WO2017204670A1

WO2017204670A1 - Suspension system of rear wheel of single-track vehicles

Info

Publication number: WO2017204670A1
Application number: PCT/PL2017/050028
Authority: WO
Inventors: Pawel MARCZAK; Jerzy Dabrowski
Original assignee: Marczak Pawel; Jerzy Dabrowski
Priority date: 2016-05-25
Filing date: 2017-05-25
Publication date: 2017-11-30
Also published as: PL229197B1; PL417330A1

Abstract

A rear suspension system incorporates a chain stay link (8) and a seat stay link (6) with bearings in four points (A), (B), (C), (D), said suspension system of a swing arm (7) that in the bottom portion of a frame incorporates a chain stay link (8) attached with its front end to a bottom bracket (5), in a pivot point (A), and attached with its rear end to the front end of said swing arm (7), said suspension system incorporates in the top portion of said frame in a pivot point (B) a seat stay link (6) attached with its rear end to said swing arm (7), in a pivot point (D), and attached with its front end to a top tube (2) of said frame, in a pivot point (C).

Description

Suspension system of rear wheel of single-track vehicles

The subject of the invention is a suspension system of the rear wheel of single-track vehicles, especially bicycles.

Suspension of the rear wheel, especially of the bicycle designed for mountain off- road use, should manifest the following features:

- suspension reacts on every type of roughness - from the smallest to the largest impacts,

- suspension operates at any speed,

- pedaling does not impact on suspension operation,

- braking does not impact on suspension operation,

- a frame rear triangle is rigid, and does not displace aside,

- a suspension system is not susceptible for clearances,

- all consumable elements are easily serviceable (replaceable),

- there is a good access to all tuning elements of a rear shock absorber,

- there is a progressive characteristics - suspension hardens along with the

increase of deflection, that prevents thumping,

- the mass of suspension is as small as possible.

The bicycle designers try to optimize the efficiency of a rear wheel shock absorber so, that the suspension does not fall into cradling when pedaling and simultaneously reacts on any roughness driven over. The simplest solutions is offsetting the pivot point of a swing arm from the axle of a bottom bracket. Such constructions of the rear suspension can be subdivided into three categories: low pivot - in the example US 6877591 , high pivot - in the example US 5244224 and virtual pivot point - in the example US 20080054595 A1 .

The suspensions with the low pivot point handle well on small roughness and at low speeds, but handle worse at high speeds, especially on higher obstructions. Additionally, the low positioned pivot point causes the disadvantageous cradling of ^'suspension when pedaling and energy loss of the driver. On the other hand, the high positioned pivot point causes that when the suspension operates the line of the wheel features the backward movement, in reference to the riding direction, as such this construction fits better to travel over the obstructions at higher speed. The problem with a such positioned pivot point is the excessive elongation of the chain, that in turn causes the excessive movement of the cranks in the direction opposite to pedaling. This effect is called pedal kickback.

An attempt to solve the problem is a suspension system with a temporary virtual pivot point (VPP). But the system does not provide the full advantages as the low pivot point and the high pivot point. Such types of construction are an average of both positions of the suspension pivot points, with often worsening of other suspension parameters, such as suspension hardening when braking.

The two-swing-arm suspension system is known from US 20140103617 A1 . None of the swing arms constitutes a direct link between the frame front portion and the rear wheel. The system consists of the frame main and rear portions and the shock absorber with the extension arm. The main frame portion includes a top tube, head tube, seat tube, bottom bracket and down tube. On the down tube, at a bottom bracket, there is a joint of the bottom swing arm including a pair of the chain stays and a first and second arm. A forward end of the shock absorber is attached pivotally to the main frame. A rearward end of the shock absorber is attached to an extension body that is attached pivotally to the swing arm. The auxiliary swing arm, connected jointly to the frame main portion with a link, includes a pair of the seat stays. The system allows to optimize the efficiency of suspension in the bicycle frame, to minimize the interaction between the rider and the frame rear portion when pedaling and to isolate braking from operation of suspension.

Extension of the solution is disclosed in US 20150137477 A1 . The suspension construction includes additionally the absorber offset from the frame plane. The shock absorber is attached directly to the frame front portion and the frame rear portion, that is called a swing arm, through the mounting flanges.

Other solution of the suspension system is disclosed in US 6203042. This solution includes a bicycle fame, that consists of a head tube, seat tube and bottom bracket in a frame bottom portion. The head tube, seat tube and bottom bracket are connected to each other through the frame elements like a chain stay, a seat stay and a section linking these elements. In the solution there is also the first pivot point for a chain stay link and the second pivot point for a seat stay link. The first pivot point is located slightly forward and above the bottom bracket, and the second pivot point is located above and forward of the first pivot point. The second pivot point of the chain stay link is connected jointly with the front portion of the chain stays. The third pivot point is located downward and rearward of the first pivot point. The three- point chain stay link is connected jointly with an absorber. The seat stay link has the first and second ends connected jointly to the frame and pair of the seat stays. The shock absorber is connected pivotally to the frame fix element with its first end and pivotally with its second. The said solution has an advantageous line of a wheel and the low located center of gravity.

The aim of the invention is to deliver the kinematics of the suspension system, which has the backward line of a wheel, while keeping the high travel parameters.

The essence of the solution consists in that the suspension system incorporates a chain stay link and seat stay link, with bearings in four points, and the suspension system of a swing arm in a frame bottom portion incorporates the chain stay link connected with its front end to a bottom bracket, in the first pivot point, and connected with its rear end to the front end of the swing arm, in the second pivot point. In the top frame portion the said suspension system incorporates the seat stay link connected with its rear end to the swing arm, in the third pivot point, and connected with its front end to the top tube of the frame, in the fourth pivot point. The chain stay link has an arm compressing the shock absorber.

The pivot point of the rear end of said seat stay link is determined by radius of a circle, center of which is located in said axle of said rear wheel mounted at the end of said swing arm, whereas the distance from said point on the radius R to the center of said pivot axle stays in the range from R = 15 mm to R = 150 mm.

The center of said axle of said rear wheel in the SAG point, through which is the line determined to said center of said wheel (E), which creates in its zero position an angle to the ground in the range from 71 ° to 76°. The shock absorber has an extension body, that allows one mounting axle of said absorber to twist up to 90°, whereas the other end of said axle is mounted to a brace or directly to a front frame portion.

The frame has a cog , over which runs said powering chain, whereas said cog is located at said seat tube or said top tube of a front frame triangle, above said support bracket.

The seat stay link is of a shape similar to the letter H or Y, and the proportion of its length to said chain stay link equals 3:1 in tolerance of 10%, and to the length of said swing arm equals 1 :1 in tolerance of 15%, whereas said seat stay link is mounted symmetrically in relation to aid frame plane P1 and is equipped with bearings in said pivot point.

The swing arm has mounting eyelets for rear brakes.

The pivotal attachment of said chain stay link to the frame front portion in a bottom bracket can be located only on one side in a bracket axle, opposite to a powering chain. The compressing arm is located to the left from a frame plane, in reference to the riding direction, and is offset from it in the range 0-50 mm.

In said left location on one side, the shock absorber passes by the top tube so that said tube shape embraces with its cross section at least 10% of the cross section of said absorber. The tube in the portion where it passes by said extension body and shock absorber is located in >60% of its cross section at the right hand side in reference to said frame plane. The shock absorber is located longitudinally to said down tube of said front triangular portion so that said tube in its cross section accommodates said absorber shape in >10%.

The advantages of the solution according to the invention is to improve traction of the rear wheel. The suspension is characterized by the low pedal kickback, and the whole construction has a low center of gravity. Additionally, when braking there is no disability of the suspension operation, and thus consecutively the stopping distance is shortened and safety is improved. The subject-matter of the invention is disclosed by an embodiment of left location of the chain stay link, in the figure, where the individual figures illustrate:

Fig. 1 - a side view of a frame,

Fig. 2 - an example of execution of a shock absorber and suspension system, in a perspective view,

Fig. 3 - a rear end of a swing arm with a pivot point D,

Fig. 4 - a frame with the marked frame plane and absorber plane, in a rear view, Fig. 5 - a suspension chart with a virtual pivot point.

The bicycle frame according to the invention is made of the front portion I and rear portion II. The front portion I embraces the main tube 1 , top tube 2 and the head tube 3 linking them both. The seat tube 4 is connected with the top tube 2. The top tube 2 reaches the support bracket 5. The rear portion II, positioned axially in relation to the front portion 1 , which incorporates the seat stay 6 and swing arm 7 advantageously made of two stays, to which rear end the rear wheel is attached. The frame front and rear portions are not connected directly, but the pivotal links - the seat stay link 6 and chain stay link 8 - constitute the intermediate elements in transmission of movement.

The suspension system exploits the links 6, 8 with bearings in four points A, B, C, D. The first front pivot point A of the chain stay link 8 is located in the axle of the support bracket 5. The second pivot point B of the chain stay link 8 is located in the front end of the swing arm 7. The first front pivot point C of the seat stay link 6 is located at the top tube 2. At the other end of the link 6, there is the pivot point D, which is equipped with bearing together with the swing arm 7.

The shock absorber X is attached with the first end to the extension body 9 and with the other end pivotally to the brace 10.

At the top tube 2, slightly below the pivot point C, there is the cog 1 1 with bearing running the chain and the securing cage 12. Running the chain over the cog 1 1 results in regulation of the pedal kickback size, so that suspension operation is not disturbed and at the same time the bicycle accelerates well. The cog 1 1 can be replaced with a roll. The solution according to the invention features in the virtual pivot point (VPP), that is disclosed schematically in Fig. 5. Owing to this, that the pivot point changes its position, it can be achieved that the suspension will operate nearly independently from the drive. This suspension features the optimal anti-compression, that means it will not squat during each push on the pedals and at the same time will react on every road roughness.

The chain stay link 8 can be attached asymmetrically only to one side of the frame front portion in the bottom bracket 5 in reference to the frame plane P1 , opposite to the powering chain and screwed at the right hand side to the bottom bracket shell 13. By an example of execution disclosing the classic location of the chain at the right hand side, in reference to the drive direction, the pivotal attachment of the chain stay link 8 to the frame front portion is located in the bottom bracket 5 at the left hand side, in reference to the drive direction.

The chain stay link 8 is equipped with bearings in the support axle so, that the bearings are separated at the edges of the bottom bracket 5 or are offset from the edge in order to enable mounting the bicycle standard cranks. The chain stay link 8 has the arm 14 that compresses the absorber X, to which is attached the extension body 9 with its own bearing. The compressing arm 14 is located to the left from the frame plane P1 , in reference to the riding direction, and is offset from it in the range of 0-50 mm. The advantageous location of the pivot point of the chain stay link 8 in the bottom bracket axle eliminated the additional point with bearings in the frame front triangle, in contrary to the conventional suspension with the dynamic pivot point. In addition to that, use of the bottom bracket 5 as the pivot point of the chain stay link 8 enhances the construction rigidity, at the same time making it simpler and reducing its mass.

The seat stay link 6 is of H- or Y-shape and the proportion of its length to the chain stay link 8 equals 3:1 in tolerance of 10%, and to the length of the swing arm equals 1 : 1 in tolerance of 15%. The seat stay link 6 is attached symmetrically in relation to the frame plain P1 and is equipped with bearings in the pivot point C in the frame front portion at the top tube 2 slightly above the cog running the chain. The other end of the seat stay chain 6 is equipped with bearings on both sides to the swing arm 7 in the pivot point D.

The bearing point of the rear pivot point D of the seat stay link 6 is determined precisely by the radius R of the circle, the center of which is located in the axle E of the rear wheel.

The distance from the point D at the radius R to the axle center E falls within the range from R = 15 mm to R = 150 mm.

Such positioning of the pivot point D in relation to the whole suspension system is advantageous because it allows to locate the clamp of the rear brakes on the swing arm 7, which during deflection of suspension changes its position angle only a little bit below 14 degrees in relation to the preliminary position. Therefore, the smaller the difference is between the preliminary and final position of the brake clamp, the less the braking impacts negatively on the suspension operation. The brake is attached to the mounting eyelet 15 at one of the stays of the swing arm 7.

The absorber X is located asymmetrically in relation to the frame plane P1 , and its plane P2 is offset from the frame plane in the range of 0-50 mm. The absorber X is located advantageously on the main tube 1 of the front triangular portion. The bottom section of this tube is shaped in the way, that it embraces the shape of the absorber in its cross section in at least 10%. The extension body 9 is attached to the absorber X and is located so that it passes by the top tube 2 at the left hand side above the bottom bracket 5. The top tube 2 is profiled in the way, that it passes by the extension body 9 and the absorber X the during the suspension operation.

By an example of execution the absorber X is connected directly neither with the front nor the rear frame portion. The brace 10 can be a fixed element of the frame front triangle portion or an detachable part screwed to the front triangle, that is disclosed in Fig. 1 . The other end of the absorber X is attached pivotally to the rear extension body 9 so that the axle of the mounting eyelet 02 is twisted at least 30° in relation to the axle of the mounting eyelet O1 . In the advantageous variation the angular difference between the mounting axles of the absorber O1 and O2 equals 90°. The possibility of the different configuration of mounting and setting the absorber X does not limit the construction.

Claims

A rear suspension system of a single-track vehicle, especially a bicycle, a frame of which consists of a front portion and a rear portion, which incorporates a pivotal swing arm with an attached rear wheel, that cooperates with a shock absorber, whereas said swing arm is attached pivotally to a pivotal seat stay link, where said system features the virtual pivot point (VPP) of said swing arm characterized in that the suspension system incorporates a chain stay link (8) and a seat stay link (6) with bearings in four points (A), (B), (C), (D), said suspension system of said swing arm (7) in a frame bottom portion incorporates said chain stay link (8) attached with its front end to a bottom bracket (5), in a pivot point (A), and attached with its rear end to the front end of said swing arm (7), in a pivot point (B), and in a frame top portion said suspension system incorporates a seat stay link (6) attached with its rear end to said swing arm (7), in a pivot point (D), and attached with its front end to a top tube (2) of said frame, in a pivot point (C), whereas said chain stay link (8) has an arm (14) compressing the shock absorber (X).

The suspension system according claim 1 characterized in that said pivot point (D) of the rear end of said seat stay link (6) is determined by radius of a circle, center of which is located in said axle (E) of said rear wheel mounted at the end of said swing arm (7), whereas the distance from said point (D) on the radius R to the center of said pivot axle (E) stays in the range from R = 15 mm to R = 150 mm.

The suspension system according claim 1 characterized in that the center of said axle of said rear wheel (E) in the SAG point, through which is the line determined to said center of said wheel (E), which creates in its zero position an angle to the ground in the range from 71 ° to 76°.

The suspension system according claim 1 characterized in that the shock absorber (X) has an extension body (9), that allows one mounting axle of said absorber to twist up to 90°, whereas the other end of said axle is mounted to a brace (10) or directly to a front frame portion (I).

5. The suspension system according claim 1 characterized in that said frame has a cog (1 1 ), over which runs said powering chain, whereas said cog (1 1 ) is located at said seat tube (4) or said top tube (2) of a front frame triangle, above said support bracket (5).

6. The suspension system according claim 1 characterized in that said seat stay link (6) is of a shape similar to the letter H or Y, and the proportion of its length to said chain stay link (8) equals 3: 1 in tolerance of 10%, and to the length of said swing arm (7) equals 1 : 1 in tolerance of 15%, whereas said seat stay link (6) is mounted symmetrically in relation to said frame plane (P1 ) and is equipped with bearings in said pivot point (C).

7. The suspension system according claim 1 characterized in that said swing arm (7) has mounting eyelets (15) for rear brakes.

8. The suspension system according claim 1 characterized in that the pivotal attachment of said chain stay link (8) to the frame front portion in a bottom bracket (5) is located only on one side in a bracket axle (5), opposite to a powering chain.

9. The suspension system according claim 8 characterized in that the compressing arm (14) is located to the left from a frame plane (P1 ), in reference to the riding direction, and is offset from it in the range 0-50 mm.

10. The suspension system according claim 8 characterized in that said shock absorber passes by said top tube (2) so that said tube (2) shape embraces with its cross section at least 10% of the cross section of said absorber (X).

1 1. The suspension system according claim 8 characterized in that said top tube (2) in the portion where it passes by said extension body (9) and shock absorber (X) is located in >60% of its cross section at the right hand side in reference to said frame plane (P1 ).

12. The suspension system according claim 8 characterized in that said shock absorber (X) is located longitudinally to said down tube (1) of said front triangular portion (I) so that said tube (1 ) in its cross section accommodates said absorber (X) shape in >10%.