WO2003101816A1

WO2003101816A1 - Damping apparatus

Info

Publication number: WO2003101816A1
Application number: PCT/IT2002/000355
Authority: WO
Inventors: Marcello Segato; Naganao Kameda
Original assignee: Uni-Sunstar B.V.
Priority date: 2002-05-31
Filing date: 2002-05-31
Publication date: 2003-12-11
Also published as: AU2002314530A1; EP1509441A1

Abstract

A damping apparatus with excellent endurance that has a simple structure and can be produced at a low cost is provided. The damping apparatus comprises linking means 21 for linking the driven sprocket 11 of chain transmission apparatus 10 of a motor two-wheel vehicle to the hub 2, which serves as an installation member therefor, so as to allow for a relative rotation thereof within a specific angular range; a base plate 22 inserted between the driven sprocket 11 and hub 2 so that it cannot rotate with respect to the hub 2; a plurality of receptacles 2a, 11a, 22a formed some distance apart from each other in the circumferential direction on the facing surfaces of hub 2, driven sprocket 11, and base plate 22; and elastic members 23 placed into the receptacles 2a, 11a, 22a and absorbing the impact forces acting between the driven sprocket 11 and hub 2 by elastic deformation between the edges of receptacles 11a of driven sprocket 11 in the circumferential direction and the opposite edges of receptacles 2a, 22a of hub 2 and base plate 22 in the circumferential direction.

Description

DAMPING APPARATUS BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a damping apparatus suitable for chain transmission apparatuses comprising a pair of sprockets and a chain stretched over the sprockets .

2. Description of the Related Art

In two-wheel motor vehicles, chain transmission apparatuses comprising a drive sprocket fixed to the output shaft of an engine, a driven sprocket fixed to a rear wheel , and a chain stretched over the two sprockets have been widely used as power transmission apparatuses for transmitting the driving power from the engine to the rear wheel .

However, the problem associated with such apparatuses was that during rapid acceleration or braking of a two-wheel motor vehicle, a large impact load was applied to the chain and the chain was elongated or the engaging portions of the chain and sprockets were rapidly worn out .

In order to resolve this problem, Japanese Utility Model Application Laid-open No. S54-43752 disclosed a hub for a motor two-wheel vehicle comprising a hub provided with fan-like damper chambers formed by radially protruding partitions, a drive plate integrally provided with drive tabs adjacent to the inner central portions of the damper chambers, and a damper composed of a synthetic rubber and inserted between the partitions and the drive tabs, wherein the rotation force from the engine was transmitted to the hub, while being damped by the damper.

On the other hand, Japanese Utility Model

Application Laid-open No. H6-37631 disclosed a damper in which a hub is provided for external fitting onto and fixing to an output shaft of an engine, a pair of side plates are provided on both sides of a ring-like flange of the hub, both side plates are integrally linked on the periphery thereof, a clutch plate with a diameter larger than that of one side plates is linked thereto, a plurality of angular window holes are formed some distance apart from each other in the circumferential direction in the intermediate portion in the radial direction in the two side plates and ring-like flanges, compression coil springs are fit in the respective window holes, and impact forces acting between the output shaft and clutch plate are absorbed by the compression coil springs, this damper being designed as a damping apparatus employed in clutch units of automotive engines.

In the hubs for motor two-wheel vehicles disclosed in the above-described publication, damper chambers of complex shape designed to accommodate a damper had to be provided in the wheel hub and drive tabs to be inserted into the damper chambers had to be integrally provided on the drive plate installed on the sprocket. As a result, the wheel and drive plate had a complex structure and the production cost was high. Moreover, since a rubber damper was used, the service life was short.

Furthermore, the damper disclosed in the above- described publication had good utility because the compression coil springs were used, thereby making it possible to adjust the damping performance by setting the appropriate spring constant and to extend the service life. However, the dampers of such a structure have not yet found application as damping apparatuses for chain transmission apparatuses of motor two-wheel vehicles employed under severe conditions under which the apparatuses are often splashed with muddy water and the like. SUMMARY OF THE INVENTION

It is an object of the present invention to provide a damping apparatus that has a simple structure, can be manufactured at a low cost, and has excellent endurance. The assignee came up with an idea that a damping apparatus for chain transmission apparatuses of low cost and with excellent endurance can be realized if a basic configuration of the damping apparatus used in clutch mechanisms of automobiles is employed in the a damping apparatus for chain transmission apparatuses. This idea led to the creation of the present invention.

The damping apparatus in accordance with the present invention comprises linking means for linking a sprocket of a chain transmission apparatus to an installation member therefor so as to allow for a relative rotation thereof within a specific angular range, a plurality of receptacles formed some distance apart from each other in the circumferential direction on the facing surfaces of the sprocket and installation member, and elastic members placed inside said receptacles and absorbing the impact forces acting between the sprocket and the installation member by elastic deformation between the edges of receptacles of the sprocket in the circumferential direction and the opposite edges of receptacles of the installation member in the circumferential direction. In such a damping apparatus, the elastic members are compressed between the edges of receptacles of the sprocket in the circumferential direction and the opposite edges of receptacles of the installation member in the circumferential direction, and the impact forces acting upon the installation member from the sprocket or upon the sprocket from the installation member are absorbed. Furthermore, since the impact forces are absorbed by elastic members filling the receptacles formed by a combination of the sprocket and installation member, the number of parts constituting the damping apparatus is decreased and the production cost thereof can be reduced. Furthermore, since the receptacles are formed on the opposite surfaces of the sprocket and installation member, the inside of the receptacles can be easily sealed and such a damping apparatus can be applied to motor two-wheel vehicles often splashed with muddy water and the like, while providing for sufficient operation stability.

A base plate having formed therein receptacles composed of angular through holes containing the elastic members may be inserted between the sprocket and installation member, and this base plate may be installed so that it cannot rotate with respect to the installation member. A plate composed of a material with a mechanical strength higher than that of the installation member can be employed for the base plate. Therefore, since part of the load acting upon the edges of the receptacles in the installation member in the circumferential direction from the elastic members is received by the base plate, the set mechanical strength of the installation member can be decreased. For example, a wheel composed of a light alloy such as an aluminum alloy is often used for the rear wheel of a motor two-wheel vehicle to decrease weight. However, such light alloys cannot guarantee a sufficient mechanical strength for the parts receiving a load acting from the elastic members. Therefore, providing the base plate is preferred because it allows the load from the elastic members to be readily received, while decreasing the weight of the wheel .

The receptacles in the base plate may be composed of through holes or open-end holes and the receptacles in the installation member may be omitted. In such a case, since no receptacles are formed in the installation member, the design modifications of the installation member can be minimized. For example, when the damping means is provided between a driven sprocket and a wheel of a rear wheel of a motor two-wheel vehicle, the damping apparatus can be installed without making significant design modifications of the wheel hub serving as an installation member. In particular, if the receptacles of the base plate are composed of open-end holes, the damping member can be assembled in advance by placing the elastic members in the receptacles. As a result, installation of the damping apparatus on the installation member can be further facilitated.

The receptacles of the sprocket may be composed of through holes and a keep plate may be provided on the outer side surface of the sprocket to prevent the elastic members from falling out. With such a structure, the receptacles in the sprocket can be easily formed by pressing, the processing cost can be reduced despite the fact that the addition of the keep plate increases- the number of parts, and the total production cost can be reduced. Furthermore, installing the keep plate makes it possible to prevent effectively the penetration of foreign matter such as dirt and sand into the receptacles . Compression coil springs may be used as elastic members. Synthetic rubber or the like can be used for the elastic members, but sufficient endurance of such elastic members is difficult to guarantee. Moreover, damping performance is difficult to adjust finely. Therefore, the elastic members are preferably composed of compression coil springs, which allows the endurance to be increased and the damping performance to be adjusted, for example, by adjusting the wire diameter.

A tubular portion inserted into the central portion of the sprocket may be formed in a protruding condition in the central portion of the installation member, and a sleeve for positioning the sprocket in the radial direction with respect to the tubular portion may be fit between the sprocket and the tubular portion. In such a damping apparatus, vibrations of the sprocket in the in- plane direction apparently increase because the sprocket is elastically supported by the installation member. Therefore, it is preferred that the sprocket be positioned in the radial direction with respect to the installation member by externally fitting the sprocket onto the tubular portion. Furthermore, since the sprocket rotates relative to the installation member, it is preferred that wear of the tubular portion be prevented by externally fitting the sprocket onto the tubular portion via the sleeve. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an exploded perspective view of a wheel and the damping apparatus installed thereon;

FIG. 2 is an exploded perspective view of the damping apparatus;

FIG. 3 is a longitudinal sectional view of the wheel and damping apparatus;

FIG. 4 is a longitudinal sectional view of the hub and damping apparatus in a position in which they contain elastic members;

FIG. 5 is a longitudinal sectional view of the hub and damping apparatus in a position in which they contain fixing bolts;

FIG. 6 is a cross-sectional view along a VI-VI line in FIG. 4;

FIG. 7 is a plan view of the sprocket; FIG. 8 is a plan view of the base plate;

FIG. 9 is a plan view of the keep plate; and FIG. 10 is a view of the damping apparatus of another configuration, which corresponds to FIG. 4. DESCRIPTION OF THE PREFERRED EMBODIMENTS The preferred embodiments of the present invention will be described below with reference to the appended drawings .

A wheel 1 shown in FIG. 1 is a rear wheel of a motor two-wheel vehicle. A damping apparatus 20 is provided over a hub 2 of wheel 1 serving as an installation member and a driven sprocket 11 of a chain .transmission apparatus 10 transmitting power from an engine (not shown in the figure) to the rear wheel and serves to absorb a shock force between the driven sprocket 11 and a drive sprocket 12 of chain transmission apparatus 10 and a chain 13 stretched over the two sprockets 11, 12, to suppress the elongation of chain 13, and to suppress wear in the engaging portions of chain 13 and the two sprockets 11, 12.

The wheel 1, as shown in FIG. 1 to FIG. 3, has a well-known structure comprising the hub 2, a ring-like rim 4, and a plurality of spokes 5 linking the hub 2 to the rim 4. A shaft hole 3 is formed in the center of hub 2 and a pair (left and right) of bearings 6 are installed some distance apart from each other in the shaft hole 3. The wheel 1 is rotatably supported by a wheel shaft 7 passing through the bearings 6. Bearings 8 are installed between the left part of wheel shaft 7 and the hub 2 so as to be positioned on the left and right sides of damping apparatus 20 so that it can smoothly receive the rotation force or impact force acting upon the driven sprocket 11 and damping apparatus 20. The bearings 8, however, may be omitted.

The damping apparatus 20, as shown in FIG. 1 to FIG. 9, comprises: linking means 21 for linking the driven sprocket 11 of chain transmission apparatus 10 to the hub 2, which serves as an installation member therefor, so as to allow for a relative rotation thereof within a specific angular range; a base plate 22 inserted between the driven sprocket 11 and hub 2 so that it cannot rotate with respect to the hub 2; a plurality of receptacles 2a, 11a, 22a formed some distance apart from each other in the circumferential direction in the facing surfaces of hub 2, driven sprocket 11, and base plate 22; elastic members 23 placed inside the receptacles 2a, 11a, 22a and absorbing the impact forces acting between the driven sprocket 11 and hub 2 by elastic deformation between the edges of receptacles 11a of driven sprocket 11 in the circumferential direction and the opposite edges of receptacles 2a, 22a of hub 2 and base plate 22 in the circumferential direction; and a flat keep plate 24 for applying pressure so that the elastic members 23 do not fall out of the driven sprocket 11. However, the base plate 22 can be omitted if the depth of receptacles 2a is set so that the entire right part of elastic members 23 can be fit therein.

An almost flat mounting surface 2b is formed almost perpendicularly to the wheel shaft 7 on the left end surface of hub 2. The base plate 22 in the form of an almost flat plate of approximately the same diameter as the mounting surface 2b, the driven sprocket 11 in the form of an almost flat plate with a diameter somewhat larger than that of the mounting surface 2b, and the keep plate 24 in the form of an almost flat plate of approximately the same diameter as the mounting surface 2b are provided as a stack on the mounting surface 2b in the order of description starting from the mounting surface 2b side. A tubular portion 2c is formed in the central portion of mounting surface 2b so as to protrude in the leftwise direction. Insertion holes lib, 22b are formed in the central portions of driven sprocket 11 and base plate 22, and the driven sprocket 11 and base plate 22 are externally fit onto the tubular portion 2c via a sleeve 25. In other words, in the damping apparatus 20 in accordance with the present invention, vibrations of driven sprocket 11 in the in-plane direction apparently increase because the driven sprocket 11 is elastically supported. For this reason, those vibrations are suppressed by externally fitting the driven sprocket 11 on the tubular portion 2c. Moreover, the vibrations of driven sprocket 11 are suppressed via the sleeve 25 so as to prevent wear of the tubular portion 2c. Furthermore, an insertion hole 24b is formed in the central portion of keep plate 24. The keep plate 24 is fit into a ring-like groove 26 formed as a step on the left surface of driven sprocket 11 and positioned coaxially with the driven sprocket 11 in the groove 26. Linking means 21 will be described below. A plurality (six in the example shown in the figure) of threaded holes 2d are formed equidistantly in the circumferential direction in the intermediate portions of mounting surface 2b in the radial direction thereof, and fixing bolts 27 are tightened and secured in the plurality of threaded holes 2d so that the threaded portions of the bolts protrude to the le t. Round bolt insertion holes 22c, 24c for insertion of fixing bolts 27 are formed in the base plate 22 and keep plate 24. Guide holes lie in the form of partial circular arc for insertion of fixing bolts 27 are formed within a specific angular range in the circumferential direction in the driven sprocket 11, making it possible for the driven sprocket 11 to rotate relative to hub 2 within the specific angular range along the guide holes lie. Spacer tubes 28 somewhat longer than the sheet thickness of driven sprocket 11 are fit onto the fixing bolts 27 inside the guide holes lie, thereby forming a gap such that, in a state in which the keep plate 24 and base plate 22 are secured to the hub 2 by tightening nuts 29 on fixing bolts 27, the driven sprocket 11 can rotate between the keep plate 24 and base plate 22.

The angular range of relative rotation of driven sprocket 11 and hub 2 is set by the formation angle of guide holes lie. It is, however, preferred, that the angular range be set to an angle almost equal to the maximum angle to which the below-described elastic member 23 composed of a compression coil spring can be deformed in the circumferential direction, or to an angle somewhat less than the maximum angle. For example, the setting can be made to allow for relative rotation within any angular range of 5-15°.

The damping apparatus 20 will be described below. Six receptacles 11a composed of angular through holes are formed some distance apart from each other in the circumferential direction between the adjacent guide holes lie in the driven sprocket 11. Six receptacles 22a composed of angular through holes are formed in the base plate 22 some distance apart from each other in the circumferential direction in the positions facing the receptacles 11a. Six receptacles 2a composed of angular open-end holes are formed in the mounting surface 2b of hub 2 some distance apart from each other in the circumferential direction in the positions facing the receptacles 11a. A pair (inner and outer) of keep tabs 24a are integrally press formed in the keep plate 24 in the positions corresponding to receptacles 11a. Since the receptacles 11a, 22a are the through holes, they can be easily formed by pressing. Furthermore, receptacles 2a may be formed by machining, but they can be also easily produced by simultaneous forming when the wheel 1 is formed by casting or the like.

Elastic members 23 consisting of compression coil springs are placed into those receptacles 2a, 11a, 22a of three types so that the center of compression coil springs is almost in the circumferential direction, and those elastic members are contained in receptacles 2a, 11a, 22a without play because they are impelled by the keep tabs 24a toward the hub 2. Further, as shown in FIG. 6, if the driven sprocket 11 is rotated in the direction shown by an arrow with respect to hub 2, base plate 22, and keep plate 24, the end portions of receptacles 2a, 22a of hub 2 and base plate 22 are brought in contact with one end of elastic members 23 in the circumferential direction, and the end portions of receptacles 11a of driven sprocket 11 are brought in contact with the other end of elastic members 23 in the circumferential direction. As a result, the elastic members 23 are compressed and the impact force between the driven sprocket 11 and wheel 1 is absorbed. Further, elastic members such as synthetic resin or synthetic rubber, plate spring or tension spring can be also used as the elastic members 23. However, it is preferred that compression coil springs be used, because such springs make it possible to adjust easily the damping performance by adjusting the wire diameter, outer diameter, or length.

A plate made of any material having a mechanical strength sufficient to receive readily the load applied to the elastic members 23 can be used for the base plate 22. For example, the base plate can be composed of a carbon steel plate such as S45C plate conforming to JIS standard. Furthermore, a sprocket made of any material having a mechanical strength sufficient to withstand the load applied during power transmission can be used for the driven sprocket 11. For example, the driven sprocket can be composed of a carbon steel plate such as S45C plate conforming to JIS standard. The keep plate 24 is preferably made of a spring steel or stainless steel to guarantee a sufficient ability to hold the elastic members 23.

In such damping apparatus 20, the keep plate 24, base plate 22, and hub 2 are rotated with respect to the driven sprocket 11, and the elastic members 23 are compressed by the impact force during rapid acceleration or rapid braking. As a result, the impact force is absorbed. Absorbing such impact forces can increase stability of riding during rapid acceleration and rapid braking and also can prevent the application of excess load to chain 13 and suppress elongation of chain 13. Furthermore, wear of the engaging portions of chain 13 and driven sprocket 11 is suppressed and the endurance of chain transmission apparatus 10 can be increased.

Another embodiment in which the configuration of damping apparatus 20 is partially modified will be described below. The components identical to those of the above-described embodiment are assigned with the same symbols and explanation thereof will be omitted.

(1) A thick base plate 22A having receptacles 22a that can contain a right half portion of elastic members 23 may be provided instead of base plate 22, as in the damping apparatus 20A shown in FIG. 10. The merit of such a configuration is that the receptacles 2a formed in the mounting surface 2b of hub 2 can be omitted and the design modification of wheel 1 is not required. Furthermore, the base plate 22A may be made even thicker and the receptacles 22a may be made as open-end holes that are open on the side of driven sprocket 11. In this case, the receptacles 2a on the mounting surface 2b of hub 2 can be omitted and an assembly of driven sprocket 11, keep plate 24, and elastic members 23 with the base plate 22 can be manufactured in advance, followed by assembling with the hub 2. As a result, the installation of the damping apparatus on the wheel 1 is facilitated.

(2) The receptacles 11a formed in the driven sprocket 11 may be formed as open-end angular grooves that are opened on the side of base plate 22, and the keep plate 24 may be omitted.

Further, in the present embodiment, the damping apparatus 20 was provided over the driven sprocket 11 and hub 2 of wheel 1. However, it can be also provided over the drive sprocket 12 and output shaft of engine . Moreover, the present invention is obviously suitable for chain transmission apparatuses 10 other than those of motor two-wheel vehicles.

The damping apparatus in accordance with the present invention makes it possible to obtain the following effects : the number or parts constituting the damping apparatus is decreased and the production cost is reduced, the inside of receptacles can be easily sealed, and the damping apparatus can be used on rear wheels of motor two-wheel vehicles often splashed with muddy water and the like, while providing for sufficient stability of operation.

Here, if the base plate is installed between the sprocket and the installation member, a low mechanical strength of the installation member can be set. For example, in case of rear wheels of motor two-wheel vehicles, light alloys that have a low mechanical strength can be used and a load from the elastic members can be readily received, while decreasing the wheel weight .

If the receptacles of the base plate are composed of through or open-end holes and the receptacles in the installation member are omitted, the design modifications of the installation member can be minimized. For example, when the damping means is provided between a driven sprocket and wheel of a rear wheel of a motor two-wheel vehicle, the damping apparatus can be installed without making significant design modifications of the wheel hub serving as an installation member. In particular, if the receptacles of the base plate are composed of open-end holes, the damping member can be assembled in advance. As a result, installation of the damping apparatus on the installation member can be further facilitated.

If the receptacles of the sprocket are composed of through holes and a keep plate is provided on the outer side surface of the sprocket to prevent the elastic members from falling out, the receptacles in the sprocket can be easily formed by pressing, the processing cost can be reduced despite the fact that the addition of the keep plate increased the number of parts, and the total production cost can be reduced. Furthermore, installing the keep plate makes it possible to prevent effectively the penetration of foreign matter such as dirt and sand into the receptacles.

Using compression coil springs as elastic members allows the endurance to be increased and the damping performance can be easily adjusted, for example, by adjusting the wire diameter.

If a tubular portion inserted into the central portion of the sprocket is formed in a protruding condition in the central portion of the installation member, and a sleeve for positioning the sprocket in the radial direction with respect to the tubular portion is fit between the sprocket and the tubular portion then vibrations of the sprocket in the in-plane direction can be suppressed by the tubular portion, the stability of sprocket operation can be improved, wear of the tubular portion caused by relative rotation of the sprocket and tubular portion can be suppressed, and endurance of the installation member can be increased.

Claims

What Is Claimed Is:

1. A damping apparatus comprising: linking means for linking a sprocket of a chain transmission apparatus to an installation member therefor so as to allow for a relative rotation thereof within a specific angular range; a plurality of receptacles formed some distance apart from each other in the circumferential direction on the facing surfaces of said sprocket and installation member; and elastic members placed inside said receptacles and absorbing the impact forces acting between the sprocket and the installation member by elastic deformation between the edges of receptacles of the sprocket in the circumferential direction and the opposite edges of receptacles of the installation member in the circumferential direction.

2. The damping apparatus according to claim 1, wherein a base plate having formed therein receptacles composed of angular through holes for containing the elastic members is inserted between said sprocket and installation member and this base plate is installed so that the base plate is not capable of rotating with respect to the installation member.

3. The damping apparatus according to claim 2, wherein the receptacles in said base plate are composed of through holes or open-end holes and the receptacles in the installation member are omitted.

4. The damping apparatus according to any claim of claims 1 to 3 , wherein the receptacles in said sprocket are composed of through holes and a keep plate preventing the elastic members from falling out is provided on the outer side surface of the sprocket.

5. The damping apparatus according to any claim of claims 1 to 4 , wherein compression coil springs are used as said elastic members.

6. The damping apparatus according to any claim of claims 1 to 5, wherein a tubular member to be inserted into the central portion of the sprocket is formed in a protruding fashion in the central portion of said installation member, and a sleeve for positioning the sprocket in the radial direction with respect to the tubular portion is mounted between the sprocket and the tubular member.