Metal deforming – With use of control means energized in response to activator... – Metal deforming by use of roller or roller-like tool element
Reexamination Certificate
2000-12-26
2002-10-15
Tolan, Ed (Department: 3725)
Metal deforming
With use of control means energized in response to activator...
Metal deforming by use of roller or roller-like tool element
C072S008300, C072S010100, C072S010800, C072S011100
Reexamination Certificate
active
06463775
ABSTRACT:
TECHNICAL FIELD
The present invention relates to methods and apparatuses for detecting chattering in cold rolling mills. In particular, the present invention relates to a method and an apparatus suitable for detecting chattering, which occurs during cold rolling of a steel strips in a cold rolling mill.
BACKGROUND ART
It has been conventionally known that a vibration phenomenon of a rolling mill called chattering occurs in some cases during cold rolling of a strip (for example “Atsuen Hyakuwa” (various stories about rolling) by Suzuki in “Kikai no Kenkyu (Studies of Machines)” published by Yokendo, Vol. 48, No. 5, pp. 583-588). When the amplitude of the vibration is small, lateral stripes formed at a certain pitch in a direction perpendicular to the rolling direction are merely observed on both front and back sides of the rolled strip. When the amplitude of the vibration is large, however, the thickness of the rolled sheet periodically varies. In the case of a significant variation in the thickness, the minimum thickness of the strip becomes even a half or less of the maximum thickness. When the amplitude of the vibration is more significant, the rapture of the strip may occur due to a further increased variation in the thickness.
FIG. 1
shows an example of observed thickness offset (&Dgr;t) of a cold-rolled strip which is rolled when chattering occurred. Periodical thickness variations occur in the longitudinal direction (L) of rolling. Among portions having such thickness variations, segments (hatched portions in the drawing) outside the tolerance limit are discarded as failure portions in the subsequent step or in an intermediate step before the product is shipped. That is, a decrease in yield and an extra maintenance operation may cause deterioration of production cost.
When the rupture of the strip occurs, the rolling line must be unavoidably stopped for a long time, resulting in significant deterioration of production efficiency.
Thus, the detection of the chattering phenomena is important. In many cases of chattering, initial vibrations with small amplitudes develop into vibrations with larger amplitudes within 2 to 3 seconds. Thus, in daily operations, the initiation of the chattering must be highly sensitively and rapidly detected to perform any countermeasure, for example, deceleration of the rolling speed.
Various methods and apparatuses have been proposed for detecting chattering.
For example, Japanese Examined Patent Application Publication No. 5-87325 discloses a method for detecting the occurrence of chattering when a difference in the thicknesses which are simultaneously observed at two or more points in the longitudinal direction of the material to be rolled exceeds a predetermined value. The measurement of the thickness is performed at an interval which is substantially the half the pitch of the generated variation in the thickness. Herein, it is known that the variation in the thickness of the rolled strip due to chattering during cold rolling is 1 to several &mgr;m and the period of the variation is several tens of msec. Thus, the thicknessmeter must have high detecting resolution and a short response time. Thicknessmeters satisfying these two requirements are considerably expensive. According to this method, two radiation thicknessmeters being expensive apparatuses must be proximately installed at a position for originally installing one apparatus. Thus this method has a problem of increased facility cost.
Japanese Unexamined Patent Application Publication No. 8-141612 discloses a method for detecting chattering using detecting signals from a vibration sensor provided in a rolling mill. The detecting signals are processed using a filter having transmission characteristics which are set based on each operational condition of the rolling mill.
Japanese Examined Patent Application Publication No. 6-35004 discloses a method for detecting chattering using signals obtained by filtering the output from a vibration velocity sensor which is mounted in a housing of a cold rolling mill. The filter transmits only vibrations in a natural frequency range of the rolling mill.
Japanese Unexamined Patent Application Publication No. 8-108205 discloses a method in which vibration parameters of the rolling mill based on the observed data and rolling parameters of the rolling mill are subjected to a frequency analysis. When a frequency component which is an integer multiple of the fundamental frequency exceeds a predetermined value, the occurrence of chattering is determined. The vibration parameters of the rolling mill are detected during the operation using vibration detectors which are installed at least at one position of the rolling mill. The vibration parameters, which are detected and analyzed, are a vibration displacement, a vibration velocity, and vibration acceleration at each position. The rolling parameters are a tension, a rolling torque, and a rolling speed of the rolling mill. The fundamental frequency is obtained by calculating the natural frequency of the mill, and inherent vibration frequencies which are generated by interlocking of gears, failure of a bearing, unsuccessful coupling between a spindle and a roll, and flaws of a roll.
In any of the above conventional technologies, the detection of chattering is performed based on detected signals from vibration sensors at one or more positions of the rolling mills. These sensors, however, detect the vibrations due to the mechanisms of the rolling mill, in addition to the vibrations due to the chattering. That is, when the frequency components of vibrations of the mechanisms of the rolling mill include in the frequency range for the frequency components of the chattering, erroneous detection of the chattering occurs.
In the conventional technologies, outputs from a plurality of vibration sensors and the frequencies of the rolling parameters must be analyzed at high speeds. Thus, the scale and the cost of the apparatus are unavoidably increased. Moreover, the vibration based on the abnormal mechanical system in the rolling mill and the vibrations of the resulting rolling parameters are merely requirements regarding the factors for generating the chattering. Thus, the occurrence of chattering due to other factors may be missed. On the other hand, an abnormal mechanical system before chattering or vibrations of the rolling parameters may lead erroneous detection of chattering. As a countermeasure against this problem, for example, Japanese Unexamined Patent Application Publication No. 8-108205 discloses a method for momentarily analyzing or calculating the frequencies based on the vibrations of individual components and the outputs of the rolling parameters of the rolling machine and the theoretical vibration based on the abnormal mechanical system. In this method, however, a vibration sensor must be installed in a mill housing or in the vicinity thereof. In this case, the vibration sensor is placed in adverse environments, for example, oil in the mill and roll-cooling water. Such adverse environments result in severe deterioration of the vibration sensor and the replacement of the vibration sensor is a bother.
On the other hand, the applicant proposed a method by an acoustic measurement, which is different from the above methods, in Japanese Unexamined Patent Application Publication No. 60-137512.
In general, vibration of a substance vibrates the air in the vicinity thereof and propagates the vibration as sound. The acoustic measurement is generally performed by detecting the pressure fluctuation of the air at a predetermined position. An acoustic sensor detects and signalizes this pressure fluctuation and the resulting signals are acoustic signals. A microphone is a typical acoustic sensor and outputs the acoustic signals as electrical signals. The sound has frequency components whereas the acoustic sensor exhibits frequency characteristics, such as a detectable frequency range and frequency-dependent sensitivity. Thus, the acoustic signals change depending on the acoustic sensor used. The time variation of the
Kodama Toshifumi
Torao Akira
Kawasaki Steel Corporation
Tolan Ed
LandOfFree
Method and apparatus for detecting chattering in cold... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus for detecting chattering in cold..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for detecting chattering in cold... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2938583