JP6693433B2 - Fixing device and image forming apparatus - Google Patents

Description

  The present invention relates to a fixing device that fixes a toner image on a recording medium and an image forming apparatus including the fixing device.

  An electrophotographic image forming apparatus such as a copying machine or a printer includes a fixing device that fixes a toner image on a recording medium such as paper. The fixing device includes, for example, a fixing member that contacts and heats the recording medium, and a pressure member that pressurizes the recording medium passing between the fixing member, and heats and melts the toner formed on the recording medium. To fix the toner image on the recording medium. Further, the fixing device includes a separation claw that comes into contact with the surface of the fixing member and separates the recording medium from the fixing member.

  For example, the fixing device of Patent Document 1 includes a fixing roller (fixing member) that fixes an image formed on a recording sheet, a separating member (separating claw) that contacts the fixing roller and separates the recording sheet from the fixing roller, And a moving unit that moves the separating member in the axial direction of the fixing roller.

  The peeling claw holding fixing device of Patent Document 2 passes through a plurality of peeling claws (separating claws) provided for peeling a recording paper (recording medium) from a fixing roller (fixing member) and a fixing roller to perform a fixing process. The number of processed sheets of the recording paper to be processed is detected, the peeling claw driving means for moving the plurality of peeling claws in parallel with the axial direction of the fixing roller, and the peeling according to the detection output of the processed number detecting means. And a control unit that controls the operation of the peeling claw driving unit so that the relative position between the claw and the fixing roller changes.

Japanese Utility Model Publication No. 5-8574 JP, 2006-330618, A

  In the fixing device, when the fixing claw is repeatedly contacted with the fixing member at the fixed position by repeating the fixing process, the load is concentrated on the contact portion of the fixing member with the separating claw and is worn, and the surface of the fixing member is scraped, The toner releasability deteriorates, and the toner adheres, causing an image defect. In order to prevent such damage to the fixing member, there is a fixing device that thrusts the separation claw in the direction of the rotation axis of the fixing member as described above.

  However, the separation claw immediately after being assembled to the fixing device may have minute scratches or foreign matter such as metal adhered to the tip contacting the fixing member. When the fixing process (printing process) is repeated, the scratches or foreign matter on the separation claw are removed by repeated contact with the recording medium, but minute scratches may occur on the surface of the fixing member. Here, when the separating claw is in the thrust operation, scratches or foreign matter on the separating claw cause minute scratches on the surface of the fixing member over the range of the thrust operation. When scratches are generated in a wide area on the surface of the fixing member, a phenomenon (white streaks in the image) occurs in which a solid area or a halftone area of the image fixed on the recording medium looks white due to light interference. Will end up. When the thrusting operation of the separation claw is not performed in order to avoid such a phenomenon, the durability is deteriorated due to the damage of the fixing member and the image quality is deteriorated as described above.

  Therefore, in view of the above circumstances, the present invention aims to prevent the image defect by suppressing the spread of scratches on the surface immediately after the start of use of the fixing member, and to maintain the durability and good image quality of the fixing member. To do.

  The fixing device of the present invention includes a rotatable fixing member that contacts a recording medium on which a toner image is formed and heats the recording medium, and a rotatable fixing member that presses the recording medium passing between the fixing member. A pressure-applying member; and a separating claw that is in contact with the surface of the fixing member and is capable of thrusting in the rotation axis direction of the fixing member and that separates the recording medium from the fixing member. The fixing member is fixed at an initial position in the rotation axis direction of the fixing member from the start of use until a predetermined starting condition is satisfied, and the fixing member is fixed when the fixing member satisfies the predetermined starting condition. It is characterized in that the thrust operation in the direction of the rotation axis of the member is started.

  The predetermined start condition may be a lapse of a predetermined cumulative drive time of the fixing member.

  The predetermined start condition may be a lapse of a predetermined cumulative number of printed sheets of the fixing member.

  An image forming apparatus of the present invention includes the above-mentioned fixing device.

  According to the present invention, it is possible to suppress the spread of scratches on the surface of the fixing member immediately after the start of use, prevent image defects, and maintain the durability and good image quality of the fixing member.

1 is a sectional view schematically showing a printer according to an embodiment of the present invention. FIG. 4 is a cross-sectional view showing the fixing device according to the embodiment of the present invention from the front. FIG. 3 is a front view showing a fixing roller drive mechanism and a separation claw drive mechanism of the fixing device according to the embodiment of the present invention. FIG. 3 is a right side view showing a support shaft, a separation pawl, and a separation pawl drive mechanism of the fixing device according to the embodiment of the present invention. FIG. 3 is a block diagram illustrating an electrical configuration of a fixing device according to an exemplary embodiment of the present invention. 6 is a flowchart illustrating an operation of the fixing device according to the exemplary embodiment of the present invention. 8 is a flowchart illustrating an operation of the fixing device according to another exemplary embodiment of the present invention. 8 is a flowchart illustrating an operation of the fixing device according to another exemplary embodiment of the present invention.

  First, the overall configuration of the printer 1 (image forming apparatus) according to the embodiment of the present invention will be described with reference to FIG. FIG. 1 is a cross-sectional view of the printer 1 as seen from the front side (front side) in the device depth direction (front-back direction) of the printer 1. In each drawing, the right and left sides of the printer 1 in the device width direction (left and right direction) are indicated by arrows L and R, respectively, and the upper and lower sides of the printer 1 in the device height direction (up and down direction) are indicated by arrow U and arrow, respectively. The front side (front side) and the back side (rear side) of the printer 1 in the device depth direction (front-back direction) are indicated by arrows Fr and Rr, respectively.

  The printer 1 includes a box-shaped printer body 2. A paper feed cassette that stores paper (recording medium) is housed in the lower portion of the printer body 2, and a paper discharge tray is provided on the upper surface of the printer body 2.

  An exposure unit composed of a laser scanning unit (LSU) is arranged above the printer body 2 below the paper discharge tray, and an image forming unit 3 is provided below the exposure unit. The image forming section 3 is rotatably provided with a photosensitive drum 5 which is an image carrier. Around the photoconductor drum 5, a charger, a developing device, a transfer roller 6, and a cleaning device are arranged along the rotation direction of the photoconductor drum 5. A toner container containing toner is arranged above the developing device, and the toner container is connected to the developing device.

  Inside the printer body 2, a paper transport path 10 is provided. In the printer 1, the device width direction is the paper conveyance direction (paper length direction), and the device depth direction is the paper width direction. At the upstream end of the transport path 10, a paper feed unit is provided near the paper feed cassette. A pair of registration rollers 11 is provided in the midstream portion of the transport path 10, and a transfer unit 12 including the photoconductor drum 5 and the transfer roller 6 is provided on the transport path 10 downstream of the pair of registration rollers 11. A fixing device 13 is provided in the downstream portion of the transport path 10, and a paper discharge unit 14 is provided in the vicinity of the paper discharge tray at the downstream end of the transport path 10. A control device 15 that controls the fixing device 13 is provided inside the printer body 2.

  Next, the image forming operation of the printer 1 having such a configuration will be described. The printer 1 starts image forming operation when image data is input from an external computer or the like and a print start instruction is given. First, in the image forming unit 3, the surface of the photoconductor drum 5 is charged by the charger and then exposed by the exposure device based on the image data, and an electrostatic latent image is formed on the surface of the photoconductor drum 5. .. This electrostatic latent image is developed into a toner image with toner by a developing device.

  On the other hand, the paper stored in the paper feed cassette is taken out by the paper feed unit and conveyed on the conveyance path 10. The sheet on the conveyance path 10 is conveyed to the transfer section 12 at a predetermined timing by the pair of registration rollers 11, and the transfer section 12 transfers the toner image on the photosensitive drum 5 to the sheet. The sheet on which the toner image is transferred is conveyed to the fixing device 13, and the fixing device 13 fixes the toner image on the sheet. The paper on which the toner image is fixed is discharged from the paper discharge unit 14 to the paper discharge tray. In the image forming unit 3, the toner remaining on the photosensitive drum 5 is collected by the cleaning device.

  Next, the fixing device 13 will be described. As shown in FIG. 2, the fixing device 13 includes a frame 20, a fixing roller 21 (fixing member), a pressure roller 22 (pressurizing member), a first heater 23, a second heater 24, and a first heater. The temperature sensor 25, the second temperature sensor 26, the output sensor 27, the support shaft 28, and a plurality of (for example, four) separation claws 29 are provided. Further, as shown in FIGS. 3 and 4, the fixing device 13 includes a fixing roller driving mechanism 30 and a separation claw driving mechanism 31.

  As shown in FIG. 2, the frame 20 is formed in a box shape, and has a paper inlet 20a on the right side and a paper outlet 20b on the left side. The frame 20 is attached to the printer body 2 so that the transport path 10 passes through the inlet 20a and the outlet 20b and penetrates the frame 20.

  The fixing roller 21 includes, for example, a cylindrical cored bar 21a and a release layer 21b that covers the cored bar 21a, and is formed in a substantially cylindrical shape that is long in the apparatus depth direction (front-rear direction). The cored bar 21a is formed of, for example, a thin tube made of metal such as aluminum or iron and having an outer diameter of 30 mm. The release layer 21b is made of a fluororesin such as PFA (tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer) or PTFE (polytetrafluoroethylene), and is centered from both ends in the rotation axis direction in order to suppress wrinkles on the paper. It is formed in an inverted crown shape whose outer diameter decreases. The fixing roller 21 is provided with the release layer 21b to realize the prevention of toner adhesion and the suppression of charging. The release layer 21b may be made of, for example, a fluororesin mixed with an abrasion resistant material (for example, silicon carbide) in order to improve the durability, and the abrasion resistant material is reduced in order to improve the release property. You may lose it or not. Note that in another different embodiment, the fixing roller 21 may stack an elastic layer (not shown) between the cored bar 21a and the release layer 21b.

  The fixing roller 21 is rotatably attached to the upper portion of the frame 20 with the device depth direction as the rotation axis direction. A fixing roller driving gear 30c (see FIG. 3) of the fixing roller driving mechanism 30 is coaxially connected to the rear end of the fixing roller 21, and the fixing roller driving gear 30c receives a rotational driving force to rotate, The fixing roller 21 rotates.

  By the way, the printer 1 may use a low melting point polyester toner in order to achieve energy saving. In this case, although the release layer 21b of the fixing roller 21 initially maintains good toner releasability, the releasability is deteriorated due to deterioration of the surface with time and the adherence of paper dust, and the toner is not released. May adhere. This phenomenon is more remarkable when the temperature of the fixing roller 21 is relatively high. Further, when the temperature of the pressure roller 22 rises when the printer 1 performs intermittent printing or the like, the fixing property of the fixing device 13 is improved, but the releasability is deteriorated even when the temperature of the fixing roller 21 is relatively low. To do. On the other hand, in order to improve the releasability of the fixing roller 21, the release layer 21b in which the abrasion resistant material is reduced or eliminated may be applied. Since the durability of the release layer 21b having reduced wear resistance is reduced, the separation claws 29 may be worn or damaged due to repeated contact.

  The pressure roller 22 includes, for example, a columnar cored bar 22a, an elastic layer 22b provided around the cored bar 22a, and a release layer 22c that covers the elastic layer 22b. It has a long cylindrical shape. The cored bar 22a is formed of a metal such as stainless steel or iron with an outer diameter of 12 mm. The elastic layer 22b is made of, for example, silicon rubber or silicon sponge and has a thickness of 9 mm. The release layer 22c is formed of, for example, a fluorine-based resin such as PFA.

  The pressure roller 22 is rotatably attached to the lower portion in the frame 20 with the device depth direction as the rotation axis direction. In particular, the pressure roller 22 is arranged, for example, on the lower left side of the fixing roller 21 so that the outer peripheral surfaces of the fixing roller 21 and the fixing roller 21 face each other. The pressure roller 22 is pressed by the fixing roller 21 so that the fixing nip N is formed between the pressure roller 22 and the fixing roller 21, and is rotated by the rotation of the fixing roller 21.

  The 1st heater 23 and the 2nd heater 24 are heat sources which consist of a halogen heater of 600W and 400W, respectively, for example. The first heater 23 and the second heater 24 generate heat by being energized by voltage application from a voltage supply unit (not shown) supplied with power from the power supply 42 (see FIG. 5). The first heater 23 is arranged inside the cored bar 21a of the fixing roller 21 at the upstream side in the sheet conveying direction and at the center in the sheet width direction (center of the sheet passing area), and the center in the rotation axis direction of the fixing roller 21 is arranged. To heat. The second heaters 24 are arranged inside the cored bar 21a of the fixing roller 21 at the downstream side in the sheet conveying direction and at both ends in the sheet width direction (non-sheet passing areas at both ends), and both ends in the rotation axis direction of the fixing roller 21. To heat. As the fixing roller 21 rotates, the circumferential portion of the fixing roller 21 heated by the first heater 23 and the second heater 24 changes.

  The first temperature sensor 25 and the second temperature sensor 26 are, for example, configured by a thermistor or the like provided in non-contact with the fixing roller 21. The first temperature sensor 25 and the second temperature sensor 26 are connected to the control device 15 (see FIG. 5) and transmit the detected temperature to the control device 15. The first temperature sensor 25 is arranged inside the frame 20 on the outer diameter side (for example, the upper side) of the fixing roller 21 and in the center in the paper width direction, and detects the temperature of the center of the fixing roller 21 in the rotation axis direction. The second temperature sensors 26 are arranged inside the frame 20 at the outer diameter side (for example, the upper side) of the fixing roller 21 and at both ends in the paper width direction, and detect the temperature at both ends in the rotation axis direction of the fixing roller 21.

  The output sensor 27 is arranged on the downstream side of the fixing nip N between the fixing roller 21 and the pressure roller 22 in the paper conveyance direction, and detects the paper output after the fixing process.

  The support shaft 28 is a metal member having a shape elongated in the rotation axis direction of the fixing roller 21, and is arranged on the fixing roller 21 side of the conveyance path 10 in the frame 20 and on the downstream side of the fixing roller 21 in the sheet conveyance direction. It The support shaft 28 is attached to the frame 20 so as to be capable of thrusting in the device depth direction (the rotation axis direction of the fixing roller 21).

  For example, both ends of the support shaft 28 in the device depth direction are pivotally supported by the frame 20. As shown in FIG. 4, on the front end face (front end face) of the support shaft 28 in the depth direction of the device, a first biasing force such as a coil spring that biases the support shaft 28 toward the rear side with respect to the frame 20. The member 28a is provided, and the end face (rear end face) on the back side is provided with a pressed portion 28b on which the support shaft 28 receives a pressing force toward the front side. Further, a plurality of resin holders 28c for mounting the plurality of separation claws 29 are provided on the support shaft 28 at predetermined intervals in the paper width direction.

  Each separation claw 29 has a base portion 29a attached to the support shaft 28 and a tip portion 29b protruding from the base portion 29a in a direction away from the support shaft 28. Each separation claw 29 is made of, for example, a resin material such as polyimide resin or PEK (polyetherketone), and is formed by being coated with a coat layer made of a fluororesin such as PFA. By providing this coat layer, toner is attached. The prevention is realized.

  The plurality of separation claws 29 are attached to the plurality of holders 28c of the support shaft 28 so that the leading ends 29b contact the fixing roller 21 in the vicinity of the fixing nip N. For example, each separation claw 29 has a swing shaft 29c extending from the base portion 29a to both sides in the sheet width direction, and is pivotally supported by each holder 28c so as to be swingable around the axis in the sheet width direction. Each separation claw 29 is provided with a second biasing member 29d such as a torsion coil spring, and each separation claw 29 is biased against each holder 28c so that the tip end 29b approaches the fixing roller 21. There is.

  In this manner, the paper stuck to the fixing roller 21 is separated (peeled) by the tip portions 29b of the separation claws 29 that come into contact with the fixing roller 21 under the constant load of the second biasing member 29d. Since each separation claw 29 is fixed to the support shaft 28 by each holder 28c and the second urging member 29d and operates integrally with the support shaft 28, good durability can be maintained. Along with the thrust operation of the support shaft 28, the plurality of separation claws 29 also perform the thrust operation in the apparatus depth direction (the rotation axis direction of the fixing roller 21).

  As shown in FIG. 3, the fixing roller driving mechanism 30 includes a driving unit 30a such as a motor, a fixing driving input gear 30b connected to the driving unit 30a, and a fixing roller driving gear 30c meshed with the fixing driving input gear 30b. With. The fixing drive input gear 30b and the fixing roller drive gear 30c are rotatably provided with the apparatus depth direction as the rotation axis direction. Each part of the fixing roller driving mechanism 30 is attached to the frame 20 (inside or outside thereof) on the back side (rear side) in the device depth direction, for example. When the drive unit 30a that receives a drive signal from the control device 15 operates, the rotational drive force generated by the drive unit 30a is connected to the fixing roller drive gear 30c via the fixing drive input gear 30b and the fixing roller drive gear 30c. It is transmitted to the fixing roller 21.

  As shown in FIG. 3, the separation claw drive mechanism 31 includes a separation claw drive input gear 31a, an input switching section 31b, a first speed adjustment gear 31c, and a second speed adjustment gear 31d, and is shown in FIG. Thus, the worm 31e, the worm wheel 31f, and the cam 31g are provided.

  The separation claw drive input gear 31a, the first speed adjusting gear 31c, the second speed adjusting gear 31d, and the worm 31e are rotatably provided with the device depth direction as the rotation axis direction, and the worm wheel 31f and the cam 31g are the device depth direction. Is rotatably provided with the device width direction (or the device up-down direction) intersecting with the axis of rotation as the rotation axis direction. Each part of the separation claw driving mechanism 31 is attached to the frame 20 (inside or outside thereof) on the back side (rear side) in the device depth direction, for example.

  The separation claw drive input gear 31a is an input state (see the solid line in FIG. 3) that meshes with the fixing roller drive gear 30c and the first speed adjusting gear 31c at the same time, and at least one of the fixing roller drive gear 30c and the first speed adjusting gear 31c. The non-input state (see the broken line in FIG. 3) that does not mesh with is movable. When the separation claw drive input gear 31a is in the input state, the rotational driving force transmitted to the fixing roller drive gear 30c is also transmitted to the first speed adjusting gear 31c via the separation claw drive input gear 31a. On the other hand, when the separation claw drive input gear 31a is in the non-input state, the rotational drive force from the fixing roller drive gear 30c to the first speed adjusting gear 31c is cut off.

  The input switching unit 31b switches between input and non-input of the rotational driving force from the fixing roller driving gear 30c in order to switch the thrust operation of each separation claw 29 between ON and OFF. In the present embodiment, the input switching unit 31b stops the thrust operation of each separation claw 29 immediately after the fixing device 13 (fixing roller 21) is assembled (when the use is started). In order to fix the separation claw drive input gear 31a to the non-input state. When the input switching unit 31b receives the start signal from the control device 15, the input switching unit 31b switches the separation claw drive input gear 31a to the input state in order to start the thrust operation of each separation claw 29.

  For example, the input switching unit 31b pivotally supports the separation pawl drive input gear 31a by a shaft support member, and urges the shaft support member by an urging member or the like to bring the separation pawl drive input gear 31a into an input state. On the other hand, the separation claw drive input gear 31a is moved to the non-input state by moving the shaft support member against the biasing force by a solenoid or the like while energizing.

  The first speed adjusting gear 31c is meshed with the second speed adjusting gear 31d, and the rotational driving force transmitted to the first speed adjusting gear 31c is also transmitted to the second speed adjusting gear 31d. The speed (rotation speed) of the rotational drive force transmitted to the second speed adjustment gear 31d is adjusted by the gear ratio of the separation claw drive input gear 31a, the first speed adjustment gear 31c, and the second speed adjustment gear 31d.

  The worm 31e is coaxially connected to the second speed adjusting gear 31d and further meshes with the worm wheel 31f. The rotational driving force transmitted to the second speed adjusting gear 31d is converted in rotational direction by the worm 31e and the worm wheel 31f and then transmitted to the worm wheel 31f.

  An eccentric, substantially elliptical cam 31g is coaxially connected to the worm wheel 31f. Each part of the separation claw drive mechanism 31 is arranged so that the outer peripheral surface of the cam 31g abuts against the pressed portion 28b of the support shaft 28, and the rotational movement of the cam 31g causes the support shaft 28 (each separation claw 29) to rotate. Converted to linear motion (thrust motion in the depth direction of the device). Since the thrust motion of the support shaft 28 and each separation claw 29 is based on the rotational motion of the elliptical cam 31g, the thrust motion is a reciprocating motion with a period corresponding to the outer peripheral length of the cam 31g. In other words, the cam 31g designed to obtain the desired thrust operation range of each separation claw 29 is applied.

  In this way, the separation claw drive mechanism 31 thrusts the support shaft 28 and each separation claw 29 in the device depth direction in accordance with the rotational driving of the fixing roller 21 when the separation claw drive input gear 31a is in the input state. On the other hand, when the separation claw drive input gear 31a is in the non-input state, the positions of the support shaft 28 and each separation claw 29 in the device depth direction are fixed. The initial positions of the separation claws 29 may be set when the support shaft 28, the separation claws 29, and the separation claw drive mechanism 31 are assembled to the fixing device 13.

  Next, the electrical configuration around the control device 15 that controls the fixing device 13 will be described with reference to FIG. The fixing device 13 may employ a main control device (not shown) that controls the printer 1 as the control device 15.

  The control device 15 includes a control unit 40 including a CPU and the like, and a storage unit 41 including ROM and RAM and the like. The controller 15 is connected to the first heater 23, the second heater 24, the first temperature sensor 25, the second temperature sensor 26, and the output sensor 27 described above. Further, the control device 15 is connected to the drive unit 30a of the fixing roller drive mechanism 30, the input switching unit 31b of the separation pawl drive mechanism 31, the power supply 42, and other parts of the fixing device 13.

  The power supply 42 is connected to each part of the fixing device 13 to supply electric power, and for example, supplies electric power to the connected control device 15. The fixing device 13 may employ, as the power supply 42, a main power supply (not shown) that supplies electric power to each unit of the printer 1.

  The control device 15 executes various functions of the fixing device 13, such as a heating control function of the first heater 23 and the second heater 24, a temperature detection function of the fixing roller 21, a thrust operation control function of each separation claw 29, and the like. The storage unit 41 stores programs and data that realize various functions of the fixing device 13. Then, the control device 15 executes arithmetic processing according to each program stored in the storage unit 41 and controls each unit connected to the control device 15. For example, when the main power source of the printer 1 is turned on, the control device 15 causes the power source 42 to supply a voltage to the first heater 23 and the second heater 24 to heat the fixing roller 21. Further, the control device 15 monitors the surface temperature of the fixing roller 21 by the first temperature sensor 25 and the second temperature sensor 26, and controls the first heater 23 and the first heater 23 so that the fixing roller 21 reaches a predetermined temperature at which fixing processing can be performed. The second heater 24 is controlled.

  The control device 15 controls switching of the thrust operation between operation and stop, as a thrust operation control function of each separation claw 29. The control device 15 determines that the printer 1 and the fixing device 13 (fixing roller 21) are activated for the first time after shipment from the factory, that is, that a predetermined amount of accumulated use has been made since the start of use, as a predetermined thrust operation start condition (start condition). To do. Then, the control device 15 sends a start signal for instructing the start of the thrust operation of each separation claw 29 to the separation claw drive mechanism 31 (input switching unit 31b) when a predetermined thrust operation start condition is satisfied. Send.

  For example, the control device 15 sets the passage of a predetermined cumulative drive time of the fixing roller 21 as the predetermined thrust operation start condition. In order to monitor the cumulative driving time of the fixing roller 21, the control device 15 detects the time when the driving unit 30a drives the fixing roller 21 and stores it in the storage unit 41. Then, the control device 15 transmits a start signal to the separation pawl drive mechanism 31 when the fixing roller 21 is driven for a predetermined accumulated drive time (for example, 3 hours) or more from the start of use.

  Such thrust operation control of each separation claw 29 will be described with reference to the flowchart of FIG. In the fixing device 13, the thrust operation of the support shaft 28 is not performed until the predetermined cumulative driving time elapses from the start of use of the fixing roller 21 (step S1) (step S2: NO), and each separation claw 29 is moved to the initial position. Has been maintained. When the fixing roller 21 is driven for a predetermined cumulative drive time or longer (step S2: YES), the fixing device 13 starts the thrust operation of the support shaft 28 and each separation claw 29 (step S3).

  According to the present embodiment, as described above, the fixing device 13 of the printer 1 (image forming apparatus) includes the rotatable fixing roller 21 that contacts the paper (recording medium) on which the toner image is formed and heats the paper. The rotatable pressing roller 22 (pressurizing member) that pressurizes the sheet passing between the (fixing member) and the fixing roller 21, and the surface of the fixing roller 21 in contact with each other in the rotation axis direction of the fixing roller 21. A plurality of separation claws 29 that are provided so as to be capable of thrust operation and separate the sheet from the fixing roller 21. Each separation claw 29 is fixed at the initial position in the rotation axis direction of the fixing roller 21 from the start of use of the fixing roller 21 until the predetermined starting condition is satisfied, and the fixing roller 21 satisfies the predetermined starting condition. At this time, the thrust operation of the fixing roller 21 in the direction of the rotation axis is started.

  As a result, the fixing device 13 immediately after the start of use fixes the separation claws 29 at the initial position in the device depth direction, thereby suppressing the range in the device depth direction in which each separation claw 29 damages the surface of the fixing roller 21. can do. Immediately after the fixing device 13 is started to be used, when the fixing roller 21 is thrust, the fixing roller 21 is minutely moved in a wide range in the depth direction of the device due to minute scratches and foreign matters attached to the separation claws 29 immediately after the start of use. There is a possibility that various scratches may occur, which may cause a phenomenon (white streaks in the image) in which a solid area or a halftone area of an image fixed on a sheet looks white due to light interference. However, according to the present embodiment, as described above, since the scratches by the separation claws 29 do not spread to a wide range on the surface of the fixing roller 21 immediately after the start of use, such a phenomenon can be suppressed.

  Even if the surface of the fixing roller 21 is scratched in a narrow range in the depth direction of the apparatus due to scratches or foreign matter on the separation claws 29 immediately after the start of use, the phenomenon such as the above-described white streaks of the image does not occur, and In the embodiment, no problematic defect occurs in the image. Further, such scratches on the surface of the fixing roller 21 are alleviated by friction with the sheet by repeating the printing process (fixing process) and finally eliminated.

  Further, since the minute scratches and foreign substances attached to each separation claw 29 immediately after the start of use are eliminated by friction with the paper and the fixing roller 21 by repeating the fixing process, each separation claw 29 after using a predetermined amount is used. The thrust operation does not damage a wide range of the fixing roller 21 in the depth direction of the apparatus. Therefore, in the present embodiment, by thrusting each separation claw 29 after using a predetermined amount, the contact position between each separation claw 29 and the fixing roller 21 changes with the fixing process, and the fixing roller by each separation claw 29 is changed. It is possible to avoid concentration of the load on a certain portion of 21. As a result, it is possible to prevent the surface of the fixing roller 21 from being scraped due to the use of the separation claws 29 and the fixing roller 21 over time, maintain the surface state of the fixing roller 21 in a good condition, and prevent toner adhesion and image defects. That is, the durability of the fixing roller 21 and good image quality can be maintained.

  Further, in the present embodiment, the thrust operation start condition for determining the cumulative use of the fixing roller 21 is set, for example, when a predetermined cumulative driving time of the fixing roller 21 has elapsed. As a result, scratches or foreign matter on the separation claws 29 immediately after the start of use may damage the fixing roller 21 without being affected by various printing forms such as continuous printing and intermittent printing, and various paper sizes. You can set the period.

  The thrust operation start condition is not limited to the predetermined cumulative drive time. For example, in another embodiment, the thrust operation start condition may be set when a predetermined cumulative number of printed sheets using the fixing roller 21 has elapsed.

  Thrust operation control of each separation claw 29 of the other embodiment will be described with reference to the flowchart of FIG. 7. The control device 15 monitors the cumulative number of printed sheets using the fixing roller 21 from the start of use of the fixing roller 21 (step S11) and stores it in the storage unit 41. In the fixing device 13, the thrust operation of the support shaft 28 is not performed until the fixing roller 21 has passed a predetermined cumulative number of printed sheets (for example, 1000 sheets) (step S12: NO), and each separation claw 29 is set to the initial position. Has been maintained. Then, when the fixing roller 21 is driven by a predetermined cumulative number of prints or more (step S12: YES), in the fixing device 13, the thrust operation of the support shaft 28 and each separation claw 29 is started (step S13).

  As a result, scratches and foreign matter on each separation claw 29 immediately after the start of use are not affected by the time for driving the fixing device 13 (fixing roller 21) without passing through the paper such as warm-up. It is possible to set a period in which 21 may be damaged.

  Alternatively, in another embodiment, the thrust operation start condition may be set by both the passage of a predetermined cumulative drive time of the fixing roller 21 and the passage of a predetermined cumulative number of printed sheets using the fixing roller 21.

  Thrust operation control of each separation claw 29 of the other embodiment will be described with reference to the flowchart of FIG. 8. The control device 15 monitors the cumulative drive time and the cumulative number of printed sheets of the fixing roller 21 from the start of use of the fixing roller 21 (step S11) and stores it in the storage unit 41. In the fixing device 13, when the fixing roller 21 has not passed the predetermined cumulative drive time (for example, 3 hours) and the predetermined cumulative print number (for example, 1000 sheets) (step S12: NO and step S13: NO), The thrust motion of the support shaft 28 is not performed, and each separation claw 29 is maintained at the initial position. Then, when the fixing roller 21 is driven for a predetermined cumulative drive time or longer (step S12: YES) and for a predetermined cumulative number of prints or more (step S13: YES), in the fixing device 13, the support shaft 28 and each separation unit are separated. The thrust operation of the pawl 29 is started (step S24).

  As a result, by considering both the cumulative drive time of the fixing roller 21 and the cumulative number of printed sheets as the thrust operation start condition for each separation claw 29, a more appropriate condition can be set.

  In the above-described embodiment, the separation claw drive input gear 31a is movable between the input state and the non-input state, and the input switching unit 31b moves the separation claw drive input gear 31a. The configuration for switching transmission and cutoff of the rotational driving force from the mechanism 30 (fixing roller driving gear 30c) to the separation claw driving mechanism 31 (second speed adjusting gear 31d) is not limited to this. For example, in another embodiment, the separation claw driving input gear 31a is arranged so as to mesh with the fixing roller driving gear 30c and the first speed adjusting gear 31c at the same time, and the input switching portion 31b is the first speed adjusting gear. It may be configured by an electromagnetic clutch or the like mounted on 31c. The input switching unit 31b includes a rotation shaft of a first speed adjusting gear 31c that receives a rotary driving force from the separation claw drive input gear 31a and a first speed adjusting gear 31c that transmits the rotary driving force to a second speed adjusting gear 31d. It is configured to be able to switch between connection and non-connection with the rotation shaft of Then, the input switching unit 31b switches connection or non-connection of these rotary shafts in accordance with a control signal from the control device 15.

  In the above-described embodiment, while the support shaft 28 is biased toward the inner side in the device depth direction by the first biasing member 28a, the support shaft 28 is moved toward the front side in the device depth direction by the outer peripheral surface of the rotating plate cam-shaped cam 31g. The configuration has been described in which the support shaft 28 and the separating claws 29 are thrust by pressing. However, the configuration for performing the thrust operation of the support shaft 28 and each separation claw 29 is not limited to this. For example, in another embodiment, the frame 20 rotatably supports the support shaft 28 in the device depth direction, and connects the outer periphery of the front cam-shaped cam 31g and the pressed portion 28b of the support shaft 28 with a follower joint. Thus, the support shaft 28 and the separation claws 29 may be configured to thrust according to the rotation of the cam 31g.

  In the above-described embodiment, the configuration in which the first heater 23 and the second heater 24, which are halogen heaters, are provided as the heat source for heating the fixing roller 21 has been described, but the configuration of the heat source is not limited to this. For example, in other embodiments, the first heater 23 and the second heater 24 may be composed of ceramic heaters or other heat sources.

  In the above-described embodiment, as the heat source for heating the fixing roller 21, the configuration in which the two first heaters 23 and the second heaters 24 are provided inside the fixing roller 21 has been described, but the heat source is not limited to this. For example, in other embodiments, one heater may be provided inside the fixing roller 21 as a heat source, or a heater may be provided outside the fixing roller 21 as a heat source.

  In the present embodiment, the case where the configuration of the present invention is applied to the printer 1 has been described, but in another different embodiment, the configuration of the present invention is applied to other image forming apparatuses such as a copying machine, a facsimile, and a multifunction machine. It is also possible.

1 Printer (image forming device)
2 printer body 3 image forming unit 13 fixing device 15 control device 21 fixing roller (fixing member)
22 Pressure roller (pressure member)
28 support shaft 28a first biasing member 28b pressed portion 28c holder 29 separation claw 29a base portion 29b tip portion 29c rocking shaft 29d second biasing member 30 fixing roller driving mechanism 30a driving portion 30b fixing driving input gear 30c fixing roller driving Gear 31 Separation Claw Drive Mechanism 31a Separation Claw Drive Input Gear 31b Input Switching Section 31c First Speed Adjustment Gear 31d Second Speed Adjustment Gear 31e Worm 31f Worm Wheel 31g Cam

Claims (2)

A rotatable fixing member that contacts the recording medium on which the toner image is formed to heat the recording medium;
A rotatable pressure member that applies pressure to the recording medium passing between the fixing member;
A separation claw that is in contact with the surface of the fixing member and is provided so as to be capable of thrusting in the rotation axis direction of the fixing member, and that separates the recording medium from the fixing member;
Equipped with
The separation claw is made of a resin material of polyimide or polyether ketone, and is formed by being coated with a coating layer of fluororesin,
The separation claw is fixed at the initial position in the rotation axis direction of the fixing member until the predetermined cumulative driving time elapses from the initial activation of the fixing member after factory shipment, and the fixing member is driven by the cumulative driving. When the time has passed, the thrust operation in the rotation axis direction of the fixing member is started ,
A drive gear that transmits a rotational drive force to the fixing member,
A separation pawl drive mechanism for switching between operation and stop of the thrust operation of the separation pawl,
The separation claw drive mechanism,
A speed adjusting gear that transmits a rotational driving force that is converted into the thrust operation of the separation pawl,
An input state that meshes with the drive gear and the speed adjusting gear at the same time, and a separation claw drive input gear that is movable between a non-input state that does not mesh with at least one of the drive gear and the speed adjusting gear,
The separation pawl drive mechanism sets the separation pawl drive input gear to the non-input state until the accumulated drive time elapses, and then from the drive gear via the separation pawl drive input gear to the speed adjustment gear. Of the separation claw to stop the thrust operation of the separation claw, and after the cumulative drive time has elapsed, the separation claw drive input gear is set to the input state and the separation claw drive input gear is passed through the separation claw drive input gear. The rotational drive force from the drive gear to the speed adjusting gear to operate the thrust operation of the separation pawl,
A fixing device, wherein the number of rotations transmitted from the drive gear to the speed adjusting gear is adjusted by a gear ratio of the separation claw drive input gear and the speed adjusting gear . An image forming apparatus comprising the fixing device according to claim 1.

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