SUSPENSION APPARATUS AND VISCOUS COUPLING

BACKGROUND OF THE INVENTION

1. Field of the Invention

[0001] The invention relates to a suspension apparatus, and more particularly, to a mechanism that adjusts the damping force of a suspension apparatus.

2. Description of the Related Art

[0002] Japanese Patent No. 2803870 describes a suspension apparatus in which an outer end portion of a pair of left and right rods are connected to a lower arm, and a roll damper, which serves as damping means, is provided between the inner end portions of the pair of rods. In this roll damper, a space is formed by a hollow casing and a side plate. In this space, outer plates that are fixed to the inner peripheral surface of the hollow casing alternately overlap with inner plates that are fixed to the outer peripheral surface of the rod, and the space is then filled with silicone oil, thus forming a viscous coupling. This viscous coupling suppresses relative rotation between the pair of left and right rods, thereby damping vibration caused by roll.

[0003] Suspension performance typically demands that damping force proportional to the stroke speed be generated. However, if damping force proportional to a high stroke speed is generated, the ride tends to be less comfortable and an excessive load is placed on the suspension apparatus. In a viscous coupling according to related art, the generated damping force is proportional to the stroke speed. If the viscous coupling of the related art is used in a suspension apparatus, riding comfort would deteriorate and an excessive load would be placed on the suspension apparatus at high stroke speeds. Also, at a given differential rotation speed, the damping force generated by the viscous coupling of the related art is the same during forward rotation as it is during reverse rotation. Therefore, if that viscous coupling was used in a suspension apparatus, the damping force characteristic during the expansion stroke would be the same as the damping force characteristic during the compression stroke, and the two

could not be made different from one another.

SUMMARY OF THE INVENTION

[0004] This invention thus provides a suspension apparatus and a viscous coupling that can be suitably used in a suspension apparatus.

[0005] A first aspect of the invention relates to a suspension apparatus. This suspension apparatus includes a viscous coupling provided on a joint portion of a link mechanism of the suspension apparatus. The viscous coupling includes a shaft, a case body that houses viscous fluid, plates that generate damping force according to relative rotation between the shaft and the case body, and damping force increase reducing means for reducing a degree of increase in damping force when the relative rotation between the shaft and the case body reaches a predetermined state. The damping force increase reducing means may be formed as a torque transfer characteristic changing mechanism that mechanically changes a torque transfer characteristic according to relative rotation between the shaft and the case body. This mechanical mechanism may autonomously change the torque transfer characteristic by changing the state of the mechanism according to the relative rotation between the shaft and the case body instead of by operating in response to a received control signal from an external device, for example. The suspension apparatus of this aspect includes a viscous coupling having damping force increase degree reducing means and is therefore able to suppress an excessive increase in the damping force.

[0006] The plates may include a plurality of first plates connected to the shaft side, and a plurality of second plates connected to the case body side. The damping force increase reducing means may include torque transfer limiting means for limiting at least some of i) the torque that is transmitted between the first plates and the shaft or ii) the torque that is transmitted between the second plates and the case body, when the relative rotation speed between the shaft and the case body is equal to or greater than a predetermined value. As a result, a decrease in riding comfort at high stroke speeds can

be suppressed.

[0007] The torque transfer limiting means may be provided with i) a portion of the plurality of first plates, or ii) a portion of the plurality of second plates. As a result, a case in which the damping force always increases proportionate to an increase in the relative rotation speed between the shaft and the case body can be avoided.

[0008] The damping force increase reducing means may include a plurality of torque transfer limiting means. As a result, the degree of increase in the damping force can be suppressed smoothly. The first plates or the second plates which are provided on the torque transfer limiting means may be connected to the shaft side or the case body side such that the distance to the other plates is different for each torque transfer limiting means. This enables the degree of increase in the damping force to be suppressed even more smoothly. An upper limit value up to which torque can be transmitted may be different for each of the plurality of torque transfer limiting means. The torque transfer limiting means may be a torque limiter.

[0009] The plates may include a plurality of first plates connected to the shaft side, and a plurality of second plates connected to the case body side, and the damping force increase reducing means may include torque transfer limiting means for i) disconnecting the first plates from the shaft or ii) disconnecting the second plates from the case body, when there is rotation between the shaft and the case body in one predetermined direction. Accordingly, different damping force characteristics can be realized depending on the direction of rotation of the shaft and the case body.

[0010] The torque transfer limiting means may be provided with i) a portion of the plurality of first plates, or ii) a portion of the plurality of second plates. This enables the damping force characteristic to be adjusted as desired.

[0011] The damping force increase reducing means may include a plurality of torque transfer limiting means. This enables the degree of increase in the damping force to be suppressed smoothly. The first plates or the second plates which are provided on the torque transfer limiting means may be connected to the shaft side or the case body side such that the distance to the other plates is different for each of the plurality of torque

transfer limiting means. This enables the degree of increase in the damping force to be suppressed even more smoothly. The torque that disconnects the first plates from the shaft or disconnects the second plates from the case body may be different for each of the plurality of torque transfer limiting means. The torque transfer limiting means may be a one-way clutch.

[0012] The first plates or the second plates which are provided on the torque transfer limiting means may be divided into a plurality of pairs with different surface areas. As a result, a desired damping force characteristic can be realized even if the plate distances are set so that they are equal.

[0013] Also, the plates may include a plurality of first plates connected to the shaft side, and a plurality of second plates connected to the case body side, and the damping force increase reducing means may include plate moving means for moving the first plates or the second plates in a direction in which the distances between one of the first plates and two of the second plates that are adjacent to and sandwich the one first plate become equal by relative rotation between the shaft and the case body. Accordingly, the degree of increase in the damping force can be reduced smoothly according to the relative rotation between the shaft and the case body.

[0014] The plate moving means may move the first plates or the second plates when the relative rotation speed between the shaft and the case body is equal to or greater than a predetermined value. Accordingly, for example, damping force proportionate to the relative rotation speed can be generated in the low speed stroke region, while the degree of increase in the damping force can be reduced when the relative rotation speed is equal to or greater than a predetermined value.

[0015] The shaft or the case body may be divided into two by a divided portion having a cam structure or a wedge structure, and the plate moving means may have urging means for urging the divided portion in a direction of engagement. The plate moving means may move the first plates or the second plates in a direction of separation by resistance against the urging means generated by relative rotation between the shaft and the case body. The degree of increase hi the damping force can be reduced

according to the relative rotation speed by forming a cam structure or a wedge structure at the divided portion. The cam structure or the wedge structure may be asymmetrical with reference to the rotational axis of the shaft.

[0016] The shaft may include a first shaft connected to an arm, and a second shaft that engages with the first shaft on the same axis. The plate moving means may include urging means for urging the second shaft in a direction such that the second shaft is pushed against the first shaft. The distances between one of the first plates and two of the second plates that are adjacent to and sandwich the one first plate may be different when the second shaft is pushed against the first shaft by the urging means. When resistance against the urging means is generated by relative rotation between the shaft and the case body, the one first plate may move in a direction in which the distances between the one first plate and the two second plates that are adjacent to and sandwich the one first plate become equal. The plate moving means can be formed with a simple structure by forming the shaft such that it at least has a first shaft and a second shaft, and having the second shaft be urged against the first shaft.

[0017] The plate moving means may be set such that distance that the first plates or the second plates move with respect to a given rotation speed differs depending on the direction of relative rotation between the shaft and the case body. This enables different damping force characteristics to be realized depending on the direction of rotation of the shaft and the case body.

[0018] A second aspect of the invention relates to a viscous coupling. This viscous coupling includes a shaft, a case body that houses viscous fluid, plates that generate damping force according to relative rotation between the shaft and the case body, and damping force increase reducing means for reducing the degree of increase in damping force when the relative rotation between the shaft and the case body reaches a predetermined state.

[0019] Thus the invention makes it possible to provide a viscous coupling that can suitably control the damping force characteristics of a suspension apparatus, as well as a suspension apparatus that uses this viscous coupling.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The foregoing and further features and advantages of the invention will become apparent from the following description of example embodiments with reference to the accompanying drawings, wherein like numerals are used to represent like elements and wherein:

FIG. 1 is a view of the mounting structure of a suspension apparatus according to a first example embodiment of the invention;

FIG. 2 is a view of the structure of a viscous coupling according to the first example embodiment of the invention;

FIG. 3A is a graph showing the relationship between generated torque and differential rotation speed according to the viscous coupling of related art, and FIG. 3B is a graph showing the relationship between generated torque and differential rotation speed according to the viscous coupling suitable for a suspension apparatus according to the first example embodiment of the invention;

FIG. 4 is a graph showing the relationship between damping force generated by the viscous coupling and relative rotation speed between a shaft and a case body;

FIG. 5 is a modified example of the structure of the viscous coupling according to the first example embodiment of the invention;

FIG. 6 is a graph showing the relationship between damping force generated by the viscous coupling and relative rotation speed between the shaft and the case body;

FIG. 7 is another modified example of the structure of the viscous coupling according to the first example embodiment of the invention;

FIG. 8 is a graph showing the relationship between damping force generated by the viscous coupling and relative rotation speed between the shaft and the case body;

FIG. 9 is still another modified example of the structure of the viscous coupling according to the first example embodiment of the invention;

FIG. 10 is a graph showing the relationship between damping force generated by

the viscous coupling and relative rotation speed between the shaft and the case body;

FIG. 11 is a view of the structure of a viscous coupling according to a second example embodiment of the invention;

FIGS. 12A and 12B are diagrams showing the positional relationship between a first shaft and a second shaft;

FIG. 13 is a graph showing the relationship between the pitch and the degree of increase in damping force;

FIGS. 14A and 14B are diagrams showing examples in which the angle of a wedge structure is set according to the direction of rotation;

FIG. 15 is a graph showing the relationship between damping force generated by the viscous coupling and relative rotation speed between a shaft and a case body;

FIGS. 16A to 16D are diagrams showing an example of the connecting structure of the first shaft and the second shaft;

FIGS. 17A and 17B are diagrams showing another example of the connecting structure of the first shaft and the second shaft;

FIGS. 18A and 18B are diagrams showing still another example of the connecting structure of the first shaft and the second shaft; and

FIGS. 19A and 19B are diagrams showing yet another example of the connecting structure of the first shaft and the second shaft.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0021] Example embodiments of the invention will be described in greater detail below with reference to the accompanying drawings. In the following description, like elements will be denoted by like reference characters and redundant descriptions will be omitted when appropriate.

[0022] FIG. 1 is a view of the mounting structure of a suspension apparatus according to a first example embodiment of the invention. A suspension apparatus 1 includes a carrier 6 that rotatably supports a wheel 3, and a lower arm 4 and an upper arm

5 which support the carrier 6 so that it is able to pivot or rock vertically. A vehicle body 2, the lower arm 4, the upper arm 5, and the carrier 6 together form a link mechanism 7. The lower arm 4 and the upper arm 5 are rotatably mounted to the vehicle body 2.

[0023] In this example embodiment, the suspension apparatus 1 has a viscous coupling 10 at a joint portion of the link mechanism 7. The link mechanism 7 in this example embodiment is a four link mechanism, and the viscous coupling 10 may be provided at i) a joint portion 8a of the lower arm 4 and the vehicle body 2, ii) ^l a joint portion 8b of the upper arm 5 and the vehicle body 2, iii) a joint portion 8c of the carrier

6 and the upper arm 5, or iv) a joint portion 8d of the carrier 6 and the lower arm 4. In the example shown in the drawing, the viscous coupling 10 forms the joint portion 8a of the lower arm 4 and the vehicle body 2. Hereinafter, the joint portions 8a to 8d will collectively be referred to as "joint portions 8" when appropriate.

[0024] The viscous coupling 10 has a case body and a shaft that protrudes from the case body. The case body is connected to one link, and the shaft is connected to a link that is adjacent to that link, thereby forming the joint portions 8 in which two adjacent links are connected so as to be able to rotate relative to one another. In the example shown in FIG. 1, the case body is fixed to the vehicle body 2 and the shaft is connected to the lower arm 4. As a result, the shaft and the case body rotate relative to one another as the lower arm 4 moves up and down, thereby generating damping force.

[0025] Incidentally, in the example embodiment described below, the structure of the link mechanism 7 is only an example. The suspension apparatus 1 may have another multi-link mechanism instead. Further, in the example shown in FIG. 1, the viscous coupling 10 is used to form the joint portion 8a, but it may also be used to form a different joint portion 8b, 8c, or 8d. Also, a plurality of the viscous couplings 10 may be used to form a plurality of the joint portions 8. The viscous coupling 10 in the example embodiment described below includes damping force increase reducing means for reducing the degree of increase in damping force when the relative rotation between the shaft and the case body reaches a predetermined state.

[0026] FIG. 2 is a view of the structure of a viscous coupling 10a according to

the first example embodiment. The viscous coupling 10a includes a shaft 20 which is connected to the lower arm 4 and rotates as the lower arm moves up and down, and a cylindrical case body.12 that is connected to a vehicle body 2 at an annular extended portion 14. Incidentally, the shaft 20 may be connected to the vehicle body 2 and the case body 12 may be connected to the lower arm 4, or the shaft 20 and the case body 12 may both be connected to other adjacent links of the link mechanism 7. The shaft 20 is supported so that it is able to rotate relative to the case body 12 via bearing 18a and 18b. A viscous fluid chamber 16 is formed between the outer peripheral surface of the shaft 20 and the inner peripheral surface of the case body 12, and is filled with viscous fluid such as silicone oil. A plurality of inner plates 24a and 24b (hereinafter collectively referred to as "inner plates 24" when appropriate) are directly or indirectly connected to the outer peripheral surface of the shaft 20. Similarly, a plurality of outer plates 22 are connected to the inner peripheral surface of the case body 12. The plurality of inner plates 24 and the plurality of outer plates 22 are arranged alternately with space in between them.

[0027] When the lower arm 4 moves up and down in response to the behavior of the wheel 3, the shaft 20 rotates such that there is relative rotation between the shaft 20 and the case body 12. As a result, the plurality of inner plates 24 which are connected to the shaft 20 and outer plates 22 which are connected to the case body 12 differentially rotate. This difference in rotation generates shearing force in the viscous fluid, which hi turn generates torque. This generated torque is the damping force of the suspension apparatus 1.

[0028] FIG. 3A is a graph showing the relationship between generated torque and differential rotation speed by the viscous coupling of the related art. When the viscous coupling is incorporated into the suspension apparatus as shown in FIG. 1, the differential rotation speed corresponds to the suspension stroke speed and the generated torque corresponds to the damping force.

[0029] A method for calculating the torque generated in the viscous coupling is shown below.

_{... (Expression x)}

where SN : distance (pitch) between plates N : fluid viscosity e : density ra-: maximum diameter of region where plates overlap ri : minimum diameter of region where plates overlap δn : differential rotation (relative rotation)

[0030] As shown in Expression 1, in the viscous coupling of the related art, torque is generated linearly with respect to the differential rotation speed so when that viscous coupling is incorporated into a suspension apparatus, the ride is comfortable for an occupant when the differential rotation speed is on the low side, but deteriorates when the differential rotation speed is on the high side. For example, in FIG. 3A, the region in which the differential rotation speed is less than R is referred to as the low side, and the region in which the differential rotation speed is equal to or greater than R is referred to as the high side. Therefore, the inventors have devised the technical concept of suitably incorporating a viscous coupling into a suspension apparatus by reducing the degree of increase in the generated torque when the differential rotation speed is high.

[0031] FIG. 3B is a graph showing the relationship between generated torque and differential rotation speed by a viscous coupling suitable for a suspension apparatus. As shown in FIG. 3B, the relationship between the differential rotation speed and the generated torque is preferably such that, on the low differential rotation speed side, the differential rotation speed and the generated torque are proportionate to each other as shown in FIG. 3A, but on the high differential rotation speed side, the slope of that relationship is reduced. Reducing the degree of increase in the damping force felt by the occupant when the suspension stroke speed is high makes it possible to keep the ride comfortable. Also, when realizing the damping force characteristic shown in FIG. 3B,

an excessive load is not placed on the suspension apparatus so the suspension apparatus can be made smaller.

[0032] Returning now to FIG. 2, the viscous coupling 10a according to the first example embodiment has a torque limiter 26 at a portion along the axis of the shaft 20. Some of the plurality of inner plates 24 are provided on this torque limiter 26. The torque limiter 26 is connected to the shaft 20 and functions as damping force increase reducing means for reducing the degree of increase in the damping force when the relative rotation between the shaft 20 and the case body 12 reaches a predetermined state. Incidentally, the phrase "degree of increase in the damping force" in this specification refers to the ratio (slope) of the amount of increase in the absolute value of the damping force to a predetermined amount of increase in the absolute value of the differential rotation speed. The torque limiter 26 is shown as the damping force increase reducing means, but another structure may also be used as long as it limits at least some of the torque that is transmitted between the inner plates 24 and the shaft 20. The torque limiter 26 employed in this example embodiment serves to keep the torque that is transmitted to the shaft 20 to a predetermined upper limit value when a load equal to or greater than that upper limit value is placed on the suspension apparatus, and operates as torque transfer limiting means for limiting some of the torque that is transmitted. That is, the torque limiter 26 blocks the transfer of torque that exceeds the upper limit value. In the viscous coupling 10a, the inner plates 24a are directly fixed to the shaft 20, while the inner plates 24b are fixed to the torque limiter 26 and thus connected to the shaft 20 indirectly.

[0033] The torque limiter 26 does not limit the transfer of torque until the relative rotation speed between the shaft 20 and the case body 12 reaches a predetermined value, i.e., until the relative rotation speed reaches R. Therefore, the damping force generated by the relative rotation between the inner plates 24a and 24b and the outer plates 22 is generated in proportion to the relative rotation speed until the relative rotation speed reaches the predetermined value. When the relative rotation speed between the shaft 20 and the case body 12 reaches the predetermined value, the torque limiter 26

limits the transfer of torque so that torque equal to or greater than the upper limit value will not be transferred to the shaft 20. As a result, when the relative rotation speed between the shaft 20 and the case body 12 increases to the predetermined value or higher, the amount of increase in the damping force of the viscous coupling 10a is kept to the amount of increase in the damping force that is generated between the inner plates 24a that are fixed to the shaft 20 and the outer plates 22. Accordingly, the riding comfort of the occupant can be improved by reducing the degree of increase in the damping force when the relative rotation speed between the shaft 20 and the case body 12 increases.

[0034] FIG. 4 is a graph showing the relationship between damping force generated by the viscous coupling 10a and relative rotation speed between the shaft 20 and the case body 12. In the drawing, the relative rotation speed in the positive direction indicates the speed on the expansion side of the suspension stroke, while the relative rotation speed in the negative direction indicates the speed on the compression side of the suspension stroke. As shown in the drawing, reducing the degree of increase in the damping force on the high side makes it is possible to avoid excessive damping force from being generated, which would reduce the riding comfort, when the relative rotation speed between the shaft 20 and the case body 12 is high.

[0035] FIG. 5 is a diagram of the structure of a viscous coupling 10b which is a modified example of the viscous coupling 10a according to the first example embodiment. The viscous coupling 10b has a plurality of torque limiters 26a, 26b, and 26c at portions along the axis of the shaft 20. Some of the plurality of inner plates 24 are provided on these torque limiters 26a, 26b, and 26c. The torque limiters 26a, 26b, and 26c are connected to the shaft 20 and function as damping force increase reducing means for reducing the degree of increase in the damping force when the relative rotation between the shaft 20 and the case body 12 reaches a predetermined state. The torque limiters 26a, 26b, and 26c serve to keep the torque transmitted to the shaft 20 to a predetermined upper limit value when a load equal to or greater than that upper limit value is placed on the suspension apparatus. Here, the upper limit values up to which torque can be transmitted from the torque limiters 26a, 26b, and 26c to the shaft 20 are all the same.

[0036] In the viscous coupling 10b, the inner plates 24c are directly fixed to the shaft 20. Also, the inner plates 24d are fixed to the torque limiter 26a, the inner plates 24e are fixed to the torque limiter 26b, and the inner plates 24f are fixed to the torque limiter 26c, so the inner plates 24d, 24e, and 24f are all connected to the shaft 20 indirectly. The viscous coupling 10b differs from the viscous coupling 10a shown in FIG. 2 in that it has the plurality of torque limiters 26a, 26b, and 26c, and the pitches between the inner plates 24, which are connected to the torque limiters, and the outer plates 22 are different.

[0037] In the viscous coupling 10b, the inner plates 24d, 24e, and 24f provided on the torque limiters 26a, 26b, and 26c, respectively, are connected to the shaft 20 side such that the distances between the outer plates 22 and the inner plates 24d, 24e, and 24f, are different for each of the torque limiters 26a, 26b, and 26c. More specifically, the distance (pitch) between the inner plates 24d fixed to the torque limiter 26a and the outer plates 22 is set to d2, the distance (pitch) between the inner plates 24e fixed to the torque limiter 26b and the outer plates 22 is set to d3, and the distance (pitch) between the inner plates 24f which are fixed to the torque limiter 26c and the outer plates 22 is set to d4. These pitches d2, d3, and d4 are all different. For example, the pitches may be such that d2 > d3 > d4. Incidentally, the pitch between the inner plates 24 fixed to the shaft 20 and the outer plates 22 is set to dl. The pitch dl may be different from the pitches d2, d3, and d4 or it may be the same as any one of those pitches d2, d3, or d4. In this viscous coupling 10b, dl is set equal to d3.

[0038] In the viscous coupling 10b, the pitches are set such that d2 > d3 = dl > d4 so the degree of increase in the damping force can be changed smoothly. As shown in Expression 1, the magnitude of the damping force is inversely proportionate to the distance (pitch) between plates so the damping force decreases as the pitch increases, and increases as the pitch decreases. The transfer torque upper limit values of the torque limiters 26a, 26b, and 26c are all the same so in a case in which the relative rotation speed increases, the generated torque of the torque limiter 26c having the smallest plate pitch reaches the upper limit value first and the transfer torque is then maintained at that

upper limit value. The generated torque of the torque limiter 26b reaches the upper limit value next and the transfer torque is then maintained at that upper limit value. The generated torque of the torque limiter 26a reaches the upper limit value last and the transfer torque is then maintained at that upper limit value. In this way, setting the pitches of the torque limiters 26 differently makes it possible to change the timing at which the transfer torque reaches the transfer torque upper limit value such that the torque can be limited by the torque limiter 26 in stages.

[0039] FIG. 6 is a graph showing the relationship between the damping force generated by the viscous coupling 10b and the relative rotation speed between the shaft 20 and the case body 12. In the drawing, the relative rotation speed in the positive direction indicates the speed on the expansion side of the suspension stroke, while the relative rotation speed in the negative direction indicates the speed on the compression side of the suspension stroke. As shown in the drawing, reducing the degree of increase in the damping force makes it is possible to avoid excessive damping force from being generated, which would reduce the ride comfort, when the relative rotation speed between the shaft 20 and the case body 12 is high. Also, having the plurality of torque limiters 26a, 26b, and 26c limit the torque in stages makes it possible to reduce the degree of increase in the damping force smoothly compared to the damping force characteristic shown in FIG. 4, which in turn improves the ride comfort for the occupant.

[0040] Incidentally, in the modified example described above, the upper limit values up to which torque can be transmitted the plurality of torque limiters 26a, 26b, and 26c are all the same. Alternatively, however, the upper limit values up to which torque can be transmitted by the plurality of torque limiters 26a, 26b, and 26c may all be set differently. In this case, the pitches between the inner plates 24 that are connected to the torque limiters 26 and the outer plates 22 can all be set the same so that the degree of increase in the damping force can be reduced in stages. Incidentally, the pitches between the inner plates 24 that are connected to the torque limiters 26 and the outer plates 22 may still be set differently even if the upper limit values up to which torque can be transmitted by the plurality of torque limiters 26 are all different.

[0041] Also, the torque limiters 26 which serve as torque transfer limiting means are connected to the outer peripheral surface of the shaft 20. Alternatively, however, those torque limiters 26 may be connected to the inner peripheral surface of the case body 12 and support the outer plates 22. In this case, the torque limiters 26 may work to limit at least some of the torque that is transmitted between the outer plates 22 and the case body 12 when the relative rotation speed between the shaft 20 and the case body 12 is equal to or greater than a predetermined value. In this case, the torque limiters 26 are connected to the case body 12 instead of the shaft 20, and thus support the outer plates 22.

[0042] FIG. 7 is a diagram of the structure of a viscous coupling 10c which is a modified example of the viscous coupling 10a according to the first example embodiment. The viscous coupling 10c has a one-way clutch 28 at a portion along the axis of the shaft 20. The one-way clutch 28 is connected to the shaft 20 and functions as damping force increase reducing means for reducing the degree of increase in the damping force when the relative rotation between the shaft 20 and the case body 12 reaches a predetermined state. The one-way clutch 28 serves to transmit torque to the shaft 20 in one rotational direction, and prevent torque from being transmitted to the shaft 20 in the other rotational direction by releasing a clutch. The one-way clutch 28 operates as torque transfer limiting means for disconnecting the shaft 20 from the inner plates 24h. Incidentally, in the other rotational direction, the clutch is set to release when a small amount of torque that is necessary to release the clutch (referred to as "clutch release torque") is applied.

[0043] In the viscous coupling 10c, the inner plates 24g are directly fixed to the shaft 20, while the inner plates 24h are fixed to the one-way clutch 28 so as to be indirectly connected to the shaft 20. For example, the one-way clutch 28 may also be provided to apply (i.e., connect) the clutch when there is relative rotation in the forward direction between the shaft 20 and the case body 12. In this case, when the shaft 20 and the case body 12 rotate relative to one another in the forward direction, damping force is generated by the relative rotation between the outer plates 22 and the inner plates 24g as well as between the outer plates 22 and the inner plates 24h. On the other hand, when

the shaft 20 and the case body 12 rotate relative to one another in the reverse direction, the inner plates 24h are disconnected from the shaft 20 after the clutch release torque has been reached such that damping force is generated by the relative rotation between the inner plates 24g and the outer plates 22. Accordingly, the degree of increase in the damping force during forward relative rotation can be made to be different than the degree of increase in the damping force during reverse relative rotation so the damping force of the suspension apparatus 1 can be set appropriately. Incidentally, whether to increase the degree of increase in the damping force on the expansion side or the compression side of the suspension stroke may be determined appropriately.

[0044] FIG. 8 is a graph showing the relationship between the damping force generated by the viscous coupling 10c and the relative rotation speed between the shaft 20 and the case body 12. In the drawing, the relative rotation speed in the positive direction indicates the speed on the expansion side of the suspension stroke, while the relative rotation speed in the negative direction indicates the speed on the compression side of the suspension stroke. When the clutch release torque (at which time the damping force is Fl) is reached on the compression side, the clutch of the one-way clutch 28 releases. As shown in the drawing, reducing the degree of increase in the damping force on the compression side makes it is possible to set the damping force characteristics appropriately for both expansion and compression of the suspension stroke, which improves the riding comfort for the occupant.

[0045] FIG. 9 is a diagram of the structure of a viscous coupling 1Od which is a modified example of the viscous coupling 10a according to the first example embodiment. The viscous coupling 1Od has a plurality of one-way clutches 28a, 28b, and 28c at portions along the axis of the shaft 20. The one-way clutches 28a, 28b, and 28c are connected to the shaft 20 and function as damping force increase reducing means for reducing the degree of increase in the damping force when the relative rotation between the shaft 20 and the case body 12 reaches a predetermined state. The one-way clutches 28a, 28b, and 28c serve to transmit torque to the shaft 20 in one rotational direction, and prevent torque from being transmitted to the shaft 20 in the other rotational direction by

releasing clutches. Incidentally, in the other rotational direction, the clutches are set to release when a small amount of torque that is necessary to release the clutches (referred to as "clutch release torque") is applied. In this example, the clutch release torques of the one-way clutches 28a, 28b, and 28c are all the same.

[0046] In the viscous coupling 1Od, the inner plates 24i are directly fixed to the shaft 20. Meanwhile, the inner plates 24j are fixed to the one-way clutch 28a, the inner plates 24k are fixed to the one-way clutch 28b, and the inner plates 241 are fixed to the one-way clutch 28c, such that they are connected to the shaft 20 indirectly. The viscous coupling 1Od differs from the viscous coupling 10c shown in FIG. 7 in that it has the plurality of one-way clutches 28a, 28b, and 28c, and the pitches between the inner plates 24, which are connected to the one-way clutches, and the outer plates 22 are different.

[0047] The inner plates 24j, 24k, and 241 provided on the one-way clutches 28a, 28b, and 28c, respectively, in the viscous coupling 1Od are connected to the shaft 20 side such that the distances between the outer plates 22 and the inner plates 24j, 24k, and 241, are different for each of the one-way clutches 28a, 28b, and 28c. More specifically, the distance (pitch) between the inner plates 24j fixed to the one-way clutch 28a and the outer plates 22 is set to d2, the distance (pitch) between the inner plates 24k fixed to the one-way clutch 28b and the outer plates 22 is set to d3, and the distance (pitch) between the inner plates 241 which are fixed to the one-way clutch 28c and the outer plates 22 is set to d4. These pitches d2, d3, and d4 are all different. For example, the pitches may be such that d2 > d3 > d4. Incidentally, the pitch between the inner plates 24i fixed to the shaft 20 and the outer plates 22 is set to dl. The pitch dl may be different from the pitches d2, d3, and d4 or it may be the same as any one of those pitches d2, d3, or d4. In this viscous coupling 1Od, dl is set equal to d3.

[0048] In the viscous coupling 1Od, the pitches are set such that d2 > d3 = dl > d4 so the degree of increase in the damping force can be changed smoothly. As shown in Expression 1, the magnitude of the damping force is inversely proportionate to the distance (pitch) between plates so the damping force decreases as the pitch increases, and increases as the pitch decreases. The clutch release torques of the one-way clutches 28a,

28b, and 28c are all the same so in a case in which the relative rotation speed increases in the negative direction, the generated torque of the one-way clutch 28c having the smallest plate pitch is the first to reach the clutch release torque, at which point the transfer torque of that one-way clutch 28c becomes zero due to the clutch being released. The generated torque of the one-way clutch 28b is the next to reach the clutch release torque, at which point the transfer torque of that one-way clutch 28b becomes zero. The generated torque of the one-way clutch 28a is the last to reach the clutch release torque, at which point the transfer torque of that one-way clutch 28a becomes zero. In this way, setting the pitches of the one-way clutches 28 differently makes it possible to change the timing at which the generated torque reaches the clutch release torque such that the clutches can be released in stages.

[0049] FIG. 10 is a graph showing the relationship between the damping force generated by the viscous coupling 1Od and the relative rotation speed between the shaft 20 and the case body 12. In the drawing, the relative rotation speed in the positive direction indicates the speed on the expansion side of the suspension stroke, while the relative rotation speed in the negative direction indicates the speed on the compression side of the suspension stroke. Releasing the clutches in stages makes it possible to reduce the degree of increase in the damping force during reverse relative rotation smoothly, thereby improving the riding comfort for the occupant, compared to the original vertical characteristic shown in FIG. 8.

[0050] Incidentally, in the modified example described above, the clutch release torques of the plurality of one-way clutches 28a, 28b, and 28c are all the same. Alternatively, however, the clutch release torques of the one-way clutches 28a, 28b, and 28c may all be set differently. In this case, the pitches between the inner plates 24 that are connected to the one-way clutches 28 and the outer plates 22 can all be set the same so that the degree of increase in the damping force can be reduced in stages. Incidentally, the pitches between the inner plates 24, which are connected to the one-way clutches 28, and the outer plates 22 may still be set differently even if the clutch release torques of those one-way clutches 28 are all different.

[0051] Also, the one-way clutches 28 which serve as torque transfer limiting means are connected to the outer peripheral surface of the shaft 20. Alternatively, however, those one-way clutches 28 may be connected to the inner peripheral surface of the case body 12 and support the outer plates 22. In this case, the one-way clutches 28 may disconnect the case body 12 from the outer plates 22 when the shaft 20 and the case body 12 rotate in one direction. In this case, the one-way clutches 28 are connected to the case body 12 instead of the shaft 20, and thus support the outer plates 22.

[0052] The modified examples of the first example embodiment described above illustrate structures in which the plates are arranged on the torque transfer limiting means so that the pitches between the inner plates 24 and the outer plates 22 are different in the viscous coupling 10b shown in FIG. 5 and the viscous coupling 1Od shown in FIG. 9. Referring to Expression 1, the generated torque also changes depending on the outer diameter of the inner plates 24. Therefore, the same effect can also be realized by changing the outer diameter of the inner plates 24 instead of changing the pitches. More specifically, in the viscous coupling 10b, by making the outer diameter of the inner plates 24d smaller than the outer diameter of the inner plates 24e, and making the outer diameter of the inner plates 24e smaller than the outer diameter of the inner plates 24f, the generated torque of the torque limiter 26c reaches the upper limit value first, the generated torque of the torque limiter 26c reaches the upper limit value next, and the generated torque of the torque limiter 26a reaches the upper limit value last. Incidentally, the distances (i.e., pitches) between the plates may all be the same. Similarly, in the viscous coupling 1Od, by making the outer diameter of the inner plates 24j smaller than the outer diameter of the inner plates 24k, and making the outer diameter of the inner plates 24k smaller than the outer diameter of the inner plates 241, the generated torque of the one-way clutch 28c reaches the clutch release torque first, the generated torque of the one-way clutch 28b reaches the clutch release torque next, and the generated torque of the one-way clutch 28a reaches the clutch release torque last. Incidentally, the distances (i.e., pitches) between the plates may all be the same. In this way, dividing the inner plates 24 into a plurality of pairs with different surface areas and

connecting the pairs of inner plates 24 to the torque transfer limiting means enables the torque transfer limit to be applied per pair of inner plates 24.

[0053] FIG. 11 is a view of the structure of a viscous coupling 1Oe according to a second example embodiment of the invention. The viscous coupling 1Oe includes a shaft 20 which is connected to a lower arm 4 and rotates as thelower arm 4 moves up and down, and a cylindrical case body 12 that is connected to a vehicle body 2 at an annular extended portion 14. Incidentally, the shaft 20 may be connected to the vehicle body 2 and the case body 12 may be connected to the lower arm 4, or the shaft 20 and the case body 12 may both be connected to other adjacent links of the link mechanism 7. The mounting structure of the viscous coupling 1Oe in the suspension apparatus 1 is the same as that shown in FIG. 1. A viscous fluid chamber 16 is formed between the outer peripheral surface of the shaft 20 and the inner peripheral surface of the case body 12, and is filled with viscous fluid such as silicone oil. A plurality of inner plates 24m are directly connected to the outer peripheral surface of the shaft 20, and a plurality of outer plates 22 are connected to the inner peripheral surface of the case body 12. The plurality of inner plates 24 and the plurality of outer plates 22 are arranged alternately with space in between them. In the viscous coupling 1Oe, the distance between adjacent inner plates 24m and the distance between adjacent outer plates 22 are the same.

[0054] The viscous coupling 1Oe includes damping force increase reducing means for reducing the degree of increase in damping force when the relative rotation between the shaft 20 and the case body 12 reaches a predetermined state. More specifically, the damping force increase reducing means has plate moving means for moving the inner plates 24m or the outer plates 22 in the direction in which the distances between one of the inner plates 24m and the two outer plates 22 that are adjacent to and sandwich that inner plate 24m become equal by relative rotation between the shaft 20 and the case body 12.

[0055] In the viscous coupling 1Oe, the shaft 20 includes a first shaft 20a which is connected to the lower arm 4 and is rotatably supported by a bearing 18a, and a second shaft 20b which is arranged on the same axis as the first shaft 20a. The second shaft

20b is retained by a support member, not shown, so as to maintain the same axial position as the first shaft 20a. The first shaft 20a is a fixed member that is supported by the bearing 18a and does not move in the axial direction. The second shaft 20b is a movable member that moves only in the axial direction. One end of the second shaft 20b engages with the first shaft 20a such that the second shaft 20b rotates together with the first shaft 20a. A wedge structure or a cam structure is provided at the portion where the first shaft 20a and the second shaft 20b are divided. With the wedge structure, a wedge shaped convex portion is formed on the end face of either the first shaft 20a or the second shaft 20b, and a corresponding wedge shaped concave portion is formed on the opposing end face of the other shaft 20a or 20b. Also, with the cam structure, a cam groove is formed in either the first shaft 20a or the second shaft 20b, and a corresponding cam shape such as a cam face is formed on the other shaft 20a or 20b. With the wedge structure or the cam structure, the second shaft 20b slides relative to the first shaft 20a such that it is displaced directly or indirectly in the axial direction. As a result, the second shaft 20b moves in the direction away from the first shaft 20a while maintaining contact with it.

[0056] The other end of the second shaft 20b is urged by a spring 30 in the direction so that it pushes against the first shaft 20a. The distances between the one inner plate 24m and the two outer plates 22 that are adjacent to and sandwich the one inner plate 24m are set differently according to the set load of the spring 30. The plurality of the inner plates 24m are joined to the second shaft 20b. In the example illustrated in the drawing, the pitch between the one inner plate 24m and the outer plate 22 next to it on the left is Sl, and the pitch between the one inner plate 24m and the outer plate 22 next to it on the right is S2 (Sl > S2).

[0057] In the viscous coupling 1Oe, the spring 30 forms the damping force increase reducing means for reducing the degree of increase in the damping force when the relative rotation between the shaft 20 and the case body 12 reaches a predetermined state. In this second example embodiment, the shaft 20 is formed by the first shaft 20a and the second shaft 20b. When torque of a predetermined value or more is applied to

the shaft 20, the force applied to the second shaft 20b in the axial direction overcomes the urging force of the spring 30 so the second shaft 20b moves in the direction away from the first shaft 20a. That is, the second shaft 20b and the spring 30 function as plate moving means for moving the inner plates 24 in the direction in which the distance (pitch) between one inner plate 24m and the two outer plates 22 that are adjacent to and sandwich the one inner plate 24m become equal.

[00S8] FIG. 12A shows the second shaft 20b pushed against the first shaft 20a by the spring 30. In this state, the force in the axial direction by the relative rotation between the shaft 20 and the case body 12 is less than the spring force. The one inner plate 24m is arranged between the two outer plates 22m and 22n. The thickness of the inner plate 24m is t, the distance (pitch) between the outer plate 22n and the inner plate 24m is Sl, the distance between the outer plate 22m and the inner plate 24m is S2, and the distance between the two outer plates 22m and 22n is S (= Sl + S2 + 1).

[0059] In the state shown in FIG. 12A, the pitch Sl between the outer plate 22n on the spring 30 side and the inner plate 24m is greater than the pitch S2 between the outer plate 22m on the first shaft side 20a and the inner plate 24m.

[0060] FIG. 12B shows the second shaft 20b moved in the direction away from the first shaft 20a by the generated torque. The relative rotation between the shaft 20 and the case body 12 generate torque, and when the force in the axial direction exceeds the urging force of the spring 30, the second shaft 20b moves in the direction that compresses the spring 30. This movement of the second shaft 20b reduces the difference between the distance Sl between the inner plate 24m and the outer plate 22n and the distance S2 between the inner plate 24m and the outer plate 22m. The second shaft 20b may also be able to move to the point at which the distances Sl and S2 are ultimately equal. Making the pitch Sl and the pitch S2 equal enables the degree of increase in the damping force generated in the viscous coupling 1Oe to be reduced to the greatest extent possible.

[0061] FIG. 13 shows the relationship between the pitch Sl and the degree of increase in the damping force. The degree of increase in the damping force shown in

FIG. 12 is when S is set equal to 5, t is set equal to 1, and the pitch Sl has been changed between 1 and 4. In this case, Sl + S2 = 4.

[0062] As shown in Expression 1, the generated torque is proportionate to 1 / (pitch). Therefore, the generated torque between the inner plate 24m and ,the outer plate 22n is proportionate to (1 / Sl), and the generated torque between the inner plate 24m and the outer plate 22m is proportionate to (1 / S2). In the drawing, the degree of increase in the damping force when Sl = S2 = 2 is 1 and Sl is changed between 1 and 4. The degree of increase in the damping force of (1 / Sl) is indicated by the black square plotted point, and the degree of increase in the damping force of (1 / S2) is indicated by the black triangular plotted point. The black circular plotted point indicates (1 / Sl + 1 /. S2).

[0063] As is evident from the simulation results, the degree of increase in the damping force indicated by (1 / Sl + 1 / S2) increases as the difference between the pitch Sl and the pitch S2 increases. When the pitch Sl and the pitch S2 is equal, the degree of increase in the damping force is the lowest. That is, the degree of increase in the damping force that is generated can be reduced by moving the inner plate 24m to reduce the difference between the pitch Sl and the pitch S2.

[0064] FIG. 14 shows an example in which the angle of the wedge structure is set according to the direction of rotation. FIG. 14A is a view showing a frame format of the force applied to an engaging surface 21a when the shaft 20 rotates in the forward direction. The cut angle of the engaging surface 21a is θl. Fl which extends perpendicular to the engaging surface 21a is broken down into F2 which extends in the axial direction and F3 which extends perpendicular to the axial direction. Meanwhile, FIG. 14B is a view showing a frame format of the force applied to an engaging surface 21b when the shaft 20 rotates in the reverse direction. The cut angle of the engaging surface 21b is θ2. F4 which extends perpendicular to the engaging surface 21b is broken down into F5 which extends in the axial direction and F6 which extends perpendicular to the axial direction.

[0065] As shown in the drawings, the cut angle θl of the engaging surface 21a

is greater than the cut angle θ2 of the engaging surface 21b so F2 during forward rotation is greater than F5 during reverse rotation. This is because the wedge structure shown is not symmetrical. Instead, the cut angles are different. Incidentally, the wedge structure is asymmetrical with reference to the rotational axis of the shaft 20. Setting the angles of the engaging surfaces 21 separately in this way enables different damping force characteristics to be created for forward rotation than for reverse rotation. Also, the desired damping force characteristics can be created by adjusting the cut angle.

[0066] FIG. 15 is a graph showing the relationship between damping force generated by the viscous coupling 1Oe and relative rotation speed between the shaft 20 and the case body 12. The damping force characteristic shown here is that of the shaft 20 (see FIG. 14) in which the cut angle of the wedge structure is asymmetrical. In the drawing, the relative rotation speed in the positive direction indicates the speed on the expansion side of the suspension stroke, while the relative rotation speed in the negative direction indicates the speed on the compression side of the suspension stroke.

[0067] In FIG. 15, the damping force Tl indicates the damping force when the force in the axial direction generated during forward rotation of the shaft 20 and the case body 12 matches the set load of the spring 30. The second shaft 20b is kept pressed against the first shaft 20a and thus does not move until the force in the axial direction reaches the set load of the spring 30. Once the force generated in the axial direction exceeds the spring force, the second shaft 20b moves in the direction away from the first shaft 20a. Accordingly, the difference in pitch between the two outer plates 22 that are adjacent to and sandwich the inner plate 24m decreases, so the degree of increase in the damping force decreases.

[0068] The damping force T2 indicates the damping force when the force in the axial direction generated during reverse rotation of the shaft 20 and the case body 12 matches the set load of the spring 30. The second shaft 20b is kept pressed against the first shaft 20a and thus does not move until the force in the axial direction reaches the set load of the spring 30. Once the force generated in the axial direction exceeds the spring force, the second shaft 20b moves in the direction away from the first shaft 20a.

Accordingly, the difference in pitch between the two outer plates 22 that are adjacent to and sandwich the inner plate 24m decreases, so the degree of increase in the damping force decreases.

[0069] The cut angle θl of the engaging surface 21a is greater than the cut angle θ2. of the engaging surface 21b so the degree of increase in the damping force starts to decrease at a lower relative rotation speed during forward rotation than during reverse rotation. Adjusting the cut angle θ in this way enables the timing at which the degree of increase in the damping force starts to be reduced to be set appropriately. Also, the degree of increase can also be adjusted. Furthermore, forming the wedge shape asymmetrical enables the timing at which the degree of increase in the damping force is reduced to be changed for expansion and compression of the suspension stroke. As a result, excessive damping force can be suppressed, which prevents the riding comfort from decreasing, when the relative rotation speed between the shaft 20 and the case body 12 is high.

[0070] FIGS. 16 and 17 are diagrams showing examples of the connecting structure of the first shaft 20a and the second shaft 20b. FIG 16A is a top transparent view of the first shaft 20a and the second shaft 20b, and FIG. 16B is a perspective transparent view of the first shaft 20a and the second shaft 20b. In this example, the first shaft 20a is formed as an inner cylinder member, and the second shaft 20b is formed as an outer cylinder member, which connect together by a cam structure. Pin holes 40a and 40b are formed in the radial direction through the second shaft 20b, while a cam groove 42a is formed on the upper surface side of the first shaft 20a and a cam groove 42b is formed on the lower surface side of the first shaft 20a. The cam grooves 42 may also extend through the cylindrical member and be formed symmetrical as shown in the drawing, but they may also be formed asymmetrical to create different damping force characteristics for forward rotation than for reverse rotation. Incidentally, the cam groove 42a and the cam groove 42b are formed symmetrical with respect to a point on the surface perpendicular to the axial direction which includes an axial center point. FIG. 16C is a diagram of a pin 44, and FIG. 16D is a diagram showing the first shaft 20a and

the second shaft 20b engaged by having the pin 44 inserted through the pin hole 40a, the cam groove 42a, the cam groove 42b, and the pin hole 40b.

[0071] FIG. 17A is a view showing the second shaft 20b in FIG. 16 being pushed against the first shaft 20a by the spring 30. FIG. 17B is a view showing the second shaft 20b after having moved in the direction away from the first shaft 20a by the force in the axial direction generated by the relative rotation between the shaft 20 and the case body 12. As shown in the drawings, when the spring force and the axial force balance out, the pin 44 slides in the cam grooves 42 such that the second shaft 20b moves in the axial direction against the spring force, which enables the degree of increase in the damping force to be reduced.

[0072] FIGS. 18 A and 18B are diagrams showing another example of the connecting structure of the first shaft 20a and the second shaft 20b. FIG. 18A is a perspective view of the second shaft 20b and FIG. 18B is a perspective view of the first shaft 20a. In this example, a cam structure is formed on an engaging surface 48 of the second shaft 20, and a pair of rollers 46a and 46b provided on the first shaft 20a engage with the engaging surface 48. The diameters of the first shaft 20a and the second shaft 20b are the same. Incidentally, when a position in the axial direction is referred to as an axial position, the engaging surface 48 of the second shaft 20b is in position symmetrical with respect to a point on the surface that is perpendicular to the axial direction which includes an axial center point of the axial position. Accordingly, the pair of rollers 46a and 46b of the first shaft 20a can engages with the engaging surface 48 on the same axis as the second shaft 20b.

[0073] The rollers 46 engage with the end surface at the most recessed axial position of the engaging surface 48 while the second shaft 20b is being pushed against the first shaft 20a by the spring 30. As the rollers 46 move along the slope of the engaging surface 48 by the force in the axial direction generated by the relative rotation between the shaft 20 and the case body 12, the second shaft 20b moves in the direction away from the first shaft 20a. As a result, the degree of increase in the damping force can be reduced. Incidentally, in order to prevent the shafts from becoming misaligned,

cylindrical holes having the same axial center may be formed in the first shaft 20a and the second shaft 20b and a shaft may be inserted through the holes. Also, a cam structure may be formed on the engaging surface of the first shaft 20a and a pair of rollers may be provided on the second shaft 20b.

[0074] FIGS. 19 A and 19B are diagrams showing yet another example of the connecting structure of the first shaft 20a and the second shaft 20b. FIG. 19A is a perspective view of the second shaft 20b and FIG. 19B is a perspective view of the first shaft 20a. In this example, a concave wedge structure is formed in an engaging surface 50 of the second shaft 20b, and a convex wedge structure is formed on an engaging surface 52 of the first shaft 20a. This wedge structure is formed of a slanted surface and a flat surface. The concave engaging surface 50 and the convex engaging surface 52 are preferably formed such that a convex portion 56 of the convex engaging surface 52 fits into a concave portion 54 of the concave engaging surface 50. Incidentally, a concave wedge structure may be formed in the engaging surface 52 of the first shaft 20a, and a convex wedge structure may be formed in the engaging surface 50 of the second shaft 20b instead.

[0075] The concave portion 54 of the engaging surface 50 engages with the convex portion 56 of the engaging surface 52 while the second shaft 20b is pushed against the first shaft 20a by the spring 30. As the slanted surface of the convex portion 56 moves along the slope of the concave portion 54 by the force in the axial direction generated by the relative rotation between the shaft 20 and the case body 12, the second shaft 20b moves in the direction away from the first shaft 20a. As a result, the degree of increase in the damping force can be reduced. Incidentally, in order to prevent the shafts from becoming misaligned, cylindrical holes having the same axial center may be formed in the first shaft 20a and the second shaft 20b and a shaft may be inserted through the holes.

[0076] In the second example embodiment, the shaft 20 is divided into two and the plate moving means is formed on the shaft side. Alternatively, however, the case body 12 may be divided into two and the plate moving means may be formed on the case

body side. In this case, the divided portion of the case body 12 is made to serve as the plate moving means by dividing the case body 12 instead of the shaft 20 and having the spring 30 urge the case body 12 instead of the shaft 20.

[0077] While the invention has been described with reference to example embodiments thereof, it is to be understood that the invention is not limited to the described embodiments or constructions. To the contrary, the invention is intended to cover various modifications and equivalent arrangements. In addition, while the various elements of the disclosed invention are shown in various example combinations and configurations, other combinations and configurations, including more, less or only a single element, are also within the scope of the appended claims.