Sensor member and image forming apparatus

An image forming apparatus, comprising:

• a sensor member that is mounted in the image forming apparatus, detects a developer, has a first end and a second end opposite to each other in a longitudinal direction of the sensor member, and is supported by the first end, the second end, a first support structure of the image forming apparatus, and a second support structure of the image forming apparatus, the first support structure supporting the first end, the second support structure supporting the second end;
• the first support structure including
• one of a first protruding portion and a first recess portion, the first recess portion supporting the first protruding portion movably in the longitudinal direction of the sensor member, wherein the other one of the first protruding portion and the first recess portion is arranged in the first end of the sensor member;
• and
• the second support structure including
• one of a second protruding portion and a second recess portion, the second recess portion supporting the second protruding portion movably in a direction defined by connecting the first end and the second end, wherein the other one of the second protruding portion and the second recess portion is arranged in the second end of the sensor member, the second protruding portion having
• a first cylinder portion that extends in a longitudinal direction of the second protruding portion, and
• a second cylinder portion that is arranged at an end side of the second protruding portion next to the first cylinder portion, the second cylinder portion having a larger external shape than an external shape of the first cylinder portion and extending in the longitudinal direction of the second protruding portion, and
• the second recess portion having
• an insertion portion that allows the second protruding portion to be inserted, and that is larger than the external shape of the second cylinder portion,
• a pass portion that is connected with the insertion portion, that is larger than the external shape of the first cylinder portion and smaller than the external shape of the second cylinder portion, and that allows the first cylinder portion to pass therethrough, and
• a positioning portion that is connected with the pass portion, and that has a shape corresponding to the external shape of the second cylinder portion, the positioning portion being fitted on the second cylinder portion and supporting the second cylinder portion such that the sensor member is positioned.