Patent Application
20120308281
1. Field of the Invention
The present invention relates to an improved externally heated fuser roller that can achieve fast warm-up time and high print quality.
2. Description of the Related Art
An image forming apparatus, such as an electrographic device, ink printer, copier, fax, all-in-one device or multi-functional device, normally uses a developing agent, such as toner or ink, that is deposited on media to form an image. The developing agent is fixed to the media using an image fixing device by applying heat and pressure. The image fixing device includes a heating device, such as a fuser. The image fixing device also includes a nip through which the media is passed. The nip is formed by the heating device and an opposing pressure roller or a back-up device. A belt or film may also be in close proximity to the heating device to aid the transport of media through the fixing device nip.
Most fusers used in electrographic machines are internally heated. These fusers usually have a metal core, one or more layers of elastomeric on the metal core, and an outside top coat for toner release. Also a heating element is present inside the metal core to supply heat to the fuser. For these kinds of fusers, two fuser parameters conflict each other. A fast thermal response time generally requires the metal core to be relatively thin, with very thin or, if possible, no elastomeric layer. However, the lack of an elastomeric layer conflicts with having acceptable toner release. Good print release ability generally requires a thick layer of elastomeric so that a favorable nip geometry can be formed.
For externally heated fusers, the heat source is outside the fuser and the fuser surface is heated directly. The thickness of the elastomeric layer does not affect the thermal response time as much when compared to the internally heated fuser. Therefore, with externally heated fusers, one can achieve relatively shorter thermal response times and still have good print release ability. However, none of the externally heated fusers are able to warm-up in 30 seconds or less. One of the recent trends is that the fuser has a short warm-up time from room temperature to working temperature, so that the first copy time could be less than 30 seconds or even in the range of 10 to 20 seconds. Mini belt (or film) fusers with ceramic heater designs can achieve this. But this design also has sliding contact between the belt and the ceramic heater and has little or no elastomeric layer on the belt. This limit on the fuser life and print quality can also affect reliability.
Given the foregoing, it would be desirable therefore to provide an improved externally heated fuser roller that can achieve a fast warm-up time and have high print quality.
Embodiments of the present disclosure overcome shortcomings of prior externally heated fusers thereby ensuring a fuser with a fast warm-up time and good fusing performance. According to an exemplary embodiment of the present disclosure, there is provided a fuser member for fusing toner onto a substrate in contact with an external heater for applying heat to the fuser member, the fuser member including a core member comprising a rigid outer surface, a heat insulation layer, a heat transport layer, and optionally a release layer, wherein the external heater is in contact with an outside surface of the fuser member, the heat transport layer having a thickness of about 0.25 to about 1 mm and a total thermal capacity of about 1 to about 200 J/mK, and the heat insulation layer having an effusivity value from about 1 to about 500 W√s/(m2K).
In some embodiments, the heat transport layer has an effusivity value between about 800 and about 5000 W√s/(m2K).
In yet another aspect, an image fixing apparatus for fixing a developed image on a recording medium is disclosed that includes a fuser roller, and a pressure device that contacts the fuser roller and forms a fixing nip portion therebetween, the fuser roller comprising a rigid metal core member, a heat insulation layer, a heat transport layer, and optionally a release layer, wherein the heat transport layer has a thickness ranging from about 0.25 to about 1 mm and a total thermal capacity ranging from about 1 to about 200 J/mK, and the heat insulation layer having an effusivity value of about 1 to about 500 W√s/(m2K).
In yet another aspect, a fuser member and an external heater in combination for fusing toner onto a substrate is disclosed, the fuser member includes a rigid outer surface, a heat insulation layer, a heat transport layer and optionally a release layer, wherein the external heater is in contact with an outside surface of the fuser member, the heat transport layer has a thickness of about 0.25 to about 1 mm and a total thermal capacity of about 1 to about 200 J/mK, and the heat insulation layer has an effusivity value from about 1 to about 500 W√s/(m2K).
The above-mentioned and other features and advantages of the various embodiments of the invention, and the manner of attaining them, will become more apparent and will be better understood by reference to the accompanying drawings, wherein:
It is to be understood that the invention is not limited in its application to the details of construction and the arrangements of components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless limited otherwise, the terms “connected,” “coupled,” and “mounted,” and variations thereof are used broadly and encompass direct and indirect connections, couplings and mountings. In addition, the terms “connected” and “coupled” and variations thereof are not restricted to physical or mechanical connections or couplings.
Reference will now be made in detail to the exemplary embodiment(s) of the present disclosure, as illustrated in the accompanying drawings. Whenever possible, the same reference numerals will be used throughout the drawings to refer to the same or like parts.
Since the normal fusing dwell time, which is the time period needed for any location on a sheet of paper to pass from fuser nip entry to nip exit and thereby be subjected to heat and pressure, is about 20 to about 60 milliseconds, heat can only penetrate a small thickness of the heat transport layer 26. Thus, even though a thicker heat transport layer 26 guarantees good fusing performance, extra thickness of the heat transport layer 26 can adversely affect the warm-up time.
With simulation experiments, the effects of two parameters of the heat transport layer 26 and the heat insulation elastic layer 24 were examined. A range of parameters for fusing performance and warm-up time of the fuser roller were used.
The experiment simulated a fusing process using the structure shown in
To determine the most effective thicknesses of heat transport layer 26, toner and an uncoated 90 g/m2 paper were used in the experiment. The fuser dwell time was 40 milliseconds. The toner temperature at the toner/paper interface was measured. The results are shown in the following tables and their corresponding graphs.
Based on the results in Table 1 and graphed in
After determining the thickness of the heat transport layer 26, the effect of effusivity value of the heat transport layer on the toner and fusing performance was then determined. The effusivity E of the heat transport layer 26 is a parameter that is used for defining the fusing performance. The effusivity E of the heat transport layer 26 was determined based on varying the thermal conductivity k and thermal capacity TC of the heat transport layer 26. To determine an acceptable effusivity value of the heat transport layer 26, the thermal conductivity k and thermal capacity TC=ρ*Cp (in J/m3K) of the heat transport layer 26 were varied independently of each other to show their effects on fusing performance. The other parameters remained the same as those appearing in Table 1. It is desired to find an acceptable range of effusivity of the heat transport layer 26 that provides a temperature of at least 125 degrees C. at the toner-paper interface.
The results in Table 2 and the graph of
The total thermal capacity (TTC) used in the experiment is defined as TTC=ρ*Cp*t*d*π, where ρ is the density, Cp is the specific heat capacity, t is the thickness and d is the diameter of the heat transport layer (HT) 26 in mm. The experimental results shown in Table 3 illustrate that a total thermal capacity TTC of the heat transport layer (HT) 26 that ranges from about 63 to about 96 J/m K gives very good warm-up times, mostly less than 4.6 seconds. Further experimental results yielded that the total thermal capacity of the heat transport layer (HT) 26 may be in the range from about 1 to about 200 J/m K, and more particularly from about 1 to about 120 J/m K.
Table 4 illustrates the results of the effect of the effusivity value of the heat insulation elastic layer (IE) 24 on fuser warm-up time (in seconds) based on the parameter settings. The parameters of the heat transport layer (HT) 24 as also shown in Table 4. The parameters such as thickness, thermal conductivity k, thermal capacity TC of the Heat Insulation Elastic Layer (IE) 26 are detailed below in Table 4.
The results as shown Table 4 indicate that the effusivity E of the heat insulation elastic layer (IE) 24 is at an acceptable value in the range of about 292 to about 358 yield acceptable warm-up times. Further experiment results showed that the effusivity (E) value of the heat insulation layer (IE) should be less than about 400 W√s/(m2K), and particularly in the range of about 100 to about 400 W√s/(m2K), for an acceptable warm-up time of less than about six seconds.
It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit and scope of the invention. Thus it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.
