Data processing: measuring – calibrating – or testing – Measurement system in a specific environment – Mechanical measurement system
Reexamination Certificate
1999-07-23
2002-03-12
Grimley, Arthur T. (Department: 2852)
Data processing: measuring, calibrating, or testing
Measurement system in a specific environment
Mechanical measurement system
C073S862280, C073S862321, C073S862326, C073S862195, C324S076820, C702S033000
Reexamination Certificate
active
06356847
ABSTRACT:
FIELD AND BACKGROUND OF THE INVENTION
The invention relates to a method and a device for determining the torque exerted on a body of revolution capable of being driven rotatably about an axis of rotation, in particular on the bottom bracket bearing shaft of a bicycle, with a first and a second measurement generator which are arranged on the body of revolution at an axial distance or a radial distance from one another and which consist of rings radially surrounding the body of revolution and composed of fields having an alternately different signal behavior, the number of fields of the two rings being identical, with a first measurement transducer assigned to the first measurement generator and with a second measurement transducer assigned to the second measurement generator, said measurement transducers both supplying output signals, from which first and second square-wave signals are formed, the average torque being determined from the distances between edges of the first and second square-wave signals over one complete revolution of the body of revolution.
A method and a device of the type initially mentioned are known from DE 40 38 413 A1. Here, one of the rings with the fields having an alternately different signal behavior is interrupted by a reference mark. This means that a measurement cycle can commence only whenever the reference mark moves past the measurement transducer assigned to it. This may mean, in an extreme situation, that an almost complete revolution of the body of revolution must first take place before a measurement cycle can commence. Furthermore, only one support point in any torque profile within one complete revolution is detected by means of this method. The calculation of the average torque or work during one or more complete revolutions can therefore be carried out correctly only when the torque is constant.
Furthermore, it is difficult to detect very small angles of rotation and low torques on the body of revolution, since limits are set by the manufacturing tolerances of, in particular, the rings surrounding the body of revolution and having the fields.
SUMMARY OF THE INVENTION
The object of the invention is, therefore, to provide a method and a device of the type initially mentioned, by means of which, along with the simple design, a measurement cycle is started, essentially without delay, after the commencement of an application of torque and it becomes possible to detect the actual average torque and the work performed.
This object is achieved, according to the invention, in that the fields having an alternately different signal behavior form uninterrupted rings, in that, over one or more complete revolutions of the nonloaded torque-free body of revolution, the edge distances T
ml
between specific edges of the first square-wave signals and the distances &agr;
ml
of specific edges of the second square-wave signals from specific edges of the first square-wave signals are in each case summed up and the torque-free ratio
&bgr;
ml
=(&agr;
ml1
+&agr;
ml2
+ . . . &agr;
min
)/ (T
ml2
+T
ml2
+ . . . T
min
)+&Sgr;&agr;
min
/&Sgr;T
min
is formed, in that, over one or more complete revolutions of the body of revolution loaded with the torque to be determined, the edge distances T
m
between specific edges of the first square-wave signals and the distances am of specific edges of the second square-wave signals from specific edges of the first square-wave signals are in each case summed up and the applied-torque ratio
&bgr;
m
=(&agr;
m1
+&agr;
m2
+ . . . &agr;
mn
)/ (T
m1
+T
m2
+ . . . T
mn
)=&Sgr;&agr;
mn
/&Sgr;T
mn
is formed, in that the work on the applied-torque body of revolution is determined from the equation
W=∫
0
2&pgr;
Md&phgr;={overscore (M)}·2&pgr;≈(&bgr;
m
−&bgr;
ml
)·k,
k being a calibration constant and &phgr; being the angle of rotation of the body of revolution, and in that the average torque exerted on the body of revolution is determined from the equation
{overscore (M)}=W/2&pgr;≈(&bgr;
m
−&bgr;
ml
)·k/2&pgr;.
The distances T
ml
, T
ml
, &agr;
ml
and &agr;
m
as well as the time t may, at the same time, be detected by means of a high-accuracy counter having a high oscillator frequency. The torque-free ratio &bgr;
ml
produces a reference value which already contains tolerance-induced deviations in the fields having a different signal behavior and the distances &agr;
ml
. This makes it possible, on the one hand, to produce the fields cost-effectively and at low outlay, since there are no high tolerances which have to be adhered to. On the other hand, the rings radially surrounding the body of revolution may be arranged on the latter, with their fields being assigned to one another in any way desired, thus making production considerably simpler and cheaper, and requiring no adjustment work. Since a measurement cycle always extends over one or more complete revolutions of the body of revolution, there is not only compensation of the tolerance-induced deviations of the fields, but a measurement cycle can also commence at any specific edge of the first square-wave signals, which means that, if there is a corresponding number of fields, the first measurement cycle already starts almost immediately after the commencement of the introduction of torque. There is no need to wait until a reference mark triggers a signal.
Furthermore, due to tolerance compensation, it is also possible to determine very low torques with high accuracy.
Over and above the average torque, the average power can also be formed according to the equation
{overscore (P)}=W/t=(&bgr;
m
−&bgr;
ml
)·k/t,
t being the time of one or more complete revolutions of the body of revolution.
So that variations in the application of torque to the body of revolution can be indicated in a simple way, one or more further measurement cycles may be carried out automatically after a measurement cycle has elapsed.
Since the calibration constant and the torque-free ratio &bgr;
ml
are invariable quantities, in order to reduce the computer capacity, the calibration constant k and/or the torque-free ratio &bgr;
ml
may be determined in a separate procedure and stored retrievably as constant storage values for each torque determination.
In order to form the torque-free ratio &bgr;
ml
or the applied-torque ratio &bgr;
m
, the edge distances between the adjacent equally directed or the adjacent oppositely directed edges of the first square-wave signals may be summed up.
In the same way, in order to form the torque-free ratio &bgr;
ml
or the applied-torque ratio &bgr;
m
, the distances of specific edges of the first square-wave signals from the adjacent equally directed or adjacent oppositely directed edges of the second square-wave signals may be summed up.
If very high torques are applied to the body of revolution, the torsion of the latter may lead to a distance &agr;
m
extending beyond the end of the distance T
m
assigned to it into the next following distance T
ml
. This would result in false determination of the torque. In order to avoid such false torque determination, when the torque-free ratio &bgr;
ml
is formed, the distances &agr;
ml
between specific edges of the second square-wave signals may be compared with a specific predetermined edge distance &agr;
max
and, if &agr;
ml
>&agr;
max
is detected, the measurement cycle may be discontinued and a new measurement cycle may be commenced, in which, instead of the distances &agr;
ml
, those distances &agr;
ml
′ are summed up, the start of which corresponds to the start of &agr;
ml
and the ends of which are those oppositely directed edges of the second square-wave signals which precede the ends of the distances &agr;
ml
.
In order to avoid further torque detection when the body of revolution is at a standstill or virtually at a standstill after torque has been detected, after the commencement of a measurement cycle for determining the torque the instantaneous rotational speed or angular speed o
Farber Martin A.
Grimley Arthur T.
Le John
LandOfFree
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