JP4436405B2 - Image forming and recording apparatus - Google Patents

Description

  The present invention relates to an image forming recording apparatus that performs printing on a recording medium such as paper or an OHP sheet, and more particularly to a fixing apparatus that fixes unfixed toner held on the recording medium.

  As a fixing device that can take a long time to heat and press the recording medium in order to realize high-speed fixing, the toner adhering surface of the recording medium is brought into contact with the fixing roller, and the non-adhering surface of the recording medium is used as an endless belt. 2. Description of the Related Art There is known a pressure belt type fixing device that is configured to contact and pressurize with a pressure member. In the pressure belt type fixing device, appropriate heat energy and pressure energy can be applied in a paper passage section where the fixing roller and the endless belt are in contact (hereinafter referred to as a nip portion, and the width thereof is referred to as a nip width). is important.

  Japanese Patent Application Laid-Open No. 8-166734 (Patent Document 1) discloses a heat fixing roll that is built in a heating unit and is driven to rotate, a pressure belt that is brought into contact with the heat fixing roll, and this pressure application. It is provided as one of a plurality of rolls that stretch the belt, and is compressed into the elastic layer of the heat fixing roll at the downstream portion in the rotation direction of the heat fixing roll of the pressure fixing portion between the heat fixing roll and the pressure belt. There is provided a fixing device of an image forming apparatus, which includes a pressure roll that presses to cause deformation, and a pressure auxiliary roll that is provided upstream of the pressing portion and is pressed to the heat fixing roll via a pressure belt. Are listed. In this fixing device, the sum of the pressing force of the pressure auxiliary roll and the heat fixing roll and the pressing force due to the tension of the pressure belt that is in contact with the heat fixing roll is equal to the pressing force of the pressure roll. Or it is set to be more. As a result, the frictional force between the heat fixing roll and the recording sheet is dominant between the pressing portion of the pressure auxiliary roll and the pressing portion of the pressure roll, that is, in a portion where the distortion generated on the peripheral surface of the heat fixing roll is small. Thus, the recording sheet is conveyed at a speed close to the peripheral speed of the portion where the heat fixing roll is not deformed.

  Japanese Patent Application Laid-Open No. 2001-228731 (Patent Document 2) uses a pressing pad as a pressing member, and prevents an increase in the driving torque of the belt (endless belt) over time for reducing friction. In order to ensure stable and stable running performance, a fixing device is described in which a porous resin member is provided at a portion of the pressure member facing the endless belt, and a lubricant is held in the porous resin member. In this fixing device, means (felt) for supplying the lubricant is provided on the inner peripheral surface of the endless belt in order to stably supply the lubricant.

JP-A-8-166734 JP 2001-228731 A

  In the fixing device disclosed in Japanese Patent Laid-Open No. 8-166734, paying attention to the relationship between the peripheral speed of the heat fixing roll and the conveyance speed of the recording sheet, the pressing force by the pressure auxiliary roll and the tension of the pressure belt The pressure setting force and the pressing force of the pressure roll are set, and the operation or function distribution such as preheating of the recording medium at the nip, melting of the toner, fixing of the toner and peeling of the recording medium from the fixing roller is performed. Therefore, it cannot be said that consideration is given to the distribution of each pressing force at that time. In addition, the pressing force of the pressure roll is maximum among the pressing force by the pressure auxiliary roll, the pressing force by the tension of the pressure belt, and the pressing force of the pressure roll.

  A first object of the present invention is to provide an image forming and recording apparatus capable of realizing high-speed fixing, shortening the first print time, and realizing oil-less fixing.

  Further, in the fixing device disclosed in Patent Document 2 (Japanese Patent Laid-Open No. 2001-228731), since the felt for supplying the lubricant is pressed against the inner peripheral surface of the endless belt, consideration is given to lubricant leakage from the end of the endless belt. Is necessary, and has a problem from the viewpoint of usability.

  A second object of the present invention is to provide an image forming and recording apparatus provided with a fixing device that can maintain a low driving torque of a pressure belt type fixing device for a long time, is inexpensive, and is easy to use. .

  In order to achieve the first object, a fixing device according to the present invention includes a fixing roller having a built-in heater and a belt pressure unit, and fixes the unfixed toner image on a recording medium. The belt pressure unit includes an endless belt and a pressure member that presses the endless belt against the fixing roller from the back surface. The pressure member includes both a rotating pressure member and a non-rotating pressure member. And when the pressure member is divided into an inlet pressure member, a central pressure member, and an outlet pressure member from the recording medium entrance side, the central pressure member is the non-rotating pressure member. I made it.

  Alternatively, the three pressure members are provided along the paper conveyance direction, and the second pressure member is a non-rotating pressure member.

  In order to achieve the second object, the image forming apparatus of the present invention includes a fixing device having a fixing roller having a built-in heater and a belt pressurizing unit, and the belt pressurizing unit is provided on the back surface of the endless belt. A pressing member that presses, the pressing force of the pressing member has three peaks, the pressing force of the second peak is larger than the pressing force of the other two peaks, and the pressing force of the second peak The applied pressure was applied by a non-rotating pressure member.

  The fixing device and the image forming recording apparatus of the present invention can take a long time for heating and pressurizing toner, and can realize high-speed fixing.

  Embodiments of the image forming and recording apparatus according to the present invention will be described.

The normal image forming and recording apparatus to which the present invention relates has the following problems.
(A) In a color image forming and recording apparatus that transfers toner onto a sheet by a single intermediate transfer member that can be configured at low cost, the same four-color printing speed (in pages / minute) that has an intermediate transfer member for each color. ) 4 times the fixing speed {expressed by the peripheral speed (mm / sec) of the fixing roller} as compared with the color image forming and recording apparatus), and high-speed fixing must be realized.
(B) In order to shorten the time (first print time) from when the image forming recording apparatus is turned on until the first printing starts, it is necessary to reduce the rubber thickness of the rubber layer on the surface of the fixing roller having a large heat capacity. In that case, it is necessary to apply a large heat and pressure to the toner as compared with the case where the rubber is thick.
(C) In an oilless fixing method in which no oil is supplied to the surface of the fixing roller for improving the usability of the image forming and recording apparatus, the toner impregnated with wax is covered with a hard shell. You need to apply great heat and pressure.
When a pressure belt type fixing system that satisfies all of the above (a), (b), and (c) has been studied, it has been found that it cannot be realized by the conventional pressure means and pressure conditions.
In the embodiments described below, in a color image forming and recording apparatus that performs toner transfer onto a sheet with a single intermediate transfer member, high-speed fixing can be realized, first print time can be shortened, and oilless fixing can be realized. An image forming and recording apparatus having a fixing device is provided.

  One embodiment of an image forming recording apparatus and a fixing apparatus according to the present invention will be described with reference to FIGS.

  The configuration of the fixing device of the image forming and recording apparatus of the present embodiment will be described with reference to FIG. The fixing device 1 includes a fixing roller 2 and a belt pressure unit 3. The fixing roller 2 includes a cored bar 4 made of iron or aluminum and a rubber layer 5, and a heater 6 is built therein. In order to improve the releasability of the toner, a fluororesin layer may be provided on the surface of the rubber layer 5. The belt pressurizing unit 3 includes a belt pressurizing unit 9 including a belt 7, a belt pressurizing member 8, and a spring. Hereinafter, a portion where the belt 7 is pressed against the fixing roller 2 is referred to as a nip portion, and a width thereof is referred to as a nip width. The pressure conditions (pressure width, surface pressure) of the belt in the nip part have a great influence on the fixing performance. In order to realize high-speed fixing of about 200 mm / s, it is necessary to secure a nip width of about 9 mm as shown in the relationship between the fixing speed and the nip width in FIG. 2, and an appropriate surface pressure is applied to each part of the nip portion. In order to add, the pressurizing member 8 for pressurizing the belt 7 is constituted by three pieces 8a, 8b and 8c.

  The time required to raise the temperature to a predetermined temperature in order to make the fixing device ready for printing is called a warm-up time. In order to shorten the warm-up time to about 30 seconds, it is desirable that the diameter of the fixing roller be 40 mm or less as shown in FIG. When oilless toner is used, it is harder (higher elastic modulus) than oil external supply type toner, and therefore it is necessary to apply pressure appropriately. In order to secure a wide nip width with a small-diameter fixing roller and apply an appropriate pressure, the pressure member 8 is also required to have a structure that follows the shape of the fixing roller 2.

  The role of the pressure member at the nip is shown in FIG. There is a role of paper preheating, toner melting, toner paper fixing, and paper peeling from the nip entrance, and the contribution of nip width, surface pressure, and pressure to each is shown. The applied pressure corresponds to the product of the nip width and the surface pressure.

  When the pressure members 8 are divided and it is considered that each pressure member is realized by a pressure pad having a simple structure and a flat surface (the nip width is 3 to 4 mm at the maximum for each pressure member), FIG. As shown in FIG. 5, it was found that the fixing could be realized with two pressure members at a fixing speed of 100 mm / s, but three pressure members were necessary at 200 mm / s.

  In the table, the pressing force of each pressure member under the condition that fixing can be realized is shown together, and how much each pressing member plays a role from the pressing force required for each role and the pressing force that realized fixing. An estimate of whether or not From this, it has been found that when the fixing speed is increased, the role of the entire fixing device cannot be fulfilled unless the number of pressure members responsible for toner melting and toner paper fixing is increased.

Since the pressure applied to each pressure member during high-speed fixing is divided as follows, the center is larger than the inlet and the outlet.
Inlet pressurizing member (paper preheating + most of toner melting): pressure (△ + ○, medium)
Central pressure member (part of toner melting + most part of toner paper fixing): pressure (△ + ◎, large)
Outlet pressure member (part of toner paper fixing + whole paper peeling): pressure (△ + ○, medium)
From now on, three pressure members are used to realize high-speed fixing, a short warm-up time, and oilless toner fixing, and the pressure is made larger than the first and third pressure members on the second pressure member from the paper entry side. .

  The pressing condition {pressing force (= surface pressure * nip width)} of each pressing member 8a, 8b, 8c will be described from two viewpoints of (A) fixing property and (B) sheet peeling.

(A) Relationship between the pressing condition of each pressing member to the fixing property The pressing condition for realizing the fixing will be described with reference to FIGS. 5 and 6 are based on the conditions that the three pressure members as shown in FIG. 1 can be fixed at 140 ° C., the pressure conditions of the two pressure members are fixed, and the other one pressure is applied. The pressure conditions that can be fixed at the same fixing temperature (140 ° C.) by changing the pressure conditions of the members are plotted. FIG. 5 shows the result at a low fixing speed (100 mm / s), and FIG. 6 shows the result at a high fixing speed (200 mm / s).

  As a result, at the low fixing speed (100 mm / s), the outlet pressure member varies in the pressure condition of the equal fixing temperature, and the surface pressure that should be important for fixing may be low. This indicates that the outlet pressurizing member does not need to be pressurized if the pressurizing condition of the central pressurizing member is set (two pressurizing members are sufficient).

  On the other hand, at a high fixing speed (200 mm / s), the outlet pressure member can also draw an equal fixing temperature line, indicating that three pressure members are required.

  From this result, the surface pressure of the three pressure members has a relationship of the size of the center> the inlet and the outlet.

  Furthermore, what can be said from FIG. 5 and FIG. 6 is that the absolute value of the gradient of the surface pressure / nip width in the figure is inlet> center> outlet, and the contribution of nip width is inlet> center> outlet. Therefore, by setting the nip width of each pressure member to the inlet> the center> the outlet, good fixing can be realized with a small surface pressure.

(B) Relation of pressure condition of each pressure member to sheet peeling In the fixing device, since the nip portion has a convex shape on the fixing roller side, the sheet comes out from the nip outlet when the sheet is fed. The paper is wound around the fixing roller 2 side. The behavior of the paper being wound is that the pressure of the outlet pressurizing member 8c is increased and the rubber layer 5 of the fixing roller 2 is elastically deformed so that the shape of the nip outlet is locally concave on the fixing roller side. This is effective, and the pressure of the outlet pressurizing member and the state of sheet peeling will be described with reference to FIG.

  FIG. 7 shows the test results when the guide 30 for scooping up the paper from the nip and removing the thick paper curl is attached. In FIG. 7, (a) the leading edge breaks because the paper appears to wind up, so that a part of the paper enters the gap between the guide 30 and the fixing roller 2, but the paper is picked up by the guide and discharged. (B) Wrapping (jam) indicates a state in which the paper enters the gap between the guide 30 and the fixing roller 2 and is not discharged. Both are phenomena that occur when the pressure condition of the outlet pressure member is not appropriate.

From the results shown in FIG. 7, there is no problem with 0.1 (MPa) for standard paper (basis weight of about 80 g / m ² ), but 0.2 (MPa) for thin paper (basis weight of about 60 g / m ² , low paper rigidity). )is necessary. The pressure of the outlet pressure member greatly contributes to the sheet peeling.

  Based on the above knowledge, the pressure distribution at the nip portion of the fixing device was changed to the pressure distribution as shown in FIG. 8 to realize high-speed fixing at 200 mm / s and a fixing temperature of 140 ° C. The conditions are summarized as follows.

There are three peaks corresponding to the three locations where the pressure members 8a, 8b, 8c abut.
(1) Nip width: inlet pressure member (example 4.5 mm)> center pressure member (example 3.5 mm)> outlet pressure member (example 2 mm)
(2) Surface pressure: central pressure member (example 0.5 MPa)> outlet pressure member (example 0.22 MPa), inlet pressure member (example 0.2 MPa)
(3) Pressure (corresponding to the product of nip width and surface pressure): Center pressure member> Inlet pressure member, outlet pressure member in this order, and considering the results of FIG. The specific range of is as follows.
(A) Inlet pressure member: (1) Nip width: 3 (mm) to 7 (mm), (2) Surface pressure: 0.05 (MPa) to 0.2 (MPa)
(B) Central pressure member: (1) Nip width: 2 (mm) to 4 (mm), (2) Surface pressure: 0.2 (MPa) to 0.5 (MPa)
(C) Outlet pressurizing member: (1) 3 (mm) from 1 (mm), (3) Surface pressure: 0.3 (MPa) from 0.1 (MPa)
Thus, since the pressure conditions required by the inlet pressure member, the central pressure member, and the outlet pressure member are required, each pressure member 8a, 8b, 8c is an independent pressure means 9a, 9b, It is desirable to be pressurized by 9c.

  The belt pressure member 8 may be a rotary pressure member (pressure roller) that presses the roller against the belt back surface, or a non-rotation pressure member (pressure pad) that presses the flat surface against the belt back surface.

From this, there is a difference between the pressure roller and the pressure pad from the following viewpoints.
(1) Ensuring nip width: pressure pad is advantageous (2) Applying surface pressure: equivalent (3) Belt rotation load: Pressurizing roller is advantageous From now on, it is important to secure nip width as an inlet pressure member A pressure pad is suitable. Since the central pressure member requires both surface pressure and nip width, the pressure roller or pressure pad and the outlet pressure member require surface pressure without requiring a nip width. Therefore, it is desirable to use a pressure roller or a pressure pad.

However, since it is structurally large to arrange two pressure rollers adjacent to each other, considering that it is desirable not to arrange the pressure rollers adjacent to each other, the pressure member 8 in FIG.
(1) Inlet pressure member: pressure pad, central pressure member: pressure pad, outlet pressure member: pressure pad,
(2) Inlet pressure member: pressure pad, central pressure member: pressure roller, outlet pressure member: pressure pad,
(3) Inlet pressure member: pressure pad, central pressure member: pressure pad, outlet pressure member: pressure roller,
One of the configurations is desirable. With such a configuration, the pressing conditions described in this embodiment can be realized, and high-speed fixing can be realized.

  In order to shorten the warm-up time in the fixing device, it is effective to reduce the heat capacity of the heating member and to insulate the heat radiating member. For reducing the heat capacity of the heating member, it is effective to reduce the core metal thickness and rubber thickness of the fixing roller. It is effective to provide the heat insulating elastic layer 12 on the surface of the pressure member 8 as heat insulation of the heat radiating member. Although the example which provided the heat insulation elastic layer 12 only in the inlet pressurization member 8a was shown in FIG. 1, it is not limited to this.

  FIG. 9 shows a calculation example of steady heat conduction when the surface of the fixing roller is 150 ° C. and the end of the pressure member is 20 ° C. based on the thermal resistance. As a rough calculation, when there is no heat insulating elastic layer 12 on the surface of the pressure member 8, a large temperature gradient is generated inside the fixing roller rubber and inside the belt. This is because the fixing roller rubber layer and the belt have the highest thermal resistance. On the other hand, when a fixing roller rubber layer and a heat insulating elastic layer having a thermal resistance greater than that of the belt are provided on the surface of the pressure member, a large temperature gradient is generated in the heat insulating elastic layer on the surface of the pressure member as indicated by a broken line in FIG. With such a configuration, when the surface of the fixing roller is heated to 150 ° C., it is possible to lower the temperature of the inner surface of the core metal from the point where the pressure member surface does not have the heat insulating elastic layer. The warm-up time can be shortened.

  FIG. 10 shows the warm-up time with and without the heat insulating elastic layer 12 made of silicon rubber on the inlet pressure member. The warm-up time is reduced by providing an elastic elastic layer.

  From the viewpoint of fixing performance, it is advantageous to provide the elastic elastic layer 12 on the inlet pressure member 8a. As described with reference to FIG. 6 in the embodiment, since the inlet pressure member has a high sensitivity to the fixing temperature of the nip width, the provision of the heat insulating elastic layer 12 on the surface can increase the nip width due to its elastic deformation. Therefore, this is also advantageous. Further, since the central pressure member 8b and the outlet pressure member 8c are highly sensitive to the fixing temperature of the surface pressure, it is desirable that the heat insulating elastic layer is not provided.

  As a material, as the heat insulating elastic layer provided on the pressure member, for example, silicon rubber having a low thermal conductivity is desirable. Moreover, it is desirable that the pressure member not provided with the heat insulating elastic layer is made of aluminum, iron or the like.

Next, means for reducing the driving torque for driving the fixing device will be described.
The static friction coefficient at the time of pressure contact between the non-rotating type pressure member surface material and the belt back surface material will be described with reference to FIG. Here, a measurement result for a case where a polyimide belt having high heat resistance is used as the belt material is shown.
(1) When the non-rotating pressure member surface material is stainless steel: 0.1
(2) When the non-rotating pressure member surface material is silicon rubber: 1.0
(3) When the surface material of the non-rotating pressure member is a fluorine fiber sheet (no lubricant (fluorine oil)): 0.08
(4) When the non-rotating pressure member surface material is a fluorine fiber sheet (with lubricant (fluorine oil)): 0.03
From this, by providing a fluorine fiber sheet on the silicon rubber layer as the surface material of the non-rotating type pressure member, the friction coefficient can be lowered as in (1) when there is no lubricant. Furthermore, it has been clarified that the friction coefficient can be remarkably lowered by providing a lubricant. As the lubricant, fluorine oil having a high affinity with fluorine fibers may be used.

  Therefore, as shown in FIG. 12, it is desirable to provide a sheet-like member 31 made of fluorine fiber on the surface of the non-rotating type pressurizing member (inlet pad 8a, central pad 8b). One end (upstream side with respect to the rotation direction of the fixing roller) 32 of the sheet-like member 31 is fixed. With such a structure, it does not peel off even when the fixing roller rotates, and plays a role as a low friction material between the rotating endless belt and the stationary pressure pads 8a and 8b in a non-rotating state.

  FIG. 13 shows the relationship between the fixing device driving torque and the fixing device rotation time with and without the lubricant. From this, without the lubricant, the drive torque increases in a short time, while with the lubricant, the drive torque does not increase even when the fixing device is rotated for a long time.

  As described above, by using the sheet-like member 31 and the lubricant, the driving torque of the fixing device can be lowered, and the change in the driving torque can be reduced even if the fixing device is rotated for a long time.

  In order to realize an increase in driving torque when the fixing device is further rotated for a longer time with a configuration with less lubricant leakage, it is desirable to provide the sheet-like member 31 with the lubricant supply portion 33.

  When the fixing device (sheet-like member 31, with lubricant) was further rotated for a long time without providing the lubricant supply unit 33, the driving torque increased as shown by the broken line in FIG. . This is considered to be because the mass of the lubricant held in the sheet-like member 31 is lowered as shown by the broken line in FIG. In a conventional belt fixing device, a configuration is known in which a lubricant supply unit (made of felt or the like) is provided so as to be in contact with the inner peripheral surface of the belt. However, in such a configuration, the lubricant supply unit is arranged so as to bite into the belt in order to reliably realize contact of the lubricant supply unit with the belt. For this reason, there is a problem that the lubricant supply part is pushed by the belt and the leakage of the lubricant to both ends in the axial direction is large. In this embodiment, as shown in FIG. 12, the lubricant supply section 33 is provided not at the position between the pressure member / belt of the sheet-like member but at the position where it does not come into contact with the inner peripheral surface of the belt. The contact member 31 is provided in contact with the cylindrical member 31. Thereby, the lubricant can be moved from the lubricant supply unit 33 to the sheet-like member 31 by concentration diffusion. Accordingly, when the concentration of the lubricant is lowered at a portion where the sheet-like member 31 is sandwiched between the pressure members 8a and 8b and the belt 7, the lubricant moves from the lubricant supply portion 33 to the portion by diffusion. Here, the lubricant supply unit 33 is made of a heat-resistant fiber such as an aramid fiber and has a configuration in which fluorine oil is held.

By adopting such a configuration, the time change of the lubricant holding mass of the sheet-like member becomes as shown by the solid line in FIG. 15, the change can be reduced, and the driving torque of the fixing device changes as shown by the solid line in FIG. Can be reduced.
In addition, a comparison is made between the configuration in which a lubricant supply unit (made of felt or the like) is provided so as to be in contact with the inner peripheral surface of a belt known in the art and the configuration of the present embodiment and the amount of lubricant leakage during rotation for a certain time. Then, as shown in FIG. 16, the amount of leakage can be significantly reduced by adopting the configuration of the present embodiment.

  The pressing member 8c can be a non-rotating type pressing member, and the sheet-like member 31 straddles a plurality of non-rotating type pressing members or is separated for each non-rotating type pressing member. It may be provided. One lubricant supply unit 33 may be provided in common for the plurality of non-rotating pressure members, or may be provided separately for each non-rotating pressure member.

  As described above, a sheet-like member made of fluorine fibers (for example, knitted non-porous fluorine resin) is provided between the non-rotating pressure member and the belt, and the portion of the sheet-like member that does not contact the belt By providing the lubricant supply member in the structure, the lubricant can be supplied by diffusion. With such a configuration, the lubricant diffuses and spreads due to the concentration gradient inside the fluorine fiber sheet. Therefore, when the concentration of the lubricant in the portion between the pressure unit and the belt decreases, the lubricant can be supplemented. it can. Therefore, compared with the structure which presses a lubricant supply member to a belt, the leakage from the edge part of a lubricant can be reduced significantly. As a result, it is possible to realize a configuration that can reduce the time change of the driving torque of the fixing device and can reduce the leakage of the lubricant.

Next, the configuration of the image forming and recording apparatus of the present invention having the fixing device described above will be described with reference to FIG.
A photosensitive belt 25 that is stretched in the vertical direction by a driving roller 23 and a driven roller 16 that also serves as a tension roller that applies tension to the belt, rotates at a constant speed in the direction of the arrow, and an intermediate transfer member that is disposed in contact with the photosensitive belt 25. 27, a charger 17 for uniformly charging the surface of the photosensitive belt 25, an exposure device 14 for exposing the uniformly charged surface of the photosensitive belt 25 to form an electrostatic latent image on the surface, and Recording is performed from four developing units 15a, 15b, 15c, and 15d that are arranged so as to be in contact with the horizontal surface of the photosensitive belt 25 and form a toner image by developing an electrostatic latent image, and a cassette 13 that stores a recording medium 28 such as paper. A feed roller 20 for feeding the medium, a registration roller 21 for correcting the posture of the recording medium fed from the cassette 13, and a transfer roller 22 for transferring the toner image to the recording medium. The fixing device 1, the paper discharge unit 24 for discharging the fixed recording medium to the outside of the apparatus, the erase lamp 19 for removing the charge remaining on the surface of the photosensitive belt 25, the blade 18 for removing the residual toner, and the transfer A cleaner 26 for removing toner remaining on the surface of the intermediate transfer member 27 later is provided.

  Here, the driving roller 23 and the driven roller 16 may be upside down. Further, the intermediate transfer member 27 may be constituted by a drum or a belt. In the case of a belt, a roller for applying tension to the belt is provided on each inner surface of the contact portion with the photoconductor 25 and the contact portion with the transfer roller 22.

Next, a color image forming method using this apparatus will be described.
When a print signal is sent from an information processing device (not shown) to the printer main body in a print standby state after the power is turned on, the exposure device 14 uniformly charges the laser light to the portion corresponding to the toner image by the charger 17. The photosensitive belt 25 is irradiated to form an electrostatic latent image on the photosensitive belt 25.
First, an electrostatic latent image corresponding to a cyan toner image is formed on the photosensitive belt 25 by the exposure device 14, and developed by the cyan developing device 15d to form a toner image. Here, 15d is a developing unit using cyan toner, 15c is a developing unit using magenta toner, 15b is a developing unit using yellow toner, and 15a is a developing unit using black toner. The developing function is imparted to or eliminated from each developing device by controlling the bias voltage. The toner image formed on the photosensitive belt 25 is transferred to the surface of the intermediate transfer member 27 at a contact portion with the intermediate transfer member 27 and is held on the surface.
On the other hand, on the photosensitive belt 25 after the toner image is transferred, the charge remaining on the surface of the photosensitive belt 25 is removed by the erase lamp 19 and then the toner remaining without being transferred is removed by the blade 18.
After the process of returning the surface of the photosensitive belt 25 to the initial state is completed, a magenta toner image as the next color is similarly formed on the surface of the photosensitive belt 25 and held on the surface of the intermediate transfer body 27. The cyan toner image is superimposed and transferred and held on the intermediate transfer member 27.

  The same process is repeated for yellow and black colors, and four color toner images are superimposed on the intermediate transfer member 27 and simultaneously held on the surface.

  In order to transfer the four color toner images formed on the surface of the intermediate transfer member 27 onto the recording medium 28 in this way, the recording medium 28 stored in the cassette 13 is rotated one by one by rotating the paper feed roller 20. The sheet is separated and conveyed to the registration roller 21 to correct the skew of the recording medium 28 and then stopped. Next, the rotation of the registration roller 21 is started at a timing that matches the toner image on the intermediate transfer member. At the same time as the leading edge of the conveyed recording medium comes into contact with the intermediate transfer body 27, the transfer roller 22 is pressed from the back surface of the recording medium to electrostatically transfer the four color toner images on the surface of the intermediate transfer body 27 onto the recording medium 28 at a time. . The four color toner images thus formed on the recording medium 28 are fixed by passing between the fixing roller and the pressure roller of the fixing device 1 and discharged to the paper discharge unit 24 of the printer 29, and a series of printing processes is performed. finish.

  By including the fixing device having the above-described configuration in such an image forming recording apparatus, high-speed fixing, a short warm-up time, and oilless toner fixing can be realized. In addition, a sheet-like member is provided between the non-rotating type pressure member and the endless belt to reduce friction, and by applying a lubricant, the friction can be further reduced to reduce the time variation of the fixing device drive torque. it can. Furthermore, by providing a lubricant supply part at the non-pressurized part of the sheet-like member between the non-rotating type pressure member and the endless belt and at the non-contact part with the inner peripheral surface of the belt, the change of the fixing device driving torque over time Further reduction can be realized with less lubricant leakage.

1 is a diagram illustrating a structure of a fixing device according to an embodiment of an image forming recording apparatus according to the present invention. FIG. 5 is a diagram illustrating an example of a relationship between a fixing speed and a necessary nip width according to an embodiment of the present invention. FIG. 4 is a diagram illustrating a relationship example between a fixing roller diameter and a warm-up time of a fixing device according to an embodiment of the present invention. FIG. 4 is a diagram illustrating a role at a nip portion of a fixing device according to an embodiment of the present invention. FIG. 4 is a diagram illustrating a relationship between a pressing condition and a fixing temperature of a fixing device according to an embodiment of the present invention. FIG. 9 is another diagram showing the relationship between the pressurizing condition and the fixing temperature of the fixing device according to the embodiment of the present invention. FIG. 4 is a diagram illustrating a sheet peeling characteristic of a fixing device according to an embodiment of the present invention. FIG. 3 is a diagram illustrating a pressure distribution of the fixing device at a nip portion of the fixing device according to an embodiment of the present invention. FIG. 6 is a diagram illustrating an example of calculating a temperature distribution of a fixing unit of a fixing device according to an embodiment of the present invention. FIG. 4 is a diagram illustrating a warm-up time of a fixing device according to an embodiment of the present invention. FIG. 4 is a diagram illustrating a coefficient of static friction between a non-rotating pressure member surface material and a belt back surface material of a fixing device according to an embodiment of the present invention. 1 is a diagram illustrating a structure of a fixing device according to an embodiment of the present invention. FIG. 4 is a diagram illustrating a difference in driving torque depending on the presence or absence of a lubricant in a fixing device according to an embodiment of the present invention. FIG. 4 is a diagram illustrating a change over time in driving torque of a fixing device according to an embodiment of the present invention. The figure which shows the time change of the lubricant holding | maintenance mass of the sheet-like member of the fixing device which concerns on one Example of this invention. The figure which shows the difference in the lubricant leakage amount of a fixing device. 1 is a diagram showing a configuration of an image forming recording apparatus according to the present invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Fixing device, 2 ... Fixing roller, 3 ... Belt press part, 4 ... Core metal, 5 ... Fixing roller rubber layer, 6 ... Heater, 7 ... Belt, 8 ... Pressure member, 9 ... Pressure member pressurizing means DESCRIPTION OF SYMBOLS 10 ... Paper, 11 ... Unfixed toner, 12 ... Pressure member surface heat insulation elastic layer, 13 ... Cassette, 14 ... Exposure apparatus, 15 ... Developing device, 16 ... Driven roller, 17 ... Charger, 18 ... Blade, 19 ... Erase lamp, 20... Feed roller, 21. Registration roller, 22. Transfer roller, 23. Drive roller, 24. Paper discharge unit, 25... Photosensitive belt, 26. Medium 29... Image forming apparatus 30. Guide 31. Sheet member 32. Sheet member end 33 33 Lubricant supply unit.

Claims (3)

A fixing roller with a built-in heater;
A belt pressure unit,
In a fixing device for fixing an unfixed toner image on a recording medium,
The belt pressing part includes an endless belt, and a pressure member that form a nip pressing said endless belt to said fixing roller from the back,
The pressure member includes both a rotary pressure member and a non-rotational pressure member,
The pressure member is divided into an inlet pressure member, a central pressure member, and an outlet pressure member from the inlet of the nip on the recording medium entry side ,
Both the inlet pressure member and the central pressure member are the non-rotating pressure member , the outlet pressure member is the rotary pressure member,
The pressing force (= surface pressure * nip width) of the central pressing member is larger than the pressing force of the inlet pressing member and the pressing force of the outlet pressing member,
The outlet pressure member has a surface pressure in the range of 0.1 MPa to 0.3 MPa,
A fixing device for fixing an unfixed toner image using toner containing wax on a recording medium without supplying oil to the surface of the fixing roller .   The fixing device according to claim 1, wherein the fixing speed is greater than 200 mm / s.   An image forming and recording apparatus comprising the fixing device according to claim 1.

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