Fixing apparatus and image forming apparatus having the same

1. A fixing apparatus having a fixing rotary member and a pressure rotary member, wherein the pressure rotary member is configured to be separable from and in pressure contact with the fixing rotary member, and wherein the fixing rotary member and the pressure rotary member are configured to fix a toner image onto a sheet, the fixing apparatus comprising:

a pressure unit which includes the pressure rotary member and which is configured to be movable between a fixing position in which the pressure rotary member is in pressure contact with the fixing rotary member and a waiting position in which the pressure rotary member is separated from the fixing rotary member;

a guide member which forms a conveying path to guide a sheet on which the toner image is fixed by the fixing rotary member and the pressure rotary member;

a sheet detecting member which is configured to be movable by being pressed by the sheet in the conveying path, wherein the sheet detecting member is movable between a detecting position in which the sheet detecting member is projected into the sheet conveying path so that the sheet detecting member can be pressed by the sheet in the conveying path, and a retreat position in which the sheet detecting member is retreated from the sheet conveying path; and

a detecting sensor configured to detect a presence or absence of the sheet in the sheet conveying path based on a position of the sheet detecting member,

wherein the sheet detecting member is moved to the detecting position in association with a movement of the pressure unit to the waiting position, and is moved to the retreat position in association with a movement of the pressure unit to the fixing position.

2. A fixing apparatus according to claim 1 , further comprising:

a holder configured to hold the sheet detecting member; and

an interlocking member configured to rotate the holder in association with the movement of the pressure unit so that the sheet detecting member is moved between the detecting position and the retreat position.

3. A fixing apparatus according to claim 1 , wherein a surface of the sheet detecting member is substantially coplanar with a sheet contact surface of the guide member when the sheet detecting member is moved to the retreat position.

4. A fixing apparatus according to claim 1 , wherein the pressure rotary member is a fixing belt in a shape of an endless belt.

5. An image forming apparatus comprising:

an image forming portion configured to form a toner image on a sheet; and

a fixing apparatus configured to fix the toner image formed by the image forming portion onto the sheet, the fixing apparatus including,

a fixing rotary member and a pressure rotary member, wherein the pressure rotary member is configured to be separable from and in pressure contact with the fixing rotary member, and wherein the fixing rotary member and the pressure rotary member are configured to fix a toner image onto a sheet;

a pressure unit which includes the pressure rotary member and which is configured to be movable between a fixing position in which the pressure rotary member is in pressure contact with the fixing rotary member and a waiting position in which the pressure rotary member is separated from the fixing rotary member;

a guide member which forms a conveying path to guide a sheet on which the toner image is fixed by the fixing rotary member and the pressure rotary member;

a sheet detecting member which is configured to be movable by being pressed by the sheet in the conveying path, wherein the sheet detecting member is movable between a detecting position in which the sheet detecting member is projected into the sheet conveying path so that the sheet detecting member can be pressed by the sheet in the conveying path, and a retreat position in which the sheet detecting member is retreated from the sheet conveying path; and

a detecting sensor configured to detect a presence or absence of the sheet in the sheet conveying path based on a position of the sheet detecting member,

wherein the sheet detecting member is moved to the detecting position in association with a movement of the pressure unit to the waiting position, and is moved to the retreat position in association with a movement of the pressure unit to the fixing position.

6. A sheet conveying apparatus comprising:

a first rotary member;

a second rotary member configured to convey a sheet with the first rotary member and which is separable from and in contact with the first rotary member;

a sheet detecting member which is movable by being pressed by the sheet; and

a detecting sensor configured to detect a presence or absence of the sheet based on a position of the sheet detecting member,

wherein the sheet detecting member is movable between a detecting position for detecting a presence or absence of the sheet by the detecting sensor in which the sheet detecting member can be pressed by the sheet and a retreat position in which the sheet detecting member is retreated from the detecting position, and

wherein the sheet detecting member is moved to the detecting position from the retract position in association with a movement of the second rotary member away from the first rotary member.

7. A sheet conveying apparatus according to claim 6 , further comprising:

an interlocking member configured to interlock the detecting member with the movement of the second rotary member.