Device for calculating a torque of a rotating member

Details Device for calculating a torque of a rotating member Device for calculating a torque of a rotating member

2000-10-31

2002-10-08

Noori, Max (Department: 2855)

Measuring and testing

Dynamometers

Responsive to torque

Reexamination Certificate

active

06460422

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a torque measuring device for measuring a rotation rate and a torque of a a member of body to be measured such as rotating machine with a non-contact access at a remote portion.
A conventional art for measuring the torque of the rotating machine with a non-contact access is disclosed in Japanese Patent Laid-open Publication No. HEI 6-34462 as “a torque detecting device”. This torque detecting device detects the torque generated in a shaft portion of a power transmission device of an automobile, for example.
FIG. 29
shows an arrangement of this torque detecting device. As shown in
FIG. 29
, a torque detecting device is provided with a linear optical reflector
2
for efficiently reflecting a light on an outer circumferential surface of a shaft
1
as a body of rotation to be measured. A first detecting portion
3
and a second detecting portion
4
are disposed so as to be opposed to the linear optical reflector
2
and are provided with light emitting elements
3
a
and
4
a,
and light receiving elements
3
b
and
4
b,
respectively. These detecting portions
3
and
4
has structures for generating lights towards different two positions in an axial direction of the shaft
1
by the light emitting elements
3
a
and
4
a
and to detect the reflected lights by the light receiving elements
3
b
and
4
b.
Thus, rotation of the shaft
1
allows the light receiving elements
3
b
and
4
b
to detect signals obtained from the optical reflector
2
for every rotation period. The detected signals are formed by a waveform adjusting circuit to gain a pulse signal from the light receiving element
3
b
and a pulse signal of the light receiving element
4
b,
as shown in
FIG. 30. A
period T of the pulse signal represents the rotation time for the period. Further, by using a delay time t of the pulse signal of the receiving element
4
b
against the pulse signal of the receiving element
3
b,
the torque F
t
can be calculated according to the following mathematical equation (1) as below.
(Mathematical Equation 1)
F
t
=2&pgr;
Kx·t
/T  (1)
K: twisted spring constant of shaft
1
X: measured distance between two positions
Thus, the above-mentioned torque detecting device irradiates the light from the light emitting elements
3
a
and
4
a
to the shaft
1
and receives the light reflected by the optical reflector
2
at the light receiving elements
3
b
and
4
b.
Then, based on the detected signals from the optical reflector
2
as shown in
FIG. 31
, the torque detecting device generates a pulse signal shown in
FIG. 30
so as to calculate the rotation rate and the torque from a period of this pulse signal.
The conventional art for measuring the torque of the rotating machine is disclosed in Japanese Patent Laid-open Publication No. HEI 7-325095 as “a rotation rate measuring device”.
FIG. 32
shows a diagram of this rotation rate measuring device. In
FIG. 32
, only major portions are given with reference numerals. In the rotation rate measuring device shown in
FIG. 32
, a light from a laser diode
5
, which is generated in shape of pulse at a predetermined frequency, is made into a parallel light by a collimeter lens
6
, and the light is then irradiated as the parallel light to a rotation member or body
7
to be measured. Since the reflecting light of the irradiated light is varied depending on irregularities
8
or the like, which are formed on the surface of the rotation body
7
, the intensity of the reflected light changes according to the rotation of the rotation member
7
.
In the rotation rate measuring device in
FIG. 32
, the thus reflected light is received by a photodiode
10
by using a lens
9
and the rotation rate is calculated through the signal processing of this received signal. In the signal processing, at first, the rotation ratemeasuring device extracts the signal of the reflected light of the laser beam, which is given with pulse modulation, by a bandpass filter (BPF)
11
. The bandpass filter (BPF)
11
passes frequency component of 500 kHz therethrough. Then, a low pass filter (LPF)
12
removes a signal component with a high frequency. After removing the signal component with a high frequency, the change of time becomes the change of intensity for the reflected light, corresponding to the rotation period of the rotation body
7
.
Next, a control circuit
13
digitizes the signal to give the fast Fourier transform action to the signal. Then, a frequency distribution can be measured as shown in FIG.
33
. The rotation frequency of the rotation body
7
becomes a frequency f
0
, which has a large distribution frequency. In this case, the rotation frequency T is
1
/f
0
.
When calculating the torque, this rotation rate measuring devices should be set on two positions. In this case, a delay time t of a detection signal shown in
FIG. 30
can be gained according to a mathematical equation (2), so that the torque can be calculated by using the following mathematical equation (1).
(Mathematical Equation 2)
t=|
1/
f
1
−1/
f
0
|  (2)
f
1
: rotation frequency, which is calculated by other rotation rate measuring device
However, in the torque detecting device mentioned hereinbefore for measuring the torque of the rotation machine with the non-contact state, a rising time of a detection signal shown in
FIG. 31
is usually defined by about several tens of &mgr;m. Accordingly, it is not possible to generate a pulse signal at an accuracy in time higher than this rising time and to obtain a frequency of the pulse signal. Therefore, in the case that the rotation rate is minutely varied for every rotation, there is a problem such that the rotation rate and the torque for every rotation is not obtainable with a high accuracy. For example, there is an expectation for a generator having an axis diameter of 850 mm and the rotation rate of 3000 rpm to obtain the torque by calculating the frequency of the pulse signal with a measuring accuracy of 100 ns for every rotation in order to monitor a generation efficiency with a high accuracy.
On the other hand, in the rotation rate measuring device mentioned hereinbefore for measuring the rotation rate of a machine with at the non-contact state, a signal corresponding to the rotation period of the rotation body
7
to be measured is extracted to be subjected to the Fourier transform, so that the rotation frequency f
0
is specified from the frequency distribution. In this device, in the case that the distribution of the rotation frequency f
0
is ideally large as shown in
FIG. 33
, it is possible to specify the rotation frequency f
0
.
However, it is general that the rotation rate of the rotation body finely varies, and as shown in
FIG. 34
, the rotation rate of the rotation body owns a distribution having a center in the rotation frequency f
0
. In the case of such frequency distribution, it is difficult to specify the rotation frequency f
0
, thus providing a problem such that the rotation rate and the torque cannot be calculated with a high accuracy by using the mathematical equations (1) and (2). Further, the described device involves a problem such that it is not possible to calculate the torque by obtaining the rotation rate for every rotation in principle in order to specify the rotation frequency f
0
from the frequency distribution.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to substantially eliminate defects or drawbacks encountered in the prior art mentioned above and to provide a torque measuring device for obtaining a rotation frequency for every rotation with a measuring accuracy higher than lOns with respect to a rotation member or body to be measured, of which the rotation rate varies minutely.
Another object of the present invention is to provide a torque measuring device capable of measuring axial change direction and axial moving amount and accurately measuring the torque even in a case where the axial change direction and the axial moving amount are different at dr

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