An image forming apparatus includes an image bearing member having a photoconductive surface including an image forming area configured to bear an electrostatic latent image and a non-image forming area. A charging roller has a circular cross section with a first radius, the charging roller including a metallic core having a same rotational axis as the charging roller and a charging surface configured to charge the photoconductive surface of the image bearing member. A pair of gap forming members is disposed on longitudinal ends of the charging surface of the charging roller and is configured to contact longitudinal ends of the image bearing member to form a gap at least between the image forming area of the photoconductive surface of the image bearing member and the charging surface of the charging roller, each of the gap forming members having a circular cross section with a second radius such that a ratio of the second radius to the first radius is substantially constant through an entire rotational phase of the charging roller.