Electricity: motive power systems – With particular motor-driven load device – Power- or motion-transmitting mechanism
Reexamination Certificate
2001-08-09
2003-05-20
Ro, Bentsu (Department: 2837)
Electricity: motive power systems
With particular motor-driven load device
Power- or motion-transmitting mechanism
C180S065700, C477S008000
Reexamination Certificate
active
06566826
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a power transmitting apparatus for a hybrid vehicle and a method of controlling such a power transmitting apparatus.
2. Description of the Related Art
There is known a power transmitting apparatus for a hybrid vehicle which has two power distributors and two motors that can operate in both propulsive and regenerative modes. For example, reference should be made to “Basic configuration of a parallel differential structured electric transmission system for hybrid electric vehicles” and “Characteristic evaluation of a parallel differential structured electric transmission system for hybrid electric vehicles”, Society of Automotive Engineers of Japan, Inc. Convention Preprint No. 2-00, May 2000.
A conceptual arrangement of the known power transmitting apparatus is shown in
FIG. 6
of the accompanying drawings.
In the power transmitting apparatus, the rotational drive power from an output shaft
100
a
of an engine
100
is distributed and transmitted to input shafts
101
a,
102
a
of respective two power distributors
101
,
102
through gears, not shown. The power distributors
101
,
102
comprise differential gear mechanisms or planetary gear mechanisms, and have two output shafts
101
b,
101
c
and two output shafts
102
b,
102
c,
respectively. The power distributors
101
,
102
operate to generate a torque at a constant speed reduction ratio on their two output shafts regardless of the difference between the rotational speeds of the output shafts.
The output shafts
101
b,
102
b
of the power distributors
101
,
102
are connected to a common power output shaft
105
by respective rotation transmitting mechanisms
103
,
104
which have different speed reduction ratios &agr;, &bgr; (&agr;, &bgr;). The other output shafts
101
c,
102
c
of the power distributors
101
,
102
are connected to respective rotatable shafts
106
a,
107
a
of motors
106
,
107
. The common power output shaft
105
is connected to the axle of drive wheels of a vehicle (hybrid vehicle), not shown. More precisely, the speed reduction ratios &agr;, &bgr; represent speed reduction ratios including those of the power distributors
101
,
102
. For illustrative purposes, however, the speed reduction ratios of the power distributors
101
,
102
are herein assumed to be “1”.
When the engine
100
is operated and the motors
106
,
107
are controlled to operate in propulsive and regenerative modes, respectively, to equalize the electric power consumed by the motor
106
with the electric power generated by the motor
107
, part of the mechanical energy produced by the output shaft
100
a
of the engine
100
is converted into electric energy by the motor
107
, and the electric energy is then converted back into mechanical energy by the motor
106
. The mechanical energy produced by the motor
106
is transmitted to the power output shaft
105
. The remainder of the mechanical energy from the engine
100
is mechanically transmitted to the power output shaft
105
without going through the motors
106
,
107
.
Since equilibrium is maintained between the energy consumed by the motor
106
and the energy generated by the motor
107
(it is assumed that energy losses caused by the motors
106
,
107
are ignored), a torque Te produced by the output shaft
100
a,
i.e., a torque as a load on the engine
100
, and a torque Tv transmitted to the power output shaft
105
are related to each other as indicated by the following equation (1):
Tv=
(&ohgr;
e/&ohgr;v
)·
Te
(1)
where &ohgr;e represents the rotational speed of the output shaft
100
a
and &ohgr;v the rotational speed of the power output shaft
105
. Therefore, &ohgr;e/&ohgr;v represents a speed reduction ratio for transmitting the rotation from the output shaft
100
a
to the power output shaft
105
.
The speed reduction ratio &ohgr;e/&ohgr;v between the output shaft
100
a
and the power output shaft
105
can be changed to any speed reduction ratio between the speed reduction ratio &agr; of the rotation transmitting mechanism
103
and the speed reduction ratio &bgr; of the rotation transmitting mechanism
104
by controlling the torques generated at the motors
106
,
107
.
Consequently, when the vehicle is propelled by the engine
100
as a propulsion source, the speed reduction ratio &ohgr;e/&ohgr;v between the output shaft
100
a
and the power output shaft
105
, i.e., a transmission ratio, can continuously be changed by controlling the torques of the motors
106
,
107
while equalizing the electric power consumed by the motor
106
and the electric power generated by the motor
107
with each other. The power transmitting apparatus thus serves as an electric continuously variable transmission system for transmitting the output of the engine
1
to the power output shaft
105
to propel the vehicle, without the need for a mechanical transmission such as a pulley and belt type CVT or the like.
Another known electric continuously variable transmission system comprises a power transmitting apparatus having one power distributor and two motors. This electric continuously variable transmission system requires the motors to generate a greater torque than the power transmitting apparatus shown in
FIG. 6
in its operation for continuously variable transmission. Consequently, the electric continuously variable transmission system is disadvantageous in that it needs large-capacity motors and their drive circuits and tends to cause an energy loss because more energy is transmitted from engine via the motors to the axle.
With the power transmitting apparatus shown in
FIG. 6
, if the torques of the motors
106
,
107
are represented respectively by T
1
, T
2
, then in the state of equilibrium, the torque Te of the output shaft
100
a,
i.e., the torque as the load on the engine
100
, and the torque Tv of the power output shaft
105
are related to each other according to the following equations (2), (3) (it is assumed that each of the power distributors
101
,
102
comprises a differential gear mechanism):
Te/
2=T
1
+T
2
(2)
Tv=&agr;·
T
1
+&bgr;T
2
(3)
By controlling the torques T
1
, T
2
of the motors
106
,
106
, it is possible to impart a desired load torque Te to the output shaft
100
a
of the engine
100
and to generate a desired torque Tv on the power output shaft
105
. The torques T
1
, T
2
of the motors
106
,
107
are controlled to cause the load torque Te on the output shaft
100
a
to become “0”, and a torque is generated on the power output shaft
105
to propel the vehicle, thereby holding the engine
100
at rest and propelling the vehicle with the drive power from the motor (EV mode=electric vehicle mode). In order to cause the load torque Te on the output shaft
100
a
to become “0”, the motors
106
,
107
are operated in the propulsive mode and the regenerative mode, respectively, and part of the propulsive torque of the motor
106
, i.e., part of the torque transmitted from the motor
106
to the engine
100
, and part of the regenerative torque of the motor
107
, i.e., part of the torque transmitted from the motor
107
to the engine
100
, cancel out each other.
The hybrid vehicle which incorporates the power transmitting apparatus shown in
FIG. 6
can travel at different transmission ratios with the engine
100
used as the propulsion source, or can travel in the EV mode with the motor used as the propulsion source. If necessary, it is possible to add the assistive propulsive power from the motor to the propulsive power from the engine
100
by, for example, making the electric power consumed by the motor
106
which produces the propulsive power greater than the electric power generated by the motor
107
which operates in the regenerative mode, or to charge the power supply for the motor by, for example, making the electric power generated by the motor
107
greater than the electric power consumed by the motor
106
.
Generally, a motor that needs to pr
Imai Nobuyuki
Tamagawa Yutaka
Armstrong Westerman & Hattori, LLP
Honda Giken Kogyo Kabushiki Kaisha
Ro Bentsu
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