JP5328232B2 - Pressurizing mechanism and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stabilize pressure by a compression spring by stably holding the compression spring, while simplifying the configuration and reducing the cost. <P>SOLUTION: A pressure mechanism includes: a bracket 110 which holds a fixing roller 100; a pressure lever 120 which is provided to be rotatable around a rotation center axis 112 provided in the bracket 110 and holds a pressure roller 101; and the compression spring 200 which presses the pressure lever 120 toward the bracket 110, so as to bring the fixing roller 100 and the pressure roller 101 into press-contact with each other. The pressure mechanism includes a tension spring 210 which has an outer diameter smaller than the inner diameter of the compression spring 200 and comes into contact with the inside of the compression spring 200, to hold the compression spring 200. The tension spring 210 is provided in the pressure lever 120 together with the compression spring 200 and has a hook part 210a engaged with the bracket 110. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a pressing mechanism for pressing a pair of pressing members, and an image forming apparatus having the pressing mechanism.

  For example, an image forming apparatus using an electrophotographic method forms a toner image on an image carrier, transfers the toner image to a recording material with electrostatic force and pressure, and transfers the transferred toner image with heat and pressure. By fixing the image on the recording material, an image is recorded and formed on the recording material.

  In the pressurizing mechanism that applies pressure in the above-described transfer and fixing processes, a tension spring or a compression spring is used as a general method for applying pressure. A pressurizing mechanism using a tension spring can be easily stretched on a thin plate-like pressure applying member or the like, and the pressurizing mechanism can be structurally stable (Patent Document 1). On the other hand, a pressurizing mechanism using a compression spring needs to be provided with pressure receiving surfaces at both ends of the compression spring so that a fulcrum, a force point, and an action point are arranged in a line to stabilize the pressure. Specifically, a pressure receiving surface having a width equal to or larger than the outer diameter of the compression spring is provided at both ends of the compression spring, and the compression spring is held by bolts, nuts, etc., or the plate-like member is bent and pressed. The pressure is stabilized by providing a receiving surface and placing a compression spring, or by placing a compression spring on the plate thickness surface of the plate-like member so that the fulcrum, force point, and action point are in a line (see Patent Documents 2, 3, 4).

JP 2002-287559 A Shokai 58-50460 JP 63-157180 A Japanese Patent No. 3885534

  However, when a tension spring is used for applying pressure, a configuration in which the tension spring is pulled more in order to release the pressure is required. Therefore, a configuration using a compression spring is advantageous for applying more accurate pressure. However, as described above, the configuration using the compression spring requires a configuration for stabilizing the pressure, unlike the configuration using the tension spring. For example, a structure in which the width of the pressure receiving surface is made wider than the diameter of the compression spring and the compression spring is held by bolts and nuts is highly rigid and highly stable, but is an excessive structure and structure with respect to strength. Further, in the plate member, the pressure point is offset from the fulcrum and the action point by providing the pressure receiving surface by bending. For this reason, in addition to the generation of torsional force and moment force, it is necessary to ensure the strength of the pressure receiving surface against the torsional force and moment force. Even if a compression spring is placed on the plate thickness surface of the plate-like member to avoid torsional force and moment force, the compression spring can only be received with the width of the plate thickness, so the unstable condition of the pressure receiving surface cannot be overcome. There was a problem.

  An object of the present invention is to stably hold a compression spring and to stabilize the pressure applied by the compression spring while simplifying the configuration and reducing the cost.

  In order to achieve the above object, the present invention is provided with a first holding member that holds the first pressure contact member, and a rotation center axis that is provided on the first holding member. A second holding member that holds the second pressing member, and a compression spring that pressurizes one holding member toward the other holding member in order to press-contact the first pressing member and the second pressing member. And a guide member that has an outer diameter smaller than the inner diameter of the compression spring and that holds the compression spring in contact with the inside of the compression spring, the guide member being the compression spring And a hook portion that is provided on the one holding member and engages with the other holding member.

  According to the present invention, since the compression spring is stably held by the guide member, the pressure applied by the compression spring can be stabilized while simplifying the configuration and reducing the cost.

  Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. However, the dimensions, materials, shapes, and relative arrangements of the components described in the following embodiments should be appropriately changed according to the configuration of the apparatus to which the present invention is applied and various conditions. Therefore, unless specifically stated otherwise, the scope of the present invention is not intended to be limited thereto.

[First Embodiment]
The pressurizing mechanism according to the first embodiment will be described. Here, a configuration in which a pressure mechanism is used for the fixing device in the image forming apparatus will be described as an example.

  First, a schematic configuration of the image forming apparatus will be briefly described, and then a configuration using a pressure mechanism in the fixing device will be described.

  FIG. 1 is a cross-sectional view of a color electrophotographic printer which is an example of an image forming apparatus provided with a pressure mechanism according to the present embodiment. Hereinafter, the color electrophotographic printer is simply referred to as “printer”.

  The sheet is a sheet on which a toner image is formed. Specific examples of the sheet include plain paper, a resin sheet that is a substitute for plain paper, cardboard, and overhead projector.

  The printer 1 shown in FIG. 1 includes an image forming unit 10 for each color of Y (yellow), M (magenta), C (cyan), and Bk (black). The photosensitive drum 11 is charged in advance by a charger 12. Thereafter, a latent image is formed on the photosensitive drum 11 by the laser scanner 13. The latent image becomes a toner image by the developing device 14. The toner image on the photosensitive drum 11 is sequentially transferred to the intermediate transfer belt 31 by the primary transfer blade 17. After the transfer, the toner remaining on the photosensitive drum 11 is removed by the cleaner 15. As a result, the surface of the photosensitive drum 11 becomes clean and prepares for the next image formation.

  On the other hand, the sheets P are sent one by one from the feeding cassette 20 or the multi-feed tray 25 and fed to the registration roller pair 23. The registration roller pair 23 receives the sheet P once, and straightens it when the sheet is skewed. The registration roller pair 23 feeds the sheet P between the intermediate transfer belt 31 and the secondary transfer roller 35 in synchronization with the toner image on the intermediate transfer belt 31. The color toner image on the intermediate transfer belt 31 is transferred onto the sheet P by the secondary transfer roller 35. Thereafter, the toner image on the sheet P is fixed on the sheet P by being heated and pressed by the fixing device 40.

  When a toner image is formed on only one side of the sheet, the sheet P is discharged to the discharge tray 64 disposed on the side surface of the printer 1 or the discharge disposed on the upper surface of the printer 1 by switching the switching member 61. It is discharged to the tray 65. When the sheet P is discharged face up (the toner image is on the upper side), the sheet P is discharged onto the discharge tray 64. When the sheet P is discharged face down (the toner image is on the lower side), the sheet P is discharged onto the discharge tray 65. The

  When forming toner images on both sides of the sheet, the sheet P on which the toner image has been fixed by the fixing device 40 is guided upward by the switching member 61, and when the trailing edge reaches the reversal point R, the sheet P is conveyed by the conveyance path 73. Switched back and upside down. Thereafter, the sheet P is conveyed through the double-sided conveyance path 70, and a toner image is formed on the other side through the same process as the single-sided image formation, and is discharged onto the discharge tray 64 or the discharge tray 65. The portion constituted by the switching member 61, the switchback conveyance path 73, and the like is an example of a reversing unit that reverses the front and back surfaces of the sheet.

  Next, the pressure mechanism used in the fixing device will be described with reference to FIGS. FIG. 2 is an external perspective view of the fixing device 40 having a pressure mechanism. FIG. 3 is a front view showing details of the pressure mechanism of the fixing device 40. FIG. 4 is a plan view showing details of the pressure mechanism of the fixing device 40. FIG. 5 is a side view showing details of the pressure mechanism of the fixing device 40. FIG. 6 is a structural perspective view showing details of the pressure mechanism part excluding the spring of the fixing device 40.

  As shown in FIG. 2, the fixing device 40 heats and presses the transferred toner image to fix it on the sheet, and a fixing roller (first pressing member) 100 that is a pair of pressing members and a pressurizing member. A roller (second press contact member) 101 is provided. The fixing roller 100 and the pressure roller 101 are hollow cylindrical bodies having a release layer having a low friction coefficient on the surface, and are provided with a heating member 102 for heating inside. A predetermined pressure is applied between the fixing roller 100 and the pressure roller 101 by a pressure mechanism described later. Then, by passing the sheet P between the fixing roller 100 and the pressure roller 101, the toner image is heated and pressed to be fixed.

As a fixing device 40 here, although a pair of pressure rollers scheme, not shall be limited to the fixing method. For example, a belt fixing system in which the pressure roller side and the fixing roller side are conveyance belt units may be used.

  As shown in FIGS. 2 and 3, the fixing roller 100 is rotatably supported by a fixing roller support member 111 provided on plate-like brackets (first holding members) 110 disposed at both ends. The pressure roller 101 is rotatably supported by a pressure roller support member 121 provided on a plate-shaped pressure lever (second holding member) 120 disposed at both ends. The pressure lever 120 is supported so as to be rotatable about a rotation center shaft 112 provided on the bracket 110.

  As shown in FIGS. 2 to 6, a compression spring 200 is disposed on the pressure lever 120 at a position opposite to the rotation center shaft 112 with the pressure roller 101 interposed therebetween. The compression spring 200 presses the pressure lever 120 that is one holding member toward the bracket 110 that is the other holding member in order to press the fixing roller 100 and the pressure roller 101 with a predetermined pressure. . A portion where the compression spring 200 and the pressure lever 120 abut and engage with each other is a protrusion 220 (see FIG. 6) that supports the inner diameter portion of the compression spring 200 on the pressure lever 120. Are arranged at predetermined positions.

  A tension spring (guide member) 210 having a pressure center line substantially coincident with the pressure center line of the compression spring 200 and having an outer diameter smaller than the inner diameter of the compression spring 200 is disposed at the inner diameter portion of the compression spring 200. . The tension spring 210 as a guide member is disposed on the pressure lever 120 together with the compression spring 200, and holds the compression spring 200 at a predetermined position of the pressure lever 120 in order to prevent the compression spring 200 from falling or tilting. Further, the tension spring 210 has a hook portion 210a that engages with the bracket 110 at one end portion.

  A pressure receiving member 201 is provided at the other end of the compression spring 200 with one end supported by the protrusion 220. The pressure receiving member 201 is stretched around the other end portion of the tension spring 210 disposed on the inner diameter portion of the compression spring 200. Further, one end portion (hook portion 210 a) of the tension spring 210 is engaged with and stretched in a hole 221 provided in the bracket 110. That is, the tension spring 210 has a function of connecting the pressure lever 120 and the bracket 110 while holding the compression spring 200 in a predetermined position. This eliminates the need for a support member (for example, a stepped screw and a screw portion of a holding member) used in the conventional compression spring configuration, and enables a simple and low-cost configuration.

  Further, the relationship between the set pressures of the compression spring 200 and the tension spring 210 is the relationship of the pressure of the compression spring 200 <the tension pressure of the tension spring 210, or the pressure of the compression spring 200 <the initial tension of the tension spring 210. That is, the tensile pressure or initial tension of the tension spring 210 is larger than the pressure of the compression spring, and even when the pressure of the compression spring 200 is applied, the distance between the pressure receiving member 201 and the bracket 110 can be kept substantially constant. Yes. As described above, the tensile force of the tension spring 210 surely exceeds the pressure of the compression spring 200, so that the transmission pressure to the pressure lever 120 and the bracket 110 by the compression spring 200 can be reliably obtained.

  Further, as shown in FIG. 5, the pressure center line of the compression spring 200, the pressure center line of the tension spring 210, and the pressure lever 120 center line 333 in which the compression spring 200 and the tension spring 210 are disposed are substantially matched. Arranged.

  Further, as shown in FIGS. 4 and 5, the pressure point 331 on the pressure center line of the compression spring 200, the pressure application point 332 on the center axis of the pressure roller support member 121, and the center axis of the rotation center shaft 112. Three points of the pressure fulcrum 330 on the upper side are arranged (substantially coincide) on the pressure lever center line 333 of the pressure lever 120. In addition to this and the effect that the above-described tension spring 210 stably arranges the compression spring 200, the structure is such that it is difficult for the pressure lever 120 to generate a moment force with respect to a torsional force or an inclination.

  As described above, according to the present embodiment, the holding of the compression spring 200 is stabilized by the tension spring 210, and the applied pressure can be stabilized. In addition, since the shape of the component parts can be simplified, it is possible to achieve both cost reduction by introducing a part structure with fewer processing steps and stabilization of pressure by measures for eliminating deformation of the pressure component. A highly efficient configuration can be implemented.

  Moreover, although the tension spring is used as the guide member, the tension spring is a general part, and the above-described effects can be obtained while being superior in the flowability, cost, and ease of implementation.

  Further, by holding the compression spring with a tension spring, the member that holds the end of the compression spring does not need to be bent or the like when it is plate-shaped, and can be thinned when it is block-shaped.

[Other Embodiments]
In the above-described embodiment, the configuration including the tension spring 210 having an outer diameter smaller than the inner diameter of the compression spring 200 and holding the compression spring 200 in contact with the inner side of the compression spring 200 is described, but the present invention is not limited thereto. Is not to be done. As shown in FIG. 7, the structure may include a tension spring 210 having an inner diameter larger than the outer diameter of the compression spring 200 and holding the compression spring 200 in contact with the outer side of the compression spring 200. In addition, the other structure is the same as that of embodiment mentioned above, and the same code | symbol is attached | subjected to the member which has an equivalent function. Even if comprised in this way, the effect similar to embodiment mentioned above is acquired.

  In the above-described embodiment, the configuration in which the pressure of the compression spring 200 is constant is illustrated. However, the present invention is not limited to this, and a configuration in which an adjustment mechanism that variably adjusts the pressure of the compression spring 200 is provided. good. Specifically, for example, as shown in FIG. 8, the tension spring 210 is not stretched on the pressure receiving member 201 provided at the other end of the compression spring 200, and substantially coincides with the inner diameter of the tension spring 210. A male screw portion 201 a having a nominal diameter is provided and screwed into the inner diameter portion of the tension spring 210. As a result, the pressing force of the compression spring 200 can be stabilized and the pressing force can be adjusted.

  In the embodiment described above, the tension spring is exemplified as the guide member. However, as long as the guide member is in a shape that holds the compression spring in contact with the inside or outside of the compression spring, other cylindrical members or corners are used. It may be a columnar member.

  In the above-described embodiment, the configuration in which the pressure lever is pressed toward the bracket by the compression spring is exemplified, but the present invention is not limited to this. It is good also as a structure which pressurizes a bracket toward a pressure lever with a compression spring. Alternatively, it is possible to provide a configuration in which compression springs are provided on both the pressure lever side and the bracket side to pressurize each other.

  In the above-described embodiment, the configuration in which the pressure mechanism is applied to the fixing device of the image forming apparatus is illustrated, but the present invention is not limited to this. The present invention is effective even with other units and devices as long as the pair of pressure contact members are configured to pressurize using a compression spring. For example, the image forming apparatus described above is effective in a transfer roller unit, a feeding roller unit, and the like. Further, the present invention can be applied to apparatuses other than the image forming apparatus.

  In the above-described embodiment, the printer is exemplified as the image forming apparatus, but the present invention is not limited to this. For example, the image forming apparatus may be another image forming apparatus such as a scanner, a copying machine, or a facsimile machine, or another image forming apparatus such as a multifunction machine combining these functions. The same effect can be obtained by applying the present invention to a pair of press contact members that are pressed by using a compression spring in these image forming apparatuses.

Schematic cross-sectional view showing schematic configuration of image forming apparatus External perspective view of a fixing device having a pressure mechanism Front view showing details of pressure mechanism of fixing device Plan view showing details of pressure mechanism of fixing device Side view showing details of pressure mechanism of fixing device Configuration perspective view showing details of pressure mechanism excluding spring of fixing device Front view showing details of pressure mechanism of fixing device Cross-sectional view of the main part showing details of the adjustment mechanism in the pressure mechanism

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Printer 40 ... Fixing device 100 ... Fixing roller 101 ... Pressure roller 102 ... Heating member 110 ... Bracket 111 ... Fixing roller support member 112 ... Rotation center axis 120 ... Pressure lever 121 ... Pressure roller support member 200 ... Compression spring 201 ... pressure receiving member 201a ... male screw part 210 ... tension spring 210a ... hook part 220 ... projection 221 ... hole 330 ... pressure fulcrum 331 ... pressure point 332 ... pressure application point 333 ... center line

Claims (9)

A first holding member that holds the first pressure contact member, and a second holding member that is rotatably provided with respect to the rotation center axis provided in the first holding member and holds the second pressure contact member And a compression spring that pressurizes one holding member toward the other holding member in order to press-contact the first pressing member and the second pressing member,
An outer diameter smaller than the inner diameter of the compression spring, and a guide member that holds the compression spring in contact with the inner side of the compression spring; the guide member is provided on the one holding member together with the compression spring; A pressurizing mechanism having a hook portion that engages with the other holding member. A first holding member that holds the first pressure contact member, and a second holding member that is rotatably provided with respect to the rotation center axis provided in the first holding member and holds the second pressure contact member And a compression spring that pressurizes one holding member toward the other holding member in order to press-contact the first pressing member and the second pressing member,
A guide member having an inner diameter larger than an outer diameter of the compression spring, and holding the compression spring in contact with the outer side of the compression spring; the guide member is provided on the one holding member together with the compression spring; A pressurizing mechanism having a hook portion that engages with the other holding member.   The pressurizing mechanism according to claim 1, wherein the guide member is a tension spring having an outer diameter smaller than an inner diameter of the compression spring.   The pressure center line of the compression spring, the pressure center line of the tension spring, and the center line of the one holding member in which the compression spring and the tension spring are both disposed are substantially aligned. The pressurizing mechanism according to claim 3. 5. The pressurizing mechanism according to claim 3, wherein a relationship between a set pressure of the compression spring and the tension spring is a relationship of a pressure of the compression spring <a tension force of the tension spring.   The guide member has a pressure receiving member that supports the other end portion of the compression spring, one end portion of which is supported by the one holding member, and holding the compression spring on the one holding member, The pressurizing mechanism according to any one of claims 1 to 5, wherein the one holding member and the other holding member are connected by the hook portion.   The pressurizing mechanism according to any one of claims 1 to 6, further comprising an adjusting mechanism that variably adjusts the pressure of the compression spring.   8. An image forming apparatus that includes a pair of pressure contact members and a pressure mechanism for pressing the pair of pressure contact members, and forms an image on a sheet, wherein the pressure mechanism is any one of claims 1 to 7. An image forming apparatus comprising the pressing mechanism according to the item.   The image forming apparatus according to claim 8, further comprising: a fixing device that heats and presses an image on a sheet, wherein the fixing device includes a pair of pressing members that are pressed by the pressing mechanism.

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