Ricoh AP4510 Service Manual download pdf (Page 231)

DEVELOPMENT

SM 6-27 G065

Detailed

Descriptions

Sensor Control Mode

In the sensor control mode, the amount of toner required to print the page is

calculated by the CPU; it adds up the image data value of each pixel and converts

the sum to a value between 0 and 255. (255 would mean a completely black page.)

The machine must vary toner supply for each print in order to maintain the correct

amount of toner in the developer and to account for changes in drum reflectivity

due to changes in temperature and humidity. The CPU uses data from the TD

sensor and ID sensor to determine whether or not the toner supply motor should be

switched on and to calculate how long it should remain on in order to supply more

toner to the mixture in the development unit.

TD Sensor

When new developer of standard toner concentration is installed, namely 20 g of

toner per 500 g of developer (4.0% by weight), the TD sensor must be set to its

initial setting of 4.0 V with SP2801. This initial setting is used as the toner supply

reference voltage or Vref. For every print cycle, the TD sensor directly checks the

toner density in the developer mixture, and after 10 copies these 10 readings are

averaged and this value becomes TD sensor output voltage Vt(10).

The machine compares Vt(10) with Vref. If Vt(10) is greater than Vref, the toner

concentration in the development unit judged to be low. When Vt(10) is detected to

be greater than Vref 20 times, then this indicates that the toner concentration is

consistently low, Vref is incremented by 0.1 V, and the conditions are checked

again. The result of this check determines the value of K, the toner supply rate

coefficient, which is one of the factors that is used in the toner supply motor on-

time calculation.

ID Sensor

In addition to comparing Vt(10) from the TD sensor and Vref, after every 10 copies

the ID sensor, located at the lower right area of the drum, checks both the

reflectivity (Vsg) and the pattern on the drum (Vsp), created by the laser diodes

and charge roller. If the reflected light is too strong, this indicates that toner is low

and toner is added to the development unit. (The frequency of these checks can be

adjusted with SP2210; see section 6.8.3. for full details.)

Image Pixel Count Mode

This mode should only be used only as a temporary measure while waiting for

replacement parts, such as a TD sensor. This mode controls the toner supply

amount using the same method for determining the toner bottle motor on time.

However, the values that were in effect when the toner density control mode was

changed over to image pixel count mode with SP2208-01 (Toner Supply Mode)

remain in effect and cannot be changed.

CÓPIA NÃO CONTROLADA

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Ricoh AP4510 Service Manual Page 231

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