Development apparatus

A development apparatus comprising:

• a first chamber configured to accommodate developer including toner and carriers;
• a second chamber separated from the first chamber by a partition wall;
• a first roller to which the developer is supplied, the first roller being configured to bear and convey the developer to develop an electrostatic latent image;
• a first magnet arranged within the first roller;
• a second roller to which the developer is delivered, the second roller being arranged to face the first roller, the second roller being configured to collect the developer in the second chamber after the electrostatic latent image is developed;
• and
• a second magnet arranged within the second roller,
• wherein a plurality of first grooves is formed on an outer circumferential surface of the first roller along a circumferential direction of the first roller,
• wherein a plurality of second grooves is formed on an outer circumferential surface of the second roller along a circumferential direction of the second roller, and
• wherein, in a case where a width of the first groove is d1, a number of the first grooves per circumference of the first roller is N1, a circumferential length of the first roller is L1, and a groove ratio ρ1 of the first groove is ρ1=(d1×N1)/L1, whereas a width of a second groove is d2, a number of the second grooves per circumference of the second roller is N2, a circumferential length of the second roller is L2, and a groove ratio ρ2 of the second groove is ρ2=(d2× N2)/L2, with
• 0.4
• ×
• ρ
• ⁢
• 1
• ≤
• ρ
• ⁢
• 2
• and
• 0.07
• ≤
• ρ
• ⁢
• 1
• ≤
• 0.23
• .