JPS6146077Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a bicycle gear crank device, and more particularly to a bicycle gear crank device comprising a crank and a plurality of chain gears having different numbers of teeth. Normally, this type of gear crank device uses circular chain gears with different numbers of teeth, and these circular chain gears are combined and attached to the crank, and the pedal force generated by pressing the pedal is transmitted from the crank to the chain gear, and the chain gears are connected to one of these chain gears. The gears are changed by changing the chain that is selectively hung on one of the gears.

Generally, when transmitting the pedal force to the chain gear,
While the load acting on the chain gear, that is, the load acting from the rear wheels to the rear chain gear and the front chain gear via the chain, is constant,
The pedaling force during one revolution of the crank changes greatly depending on the position of the crank arm on the crank, and as a result, the output efficiency of the chain gear relative to the pedaling force is poor. That is, the pedaling force during one revolution of the crank is the minimum pedaling force when the crank arm is located at the top dead center and the bottom dead center, and the crank arm rotates 60 to 135 degrees forward in the drive rotation direction from the top dead center. Therefore, when the crank arm is located near the top dead center and near the bottom dead center, where only a small pedal force can be obtained, the pedal force is insufficient for the load acting on the chain gear. When winning, the pedal becomes heavier and the crank arm is located in a region where a large pedal force can be obtained, the pedal force becomes excessive compared to the load acting on the chain gear, and the pedal is pressed down by an amount corresponding to the excess pedal force. This results in a loss of pedaling power,
Overall, the output efficiency of the chain gear relative to the pedal effort was poor, and the rider was easily fatigued.

By the way, in order to reduce the pedal force transmitted to the chain gear, it is possible to reduce the diameter of each front chain gear attached to the crank and reduce the gear ratio between the front chain gear and the rear chain gear. On the other hand, there is a problem in that the high-speed running performance of the bicycle deteriorates. Also, if you reduce only the diameter of the chain gear with the minimum number of teeth without reducing the diameter of each front chain gear, the gear ratio between the front chain gears will become too large, causing a problem in which shifting performance by changing chains will deteriorate. It was hot.

Therefore, in order to solve the conventional problems as described above, the applicant of the present invention created a chain gear with the minimum number of teeth.
The company had previously developed and applied for a gear crank device in which the chain gear was approximately elliptical with a major axis and a minor axis, and the other chain gear was circular. Since the angle of the chain gear relative to the crank arm of the crank cannot be changed, it has been impossible to change the angle of the chain gear relative to the crank arm in accordance with the load acting on the chain gear. That is, among the regions where a large pedaling force can be obtained (the range where the crank arm rotates 60 to 135 degrees forward in the drive rotation direction from top dead center), the region where the rotation angle from top dead center is 60 to 100 degrees. In this case, the output efficiency of the chain gear relative to the pedal force is the best, and the maximum pedal force can be obtained in the range of rotation angle from top dead center of 110 to 120 degrees. If the angle to the pedal cannot be changed, in areas where a large pedal force can be obtained, for example, when driving on flat ground with a relatively low load, the pedal is operated in a state where the output efficiency of the chain gear relative to the pedal force is the best, and when driving uphill with a large load, It was not possible to use the pedal in a state where the maximum pedal effort was obtained.

The present invention was devised in view of the above points, and it is possible to improve the output efficiency of the chain gear with respect to the pedal force, eliminate deterioration in shifting performance, and achieve the best output efficiency according to the load acting on the chain gear. To provide a gear crank device that can be used for two purposes: one in which the pedal can be operated in a state where the maximum pedal effort is obtained, and the other in which the pedal can be operated in a state where maximum pedal effort is obtained.

Therefore, in the present invention, among the plurality of chain gears, the chain gear with the least number of teeth is approximately elliptical with a major axis and a minor axis, and the other chain gears are circular, and the chain gear with the least number of teeth is It is characterized in that it is fixed to the crank arm of the crank so that its angle can be freely changed.

In the present invention, "almost elliptical" refers to not only an ellipse that draws an arc symmetrical with respect to the major and minor axes that are orthogonal to each other, but also two surfaces on the minor axis side or two surfaces on the major axis side. may be parallel to each other, or the long axis and short axis may not be perpendicular to each other.

An embodiment of the present invention will be described below based on the drawings.

The illustrated gear crank device has fitting parts 1 at both ends.
1a and 11b, and a pair of crank arms 12 and 13 attached to both end fitting portions 11a and 11b of the crankshaft 11.
A stay 14 extending in the radial direction is provided on the boss portion 12a of the
A first chain gear 2 with the minimum number of teeth and a second chain gear 3 with the maximum number of teeth are attached through the chain, and a chain is selectively hung on one of these chain gears 2 and 3. . The chain gears 2 and 3 are connected by a plurality of stops 4 at regular intervals in the axial direction.

Further, the fitting portions 11a, 11 of the crankshaft 11
b and the insertion holes 12b and 13b of the crank arms 12 and 13 into the fitting portions 11a and 11b are respectively provided with uneven stripes, and by the engagement of these uneven stripes, the crankshaft 11 of the crank arms 12 and 13 is It prevents rotation against.

Of the chain gears 2 and 3, the first chain gear 2 with the least number of teeth is, for example, approximately elliptical with the long axis X and the short axis Y orthogonal to each other, and the second chain gear 3 with the largest number of teeth is circular. In the long axis X portion of the first chain gear 2, the gear ratio between the chain gears 2 and 3 is reduced, in other words, the gear ratio between the front chain gear and the rear chain gear is increased, and in the short axis Y portion of the first chain gear 2, The gear ratio between the chain gears 2 and 3 is made large, in other words, the gear ratio between the front chain gear and the rear chain gear is made small, and the angle of the first chain gear 2 is freely changeable with respect to the crank arms 12 and 13 of the crank 1. It is to be fixed at

This angle change of the first chain gear 2 can be carried out, for example, by changing the stay 1 of the first chain gear 2 as shown in the figure.
4, an arc-shaped through hole 2 extending in the circumferential direction
1 are provided, and the stopper 4 is inserted into each of these through holes 21, so that the angle of the first chain gear 2 can be changed with respect to the crank arms 12, 13, and by tightening the stopper 4, the first chain gear 2 is held at a predetermined position. It is fixed. Another angle changing means is that a large number of through holes are provided at predetermined intervals in the circumferential direction at the attachment portion of the first chain gear 2 to the stay 14.
Further, as another means for changing the angle, as shown in FIG. 2, this can be done by changing the engagement position of the concave and convex stripes provided in the fitting portions 11a, 11b of the crankshaft 11 and the insertion holes 12b, 13b of the crank arms 12, 13. Ru. In this case, the first chain gear 2 and the second chain gear 3 or only the first chain gear 2 are supported on the crankshaft 11 directly or via an adapter, and the crank arms 11 and 12 are supported on the crankshaft 11 so that their positions can be changed. That's what I do.

Further, the length of the long axis X of the first chain gear 2 is a length corresponding to, for example, 39 to 45 teeth, for example, 39 teeth.
This is made smaller than the outer diameter of the second chain gear 3, which has a number of teeth of ~52 teeth, and the length of the short axis Y of the first chain gear 2 is set to a length corresponding to, for example, a number of teeth of 28 to 30 teeth. be.

In the above configuration, the first chain gear 2 has its long axis
Direction) When the crank arms 12 and 13 are located in a region where a large pedaling force can be obtained after passing the top dead center _O1 by tilting the crank arms rearward at a predetermined angle, the gear ratio between the front chain gear and the rear chain gear is increased; Furthermore, when the crank arms 12 and 13 are located near the top and bottom dead centers O ₁ and O ₂ where only a small pedal force can be obtained, the gear ratio between the front chain gear and the rear chain gear is reduced, and the area where a large pedal force can be obtained is reduced. For example, when traveling on flat ground with a relatively light load, the long axis When the crank arms 12 and 13 are located at the dead center O ₁ and the bottom dead center O ₂ , the crank arms 12 and 13 are rotated 60 to 100 degrees toward the front of the drive rotation from the top dead center O ₁ . When traveling, the long axis X of the first chain gear 2 is aligned with the crank arm 12,
13 _{, and} when _the long axis It is placed at a position rotated 135 degrees.

The present invention is constructed as described above, and as shown in FIG.
4, a chain C is hung between one of the chain gears 2 and 3 attached to the crank 1 and the rear chain gear G, and the pedal is attached to the tips of the crank arms 12 and 13. The pedal force is transmitted to the chain gears 2 and 3 via the crank 1, and the output of the chain gears 2 and 3 is transmitted to the rear chain gear G via the chain C.
and drive the rear wheels, and a front derailleur D disposed near the approach path of the chain C to the front chain gear connects the chain C to one of the chain gears 2 and 3. It is done as if by selectively replacing them.

Therefore, when the chain C is replaced with the first chain gear 2, assuming that the load acting on the chain gear 2 is constant, the load acting on the first chain gear 2 during one revolution of the crank arms 12, 13. , the pedal force changes, and the long axis X of the chain gear 2
In this section, the gear ratio with the rear chain gear G becomes large, requiring a large pedal force against the load on the first chain gear 2, and the short axis Y of the chain gear 2 increases.
Since the gear ratio of this part to the rear chain gear G is small, the pedaling force can be reduced relative to the load acting on the first chain gear 2.

Therefore, in a region where a large pedal force is obtained, that is, in a position where the crank arms 12 and 13 are rotated 60 to 135 degrees forward in the driving rotation direction from the top dead center _O1 ,
By increasing the gear ratio between the first chain gear 2 and the rear chain gear G, the pedal force is prevented from becoming excessive with respect to the load acting on the first chain gear 2, and the region where only a small pedal force can be obtained is achieved, that is, the crank arm 1.
2 and 13 are located near the vertical dead centers O ₁ and O ₂ , the gear ratio between the first chain gear 2 and the rear chain gear G is made small so that the pedal force is insufficient for the load acting on the first chain gear 2. By doing so, the output efficiency of the first chain gear 2 relative to the pedal effort can be improved, and fatigue can be reduced.

In addition, if you want to operate the pedals in the best output efficiency state in the region where a large pedal force can be obtained, the angle of inclination of the long axis When the axis X is located near the top dead center O ₁ and the bottom dead center O ₂ , the crank arm 12 is
It is located at a position rotated 60 to 100 degrees forward in the drive rotation direction from O _1. Also, if you want to operate the pedal in the area where the maximum pedal force can be obtained among the areas where a large pedal force can be obtained, the long axis When the angle of inclination to the crank arms 12 and 13 is 80 to 135 degrees, and the long axis X is located near the top dead center O ₁ and the bottom dead center O ₂ , the crank arm _{12 is} It is located at a position rotated 80 to 135 degrees forward in the direction of drive rotation. By doing so, depending on the load acting on the first chain gear 2, it is possible to use the pedal in a manner that allows the pedal to be operated in a state with the best output efficiency, and in a manner in which the pedal can be operated in a state that provides the maximum pedal force.
The degree of driver fatigue per unit time can be reduced.

Also, by making only the first chain gear 2 with the minimum number of teeth approximately elliptical, the gear ratio between the chain gears 2 and 3 at the long axis X portion is increased, and the chain C is replaced from this long axis X portion. This makes it possible to eliminate deterioration in shifting performance.

In addition, by tilting the long axis X of the first chain gear 2 having the minimum number of teeth toward the rear in the drive rotational direction of the crank arms 12 and 13, the load on the driver can be reduced.
Since the load can be controlled to correspond to the pedal force, it is possible to reduce fatigue and efficiently transmit the pedal force. In other words, in areas where only a small pedal force can be obtained, the gear ratio between the front chain gear and rear chain gear can be reduced to reduce the load on the driver, making it less tiring, and in areas where a large pedal force can be obtained, that pedal force Since the load on the driver can be increased accordingly, the transmission can be carried out more efficiently as a whole.

Moreover, while the crank arms 12 and 13 are moving from a region where only a small pedal force is obtained to a region where a large pedal force is obtained, the long axis X portion of the first chain gear 2 is moved from the top dead center O ₁ to the crank arm 12. , 13 in the drive rotational direction, and near the approach path of the chain C to the first chain gear 2, and can be replaced from this long axis X portion to the second chain gear 3, reducing speed changeability. can be reliably prevented.

In the above explanation, the first chain gear 2 with the minimum number of teeth and the second chain gear 3 with the maximum number of teeth have been described, but in addition, between these chain gears 2 and 3, the length of the first chain gear 2 is used. One or more intermediate chain gears that are longer than the length of the axis X and smaller than the outer diameter of the second chain gear 3 may be provided. or,
The chain gears 2 and 3 may be formed separately and connected by a stopper 4, or may be formed integrally, or may be attached to the crank arm 12.
It may also be attached to the crankshaft 11.

In addition, in the above description, the first chain gear 2 is approximately elliptical with the long axis X and the short axis Y being orthogonal to each other, but it may be an ellipse in which the long axis X and the short axis Y are not orthogonal to each other. Alternatively, the two surfaces on the long axis X side or the two surfaces on the short axis Y side may be parallel.

As described above, in the present invention, among a plurality of chain gears with different numbers of teeth, the chain gear with the minimum number of teeth is approximately elliptical with a major axis and a minor axis, and the other chain gears are circular. When driving with a chain attached to the chain gear, in a region where a large pedal force is obtained, the gear ratio between the chain gear and the rear chain gear is increased to prevent the pedal force from becoming excessive with respect to the load acting on the chain gear. However, in areas where only a small pedal force can be obtained, it is possible to reduce the gear ratio between the chain gear and the rear chain gear to prevent insufficient pedal force against the load acting on the chain gear. While improving output efficiency, the chain gear with the minimum number of teeth is fixed to the crank arm so that the angle can be changed freely, so the pedal can be operated in a state with the best output efficiency according to the load acting on the chain gear. Since the pedal can be used in two different ways, the pedal can be operated in a state where the maximum pedal force is obtained, and the driver's fatigue level per unit time can be extremely reduced.

In addition, by making only the chain gear with the minimum number of teeth almost oval, the gear ratio between the chain gears on the long axis portion can be increased and the chain can be changed from this long axis portion, which reduces the reduction in shifting performance. can be eliminated.

[Brief explanation of the drawing]

Fig. 1 is a partially cutaway front view showing one embodiment of the gear crank device of the present invention, Fig. 2 is a sectional view taken along the line of Fig. 1, Fig. 3 is a scaled side view, and Fig. 4 is an explanation showing the state of use. It is a diagram. 1... Crank, 12, 13... Crank arm, 2, 3... Chain gear, X... Long shaft, Y...
Short axis.

Claims (1)

[Scope of utility model registration request] It consists of a crank and a plurality of chain gears with different numbers of teeth. Among the chain gears, the chain gear with the least number of teeth is approximately elliptical with a major axis and a minor axis, and the other chain gears are circular. A gear crank device for a bicycle, characterized in that said chain gear having a number of teeth is fixed to a crank arm of said crank so that its angle can be freely changed.