Image forming apparatus having image forming unit and fixing device

An image forming apparatus comprising:

• an image forming unit configured to form a toner image on a sheet;
• a fixing device configured to fix the toner image formed by the image forming unit to the sheet, the fixing device including:
• a heating unit configured to heat a sheet;
• a counter roller facing the heating unit and forming a fixing nip together with the heating unit;
• and
• an urging unit configured to urge one of the heating unit and the counter roller toward the other one of the heating unit and the counter roller;
• and
• a conveyance unit configured to convey the sheet toward the fixing device,
• wherein the fixing device is configured to fix a toner image borne on the sheet to the sheet by applying heat and pressure while conveying the sheet in a sheet conveyance direction at the fixing nip,
• wherein the conveyance unit is configured to convey the sheet to the fixing device such that one end portion of the sheet, in a width direction orthogonal to the sheet conveyance direction, conveyed to the fixing device passes through a predetermined position of the fixing nip in the width direction regardless of a size of the sheet,
• wherein the counter roller includes a roller portion including a base portion and an elastic layer provided around the base portion and having elasticity,
• wherein in a case where a side on which the predetermined position is positioned with respect to a central portion of the roller portion in the width direction is defined as a first side, and a side opposite to the first side is defined as a second side, the roller portion has a first end portion which is an end portion on the first side in the width direction, and a second end portion which is an end portion on the second side in the width direction,
• wherein the urging unit is configured such that an urging force at the first end portion is larger than an urging force at the second end portion, and
• wherein the elastic layer includes a high-hardness region provided on the first side and having a hardness higher than that of the elastic layer at the central portion.

An image forming apparatus comprising:

• an image forming unit configured to form a toner image on a sheet;
• a fixing device configured to fix the toner image formed by the image forming unit to the sheet, the fixing device including:
• a heating unit configured to heat a sheet;
• and
• a counter roller facing the heating unit and forming a fixing nip together with the heating unit;
• and
• a conveyance unit configured to convey the sheet toward the fixing device,
• wherein the fixing device is configured to fix a toner image borne on the sheet to the sheet by applying heat and pressure while conveying the sheet in a sheet conveyance direction at the fixing nip,
• wherein the conveyance unit is configured to convey the sheet to the fixing device such that one end portion of the sheet, in a width direction orthogonal to the sheet conveyance direction, conveyed to the fixing device passes through a predetermined position of the fixing nip in the width direction regardless of a size of the sheet,
• wherein the heating unit includes an endless rotary member that is rotatable and flexible, a heater disposed in an internal space of the rotary member and configured to heat the rotary member, and a restriction member,
• wherein the counter roller includes a roller portion including a base portion and an elastic layer provided around the base portion and having elasticity,
• wherein in a case where a side on which the predetermined position is positioned with respect to a central portion of the roller portion in the width direction is defined as a first side, and a side opposite to the first side is defined as a second side, the restriction member has a restriction surface configured to come into contact with an end surface of the rotary member on the second side in the width direction to restrict movement of the rotary member toward the second side,
• wherein the rotary member includes a base layer and an elastic layer provided around the base layer and containing a filler, and
• wherein the base layer has a protruding portion that protrudes in a first direction extending from the first side to the second side in the width direction relative to the elastic layer and is configured to come into contact with the restriction surface in the width direction.

An image forming apparatus comprising:

• an image forming unit configured to form a toner image on a sheet;
• a fixing device configured to fix the toner image formed by the image forming unit to the sheet, the fixing device including:
• a heating unit configured to heat a sheet;
• and
• a counter roller facing the heating unit and forming a fixing nip together with the heating unit;
• and
• a conveyance unit configured to convey the sheet toward the fixing device,
• wherein the fixing device is configured to fix a toner image borne on the sheet to the sheet by applying heat and pressure while conveying the sheet in a sheet conveyance direction at the fixing nip,
• wherein the conveyance unit is configured to convey the sheet to the fixing device such that one end portion of the sheet, in a width direction orthogonal to the sheet conveyance direction, conveyed to the fixing device passes through a predetermined position of the fixing nip in the width direction regardless of a size of the sheet,
• wherein the heating unit includes an endless rotary member that is rotatable and flexible, a heater disposed in an internal space of the rotary member and configured to heat the rotary member, a first support member disposed in the internal space and configured to support the heater, and a second support member disposed in the internal space and configured to support the first support member,
• wherein the counter roller includes a roller portion including a base portion and an elastic layer provided around the base portion and having elasticity,
• wherein in a case where a side on which the predetermined position is positioned with respect to a central portion of the roller portion in the width direction is defined as a first side, and a side opposite to the first side is defined as a second side, the first support member includes a first guide portion that is provided on the first side in the width direction and is configured to guide the rotary member at a position upstream of the fixing nip in the sheet conveyance direction, and a second guide portion that is provided on the second side in the width direction and is configured to guide the rotary member at a position upstream of the fixing nip in the sheet conveyance direction,
• wherein the second support member has a facing portion that is positioned farther from the fixing nip than the first guide portion and the second guide portion in an orthogonal direction orthogonal to the sheet conveyance direction and the width direction, and faces an upstream part of an inner circumferential surface of the rotary member in the sheet conveyance direction, and
• wherein a distance from the facing portion to an upstream end of the second guide portion in the sheet conveyance direction is longer than a distance from the facing portion to an upstream end of the first guide portion in the sheet conveyance direction.

An image forming apparatus comprising:

• an image forming unit configured to form a toner image on a sheet;
• a fixing device configured to fix the toner image formed by the image forming unit to the sheet, the fixing device including:
• a heating unit configured to heat a sheet;
• and
• a counter roller facing the heating unit and forming a fixing nip together with the heating unit;
• and
• a conveyance unit configured to convey the sheet toward the fixing device,
• wherein the fixing device is configured to fix a toner image borne on the sheet to the sheet by applying heat and pressure while conveying the sheet in a sheet conveyance direction at the fixing nip,
• wherein the conveyance unit is configured to convey the sheet to the fixing device such that one end portion of the sheet, in a width direction orthogonal to the sheet conveyance direction, conveyed to the fixing device passes through a predetermined position of the fixing nip in the width direction regardless of a size of the sheet,
• wherein the heating unit includes an endless rotary member that is rotatable and flexible, a heater disposed in an internal space of the rotary member and configured to heat the rotary member, a first support member disposed in the internal space and configured to support the heater, and a second support member disposed in the internal space and configured to support the first support member,
• wherein the counter roller includes a roller portion including a base portion and an elastic layer provided around the base portion and having elasticity,
• wherein the second support member has, at an end portion thereof located on a side opposite to the roller portion with respect to the fixing nip in an orthogonal direction orthogonal to the sheet conveyance direction and the width direction, a facing portion that faces an upstream part of an inner circumferential surface of the rotary member in the sheet conveyance direction, and
• wherein the heating unit includes a cover disposed on a side opposite to the predetermined position with respect to a central portion of the roller portion in the width direction, the cover being provided between the facing portion of the second support member and the upstream part of the inner circumferential surface of the rotary member in the sheet conveyance direction.

An image forming apparatus comprising:

• an image forming unit configured to form a toner image on a sheet;
• a fixing device configured to fix the toner image formed by the image forming unit to the sheet, the fixing device including:
• a heating unit configured to heat a sheet;
• and
• a counter roller facing the heating unit and forming a fixing nip together with the heating unit;
• and
• a conveyance unit configured to convey the sheet toward the fixing device,
• wherein the fixing device is configured to fix a toner image borne on the sheet to the sheet by applying heat and pressure while conveying the sheet in a sheet conveyance direction at the fixing nip,
• wherein the conveyance unit is configured to convey the sheet to the fixing device such that one end portion of the sheet, in a width direction orthogonal to the sheet conveyance direction, conveyed to the fixing device passes through a predetermined position of the fixing nip in the width direction regardless of a size of the sheet,
• wherein the heating unit includes an endless rotary member that is rotatable and flexible, a heater disposed in an internal space of the rotary member and configured to heat the rotary member, and a restriction member,
• wherein the counter roller includes a roller portion including a base portion and an elastic layer provided around the base portion and having elasticity,
• wherein in a case where a side on which the predetermined position is positioned with respect to a central portion of the roller portion in the width direction is defined as a first side, and a side opposite to the first side is defined as a second side, the restriction member has a restriction surface configured to come into contact with an end surface of the rotary member on the second side in the width direction to restrict movement of the rotary member toward the second side, and a guide portion provided so as to protrude from the restriction surface toward the rotary member in the width direction and configured to guide the rotary member by coming into contact with an inner circumferential surface of the rotary member, and
• wherein the restriction member is configured to move to a first position and a second position such that the guide portion of the restriction member positioned at the second position is located upstream in the sheet conveyance direction of the guide portion of the restriction member positioned at the first position, and is configured to move from the first position to the second position by the rotary member pushing the restriction surface in a first direction extending from the first side toward the second side in a case where the restriction member is positioned at the first position.