Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Vehicle subsystem or accessory control
Reexamination Certificate
2002-08-02
2004-10-19
Zanelli, Michael J. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Vehicle subsystem or accessory control
C180S443000
Reexamination Certificate
active
06807471
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a total electric type or a total hydraulic type steering apparatus in which a steering wheel of a vehicle and a steered tire wheel are not mechanically connected. More particularly, the present invention relates to a steering wheel position compensating apparatus which compensates a deviation in a positional relation between a steering wheel position (a steering wheel angle) and a wheel angle of the steered tire wheel.
Conventionally, there is a structure in which a total hydraulic type steering apparatus is equipped, in an industrial vehicle, for example, a forklift or the like. In this apparatus, a working oil at an amount corresponding to an operation amount of a steering wheel is supplied to a steering cylinder, and the steering cylinder is driven, whereby the steered tire wheel is steered in correspondence to the operation amount of the steering wheel. In this kind of industrial vehicle, there is a structure in which a knob is provided in the steering wheel so that the steering wheel can be operated by one hand while performing a loading operation by the other hand. There is a case where a driver sets a position of the steering wheel knob to a target for judging where the wheel angle of the steered tire wheel is. However, in the total hydraulic type steering apparatus, there is a problem that a deviation is caused in the positional relation between the position of the steering wheel knob and the wheel angle of the steered tire wheel, for the reason of a little deviation between the steering wheel operation amount and the supplied oil amount, an oil leakage or the like.
In order to solve the problem, a steering wheel angle compensating apparatus which compensates a deviation between the steering wheel angle and the wheel angle is disclosed, for example, in Japanese Examined Patent Publication No. Hei 3-30544 and Japanese Examined Patent Publication No. Hei 4-24270. That is, as shown in
FIG. 21
, a power steering apparatus
51
is provided with a controller
52
, and the controller
52
inputs a steering wheel rotational signal &thgr;abs from a steering wheel angle sensor
53
, and inputs a cylinder stroke signal “s” from a cylinder position sensor
54
.
The controller
52
determines a target cylinder stroke from the steering wheel rotational signal &thgr;abs. Further, when a deviation between the cylinder stroke determined from the cylinder stroke signal “s” and a target cylinder stroke exceeds an allowable value, it opens an electromagnetic control valve
55
. Accordingly, a part of working oil flows back to a tank
58
from one supply line of hydraulic lines
56
and
57
via another return line, a steering wheel
59
goes in a racing state, and a steering wheel position (a knob position) is compensated to a normal position in correspondence to the wheel angle of the steered tire wheel.
Further, as a steering apparatus in which the steering wheel and the steered tire wheel are not mechanically connected, a total electric type steering apparatus shown in
FIG. 22
, is disclosed in Japanese Unexamined Patent Publication No. Hei 7-206399. An order picking truck
61
is provided with a controller
62
, and the controller
62
inputs a rotational angle of a steering wheel
63
from a potentiometer
64
and inputs a steering wheel (a wheel angle) of a steered tire wheel
65
from a potentiometer
66
. Further, the controller
62
computes a deviation in a detection electric voltage between the potentiometers
64
and
66
, and outputs a drive electric voltage corresponding to the deviation to a steering motor
67
. Accordingly, the steered tire wheel
65
is steered so as to become a wheel angle corresponding to the operation angle of the steering wheel
63
.
In this case, in the total hydraulic type steering apparatus, the steering wheel
59
and the steering cylinder
60
are connected via a hydraulic circuit. Accordingly, even when the working oil is flowed back via the electromagnetic control valve
55
during a period of executing the compensation of the steering wheel angle, a certain degree of holding force is secured in the steered tire wheel due to an existence of the working oil in the steering cylinder
60
. That is, even when an external force is applied to the steered tire wheel, the steered tire wheel is not displaced until a force sufficient for pushing out the working oil within the steering cylinder
60
so as to drive the steering cylinder
60
is applied.
On the other hand, the total electric type steering apparatus is of a so-called steer-by-wire type in which the steering wheel
63
and the steered tire wheel
65
are not connected neither in a mechanical manner nor in a hydraulic circuit manner. Accordingly, since there is established a state in which a power is not transmitted to the steered tire wheel
65
in the case where the steering wheel
63
is stopped and the steering motor
67
is in a stop state, the holding force of the steered tire wheel by an operating mechanism including the steering wheel becomes comparatively weak. In particular, in the case of applying the steering wheel position compensating apparatus to the total electric type steering apparatus mentioned above, the holding force of the steered tire wheel
65
is lowered in the case of stopping driving the steering motor
67
for causing the racing of the steering wheel
68
. For example, when the steered tire wheel steps on an obstacle (a stone or the like) on a traveling road surface, there has been a risk that the wheel angle of the steered tire wheel
65
deviates with respect to the steering wheel due to the external force.
In the case of employing the steering wheel position compensation, if the deviation exists between the steering wheel and the steered tire wheel, an output of the steering motor
67
is stopped during a period that the deviation exists, and the steering motor
67
is driven after the deviation does not exist. For example, during the straight traveling, there is executed an operation of fine operating the steering wheel
63
rightward or leftward so as to control a straight moving property. At this time, a direction of operating the steering wheel is switched little by little.
In this case, when the steering wheel is operated in a direction in which the deviation becomes small, the motor is stopped, and when the steering wheel is operated in a direction in which the deviation becomes large, the motor is driven. Accordingly, during a process of operating the steering wheel from a left turning point to a right turning point within the fine operation range, for example, within a narrow range of between 2° and 10° in one direction, the compensation is executed for canceling the deviation and the motor is stopped in a first half of the narrow range, and the compensation is inhibited for preventing the deviation from being made wide and the motor is driven in a second half of the narrow range. Accordingly, when the driver operates the steering wheel in one direction for the fine operation, a phenomenon that the motor output suddenly arises is easily generated in the second half.
In this case, there has been a problem that it is hard to secure a straight moving stability of the steering wheel operation, because the vehicle tends to be steered in a little serpentine manner even if the driver intends to generally fine operate the steering wheel for controlling the straight moving property. In particular, when turning a corner for right turn or left turn, the steering wheel is fine adjusted for getting right the straight moving property at a time of returning to the straight moving state from the curve traveling state, but a higher straight moving stability is required at a time of getting right an attitude of the vehicle. Accordingly, there has been required a countermeasure by which the positional relation between an actual position (the present rotational position) of the steering wheel and the wheel angle of the steered tire wheel is fitted, the output change of the steering motor
67
against the steerin
Kabushiki Kaisha Toyota Jidoshokki
Morgan & Finnegan , LLP
Zanelli Michael J.
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