Planetary gear transmission systems or components – Steering by driving
Reexamination Certificate
2000-07-12
2001-12-04
Estremsky, Sherry (Department: 3681)
Planetary gear transmission systems or components
Steering by driving
C475S150000, C475S221000, C180S006440
Reexamination Certificate
active
06325736
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a coupling device to be provided between left and right wheels of a vehicle, in particular between the left and right idler wheels that are not driven by an engine.
BACKGROUND ART
Conventionally, as this kind of coupling device, there is known, in Published Unexamined Patent Application No. 131855/1993, a coupling device in which: between the left and right wheels there are provided a first coupling passage which transmits the rotation of one of the left and right wheels to the other thereof with increasing speed, and a second-coupling passage which transmits the rotation of one of the wheels to the other thereof with decreasing speed; in both the coupling passages a clutch is interposed respectively; and at the time of cornering when one of the wheels becomes an inner wheel, the clutch for the first coupling passage is engaged, and at the time of cornering when one of the wheels becomes an outer wheel, the clutch for the second coupling passage is engaged so that the outer wheel is positively speeded up as compared with the inner wheel. In this manner, by generating a braking force on the inner wheel side and a driving force on the outer wheel side, the cornering performance is sought to be improved.
By the way, at the time of starting on a slippery road such as on a snowy road or the like, it is being considered to perform a starting assistance by driving the idler wheels by a driving source such as an electric motor or the like. It is desired to obtain a starting assistance function in addition to the above-described cornering control function in that the cornering performance is improved by generating a difference rotation between the left and right wheels.
The present invention has an object of providing a compact and inexpensive coupling device which meets the above-described desire and in which a difference rotation between the right and left wheels can be generated by utilizing the driving source for the starting assistance.
DISCLOSURE OF INVENTION
In order to solve the above-described problem, according to a first feature of the present invention, a coupling device to be provided between left and right wheels of a vehicle is arranged to comprise: a differential gear having a first rotational element, and second and third rotational elements one of which rotates in normal direction while the other thereof rotates in reverse direction, respectively, relative to the first rotational element; a driving source which is coupled to the first rotational element of the differential g ear; a first power transmission system which couples the second rotational element to one of the left and right wheels; and a pair of second and third power transmission systems which are selectively established via switching means and which couple the third rotational element to the other of the left and right wheels; wherein gear ratios of the first power transmission system and the second power transmission system are both set to an identical first gear ratio; and wherein a gear ratio of the third power transmission system is set to a second gear ratio which is different from the first gear ratio.
At the time of starting of the vehicle, the driving source is rotated in normal direction or in reverse direction in a state in which the s econd power transmission system is established. According to this arrangement, the driving force is equally transmitted from the differential gear to the left and right wheels via the first and second power transmission systems of the mutually identical gear ratio. The left and right wheels are both rotated either in normal direction or in reverse direction, whereby the starting assistance for forward running or reverse running is performed.
After starting, the third power transmission system is established and also the driving source is stopped. In this case, if the second gear ratio that is the gear ratio of the third power transmission system is set so as to be opposite in direction to, but be equal in absolute value to, the gear ratio of the first power transmission system, the first rotational element of the differential gear will cease to rotate as long as the left and right wheels are rotating at the same speed. Therefore, when the rotation of the first rotational element is restricted by braking the driving source, the differential limiting between the left and right wheels is performed, whereby the straight-running stability is improved.
Further, when the diving source is rotated in normal direction in a state in which the third power transmission system is established, one of the left and right wheels is speeded up relative to the other thereof and, when the driving source is rotated in the reverse direction, said the other of the left and right wheels is speeded up relative to said one of the left and right wheels. Therefore, if the driving source is rotated in normal direction or reverse direction such that the wheel which becomes an outer wheel at the time of cornering is speeded up, a driving force is added to the outer wheel and a braking force is added to the inner wheel, whereby a yawing moment in the cornering direction is generated, resulting in an improvement in the cornering performance.
In the above-described arrangement, the number of the differential gear is selected to be one and the second and third power transmission systems are selectively established. However, a similar function can also be obtained by using two differential gears. Therefore, according to a second feature of the present invention, a coupling device to be provided between left and right wheels of a vehicle, is arranged to comprise: a pair of first and second differential gears each having a first rotational element, and second and third rotational elements one of which rotates in normal direction while the other thereof rotates in reverse direction, respectively, relative to the first rotational element; a driving source which is selectively coupled via switching means to the first rotational element of the first differential gear and to the first rotational element of the second differential gear; wherein the second rotational element and the third rotational element of the first differential gear are coupled at a first gear ratio to one and the other, respectively, of the left and right wheels; wherein the second rotational element of the second differential gear is coupled to one of the left and right wheels at a second gear ratio; and wherein the third rotational element of the second differential gear is coupled to said the-other of the left and right wheels at a third gear ratio which is different from the second gear ratio.
In this arrangement, when the driving source is coupled to the first rotational element of the first differential gear, the same state is attained as at the time when the second power transmission system is established in the above-described first feature. If the driving source is rotated in normal or reverse direction in this state at the time of starting, the driving force is equally transmitted to the left and right wheels, whereby the starting assistance for forward running or reverse running is performed.
Further, when the driving source is coupled to the first rotational element of the second differential gear, the same state is attained as at the time when the third power transmission system is established in the above-described first feature. Then, if the third gear ratio is set so as to be opposite in direction to, but be equal in absolute value to, the second gear ratio, the first rotational element of the second differential gear will not rotate as long as the left and right wheels are rotating at the same speed. Therefore, if the rotation of the first rotational element of the second differential gear is restricted by braking the driving source, the differential limiting between the left and right wheels is performed, whereby the straight-running stability is improved. Further, at the time of cornering, the outer wheel is speeded up by rotating the driving source in normal or revers
Arai Kentaro
Hamada Tetsuro
Hashizume Isamu
Kanamaru Yoshihiro
Armstrong Westerman Hattori McLeland & Naughton LLP
Estremsky Sherry
Honda Giken Kogyo Kabushiki Kaisha
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