JP4961047B2 - Fixing device and image forming apparatus having the same - Google Patents

Description

  The present invention relates to a fixing device for fixing a toner image transferred onto a sheet, which is a recording medium, and an image forming apparatus including the fixing device.

  2. Description of the Related Art Image forming apparatuses such as copying machines, printers, and facsimile machines that employ an electrophotographic system are provided with a fixing device for fixing a toner image transferred onto a recording medium. As this fixing device, a two-roller type having a heating roller and a pressure roller rotating in contact with each other is generally used. In this roller-type fixing device, the heating roller and the pressure roller are in contact with each other. When the sheet on which the unfixed toner image is transferred is passed through the fixing nip portion formed in this way, the toner is melted by heat and pressure, and the toner image is fixed on the surface of the sheet as a permanent image. An endless belt-like heating member may be used instead of the heating roller.

  Here, the heating roller is configured by providing an elastic layer and a release layer on a metal core having a heat source such as a halogen heater inside, and is heated from the inside by the radiant heat of the heat source.

  By the way, from the viewpoint of saving energy and preventing the user from waiting when using the image forming apparatus, the fixing device waits for a warming time by heating a heating member such as a heating roller instantaneously. It is desired to shorten the length as much as possible.

  In the fixing device, for example, as disclosed in Patent Document 1, a heating roller is formed in a hollow shape and a heat source such as a halogen heater is provided therein, and radiant heat emitted from the heat source is applied to the heating roller and the pressure roller. In some cases, a reflective member for reflecting the pressure contact portion is provided, and the radiant heat from the heat source is concentrated on the fixing portion by the reflective member to efficiently heat the heating roller.

  Further, Patent Document 2 discloses a technique for reducing power consumption by more efficiently reflecting radiant heat by a reflecting member. In this technique, in a fixing device in which radiant heat emitted from a heat source is reflected to a heating roller by a reflecting member, the reflecting member has a substantially semicircular cross section, and a substantially central portion thereof is bent into a substantially V-shaped cross section. Thus, the radiant heat radiated from the surface of the heat source facing the reflecting member is also surely radiated to the heating roller.

JP-A-6-035354 JP-A-8-254915

  By the way, as a means for instantaneously heating the heating roller in order to shorten the waiting time (warm-up time) as much as possible, the heating roller is thinned so as to cope with fixing the toner image on each size paper. In general, a method using a plurality of halogen heaters having different heat distribution patterns is employed.

  Further, as the size of the image forming apparatus is reduced, the diameter of the heating roller is reduced, and the distance between the halogen heaters in the cross section of the fixing apparatus is shortened. For example, when two halogen heaters having different heat distribution patterns are used, the radiant heat of one halogen heater heats the other halogen heater, resulting in a decrease in radiation efficiency and the glass of the halogen heater. Since the tube is heated excessively, there arises a problem that the life of the halogen heater is shortened.

  The present invention has been made in view of the above problems, and the purpose of the process is to efficiently heat the heating member without shortening the warm-up time without heating the plurality of heat sources to each other. It is an object of the present invention to provide a fixing device capable of preventing a decrease in life due to overheating of a heat source and an image forming apparatus including the same.

In order to achieve the above object, an invention according to claim 1 includes an endless heating belt and a pressure member, and a plurality of pressure pads and a plurality of pressure pads for pressing the heating belt against the pressure member. The heat belt is heated by radiant heat radiated from each of the heat sources, and the toner on the paper that is passed through the contact portion between the heating belt and the pressure member is heated and pressurized. In a fixing device that fixes on paper,
The pressure pad has a guide portion that is in sliding contact with the inner periphery of the heating belt, and a plate-shaped reinforcing portion that stands up from the guide portion,
The plurality of heat sources are arranged on both sides of the reinforcing portion,
The reinforcing portion is formed integrally with a reflecting member at a position facing the heat source, and extends from the guide portion beyond the position of the heat source .

According to a second aspect of the present invention, in the first aspect of the present invention, the reinforcing portion and the guide portion of the pressure pad are made of a stainless steel member .

The invention described in claim 3
Image forming means for forming a toner image on the image carrier;
Transfer means for transferring the toner image formed on the image carrier by the image forming means onto paper;
An endless heating belt and a pressure member are provided, a pressure pad for pressing the heating belt against the pressure member and a plurality of heat sources are arranged inside the heating belt, and radiant heat radiated from each of the heat sources a fixing device for fixing the heating belt is heated, the heating belt and the pressure member of the abutment heating the toner on the sheet to be fed into and pressed by this onto paper by,
In an image forming apparatus comprising:
The fixing device comprises the fixing device according to claim 1 or 2.

  According to the present invention, the radiant heat radiated from each heat source is reflected by the reflecting member to heat the heating member without heating other heat sources, and the reflecting member has a cross-sectional shape of a polygon such as a rhombus. For example, since the radiant heat reflected by the reflecting member does not heat the heat source itself, the heating member can be efficiently heated to shorten the warm-up time, and the energy consumption can be kept low.

  In addition, since overheating of each heat source is prevented, the life of the heat source is prevented from being reduced and durability is improved.

1 is a side sectional view of an image forming apparatus (laser beam printer) according to the present invention. It is a cross-sectional view of the fixing device according to Reference Example 1 of the present invention. It is a cross-sectional view of the reflecting member of the fixing device according to Reference Example 1 of the present invention. It is an image figure of the radiant heat ray of a halogen heater inside the heating roller of the fixing device according to Reference Example 1 of the present invention. It is the sectional view on the AA line of FIG. FIG. 3 is a sectional view taken along line B-B in FIG. 2. It is a cross-sectional view of the heating roller of the fixing device according to Reference Example 2 of the present invention. 1 is a cross-sectional view of a fixing device according to Embodiment 1 of the present invention.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

[Image forming apparatus]
FIG. 1 is a side sectional view of a laser beam printer 1 as an embodiment of an image forming apparatus according to the present invention. The laser beam printer 1 conveys paper along a conveyance path L provided in the apparatus main body 1a. On the other hand, an image is formed on a sheet based on image data transmitted from a terminal or the like (not shown), and the conveyance path L passes through the apparatus main body 1a from the front to the rear (from right to left in FIG. 1). A horizontal portion L1 extending substantially horizontally and a vertical portion L2 rising substantially vertically from the end of the horizontal portion L1 are formed in a substantially L shape in side view.

  Further, the laser beam printer 1 includes a paper feeding unit 2 provided at a lower portion of the apparatus main body 1a, an image forming unit 3 provided at a substantially central portion in the apparatus main body 1a above the paper feeding unit 2, The fixing device 4 disposed behind the image forming unit 3, the concave paper discharge unit 5 provided on the upper surface of the apparatus main body 1 a above the fixing device 4, the horizontal part L 1 of the transport path L and the paper feed A switchback portion 6 provided between the cassette 7 and the cassette 7 is provided.

  The paper feed unit 2 stores paper and feeds the paper toward the image forming unit 3 and includes the paper feed cassette 7 and the manual feed tray 8.

  Here, the paper feed cassette 7 has a rectangular box shape with an open upper surface, and has a function of feeding sheets (not shown) stacked and accommodated therein one by one, which is shown in FIG. As shown, in the state where it is mounted in the apparatus main body 1a, it is located below the horizontal portion L1 of the transport path L as shown.

  The paper feed cassette 7 includes a lift plate 9 that contacts and separates from the inner bottom surface, a lift plate 10 that moves up and down in conjunction with the contact and separation operation of the lift plate 9, and a front end of the lift plate 9 (paper feeding direction). A lift drive shaft 11 that is attached in the vicinity of the downstream end) and rotates the lift plate 9 in the direction of the arrow in FIG. 1 and a shaft that can rotate in the vicinity of the rear end (upstream end in the sheet feeding direction) of the lift plate 10. A supporting shaft 12 is provided.

  Further, the paper feed unit 2 includes a pickup roller 13 that takes out the paper in the paper feed cassette 7 one by one, a feed roller 14 that sends out the taken paper to the horizontal part L1 of the transport path L, a retard roller 15, and a plurality of rollers. Pick-up rollers 16, 17, and 18, and a pickup that picks up the paper placed on the manual feed tray 8 in addition to the registration rollers 19 that supply the image forming unit 3 to the image forming unit 3 at a predetermined timing after temporarily waiting the fed paper. A roller 20 is provided.

  The image forming unit 3 forms an image on a sheet supplied from the sheet feeding unit 2, and is an image carrier that is rotatably disposed at a substantially central portion in the front-rear direction of the horizontal portion L 1 of the transport path L. A photosensitive drum 21, a primary charger 22, a developing device 23, a transfer roller 24 and a cleaning device 25 disposed around the photosensitive drum 21, a laser scanner unit (LSU) 26, a toner hopper 27, and the like disposed above them. I have.

  The fixing device 4 is for fixing the toner image transferred onto the paper in the image forming unit 3 to the paper, and includes a heating roller 28 and a pressure roller 29 that rotate while being pressed against each other. Yes.

  Further, the paper discharge unit 5 is for discharging the paper on which the toner image has been fixed in the fixing device 4 to the outside of the main body 1a, and is provided in the middle of the vertical portion L2 of the transport path L. And a paper discharge roller 31 provided at the end of the vertical portion L2 and a paper discharge tray 32 for stacking paper discharged outside the apparatus main body 1a.

  The switchback unit 6 is used when an image is formed on both sides of a sheet. The switchback unit 6 is provided at another position on another conveyance path L ′ disposed below the vertical portion L1 of the conveyance path L and its proper position. A plurality of transport rollers 33 are provided.

  Next, an image forming operation of the laser beam printer 1 having the above configuration will be described.

  For example, when a print start signal is transmitted to the laser beam printer 1 from a terminal such as a personal computer (personal computer), in the image forming unit 3, the photosensitive drum 21 is driven in the direction indicated by the arrow (clockwise) in FIG. ) And the surface thereof is uniformly charged to a predetermined potential by the primary charger 22. When a laser beam based on the image data transmitted from the terminal is output from the laser scanner unit 26 and irradiated onto the photosensitive drum 21, an electrostatic latent image is formed on the photosensitive drum 21. Then, the electrostatic latent image on the photosensitive drum 21 is developed by the developing device 23 using toner as a developer to be visualized as a toner image.

  At the same time, in the paper feeding unit 5, for example, the sheets stored in the paper feeding cassette 7 are picked up one by one from the uppermost one by the pickup roller 13, and the feed roller 14, the retard roller 15, and the paper feeding rollers 16, 17. , 18 are sent to the horizontal portion L1 of the conveying path L, and after being temporarily put into a standby state by the registration roller 19, are supplied to the image forming portion 3 at a predetermined timing synchronized with the toner image on the photosensitive drum 21. . In the paper feed cassette 7, the lift plate 9 is rotated in a direction away from the inner bottom surface, thereby raising the elevating plate 10 to a predetermined height position corresponding to the number of sheets stacked thereon, The uppermost one of the sheets stacked on the elevating plate 10 is picked up by the pickup roller 13. Further, when an image is formed on the paper loaded on the manual feed tray 8, the paper is taken out one by one by the pickup roller 20, and sent to the horizontal portion L1 of the transport path L by the paper feed rollers 16 and 18. .

  In the image forming unit 3, the sheet supplied to the transfer nip between the photosensitive drum 21 and the transfer roller 24 is conveyed while being pressed against the photosensitive drum 21 by the transfer roller 24, thereby its surface (transfer surface). ), The toner image on the photosensitive drum 21 is transferred. The sheet onto which the toner image has been transferred is conveyed to the fixing device 4, and is heated and pressed in the process of being sandwiched and conveyed between the heating roller 28 and the pressure roller 29 in the fixing device 4. Get fixed. The toner remaining on the surface of the photosensitive drum 21 after transfer of the toner image onto the sheet (transfer residual toner) and electric charge are removed by the cleaning device 25.

  Thus, the sheet on which the toner image is fixed on the surface by the fixing device 4 is conveyed upward by the conveying roller 30 along the vertical portion L2 of the conveying path L, and is provided on the upper portion of the apparatus main body 1a by the paper discharge roller 31. The paper is discharged and stacked on the discharged paper discharge tray 32.

  The above is a series of operations when an image is formed on one side of a sheet. When an image is formed on both sides of a sheet, a sheet on which a toner image is fixed on one side by a fixing device 4 is conveyed by a conveyance roller 30. After the sheet is fed to the vertical portion L2 of the conveyance path L, the sheet is switched back by feeding the conveyance roller 30 in the reverse direction to be fed to another conveyance path L ′. Then, the paper is transported forward (to the right in FIG. 1) along the transport path L ′ by a plurality of transport rollers 33 provided in the transport path L ′, and the paper is transported by the paper feed rollers 16, 17, 18. When the sheet is fed again to the horizontal portion L1 of the conveyance path L, the front and back of the sheet are reversed, and thereafter, the toner image on the photosensitive drum 21 is transferred to the surface of the sheet (the other side on which no image is formed) by the same operation as described above. ) And the toner image is fixed on the paper in the fixing device 4, images are formed on both sides of the paper. The sheet on which images are formed on both sides in this way is conveyed upward along the vertical portion L2 of the conveyance path L by the conveyance roller 30 and is discharged to the discharge tray 32 by the discharge roller 31 as described above.

[Fixing device]
Next, a reference example of the fixing device 4 and an embodiment of the present invention will be described.

2 is a cross-sectional view of the fixing device according to Reference Example 1 of the present invention, FIG. 3 is a cross-sectional view of the reflecting member of the identification attaching device, FIG. 4 is an image of radiant heat rays of the halogen heater inside the heating roller, and FIG. 2 is a cross-sectional view taken along line AA in FIG. 2, and FIG. 6 is a cross-sectional view taken along line BB in FIG.

  As shown in FIG. 2, the fixing device 4 includes a hollow heating roller 28 and a hollow pressure roller 29 that rotates in contact with the heating roller 28. The halogen heaters 34 and 35 are arranged in the longitudinal direction (perpendicular to the plane of FIG. 2).

  The heating roller 28 is configured by forming a surface release layer having a thickness of 20 μm on the outer surface of an iron cored bar having a thickness of 0.3 mm, and applying a heat absorbing paint on the inner surface of the cored bar, Its outer diameter is set to φ30 mm. As shown in FIGS. 5 and 6, the outer periphery of both ends in the longitudinal direction of the heating roller 28 is rotatably supported by a fixing frame 37 via a bearing 36, and a drive gear 38 is attached to the outer periphery of one end. It has been. Both ends of the halogen heaters 34 and 35 in the longitudinal direction are attached to the fixing frame 37. As shown in FIG. 6, one halogen heater 34 has a wide width corresponding to the large size paper width. Six light emitting section filaments 34a are arranged in the longitudinal direction in the area, and the other halogen heater 35 is arranged with four light emitting section filaments 35a in the longitudinal direction in a narrow area corresponding to the small size paper width. One of the halogen heaters 34 is used when a large-size sheet is passed, and its power consumption is 900 W. The other halogen heater 35 is used when a small-size sheet is passed, Its power consumption is 450W.

  The pressure roller 29 is formed by forming an elastic layer of silicone rubber on the outer surface of an iron core bar and forming a surface release layer composed of a PFA tube having a thickness of 50 μm on the surface. The diameter is set to φ25 mm. As shown in FIG. 5, the pressure roller 29 has shaft portions 29 a at both ends in the longitudinal direction rotatably supported by bearings 39, and a predetermined force (on the outer periphery of the heating roller 28 by a pair of springs 40 ( In the present embodiment, a fixing nip portion is formed between the roller and the heating roller 28 by being pressed at 120N).

By the way, in the first reference example , a reflecting member 41 having a rhombic cross section is disposed in the longitudinal direction between the halogen heaters 34 and 35 inside the heating roller 28. The reflecting member 41 is made of a stainless steel plate or aluminum plate having a thickness of 0.1 mm, and its surface is mirror-finished to ensure high reflectivity. As shown in FIGS. 5 and 6, the reflecting member 41 is fixed to the fixing frame 37 at both ends in the longitudinal direction.

  Next, the operation of the fixing device 4 will be described.

When a driving force from a motor (not shown) is transmitted to the driving gear 38 of the fixing roller 28, the fixing roller 28 is rotationally driven at a predetermined speed (250 mm / sec) in the arrow direction (clockwise) in FIG. The pressure roller 29 pressed against this is driven to rotate in the direction of the arrow (counterclockwise) in FIG. At the same time, when the halogen heater 34 or 35 is energized according to the paper size to be passed, the plurality of light emitting section filaments 34a or 35a of the halogen heater 34 or 35 generate heat, and as shown in FIG. Radiant heat rays are emitted radially from 34 or 35 and the heating roller 28 is heated from the inside. However, a part of the radiant heat rays is reflected by the reflecting member 41 as shown in the drawing and is close to the fixing nip of the fixing unit. Heat intensively. In this reference example 1 , only one of the halogen heaters 34 or 35 is used depending on the size of the paper to be passed. However, for convenience, FIG. 4 shows radiant heat emitted from both the halogen heaters 34 and 35. The state of the line is shown.

Thus, in the present Reference Example 1 , since the reflecting member 41 having a rhombus cross-sectional shape is disposed between the two halogen heaters 34 and 35, as shown in FIG. 4, it is radiated from each halogen heater 34 (35). The radiant heat is reflected by the reflecting member 41 to heat the heating roller 28 without heating the other halogen heater 35 (34), and the radiant heat reflected by the reflecting member 41 causes the halogen heater 34 (35) itself to be heated. Since the heating roller 28 is not heated, the heating roller 28 can be efficiently heated to shorten the warm-up time, and the energy consumption can be kept low.

  Further, since the overheating of the halogen heaters 34 and 35 is prevented, the lifetime of the halogen heaters 34 and 35 is prevented from being reduced, and the durability is improved.

  In the above state, the sheet having the toner image transferred onto the surface as described above is supplied to the fixing device 4, and when the sheet passes through the fixing nip formed by the heating roller 28 and the pressure roller 29, the toner is removed. The toner image is fixed on the paper as a permanent image by being heated and pressurized and melted.

< Reference Example 2>
Next, Reference Example 2 of the present invention will be described with reference to FIG.

FIG. 7 is a cross-sectional view of the heating roller of the fixing device according to Reference Example 2. In this figure, the same elements as those shown in FIG. Is omitted.

The fixing device 4 according to the reference example 2 can pass sheets of three types of sizes, large, medium, and small, and as shown in FIG. Two halogen heaters 34, 42, and 35 are arranged on the same circumference at an equal angular pitch (120 ° pitch), and these halogen heaters 34, 42, and 35 are switched according to the size of the paper to be passed. Used.

And Thus, in this reference example 2, the cross-sectional shape between the adjacent ones of the halogen heater 34,42,35 are arranged respectively reflecting member 41 of the rhombus, as in Reference Example 1, The radiant heat radiated from each halogen heater 34 (42, 35) is reflected by each reflecting member 41 to effectively heat the heating roller 28 without heating the other halogen heaters 42, 35 (34). Since the radiant heat reflected by the reflecting member 41 does not heat the halogen heater 34 (42, 35) itself, the heating roller 28 can be efficiently heated to reduce the warm-up time and the energy consumption amount. Can be kept low.

  Further, since the overheating of each of the halogen heaters 34, 42, and 35 is prevented, the life of the halogen heaters 34, 42, and 35 is prevented from being reduced, and the durability is improved.

<Embodiment 1 >
Next, Embodiment 1 of the present invention will be described with reference to FIG. FIG. 8 is a cross-sectional view of the fixing device according to this embodiment.

  The fixing device 4 according to the present embodiment uses an endless heating belt 43 as a heating member, and the heating belt 43 has an inside for pressing the heating belt 43 against the pressure roller 29 from the inside. A pressure pad 44 is disposed.

  Here, the pressure pad 44 is a stainless steel member having an inverted T-shaped cross section that is long in the direction perpendicular to the paper surface of FIG. 8, and includes a guide portion 44 a that is in sliding contact with the inner periphery of the heating belt 43, Standing vertically upward from the guide portion 44a is composed of a plate-like reinforcing portion 44b. The reinforcing portion 44b of the pressure pad 44 is formed in a hollow shape, and its heat capacity is kept small.

  In addition, halogen heaters 34 and 35 are disposed on both sides of the reinforcing portion 44b of the pressure pad 44 inside the heating belt 43, and the halogen heaters on both surfaces of the reinforcing portion 44b of the pressure pad 44 are provided. A reflection member 41 having a rhombic cross-sectional shape is integrally formed at an intermediate height position opposite to 34 and 35.

  Thus, also in this embodiment, the radiant heat radiated from each halogen heater 34 (35) is reflected by the reflecting member 41 to heat the heating belt 43 without heating the other halogen heaters 35 (34). In addition, since the radiant heat reflected by the reflecting member 41 does not heat the halogen heater 34 (35) itself, the heating belt 43 can be efficiently heated to reduce the warm-up time and energy consumption. The amount can be kept low.

  Further, since the overheating of the halogen heaters 34 and 35 is prevented, the lifetime of the halogen heaters 34 and 35 is prevented from being reduced, and the durability is improved.

  Further, the embodiment in which the present invention is applied to a laser beam printer has been described above. However, the present invention can be similarly applied to any other image forming apparatus such as a copying machine or a facsimile machine in addition to a printer. Of course.

1 Laser beam printer (image forming device)
DESCRIPTION OF SYMBOLS 1a Device main body 2 Paper feed part 3 Image forming part 4 Fixing device 5 Paper discharge part 6 Switchback part 7 Paper feed tray 8 Manual feed tray 9 Lift plate 10 Lifting plate 11 Lift drive shaft 12 Shaft 13 Pickup roller 14 Feed roller 15 Retard roller 16 to 18 Paper feed roller 19 Registration roller 20 Pickup roller 21 Photosensitive drum 22 Primary charger 23 Developing device 24 Transfer roller 25 Cleaning device 26 Laser scanner unit (LSU)
27 Toner hopper 28 Heating roller (heating member)
29 Pressure roller (pressure member)
30 Conveying roller 31 Discharging roller 32 Discharging tray 33 Conveying roller 34, 35 Halogen heater (heat source)
36 Bearing 37 Fixing frame 38 Drive gear 40 Spring 41 Reflecting member 42 Halogen heater (heat source)
43 Heating belt (heating member)
44 Pressure pad L, L 'Transport path L1 Horizontal section of transport path L2 Vertical section of transport path

Claims (3)

An endless heating belt and a pressure member are provided, a pressure pad for pressing the heating belt against the pressure member and a plurality of heat sources are arranged inside the heating belt, and radiant heat radiated from each of the heat sources the fixing device for fixing the heating belt is heated, the heating belt and the pressure member of the abutment heating the toner on the sheet to be fed into and pressed by this onto paper by,
The pressure pad has a guide portion that is in sliding contact with the inner periphery of the heating belt, and a plate-shaped reinforcing portion that stands up from the guide portion,
The plurality of heat sources are arranged on both sides of the reinforcing portion,
The fixing device is characterized in that a reflecting member is integrally formed at a position facing the heat source, and extends beyond the position of the heat source from the guide portion . 2. The fixing device according to claim 1, wherein the reinforcing portion and the guide portion of the pressure pad are made of a stainless steel member . Image forming means for forming a toner image on the image carrier;
Transfer means for transferring the toner image formed on the image carrier by the image forming means onto paper;
An endless heating belt and a pressure member are provided, a pressure pad for pressing the heating belt against the pressure member and a plurality of heat sources are arranged inside the heating belt, and radiant heat radiated from each of the heat sources a fixing device for fixing the heating belt is heated, the heating belt and the pressure member of the abutment heating the toner on the sheet to be fed into and pressed by this onto paper by,
In an image forming apparatus comprising:
An image forming apparatus comprising the fixing device according to claim 1 or 2.

Images