Isolation device having two or more springs connected in series

Abstract

In one aspect, an isolation device is provided, the isolation device comprising a hub, a pulley, and at least one isolation spring device, the at least one isolation spring device comprising a first spring and a second spring in series. The first spring stiffness is greater than the second spring stiffness. Starting during torque transfer from the first of the hub and the pulley to the second, the entire first isolation spring slides along the friction surface toward the second of the hub and the pulley during compression of the second isolation spring, thereby generating a first friction damping torque. During another manner of torque transfer, at least a portion of the first isolation spring remains stationary relative to the friction surface, so that the first friction damping torque is greater than the second friction damping torque.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of U.S. Provisional Application No. 62 / 844,904, filed May 8, 2019, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present description relates generally to isolation devices for use on accessory drives of engines, and in particular to isolation devices for use on accessory drives of hybrid engines in conjunction with a motor generator unit (MGU) or the like. Background Art

[0004] For engines, and particularly vehicle engines, isolators are often provided on accessory drives to reduce the natural frequency of external torque loads driven by the engine's crankshaft to below the peak input torque frequency within a selected range of engine operating conditions. In some isolators, in addition to providing one or more springs, friction damping is provided which damps the isolator from going into resonance. Damping can be effective for this purpose, however, it is important not to provide too much damping as this can adversely affect the performance of the isolator as its primary function of reducing the natural frequency of the external torque load.

[0005] However, in certain circumstances it would be advantageous for the isolator to have a greater amount of damping. It would therefore be advantageous to provide an isolator that has an increased amount of damping in certain circumstances, but not necessarily all the time.

[0006] Separately, it is often desirable for an isolator to have as much travel as possible in certain situations, and to have a reduced amount of travel or at least not require a large amount of travel in other situations. Summary of the invention

[0007] In one aspect, an isolation device is provided, the isolation device comprising a hub, a pulley and at least one isolation spring device. The hub can be mounted to a shaft. The pulley is rotatably mounted to the hub. The at least one isolation spring device comprises a first isolation spring and a second isolation spring. Each of the first isolation spring and the second isolation spring is a helical compression spring having a length. The first isolation spring has a first spring stiffness. The second isolation spring has a second spring stiffness and is positioned in series with the first isolation spring. The first spring stiffness is greater than the second spring stiffness. The first isolation spring and the second isolation spring are arranged such that: the first isolation spring transfers torque from the second isolation spring to the first one of the hub and the pulley, and the second isolation spring transfers torque from the first isolation spring to the second one of the hub and the pulley. Starting during the torque transfer from the first one of the hub and the pulley to the second one of the hub and the pulley, the entire first isolation spring slides along the friction surface through the first one of the hub and the pulley toward the second one of the hub and the pulley during the compression of the second isolation spring, thereby generating a first friction damping torque. Starting during torque transfer from the second of the hub and the pulley to the first of the hub and the pulley, during compression of the first isolation spring by the second of the hub and the pulley, at least a portion of the first isolation spring remains stationary relative to the friction surface and the entire second isolation spring slides along the friction surface, thereby generating a second friction damping torque. The first spring rate and the second spring rate and the length of the first isolation spring and the length of the second isolation spring are selected so that the first friction damping torque is greater than the second friction damping torque.

[0008] In another aspect, an isolation device is provided, the isolation device comprising a hub, a pulley and at least one isolation spring device. The hub can be mounted to a shaft. The pulley is rotatably mounted to the hub. The at least one isolation spring device comprises a first isolation spring and a second isolation spring. Each of the first isolation spring and the second isolation spring is a helical compression spring having a first end, a second end and a plurality of coils located between the first end and the second end. The first end of the first isolation spring and the first end of the second isolation spring face away from each other, and the second end of the first isolation spring and the second end of the second isolation spring face each other. The first isolation spring and the second isolation spring each have a diameter and extend along an arc path inside the pulley around the axis of the isolation device. The first isolation spring has a first spring stiffness, and wherein the second isolation spring has a second spring stiffness and is positioned in series with the first isolation spring, wherein the first spring stiffness is greater than the second spring stiffness. The first isolation spring and the second isolation spring are arranged such that: the first isolation spring transfers torque from the second isolation spring to the first of the hub and the pulley, and the second isolation spring transfers torque from the first isolation spring to the second of the hub and the pulley. A first spring drive surface on the first of the hub and the pulley engages with the first end of the first isolation spring, and a second spring drive surface on the second of the hub and the pulley engages with the first end of the second isolation spring. The second spring drive surface extends over a first portion of the diameter of the second isolation spring such that there is a space adjacent to the second spring drive surface toward the axis of the isolation device. The space extends over a second portion of the diameter of the second isolation spring from a side edge of the second spring drive surface to a radially inner edge of the second isolation spring relative to the axis of the isolation device. During torque transfer from the first of the hub and the pulley to the second of the hub and the pulley, at least one isolation spring device allows relative movement between the hub and the pulley within a first angular motion range, and wherein during torque transfer from the second of the hub and the pulley to the first of the hub and the pulley, at least one isolation spring device allows relative movement between the hub and the pulley within a second angular motion range. The second spring stiffness and the size of the space are selected so that: at a selected torque transmission level during torque transmission between the hub and the pulley through the first isolation spring and the second isolation spring, the selected torque transmission level drives the coils of the second isolation spring to contact each other on the radial inner side of the second isolation spring relative to the axis of the isolation device, which in turn drives at least one of the coils at the free end of the second isolation spring to tilt into the space, which in turn allows the first angular motion range to exceed the second angular motion range. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] For a better understanding of the embodiments described herein and to more clearly show how these embodiments may be implemented, reference will now be made, by way of example only, to the accompanying drawings, in which:

[0010] Figure 1 is a front view of an engine having an isolation device according to an embodiment of the present disclosure.

[0011] Figure 2 yes Figure 1 A perspective view of the isolation device shown in FIG.

[0012] Figure 3 yes Figure 2 An exploded perspective view of the isolation device shown in FIG.

[0013] FIG. 4 is an isolation spring arrangement of an isolation device from the prior art.

[0014] Figure 5 Is from Figure 2 The isolation spring device of the isolation device shown in FIG.

[0015] Figure 6 yes Figure 1 A perspective view of a portion of an isolation device shown in , illustrating the torque transmission from a hub of the isolation device to a pulley of the isolation device.

[0016] Figure 7 yes Figure 1 A perspective view of a portion of an isolation device shown in , illustrating the torque transmission from a pulley of the isolation device to a hub of the isolation device.

[0017] Figure 8 It's a picture. Figure 1 FIG. 5 is a graph showing the torque output by the isolation device shown in FIG. 5 on a test machine simulating an engine.

[0018] Fig. 9 is a graph illustrating torque output from a prior art isolation device.

[0019] Fig. 10A yes Figure 6 0026] A plan view of a portion of an isolation device shown in 0026 showing a first range of motion that may be achieved during torque transfer from a hub to a pulley.

[0020] Fig. 10B yes Figure 7 A plan view of a portion of an isolation device shown in , illustrating a second range of motion that may be achieved during torque transfer from a pulley to a hub.

[0021] Fig.11AThe invention is an enlarged plan view of an isolation spring device, of a coil of one of the isolation springs in the isolation spring device, immediately before the coil is tilted.

[0022] Fig. 11B is an enlarged plan view of the isolation spring device immediately after the coil of one of the isolation springs in the isolation spring device is tilted.

[0023] Fig.12 yes Figure 2 A cross-sectional view of a portion of the isolation device shown in FIG.

[0024] Fig.13 yes Figure 2 An enlarged view of one of the isolation springs in the isolation spring arrangement of the isolation device shown in , wherein certain surfaces of the isolation spring are optionally flattened.

[0025] Fig.14 yes Figure 2 A perspective view of a variant of an isolating device is shown in , wherein each isolating spring device includes a first isolating spring, a second isolating spring and a third isolating spring that are all connected in series with each other.

[0026] Fig.15 yes Figure 2 A perspective view of another variant of the isolation device shown in , wherein each isolation spring device includes a first isolation spring, a second isolation spring and a third isolation spring, wherein two of the springs are connected in series and the third spring is connected in parallel with the two springs in series.

[0027] Fig.16 yes Figure 2 A perspective view of yet another variation of the isolation device shown in , the variation comprising a connector connecting isolation springs constituting an isolation spring device.

[0028] Unless specifically stated otherwise, objects depicted in the drawings are not necessarily drawn to scale. DETAILED DESCRIPTION

[0029] For simplicity and clear illustration, reference numerals may be repeated in the accompanying drawings to indicate corresponding or similar elements where deemed appropriate. In addition, many specific details are set forth to provide a thorough understanding of one or more embodiments described herein. However, it will be appreciated by those of ordinary skill in the art that the embodiments described herein may be practiced without these specific details. In other cases, well-known methods, processes, and components are not described in detail to avoid obscuring the embodiments described herein. It should be understood at the outset that, although exemplary embodiments are illustrated in the accompanying drawings and described below, the principles of the present disclosure may be implemented using any number of technologies, whether currently known or not. The present disclosure should not be limited in any way to the exemplary embodiments and technologies illustrated in the accompanying drawings and described below.

[0030] Unless the context indicates otherwise, the various terms used throughout this specification can be read and understood as follows: "or" used throughout is inclusive, just like "and / or"; singular articles and pronouns used throughout include their plural forms, and conversely, plural forms of articles and pronouns include their singular forms; similarly, gender pronouns include their complementary pronouns, so that the pronouns should not be understood as limiting anything described herein to use, implementation, execution, etc. by a single gender; "exemplary" should be understood as "illustrative" or "exemplary" rather than necessarily "preferred" over other embodiments. Definitions of terms may be further elaborated herein; as will be understood by reading this specification, these definitions may apply to previous and subsequent instances of those terms. It will also be noted that the use of the term "one" will be understood to mean "at least one" in all cases unless otherwise explicitly stated or unless it is understood to be clearly necessary to mean "one".

[0031] Without departing from the scope of the present disclosure, the systems, devices and methods described herein may be modified, added or omitted. For example, the components of the systems and devices may be integrated or separated. In addition, the operation of the systems and devices disclosed herein may be performed by more, fewer or other components, and the described methods may include more, fewer or other steps. In addition, the steps may be performed in any suitable order. As used herein, "each" refers to each component of a group or each component of a subgroup of a group.

[0032] Reference Figure 1, which shows an engine 10 for a vehicle. The engine 10 comprises a crankshaft 12 driving an endless drive element, which may be, for example, a belt 14. The engine 10 drives a plurality of accessories 16 (shown in dashed outline) such as a motor / generator unit (MGU) and an air conditioning compressor via the belt 14. Each accessory 16 comprises an accessory shaft 15 having a pulley 13 thereon, which is driven by the belt 14. Furthermore, an idle pulley shown at 17a on an idle shaft 17b and a tensioning pulley 19a rotatably mounted on a tensioning arm 19b, which forms part of a belt tensioner 19, are shown in this embodiment. The functions of the idle pulley 17a and the belt tensioner 19 are well known to those skilled in the art.

[0033] An isolating device 20 may be provided at one or more locations instead of a pulley to control torque transfer between the crankshaft 12 and the accessory shaft 15. Figure 1 In the embodiment of the invention, an isolating device 20 is provided on the crankshaft 12. The isolating device 20 transmits torque between the crankshaft 12 and the belt 14, but attenuates torsional vibrations from the crankshaft 12 that are transmitted to the belt 14. Such torsional vibrations, oscillations in the speed of the crankshaft 12, are inherent to an internal combustion piston engine. These oscillations are isolated from the belt 14 by the isolating device 20, and thus the stresses otherwise caused by the belt 14 and the accessory shaft 15 are reduced.

[0034] Reference Figure 2 and Figure 3 , which respectively show an assembled perspective view and an exploded perspective view of the isolation device 20. The isolation device 20 includes a hub 22, a pulley 24, a first isolation spring device and a second isolation spring device, each shown at 28. Figure 2 and Figure 3 In the example shown, the isolation device 20 also includes optional elements including a bushing 29 , a seal 30 , and a thrust plate 35 .

[0035] In the illustrated embodiment, the hub 22 includes a shaft adapter 22a and a driver 22b. The shaft adapter 22a is adapted to be mounted to the crankshaft 12 in any suitable manner. For example, the shaft adapter 22 may have a shaft mounting aperture 36 therethrough that defines the axis of rotation A of the isolation device 20. The shaft mounting aperture 36 may be configured to closely receive the end of the crankshaft 12. A plurality of shaft mounting fasteners 37 such as bolts ( Figure 1 ) can be inserted through the distal ends 38 of the shaft adapter 22a and the driver 22b to fixedly mount the shaft adapter 22a and the driver 22b to the crankshaft 12 so that the hub 22 and the crankshaft 12 rotate synchronously together about the axis A.

[0036] The driver 22b includes first and second driver arms 100, shown at 100a and 100b, respectively. Each driver arm 100 has a first hub / spring interface surface 102 and a second hub / spring interface surface 104. The first hub / spring interface surface 102 and the second hub / spring interface surface 104 are positioned to engage the ends of the isolation spring assembly 28, as further described below.

[0037] The pulley 24 is rotatably coupled to the shaft adapter 22. The pulley 24 has an outer surface including a belt engagement surface 40 configured to engage with the belt 14 ( Figure 1 ). The belt 14 can thus be a poly-V belt.

[0038] The pulley 24 may be formed of a main pulley portion 24 a including a belt engaging surface 40 thereon and a pulley cover 24 b cooperating with the main pulley portion 24 a to define a spring housing 42 for retaining the first and second isolation spring arrangements 28 .

[0039] The pulley 24 also includes an inner surface 43. The bushing 27 engages the inner surface 43 of the pulley 24 and rotatably supports the pulley 24 on the shaft adapter 22a. The bushing 27 can be a polymer member having a selected low coefficient of friction. Suitable materials for the bushing 27 include, for example, some forms of nylon.

[0040] The pulley 24 includes two pairs of lugs formed by pressing inwardly into the material of the main pulley portion 24a and the pulley cover 24b. The first pair of lugs 109a are formed at Figure 3 The second pair of lugs 109b are shown in Fig.12 . The first pair of lugs 109a face each other, and the second pair of lugs 109b also face each other. The pulley 24 includes a first pulley / spring interface surface 106 and a second pulley / spring interface surface 108, which are positioned to engage with the end of the isolation spring device 28, as further described below. In the illustrated embodiment, the first pulley / spring interface surface 106 is disposed on a first side of the lugs 109a and 109b, and the second pulley / spring interface surface 108 is disposed on a second side of the lugs 109a and 109b.

[0041] As described above, the isolation spring arrangement 28 is configured to accommodate oscillations in the speed of the crankshaft 12 relative to the belt 14. The isolation spring arrangement 28 may each include a first isolation spring 110 and a second isolation spring 112. The first isolation spring 110 and the second isolation spring 112 ( Figure 5) are each a helical compression spring and preferably extend along an arc path inside the pulley 24. Each of the first isolation spring 110 and the second isolation spring 112 has a first end 114, a second end 116, and a plurality of coils 118 between the first end 114 and the second end 116. The first ends 114 of the first isolation spring 110 and the second isolation spring 112 face away from each other, while the second ends 116 of the first isolation spring 110 and the second isolation spring 112 face each other. The first isolation spring 110 and the second isolation spring 112 have lengths L1 and L2 ( Figure 5 ), and have diameters D1 and D2 respectively ( Figure 5 ). The first isolation spring 110 and the second isolation spring 112 have respective first spring stiffness K1 and second spring stiffness K2. In the illustrated embodiment, the diameters D1 and D2 are substantially equal, but they need not be strictly equal. In the illustrated embodiment, the length L1 is greater than the length L2, but this need not be the case in all embodiments. In the illustrated embodiment, the first spring stiffness K1 is greater than the second spring stiffness K2, but this need not be the case in all embodiments.

[0042] The first isolation spring 110 and the second isolation spring 112 are arranged in series with each other so that the first isolation spring 110 transfers the torque from the second isolation spring 112 to the first one of the hub 22 and the pulley 24 and the second isolation spring 112 transfers the torque from the first isolation spring 110 to the second one of the hub 22 and the pulley 24. Figure 6 In the example shown, the first of the hub 22 and the pulley 24 is the hub 22 and the second of the hub 22 and the pulley 24 is the pulley 24. As can be seen in this example, the first end 114 of the second isolation spring 112 remains rotationally fixed relative to the pulley 24, while the driver 22b is engaged with the first end 114 of the first isolation spring 110.

[0043] Because the first spring stiffness K1 is greater than the second spring stiffness K2, what first occurs during the torque transmission from the first of the hub 22 and the pulley 24 to the second of the hub 22 and the pulley 24 is that the entire first isolation spring 110 slides along the friction surface 120 (friction surface 120 is the surface of the pulley cover 24b in this case) through the first of the hub 22 and the pulley 24 toward the second of the hub 22 and the pulley 24 during the compression of the second isolation spring 112, thereby generating a first friction damping torque TF1. This damping torque can be Figure 81. The damping torque TF1 is formed by the friction generated by the movement of the first isolation spring 110 along the friction surface 120 and the movement of a portion of the second isolation spring 112 along the friction surface 120. In this example, only a portion of the second isolation spring 112 moves along the friction surface 120 or moves significantly because the first end 114 of the second isolation spring 112 is engaged with the second pulley / spring interface surface 108.

[0044] In this initial range of torque transfer (such as Figure 8 202), the effective spring rate of the isolation spring device 28 is equal to 1 / (1 / K1+1 / K2). Once the torque transmission through the first isolation spring 110 and the second isolation spring 112 reaches the selected first torque transmission level TS1 ( Figure 8 ), the first isolation spring 110 is fully compressed, and only the second isolation spring 112 is further compressed, which defines a second range of torque transmission. In this second stage of torque transmission, the effective spring stiffness of the isolation spring device 28 is only the spring stiffness K2, because the first spring is actually a rigid component that has been fully compressed. The second range of torque transmission is Figure 8 It is shown as 204 in FIG.

[0045] In contrast, Figure 7 (as well as Figure 8 250) illustrates the torque transfer from the second of the hub 22 and the pulley 24 to the first of the hub 22 and the pulley 24. It can be seen that the first end 114 of the second isolation spring 112 is engaged with the first pulley / spring interface surface 106. Therefore, initially, during the compression of the first isolation spring 110 by the second of the hub 22 and the pulley 24, a portion of the second isolation spring 112 remains stationary relative to the friction surface 120 and the entire second isolation spring 112 slides along the friction surface 120, thereby generating a second friction damping torque TF2 ( Figure 8 ).

[0046] The first spring stiffness K1 and the second spring stiffness K2 and the length L1 of the first isolation spring 110 and the length L2 of the second isolation spring 112 affect the first friction damping torque TF1 and the second friction damping torque TF2 and can be selected so that the first friction damping torque TF1 is greater than the second friction damping torque TF2. The magnitude of the difference between the first friction damping torque TF1 and the second friction damping torque TF2 depends at least in part on factors such as the specific lengths selected for L1 and L2 and the specific spring stiffness selected for K1 and K2.

[0047] In addition, Figure 7 In the example shown in Figure 8Once the torque transmission through the first isolation spring 110 and the second isolation spring 112 reaches the selected second torque transmission level TS2 ( Figure 8 ), the first isolation spring 110 will be fully compressed again, and only the second isolation spring 112 continues to be further compressed, which defines the second range of torque transmission. It can be seen that due to the increase in the amount of damping torque starting during the torque transmission from the first of the hub 22 and the pulley 24 to the second of the hub 22 and the pulley 24 relative to the first of the hub 22 and the pulley 24 during the torque transmission, the selected first torque transmission level TS1 when the first isolation spring 110 is fully compressed and the isolation spring device 28 enters the second torque transmission range is higher than the selected second torque transmission level TS2 when the first isolation spring 110 is fully compressed and the isolation spring device 28 enters the second torque transmission range.

[0048] In contrast, the prior art isolation spring device is shown at 280 in FIG. 4 and has Fig. 9 The torque curve is shown at 300. Fig. 9 The torque curve 300 shown in FIG. 1 is derived mathematically and therefore appears to be more accurate than that derived from a simulated engine. Figure 8 4. The torque curve shown in FIG. 4 is clearer. The isolation spring assembly 280 shown in FIG. 4 includes a nested first isolation spring 282 and a second isolation spring 284 (i.e., such that the second isolation spring 284 is nested within the first isolation spring 282 and is shorter than the first isolation spring 282). In the case of nested springs, the amount of friction damping provided depends more or less solely on the friction between the outer spring (i.e., the first isolation spring 282) and the friction surface (not shown) against which it rubs. Therefore, whether the hub of such an isolator transmits torque to the pulley, or the pulley transmits torque to the hub, there is essentially no difference in the amount of damping torque. Therefore, curve 300 represents both ways of torque transmission, (i.e., regardless of which end of the isolation spring assembly 280 moves relative to the friction surface against which the isolation spring assembly 280 slides).

[0049] These characteristics of the isolation device 20 described herein may be advantageous in many situations or applications. For example, where the engine 10 is equipped with the MGU 16a, the engine 10 may have two starting modes, including a first starting mode (referred to as a key start) in which the engine 10 is started via a starter motor engaged with a flywheel until combustion takes over, and a second starting mode (referred to as an MGU start) in which the MGU drives the crankshaft 12 via the belt 14 until combustion takes over. During a key start, it may be desirable to have a relatively high amount of friction in the initial range of torque transfer through the isolation device 20, and it may be desirable to shift the torque of the isolation spring device 28 into the second torque transfer range as far back as possible. This inhibits the isolation device 20 from cycling between the first torque transfer range and the second torque transfer range. However, during MGU start, friction damping may be less desirable for some reasons. For example, during MGU start, the likelihood of resonance is lower.

[0050] Another feature of the isolation device 20 is shown in FIGS. Fig.12 1 and refers to hub / spring interface surfaces 102 and 104, and in particular, to pulley / spring interface surfaces 106 and 108. For purposes of discussing this feature, the one of the hub / spring interface surfaces 102 and 104 or the pulley / spring interface surfaces 106 and 108 that engages the first end 114 of the first isolation spring 110 will be referred to as the first spring drive surface 140, and the one of the hub / spring interface surfaces 102 and 104 or the pulley / spring interface surfaces 106 and 108 that engages the first end 114 of the second isolation spring 112 will be referred to as the second spring drive surface 142. Figure 6 In the example case shown in , the first spring drive surface 140 is the first hub / spring interface surface 104 and the second spring drive surface 142 is the first pulley / spring interface surface 106 .

[0051] from Figure 6 and Fig.12 It can be seen that the second spring drive surface 142 extends over a first portion 144 of the diameter D2 of the second isolation spring 112 such that there is a space 146 adjacent to the second spring drive surface 142 towards the isolation device axis A. The space 146 extends over a second portion 148 of the diameter D2 of the second isolation spring 112 from a side edge of the second spring drive surface 142 to a radially inner side 150 of the second isolation spring 112 relative to the isolation device axis A.

[0052] from Fig. 10A and Fig. 10BIt can be seen that during torque transfer from the first of the hub 22 and the pulley 24 to the second of the hub 22 and the pulley 24, the isolation spring device 28 allows the hub 22 and the pulley 24 to move within a first angular range of motion ( Fig. 10A 2 and the pulley 24, and wherein the isolation spring arrangement allows the relative movement between the hub 22 and the pulley 24 during torque transfer from the second one of the hub 22 and the pulley 24 to the first one of the hub 22 and the pulley 24. Fig. 10B Relative movement over the second angular movement range R2 shown in .

[0053] The second spring stiffness K2 and the size of the space 146 are selected so that: at the selected torque transmission level TS3 during torque transmission between the hub 22 and the pulley 24 through the first isolation spring 110 and the second isolation spring 112, the selected torque transmission level TS3 drives the coils 118 of the second isolation spring 112 to contact each other on the radial inner side 150 of the second isolation spring 112 relative to the isolation device axis A, and drives at least one of the coils 118 at the first end 114 of the second isolation spring 112 to tilt into the space 146, which in turn allows the first angular motion range to exceed the second angular motion range.

[0054] The reason for this is that the first spring rate K1 of the first isolation spring 110 is relatively high. Therefore, when the first spring drive surface 140 is one of the pulley / spring interface surfaces 106 and 108, the first isolation spring 110 has no tendency to tilt into the space 146 to extend the available range of motion. Such an extension of the first range of motion relative to the second range of motion is advantageous in certain circumstances. For example, when the engine is started via a key, it is advantageous to provide as large a range of motion as possible to prevent the isolation device 20 from being locked. However, in contrast, during MGU startup, it is sometimes considered advantageous to have a shorter range of motion before the isolation device is locked in order to provide high torque to the crankshaft 12 relatively quickly.

[0055] Space 146 may extend over any suitable amount of the diameter of second isolation spring 112. In an embodiment, space 146 may extend over at least 30% of the diameter of second isolation spring 112. In an embodiment, space 146 may extend over at least one third of the diameter of second isolation spring 112.

[0056] It will be noted that Figures 3 to 12The first and second isolation springs shown in the illustrated embodiment are coiled opposite to each other. Therefore, when torque is transmitted to each other through the respective second ends 116 of the first and second isolation springs, it is unlikely that the first and second isolation springs 110, 112 will become tangled. In contrast, if the first and second isolation springs 110, 112 were coiled in the same manner (e.g., both were right-handed or left-handed), tangling would be possible.

[0057] Reference Fig.13 , which shows an optional feature on the second isolation spring 112. In order to reduce the stress on the coils 118 and the slippage between the coils 118 of the isolation spring 112 when the torque applied by the isolation spring device 28 causes the coils 118 of the second isolation spring 112 to contact each other, the mating surface shown at 180 (also referred to as the coil inner surface 180) of the coil 118 is flattened before the raw wire is formed into the second isolation spring 112.

[0058] Reference Fig.14 , which shows a variation of the isolation device 20, wherein each isolation spring device 28 includes a first isolation spring 110, a second isolation spring 112, and a third isolation spring 182 connected in series with the first isolation spring 110 and the second isolation spring 112. In the embodiment shown, the third isolation spring 182 has a third spring stiffness K3 greater than the second spring stiffness K2, and the third spring stiffness K3 may be greater than or less than the first spring stiffness K1. The above-mentioned advantages regarding the increase in the amount of damping torque, the change in torque when the isolation device enters the second range of torque transmission, and the increased range of motion during torque transmission are all present in this variation.

[0059] Reference Fig.15 , which shows another variation of the isolation device 20, wherein each isolation spring device 28 includes a first isolation spring 110, a second isolation spring 112, and a third isolation spring 186 connected in parallel with the first isolation spring 110 and the second isolation spring 112. In the illustrated embodiment, the third isolation spring 182 has a third spring stiffness K3 greater than the second spring stiffness K2, and the third spring stiffness K3 may be greater than or less than the first spring stiffness K1. The above-mentioned advantages regarding the increase in the amount of damping torque, the change in torque when the isolation device enters the second range of torque transmission, and the increased range of motion during torque transmission are all present in this variation.

[0060] exist Fig.161 shows a variation of the isolation device 20. It can be seen that a connector 190 is provided, which holds the second ends 116 of the first isolation spring 110 and the second isolation spring 112. The connector includes a plate 192, a first protrusion 194, and a second protrusion 196, wherein the plate 192 engages the second ends 116 of the first isolation spring 110 and the second isolation spring 112, the first protrusion 194 extends from the plate 192 into the first isolation spring 110 (i.e., extends into the hollow 195 in the first isolation spring 110), and the second protrusion 196 extends from the plate 192 into the second isolation spring 112 (i.e., extends into the hollow 197 in the second isolation spring 112). The plate 192 and the protrusions 194 and 196 hold the second ends 116 of the first isolation spring 110 and the second isolation spring 112 parallel to each other to maintain torque transmission across the second ends 116 between the first isolation spring 110 and the second isolation spring 112.

[0061] It should be noted that while the embodiments herein show the isolation device 20 on the crankshaft 12, alternatively, the isolation device 20 may be disposed on the shaft of the MGU 16a or any other suitable accessory. In these embodiments, the arrangement of the first isolation spring 110 and the second isolation spring 112 may need to be reversed, depending on when the application requires greater friction, longer travel, and any other features described herein.

[0062] Those skilled in the art will appreciate that there are many more possible alternative embodiments and modifications, and the above examples are only illustrations of one or more embodiments. Therefore, the scope is limited only by the appended claims and any amendments made thereto.

Claims

1. An isolation device, comprising: a hub mountable to the shaft; a pulley rotatably mounted to the hub, wherein the pulley has a belt engaging surface positioned to engage an engine accessory drive belt for transmitting torque therewith; and at least one isolation spring arrangement, the at least one isolation spring arrangement comprising a first isolation spring and a second isolation spring, wherein each of the first isolation spring and the second isolation spring is a helical compression spring having a length, wherein the first isolation spring has a first spring rate, and wherein the second isolation spring has a second spring rate and is positioned in series with the first isolation spring, wherein the first spring rate is greater than the second spring rate, wherein the first isolation spring and the second isolation spring are arranged such that: the first isolation spring transfers torque from the second isolation spring into a first one of the hub and the pulley and the second isolation spring transfers torque from the first isolation spring into a second one of the hub and the pulley, wherein, starting during torque transfer from the first one of the hub and the pulley to the second one of the hub and the pulley, the entire first isolation spring slides along the friction surface through the first one of the hub and the pulley toward the second one of the hub and the pulley during compression of the second isolation spring, thereby generating a first friction damping torque, and wherein, starting during torque transmission from the second one of the hub and the pulley to the first one of the hub and the pulley, during compression of the first isolation spring by the second one of the hub and the pulley, at least a portion of the first isolation spring remains stationary relative to the friction surface and the entire second isolation spring slides along the friction surface, thereby generating a second friction damping torque, and The first spring stiffness and the second spring stiffness and the length of the first isolation spring and the length of the second isolation spring are selected such that the first friction damping torque is greater than the second friction damping torque.

2. The isolation device according to claim 1, wherein: The first isolation spring and the second isolation spring directly abut each other.

3. The isolation device according to claim 1, wherein: The first isolation spring directly abuts the first one of the hub and the pulley, and the second isolation spring directly abuts the second one of the hub and the pulley.

4. The isolation device according to claim 1, wherein: The first one of the hub and the pulley is the hub, and the second one of the hub and the pulley is the pulley.

5. The isolation device according to claim 1, wherein: The first one of the hub and the pulley is the pulley, and the second one of the hub and the pulley is the hub.

6. The isolation device according to claim 1, wherein: Each of the at least one isolation spring arrangements further includes a third isolation spring acting in series with the first isolation spring and the second isolation spring.

7. The isolation device according to claim 1, wherein: Each of the at least one isolating spring arrangements further comprises a third isolating spring acting in parallel with the first isolating spring and the second isolating spring.

8. The isolation device according to claim 1, wherein: A connector is positioned between the first isolation spring and the second isolation spring such that both the first isolation spring and the second isolation spring directly abut the connector.

9. The isolation device according to claim 1, wherein: The friction surface is disposed on a spring housing included in the pulley and at least partially enclosing the first isolation spring and the second isolation spring.

10. The isolation device according to claim 9, wherein: The first isolation spring and the second isolation spring extend in an arcuate path along the interior of the spring housing about the isolation device axis, and wherein the friction surface is a surface of the spring housing that engages a radially outer surface of the first isolation spring, wherein the radially outer surface of the first isolation spring is radially outward relative to the isolation device axis.

11. The isolation device according to claim 1, further comprising a connector that holds the second end of the first isolation spring and the second end of the second isolation spring, wherein: The connector includes a plate, a first protrusion, and a second protrusion, wherein the plate engages the second end of the first isolation spring and the second end of the second isolation spring, the first protrusion extends from the plate into the first isolation spring, and the second protrusion extends from the plate into the second isolation spring, wherein the plate and the protrusion hold the second end of the first isolation spring and the second end of the second isolation spring parallel to each other to maintain torque transmission across the second ends between the first isolation spring and the second isolation spring.

12. The isolation device according to claim 1, wherein: Each of the first isolation spring and the second isolation spring is a helical compression spring having a first end, a second end, and a plurality of coils between the first end and the second end, wherein the first end of the first isolation spring and the first end of the second isolation spring face away from each other, and the second end of the first isolation spring and the second end of the second isolation spring face each other, wherein the first isolation spring and the second isolation spring each have a diameter and extend along an arc path inside the pulley around the isolation device axis, wherein a first spring drive surface on the first of the hub and the pulley engages with a first end of the first isolation spring, and a second spring drive surface on the second of the hub and the pulley engages with a first end of the second isolation spring, wherein the second spring drive surface extends over a first portion of a diameter of the second isolation spring such that there is a space adjacent to the second spring drive surface toward the axis of the isolation device, wherein the space extends over a second portion of the diameter of the second isolation spring from a side edge of the second spring drive surface to a radially inner edge of the second isolation spring relative to the axis of the isolation device, wherein during torque transfer from the first one of the hub and the pulley to the second one of the hub and the pulley, the at least one isolation spring arrangement permits relative movement between the hub and the pulley within a first range of angular motion, and wherein during torque transfer from the second one of the hub and the pulley to the first one of the hub and the pulley, the at least one isolation spring arrangement permits relative movement between the hub and the pulley within a second range of angular motion, Wherein, the second spring stiffness and the size of the space are selected so that: at a selected torque transmission level during torque transmission between the hub and the pulley through the first isolation spring and the second isolation spring, the selected torque transmission level drives the coils of the second isolation spring to contact each other on the radial inner side of the second isolation spring relative to the axis of the isolation device, which in turn drives at least one of the coils at the free end of the second isolation spring to tilt into the space, which in turn allows the first angular motion range to exceed the second angular motion range.

13. The isolation device according to claim 1, wherein: The second isolation spring includes a plurality of coils, wherein the coils have coil interior surfaces that are planar and capable of engaging one another when torque transmission through the isolation device is at a selected torque transmission level.

14. An isolation device comprising: a hub mountable to the shaft; a pulley rotatably mounted to the hub; as well as at least one isolation spring device, the at least one isolation spring device comprising a first isolation spring and a second isolation spring, wherein each of the first isolation spring and the second isolation spring is a helical compression spring having a first end, a second end, and a plurality of coils located between the first end and the second end, wherein the first end of the first isolation spring and the first end of the second isolation spring face away from each other, and the second end of the first isolation spring and the second end of the second isolation spring face each other, wherein the first isolation spring and the second isolation spring each have a diameter and extend along an arc path inside the pulley around the isolation device axis, wherein the first isolation spring has a first spring rate, and wherein the second isolation spring has a second spring rate and is positioned in series with the first isolation spring, wherein the first spring rate is greater than the second spring rate, wherein the first isolation spring and the second isolation spring are arranged such that: the first isolation spring transfers torque from the second isolation spring to a first one of the hub and the pulley, and the second isolation spring transfers torque from the first isolation spring to a second one of the hub and the pulley, wherein a first spring drive surface on the first of the hub and the pulley engages with a first end of the first isolation spring, and a second spring drive surface on the second of the hub and the pulley engages with a first end of the second isolation spring, wherein the second spring drive surface extends over a first portion of a diameter of the second isolation spring such that there is a space adjacent to the second spring drive surface toward the axis of the isolation device, wherein the space extends over a second portion of the diameter of the second isolation spring from a side edge of the second spring drive surface to a radially inner edge of the second isolation spring relative to the axis of the isolation device, wherein during torque transfer from the first one of the hub and the pulley to the second one of the hub and the pulley, the at least one isolation spring arrangement permits relative movement between the hub and the pulley within a first range of angular motion, and wherein during torque transfer from the second one of the hub and the pulley to the first one of the hub and the pulley, the at least one isolation spring arrangement permits relative movement between the hub and the pulley within a second range of angular motion, Wherein, the second spring stiffness and the size of the space are selected so that: at a selected torque transmission level during torque transmission between the hub and the pulley through the first isolation spring and the second isolation spring, the selected torque transmission level drives the coils of the second isolation spring to contact each other on the radial inner side of the second isolation spring relative to the axis of the isolation device, which in turn drives at least one of the coils at the free end of the second isolation spring to tilt into the space, which in turn allows the first angular motion range to exceed the second angular motion range.

15. The isolation device according to claim 14, wherein: The space extends over at least 30% of the diameter of the second isolating spring.

16. The isolation device according to claim 14, wherein: The space extends over at least one third of the diameter of the second isolating spring.

17. The isolation device according to claim 14, wherein: The first one of the hub and the pulley is the hub, and the second one of the hub and the pulley is the pulley.

18. The isolation device of claim 14, further comprising a connector that holds the second end of the first isolation spring and the second end of the second isolation spring, wherein: The connector includes a plate, a first protrusion, and a second protrusion, wherein the plate engages the second end of the first isolation spring and the second end of the second isolation spring, the first protrusion extends from the plate into the first isolation spring, and the second protrusion extends from the plate into the second isolation spring, wherein the plate and the protrusion hold the second end of the first isolation spring and the second end of the second isolation spring parallel to each other to maintain torque transmission across the second ends between the first isolation spring and the second isolation spring.

19. The isolation device according to claim 14, wherein: Each of the at least one isolation spring arrangements further includes a third isolation spring acting in series with and positioned between the first isolation spring and the second isolation spring.

20. The isolation device according to claim 14, wherein: The second isolation spring includes a plurality of coils, wherein the coils have coil interior surfaces that are planar and capable of engaging one another when torque transmission through the isolation device is at a selected torque transmission level.

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