JPH0310143Y2 - - Google Patents

Description

[Detailed explanation of the idea] [Industrial application field]

This invention relates to a rear derailleur for bicycles that changes speed by changing the chain to one selected sprocket of a multi-stage freewheel attached to the rear wheel of a bicycle. This invention relates to an improved system that maintains constant speed and improves shift response.

[Conventional technology]

A bicycle rear derailleur is equipped with a tensioner that rotatably supports a guide pulley at the top and a tension pulley at the bottom, and can move this tensioner in parallel in the direction of the hub axis using a control mechanism such as a pantograph link mechanism. There is. The tensioner is capable of swinging back and forth about an upper portion of the movable member of the control mechanism, and is elastically biased so that its lower portion rotates rearward. The chain is engaged with the tension pulley of the tensioner and the guide pulley in that order, and after leaving the guide pulley, the chain runs so as to be engaged with one of the sprockets of the freewheel. When the tensioner moves in the direction of the hub axis, the guide pulley swings the chain in front of the freewheel laterally,
This will allow the chain to be moved to the sprocket next to the sprocket it was previously attached to. If the chain is replaced with a sprocket of a different diameter, the required effective length of the chain will change;
The tensioner itself is designed so that its lower part rotates elastically toward the rear.
automatically adjusted. That is, the tension pulley that initially supports the chain introduced into the tensioner is moved in the front and back direction by rotation of the tensioner, so that slack in the chain is removed and an appropriate tension is always applied to the chain.

[Problem that the invention attempts to solve]

By the way, in the bicycle rear derailleur,
In order to improve its shifting performance, the periphery of the guide pulley, which moves the chain before it engages the freewheel in the direction of the hub axis and directly changes the chain, and the tips of the teeth of each sprocket of the freewheel. It is necessary that the two be as close as possible. It is clear that if this is too far apart, an excessive amount of overshift will be required and the speed change response will deteriorate. As an idea to temporarily solve this problem, as shown in Japanese Patent Publication No. 55-10428, a tensioner is used to elastically bias the movable member of the pantograph link mechanism clockwise when viewed from the side of the bicycle. A guide pulley is attached to the first arm, and a tension pulley is attached to the second arm, which is supported while being resiliently biased clockwise around the support shaft of the guide pulley. There is something. According to this derailleur, compared to a derailleur equipped with a normal tensioner in which a guide pulley and a tension pulley are pivotally supported on a single frame that is rotatably supported while elastically biasing a movable member, the derailleur has the following features. There are advantages. That is, since the guide pulley always tries to approach the multi-stage freewheel, the distance between the guide pulley and each sprocket of the freewheel becomes small. In addition, the first arm that supports the guide pulley and the second arm that supports the tension pulley are both rotatable within a certain range, and each is elastically biased separately, making it easy to remove. The amount of chain slack that can be achieved is large, that is, the gear capacity is large.

[Problem that the invention attempts to solve]

However, the rear derailleur disclosed in the above publication still has the following problems.
That is, first of all, balance should be established between the elasticity that should be applied to the first arm to substantially bias the guide pulley and the elasticity that should be imparted to the second arm to substantially bias the tension pulley. very difficult to take. That is, when the chain is applied, the tension applied to the chain is shared by the spring that biases the first arm and the spring that biases the second arm. This means that the position of the guide pulley relative to the freewheel depends on the amount of slack in the chain. Even if the chain is replaced with a sprocket of a different diameter in the front gear, the amount of slack in the chain changes, so the above two steps are taken so that the spacing between each freewheel sprocket and the guide pulley is constant. Balancing the two springs is extremely difficult. In particular, when the difference in diameter between the largest diameter sprocket and the smallest diameter sprocket in the freewheel is large, it is impossible to maintain a constant distance between the guide pulley and each of these sprockets. This idea was devised under the above circumstances, and while taking advantage of the large gear capacity of the conventional rear derailleur mentioned above, it is possible to reduce the diameter difference between the freewheel's largest diameter sprocket and the smallest diameter sprocket. To provide a rear derailleur for a bicycle which is improved so that the distance between a guide pulley and each sprocket of a freewheel can be kept constant even if the distance is large.

[Means to solve the problem]

In order to solve the above problems, this invention adopts the following technical means. That is, this invention includes a base member attached to a bicycle frame, a pair of inner and outer link members swingably connected to the base member,
A first arm elastically biased in a clockwise direction is attached to the movable member of the pantograph link mechanism, which includes a movable member swingably connected to the link members at the distal end of the link member. a guide pulley is pivotally supported on the distal end side of the first arm, and a second arm resiliently biased clockwise is supported on the proximal end side of the first arm; The bicycle rear derailleur is configured with a tension pulley pivotally supported on its tip side, and the first arm rotates counterclockwise around the support shaft in conjunction with the movement of the movable member toward the large diameter sprocket. The present invention is characterized in that a rotating regulating piece is provided, and this regulating piece is engaged with the first arm so as to oppose the biasing force applied to the first arm.

[Action and effect]

When the derailleur operating means is operated to deform the pantograph link mechanism so that its movable member moves to the large diameter sprocket side of the freewheel, that is, when the guide pulley is moved to the large diameter sprocket side, the pantograph link mechanism is interlocked with this movement. the regulating piece moves the first arm in a direction that opposes the elastic force applied thereto;
In other words, it is forced to rotate counterclockwise. The first arm is always elastically biased in the clockwise direction, and the guide pulley is elastically trying to approach each sprocket of the freewheel, but the above operation causes the guide pulley to move toward the larger diameter sprocket. As time goes on, it will be forced downward. Therefore, even if the difference in diameter between the freewheel's largest diameter sprocket and the smallest diameter sprocket is large, the trajectory of the guide pulley during gear shifting should be parallel to the line connecting the tips of the teeth of each sprocket, and The distance from the guide pulley can be kept constant. This results in extremely good shift response. Note that this is an effect that can be achieved regardless of changes in chain slack due to changing the chain to the front gear. Furthermore, the rotation range of the first arm is restricted by the restriction piece so that the guide pulley does not approach each sprocket unnecessarily; therefore, the spring is stored below the restriction piece. It can be rotated while This means that the derailleur of this invention has a correspondingly large gear capacity. As a result, even if, for example, the chain is caught on an external object and the part that was previously introduced into the tension pulley is pulled forward, this force will be transferred in the direction in which both the first and second arms store the spring force. By rotating the derailleur, it is absorbed without any problem, and the derailleur itself will not be damaged.

[Explanation of Examples]

Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings. The rear derailleur 4 includes a pantograph link mechanism 10 and a tensioner T attached to a movable member 9 of the pantograph link mechanism 10.
The pantograph link mechanism 10 includes a base member 5 attached to a backhawk 3 of a bicycle frame.
and a pair of inner and outer link members 7, 8 whose proximal ends are connected so as to be swingable laterally and extend forward.
and a movable member 9 rotatably connected to the link members 7 and 8 at the distal ends of the link members 7 and 8. A gear portion 7a is formed at the tip of the inner link member 7 for rotating a ring 18 having a regulating piece 19, which will be described later. In addition, this pantograph link mechanism 1
A return spring is incorporated in the pantograph link mechanism 10 to urge the constantly movable member 9 to move outward, that is, toward the small diameter gear of the freewheel. , the deformation operation is performed by a known operation mechanism by pulling the operation cable 11 connected thereto. The movable member 9 has upper and lower walls 12 and 13 that pivotally support the link members 7 and 8, a side wall 14 that connects these walls 12 and 13, and a side wall 14 that connects the lower wall 13 and the side wall 14, and connects each gear of the freewheel. Bottom wall 1 parallel to
5. A through hole 16 having an internal thread is formed in the center of the bottom wall 15, and a bulging boss portion 17 surrounding the through hole 16 is integrally formed on the outer wall thereof. A ring 18 having a regulating piece 19 extending radially outward is rotatably fitted around the boss portion 17 . A gear portion 20 is formed at a suitable portion of the outer circumference of this ring 18, and this gear portion 20 is a gear portion 7a formed at the tip of the inner link member 7.
is engaged with. As a result, when the pantograph link mechanism 10 is deformed so that its movable member 9 moves inward, that is, toward the large diameter gear of the freewheel, the ring 18 moves counterclockwise when viewed from the side of the bicycle, as shown in FIG. Now rotate in the clockwise direction. The bottom wall 15 of the movable member 9 has a through hole 16 therein.
A support shaft 26 is screwed into the support shaft 26, and the first arm 22 is rotatably supported on the base end side thereof. This first arm 22 is always elastically biased clockwise when viewed from the side of the bicycle by a torsion spring 27 inserted into the support shaft 26 . Further, an outwardly directed pin 23 is provided at a proper portion of the base of the first arm 22, and this is attached to the bottom wall 1 of the movable member 9.
5, and its rotation range is basically restricted. Further, the pin 23 is engaged with a regulating piece 19 of the ring 18, so that when the ring 18 is rotated counterclockwise when viewed from the side of the bicycle, it is pushed by the regulating piece 19 and One arm 22 will be rotated in the same direction. A guide pulley 28 is rotatably supported at the distal end of the first arm 22, and a second arm 29 is rotatable at its proximal end about the same axis as the support shaft of the guide pulley 28. Supported by The second arm 29, like the first arm 22,
The torsion spring 30 elastically biases the bicycle in a clockwise direction when viewed from the side of the bicycle. A tension pulley 30 is rotatably supported at the tip of the second arm 29. In the above configuration, as the movable member 9 of the pantograph link mechanism 10 moves toward the large-diameter gear of the freewheel 1, that is, to the right in FIGS. 2 and 3, the ring 1 with the regulating piece 19
8 rotates counterclockwise when viewed from the side of the bicycle, and the regulating piece 19 pushes down the pin 23 of the first arm 22, so that the first arm 22 rotates counterclockwise when viewed from the side of the bicycle, that is, the first arm 22 rotates counterclockwise when viewed from the side of the bicycle. In Figure 5, it is rotated clockwise. Then, the guide pulley 28 moves as shown in the imaginary line in FIG. 3 and in FIG.
It is gradually pushed down. As a result, the movable member 9
As the freewheel 1 moves in the lateral direction, the guide pulley 28 becomes able to move parallel to a line connecting the tooth tips of the respective sprockets of the freewheel 1. As a result, good shift response is maintained both when the guide pulley 28 is on the small diameter sprocket side of the freewheel and when it is on the large diameter sprocket side. Note that the regulation piece 19 that rotates due to the movement of the movable member 9 is connected to the first arm 22 or the guide pulley 28.
Since it only restricts the upward movement, it can move downward against the elasticity of the spring 27. Therefore, even if a large tension is applied to the chain due to the chain being caught on an external object, this large tension can be absorbed by the first arm 22 and second arm 29 counterclockwise when viewed from the side of the bicycle. It is absorbed by rotating. At the same time, the first arm 22
Since both the second arm 29 and the second arm 29 are elastically biased, so-called gear capacity can be increased. It should be noted that the scope of the present invention is, of course, limited to the embodiments shown in the drawings. That is, in the illustrated example, a gear part is formed at the tip of the inner link of the pantograph link mechanism as a mechanism for rotating the regulating piece in conjunction with the movement of the movable member toward the large-diameter sprocket side, and the gear part is formed at the tip of the inner link of the pantograph link mechanism. The gear part is formed on the outer link, and an intermediate gear is rotatably attached between the gear part and the ring. Various modifications can be considered, such as configuring the gear to mesh with both a gear part provided on the outer link and a gear part provided at the lower part of the ring.

[Brief explanation of the drawing]

Fig. 1 is an overall side view of the bicycle rear derailleur according to the present invention, Figs. 2 and 3 are front views explaining its operation, Fig. 4 is a perspective view showing its main components in an exploded state, and Fig. FIG. 5 is an explanatory diagram of the action seen from the wheel side of the bicycle. 4... Rear derailleur, 5... Base member,
7, 8...link member, 9...movable member, 10...
...Pantograph link mechanism, 19...Regulation piece, 2
2...First arm, 28...Guide pulley, 29
...Second arm, 31...Tension pulley.

Claims (1)

[Scope of claim for utility model registration] A base member attached to a bicycle frame,
The above-mentioned movable pantograph link mechanism includes a pair of inner and outer link members that are swingably connected to the base member, and a movable member that is swingably connected to the link members at the tip of the link member. A first arm elastically biased in the clockwise direction is supported on the base end side of the member, a guide pulley is pivotally supported on the distal end side of the first arm, and a clock is attached to the distal end side of the first arm. A rear derailleur for a bicycle, which is constructed by supporting a second arm elastically biased in the rotational direction at its base end side and supporting a tension pulley at its distal end side, the large diameter sprocket side of the movable member A regulating piece is provided that rotates counterclockwise around the spindle of the first arm in conjunction with the transition to the first arm. characterized in that they are opposedly engaged;
Rear derailleur for bicycles.