Developing device, process cartridge, and image forming apparatus, method of developing latent image

A developing device comprising:

• a cylindrical developer carrier to rotate on a developer carrier shaft including a plurality of magnetic poles arranged therein, to carry a developer including magnetic particles and toner, and to supply the developer to an electrostatic latent image formed on an image carrier to develop the electrostatic latent image, wherein the plurality of magnetic poles include magnetic poles disposed adjacent to each other and having a same polarity,
• a first magnetic pole of the magnetic poles disposed adjacent to each other being located downstream with respect to a rotation direction of the cylindrical developer carrier,
• a second magnetic pole of the magnetic poles disposed adjacent to each other being located upstream with respect to the rotation direction of the cylindrical developer carrier;
• a first developer agitating/conveying member to rotate on a first shaft parallel to the developer carrier shaft, to agitate and convey developer along the first shaft, and to supply the developer to the cylindrical developer carrier;
• a second developer agitating/conveying member to rotate on a second shaft parallel to the developer carrier shaft, to agitate and convey the developer in a reverse direction from a direction the first developer agitating/conveying member conveys the developer, wherein the second developer agitating/conveying member conveys the developer to the first developer agitating/conveying member while agitating the developer,
• wherein the cylindrical developer carrier includes,
• a first point where magnetic flux density generated by the second magnetic pole in a normal direction becomes maximum,
• a second point upstream from the first point with respect to a rotating direction of the cylindrical developer carrier, where the magnetic flux density in the normal direction becomes substantially zero, and
• a third point downstream from the first point with respect to the rotating direction of the cylindrical developer carrier, where the magnetic flux density in the normal direction becomes substantially zero, wherein the third point is formed upstream from a line joining a center of the cylindrical developer carrier and a center of the second developer agitating/conveying member with respect to the rotating direction of the cylindrical developer carrier;
• a fourth point where magnetic flux density generated by the first magnetic pole in the normal direction becomes maximum;
• a fifth point upstream from the fourth point with respect to rotating direction of the cylindrical developer carrier, where the magnetic flux density in the normal direction becomes substantially zero;
• and
• a sixth point downstream from the fourth point with respect to the rotating direction of the cylindrical developer carrier, where the magnetic flux density in the normal direction becomes substantially zero, wherein the fifth point is formed downstream from a line joining the center of the cylindrical developer carrier and a center of the first developer agitating/conveying member with respect to the rotating direction of the cylindrical developer carrier,
• wherein the cylindrical developer carrier includes only three magnetic poles.

A developing device comprising:

• a cylindrical developer carrier to rotate on a developer carrier shaft including a plurality of magnetic poles arranged therein, to carry a developer including magnetic particles and toner, and to supply the developer to an electrostatic latent image formed on an image carrier to develop the electrostatic latent image, wherein the plurality of magnetic poles include magnetic poles disposed adjacent to each other and having a same polarity,
• a first magnetic pole of the magnetic poles disposed adjacent to each other being located downstream with respect to a rotation direction of the cylindrical developer carrier,
• a second magnetic pole of the magnetic poles disposed adjacent to each other being located upstream with respect to the rotation direction of the cylindrical developer carrier;
• a first developer agitating/conveying member to rotate on a first shaft parallel to the developer carrier shaft, to agitate and convey developer along the first shaft, and to supply the developer to the cylindrical developer carrier;
• a second developer agitating/conveying member to rotate on a second shaft parallel to the developer carrier shaft, to agitate and convey the developer in a reverse direction from a direction the first developer agitating/conveying member conveys the developer, wherein the second developer agitating/conveying member conveys the developer to the first developer agitating/conveying member while agitating the developer,
• wherein the cylindrical developer carrier includes,
• a first point where magnetic flux density generated by the second magnetic pole in a normal direction becomes maximum,
• a second point upstream from the first point with respect to a rotating direction of the cylindrical developer carrier, where the magnetic flux density in the normal direction becomes substantially zero, and
• a third point downstream from the first point with respect to the rotating direction of the cylindrical developer carrier, where the magnetic flux density in the normal direction becomes substantially zero, wherein the third point is formed upstream from a line joining a center of the cylindrical developer carrier and a center of the second developer agitating/conveying member with respect to the rotating direction of the cylindrical developer carrier;
• a fourth point where magnetic flux density generated by the first magnetic pole in the normal direction becomes maximum;
• a fifth point upstream from the fourth point with respect to rotating direction of the cylindrical developer carrier, where the magnetic flux density in the normal direction becomes substantially zero;
• a sixth point downstream from the fourth point with respect to the rotating direction of the cylindrical developer carrier, where the magnetic flux density in the normal direction becomes substantially zero, wherein the fifth point is formed downstream from a line joining the center of the cylindrical developer carrier and a center of the first developer agitating/conveying member with respect to the rotating direction of the cylindrical developer carrier;
• and
• a wall unit to separate the first developer agitating/conveying member and the second developer agitating/conveying member, wherein
• the second developer agitating/conveying member is located directly below the first developer agitating/conveying member, and
• an end of the wall unit, from which the developer is supplied to the cylindrical developer carrier, is disposed at least above the line joining the center of the cylindrical developer carrier and the center of the first developer agitating/conveying member.

A developing device comprising:

• a cylindrical developer carrier to rotate on a developer carrier shaft including a plurality of magnetic poles arranged therein, to carry a developer including magnetic particles and toner, and to supply the developer to an electrostatic latent image formed on an image carrier to develop the electrostatic latent image, wherein the plurality of magnetic poles include magnetic poles disposed adjacent to each other and having a same polarity,
• a first magnetic pole of the magnetic poles disposed adjacent to each other being located downstream with respect to a rotation direction of the cylindrical developer carrier,
• a second magnetic pole of the magnetic poles disposed adjacent to each other being located upstream with respect to the rotation direction of the cylindrical developer carrier;
• a first developer agitating/conveying member to rotate on a first shaft parallel to the developer carrier shaft, to agitate and convey developer along the first shaft, and to supply the developer to the cylindrical developer carrier;
• a second developer agitating/conveying member to rotate on a second shaft parallel to the developer carrier shaft, to agitate and convey the developer in a reverse direction from a direction the first developer agitating/conveying member conveys the developer, wherein the second developer agitating/conveying member conveys the developer to the first developer agitating/conveying member while agitating the developer;
• a wall unit to separate the first developer agitating/conveying member and the second developer agitating/conveying member, wherein
• the second developer agitating/conveying member is located directly below the first developer agitating/conveying member, and
• an end of the wall unit, from which the developer is supplied to the cylindrical developer carrier, is disposed at least above the line joining the center of the cylindrical developer carrier and the center of the first developer agitating/conveying member,
• wherein the cylindrical developer carrier includes,
• a first point where magnetic flux density generated by the second magnetic pole in a normal direction becomes maximum,
• a second point upstream from the first point with respect to a rotating direction of the cylindrical developer carrier, where the magnetic flux density in the normal direction becomes substantially zero, and
• a third point downstream from the first point with respect to the rotating direction of the cylindrical developer carrier, where the magnetic flux density in the normal direction becomes substantially zero, wherein the third point is formed upstream from a line joining a center of the cylindrical developer carrier and a center of the second developer agitating/conveying member with respect to the rotating direction of the cylindrical developer carrier;
• a fourth point where magnetic flux density generated by the first magnetic pole in the normal direction becomes maximum;
• a fifth point upstream from the fourth point with respect to rotating direction of the cylindrical developer carrier, where the magnetic flux density in the normal direction becomes substantially zero;
• a sixth point downstream from the fourth point with respect to the rotating direction of the cylindrical developer carrier, where the magnetic flux density in the normal direction becomes substantially zero, wherein the fifth point is formed downstream from a line joining the center of the cylindrical developer carrier and a center of the first developer agitating/conveying member with respect to the rotating direction of the cylindrical developer carrier,
• the first developer agitating/conveying member and the second developer agitating/conveying member are disposed in a vertical direction.