Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Control of power distribution between vehicle axis or wheels
Reexamination Certificate
2001-05-24
2002-11-12
Louis-Jacques, Jacques H. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Control of power distribution between vehicle axis or wheels
C701S089000, C180S233000, C180S248000
Reexamination Certificate
active
06480778
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a continuously variable speed-changing device and, more specifically, to a device for changing the speeds of the front and rear wheels in a four-wheel-drive vehicle, capable of variably driving the front wheels and the rear wheels independently from each other by using a toroidal type continuously variable speed-changing device.
DESCRIPTION OF THE PRIOR ART
There has heretofore been proposed a four-wheel-drive vehicle equipped with a continuously variable speed-changing mechanism for the front wheels and with a continuously variable speed-changing mechanism for rear wheels in order to variably drive the front wheel drive shafts and the rear wheel drive shafts independently from each other via the continuously variable speed-changing mechanisms, in an attempt to decrease the weight of the four-wheel-drive mechanisms, to avoid the loss of power and to improve the fuel efficiency.
When the four-wheel-drive vehicle turns in accordance with the operation of the steering wheel, there occurs the so-called inside-outside wheel difference that the front wheels turn on the center of rotation with the radii of turn which are on the outer sides of the radii of turn of the rear wheels. The difference in the rotational speed between the front right wheel and the front left wheel is absorbed by a differential for the front wheels provided for the front axles, and the difference in the rotational speed between the rear right wheel and the rear left wheel is absorbed by a differential for the rear wheels provided for the rear axles. When turning, however, the front wheels and the rear wheels travel different distances since the average radius of turn is not the same between the front wheels and the rear wheels. When no countermeasure is taken, like in the four-wheel-drive vehicle of the directly coupled type, therefore, the rotation of the front wheels does not meet the rotation of the rear wheels, giving rise to the occurrence of a so-called tight corner braking phenomenon. The tight-corner braking phenomenon is an undesirable phenomenon impairing smooth turning of the vehicle; i.e., the drive system is greatly twisted due to a difference in the rotation between the front wheels and the rear wheels, the slip and drive of the wheels are repeated making it difficult to smoothly operate the vehicle and, in extreme cases, making it difficult to run the vehicle.
A typical example of the continuously variable speed-changing device in the four-wheel-drive vehicle can be typified by a toroidal type continuously variable speed-changing device disclosed in Japanese Laid-open Patent Publication (Kokai) No. 157151/1993 (JP-A 5-157151). This continuously variable speed-changing device includes an input shaft supported by a casing, and a continuously variable speed-changing mechanism for the front wheels and a continuously variable speed-changing mechanism for the rear wheels that are arranged, spaced apart, in the axial direction of the input shaft. The continuously variable speed-changing mechanism for the front wheels changes the input rotational speed of the input shaft and outputs it to the front wheel drive shafts. The continuously variable speed-changing mechanism for the rear wheels changes the input rotational speed of the input shaft and outputs it to the rear wheel drive shafts. These continuously variable speed-changing mechanisms have been so constituted as to variably drive the front wheels and the rear wheels independently from each other.
The above continuously variable speed-changing mechanism for the front wheels has substantially the same constitution as that of the continuously variable speed-changing mechanism for the rear wheels. Therefore, the constitution of the continuously variable speed-changing mechanism for the front wheels will now be briefly described. The continuously variable speed-changing mechanism for the front wheels includes an input disk which is secured to the input shaft and has one surface in the axial direction thereof formed as an input side recessed surface of an arcuate shape in cross section, and an output disk having one surface in the axial direction thereof formed as an output side recessed surface of an arcuate shape in cross section. The output disk is so disposed as to rotate relative to the input shaft and to surround the outer peripheral surface of the input shaft and has its output side recessed surface disposed so as to be opposed to the input side recessed surface of the input disk in the axial direction. A pair of power rollers are disposed between the input side recessed surface of the input disk and the output side recessed surface of the output disk so as to rotate relative to the input disk and the output disk. The power rollers are supported by trunnions so as to rotate. The axes of rotation of the power rollers are arranged at right angles with the axes of the trunnions that will be described later.
The trunnions are so supported as to rotate about their axes relative to the casing and to move in the axial direction. The axes of the trunnions extend in parallel with each other in the tangential direction relative to the input shaft at symmetrical positions with the input shaft interposed therebetween at an equal distance. On the cross sections of the input disk and of the output disk opposed to each other in the axial direction, the center of arc of the input side recessed surface of the input disk and the center of arc of the output side recessed surface of the output disk are arranged on a common center of arc. Further, the axial centers of the trunnions are arranged to be in agreement with the centers of the corresponding arcs. The axes of the trunnions define tilting axes along which the corresponding power rollers rotate. The power rollers are so constituted as to possess spherically protruded surfaces in the peripheries thereof, the protruded surfaces being brought into a pressed contact (point contact) with the input side recessed surface of the input disk and with the output side recessed surface of the output disk. The trunnions are moved in the axial directions but in the opposite directions relative to each other by the actuators such as hydraulic cylinders, whereby the power rollers rotate about the axes which are tilted by an angle corresponding to the amount of motion of the trunnions and changing of the speed between the input disk and the output disk is performed. According to the toroidal type continuously variable speed-changing device as described above, the rotational forces of the output disks of the continuously variable speed-changing mechanism for the front wheels and of the continuously variable speed-changing mechanism for the rear wheels are output to the front wheels and to the rear wheels independently from each other, to execute the full-time four-wheel drive. Constitutions of trunnions of the toroidal type continuously variable speed-changing device have been disclosed in, for example, Japanese Utility Model Publication (Kokoku) No. 11425/1994 and Japanese Laid-open Patent Publication (Kokai) No. 269039/1997 (JP-A 9-269039).
In the continuously variable speed-changing device, when a steering angle is given to the front wheels, the tilting angle of the power rollers of the continuously variable speed-changing mechanism for the front wheels is differed from the tilting angle of the power rollers of the continuously variable speed-changing mechanism for the rear wheels to drive the four wheels with little loss of power while absorbing the difference in rotational speed between the front wheels and the rear wheels when the vehicle turns, without using the center differential. That is, the tilting angle of the power rollers in the continuously variable speed-changing mechanism for the rear wheels is slightly decreased compared to that of when traveling straight and the tilting angle of the power rollers in the continuously variable speed-changing mechanism for the front wheels is slightly increased compared to that of when traveling straight, so that the rotati
Koga Hidetaka
Tanaka Hirohisa
Antonelli Terry Stout & Kraus LLP
Isuzu Motors Limited
Louis-Jacques Jacques H.
LandOfFree
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