Planetary gear transmission systems or components – Electric or magnetic drive or control
Reexamination Certificate
2001-11-19
2003-04-01
Estremsky, Sherry (Department: 3681)
Planetary gear transmission systems or components
Electric or magnetic drive or control
C475S002000, C475S005000, C475S150000, C180S065230, C180S065700
Reexamination Certificate
active
06540636
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a power transmission mechanism for a front and rear-wheel drive vehicle in which one of pairs of front and rear drive. Wheels is driven by an engine whereas the other pair is driven by an electric motor.
2. Description of the Related Art
Known as a conventional power transmission mechanism of this type is a power transmission mechanism which is disclosed in, for example, JP-A-9-315164. This power transmission mechanism is applied to a hybrid vehicle in which front wheels are driven by an engine whereas rear wheels are driven by an electric motor. The power transmission mechanism comprises a viscous coupling provided between the electric motor for driving the rear wheels and the rear wheels, and two clutches for providing engagement and disengagement between the viscous coupling and the left and right rear wheels, respectively. In this power transmission mechanism, when driving the rear wheels, the power of the electric motor is transmitted to the left and right rear wheels via the viscous coupling and the left and right clutches. On the contrary, at other times than of driving the rear wheels, the two clutches disengage the viscous coupling from the left and right rear wheels, whereby the electric motor is prevented from constituting a rotational resistance while running, to improve the fuel economy. In addition, the viscous coupling and the electric motor are coupled together via a speed reduction mechanism which is constituted by two bevel gears which mesh with each other.
In a hybrid vehicle as described above, an electric motor is installed in addition to an engine, and therefore it is desirable to have a power transmission mechanism made as small as possible. In the above conventional power transmission mechanism, however, the speed reduction is implemented only in one stage by the two bevel gears except for the speed reduction implemented by the viscous coupling. Therefore, when trying to ensure a desired running performance, the motor cannot be made smaller but a larger motor has to be used. Thus, it becomes difficult to have a miniaturized power transmission mechanism. In other words, a miniaturized electric motor reduces the power that is to be transmitted to the rear wheels in accordance with the degree of miniaturization thereof, leading to the deterioration of the running performance. In order to compensate for the decrease in running performance, there is considered the increasing of the reduction ratio of the speed reduction mechanism. In such a case, however, the bevel gear on the downstream side or on the viscous coupling side becomes larger, and this causes an enlargement of the speed reduction mechanism in contradiction to the desire, making it difficult to miniaturize the power transmission mechanism.
SUMMARY OF THE INVENTION
The invention was made in view of the above situation, and an object thereof is to provide a power transmission mechanism for a front and rear-wheel drive vehicle which can realize the miniaturization of the power transmission mechanism while maintaining a desired running performance, whereby the fuel economy is improved.
With a view to attaining the object, according to a first aspect of the invention, there is provided a power transmission mechanism
1
for a front and rear-wheel drive vehicle
2
in which one of pairs of front and rear drive wheels (for example, front wheels
4
,
4
in an embodiment (hereinafter, the same in this first aspect) ) is driven by an engine
3
whereas the other pair (rear wheels
6
,
6
) is driven by an electric motor
5
for transmitting the power from the electric motor
5
to the other pair of drive wheels (rear wheels
6
,
6
), the power transmission mechanism comprising an output shaft
11
adapted to rotate together with the electric motor
5
, a rotatable middle shaft
12
which is parallel with the output shaft
11
, a drive shaft
13
which is parallel with the output shaft
11
and is adapted to rotate together with the other pair of drive wheels (rear wheels
6
,
6
), a middle shaft speed reduction mechanism (a first pair of reduction gears
14
b
) having an output shaft speed reduction member (a reduction gear
14
a
) provided on the output shaft
11
and a first middle shaft speed reduction member (a reduction gear
14
b
) provided on the middle shaft
12
and adapted to reduce the speed of the middle shaft
12
relative to the output shaft
11
through coupling of the output shaft speed reduction member (the reduction gear
14
a
) and the first middle shaft speed reduction member (the reduction gear
14
b
), a drive shaft speed reduction mechanism (a second pair of reduction gears
15
) having a second middle shaft speed reduction member (a reduction gear
15
a
) provided on the middle shaft
12
and a drive shaft speed reduction member (a reduction gear
15
b
) provided on the drive shaft
13
and adapted to reduce the speed of the drive shaft
13
relative to the middle shaft
12
through coupling of the second middle shaft speed reduction member (the reduction gear
15
a
) and the drive shaft speed reduction member (the reduction gear
15
b
), and a differential (a rear differential
20
) disposed closer to the electric motor
5
in an axial direction of the drive shaft
13
than the drive shaft speed reduction mechanism (the second pairs of reduction gears
15
) for coupling the drive shaft speed reduction member (the reduction gear
15
b
) and the drive shaft
13
,
13
.
According to the power transmission mechanism for a front and rear-wheel drive vehicle, the power of the electric motor is reduced in speed in one stage by the middle shaft speed reduction mechanism between the output shaft and the middle shaft and is then reduced in another stage by the drive shaft speed reduction mechanism between the middle shaft and the drive shaft, whereby the power is transmitted to the drive shaft and the other pair of drive wheels which are made integral with the drive shaft via the differential
20
after it has been reduced in speed in two stages. Thus, since the power of the electric motor is transmitted to the other pair of drive wheels in a state in which the power is reduced in speed in two stages by the two speed reduction mechanisms, a larger reduction ratio can be obtained without enlarging the speed reduction mechanism when compared to the conventional power transmission mechanism in which a set of gears is used to reduce in speed the power of the electric motor. As a result, the electric motor can be made smaller while maintaining the running performance. In addition, since the two speed reduction mechanisms are constituted by the three rotating shafts (the output shaft, the middle shaft and the drive shaft) which are parallel with one another and the four speed reduction members in total which are provided on these rotating shafts, the axial dimensions of the respective rotating shafts can be. Controlled.
Consequently, being different from the conventional power transmission mechanism, with the power transmission mechanism according to the first aspect of the invention, the power transmission can be miniaturized, and as a result the fuel economy can be improved. Furthermore, since the differential is disposed closer to the electric motor than the drive shaft speed reduction mechanism in the axial direction of the drive shaft, the electric motor and the differential which are heavier in weight of the constituent components of the power transmission mechanism can be disposed centrally between the left and right drive wheels with a dynamically good balance, and the lengths of the two drive shafts for connecting the differential with the left and right drive wheels can be made substantially equal to each other, whereby the left and right drive wheels can be driven with an ideally good balance.
According to a second aspect of the invention, there is provided a power transmission mechanism
1
for a front and rear-wheel drive vehicle
2
as set forth in the first aspect of the invention, further com
Amanuma Hirokatsu
Honda Kenji
Maruyama Taiji
Uchiyama Naoki
Armstrong Westerman & Hattori, LLP
Estremsky Sherry
Honda Giken Kogyo Kabushiki Kaisha
Lewis Tisha D.
LandOfFree
Power transmission mechanism for a front and rear-wheel... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Power transmission mechanism for a front and rear-wheel..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Power transmission mechanism for a front and rear-wheel... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3071644