The present invention relates generally to electrophotographic imaging devices, and, more particularly, to providing power management for optimum fuser performance.
Electrophotographic marking is a well-known, commonly used method of copying or printing documents. Generally, the electrophotographic process includes charging a photoconductive member to a substantially uniform potential so as to sensitize the surface thereof. A charged portion of the photoconductive surface is exposed at an exposure station to a light image presentation of a document to be printed or reproduced. That light image discharges the photoconductor, creating an electrostatic latent image of the desired document on the photoconductor""s surface. Toner particles are then deposited on to that latent image, forming a toner image. The toner image is subsequently transferred from the photoconductor onto a substrate, such as a sheet of paper or other print medium. The transferred toner image is then fused to the substrate, usually using heat and/or pressure, thereby creating a permanent image so as to form a xe2x80x9chardcopyxe2x80x9d of the desired document. The surface of the photoconductor is then cleaned of residual developing material and recharged in preparation for the production of another image.
When fusing toner onto a substrate it is beneficial to heat the toner to a point where the toner coalesces and becomes tacky. The heat causes the toner to flow into the fibers or pores of the substrate. Adding pressure increases the toner flow. Then as the toner cools it becomes permanently attached to the substrate. To produce the heat and pressure for fusing, most fusers include a heated element and a pressure-inducing element that act together to form a nip. When a toner bearing substrate passes through that nip, heat from the heated element and pressure within the nip fuses the toner with substrate.
One type of fuser uses a heated roller, called fuser roller, and a nip-forming roller call a backup or pressure roller. Fuser rollers have been heated in different ways, including the use of an internal radiant heater, inductive heating, and by an internal resistive heating element. While fusers having a fuser roller and a backup roller have been very successful, they generally suffer from at least one significant problem: excessive warm-up time. When a typical prior art fuser roller using machine is initially turned on, or recovering from a xe2x80x9csleepxe2x80x9d mode, it might take several minutes for the fuser roller to warm-up to a point at which fusing can be performed. Furthermore, to conserve energy and to prolong the life of various internal components it is beneficial to remove power from the fuser roller heater when the fuser roller is not being used. However, it could then take several more minutes to re-heat the fuser roller. These delays are highly objectionable.
The temperature of the fuser is critical. In order to provide a printer, such as a laser printer, that better accommodates a wide variety of print medium, lasers printers have been developed that allow a user to control the fuser temperature as a function of the print media type and other printer environmental conditions, such as ambient temperature and media moisture content. To provide quick response to fuser temperature change demand, the printer power supply must be capable of providing sufficient power when it is required.
The demands on a printer power supply are varied and heavy, especially at initially power-up. The fuser, for example, typically places a high demand, especially at initial power-up, on the power supply. Further, in some conventional printers, especially more complex, high end printers, instantaneous power consumption can suddenly jump to very high values with respect to the printer power supply output current rating. This situation would be exacerbated if fuser would also be energized during that same time interval. Therefore, the printer power supply output rating was required to be quite large as compared to its xe2x80x9cnormalxe2x80x9d output loading during standard operating conditions of the printer. To reduce the cost of a printer, efforts have been made to reduce the size of the power supply by reducing peak power consumption.
Reducing peak power consumption in electrical systems has been practiced for many years with respect to industrial plants and commercial buildings. It is also known to purposefully control the initial energization of multiple printers and various electrical devices within a printers, such as paper-handling devices. For example, it is known to delay the initial energization of one or more printers, or of the fuser in one or more printers, in a group of multiple printers so as to not exceed the capacity of a circuit power source. It is also known to control the operation of printer paper-handling devices so as to prevent the energization of certain devices during the same time interval to reduce the peak power consumption being drawn from the printer power supply.
According there is a need for a printer that purposefully controls the energization of various electrical devices, both during initial power-up and normal operation of the printer, such that the printer power supply can provide sufficient power at all times to meet the demands of the fuser.
In a preferred embodiment, the present invention provides fuser power management logic that purposefully controls the energization of various electrically powered components in an electrophotographic imaging device, both during initial power-up and normal operation of the imaging device, thereby ensuring that sufficient power is available to the fuser to provide a quality image output and efficient operation of the imaging device.
A preferred embodiment of the present invention provides an electrophotographic imaging device includes a power supply providing electrical power to the electrically powered components of the imaging device and an image fixing device. A controller includes power management circuitry which manages the distribution of electrical power to the electrically powered components and to the image fixing device. The power management circuitry monitors both the total amount of electrical power provided by the power supply to the imaging device components and the electrical power provided to individual components. Whenever, due to print job requirements, for example, a requirement to provide additional electrical power to the image fixing device exists, the power management circuitry provides electrical power first from surplus electrical power where surplus electrical power is the difference between the capacity of the power supply and the total amount of electrical power being provided by the power supply. In the event insufficient surplus electrical power is available to meet the requirement for increased electrical power, the power management circuitry will provide electrical power secondly by selectively redirecting electrical power from one or more electrically powered components to the image fixing assembly.
In another preferred embodiment of the present invention, during an initial start-up phase or recovery from a standby or sleep mode of an electrophotographic imaging device, for example, the power management circuitry provides the maximum electrical power available to the image fixing device while delaying the application of electrical power to one or more of the remaining electrically powered components until the expiration of a predetermined time interval. Alternatively, the power management circuitry will provide the maximum amount of electrical power available to the image fixing device while delaying the application of electrical power to one or more of the remaining electrically powered components until the image fixing device has been heated to a desired operating temperature.
In a preferred embodiment, the present invention may be implemented as a method of managing the electrical power provided to an image fixing assembly utilizing the apparatus described above. The method preferably includes monitoring the total amount of electrical power provided by a power supply to electrically powered components of an electrophotographic imaging device, and providing additional electrical power to the image fixing assembly when a requirement for increased electrical power for the image fixing assembly exists, first from surplus electrical power where surplus electrical power is the difference between the capacity of the power supply and the total amount of electrical power being provided by the power supply.
Secondly, in the event insufficient surplus electrical power is available to meet the requirement for increased electrical power, selectively redirecting electrical power from one or more electrically powered components to the image fixing assembly.
Other embodiments and advantages of the present invention will be readily appreciated as the same become better understood by reference to the following detailed description, taken in conjunction with the accompanying drawings. The claims alone, not the preceding summary or the following detailed description, define the invention.