Method of and apparatus for controlling image density of toner image based on high and low-density correlation data

An image forming method in which a light beam is irradiated over a surface of a photosensitive member at an optimal exposure energy to form an electrostatic latent image, and said electrostatic latent image is visualized with toner while applying an optimal developing bias to developer means, said method comprising:

• a first step of calculating, as lower-density side correlation data, correlation data between exposure energies and developing biases which are necessary to form a toner image at a lower-density side target density;
• a second step of calculating, as higher-density side correlation data, correlation data between exposure energies and developing biases which are necessary to form a toner image at a higher-density side target density which is higher than said lower-density side target density;
• a third step of calculating a product set of said lower-density side correlation data and said higher-density side correlation data;
• and
• a fourth step of setting an exposure energy and a developing bias constituting one piece of correlation data belonging to the product set respectively as said optimal exposure energy and said optimal developing bias.

An image forming method in which after an optimal charging bias is supplied to charging means and a surface of a photosensitive member is charged, a light beam is irradiated over the surface of said photosensitive member with an optimal exposure energy to form an electrostatic latent image, and said electrostatic latent image is visualized with toner while applying an optimal developing bias to developer means, said method comprising:

• a first step of calculating, as lower-density side correlation data, correlation data between charging biases, exposure energies and developing biases which are necessary to form a toner image at a lower-density side target density;
• a second step of calculating, as higher-density side correlation data, correlation data between charging biases, exposure energies and developing biases which are necessary to form a toner image at a higher-density side target density which is higher than said lower-density side target density;
• a third step of calculating a product set of said lower-density side correlation data and said higher-density side correlation data;
• and
• a fourth step of setting a charging bias, an exposure energy and a developing bias constituting one piece of correlation data belonging to said product set respectively as said optimal charging bias, said optimal exposure energy and said optimal developing bias.

An image forming apparatus, comprising:

• developer means which visualizes an electrostatic latent image formed on a photosensitive member with toner;
• control means which sets a density adjustment factor influencing the image density of a toner image to a film-thickness-equivalent value which corresponds to the film thickness of said photosensitive member, and accordingly controls the image density of a toner image which is formed on said photosensitive member, and
• memory means which stores film-thickness-equivalent values at various film thickness values of said photosensitive member while associating said film-thickness-equivalent values with said film thickness values, and wherein
• said control means comprises:
• film thickness deriving means which calculates the film thickness of said photosensitive member;
• and
• optimization means which reads from said memory means a film-thickness-equivalent value corresponding to the film thickness of said photosensitive member calculated by said film thickness deriving means, and sets said density adjustment factor to this film-thickness-equivalent value,
• the image forming apparatus further comprising:
• exposure means which irradiates a surface of said photosensitive member with a light beam and accordingly forms an electrostatic latent image, and wherein
• said control means determines that an exposure energy of said light beam and a developing bias which is supplied to said developer means are said density adjustment factor, and stores one piece of correlation data belonging to a product set of lower-density side correlation data and higher-density side correlation data as said film-thickness-equivalent value in said memory means, said lower-density side correlation data being between said plurality of density adjustment factors and for forming a toner image at a lower-density side target density, said higher-density side correlation data being between said plurality of density adjustment factors and for forming a toner image at a higher-density side target density which is higher than said lower-density side target density.

An image forming apparatus comprising:

• developer means which visualizes an electrostatic latent image formed on a photosensitive member with toner;
• control means which sets a density adjustment factor influencing the image density of a toner image to a film-thickness-equivalent value which corresponds to the film thickness of said photosensitive member, and accordingly controls the image density of a toner image which is formed on said photosensitive member,
• an image carrier which carries a toner image which is formed on said photosensitive member;
• and
• density measuring means which measures the image density of a toner image formed on said photosensitive member or said image carrier, and wherein
• said control means is capable of changing said density adjustment factor within a predetermined programmable range, and
• said control means comprises:
• film thickness deriving means which calculates the film thickness of said photosensitive member;
• programmable range setting means which modifies and sets said programmable range in accordance with the film thickness of said photosensitive member calculated by said film thickness deriving means;
• and
• optimization means which forms toner images as patch images while modifying and setting a value of said density adjustment factor to multiple levels within said programmable range set by said programmable range setting means, causes said density measuring means measure the image densities of said patch images, calculates said film-thickness-equivalent value based on a result of said detection, and sets said density adjustment factor to said film-thickness-equivalent value.

An image forming apparatus, comprising:

• exposure means which irradiates a surface of a photosensitive member with a light beam and accordingly forms an electrostatic latent image;
• developer means which visualizes an electrostatic latent image formed on said photosensitive member with toner and accordingly visualizes a toner image;
• and
• control means which controls a density adjustment factor influencing the image density of a toner image, to thereby control the image density of a toner image formed on said photosensitive member to a reference target density, and wherein
• said density adjustment factor is modified and set in accordance with a necessity and the image density of a toner image is accordingly changed to an image density which is deviated from said reference target density.