JP2000006877A - Power unit for electric vehicles - Google Patents

Abstract

(57) [Problem] To provide a transmission in a power unit while reducing the size, weight and cost of the power unit. An input shaft (21a) of a transmission (21) is connected to a resultant shaft (3) rotating by a combined force of human power and the power of a motor (7). The resultant shaft 3 and the output shaft 21b of the transmission 21 are connected via a planetary gear mechanism 22 to a cylindrical rotary shaft 29 for driving rear wheels.
The planetary gear mechanism 22 is formed such that rotations of the resultant shaft 3 and the transmission output shaft 21b are combined and transmitted to the cylindrical rotary shaft 29.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power unit for an electric vehicle mounted on an electric bicycle or an electric wheelchair.

[0002]

2. Description of the Related Art Conventionally, as a power unit mounted on an electric bicycle, for example, there is a power unit mounted on a hanger portion of a body frame. In this type of power unit, a motor is arranged near a pedal crankshaft, and the power of this motor and the pedaling force (manpower) when the pedal is depressed are synthesized by a resultant shaft provided coaxially with the pedal crankshaft. Then, a structure is employed in which the rear wheel is driven by this resultant force. An electric bicycle equipped with this power unit has a chain sprocket attached to the resultant shaft, and power is transmitted to the rear wheels via a chain wound around the chain sprocket and a transmission mounted on a rear wheel hub. It is composed.

[0003]

SUMMARY OF THE INVENTION The inventors have considered providing a transmission for shifting the rotation of a rotating member for driving the rear wheels (the chain sprocket) in the power unit configured as described above. However, simply incorporating a transmission in the power unit increases the size of the power unit. I can't respond. It should be noted that adding a transmission does not significantly increase the manufacturing cost.

The present invention has been made to solve such a problem, and an object of the present invention is to make a power unit incorporate a transmission while reducing the size, weight, and price of the power unit.

[0005]

A power unit for an electric vehicle according to the present invention is configured such that an input shaft of a transmission is connected to a resultant shaft that is rotated by a combined force of human power and motor power, and the resultant shaft and the transmission are connected. Is connected via a planetary gear mechanism, and the planetary gear mechanism is configured such that rotations of the resultant shaft and the output shaft of the transmission are combined and transmitted to a wheel driving rotary member. .

According to the present invention, the resultant force of the human power and the power of the motor is distributed to the resultant shaft and the transmission, combined by the planetary gear mechanism, and transmitted to the wheel driving rotary member. Therefore,
Since a part of the resultant force is transmitted to the transmission, the load applied to the transmission is reduced as compared to a case where all of the resultant force is transmitted to the transmission, and the transmission has relatively high strength. However, a small one can be used.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a power unit for an electric vehicle according to the present invention will be described below in detail with reference to FIG.

FIG. 1 is a simplified diagram showing a power unit for an electric vehicle according to the present invention. In FIG. 1, the reference numeral 1 indicates a power unit according to this embodiment. The power unit 1 is mounted on a hanger portion of an electric bicycle and drives rear wheels.
Are penetrated through a cylindrical resultant shaft 3, these two shafts are connected to each other via an elastic body 4 such as a compression coil spring or a torsion spring, and the resultant shaft 3 is connected to the resultant shaft 3 via a speed reducer 5 and a one-way clutch 6. The motor 7 is connected.

The one-way clutch 6 has a structure in which power is transmitted only from the motor 7 toward the resultant shaft 3. A one-way clutch 8 is also provided between the pedal crankshaft 2 and the elastic body 4 so that the power is transmitted from the pedal crankshaft 2 to the resultant shaft 3. A motor drive system for transmitting power from the motor 7 to the resultant shaft 3 includes a rotation direction of the pedal crankshaft 2 when the pedal crankshaft 2 is rotated so that the vehicle body moves forward,
The rotation direction of the resultant shaft 3 is configured to match.

The pedal crankshaft 2 is rotatably supported by a power unit housing (not shown), and has cranks 10 having pedals 9 at both ends.
In this embodiment, a series of human power transmission paths from the pedal crankshaft 2 to the rear wheels constitute a human power drive system. That is, the power unit 1 connects the pedal crankshaft 2 and the resultant shaft 3 of the human-powered driving system to each other via the elastic body 4 and connects the motor driving system to the resultant-powered shaft 3 to thereby provide a human-powered (pedal 9) pedal. Is combined with the power of the motor 7, and the resultant force causes the resultant shaft 3 to rotate.

The power of the motor 7 is controlled according to human power. In this embodiment, human power is detected by a human power detecting means 11 described later, and a current corresponding to the human power is supplied to the motor 7.
It is configured to supply to. Here, human power detecting means 1
1 will be described.

The human power detecting means 11 comprises a pair of planetary gear mechanisms 12 and 13 and a rotation detecting sensor 14.
The pair of planetary gear mechanisms 12 and 13 include a sun gear 12
a and 13a, the number and number of the planetary gears 12b and 13b, and the number of teeth of the outer peripheral gears 12c and 13c are equal to each other. They are arranged so that their axial directions are parallel and are spaced apart in a direction perpendicular to the axial direction. The outer peripheral gears 12 c and 13 c are gear-coupled to the pedal crankshaft 2 and the resultant shaft 3. The components of these planetary gear mechanisms 12 and 13, that is, gears, support shafts,
The planetary gear support carriers 12d and 13d are formed of a lightweight and inexpensive material such as plastic.

A rotation angle detection sensor 14 is connected to the rotation shaft of the planetary gear support carrier 12d of the first planetary gear mechanism 12, and the planetary gear support carrier 13d of the second planetary gear mechanism 13 is connected to the power unit housing. It is fixed so that it cannot be connected to and rotated. Also, the sun gear 12 of the first and second planetary gear mechanisms 12 and 13
a and 13a are connected to each other by a connecting shaft so that their rotations coincide with each other.

Among the gears for connecting the outer peripheral gears 12c and 13c to the pedal crankshaft 2 and the resultant shaft 3, gears 16 and 18 provided on the outer peripheral gears 12c and 13c are formed so as to have the same number of teeth. The gears 15 and 17 meshing with the gears 12c and 13c are also formed to have the same number of teeth. That is, the number of teeth is set so that the rotations of the outer peripheral gears 12c and 13c match when the rotations of the pedal crankshaft 2 and the resultant shaft 3 match. The one-way clutch 8 is interposed between the pedal crankshaft 2 and the gear 15.

The rotation angle detection sensor 14 is constituted by a potentiometer for detecting the rotation of the carrier 12d for supporting the planetary gears, and is supported by a power unit housing and connected to a controller (not shown). Further, the rotation angle detection sensor 14 includes a return spring 14a formed of a torsion coil spring. The return spring 14a is elastically mounted between the rotation shaft of the rotation angle detection sensor 14 and the body so as to urge the carrier 12d to rotate in one direction.

The controller controls the power of the motor 7 in accordance with human power.
The magnitude of the human power is obtained from the rotation angle of the planetary gear support carrier 12d detected by the motor 4 and the current corresponding to the magnitude of the human power is output to the motor 6.

Next, the operation of the human power detecting means 11 will be described. The rotation of the outer peripheral gears 12c and 13c of the first and second planetary gear mechanisms 12 and 13 coincide when the rotations of the pedal crankshaft 2 and the resultant shaft 3 coincide. At this time, the planetary gear support carrier 12d of the first planetary gear mechanism 12 is in a stopped state, and the rotation angle detection sensor 14 does not detect rotation. At this time, the power supply to the motor 7 is cut off.

If the pedal crankshaft 2 acts upon the pedal crankshaft 2 to deform the elastic body 4 and generate a phase difference between the two shafts even when traveling uphill, accelerating, or traveling at a constant speed, the two planetary gear mechanisms 12 , 13 are released, the phase of the outer gear 12c of the first planetary gear mechanism 12 advances from the other outer gear 13c, and the planetary gear 12b revolves by that much, and the planetary gear support carrier 12d rotates. The rotation of the carrier 12d is detected by the rotation angle detection sensor 14, and the controller supplies the motor 6 with a current proportional to the magnitude of the human power. As a result, the power of the motor 7 increases by an amount corresponding to the increase in the human power, and the power of the motor 7 is applied to the resultant shaft 3.

The resultant shaft 3 is connected at one end to an input shaft 21a of the transmission indicated by reference numeral 21 and is connected at the other end to a planetary gear mechanism 22, which will be described later. Gears 23 and 24 connecting the resultant shaft 3 and the input shaft 21a are
In this embodiment, the teeth are formed so as to have the same number.

The planetary gear mechanism 22 has an outer peripheral gear 25 connected to the resultant shaft 3, a sun gear 26 gear-coupled to an output shaft 21 b of the transmission 21, and interposed between these two gears 25, 26. It comprises a planetary gear 27 and a carrier 28 that supports the planetary gear 27 so that it can rotate and revolve. The carrier 28 has a cylindrical rotating shaft 29 that constitutes a rotating member for driving wheels according to the present invention. A chain sprocket 30 is attached to one end of the cylindrical rotary shaft 29.
And a chain 31 for transmitting power from the power unit 1 to a rear wheel (not shown) is wound around the chain sprocket 30. Gears 32, 33 connecting the sun gear 26 and the output shaft 21b of the transmission 21.
Are formed such that the number of teeth is the same in this embodiment.

Power unit 1 constructed as described above
The pedal crankshaft 2
Rotates, and human power is transmitted to the resultant shaft 3 via the elastic body 4. On the other hand, the power of the motor 7 controlled according to human power is transmitted to the resultant shaft 3 from the motor drive system. For this reason,
The resultant shaft 3 is rotated by the resultant force of the human power and the power of the motor 7.

The rotation of the resultant shaft 3 is transmitted to the transmission 21 via gears 23 and 24, and the planetary gear mechanism 22
To the outer peripheral gear 25. At the same time, the transmission 2
The rotation of the first output shaft 21b is transmitted to the sun gear 26 of the planetary gear mechanism 22 via the gears 32 and 33. Then, the rotation of the outer peripheral gear 25 and the rotation of the sun gear 26 are combined, and the carrier 28 rotates together with the cylindrical rotary shaft 29 and the chain sprocket 30. That is, the rotation of the resultant shaft 3 and the rotation of the output shaft 21 b of the transmission 21 are combined and transmitted to the cylindrical rotation shaft 29 of the carrier 28, and this rotation is transmitted from the chain sprocket 30 to the rear wheel via the chain 31. Is transmitted.

For example, in the power unit 1 shown in this embodiment, the number of teeth of the outer gear 25 is set to 60, the number of teeth of the sun gear 26 is set to 30, and the number of teeth of the planetary gear 27 is set to 15. By setting the transmission ratio of the transmission 21 to 1: 4, that is, setting the rotation of the output shaft 21b to be four times as high as the rotation of the input shaft 21a,
9 and the number of rotations of the chain sprocket 30 are
Twice the number of revolutions.

When the power unit 1 is formed under the above conditions, the load torque viewed from the chain 31 is distributed to the resultant shaft 3 and the transmission 21 by the planetary gear mechanism 22. When the number of teeth of each gear is set as described above, the planetary gear mechanism 22 rotates the outer peripheral gear 25 once with the sun gear 26 fixed so as not to rotate.
When the sun gear 26 is rotated one turn while the outer peripheral gear 25 is fixed, the carrier 28 is rotated by １ ／ rotation. Therefore, the rate at which the load torque is distributed is:
As shown in FIG. 1, when the total load torque is T, the load torque distributed to the outer peripheral gear 25 is (2/3) T,
The load torque distributed to the sun gear 26 is (1/3) T.

The sun gear 26 and the output shaft 21b of the transmission 21
The gears 32 and 33 connecting the gears do not shift with the same number of teeth, so that a load torque of (１ ／) T also acts on the output shaft 21b. When the transmission 21 is formed so as to increase the speed at a speed ratio of four times as described above, four times the load torque acts on the input shaft 21a of the transmission 21 when viewed from the output side. That is, the load torque acting on the input shaft 21a is (4/3) T. Since the gears 23 and 24 connecting the input shaft 21a and the resultant shaft 3 also do not shift with the same number of teeth, a load torque of (4/3) T acts on the resultant shaft 3 from the input shaft 21a side.

As a result, the resultant shaft 3 has the planetary gear mechanism 22
The (2/3) T load torque transmitted from the transmission 21 and the (4/3) T load torque transmitted from the transmission 21 act, which is twice the load torque T acting on the chain sprocket 30. Load torque acts. That is, when the chain sprocket 30 is set to rotate at twice the number of rotations of the resultant shaft 3, a 2T load torque acts on the resultant shaft 3.

Since the total load torque T and the torque acting on the resultant shaft 3 when the resultant shaft 3 is rotated by the combined force of human power and the power of the motor 7 are balanced, the power unit 1 according to this embodiment is balanced. According to the above, when the transmission 21 does not shift (when input: output = 1: 1), the resultant force is 1
When 加 え is applied to the transmission and the gear ratio of the transmission 21 is quadrupled (input: output = 1: 4), 4/3 of the resultant force is applied.

On the other hand, if a structure in which a transmission is interposed between the resultant shaft 3 and the chain sprocket 30 without using the planetary gear mechanism 22 is employed, the resultant force is equal to the resultant force when no gear shifting is performed. A load is applied to the transmission, and the speed of the transmission is changed to change the rotation of the chain sprocket to two
When the transmission is doubled, a load twice as large as the resultant shaft is applied to the transmission. That is, as compared with the case where the above-mentioned structure without the planetary gear mechanism is employed, the transmission 21
The load applied during running becomes smaller.

Therefore, in the power unit 1 configured as described above, a part of the torque of the resultant shaft 3 (a part of the resultant force) that rotates during traveling is transmitted to the transmission 21, so that all of the resultant force is transmitted. Is transmitted to the transmission, the load applied to the transmission can be reduced. Therefore, a transmission having relatively low strength, that is, a transmission that is small, lightweight, and inexpensive can be used.

It should be noted that the number of teeth of each gear of the planetary gear mechanism 22 is not limited to the number of teeth described above, but can be changed as appropriate. Further, the gear ratio of the transmission 21 can also be appropriately changed similarly, and the transmission 21 may be a continuously variable transmission. Although the power unit mounted on the hanger portion of the electric bicycle has been described in this embodiment, the power unit according to the present invention may be provided on a hub of the rear wheel of the electric bicycle. When this configuration is adopted, the rotation shaft on the rear wheel side of the manual drive system is used as the input shaft, the resultant shaft connecting the motor in the hub, and the input shaft are arranged on the same axis, and these are elastic bodies. Connected to each other via. At the same time, the transmission and the planetary gear mechanism are connected to the resultant shaft, and the planetary gear mechanism is connected to a member that rotates with the rear wheel. Furthermore, in the above-described embodiment, an example in which the present invention is applied to a power unit for an electric bicycle has been described, but the present invention can also be applied to a power unit of another electric vehicle such as an electric wheelchair.

[0031]

As described above, according to the present invention, the resultant force of the human power and the power of the motor is distributed to the resultant shaft and the transmission, synthesized by the planetary gear mechanism, and transmitted to the rotating member for driving the wheel. . For this reason, since a part of the resultant force is transmitted to the transmission, the load applied to the transmission is reduced as compared with a case where all of the resultant force is transmitted to the transmission, and the relative transmission as the transmission is reduced. A material having a relatively small strength can be used. That is, a small, lightweight, and inexpensive transmission can be used.

Therefore, it is possible to provide a power unit for an electric vehicle that can be reduced in size, weight, and cost while incorporating a transmission.

[Brief description of the drawings]

FIG. 1 is a simplified configuration diagram showing a power unit for an electric vehicle according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Power unit, 2 ... Pedal crankshaft, 3 ... Combined shaft, 7 ... Motor, 21 ... Transmission, 21a ... Input shaft, 21
b: output shaft, 22: planetary gear mechanism, 25: outer peripheral gear, 2
6 ... Sun gear, 27 ... Planetary gear, 28 ... Carrier, 29
... cylindrical rotary shaft, 30 ... chain sprocket.

Claims (1)

[Claims] An input shaft of a transmission is connected to a resultant shaft that is rotated by a combined force of a human power and a power of a motor, and the resultant shaft and the output shaft of the transmission are connected to each other via a planetary gear mechanism for driving wheels. Connected to a rotating member, this planetary gear mechanism,
A power unit for an electric vehicle, wherein the rotation of the resultant shaft and the output shaft of the transmission are combined and transmitted to a wheel driving rotary member.