CA2910627A1 - Orbital accessory drive tensioner with biasing member - Google Patents

Abstract

A tensioner for maintaining tension in an endless drive member. The tensioner comprises a base, a tensioner arm, and a tensioner arm biasing member. The base is mountable to a frame of a motor/generator unit (MGU), or an alternator, or a similar device. The tensioner arm has a tensioner pulley thereon, wherein the tensioner arm is mounted for translation along an arc relative to the base. The tensioner arm biasing member is elastically compliant in compression or extension and has a first end that is engaged with the tensioner arm and a second end that is engaged with the base.

Furthermore, the tensioner pulley is positioned to engage the endless drive member on one side of the MGU, alternator or similar device.

Description

ORBITAL ACCESSORY DRIVE TENSIONER WITH BIASING MEMBER
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional Application No.
62/072,872, filed on October 30, 2014, the contents of which are incorporated herein by reference in its entirety.
FIELD

[0002] This disclosure relates to tensioners for endless drive members and, in particular, to a tensioner that operates to tension an endless drive member driven by a vehicular engine.
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. In general, a tensioner is used to maintain tension on the belt, to inhibit belt slip during transient events and to inhibit the belt from coming off the associated pulleys of the driving and driven components.

[0004] In some vehicles, the engine is the sole means of driving the belt and the associated components. Typically, one of the driven components in such a case is an alternator, which is driven by the belt to generate electricity that is used to charge the vehicle's battery.

[0005] In other vehicles, a secondary motive device is provided for driving the belt.
The secondary motive device (e.g. a motor/generator unit (MGU)) can be used for a number of purposes, such as, for example, driving one or more accessories via the belt when the engine is temporarily off while the vehicle is stopped for a short period of time (e.g. at a stoplight). Another purpose is for use as part of a belt alternator start (BAS) drive system wherein the MGU is used to start the engine through the belt.
Another purpose is to supply additional power to the engine when needed (e.g. when the vehicle is under hard acceleration).
SUMMARY OF THE DISCLOSURE

[0006] In one embodiment, there is provided a tensioner for maintaining tension in an endless drive member. The tensioner includes, but is not necessarily limited to, a base, a tensioner arm and a tensioner arm biasing member. The base is mountable to a frame of an MGU, or an alternator, or a similar device. The tensioner arm has a tensioner pulley thereon, wherein the tensioner arm is mounted for translation along an arc relative to the base. The tensioner arm biasing member is elastically compliant in compression or extension and has a first end that is engaged with the tensioner arm and a second end that is engaged with the base. The tensioner pulley is positioned to engage the endless drive member on one side of the MGU, alternator or similar device.
BRIEF DESCRIPTIONS OF THE DRAWINGS

[0007] 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:

[0008] FIG. 1 is a side view of an engine having a tensioner, according to a first set of non-limiting embodiments;

[0009] FIG. 2 is a perspective view of the tensioner depicted in FIG. 1;

[0010] FIG. 3 is a side elevation view of the tensioner depicted in FIG.
1;

[0011] FIG. 4 is an exploded view of the tensioner depicted in FIG. 1;

[0012] FIG. 5 is a sectional view of the tensioner depicted in FIG. 1;

[0013] FIG. 6 is a perspective view of a tensioner, according to a second set of non-limiting embodiments;

[0014] FIG. 7 is a top plan view of the tensioner depicted in FIG. 6;

[0015] FIG. 8 is a side elevation view the tensioner depicted in FIG. 6;

[0016] FIG. 9 is a perspective view of a tensioner, according to a third set of non-limiting embodiments;

[0017] FIG. 10 is a top plan view of the tensioner depicted in FIG. 9;

[0018] FIG. 11 is a side elevation view of the tensioner depicted in FIG. 10;

[0019] FIG. 12 is a perspective view of a tensioner, according to a fourth set of non-limiting embodiments;

[0020] FIG. 13 is a top plan view of the tensioner depicted in FIG. 12;
and

[0021] FIG. 14 is a side elevation view of the tensioner depicted in FIG. 14.
DETAILED DESCRIPTION

[0022] Described herein are tensioners that can be used with various engine accessories, such as a MGU, alternator or similar device. In some embodiments, the described tensioners are intended for use in with a non-hybrid engine (i.e., one that does not include a Belt-Alternator Start [BAS] or Belt Starter Generator [BSG]
system), and which may have a regular alternator. The described tensioners are "orbital"
tensioners in that in operation the tensioner at least partially surrounds an axis about which the tensioner arm rotates, wherein that axis may be coaxial with an axis of rotation of an input/output shaft of the associated accessory (also referred to as an accessory shaft, or an accessory drive shaft).

[0023] In some embodiments, the described tensioners can also be used with hybrid engine designs having BAS capabilities, which have engine start and stop capability. In some embodiments, the tensioner may include a second pulley that is configured to engage with a span of an endless drive member on an opposing side of the associated accessory, such as an alternator.

[0024] The described tensioners include at least a base, a tensioner arm, a tensioner arm biasing member and a tensioner pulley. The tensioner also includes hardware associated with the tensioner pulley, including fasteners, such as bolts, a dust shield for the pulley, one or more sliding disks and a rear plate. The rear plate is a biasing element that is configured to maintain engagement between the base and at least one of the sliding disks.

[0025] Reference is made to FIG. 1, which shows an example engine 100 of a vehicle (not shown). It will be noted that the engine 100 is shown as a simple shape for illustrative purposes. It will be understood that the engine 100 may have any suitable shape and may be any suitable type of engine such as a spark-ignition engine or a diesel engine. The vehicle may be any suitable vehicle, such as an automobile, a truck, a van, a minivan, a bus, an SUV, a military vehicle, a boat or any other suitable vehicle.

[0026] The engine 100 includes a crankshaft 105. The crankshaft 105 has a crankshaft pulley 110 thereon. The crankshaft pulley 110 drives one or more vehicle accessories via a belt 115. The term 'belt' is used herein for convenience, however for the purpose of the claims and for the scope of this disclosure it will be understood that the belt 115 may alternatively be any other type of suitable endless drive member. It will further be noted that, in cases where the endless drive member is a belt, it may be any suitable type of belt, such as a flat belt, a V belt, a poly-V belt, a timing belt, or any other suitable type of belt. The term 'pulley' is similarly used for convenience and any other suitable rotary drive member may be used instead, such as a sprocket.

[0027] The accessories may include, for example, an alternator 120, an air conditioning compressor 125, a water pump 130 and/or any other suitable accessories.
In some embodiments, the engine 100 further includes a plurality of idlers (not shown) that are positioned to provide a selected amount of belt wrap about the pulleys of some of the accessories.

[0028] In some embodiments, the alternator 120 is replaced with a MGU or a similar device. In some such embodiments, the engine 100 may be stopped temporarily in some situations (such as when the vehicle is stopped at a stoplight) and may then be started again via the belt 115 when it is time for the vehicle to move. To achieve this, the MGU (or some other suitable secondary motive device engaged with the belt 115) is operated as an electric motor to drive the crankshaft 105 via the belt 115, enabling the engine 100 to be started via the belt 115 (i.e., a belt-alternator start (BAS) drive system).

[0029] Each of the driven accessories has a shaft, and a pulley that may be connectable and disconnectable from the respective shaft via a clutch. For example, the alternator shaft and pulley are shown at 135 and 140 respectively. In another example, the air conditioning compressor shaft and pulley are shown at 145 and respectively. Each of the accessories may optionally be clutched to permit each to be disconnected when not needed, while the belt 115 is still being driven.

[0030] Providing tension in the belt 115 is beneficial in that it reduces the amount of slip that can occur between the belt 115 and the driven accessory pulleys, and between the belt 115 and the crankshaft 105. In FIG. 1, the direction of rotation of the crankshaft 105 is shown at DIR1. Regardless of whether the engine 100 is a hybrid or non-hybrid configuration, when the engine 100 is driving the belt 115 it will be understood that a relatively higher tension will exist on a first, or 'normally tight-side' belt span, shown at 115a, and a relatively lower tension will exist on a second, or 'normally right-side' belt span, shown at 115b. In cases where the engine 100 is a hybrid engine and the alternator is replaced with an MGU or the like, the belt span 115a will become the lower-tension side and the belt span 115b will become when the MGU is operating.
However, such events will occur less frequently than when the engine 100 is driving the belt 115 and the MGU is not operating as a motor.

[0031] An example of a tensioner 200 is shown in Figure 1. In accordance with a first set of embodiments, FIGS. 2 to 5 show an example tensioner 200 for maintaining tension in an endless drive member, such as the belt 115, and more particularly in the belt span 115b. The tensioner 200 includes a base 205, a tensioner arm 210 having a tensioner pulley 215 and a tensioner arm biasing member 220.

[0032] The base 205 is mountable to a frame 225 (FIG. 1) of the alternator 120. In some embodiments, the base 205 is mountable to a frame of a MGU or similar device.
In the example shown, the base 205 includes a plurality of fasteners 230 (FIG.
1) which are received in a plurality of fastener apertures 232 (FIG. 2) for mounting the base 205 to the frame 225 (also referred to herein as the housing 225 of the alternator 120).

[0033] The tensioner arm 210 is mounted for translation along an arc 235 (FIG. 2) relative to the base 205. In some embodiments, the arc 235 is generally concave in a direction towards the alternator pulley 140. For example, the tensioner arm 210 can be rotatably mounted to the base 205 in a surrounding relationship with the alternator shaft 135 of the alternator 120 and, in use, rotates about a tensioner arm axis A
(FIGS. 1 and 4) along the arc 235. As shown in FIG. 1, the tensioner arm axis A may be coaxial with the axis of rotation of the alternator shaft 135, which is shown at B. The tensioner arm 210 may also be made from aluminum or any other suitable material.

[0034] Referring to FIG. 4, which shows an exploded view of the tensioner 200, and FIG. 5, which shows a sectional view of the tensioner 200, the tensioner 200 includes a first sliding disk 240a and a second sliding disk 240b. In some embodiments, the first sliding disk 240a and the second sliding disk 240b can be configured to apply a desired amount of friction to the tensioner arm 210 to provide a desired amount of damping to the movement of the tensioner arm 210 on the base 205. When used to intentionally apply a selected amount of damping to the movement of the tensioner arm 210, the first sliding disk 240a and the second sliding disk 240b may be referred to as a first damping disk 240a and a second damping disk 240b. In some embodiments, the first sliding disk 240a and the second sliding disk 240b are bushings. Suitable material of construction of the first sliding disk 240a and the sliding disk 240b may be, for example, polyamide 4.6 or 6.6 or some other suitable polymeric material.

[0035] In the example tensioner 200, a rear plate 245 is provided and connected to the tensioner arm 210 such that the rear plate 245 cooperates with the tensioner arm 210 to clamp the base 205, the first sliding disk 240a and the second sliding disk 240b together while still permitting sliding movement of the tensioner arm 210 relative to the base 205. With this arrangement, the second sliding disk 240b is positioned between the rear plate 245 and a first face 250 (FIG. 5) of the base 205, and the first sliding disk 240a is positioned between the tensioner arm 210 and the a second face 255 (FIG. 5) of the base 205. During movement of the tensioner arm 210 when the tensioner 200 is in use, the sliding occurs by the rear plate 245 on the first sliding disk 240a and/or by the first sliding disk 240a on the base 205, and sliding also occurs by the tensioner arm 210 on the second sliding disk 240b and/or by the second sliding disk 240b on the base 205. As a result of the aforementioned sliding movement, the first sliding disk 240a and the second sliding disk 240b apply a frictional force (i.e., a damping force) to the tensioner arm 210.

[0036] In the example tensioner 200, the first sliding disk 240a and the second sliding disk 240b are complete circles, covering the entire circumference of the tensioner arm 210 and the base 205. However, in some embodiments, one or more of the first sliding disk 240a and the second sliding disk 204b covers less than the entire circumference of the tensioner arm 210 and the base 205 (and in some example embodiments shown, less than 180 degrees of arc). The second sliding disk 240b is positioned in a first region of the tensioner 200 that is outside of a second region that lies under the belt 115 (FIG. 1). In the first region there is less of a height constraint on the tensioner components, whereas in the second region there can be significant height constraint. The part of the circumference of the tensioner arm 210 and base 205 where the second sliding disk 240b is not routed is in the second region of the tensioner 200, so as help keep the height of the tensioner 200 sufficiently low to avoid interference with the belt 115.

[0037] The rear plate 245 includes clip portions 260 (FIGS. 4 and 5) that clip onto receiving members on the tensioner arm 210. For example, the flange portion (FIG. 4) of the rear plate 245 may be relatively thin in cross-section so as to render it resilient, and may be shaped to apply a spring force on the second sliding disk 240b.
This arrangement can be configured so that a consistent force is applied to the second sliding disk 240b by the rear plate 245 reducing the need for assembly worker expertise.

[0038] It will be further noted that the first sliding disk 240a and the second sliding disk 240b also provide damping that is substantially independent of the hub load incurred by the tensioner pulley 215. Additionally, it will be noted that the use of two sliding disks, the first sliding disk 240a and the second sliding disk 240b, both of which are at relatively large diameters (i.e., large moment arms) from the tensioner arm axis A, reduces the average amount of force that each of the first sliding disk 240a and the second sliding disk 240b must apply to achieve a selected damping load.

[0039] The first sliding disk 240a and the second sliding disk 240b may have surface properties that provide symmetric damping in the sense that the damping force exerted by the first sliding disk 240a and the second sliding disk 240b may the same irrespective of the direction of movement of the tensioner arm 210.
Alternatively, however, the first sliding disk 240a and the second sliding disk 240b may be provided with surface properties (e.g., a 'fish-scale' effect) that provides lower damping in one direction and higher damping in the opposite direction. Other means for achieving asymmetrical damping are alternatively possible, such as the use of a ramp structure whereby the tensioner arm 210 rides up the ramp structure urging it into progressively stronger engagement with a damping member (so as to increase the damping force) during rotation in a first direction and wherein the tensioner arm 210 rides down the ramp structure urging it into weaker engagement with the damping member thereby reducing the damping force during movement in the second direction.

[0040] In other embodiments, the first sliding disk 240a and the second sliding disk 240b may be configured to provide relatively little frictional resistance thereby increasing the responsiveness of the tensioner 200.

[0041]
Optionally, the rear plate 245 may be threadably connected to the tensioner arm 210 (e.g., via engagement of threaded fasteners with threaded apertures in the tensioner arm 210) so as to permit adjustment of a gap between the rear plate 245 and the tensioner arm 210, and adjustment of the clamping force therebetween.
This permits adjustment of a damping force exerted on the tensioner arm 210 via the first sliding disk 240a and the second sliding disk 240b. In some embodiments, the first sliding disk 240a and the second sliding disk 240b are replaced by a single sliding member or bushing that is C-shaped and acts between the rear plate 245, the tensioner arm 210 and the base 205.

[0042] It will be noted that the first sliding disk 240a and the second sliding disk 240b have radially extending portions, shown at 270a and 270b respectively (FIG. 4), which are the portions of the first sliding disk 240a and the second sliding disk 240b that act on the first face 250 and the second face 255 of the base 205.
Additionally however, the first sliding disk 240a and the second sliding disk 240b further include axially extending portions 275a and 275b (FIG. 5) that act between the radially outer face 280 of the tensioner arm 210 and the radially inner ring-receiving wall 285 of the base 205.

[0043]
The tensioner arm 210 has the tensioner pulley 215 rotatably mounted thereon, for rotation about a tensioner pulley axis P (FIGS. 4 and 5), which is spaced from the tensioner arm axis A. Referring to FIG. 1, the tensioner arm 210 is biased in a free arm direction towards the leading belt span 115d of the belt 115 on one side of the alternator pulley 140. The tensioner arm 210 may be biased in the free arm direction by the tensioner arm biasing member 220.

[0044]
The tensioner arm biasing member 220 may be any suitable kind of biasing member and is elastically compliant in compression, extension, torsion, or in any other flexure mode (i.e., the tensioner arm biasing member 220 will return to an original state, such an original length, after being stretched, compressed, torqued or otherwise flexed under an applied load). The tensioner arm biasing member 220 has a first end 292 that is engaged with the tensioner arm 210 and a second end 302 that is engaged with the base 205 (FIG. 2).

[0045] For example, as shown in FIGS. 1 to 5, the tensioner arm biasing member 210 can include a helical compression spring 290 and a strut 310 that is engaged between the tensioner arm 210 and the base 205. The strut 310 is coupled to the base 205 at a first strut end 315a and is coupled to the tensioner arm 210 at a second strut end 315b. The first strut end 315a can be coupled to the base 205 via a first strut fastener 320a engaged with a first strut lug 325a and the second strut end 315b is coupled to the tensioner arm 210 via a second strut fastener 320b that is engaged with a second strut lug 325b of the strut 310 (FIG. 3). The strut 310 is axially surrounded by the helical compression spring 290. The strut 310 includes a piston 330 and a shaft 335 that is configured to slidably engage the piston 330. The strut 310 is configured to provide a selected resistance to the movement of the tensioner arm 210 relative to the base 205. The strut 310 can be a hydraulic strut that uses any suitable hydraulic fluid, including a suitable gas, to provide the selected resistance to the movement of the tensioner arm 210 along the arc 235. In some embodiments, the selected resistance is such that the strut 310 simply guides the helical compression spring 290. In some embodiments, the selected resistance is such that the strut 310 provides a selected amount of damping to the movement of the tensioner arm 210 along the arc 235.
It is understood that a person skilled in the art would be able to determine the selected resistance through routine experimentation. In some embodiments, the strut 310 is replaced with a suitable gas spring.

[0046] The helical compression spring 290 includes a first spring end 295 and a second spring end 305. The first spring end 295 is engaged with the first strut end 315a and the second spring end 305 is coupled to the second strut end 315b. In particular, the first spring end 295 engages a first drive surface 300a on the first strut end 315a and the second spring end 305 engages a second drive surface 300b on the second strut end 315b. Although the tensioner arm biasing member 220 is depicted as a helical compression spring, in some embodiments, the tensioner arm biasing member 220 is a helical extension spring.

[0047] In the example tensioner 200, the tensioner arm biasing member 220 has a common axis with the arc 235 (FIG. 2). Furthermore, in some embodiments, the tensioner arm biasing member 220 generally extends along a linear path. For example, the tensioner arm biasing member 220 can be oriented such that the helical compression spring 290, with the strut 310, extends and contracts along a biasing axis C that is generally arcuate about a common axis with the arc 235 (FIGS. 2 and 4). In some embodiments, the tensioner arm biasing member 220 can extend along a path that is not necessarily arcuate or that is arcuate but not about a common axis with the arc 235.

[0048] The tensioner pulley 215 is positioned to engage the belt 115 on one side of the alternator 120. In the example tensioner 200, the tensioner pulley 215 is positioned to engage the belt span 115d. However, in some embodiments, the tensioner pulley 215 is positioned to engage the belt span 115c and the crankshaft pulley 110 rotates in a direction opposite that of DIR1 shown in FIG. 1.

[0049] During operation, when the tensioner pulley 215 is engaged with the leading belt span 115d, the belt span 115d applies a hub load to the tensioner pulley 215. This hub load acts on the tensioner arm 210 through the tensioner pulley 215. The force on the tensioner arm 210 is transferred through the tensioner arm biasing member 220, and into the base 205 itself. The tensioner arm biasing member 220 resists the pivoting of the tensioner arm 210 and urges the tensioner arm biasing member 220 to pivot about the tensioner arm axis A in the opposite rotational direction to the direction of the pivoting of the tensioner arm 210 to press the tensioner pulley 215 into the belt 115 and to maintain tension in the belt 115.

[0050] The tensioner pulley 215 may include a pulley body 340, a bearing 345 and a pulley mounting fastener 350 that is used to mount (e.g., by threaded engagement) the tensioner pulley 215 to the tensioner arm 210 (FIGS.4 and 5). An optional dust shield 355 is provided to protect the bearing 345 from dust during operation of the tensioner 200. The dust shield 355 may be a separate component that sandwiches the bearing 345 to inhibit the migration of dust and debris into the bearing 345. In some embodiments, the dust shield 355 is provided as an integral portion of the tensioner arm 210.

[0051] The bearing 345 may be a ball bearing, as shown, or it may be any other suitable type of bearing. The bearing 345 could also be a bushing in some embodiments.

[0052] FIGS. 6 to 8 depict a second example tensioner, tensioner 400.
The tensioner 400 differs from the tensioner 200 in that the tensioner arm biasing member 405 does not include a strut. Instead, the tensioner arm biasing member 405 includes a helical compression spring 410 having a first spring end 415 that is engaged with the tensioner arm 210 and a second spring end 420 that is engaged with the base 205. For example, the first spring end 415 can engage a first drive surface 425a on the tensioner arm 210 and the second spring end 420 can engage a second drive surface 425b on the base 205 (FIG. 8).

[0053] As in the tensioner arm biasing member 220, the tensioner arm biasing member 405 may be any suitable kind of biasing member and is elastically compliant in compression or extension (i.e., the tensioner arm biasing member 405 will return to an original state, such an original length, after being stretched or compressed under an applied load). For example, instead of a helical compression spring, the tensioner arm biasing member 405 can include a helical extension spring. Furthermore, the stiffness of the spring included in the biasing member 405 may be varied to require a selected amount of force to extend or compress the spring, thereby providing at least some control over the translation of the tensioner arm 210 along the arc 235 relative to the base 205. In some embodiments, the spring is configured to provide a selected amount of damping.

[0054] Similarly to the tensioner arm 210, the tensioner arm biasing member 405 is positioned has a common axis with the arc 235 (FIG. 7). For example, the tensioner arm biasing member 405 can be oriented such that the helical compression spring 410, extends and contracts along a biasing axis D that optionally has a common axis with the arc 235 (FIG. 7). Furthermore, in some embodiments, the tensioner arm biasing member 405 can extend along a generally linear path that is tangential to the arc 235.

In some embodiments, the tensioner arm biasing member 405 can extend along a generally linear path that is not necessarily tangential to the arc 235.

[0055] FIGS. 9 to 11 depict a third example tensioner, tensioner 500.
The tensioner 500 includes a tensioner arm 515 and a base 520. The tensioner arm 515 and the tensioner arm 210 are similarly configured except that the tensioner arm 515 includes two drive surfaces, a first tensioner arm drive surface 525a and a second tensioner arm drive surface 525b, for engagement with a first tensioner arm biasing member 505 and a second tensioner arm biasing member 510, respectively. The base 520 is similarly configured to the base 205 except that the base 520 includes two drives surfaces, a first base drive surface 530a and a second base drive surface 530b, for engagement with the first tensioner arm biasing member 505 and the second tensioner arm biasing member 510, respectively.

[0056] Each of the first tensioner arm biasing member 505 and the second tensioner arm biasing member 510 is elastically compliant in compression or extension (i.e., the first tensioner arm biasing member 505 will return to an original state, such an original length, after being stretched or compressed under an applied load). The first tensioner arm biasing member 505 and the second tensioner arm biasing member 510 can be any suitable type of biasing member. In some embodiments, the first tensioner arm biasing member 505 and the second tensioner arm biasing member 510 generally extend along arcuate paths 555 and 560 (FIG. 10).

[0057] The first tensioner arm biasing member 505 and the second tensioner arm biasing member 510 operate in parallel with each other between the tensioner arm 515 and the base 520. Having two tensioner arm biasing members operating in parallel can provide a more compact tensioner package. For example, in the example tensioner 500, the first tensioner arm biasing member 505 and the second tensioner arm biasing member 510 each include an arcuate, helical compression spring, a first arcuate helical compression spring 535 and a second arcuate helical compression spring 540.
The first arcuate helical compression spring 535 includes a first spring end 545a that is engaged with the first tensioner arm drive surface 525a and a second spring end 545b that is engaged with the first base drive surface 530a. The second arcuate helical compression spring 540 includes a first spring end 550a that is engaged with the second tensioner arm drive surface 525b and a second spring end 550b that is engaged with the second base drive surface 530b. By using two tensioner arm biasing members that operate in parallel, springs having smaller diameters may be used to achieve the same effective spring rate as a single spring with a larger diameter.

[0058] In some embodiments, the first arcuate helical compression spring 535 and the second arcuate helical compression spring 540 have the same spring rate.
In some embodiments, the first arcuate helical compression spring 535 and the second arcuate helical compression spring 540 have different spring rates. In some embodiments, the first arcuate helical compression spring 535 and the second arcuate helical compression spring 540 operate in series between the tensioner arm 515 and the base 520.

[0059] In some embodiments, the tensioner 500 includes more than two tensioner arm biasing members.

[0060] In some embodiments, the first tensioner arm biasing member 505 and the second tensioner arm biasing member 510 include arcuate helical extension springs rather than arcuate helical compression springs. In some embodiments, the first tensioner arm biasing member 505 and the second tensioner arm biasing member include a combination of arcuate helical compression and arcuate helical extension springs.

[0061] The stiffness of the springs included in the first tensioner arm biasing member 505 and the second tensioner arm biasing member 510 may be varied (e.g., by changing the diameter of the springs) to require a selected amount of force to extend or compress the springs, thereby providing at least some control over the translation of the tensioner arm 515 relative to the base 520. In some embodiments, the springs are configured to provide a selected amount of damping.

[0062] FIGS. 12 to 14 depict a fourth example tensioner, tensioner 600.
The tensioner 600 includes a base 605 and a tensioner arm 610. The base 605 and the tensioner arm 610 are configured similarly to the base 205 and the tensioner arm 210.
The tensioner 600 includes a tensioner arm biasing member 615 that is elastically compliant in compression or extension (i.e., the tensioner arm biasing member 615 will return to an original state, such an original length, after being stretched or compressed under an applied load). The tensioner arm biasing member 615 may be any suitable biasing member. In some embodiments, as shown in FIG. 13, the tensioner arm biasing member 610 generally extends along an arcuate path 635.

[0063] The tensioner arm biasing member 615 includes a first end that is engaged with the tensioner arm 610 and a second end that is engaged with the base 605.
For example, as shown in FIGS. 12 to 14, the tensioner arm biasing member 615 includes a single arcuate helical compression spring 620 having a first spring end 625a that is engaged with a tensioner arm drive surface 630a and a second spring end 625b that is engaged with a base drive surface 630b. Although the tensioner arm biasing member 615 is depicted as an arcuate helical compression spring, in some embodiments, the tensioner arm biasing member 615 is an arcuate helical extension spring.

[0064] The stiffness of the spring included in the tensioner arm biasing member 615, such as the arcuate helical compression spring 620, may be varied to require a selected amount of force to extend or compress the arcuate helical compression spring 620, thereby providing at least some control over the translation of the tensioner arm 610 relative to the base 605. In some embodiments, the spring is configured to provide a selected amount of damping.

[0065] 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.

TABLE OF ELEMENTS:
Reference # Item Figure #
100 Engine 1 105 Crankshaft 1 110 Crankshaft Pulley 1 115 Belt (Endless Drive Member) 1 115a Trailing Belt Span (Relative to 1 Crankshaft Pulley) 115b Leading Belt Span (Relative to 1 Crankshaft Pulley) 115c Trailing Belt Span (Relative to Alternator) 115d Leading Belt Span (Relative to Alternator) 120 Alternator 1 125 Water Pump 1 130 Air Conditioning Compressor 1 135 Alternator Shaft 1 140 Alternator Pulley 1 145 Air Conditioning Compressor Shaft 1 150 Air Conditioning Compressor Pulley 1 200 (First Example) Tensioner 2 to 5 205 Base 2 to 5 210 Tensioner Arm 2 to 5 215 Tensioner Pulley 2 to 5 220 Tensioner Arm Biasing Member 2 to 4 225 Frame/Housing of the Alternator 1 230 Fasteners (for Mounting the Base to the 1 Frame of the Alternator) 235 Arc (along which the Tensioner Arm 210 2 translates) A Tensioner Arm Axis 1,4 Axis of Rotation of Alternator Shaft 1 240a First Sliding Disk 4 240b Second Sliding Disk 4 245 Rear Plate 4, 5 250 First Face (of the Base) 5 255 Second Face (of the Base) 5 260 Clip Portions (of the Rear Plate) 5 265 Flange Portion (of the Rear Plate) 4 270a Radially Extending Portion (of First 4 Sliding Disk) 270b Radially Extending Portion (of Second 4 Sliding Disk) 275a Axially Extending Portion (of the First 5 Sliding Disk) 275b Axially Extending Portion (of the Second 5 Sliding Disk) 280 Radially Outer Face of the Tensioner 5 Arm 285 Radially Inner Ring-Receiving Wall 5 290 Helical Compression Spring 2, 4 292 First End (of the Biasing Member) 2 295 First Spring End (of the Helical 2, 3 Compression Spring 290) 300a First Drive Surface (on the First Strut 3 End) 300b Second Drive Surface (on the Second 4 Strut End) 302 Second End (of the Biasing Member) 2 305 Second Spring End (of the Helical 2 Compression Spring 290) 310 Strut 3 315a First Strut End 3 315b Second Strut End 3 320a First Strut Fastener 3 320b Second Strut Fastener 3 325a First Strut Lug 3 325b Second Strut Lug 3 330 Piston 3 335 Shaft 3 Biasing Axis 2, 4 340 Pulley Body 4, 5 345 Bearing 5 350 Pulley Mounting Fastener 4, 5 355 Dust Shield 4, 5 400 (Second Example) Tensioner 6 405 Tensioner Arm Biasing Member 6 410 Helical Compression Spring 6 415 First Spring End (of Helical 6 to 8 Compression Spring 410) 420 Second Spring End (of Helical 6 to 8 Compression Spring 410) 425a First Drive Surface (on the Tensioner 8 Arm 410) 425b Second Drive Surface (on the Base 205) 8 Biasing Axis 7 500 (Third Example) Tensioner 9 505 First Tensioner Arm Biasing Member 9 510 Second Tensioner Arm Biasing Member 9 515 Tensioner Arm 9 520 Tensioner Arm Base 9 525a First Tensioner Arm Drive Surface 9 525b Second Tensioner Arm Drive Surface 9 530a First Base Drive Surface 9 530b Second Base Drive Surface 9 535 First Arcuate Helical Compression 9 Spring 540 Second Arcuate Helical Compression 9 Spring 545a First Spring End (of the First Arcuate 11 Helical Compression Spring) 545b Second Spring End (of the First Arcuate 11 Helical Compression Spring) 550a First Spring End (of the Second Arcuate 11 Helical Compression Spring) 550b Second Spring End (of the Second 11 Arcuate Helical Compression Spring) 555 Arcuate Path 10 560 Arcuate Path 10 600 (Fourth Example) Tensioner 12 605 Base 12 610 Tensioner Arm 12 615 Tensioner Arm Biasing Member 12 620 Arcuate Helical Compression Spring 12 625a First Spring End (of the Arcuate Helical 14 Compression Spring) 625b Second Spring End (of the Arcuate 14 Helical Compression Spring) 630a Tensioner Arm Drive Surface 14 630b Base Drive Surface 14 635 Arcuate Path 13

Claims (7)

WHAT IS CLAIMED IS:

1. A tensioner for maintaining tension in an endless drive member, comprising:
a base that is mountable to a frame of an accessory, (such as a motor-generator unit, an alternator, or any other accessory that has an accessory pulley that is engaged with the endless drive member);
a tensioner arm having a tensioner pulley thereon, wherein the tensioner arm is mounted for translation along an arc relative to the base;
wherein the tensioner pulley is positioned to engage the endless drive member on one side of the accessory during use; and a tensioner arm biasing member that is elastically compliant having a first end that is engaged with the tensioner arm and a second end that is engaged with the base to bias the tensioner pulley towards the endless drive member.

2. A tensioner as claimed in claim 1, wherein the arc is generally concave in a direction towards the accessory pulley.

3. A tensioner as claimed in claim 1, wherein the tensioner arm biasing member is generally tangential to the arc.

4. A tensioner as claimed in claim 1, wherein the tensioner arm biasing member generally extends along an arcuate path.

5. A tensioner as claimed in claim 1, wherein the tensioner arm biasing member generally extends along a linear path.

6. A tensioner as claimed in claim 1, wherein the tensioner arm biasing member is a first tensioner arm biasing member and wherein the tensioner further comprises a second tensioner arm biasing member that operates in parallel with the first tensioner arm biasing member between the tensioner arm and the base.

7. A tensioner as claimed in claim 1, further comprising a strut engaged between the tensioner arm and the base, wherein the strut has a selected resistance to movement.