Electricity: motive power systems – Limitation of motor load – current – torque or force
Reexamination Certificate
2002-10-10
2004-05-25
Leykin, Rita (Department: 2837)
Electricity: motive power systems
Limitation of motor load, current, torque or force
C318S432000, C701S041000
Reexamination Certificate
active
06741053
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a steering control device for use in an automobile or the like.
2. Description of the Related Art
There are various methods for realizing a torque sensor for detecting a steering torque in a steering system of an automobile or the like. In particular, a variety of methods have been proposed for a signal processing unit that converts the detected steering torque into an electrical signal.
FIG. 11
is a block diagram showing a signal processing circuit in a typical conventional torque sensor disclosed in Japanese Patent No. 3051903, for example.
The torque sensor of this conventional technique includes, as a torque detecting unit mounted to a steering column, a torsion bar for converting the steering torque into a torsion angle, a torque detecting coil for converting the torsion angle converted by the torsion bar into an inductance value, and a temperature compensating coil for compensating for a temperature characteristic of the torque detecting coil.
Further, as a signal processing circuit connected to each coil, the torque sensor is provided with an exciting circuit for each coil, a differential amplifying circuit to compensate for the temperature characteristic of the coil, and a wave detecting circuit for detecting a steering torque signal.
Hereinafter,
FIG. 11
is used to explain the signal processing circuit of the present torque sensor in more detail. In
FIG. 11
, reference numeral
12
is the torque detecting coil and reference numeral
13
is the temperature compensating coil for compensating the temperature characteristic of the torque detecting coil
12
.
Reference numeral
14
is an oscillating circuit for oscillating an alternating voltage of a given frequency and reference numeral
15
is a reference voltage circuit for generating a reference voltage. The torque detecting coil
12
and the temperature compensating coil
13
are driven and excited at a given frequency based on the outputs of the oscillating circuit
14
and the reference voltage circuit
15
.
Further, reference numeral
16
is the differential amplifying circuit for reading out the difference between the terminal voltages of the torque detecting coil
12
and of the temperature compensating coil
13
to compensate the temperature characteristic of the torque detecting coil
12
, and also to amplify the difference between the terminal voltages.
Reference numeral
17
is a synchronous timing circuit for outputting a timing signal in accordance with the given frequency alternating current outputted from the oscillating circuit
14
. Reference numeral
18
is the detecting circuit for eliminating frequency elements that are driven by the oscillating circuit
14
from the amplifying circuit
16
output signal, based on the timing outputted by the synchronous timing circuit
17
, to obtain the steering torque signal.
FIG. 12
shows waveforms of each part in the signal processing circuit in the conventional torque sensor as described above. In
FIG. 12
, (a) indicates a waveform V
o
of an alternating voltage signal of a predetermined frequency, which is output from the oscillating circuit
14
. In
FIG. 12
, (b) is a timing signal V
T
produced when the alternating voltage signal waveform V
o
goes through the synchronous timing circuit
17
and is inputted into the detecting circuit
18
.
Here, in
FIG. 12
, (c) through (f) indicate waveforms at each part when a steering wheel not shown in the diagram is rotated to the right, for example, and torque is applied to the steering column.
A solid line in (c) shown in
FIG. 12
indicates an output voltage V
2
from the circuit with the torque detecting coil
12
. A broken line in (c) shown in
FIG. 12
indicates an output voltage V
1
from a circuit with the temperature compensating coil
13
. The voltage difference between the output voltages V
1
and V
2
is amplified by the differential amplifying circuit
16
as output voltage having an alternating current waveform V
3
in (d) shown in FIG.
12
.
Further, in (e) shown in
FIG. 12
, detection of the alternating current waveform V
o
is performed by the detecting circuit
18
when the timing signal V
T
is positive, whereby an output voltage V
4
having pulsating flow waveform is obtained from the voltage during a positive period of the alternating current waveform V
3
.
In (f) shown in
FIG. 12
, the output voltage V
4
is smoothed and a voltage level V
L
, which is equivalent to an average value of the output voltage V
4
, is detected at a level that is higher than a non-steering time voltage level V
N
discussed below.
Similarly, in
FIG. 12
, (g) through (j) indicate waveforms at each part when the steering wheel, which is not shown in the diagram, is rotated to the left and torque is applied to the steering column. In (j) shown in
FIG. 12
, the output voltage V
4
is smoothed and a voltage level V
L
, which is equivalent to an average value of the output voltage V
4
, is detected at a level that is lower than the non-steering time voltage level V
N
discussed below.
Next, since the torque is not applied at a time when the steering wheel is not being steered, the output voltages V
1
and V
2
have identical voltage waveforms, as in (k) shown in FIG.
12
. As a result, the difference voltage at the differential amplifying circuit
16
is not generated, as in (l) shown in
FIG. 12
, and a change does not occur at the detecting circuit
18
, as in (m) shown in FIG.
12
. Accordingly, the voltage level becomes a voltage level V
N
, which is lower than the smoothed output level V
H
obtained when the above-mentioned right-rotation steering is performed, but is higher than the voltage level V
L
obtained when the left-rotation steering is performed, as in (n) shown in FIG.
12
.
As described above, in the signal processing circuit in the conventional torque sensor, the temperature characteristic of the torque detecting coil
12
is compensated so that the steering torque signals having the voltage levels shown in (f), (j) and (n) shown in
FIG. 12
are detected.
In the torque detecting unit in the conventional steering control device described above, even when the identical construction such that it is composed of the torque detecting coil and the temperature compensating coil is the same (unchanged), various methods may be considered for constructing the circuits that excite the coils and detect the terminal voltages in addition to the above-mentioned conventional technique. Therefore, various types of circuits have been proposed by each torque sensor manufacturer.
As a result, when the torque sensor composed of the circuits designated by the torque sensor manufacturers is incorporated into the torque detecting unit of the steering control device, the number of models necessary for performing signal processing on the output signals from the torque detecting unit increases, so that a vast number of development steps and management steps becomes necessary.
SUMMARY OF THE INVENTION
The present invention has been made to solve the above-mentioned problems, and has as an object to realize a steering control device which is capable of handling a variety of torque sensors with the same single signal processing circuit, and in which a cost increase is suppressed while taking sufficient failsafe measures.
A steering control device according to the present invention comprises: a torque sensor for detecting a signal corresponding to a steering torque in a steering system; a first microcontroller for outputting a steering torque signal equivalent to the steering torque; a second microcontroller for controlling an actuator based on the steering torque signal; actuator driving means for driving the actuator controlling the steering system; and storage means in which a steering torque neutral point compensation data is stored in advance. Also, the first microcontroller compensates a neutral point of the steering torque signal based on the neutral point compensation data stored in the storage means.
Also, a steering control device com
Kifuku Takayuki
Ohmae Katsuhiko
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