JP2014215536A - Fixing device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device that can reduce heat-up time of a fixing nip part and prevent the occurrence of spark discharge.SOLUTION: A fixing device includes a heating rotating member 31 including a rotating body 41 that is in pressure contact with a pressure rotating member 32, a resistance heating element 42 that is located on the inner peripheral side of the rotating body 41 and configured separated from the rotating body 41, and a pair of power feed bodies 43 that are in electrical conduction with the resistance heating element 42. The resistance heating element 42 matches the rotating body 41 and a fixing nip part 33 in the longitudinal direction. At least one of the pair of power feed bodies 43 is configured by a movement actuator 54 to be movable along the longitudinal direction of the fixing nip part 33. The fixing device further includes a switching regulator 69 that changes a voltage applied to both power feed bodies 43 according to size information on a recording material P passing through the fixing nip part 33 in changing a position of at least one of the pair of power feed bodies 43.

Description

  The present invention relates to a fixing device that allows a recording material with an unfixed toner image to pass through a fixing nip portion between a heating rotary member and a pressure rotary member, and an image forming apparatus including the fixing device. The image forming apparatus includes various apparatuses such as a copying machine, a printer, a facsimile machine, and a multifunction machine having these functions in a complex manner.

  Conventionally, as a fixing device of an image forming apparatus employing an electrophotographic method, Patent Document 1 discloses that a pressure roller is pressed against a fixing roller having a resistance heating layer provided on an inner peripheral surface, and a fixing roller, a pressure roller, A self-heating type is disclosed in which a fixing nip portion is formed between the two and a fixing roller is heated by energizing a resistance heating layer. In this case, a pair of power feeding members that contact the resistance heating layer on the inner peripheral surface of the fixing roller is provided on a roller shaft that rotatably supports the fixing roller. One power supply body is provided so as to be rotatable and immovable on the roller shaft. The other power feeding body is configured to be movable and rotatable along the roller axis. The fixing roller itself generates heat by energizing the resistance heating layer from the roller shaft through each power supply body. The heat generation width of the fixing roller is changed by the movement of the other power feeding body according to the size of the recording material passing through the fixing nip portion.

  Since the fixing device of Patent Document 1 is configured to generate heat (self-heating type), the heating efficiency is higher than the case of a fixing roller incorporating a lamp type or induction heating type heater, and the heating rate is higher. There is an advantage that the time required for the fixing nip temperature to reach the fixing temperature can be shortened quickly.

JP-A-11-202664

  In the fixing device of Patent Document 1, for the purpose of conveying a recording material, a fixing roller provided with a resistance heating layer on the inner peripheral surface rotates around a roller axis. For this reason, both power feeding members are in contact with the resistance heating layer of the rotating fixing roller while sliding to supply power. When the other power feeding body is moved along the roller axis in such a state, the contact state with the resistance heating layer changes, and the fixing roller rotates in a deformed state although it is minute. In this case, there is a problem that a minute gap is formed between the resistance heating layer and each power supply member to generate a spark discharge, and the fixing roller is damaged and deteriorated by the spark discharge.

  When the other power feeder is moved to shorten the distance between the two power feeders, the resistance between the two power feeders in the resistance heating layer decreases by the shortened distance. For this reason, if the voltage applied to both power feeding bodies does not change before and after the movement of the other power feeding body, the current increases by the amount of decrease in resistance and the amount of heat generated per unit area increases. In this case, there is a problem that a difference occurs in heat loss between a portion where the recording material passes and a portion where the recording material does not pass on the outer peripheral surface of the fixing roller, resulting in partial temperature unevenness, leading to paper wrinkles and fixing unevenness.

  The invention of the present application has been made in view of the above problems, and a fixing device capable of preventing the occurrence of spark discharge while reducing the time until the temperature of the fixing nip reaches the fixing temperature, and An object of the present invention is to provide an image forming apparatus provided with this.

  According to a first aspect of the present invention, there is provided a heating rotating member having a resistance heating element that generates heat when energized, and a pressure rotating member pressed against the heating rotating member, and a fixing nip portion between the heating rotating member and the pressure rotating member. And a fixing device that passes and fixes a recording material with an unfixed toner image, wherein the heating rotary member is positioned on a rotary body that is in pressure contact with the pressure rotary member, and an inner peripheral side of the rotary body. The resistance heating element is configured separately from the rotating body, and a pair of power feeding bodies that are electrically connected to the resistance heating element. The longitudinal direction of the resistance heating element is the length of the rotating body and the fixing nip portion. When the position of at least one of the pair of power feeders is changed, at least one of the pair of power feeders is configured to be movable along the longitudinal direction of the fixing nip portion by a moving actuator. ,Previous Depending on the size information of the recording medium passing through the fixing nip, it is that further comprises an applied voltage changing unit operable to change the applied voltage to both current collector.

  According to a second aspect of the present invention, in the fixing device according to the first aspect, a temperature detection member that detects a temperature of the rotating body is provided, and each of the power feeding bodies moves in conjunction with the temperature detection member. The member is attached.

  According to a third aspect of the present invention, in the fixing device according to the second aspect, the detecting portion of each temperature detecting member is located on the inner side in the longitudinal direction of the rotating body with respect to the corresponding power feeding body. It is.

  According to a fourth aspect of the present invention, in the fixing device according to any one of the first to third aspects, at least one of size information of the recording material passing through the fixing nip portion and detection information of the temperature detecting members. Based on the above, it further comprises position changing means for driving the moving actuator to change the position of at least one of the pair of power feeding bodies.

  According to a fifth aspect of the present invention, in the fixing device according to the fourth aspect, when the size information of the recording material passing through the fixing nip portion is used, the moving actuator is driven at a first speed, and each temperature detection is performed. When the detection information of the member is used, the moving actuator is driven at a second speed that is slower than the first speed.

  According to a sixth aspect of the present invention, in the fixing device according to the second or third aspect, the energization to the resistance heating element is stopped when the difference between the detection information of the two temperature detecting means is large.

  According to a seventh aspect of the present invention, there is provided an image forming apparatus comprising the fixing device according to any one of the first to sixth aspects.

  According to the invention described in the claims of the present application, the heating rotating member includes a rotating body pressed against the pressurizing rotating member, and a resistor that is located on the inner peripheral side of the rotating body and is configured separately from the rotating body. A heating element, and a pair of power supply bodies that are electrically connected to the resistance heating element, wherein a longitudinal direction of the resistance heating element coincides with a longitudinal direction of the rotating body and the fixing nip portion, and at least of the pair of power supply bodies One is configured to be movable along the longitudinal direction of the fixing nip portion, and when changing the position of at least one of the pair of power feeding bodies, according to the size information of the recording material passing through the fixing nip portion, Since it further comprises an applied voltage changing means for changing the applied voltage to both power feeding bodies, the heating width of the heating rotating member (rotating body) is changed steplessly, and the recording material size (length in the width direction) is changed. ) The heating rotation corresponding to While the material (the rotating body) can be heated, the resistance heating element can be maintained in a very good contact state between the resistance heating element and the feeding element even when the feeding elements are moving. And both the power feeders can be stably energized. In addition, the applied voltage per unit region of the resistance heating element can be made constant by changing the voltage applied to the both power supply bodies in accordance with the resistance between the power supply bodies in the resistance heating element. Therefore, it is possible to reliably suppress the occurrence of spark discharge, prevent damage and deterioration of the heating rotating member due to spark discharge, and reduce power consumption during the fixing process to save energy.

It is a schematic explanatory drawing of a printer. FIG. 2 is an exploded perspective view showing an outline of a fixing device. FIG. 3 is a side sectional view of the fixing device. It is explanatory drawing which shows the relationship between the size of a recording material, and a heat generation width | variety, (a) is the case where a recording material of the maximum size is passed with the heat generation width corresponding to the maximum sheet passing width, and (b) corresponds to the maximum sheet passing width. When a recording material of a small size with a heat generation width is passed, (c) is a case of passing a recording material of a minimum size with a heat generation width corresponding to the minimum sheet passing width. It is a functional block diagram of a controller. It is a flowchart of electric power feeding body movement control.

  Hereinafter, an embodiment embodying the present invention will be described with reference to the drawings when applied to a tandem color digital printer (hereinafter referred to as a printer) which is an example of an image forming apparatus. In addition, in the following description, when using a term indicating a specific direction or position (for example, “left / right”, “up / down”, etc.) as necessary, the direction orthogonal to the paper surface in FIG. ing. These terms are used for convenience of explanation, and do not limit the technical scope of the present invention.

(1). Overview of Printer First, an overview of the printer 1 will be described with reference to FIG. As shown in FIG. 1, the printer 1 includes an image process device 3, a paper feeding device 4, a fixing device 5, and the like in a housing 2. Although not shown in detail, the printer 1 is connected to a network such as a LAN, and is configured to execute printing based on the command when receiving a print command from an external terminal (not shown). Yes.

  The paper feeding device 4 located at the lower part in the housing 2 includes a paper feeding cassette 21 that accommodates the recording material P, a pickup roller 22 that feeds the recording material P in the paper feeding cassette 21 from the uppermost layer, and a fed recording material P. A pair of separation rollers 23 for separating the recording materials one by one, a pair of timing rollers 24 for conveying the recording material P separated into one sheet to the image processing apparatus 3 at a predetermined timing, and the like. The recording material P in each paper feed cassette 21 is sent to the transport path 30 one by one from the top layer by the rotation of the pickup roller 22 and the separation roller 23. The conveyance path 30 passes from the paper feed cassette 21 of the paper feed device 4 to the casing 2 through the nip portion of the timing roller pair 24, the secondary transfer nip portion of the image processing device 3, and the fixing nip portion 33 of the fixing device 5. It reaches the discharge roller pair 26 at the top.

  The recording material P in the paper feed cassette 21 is set to a center reference that is conveyed in the arrow S direction toward the conveyance path 30 with the center of the sheet passing width (width dimension orthogonal to the arrow S direction) as a reference. Although illustration is omitted, the paper feed cassette 21 is provided with a pair of side part regulating plates for bringing the recording material P before paper feeding closer to the center. The pair of side regulating plates are configured to move in a close-up manner in conjunction with each other in the sheet passing width direction. By sandwiching the recording material P in the paper feed cassette 21 from both sides in the sheet passing width direction by the pair of side portion regulating plates, the recording material P in the paper feed cassette 21 is set to the center reference regardless of the standard. Therefore, the transfer process in the image processing apparatus 3 and the fixing process in the fixing apparatus 5 are also executed on the basis of the center.

  The image processing device 3 positioned above the paper feeding device 4 plays a role of transferring a toner image formed on a photosensitive drum 13 which is an example of an image carrier to a recording material P, and is an intermediate transfer member. And a total of four image forming sections 7 corresponding to the respective colors of yellow (Y), magenta (M), cyan (C) and black (K).

  The intermediate transfer belt 6 is an endless belt made of a conductive material, and is also an example of an image carrier. The intermediate transfer belt 6 is wound around a driving roller 8 located on the right side of the central part in the housing 2 and a driven roller 9 located on the left side of the central part. A secondary transfer roller 10 is disposed outside the portion of the intermediate transfer belt 6 that is wound around the drive roller 8. The intermediate transfer belt 6 rotates in the counterclockwise direction in FIG. 1 by rotating the driving roller 8 counterclockwise in FIG. 1 by power transmission from a main motor (not shown).

  A secondary transfer roller 10 is disposed on the outer peripheral side of the portion of the intermediate transfer belt 6 that is wound around the drive roller 8. The secondary transfer roller 10 is in contact with the intermediate transfer belt 6, and a portion between the intermediate transfer belt 6 and the secondary transfer roller 10 (contact portion) is a secondary transfer nip portion as a secondary transfer region. . The secondary transfer roller 10 rotates in the clockwise direction in FIG. 1 with the rotation of the intermediate transfer belt 6 or with the movement of the recording material P that is nipped and conveyed by the secondary transfer nip portion. A transfer belt cleaner 12 for removing untransferred toner on the intermediate transfer belt 6 is disposed on the outer peripheral side of the portion of the intermediate transfer belt 6 wound around the driven roller 9. The transfer belt cleaner 12 is in contact with the intermediate transfer belt 6.

  The four image forming units 7 are arranged along the intermediate transfer belt 6 in the order of yellow (Y), magenta (M), cyan (C), and black (K) from the left in FIG. They are arranged side by side. In FIG. 1, for convenience of explanation, symbols Y, M, C, and K are attached to each image forming unit 7 according to the reproduction color. Each image forming unit 7 includes a photosensitive drum 13 as an example of an image carrier that rotates clockwise in FIG. Around the photosensitive drum 13, a charging device 14, an exposure device 19, a developing device 15, a primary transfer roller 16, and a photosensitive cleaner 17 are arranged in this order along the clockwise rotation direction in FIG. 1.

  The photosensitive drum 13 is negatively charged and is configured to rotate clockwise in FIG. 1 by power transmission from the main motor. The charging device 14 uniformly charges the surface of the photosensitive drum. The developing device 15 makes the electrostatic latent image formed on the photosensitive drum 13 visible by reversal development using toner having a negative polarity.

  The primary transfer roller 16 is located on the inner peripheral side of the intermediate transfer belt 6 and faces the photosensitive drum 13 of the corresponding image forming unit 7 with the intermediate transfer belt 6 interposed therebetween. The primary transfer roller 16 also rotates counterclockwise in FIG. 1 as the intermediate transfer belt 6 rotates. Between the intermediate transfer belt 6 and the primary transfer roller 16 (contact portion) is a primary transfer nip portion as a primary transfer region. The photoreceptor cleaner 17 is for removing untransferred toner remaining on the photoreceptor drum 13, and is in contact with the photoreceptor drum 13. An exposure device 19 is disposed below the four image forming units 7. The exposure device 19 forms an electrostatic latent image on each photosensitive drum 13 by laser light based on image information from an external terminal or the like.

  Each image forming unit 7 is a cartridge (integrated structure) in which the photosensitive drum 13, the charging device 14, the exposure device 19, the developing device 15, and the photosensitive cleaner 17 are collectively accommodated in the housing 20. A so-called process cartridge is detachably attached to the housing 2. A hopper (not shown) that accommodates toner to be supplied to each developing device 15 is disposed above the intermediate transfer belt 6.

  In each image forming unit 7, when a laser beam corresponding to an image signal is projected from the exposure device 19 onto the photosensitive drum 13 charged by the charging device 14, an electrostatic latent image is formed. The electrostatic latent image is reversely developed with toner supplied from the developing device 15 and becomes a toner image of each color. The toner images on the respective photosensitive drums 13 are primarily transferred from the photosensitive drum 13 to the outer peripheral surface of the intermediate transfer belt 6 in the order of yellow, magenta, cyan, and black at the corresponding primary transfer nip portions, and are superimposed. . Untransferred toner remaining on the photosensitive drum 13 is scraped off by the photosensitive cleaner 17 and removed from the photosensitive drum 13. When the recording material P passes through the secondary transfer nip portion, the superimposed four color toner images are secondarily transferred onto the recording material P all at once. Untransferred toner remaining on the intermediate transfer belt 6 is scraped off by the transfer belt cleaner 12 and removed from the intermediate transfer belt 6.

  The fixing device 5 positioned above the secondary transfer roller 10 in the image processing apparatus 3 includes a fixing roller 31 as a heating rotating member having a resistance heating element 42 (details will be described later) serving as a heat source, and a pressure contact with the fixing roller 31. And a pressure roller 32 as a pressure rotating member. A contact portion between the fixing roller 31 and the pressure roller 32 is a fixing nip portion 33 which is a fixing region. The recording material P on which an unfixed toner image is placed after passing through the secondary transfer nip portion is heated and pressurized when passing through the fixing nip portion 33 between the fixing roller 31 and the pressure roller 32, and the recording material P An unfixed toner image is fixed on P. Thereafter, the recording material P is discharged onto the paper discharge tray 27 by the rotation of the discharge roller pair 26.

  A control unit 28 that performs overall control of the printer 1 is disposed between the image processing apparatus 3 and the sheet feeding apparatus 4 in the housing 2. The controller 28 incorporates a controller 35 that executes various arithmetic processes, storage, and control.

(2). Next, the detailed structure of the fixing device 5 and its periphery will be described with reference to FIGS. 2 and 3. As described above, the fixing device 5 includes the fixing roller 31 and the pressure roller 32 that are rotatable in a state in which the fixing devices 5 extend in the sheet passing width direction and are in pressure contact with each other. In the embodiment, power is transmitted to the pressure roller 32 from a fixing motor (not shown) as a driving source via a power transmission system such as a gear or a belt. With the rotation of the pressure roller 32 or the recording material P passing through the fixing nip 33, the fixing belt 41 constituting the fixing roller 31 rotates in the direction opposite to the rotation direction of the pressure roller 32.

  The fixing roller 31 includes a fixing belt 41 that is an example of a rotating body that is in pressure contact with the pressure roller 32, a resistance heating element 42 that is located on the inner peripheral side of the fixing belt 41 and is configured separately from the fixing belt 41, A pair of power feeding bodies 43 that are electrically connected to the resistance heating body 42 are provided. The fixing belt 41 has a cylindrical shape that is long in the sheet passing width direction, and holds the cylindrical shape by its own tension. In the embodiment, the long holding block 44 having a substantially arc-shaped cross section is disposed near the fixing nip portion 33 on the inner peripheral side of the fixing belt 41. A resistance heating element 42 is disposed on the lower surface side of the holding block 44. The fixing belt 41 and the holding block 44 extend in the sheet passing width direction.

  The resistance heating element 42 includes a long insulating substrate 45 made of glass or insulating ceramic, a long thin film heating film piece 46 having a uniform resistance, and a bowl-shaped pressing cover 47 opened upward. ing. The insulating substrate 45 with the heating film piece 46 is accommodated in the pressing cover 47 so that the heating film piece 46 faces the lower surface side of the holding block 44, and the pressing cover 47 is attached to the lower surface side of the holding block 44. Yes. The lower surface side of the pressure cover 47 is in contact with the pressure roller 32 via the fixing belt 41. A portion pressed by the pressure cover 47 of the fixing belt 41 and the pressure roller 32 are in pressure contact with each other to form a fixing nip portion 33. The resistance heating element 42 extends in the sheet passing width direction. Accordingly, the longitudinal direction of the resistance heating element 42 matches the longitudinal direction of the fixing belt 41 and the fixing nip portion 33. The heat generating film piece 46 is formed by dispersing a conductive filler in a resin material such as a heat-resistant resin and adjusting the electric resistivity to a predetermined value, and generates Joule heat when energized.

  A U-shaped (bifurcated) bearing bracket 48 is erected in a longitudinally middle portion on the upper surface side of the holding block 44. A screw shaft 50 extending in the sheet passing width direction is supported on the bearing bracket 48 so as to be rotatable and cannot be removed. A right screw portion 51 and a left screw portion 52 are formed separately on both sides of the screw shaft 50 with the bearing bracket 48 interposed therebetween. The right screw portion 51 and the left screw portion 52 are in a reverse screw relationship. A slider 53 that constitutes the power feeding body 43 is screwed into each of the screw portions 51 and 52.

  One end of the screw shaft 50 is connected to a drive motor 54 as a moving actuator via a power transmission system such as a gear or a belt so as to be able to transmit power. In this case, the transmission gear 57 fixed to one end side of the screw shaft 50 is meshed with the motor gear 56 fixed to the motor shaft 55 of the drive motor 54. The rotational power of the drive motor 54 is transmitted to the screw shaft 50 via the motor gear 56 and the transmission gear 57. By forward and reverse rotation of the screw shaft 50, both sliders 53 move in the opposite direction in conjunction with each other along the longitudinal direction (paper passing width direction) of the screw shaft 50. In the case of a printer that adopts one-side reference instead of the center reference as in the embodiment, at least one of the pair of power feeding bodies 43 can be moved along the longitudinal direction of the fixing nip portion 33 by the drive motor 54. It is sufficient if it is composed.

  On both sides of the holding block 44 with the bearing bracket 48 interposed therebetween, a guide groove hole 60 having a downward convex section extending in the sheet passing width direction is formed so as to penetrate vertically. The guide slot 60 is stepped with a wide lower side and a narrow upper side. The heating film piece 46 of the resistance heating element 42 faces the opening on the narrow portion 62 side in the guide groove 60.

  In the holding block 44, electrode wires 63 extending in the sheet passing width direction are embedded inside both sides of the bearing bracket 48. In the embodiment, one electrode wire 63 is embedded in the holding block 44 corresponding to one guide slot 60. Accordingly, a total of two electrode wires 63 exist in the holding block 44. Each electrode line 63 protrudes outward from each longitudinal end of the holding block 44. The outward projecting portions 64 of both electrode lines 63 are electrically connected to a power source 67 (an AC power source in the embodiment) via a feeder line 66. Each electrode wire 63 is formed with an overhanging portion 65 that projects toward the wide portion 61 side of the guide slot 60. The overhanging portion 65 of each electrode wire 63 protrudes on the bottom surface of the wide portion 61 of the guide slot 60.

  On the other hand, the lower side of each slider 53 opens downward. A reverse L-shaped conductive contact 70 is accommodated in a downward opening of each slider 53 via a compression spring 71 as an urging member. The lower side of the slider 53 is fitted into the wide portion 61 of the guide slot 60, and the lower side of the conductive contact 60 is fitted into the narrow portion 62. By forward / reverse rotation of the screw shaft 50, the sliders 53 move in the opposite direction in conjunction with each other along the corresponding guide slots 60. The moving range of each slider 53 is regulated by the guide slot 60.

  In a state where the slider 53 and the conductive contact 70 are fitted in the guide groove 60, the lower end surface of the conductive contact 70 abuts on the heating film piece 46 of the resistance heating element 42 and the conductive contact 70 is halfway. The flat surface comes into contact with the overhanging portion 65 of the electrode wire 63. Due to the pressing biasing force of the compression spring 71, the contact state between the conductive contact 70 and the heating film piece 46 of the resistance heating element 42 and the contact state between the conductive contact 70 and the overhanging portion 65 of the electrode wire 63 are good. Maintained. In other words, the electrical connection state between the electrode wire 63 and the resistance heating element 42 through the conductive contact 70 is favorably maintained. The contact area of the lower end surface of the conductive contact 70 with respect to the heat generating film piece 46 is set in a range that does not exceed the allowable current density of the conductive contact 70.

  By maintaining the lower end surface of each conductive contact 70 in contact with the heating film piece 46 of the resistance heating element 42, the power supply line 66, each electrode line 63, and each power supply body 43 (conductive contactor 70). ) Is supplied to the resistance heating element 42. The resistance heating element 42 generates heat by the current flowing through the resistance heating element 42, and the fixing belt 41 is heated by the resistance heating element 42. Due to the perspective movement of both sliders 53 based on the forward and reverse rotation of the screw shaft 50, both the conductive contacts 70 move while sliding on the heating film piece 46 of the heating resistor 42, and both the two via the resistance heating element 42. The energization distance D between the power feeding bodies 43 is changed steplessly. That is, the resistance heating element 42 and the heat generation width D of the fixing belt 41 are changed steplessly.

  In the embodiment, the energizing distance D between the two power feeding bodies 43 via the resistance heating element 42 corresponds to the length in the width direction (minimum sheet passing width) of the recording material P of the minimum size that can pass through the fixing nip portion 33. Can be changed steplessly from the minimum distance (see FIG. 4C) to the maximum distance (see FIG. 4A) corresponding to the length in the width direction (maximum sheet passing width) of the maximum size recording material P. It has become. The power supply line 66 has a relay 68 that controls on / off of power supply to the resistance heating element 42 and a switching regulator as an applied voltage changing unit that applies a voltage corresponding to the heating width D to the resistance heating element 42. 69 is interposed (see FIG. 5).

  As shown in FIG. 4, the screw shaft 50 and the two power feeding bodies 43 are located above the longitudinal center line NL of the fixing nip portion 33. Accordingly, both the power feeding bodies 43 move in the opposite direction in conjunction with each other along the longitudinal center line NL of the fixing nip portion 33. A combination of the slider 53, the compression spring 71, and the conductive contact 70 constitutes the power feeding body 43.

  Each power supply body 43 is provided with a temperature sensor 72 as a temperature detection member that detects the temperature of the fixing belt 41. In the embodiment, a base end side of a support arm 74 made of, for example, a leaf spring material or the like is attached to each slider 53. The support arm 74 extends toward the inner side in the sheet passing width direction (the inner side in the longitudinal direction of the fixing belt 41) than the slider 53. A detection unit 73 of the temperature sensor 72 is attached to the distal end side of the support arm 74. The detection unit 73 of the temperature sensor 72 is in pressure contact with the inner peripheral surface of the fixing belt 41 by the elastic restoring force of the support arm 74. Each temperature sensor 72 moves together in conjunction with the movement of the corresponding slider 53 (power supply body 43).

(3). Structure for executing power feeding body movement control and control mode thereof Next, a structure for executing power feeding body movement control and a control mode thereof will be described with reference to FIGS. 5 and 6. The controller 35 built in the control unit 28 that controls the overall control of the printer 1 includes a CPU that executes various arithmetic processes and controls, a communication interface (I / F) unit for connection with an external terminal, an EPROM, a flash memory, and the like. Storage means, a RAM for temporarily storing a control program and data, a counter for measuring the number of conveyed recording materials P, a timer for measuring time, an input / output interface, and the like. The controller 35 is electrically connected to a temperature sensor 72 of each power supply body 43, a drive motor 54 that rotates the screw shaft 50, a relay 68, a switching regulator 69, and the like. The controller 35 constitutes position changing means.

  The controller 35 changes the position of the pair of power feeding bodies 43 in accordance with the size of the recording material P, so that the energization distance D between the power feeding bodies 43 via the resistance heating body 42 (the heating width D of the fixing belt 41). ) Can be changed and adjusted. The algorithm shown in the flowchart of FIG. 6 is stored in advance in the storage means of the controller 35 as a program, and is read by the RAM and then executed by the CPU.

  As shown in FIG. 6, when the controller 35 receives a command from an external terminal or the like, the power feeding body movement control is started. Data on the size of the material P and the planned number of printed sheets is acquired (S01), and the energization distance D between the power feeding bodies 43 is determined based on the size difference of the recording material P between the previous job and the current job and the number of the planned number of printed sheets. It is determined whether or not the change is necessary (S02). The size information of the recording material P includes the orientation of the recording material P such as A4 portrait and A4 landscape, for example. For example, in the current job, when the recording material P is changed from a large size to a small size and the planned number of printed sheets is large, if the energization distance D between the two power feeding bodies 43 is made the same as the large size state, the fixing belt 41 A portion outside the sheet passing width is heated to a temperature equal to or higher than the fixing temperature to cause partial temperature unevenness (see FIG. 4B), which may cause paper wrinkles and uneven fixing. Therefore, when it is determined that the energization distance D needs to be changed (S02: YES), the energization from the power source 67 to the resistance heating element 42 is stopped by turning off the relay 68 (S03).

  Next, the moving amount Ms of each power supply body 43 in the current job is determined from the size difference of the recording material P between the previous job and the current job, and each power supply body is determined from the temperature table corresponding to each size of the recording material P. A specified temperature Ts used for fine adjustment of the 43 position is determined (S04). In this case, the rotation direction of the drive motor 54 and the rotation speed or rotation time are determined as parameters corresponding to the movement amount Ms. The distance between the two power feeding bodies 43 after moving the moving amount Ms is slightly shorter than the energizing distance D corresponding to the width direction length of the recording material P in the current job. For this reason, after moving the moving amount Ms, the lower end surface of the conductive contact 70 of each power feeding body 43 is placed at a specified position overlapping the end portion in the width direction of the recording material P in the current job. Each specified temperature Ts in the temperature table is set for each size of the recording material P based on the position of each power supply body 43 and the temperature distribution of the fixing belt 41 (which may be referred to as the temperature distribution of the resistance heating element 42). Thus, the fixing temperature can be ensured even when the recording material P is located outside the end in the width direction during continuous printing. The temperature table is obtained by experiments or the like and is stored in advance in the storage means of the controller 35.

  Then, the drive motor 54 is driven at a high speed (corresponding to the first speed) based on the rotation direction and the rotation speed or the rotation time (first speed) determined in step S04, so that both power feeding bodies 43 are screw shafts 50. Is moved at high speed by the amount of movement Ms along the longitudinal direction (S05). As described above, the distance between the two power feeding bodies 43 after moving the movement amount Ms is slightly shorter than the energization distance D corresponding to the width direction length of the recording material P in the current job. The lower end surface of the 43 conductive contacts 70 moves to a specified position overlapping the end portion in the width direction of the recording material P in the current job. When both the power feeding bodies 43 move at high speed by the amount of movement Ms and reach the specified positions (S06: YES), the switching regulator 69 corresponds to the energization distance D (which may be referred to as the heat generation width D) in the current job. The applied voltage is set, and the resistance heating element 42 is energized from the power supply 67 when the relay 68 is turned on (S07). In the embodiment, since energization is stopped when each power feeding body 43 is moved at high speed, there is no possibility of generating a spark discharge even if a minute gap is formed between the resistance heating element 42 and each power feeding body 43. .

  In the configuration of the embodiment, the minute gap formed between the resistance heating element 42 and each power supply body 43 due to vibration during high-speed movement is approximately 100 μm or less. For example, the configuration of Patent Document 1 is formed. The size was 1/5 to 1/2 of the minute gap. Therefore, according to the configuration of the embodiment, the contact state between the resistance heating element 42 and each power supply body 43 can be maintained extremely well, and even when each power supply body 43 is moved at high speed while being energized, almost no spark discharge occurs. It is.

  Next, the drive motor 54 is driven at a low speed (corresponding to a second speed (slower than the first speed)) in a direction opposite to the rotation direction determined in step S04, and both power feeding bodies 43 are connected to step S05. Is moved at a low speed in the reverse direction (S08), and the position of both power feeding bodies 43 is finely adjusted while accurately grasping the temperature distribution (heat generation width D) of the fixing belt 41 (resistance heating element 42). When the detected temperatures T1 and T2 of the two temperature sensors 72 have substantially reached the specified temperature Ts (S11: YES), the drive motor 54 is stopped (S12), and then the fixing process is started.

  Here, as shown in FIG. 4, in a state where the detected temperatures T <b> 1 and T <b> 2 of the two temperature sensors 72 almost reach the specified temperature Ts, the detection unit 73 of each temperature sensor 72 detects the temperature within the heat generation width D of the fixing belt 41. Of the distribution, the shoulder-like area 81 located outside the stable area 80 is detected. The temperature in the stable range 80 is approximately the fixing temperature, and the temperature in the shoulder-shaped region 81 (temperature near the boundary of the heat generation width D) is slightly lower than the fixing temperature (for example, about 70% of the fixing temperature).

  If the difference (absolute value) between the detected temperatures T1 and T2 of the two temperature sensors 72 is equal to or higher than a predetermined temperature T0 (about 50 to 100 ° C. in the embodiment) (S10: YES), the power supply 67 is turned off by turning off the relay 68. To the resistance heating element 42 is stopped (S13). Due to the structure of the fixing roller 31, the detected temperatures T1 and T2 of the two temperature sensors 72 have substantially the same value, but the difference (absolute value) between the detected temperatures T1 and T2 of the two temperature sensors 72 is a predetermined temperature T0. If it is above, the abnormal state, for example, a crack has occurred. Therefore, in such a case, power supply is immediately stopped to ensure safety.

(4). Summary As is apparent from the above description, according to the embodiment, the fixing roller 31 is separated from the fixing belt 41 that is positioned on the inner peripheral side of the fixing belt 41 and the fixing belt 41 that is in pressure contact with the pressure roller 32. And a pair of power feeding bodies 43 connected to the resistance heating element 42. The longitudinal direction of the resistance heating element 42 coincides with the longitudinal directions of the fixing belt 41 and the fixing nip 33, and Since at least one of the power feeding bodies 43 is configured to be movable along the longitudinal direction of the fixing nip portion 33 by the drive motor 54, the heat generation width D of the fixing roller 31 (fixing belt 41) is changed steplessly. Thus, the fixing roller 31 (fixing belt 41) can be heated by an amount corresponding to the size (length in the width direction) of the recording material P, but resistance is maintained even when each power feeding body 43 is moved. The close contact between the heating element 42 and each of the power feeding bodies 43 can be maintained very well, and the resistance heating element 42 and both the feeding bodies 43 can be energized stably. Therefore, the occurrence of spark discharge can be avoided, and damage and deterioration of the fixing roller 31 due to spark discharge can be remarkably suppressed. Moreover, it is needless to say that wasteful power consumption can be suppressed and the temperature raising time can be shortened.

  In the embodiment, since the pair of power feeding bodies 43 are located above the longitudinal center line NL of the fixing nip portion 33, both the power feeding bodies 43 move linearly along the longitudinal direction of the resistance heating element 42. Become. Therefore, a relatively uniform temperature distribution with little unevenness can be secured within the heat generation width D of the resistance heating element 42, and the fixability of the toner image on the recording material P can be improved.

  Further, since the temperature sensor 72 for detecting the temperature of the fixing belt 41 is provided, and the temperature sensor 72 is attached to each power supply body 43 so as to move in conjunction with the temperature sensor 72. The temperature near the boundary of the heat generation width D of the fixing belt 41 can be sequentially detected. Accordingly, both power feeding bodies 43 are moved along the longitudinal direction of the fixing nip portion 33 (resistance heating element 42) while accurately grasping the heat generation width D of the fixing belt 41 (resistance heating element 42) by the two temperature sensors 72. It becomes possible.

  In addition, since the detection units 73 of the temperature sensors 72 are positioned on the inner side in the longitudinal direction of the fixing belt 41 with respect to the corresponding power supply bodies 43, the detection units 73 are always within the heat generation width D of the fixing belt 41. Will exist. Accordingly, the temperature in the vicinity of the boundary in the heat generation width D of the fixing belt 41 can be accurately and accurately detected even though the temperature sensor 72 moves in conjunction with the power feeding body 43.

  According to the embodiment, based on at least one of the size information of the recording material P passing through the fixing nip portion 33 and the detection information of each temperature sensor 72, the drive motor 54 is driven and at least one of the pair of power feeding bodies 43. Since the controller 35 for changing one position is further provided, both the power feeding bodies 43 are moved by an amount corresponding to the size (length in the width direction) of the recording material P, and the fixing roller 31 (fixing belt 41) generates heat. The stepless change of the width D can be executed smoothly. The movement accuracy of at least one of the pair of power feeding bodies 43 can be improved.

  Further, when changing the position of at least one of the pair of power feeding bodies 43, a switching regulator 69 that changes the voltage applied to both power feeding bodies 43 according to the size information of the recording material P passing through the fixing nip 33 is provided. Thus, the applied voltage per unit region of the resistance heating element 42 can be made constant by changing the voltage applied to both the feeding elements 43 in accordance with the resistance between the both feeding elements 43 in the resistance heating element 42. Therefore, it is possible to reliably suppress the occurrence of spark discharge and to save energy by reducing power consumption during the fixing process.

  Further, when using the size information of the recording material P passing through the fixing nip portion 33, the drive motor 54 is driven at the first speed (high speed), and when using the detection information of each temperature sensor 72, the drive motor 54 is used. Are driven at a second speed (low speed) that is slower than the first speed, and therefore, when the size of the recording material P is switched, or when the position of the power feeding body 43 is finely adjusted according to the heat generation width D Depending on the situation, the power feeding body 43 can be moved quickly or slowly, and the power feeding body 43 can be moved appropriately and accurately.

  In addition, if the difference between the detected temperatures T1 and T2 of the two temperature sensors 72 is large, the energization to the resistance heating element 42 is stopped. Therefore, even if an abnormal state such as a crack occurs, the energization is immediately stopped for safety. Can be secured.

(5). Others The present invention is not limited to the above-described embodiment, and can be embodied in various forms. For example, a printer has been described as an example of the image forming apparatus. Further, the length of the support arm 74 of each temperature sensor 72 may be adjustable. For example, when the basis weight of the recording material P is large or the recording material P is glossy paper, the support arm 74 is lengthened, and the detection unit 73 of each temperature sensor 72 is further moved inward in the sheet passing width direction (inner longitudinal direction of the fixing belt 41). ). In addition, the configuration of each unit is not limited to the illustrated embodiment, and various modifications can be made without departing from the spirit of the present invention.

P Recording material 1 Printer 5 Fixing device 31 Fixing roller 32 Pressing roller 33 Fixing nip part 35 Controller (position changing means)
41 fixing belt 42 resistance heating element 43 power supply 50 screw shaft 51 right screw part 52 left screw part 53 slider 54 drive motor 66 power supply line 67 power supply 69 switching regulator (applied voltage changing means)
70 conductive contact 72 temperature sensor (temperature detection means)
73 Detector

Claims (7)

A heating rotating member having a resistance heating element that generates heat when energized and a pressure rotating member pressed against the heating rotating member are provided, and an unfixed toner image is attached to a fixing nip portion between the heating rotating member and the pressure rotating member. A fixing device for passing the recording material through and fixing the recording material,
The heating rotating member includes: a rotating body that is pressed against the pressurizing rotating member; the resistance heating element that is positioned on the inner peripheral side of the rotating body and configured separately from the rotating body; and the resistance heating element A pair of conductive bodies that conduct,
The longitudinal direction of the resistance heating element coincides with the longitudinal direction of the rotating body and the fixing nip portion, and at least one of the pair of power feeding bodies is movable along the longitudinal direction of the fixing nip portion by a moving actuator. Configure
When changing the position of at least one of the pair of power feeding bodies, the apparatus further comprises an applied voltage changing means for changing the voltage applied to the both power feeding bodies according to the size information of the recording material passing through the fixing nip portion. ing,
Fixing device. A temperature detection member for detecting the temperature of the rotating body is provided, and the temperature detection member is attached to each power feeding body so as to move in conjunction with the temperature detection member.
The fixing device according to claim 1. The detection part of each said temperature detection member is located in the longitudinal direction inside of the above-mentioned rotating body rather than the above-mentioned electric power feeding object corresponding to this,
The fixing device according to claim 2. Based on at least one of the size information of the recording material passing through the fixing nip portion and the detection information of each temperature detection member, the position of at least one of the pair of power feeding bodies is changed by driving the moving actuator. Further comprising position changing means,
The fixing device according to claim 1. When the size information of the recording material passing through the fixing nip is used, the moving actuator is driven at a first speed, and when the detection information of each temperature detecting member is used, the moving actuator is moved to the first speed. Drive at a second speed slower than the speed,
The fixing device according to claim 4. If the difference between the detection information of the two temperature detection means is large, stop energization to the resistance heating element,
The fixing device according to claim 2. The fixing device according to claim 1 is provided.
Image forming apparatus.

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