Vehicle equipped with a suspension using a Watt type four-bar link

Abstract

A saddle-ride type vehicle (1; 107; 207) according to the present invention includes rear drive wheels (5; 105; 205) and front steering wheels (7; 107; 207). The front steering wheels (7; 107; 207X, 207Y) are connected to rotatable arms (9; 109; 209X, 209Y) that are provided to rotate about a steering axis (AA). Wheel supports (37; 137) are connected to the rotatable arms (9; 109; 209) via suspensions (17; 117; 217X, 217Y) that include shock absorbers (22; 122). The suspensions (17; 117) include Watt-type four-bar links.

Description

Technical Field

[0001] The present invention relates to improvements in saddle-type vehicles having two, three or four wheels. More specifically, the present invention relates to improvements in the front suspension of an inclined saddle-type vehicle having one or two rear drive wheels and one or two front steering wheels, such as a two-wheeled or three-wheeled motorcycle, a two-wheeled or three-wheeled scooter, or a quad bike.

Background Art

[0002] Two-wheeled, three-wheeled or four-wheeled saddle-type vehicles typically have one or two rear drive wheels connected to the vehicle frame by their rear suspensions and one or two front steering wheels connected to handlebars and equipped with respective front suspensions. The suspension connects the sprung mass of the vehicle to the unsprung mass and allows relative movement between the sprung mass and the unsprung mass. The suspension is usually a shock-absorbing suspension, equipped with respective shock absorbers, and in turn with an elastic member, typically a spring, and a brake or damper in turn. The suspension further has a mechanical member that connects the sprung mass to the unsprung mass in a relatively movable state between the sprung mass and the unsprung mass so that the impact transmitted to the wheels by the roughness or unevenness of the ground is not transmitted to the vehicle frame or is transmitted in a damped form.

[0003] In saddle - type vehicles such as motorcycles, scooters, and quad bikes, the suspension of the front steering wheel enables relative movement between, on the one hand, the handlebar and the steering column, and on the other hand, between the front steering wheel or the wheel. Some suspensions of the front steering wheel of saddle - type vehicles use telescopic forks having members that slide inside each other to enable the relative movement. The telescopic forks use cylindrical pairs having members that slide relative to each other, and these forks have problems specific to this type of relative movement. On the other hand, some other types of suspensions use rotary pairs having members that rotate relative to each other. In this case, a typical four - bar linkage is interposed between the sprung mass and the unsprung mass and is deformed to enable spring movement between the sprung mass (the vehicle frame and the members connected thereto) and the unsprung mass (the wheel and the brake). The rotary pair is represented by a hinge that connects the components of the four - bar linkage to each other.

[0004] A suspension using a kinematic mechanism having a rotary pair for connection between the sprung mass and the unsprung mass has the advantages of the rotary pair over the translational pair and the cylindrical pair, but does not allow linear movement of the axis of the front steering wheel. In fact, during spring movement, for example when the suspension compresses and extends due to road irregularities or during braking due to dynamic forces generated in the frame and transmitted to the wheel via the suspension, the axis of the wheel undergoes non - linear movement that results in lateral frictional movement of the wheel on the ground, which can cause problems such as bounce.

[0005] Therefore, it is beneficial to provide a front - steering - wheel suspension for a saddle - type vehicle having two or more wheels that can combine the advantages of a telescopic fork suspension and a suspension using a kinematic mechanism having a rotary pair. SUMMARY OF THE INVENTION

[0006] According to one aspect, the straddle-type vehicle disclosed herein includes at least one rear drive wheel and at least one first front steering wheel, and the first front steering wheel is connected to a rotatable arm having a rotational movement about a steering axis. The wheel support is connected to the rotatable arm via a suspension, and the suspension connects the wheel support and the wheel provided thereon to the rotatable arm. The suspension has a shock absorber. The wheel support supports the front steering wheel and defines the rotation axis of the wheel. For example, the wheel mounting shaft may be fixed to the wheel support, or the wheel support may have a support member that supports the wheel axis. Characteristically, the suspension includes a Watt-type four-bar link, which is also known as a Watt mechanism.

[0007] In an advantageous embodiment, the wheel support is constrained by a connecting rod such that the rotation axis of the wheel is parallel to the axes of the first crank first hinge and the second hinge, and the axes of the first hinge and the second hinge of the second crank.

[0008] In this case, the components of the Watt-type four-bar link move on each plane orthogonal to the rotation axis of the first steering wheel. When these elements are schematized as one-dimensional elements, they will exist on a plane orthogonal to the rotation axis of the front steering wheel.

[0009] In this case, the wheel support may be rigidly connected to the connecting rod and form a housing for the support bearing of the front steering wheel.

[0010] In order to obtain a particularly compact configuration of the suspension, in some advantageous embodiments, the first hinge of the first crank and the second hinge of the second crank include the rotation axis of the front steering wheel and are provided on one side of a plane leading to an arm rotatable through the restraint point of the shock absorber. Conversely, the second hinge of the first crank and the first hinge of the second crank are on the other side of the said plane. In fact, the above-mentioned plane divides the space into a first half-space including the first hinge of the first crank and the second hinge of the second crank, and a second half-space including the second hinge of the first crank and the first hinge of the second crank.

[0011] In fact, with respect to the forward direction of the vehicle, the first hinge of the first crank and the second hinge of the second crank are in a rearward position, while the second hinge of the first crank and the first hinge of the second crank are in a forward position.

[0012] Alternatively, with respect to the forward direction of the vehicle, the first hinge of the first crank and the second hinge of the second crank can be arranged in a forward position, and the second hinge of the first crank and the first hinge of the second crank can be arranged in a rearward position.

[0013] In other embodiments, the first hinge and the second hinge of the first crank, and the first hinge and the second hinge of the second crank are substantially parallel to each other and have an axis orthogonal to the plane including the rotation axis of the front steering wheel. In fact, each element of the Watt's four-bar linkage in this case moves on respective planes parallel to the rotation axis of the front steering wheel, and the moving planes of the components of the Watt's four-bar linkage are parallel to each other.

[0014] In order to obtain a particularly compact configuration of the Watt's four-bar linkage, in some embodiments, the first hinge of the first crank and the second hinge of the second crank are arranged on one side of a plane orthogonal to the rotation axis of the front steering wheel and leading to an arm rotatable through the restraint point of the shock absorber, and the second hinge of the first crank and the first hinge of the second crank can be arranged on the other side of the said plane.

[0015] In practice, the first hinge of the first crank and the second hinge of the second crank are closer to the front steering wheel, while the second hinge of the first crank and the first hinge of the second crank are at a greater distance from the front steering wheel.

[0016] In some embodiments, the wheel support is hingedly coupled to the connecting rod about an axis substantially parallel to the axes of the first and second hinges of the first and second cranks. The arrangement of the hinges of the four-bar linkage with respect to the plane passing through the position of the wheel and the hinge axis between the wheel support and the connecting rod places the first hinge of the first crank and the second hinge of the second crank on one side of this plane, for example, in the half-space where the front steering wheel defined by this plane is located, and conversely, places the second hinge of the first crank and the first hinge of the second crank on the other side of the plane, i.e., in the half-space that does not include the front steering wheel defined by the plane.

[0017] In a practical embodiment, the wheel support supports the wheel in a position such that the axis of rotation of the wheel is orthogonal to the axis that hingedly couples the wheel support to the connecting rod.

[0018] The vehicle may have a disc brake for the front steering wheel, comprising a disc and a caliper integral with the front steering wheel, and the caliper is rigidly connected to the wheel support. In other examples, the caliper is rigidly connected to a support member rotatably provided with respect to the connecting rod and the wheel support.

[0019] According to another aspect, a saddle-riding type vehicle includes at least one rear drive wheel and at least one first front steering wheel, wherein the front steering wheel is connected by a suspension to a rotatable arm having a rotational movement about a steering axis. A wheel support that supports the front steering wheel and defines the axis of rotation of the wheel is connected to the rotatable arm via a suspension. The suspension has a four-bar link including a first crank hinged to an arm rotatable at a first end and hinged to a connecting rod at a second end, and a second crank hinged to an arm rotatable at a first end and hinged to the connecting rod at a second end. The wheel support is constrained at a constraint point of the connecting rod, and the four-bar link is configured such that the constraint point moves along a substantially linear locus during deformation of the four-bar link as a result of spring movement of the suspension. A saddle-riding type vehicle is provided. The present invention will be better understood by following the description and the accompanying drawings showing non-limiting examples of embodiments of the present invention.

Brief Description of the Drawings

[0020]

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Mode for Carrying Out the Invention

[0021] Figs. 1, 2, 3, 4A, 4B, 4C, 4D, 5 and 6 are views showing a Watt four-link type suspension according to the first embodiment, that is, a two-wheeled vehicle provided with a Watt mechanism.

[0022] In Figs. 1, 2 and 3, the vehicle 1 is schematically illustrated. In these drawings, the parts of the vehicle that are not necessary for understanding the structure and operation of the suspension have been removed or omitted. The vehicle 1 includes a frame 3, a rear drive wheel 5, and a front steering wheel 7. The wheels 5 and 7 are connected to the frame 3 by a suspension. The rear suspension that connects the drive wheel 5 to the frame is not shown and can be configured in any known manner. Hereinafter, the front suspension that connects the front steering wheel 7 to the frame 3 will be described in detail.

[0023] The front steering wheel 7 is connected to a rotatable arm 9. The arm 9 is firmly connected to a steering column 11 rotatably accommodated in a steering tube 13 and is steered by a handlebar 15 to rotate about a steering axis A-A. By rotating the rotatable arm 9 about the axis A-A, it becomes possible to steer the vehicle 1.

[0024] The front steering wheel 7 is connected to an arm 9 that is rotatable by a suspension indicated as a whole by reference numeral 17. By the suspension 17, a frame 3 including a steering tube 13, a steering column 11, a handlebar 15, and the rotatable arm 9 can perform a spring movement with respect to the front steering wheel 7. The suspension 17 is a shock absorber type suspension and includes a movement mechanism for connecting the front steering wheel 7 and the rotatable arm 9, and a shock absorber. The shock absorber includes an elastic element and a brake or a damper in sequence. In the illustrated embodiment, the shock absorber is indicated by reference numeral 22, the elastic element is indicated by reference numeral 21, and the brake or the damper is indicated by reference numeral 19. The brake or the damper 19 is in the form of a coil spring and is coaxially accommodated inside the elastic element 21.

[0025] The front steering wheel 7 is supported by the suspension 17 so as to rotate about its rotation axis B-B.

[0026] Reference numeral 23 indicates a disk of the front brake of the vehicle 1. The brake 23 further includes a caliper 25 that can be supported by the suspension 17 in a manner described later.

[0027] The suspension 17 includes components connected to each other by a rotary pair, that is, components that move relative to each other according to one degree of freedom represented by a rotational movement about each hinge axis. Therefore, the suspension does not have elements with mutual translational movement.

[0028] Advantageously, the movement mechanism having a rotary pair connecting the front steering wheel 7 to the rotatable arm 9 may have a Watt type four-bar link, that is, a Watt mechanism. The Watt type four-bar link has, in addition to the rotatable arm 9, a first crank 31 and a second crank 33. The two cranks 31 and 33 are hinge-connected to the rotatable arm 9 and a connecting rod 35 that is part of the Watt type four-bar link.

[0029] More specifically, the first crank 31 is hinge-connected to the connecting rod 35 by a second hinge 31B on an arm 9 rotatable by a first hinge 31A. In contrast, the second crank 33 is hinge-coupled to the connecting rod 35 by a second hinge 33B on an arm 9 rotatable by a first hinge 33A, respectively. The hinges 31A, 31B, 33A, and 33B form a rotational pair of a Watt four-bar linkage.

[0030] The cranks 31 and 33 are approximately the same length and shorter than the connecting rod 35. The lengths of the components 31, 33, and 35 are the distances between the axes of the respective hinges. Thus, for example, the length of the first crank 31 is given by the axial distance between the hinges 31A and 31B, the length of the second crank 33 is given by the axial distance between the hinges 33A and 33B, and the length of the connecting rod 35 is given by the axial distance between the hinges 31B and 33B.

[0031] The wheel support 37 indicated by reference numeral 37 is constrained at a constrained point of the connecting rod 35 that is substantially equidistant from the axes between the hinges 31B and 33B. In practice, the wheel support 37 defines the rotational axis B-B of the wheel and holds the axis perpendicular to the connecting rod 35 at an intermediate position between the axes of the hinges 31B and 33B. In the embodiments of FIGS. 1 to 6, the calipers 25 of the disc brakes 23 and 25 are firmly fixed to the wheel support 37, as particularly shown in the exploded view of FIG. 4C.

[0032] In the embodiments of FIGS. 1 to 6, the shock absorber 22 is also hinge-connected to the connecting rod 35. More specifically, the shock absorber 22 is hinge-connected to the connecting rod 35 at one end 22B and to the rotatable arm 9 at the other end 22A. The constraint between one side of the shock absorber 22 and the rotatable arm 9 and the constraint between the other side of the shock absorber 22 and the connecting rod 35 can be formed by ball hinges.

[0033] As can be easily understood from FIGS. 4A and 4B showing the extended position and the compressed position of the suspension 17 and the shock absorber 22, the spring movement of the front steering wheel 7 is caused by the deformation movement of the Watt type four-bar link. More specifically, it is executed by the pivot movement of the cranks 31 and 33 around the axes 31A and 33A which are hinge-connected to the rotatable arms 9, the rotational translation movement of the connecting rod 35, and the extension and compression of the shock absorber 22 according to this pivot movement.

[0034] As a result of the characteristics of the Watt type four-bar link, within at least a certain angle of the pivot movement of the cranks 31 and 33, the center of the connecting rod 35 on the rotation axis B-B of the front steering wheel 7 moves along a substantially straight trajectory. The elements constituting the Watt type four-bar link are attached so that the trajectory of the rotation axis B-B of the front steering wheel 7 is substantially linear throughout the entire stroke from the maximum extended position to the maximum compressed position of the suspension 17.

[0035] This feature of the suspension configured in this way can be more easily understood from the schematic diagram of FIG. 4D. In this drawing, the suspension, the rotatable arm 9, and the front steering wheel 7 are schematically represented. FIG. 4D shows three different positions of the suspension, namely the intermediate position (a), the fully compressed position (b), and the fully extended position (c). As a result of the characteristics of the Watt type four-bar link 9, 31, 33 and 35, the center of the front steering wheel 7 which coincides with the axis of its rotation axis B-B moves along a substantially straight trajectory T-T.

[0036] In this specification, "substantially straight", "substantially linear" or "approximately linear" means a trajectory that differs by less than 2 mm, preferably less than 1 mm, from a completely straight trajectory at any position taken by the Watt type four-bar link during the normal use of the vehicle, i.e., within the operating range of the suspension.

[0037] Returning to the description of the structural features of the first embodiment, particularly as shown in FIGS. 4A and 4B, the first hinge 31A for connecting the first crank 31 to the rotatable arm 9 and the second hinge 33B for connecting the second crank 33 to the connecting rod 35 include the rotation axis B-B of the front steering wheel 7 and are disposed on one side of a plane P-P that is substantially parallel to the trajectory of the rotation axis B-B in the spring movement. Further, the second hinge 31B for connecting the first crank 31 to the connecting rod 35 and the first hinge 33A for connecting the second crank 33 to the rotatable arm 9 are disposed on the other side of the plane P-P. In practice, the hinges 31A and 33B are in a rear position relative to the hinges 31B and 33A (relative to the normal forward direction during forward travel of the vehicle 1). According to yet another definition, the hinges 31A and 33B include the rotation axis B-B of the front steering wheel 7 and are located on one side (more precisely, behind) of a plane that includes the upper connection point 22A of the shock absorber 22 and passes through the rotatable arm 9, i.e., a plane that includes the rotation axis B-B of the front steering wheel 7 and in which this axis translates during spring movement.

[0038] This particular arrangement of the components forming the Watt type four-bar link makes it possible to create a compact arrangement suitable for forming a kinematic mechanism for connecting the unsprung mass and the sprung mass in the suspension of the front steering wheel of a straddle-type vehicle 1 such as a motorcycle or a scooter.

[0039] The embodiments described with reference to FIGS. 1 to 6 are subject to various modifications, some of which will be described below with reference to FIGS. 7 to 20.

[0040] Figures 7 and 8 are side and axonometric views of the front steering wheel 7 with the associated suspension 17 and rotatable arm 9, in an embodiment where the restraint point of the shock absorber 22 with respect to the movement mechanism of the suspension 17 in particular is different from the embodiments described above. More specifically, the shock absorber 22 with the brake or damper 19 and spring 21 is still constrained to the connecting rod 35, but the area is upward instead of downward, i.e., it is arranged on the side facing the first crank 31 of the connecting rod 35, whereas in FIGS. 1 to 6, the restraint portion 22B was arranged on the side facing the second crank 33 of the connecting rod 35. The remaining parts denoted by the same reference numerals as those used in FIGS. 1 to 6 are substantially equivalent to those described above.

[0041] Figures 9 and 10 show yet another embodiment similar to FIGS. 7 and 8, and the same or equivalent parts are labeled with the same reference numerals as those used in FIGS. 1 to 8. The configuration of FIGS. 9 and 10 is substantially symmetric to that of FIGS. 7 and 8. In FIGS. 7 and 8 (similarly to FIGS. 1 to 6), the upper crank 31 is oriented such that the hinge 31A for connecting to the rotatable arm 9 is located at the end facing the rear of the crank 31, and the hinge 31B for connecting to the connecting rod 35 is located at the end facing the front of the crank 31, and the lower crank 33 is oriented in the opposite direction, i.e., the hinge 33A for connecting to the rotatable arm 9 is located at the end facing the front, and the hinge 33B for connecting to the connecting rod 35 is located at the end facing the rear. In the configuration of FIGS. 9 and 10, the arrangement is reversed, and the upper crank 31 has the first hinge 31A at the end facing the front and the second hinge 31B at the end facing the rear. In the lower crank 33, the end of the hinge 33B faces the front, and the end of the hinge 33A faces the rear.

[0042] Figures 11 and 12 show side and axonometric views of yet another embodiment similar to the embodiments of Figures 7 and 8. The same reference numerals indicate parts that are identical or equivalent to those described above. The main difference between the embodiments of Figures 1 to 10 and the embodiments of Figures 11 and 12 is that in this embodiment, the lower end of the shock absorber 19 is constrained at a point 22B on the axis of rotation B-B of the front steering wheel 7. The resulting configuration is particularly compact. The suspension 17 with the shock absorber 22 and the pivot arm 9 can be closed with a casing 41.

[0043] Figure 15 is a side view of yet another embodiment, in which the same reference numerals indicate parts that are identical or equivalent to those of the embodiments previously described. The embodiment of Figure 15 is substantially the same as the embodiments of Figures 1 to 6, and the main difference is that the shock absorber 22 is connected at its bottom by a hinge 22B to a crank 33 instead of a connecting rod 35.

[0044] Figure 16 shows an embodiment substantially the same as the embodiments of Figures 1 to 6, differing in that the shock absorber 22 is connected at its bottom by a hinge 22B to the position of the axis of rotation B-B of the front steering wheel 7.

[0045] As previously explained, and particularly as apparent from Figure 4C, the calipers 25 of the disc brakes 23 and 25 can be firmly constrained to the connecting rod 35. In this embodiment, the caliper 25 rotates integrally with the connecting rod 35. This occurs particularly during braking. Depending on the position of the caliper 25 relative to the axis of rotation B-B of the front steering wheel 7, this movement can have a non-negligible pro-dive or anti-dive effect due to the fact that the instantaneous center of rotation of the connecting rod approaches the point of contact of the front steering wheel 7 with the ground. This instantaneous center of rotation is determined by the intersection of the extensions of two straight line segments connecting the hinges 31A and 31B and 33A and 33B to each other. This pro-dive or anti-dive effect may not be desirable.

[0046] In order to prevent or reduce the pro-dive or anti-dive effect of the suspension during braking, in some embodiments, the caliper 25 can be firmly connected to a member that is coaxially attached to the front steering wheel 7, and thus the connecting rod 35, but is not integral therewith and has an instantaneous rotation center at a more distant position.

[0047] An embodiment of this type is shown in FIGS. 17, 18, and 19. In these drawings, the same reference numerals indicate parts that are the same as or equivalent to those of the embodiments already described with reference to FIGS. 1 to 6, and the description thereof will be omitted here. The support member of the disc brake caliper 25 can be seen particularly in the exploded perspective view of FIG. 19. The support member is indicated by reference numeral 45. This may have a hole for accommodating the axle 7A of the front steering wheel 7 or a bearing 47 into which an extension of this axle is inserted. The connecting rod 35 of the Watt's four-bar link is also loosely supported on the axle 7A. The member 45 can be firmly connected to one end 22B of the shock absorber 22. Due to the interlock restraint between the shock absorber 22 and the member 45, the caliper 25 is held against rotation about the axis B-B during braking. Since the connecting rod 35 and the support member 45 of the caliper 25 rotate freely relative to each other, the connecting rod 35 and the support member 45 can rotate freely relative to each other about the axis of rotation B-B. In this case, since the member to which the caliper is firmly connected is the shock absorber 22 whose instantaneous rotation center is located at a large distance close to infinity, the pro-dive effect or the anti-dive effect is very limited or negligible.

[0048] The above-described suspension can be used in a saddle-riding type vehicle in the form of a motorcycle as schematically shown in FIGS. 1, 2, and 3, but it can also be used in other types of saddle-riding type vehicles. FIG. 20 shows a scooter 1 as an example, and this scooter 1 is provided with a Watt's four-bar link suspension for the front steering wheel 7 configured as described above.

[0049] In all of the embodiments shown in FIGS. 1 to 20, the hinges connecting the cranks 31 and 33 to the connecting rods 35 and the rotatable arm 9 are arranged such that their hinge axes are parallel to each other and parallel to the rotation axis B-B of the front steering wheel 7. In this way, substantially, the Watt's four-bar linkage formed by the components 9, 31, 33, and 35 is arranged on a plane orthogonal to the rotation axis B-B of the front steering wheel 7. Therefore, the rotation axes of the rotation pairs of the Watt's four-bar linkage are oriented in the right-left direction, i.e., in the lateral direction with respect to the central plane of the vehicle 1.

[0050] This configuration results in a particularly efficient suspension, but it is not the only possible embodiment of a four-bar linkage suspension that can obtain a substantially linear trajectory of the rotation axis of the front steering wheel 7 during the spring movement of the wheel using a kinematic mechanism that has only rotation pairs and no translation pairs or cylindrical pairs, i.e., lacks members having relative translational motion.

[0051] In other embodiments, the hinges connecting the members forming the Watt's four-bar linkage can be arranged such that their axes are parallel to each other and can be oriented at 90° with respect to the rotation axis B-B of the front-wheel steering wheel 7, i.e., in a direction orthogonal to the plane containing the rotation axis B-B of the front-wheel steering wheel 7. In other words, the hinge axes of the rotation pairs connecting the components of the four-bar linkage are oriented to be located on a vertical plane parallel to the central plane of the vehicle, i.e., a vertical plane extending in the traveling direction of the vehicle.

[0052] Embodiments of this type are shown in FIGS. 21 to 25. Components corresponding to those already described with reference to the previous figures are denoted by the same reference numerals increased by "100". FIGS. 21 to 25 show only the front steering wheel 107 with each suspension 117 and the rotatable arm 109, and do not show a vehicle that can be the same vehicle as the vehicle denoted by reference numeral 1 in FIG. 1 or FIG. 20.

[0053] Figures 21, 22, and 23 show an assembly with a front steering wheel 107, a rotatable arm 109 having its steering axis A - A, and a suspension 117 with all its components. Figure 24 shows the same assembly with the rotatable arm 109 removed, and Figure 25 shows the assembly with the Watt - type four - bar link also removed to show the wheel support, the wheel, a shock absorber 122 having a brake or damper 119, and a spring 121.

[0054] More specifically, this embodiment is provided with a suspension 117 having a Watt - type four - bar link with a rotatable arm 109, a first crank 131, a second crank 133, and a connecting rod 135. In fact, each crank 131 and 133 is a double crank. The two members of each crank are located outside the centrally - located connecting rod 135.

[0055] The crank 131 is hinged to the rotatable arm 109 by a first hinge 131A and to the connecting rod 135 by a second hinge 131B. Similarly, the crank 133 is hinged to the rotatable arm 109 by a first hinge 133A and to the connecting rod 135 by a second hinge 133B. The axes of the hinges 131A, 131B, 133A, and 133B are parallel to each other and are oriented at 90° with respect to the rotation axis B - B of the front steering wheel 107. The orientation direction of the hinge axes of the Watt - type four - bar link is indicated by the reference C - C in this embodiment, particularly shown in Figure 23. In fact, the hinge axes of the four - bar link are orthogonal to the plane containing the rotation axis B - B of the front steering wheel 107 and are oriented substantially parallel to the direction of the spring movement.

[0056] Cranks 131 and 133 have substantially the same length. Connecting rod 135 is hinged to wheel support 137 at the central portion between the axes of hinges 131B and 133B. Wheel support 137 is hinged to connecting rod 135 about a hinge axis directed in the C-C direction, i.e., an axis parallel to the axis of the hinge of the Watt's four-bar linkage. The hinge axis connecting wheel support 137 and connecting rod 135 intersects and is orthogonal to the rotation axis B-B of the front steering wheel.

[0057] In the illustrated embodiment, wheel support 137 has a fork shape surrounding connecting rod 135, particularly as shown in FIGS. 24 and 25. Wheel support 137 may also have a restraint member for connecting to shock absorber 122. In the embodiment shown in FIGS. 21 to 25, the restraint between wheel support 137 and shock absorber 122 is an interlock connector.

[0058] Wheel support 137 forms a rotational seat for the axle of front steering wheel 107 (not shown).

[0059] Particularly as shown in FIG. 21, hinges 131B and 133A are arranged on one side of a plane that is orthogonal to the rotation axis B-B of front steering wheel 107 and substantially parallel to the spring movement direction of suspension 117, and hinges 131A and 133B are arranged on the other side. Viewed differently, hinges 131B and 133A are on one side of a plane orthogonal to the rotation axis B-B of front steering wheel 107, and hinges 131A and 133B are on the other side of the plane. The reference plane can be, for example, a plane passing through hinge 122A connecting shock absorber 122 and arm 109 in addition to being orthogonal to the rotation axis B-B of front steering wheel 7, or a plane orthogonal to the rotation axis B-B of the front steering wheel and including the hinge axis (directed in the C-C direction) between connecting rod 135 and wheel support 137.

[0060] During the spring movement of the front steering wheel 107, the four-bar link of the suspension 117 is deformed by the pivotal movement of the cranks 131 and 133 with respect to the rotatable arm 109 and the associated pivotal movement of the connecting rod 135 about the hinge axis for connection to the wheel support 137. The configuration of the Watt-type four-bar link formed by the components 109, 131, 133, and 135 is also such that the hinge between the connecting rod 135 and the wheel support 137, and thus the hinge axis C-C, moves along a substantially straight trajectory throughout the movable range of the spring movement. Since the wheel support 137 is rigidly connected to the shock absorber 122, the swinging of the connecting rod 135 does not affect the camber angle of the front steering wheel 107.

[0061] In the above-described embodiments, a two-wheeled vehicle having a single front steering wheel 7 or 107 has been referred to. However, the suspension according to the present invention can also be used in an inclined saddle-riding type vehicle having two front steering wheels, for example, equipped with one or two four-bar links adapted to ensure the rolling movement of the vehicle during travel. FIGS. 26 to 28 schematically show an inclined saddle-riding type vehicle 201 equipped with a frame 203, rear drive wheels 205, and two front steering wheels 207X and 207Y on the left and right. The two front steering wheels 207X and 207Y are arranged side by side in the lateral direction of the vehicle 201, that is, in the left-right direction.

[0062] In the embodiment schematically shown in FIGS. 26, 27, and 28, the reference numerals 209X and 209Y denote two rotatable arms having the same function as the single rotatable arms 9, 109 described with reference to the previous embodiments of vehicles having a single front steering wheel. Each rotatable arm 209X, 209Y is adapted to rotate about the steering axis A-A.

[0063] For this purpose, each rotatable arm 209X, 209Y is rotatably received in a support or upright 226X and 226Y which is part of a rolling four-bar linkage 220. The two supports or uprights 226X and 226Y are connected to each other by respective upper and lower cross members 222 and 224. The cross members 222 and 224 and the supports 226X and 226Y form a rolling four-bar linkage 220, are parallel to each other, and are hinged to each other about a hinge axis on a plane oriented in the longitudinal direction of the vehicle 201.

[0064] Reference numeral 215 indicates a handlebar which imparts a steering motion about axis A-A to the support arms 209X and 209Y via a steering column 211 acting on a steering bar 230.

[0065] The rolling four-bar linkage mechanism is known per se and does not require further detailed description.

[0066] Each front steering wheel 207X and 207Y is connected to its rotatable arms 209X, 209Y by suspensions 217X and 217Y which can be designed in any one of the manners described with reference to FIGS. 1 to 25. In FIGS. 26 to 28, the suspensions 217X and 217Y are configured as shown in FIGS. 1 to 6.

Claims

1. A saddle-riding type vehicle (1; 107; 207) including at least one rear drive wheel (5; 105; 205) and at least one front steering wheel (7; 107; 207X, 207Y), wherein the front steering wheel is connected to a rotatable arm (9; 109; 209X, 209Y) that performs a rotational movement about a steering axis (A - A). In a vehicle where a wheel support (37; 137) is connected to the rotatable arm (9; 109; 209Y, 209Y) via a suspension (17; 117; 217X, 217Y) having a shock absorber (22; 122), the wheel support (37; 137) supports the front steering wheel (7; 107; 207X, 207Y) and defines a rotational axis (B - B) of the front steering wheel (7; 107; 207X, 207Y). The suspension (17; 117) includes a Watt type four-bar link. The Watt type four-bar link includes a first crank (31; 131) hinge-coupled to the rotatable arm (9; 109) by a first hinge (31A; 131A) and hinge-coupled to a connecting rod (35; 135) of the Watt type four-bar link by a second hinge (31B; 131B); and a second crank (33; 133) hinge-coupled to the rotatable arm (9; 109) by a first hinge (33A; 133A) and hinge-coupled to the connecting rod (35; 135) by a second hinge (33B; 133B). The vehicle further includes The wheel support (37; 137) is connected to the connecting rod (35; 135) at an intermediate point between the second hinge (31B; 131B) of the first crank (31; 131) and the second hinge (33B; 133B) of the second crank (33; 133). The shock absorber (22; 122) is connected to the rotatable arm (109; 209X, 209Y) on one side and to the Watt type four-bar link or the wheel support (37; 137) on the other side. The saddle-riding type vehicle is characterized by the above. Claim 2: The wheel support (37; 137) is constrained at the restraint point of the connecting rod (35; 135) such that the rotation axis (B-B) of the front steering wheel (7; 107) is approximately equidistant from the second hinge (31B; 131B) of the first crank (31; 131) and the second hinge (33B; 133B) of the second crank (33; 133). The saddle-riding type vehicle according to claim 1, characterized in that Claim 3 The wheel support (37) is constrained by the connecting rod (35) such that the rotation axis (B-B) of the front steering wheel (7) is parallel to the axes of the first hinge (31A, 33A) and the second hinge (31B, 33B) of the first crank (31) and the second crank (33). The saddle-riding type vehicle according to claim 2, characterized in that Claim 4 The wheel support (37) is firmly connected to the connecting rod (35) and forms a housing for the bearing that supports the front steering wheel (7). The saddle-riding type vehicle according to claim 3, characterized in that Claim 5 The first hinge (31A) and the second hinge (31B) of the first crank (31), and the first hinge (33A) and the second hinge (33B) of the second crank (33) have axes parallel to the rotation axis (B-B) of the front steering wheel (7). The saddle-riding type vehicle according to any one of claims 2 to 4, characterized in that Claim 6 The first hinge (31A) of the first crank (31) and the second hinge (33B) of the second crank (33) are on the first side of a plane that includes the rotation axis (B-B) of the front steering wheel (7) and passes through the restraint point (22A) of the shock absorber (22) with respect to the rotatable arm (9), The second hinge (31B) of the first crank (31) and the first hinge (33A) of the second crank (33) are on the second side of the plane. The saddle-riding type vehicle according to any one of claims 2 to 5, characterized in that Claim 7 With respect to the forward direction of the vehicle (1) the first hinge (31A) of the first crank (31) and the second hinge (33B) of the second crank (33) are in the rear position, the second hinge (31B) of the first crank (31) and the first hinge (33A) of the second crank (33) are in the front position, or the first hinge (31A) of the first crank (31) and the second hinge (33B) of the second crank (33) are in the front position, and the second hinge (31B) of the first crank (31) and the first hinge (33A) of the second crank (33) are in the rear position The saddle - riding type vehicle according to any one of claims 2 to 6, characterized in that

8. The first hinge (131A) and the second hinge (131B) of the first crank (131), and the first hinge (133A) and the second hinge (133B) of the second crank (133) are substantially parallel to each other and have an axis orthogonal to the plane including the rotation axis (B - B) of the front steering wheel (107) The saddle - riding type vehicle according to claim 2, characterized in that

9. The first hinge (131A) of the first crank (131) and the second hinge (133B) of the second crank (133) are orthogonal to the rotation axis (B - B) of the front steering wheel (107) and are on the first side of a plane passing through the restraint point (122A) of the shock absorber (122) and reaching the rotatable arm (109), The second hinge (131B) of the first crank (133) and the first hinge (133A) of the second crank (133) are on the second side of the plane The saddle - riding type vehicle according to claim 8, characterized in that

10. The wheel support (137) is hinge - coupled to a connecting rod (135) around an axis (C - C) substantially parallel to the axes of the first hinges (131A, 133A) and the second hinges (131B, 133B) of the first crank (131) and the second crank (133) The straddle-type vehicle according to claim 8 or 9, characterized in that...

11. The arrangement of the hinges of the Watt's four-bar link with respect to the plane including the hinge axis (C-C) between the wheel support (137) and the connecting rod (135), which is orthogonal to the rotation axis (B-B) of the wheel (107), is such that the first hinge (131A) of the first crank (131) and the second hinge (133B) of the second crank (133) are on one side of the plane, and the second hinge (131B) of the first crank (131) and the first hinge (133A) of the second crank (133) are on the other side of the plane. The straddle-type vehicle according to claim 10, characterized in that...

12. The wheel support (137) supports the front steering wheel (107) at a position where the rotation axis (B-B) of the front steering wheel (107) is orthogonal to the axis to which the wheel support (137) is hinged to the connecting rod (135). The straddle-type vehicle according to claim 10 or 11, characterized in that...

13. It has a disc brake including a disc (23; 123) and a caliper (25; 125) integrated with the front steering wheel (7; 107; 207X, 207Y), and the caliper is firmly connected to the wheel support (37; 137). The straddle-type vehicle according to any one of claims 1 to 12, characterized in that...

14. It has a disc brake including a disc (23; 123) and a caliper (25; 125) integrated with the front steering wheel (7; 107; 207X, 207Y), and the caliper is firmly connected to a support member provided idly with respect to the connecting rod (35; 135) and the wheel support (37; 137). The straddle-type vehicle according to any one of claims 1 to 12, characterized in that...

15. The shock absorber (22; 122) is, On one hand, it is connected to a rotatable arm (9; 109; 209X, 209Y), and on the other hand, it is firmly connected to the connecting rod (35; 135) of a Watt type four-bar link The straddle-type vehicle according to any one of claims 1 to 14, characterized in that.

16. The shock absorber (22; 122) is connected on one side to a rotatable arm (9; 109; 209X, 209Y), and on the other side, it is connected to a point firmly connected to the wheel support (37, 137). The straddle-type vehicle according to any one of claims 1 to 15, characterized in that.

17. The shock absorber (22; 122) is connected on one side to a rotatable arm (9; 109; 209X, 209Y), and on the other side, it is connected to the axis of the front steering wheel (7; 107; 207X, 207Y) rotatably supported by the wheel support (37; 137). The straddle-type vehicle according to any one of claims 1 to 14, characterized in that.

18. The shock absorber (22; 122) is connected on one side to a rotatable arm (9; 109; 209X, 209Y), and on the other side, it is connected to the connecting rod (35; 135) of a Watt type four-bar link. The straddle-type vehicle according to any one of claims 1 to 14, characterized in that.

19. The front steering wheel includes a first front steering wheel (207X) and a second front steering wheel (207Y) which are two front steering wheels, Each of the front steering wheels (207X, 207Y) is connected to a first rotatable arm (209X) and a second rotatable arm (209Y) having a rotational movement about each steering axis (A - A), and is connected to the wheel support of each of the first and second front steering wheels via the first and second suspensions (217X, 217Y). The second suspension includes a Watt-type four-bar link that is substantially symmetric to the Watt-type four-bar link of the first front steering wheel with respect to the center plane of the vehicle, and a shock absorber. The first front steering wheel (207X) and the second front steering wheel (207Y) are connected to the frame (203) of the vehicle (201) by using a rolling-type four-bar link (220) hinged to the frame (203). The saddle-riding type vehicle according to any one of claims 1 to 18, characterized in that.

20. A first rotatable arm (209X) to which the first front steering wheel (207X) is connected is rotatably supported by a left vertical portion (226X) of a rolling-type four-bar link (220), and a second rotatable arm (209Y) to which the second front steering wheel (207Y) is connected is rotatably supported by a right vertical portion (226Y) of the rolling-type four-bar link (220). The right vertical portion and the left vertical portion are connected to each other by a first cross member (222) and a second cross member (224). The first cross member (222) extends in the left-right direction of the vehicle and has a first end hinged to the left vertical portion (226X) and a second end hinged to the right vertical portion (226Y). The second cross member (224) extends in the left-right direction of the vehicle and has a first end hinged to the left vertical portion (226X) and a second end hinged to the right vertical portion (226Y). The saddle-riding type vehicle according to claim 19, characterized in that.

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