Image forming apparatus having fan to suck air into the image forming apparatus

An image forming apparatus includes an image forming unit, a stacking unit, a frame, an outer surface member, an electronic circuit board, and a fan. The image forming unit, supported by the frame, forms an image on a recording material that then is stacked on the stacking unit. The outer surface member is disposed on an outer side relative to the frame and includes a through-hole. The electronic circuit board is disposed between the frame and the outer surface member. The fan sucks air from an outside to an inside of the image forming apparatus via the through-hole. The electronic circuit board is disposed on an upstream side of the fan in a direction of an air flow generated into air by the fan. The stacking unit is disposed on a downstream side of the fan in the direction of the air flow generated by the fan.

BACKGROUND

Field

The present disclosure relates to an image forming apparatus that forms and fixes an image on a recording material.

Description of the Related Art

An image forming apparatus such as a laser beam printer includes many fans, most of which are used for the purpose of cooling.

Examples of targets that require cooling include an electronic circuit board that converts alternating-current (AC) power from an external outlet into a current and voltage to be used by an image forming apparatus, an electronic component such as a motor that generates heat, heat generated by frictions in a drive unit, a toner fixing unit, and a recording material that has passed through the toner fixing unit.

For example, Japanese Patent Application Laid-Open No. 2017-44817 discloses a configuration for sending air to an electronic circuit board by using a fan to cool the electronic circuit board.

In conventional configurations where a fan is disposed for each individual purpose, a plurality of fans is required to send air to the inside of an image forming apparatus, resulting in an increase in size of the image forming apparatus.

SUMMARY

According to an aspect of the present disclosure, an image forming apparatus includes an image forming unit configured to form an image on a recording material, a stacking unit on which the recording material having the image formed thereon by the image forming unit is stacked, a frame configured to support the image forming unit, an outer surface member disposed on an outer side relative to the frame and having a through-hole, an electronic circuit board disposed between the frame and the outer surface member, and a fan configured to suck air from an outside of the image forming apparatus to an inside of the image forming apparatus via the through-hole, wherein the electronic circuit board is disposed on an upstream side of the fan in a direction of an air flow generated into air by the fan, and wherein the stacking unit is disposed on a downstream side of the fan in the direction of the air flow generated by the fan.

DESCRIPTION OF THE EMBODIMENTS

A first exemplary embodiment of the present disclosure will be described below.

FIG.1is a schematic view illustrating a color laser beam printer as an example of an image forming apparatus100. In a configuration of the image forming apparatus100, by rotating a cartridge door100ato be opened and pulling a cartridge support member100bthat supports a plurality of cartridges105out from the inside of the image forming apparatus100, the cartridges105can be replaced. In the following description, a face of the image forming apparatus100where the cartridge door100ais disposed is referred to as the front face, a face opposite the front face is referred to as the rear face, and a direction in which the front and rear faces oppose each other is referred to as an anteroposterior direction. When the image forming apparatus100is viewed from a direction facing the front face, a side face on the right-hand side is referred to as the right face, and a side face on the left-hand side is referred to as the left face.

The image forming apparatus100includes an image forming unit101, a recording material supply unit102, and a fixing unit103. The image forming unit101includes at least the cartridges105. In the present exemplary embodiment, the image forming unit101includes a laser scanner104, the cartridges105, an intermediate transfer belt106, and a secondary transfer roller107. The laser scanner104is configured to irradiate each of the cartridges105with a laser beam.

The cartridge105includes a toner container108that stores a toner, a photosensitive drum109irradiated with a laser beam from the laser scanner104, a charging roller110that charges the photosensitive drum109, and a developing roller111that applies toner to the photosensitive drum109. In the present exemplary embodiment, the image forming unit101includes four cartridges105. Each of the four cartridges105stores a yellow, a magenta, a cyan, or a black toner and is disposed perpendicularly below the laser scanner104.

The intermediate transfer belt106is disposed perpendicularly below the four cartridges105. The intermediate transfer belt106is an endless belt. The intermediate transfer belt106is supported by a belt drive roller112, primary transfer rollers113, and a tension roller114that are disposed on the inner side of the intermediate transfer belt106. The intermediate transfer belt106is given tension by the tension roller114and is rotatable as drive is transmitted from the belt drive roller112. Four primary transfer rollers113are in contact with respective photosensitive drums109of the four cartridges105across the intermediate transfer belt106at a predetermined pressure. The secondary transfer roller107is disposed to face the belt drive roller112across the intermediate transfer belt106and is in contact with the intermediate transfer belt106at a predetermined pressure.

The recording material supply unit102includes a storage tray115, a supply roller116, a separation unit117, and a conveyance unit118. The storage tray115, which is a storage unit for storing recording materials P, is configured to be attachable to and detachable from the image forming apparatus100by being drawn out toward the front side. The storage tray115is provided with a lift plate119that moves up and down depending on the number of stacked recording materials P. The supply roller116is disposed at a position facing the storage tray115across the stacked recording materials P. The separation unit117is disposed in a conveyance guide120and on the downstream side of the supply roller116, and includes a conveyance roller121and a separation roller122. The conveyance roller121and the separation roller122are each provided with a rubber member on a surface thereof. The separation roller122having a built-in torque limiter is configured to generate predetermined load torque. The separation roller122is in contact with the conveyance roller121at a predetermined pressure. When the conveyance roller121is driven, the separation roller122is driven while generating predetermined load torque on the conveyance roller121. The conveyance unit118is disposed on the downstream side of the separation unit117and on the upstream side of a nip portion of the secondary transfer roller107. The conveyance unit118includes a registration roller pair123and a shutter member124. The shutter member124is configured to be rotatable with a predetermined load and is disposed on the upstream side of the nip portion of the registration roller pair123. The fixing unit103includes a fixing roller125, a pressure heat member126, and a discharge roller pair127. The fixing roller125is disposed on the downstream side of the secondary transfer roller107and is in contact with the pressure heat member126at a predetermined pressure. The pressure heat member126includes a heating member128. The discharge roller pair127is disposed on the downstream side of the fixing roller125.

When a print signal is input, the image forming apparatus100starts a printing operation. The laser scanner104irradiates surfaces of the four photosensitive drums109with a laser beam based on image information to be printed. The surface of each photosensitive drum109is charged by the charging roller110, and an electrostatic latent image is formed on the surface of the photosensitive drum109with the radiated laser beam. The electrostatic latent image on the surface of the photosensitive drum109is supplied with toner by the developing roller111and then developed to generate a toner image. The toner image generated on the surface of the photosensitive drum109is transferred onto the intermediate transfer belt106by a voltage applied to a corresponding primary transfer roller113. While toner images are being transferred from the cartridges105to the intermediate transfer belt106, the intermediate transfer belt106is driven by the belt drive roller112and conveys the toner images to the nip portion of the secondary transfer roller107. In parallel with the above-described operation, the supply roller116in the recording material supply unit102conveys a recording material P stacked on the storage tray115to the separation unit117. If a plurality of recording materials P is conveyed to the separation unit117, one recording material P is separated by the load torque of the separation roller122at the nip portion and then conveyed to the conveyance unit118. In the conveyance unit118, a leading edge of the recording material P comes in contact with the shutter member124. Since the shutter member124is provided with a predetermined rotational load, the recording material P pushes the shutter member124aside and enters the nip portion of the registration roller pair123while forming a loop by a conveyance force of the separation unit117. If the recording material P skews, the leading edge of the recording material P obliquely in contact therewith is made straight with respect to the shutter member124by the loop formed before being held by the registration roller pair123, thus the skew is corrected. The recording material P that has passed the registration roller pair123is conveyed to the nip portion formed between the secondary transfer roller107and the belt drive roller112at a controlled conveyance speed. At the nip portion, the toner images conveyed by the intermediate transfer belt106are transferred onto the recording material P. The recording material P with the toner images transferred thereon is conveyed to a contact portion between the fixing roller125and the pressure heat member126. When the recording material P is pressed and heated, toner melts and is fixed on the surface. Then, the recording material P is discharged to the outside of the apparatus by the discharge roller pair127and then sequentially stacked on a discharge tray129disposed on the top surface of the apparatus.

FIG.2is a perspective view illustrating the image forming apparatus100. An outer surface member130is disposed on a side face (right side face) of the image forming apparatus100. The outer surface member130is provided with a handle, louvers137(137a1to137a4), and an inlet opening130a. The handle is formed on the outer surface member130in the vicinity of the center of the image forming apparatus100in the anteroposterior direction, as an inwardly recessed portion of a portion continuous to the bottom surface of the image forming apparatus100. Although not illustrated, another handle is similarly disposed on another outer surface member130on the opposite side of the image forming apparatus100. By a user hooking his/her fingers into the handles on both sides of the image forming apparatus100, the image forming apparatus100can be lifted up. The handles are positioned in consideration of the center of gravity of the image forming apparatus100so that the apparatus orientation remains stable when lifted up. The plurality of louvers137are provided on both sides of the handle in the anteroposterior direction of the image forming apparatus100. More specifically, the outer surface member130has a plurality of through-holes disposed via the louvers137. Air can be drawn into the apparatus via the plurality of through-holes. The inlet opening130a, which enables a power cord to be plugged into the image forming apparatus100, is disposed on the rear face, which is adjacent to and orthogonal to the side faces on which the handles and the louvers137are disposed, of the outer surface members130. The inlet opening130ais formed so that an inlet138disposed in a power supply unit133(described below) is exposed on the inside. The image forming apparatus100is supplied with power when the power cord connected to a commercial power supply is plugged into the inlet138.

An internal structure and arrangement of components of the image forming apparatus100will be described below with reference toFIGS.3to7.FIG.3is a horizontal cross-sectional view illustrating the image forming apparatus100.FIG.4is a front right perspective view illustrating the image forming apparatus100when the outer surface members130on the right, left, and rear faces are removed.FIG.5is a vertical cross-sectional view illustrating the vicinity of a power circuit board133ataken along the line A-A inFIG.3.FIG.6is a vertical cross-sectional view illustrating the vicinity of a blower apparatus141taken along the line B-B inFIG.3.FIG.7is an enlarged view illustrating the vicinity of a sheet ejection opening when the outer surface members130on the right and left side faces are removed.

An image formation unit136including the image forming unit101, the recording material supply unit102, and the fixing unit103is disposed at the center of the image forming apparatus100. In the image forming apparatus100, a framework132having a right framework132R and a left framework132L is disposed to sandwich the image formation unit136from the right and left sides to support the image formation unit136.

The power supply unit133and a drive unit134including motors and gears for driving the rollers of the image formation unit136are disposed outside the right framework132R. More specifically, the outer surface member130and the right framework132R are disposed to face each other, and the drive unit134is attached to the right framework132R between the outer surface member130and the right framework132R. On a right outer surface member130R, the louvers137a1and137a4are arranged along the two short sides extending in the vertical direction of the power circuit board133aand the louvers137a2and137a3are arranged along the lower long side extending in the horizontal direction to surround the power supply unit133. Thus, outside air can enter an area of the power supply unit133from the outside of the image forming apparatus100via the through-holes between the louvers137.

The power supply unit133includes the power circuit board133aand a board support member133bas electronic circuit boards. The power circuit board133ais a low-voltage power circuit board having a substantially rectangular shape. The power circuit board133ais mounted with many electronic elements including a large electronic element that generates heat mounted on the front surface and a short electronic element mounted on the back surface.

The power circuit board133ais a low-voltage power circuit board that receives AC power from an external commercial power supply and converts the AC power into direct-current (DC) power. The power circuit board133aincludes a low-voltage power transformer, a heat sink, and an electrolytic capacitor as large-sized electronic components.

The board support member133bis attached to the back surface of the power circuit board133a. The power circuit board133ais fixed to the right framework132R via the board support member133bso that the short sides of the power circuit board133aare substantially vertical, the long sides thereof are substantially horizontal, and the back surface thereof faces outward of the image forming apparatus100.

The drive unit134is provided with a motor as a driving source and a drive transmission member (not illustrated) including a gear, to enable transmission of driving force of the motor to the image forming unit101.

On the other hand, a control circuit board135that controls operations is disposed on the outside of the left framework132L. More specifically, a left outer surface member130L and the left framework132L are disposed to face each other, and the control circuit board135is attached to the left framework132L between the left outer surface member130L and the left framework132L.

The outside of the framework132, which includes the right framework132R and the left framework132L, is covered by the outer surface members130in this way. Such a structure reduces leakage of operating sound to the outside of the image forming apparatus100, and prevents occurrence of an unintended air flow from anywhere other than the louvers137a1to137a4disposed on the outer surface members130to the inside of the image forming apparatus100.

The image forming apparatus100includes a partition member139, as illustrated inFIGS.4to6. By combining the partition member139with the right outer surface member130R, a first duct140is formed between the right outer surface member130R and the right framework132R. In other words, the power supply unit133is surrounded by the right framework132R, the partition member139, and the right outer surface member130R to be separated from other components inside and outside the image forming apparatus100.

One opening of the first duct140is connected to a space formed by the right framework132R, the partition member139, and the right outer surface member130R, which surrounds the power supply unit133. The other opening of the first duct140is connected to a suction port141aof the blower apparatus (blower fan)141disposed vertically above the power supply unit133(FIGS.4to7). Thus, the first duct140serves as a sealed air duct that connects between the space surrounding the power supply unit133and the blower fan141.

A type of centrifugal fan is used as the blower fan141according to the present exemplary embodiment. The blower fan141is disposed so that rotary vanes is substantially horizontal. The suction port141ais disposed in a direction of the first duct140, i.e., vertically downward. More specifically, the blower fan141and the power circuit board133aare disposed so that an image of the blower fan141projected from the vertical direction to a horizontal plane overlaps with an image of the power circuit board133aprojected from the vertical direction to the horizontal plane. An exhaust port141bof the blower fan141is connected to cooling air outlet ports143from which air is blown toward an image forming surface of the recording material P that has passed through the discharge roller pair127and is just before being stacked on the discharge tray129, as illustrated inFIG.7. The present exemplary embodiment include a second duct142that constitutes a sealed air duct. One end of the second duct142is connected to the exhaust port141bof the blower fan141, and the other end thereof constitutes the cooling air outlet ports143.

(Cooling Inside of Image Forming Apparatus100)

In the image forming apparatus100, the power circuit board133ahas a function of converting a commercial power supply into a predetermined voltage and current to operate the image forming apparatus100. Since the power circuit board133ais a heat source that generates heat at the time of conversion, the power circuit board133aneeds to be cooled.

Meanwhile, since the fixing unit103heats a toner image to fix it to the recording material P, the recording material P is hot immediately after image fixing. The recording material P may possibly be discharged to and stacked on the discharge tray129before the fixed toner cools and settles, resulting in stuck recording material P depending on the paper type and image condition. To prevent this, the recording material P immediately after discharge needs to be cooled with blown air.

In the present exemplary embodiment, the power circuit board133ais cooled by using an air current generated on the upstream side of the blower fan141, and the recording material P immediately after the image fixing is cooled by using an air current generated on the downstream side of the blower fan141. A cooling operation for cooling the power circuit board133aand the recording material P immediately after the image fixing will be described in detail below.

When power of the image forming apparatus100is turned on and the blower fan141is driven, a suction side on the upstream side of the suction port141aprovides a negative pressure. Thus, outside air flows into the vicinity of the power supply unit133from the louvers137disposed on the outer surface member130around the power supply unit133through the first duct140connected to the suction port141a, as indicated by an arrow a (FIG.6). The outside air flows along the front surface side of the power circuit board133aas indicated by an arrow b to cool the electronic elements on the power circuit board133athat is a first heat source component. As illustrated inFIG.5, the louvers137a1to137a4are disposed in the vicinity of three sides other than the upper long side of the power circuit board133a, and the first duct140is disposed in the vicinity of the upper long side. Thus, air currents (indicated by arrows b1, b2, b3, and b4) that are sucked from the louvers137a1to137a4, respectively, flow short distances in average, making it possible to efficiently cool the entire power circuit board133awith the air currents.

If a temperature rise of the electronic elements on the power circuit board133ais uneven, it is desirable to decrease an opening area of the louver137corresponding to a portion having a small temperature rise and increase an opening area of the louver137corresponding to a portion having a large temperature rise. This enables adjusting the amount of outside air to be taken in via each of the louvers137to achieve a balance of cooling.

The air that has cooled the power circuit board133apasses through the first duct140, as indicated by the arrow c inFIGS.5and6, and then is sucked by the blower fan141. The sucked air is accelerated by the blower fan141and then sent to the second duct142connected to the exhaust side, which is on the downstream side of the exhaust port141b. One end of the second duct142is connected to the exhaust port141bof the blower fan141, and the other end thereof constitutes the cooling air outlet ports143from which air is exhausted to the outside of the image forming apparatus100. At this time, outside the image forming apparatus100, the air exhausted from the cooling air outlet ports143is blown onto the image forming surface of the hot recording material P, which has been subjected to the image fixing and discharged from the discharge roller pair127, as indicated by an arrow d, thus cooling the recording material P.

The air blown onto the recording material P from the cooling air outlet ports143of the second duct142is the air that has cooled the power circuit board133a, and thus is hotter than outside air. However, the temperature of the air is sufficiently lower than the temperature of the recording material P immediately after being heated by the fixing unit103and the solidification temperature of toner melted by the fixing unit103. Thus, the air cools the recording material P to prevent sticking of the recording materials P stacked on the discharge tray129.

In this way, disposing the cooling target on each of the suction side on the upstream side of the blower fan141and the exhaust side on the downstream side thereof enables efficiently cooling a plurality of cooling targets by using one fan. This makes it possible to save space and cost without disposing a fan for each of the plurality of cooling targets or disposing a larger and more powerful fan while disposing a duct for branching an air flow. In addition, use of only one fan enables reducing a fan noise. By disposing the cooling targets before and after the fan, a distance from suction portions (the plurality of through-holes disposed via the louvers137) disposed on the outer surface members130of the image forming apparatus100to the fan to be a noise source can be ensured. This also enables reducing the leakage of the operating sound to the outside of the image forming apparatus100and reducing a noise of the image forming apparatus100.

While, in the first exemplary embodiment, one cooling target is disposed on each of the upstream and downstream sides of the blower apparatus141, the cooling target to be disposed on each of the upstream and downstream sides is not limited to one. Further, the blower apparatus141may be configured to send air not only in the vicinity of the cooling targets but also in the vicinity of blowing targets for other applications.

An example of other applications is ventilation. In the electrophotographic process, the photosensitive drum109is charged to form an electrophotographic image. In the process, ozone is generated by corona discharge, and a discharge product such as nitrogen oxide (NOx) is generated in the image forming apparatus100and may adhere to the photosensitive drum109. If the discharge product adheres to the photosensitive drum109, moisture is likely to adhere thereto. As a result, the moisture on the photosensitive drum109causes a charge flow on the surface of the photosensitive drum109, resulting in an image defect.

Thus, in a second exemplary embodiment, blowing targets that are cooling targets are disposed on the upstream and downstream sides of the blower apparatus141as in the first exemplary embodiment, and the photosensitive drum109is disposed as another blowing target on the downstream side of the blower apparatus141to prevent adhesion of a discharge product and occurrence of an image defect. A configuration of the present exemplary embodiment will be described in detail below.

The second exemplary embodiment will be described below with reference toFIGS.8and9.FIG.8is a top view illustrating the image forming apparatus100according to the second exemplary embodiment when the top outer surface member and the laser scanner are removed.FIG.9is an enlarged view illustrating the vicinity of a third duct added in the second exemplary embodiment. In the image forming apparatus100according to the second exemplary embodiment, the power supply unit133is disposed, and the first duct140and the blower fan141are disposed vertically above the power supply unit133, as in the first exemplary embodiment. The exhaust port141bof the blower fan141is connected with a second duct142that is different from the one according to the first exemplary embodiment. Unlike the second duct142according to the first exemplary embodiment, the second duct142is provided with a branch port144in addition to the cooling air outlet ports143. The branch port144is connected with a third duct145.

One end of the third duct145is connected to the branch port144, and the other end thereof has a branching shape that constitutes four ventilation air outlet ports146. The ventilation air outlet ports146are oriented toward the respective photosensitive drums109of the cartridges105for four colors, and air is blown to the photosensitive drums109as indicated by arrows e.

The left framework132L is provided with holes (not illustrated) in the vicinity of the photosensitive drums109. The left outer surface member130L disposed outside the left framework132L is provided with louvers (not illustrated).

(Cooling Inside of Image Forming Apparatus100)

The configurations and effects of the power circuit board133a, the blower fan141for cooling the recording material P after the image fixing, the first duct140, and the second duct142are similar to those according to the first exemplary embodiment.

When power of the image forming apparatus100is turned on and the blower fan141is driven, the suction side on the upstream side of the suction port141aprovides a negative pressure. Thus, outside air flows into the vicinity of the power supply unit133from the louvers137disposed on the outer surface member130around the power supply unit133through the first duct140connected to the suction port141a, as indicated by the arrow a (FIG.6). The outside air flows along the front surface side of the power circuit board133aas indicated by the arrow b to cool the electronic elements on the power circuit board133athat is a first heat source component.

The air that has cooled the power circuit board133apasses through the first duct140, as indicated by the arrow c inFIGS.5and6, and then is sucked by the blower fan141. The sucked air is accelerated by the blower fan141and then sent to the second duct142connected to the exhaust side, which is on the downstream side of the exhaust port141b. One end of the second duct142is connected to the exhaust port141bof the blower fan141, and the other end thereof constitutes the cooling air outlet ports143from which air is exhausted to the outside of the image forming apparatus100. At this time, outside the image forming apparatus100, the air exhausted from the cooling air outlet ports143is blown onto the image forming surface of the hot recording material P, which has been subjected to the image fixing and discharged from the discharge roller pair127, as indicated by an arrow d, thus cooling the recording material P.

In the present exemplary embodiment, on the other hand, the second duct142has the branch port144in addition to the cooling air outlet ports143, and the air sucked by the blower fan141is sent to the third duct145connected to the branch port144. One end of the third duct145is connected to the branch port144, and the other end thereof constitutes the four ventilation air outlet ports146. Air is blown to the photosensitive drums109of the cartridges105for four colors. This enables the image forming apparatus100to prevent the adhesion of a discharge product to the photosensitive drums109and the occurrence of an image defect.

Since the purpose of sending air from the third duct145is ventilation, an effect of preventing the occurrence of an image defect can be obtained without issue, even with warmed air after the power circuit board133ais cooled.

Then, the air blown to the photosensitive drums109passes through the holes provided in the left framework132L, passes between the left outer surface member130L and the left framework132L, and is discharged from the through-holes between the louvers disposed on the left outer surface member130L to the outside of the image forming apparatus100.

In this way, the cooling target is disposed on each of the suction side on the upstream side of the blower fan141and the exhaust side on the downstream side thereof, and the blowing target is disposed on the exhaust side on the downstream side of the blower fan141. This enables efficiently utilizing the air current that can be generated by one fan. More specifically, this makes it possible to save space and cost without disposing a fan for each of the plurality of cooling and blowing targets or disposing a larger and more powerful fan. In addition, use of only one fan enables reducing a fan noise. By disposing the cooling and blowing targets before and after the fan, a distance from the louvers137that cover the openings of the image forming apparatus100to the fan as a noise source can be ensured. This also enables reducing the leakage of the operating sound to the outside of the image forming apparatus100and reducing a noise of the image forming apparatus100.

While, in the first and the second exemplary embodiments, the blower fan that is a type of centrifugal fan is used as the blower apparatus141, the blower apparatus141is not limited thereto but may be an axial fan or a rotary fan.

In general, an axial fan can be introduced at a lower cost than a blower fan. However, since an axial fan provides a lower static pressure than a blower fan, a pressure loss of the air duct needs to be reduced, i.e., the air duct needs to be wide and short.

This application claims the benefit of Japanese Patent Application No. 2020-180573, filed Oct. 28, 2020, which is hereby incorporated by reference herein in its entirety.