Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Construction or agricultural-type vehicle
Reexamination Certificate
1997-03-18
2001-05-29
Cuchlinski, Jr., William A. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Construction or agricultural-type vehicle
C187S226000, C060S426000, C060S428000, C091S420000, C091S435000, C091S388000, C091S448000, C091S403000
Reexamination Certificate
active
06240353
ABSTRACT:
BACKGORUND OF THE INVENTION
1. Field of the Invention
The present invention relates to axle supporting apparatus for industrial vehicles, and more particularly, to an apparatus for locking swingable axles of industrial vehicles.
2. Description of the Related Art
A typical forklift truck has a rear axle that is supported by a body frame. The rear axle is swung with respect to the body frame by lateral acceleration, or centrifugal force, that is produced when the traveling forklift truck changes directions. This degrades the traveling stability of the forklift truck. Thus, the traveling speed of the forklift truck must be decreased when changing directions.
Japanese Unexamined Patent Publication No. 58-211903 describes a forklift truck that locks the swinging of an axle when the truck turns. The forklift truck has a detecting means that detects centrifugal force when the truck is turned. When the centrifugal force becomes greater than a predetermined level, the swinging of the axle with respect to the body frame is restricted. In other words, the axle is locked. This enables stable turning of the forklift truck without having a slow down the vehicle. However, when the forklift truck successively changes direction within a short period of time, for example, when the vehicle turns right and then turns left immediately afterward, the centrifugal force, for an instant, is less than the predetermined level. This releases the locking of the axle regardless of the vehicle changing directions. As a result, the forklift truck becomes unstable when successively turned in different directions.
Japanese Unexamined patent Publication No. 58-214406 described a forklift truck that locks its axle when the rotated angle of the steering wheel and the speed of the vehicle become greater than predetermined values. However, when the vehicle is successively turned in different directions, for an instant, the rotated angle of the steering wheel becomes smaller than the predetermined angle. Thus, in the same manner as the forklift truck of Publication No. 58-211903, this releases the locking of the axle and causes instability.
Among the four wheels (two front wheels and two rear wheels) of a forklift truck, one of the wheels may be lifted from the ground depending on the weight of the object held by the forks when the axles are locked during turning. For example, when a heavy object is held on the forks, the center of gravity of the vehicle is displaced toward the front of the forklift truck. This may lift one of the rear wheels from the ground if one of the axles are locked. If the axles are locked when a relatively light object is held on the forks, the balance weight provided at the rear of the vehicle may cause one of the front wheels to raise from the ground.
Typically, torque is transmitted to the front wheels to drive forklift trucks. The steering angle is transmitted to the rear wheels to steer the vehicle. Accordingly, if the rear axle is locked when a relatively light object is held on the forks, one of the front wheels, which function as the drive wheels, may be lifted away from the ground. This decreases traction between the front wheels and the ground. As a result, the driving force of the vehicle becomes insufficient. This hinders smooth operation of the forklift truck.
If a heavy object is held on the forks, the center of gravity, which is near the front of the vehicle, increases the traction force of the front wheels. Accordingly, the locking of the axle does not affect the driving force of the vehicle. However, when the center of gravity is near the front of the vehicle, the vehicle tends to swing in a forward direction. As a result, the forklift truck becomes unstable when lifting and lowering objects and when traveling with the heavy object held on the forks. This tendency is stronger is the object is held at a high position, which raises the center of gravity.
SUMMARY OF THE INVENTION
Accordingly, it is an objective of the present invention to provide an industrial vehicle that is capable of traveling in a stable manner.
A further objective of the present invention is to provide an industrial vehicle that is capable of lifting and lowering objects in a stable manner.
For achieving the above objectives, an improved control apparatus for an industrial vehicle is provided. The vehicle includes a rear axle, said rear axle being swingable during straight travel of the vehicle and lockable during turning of the vehicle. The apparatus comprises holding means for selectively locking and unlocking the rear axle, memory means for storing a first value and a second value of an angular velocity rate, wherein said angular velocity rate represents an angular velocity per unit time, wherein said first value is predetermined to indicate turning of the vehicle when the angular velocity rate is greater than the first value, and wherein said second value is predetermined to indicate the straight travel of the vehicle when the angular velocity rate is smaller than the second value, and control means for selectively activating and deactivating the holding means. The control means activates the holding means to lock the rear axle when the angular velocity rate is greater than the first value, and said control means deactivates the holding means to unlock the rear axle when the angular velocity rate is kept smaller than the second value for a predetermined time period after the angular velocity rate has become smaller than the second value.
REFERENCES:
patent: 3938823 (1976-02-01), Hiruma
patent: 4393959 (1983-07-01), Acker
patent: 4511974 (1985-04-01), Nakane et al.
patent: 5087068 (1992-02-01), Fukanaga et al.
patent: 5535663 (1996-07-01), Yamashita et al.
patent: 5673558 (1997-10-01), Sugiyama et al.
patent: 5791372 (1998-08-01), Mukumoto
patent: 5832807 (1998-11-01), Rausch et al.
patent: 5921279 (1999-07-01), Barber
patent: 5942839 (1999-08-01), Ohnishi et al.
patent: 5947441 (1999-09-01), Zenker et al.
patent: 40 19732 A1 (1991-01-01), None
patent: 0 415 423 A1 (1991-03-01), None
patent: 49-77619 (1974-07-01), None
patent: 57-109007 (1982-07-01), None
patent: 58-167215 (1983-10-01), None
patent: 58-167214 (1983-10-01), None
patent: 58-167400 (1983-10-01), None
patent: 58-214406 (1983-12-01), None
patent: 58-211903 (1983-12-01), None
patent: 62-39386 (1987-02-01), None
patent: 5-193322 (1993-08-01), None
patent: 6-247118 (1994-09-01), None
patent: 7-032848 (1995-02-01), None
Hyodo Masaya
Ishikawa Kazuo
Cuchlinski Jr. William A.
Kabushiki Kaisha Toyoda Jidoshokki Seisakusho
Mancho Ronnie
Morgan & Finnegan L.L.P.
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