JP2018020739A - Gear plate for bicycle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gear plate for a bicycle that, even if the position where the maximum tread force is applied to a pedal varies, is able to cope with it.SOLUTION: A gear plate 3 for a bicycle comprises: a ring part 31; and a plurality of teeth 32 arranged at equal pitch in a circumferential direction with an inter-tooth part 33 between them on its outer periphery, each tooth having a pressure transmission side face 321 with which a roller comes into contact during transmission of drive force to a chain and a non-pressure transmission side face 322 located on the side opposite the pressure transmission side face 321. The plurality of teeth 32 includes: a large-diameter area 32A in which the pitch diameter PD of a series of teeth 32 around an axial line O1 is relatively large, and a small-diameter area 32B in which the pitch diameter of the series of teeth 32 around the axial line O1 is relatively small. The plurality of teeth 32 includes a pressure angle maximum area in which the pressure angle at a pressure point when the roller center on the pressure transmission side face 321 is on the pitch diameter PD during transmission of drive force to the chain is set to 25 to 35°. The pressure angle maximum area is provided in a large-diameter area 32A.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a bicycle gear plate.

  Conventionally, various improvements have been attempted with respect to bicycle gear plates. For example, Patent Document 1 proposes a technique for suppressing the generation of noise when the roller chain is engaged or detached by devising the shape of the teeth formed on the outer periphery of the gear plate.

  On the other hand, as the gear plate, a non-circular gear in which teeth are formed along the outer periphery of a non-circular ring portion is known. In a bicycle, for example, during one rotation of the crank arm, when the pedal is positioned forward with respect to the base end portion of the crank arm, it is considered that the maximum pedaling force can be applied to the pedal. In the case of a non-circular gear, if the long diameter part of the non-circular gear is attached along the vertical direction when the pedal is in a position where the maximum pedaling force can be applied, when the maximum pedaling force is applied, The rotational speed is the same as that of a round gear having a larger number of teeth than the actual number of teeth of a non-round gear. That is, it is considered that the use of a non-circular gear enables high-speed traveling as compared to the case where a circular gear with the same number of teeth is used. Further, when the dimensional ratio of the long diameter portion to the short diameter portion of the non-circular gear is increased, the traveling speed of the chain wound around the non-circular gear is increased when the long diameter portion of the non-circular gear is along the vertical direction. Become faster. Non-circular gears having such characteristics are often used in competition bicycles.

  However, the position of the crank arm when the maximum pedaling force is exerted on the pedal varies depending on the bicycle user. With respect to this point, if the mounting position of the gear plate in the circumferential direction with respect to the crank arm can be changed, it is possible to adjust the position of the crank arm and the gear plate in the circumferential direction according to the individual difference. However, the structure in which the mounting position of the gear plate in the circumferential direction can be adjusted has a complicated structure. Further, even the same user may vary in the position where the maximum pedaling force is exerted on the pedal due to conditions or the like. Therefore, even if the configuration in which the mounting position of the gear plate in the circumferential direction can be adjusted is employed, it is difficult to cope with variations in the pedaling force of the same user as described above.

Japanese Patent Laid-Open No. 2005-9516

  The present invention has been conceived under such circumstances, and even when a variation occurs at a position where the maximum pedaling force is applied to the pedal, the bicycle gear is suitable for dealing with the variation. It is an object to provide a board.

  In order to solve the above problems, the present invention takes the following technical means.

  The bicycle gear plate provided by the present invention is arranged on the ring portion and the outer periphery of the ring portion at an equal pitch in the circumferential direction across the interdental portion, and the roller contacts when the driving force is transmitted to the chain. A bicycle gear plate comprising a plurality of teeth, each having a pressure transmission side surface and a non-pressure transmission side surface located on the opposite side of the pressure transmission side surface in the circumferential direction across the tooth tip portion, The plurality of teeth includes a long diameter region having a relatively large pitch diameter of the teeth continuous in the circumferential direction around the axis of the ring portion as viewed in the thickness direction, and the circumference around the axis of the ring portion. A plurality of teeth, the center of the roller on the pressure transmission side surface is on the pitch diameter when the driving force is transmitted to the chain. In Pressure angle at the pressure points to be scheduled if that comprises a pressure angle maximum area set to 25 to 35 °, the pressure angle maximum area is characterized in that provided on at least the major diameter region.

  In a preferred embodiment, the long-diameter region is provided at two positions located on the opposite sides in the circumferential direction around the axis line, of the outer periphery of the ring portion.

  In a preferred embodiment, in the major axis region, the pitch diameter of the teeth continuous in the circumferential direction is elliptical.

  In a preferred embodiment, the pressure angle in the maximum pressure angle region is set to 28 to 32 °.

  In a preferred embodiment, the pressure transmission side surface of each tooth in the long diameter region is concavely curved with a curvature smaller than the outer peripheral curvature of the roller in the vicinity of the pressure point in the height direction of the tooth. ing.

  In a preferred embodiment, the root of each tooth is curved concavely with a larger curvature than the outer peripheral curvature of the roller.

  Other features and advantages of the present invention will become more apparent from the detailed description given below with reference to the accompanying drawings.

It is a front view showing an example of a bicycle gear crank configured to include a bicycle gear plate according to the present invention. FIG. 2 is a rear view of the bicycle gear crank shown in FIG. 1. FIG. 2 is a side view of the bicycle gear crank shown in FIG. 1. It is a figure which shows the gear board for bicycles. It is a principal part enlarged view which shows typically the state by which the chain was hung around the bicycle gear board. It is a principal part enlarged view which shows typically the state (at the time of driving force transmission) where the chain was wound around the bicycle gear board.

  Hereinafter, preferred embodiments of the present invention will be specifically described with reference to the drawings.

  1 to 3 show an example of a bicycle gear crank that includes a bicycle gear plate according to the present invention. The bicycle gear crank A1 of the present embodiment includes a crank arm 1 and an outer gear 2 and an inner gear 3 as gear plates.

  As shown in FIGS. 1 and 2, the crank arm 1 has a boss portion 11 for attaching a crankshaft (not shown) to the base end portion, and a pedal (not shown) screw at the distal end portion. A screw hole 12 for attaching the shaft is provided. Further, in the present embodiment, the crank arm 1 has a plurality of (in this embodiment, five) stay portions 13 extending radially, and the outer gear 2 and the inner gear 3 are attached to the stay portions 13.

  The outer gear 2 is a large-diameter gear that is formed by pressing or cutting a plate material having a predetermined plate thickness and has more teeth than the inner gear 3. In the present embodiment, the outer gear 2 is a perfect circle gear. The outer gear 2 has a plurality (five in this embodiment) of inwardly extending portions 21, and the inwardly extending portions 21 are overlapped with the stay portion 13, and the stay portion 13 (crank arm) is fastened by bolt fastening. It is fixed to 1).

  In this embodiment, the inner gear 3 is an example of a configuration to which the bicycle gear plate referred to in the present invention is applied. The inner gear 3 is formed by pressing or cutting a plate material having a predetermined plate thickness, for example, and is a small-diameter gear having fewer teeth than the outer gear 2. The inner gear 3 has a plurality (five in the present embodiment) of inwardly extending portions 34, and the inwardly extending portions 34 are overlapped with the stay portion 13, and the stay portion 13 (crank arm) is fastened by bolt fastening. It is fixed to 1). More specifically, the inner gear 3 has an annular ring portion 31 and a plurality of teeth 32 formed on the outer periphery of the ring portion 31. The plurality of teeth 32 are formed at an equal pitch in the circumferential direction of the ring portion 31 with the interdental portion 33 interposed therebetween. The number of teeth 32 in the inner gear 3 is about 38, for example.

  As shown in FIG. 4, in this embodiment, the ring part 31 is substantially elliptical. The plurality of teeth 32 are formed at an equal pitch in the circumferential direction of the ring portion 31 with the interdental portion 33 interposed therebetween.

  The plurality of teeth 32 include a long diameter region 32A and a small diameter region 32B. The long diameter region 32A is a region where the pitch diameter PD of the teeth 32 continuous in the circumferential direction around the axis O1 when the ring portion 31 is viewed in the thickness direction is relatively large. In FIG. 4, the maximum dimension of the pitch diameter PD is represented by PD1. The small diameter region 32B is a region where the pitch diameter PD of the teeth 32 continuous in the circumferential direction around the axis O1 is relatively small. In FIG. 4, the minimum dimension of the pitch diameter PD is represented by PD2.

  As shown in FIG. 4, the long diameter region 32 </ b> A is provided at two locations located on the opposite sides in the circumferential direction around the axis O <b> 1 in the outer periphery of the ring portion 31. In the present embodiment, in the long diameter region 32A, the pitch diameter PD of the teeth 32 continuous in the circumferential direction is elliptical. Further, the pitch diameter PD of all the teeth 32 is elliptical.

  In a state in which the bicycle gear crank A1 is attached to a crankshaft (not shown), the center of the outer gear 2 and the center of the inner gear 3 correspond to the crankshaft. When the driving force is transmitted, the outer gear 2 and the inner gear 3 rotate in the clockwise direction (arrow P direction) in FIG. 1 and the counterclockwise direction (arrow P direction) in FIG. A chain 4 (see FIG. 5) that travels away from a rear gear (not shown) is hooked on the bicycle gear crank A1 (outer gear 2 or inner gear 3) on the upper portion of the outer gear 2 or inner gear 3, and the outer gear 2 or inner gear 3 And then detaches from the lower part of the outer gear 2 or the inner gear 3 toward the rear gear. That is, the outer gear 2 and the inner gear 3 function as a driving-side front gear that pulls the chain 4 and transmits a driving force thereto.

  FIG. 5 schematically shows a state where the chain 4 is wound around the inner gear 3. FIG. 5 shows a state in which the inner gear 3 stops without rotating. The pitch of the teeth 32 and the inter-tooth portion 33 in the inner gear 3 is made to correspond to the pitch of the chain 4, that is, the pitch between the rollers 41.

  Each tooth 32 has a pressure transmission side 321 and a non-pressure transmission side 322. The pressure transmission side surface 321 is a portion where the roller 41 contacts when the driving force is transmitted to the chain 4. The non-pressure transmission side surface 322 is located on the opposite side of the pressure transmission side surface 321 in the circumferential direction of the ring portion 31 with the tooth tip portion interposed therebetween.

  When the driving force is transmitted, the chain 4 that has traveled away from the rear gear as described above is engaged with the inner gear 3 such that the roller 41 is fitted into the interdental portion 33. As described above, the inner gear 3 functions as a front gear on the driving side, so that the tooth side surface in the rotational direction (direction of arrow P) contacts the roller 41 as the pressure transmission side surface 321 and presses the roller 41. A driving force is transmitted to the chain 4. When the center of each roller 41 corresponds to the pitch diameter PD of the inner gear 3, the point where the pressure transmission side surface 321 contacts and presses the roller 41 is referred to as a pressure point p1.

  The teeth 32 and the interdental portion 33 formed on the inner gear 3 are not symmetrical with respect to the front-rear direction. The pressure angle α at the pressure point p1 on the pressure transmission side surface 321 is 25 to 35 °, more preferably 28 to 32 °, which is compared with the pressure angle (20 ° or less) in a general bicycle gear. And greatly increased. In the embodiment shown in the figure, the pressure angle α is set to 30 °. The plurality of teeth 32 whose pressure angle α is increased to 25 to 35 ° is the maximum pressure angle region in the present invention. At least for the plurality of teeth 32 corresponding to the long diameter region 32A, the pressure angle α is set to 25 to 35 ° (preferably 28 to 32 °). In the present embodiment, the pressure angle α of all the teeth 32 is 25 to 35 ° (preferably 28 to 32 °).

  In the vicinity of the pressure point p <b> 1 of each tooth 32, the pressure transmission side surface 321 is gently curved concavely with a curvature smaller than the curvature of the outer periphery of the roller 41. Therefore, the apparent pressure angle when the roller 41 is shifted downward in the tooth height direction from the pressure point p1 is further larger than the pressure angle α at the pressure point p1, while the roller 41 has a tooth height higher than the pressure point p1. The apparent pressure angle when moving in the upward direction becomes gradually smaller than the pressure angle α at the pressure point p1.

  The position of the bottom of each tooth 32 is lower than that of a general bicycle gear, and the curvature near the bottom is larger than the curvature of the outer periphery of the roller 41. Therefore, the roller 41 never contacts the tooth bottom. Further, the height of each tooth 32, in particular, the dimension above the pitch diameter PD is larger than that of a general bicycle gear.

  At the time of transmitting the driving force, the inner gear 3 rotates in the direction of arrow P by applying a pedaling force to the pedal, and the driving force is transmitted to the chain 4. Here, as described above, since the pressure angle at the pressure point p1 is relatively large at 30 ° for the plurality of teeth 32 corresponding to at least the long diameter region 32A, the load to be transmitted from the pressure transmission side surface 321 to the roller 41 is large. When the pressure increases, as shown in FIG. 6, the roller 41 is shifted upward in the tooth height direction from the pressure point p <b> 1 by the slope effect of the pressure transmission side surface 321. That is, when the driving force is transmitted, the roller 41 located at the position corresponding to the long diameter region 32A is displaced radially outward from the pitch diameter PD. In FIG. 6, the chain 4 is traveling in the direction of the arrow Q, and the chain 4 is engaged with the teeth 32 of the long diameter region 32 </ b> A at the upper position of the inner gear 3.

  According to the present embodiment, the roller 41 of the chain 4 shifts radially outward as described above in the long-diameter region 32A where a large pedaling force is applied to the pedal when the driving force is transmitted. As a result, when the driving force is transmitted, the chain 4 hung on the inner gear 3 has the maximum pitch diameter in the range hung on the long diameter region 32A when the tension is applied to the maximum. The driving force is transmitted to the chain 4 with higher efficiency. Therefore, even if there is a variation in the position where the maximum pedaling force is applied to the pedal, highly efficient driving force transmission is achieved.

  In this embodiment, the pressure transmission side surface 321 of the tooth 32 is gently concavely curved with a curvature smaller than the curvature of the outer periphery of the roller 41. Therefore, when the driving force is transmitted, the roller 41 can smoothly shift the pressure transmission side surface 321 upward in the tooth height direction.

  While specific embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications can be made without departing from the spirit of the invention. The specific shape of each part of the bicycle gear plate according to the present invention is not limited to the above embodiment.

  In the above embodiment, the present invention is applied to the inner gear 3 in the bicycle gear crank A1 having two front gears. However, the present invention may be applied to both the outer gear and the inner gear, or only the outer gear. Further, in a configuration including only one front gear, the present invention may be applied to the front gear.

  In the above embodiment, the pitch diameter of the teeth 32 continuous in the long diameter region 32A is elliptical, but the present invention is not limited to this. For example, the pitch diameter of the teeth 32 in the long diameter region 32A may be a perfect circular arc shape, and the pitch diameter of the teeth 32 in the small diameter region 32B adjacent to the long diameter region 32A may be elliptical.

A1 Bicycle gear crank O1 Axis line PD Pitch diameter p1 Pressure point α Pressure angle 1 Crank arm 11 Boss part 12 Screw hole 13 Stay part 2 Outer gear 21 Inward extension part 3 Inner gear 31 Ring part 32 Teeth 32A Long diameter area 32B Small diameter area 321 Pressure transmission side surface 322 Non-pressure transmission side surface 33 Interdental portion 34 Inwardly extending portion 4 Chain 41 Roller

Claims (6)

The ring part and the outer periphery of the ring part are arranged at an equal pitch in the circumferential direction with the inter-tooth part interposed therebetween, and the pressure transmission side surface with which the roller contacts when the driving force is transmitted to the chain, and the tooth tip part A bicycle gear plate comprising a plurality of teeth, each having a non-pressure transmission side surface located opposite to the pressure transmission side surface in the circumferential direction,
The plurality of teeth includes a long diameter region having a relatively large pitch diameter of the teeth continuous in the circumferential direction around the axis of the ring portion as viewed in the thickness direction, and the circumference around the axis of the ring portion. A small-diameter region in which the pitch diameter of the teeth continuous in the direction is relatively small,
When the driving force is transmitted to the chain, the plurality of teeth has a pressure angle at a pressure point that is planned when the center of the roller is on the pitch diameter on the pressure transmission side surface is set to 25 to 35 °. Including the maximum pressure angle region,
The bicycle pressure plate, wherein the maximum pressure angle region is provided at least in the long diameter region.   2. The bicycle gear plate according to claim 1, wherein the long-diameter region is provided at two positions on the opposite side in the circumferential direction with the axis as a center in the outer periphery of the ring portion.   The bicycle gear plate according to claim 1 or 2, wherein a pitch diameter of the teeth continuous in the circumferential direction is elliptical in the long diameter region.   The bicycle gear plate according to any one of claims 1 to 3, wherein the pressure angle in the maximum pressure angle region is set to 28 to 32 °.   The pressure transmission side surface of each tooth in the long diameter region is curved concavely with a smaller curvature than the outer peripheral curvature of the roller in the vicinity of the pressure point in the height direction of the tooth. 4. The bicycle gear plate according to any one of 4 above.   The bicycle gear plate according to any one of claims 1 to 5, wherein a tooth bottom portion of each of the teeth is concavely curved with a curvature larger than an outer peripheral curvature of the roller.

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