Patent Grant
8515323
1. Field of the Invention
The present invention relates to a fixing apparatus and an image forming apparatus including a heat fixing member and a pressure applying member pressure contacting the fixing member.
In particular, the present invention relates to a fixing apparatus and image forming apparatus capable of fixing a toner image to a recording member while directing and conveying the recording member to and through a nip formed between the fixing member and pressure applying member in such a manner that the toner image contacts the fixing member.
2. Discussion of the Background
It has been well known that a fixing apparatus of the above-described type is adopted in an image forming apparatus, such as a copier, a printer, a facsimile, a combined machine having at least one of them, and etc. In such a type of the fixing apparatus, since the toner fuses when passing the nip formed between the fixing and pressure applying members, the toner likely functions as adhesive agent and the recording member ejected from the nip is not separated and wraps around the surface of the fixing member. In particular, in an image forming apparatus farming a full-color image, since different color toner images are superimposed on a recording member and fixed by a fixing apparatus, a supply of toner necessarily fuses in the nip, and thus adhesive force of the toner increases. As a result, the recording member more readily wraps around the fixing member.
Then, in the past, a separation member including a plurality of separation claws is configured to contact a surface of a fixing member and separate a recording member ejected from a nip from the surface of the fixing member in order for the recording member not to wrap around the surface of the fixing member. However, since the separation claw contacts the surface of the fixing member via its tip, the surface likely is cut (e.g, damaged). As a result, a mark appears on a toner image after passing through the nip in accordance with the cut, and resulting in inferior toner image quality as a result of fixing.
To remove such a disadvantage, a fixing apparatus is proposed to arrange a separation claw separating from a surface of the fixing member. However, a recording member ejected from the nip likely enters into a gap formed between the fixing member and separation claw while sticking the surface of the fixing member. As a result, a separation function of the recording member is weakened and the wrapping likelihood of the recording member around the fixing member increases.
In addition, there exists a case when a fixed toner image is formed on a backside surface of the recording member carrying a toner image on the other side to be fixed. In such a situation, since the toner image on the backside surface is fused by heat while passing through the nip, the recording member likely wraps around the surface of the pressure applying member. To avoid such a problem, a separation claw preferably contacts the surface of the pressure applying member. However, a similar problem arises as described in the above.
The present invention has been made in view of such problems and to address and resolve such problems. Accordingly, it is an object of the present invention to provide a novel fixing apparatus including a fixing member and a pressure applying member configured to pressure contact the fixing member. The fixing apparatus directs and conveys a recording member through a nip formed between the fixing member and pressure applying member so that a toner image carried on the recording member can contact the fixing member to be fixed thereto with heat and pressure. The fixing apparatus is configured to direct a margin formed in a transfer direction tip of the recording member across a virtual linear extension line drawn from a downstream end to an upstream end both in the nip toward the pressure applying member, when only the margin exits from the nip. A fixing member side separation device is provided so as to separate the recording member ejected from the nip not contacting the surface of the fixing apparatus. In addition, a gap between the downstream end of the nip and the tip of the fixing member side separation device is set smaller than the width of the margin of the downstream end.
In yet another embodiment, a JIS-A hardness of the surface of the pressure applying member of the nip at the downstream end may be larger than that of the downstream end of the fixing member.
In another embodiment, a pressure applying member side separation device is provided with its tip contacting the surface of the pressure applying member.
In yet another embodiment, a JIS-A hardness of the surface of the fixing member in the nip in the downstream end is substantially the same as that of the downstream end of the surface of the pressure applying member.
In yet another embodiment, a JIS-A hardness of the surface of the fixing member of the nip in the downstream end is higher than that of the downstream end of the pressure applying member.
In yet another embodiment, a fixing member side separation device is provided with its tip contacting the surface of the fixing member.
In yet another embodiment, gap maintaining members are provided on respective tips of the fixing member side separation devices disposed in a direction perpendicular to the transfer direction so as to contact the surface of a non-transfer member passage area of the fixing member so that a gap formed between the tip of the fixing member side separation device and the surface of the fixing member is maintained.
In yet another embodiment, gap maintaining members are also provided on respective tips of the pressure applying member side separation devices so as to contact the surface of a non-transfer member passage area of the pressure applying member so that a gap formed between the tip of the pressure applying member side separation device and the surface of the pressure applying member is maintained.
In yet another embodiment, the fixing member side separation device is a single separation member type.
In yet another embodiment, the pressure applying member side separation device is a single separation member type.
In yet another embodiment, the fixing member side separation device includes an opening for ventilation.
In yet another embodiment, the pressure applying member side separation device includes an opening for ventilation.
In yet another embodiment, the fixing member side separation device is formed from a sheet like separation member, and is biased by a tension applying member in a direction perpendicular to the transfer direction.
In yet another embodiment, the pressure applying member side separation device is formed from a sheet like separation member, and is biased by a tension applying member in a direction perpendicular to the transfer direction.
In yet another embodiment, the toner includes, at least, plastic, colorant, and wax.
A more complete appreciation of the present invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by the following detailed description when considered in connection with the accompanying drawings, wherein:
Referring now to the drawings, wherein like reference numerals and marks designate identical or corresponding parts throughout several views, in particular, in
The sheet-feeding device 3 may include a cassette 11 containing recording members P such as transfer sheets, plastic sheets, etc. The recording members P may be fed from the cassette 11 from the upper most one by rotation of a feeding roller 12. The recording member may then be fed to a transfer station formed between the PC member 5 and transfer apparatus 9. Then, the toner image on the PC member 5 may be transferred onto recording member as described above. Thus, the recording member carrying the toner image in such a manner may then be transferred through the fixing apparatus 4 as illustrated by an arrow “A”, and passes therethrough. At that time, the toner image on the recording member may be fixed. The recording-member passing through the fixing apparatus 4 may then be ejected on a tray 14 outside the image forming apparatus.
The nip N formed between these rollers 15 and 16 may be controlled by a heating device to maintain an appropriate temperature for fixing a toner image. In the example, halogen heaters 17 and 18 may be disposed inside the fixing and pressure rollers 15 and 16 as heat sources, respectively. These heaters 17 and 18 may be controlled by a temperature control device (not shown) to turn ON/OFF in order to maintain the appropriate temperature.
The recording member “P” carrying a not yet fused toner image “T” may be conveyed to the fixing apparatus 4 in a direction illustrated by an arrow “A”. The recording member “P” may pass through the nip “N” while directing the toner image “T” to the surface of the fixing roller 15.
Thereby, the toner image “T” on the recording member “P” may be fixed thereonto by the heat and pressure.
A basic configuration employed in the below described various examples will be substantially the same to that described above. Instead of using the above-described configuration of rollers 15 and 16 of
Now, when a toner image “T” carried on the recording member “P” passes through the nip “N” of the fixing apparatus 4 illustrated in
A toner image may be formed on an image region, slashed and having a note “IA”, of the recording member as illustrated in
A JIS-A (Japanese Industrial Standard-A) hardness of the surface of the pressure roller 16 may be set higher than that of the surface of the fixing roller 15, and is preferably twenty to forty times thereof. In such a manner, by setting a surface hardness of these rollers 15 and 16, the pressure roller 16 may break into and deform the surface of the fixing roller 15 side the surface by pressure as illustrated in
Accordingly, as illustrated in
When the recording member P is further transferred in
However, since the fixing member side separation device 19 is disposed in the vicinity of the fixing roller 15 the recording member P may collide and is then guided by the fixing member side separation device 19 as illustrated in
Thus, since the recording member P ejected from the nip N is prevented from wrapping around the surface of the fixing roller 15, and the fixing member side separation device 19 does not contact the surface of the fixing roller 15, a problem that the surface of the fixing roller 15, which has a low hardness and is easily damaged by the fixing member side separation device 19, may be blocked.
The image forming apparatus of
Now, a specific construction of the fixing apparatus 4 is described with reference to
Respective surface hardness of the fixing roller 15 and pressure roller 16 may be set to 45 and 80 degrees by the Japanese Industrial Standard “JIS-A”. In such a manner, since the pressure roller 16 is harder, the fixing roller 15 may be elastically deformed while the pressure roller 16 breaks into the surface of the fixing roller 15. Simultaneously, a nip “N” may be formed along an outer shape of the pressure roller 16.
In the fixing apparatus 4 of
By recognizing the importance of the above-described functions of both guide rollers 15B and 15C, one side guide roller 15B will be termed by an opposing roller, and another guide roller 15C will be termed by a tension roller when required in the below described description.
Further, in the respective tension roller 15C and pressure roller 16 of the fixing apparatus of
Also in this example, a recording member P carrying a toner image “T” to be fixed may pass through the nip “N” while the toner image “T” contacts the surface of the fixing belt 15A as shown by an arrow A.
Thus, the toner image “T” may be fixed onto the recording member P by the heat and pressure.
Also, the JIS-A surface hardness of the pressure roller 16 in the fixing apparatus 4 of
Thus, the wrapping of the recording member P around the fixing member composed of the fixing belt 15A as well as damaging on the fixing belt 15A by the fixing member side separation device 19 can be absolutely or substantially avoided substantially in the same manner as in the fixing apparatuses of
Now, a specific configuration of the fixing apparatus 4 is now described with reference to
Further, since the fixing roller 15 of the fixing apparatus of
Another fixing apparatuses are now described with reference to
Various differences of the fixing apparatuses of
As illustrated in
Also in the fixing apparatus of
Still another fixing apparatus 4 may be described with reference to
The difference between these fixing apparatuses of
When only the margin M1 of the tip of the recording member P exits from the nip N in the fixing apparatus of
Further, the image forming apparatus 1 is configured to form a toner image only on one side surface of the recording member P. However, an image forming apparatus capable of performing the below described functions is widely known. Specifically, the image forming apparatus is capable of transferring a toner image formed on a PC member onto one side surface of the recording member, fixing the toner image with a fixing apparatus, inverting upside down arid transferring the recording member again to the PC member, transferring a toner image formed on the PC member onto the other surface of the recording member, and fixing the toner image with the fixing apparatus. When toner images respectively formed on the one and other sides of the recording member require to be distinguished, the former may be termed as a first toner image, and the latter may be termed as a second toner image.
When the second toner image is transferred through the nip and is fixed, the first toner image fixed to the one side surface of the recording member may also pass and contact the pressure applying member. At that time, since the pressure applying member is also heated, the heat fuses the first toner image. As a result, the recording member ejected from the nip may likely wrap around the pressure applying member.
Then, a pressure applying member side separation device 22 for separating a recording member P ejected from the nip N from a pressure applying member (a pressure roller 16 in this example) may be employed in a fixing apparatus 4 of
As illustrated in
Since the tip of the pressure applying member side separating device 22 contacts the surface of the pressure applying member composed of the pressure roller 16, the recording member attempting to wrap around the surface of the pressure roller 16 may surely be separated therefrom. At that time, as described earlier, since the surface hardness of the pressure roller 16 is higher than that of the fixing roller 15, and accordingly, the surface of the pressure roller 16 is hardly damaged, the surface of the pressure roller 16 can be prevented from being damaged by the pressure applying member side separating device 22.
Further, as illustrated in
When the recording member P entering the nip N carries the first toner image TA already fixed on to one side surface and the second toner image T to be fixed by the fixing apparatus 4 on the other side surface, and passes through the nip N, the first toner image TA fuses. However, similar to the fixing member side separation device 19, the pressure applying member side separation device 19A may prevent the recording member from wrapping around the surface of the pressure roller 16. Further, since the pressure applying member side separation device 19A is distanced from the surface of the pressure roller 16, a problem of damaging the surface may be blocked.
Further, as illustrated in
At that time, the toner of the first toner image TA is heated and fused. However, to prevent the recording member P from wrapping around the surface of the pressure roller 16 due to melting toner of the first toner image, the pressure applying member side separation device 19A may be arranged so as to separate the recording member exiting from the nip N from the surface of the pressure applying member formed from the pressure roller 16 separated from the surface of the pressure applying member. A condition may be illustrated in
As illustrated in
When the image region IA of the recording member P (see
In addition, the fixing member side separation device 22A made of such as a sheet like separation member contact the surface of the fixing roller 15. Thus, even though the recording member P ejected from the nip N adheres to the surface of the fixing roller 15, the recording member P may immediately be separated from the surface of the fixing roller 15 by the fixing member side separation device 22A, and does not wrap around the surface of the fixing roller 15. Even if the fixing member side separation device 22A contact the surface of the fixing roller 15, the damage on the surface may be prevented, because the surface of the fixing roller 15 is harder. Thus, by contacting the fixing member side separation device 22A to the surface of the fixing roller 15, wrapping of the recording member P around the fixing roller 15 may credibly be blocked. The recording member P exiting from the nip N may be guided and is transferred by the pressure applying member side separation device 19A and guide member 21A arrange above the pressure applying member side separation device 19A. As described above, wrapping of the recording member P around both the fixing and pressure rollers 15 and 16, and damage on both of the surfaces of the fixing and pressure rollers 15 and 16 can be blocked. As a result, quality of the first and second toner images of the recording member P passing through the nip N may avoid from being decreased.
One example of a specific configuration of the fixing apparatus 4 may now be described with reference to
Briefly, a fixing member heated by the heaters 17A and 17B may be formed from a fixing belt 15A wound and rotated around a guide member formed from an opposing roller 15B and a tension roller 15C in this example, in a direction shown by an arrow B. A pressure applying member pressure contacting the fixing member may be formed from a pressure roller 16 contacting at least one guide members, i.e., the opposing roller 15B in this example, via the fixing belt 15A, and rotating in a direction shown by an arrow. The JIS-A surface hardness of the pressure roller 16 may be set lower than that on a portion of the fixing belt contacting the opposing roller 15B.
The recording member P carrying a second toner image T to be fixed may pass through a nip N formed by pressure contact of the fixing belt 15A and pressure roller 16 with the second toner image T being directed to contact the fixing belt 15A. When only a margin M1 formed in the transfer direction tip of the transferred recording member P exits from the nip N, the tip margin M1 may be directed to the fixing member (i.e., the fixing belt 15A) side across an extension line LCC extended from the straight line LC drawn from the downstream end NE to the upstream end NS of the nip N in the transfer direction.
As shown by an arrow A, the first toner image TA having already been fixed may be formed on the one side surface of the recording member P entering into the nip N. In addition, the pressure applying member (i.e., the pressure roller 16) side separation device 19A may be arranged separately from the surface of the pressure applying member so as to separate the recording member P ejected from the nip N. Further, a gap GA formed between a downstream end NE of the nip N and a tip of the pressure applying member side separation device 19A, which faces the pressure applying member, may be set smaller in size than the width “W” of the margin M1 formed in the tip of the recording member P in the transfer direction A. Owing to this configuration and similar to the fixing apparatus of
Also in the cases of the fixing apparatuses of
The position of the surface of the fixing roller 15 is not constant because of receiving influence of heat expansion and eccentricity of the roller. However, when the fixing member side separation device 19 is positioned in the above-described manner, the gap G can be maintained substantially constant along the entire longitudinal direction of the fixing member side separation device 19. In addition to that, the gap holding members 29 contact the recording sheet non-passing areas PA, the gap holding members 29 may almost never damage the recording member passing area PB. In addition, influence from the gap holding member 29 contacting the fixing roller 15 may be avoided.
Similar to those described above, when the fixing members of
By employing the gap holding member in respective ends of the fixing member side separation device in the direction perpendicular to the recording member transfer direction, while enabling the respective gap holding members to contact the recording member non-passing areas, and holding the interval between the tip of the fixing member side separation device and surface of the fixing belt 15A in the above-described manner, the tip of the fixing member side separation device can readily be approximated and correctly positioned regarding the fixing member. Also, in order to position the pressure applying member side separation device 19A when approximating the surface of the pressure roller 16, the configuration illustrated in
As illustrated in the drawing, both the fixing member side separation device 19 and the pressure applying member side separation device 19A are made from sheet like separation members 20 and 20A, and in particular, if those thickness are thin, waving due to heat expansion of these separation members, and deformation due to contacting of the recording member to the separation members 20 and 20A may arise. As a result, a gap between each of the separation members 20 and 20A and fixing member or pressure applying member may likely be uneven in a longitudinal direction of the separation member. Then, if both the fixing member side separation device 19 and the pressure applying member side separation device 19A are made from sheet like separation members 20 and 20A, a tension applying device for pulling the separation members 20 and 20A in a direction perpendicular to a recording member transfer direction may preferably be employed. Then, the above-described problem may be blocked.
The separation member 20 may be secured to the gap holding member 29 via respective ends in the longitudinal direction, and the both of the gap holding members 29 are supported by the supporting members 31 via screws 30. However, the separation member 210 may be maintained flat by screwing the screws 30, and pulling the separation member 20 in a direction shown by an arrow, and applying a tension thereto. Thereby, a gap between the separation member 20 and fixing roller 15 can be maintained constant. In such a manner, the screws 30 may constitute an exemplary tension-applying device for pulling the separation member. A tension-applying device for pulling the separation member 20A of the pressure applying member side separation device 19A may similarly be configured.
For the sheet like separation members 20 and 20A, a thin plate of heat resistance plastic or metal may be employed. For example, fluorine plastic, and polyimide having a thickness of 0.1 mm may be employed. In addition, if a metal sheet or metal plate member having a thickness of 0.2 mm is employed for the sheet like separation members 20 and 20A, since rigidity is enhanced, a gap between the separation member and fixing member or pressure applying member can be maintained constant without employing the above-described tension applying device.
Further, in order to credibly avoid wrapping of the recording member around either the fixing or pressure applying member in the above-described respective fixing apparatuses, release agent such as silicone oil can be coated on each of these apparatuses. However, when employing such a configuration, the oil adheres and soils the recording member, and maintenance may be complex due to oil coating. In addition, a coating member for coating oil may be necessitated, thereby resulting in cost increase for the fixing apparatus.
Then, if wax including toner is used so as to form a toner image with plastic and coloring agent, so called oil less image formation may be realized without coating release agent. As a result, the above-described problem can be removed.
The above-described respective configurations may be widely applied to fixing apparatuses other than those described above. Even though the guide roller formed from a roller 15B and tension roller 15C are employed for a guide member for winding the fixing belt 15a in the fixing apparatus of
In addition, a pressure belt wound and driven by a plurality of guide members as described earlier can configure the pressure applying member. In such a case, when the pressure belt portion wound around the guide member contacts and forms a nip with the fixing member, the JIS-A surface hardness of the pressure belt may be obtained by measuring a surface of the pressure belt portion contacting and wound around the guide member.
Another embodiment is now described with reference to
As illustrated in
The fixing roller 25 may have a diameter of 60φ, for example. Also included may be a ring like elastic layer 252 molded and processed for obtaining a nip width “LO” around the outer surface of a Fe core metal 251. Such a ring like elastic layer 252 may be made of heat resistance elastic member such as liquid type foam silicone rubber. The ring like elastic layer 252 may include a release agent ring state layer 253 so as to wrap and integrally is coated on the outer surface of the ring like elastic layer 252. Such a release agent ring state layer 253 may be formed from heat resistance plastic having prescribed intensity in conjunction with releasability. A halogen type heater 254 may be arranged inside the metal core of the fixing roller 25 so as to accelerate increasing in temperature of the fixing roller.
As illustrated in
The surface hardness of the fixing roller 25 may be around 30 to 50 Hs (Asker: measurement in conformity to Japanese Rubber Association Standard). The pressure roller 26 may include a heat resistance elastic layer 262 such as silicone rubber, and a surface release layer 263 forming an endless pressure surface Fc made of fluorine plastic on the outer surface of an Al or Fe core metal 261. In this example, the surface hardness of the pressure roller 26 may be higher than that of the surface of the fixing roller 25, and accordingly, a fixing use nip having a width LO is formed with its both ends being concave downward in a contact portion of the fixing belt and pressure roller to improve separation performance of the recording sheet having the toner. In the embodiment, a thickness of the elastic layer 262 may amount to about 0.5 mm to 2 mm, and the surface hardness may be 70 to 90 Hs (Asker C type). A halogen heater 624 may be arranged in the pressure roller 126 so as to accelerate increasing in temperature thereof. As illustrated in
A journal 261′ integral with an end of the core metal of the pressure roller 126 may be movably attached to the fixing apparatus use base frame 129 so as to move up and down in order for the pressure applying roller 126 to separate from the fixing roller 125. Specifically, the journal 261′ may be supported by a lever 134 via a pivot section 265 pivotally supporting the journal 261′. A key axis of the lever 134 may pivotally be connected to the fixing apparatus use base frame 129 and a swinging end thereof is pivotally engaged with a tension spring 35 whose one end is engaged with the fixing apparatus use base frame 29.
Thus, the lever 134 may elastically receive upward tension force. Thus, the tension spring 135 may enable the pressure roller 26 to pressure contact the fixing roller 25. The fixing apparatus 110 may include a rotational driving unit (not shown) that transmits rotational driving force to the pressure roller 126. Such rotational driving force can be transmitted to the fixing roller 125. As illustrated in
The pair of guide member 130 may symmetrically be shaped. Each of the pair of guide members 130 may be formed from a bearing section 301 pivotally supporting the journal 251′, and an attaching wall 302 disposed at its one side and secured to the fixing apparatus use base frame 129 via the bracket 136, and a sheet reception section 303 extending from the other end of the bearing section 301. Since the pair of left and right guide members 30 is secured to the fixing apparatus use base frame 129 via the bracket 136, it may not rotate even if the fixing roller 125 rotates. The sheet reception section 303 may be a thick plate like and form a concave sheet groove 301 while maintaining a gap “j” with the other surface f1 of the bearing section 304 at an upper opening.
As illustrated in
The separation sheet may include a straight portion 282 and a concave portion 283 having a curvature almost along the outer diameter shape of the release layer. The separation sheet may maintain a prescribed gap “d” at its tip with a releasing layer in the vicinity thereof. Also include may be a tip 281 of a tip of the concave section 283. The tip 281 may be distanced from the nip exit end of the fixing roller by a prescribed length L1. Further, typically, a distance from a tip of a recording paper S to that of an image may be called as a tip blank width as described earlier. However, when the paper exits from the nip exit “g”, the recording sheet “S” may indeed not wrap around the fixing roller 25 unless the tip blank width exits from the nip.
However, a mechanism likely withdrawing and wrapping the recording sheet “S” around the fixing roller 125 due to adhesive force caused by the fixing roller 125 just when the image tip exits from the exit “g” may be employed. To avoid wrapping of the recording sheet “S”, if the distance “L1” from the tip of the separation sheet 128 and that of the nip exit “g” (i.e., a distance from the end of the nip exit “g”) is smaller than the tip blank width, the recording sheet S may not wrap around the fixing roller 125 and relatively readily be separated by the separation sheet 128. Then, the recording sheet may be transferred and ejected onto an ejection tray by the ejection rollers 138 and 139. Since the tip blank width in the fixing apparatus 110 of
The separation sheet 128 may generally have substantially the same thickness at its tip 281 to the other. However, as illustrated in
Further, a surface roughness of the edge section “e” may be less than 0.2 μm (Ra). Thus, the recording member separation performance may credibly be maintained, and durability of the fixing roller 25 may be improved. In addition, thin film coating can be performed with such as fluorine plastic on the surface of the separation sheet 128, so that damaging on the fixing roller 125 can be lowered even if the separation sheet 128 contacts the fixing roller 125, in particular, in the release layer 253. In addition, the separation sheet 128 and releasing layer 253 of the fixing roller 125 of
However, adjusting the gap to less than 50 μm may practically be difficult due to a straightness of the tip portion of the separation sheet 128, and vibration of the fixing roller when rotated. If the gap “d” is narrowed, the fixing roller 125 may dispose heat and lower its surface temperature as another problem when the fixing roller 125 contacts or is in the vicinity of the separation sheet 128. According to the present embodiment, a pair of left and right guide members 130 of
The toner image “t” on a recording sheet S having reached the fixing apparatus 110 may be heated by the fixing roller 125 up to a level where its viscosity is lowered, and then penetrates into a texture of the recording sheet by an operation of the pressure force of the pressure roller 115. The toner may then be firmly fixed to the sheet texture when cooled and consolidated. However, if temperature of a toner layer is less than its softening temperature Ts when separated from the fixing roller 125, the toner plastic may not sufficiently be softened, and accordingly, not penetrate into the texture of the sheet S, thereby resulting in insufficient fixing intensity.
In contrast, if the temperature of a toner layer is less than its flowage starting temperature Tf when separated from the fixing roller 25, the toner plastic viscosity may be too low, and accordingly, releasability of the toner from the release layer 253 of the fixing roller 25 may be insufficient even though sufficiently penetrating into the texture of the recording sheet S. In addition, a problem such as offset or wrapping may arise on the fixing roller 25. Accordingly, a control temperature for fixing maybe determined so that a toner layer surface temperature after fixing will fall within a range from Ts to Tf.
Preferably, a control system may be used if its temperature deviation is small at around the its center area.
Even if fixing from thin to thick sheets by substantially the same temperature, since heat capacity of the sheet is different from the other, the higher the toner layer surface temperature after fixing is, the thinner the sheet is, vice versa. As a result, even the offset phenomenon does not arise when the thin sheet passes, an adhesive force between surfaces of the respective fixing and pressure rollers may be large. In addition, separation after passage of the recording sheet through the nip may be difficult, and in the extreme case, the tip may wrap around the curvature of the fixing roller 25 and is carried. Depending upon the largeness of the adhesive power, when the tip is slightly peeled off, the recording sheet may be withdrawn by its gravity. However, a certain portion may not be peeled off and wraps therearound. Such adhesive power has been known to vary in accordance with changes in environment, toner adhering amount, and temperature of a fixing roller 125 or the like. Among these, a wrapping phenomenon of a thin sheet likely wrapping around a fixing roller is now described.
After the recording sheet S is sand witched into the nip between the fixing and pressure rollers 125 and 115, the toner image may be fixed onto the recording sheet S while receiving operations of heat and pressure. A nip shape formed by the fixing and pressure rollers 25 and 15 pressure contacting each other may be determined from a relation between thickness and hardness of rubber layers of the respective fixing roller 125 and pressure roller 126.
As one example of embodiments, the fixing roller 125 may have a diameter of 60φ and a thickness of 2 mm for a Si rubber, and 20 degree by the JIS-A hardness standard for a rubber layer. The pressure roller 126 may also have a diameter of 60φ and a thickness of 2 mm for a Si rubber, and 30 degree by the JIS-A hardness standard for a rubber layer. In addition, the PFA tubes each having a thickness of 50 μm may be employed on the respective uppermost layers. In such a combination of rollers, if tack strength caused between the surfaces of the respective toner layer and fixing roller is negligible, the recording sheet S at the exit may slightly be directed downwardly from the horizontal line. When considering stable transfer performance, a discharge angle of the recording sheet S may preferably be directed slightly downwardly. However, if it is directed excessively downwardly, the first surface side of a duplex fixing image likely wraps around the pressure roller 126. Thus, sufficient attention should be paid when both the fixing and pressure rollers are designed.
The fixing apparatus 110a employed in the color copier 101a may now be described. The fixing apparatus 110a may be employed in the conventional color image forming apparatus 1a not coating silicone oil as release agent for the fixing belt 140 and instead using oil less toner. However, it may be applicable to a color printer, facsimile, and duplicator or the like, so that these apparatuses can improve marketable product performance as image forming apparatuses capable of credibly securing recording member separation performance if employing the fixing apparatus 110a.
As illustrated in
A base material of the fixing belt 40 may be made of heat resistance plastic. For the heat resistance plastic, polyimede, polyamideimide, and polyetherketone (PEEK) may be employable. A thickness of the base material may preferably amount to about 30 to about 100 μm. Since the surface of the fixing belt 133 pressure contacts the non fixed toner image and recording sheet S, a surface layer having excellent releasability and heat resistance may be necessitated. Thus, a surface release layer 401 such as fluorine series plastic or the like (see
The heating roller 142 may be made of metal, such as AL, Fe, etc., having a diameter of from about 20φ to 30φ. The heating roller 142 may be a thin roller having a thickness (t) of from about 0.3 to 1.0 mm and include a halogen heater 147 inside thereof. Temperature of the heating roller 132 may be detected by a temperature control element 146. Detected temperature information may be output to an image processing section 148 so as to control the heating roller to fall within a prescribed set temperature range. Thereby, it may function to heat the fixing belt 140 up to a desirable temperature.
Further, the heating roller 142 may double as a tension roller, so that it may be suspended by a tension spring (not shown) in a direction as shown by an arrow P1 in the drawing. The fixing roller 141 may have a diameter of from 20φ to 30φ, and heat resistance elastic member 412 formed from heat resistance elastic member, such as form silicone rubber, liquid type silicone rubber, etc., may be provided so as to secure a nip width “L” on the outer circumference of the Fe core metal 411. Such an elastic layer 412 may have a thickness of from about 3 mm to about 6 mm. A surface hardness of the fixing roller 141 may be from about 30 to 50 Hs (Asker-C type).
The pressure roller 43 may be formed from a Fe or Al core metal 431 having a heat resistance elastic layer 432 such as fluorine series rubber, silicone rubber, etc., and a surface layer 343 formed from fluorine series plastic each coated on the core metal 431. In the current embodiment, to improve separation performance of a recording sheet carrying toner, a surface hardness of the pressure applying roller 143 may be larger that that of the fixing roller 141. Specifically, a nip for fixing use having a width L″ may be formed between the fixing belt 142 and pressure applying roller 43 with it both ends being concave downwardly. In the current embodiment, a thickness of the elastic layer 432 of the pressure applying roller 143 may amount from about 0.5 to about 2 mm. Its surface hardness may be from about 70 to about 90 Hs (Asker-C type). A halogen heater 434 may preferably be included inside the pressure-applying roller 143 so as to accelerate increasing in temperature of the pressure-applying roller.
The fixing apparatus 110a may include a rotation driving series (not shown) so as to transmit a rotation driving force to the pressure roller 143 via a transmission device (not shown). In addition to that, the rotation driving force can be transmitted to the fixing roller 141 in a certain case. Such a fixing apparatus 10a may hold a nip N formed from a section where the fixing belt 140 contacts and is wound around the fixing roller 141 to where the pressure roller 143 contacts with a width of L2. Thus, stable transfer and fixing performances may be obtained by decreasing image crush by the nip N.
A separation sheet 128a may be oppositely arranged to a separation surface of the fixing belt 140 winding and contacting the fixing roller 141. Such a separation sheet 128a may similarly be formed to that 128 of
The tip portion 281 of the separation sheet 128a may be located at a position distanced from the exit end of the nip N formed between the fixing belt 140 winding and contacting the fixing roller 141 and the pressure applying roller 43 by a prescribed length L1. In addition, the tip portion 281 of the separation sheet 128a may be shape similarly to that 128 of
Also in this case and similar to the separation sheet 28 of
The separation sheet 128a can be attached in a manner as illustrated in
The above-described embodiment can be employed in a mono-color image forming apparatus, facsimile, and printer or the like, and substantially the same function and effect can be obtained.
Obviously numerous additional modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the present invention may be practiced otherwise than as specifically described herein.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2001-167346 | Jun 2001 | JP | national |
| 2001-222186 | Jul 2001 | JP | national |
| 2001-261814 | Aug 2001 | JP | national |
This application is a continuation of U.S. application Ser. No. 12/026,291, filed Feb. 5, 2008 now U.S. Pat. No. 7,693,471, which is a continuation of Ser. No. 11/557,238, filed Nov. 7, 2006, now U.S. Pat. No. 7,346,305, issued Mar. 18, 2008, which is a divisional of Ser. No. 10/901,068, filed Jul. 29, 2004, now U.S. Pat. No. 7,224,928, issued May 29, 2007, which is a continuation of Ser. No. 10/158,852, filed Jun. 3, 2002, now U.S. Pat. No. 6,795,676, issued Sep. 21, 2004, and which claims priority under 35 USC. §119 to Japanese Patent Application Nos. 2001-167346, 2001-222186, and 2001-261814 filed on Jun. 1, 2001, Jul. 23, 2001, and Aug. 30, 2001, respectively, the entire contents of each of which are herein incorporated by reference.
| Number | Name | Date | Kind |
|---|---|---|---|
| 5293202 | Adachi et al. | Mar 1994 | A |
| 5499087 | Hiraoka et al. | Mar 1996 | A |
| 5671471 | Mizuno et al. | Sep 1997 | A |
| 5802434 | Takehara et al. | Sep 1998 | A |
| 5923930 | Tsukamoto et al. | Jul 1999 | A |
| 5962176 | Ohno et al. | Oct 1999 | A |
| 5978644 | Sato et al. | Nov 1999 | A |
| 5999788 | Kanesawa et al. | Dec 1999 | A |
| 6029038 | Uehara et al. | Feb 2000 | A |
| 6055390 | Kurotaka et al. | Apr 2000 | A |
| 6078766 | Kurotaka | Jun 2000 | A |
| 6088549 | Kagawa et al. | Jul 2000 | A |
| 6088558 | Yamada et al. | Jul 2000 | A |
| 6108906 | Fujita et al. | Aug 2000 | A |
| 6115576 | Nakano et al. | Sep 2000 | A |
| 6122479 | Fujita et al. | Sep 2000 | A |
| 6198888 | Kurotaka et al. | Mar 2001 | B1 |
| 6243559 | Kurotaka et al. | Jun 2001 | B1 |
| 6246858 | Condello et al. | Jun 2001 | B1 |
| 6262787 | Kamoi et al. | Jul 2001 | B1 |
| 6295435 | Shinohara et al. | Sep 2001 | B1 |
| 6298214 | Koga | Oct 2001 | B1 |
| 6347212 | Kosugi et al. | Feb 2002 | B1 |
| 6366751 | Shakuto et al. | Apr 2002 | B1 |
| 6564030 | Baughman et al. | May 2003 | B2 |
| 6577840 | Hachisuka et al. | Jun 2003 | B2 |
| 6795676 | Kikuchi et al. | Sep 2004 | B2 |
| 6795678 | Yura et al. | Sep 2004 | B2 |
| 6975829 | Aruga | Dec 2005 | B2 |
| 7062211 | Baba et al. | Jun 2006 | B2 |
| 7139520 | Echigo et al. | Nov 2006 | B2 |
| 7177580 | Nakafuji et al. | Feb 2007 | B2 |
| 7260351 | Nakayama | Aug 2007 | B2 |
| 7269384 | Someya et al. | Sep 2007 | B2 |
| 7299003 | Kurotaka et al. | Nov 2007 | B2 |
| 7570911 | Nakafuji et al. | Aug 2009 | B2 |
| Number | Date | Country |
|---|---|---|
| 53-81241 | Jul 1978 | JP |
| 55-157261 | Nov 1980 | JP |
| 64-13179 | Jan 1989 | JP |
| 64-17556 | Jan 1989 | JP |
| 03-197989 | Aug 1991 | JP |
| 04-174483 | Jun 1992 | JP |
| 6-138790 | May 1994 | JP |
| 08146806 | Jun 1996 | JP |
| 8-314305 | Nov 1996 | JP |
| 08-334919 | Dec 1996 | JP |
| 09-22210 | Jan 1997 | JP |
| 9-305054 | Nov 1997 | JP |
| 10274894 | Oct 1998 | JP |
| 10-301324 | Nov 1998 | JP |
| 10307496 | Nov 1998 | JP |
| 10-319671 | Dec 1998 | JP |
| 284885 | Jan 1999 | JP |
| 1138807 | Feb 1999 | JP |
| 2000-089603 | Mar 2000 | JP |
| 2000-98791 | Apr 2000 | JP |
| 2000-267479 | Sep 2000 | JP |
| 2000-305393 | Nov 2000 | JP |
| 2001-6849 | Jan 2001 | JP |
| 2001-83832 | Mar 2001 | JP |
| 2001-125420 | May 2001 | JP |
| 2001-183928 | Jul 2001 | JP |
| 2001-215825 | Aug 2001 | JP |
| 2001-282030 | Oct 2001 | JP |
| 3220585 | Oct 2001 | JP |
| 2002-072749 | Mar 2002 | JP |
| WO 9917168 | Apr 1999 | WO |
| Entry |
|---|
| Japanese Office Action issued on Nov. 16, 2010 in corresponding Japanese Application No. 2001-261814. |
| Japanese Office Action dated Jul. 4, 2007 for Japanese Patent Application No. 2002-158213. |
| Japanese Office Action dated Sep. 10, 2007 for Japanese Patent Application No. 2002-158213. |
| Japanese Office Action dated Feb. 18, 2008 for Japanese Patent Application No. 2002-158213. |
| Japanese Office Action dated Mar. 9, 2009 for Japanese Patent Application No. 2002-158213. |
| Japanese Office Action dated May 7, 2009 for Japanese Patent Application No. 2002-158213. |
| Number | Date | Country | |
|---|---|---|---|
| 20100046994 A1 | Feb 2010 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 10901068 | Jul 2004 | US |
| Child | 11557238 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 12026291 | Feb 2008 | US |
| Child | 12613851 | US | |
| Parent | 11557238 | Nov 2006 | US |
| Child | 12026291 | US | |
| Parent | 10158852 | Jun 2002 | US |
| Child | 10901068 | US |
