fastener (not shown) may be inserted through a distal end 38 of the aperture 36 to fixedly mount the hub 22 to the shaft 15 so that the two co-rotate together about the axis A.

[0042] The pulley 24 is rotatably coupled to the hub 22. The pulley 24 has an outer surface 40 which is configured to engage the belt 14. The outer surface 40 is shown as having grooves 42. The belt 14 may thus be a multiple-V belt. It will be understood however, that the outer surface 40 of the pulley 24 may have any other suitable configuration and the belt 14 need not be a multiple-V belt. For example, the pulley 24 could have a single groove and the belt 14 could be a single V belt, or the pulley 24 may have a generally flat portion for engaging a flat belt 14.

[0043] The pulley 24 further includes an inner surface 43. The bearing 26 engages the inner surface 43 of the pulley 24 and rotatably supports the pulley 24 on the hub 22 at a first (proximal) axial end 44 of the pulley 24. The bearing 26 may be any suitable type of bearing, such as a sealed ball bearing.

[0044] At a second (distal) axial end 46 of the pulley 24, the inner surface 43 of the pulley 24 is slidably supported on a pulley support surface 48 of the hub 22. The bearing 26 and the pulley support surface 48 together support the pulley 24 for rotation relative to the hub 22. The sliding support provided by the pulley support surface 48 is described in more detail further below.

[0045] The isolation spring 28 is provided to accommodate oscillations in the speed of the belt 14 relative to the shaft 15. The isolation spring 28 may be a torsion spring that has a first end 49 (Figure 2b) that is held in an annular slot 50 (Figure 2) and that abuts a radial wall (not shown) in the hub 22. The isolation spring 28 may further have a second end 52 that is held in an annular slot 54 and that abuts a radial wall (not shown) in the carrier 30. In the embodiment shown, the isolation spring 28 has a plurality of coils 58 between the first and second ends 49 and 52. An example of a suitable engagement between the isolation spring 28, the hub 22 and the carrier 30 is shown and described in US Patent 7,712,592, the contents of which are hereby incorporated by reference.

[0046] In the embodiment shown, a sleeve 57 is provided between the isolation spring 28 and the wrap spring clutch 32. The sleeve 57 limits the amount of room available for radial expansion of the isolation spring 28.

[0047] The isolation spring 28 may be compressed axially slightly in the decoupler 20 such that it urges the carrier 30 axially into abutment with a thrust plate, shown at 59, which is in abutment with the bearing 26, which is press-fit between the hub 22 and the pulley 24. [0048] The helical wrap spring clutch 32 has a first end 60 (Figure 2b) that is engageable with a radial wall 62 of the carrier 30 and that may be fixedly connected to the carrier 30. The helical wrap spring clutch 32 has a second end 64 that may be free floating. The helical wrap spring clutch 32 includes a plurality of coils 66 between the first and second ends 60 and 64.

[0049] The pulley 24 and the hub 22 cooperate to define a chamber 68 in which the wrap spring clutch 32 is disposed. The end cap 34 (Figure 2b) is provided to act as a seal member to seal off the second (distal) end of the gap G. Thus, the chamber 68 is sealed by the end cap 34 at one end and by the bearing 26 at the other end. The end cap 34 may be mounted to the second end 46 of the pulley 24. Lubricant may be provided in the chamber 68 for lubricating the wrap spring clutch 32. The term 'cavity' may also be used in place of the term 'chamber' in this disclosure.

[0050] Some examples of problems that can occur with a clutched device if the cavity becomes overpressurized and/or if certain contaminants are permitted to make their way into the cavity include:

1. Allowing for the initiation of corrosion and oxidation of the steel and aluminum components;

2. Allowing for the flow and travel of contamination into damping interfaces, resulting in the increased potential for stiction and seizing of the various moving damping interfaces;

3. Allowing for the uncontrolled absorption of water by any internal plastic damping components, resulting in unpredictable swelling of the plastic components, and the negative impact on the attendant tolerances; and

Allowing for the build-up and release of internal pressures within the clutched device during repetitive engine heating and cooling cycles, resulting in unwanted expansion and movement and loading of various clutched device components.

[0051] Referring to Figure 2b, a vent structure 99 is provided for the decoupler 20 to permit venting of the cavity in the clutched device to prevent the cavity from becoming overpressurized and, in some embodiments performs one or more of: inhibiting contaminants from entering the cavity and inhibiting lubricant in the cavity (if there is any) from leaving the cavity. Put another way, in some embodiments, the vent structure 99 opens into the cavity 68 and permits at least partial equalization of pressure between the cavity 68 and the ambient environment of the clutched device (in this case, the decoupler 20), while inhibiting ingress of contaminants into the cavity 68. While the decoupler 20 shown is for use between a belt and an alternator, the vent structure 99 could be provided on a decoupler for use between an engine crankshaft and a belt. Alternatively, the vent structure 99 may be used on any other suitable clutched device (e.g. a clutched, belt-driven water pump) having a first clutch member, a second clutch member, and a clutching structure that is positionable in an engagement position to operatively engage the first clutch member to the second clutch member, and that is positionable in a disengagement position to disengage the first clutch member from the second clutched member. In the example shown in Figures 2a and 2b, the clutched device is the decoupler 20, the first clutch member is the pulley 40, the second clutch member is the carrier 30, and the clutching structure is the wrap spring clutch 32.

[0052] The term 'contaminant' is intended to be interpreted broadly, and may include particulate, such as dust and debris, liquids such as liquid water, and gases, such as oxygen in some cases. The vent structure 99 (which may simply be referred to as the 'vent') may be provided in several different forms, as described below. Vent Provided by Mechanical Seal

[0053] In some embodiments, the vent structure 99 includes a seal member with an aperture that is self-closing when the pressure in the cavity 68 and the pressure in the ambient environment outside the decoupler 20 are equal, but that opens to permit the venting of increased pressure that develops in the cavity.

[0054] An example of this is shown in Figures 3A-3E. In the embodiment shown in Figures 3A-3E, the end cap 34 includes a backing plate 136 that has an end cap aperture 150 and a flexible seal member 152 that covers an outer surface 151 of the backing plate 136 and which covers the aperture 150. The seal member 152 may be made from an elastomeric material, such as rubber. The seal member 152 is sealingly fixed to the outer surface 151 of the backing plate 136 of the end cap 34, for example, with the use of an adhesive, except in a region 153 of the backing plate 136 surrounding around the aperture 150. The seal member 152 may comprise one or more seal member vent apertures 155, which are not directly over the aperture 150 but which are over the region 153, as best seen in Figures 3C and 3D. As can be seen in Figure 3C, when the pressure in the chamber 68 is substantially equal to the ambient pressure outside the decoupler 20, the seal member 152 lies in abutment with the outer surface 151 of the backing plate 136 in the region 153 such that the vent apertures 155 abut the backing plate 136 and are therefore substantially blocked from fluid communication with the aperture 150. The vent holes 155 are therefore sealed by the backing plate 136 preventing ingress of contaminants into the decoupler 20 (as illustrated by the arrows in the figure) when the pressure inside the decoupler 20 is not great enough to cause venting. [0055] As seen in Figures 3D and 3E, when a suitable pressure within the chamber 68 (Figure 2a) behind the end cap 34 increases sufficiently, the pressure may deform the seal member 152 above the aperture 150 creating a protuberance 157 in the seal member 152 because the seal member 152 is sealingly fixed to the outer surface of the backing plate 136 except above the aperture 150 and the region 153. With the creation of the protuberance 157 under pressure, the vent holes 155 are lifted away from the backing plate 136 and gases and vapor may escape through the vent holes 155 (as illustrated by the arrows in the figure). Pressure of escaping gases and vapor prevent ingress of contaminants into the decoupler while the protuberance 157 is present (i.e. while the vent apertures 155 are lifted away from the backing plate 136).

[0056] The amount of pressure in the chamber 68 that is needed before the seal member 152 lifts away from the backing plate 136 may be controlled by the properties of the flexible seal member 152 (e.g. durometer and thickness) and the size of the region 153 of the backing plate 136 that is not adhered to the seal member 152. In other words, selection of the durometer and thickness of the seal member 152 and the size of the region 153 permits adjustment of the pressure required to create the protuberance 157, and therefore adjustment of the desired level of pressure buildup in the chamber 68 before venting occurs.

[0057] Another embodiment of a vent structure 99 is shown in Figures 4A- 4E. In this embodiment the apertures 155 are formed by slits 165 in the flexible seal member 152 of the end cap 34 that separate a valve region 163 of the seal member 152 from the remainder of the seal member 152. The flexible seal member 152 may be sealingly fixed to an outer surface of the backing plate 136 of the end cap 34, for example with the use of an adhesive, except in the rectangular valve region 163 which surrounds the aperture 150. The vent slits 165, which are not directly over the aperture 150 but are over or directly adjacent to the region 163, as best seen in Figures 4C and 4D. [0058] As seen in Figure 4C, because the vent slots 165 in the seal member 152 are located above or directly adjacent to the region 163, when the pressure is equalized between an outer environment and the chamber 68, no protuberance is formed and the flexible seal member 152 lies flat against the backing plate 136. The vent slits 165 are therefore sealed by engagement the backing plate 136 preventing ingress of contaminants into the decoupler 20 through the aperture 150 (see arrows).

[0059] As seen in Figures 4D and 4E, when pressure in the chamber 68 behind the end cap 34 increases sufficiently, the pressure may deform the flexible seal member 152 above the aperture 150 creating a protuberance 167 in the flexible seal member 152 because the seal member 152 is sealingly fixed to the outer surface of the backing plate 136 except above the aperture 150 and the region 163. With the creation of the protuberance 167 under pressure, the vent slits 165 may be opened as the seal in region 163 under or to one side of the slits 165 may lift away from the backing plate 136 and gases and vapor may escape through the vent slits 165 (see arrows). Pressure of escaping gases and vapor prevent ingress of contaminants into the decoupler while the protuberance 167 is present.

[0060] The amount of pressure in the chamber 68 that is needed before the seal member 152 lifts away from the backing plate 136 is controlled by properties of the seal member 152, such as durometer and thickness, and the size of the region 163. Tuning the durometer and thickness of the seal member 152 and the size of the region 163 permits adjustment of the pressure required to create the protuberance 167.

[0061] With reference to Figures 5A-5D, in another embodiment, the entire seal member 152 is adhered to the backing plate except directly over the aperture 150 is required as an opening in the seal member 152 is directly over the aperture 150 in the backing plate 136 of the end cap 34. The seal member 152 may comprise a vent slit 175, which is over the aperture 150, as best seen in Figures 5B and 5C. The vent slit 175 is bounded by regions 177a, 177b of the seal member 152 that are over the aperture 150 and not fixed to the surface of the backing plate 136. As seen in Figures 5C and 5D, when pressure behind the end cap 34 increases sufficiently, the pressure may deform the seal member 152 above the aperture 150 opening the vent slit 175 by deflecting edges of the regions 177a, 177b of the seal member 152 away from each other. Only the regions 177a, 177b of the seal member 152 are deformed because the remainder of the seal member 152 is sealingly fixed to the outer surface of the backing plate 136 except above the aperture 150. With the deflection of the regions 177a, 177b under pressure, the vent slit 175 opens and gases and vapor may escape through the vent slit 175. Pressure of escaping gases and vapor prevent ingress of contaminants into the decoupler while the regions 177a, 177b are deflected. As seen in Figure 5B, because the edges of the regions 177a, 177b forming the vent slit 175 in the seal member 152 abut each other when the pressure is equalized between an outer environment and the inside of the decoupler 20, the vent slit 175 is closed preventing ingress of contaminants into the decoupler 20 when the pressure inside the decoupler 20 is not great enough to cause venting. Since the pressure in the decoupler 20 should not be lower than the pressure in the outer environment, a reverse flow of gases and vapor into the decoupler 20 should not occur. The pressure in the chamber 68 at which the slit 175 opens may be controlled by the design of the seal member 152 (e.g. durometer and thickness) and the size of the aperture 150. Tuning the durometer and thickness of the seal member 152 and the size of the aperture 150 permits adjustment of the pressure required to deflect the regions 177a, 177b of the seal member 152, and therefore adjustment of the desired level of pressure relief.

[0062] With reference to Figures 6A-6D, in another embodiment of the one-way vent structure 99, a two-part valve label 260 is nested within the aperture 250 in the cover seal 252 of the end cap 34 over the aperture 150 in the backing plate 136 of the end cap 34. As seen in Figure 6B, the valve label 260 comprises a flexible sealing tab 261 , for example made of an elastomeric material, sealingly fixed to an upper surface of a rigid label base 262, for example made of a rigid plastic material, having a label aperture 265 therein. The flexible sealing tab 261 is sealingly fixed to the rigid label base 262 along a perimeter of the sealing tab 261 leaving a portion 263 of the perimeter un-fixed to the rigid label base 262. The label aperture 265 aligns with aperture 150 in the backing plate 136 when the valve label 260 is nested in the aperture 250 in the cover seal 252, as best seen in Figure 6D. The valve label 260 may be sealingly fixed on the backing plate 136 over tthe aperture 150 in any suitable fashion, for example by over-molding or an adhesive.

[0063] As seen in Figures 6C and 6D, when pressure in the chamber 68 behind the end cap 34 increases sufficiently, the pressure may deform the flexible sealing tab 261 above the aperture 150 into a protuberance 267 in the flexible sealing tab 261 because the flexible sealing tab 261 is sealingly fixed to the outer surface of the rigid label base 262 except above the aperture 150 and the portion 263 of the perimeter of the flexible sealing tab 261 not fixed to the rigid label base 262. With the formation of the protuberance under pressure, the portion 263 of the perimeter of the flexible sealing tab 261 may lift away from the rigid label base 262 providing vents 264 through which gases and vapor may escape. Pressure of escaping gases and vapor prevent ingress of contaminants into the decoupler while the protuberance 267 is present. As seen in Figure 6C, when the pressure is equalized between an outer environment and the inside of the decoupler 20, no protuberance is formed and the flexible sealing tab 261 lies flat against the rigid label base 262. The vents 264 are therefore sealed by the rigid label base 262 preventing ingress of contaminants into the decoupler 20 when the pressure inside the decoupler 20 is not great enough to cause venting. The pressure at which the flexible sealing tab 261 opens may be controlled by the design of the flexible sealing tab 261 (e.g. durometer and thickness) and the size of the portion 263 of the perimeter of the flexible sealing tab 261 left un- fixed. Tuning the durometer and thickness of the flexible sealing tab 261 and the size of the portion 263 permits adjustment of the pressure required to form the protuberance, and therefore adjustment of the desired level of pressure relief.

Vent Provided by Membrane

[0064] In some embodiments, the vent structure 99 includes a membrane, (e.g. a semi-permeable membrane) that permits flow-through of air into and out of the cavity 68 but that prevents the pass-through of contaminants and moisture into the cavity 68.

[0065] In embodiments where lubricant exists in the cavity 68, the membrane may be selected to be oleophobic. This may be provided by the membrane itself (i.e. the membrane may have inherent oleophobic properties, optionally by way of an oleophobic substance incorporated within it) and/or it may be provided with an oleophobic coating. An oleophobic membrane will inhibit any lubricant in the cavity from adhering to the membrane thereby reducing the likelihood of any lubricant passing through the membrane to the exterior of the clutched device (e.g. decoupler 20), and also inhibits clogging of the membrane. Other surfaces in the cavity 68 may be coated with an oleophilic coating that promotes the adherence of lubricant thereto, or an oleophobic coating to inhibit the adherence of lubricant thereto, so as to control where lubricant stays and doesn't stay within the cavity 68. Oleophobic membranes are commercially available and may be obtained from Nitto Denko Automotive, Inc., Donaldson Company, Inc., Pan Asian Micro-vent Tech (Changzhou) Co., Ltd. or Able Seal & Design Inc., for example.

[0066] US Patent No. 4,384,725 is hereby incorporated by reference in its entirety. The structure described in that patent includes an oleophobic coating used to assist with preventing the escape of a liquid lubricant from a bearing. Concepts in the 725 patent can be applied to the structure shown in the figures. [0067] Additionally, hydrophobic and/or hydrophilic coatings can be used on the membrane and on other surfaces in the clutched device cavity to control how easily water (both in liquid form and in vapour form) is passed through the membrane. The membrane can be configured to have One-way' permeability to something such as water, in the sense that it will permit water to pass through the membrane in one direction but not in the other. As a result, any water that migrates into the cavity 68 may be permitted to leave the cavity 68 through the membrane, but water is inhibited from entering the cavity 68 though the membrane. In some embodiments, the membrane may be permeable to water vapour but may be relatively impermeable to liquid water.

[0068] Another example is oxygen, whose presence in the cavity 68 can lead to oxidation of the surfaces in the cavity 68. The membrane may be configured to have one-way permeability to oxygen that facilitates the flow of oxygen out of the cavity but that inhibits the flow of oxygen into the cavity 68. Thus, the cavity 68 may have a relatively low concentration of oxygen therein, as compared to the ambient environment.

[0069] In an embodiment the vent structure 99 may be as shown in Figure 7 wherein the vent structure 99 includes a semi-permeable membrane 301 (e.g. made of (e.g. expanded polytetrafluoroethylene (ePTFE)) is sealingly fixed on an outer surface 151 of the backing plate 136 of the end cap 34 over the aperture 150 in the backing plate 136. The membrane 301 is nested in the aperture 250 in the cover seal 252 that covers the backing plate 136. The semi-permeable membrane permits passage of gases into and out of the decoupler 20, but blocks the passage of solids (e.g. dust) and liquids (e.g. water and lubricant. When the air pressure inside the decoupler 20 increases due to increasing temperature, gases may leave the decoupler 20 through the membrane 301. When the air pressure inside the decoupler 20 subsequently reduces as the temperature cools, gases may re-enter the decoupler 20 thereby preventing a vacuum effect. While an oleophobic membrane is commonly used, if under-hood conditions do not necessitate an oleophobic membrane, a hydrophobic membrane could be used instead, which prevents water and other high surface tension fluids from entering the decoupler 20.

[0070] In another embodiment the vent structure 99 may be as shown in Figure 8 in which a snap-in vent 310 with a semi-permeable membrane 31 1 inserted through an aperture 320 in the end cap 34. Snap-in vents of this nature are commercially available, for example from W. L. Gore & Associates, Inc of Newark, Delaware. The snap-in vent 310 comprises the membrane 31 1 housed in a vent body 312 covered by a cover 313. The vent body 312 comprises a stem 314 having an outwardly extending annular snap ring 315 for mating connection with the installation housing 320. When the vent 310 is snapped into the end cap 34, an upper surface 316 of the snap ring 315 engages a lower surface 317 of the end cap 34 to prevent the vent 310 from being withdrawn from the aperture 320. The vent 310 is further secured snugly and sealingly in the aperture 320 by an o-ring 318. While an oleophobic membrane is commonly used (e.g. ePTFE), if under-hood conditions do not necessitate an oleophobic membrane, a hydrophobic membrane could be used instead, which prevents water and other high surface tension fluids from entering the decoupler 20.

Vent Provided By Aperture

[0071] In other embodiments, a passageway that extends from the cavity 68 out to the ambient environment, optionally along a path that is circuitous may be provided. The passageway may be sized to permit gases to flow through it to equalize the pressure between the cavity 68 and the ambient environment, but the circuitous path of the aperture inhibits the entry of contaminants into the cavity 68 therethrough, and also inhibits the flow of water therethrough into the cavity 68. To assist in preventing water to flow into the cavity 68 a hydrophilic coating may be applied to the surfaces of the aperture. Because the coating holds on to water when it is contacted by water, it resists the flow of water therepast. To assist in preventing the flow of lubricant (e.g. oil, grease) out of the cavity 68, the walls of the aperture may be coated with an oleophilic coating, which holds on to oils and the like and thus resists their flow through the aperture, thereby assisting in retaining the lubricant in the cavity. The surfaces in the cavity 68 may themselves also be coated to inhibit the oil from reaching the passageway at all. For example, surfaces that are intended to have lubricant thereon may be provided with oleophilic coatings and an oleophobic coating may be used on other surfaces in the cavity 68 to inhibit oil from remaining on them.

[0072] A feature of the path that may be used may be similar to a P-trap in the plumbing industry such that some water would, under gravity, sit in a U- shaped portion of the path and would not progress through the path to the end (i.e. would not drain fully from the path).

[0073] In an embodiment, one or more apertures are provided in the bottom of the clutched device (i.e. through the hub or shaft) at the interface where the clutched device is attached to the accessory. The holes could intersect with one or more slots molded or machined into the hub or shaft at the interface between the clutched device and the accessory and/or mounting plate. The orientation and direction of the slots relative to gravity may play a role of the vent slot orientation.

[0074] To prevent water or contamination ingress to flow backwards into the clutched device, any such slots would be formed in a labyrinth (also referred to as a tortuous flow path or a circuitous flow path) (e.g. such as a path with many changes in direction or a zig zagged path) in order to mechanically impede the flow or capillary movement action of water back into the clutched device therethrough. This improves the resistance of the clutched device to water that could result from the vehicle negotiating a body of water, or alternatively, as a result of high velocity water impingement resulting from normal road spray and/or vehicle power washing and underbody spray operations. [0075] In an example, a vent structure 99 provided by a passageway (groove 140) is shown in Figure 9. To vent the decoupler 20, a groove 140 may be provided along an outside surface of the hub 22 extending longitudinally from a bearing end of the hub 22. The groove 140 is therefore between the hub 22 and an inner diameter of the bearing 26 of the decoupler 20, the groove 140 opening out beneath the bearing 26 into the environment outside the decoupler 20.

[0076] In another embodiment of a vent structure 99 provided by a passageway, reference is made to Figures 10A and 10B. To vent the decoupler 20, a groove 142 may be provided radially across an end surface of the hub 22 so that the groove 142. When the decoupler 20 is installed in the accessory 147, the end of the hub 22 abuts in sealing arrangement with a complementary surface 143 of an automobile accessory 147 (e.g. an alternator). The complementary surface 143 may be on a bearing inner race or, for example, on a spacer between the hub 22 and the bearing inner race of the accessory 147. The groove 142 provides an opening after installation to vent air for pressure equalization.

[0077] In another embodiment of a vent structure provided by a passageway reference is made to Figure 1 1. A protrusion 155 moulded onto and extending outward from the dynamic sealing area of the bearing 26 provides a space between the bearing 26 and a bearing inner race of an automobile accessory (e.g. an alternator) that permits the venting of gases when the accessory is new. Over time, when venting is perhaps no longer necessary, the protrusion 155 will wear down and the bearing 26 will no longer vent internal pressure in decoupler 20.

[0078] It will be noted that one of more of the vent structures described above may be provided in combination with each other, either in series (whereby one vent structure would connect from the cavity 68 to another vent structure, which would in turn connect to the exterior of the clutched device), or in parallel (whereby each vent structure connects independently between the cavity and the exterior of the clutched device.

[0079] While the above description constitutes a plurality of embodiments, it will be appreciated that the examples shown and described herein are susceptible to further modification and change without departing from the fair meaning of the accompanying claims.

Claims

CLAIMS:

1. A clutched device, comprising:

a first clutch member;

a second clutch member wherein a cavity is provided between the first and second clutched members;

a clutching structure provided in the cavity that acts between the first and second clutch members and positionable in an engagement position wherein the clutching member operatively connects the first clutched member to the second clutch member, and positionable in a disengagement position wherein the clutching member operatively disconnects the first clutch member from the second clutch member; and

a vent structure that opens into the cavity and that permits at least partial equalization of pressure between the cavity and the ambient environment of the clutched device, while inhibiting ingress of contaminants into the cavity.

2. A clutched device as claimed in claim 1 , wherein the vent structure includes a seal with an aperture that opens as a result of a higher pressure in the cavity than exists in the ambient environment and that closes when the pressure in the cavity is substantially the same as the pressure in the ambient environment.

3. A clutched device as claimed in claim 1 , wherein the vent structure includes a membrane that permits the flow-through of gas between the cavity and the ambient environment.

4. A clutched device as claimed in claim 3, wherein the membrane has a one-way permeability to water, and is arranged to permit water to flow through the membrane out of the cavity but to inhibit the flow of water through the membrane into the cavity.

5. A clutched device as claimed in claim 3, wherein the membrane is configured to inhibit water flow into the cavity.

6. A clutched device as claimed in claim 3, wherein the membrane is configured to inhibit lubricant flow therethrough out of the cavity.

7. A clutched device as claimed in claim 3, wherein the membrane is configured to inhibit ingress of contaminants into the cavity.

8. A clutched device as claimed in claim 3, wherein the membrane is configured to have a relatively lower permeability to the passage of oxygen therethrough into the cavity but and a relatively higher permeability to the passage of oxygen therethrough out of the cavity.

9. A clutched device as claimed in claim 1 , wherein the vent structure includes an aperture that passes between the cavity and the ambient environment, wherein the aperture is sized to permit the flow therethrough of gases but to inhibit the flow therethrough of contaminants when the second clutched member is installed in an accessory.

10. A clutched device as claimed in claim 9, wherein a portion of the aperture is a groove that extends along an exterior surface of the second clutched member and that forms a closed channel when the second clutched member is installed in an accessory.

1 1. A clutched device as claimed in claim 9, wherein the aperture has an aperture wall that includes an oleophilic coating thereon to inhibit the flow of lubricant through the aperture.

12. A clutched device as claimed in claim 1 , wherein the vent structure is configured to inhibit the egress of lubricant out of the cavity.

13. A clutched device as claimed in claim 1 , wherein the vent structure is configured to inhibit the ingress of water into the cavity.

14. A clutched device as claimed in any one of claims 1 and 13, wherein the vent structure is configured to facilitate the egress of water out of the cavity.

15. A clutched device as claimed in claim 1 , wherein the first clutched member is a pulley and the second clutched member is a hub or shaft.

16. A clutched device as claimed in claim 15, wherein the clutching structure is a wrap spring.

17. A clutched device as claimed in claim 16, further comprising an isolator spring that acts between the first and second clutched members.