Motor vehicles – Having at least one wheel both driven and steerable
Reexamination Certificate
1998-11-06
2001-03-20
Mai, Lanna (Department: 3611)
Motor vehicles
Having at least one wheel both driven and steerable
C180S420000, C180S434000, C180S435000, C180S436000, C280S093502, C280S093501
Reexamination Certificate
active
06202781
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a power steering device for vehicles such as tractors. Vehicles such as tractors are known wherein a cylinder for a double rod-type power steering device is attached to an axle case of a differential gear device so as to steer the steering driving wheels. Such technique is disclosed in Japanese Examined Patent Publication No. 12612/1991 and Japanese Unexamined Patent Publication No. 257411/1995.
Japanese Examined Patent Publication 12612/1991 discloses a power steering device support mechanism for front-wheel drive vehicles, wherein in order to increase the maximum swing angle of the front axle, a slot parallel to the front axle is formed at a front portion of the front axle case, and a cylinder of a power steering device is inserted in the slot. However, due to the presence of an inside wall between the differential gear housing and the pair of front axle housings and direct connections between the piston rods and tie rods, a considerably large distance inevitably exists between the front axle and the piston rods of the power steering device support mechanism disclosed therein, which increases the intersection angle between the axis of the piston rods and the axes of the tie rods during steering and consequently increases the force imparted to the piston rods perpendicularly to the axis thereof, thus causing the problems of inferior steering performance and low durability of the power steering device.
To overcome the above problems, Japanese Unexamined Patent Publication No. 257411/1996 proposes a power steering device support mechanism wherein a front axle case is divided into three parts, and a differential gear device and part of a cylinder of the power steering device are accommodated together in a center case. This arrangement decreases the distance between the axis of the front axle and that of piston rods so as to make smaller the intersection angle between the axis of the piston rods and the axes of the tie rods during steering. Thus this arrangement inhibits the application of force perpendicular to the axis of the piston rods and thereby improves steering performance and durability of the power steering device.
However, the steering device disclosed in Japanese Unexamined Patent Publication No. 257411/1996, as well as that of Japanese Unexamined Patent Publication No. 12612/1991, comprises a cylinder which penetrates a front axle case. This construction causes problems of increased costs for enlarged front axle case, complicated assembly work and troublesome maintenance due to difficulty in taking out the power steering device alone.
In consideration of the above disadvantages of the prior art, an object of the present invention is to provide a power steering device for vehicles which can be manufactured without increasing costs, is easily attached to and taken out from the axle case, and minimizes the intersection angle between the axis of piston rods and the axes of tie rods in steering operation so as to improve steering performance and durability.
SUMMARY OF THE INVENTION
To achieve the above-mentioned object, the present invention provides a power steering device for vehicles which comprises:
an axle case for housing a differential gear device and a pair of right and left axles extending from the differential gear device;
a first bracket attached to the axle case and extending therefrom in one direction longitudinal of the vehicle body;
a second bracket spaced from the first bracket axially of the axle case and attached to the axle case so as to extend in the same direction as the first bracket;
a wheel steering generator positioned at said longitudinal direction side relative to the axle case and comprising a cylinder and a pair of right and left piston rods projecting from the cylinder,
the cylinder being supported in parallel to the axis of the axles by the first and second brackets;
steering knuckles supported at their outer ends by steering wheels and connected at their inner ends to the axle case rotatably around king pins;
tie rods connected at their outer ends to the inner ends of the steering knuckles and extending at their inner ends towards the inner ends of the axles;
coupling members provided in parallel with said longitudinal direction,
each coupling member being connected at one end to the inner end of the tie rod and extending in said longitudinal direction and being rotatably connected to the outer end of the piston rod;
a guide bar positioned in parallel with the pair of piston rods and fixed thereto; and
support members attached to the axle case and extending to the guide bar so as to support the guide bar in such a way that the guide bar is slidable with the piston rods but not tiltable vertically.
In the specification and claims, the direction extending from the front axle case to either of the front wheels is referred to as “outer direction”, and the opposite direction is referred to as “inner direction”.
REFERENCES:
patent: 4037680 (1977-07-01), Grove
patent: 4941543 (1990-07-01), Ewen
patent: 5094312 (1992-03-01), Hakel
patent: 5282644 (1994-02-01), Larson
patent: 5489114 (1996-02-01), Ward et al.
patent: 5544715 (1996-08-01), Phillips
patent: 5823288 (1998-10-01), Buff
patent: 5921343 (1999-07-01), Yamakaji
patent: 3-12612 (1991-03-01), None
patent: 7-257411 (1995-10-01), None
patent: 7-257412 (1995-10-01), None
patent: 7-257413 (1995-10-01), None
patent: 7-257414 (1999-10-01), None
Kanzaki Kokyukoki Mfg. Co. Ltd.
Knobee Martens Olson & Bear LLP
Mai Lanna
To Toan C
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