JP2007030494A - Water-cooling system for thermal head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To cool a thermal head part by a water-cooling system and properly control temperature, thereby dramatically extending the life of a thermal head to enable high-speed stable continuous printing and toner fixing. <P>SOLUTION: (1) A water pillow for cooling is arranged on a thermal head. Cooling water is circulated through a water tank, a circulating pump, the water pillow, and a radiator in this order. A fan is attached to a radiator to improve the heat dissipation effect. (2) The cooling water is not supplied to the water pillow on the thermal head at first but is supplied at a temperature above a set temperature. (3) Further, pump discharge and rotational frequency of the fan of the radiator are changed according to a temperature variation of the thermal head to properly perform heating control of the thermal head. (4) In the case of using the thermal head in which resistance of a minute heating element varies when temperature varies due to heating, arrangement of a special temperature sensor becomes unnecessary. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to a technique for a system using a thermal head in a laser printer, a copying machine, a FAX apparatus, or the like.

Technical background

In a laser printer, a copying machine, a FAX apparatus, etc., it is an inevitable problem to continuously print paper at a high speed.

More particularly, the present invention relates to a method for preventing the thermal head from overheating due to a heat storage action and realizing appropriate temperature control when printing is performed continuously at high speed or toner is fixed using the thermal head.
Japanese Patent Application No. 2003-436619 “Toner Fixing Method” Japanese Patent Application No. 2004-118389 “Toner Fixing Method”

When printing and toner fixing are continuously performed using a thermal head, heat generation energy gradually begins to remain in the thermal head, resulting in a situation where the head temperature rises and is exposed to a very high temperature. This affects the characteristic life of the thermal head itself, and cannot be ignored as the speed is increased, and high-speed and stable printing and toner fixing are limited.

In order to cool and remove the residual energy generated in the thermal head, a cooling water pillow is placed on the thermal head to circulate the cooling water in the order of water tank, circulation pump, water pillow, and radiator. If necessary, a fan is attached to the radiator. To enhance the heat dissipation effect.

In addition, the temperature of the thermal head is measured, and the pump discharge amount and the rotation speed of the radiator fan are changed according to the temperature change of the thermal head, and appropriate temperature control of the thermal head is performed.

Further, in order not to inhibit the temperature rise at the start of heating of the thermal head, initially, the cooling water is not supplied to the cooling water pillow on the thermal head, and the supply of the cooling water is started at a set temperature or higher.

In addition, if a thermal head that changes the resistance value of the micro heating element when the temperature of the micro heating element changes due to heat generation, an accurate temperature change can be obtained at high speed without a special temperature sensor. Temperature control can be realized.

By cooling the thermal head portion by a water cooling method and performing appropriate temperature control, there is an effect that the thermal head life is drastically increased, and high-speed and stable continuous printing and toner fixing are possible.

At the start of printing and toner fixing, the thermal head needs to quickly rise in temperature to a predetermined temperature in an appropriate time. However, if there is cooling water in the cooling water pillow on the thermal head, it quickly hinders temperature rise. For this reason, the discharge amount control of the cooling water pump and the air flow control of the radiator fan are controlled according to the temperature of the thermal head, and the cooling water pillow on the thermal head is provided with a taper so that the cooling water flows out properly in the direction of gravity. A mechanism that can quickly increase the temperature at the start of heating is adopted.

Further, by using a thermal head in which the resistance value of the minute heating element changes with temperature, an accurate temperature change can be obtained at high speed, and more appropriate temperature control can be realized.

The thermal head water cooling system according to the present invention can be easily used for various devices incorporating a thermal head such as a copying machine and a FAX. Here, an embodiment applied to a toner fixing unit of a laser printer will be described.

FIG. 1 is an overall configuration diagram of a thermal head water cooling system.
The cooling water in the 110 cooling water tank installed in the 130 housing is supplied to the 112 pump through the 111 water channel, and the cooling water discharged from the 112 pump is sent to the 105 cooling water pillow through the 113 water channel. At this time

As described in the above, the cooling water pillow 105 has a tapered shape on the outlet side, so that water drains well, and the cooling water does not enter the inside at the start of printing, so that the temperature rise is not hindered. Yes.
The cooling water discharged from the 105 cooling water pillow is sent to the 115 radiator through the 114 water passage, dissipates the heat generated by the 103 thermal head, and is returned to the 110 cooling water tank through the 116 water passage.

Also

As described above, by using a thermal head in which the resistance value of the minute heating element varies depending on the temperature, the head temperature can be known from time to time with the 103 thermal head. The rotation speed of the radiator fan can be changed appropriately. In addition, when the temperature falls below a preset temperature, the operation of the 112 pump and 120 radiator fan is stopped, the inside of the 105 cooling water pillow is made into a state without cooling water, and the 103 thermal head easily rises to an appropriate temperature. ing.

At this time, the 112 pump is desirably self-contained because the cooling water is not fed into the 105 cooling water pillow, so that it is inevitable that air enters the cooling water circulation path. In order to allow repeated use of the built-in cooling water, it is desirable to use purified water with no impurities and antifreeze with propylene glycol added as an additive. However, the use of other liquids with cooling effects would depart from the spirit of this patent. do not do. Furthermore, the use of other types of pumps for 112 pumps does not depart from the spirit of this patent.

This patent also has a structure in which the temperature change of the thermal head is detected by a temperature sensor such as a thermocouple to stop and start the 112 pump and 120 radiator fan, and change the discharge amount of the 112 pump and the rotation speed of the 120 radiator fan. It does not deviate from the purpose.

Further, when there is a sufficient cooling effect, it does not depart from the gist of this patent even if a 120 radiator fan is not installed.

FIG. 2 is an explanatory diagram of the toner fixing unit.
When 101 paper to which unfixed toner powder adheres passes through the 103 thermal head section and 104 platen roller through the 102 heat resistant film belt for preventing the toner powder from diffusing, it remains on the 103 thermal head. The thermal energy to be cooled can be removed by circulating the cooling water through the 105 cooling water pillow.

3, 4 and 5 are detailed views showing the structure of the 105 cooling water pillow.
The cooling water pillow cooling unit 105a, the cooling water cover for cooling water 105b, the nozzle for 105c inlet and the nozzle for 105d outlet are composed of four parts, and the thermal energy remaining in contact with the 103 thermal head part is removed.
The water pillow cooling unit 105a is made of a metal having a high thermal conductivity or a non-ferrous metal, and cools by contacting the cooling water. The 105a cooling water pillow cooling section has a structure with a good drainage that tapers from the 105c inlet nozzle to the 105d outlet nozzle, so that the cooling water does not enter the 105 cooling water pillow at the start of toner fixing. The cooling water cover for cooling water 105b is a material having a heat insulation effect, and does not hinder an appropriate temperature rise of the 103 thermal head due to excessive heat dissipation at the start of toner fixing.

High-speed continuous printing is an inevitable problem in laser printers, copiers, and fax machines that use thermal heads. It is necessary to fix the unfixed toner transferred to the paper at a high speed and stably at a high speed.
If the residual heat energy generated by continuous printing or toner fixing is not efficiently dissipated, the head life may be significantly reduced. In order to solve this problem, the thermal head part is cooled by a water cooling method, so that the life of the thermal head is drastically increased, and it is possible to perform printing and toner fixing stably at high speed continuously. .
Although the present invention has been described with respect to a toner fixing system, it can be used in various devices where the lifetime due to residual thermal energy using a thermal head is a problem.

Overall configuration of the cooling device when applied to the toner fixing part of a laser printer Toner fixing unit explanatory diagram when applied to the toner fixing unit of a laser printer Side view of cooling water pillow Horizontal cross section of cooling water pillow Vertical section of cooling water pillow

Explanation of symbols

101 Paper 102 Heat-resistant film belt 103 Thermal head 104 Platen roller 105 Cooling water pillow 105a Cooling water pillow cooling unit 105b Cooling water pillow cooling water cover 105c Inlet nozzle 105d Outlet nozzle 110 Cooling water tank 111 Water channel 112 Pump 113 Water channel 114 Water channel 115 Radiator 116 water channel 120 radiator fan 130 housing

Claims (5)

In a system in which thermal energy generated by a thermal head is used to print or transfer toner powder transferred onto a sheet, the cooling water pillow is placed on the thermal head in order to appropriately control the heating of the thermal head. A thermal head water cooling system in which the cooling water is circulated in the order of water tank, circulation pump, water pillow, and radiator, and a fan is attached to the radiator if necessary. In a system that uses thermal energy generated by a thermal head to print or transfer toner powder that has been transferred and melted, a thermal that changes the pump discharge amount and the rotational speed of the radiator fan by changing the temperature of the thermal head Head water cooling system In a system in which thermal energy generated by a thermal head is used to print or transfer toner powder that has been transferred and melted and fixed, in order not to inhibit the temperature rise at the start of heating of the thermal head, the thermal head is initially Thermal head water cooling system that starts supplying cooling water when the temperature rises above the set value without supplying cooling water to the cooling water pillow above In a system in which thermal energy generated by a thermal head is used to print or transfer toner powder transferred onto a sheet, the resistance value of the minute heating element changes when the temperature of the minute heating element changes due to heat generation. Thermal head water cooling system that realizes appropriate temperature control by using a thermal head, without adding a special temperature sensor due to a change in resistance value of the minute heating element corresponding to the temperature of the thermal head In a system in which thermal energy generated by a thermal head is used to print or transfer toner powder transferred onto a sheet, the resistance value of the minute heating element changes when the temperature of the minute heating element changes due to heat generation. Thermal head water cooling system that uses a thermal head to change the pump discharge amount and the number of revolutions of the radiator fan without adding a special temperature sensor due to the change in resistance of the minute heating element corresponding to the temperature of the thermal head

Images