Bicycle front derailleur

Abstract

The present invention relates to a bicycle front derailleur, comprising: a connecting rod assembly, which is swingably arranged on a base with a pivot point as a rotation center, and comprises a cable attachment portion, wherein the cable attachment portion comprises a curved surface for a control cable to be placed on, the curved surface defines a cable tangent point tangent to the control cable and a cable pasting section for pasting the control cable, the curved surface comprises a first side portion, the cable pasting section is located between the cable tangent point and a second side portion of the curved surface, a first radius is defined between the cable tangent point and the pivot point, and a second radius is defined between any cable joint point of the cable pasting section and the pivot point.

Description

Technical Field

[0001] The invention relates to a front derailleur of a bicycle. Background Art

[0002] The front derailleur of a bicycle controls the tension of a cable through a shifting mechanism so that a pulling link mechanism drives a chain guide to move to the inside or outside of a frame to move the chain to achieve a gear shifting effect.

[0003] Generally, the distance between the innermost small sprocket and the outermost large sprocket of the speed change sprocket on the market is fixed. Due to the slightly different frame structures, when the bicycle front derailleur is installed on different frames, the initial position of the chain guide relative to the frame will also be different, such as being located on the inner side close to the frame or being biased to the outer side away from the frame. However, different initial positions of the chain guide require different cable pulling strokes to drive the link mechanism to swing at different angles. For example, when the initial position of the chain guide is farther away from the frame, the angle required for the link mechanism to swing is larger, resulting in that the bicycle front derailleur cannot be applied to all frames.

[0004] Therefore, it is necessary to provide a novel and progressive bicycle front derailleur to solve the above-mentioned problems. Summary of the invention

[0005] The main purpose of the present invention is to provide a bicycle front derailleur that can be matched with different bicycle frames and can allow a chain guide to move the same displacement with the same cable pulling stroke.

[0006] To achieve the above-mentioned object, the present invention provides a bicycle front derailleur, comprising: a base for installation on a bicycle frame; a connecting rod assembly, which is swingably arranged on the base with a pivot point as a rotation center, and comprises a cable attachment portion, the cable attachment portion comprises a curved surface for a control cable to be placed on, the cable attachment portion can be driven by the control cable, the curved surface defines a cable tangent point tangent to the control cable and a cable placement section for placement on the control cable, the curved surface has a cable tangent point tangent to the control cable and a cable placement section for placement on the control cable, the curved surface has a cable tangent point tangent to the control cable and a cable placement section for placement on the control cable, the curved surface has a cable tangent point tangent to the control cable and a cable tangent point tangent to the control cable, the ... The control cable has a first side portion of a pulling end and a second side portion for approaching a fixed end of the control cable, the cable placement section is located between the cable tangent point and the second side portion, a first radius is defined between the cable tangent point and the pivot point, and a second radius is defined between any cable joining point of the cable placement section and the pivot point; and a chain guide member is swingably disposed on the linkage assembly, the chain guide member can be moved by the cable attachment portion, the chain guide member can swing relative to the linkage assembly with a pivot point as a swing center, the An outer arm radius is defined between the pivot point and the pivot point, and the chain guide is used to drive a chain to move between a large tooth plate of a tooth plate group and a small tooth plate of a tooth plate group, and the large tooth plate and the small tooth plate are arranged in an axial direction; wherein the chain guide can move between a first position and a second position, when the chain guide is located at the first position, the chain guide is provided with a chain located at a large tooth plate of a tooth plate group, and the pivot point is located on a first vertical reference line, and the first vertical reference line is perpendicular to the axial direction; when the chain guide is located at the second position, the chain guide is provided with a chain located at a large tooth plate of a tooth plate group, and the pivot point is located on a first vertical reference line, and the first vertical reference line is perpendicular to the axial direction; when the chain guide is located at the second position, the chain guide is provided for the chain to be located at the small sprocket of the sprocket set, the pivot point is located on a second vertical reference line, the second vertical reference line is perpendicular to the axial direction, and a displacement is defined between the first vertical reference line and the second vertical reference line; wherein the outer arm radius is R1, the first radius is R2, and the second radius is R3; wherein a first angle is defined between the outer arm radius when the chain guide is in the first position and the outer arm radius when the chain guide is in the second position, and the first angle is θ1; wherein, Wherein, X is 1.35 to 1.88.

[0007] As a preferred embodiment of the above technical solution, preferably, X is 1.45 to 1.78.

[0008] As a preferred embodiment of the above technical solution, preferably, the cable tangent point and any of the cable joining points are spaced apart along an extension direction of the curved surface and define a travel distance therebetween, the cable attachment portion can be driven by the control cable to move between a first position and a second position by the travel distance, the chain guide can be driven by the cable attachment portion to move between a third position and a fourth position, and the chain guide is farther away from the base in the third position than in the fourth position; wherein, when the cable attachment portion is located at the first position, the chain guide is located at the third position, and the cable tangent point is located at a position farthest from the fixed end in an extension direction of the control cable; when the cable attachment portion is at the second position, the chain guide is at the fourth position, and the cable joining point is located at a position farthest from the fixed end in the extension direction of the control cable.

[0009] As a preferred embodiment of the above technical solution, preferably, the first radius is larger than an average radius between the pivot point and the curved surface, and the second radius is smaller than the average radius between the pivot point and the curved surface.

[0010] As a preferred embodiment of the above technical solution, preferably, the outer arm radius is larger than the average radius.

[0011] As a preferred embodiment of the above technical solution, preferably, the second radius defined between the cable placement section and the pivot point gradually decreases from the cable tangent point toward the second side portion.

[0012] As a preferred embodiment of the above technical solution, preferably, the cable attachment portion further includes a limiting portion, the limiting portion includes a convex portion and at least one stop convex portion, the convex portion and each of the stop convex portions are arranged on two opposite sides of the curved surface, the convex portion includes a first limiting section and a second limiting section transverse to the first limiting section, the first limiting section is arranged between the curved surface and the second limiting section, the second limiting section corresponds to the curved surface and is spaced apart from the curved surface.

[0013] As a preferred embodiment of the above technical solution, preferably, the connecting rod assembly includes a first connecting rod, a second connecting rod, an elastic member and a connecting rod, the first connecting rod and the second connecting rod are respectively swingably arranged between the base and the chain guide, the second connecting rod is provided with the elastic member, and the elastic member biases the chain guide, the first connecting rod includes a long lug, a short lug spaced apart from the long lug and a groove formed between the long lug and the short lug, the long lug includes the cable attachment portion, the base includes a pivot lug, the pivot lug is arranged in the groove, and the connecting rod pivots through the long lug, the short lug and the pivot lug.

[0014] As a preferred embodiment of the above technical solution, it is more preferable that a fixing piece and a pressing piece are further included, and the cable attachment portion further includes a resting surface, which is laterally connected to the curved surface, and the resting surface is provided with a groove, and the fixed end of the control cable is provided in the groove, and the fixing piece passes through the pressing piece and the resting surface to press the control cable down to position it in the groove.

[0015] As a preferred embodiment of the above technical solution, preferably, the first radius is larger than the second radius; the first radius is larger than an average radius between the pivot point and the curved surface, and the second radius is smaller than the average radius between the pivot point and the curved surface; the outer arm radius is larger than the average radius; the second radius defined between the cable placement section and the pivot point gradually decreases from the cable tangent point toward the second side portion; the cable attachment portion further includes a limiting portion, the limiting portion includes a convex portion and at least one stop convex, the convex portion and each of the stop convex are arranged on the On the two opposite sides of the curved surface, the convex portion includes a first limiting section and a second limiting section transverse to the first limiting section, the first limiting section is arranged between the curved surface and the second limiting section, the second limiting section corresponds to the curved surface and is spaced apart from the curved surface; the limiting portion includes a plurality of stop convexities, the plurality of stop convexities are spaced apart along the extension direction of the curved surface and the plurality of stop convexities are staggered with the second limiting section of the convex portion; the connecting rod assembly includes a first connecting rod, a second connecting rod, an elastic member and a connecting rod, the first connecting rod and the second connecting rod are spaced apart from each other. The two connecting rods are respectively swingably arranged between the base and the chain guide, the second connecting rod is provided with the elastic member, and the elastic member biases the chain guide, the first connecting rod includes a long lug, a short lug spaced apart from the long lug, and a groove formed between the long lug and the short lug, the long lug includes the cable attachment portion, the base includes a pivot lug, the pivot lug is arranged in the groove, and the connecting rod passes through the long lug, the short lug and the pivot lug; the bicycle front derailleur further includes a fixing member and a pressing member, the cable attachment portion further includes The invention further comprises a support surface, the support surface being laterally connected to the curved surface, the support surface being provided with a groove, the fixed end of the control cable being provided in the groove, the fixing member passing through the pressing member and the support surface so as to press down the fixed end of the control cable to be positioned in the groove; a maximum radius is defined between the curved surface and the pivot point, the maximum radius corresponds to a most convex point position of the curved surface, the curved surface is defined from the most convex point position to the second side portion as a top side section, the maximum radius being greater than the radius between any point on the top side section and the pivot point. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, a brief introduction is given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0017] Figure 1 It is a three-dimensional diagram of a preferred embodiment of the present invention.

[0018] Figure 2 It is an exploded view of a preferred embodiment of the present invention.

[0019] Figure 3 It is a partial enlarged view of a preferred embodiment of the present invention.

[0020] Figure 4 This is a diagram of a preferred embodiment of the present invention installed on a vehicle frame.

[0021] Figures 5 and 6 This is a preferred embodiment of the present invention installed on another vehicle frame.

[0022] Figure 7 A usage status diagram of a preferred embodiment of the present invention.

[0023] Figure 8 The figure is a table of actuation angle and actuation stroke of a preferred embodiment of the present invention.

[0024] Fig. 9 It is a three-dimensional diagram of another preferred embodiment of the present invention.

[0025] Wherein, 1: bicycle front derailleur; 2, 2': bicycle frame; 3: control cable; 4: pulling end; 5: fixing end; 6: small tooth plate; 7: large tooth plate; 8: tooth plate group; 9: chain; 10, 10': base; 11: pivot ear; 12: buckle; 13: locking piece; 20: connecting rod group assembly; 21: cable attachment part; 211: resting surface; 212: groove; 22: curved surface; 221: first side portion; 222: second side portion; 223: most convex point position; 23: cable tangent point; 24: cable placement section; 241: cable engagement point; 25: first connecting rod; 251: long lug ; 252: short lug; 253: groove; 26: second connecting rod; 27: elastic member; 28: connecting rod; 29: limiting portion; 291: convex portion; 292: stop convex portion; 293: first limiting section; 294: second limiting section; 30: chain guide; 40: fixing member; 50: pressing member; A: axial direction; B: pivot point; L: travel distance; L1: first vertical reference line; L2: second vertical reference line; P: pivot point; R2: first radius; R3: second radius; R1: outer arm radius; R4: maximum radius; Y: displacement; θ2, θ2': second angle; θ1: first angle. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] Please refer to Figures 1 to 8 , which shows a preferred embodiment of the present invention. The bicycle front derailleur 1 of the present invention includes a base 10, a connecting rod assembly 20 and a chain guide 30.

[0028] The base 10 is for installation on a bicycle frame; the linkage assembly 20 is swingably disposed on the base 10 with a pivot point P as a rotation center. The linkage assembly 20 includes a cable attachment portion 21, and the cable attachment portion 21 includes a curved surface 22 for a control cable 3 to be placed thereon. In the present embodiment, the curved surface 22 is an arc convex surface. The cable attachment portion 21 can be driven by the control cable 3. The curved surface 22 defines a cable tangent point 23 tangent to the control cable 3 and a cable pasting section 24 for pasting the control cable 3. It is further explained that the cable tangent point 23 and the cable pasting section 24 will correspond to different positions of the curved surface 22 according to different angles of the initial position of the chain guide 30 relative to the frame and the initial position of the linkage assembly 20 relative to the base 10. The curved surface 22 has a first side portion 221 for approaching a pulling end 4 of the control cable 3 and a second side portion 222 for approaching a fixed end 5 of the control cable 3. The cable placement section 24 is located between the cable tangent point 23 and the second side portion 222. A first radius R2 is defined between the cable tangent point 23 and the pivot point P. A second radius R3 is defined between any cable joint point 241 of the cable placement section 24 and the pivot point P. The chain guide 30 is swingably disposed on the linkage assembly 20. The chain guide 30 can be moved by the cable attachment portion 21. In this embodiment, the first radius R2 is greater than the second radius R3. The first radius R2 is larger than an average radius between the pivot point P and the curved surface 22 (the average value of all radii defined between the pivot point P and the curved surface 22), and the second radius R3 is smaller than the average radius between the pivot point P and the curved surface 22. The second radius R3 defined between the cable placement section 24 and the pivot point P gradually decreases from the cable tangent point 23 toward the second side portion 222. The chain guide 30 is swingable relative to the connecting rod assembly 20 with a pivot point B as a swing center. The chain guide 30 is used to drive a chain to move between a large sprocket 7 of a sprocket set 8 and a small sprocket 6 of a sprocket set 8. The large sprocket 7 and the small sprocket 6 are arranged in an axial direction A. An outer arm radius R1 is defined between the pivot point P and the pivot point B, and the outer arm radius R1 is larger than the average radius. The cable tangent point 23 and any of the cable joint points 241 are spaced apart along an extension direction of the curved surface 22 and define a travel distance L (i.e., arc length) therebetween. The cable attachment portion 21 can be driven by the control cable 3 by the travel distance L to a first position (e.g., Figure 5 ) and a second position (such as Figure 6 ), the chain guide 30 can be driven by the cable attachment portion 21 to move between a third position (such as Figure 5 ) and a fourth position (such as Figure 6), the chain guide 30 is further away from the base 10 in the third position than in the fourth position; wherein, when the cable attachment portion 21 is in the first position, the chain guide 30 is in the third position, and the cable tangent point 23 is located at a position farthest from the fixed end 5 in an extension direction of the control cable 3; when the cable attachment portion 21 is in the second position, the chain guide 30 is in the fourth position, and the cable engagement point 241 is located at the control The position farthest from the fixed end 5 in the extension direction of the cable 3; a maximum radius R4 is defined between the curved surface 22 and the pivot point P, and the maximum radius R4 corresponds to a most convex point position 223 of the curved surface 22, and the curved surface 22 defines a top side section from the most convex point position 223 to the second side portion 222, and the maximum radius R4 is greater than the radius between any point on the top side section and the pivot point P; wherein the chain guide 30 can be in a first position and a When the chain guide 30 is located at the first position, the chain guide 30 provides a chain 9 located on a large sprocket 7 of a sprocket set 8, and the pivot point B is located on a first vertical reference line L1, and the first vertical reference line L1 is perpendicular to the axial direction A; when the chain guide 30 is located at the second position, the chain guide 30 provides the chain 9 located on the small sprocket 6 of the sprocket set 8, and the pivot point B is located on a second vertical reference line L2, and the second vertical reference line L2 is perpendicular to the axial direction A, and a displacement Y is defined between the first vertical reference line L1 and the second vertical reference line L2; wherein the outer arm radius is R1, the first radius is R2, and the second radius is R3; wherein a first angle θ1 is defined between the outer arm radius R1 when the chain guide 30 is at the first position and the outer arm radius R1 when the chain guide 30 is at the second position, and the first angle is θ1; wherein,

[0029] Wherein, X is 1.05 to 2.15; preferably, X is 1.25-1.95. Thus, when the initial position of the chain guide 30 is different (such as being installed on different frames) or the position of the chain line is different, the chain guide 30 can still move the same displacement Y (such as the displacement of the large plate) with the same pulling stroke (i.e., driving the cable attachment portion 21 to swing the same stroke distance L).

[0030] For example, when the outer arm radius R1 is 17.1 mm, the CL value (chain line value) of the tooth plate group 8 is set to 43.5 mm, and the first angle θ1 is 28.86 degrees, the displacement Y=8.50 mm can be satisfied, which is 14.65 mm relative to the first radius R2 and 12.77 mm relative to the second radius R3. Substituting into the equation That is, X is 1.57.

[0031] When the outer arm radius R1 = 17.1 mm, the CL value (chain line value) of the tooth plate group 8 is set to 47 mm, and the first angle θ1 is 29.59 degrees, which can satisfy the displacement Y = 8.50 mm, 14.65 mm relative to the first radius R2, and 12.77 mm relative to the second radius R3. Substituting into the equation That is, X is 1.63.

[0032] When the outer arm radius R1 is 18 mm, the CL value (chain line value) of the tooth plate group 8 is set to 43.5 mm, and the displacement Y=8.50 mm can be satisfied when the first angle θ1 is 27.42 degrees. The displacement is 14.65 mm relative to the first radius R2 and 12.86 mm relative to the second radius R3. Substituting into the equation That is, X is 1.56.

[0033] When the outer arm radius R1 = 18, the CL value (chain line value) of the tooth plate group 8 is set to 47mm, and the displacement Y = 8.50mm can be satisfied when the first angle θ1 is 28.00 degrees, which is 13.4mm relative to the first radius R2 and 11.67mm relative to the second radius R3. Substituting into the equation That is, X is 1.61.

[0034] When the outer arm radius R1 = 16, the CL value (chain line value) of the tooth plate group 8 is set to 43.5mm, and the displacement Y = 8.50mm can be satisfied when the first angle θ1 is 30.85 degrees. The displacement is 14.65mm relative to the first radius R2 and 12.65mm relative to the second radius R3. Substituting into the equation That is, X is 1.59.

[0035] When the outer arm radius R1 = 16, the CL value (chain line value) of the tooth plate group 8 is set to 47mm, and the displacement Y = 8.50mm can be satisfied when the first angle θ1 is 31.82 degrees. The displacement is 13.41mm relative to the first radius R2 and 11.38mm relative to the second radius R3. Substituting into the equation That is, X is 1.67.

[0036] Therefore, the X setting range is 1.56 to 1.67, and the relative error state X is 1.35 to 1.88. Preferably, X is 1.45 to 1.78.

[0037] The link assembly 20 includes a first link 25, a second link 26, an elastic member 27 and a connecting rod 28 (the pivot point P). The first link 25 and the second link 26 are respectively swingably disposed between the base 10 and the chain guide 30. The second link 26 is provided with the elastic member 27, and the elastic member 27 biases the chain guide 30. The first link 25 includes a long lug 251, a short lug 252 spaced from the long lug 251, and a groove 253 formed between the long lug 251 and the short lug 252. The long lug 251 includes the cable attachment portion 21. The base 10 includes a pivot lug 11, and the pivot lug 11 is disposed in the groove 253. The connecting rod 28 passes through the long lug 251, the short lug 252 and the pivot lug 11, and the supporting force and the combining force of the pivot fulcrum are good.

[0038] To elaborate, Figure 4 and Figure 6 The bicycle front derailleur 1 is provided for installation on different frames 2, 2'. Figure 6 The distance between the chain guide 30 and the frame 2' is less than Figure 4 The distance between the chain guide 30 and the frame 2 is Figure 4 and Figure 6 The same pulling stroke drives the cable attachment portion 21 to move the same stroke distance L and swing to different swing angles. Figure 4 The displacement of the chain guide 30 (i.e., the distance between the large tooth 7 and the small tooth 6 of the toothed disc) is Figure 5 The displacement of the chain guide 30 is the same. To further illustrate, the second angle θ2 (i.e., the swing angle) between the first radius R2 and the second radius R3 is equal to the first angle θ1 that drives the pivot point B to swing. Figure 6 The second angle θ2' is less than Figure 4 The second angle θ2 of Figure 8 , the initial position of the chain guide 30 is close to the position of the frame, and in the figure, the stroke amount is 3 to the stroke amount 11 (that is, the displacement amount is 8), and the angle (swing angle) of the connecting rod assembly 20 is about 25 degrees; the initial position of the chain guide 30 is farther away from the position of the frame, and in the stroke amount 4 to the stroke amount 12 (that is, the displacement amount is also 8), the angle (swing angle) of the connecting rod assembly 20 is about 30 degrees. Therefore, it means that with the same displacement of the chain guide 30, the farther the chain guide 30 is from the frame, the larger the angle (swing angle) required for the connecting rod assembly 20 is.

[0039] The cable attachment portion 21 further includes a limiting portion 29, which includes a convex portion 291 and at least one stop protrusion 292. The convex portion 291 and each of the stop protrusions 292 are arranged on two opposite sides of the curved surface 22. The convex portion 291 includes a first limiting section 293 and a second limiting section 294 transverse to the first limiting section 293. The first limiting section 293 is arranged between the curved surface 22 and the second limiting section 294. The second limiting section 294 corresponds to the curved surface 22 and is spaced apart from the curved surface 22. The limiting portion 29 includes a plurality of stop protrusions 292, which are spaced apart along the extension direction of the curved surface 22 and are staggered with the second limiting section 294 of the protrusion 291, thereby reducing the contact area between the control cable 3 and the limiting portion 29 to achieve lateral and upward limiting, making it difficult for the control cable 3 to separate from the curved surface 22 and reducing friction.

[0040] The bicycle front derailleur 1 further includes a fixing member 40 and a pressing member 50. The cable attachment portion 21 further includes a resting surface 211. The resting surface 211 is laterally connected to the curved surface 22. The resting surface 211 is provided with a groove 212. The groove 212 is provided for the fixed end 5 of the control cable 3 to be arranged in the groove 212. The fixing member 40 passes through the pressing member 50 and the resting surface 211 to press the control cable 3 downward to position it in the groove 212, so as to increase the downward force and stably position the control cable 3.

[0041] In this embodiment, the base 10 includes a buckle 12 for mounting on the bicycle frame. Fig. 9 , which shows another preferred embodiment of the present invention, the base 10 ′ of the bicycle front derailleur includes a locking member 13, and the base 10 ′ is locked to the frame of the bicycle by the locking member 13.

[0042] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A bicycle front derailleur, characterized in that: include: A base for mounting on a bicycle frame; A linkage assembly is swingably disposed on the base with a pivot point as a rotation center, comprising a cable attachment portion, the cable attachment portion comprising a curved surface for a control cable to rest on, the cable attachment portion being capable of being driven by the control cable, the curved surface defining a cable tangent point tangent to the control cable and a cable placement section for placement on the control cable, the curved surface having a first side portion for proximity to a pulling end of the control cable and a second side portion for proximity to a fixed end of the control cable, the cable placement section being located between the cable tangent point and the second side portion, a first radius being defined between the cable tangent point and the pivot point, and a second radius being defined between any cable junction point of the cable placement section and the pivot point; and a chain guide, the chain guide can be driven to move by the cable attachment portion, the chain guide can swing relative to the connecting rod assembly with a pivot point as a swing center, an outer arm radius is defined between the pivot point and the pivot point, the chain guide is used to drive a chain to move between a large sprocket of a sprocket group and a small sprocket of a sprocket group, the large sprocket and the small sprocket are arranged in an axial direction; The chain guide can be moved between a first position and a second position. When the chain guide is located at the first position, the chain guide provides a chain to be located on a large sprocket of a sprocket set, and the pivot point is located on a first vertical reference line, which is perpendicular to the axial direction. When the chain guide is located at the second position, the chain guide provides the chain to be located on the small sprocket of the sprocket set, and the pivot point is located on a second vertical reference line, which is perpendicular to the axial direction. A displacement is defined between the first vertical reference line and the second vertical reference line. Wherein, the outer arm radius is R1, the first radius is R2, and the second radius is R3; Wherein, a first angle is defined between the outer arm radius when the chain guide is in the first position and the outer arm radius when the chain guide is in the second position, and the first angle is θ1; in, Wherein, X is 1.35 to 1.

88.

2. The bicycle front derailleur according to claim 1, characterized in that: The X is 1.45 to 1.

78.

3. The bicycle front derailleur according to claim 1, characterized in that: The cable tangent point and any of the cable joining points are spaced apart along an extension direction of the curved surface and define a travel distance therebetween. The cable attachment portion can be driven by the control cable to move between a first position and a second position by the travel distance. The chain guide can be driven by the cable attachment portion to move between a third position and a fourth position. The chain guide is further away from the base in the third position than in the fourth position. When the cable attachment portion is located at the first position, the chain guide is located at the third position, and the cable tangent point is located at a position farthest from the fixed end in an extension direction of the control cable. When the cable attachment portion is at the second position and the chain guide is at the fourth position, the cable joining point is located at a position farthest from the fixed end in the extension direction of the control cable.

4. The bicycle front derailleur according to claim 1, characterized in that: The first radius is greater than an average radius between the pivot point and the curved surface, and the second radius is less than the average radius between the pivot point and the curved surface.

5. The bicycle front derailleur according to claim 4, characterized in that: The outer arm radius is greater than the average radius.

6. The bicycle front derailleur according to claim 1, characterized in that: The second radius defined between the cable placement section and the pivot point gradually decreases from the cable tangent point toward the second side portion.

7. The bicycle front derailleur according to claim 1, characterized in that: The cable attachment portion further includes a limiting portion, which includes a convex portion and at least one stop convex portion, the convex portion and each of the stop convex portions are arranged on two opposite sides of the curved surface, the convex portion includes a first limiting section and a second limiting section transverse to the first limiting section, the first limiting section is arranged between the curved surface and the second limiting section, and the second limiting section corresponds to the curved surface and is spaced apart from the curved surface.

8. The bicycle front derailleur according to claim 1, characterized in that: The link assembly includes a first link, a second link, an elastic member and a connecting rod. The first link and the second link are respectively swingably disposed between the base and the chain guide. The second link is provided with the elastic member, which biases the chain guide. The first link includes a long lug, a short lug spaced apart from the long lug and a groove formed between the long lug and the short lug. The long lug includes the cable attachment portion. The base includes a pivot lug disposed in the groove. The connecting rod pivots through the long lug, the short lug and the pivot lug.

9. The bicycle front derailleur according to claim 1, characterized in that: It also includes a fixing piece and a pressing piece. The cable attachment portion also includes a resting surface, which is laterally connected to the curved surface. The resting surface is provided with a groove, in which the fixed end of the control cable is provided. The fixing piece passes through the pressing piece and the resting surface to press the control cable down to position it in the groove.

10. The bicycle front derailleur according to claim 3, characterized in that: The first radius is larger than the second radius; the first radius is larger than an average radius between the pivot point and the curved surface, and the second radius is smaller than the average radius between the pivot point and the curved surface; the outer arm radius is larger than the average radius; the second radius defined between the cable placement section and the pivot point gradually decreases from the cable tangent point toward the second side portion; the cable attachment portion further includes a limiting portion, the limiting portion includes a convex portion and at least one stop convex, the convex portion and each of the stop convex portions are arranged on two opposite sides of the curved surface, the convex portion The invention comprises a first limiting section and a second limiting section transverse to the first limiting section, wherein the first limiting section is arranged between the curved surface and the second limiting section, and the second limiting section corresponds to the curved surface and is arranged at intervals from the curved surface; the limiting portion comprises a plurality of stop convexities, wherein the plurality of stop convexities are arranged at intervals along the extension direction of the curved surface and the plurality of stop convexities are arranged at offsets from the second limiting section of the convex portion; the connecting rod assembly comprises a first connecting rod, a second connecting rod, an elastic member and a connecting rod, wherein the first connecting rod and the second connecting rod can swing respectively The first link comprises a long lug, a short lug spaced apart from the long lug, and a groove formed between the long lug and the short lug, the long lug comprises the cable attachment portion, the base comprises a pivot lug, the pivot lug is arranged in the groove, the connecting rod passes through the long lug, the short lug and the pivot lug; the bicycle front derailleur further comprises a fixing member and a pressing member, the cable attachment portion further comprises a bearing member The support surface is laterally connected to the curved surface, and the support surface is provided with a groove, in which the fixed end of the control cable is provided, and the fixing piece passes through the pressing piece and the support surface to press down the fixed end of the control cable to be positioned in the groove; a maximum radius is defined between the curved surface and the pivot point, and the maximum radius corresponds to a most convex point position of the curved surface, and the curved surface defines a top side section from the most convex point position to the second side portion, and the maximum radius is greater than the radius between any point on the top side section and the pivot point.

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