Image forming apparatus

1. An image forming apparatus comprising:

an image forming device configured to form a toner image on a sheet;

a fixing unit, including first and second rotatable members configured to form a nip, configured to fix the toner image formed on the sheet by said image forming device;

a mounting portion to which said fixing unit is detachably mountable substantially along a longitudinal direction thereof;

a movable pressing portion configured to move said first rotatable member toward said second rotatable member at a pressing position;

a moving mechanism configured to move said pressing portion along a direction substantially perpendicular to the longitudinal direction toward the pressing position in a space of said mounting portion through which said fixing unit passes during mounting and demounting; and

a retracting mechanism configured to retract said pressing portion from the pressing position to an outside of the space.

2. An image forming apparatus according to claim 1 , further comprising a guide mechanism configured to guide slide movement of said fixing unit during the mounting and demounting of said fixing unit.

3. An image forming apparatus according to claim 2 , wherein the slide movement is linear movement.

4. An image forming apparatus comprising:

an image forming device configured to form a toner image on a sheet;

a fixing unit, including first and second rotatable members configured to form a nip, configured to fix the toner image formed on the sheet by said image forming device;

a mounting portion to which said fixing unit is detachably mountable substantially along a longitudinal direction thereof;

a pressing portion configured to generate a pressing force between said first rotatable member and said second rotatable member, said pressing portion being movable between a first position in a space of said mounting portion through which said fixing unit passes during mounting and demounting and a second position outside the space, wherein at the first position, said pressing portion generates the pressing force; and

a moving mechanism configured to move said pressing portion between the first position and the second position along a direction substantially perpendicular to the longitudinal direction.

5. An image forming apparatus according to claim 4 , further comprising a guide mechanism configured to guide slide movement of said fixing unit during the mounting and demounting of said fixing unit.

6. An image forming apparatus according to claim 5 , wherein the slide movement is linear movement.

7. An image forming apparatus comprising:

an image forming device configured to form a toner image on a sheet;

a fixing unit, including first and second rotatable members configured to form a nip, configured to fix the toner image formed on the sheet by said image forming device;

a mounting portion to which said fixing unit is detachably mountable substantially along a longitudinal direction thereof;

a movable pressing portion configured to move said first rotatable member toward said second rotatable member at a pressing position;

a moving mechanism configured to move said pressing portion along a direction substantially perpendicular to the longitudinal direction toward the pressing position where said pressing portion overlaps with said fixing unit when said fixing unit mounted in said mounting portion is viewed along the longitudinal direction; and

a retracting mechanism configured to retract said pressing portion from the pressing position so as not to overlap with said fixing unit when said fixing unit mounted in said mounting portion is viewed along the longitudinal direction.

8. An image forming apparatus according to claim 7 , further comprising a guide mechanism configured to guide slide movement of said fixing unit during the mounting and demounting of said fixing unit.

9. An image forming apparatus according to claim 8 , wherein the slide movement is linear movement.

10. An image forming apparatus comprising:

an image forming device configured to form a toner image on a sheet;

a fixing unit, including first and second rotatable members configured to form a nip, configured to fix the toner image formed on the sheet by said image forming device;

a mounting portion to which said fixing unit is detachably mountable substantially along a longitudinal direction thereof;

a pressing portion configured to generate a pressing force between said first rotatable member and said second rotatable member, said pressing portion being movable between a first position where said pressing portion overlaps with said fixing unit when said fixing unit mounted in said mounting portion is viewed along the longitudinal direction and a second position where said pressing portion does not overlap with said fixing unit when said fixing unit mounted in said mounting portion is viewed along the longitudinal direction, wherein at the first position, said pressing portion generates the pressing force; and

a moving mechanism configured to move said pressing portion between the first position and the second position along a direction substantially perpendicular to the longitudinal direction.

11. An image forming apparatus according to claim 10 , further comprising a guide mechanism configured to guide slide movement of said fixing unit during the mounting and demounting of said fixing unit.

12. An image forming apparatus according to claim 11 , wherein the slide movement is linear movement.