To maintain image quality and machine quality, this machine has a low-temperature PPM mode and a high-temperature PPM mode, and implements 3 levels of PPM down according to the usage situation and machine state.
Low-temperature PPM mode
In a low-temperature environment, the fusing lamp cannot keep up, and it may be difficult to maintain the fusing target temperature. To handle this, the detection temperature of the fusing center thermopile is checked every few seconds, and if the detected temperature is below a threshold value, the PPM is decreased by 1 level.
This low temperature PPM reduction is performed in the following 3 levels:
Mode | Level |
|---|---|
| Normal PPM | 100% |
PPM down 1 | 80% |
PPM down 2 | 65% |
PPM down 3 | 50% |
High-temperature PPM mode
To shorten warm-up time and reduce the TEC value, this machine uses a fusing unit with a low heat capacity.
For this reason, the temperature of those parts of the fusing belt where paper does not pass easily increases, and the areas outside of the paper width may get extremely hot. In order to prevent the belt from breaking due to this excessive temperature rise, PPM down is implemented depending on the usage conditions. PPM down can be implemented in the following 3 levels depending on the temperature detected by the temperature sensor, or the time that paper has continuously passed through the fusing unit.
- The down level % is a value for the case where a typical paper type (normal paper: A4) passes through the SEF at normal speed. There may be some differences depending on paper size/paper thickness.
Mode | Level |
|---|---|
Normal PPM | 100% |
PPM down 1 | 80% |
PPM down 2 | 50% |
PPM down 3 | 30% |
PPM down determination using a temperature sensor
The temperature sensor is checked at given intervals, and if the detected temperature is above a threshold value, the PPM is decreased by 1 level.
Since the points at which temperature tends to increase depend on the paper size, the sensor used is changed depending on the paper size.
Paper width (length) | Check sensor |
|---|---|
A3/DLT/B4 | Pressure roller thermistor (edge) |
LT/A4 | Thermopile (edge) |
B5/A5/B6/A6 | Pressure roller thermistor (center) |
PPM down determination using paper passage time
Depending on the paper size, it may not be possible use a sensor to determine the points on the fusing belt which rise in temperature.
Therefore, time conditions are also used to determine PPM down, and if the time that paper continuously passes through above a threshold value, PPM is decreased by 1 level.
When PPM down is performed as a result of time conditions, PPM does not increase after that.