Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Vehicle subsystem or accessory control
Reexamination Certificate
2003-07-11
2004-12-14
Camby, Richard M. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Vehicle subsystem or accessory control
C701S042000, C180S446000
Reexamination Certificate
active
06832144
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
The present application claims priority under 35 U.S.C. §119 to Japanese Patent Application No. JP2002-203421. The contents of these applications are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a vehicle operation control method and vehicle operation control apparatus for controlling an actual steering angle of a driven wheel based on a steering angle of a steering wheel and vehicle velocity.
2. Description of Related Art
As a vehicle operation control apparatus including a transmission ratio changing mechanism for changing the transmission ratio by driving a motor, provided halfway of a steering transmission system which connects a steering wheel to driven wheels, a vehicle operation control apparatus
100
which comprises a steering wheel
21
, a first steering shaft
22
, a second steering shaft
23
, an EPS actuator
24
, a rod
25
, a steering angle sensor
26
, a vehicle velocity sensor
27
, a torque sensor
28
, an EPS ECU
30
, a gear ratio changing mechanism
32
(transmission ratio changing mechanism), a VGRS ECU
40
and the like, as shown in
FIG. 1
, is available. In the meantime, such “a transmission ratio changing mechanism for changing a transmission ratio by driving an electric motor, located halfway of a steering transmission system which connects the steering wheel to the driven wheel” is sometimes called variable gear ratio system (referred to as VGRS, hereinafter) depending on a case.
That is, an end of the first steering shaft
22
is connected to the steering wheel
21
and an input side of the gear ratio changing mechanism
32
is connected to the other end side of this first steering shaft
22
. This gear ratio changing mechanism
32
comprises a motor, a reduction gear and the like. An end side of the second steering shaft
23
is connected to this output side of the gear ration changing mechanism and an input side of the EPS actuator
24
is connected to the other end side of the second steering shaft
23
. The EPS actuator
24
is an electric type powered steering system, which is capable of converting a rotary motion inputted by the second steering shaft
23
through a rack and pinion gear (not shown) to a motion in the axial direction of the rod
25
and outputting it. Further, this EPS actuator
24
generates an assist force depending on a steering condition by means of an assist motor which is controlled by the EPS ECU
30
so as to assist steering by a driver. In the meantime, this rod
25
is mounted on driven wheels FR, FL.
A rotation angle (steering angle) of the first steering shaft
22
is detected by a steering angle sensor
26
and inputted to the VGRS ECU
40
as a steering angle signal. A steering torque by the second steering shaft
23
is detected by a torque sensor
28
and inputted to the EPS ECU
30
as a torque signal. Further, a vehicle velocity is detected by a vehicle velocity sensor
27
and inputted to the EPS ECU
30
and VGRS ECU
40
as a vehicle velocity signal. Additionally, the EPS actuator
24
contains a tire angle sensor (not shown) capable of detecting a tire angle (actual steering angle) from a moving amount of rod
25
.
With such a structure, ratio between input gear and output gear is changed depending on vehicle velocity at real time by means of a motor and reduction gear in the gear ratio changing mechanism
32
and VGRS ECU
40
so as to change a ratio of output angle of the second steering shaft
23
relative to the steering angle of the first steering shaft
22
. The EPS actuator
24
and the EPS ECU
30
generate an assist force for assisting steering of the vehicle driver by means of an assist motor depending on vehicle driver's steering condition and vehicle velocity detected by means of the torque sensor
28
and the vehicle velocity sensor
27
.
Consequently, the steering gear ratio corresponding to the vehicle velocity can be set. For example, an output angle to a second steering shaft
23
by the gear ratio changing mechanism
32
can be set to be increased with respect to the steering angle of the steering wheel at the time of vehicle stop or traveling at a low velocity. Further, the output angle of the gear ratio changing mechanism
32
can be set to be decreased with respect to the steering angle of the steering wheel
21
at the time of traveling at a high velocity. Meanwhile, an appropriate assist force corresponding to the vehicle velocity can be generated by means of an assist motor.
For example, if a vehicle is stopped or traveling at a low velocity, the steering gear ratio by the gear ratio changing mechanism
32
is set low and an assist force is intensified by an assist motor, so that the driven wheels can be steered largely even with a light steering operation. This facilitates the steering operation of a vehicle driver. On the other hand, if the vehicle is traveling at a high velocity, the assist force by the assist motor drops and the steering ratio by the gear ratio changing mechanism
32
is set high. Consequently, the steering operation becomes heavy and even if the steering wheel
21
is turned largely, it comes that the driven wheels are steered a little. Consequently, it can be expected that vehicle control stability is further improved.
However, in such a vehicle operation control apparatus
100
, a steering gear ratio is set up corresponding to a vehicle velocity by a gear ratio changing mechanism
32
controlled by the VGRS ECU
40
. Thus, when a vehicle driver executes a quick steering by turning the steering wheel
21
suddenly, a follow-up delay by the control of the gear ratio changing mechanism
32
occurs. Consequently, because the steering control on the driven wheels FR, FL continues toward an object angle even after the vehicle driver terminates his steering operation, the vehicle driver is provided with a feeling of disharmony in his driving operation, thereby the steering feeling being worsened.
Thus, in order to prevent the steering feeling from being worsened due to this follow-up delay, the JP 11-208499 A has proposed a “vehicle steering apparatus” in which if a control deviation between an object rotation angle by a transmission ratio changing mechanism and its output angle exceeds a predetermined threshold, this control deviation is adjusted so as to block the control deviation from exceeding a predetermined threshold.
With such a structure, when the steering wheel
21
is turned back slowly at the time of its turning-back even if it is turned suddenly at the time of its additional turning, a difference in steering amount of driven wheels FR, FL occurs although the same amount steering operation is executed at the times of the additional turning and turning-back. Thus, even if a vehicle driver returns the steering wheel
21
to its neutral position, the driven wheels FR, FL are not returned to the neutral position, so that the neutral position is deviated. Consequently, the vehicle driver is supplied with a feeling of disharmony in his steering, thereby the steering feeling being worsened.
JP 2000-344121 A has proposed a “vehicle steering control apparatus” in which the control deviation between the object angle and output angle of the VGRS adjusted at the time of a quick steering is memorized and when the steering wheel
21
is operated, its phase is corrected gradually so that this memorized control deviation becomes zero, thereby the deviation in the neutral position being corrected. However, even with such a structure, the deviation in the neutral position just after the quick steering cannot be blocked because correction of the deviation in the phase is carried out gradually.
SUMMARY OF THE INVENTION
Accordingly, the present invention has been achieved to solve the above-described problem and an object of the present invention is to provide a vehicle operation control method and vehicle operation control apparatus capable of improving the steering feeling.
In order to achieve the above object, according to the present invention, a vehi
Imoto Yuzo
Kohno Toshio
Momiyama Minekazu
Muragishi Yuji
Takeuchi Shinji
Camby Richard M.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Toyoda Koki Kabushiki Kaisha
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