Photocopying – Projection printing and copying cameras – Identifying – composing – or selecting
Reexamination Certificate
1999-01-19
2001-01-16
Adams, Russell (Department: 2851)
Photocopying
Projection printing and copying cameras
Identifying, composing, or selecting
C355S069000, C355S077000, C399S037000
Reexamination Certificate
active
06175402
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a load control apparatus for use in an image forming apparatus, such as a copier, a facsimile, a printer and a hybrid machine having a plurality of functions of the image forming apparatus, and in particular, relates to a load control apparatus capable of avoiding damage to a load of the image forming apparatus.
2. Discussion of the Background Art
A variety of technologies have been developed that avoid damage to a load, such as a motor and so on, by stopping the load in an emergency to keep the load operating safely. For example, the below-described technologies are well known.
As described in the Japanese Laid Open Patent Publication No. 5-286642, a sheet cassette in an image forming apparatus is moved by a motor between a setting position and a removing position. A sensor is provided to detect an obstacle that may exist between the setting position and the removing position. The motor is controlled to stop driving when the sensor detects the obstacle.
Further, as described in the Japanese Laid Open Patent Publication No. 5-304718, a sensor is provided to measure an amount of current. The sensor outputs a signal when a current larger than a rated current flows. A message or a mark indicating an overload state is displayed when the signal is output. A current fuse is then promoted to melt down, since the current flow is amplified through a safety circuit which avoids problems from occurring with parts of the motor.
Further, as described in the Japanese Laid Open Patent Publication No. 6-6996, a sensor is provided to detect a reverse revolution of a motor that drives a reciprocating device. The sensor outputs a signal when the motor does not revolve in a reverse direction within a prescribed time period after the reverse revolution is commanded. The motor is controlled to stop when the sensor does not output the signal.
In recent years, a plurality of motors, such as stepping motors, are increasingly employed in an image forming apparatus and so on. A base plate that supports the stepping motor is directly mounted on mold parts of the image forming apparatus. Thus, if for some reason the stepping motor is supplied with power for a long time, the stepping motor may generate heat, thereby having an abnormally high temperature. As a result, the mold parts may melt and become deformed. Further, the operational safety features required of the stepping motor may be lost.
In addition, if a central processing unit (hereinafter referred to as a CPU) of a microcomputer of the image forming apparatus controls a plurality of stepping motors by itself, almost all of the operations of the CPU are occupied by control operations for the stepping motors. Thus, a hardware circuit, such as an application specific integrated circuit (hereinafter referred to as an ASIC) has sometimes been recently employed to control the stepping motor for the CPU.
In a case of using such an ASIC, no problem occurs when a prescribed allowable amount of power supply voltage is applied having an alternating current (hereinafter referred to as AC), for example, which is more or less 15 percent of a rated voltage for the case of a copier.
However, if a plurality of copiers employing the ASIC are connected to an AC power supply constituted by one circuit, electrical power lower than the prescribed allowable range may be supplied to each of the copiers. Accordingly, a voltage, which is outside the allowable range, may be applied to the microcomputer and the ASIC. As a result, the microcomputer and the ASIC sometimes operate in an unexpected manner. For example, the ASIC may unexpectedly continue to output signals for driving the stepping motor.
SUMMARY OF THE INVENTION
Therefore, an object of the present invention is to provide an image forming apparatus having a novel load control apparatus. One example of an image forming apparatus having a load control device includes a load that executes a prescribed image forming process, a relay that selectively connects the load with a power supply, and a central processing unit that outputs a plurality of control signals. Also included is an application specific integrated circuit that outputs a load driving signal to the load in response to a control signal sent from the central processing unit, an output condition observing device that observes an output condition of the application specific integrated circuit, and a timer that starts counting pulses when the output condition is active and does not start counting pulses when the output condition is not active. In addition, the load stops driving when the timer has counted a prescribed time period.
In another embodiment, a load stops driving when a relay that connects a power supply with the load is turned OFF. The relay is turned OFF when a timer that counts pulses, during an active output condition of an application specific integrated circuit, has counted a prescribed time period.
In still another embodiment, a load stops driving when an initializing device initializes an application specific integrated circuit. The initializing device initializes the ASIC when a timer that counts pulses, during an active output condition of the ASIC, has counted a prescribed time period.
In still another embodiment, a load stops driving when a main power supply stops applying power to an application specific integrated circuit. The main power is stopped when a timer that counts pulses, during an active output condition of an ASIC, has counted a prescribed time period.
In still another embodiment, provided is an output condition observing device having a function of observing an operation condition of the image forming apparatus. A relay quickly disconnects the load with a power supply when a timer that counts pulses, during an active output condition of the application specific integrated circuit, has counted a prescribed time period and an image formation is not executing, or after the timer has counted the prescribed time period and the image formation has completed.
In still another embodiment, an initializing device initializes an application specific integrated circuit and a load stops driving only when a timer that counts pulses, during an active output condition of the application specific integrated circuit, has counted a prescribed time period and an image formation is not executing, or after the timer has counted the prescribed time period and the image formation has completed.
In still another embodiment, provided is an output condition observing device including a function of observing an operation condition of the image forming apparatus. A load stops driving only when a main power supply is not applied to the application specified integrated circuit, a timer that counts pulses, during an active output condition of the application specific integrated circuit, has counted a prescribed time period, and an image formation is not executing, or after the timer has counted the prescribed time period and the image formation has completed.
REFERENCES:
patent: 5710955 (1998-01-01), Nishimura et al.
patent: 5-19373 (1993-01-01), None
patent: 5-49158 (1993-02-01), None
patent: 5-289572 (1993-11-01), None
patent: 6-130853 (1994-05-01), None
patent: 61-175702 (1996-08-01), None
Adams Russell
Kim Peter B.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Ricoh & Company, Ltd.
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