JP2017096992A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain, with a simple configuration, a pressure contact force between a fixing roller and a pressure roller by predicting a change in hardness of the fixing roller from information on the operation of a fixing part.SOLUTION: An image forming apparatus 100 comprises: mechanism parts (81, 82, 84, and 85) that change the distance between shafts of a fixing roller 41 and a pressure roller 44; a life information acquisition part 92 that acquires life information that is information on an integrated operation state of a fixing part 40; a life/adjustment amount table memory 902 that stores the relationship between the life information and the distance between the shafts when the pressure contact force between the fixing roller 41 and pressure roller 44 is maintained constant; and an inter-shaft distance adjustment motor 110 that drives an eccentric cam 85 to adjust the distance between the shafts to one corresponding to the acquired life information.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an image forming apparatus including a fixing unit that heat-fixes a toner image on a sheet.

  In a fixing unit of an image forming apparatus, in general, a fixing roller and a pressure roller are arranged to face each other directly or in a pressure contact state with a fixing belt interposed therebetween, and a predetermined pressure contact force is applied to a sheet carried into the pressure contact position. Is heated to melt the toner transferred on the paper and fix the melted toner on the paper surface. Accordingly, it is important for the fixing performance to maintain a predetermined pressing force in addition to the fixing temperature. This pressing force is performed using a member that urges the pressure roller toward the fixing roller.

  By the way, since the surface layer portion of the fixing roller is compressed and the outer diameter fluctuates due to the use of pressure contact at a high temperature, it is necessary to adjust the pressure contact force according to the outer diameter fluctuation. Japanese Patent Laid-Open No. 2004-26883 provides a detecting means for detecting a facing distance to the fixing roller at a position facing the fixing roller via the fixing belt, detects a change in the outer diameter of the fixing roller, and detects the rotational position of the eccentric cam. A configuration for adjusting the is described.

JP 2010-204222 A

  By the way, for example, as a material that generates a predetermined pressure contact force, a peripheral surface of a fixing roller is often used with a sponge as a heat insulating material. There is a phenomenon that crushing of the foam cells constituting the sheet proceeds, the density decreases, the hardness gradually decreases, and the surface pressure with the paper decreases. When the surface pressure decreases, the fixing performance indicating the fixing strength and the like decreases, so that the image quality of the printed image decreases. As a result of the change in hardness, the same pressure contact force cannot be obtained even if the pressure roller position is simply adjusted in accordance with the outer diameter change. The configuration of Patent Document 1 is detection of the outer diameter via the fixing belt, and only adjusts the rotational position of the cam in accordance with fluctuations in the outer diameter. As a result, it is difficult to maintain the pressure contact force.

  The present invention has been made in view of the above, and by predicting a change in the hardness of the fixing roller from the operation information of the fixing unit and adjusting the distance between the axes of the fixing roller and the pressure roller, the pressure contact force can be achieved with a simple configuration. An image forming apparatus capable of maintaining the above is provided.

  An image forming apparatus according to the present invention includes an image forming apparatus including a fixing unit that heat-fixes the toner image onto a sheet while passing the sheet on which the toner image is transferred through a pressure contact position between a fixing roller and a pressure roller. The mechanism that changes the inter-axis distance between the fixing roller and the pressure roller, the operation information acquisition unit that acquires the operation information of the fixing unit, and the pressure contact force between the fixing roller and the pressure roller is constant. A storage unit that stores the relationship between the motion information and the inter-axis distance when maintained, and an adjustment drive unit that drives the mechanism unit so as to be the inter-axis distance corresponding to the acquired motion information. It is provided.

  According to the present invention, the inter-axis distance corresponding to the acquired motion information is set in the adjustment drive unit. Therefore, the distance between the axes is adjusted so that the pressure contact force between the fixing roller and the pressure roller is kept constant.

  The fixing roller is provided with a sponge layer on the peripheral surface. According to this configuration, the pressure contact force between the fixing roller and the pressure roller can be maintained constant corresponding to the change in hardness with respect to the progress of crushing of the foamed cells constituting the sponge according to the heat pressure state.

  The mechanism includes a moving mechanism that allows one of a side plate that pivotally supports the fixing roller and a side plate that pivotally supports the pressure roller to move in an increasing / decreasing direction of the inter-axis distance, and the both side plates. An urging member interposed; and an eccentric cam that abuts a part of the moving mechanism portion and changes the distance between the shafts according to the amount of rotation; and the adjustment driving portion rotates the eccentric cam. The motor is connected to a shaft. According to this configuration, since the pressure contact force between the fixing roller and the pressure roller is adjusted via the biasing member, even when sheets having different thicknesses are used, the difference in the paper thickness is absorbed by the biasing force. The

  Further, when a swing shaft provided on one side plate of the both side plates is employed as the moving mechanism portion, the configuration becomes simple.

  Further, the operation information is at least one information of an integrated value of the number of rotations of the fixing roller and an integrated value of the number of sheets passing through the fixing unit. According to this configuration, it is possible to accurately obtain an integrated operation state of the fixing roller.

  The adjustment driving unit may return to an initial position where the pressure contact force is reduced while the operation of the fixing unit is stopped. According to this configuration, stress on the fixing roller is reduced.

  According to the present invention, it is possible to maintain the pressure contact force between the fixing roller and the pressure roller by predicting from the operation information of the fixing unit while having a simple configuration.

1 is a side view illustrating a schematic configuration of an image forming apparatus. FIG. 2 is a block diagram of a portion of the image forming apparatus that mainly relates to fixing. FIG. 7 is a diagram showing the relationship between the number of sheets to be fixed and the distance adjustment between axes, in which the pressure contact force between the fixing roller and the pressure roller is maintained constant, and the contents of the life / adjustment amount table memory. It is side surface sectional drawing which shows the outline of 1st Embodiment of the center distance adjustment part. It is side surface sectional drawing which shows the outline of 2nd Embodiment of the center distance adjustment part. It is side surface sectional drawing which shows the outline of 3rd Embodiment of an interaxial distance adjustment part.

  As shown in FIG. 1, the image forming apparatus 100 includes an image forming unit 10, an intermediate transfer unit 20, a secondary transfer unit 30, a fixing unit 40, a paper feeding unit 50, a paper conveyance path 60, and a reading unit 71. An automatic document feeder 72 is mounted on the upper part of the apparatus main body. The image forming apparatus 100 prints color or monochrome image data read via the reading unit 71 or color or monochrome image data input from an external device (not shown) on a sheet in color or single color.

  The image forming unit 10 includes the light beam scanning unit 1 and image forming units 10 </ b> A to 10 </ b> D for each color having the same structure. The light beam scanning unit 1 includes a semiconductor laser, and reads image data of R, G, and B pixels corresponding to a color document read by the reading unit 71 from black (K), cyan (C), magenta ( M) and yellow (Y) density data, and the surfaces of the photosensitive drums 2A to 2D of the image forming units 10A to 10D are axially irradiated with laser light modulated with a duty ratio corresponding to each density data after the conversion. Exposure scanning is performed along (main scanning direction) to form respective electrostatic latent images. The image forming unit 10A, which is representatively described, includes a photosensitive drum 2A as an image carrier, and includes a charger 3A, a developing unit 4A, and a cleaner unit 5A around the rotation direction (sub-scanning direction). Yes.

  The intermediate transfer unit 20 includes an intermediate transfer belt 21, a driving roller 22, a driven roller 23, and primary transfer rollers 24A to 24D, and receives toner images (developer images) formed on the peripheral surfaces of the photosensitive drums 2A to 2D. Then, primary transfer is performed on the surface of the intermediate transfer belt 21 as an image carrier. The secondary transfer unit 30 secondarily transfers the toner image on the surface of the intermediate transfer belt 21 onto a sheet.

  The fixing unit 40 heat-melts and fixes the toner image transferred to the paper, and discharges it to a paper discharge tray. A more detailed configuration of the fixing unit 40 will be described with reference to FIG. The paper feed unit 50 includes a paper feed cassette 51 and a manual feed tray 52, and feeds the selected paper to the paper transport path 60 from the corresponding paper feed cassette or the like.

  As shown in FIG. 4, the fixing unit 40 includes a fixing roller 41, a heating roller 42 including a lamp heater 421 as a heating source, and an endless fixing belt 43 stretched between the rollers 41 and 42. . The pressure roller 44 is disposed to face the fixing roller 41 with the fixing belt 43 interposed therebetween. The pressure roller 44 is pressed against the fixing roller 41 via the fixing belt 43 by an inter-axis distance adjusting unit 80 (see FIGS. 4 to 6) described later.

  One of the rollers 41 and 42 is rotationally driven by a fixing motor (not shown). As a result, the fixing belt 43 is driven to rotate, and then the pressure roller 44 is driven to rotate.

  Here, an example of the structure of the fixing unit 40 (mainly the fixing roller 41 to the pressure roller 44) will be described with reference to FIG. The fixing roller 41 and the heating roller 42 are pivotally supported on the side plate 40a at both axial ends, and the pressure roller 44 is pivotally supported on the side plate 40b at both axial ends. A more specific structure of the side plates 40a and 40b will be described later.

  In the fixing roller 41, a sponge 412 having a predetermined thickness, for example, several mm, is provided as an elastic layer on the peripheral surface of a core metal 411 made of an alloy such as stainless steel. The sponge 412 is a foamed material formed by kneading a foaming material into a synthetic resin such as silicon sponge rubber, for example, and is a porous soft material with numerous fine pores inside. By providing the sponge 412 around the fixing roller 41, heat insulation is obtained, and the fixing belt 43 and the pressure roller 44 are brought into contact with each other with a predetermined and uniform pressing force in the axial direction. As is well known, the pressure roller 44 has a core metal, an elastic layer such as silicon solid rubber, and a release layer from the center side. In the present embodiment, the fixing belt 43 is made of a resin material such as silicon rubber.

  In this structure, when the paper Pa onto which the toner has been transferred is conveyed from below (upstream in the conveyance direction), the paper Pa is predetermined between the fixing belt 43 and the pressure roller 44 rotated by the fixing motor. It is sent upward (downstream in the conveying direction) while being held by the pressure contact force. During this time, the toner is melted by receiving fixing heat from the lamp heater via the fixing belt 43 and fixed on the paper Pa by a predetermined pressure contact force.

  FIG. 2 is a block diagram mainly showing components related to fixing, and the image forming apparatus 100 includes a control unit 90 configured by, for example, a micro computer. The control unit 90 is connected to an operation unit 101 configured with an input operation from an operator, for example, a touch panel that receives a print command, a fixing roller rotation sensor 401, and a paper sensor 402. The control unit 90 is further connected to a storage unit 901 including an inter-axis distance adjustment motor 110, a life / adjustment amount table memory 902 to be described later, a memory area for storing a control program, and a work area for executing data processing. Yes.

  The fixing roller rotation sensor 401 detects one rotation of the fixing roller, and uses, for example, a known rotary encoder attached to a rotation shaft. The sheet sensor 402 uses an optical sensor or a mechanical switch arranged at the fixing unit 40 in the sheet conveyance path 60 and detects the sheet passing through the fixing unit 40 for each sheet.

  The control unit 90 functions as an image formation processing unit 91, a life information acquisition unit 92, and an inter-axis distance adjustment processing unit 93 by executing a control program. The life information acquisition unit 92 acquires operation information of the fixing unit 40. The operation information is life information such as the number of rotations of the fixing roller 41 and the number of sheets passing through the fixing unit 40. The inter-axis distance adjustment processing unit 93 adjusts the inter-axis distance between the fixing roller 41 and the pressure roller 44, that is, the pressure contact force is maintained constant. The inter-axis distance adjustment motor 110 adjusts the inter-axis distance based on life information of the fixing unit 40, for example, an integrated operation status.

  The image forming processing unit 91 receives a print command from the operation unit 101, thereby causing the image forming unit 10, the intermediate transfer unit 20, the secondary transfer unit 30, the fixing unit 40, the paper feeding unit 50, the paper conveyance path 60, and the reading unit. The operation of each unit 71 is controlled. In the pause period from the end of the printing process until the next print command is input, each unit is in a pause state.

  In the present embodiment, the life information acquisition unit 92 includes a fixing roller rotation number integration unit 921 and a fixing sheet passing number integration unit 922. The fixing roller rotation number accumulating unit 921 is configured to cumulatively acquire the rotation number of the fixing roller 41 from the start of operation after the image forming apparatus 100 is installed, and updately store it in the storage unit 901. The fixing roller rotation number integrating unit 921 acquires the integrated rotation number of the fixing roller 41 from the rotation signal detected by the fixing roller rotation sensor 401. Note that the fixing roller rotation number integrating unit 921 counts, for example, rotation driving pulses using the rotation driving signal output to the fixing motor that rotates the fixing roller 41, and replaces the rotation driving pulse with the rotation number of the fixing roller 41. May be integrated.

  The fixing sheet passing number integrating unit 922 receives the signal detected by the sheet sensor 402 and calculates an integrated value of sheets that have passed through the fixing unit 40. Note that the fixing sheet passing number integrating unit 922 may simply count the number of sheets fed when a print job is executed.

  FIG. 3 shows the relationship between the operation state of the fixing unit and the inter-axis distance in which the pressure contact force between the fixing roller 41 and the pressure roller 44 is maintained constant. As the operation status information of the fixing unit 40, at least one of the integrated value of the rotation speed of the fixing roller 41 and the integrated value of the number of sheets to be fixed is used. Note that since the integrated value of the rotation speed and the integrated value of the number of sheets to be fixed have a high correlation, only one of the information may be applied, or both may be applied based on the correlation.

  The fixing roller 41 gradually decreases in hardness as the rotational speed increases. This is because the sponge 412 provided on the peripheral surface of the fixing roller 41 is rotationally driven while being pressed and deformed by the opposing pressure roller 44, so that the foamed cells constituting the sponge 412 are crushed and the hardness gradually increases. By lowering.

  The hardness of the sponge 412 has a strong decreasing gradient until the initial operation state, for example, the number of sheets to be fixed is about 10K (10,000 sheets), and then the outer diameter is reduced by continuing to receive the pressure contact force. As the hardness increases and approaches saturation, it tends to stabilize asymptotically. Therefore, in FIG. 3, the distance between the axes is greatly reduced from the initial value (initial distance between the axes) according to the increase in the number of sheets passing through the fixing in the initial stage, and the degree of reduction is lowered from the middle. After that, it is constantly stable.

  The life / adjustment amount table memory 902 may store the adjustment amount for each predetermined number of sheets to be fixed, in the form of the chart of FIG. 3, or the accumulated rotation speed obtained from a test, experiment, experience, or the like A regression line (curve) equation may be created and stored in advance based on the relationship between the number of sheets and the number of sheets to be fixed. Here, the adjustment amount may be a change from the initial value, or may be treated as an inter-axis distance value itself. Each time a print command is input, the distance between the axes may be obtained from a table or using a regression equation and output to the distance adjustment motor 110. Alternatively, every time the number of sheets to be fixed reaches a predetermined number or increases by a predetermined number, the inter-axis distance is obtained from the table or using a regression equation and output to the inter-axis distance adjustment motor 110. Also good. By adopting the life / adjustment amount table memory 902, the means for detecting the outer diameter variation of the fixing roller 41 can be omitted, and the configuration is simplified correspondingly.

  Next, the inter-axis distance adjusting unit 80 according to the first embodiment shown in FIG. 4 adjusts the inter-axis distance from the fixing roller 41 by moving the pressure roller 44 using the urging force of the urging member. By doing so, the pressure contact force is maintained.

  The inter-shaft distance adjusting unit 80 is provided around the side plate 40a for supporting the fixing roller 41, the side plate 40b for supporting the pressure roller 44, and the side plate around the swing shaft 81 at an appropriate position on the lower side, which is provided therebetween and supports the side plate 40b. The distance between the axes is adjusted in the increasing / decreasing direction by rotating 40b. The inter-axis distance adjusting unit 80 includes a spring 82 as an urging member interposed between the side plate 40a and the side plate 40b, and both ends thereof are locked to locking portions 83a and 83b at appropriate positions on the upper side of the side plates 40a and 40b. Has been. The locking portion 83a is attached to the distal end portion of the swing arm 84, and the base end portion of the swing arm 84 is supported by the swing shaft 841 of the side plate 40a. The swing shaft 841 swings the swing arm 84 in the direction in which the spring 82 expands and contracts. The eccentric cam 85 is connected to the output shaft of the inter-shaft distance adjusting motor 110 via the rotation shaft 851 so as to be in a position where it comes into contact with the right side surface of the locking portion 83a. The inter-axis distance adjustment motor 110 is attached to the side plate 40a.

  With this configuration, the eccentric cam 85 presses the locking portion 83a against the urging force of the spring 82 in the counterclockwise direction in the example of FIG. The expansion and contraction of the spring 82 changes depending on the rotational position of the eccentric cam 85, and the side plate 40b rotates around the swing shaft 81, and the inter-shaft distance is adjusted so that the pressure contact force is maintained.

  The rotational position of the eccentric cam 85 can be controlled by previously storing the axial distance and rotational position information (rotation amount of the inter-axis distance adjusting motor 110) in the storage unit 901 in association with each other. The life / adjustment amount table memory 902 may store the life and rotation position information (the rotation amount of the inter-axis distance adjustment motor 110) in association with each other. The rotation control of the inter-axis distance adjusting motor 110 can be performed by simply counting the motor driving pulse signal or detecting the rotation amount using a known rotary encoder or the like.

  Next, the inter-axis distance adjusting unit 180 according to the second embodiment shown in FIG. 5 moves the pressure roller 44 by using the urging force of the urging member, so that the inter-axis distance from the fixing roller 41 is increased. The pressure contact force is maintained by adjusting. Hereinafter, the points different from FIG. 4 will be mainly described.

  The inter-axis distance adjusting unit 180 adjusts the inter-axis distance in the increasing / decreasing direction by rotating the side plate 40b around the swing shaft 181. The inter-axis distance adjusting unit 180 includes a spring 182 and both ends thereof are locked to the locking portions 183a and 183b of the side plates 40a and 40b. The locking portion 183a is attached to one end (right end side in FIG. 5) of the plate-like slider 186. The slider 186 is slidable in the extending / contracting direction of the spring 182. That is, the slider 186 has a long hole 1861 that is elongated in the direction of expansion and contraction of the spring 182 at an appropriate place in the plate shape. On the other hand, two pins 187 spaced apart in the left-right direction are formed on the side surface of the side plate 40a. Is erected. Then, the long hole 1861 is fitted to the two pins 187 so that the slider 186 can slide in the left-right direction. The eccentric cam 185 is connected to the output shaft of the inter-shaft distance adjusting motor 110 via the rotation shaft 1851 so as to be in a position where it comes into contact with the right end surface of the slider 186. The inter-axis distance adjustment motor 110 is attached to the side plate 40a.

  With this configuration, the eccentric cam 185 presses the slider 186 toward the left in the example of FIG. 5 against the urging force of the spring 182. The expansion and contraction of the spring 182 changes depending on the rotational position of the eccentric cam 185, and the side plate 40b rotates around the swing shaft 181 so that the inter-axis distance is adjusted so that the pressure contact force is maintained. The control of the rotational position of the eccentric cam 185 is the same as described in FIG. In the slide method, the relationship between the rotational position of the eccentric cam 185 and the slide amount is easy to understand. Further, as shown in FIGS. 4 and 5, since the inter-axis distance is adjusted via the spring (biasing member), the difference in the paper thickness of the paper to be passed is absorbed.

  Next, the inter-axis distance adjusting unit 280 according to the third embodiment shown in FIG. 6 maintains the press contact force by moving the pressure roller 44 mechanically and adjusting the inter-axis distance with the fixing roller 41. It is something to be made. Hereinafter, points different from FIGS. 4 and 5 will be mainly described.

  The inter-axis distance adjusting unit 280 has a side plate 2801 fixedly provided on the opposite side (right side in FIG. 6) of the side plate 40a with the side plate 40b interposed therebetween, and the spring 282 is interposed between the side plate 40b and the side plate 2801. . Both ends of the spring 282 are locked to the locking portion 283b and the locking portion 283c. Therefore, the spring 282 urges the side plate 40b in the separating direction that increases the distance between the axes. The eccentric cam 285 is connected to the output shaft of the inter-shaft distance adjusting motor 110 via the rotation shaft 2851 so as to be in a position where it comes into contact with the right end surface of the side plate 40b. The inter-axis distance adjusting motor 110 is attached to the side plate 2801.

  With this configuration, the eccentric cam 285 presses the side plate 40 b in the left direction in the example of FIG. 6 against the urging force of the spring 282. The side plate 40b rotates around the swing shaft 181 depending on the rotational position of the eccentric cam 285, and the inter-axis distance is adjusted so that the pressure contact force is maintained. The control of the rotational position of the eccentric cam 185 is the same as described in FIG. Since the eccentric cam 285 directly sets the movement amount of the side plate 40b, that is, the inter-axis distance, the configuration is simplified.

  Note that the fixing roller 41 and the pressure roller 44 may be always in a pressure contact state, but the control unit 90 returns to the non-pressure contact position or the low pressure contact position during standby to relax the pressure contact state (FIG. 4). In FIG. 5, the eccentric cams 85 and 185 are brought into contact with each other at the minimum eccentric position to loosen the pressure contact force), and each time a print job is received, adjustment and setting to a position corresponding to the life information can reduce stress. preferable.

  In the above embodiment, the fixing unit 40 using the fixing belt 43 has been described. However, the present invention can also be applied to a mode in which the fixing roller 41 and the pressure roller 44 are in direct pressure contact without using the fixing belt. In this case, an urging member that applies a pressure contact force between both rollers may be provided on the fixing roller 41 side.

  In the above-described embodiment, the side plate 40b is swung around the swing shaft 81. Instead, a mechanism is provided that includes a slide guide mechanism that allows the side plate 40b to move toward and away from the side plate 40a. It is good.

  In the embodiment shown in FIGS. 4 and 5, the side plate 40b is moved by the biasing member interposed between the side plate 40a. For example, the side plate 40c is provided between the side plates 40a and 40b, and is installed on the side plate 40a. It is good also as a structure which gives the member of the center distance adjustment part 80 to the side plate 40c. In this case, there is no need to change the structure on the fixing roller 41 side.

  In addition, the description of the above-described embodiment is an example in all respects, and should be considered not restrictive. The scope of the present invention is shown not by the above embodiments but by the claims. Furthermore, the scope of the present invention is intended to include all modifications within the meaning and scope equivalent to the scope of the claims.

DESCRIPTION OF SYMBOLS 100 Image forming apparatus 40 Fixing part 41 Fixing roller 412 Sponge 44 Pressure roller 80 Center distance adjustment part 81 Oscillation shaft (moving mechanism part)
82 Spring (biasing member)
85 Eccentric cam 92 Life information acquisition unit (motion information acquisition unit)
921 Fixing roller rotation number integration unit 922 Fixing sheet passing number integration unit 93 Axial distance adjustment processing unit 902 Life / adjustment amount table memory (storage unit)
110 Axial distance adjustment motor (adjustment drive unit, motor)

Claims (6)

An image forming apparatus including a fixing unit that heat-fixes the toner image on a sheet while passing the sheet on which the toner image is transferred through a pressure contact position between a fixing roller and a pressure roller.
A mechanism for changing an inter-axis distance between the fixing roller and the pressure roller;
An operation information acquisition unit for acquiring operation information of the fixing unit;
A storage unit that stores the relationship between the operation information and the inter-axis distance when the pressure contact force between the fixing roller and the pressure roller is maintained constant;
An image forming apparatus comprising: an adjustment driving unit that drives the mechanism unit so that the inter-axis distance corresponding to the acquired operation information is obtained. The image forming apparatus according to claim 1, wherein the fixing roller is provided with a sponge layer on a peripheral surface. The mechanism includes a moving mechanism that allows one of a side plate that pivotally supports the fixing roller and a side plate that pivotally supports the pressure roller to move in an increasing / decreasing direction of the inter-axis distance, and an intervening space between the both side plates. An urging member, and an eccentric cam that contacts a part of the moving mechanism and changes the distance between the shafts according to the amount of rotation,
The image forming apparatus according to claim 1, wherein the adjustment driving unit is a motor connected to a rotation shaft of the eccentric cam. The image forming apparatus according to claim 1, wherein the moving mechanism portion is a swing shaft provided on one side plate of the both side plates. 5. The image formation according to claim 1, wherein the operation information is at least one of an integrated value of the number of rotations of the fixing roller and an integrated value of the number of sheets passing through the fixing unit. apparatus. The image forming apparatus according to claim 1, wherein the adjustment driving unit returns to an initial position where the pressure contact force is reduced while the operation of the fixing unit is paused.

Images