| 摘要 |
<p>The device for fixing a powder image on a receiving support (7) by means of heat consists of an image transfer roller (8) internally provided with a heating element (9) having the same heat-generating power over the entire length of the image transfer roller (8), and a heating element (10) which has a higher heat-generating power in the edge zones (24,25) of the image transfer roller (8) than in the middle zone (23) of said roller (8), and a pressure roller (11) internally provided with a heating element (12) which like the heating element (10) has a higher heat-generating power in the edge zones (24,25) than in the middle zone (23). The device may be in a warm-up condition in which the temperature of the rollers (8,11) is not yet at the working level, a stand-by condition in which said temperature is at the working level but in which no fixing is carried out, and a fixing condition in which fixing is carried out. During warm-up, all the heating elements generate the maximum power. During stand-by, heating element (9) is switched off and the effective powers of heating elements (10) and (12) are set to a much lower value, so that the ratio between the amount of heat generated in the edge zones (24,25) and the amount of heat generated in the middle zone (23) is greater than during the warm-up. During fixing, the effective powers of the heating elements (9,10,12) are set to a higher value than during stand-by, but the said ratio is then lower than during stand-by.</p> |
