FIELD

The present invention relates to suspension arrangement of a track system of a snow vehicle, such as a snowmobile or a snow bike.

BACKGROUND

Snowmobile is a vehicle driven on snow by means of a track. Steering of the snowmobile takes place by turning a steering handle, which turns a ski or pair of skis at the front end of the snowmobile.

The snowmobile can be driven on uneven show with high speed, whereby the importance of the suspension system of the snowmobile is empha sized. The suspension of the snowmobile is typically implemented by providing separate suspension arrangements at the front and rear ends of the snowmobile.

The known solutions for implementing the suspension of the track of the snowmobile are associated with plurality of disadvantages. The suspension arrangements are very prone for breakage, they are heavy, and the suspension travels are relatively limited.

BRIEF DESCRIPTION

The objective with the present invention is to provide a solution to at least alleviate the above-mentioned problems. The objective is achieved with an invention that is the scope of the independent claim. Some advantageous em bodiments are disclosed in the dependent claims.

The invention provides significant advantages in durability of the sus pension. Furthermore, less parts are needed to implement the suspension, which reduces the weight of the snowmobile. Furthermore, the suspension travel can be increased, which achieves improved suspension when compared to known solutions.

FIGURES

The invention and its preferred embodiments are shown in following figures, where

Figure 1 shows a snowmobile and a suspension arrangement ar ranged in connection to the snowmobile;

Figure 2 shows a suspension arrangement illustrated from as a side view; and Figure 3 shows the support arm circumventing the track.

DETAILED DESCRIPTION

The embodiments relate to suspension of the track of a snow vehicle. The snow vehicle refers here to a snowmobile, snow bike or corresponding vehi cle drivable on snow by means of a track. In the following reference is made, for simplicity, to a snowmobile but the embodiments are as well applicable to other vehicles movable by means of a track.

The embodiments relate thus especially to suspension or shock ab sorption of the track of a snowmobile. The embodiments provide special ad vantages in provision front suspension of the track but are also applicable in providing rear suspension of the track. According to the embodiments, the sus pension is arranged such that suspension members, such as shock absorbers and/or coil springs are arranged such that they reside at partly between the track and the frame of the snow mobile. Preferably the suspension means are com pletely between the track and frame in a so-called rear frame tunnel. In other embodiments, e.g. the upper end of the suspension member may be placed above the frame structure.

Figure 1 shows one embodiment of the invention. The figure shows a snow mobile 100 having streering means, such as handlebars 104, in the front end of the frame 102, and a pair of skis 106 turnable by means of the handlebars. The front end comprises preferably a damping arrangement 108 for damping im pacts that are subjected to the front end. The damping arrangement 108 may comprise one or more springs and/or shock absorbers.

The snowmobile comprises also a track 1 10, which track is arranged rotatable around two or more wheels 1 12, 1 14. The wheel 1 12 in the front end is preferably the driving wheel, so called drive wheel, whose power generation may be produced by means of a combustion engine or an electric motor. The snow mobile comprises also a slide rail, and the top side of the ground facing portion of the track is capable of sliding against the lower side of the slide rail. According to the embodiments, the snowmobile comprises a suspen sion arrangement for damping impacts taking place at the track area. The sus pension arrangement may comprise one or more suspension structures 120, 130. Preferably the suspension arrangement comprises two suspension structures, a first/front suspension structure 120 and a second/rear suspension structure 130. The front and rear suspension structures may be principally similar.

The suspension structure comprises a pair of support arms, or a first support arm 122A and a second support arm 122B, which are placed side to side on different sides of the snowmobile. The support arms may have fixed or con stant length, whereby their length does not change during driving of the snowmo bile. The rear suspension structure 130 comprises similarly two support arms on both sides of the snowmobile. Even though the principal structure of the front support structure 120 and the rear support structure are similar, the dimensions may be slightly different. The support arms in the front support structure may be slightly shorter than the support arms of the rear support structure. By way of an example, the length of the front support arm may be between 50 to 1 10 cm, pref erably 55 to 95 cm, most preferably between 60 to 80 cm and the length of the rear support arm may be between 60 to 120 cm, preferably between 65 to 100 cm, even more preferably between 65 to 85 cm, the mentioned measures as all mentioned measures depending on the type and sized of the snowmobile. The support arms may be made of metal, for instance, or they be made of some du rable composite material.

The support arms 122A, 122B have been fastened from their upper end fixedly to the frame 102 of the snowmobile and from their lower ends the support arms are fastened to the slide rail. Thus, in the embodiments, the slide rail is directly connected/coupled to the frame by means of the support arms of the support structure. The embodiments thus avoid complicated lever arm ar rangements, where the suspension system comprises plurality of lever arms cou pled to each other. Such systems are heavy and prone to breakage. The fas tening of the support arm 122A to the frame of the snowmobile, and to the slide rail are rotatable fastenings, that is the support arm 122A can turn around its fastening points. The fastening to the slide rail can be made by means of a bolt, a bearing and a nut. The fastening to the frame 102 can be carried out means of a shaft 124 passing through, and extending to both sides of the frame, and by means of a bearing surrounding the shaft and nuts. The attachment points of the support arms of the front support struc ture to the slide rail is 10 to 50 cm from the front end of the slide rail, preferably between 20 to 40 centimeters, and more preferably between 25 to 35 centime ters. The rear support structure may be attached substantially to the rear end of the slide rail.

The angles between the supports arm and the horizontal direction are, at rest of the snow vehicle, between 20 to 60 degrees, preferably between 30 to 50 degrees, and more preferably between 35 to 45 degrees.

The suspension structure comprises thus a pair of support arms, which support arms are arranged side-to-side on both sides of the track system. Pref erably the fastening points of the support arms to the slide rail are longitudinally in mutually corresponding positions on both sides of the slide rail, and the fas tening points of the support arms to the frame are accordingly in corresponding positions on both sides of the frame.

The fastening point of the support arms that are to be fastened to the frame are preferably as close as possible to the rotation axis of the drive wheel in order to ensure as good as possible tightness of the track. Preferably the fas tening point of the support arm is as close as possible to a vertical line passing via the rotation axis of the drive wheel. Preferably the fastening point lies on the mentioned vertical line, but preferably less than 10 cm distance from the line, and even more preferably less than 5 cm distance from the line. In this way it is en sured that the track system may turn around a circular path.

The support arms are longitudinal bars but are not necessarily com pletely straight bars. In practice, the track 1 10 can be, for instance, slightly broader than the slide rail, whereby the support arm 122A needs to have a struc ture that can circumvent the portion of the track that sets above the slide rail. Starting from the attachment point to the slide rail, the support arm can first direct a certain distance directly upwards, then have a portion that directs outwards and/or upwards towards the side of the snowmobile, and then follows an inwards and towards the snowmobile directing portion before attachment to the frame of the snowmobile.

Figure 1 shows also a cross-bar 126 which is arranged between the support arms 122A and 122B above the track. The cross-bar is attached to the support arms by means of welding, for instance, whereby the support arms and cross-bar form a uniformly turning rigid whole. The attachment points of the non-rotatable rigid attachment of the cross-bars to the support arms may be slightly different in the front and rear sus pension structures. However, in both support structures, the attachment point is between the ends of the support arms.

In the front suspension structure 120, the cross-bar may be attached to the support arms 122A and 122B to a distance between 30 to 70 centimeters from the attachment point of the support arm to the slide rail, preferably between 35 to 65 centimeters, and more preferably between 45 to 55 centimeters. In the front support structure, the attachment point of the cross-bar is between 60 to 80 percent of the length of the support bar when seen from the attachment point to the slide rail, more preferably between 65 to 75 percent of the length of the sup port arm. That is, the cross-bar resides closer to the attachment point to the frame than the attachment point to the slide rail.

In the rear support structure, the attachment point of the cross-bar to the support arms is preferably between 30 to 70 percent of the length of the sup port arm when seen from the attachment point to the slide rail, preferably between 40 to 60 percent and even more preferably between 45 to 55 percent of the length of the support arm.

According to the embodiments, the suspension member 128, which can comprise a shock absorber and/or a coil spring, is attached from its lower end to the mentioned cross-bar 126. The suspension member may be attached to the cross-bar in rotatable manner but, in any case, in such a manner that the suspension member is unable to move in the longitudinal direction of the cross bar or the transverse direction of the frame of the snowmobile.

From its upper end, the suspension member is attached pivotably with respect to the frame of the snowmobile. In one embodiment, the attachment of the upper end of the suspension member to the frame of the snowmobile is im plemented such that the suspension member is attached fixedly to a pipe, which pipe is capable of rotating with respect to a shaft placed inside the pipe, which pipe, on the other hand, is arranged rigidly to the frame of the snowmobile.

The rear suspension structure 130 is preferably principally similar to the front suspension structure 120. Thereby also the rear suspension structure comprises support arms, which are attached to the frame of the snowmobile and to the slide rail. Between the support arms there is arranged a cross-bar, and the suspension member is arranged between the cross-bar and the frame of the snowmobile. In one embodiment, the first suspension structure 120 and the second suspension structure 130 are mechanically connected to each other, whereby the co-operation of the suspension structures can be ensured. The mechanical con nection can be provided, for instance, in such a way that there is arranged a rigid or a detachably rigid side support arm between the support arms residing on the same side of the snowmobile. The side support arm is preferably arranged such that the front end, residing at the front end of the snowmobile, of the side support arm is arranged slightly lower than the end of side support bar that is arranged at the rear end of the snowmobile. The length of the side support arm depends on the type and size of the snowmobile but preferably the length of the side support arm is between 50 to 120 cm, preferably between 50 to 100 cm, most preferably between 50 to 80 cm. The angle between the side support bar to the horizontal direction is between 0 to 25 degrees, preferably between 2 to 20 degrees, most preferably between 5 to 15 degrees such that the rear end is vertically higher than the front end.

The one preferred embodiment shown in Figure 1 is characterized by that the suspension member 128 is arranged in the area or the space between the track 1 10 and the frame 102 of the snowmobile. The suspension members thus reside, in vertical direction, in the space above the track and below the frame. Preferably, the suspension members are arranged into a so-called frame tunnel of the snowmobile.

Even though Figure 1 shows that the suspension means reside pref erably between the track and the frame, it is alternatively possible to place the suspension member partly above the frame if there not enough space to place the suspension member completely under the frame. In such a case there may be a though hole or bushing in the frame such that the suspension member can fit through the frame. Flowever, even in this embodiment, the suspension member is mainly located under the frame. Thereby, at least half of the longitudinal direc tion of the suspension member resides below the top surface of the frame.

Figure 2 shows the suspension arrangement viewed from a side. Fig ure 2 shows a drive wheel 212, a rear wheel 214 and a track 210 moving with respect to the wheels. Figure 2 shows also a slide rail 216 under which the track 210 can slide.

The front suspension structure comprises a first support arm 222A which is attached from its upper end to the frame 202 of the snowmobile and from its lower end to the slide rail. Both attachments are rotatable attachments and preferably the lower end attachment to the slide rail is fixed such that the support arm 222A cannot move in the longitudinal direction of the slide rail 216. The first support arm 232 belonging to the second suspension structure may, however, be slidably attached to the slide rail 216. This means that the slide rail may have a longitudinal slot in which slot the end of the support arm 232A can move. In this way the tightness of the track is ensured when the track system moves in vertical direction during driving in situations when suspension is needed.

Figure 2 shows a suspension member 228 belonging to the first sus pension structure. As it can be seen, the suspension member is arranged to an angle with respect to the support arm when the snowmobile is at rest. In some embodiments, the angle between the suspension direction of the longitudinal sus pension member and the upper end of the support arm is between 20 to 120 degrees, preferably between 50 to 1 10 degrees, more preferably between 80 to 95 degrees. Preferably the angle is over 90 degrees being between 90 to 150 degrees when compared to the upper end of the support arm. That is, compared to Figure 2, the upper end of the suspension member can be even more to the right. In this way, when the snowmobile is driven in Figure 2 to the left, and the track system hits a hump or pit, the suspension member resides substantially perpendicularly with respect to the surface of the hump thereby providing maxi mal attenuation.

At the rear end of the track system, the suspension member 238 is, in turn, tilted to the opposite direction compared to the front suspension member 228. The angle is preferably under 90 degrees being between 30 to 90 degrees, for instance. With respect to the upper end of the support arm of the second sup port structure, the suspension direction of the linear suspension member 238 is arranged to an angle between 20 to 100 degrees, preferably between 30 to 75 degrees, even more preferably between 35 to 55 degrees.

Figure 3 illustrates the installation and the design of the support arm 322A. The figure shows the top side of the track 310 and it can be seen how the point where the support arm is attached to the slide rail sets inner when compared to the outer edge of he track 310, whereby there is formed a portion to the support arm that circumvents the track. The circumventing portion may be made of piece- wise linear portions or it may alternatively be curved.

The turning attachment of the support arm to the opening in the slide rail may be provided by the means of a bolt 340, bearing 342, washer 344 and a nut 346. According to the embodiments, impacts targeted to the track system of the snow vehicle are attenuated by receiving the impacts with one or more suspension structures attached to the frame and slide rail of the snow vehicle, whereby the swinging of the suspension structures in the impact situation are attenuated by a suspension member operatively coupled to the suspension struc ture. Practically, when driving the snow vehicle, the rigid support arms of the sup port structure can turn about the attachment points of the upper ends whereby the track system/track can rise towards the frame of the snow vehicle.

The invention provides several advantages. One significant advantage is that the non-suspended mass of the snowmobile is significantly reduced, typi cally even about 20 kg when compared to suspension structures that are imple mented within the area defined by the track system. It is clear that the solution according to the invention provides cost advantages compared to known solu tions as the is need for less parts and thereby service objects. The lower mass provides also savings in fuel consumption.

The invention can also provide significant advantages in durability of the suspension. One object in snowmobiles that is very prone to breakage is the so-called hanger bracket or the breakage of the suspension of the front end of the track system. The reason for this is that the front suspension member is typi cally oblique with respect to the impact direction. By means of the invention, the suspension member can be arranged to a position in which it receives the impacts in advantageous manner in natural operating position, that is, the impact is di rected in the linear direction of a mainly linearly operating suspension member. The invention also avoids use of latches or lever arms in the implementation of the suspension.

The invention provides the advantage the real suspension travel or the movement travel of the rear end of the snowmobile increases as much as 15 to 20 cm. This is caused by the fact that the track can be implemented as very low, whereby the distance between the upper surface and lower surface is significantly shorter than in structures where the suspension is arranged inside the track. As the track system is low, it can be allowed a longer travel in vertical direction, which naturally leads to better suspension.

By means of the invention, the contact surface of the track to the ground increases because the lower structure allows extending the track further in longitudinal direction of the snowmobile. The invention allows easier adjustment of the height of the suspen sion and the attenuation force, because the suspension elements are easy to handle as they are above the track. In one embodiment, there are plurality of attachment points in the frame for the support arms, whereby the positions of the support arms and thereby the suspension are easy to adjust.

It is evident that when the technology develops the inventive idea can be implemented in various ways. The invention and the embodiments are thus not limited to the embodiments shown above but can vary in the scope of the patent claims.