Motor vehicles – Steering gear – With fluid power assist
Reexamination Certificate
1999-05-14
2001-06-26
Johnson, Brian L. (Department: 3618)
Motor vehicles
Steering gear
With fluid power assist
C180S422000, C701S041000, C701S042000
Reexamination Certificate
active
06250417
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a power steering apparatus for detecting a steering force to be applied to a steering wheel, and driving an electric motor so as to assist steering while using a hydraulic pump driven by the electric motor as a generating source of a hydraulic pressure when the detected steering force is larger than a predetermined value.
In a power steering apparatus which assists steering by using a hydraulic pump driven by an electric motor as a generating source of a hydraulic pressure, it is considered that when a steering wheel is not operated and a vehicle travels straight, the electric motor is terminated so that an electric power consumption is reduced.
FIG. 1
is a block diagram showing a configuration of such a power steering apparatus. In this power steering apparatus, a motor driving circuit
2
applies a voltage to an electric motor
4
according to a target value of an applied voltage (drive voltage) instructed by a drive voltage determination unit
1
c
so as to rotate the electric motor
4
. The electric motor
4
drives a hydraulic pump
5
so as to discharging a hydraulic oil to a control valve
6
and generate a hydraulic pressure.
When a steering wheel
7
is operated and a gear apparatus (not shown) including a pinion gear
6
c
provided at a lower end of a steering wheel shaft is actuated, the control valve
6
controls a pressure of a hydraulic oil to be press-fed to pipe lines
6
a
and
6
b
connected with a hydraulic cylinder (not shown). As a result, the hydraulic cylinder is actuated, and a steering assisting force according to an operating amount is generated in an operating direction of the steering wheel
7
.
The hydraulic oil circulates a hydraulic circuit composed of the hydraulic pump
5
, control valve
6
, hydraulic cylinder, a supply tank
5
a
and the like.
A rotational velocity sensor
4
b
for detecting a rotational velocity of the electric motor
4
is added to the electric motor
4
, and a rotational velocity detection signal outputted by the rotational velocity sensor
4
b
is given to a rotational velocity detection circuit
4
a
so as to be converted into a rotational velocity signal and be given to a calculation circuit
1
b.
The calculation circuit
1
b
subtracts the rotational velocity signal outputted by the rotational velocity detection circuit
4
a
from a rotational velocity instruction signal outputted by an instructing rotational velocity determination unit
3
so as to input the resultant into the drive voltage determination unit
1
c.
A rotational velocity of the electric motor
4
is set in the instructing rotational velocity determination unit
3
so that the hydraulic pump
5
can generate a hydraulic pressure which is required for the steering assistance.
The drive voltage determination unit
1
c
instructs the motor driving circuit
2
about an applied voltage by feedback control (PI control) based on a difference between the rotational velocity instruction signal outputted by the instructing rotational velocity determination unit
3
and the rotational velocity signal outputted by the rotational velocity detection circuit
4
a.
Meanwhile, a steering force detector
7
a
composed of a torque sensor and the like for detecting a steering force applied to the steering wheel
7
is provided to the steering wheel shaft of the steering wheel
7
, and a steering force signal outputted by the steering force detector
7
a
is given to a steering force detection circuit
7
b.
When the given steering force signal indicates a steering force which is larger than a predetermined steering force, the steering force detection circuit
7
b
turns on a power supply of the motor driving circuit
2
. The motor driving circuit
2
whose power supply was turned on starts the electric motor
4
by the applied voltage instructed by the drive voltage determination unit
1
c
thereat.
In addition, on the contrary, when the given steering force signal indicates a steering force which is smaller than the predetermined steering force, the steering force detection circuit
7
b
turns off the power supply of the motor driving circuit
2
.
Here, the similar technology to the above-mentioned power steering apparatus is disclosed in Japanese Patent Application Laid-Open No. 58-156457 (1983).
In the above-mentioned power steering apparatus, when the motor driving circuit
2
is turned on and the electric motor
4
is started by the applied voltage instructed from the drive voltage determination unit
1
c
thereat, as shown in
FIG. 2
, the rotational velocity of the electric motor
4
overshoots, and accordingly an unnecessary large inrush current is generated and unnecessary electric energy is consumed. Moreover, in some cases, the rotational velocity is not stabilized immediately.
BRIEF SUMMARY OF THE INVENTION
The present invention has been made with the aim of solving the above problems, and it is an object of the present invention to provide a power steering apparatus in which an unnecessary inrush current is not generated in an electric motor, an unnecessary electric energy can be reduced, a rotational velocity of the electric motor does not overshoot, and the rotation of the electric motor can immediately be controlled at a target (necessary) rotational velocity stable.
A power steering apparatus of the present invention for assisting steering by utilizing a hydraulic pump driven by an electric motor as a generating source of a hydraulic pressure, is characterized by including: a rotational velocity detector for detecting a rotational velocity of the electric motor; a first driving quantity determinator for determining a quantity of driving electricity such that the rotational velocity detected by the rotational velocity detector is to be a first rotational velocity, on the occasion of starting of the electric motor; and a second driving quantity determinator for determining a quantity of driving electricity, which gradually increases, after the electric motor is started by the quantity of driving electricity determined by the first driving quantity determinator, until the rotational velocity detected by the rotational velocity detector reaches a second rotational velocity, wherein the electric motor is driven by the quantity of driving electricity determined by the first and second driving quantity determinators.
In this power steering apparatus, the hydraulic pump driven by the electric motor is utilized as a generating source of a hydraulic pressure so that the steering is assisted, and the rotational velocity detector detects the rotational velocity of the electric motor. On the occasion of starting of the electric motor, the first driving quantity determinator determines a quantity of driving electricity so that the rotational velocity is to be the first rotational velocity. After the electric motor is started by the quantity of driving electricity determined by the first driving quantity determinator, the second driving quantity determinator determines a gradually increasing quantity of driving electricity until the rotational velocity detected by the rotational velocity detector reaches the second rotational velocity, while the electric motor is driven by the determined quantities of driving electricity.
Another power steering apparatus of the present invention for driving a hydraulic pump which generates a hydraulic pressure for steering assistance by an electric motor is characterized by including: a rotational velocity detector for detecting a rotational velocity of the electric motor; and a driving quantity determinator for determining a quantity of driving electricity of the electric motor based on the rotational velocity detected by the rotational velocity detector, wherein the driving quantity determinator determines the quantity of driving electricity so that the rotational velocity becomes a first rotational velocity on the occasion of starting of the electric motor, and the driving quantity determinator gradually increases the quantity of driving electricity after the electric m
Kaji Hiroaki
Sakamaki Masahiko
Darby & Darby
Johnson Brian L.
Koyo Seiko Co. Ltd.
Yeagley Daniel
LandOfFree
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