Image formation device

Abstract

To provide an image formation device capable of inhibiting a protection element from being fused even when applied lightning surge is not properly discharged due to discharge gap.SOLUTION: A power source substrate 25 comprises: first and second input terminals T1, T2 connected to a live side and a neutral side of a commercial power supply; an AC / DC conversion circuit 30 connected to the first and second input terminals T1, T2 and converting commercial AC voltage into DC voltage; fuses FS1, FS2 that fuse when excess current flows between the AC / DC conversion circuit 30 and the first input terminal T1; a first discharge gap 41 including a first discharge electrode 41A connected to the first input terminal T1 and a first ground electrode 41B connected to ground; a second discharge gap 42 including a second discharge electrode 42A connected to the second input terminal T2 and a second ground electrode 42B connected to the ground; and a resistive element 45A arranged between at least one of the first ground electrode 41B and the second ground electrode 42B and the ground.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present application relates to an image forming apparatus having a discharge gap. [Background technology]

[0002] Patent Document 1 describes an image forming apparatus equipped with a power supply board having a first input terminal connected to the live side of a commercial power supply, a second input terminal connected to the neutral side of the commercial power supply, an AC / DC conversion circuit connected to the first input terminal and the second input terminal, a fuse connected between the first input terminal and the AC / DC conversion circuit, and a discharge gap arranged between the first input terminal and ground. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2023-50447 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the image forming device described in Patent Document 1, for example, a lightning surge applied to the first input terminal may not be discharged properly in the discharge gap due to wear of the discharge gap, and an overcurrent due to the lightning surge may flow to ground via the fuse, the X capacitor, and the second input terminal, causing the fuse to melt. As a result, the power supply board may have to be replaced.

[0005] An object of the present invention is to provide an image forming apparatus capable of suppressing melting of a protective element even when an applied lightning surge does not discharge well in a discharge gap. [Means for solving the problem]

[0006] In order to achieve the above object, the image forming apparatus of the present application comprises an image forming unit that forms an image on a sheet, and a power supply board that supplies a voltage to the image forming unit, and the power supply board has a first input terminal and a second input terminal arranged on the power supply board, the first input terminal being connected to the live side of a commercial power supply and the second input terminal being connected to the neutral side of the commercial power supply, AC / DC conversion circuits connected to the first input terminal and the second input terminal, respectively, that convert the AC voltage supplied from the commercial power supply into a DC voltage, a protection element that melts when an overcurrent flows between the AC / DC conversion circuit and the first input terminal, a first discharge electrode connected to the first input terminal, a first grounding electrode that forms a discharge gap between the first discharge electrode and is connected to ground, a second discharge electrode connected to the second input terminal, a second grounding electrode that forms a discharge gap between the second discharge electrode and is connected to ground, and a resistance element arranged between at least one of the first grounding electrode and the second grounding electrode and the ground. Effect of the Invention

[0007] In the image forming apparatus of the present application, a resistive element is disposed between at least one of the first and second ground electrodes and the ground, so that even if at least one of the discharge gaps is worn out and no discharge occurs due to a lightning surge, the value of the overcurrent flowing through the protective element due to a lightning surge is suppressed by the resistive element, thereby making it possible to suppress the meltdown of the protective element. [Brief description of the drawings]

[0008] [Figure 1] 1 is a side cross-sectional view of a main portion of a monochrome laser printer according to an embodiment of the present application. [Diagram 2] 2 is a diagram showing a method of grounding the frame in the monochrome laser printer of FIG. 1. [Diagram 3] 2 is a diagram showing a portion of wiring on a power supply board included in the monochrome laser printer of FIG. 1. [Figure 4] 4A to 4C are diagrams showing specific examples of various resistance elements arranged between a second ground electrode provided on the power supply board in FIG. 3 and an FG screw. [Diagram 5] FIG. 13 is a diagram showing changes in impedance characteristics with respect to the frequency of an applied voltage according to the capacitance of a capacitor. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, embodiments of the present application will be described in detail with reference to the drawings.

[0010] 1 is a cross-sectional view showing a schematic configuration of a monochrome laser printer 1 according to an embodiment of the present application. The monochrome laser printer 1 is an example of an image forming apparatus. Hereinafter, the monochrome laser printer 1 will be abbreviated to printer 1.

[0011] The printer 1 forms a toner image on the sheet S supplied from a supply tray 3 or a manual feed tray 4 located at the bottom inside the main body housing 2, using a process unit 6. After that, the printer 1 heats the sheet S on which the toner image has been formed using a fuser 7 to perform a fixing process. Furthermore, the printer 1 discharges the sheet S to a discharge tray 8 located at the top of the main body housing 2, using discharge rollers 24.

[0012] The process unit 6 includes a scanner unit 10, a developing cartridge 13, a photosensitive drum 17, a charger 18, a transfer roller 19, and the like.

[0013] The scanner unit 10 is disposed at the upper part of the main body housing 2, and includes a laser emitting unit (not shown), a polygon mirror 11, a plurality of reflecting mirrors 12, a plurality of lenses (not shown), etc. In the scanner unit 10, the laser light emitted from the laser emitting unit is irradiated by high-speed scanning onto the surface of the photosensitive drum 17 via the polygon mirror 11, the reflecting mirror 12, and the lenses, as indicated by the dashed dotted line.

[0014] The developing cartridge 13 is detachably attached to the main body housing 2, and contains toner therein. A developing roller 14 and a supply roller 15 are disposed opposite each other at a 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 by the developing roller 14.

[0015] A charger 18 is disposed above the photoconductor drum 17 with a gap therebetween. A transfer roller 19 is disposed below the photoconductor drum 17 facing the photoconductor drum 17. While the surface of the photoconductor drum 17 is rotated, it is first uniformly charged, for example, to a positive polarity by the charger 18. Next, an electrostatic latent image is formed on the photoconductor drum 17 by a laser beam from the scanner unit 10.

[0016] Thereafter, when the photosensitive drum 17 rotates in contact with the developing roller 14, 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, the toner image is transferred to the sheet S by a transfer bias applied to the transfer roller 19 while the sheet S passes between the photosensitive drum 17 and the transfer roller 19.

[0017] The fixing unit 7 is disposed downstream of the process unit 6 in the sheet conveying direction, and includes a fixing roller 22, a pressure roller 23 that presses the fixing roller 22, and a heater 26 that heats the fixing roller 22. The heater 26 is connected to a power supply board 25, and is controlled by an AC voltage supplied from the power supply board 25. The printer 1 also includes a display unit 27 that displays printing information and the like.

[0018] Fig. 2 shows a method of grounding the frame of the printer 1. As shown in Fig. 2, the power supply board 25 is housed in, for example, a metallic enclosure 50. The enclosure 50 is attached in parallel to, for example, the right side surface of the main body housing 2.

[0019] A commercial AC voltage (for example, AC 100V) is supplied to the power supply board 25 by inserting a power plug P into a socket O. In the example of FIG. 2, the socket O is an earth (E) pole-equipped socket, and has an earth pole E in addition to a live electrode L and a neutral electrode N. When a three-pin power plug P is inserted into this socket O, an AC voltage is supplied to the power supply board 25 via power cables PCL and PCN. The earth terminal of the power plug P is connected to one end of an earth cable EC, and the other end of the earth cable EC is connected to the enclosure 50 via metal screws 60. Furthermore, the power supply board 25 is connected to the enclosure 50 at its four corners via FG (frame ground) screws 70. In this manner, the power supply board 25 is frame-grounded.

[0020] The power supply board 25 is a low-voltage power supply board that converts a commercial AC voltage into a DC voltage of, for example, 24 V, as described later, and outputs it to the process unit 6, the main board (not shown), the high-voltage power supply board (not shown), etc. The DC 24 V output to the process unit 6 is used as a voltage for driving the scanner unit 10, the photosensitive drum 17, the transfer roller 19, etc. The DC 24 V output to the high-voltage power supply board is boosted to a high voltage of, for example, 8 KV by the high-voltage power supply board, and is supplied to the charger 18, etc. The DC 24 V output to the main board is converted to, for example, 3.3 V by a DC / DC converter (not shown) mounted on the main board, and is used as a power source for a control unit (not shown) such as an ASIC. Also, the power supply board 25 supplies the input commercial AC voltage as it is to the heater 26 of the fixing unit 7, as described above.

[0021] Fig. 3 shows a portion of the wiring on the power supply board 25. As shown in Fig. 3, the power supply board 25 has a first input terminal T1, a second input terminal T2, an AC / DC conversion circuit 30, a first fuse FS1, a second fuse FS2, a first discharge gap 41, and a second discharge gap 42.

[0022] The first input terminal T1 and the second input terminal T2 are disposed at an end of the power supply board 25. The first input terminal T1 is a live terminal connected to an electrode L on the live side of the commercial power supply. The second input terminal T2 is a neutral terminal connected to an electrode N on the neutral side of the commercial power supply.

[0023] The AC / DC conversion circuit 30 converts the AC voltage supplied from the commercial power supply via the first input terminal T1 and the second input terminal T2 into a DC voltage. The AC voltage is supplied from the first input terminal T1 and the second input terminal T2 to the AC / DC conversion circuit 30 via a power supply line PLL connected to the first input terminal T1 and a power supply line PLN connected to the second input terminal T2. The AC / DC conversion circuit 30 includes a rectifier diode 31, an electrolytic capacitor 32, a transformer 33, and a control IC 34. The rectifier diode 31 rectifies the AC voltage supplied from the commercial power supply. The electrolytic capacitor 32 smoothes the rectified AC voltage output from the rectifier diode 31 to produce a constant DC voltage, which is then supplied to the transformer 33. The AC / DC conversion circuit 30 converts the AC voltage supplied from the commercial power supply into a DC voltage of, for example, 24V. The control IC 34 controls the entire AC / DC conversion circuit 30.

[0024] On the power supply line PLL, a first fuse FS1 and a second fuse FS2 are connected in series in this order on the way from the first input terminal T1 to the AC / DC conversion circuit 30. A power supply line branched from the power supply line PLL between the first fuse FS1 and the second fuse FS2 is connected to one end of a power supply input terminal (not shown) of the fuser 7. A power supply line branched from the power supply line PLN is connected to the other end of the power supply input terminal of the fuser 7. The first fuse FS1 melts when an abnormal overcurrent flows from the first input terminal T1 to the fuser 7, thereby preventing the abnormal overcurrent from flowing to the fuser 7. The second fuse FS2 melts together with the first fuse FS1 when an abnormal overcurrent flows from the first input terminal T1 to the AC / DC conversion circuit 30, thereby preventing the abnormal overcurrent from flowing to the AC / DC conversion circuit 30.

[0025] A first discharge gap 41 is formed between the first input terminal T1 and the ground (GND), and a second discharge gap 42 is formed between the second discharge gap 42 and the ground (GND). The first discharge gap 41 is composed of a first discharge electrode 41A connected to the first input terminal T1 and a first ground electrode 41B connected to the ground. The second discharge gap 42 is composed of a second discharge electrode 42A connected to the second input terminal T2 and a second ground electrode 42B connected to the ground. However, the second ground electrode 42B is connected to one of the FG screws 70 via a wiring pattern 45 on the power supply board 25. That is, the second ground electrode 42B is grounded via the FG screw 70 as described above. The first ground electrode 41B is also connected to another one of the FG screws 70 or the same one via a wiring pattern (not shown) on the power supply board 25.

[0026] In addition, a capacitor C1 is connected between the power supply line PLL and the power supply line PLN. The capacitor C1 is a so-called X capacitor, and is intended to reduce noise occurring between the power supply line PLL and the power supply line PLN.

[0027] In the power supply board 25 thus configured, for example, when the first discharge gap 41 is worn and cannot discharge properly, and a lightning surge is applied to the first input terminal T1, an overcurrent caused by the lightning surge flows to the ground via the first fuse FS1, the second fuse FS2, the second discharge gap 42, the wiring pattern 45, and the FG screw 70, and one or both of the first fuse FS1 and the second fuse FS2 may melt. It is desirable that the first fuse FS1 and the second fuse FS2 melt when an abnormal overcurrent occurs in the fixing unit 7 or the AC / DC conversion circuit 30, and not that the overcurrent is caused by a lightning surge. Therefore, in the printer 1 of this embodiment, the resistance value (impedance) of the wiring pattern 45 is increased to reduce the current value of the overcurrent caused by the lightning surge, thereby suppressing the melting of the first fuse FS1 and the second fuse FS2.

[0028] 4(a) to 4(d) show various methods for increasing the resistance value of the wiring pattern 45. FIG.

[0029] 4(a) shows a method of using a wiring pattern 45A consisting of multiple wires of the same width instead of the wiring pattern 45. Since the resistance value of a wiring, i.e., a conductor, increases as the width of the wiring increases, when a lightning surge of the same voltage value is applied to the first input terminal T1, the value of the overcurrent flowing through the wiring pattern 45A becomes smaller than the value of the overcurrent flowing through the wiring pattern 45. This makes it possible to suppress the melting of the first fuse FS1 and the second fuse FS2.

[0030] FIG. 4(b) shows a method using a wiring pattern 45B which is a wiring pattern consisting of multiple wires, similar to the wiring pattern 45A in FIG. 4(a), but which, unlike the wiring pattern 45A in FIG. 4(a), has wires of different widths.

[0031] In the wiring pattern 45A shown in Fig. 4(a), the width of each wire is the same, so that an overcurrent of approximately the same current value flows through each wire. Therefore, depending on the magnitude of the overcurrent, there is a risk that all the wires will burn out at the same time. Therefore, in the wiring pattern 45B shown in Fig. 4(b), the width of each wire is made different and the wires are burned out in order from the widest, thereby suppressing the melting of the first fuse FS1 and the second fuse FS2 and preventing all the wires from burning out at the same time due to a single lightning surge.

[0032] 4(c) shows a method in which wiring patterns 45C, 45C in which the wiring is divided are used instead of the wiring pattern 45, and multiple (for example, two) resistors R1, R1 are arranged between the divided wiring patterns 45C, 45C. As a result, the value of the overcurrent flowing between the wiring patterns 45C, 45C via the resistors R1, R1 becomes smaller than the value of the overcurrent flowing through the wiring pattern 45. This makes it possible to suppress the melting of the first fuse FS1 and the second fuse FS2. The number of resistors R1 may be determined according to the specifications of the resistor R1 and the value of the overcurrent flowing through each resistor R1, and may be one or three or more.

[0033] FIG. 4(d) shows a method in which wiring patterns 45C, 45C are used as in the connection method in FIG. 4(c), but unlike the connection method in FIG. 4(c), a capacitor having a predetermined capacitance is disposed between the wiring patterns 45C, 45C as a resistive element 47. FIG. 5 shows how the impedance characteristics change with respect to the applied voltage frequency according to the capacitance of the capacitor. As shown in FIG. 5, when a voltage of the same frequency is applied to a capacitor, the smaller the capacitance of the capacitor, the higher its impedance. Since the frequency of a lightning surge is approximately 1 MHz, if a capacitor having a capacitance whose impedance is equal to or greater than a predetermined value at that frequency is used as the resistive element 47, the meltdown of the first fuse FS1 and the second fuse FS2 can be suppressed.

[0034] Alternatively, a surge absorber or an inductor may be used as the resistive element 47 connected between the wiring patterns 45C, 45C. The inductor may be a wound component such as a coil. The inductor may be a chip inductor in which a coil pattern is printed in multiple layers on a ferrite sheet.

[0035] The surge absorber operates to suppress an overcurrent caused by a lightning surge, and can therefore suppress the blowing of the first fuse FS1 and the second fuse FS2.

[0036] Furthermore, the inductor has a large impedance at the high frequency of a lightning surge, and suppresses an overcurrent caused by a lightning surge when the overcurrent occurs, thereby making it possible to suppress the blowing of the first fuse FS1 and the second fuse FS2.

[0037] In this embodiment, the resistive element is disposed between the second discharge gap 42 and the ground (GND), but the resistive element may be disposed between the first ground electrode 41B and the ground (GND). Furthermore, the resistive element may be disposed both between the second discharge gap 42 and the ground (GND) and between the second discharge gap 42 and the ground (GND).

[0038] As described above, the printer 1 of this embodiment includes a process unit 6 that forms an image on a sheet, and a power supply board 25 that supplies a voltage to the process unit 6. The power supply board 25 includes a first input terminal T1 and a second input terminal T2 arranged on the power supply board 25, the first input terminal T1 being connected to the live side of a commercial power source, and the second input terminal T2 being connected to the neutral side of the commercial power source, an AC / DC conversion circuit 30 that is connected to the first input terminal T1 and the second input terminal T2, respectively, and converts an AC voltage supplied from the commercial power source into a DC voltage, a first fuse FS1 and a second fuse FS2 that melt when an overcurrent flows between the AC / DC conversion circuit 30 and the first input terminal T1, The power supply has a first discharge electrode 41A connected to the first input terminal T1, a first ground electrode 41B which forms a first discharge gap 41 between itself and the first discharge electrode 41A and is connected to ground, a second discharge electrode 42A connected to the second input terminal T2, a second ground electrode 42B which forms a second discharge gap 42 between itself and the second discharge electrode 42A and is connected to ground, and resistive elements 45A, 45B, R1, 47 arranged between at least one of the first ground electrode 41B and the second ground electrode 42B and the ground.

[0039] In this manner, in the printer 1 of this embodiment, the resistance elements 45A, 45B, R1, 47 are disposed between at least one of the first ground electrode 41B and the second ground electrode 42B and the ground, so that even if at least one of the first discharge gap 41 and the second discharge gap 42 is worn and no discharge occurs due to a lightning surge, the value of the overcurrent flowing through the first fuse FS1 and the second fuse FS2 due to a lightning surge is suppressed by the resistance elements 45A, 45B, R1, 47. This makes it possible to suppress the melting of the first fuse FS1 and the second fuse FS2.

[0040] The present invention is not limited to the above-described embodiment, and various modifications are possible without departing from the spirit of the present invention.

[0041] (1) In the above embodiment, a printer that forms a monochrome image on a sheet is exemplified as the image forming apparatus, but the image forming apparatus is not limited to this and may be, for example, a printer configured to be able to form a color image on a sheet. Also, the image forming apparatus is not limited to a printer and may be, for example, a copier or multifunction machine equipped with a document reading device such as a flatbed scanner.

[0042] (2) In the above embodiment, the number of wires included in wiring pattern 45A is five, and the number of wires included in wiring pattern 45B is four, but the number of wires is not limited to this, and may be more or less than this. In addition, the width of each wire is not limited to the width shown in Figures 4(a) and 4(b).

[0043] (3) In the above embodiment, the wiring patterns 45A and 45B, the resistor R1, a capacitor with a predetermined capacity, a surge absorber, and an inductor are exemplified as resistive elements, but they are not limited to these as long as they suppress the value of an overcurrent caused by a lightning surge. For example, if a FG screw 70 with a higher resistance value is used, the wiring pattern 45 may be a solid pattern. [Explanation of symbols]

[0044] 1...monochrome laser printer (image forming apparatus), 6...process section (image forming section), 25...power supply board, 41...first discharge gap, 41A...first discharge electrode, 41B...first ground electrode, 42...second discharge gap, 42A...second discharge electrode, 42B...second ground electrode, 45, 45A to 45C...wiring pattern, 47...resistance element, 50...enclosure, 60...screw, 70...FG screw, EC...earth cable, PCL, PCN...power cable, R1...resistor, T1...first input terminal, T2...second input terminal.

Claims

1. an image forming unit that forms an image on a sheet; a power supply board for supplying a voltage to the image forming unit; Equipped with The power supply board includes: a first input terminal and a second input terminal arranged on the power supply board, the first input terminal being connected to a live side of a commercial power supply and the second input terminal being connected to a neutral side of the commercial power supply; an AC / DC conversion circuit connected to the first input terminal and the second input terminal, respectively, for converting an AC voltage supplied from the commercial power source into a DC voltage; a protection element that melts down when an overcurrent flows between the AC / DC conversion circuit and the first input terminal; A first discharge electrode connected to the first input terminal; a first ground electrode that forms a discharge gap between itself and the first discharge electrode and is connected to a ground; A second discharge electrode connected to the second input terminal; a second ground electrode that forms a discharge gap between itself and the second discharge electrode and is connected to a ground; a resistive element disposed between at least one of the first ground electrode and the second ground electrode and a ground; having 1. An image forming apparatus comprising:

2. The resistive element is disposed between the second ground electrode and ground.

2. The image forming apparatus according to claim 1,

3. The resistor element is a wiring pattern consisting of a plurality of wires.

2. The image forming apparatus according to claim 1,

4. The width of each of the plurality of wirings is the same.

4. The image forming apparatus according to claim 3.

5. The widths of the plurality of wirings are different.

4. The image forming apparatus according to claim 3.

6. The resistive element is a resistor.

2. The image forming apparatus according to claim 1,

7. The resistive element is a capacitor having a capacitance such that its impedance is equal to or greater than a predetermined value at the frequency of a lightning surge.

2. The image forming apparatus according to claim 1,

8. The resistive element is a surge absorber.

2. The image forming apparatus according to claim 1,

9. The resistive element is an inductor.

2. The image forming apparatus according to claim 1,

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