JP2013088517A - Image heating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve image quality and durability by removing cut scratch of a fixing belt by reciprocally operating the fixing belt with an inexpensive configuration.SOLUTION: The image heating device is provided with a cam that performs a reciprocal operation interlocking the pressure release of a fixing device. The integral multiple of a rotation angle made for one operation of the cam is not 360.

Description

  The present invention relates to an image heating apparatus that heats a toner image formed on a recording material by an electrophotographic method capable of forming an image on the recording material such as a multifunction machine, a copying machine, a printer, and a fax machine.

  2. Description of the Related Art Conventionally, in an image forming apparatus using an electrophotographic system or the like, an image heating apparatus that heats an image formed on a recording material with toner at a nip portion formed by an image heating member and a pressure member is used. When the recording material is held in the nip portion, the edge portion of the recording material end is in contact with the image heating member. Further, since the end portion of the recording material becomes a starting point of deflection of the pressure member when the recording material is held, a large pressure is likely to be generated on the surface of the image heating member corresponding to the end portion of the recording material.

  Further, in the case of the image heating apparatus as described above, the heat is taken away by the paper in the paper passing area, whereas the problem of the temperature rise at the end that becomes very high in the non-paper passing area as compared with the paper passing area is caused. is there. A temperature difference occurs in the longitudinal direction of the image heating member due to the temperature rise at the edge, and the PTFE on the surface of the image heating member or the pressure member at the edge portion (paper edge portion) of the recording material due to the difference in the conveyance speed due to this temperature difference, There is a problem that a coating layer of fluororesin such as PFA is worn and the surface of the image heating member or the pressure member is likely to be scratched (this scratch is hereinafter referred to as a paper edge scratch).

  When a wide recording material is passed such that the position of the scratch is within the print area in the state where the scratch has occurred, unevenness due to a small scratch formed on the surface of the image heating member or the pressure member during image heating is generated. It is transferred to the toner on the recording material and the image quality is degraded. Further, when the edge flaw progresses, a small amount of offset toner or paper dust accumulates on the flawed part, and if a certain amount or more accumulates, it can adhere to the surface of the recording material and cause the image to become dirty. In addition, this scratch can be a starting point of destruction of the rubber layer of the image heating member or the pressure member. This paper edge scratch is a problem to be solved in order to extend the life of the image heating apparatus.

  In order to solve these problems in the image heating apparatus, according to Patent Document 1, the front and rear side plates that rotatably support the fixing roller and the pressure roller by rotating the cam reciprocate in the longitudinal direction of the roller ( Reciprocating).

JP 2000-194216 A

  When a reciprocating mechanism that returns to the same position as the cam makes a round is employed, the following problems occur. That is, in a configuration in which the reciprocating operation is performed by rotating the cam at a predetermined angle at each predetermined timing, when the rotation angle of the cam for one round is a divisor of 360 ° for one round, the stop position after the reciprocating operation Are often the same, which hinders the longevity of the image heating apparatus.

  Therefore, an object of the present invention is to reduce the frequency at which the stop position after the reciprocating operation becomes the same even when the reciprocating operation is performed by continuously rotating the cam at a preset angle.

  Therefore, the present invention provides a rotatable image heating member that heats a toner image formed on a recording material, a pressure member that presses the image heating member and forms a nip portion that sandwiches and conveys the recording material, and a cam. And a reciprocating mechanism that reciprocates the image heating member and the pressure member forming the nip portion by rotating the cam at a preset setting angle in the rotation axis direction of the image heating member, In the image heating apparatus having the rotation mechanism that rotates the cam so that the rotation angle of the cam becomes a preset setting angle for each set reciprocating operation, the value of the setting angle is smaller than 360, The integer multiple of the set angle is a value that does not become 360.

  According to the present invention, even if the reciprocating operation is performed by continuously rotating the cam at a preset angle, the service life of the image heating apparatus is increased by reducing the frequency at which the stop position after the reciprocating operation becomes the same. Can be achieved.

Schematic of the image forming apparatus according to the present embodiment Schematic of the fixing device according to the present embodiment Schematic of the pressure release mechanism according to this embodiment Schematic of the pressure release mechanism according to this embodiment Diagram of recording material being passed through the fixing device Schematic of the pressure release mechanism according to this embodiment Schematic of reciprocating operation according to the present invention Diagram showing reciprocating cam profile

Example 1
Below, based on an embodiment, the present invention is explained in detail using a drawing.
FIG. 1 shows a configuration of an apparatus main body 100 of an image forming apparatus that forms an image on a recording material using toner, and a fixing device that applies heat and pressure to a toner image transferred onto the recording material S (fixing processing) Image heating device). However, although a full-color image forming apparatus using an intermediate transfer belt is illustrated as a specific example of the image forming apparatus, the image forming apparatus is not limited to the configuration.

  In this embodiment, as shown in FIG. 1, in the apparatus main body 100, image forming units 200Y, 200M, 200C, and 200K corresponding to the four color toner image formation are arranged in series. Then, a tandem method is employed in which processes until a visible image is processed in parallel for each color. In this embodiment, except for the color of the toner, the image forming configuration for forming a toner image on the photoconductor 20 whose image forming unit is an image carrier is common, so that the yellow image forming unit 200Y is representative. A configuration for forming a toner image on the photoreceptor will be described.

  The surface of the photoreceptor 20Y, which is an image carrier, is uniformly charged by the charging device 21Y so as to have a predetermined potential. Thereafter, the surface of the photoreceptor 20Y is exposed by the exposure device 22Y, whereby an electrostatic latent image is formed on the photoreceptor 20Y. Then, the electrostatic latent image on the photoreceptor 20Y is developed by using the developer by the developing device 23Y, and a toner image is formed. The toner image on the photoreceptor 20Y developed by the developing device 23Y is transferred to the intermediate transfer belt 25 by an endless belt by the primary transfer device 24Y.

  The toner images formed on the respective photoconductors by the same processes as described above in the respective image forming units are similarly transferred to the intermediate transfer belt 25 in a superimposed manner, so that the color toner is transferred onto the intermediate transfer belt 25. An image is formed. Then, the color toner image on the intermediate transfer body 25 on which all colors have been primary-transferred is collectively transferred onto the recording material S by the secondary transfer device 26. The recording material S is conveyed to the secondary transfer device 26 by a paper feeding device. The recording material S carrying an unfixed toner image is conveyed to the fixing device 27 according to this embodiment of the belt system. In the fixing device 27, the toner image on the recording material S is fixed on the recording material S by heating and pressing at the fixing nip portion. Then, the recording material S after fixing is discharged to the discharge tray 28. When an image is formed on the back surface side, the recording material is reversed by the recording material reversing path 29, and then the image is formed on the back surface side by the secondary transfer unit again by the image forming process similar to the above through the duplex conveying path 30. Is formed.

Next, the configuration of the fixing device 27 will be described with reference to FIGS.
Reference numeral 300 denotes a ceramic heater (hereinafter referred to as a heater) as a heating means. The heater 300 is provided with a resistor layer that generates heat when energized on a planar ceramic substrate, and a protective layer is provided on the resistor layer.

  Reference numeral 301 denotes a heater holder as a support member for fixing and supporting the heater 300. The heater holder 301 is a heat insulating member such as a heat resistant resin having a substantially semicircular arc shape in cross section. The heater 300 is fitted on the lower surface of the heater holder 301 along the longitudinal direction (the width direction of the recording material orthogonal to the recording material conveyance direction) with the heater surface side exposed downward to fit into the groove. It is fixed and arranged with an agent or the like.

  Reference numeral 302 denotes a heat-resistant fixing belt as a rotatable image heating member that heats the toner image on the recording material, and is loosely fitted to the heater holder 301 including the heater 300 described above. In order to reduce the heat capacity and improve the quick start property, the fixing belt 302 is a metal layer made of SUS or Ni having a thickness of 100 μm or less, preferably about 20 to 50 μm, as a base layer of the belt. An elastic layer made of a heat-resistant rubber such as silicon rubber or fluorine rubber or a foam of silicon rubber is overlaid on the outer peripheral surface of the metal layer. Furthermore, the surface layer is a composite layer belt coated with a release layer of PTFE, PFA or the like of about 5 to 50 μm. In addition, a protective layer made of polyimide having a thickness of about several μm is provided on the inner surface of the base layer to reduce friction between the heater 300 and the metal layer of the fixing belt 302. Reference numeral 303 denotes a stay disposed inside the support member 301 and supports the heater holder 301.

  Reference numeral 304 denotes a pressure roll as a pressure member for forming a fixing nip portion for nipping and conveying the fixing belt 302 and the recording material. The pressure roll is composed of a cored bar 304b, an elastic layer 304a made of heat-resistant rubber such as silicon rubber or fluorine rubber, and a release layer such as PTFE or PFA. The pressure roll 304 is disposed by rotatably supporting both ends of the cored bar 304b on both side plates 400.

  The assembly of the heater 300, the heater holder 301, the fixing belt 302, and the stay 303 is arranged above the pressure roll 304 in parallel with the pressure roll 304 with the heater 300 side facing downward. The stay 303 is pressed downward by a pressurizing variable mechanism 500 to be described later, whereby the pressure roller 304 is pressed against the lower surface of the heater 300 via the fixing belt 302 to form a fixing nip portion.

  Reference numerals 305 a and 305 b denote flange members that are fitted and disposed on the front and back ends of the cylindrical heater holder 301. The heater holder 301 of the fixing belt 302 receives the end of the inner peripheral surface of the fixing belt 302. It plays a role of regulating the movement along the length of the.

  The flanges 305 engage with the front and rear side plates 400 of the fixing device, respectively, and can move in the vertical direction.

  Reference numeral 306 denotes a separation guide, which is separated from the fixing belt 302 by a certain distance (gap) so that the discharged paper is not wound around the fixing belt 302 and does not touch the fixing belt 302 and damage the fixing belt 302. ) And disposed downstream in the transport direction. The separation guide 306 engages with a part of the flange 305 and is fixed by a biasing member such as a spring.

  Energization of the heater 300 is controlled by a CPU that is an energization control unit so that a temperature detected by a thermistor that is a temperature detection member (not shown) becomes a preset temperature.

  The pressurizing variable mechanism 500 will be described with reference to FIG. In this embodiment, a configuration using a pressure cam 501 is employed. The variable pressure mechanism 500 includes a pressure cam 501, a pressure plate rotation shaft 502, a pressure cam rotation shaft 504, a pressure plate 505, a pressure adjustment screw 506, a pressure support plate 507, and a pressure spring 508. ing.

  The pressure plate 505 and the pressure support plate 507 are supported by a pressure plate rotation shaft 502, and the pressure plate 505 can move freely with respect to the pressure support plate 507. The pressure support plate 507 is supported on the side plate 400 by a pressure support plate rotation shaft 503, and a tip 507 a portion provided at the tip of the pressure support plate 507 is a means such as a screw with respect to the side plate 400. It is fixed with.

  A pressure adjustment screw 506 is fastened to the pressure support plate 507. By tightening the pressure adjustment screw 506, the seat surface of the pressure adjustment screw 506 shortens the spring length of the pressure spring 508, and The applied spring load can be increased. Since the pressure plate 505 is rotatably supported with respect to the pressure support plate 507 as described above, a moment is generated around the pressure plate rotation shaft 502 by the compression force of the pressure spring 508.

  Since the pressure plate 505 is disposed so as to contact the flange 305, the flange 305 is pushed toward the pressure roller 304 by a moment generated in the pressure plate 505, and a fixing nip is formed between the pressure roller 304 and the fixing belt 302. Will be formed.

  When releasing the applied pressure, the pressure cam 501 having a predetermined eccentric amount rotates to push up the pressure plate 505 and rotate the pressure plate 505 until the contact between the pressure plate 505 and the flange 305 is released. The pressure is released. A driving source M is provided outside the pressurizing cam 501, and the CPU, which is a control unit, operates the driving source (motor) to rotate the pressurizing cam rotating shaft 504, thereby releasing the pressure. Usually, the applied pressure is set to 300 N, for example. In FIG. 3, the fixing device is described with reference to the back side direction when set in the image forming apparatus. As shown in FIG. 4, there is the same mechanism on the front side, and the driving force is transmitted from the driving source M to the pressure cam rotating shaft 504 and rotated, whereby the front pressure cam is rotated at the same time. The pressure can be released.

  When the printing operation is started by the operation described above, the toner T transferred to the recording material P passes through the nip portion formed between the fixing belt 302 and the pressure roll 304 maintained at a predetermined temperature. As a result, the toner T is fixed to the recording material P. Then, the recording material passes through the lower surface of the separation guide 306 and is discharged. When the printing operation is completed, the pressure release state is maintained by the pressurizing variable means 500.

  FIG. 5 shows a state of the fixing device during the printing operation. During printing, a fixing nip is formed between the fixing belt 302 and the pressure roll 304 by the variable pressure mechanism 500, and the fixing process is completed when the recording material passes through the fixing nip portion. Here, there are minute burrs formed at the end of the recording material when the recording material is cut, and the burrs cause minute scratches on the surface of the fixing belt 302 corresponding to the end of the recording material during the fixing process. . In addition, when the same size recording material is continuously fixed, the surface of the fixing belt 302 on the portion of the fixing belt 302 where the recording material passes (sheet passing portion) and where the recording material does not pass (non-sheet passing portion). A temperature difference will occur. This is because the heat of the fixing belt 302 is used for fixing the toner in the paper passing portion, and the heat of the fixing belt 302 is not used in the non-paper passing portion. Due to this temperature difference, the surface speed in the non-sheet passing area of the fixing belt becomes relatively higher than that in the sheet passing area. As a result, a minute slip is generated in the end region of the recording material, and minute irregularities are formed on the surface of the fixing belt 302 (the fixing belt surface scratches due to these recording material end portions are hereinafter referred to as edge scratches). It can be a cause.

  As means for reducing the edge scratches, a method of reducing the edge scratches by reciprocating the entire fixing device with respect to the recording material as described in the prior art and shifting the recording material end passage position relative to the fixing belt and the fixing roller. There is.

  Therefore, the present invention provides an apparatus that effectively reduces edge scratches with a simple configuration. A fixing device to which the present invention is applied will be described with reference to FIGS.

  As shown in FIG. 6, in the present invention, a reciprocating mechanism 600 is provided on the opposite side of the pressure plate rotation shaft 502 from the pressure spring 508. The reciprocating mechanism 600 according to the present embodiment moves the fixing belt in the width direction of the fixing belt corresponding to the rotation axis direction of the image heating member. The reciprocating mechanism 600 includes a swing member 601, a gear 602, and a reciprocating cam member 603. The swing member 601 is provided with a protrusion 601 a on a part of its circumference, and a part of the swing member 601 protrudes from the end of the pressure plate 505.

  When the pressure is released, the pressure cam 501 rotates to rotate the pressure plate 505 around the pressure plate rotation shaft 502 in the counterclockwise direction shown in the drawing. Then, the protruding shape provided at the end of the pressure plate 505 contacts the protrusion 601a of the swing member 601 and the swing member 601 rotates in the direction of the arrow in the figure.

  A one-way clutch is disposed inside the swing member 601, and a rotational force is transmitted to the shaft 604 by the clockwise rotation of the swing member 601.

  The gear 602 is fitted coaxially with the shaft 601, and as a result, the gear 602 is rotated by the rotation of the swing member 601.

  The driving force by the gear 602 is connected by a gear or the like and finally rotates the reciprocating cam 603. As shown in FIG. 7, the reciprocating cam 603 has a groove shape 603a on its cylindrical surface. Further, the groove 603a is cut into a shape that is displaced in the axial direction of the cam as it rotates in the circumferential direction, that is, a V-shape. The V-shaped groove is shaped so as to return to the same position around the reciprocating cam 603. For example, it is designed to reciprocate in the range of 3 mm in one round. That is, when the rotation angle reaches 360 °, it returns to the same position for the first time.

  A protrusion 605 is fitted in the groove 603a. When the reciprocating cam 603 rotates, the protrusion 605 fitted in the groove 603a moves in the axial direction of the reciprocating cam 603 along the groove 603a. The protrusion 605 is formed from a part of the flange fitting member 606. Further, the flange fitting member 606 is fitted so that the flange 305 can move in the vertical direction and is fixed in the front-rear direction of the fixing device. This is because the side plate 400 and the reciprocating shaft 410 are integrated, and the flange fitting member 606 is fixed by the reciprocating shaft 410 so as to be movable in the front-rear direction. For this reason, when the reciprocating cam 603 rotates, the flange fitting member 606 moves in the front-rear direction of the fixing device, and as a result, the flange 305 can move in the front-rear direction of the fixing device. Since the position in the longitudinal direction of the fixing belt 302 is determined by contacting the flange 305, the position in the longitudinal direction of the fixing belt 302 can be changed by moving the flange 305.

  When pressure is applied again to the fixing device, the pressure cam 501 rotates and the pressure plate 505 returns to the position of the pressure state. At this time, the swinging member 601 also returns to the pressurized state. This is because one end of the spring 607 is hooked on the swing member 601. Further, since the one-way clutch inside the swing member 601 transmits the rotation in only one direction, the shaft 604 is not rotated when the swing member 601 returns to the pressurized state.

  By the operation described above, it is possible to reciprocate the fixing belt 302 in the longitudinal direction without the need for a special drive source in the reciprocating operation interlocked with the pressure release of the fixing device.

  In this embodiment, the rotation angle of the reciprocating cam 603 is set so that an integral multiple of the set angle does not become 360. The rotation angle of each reciprocating cam is set to 10.5 °. That is, the rotation angle of the reciprocating cam that operates when releasing pressure once is 10.5 °. By this setting, the interval until the reciprocating cam 604 at the time of pressure release becomes the same phase can be lengthened. As a result, the interval until the reciprocating cam 604 becomes the same phase can be increased even if the frequency of the reciprocating operation at different set angles is changed to a very low frequency in order to change the phase. As a result, the interval until the position of the fixing belt 302 in the longitudinal direction becomes the same can be lengthened, and a phenomenon that a specific position of the fixing belt 302 easily overlaps the end of the recording material can be prevented. . On the other hand, for example, as shown in FIG. 8, when the rotation angle of the reciprocating cam 604 is 90 °, the pressure returns to the original phase when the pressure is released twice. It will end up. In order to avoid this, the frequency of performing the reciprocating operation at different set angles increases, and there arises a problem that the control of the reciprocating operation becomes complicated.

  In the present embodiment, the set angle is such that an integral multiple of the number obtained by rounding down the second decimal place is not 360. The set angle in this embodiment is 10.5 °, but in the case of 10.52 °, the second decimal place is rounded down to determine whether an integer multiple of 10.5 is 360. And

  When the rotation angle has a movement error, at least the set angle is a center value. In this embodiment, the set angle corresponds to 10.5 °, and the pulse width of the motor is determined so as to be this operating angle, so the movement error is ± 0.1 °. As a result, the movement angle is 10.5 ° ± 0.1 °. In this embodiment, the set angle is set in consideration of the movement error so that an integral multiple of any angle obtained by rounding down the second decimal place including the movement error does not become 360.

  In this embodiment, the set angle is set for the configuration in which the reciprocating cam is operated when the pressure is released. However, the present invention is not limited to this reciprocating mechanism. For example, even if the reciprocating motor is rotated by a reciprocating motor at predetermined intervals and employed in a rotating mechanism that performs a reciprocating operation, the setting angle that moves for each reciprocating operation of the present invention is set. The same effect can be obtained. At that time, the rotation amount of the motor is controlled by the control unit (CPU) so that the cam rotates at the set angle.

  As described above, according to the present invention, even if the reciprocating operation is performed by continuing to rotate the cam at a preset angle, the frequency at which the stop position after the reciprocating operation becomes the same can be reduced. The life of the heating device can be extended.

27 Fixing Device 302 Fixing Belt 400 Side Plate 410 Reciprocating Shaft 500 Pressurizing Variable Meaning 501 Pressure Cam 502 Pressure Plate Turning Shaft 504 Pressure Cam Turning Shaft 505 Pressure Plate 506 Pressure Adjustment Screw 507 Pressure Support Plate 508 Pressure Spring 600 Reciprocating mechanism 601 Swing member 602 Gear 603 Reciprocating cam 604 Shaft 605 Projection

Claims (2)

A rotatable image heating member that heats a toner image formed on a recording material, a pressure member that presses the image heating member and forms a nip portion that sandwiches and conveys the recording material, and a cam. A reciprocating mechanism that reciprocates the image heating member and the pressure member that form the nip portion by rotating at a set angle in the rotation axis direction of the image heating member, and for each preset reciprocating operation. In an image heating apparatus having a rotation mechanism that rotates the cam so that the rotation angle of the cam becomes a preset setting angle,
The value of the set angle is a value smaller than 360, and an integer multiple of the set angle is a value that does not become 360.   2. The image heating apparatus according to claim 1, wherein the value of the set angle is 360 times an integer multiple of the value of the set angle, rounded down to the second decimal place.

Images