Image forming apparatus

Abstract

An image forming apparatus includes: an image forming section; an AC-DC power supply unit to which an AC voltage supplied by a commercial power supply is inputted and which converts the AC voltage into a DC voltage; a control unit for controlling the image forming unit on the basis of a control value obtained by AD-converting a signal from the image forming unit; and a DC-DC conversion unit for converting the DC voltage output from the AC-DC power supply unit into a plurality of DC voltages, and outputting a first DC voltage and a second DC voltage different from the first DC voltage among the plurality of DC voltages to the control unit, the control unit acquiring two AD conversion values obtained by AD-converting the first DC voltage and the second DC voltage, respectively, and outputting the two AD conversion values to the AC-DC power supply unit. A gain correction value and an offset correction value for linearly correcting the control value are calculated on the basis of the two acquired AD conversion values, and the control value is corrected on the basis of the gain correction value and the offset correction value.

Description

Technical Field

[0001] The present invention relates to a technology for correcting a conversion result of an AD conversion circuit used in an image forming apparatus. Background Art

[0002] Conventional image forming devices include: a high-voltage power supply substrate having a charging circuit and a transfer circuit; and a control unit to which a sensor signal from a sensor is input. The control unit performs AD conversion on the feedback signal output from the high-voltage power supply substrate and the sensor signal, and controls the image forming device based on the result of the AD conversion.

[0003] Patent Document 1 discloses an image forming apparatus that determines whether a high-voltage power supply circuit is an old version or a new version based on a feedback voltage from a high-voltage power supply substrate.

[0004] Patent Document 1: Japanese Patent Application Publication No. 2009-31993 Summary of the invention

[0005] However, when the control unit performs AD conversion using an AD conversion circuit with large AD conversion error and poor accuracy, control based on sensor signals and version determination of the high-voltage power supply board may not be properly performed.

[0006] An object of the present invention is to provide an image forming apparatus capable of obtaining a high-precision AD conversion result even when using an AD conversion circuit having a large AD conversion error and poor precision.

[0007] In order to achieve the above-mentioned purpose, the present invention provides an image forming device, comprising: an image forming unit; an AC-DC power supply unit, which is input with an AC voltage supplied by a commercial power supply and converts the AC voltage into a DC voltage; a control unit, which is used to control the image forming unit, and controls the image forming unit based on a control value obtained by AD-converting a signal from the image forming unit; and a DC-DC conversion unit, which is used to convert the DC voltage output from the AC-DC power supply unit into multiple DC voltages, and output a first DC voltage and a second DC voltage different from the first DC voltage among the multiple DC voltages to the control unit, the control unit obtains two AD conversion values ​​obtained by AD-converting the first DC voltage and the second DC voltage, respectively, calculates a gain correction value and an offset correction value for linearly correcting the control value based on the two AD conversion values ​​obtained, and corrects the control value based on the gain correction value and the offset correction value.

[0008] The control unit performs AD conversion on the first DC voltage and the second DC voltage, and calculates a gain correction value and an offset correction value for linear correction of the control value based on the two AD conversion values. The first DC voltage and the second DC voltage are known DC voltages and are also voltages input to the control unit, so the voltage fluctuation is small. In order to obtain the gain correction value and the offset correction value for linear correction, at least two AD conversion values ​​of the two DC voltages are required to be AD converted respectively. The inventor of the present invention has found a method of using two voltages input to the control unit. The control unit obtains the gain correction value and the offset correction value from the two AD conversion values, and performs linear correction on the control value using the gain correction value and the offset correction value, thereby being able to appropriately control the image forming unit.

[0009] In the image forming apparatus of the present invention, the control unit includes a CPU and an AD conversion circuit, the DC-DC conversion unit outputs the first DC voltage to the CPU, and the CPU is driven by the first DC voltage.

[0010] Since the first DC voltage is a voltage for driving the CPU, the first DC voltage can be used as one of two voltages required for obtaining the gain correction value and the offset correction value with a small voltage fluctuation.

[0011] In the image forming apparatus of the present invention, the DC-DC conversion section includes a linear regulator, and the linear regulator converts the DC voltage into the second DC voltage and outputs the second DC voltage to the control section.

[0012] Since the second DC voltage is a voltage converted by a linear regulator, the voltage fluctuation is small and the second DC voltage can be used as the other of the two voltages required to obtain the gain correction value and the offset correction value.

[0013] The image forming device of the present invention comprises: a photosensitive drum; a charger for charging the photosensitive drum; a developing roller for supplying developer to the photosensitive drum; a transfer roller for transferring the developer image formed on the surface of the photosensitive drum to a sheet passing between the transfer roller and the photosensitive drum; and a high-voltage power supply substrate for applying the high-voltage voltage converted from the DC voltage to the charger, the developing roller and the transfer roller, respectively, the control section performs AD conversion on a feedback signal which is a signal corresponding to the output voltage applied by the high-voltage power supply substrate to obtain the control value, and determines the type of the high-voltage power supply substrate based on the result of linearly correcting the control value using the gain correction value and the offset correction value.

[0014] In this way, the control value is obtained by AD converting the feedback signal which is a signal corresponding to the output voltage applied by the high-voltage power supply substrate, and the type of the high-voltage power supply substrate is determined based on the result of linear correction of the control value using the gain correction value and the offset correction value, thereby further improving the accuracy of determining the type of the high-voltage power supply substrate.

[0015] In the image forming apparatus of the present invention, the control section changes parameters for controlling the high-voltage power supply substrate according to the determined type of the high-voltage power supply substrate.

[0016] Thus, the parameters for controlling the high-voltage power supply substrate are changed to optimal parameters corresponding to the type of the high-voltage power supply substrate, so that the high-voltage power supply substrate can be accurately controlled.

[0017] The image forming device of the present invention comprises: a photosensitive drum; a charger for charging the photosensitive drum; a developing roller for supplying developer to the photosensitive drum; a transfer roller for transferring the developer image formed on the surface of the photosensitive drum to a sheet passing between the transfer roller and the photosensitive drum; and a high-voltage power supply substrate for applying the high-voltage voltage converted from the DC voltage to the charger, the developing roller and the transfer roller, respectively, the control section performs AD conversion on a feedback signal which is a signal corresponding to the output voltage applied by the high-voltage power supply substrate to obtain the control value, and performs control based on the result of linear correction of the control value using the gain correction value and the offset correction value so that the voltage value of the high-voltage voltage becomes the target voltage value.

[0018] In this way, a control value is obtained by AD converting a feedback signal that is a signal corresponding to the output voltage applied to the high-voltage power supply substrate, and control is performed based on the result of linearly correcting the control value using a gain correction value and an offset correction value so that the voltage value of the high-voltage voltage becomes a target voltage value, thereby enabling the voltage value of the high-voltage voltage to be controlled to a desired target voltage.

[0019] The image forming device of the present invention comprises: an image forming unit comprising: a fixing device for fixing an image formed on a sheet onto the sheet; and a first temperature sensor for detecting the temperature of the fixing device and outputting it as a first temperature detection signal; the control unit performs AD conversion on the first temperature detection signal output from the first temperature sensor, uses the AD conversion value of the first temperature detection signal as the control value, and performs linear correction using the gain correction value and the offset correction value.

[0020] Thus, it is possible to obtain a digital first temperature detection signal that is closer to the analog first temperature detection signal output from the first temperature sensor.

[0021] The image forming device of the present invention further includes: a second temperature sensor for detecting the temperature inside the image forming device and outputting it as a second temperature detection signal; and a temperature and humidity sensor for detecting the temperature and humidity outside the image forming device and outputting them as a third temperature detection signal and a humidity detection signal. The control unit performs AD conversion on the second temperature detection signal output from the second temperature sensor, and performs AD conversion on the third temperature detection signal and the humidity detection signal output from the temperature and humidity sensor, and sets the target temperature of the fixing device based on the result of linear correction of each AD conversion value of the second temperature detection signal, the third temperature detection signal and the humidity detection signal using the gain correction value and the offset correction value.

[0022] In this way, the second temperature detection signal output from the second temperature sensor is AD converted, and the third temperature detection signal and the humidity detection signal output from the temperature and humidity sensor are AD converted, and the target temperature of the fixing device is set based on the result of linear correction of each AD conversion value of the second temperature detection signal, the third temperature detection signal and the humidity detection signal using the gain correction value and the offset correction value, thereby enabling the target temperature of the fixing device to be set to the desired target temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a side sectional view of the main part of the monochrome laser printer according to the first embodiment of the present invention.

[0024] Figure 2 It is shown Figure 1 Block diagram of the control structure of a black and white laser printer.

[0025] Figure 3 It is shown that the Figure 2 A flowchart of the process of substrate judgment processing executed by the control circuit on the main substrate, especially the CPU.

[0026] Figure 4 It is shown Figure 3 Flowchart of the detailed process of Gain and Offset acquisition processing included in the substrate judgment processing.

[0027] Figure 5 It is shown Figure 4 Flowchart of the detailed procedure of the measured AD value acquisition processing included in the Gain and Offset acquisition processing.

[0028] Figure 6 It is used to illustrate Figure 4 Gain and Offset to obtain the processed graph.

[0029] Figure 7 (a) is a diagram for explaining a method of acquiring a corrected AD value, and (b) is a diagram showing an example of table data used in the substrate determination process.

[0030] Figure 8 This is a diagram showing an example of control parameters used according to the type of substrate determined in the substrate determination process.

[0031] Fig. 9 It is shown that the Figure 2 Flowchart of the process of high voltage control processing executed by the control circuit on the main substrate, especially the CPU.

[0032] Fig.10 (a) is a flowchart showing the process of power-on processing executed by the CPU of the control circuit of the black-and-white laser printer of the second embodiment of the present invention, in particular, and (b) is a flowchart showing the process of high-voltage voltage control processing.

[0033] Fig.11 This is a flowchart showing the procedure of the fixing control process executed by the CPU of the control circuit in the monochrome laser printer according to the second embodiment of the present invention. DETAILED DESCRIPTION

[0034] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0035] (First Embodiment)

[0036] Figure 1 1 is a cross-sectional view showing a schematic structure of a monochrome laser printer 1 according to an embodiment of the present invention. The monochrome laser printer 1 is an example of an image forming apparatus. Hereinafter, the monochrome laser printer 1 is simply referred to as a printer 1 .

[0037] The printer 1 forms a toner image on a sheet S supplied from a supply tray 3 or a manual tray 4 disposed at a lower portion of the main body housing 2 using a processing unit 6. Then, the printer 1 heats the sheet S on which the toner image is formed and performs a fixing process using a fixing device 7. Furthermore, the printer 1 discharges the sheet S to a discharge tray 8 disposed at an upper portion of the main body housing 2 using a discharge roller 24. The processing unit 6 and the fixing device 7 constitute an image forming unit.

[0038] The processing section 6 includes a scanner 10 , a developing cartridge 13 , a photosensitive drum 17 , a charger 18 , a transfer roller 19 , and the like.

[0039] The scanning unit 10 is arranged at the upper part of the main body housing 2, and includes a laser light emitting unit (not shown), a polygon mirror 11, a plurality of reflectors 12, and a plurality of lenses (not shown). In the scanning unit 10, the laser light emitted from the laser light emitting unit is irradiated onto the surface of the photosensitive drum 17 via the polygon mirror 11, the reflector 12, and the lens at a high speed scanning as indicated by the single-dot chain line.

[0040] The developing cartridge 13 is detachably mounted on the main body housing 2, and contains toner therein. In addition, a developing roller 14 and a supply roller 15 are arranged in a state facing each other at the toner supply port of the developing cartridge 13. The toner in the developing cartridge 13 is supplied to the developing roller 14 by the rotation of the supply roller 15, and is carried on the developing roller 14.

[0041] A charger 18 is disposed above the photosensitive drum 17 at a distance. A transfer roller 19 is disposed below the photosensitive drum 17 and faces the photosensitive drum 17. The surface of the photosensitive drum 17 is first uniformly charged, for example, positively charged, by the charger 18 while rotating. Then, an electrostatic latent image is formed on the photosensitive drum 17 by laser light from the scanner 10.

[0042] Thereafter, when the photosensitive drum 17 contacts the developing roller 14 and rotates, the toner carried on the developing roller 14 is supplied to the electrostatic latent image on the surface of the photosensitive drum 17, thereby forming a toner image. Thereafter, when the sheet S passes between the photosensitive drum 17 and the transfer roller 19, the toner image is transferred to the sheet S by a transfer bias applied to the transfer roller 19.

[0043] The fixing device 7 is arranged downstream of the processing unit 6 in the sheet conveying direction and includes a fixing roller 22, a pressure roller 23 for pressing the fixing roller 22, and a heater 31 for heating the fixing roller 22. The printer 1 also includes a display unit 27 for displaying print information and the like.

[0044] Next, refer to Figure 2 The control structure of the printer 1 is described. Figure 2 As shown, the printer 1 further includes a control circuit 101, a ROM 102, a RAM 103, and a nonvolatile memory 104. The control circuit 101, the ROM 102, the RAM 103, the nonvolatile memory 104, DC-DC (Direct Current-Direct Current) converters 105A to 105D, and an LDO 106 are mounted on the main substrate 100. LDO is a low drop out regulator, which is a type of linear regulator.

[0045] The control circuit 101 is composed of, for example, a general-purpose SoC (System on a Chip) having a CPU 101A, and controls the various parts of the printer 1 as a whole. The control circuit 101 includes a pulse output / timing circuit 101B and an AD (analog-to-digital) conversion circuit 101C in addition to the CPU 101A. The control circuit 101 is electrically connected to the ROM 102, the RAM 103, and the nonvolatile memory 104. The ROM 102, the RAM 103, and the nonvolatile memory 104 are connected to the ROM 102, the RAM 103, and the nonvolatile memory 104. Figure 2 The control circuit 101 is externally mounted in the embodiment, but is not limited thereto and may also be built in the control circuit 101 .

[0046] The ROM 102 stores various control programs and various settings for controlling the printer 1. Figure 3 ) and high voltage control processing (refer to Fig. 9 ) are included in the various control programs. In addition, a part of the various control programs and various settings may also be stored in the non-volatile memory 104.

[0047] The RAM 103 is used as a work area for reading various control programs and a storage area for temporarily storing image data included in a print job. The CPU 101A of the control circuit 101 reads the control programs from the ROM 102 or the nonvolatile memory 104 and the signals output from various sensors, stores the processing results in the RAM 103 or the nonvolatile memory 104, and controls each part of the printer 1.

[0048] The low-voltage power supply substrate 113 is connected to the DC-DC converter 105A of the main substrate 100. The low-voltage power supply substrate 113 includes an AC-DC (alternating current-direct current) converter (not shown), and converts the input AC voltage (for example, commercial AC100V) into a DC voltage (for example, DC24V) through the AC-DC converter, and outputs it to the DC-DC converter 105A and the high-voltage power supply substrate 112. The low-voltage power supply substrate 113 also outputs the input AC voltage to the fixing device 7 as it is.

[0049] The DC-DC converter 105A converts the DC24V from the low voltage power supply substrate 113 into, for example, DC5.3V, and outputs it to the DC-DC converter 105B, the DC-DC converter 105D, and the LDO 106. The DC-DC converter 105B converts the input DC5.3V into, for example, DC3.3V, and outputs it to the DC-DC converter 105C. The DC-DC converter 105C converts the input DC3.3V into, for example, DC1.8V, and outputs it to the AD input range setting port VAVDH of the AD conversion circuit 101C. Thus, the AD conversion circuit 101C can perform AD conversion on the analog voltage values ​​in the range of 0V to a maximum of 1.8V input to the AD conversion input ports AD1 to AD6, respectively.

[0050] LDO 106 converts DC5.3V from DC-DC converter 105A into, for example, DC3.3V. LDO 106 is a type of linear regulator, and therefore outputs a voltage with a stable value having a small fluctuation range. LDO 106 outputs DC3.3V to AD conversion input port AD1 of AD conversion circuit 101C. As described above, AD conversion circuit 101C can only perform AD conversion of a voltage of a maximum of 1.8V, and therefore, for example, a voltage divided into 1.48V is input to AD conversion input port AD1. The output voltage of LDO 106 is AD-converted by AD conversion circuit 101C, and therefore, in order to indicate that it is an analog DC voltage before AD conversion, it is recorded as 3.3AVDC. Here, AV is an abbreviation for analog voltage.

[0051] In addition to the AD conversion input port AD1, the LDO 106 also supplies 3.3AVDC to the thermistor 120 provided in the fixing device 7 and the internal thermistor 130 provided in the main body housing 2 of the printer 1. For example, the thermistor 120 is arranged one at a position opposite to the center position of the fixing roller 22 and one at a position opposite to one end of the fixing roller 22 in a state of not contacting the center position and one end of the fixing roller 22, and outputs temperature signals CENTER and EDGE corresponding to the temperature of the center position and one end of the fixing roller 22, and outputs them to the AD conversion input port AD3. The internal thermistor 130 outputs the internal temperature signal corresponding to the internal temperature in the main body housing 2 to the AD conversion input port AD5. The temperature signals CENTER, EDGE and the internal temperature signal respectively input to the AD conversion input ports AD3 and AD5 are also divided so as not to exceed the maximum 1.8V. This is also the same for the voltage values ​​of the signals input to the other AD conversion input ports AD4 and AD6.

[0052] The DC-DC converter 105D converts the DC 5.3 V from the DC-DC converter 105A into, for example, DC 0.89 V. The DC-DC converter 105D supplies the DC 0.89 V as the power supply voltage Vcore to the CPU 101A, and also outputs it to the AD conversion input port AD2. The power supply voltage Vcore is a power supply voltage for driving the CPU 101A, and is 0.89 V, which is lower than other power supply voltages 1.8 V or 3.3 A VDC, so the voltage fluctuation range is small and stable.

[0053] The pulse output / timing circuit 101B of the control circuit 101 is electrically connected to the fixing device 7. The pulse output / timing circuit 101B starts supplying the AC voltage from the low-voltage power supply substrate 113 to the heater 31 by outputting an on signal to the fixing device 7 according to the instruction of the CPU 101A, and stops supplying the AC voltage from the low-voltage power supply substrate 113 to the heater 31 by not outputting an on signal to the fixing device 7. The supply of the AC voltage from the low-voltage power supply substrate 113 to the heater 31 is performed by wave number control and phase control of the AC voltage based on the zero-crossing signal from the fixing device 7. When the fixing device 7 starts the fixing operation, the CPU 101A monitors whether the temperature of the fixing device 7 reaches the target temperature, and judges whether the target temperature is reached based on the temperature signals CENTER and EDGE from the thermistor 120. When the target temperature is not reached, the CPU 101A instructs the pulse output / timing circuit 101B to output an on signal, and when the target temperature is exceeded, the CPU 101A instructs the pulse output / timing circuit 101B not to output an on signal.

[0054] The high-voltage power supply substrate 112 applies the high-voltage charging voltage CHG, the developing voltage DEV and the transfer voltage to the charger 18, the developing roller 14 and the transfer roller 19, respectively, based on the DC24V from the low-voltage power supply substrate 113. The high-voltage power supply substrate 112 also applies the gate voltage GRID to the charger 18. Based on the control signal from the control circuit 101, the control is performed so that the gate voltage GRID, the developing voltage DEV and the transfer current TR flowing through the transfer roller 19 are target values. The high-voltage power supply substrate 112 outputs the FB (feedback) signal (FB-CHG signal, FB-GRID signal, FB-DEV signal and FB_TR signal) output from the charger 18, the developing roller 14 and the transfer roller 19 to the AD conversion input port AD4 according to the applied charging voltage CHG, the gate voltage GRID, the developing voltage DEV and the transfer current TR. The FB-TR signal is output to the AD conversion input port AD4 as a signal converted from the transfer current TR to voltage. The CPU 101A reads the AD value of the FB signal AD-converted by the AD conversion circuit 101C from the AD conversion circuit 101C, and changes the control signal so that the AD value of the FB signal approaches the target AD value. As a result, the values ​​of the gate voltage GRID, the development voltage DEV, and the transfer current TR approach the target values.

[0055] The CPU 101A reads the AD value of the FB-CHG signal through the AD conversion circuit 101C, converts the read AD value into a charged voltage, determines whether the charged voltage CHG is a voltage above a threshold, and determines the type of the high-voltage power supply substrate 112 .

[0056] The external temperature and humidity sensor 140 is provided outside the main body casing 2 , and outputs a temperature signal and a humidity signal corresponding to the temperature and humidity outside the machine to the AD conversion input port AD6 .

[0057] according to Figures 3 to 9 , the control processing performed by the printer 1 configured as described above is described in detail.

[0058] Figure 3 The following is a procedure of a board determination process executed by the control circuit 101, particularly the CPU 101A. The board determination process is used to determine the type of the high voltage power board 112 currently installed in the printer 1, and is started when the printer 1 is powered on.

[0059] The types of the high-voltage power supply substrate 112 include different versions and different manufacturers. The type of the high-voltage power supply substrate 112 is determined, for example, based on the voltage value of the FB-CHG signal in the FB signal output by the high-voltage power supply substrate 112. Specifically, if the voltage value of the FB-CHG signal is within the first range, the type of the high-voltage power supply substrate 112 is determined to be substrate A, and if the voltage value of the FB-CHG signal is within the second range, the type of the high-voltage power supply substrate 112 is determined to be substrate B. Since the voltage value of the FB-CHG signal is an analog value, the CPU 101A determines whether the voltage value of the FB-CHG signal after AD conversion by the AD conversion circuit 101C is within the first range or the second range. However, when the AD conversion error of the AD conversion circuit 101C is large and the accuracy is low, the voltage value of the FB-CHG signal after AD conversion is greatly deviated from the voltage value of the FB-CHG signal before AD conversion. Even if the voltage value of the FB-CHG signal before AD conversion is within the first range, the voltage value of the FB-CHG signal after AD conversion may be within the second range, so the type of the high-voltage power supply substrate 112 may be misjudged. Therefore, in the substrate judgment process, for example, a Gain correction value and an Offset correction value for linear correction are calculated for the AD value actually obtained by AD conversion by the AD conversion circuit 101C, that is, the measured AD value, and the substrate is judged based on the corrected AD value (corrected AD value of the FB-CHG signal) obtained by correcting the measured AD value based on the Gain correction value and the Offset correction value. Thus, the accuracy of substrate judgment can be improved. Moreover, in the substrate judgment process, the parameters used in the judged substrate are also determined. Thus, when controlling the substrate, the determined parameters can be read and directly used for control, which is very convenient.

[0060] exist Figure 3 In the process, first, the CPU 101A executes Gain and Offset acquisition processing (S10). Figure 4 The detailed process of Gain and Offset acquisition is shown in Figure 4 In the process, first, the CPU 101A executes a measured AD value acquisition process of the power supply voltage Vcore (DC 0.89 V), which is the input voltage of the AD conversion input port AD2 of the AD conversion circuit 101C (S30).

[0061] Figure 5 The detailed process of obtaining the measured AD value is shown in FIG. Figure 5In the process, first, the CPU 101A initializes the counter n to "1" (S50), then reads the AD value of the designated port and stores the AD value in the area AD[n] reserved by the RAM 103 (S52). The designated port at this time is the AD conversion input port AD2, n=1.

[0062] Next, the CPU 101A determines whether n=10 (S54). If n<10 (S54: No), the CPU 101A increments the counter n (S56), and then returns the process to S52. Then, the CPU 101A adds "1" to the counter n, reads the AD value of the designated port, and stores it in the area AD[n]. If n=10 (S54: Yes), the CPU 101A proceeds to the next step S58. If the determination in S54 is "Yes", 10 measured AD values ​​are stored in the areas AD[1] to AD

[10] .

[0063] In S58, the CPU 101A stores the largest AD value among the 10 AD values ​​stored in the areas AD[1] to AD

[10] in the area AD_max, and in the next S60, the CPU 101A stores the smallest AD value among the 10 AD values ​​stored in the areas AD[1] to AD

[10] in the area AD_min.

[0064] Then, the CPU 101A averages the eight AD values ​​excluding the largest AD value AD_max and the smallest AD value AD_min from among the ten AD values ​​stored in the areas AD[1] to AD

[10] , stores the average value in the area AD_avg (S62), and terminates the measured AD value acquisition process.

[0065] In this way, the average of the AD values ​​is taken after removing the largest AD value and the smallest AD value. This is because the largest AD value and the smallest AD value may contain a conversion error that exceeds the normal conversion error of the AD conversion circuit 101C. In the absence of this possibility, all 10 AD values ​​may be used to take the average. In addition, the number of measured AD values ​​used for averaging is not limited to 10, and may be more or less than it. However, in the case of too few such as 1 or 2, it may not be possible to correctly reflect the conversion error of the AD conversion circuit 101C, so it is not preferred.

[0066] return Figure 4, the CPU 101A substitutes the average AD value AD_avg of the input voltage of the AD conversion input port AD2 into y1 (S32). In the following S34 and S36, the CPU 101A changes the AD conversion input port AD2 to the AD conversion input port AD1, performs an actual AD value acquisition process on the input voltage of the AD conversion input port AD1, i.e., 3.3AVDC (actually, 1.48V) from the LDO 106 (S34), and substitutes the average AD value AD_avg of the input voltage of the AD conversion input port AD1 obtained by the actual AD value acquisition process into y2 (S36).

[0067] Next, the CPU 101A calculates the Gain and Offset of the correction straight line C in S38 and S40. Figure 6 FIG. 1 is a diagram for explaining an example of a correction straight line C and the reason why the correction straight line C is necessary. Figure 6 In FIG. 1 , the vertical axis is the measured AD value and the horizontal axis is the ideal AD value. Alternatively, the vertical axis may be the ideal AD value and the horizontal axis may be the measured AD value. In addition, the AD conversion circuit 101C converts the analog voltage in the range of 0 to 1.8 V into a digital value with a resolution of 0 to 4095.

[0068] When an AD conversion circuit without conversion error is used as the AD conversion circuit 101C, since the measured AD value = the ideal AD value, Figure 6 As shown by the middle dotted line, it is a straight line L passing through the origin O and inclined at 45 degrees. However, if there is a conversion error in the AD conversion circuit 101C, it deviates from the straight line L. This deviation occurs linearly and is approximated by the straight line C.

[0069] If the slope (Gain) and the intercept (Offset) are determined, the correction straight line C is uniquely determined. Therefore, the CPU 101A calculates the Gain and the Offset of the correction straight line C in S38 and S40. The Gain and the Offset of the correction straight line C can be calculated by the following equations.

[0070] Gain=(y2-y1) / (x2-x1) (1)

[0071] Offset = y2 - Gain × x2 (2)

[0072] Here, x1 is the AD-converted value obtained by calculating the input voltage 0.89V of the AD conversion input port AD2, and x2 is the AD-converted value obtained by calculating the input voltage 1.48V of the AD conversion input port AD1. Figure 6In the equation (1), if point A is represented by coordinates (x1, y1) and point B is represented by coordinates (x2, y2), then the slope from point A to point B (= the slope of the correction line C), i.e., Gain, can be calculated using equation (1).

[0073] Then, when Gain is calculated, the correction line C is:

[0074] y=Gain×x+Offset (3)

[0075] Since the correction line C passes through point B (x2, y2), when the coordinates of point B (x2, y2) are substituted into equation (3),

[0076] y2=Gain×x2+Offset(3)'

[0077] If the equation (3)' is transformed, it becomes the equation (2), and the Offset is calculated.

[0078] Then, the CPU 101A stores the calculated Gain and Offset in the RAM 103 (S42), and then terminates the Gain and Offset acquisition process.

[0079] return Figure 3 The CPU 101A obtains the input voltage of the AD conversion input port AD4, that is, the measured AD value Y_CHG of the voltage of the FB-CHG signal in the FB signal (S12). Then, the CPU 101A obtains the corrected AD value X_CHG for the measured AD value Y_CHG from the correction line C (S14).

[0080] Figure 7 (a) in FIG. 1 is a diagram for explaining the process of S14. Since the correction straight line C is generally as shown in equation (3), x is as shown in equation (4) below.

[0081] x=(y-Offset) / Gain (4)

[0082] Therefore, the corrected AD value X_CHG is calculated by the following equation (5).

[0083] X_CHG=(Y_CHG-Offset) / Gain (5)

[0084] Next, CPU 101A determines whether the corrected AD value X_CHG is within the first range (S16). If the corrected AD value X_CHG is within the first range (S16: Yes), it determines that the type of the high-voltage power supply substrate 112 is substrate A (S18). After determining the parameters of substrate A (S20), the substrate judgment process is ended.

[0085] On the other hand, when the correction AD value X_CHG is not within the first range (S16: No), CPU 101A determines whether the correction AD value X_CHG is within the second range (S22). When the correction AD value X_CHG is within the second range (S22: Yes), it is determined that the type of the high-voltage power supply substrate 112 is substrate B (S24). After determining the parameters of substrate B (S26), the substrate judgment process is ended.

[0086] Figure 7 (b) in FIG. 1 shows an example of each of the first range and the second range. Figure 8 (a) shows the parameters of each FB signal in the first range (substrate A). Figure 8 (b) shows the parameters of each FB signal in the second range (substrate B).

[0087] return Figure 3 When the correction AD value X_CHG is not within the second range (S22: No), the CPU 101A displays an error on the display unit 27 (S28), and then ends the substrate determination process.

[0088] Fig. 9 2 shows the procedure of the high voltage control process. The high voltage control process is started when the CPU 101A receives a print job and operates the high voltage power source board 112 to print on the sheet S based on the print job. Fig. 9 In the process, first, the CPU 101A sets target values ​​(grid voltage GRID, development voltage DEV, and transfer current TR) (S70). The target values ​​are set according to the environment in which the printer 1 is located, and the detailed description thereof is omitted.

[0089] Next, the CPU 101A reads out the parameters corresponding to the type of the high voltage power supply substrate 112 (S72). Figure 3 The substrate judgment process is completed, so the judgment of whether the high-voltage power supply substrate 112 is substrate A or substrate B is completed, and the determination of the parameters to be used is also completed. However, in the substrate judgment process, it is sometimes impossible to judge whether the high-voltage power supply substrate 112 is substrate A or substrate B, but this situation does not exist in the high-voltage voltage control process. Therefore, the CPU 101A can read Figure 8 The parameters shown in (a) and Figure 8 One of the parameters shown in (b) in .

[0090] Then, the CPU 101A performs feedback control based on the read parameters to achieve the set target value (S74). Now, assuming that the high-voltage power supply substrate 112 is determined to be substrate A, the read parameters Figure 8For example, when 850V is set as the target voltage of the GRID voltage, the target FB voltage of the GRID voltage is 2.38V, and its AD value, i.e., the target AD value, is 737. Therefore, the CPU 101A outputs a control signal to the high-voltage power supply substrate 112 so that the measured AD value of the FB voltage of the GRID voltage among the input voltages of the AD conversion input port AD4 approaches the target AD value 737. The specific control of the other development voltages DEV and the transfer current TR is also the same as the control of the GRID voltage.

[0091] As described above, the printer 1 of the present embodiment includes: an image forming unit (6, 7); a low voltage power supply substrate 113 to which an AC voltage supplied by a commercial power supply is input and which converts the AC voltage into a DC voltage; a control circuit 101 to control the image forming unit (6, 7) and to control the image forming unit (6, 7) based on a control value obtained by AD-converting a signal from the image forming unit (6, 7); and DC-DC converters 105A to 105D, 106 to convert a DC voltage output from the low voltage power supply substrate 113 into a plurality of DC voltages and to output a power supply voltage Vcore and 3.3AVDC different from the power supply voltage Vcore among the plurality of DC voltages to the control circuit 101. The control circuit 101 obtains two AD conversion values ​​obtained by AD-converting the power supply voltage Vcore and 3.3AVDC, respectively, and calculates Gain and Offset for linearly correcting the control value based on the obtained two AD conversion values, and corrects the control value based on Gain and Offset.

[0092] Thus, in the printer 1 of the present embodiment, the control circuit 101 performs AD conversion on the power supply voltage Vcore and 3.3AVDC, and calculates Gain and Offset for linear correction of the control value based on the two AD conversion values. The power supply voltage Vcore and 3.3AVDC are known DC voltages and are also voltages input to the control circuit 101, so the voltage fluctuation is small. In order to obtain Gain and Offset for linear correction, at least two AD conversion values ​​obtained by AD conversion of the two DC voltages are required, and the inventors of the present invention have found a method of using the two voltages input to the control unit. The control circuit 101 obtains Gain and Offset from the two AD conversion values, and performs linear correction on the control value using Gain and Offset, thereby being able to appropriately control the image forming unit (6, 7).

[0093] The control circuit 101 includes a CPU 101A and an AD conversion circuit 101C. The DC-DC converters 105A to 105D and 106 output a power supply voltage Vcore to the CPU 101A, and the CPU 101A is driven by the power supply voltage Vcore.

[0094] Since the first DC voltage is a voltage for driving the CPU 101A, the first DC voltage can be used as one of two voltages required for obtaining Gain and Offset with less voltage fluctuation.

[0095] In addition, the DC-DC converters 105A to 105D and 106 include an LDO 106 that converts a DC voltage into 3.3A VDC and outputs the converted voltage to the control circuit 101 .

[0096] Since 3.3AVDC is a voltage converted by the LDO 106, the voltage fluctuation is small and can be used as the other of the two voltages required to obtain Gain and Offset.

[0097] In addition, the image forming section 6, 7 includes: a photosensitive drum 17; a charger 18 for charging the photosensitive drum 17; a developing roller 14 for supplying a developer to the photosensitive drum 17; a transfer roller 19 for transferring a developer image formed on the surface of the photosensitive drum 17 to a sheet S passing between the transfer roller 19 and the photosensitive drum 17; and a high-voltage power supply substrate 112 for applying a high voltage voltage obtained by converting a DC voltage to the charger 18, the developing roller 14, and the transfer roller 19. The control circuit 101 obtains a control value by performing AD conversion on an FB signal that is a signal corresponding to an output voltage applied from the high-voltage power supply substrate 112, and determines the type of the high-voltage power supply substrate 112 based on the result of linear correction of the control value using Gain and Offset.

[0098] In this way, the control value is obtained by AD converting the FB signal, which is a signal corresponding to the output voltage applied to the high-voltage power supply substrate 112, and the type of the high-voltage power supply substrate 112 is determined based on the result of linear correction of the control value using Gain and Offset, thereby further improving the accuracy of determining the type of the high-voltage power supply substrate 112.

[0099] In addition, the control circuit 101 changes parameters for controlling the high-voltage power supply substrate 112 according to the determined type of the high-voltage power supply substrate 112 .

[0100] Thus, the parameters for controlling the high-voltage power source substrate 112 are changed to optimal parameters corresponding to the type of the high-voltage power source substrate 112 , so that the high-voltage power source substrate 112 can be accurately controlled.

[0101] (Second Embodiment)

[0102] Next, the second embodiment of the present invention will be described. This embodiment differs from the first embodiment in that only a portion of the control processing executed by the CPU 101A is different, so the description will be centered on the different portions, and the description of the remaining portions will be appropriately omitted. In addition, the hardware of this embodiment is the same as that of the first embodiment. Figure 1 and Figure 2 Documented hardware.

[0103] Fig.10 (a) in FIG. 1 shows the power-on processing executed by the printer 1 of this embodiment, particularly the CPU 101A. The power-on processing starts when the power of the printer 1 is turned on.

[0104] like Fig.10 As shown in (a), when the power is turned on, the process is to only extract Figure 3 The Gain and Offset acquisition process is the first process in the substrate determination process. The Gain and Offset acquisition process acquires the Gain and Offset of the correction line C and stores them in the RAM 103 as described in the first embodiment.

[0105] Fig.10 (b) shows the process of high voltage control processing in this embodiment, which is different from the process of high voltage control processing in the first embodiment ( Fig. 9 ) corresponds to. Fig.10 (b) and Fig. 9 It is known that in Fig.10 In (b) of FIG. 1 , each process of S 76 and S 78 is added, and the process of S 74 is slightly changed by adding the process of S 78. Specifically, in the high voltage control process of the first embodiment, the feedback control of the high voltage power supply substrate 112 is performed without correcting the AD value of the input FB signal of the AD conversion input port AD4. In contrast, in the high voltage control process of the present embodiment, after correcting the AD value of the input FB signal of the AD conversion input port AD4 (S 76, S 78), feedback control is performed so that the corrected AD value becomes the target AD value (S 74'). The processes of S 76 and S 78 are similar to those of FIG. Figure 3 The processing of S12 and S14 is the same, so further description is omitted.

[0106] according to Fig.10 The high voltage control process in (b) is Fig. 9 Compared with the high voltage control process of S70, the voltage or current output from the high voltage power source substrate 112 can be controlled to be closer to the target value set in S70.

[0107] Fig.11 FIG. 2 shows a procedure of a fixing control process executed by the CPU 101A to control the fixing temperature of the fixing device 7. The fixing control process is similar to the Fig.10 The high voltage control process (b) in FIG. 1 is similarly started when, for example, the CPU 101A receives a print job and performs printing on a sheet S according to the print job.

[0108] exist Fig.11 In the embodiment of the present invention, first, the CPU 101A obtains the measured AD value of the internal temperature signal output by the internal thermistor 130 and the measured AD values ​​of the external temperature signal and the external humidity signal output by the external temperature and humidity sensor 140 (S80). Specifically, the CPU 101A obtains the measured AD value of the internal temperature signal by reading the digital value after the analog input voltage of the AD conversion input port AD5 is converted by the AD conversion circuit 101C. Similarly, the CPU 101A obtains the measured AD value of the external temperature signal and the external humidity signal by reading the digital value after the analog input voltage of the AD conversion input port AD6 is converted by the AD conversion circuit 101C. Since two analog signals are input to the AD conversion input port AD6, it is necessary to switch them one by one to obtain each measured AD value.

[0109] Next, the CPU 101A obtains each corrected AD value for each measured AD value from the correction line C (S82). This obtaining process is similar to that of the first embodiment. Figure 3 The acquisition process is the same as that described in S14, so its description is omitted.

[0110] Next, the CPU 101A sets the target temperature of the fixing device 7 (S84). As a setting method, for example, the following method can be considered: based on each correction AD value obtained in S82, the target temperature table stored in the non-volatile memory 104 is searched, and the search result is set as the target temperature. Of course, it is not limited to this, and each correction AD value obtained in S82 can also be substituted into a prescribed calculation formula to obtain and set the target temperature through calculation. In addition, as described above, two temperature signals CENTER and EDGE are output from the thermistor 120 for detecting the temperature of the fixing device 7, so the target temperature of the fixing device 7 is the target temperature of the two temperature signals CENTER and EDGE.

[0111] Next, the CPU 101A obtains the measured AD values ​​of the temperature signals CENTER and EDGE of the heater 31 outputted from the thermistor 120 (S86). Specifically, the CPU 101A obtains the measured AD values ​​of the temperature signals CENTER and EDGE of the fixing device 7 by reading the digital value obtained by converting the analog input voltage of the AD conversion input port AD3 by the AD conversion circuit 101C. Then, the CPU 101A obtains the corrected AD values ​​for the measured AD values ​​from the correction line C in the same manner as in S82 (S88).

[0112] Then, the CPU 101A performs feedback control so that each correction AD value acquired in S88 becomes the target temperature set in S84 (S90), and then ends the fixing control process.

[0113] As described above, the printer 1 of the present embodiment includes: an image forming unit (6, 7); a low voltage power supply substrate 113 to which an AC voltage supplied by a commercial power supply is input and which converts the AC voltage into a DC voltage; a control circuit 101 to control the image forming unit (6, 7) and to control the image forming unit (6, 7) based on a control value obtained by AD-converting a signal from the image forming unit (6, 7); and DC-DC converters 105A to 105D, 106 to convert a DC voltage output from the low voltage power supply substrate 113 into a plurality of DC voltages and to output a power supply voltage Vcore and 3.3AVDC different from the power supply voltage Vcore among the plurality of DC voltages to the control circuit 101. The control circuit 101 obtains two AD conversion values ​​obtained by AD-converting the power supply voltage Vcore and 3.3AVDC, respectively, and calculates Gain and Offset for linearly correcting the control value based on the obtained two AD conversion values, and corrects the control value based on Gain and Offset.

[0114] Thus, in the printer 1 of the present embodiment, the control circuit 101 performs AD conversion on the power supply voltage Vcore and 3.3AVDC, and calculates Gain and Offset for linear correction of the control value based on the two AD conversion values. The power supply voltage Vcore and 3.3AVDC are known DC voltages and are also voltages input to the control circuit 101, so the voltage fluctuation is small. In order to obtain Gain and Offset for linear correction, at least two AD conversion values ​​obtained by AD conversion of the two DC voltages are required, and the inventors of the present invention have found a method of using the two voltages input to the control unit. The control circuit 101 obtains Gain and Offset from the two AD conversion values, and performs linear correction on the control value using Gain and Offset, thereby being able to appropriately control the image forming unit (6, 7).

[0115] In addition, the image forming section 6, 7 includes: a photosensitive drum 17; a charger 18 for charging the photosensitive drum 17; a developing roller 14 for supplying a developer to the photosensitive drum 17; a transfer roller 19 for transferring a developer image formed on the surface of the photosensitive drum 17 to a sheet S passing between the transfer roller 19 and the photosensitive drum 17; and a high-voltage power supply substrate 112 for applying a high voltage voltage obtained by converting a DC voltage to the charger 18, the developing roller 14, and the transfer roller 19. The control circuit 101 obtains a control value by performing AD conversion on an FB signal that is a signal corresponding to an output voltage applied from the high-voltage power supply substrate 112, and controls the voltage value of the high voltage to a target voltage value based on a result of linear correction of the control value using Gain and Offset.

[0116] In this way, the control value is obtained by AD converting the FB signal, which is a signal corresponding to the output voltage applied by the high-voltage power supply substrate 112, and control is performed based on the result of linear correction of the control value using Gain and Offset so that the voltage value of the high-voltage voltage becomes the target voltage value, and the voltage value of the high-voltage voltage can be controlled to the desired target voltage.

[0117] In addition, the image forming section (6, 7) includes: a fixing device 7 that fixes the image formed on the sheet S on the sheet S; and a thermistor 120 that detects the temperature of the fixing device 7 and outputs it as temperature signals CENTER and EDGE. The control circuit 101 performs AD conversion on the first temperature detection signal output from the thermistor 120, uses the AD conversion values ​​of the temperature signals CENTER and EDGE as control values, and performs linear correction using Gain and Offset.

[0118] Thus, it is possible to obtain digital temperature signals CENTER and EDGE that are closer to the analog temperature signals CENTER and EDGE output from the thermistor 120 .

[0119] In addition, the printer 1 is provided with an internal thermistor 130 that detects the internal temperature of the printer 1 and outputs it as a second temperature detection signal, and an external temperature and humidity sensor 140 that detects the temperature and humidity outside the printer 1 and outputs them as a third temperature detection signal and a humidity detection signal. The control circuit 101 performs AD conversion on the internal temperature signal output from the internal thermistor 130, and performs AD conversion on the external temperature signal and the external humidity signal output from the external temperature and humidity sensor 140, and sets the target temperature of the fixing device 7 based on the result of linear correction of each AD conversion value of the internal temperature signal, the external temperature signal, and the external humidity signal using Gain and Offset.

[0120] In this way, the internal temperature signal output from the internal thermistor 130 is AD converted, and the external temperature signal and the external humidity signal output from the external temperature and humidity sensor 140 are AD converted. The target temperature of the fixing device 7 is set based on the result of linear correction of the AD conversion values ​​of the internal temperature signal, the external temperature signal and the external humidity signal using Gain and Offset, so that the target temperature of the fixing device 7 can be set to the desired target temperature.

[0121] The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the invention.

[0122] (1) In the above embodiments, a printer that forms a monochrome image on a sheet is used as an example of an image forming device, but the present invention is not limited thereto. For example, a printer that can form a color image on a sheet may be used. In addition, the image forming device is not limited to a printer. For example, a copier or a multifunction machine that has a document reading device such as a flatbed scanner may be used.

[0123] (2) In the above-mentioned embodiments, the measured AD value is corrected by linear correction using the correction line C. However, the measured AD value may be corrected by nonlinear correction using a nonlinear curve.

[0124] (3) In the above-mentioned embodiments, the AD conversion circuit 101C has six AD conversion input ports AD1 to AD6, but the number of the AD conversion input ports is not limited to 6, and may be more or less than 6. In addition, although the circuit structure of the AD conversion circuit 101C is not described, the present invention can be applied regardless of the circuit structure as long as an AD value including an AD conversion error is output.

[0125] (4) In the above-mentioned embodiments, two thermistors 120 are provided in the fixing device 7, and the temperature signals CENTER and EDGE are outputted corresponding to the temperature of the center position and one end portion of the fixing roller 22. However, the present invention is not limited thereto. For example, three thermistors 120 may be provided to output temperature signals corresponding to the temperature of the center position and the two end portions, or only one thermistor may be provided to detect the temperature of the fixing roller 22 as a whole.

[0126] (5) In the first embodiment described above, the FB-CHG signal in the FB signal output by the high-voltage power supply substrate 112 is used to determine the substrate. However, the signal is not limited to this as long as it can determine the substrate. Other signals in the FB signal may be used, and signals other than the FB signal may be used.

Claims

1. An image forming device, comprising: an image forming unit; An AC-DC power supply unit, which receives an AC voltage supplied by a commercial power source and converts the AC voltage into a DC voltage; a control unit configured to control the image forming unit based on a control value obtained by AD converting a signal from the image forming unit; as well as a DC-DC conversion unit configured to convert the DC voltage output from the AC-DC power supply unit into a plurality of DC voltages, and output a first DC voltage and a second DC voltage different from the first DC voltage among the plurality of DC voltages to the control unit, The control unit obtains two AD conversion values ​​obtained by AD-converting the first DC voltage and the second DC voltage respectively, calculates a gain correction value and an offset correction value for linearly correcting the control value based on the two AD conversion values ​​obtained, and corrects the control value based on the gain correction value and the offset correction value.

2. The image forming apparatus according to claim 1, wherein: The control unit includes a CPU and an AD conversion circuit. The DC-DC converter outputs the first DC voltage to the CPU. The CPU is driven by the first DC voltage.

3. The image forming apparatus according to claim 2, wherein: The DC-DC converter includes a linear regulator that converts the DC voltage into the second DC voltage and outputs the second DC voltage to the control unit.

4. The image forming apparatus according to claim 1, wherein: The image forming unit includes: Photosensitive drum; A charger, used for charging the photosensitive drum; A developing roller, used for supplying a developer to the photosensitive drum; a transfer roller for transferring the developer image formed on the surface of the photosensitive drum to a sheet passing between the transfer roller and the photosensitive drum; as well as a high-voltage power supply substrate for applying the high-voltage voltage converted from the DC voltage to the charger, the developing roller and the transfer roller, respectively; The control unit performs AD conversion on a feedback signal that is a signal corresponding to an output voltage applied by the high-voltage power supply substrate to obtain the control value, and determines the type of the high-voltage power supply substrate based on a result of linear correction of the control value using the gain correction value and the offset correction value.

5. The image forming apparatus according to claim 4, wherein: The control unit changes a parameter for controlling the high-voltage power source substrate according to the determined type of the high-voltage power source substrate.

6. The image forming apparatus according to claim 1, wherein: The image forming unit includes: Photosensitive drum; A charger, used for charging the photosensitive drum; A developing roller, used for supplying a developer to the photosensitive drum; a transfer roller for transferring the developer image formed on the surface of the photosensitive drum to a sheet passing between the transfer roller and the photosensitive drum; as well as a high-voltage power supply substrate for applying the high-voltage voltage converted from the DC voltage to the charger, the developing roller and the transfer roller, respectively; The control unit performs AD conversion on a feedback signal which is a signal corresponding to the output voltage applied by the high-voltage power supply substrate to obtain the control value, and performs control based on the result of linear correction of the control value using the gain correction value and the offset correction value so that the voltage value of the high voltage becomes the target voltage value.

7. The image forming apparatus according to claim 1, wherein: The image forming unit includes: a fixing device for fixing the image formed on the sheet to the sheet; as well as a first temperature sensor, configured to detect the temperature of the fixing device and output the temperature as a first temperature detection signal; The control unit AD-converts the first temperature detection signal output from the first temperature sensor, uses the AD-converted value of the first temperature detection signal as the control value, and performs linear correction using the gain correction value and the offset correction value.

8. The image forming apparatus according to claim 7, wherein: Also includes: a second temperature sensor, configured to detect the internal temperature of the image forming device and output the second temperature detection signal; as well as a temperature and humidity sensor for detecting the temperature and humidity outside the image forming device and outputting them as a third temperature detection signal and a humidity detection signal, The control unit performs AD conversion on the second temperature detection signal output from the second temperature sensor, and performs AD conversion on the third temperature detection signal and the humidity detection signal output from the temperature and humidity sensor, and sets the target temperature of the fixing device based on the result of linear correction of each AD conversion value of the second temperature detection signal, the third temperature detection signal and the humidity detection signal using the gain correction value and the offset correction value.

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