Image forming apparatus

Abstract

To prevent causing a failure in a power substrate even when lightening surges are repeatedly input.SOLUTION: An image forming apparatus 1 comprises a power substrate 3, and a metal enclosure EC. The power substrate 3 has: an AC / DC conversion circuit 31 that is connected to a first input terminal T1 and a second input terminal T2 and converts AC voltage supplied from a commercial power supply P into DC voltage; a first discharge electrode 51 that is connected to the first input terminal T1; a first ground electrode 61 that forms a first discharge gap GL with the first discharge electrode 51 and is connected to the metal enclosure EC; a second discharge electrode 52 that is connected to the second input terminal T2; and a second ground electrode 62 that forms a second discharge gap GN with the second discharge electrode 52 and is connected to the metal enclosure EC. The metal enclosure EC has projections that form third discharge gaps G3L, G3N with the input terminals T1, T2, and extend toward the input terminals T1, T2.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus equipped with a power supply board that supplies a DC voltage to an image forming unit. [Background technology]

[0002] Conventionally, image forming apparatuses equipped with a power supply board have a power supply board with two input terminals to which a power line is connected, and the power supply board converts AC voltage supplied from the power line into DC voltage and supplies it to an image forming unit, etc. The power supply board of a conventional image forming apparatus has a discharge electrode connected to the input terminal and a ground electrode that is electrically grounded, and a discharge gap is formed between the discharge electrode and the ground electrode. When a lightning surge is input to the power supply board via the power cable, the conventional image forming apparatus is configured so that the lightning surge passes through the input terminal, the discharge gap, and escapes to earth via a metal enclosure connected to the ground electrode. Patent Document 1 discloses a technology in which a power supply board is provided with 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 that converts AC voltage supplied from the commercial power supply via the first input terminal and the second input terminal into DC voltage, 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] Japanese Patent Application Publication No. 2023-50447 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in conventional image forming devices, when lightning surges are repeatedly input and discharge across the discharge gap is repeatedly performed, the discharge electrode and ground electrode wear out, and discharge beyond the discharge gap becomes insufficient, resulting in a problem of power supply board failure and requiring earlier replacement.

[0005] SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus that can prevent damage to a power supply board even when lightning surges are repeatedly input. [Means for solving the problem]

[0006] In order to achieve the above object, the present invention provides an image forming unit, comprising: an image forming unit; a power supply board that supplies a DC voltage to the image forming unit; and a metal enclosure that covers the entire power supply board and is grounded, wherein 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 power cable connected to a commercial power source and the second input terminal being connected to the neutral side of the power cable; AC / DC conversion circuits that are connected to the first input terminal and the second input terminal, respectively, and convert the AC voltage supplied from the commercial power source to the DC voltage; a first discharge electrode connected to the first input terminal, a first ground electrode that forms a first discharge gap between itself and the first discharge electrode and is connected to the metal enclosure; a second discharge electrode connected to the second input terminal, and a second ground electrode that forms a second discharge gap between itself and the second discharge electrode and is connected to the metal enclosure, and the metal enclosure forms a third discharge gap between itself and at least one of the first input terminal and the second input terminal, and has a protrusion that extends toward the input terminal.

[0007] In this configuration, a first input terminal is connected to the live side of a power cable, and a second input terminal is connected to the neutral side of the power cable. A first discharge gap is formed between a first discharge electrode connected to the first input terminal and a first ground electrode, and a second discharge gap is formed between a second discharge electrode connected to the second input terminal and a second ground electrode. The first and second ground electrodes are connected to a grounded metal enclosure.

[0008] A lightning surge input to the power supply board via the power cable is conducted to the first discharge electrode via the first input terminal, crosses the first discharge gap, and reaches the first ground electrode, or is conducted to the second discharge electrode via the second input terminal, crosses the second discharge gap, and reaches the second ground electrode. The lightning surge is earthed from the first or second ground electrode by the metal enclosure and is released.

[0009] In this configuration, the metal enclosure has a protrusion extending toward at least one of the first and second input terminals, so that a new discharge gap, a third discharge gap, is formed between the power supply board and the protrusion of the metal enclosure extending toward the at least one input terminal.

[0010] With this configuration, even when the first discharge electrode and the first ground electrode, or the second discharge electrode and the second ground electrode, wear and it becomes difficult to discharge through the first or second discharge gap, the lightning surge can be released toward the metal enclosure through the third discharge gap, which is the new discharge gap. Therefore, an image forming apparatus with this configuration can prevent damage to the power supply board even when lightning surges are repeatedly input. [Effects of the Invention]

[0011] According to the present invention, even if lightning surges are repeatedly input, it is possible to prevent the power supply board from being damaged. [Brief explanation of the drawings]

[0012] [Figure 1]1 is a cross-sectional view showing a schematic configuration of an image forming apparatus according to an embodiment of the present invention. [Figure 2] FIG. 2 is a block diagram showing the electrical configuration of the image forming apparatus. [Figure 3] 3A is a diagram showing an outline of the internal configuration of the image forming apparatus as seen from above, and an enlarged view of the power supply board in FIG. 3A. FIG. [Figure 4] FIG. 2 is a schematic circuit diagram showing a main part of a circuit configuration related to a power supply board. [Figure 5] FIG. 2 is a schematic external view of the solder surface side of the power supply substrate. [Figure 6] FIG. 1 is a schematic cross-sectional side view of a metal enclosure that houses a power supply board. [Figure 7] FIG. 2 is a schematic cross-sectional view of a metal enclosure that houses a power supply board. [Figure 8] FIG. 10 is a schematic external view of a power supply board viewed from the component surface side in a modified example in which discharge is performed on the component surface side. [Figure 9] FIG. 2 is a schematic cross-sectional view of a metal enclosure that houses a power supply board. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0014] <General configuration of image forming apparatus> Fig. 1 is a cross-sectional view showing a schematic configuration of an image forming apparatus 1. In Fig. 1, the right side of the page is the front side of the image forming apparatus 1. For a user looking at the image forming apparatus 1 from the front side, the far side of the page is the right-hand side and the near side of the page is the left-hand side.

[0015] The image forming apparatus 1 is, for example, a laser printer that uses toner to form an image on a sheet S. In this example, the image forming apparatus 1 is a monochrome printer that performs image formation processing for a monochrome image. The image forming apparatus 1 may also be, for example, a color printer that performs image formation processing for a full-color image.

[0016] As shown in FIG. 1, the image forming apparatus 1 includes a housing 2, a paper feed unit 20, an image forming unit 4, discharge rollers 5, and a discharge tray 7. The housing 2 constitutes an outer container of the image forming apparatus 1. The paper feed unit 20 supplies a sheet S toward registration rollers 21. The sheet S is paper on which an image formation process is performed. The registration rollers 21 align the leading edge of the sheet S supplied from the paper feed unit 20 and transport the sheet S toward the image forming unit 4.

[0017] The image forming unit 4 forms an image, in this example, a developer image, on the sheet S fed by the paper feed unit 20. The image forming unit 4 includes an exposure unit 10, a transfer unit 19, a charging unit 18, a developing unit 13, a fixing unit 6, a photosensitive drum 17, and a high-voltage power supply board 8 (see FIG. 2).

[0018] The exposure unit 10 includes a laser light source (not shown), a polygon mirror 11, and a reflecting mirror 12. The polygon mirror 11 is a rotating polygonal mirror with six reflecting surfaces on the side surfaces of a regular hexagonal prism. The polygon mirror 11 deflects the light beam LB emitted from the laser light source in a direction toward the photosensitive drum 17.

[0019] The exposure unit 10 deflects the light beam LB using a polygon mirror 11. The exposure unit 10 emits the light beam LB from the polygon mirror 11 to the surface of the photosensitive drum 17 via a reflecting mirror 12. The exposure unit 10 scans the surface of the photosensitive drum 17 with the light beam LB to expose the photosensitive drum 17. An electrostatic latent image that constitutes a toner image is formed on the photosensitive drum 17.

[0020] The transfer unit 19 includes a transfer roller that sandwiches the sheet S between itself and the photosensitive drum 17. The transfer unit 19 transfers the toner image from the photosensitive drum 17 to the sheet S. The charging unit 18 includes, for example, a charging wire and a grid unit (not shown). In the charging unit 18, a charging voltage is applied to the charging wire by the high-voltage power supply board 8. In the charging unit 18, a corona discharge is generated by applying a grid voltage to the grid unit. This causes the surface of the photosensitive drum 17 to be uniformly charged. The developing unit 13 includes a developing roller 14 and a toner cartridge 15 that contains toner.

[0021] <Image formation operation> In the image forming apparatus 1 configured as described above, an electrostatic latent image based on print data is formed on the surface of the photosensitive drum 17 by the light beam LB from the exposure unit 10. The development roller 14 supplies toner from inside the toner cartridge 15 to the surface of the photosensitive drum 17. This makes the electrostatic latent image visible, and a toner image is formed on the surface of the photosensitive drum 17. A sheet S fed from the paper feed unit 20 is transported to a transfer position between the photosensitive drum 17 and the transfer unit 19. This causes the toner image formed on the surface of the photosensitive drum 17 to be transferred onto the sheet S.

[0022] The sheet S onto which the toner image has been transferred is transported to the fixing unit 6 by the photosensitive drum 17 and the transfer unit 19. The fixing unit 6 includes a heating roller 22 having a heater and a pressure roller 23. The fixing unit 6 thermally fixes the toner image on the sheet S transported from the photosensitive drum 17 and the transfer unit 19. The sheet S onto which the toner image has been thermally fixed is discharged onto the discharge tray 7 by discharge rollers 5.

[0023] <Electrical configuration of image forming apparatus> Fig. 2 is a block diagram showing the electrical configuration of the image forming apparatus 1. As shown in Fig. 2, the image forming apparatus 1 includes a main circuit board MK, an image forming unit 4, and a power supply board 3 that supplies a DC voltage to the image forming unit 4.

[0024] The main board MK includes an ASIC (application specific integrated circuit) with a CPU, a ROM, a RAM, and an application circuit MK1.

[0025] The CPU of the ASIC controls the image forming unit 4 and other components in accordance with the control program read from the ROM. The ROM stores the programs executed by the CPU of the ASIC. The RAM serves as a working area from which the various control programs are read, or temporarily stores data.

[0026] One terminal of the commercial power supply P is connected to the first input terminal T1. The other terminal of the commercial power supply P is connected to the second input terminal T2. The AC / DC conversion circuit 31 on the power supply board 3 is connected to the first input terminal T1 and the second input terminal T2, respectively, and receives an AC voltage from the commercial power supply P. The AC / DC conversion circuit 31 converts the AC voltage into a DC voltage of 24 V. The DC voltage is supplied to the application circuit MK1 on the main board MK.

[0027] The application circuit MK1 supplies a 24V DC voltage supplied from the power supply board 3 to the high-voltage power supply board 8 of the image forming unit 4, the photosensitive drum 17, and the exposure unit 10. The DC voltages supplied to the photosensitive drum 17 and the exposure unit 10 are used as voltages to drive them. The high-voltage power supply board 8 boosts the 24V DC voltage supplied from the application circuit MK1 to a high voltage such as 8 KV. The boosted voltage is supplied to the charging unit 18, the developing unit 13, and the transfer unit 19.

[0028] The fixing unit 6 of the image forming unit 4 is supplied with AC voltage from a commercial power source P.

[0029] <Power supply board layout> The position where the power supply board 3 is arranged inside the housing 2 will be described with reference to FIGS. 3(A) and 3(B).

[0030] FIG. 3(A) is a diagram showing the general internal configuration of image forming apparatus 1 as viewed from above. Image forming apparatus 1 includes a main circuit board MK, a resin frame JF, a drive system member KB, and one of two sheet metal frames BF on the left side. Image forming apparatus 1 includes a power supply board 3 that supplies DC voltage to image forming unit 4, the other of the two sheet metal frames BF, and a fan FN on the right side. A high-voltage power supply board 8 (see FIG. 2) is disposed above power supply board 3, i.e., on the front side of the drawing. The fixing unit 6 and photosensitive drum 17 are axially supported between the two sheet metal frames BF and are rotationally driven by drive system member KB.

[0031] The commercial power supply P supplies AC voltage from two electrodes L and N. The electrode N on the grounded side is the "neutral side," and the electrode L on the ungrounded side is the "live side." A power plug PLG is inserted into the two electrodes L and N of the commercial power supply P. This connects the power cable PCL to the electrode L on the ungrounded side of the commercial power supply P, and the power cable PCN to the electrode N on the grounded side of the commercial power supply P.

[0032] <Detailed configuration of the power supply board> As shown in FIG. 3(A), the power supply board 3 is installed between the right side surface of the housing 2 of the image forming apparatus 1 and the sheet metal frame BF. AC voltage is supplied to the power supply board 3 from a commercial power source P via a power plug PLG, a power cable PCL (see FIG. 4 described later), and PCN. The entire power supply board 3, including the AC / DC conversion circuit 31, is housed in a metal enclosure EC. The metal enclosure EC is grounded. The metal enclosure EC is housed in the housing 2.

[0033] Fig. 3(B) is an enlarged view of the power supply board 3 in Fig. 3(A). The power supply board 3 has two board surfaces, a solder surface S1 and a component surface S2. The solder surface S1 is a surface for soldering leads of electronic components attached to the power supply board 3. The component surface S2 is a surface for attaching the electronic components. An AC / DC conversion circuit 31 is installed on the component surface S2. The first input terminal T1 and the second input terminal T2 are arranged on the power supply board 3, specifically on the solder surface S1.

[0034] The second input terminal T2 is connected to the neutral-side power cable PCN. A terminal end PCN1 of the power cable PCN passes through the power supply board 3 and is soldered to the second input terminal T2 arranged on the solder surface S1 of the power supply board 3. Although not shown in FIG. 3(B), the first input terminal T1 is connected to the live-side power cable PCL. A terminal end PCL1 of the power cable PCL passes through the power supply board 3 and is soldered to the first input terminal T1 arranged on the solder surface S1 of the power supply board 3.

[0035] <Power supply board circuit configuration> FIG. 4 is a circuit diagram showing the main part of the circuit configuration related to the power supply board 3, and for ease of explanation, the internal configuration of the AC / DC conversion circuit 31 is shown in a schematic form.

[0036] 4, the power supply substrate 3 has a first input terminal T1, a second input terminal T2, an AC / DC conversion circuit 31, and two fuses FS. The first input terminal T1 and the second input terminal T2 are arranged on the solder side S1 of the power supply substrate 3. The AC / DC conversion circuit 31 and the fuses FS are arranged on the component side S2 of the power supply substrate 3.

[0037] The first input terminal T1 and the second input terminal T2 are arranged at the end of the power supply board 3. The first input terminal T1 is a live terminal connected to an electrode L on the live side of the commercial power supply P. The second input terminal T2 is a neutral terminal connected to an electrode N on the neutral side of the commercial power supply P.

[0038] The AC / DC conversion circuit 31 converts the AC voltage supplied from the commercial power supply P via the first input terminal T1 and the second input terminal T2 into a DC voltage. The AC / DC conversion circuit 31 includes a rectifier diode 311, an electrolytic capacitor 312, a transformer 313, and a control IC 314. The rectifier diode 311 converts the AC voltage supplied from the commercial power supply P into a DC voltage. The electrolytic capacitor 312 smoothes the DC voltage output from the rectifier diode 311. The smoothed and constant DC voltage is supplied to the transformer 313. The transformer 313 converts the DC voltage supplied from the electrolytic capacitor 312 into a 24V DC voltage and supplies it to the image forming unit 4. The control IC 314 controls the entire AC / DC conversion circuit 31.

[0039] The two fuses FS are connected in the power supply line 81 on the first input terminal T1 side between the first input terminal T1 and the AC / DC conversion circuit 31. These two fuses FS prevent an abnormal current from flowing from the first input terminal T1 to the AC / DC conversion circuit 31.

[0040] A capacitor C is interposed between the power supply line 81 on the first input terminal T1 side and the power supply line 82 on the second input terminal T2 side. The capacitor C functions as a so-called X capacitor, and reduces normal mode noise in the conducted noise voltage by short-circuiting the power supply lines 81 and 82 at high frequencies.

[0041] The power supply board 3 is provided with a first capacitor 100L and a second capacitor 100N as electronic components arranged on the component side S2. One electrode of the first capacitor 100L is connected to the power supply line 81, and the other electrode is connected to a grounded metal enclosure EC. One electrode of the second capacitor 100N is connected to the power supply line 82, and the other electrode is connected to the grounded metal enclosure EC. These first and second capacitors 100L and 100N function as a so-called Y capacitor, and prevent common-mode noise from flowing to the power supply side. The first capacitor 100L and the second capacitor 100N are each an example of a capacitor.

[0042] The first capacitor 100L has a first lead 100L1 and a second lead 100L2. The first lead 100L1 passes through the power supply substrate 3 and is connected to the first input terminal T1 (see FIG. 7, which will be described later). An end of the first lead 100L1 extends from the first input terminal T1 toward the metal enclosure EC. The second capacitor 100N has a first lead 100N1 and a second lead 100N2. The first lead 100N1 passes through the power supply substrate 3 and is connected to the second input terminal T2 (see FIG. 7, which will be described later). An end of the first lead 100N1 extends from the second input terminal T2 toward the metal enclosure EC. The end of the power supply substrate 3 opposite the side where the first and second input terminals T1 and T2 are provided is fixed to the metal enclosure EC via a screw 93 (see FIG. 6, which will be described later) and is thereby electrically grounded. The first lead 100L1 and the second lead 100L2 of the first capacitor 100L are connected to the metal enclosure EC via a circuit pattern PP, which will be described later, and are thereby electrically grounded.

[0043] <Lightning surge protection> In the image forming apparatus 1, a lightning surge may be input to the power supply board 3 via the power cables PCL and PCN. As a countermeasure, discharge gaps G1 and G2 are provided on the power supply board 3. As shown in Fig. 4, the power supply board 3 is provided with a first discharge electrode 51 connected to the first input terminal T1, a second discharge electrode 52 connected to the second input terminal T2, a first ground electrode 61, and a second ground electrode 62.

[0044] FIG. 5 shows a schematic view of the appearance of the solder surface S1 of the power supply board 3. As shown in FIG. 5, a circuit pattern PP is formed on the solder surface S1 by printing. On the solder surface S1, a first discharge gap GL is formed between the first discharge electrode 51 and the first ground electrode 61. A second discharge gap GN is formed between the second discharge electrode 52 and the second ground electrode 62. As a result, when a lightning surge is input to the power supply board 3 via the power cables PCL and PCN, the surge is guided to the first discharge electrode 51 via the first input terminal T1, crosses the first discharge gap GL, and reaches the first ground electrode 61, or is guided to the second discharge electrode 52 via the second input terminal T2, crosses the second discharge gap GN, and reaches the second ground electrode 62. The first ground electrode 61 and the second ground electrode 62 are connected to the metal enclosure EC via screws 91 and 92, and are thereby grounded. Therefore, the lightning surge is earthed from the first ground electrode 61 or the second ground electrode 62 by the metal enclosure EC and is released.

[0045] <Issues with the first and second discharge gaps> However, if lightning surges are repeatedly input to the power supply substrate 3, causing repeated discharges between the first discharge gap GL and the second discharge gap GN, the discharge electrodes 51, 52 and the ground electrodes 61, 62 will wear out, resulting in insufficient discharge beyond each discharge gap GL, GN, which may result in failure of the power supply substrate 3 and may require earlier replacement.

[0046] In response to the above, the metal enclosure EC is provided with a protrusion that forms a third discharge gap between itself and at least one of the first input terminal T1 and the second input terminal T2, as shown in Figures 6 and 7. In this example, the metal enclosure EC is provided with a first protrusion ECL and a second protrusion ECN. The first protrusion ECL and the second protrusion ECN are each an example of a protrusion.

[0047] <Third discharge gap> The protrusions ECL and ECN are provided on the surface EC1 of the metal enclosure EC facing the solder surface S1 so as to protrude toward at least one input terminal. In this example, the first protrusion ECL extends toward the first input terminal T1. In particular, in this example, the first protrusion ECL extends toward the end of the first lead 100L1 of the first capacitor 100L, forming a third discharge gap G3L with the end of the first lead 100L1. In addition, in this example, the second protrusion ECN extends toward the second input terminal T2. In particular, in this example, the second protrusion ECN extends toward the end of the first lead 100N1 of the second capacitor 100N, forming a third discharge gap G3N with the end of the first lead 100N1.

[0048] <Effects of the embodiment> As described above, in this embodiment, the first input terminal T1 is connected to the live-side power cable PCL, and the second input terminal T2 is connected to the neutral-side power cable PCN. A first discharge gap GL is formed between the first discharge electrode 51 connected to the first input terminal T1 and the first ground electrode 61, and a second discharge gap GN is formed between the second discharge electrode 52 connected to the second input terminal T2 and the second ground electrode 62. The first ground electrode 61 and the second ground electrode 62 are connected to the grounded metal enclosure EC.

[0049] A lightning surge input to the power supply board 3 via the power cables PCL and PCN is conducted to the first discharge electrode 51 via the first input terminal T1, crosses the first discharge gap GL and reaches the first ground electrode 61, or is conducted to the second discharge electrode 52 via the second input terminal T2, crosses the second discharge gap GN and reaches the second ground electrode 62. The lightning surge is earthed from the first ground electrode 61 or the second ground electrode 62 by the metal enclosure EC and is released.

[0050] In this embodiment, the metal enclosure EC has protrusions ECL, ECN extending toward at least one of the first input terminal T1 and the second input terminal T2, so that new discharge gaps, or third discharge gaps G3L, G3N, are formed between the power supply board 3 and the extending protrusions ECL, ECN of the metal enclosure EC.

[0051] As a result, even when the first discharge electrode 51 and the first ground electrode 61, or the second discharge electrode 52 and the second ground electrode 62, wear and it becomes difficult to discharge through the first or second discharge gap GL, GN, the lightning surge can be released toward the metal enclosure EC through the new discharge gaps, the third discharge gaps G3L, G3N. Furthermore, the image forming apparatus 1 of this embodiment can prevent the power supply board 3 from breaking down even when lightning surges are repeatedly input.

[0052] Furthermore, particularly in this embodiment, the metal enclosure EC has two protrusions ECL, ECN extending toward the first and second input terminals T1, T2, respectively. As a result, two third discharge gaps G3L, G3N can be formed between the power supply board 3 and the two protrusions ECL, ECN extending toward the first and second input terminals T1, T2, respectively.

[0053] Furthermore, particularly in this embodiment, the first and second input terminals T1, T2 are provided on the solder surface S1 of the power supply board 3, and protrusions ECL, ECN are provided on the surface EC1 of the metal enclosure EC that faces the solder surface S1. As a result, when a lightning surge is input to the power supply board 3, it can be discharged from the solder surface S1 of the power supply board 3 to the protrusions ECL, ECN of the metal enclosure EC that faces the solder surface S1.

[0054] Furthermore, particularly in this embodiment, the ends of the first leads 100L1, 100N1 of the capacitors 100L, 100N attached to the component side S2 of the power supply board 3 extend toward the metal enclosure EC, and third discharge gaps G3L, G3N are formed between the first leads 100L1, 100N1 and the protrusions ECL, ECM of the metal enclosure EC. As a result, when a lightning surge is input to the power supply board 3, discharge can be performed from the first leads 100L1, 100N1 of the capacitors 100L, 100N on the solder side S1, via the third discharge gaps G3L, G3N, to the protrusions ECL, ECM of the metal enclosure EC.

[0055] Furthermore, particularly in this embodiment, ends of the first leads 100L, 100N of the first and second capacitors 100L, 100N extend from the first and second input terminals T1, T2, respectively, toward the metal enclosure EC, and third discharge gaps G3L, G3N are formed between the first leads 100L, 100N and the first and second protrusions ECL, ECN of the metal enclosure EC, respectively. This allows current to be discharged from the first leads 100L, 100N of the two capacitors 100L, 100N on the solder surface S1 to the two protrusions ECL, ECN of the metal enclosure EC, respectively, via the third discharge gaps G3L, G3N.

[0056] The present invention is not limited to the above-described embodiment, and various modifications are possible within the scope of the spirit and technical concept of the present invention. Such modifications will be described below in order.

[0057] (1) Discharge on the component side Fig. 8 shows a schematic external view of the power supply board 3 in this modification as seen from the component surface S2 side, and Fig. 9 shows a conceptual cross-sectional view of the metal enclosure EC that houses the power supply board 3. Note that Fig. 8 roughly corresponds to a view taken along the arrow BB in Fig. 9.

[0058] 8 and 9, in this modification, as in the above embodiment, the first input terminal T1 and the second input terminal T2 are arranged on the solder side S1 of the power supply board 3. Jumper wires 200L and 200N are provided on the component side S2. One end of the jumper wires 200L and 200N passes through the power supply board 3 and is connected to at least one of the first input terminal T1 and the second input terminal T2. The other end of the jumper wires 200L and 200N passes through the power supply board 3 and is connected to dummy terminals D1 and D2 on the solder side S1.

[0059] The metal enclosure EC has protrusions ECL′, ECN′. The protrusions ECL′, ECN′ extend toward the body portions 200La, 200Na of the jumper wires 200L, 200N. The protrusions ECL′, ECN′ form third discharge gaps G3L′, G3N′ between themselves and the body portions 200La, 200Na.

[0060] In detail, the jumper wires 200L, 200N include a first jumper wire 200L and a second jumper wire 200N. One end of the first jumper wire 200L is connected to the first input terminal T1. The other end of the first jumper wire 200L is connected to the first dummy terminal D1 on the solder surface S1. One end of the second jumper wire 200N is connected to the second input terminal T2. The other end of the second jumper wire 200N is connected to the second dummy terminal D2 on the solder surface S1. The first jumper wire 200L and the second jumper wire 200N are each an example of a jumper wire. The first dummy terminal D1 and the second dummy terminal D2 are each an example of a dummy terminal.

[0061] The metal enclosure EC has a third protrusion ECL' and a fourth protrusion ECN' on a surface EC2 facing the component surface S2, which protrude toward the body portions 200La, 200Na of the first jumper wire 200L and the second jumper wire 200N, respectively. The third protrusion ECL' forms a third discharge gap G3L' between itself and the body portion 200La of the first jumper wire 200L. The fourth protrusion ECN' forms a third discharge gap G3N' between itself and the body portion 200Na of the second jumper wire 200N. The third protrusion ECL' and the fourth protrusion ECN' are each an example of a protrusion.

[0062] <Effects of the modified version> This modification also achieves the same effects as the above embodiment. That is, first and second input terminals T1, T2 and dummy terminals D1, D2 are provided on the solder surface S1 of the power supply board 3. One end of the jumper wires 200L, 200N is connected to at least one input terminal, and the other end of the jumper wires 200L, 200N is connected to the dummy terminals D1, D2. Third discharge gaps G3L', G3N' are formed between the bodies 200La, 200Na of the jumper wires 200L, 200N and the protrusions ECL', ECN' of the metal enclosure EC.

[0063] Projections ECL', ECN' are provided on a surface EC2 of the metal enclosure EC facing the component surface S2 so as to extend toward the bodies 200La, 200Na of the jumper wires 200L, 200N. This allows discharge from the jumper wires 200L, 200N on the component surface S2 of the power supply board 3 to the projections ECL', ECN' of the metal enclosure EC via the third discharge gaps G3L', G3N' when a lightning surge is input to the power supply board 3.

[0064] (2) Other The image forming apparatus according to the present invention can be applied not only to printers but also to multifunction machines, copiers, etc. The printer is not limited to a laser type, and may be an inkjet type.

[0065] In addition to the above, the methods according to the above embodiments and modifications may be used in appropriate combination.

[0066] Although not specifically illustrated, the present invention can be implemented with various modifications within the scope of the invention. [Explanation of symbols]

[0067] 1. Image forming device 3 Power Supply Board 4 Image forming unit 31 AC / DC conversion circuit 51 1st discharge electrode 52 2nd discharge electrode 61 1st ground electrode 62 2nd ground electrode 100L First capacitor (example of a capacitor) 100L1 1st lead 100L2 2nd lead 100N Secondary capacitor (an example of a capacitor) 100N1 1st lead 100N2 2nd lead 200L No. 1 jumper wire (example of a jumper wire) 200La body part 200N second jumper wire (example of a jumper wire) 200Na body part D1 First dummy terminal (an example of a dummy terminal) D2 Second dummy terminal (an example of a dummy terminal) EC Metal Enclosure EC1: Surface opposite to solder surface EC2: Surface opposite to component surface ECL first protrusion (example of protrusion) ECL' Third protrusion (an example of a protrusion) ECN second protrusion (example of protrusion) ECN' 4th protrusion (example of protrusion) G3L Third discharge gap G3L' Third discharge gap G3N Third Discharge Gap G3N' Third discharge gap GL First discharge gap GN Second Discharge Gap P Commercial power supply PCL Power Cable PCN Power Cable S seat S1 solder side S2 Part side T1 First input terminal T2 Second input terminal

Claims

1. an image forming unit; a power supply board for supplying a DC voltage to the image forming unit; a metal enclosure that covers the entire power supply board and is grounded; 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 power cable connected to a commercial power source, and the second input terminal being connected to a neutral side of the power cable; 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 supply into the DC voltage; a first discharge electrode connected to the first input terminal; a first ground electrode that forms a first discharge gap between itself and the first discharge electrode and is connected to the metal enclosure; a second discharge electrode connected to the second input terminal; a second ground electrode that forms a second discharge gap between itself and the second discharge electrode and is connected to the metal enclosure; and The metal enclosure comprises: a third discharge gap is formed between the first input terminal and the second input terminal and the ... second input terminal and the third discharge gap and the third discharge gap is formed An image forming apparatus characterized by:

2. 2. The image forming apparatus according to claim 1, The metal enclosure comprises: The two protrusions extend toward the first input terminal and the second input terminal, respectively. An image forming apparatus characterized by:

3. 2. The image forming apparatus according to claim 1, the first input terminal and the second input terminal are arranged on a solder surface of the two board surfaces, namely, the front and rear surfaces of the power supply board, to which leads of electronic components attached to the power supply board are soldered; The protrusion is a projection provided on a surface of the metal enclosure facing the solder surface so as to protrude toward the at least one input terminal; An image forming apparatus characterized by:

4. 4. The image forming apparatus according to claim 3, The electronic component is a capacitor having a first lead and a second lead, the first lead of the capacitor passes through the power supply board and is connected to the at least one input terminal, and the second lead of the capacitor is electrically grounded; an end of the first lead extends from the first input terminal toward the metal enclosure; The protrusion is extending toward the end of the first lead and forming the third discharge gap between itself and the end of the first lead; An image forming apparatus characterized by:

5. 5. The image forming apparatus according to claim 4, the electronic components are a first capacitor and a second capacitor, each having the first lead and the second lead; the first lead of the first capacitor is connected to the first input terminal through the power supply board, an end of the first lead of the first capacitor extends from the first input terminal toward the metal enclosure, and the second lead of the first capacitor is electrically grounded; the first lead of the second capacitor is connected to the second input terminal through the power supply board, an end of the first lead of the second capacitor extends from the second input terminal toward the metal enclosure, and the second lead of the second capacitor is electrically grounded; the metal enclosure has a first protrusion and a second protrusion extending toward the first input terminal and the second input terminal, respectively; the first protrusion forms the third discharge gap between itself and an end of the first lead of the first capacitor; the second protrusion forms the third discharge gap between itself and the end of the first lead of the second capacitor; An image forming apparatus characterized by:

6. 2. The image forming apparatus according to claim 1, the first input terminal and the second input terminal are arranged on a solder surface of the two board surfaces, namely, the front and rear surfaces of the power supply board, to which leads of electronic components attached to the power supply board are soldered; Furthermore, it is equipped with a jumper wire, one end of the jumper wire passes through the power supply substrate and is connected to at least one of the first input terminal and the second input terminal, and the other end of the jumper wire passes through the power supply substrate and is connected to a dummy terminal on the solder surface; The protrusion is extending toward the body portion of the jumper wire and forming the third discharge gap between the body portion and the jumper wire; An image forming apparatus characterized by:

7. 7. The image forming apparatus according to claim 6, The jumper wires include a first jumper wire and a second jumper wire, the one end of the first jumper wire is connected to the first input terminal, and the other end of the first jumper wire is connected to a first dummy terminal on the solder surface; the one end of the second jumper wire is connected to the second input terminal, and the other end of the second jumper wire is connected to a second dummy terminal on the solder surface; the metal enclosure has a third protrusion and a fourth protrusion extending toward the body portions of the first jumper wire and the second jumper wire, respectively; the third protrusion forms the third discharge gap between itself and the body of the first jumper wire; The fourth protrusion forms the third discharge gap between itself and the body of the second jumper wire. An image forming apparatus characterized by:

Images