JPH09109980A - Crank mechanism for bicycle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a crank mechanism for a bicycle capable of obtaining the driving force effectively. SOLUTION: A crank arm 2 is provided in a crank shaft 1 supported in a bearing part 20 fixed to a bicycle body 10, and an extension member 3 is rotatably provided in the crank arm 2 so that an extension crank 11 is formed. A pedal shaft 5 which supports a pedal 6 rotatably is provided in the extension crank 11 and an oscillation arm 8 is provided in the extension member 3 through a combination arm 7. Then, the oscillation arm 8 is rockably journaled 8c to a support member 9 fixed to the bicycle body 10. The direct distance between a tip 3c of the extension crank 11 and the crank shaft 1 is made such that the distance when the extension crank 11 is positioned on the stepping side is longer than the one when the extension crank 11 is positioned on the return side.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bicycle crank mechanism.

In a conventional bicycle, the crank mechanism is provided by fixing one end of a crank arm to both ends of a crank shaft and fixing a pedal shaft supporting a rotatable pedal to the other end of the crank arm. It is a thing.

[0003]

The crank mechanism in a bicycle is for converting the reciprocating motion of the rider's foot into a rotational motion, and the rotational motion is transmitted to the rear wheel of the bicycle so that the bicycle can obtain propulsive force. Becomes

To be able to obtain its propulsive force effectively and easily in a bicycle is generally desired and is one of the greatest goals in developing a bicycle. is there.

In view of the above circumstances, an object of the present invention is to obtain a bicycle crank mechanism which can effectively and easily obtain a propulsive force.

[0006]

According to the present invention, which achieves the above object, a bearing portion (20) fixed to a bicycle body (10).
A crank arm (2) is provided on a crank shaft (1) supported by the crank arm (2), and an extension member (3) is rotatably provided on the crank arm (2) to form an extension crank (11). ) Is provided with a pedal shaft (5) for rotatably supporting a pedal (6), and the extension member (3) is provided with a swing arm (8) via a connecting arm (7). ) Is pivotally attached (8c) to a support member (9) fixed to the bicycle body (10), and a linear distance (between the tip (3c) of the extension crank (11) and the crankshaft (1) ( R) is a bicycle crank mechanism in which the extension crank (11) is longer when the extension crank (11) is located on the depression side than when the extension crank (11) is located on the return side.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described with reference to the accompanying drawings.

A crank arm 2 is fixedly provided on a crank shaft 1 which is rotatably supported in a bearing portion 20 fixed to a bicycle body 10. As an example of the crank arm 2 and the extension member 3, a bifurcated arm 3d formed in a bifurcated shape.
The end of one leg portion 3a is rotatably attached by a crank pin 4 to form an extension crank 11.
A pedal shaft 5 is provided at the end of the other leg portion 3b of the bifurcated arm 3d in the extension crank 11 so as to be positioned on the same axis as the crank pin 4, and the pedal shaft 5 is rotatable by the pedal shaft 5. A pedal 6 supported by is provided.
Further, one end of the connecting arm 7 is fixed to the bifurcated arm 3d, and the other end of the connecting arm 7 and one end of the swing arm 8, that is, the swing end 8a are axially attached to the other end of the swing arm 8. A supporting member 9 fixed to the bicycle main body 10 is pivotally mounted 8 so that the supporting member 9 can swing.
c.

In this crank mechanism, when the rider depresses the pedal 6, the extension crank 11 makes a rotary motion about the crankshaft 1 as a rotation axis, and in conjunction with the rotation of the extension crank 11, the connecting arm 7 is connected. The swinging arm 8 swings through the shaft mounting portion 8c as a shaft. At this time, the angle formed by the bifurcated arm 3d and the crank arm 2 changes, so that the linear distance between the tip 3c of the extension crank 11 and the crankshaft 1 changes.

Reference numeral 30 is a chain case. Also, in the figure, arrow A1 is the front wheel side of the bicycle, and arrow A2 is the rear wheel side.

The locus of movement of each member in the crank mechanism of the present invention will be described with reference to FIGS. Each of these figures shows the locus of one rotation from the position of each member (hereinafter referred to as the home position) when the pedal 6 is at the highest position, and is divided into eight parts. The central axis of is shown by a solid line to show the positional relationship of each member.

The pedal 6 is shown in FIGS.
The locus of one rotation is shown by the dotted line.

FIG. 4 shows the position of each member at the home position. The angle formed by the crank arm 2 and the bifurcated arm 3d is θ ₁ , and the tip 3c of the extension crank 11 and the crankshaft 1 are formed. The straight line distance is R ₁ .

When the extension crank 11 is rotated from the home position to the stepping side (front wheel side of the bicycle) and is in the position shown in FIG. 5, the angle formed by the crank arm 2 and the bifurcated arm 3d is θ ₂ and the angle θ ₁ larger, the linear distance between the tip 3c and the crankshaft 1 is longer than the distance R ₁ is R _2.

When the extension crank 11 further rotates and is in the position shown in FIG. 6, the crank arm 2 and the bifurcated arm 3 are provided.
The angle formed by d is θ _3, which is smaller than the angle θ 2, and the tip 3
The straight line distance between c and the crankshaft 1 is R3, and the distance R is
Shorter than 2.

In this embodiment, each arm is shown in FIG.
Since the inclination direction of the bifurcated arm 3d with respect to the crank arm 2 is reversed from the position of 2 to the position of FIG. 6, the linear distance between the tip 3c and the crank shaft 1 is the distance R ₂ to the distance R _2. There will be a position that becomes the longest while changing to ₃ .

When the extension crank 11 further rotates and is in the position shown in FIG. 7, the angle formed by the forked arm and the crank arm 2 is θ ₄ , which is smaller than the angle θ ₃ , and the tip 3
The straight line distance between c and the crankshaft 1 is R ₄ , and the distance R is
_Shorter than ₃ .

When the extension crank 11 is at the position shown in FIG. 8, that is, when the pedal 6 is at the lowest position, the bifurcated arm 3
The angle between d and the crank arm 2 is θ ₅ , and the angle θ
_It is smaller than _4, and the linear distance between the tip 3c and the crankshaft 1 is R ₅ , which is shorter than the distance R 4. Since the position of the tip 3c at this time is higher than the position of the pedal 6, the bifurcated arm 3d does not hit the ground.

When the extension crank 11 is rotated from the depression side to the return side (the rear wheel side of the bicycle) and is in the position shown in FIG. 9, the angle between the forked arm 3d and the crank arm 2 is θ.
_6, which is smaller than the angle θ 5, and the linear distance between the tip 3c and the crankshaft 1 is R ₆ , which is shorter than the distance R ₅ .

Further, the extension crank 11 is further rotated, and FIG.
At the position shown in FIG. 3, the angle formed by the bifurcated arm 3d and the crank arm 2 is θ ₇ , which is larger than the angle θ ₆ ,
Linear distance between the tip 3c and the crankshaft 1 is R _7, it is longer than the distance R6.

In this embodiment, each arm is shown in FIG.
Since the inclination direction of the bifurcated arm 3d with respect to the crank arm 2 is reversed from the position of FIG. 10 to the position of FIG. 10, the linear distance between the tip 3c and the crankshaft 1 is the distance R ₆ to the distance R _{6. While} changing to ₇ , there will be a position where the length becomes the shortest.

The extension crank 11 is further rotated, and
At the position shown in FIG. 3, the angle formed by the bifurcated arm 3d and the crank arm 2 is θ ₈ , which is larger than the angle θ ₇ ,
Tip 3c and the linear distance between the crank shaft 1 is longer than the distance R ₇ is R _8.

Then, each arm returns to the home position shown in FIG.

As described above, in this crank mechanism, the angle formed by the bifurcated arm 3d and the crank arm 2 which starts with the reference sign θ (hereinafter collectively referred to as the angle θ) is interlocked with the rotation of the extension crank 11. The length of the linear distance between the tip 3c of the extension crank and the crankshaft 1 that starts with the reference symbol R (hereinafter collectively referred to as the linear distance R) changes. This straight line distance R is the longest from the depression side to FIGS. 5 to 6, and conversely the shortest from the return side to FIGS. 9 to 10.

Although not shown in the drawings, this crank mechanism is provided with mechanisms having the same structure on both left and right sides of the crank shaft 1 through the crank shaft 1, and the respective crank arms 2 are 180 degrees apart from each other, like a general bicycle. The shift allows the rider of the bicycle to alternately step on the pedal 6 with his left and right feet.

Since the moving loci of the respective members constituting the left and right crank mechanisms are also displaced by the amount of the crank arm 2 being displaced by 180 degrees, for example, one side from the stepping side to FIGS. 5 to 6. , The other side is around the return side from FIG. 9 to FIG. As described above, the straight-line distance R is the longest from FIG. 5 to FIG. 6 and the shortest from FIG. 9 to FIG. 10, so the straight-line distance R is from the FIG. 5 to FIG. One side, that is, the side of the crank mechanism located on the step-in side is longer than the side located around FIGS. 9 to 10, that is, the side of the crank mechanism located on the return side. Become.

The left and right crank mechanisms are composed of members having the same mass, but if there is a difference in the linear distance R between the left and right crank mechanisms, the bifurcated arm 3d.
There is a difference in length between the position of the center of gravity and the linear distance between the crankshaft 1 and the position of the center of gravity of the extension crank 11 formed by the bifurcated arm 3d and the crank arm 2 in the left and right crank mechanisms. Become. In this case, the left and right crank mechanisms are not balanced with the crankshaft 1 as a fulcrum, and the linear distance R
On the longer side, that is, the extension crank 11 on the far side of the position of the center of gravity of the extension crank 11, causes a moment due to gravity to rotate the extension crank 11 in a direction inclining to the ground side.

Therefore, in the left and right crank mechanisms, when one side is on the stepping side from FIGS. 5 to 6, and the other side is on the return side from FIGS. 9 to 10, the stepping side 5 to FIG. 6, there is generated a moment to rotate the extension crank 11 in a direction in which the extension crank 11 on the side inclining to the ground side, that is, in the stepping direction of the pedal 6. Since the moment when the rider depresses the pedal 6 is added to this moment, both of them synergistically rotate the extension crank 11, and the bicycle can be effectively and easily propelled.

Further, as described above, the straight line distance R becomes the longest from FIGS. 5 to 6 and the shortest from FIGS. 9 to 10, so that the left and right crank mechanisms are located at that position. In some cases, the difference in length of the straight line distance R is the largest. Therefore, the moment due to gravity for rotating the extension crank 11 caused by the difference in length becomes the largest.

When the force by which the rider of the bicycle steps on the pedal 6 works most effectively to rotate the extension crank 11, it is when the extension crank 11 is in the position of FIGS. The time is synchronized with the time when the moment for rotating the extension crank 11 based on the difference between the lengths of the straight line distances R is the largest. By doing so, the synergistic effect of matching the moment generated by the rider's stepping on the pedal 6 with the moment generated by the difference in the length of the straight line distance R causes the extension crank 11 to rotate most effectively here. It will act on. Therefore, the bicycle can be propelled most effectively and easily here.

More specifically, when the extension crank 11 is rotating while the bicycle equipped with the crank mechanism of the present invention is traveling, the extension crank 11 rotates while becoming longer on the stepping side and shorter on the return side. Therefore, the moment of inertia of the extension crank 11 on the stepping side is larger than that on the return side, and in this state, the moment of stepping on the rider's pedal 6 is added in synchronization, so that the bicycle is more effectively propelled during traveling. Can be made.

[0032]

As described above, in the crank mechanism of the present invention, the moment generated by the rider's stepping on the pedal and the moment generated by the difference in the position of the center of gravity of the extension cranks of the left and right crank mechanisms. Therefore, since both of them synergistically rotate the extension crank 11, the bicycle equipped with this crank mechanism can effectively and easily propel the bicycle.

Further, when the force with which the rider of the bicycle steps on the pedal acts most effectively to rotate the extension crank, and when the moment generated by the difference in the position of the center of gravity of the extension crank in the left and right crank mechanisms is the largest. Since the and are synchronized with each other, the synergistic effect due to the fact that the moment generated by the rider's stepping on the pedal 6 and the moment generated by the difference in the straight line distance R coincide with each other is most effectively extended here. It will act to rotate the crank 11. Therefore, the bicycle can be propelled most effectively and easily here.

Further, during running, the state in which the inertial moment of the extension crank is large and the moment due to the depression of the pedal of the rider can be matched, and the bicycle can be more effectively propelled.

[Brief description of the drawings]

FIG. 1 is a perspective view of a main part of a bicycle including a bicycle crank mechanism according to an embodiment of the present invention.

FIG. 2 is a front view of the same.

FIG. 3 is a side view of the same.

FIG. 4 is an explanatory view showing the positional relationship of each member of the crank mechanism of the bicycle according to the embodiment of the present invention.

FIG. 5 is an explanatory diagram of another state of the above.

FIG. 6 is an explanatory diagram in still another state of the above.

FIG. 7 is an explanatory diagram of still another state of the above.

FIG. 8 is an explanatory diagram of still another state of the above.

FIG. 9 is an explanatory diagram of still another state of the above.

FIG. 10 is an explanatory diagram of still another state of the above.

FIG. 11 is an explanatory diagram of still another state of the above.

[Explanation of symbols]

 1 crankshaft 2 crank arm 3 extension member 3c tip 3d bifurcated arm 5 pedal shaft 6 pedal 7 connecting arm 8 swinging arm 9 support member 10 bicycle body 20 bearing portion

Claims (2)

[Claims] A crank arm (2) is provided on a crank shaft (1) supported by a bearing portion (20) fixed to a bicycle body (10), and an extension member (3) is provided on the crank arm (2). An extension crank (11) is rotatably provided and a pedal shaft (5) for rotatably supporting a pedal (6) is provided on the extension crank (11), and the extension member (3) is provided.
A swinging arm (8) is provided on the connecting arm (7),
The swing arm (8) is swingably attached (8c) to a support member (9) fixed to the bicycle body (10), and the tip (3c) of the extension crank (11) and the crankshaft (1). ), The linear distance (R) with the extension crank (11) is longer when the extension crank (11) is located on the depression side than when the extension crank (11) is located on the return side. Bicycle crank mechanism characterized by. 2. The bicycle crank mechanism according to claim 1, wherein a pedal shaft (5) provided on the extension crank (11) is provided on the extension member (11).