Image forming system and latent image carrier replacement time detection method

An image forming system comprising:

• an image forming apparatus including a replaceable latent image carrier, and configured to form a latent image on a surface of the latent image carrier, develop the latent image into a visible image, and transfer the visible image onto a recording medium;
• a physical property detector configured to detect predetermined physical properties of the image forming apparatus in one of a continuous manner and an intermittent manner;
• a data storage device configured to store, as a specific physical property, data on at least one of the physical properties detected by the physical property detector, which changes before and after replacement of the latent image carrier;
• a latent image carrier replacement time detector configured to detect, on the basis of changes over time of the specific physical property stored in the data storage device, a latent image carrier replacement time;
• a cumulative usage information storage device configured to store data on a cumulative usage of the latent image carrier;
• a cumulative usage resetting device configured to reset the data on the cumulative usage stored in the cumulative usage information storage device;
• and
• a reset time storage device configured to store data on a reset time at which the cumulative usage resetting device resets the data on the cumulative usage,
• wherein the latent image carrier replacement time detector is configured to detect the latent image carrier replacement time by using the data on the reset time stored in the reset time storage device.

A latent image carrier replacement time detection method of detecting a latent image carrier replacement time of a latent image carrier in an image forming apparatus which forms a latent image on a surface of the latent image carrier, develops the latent image into a visible image, and transfers the visible image onto a recording medium, the latent image carrier replacement time detection method comprising:

• detecting predetermined physical properties of the image forming apparatus in one of a continuous manner and an intermittent manner;
• storing, as a specific physical property, data on at least one of the detected physical properties, which changes before and after replacement of the latent image carrier;
• detecting, on the basis of changes over time of the stored specific physical property, the latent image carrier replacement time;
• and
• calculating an approximate equation which approximates values of the specific physical property detected in an approximation period to a functional equation,
• wherein the detecting includes detecting the latent image carrier replacement time on the basis of an approximate value obtained from the approximate equation,
• wherein the calculating includes calculating, on the basis of successive first and second approximation periods, a difference between an approximate value corresponding to an end of the first approximation period obtained by the approximate equation approximating values of the specific physical property detected in the first approximation period and an approximate value corresponding to a beginning of the second approximation period obtained by the approximate equation approximating values of the specific physical property detected in the second approximation period, and
• wherein, when the difference is at least a specified value, the detecting includes detecting, as the latent image carrier replacement time, a time corresponding to a boundary between the first and second approximation periods.