The present invention relates to a front fork assembly and to a front fork comprising the same. The present invention further relates to a motorcycle that is provided with such a front fork assembly or front fork.
A motorcycle comprises a front fork that connects a motorcycle's front wheel and axle to the motorcycle frame. It typically comprises a telescopic unit, which unit comprises a first elongated tubular section and a second elongated tubular section, wherein the first tubular section is at least partially received in the second tubular section in a slideable manner, such that the first and second tubular sections can perform a telescopic motion with respect to each other along their longitudinal axes.
Near its top, the front fork is mounted to the frame of the motorcycle, typically using a coupling element known as a triple tree. Typically, the first tubular section is mounted above the second tubular section. This configuration will hereinafter be referred to as the regular configuration. Alternatively, the first tubular section may be mounted closer to the wheels. This later configuration is known as an upside-down fork.
With respect to the suspension, several types of front forks can be distinguished. A first type comprises a spring or other resilient member mounted to or in the telescopic unit. This resilient member is configured for subjecting the telescopic motion to a spring force. Moreover, the resilient member defines an unsprung section and a sprung section of the telescopic unit when this unit is mounted in the motorcycle. However, the resilient member may also be mounted spaced apart from the telescopic unit. For example, in a Telelever® configuration, the first and second tubular sections are each independently hingedly connected to the motorcycle frame using respective arms and/or frame parts. In this configuration, the resilient member is mounted between the arms and/or frame parts. In an embodiment, the second tubular section, being located close to the wheel axis, is connected to the motorcycle frame using an arm that on one end is hingedly connected to the motorcycle frame and on the other end is hingedly connected to the second tubular section. An upper end of the first tubular section is hingedly connected to a frame part of the motorcycle frame using a ball joint. The resilient member can in this case be mounted in between this frame part and the aforementioned arm.
A common problem encountered when driving a motorcycle relates to the front or rear wheels losing contact with the ground. These problems are referred to as wheel-hop or chatter. A known solution to counter these problems is to use tuned mass dampers mounted at different positions on the motorcycle, as disclosed by JP 5702071.
JP2014008932A discloses a front fork assembly as defined by the preamble of claim 1 This document discloses a telescopic unit having the second tubular section mounted near the steering bar and the first tubular section near the wheel axle. The telescopic movement of the tubular sections is subjected to a spring force that is provided by a spring. According to this document, a tuned mass damper, operating in a frequency range between 15-25 Hz, is mounted in the first tubular section above the spring. The tuned mass damper comprises a mass that is able to perform an oscillatory movement parallel to the longitudinal axes of the telescopic unit.
A front fork assembly is further disclosed in U.S. Pat. No. 6,050,558. In this document, an application of an inertial suspension stabilizer in competition motorcycles is described. Here, the stabilizer is mounted to the horizontal stabilizing bar of the front-side suspension or it is mounted in the axle of the wheel. In this known stabilizer, a mass element is configured to move in a horizontal direction to reduce lateral movement.
The applicant has found that, although the abovementioned solution provides an improvement over other existing designs, the steering properties and traction of the motorcycle during heavy braking and corner entry may still be unsatisfactory.
It is an object of the invention to provide a solution in which the abovementioned problem does not occur or at least to a lesser extent.
According to the invention, this object is achieved with the front fork assembly as defined in claim 1 which is characterized in that the tuned mass damper is fixedly attached to the unsprung section of the telescopic unit.
The applicant has found that by fixedly attaching the tuned mass damper to the unsprung section of telescopic unit, the variation in the force and/or force component pushing the tire to the road surface can be reduced, thereby improving riding characteristics such as the steering properties and traction.
The present invention relates to the regular configuration wherein the first tubular section is connected to the steering bar and the second tubular section to the front wheel bearing axis, and to the upside-down configuration, wherein the second tubular section is connected to the steering bar and the first tubular section to the front wheel bearing axis. In both configurations, the resilient member, which is configured for subjecting the telescopic motion to a spring force, is mounted in or on the first or second tubular section, depending on which section corresponds to the unsprung section of the telescopic unit.
The present invention also relates to the Telelever® configuration, wherein the first tubular section is connected to the steering bar and the second tubular section to the front wheel bearing axis, but wherein the resilient member for subjecting the telescopic motion to a spring force is arranged spaced apart from these sections.
The tuned mass damper may comprise a mass element guiding device and a mass element, wherein the mass element guiding device is configured for guiding the mass element to allow the mass element to slide relative to the mass element guiding device when performing the oscillatory movement. As an example, the mass element guiding device may comprise a housing that is elongated along a direction parallel to the longitudinal axis of the first and second tubular sections, and wherein the mass element is slideably arranged in the housing, wherein the mass element is able to slide back and forth in the housing along the longitudinal direction of the housing.
The tuned mass damper may comprise a further resilient member arranged in between the housing and the mass element for subjecting the sliding movement of the mass element relative to the housing to a spring force, wherein the further resilient member preferably comprises a compressed gaseous medium and/or a spring, more preferably a resilient member made out of elastic material.
The further resilient member need not be fixedly coupled to the housing and/or the mass element. For instance, the further resilient member may comprise a coil spring that is arranged in between a first end of the housing and the mass element. In this case, the first end of the housing and/or the mass element is provided with guiding structures, such as protrusions, to ensure that the spring is guided to the correct position relative to the housing and/or mass element.
Regardless the mounting of the spring, i.e. fixedly or loosely attached, it may be pre-biased or not. Moreover, the housing may comprise a pair of said further resilient members arranged on respective sides of the mass element.
The tuned mass damper may have an oscillation frequency that is tuned to a dominant oscillation frequency of the unpsrung section encountered while driving. For instance, when the motorcycle encounters a bump, an oscillation may be triggered. During this oscillation, the front wheel will move back and forth in along the longitudinal axis of the telescopic unit. This oscillation will reduce the contact force between the front wheel and the ground. In extreme cases, the front wheel may loose contact with the ground altogether. By designing the tuned mass damper to have an oscillation frequency that corresponds to this dominant oscillation frequency, the variation in contact force can be reduced. For most motorcycles, this results in an oscillation frequency of the mass element that lies in the range between 8 and 20 Hz, more preferably between 10 and 17 Hz.
The present invention is not limited to tuned mass dampers that show a particular damping. More specifically, the present invention could equally apply to tuned mass dampers that have resilient members to couple the mass element to the housing, but wherein the resilient members or other components, do not present a significant amount of damping. An example of such a tuned mass damper, is a mass element fixedly connected on both ends to an ideal spring.
As an example, the housing may comprise an evacuated airtight chamber in which the mass element is slideably received. In this case, the mass element will not be substantially damped by compressed air when it moves back and forth relative to the housing. Depending on the application, such damping may however be desired.
The housing may comprise a liquid filled container in which the mass element is slideably received. In this case, the mass element is damped by the liquid.
The container may have an upper and lower section. In this case, a bypass conduit may be provided between an upper and lower section of the container. For example, during its movement towards an end of the upper section, the mass element will push liquid through the conduit towards the lower section. In a further embodiment, the flow resistance of the bypass conduit may be adjustable. For instance, an adjustable throttle valve may be provided in the bypass conduit.
The mass element itself may comprise at least one through hole to allow the liquid to pass between the upper and lower section. In the example above, during its movement towards an end of the upper section, liquid is able to flow through the at least through hole towards the lower section. In a further embodiment, the flow resistance of the at least one through hole may be adjustable. For example, the tuned mass damper may comprise an adjusting element for controlling a throttle opening between the at least one through hole and the upper or lower section.
Alternatively, the mass element guiding device may comprise a guiding rod that is fixedly attached to the unsprung section of the telescopic unit, and wherein the mass element comprises a longitudinal through hole, wherein the guiding rod is arranged at least partially inside the longitudinal through hole. In this case, the mass element slides along the guiding rod. The guiding rod can be mounted to an outside of the telescopic unit. This allows common motorcycle components typically found near the placement area of the tuned mass damper. For example, the mass element can be formed by and/or can be comprised in a front mudguard and/or front fender of the motorcycle.
The resilient member for subjecting the telescopic motion to a spring force can be mounted in the second tubular section. Alternatively, it may be mounted around the first tubular section, wherein the first and second tubular sections each comprise a support, wherein the resilient member is mounted in between the supports.
The resilient member for subjecting the telescopic motion to a spring force may comprise a spring, an elastic material, such as Cellasto®, and/or wherein the resilient member is formed by a gas cylinder.
A first end of the telescopic unit may be connectable to a wheel bearing axis of the motorcycle, and a second end of the telescopic unit opposite to the first end may be connectable to a steering device of the motorcycle, wherein the tuned mass damper is arranged in between the first end and the resilient member. In the regular configuration, the first end corresponds to an end of the second tubular section. In the upside-down configuration, the first end corresponds to an end of the first tubular section.
In the regular configuration, the tuned mass damper can be arranged in the second tubular section. The front fork assembly may comprise a damper for damping the telescopic motion, wherein the damper is arranged inside the second tubular section in between second end and the tuned mass damper.
In the upside-down configuration, the tuned mass damper can be mounted to or in the first tubular section. Also in this configuration, a damper may be provided for damping the telescopic motion, wherein the damper can be arranged in the second tubular section.
According to a further aspect, the present invention provides a front fork for a motorcycle, comprising a first and second fork member that are spaced apart in a parallel manner, wherein at least one of the fork members comprises the front fork assembly as described above.
The first and second fork member may be substantially identical. Alternatively, the first fork member may comprise the front fork assembly as described above, but the second fork member may only comprise a further telescopic unit that is configured as the telescopic unit in the first fork member. In other words, the tuned mass damper can be only comprised in the first fork member. In such embodiments, it may be advantageous to arrange the damper for damping the telescopic motion of the further telescopic unit and the tuned mass damper in different fork members in view of available space in the fork members,
According to a further aspect, the present invention provides a motorcycle comprising the front fork assembly or the front fork as described above.
Next, the invention will be described in more detail referring the appended drawings, wherein:
In the description below, elements or components that are identical or which have similar functionality will be referred to using the same reference signs.
In each of these configurations, the front fork comprises a pair of fork members, i.e. a left fork member L and a right fork member R. Each of these members comprises a first tubular section 101, 102 and a second tubular section 103, 104 that can move telescopically with respect to each other. Here, first tubular section 101, 102 and second tubular section 103, 104 are part of respective telescopic units.
Fork members L, R are mutually coupled by means of a triple tree 105, also referred to a yoke. Triple tree 105 comprises two plate members 105A, 105B having appropriate through holes through which first tubular sections 101, 102 (
The front fork according to the invention also comprises a wheel bearing axis 107 that is, depending on the configuration, coupled to either the first 101, 102 or the second 103, 104 tubular sections.
In the Telelever® configuration shown in
The connection between first arms 180 and second tubular section 103, 104 comprises a plate member 105B that is fixedly attached to second tubular section 103, 104. Plate member 105B defines a pivot point 106B around which front fork 300 is able to pivot to enable steering of the motorcycle. First arms 180 are on one end fixedly connected to plate member 105B, and on another end hingedly to second arm 181, by means of a hinge 185.
Third arms 182 are hingedly coupled to the frame of the motorcycle. A spring 171 and damper 172 are hingedly mounted between third arms 182 and first arms 180, using hinges 183, 184. Third arms 182 are fixedly connected to a plate member 105A. Also this latter plate defines a pivot point 106A around which front fork 300 is able to pivot, see
Compared to
The front fork according to the invention comprises a Tuned Mass Damper (TMD) that is either mounted externally (
Front forks 400-600 illustrated in
As shown in
In the embodiments in
The embodiments in
In each of the embodiment in
Front forks 100-600 each comprise a resilient member in the form of a spring 171 for subjecting the telescopic motion of first and second tubular sections to a spring force. For example,
Damper 172 comprises a nitrogen filled membrane and a bottom valve 211. It further comprises a main piston 212 that is provided with a compression and rebound shim setting. Piston 212 is connected with a spindle 214 that is fixedly attached to first tubular section 101. A sealing and bearing 213 is provided by which spindle 214 is able to actuate piston 212. Damping is achieved when first tubular section 101 moves inward relative to second tubular section 103. This will cause main piston 212 to move through a fluid, such as oil, inside damper 172. Piston 212 is provided with through openings to throttle the flow of fluid between the chambers on opposite sides of piston 212.
Here, it is noted that both spring 171 and damper 172 are known in the art and require no further elaboration. Although front forks 100, 200, 400, 500 have a spring that is mounted inside first tubular section 101, 102, it should be noted that it is equally possible to arrange the spring around first tubular section 101, 102. For example, first tubular sections 101, 102 and second tubular sections 103, 104 could each be provided with supports, in between which supports the spring could be mounted.
Spring 171 defines an unsprung section and a sprung section of the telescopic unit when this unit is mounted in the motorcycle. More in particular, the unsprung section in
Guiding rod 201 is fixedly connected to two supports 205. These supports cooperate with mounting structures 207 for the mounting of spring coils 206.
Mass element 203 can be connected to a mudguard. The present invention does however not exclude other motorcycle components to be connected to mass element 203.
Although the present invention has been described using detailed embodiments thereof, the skilled person will understand that the present invention is not limited thereto, but that modifications are possible without deviating from the scope of the invention, which is defined by the appended claims.
Number | Date | Country | Kind |
---|---|---|---|
2016884 | Jun 2016 | NL | national |
Filing Document | Filing Date | Country | Kind |
---|---|---|---|
PCT/NL2017/050347 | 5/30/2017 | WO | 00 |