JP2019164326A - Power supply device, power supply control method, and image forming apparatus - Google Patents

Abstract

To reduce the fall time of a DC voltage in a configuration in which an AC power supply is connected in series with a DC power supply.SOLUTION: A power supply device comprises: a DC power supply that outputs a DC voltage; an AC power supply that outputs a superimposed voltage in which an AC voltage is superimposed on the DC voltage; a bypass capacitor that stores part of electric charge of an AC current in order to inhibit influx of a current from the AC power supply to the DC power supply; and a power supply control unit that, during a transfer period and a non-transfer period related to image formation, switches control of the DC voltage from constant current control to constant voltage control, and causes the bypass capacitor to store the electric charge of the AC current in a short time.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a power supply device, a power supply control method, and an image forming apparatus.

  In recent years, in the production print market, technology for printing on uneven paper has been demanded. When transferring toner onto normal recording paper, only the power source is used. However, since the toner on the concave and convex portions of the concave and convex paper is harder to transfer than the convex portion, when forming an image on recording paper with large concave and convex portions, the toner is not transferred to the concave portion and abnormalities such as white spots and uneven density occur in the image. May end up. In order to prevent this abnormality, there is already a technique for transferring an image onto a recording paper by connecting a DC power supply and an AC power supply in series and applying a superimposed voltage (DC + AC) in which an AC voltage is superimposed on a DC voltage to a transfer unit. Are known.

  In recent years, there has been a demand for higher speed copying machines in the market. Therefore, in order to increase the number of printed sheets per minute (ppm), it is necessary to shorten the space between the recording sheets (paper interval). A high voltage is required when transferring an image to a recording sheet. Therefore, when the space between the sheets is shortened, it is necessary to shorten the rise / fall time necessary for voltage output.

  Patent Document 1 discloses a technique aimed at reducing the voltage rise time. According to Patent Document 1, the transfer bias power source is started up by constant voltage control so that the DC component of the transfer bias becomes a preset target voltage, and then the toner image on the image carrier is transferred to the recording medium. Switch to constant current control so that the target current is set in advance.

  However, in a configuration in which an AC power supply is connected in series to a DC power supply, a DC voltage output from the DC power supply flows into the bypass capacitor before the electric charge is discharged and accumulated in the bypass capacitor. Therefore, compared to the case of a single DC power supply, it takes more time for the DC voltage output from the DC voltage to fall from the -potential to the + potential, resulting in poor image quality and wasteful consumption of toner between papers. There are problems such as.

  The present invention has been made in view of the above, and in a configuration in which an AC power supply is connected in series to a DC power supply, a power supply device, a power supply control method, and an image forming apparatus capable of reducing the fall time of the DC voltage The purpose is to provide.

  In order to solve the above-described problems and achieve the object, the present invention provides a DC power source that outputs a DC voltage, an AC power source that outputs a superimposed voltage in which an AC voltage is superimposed on the DC voltage, and the AC power source In order to prevent the current from flowing into the DC power supply, a bypass capacitor that stores a part of the AC current charge, and the DC voltage control from constant current control to constant during the transfer period from image transfer to non-transfer period. A power supply control unit that switches to voltage control and accumulates the charge of the alternating current in the bypass capacitor in a short time.

  According to the present invention, it is possible to shorten the fall time by only controlling without increasing the cost of the power source and to prevent the image quality from being deteriorated.

FIG. 1 is a diagram schematically illustrating an example of a hardware configuration of the printing apparatus according to the embodiment. FIG. 2 is an explanatory diagram of an image forming unit provided in the printing apparatus. FIG. 3 is a diagram illustrating an example of a functional block configuration of the secondary transfer power source. FIG. 4 is a diagram illustrating an example of a circuit configuration of the secondary transfer power supply. FIG. 5 is a block diagram illustrating an example of a configuration of an engine control unit included in the printing apparatus. FIG. 6 is a diagram illustrating an example of a state of falling of the DC output output to the load during the constant voltage control. FIG. 7 is a diagram illustrating the switching control sequence and the fall time. FIG. 8 is a flowchart illustrating an example of the flow of printing processing executed by the DC power supply and the power supply control unit.

  Hereinafter, embodiments of a power supply device, a power supply control method, and an image forming apparatus will be described in detail with reference to the accompanying drawings. In the following, an example in which a power supply device and an image forming apparatus are applied to an electrophotographic printing apparatus will be described as an embodiment. Regardless of the color or monochrome of the printing apparatus. In addition to the printing apparatus, the present invention can also be applied to an electrophotographic copying machine or a multifunction peripheral (MFP). The multifunction machine is an apparatus having at least two functions among a printing function, a copying function, a scanner function, and a facsimile function.

  FIG. 1 is a diagram schematically illustrating an example of a hardware configuration of the printing apparatus 1 according to the embodiment. FIG. 2 is an explanatory diagram of an image forming unit provided in the printing apparatus 1.

  As shown in FIG. 1, the printing apparatus 1 includes an image forming unit 10Y, 10M, 10C, and 10K, an intermediate transfer belt 60, support rollers 61 and 62, a secondary transfer unit counter roller (repulsive roller) 63, and the like. A secondary transfer roller 64, a paper cassette 70, a paper feed roller 71, a transport roller pair 72, a fixing device 90, and a secondary transfer power source 200.

  The image forming units 10Y, 10M, 10C, and 10K are arranged along the intermediate transfer belt 60 in the order of the image forming units 10Y, 10M, 10C, and 10K from the upstream side in the moving direction (arrow a direction) of the intermediate transfer belt 60. Has been placed. Each of the image forming units 10Y, 10M, 10C, and 10K forms yellow, magenta, cyan, and black toner images (color component images) by an image forming process, and transfers the toner images to the intermediate transfer belt 60. .

  The image forming units 10Y, 10M, 10C, and 10K all have common components. Here, the constituent elements of the image forming units 10Y, 10M, 10C, and 10K and the steps according to the image forming process, the charging process, the irradiation process, the developing process, and the transfer process will be described in the order of the image forming unit 10Y. To do. Since the other image forming units 10M, 10C, and 10K are described in the same manner as the image forming unit 10Y, the reference numeral Y indicating the component of the image forming unit 10Y is replaced with M, C, and K, respectively. The description is omitted.

  As shown in FIG. 2, the image forming unit 10Y includes a photosensitive drum 11Y, a charging device 20Y, a developing device 30Y, a primary transfer roller 40Y, and a cleaning device 50Y.

  The photosensitive drum 11Y is an image carrier and is driven to rotate in the direction of arrow b. The photoreceptor drum 11Y is an organic photoreceptor having an outer diameter of 60 mm, for example. When forming a color image, the photosensitive drums 11Y, 11M, 11C, and 11K for each color are rotationally driven in synchronization. However, when forming a monochrome image, the photosensitive drum 11K for black is used for other photosensitive drums. It is driven to rotate independently of the body drums 11Y, 11M, and 11C.

  The developing device 30Y includes a storage container 31Y, a developing sleeve 32Y stored in the storage container 31Y, and a screw member 33Y stored in the storage container 31Y. The storage container 31Y stores a two-component developer having yellow toner and a carrier. The developing sleeve 32Y is a developer carrier, and is disposed so as to face the photosensitive drum 11Y through the opening of the storage container 31Y. The screw member 33Y is a stirring member that conveys the developer while stirring. The screw member 33Y is disposed on the developer supply side on the developing sleeve side and the receiving side that receives the supply from the toner replenishing device, and is rotatably supported by the receiving container 31Y by a bearing member (not shown).

  The primary transfer roller 40Y is an elastic roller having a conductive sponge layer, for example, and is disposed so as to be pressed against the photosensitive drum 11Y from the back surface of the intermediate transfer belt 60. The elastic roller is applied with a constant current controlled bias as a primary transfer bias. For example, the primary transfer roller 40Y has an outer shape of 16 mm, a mandrel diameter of 10 mm, and a sponge layer resistance R of about 3E7Ω. The resistance R of the sponge layer is determined from the current I flowing when a voltage V of 1000 V is applied to the mandrel of the primary transfer roller 40Y with a grounded metal roller having an outer diameter of 30 mm pressed by 10 N, from the current I. It is a value calculated using the law (R = V / I).

  In the charging process, the charging device 20Y charges the surface of the rotationally driven photosensitive drum 11Y to a predetermined polarity (in this example, a negative polarity).

  In the irradiation process, the irradiation device irradiates the charged surface of the photosensitive drum 11Y with the laser light L that has been optically modulated, thereby forming an electrostatic latent image on the surface of the photosensitive drum 11Y. As a result, the portion where the absolute value of the potential of the surface portion of the photosensitive drum 11Y is lowered by the irradiation with the laser beam L becomes an electrostatic latent image (image portion), and the absolute value of the potential is kept high without being irradiated with the laser beam L. The sagging part becomes the background part.

  In the developing process, the developing device 30Y develops the electrostatic latent image formed on the photoreceptor drum 11Y with yellow toner, and forms a yellow toner image on the photoreceptor drum 11Y.

  In the transfer process, the primary transfer roller 40Y transfers the yellow toner image formed on the photosensitive drum 11Y to the intermediate transfer belt 60. Note that a small amount of untransferred toner remains on the photosensitive drum 11Y even after the toner image is transferred.

  In the cleaning process, the cleaning device 50Y wipes off the untransferred toner remaining on the photosensitive drum 11Y. The cleaning device 50Y includes a cleaning blade 51Y and a cleaning brush 52Y. The cleaning blade 51Y cleans the surface of the photoconductive drum 11Y while being in contact with the photoconductive drum 11Y from the counter direction with respect to the rotation direction of the photoconductive drum 11Y. The cleaning brush 52Y cleans the surface of the photosensitive drum 11Y while being in contact with the photosensitive drum 11Y while rotating in the direction opposite to the rotation direction of the photosensitive drum 11Y.

  Returning to FIG. 1, description of the remaining portion will be continued. The intermediate transfer belt 60 is an endless belt that is wound around a plurality of rollers such as support rollers 61 and 62 and a secondary transfer unit facing roller 63, and one of the support rollers 61 and 62 is driven to rotate by an arrow. Move endlessly in direction a.

  First, a yellow toner image is transferred to the intermediate transfer belt 60 by the image forming unit 10Y. Subsequently, the magenta toner image is transferred by the image forming unit 10M, the cyan toner image is transferred by the image forming unit 10C, and the image forming unit 10K is pressed. Black toner images are sequentially superimposed and transferred. As a result, a full-color toner image (full-color image) is formed on the intermediate transfer belt 60. The intermediate transfer belt 60 conveys the formed full-color toner image between the secondary transfer portion facing roller 63 and the secondary transfer roller 64.

  For example, the intermediate transfer belt 60 has a thickness of 20 to 200 μm (preferably about 60 μm) and a volume resistivity of 6.0 to 13.0 Log Ωcm (preferably 7.5 to 12.5 Log Ωcm, more preferably about 9 Log Ωcm) and an endless carbon-dispersed polyimide resin having a surface resistivity of 9.0 to 13.0 Log Ωcm (preferably 10.0 to 12.0 Log Ωcm). The volume resistivity is a resistance measurement value at 100 V, 10 sec, manufactured by Mitsubishi Chemical Hiresta HRS probe, and the surface resistivity is a resistance measurement value at 500 V, 10 sec, manufactured by Mitsubishi Chemical Hiresta HRS probe. The support roller 62 is grounded.

  In the paper cassette 70, a plurality of recording papers are stacked and stored in each tray. It is assumed that the recording paper has a different paper type and size for each tray. In the present embodiment, the recording paper is, for example, plain paper or a highly rugged resack paper, but is not limited to this.

  The paper feed roller 71 is in contact with the recording paper P positioned at the top of the tray of the paper cassette 70 and feeds the recording paper P in contact therewith.

  The transport roller pair 72 transports the recording paper P fed by the paper feed roller 71 between the secondary transfer portion facing roller 63 and the secondary transfer roller 64 (in the direction of arrow c) at a predetermined timing.

  The secondary transfer portion facing roller 63 and the secondary transfer roller 64 are full-color toner images conveyed by the intermediate transfer belt 60 at the secondary transfer nip between the secondary transfer portion facing roller 63 and the secondary transfer roller 64. Are collectively transferred onto the recording paper P conveyed by the conveying roller pair 72.

  The secondary transfer portion facing roller 63 is, for example, a conductive NBR rubber layer having an outer shape of 24 mm and a mandrel diameter of 16 mm. In addition, the value of resistance R of the conductive NBR rubber layer is 6.0 to 12.0 LogΩ (or SUS), and preferably 4.0 LogΩ. The secondary transfer roller 64 is, for example, a conductive NBR rubber layer having an outer shape of 24 mm and a mandrel diameter of 14 mm. In addition, the value of resistance R of the conductive NBR rubber layer is 6.0 to 8.0 LogΩ, and preferably 7.0 to 8.0 LogΩ. The volume resistance of the secondary transfer roller 64 is a resistance measurement value measured by rotation measurement. Weight: 5 N / one side, bias application: 1 KV applied to the transfer roller shaft, resistance of one roller rotation measured during 1 min measurement, average The value is a volume resistance.

  A secondary transfer power supply 200 for transfer bias is connected to the secondary transfer portion facing roller 63. The secondary transfer power source 200 applies a voltage to the secondary transfer unit facing roller 63 in order to transfer the full-color toner image to the recording paper P at the secondary transfer nip. Specifically, the secondary transfer power supply 200 applies only a DC voltage (hereinafter sometimes referred to as “DC bias”) to the secondary transfer unit facing roller 63 according to a user setting, A superimposed voltage (hereinafter sometimes referred to as “superimposed bias”) superimposed with an AC voltage is applied to the secondary transfer unit facing roller 63. As a result, a potential difference is generated between the secondary transfer portion facing roller 63 and the secondary transfer roller 64, and a voltage is generated in which the toner travels from the intermediate transfer belt 60 to the recording paper P side. Can be transferred to. Here, the potential difference in the present embodiment is (potential of the secondary transfer portion facing roller 63) − (potential of the secondary transfer roller 64).

  The fixing device 90 fixes the full-color toner image on the recording paper P by heating and pressing the recording paper P to which the full-color toner image has been transferred. Then, the recording paper P on which the full-color toner image is fixed is discharged outside the printing apparatus 1.

  FIG. 3 is a diagram illustrating an example of a functional block configuration of the secondary transfer power supply 200. As shown in FIG. 3, the secondary transfer power supply 200 includes a DC power supply 210 and an AC power supply 220. The DC power source 210 functions as a power source for toner transfer, and the AC power source 220 functions as a power source for toner vibration. The DC power supply 210 and the AC power supply 220 operate based on a control signal from a power supply control unit 400 (for example, a CPU) and apply a drive voltage to the load 500 of the secondary transfer power supply 200. The load 500 of the secondary transfer power source 200 corresponds to the secondary transfer roller 64, the secondary transfer unit facing roller 63, and the like, and is applied between the secondary transfer roller 64 and the secondary transfer unit facing roller 63 by applying a driving voltage. Change the field strength and direction.

  The DC power supply 210 includes a constant current power supply (DC−) control circuit 211, a constant voltage power supply (DC−) control circuit 212, a constant voltage power supply (DC +) control circuit 213, a transformer (DC−) drive circuit 214, and a transformer (DC +). It has a drive circuit 215, a DC voltage transformer (DC +) 216, and a DC voltage transformer (DC−) 217.

  The AC power supply 220 is a power supply for toner vibration, and includes an AC power supply control circuit 221, a transformer (AC) drive circuit 222, and an AC voltage transformer (AC) 223.

  FIG. 4 is a diagram illustrating an example of a circuit configuration of the secondary transfer power supply 200. As shown in FIG. 4, the DC power supply 210 includes a constant voltage control circuit (DC−) 316, a constant current control circuit (DC−) 317, a constant voltage control circuit (DC +) 318, a DC drive circuit (DC−) 319, DC drive circuit (DC +) 320, DC voltage detection circuit (DC-) 321, DC voltage detection circuit (DC +) 323, DC current detection circuit (DC-) 322, DC voltage output unit 330, switching circuit 336, transformer (DC −) 334 and a transformer (DC +) 335.

  The DC power supply 210 receives a -CV_PWM, -CC_PWM, + CV_PWM signal, and a switching signal from the power supply control unit 400. The -CV_PWM signal is connected to the constant voltage control circuit (DC-) 316, the -CC_PWM signal is connected to the constant current control circuit (DC-) 317 and the switching circuit 336, and the + CV_PWM signal is connected to the constant voltage control circuit (DC +) 318. Is done.

  The switching signal is input to the switching circuit 336 and then connected to each control circuit. Control signals output from the constant voltage control circuit (DC−) 316 and the constant current control circuit (DC−) 317 are input to the direct current drive circuit (DC−) 319 to drive the transformer (DC−) 334 to generate direct current voltage. (DC−) is applied to the DC voltage output unit 330. The control signal output from the constant voltage control circuit (DC +) 318 is input to the DC drive circuit (DC +) 320, drives the transformer (DC +) 335, and the DC voltage (DC +) is applied to the DC voltage output unit 330. The This will be described in detail below.

  The switching circuit 336 is a selector switch that switches the control of the DC voltage to one of the constant voltage control circuit (DC−) 316, the constant current control circuit (DC−) 317, and the constant voltage control circuit (DC +) 318. . For example, the switching circuit 336 switches the reference voltage input by turning it on or off.

  The constant voltage control circuit (DC−) 316, the constant current control circuit (DC−) 317, and the constant voltage control circuit (DC +) 318 are each configured with a comparator.

  The constant voltage control circuit (DC−) 316 inputs a value obtained by integrating the control signal (−CV_PWM signal) from the power supply control unit 400 as a reference voltage value, and outputs the constant voltage control circuit (DC−) 316. Depending on the level, the voltage value taken out via the direct current drive circuit (DC−) 319 and the transformer (DC−) 334 is input as a voltage value for comparison. The constant voltage control circuit (DC−) 316 controls the output signal so that the comparison voltage value becomes the reference voltage value.

  The constant current control circuit (DC−) 317 inputs a value obtained by integrating the control signal (−CC_PWM signal) from the power supply control unit 400 as a reference current value, and outputs the constant current control circuit (DC−) 317. The current value of the current taken out via the direct current drive circuit (DC−) 319 and the transformer (DC−) 334 according to the level is input as a current value for comparison. The constant current control circuit (DC-) 317 controls the output signal so that the current value for comparison becomes the reference current value.

  The constant voltage control circuit (DC +) 318 inputs a value obtained by integrating the control signal (+ CV_PWM signal) from the power supply control unit 400 as a reference voltage value, and depends on the output level of the constant voltage control circuit (DC +) 318. The voltage value of the voltage taken out via the DC drive circuit (DC +) 320 and the transformer (DC +) 335 is input as a voltage value for comparison. The constant voltage control circuit (DC +) 318 controls the output signal so that the voltage value for comparison becomes the reference voltage value.

  The direct current drive circuit (DC−) 319 is driven based on the input signal.

  The transformer (DC−) 334 includes a primary winding (N1_DC−) and a secondary winding (N2_DC−), and includes a diode and a capacitor in the secondary winding (N2_DC−). The current generated in the secondary winding (N2_DC-) by the electromagnetic induction from the primary winding (N1_DC-) by driving the direct current drive circuit (DC-) 319 is smoothed by the diode and the capacitor.

  The DC voltage detection circuit (DC−) 321 outputs the value of the voltage generated in the secondary winding (N2_DC−) to the constant voltage control circuit (DC−) 316.

  The direct current detection circuit (DC−) 322 outputs the value of the current generated in the secondary winding (N2_DC−) to the constant current control circuit (DC−) 317.

  The DC drive circuit (DC +) 320 is driven based on the input signal.

  The transformer (DC +) 335 includes a primary winding (N1_DC +) and a secondary winding (N2_DC +), and includes a diode and a capacitor in the secondary winding (N2_DC +). The current generated in the secondary winding (N2_DC +) by electromagnetic induction from the primary winding (N1_DC +) by driving the direct current drive circuit (DC +) 320 is smoothed by the diode and the capacitor.

  The DC voltage detection circuit (DC +) 323 outputs the value of the voltage generated in the secondary winding (N2_DC +) to the constant voltage control circuit (DC +) 318.

  The voltage generated in the secondary winding (N2_DC−) and the voltage generated in the secondary winding (N2_DC +) are output as DC voltages to the AC power supply 220 through the DC voltage output unit 330.

  The AC power supply 220 includes an AC drive circuit 325, a constant voltage control circuit (AC) 324, an AC voltage detection circuit 327, a transformer 333, a high voltage output unit 329, and an AC bypass capacitor 326 that is a bypass capacitor.

  The AC power supply 220 receives AC_PWM and AC_CLK signals from the power supply control unit 400. The AC_PWM signal is connected to a constant voltage control circuit (AC) 324. The AC_CLK signal and the control signal output from the constant voltage control circuit (AC) 324 are input to the AC drive circuit 325, and the transformer (AC) 333 is driven to output an AC voltage. The output is superimposed on the DC voltage and AC voltage from the DC power supply 210 and applied to the high voltage output unit 329. The high voltage output is applied to the load 500. This will be described in detail below.

  The constant voltage control circuit (AC) 324 inputs a value obtained by integrating the control signal (AC_PWM signal) from the power supply control unit 400 as a reference voltage value, and depends on the output level of the constant voltage control circuit (AC) 324. The voltage value of the AC voltage taken out via the AC drive circuit 325 and the transformer 333 is input as a voltage value for comparison. The constant voltage control circuit (AC) 324 controls the output signal so that the voltage value for comparison becomes the reference voltage value.

  The AC drive circuit 325 is driven based on an input signal and a clock signal (AC_CLK signal).

  The transformer (AC) 333 has a primary side winding (N1_AC) and a secondary side winding (N2_AC), and has an AC bypass capacitor 326 in the secondary side winding (N2_AC). The voltage generated in the secondary winding (N2_AC) by electromagnetic induction from the primary winding (N1_AC) by driving the AC drive circuit 325 is superimposed on the DC voltage output to the AC power supply 220 through the DC voltage output unit 330. Then, it is applied to the load 500 through the high voltage output unit 329.

  The AC voltage detection circuit 327 outputs the voltage value of the AC voltage generated in the secondary winding (N2_AC) to the constant voltage control circuit (AC) 324 as a voltage value for comparison.

  Note that the FB_V (AC−) signal, the FB_V (DC−) signal, the FB_V (CC−) signal, and the FB_V (DC +) signal illustrated in FIG. 4 are signals that the power supply control unit 400 reads from the DC power supply 210 and the AC power supply 220. Represents.

  Next, circuits and signals when outputting constant voltage control (DC-) will be described.

  The -CV_PWM signal output from the power supply control unit 400 is integrated and input to the constant voltage control circuit (DC-) 316. The value of the integrated -CV_PWM signal becomes a reference voltage in the constant voltage control circuit (DC-) 316. The DC voltage detection circuit (DC−) 321 detects the DC voltage (DC−) output from the DC power supply 210 and inputs the output value of the detected DC voltage to the constant voltage control circuit (DC−) 316.

  The constant voltage control circuit (DC−) 316 actively drives the DC drive circuit (DC−) 319 of the DC high voltage transformer when the output value of the DC voltage detected with respect to the reference voltage is small. When the output value reaches the reference voltage (upper limit), the driving of the DC drive circuit (DC-) 319 of the DC high voltage transformer is restricted. Thereby, the DC power supply 210 ensures constant voltage (DC−). At this time, when the duty of the -CV_PWM signal is low, the integration time increases, and when the duty is high, the integration time decreases, and it takes time corresponding to the high voltage output. Further, the DC voltage detection circuit (DC−) 321 feeds back the output value of the detected DC voltage to the power supply control unit 400 as an FB_V (DC−) signal.

  Next, circuits and signals when outputting constant current control (DC-) will be described.

  The -CC_PWM signal output from the power supply control unit 400 is integrated and input to the constant current control circuit (DC-) 317. The value of the integrated -CC_PWM signal becomes a reference voltage in the constant current control circuit (DC-) 317. The direct current detection circuit (DC−) 322 detects the direct current (DC−) output from the direct current power supply 210 and inputs the output value of the detected direct current voltage to the constant current control circuit (DC−) 317. The constant current control circuit (DC−) 317 actively drives the DC drive circuit (DC−) 319 of the DC high voltage transformer when the output value of the DC voltage detected with respect to the reference voltage is small. When the output value of the current reaches the reference voltage (upper limit), the driving of the direct current drive circuit (DC−) 319 of the direct current high voltage transformer is restricted. As a result, the DC power supply 210 ensures constant current (DC−). At this time, when the duty of the -CC_PWM signal is low, the integration time increases, and when the duty is high, the integration time decreases, and it takes time corresponding to the output until output. The direct current detection circuit (DC−) 322 feeds back the detected output value of the direct current voltage to the power supply control unit 400 as an FB_I (DC−) signal.

  Next, circuits and signals when outputting constant voltage control (DC +) will be described.

  The + CV_PWM signal output from the power supply control unit 400 is integrated and input to the constant voltage control circuit (DC +) 318. The value of the integrated + CV_PWM signal becomes a reference voltage in the constant voltage control circuit (DC +) 318. The DC voltage detection circuit (DC +) 323 detects the DC voltage (DC +) output from the DC power supply 210 and inputs the output value of the detected DC voltage to the constant voltage control circuit (DC +) 318. Then, the constant voltage control circuit (DC +) 318 actively drives the DC drive circuit (DC +) 320 of the DC high voltage transformer when the output value of the detected DC voltage with respect to the reference voltage is small, and outputs the DC voltage. When the value reaches the reference voltage (upper limit), the driving of the DC drive circuit (DC +) 320 of the DC high voltage transformer is restricted. Thereby, the direct-current power supply 210 ensures constant voltage (DC +). At this time, when the Duty of the + CV_PWM signal is low, the integration time increases. When the Duty is high, the integration time decreases, and it takes time to output a high voltage. The DC voltage detection circuit (DC +) 323 feeds back the detected output value of the DC voltage to the power supply control unit 400 as an FB_V (DC +) signal.

  Here, driving of the transformer (DC-) 334 will be described by taking as an example a case where the DC driving circuit (DC-) 319 is driven.

  By driving the direct current drive circuit (DC−) 319 according to the control of the constant current control circuit (DC−) 317 and the constant voltage control circuit (DC−) 316, the primary winding (N1_DC−) of the direct current high voltage transformer and The output generated by the secondary winding (N2_DC−) of the DC high-voltage transformer is smoothed by a diode and a capacitor and then applied to the DC voltage output unit 330 as a DC voltage.

  Next, AC voltage output and a transformer (AC) will be described.

  The AC power supply 220 receives the AC_PWM signal and the AC_CLK signal from the power supply control unit 400. The AC_PWM signal is input to the constant voltage control circuit (AC) 324. The value of the input AC_PWM signal becomes a reference voltage in the constant voltage control circuit (AC) 324. The AC voltage detection circuit 327 detects an AC voltage on the low voltage side of the AC bypass capacitor 326 that is an output line of the secondary transfer power supply 200, and inputs the detected output value of the AC voltage to the constant voltage control circuit (AC) 324. To do. The constant voltage control circuit (AC) 324 actively drives the AC drive circuit 325 of the AC high voltage transformer when the AC voltage is smaller than the reference voltage, and AC when the AC voltage is larger than the reference voltage. The drive of the AC drive circuit 325 of the high voltage transformer is regulated. Thereby, the AC power supply 220 ensures constant voltage (AC). The AC_CLK signal is input to the AC drive circuit 325. The AC_CLK signal determines the AC frequency and shape (Sin wave, rectangular wave, etc.). Further, the AC voltage detection circuit 327 feeds back the detected output value of the AC current to the power supply control unit 400 as an FB_V (AC−) signal.

  However, when the AC power supply 220 is not driven, the DC voltage applied to the secondary winding (N2_AC) is directly output (applied) from the high voltage output unit 329 to the load 500.

  Here, the property of the AC bypass capacitor 326 in the secondary transfer power supply 200 will be described.

  The AC bypass capacitor 326 stores a part of the charge of the AC current in order to prevent the AC current output from the AC power supply 220 from flowing into the DC power supply 210. Since the AC bypass capacitor 326 has a very high impedance with respect to the DC output, it is possible to superimpose the DC output on the AC power supply 220 with low loss.

  On the other hand, at the start and end of the secondary transfer, the power supply control unit 400 reverses the potential of the DC voltage output unit 330 under the control of the secondary transfer power supply 200 in order to reverse the polarity of the DC output with respect to the load 500. Switch to the polarity.

  However, charges are accumulated in the AC bypass capacitor 326 at the time of switching, and sufficient power cannot be supplied to the load 500 until the charges in the AC bypass capacitor 326 are discharged. For this reason, it takes time until the DC output is stabilized. “Falling” refers to a state from a state having a potential difference to a state having no potential difference or a potential difference having a different polarity.

  As described above, the DC bias output from the DC power supply 210 flows into the AC bypass capacitor 326 until the electric charge discharges the negative potential into the AC bypass capacitor 326 and then stores the positive potential. It is because it ends. This is because the upper limit of the amount of charge output as the DC bias is determined by the current value, so that it takes time until the charge is discharged and stored in the AC bypass capacitor 326.

  In the present embodiment, the power supply control unit 400 temporarily performs constant voltage control of the secondary transfer power supply 200 at the start and end of the secondary transfer, whereby the secondary transfer starts and ends. In, the fall time of each DC output is shortened.

  FIG. 5 is a block diagram illustrating an example of the configuration of the engine control unit 300 included in the printing apparatus 1. As shown in FIG. 5, the printing apparatus 1 includes an engine control unit 300, a secondary transfer power source 200, and a secondary transfer unit facing roller 63.

  The engine control unit 300 performs engine control, for example, control related to image formation, and includes an I / O control unit 310, a RAM (Random Access Memory) 350, a ROM (Read Only Memory) 360, and a CPU 340. Is provided.

  The I / O control unit 310 controls input / output of various signals, and controls input / output of signals exchanged with the secondary transfer power supply 200.

  The RAM 350 is a volatile storage device (memory), and is used as a work area for the CPU 340 and the like.

  A ROM 360 (an example of a storage unit) is a non-volatile storage device (memory) for reading, and stores various programs executed by the printing apparatus 1 and data used for various processes executed by the printing apparatus 1. To do. The ROM 360 may be realized by a flash memory or the like so that writing can be performed. For example, the ROM 360 specifies specific information for specifying a constant voltage switching timing for causing the DC power source 210 to switch to constant voltage control and a constant current switching timing for causing the DC power source 210 to switch to constant current control (an example of a predetermined timing). Remember. The identification information specifies, for example, a constant voltage switching timing and a constant current switching timing based on a printing start reference signal indicating a printing start reference.

  The CPU 340 accepts an input of a print start reference signal or accepts user settings from an operation unit (not shown) such as an operation panel. For example, when the recording paper is plain paper, the user inputs “high voltage output with only DC bias” as the user setting of the high voltage output from the operation unit, and when the recording paper is a lazac paper with large unevenness, Then, “High voltage output with superimposed bias” is input as the user setting of the high voltage output. Then, the CPU 340 causes the secondary transfer power source 200 to output a high voltage according to the user setting via the I / O control unit 310. The CPU 340 includes a power control unit 342.

  The power supply control unit 400 controls the output of the DC voltage from the DC power supply 210 based on the specific information stored in the ROM 360 when the secondary transfer power supply 200 performs high voltage output (DC voltage output or superimposed voltage output). To do. Specifically, power supply control unit 400 causes DC power supply 210 to switch to constant voltage control and constant current control based on the specific information.

  Hereinafter, features of the printing apparatus 1 according to the present embodiment will be described.

  FIG. 6 is a diagram illustrating an example of a state of a fall of the DC output output to the load 500 during the constant voltage control. FIG. 6 shows, as an example, how the DC output falls from the reverse DC bias (−10 kV) to the DC bias (1 kV) at the end of the secondary transfer. Here, the bias is a voltage applied from the DC power supply 210 to the load 500. A reverse bias is when the potential is negative.

  Transfer is performed with a reverse DC bias (−10 kV) by constant current (DC−) control during the transfer period t1 shown in FIG. 6, and switching to constant voltage (DC +) control is performed during the rising period t3 of the non-transfer period t2. The DC output is made to reach the target DC bias (1 kV). In this case, the target value can be reached in a short time such as 200 ms as an example.

  After that, although not shown, when the next transfer period comes, the direct current output reaches the reverse DC bias (−10 kV) in a short time by constant voltage (DC +) control. In the case of constant voltage control, the amount of charge output as a DC bias is theoretically infinite, and charge can be accumulated in the AC bypass capacitor 326 in a short time.

  Next, specific control of the secondary transfer power supply 200 will be described.

  FIG. 7 is a diagram illustrating the switching control sequence and the fall time. Here, we focus on falling.

  When the constant voltage switching timing comes, the power source control unit 400 instructs the DC power source 210 to switch from the constant current control (DC−) to the constant voltage control (DC−) to the DC power source 210 (from low to high). Switch signal). In response to this, the DC power supply 210 switches from constant current control (DC−) to constant voltage control (DC−) when a switching signal instructing switching to constant voltage control is input.

  Subsequently, the power supply control unit 400 completes switching from the constant current control (DC−) to the constant voltage control (DC−) of the DC power supply 210 and outputs + CV_PWM after a predetermined time. In response to this, the DC power supply 210 switches from constant voltage control (DC−) to constant voltage control (DC +). Here, the predetermined time can be varied.

  As described above, when constant voltage control is performed, the AC bypass capacitor 326 can be discharged and stored in a short time. However, in actual use, the amount of charge output as a DC bias is finite. For this reason, it takes a lot of time only with the normal constant voltage control (DC +) in which the DC bias value is set to the target value (1 kV) from the output of the reverse DC bias (−10 kV).

  However, by setting the constant voltage control (DC +) after the constant voltage control (DC−), it is possible to shorten the fall time compared to the normal sequence. Two reasons why the constant voltage control (DC +) is performed after the constant voltage control (DC−) rather than the constant voltage control (DC +) alone can shorten the fall time.

  The first reason is the difference in power of the transformer.

  The transformer (DC−) 334 that generates the reverse DC bias is related to the fact that the amount of current that can be passed is larger than the transformer (DC +) 335 that generates the DC bias. Note that the transformer (DC +) 335 only needs to be able to output up to 1 kV in actual use, and is smaller due to the size, cost, and the like suitable for it.

  The second reason is the difference from the control signal to driving.

  According to the sequence shown in FIG. 7, -CV_PWM is always ON except for the first startup. For this reason, constant voltage control (DC-) is always waiting before sending a control signal to the drive circuit. This is because the control signal is taken away from the constant current control (DC−) when the switching signal is input in this state. + CV_PWM also takes PWM integration time from when it is turned on until it starts output. However, -CV_PWM can also shorten its integration time.

  Therefore, the fall time from the reverse DC bias of −10 kV to the DC bias of 1 kV can be 45 ms.

  Here, the user may set the timing from the constant voltage control (DC−) to the constant voltage control (DC +). Alternatively, when the capacitance in the AC bypass capacitor 326 is detected from the AC voltage FB signal, FB_V (AC−), and it is detected that a charge of a predetermined capacity or more has been discharged to the AC bypass capacitor 326, You may switch from voltage control (DC-) to constant voltage control (DC +). The life (state) of the AC bypass capacitor 326 may be predicted and notified to the user by detecting the capacity inside the AC bypass capacitor 326 from FB_V (AC−). Alternatively, the internal capacitance of the AC bypass capacitor 326 may be detected to notify the user of the optimal switching timing based on the paper type or image.

  Here, as an example, switching from constant voltage control (DC−) to constant voltage control (DC +) is performed, but constant voltage control (DC +) → constant voltage control (DC−) → constant voltage control (DC +). But you can.

  Next, the operation of the printing apparatus 1 according to the present embodiment will be described.

  FIG. 8 is a flowchart illustrating an example of the flow of printing processing executed by the DC power supply 210 and the power supply control unit 400.

  As shown in FIG. 8, first, the power supply controller 400 inputs a constant voltage control (DC-) signal to the DC power supply 210 to turn it on (step S1).

  Next, the power supply control unit 400 waits until a switching timing for switching to constant current control (DC-) after a predetermined operation (step S2: No).

  When the switching timing comes (step S2: Yes), the power supply control unit 400 turns off the constant voltage control (DC−) (step S3) and switches the constant current control (DC−) to ON (step S4).

  Thereafter, the power supply control unit 400 waits until a switching timing for switching to constant voltage control (DC−) after a predetermined operation (step S5: No).

  When it is time to switch (step S5: Yes), the power controller 400 turns off the constant current control (DC-) (step S6) and switches the constant voltage control (DC-) to ON (step S7).

  Thereafter, the power supply control unit 400 waits until a switching timing for switching to constant voltage control (DC +) after a predetermined operation (step S8: No).

  When it is time to switch (step S8: Yes), the power supply controller 400 turns off the constant voltage control (DC−) (step S9) and switches the constant voltage control (DC +) to ON (step S10).

  When the constant voltage control (DC +) is on and the next printing is performed (step S11: No), the power supply control unit 400 turns off the constant voltage control (DC +) (step S12) and returns to step S1.

  On the other hand, when the constant voltage control (DC +) is ON and there is no next printing (step S11: Yes), the power supply control unit 400 ends the printing process.

  As described above, in the present embodiment, the DC power supply 210 includes the constant voltage control mechanism and the constant current control mechanism, and the DC voltage output is controlled by the constant current when the DC voltage falls, and the predetermined condition is satisfied. When is established, the output is switched to the constant voltage control, so that the fall time can be shortened only by the control without increasing the cost of the power source, and the deterioration of the image quality can be prevented.

  The program executed by the power supply control unit 400 of the above embodiment is provided by being incorporated in advance in a ROM or the like.

  Further, the program executed by the power supply control unit 400 of the above embodiment may be provided by being stored on a computer connected to a network such as the Internet and downloaded via the network. In addition, the program executed by the power control unit 400 of the above embodiment may be provided or distributed via a network such as the Internet.

  In addition, the program executed by the power supply control unit 400 of the above-described embodiment can be installed in a file that can be installed or executed, and a computer such as a CD-ROM, CD-R, memory card, DVD, or flexible disk (FD). May be stored in a readable storage medium and provided.

  The program executed by the power control unit 400 in the above embodiment has a module configuration for realizing the power control unit 400 on a computer. As actual hardware, for example, the CPU reads out a program from the ROM to the RAM and executes the program, whereby the above-described units are realized on the computer.

DESCRIPTION OF SYMBOLS 1 Power supply device, image forming apparatus 210 DC power supply 220 AC power supply 326 Bypass capacitor 400 Power supply control unit

Japanese Patent Laying-Open No. 2015-194663

Claims (10)

DC power supply that outputs DC voltage;
An AC power supply that outputs a superimposed voltage obtained by superimposing an AC voltage on the DC voltage;
A bypass capacitor that partially stores the charge of the alternating current to prevent the flow of current from the alternating current power supply to the direct current power supply;
A power supply control unit that accumulates the charge of the alternating current in the bypass capacitor in a short time by switching the control of the direct current voltage from constant current control to constant voltage control during the transfer period from image transfer to non-transfer period;
A power supply apparatus comprising: The power supply control unit controls the output of the DC voltage by the DC power supply during the constant voltage control.
The power supply device according to claim 1. The power supply control unit outputs a switching signal that instructs the DC power supply to switch from the constant current control to the constant voltage control at a predetermined timing during the constant current control.
The power supply device according to claim 1, wherein the power supply device is a power supply device. The power supply control unit outputs a switching signal that instructs the DC power supply to switch from the constant voltage control to the constant current control at a predetermined timing during the constant voltage control.
The power supply device according to claim 1, wherein the power supply device is a power supply device. The predetermined timing is a timing specified with reference to a print start reference signal.
The power supply device according to claim 3 or 4, wherein The power supply control unit switches from constant voltage control (DC−) to constant voltage control (DC +) as the constant voltage control based on the charge capacity stored in the bypass capacitor.
The power supply device according to claim 1. The power supply control unit notifies the user of the state of the bypass capacitor based on the charge capacity stored in the bypass capacitor.
The power supply device according to claim 1. The power supply control unit sets a constant voltage control direct current control signal for controlling the direct current voltage (DC−) output magnitude and the direct current (DC−) output magnitude with respect to the direct current power supply. A direct current control signal for controlling the constant current, a direct current control signal for controlling the constant voltage that controls the magnitude of the output of the direct current voltage (DC +), the constant voltage control (DC−), and the constant current control ( DC−) and a switching signal instructing switching of the constant voltage control (DC +).
The power supply device according to claim 1. A direct current power source that outputs a direct current voltage, an alternating current power source that outputs a superimposed voltage obtained by superimposing an alternating current voltage on the direct current voltage, and a charge of the alternating current to prevent the current from flowing from the alternating current power source to the direct current power source are combined. A power supply control method in a power supply device comprising:
Including the step of accumulating the charge of the alternating current in the bypass capacitor in a short time by switching the control of the direct current voltage from constant current control to constant voltage control during a transfer period from image transfer to non-transfer period.
And a power control method. DC power supply that outputs DC voltage;
An AC power supply that outputs a superimposed voltage obtained by superimposing an AC voltage on the DC voltage;
A bypass capacitor that partially stores the charge of the alternating current to prevent the flow of current from the alternating current power supply to the direct current power supply;
A power supply control unit that accumulates the charge of the alternating current in the bypass capacitor in a short time by switching the control of the direct current voltage from constant current control to constant voltage control during a non-transfer period from an image transfer period;
An image forming apparatus comprising:

Images