Image forming apparatus and transfer device having attachable developing unit

1. An image forming apparatus comprising:

a main body portion including

an image carrier that is rotatable,

an image-carrier driving unit that rotates the image carrier,

a latent-image forming unit that forms an electrostatic latent image on the image carrier,

a developing-unit attachment section to which a developing unit is attached, the developing unit developing the electrostatic latent image that is formed on the image carrier by the latent-image forming unit, and

a transfer-unit attachment section to which a transfer unit is attached, the transfer unit facing the image carrier, being rotatable, and transferring an image formed on the image carrier by the latent-image forming unit and the developing unit attached to the developing-unit attachment section onto a recording medium interposed between the transfer unit and the image carrier at a transfer position at which the transfer unit faces the image carrier,

wherein the developing-unit attachment section provided in the main body portion is capable of receiving, as the developing unit, a first developing unit or a second developing unit, the first developing unit having a plurality of developing members and the second developing unit having a single developing member,

wherein the transfer-unit attachment section provided in the main body portion is capable of receiving, as the transfer unit, a first transfer unit or a second transfer unit, the first transfer unit including a first transfer member that is rotatable and has a function of retaining the recording medium and a first transfer driving unit that rotates the first transfer member, and the second transfer unit including a second transfer member that is rotatable and that does not have a function of retaining the recording medium, and

wherein, when the first developing unit is attached to the developing-unit attachment section provided in the main body portion and the first transfer unit is attached to the transfer-unit attachment section provided in the main body portion, the first transfer driving unit provided in the first transfer unit is mechanically connected to the first developing unit.

2. The image forming apparatus according to claim 1 , wherein, when the second developing unit is attached to the developing-unit attachment section provided in the main body portion and the second transfer unit is attached to the transfer-unit attachment section provided in the main body portion, the image-carrier driving unit provided in the main body portion is mechanically connected to the second developing unit.

3. The image forming apparatus according to claim 1 , wherein the first developing unit includes a rotary developing unit in which the plurality of developing members rotate around an axis and in which one of the plurality of developing members stops at a developing position at which the rotary developing unit faces the image carrier, each of the plurality of developing members including a rotating member that is rotatable, and

wherein, when the first developing unit is attached to the developing-unit attachment section and the first transfer unit is attached to the transfer-unit attachment section in the main body portion, the rotary developing unit is rotated around the axis or stopped by the first transfer driving unit provided in the first transfer unit.

4. The image forming apparatus according to claim 1 , wherein the first developing unit includes a rotary developing unit in which the plurality of developing members rotate around an axis and in which one of the plurality of developing members stops at a developing position at which the rotary developing unit faces the image carrier, each of the plurality of developing members including a rotating member that is rotatable, and

wherein, when the first developing unit is attached to the developing-unit attachment section and the first transfer unit is attached to the transfer-unit attachment section in the main body portion, the rotating member provided in the developing member that is stopped at the developing position is rotated by the first transfer driving unit provided in the first transfer unit.

5. The image forming apparatus according to claim 1 , wherein the main body portion further includes a main-body power source that supplies electricity to the image-carrier driving unit, and

wherein the first transfer unit further includes a first-transfer-unit power source that supplies electricity to the first transfer driving unit when the first transfer unit is attached to transfer-unit attachment section provided in the main body portion.

6. The image forming apparatus according to claim 1 , wherein the main body portion further includes a main-body controller that controls the image-carrier driving unit, and

wherein the first transfer unit further includes a first-transfer-unit controller that controls the first transfer driving unit when the first transfer unit is attached to transfer-unit attachment section provided in the main body portion.

7. The image forming apparatus according to claim 1 , wherein a diameter of the first transfer member provided in the first transfer unit is larger than a diameter of the second transfer member provided in the second transfer unit.