JP2007271917A - Fixing apparatus and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing apparatus maintaining high image quality by setting an optimal fixing condition according to the type of paper, improving durability by preventing occurrence of permanent deformation in a fixing roller and a pressurizing roller due to excessive pressurizing force and furthermore downsizing a pressurizing means and reducing the total height. <P>SOLUTION: The fixing apparatus is provided with a heating rotating body which is heated by a heat source and a pressurizing rotating body which is brought into a pressurized contact with the heating rotating body. Fixing is carried out by holding and transporting a recording medium carrying an unfixed image at a fixing nip part formed by the heating rotating body and the pressurizing rotating body. The fixing apparatus is provided with: a pressurizing means to apply pressure to bring the pressurizing rotating body into a pressurized contact with the heating rotating body by energizing a rocking member which supports the pressurizing rotating body to be freely rotated and which can be rocked; and a pressure varying means rocking the rocking member by a cam with a plurality of cam surfaces and a driving means rotating the cam and having the pressurizing rotating body selectively apply a specified pressure to the heating rotating body. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an unfixed toner image formed on a transfer material, mounted on an image forming apparatus such as a copying machine, a printer, a facsimile machine, or a multifunction machine having these functions. And a fixing device for fixing an image by applying pressure and heating.

  2. Description of the Related Art Conventionally, a fixing device used in an electrophotographic image forming apparatus such as a copying machine, a printer, a facsimile machine, and a multifunction machine having these functions is in contact with a fixing roller maintained at a predetermined temperature and the fixing roller. A heating roller fixing system that presses and heats a transfer material on which an unfixed toner image is formed is sandwiched and conveyed by a fixing nip formed by a pressure roller from a low-speed machine to a high-speed machine, from a monochrome machine Widely used in color machines.

  Also, a fixing belt is used for the fixing device, the heat capacity is reduced by the fixing belt, and the heat conduction efficiency is greatly improved by bringing the temperature-controlled heater into direct pressure contact with the fixing belt, and power saving and warming up time are almost required. A belt-fixing type fixing device and an image forming apparatus designed for quick start are proposed and have been used recently.

  If the fixing roller and the pressure roller are always in pressure contact with each other, there is a problem that the pressure is locally applied to the fixing nip portion where both the rollers are pressed against each other to cause deformation, and the durability of both rollers is reduced. is there. For this reason, when the fixing device is in a non-fixing processing state, a mechanism for releasing the pressure contact between both rollers is employed.

  In the fixing device of the heat roller type proposed in Patent Document 1, the nip pressure application mechanism that urges the pressure roller toward the heating roller cancels the action of the spring when the nip is released, and the pressure roller It has a mechanism which makes it separate from.

  The fixing device of the heat roller type proposed in Patent Document 2 includes a pressure unit that applies pressure to press the pressure roller against the fixing roller, and a pressure applied to the fixing roller against the pressure force of the pressure roller. Pressure release means for releasing the pressure contact state of the pressure roller.

  The heat roller type fixing device proposed in Patent Document 3 includes a pressure unit and a pressure release unit, and the pressure release unit is driven by a drive source that rotationally drives the fixing roller and the pressure roller. The pressure applied to the fixing roller and the pressure roller is released by rocking the rocking member with a cam that is rotationally driven by the means.

The fixing device of the heat roller type proposed in Patent Document 4 has a variable pressing force between the fixing roller and the pressure roller, and simultaneously fixes when the pressing force between the fixing roller and the pressure roller is changed. The pressure contact angle between the roller and the pressure roller is changed.
JP-A-5-173446 JP 11-125985 A JP 2000-122460 A JP 2003-295679 A

  The fixing devices proposed in Patent Documents 1 to 4 press a fixing roller and a pressure roller with a constant pressure by a pressing unit regardless of the type of paper to be fixed. The paper must be set to meet the fixing conditions that require high temperature heating and large pressing force. When such fixing conditions are set, the fixing conditions are excessive for thin paper, causing problems such as curling.

  Further, in the conventional fixing device, since the pressure releasing mechanism is disposed at the lower portion of the fixing device and requires a large space, there is a problem that the overall height of the fixing device is increased and the size is increased.

  The present invention solves the problems of the conventional fixing device as described above, and achieves the following objects.

  1. An object of the present invention is to provide a fixing device that maintains a high-quality image by setting an optimal fixing condition according to the type of paper.

  2. By optimally setting the pressing force of the fixing roller and pressure roller, even if both rollers have elastic layers, it is possible to prevent permanent deformation due to excessive pressing force and improve durability. Objective.

  3. The purpose is to reduce the overall height of the fixing device by reducing the size of the fixing release mechanism of the fixing device.

The above object can be achieved by the following solutions.
1. A heating rotator that is heated by a heating source and a pressure rotator that is in pressure contact with the heating rotator. In a fixing device that clamps and conveys a recording medium to be fixed and urges a swingable swinging member that rotatably supports the pressure rotator, and presses the pressure rotator against the heating rotator. And a drive means for rotating the cam to pressurize the pressurizing rotating body to the heating rotating body. And a pressurizing variable means for selectively giving to the pressure of the fixing device.
2. 2. An image forming apparatus comprising the fixing device according to 1 above, wherein the toner image formed on the image carrier is transferred to a transfer material, and the toner image is fixed to the transfer material.

  The image forming apparatus of the present invention can obtain the following effects by the configuration described above.

  1. By setting optimum fixing conditions according to the type of paper, it is possible to maintain a high-quality image.

  2. By optimally setting the pressing force of the fixing roller and the pressure roller, even if both rollers have an elastic layer, permanent deformation is prevented by excessive pressing force, and durability is improved.

  3. The press release mechanism of the fixing device can be downsized, and the overall height of the fixing device can be reduced.

  Embodiments of the present invention will be described below.

[Image forming apparatus]
FIG. 1 is a configuration diagram of an image forming apparatus including an image forming apparatus main body A and an automatic document feeder DF.

  The image forming apparatus main body A includes an image forming unit 1, a fixing device 10, and a paper conveyance system. The image forming unit 1 includes a charging unit 3, an image exposure unit 4, a developing device 5, a transfer unit 6, a charge removing unit 7 </ b> A, a separation claw 7 </ b> B, a cleaning unit 8, and the like disposed around the image carrier 2. .

  The paper transport system includes a first transport unit including a paper feed cassette 20, a first paper feed unit 21, a second paper feed unit 22, a transport unit 23, a paper discharge unit 24, and a manual paper feed unit 25; It is composed of a circulation refeeding section that circulates and refeeds paper.

  The paper feed cassette 20 and the first paper feed means 21 are formed by a plurality of paper feed means (three stages in the figure), and accommodate and feed paper of various sizes.

  The document d placed on the document table of the automatic document feeder DF is conveyed by the paper feeding means 26, and the document image is read by the image reading device.

  In the image forming unit 1, processes such as charging, exposure, development, transfer, separation, and cleaning are performed. An image is transferred to the paper S fed from the paper feed cassette 20 and the manual paper feed means 25 by the transfer means 6. The sheet S carrying the image is fixed by the fixing device 10 and discharged from the paper discharge unit 24.

[Fixing device]
FIG. 2 is a cross-sectional view showing an embodiment of the heating roller type fixing device 10.

  The fixing device 10 includes a fixing roller (heating rotator) 11 heated by a heating source 13, a pressure roller (pressure rotator) 12 heated by a heating source 14, and the like.

  Around the fixing roller 11, a cleaning unit 18, a temperature sensor TS 1, a thermostat for preventing an abnormal temperature (not shown), and the like are arranged. A temperature sensor TS2, a thermostat for preventing abnormal temperature, and the like are also disposed around the pressure roller 12.

  As the heating sources 13 and 14, a halogen lamp, induction heating means, or the like is used.

  The fixing roller 11 includes a heat conductive substrate (core metal) 111, an elastic layer 112, a covering layer 113, and the like.

  The temperature sensor TS <b> 1 detects the surface temperature of the fixing roller 11. The control means controls the surface temperature of the fixing roller 11 to a predetermined temperature based on the detection signal of the temperature sensor TS1.

  When the sheet S is introduced into the fixing nip N where the fixing roller 11 and the pressure roller 12 are in pressure contact, the heat of the fixing roller 11 heated by the heating source 13 is applied to the sheet S, and the toner image on the sheet S is applied. t is fixed by heating.

  The fixing roller 11 is a cylindrical member having an outer diameter of 20 to 70 mm. As the cylindrical heat conductive substrate 111, an aluminum material having good heat conductivity is mainly used, and a nonmagnetic stainless steel material, heat resistant glass, or the like is also used. The heat conductive substrate 111 has a required mechanical strength and a thickness (wall thickness) of 0.8 to 10 mm.

  The elastic layer 112 is made of synthetic rubber such as silicone rubber or fluorine rubber, for example. Further, in order to cope with speeding up of image formation, a method of improving thermal conductivity by blending 5-30% by mass of a metal oxide powder such as silica, alumina, magnesium oxide or the like as a filler in the synthetic rubber is preferable. . The mixed filler is preferably a highly conductive one like the conductive carbon black. By doing in this way, the electrical resistance (volume resistivity) of the elastic layer 112 can be easily set low. The elastic layer 112 has a thickness (wall thickness) of 0.3 to 3 mm, preferably 1 to 3 mm, and a JIS-A rubber hardness of 5 Hs to 30 Hs.

  In order to improve the releasability from the toner on the outside (outer peripheral surface) of the elastic layer 112, a 20 to 80 μm thick PFA (fluororesin) tube or a fluororesin (PFA or PTFE) paint is used. A heat-resistant coating layer 113 having a good thermal conductivity and a heat-resistant coating layer 113 is provided which is applied with 20 to 100 μm, or formed with silicone rubber or fluororubber having a layer thickness of 20 to 500 μm. The covering layer 113 improves the releasability with the toner and enhances the durability of the elastic layer 112.

  The lower cylindrical pressure roller 12 that forms a pair with the fixing roller 11 is a cylindrical member, and includes a heat conductive base 121, an elastic layer 122, and a coating layer 123. The constituent members of the pressure roller 12 are formed with substantially the same material and characteristics as the constituent members of the fixing roller 11.

  For example, a thermally conductive substrate 121 using STKM having a thickness of 1 to 3 mm, and a sponge-like thickness using, for example, a silicone rubber layer, a fluorine rubber layer, or a foamed material of silicone rubber on the outer peripheral surface of the thermally conductive substrate 121. (Thickness) A roller having an outer diameter of about 30 to 700 mm formed by an elastic layer 122 made of a thick rubber layer having a thickness of 0.3 to 5 mm and a rubber hardness of 30 Hs to 70 Hs (JIS-A rubber hardness). Is done. On the outer side (outer peripheral surface) of the elastic layer 122, a coating layer 123 is formed that covers a tube of heat-resistant fluororesin such as PFA or PTFA having releasability.

  A flat fixing nip between an upper fixing roller 11 rotatably supported at a fixed position and a lower pressing roller 12 pressed against the fixing roller 11 by a spring biased pressing means 15. The portion N is formed and the toner image t is fixed.

  The pressurizing means 15 has a swingable swinging member 151 and a support shaft 152 that engages with one end of the swinging member 151 and supports the swinging member 151 swingably.

  At the other end of the oscillating member 151, a pressurizing variable means 16 including a spring 161, a movable member 162, a bearing 163, a cam 164, and a cam shaft 165 is disposed. The outer peripheral surface of the cam 164 is in contact with a movable member 162 that rotatably supports the bearing 163. The spring 161 supported by the movable member 162 presses the other end of the swing member 151 and swings the swing member 151 about the support shaft 152. The swing member 151 pushes up the pressure roller 12 via the bearing 153 and presses the pressure roller 12 against the fixing roller 11 to form a fixing nip portion N.

  The sheet S that has passed through the fixing nip N of the fixing device 10 is separated from the outer peripheral surface of the fixing roller 11 by the separation claws 17A and 17B, and is nipped by a conveyance roller (not shown) and conveyed outside the apparatus.

  The cleaning means 18 disposed around the fixing roller 11 winds the cleaning web 181 that contacts and cleans the fixing roller 11, the cleaning roller 182 that rotates by pressing the cleaning web 181 against the fixing roller 11, and the cleaning web 181. The web former winding shaft 184 to be accommodated, the web winding shaft 183 for winding the cleaning web 181, driving means (not shown) for driving and rotating the web winding shaft 183, and the like.

  FIG. 3 is a cross-sectional view of a fixing device of a fixing belt type. Note that the same reference numerals as those in FIG. 2 are given to the pressure roller 12, the heating source 14, the pressure means 15, and the pressure variable means 16 having the same functions as those in FIG. Omitted. Further, differences from FIG. 2 will be described.

  The fixing device 30 includes a fixing support roller 32 disposed inside a fixing belt (heating rotator) 31, a heating roller 33, a heating source 34, a cleaning unit 40 disposed outside the fixing belt 31, and the like. .

  The fixing belt 31 is composed of an endless belt member, and is wound around the outer periphery of the fixing support roller 32 and the heating roller 33.

  The fixing support roller 32 faces the pressure roller 12 and supports the fixing belt 31 on one of the inner peripheral surfaces of the fixing belt 31.

  The heating roller 33 supports the fixing belt 31 on the other inner peripheral surface of the fixing belt 31. Inside the heating roller 33, a heating source 34 as a heating element is disposed.

  The surface temperature of the fixing belt 31 is detected by the temperature sensor TS1, and is maintained at a predetermined temperature by a control unit (not shown). The surface temperature of the pressure roller 12 is detected by the temperature sensor TS2, and is maintained at a predetermined temperature by a control means (not shown).

  The fixing support roller 32 is rotatably arranged at a fixed position, and the heating roller 33 is elastically biased in a direction away from the fixing support roller 32 by a pressing means such as a spring (not shown). As a result, the fixing belt 31 is stretched with an appropriate pressure.

  A driving means (not shown) rotates the fixing support roller 32 and rotates the fixing belt 31 in a driven manner. Alternatively, the driving unit may rotationally drive the pressure roller 12, convey the fixing belt 21 by the pressure roller 12, and rotate the fixing belt 21 in a driven manner. Further, driving may be input to both the fixing support roller 32 and the pressure roller 12.

  A fixing nip portion N is formed between the fixing support roller 32 and the pressure roller 12 with the fixing belt 31 heated by the heating roller 33 interposed therebetween. The fixing device 30 fixes the single color toner image or the multicolor toner image on the paper S through the fixing nip portion N by heating and pressing.

  The cleaning means 40 for cleaning the fixing belt 31 includes a cleaning roller 41, a cleaning web 42, a web former winding shaft 43, a web winding shaft 44, an intermediate roller 45, and the like. The cleaning web 42 is taken up by a driving means (not shown). It is done.

  FIG. 4 is a cross-sectional view in the cam shaft direction of the pressure varying means 16 of the fixing device 10.

  The cam shaft 165 penetrates from the front side F to the back side R of the fixing device 10 and is rotatably supported by two bearings 166F and 166R disposed in the fixing device 10. On the front side F of the cam shaft 165, the pressure varying means 16F is arranged on the rear side R, and the pressure varying means 16R is arranged on the rear side R. Since the pressurizing variable means 16F and the pressurizing variable means 16R have the same configuration, the components are given the same reference numerals.

  Two cams 164 and two bearings 163 that come into contact with the two cams 164 are arranged in the pressurizing variable means 16F. The two bearings 163 are rotatably supported on both side surfaces of the movable member 162. The spring 161 held by the movable member 162 pushes up the swinging member 151.

  Similarly, two cams 164, two bearings 163, a movable member 162, and a spring 161 are arranged in the pressurizing variable means 16R.

  Therefore, since the swing member 151 is supported and swings by the four cams 164 fixed to the cam shaft 165, the load applied to one cam 164 can be reduced. Further, since the cam 164 can have a small diameter, the overall height of the fixing device 10 can be reduced and the size can be reduced.

  FIG. 5 is a cross-sectional view taken along the line AA of the fixing device 10 shown in FIG. 4 and shows a driving means for the cam shaft 165.

  By driving rotation of the motor M, the motor M rotates the cam shaft 165 via a reduction gear train composed of a worm gear G1 fixed to the rotation shaft of the motor M and a plurality of spur gears G2 to G9.

  6 is a BB cross-sectional view of the fixing device 10 shown in FIG.

  The pressurizing variable means 16F pushes up the bearing 163 and pushes up the movable member 162 supporting the bearing 163 by the cam 164 fixed to the cam shaft 165 driven and rotated by the motor M. When the spring 161 held by the movable member 162 pushes up one end of the swinging member 151, the swinging member 151 swings around the support shaft 152.

  FIG. 7 is an enlarged front view of the cam 164 and related members.

  The cam 164 has four planar portions and curved surface portions. The first surface portion 164A is a position at a distance L1 from the center of the cam shaft 165. The second surface portion 164B is a position at a distance L2 from the center of the cam shaft 165. The third surface portion 164C is a position at a distance L3 from the center of the cam shaft 165. The fourth surface portion 164D is a position at a distance L4 from the center of the cam shaft 165. These distances are set to L1 <L2 <L3 <L4.

  Stop positions of the first surface portion 164A, the second surface portion 164B, the third surface portion 164C, and the fourth surface portion 164D of the cam 164 due to the rotation of the cam shaft 165 are detected by the position detection means PS shown in FIG.

  FIG. 8 is a sectional view showing the rotation process of the cam 164 and the swinging process of the swinging member 151.

  FIG. 8A is a cross-sectional view taken along the line AA in a state where the pressure roller 12 is separated from the fixing roller 11.

  When the cam shaft 165 is rotated and the bearing 163 comes into contact with the first surface portion 164A, the outer peripheral surface of the bearing 163 and the center of the cam shaft 165 become the minimum distance L1, and the biasing force of the spring 161 becomes the minimum value. The swinging member 151 is swung about the support shaft 152 to the lower first position, and the pressure roller 12 is separated from the fixing roller 11.

  FIG. 8B is a cross-sectional view taken along the line B-B in a state where the cam shaft 165 is rotated and the bearing 163 is in contact with the second surface portion 164B.

  When the cam shaft 165 is rotated and the bearing 163 comes into contact with the second surface portion 164B, the outer peripheral surface of the bearing 163 and the center of the cam shaft 165 become a distance L2, and the swing member 151 is centered on the support shaft 152. It is swung and lifted from the first position and stopped at the second position, and the pressure roller 12 is lightly pressed against the fixing roller 11 to form the fixing nip portion N1.

  FIG. 8C is a cross-sectional view taken along the line C-C in a state where the cam shaft 165 is rotated and the bearing 163 is in contact with the third surface portion 164C.

  When the cam shaft 165 is further rotated and the bearing 163 comes into contact with the third surface portion 164C, the outer peripheral surface of the bearing 163 and the center of the cam shaft 165 become a distance L3, and the swing member 151 is centered on the support shaft 152. The pressure roller 12 is pressed against the fixing roller 11 to form a fixing nip portion N2.

  FIG. 8D is a DD cross-sectional view in a state where the cam shaft 165 is rotated and the bearing 163 is in contact with the fourth surface portion 164D.

  When the cam shaft 165 is further rotated and the bearing 163 contacts the fourth surface portion 164D, the outer peripheral surface of the bearing 163 and the center of the cam shaft 165 become the distance L4, and the biasing force of the spring 161 becomes the maximum value, The moving member 151 is swung about the support shaft 152 and further lifted from the third position and stopped at the fourth position, and the pressure roller 12 is most strongly pressed against the fixing roller 11 to thereby fix the fixing nip portion N3. Form.

  Table 1 shows the fixing nip portion and the paper type conditions at the cam 164 position.

  When the paper type of the paper S is selected and set in the operation unit 9 of the image forming apparatus main body A, the cam 164 moves the swing member 151 at any of the cam positions of the second surface portion 164B, the third surface portion 164C, and the fourth surface portion 164D. By pressing, a fixing nip width is formed in the fixing nip portions N1, N2, and N3, and a fixing load is applied. Alternatively, the first surface portion 164 </ b> A separates the pressure roller 12 from the fixing roller 11.

  FIG. 9 is a cross-sectional view of adjusting means for adjusting the position of the cam shaft 165.

  Adjusting means 19 for adjusting the axial position of the cam shaft 165 is provided in the vicinity of the pressure varying means 16F on the non-driving side of the cam shaft 165, that is, on the rear side R of the fixing device 10 shown in FIG. The adjusting means 19 moves the support member 192 formed with the inclined surface 191 with which the shaft end portion on the non-drive side of the cam shaft 165 contacts, the holding member 193 holding the support member 192 movably, and the support member 192. An adjustment screw 194 and the like are included.

  By grasping and operating the adjustment screw 194, the support member 192 moves on the holding member 193 in the horizontal direction, and the cam shaft 165 contacting the inclined surface 191 moves in the vertical direction. By moving the support member 192 using the adjusting screw 194, the inclination of the cam shaft 165 is adjusted, the relative positions of the pressurizing variable means 16F and 16R arranged at both ends of the cam shaft 165, and the pressurizing means 15 The relative positions of the front surface side F and the back surface side R are adjusted so that the pressing force of the fixing nip N formed by the pressure roller 12 and the fixing roller 11 is made uniform.

  In the above-described embodiment, the multicolor image forming apparatus capable of forming a color image is exemplified. However, the present invention is not limited to this. For example, the present invention is also applied to a single color image forming apparatus capable of forming a monochrome image. The fixing device can be applied.

1 is a configuration diagram of an image forming apparatus including an image forming apparatus main body and an automatic document feeder. FIG. 3 is a cross-sectional view showing an embodiment of a fixing device of a heating roller type. FIG. 3 is a cross-sectional view of a fixing device using a fixing belt. Sectional drawing of the cam shaft direction of the pressure variable means of a fixing device. FIG. 5 is a cross-sectional view taken along the line AA of the fixing device illustrated in FIG. 4. FIG. 5 is a cross-sectional view of the fixing device shown in FIG. 4 along BB. The enlarged front view of a cam and related members. Sectional drawing which shows the rotation process of a cam and the rocking | swiveling member. Sectional drawing of the adjustment means which adjusts the position of a cam shaft.

Explanation of symbols

10 Fixing Device 11 Fixing Roller (Heating Rotator)
12 Pressure roller (Pressure rotating body)
15 Pressurizing means 151 Oscillating member 152 Support shaft 16, 16F, 16R Pressurizing variable means 161 Spring 162 Movable member 163 Bearing 164 Cam 164A First surface portion 164B Second surface portion 164C Third surface portion 164D Fourth surface portion 165 Cam shaft 19 Adjustment Means 191 Inclined surface 192 Support member 193 Holding member 194 Adjustment screw 30 Fixing device 31 Fixing belt (heating rotator)
32 Fixing support roller 33 Heating roller A Image forming apparatus main body S Recording medium (paper)
N, N1, N2, N3 Fixing nip part PS Position detection means

Claims (9)

A heating rotator that is heated by a heating source and a pressure rotator that is in pressure contact with the heating rotator, and carries an unfixed image at a fixing nip formed by the heating rotator and the pressure rotator. In a fixing device that clamps and conveys a recording medium to be fixed,
Pressurizing means for biasing a swingable swinging member that rotatably supports the pressurizing rotating body to apply pressure to press the pressurizing rotating body against the heating rotating body;
A pressurizing variable unit that swings the swinging member by a cam having a plurality of cam surfaces and a driving unit that rotates the cam, and selectively applies the pressurizing rotating body to the heating rotating body at a predetermined pressure;
And a fixing device. The fixing device according to claim 1, wherein the cam is fixed to both shaft ends of a rotation shaft that is installed in a width direction orthogonal to the conveyance direction of the recording medium. The fixing device according to claim 1, wherein a plurality of the cams are arranged at both ends of the rotating shaft. The drive means has a motor as a drive source and drive transmission means connected to the motor, and rotationally drives the cam fixed to the rotary shaft connected to the drive transmission means. The fixing device according to any one of claims 1 to 3. 2. The position detecting means is disposed in the vicinity of the rotating shaft to which the cam is fixed, and the rotational phase of the cam is detected to vary the spring bias by the swing member. 5. The fixing device according to any one of 4 above. The fixing device according to claim 1, further comprising an adjusting unit that adjusts a position of the rotating shaft on a non-driving side of the rotating shaft. The fixing device according to claim 1, wherein the heating rotator is a fixing roller having a heating source. The fixing device according to claim 1, wherein the heating rotator is a fixing belt that winds a heating roller having a heating source and a fixing support roller in pressure contact with the pressure rotator. 9. An image comprising the fixing device according to claim 1, wherein the toner image formed on the image carrier is transferred to a transfer material, and the toner image is fixed to the transfer material. Forming equipment.

Images