JP4535958B2 - Transmission - Google Patents

Description

  The present invention relates to a transmission in which a plurality of gear ratios can be obtained by switching an endless transmission band (for example, a chain) spanned between a driving wheel (for example, a driving sprocket) and a driven wheel (for example, a driven sprocket), The transmission is installed in a bicycle, for example.

In the transmission that changes the gear ratio by changing the chain, each of the plurality of sprockets constituting the sprocket group rotatably provided on the rear axle of the bicycle is divided into a plurality of sections in the circumferential direction for shifting. Some sections are axially movable relative to other sections. (See Patent Document 1)
Japanese Patent Publication No. 2-501560 (Figs. 25-28)

In such a transmission, if an attempt is made to increase the obtained gear ratio, the number of sprockets increases, the width of the sprocket group in the axial direction increases, and the transmission increases in size in the axial direction. Further, since it is necessary to secure an axial space for each section to move, the width of the transmission in the axial direction is further increased.
In addition, the smoother speed change becomes possible as the number of sections of the sprocket increases. However, when the number of sections is increased, the number of sections in the circumferential direction increases as the number of sections increases. Since the width of each section is reduced, it is necessary to provide a means for preventing the section in the state where the chain cannot be wound from moving in the axial direction, which complicates the structure of the transmission and increases the weight. .
In addition, in order to ensure ease of maintenance and simplify the structure of the transmission, when the transmission switching mechanism is arranged outside the sprocket group without being built in, the transmission switching mechanism and the sprocket group are as compact as possible. This arrangement contributes to miniaturization of the transmission.
Further, in the shift switching mechanism for moving the sprocket in the axial direction, when the cam member driven by the shift operation of the driver moves each section of the sprocket in the axial direction, if the cam member becomes large and its weight increases, The responsiveness to the speed change operation is reduced, and the speed change of the speed ratio is reduced. For this reason, in order to improve the speed of switching of the gear ratio, it is preferable to reduce the weight of a member such as a cam member that is interposed between the actuator and the sprocket.

  The present invention has been made in view of such circumstances, and the inventions according to claims 1 to 7 can reduce the size of the transmission device in the axial direction and increase the speed change shock without increasing the number of divisions of one sprocket group. It aims at reducing. The invention described in claims 2 to 4 further aims to reduce the size of the transmission, and the invention described in claim 5 further aims to improve the applicability of the transmission to a bicycle. The inventions of claims 6 and 7 further aim to improve the speed of switching of the shift.

  The invention according to claim 1 includes a drive wheel provided to be integrally rotatable on the drive shaft, a driven wheel provided to be integrally rotatable on the driven shaft, an endless transmission band, and a speed change switching mechanism, wherein the speed change change mechanism In the transmission that obtains a plurality of gear ratios by switching the endless transmission band that is stretched over the drive wheel and the driven wheel, the plurality of the drive wheels and the plurality of the driven wheels are respectively driven-side wheels. Group and driven side wheel group, the driving side wheel group and the driven side wheel group are each composed of a plurality of driving side partial wheel groups and a plurality of driven side partial wheel groups divided in the circumferential direction, Each drive-side partial wheel group and each driven-side partial wheel group are axially arranged with respect to the drive shaft and the driven shaft, respectively. And the shift switching mechanism is configured to shift the endless transmission band by moving the drive side partial wheel groups and the driven side partial wheel groups in the axial direction for each of the partial wheel groups. It is.

  According to this, since a plurality of gear ratios can be obtained by the combination of the operation positions in the axial direction of each drive side partial wheel group and each driven side partial wheel group controlled by the speed change mechanism, one wheel group Compared to the case where the position of the plurality of partial wheel groups in the axial direction is changed to obtain the same number of gear ratios, the width of the driving wheel group and the driven wheel group in the axial direction and the space for movement are reduced. it can. In order to obtain a specific transmission ratio, when the driving side partial wheel group and the driven side partial wheel group are simultaneously moved in the axial direction, the total number of the driving side partial wheel group and the driven side partial wheel group Since the wheel groups are involved in shifting, it is not necessary to excessively increase the number of partial wheel groups in one wheel group in order to reduce shift shock.

  According to a second aspect of the present invention, in the transmission according to the first aspect, the shift switching mechanism is a position defining that defines an operating position in the axial direction of each of the driving side partial wheel groups and each of the driven side partial wheel groups. The transmission drum is rotated to guide the driving side partial wheel group and the driven side partial wheel group to the transmission position along the position defining portion. To do.

  According to this, in order to obtain a desired gear ratio, one common transmission drum guides the driving-side partial wheel group and the driven-side partial wheel group to the operation position in the axial direction, thereby simplifying the shift switching mechanism. In addition, various shift characteristics can be obtained with a simple structure due to the shape of the position defining portion set in advance.

  According to a third aspect of the present invention, in the transmission according to the second aspect, in a side view, a distance between the driving wheel having the maximum outer diameter and the driven wheel having the maximum outer diameter is determined by the position defining in the transmission drum. It is smaller than the outer diameter of the outer peripheral surface provided with the portion.

  According to this, the driving wheel group and the driven wheel group can be arranged close to each other, and the speed change drum can be arranged close to both wheel groups, so that the speed change mechanism can be downsized. become.

  According to a fourth aspect of the present invention, in the transmission according to the third aspect, the driving wheel having the maximum outer diameter and the driven wheel having the maximum outer diameter are, in a side view, the rotation center line of the driving wheel group and the driven wheel. Each of the transmission drums has a common tangent passing through a contact located on one side with respect to a reference straight line passing through the rotation center line of the side wheel group, and the shift drum is disposed at a position intersecting the common tangent in a side view. Is.

  According to this, since the speed change drum is disposed close to the drive side wheel group and the driven side wheel group on one side with respect to the reference straight line, both the wheel group and the speed change switching mechanism are compactly disposed.

  According to a fifth aspect of the present invention, in the transmission according to any one of the second to fourth aspects, the driving wheel group, the driven wheel group, and the transmission drum are arranged in the center in the front-rear direction of the bicycle body. It is accommodated in one transmission case arranged in the section and is rotatably supported by the transmission case.

  According to this, in the transmission installed in the bicycle, the drive side wheel group and the driven side wheel group can be easily supported, and the speed change case is arranged at the center of the bicycle body, so that the weight distribution in the bicycle is possible. Is further optimized, and foreign matter such as dust is prevented from adhering to the position defining portion of the transmission drum.

  According to a sixth aspect of the present invention, in the transmission according to any one of the second to fifth aspects, the transmission drum is disposed outward in a radial direction of the driving side wheel group and the driven side wheel group, Each drive-side partial wheel group and each driven-side partial wheel group are each provided with a guided member having a protruding portion that protrudes outward in the radial direction from the partial drive wheel having the maximum outer diameter. The switching mechanism includes a movable guide member that is guided by the position defining portion and is movable in the axial direction, and the movable guide member defines the position of the protruding portion in the axial direction, thereby allowing the switching member to pass through the guided member. The drive-side partial wheel group and the driven-side partial wheel group are guided to the shift position.

  According to this, since the guided member can be disposed close to the transmission drum, the movable guiding member disposed between the transmission drum and the guided member can be reduced in size and weight. Further, since the required rigidity can be imparted to the guided member by utilizing the rigidity of the partial drive wheel or the partial driven wheel having the maximum outer diameter, the guided member can be reduced in weight.

  According to a seventh aspect of the present invention, in the transmission according to any one of the second to sixth aspects, the transmission includes a speed change operation member that rotationally drives the speed change drum, and the position defining portion is one direction of the speed change operation member. Are formed in a shape that obtains a gear ratio that is arranged in descending order only by the operation to and in ascending order only by the operation in the other direction, and the shift switching mechanism includes the driving-side partial wheel group and the driven-side partial wheel group Can be shifted over three or more gear ratios by moving between an operating position before shifting and an operating position after shifting one by one in the axial direction by being guided by the position defining member. It is.

  According to this, since the position defining portion is formed in a shape that can obtain a gear ratio that is arranged in descending order only by operation in one direction of the speed change operation member and that is arranged in ascending order only by operation in the other direction. The speed change operation for obtaining a desired speed ratio from the speed ratio becomes easier. In addition, the drive-side partial wheel group and the driven-side partial wheel group are actuated after the next shift in the axial direction from the operating position before the shift by only the operation in one direction or the other direction. By shifting to the position, it is possible to shift over three or more speed ratios with another speed ratio sandwiched between the speed ratio before the speed change and the speed ratio after the speed change that is a desired speed ratio.

According to invention of Claim 1, the following effect is show | played. That is, since the width in the axial direction of the drive side wheel group and the driven side wheel group can be reduced, the transmission can be reduced in size in the axial direction, and moreover, without changing the number of divisions of one wheel group excessively. Since the number of participating partial wheel groups can be increased, the shift shock can be reduced while suppressing the complexity and weight increase of the structure of the transmission, such as the structure for preventing the partial wheel group from moving in the axial direction. be able to.
According to invention of Claim 2, in addition to the effect of the invention of the cited claim, there exists the following effect. That is, since the speed change mechanism is simplified, the speed change device is reduced in size.
According to invention of Claim 3, in addition to the effect of the invention of the cited claim, there exist the following effects. In other words, the drive-side wheel group and the driven-side wheel group can be arranged close to each other, and further, the speed change mechanism can be miniaturized, so that the speed change device is miniaturized.
According to invention of Claim 4, in addition to the effect of the invention of the cited claim, there exists the following effect. That is, since the drive side wheel group, the driven side wheel group, and the shift switching mechanism are arranged in a compact manner, the transmission is reduced in size.
According to the invention described in claim 5, in addition to the effect of the invention described in the cited claim, the following effect is produced. That is, the applicability of the transmission to the bicycle is improved in terms of ease of support of the drive side wheel group and the driven side wheel group, weight distribution in the bicycle, and prevention of foreign matter adhering to the transmission drum.
According to the invention described in claim 6, in addition to the effect of the invention described in the cited claim, the following effect is exhibited. That is, since the movable guide member and the guided member of the speed change mechanism can be reduced in weight, the influence of inertia is reduced and the speed of speed change is improved.
According to the invention described in claim 7, in addition to the effect of the invention described in the cited claim, the following effect is exhibited. That is, a gear shifting operation for obtaining a desired gear ratio from an arbitrary gear ratio is facilitated, and a gear shifting over three or more gear ratios can be performed by an operation in only one direction of the gear shifting operation member or an operation in only the other direction. This makes it possible to improve the speed of shifting.

Hereinafter, embodiments of the present invention will be described with reference to FIGS.
Referring to FIG. 1, a bicycle B as a vehicle, which is a machine equipped with a transmission T to which the present invention is applied, transmits a crankshaft 12 and power of the crankshaft 12 to a rear wheel Wr as a drive wheel. A transmission device. The transmission includes a transmission T, an output shaft 14 that is rotationally driven by the power after the shift from the transmission T, and an output transmission mechanism that transmits the power of the output shaft 14 to the rear wheel Wr.

  The body of the bicycle B includes a body frame F and a swing arm 10. The vehicle body frame F includes a head pipe 1 that pivotally supports a front fork 6 having a lower end portion that pivotally supports a front wheel Wf and a handle 7 attached to the upper end portion, and a bifurcated shape that extends rearward and obliquely downward from the head pipe 1. A pair of left and right underframes connecting the main frame 2, a down frame 3 extending obliquely rearward and downward from the front end of the main frame 2, and a pair of rear ends of the main frame 2 and a rear end of the down frame 3 4 and a saddle frame 5 extending from the main frame 2 and supporting the saddle 8.

  In the specification or claims, the axial direction, the radial direction, and the circumferential direction are respectively the rotation center lines of a drive wheel group (for example, a drive sprocket group) and a driven wheel group (for example, a driven sprocket group) that are parallel to each other. L1, L2 (refer to FIG. 2), the radial direction around the rotation center line L1 or the rotation center line L2, and the circumferential direction around the rotation center line L1 or the rotation center line L2, and a side view Means viewing from the axial direction. Further, the top, bottom, front, back, left and right coincide with the top, bottom, front, back, left and right of the bicycle B, respectively.

  A pivot shaft 9 (see also FIG. 3) provided on a pair of rear portions 2a of the main frame 2 can swing the front end portions of a pair of left and right swing arms 10 that support the rear wheel Wr at the rear end portion. Supported by Both swing arms 10 are connected to the main frame 2 via the suspension 11 so that they can swing up and down around the pivot shaft 9 together with the rear wheel Wr.

  Between the rear part 2a of the main frame 2 and the underframes 4 at the lower part of the body frame F, at the center part in the longitudinal direction of the body of the bicycle B or between the front wheel Wf and the rear wheel Wr. The transmission T, the main shaft 12a of the crankshaft 12 and the output shaft 14 that are rotatably supported by the transmission T are disposed in the space. The output transmission mechanism is disposed on the right side of the transmission device T.

  Referring also to FIGS. 2 and 3, the transmission T is made of a single metal transmission case 20 composed of a pair of left and right first and second case portions 20 a and 20 b that are coupled by bolts at the periphery. Is provided. The transmission case 20 is fixed to the main frame 2 and the underframes 4 by bolts B1 at a pair of attachment portions formed at the peripheral portions of the case portions 20a and 20b.

  The pedal-type crankshaft 12 is connected to a pair of main shafts 12a that are disposed through the lower portion of the transmission case 20 in the left-right direction and left and right ends of the main shaft 12a that protrudes outside the transmission case 20. And a crank arm 12b. The main shaft 12a is rotatably supported by the first and second case portions 20a and 20b via a pair of bearings 15, and a pedal 13 is rotatably attached to each crank arm 12b.

  The output shaft 14 and the pivot shaft 9 are obliquely above and forward of the main shaft 12a, the rotation center line L2 of the output shaft 14 and the swing center line of the swing arm 10 are parallel to each other, and are parallel to the rotation center line L1 of the crankshaft 12. In addition, they are arranged so as to be within the rotation locus of the crank arm 12b. The output shaft 14 is rotatably supported by the first and second case portions 20a and 20b via a pair of bearings 16, and is housed in the transmission case 20 together with the main shaft 12a.

  The pivot shaft 9 that is fastened and fixed to the main frame 2 is inserted into a later-described transmission drum 40 in a state of being coaxial with the transmission drum 40, that is, in a state in which the oscillation center line and the rotation center line L3 coincide with each other. Further, the transmission case 20 is supported by extending through the first and second case portions 20a and 20b.

  Referring to FIGS. 1 and 3, an output drive sprocket 17 is coupled to the output shaft 14 at the end protruding rightward from the second case portion 20b, and the output is driven and connected to the drive sprocket 17 and the rear wheel Wr. An endless chain 19 is wound around the driven sprocket 18. The driving sprocket 17, the driven sprocket 18, and the chain 19 constitute the output transmission mechanism.

  Referring to FIGS. 2 and 3, the transmission device T includes, in addition to the transmission case 20, a winding transmission mechanism, a transmission switching mechanism M that switches the transmission mechanism to a predetermined transmission ratio according to a transmission operation, A shift operation mechanism 60 (see FIG. 1) for operating the shift switching mechanism M is provided at the shift positions S1 to S11 (see FIG. 5) at which the gear ratio is obtained. The transmission mechanism and the transmission switching mechanism M are housed in a transmission case 20.

  The speed change mechanism is a drive side wheel group composed of a plurality of first predetermined number, here four drive sprockets 21 to 24 as drive wheels, provided so as to be integrally rotatable on a crankshaft 12 as a drive shaft. Drive-side sprocket group R and driven-side wheel group composed of a plurality of second predetermined numbers, here, driven sprockets 25 to 28 as four driven wheels, which are provided so as to be integrally rotatable with the output shaft 14 as the driven shaft. As a driven side sprocket group N, an endless chain 29 as an endless transmission band for shifting, and a tensioner 35.

  The chain 29 is stretched over a specific drive sprocket and a specific driven sprocket, which are each one sprocket selected by the shift switching mechanism M in the sprocket group R and the sprocket group N, and the transmission T is transmitted by the specific drive sprocket and the specific driven sprocket. The transmission ratio is determined. Further, the chain 29 always travels on a track surface 29a orthogonal to the axial direction at a substantially central position that is a fixed position in the axial direction in the transmission case 20. In FIG. 3, the sprocket group R and the sprocket group N at the first shift position S1, which is the lowest speed position that is the maximum speed ratio among the speed ratios obtained by the transmission device T, are indicated by solid lines, and the minimum speed ratio and The sprocket group R and the sprocket group N at the eleventh shift position S11 which is the highest speed position are indicated by a two-dot chain line.

Next, the sprocket group R and the sprocket group N will be described. Since both the sprocket groups R and N have the same structure, the members corresponding to the sprocket group R or explanations are shown in parentheses for the sprocket group N. .
The sprocket group R (sprocket group N) has a plurality of third predetermined numbers (fourth predetermined number) divided in the circumferential direction so as to have the same center angle, here four (five) drive side partial wheels. It consists of driving side partial sprocket groups R1 to R4 (driven side partial sprocket groups N1 to N5) as a group (driven side partial wheel group), and all the partial sprocket groups R1 to R4 (N1 to N5) are partial sprocket groups. Each of R1 to R4 (N1 to N5) can move in the axial direction independently of each other with respect to the crankshaft 12 (output shaft 14). For this purpose, the main shaft 12a (output shaft 14) is provided with a plurality of grooves 12c (14c) extending parallel to the axial direction, and the bosses of the partial sprocket groups R1 to R4 (N1 to N5) have grooves 12c. (14c) is provided with a ridge Rc (Nc) extending parallel to the axial direction so as to be slidably fitted in the axial direction. And the connection which consists of the groove | channel 12c (14c) as a fitting part of the crankshaft 12 (output shaft 14) and the protrusion Rc (Nc) as a fitting part of each partial sprocket group R1-R4 (N1-N5). Depending on the structure, each of the partial sprocket groups R1 to R4 (N1 to N5) can reciprocate in parallel with the crankshaft 12 (output shaft 14) in the axial direction and can rotate integrally with the crankshaft 12 (output shaft 14). Connected to

Each of the drive sprockets 21 to 24 (driven sprockets 25 to 28) is divided in the circumferential direction so as to have the same central angle as each of the partial sprocket groups R1 to R4 (N1 to N5). consists R4 (N1-N5) to the third predetermined number belonging respectively partial driving sprocket 21 _{1-24 4} as partial driving wheel (fourth predetermined number) (partial driven wheel) (partial object moving sprocket 25 _{1-28 5)} Is done. Further, all the driving sprockets 21 to 24 (driven sprockets 25 to 28) have different outer diameters, from the left (right) side as one (other) side in the axial direction to the other (one) in the axial direction. From the fourth drive sprocket 24 (first driven sprocket 25) having the largest outer diameter to the third and second drive sprockets 23 and 22 (second and third driven sprockets 26 and 27) ) To the first driving sprocket 21 (fourth driven sprocket 28) having the smallest outer diameter, the outer diameter is arranged on the main shaft 12a (output shaft 14) so that the outer diameter gradually decreases. In this embodiment, four (5) partial drive sprockets 21 _{1 to} 24 ₁ , 21 _{2 to} 24 ₂ , 21 _{3 to} 24 ₃ , and 21 _{4 to} 24 of each partial sprocket group R 1 to R 4 (N 1 to N 5). ₄ (partially driven sprockets 25 _{1 to} 28 ₁ , 25 _{2 to} 28 ₂ , 25 _{3 to} 28 ₃ , 25 _{4 to} 28 ₄ , 25 _{5 to} 28 ₅ ) are integrally molded, but each partially driven sprocket 21 _{1 to} 24 ₁ , 21 _{2 to} 24 ₂ , 21 _{3 to} 24 ₃ , 21 _{4 to} 24 ₄ , (partially driven sprockets 25 _{1 to} 28 ₁ , 25 _{2 to} 28 ₂ , 25 _{3 to} 28 ₃ , 25 _{4 to} 28 ₄ , 25 _{5 to} 28 ₅ ) may be formed of separate members, and may be combined by a connecting means such as a rivet to be integrated.

For each of the partial drive sprockets 24 _{1 to} 24 ₄ (partially driven sprockets 25 _{1 to} 25 ₅ ) having the maximum outer diameter of each of the partial sprocket groups R1 to R4 (N1 to N5), the transmission switching mechanism M is provided with the partial sprocket group R1 to R1. In order to move R4 (partial sprocket group N1 to N5) to the operating positions A1 to A4 and A5 to A8 (see FIG. 5) in the axial direction, the partial sprocket group is guided by the sliders 50 and 55 of the speed change mechanism M. A guided member 31 (32) capable of moving in the axial direction together with R1 to R4 (N1 to N5) is coupled by a screw B2 and provided integrally. The guided member 31 (32) is a partial drive sprocket 24 ₁ having a maximum outer diameter between the first case portion 20a (second case portion 20b) and the partial sprocket groups R1 to R4 (N1 to N5) in the axial direction. ˜24 ₄ (partially driven sprockets 25 _{1 to} 25 ₅ ) have a protruding portion 31a (32a) protruding outward in the radial direction, and the protruding portion 31a (32a) can contact the slider 50 (55) The abutting portion is configured.

  As shown in FIG. 2, the distance d1 (that is, the minimum distance) between the drive sprocket 24 having the maximum outer diameter and the driven sprocket 25 having the maximum outer diameter in a side view is the distance between the outer peripheral surface 40 a of the transmission drum 40. The main shaft 12a and the output shaft 14, and thus the driving side sprocket group R and the driven side sprocket group N are arranged with respect to the transmission case 20 or the body of the bicycle B so as to be smaller than the outer diameter d2.

  Referring to FIGS. 2 and 4, the tensioner 35 includes an arm 35c that is swingably supported by a support portion 35b provided in an attachment portion 35a provided by being fixed to the second case portion 20b by a bolt B3, A tension pulley 35e that is rotatably supported by a support portion 35d provided at the tip of 35c, a guide pulley 35f that is rotatably supported by the support portion 35b, and a tension spring 35g. The tensioner 35 applies an appropriate tension to the chain 29 by the spring force of the tension spring 35g.

  Referring to FIGS. 2 and 3, the speed change mechanism M for obtaining a plurality of gear ratios by changing the chain 29 spanned between the drive sprockets 21 to 24 and the driven sprockets 25 to 28 is a pair of bearings. Cylindrical single speed change drum 40 rotatably supported by first and second case portions 20a and 20b through 49, and speed change positions at which respective speed ratios are obtained corresponding to the rotation positions of speed change drum 40 Shift position setting means 45 comprising a moderation mechanism for setting S1 to S11 (see FIG. 5), and driven by a rotating speed change drum 40, can reciprocate in parallel in the axial direction, and each of the partial sprocket groups R1 to R4 and A pair of sliders 50 and 55 as a drive side movable guide member and a driven side movable guide member for guiding each partial sprocket group N1 to N5 in the axial direction, and each slider 50 and 55 are supported so as to be movable in the axial direction. Branch A pair of rods 58 which are holding members, and driving side fixed guide members 71 and 72 and driven side fixed guide members 75 and 76 provided in the transmission case 20 are provided.

  The transmission drum 40 is disposed outward in the radial direction of the sprocket group R and the sprocket group N, and, as shown in FIG. 2, the driving sprocket 24 having the maximum outer diameter and the driven sprocket having the maximum outer diameter as viewed from the side. 25, the reference straight line L4 passing through both the rotation center lines L1 and L2 is disposed at a position intersecting the common tangent line L5 passing through the contacts C1 and C2 located on one side or the side where the speed change drum 40 is disposed. Moreover, they are arranged at positions overlapping the sprocket group R and the sprocket group N when viewed from the direction orthogonal to the reference straight line L4.

  Referring also to FIG. 5, the outer peripheral surface 40a of the transmission drum 40 is a drive side position defining portion that defines the positions of the partial sprocket groups R1 to R4 and the partial sprocket groups N1 to N5 in the axial direction. A cam groove 41 and a cam groove 42 as a driven side position defining portion are provided. The cam groove 41 is provided on one side in the axial direction with respect to the raceway surface 29a of the chain 29, and the cam groove 42 is provided on the other side in the axial direction.

  The cam grooves 41 and 42 with which the pins 50a and 55a of the corresponding sliders 50 and 55 are engaged are set for each predetermined rotation amount of the speed change drum 40 (in this embodiment, this predetermined rotation amount is constant). At the shift positions S1 to S11, the slider 50 occupies a predetermined position in the axial direction as many as the drive sprockets 21 to 24, in this embodiment, one of the first to fourth predetermined positions P1 to P4. It is formed in a shape that occupies one of the predetermined positions in the axial direction as many as the driven sprockets 25 to 28, in this embodiment, any one of the first to fourth predetermined positions P5 to P8. In FIG. 5, the positions of the pins 50a and 55a when the sliders 50 and 55 occupy the respective shift positions S1 to S11 are solid lines for the first shift position S1 and two points for the remaining shift positions S2 to S11. It is indicated by a chain line. In FIG. 5, for convenience of explanation, when the sliders 50 and 55 occupy the predetermined positions P1 to P4 and P5 to P8, the operation occupied by the partial sprocket groups R1 to R4 or the partial sprocket groups N1 to N5. The positions A1 to A4 and A5 to A8 are shown in parentheses corresponding to the predetermined positions P1 to P4 and P5 to P8.

  In response to the slider 50 occupying each of the predetermined positions P1 to P4, in the sprocket group R, the partial sprocket groups R1 to R4 on the main shaft 12a are the first when the first operating position A1 is occupied. 1 drive sprocket 21, second drive sprocket 22 when occupying the second operation position A2, third drive sprocket 23 when occupying the third operation position A3, or fourth drive sprocket 24 when occupying the fourth operation position A4 , Selected as the specific drive sprocket. On the other hand, in response to the slider 55 occupying each of the predetermined positions P5 to P8, in the sprocket group N, the first driven sprocket 25 when each of the partial sprocket groups N1 to N5 occupies the first operating position A5. The second driven sprocket 26 when occupying the second operating position A6, the third driven sprocket 27 when occupying the third operating position A7, or the fourth driven sprocket 28 when occupying the fourth operating position A8 is the specific drive. Selected as a sprocket.

  Therefore, the obtained gear ratio is based on the predetermined positions P1 to P4 of the slider 50 set based on the shape of the cam groove 41 or the operating positions A1 to A4 of the partial sprocket groups R1 to R4 and the shape of the cam groove 42. The predetermined positions P5 to P8 of the slider 55 or the operating positions A5 to A8 of the partial sprocket groups N1 to N5 are determined. In this transmission device T, as shown by a solid line in FIG. 11, a plurality of transmission ratios that do not form an overlapping region, here, 11 types of transmission ratios are obtained. Here, the speed ratio that does not form an overlapping region is the minimum from the maximum speed ratio that is sequentially obtained by a speed change operation of a speed change lever 61 (see FIG. 1) described later in a speed change device that includes a plurality of drive sprockets and a plurality of driven sprockets. This means that all the gear ratios up to the gear ratio are arranged in descending order (that is, the order in which the gear ratio is sequentially reduced).

Therefore, a transmission (comparative example in FIG. 11) including three drive sprockets and nine driven sprockets and a derailleur (transmission switching mechanism) shown by a broken line in FIG. 11 and a transmission T (the present invention in FIG. 11). ) And the comparative example in which a plurality of gear ratios (the gear shift position is 27) forming an overlapping region are obtained although the minimum gear ratio and the maximum gear ratio are substantially equal to each other. In contrast, in the transmission T, the total number of drive sprockets 21 to 24 and driven sprockets 25 to 28 is small. In the comparative example, for example, for shifting from the gear ratio at the tenth gear position to the gear ratio (third gear position) next to the gear ratio, one shift operation on the drive sprocket side and the driven sprocket are performed. In contrast, the transmission T requires only one operation of the shift lever 61 to shift from an arbitrary gear ratio to the gear ratio closest to the gear ratio. The gear change is performed quickly.
Therefore, the cam grooves 41 and 42 are arranged in descending order only by operation in one direction of the shift lever 61 as an upshifting operation, and are in ascending order only by operation in the other direction as a downshifting operation (that is, the gear ratio). Are formed in such a shape that the gear ratios arranged in order of increasing) can be obtained.

  2 and 6, the shift position setting means 45 is integrally formed at the right end of the shift drum 40, rotates integrally with the shift drum 40, and corresponds to the number of shift positions S1 to S11. A positioning member 46 having recesses 46a as a number of engaging portions, and a locking member 47 that engages with the recesses 46a provided on the outer peripheral surface of the positioning member 46 at rotational positions corresponding to the shift positions S1 to S11. Have. The locking member 47 that presses the positioning member 46 by the elastic force rotates to a lever 47b that is swingably supported by a bolt 47a as a support shaft fixed to the second case portion 20b, and to the tip of the lever 47b. The roller 47c is supported so as to be engaged with the recess 46a, and a spring 47d that generates an elastic force that urges the roller 47c to press the roller 47c against the positioning member 46. When the roller 47c is engaged with each recess 46a, the speed change drum 40 driven and rotated by the speed change operation mechanism 60 is positioned in a stable state at each speed change position S1 to S11.

  Referring to FIGS. 1 to 3, the speed change operation mechanism 60 connected to the connection portion 65 at the left end of the speed change drum 40 in the speed change case 20 is a speed change lever 61 as a speed change operation member operated by the driver. In order to transmit the operation of the speed change lever 61 to the speed change drum 40, an operation cable 62 is provided as an operation force transmission member for operatively connecting the speed change lever 61 and the speed change drum 40.

  The operation cable 62 includes an outer cable 62a and an inner cable 62b that is inserted inside the outer cable 62a and coupled to the speed change lever 61 at the base end portion and coupled to the connecting portion 65 at the distal end portion. Then, when the speed change lever 61 is operated in one direction or the other direction and the inner cable 62b is pulled or pushed, the speed change drum 40 does not move in the axial direction, and the other direction is the one direction and the opposite direction. Is driven to rotate.

  Referring to FIG. 2, sliders 50 and 55, which are respectively guided by both cam grooves 41 and 42 (see FIG. 5) and are movable in the axial direction, are respectively shown in the side views as to the rotation center lines L1 and L2 and the speed change drum 40. At the position intersecting with the straight line connecting the rotation center line L3 between the speed change drum 40 and the sprocket group R and at the outer side in the radial direction of the driven sprocket 25 at the outer side in the radial direction of the sprocket 24. It is arranged between the sprocket group N.

  Furthermore, both sliders 50 and 55 are arranged in a driving-side non-winding region or a driven-side non-winding region, which is a space portion inside the chain 29, as viewed from the side. The two unwound regions are respectively from the unwinding start position of the chain 29 to the start of winding in the individual drive sprockets 21 to 24 and the individual driven sprockets 25 to 28 in the rotation direction of the crankshaft 12 and the output shaft 14, respectively. An area where a non-winding portion composed of a portion where the chain 29 is not wound is located, and at least one of the partial sprocket groups R1 to R4 and N1 to N5 is movable in the axial direction at the time of shifting. The partial sprocket groups R1 to R4 and N1 to N5 have a range in which they can be located.

Referring also to FIGS. 3 and 7, cylindrical pins 50a and 55a are connected to the speed change drum 40 so as to be movable relative to each other and receive driving force from the speed change drum 40 via cam grooves 41 and 42. Each of the sliders 50, 55 having guide holes is provided with guide grooves 51, 56 that open inward in the radial direction and whose axial width changes in the rotational direction. In each of the guide grooves 51 and 56, the protrusions 31a (32a) of the guided members 31 and 32 are introduced into the sliders 50 and 55, and the protrusions 31a (32a) are retracted from the sliders 50 and 55. It is comprised from the derivation | leading-out parts 51b and 56b and the control parts 51c and 56c which connect the introduction parts 51a and 56a and the derivation | leading-out parts 51b and 56b. The introduction parts 51a and 56a enable the chain 29 to be switched to the drive sprockets 21 to 24 or the driven sprockets 25 to 28 based on the movement of the sliders 50 and 55 for each of the predetermined positions P1 to P4 and P5 to P8. to have a guide groove 73 _{1-73 4 77 1-77 4} three and which can be opposed by the width in the direction of rotation of the inlet-side guide member 71 and 75 to be described later, deriving unit 51b, 56b are having a width approximately equal to the width of the inlet portion of the guide groove _{72d 4,} 78 ₁ to 78 ₄ of the outlet-side guide member 72, 76 to be described later. The pair of wall surfaces 52a, 52b, 57a, 57b of the control portions 51c, 56c, which are tapered in the rotation direction, move the sliders 50, 55 between predetermined positions P1 to P4, P5 to P8 during shifting. When the projecting portion 31a (32a) comes into contact, the partial sprocket group R1 to R4 or the partial sprocket group N1 to N5 is moved in the axial direction via the guided member 31 (32). Further, the guide grooves 51 and 56 are arranged so that the protruding portions 31a (32a) do not come into contact with the sliders 50 and 55 when the predetermined positions P1 to P4 and P5 to P8 of the sliders 50 and 55 are not changed. It has a shape that can pass through 56.

  The speed change operation mechanism M is configured so that each of the partial sprockets can be operated with only the operation in one direction of the speed change lever 61 or only in the other direction by the slider having the shape of the cam grooves 41 and 42 and the guide grooves 51 and 56. The groups R1 to R4 and the partial sprocket groups N1 to N5 are guided by the cam grooves 41 and 42 and moved between the operation position before the shift and the operation position after the shift immediately adjacent to each other in the axial direction. Allows shifting over more than one gear ratio.

  Specifically, referring to FIG. 5, the operation positions A1 and A2 (or predetermined positions P1 and P2) adjacent in the axial direction with respect to the sprocket group R and the operation positions A5 and A6 adjacent to the sprocket group N in the axial direction (or Shift between the shift position S1 and the shift position S4 between the predetermined positions P5 and P6), similarly, the operation positions A2, A3 (or the predetermined positions P2, P3)) and the operation positions A5, A6 (or the predetermined positions). Shift between the shift positions S3 and S6 between the positions P5 and P6), the operating positions A3 and A4 (or predetermined positions P3 and P4) and the operating positions A5 and A6 (or predetermined positions P5 and P6) Between the operating positions A3 and A4 (or predetermined positions P3 and P4) and the operating positions A7 and A8 (or predetermined positions P7 and P8). Position S9 In the shift with the shift position S11, the partial sprocket groups R1 to R4 and the partial sprocket groups N1 to N5 are cam grooves only by operating the shift lever 61 in one direction or only in the other direction. Shifting over three or more gear ratios becomes possible by moving between the operating position before shifting and the operating position after one shift in the axial direction guided by 41 and 42. Thus, for example, when shifting from the shift position S1 to the shift position S4, all the partial sprocket groups R1 to R4 and N1 to N5 do not occupy the operating positions A1, A6; A2, A5 at the shift positions S2, S3. It becomes possible to shift over another gear ratio between the gear ratio before the gear shift and the desired gear ratio after the gear shift, for example, it becomes possible to shift to the gear shift position S4.

  2 and 8, a pair of support rods 58 having the same basic structure with respect to the sliders 50 and 55 pass through through holes provided in the sliders 50 and 55, respectively, The two case portions 20a and 20b are fixed and provided so as to be parallel to the axial direction. Each support rod 58 is a stepped columnar member having a small-diameter portion 58a inserted into the sliders 50 and 55 and a large-diameter portion 58b forming a stopper portion, and the sliders 50 and 55 are formed in the small-diameter portion 58a. It is slidably supported. The tip of the small-diameter portion 58a is inserted into the bottomed insertion hole of the first case portion 20a and supported by the first case portion 20a, and the large-diameter portion 58b is inserted into the through hole of the second case portion 20b. While supported by the portion 20b, the transmission case 20 is held by a retaining member 59 fixed to the second case portion 20b with a bolt.

Referring to FIGS. 2, 7, and 9, the drive side guide members 71 and 72 and the driven side guide members 75 and 76 are opposed to the sliders 50 and 55 with the sliders 50 and 55 interposed in the rotational direction, respectively. It is comprised from the inlet side guide members 71 and 75 located in the rotation direction side, and the outlet side guide members 72 and 76 located in the rotation direction side with respect to the sliders 50 and 55. Each of the guide members 71, 72, 75, 76 attached to the first case portion 20a or the second case portion 20b by being coupled to and attached to the first case portion 20a or the second case portion 20b by a bolt B4 (see FIG. 9) inserted through the insertion hole 79 on the outside. Guide portions 71a, 72a, 75a, and 76a that extend in parallel in the axial direction through the case portion 20a or the second case portion 20b and are curved in an arc shape in a side view are provided. In the guide portions 71a, 72a, 75a, 76a, the protruding portions 31a (32a) of the guided members 31 (32) correspond to the sliders 50, 55 occupying the predetermined positions P1-P4, P5-P8. There passable plurality of guide grooves 73 ₁ to 73 _4, 74 ₁ to 74 _4, 77 ₁ to 77 _4, 78 ₁ to 78 _4, the drive sprocket 21 to 24 or the driven sprocket 25 to 28 adjacent to each other in the axial direction Four are provided, which is the number corresponding to the number of the drive sprockets 21 to 24 or the driven sprockets 25 to 28, with an interval equal to the interval in the axial direction.

Each guide groove 73 _{1-73 4} 74 _{1-74 4} 77 _{1-77 4} 78 _{1-78 4} plane perpendicular protruding portions 31a and (32a) to the rotational center line L1, L2 (or axial) Are provided in parallel to the rotational surfaces of the drive sprockets 21 to 24 or driven sprockets 25 to 28, and the inlet portions thereof are protruding portions 31a (32a) (therefore, partial sprocket groups R1 to R4, N1). To N5) are also slightly shifted in the axial direction from the normal operating positions A1 to A4 and A5 to A8 in the axial direction, 73 _{1 to} 73 ₄ , 74 ₁ to 74 ₄ , 77 _{1 to} 77 ₄ , 78 _1-78 so as to be able to smoothly enter the _4, it is gradually widened in the axial direction toward the non-rotating direction.

Then, the guide member 71,72,75,76, each guide groove 73 _{1-73 4} 74 _{1-74 4} 77 _{1-77 4} 78 _1-78 protrusion 31a which is fitted to a ₄ (32a) is The movement in the axial direction is restricted, and the drive side partial sprocket groups R1 to R4 or the driven side partial sprocket groups N1 to N5 are prevented from moving in the axial direction via the guided members 31 and 32. Therefore, each guide part 71a, 72a, 75a, 76a includes at least the non-winding region in the drive side sprocket group R or the driven side sprocket group N, and each of the drive sprockets 21-24 or each of the drive sprockets 21-24. It arrange | positions over the range in the circumferential direction containing the largest unwound part of the said unwound parts.

With reference to FIG. 5 and FIG. 10, the operation of the transmission device T at the time of shifting will be described.
For example, referring to FIG. 10 (A) showing the shift from the first shift position S1 to the second shift position S2, the shift drum 40 rotates in the upshift direction by operating the shift lever 61 (see FIG. 1). When the second shift position S2 set by the shift position setting means 45 (see FIG. 2) is reached, the slider 50 guided along the cam groove 41 does not move in the axial direction on the drive side. in position P1, thus the protruding portion 31a of the guide member 31 without moving in the axial direction, passes through the first guide groove 74 of the _first guide groove 73 ₁ and the guide member 72 of the guide member 71, each portion The sprocket groups R1 to R4 are also in the first operating position A1 without moving in the axial direction. On the other hand, on the driven side, the slider 55 is pivoted from the first predetermined position P5 (indicated by a two-dot chain line in FIG. 10A) to the second predetermined position P6 (indicated by a solid line in FIG. 10A). The projecting portion 32a of the guided member 32 that has moved in the direction and entered the slider 55 is guided so as to move in the axial direction in contact with the wall surface 57a of the control portion 56c. derived from 77 ₁ to the second guide groove 78 _{and second} guide member 76 (see the arrow in dotted line in FIG. 10 (a).). Therefore, partial sprocket cluster N1~N5 passing through the slider 55 (e.g., partial sprocket cluster N1) occupies the second operating position A6 to move in the axial direction, on the second part the driven sprocket 26 ₁ raceway surface 29a To position. By the subsequent rotation of the sprocket cluster N, in a state where the projecting portion 32a is guided by the guide member 76, the second portion the driven sprocket 26 ₁ of the chain 29 is wound. Similarly, sequentially portion sprocket cluster N2~N5 as the rotation of the sprocket cluster N is moved in the axial direction by the slider 55, the first partial drive sprocket 21 ₁ to 21 ₄ and the second part the driven sprocket 26 chain 29 are all _{1-26 5} is wound, shifting to the second shift position S2 is completed.

Referring to FIG. 10 (B) showing the shift from the ninth shift position S9 to the tenth shift position S10, the shift drum 40 at the ninth shift position S9 is shifted up by the operation of the shift lever 61 (FIG. 1). Rotate in the direction and reach the tenth shift position S10 set by the shift position setting means 45, on the drive side, the slider 50 guided along the cam groove 41 is in the fourth predetermined position P4 (FIG. 10B). To the third predetermined position P3 (indicated by a solid line in FIG. 10B), the protruding portion 31a that has entered the slider 50 enters the wall surface 52b of the control portion 51c. contact is guided so as to move axially, the dotted line derived from the fourth guide groove 73 ₄ of the guide member 71 by the slider 50 to the third guide groove 73 ₃ of the guide member 72 ((FIG. 10 (B) For this reason, the partial sprocket that has passed through the slider 50 Group R1 to R4 (e.g., the first partial sprocket group R1) occupies a third operating position A3 to move in the axial direction, a third partial drive sprocket 23 ₁ is located on the raceway surface 29a. Then, subsequent sprocket cluster rotation of R, in a state where the projecting portion 31a is guided by the guide member 72, the third partial drive sprocket 23 ₁ of the chain 29 is wound. on the other hand, the driven side, the slider 55 is a third predetermined position P7 ( 10B (shown by a two-dot chain line) to a fourth predetermined position P8 (shown by a solid line in FIG. 10B) in the axial direction, the protrusion 32a that has entered the slider 55 has a wall surface. to 57a abut guided for axial movement, the dotted derived from the third guide groove 77 ₃ of the guide member 75 to the fourth guide groove 78 ₄ of the guide member 76 by the slider 55 (FIG. 10 (B) (See arrow for.) Therefore, slider 5 5 parts sprocket cluster passing through the N1-N5 (e.g., the first partial sprocket set N1) occupies a fourth operating position A8 to move axially, ₁ fourth portion the driven sprocket 28 is located on the raceway surface 29a . then, the subsequent rotation of the sprocket cluster N, in a state where the projecting portion 32a is guided by the guide member 76, a fourth portion the driven sprocket 28 ₁ of the chain 29 is wound. in the same manner, sprocket cluster R and sprocket sequentially portion sprocket cluster R2~R4 as the rotation of the group N, N2 to N5 is moved by the slider 50, 55 in the axial direction, respectively, third partial drive sprocket 23 chain 29 are all _{1-23 4} and the fourth portion the driven It is wound around the sprocket 28 _{1-28 5.}
Thereby, the shift to the tenth shift position S10 is completed.

  The shift between the ninth shift position S9 and the tenth shift position S10, the shift between the second shift position S2 and the third shift position S3, and the shift between the fourth shift position S4 and the fifth shift position S5. Sprockets between specific shift positions S2, S3; S4, S5; S6, S7; S9, S10, such as the shift between the sixth shift position S6 and the seventh shift position S7. In the group R and the sprocket group N, the chain 29 is switched simultaneously.

Next, operations and effects of the embodiment configured as described above will be described.
The drive-side sprocket group R of the transmission T is composed of a plurality of drive-side partial sprocket groups R1 to R4 that are movable in the axial direction with respect to the crankshaft 12, and the driven-side sprocket group N is in the axial direction with respect to the output shaft 14. The shift switching mechanism M includes a plurality of driven side partial sprocket groups N1 to N5, each of which is divided into the partial sprocket groups R1 to R4 and N1 to N5. Each of the partial sprocket groups R1 to R4 and the partial sprocket groups N1 to N5 controlled by the speed change mechanism M is operated in the axial direction by moving the shaft 29 in the axial direction every time. Since a plurality of gear ratios can be obtained by the combination of A8, a plurality of partial sprocket groups in one sprocket group in the axial direction Compared with the case where the same gear ratio is obtained by changing the position, the width of the sprocket group R and the sprocket group N in the axial direction and the space for movement can be reduced, so that the transmission T can be downsized in the axial direction. . In order to obtain a specific transmission ratio, when the partial sprocket groups R1 to R4 and the partial sprocket groups N1 to N5 are simultaneously moved in the axial direction, the partial sprocket groups R1 to R4 and the partial sprocket groups N1 to N5 are combined. Since a certain number of partial sprocket groups are involved in shifting, it is not necessary to excessively increase the number of partial sprocket groups in one sprocket group in order to reduce shift shock. As a result, the number of partial sprocket groups involved in gear shifting can be increased without excessively increasing the number of divisions of one drive-side sprocket group R or driven-side sprocket group R. The shift shock can be reduced while suppressing the complication and weight increase of the structure of the transmission T such as the structure for preventing the movement.

  The transmission switching mechanism M includes a single transmission drum 40 provided with cam grooves 41 and 42 that define the operation positions A1 to A4 and A5 to A8 of the partial sprocket groups R1 to R4 and the partial sprocket groups N1 to N5. The transmission drum 40 rotates to guide the partial sprocket groups R1 to R4 and the partial sprocket groups N1 to N5 to the transmission positions S1 to S11 along the cam grooves 41 and 42, respectively. In order to obtain the gear ratio, the common one speed change drum 40 guides the partial sprocket groups R1 to R4 and N1 to N5 to the axial operation positions A1 to A4 and A5 to A8, so that the speed change mechanism M is simple. In addition, various gear shifting characteristics can be obtained with a simple structure due to the shapes of the cam grooves 41 and 42 set in advance. As a result, since the speed change mechanism M is simplified, the speed change device T is reduced in size.

  When viewed from the side, the distance d1 between the drive sprocket 24 having the maximum outer diameter and the driven sprocket 25 having the maximum outer diameter is smaller than the outer diameter d2 of the outer peripheral surface 40a of the transmission drum 40, so that the sprocket group R and the sprocket group N can be arranged close to each other, and the transmission drum 40 can be arranged close to both the sprocket groups R and N, so that the transmission switching mechanism M can be downsized, and the transmission T can be reduced in size. It becomes.

  The drive sprocket 24 having the maximum outer diameter and the driven sprocket 25 having the maximum outer diameter have a common tangent line L5 passing through the contacts C1 and C2 that are located on one side with respect to the reference straight line L4 when viewed from the side. 40 is arranged at a position intersecting the common tangent L5 in a side view, so that the speed change drum 40 is arranged close to the sprocket group R and the sprocket group N on one side with respect to the reference straight line L4. Since both the sprocket groups R and N and the shift switching mechanism M are arranged in a compact manner, the transmission T is reduced in size.

  Since the pivot shaft 9 is coaxially inserted through the speed change drum 40, the speed change mechanism M including the speed change drum 40 and the two sprocket groups R and N need to be arranged so as to avoid interference with the pivot shaft 9. This contributes to a compact arrangement of the speed change mechanism M and the two sprocket groups R and N.

  Both sprocket groups R and N and the speed change drum 40 are housed in one speed change case 20 disposed at the center in the front-rear direction of the body of the bicycle B and are rotatably supported by the speed change case 20. In the transmission device T installed in the bicycle B, the sprocket group R and the sprocket group N can be easily supported, and the transmission case 20 is disposed at the center of the body of the bicycle B. Further, foreign matter such as dust is prevented from adhering to the cam grooves 41 and 42 of the speed change drum 40. As a result, the applicability of the transmission device T to the bicycle B is improved in terms of ease of support of the sprocket group R and sprocket group N, weight distribution in the bicycle B, and prevention of foreign matter adhering to the transmission drum 40.

The transmission drum 40 is disposed outward in the radial direction of the driving side sprocket group R and the driven side sprocket group N, and each partial sprocket group R1 to R4 and each partial sprocket group N1 to N5 has a portion with the maximum outer diameter, respectively. Guided members 31 and 32 having projecting portions 31a and 32a projecting radially outward from the drive sprockets 24 _{1 to} 24 ₄ and the partially driven sprockets 25 _{1 to} 255 ₅ are provided. The sliders 50 and 55 are guided by the grooves 41 and 42 and are movable in the axial direction. The sliders 50 and 55 define the positions of the projecting portions 31a and 32a in the axial direction. Since each of the partial sprocket groups R1 to R4 and N1 to N5 is guided to the shift positions S1 to S11, the guided members 31 and 32 can be arranged close to the shift drum 40. Can lightweight and miniaturized slider 50 and 55 disposed between the guide members 31 and 32, and the maximum outer diameter of the portion drive sprocket 24 _{1-24 4} and partially the driven sprocket 25 to the guided member 31, 32 since it is possible to impart the required rigidity by utilizing the rigidity of _to 253 _5, it is possible to reduce the weight of the guided member 31, to reduce the influence of inertia, which improves the rapidity of switching the shift .

  The shift lever 61 for rotating the shift drum 40 is provided, and the cam grooves 41 and 42 are arranged in descending order only by operation in one direction of the shift lever 61 and are arranged in ascending order only by operation in the other direction. The shift switching mechanism M is formed in the obtained shape, and the partial sprocket groups R1 to R4 and the partial sprocket groups N1 to N5 are guided by cam grooves 41 and 42, respectively, and are adjacent to the operation position before the shift in the axial direction. By moving to and from the operating position after shifting, it is possible to shift over three or more gear ratios, so that the cam grooves 41 and 42 can be moved in descending order only by operating the shifting lever 61 in one direction. Since the gear ratios are formed in such a shape that the gear ratios arranged in ascending order can be obtained only by the operation in the other direction, a gear shift operation for obtaining a desired gear ratio from an arbitrary gear ratio becomes easy. In addition, the partial sprocket groups R1 to R4 and the partial sprocket groups N1 to N5 are shifted one by one in the axial direction from the operating position before the shift by only the operation in one direction of the speed change lever 61 or the operation in the other direction. By shifting to the operating position, it is possible to shift over three or more speed ratios with another speed ratio sandwiched between the speed ratio before the speed change and the speed ratio after the speed change that is the desired speed ratio. As a result, speeding up of shifting is improved.

  The guide members 71, 72, 75, 76 include at least the unwound region in the sprocket group R or sprocket group N, and among the unwound portions of the drive sprockets 21 to 24 or the driven sprockets 25 to 28. It is possible to occupy the operating position by moving each partial sprocket group R1-R4, N1-N5 in the axial direction at the time of shifting by being arranged over the range in the circumferential direction including the largest unwound portion of In addition, even when the sliders 50 and 55 are downsized, the partial sprocket groups R1 to R4 and N1 to N5 move in the axial direction in the non-winding region before and after passing through the sliders 50 and 55. Is definitely prevented.

Hereinafter, an embodiment in which a part of the configuration of the above-described embodiment is changed will be described with respect to the changed configuration.
The endless transmission band may be a belt, in which case the drive wheel and the driven wheel are both pulleys.
The first predetermined number and the second predetermined number may be different values, and the first to fourth predetermined numbers may be arbitrary values.
The guided member may be integrally formed with the partial sprocket group.
The transmission may be installed in a vehicle or machine other than a bicycle.

1 is a schematic left side view of a bicycle including a transmission to which the present invention is applied. FIG. 4 is a left side sectional view of a main part in a state in which a speed change mechanism and a speed change switching mechanism of the transmission of FIG. 1 are housed in a speed change case, and is a cross-sectional view taken along the line II-II in FIG. It is the III-III sectional view taken on the line of FIG. It is the IV-IV sectional view taken on the line of FIG. FIG. 3 is a development view of an outer peripheral surface of a transmission drum of the transmission of FIG. 2. It is the VI-VI sectional view taken on the line of FIG. (A) is the expanded view of the cross section in the VIIA-VIIA line of FIG. 2, (B) is the expanded view of the cross section in the VIIB-VIIB line of FIG. It is the VIII-VIII sectional view taken on the line of FIG. It is the IX-IX sectional view taken on the line of FIG. FIGS. 3A and 3B are diagrams for explaining the operation of the transmission shown in FIG. 2, in which FIG. 3A shows the operation at the time of shifting from the first shifting position to the second shifting position, and FIG. The operation at the time of shifting to the position is shown. It is a graph which shows the relationship between the transmission position of the transmission of FIG.

Explanation of symbols

12 ... Crankshaft, 14 ... Output shaft, 20 ... Shift case, 21-24 ... Drive sprocket, 25-28 ... Driven sprocket, 29 ... Chain, 31, 32 ... Guided member, 40 ... Shift drum, 50, 55 ... Slider, T ... transmission device, B ... bicycle, M ... speed change mechanism, R ... drive side sprocket group, N ... driven side sprocket group.

Claims (7)

A drive wheel provided on the drive shaft so as to be integrally rotatable, a driven wheel provided on the driven shaft so as to be integrally rotatable, an endless transmission band, and a speed change mechanism, wherein the speed change mechanism is the drive wheel and the driven wheel. In a transmission that can obtain a plurality of gear ratios by switching the endless transmission band that is passed over to
The plurality of driving wheels and the plurality of driven wheels constitute a driving wheel group and a driven wheel group, respectively, and the driving wheel group and the driven wheel group are respectively divided in the circumferential direction. Each of the drive-side partial wheel groups and each of the driven-side partial wheel groups is movable in the axial direction with respect to the drive shaft and the driven shaft, respectively. And the shift switching mechanism shifts the endless transmission band by moving the drive side partial wheel groups and the driven side partial wheel groups in the axial direction for each of the partial wheel groups. apparatus.   The shift switching mechanism includes a single shift drum provided with a position defining portion that defines an operation position in the axial direction of each drive-side partial wheel group and each driven-side partial wheel group, The transmission according to claim 1, wherein the driving side partial wheel group and the driven side partial wheel group are guided to a shift position along the position defining portion by rotating. In a side view, the distance between the driving wheel having the maximum outer diameter and the driven wheel having the maximum outer diameter is smaller than the outer diameter of the outer peripheral surface provided with the position defining portion in the transmission drum. The transmission according to claim 2.
  The driving wheel having the maximum outer diameter and the driven wheel having the maximum outer diameter are either one with respect to a reference straight line passing through the rotation center line of the driving wheel group and the rotation center line of the driven wheel group in a side view. 4. The transmission according to claim 3, further comprising a common tangent passing through a contact located on the side of the first transmission line, wherein the transmission drum is disposed at a position intersecting the common tangent in a side view.   The driving wheel group, the driven wheel group, and the speed change drum are housed in one speed change case disposed in the center of the bicycle body in the front-rear direction and are rotatably supported by the speed change case. The transmission according to any one of claims 2 to 4, wherein:   The speed change drum is disposed outward in a radial direction of the driving wheel group and the driven wheel group, and each driving side partial wheel group and each driven side partial wheel group have a maximum outer diameter, respectively. A guided member having a protruding portion that protrudes outward in the radial direction from the partial drive wheel is provided, and the shift switching mechanism includes a movable guide member that is guided by the position defining portion and is movable in the axial direction. When the movable guide member defines the position of the protruding portion in the axial direction, the drive-side partial wheel group and the driven-side partial wheel group are guided to the shift position via the guided member. The transmission according to any one of claims 2 to 5, wherein: A speed change operation member that rotates the speed change drum, and the position defining portion has a speed change ratio that is arranged in descending order only by operation in one direction of the speed change operation member, and arranged in ascending order only by operation in the other direction. The shift switching mechanism is formed after the shift, in which the drive-side partial wheel group and the driven-side partial wheel group are guided by the position defining member and adjacent to the operation position before the shift in the axial direction. The speed change device according to any one of claims 2 to 6, wherein a speed change over three or more speed ratios is enabled by moving between the operating position and the operating position.

Images