Planetary gear transmission systems or components – Input from independent power sources – Including electric motor input
Reexamination Certificate
2000-10-06
2002-06-25
Wright, Dirk (Department: 3617)
Planetary gear transmission systems or components
Input from independent power sources
Including electric motor input
Reexamination Certificate
active
06409623
ABSTRACT:
This application is based on Japanese Patent Application No. 11-287933 filed October 8, the contents of which are incorporated hereinto by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a rear driving apparatus for driving an automotive vehicle in the reverse direction, and more particularly to technologies associated with a synthesizing/distributing device of gear type used in the rear driving apparatus.
2. Discussion of Related Art
There is known a hybrid automotive vehicle equipped with a drive system including (a) an engine operated by combustion of a fuel to produce a drive force, (b) an electric motor, (c) an output member operatively connected to drive wheels, (d) a planetary gear device associated with the engine, electric motor and output member, for synthesizing and distributing a drive force or forces, and (e) a plurality of frictional coupling devices such as clutches and brakes for selectively connecting and disconnecting rotary elements of the planetary gear device and the output member to and from each other or a stationary member. An example of such a hybrid vehicle drive system is disclosed in JP-A-9-37411, wherein various drive modes are selectively established for driving the vehicle, by controlling the operating states of the clutches and brakes. For instance, the drive modes include a motor-drive mode in which the vehicle is driven by the electric motor as a drive power source, and an engine-drive mode in which the vehicle is driven by the engine as the vehicle drive source.
In a hybrid vehicle as described above, only the electric motor is generally used as the drive power source to drive the vehicle in the reverse direction. However, the drive force produced by the electric motor may be insufficient when the vehicle is driven in the reverse direction on an uphill. In particular, the drive torque produced by the electric motor is limited when the amount of electric energy stored in an electric energy storing device is reduced below a certain lower limit.
The assignee of the present application disclosed in JP-A-2000-92612 (published on Mar. 31, 2000 after the present invention was made) a hybrid vehicle equipped with a drive system including (a) an engine, (b) an electric motor, (c) an output member operatively connected to drive wheels, (d) a double-pinion type planetary gear device having a sun gear connected to the engine, a carrier connected to the electric motor, and a ring gear, (e) a brake for fixing the ring gear to a stationary housing, (f) a first clutch for connecting the carrier to the output member, (g) a second clutch for connecting the ring gear to the output member, and (h) a control device adapted to engage the first clutch and operate the electric motor in the reverse direction, for rotating the drive wheel through the output member for driving the vehicle in the reverse direction, the control device being further adapted to engage the brake and operate the engine as needed, so as to provide an assisting drive torque for driving the vehicle in the reverse direction. The drive system of this hybrid vehicle is capable of providing a sufficiently large drive force for driving the vehicle in the reverse direction. However, the drive system suffers from a relatively large variation in the rear drive force upon an engaging action of the brake, resulting in a risk of a stall of the engine when the running speed of the vehicle is relatively low. Thus, the drive system disclosed in JP-A-2000-92612 is not practically available.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a rear driving apparatus for driving an automotive vehicle in the reverse direction, which apparatus permits the engine to be operated to provide an assisting rear drive torque through a synthesizing/distributing device of a gear type even at a relatively low running speed of the vehicle, while minimizing a variable in the rear drive force.
The above object may be achieved according to a first aspect of the present invention, which provides a vehicle rear driving apparatus for driving an automotive vehicle in a reverse direction, the automotive vehicle having a drive power source, an output member operatively connected to a drive wheel of the vehicle for driving the vehicle, a synthesizing/distributing device of gear type including a housing, a first rotary element, a second rotary element and a third rotary element, the first and second rotary elements being rotated in respective opposite directions when the third rotary element is stationary, and connected to the drive power source and the output member, respectively, and a brake for fixing the third rotary element to the housing, the vehicle rear driving apparatus being characterized in that the brake is a frictional coupling device capable of effecting a slipping engagement, and that reverse friction-drive control means is provided, the reverse friction-drive control means being operable when the first rotary element is rotated in a forward direction with an operation of the drive power source, while the third rotary element is rotated in the forward direction with a rotary motion of the first rotary element, the reverse friction-drive control means controlling the brake to effect the slipping engagement so as to restrict a rotary motion of the third rotary element, for thereby causing a drive torque to act on the second rotary element in a reverse direction to drive the vehicle in the reverse direction.
In the vehicle rear driving apparatus constructed according to a first aspect of this invention, the reverse friction-drive control means is operated when the first rotary element is rotated in the forward direction with an operation of the drive power source while the third rotary element is rotated in the forward direction with a rotary motion of the first rotary element. The reverse friction-drive control means is adapted to effect the slipping engagement so as to restrict a rotary motion of the third rotary element, for thereby causing a drive torque to act on the second rotary element in a reverse direction to drive the vehicle in the reverse direction. Thus, the vehicle can be driven with a sufficiently large drive force by utilizing an engine, for example. Further, the slipping engagement of the brake makes it possible to reduce a variation in the vehicle drive force, and permits the vehicle to be driven in the reverse direction even at a relatively low speed while maintaining a relatively high operating speed of the drive power source such as an engine.
The synthesizing/distributing device of gear type may be a planetary gear device of single- or double-pinion type, or differential gear device of bevel gear type. The frictionally coupling brake capable of effecting a slipping engagement is preferably a hydraulically operated friction brake of multiple-disc type. However, the brake may be an electromagnetically operated brake. A clutch or clutches, or other brake or brakes may be disposed between the second rotary element and the output member.
The drive power source preferably includes an engine which is operated by combustion of a fuel, and may include any other type of power source such as an electric motor. The vehicle rear driving apparatus according to the first aspect of the invention need not comprise reverse-motor-drive control means for driving the vehicle in the reverse direction with only an electric motor while the brake is held in the released state, as described below with respect to a second aspect of the invention.
The vehicle rear driving apparatus according to the first aspect of the invention described above is advantageously applicable to a hybrid vehicle wherein the drive power source includes an engine operable by combustion of a fuel, and an electric motor, and the synthesizing/distributing device comprises a planetary gear device including a sun gear as the first rotary element, a carrier as the second rotary element, and a ring gear as the third rotary element, the engine being connected to the sun ge
Hoshiya Kazumi
Oba Hidehiro
Toyota Jidosha & Kabushiki Kaisha
Wright Dirk
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