Image forming apparatus

Abstract

To effectively prevent a reduction in the temperature of a fixing unit, and further prevent an increase in the temperature of a drum unit.SOLUTION: Cooling air is caused to flow in a space SP between a drum unit 120 and a fixing unit 13 on a side face support plate of a body frame of an image forming apparatus, thereby cooling the drum unit 120. The image forming apparatus comprises a movement mechanism that moves the fixing unit 13 in an upper direction of the vertical direction, in conjunction with a switching operation between a pressurized state and a released state of a fixing nip part N2 performed by a fixing pressure release unit 14, and thereby reduces a gap formed between the fixing unit 13 and a partition plate (body frame) for partitioning the fixing unit 13 and the drum unit 120 from each other, which prevents the cooling air from flowing to the fixing unit 13.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus, and more particularly to a technique for suppressing a temperature drop in a fixing unit. [Background technology]

[0002] A typical image forming apparatus includes a photosensitive drum as an image carrier, a charging device that charges the photosensitive drum, an exposure device that irradiates the charged surface of the photosensitive drum with laser light based on an original document to form a latent image of the original document on the surface of the photosensitive drum, a developing device that visualizes the latent image with toner, a transfer roller that transfers the toner image formed by the visualized image onto recording paper, a fixing device that fixes the transferred toner image to the recording paper, and a cleaning device that removes toner remaining on the surface of the photosensitive drum.

[0003] In recent years, image forming devices have become increasingly compact, and the gaps between units within the device have become narrower, so that drum units having photosensitive drums are sometimes placed close to the fixing units that make up the fixing device.However, if the fixing heat from the fixing device is transmitted to the drum unit, it may have an adverse effect on the drum unit.

[0004] As an invention that solves such problems, for example, Patent Document 1 below discloses an invention in which an insulating member is provided between the fixing unit and the drum unit (process cartridge), thereby insulating the fixing unit from the drum unit and preventing heat conduction from the fixing unit to the drum unit. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-113467 Summary of the Invention [Problem to be solved by the invention]

[0006] However, if a heat insulating member such as that described in Patent Document 1 is disposed between the fixing unit and the drum unit, it becomes difficult to make the device compact.

[0007] Another possible solution to thermally insulating the drum unit from the fixing unit is to flow cooling air between the two units. However, this could lead to a new problem in that the fixing belt and other components inside the fixing unit are cooled by the cooling air, reducing the energy-saving performance of the fixing unit.

[0008] If a partition plate is provided on the main frame of the image forming apparatus to separate the drum unit and the fixing unit, the cooling air passing between the drum unit and the fixing unit can be prevented from flowing toward the fixing unit, but the cooling air flows toward the fixing unit through the gap formed between the fixing unit and the partition plate, cooling the fixing unit. Note that this gap is necessary for the convenience of assembling the apparatus.

[0009] The present invention has been made in view of the above circumstances, and has as its object to effectively suppress a drop in temperature of the fixing unit and also to suppress a rise in temperature of the drum unit. [Means for solving the problem]

[0010] According to one aspect of the present invention, there is provided an image forming apparatus including: a fixing unit having a drum unit with an image carrier that carries a toner image, a fixing member, and a pressure member that forms a fixing nip portion together with the fixing member, and that fixes the toner image formed on a recording medium at the fixing nip portion; a fixing pressure release unit that is disposed below the fixing unit and that switches the states of the fixing member and the pressure member between a pressure state in which pressure is applied to the fixing nip portion and a release state in which pressure applied to the fixing nip portion is released; a main body frame that has side support plates extending vertically and a partition plate that is disposed above the fixing unit and that separates the drum unit from the fixing unit; and a cooling air generating unit that generates a cooling air and a cooling duct provided on the outside of the side support plate through which the air blown by the cooling fan flows. The side support plate is formed with an air outlet for blowing the air in the cooling duct into the space between the drum unit and the fixing unit. The fixing pressure release unit has a rotating gear that engages with a nip pressure adjustment gear on the fixing unit side at its lower part. The fixing unit performs a switching operation to switch between the pressurized state and the released state by a rotational driving force supplied to rotate the nip pressure adjustment gear from the rotating gear, and is provided with a moving mechanism that moves the fixing unit vertically upward in conjunction with the switching operation. [Effects of the Invention]

[0011] According to the present invention, the gap formed between the fixing unit and the partition plate can be narrowed, thereby reducing the amount of air, such as cooling air, that enters the fixing unit from outside. Furthermore, since the gap formed between the fixing unit and the partition plate can be narrowed to reduce the amount of air that enters the fixing unit from outside, it is also possible to flow cooling air into the space between the drum units and suppress a temperature rise in the drum unit. Therefore, according to the present invention, it is possible to effectively suppress a temperature drop in the fixing unit and further suppress a temperature rise in the drum unit. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a perspective view showing the appearance of an image forming apparatus according to an embodiment of the present invention; [Figure 2] 1 is a cross-sectional side view schematically showing an image forming unit and its surroundings in an image forming apparatus; [Figure 3] FIG. 2 is a side view schematically showing the fixing unit and its surroundings. [Figure 4] FIG. 2A is a perspective view showing a fixing unit, and FIG. 2B is a perspective view showing a fixing pressure releasing unit. [Figure 5] FIG. 2A is a perspective view showing the structure of a main body frame of an image forming apparatus, and FIG. 2B is a front view showing the structure of the main body frame. [Figure 6] FIG. 1A is a side view showing the structure of a side support plate of the main body frame, and FIG. 1B is a view showing the state in which the cooling duct has been removed from the side support plate. [Figure 7] FIG. 1A is a side view showing a cooling duct, and FIG. 1B is a perspective view showing the inside of the cooling duct. [Figure 8] 10 is a perspective view of the air outlet and its surroundings as viewed from the front right with the drum unit removed from the main body frame. FIG. [Figure 9] 9(A) and 9(B) are enlarged views of a portion of the view shown in FIG. 8. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0013] An image forming apparatus according to one embodiment of the present invention will be described below with reference to the drawings. Fig. 1 is a perspective view showing the appearance of an image forming apparatus according to one embodiment of the present invention. Fig. 2 is a cross-sectional side view showing a schematic view of an image forming unit and its surroundings in an image forming apparatus according to one embodiment of the present invention. Image forming apparatus 1 is, for example, a printer.

[0014] Image forming apparatus 1 houses image forming unit 12 inside main body frame 2 (see FIG. 5(A)). Main body frame 2 has openings on the front, back, and top, which are covered by front cover 3, top cover 4, and back cover 6. The left and right sides are also covered by side covers 6. Front cover 3 and top cover 4 are rotatably supported by main body frame 2 and can be opened and closed to a position that covers the opening of main body frame 2 and a position that opens it. Toner container 171, developing device 124, and drum unit 120 can be attached and detached through the openings in main body frame 2 when front cover 3 and top cover 4 are open.

[0015] The image forming unit 12 forms a toner image on a recording medium, namely, recording paper, and includes a photosensitive drum 121, a charging device 122, an exposure device 123, a developing device 124, a transfer roller 126, a cleaning device 60, and a toner container 171. The photosensitive drum 121, the charging device 122, and the cleaning device 60 are unitized to form a drum unit 120.

[0016] Photoconductor drum 121 is an image carrier that carries toner, is rotatable about a rotation axis, and carries a toner image on its surface. Charging device 122 charges the surface of photoconductor drum 121. Exposure device 123 forms a latent image on the surface of photoconductor drum 121 by irradiating it with laser light L based on image data transmitted from an external device (for example, a personal computer).

[0017] The developing device 124 has a developing roller 1241, and visualizes with toner the latent image formed on the surface of the photosensitive drum 121. A transfer nip N1 is formed between the transfer roller 126 and the photosensitive drum 121, and the toner image is transferred onto the recording paper.

[0018] The cleaning device 60 includes a cleaning roller 61 and a cleaning blade 62. The cleaning roller 61 and the cleaning blade 62 come into contact with the surface of the photosensitive drum 121 to remove toner and other deposits remaining on the surface of the photosensitive drum 121, thereby cleaning the surface of the photosensitive drum 121.

[0019] The fixing unit 13 fixes the toner image to the recording paper by thermocompression, and includes a heating roller 131 incorporating a heater 132, and a pressure roller 133. The heating roller 131 and the pressure roller 133 form a pair, and when the recording paper is nipped and transported through a fixing nip N2 between the heating roller 131 and the pressure roller 133, the unfixed toner image melts with the heat of the heater 132 and is fixed to the recording paper by the pressure of the heating roller 131 and the pressure roller 133. The heating roller 131 and the pressure roller 133 are examples of the fixing member and the pressure member, respectively, in the claims.

[0020] 3 is a side view schematically showing the fixing unit 13 and its surroundings. A space SP is formed between the drum unit 120 and the fixing unit 13.

[0021] The fixing pressure release unit 14 is provided below the fixing unit 13, and switches the state of the fixing nip portion N2 by switching the states of the heating roller 131 and the pressure roller 133 between a pressurized state in which pressure is applied to the fixing nip portion N2 (a state in which the pressure roller 133 presses the heating roller 131) and a released state in which the pressure applied to the fixing nip portion N2 is released (a state in which the pressure roller 133 is released from pushing up against the heating roller 131). The fixing pressure release unit 14 includes a gear train consisting of a first gear 141 and a second gear (an example of a rotary gear) 142, etc., and a drive motor 143 that can rotate forward and backward, and transmits driving force from the drive motor 143 to the fixing unit 13 via the gear train.

[0022] The fixing unit 13 includes a heating roller 131, a pressure roller 133, a third gear (an example of a nip pressure adjusting gear) 134, and a guide member 135. The state of the fixing nip N2 is switched between a pressurized state and a released state by, for example, applying a driving force from a drive motor 143 of the fixing pressure release unit 14 to an eccentric cam (not shown) provided in the fixing unit 13 via a first gear 141, a second gear 142, a third gear 134, and the like. The pressure roller 133 is pressed against the heating roller 131 by a biasing means (not shown), thereby placing the fixing nip N2 in a pressurized state. Rotating the eccentric cam forward or backward by a predetermined angle switches the state between a released state in which the pressure roller 133 is separated from the heating roller 131 and a pressurized state in which the pressure roller 133 is pressed against the heating roller 131.

[0023] When the eccentric cam is driven to rotate from the pressurized state to the released state, a driving force acts between the third gear 134 and the second gear 142 to rotate the eccentric cam. On the other hand, when the eccentric cam is driven to rotate from the released state to the pressurized state, a rotational moment acts on the eccentric cam by the biasing means, and a braking force acts between the third gear 134 and the second gear 142. A force acting upward is transmitted to the fixing unit 13 by the driving force or braking force between the third gear 134 and the second gear 142.

[0024] When the second gear 142 rotates clockwise in Fig. 3, the third gear 134, whose tooth surface meshes with that of the second gear 142, rotates counterclockwise in Fig. 3, and the driving force from the drive motor 143 is transmitted from the tooth surface of the second gear 142 to the tooth surface of the third gear 134. Conversely, when the second gear 142 rotates counterclockwise and the third gear 134 rotates clockwise, the third gear 134 presses against the tooth surface of the second gear 142, and a braking force is transmitted to the third gear 134. Arrow F in the figure represents a vector of the transmitted force from the tooth surface of the second gear 142 to the tooth surface of the third gear 134, which is associated with the driving force and braking force acting on the third gear 134. The direction indicated by arrow F indicates the vector direction of the transmitted force.

[0025] In the configuration of the fixing unit 13 and the fixing pressure releasing unit 14 shown in Fig. 3, the transmission force F is inclined upward to the right in Fig. 3 and has a rightward component and an upward component. Therefore, the transmission force F applies a force to the fixing unit 13 that moves the fixing unit 13 upward.

[0026] The guide member 135 extends in a direction perpendicular to the conveying direction of the recording medium (the depth direction of the paper in Figure 3), presses down on the top surface of the recording paper conveyed from the drum unit 120, and guides the recording medium to the entrance of the fixing nip portion N2.

[0027] The guide member 135 is rotatable about a rotation axis A extending in a direction perpendicular to the conveying direction of the recording medium, and is displaceable to a first position (the position shown in FIG. 3) where it guides the recording medium to the entrance of the fixing nip portion N2, or to a second position where it blocks the entrance of the fixing nip portion N2.

[0028] Guide member 135 rotates around rotation axis A by a link mechanism (not shown). For example, when drum unit 120 is attached to main body frame 5, a part of drum unit 120 acts on the link mechanism, causing guide member 135 to rotate around rotation axis A and move from the second position to the first position.

[0029] The rotation shaft A may be connected to a first gear 134, and the guide member 135 may be displaced to a first position when the fixing nip portion N2 is in a pressurized state, and displaced to a second position when the fixing nip portion N2 is in a released state. A control unit, such as a CPU, that controls the operation of the image forming apparatus 1 controls the drive source to displace the guide member 135 to the first position and the second position. The control unit controls the drive source to displace the guide member 135 to the first position when the fixing pressure release unit 14 pressurizes the fixing nip portion N2 of the fixing unit 13, and controls the drive source to displace the guide member 135 to the second position when the fixing pressure release unit 14 presses the fixing nip portion N2 of the fixing unit 13.

[0030] Fig. 4(A) is a perspective view showing the fixing unit 13, and Fig. 4(B) is a perspective view showing the fixing pressure releasing unit 14. The fixing unit 13 includes the above-mentioned guide member 135, a case 136 extending in the left-right direction, a pair of left and right covers 137L, 137R, a conveyance guide 138 for guiding the recording paper conveyed from the drum unit 120 to the fixing nip portion N2, and shielding members 139L, 139R (hereinafter simply referred to as "shielding member 139"). The shielding members 139L, 139R will be described in detail later.

[0031] Fig. 5(A) is a perspective view showing the structure of the main body frame of the image forming apparatus 1, and Fig. 5(B) is a front view showing the structure of the main body frame. The main body frame 2 has a pair of side support plates 21L and 21R extending vertically. The side support plate 21L is provided on the left side of the main body frame 2, and the side support plate 21R is provided on the right side of the main body frame 2. The drum unit 120 and the fixing unit 13 are installed in the space sandwiched between the side support plates 21L and 21R.

[0032] 6(A) is a side view showing the structure of side support plate 21L of main body frame 2. On the outside of side support plate 21L, there are provided cooling fan 22 that generates cooling air and cooling duct 23 through which the air blown by cooling fan 22 flows.

[0033] Fig. 6(B) is a diagram showing a state in which cooling duct 23 has been removed from side support plate 21L. Fig. 7(A) is a side view showing cooling duct 23, and Fig. 7(B) is a perspective view showing the inside of cooling duct 23. As shown in Fig. 6(B), side support plate 21L is formed with air outlet 24 for blowing air from inside cooling duct 23 into the space between drum unit 120 and fixing unit 13.

[0034] Fig. 8 is a perspective view of the air outlet 24 and its surrounding area, as viewed from the front right side, with the drum unit 120 removed from the main body frame 2. Figs. 9(A) and (B) are enlarged views of a portion of the view shown in Fig. 8, and in Fig. 9(B), the arrow indicates the direction in which the cooling air flows from the air outlet 24.

[0035] The cooling air from air outlet 24 flows through space SP (FIG. 3) formed between drum unit 120 and fixing unit 13. As shown in FIGS. 8 and 9, main body frame 2 has partition plate 25 arranged above fixing unit 13 to separate drum unit 120 from fixing unit 13. Shielding member 139 provided in fixing unit 13 shields an opening formed between the main body of fixing unit 13 and partition plate 25. Gap CL is a gap formed between shielding member 139 (fixing unit 13) and partition plate 25.

[0036] The image forming apparatus 1 includes a movement mechanism that moves the fixing unit 13 vertically upward in conjunction with the switching operation of the fixing nip portion N2 between a pressure state and a released state by the fixing pressure release unit 14. When the fixing unit 13 is moved upward by the movement mechanism in this manner, the shielding member 139 moves upward, and the gap CL formed between the fixing unit 13 and the partition plate 25 is closed by the shielding member 139, and the gap CL becomes narrower than when the fixing nip portion N2 is in the released state and the fixing unit 13 is not moving upward as described above.

[0037] That is, the fixing unit 13 performs a switching operation to switch between the pressure-applied state and the release state by the rotational driving force supplied from the second gear 142 to the third gear 134, and at this time, the above-mentioned moving mechanism is a configuration within the image forming apparatus 1 that moves the fixing unit 13 vertically upward in conjunction with the switching operation.

[0038] As described above, the fixing unit 13 receives a force that moves the fixing unit 13 upward from the second gear 142 via the third gear 134, based on the driving force of the drive motor 143 of the fixing pressure release unit 14. Therefore, the fixing unit 13 can be moved vertically by the upward moving force. In order to transmit the upward moving force, which is included in the transmission force F, to the fixing unit 13, the movement mechanism restricts the horizontal movement of the fixing unit 13 due to the force that moves the fixing unit 13 horizontally, which is included in the transmission force F.

[0039] In this embodiment, a convex portion 130 is provided on a side of the fixing unit 13 that is the horizontal side along which the fixing unit 13 moves due to a force included in the transmission force F that moves the fixing unit 13 in the horizontal direction. A regulating member 101 is provided inside the main body (main body frame 2) of the image forming apparatus 1, abutting against the convex portion 130 in the horizontal direction or with a gap d therebetween. The gap d is a predetermined distance that allows the fixing unit 13 to move horizontally. The regulating member 101 prevents the fixing unit 13 from moving horizontally when the force included in the transmission force F that moves the fixing unit 13 in the horizontal direction causes the fixing unit 13 to move horizontally. This allows only the force included in the transmission force F that moves the fixing unit 13 upward to act on the fixing unit 13, causing the fixing unit 13 to move upward. The convex portion 130 and the regulating member 101 constitute the movement mechanism.

[0040] Furthermore, when the fixing nip N2 of the fixing unit 13 is in a pressurized state due to the switching operation, the gap CL is blocked by the shielding member 139, and the guide member 135, which is displaced to the first position, forms a cooling duct that guides the cooling air blown out from the air outlet 24 toward the drum unit 120, with the outer wall surface of the drum unit 120 facing the fixing unit 13 and the outer wall surface of the fixing unit 13 facing the drum unit 120. In other words, when the gap CL is blocked by the shielding member 139, the guide member 135, which is displaced to the first position, moves to a position where the cooling duct can be formed. Note that, although the example described above employs a configuration in which the guide member 135 rotates about the rotation axis A to form the cooling duct, a separate member for forming the cooling duct may also be provided in the fixing unit 13.

[0041] According to the above embodiment, it is possible to narrow the gap CL formed between the fixing unit 13 and the partition plate 25, thereby reducing the amount of cooling air flowing toward the fixing unit 13. Furthermore, because the gap CL is blocked by the shielding member 139, it is possible for cooling air to flow into the space SP between the drum unit 120 and the fixing unit 13. This also makes it possible to suppress a temperature rise in the drum unit 120. Therefore, according to the above embodiment, it is possible to effectively suppress a temperature drop in the fixing unit 13 and further suppress a temperature rise in the drum unit 120.

[0042] In addition, the outer wall surface of the drum unit 120 facing the fixing unit 13, the outer wall surface of the fixing unit 13 facing the drum unit 120, and the guide member 135 provided on the fixing unit 13 all function as a cooling duct that guides cooling air to the drum unit 120, making it possible to more effectively cool the drum unit 120 with the cooling air from the cooling fan 22.

[0043] The present invention is not limited to the configuration of the above embodiment, and various modifications are possible. In addition, in the above embodiment, the configuration and processing shown in the above embodiment using Figures 1 to 9 are merely one embodiment of the present invention, and it is not intended that the present invention be limited to these configurations and processing. [Explanation of symbols]

[0044] 1. Image forming device 2 Main frame 13 Fuser unit 14 Fixing pressure release unit 21L side support plate 22 Cooling fan 23 Cooling duct 24 Air outlet 25 Divider 120 drum unit 131 heated roller 133 Pressure Roller 135 Guide member 139 Shielding material N2 fixing nip

Claims

1. a drum unit having an image carrier that carries a toner image; a fixing unit including a fixing member and a pressure member that forms a fixing nip portion with the fixing member, and that fixes a toner image formed on a recording medium at the fixing nip portion; a fixing pressure release unit disposed below the fixing unit, the fixing pressure release unit switching states of the fixing member and the pressure member between a pressure state in which pressure is applied to the fixing nip portion and a release state in which pressure applied to the fixing nip portion is released; a main body frame including a side support plate extending in a vertical direction and a partition plate disposed above the fixing unit for separating the drum unit from the fixing unit; a cooling fan that generates cooling air; a cooling duct provided on the outer side of the side support plate through which air blown by the cooling fan flows, an air outlet for blowing air from the cooling duct into a space between the drum unit and the fixing unit is formed in the side support plate; the fixing pressure release unit includes a rotary gear that meshes with a lower portion of a nip pressure adjustment gear on the fixing unit side, and the fixing unit performs a switching operation of switching between the pressurized state and the released state by a rotational driving force that is supplied to rotate the nip pressure adjustment gear from the rotary gear; The image forming apparatus includes a moving mechanism that moves the fixing unit vertically upward in conjunction with the switching operation.

2. the fixing unit has a shielding member that shields an opening formed between a main body of the fixing unit and the partition plate, 2. The image forming apparatus according to claim 1, wherein when the fixing unit is moved upward by the fixing pressure release unit and the moving mechanism in conjunction with the switching operation, the shielding member moves to a position where the gap formed between the shielding member and the partition plate becomes narrower.

3. the fixing unit includes a guide member extending in a direction perpendicular to a conveyance direction of the recording medium and guiding the recording medium to an entrance of the fixing nip portion; a cooling fan for generating cooling air is provided adjacent to the fixing unit; an air outlet for blowing cooling air from the cooling fan into a space between the drum unit and the fixing unit is provided in the main body of the image forming apparatus; 3. An image forming apparatus as described in claim 1 or claim 2, wherein when the drum unit is attached to the main frame, the guide member forms a cooling duct through which cooling air blown out from the air outlet flows, by means of an outer wall surface of the drum unit facing the fixing unit and an outer wall surface of the fixing unit facing the drum unit.

Images