JP5153459B2 - Fixing apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to a fixing device that fixes a toner image on a recording sheet to the recording sheet, and an image forming apparatus including the fixing device.

Generally, a fixing device for fixing a toner image on a recording sheet to the recording sheet includes a fixing roller for fixing the toner image by heat, and a pressure roller pressed against the fixing roller, and the recording sheet Is passed between the fixing roller and the pressure roller to thermally fix the toner image. As a method of generating heat for fixing, there are a method using a heat roller and a fixing belt with a built-in heat source, a method using a fixing roller itself or a pressure roller as a heat roller, and the like. Conventionally, as a means for preventing the heat roller from falling off, a sliding bearing made of, for example, PPS resin is provided at the end of the heat roller. There is one that controls the movement of the heat roller in the axial direction (so-called retaining prevention) (see Patent Document 1).
Japanese Patent Laying-Open No. 2005-37825 (paragraph (0049) to paragraph (0052), FIG. 5)

  However, in the above-described retaining means, the end surface of the heat roller is in sliding contact with the inner surface of the sliding bearing, so that the resin on the inner surface of the closing surface may be scraped off by the heat roller to generate chips. Since both ends of the heat roller are blocked by the blocking surface, the scrap is accumulated inside the heat roller. If, for example, a heater is provided inside the heat roller as a heat source of the heat roller, a part of the chips accumulated in the heat roller may fall on the heater when the heat roller rotates. . In such a case, there is a case in which the chips dropped on the heater are melted by the heat of the heater to cover the surface of the heater and deteriorate the heating characteristics of the heater.

  The present invention has been made to solve the above-described problem, and an object of the present invention is to provide a fixing device that suppresses the generation of chips and does not accumulate in the heat roller even when the chips are generated. .

A fixing device according to one aspect of the present invention is a fixing device that fixes a toner image on a recording sheet to the recording sheet, and is disposed at a heat roller having a built-in heat source and an end of the heat roller, A sliding bearing that rotatably supports the heat roller, wherein the sliding bearing is in sliding contact with the outer peripheral surface of the heat roller and rotatably supports the heat roller; and an end surface of the heat roller; possess a protrusion for restricting movement in the axial direction of the heat roller in contact, an opening for exposing the heat roller end face, wherein the opening is assembled state of the heat roller of the sliding bearing in, it characterized that you have positioned below the heat roller end face.

  According to this configuration, since the sliding bearing that rotatably supports the heat roller has the opening that exposes the end surface of the heat roller, the area that is in sliding contact with the end surface of the heat roller is reduced by the amount of the opening. Therefore, generation | occurrence | production of the scraps by a sliding bearing being scraped by the heat roller end surface can be suppressed.

Further, the opening portion, wherein in the assembled state of the sliding bearing of the heat roller, because it is positioned below the heat roller end face, even cutting piece occurs sliding bearing is scraped by the heat roller end face , The chip falls by gravity from the opening. Therefore, it is possible to prevent the chips from accumulating inside the heat roller.

Further in the above structure, the protruding portion is in the assembled state of the heat roller of the sliding bearing, it has to desirable are formed a pair symmetrically. According to this configuration, since the protruding portion is formed symmetrically, the end surface of the heat roller is in contact with the protruding portion evenly on the left and right. Therefore, the heat roller is regulated by the protrusion without tilting its end face. Therefore, it is possible to prevent the rotation of the heat roller from being eccentric. In addition, the area in sliding contact with the end face of the heat roller can be minimized.

As a fixing roller the heat roller, a heat source for heating the fixing roller, but it may also be incorporated in the fixing roller.

The image forming apparatus according to another aspect of the present invention includes an image forming unit for transferring a toner image on a recording sheet, you comprising: a, and any fixing device described above.

  According to the present invention, in the fixing device that prevents the heat roller from slipping out by the sliding bearing at the end of the heat roller, or in the image forming apparatus including the fixing device, the generation of scraps due to the sliding bearing being scraped by the heat roller. Can be suppressed. Therefore, it is possible to reduce problems such as the heat source inside the heat roller, for example, the scraps dropped on the heater being melted by the heat of the heater to cover the surface of the heater and deteriorating the heating characteristics of the heater. That is, since the failure rate of the fixing device is reduced, the product life can be extended and the maintenance cost can be reduced.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to FIGS.

  FIG. 1 is a side sectional view showing an example of a printer 10 to which a fixing device according to an embodiment of the present invention is applied. In FIG. 1, the Y-Y direction is referred to as the front-rear direction, in particular, the -Y direction is referred to as the front, and the + Y direction is referred to as the rear.

  The printer 10 includes a sheet feeding device 30 that feeds out sheets P1 one by one from a bundle of stacked sheets P1 (recording sheets) (hereinafter referred to as sheet bundle P), and a partition plate in the apparatus body 11 at the bottom of the apparatus body 11. The image forming unit 20 that transfers the toner image onto the paper P1 supplied from the paper feeding device 30 and the fixing that fixes the toner image on the paper P1 transferred by the image forming unit 20 to the paper P1 above the position 115. Device 27. The paper P1 on which the toner image is fixed by the fixing device 27 is discharged to a paper discharge tray 117 formed on the top of the apparatus main body 11.

  The sheet feeding device 30 has a sheet cassette 31 on which the sheet bundle P is stacked and detachably attached to the apparatus main body 11, and the uppermost sheet from the sheet bundle P at a corresponding position on the front side of the sheet cassette 31. And a large-diameter paper feed roller 311 for feeding out the paper P1. The apparatus main body 11 is provided with a small-diameter conveying roller 312 at a position directly above the paper feed roller 311.

  The paper P1 fed out of the paper cassette 31 by driving the paper feed roller 311 passes through a transport roller 312 and passes through a pair of registration rollers 314 provided at the downstream end of the paper feed transport path 313 and the paper feed transport path 313 in the paper transport direction. The paper is sequentially fed to the image forming unit 20. The front wall 38 of the paper cassette 31 is a guide surface that guides the paper P1 from the paper feed roller 311 to the image forming unit 20.

  The image forming unit 20 transfers the toner image onto the paper P1 based on image information transmitted from a computer or the like. The image forming unit 20 is positioned immediately above the photoconductive drum 21 so as to be along the peripheral surface of the photoconductive drum 21 that is rotatably provided around a drum center extending in the left-right direction (direction orthogonal to the paper surface of FIG. 1). The charger 22, the exposure device 23, the developing device 24, the transfer roller 25, and the cleaning device 26 are arranged in the clockwise direction from the front side.

  The photosensitive drum 21 is for forming an electrostatic latent image corresponding to image data transmitted from an external device such as a computer and a toner image along the electrostatic latent image on the peripheral surface thereof. . The charger 22 forms a uniform charge on the peripheral surface of the photosensitive drum 21 rotating clockwise around the drum center. In this embodiment, the photosensitive drum is subjected to corona discharge from the wire. A corona discharge type that applies electric charges to the peripheral surface of 21 is employed. Instead of this, a charging roller system may be employed in which the peripheral surface of the photosensitive drum 21 is rotated while being in contact with the peripheral surface of the photosensitive drum 21 and charges are applied to the peripheral surface of the photosensitive drum 21.

  The exposure device 23 irradiates the peripheral surface of the rotating photosensitive drum 21 with laser light to which intensity is applied based on image data transmitted from an external device such as a computer. The electrostatic latent image is formed on the peripheral surface of the photosensitive drum 21 by erasing the electric charge in the portion irradiated with the laser light.

  The developing device 24 supplies toner from the toner container 241 that stores toner to the circumferential surface of the photosensitive drum 21, and attaches the toner to a portion of the circumferential surface of the photosensitive drum 21 where the electrostatic latent image is formed. As a result, a toner image is formed on the peripheral surface of the photosensitive drum 21.

  The transfer roller 25 transfers a positively charged toner image formed on the peripheral surface of the photosensitive drum 21 to the paper P1 with respect to the paper P1 sent to a position immediately below the photosensitive drum 21. The transfer roller 25 applies a negative charge having a polarity opposite to that of the toner image to the sheet P1.

  The paper P1 that has reached the position directly below the photosensitive drum 21 is subjected to a transfer process while being pressed and clamped between the transfer roller 25 and the photosensitive drum 21. This transfer process is a process of peeling off the toner image on the circumferential surface of the photosensitive drum 21 that is positively charged toward the surface of the negatively charged sheet P1.

  The cleaning device 26 is for removing the toner remaining on the peripheral surface of the photosensitive drum 21 after the transfer process to the paper P1 and cleaning it. The peripheral surface of the photosensitive drum 21 cleaned by the cleaning device 26 is directed again to the charger 22 for the next image forming process.

  The fixing device 27 fixes the toner image on the paper P1 transferred by the image forming unit 20 to the paper P1. The fixing device 27 includes a fixing roller 271 (heat roller) for fixing the toner image by heat, and a pressure roller 272 pressed against the fixing roller 271 below the fixing roller 271. In the present embodiment, a halogen heater 273 is incorporated in the fixing roller 271 as a heat source for heating the fixing roller 271. The sheet P1 after the transfer processing is between the fixing roller 271 that is driven to rotate clockwise around the roller center and the pressure roller 272 that is driven to rotate counterclockwise around the roller center. Pass through the nip. When the sheet P1 receives heat from the fixing roller 271, the toner image on the sheet P1 is fixed by the heat. The sheet P1 on which the toner image is fixed is discharged to the discharge tray 117 through the discharge conveyance path 315.

  FIG. 2 is a perspective view showing a main part of the fixing device 27 according to the embodiment of the present invention. In the following description, the XX direction in FIG. 2 is referred to as the left-right direction, the YY direction is referred to as the front-rear direction, the ZZ direction is referred to as the up-down direction, and in particular, the -X direction is leftward, the + X direction is rightward, The −Y direction is referred to as the front, the + Y direction as the rear, the −Z direction as the upper side, and the + Z direction as the lower side.

  The fixing device 27 includes a sliding bearing 274 in addition to the fixing roller 271 and the pressure roller 272 described above. The slide bearing 274 is disposed at both ends of the fixing roller 271.

  The fixing roller 271 is made of, for example, a thin cylindrical body made of aluminum or stainless steel, and is heated by a halogen heater 273 that is a heating source. In the present embodiment, an example in which the halogen heater 273 is built in as a heating source is shown, but the heating source may be arranged outside the fixing roller 271.

  The pressure roller 272 is made of, for example, an elastic body made of silicon rubber. The pressure roller 272 is located at a position slightly below the fixing roller 271 and further downstream in the sheet conveyance direction (leftward in FIG. 2) than immediately below the fixing roller 271. Be placed. The pressure roller 272 forms a nip portion with the facing fixing roller 271. The pressure roller 272 is fixed so that the contact width (nip length) in the circumferential direction (left-right direction in FIG. 2) between the fixing roller 271 and the pressure roller 272 at the nip portion is a nip length suitable for the fixing process. The roller 271 is arranged in a pressed state.

  The sliding bearing 274 supports the fixing roller 271 to be rotatable. Since the fixing roller 271 that is heated to a high temperature is supported, the sliding bearing 274 is a molded product of a heat-resistant resin such as a PPS resin or a fluororesin. The sliding bearing 274 is formed on the bearing main body portion 274a, a protrusion 2741 formed on the outer surface of the bearing main body portion 274a (the front side in the case of the front sliding bearing 274 in FIG. 2), and the outer peripheral surface of the bearing main body portion 274a. Flange portion 274b.

  The bearing body 274 a is a cylinder whose inner diameter is slightly larger than the outer diameter of the fixing roller 271, and the hollow portion is fitted into the fixing roller 271. The inner peripheral surface of the bearing main body portion 274a is in sliding contact with the outer peripheral surface of the fixing roller 271 so as to rotatably support the fixing roller 271.

  The protruding portion 2741 is a base portion that protrudes outward from the left and right ends of the outer surface of the bearing body portion 274a in parallel with the axial direction (front-rear direction in FIG. 2) when viewed from above when the sliding bearing 274 is assembled to the fixing roller 271. It is a substantially L-shaped member having 2741a and a retaining portion 2741b that bends in the axial direction of the sliding bearing 274 from the protruding end of the base portion 2741a. The protrusions 2741 are paired symmetrically on the left and right center line of the slide bearing 274 and symmetrically with the vertical center line of the slide bearing 274 in the assembled state of the slide bearing 274 to the fixing roller 271. It is formed.

  The retaining portion 2741b is in contact with the end surface of the fixing roller 271 on its inner surface (the rear side in the front sliding bearing 274 in FIG. 2) and restricts the movement of the fixing roller 271 in the axial direction (so-called fixing roller removal). Stop).

  The base portion 2741a protrudes from the outer surface of the bearing body portion 274a with a predetermined length in such a manner that a part of the bearing body portion 274a is further extended outward. In the present embodiment, the width of the base portion 2741a (the length in the vertical direction in FIG. 2) is about one third of the inner diameter of the sliding bearing 274.

  The retaining portion 2741b has a substantially rectangular shape when viewed from the front. It is desirable that the vertical length of the rectangle is as narrow as possible within a range that is narrower than the inner diameter of the fixing roller 271 and that does not impair the strength required for the retaining portion 2741b. In the present embodiment, it is about one third of the inner diameter of the sliding bearing 274 and is equal to the width of the base portion 2741a. The length of the rectangle in the left-right direction is such that the free end of the retaining portion 2741 b is positioned on the axial side of the inner peripheral portion of the fixing roller 271 and does not contact the heat roller 273. The thickness of the retaining portion 2741b in the front-rear direction is set such that the retaining portion 2741b does not impair the strength necessary for retaining.

  A flange portion 274b is formed on the outer peripheral surface of the bearing body portion 274a. The movement of the sliding bearing 274 in the axial direction is restricted by a fixing member (not shown) coming into contact with the outer side surface or the inner side surface of the flange portion 274b.

  A gear 279 is coaxially and fixedly attached to one end portion of the outer peripheral surface of the fixing roller 271. A driving force is applied to the fixing roller 271 via a gear 279 from a driving source (not shown). Note that one surface (the axially outer surface (rear side in FIG. 2)) of the gear 279 is in contact with the inner surface (front side in FIG. 2) of the slide bearing 274 located rearward in FIG.

  FIG. 3 is a front view of FIG. 2 as viewed from the direction of arrow A, and illustrates the fixing approach guide 278 omitted in FIG. As shown in FIG. 3, the sheet P <b> 1 on which the toner image is transferred in the image forming unit 20 and conveyed to the fixing device 27 is nipped between the fixing roller 271 and the pressure roller 272 by the fixing approach guide 278. Led to. The sheet P1 presses the nip portion between the rotating fixing roller 271 and the pressure roller 272 that is pressed against the fixing roller 271 and is rotated in the opposite direction to the fixing roller 271. Pass while being. At that time, heat of the fixing roller 271 is transmitted from the surface of the fixing roller 271 to the paper P1. The toner image on the paper P1 is fixed by the heat.

  FIG. 4 is a view showing only the portion where the front sliding bearing 274 is arranged in the fixing device shown in FIG. FIG. 4A is a front view of the portion where the front sliding bearing 274 is disposed as viewed from the direction of arrow A in FIG. FIG. 4B is a side view of the portion where the front sliding bearing 274 is disposed as viewed from the direction of arrow B in FIG. 4C is a cross-sectional view of FIG. 4B (the cross-sectional view taken along the line CC in FIG. 2). In FIG. 4, the halogen heater 273 is omitted.

  FIG. 10 is a view showing a conventional plain bearing corresponding to FIG. (A), (B), and (C) in FIG. 10 correspond to (A), (B), and (C) in FIG. 4, respectively.

  Based on FIG.4 and FIG.10, the difference between the conventional sliding bearing and the sliding bearing which concerns on this embodiment is demonstrated. In the following description, the XX direction in FIGS. 4 and 10 is referred to as the left-right direction, the Ya-Yb direction is referred to as the inner / outer direction, and the ZZ direction is referred to as the up / down direction. On the other hand, the + X direction is the right side, the Ya direction is the outside, the Yb direction is the inside, the -Z direction is the upper side, and the + Z direction is the lower side.

  As shown in FIG. 10A, in the conventional sliding bearing 274, the outer portion thereof is a closing surface 2746. The closing surface 2746 has a donut shape, and includes a retaining portion 2746b for retaining the fixing roller 271 and a heat roller disposing hole 2746c through which the halogen heater 273 passes. The inner surface of the retaining portion 2746b is in sliding contact with the entire circumference of the end surface 271a of the fixing roller 271 (not visible by being hidden by the retaining portion 2746b in FIG. 10A).

  Since the outside of the conventional sliding bearing 274 is a closed surface that is in sliding contact with the entire circumference of the end surface 271a of the fixing roller 271, as shown in FIG. 10B, the end surface 271a of the fixing roller 271 is completely exposed. Not done.

  On the other hand, as shown in FIG. 4A, the sliding bearing 274 according to the present embodiment does not slidably contact the entire circumference of the end surface 271a of the fixing roller 271, but has a protrusion 2741 that slidably contacts only a part thereof. In a state of being assembled to the roller 271, a pair is provided symmetrically in front view.

  Therefore, as shown in FIG. 4B, openings 275 are formed vertically on the outside of the plain bearing 274 according to this embodiment. From the opening 275, the end surface 271a of the fixing roller 271 is exposed.

  In the conventional sliding bearing 274, the end surface 271a of the fixing roller 271 is completely covered by the retaining portion 2746b, and is prevented from slipping over the entire circumference at the contact portion between them, which is a region indicated by an arrow b in FIG. It is in sliding contact with the inside of the portion 2746b. Therefore, when the inside of the retaining portion 2746b is scraped by sliding contact with the end surface 271a and scraps are generated, the scraps accumulate in the cylindrical fixing roller 271 because there is no escape.

  On the other hand, the sliding bearing 274 of this embodiment is in sliding contact with the end surface 271a of the fixing roller 271 only on the inside of the retaining portion 2741b of the protruding portion 2741, which is the region indicated by the arrow a in FIG. That is, the contact area with the end surface 271a is greatly reduced as compared with a conventional sliding bearing that is in sliding contact with the entire circumference of the end surface 271a. Therefore, it is possible to greatly suppress the generation of scraps due to the sliding bearing 274 being scraped to the end face of the fixing roller 271.

  In addition, even when scraps are generated by scraping the sliding bearing 274 on the end surface 271a of the fixing roller 271, the projecting portions 2741 have openings 275 below the projecting portions 2741; To do. For this reason, the chips do not accumulate inside the fixing roller 271.

  Further, if the chips do not accumulate inside the fixing roller 271, when the halogen heater 273 is built in the fixing roller 271 as a heating source, the chips from the inner wall of the fixing roller 271 when the fixing roller 271 rotates. It does not fall on the halogen heater 273.

  According to the embodiment described above, it is possible to suppress generation of scraps due to the sliding bearing being scraped by the fixing roller. In addition, even if scraps are generated, the scraps do not accumulate inside the fixing roller. Therefore, it is possible to prevent the scraps from dropping to a heating source such as a halogen heater inside the fixing roller. Accordingly, it is possible to prevent problems such as the chip being melted by the heat of the heater and covering the surface of the heater to deteriorate the heating characteristics of the heater. That is, since the failure rate of the fixing device is reduced, the product life can be extended and the maintenance cost can be reduced.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to this, For example, the following modified embodiment can be taken.

  (1) In the above-described embodiment, the shape of the retaining portion 2741b is substantially rectangular in a front view viewed from the outside of the sliding bearing 274. Instead of this, as shown in FIG. 5, a retaining portion 2742b having an arc on the free end side may be used.

  (2) Further, as shown in FIG. 6, the retaining portion 2743b may have a tapered shape that becomes thinner from the base portion toward the free end in a front view as seen from the outside of the sliding bearing 274. At this time, the radial section of the base portion 2743a has a substantially sector shape that becomes thinner toward the axial center in accordance with the shape of the retaining portion 2743b.

  (3) Further, as shown in FIG. 7, instead of the projecting portion 2741, a projecting portion 2744 having a retaining portion 2744b whose vertical width is narrower than the vertical width of the base 2744a may be used.

  (4) In the above embodiment, the opening 275 is formed vertically on the outside of the sliding bearing 274. Instead of this, a sliding bearing 274 having an opening 275 only at the lower portion may be used as shown in FIG. The shape of the opening 275 is such that the lower portion of the conventional plain bearing 274 shown in FIG. 10 is viewed from the front in the assembled state to the fixing roller 271 from the outer surface of the closing surface 2746 to the outer surface of the flange portion. The shape is cut into a wide fan shape.

  According to this configuration, the inner side of the retaining surface 2745 b is in sliding contact with the end surface 271 a of the fixing roller 271. The scrap generated from the retaining surface 2745b by this sliding contact is reduced by the amount corresponding to the opening 275, compared to the conventional sliding bearing 274. Therefore, the generation of scraps due to the sliding bearing being scraped to the end face of the fixing roller is suppressed. Further, similarly to the above embodiment, it is possible to prevent the scraps from dropping due to gravity from the opening 275 and accumulating the scraps inside the fixing roller.

  (5) In the above embodiment, the flange portion 274b is formed on the outer peripheral surface of the bearing main body 274a of the sliding bearing 274 in order to restrict the movement of the sliding bearing 274 in the axial direction. Instead, as shown in FIG. 9, a tab-like second protrusion 274b 'may be provided at any position on the outer periphery of the bearing body 274a. In this modified embodiment, the movement of the sliding bearing 274 in the axial direction is restricted by the second protrusion 274b 'coming into contact with the fixing member.

  (6) In the above embodiment, as a method of generating heat for fixing, the present invention is applied by incorporating the halogen heater 273 in the fixing roller 271 and using the fixing roller 271 itself as a heat roller. Alternatively, the present invention may be applied by incorporating a halogen heater 273 in the pressure roller 272 and using the pressure roller 272 as a heat roller. Further, the present invention may be applied to a roller in which a halogen heater 273 is incorporated in a roller that is in contact with the outer periphery of the fixing roller 271 and heats the fixing roller 271 to form a heat roller. Further, the present invention may be applied to a heating roller in which a fixing belt is stretched between the fixing roller 271 and the heating roller, and a halogen heater 273 is built in the heating roller.

1 is a side sectional view illustrating an example of a printer 10 to which a fixing device according to an embodiment of the present invention is applied. 1 is a perspective view showing a fixing device according to an embodiment of the present invention. 1 is a front view showing a fixing device according to an embodiment of the present invention. FIG. 3 is a diagram showing only a portion where the sliding bearing 274 is arranged, extracted from the fixing device shown in FIG. 2, and (A) is a front view of the portion where the sliding bearing 274 shown in FIG. (B) is the side view similarly seen from B direction, (C) is sectional drawing of FIG. 3 (B). It is a figure which shows the deformation | transformation embodiment of this invention. It is a figure which shows the deformation | transformation embodiment of this invention. It is a figure which shows the deformation | transformation embodiment of this invention. It is a figure which shows the deformation | transformation embodiment of this invention. It is a figure which shows the deformation | transformation embodiment of this invention. It is a figure which shows the conventional sliding bearing.

27 Fixing Device 271 Fixing Roller (Heat Roller)
272 Pressure roller 273 Halogen heater (heat source)
274 Sliding bearing 274a Bearing body part 2741 Protruding part 2741a Base part 2741b Retaining part 274b Flange part 275 Opening part 279 Gear

Claims (4)

In a fixing device for fixing a toner image on a recording sheet to the recording sheet,
A heat roller with a built-in heat source;
A sliding bearing disposed at an end of the heat roller and rotatably supporting the heat roller;
The sliding bearing is
A bearing main body that slidably contacts the outer peripheral surface of the heat roller and rotatably supports the heat roller;
A protrusion that abuts the end face of the heat roller and restricts movement of the heat roller in the axial direction;
Have a, an opening for exposing the heat roller end face,
The fixing device wherein the opening is in the assembled state of the heat roller of the sliding bearing, characterized that you have positioned below the heat roller end face. 2. The fixing device according to claim 1 , wherein the protrusions are formed in a pair symmetrically in a state in which the sliding bearing is assembled to the heat roller. The fixing device according to claim 1, wherein the heat roller is a fixing roller, and a heat source for heating the fixing roller is built in the fixing roller. An image forming unit for transferring a toner image onto a recording sheet;
An image forming apparatus comprising: the fixing device according to claim 1 .

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