JP3962740B2 - Fixing device - Google Patents

Description

  The present invention relates to a fixing device applied to an electrophotographic copying machine, a laser beam printer, a facsimile, and the like.

  2. Description of the Related Art In electrophotographic image forming apparatuses such as copying machines, printers, and facsimile machines, a fixing device is provided for fusing and fixing a toner image transferred on a recording medium (sheet).

  In recent years, a belt nip type fixing device has been developed in order to reduce the size and power consumption of an electrophotographic apparatus (see Patent Document 1). The belt nip type fixing device is, for example, a device that performs heat fixing between a rotating fixing roll and an endless belt that rotates in contact with the fixing roll. In order to form a nip by pressing the endless belt against the fixing roll, a pressure applying member arranged in a non-rotating state is provided inside the endless belt.

  Patent Document 1 describes an endless belt made of a polyimide resin film and a pressure applying member covered with a glass fiber sheet impregnated with polytetrafluoroethylene. Since the pressure applying member always slides on the inner side of the rotating endless belt, a material that is not easily worn and has low frictional resistance is required. Furthermore, Patent Document 1 also describes that a lubricant is applied to the inside of an endless belt in order to improve slidability.

  In Patent Document 2, a lubricant-impregnated member for applying a lubricant in contact with the inner peripheral surface of an endless belt is provided on an endless belt portion positioned on the fixing roll side between pressure-contact support rolls of the endless belt. The structure provided so that it may contact | abut to an internal peripheral surface is described. In Patent Document 2, it is described that the following problems occur due to excessive or insufficient lubricant.

  That is, in a fixing device having a mechanism for adjusting the position in the thrust direction of the belt by supporting the inner side of the endless belt and swinging the belt when the amount of lubricant applied to the inner peripheral surface of the belt is too large. Further, there is a problem that the frictional resistance is excessively lowered by the lubricant having excessive resistance between the inner surface of the belt and the support roller, and the belt cannot be swung even if the angle of the support roller that performs the belt swing is displaced.

  The lubricant applied to the inner surface of the belt also in a fixing device having a mechanism for adjusting the position in the thrust direction of the belt by providing a guide member at the end without causing the endless belt to swing by the support roller. Oozes out from the end of the endless belt in the thrust direction and wraps around the surface, causing a problem that the recording medium to be transported at the fixing nip portion slips or a trace of lubricant adheres to the image. .

On the other hand, when the amount of lubricant applied is too small, the time until the amount of lubricant existing inside the endless belt decreases is shortened, and the frictional resistance between the endless belt and the pressure applying member gradually increases, and the endless belt It has been pointed out that the smooth rotation of the motor is hindered, and as a result, the life of the fixing device is shortened.
JP-A-8-262903 JP-A-11-45018

  That is, for example, when a lubricant application device is configured with a simple configuration in which a nonwoven fabric such as felt is impregnated with a lubricant, the coating amount itself increases in the initial state where the amount of lubricant is large, and conversely, the lubricant As the amount of coating decreases, the coating amount decreases, causing the above-described problems. In addition, the lubricant retained by the lubricant-impregnated member may flow downward from other than the application surface of the lubricant application device due to the influence of gravity and its wettability, so that it is originally applied to the endless belt. In some cases, the amount of lubricant to be reduced decreases, resulting in a problem that the life of the fixing device is shortened.

  In order to deal with such problems, for example, the lubricant application device is separated into functions such as an oil pan, a replenishment unit, an oil application roller, and an oil application amount regulating blade, thereby providing a configuration that exhibits stable lubricant application performance. It can be taken and is actually implemented in a great number of electrophotographic apparatuses. However, of course, this increases the size of the device, so it is very difficult to install it inside or outside the fixing device corresponding to the above-mentioned small size and low power consumption, and it is one of the main causes of cost increase. It is reality.

  An object of the present invention is to provide a fixing device capable of stably applying a lubricant with a simple configuration.

To achieve the above object, a fixing device according to the present onset Ming, a fixing rotator, and an endless belt to form a fixing nip between the fixing rotary body, its either inside the belts Te in the fixing nip supporting a pressing member for pressing toward the RaJo deposition rotating body, and the lubricant impregnated member impregnated with lubricant to supply lubricant between the pressure member and the belt, the lubricant impregnated member a support member for, in the fixing device having,
In the lubricant-impregnated member, the tip side contacting the inner surface of the belt is positioned below the support member so as to supply the lubricant downward, and the void ratio on the tip side of the lubricant-impregnated member is higher than that of the other end side. It is characterized in that it is configured to prevent excessive outflow of lubricant from the tip side by utilizing capillary action by increasing the size .

  According to the present invention, the lubricant that resists gravity can be pumped upward by capillary action, so that the shortage of lubricant is eliminated at the upper part of the lubricant-impregnated member, and the excess of lubricant can be suppressed at the lower part. Therefore, according to the present invention, it is possible to stably supply the lubricant from the beginning to the long term with a very simple configuration in which the lubricant-impregnated member with the adjusted porosity is provided.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

< Reference embodiment>
(Configuration of fixing device)
FIG. 1 is a cross-sectional view schematically showing a configuration of a fixing device according to a reference embodiment of the present invention. The fixing device, for example, electrophotographic copying machines, printers, image forming apparatus built-in is used, such as a facsimile apparatus.

The fixing device generally includes a heat fixing roll (fixing rotating body) 10 having a built-in heating source, an endless belt (endless belt) 21, and a predetermined range of the inner surface of the endless belt 21 pressed against the heat fixing roll 10. And a pressure applying member (pressure member) 30 that forms a fixing nip between the outer peripheral surface of the heat fixing roll 10 and the outer surface of the endless belt 21. The endless belt 21 is stretched by a separation roll 22, a steering roll 23, and an inlet roll 24 that are three support rolls, and constitutes a belt unit 20. Inside the belt unit 20, there is provided a lubricant application device 1 that contacts the inner surface of the endless belt 21 and applies a lubricant.

  The heat fixing roll 10 has an elastic layer 12 made of an elastic material such as silicone rubber on a cylindrical cored bar 11 made of a metal having high thermal conductivity such as aluminum, and heat resistance such as a PFA tube. And a roll structure in which a release layer 13 having excellent release properties is sequentially laminated. A halogen lamp 14 as a heating source is disposed inside the cylinder of the core metal 11. A temperature sensor 15 for measuring the surface temperature of the heat fixing roll 10 is disposed on the surface of the heat fixing roll 10.

  The heat fixing roll 10 is rotatably supported by a support mechanism (not shown), and is rotated at a predetermined speed in the direction of an arrow in the drawing by a drive device (not shown). Further, the halogen lamp 14 is feedback-controlled by a temperature controller (not shown) based on a measurement signal from the temperature sensor 15 so that the surface of the heat fixing roll 10 is maintained at a predetermined temperature.

  The endless belt 21 is formed of a heat resistant resin film such as a polyimide film. The endless belt 21 is wound around three support rolls, a separation roll 22, a steering roll 23, and an inlet roll 24 that are rotatably supported.

  The separation roll 22 is a pressure roll that is in pressure contact with the heat fixing roll 10 via the endless belt 21 by a pressure mechanism (not shown). With this separation roll 22, the elastic layer 12 of the heat fixing roll 10 is deformed, and the toner image that has advanced into the fixing nip due to the deformation strain is separated from the heat fixing roll 10.

  The steering roll 23 has bearings (not shown) at both ends. This bearing is moved back and forth by a driving device (not shown) based on a signal from a sensor (not shown) that detects the position of the end of the endless belt 21. Thereby, the meandering of the endless belt 21 is corrected.

  The inlet roll 24 is disposed on the inlet side of the recording medium (sheet) P. The inlet roll 24 is disposed at substantially the same height as the pressure applying member 30 so that the sheet is introduced flat with respect to the fixing nip.

  The pressure applying member 30 has a structure in which an elastic layer 32 such as silicone rubber is laminated on a support plate 31 and a low friction layer 33 such as a fluororesin coat is further laminated thereon. The pressure applying member 30 has a pressure mechanism (not shown), and applies pressure from the inside of the endless belt 21 toward the heat fixing roll 10 in the fixing nip.

(Configuration of lubricant application device)
The lubricant application device 1 includes a lubricant impregnated member (also referred to as a lubricant application member) 2 impregnated with a lubricant, and support members 3 and 4 that sandwich and fix the lubricant impregnated member 2 up and down. Has been. The lubricant application device 1 is arranged such that the tip of the lubricant impregnated member 2 (the upper end portion in the present embodiment) is in contact with the inner surface of the endless belt 21 by a fixture (not shown). Supply lubricant to the inner surface.

As the lubricant, for example, silicone oil having a viscosity of 1000 CS can be suitably used. The lubricant-impregnated member 2 is made of a nonwoven fabric such as a heat-resistant felt. The lubricant-impregnated member 2 has a large number of gaps, and in this embodiment, the porosity on the front end side (upper end side) for supplying the lubricant upward is smaller than that on the other end side (lower end side). It has been adjusted.

  In this embodiment, the porosity of the end (contact side end) on the side in contact with the endless belt 21 is 50%, and the porosity of the other end (non-contact side end) is 90%. In addition, the void ratio is gradually increased from the end on the contact side to the end on the non-contact side. Since the lubricant (silicone oil or the like) contained in the lubricant impregnated member 2 gradually moves toward the endless belt 21 at the contact portion with the endless belt 21, the amount of lubricant retained at the upper end of the lubricant impregnated member 2 is increased. Decrease. However, according to the configuration of the present embodiment, the lubricant moves from the larger porosity to the smaller one against the gravity due to the capillary phenomenon, so the upper end portion (the end portion on the contact side) of the lubricant impregnated member 2 ) Eliminates the lack of lubricant. Therefore, compared with the lubricant-impregnated member having a uniform porosity, the amount of lubricant retained at the end portion on the contact side of the lubricant-impregnated member 2 is kept high for a long period of time.

The porosity of the lubricant-impregnated member 2 is determined by measuring the weight of the lubricant-impregnated member 2 by immersing the entire lubricant-impregnated member 2 in the lubricant and withdrawing the lubricant impregnated member 2 after a certain time (for example, after 5 minutes). The following formula is used.

Porosity = ((weight of member after impregnation of lubricant) − (weight of member before impregnation of lubricant)) / (weight of member after impregnation of lubricant)

  However, since the porosity of the lubricant-impregnated member 2 is different for each part, the porosity for each part was calculated by cutting the part and performing the above measurement.

  Since the porosity is an index corresponding to the retention capacity of the lubricant by the lubricant-impregnated member, a large porosity means that the lubricant retention capacity is low, whereas a low porosity is It means that the lubricant retention ability is high.

  The material of the lubricant impregnated member 2 may be any material as long as it exhibits affinity and wettability to the lubricant. In the present embodiment, aramid resin fibers having high heat resistance are used. However, any material such as PET, polyester, Teflon (registered trademark) resin may be used as long as the function of the present invention can be achieved.

  Nonwoven fabrics are generally manufactured by (1) a dry assembly, a wet method, a spunbond method or the like to produce an aggregate (fleece) in a coarse state of fiber binding, and then (2) a chemical bond method, a thermal bond It is manufactured by increasing the bonding force between the fibers by a method such as a method or a needle punch method.

  An example of a method for manufacturing the lubricant-impregnated member 2 having different porosity for each part as in this embodiment will be described with reference to FIG. In this example, two or more kinds of fibers having different thicknesses are used, and the distribution amount of each fiber is made different between the front end side (upper end side) and the other end side (lower end side) of the lubricant-impregnated member 2, thereby providing a gap. Adjust the rate.

First, two types of fibers having different fiber thicknesses are prepared. In this embodiment, 2 denier thin aramid resin fiber α and 32 denier thick aramid resin fiber β are used. These fibers are mixed and spread so that the left side has a large amount of fiber α, the right side has a large amount of fiber β, and the amount gradually changes. At that time, the weight per unit volume is packed so as to be substantially the same in any part. After the desired amount is spread all over, the emulsion-based fiber adhesive is mixed while sprayed, and subjected to hot-pressure treatment to bond the fibers. Thereafter, the lubricant impregnated member 2 is obtained by cutting into a desired size.

  In addition to the manufacturing method as shown in FIG. 2, various methods for manufacturing the non-woven fabric so that the porosity is different for each part can be considered. As a result, the porosity is a desired value, and any manufacturing method may be adopted as long as the same effect can be obtained.

(Comparative experiment)
FIG. 3 is a graph showing a result of comparing the amount of application of the lubricant-impregnated member 2 of the present embodiment with the amount of application of the lubricant-impregnated member having a uniform porosity. The horizontal axis in FIG. 3 is the time during which the belt nip type fixing device in FIG. 1 is continuously rotated in a heated state (so-called durability time), and the vertical axis indicates the current value of the motor that rotationally drives the heat fixing roll 10. It is a thing. That is, as the amount of lubricant applied to the endless belt 21 decreases, the resistance at the press contact portion gradually increases, and as a result, the current value of the motor necessary for rotating the heat fixing roll 10 increases. Indirectly, the amount of lubricant applied is measured.

  The graph of FIG. 3 shows the experimental results of the required driving current of the fixing motor with respect to the durability time of each of the lubricant-impregnated member A and the lubricant-impregnated member B. In this experiment, the time (life) until reaching the current limit (about 2.5 A) when rotating the heat fixing roll 10 is examined. Here, the lubricant-impregnated members A and B have the same shape with a thickness of 5 mm, a height of 20 mm, and a width of 300 mm, and are impregnated with 10 g of silicone oil as a lubricant. However, the lubricant-impregnated member A has a uniform porosity of 75%, whereas the lubricant-impregnated member B has a porosity of 90% at the non-contact side end, and the contact-side end. It is adjusted so that it may gradually change from 50% in the part to 90% to 50%.

  From this experimental result, the life of the fixing device having the lubricant-impregnated member A having a constant porosity is almost 70 hours, whereas the life of the fixing device having the lubricant-impregnated member B having the adjusted porosity is about 200. You can see that it extends to time. The amount of silicone oil retained by the lubricant-impregnated member when it reached the end of its life was approximately 6.5 g of silicone oil remaining in the lubricant-impregnated member A, whereas the amount of silicone oil retained in the lubricant-impregnated member A In B, about 1.2 g of silicone oil remained. That is, in the lubricant-impregnated member A having a uniform porosity as a whole, the silicone oil remains at the non-contact side end portion, but almost remains at the contact side end portion. Absent. On the other hand, in the lubricant-impregnated member B in which the porosity is gradually changed, silicone oil remains almost uniformly in each part of the lubricant-impregnated member B.

  Further, when the amount of the silicone oil is increased to 30 g so that the life of the fixing device of the lubricant-impregnated member A is the same as that of the lubricant-impregnated member B, the meandering control of the endless belt 21 of the fixing device works well in the initial state. Further, it was found that the silicone oil that wraps around from the inner surface of the belt stays in the fixing nip, and oil streaks are generated when the recording medium is passed through the nip.

As described above, as in this embodiment, the void ratio on the upper end side (side contacting the endless belt 21) of the lubricant-impregnated member 2 is small and the void ratio on the other end side is large. By gradually changing the porosity, it became possible to obtain a stable lubricant application ability from the initial stage to the end of the endurance life. In the reference embodiment has been gradually differentiated to configure the porosity, stepwise (two steps, three steps, etc.) the porosity can be also exhibits the work-effective configuration of changing the.

< One Embodiment>
(Configuration of fixing device)
Figure 4 is a cross-sectional view schematically showing a configuration of a fixing device according to an embodiment of the present invention. The fixing device, for example, electrophotographic copying machines, printers, image forming apparatus built-in is used, such as a facsimile apparatus. 4, the same components as those of the fixing device of FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.

  The fixing device generally includes a heat fixing roll (fixing rotating body) 10 having a built-in heating source, an endless belt (endless belt) 21, and a predetermined range of the inner surface of the endless belt 21 pressed against the heat fixing roll 10. And a pressure applying member (pressure member) 30 that forms a fixing nip between the outer peripheral surface of the heat fixing roll 10 and the outer surface of the endless belt 21. Inside the endless belt 21, there is provided a lubricant application device 5 that contacts the inner surface of the endless belt 21 and applies a lubricant.

  The endless belt 21 of the present embodiment rotates following the rotation of the heat fixing roll 10. An end portion regulating member (not shown) is provided at both ends of the endless belt 21, and the meandering of the endless belt 21 is regulated by the end portion regulating member.

(Configuration of lubricant application device)
The lubricant application device 5 includes a lubricant impregnated member 6 impregnated with a lubricant and a support member 7 that sandwiches and fixes the lubricant impregnated member 6. The lubricant application device 5 is disposed by a fixture (not shown) so that the tip side (the lower end side in the present embodiment) of the lubricant impregnated member 6 is in contact with the inner surface of the endless belt 21.

  The lubricant-impregnated member 6 of the present embodiment is configured by combining a plurality of lubricant-impregnated members (hereinafter simply referred to as “members”) 6 a and 6 b having different porosity. The void ratio of the upper member 6b is set smaller than that of the lower member 6a in contact with the endless belt 21. The two members 6a and 6b are bonded and integrated by a chemical bond or the like. As the lubricant, for example, silicone oil having a viscosity of 1000 CS can be suitably used.

  Thus, by making the porosity of the tip side (lower end side) of the lubricant impregnated member 6 larger than that of the other end side (upper end side), the lubricant is moved upward (the one with the lower porosity) by capillary action. Can be made. Therefore, it is possible to suppress problems that the lubricant application amount becomes excessive or flows out to the front side (outer surface) of the endless belt 21.

  In this case, silicone oil (viscosity 1000CS) is used as the lubricant. However, since silicone oil generally changes in actual viscosity depending on temperature, it will move by capillary action according to the temperature control temperature of the fixing device. The amount of oil will change. Furthermore, since the temperature depends on the amount of heat transferred from the pressure applying member 30, the optimum thickness, width, porosity, etc. of the members 6a and 6b are preferably adjusted optimally for each fixing device.

  In the fixing device according to the present embodiment, the temperature of the upper side of the member 6b is 110 ° C., the temperature of the contact portion of the member 6a with the endless belt 21 is 120 ° C., and the temperature near the joining surface of the members 6a and 6b is 80 ° C. In addition, it was found from experiments that the optimum amount of lubricant applied to the endless belt 21 is about 60 mg / hrs (rotation time). Therefore, the member 6a is configured with a width of 300 mm, a length of 15 mm, a thickness of 6 mm, and a porosity of 45%, the member 6b is configured with a width of 300 mm, a length of 15 mm, a thickness of 25 mm, and a porosity of 75%, and 30 g of lubricant is used as the member. When only 6b was initially impregnated, the optimum coating amount was maintained for 150 hours.

  That is, even with the configuration of the present embodiment, it is possible to obtain a stable lubricant application capability from the initial stage to the end of the endurance life.

  The above embodiment is merely an example of the present invention. The scope of the present invention is not limited to the above embodiment, and various modifications can be made within the scope of the technical idea.

  For example, the setting of the shape, size, and porosity of the lubricant-impregnated member is not limited to that of the above embodiment. These settings may be appropriately changed according to various conditions of the fixing device.

FIG. 1 is a cross-sectional view schematically illustrating a configuration of a fixing device according to a reference embodiment. FIG. 2 is a diagram schematically showing a method of manufacturing the lubricant-impregnated member of FIG. FIG. 3 is a graph showing the relationship between the durability time and the required driving current of the fixing motor in the fixing device of FIG. 1 and the fixing device of the comparative example. Figure 4 is a cross-sectional view schematically showing a configuration of a fixing device according to an embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Lubricant application apparatus 2 Lubricant impregnation member 3, 4 Support member 5 Lubricant application apparatus 6 Lubricant impregnation member 6a, 6b Lubricant impregnation member 7 Support member 10 Heating fixing roll (fixing rotary body)
11 Metal core 12 Elastic layer 13 Release layer 14 Halogen lamp (heating source)
DESCRIPTION OF SYMBOLS 15 Temperature sensor 20 Belt unit 21 Endless belt 22 Separation roll 23 Steering roll 24 Inlet roll 30 Pressure application member 31 Support plate 32 Elastic layer 33 Low friction layer

Claims (1)

A fixing rotator, and an endless belt to form a fixing nip between the fixing rotary member, a pressure member for pressing toward the belts on the inside or RaJo adhesive rotator Te in the fixing nip, the In a fixing device having a lubricant-impregnated member impregnated with a lubricant to supply a lubricant between a pressure member and a belt, and a support member that supports the lubricant-impregnated member ,
In the lubricant-impregnated member, the tip side contacting the inner surface of the belt is positioned below the support member so as to supply the lubricant downward, and the void ratio on the tip side of the lubricant-impregnated member is higher than that of the other end side. A fixing device configured to prevent excessive outflow of lubricant from the tip side by utilizing a capillary phenomenon by increasing the size .

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