Image forming apparatus

1. An image forming apparatus comprising:

an optical scanning unit having a light transmitting portion disposed across the optical scanning unit, and the light transmitting portion's surface is oriented along its longitudinal axis; and

a cleaning mechanism that includes:

a cleaning rod with a pad at a front end portion thereof to be capable of cleaning the surface of the light transmitting portion by sliding on the light transmitting portion surface; and

a retaining mechanism that retains the cleaning rod slidably in the longitudinal direction of the light transmitting portion surface, and that retains the pad positioned above the optical scanning unit and substantially spaced apart from the optical scanning unit in a state where the cleaning rod is at an insertion completed position.

2. An image forming apparatus comprising:

an optical scanning unit having a light transmitting portion disposed across the optical scanning unit, and the light transmitting portion's surface is oriented along its longitudinal axis; and

a cleaning mechanism that includes:

a cleaning rod with a pad at a front end portion thereof to be capable of cleaning the surface of the light transmitting portion by sliding on the light transmitting portion surface; and

a retaining mechanism that retains the cleaning rod slidably in the longitudinal direction of the light transmitting portion surface, and that retains the pad positioned above the optical scanning unit and substantially spaced apart from the optical scanning unit in a state where the cleaning rod is at an insertion completed position,

the retaining mechanism that includes:

a guide rail that retains the front end portion of the cleaning rod so that the pad is substantially spaced apart from the surface of the optical scanning unit, when the cleaning rod is inserted, and that is engaged with the front end portion of the cleaning rod to bring the pad substantially into contact with the light transmitting portion surface of the optical scanning unit, when the cleaning rod is pulled; and

a receiving portion that receives the front end portion of the cleaning rod separated from an end portion of the guide rail before the insertion completed portion at a position substantially spaced apart from the surface of the optical scanning unit, when the cleaning rod is inserted.

3. The image forming apparatus according to claim 2 , wherein the receiving portion is substantially tilted to a direction of inserting the cleaning rod.

4. The image forming apparatus according to claim 2 , wherein the retaining mechanism includes a biasing member that biases the front end portion of the cleaning rod to be engaged with the receiving portion, toward the optical scanning unit.

5. The image forming apparatus according to claim 4 , wherein:

the retaining mechanism includes a guiding member having an inserting opening, the front end portion of the cleaning rod being inserted into the inserting opening;

the front end portion of the cleaning rod has a reverse insertion preventing projection to be fitted into a reverse insertion preventing groove defined at the inserting opening; and

the biasing member is engaged with the reverse insertion preventing projection.

6. The image forming apparatus according to claim 2 , wherein the retaining mechanism includes a guide portion that guides the front end portion of the cleaning rod moving between the optical scanning unit and the guide rail onto the guide rail so that the pad is substantially spaced apart from the optical scanning unit, when the cleaning rod is pulled and after the pad passes sliding on the surface of the light transmitting portion.

7. An image forming apparatus comprising:

an optical scanning means having a light transmitting portion disposed across the optical scanning means, and the light transmitting portion's surface is oriented along its longitudinal axis; and

a cleaning mechanism that includes:

a cleaning rod means with a pad at a front end portion thereof to be capable of cleaning

the surface of the light transmitting portion by sliding on the light transmitting portion surface; and

a retaining means for retaining the cleaning rod slidably in the longitudinal direction of the light transmitting portion surface, and for retaining the pad positioned above the optical scanning means and substantially spaced apart from the optical scanning means in a state where the cleaning rod is at an insertion completed position.