JPH0420833B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a bicycle transmission device capable of automatic continuously variable transmission, and is used in the field of manufacturing bicycles.

(Prior Art) Conventional bicycle transmission devices have a multi-gear transmission structure and have been widely put into practical use. However, multi-gear structures require manual and step-by-step shifting, and in order to increase the number of gears, it is necessary to increase the number of gears, which not only complicates the structure, but also
It also becomes cumbersome to operate. Furthermore, since the gear cannot be changed when the vehicle is stopped, there is a problem in that if the vehicle is stopped with the high-speed gear selected, a large amount of force is required to restart the vehicle.

In order to solve these problems, the applicant of the present application previously proposed a transmission device that combined a variable pulley and a V-belt (Japanese Patent Application No. 1983-
No. 278516 (Japanese Unexamined Patent Publication No. 155081-1981)).

(Problems to be solved by the invention) According to the above-mentioned earlier application, it is possible to obtain a device that has a simple structure and is capable of continuously variable speed, but in many cases the V-belt and pulley contact each other only at the side walls. Therefore, slips are likely to occur between the two,
Improvements in power transmission efficiency were desired.

(Means for Solving the Problems) In the transmission device of the present invention, a pulley is fixed to a pedal shaft that is attached to the frame of a bicycle so as to be able to move up and down, and an elastic body is attached to the groove of the pulley. A belt is attached between the wheel and the pulley.

The elastic body is for changing the diameter of the pulley, and is not limited to the pressurized air tube shown in the embodiment, as long as it can provide appropriate elastic deformation. In addition, if tooth shapes or other irregularities are provided on the back side of the belt, the protrusions will bite into the surface of the elastic body, resulting in a large frictional force.
Power transmission efficiency is further improved.

(Operation of the Invention) In this invention, the rotational force of the pedal shaft is transmitted to the pulley of the rear wheel via the pulley and the belt, and the rear wheel rotates.

If you try to rotate the pedal shaft by applying a large force to the pedal when a large amount of force is required, such as during initial movement, the pedal shaft will fall and the distance between the center of the pulley and the rear wheel pulley will become longer. . Therefore, the belt pushes down the elastic body attached to the groove of the pulley more strongly, so the effective radius of the pulley (distance from the center of the pulley to the contact surface of the belt)
becomes smaller. Therefore, the speed increasing ratio between the pulley on the pedal shaft and the pulley on the rear wheel becomes small, and the rear wheel rotates at a relatively low speed and with a large force.

Conversely, as the running resistance of the bicycle decreases and the force applied to the pedals weakens, the pedal axis gradually rises and the distance between the center of the pulley and the rear wheel pulley becomes shorter. Therefore, the elastic body pushes up the belt and gradually returns to its original shape, and the effective radius of the pulley increases, so the speed increasing ratio between the pulley on the pedal shaft and the rear wheel pulley increases, and the rear wheel can move at a relatively high speed. Rotate.

As described above, according to this device, continuously variable speed is automatically performed in proportion to the load, but the back surface of the belt is always in contact with the elastic body. Therefore, the possibility of slippage occurring between the belt and the pulley is also eliminated.

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

(Example) The base end of a pedal shaft mounting rod 2 is rotatably fixed to a bicycle frame 1 by a shaft 3 in a forward-sloping manner, and a pedal shaft 4 is rotatably fixed to the tip of the mounting rod 2. A pulley 5 is fixed to the pedal shaft 4, and a V-belt 8 is mounted between the pulley 5 and a pulley 7 fixed to the shaft of the rear wheel 6.

Two annular tubes 9, 9 filled with air are fitted into the groove 5a of the pulley 5. 2
The book tubes 9, 9 are respectively installed along the inner surface of the groove 5a, and the lower part is enlarged, and together they
It is designed to cover the entire bottom of the. In addition, the V
Tooth profiles 10 and 11 are provided on both the front and back surfaces of the belt 8. The tooth profile 10 on the front surface improves the flexibility of the V-belt, and the tooth profile 11 on the back surface bites into the tube 9 and has the effect of improving power transmission efficiency. play.

In the figure, 12 is a pedal rod, and 13 is a pedal.

According to the above embodiment, when a large force is required, such as when starting or climbing a slope, by strongly depressing the pedal 13, the mounting rod 2 rotates as shown by the arrow 14 in FIG. 3, and the pulley 5 descends. This increases the distance from the rear wheel pulley. Therefore, the V-belt 8 strongly presses the annular tubes 9, 9, so that the annular tubes 9, 9 are deformed toward the bottom side of the groove 5a, and the substantial radius of the pulley 5 becomes smaller. Therefore, the speed increasing ratio between the pedal shaft 4 and the pulley 7 of the rear wheel becomes small. Further, at this time, since the tooth profile 11 provided on the back surface of the V-belt 8 bites into the annular tube 9, there is no possibility of slippage occurring between the belt and the pulley.

On the other hand, if you reduce the force with which you press the pedal 13,
The annular tubes 9, 9 are returned to a balance position with the pressurizing force by the air pressure, and the substantial radius of the pulley 5 becomes larger. Therefore, the speed increasing ratio between the pedal shaft 4 and the pulley 7 of the rear wheel increases.

In this way, the speed increasing ratio changes automatically depending on the magnitude of the force with which the pedal is depressed, resulting in continuously variable speed.

Furthermore, in this embodiment, since tooth profiles are also provided on the surface of the V-belt, good flexibility can be obtained even if a thick V-belt is used.

(Effects of the Invention) According to the present invention, since the annular tube is attached to the pulley, the substantial radius of the pulley changes due to the elastic deformation of the annular tube. Therefore, the speed increasing ratio can be changed automatically and steplessly in response to the pedal depression force.

In this way, this device can perform stepless speed change without any special operation.
It is suitable for a transmission device for indoor exercise bicycles or bicycles for the elderly and women.

[Brief explanation of drawings]

FIG. 1 is a front sectional view of an embodiment of the present invention, FIG. 2 is a side view showing the state in which the annular tube and belt are engaged, and FIG. 3 is a side view of a bicycle to which the device of the embodiment is installed. 1... Frame, 2... Pedal shaft mounting rod, 4...
...Pedal shaft, 5...Pulley, 8...Belt, 9
...Tube, 10, 11...Tooth profile.

Claims (1)

[Scope of Claims] 1. A base end of a mounting rod is rotatably attached to a bicycle frame, the tip of the mounting rod is tilted forward and can be raised and lowered, and a pedal shaft is attached to the tip of the mounting rod, A bicycle transmission device 2 in which a pulley is fixed to the pedal shaft, an elastic body is attached to the groove of the pulley, and a belt is installed between the pulley and the rear wheel pulley. The bicycle transmission device 3 according to claim 1, in which the belt is a V-belt having a tooth profile on the back side.