JPS6243907B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a chain gear of a gear crank device for a bicycle. More specifically, the present invention relates to a chain gear of a gear crank device consisting of a crankshaft, a pair of crank arms, and a chain gear. It is possible to obtain a high work rate, reduce the physical burden on the driver, and enable smooth pedaling without a jerky feeling.

In general, a gear crank device for a bicycle is attached to the bottom bracket of the bicycle and has a drive chain stretched between it and a rear chain gear provided on the rear wheel hub, and when a pedal provided on the crank arm is depressed, the torque is transferred from the chain gear. The signal is transmitted to the rear chain gear via the drive chain to drive the rear wheels and propel the bicycle.

When the pedal is depressed, that is, when pedaling,
The driver rotates the pedals around the axis of the crankshaft, and looking at the movement of the feet, the movement is similar to a pendulum movement, similar to when walking.
In other words, like pendulum motion, it has a unique period and speed pattern based on the length between the fulcrum and the center of gravity.

On the other hand, when the driver sits on the seat and drives the pedals, the torque output from the driver's feet depends on the pedal position during the pedaling cycle, as shown by the chain line in Figure 3. In the area between the top and bottom dead centers, the crank arm moves approximately forward in the drive rotation direction of the crank arm from the top dead center in the area between the top and bottom dead centers. It reaches its maximum when rotated by 70°±5°, and reaches its minimum near the vertical dead center.

This is due to the movement of the legs during pedaling and the position of the pedals related to the movement of the legs, and this is the same even if the size and type of bicycle changes, and even if riders have different muscle outputs. It emerges as a result of trends.

By the way, in the case of an oval chain gear, the pitch diameter of each tooth of the chain gear can be changed, and therefore, when the rear chain gear is kept constant, the gear ratio can be changed, so when the chain gear is used as a front chain gear, In the region where the maximum torque can be obtained during pedaling, the maximum gear ratio is set so that more work can be done using this torque, and at the top and bottom dead center where only the minimum torque can be obtained, the minimum gear ratio is set. Conceivable.

However, with the above configuration, in the region where the maximum torque is obtained, that is, in the region displaced approximately 70°±5° in the drive rotation direction from the vertical dead center, the maximum gear ratio is set, so the circumferential speed of pedaling is It will be slower, the work rate will be worse, and at top and bottom dead center,
Since the minimum gear ratio increases the circumferential speed of pedaling, this actually puts a physical burden on the driver.

In other words, from the movement of the legs during pedaling, in the area between the top and bottom dead centers, the energy consumption required to move the legs can be reduced, and the muscle output can be maximized, so the faster the circumferential speed of pedaling, the faster the energy consumption will be reduced. For example, from the relationship of power = torque x speed, even though the power can be improved, since the speed is slowed down in this region, the power becomes worse. Since the energy required to move the is greater than the area between the vertical dead center, if the circumferential speed of pedaling is slowed down near the vertical dead center, the muscles will not be able to produce muscle output near the vertical dead center, where muscle output cannot be produced in the first place. This can reduce the strain on the muscles, but since the top dead center is reached earlier, the strain on the muscles is further increased.

As described above, in pedaling, the foot movements have a predetermined cycle and speed pattern, and by giving motions that do not match these patterns, the peak of muscle output increases, and the driver can improve the performance even during the same task. He invented it after discovering that it imposes an extra physical burden.

That is, in the present invention, when pedaling, when the torque of the foot increases, the power can be improved by increasing the peripheral speed of pedaling in accordance with the increase in torque, and when the torque decreases from the maximum value. Focusing on the fact that the burden on the muscles can be reduced by slowing the circumferential speed of pedaling in response to the decreasing change in torque, the chain gear is made non-circular with different pitch diameters, and the maximum pitch diameter portion and the maximum pitch diameter are The crank arm is located forward in the driving rotational direction of the crank arm from a bisector of a minimum pitch diameter portion rearward in the driving rotational direction and rearward in the driving rotational direction from the maximum pitch diameter portion. Then, the rate of change in the pitch diameter from the maximum pitch diameter portion forward in the drive rotation direction to the minimum pitch diameter portion rearward in the drive rotation direction with respect to the coupling position of the crank arm is determined from the minimum pitch diameter portion to the crank arm It is characterized in that the rate of change in pitch diameter is greater than the maximum pitch diameter portion at the front in the driving rotation direction with respect to the coupling position.

That is, in the region between the top and bottom dead centers where large torque can be obtained, the pitch diameter is made smaller in response to the change in torque, and the circumferential speed of pedaling is increased in response to the change in torque. In addition, at the vertical dead center where only a small torque can be obtained, the pitch diameter is increased in accordance with the change in torque, and the circumferential speed of pedaling is slowed in accordance with the change in torque. Match the speed pattern of foot movement at a point,
This improves the work rate in one cycle of pedaling, reduces the amount of muscle output (energy consumption) relative to the amount of work, and makes it possible to pedal without feeling jerky while reducing the physical load on the driver. This is the basic idea.

Note that, in the present invention, the torque of the foot refers to the joint torque output by the movement of the joints due to muscle contraction and extension.

Next, one embodiment of the present invention will be described based on the drawings.

The gear crank device shown in FIG. 1 includes a crankshaft 11 having fitting portions 11a and 11b at both ends,
A stay 14 extending in the radial direction is attached to the boss portion 12a of the crank arm 12 on one side of the crank 1, which is composed of a pair of crank arms 12 and 13 attached to both end fitting portions 11a and 11b of the crankshaft 11. a first chain gear 2 with the minimum number of teeth;
A second chain gear 3 having the maximum number of teeth is attached, 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.

Therefore, at least one of the chain gears 2 and 3, the first chain gear 2 having the least number of teeth, as shown in the drawing, is made non-circular with different pitch diameters, and the pitch diameter D of the first chain gear 2 is made non-circular. It is changed at different rates of change as follows.

That is, the first chain gear 2 is attached to the crank arms 12, 13 forward of the bisecting line between the maximum pitch diameter portion A and the minimum pitch diameter portion B in the drive rotational direction of the crank arms 12, 13, and , the crank arms 12 and 13 are positioned and connected at the rear of the driving rotation from the maximum pitch diameter portion A, and the connecting positions (dead centers O ₁ , O ₂ ) of the crank arms 12 and 13 are thus connected. On the other hand, the minimum pitch diameter portion B is located forward in the driving rotation direction and rearward from the maximum pitch diameter portion A in the driving rotation direction.
The rate of change in the pitch diameter from the minimum pitch diameter portion B to the maximum pitch diameter portion A is made greater than the rate of change in the pitch diameter from the minimum pitch diameter portion B to the maximum pitch diameter portion A in front of the coupling position of the crank arms 12 and 13 in the drive rotation direction.

To explain more specifically, in FIG. 2, the first tooth G1 and the 22nd tooth G2 of the maximum pitch diameter portion A
2, the 9th tooth G9 and the 10th tooth of the minimum pitch diameter portion B
The rate of change in pitch diameter from the third tooth G10 to the 30th tooth G30 and the 31st tooth G31, that is, from the third tooth G3 to the fourth tooth G
Rate of change to 4 and from 24th tooth G24 to 25th tooth G25
The rate of change in the pitch diameter leading to
, the rate of change in pitch diameter from the 22nd tooth G22, the 30th tooth G30, and the 31st tooth G31 of the maximum pitch diameter portion A to the first tooth G1, that is, the 14th to 17th teeth G14.
- G17 and the rate of change in the pitch diameter of the 35th to 38th teeth G35 to G38 are set to the next largest rate of change.

In addition, in the case shown in FIG. 2, the crank arms 12 and 13 are rotated in the drive rotation direction (second
When the crank arms 12 and 13 rotate past the vertical dead center toward the region where maximum torque can be obtained, that is, the torque of the legs increases. At this time, the pitch diameter D of the first chain gear 2 decreases in response to this increase in torque, and the pitch diameter D of the first chain gear 2 decreases.
3 is located in the region where the maximum torque can be obtained, the pitch diameter D of the first chain gear 2 is minimized, and the gear ratio of the front chain gear and the rear chain gear is made small in response to the increase in the torque. The angular velocity of the pedal can be increased in response to the increase in torque, and when the crank arms 12, 13 rotate from a position where maximum torque is obtained to a region where only minimum torque is obtained, That is, when the torque decreases from the maximum value, the pitch diameter D of the first chain gear 2 is increased in response to the decrease in torque, and the gear ratio between the front chain gear and the rear chain gear is adjusted to decrease the torque. The pitch diameter D of the chain gear 2 is increased to correspond to the change, and the pitch diameter D of the chain gear 2 is maximized when the crank arms 12 and 13 are located near the vertical dead center O ₁ and O ₂ where only a small torque can be obtained. The gear ratio between the front chain gear and the rear chain gear is maximized so that the angular velocity of the pedal becomes slower in response to the change in torque.

To describe this configuration in more detail, the torque of the foot changes as shown by the chain line in FIG. 3 during one rotation of the crank arms 12, 13, that is, during pedaling.

At the maximum pitch diameter portion A of the first chain gear 2, the gear ratio with respect to the rear chain gear RG becomes large, and the angular velocity of the pedal becomes slow, and at the minimum pitch diameter portion B of the first chain gear 2, the gear ratio with the rear chain gear RG increases. becomes smaller, and the angular velocity of the pedal becomes faster.

Based on the above, in the region where a large torque is obtained during pedaling, that is, in the position where the crank arms 12 and 13 are rotated 30 to 120 degrees forward in the drive rotation direction from the top dead center _O1 , the third As shown by the solid line in the figure, the pitch diameter D of the first chain gear 2 is made smaller in response to the change in leg torque, and the gear ratio between the first chain gear 2 and the rear chain gear RG is made smaller in response to the change in torque. Therefore, the angular velocity of the pedal is increased in response to the change in torque, improving the power in the region where large torque can be obtained, and matching the speed pattern of the foot movement.
In a region where only a small torque can be obtained, that is, when the crank arms 12 and 13 are located near the vertical dead centers O ₁ and O ₂ , the pitch diameter D of the first chain gear 2 increases in response to the change in torque. As the gear ratio between the first chain gear 2 and the rear chain gear RG increases in response to the change in torque, the angular velocity of the pedal is decreased in response to the change in torque, and only a small torque can be obtained. In this area, even though there is no output to begin with, increasing the speed reduces the strain on the muscles, and by matching the speed pattern of foot movements, the physical strain on the driver is reduced.

As described above, in the region between the top and bottom dead center where a large torque can be obtained, the pitch diameter D becomes the minimum in response to the change in foot torque, and the angular velocity of the pedal can be increased in response to the change in torque, so that the pitch diameter D becomes the minimum. It is possible to achieve a work rate of .

This also means that less torque is required for unit work since power = torque x angular velocity. Moreover, in the above region, the foot movement can be made quickly, so that it matches the speed pattern of foot movement similar to pendulum motion.

In addition, in the area where large torque cannot be obtained, that is, near the vertical dead center, the pitch diameter D becomes maximum in response to the change in torque, and the angular velocity of the pedal can be reduced in response to the change in torque, so the power is reduced. It's not a good idea, but since large torque cannot be produced in this region, it has little effect on the overall amount of work.Therefore, reducing the work rate will put more physical strain on the driver. There is no such thing. Furthermore, since the movement of the foot can be slowed down in the above region, it is possible to match the speed pattern of the movement of the foot.

As mentioned above, since the power in the area where large torque can be obtained can be improved in response to changes in torque, a high power can be obtained overall, and moreover, pedaling can be performed that matches the speed pattern of the foot movement. This reduces energy consumption during pedaling, reduces the physical burden on the driver, and enables smooth pedaling without any jerky feeling.

Incidentally, the maximum pitch diameter portion A of the chain gear 2
and minimum pitch diameter portion B is 1.1:1, a circular chain gear with the same number of teeth as the chain gear 2 (for example, 42 teeth) is used, and it is combined with a crank arm of the same length. So, if the maximum torque is 30Kgm and the minimum torque is 5Kgm, the ratio of the angular velocity of the pedal to the circular chain gear is 0.95 on the maximum pitch diameter side and 1.05 on the minimum pitch diameter side,
In addition, in the chain gear 2, the maximum pitch diameter side corresponds to the region where only the minimum torque can be produced, and the minimum pitch diameter side corresponds to the region where the maximum torque can be produced, so from power = torque x speed, when using the chain gear 2 The maximum torque is 28.5Kgm,
The minimum torque is 5.25Kgm.

Therefore, the torque at the maximum pitch diameter is 0.25Kgm.
Although it increases, it decreases by 1.5Kgm on the minimum pitch diameter side, and the rate of decrease is large. In this way, in the actual measured values, the maximum torque is 5% to 8%.
%, so even if the minimum torque increases, the integral value of torque in one pedaling cycle will be 2 to 3%.
Moreover, since the movement of the foot during pedaling can be matched to the speed pattern of this movement with its own cycle, the energy required to move the foot can also be reduced, and the integral of the electromyogram measured at the same time can be reduced. The value could also be reduced by 2-3%.

Note that the present invention can be applied to all types of bicycles, including standard types and minicycle types, but when applied to standard type bicycles, the crank arm 12 is connected to the long axis of the chain gear 2. It is deviated backward in the direction of rotation, and this deviation angle is set to 15°±5°.

Furthermore, as explained above, the chain gear 2 is combined with the crank arm 12 in such a way that the pitch diameter D becomes the minimum when the torque is maximum, and the pitch diameter D becomes the maximum when the torque is the minimum. The movement of the foot accelerates the mass of the foot, so
Although the muscles are actually outputting torque, there is a torque that does not act on the pedals, and just before bottom dead center, the mass of the foot is decelerated, so the torque is generated on the pedals even though the muscles are not actually working. Therefore, the minimum pitch diameter portion B and the maximum pitch diameter portion A of the chain gear 2
are the crank arm 1 for the positions where the leg torque is maximum and minimum as shown in FIG.
It is preferable to deviate about 10 degrees forward in the driving rotation direction of No. 2.

In the embodiment described above, the second chain gear 3 is circular, and in use, the crankshaft 11 of the crank 1 is connected to the bottom bracket 6 of the bicycle frame via the balls 5, 5 as shown in FIG. A chain C is supported to rotate freely, and a chain C is stretched between one of the chain gears 2 and 3 attached to the crank 1 as shown in Fig. 4 and the rear chain gear RG.
Torque from pedals attached to the tips of the crank arms 12, 13 is transmitted to the chain gears 2, 3 via the crank 1, and the output of the chain gears 2, 3 drives the rear chain gear RG via the chain C. , a front derailleur configured to drive the rear wheels and disposed near the approach path of the chain C to the front chain gear.
FD connects the chain C to the chain gear 2,
This is done by selectively replacing any one of the three.

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 other cases, the second chain gear 3 may be omitted and formed into a non-circular shape. Only a chain gear may be used. Further, when using a plurality of chain gears having different numbers of teeth, one or all of the chain gears may be formed into a non-circular shape.

As described above, the present invention provides a non-circular crank arm with different pitch diameters, and the crank arm is bisected by the bisector of the maximum pitch diameter portion and the minimum pitch diameter portion rearward of the maximum pitch diameter portion in the drive rotation direction. When the crank arm is located forward in the driving rotational direction and rearward of the maximum pitch diameter portion in the driving rotational direction and connected, the crank arm is located forward in the driving rotational direction with respect to the connecting position of the crank arm and from the maximum pitch diameter portion. The rate of change in pitch diameter from the minimum pitch diameter portion to the minimum pitch diameter portion at the rear in the drive rotation direction is greater than the rate of change in pitch diameter from the minimum pitch diameter portion to the maximum pitch diameter portion at the front in the drive rotation direction with respect to the coupling position of the crank arm. Therefore, when pedaling, it is possible to improve the work rate, and it is also possible to perform pedaling that matches the speed pattern of the foot movement during pedaling, and therefore, the physical burden on the driver can be reduced, and the pedal is nimble and This allows for smooth pedaling without any jerky feeling.

In other words, in a region where large torque can be obtained, the circumferential speed of pedaling can be increased in response to the change in torque, which increases the power and enables pedaling at a speed that matches the movement of the feet. The energy consumption required to move the wheel can be reduced compared to reducing the circumferential speed, and furthermore, in areas where large torque cannot be obtained,
Since the circumferential speed of pedaling can be reduced in response to the change in torque, the power rate will decrease somewhat, but since it is possible to pedal at a speed that matches the movement of the feet, energy consumption is reduced compared to when the circumferential speed is increased. Therefore, the physical strain can be reduced, and light pedaling becomes possible, and the feeling of jerkiness can be reduced.

In addition, although the power efficiency decreases in areas where large torque cannot be obtained, the work efficiency can be increased in areas where large torque can be obtained, so overall, in areas where large torque can be obtained with circular chain gears or elliptical chain gears. Compared to the case where the circumferential speed is slow in areas where large torque cannot be obtained and the circumferential speed is increased in areas where large torque cannot be obtained, the overall burden on the same work can be reduced.

[Brief explanation of the drawing]

Figure 1 is a partially cutaway front view of the gear crank device.
Fig. 2 is an enlarged front view showing one embodiment of the chain gear of the present invention, Fig. 3 is an explanatory diagram showing the relationship between the rotation angle of the crank arm, the torque of the foot, and the pitch diameter of the chain gear, and Fig. 4 is the state of use. FIG. 2...Chain gear, D...Pitch diameter, 11...Crankshaft, 12, 13...Crank arm.

Claims (1)

[Claims] 1 A chain gear of a gear crank device consisting of a crankshaft, a pair of crank arms, and a chain gear, and as a non-circular shape close to an oval with different pitch diameters, the maximum pitch diameter portion and the maximum pitch diameter portion are When the crank arm is positioned and connected in front of the bisector of the minimum pitch diameter portion of the crank arm in the drive rotation direction and rearward of the maximum pitch diameter portion in the drive rotation direction, The rate of change in pitch diameter from the maximum pitch diameter portion to the minimum pitch diameter portion rearward in the drive rotation direction at the front in the drive rotation direction with respect to the connection position of the crank arm is calculated from the minimum pitch diameter portion to the crank arm connection position. A chain gear for a bicycle gear crank device, characterized in that the rate of change in pitch diameter is greater than the maximum pitch diameter portion at the front in the drive rotation direction.