Image forming apparatus

Abstract

To provide an image forming apparatus designed for further power saving.SOLUTION: An image forming apparatus comprises: a high voltage power supply substrate (30) having a high voltage generating unit (73) that generates high voltage by raising low voltage input thereto, and a high voltage maintaining unit (72) that maintains the high voltage at a predetermined value; a low voltage power supply (63) that inputs low voltage to the high voltage generating unit (73) and the high voltage maintaining unit (72); and an on-off circuit (62) that switches whether or not to input the low voltage to the high voltage generating unit (73) and the high voltage maintaining unit (72) from the low voltage power supply (63).SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to an image forming apparatus.

Background Art

[0002] An image forming apparatus has a high-voltage generation power supply that supplies a high voltage to a charger, a transfer roller, etc. From the viewpoint of power saving, the high-voltage generation power supply of the image forming apparatus stops supplying the high voltage that was being supplied to the charger, the transfer roller, etc.

[0003] Patent Document 1 discloses an image forming apparatus provided with a low-voltage power supply cutoff unit in a high-voltage generation power supply. When the opening / closing cover of the image forming apparatus is opened, an interlock switch interlocked with the opening of the opening / closing cover shuts off the first low-voltage line. Due to the cutoff of the first low-voltage line, the first low voltage is not supplied to the low-voltage power supply cutoff unit, and the low-voltage power supply cutoff unit shuts off the supply of the second low voltage from the second low-voltage power supply to the second reference voltage generation unit.

[0004] A conventional image forming apparatus has a high-voltage generation unit that boosts the input voltage and supplies the boosted high voltage to the image forming unit, and a high-voltage maintenance unit that maintains the high voltage at a predetermined value. When shifting to the power-saving mode, the conventional image forming apparatus stops supplying the high voltage to the image forming unit by shutting off the drive voltage to the high-voltage maintenance unit.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, when shifting to the power-saving mode, in a conventional image forming apparatus, there has been a problem that the voltage input to the high-voltage generation unit continues to be supplied, and a weak current continues to flow through the transformer of the high-voltage generation unit due to the supply of the voltage.

[0007] An object of the present invention is to provide an image forming apparatus capable of further power saving.

Means for Solving the Problems

[0008] In order to solve the above problems, an image forming apparatus according to Embodiment 1 of the present invention includes an image forming unit that forms an image on a sheet, and a high-voltage power supply board that applies an output voltage to the image forming unit, the high-voltage power supply board including a high-voltage generation unit that generates a high voltage by boosting an input low voltage, and a high-voltage maintenance unit that maintains the high voltage at a predetermined value, the high-voltage maintenance unit being driven by an input low voltage, and a low-voltage power supply that inputs a low voltage to the high-voltage generation unit and the high-voltage maintenance unit, and an on-off circuit that switches whether to input a low voltage to the high-voltage generation unit and the high-voltage maintenance unit from the low-voltage power supply.

[0009] According to the image forming apparatus having the above configuration, the on-off circuit switches whether to input a low voltage to the high-voltage maintenance unit and the high-voltage generation unit. Thereby, the on-off circuit can stop driving the high-voltage maintenance unit and cut off the weak current flowing through the high-voltage generation unit.

[0010] Further, an image forming apparatus according to Embodiment 2 of the present invention includes, in Embodiment 1, a control board on which a control unit and the on-off circuit are arranged, and when a first signal is transmitted from the control unit to the on-off circuit, the on-off circuit inputs a low voltage to the high-voltage generation unit and the high-voltage maintenance unit, and when a second signal is transmitted from the control unit to the on-off circuit, the on-off circuit does not input a low voltage to the high-voltage generation unit and the high-voltage maintenance unit.

[0011] According to the image forming apparatus having the above configuration, the control unit can switch whether to input a low voltage to the high voltage generation unit and the high voltage maintenance unit in the on-off circuit by transmitting the first signal and the second signal to the on-off circuit.

[0012] Also, according to the image forming apparatus having the above configuration, since the on-off circuit is arranged on the control board, the wiring between the control board and the high voltage power supply board becomes one. That is, this one wiring is a voltage line for inputting a low voltage from the on-off circuit to the high voltage power supply board.

[0013] Further, the image forming apparatus according to Embodiment 3 of the present invention includes, in Embodiment 1, a control board on which the control unit is arranged, the on-off circuit is arranged on the high voltage power supply board, and when the first signal is transmitted from the control unit to the on-off circuit, the on-off circuit inputs a low voltage to the high voltage generation unit and the high voltage maintenance unit, and when the second signal is transmitted from the control unit to the on-off circuit, the on-off circuit does not input a low voltage to the high voltage generation unit and the high voltage maintenance unit.

[0014] According to the image forming apparatus having the above configuration, the control unit can switch whether to input a low voltage to the high voltage generation unit and the high voltage maintenance unit in the on-off circuit by transmitting the first signal and the second signal to the on-off circuit.

[0015] Also, according to the image forming apparatus having the above configuration, since the on-off circuit is arranged on the high voltage power supply board, the wiring between the control board and the high voltage power supply board becomes two. That is, these two wirings are a communication line for transmitting the first signal and the second signal from the control unit to the on-off circuit and a voltage line for inputting a low voltage to the on-off circuit.

[0016] Further, the image forming apparatus according to aspect 4 of the present invention further includes an interlock switch that opens in conjunction with the opening of the cover of the image forming apparatus in aspect 2 or 3, and the on-off circuit does not input a low voltage to the high voltage generation unit and the high voltage maintenance unit regardless of the transmission of the first signal and the second signal from the control unit when the interlock switch is open.

[0017] According to the image forming apparatus having the above configuration, when the cover of the image forming apparatus is opened, the interlock switch opens. In this case, regardless of whether the first signal or the second signal is transmitted from the control unit, the on-off circuit stops the input of the low voltage to the high voltage maintenance unit and the high voltage generation unit. Therefore, when the cover of the image forming apparatus is opened, the input of the low voltage to the high voltage generation unit and the high voltage maintenance unit can be surely stopped.

Effect of the Invention

[0018] According to one aspect of the present invention, it is possible to provide an image forming apparatus that is more power-saving.

Brief Description of the Drawings

[0019]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Modes for Carrying Out the Invention

[0020] 〔Embodiment 1〕 Hereinafter, an embodiment of the present invention will be described below with reference to the drawings. The image forming apparatus 1 according to Embodiment 1 is an apparatus that forms an image on a sheet.

[0021] <Overall Configuration of Image Forming Apparatus 10> FIG. 1 is a schematic cross-sectional view showing the internal configuration of the image forming apparatus 10 according to Embodiment 1. In the following description, the right side in FIG. 1 is taken as the front of the image forming apparatus. Further, the image forming apparatus 10 is an LED color printer that forms a color image with colorants of four colors (black K, yellow Y, magenta M, cyan C). Hereinafter, when distinguishing each component by color, K (black), Y (yellow), M (magenta), and C (cyan) indicating each color are attached to the end of the reference numeral of the component. Furthermore, the image forming apparatus 10 is not limited to an LED color printer, and may be, for example, a laser color printer, a facsimile apparatus, or a so-called multifunction device having a printing function and a reading function (scanner function).

[0022] The image forming apparatus 10 includes a main body casing 11, and a paper feed tray 21 on which a sheet of paper 3, which is an example of a sheet, is loaded is provided at the bottom of the main body casing 11. The front surface of the main body casing 11 is an access port for accessing an image forming unit 25 described later, and a front cover 15 is rotatably installed at the access port. The front cover 15 is an example of a cover. Thereby, the access port can be closed or opened. An open / close sensor 22 is disposed adjacent to the front cover 15. The open / close sensor 22 generates a detection signal according to the opening and closing of the front cover 15 and supplies the detection signal to the high-voltage power supply board 30.

[0023] A paper feed roller 19 is provided above the front end of the paper feed tray 21. As the paper feed roller 19 rotates, the uppermost sheet of paper 3 accumulated in the paper feed tray 21 is sent out to a registration roller 18. The registration roller 18 corrects skew of the sheet of paper 3 and then conveys the sheet of paper 3 onto a belt unit 23 of the image forming unit 25.

[0024] The image forming unit 25 related to image formation includes a belt unit 23, an exposure unit 27, a process cartridge 24, a developing roller 31, a photosensitive drum 32, a transfer roller 34, a fixing unit 35, a belt cleaning device 16, and the like.

[0025] The belt unit 23 includes a pair of front and rear belt support rollers 17 and a belt 36. When the rear belt support roller 17 is rotationally driven, the belt 36 circulates and moves counterclockwise on the paper surface, and the sheet 3 on the upper surface of the belt 36 is conveyed rearward. Further, inside the belt 36, a transfer roller 34 is provided at a position facing the photosensitive drum 32 with the belt 36 interposed therebetween. The belt unit 23 has TRCC1 to TRCC4 terminals for receiving the transfer voltages TRCC1 to TRCC4 (output voltages) applied to the respective transfer rollers 34. The belt unit 23 is mounted on a belt unit mounting portion 13 installed on a main body frame (not shown). On the belt unit mounting portion 13, respective electrode terminals (not shown) are provided at positions corresponding to the respective TRCC1 to TRCC4 terminals. Each electrode terminal is connected to respective transfer voltage generation circuits 70K to 70C via respective voltage application lines (not shown).

[0026] The exposure unit 27 includes four LED units 37 corresponding to respective colors. Based on the image data to be formed, respective light emitting portions (not shown) are subjected to light emission control, whereby the lights L1 to L4 emitted from the respective light emitting portions irradiate the surface of the photosensitive drum 32, and the surface thereof is exposed.

[0027] The image forming unit 25 includes a process cartridge 24 corresponding to the above four colors. The process cartridge 24 includes a monochrome cartridge 24K and color cartridges 24Y, 24M, and 24C.

[0028] The monochrome cartridge 24K includes a photosensitive drum 32 whose surface is covered with a positively chargeable photosensitive layer and which is a high resistor, a charger 33, a drum cleaning roller 38, a drum cleaning shaft (not shown), and a developing cartridge (not shown).

[0029] A high roller voltage DCLNA is applied to the drum cleaning roller 38 to recover the toner remaining on the photoreceptor drum 32 by the application of the roller voltage DCLNA.

[0030] Also, the drum cleaning shaft is made of a conductive metal, and the paper dust on the drum cleaning roller 38 is removed by applying a shaft voltage DCLNB that is higher than the roller voltage DCLNA. That is, the cleaning shaft removes the paper dust mixed inside the main body casing 11 by using the shaft voltage DCLNB.

[0031] Normally, the toner is charged with a positive polarity and the paper dust is charged with a negative polarity. Therefore, the toner and the paper dust are individually removed from the photoreceptor drum 32 by utilizing the difference in charging polarities. During printing, a negative voltage, for example, a roller voltage DCLNA of -400V, is applied to the drum cleaning roller 38 to recover only the toner from the photoreceptor drum 32 onto the drum cleaning roller 38. Then, during printing, a positive voltage, for example, a roller voltage DCLNA of 600V, is applied to the drum cleaning roller 38, and a shaft voltage DCLNB of 700V is applied to the drum cleaning shaft. At this time, the paper dust is recovered to the drum cleaning shaft via the drum cleaning roller 38. The toner is ejected onto the photoreceptor drum 32, then adhered to the surface of the belt 36, and recovered by the belt cleaning device 16.

[0032] The belt cleaning device 16 includes a belt cleaning roller 16a and a belt cleaning shaft 16b. By applying a belt cleaning roller voltage BCLN (output voltage) to the belt cleaning roller 16a, the toner adhered to the surface of the belt 36 is recovered via the belt cleaning roller 16a and the belt cleaning shaft 16b. The belt cleaning device 16 has a BCLN terminal for receiving the belt cleaning roller voltage BCLN. The belt cleaning device 16 is mounted on a cleaning device mounting portion 14 installed on a main body frame (not shown).

[0033] Further, the monochrome cartridge 24K has a CHG terminal for receiving a charging voltage CHG (output voltage), a GRID terminal for receiving a grid voltage GRID, a DEV terminal for receiving a developing bias DEV, a DCLNA terminal for receiving a roller voltage DCLNA, and a DCLNB terminal for receiving a shaft voltage DCLNB.

[0034] On the other hand, each of the color cartridges 24Y, 24M, 24C also includes a photoreceptor drum 32, a charger 33, a drum cleaning roller 38, and a developing cartridge (not shown).

[0035] Also, each of the color cartridges 24Y, 24M, 24C has a CHG terminal, a GRID terminal, a DEV terminal, and a DCLNA terminal, respectively.

[0036] Each developing cartridge includes, inside an upper portion of a box-shaped main body casing 11, a toner storage chamber (not shown) for storing toners of respective colors as developers, a supply roller 39, and a developing roller 31.

[0037] The toner discharged from the toner storage chamber is supplied to the developing roller 31 by the rotation of the supply roller 39 and is positively triboelectrically charged between the supply roller 39 and the developing roller 31. Further, the toner supplied onto the developing roller 31 is sufficiently charged with the application of the developing bias DEV and is carried on the developing roller 31 as a thin layer of a certain thickness.

[0038] At the time of image formation, the photoreceptor drum 32 is rotationally driven, and accordingly, the surface of the photoreceptor drum 32 is uniformly positively charged by the charger 33. Then, the positively charged portion is exposed by the high-speed scanning of light from the LED unit 37, and an electrostatic latent image corresponding to the image to be formed on the paper 3 is formed on the surface of the photoreceptor drum 32.

[0039] Next, due to the rotation of the developing roller 31, when the positively charged toner carried on the developing roller 31 comes into contact with the photosensitive drum 32 facing it, it is supplied to the electrostatic latent image formed on the surface of the photosensitive drum 32. As a result, the electrostatic latent image on the photosensitive drum 32 is visualized, and a toner image with toner adhering only to the exposed portions is carried on the surface of the photosensitive drum 32.

[0040] Thereafter, the toner image carried on the surface of each photosensitive drum 32 is sequentially transferred to the sheet 3 conveyed by the belt 36 as the sheet 3 passes through each transfer position between the photosensitive drum 32 and the transfer roller 34 by the negative transfer voltage TRCC applied to the transfer roller 34. The sheet 3 onto which the toner image has been thus transferred is then conveyed to the fixing unit 35.

[0041] The fixing unit 35 includes a heating roller 29 having a heat source and a pressure roller 28 that presses the sheet 3 toward the heating roller 29 side, and thermally fixes the toner image transferred onto the sheet 3 onto the paper surface. Then, the sheet 3 thermally fixed by the fixing unit 35 is conveyed upward and is configured to be discharged onto a paper discharge tray provided on the upper surface wall 11A of the main body casing 11.

[0042] Also, inside the main body casing 11, a high-voltage power supply board 30, a low-voltage power supply board 12, and a control board 20 that controls the high-voltage power supply board 30 and the low-voltage power supply board 12 are provided.

[0043] <Configuration of the High-Voltage Power Supply 100> Next, with reference to FIG. 2, the configuration of the high-voltage power supply 100 will be described. FIG. 2 shows a schematic circuit configuration of the high-voltage power supply 100. The high-voltage power supply 100 generates a plurality of high voltages to be applied to each electrical load provided in the image forming apparatus 10 respectively. Each electrical load is the transfer roller 34, the belt cleaning roller 16a, the drum cleaning roller 38, the charger 33, and the developing roller 31, etc.

[0044] The high-voltage power supply 100 includes a control board 20, a high-voltage power supply board 30, and a low-voltage power supply board 12. Also, although circuits corresponding to respective colors are actually provided on the high-voltage power supply board 30, since the configurations of the respective circuits are substantially the same, only the configuration corresponding to a single color is shown in FIG. 2.

[0045] Note that in FIG. 2, among the plurality of high voltages generated by the image forming apparatus 10, only the transfer voltage generation circuits 70K to 70C that generate the transfer voltages TRCC1 to TRCC4 applied to the respective transfer rollers 34K to 34C, and the belt cleaning voltage generation circuit 80 that generates the belt cleaning roller voltage BCLN applied to the belt cleaning roller 16a are shown. Also, since the configurations of the transfer voltage generation circuits 70Y, 70M, and 70C of the transfer rollers 34Y to 34C corresponding to the respective color cartridges 24Y, 24M, and 24C are the same as those of the transfer voltage generation circuit 70K of the transfer roller 34K corresponding to the monochrome cartridge 24K, the details of the internal configuration are omitted in FIG. 2 and the description thereof is also omitted.

[0046] The control board 20 includes a control unit 61 and a power on / off circuit 62. The high-voltage power supply board 30 includes a transfer voltage generation circuit 70K, a belt cleaning voltage generation circuit 80, and an interlock switch 90. The low-voltage power supply board 12 includes a low-voltage power supply 63.

[0047] The control unit 61 controls the respective transfer voltage generation circuits 70K to 70C, the belt cleaning voltage generation circuit 80, and the power on / off circuit 62 according to a predetermined processing program stored in a ROM (Read Only Memory) (not shown).

[0048] The power on / off circuit 62 is connected to the ENABLE / DISENABLE terminal of the control unit 61 via a signal line S2. Also, the power on / off circuit 62 is connected to the low-voltage power supply 63 via a voltage line S1.

[0049] The on-off circuit 62 switches whether to input a low voltage to the low-voltage supply line PL, which is the output line of the on-off circuit 62, based on the ENABLE signal / DISENABLE signal from the ENABLE / DISENABLE terminal of the control unit 61. The ENABLE signal is an example of the first signal. The DISENABLE signal is an example of the second signal. More specifically, when the ENABLE signal is input from the control unit 61 to the on-off circuit 62, the on-off circuit 62 inputs a low voltage to the low-voltage supply line PL. When the DISENABLE signal is input from the control unit 61 to the on-off circuit 62, the on-off circuit 62 does not input a low voltage to the low-voltage supply line PL.

[0050] The low-voltage supply line PL inputs a low voltage to the high-voltage maintenance unit 72 and the high-voltage generation unit 73 of each transfer voltage generation circuit 70K to 70C arranged on the high-voltage power supply board 30. Also, the low-voltage supply line PL inputs a low voltage to the high-voltage maintenance unit 82 and the high-voltage generation unit 83 of the belt cleaning voltage generation circuit 80. Note that the value of the low voltage input to each member arranged on the high-voltage power supply board 30 may be the same or different.

[0051] The low-voltage power supply 63 supplies a low voltage to the on-off circuit 62 via the voltage line S1. For example, in Embodiment 1, the low voltage is 24V.

[0052] The interlock switch 90 is provided on the high-voltage power supply board 30. When the front cover 15 of the image forming apparatus 10 is opened, the open / close sensor 22 in FIG. 1 operates. The open / close sensor 22 is interlocked with the interlock switch 90, and when the front cover 15 is opened, the interlock switch 90 opens in conjunction with the operation of the open / close sensor 22. Also, when the front cover 15 is closed, the interlock switch 90 closes in conjunction with the operation of the open / close sensor 22. One end of the interlock switch 90 is connected to the on-off circuit 62 and the control unit 61, and the other end of the interlock switch 90 is grounded to GND.

[0053] Between the control board 20, the low-voltage power supply board 12, and the high-voltage power supply board 30, transmission and reception of PWM signals, ENABLE signals / DISENABLE signals, etc., and supply of low voltage are performed by harness wires. In the present embodiment, since the on-off circuit 62 is arranged on the control board 20, only one low-voltage supply line PL1, which is a harness wire, is wired between the on-off circuit 62 and the high-voltage power supply board 30.

[0054] Hereinafter, the transfer voltage generation circuit 70K among the transfer voltage generation circuits 70K to 70C will be described as a representative, and the remaining transfer voltage generation circuits 70Y to 70C will be omitted because they are repetitions of the same content.

[0055] The transfer voltage generation circuit 70K is, for example, a self-excited high-voltage generation circuit, and is composed of a high-voltage maintenance unit 72 and a high-voltage generation unit 73. The high-voltage maintenance unit 72 includes a reference voltage generation circuit 71, an operational amplifier IC1, and voltage-dividing resistors R1 and R2. The high-voltage generation unit 73 includes a transistor Tr1, a transformer T1, a diode D1, and a capacitor C1. The transfer voltage generation circuit 70K generates a transfer voltage TRCC1 to be supplied to the transfer roller 34K corresponding to the monochrome cartridge 24K. The transfer voltage TRCC1 is a high voltage with a negative polarity. Also, the transfer voltage generation circuit 70K is a voltage generation circuit having a hard control configuration in which feedback regarding the output is not given to the control unit 61.

[0056] The reference voltage generation circuit 71 generates a reference voltage Vth according to the PWM signal from the PWM1 port of the control unit 61, and supplies the reference voltage Vth to the non-inverting input of the operational amplifier IC1.

[0057] On one hand, the divided voltage Vd by the voltage dividing resistors R1 and R2 is input to the inverting input of the operational amplifier IC1. The operational amplifier IC1 generates a drive signal Sd1 for driving the primary side of the transformer T1 based on the reference voltage Vth and the divided voltage Vd. Also, a low voltage supply line PL is connected to the drive voltage input terminal of the operational amplifier IC1. One end of the voltage dividing resistor R1 is connected to one end of the secondary winding of the transformer T1, and the other end is connected to the inverting input of the operational amplifier IC1. Also, one end of the voltage dividing resistor R2 is connected to the inverting input of the operational amplifier IC1, and the other end is grounded to GND.

[0058] Also, one end of the primary winding of the transformer T1 is connected to the low voltage supply line PL, and the other end of the primary winding is connected to the collector of the transistor Tr1. The drive signal Sd1 is supplied to the base of the transistor Tr1, and by controlling the base current of the transistor Tr1 by the drive signal Sd1, the secondary side voltage of the transformer T1, that is, the transfer voltage TRCC1, is generated. At this time, the operational amplifier IC1 operates to eliminate the difference between the reference voltage Vth and the divided voltage Vd, and by this operation, the current I1 flowing through the voltage dividing resistors R1 and R2 is maintained at a predetermined value. That is, the transfer current due to the application of the transfer voltage TRCC1 to the transfer roller 34K is maintained at a predetermined value.

[0059] The diode D1 and the capacitor C1 rectify and smooth the secondary side voltage of the transformer T1 to generate the transfer voltage TRCC1 of the DC voltage.

[0060] Here, the reference voltage generation circuit 71, the operational amplifier IC1, and the voltage dividing resistors R1 and R2 constitute the high voltage maintenance unit 72, and the transistor Tr1, the transformer T1, the diode D1, and the capacitor C1 constitute the high voltage generation unit 73. In this embodiment, the transfer voltage generation circuit 70K is controlled by a constant current. Note that it is not limited to this, and the transfer voltage generation circuit 70K may be controlled by a constant voltage.

[0061] Here, the low-voltage supply line PL of the on-off circuit 62 is connected to the operational amplifier IC1 of the high-voltage maintenance unit 72 of the transfer voltage generation circuit 70K. When the on-off circuit 62 does not input a low voltage, the operational amplifier IC1 stops driving and the drive signal Sd1 is not transmitted to the base of the transistor Tr1. As a result, the high-voltage generation unit 73 does not generate the transfer voltage TRCC1.

[0062] Also, the low-voltage supply line PL is connected to one end of the transformer T1 of the high-voltage generation unit 73. When the on-off circuit 62 does not input a low voltage, a low voltage is not applied to one end of the transformer T1 and no current flows through the transformer T1.

[0063] The belt cleaning voltage generation circuit 80 is, for example, a self-excited high-voltage generation circuit similar to the transfer voltage generation circuit 70K, and includes a drive circuit 81, a transistor Tr2, a transformer T2, a diode D2, a capacitor C2, and a current detection circuit 84. The drive circuit 81 and the current detection circuit 84 constitute the high-voltage maintenance unit 82. The transistor Tr2, the transformer T2, the diode D2, and the capacitor C2 constitute the high-voltage generation unit 83. The belt cleaning voltage generation circuit 80 generates a belt cleaning voltage BCLN for the belt cleaning roller 16a. The belt cleaning voltage BCLN is a high voltage of positive polarity. Also, the belt cleaning voltage generation circuit 80 is a voltage generation circuit with a soft control configuration in which feedback regarding the output is made to the control unit 61.

[0064] The drive circuit 81 generates a drive signal Sd2 for driving the primary side of the transformer T2 according to the PWM signal from the PWM5 port of the control unit 61. Also, the drive voltage input terminal of the drive circuit 81 is connected to the low-voltage supply line PL.

[0065] Also, a low-voltage supply line PL is connected to one end of the primary winding of transformer T2. The drive signal Sd2 is supplied to the base of transistor Tr2, and by controlling the base current of transistor Tr2 with the drive signal Sd2, the secondary-side voltage of transformer T2, that is, the belt cleaning voltage BCLN, is generated. At this time, the control unit 61 controls the belt cleaning voltage generation circuit 80 so that the belt cleaning voltage BCLN or the belt cleaning current becomes constant by controlling the pulse width of the PWM signal based on the current detection signal Sid from the current detection circuit 84.

[0066] Diode D2 and capacitor C2 rectify and smooth the secondary-side voltage of transformer T2 to generate the belt cleaning voltage BCLN.

[0067] The current detection circuit 84 includes resistor R3 and resistor R4. One end of resistor R3 is connected to the +5V voltage and one end of the secondary winding of transformer T2, and the other end is connected to the A / D port of the control unit and one end of the voltage-dividing resistor R4. The other end of resistor R4 is grounded to GND. The current detection signal Sid is a signal for detecting the current Id flowing through resistor R4, and is input to the A / D port as the voltage value at the connection point of resistor R3 and resistor R4.

[0068] The control unit 61 receives the current detection signal Sid from the current detection circuit 84, and based on the current detection signal Sid, sends a PWM signal for applying a predetermined value of the belt cleaning voltage BCLN to the belt cleaning roller 16a to the drive circuit 81.

[0069] That is, the control unit 61 receives the current detection signal Sid, and calculates the current value from the voltage value of the current detection signal Sid and the resistance value of resistor R4. Then, the control unit 61 controls the pulse width of the PWM signal based on the current value so that the belt cleaning voltage BCLN becomes a predetermined value.

[0070] Here, the low-voltage supply line PL of the on-off circuit 62 is connected to the drive circuit 81 of the high-voltage maintenance unit 82 of the belt cleaning voltage generation circuit 80. When the on-off circuit 62 does not input a low voltage, the drive circuit 81 stops driving, the drive signal Sd2 is not transmitted to the transformer T2, and the high-voltage generation unit 83 cannot generate the belt cleaning voltage BCLN.

[0071] And the low-voltage supply line PL is connected to one end of the transformer T2 of the high-voltage generation unit 83. When the on-off circuit 62 does not input a low voltage, a low voltage is not applied to one end of the transformer T2 either, and no current flows through the transformer T2.

[0072] When the on-off circuit 62 does not input a low voltage to each of the high-voltage maintenance units 72 and 82 and each of the high-voltage generation units 73 and 83, it can stop the generation of the transfer voltage TRCC1 and the belt cleaning voltage BCLN at once.

[0073] <Circuit diagram of the on-off circuit 62> Figure 3 shows the circuit diagram of the on-off circuit 62. The on-off circuit 62 includes resistors R11, R12, R13, R14, R15, R16, R17, R19, R20, transistors Tr11, Tr12, Tr13, capacitors C11, C12, C13, C14, a diode ZD11, and a fuse F1.

[0074] One end of the interlock switch 90 is connected to the terminal P1 of the on-off circuit 62 and is connected to the cover open switch terminal of the control unit 61 via the resistor R19. Also, one end of the interlock switch 90 is connected to the base of the transistor Tr12 via the resistor R18. And one end of the interlock switch 90 is connected to the 3.3V power supply via the resistor R19, is connected to the cathode of the Zener diode ZD11, and is connected to the capacitor C14. The other end of the interlock switch 90 is grounded to GND.

[0075] The ENABLE / DISABLE terminal of the control unit 61 is connected to the collector of the transistor Tr12 via the resistor R12 of the on-off circuit 62 and to the base of the transistor Tr11 via the resistor R13.

[0076] The low-voltage power supply 63 is connected to the terminal P3 of the on-off circuit 62. The terminal P3 is connected to the source of the transistor Tr13 via the fuse F1. Also, the terminal P3 is connected to the collector of the transistor Tr11 via the fuse F1, the resistor R15, and the resistor R14.

[0077] The drain of the transistor Tr13 is connected to the low-voltage supply line PL, and a low voltage is input to the transfer voltage generation circuit 70K and the belt cleaning voltage generation circuit 80 arranged on the high-voltage power supply board 30 via the terminal P2.

[0078] Using FIG. 4, the operation of the on-off circuit 62 will be described. When the front cover 15 is opened, the detection signal of the open / close sensor 22 becomes High level. When the detection signal becomes High level, the interlock switch 90 opens. In this case, regardless of whether the signal transmitted from the ENABLE / DISABLE terminal of the control unit 61 is an ENABLE signal or a DISABLE signal, the on-off circuit 62 does not input a low voltage. That is, the voltage of the low-voltage supply line PL becomes 0V.

[0079] In this way, when the front cover 15 is open, from the perspective of power saving, the on-off circuit 62 stops the input of the low voltage to the transfer voltage generation circuit 70K and the belt cleaning voltage generation circuit 80. As a result, the transfer voltage generation circuit 70K and the belt cleaning voltage generation circuit 80 stop generating a high voltage.

[0080] On the one hand, when the front cover 15 is closed, the detection signal of the open / close sensor 22 becomes the Low level. When the detection signal becomes the Low level, the interlock switch 90 closes. In this case, if the signal transmitted from the ENABLE / DISABLE terminal of the control unit 61 is a DISENABLE signal, the on / off circuit 62 does not input a low voltage. That is, the voltage of the low voltage supply line PL becomes 0V. If the signal transmitted from the ENABLE / DISABLE terminal of the control unit 61 is an ENABLE signal, the on / off circuit 62 inputs a low voltage. That is, the voltage of the low voltage supply line PL becomes 24V.

[0081] In this way, when the front cover 15 is closed, based on the ENABLE / DISABLE signal of the control unit 61, the on / off circuit 62 switches whether to input 24V to the low voltage supply line PL or not.

[0082] By the on / off circuit 62 not inputting a low voltage to the transfer voltage generation circuit 70K and the belt cleaning voltage generation circuit 80 connected to the low voltage supply line PL, the driving of the transfer voltage generation circuit 70K and the belt cleaning voltage generation circuit 80 is stopped, and the current flow of the high voltage generation units 73 and 83 is blocked. Thereby, further power saving of the image forming apparatus 10 can be realized.

[0083] 〔Embodiment 2〕 Other embodiments of the present invention will be described below. For convenience of explanation, members having the same functions as the members described in the above embodiment are denoted by the same reference numerals, and the description thereof will not be repeated.

[0084] FIG. 5 shows the configuration of the high voltage power supply 100A of the image forming apparatus 10 according to Embodiment 2. The difference from Embodiment 1 is that the on / off circuit 62A is arranged on the high voltage power supply board 30A. In Embodiment 1, since the on / off circuit 62 was arranged on the control board 20, the low voltage supply line PL was connected between the control board 20 and the high voltage power supply board 30.

[0085] In this embodiment, a voltage line S1 from a low-voltage power supply 63 and a signal line S2 from a control unit 61 are connected to the on-off circuit 62A. That is, two harness lines are connected to the high-voltage power supply board 30A.

[0086] 〔Supplementary Notes〕 The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope indicated in the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention.

Explanation of Reference Numerals

[0087] 10 Image forming apparatus 12 Low-voltage power supply board 20, 20A Control board 30, 30A High-voltage power supply board 61 Control unit 62, 62A On-off circuit 63 Low-voltage power supply 70K Transfer voltage generation circuit 80 Belt cleaning voltage generation circuit 72, 82 High-voltage maintenance unit 73, 83 High-voltage generation unit 90 Interlock switch S1 Voltage line S2 Signal line PL Low-voltage supply line 100 High-voltage power supply 15 Front cover

Claims

1. An image forming unit that forms an image on a sheet; A high voltage power supply board that applies an output voltage to the image forming unit, the high voltage power supply board including: a high voltage generation unit that generates a high voltage by boosting an input low voltage; and a high voltage maintenance unit that maintains the high voltage at a predetermined value, the high voltage maintenance unit being driven by the input low voltage and outputting a drive signal to the high voltage generation unit to generate the high voltage A high voltage power supply board having a high voltage maintenance unit; A low voltage power supply that inputs a low voltage to the high voltage generation unit and the high voltage maintenance unit; An on-off circuit that switches whether to input a low voltage from the low voltage power supply to the high voltage generation unit and the high voltage maintenance unit via a low voltage supply line; An image forming apparatus including a control board on which a control unit and the on-off circuit are disposed, The high voltage generation unit includes: A transformer including a primary winding and a secondary winding; and a switching element to which the drive signal is input from the high voltage maintenance unit; One end of the primary winding of the transformer is connected to the low voltage supply line; The other end of the primary winding of the transformer is grounded via the switching element; The switching element switches the conduction between one end and the other end of the primary winding according to the drive signal to generate the high voltage from the secondary winding of the transformer; The on-off circuit includes: Is connected to one end of the primary winding of the transformer via one low voltage supply line; When a first signal is transmitted from the control unit to the on-off circuit, a low voltage is applied to one end of the primary winding of the transformer and the high voltage maintenance unit; When a second signal is transmitted from the control unit to the on-off circuit, the on-off circuit does not input a low voltage to one end of the primary winding of the transformer and the high voltage maintenance unit. An image forming apparatus characterized by this.

2. Comprising a control board on which a control unit is disposed, The on-off circuit is disposed on the high voltage power supply board, When a first signal is transmitted from the control unit to the on-off circuit, the on-off circuit inputs a low voltage to one end of the primary winding of the transformer and the high voltage maintenance unit, When a second signal is transmitted from the control unit to the on-off circuit, the on-off circuit does not input a low voltage to one end of the primary winding of the transformer and the high voltage maintenance unit. The image forming apparatus according to claim 1, characterized by this.

3. The image forming apparatus further includes an interlock switch that opens in conjunction with the opening of the cover of the image forming apparatus. The on-off circuit according to claim 2, wherein when the interlock switch is open, regardless of transmission of the first signal and the second signal from the control unit, a low voltage is not input to one end of the primary winding of the transformer and the high-voltage maintaining unit.

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