Plurality of boards mounted on image forming apparatus

A first connector is soldered to a first board. A second connector is soldered to a second board. A third connector and a fourth connector are soldered to a relay board. The third connector is connected to the first connector via a first power line. The fourth connector is connected to the second connector via a second power line. A surface to which the first connector is soldered on the first board is opposite to a surface to which the first connector is attached on the first board. A surface to which the second connector is soldered on the second board is a surface to which the second connector is attached on the second board. Only surface-mount devices are used as electronic components soldered to the second board.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a plurality of boards mounted on an image forming apparatus.

Description of the Related Art

An image forming apparatus includes many loads that are driven to form an image on a sheet P. The loads of the image forming apparatus include, for example, a motor that drives photosensitive drums, a high-voltage power supply that generates a voltage to be applied to charging devices or developing devices, and a heater of a fixing device. In recent years, provision of a power supply board that generates a voltage to be supplied to these loads and a control board that controls the loads as separate boards has been considered. In this configuration, a connector provided on the control board and a connector provided on the power supply board are connected by cables such as a wire harness.

Japanese Patent Laid-Open No. 2005-26245 suggests mounting of a surface-mount-type connector and a DIP-type connector on a single circuit board. A DIP-type connector denotes a connector in which a connector lead is inserted through a through-hole provided on a circuit board and the lead is soldered to a back surface of the circuit board. A surface-mount-type connector denotes a connector in which a connector lead is soldered to a land provided on a front surface of the circuit board.

A DIP-type electronic component is attached to a board using a flow mounting method. The flow mounting method is a method whereby an electronic component is soldered to a board by producing an upwelling of liquid solder. On the other hand, a surface-mount-type electronic component is attached to a board using a reflow mounting method. The reflow mounting method is a method whereby an electronic component is soldered to a board by applying cream-like solder between the board and the electronic component and heating the board in a reflow oven.

In the meantime, in a case where a DIP-type electronic component and a surface-mount-type electronic component are attached to one board, a flow mounting method and a reflow mounting method need to be implemented with respect to this board. Therefore, a board to which both of a DIP-type electronic component and a surface-mount-type electronic component are attached has a high manufacturing cost.

SUMMARY OF THE INVENTION

The present application provides an image forming apparatus comprising the following elements. An image forming unit is configured to form an image on a sheet. A fixing unit includes a heater, and is configured to fix the image on the sheet. A first board includes a power supply circuit that generates a predetermined direct-current voltage from an alternating-current voltage supplied from a commercial alternating-current power supply. The power supply circuit is configured to apply the alternating-current voltage to the heater. A second board is configured to control the image forming unit based on the predetermined direct-current voltage generated by the power supply circuit. A first connector is soldered to the first board. A second connector is soldered to the second board. A relay board to which a third connector and a fourth connector are soldered. The third connector is connected to the first connector of the first board via a first power line. The fourth connector is connected to the second connector of the second board via a second power line. A surface to which the first connector is soldered on the first board is opposite to a surface to which the first connector is attached on the first board. A surface to which the second connector is soldered on the second board is a surface to which the second connector is attached on the second board. Only surface-mount devices are used as electronic components soldered to the second board, including the second connector. The number of pins in the second connector is larger than the number of pins in the first connector. The number of pins in the fourth connector is larger than the number of pins in the third connector. The predetermined direct-current voltage generated by the power supply circuit is supplied to the second board by way of the relay board.

DESCRIPTION OF THE EMBODIMENTS

FIG. 1is a cross-sectional view showing an image forming apparatus100. The image forming apparatus100includes an image reader102and a printer103. The image reader102is a reading unit that reads an original. A light source23irradiates an original21placed on a glass platen22with light. An optical system24directs reflected light from the original21to a CCD sensor25to form an image. CCD is an abbreviation for a charge-coupled device. The CCD sensor25includes red, green, and blue line sensors, and generates color component signals corresponding to red, green, and blue. An image processing unit28executes image processing (e.g., shading correction) with respect to image data obtained by the CCD sensor25, and outputs the resultant image data to a printer control unit29of the printer103.

An image forming unit10of the printer103is an image forming engine of an electrophotographic type, which forms toner images corresponding to image data on a sheet P. The image forming unit10includes four stations that respectively form toner images of colors Y (yellow), M (magenta), C (cyan), and K (black). Note that the present invention is also applicable to a monochrome printer that forms a single-color image. As shown inFIG. 1, the image forming unit10includes four photosensitive drums1that respectively correspond to the colors in order from left. The letters Y, M, C, and K appended to reference numerals indicate toner colors, but they are omitted in the explanation of matters that are common to the four colors. A charging device2, an exposure device3, a developing device4, a primary transfer device7, a drum cleaner5, and the like are disposed around each photosensitive drum1. Here, the photosensitive drum1, the charging device2, and the drum cleaner5are integrated as a process cartridge8. The process cartridge8is attachable to and removable from the image forming apparatus100. Furthermore, the image forming apparatus100includes an intermediate transfer belt31on which toner images are formed, a secondary transfer device27that transfers the toner images on the intermediate transfer belt31to a sheet P, and a fixing device40that fixes the toner images on the sheet P. Note that the intermediate transfer belt31is wound around three rollers34,36,37, and rotates in a predetermined direction as the roller37rotates in a direction of an arrow. The intermediate transfer belt31is provided with a belt cleaner35.

Configurations of the units of the image forming apparatus100will now be described. The photosensitive drums1are aluminum cylinders with a photosensitive layer formed on a surface thereof. The photosensitive drums1function as photosensitive members. The charging devices2include, for example, a metallic wire, a charging roller, or a charging brush to which a charging voltage is supplied. The exposure devices3may be configured to include a light source310that emits laser light (FIG. 7) and a rotatable polygon mirror that deflects laser light from the light source310. Alternatively, the exposure devices3may be configured in such a manner that a plurality of light sources310that emit laser light are aligned in a direction of axial lines of the photosensitive drums1. The direction of axial lines denotes a direction parallel to rotation axes of the photosensitive drums1. Laser light from the exposure devices3scan the photosensitive drums1. The developing devices4house developer (toner). The developing devices4include a developing roller for supplying the developer to the photosensitive drums1. The developer is carried on a surface of the developing roller due to a magnet provided inside the developing roller. Note that, although the developer described in the present embodiment is assumed to be two-component developer including non-magnetic toner and magnetic carrier, the developer may be, for example, single-component developer composed of magnetic toner. The primary transfer devices7are, for example, transfer rollers or transfer blades to which a primary transfer voltage is supplied. The primary transfer devices7press the intermediate transfer belt31against the photosensitive drums1, thereby forming nip portions (primary transfer nip portions) between the photosensitive drums1and the intermediate transfer belt31. The drum cleaners5are, for example, cleaning blades made of an elastic material that comes into contact with the surfaces of the photosensitive drums1, or fur brushes that collect toner by coming into contact with the surfaces of the photosensitive drums1. The secondary transfer device27is, for example, a transfer roller to which a secondary transfer voltage is supplied, or a transfer belt wound around a plurality of rollers. The secondary transfer device27presses the intermediate transfer belt31, thereby forming a nip portion (secondary transfer nip portion) between the intermediate transfer belt31and the secondary transfer device27. The belt cleaner35is, for example, a cleaning blade that comes into contact with a surface of the intermediate transfer belt31, or a fur brush that comes into contact with the surface of the intermediate transfer belt31.

Below, a procedure for forming a black toner image will be described as a representative for the four colors. Note that, as a procedure for forming toner images of other colors is similar to the procedure for forming a black toner image, its detailed explanation will be omitted. When image formation has been started, the photosensitive drum1rotates in a predetermined direction (a direction of an arrow). The charging device2charges the surface of the photosensitive drum1. The exposure device3exposes the surface of the photosensitive drum1based on image data output from the printer control unit29. As a result, an electrostatic latent image is formed on the photosensitive drum1. The developing device4develops the electrostatic latent image using toner. Through the above-described process, a toner image is formed on the photosensitive drum1. Using the primary transfer voltage, the primary transfer device7transfers the toner image carried on the photosensitive drum1to the intermediate transfer belt31. The drum cleaner5removes toner that is left on the photosensitive drum1without getting transferred to the intermediate transfer belt31at the primary transfer nip portion.

A feeding cassette20houses sheets P. Sheets P are placed in a multi-feeding tray30. A sheet P fed from the feeding cassette20or the multi-feeding tray30is transported toward a pair of registration rollers26. The pair of registration rollers26temporarily stops the sheet P fed from the feeding cassette20or the multi-feeding tray30, and transports the sheet P to the secondary transfer nip portion so that the toner image on the intermediate transfer belt31is transferred to a desired position on the sheet P. While the sheet P is passing through the secondary transfer nip portion, the secondary transfer voltage is applied to the secondary transfer device27. As a result, the secondary transfer device27secondary-transfers the toner image on the intermediate transfer belt31to the sheet P. Note that the belt cleaner35removes toner that is left on the intermediate transfer belt31without getting transferred to the sheet P at the secondary transfer nip portion. The sheet P to which the toner image has been transferred is transported to the fixing device40. The fixing device40fixes the toner image on the sheet P.

A door50is a door used in maintenance. When a sheet is jammed, a user or a person in charge of maintenance opens the door50and removes the sheet.

[Electrical Components That Compose Image Forming Apparatus]

FIG. 2shows electrical components that compose a part of the printer control unit29. A control board200is a circuit board assembly composed of one or a plurality of printed boards. A CPU201, a storage apparatus202, and an image processing circuit203are mounted on the control board200. The storage apparatus202and the image processing circuit203are connected to the CPU201via a communication bus. The CPU201executes control programs stored in the storage apparatus202, and controls a main power supply board230, a high-voltage power supply board210, a motor assembly220, and the like in accordance with the control programs. The storage apparatus202includes memories, such as a ROM and a RAM. The image processing circuit203executes, for example, tone correction control to control tones of an output image. The tone correction control is processing for converting image signal values included in image data based on a tone correction table.

The motor assembly220is a collection of various motors that are driven in accordance with a drive signal (control signal) output from the CPU201. A motor M1drives a feeding roller48. A motor M2is a motor that drives the pair of registration rollers26. A motor M3is a motor that drives a fixing roller provided in the fixing device40. A motor M4is a motor that drives a pair of discharge rollers49.

The main power supply board230includes a power supply circuit211xthat convers an alternating-current voltage supplied from a commercial alternating-current power supply into various levels of direct-current voltages (e.g., 3.3 V, 5 V, 12V, and 24V). The main power supply board230supplies a direct-current voltage to the control board200, supplies a direct-current voltage to the motor assembly220, and supplies a direct-current voltage to the high-voltage power supply board210.

The high-voltage power supply board210includes a plurality of power supply circuits that convert the direct-current voltage supplied from the main power supply board230into various levels of direct-current voltages (e.g., a high voltage of several hundred volts) and alternating-current voltages. A power supply circuit211agenerates a charging voltage and supplies the charging voltage to the charging devices2. A power supply circuit211bgenerates a primary transfer voltage and supplies the primary transfer voltage to the primary transfer devices7. A power supply circuit211cgenerates a developing voltage and supplies the developing voltage to the developing devices4. A power supply circuit211dgenerates a secondary transfer voltage and supplies the secondary transfer voltage to the secondary transfer device27. The CPU201supplies, to the power supply circuits211ato211d, signals of instructions on voltage values and signals of instructions on starting and stopping the voltage output.

FIG. 3Ashows a mode of connection between a plurality of printed circuit boards that compose a circuit board assembly350. A first harness unit301ais a wire harness connecting the control board200and an IF conversion board300. IF is an abbreviation for an interface. A second harness unit301bis a wire harness connecting the IF conversion board300and the main power supply board230. The IF conversion board300is a printed board for absorbing the difference between an interface on the control board200side and an interface on the main power supply board230side.

FIG. 3Bshows the second harness unit301b. The second harness unit301bincludes n cables304a, a connector302cprovided at one end of the cables304a, and a connector302dprovided at the other end of the cables304a. In the present example, n is four. Among the cables304a, two cables are power supply lines, and the other two cables are grounding lines. Each of the connectors302c,302dhas n conductive pins. Each of the n conductive pins is electrically connected to one of the n cables304a. The connector302cfits into and is electrically connected to a connector302aprovided on the IF conversion board300. The connector302cis a plug. The connector302ais a receptacle. The connector302dfits into and is electrically connected to a connector302bprovided on the main power supply board230. The connector302dis a plug. The connector302bis a receptacle.

The main power supply board230supplies power to all electrical loads that compose the image forming apparatus100, including the control board200, the motor assembly220, the high-voltage power supply board210, and the like. A current that can be output from the main power supply board230may be, for example, approximately 20 A. Therefore, DIP-type electrical components that can withstand a high current are used as electrical components mounted on the main power supply board230. That is, the connector302bis a DIP-type connector. Various DIP-type electrical components, including the connector302b, are mounted on a first surface of the main power supply board230. A lead of the connector302bis inserted into a through-hole that penetrates the board from the first surface to a second surface. A land is provided on the second surface of the main power supply board230. The lead of the connector302bis soldered to this land using a flow mounting method. In the flow mounting method, the second surface comes into contact with a solder pool housing molten solder, thereby soldering the lead and the land together. That is, the surface to which the connector302bis soldered is opposite to the surface to which the connector302bis attached.

The connector302amounted on a first surface of the IF conversion board300also needs to be a DIP-type connector that can withstand a high current. This is because a high current flows from the main power supply board230to the connector302avia the second harness unit301b. A lead of the connector302ais inserted into a through-hole that penetrates the IF conversion board300from the first surface to a second surface of the board. A land is provided on the second surface of the IF conversion board300. The lead of the connector302ais soldered to this land using the flow mounting method. That is, the surface to which the connector302ais soldered is opposite to the surface to which the connector302ais attached. Note that a current of 10 A can flow through one pin in the connector302a. Also note that it is sufficient for a current that flows through one pin in the connector302ato be higher than 6 [A].

FIG. 3Cshows the first harness unit301a. The first harness unit301aelectrically connects the IF conversion board300and the control board200. The first harness unit301aincludes m cables304b, a connector302gprovided at one end of the cables304b, and a connector302hprovided at the other end of the cables304b. In the present example, m is eight. Among the cables304b, four cables are power supply lines, and the other four cables are grounding lines. Each of the connectors302g,302hhas m conductive pins. Each of the m conductive pins is electrically connected to one of the m cables304b. The connector302hfits into and is electrically connected to a connector302fprovided on the IF conversion board300. The connector302his a plug. The connector302fis a receptacle. The connector302gfits into and is electrically connected to a connector302eprovided on the control board200. The connector302gis a plug. The connector302eis a receptacle.

As the connector302aprovided on the IF conversion board300is a DIP-type connector as stated earlier, the connector302fmay be a DIP-type connector as well. By using DIP-type connectors as both of the connectors302a,302f, a mounting cost is reduced. However, the connector302fmay be a surface-mount-type connector.

Incidentally, all of the electrical components mounted on the control board200are surface-mount-type electrical components in view of reduction of a board area, reduction of cost, and the manufacturing quality. Therefore, a surface-mount-type connector is used also as the connector302e. Here, it is assumed that a current of 5 A can flow through one pin in a surface-mount-type connector.

As described above, the control board200is composed of surface-mount-type electrical components (surface-mount devices). Therefore, a land and a lead of an electrical component, which are provided on a mount surface of the control board200, are soldered together using a reflow mounting method. In the reflow mounting method, the land and the lead are soldered together by thermal melting of a solder paste applied to the land. That is, the surface to which the surface-mount devices are soldered is the same as the surface to which the surface-mount devices are attached.

FIG. 3Dis a diagram for describing the IF conversion board300. The number of pins in the connector302bof the main power supply board230is different from the number of pins in the connector302eof the control board200. Furthermore, the amount of current that can flow through one pin in the connector302bof the main power supply board230is different from the amount of current that can flow through one pin in the connector302eof the control board200. That is, an interface of the main power supply board230is different from an interface of the control board200. For this reason, the IF conversion board300is suggested in the present embodiment.

As shown inFIG. 3D, the IF conversion board300includes conductive wiring patterns305that connect the connector302aand the connector302f. To electrically connect one pin in the connector302aand two pins in the connector302f, the wiring patterns305branch out from one into two. This resolves the problem of the difference in the amount of current that can flow through each pin.

FIG. 4Ais a perspective view showing the DIP-type connectors302a,302b.FIG. 4Bis a plan view of the DIP-type connectors302a,302b.FIG. 4Cis a side view of the DIP-type connectors302a,302b. The connectors302a,302binclude a connector case401amade of resin (an insulating member), connector pins402aas conductive members, and connector leads403aas conductive members. The connector leads403amay be parts of the connector pins402a. The connector leads403aand the connector pins402amay be electrically connected via conductive members.

The IF conversion board300, on which the connector302ais mounted, is provided with through-holes404athat penetrate the board from the first surface (the surface on which components are mounted) to the second surface. The connector pins402aof the connector302aare inserted through the through-holes404afrom the first surface side of the IF conversion board300. Lands405aare provided on the second surface of the IF conversion board300. The connector leads403athat project on the second surface via the through-holes404aare soldered to the lands405ausing the flow mounting method.

The main power supply board230, on which the connector302bis mounted, is provided with through-holes404athat penetrate the board from the first surface to the second surface. The connector pins402aof the connector302bare inserted through the through-holes404afrom the first surface side of the main power supply board230. Lands405aare provided on the second surface of the main power supply board230. The connector leads403athat project on the second surface via the through-holes404aare soldered to the lands405ausing the flow mounting method.

FIG. 5Ais a perspective view showing the DIP-type connector302f.FIG. 5Bis a plan view of the DIP-type connector302f.FIG. 5Cis a side view of the DIP-type connector302f. The connector302fincludes a connector case401cmade of resin (an insulating member), connector pins402cas conductive members, and connector leads403cas conductive members. The connector leads403cmay be parts of the connector pins402c. The connector leads403cand the connector pins402cmay be electrically connected via conductive members.

The IF conversion board300, on which the connector302fis mounted, is provided with through-holes404cthat penetrate the board from the first surface (the surface on which components are mounted) to the second surface. The connector pins402cof the connector302care inserted through the through-holes404cfrom the first surface side of the IF conversion board300. Lands405care provided on the second surface of the IF conversion board300. The connector leads403cthat project on the second surface via the through-holes404care soldered to the lands405cusing the flow mounting method. That is, the surface to which the connector302fis soldered is opposite to the surface to which the connector302fis attached.

FIG. 6Ais a perspective view showing the surface-mount connector302e.FIG. 6Bis a plan view of the surface-mount connector302e.FIG. 6Cis a side view of the surface-mount connector302e. The connector302eincludes a connector case401bmade of resin (an insulating member), connector pins402bas conductive members, and connector leads403bas conductive members. The connector leads403bmay be parts of the connector pins402b. The connector leads403band the connector pins402bmay be electrically connected via conductive members. The connector leads403bextend from a bottom surface or a side surface of the connector case401bto a side of the connector case401b(in an x direction).

Lands405bare provided on a first surface (a surface on which components are mounted) of the control board200on which the connector302eis mounted. The connector leads403bare soldered to the lands405busing the reflow mounting method. That is, a solder paste is printed on the lands405b, the connector leads403bare placed on the solder paste, the solder paste is melted by applying heat to the solder paste, and the connector leads403bare joined to the lands405bby soldering. Note that the DIP-type connector302fmay be replaced by the connector302e. In this case, the lands405bare provided on the first surface of the IF conversion board300.

FIG. 7shows a part of a circuit diagram of the control board200, the main power supply board230, and the IF conversion board300. An alternating-current voltage is applied from the commercial alternating-current power supply to the main power supply board230. The main power supply board230further applies the alternating-current voltage supplied from the commercial alternating-current power supply to a heater41of the fixing device40. That is, the alternating-current voltage is applied to the heater41via the main power supply board230.

The alternating-current voltage supplied from the commercial alternating-current power supply is supplied to the power supply circuit211xincluded in the main power supply board230via a filter700. Then, the power supply circuit211xgenerates predetermined direct-current voltages from the alternating-current voltage. Here, the power supply circuit211xaccording to the present embodiment generates direct-current voltages of 3.3 V, 5 V, 12 V, and 24 V.

The direct-current voltages of 3.3 V, 5 V, and 12 V are supplied to the control board200via, for example, connectors701ato701c. The direct-current voltage of 3.3 V is applied to, for example, a sensor702provided in the image forming apparatus100. The direct-current voltage of 5 V is applied to, for example, a photointerrupter703provided in the image forming apparatus100. The direct-current voltage of 12 V is applied to, for example, a fan provided in the image forming apparatus100.

On the other hand, the direct-current voltage of 24 V is supplied to the control board200via the IF conversion board300. The control board200supplies the direct-current voltage of 24 V to the high-voltage power supply board210and the motor assembly220shown inFIG. 2. The control board200further supplies the direct-current voltage of 24 V to the light sources310of the exposure devices3.

Furthermore, the image forming apparatus100has an interlock mechanism500that blocks power supply to the heater41and the light sources310in response to opening of the door50. The interlock mechanism500is realized by a switch that mechanically opens when the door50of the image forming apparatus100is opened. The interlock mechanism500is electrically connected to an interlock circuit501of the IF conversion board300. The interlock circuit501is also electrically connected to an interlock circuit502of the main power supply board230.

When the switch of the interlock mechanism500opens, a relay of the interlock circuit501blocks the direct-current voltage of 24 V supplied to the light sources310, and a relay of the interlock circuit502blocks the alternating-current voltage supplied to the heater41. Accordingly, when the door50is opened, power supply to the loads can be stopped, even if the image forming apparatus100is in operation.

A description is now given of an ingenious way of using only surface-mount devices as electronic components attached to the control board200. Assuming that the main power supply board230and the control board200are directly connected via cables, the number of pins in the connector of the control board200to which the cables are connected, is determined by the number of pins in the connector of the main power supply board230. Also, the radius of pins in a surface-mount-type connector, which is a surface-mount device, is smaller than the radius of pins in a DIP-type connector. Therefore, when the number of pins in the connector of the control board200is limited by the number of pins in the connector of the main power supply board230, there is a possibility that a high current flows into the pins in the connector of the control board200, thereby damaging the pins in the connector. In view of this, in the image forming apparatus100according to the present embodiment, the IF conversion board300is electrically connected between the main power supply board230and the control board200as shown inFIG. 7.

On the IF conversion board300, the number of pins in the connector302f, which is connected to the control board200via the cables304b, is larger than the number of pins in the connector302a, which is connected to the main power supply board230via the cables304a. That is, the IF conversion board300converts the number of pins in the connector302finto the number of pins in the connector302a. This can suppress the flow of the high current through the connector302eof the control board200, even when the direct-current voltage of 24 V from the main power supply board230is supplied to the control board200.

All of the electronic components attached to the main power supply board230according to the present embodiment are DIP-type electronic components. That is, no surface-mount device is attached to the main power supply board230according to the present embodiment. Accordingly, the reflow mounting method can be skipped in manufacturing the main power supply board230. Therefore, the manufacturing cost of the main power supply board230is reduced. Furthermore, in the case of a DIP-type connector, the area occupied by the connector can be reduced by reducing the number of pins. In this way, a degree of freedom in design is increased by downsizing the main power supply board230in the image forming apparatus100according to the present embodiment.

The following technical ideas are derived from the above-described embodiment. The main power supply board230is one example of a first board that applies a commercial alternating-current power source to the heater. The power supply circuit211xis one example of a power supply circuit that generates predetermined direct-current voltages from the alternating-current voltage of the commercial alternating-current power supply. The control board200is one example of a second board that controls the image forming unit10based on the predetermined direct-current voltages generated by the power supply circuit211x. The connector302bis one example of a first connector soldered to the main power supply board230. The connector302eis one example of a second connector soldered to the control board200. The connector302ais one example of a third connector connected to the connector302bvia the cables304a. The cables304aare one example of first power lines. The connector302fis one example of a fourth connector connected to the connector302evia the cables304b. The cables304bare one example of second power lines. The IF conversion board300is one example of a relay board to which the connector302aand the connector302fare soldered. According to the present invention, as the IF conversion board300is provided, only surface-mount devices can be used as electronic components soldered to the control board200.

Electronic components soldered to the first board include the first connector. These electronic components need not include a surface-mount device. Electronic components soldered to the relay board, including the third connector and the fourth connector, need not include a surface-mount device. A current that flows through one pin in the first connector may be higher than 6 [A]. Note that an electronic component for blocking the alternating-current voltage applied from the commercial alternating-current power supply to the heater may be attached to the relay board. An electronic component for blocking power supply to the light sources may be attached to the relay board. An electronic component for blocking power supply to the developing devices may be attached to the relay board. One example of these blocking functions is the interlock circuit501.

As shown inFIG. 2, the CPU201and the storage apparatus202are examples of a CPU and a memory. These are examples of surface-mount-type electrical components mounted on a first board. A first connector mounted on the first board is a surface-mount-type connector. Therefore, the CPU and the memory are not touched by the hands of a person who performs the mounting operation, which makes it unlikely for the CPU and the memory to suffer electrostatic breakdown. As shown inFIG. 2, the power supply circuit211xis one example of a power supply circuit mounted on a second board. As shown inFIG. 3Aand the like, the power supply circuit211xsupplies power to surface-mount-type electrical components mounted on the first board via a second connector, a second harness unit, a fourth connector, wiring patterns, a third connector, a first harness unit, and the first connector. Because the power supply circuit211xsupplies a high current to the control board200, the plurality of intervening connectors must be able to allow the high current to flow through themselves. However, a rated current value of a surface-mount-type connector is smaller than a rated current value of a DIP-type connector. In view of this, by providing an intervening third board such as the IF conversion board300, a surface-mount-type connector can be used on the first board such as the control board200. As shown inFIGS. 3B to 3Dand the like, the number of a plurality of connector pins provided in the third connector may be m. The number of a plurality of connector pins provided in the fourth connector may be n (n<m). As shown inFIG. 3D, the wiring patterns305are wired so as to absorb the difference between the number of the plurality of connector pins provided in the third connector and the number of the plurality of connector pins provided in the fourth connector. As shown inFIG. 3D, the wiring patterns305include wires that branch out from one into k so as to connect k connector pins provided in the third connector (k>1) and one connector pin provided in the fourth connector. The amount of current (rated current value) that can flow through one connector pin among the k connector pins provided in the third connector may be 1/k of the amount of current (rated current value) that can flow through one connector pin provided in the fourth connector. The interface difference between the plurality of connectors may be absorbed in this manner. The third connector may be a DIP-type connector, or may be a surface-mount-type connector. Furthermore, only the third connector may be a surface-mount-type electrical component mounted on the third board. Furthermore, surface-mount-type electrical components mounted on the third board may be electrical components that are not likely to undergo dielectric breakdown. Surface-mount-type electrical components mounted on the third board may be passive elements. Note that surface-mount-type electrical components mounted on the first board include active elements. Active elements are likely to undergo dielectric breakdown. In the present embodiment, however, as a surface-mount-type connector is mounted on the first substrate, active elements are not touched by the hands of a person who performs the mounting operation. Thus, active elements are not likely to undergo dielectric breakdown.

As shown inFIG. 1, the photosensitive drums1are one example of an image carrier. The charging devices2are one example of a charging unit that charges an image forming surface of the image carrier using a charging voltage. The exposure devices3are one example of a light irradiation unit that forms an electrostatic latent image by irradiating the image forming surface with light. The developing devices4are one example of a developing unit that forms a toner image by applying toner to the electrostatic latent image using a developing voltage and developing the electrostatic latent image. The primary transfer device7and the secondary transfer device27are one example of a transfer unit that transfers the toner image to a sheet using a transfer voltage. The power supply circuit211xand the power supply circuits211ato211dare one example of a power supply circuit that generates at least one of the charging voltage, developing voltage, and transfer voltage. Note that the main power supply board230is one example of a power supply board that supplies power to the power supply circuits211ato211d.

In the foregoing embodiment, the main power supply board230is realized by one board. However, an AC driver board240that applies the alternating-current voltage supplied from the commercial alternating-current power supply to the heater41, and the main power supply board230that converts the alternating-current voltage supplied from the commercial alternating-current power supply into predetermined voltages, may be different boards.FIG. 8shows an exemplary modification of a circuit diagram of the image forming apparatus100including the AC driver board240. In this configuration also, the IF conversion board300is electrically connected between the main power supply board230and the control board200. This can suppress the flow of the high current to the connector302eof the control board200, even when the direct-current voltage of 24 V from the main power supply board230is supplied to the control board200. Also, only surface-mount devices can be used as electronic components soldered to the control board200.

In the exemplary modification shown inFIG. 8also, the first connector is soldered to the main power supply board230, and the second connector is soldered to the control board200. The IF conversion board300functions as a relay board. That is, the third connector, which is connected to the first connector of the main power supply board230via the first power lines, is soldered to the IF conversion board300. The fourth connector, which is connected to the second connector of the control board200via the second power lines, is soldered to the IF conversion board300. The surface (solder side) to which the first connector is soldered on the main power supply board230is opposite to the surface (components side) to which the first connector is attached and mounted on the main power supply board230. The surface (solder side) to which the second connector is soldered on the control board200is the surface (components side) to which the second connector is attached and mounted on the control board200. Here, only surface-mount devices are used as electronic components soldered to the control board, including the second connector. The number of pins in the second connector is larger than the number of pins in the first connector. The number of pins in the fourth connector is larger than the number of pins in the third connector. The predetermined direct-current voltages generated by the main power supply board230are supplied to the control board200by way of the relay board.

Electronic components soldered to the main power supply board230, including the first connector, do not include a surface-mount device. Electronic components soldered to the IF conversion board300, including the third connector and the fourth connector, do not include a surface-mount device. A current that flows through one pin in the first connector may be higher than 6 [A].

An electronic component (e.g., the interlock circuit501) for blocking the alternating-current voltage applied from the commercial alternating-current power supply to the heater41may be attached and mounted to the IF conversion board300. An electronic component (e.g., the interlock circuit501) for blocking power supply to the light sources310may be attached and mounted to the IF conversion board300. An electronic component (e.g., the interlock circuit501) for blocking power supply to the developing devices may be attached and mounted to the IF conversion board300.

Other Embodiments

This application claims the benefit of Japanese Patent Application No. 2018-099797, filed May 24, 2018 which is hereby incorporated by reference herein in its entirety.