[0001] This application claims the benefit of U.S. Provisional Application No. 62/296,731 filed on February 18, 2016, the contents of which are incorporated herein by reference in their entirety.

FIELD

[0002] This disclosure relates to isolation devices for isolating vibration between an engine, particularly a vehicular engine and components driven by the engine via an endless drive member, and more particularly for isolating vibration between the engine and the endless drive member.

BACKGROUND OF THE DISCLOSURE [0003] It is common for vehicle engines to drive a plurality of accessories using an accessory drive system that includes a belt. Isolation devices have been used for some time to inhibit torsional vibrations from the crankshaft from being transmitted or from being transmitted at full amplitude to the accessories through the belt.

[0004] In the automotive industry, there is generally significant pressure to reduce the cost of components, and to reduce their complexity. Accordingly, it would be advantageous to provide an isolation device that was less expensive than other such devices. Furthermore there is generally a continuing need for improvements in general with isolation devices. SUMMARY OF THE DISCLOSURE

[0005] In an aspect an isolation device is provided and includes a hub, a pulley, and at least one isolation spring. The hub includes a shaft adapter that mounts fixedly to a shaft of a device, and a drive plate that is adjacent the shaft adapter. The shaft adapter and the drive plate each have a fastener pass-through aperture, permitting a fastener to be inserted therethrough into a threaded aperture in an end of the shaft of the device so as to clamp the shaft adapter and the drive plate fixedly to the shaft. The drive plate has a first frictional drive surface and a second frictional drive surface, which are positioned to transfer torque frictionally between the drive plate and the shaft adapter. The first frictional drive surface is hardened and blasted with a particulate. The pulley is rotatably mounted to the hub. The at least one isolation spring is positioned to transfer torque between the hub and the pulley. Each of the at least one isolation spring is an arcuate helical compression spring.

[0006] In another aspect an isolation device is provided and includes a hub, a pulley, and at least one isolation spring. The hub includes a shaft adapter that mounts fixedly to a shaft of a device, and a drive plate that is adjacent the shaft adapter. The shaft adapter and the drive plate each have a fastener pass-through aperture, permitting a fastener to be inserted therethrough into a threaded aperture in an end of the shaft of the device so as to clamp the shaft adapter and the drive plate fixedly to the shaft. The drive plate has a first frictional drive surface and a second frictional drive surface, which are positioned to transfer torque frictionally between the drive plate and the shaft adapter. The first frictional drive surface has a surface roughness of at least about 3.2 Ra. The pulley is rotatably mounted to the hub. The at least one isolation spring is positioned to transfer torque between the hub and the pulley, wherein each of the at least one isolation spring is an arcuate helical compression spring.

[0007] In another aspect, a method is provided for forming an isolation device, comprising: a) providing a shaft adapter;

b) providing a drive plate; c) providing a pulley;

d) providing at least one isolation spring;

e) hardening the drive plate;

f) blasting the drive plate with a particulate after step e) to increase a surface roughness of the drive plate; and

g) assembling the shaft adapter, the drive plate, the pulley, and the at least one isolation spring into an isolation device such that the shaft adapter is fixedly mounted to an end of a shaft of a device and the drive plate is frictionally engaged with the shaft adapter, and such that the pulley is rotatably mounted relative to the shaft adapter and the drive plate and the at least one isolation spring is mounted to transfer rotary torque between the drive plate and the pulley.

BRIEF DESCRIPTIONS OF THE DRAWINGS

[0008] For a better understanding of the various embodiments described herein and to show more clearly how they may be carried into effect, reference will now be made, by way of example only, to the accompanying drawings in which:

[0009] Figure 1 is a side view of an engine having an isolation device, according to a non-limiting embodiment of the present disclosure;

[0010] Figure 2A is an exploded perspective view of the isolation device shown in Figure 1 ;

[0011] Figure 2B is a perspective view of the isolation device shown in Figure 1 ;

[0012] Figure 3 is a sectional perspective view of a portion of the isolation device shown in Figure 1 , with an optional torsional vibration damper included;

[0013] Figure 4 is a graph of the torque transferred between a drive plate in the isolation device and a shaft to which the drive plate is mounted, for an example of the drive plate that has a surface roughness as stamped; [0014] Figure 5 is a graph of the torque transferred between the drive plate in the isolation device and the shaft, for an example of the drive plate that has a surface roughness after sand blasting;

[0015] Figure 6 is a graph of the torque transferred between the drive plate in the isolation device and the shaft, for an example of the drive plate that has a surface roughness after shot peening, which takes place after hardening;

[0016] Figure 7 is a graph of the torque transferred between the drive plate in the isolation device and the shaft, for an example of the drive plate that has a surface roughness after shot peening, which takes place before hardening; and [0017] Figure 8 is a flow diagram illustrating a method of forming the isolation device.

DETAILED DESCRIPTION

[0018] Reference is made to Figure 1 , which shows an endless drive arrangement 10 for an engine 12. The endless drive arrangement 10 provides an endless drive member 14 that is used to transfer power between the engine 12 and one or more accessories. The endless drive member 14 may be a belt or any other suitable endless drive member. Furthermore, the endless drive member 14 may be referred to herein as a belt 14 for readability, but it will be understood that it may be any suitable endless drive member. The accessories may include, for example, one or more of an alternator (or Motor-Generator Unit in some hybrid vehicles), a water pump, an air conditioning compressor. Each accessory includes a pulley 16 mounted to an accessory shaft 18. The engine 12 has a crankshaft 20. A tensioner 22 is used to maintain tension on the belt 14. [0019] An isolation device 24 is provided in the endless drive arrangement 10 to reduce the transmission of torsional vibrations through the belt 14 to the components engaged by the belt 14. [0020] The isolation device 24 is shown in more detail in the exploded view shown in Figure 2A, the perspective view shown in Figure 2B and the sectional view in Figure 3. The isolation device 24 includes a hub 26, a pulley 28, at least one isolation spring 30 that is used to transfer torque between the hub 26 and pulley 28. [0021] The hub 26 includes a shaft adapter 26a, a drive plate 26b and an optional torsional vibration damper (TVD) 26c. The shaft adapter 26a is fixedly mountable in any suitable way to a rotating member (e.g. a device shaft, such as the engine crankshaft 20), for rotation about an isolation device axis A. Thus the hub 26 may be said to be connectable to a shaft of a device. For example, the crankshaft 20 may include threaded receiving aperture 31 that aligns with fastener pass-through apertures shown at 32a on the shaft adapter 26a, at 32b on the driver 26b and at 32c on the TVD 26c. A threaded fastener 36 (Figure 2A) may be used to pass through the apertures 32c, 32b and 32a and into the threaded receiving aperture on the crankshaft 20 to clamp the driver 26b and the shaft adapter 26a (and the optional TVD 26c) to the crankshaft 20. The drive plate 26b and the shaft adaptor 26a may be made from any suitable materials such as a suitable steel. In the example shown, the drive plate 26b is clamped between the shaft adapter 26a and the torsional vibration damper 26c.

[0022] The pulley 28 is engageable with the belt 14 (Figure 1) and is rotatably mounted to the hub 26 e.g. by means of a bearing member 38 (Figure 2A) that directly supports the pulley 28 on the shaft adapter 26a, so that the pulley 28 is rotatable relative to the hub 26. The pulley 28 may be made up of a first pulley portion 28a (which may be a main pulley portion that has the belt engagement surface 40 (e.g. a multi-grooved shape) that is configured for engagement with the belt 14), and a second pulley portion 28b (which may be a pulley cover that is press fit or otherwise fixedly connected to the first pulley portion 28a). In the example shown in Figures 2A and 2B, the first pulley portion 28a may be metallic and may be formed from a process involving several steps including machining. The second pulley portion 28b may be formed from sheet metal and thus may have its features formed using a stamping process or the like. [0023] The bearing member 38 may be any suitable type of bearing member, such as, for example, a bushing made from Nylon impregnated with PTFE (Teflon™) or the like.

[0024] The at least one isolation spring 30 transfers torque (and therefore rotary power) between the hub 26 and the pulley 28. The at least one isolation spring 30 elastically deforms to isolate the belt 14 and the crankshaft 20 from vibrations or other sudden changes in torque in one or the other of the hub 26 and the pulley 28. In the embodiment shown the at least one isolation spring 30 includes first and second isolation springs 30a and 30b, which are arcuate, helical compression springs. However, any other suitable type of springs could be used, such as, for example, arcuate closed cell foam springs. The isolation springs 30a and 30b are shown in a spring shell 33 that is fixed into the pulley 28 to transfer torque to or from the pulley 28. The spring shell 33 has a plurality of depressions 35 that engage lugs 37 on the pulley 28 to transfer torque therebetween. The ends of the springs 30a and 30b engage lugs 39 in the spring shell 33 and transfer torque to and from the pulley 28. The lugs on the spring shell 33 have an axial gap therebetween. The drive plate 26b has a plurality of drive arms 41 thereon that pass through the gap and that also engage the ends of the springs 30a and 30b so as to transfer between to or from the springs 30a and 30b. An example of such an arrangement is shown in PCT publication WO2015010187A1 , the contents of which are incorporated herein by reference.

[0025] Thus, torque is transferred from the crankshaft 20 to the belt 14 through the shaft adapter 26a, then through the drive plate 26b, then through the springs 30 and then through the pulley 28. Similarly, torque is transferred from the belt 14 to the crankshaft 20 through the pulley, then through the springs 30, then through the drive plate 26b and then through the shaft adapter 26a.

[0026] The drive plate 26b has a first frictional drive surface 50 and optionally a second frictional drive surface 52. In the embodiment shown, the first frictional drive surface 50 is engaged with the shaft adapter 26a, which is, in turn, engaged with the crankshaft 20. The second frictional drive surface 52 is engaged with the TVD 26c. [0027] In order to ensure that the single fastener 36 can be fastened such that there is sufficient frictional engagement between the drive plate 26b and the shaft adapter 26a, and optionally between the drive plate 26b and the TVD 26c (if the TVD 26c is provided), some or all of the surface of the drive plate 26b has a surface that is hardened and blasted with a particulate so as to increase the surface roughness of the drive plate 26b at least where the drive plate 26b engages the shaft adapter 26a. The particulate may be, for example, a G16 steel grit, which means that it will have the following properties: a maximum of 5% will be captured on a No. 12 screen, a maximum of 85% will be captured on a No. 16 screen and a maximum of 96% will be captured on a No. 18 screen. Other types of grit having other properties and other size distributions may alternatively be used.

[0028] The blasting of the drive plate 26b results in a roughening of the drive plate 26b and in particular a roughening of the first frictional drive surface 50 and the optionally provided second frictional drive surface 52. [0029] It is contemplated that the entire surface of the drive plate 26b is blasted with the particulate prior to assembly of the isolation device 24, however, it will be understood that it is alternatively possible for only a portion of the overall surface to be blasted such as the first frictional drive surface 50, and optionally the second frictional drive surface 52. [0030] In some embodiments it may be possible to carry out the blasting prior to hardening of the drive plate 26b. Blasting prior to hardening has been found to increase the surface roughness of the drive plate 26b by more than if the blasting was carried out after the hardening was done. However, in some instances blasting prior to hardening can cause warping of the drive plate 26b. It has been found that a sufficient amount of surface roughness was achieved when carrying out the blasting after a hardening step was carried out. Figures 4-7 illustrate the surface roughness achieved using different strategies. For example, Figure 4 shows the amount of torque that is transferred between the drive plate 26b and the crankshaft 20 based on the angular position of the drive plate 26b, using an example of the drive plate 26b that has not had any blasting - the drive plate has the surface finish of a stamped part. As can be seen, the maximum torque transferred is about 640Nm. The Ra value for the sample has been found to be about 1.4. The example shown in Figure 5 shows a maximum torque transfer of about 680Nm and has a surface roughness of about 3.2 Ra, resulting from a sand blasting step. The example shown in Figure 6 shows a maximum torque transfer of about 1100Nm and has a surface roughness of about 5.5 Ra, resulting from a shot peening step after hardening has been carried out. The example shown in Figure 7 shows a maximum torque transfer of about 1300Nm and has a surface roughness of about 9.5 Ra, resulting from a shot peening step prior to hardening. [0031] It has been found that, for the purposes of transferring torque between the crankshaft 20 and the accessories driven by the crankshaft 20 on a typical engine, a surface roughness of 5.5 Ra is sufficient.

[0032] It has been found that the blasting step surface hardens the drive plate 26b to some extent, beyond the hardening that is carried out on the drive plate 26b prior to the blasting step.

[0033] In the embodiment shown, the isolation device 24 further includes a seal member 88, a seal biasing member 90 and a dust shield 92. These cooperate to prevent leakage of lubricant (e.g. grease) out from the interior space of the pulley 28 and to inhibit dust and debris from entering into the interior space of the isolation device 24. The seal member 88 additionally acts as another thrust bushing which is urged into engagement with the pulley 28 (specifically the cover member 28b), by the seal biasing member 90, so as to urge the pulley 28 and the bushing 38 over to a datum point against a shoulder on the shaft adapter 26 at one end of the support surface 34. The dust shield 92 could instead be some other component such as the torsional vibration damper 26c.

[0034] It will be noted that the shaft adapter 26a has several features there on, such as locking apertures 96 and 98 which mate with corresponding projections (not shown, but which would be understood by a person skilled in the art) on the shaft 20 so as to fix the shaft adapter 26a rotationally to the shaft 20. As a result, the shaft adapter 26a does not itself require a surface roughening treatment in order to be able to transfer a sufficient amount of torque from the shaft 20. Alternatively the shaft adapter 26a may itself have a suitable surface roughness to be fixed rotationally to the shaft 20 by friction once clamped thereto by the fastener 36. [0035] Referring to Figure 8, a method of forming an isolation device is shown at 100. The method begins at step 102. At steps 104, 106, 108 and 110, the shaft adapter 26a, the drive plate 26b, the pulley 28 and the at least one isolation spring 30 are provided. It will be understood that these four steps may occur in any suitable order, and may occur simultaneously, sequentially or with any suitable amount of overlap with one another. At step 112, the drive plate 26b is hardened. The hardening of the drive plate 26b may be carried out by any suitable known process, such as by carburizing, nitriding, carbonitriding, nitrocarburizing, bonding, or flame hardening. At step 1 14, the drive plate 26b is blasted with particulate to increase its surface roughness. The particulate may be any suitable particulate described herein. Step 1 14 is preferably carried out after step 112, as noted above. Alternatively, step 1 14 may be carried out before step 1 12, however, any surface compression hardening that will occur as a result of the blasting step is potentially going to be eliminated during the hardening step (step 1 12). It will further be understood that steps 1 12 and 14 need not take place after all of steps 104, 106, 108 and 110. It is possible for all of the steps 104, 106, 108, 1 10, 1 12 and 1 14 to take place in various suitable orders and/or with degrees of overlap. After the above steps are carried out, the shaft adapter is assembled at step 116. In other words, step 116 includes assembling the shaft adapter 26a, the drive plate 26b, the pulley 28, and the at least one isolation spring 30 into an isolation device 24 such that the shaft adapter is fixedly mounted to an end of a shaft of a device (e.g. the crankshaft 20), and the drive plate is frictionally engaged with the shaft adapter, and such that the pulley 28 is rotatably mounted relative to the shaft adapter 26a and the drive plate 26b, the at least one isolation spring 30 is mounted to transfer torque between the drive plate 26b and the pulley 28. Optionally, the method 100 may further include providing the TVD 26c and may further include incorporating the TVD 26c in the isolation device during the assembly step (step 116). [0036] It is alternatively possible in any of the embodiments described herein that the drive plate 26b may not need to be hardened prior to or after the surface roughening step provided by the blasting with the particulate. It is possible that the hardening that arises naturally as a result of the blasting step is sufficient to provide the drive plate 26b with sufficient strength for its operation.

[0037] The isolation device shown herein has not been shown to include a one-way clutch, however in alternative embodiments, the surface roughening of the drive plate may be applied to an isolation device that does include a one-way clutch in addition to one or more isolation springs so as to provide both an isolation function and a decoupling function.

[0038] Persons skilled in the art will appreciate that there are yet more alternative implementations and modifications possible, and that the above examples are only illustrations of one or more implementations. The scope, therefore, is only to be limited by the claims appended hereto.