CN-114296329-B - Image forming apparatus having a plurality of image forming units

CN114296329BCN 114296329 BCN114296329 BCN 114296329BCN-114296329-B

Abstract

The present disclosure relates to an image forming apparatus including an image bearing member, a charging member for charging a surface of the image bearing member, an exposure unit, a developing member for forming a toner image, a transfer member, an irradiation unit, and a blocking member. The irradiation unit includes a light source provided at one end of the irradiation unit in a rotation axis direction of the image bearing member, and a guide configured to guide light emitted from the light source in the rotation axis direction, the irradiation unit irradiating a surface of the image bearing member with light after the transfer member transfers the toner image to a transfer receiving member, the blocking member blocking the light irradiated from the irradiation unit in the rotation axis direction such that an amount of blocking the light irradiated from the irradiation unit in the rotation axis direction is different.

Inventors

NOGAMI KAZUAKI
Three Zhao fan
KAWANAMI TAKEO

Assignees

佳能株式会社

Dates

Publication Date: 20260512
Application Date: 20210924
Priority Date: 20201008

Claims (14)

1. An image forming apparatus, the image forming apparatus comprising: An image bearing member configured to be rotatable; a charging member configured to charge a surface of the image bearing member; an exposure unit configured to form an electrostatic latent image on the surface of the image bearing member charged by the charging member; a developing member configured to develop the electrostatic latent image formed by the exposing unit with toner to form a toner image; a transfer member configured to transfer the toner image formed by the developing member on the surface of the image bearing member to a transfer receiving member; an irradiation unit having a light source arranged at one end of the irradiation unit in a rotation axis direction of the image bearing member and a light guide configured to guide light emitted from the light source in the rotation axis direction, wherein the irradiation unit is configured to irradiate the surface of the image bearing member with the light after the transfer member transfers the toner image to the transfer receiving member, and A blocking member configured to block light irradiated from the irradiation unit in the rotation axis direction, Wherein the blocking member is configured such that an amount of blocking light irradiated from the irradiation unit in the rotation axis direction is different, Wherein the light guide includes a first portion near the light source, a second portion distant from the light source in a direction of a rotation axis of the image bearing member, and Fresnel portions dispersing light for illuminating the image bearing member, Wherein an amount of light irradiated from the irradiation unit is blocked by the blocking member in the rotation axis direction to be larger at the first portion than at the second portion, and Wherein the width of the light guide perpendicular to the fresnel portion at the second portion is wider than the width of the light guide perpendicular to the fresnel portion at the first portion.
2. The image forming apparatus according to claim 1, further comprising: A cartridge having the image bearing member, the charging member, and the developing member, and A tray that holds the cartridge and is insertable and removable with respect to the image forming apparatus while holding the cartridge, Wherein the blocking member is disposed on the tray.
3. The image forming apparatus according to claim 1, wherein an amount of light irradiated from the irradiation unit blocked by the blocking member at one end of the irradiation unit is larger than an amount of light irradiated from the irradiation unit blocked by the blocking member at a center of the irradiation unit in the rotation axis direction.
4. The image forming apparatus according to claim 3, wherein the blocking member blocks an amount of light irradiated from the irradiation unit in the rotation axis direction, as being closer to the light source.
5. An image forming apparatus according to claim 3, wherein said blocking member is configured such that a length of said blocking member in a second direction parallel to a broken line connecting said light guide and said image bearing member becomes longer as being closer to said light source.
6. The image forming apparatus according to claim 3, wherein the blocking member includes a plurality of filters that transmit the light irradiated from the irradiation unit and are arranged in the rotation axis direction and have different light transmittances.
7. The image forming apparatus according to claim 6, wherein the blocking member is configured such that light transmittance becomes higher as being farther from the light source in the rotation axis direction.
8. The image forming apparatus according to claim 1, wherein the blocking member blocks an amount of light irradiated from the irradiation unit in the rotation axis direction, as being closer to the light source.
9. The image forming apparatus according to claim 1, wherein the blocking member is configured such that a length of the blocking member in a second direction parallel to a broken line connecting the light guide and the image bearing member becomes longer as it is closer to the light source.
10. The image forming apparatus according to claim 1, further comprising a cartridge having the image bearing member, the charging member, and the developing member, and being insertable and removable with respect to the image forming apparatus, Wherein the blocking member is disposed on the cartridge.
11. The image forming apparatus according to claim 1, wherein the blocking member is configured such that a length of the blocking member in a first direction orthogonal to a broken line connecting the light guide and the image bearing member becomes longer as it becomes closer to the light source.
12. The image forming apparatus according to claim 11, wherein the blocking member is a first blocking member, the image forming apparatus further comprising a second blocking member disposed on a side opposite to the first blocking member with respect to the broken line.
13. The image forming apparatus according to claim 1, wherein the light guide has a circular shape, a rectangular shape, or a polygonal shape in a cross section orthogonal to the rotation axis direction.
14. An image forming apparatus, the image forming apparatus comprising: An image bearing member configured to be rotatable; a charging member configured to charge a surface of the image bearing member; an exposure unit configured to form an electrostatic latent image on the surface of the image bearing member charged by the charging member; a developing member configured to develop the electrostatic latent image formed by the exposing unit with toner to form a toner image; a transfer member configured to transfer the toner image formed by the developing member on the surface of the image bearing member to a transfer receiving member; An irradiation unit having a light source arranged at one end of the irradiation unit in a rotation axis direction of the image bearing member and a light guide configured to guide light emitted from the light source in the rotation axis direction, wherein the irradiation unit is configured to irradiate the surface of the image bearing member with light after the transfer member transfers the toner image to the transfer receiving member, and A blocking member configured to block light irradiated from the irradiation unit, Wherein a length of the blocking member toward the broken line at one end of the irradiation unit is longer than a length of the blocking member toward the broken line at a center of the irradiation unit in the rotation axis direction in a first direction orthogonal to the broken line connecting the light guide and the image bearing member, Wherein the light guide includes a first portion near the light source, a second portion distant from the light source in a direction of a rotation axis of the image bearing member, and Fresnel portions dispersing light for illuminating the image bearing member, Wherein an amount of light irradiated from the irradiation unit is blocked by the blocking member in the rotation axis direction to be larger at the first portion than at the second portion, and Wherein the width of the light guide perpendicular to the fresnel portion at the second portion is wider than the width of the light guide perpendicular to the fresnel portion at the first portion.

Description

Image forming apparatus having a plurality of image forming units Technical Field The present disclosure relates to an image forming apparatus. Background The image forming apparatus uniformly charges a photosensitive drum as an image bearing member to a predetermined potential by discharging from a charging member, and then exposes according to an image pattern, thereby forming an electrostatic latent image on the photosensitive drum. After that, the image forming apparatus develops the electrostatic latent image on the photosensitive drum with toner to develop into a toner image, and transfers the toner image onto a recording material such as paper. When charging the photosensitive drum surface, if there is residual charge on the photosensitive drum surface, the surface potential of the photosensitive drum may become uneven. Therefore, an image defect called a drum ghost (dry color) may occur due to a potential difference formed on the photosensitive drum between an image forming region where a toner image is formed and a non-image forming region where a toner image is not formed. Therefore, in order to eliminate the potential difference formed on the photosensitive drum surface, it is known to provide a so-called charge eliminating means that eliminates the surface potential of the photosensitive drum to a predetermined potential by irradiating the photosensitive drum surface with light before the charging step. The charge eliminating means is called a pre-exposure unit. The pre-exposure unit may be an LED (light emitting diode) or a combination of an LED circuit board and a light guiding unit such as a light guide. These techniques are useful as a system for removing charge over the entire length of the photoreceptor drum. However, in recent years, in view of cost, a light guide in which LEDs are disposed at the ends in the longitudinal direction of the photosensitive drum is generally employed instead of disposing LEDs over the entire range in the longitudinal direction of the photosensitive drum (japanese patent laid-open nos. 2018-132743 and 2009-053603). However, when a light guide is used as the pre-exposure unit, there are the following problems. When the photoconductive member is used, electric charges are eliminated from the photosensitive drum by irradiating light from the end portion in the longitudinal direction. Therefore, the light amount on the photosensitive drum surface becomes large on the light incident side, and the charge eliminating amount of the photosensitive drum becomes uneven in the longitudinal direction. In order to eliminate the charge eliminating unevenness in the longitudinal direction, there is known a method of measuring the charge eliminating amount on the photosensitive drum after pre-exposure and adjusting the charge eliminating amount so that the charge eliminating amount in the longitudinal direction becomes uniform when an image is exposed by the exposure unit. There is also known a method of adjusting the sensitivity of the photosensitive drum in the longitudinal direction by changing the layer thickness of the photosensitive drum, thereby equalizing the electric charges to eliminate the unevenness. However, according to the conventional technique, it is necessary to provide a detector configured to detect the charge eliminating amount on the photosensitive drum and to manage the layer of the photosensitive drum in the longitudinal direction, which requires a large amount of labor and cost. Further, in the conventional technique, since the amount of light irradiated onto the incident side of the photosensitive drum itself cannot be reduced, it is difficult to solve the concern about the lifetime due to the influence of light irradiation on the photosensitive drum (hereinafter also referred to as light deterioration). Disclosure of Invention An image forming apparatus is disclosed which aims to suppress charge elimination unevenness of a photosensitive drum in a longitudinal direction, the photosensitive drum being configured to be provided with a photoconductor in a pre-exposure unit. According to an aspect of the present disclosure, the image forming apparatus includes a rotatable image bearing member, a charging member configured to charge a surface of the image bearing member, an exposure unit configured to form an electrostatic latent image on the surface of the image bearing member charged by the charging member, a developing member configured to develop the electrostatic latent image formed by the exposure unit with a developer to form a toner image, a transfer member configured to transfer the toner image formed by the developing member on the surface of the image bearing member to a transfer receiving member, an irradiation unit having a light source provided at one end of the irradiation unit in a rotation axis direction of the image bearing member and a guide configured to guide light emitted from the light source in the rotation axis direction, wherein