JP2010282055A - Fixing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device which includes a heating member for melting unfixed toner on recording material, a pressurizing member that brings the recording material into a pressurized contact with the heating member, a bearing for supporting both ends of the pressurizing member and a holding means for the bearing, in which thrust-direction position accuracy of the pressurizing member with respect to the bearing holding means is improved only in a non-drive side of the pressurizing member. <P>SOLUTION: The thrust-direction position accuracy of the pressurizing member is improved by forming a regulating section for regulating the thrust-direction position of the pressurizing member with respect to the bearing holding means only on the non driven side of the pressurizing member. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a technique which is provided in an image forming apparatus using an electrophotographic system such as a copying machine, a printer, and a facsimile machine, and is particularly effective for use in the fixing device.

  Conventionally, as a heat fixing device for fixing an unfixed image formed on a recording material by an electrophotographic copying machine, a printer, a facsimile, etc., a contact heating type heat roller fixing method having good thermal efficiency and safety, energy saving A type of film heating method is adopted. A heat roller fixing type heat fixing device is basically composed of a heating roller (fixing roller) as a heating rotator and an elastic pressure roller as a pressure rotator pressed against the heating roller, and the pair of rollers is rotated. Recording material (transfer material sheet / electrostatic recording paper / electrofax paper / printing) as a heated material in which an unfixed image (toner image) is formed and supported on the pressure nip portion (fixing nip portion) of both roller pairs Paper) and the like, and the pressure nip portion is nipped and conveyed to fix the unfixed toner image as a fixed image on the recording material surface by heat from the fixing roller and the pressure of the pressure nip portion. is there.

  In addition, a film heating type heat fixing apparatus has been proposed in, for example, Patent Document 1 and the like, and a heat-resistant film (fixing film) that is a rotating body for heating is adhered to a heating element with a rotating body for pressure (elastic roller). A recording material (hereinafter referred to as a transfer material) carrying an unfixed toner image is introduced into a pressure nip formed by a heated body (heater) and a pressure member with the fixing film interposed therebetween. The toner is conveyed together with the fixing film, and the unfixed toner image is fixed on the transfer material as an image by the heat from the heater applied through the fixing film and the pressing force of the pressure nip portion.

  In a conventional heat fixing device comprising a pressure member, a heating member, a bearing for supporting both ends of the pressure member, and a means for holding the bearing, when the pressure member 1 is positioned in the thrust direction, as shown in FIG. The pressure member 1 is provided with steps 2 at both ends of the shaft, and the shaft step 2 is abutted against the side surface of the bearing 3 engaged with the bearing holding means 4 to thereby define the thrust direction position of the pressure member 1. Was. Alternatively, as shown in FIG. 2, means 5 for restricting the position in the thrust direction, such as an E-type retaining ring, is provided on both sides of the shaft of the pressure member 1 on the outside of the bearing 3 that supports both ends of the shaft of the pressure member 1. On the other hand, the thrust member 5 is regulated in position in the thrust direction by abutting means 5 for regulating the position in the thrust direction such as an E-type retaining ring against the side surface of the bearing 3.

JP-A-4-204984

  However, there is a large geometric tolerance due to the long step between the shaft ends to define the position of the pressure member, or the distance between the grooves of the E-type retaining ring, and bearings on both sides of the pressure member. Since the distance between the holding means is long, the geometric tolerance is large, and the pressure member is thermally expanded due to the heating by the heating member, so that the positioning portion of the pressure member is displaced. It was necessary to provide a relatively large clearance for positioning in the direction. Therefore, the positioning accuracy of the pressure member is lowered, and various problems occur because the pressure member is displaced in the thrust direction by the clearance. For example, a detachable fixing device has a swing gear on the main body side, and transmits power from the main body to the fixing device by meshing with a driving gear of the fixing device. At that time, the swing gear on the main body moves in the direction to bite into the drive gear of the fixing device, and the drive gear for rotating the pressure member shifts in the thrust direction, so that the meshing width of the gear is reduced, and the drive gear Will be removed. In addition, the gear width must be increased in order to prevent the above-described wheel removal, resulting in an increase in the size of the apparatus. In addition, due to a decrease in the relative positional accuracy between the pressure member and the heating member, the amount of heat transferred from the heating member to the pressure member at the end of the pressure nip changes, and the fixability is lowered. In particular, in the on-demand fixing method, the influence of a decrease in fixability at the end due to a decrease in relative positional accuracy between the pressure member and the heating member is large. Further, a contact spring is provided at the non-driving side end portion of the shaft of the pressure member to apply a bias. However, even if the pressure member is displaced in the thrust direction, the contact spring is in contact with the shaft of the pressure member. Therefore, it is necessary to lengthen the non-driving side end of the shaft of the pressurizing member, leading to problems such as an increase in the size of the apparatus.

  In addition, when using a means such as an E-type retaining ring with a groove to restrict the position in the thrust direction, a large torque is applied to the drive side of the pressure member, so stress concentration occurs in the groove on the drive side shaft. There is a problem that the strength of the shaft of the pressurizing member is insufficient. In particular, in a film heating type fixing device, it is necessary to arrange a heater and a heater connector between the bearing unit and the drive unit, and the distance between the drive unit to which the force is applied and the bearing to which the force is applied is long, and the bending applied to the shaft during driving is large. If the moment is increased and there is a groove in the bearing, there is a problem that the strength of the shaft is insufficient.

  An object of the present invention is to provide a configuration in a fixing device that improves the positioning accuracy of the pressure member in the thrust direction and sufficiently secures the shaft strength of the pressure member.

  In a fixing device comprising a heating member that melts unfixed toner on a recording material, a pressure member that presses the recording material against the heating member, a bearing that supports both ends of the pressure member, and a bearing holding means. Only a non-driving side portion of the pressure member is formed with a restricting portion for restricting a thrust direction position of the pressure member with respect to the bearing holding means.

  The present invention comprises a heating member for melting unfixed toner on a recording material, a pressure member for pressing the recording material against the heating member, a bearing for supporting both ends of the pressure member, and a bearing holding means. In the fixing device, a restricting portion for restricting the thrust direction position of the pressure member relative to the bearing holding means is formed only on the non-driving side portion of the pressure member. As a result, the thrust member position in the thrust direction is defined on the non-driving side bearing side surface, so that the distance between both side surfaces of the non-driving side bearing is shorter than the method in which the position is defined at both ends of the pressure member. Therefore, the geometric tolerance of the pressing member and the influence of thermal expansion due to heating by the heating member are small, and the positional accuracy of the pressing member in the thrust direction is improved. As a result, the relative positional accuracy between the pressure member and the heating member is improved, and the fixing stability of the non-driving side end is improved.

  Also, when using a means for regulating the thrust direction position such as an E-type retaining ring, if it is provided outside the bearing on the non-driving side of the pressure member, stress concentration is applied to the shaft such as the E-type retaining ring groove. Even if there is a portion, the force applied to the drive side is received by the bearing, so no force is applied to the E type retaining ring groove on the outside of the non-drive side bearing. Thereby, the strength of the shaft of the pressure member can be sufficiently secured.

1 is a schematic configuration diagram of an image forming apparatus according to a conventional embodiment. 1 is a schematic configuration diagram of an image forming apparatus according to a conventional embodiment. 1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention. 1 is a schematic configuration diagram of a non-driving side of an image forming apparatus according to an embodiment of the present invention. Sectional drawing of the heat fixing device which concerns on embodiment of this invention. 1 is a schematic configuration diagram of a non-driving side of an image forming apparatus according to an embodiment of the present invention. FIG. 3 is an enlarged view of a driving unit of the heat fixing device according to the embodiment of the present invention. FIG. 3 is an enlarged view of a contact portion of the heat fixing device according to the embodiment of the present invention. FIG. 3 is an enlarged view of a contact portion of the heat fixing device according to the embodiment of the present invention. 1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention.

Example 1
Hereinafter, embodiments of the present invention will be described with reference to FIGS.

  This embodiment is applied to a laser beam printer using a transfer type electrophotographic process. FIG. 3 is a schematic configuration diagram of an example of the fixing device. 6 is an elastic pressure roller as a pressure member, 7 and 8 are bearings of the pressure roller, 9 and 10 are sheet metals that hold the bearing, 11 is an E-type retaining ring, and 12 is a heating member. It is a fixing roller as a member. As shown in FIG. 4, the shaft on the non-driving side of the pressure roller 6 is supported by a bearing 7, and the bearing 7 is engaged with a sheet metal 9. Similarly, the pressure roller 6 is supported by a bearing 8 on the driving side, and the bearing 8 is engaged with a sheet metal 10. The fixing roller 12 is pressed against the pressure roller 6 by a spring 13. FIG. 5 is a schematic cross-sectional view of the fixing roller 12 and the pressure roller 6, and the fixing roller 10 includes a fixing film 14 and a heater 15. As shown in FIG. 6, the step 16 between the shafts of the E-type retaining ring 11 and the pressure roller 6 is arranged on both sides of the bearing 7 on the non-driving side. As a result, the thrust roller 6 moves in the thrust direction until either the side surface of the E-type retaining ring 11 or the side surface of the shaft step 16 abuts against the bearing side surface. Compared to the conventional method in which E-type retaining rings are attached to both ends of the pressure roller to define the position in the thrust direction, the method of defining the position only on the non-driving side is the positioning of the E-type retaining ring 11 and the pressure roller 6. Since the distance from the step 16 is short, the influence of the geometric tolerance and thermal expansion of the pressure roller is small, and the positioning accuracy is improved. Further, since the relative positional accuracy of the pressure roller 6 and the fixing roller 12 on the non-driving side is improved, the fixing stability is improved, and in particular, the fixing stability on the non-driving side is improved. As shown in FIG. 7, the detachable fixing device has a swing gear on the main body side, and transmits power from the main body to the fixing device by meshing with the drive gear of the fixing device. Even if it works in the direction of biting into the drive gear 19 of the fixing device, the positional accuracy of the pressure roller is improved, so that the meshing width of the gear can be ensured and the drive gear can be prevented from being removed. Further, since the positional accuracy of the pressure roller is improved, as shown in FIG. 8, it is easy to guarantee the position of the contact provided on the non-driving side for applying a bias, so that the length of the shaft with which the contact spring 20 contacts is increased. The length can be shortened. For this reason, it is possible to reduce the size in the thrust direction. Further, since the position system of the pressure roller shaft end face is improved, a shape that contacts with the shaft end face such as the contact spring 21 can be applied as shown in FIG. Conventionally, the stress applied from the drive gear was concentrated in the groove of the E-shaped retaining ring. However, in the method of defining the position only on the non-drive side, the force applied to the drive gear 19 is received by the bearing 7 and the bearing 8, Since no force acts on the groove of the E-type retaining ring outside the bearing 7 and stress concentration does not occur, the shaft strength of the pressure roller 6 can be sufficiently secured. Even if grease applied to the bearing 7 to improve the slidability flows to the contact spring 20 side due to rotation of the shaft of the pressure roller 6 or movement in the thrust direction by the clearance, the E-type stopper Since there is a groove in the ring 11, the grease does not reach the contact spring 20, and no contact failure occurs.

(Example 2)
The schematic configuration of the laser beam printer using the transfer type electrophotographic process according to the second embodiment of the present invention is the same as the configuration described in the first embodiment of the present invention. Reference numerals are assigned and detailed description is omitted.

  First, a detailed description will be given of a method for restricting the thrust direction position of the pressure roller on the non-driving side of the pressure roller with reference to FIG. In FIG. 10, reference numeral 22 denotes a groove formed on the shaft of the pressure roller 6. The groove 22 is a width obtained by adding a clearance to the width of the bearing 7, and the position of the pressure roller 6 in the thrust direction is restricted by the step of the groove 22 abutting against the side surface of the bearing. Since the position of the pressure roller 6 in the thrust direction is restricted by a short distance as the width of the groove, the geometric tolerance of the pressure roller and the influence of thermal expansion due to heating from the heater are small, and the positioning accuracy is improved. As a result, similar to the description in the first embodiment, it is possible to improve the fixing stability, secure the meshing width of the drive gear, shorten the shaft length, and change the contact spring shape. Further, compared to the case where the E-type retaining ring is used, it is not necessary to cut the groove of the E-type retaining ring, so that the strength of the shaft of the pressure roller 6 can be increased.

Claims (1)

  In a fixing device comprising a heating member that melts unfixed toner on a recording material, a pressure member that presses the recording material against the heating member, a bearing that supports both ends of the pressure member, and a bearing holding means. A fixing device, wherein a restricting portion for restricting a thrust direction position of the pressure member with respect to a bearing holding unit is formed only on a non-driving side portion of the pressure member.

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