JP5049575B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as a printer, a copying machine, and a facsimile.

  Actuator elements are generally called artificial muscles by distinguishing actuators that deform such as expansion and contraction from ordinary motors and solenoids. Currently, the actuator element includes a rubber system (pneumatic drive) and an electrochemical system (polymer system). In addition, there is a metal type using a shape memory alloy called Biometal (registered trademark) as a raw material. Since it is a metal actuator that moves softly and quietly like a living organism, a thin thread-like actuator is commercially available.

  Patent Document 1 (Japanese Patent Application Laid-Open No. 2004-282992) discloses a light-weight soft polymer actuator as an electrochemical system (polymer system) known as an actuator element. In addition, similar sheet-like actuator elements have been studied in various directions.

  There is a composite sheet-like actuator element in which the displacement performance is greatly improved by forming gold as an electrode on an ion exchange resin by special chemical plating and greatly increasing the electrode surface area. The sheet-like actuator element has a feature that moves rapidly and greatly by applying a voltage. Furthermore, the operation of the sheet-like actuator element can be electrically controlled, the material is flexible, and the structure is made of resin and is lightweight. Further, there is no operation sound such as noise during driving, and the shape and size can be determined relatively arbitrarily. Furthermore, the plate thickness can be manufactured from 0.1mm to 10mm, operates at low power (0.05-0.2W), generates electromotive force with the deformation of the element, and can be used as a displacement sensor. There is also. Compared to conventional electric motors, cylinder solenoids, and the like, it is easier to reduce the size and weight, so it is known as an alternative.

  The front and back surfaces of the ion-conducting actuator are made of plastic having electrode plate layers and containing a hydrated polymer electrolyte inside the electrode plates. The operating principle of the ion conduction actuator is that when positive and negative voltages are applied to the electrodes on the front and back surfaces, the cations in the polymer move to the cathode side with moisture, and the water content is biased. This causes a difference in expansion between the front and back surfaces, resulting in deformation. When a voltage is applied, the actuator plate is deformed into a curved shape.

  The conductive polymer actuator of Emex Co. is an actuator using a flexible and tough polypyrrole film, and expands and contracts when a voltage is applied in the longitudinal direction of the strip film. There is also a composite conductive polymer actuator in which a polypyrrole film is formed on the surface of a metal coil. When this actuator element is used, it can be operated by applying a voltage to the element, and both expansion and contraction pushing and pulling can be performed by applying plus and minus.

  There is a sample that generates a differential force with a stretching stroke of 1.3 mm and a gf of 25 gf, in which a fibrous one is a coil having an outer diameter of Φ0.25 mm and a length of 15 mm.

  As a fiber in which the differential force is increased by bundling the fibers, a sample with 10 fibers and a coil outer diameter of Φ1 mm and a length of 20 mm has a stroke of 1.7 mm and a differential force of 230 gf.

  Patent Document 2 (Japanese Patent Laid-Open No. 2003-22547) discloses a Ni-Ti-based shape memory alloy actuator as a metal-based material known as an actuator element.

In addition, Toki Corporation's Biometal Fiber (registered trademark), known as a metal actuator element, utilizes the property of expanding and contracting due to the action of ions inside the metal when electric energy is applied to the wire-like metal. is there. It is an artificial muscle type fibrous actuator (driving device) that can be contracted and relaxed and stretched by itself like a muscle. It is characterized by soft and quiet movement like a living thing, usually flexible and supple like a nylon thread, but it generates heat and contracts when an electric current is applied, and it is hard and stiff like a piano wire. The exercise that contracts. Biometal fiber (registered trademark) can be moved by a temperature change caused by external heating. It contracts when heated to 70 ° C. and stretches when cooled. Biometal Fiber (registered trademark) exhibits excellent durability and operating characteristics because it is structurally stable. Because it can produce a large force even if it is thin, it is ideal for millimeter and micro size actuators.

  Biometal (registered trademark), as shown in Patent Document 3 (Japanese Patent Publication No. 6-15154), can use Ti-Ni-based shape memory alloy as a raw material and draw out excellent stretch properties in the fiber longitudinal direction. Thus, the fibrous actuator is anisotropically structured. Since it is organized in the fiber direction, it exhibits a huge and stable self-stretching property, and in a predetermined operating range, a change in the inside of the material hardly occurs and is in an extremely stable state.

  Here, there is a transfer roller used as means for transferring an unfixed toner image onto a sheet used in an image forming process of the image forming apparatus.

  The transfer roller is defined by a material such as conductive rubber formed in a cylindrical shape around the shaft between the longitudinal bearings or urethane foam with conductivity, for a metal shaft supported at both ends by a bearing. The desired resistance value is set.

  A part of the outer periphery of the transfer roller is urged against the image bearing member by a repulsive action of a pressure spring to form a nip portion.

The charged toner of the image carrier is attracted toward the transfer roller so that the toner image is transferred onto the paper passing through the nip portion.
JP 2004-282929 A Japanese Patent Laid-Open No. 2003-22547 Japanese Patent Publication No. 6-15154

  The transfer roller is pressed against the image carrier with a light pressure. If the transfer roller made of a sponge-like foam material is energized for a long time and the nip is kept, the outer diameter of the transfer roller will be semi-permanently distorted. The applied pressure deforms in accordance with the outer diameter of the photosensitive drum as an image carrier. As a result, the resistance value at the nip changes, and the transfer characteristics change, thereby causing unevenness in the image of the transfer roller in the transferred image.

  As a countermeasure, the amount of deformation is reduced by reducing the biasing force on the image carrier. The biasing force is about 0.5N to 2.5N. However, the paper used in the image forming apparatus has different stiffness, and if the transfer pressure is lightened, the adhesiveness of the nip portion becomes unstable, causing problems. For example, there are problems such as an image with poor transfer or a thick character in the image, in which a toner image in the character outline portion is not transferred and a void is formed as an image.

Further, depending on the elastic force of the paper and the curl situation, there is a problem that the transfer roller vibrates and an image blur is generated due to the influence of the vibration. For example, there has been a problem that an image blur due to an image failure occurs due to a rush shock when the paper enters the nip portion or a paper rear end shock when the paper passes such as a paper conveyance guide.

  As described above, reducing the nip pressure to prevent deformation of the transfer roller can not sufficiently solve the problem caused by the nip mark, and is unavoidably present within the allowable range of image quality while minimizing the nip pressure. The pressure has been adjusted to barely fasten.

  On the other hand, there are some which are provided with a pressure releasing means for releasing the pressure so that the nip portion is separated in the shipping state. However, there is also a problem that it takes time and effort to remove the pressure release member during use or installation. Further, there is a mechanism that uses a link mechanism as a mechanical pressure releasing means, but the weight of the link mechanism has an influence on the transfer pressure and is likely to become unstable, so there is a need for further improvement.

  Further, a fixing device is used in the image forming apparatus. The fixing device forms a nip on the paper conveyance path by a heating roller containing a heater inside the frame and a pair of pressure rollers arranged in parallel to the heating roller, and passes the unfixed toner transfer paper on the paper on the paper. The toner image is fixed to the toner image.

  The fixing method is performed by heating with a heater and pressing with a nip pressure. In the case of a jam or the like, the nip pressure is released so that the paper on the nip can be removed.

  However, normally, the pressure roller always remains pressurized, and the nip pressure causes distortion of the pressure roller, which is an elastic body, and the roundness of the pressure roller is significantly reduced, which adversely affects the image. It was known that nip marks would occur.

  An object of the present invention is to provide an image forming apparatus that prevents a roundness of a transfer roller or the like from being lowered.

In order to achieve the above object, the present invention provides a transfer roller, a photosensitive drum facing the transfer roller, a pressurizing unit that pressurizes the transfer roller against the photosensitive drum, and a nip pressure in a nip formed by the pressurization. In the image forming apparatus having pressure release means for releasing the pressure, the pressure means is a spring that biases a bearing that pivotally supports a longitudinal end portion of the transfer roller in the direction of the photosensitive drum, and the pressure release The means has an actuator element that deforms when energized or when deenergized from the energized state, and when the actuator element changes from energized to deenergized, by deforming, against the biasing force of the spring moving the bearing in the opposite direction to biasing spring, characterized that you separate the said photosensitive drum and the transfer roller To.

The present invention also provides an image forming unit for transferring a toner image to a sheet material, a fixing unit having a heater, a pressure rotating body facing the fixing unit, and pressurizing the fixing unit to the pressure rotating body. A pressure release means, and a pressure release means for releasing the nip pressure at the nip between the fixing means and the pressure means, formed by the pressure of the pressure means. In an image forming apparatus that fixes an image on a sheet material and forms an image on the sheet material, the pressure release unit includes an actuator element that deforms when energized or when de-energized from an energized state. When the actuator is de-energized, the actuator element is deformed so as to resist the pressure applied by the pressurizing means and releases the pressurization at the nip by the pressurizing means.
The present invention also provides a first rotating body, a second rotating body facing the first rotating body, a pressurizing unit that pressurizes the second rotating body against the first rotating body, and the pressurizing unit. An image forming apparatus comprising: a pressure release unit that releases pressure; and the pressure release unit includes an actuator element that is deformed when energized or when de-energized from an energized state. if it becomes non-energized from the state of being energized, the actuator element is deformed so that is separated and the said first rotary member and Koko the pressure second rotor of said pressure means When the pressure applied by the pressurizing unit is released and the actuator element is energized, the actuator element is deformed so that the pressurizing unit pressurizes the second rotating body.

  It is possible to prevent a decrease in roundness of the transfer roller or the like.

  Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of the components described in this embodiment are not intended to limit the scope of the present invention only to those unless otherwise specified. .

<Image forming apparatus>
FIG. 1 is a sectional view of an image forming apparatus according to the present invention. As shown in FIG. 1, the image forming apparatus main body 900 includes a document placing table 906, a light source 907, a reading element (CIS: contact image sensor) 908, a paper feeding unit 909, an image forming unit 902, and the like.

  The sheet feeding unit 909 includes cassettes (storage containers) 910 and 911 that store the sheet material S and are detachable from the apparatus main body 900. Each cassette 910 and 911 includes a sheet feeding roller (sheet feeding unit). Are arranged respectively.

  The image forming unit 902 includes a cylindrical photosensitive drum 914 as a first rotating body, a developing unit 915, a transfer charging unit 916 as a second rotating body, a separation charging unit 917, a cleaner 918, and a primary charging unit 919. Etc. are arranged respectively. A conveyance guide 920, a fixing device 904, a discharge roller 905, and the like are disposed on the downstream side of the image forming unit 902.

  Next, the operation of this image forming apparatus will be described.

  When a paper feed signal is output from a control device (not shown) provided in the apparatus main body 900, light is applied from the light source 907 to the document D placed on the document placement table 906. The light reflected from the document D is replaced with an electric image signal via a reading element (CIS: contact image sensor) 908. The electric image signal is transmitted to the laser scanner device 921 and irradiated to the photosensitive drum 914 from the laser light emitting element (not shown) via the polygon mirror 922 and the lenses 923 and 924. The photosensitive drum 914 is charged in advance by a primary charger 919, and an electrostatic latent image is formed by light irradiation. The electrostatic latent image is developed by a developing device 915 and visualized as a toner image. The

  On the other hand, the sheet material S fed from the sheet feeding unit 909 is corrected for skew by the registration rollers 810, and further sent to the image forming unit 902 at the same timing. In the image forming unit 902, the toner image on the photosensitive drum 914 is transferred to the sheet material S by the transfer charger 916, and the sheet material S that has received the transfer of the toner image is reversed in polarity from the transfer charger 916 by the separation charger 917. It is charged and separated from the photosensitive drum 914.

  As described above, the sheet material S separated from the photosensitive drum 914 is conveyed to the fixing device 904 by the conveyance guide 920, and the unfixed transfer image is permanently fixed to the sheet material S by pressurization and heating in the fixing device 904. Then, the sheet material S on which the image is fixed is discharged from the apparatus main body 900 by a discharge roller 905.

(First embodiment)
FIG. 2 is a perspective view showing a partial schematic view of the image forming apparatus using the actuator element according to the first embodiment of the present invention. FIG. 3A is a side view of a partial schematic view of an image forming apparatus using an actuator element, and FIG. 3B is a front view thereof.

2 and 3, the photosensitive drum 914 shown in FIG. 1 and a transfer roller 916 which is the transfer charger shown in FIG. 1 arranged in parallel with the photosensitive drum 914 are provided.

  The photosensitive drum 914 has a photosensitive layer formed on the surface of a cylindrical drum. Further, the drum gear 1 is integrally fitted at one end. The other end is fitted with a drum flange 2 which is held by a process cartridge or the like so as to rotate. A rotational force is given by a gear train or the like from a shaft support drive source (not shown), and it rotates while maintaining a process speed that is a rotational speed necessary for image formation by electrical control by a controller or a driver as control means.

  On the other hand, the transfer roller 916, which is a transfer charger, is formed by winding a conductive sponge or solid molded rubber in the substantially central longitudinal direction of the shaft 6 so as to have a specified appropriate resistance value. It is formed with high precision so as to be concentric with the shaft 6.

  The bearings 12 and 14 provided by holding means extending from the frame body 5 in the vicinity of both ends are fitted, and at least one of the bearings is provided with a conductive bearing provided with conductivity. Yes.

  The bearing holding means is guided by a bearing guide 7 extended from a resin frame 5 fixed to the apparatus so that the bearings 12 and 14 molded of a plastic material are slid, and can move in the normal direction of the photosensitive drum. Slide. Further, the bearings 12 and 14 are provided with a bearing snap fit 14b and a bearing snap fit 14c, which are respectively stopped by a snap fit 8 and a snap fit 15 extending from the frame 5 to function as a stopper to prevent the bearing 12 and 14 from coming off. It has become.

  A spring 18 is provided between the bearings 12 and 14 and the frame 5, and a compression spring is fitted so as to urge the bearings 12 and 14 in the direction of the photosensitive drum 914.

  As a result, the transfer roller 916 is pressed against the photosensitive drum 914 with a spring force, and the nip 20 is formed by the elasticity of the transfer roller 916.

  When the image forming apparatus is in use, the sheet is conveyed from the sheet feeding means to the nip 20 and transferred with a bias voltage so that the toner image on the photosensitive drum is transferred to the sheet when passing through the nip portion. Therefore, an electric current flows from the roller surface of the transfer roller 916 to the shaft 6, further flows from the shaft to the spring 18 through the conductive bearings 12 and 14, and passes through the conductive plate 11 made of a metal plate to the terminal 19. Are connected to a high voltage power source.

  When image formation is not performed, if a spring pressure is always applied in the nip 20, especially in the case of a sponge roller, the outer shape of the photosensitive drum 914 is deformed. In the past, materials such as foamed urethane with strong elasticity were used to minimize the effect. If the urethane foam is to have a constant roller thickness and an appropriate resistance value, it is required that the mixing ratio of the conductive material is strict. Furthermore, since the density and size of the foamed cells, such as the foaming rate, affect the conductive resistance, the management of the molding process is strict, and after molding it is necessary to polish the outer diameter, resulting in high yields and waste of materials. However, there was a problem that it was expensive in terms of cost.

  When the photosensitive drum 914 and the transfer roller 916 are rotating with a nip formed between them, there is almost no influence of the nip pressure because no stress is applied to only one place.

  Therefore, releasing the nip in a non-use state or in a non-rotating state has a great merit in improving the image quality and is advantageous in terms of cost.

  In the present embodiment, the holding portions 10 and 17 are provided in the vicinity of the bearings 12 and 14 of the frame body 5, respectively, and the actuator element 9 is hooked on the holding portions 10 and 17, and is deformed so as to extend over the bearings 12 and 15. Thus, the nip 20 is separated. By separating the photosensitive drum 914 and the transfer roller 916 from each other, it is possible to prevent a decrease in the roundness of the transfer roller. Needless to say, a reduction in the roundness of the transfer roller 916 can be prevented by reducing the nip pressure without separation.

  When the holding unit 10 and the holding unit 17 are not energized, the actuator element is in a contracted state and overcomes the urging force of the spring 18 and pulls the bearings 12 and 14, so the photosensitive drum 914 and the transfer roller 916. There is a gap between them.

  When a voltage is applied between the holding part 10 and the holding part 17, the actuator element 9 extends and becomes loose. Energization of the actuator element 9 is performed through the holding portions 10 and 17 and the conductive bearings 12 and 14. Then, the biasing force of the spring 18 pushes up the bearings 12 and 14 as they are, and the transfer roller 916 is not affected by the actuator element 9 at all, and the nip 20 can be formed only by the force of the spring 18. For this reason, it is possible to prevent the influence of the nip pressure, which is a transfer pressure that requires delicate and highly accurate pressure management. The actuator element 9 is preferably used in a bundle of flexible chemical fibers, and can be expanded and contracted slowly by energization, so that the shock at the time of nip contact can be suppressed, so the influence of the operation can be canceled. .

  The bearings 12 and 14 are provided with bearing flanges to prevent the actuator elements 9 from falling off the bearings 12 and 14 even if the actuator elements 9 are extended and loosened.

  The urging force for forming an appropriate nip is generally 50 gf to 250 gf, and varies depending on the sheet conveyance speed of the image forming apparatus and the size of the photosensitive drum and transfer roller. On the other hand, since the actuator element is a fiber having a diameter of 0.1 mm and has a stretching force of about 100 gf, it is possible to sufficiently separate the transfer roller from the photosensitive drum by using several bundles (wire shape). is there. In addition, even if one of them is disconnected, it is possible to prevent the operation from being hindered.

  Furthermore, when performing control to separate for each copy, the number of expansions and contractions has a life of about 100,000 times, so if the personal endurance life is short, the number of copies is less than 100,000, so it can be used sufficiently. is there. In addition, although there are products that make 1 million copies in large image forming apparatuses, they can be removed and replaced if there is a problem during service maintenance.

  On the other hand, it is also possible to configure the circuit so that the transfer roller is separated only when the power is turned off in a non-use state. In this case, a durable problem can be avoided.

  The actuator element has a small current during operation, and the material is electrochemical such as PS, PC, PMAA. When the actuator fiber diameter is 0.1 mm, the length is 300 mm, and the maximum tension is 100 gf, the input is 8.2 V and is about 192 mA. For this reason, the power consumption is small and does not affect the power load of the image forming apparatus.

(Second Embodiment)
4, FIG. 5 (A) and FIG. 5 (B) show a second embodiment. FIG. 4 is a perspective view, and FIG. 5 is a side view showing the second embodiment, and FIG. 5B is a front view.

4 and 5, the photosensitive drum 914 shown in FIG. 1 and a transfer roller 916 which is the transfer charger shown in FIG. 1 arranged in parallel with the photosensitive drum 914 are provided.

  The photosensitive drum 914 has a photosensitive layer formed on the surface of a cylindrical drum. Further, the drum gear 1 is integrally fitted at one end. The other end is fitted with a drum flange 2 which is held by a process cartridge or the like so as to rotate. A rotational force is given by a gear train or the like from a shaft support drive source (not shown), and it rotates while maintaining a process speed that is a rotational speed necessary for image formation by electrical control by a controller or a driver as control means.

  On the other hand, the transfer roller 916, which is a transfer charger, is formed with a specified appropriate resistance value by winding sponge or solid molded rubber or the like with conductivity in the substantially central longitudinal direction of the shaft 6. It is accurately formed so as to be concentric with the shaft 6.

  The bearings 12 and 14 provided by holding means extending from the frame body 5 in the vicinity of both ends are fitted, and at least one of the bearings is provided with a conductive bearing provided with conductivity. Yes.

  The bearing holding means is guided by a bearing guide 7 extended from a resin frame 5 fixed to the apparatus so that the bearings 12 and 14 molded of a plastic material are slid, and can move in the normal direction of the photosensitive drum. Slide. Further, the bearings 12 and 14 are provided with a bearing snap fit 14b and a bearing snap fit 14c, which are respectively stopped by a snap fit a8 and a snap fit 15 extending from the frame 5 to function as a stopper to prevent the bearing 12 and 14 from coming off. It has become.

  A spring 18 is provided between the bearings 12 and 14 and the frame 5, and a compression spring is fitted so as to urge the bearings 12 and 14 in the direction of the photosensitive drum 914.

  As a result, the transfer roller 916 is pressed against the photosensitive drum 914 with a spring force, and the nip 20 is formed by the elasticity of the transfer roller 916.

  When the image forming apparatus is in use, the sheet is conveyed from the sheet feeding means to the nip 20 and transferred with a bias voltage so that the toner image on the photosensitive drum is transferred to the sheet when passing through the nip portion. For this purpose, a current flows from the roller surface of the transfer roller 916 to the shaft 6, further flows from the shaft to the spring 18 through the conductive bearings 12, 14, and is connected to the terminal 19 through the conductive plate 11 made of a metal plate. Is connected to a high voltage power source.

  When image formation is not performed, if a spring pressure is always applied in the nip 20, especially in the case of a sponge roller, the outer shape of the photosensitive drum 914 is deformed. In the past, materials such as foamed urethane with strong elasticity were used to minimize the effect. If the urethane foam is to have a constant roller thickness and an appropriate resistance value, it is required that the mixing ratio of the conductive material is strict. Furthermore, since the density and size of the foamed cells, such as the foaming rate, affect the conductive resistance, the management of the molding process is strict, and after molding it is necessary to polish the outer diameter, resulting in high yields and waste of materials. However, there was a problem that it was expensive in terms of cost.

  When the photosensitive drum 914 and the transfer roller 916 are rotating with a nip formed between them, there is almost no influence of the nip pressure because no stress is applied to only one place.

4 and 5, the actuator element 27 in which a wire is formed in a coil spring shape is used as means for releasing and separating the nip between the transfer roller 916 and the photosensitive drum 914. The actuator element 27 is fixed to the frame. In the vicinity of both ends of the photosensitive drum 914, an insulator fixed by a member extending from the frame of the image forming apparatus, for example, a frame 21 and a frame 22 made of plastic (the peripheral portions are omitted for convenience) There is. The frame 21 and the frame 22 are respectively provided with a seating surface 23 and a seating surface 25 that support the actuator element 27. Further, a guide 24 and a guide 26 for preventing buckling of the actuator element 27 are provided. The actuator element 27 is mounted in the guide 24 and the guide 26, and the terminal 28 is connected to the power source through the holes provided in the seating surfaces 23 and 25, respectively, and the actuator element 27 is deformed so that the actuator element 27 expands and contracts. be able to. The compression coil spring-like actuator element 27 is attached to the end portion of the wire so as to have a space for expansion and contraction by connecting a bent wire or the like so as not to affect the expansion and contraction operation.

  When a voltage is applied across the terminals 28 of the actuator element 27, the actuator element 27 is energized to generate heat. Simultaneously with heat generation, the coil contracts, and the bearings 12 and 14 that are in contact with each other are lifted by the biasing force of the spring 18, and the transfer roller 916 contacts the photosensitive drum 914. In addition, the actuator element 27 shrinks, leaving a gap away from the bearings 12, 14. Only the abutting force of the spring 18 is applied to the photosensitive drum 914, so that a prescribed pressure can be maintained.

  On the other hand, when the power supply to the terminal 28 is turned off, the temperature of the actuator element 27 decreases, and at the same time, the actuator element 27 expands and comes into contact with the upper surfaces of the bearings 12 and 14 and is pressurized. Eventually, when the pressure applied by the spring 18 is exceeded, the bearings 12 and 14 are pushed down, and the nip portion between the photosensitive drum 914 and the transfer roller 916 is separated. As a result, the transfer roller is not subjected to external pressure such as nip pressure at times other than image formation in a non-use state, so that deformation can be prevented.

(Third embodiment)
6 and 7 are partial schematic views of an image forming apparatus using an actuator element according to a third embodiment of the present invention. FIG. 6 is a partial schematic perspective view of an image forming apparatus using an actuator element. FIG. 7 shows a side view of FIG. 7A and a front view of FIG. 7B.

  6 and 7, the ribbon-like actuator element 34 contracts when energized. The photosensitive drum 914 forms a nip with the transfer roller 916.

  The transfer roller 916 is pivotally supported by the bearings 12 and 14 and is urged by a spring 18 that pressurizes the transfer roller 916 against the photosensitive drum 914. In the front view of FIG. 7B, the support shaft 30, the support shaft 36, and the seat surface 35 provided on the frame 5 are provided.

  An arm 29 made of a resin material is fitted to the support shaft 30 so as to be rotatable like a seesaw.

  A support shaft 32 and a seat surface 31 are provided at one end of the arm. An actuator element 34 is stretched between the support shaft 32 and the support shaft 36. In addition, the spring 33 is disposed between the seat surface 35 and the seat surface 31 and biases the spring force so as to pressurize the actuator element 34 in the direction of applying tension to the actuator element 34 with the support shaft 30 as a fulcrum. Both ends of the actuator element 34 hung on the support shaft 32 and the support shaft 36 are connected to lead wires to apply a voltage.

When a voltage is applied, the actuator element 34 starts to move in a contracting direction and overcomes the force of the spring 33 to rotate the arm 29. The action portion 37 of the arm 29 rotates in the direction of the photosensitive drum 914, and at the same time, the bearings 12 and 14 are lifted by the biasing force of the spring 18, so that the transfer roller 916 contacts the photosensitive drum 914 to form the nip 20. It moves to. Further, the action portion 37 is separated from the bearings 12 and 14 to completely release the pressing force so that only the pressing force of the springs 12 and 14 acts on the nip 20.

  On the other hand, when the power supply to the actuator element 34 is turned off, the arm 29 rotates in the opposite direction to push down the bearings 12 and 14 and separate the nip 20.

  As a result, the non-use pressure applied to the transfer roller can be released.

  As described above, the transfer roller can be protected by releasing the nip portion between the transfer roller and the photosensitive drum except during the image forming operation, and the memory effect due to the influence of the nip portion of the photosensitive drum, etc. Can be prevented, and the image quality can be improved.

  Further, when a jam occurs during paper conveyance, a nip is conventionally formed between the photosensitive drum and the transfer roller. During jam processing, the unfixed toner image generated when the unfixed toner image on the paper is pulled out upstream in the paper transport direction is rubbed by the friction generated at the nip, and the rub marks at the nip Damage can be eliminated. Further, the toner remaining in the nip portion adheres to the transfer roller at the moment when the paper is removed, so that the toner enters the cell of the foamed sponge-like transfer roller and the hardness of the roller increases. According to the present exemplary embodiment, it is possible to minimize transfer performance deterioration caused by a change in transfer pressure, a bad influence due to a decrease in nip width, and a bad influence on transfer force.

  As a result, the life of the transfer roller and the photosensitive drum can be extended, and the number of maintenances can be reduced and the number of parts such as service parts can be reduced due to a decrease in toner contamination.

  In the case of an actuator element, there is no operation shock generated by releasing the pressure of a conventional solenoid-operated transfer roller. The actuator element starts to move slowly, and comes into contact with or separates from the nip portion without generating an impact due to the balance with each biasing spring. For this reason, it is possible to protect the photosensitive drum, which cannot be achieved with the conventional solenoid configuration.

  Since the nip can be automatically separated by turning off the applied voltage, complicated operations such as pressure release mechanism and lever operation at the time of jam processing are unnecessary, jam handling performance is improved, and the user An easy-to-use image forming apparatus that is easy to use can be provided.

(Fourth embodiment)
8 to 11 are explanatory views of the fixing device according to the fourth embodiment. FIG. 12 is a side view showing a conventional fixing device. FIG. 8 is a side view of the fixing device showing the fourth embodiment. FIG. 9 is a perspective view of a fixing device showing the fourth embodiment. FIG. 10 is a cross-sectional view of a fixing device showing the fourth embodiment. FIG. 11 is a schematic cross-sectional view of a fixing device showing a fourth embodiment.

  The fixing device (fixing means) used in the image forming apparatus uses a heater 74 for fixing as shown in the cross-sectional views of FIGS. 10 and 11, and the heater 74 is bonded to a heater holder 84. It is held in the stay 86. A cylindrical fixing film 75 is provided on the outside thereof.

  The fixing film 75 is an endless belt having high heat resistance such as polyimide, and has a heater 74 inside, and a pressure roller (pressure rotator) 71 as a first rotator is arranged at an opposing position, so It is pressed. As a result, a nip is formed, and an unfixed image is fixed on the sheet by pressurization and heating.

  The sheet is guided by the inlet upper guide 76 and the inlet lower guide 77 and enters the nip portion, and the second rotator is formed in the nip portion by the rotational force connected to the pressure roller 71 from the driving source. It rotates with the fixing film 75. The paper is nipped and fixed on the fixing film 75 and conveyed, passes through the nip portion of the paper discharge roller 81 and the paper discharge roller 82, and passes between the paper discharge upper guide 79 and the paper discharge lower guide 80. Sent to the department.

  Further, the pressure roller 71 is provided with a heat radiating roller 83, which adsorbs toner stains on the surface of the heat radiating roller 83, and serves as a heat pipe to keep the temperature in the roller longitudinal direction uniform. Has been.

  Next, FIG. 12 is a side view showing a pressure mechanism of a conventional fixing device. In the figure, the heater unit has a U-groove shape with respect to the frame side plate 72 via a bearing that holds the pressure roller 71. It is supported by the part.

  Similarly, the frame side plate 72 is provided with a guide 53 and a guide 68, in which both longitudinal support portions of the heater holder 70 are guided and held so as to be slidable. Protrusions are provided on both longitudinal support portions of the heater holder 70 so as to come into contact with the rotating arm 88a. The rotating arm 88a shown in FIG. 12 shows a pressurized state. The rotating arm 88a is pivotably held at one end by a fulcrum 66, and a hole of the rotating arm 88a is formed on the opposite side of the abutting portion 69 via a pressure adjusting screw 63 and a pressure spring 64. It is attached with a screw portion 94 penetrating therethrough and provided on the adjustment plate 93. The urging force of the pressure spring 64 is rotated in the clockwise direction (first direction) by the fulcrum 66 so as to abut against the pressure roller 71 by pushing down the abutting portion 69 of the fixing means so as to form a nip. It has been made.

  On the other hand, in the case of jam processing, it is common that the paper transport unit (described in FIG. 1) is released and the door is opened to remove the jammed paper by the user. The applied pressure is released. There are two types of pressure release, one that is linked with the door, and the other that is released by the user individually moving the pressure release lever.

  These pressure releases are connected to the rack 90, and when the rack 90 moves in the direction of the arrow 100, the meshed gear 89 interlocks and rotates about the shaft 91 in the direction of the arrow 101. The arm 92 provided integrally with the gear 89 is also rotated in the direction of the arrow 102 to push up the rotating arm 88a. Then, the rotation arm 88a moves in the counterclockwise direction (second direction) while being held at the fulcrum 66, and the position of the rotation arm 88b indicated by the dotted line is also expanded in the upward direction in the figure. Pushed up. As a result, the pressure applied to the heater nip is canceled and the paper can be pulled out.

  However, normally, the pressure of the fixing device of the image forming apparatus remains pressurized, and the pressure roller 71 always receives contact pressure with the heater surface. In general, the pressure roller 71 uses a rubber material, specifically silicon rubber, around the metal shaft, and has a function of optimizing the pressing force and the pressing time required for fixing as an elastic body. . That is, the pressurization time when the paper is fed at the process transport speed and passes through the fixing device is determined by the time during which the paper transport speed passes through the nip portion. Further, the amount of heat corresponding to toner melting is determined so that the unfixed toner image can be optimally fixed by heat, pressure, and passage time. For this purpose, the rubber hardness of the silicon rubber is adjusted to give an appropriate flexibility or is foamed to be optimized in the form of a sponge.

It is known that when the pressure roller 71 is applied with pressure for a long period of time, the elastic restoring force decreases and deforms following the shape of the nip. The outer shape of the pressure roller is distorted, adversely affecting the fixing performance. Since the deformed portion has increased hardness and becomes substantially flat in the radial direction, the rotating pressure roller cannot maintain a constant nip width. When a sheet on which a solid image such as a halftone image or a photograph is transferred is conveyed here, a nip mark appears in the image, and an improperly fixed horizontal stripe pattern appears at the rotation circumferential pitch of the pressure roller 71. It will degrade the quality.

  In the present embodiment, the purpose is to solve the problem of the image defect. When the image forming apparatus is stopped, the pressing force is automatically released, and the pressure roller at the nip portion is released. It is intended to always prevent deformation.

  8 and 9 are diagrams showing a fixing device using an actuator element in order to solve this problem. FIG. 8 is a side view of the fixing device showing the present embodiment. FIG. 9 is a perspective view of a fixing device showing the present embodiment.

  8 and 9, the heater unit is supported by a U-shaped portion with respect to the frame side plate 72 via a bearing that holds the pressure roller 71.

  Similarly, the frame side plate 72 is provided with a guide 53 and a guide 68, in which both longitudinal support portions of the heater holder 70 are guided and held so as to be slidable. Protrusions are provided on both longitudinal support portions of the heater holder so as to come into contact with the rotating arm 65. The rotating arm 65 shown in FIG. 8 shows a pressurized state. One end portion is swingably held by a fulcrum 66, and the adjustment plate 52 passes through a hole of the rotating arm 65 via a pressure adjusting screw 63 and a pressure spring 64 on the opposite side of the abutting portion 69. It is attached with the screw part 51 provided in the. The urging force of the pressure spring 64 is rotated clockwise by a fulcrum 66 and is pressed against the pressure roller 71 by pushing down the abutting portion 69 so as to form a nip.

  On the other hand, in the case of jam processing, when the paper transport unit (described in FIG. 1) is released and the door is opened, the interlock switch is turned off (not shown) to remove the jammed paper by the user. Is. An actuator element 58 is provided on the frame column 57. The actuator element 58 is provided with a non-conductive holding member 56 and a holding member 61 at both ends, and is electrically connected to the actuator element 58, the tab terminal 55, and the tab terminal 59 inside. The actuator element 58 is insulated from the frame column 57, the mounting seat surface 60, and the rotating arm 65, which are metal sheets. One end of the actuator element 58 is fitted and held on the rotating arm 65 by a step screw 54. The opposite one end is fitted and held on the mounting seat surface 60 by a step screw 62.

  The actuator element 58 operates by applying a control voltage from the controller to the contact between the tab terminal 55 and the tab terminal 59. The actuator element extends when energized, and contracts when the applied voltage is turned off. Thus, the actuator element is deformed by energization.

  The actuator element 58 is expanded and contracted to release the pressure applied to the fixing portion (nip portion). The release of pressure is linked to the OFF of the interlock switch linked to the door. In the so-called standby state where the image forming process is stopped, the energization to the actuator element 58 is cut off so as to release the pressure.

  Further, when the image forming apparatus that is not in use is turned off, the actuator element is not energized, so that the pressure is automatically released.

This release of pressure can be achieved by changing the position of the rotating arm 65 connected via the step screw 54 by the vertical movement of the holding member at one end of the actuator element 58 extending and contracting. That is, in FIG. 8, the pivot arm 65 is supported by the fulcrum 66 and pivots upward, and the abutting portion 69 of the heater holder 70 also slides upward. As a result, the pressure applied to the heater nip is canceled and the pressure applied to the pressure roller can be prevented.

  As described above, the pressure applied to the fixing device can be automatically released. Moreover, even when electrical control of a non-use state or power outage is impossible, the nip of the pressure roller can be automatically released. As a result, it is possible to eliminate the deformation of the pressure roller due to the influence of the nip, and it is possible to provide an excellent fixing device that maintains stable high-quality image quality.

  As another application of the present invention, the pressure at the nip portion in the conveying portion of the image forming apparatus can be automatically released, so that the primary charger or the other paper conveying portion that always forms the nip is held. It can be used for parts around rollers and photosensitive drums. Moreover, the operation | work which cancels | releases the pressure which a user inserts in a device and can be avoided.

1 is a cross-sectional view of an image forming apparatus showing an embodiment of the present invention. 1 is a perspective view showing a partial schematic view of an image forming apparatus using an actuator element according to a first embodiment. 1A and 1B are a side view (a) and a front view (b) of a partial schematic view of an image forming apparatus using an actuator element according to the first embodiment. It is a perspective view which shows 2nd Embodiment. It is the side view (a) which shows 2nd Embodiment, and a front view (b). It is a perspective view which shows 3rd Embodiment. It is the side view (a) which shows 3rd Embodiment, and a front view (b). FIG. 10 is a side view of a fixing device showing a fourth embodiment. FIG. 9 is a perspective view of a fixing device showing a fourth embodiment. It is sectional drawing of the fixing device which shows 4th Embodiment. It is a schematic sectional drawing of the fixing device which shows 4th Embodiment. It is a side view which shows the conventional fixing device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Drum gear 2 ... Drum flange 3 ... Actuator element 4 ... Spring 5 ... Transfer frame 6 ... Shaft 7 ... Bearing guide 8 ... Snap fit a
9 ... Actuator element 10 ... Holding part a
DESCRIPTION OF SYMBOLS 11 ... Conduction plate 12 ... Bearing 13 ... Transfer drive gear 14 ... Bearing 14a ... Bearing flange 14b ... Bearing snap fit a
14c ... Bearing snap fit b
15 ... snap fit b
16 ... snap fit 17 ... holding part b
18 ... Spring 19 ... Terminal 20 ... Nip 21 ... Frame a
22 ... frame b
23 ... Seating surface a
24 ... Guide a
25 ... Seat surface b
26 ... Guide b
27 ... Actuator element 28 ... Terminal 29 ... Arm 30 ... Support shaft 31 ... Seat surface 32 ... Support shaft 33 ... Spring 34 ... Actuator element 35 ... Seat Surface 36 ... support shaft 37 ... acting part 50 ... heater 51 ... screw part 52 ... adjusting plate 53 ... guide A
54 ... Corrugated screw 55 ... Tab terminal A
56 ... Holding member A
57 ... Frame support 58 ... Actuator element 59 ... Tab terminal B
60 ... Mounting seat surface 61 ... Holding member B
62 ... Step screw 63 ... Pressure adjusting screw 64 ... Pressure spring 65 ... Rotating arm 66 ... fulcrum 67 ... Holding plate 68 ... Guide B
69 ... Abutting portion 70 ... Heater holder 71 ... Pressure roller 72 ... Frame side plate 73 ... Frame support stay 74 ... Heater 75 ... Fixing film 76 ... Upper entrance guide 77 ... Entrance lower guide 78 ... Shaft 79 ... Delivery upper guide 80 ... Delivery lower guide 81 ... Delivery roller 82 ... Delivery roller 83 ... Radiation roller 84 ... Heater holder 85 ... frame stay 86 ... heater stay 87 ... frame stay 88a ... rotating arm 88b ... rotating arm 89 ... gear 90 ... rack 91 ... shaft 92 ... Arm 93 ... Adjustment plate 94 ... Screw part 100 ... Arrow 101 ... Arrow 102 ... Arrow 103 ... Arrow 900 ... Image forming apparatus main body 902 ... Image formation Part 904 .. fixing Place 906 ... Document placement table 907 ... Light source 909 ... Paper feed unit 910, 911 ... Cassette 914 ... Photosensitive drum 915 ... Developer 916 ... Transfer charger 917 Separation charger 918 ... Cleaner 919 ... Primary charger 921 ... Laser scanner 930 ... Right door 931 ... Multi paper feed means 932 ... Operation unit 933 ... HDD off switch button

Claims (8)

A transfer roller;
A photosensitive drum facing the transfer roller;
A pressing means for pressing the transfer roller to the photosensitive drum;
Pressure releasing means for releasing the nip pressure in the nip formed by the pressurization;
In an image forming apparatus having
The pressure means is a spring that biases a bearing that pivotally supports the longitudinal end of the transfer roller in the direction of the photosensitive drum,
The pressure release means has an actuator element that deforms when energized or when deenergized from the energized state,
The actuator elements, at the non-energized state from a state which is energized, by deforming, against the biasing force of the spring moving the bearing in the opposite direction to biasing spring, the transfer an image forming apparatus comprising that you separate the said photosensitive drum and rollers.   The image forming apparatus according to claim 1, wherein an image forming process of the image forming apparatus is stopped in a non-energized state where the actuator element is not energized. The pressure releasing means, an image forming apparatus according to claim 1 or 2, characterized in that the wire-shaped actuator element. Said pressure releasing means is a coil spring-shaped actuator element, an image forming apparatus according to claim 1 or 2, characterized in that it is provided with the bearing so as to sandwich between the spring. The pressure release means is
A release arm having one end provided at a position sandwiching the bearing with the spring;
The actuator element provided at the other end of the release arm;
The image forming apparatus according to any one of claims 1 to 3, characterized in that it has a. An image forming unit that transfers a toner image to a sheet material;
Fixing means having a heater;
A pressure rotator facing the fixing means;
A pressure unit that pressurizes the fixing unit against the pressure rotator;
A pressure release means for releasing a nip pressure at a nip between the fixing means and the pressure means, formed by the pressure of the pressure means;
In the image forming apparatus for forming an image on the sheet material by fixing the toner image on the sheet material in the nip,
The pressure release means has an actuator element that deforms when energized or when deenergized from the energized state,
2. The image forming apparatus according to claim 1, wherein the actuator element is deformed to resist the pressure applied by the pressurizing unit when the power is not supplied, and the pressurization at the nip by the pressurizing unit is released. The pressure release means has a rotating arm that has one end as a fulcrum provided on the fixing means side and the other end rotating in the first direction to push down the fixing means to the pressure rotating body side, An actuator element is provided at the other end of the pivot arm;
The actuator elements, according to claim if it becomes non-energized from the state of being energized, the first direction, wherein the rotating the rotary arm in a second direction which is opposite to the direction 6 The image forming apparatus described in 1. A first rotating body;
A second rotating body facing the first rotating body;
Pressurizing means for pressurizing the second rotating body to the first rotating body;
An image forming apparatus comprising: a pressure releasing unit that releases the pressure of the pressing unit;
The pressure release means has an actuator element that deforms when energized or when deenergized from the energized state,
If it becomes non-energized from the state of being energized, the actuator element is deformed so that is separated and the said first rotary member while resisting the pressure second rotor of said pressure means The image forming apparatus, wherein when the pressure applied by the pressure unit is released and the actuator element is energized, the actuator element is deformed so that the pressure unit pressurizes the second rotating body. .

Images