Image Forming Apparatus Having Supporting Member That Supports Bottom Portion Of Feeding Tray

Abstract

A feeding tray is detachably mounted on a base member and includes a bottom portion. The bottom portion has a first side that is configured to hold a recording sheet and a second side opposite the first side. An image forming unit forms an image on the recording sheet. A feeding roller is configured to rotatingly contact the recording sheet held in the feeding tray, thereby feeding the recording sheet toward the image forming unit in a conveying direction. A roller arm has one end that rotatably supports the feeding roller and another end opposite the one end. The roller arm is configured to swing about the another end, thereby generating a pressing force for pressing the feeding roller against the recording sheet. A supporting member is provided at the second side of the bottom portion and is configured to support the bottom portion against the pressing force.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a perspective view of an image forming apparatus according to a first embodiment of the invention;

FIG. 2 is a vertical cross-sectional view of a sheet feeding unit and an image forming unit of the image forming apparatus according to the first embodiment;

FIG. 3 is a perspective view of a feeding tray and the sheet feeding unit in which a second tray is not mounted;

FIG. 4 is a perspective view of the feeding tray and the sheet feeding unit in which the second tray is mounted;

FIG. 5 is a plan view of the feeding tray and the sheet feeding unit as viewed from above in which the second tray is not mounted;

FIG. 6 is a perspective view of the sheet feeding tray as viewed from above, in which a grip part is removed;

FIG. 7 is a perspective view of the sheet feeding tray as viewed from below, in which the grip part is removed;

FIG. 8 is a cross-sectional view taken along a line VIII-VIII shown in FIGS. 6 and 7;

FIG. 9A is a bottom view of a base member that constitutes a lower part and side parts of a main body casing;

FIG. 9B is a cross-sectional view taken along a line IXB-IXB shown in FIG. 9A;

FIG. 10 is a cross-sectional view taken along a line X-X in FIG. 9A;

FIG. 11 is an enlarged schematic view of an encircled part XI in FIG. 10;

FIG. 12 is a cross-sectional view taken along the line X-X in FIG. 9A when the sheet feeding tray is mounted in the base member (main body casing);

FIG. 13 is an enlarged schematic view of an encircled part XIII in FIG. 12;

FIG. 14 is a cross-sectional view taken along a line XIV-XIV in FIG. 5;

FIG. 15 is a cross-sectional view of the sheet feeding unit taken along a line XV-XV in FIG. 5;

FIG. 16 is a cross-sectional view of the sheet feeding unit taken along the line XIV-XIV in FIG. 5;

FIG. 17A is a cross-sectional view of a sheet feeding roller taken along a line XVII-XVII in FIG. 5, in which the sheet feeding roller (rotational shaft) is disposed in parallel with a center line of a through hole;

FIG. 17B is a cross-sectional view of the sheet feeding roller taken along the line XVII-XVII in FIG. 5, in which the sheet feeding roller (rotational shaft) is inclined relative to the center line of the through hole;

FIG. 18A is a vertical cross-sectional view for showing how a second torsion coil spring operates, where a roller arm is positioned on a bottom surface of the sheet feeding tray;

FIG. 18B is a vertical cross-sectional view for showing how the second torsion coil spring operates, where the roller arm is positioned on a bottom surface of the second tray;

FIG. 18C is a vertical cross-sectional view for showing how the second torsion coil spring operates, where the roller arm is positioned on an uppermost recording sheet when recording sheets are accommodated in the second tray to full capacity;

FIG. 19 is a perspective view of the sheet feeding unit as viewed from below;

FIG. 20A is an explanatory diagram for illustrating a swinging motion of the roller arm, in which a drive force is not supplied to the sheet feeding roller or conveying resistance acting on the recording sheet is small;

FIG. 20B is an explanatory diagram for illustrating the swinging motion of the roller arm, in which an outer periphery of the sheet feeding roller is greatly deformed due to an increased pressing force;

FIG. 20C is an explanatory diagram for illustrating the swinging motion of the roller arm, in which support ribs support a bottom plate of the sheet feeding tray at an upstream side relative to the sheet feeding roller in the conveying direction;

FIG. 21 is a bottom view of a base member according to a second embodiment of the invention;

FIG. 22A is an explanatory diagram for illustrating a swinging motion of the roller arm according to a comparative example, in which a drive force is not supplied to the sheet feeding roller or conveying resistance acting on the recording sheet is small; and

FIG. 22B is an explanatory diagram for illustrating the swinging motion of the roller arm, in which the arm angle is increased and the sheet feeding roller moves toward the upstream side in the conveying direction and depresses the recording sheet.

Claims

1. An image forming apparatus comprising: a base member;a feeding tray detachably mounted on the base member and including a bottom portion, the bottom portion having a first side that is configured to hold a recording sheet and a second side that is opposite to the first side;an image forming unit that forms an image on the recording sheet;a feeding roller that is configured to rotatingly contact the recording sheet held in the feeding tray, thereby feeding the recording sheet toward the image forming unit in a conveying direction;a roller arm having one end that rotatably supports the feeding roller and another end that is opposite to the one end, the roller arm being configured to swing about the another end, thereby generating a pressing force for pressing the feeding roller against the recording sheet; anda supporting member that is provided at the second side of the bottom portion and that is configured to support the bottom portion against the pressing force.

2. The image forming apparatus according to claim 1, further comprising a driving transmission mechanism that rotates the feeding roller in the conveying direction and that swingably moves the roller arm toward the recording sheet to generate the pressing force.

3. The image forming apparatus according to claim 1, wherein the supporting member is integrally formed with the bottom portion.

4. The image forming apparatus according to claim 1, wherein the supporting member supports the bottom portion at an upstream position relative to the feeding roller in the conveying direction.

5. The image forming apparatus according to claim 1, further comprising a base-side supporting member that is provided at the base member and that is configured to contact the supporting member to receive the pressing force.

6. The image forming apparatus according to claim 5, wherein the base-side supporting member is configured to contact an installation surface on which the base member is placed when the image forming apparatus is intended to be used.

7. The image forming apparatus according to claim 6, wherein the base-side supporting member has a large thickness part at a position corresponding to the supporting member, the large thickness part having a larger thickness than a remaining part of the base-side supporting member.

8. The image forming apparatus according to claim 5, wherein a flexural rigidity of the base-side supporting member is greater than a flexural rigidity of the bottom portion.

9. The image forming apparatus according to claim 5, wherein the base-side supporting member has a plate shape that is substantially parallel to the bottom portion; and wherein the base-side supporting member is formed with a cutout portion at an upstream side thereof in a mounting direction for mounting the feeding tray, the cutout portion having a substantially V-shape that is convex in the mounting direction.

10. The image forming apparatus according to claim 1, wherein the supporting member comprises a plurality of ribs each protruding from the second side of the bottom portion and extending in the conveying direction.