Planetary gear transmission systems or components – Input from independent power sources – Including electric motor input
Reexamination Certificate
2001-04-09
2004-08-03
Pang, Roger (Department: 3681)
Planetary gear transmission systems or components
Input from independent power sources
Including electric motor input
C475S231000
Reexamination Certificate
active
06770005
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a power transmission system, such as for an electric automobile using an electric motor as a drive power source or an electric automobile using a fuel engine (an ordinary engine making use of an explosion of fuel) and an electric motor both as a drive power source, and to an operation method for the same.
2. Description of the Related Art
There is disclosed in Japanese Patent Application Laid-Open Publication No. 9-226394 a drive system
2001
for electric automobiles shown in FIG.
22
.
The drive system
2001
for electric automobiles includes an electric motor
2003
, a reduction gear set
2005
, and a differential apparatus
2007
.
The electric motor
2003
is driven by a vehicle-mounted battery to produce drive power, which is decreased in speed by the reduction gear set
2005
within a range of the number of revolutions of a travelling wheel and increased in torque, and resultant drive power is distributed via the differential apparatus
2007
to wheels.
In the drive system
2001
, as shown in
FIG. 22
, the electric motor
2003
and the reduction gear set
2005
as well as this reduction gear set
2005
and the differential apparatus
2007
are connected directly with no clutch disposed on the way.
On the other hand,
FIG. 23
shows an example of a power transmission system for a four-wheel driven vehicle having an ordinary engine as a drive power source.
This power transmission system includes a transversely arranged engine
2101
, a transmission
2103
, a belt-driving transfer
2105
, a front differential
2107
(as a differential apparatus for distributing drive power from the engine
2101
to left and right front wheels), front axles
2109
and
2111
, left and right front wheels
2113
and
2115
, a rear-wheel end propeller shaft
2117
, a coupling
2118
, a rear differential
2119
, rear axles
2121
and
2123
, left and right rear wheels
2125
and
2127
.
The drive power from the engine
2101
is transmitted from an output gear
2129
of the transmission
2103
via a ring gear
2131
to a differential case
2133
, to be distributed from the front differential
2107
via the front axles
2109
and
2111
to the left and right front wheels
2113
and
2115
, or to be transmitted via the differential case
2133
m
the transfer
2105
, and the propeller shaft
2117
to the rear wheel end.
In this arrangement, the coupling
2118
disposed in a power transmission subsystem at the rear wheel end is employed for control of torque transmission to the rear wheels
2125
and
2127
.
For example, when the coupling
2118
is connected, drive power from the engine
2101
is distributed from the rear differential
2119
via the rear axles
2121
and
2123
to the left and right rear wheels
2125
and
2127
, rendering the vehicle four-wheel driven.
When the coupling
2118
is disconnected, the rear differential
2119
and subsequent elements of the rear wheel end subsystem are cut off, rendering the vehicle two-wheel driven.
In the conventional electric automobiles, an electric motor is connected directly to wheels, and even in a case of interruption of power supply to the electric motor, such as when travelling by inertia, the electric motor is forced to rotate together with wheel rotation, with burdens on the electric motor.
For example, if the electric motor is a brush type like a DC motor, brushes receive a great influence on the durability, resulting in increased maintenance costs, such as by increase in number of services for brush replacement.
Further, when caused to rotate by wheels, the electric motor serves as a generator, producing electromotive forces (emf). As the rotation is increased in speed by the reduction gear set, there is produced a greater emf, resulting in burdens, such as on a battery or alternator (not shown) or on circuit elements such as a regulator constituted as an integrated circuit, causing a reduced durability.
SUMMARY OF THE INVENTION
The present invention is made with such points in view. It therefore is an object of the present invention to provide a power transmission system with a compact size, light weight, and well adaptation for vehicle-mounting, preventing an electric motor from being caused to rotate by rotation of wheels, and an operation method for the same.
To achieve the object, according to a 1
st
aspect of the invention, there is provided a power transmission system comprising a speed reducing mechanism for speed-reducing drive power of an electric motor, a differential apparatus for distributing speed-reduced drive power to axle ends, and a clutch configured for interruptive transmission of drive power between the speed-reducing mechanism and the differential apparatus.
Accordingly, in case power supply to the electric motor is interrupted, such as when travelling by inertia, connection of the clutch is canceled, thereby disconnecting the electric motor from wheels.
Thus, the electric motor is set free from being rotated by rotation of the wheels, and kept from generating emf that otherwise might have imposed loads on a battery, alternator, or controller's circuit elements, allowing these to have maintained performances, with a greatly improved durability.
Because mechanical rotation is prevented, burdens on and temperature rise of magnetic field or rotor side windings of the electric motor are reduced, as well as burdens on bearings, with a greatly improved durability.
In case of a brush type electric motor, such as a DC motor, the brushes have greatly improved durability, with a commensurate reduction in frequency of their replacement, with reduction of maintenance cost.
According to a 2
nd
aspect second aspect of the invention, a power transmission system according to the 1
st
aspect further comprises a main drive power source, and the electric motor used as an auxiliary drive power source relative to the main drive power source.
Accordingly, in a four-wheel driven vehicle using both a main drive power source (engine) and an electric motor, when the electric motor is rotated with the clutch in connection, the vehicle enters a four-wheel driven state with improvements such as in abilities of start, acceleration, and riding performances such as on differences in level or cavities in road.
In a two-wheel driven travel at the engine side, or upon occurrence of a rollback by front wheels idling such as on an inclined road low of surface frictional resistance in a four-wheel driven travel, the clutch is disconnected to interrupt connection between the electric motor and wheels, whereby the electric motor is kept from being rotated by rotation of wheels, allowing for like effects to the 1
st
aspect to be achieved.
According to a 3
rd
aspect of the invention, in a power transmission system according to the 1
st
or 2
nd
aspect, the speed-reducing mechanism comprises a plurality of reduction gear sets including a first reduction gear set for inputting thereto drive power from the electric motor, the first reduction gear set comprising a planetary gear, whereby like effects to the 1
st
or 2
nd
aspect are achieved.
In addition, by use of the planetary gear in the first reduction gear set, the speed-reducing mechanism which is constituted with a plurality of stages can be made small in size.
In particular, in the case the electric motor is used as an auxiliary drive power source relative to the main drive power source, the input from the electric motor to the speed-reducing mechanism is has a smaller value than a case the electric motor is used as a main drive power source, and the arrangement in which the first reduction gear set is constituted with the planetary gear allows an efficient reduction in size of the speed-reducing mechanism.
According to a 4
th
aspect of the invention, in a power transmission system according to the 3
rd
aspect, the speed-reducing mechanism is provided with an oil pump for supplying lubricant to the planetary gear, whereby like effects to the 3
rd
aspect can be achieved, in addition to effective lubricatio
Aikawa Masashi
Yamazaki Nobushi
Morrison & Foerster / LLP
Pang Roger
Tochigi Fuji Sangyo Kabushiki Kaisha
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