JP2017125976A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus in which uneven air suction in a longitudinal direction of a duct can be suppressed even when an exhaust port of the duct is disposed at one end in the longitudinal direction.SOLUTION: A printer 1 includes: an image forming part (5) using toner (S) containing wax; a transfer part (12a) for transferring an image onto a sheet (P); a belt unit (101) and a pressurizing roller (102) for heating a sheet conveyed from the transfer part in a nip part (101b); a duct (52) having a suction port (52a) for sucking air from a sheet entrance (400) and an exhaust port (61b) for exhausting the air, the suction port disposed between the transfer part and the nip part in the conveyance direction of the sheet; a filter (51) disposed in the duct for collecting dust (D); and a fan (61) for sucking air into the duct. A suction port covered with a filter is disposed on a side face of the duct.SELECTED DRAWING: Figure 7

Description

  The present invention relates to an image forming apparatus that forms a toner image on a recording material. This image forming apparatus is used as a copying machine, a printer, a facsimile, and a multifunction machine having a plurality of these functions.

  An electrophotographic image forming apparatus forms an image on a recording material (paper, sheet) using toner containing a release agent. The image forming apparatus includes a fixing device that heats and presses a recording material carrying a toner image to fix the image on the recording material.

  The fixing device described in Patent Document 1 forms a nip between a fixing roller and a pressure roller, and fixes a toner image on the recording material by passing the recording material through the nip.

  Further, the image forming apparatus disclosed in Patent Document 1 includes a configuration for collecting fine particles generated from the heating roller. More specifically, openings are provided at both ends in the longitudinal direction of the fixing device, and ducts for guiding fine particles are connected to the openings. The duct extends toward a region outside the fixing device in the longitudinal direction, and a filter member, an exhaust fan, and an exhaust port are provided in the region. When the exhaust fan exhausts toward the outside of the apparatus, the air sucked from the vicinity of the heating roller passes through the filter, and the fine particles are collected by the filter. In Patent Document 1, the rubber layer of the heating roller is cited as a cause of generation of fine particles, but fine particles are also generated by heating a toner containing a release agent (Patent Document 2). The fine particles resulting from the release agent are likely to be generated particularly in the vicinity of the nip entrance.

JP 2011-180340 A JP 2013-190651 A

  As described above, the image forming apparatus disclosed in Patent Document 1 has a configuration in which air is sucked from openings at both ends in the longitudinal direction of the fixing device and guided to an exhaust port at one end in the longitudinal direction. As described above, the configuration in which the duct is extended along the longitudinal direction and the exhaust is performed from one end side in the longitudinal direction is advantageous in that the duct can be reduced in size.

  However, the opening at the other end in the longitudinal direction of the fixing device is farther from the exhaust port than the opening at one end in the longitudinal direction. Since the air suction force decreases at an opening far from the exhaust port, it is difficult to guide the fine particles to the filter. That is, it is difficult for this image forming apparatus to collect fine particles generated from the other end in the longitudinal direction of the fixing device.

  If the air suction force at the other end side in the longitudinal direction of the duct is improved by increasing the air volume of the fan, the air suction force at one end side in the longitudinal direction of the duct becomes too high, and the heating roller locally There is a risk of cooling. When the temperature of the heating roller is locally lowered, image defects such as gloss unevenness are caused, and therefore another solution is desired.

  In the image forming apparatus, even when an exhaust port is provided on one end side in the longitudinal direction of the fixing device, it is desirable that uneven air intake is suppressed on one end side and the other end side in the longitudinal direction of the fixing device.

  An object of the present invention is to suppress uneven suction in the longitudinal direction even when a duct exhaust port for collecting fine particles caused by toner containing a release agent is provided on one end side in the longitudinal direction. An image forming apparatus is provided.

  The present invention relates to an image forming unit that forms an image using toner containing a release agent, a transfer unit that transfers an image formed by the image forming unit to a recording material, and a recording material conveyed from the transfer unit A pair of rotators for heating and fixing the image on the recording material by nipping and conveying the nip portion, an intake port for sucking air from the vicinity of the pair of rotators, and air sucked by the intake port A duct having an exhaust port for exhausting the air to the outside of the apparatus, the duct having the intake port provided between the transfer portion and the nip portion in the recording material conveyance direction, and a release agent provided in the duct In a longitudinal direction of the nip portion, an image forming apparatus having a filter for collecting particulates resulting from the above and a fan that is provided in the duct and generates an air flow from the intake port toward the exhaust port. The exhaust is provided with the exhaust port in a region outside the nip portion in the longitudinal direction, and the intake port is provided in a region inside the both end portions of the nip portion among side surfaces extending along the longitudinal direction. The fan is provided in a region outside the nip portion, and the filter is provided in a region inside the both end portions of the nip portion so as to cover the intake port. .

  According to the present invention, even when the exhaust port of the duct for collecting the fine particles caused by the toner containing the release agent is provided at one end side in the longitudinal direction, the uneven intake air in the longitudinal direction is suppressed. An image forming apparatus that can be provided can be provided.

1 is a diagram illustrating a configuration of an image forming apparatus. (A) is a figure which shows the cross section of a belt unit. (B) is a figure which shows the pressurization mechanism of a belt unit. (A) is a figure which shows the mode of the wax adhesion area | region on the fixing belt which expands with progress of a fixing process. (B) is a figure which shows the relationship between the adhesion area | region of a wax, and the generation | occurrence | production area | region of the dust D. FIG. FIG. 4 is a diagram illustrating a state in which dust is collected in the vicinity of the fixing device. (A) is a figure which shows the shape of the duct of an Example. (B) is a figure which shows the shape of the duct of a comparative example. (A) is a figure which shows the flow of the air in the duct of an Example. (B) is a figure which shows the flow of the air in the duct of a comparative example. FIG. 4A is an exploded perspective view of a filter unit. (B) It is the figure which looked at the filter unit.

  Hereinafter, the present invention will be described in detail with reference to examples. Unless otherwise specified, the various configurations described in the embodiments may be replaced with other known configurations within the scope of the idea of the present invention.

<Example>
(1) Overall Configuration of Image Forming Apparatus Before describing the features of this embodiment, the overall configuration of the image forming apparatus will be described. FIG. 4 is a diagram illustrating the configuration of the image forming apparatus. The printer 1 forms an image in an image forming unit using an electrophotographic process, transfers the image to a sheet in a transfer unit, and fixes the image on the sheet P by heating the sheet on which the image has been transferred in a fixing unit. It is a device to let you. The printer 1 used in the description of this embodiment is a four-color full-color multifunction printer (color image forming apparatus) using an electrophotographic process. The printer 1 may be a monochrome multifunction printer or a single function printer. Hereinafter, it demonstrates in detail using figures.

  The printer 1 includes a control circuit 200 that controls each component in the apparatus. The control circuit 200 is an electric circuit including a calculation unit such as a CPU and a storage unit such as a ROM. The control circuit 200 functions as a control unit that performs various controls when the CPU reads a program stored in a ROM or the like. The control circuit 200 is electrically connected to various components such as an external information terminal 300) such as a personal computer, an input device B such as an image reader 2, and an operation panel (not shown), and can exchange signal information. It is. The control circuit 200 controls the various components in the apparatus based on the image signal input from the input apparatus B to form an image on the sheet P.

  The sheet P is a recording material (paper) on which an image is formed. Examples of the sheet P include plain paper, cardboard, OHP sheet, coated paper, label paper, and the like.

  As shown in FIG. 1, the printer 1 includes first to fourth image forming stations 5Y, 5M, 5C, and 5K (hereinafter referred to as stations) as image forming units 5 that form toner images. The stations 5Y, 5M, 5C, and 5K are provided side by side from the left side to the right side as shown in FIG.

  The stations 5Y, 5M, 5C, and 5K are configured in substantially the same manner except that the color of the toner used is different. Therefore, when the detailed configuration of the stations 5Y, 5M, 5C, and 5K is described, the station 5K is described as an example. The station 5K includes a rotating drum type electrophotographic photosensitive member (hereinafter referred to as a drum) 6 as an image carrier on which an image is formed. Further, the station 5K includes a cleaning member 41 as a process unit that acts on the drum 6, a developing unit 9, and a charging roller (not shown).

  The first station 5Y accommodates yellow (Y) developer (hereinafter referred to as toner) in the toner accommodating chamber of the developing unit 9. The second station 5M stores magenta (M) toner in the toner storage chamber of the developing unit 9. The third station 5C stores cyan (C) toner in the toner storage chamber of the developing unit 9. The fourth station 5 </ b> K stores black (K) toner in the toner storage chamber of the developing unit 9.

  A laser scanner unit 8 as image information exposure means for the drum 6 is disposed below the image forming unit 5. An intermediate transfer belt unit 10 (hereinafter referred to as a transfer unit) is provided above the image forming unit 5.

  The transfer unit 10 includes an intermediate transfer belt (hereinafter referred to as a belt) 10c and a driving roller 10a that drives the intermediate transfer belt 10c. The first to fourth primary transfer rollers 11 are arranged in parallel inside the belt 10c. Each primary transfer roller 11 is disposed to face the drum 6 of each station.

  Each drum 6 of the image forming unit is in contact with the lower surface of the belt 10 c at the position of each primary transfer roller 11 at the upper surface portion. This contact portion is called a primary transfer portion.

  The driving roller 10a is a roller that rotationally drives the belt 10c, and a secondary transfer roller 12 is disposed outside the portion of the belt 10c that is backed up by the driving roller 10a. The belt 10c is in contact with a secondary transfer roller 12 as a transfer unit, and this contact portion is referred to as a secondary transfer portion 12a. A transfer belt cleaning device 10d is disposed outside the portion of the belt 10c backed up by the tension roller 10b. Under the laser scanner unit 8, a cassette 3 for storing sheets P is disposed.

  As shown in FIG. 1, the printer 1 is provided with a sheet conveyance path (vertical path) Q for conveying the sheet P picked up from the cassette 3 upward. In this sheet conveyance path Q, a roller pair of a feeding roller 4a and a retard roller 4b, a registration roller pair 4c, a secondary transfer roller 12, a fixing device 103, and a discharge roller pair 14 are arranged in order from the lower side to the upper side. ing. A discharge tray 16 is disposed below the image reader 2.

(1-1) Image Forming Sequence of Image Forming Apparatus When the printer 1 performs an image forming operation, the control circuit 200 performs the following control. The control circuit 200 drives the drums 6 of the first to fourth stations 5Y, 5M, 5C, and 5K to rotate clockwise at a predetermined speed in the drawing in accordance with the image formation timing. The control circuit 200 controls the driving of the driving roller 10 a so that the belt 10 c rotates in a direction corresponding to the rotational speed of the drum 6 and in a forward rotation direction with respect to the rotational direction of the drum 6. Further, the control circuit 200 operates the laser scanner unit 8 and the charging roller (not shown).

  By performing the control described above, the printer 1 forms a full-color image as follows.

  First, a charging roller (not shown) uniformly charges the surface of the drum 6 to a predetermined polarity and potential. Next, the laser scanner unit 8 scans and exposes the surface of the drum 6 using a laser beam modulated in accordance with image information signals of Y, M, C, and K colors. Thus, an electrostatic latent image corresponding to the corresponding color is formed on the surface of each drum 6. The formed electrostatic latent image is developed as a toner image by the developing unit 9. The toner images of each color of YMCK formed as described above are synthesized by being primarily transferred onto the belt 10c in order in the primary transfer portion. Thus, a full-color unfixed toner image is formed on the belt 10c by combining four color toner images of Y color + M color + C color + K color. The unfixed toner image is conveyed to the transfer unit 12a by the rotation of the belt 10c. The surface of the drum 6 after the toner image is primarily transferred to the belt 10 c is cleaned by the cleaning member 41.

  On the other hand, the sheet P in the cassette 3 is fed by one sheet by the feeding roller 4a and the retard roller 4b and conveyed to the registration roller pair 4c. The sheet P is conveyed to the secondary transfer portion in synchronization with the toner image on the registration roller pair 4c belt 10c. The secondary transfer roller 12 is applied with a secondary transfer bias having a polarity opposite to the normal charging polarity of the toner. For this reason, when the sheet P is nipped and conveyed by the secondary transfer portion, the four-color toner images on the belt 10c are secondarily transferred onto the sheet P all at once.

  When the sheet P conveyed from the secondary transfer unit is separated from the belt 10c and conveyed to the fixing device 103, the toner image is thermally fixed on the sheet P. The sheet P conveyed from the fixing device 103 is discharged to the discharge tray 16 through the guide member 15 and the discharge roller pair 14. The residual toner remaining on the surface of the belt 10c after the toner image on the sheet P is secondarily transferred is removed from the belt surface by the transfer belt cleaning device 10d.

(2) Fixing Device Next, the fixing device 103 and dust D generated in the vicinity of the fixing device 103 will be described.

(2-1) Fixing device 103
FIG. 2A is a diagram showing a cross section of the fixing unit. FIG. 2B is a diagram illustrating a pressure configuration of the fixing belt unit. The fixing device 103 according to the present exemplary embodiment is a low heat capacity fixing device that fixes a toner image onto a sheet P using a small-diameter fixing belt 105 (hereinafter referred to as a belt) heated by a heater 101a. The fixing device 103 includes a fixing belt unit 101 (referred to as a fixing unit) including a belt 105 as a rotating body, a pressure roller 102 as a rotating body, a planar heater 101a as a heating unit, and a housing 100. And. As shown in FIG. 2A, the casing 100 is provided with a sheet inlet 400 and a sheet outlet 500, and the sheet P can pass through the nip portion 101 b between the fixing unit 101 and the pressure roller 102. it can. In this embodiment, since the sheet inlet 400 is disposed below the sheet outlet 500 in the gravitational direction, the sheet P is conveyed upward from below in the gravitational direction. This configuration is referred to as a vertical path configuration.

  The sheet entrance 400 is provided with a plurality of rollers 100 a made of a thin plate-like rotating disk in the direction of the rotation axis of the belt 105. The roller 100a suppresses the toner from adhering to the housing 100 by guiding the sheet P that is out of the conveyance path.

  A guide member 15 that guides the conveyance of the sheet through the nip portion 101b is provided downstream of the sheet outlet 500 in the sheet conveyance direction. In the following description, the downstream side in the transport direction of the sheet P is referred to as the downstream side, and the upstream side in the transport direction of the sheet P is referred to as the upstream side.

(2-2) Configuration of Fixing Unit 101 The fixing unit 101 abuts on a pressure roller 102, which will be described later, and forms a nip portion 101b with the pressure roller 102. A toner image is formed on the sheet P in the nip portion 101b. It is a fixing unit for fixing. The fixing unit 101 is an assembly composed of a plurality of members, as shown in FIG. The fixing unit 101 includes a planar heater 101a, a heater holder 104 that holds the heater 101a, a pressure stay 104a that supports the heater holder 104, an endless belt 105, and one end side and the other end side in the width direction of the belt 105. And flanges 106L and 106R for holding the

  The heater 101 a is a heating member that contacts the inner surface of the belt 105 and heats the belt 105. In this embodiment, a ceramic heater that generates heat when energized is used as the heater 101a. The ceramic heater includes a thin and thin ceramic substrate and a resistance layer provided on the surface of the substrate. The ceramic heater is a low-heat capacity heater that quickly generates heat by energizing the resistance layer.

  The heater holder 104 is a holding member that holds the heater 101a. The holder 104 of the present embodiment has a semicircular cross section and regulates the shape of the belt 105 in the circumferential direction. It is desirable to use a heat resistant resin as the material of the holder 104.

  The pressure stay 104a is a member that uniformly presses the heater 101a and the holder 104 against the belt 105 in the longitudinal direction. It is desirable that the pressure stay 104a be made of a material that is not easily bent even when a high pressure is applied. In this embodiment, SUS304, which is stainless steel, is used as the material of the pressure stay 104a. A thermistor TH is provided on the pressure stay 104a. The thermistor TH outputs a signal corresponding to the temperature of the belt 105 to the control circuit 200.

  The belt 105 is a rotating body that contacts the sheet P and applies heat to the sheet P. The belt 105 is a cylindrical (endless) belt, and has flexibility as a whole. The belt 105 is provided so as to cover the heater 101a, the heater holder 104, and the pressure stay 104a from the outside.

  The flanges 106L and 106R are a pair of members that rotatably hold the end portion of the belt 105 in the longitudinal direction. As shown in FIG. 2B, the flanges 106L and 106R each have a flange portion 106a, a backup portion 106b, and a pressed portion 106c. The flange portion 106 a is a portion that receives the end face of the belt 105 and restricts the movement of the belt 105 in the thrust direction, and has an outer shape larger than the diameter of the belt 105. The backup unit 106 b is a part that holds the inner surface of the fixing belt and maintains the cylindrical shape of the belt 105. The pressed portion 106c is provided on the outer surface side of the flange portion 106a and receives a pressing force by pressure springs 108L and 108R (see FIG. 2) described later.

(2-2-1) Constitution of Fixing Belt The belt 105 includes an endless (cylindrical) base layer 105a, a primer layer 105b, an elastic layer 105c, and a release layer 105d in order from the inside to the outside.

  The base layer 105 a is a layer for ensuring the strength of the belt 105. The base layer 105a is a base layer made of metal such as SUS (stainless steel), and has a thickness of about 30 μm so as to withstand thermal stress and mechanical stress.

  The primer layer 105b is a layer for bonding the base layer 105a and the elastic layer 105c. The primer layer is formed by applying a primer with a thickness of about 5 μm on the base layer 105a.

  The elastic layer 105c is deformed when the toner image is pressed in contact with the nip portion 101b, and serves to closely attach the release layer 105d to the toner image. As the elastic layer 105c, heat-resistant rubber can be used.

  The release layer 105 d is a layer having a function of preventing toner and paper powder from adhering to the belt 105. As the release layer 105d, a fluororesin such as a PFA resin excellent in releasability and heat resistance can be used. The thickness of the release layer 105d in this embodiment is 20 μm in consideration of heat transfer properties.

(2-3) Configuration and Pressing Method of Pressure Roller The pressure roller 102 is a nip forming member that abuts on the outer peripheral surface of the belt 105 and forms a nip with the belt 105. The pressure roller 102 of this embodiment is a roller member composed of a plurality of layers. More specifically, the pressure roller 102 includes a metal (aluminum or iron) cored bar 102a, an elastic layer 102b formed of silicon rubber or the like, and a release layer 102c that covers the elastic layer 102b. The release layer 102c is a tube made of a fluorine-based resin such as PFA and is bonded onto the elastic layer 102b.

  As shown in FIG. 2B, one end side of the cored bar 102a is rotatably supported by the side plate 107L via a bearing 113. The other end side of the cored bar 102a is rotatably supported by the side plate 107R via a bearing 113. At this time, a portion of the pressure roller 102 having the elastic layer 102b and the release layer 102c is located between the side plate 107L and the side plate 107R.

  The other end of the cored bar 102a is connected to a gear G. When the gear G is driven by a drive motor (not shown), the pressure roller 102 is rotationally driven.

  The fixing unit 101 is supported by the side plate 107L and the side plate 107R so as to be slidable in the direction of approaching and separating from the pressure roller 102. Specifically, the flanges 106L and 106R are provided so as to fit into the guide grooves of the side plate 107L and the side plate 107R. The pressed portions 106c of the flanges 106L and 106R are pressed with a predetermined pressing force T in the direction toward the pressure roller 102 by the pressure springs 108L and 108R supported by the spring support portions 109R and 109L.

  The flanges 106 </ b> L and 106 </ b> R, the pressure stay 104 a, and the heater holder 104 are all urged toward the pressure roller 102 by the pressing force T. Here, in the fixing unit 101, the side having the heater 101 a faces the pressure roller 102. Therefore, the heater 101a presses the belt 105 toward the pressure roller 102. With such a configuration, the belt 105 and the pressure roller 102 are deformed, and a nip portion 101 b is formed between the belt 105 and the pressure roller 102.

  As described above, when the pressure roller 102 rotates while the fixing unit 101 and the pressure roller 102 are in close contact with each other, a rotational torque acts on the belt 105 by the frictional force between the belt 105 and the pressure roller 102 in the nip portion 101b. . The belt 105 rotates following the pressure roller 102 (R105). At this time, the rotation speed of the belt 105 substantially corresponds to the rotation speed of the pressure roller 102. In other words, in this embodiment, the pressure roller 102 has a function as a drive roller that rotationally drives the belt 105. At this time, since the inner circumferential surface of the belt 105 and the heater 101a slide, it is desirable to apply grease to the inner surface of the belt 105 to reduce sliding resistance.

(2-4) Fixing Process Using the above-described configuration, the fixing device 103 performs a fixing process during the image forming process. When performing the fixing process, the control circuit 200 controls a drive motor (not shown) to rotate the pressure roller 102 in the rotation direction R102 (FIG. 4A) at a predetermined speed, and the belt 105 is driven to rotate. Let

  Further, the control circuit 200 starts energizing the heater 101a via a power supply circuit (not shown). The heater 101 a that has generated heat due to this energization applies heat to the sliding belt 105. Thus, the belt 105 to which heat is applied gradually becomes high temperature. The control circuit 200 controls the power supplied to the heater 101a based on a signal output from the thermistor TH so that the temperature of the belt 105 becomes the target temperature TP. The target temperature TP of this embodiment is about 170 ° C.

  When the belt 105 is heated to the target temperature TP, the control circuit 200 controls each component to convey the sheet P carrying the toner image S to the fixing device 103. The sheet P conveyed to the fixing device 103 is nipped and conveyed by the nip portion 101b.

  In the process where the sheet P is nipped and conveyed in the nip portion 101 b, the heat of the heater 101 a is applied via the belt 105. The unfixed toner image S is melted by the heat of the heater 101a and fixed on the sheet P by the pressure applied to the nip portion 101b. The sheet P that has passed through the nip portion 101 b is guided to the discharge roller pair 14 by the guide member 15 and discharged onto the discharge tray 16 by the discharge roller pair 14. In the present embodiment, the above-described process is called a fixing process.

(3) Generation of Dust D Next, generation of ultrafine particles (hereinafter referred to as dust D) caused by a release agent (hereinafter referred to as wax) contained in the toner S and properties of the dust D will be described. .

(3-1) Wax Contained in Toner S As described above, the fixing device 103 fixes the toner image on the sheet by bringing the high-temperature belt 105 into contact with the sheet P. When the fixing process is performed using such a configuration, a part of the toner S may be transferred (attached) to the belt during the fixing process. This is called an offset phenomenon. Since the offset phenomenon causes image defects, it is desirable to solve this.

  In this embodiment, therefore, wax (release agent) is included in the toner S used for forming the toner image. The toner S is configured so that the internal wax dissolves and exudes when heated. Therefore, when a fixing process is performed on the image formed with the toner S, the surface of the belt 105 is covered with the dissolved wax. The belt 105 whose surface is covered with wax makes it difficult for the toner S to adhere due to the releasing action of the wax.

  In this embodiment, in addition to pure wax, a compound containing the molecular structure of wax is called wax. For example, a compound in which a resin molecule of a toner reacts with a wax molecular structure such as a hydrocarbon chain is also referred to as a wax. Moreover, as a mold release agent, you may use the substance which has mold release effects, such as silicone oil, besides wax.

  When the belt 105 is maintained at the target temperature Tp, it is desirable that the wax dissolves instantaneously at the nip portion 101b and exudes from the toner S. In this example, paraffin wax having a melting point Tm of 75 ° C. was used while the target temperature Tp was 170 ° C.

  When the wax melts, some of the wax is vaporized (volatilized). This is considered to be because the size of molecular components contained in the wax varies. That is, the wax contains a low molecular component having a short chain and a low boiling point, and a high molecular component having a long chain and a high boiling point, and it is considered that the low molecular component having a low boiling point is vaporized first.

  When the vaporized (gasified) wax component is cooled in the air, fine particles (dust D) of about several nm to several hundred nm are generated. However, it is assumed that many of the generated fine particles have a particle size of several nm to several tens of nm.

  This dust D is a wax component having adhesiveness and easily adheres to various parts of the internal configuration of the printer 1. For example, when the dust D is carried to the periphery of the guide member 15 and the discharge roller pair 14 due to the rising air flow caused by the heat of the fixing device 103, the wax adheres to the guide member 15 and the discharge roller pair 14 and the volume is fixed. There is a risk that. If the guide member 15 or the discharge roller pair 14 is soiled with wax, the wax adheres to the sheet P and causes image defects.

(3-2) Particles (dust) generated from wax during fixing processing
According to the study by the present inventors, it has been found that most of the dust D described above exists in the vicinity of the sheet entrance (FIG. 4) of the sheet of the fixing device 103. Further, it was found that the dust D has a large particle size and easily adheres to neighboring members when the temperature is high. Details will be described below.

(3-2-1) Dust D Generation Location Next, the dust D generation location will be described with reference to FIG. FIG. 3A is a diagram illustrating a state of the wax adhesion region on the fixing belt that expands as the fixing process proceeds. FIG. 3B is a diagram showing the relationship between the wax adhesion region and the dust D generation region. As a result of verification by the present inventors, it was found that the amount of dust D generated from the fixing device 103 is larger on the upstream side of the nip portion 101b than on the downstream side of the nip portion 101b. The mechanism will be described below.

  Since the surface (release layer 105d) of the belt 105 immediately after passing through the nip portion 101b is deprived of heat by the sheet P, its temperature is lowered to about 100 ° C. On the other hand, the temperature of the inner surface / back surface (base layer 105a) of the belt 105 is kept high by contact with the heater 101a. Therefore, after the belt 105 passes through the nip portion 101b, the heat of the base layer 105a maintained at a high temperature is transmitted to the release layer 105d via the primer layer 105b and the elastic layer 105c. Therefore, the temperature of the surface of the belt 105 (release layer 105d) rises after passing through the nip portion 101b in the process of rotating in the R105 direction (FIG. 3), and reaches a maximum near the inlet side of the nip portion 101b. Reach temperature.

  On the other hand, the wax that exudes from the toner S on the sheet P is present at the interface between the belt 105 and the toner image when the fixing process is performed. Thereafter, a part of the wax adheres to the belt 105. As shown in FIG. 3A, when a part of the front end side of the sheet P passes through the nip portion 101b, the wax transferred from the toner S to the belt 105 exists in the region 135a. In this region, since the temperature of the belt 105 is low and the wax is difficult to volatilize, dust D is hardly generated. As the sheet P advances through the nip portion 101b, the wax is in a state of being present on substantially the entire circumference (135b) of the belt 105. Among these, in the region 135c, since the belt is at a high temperature, the wax tends to volatilize. Then, dust D is generated when the volatilized wax from the region 135c condenses. Therefore, a lot of dust D exists in the vicinity of the region 135c, that is, in the vicinity of the inlet of the nip portion 101b (upstream side).

(4) Method for Collecting Dust D As described above, dust D is likely to be generated in the vicinity of the sheet inlet 400. Therefore, it is desirable for the image forming apparatus to remove the dust D in the vicinity of the sheet entrance 400.

  Based on the properties of the dust D described above, a method for collecting the dust D will be described.

  FIG. 4A is a diagram illustrating the arrangement position of the filter unit. FIG. 5A is an exploded perspective view of the filter unit. FIG. 5B is a diagram showing how the filter unit operates.

(4-1) Configuration of Filter Unit As shown in FIG. 4A, the filter unit 50 is positioned between the fixing unit 101 and the transfer unit 10 in the sheet P conveyance direction. . Alternatively, it is located between the nip portion 101b of the fixing device 103 and the transfer portion 12a of the transfer unit in the conveyance direction of the sheet P.

  The filter unit 50 collects the dust D by inhaling air containing the dust D as shown in FIG. The filter unit 50 includes a filter 51 for collecting the dust D, a fan 61 for sucking air, and a duct 52 for guiding the air so that the air near the sheet inlet 400 passes through the filter 51. ing.

  The fan 61 is an intake portion for sucking air in the vicinity of the seat inlet 400 to the outside of the apparatus. Alternatively, the fan 61 is an exhaust unit that blows air in the duct 52 toward the outside of the machine. The fan 61 is provided in an area outside the sheet P passing area in the longitudinal direction of the fixing unit 101. The fan is provided in a region outside the nip portion 101 b in the longitudinal direction of the fixing unit 101. The fan 61 includes an intake port 61a and an exhaust port 61b, and generates an air flow from the intake port 61a toward the exhaust port 61b. The intake port 61a is connected to the exhaust port 52e of the duct 52 and is an opening for sucking air in the duct 52. The exhaust port 61b is provided toward the outside of the printer 1 and is an opening for discharging the air sucked from the intake port 52a toward the outside of the apparatus. The area of the exhaust port 61b is smaller than the area of the intake port 52a. Therefore, the configuration can be reduced in size.

  A blower fan may be used as the fan 61. The blower fan is characterized by high static pressure, and even if there is a ventilation resistor like the filter 51, a constant air volume (intake volume) can be secured.

  The duct 52 is a guide unit for guiding the air in the vicinity of the sheet inlet 400 toward the outside of the apparatus. The duct 52 includes an intake port 52a in the vicinity of the seat inlet 400 and an exhaust port 52e apart from the vicinity of the seat inlet 400.

  The intake port 52a is an opening located between the nip portion 101b and the secondary transfer roller 12, and is provided to face the nip portion side. With such a configuration, the intake port 52a can receive the dust D carried by the airflow F3 as shown in FIG.

  The exhaust port 52e is provided on the side surface opposite to the intake port 52a among the plurality of side surfaces of the duct 52 outside the intake port 52a in the longitudinal direction. As described above, the exhaust port 52e is connected to the intake port 61a.

  Further, the filter 51 can be attached to the duct 52 so as to cover the intake port 52a. Specifically, the duct 52 includes an edge 52c of the intake port 52a and a rib 52b including a curved portion 52d. When the filter 51 is fixed to the duct 52 so as to be supported by the edge portion 52c and the rib 52b, the air inlet 52a is covered with the filter 51. The filter 51 of this embodiment is adhered to the edge portion 52c and the rib 52b without a gap by a heat-resistant adhesive. Therefore, the air passing through the intake port 52a always passes through the filter 51.

  The arrangement position of the filter 51 is not limited to the intake port 52a. In FIG. 4, the filter 51 may be provided at a position recessed by a predetermined length (for example, 3 mm) in the arrow F4 direction from the intake port 52a. At this time, the length of the filter 51 in the longitudinal direction is equal to or larger than the width of the minimum size sheet P. Further, the longitudinal length of the air inlet 52 a is not less than the longitudinal length of the filter 51. A portion of the duct 52 that satisfies the above-described condition is referred to as the vicinity of the intake port 52a. That is, the filter 51 is provided in the vicinity of the intake port 52a.

(4-1-1) Properties of the filter The filter 51 is a filtering member for filtering (collecting and removing) the dust D from the air passing through the intake port 52a. When collecting the dust D caused by the wax, the filter 51 is preferably an electrostatic nonwoven fabric filter. The electrostatic nonwoven fabric filter is a non-woven fabric formed of fibers that retain static electricity, and can filter dust D with high efficiency.

  The electrostatic nonwoven fabric filter has higher filtration performance as the fiber density is higher, but on the other hand, pressure loss tends to increase. This relationship is the same when the thickness of the electrostatic nonwoven fabric is increased. Moreover, if the charging strength (static strength) of the fiber is increased, the filtration performance can be improved while keeping the pressure loss constant. It is desirable that the thickness and fiber density of the electrostatic nonwoven fabric and the charging strength of the fibers are appropriately set according to the filtration performance required for the filter. The electrostatic non-woven fabric used for the filter 51 of the present embodiment has the fiber density, thickness, and charging strength set so that the ventilation resistance is about 40 Pa and the recovery rate is about 95% when the passing wind speed is 10 cm / s. Has been. When trying to filter the toner in the exhaust air, the electrostatic nonwoven fabric is used with a ventilation resistance of 10 Pa or less at a passing wind speed of 10 cm / s. Therefore, it can be said that the filter 51 of this embodiment uses an electrostatic nonwoven fabric having a relatively large ventilation resistance.

  The electrostatic nonwoven fabric used for the filter 51 desirably has a ventilation resistance of 30 Pa or more and 150 Pa or less at a passing wind speed of 10 cm / s. When the ventilation resistance of the electrostatic nonwoven fabric is larger than 150 Pa, it is difficult for the exhaust fan that can be mounted on the printer 1 to obtain the wind speed required for collecting the dust D. In addition, the wind speed calculated | required for collection | recovery of the dust D is 5 cm / s or more and 70 cm / s or less.

  If the airflow resistance of the electrostatic nonwoven fabric is less than 30 Pa, the air velocity passing through the filter 51 tends to be uneven in the longitudinal direction.

  The higher the wind speed of the air passing through the filter 51, the greater the amount of air per unit time passing through the filter 51. However, the higher the wind speed of the air passing through the filter 51, the lower the temperature of the air in the vicinity of the sheet inlet 400. Therefore, when increasing the recovery efficiency of the dust D, it is desirable that the wind speed of the air passing through the filter 51 is an appropriate speed. Specifically, it is desirable that the wind speed of the air when passing through the filter 51 is 5 cm / s or more and 70 cm / s or less. In the configuration of this embodiment, the recovery rate of dust D in the filter 51 is approximately 100% at a wind speed of 5 cm / s and approximately 70% at a wind speed of 70 cm / s. Therefore, dust D can be recovered with high efficiency at wind speeds in this range. The fan 61 can adjust the wind speed of the air passing through the filter 51 in the range of 5 cm / s to 70 cm / s. The air velocity passing through the filter 51 and the ventilation resistance of the filter 51 were measured with a multi-nozzle fan air flow measuring device F-401 (Tsukubarika Seiki).

(4-1-2) Filter Dimensions As shown in FIG. 2A, the filter 51 has an elongated shape with the direction perpendicular to the sheet conveying direction (the direction along the length of the nip portion 101b) as the longitudinal direction. ing. With such a shape, dust D generated in the vicinity of the nip portion 101b can be reliably collected in a wide range in the longitudinal direction.

  A region indicated by hatching on the sheet P in FIG. 2B indicates a region Wp-max in which image formation is possible when the sheet P having a predetermined width size is used. In practice, an image is formed on the back side of the sheet P visible in FIG. As illustrated in FIG. 2B, the region Wp-max is a region that is equal to or smaller than the width size of the sheet P. In this area, a toner image is formed on the sheet P. In this area, wax adheres to the belt 105, and dust D is generated in this area.

  By the way, the fixing device 103 according to the present exemplary embodiment conveys the sheet P with reference to the center in the width direction of the belt 105. Therefore, in the region Wp-max in the minimum size sheet P that can be introduced into the apparatus, dust D is easily generated regardless of the width size of the sheet P. Therefore, in order to efficiently collect the dust D, it is preferable to reliably collect the dust D at least in this region. Therefore, the dimension Wf of the filter 51 is not less than the width Wp-min of the minimum size sheet P. Further, the dust D can be generated in the region Wp-max in the maximum size sheet P that can be introduced into the apparatus. Therefore, in order to reliably collect the dust D, it is more desirable to collect the dust D in the entire region. Therefore, the dimension Wf of the filter 51 is desirably equal to or larger than the width Wp-max of the maximum size sheet P.

In this embodiment, the maximum usable sheet size is A3 size, and the minimum usable sheet size is a postcard size. The width of the sheet P in the conveyance direction is 297 mm for the A3 size and 100 mm for the postcard size.
The positional relationship among the filter width Wf (intake port 52a), the minimum sheet width Wp-min, the maximum sheet width Wp-maxm, and the nip portion 101b is as shown in FIG. That is, the filter width Wf (intake port 52a), the minimum sheet width Wp-min, the maximum sheet width Wp-maxm, and the nip portion 101b overlap in the longitudinal direction of the nip portion 101b.

  Further, the length of the filter 51 in the short direction is longer than the length of the sheet inlet 400 in the short direction. In the present embodiment, the length of the filter 51 in the short direction is 15 mm. Therefore, the dust D generated in the vicinity of the sheet inlet 400 can be efficiently recovered.

(4-1-3) Arrangement of Filter The filter 51 is arranged in the vicinity of the belt 105 as shown in FIG. The filter 51 is in a positional relationship facing the sheet P entering the fixing device 103. When considering the collection efficiency of dust D, it is desirable that the filter 51 is as close as possible to the nip portion 101b. However, if the filter 51 and the belt 105 are too close to each other, the filter 51 may be thermally deteriorated due to radiation from the belt 105, and the filtration performance may be reduced. Therefore, it is desirable that the filter 51 is disposed at an appropriate distance with respect to the nip portion 101b. Specifically, it is desirable that the nearest distance (shortest distance) between the filter 51 and the belt 105 is 5 mm or more. On the other hand, in order to reliably collect the dust D, it is desirable that the filter 51 is disposed within 100 mm with reference to the nip portion 101b.
Therefore, the nearest distance between the filter 51 and the belt 105 (roller 102) is 5 mm or more and 100 mm or less.

(4-2) Examination In order to confirm the effect of this example, verification was performed using a comparative example.

(4-2-1) Examination of Duct The filter unit 50 draws in air near the seat inlet 400 as described above.
The air sucked into the filter unit 50 is guided to the outside of the printer 1 by the duct 52. Here, the structure of the duct 52 is examined. FIG. 6A is a cross-sectional view taken along the line AA of FIG. 1 showing the configuration of the duct of this embodiment. FIG. 6B is a cross-sectional view taken along the line AA of FIG. 1 showing the configuration of the duct of the comparative example.

  As shown in FIG. 6A, the printer 1 of this embodiment is provided with an exhaust port 61b on the rear side surface (the back side in FIG. 1, the upper side in FIG. 6A). In this configuration, the duct 52 and the main body frame 209 can be connected by slightly extending one end side of the duct 52 and providing the connecting portion 52e. The main body frame 209 is provided with a first fan 61, and the duct 52 is connected to the exhaust port 61b via the first fan. At this time, the filter unit 50 of this embodiment is supported by the main body frame 209 via the connection portion 52e and the support member 211.

  On the other hand, as shown in FIG. 6B, the printer 1 of the comparative example is provided with a fan 61 on the side surface (left side in FIG. 1, left side in FIG. 6B). In this configuration, a connecting portion 52 e that connects the fan 61 and the duct 52 extends in the left-right direction of the printer 1. At this time, the filter unit 50 of the comparative example is supported by the main body frame 209 via the connection portion 52e and the two support members 211. Further, the duct 52 is required to have a tapered shape as shown in FIG. 6B so that air easily flows into the connecting portion 52e. Therefore, the volume of the filter unit 50 of the comparative example corresponds to three times the volume of the filter unit 50 of the present embodiment. If the filter unit 50 is large, the in-machine space of the printer 1 is compressed, and the degree of freedom in designing other configurations is reduced. As the filter unit 50 is larger, the cost of the filter unit 50 increases. As the filter unit 50 is larger, the number of parts increases and the risk of air leakage from the joint increases. Such air leakage may cause image defects.

  Therefore, when the duct 52 extending along the longitudinal direction of the nip portion 101b is provided, the exhaust port 61 is desirably provided on the side surface of the printer on one end side in the longitudinal direction. The printer 1 according to the present embodiment has a front door (not shown) and an operation unit (not shown) on the front side (the front side in FIG. 1 and the lower side in FIG. 6A). It is not preferable to provide the mouth 61b. Therefore, in this embodiment, the exhaust port 61b is provided on the rear side surface side.

  As described above, in this embodiment, one end of the duct 52 in the longitudinal direction and the first fan 61 are connected via the connecting portion 52e. Here, it is desirable that the diameter of the first fan be large in consideration of efficient exhaust with a large air volume, and that the cross section in the short direction of the duct 52 be small in consideration of increasing the suction pressure in the duct 52. . Therefore, it is desirable that the connecting portion 52e has a larger cross-sectional dimension on the first fan 61 side than on the duct 52 side. In addition, it is desirable that the duct 52e and the duct 52 are integrally formed because they can be manufactured at low cost and air leakage is easily prevented.

(4-2-2) Examination of Filter Next, the arrangement configuration of the filter 51 for collecting the dust D will be examined. As described above, the filter unit 50 exhausts air from one end side in the longitudinal direction of the duct 52. In the filter unit 50 having such a configuration, when the air flow in the duct 52 was verified, it was found that the air flow in the duct 52 changes depending on the arrangement position of the filter 51. Fig.7 (a) is a figure which shows the flow of the air in the duct of an Example. FIG.7 (b) is a figure which shows the flow of the air in the duct of a comparative example. In the filter unit 50 of the present embodiment, a filter 51 is provided at an intake port 52 a of a duct 52. On the other hand, the filter 51 is provided in the filter unit 50 and the connection part 52e of the comparative example.

  As shown in FIG. 7A, the filter unit 50 of the present embodiment can uniformly intake air over the entire area of the intake port 52a in the longitudinal direction. On the other hand, as shown in FIG. 7B, in the filter unit 50 of the comparative example, strong intake is performed in the region near the fan 61 in the longitudinal direction of the intake port 52 a, and weak in the region far from the fan 61. Inhalation is taking place. That is, in the filter unit 50 of the comparative example, the intake force is uneven in the longitudinal direction of the intake port 52a.

  The reason why the filter unit 50 of the present embodiment can uniformly intake air is that a filter 51 having a ventilation resistance much larger than the ventilation resistance in the duct 52 is provided at the intake port 52a. As described above, the filter 51 has a characteristic of preventing the passage of air so as to collect the dust D. When exhaust by the fan 61 is performed in a state where the passage of air is blocked by the filter 51, the space between the filter 51 and the fan 61 is in a negative pressure state. When the space between the fan 61 and the filter 51 is in a negative pressure state, the suction pressure acts uniformly on the entire area of the filter 51, so that the air uniformly passes through the entire area of the filter 51. In other words, by arranging the filter 51, which is a ventilation resistor, at the intake port 52a, the entire back region of the filter 51 can be maintained at a constant negative pressure. That is, the negative pressures at the points 53a, 53b, and 53c shown in FIG. 3B are substantially the same value. If the negative pressures at the points 53a, 53b, and 53c are the same level, the wind speed of the air F4 sucked into the filter 51 is uniform over the entire surface of the filter 51. As a result of the uniform wind speed, the filter unit 50 can efficiently collect the dust D generated from the belt 105 (with a minimum air volume). When the amount of intake air by the filter unit 50 is small, the amount of air flowing into the vicinity of the belt 105 is also small. Therefore, the temperature drop of the air near the belt 105 can be reduced. As a result, the generation of dust D can be suppressed, and the recovery efficiency of dust D is also improved. Further, since the temperature drop of the belt 105 can be suppressed, it is advantageous for energy saving.

  On the other hand, the filter unit 50 of the comparative example in which the filter 51 is provided in the connection part 52e can make only a part of the connection part 52e negative pressure. In this configuration, air can be uniformly passed through the entire area of the filter 51, but air cannot be passed uniformly through the intake port 52a. For this reason, the intake air unevenness occurs in the filter unit 50 of the comparative example. In the case of the configuration of the comparative example, the amount of air passing through the end region on the side farther from the fan 61 in the region of the intake port 52a is the amount of air passing through the end region on the side closer to the fan 61 in the region of the intake port 52a. 20%. Therefore, in the configuration of the comparative example, it is difficult to collect the dust D from the end region on the side far from the fan 61 in the region of the intake port 52a. When the air volume of the fan 61 is increased so that dust D can be sufficiently collected in the end region far from the fan 61 in the region of the intake port 52a, the side closer to the fan 61 in the region of the intake port 52a. The air volume at the end region of the slab increases too much. As a result, the belt 105 is locally cooled to cause image defects. Therefore, it is difficult to efficiently collect the dust D when air intake unevenness occurs like the filter unit 50 as in the comparative example.

  According to this embodiment, in the vicinity of the nip portion 101b, air can be sucked in evenly along the longitudinal direction of the nip portion 101b, and the dust D can be recovered efficiently. According to the present embodiment, it is possible to suppress the intake pressure from locally increasing in the vicinity of the nip portion 101 b and to suppress a local temperature decrease of the fixing belt 105. According to the present embodiment, in the vicinity of the nip portion 101b, the air at the end portion in the longitudinal direction of the nip portion 101b can be reliably sucked, and the dust D at the end portion in the longitudinal direction of the nip portion 101b can be reliably collected.

(Other examples)
Although the present invention has been described with reference to the embodiments, the present invention is not limited to the configurations described in the embodiments. Numerical values such as dimensions exemplified in the embodiments are examples, and may be appropriately set within a range where the effects of the present invention can be obtained. Moreover, you may replace the one part structure as described in an Example with the other structure which has the same function in the range with which the effect of this invention is acquired.

  The intake surface 51a of the filter 51 may not have a curved shape. The intake surface 51a has a planar shape and dust D can be collected. As the filter 51, another filter such as a honeycomb filter may be used instead of the nonwoven fabric filter. When an electrostatic filter which is a nonwoven fabric filter subjected to electrostatic processing is used as the filter 51, the dust D may be collected by the filter 51 after being charged by the charging device. The arrangement configuration of the filter 51 is not limited to that described in the embodiment. For example, two or more filters 51 may be installed at both longitudinal ends of the belt 105. The filter 51 may be installed on the pressure roller side with respect to the sheet conveyance path.

  The fixing device 103 is not limited to a configuration that conveys a sheet in a vertical path. For example, the fixing device 103 may be configured to convey a sheet in a horizontal path or obliquely.

  The heating rotator for heating the toner image on the sheet is not limited to the belt 105. The heating rotator may be a roller or a belt unit in which a belt is stretched between a plurality of rollers. . However, the configuration of Example 1 in which the surface of the heating rotator becomes hot and dust D is likely to be generated can achieve a greater effect.

  The nip forming member that forms the nip portion with the heating rotator is not limited to the pressure roller 102. For example, a belt unit in which a belt is stretched between a plurality of rollers may be used.

  The heat source for heating the heating rotator is not limited to a ceramic heater such as the heater 101a. For example, the heating source may be a halogen heater. Further, the heating rotator may be directly heated by electromagnetic induction. Even in such a configuration, dust D is likely to be generated in the vicinity of the sheet entrance 400, and therefore the configuration of the first embodiment can be applied.

  The image forming apparatus described using the printer 1 as an example is not limited to an image forming apparatus that forms a full-color image, and may be an image forming apparatus that forms a monochrome image. In addition, the image forming apparatus can be implemented in various applications such as a copying machine, a FAX, and a multifunction machine having a plurality of these functions in addition to necessary equipment, equipment, and housing structure.

DESCRIPTION OF SYMBOLS 50 Filter unit 51 Filter 52 Duct 52a Inlet 61 Fan 101 Fixing belt unit 101a Heater 101b Nip part 102 Pressure roller 103 Fixing device 105 Fixing belt 400 Sheet inlet 500 Sheet outlet P Sheet S Toner

Claims (9)

An image forming unit that forms an image using toner containing a release agent, a transfer unit that transfers an image formed by the image forming unit to a recording material, and a recording material conveyed from the transfer unit to the nip unit A pair of rotating bodies that are heated by pinching and conveying to fix an image on a recording material;
A duct having an air inlet for sucking air from the vicinity of the pair of rotating bodies and an air outlet for exhausting the air sucked by the air inlet to the outside of the apparatus; A duct provided with the intake port between the nip portions, a filter provided in the duct for collecting fine particles caused by a release agent, and provided in the duct from the intake port toward the exhaust port An image forming apparatus having a fan for generating airflow,
In the longitudinal direction of the nip portion, the duct is provided with the exhaust port in a region outside the longitudinal direction with respect to the nip portion, and on the inner side of both end portions of the nip portion among side surfaces extending along the longitudinal direction. And the fan is provided in a region outside the nip portion, and the filter is provided in a region inside both ends of the nip portion so as to cover the intake port. An image forming apparatus.   The image forming apparatus according to claim 1, wherein an area of the exhaust port is smaller than an area of the intake port.   3. The image forming apparatus according to claim 1, wherein the filter and the air inlet are larger than a width of a recording material of a minimum size that can be introduced into the apparatus in the longitudinal direction.   4. The image forming apparatus according to claim 1, wherein the filter and the air inlet are larger than a width of a recording material of a maximum size that can be introduced into the apparatus in the longitudinal direction.   5. The image forming apparatus according to claim 1, wherein the nearest distance between the filter and the pair of rotating bodies is 5 mm or more and 100 mm or less.   The image forming apparatus according to claim 1, wherein a ventilation resistance of the filter is 30 Pa or more and 150 Pa or less.   The image forming apparatus according to any one of claims 1 to 6, wherein a wind speed of air passing through the filter is 5 cm / s or more and 70 cm / s or less.   The image forming apparatus according to claim 1, wherein the filter is a nonwoven fabric. The image forming apparatus according to claim 1, wherein the duct is provided so that the air inlet port faces the nip portion.

Images