JP6418404B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus.

  Conventionally, various rotating bodies such as a developing roller, a photosensitive drum, a transfer roller, and a fixing roller are mounted on an image forming apparatus. These rotators are connected to a motor or the like as a drive source via a gear. The gear is rotatably supported by a resin boss protruding from a predetermined wall surface (see, for example, Patent Document 1). Grease is applied to the boss and gear as a lubricant.

JP 2006-208941 A

  However, when the gear is supported by the boss portion as described above, stress concentration occurs at the connection portion between the outer peripheral surface of the boss portion and the predetermined wall surface. If grease scattered as the gear rotates adheres to the stress concentration portion, there is a problem that cracks (hereinafter referred to as chemical destruction) occur in the stress concentration portion as time passes. This chemical breakdown is caused by stress acting on the resin member to create gaps between the molecules of the resin member. Grease penetrates into the gaps, the intermolecular cohesive force decreases, and the grease slips through the molecules. . In order to prevent chemical destruction, either grease or stress concentration generated in the boss portion may be removed. However, the grease is indispensable for maintaining the lubricity of the gear, and it is difficult to avoid the stress concentration due to the shape of the boss portion.

  Therefore, it is conceivable to form the boss portion using a crystalline resin that is relatively difficult to cause chemical destruction among the resin members. However, if the resin member is limited to the crystalline resin, there is a risk of demerits in cost and performance.

  The present invention has been made in view of the above points, and an object of the present invention is to provide stress concentration in a boss portion in an image forming apparatus including a boss portion made of a resin member and a gear supported by the boss portion. This is to reliably prevent chemical breakdown from occurring regardless of the type of resin member.

  An image forming apparatus according to an aspect of the present invention is directed to an image forming apparatus including a boss portion made of a cylindrical resin member protruding from a predetermined wall surface and a gear rotatably supported by the boss portion.

  And the mixed component of an adhesive agent component and a hydrophilic component is apply | coated to the stress concentration part which is a connection part with the said predetermined wall surface in the outer peripheral surface of the said boss | hub part.

  According to the present invention, in an image forming apparatus including a boss portion made of a resin member and a gear supported by the boss portion, chemical breakdown occurs in the stress concentration portion of the boss portion regardless of the type of the resin member. It can be surely prevented.

FIG. 1 is a schematic diagram illustrating an image forming apparatus according to an embodiment. FIG. 2 is a schematic view showing a gear support structure.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The present invention is not limited to the following embodiment.

<Embodiment>
FIG. 1 shows an image forming apparatus 1 including a driving device according to this embodiment. The image forming apparatus 1 is a monochrome laser printer in this embodiment.

  The image forming apparatus 1 includes a paper feeding unit 10, an image forming unit 20, a fixing unit 40, a paper discharge unit 50, and a housing 60. A plurality of transport roller pairs 11 to 13 that sandwich and transport the paper P are disposed on the paper transport path T from the paper supply unit 10 to the paper discharge unit 50.

  The paper feeding unit 10 is disposed in the lower part of the housing 60. The paper feed unit 10 includes a paper feed cassette 10a in which sheet-like paper P is accommodated, and a pickup roller 10b for taking out the paper P in the paper feed cassette 10a and sending it out of the cassette. The paper P sent out of the cassette from the paper feed cassette 10 a is supplied to the image forming unit 20 through the transport roller pair 11.

  The image forming unit 20 includes a photosensitive drum 21, a charger 23, an exposure device 25, a developing device 27, a transfer device 29, and a toner container (not shown). In the image forming unit 20, the peripheral surface of the photosensitive drum 21 is charged by the charger 23, and then the original image data (for example, image data of the original image received from the external terminal) is applied to the surface of the photosensitive drum 21 by the exposure device 25. ) To form an electrostatic latent image. The electrostatic latent image formed (supported) on the surface of the photosensitive drum 21 is developed as a toner image by the developing device 27. The toner image developed by the developing device 27 is transferred onto the paper P supplied from the paper supply unit 10 by the transfer device 29. The transferred paper P is supplied to the fixing unit 40 by the transfer roller 29 a of the transfer device 29 and the photosensitive drum 21.

  The fixing unit 40 includes a heating roller 41 and a pressure roller 42 that is pressed against the heating roller 41 with a predetermined pressing load. Inside the heating roller 41, a halogen lamp (not shown) as a heating means is arranged. The peripheral surface of the heating roller 41 is heated by the heat generated from the halogen lamp.

  The fixing unit 40 presses and heats the paper P supplied from the image forming unit 20 between the heating roller 41 and the pressure roller 42 to fix the toner image on the paper P. Then, the sheet P on which the toner image is fixed by the fixing unit 40 is sent out downstream by the rollers 41 and 42. The fed paper P is discharged to a paper discharge unit 50 formed on the upper surface of the housing 60 by a plurality of transport roller pairs 12 and 13 provided along the paper transport path T.

  The conveying roller pairs 11 to 13 are rotationally driven by a driving device. This drive device has a motor as a power source and a gear 14 for transmitting the drive force of the motor to a drive pulley (not shown).

  As shown in FIG. 2, the inner peripheral surface of the gear 14 is slidably fitted to the outer peripheral surface of the boss portion 15 b formed on the side wall surface 15 a of the resin frame 15. Thus, the gear 14 is rotatably supported with respect to the boss portion 15b.

  The boss portion 15 b has a cylindrical shape and is integrally formed with the resin frame 15. The boss 15b protrudes horizontally from the side wall surface 15a of the resin frame 15 toward the inside of the apparatus. Grease is applied to the tooth surfaces of the gear 14 and the sliding portions of the gear 14 and the boss 15b in order to ensure lubricity.

  Here, stress concentration occurs in a connection portion (hereinafter referred to as a stress concentration portion) C with the resin frame 15 on the outer peripheral surface of the boss portion 15b. The stress concentration portion C has a circular shape surrounding the outer periphery of the boss portion 15b when viewed from the axial direction of the boss portion 15b. When grease adheres to the stress concentration portion, there is a problem that cracks occur in the stress concentration portion C as time passes. This crack is also called chemical destruction. Chemical breakdown is caused by stress acting on the resin member to create gaps between the molecules of the resin member. Grease penetrates into the gaps, intermolecular cohesion is reduced, and the grease slips through the molecules.

  In the present embodiment, a mixed component of an adhesive component and a hydrophilic component is applied to a predetermined region R (see FIG. 2) including the stress concentration portion C on the outer peripheral surface of the boss portion 15b in order to prevent this chemical destruction. I made it. Thus, by including a hydrophilic component in a mixed component, oil repellency can be provided to a mixed component. Therefore, it is possible to prevent a solvent such as grease from penetrating into the stress concentration portion C and reliably prevent chemical breakdown from occurring in the stress concentration portion C. In addition, as a resin member constituting the boss portion 15b, an amorphous resin (PS: polystyrene, ABS, PC: polycarbonate), which is more susceptible to chemical destruction than crystalline resins (PP: polypropylene, PE: polyethylene, POM: polyacetal, etc.) Etc.), the occurrence of chemical destruction can be reliably suppressed by the oil repellent action of the hydrophilic component. Therefore, the material selection skill increases by the amount that the resin member is not limited to the amorphous resin, and a more advantageous product design in terms of cost and performance is possible.

  Here, if the mass ratio of the hydrophilic component in the mixed component is higher than that of the adhesive component, the hydrophilic component cannot be sufficiently fixed to the surface of the boss portion 15b by the adhesive component, and the oil repellency on the surface of the boss portion 15b. (Hydrophilicity) is insufficient. On the other hand, if the mass ratio of the hydrophilic component in the mixed component is excessively low compared to the adhesive component, the adhesion of the hydrophilic component to the boss portion 15b surface is improved, but the absolute amount of the hydrophilic component is insufficient. The oil repellency (hydrophilicity) on the surface of the boss 15b cannot be sufficiently ensured. The inventors have intensively studied, and if the mass ratio of the adhesive component and the hydrophilic component is in the range of 1:10 to 5: 5, ensuring the adhesion of the hydrophilic component on the surface of the boss portion 15b and the absolute value of the hydrophilic component The experimental result was obtained that it was possible to ensure the quantity. Details of this experiment will be described later.

  As shown in FIG. 2, the predetermined region R where the mixed component is applied extends from the connection position (stress concentration portion C) with the side wall surface 15a on the outer peripheral surface of the boss portion 15b to a position separated by T / 2 in the boss axial direction. It is an area. Here, T is the distance from the connection position with the side wall surface 15a on the outer peripheral surface of the boss portion 15b to the support region G of the gear 14 on the outer peripheral surface of the boss portion 15b.

  According to this configuration, since there is a sufficient space between the predetermined region R to which the mixed component is applied and the gear support region G, the mixed component applied to the predetermined region R adheres to the support region G. Can be prevented. Therefore, it is possible to prevent the mixed component from entering the slight gap between the inner peripheral surface of the gear 14 and the outer peripheral surface of the boss portion 15b and increasing the rotational frictional force of the gear 14. Further, since the application range of the mixed component is wider than in the case where the mixed component is applied only to the stress concentration portion C, the application operation can be easily performed.

<Example>
Next, the result of the chemical destruction test performed about each of Examples 1-3 and the comparative example is demonstrated. In Example 1, the mass ratio of the adhesive component and the hydrophilic component in the mixed component was 1:10, and in Example 2, the mass ratio of the adhesive component and the hydrophilic component in the mixed component was 5: 5, In Example 3, the mass ratio of the adhesive component to the hydrophilic component in the mixed component was 5: 1. In the comparative example, the mixed component was not applied to the stress concentration portion C. In each example and comparative example, a water-dispersible silica agent was used as the hydrophilic material. The main components are silica, acrylic and sodium hydroxide. A PVA adhesive was used as an adhesive component. ABS resin, which is an amorphous resin, was used as the resin material for forming the boss portion 15b. As described in the above embodiment, the mixed component application range is T / 2 from the connection position with the side wall surface 15a on the outer peripheral surface of the boss portion 15b, that is, within the predetermined region R. Then, after applying the mixed component to the predetermined region R and sufficiently drying the adhesive component in the mixed component, the grease was applied to the stress concentration portion C on the outer peripheral surface of the boss portion 15b. As the grease, a synthetic hydrocarbon oil-based grease was used. Then, a shear load of 10 N (load in a direction perpendicular to the axial direction of the boss 15b) is applied to the gear support region G at the tip of the boss 15b and left overnight, and chemical breakdown occurs in the stress concentration portion C. It was confirmed visually using a loupe.

  As a result, in Example 1 and Example 2, no chemical destruction (cracking) was confirmed, and in the comparative example, occurrence of chemical destruction (cracking) was confirmed. In Example 3, although the occurrence of chemical destruction was confirmed, the magnitude thereof was sufficiently smaller than that of the comparative example. According to this experimental result, it can be seen that the occurrence of chemical breakdown is suppressed by applying a mixed component of the hydrophilic component and the adhesive component to the stress concentration portion of the boss portion 15b. Further, when the mass ratio of the hydrophilic component and the adhesive component in the mixed component is within the range of 1:10 to 5: 5 (Example 1 and Example 2), the mass ratio is out of the range (for example, Example 3). It can be seen that the effect of suppressing chemical destruction is even higher than in the case of).

<< Other embodiments >>
In the above embodiment, an example in which the image forming apparatus 1 is a monochrome laser printer has been described. However, the present invention is not limited to this. That is, the image forming apparatus 1 may be, for example, a copying machine, a facsimile machine, or a multifunction machine (MFP).

  As described above, the present invention is useful for an image forming apparatus.

G Gear support region T Distance R Predetermined region 1 Image forming apparatus 14 Gear 15a Side wall surface (predetermined wall surface)
15b Boss

Claims (4)

An image forming apparatus including a boss portion made of a cylindrical resin member protruding from a predetermined wall surface and a gear rotatably supported by the boss portion,
An image forming apparatus in which a mixed component of an adhesive component and a hydrophilic component is applied to a stress concentration portion that is a connection portion between the outer peripheral surface of the boss portion and the predetermined wall surface. The image forming apparatus according to claim 1.
The mixed component is applied to a predetermined region including the stress concentration portion on the outer peripheral surface of the boss portion,
When the distance from the connection position with the predetermined wall surface on the outer peripheral surface of the boss portion to the gear support region on the outer peripheral surface of the boss portion is T,
The image forming apparatus, wherein the predetermined area is an area from a connection position with the predetermined wall surface on an outer peripheral surface of the boss portion to a position separated by a distance T / 2 in the boss axis direction. The image forming apparatus according to claim 1 or 2,
The image forming apparatus, wherein a mixing ratio of the adhesive component and the hydrophilic component in the mixed component is within a range of 1:10 to 5: 5. The image forming apparatus according to any one of claims 1 to 3,
The image forming apparatus in which the resin forming the boss is an amorphous resin

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