Electricity: measuring and testing – Fault detecting in electric circuits and of electric components – Of electrically operated apparatus
Reexamination Certificate
1999-10-04
2001-07-31
Brown, Glenn W. (Department: 2858)
Electricity: measuring and testing
Fault detecting in electric circuits and of electric components
Of electrically operated apparatus
C375S222000, C379S093320, C714S025000, C710S109000
Reexamination Certificate
active
06268733
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to analog current analysis of electromechanical components. More specifically, this invention relates to field service testing of digitally controlled electromechanical components using analog current analysis.
BACKGROUND OF THE INVENTION
Modern electrophotographic printers are complex machines that use a significant number of electromechanical devices, such as solenoids, electric motors, and relays to provide force responses. Such devices are subject to both mechanical and electrical degradation. Since low down time is critical, in the event of machine failure rapid diagnoses and repair of such printers is very important. Ideally, field service representatives would have an ability to anticipate problems so that corrective action could be taken before actual failure.
Diagnosing some electromechanical devices, in particular electric motors, using analog current signature analysis is well known. Such analysis is performed by monitoring the electrical current into a device being tested, comparing that current to a current baseline, and then determining whether the device being tested is acceptable. While beneficial, analog current signature analysis has been limited to situations where ready access is available to the device being tested.
Unfortunately, with most electrophotographic printers access to most electromechanical devices is severely limited. This precludes easy testing. Additionally, even when accessible, most electromechanical devices are not easily tested during operation since device power is applied only for short periods of time commanded by a microprocessor. Since an electromechanical device being tested might not be powered until a prior operation is performed by another electromechanical device that is controlled by another microprocessor, a very complex synchronization scheme might be required to simply test one electromechanical device.
Because of their complexity modern, high speed electrophotographic printers are often divided into discrete modules (subsystems) that intercommunicate with a master controller via a serial control bus. A typical bus might include a transmit line (Tx), a receive line (Rx), a clock line (Clk), a return line (Return) and a power line. The transmit, receive, clock, and return lines provide digital control while the power line and the return line provide power distribution.
Therefore, the ability to field-service test modular, digital-bus controlled electrophotographic printers using analog current analysis of power devices would be beneficial.
SUMMARY OF THE INVENTION
The principles of the present invention provide for field-service analog current analysis of electromechanical devices using a digital bus. A field-service instrument according to the principles of the present invention includes an interface to a digital control bus. That interface includes a current sensor for monitoring the current on a return line. The field-service instrument further includes a bus controller that applies digital control signals to the control bus via the interface. Those digital control signals cause electrical power to be applied to an electromechanical device being tested. A current monitor monitors the current drawn by the electromechanical device such that a current profile of that electromechanical device over a time is determined. The field-service instrument further includes a fault determination network that compares the current profile of the electromechanical device being tested with a baseline current profile. The fault determination network then determines whether the electromechanical device being tested is acceptable. Beneficially, the baseline current profile includes information useful for enabling the fault determination network to identify a degraded electromechanical device so that fault correction before actual failure is feasible.
REFERENCES:
patent: 4636939 (1987-01-01), Fildes
patent: 5357519 (1994-10-01), Martin et al.
patent: 6097794 (1999-02-01), Suffern et al.
Abbata Salvatore A.
Lewandowski Robert
Brown Glenn W.
Hamdan Wasseem H.
Henn David E.
Kelly John M.
Xerox Corporation
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