JPH11208565A - Electric motor assist unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compact electric motor assist unit for a bicycle, capable of highly accurate electric motor assist control by the stable detection of a pedaling power of man power without being influenced by the setting position, and of easily installing it in an ordinary bicycle by way of a post-setup. SOLUTION: In this electric motor assist unit for a bicycle, which is constituted so as to install a driving sprocket 13 of this assist unit 4 in a roller chain 7 to be tensely installed in space between a front sprocket 8 and a rear-wheel sprocket 28 being driven by a pedal 5 after being engaged with each other, a tension detecting tension pulley 14 is installed in this assist unit 4 after making it opposite to the driving sprocket 13 and the roller chain 7 is suspensibly rotated in space between the driving sprocket 13 and the tension pulley 14, while the assist unit 4 is attached to a chain stay 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric assist unit to which an auxiliary power unit such as an electric motor can be attached as a retrofit type to an ordinary bicycle.

[0002]

2. Description of the Related Art Conventionally, as an electric assist bicycle equipped with an auxiliary power device such as an electric motor, for example, Japanese Patent Application Laid-Open No.
There is one disclosed in Japanese Patent Publication No. 0878. This one is
A type is used in which the power generated on the crankshaft by pedaling manually and the power transmitted from the electric motor are output coaxially from the crankshaft. For that purpose, a specially designed unit around the crankshaft was used, and the body frame was also designed to fit. In such a crank coaxial output type, it is necessary to adapt the frame to the electric unit as a dedicated frame, so that the cost is increased without using a normal frame manufacturing process.
In addition, the structure around the crankshaft is complicated and large in order to make the output of the human power and the output of the electric motor coaxial, and the reduction ratio of the electric motor having a large rotational speed compared to the rotational speed of the crankshaft is not only increased. And the matching between them was troublesome.

[0003] For this reason, as disclosed in Japanese Patent Application Laid-Open No. 7-143603 shown in FIG. 8 and in Japanese Patent Application Laid-Open No. 8-207787 shown in FIG. There has been proposed an electric assist unit having a configuration in which auxiliary power is added by a separate shaft. 8, the rear wheel chainwheel 11 assisted by an auxiliary power from an electric motor (not shown) will be described.
0 simultaneously receives the rotational driving force from the chain 112 to which the driving force from the pedaling force by the human power is transmitted. Normally, in this type of electric assist unit, the state of the pedaling force by human power is detected to control the output of the auxiliary power, that is, the power supply, which is the electric assist unit. As means for detecting the change, the swing around the shaft portion 132a of the idler pulley 134 pulled by the spring 136 attached to the attachment portion 135 as shown in FIG. Proximity switch 1
The auxiliary power from the electric assist unit is turned on and off according to a signal pattern generated by turning on and off the control unit 15.

In the prior art shown in FIG. 9, an electric motor 214, which is an auxiliary power, is fixed to a motor stay 220 fixed to a seat tube 211, and a support shaft of a lever 212 is made coaxial with the motor 214. The longitudinal center line O is arranged parallel to the chain 209.
The output shaft 14 has a drive pinion 221 as a reduction gear.
Is fixed to drive the large-diameter auxiliary gear 222, and the auxiliary sprocket 213 integral with the gear 222 meshes with the chain 209. Accordingly, if the pedaling force by human power increases and the tension of the chain 209 increases, the pressure of the load cell 215 increases due to the swing of the lever 212, and the motor 214 operates.

[0005]

FIG. 8 and FIG.
Can be mounted on a normal bicycle separately from the human-powered crankshaft, and an electric power assist unit, which is an auxiliary power unit, can be manufactured at low cost. Although it was possible to provide a power-assisted bicycle that could be provided, the tension of the chain installed for detecting the pedaling force by human power as described above, that is, the mounting position of the tension detecting device required extremely high precision. In the conventional example of FIG. 8, an idler pulley 134 as a chain tension detecting device is mounted on the rear frame 113b, and in the conventional example of FIG.
Fixed to 1.

In the conventional examples disclosed in FIGS. 8 and 9 described above, the respective tension pulleys and the like are mounted on a rear frame or a seat tube in which the mounting position is easily changed with respect to the chain. FIG. 10 shows a state in which the chain is stretched at three points of a driving sprocket, a rear wheel sprocket, and a tension pulley which is a tension detecting device for a chain installed between them. FIG.
0 (A) and (B) show the case where the upper and lower mounting positions of the tension pulley are L1 and L2 (L1> L2), respectively, and FIGS. 10 (C) and (D) show the front and rear mounting positions of the tension pulley. Are assumed to be L1 and L2 (L1> L2), respectively, and the tension Ta applied to the chain in FIG.
Although the component force Tc of the (reaction force Tb) is obtained, in FIG. 10B, even if the same pedal force Ta ′ (reaction force Tb ′) by human power is applied, Tc ′ applied to the tension pulley increases more than Tc. Would. This indicates that when the mounting error of the tension pulley is large in the vertical direction, the variation in the sensor output with respect to the same pedaling force increases.

If the state shown in FIG. 10C is the normal position of the front and rear sprockets and the tension pulley, when the tension pulley approaches the front sprocket from this state, the tension applied to the chain is Ta = Ta '. Even so, Tc 'applied to the tension pulley becomes larger than Tc. In this case, when the position of the tension pulley changes because the distance between the tension pulley and the front sprocket is short, the angle of Ta with respect to the tension pulley easily changes. (Conversely, since the distance from the rear wheel sprocket is large, the angle of Tb with respect to the tension pulley is unlikely to change. As described later, the arrangement of this point is a constituent requirement in the present invention.) In the conventional electric assist unit disclosed in FIGS. 8 and 9 described above, it is easy to cause a large error in the human-powered treading force detected due to the displacement of the mounting position of the tension pulley, and high-precision control is impossible. In particular, FIG.
In the conventional example, the movable trajectory of the detection pulley on the chain and the biasing direction of the spring do not match in the entire movable trajectory of the pulley, and the linearity of the detection signal is impaired, so that high-precision control is impossible. .

Accordingly, the present invention solves the above-mentioned problems of the conventional electric assist unit, and enables high-precision electric assist control by stable detection of a manual pedaling force without being affected by a mounting position. An object of the present invention is to provide a compact electric assist unit that can be easily attached to a normal bicycle by retrofitting.

[0009]

SUMMARY OF THE INVENTION Accordingly, the present invention provides a method in which a drive sprocket of an assist unit is fitted to a roller chain stretched between a front sprocket driven by a pedal and a rear wheel sprocket. In the bicycle electric assist unit configured, the assist unit is provided with a tension pulley for detecting the tension of the roller chain facing the drive sprocket, and the roller chain is suspended between the drive sprocket and the tension pulley. The assist unit is attached to a chain stay. Further, the present invention is characterized in that the tension pulley is arranged on a rear wheel side with respect to a driving sprocket. Further, the present invention is characterized in that the assist unit is mounted between a crankshaft and a rear wheel. Further, the present invention is characterized in that the driving sprocket in the assist unit is mounted on the pulling side of the roller chain. Further, the present invention is characterized in that the tension pulley is biased by a torsion bar, and these are used as means for solving the problem.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 6 show a first embodiment of an electric assist unit according to the present invention. FIG. 1A is an overall side view of a bicycle equipped with the electric assist unit according to the present invention, and FIG. 2 is an enlarged view of a main part, FIG. 2 is a side view of the assist unit, FIG. 3 is a partial cross-sectional plan view showing a state where the assist unit is attached to a chain stay, and FIG.
FIG. 5 is a side sectional view of the tension detector, and FIG.
FIG. 5 is a view of the tension detection unit as viewed from the rear. In the present embodiment, as shown in FIG. 1A, the electric assist unit of the present invention is configured as follows. The vehicle body 1 has a normal bicycle shape, and is driven by a crank 6 associated with the depression of a pedal 5 at a lower hanger portion (38, see FIG. 3) of a vertical pipe 9 having a saddle inserted at an upper end thereof. A front sprocket 8 is pivotally supported, and a rear wheel 3 is pivotally supported at the intersection of a back fork 10 and a chain stay 11 extending rearward from above and below the vertical pipe 9. A roller chain 7 is stretched between a front sprocket 8 and a rear wheel sprocket 28 installed on a hub such as an internal transmission in the rear wheel 3. A battery, which is a power source of the electric assist unit, and the controller 2 are mounted on a portion above the front wheel where a basket or the like is usually arranged.

As shown in FIG. 1 (B), in this embodiment, an assist unit 4, which will be described in detail later, is provided between a crankshaft and a rear wheel 3 on a pulling side of a roller chain 7, that is, a front sprocket 8. The assist unit 4 is mounted on the chain stay 11 such that the drive sprocket 13 is positioned on the upper side of the drawing with respect to the chain stay 11 which is on the traction side during the rotational drive.
The assist unit 4 includes a driving electric motor 12
And a driving sprocket 13 driven by the electric motor 12, and a tension pulley 14 for detecting the tension of the roller chain 7 by a pulley arm 15 facing the driving sprocket 13.
While the roller chain 7 is suspended between the driving sprocket 13 and the tension pulley 14,
The tension pulley 14 is arranged on the rear wheel 3 side with respect to the driving sprocket 13 and the assist unit 4 is attached to the chain stay 11. Therefore, the combined force of the assist unit and the human power is input to the tension pulley 14 of the assist unit 4 as the tension.

FIG. 2 is a side view showing only the external appearance of the assist unit 4 of the present invention, and the cases 23, 24 and 25 are divided into three in the axial direction (the direction perpendicular to the plane of the drawing).
In FIG. 4, an electric motor 12 for auxiliary power is provided.
Is arranged at the bottom, and the driving sprocket 1 is
3 is located at the top. A tension pulley 14 for detecting the tension of the roller chain is pivotally supported by a pulley arm 15 on the same surface as the drive sprocket 13 so as to face the drive sprocket 13 and is positioned at the center of the swing of the pulley arm 15. The magnitude of the tension of the roller chain suspended between the driving sprocket 13 and the tension pulley 14, that is, the magnitude of the pedaling force due to human power is measured by detecting the torsional rotation angle of the torsion bar described later with the potentiometer 36. It is configured to be able to. Note that reference numeral 2
Reference numeral 9 denotes a rotation sensor for detecting the rotation speed of the driving sprocket 13, that is, the rotation speed of the roller chain or the crankshaft (39, see FIG. 3).

FIG. 3 is a partially sectional plan view showing a state in which the assist unit is attached to the chain stay. The tension pulley 14 is supported at one end of a pulley arm 15 by a pulley shaft 30, and the pulley arm 1
The torsion bar 31 is spline-fitted to the swing center of 5, and the other end of the torsion bar 31 is fixed to the wall surface of the case 24. The cylindrical portion of the pulley arm 15 is pivotally supported on the case 25 on the side where the drive sprocket 13 and the tension pulley 14 are disposed via an oilless bush 32. The swing angle of the tension pulley 14, that is, the rotation angle of the pulley arm 15, is detected as the torque of the torsion bar 31, and the first plate end of the sensor plate 33 constituting the amplification mechanism is formed via the projection 15a of the pulley arm 15. 33a, and the second plate end 33b at a position far from the axis of the plate shaft 34 by the swing of the sensor plate 33 around the plate shaft 34.
And is detected as the displacement of the shaft 37 of the potentiometer 36. The torque detected by the potentiometer 36 (the tension pulley 14
, A combined force of the human power and the electric motor is applied to the pedal, so that the torque here is converted into an electric signal, and the pedal is manually operated by an appropriate control unit (see reference numeral 2 in FIG. 1). Electric assist control according to the pedaling force is performed.

FIG. 4 is a longitudinal sectional view of the assist unit 4 as viewed from the rear of the bicycle. The electric motor 12 is controlled by an electric motor 12 in response to a control signal from a control unit that receives a sensor output from a potentiometer 36. 2 shows a power transmission path. A gear 16 is fixed to the motor shaft 12a, and its rotation is transmitted to the gear 17, but the rotation is transmitted to the one-way clutch 19 because the gear 17 is fixed to the flange body 18 and the bolt. The one-way clutch 19 transmits rotation from the gear 17 side to the shaft 20 when the electric motor 12 rotates forward. That is, on the contrary, the shaft 20
Therefore, the rotation cannot be transmitted to the gear 17. Therefore, even if the power of the electric motor 12 is lost during the control process,
By applying a driving force by depressing a pedal by human power, the roller chain is driven, and the driving shaft 22, the gear 21, and the shaft 20 are rotated accordingly. It is not transmitted, and the electric motor 12 is
Rotation from the side can be prevented.

FIG. 4 also shows a state in which the assist unit 4 is attached to the bicycle. A convex portion is provided at a portion (bottom portion) of the case 24 of the assist unit 4 that contacts the chain stay 11. A threaded hole is formed in the projection, and the bicycle chain stay 11 is mounted using the mounting plate 26.
The assist unit 4 is fixed on the upper side. Mounting bolt 27
Although not shown, two are arranged side by side also on the paper back side of FIG. 4, that is, in the front direction of the bicycle. Since the assist unit 4 is mounted on the chain stay 11, even if an error occurs in the mounting position, it is a difference only in the direction along the chain stay 11.

FIGS. 5 and 6 are a side sectional view of the tension detector (in the direction of the arrow in FIG. 5C) and a view from behind (in the direction of the arrow in FIG. 6C).
The torsion bar 31 is twisted by a torque generated in the torsion bar 31 due to the tension described above, and the torsion bar 31 is rotated by a predetermined angle. However, this angle is actually about several degrees, and a structure configured to mechanically amplify the angle is as follows. The role of the sensor plate 33 described in FIG. As shown in FIG. 6 (see also FIG. 3), the sensor plate 33 and the plate shaft 34 are integrally formed by welding or the like.
Is housed in a recess formed in the case 25 and is rotatably locked by a spring-shaped holding plate 35. Further, a chamfer is provided on the plate shaft 34, and the sensor plate 3 is
3 is configured to stand upright on the wall surface of the case 25.

On the other hand, the potentiometer shaft 37 is always urged in the direction in which the potentiometer shaft 37 protrudes. However, the pressing plate 35 causes the sensor plate 33 to rotate in the rotational direction (counterclockwise in FIG. 5 and 6A unless the external force is applied. As described above, the sensor plate 33 is in a state in which the second plate end 33b contacts the protrusion 15a of the pulley arm 15 and does not rotate any more. As shown in FIG. 6B, the projection 15 a of the pulley arm is connected to the second plate end 33 of the sensor plate 33.
When b is pushed up, it is taken out as an amplified displacement of the first plate end 33a at a position far from the axis of the plate shaft 34 due to the swing of the sensor plate 33 around the plate axis 34, and is converted into the movement amount of the potentiometer shaft 37. Is done. Since the projection 15a of the pulley arm 15 rotates only in the rotational direction about the torsion bar 31, when the projection 15a of the pulley arm 15 rotates, the potentiometer shaft 37 also moves. When tension is applied to the tension pulley 14, the pulley arm 15 rotates around the torsion bar 31 while twisting the torsion bar 31. That is, when a pedal force is applied to the pedal by human power and tension is applied to the roller chain, an output change of the potentiometer 36 is obtained.

FIG. 7 shows a second embodiment of the electric assist unit according to the present invention, and is an enlarged view of a main part of a bicycle to which the electric assist unit is mounted. The present embodiment is characterized in that the assist unit 4 is mounted on the feed side of the roller chain 7. The assist unit 4 assists the roller chain 7 between the crankshaft and the rear wheel 3, that is, assists the drive sprocket 13 so that the drive sprocket 13 is positioned below the chain stay 11 on the delivery side when the front sprocket 8 is driven to rotate. The unit 4 is mounted on a chain stay 11. The electric motor 12 according to the present embodiment is disposed above the assist unit 4 and is driven by the electric motor 12.
And a tension pulley 14 that is supported by a pulley arm 15 in opposition to the drive sprocket 13, is disposed below the assist unit 4. A roller chain 7 is suspended between the driving sprocket 13 and the tension pulley 14, and the tension pulley 1
Reference numeral 4 denotes an arrangement in which the assist unit 4 is attached to the chain stay 11 by being disposed on the rear wheel 3 side with respect to the drive sprocket 13. Therefore, in the present embodiment, the first
Unlike the embodiment, in contrast to the tension applied to the pulling side of the roller chain 7 in response to the pedaling force by the human power, the so-called slack generated on the delivery side of the roller chain 7 is detected, and the pedaling force of the pedal by the human power is detected. Is to be detected. Roller chain 7 by pedal force
Can be moved by the function of the one-way clutch 19 shown in FIG.

The embodiments of the present invention have been described above. However, within the scope of the present invention, the type of the assist unit, the shape of the torsion bar in the assist unit, the shape of the sensor plate which is the amplification mechanism, and the Model, type of motor such as an electric motor as an auxiliary power, its arrangement (for example, the electric motor and the drive sprocket may be arranged coaxially if space permits), the type of potentiometer, and the chain stay of the assist unit. The mounting form and the like can be appropriately selected.

[0020]

As described above in detail, according to the electric assist unit of the present invention, an assist unit having a simple structure including a human-powered torque detecting unit and an output unit of an electric motor is retrofitted to a normal bicycle. It is possible to reduce the strength and volume of the device itself, so that the power generated on the crankshaft by manual power and the power transmitted from the electric motor can be In order to output coaxially, the area around the crankshaft is specially designed, so that the structure is complicated and large, and there is no increase in cost. Further, in the related art, in order to output the power of the electric motor as the auxiliary power, the output shaft must be reduced to the rotation speed of the output shaft in relation to human power. Since the small drive sprocket shaft was used, the number of rotations of the output shaft by the drive sprocket became larger than the crankshaft output, and the reduction ratio could be reduced. As a result, parts such as gears required for deceleration can be reduced, and the configuration can be simplified, lightened, and space-saving can be realized. Furthermore, the adoption of a torsion bar in the torque detector achieves further simplification of the configuration, lighter weight, and space saving, and the trajectory of the tension pulley for signal detection is always biased by the torsion bar (torsion direction). ), The biasing force on the movable trajectory of the tension pulley is always constant,
High-accuracy assist control has become possible by stable torque measurement.

In particular, according to the present invention, since the assist unit including the tension detecting portion of the roller chain is mounted on the chain stay, the distance between the drive sprocket of the assist unit and the chain stay is constant. Therefore, when mounting, the chain angle of the front sprocket side with respect to the tension pulley for detection can always be kept constant, so that the magnitude of the component force acting on the tension pulley due to the roller chain tension does not change. In addition, the tension pulley is located on the rear wheel side with respect to the drive sprocket in the assist unit and at a large distance from the rear wheel axle, so if it is on the chain stay, the mounting position of the assist unit will vary slightly. Even if the rear wheel axle is adjusted at the rear end of the chain stay to adjust the normal chain tension, the detection accuracy of the chain tension will not be affected much. .

[Brief description of the drawings]

FIG. 1 shows a first embodiment of an electric assist unit of the present invention. FIG. 1 (A) is an overall side view of a bicycle equipped with the electric assist unit of the present invention, and FIG. It is an enlarged view of a part.

FIG. 2 shows a first embodiment of the electric assist unit of the present invention, and is a side view of the assist unit.

FIG. 3 is a partial cross-sectional plan view of the electric assist unit according to the first embodiment of the present invention, showing a state where the assist unit is attached to a chain stay.

4 shows a first embodiment of the electric assist unit of the present invention, and is a longitudinal sectional view of FIG.

FIG. 5 is a side cross-sectional view of a tension detector, showing the first embodiment of the electric assist unit of the present invention.

FIG. 6 is a view showing the first embodiment of the electric assist unit according to the present invention, and is a view of the tension detector as viewed from the rear.

FIG. 7 shows an electric assist unit according to a second embodiment of the present invention, and is an enlarged view of a main part of a bicycle to which the electric assist unit is mounted.

FIG. 8 is a main part side view showing a first conventional example of the electric assist unit.

FIG. 9 is a main part side view showing a second conventional example of the electric assist unit.

FIG. 10 is a diagram illustrating an error in detecting a tension of a chain.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Bicycle body 2 Battery and control unit 3 Rear wheel 4 Assist unit 5 Pedal 6 Crank 7 Roller chain 8 Front sprocket 9 Vertical pipe 10 Backhawk 11 Chainstay 12 Electric motor 12a Motor shaft 13 Drive sprocket 14 Tension pulley 15 Pulley arm 16, 17 Gear 18 Flange Body 19 One-way Clutch 20 Shaft 20a Gear 21 Gear 22 Drive Shaft 23-25 Case 26 Mounting Plate 27 Mounting Bolt 28 Rear Wheel Sprocket 29 Rotation Sensor 30 Pulley Shaft 31 Torsion Bar 32 Oilless Bush 33 Sensor Plate 33a First plate end 33b Second plate end 34 Plate shaft 35 Holding plate 36 Potentiometer 37 Potentiometer shaft 38 Hanger 39 Crankshaft

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor: Yuki Sato 3-1-1 Nakazuma, Ageo-shi, Saitama Bridgestone Cycle Co., Ltd.

Claims (5)

[Claims] 1. An electric assist unit for a bicycle, wherein a driving sprocket of an assist unit is meshed and mounted on a roller chain stretched between a front sprocket and a rear wheel sprocket driven by a pedal. The assist unit was provided with a tension pulley for detecting the tension of the roller chain facing the drive sprocket, the roller chain was suspended between the drive sprocket and the tension pulley, and the assist unit was attached to a chain stay. An electric assist unit characterized in that: 2. The electric assist unit according to claim 1, wherein the tension pulley is disposed on a rear wheel side with respect to a driving sprocket. 3. The assist unit is mounted between a crankshaft and a rear wheel.
The electric assist unit according to 1. 4. The electric assist unit according to claim 1, wherein a driving sprocket of the assist unit is mounted on a pulling side of a roller chain. 5. The tension pulley is urged by a torsion bar.
The electric assist unit according to any one of the above.