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Title:
IMPROVED ISOLATION DEVICE
Document Type and Number:
WIPO Patent Application WO/2018/132925
Kind Code:
A1
Abstract:
In an aspect an isolator includes a hub connectable to a rotatable shaft, a pulley and an isolation spring. The pulley is rotatably mounted to the hub and engages a belt. Over a selected first angular range of relative movement between the pulley and the hub, torque transfer between the hub and the pulley takes place via a first torque transfer member and a second torque transfer member which are slidably movable relative to one another to generate a frictional force that limits the torque that can be transferred within the selected first angular range. Outside of this range, a first limit surface engages a second limit surface to prevent relative sliding movement between the first and second torque transfer members, such that increasing relative movement between the hub and the pulley results in increasing flexure of the spring and increased torque transferred between the hub and the pulley.

Inventors:
DELL JAMES W (CA)
Application Number:
PCT/CA2018/050074
Publication Date:
July 26, 2018
Filing Date:
January 22, 2018
Export Citation:
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Assignee:
LITENS AUTOMOTIVE INC (CA)
International Classes:
F16H7/18; B60K25/02; F02B67/06; F16D3/10; F16D3/14; F16F15/123; F16F15/129; F16H55/36
Domestic Patent References:
WO2010099605A12010-09-10
WO2008058499A22008-05-22
Attorney, Agent or Firm:
MILLMAN IP INC. (CA)
Download PDF:
Claims:
WHAT IS CLAIMED IS:

1 . An isolation device, comprising:

a hub defining an axis and connectable to a rotatable shaft;

a rotary drive member that is rotatably mounted to the hub and having an endless drive member engagement surface that is engageable with the endless drive member; and

an isolation spring, wherein, over a selected first angular range of relative movement between the rotary drive member and the hub, torque transfer between the hub and the rotary drive member takes place via a first torque transfer member and a second torque transfer member which are slidably movable relative to one another to generate a frictional force, wherein the frictional force limits the torque that can be transferred within the selected first angular range, and wherein, outside of the selected first angular range, a first limit surface on the first torque transfer member engages a second limit surface on the second torque transfer member to prevent relative sliding movement between the first and second torque transfer members, such that increasing relative angular movement between the hub and the rotary drive member results in increasing flexure of the isolation spring and increased torque transferred between the hub and the rotary drive member.

2. An isolation device as claimed in claim 1 , wherein the first torque transfer member is a spring shell that holds the isolation spring and the second torque transfer member is the rotary drive member.

3. An isolation device as claimed in claim 1 , wherein the first limit surface is an end of a channel on one of the first and second torque transfer members and the second limit surface is an edge of a lug on the other of the first and second torque transfer members.

4. An isolation device as claimed in claim 1 , further comprising a damping arrangement biasing member that urges the first and second torque transfer members into engagement with one another so as to generate the frictional force.

5. An isolation device as claimed in claim 3, wherein an angular length of the channel minus an angular length of the lug determine the first angular range.

6. An isolation device as claimed in claim 1 , wherein the isolation spring is one of a plurality of isolation springs that act in parallel.

7. An isolation device as claimed in claim 1 , wherein the isolation spring is an arcuate helical compression spring.

Description:
IMPROVED ISOLATION DEVICE CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application No. 62/449,094 filed on January 22, 2017, 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 defining an axis and connectable to a rotatable shaft, a rotary drive member and an isolation spring. The rotary drive member is rotatably mounted to the hub and has an endless drive member engagement surface that is engageable with the endless drive member. Over a selected first angular range of relative movement between the rotary drive member and the hub, torque transfer between the hub and the rotary drive member takes place via a first torque transfer member and a second torque transfer member which are slidably movable relative to one another to generate a frictional force. The frictional force limits the torque that can be transferred within the selected first angular range. Outside of the selected first angular range, a first limit surface on the first torque transfer member engages a second limit surface on the second torque transfer member to prevent relative sliding movement between the first and second torque transfer members, such that increasing relative angular movement between the hub and the rotary drive member results in increasing flexure of the isolation spring and increased torque transferred between the hub and the rotary drive member.

BRIEF DESCRIPTIONS OF THE DRAWINGS

[0006] 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:

[0007] Figure 1 is a perspective view of an engine having an isolation device, according to a non-limiting embodiment of the present disclosure;

[0008] Figure 2 is a perspective view of the isolation device shown in Figure 1 ; [0009] Figure 3 is a perspective exploded view of the isolation device shown in Figure 1 ; [0010] Figure 4 is a transparent view of a portion of the isolation device shown in Figure 1 ;

[0011] Figures 5A and 5B are magnified sectional views of a channel and lug from a spring shell and a pulley cover from the isolation device shown in Figure 1 ; [0012] Figure 6 is a sectional perspective view of the isolation device shown in Figure 1 ; and

[0013] Figure 7 is a graph illustrating torque curves for isolation devices of the prior art and an example isolation device in accordance with the present disclosure.

DETAILED DESCRIPTION

[0014] 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 15. 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 15 may include, for example, one or more of an alternator (or Motor-Generator Unit in some hybrid vehicles), a water pump, and an air conditioning compressor. Each accessory 15 includes an accessory 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.

[0015] 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. [0016] The isolation device 24 is shown in a magnified view in Figure 2, in an exploded view in Figure 3, in a transparent view with some portions removed in Figure 4, and in a magnified sectional view in Figure 5. The isolation device 24 includes a hub 26, a pulley 28, and at least one isolation spring 30 that is used to transfer torque between the hub 26 and pulley 28.

[0017] The hub 26 includes a shaft adapter 26a and a driver 26b. 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 apertures 31 that align with fastener pass-through apertures shown at 32a on the shaft adapter 26a, and at 32b on the driver 26b. A plurality of threaded fasteners 36 (Figure 3) may be used to pass through the apertures 32b and 32a and into the threaded receiving apertures 31 on the crankshaft 20 to clamp the driver 26b and the shaft adapter 26a to the crankshaft 20. The driver 26b and the shaft adaptor 26a may be made from any suitable materials such as a suitable steel. In the example shown, the driver 26b is clamped between the shaft adapter 26a, and some plate-like members shown at 90 and 92 and which are described further below.

[0018] The pulley 28 has a belt engagement surface 29 which 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 (Figures 3, 4) 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 referred to as the main pulley portion and which has the belt engagement surface 29 (e.g. a multi-grooved profile for engagement with a poly-V belt) 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 main pulley portion 28a). In the example shown in Figures 3 and 5, the main 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. The pulley 28 is but an example of a rotary drive member that transfers power to and from the endless drive member (in this example, the belt 14). It will be understood that the pulley 28 could alternatively be any other suitable rotary drive member. Analogously, the belt engagement surface 29 of the pulley 28 may be referred to as an endless drive member engagement surface 29.

[0019] 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.

[0020] The at least one isolation spring 30 transfers torque 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. The isolation springs 30a and 30b are shown in a spring shell 33 that is mounted into the pulley 28 to transfer torque to or from the pulley 28. The spring shell 33 has a plurality of channels 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 thereby transfer torque to and from the pulley 28. The lugs 39 on the spring shell 33 have an axial gap G (Figure 3) therebetween. The driver 26b has a plurality of drive arms 41 thereon that pass through the gap G and that 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.

[0021] Thus, torque is transferred from the crankshaft 20 to the belt 14 through the shaft adapter 26a, then through the driver 26b, then through the springs 30, through the spring shell 33 and then through the pulley 28. Similarly, torque is transferred from the belt 14 to the crankshaft 20 through the pulley 28, then through the spring shell 33, then through the springs 30, then through the driver 26b and then through the shaft adapter 26a.

[0022] One of the lugs 37 and one of the channels 35 are shown more clearly in Figures 4, 5A and 5B. As can be seen, the channel 35 has a first end 35a and a second end 35b. During operation of the engine 12, sometimes the transfer of torque changes direction in the sense that initially it may be transferred from hub 26 to pulley 28 and then changes to being transferred from pulley 28 to hub 26, or vice versa. In an example, illustrated in Figure 5A is a situation in which the hub 26 is being rotated clockwise and is transferring torque to the pulley 28. It can be seen, that the first end 35a of the channel 35 is abutted with the lug 37 on the pulley cover 28b and thereby transfers torque from the spring shell 33 into the pulley cover 28b via the lug 37 and channel 35 and therefore into the pulley 28. When the torque transfer changes direction, the pulley cover 28b will move clockwise in the channel 35 until the lug 37 engages the second end 35b of the channel 35, at which point torque is transferred via the lug 37 and the channel 35 from the pulley 28 into the spring shell 33, and into the driver 26b via the springs 30, as shown in Figure 5B.

[0023] During the period when the lug 37 is sliding in the channel 35, moving from one end 35a (or 35b) to the other end 35b (or 35a), a first friction surface, shown at 100 on the spring shell 33 (Figure 6) slidingly engages a second friction surface 102 on the pulley 28 (e.g. on the pulley cover 28b) and thus a frictional damping force is transferred between the spring shell 33 and the pulley 28. In the embodiment shown, a damping arrangement biasing member 104 may be provided to urge the first and second friction surfaces 100 and 102 into engagement with a selected biasing force. [0024] Once the lug 37 reaches one end or the other of the channel 35, there is no longer any relative movement between the spring shell 33 and the pulley 28, and therefore, the damping force provided by the engaged first and second friction surfaces 100 and 102 is no longer present. It will be noted further that, during the period where the pulley cover 28b and the spring shell 33 move relative to one another, the torque transferred between the pulley 28 and the hub 26 is constant, and is based on (and limited by) the frictional damping force, which is effectively the only means for transferring torque during this relative movement.

[0025] The biasing member 104 may be a disc spring and may be positioned to apply any suitable spring force on the spring shell 33. The coefficient of friction between the surfaces 100 and 102 and the biasing force applied by the biasing member 104 may be selected to provide any suitable damping force during the aforementioned relative movement. In the example shown, the spring shell 33 may be made from Nylon and the pulley cover 28b may be made from a metal such as steel or aluminum. [0026] Figure 7 is a graph illustrating the torque displacement curve for an isolation device according to the present disclosure, and also two isolation devices known in the art. As can be seen, for the isolation device represented by curve 1 10, there is substantially no torque transfer over a certain range of angular movement between the pulley and the hub of the isolation device (represented by region 1 10a). This is disadvantageous because it can lead to resonance and severe accelerations and decelerations on the components of the isolation device (and other components connected thereto such as the belt 14. Curve 1 12 represents an isolation device in which there is an initial region (shown at 1 12a) in which there is progressive flexure of secondary springs that are provided and which have a significantly lower rate than the primary isolation springs. After a certain amount of angular movement, the primary isolation springs begin to act and the effective spring rate increases (as can be seen in regions 1 12b). This arrangement performs well, but employs the aforementioned secondary springs, at added cost and complexity. Curve 114 is the curve representing an isolation device according to the present disclosure (e.g. isolation device 24). As can be seen, a selected, constant torque is applied throughout a selected angular range of movement between the hub 26 and the pulley 28, represented by region 1 14a of the graph. Outside of this region (i.e. once the lugs 37 engage the end 35a or 35b of the channel 35), the springs 30 incur increasing or decreasing compression and as a result, the torque curve increases and decreases with angular position outside of the region 1 14a (i.e. in regions 1 14b of the curve 114.

[0027] 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.

[0028] While it has been shown for the lugs 37 to be on the pulley 28 (specifically on the pulley cover 28b), and for the channels 35 to be on the spring shell 33, it is alternatively possible for the lugs 37 to be on the spring shell 33 and for the channels 35 to be on the pulley cover 28b. Thus it may be said that there is a lug (or at least one lug) on one of the spring shell 33 and the pulley 28, and a channel (or at least one channel) on the other of the spring shell 33 and the pulley 28. [0029] In an alternative embodiment, the relative movement may be between other components, such as the driver 26a and the shaft adapter 26b instead of being between the spring sleeve 33 and the pulley 28. In yet another embodiment, the relative movement may be between the pulley cover 28b and the main pulley portion 28a. The spring shell 33 and the pulley 28b are but an example of a torque transfer member and a second torque transfer member. Thus it may be said that, over a selected first angular range of relative movement between the rotary drive member (e.g. the pulley 28) and the hub 26, torque transfer between the hub 26 and the rotary drive member takes place via a first torque transfer member (e.g. the spring shell 33) and a second torque transfer member (e.g. the pulley cover 28b) which are slidably movable relative to one another to generate a frictional force, wherein the frictional force limits the torque that can be transferred within the selected first angular range (the range shown at 1 14a in Figure 7, or the range defined by the angular length of the channel 35 minus the angular length of the lug 37) and wherein, outside of the selected first angular range, a first limit surface (e.g. the end 35a or the end 35b of the channel 35) on the first torque transfer member engages a second limit surface (e.g. the edge of the lug 37) on the second torque transfer member to prevent relative sliding movement between the first and second torque transfer members, such that increasing relative angular movement between the hub 26 and the rotary drive member results in increasing flexure of the isolation spring 30 and increased torque transferred between the hub and the pulley. [0030] While it has been shown for there to be two lugs 37 and two channels 35, it is alternatively possible for there to only provide one lug 37 and one channel 35 or three or more lugs 37 and three or more channels 35.

[0031] 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.