Patent Grant
11281131
This application claims priority from Japanese Patent Application No. 2020-016718 filed on Feb. 4, 2020, the disclosure of which is incorporated herein by reference in its entirety.
The present invention relates to a fixing device for thermally fixing a toner image on a sheet.
A fixing device known in the art comprises a heating member that heats a sheet, a temperature sensor that detects the temperature of the heating member, a plastic holder that holds the temperature sensor, and an L-shaped metal frame on which the holder is fixed.
It would be desirable to increase the rigidity of the metal frame to improve positional accuracy of the temperature sensor.
In one aspect, a fixing device is disclosed herein, that comprises a first fixing member, a second fixing member, a heater, a temperature sensor, a sensor holder, and a first frame. The first fixing member includes a roller. The second fixing member is configured to form a nip in combination with the first fixing member. The heater heats the first fixing member or the second fixing member. The temperature sensor detects a temperature of the first fixing member or the second fixing member. The sensor holder is configured to hold the temperature sensor. The sensor holder is fixed on the first frame. The first frame is made of metal.
The first frame comprises a first bend, a second bend, a third bend, a first wall, a second wall, a third wall, and a fourth wall. The first bend, the second bend, and the third bend each form a bent shape in a cross section orthogonal to an axial direction of the roller. The second wall is connected to the first wall via the first bend. The third wall is connected to the second wall via the second bend. The fourth wall is connected to the third wall via the third bend.
The first wall and the second wall form an acute angle.
The above and other aspects, their advantages and further features will become more apparent by describing in detail illustrative, non-limiting embodiments thereof with reference to the accompanying drawings, in which:
A detailed description will be given of a non-limiting embodiment with reference made to the drawings where appropriate.
As shown in
The housing 2 comprises an output tray 21. The output tray 21 is provided on a top surface of the housing 2.
The feeder unit 3 is arranged in a lower part of the housing 2. The feeder unit 3 comprises a sheet tray 31 that holds sheets S, and a feeding mechanism 32 for feeding the sheets S in the sheet tray 31 to the image forming unit 4.
The image forming unit 4 has a function of transferring a toner image to a sheet S to form an image on the sheet S and comprises an exposure device 5, four process cartridges 6, and a transferring unit 7.
The exposure device 5 is provided in an upper part of the housing 2, and comprises a light source, a polygon mirror, etc. (not shown). The exposure device 5 is configured to rapidly scan a surface of a photoconductor drum 61 with a light beam (see alternate long and short dashed lines) in accordance with image data, to thereby expose the surface of the photoconductor drum 61 to light.
Each process cartridge 6 comprises the photoconductor drum 61, a charger 62, and a development roller 63. The four process cartridges 6 respectively contain toners of yellow, magenta, cyan, and black.
The transferring unit 7 comprises a drive roller 71, a follower roller 72, a conveyor belt 73, and four transfer rollers 74. The conveyor belt 73 is an endless belt that is looped around and runs between the drive roller 71 and the follower roller 72. The transfer rollers 74 are positioned on the inner side of the conveyor belt 73. The conveyor belt 73 is held between the transfer rollers 74 and corresponding photoconductor drums 61.
The surface of the photoconductor drum 61 is charged by the charger 62. Thereafter, the exposure device 5 exposes the surface of the photoconductor drum 61 to light to form an electrostatic latent image on the surface of the photoconductor drum 61 in accordance with the image data.
The development roller 63 supplies toner to the electrostatic latent image formed on the photoconductor drum 61. Accordingly, a toner image is formed on the photoconductor drum 61. Thereafter, a sheet S is conveyed by the conveyor belt 73 through between the photoconductor drum 61 and the transfer roller 74, so that the toner image on the photoconductor drum 61 is transferred to the sheet S.
The fixing device 8 thermally fixes the toner image on the sheet S. The details of the fixing device 8 will be described later.
The conveying unit 9 is configured to convey a sheet S ejected from the fixing device 8 to the outside of the housing 2 or toward the image forming device 4 again. The conveying unit 9 comprises a first conveyance path 91, a second conveyance path 92, a reconveyance path 93, a first conveyance roller 94, a second conveyance roller 95, a first switchback roller SR1, a second switchback roller SR2, a plurality of reconveyance rollers 96, a rotatable first flapper FL1, and a rotatable second flapper FL2.
The first conveyance path 91 guides a sheet S ejected from the fixing device 8 toward the output tray 21. The second conveyance path 92 guides a sheet S ejected from the fixing device 8 toward the output tray 21 along a route different from the first conveyance path 91. The reconveyance path 93 guides a sheet S drawn into the housing 2 to the feeding mechanism 32 upstream of the image forming unit 4. The sheet S is drawn into the housing 2 by the first switchback roller SR1 which will be described later. The reconveyance rollers 96 are provided in the reconveyance path 93 and convey a sheet S in the reconveyance path 93 toward the feeding mechanism 32.
The first conveyance roller 94 is provided in the fixing device 94. The first conveyance roller 94 conveys a sheet S with a toner image thermally fixed thereon toward the second flapper FL2.
The second conveyance roller 95, the first switchback roller SR1, and the second switchback roller SR2 are rotatable in forward and reverse directions. The second conveyance roller 95, the first switchback roller SR1, and the second switchback roller SR2 convey a sheet S toward the outside of the housing 2, specifically to the output tray 21 when rotated in the forward direction, and draw a sheet S into the housing 2 when rotated in the reverse direction.
The second conveyance roller 95 and the first switchback roller SR1 are provided in the first conveyance path 91. The first switchback roller SR1 is located closer to the output tray 21 than the second conveyance roller 95. The second switchback roller SR2 is provided in the second conveyance path 92.
The appropriate switching of the positions of the first flapper FL1 and the second flapper FL2 allows the conveying unit 9 to convey a sheet S from the fixing device 8 toward the first conveyance path 91 or the second conveyance path 92, or to convey a sheet S from the first conveyance path 91 or the second conveyance path 92 to the reconveyance path 93.
As shown in
The first fixing member 81 comprises a rotatable roller 81A. The two heaters H are arranged inside the roller 81A and heat the first fixing member 81.
The second fixing member 82 forms a nip NP in combination with the first fixing member 81. The nip NP is formed between the first fixing member 81 and the second fixing member 82. The second fixing member 82 comprises an endless belt 82A, and two pads 82B. The belt 82A is sandwiched between the first fixing member 81 and the two pads 82B.
The center thermistor TS1 is a noncontact sensor that detects the temperature of the first fixing member 81 heated by the heaters H. To be more specific, the center thermistor TS1 detects the temperature of the roller 81A approximately in the midsection of the roller 81A between the axial ends of the roller 81A. The center thermistor TS1 is located at a distance from the roller 81A. In this description, the direction of the rotation axis of the roller 81A is also simply referred to as “axial direction”.
The sensor holder 800 is a member that holds the center thermistor TS1. The fixing frame 500 includes an upper frame 520 as an example of a first frame. The sensor holder 800 is fixed to the upper frame 520.
The upstream guide 700 guides a sheet S at a location upstream of the nip NP in a conveyance direction of the sheet S. In this description, the conveyance direction of the sheet is also simply referred to as “conveyance direction”.
The rear guide 300 guides a sheet S ejected from the nip NP. The rear guide 300 supports a first roller 94A in a manner that permits the first roller 94A to rotate. The first roller 94A is paired with a second roller 94B and located above the second roller 94B. The first roller 94A and the second roller 94B constitute the first conveyance roller 94 described above.
The upper frame 520 is formed of sheet metal with a shape of a letter W in a cross section orthogonal to the axial direction. As shown in
As shown in
In other words, the second wall W2 is connected to the first wall W1 via the first bend C1. The third wall W3 is connected to the second wall W2 via the second bend C2. The fourth wall W4 is connected to the third wall W3 via the third bend C3.
The second bend C2 is bent in a direction opposite to a direction in which the first bend C1 and the third bend C3 are bent. To be more specific, for example, if the first bend C1 and the third bend C3 are configured as mountain folds, the second bend C2 is configured as a valley fold. The second bend C2 and the third bend C3 each form a right angle, whereas the first bend C1 forms an acute angle.
In other words, the first wall W1 and the second wall W2 form an acute angle, the second wall W2 and the third wall W3 form a right angle, and the third wall W3 and the fourth wall W4 form a right angle.
The first wall W1 is arranged upstream of the nip NP in the conveyance direction of a sheet S. The first bend C1 is bent from an upper end of the first wall W1 toward a downstream side in the conveyance direction.
The second wall W2 extends along a horizontal plane from the first bend C1 toward the downstream side in the conveyance direction. The second bend C2 is bent from a downstream end of the second wall W2 in a direction away from the first fixing member 81. The first bend C1 is bent downward from an upstream end of the second wall W2 in the conveyance direction. The second bend C2 is bent upward from the downstream end of the second wall W2 in the conveyance direction. That is, the first bend C1 bends downward and the second bend C2 bends upward.
The third wall W3 is located downstream of the nip NP in the conveyance direction. The third bend C3 is bent from an upper end of the third wall W3 toward the downstream side in the conveyance direction. That is, the second bend C2 and the third bend C3 bend in opposite directions orthogonal to a surface of the third wall W3.
The fourth wall W4 extends from the third bend C3 toward the downstream side in the conveyance direction. The fourth wall W4 is parallel to the second wall W2.
The second wall W2 is arranged over the roller 81A. The first wall W1 extends downward from the first bend C1. A lower end W11 of the first wall W1 is located below an upper end E1 of the roller 81A, more specifically, below the axis X1 of the roller 81A.
In other words, the second wall W2 is located on a side of the first fixing member 81 which is opposite to a side on which the second fixing member 82 is located, in an opposing direction in which the first fixing member 81 and the second fixing member 82 are opposed to each other. The first wall W1 extends from the first bend C1 on the second fixing member 82 side with respect to a plane orthogonal to the opposing direction and intersecting the first bend C1. The lower end W11 of the first wall W1 located on the second fixing member 82 side is located is closer to a plane orthogonal to the opposing direction and intersecting the second fixing member 82 than a point E2 of the roller 81A farthest from the plane.
The lower end W11 of the first wall W1 may be located closer to the plane orthogonal to the opposing direction and intersecting the second fixing member 82 than the axis X1 of the roller 81A.
The upper frame 520 includes a part arranged between the upstream guide 700 and the heater H. To be more specific, the first wall W1, the first bend C1, and a part of the second wall W2 are arranged between the upstream guide 700 and the heater H. The upstream guide 700 is spaced apart from the upper frame 520. That is, the upstream guide 700 and the upper frame 520 are arranged with a gap left therebetween so that they do not contact each other.
As shown in
The base 810 comprises an upper surface 811 that faces the second wall W2 of the upper frame 520 from below, and a front surface 812 that faces the first wall W1 of the upper frame 520 from the downstream side in the conveyance direction. The base 810 has a locating protrusion 813 and a hole 814 on the upper surface 811.
The second wall W2 of the upper frame 520 has a locating hole W21 that engages with the locating protrusion 813, and a mounting hole W22 formed in a position corresponding to hole 814. The sensor holder 800 is fixed to the second wall W2 by inserting a screw SC1 into the hole 814 of the sensor holder 800 and fastening the screw SC1 to the mounting hole W22 of the second wall W2.
The first holder 820 and the second holder 830 protrude from the upper surface 811 and the front surface 812. The upper frame 520 has a first opening 521 through which the first holder 820 extends and a second opening 522 through which the second holder 830 extends. The first opening 521 and the second opening 522 are formed across the first wall W1, the first bend C1, and the second wall W2.
The engagement claws 840 are provided for temporary holding the sensor holder 800 on the second wall W2. The engagement claws 840 protrude upward from the upper surface 811 of the base 810 and then extend in one direction along the axial direction. The three engagement claws 840 are configured to extend through the holes W23, W24 and the second opening 522 formed in the second wall W2 and to engage the edges of the holes W23, W24 and the second opening 522 from above.
The second wall W2 has an attachment flange W25 for attaching a side thermistor TS3. The side thermistor TS3 is a sensor that contacts an axial end of the roller 81A and detects a temperature of the roller 81A.
As shown in
Each side frame 510 has a support hole 511 that supports the first fixing member 81 via a bearing (not shown), and a support groove 512 that supports the second fixing member 82 in such a manner as to allow the second fixing member 82 to move along the opposing direction. Each end of the support shaft 540 is fixed to a corresponding side frame 510.
Each side frame 510 has a positioning shaft PS fixed thereon by staking. When the fixing device 8 is assembled in the housing 2, the positioning shaft PS is inserted in a recess formed in a frame of the housing 2. In this way, the fixing device 8 can be located in a predetermined position inside the housing 2.
As shown in
As shown in
As shown in
As shown in
Next, the structure for assembling the fixing frame 500, the rear guide 300, and the upstream guide 700 at both ends will be explained with reference to
As shown in
The first screw-fastening portion FX1 and the first protrusion P1 are located closer to the first bend C1 than to the second bend C2. More specifically, the distance from the first bend C1 to the first screw-fastening portion FX1 and the first protrusion P1 is shorter than the distance from the first screwing portion FX1 and the first protrusion P1 to the second bend C2, in a direction from the first bend C1 toward the second bend C2. The direction from the first bend C1 to the second bend C2, put in another way, is the width direction of the second wall W2.
The third wall W3 includes a second protrusion P2 that protrudes in the axial direction on each end. The side frame 510 has a second engagement hole H2 that engages with the second protrusion P2.
The fourth wall W4 includes a second screw-fastening portion FX2 on each end that is fastened onto the side frame 510 by a screw SC3. The second screw-fastening portion FX2 extends from an end of the fourth wall W4 so as to approach the second protrusion P2, to be more specific, downward. The extreme end of the second screw-fastening portion FX2 is located adjacent to the second protrusion P2. A hole H12 that receives the screw SC3 is formed in the side frame 510.
The first wall W1 includes a third protrusion P3 that protrudes in the axial direction on each end. The side frame 510 has a third engagement hole H3 that engages with the third protrusion P3. The side frame 510 has a hole H13 that receives a screw SC4 that is fixed on an end of the support shaft 540.
The torsion spring 330 comprises coils 331, a first arm 332, and second arms 333. The first arm 332 extends from the coils 331 in one direction and engages with the guide body 320. Each of the second arms 333 extends from a corresponding coil 331 in another direction and engages with the roller holder 310 (see
The guide body 320 includes on each end a protrusion 323 that protrudes toward the third wall W3, and a screw-fastening portion 324 that is fastened onto the third wall W3 by a screw SC5. The third wall W3 has at each end an engagement hole W32 that engages with the protrusion 323, and a hole W33 that receives the screw SC5.
The upstream guide 700 includes on each end a protrusion 710 that protrudes toward the side frame 510, and a screw-fastening portion 720 that is fastened onto the side frame 510 by a screw SC6. As shown in
More specifically, the side frame 510 includes a base 510A and a flange 510B. Various holes, such as the first engagement hole H1 for attaching the upper frame 520 etc., are formed in the base 510A. The flange 510B extends from an end of the base 510A on the upstream guide 700 side toward the upper frame 520. The hole 514 is formed in the flange 510B. The engagement groove 513 is formed on the end of the base 510A on the upstream guide 700 side adjacent to the flange 510B.
In the illustrative, non-limiting embodiment described above, the following advantageous effects can be achieved.
Since the rigidity of the upper frame 520 can be increased by forming the first bend C1 of the upper frame 520 at an acute angle, the center thermistor TS1 and the thermostat TS2 which are held on the rigidity-increased upper frame 520 via the sensor holder 800 can be provided with improved positional accuracy.
Since the sensor holder 800 is fixed to the second wall W2 connected to the first bend C1 forming an acute angle and thus provided with an increased rigidity, the positional accuracy of the center thermistor TS1 and the thermostat TS2 can be further improved.
Since the upper frame 520 has the openings 521, 522 through which a part of the sensor holder 800 extends, the sensor holder 800 can be properly fixed to the second wall W2 even if the sensor holder 800 has a complex shape.
Since the lower end W11 of the first wall W1 is located below the axis X1 of the roller 81A, the width of the first wall W1 becomes greater compared to a structure where the lower end of the first wall is located above the axis of a roller, and thus the rigidity of the second wall W2 increases. Further, since it is possible to surround the roller 81A with the first wall W1 and the second wall W2, air heated by the roller 81A can be restrained from escaping from the upper frame 520.
Since the first protrusion P1 engages with the first engagement hole H1, the second wall W2 on which the sensor holder 800 is fixed is positioned on the side frame 510, and thus the positional accuracy of the center thermistor TS1 can be improved.
Since the second wall W2 includes the first screw-fastening portion FX1 and the first protrusion P1, it is possible to arrange the first screw-fastening portion FX1 near the first protrusion P1, and thus the positional accuracy of the first screw-fastening portion FX1 with respect to the first protrusion P1 can be improved.
Since the first screw-fastening portion FX1 and the first protrusion P1 are arranged closer to the first bend C1 having an increased rigidity, the fixing strength and positional accuracy of the upper frame 520 can be improved.
Since the third wall W3 is positioned in place on the side frame 510 by the second protrusion P2 engaging with the second engagement hole H2, the positional accuracy of the upper frame 520 can be improved. Further, the positional accuracy of the rear guide 300 fixed to the third wall W3 can be improved.
Since the second screw-fastening portion FX2 extends so as to approach the second protrusion P2, it is possible to arrange the second screw-fastening portion FX2 near the second protrusion P2, and thus the positional accuracy of the second screw-fastening portion FX2 with respect to the second protrusion P2 can be improved.
Since a gap is left between the upstream guide 700 and the upper frame 520, the transfer of heat from the upper frame 520 to the upstream guide 700 can be restrained.
Since the harness HN is located on the surface 701 of the upstream guide 700 facing away from the upper frame 520, the transfer of heat from the heater H to the harness HN can be restrained by the upstream guide 700, and thus the temperature of the harness HN can be restrained from increasing.
The present invention is not limited to the above-described embodiment and may be implemented in various other forms as described below.
Although the first fixing member 81 is heated by a heater H in the above-described embodiment, the second fixing member may be heated by a heater. In this case, the temperature sensor may be arranged to detect the temperature of the second fixing member.
The first fixing member 81 described above is exemplified as a cylindrical roller including a heater H. However, the first fixing member may be a pressure roller including a shaft and a rubber layer formed around the shaft or may be an endless belt with an inner peripheral surface heated by a heater. An outside heating system where a heater is arranged outside the first fixing member to heat an outer peripheral surface of the first fixing member or an IH (Induction Heating) system is also possible. Further, a heater may be provided in the second fixing member so that the first fixing member contacting the outer peripheral surface of the second fixing member may be indirectly heated. Also, the first fixing member and the second fixing member may each include a heater. The second fixing member may be a pressure roller including a shaft and a rubber layer formed around the shaft.
Although one bend of the plurality of bends of the upper frame 520 described above forms an acute angle, there may be a plurality of acutely-angled bends. In the above-described embodiment, the first bend forms an acute angle, but the second bend and/or the third bend may form an acute angle. Further, it is sufficient if there is at least one bend that forms an acute angle, and the other bends may form an obtuse angle.
However, for the reason described below, it is preferable that only the first bend C1 forms an acute angle. When a sheet metal having a high rigidity is bent to form an acute angle using a stamping die, it is necessary to bend the sheet metal to an angle of 90 degrees in one die and then bend the sheet metal further in a different die. Therefore, the cost for equipment of the dice increases and/or the work process becomes complicated if the number of bends forming an acute angle increases. Thus the number of bends that form an acute angle is preferably one. Further, an acute bend formed by two pressing processes as described above would make the precision of the angle lower. Since the sensor holder 800 and the rear guide 300 are attached to the surface of the second wall W2 and the third wall W3, it is desirable to increase positional accuracy of the second wall W2 and the third wall W3. Thus, the second bend C2 is preferably bent at 90 degrees. Since the fourth wall W4 includes a second screw-fastening portion FX2 at its ends, the second screw-fastening portion FX2 cannot be arranged if the third bend C3 forms an acute angle. Thus, it is preferable that only the angle of the first bend C1, that is, the angle formed by the surface of the first wall W1 and the surface of the second wall W2 be an acute angle.
The temperature sensor exemplified in the above description is a center thermistor TS1 that detects the temperature of the first fixing member without contacting the first fixing member. However, the temperature sensor may detect the temperature of the ends of the first fixing member or the second fixing member as the side thermistor TS3, or may contact the first fixing member or the second fixing member to detect the temperature.
Although the sensor holder 800 described above is fixed to the second wall W2, the sensor holder may be fixed to another wall such as the first wall.
Although the first frame and the second frame described above are fixed together by screws, the first frame and the second frame may be fixed by other fixing methods. Alternative fixing methods may include a method using a plastic clip to fix the frames or a method that fixes the frames by tightly fitting a plastic dowel into the frames.
The elements described in the above embodiment and its modified examples may be implemented selectively and in combination.
| Number | Date | Country | Kind |
|---|---|---|---|
| JP2020-016718 | Feb 2020 | JP | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 6980764 | Otsuka | Dec 2005 | B2 |
| 8498561 | Yamaguchi | Jul 2013 | B2 |
| 8588668 | Ishii | Nov 2013 | B2 |
| 20140105657 | Saiki | Apr 2014 | A1 |
| Number | Date | Country |
|---|---|---|
| H03-145684 | Jun 1991 | JP |
| 2000-172112 | Jun 2000 | JP |
| 2002260825 | Sep 2002 | JP |
| 2016109724 | Jun 2016 | JP |
| 2019-015880 | Jan 2019 | JP |
| Number | Date | Country | |
|---|---|---|---|
| 20210240112 A1 | Aug 2021 | US |
