Developing apparatus and image forming apparatus that incorporates the developing apparatus
View Patent ↗A developing apparatus includes a developing roller and a sealing member. The developing roller applies toner to an electrostatic latent image to develop the electrostatic latent image. The sealing member presses the developing roller to seal the developer. The apparatus includes a developing roller with a shaft and a resilient layer formed on the shaft. The developing roller rotates about the shaft. The resilient layer covers the outer circumferential surface of the developing roller and is in contact with the sealing member. The resilient layer has a diameter that becomes larger nearer longitudinal ends of the developing roller. The diameter has a maximum value and a minimum value. The difference between the maximum value and the minimum value is such that 10 μm<ΔΦ<300 μm, where ΔΦ is a difference between the maximum value and the minimum value.
1. A developing apparatus including
a developing roller that rotates and applies developer to an electrostatic latent image formed on a photoconductive body to develop the electrostatic latent image into a visible image, and
a sealing member that is in pressure contact with the developing roller to seal the developer,
wherein the developing roller comprises:
a shaft that rotates; and
a resilient layer that covers an outer circumferential surface of said shaft, said resilient layer being in contact with the sealing member,
wherein said resilient layer has a diameter that becomes larger nearer a longitudinal end of the developing roller in a region where the sealing member is in contact with the developing roller.
2. The developing apparatus according to claim 1 , wherein the diameter has a maximum value and a minimum value, a difference between the maximum value and the minimum value is such that 10 μm<Δφ<300 μm
whereΔφ is a difference between the maximum value and the minimum value.
3. A developing apparatus including
a developing roller that rotates and applies developer to an electrostatic latent image formed on a photoconductive body to develop the electrostatic latent image into a visible image, and
a sealing member that is in pressure contact with the developing roller to seal the developer,
wherein the developing roller comprises:
a shaft that rotates; and
a resilient layer that covers an outer circumferential surface of said shaft, said resilient layer being in contact with the sealing member,
wherein said resilient layer has a diameter that becomes larger nearer a longitudinal end of the developing roller;
wherein the diameter has a maximum value and a minimum value, a difference between the maximum value and the minimum value is such that 10 μm<Δφ<300 μm
where Δφ is a difference between the maximum value and the minimum value; and
wherein an average diameter of particles of the developer is such that Δφ>(50/ψ)+5 μm
where ψ is the average diameter of the particles of the developer.
4. The developing apparatus according to claim 1 , wherein said resilient layer has a resin coating formed on it.
5. The developing apparatus according to claim 4 , wherein the resin coating has a thickness such that 2 μm <t<100 μm
where t is the thickness.
6. The developing apparatus according to claim 1 , wherein said resilient layer has an outer diameter that becomes larger nearer a longitudinal middle portion of the resilient layer.
7. The developing apparatus according to claim 6 , wherein
said resilient layer has a first diameter at the longitudinal middle portion of said resilient layer and a second diameter at a longitudinal end of said resilient layer,
the first diameter and the second diameter are related such that φend<φmid
where φmid is the first diameter and φend is the second diameter.
8. The developing apparatus according to claim 6 ,
wherein said resilient layer has a first diameter at a longitudinal middle portion and a second diameter at a point between the longitudinal middle portion and a longitudinal end, the second diameter being a smallest diameter across a length of said resilient layer,
wherein the first diameter and the second diameter are related such that 10 μm<(φmid−φA)<500 μm
where φmid is the first diameter in μm and φA is the second diameter in μm.
9. The developing apparatus according to claim 1 , wherein the longitudinal end has a surface that lies in a plane at an angle other than 90 degrees with an axis of rotation of the developing roller.
10. The developing apparatus according to claim 1 , wherein said resilient layer has an outer surface that extends to continuously become further away from an axis of rotation of the developing roller with decreasing distance from a longitudinal end of the developing roller.
11. The developing apparatus according to claim 1 , wherein said resilient layer has an outer surface that extends to become further away from a rotational axis of the developing roller nearer a longitudinal end of said resilient layer, the outer surface becoming further away from the rotational axis stepwise.
12. The developing apparatus according to claim 1 , wherein said resilient layer has an outer surface that becomes continuously closer to a rotational axis of the developing roller nearer a longitudinal end of said resilient layer.
13. The developing apparatus according to claim 1 , further comprising a sealing member disposed to press a surface of a longitudinal end of the developing roller to seal the developer.
14. An image forming apparatus incorporating a developing apparatus according to claim 1 .