Developing device and image forming apparatus provided with same

An image forming apparatus, comprising:

• a developing device;
• a photoreceptor on which surface an electrostatic latent image is formed, the electrostatic latent image being developed by the developing device;
• a transfer device for transferring, to a paper, a toner image formed on the surface of the photoreceptor by developing the electrostatic latent image;
• and
• a fixing device for fixing the toner image to the paper to which the toner image is transferred,
• the developing device, comprising:
• a developing tank for storing a developer containing a toner and a magnetic carrier, the developing tank including, inside thereof, a developer carrying path that extends in one direction;
• and
• a stirring carrying member which is provided in the developer carrying path and which rotates so that the stirring carrying member carries the developer included in the developer carrying path while stirring the developer,
• the developing device developing by use of the developer carried from the developer carrying path by the stirring carrying member,
• the developing tank having an upper wall above the developer carrying path, the upper wall having a toner supply opening through which a toner is supplied to the developer carrying path from an outside,
• the developer carrying path being defined by first and second sidewalls present respectively in both sides of the width direction of the developer carrying path, the first sidewall facing downward rotation of the stirring carrying member,
• the first sidewall having an inner wall surface that has an upper part inclining from a direction perpendicular to a horizontal surface toward the developer carrying path, and
• an angle α, made by (i) a tangential line of the inner wall surface of the first sidewall at a position of the inner wall surface of the first sidewall which position is at a height of a top part of an outer circumference of the stirring carrying member and (ii) a horizontal line, being not less than 100° but not more than 150°,
• wherein:
• the upper part of the inner wall surface of the first sidewall reaches the toner supply opening,
• an angle made by the direction perpendicular to the horizontal surface and the inner wall surface of the first sidewall increases gradually from a position of the inner wall surface of the first sidewall which position is at a height of the rotary shaft of the stirring carrying member to a position of the inner wall surface of the first sidewall which position reaches the toner supply opening, and
• a distance between the inner wall surface of the first sidewall and the outer circumference of the stirring carrying member increases gradually from the position of the inner wall surface of the first sidewall which position is at the height of the rotary shaft of the stirring carrying member to the position of the inner wall surface of the first sidewall which position reaches the toner supply opening.