Motor vehicles – With means for detecting wheel slip during vehicle...
Reexamination Certificate
2000-08-07
2001-12-18
Boehler, Anne Marie (Department: 3618)
Motor vehicles
With means for detecting wheel slip during vehicle...
C701S082000, C701S084000
Reexamination Certificate
active
06330927
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a tire slip control device for a vehicle such as a loading vehicle. More particularly, the present invention relates to a tire slip control device for controlling slip of tires occurring when a torque converter stalls (i.e., when an output side of the torque converter is restricted and a slip ratio of the torque converter is thereby increased to 100% with the maximum torque being transmitted) or is in an almost-stall condition.
2. Description of the Related Art
For example, as shown in
FIG. 5
, a wheel loader
51
for loading operation is generally adapted to increase an engine speed (revolution speed of an engine E) to its maximum when pushing a bucket
52
into earth and sand or rocks to excavate and scoop up the same. At this time, a torque converter TC operates in a stall condition. However, driving wheels W tend to slip if a driving force is higher than a static frictional force. Such slip causes tires to wear in a short time. Also, slip on rubble causes the tires to be damaged. In particular, in case of a construction machine such as the wheel loader, the wear of the tires brings about an increase in maintenance cost. In
FIG. 5
, reference numeral TM denotes a transmission.
Conventionally, when such slip occurs, this is detected and the driving force to be transmitted to the wheels is restricted to suppress the slip. The prior arts are disclosed in Japanese Patent Application Publication No. Hei. 4-2560, Japanese Patent Application Publication No. Hei. 6-58345, Japanese Patent Application Publication No. Hei. 7-109240, and Japanese Patent No. 2528456.
In the conventional tire slip judgment method according to these prior arts, it is judged that slip has occurred by detecting difference of a revolution speed between right and left driving wheels, by detecting difference of acceleration between the right and left driving wheels, or by detecting difference of a revolution speed between driving wheels and driven wheels.
When the occurrence of slip is confirmed, a rotational driving force of the driving wheels is controlled to suppress the slip. Specifically, in order to suppress the slip, the rotational driving force of the driving wheels is suppressed by braking, the rotational driving force of the driving wheels is suppressed by incompletely engaging a clutch, and the rotational driving force of the driving force is suppressed by reducing fuel supply to the engine to thereby reduce output torque and rotation of the engine.
However, when it is judged that the slip has occurred by detecting the difference of the revolution speed between the right and left driving wheels to thereby detect the slip, it is necessary to provide rotation detectors on right and left axles of the driving wheels, respectively. In addition, when there is an error due to the difference of the revolution speed between inner and outer wheels that is generated when a car body is turning or both of the driving wheels have slipped, it is impossible to judge whether or not the slip has occurred. The same problems occur when detecting the difference of acceleration between the right and left driving wheels. Furthermore, when detecting the difference of the revolution speed between the driving wheels and the driven wheels, it is necessary to additionally provide the rotation detectors on the driving wheels and driven wheels. Consequently, the conventional slip judgment method based on the difference of the revolution speed between the driving wheels and the driven wheels is not applicable to four-wheel-drive vehicles such as the wheel loader.
SUMMARY OF THE INVENTION
The present invention is directed to solving the above-described problems, and an object of the present invention is to provide a low-cost and highly reliable tire slip control device capable of controlling slip of driving wheels by accurately detecting the slip without the necessity of additionally providing a sensor.
In general, a driving force of a vehicle is changed from a high driving force to a low driving force with a change from low-speed traveling to high-speed traveling. At this time, if tire slip occurs because the driving force has exceeded the static frictional force, the change of the driving force per unit time becomes greater than the change of the driving force per unit time at normal accelerated traveling. In case of power transmission by a torque converter, the driving force is represented by an input speed (input revolution speed) of the torque converter, and the ratio of the input speed and an output speed (output revolution speed) of the torque converter at that point of time.
The tire slip control device of the present invention utilizes such characteristics, and comprises an engine; a torque converter connected to an output shaft of the engine; a transmission for transmitting a traveling driving force from the torque converter to an axle; an engine rotation detector; an output rotation detector for the transmission; and means for restricting the traveling driving force, wherein the means for restricting the traveling driving force judges that slip has occurred and restricts the traveling driving force when a rate of change of the ratio of an output speed of the transmission to an engine speed per unit time exceeds a first predetermined value in an initial condition in which the output speed of the transmission is a second predetermined value or smaller in a high-speed rotation area of a predetermined engine speed or larger.
With such configuration, at the occurrence of slip of the driving wheels, i.e., when the engine is rotating at a high speed or the vehicle is stationary or is almost stationary, it is possible to detect that the change of rotation of the driving wheels greater than normal change of vehicle acceleration has occurred. For this slip detection, it is not necessary to provide an additional detector. Further, slip of right and left driving wheels can be detected. Upon detecting that slip has occurred, the traveling driving force is restricted to stop the slip.
It should be noted that the output rotation detector of the transmission may be provided on a transmission shaft from an output shaft of the transmission to a differential gear, not to mention the output shaft of the transmission. Moreover, it is possible to provide the detector on one of a transmission shaft and gears placed on an output side of a change gear in an internal mechanism of the transmission.
Another embodiment of the tire slip control device of the present invention comprises: an engine; a torque converter connected to an output shaft of the engine; a transmission for transmitting a traveling driving force from the torque converter to an axle; an engine rotation detector; an output rotation detector for the transmission; and means for restricting the traveling driving force, wherein the means for restricting the traveling driving force judges that slip has occurred and restricts the traveling driving force when a rate of increase of an output speed of the transmission per unit time exceeds a first predetermined value in an initial condition in which the output speed of the transmission is a second predetermined value or smaller in a high-speed rotation area of a predetermined engine speed or larger.
With this configuration, the same effects as a control device that judges occurrence of slip by using the rate of change of the ratio of the revolution speed per unit time can be achieved. The output rotation detector for the transmission may be provided as described above.
Still another embodiment of the tire slip control device of the present invention comprises an input rotation detector for the transmission for replacing the output rotation detector for the transmission of the above tire slip control device. Since members provided on the input side of the transmission are connected to the wheels via respective transmission shafts, the occurrence of tire slip can be detected from the rotation of the members provided on the input side of the transmission
Boehler Anne Marie
Kawasaki Jukogyo Kabushiki Kaisha
Marshall Gerstein & Borun
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