Sliding member for fixing device, fixing device, and image forming apparatus

1. A sliding member for a fixing device, comprising at least a fluororesin layer that has a sliding surface, the sliding surface having a plurality of recesses that are dotted over the sliding surface, the sliding member satisfying conditions (1) and (2) below:

(1) the dotted recesses exhibit an array pattern including a grid array, the grid array having a plurality of basic arrays that are contiguous, the basic arrays each including a basic grid and a central point of the basic grid, the basic grid being defined by four grid points and having one side parallel to a sliding direction, at least one of the central points of the basic arrays in the grid array being displaced from the grid array; and

(2) at least one recess exists on every straight line that defines a width of a central portion of the sliding surface along the sliding direction,

wherein each of the basis arrays is configured such that no recesses other than recesses corresponding to the four grid points exist on a perimeter defined by the four grid points.

2. The sliding member for a fixing device according to claim 1 , wherein in each of the basic grids of the array pattern, grid points of the four grid points lying along a direction orthogonal to the sliding direction are separated by a distance that is not more than approximately three times a diameter of the recesses.

3. The sliding member for a fixing device according to claim 2 , wherein:

the dotted recesses have a period of not less than approximately 0.2 mm and not more than approximately 2.0 mm; and

each one of the recesses has an area of not less than approximately 7×10 −3 mm 2 and not more than approximately 3.2 mm 2 .

4. The sliding member for a fixing device according to claim 2 , wherein in the sliding surface, the recesses occupy a total area of not less than approximately 10% and not more than approximately 60%.

5. The sliding member for a fixing device according to claim 1 , wherein:

the dotted recesses have a period of not less than approximately 0.2 mm and not more than approximately 2.0 mm; and

each one of the recesses has an area of not less than approximately 7×10 −3 mm 2 and not more than approximately 3.2 mm 2 .

6. The sliding member for a fixing device according to claim 5 , wherein in the sliding surface, the recesses occupy a total area of not less than approximately 10% and not more than approximately 60%.

7. The sliding member for a fixing device according to claim 1 , wherein in the sliding surface, the recesses occupy a total area of not less than approximately 10% and not more than approximately 60%.

8. The fixing device comprising:

a first rotary body;

a second rotary body that is placed in contact with an outer surface of the first rotary body;

a pressing member that is placed inside the second rotary body, the pressing member pressing the second rotary body against the first rotary body from an inner surface of the second rotary body;

the sliding member lies between the inner surface of the second rotary body and the pressing member, the sliding member being the sliding member for the fixing device according to claim 1 ; and

a heat source that heats at least one of the first rotary body and the second rotary body.

9. The fixing device according to claim 8 , wherein the inner surface of the second rotary body has a surface roughness Ra of not less than approximately 0.1 μm and not more than approximately 2.0 μm.

10. An image forming apparatus comprising:

an image carrier;

a charging section that charges a surface of the image carrier;

a latent image forming section that forms a latent image on the surface of the image carrier that has been charged;

a developing section that develops the latent image with a toner to form a toner image;

a transfer section that transfers the toner image to a recording medium; and

a fixing section that fixes the toner image to the recording medium, the fixing section being the fixing device according to claim 8 .

11. The sliding member for a fixing device according to claim 1 , wherein the at least one of the central points corresponds to a closest recess to a center of the basic grid.

12. The sliding member for a fixing device according to claim 1 , wherein each of the basic arrays is configured such that no recesses other than recesses corresponding to the four grid points and the central point exist inside a perimeter defined by the four grid points.

13. A sliding member for a fixing device, the sliding member comprising:

a fluororesin layer comprising a sliding surface,

wherein the sliding surface comprises a plurality of recesses arranged in a grid array,

wherein the grid array comprises a plurality of basic arrays,

wherein each of the basic arrays comprises:

a basic array perimeter defined by four of the recesses; and

a fifth one of the recesses provided inside the basic array perimeter;

wherein one side of the basic array perimeter is parallel to a sliding direction,

wherein the basic array is configured such that a center of the basic array perimeter is nonconcentric with any center of any recess,

wherein at least one recess exists on every straight line that defines a width of a central portion of the sliding surface along the sliding direction, and

wherein the basic array perimeter is configured such that no recesses other than the four of the recesses exist on the basic array perimeter.

14. The sliding member according to claim 13 , wherein the fifth one of the recesses is a closest recess to the center of the basic array perimeter.

15. The sliding member according to claim 13 , wherein the basic array perimeter is configured such that no recesses other than the four of the recesses and the fifth one of the recesses exist inside the basic array perimeter.

16. A sliding member for a fixing device, the sliding member comprising:

a fluororesin layer comprising a sliding surface,

wherein the sliding surface comprises a plurality of recesses arranged in a grid array,

wherein the grid array comprises a plurality of basic arrays,

wherein each of the basic arrays comprises:

a basic array perimeter defined by four of the recesses; and

a fifth one of the recesses provided inside the basic array perimeter;

wherein one side of the basic array perimeter is parallel to a sliding direction,

wherein the basic array is configured such that a center of the basic array perimeter is nonconcentric with any center of any recess,

wherein at least one recess exists on every straight line that defines a width of a central portion of the sliding surface along the sliding direction, and

wherein the basic array perimeter is configured such that no recesses other than the four of the recesses and the fifth one of the recesses exist inside the basic array perimeter.