JP2016048325A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress depletion of a lubricant applied from a lubricant application roller onto the inner surface of a pressure belt, in a fixation device comprising a fixation roller, the pressure belt, a pressure pad that presses the pressure belt against the fixation roller, and a slide sheet that covers the pressure pad.SOLUTION: The lubricant application roller is disposed so as to contact with a slide sheet.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an image forming apparatus, such as a copying machine or a laser beam printer, which forms a recorded image on a recording material by transferring and fixing a developed image (toner image) formed on an image carrier by an electrophotographic method.

  2. Description of the Related Art Conventionally, an electrophotographic image forming apparatus develops a latent image formed on a photosensitive drum as an image carrier to form a visible image, and uses the visible image (toner image) on a sheet using electrostatic force. Then, the transferred image is fixed by heat, and the image is recorded and formed on the sheet.

  In an image forming apparatus such as an electrophotographic apparatus or an electrostatic recording apparatus, a toner image is formed on a sheet, and the image is formed by fixing the image by heating and pressing it. One such fixing device is a belt fixing device using a fixing roller and a belt. In this fixing device, the fixing nip width along the recording material conveyance direction can be easily set large by adjusting the width of the belt against the fixing roller of the belt. Accordingly, since the fixing nip width can be secured without depending on the diameter of the fixing roller, the fixing roller can have a small diameter and a small heat capacity, and the start-up time can be shortened. That is, the belt fixing device can melt a larger amount of toner, and thus is suitable for an image forming apparatus using a large amount of toner such as a color image forming apparatus.

  FIG. 5 is a schematic diagram of a belt fixing device described in Patent Document 1. A fixing roller 51 is rotatably arranged. A belt unit 53 is provided below the fixing roller 51.

  A heater 58 such as a halogen lamp is disposed inside the fixing roller 51. Further, a thermistor (not shown) is disposed in contact with or not in contact with the fixing roller 51, and the temperature of the surface of the fixing roller 51 is adjusted by controlling the voltage to the heater 58 through a temperature adjusting circuit. Yes.

  The belt unit 53 includes a fixing belt 52 that is a flexible endless belt, and first to third three rollers 55, 56, and a plurality of belt suspension members each having the fixing belt 52 suspended. 57, a pressure pad 100 and the like. A sliding sheet 103 is provided on the pressure pad 100.

  The separation roller 56 and the pressure pad 100 are in pressure contact with the fixing roller 51 via the fixing belt 52, so that the fixing nip portion N ′ that is a contact portion between the fixing roller 51 and the fixing belt 52 is a recording material. It is formed wide in the transport direction.

  In this belt fixing device, the sliding sheet 103 is brought into pressure contact with the pressure pad 100 and the fixing roller 51 and slides on the fixing belt 52. Conventionally, the frictional force and wear of this sliding surface have been a problem. When the frictional force on the sliding surface is large, a phenomenon occurs in which the fixing belt 52 slips from the fixing roller due to frictional resistance, and the toner image on the sheet shifts. Further, the frictional resistance is further increased by wear of the sliding sheet 103 and the fixing belt 52.

  In order to improve these, a lubricant is often interposed between the fixing belt and the sliding sheet. However, if the fixing belt 52 rotates for a long time, the lubricant accumulates at the fixing nip inlet side, and the lubricant interposed between the fixing belt and the sliding sheet gradually decreases. As a result, there is a problem that the frictional resistance on the sliding surface gradually increases.

  In the belt-type image heating apparatus, the surface of the lubricant application member is prevented from being soiled in the standby state, the problem caused by the surface soiling is solved, and the life of the apparatus is reduced, the size is reduced, and the reliability is improved.

  This configuration will be described with reference to FIG. A fixing roller 51 that heats an image on the sheet at the fixing nip N; a fixing belt 52 that forms a fixing nip with the fixing roller 51; and a belt that is slidable on the inner surface of the belt at the fixing nip. In an image heating apparatus having a pressure pad 100 that is pressed against the belt and a lubricant application member 59 that applies a lubricant to the inner surface of the belt, the lubricant application member 59 is used when the belt is in pressure contact with the fixing roller. And the lubricant application member 59 is separated from the inner surface of the belt when the belt is not in pressure contact with the fixing roller.

  By adopting a configuration in which the lubricant application member 59 is separated from the inner surface of the belt in the standby state, the lubricant is not applied to the belt wastefully in the standby state, and contamination on the surface of the lubricant application member is reduced. Only when the belt is in pressure contact with the fixing roller, a stable lubricant amount can be supplied from the lubricant application member 59 to the inner surface of the belt, and good image heating can be maintained.

JP 2007-079036 A

  In the fixing device using the belt system, in Patent Document 1, the lubricant application member is separated from the inner surface of the belt in the standby state, so that the belt is fixed without wastefully applying the lubricant to the belt in the standby state. A configuration in which the lubricant is applied only when the roller is in pressure contact is used.

  However, in the state where the fixing roller and the belt are in contact with each other and the nip is formed by the pressure pad and the fixing roller, the pressure pad slides on the belt while pressing the belt via the sliding sheet. The applied lubricant gradually accumulates at the nip entrance of the pressure pad as the belt rotates. Since the sliding sheet slides against the belt, the sliding sheet acts like a scraper that scrapes off the lubricant applied to the inner surface of the belt at the entrance of the nip. As a result, the amount of lubricant applied to the inner surface of the belt gradually decreases, and the frictional force and wear amount on the sliding surface increase, thereby reducing the life of the belt unit.

  The image forming apparatus according to the present invention includes a rotatable rotating member, a belt that presses and rotates with the rotating member, a pressure member that presses the belt against the rotating member to form a nip inside the belt, In a fixing device having a lubrication sliding member for reducing friction and wear between the pressure member and the belt, a lubricant interposed in the belt, and a lubricant application member upstream of the nip portion. The lubricant application member is in contact with the lubrication sliding member and the inner surface of the belt.

  According to the present invention, the problem that the lubricant intervening between the fixing belt and the sliding sheet is depleted due to the accumulation of the lubricant at the nip inlet as described above is reduced at the nip inlet. In order to collect the accumulated lubricant, the lubricant application member is brought into contact with the sliding sheet on the nip entrance side, and the lubricant is adhered to the lubricant application member. Then, the recovered lubricant can be applied to the belt again by bringing the lubricant application member into contact with the belt. Here, the lubricant application member is a rotating body, and the lubricant adhered by rotating can be reapplied to the fixing belt. As a result, the reduction of the lubricant on the inner surface of the belt can be suppressed, and the life of the belt unit can be improved.

1 is a schematic configuration diagram of an image forming apparatus according to a first exemplary embodiment. 1 is a schematic configuration diagram of a fixing device in Embodiment 1. FIG. 1 is a schematic configuration diagram of lubricant reapplication in Example 1. FIG. 3 is a schematic diagram of a drive mechanism for a lubricant application roller in Embodiment 1. FIG. It is a mode of the lubricant collected in the nip entrance in the conventional example. It is a schematic block diagram of the fixing device in the conventional example. 5 is a schematic configuration diagram of a lubricant application roller in Embodiment 2. FIG.

  Hereinafter, the present invention will be described more specifically with reference to examples. Although these examples are examples of the best mode of the present invention, the present invention is not limited to these examples.

[Example 1]
First, FIG. 1 shows a full-color intermediate transfer system as a specific example of the image forming apparatus according to the present embodiment. In this case, the apparatus main body 500 of the image forming apparatus has, as image forming means, image forming units 200Y, 200M, 200C corresponding to, for example, Y (yellow), M (magenta), C (cyan), and K (black). 200K is arranged in series. In other words, the image forming apparatus adopts a tandem method in which processes up to visualization are processed in parallel for each color.

  Hereinafter, in order to prevent the description from becoming complicated, the four image forming units Y, M, C, and K will be described by being represented by reference numeral 200, and the same applies to the following respective process means. Further, the arrangement order of the image forming units for each color of Y, M, C, and K is not limited thereto. Note that the present invention is not limited to a full-color intermediate transfer image forming apparatus, and may be a monochrome image forming apparatus.

  Each image forming unit 200 includes the following process means. Corresponding to each color of Y, M, C, and K, it has an image carrier 120 that carries an electrostatic latent image on its surface, a primary charging device 121, an exposure device 122, and a developing device 123. The primary charging device 121 applies a charging bias voltage having a set potential to the surface of the corresponding image carrier 120 to uniformly charge, and the exposure device 122 exposes it to form an electrostatic latent image. The electrostatic latent image is developed with toner by the developing device 123 and is visualized as a toner image.

  The toner images formed and carried on the surface of the image carrier 120 are sequentially superposed on the intermediate transfer member 125 by an endless belt by the primary transfer device 124 for primary transfer. When the sheet fed from the sheet feeding cassettes 130a and 130b passes through the sheet end compression unit 50, the thickness of the end of the sheet is reduced. As a result, the sheet damage to the fixing device 1 and the secondary transfer device 126 is reduced.

  Then, the toner image on the intermediate transfer body 125 on which all the colors Y, M, C, and K are primarily transferred by the primary transfer device 124 is then secondarily transferred collectively onto the sheet by the secondary transfer device 126. The The sheet carrying the transferred toner image is conveyed to the fixing device 1. In the fixing device 1, the sheet is sandwiched at the fixing nip portion and is fixed by applying heat and pressure to the unfixed toner image. Thereafter, the sheet is conveyed toward the discharge tray 150 of the apparatus main body 500 or the sheet material double-sided conveyance path 140.

  As described above, the apparatus main body 500 executes a series of image forming processes such as charging, exposure, development, transfer, and fixing, and forms and discharges a color toner image on a sheet of recording paper or an OHP sheet. In the case of a monochrome image forming apparatus, only a black (K) image carrier exists, and a toner image formed on the image carrier is transferred to a sheet by a transfer device.

  Next, the configuration of the image heat fixing apparatus according to the present invention will be described in detail with reference to FIGS.

  FIG. 2 is a schematic configuration diagram of a belt fixing device as an image heating device in the present embodiment. A fixing roller 51 as a heating rotator (fixing rotator) has a 2 mm-thick silicone rubber layer formed as an elastic layer 51b around a cored bar 51a made of an aluminum alloy having a thickness of 2 mm. A 50 μm-thick PFA tube 51 c as a release layer is covered. As a result, the outer diameter of the fixing roller 51 is φ60.

  The fixing belt 52, which is an endless belt, is configured to have a polyimide base layer 52a having a thickness of 100 μm. A silicone rubber layer 52b having a thickness of 0.2 mm is coated on the base layer, and as a result, the outer diameter is φ90. The fixing belt 52 in this example is a seamless belt.

  The fixing belt 52 is stretched around an entrance roller 55, a separation roller 56, a steering roller 57, a lubricant application roller 59, and a pressure pad 100. The entrance roller 55, the separation roller 56, the lubricant application roller 59, and the steering roller 57 are configured to rotate together with the belt. Specifically, the fixing belt 52 is configured to rotate by a driving force input to the separation roller 56 from a driving source (not shown), and the inlet roller 55, the steering roller 57, and the lubricant application roller 59 are driven by the belt. It is configured to rotate.

  As shown in FIG. 3, the pressure pad 100 has a double structure in which a silicone rubber layer 101 is pasted on an aluminum pressure pad base 102, and a pad holder 104 for fixing the pressure pad and suppressing deflection is provided. Have. The separation roller 56 and the pressure pad 100 press the fixing belt 52 toward the fixing roller 51 by a pressing mechanism (spring) (not shown). Further, in order to reduce the sliding resistance between the pressure pad 100 and the fixing belt 52, that is, to reduce the sliding resistance between the surface of the elastic layer 101 and the inner surface of the fixing belt 52, the entire elastic layer 101 is covered. A sliding sheet 103 is provided. As the sliding sheet 103, a PI sheet coated with PTFE is used. In this example, the thickness of the sliding sheet 103 is 100 μm.

  In this example, 490 N (50 kgf) is applied to the pressure pad 100 and 490 N (50 kgf) is applied to the separation roller 56. As a result, the pressure pad 100 and the elastic layer of the fixing roller 51 form a flexible nip N. The pressure pad base 102 is an aluminum member, and the elastic layer 56b is made of silicone rubber having a rubber hardness Hs of 30 °. The elastic layer 101 of the pressure pad has a shape having a radius of curvature of 30 mm, and is in a shape in contact with a straight line parallel to the pressure pad base 102 at the nip entrance. The rubber thickness was 3 mm.

  The entrance roller 55 is a roller disposed on the entrance side where the recording material enters the fixing device, and the rotation center position is fixed so that the conveyance path of the recording material does not change. The steering roller 57 applies a predetermined tension to the fixing belt 52, and at least one of the ends of the steering roller 57 is shown in the drawing in order to prevent the fixing belt 52 from moving in the roller axial direction with respect to the entrance roller 55. The fixing belt 52 is supported so as to be movable in the direction of arrow A, and is controlled by driving means and control means (not shown) so that the fixing belt 52 stays at a certain thrust position with respect to the entrance roller 55.

  The lubricant application roller 59 has an outer diameter of 8 mm by winding a non-woven fabric around a SUS shaft having a diameter of 4 mm. 8 ml of silicone oil J is immersed in this non-woven fabric as a lubricant. The lubricant application roller 59 is brought into contact with the sliding sheet 103 on the nip entrance side, and the silicon oil J scraped from the inner surface of the belt 52 is adhered to the lubricant application roller 59. Then, the recovered silicone oil J can be applied again to the belt by bringing the lubricant application roller 59 into contact with the belt 52.

  The lubricant application roller is a rotating body, and is rotated from the separation roller 56 via the timing belt 300 and pulleys 301 and 302 as shown in FIG. The timing belt 300 is always free from slack by the tensioner 303. The lubricant application roller is pressed against the L-shaped sheet metal 105 by the pressure springs 304a and 304b. The lubricant applied by rotating the lubricant application roller can be applied again to the fixing belt. The sliding sheet 103 is arranged along the lower side of the lubricant application roller 59 so as to cover the lowest point of the lubricant application roller 59 in the gravity direction. As a result, the silicon oil J scraped off by the sliding sheet flows down from the nip entrance toward the lubricant application roller 59 on the sliding sheet 103 and adheres to the lubricant application roller 59.

  5 and 6 show a conventional belt unit configuration. In the conventional configuration, silicon oil J accumulates at the nip entrance, and gradually increases and accumulates in the pad holder 104. It has been confirmed that up to 4 ml of silicon oil is collected in this part. As a result, the amount of silicon oil present on the inner surface of the belt gradually decreases, the sliding surface increases in frictional force, and the life of the belt unit decreases.

  By using this configuration, the silicon oil J that accumulates on the pad holder 104 can be applied to the inner surface of the belt again. Since the total lubricant present on the inner surface of the belt is 14 ml, 29% of the entire lubricant can be effectively used if 4 ml can be reapplied. Therefore, it is possible to suppress an increase in frictional force on the sliding surface and an increase in wear due to depletion of the lubricant, which is a conventional problem, and it is possible to extend the life of the belt unit.

[Example 2]
In this embodiment, since the configuration other than the lubricant application roller is the same as that of the first embodiment, the description of the configuration other than the lubricant application roller is omitted.

  This embodiment shows a mechanism for restricting leakage of silicon oil J collected at the nip inlet from the longitudinal direction.

  FIG. 7 shows the configuration of this embodiment. The lubricant application roller 59 is wound around a SUS shaft having a diameter of φ4 mm by winding a non-woven fabric so that the outer diameter is φ8 mm. Bushings 60a and 60b having an outer diameter of φ8.1 mm are provided at the end of the lubricant application roller. The bushes 60a and 60b have an inner diameter of 6 mm, and a sliding bearing with an outer diameter of 6 mm and an inner diameter of 4 mm is press-fitted for sliding rotation with the SUS shaft. The material of the bushes 60a and 60b is a heat-resistant rubber, which is easily deformed by the applied pressure and has an outer diameter of φ8 mm. The bushing 60a, 60b regulates silicon oil that tends to leak from the end. The nonwoven fabric has good oil absorption efficiency and immediately absorbs silicon oil regulated by the bushes 60a and 60b.

  By using this configuration, the silicone oil J that accumulates on the pad holder 104 can be applied again to the inner surface of the belt, and the silicone oil that leaks from the end in the longitudinal direction can be regulated. Therefore, it is possible to suppress an increase in frictional force on the sliding surface and an increase in wear due to depletion of the lubricant, which is a conventional problem, and it is possible to extend the life of the belt unit.

200 Image forming unit, 120 Image carrier, 121 Primary charging device, 122 Exposure device,
123 Developer

Claims (4)

A rotatable rotating member, a belt that presses and rotates against the rotating member, a pressure member that presses the belt against the rotating member to form a nip inside the belt, and a space between the pressure member and the belt In a fixing device having a lubricant sliding member for reducing friction and wear of the belt, a lubricant inside the belt, and a lubricant application member upstream of the nip portion, the lubricant application member is the lubricant slide. An image forming apparatus, wherein the image forming apparatus contacts the moving member and the inner surface of the belt. 2. The image formation according to claim 1, wherein the lubrication sliding member has an inclination in a gravity direction from an upstream end of the nip portion to a contact portion between the lubricant application member and the lubrication sliding member. apparatus. The image forming apparatus according to claim 2, wherein the lubricating sliding member is disposed so as to cover a lowest point in a gravity direction of the lubricant applying member. The image forming apparatus according to claim 1, wherein the lubricant application member has a lubricant leakage restricting member at both ends.