IMAGE FORMING APPARATUS AND DEVELOPING DEVICE
An image forming apparatus includes: an image carrier that carries an image; a transport-path forming part that forms a transport path for developer used to develop the image carried by the image carrier; a transport member that transports the developer in the transport path; and a concentration detector that detects toner concentration in the developer in the transport path. The transport path includes a first portion and a second portion. Difference in sectional area between the second portion and the transport member in a direction intersecting a direction in which the developer is transported is smaller than difference in sectional area between the first portion and the transport member. The second portion is located downstream of the first portion in the direction in which the developer is transported. The concentration detector is disposed in the second position of the transport path.
1 . An image forming apparatus comprising:
an image carrier that carries an image;
a transport-path forming part that forms a transport path for developer used to develop the image carried by the image carrier;
a transport member that transports the developer in the transport path; and
a concentration detector that detects toner concentration in the developer in the transport path, wherein
the transport path includes a first portion and a second portion, difference in sectional area between the first portion and the transport member in a direction intersecting a direction in which the developer is transported being different from difference in sectional area between the second portion and the transport member,
the difference in sectional area between the second portion and the transport member in the direction intersecting the direction in which the developer is transported is smaller than the difference in sectional area between the first portion and the transport member,
the second portion is located downstream of the first portion in the direction in which the developer is transported,
the concentration detector is disposed in the second portion of the transport path, and,
a≤0.7b where a is difference between a radius of the second portion of the transport path and a radius of the transport member in the second portion, and b is a length from an upstream end of the second portion to an upstream end of the concentration detector in the direction in which the developer is transported.
2 . The image forming apparatus according to claim 1 , wherein
the transport member has a shaft part, and
a sectional area of a portion of the shaft part located in the second portion is larger than a sectional area of a portion of the shaft part located in the first portion.
3 . The image forming apparatus according to claim 2 , wherein the transport member has a blade part on at least a portion of the shaft part located in the first portion and does not have the blade part on the portion of the shaft part located in the second portion.
4 . The image forming apparatus according to claim 2 , wherein, in the second portion, the shaft part faces an inner wall of the transport path.
5 . The image forming apparatus according to claim 3 , wherein, in the second portion, the shaft part faces an inner wall of the transport path.
6 . The image forming apparatus according to claim 3 , wherein h>(r A −r S ) where h is a height of the blade part projecting from the portion of the shaft part located in the second portion toward an inner wall of the transport path, r S is a radius of the portion of the shaft part located in the second portion, and r A is a radius of the blade part of the transport member.
7 . The image forming apparatus according to claim 4 , wherein h>(r A −r S ) where h is a height of the blade part projecting from the portion of the shaft part located in the second portion toward the inner wall of the transport path, r S is a radius of the portion of the shaft part located in the second portion, and r A is a radius of the blade part of the transport member.
8 . The image forming apparatus according to claim 5 , wherein h>(r A −r S ) where h is a height of the blade part projecting from the portion of the shaft part located in the second portion toward the inner wall of the transport path, r S is a radius of the portion of the shaft part located in the second portion, and r A is a radius of the blade part of the transport member.
9 . The image forming apparatus according to claim 1 , wherein a sectional area of the second portion of the transport path is smaller than a sectional area of the first portion of the transport path.
10 . The image forming apparatus according to claim 2 , wherein a sectional area of the second portion of the transport path is smaller than a sectional area of the first portion of the transport path.
11 . The image forming apparatus according to claim 3 , wherein a sectional area of the second portion of the transport path is smaller than a sectional area of the first portion of the transport path.
12 . The image forming apparatus according to claim 4 , wherein a sectional area of the second portion of the transport path is smaller than a sectional area of the first portion of the transport path.
13 . The image forming apparatus according to claim 5 , wherein a sectional area of the second portion of the transport path is smaller than a sectional area of the first portion of the transport path.
14 . The image forming apparatus according to claim 6 , wherein a sectional area of the second portion of the transport path is smaller than a sectional area of the first portion of the transport path.
15 . The image forming apparatus according to claim 7 , wherein a sectional area of the second portion of the transport path is smaller than a sectional area of the first portion of the transport path.
16 . The image forming apparatus according to claim 8 , wherein a sectional area of the second portion of the transport path is smaller than a sectional area of the first portion of the transport path.
17 . A developing device comprising:
a transport-path forming part that forms a transport path for developer used to develop an image carried by an image carrier;
a transport member that transports the developer in the transport path; and
a concentration detector that detects toner concentration in the developer in the transport path, wherein
the transport path includes a first portion and a second portion, difference in sectional area between the first portion and the transport member in a direction intersecting a direction in which the developer is transported being different from difference in sectional area between the second portion and the transport member,
the difference in sectional area between the second portion and the transport member in the direction intersecting the direction in which the developer is transported is smaller than difference in sectional area between the first portion and the transport member,
the second portion is located downstream of the first portion in the direction in which the developer is transported,
the concentration detector is disposed in the second position of the transport path, and
a≤0.7b where a is a difference between a radius of the second portion of the transport path and a radius of the transport member in the second portion, and b is the length from the upstream end of the second portion to an upstream end of the concentration detector in the direction in which the developer is transported.
18 . A developing device comprising:
a transport-path forming part that forms a transport path for developer used to develop an image carried by an image carrier;
a transport member that transports the developer in the transport path; and
a concentration detector that detects toner concentration in the developer in the transport path,
wherein the concentration detector is disposed at a position in the transport path where pressure applied to the developer falls within a predetermined range.