Patent Description:
There are electrophotographic image forming apparatuses that include, as a load that consumes electrical power, a fixing heater (fixing means) to fix a toner image on a recording medium such as transfer paper. To control the power of an image forming apparatus, for example, the power consumed by loads other than the fixing heater is detected, and the total power used by the image forming apparatus is controlled not to exceed the rated power (for example, <NUM> W) of the image forming apparatus.

For example, an image forming apparatus disclosed in <CIT> includes fixing means connected to an alternating-current (AC) power supply; a direct-current (DC) power supply having a primary side connected to the AC power supply and a secondary side connected to a load to supply DC power to the load; detection means that detects a secondary current of the DC power supply; and control means that controls power supply to the fixing means based on a detection signal of the secondary current.

The image forming apparatus disclosed in <CIT> supplies the fixing means with the amount of power calculated by subtracting the power consumption of the DC load from the rated power. However, there are variations in the power consumed by the fixing means of the image forming apparatus depending on individual difference of the fixing means. In the technology disclosed in <CIT>, power supply to the fixing means is not optimized because the individual difference of the fixing means is not considered. <CIT> discloses an induction heating apparatus for a fixing device of an image forming apparatus including a rectifying circuit for rectifying a commercial power supply, an excitation coil, a switching element for switching the supply of the output of the rectifying circuit to the excitation coil, and a switching signal output unit for outputting a switching signal for the switching element thereby supplying the excitation coil with a high frequency current. The apparatus limits a current supply time to the excitation coil in such a manner that the maximum output for induction heating is set according to the commercial power supply voltage, thereby reducing the first print time without a power consumption in excess of the rating. <CIT> discloses an image forming apparatus including a first power calculator for calculating a power consumption amount of driving load unit and a post-processing device based on at least one of measured values of a voltage and a current, which are sup- plied to the driving load unit and the post-processing device; second and third power calculators for calculating power consumption amounts of a fixing heater driving unit and a controller based on an operating state and an operating time of the image forming apparatus; and a power summing-up unit for calculating a power consumption amount of the image forming apparatus by summing up the power consumption amount calculated by the first power calculator and the power consumption amount predicted by each of the second and third power calculators. <CIT> discloses an image forming apparatus including an image forming unit for forming a toner image on a sheet of paper; a fixing unit for fixing the toner image formed on the sheet of paper by heat; a power control unit for, when power to be supplied to the fixing unit is increased, determining an amount of increase of the power; and a current limiting unit for determining whether current consumption of the image forming apparatus exceeds an upper limit value in response to an increase of the amount of increase determined by the power control unit and, if it is determined that the current consumption exceeds the upper limit value, decreasing the amount of increase of the power determined by the power control unit.

In view of the foregoing, an object of the present disclosure is to optimize power supplied to a load.

In order to achieve the above-described object, there is provided a power control device as described in appended claims. Advantageous embodiments are defined by the dependent claims.

A power control device according to claim <NUM> includes among other features measurement means for measuring electrical power supplied to a load; correction means for correcting a measurement value measured by the measurement means based on a measurement tolerance of the measurement means; and control means. The control means controls the power supplied to the load based on a corrected power value corrected by correction means and a power consumption upper limit of the load.

Advantageously, a power consumption apparatus includes the above-described power control device and the load driven with the supplied power.

Advantageously, an image forming apparatus includes the above-described power control device and a fixing heater as the load, to fix a toner image on a recording medium.

Additionally, there is provided a method for controlling power according to claim <NUM> The method includes among other features measuring, with measurement means, electrical power supplied to a load to output a measurement value; correcting the measurement value based on a measurement tolerance of the measurement means to output a corrected power value; and controlling the power supplied to the load based on the corrected power value and a power consumption upper limit of the load.

Additionally, there is provided carrier means carrying computer readable code for controlling a computer to carry out the above-described method.

Accordingly, the power supplied to the load can be optimized.

Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views thereof, embodiments according to the present disclosure are described.

The suffixes Y, M, C, and K attached to each reference numeral indicate only that components indicated thereby are used for forming yellow, magenta, cyan, and black images, respectively, and hereinafter may be omitted when color discrimination is not necessary.

The embodiments of the present disclosure relates to an electrophotographic image forming apparatus that controls power supply to a fixing heater and has the following features.

The power consumption of the fixing heater is individually detected, and the power supply to the fixing heater is controlled in accordance with the detected power consumption. As the power consumption of the individual fixing heater deviates from a design value more to the minus-side, the power supplied to the fixing heater is increased, thereby supplying the power required by the fixing heater.

<FIG> is a view illustrating an external appearance of a multifunction copier (an image forming apparatus) according to an embodiment of the present disclosure.

A multifunction copier <NUM> illustrated in <FIG> is a full-color digital copier (an image forming apparatus) having multiple functions. The multifunction copier <NUM> includes an operation board <NUM> (an operation unit), a color scanner <NUM> (a reading unit) provided with an automatic document feeder (ADF) <NUM>, and a printer unit <NUM>.

The operation board <NUM> and the color scanner <NUM> are units separable from the printer unit <NUM>. The color scanner <NUM> includes a control board having a power device driver, a sensor input, and a controller. The color scanner <NUM> directly or indirectly communicates with an engine controller and reads a document image at a controlled timing. For example, the multifunction copier <NUM> is connected to a personal computer (PC) and a private branch exchange (PBX).

Referring to <FIG>, a description is given below of a mechanism of the printer unit that functions as an image forming engine of the multifunction copier illustrated in <FIG>. The printer unit <NUM> in the present embodiment is a laser printer.

The printer unit <NUM> includes a sheet feeder unit <NUM>, an exposure device <NUM>, an image forming unit <NUM>, a toner filling section <NUM>, a primary transfer unit <NUM>, a secondary transfer unit <NUM>, a fixing device <NUM>, a conveyor <NUM>, and an output stack <NUM>.

The printer unit <NUM> in the present embodiment is a full-color image forming apparatus that employs a four-drum system (tandem system) combining a direct transfer system and an indirect transfer system. More specifically, four image forming units <NUM>, 230C, 230Y, and <NUM> that form magenta (M), cyan (C), yellow (Y), and black (K) toner images, respectively, are arranged, in this order, opposite a primary transfer belt <NUM>.

In a lower part of the printer unit <NUM>, the sheet feeder unit <NUM> is disposed. The sheet feeder unit <NUM> includes sheet feeding trays <NUM> and <NUM> that store sheets of recording media (e.g., transfer paper) and sheet feeding rollers <NUM> (conveyance rollers). A conveyance passage (conveyance guide) for conveying the sheet is formed between the sheet feeding roller <NUM> and a registration roller pair <NUM>. The sheet on top of sheets stored in the sheet feed tray <NUM> or <NUM> is conveyed by the sheet feeding roller <NUM> one by one to the registration roller pair <NUM> via a plurality of conveyance guides.

The exposure device (writing unit) <NUM> includes a light source <NUM> such as a laser diode (LD) light source. The exposure device <NUM> irradiates, with light, uniformly charged surfaces of photoconductors <NUM> to <NUM> according to optical data corresponding to a full-color image by a known laser method, thus forming latent images on the photoconductors <NUM> to <NUM>. In the present embodiment, the exposure device <NUM> employs a laser system, but an exposure device including a light emitting diode (LED) array and image forming means can be used.

The image forming units <NUM> to <NUM> includes the photoconductors <NUM> to <NUM> supported and rotatable in the direction indicated by an arrow. Around each of the photoconductor <NUM> to <NUM>, a drum cleaner <NUM>, a discharger <NUM>, a charging device <NUM>, and a developing device <NUM> are disposed.

Above the primary transfer belt <NUM> and below the output stack <NUM>, the toner filling section (storage section) <NUM> is disposed. The toner filling section <NUM> stores toner bottles (toner cartridges) 241Y, <NUM>, 241C, and <NUM> that store refill toner. There are four colors of toner, magenta, cyan, yellow, and black, and the toner bottles 241Y to <NUM> are replaceable. The toner of each color is appropriately supplied from one of the toner bottles 241Y to <NUM> to the developing device <NUM> of the corresponding color by a powder pump or the like.

Between the charging device <NUM> and the developing device <NUM>, a space is secured for passage of the light (optical data) emitted from the LD light source <NUM> of the exposure device <NUM>.

Regarding the four photoconductors <NUM> (<NUM>, 231C, 231Y, and <NUM>), structures of image forming components provided therearound are the same, differing the colors of the colorants (toners) handled by the developing devices <NUM>. In the present embodiment, the photoconductors <NUM> to <NUM> are drum-shaped, but belt-shaped photoconductors can be used.

Some of the four photoconductors <NUM> to <NUM> are in contact with the primary transfer belt <NUM> of the primary transfer unit <NUM>. In the primary transfer unit <NUM>, the primary transfer belt <NUM> is supported by and stretched between a support roller <NUM> that rotates and a drive roller <NUM> to be able to rotate in the direction indicated by arrow Y1. The primary transfer belt <NUM> has an endless (loop) shape.

Primary transfer rollers <NUM>, 254C, 254Y, and <NUM> are arranged inside the loop of the primary transfer belt <NUM> and opposed to the photoconductors <NUM> to <NUM> of corresponding colors, respectively, with the primary transfer belt <NUM> interposed therebetween.

Outside the loop of the primary transfer belt <NUM>, a first belt cleaner <NUM> to clean the primary transfer belt <NUM> is disposed. The first belt cleaner <NUM> wipes off toner remaining on the surface of the primary transfer belt <NUM> after a toner image is transferred from the primary transfer belt <NUM> onto a sheet or a secondary transfer belt <NUM>.

The secondary transfer belt <NUM> of the secondary transfer unit <NUM> is disposed on the right of the primary transfer belt <NUM> in the drawing. The primary transfer belt <NUM> and the secondary transfer belt <NUM> are in contact with each other and form a secondary transfer nip.

The secondary transfer belt <NUM> is supported by and stretched between a drive roller <NUM> and a support roller <NUM> to be able to rotate in the direction indicated by arrow Y2. The secondary transfer belt <NUM> has an endless shape (loop-shaped). A secondary transfer roller <NUM> is disposed inside (back side) of the loop of the secondary transfer belt <NUM> at position of the secondary transfer nip. A charger <NUM>, a second belt cleaner <NUM> for the secondary transfer belt <NUM>, and the like are disposed outside the loop of the secondary transfer belt <NUM>. The second belt cleaner <NUM> wipes off toner remaining on the surface of the secondary transfer belt <NUM> after the toner image is transferred to the sheet.

Above the secondary transfer unit <NUM>, the fixing device <NUM> is disposed. The fixing device <NUM> includes a heating roller <NUM> and a pressure roller <NUM> disposed opposite the heating roller <NUM>. The heating roller <NUM> includes fixing heaters <NUM> (273a and 273b in <FIG>). When the sheet carrying the toner image is conveyed between the heating roller <NUM> and the pressure roller <NUM>, the toner image is fixed on the sheet with heat and pressure.

A sheet ejection roller pair <NUM> and a guide <NUM>, which construct the conveyor <NUM>, are disposed downstream from the fixing device <NUM> in the direction of conveyance of the sheet (hereinafter "sheet conveyance direction"), and the output stack <NUM> is disposed further downstream thereof.

A description is given of operation of each unit in double-sided printing.

First, each of the image forming units <NUM> to <NUM> forms an image to be formed on one side (first side) of the sheet. More specifically, the light from the LD light source <NUM> of the exposure device <NUM> passes through optical components and reaches the surfaces of the photoconductors <NUM> to <NUM> uniformly charged by the charging device <NUM>. With the light, an electrostatic latent image corresponding to the writing information (image information corresponding to the color) is formed on the surface of each of the photoconductors <NUM> to <NUM>.

The latent images on the photoconductors <NUM> to <NUM> are developed by the developing devices <NUM>, and images rendered visible with toner (toner images) are formed and carried on the surfaces of the photoconductors <NUM> to <NUM>.

The toner images are transferred by the primary transfer rollers <NUM> to <NUM> onto the surface of the primary transfer belt <NUM> rotating in synchronization with the photoconductors <NUM> to <NUM>.

Then, the drum cleaners <NUM> clean the toner remaining on the surfaces of the photoconductors <NUM> to <NUM>, and the dischargers <NUM> discharge the surfaces of the photoconductors <NUM> to <NUM>. Thus, the surfaces of the photoconductors <NUM> to <NUM> are prepared for the next image forming cycle.

The magenta toner image is transferred from the photoconductor <NUM> to the primary transfer belt <NUM> rotating in the direction indicated by arrow Y1 at a portion facing the image forming unit <NUM>. Subsequently, the cyan toner image is transferred from the photoconductor 231C to the primary transfer belt <NUM> at a portion facing the image forming unit 230C. The cyan toner image thus transferred is superimposed on the magenta toner image on the primary transfer belt <NUM>. Thereafter, the yellow and black toner images are sequentially transferred and superimposed on the toner images on the primary transfer belt <NUM>. The four color toner images form a full-color toner image on the primary transfer belt <NUM>. In the case of monochrome printing, the printer unit <NUM> can form a monochrome black (K) image using only the image forming unit <NUM>.

The secondary transfer belt <NUM> rotates in the direction indicated by arrow Y2 in synchronization with the rotating primary transfer belt <NUM>. In the secondary transfer nip, which is formed by the secondary transfer roller <NUM> and the drive roller <NUM> pressing against the secondary transfer belt <NUM> and the primary transfer belt <NUM>, the toner image is transferred from the primary transfer belt <NUM> to the secondary transfer belt <NUM>.

In the present embodiment, while the four image forming units <NUM> to <NUM>, which construct a so-called tandem system, form images on the respective photoconductors <NUM> to <NUM>, the primary transfer belt <NUM> and the secondary transfer belt <NUM> rotate to proceed with image formation. Accordingly, the time of image formation can be reduced.

When the primary transfer belt <NUM> rotates to a predetermined position, toner images to be formed on the other side (second side) of the sheet are formed on the photoconductors <NUM> to <NUM> in the above-described steps, and the sheet feeding is started.

In accordance with the formation of the toner images in the image forming units <NUM> to <NUM>, the sheet on the top on the sheet feeding tray (cassette) <NUM> or <NUM> is pulled out and conveyed to the registration roller pair <NUM>.

The sheet is sent between the primary transfer belt <NUM> and the secondary transfer belt <NUM> at a timing adjusted by the registration roller pair <NUM>. The toner image on the surface of the primary transfer belt <NUM> is transferred by the secondary transfer roller <NUM> to one side (the second side) of the sheet.

The sheet is further conveyed upward in the drawing, and the toner image on the surface of the secondary transfer belt <NUM> is transferred to the second side of the sheet by the charger <NUM>. The sheet is conveyed, timed to coincide with the transfer. Accordingly, the toner image is transferred at a proper position.

The sheet carrying the transferred toner images on both sides thereof is sent to the fixing device <NUM>. The heating roller <NUM> and the pressure roller <NUM> fuse the toner images on both sides of the sheet at a time and fixe the toner images on the sheet.

Then, the sheet is guided by the guide <NUM> and ejected by the sheet ejection roller pair <NUM> to the output stack <NUM> on the upper side of the main body frame.

When the conveyor <NUM> and the output stack <NUM> are constructed as illustrated in <FIG>, the sheet is stacked on the output stack <NUM> such that the side (page) carrying one of the two images transferred first onto the sheet, that is, the side to which the toner image is directly transferred from the primary transfer belt <NUM>, is faced down. Therefore, in order to align the pages, the image of the second page is formed first, the second page toner image is held on the secondary transfer belt <NUM>, and the image of the first page is directly transferred from the primary transfer belt <NUM> to the sheet.

The image transferred directly from the primary transfer belt <NUM> to the sheet is formed as a normal image on the photoconductor <NUM>, and the toner image transferred from the secondary transfer belt <NUM> to the sheet is formed as a reverse image (mirror image) on the surface of the photoconductor in the exposure. The order of image formation for such page alignment and the image processing for switching between the normal image and the reverse image (mirror image) are executed by controlling the reading and writing of image data from and to a memory on a controller <NUM>.

After the transfer of the toner image from the secondary transfer belt <NUM> onto the sheet, the second belt cleaner <NUM> removes toner and paper dust remaining on the secondary transfer belt <NUM>. The second belt cleaner <NUM> includes a brush roller, a collection roller, a blade, etc..

In <FIG>, the brush roller of the second belt cleaner <NUM> is separated from the surface of the secondary transfer belt <NUM>. However, the brush roller can pivot about a fulcrum to contact the secondary transfer belt <NUM> and move away therefrom. Before the transfer onto the sheet and when the secondary transfer belt <NUM> carries the toner image, the brush roller is separated therefrom. When cleaning is necessary, the brush roller pivots counterclockwise in the drawing and contacts the secondary transfer belt <NUM>. The removed toner is collected in a toner collecting section.

The image forming process of double-sided printing in "duplex transfer mode" is described above. The double-sided printing is made always by the image forming process described above.

For single-sided printing, there are two modes, "one-sided transfer mode using the secondary transfer belt <NUM>" and "one-sided transfer mode using the primary transfer belt <NUM>.

When the former one-side transfer mode using the secondary transfer belt <NUM> is set, a visible image formed by three-colors or four-color superimposition or a single black color on the primary transfer belt <NUM> is transferred onto the secondary transfer belt <NUM> and then transferred onto one side of the sheet. Image transfer onto the other side of the sheet is not performed. In this case, the printed sheet is ejected onto the output stack <NUM> such that the print side of the printed sheet is faced up.

When the latter one-sided transfer mode using the primary transfer belt <NUM> is set, a visible image formed by three-color or four-color superposition or single black color on the primary transfer belt <NUM> is transferred not onto the secondary transfer belt <NUM> but directly to one side of the sheet. Image transfer onto the other side of the sheet is not performed. In this case, the printed sheet is ejected onto the output stack <NUM> such that the print side of the printed sheet is faced down.

<FIG> is a block diagram illustrating a hardware configuration of the controller <NUM> illustrated in <FIG>.

The controller <NUM> is a computer that includes a central processing unit (CPU) <NUM>, a read only memory (ROM) <NUM>, a random access memory (RAM) <NUM>, and an input/output (I/O) unit <NUM>, which are connected via a bus <NUM>.

The CPU <NUM> is a processor that controls the entire printer unit <NUM>. The ROM <NUM> is a nonvolatile memory that stores control programs executed by the CPU <NUM>, data, and the like. The RAM <NUM> is a volatile memory used as a work area and the like of the CPU <NUM>. The I/O unit <NUM> is a unit that receives a detection signal from a sensor and outputs a control signal to each unit.

Various functions of the controller <NUM> are implemented as the CPU <NUM> reads out a control program stored in the ROM <NUM>, loads the control program in the RAM <NUM>, and launches the program.

<FIG> is a block diagram illustrating main components relating to power control of the multifunction copier according to a first embodiment.

The multifunction copier <NUM> includes a noise removal filter <NUM> coupled to a commercial AC power supply <NUM> and a rectifier <NUM> coupled to the subsequent stage of the noise removal filter <NUM>. The rectifier <NUM> converts the AC voltage after noise removal into a predetermined DC voltage. The noise removal filter <NUM> removes noise and inrush current input from the AC power supply <NUM> and includes a varistor, a capacitor, a choke coil, and the like. The rectifier <NUM> is, for example, a diode bridge, and supplies the converted DC voltage to a subsequent DC load (an example of a second load). The DC load is a load that consumes DC power.

The fixing heaters <NUM> (273a and 273b), which are AC loads (examples of a first load), are connected via a power sensor <NUM> between the noise removal filter <NUM> and the rectifier <NUM>. The fixing heaters <NUM> are loads that consume AC power. A power controller <NUM> turns a switch <NUM> (274a or 274b) on and off with a turn-on control signal, to control the AC power supplied to each fixing heater <NUM>.

The power sensor <NUM> and the power controller <NUM> construct the power control system <NUM>. Each function of the power controller <NUM> is implemented by the controller <NUM> illustrated in <FIG>.

The power control system that controls AC power supplied to the fixing heaters <NUM> is described.

<FIG> is a block diagram that schematically illustrates a functional configuration of the power control system.

The power control system <NUM> (power control device) includes the power sensor <NUM> and the power controller <NUM>. The power sensor <NUM> detects the power supplied to the fixing heaters <NUM> and outputs measured power values. The power controller <NUM> controls the power supplied to the fixing heaters <NUM> based on the measured power values output from the power sensor <NUM>.

The power sensor <NUM> is a sensor module including a current detection unit <NUM>, a voltage detection unit <NUM>, and a power calculation unit <NUM>.

The current detection unit <NUM> detects alternating currents supplied to the fixing heaters <NUM> and outputs analog current detection signals. The voltage detection unit <NUM> detects AC voltages applied to the fixing heaters <NUM> and outputs analog voltage detection signals. The power calculation unit <NUM> performs analog to digital conversion of the analog current detection signal and the voltage detection signal, and calculates, based on the digital current detection signal and the digital voltage detection signal thus obtained, the power (measured power value) supplied to the fixing heaters <NUM>. The power calculation unit <NUM> is, for example, an integrated circuit (IC) incorporating elements required for calculating the measured power value.

The power controller <NUM> includes a correction unit <NUM> and a turn-on control unit <NUM>.

The correction unit <NUM> corrects the measured power value output from the power sensor <NUM> based on the measurement precision (measurement tolerance) of the power sensor <NUM>. The correction unit <NUM> includes a primary correction unit <NUM> and a secondary correction unit <NUM>. The primary correction unit <NUM> performs primary correction on the measured power value based on data (sensor precision data <NUM>) relating to the measurement precision of the power sensor <NUM>, and outputs a primary correction power value. The secondary correction unit <NUM> performs secondary correction on the primary correction power value based on data (heater tolerance data <NUM>) on a tolerance relating to the power consumption of the fixing heater <NUM>, and outputs a secondary correction power value (final corrected power value).

The turn-on control unit <NUM> controls the power supplied to the fixing heaters <NUM> based on the corrected power values corrected by the correction unit <NUM>. The turn-on control unit <NUM> calculates a turn-on command value based on the secondary correction power value, generates the turn-on control signal based on the turn-on command value, and outputs the signal to the switch <NUM>. Further, the turn-on control unit <NUM> controls the power to be supplied to the fixing heaters <NUM> based on the secondary correction power value and the power to be supplied to other loads (in this case, particularly, the DC load) of the multifunction copier <NUM>.

The turn-on control unit <NUM> can control the power supplied to the fixing heaters <NUM> by various methods such as pulse-width modulation (PWM) control, phase control, and half-wave control. The turn-on control signal output from the turn-on control unit <NUM> is to turn the switch <NUM> on and off at a predetermined timing, with the driver that drives the fixing heater <NUM>. The power supplied to each fixing heater <NUM> is controlled to a desirable amount by turning on and off the switch <NUM> at a predetermined timing according to the turn-on control signal.

The tolerance of the power consumption of the fixing heater <NUM> is the difference between a designed reference value (or designed reference power consumption) relating to the power consumption of the fixing heater <NUM> and a tolerable limit of the actual power consumption. The tolerance is expressed as a difference from the reference value (absolute error), a ratio to the reference value (relative error), or a percentage (relative error).

For example, a description is given of a case where the specified power consumption is expressed as <NUM> W±<NUM>%. In this case, the designed reference value of the power consumption when power is constantly supplied (a state of always-on, a turn-on duty of <NUM>%) is <NUM> W, and the power consumed by each fixing heater falls in a range of from <NUM> W to <NUM> W. In other words, the fixing heater having the specified consumption of <NUM> W±<NUM>% has a plus tolerance of <NUM>% (<NUM> W) and a minus tolerance of <NUM>% (<NUM> W) with respect to the designed reference value of <NUM> W for power consumption. Hereinafter, the power consumption value <NUM> W obtained by adding the plus tolerance to the designed reference value is referred to as "power consumption upper limit.

For example, when the printer unit <NUM> needs a maximum of <NUM> W for fixing power, a fixing heater capable of outputting at least <NUM> W is selected as a fixing heater mounted on the printer unit <NUM>. When the tolerance of the fixing heater is ±<NUM>%, a fixing heater having a specified power consumption of <NUM> W±<NUM>% is selected since the power consumption is <NUM> W when the minus tolerance is added thereto. Hereinafter, a fixing heater that is a reference for selecting a fixing heater to be mounted in the printer unit is referred to as a "fixing heater as selection reference. " The "fixing heater as selection reference" in this example is synonymous with such a fixing heater that the actual power consumption has a minus tolerance with respect to the designed reference value. That is, the fixing heater as selection reference consumes <NUM> W in the case of always-on. In this specification, it does not manner whether or not such a fixing heater actually exists.

The measurement error (tolerance) of the power sensor <NUM> is a value of allowable limit of the possible value as measurement value by the power sensor <NUM> with respect to the true value of the amount to be measured (here, power consumption). The allowable limit is expressed as a difference (absolute error) from the true value, a ratio to the true value (relative error), or a percentage (relative error) within the measurement range.

For example, in a case where the power sensor <NUM> having a tolerance of ±<NUM>% outputs a measurement value of <NUM> W, as the power consumption of the fixing heater <NUM>, the true value of the power consumption falls within the range of <NUM> W to <NUM> W. That is, in the case of the power sensor <NUM> having the tolerance of ±<NUM>%, the maximum value of the plus-side error is <NUM>% (<NUM> W) and the maximum value of the minus-side error is <NUM>% (<NUM> W) with respect to the true value.

In <FIG>, charts (a) to (c) are schematic diagrams illustrating methods for correcting measured power consumption.

Features of the present embodiment are particularly effective in a case where a maximum measurement tolerance allowable between the actual power consumption of the fixing heater <NUM> in the state of always-on and the measured power consumption measured by measurement means is smaller than the tolerance allowable between the designed reference power consumption of the fixing heater <NUM> and the amount of power actually consumed by the fixing heater <NUM> in the state of always-on.

A description is given below of the method of correcting the measured power consumption of the fixing heater <NUM>, using the following example. In the example, the fixing heater <NUM> having the specified consumption of 1000W±<NUM>% selected as described above is constantly energized (turn-on duty is <NUM>%), and the power sensor <NUM> having the tolerance of ±<NUM>% measures the power consumption.

As illustrated in charts (a) and (b) in <FIG>, the correction unit <NUM> basically calculates a final corrected power value (secondary correction power value) by adding a plus tolerance of the power sensor <NUM> to the measurement value.

For example, as illustrated in the chart (a) in <FIG>, when the power sensor <NUM> outputs the measurement value of <NUM> W, the correction unit <NUM> calculates the corrected power value as <NUM> W. That is, for the fixing heater in the state of always-on, the maximum power secured to be supplied to the fixing heater is calculated as <NUM> W by adding <NUM> W to the maximum power <NUM> W required for fixing.

Note that the power consumption of the fixing heater in the state of always-on is not smaller than <NUM> W due to the relationship between the specifications and the tolerance of the fixing heater <NUM>. Even when the power sensor <NUM> outputs a measurement value of <NUM> W, the power value is corrected to <NUM> W by adding the maximum plus tolerance, and the corrected power value falls within the tolerable range of the fixing heater <NUM>.

As illustrated in the chart (b) in <FIG>, when the power sensor <NUM> outputs a measurement value of <NUM> W, the correction unit <NUM> corrects the measurement value to <NUM> W. That is, for the fixing heater in the state of always-on, the maximum power secured to be supplied to the fixing heater is calculated as <NUM> W by adding <NUM> W to the maximum power <NUM> W required for fixing.

As illustrated in the chart (c) in <FIG>, when the value obtained by adding the maximum plus tolerance of the power sensor <NUM> to the measurement value (e.g., <NUM> W) output from the power sensor <NUM> exceeds <NUM> W, the correction unit <NUM> calculates the final corrected power value (secondary correction power value) to be <NUM> W, which is the power consumption upper limit of the fixing heater <NUM>. This is because the power consumption of the fixing heater in the state of always-on does not exceed <NUM> W according to the specifications of the selected fixing heater <NUM>.

In <FIG>, charts (a) and (b) illustrate examples of power distribution to the loads of the multifunction copier.

The charts (a) and (b) in <FIG> are for the example in which the maximum power (rated power) usable by the multifunction copier <NUM> is <NUM> W, the maximum power required for fixing is <NUM> W, and the fixing heater <NUM> having a specified consumption of <NUM> W±<NUM>% is mounted on the printer unit <NUM> of the multifunction copier <NUM>.

The chart (a) in <FIG> illustrates a conventional power distribution example.

A power distribution α is an example of power distribution when the fixing heater is constantly energized. When a maximum of <NUM> W is required as power for fixing, at least <NUM> W is secured as power to be supplied to the fixing heater. However, the power consumption of the fixing heater in the state of always-on has the tolerance range, and the actual power consumption of each fixing heater is not known. Even in the printer unit equipped with a fixing heater having the maximum plus tolerance (consumes <NUM> W in the state of always-on), it is necessary to distribute the power so that the power consumed by the entire multifunction copier does not exceed the rated power. Therefore, reserve power (power for tolerance adjustment) expressed as <NUM> W - <NUM> W = 100W is secured for the fixing heater. Therefore, when the fixing heater is constantly energized, the maximum power that can be used by the DC load is <NUM> W.

It is assumed that the power consumption of the DC load increases as in a power distribution β, and the DC load requires power supply of <NUM> W. In this case, in order to prevent the total power consumption from exceeding the rated power of the multifunction copier, the power supplied to the fixing heater is reduced. However, it is necessary to continuously reserve a power of <NUM> W for the tolerance adjustment of the fixing heater. Therefore, in the conventional power control method, the power supplied to the fixing heater (turn-on duty of the fixing heater) is adjusted so that the power supplied to the fixing heater as selection reference becomes <NUM> W. As described above, when the power consumption of the DC load increases, the power supplied to the fixing heater is limited. Accordingly, disadvantageously, the multifunction copier requires a longer time for startup and recovery from standby.

The chart (b) in <FIG> illustrates an example of power distribution according to an embodiment of the present disclosure.

Power distribution A illustrates an example of power distribution when the fixing heater is constantly energized. As in the conventional example, at least <NUM> W is secured as the power supplied to the fixing heater. In the case where the power consumption of the fixing heater in the state of always-on is corrected to <NUM> W based on the measurement of the power consumption of the fixing heater, the power for tolerance adjustment (reserve power) is calculated as <NUM> W - <NUM> W = <NUM> W. That is, an additional power of <NUM> W, which is a difference from the conventional reserve power of <NUM> W, is distributable to the DC load. Therefore, the maximum power that can be used by the DC load in the state where the fixing heater is always-on is <NUM> W.

When the power consumption of the DC load increases as in the power distribution B and it becomes necessary to supply a power of <NUM> W to the DC load, the power supplied to the fixing heater is reduced similar to the conventional example, thereby preventing the total power consumption from exceeding the rated power of the multifunction copier. In the power control method according to the present embodiment, the difference (<NUM> W - <NUM> W = <NUM> W) between the power of <NUM> W supplied to the DC load and the power of <NUM> W secured to the DC load in the state of always-on is distributed from the fixing heater to the DC load. Therefore, the power calculated as 950W - 100W = 850W can be supplied to the fixing heater as selection reference while the reserve power of 50W is continuously secured for the tolerance adjustment of the fixing heater. That is, the power supplied to the fixing heater can be increased by <NUM> W compared with the conventional power distribution β, and the restriction on the power supplied to the fixing heater is relaxed.

Further, as in a power distribution C, when the power consumption measured by the power sensor <NUM> is <NUM> W, the corrected power value is 950W. Therefore, in the power distribution in the state of always-on, the power supplied to the fixing heater is <NUM> W and the power supplied to the DC load is <NUM> W. Then, securing the reserve power is not necessary.

<FIG> is a flowchart illustrating processing relating to power control of the fixing heater performed by the power control system according to the present embodiment. This process is executed in the state where the fixing heater is always-on (the fixing heater operates with the turn-on duty of <NUM>%), such as at the start-up of the multifunction copier.

In S1, the power sensor <NUM> measures the power consumption of the fixing heater <NUM> (measurement step). That is, the power calculation unit <NUM> inputs the analog current detection signal from the current detection unit <NUM>, inputs the analog voltage detection signal from the voltage detection unit <NUM>, calculates the power consumption of the fixing heater <NUM> based on digital signals converted from both the analog signals, and output the calculated value as the measured power value.

In S2, the correction unit <NUM> performs a primary correction on the measured power value based on the tolerance data of the power sensor <NUM> (primary correction step). That is, the correction unit <NUM> adds the maximum plus tolerance of the power sensor <NUM> to the measured power value output from the power sensor <NUM>, thus calculating the primary correction power value.

In S3, the correction unit <NUM> compares the primary correction power value with the power consumption upper limit of the fixing heater <NUM>, to determine whether the primary correction power value is equal to or greater than the power consumption upper limit. When the power of the fixing heater <NUM> in specifications is <NUM> W±<NUM>%, the power consumption upper limit of the fixing heater <NUM> is <NUM> W. When the primary correction power value is equal to or greater than the power consumption upper limit of the fixing heater <NUM> (Yes in S3), the process proceeds to S4. When the primary correction power value is less than the power consumption upper limit of the fixing heater <NUM> (No in S3), the process proceeds to S5.

In S4, the correction unit <NUM> sets the power consumption upper limit of the fixing heater <NUM> as the secondary correction power value, which is a final corrected power value (secondary correction step).

In S5, the correction unit <NUM> sets the primary correction power value calculated in S3 as the secondary correction power value, which is the final corrected power value (secondary correction step).

In S6, the turn-on control unit <NUM> determines the power to be distributed to the fixing heater <NUM> based on the secondary correction power value, and controls the power supplied to the fixing heater <NUM> based on the determined power (control step). Specifically, the turn-on control unit <NUM> generates a turn-on control signal corresponding to the determined power to control the switch <NUM>, thereby controlling the power supplied to the fixing heater <NUM>.

After the above-described correction processing is performed, the turn-on control unit <NUM> controls the power supplied to the fixing heater <NUM> based on the secondary correction power value and the power supplied to the DC load.

As described above, the control method according to the present embodiment can reduce the power reserved for adjusting the tolerance relating to the power consumption of the fixing heater and increase the power that can be supplied to the DC load. Thus, the power limitation on the heater can be relaxed.

In a printer unit <NUM> that includes a plurality of fixing heaters <NUM> (273a, 273b, and so on), the secondary correction power value can be set for each of the plurality of fixing heaters as follows.

First, the power controller <NUM> calculates the secondary correction power value of the fixing heater 273a by setting one of the fixing heaters (e.g., the fixing heater 273a) in the state of always-on and setting another fixing heater (e.g., the fixing heater 273b) in the state of turn-off (turn-on duty <NUM>%). Next, the power controller <NUM> calculates the secondary correction power value of the fixing heater 273b by setting one of the fixing heaters (e.g., the fixing heater 273a) in the state of turn-off and setting another fixing heater (e.g., the fixing heater 273b) in the state of always-on.

By executing the above-described processing with the power controller <NUM>, power of each fixing heater can be measured using a smaller number of power sensors than the number of fixing heaters, and the secondary correction power value of each fixing heater can be obtained.

<FIG> is a block diagram illustrating main components relating to power control of a multifunction copier according to the second embodiment. The multifunction copier <NUM> according to the present embodiment includes a plurality of fixing heaters 273a and 273b and power sensors 410a and 410b respectively for the fixing heaters 273a and 273b.

The configuration and operation of the power sensors 410a and 410b and other configurations are the same as those in the first embodiment, and redundant descriptions are avoided.

As in the present embodiment, the power sensor can be provided for each fixing heater. In the multifunction copier including a plurality of fixing heaters, providing a power sensor for each of a plurality of fixing heaters can reduce the time required to calculate the secondary correction power value.

<FIG> is a block diagram illustrating main components relating to power control of a multifunction copier according to the third embodiment. The elements substantially same to those of the first embodiment are assigned with the same reference numerals, and redundant descriptions are avoided. In the multifunction copier <NUM> according to the present embodiment, the voltage detection unit <NUM> of the power sensor <NUM> is disposed on the DC load system line (subsequent to the rectifier <NUM>).

The operations of the power sensor <NUM> and other configurations are the same as those of the first embodiment, and thus redundant descriptions are avoided.

As described above, the voltage detection unit <NUM> can be disposed either on the AC load system line (before the rectifier <NUM>) or on the DC load system line.

Each function of the above-described embodiments can be implemented by one or a plurality of processing circuits. Here, the "processing circuit or circuitry" in the present specification includes a programmed processor to execute each function by software, such as a processor implemented by an electronic circuit, and devices, such as an application specific integrated circuit (ASIC), a digital signal processors (DSP), a field programmable gate array (FPGA), and conventional circuit components arranged to perform the recited functions.

The multifunction copier <NUM> described in the above-described embodiments includes a plurality of loads (first load and second load) that consume power, and the multifunction copier <NUM> is an example of a power consumption apparatus that consumes power when each load is driven. Aspects of the present disclosure are applicable to such power consumption apparatuses in general.

That is, one aspect of the present disclosure is detecting the power supplied to the first load (an AC load, e.g., a fixing heater) and calculating a corrected power value based on the precision of the power sensor, thereby reducing the reserve power conventionally reserved for tolerance adjustment. The reduction in the reserve power can be distributed to the second load (e.g., a DC load). Accordingly, even when the power consumed by the second load increases, the power to be distributed from the first load to the second load can be reduced. Therefore, even when the power consumed by the second load increases, sufficient power can be supplied to the first load.

Each of the various aspects of the present disclosure provides the following effect.

A power control device (e.g., the power control system <NUM>) according to the present aspect includes measurement means (e.g., the power sensor <NUM>) for measuring the power supplied to a first load (e.g., the fixing heater <NUM> as an example of the AC load), correction means (e.g., the correction unit <NUM>) for correcting a measurement value measured by the measurement means based on a measurement tolerance of the measurement means, and control means (e.g., the turn-on control unit <NUM>) for controlling the power supplied to the first load based on the corrected power value corrected by the correction means and a power consumption upper limit of the load.

The load is a component that is driven with power supplied from a power supply (e.g., a commercial AC power supply) and consumes the power. The load can be either a component that consumes AC power or a component that consumes DC power. The load whose power is measured by the measurement means can be either one load or a plurality of loads. The power consumption upper limit of the load is calculated as a sum of the maximum plus tolerance allowed for the load and the designed reference power consumption (or the reference power consumption in specifications) of the load.

The power control device according to the present aspect is mounted in a power consumption apparatus (e.g., the multifunction copier <NUM>) that includes, for example, a plurality of loads (e.g., an AC load, an example of the first load and a DC load, an example of the second load) driven with power and consumes power.

A load constructed of a plurality of components has an individual difference in power consumption inherent to variations of the components and the like. Therefore, a predetermined difference is allowed between the designed reference value of the power consumed by the load in the state of always-on and the actual power consumption. In operating the power consumption apparatus, it is necessary to secure the power (reserve power) equivalent to the power consumption tolerance allowed for the load, to prevent the power consumption of the entire device from exceeding the rated power.

Further, an error between the measurement value measured by the measurement means and the true value is allowed within a predetermined range.

According to the present aspect, the power control device measures the power supplied to the first load (e.g., an AC load) and controls the power supplied to the first load based on the corrected measurement value. Therefore, the reserve power exceeding the designed reference value can be minimized to fit the individual difference of the first load. According to the present aspect, the more the actual power consumption of the load in the state of always-on deviates to the negative side from the designed reference power consumption, the smaller the preliminarily secured reserve power can be.

Therefore, according to the present aspect, the reserve power can be set for each first load, and the power distributed to the second load can be further increased. Further, even when the power consumed by the second load increases and the reduction of the power supplied to the first load is required, the reduction of the power supplied to the first load can be minimized.

In the power control device (the power control system <NUM>) according to the present aspect, the maximum measurement tolerance allowable between the actual power consumption of the first load (e.g., the fixing heater <NUM>, an example of the AC load) in the state of always-on and the measured power consumption by the measurement means (the power sensor <NUM>) is smaller than the maximum tolerance allowable between the designed reference power consumption of the load and the amount of power actually consumed by the load in the state of always-on.

In the present disclosure, it is possible to use measurement means having a maximum measurement tolerance greater than the maximum tolerance in power consumption of the first load.

However, when the measurement means having the maximum measurement tolerance smaller than the maximum tolerance in power consumption of the first load is used as in the present aspect, the rate of apparatuses capable of increasing the power supplied to the first load increases, and thus aspects of the present disclosure are particularly effective.

In the power control device (the power control system <NUM>) according to the present aspect, the correction means (the correction unit <NUM>) is configured to add the maximum plus measurement error allowed for the measurement means (the power sensor <NUM>) to the measurement value to calculate the primary correction power value, and set the primary correction power value as the corrected power value in a case where the primary correction power value is equal to or smaller than the power consumption upper limit.

Even when the actual power consumed by the first load (the fixing heater <NUM> as an example of the AC load) is greater than the measurement value, the actual power consumption does not exceed the primary correction power value that is the sum of the measurement value and the maximum plus measurement error.

According to the present aspect, since a value that is equal to or greater than the actual power consumption is set as the corrected power value, power supply to the load can be optimized within the range of the rated power of the power consumption apparatus including the first load. In addition, the present aspect can solve inconveniences such as a delay of recovery of the first load (and the apparatus including the first load) and a decrease in productivity, which occurs when the power supplied to the first load increases.

In the power control device (the power control system <NUM>) according to the present aspect, the correction means (e.g., the correction unit <NUM>) is configured to add the maximum plus measurement error allowed for the measurement means (the power sensor <NUM>) to the measurement value to calculate the primary correction power value, and sets the power consumption upper limit as the corrected power value in a case where the primary correction power value is greater than the power consumption upper limit.

Since the power consumption upper limit of the load is the sum of the maximum plus tolerance allowed for the load to the designed reference power consumption (or the reference power consumption in specifications) of the load, the actual power consumption does not exceed the power consumption upper limit.

According to the present aspect, since the power consumption upper limit is set as the corrected power value, the power supply to the load can be optimized within the range of the rated power of the power consumption apparatus including the first load. In addition, the power limitation on the first load can be minimized.

The power consumption apparatus (e.g., the multifunction copier <NUM>) according to the present aspect includes the power control device (e.g., the power control system <NUM>) and the load (e.g., the fixing heater <NUM> as an example of the AC load) driven with the power externally supplied.

The power consumption apparatus according to the present aspect provides the effects of the above-described aspects.

The power consumption apparatus (e.g., the multifunction copier <NUM>) according to the present aspect includes the load (the fixing heater <NUM> as the AC load) that is the target of measurement by the measurement means (e.g., the power sensor <NUM>) and control by the control means (e.g., the turn-on control unit <NUM>) and another load (e.g., a DC load) that is different from the load being such a target and driven with supplied power.

In the present aspect, an image forming apparatus (the multifunction copier <NUM>) to form a toner image on a recording medium includes the power control device (the power control system <NUM>) and a fixing heater (the fixing heater <NUM>) that is the load and fixes the toner image on the recording medium.

The image forming apparatus according to the present aspect provides the effects of the above-described aspects.

In particular, in the present embodiment, since the power supplied to the fixing heater can be maximized in accordance with the individual difference of the fixing heater, inconveniences such as a delay in the recovery of the first load (and the apparatus including the first load) and a decrease in productivity can be solved.

Claim 1:
A power control device (<NUM>) comprising:
measurement means (<NUM>) for measuring electrical power supplied to a load (<NUM>); and
control means (<NUM>) for controlling the power supplied to the load (<NUM>), correction means (<NUM>) being for:
adding a maximum plus measurement error of the measurement means (<NUM>) to the measurement value to calculate a primary correction power value;
determining whether the primary correction power value is greater than a power consumption upper limit, the power consumption upper limit being obtained by adding a designed reference power consumption value of the load (<NUM>) and its maximum plus tolerance;
setting the primary correction power value as the corrected power value in response to a determination that the primary correction power value is not greater than the power consumption upper limit, and
setting the power consumption upper limit as the corrected power value in response to a determination that the primary correction power value is greater than the power consumption upper limit so that the corrected power value does not exceed the power consumption upper limit, wherein
the control means (<NUM>) is for controlling the power supplied to the load (<NUM>) based on the corrected power value corrected by the correction means (<NUM>).