JP2020129050A - Image forming apparatus - Google Patents

Abstract

To provide an image forming apparatus that can detect a change in state of a cleaning blade and perform stick-slip prevention control according to the detected state of the cleaning blade.SOLUTION: An image forming apparatus comprises: an image carrier; a driving device; a developing device; a cleaning blade; a cooling fan; a torque detection unit; and a control unit. The image carrier has an electrostatic latent image formed on its surface. The driving device drives to rotate the image carrier. The developing device develops the electrostatic latent image formed on the surface of the image carrier into a toner image. The cleaning blade is arranged to contact the surface of the image carrier and cleans the surface of the image carrier. The cooling fan cools the cleaning blade. The torque detection unit detects the torque in driving to rotate the image carrier. The control unit controls the drive of the cooling fan. When the period of variations in torque detected by the torque detection unit is less than a predetermined value, the control unit drives the cooling fan.SELECTED DRAWING: Figure 7

Description

The present invention relates to an image forming apparatus that forms an image on recording paper, and more particularly to an image forming apparatus that includes a cleaning blade that contacts an image carrier on the surface of which a toner image is formed.

In an image forming apparatus such as a printer, a copying machine, a facsimile, or a multifunctional machine having these functions, a photoconductor drum that is an example of an electrophotographic photoconductor, a charging device that charges the surface of the photoconductor drum, and a photoconductor It is known that a cleaning device is provided which is disposed in contact with the surface of a drum and removes toner and external additives remaining on the surface of the photosensitive drum.

As the cleaning device, for example, a device in which an end of a cleaning blade formed of an elastic material such as urethane rubber in a plate shape is pressed against the surface of the photosensitive drum to remove toner and external additives is widely used. Has been done. The cleaning blade also has a role of removing ozone, active substances such as NOx and SOx, and their reaction products, so-called discharge products, which are generated by charging the surface of the photosensitive drum.

The cleaning blade formed of an elastic material is stretched (pulled in) with the rotation of the photoconductor drum, elastically deforms, and vibrates when restored, so-called stick-slip operation is repeated. Here, the frictional force between the photosensitive drum and the cleaning blade changes depending on the surface state (unevenness) of the photosensitive drum. When the frictional force is increased, the stick-slip operation of the cleaning blade is increased, the toner and the external additive cannot be effectively removed, and the edge of the cleaning blade is damaged.

Therefore, a method of controlling cleaning by a cleaning blade according to the surface state of the photosensitive drum has been proposed. For example, in Patent Document 1, a torque measuring unit that measures the driving torque of the image carrier and a torque measuring unit are provided. The torque rise detection unit that detects the presence of a partial torque rise of the drive torque measured by the above, the polishing cleaning means for the surface of the image carrier, and the torque rise detection unit must detect the presence of a partial torque rise. As an example, an image forming apparatus is disclosed that includes a cleaning control unit that causes an abrasive cleaning unit to abrasively clean the surface of an image bearing member.

Further, in Patent Document 2, it is possible to execute a frictional resistance suppressing process of discharging toner from a developing device to an image carrier during non-image formation to suppress a frictional resistance between the cleaning member and the surface of the image carrier. An image forming apparatus is disclosed which adjusts the amount of toner discharged from the developing device to the image carrier side when executing the frictional resistance suppressing process according to the estimation result of the surface state of the carrier. It is also described that the arithmetic mean roughness of the surface of the image carrier is estimated based on the torque detected by the torque detector.

JP, 2009-15179, A JP, 2016-164645, A

Conventionally, since a non-contact charging type charging device such as a scorotron charging type has been widely used, the cleaning blade is mainly intended to remove toner and discharge products on the surface of the photosensitive drum, and with respect to slipping of external additives, It wasn't a problem.

In recent years, the charging method of the charging device has been changed from a non-contact charging method to a contact charging method that produces a small amount of ozone. In the contact charging method, the external additive that has slipped through the cleaning blade adheres to a charging member such as a charging roller to cause charging failure. In particular, since the external additive easily slips through the cleaning blade due to the reduction in the particle size of the toner, the cleaning blade is also required to have a role of blocking the external additive.

In order to enhance the blocking effect of the external additive by the cleaning blade, it is effective to stabilize the edge by adopting a high hardness and low repulsion material as the material of the cleaning blade, instead of sticking the edge. is there. However, elastic deformation of the high hardness and low repulsion material has temperature dependency, and the edge is stable at low temperature, but when the temperature becomes high, the elastic deformation amount increases and the edge performs stick-slip operation. Therefore, slipping of the external additive from the cleaning blade in a high temperature environment has been a problem.

In view of the above problems, it is an object of the present invention to provide an image forming apparatus capable of detecting a state change of a cleaning blade and performing stick-slip suppression control according to the detected state of the cleaning blade. ..

In order to achieve the above object, the first configuration of the present invention is an image including an image carrier, a driving device, a developing device, a cleaning blade, a cooling fan, a torque detection unit, and a control unit. It is a forming device. An electrostatic latent image is formed on the surface of the image carrier. The drive device rotationally drives the image carrier. The developing device develops the electrostatic latent image formed on the surface of the image carrier into a toner image. The cleaning blade is arranged so as to contact the surface of the image carrier, and cleans the surface of the image carrier. The cooling fan cools the cleaning blade. The torque detector detects a torque when the image carrier is driven to rotate. The control unit controls driving of the cooling fan. The control unit drives the cooling fan when the fluctuation cycle of the torque detected by the torque detection unit is less than the predetermined value.

According to the first configuration of the present invention, the change in the repulsion elastic modulus of the cleaning blade due to the temperature change is estimated by the fluctuation cycle of the drive torque of the image carrier, and the cleaning blade is cooled according to the estimation result. It is possible to prevent the external additive from slipping through the pressure contact portion between the member and the image carrier, and to reduce the frictional force between the cleaning member and the image carrier. As a result, the image carrier can be stably cleaned over a long period of time. Further, since the state of the cleaning blade can be estimated more accurately than the method in which the temperature inside the machine is detected to perform cooling, appropriate cooling control can be performed. Further, since the cooling fan is driven only when necessary, toner scattering can be suppressed.

A schematic sectional view showing a schematic configuration of a tandem type color printer as an image forming apparatus 11 according to an embodiment of the present invention. The figure which shows the schematic structure of the principal part including the image forming part 15 of the image forming apparatus 11. Block diagram showing a control path of the image forming apparatus 11 A graph showing the relationship between the environmental temperature of the cleaning blade 42 used in the image forming apparatus 11 and the impact resilience. A graph showing the fluctuation cycle of the torque of the drive motor 48 when the temperature of the cleaning blade 42 is 25°C. A graph showing the fluctuation cycle of the torque of the drive motor 48 when the temperature of the cleaning blade 42 is 40°C. Flowchart showing an example of blade cooling control in the image forming apparatus 11 of the present embodiment.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic sectional view showing a schematic configuration of an image forming apparatus 11 according to an embodiment of the present invention. FIG. 2 is a diagram showing a schematic configuration of a main part including the image forming unit 15 of the image forming apparatus 11 shown in FIG.

As shown in FIG. 1, the image forming apparatus 11 according to this embodiment is a tandem type color printer. The image forming apparatus 11 includes, inside the printer body 12, a paper feed cassette 13 that stores recording paper (not shown), a paper feed unit 14 that feeds the recording papers one by one from the paper feed cassette 13, and a paper feed unit 14. An image forming unit 15 that performs an image forming process on recording paper supplied from the paper cassette 13 or a manual feed tray (not shown), and a recording paper conveyance path that conveys the recording paper supplied from the paper feed cassette 13 or the manual feed tray. 16, a secondary transfer unit 17 that transfers the toner image formed in the image forming unit 15 to a recording sheet that is conveyed along the recording sheet conveyance path 16, and a toner image that is transferred in the secondary transfer unit 17 is recorded. And a fixing unit 18 for fixing to paper.

The image forming unit 15 employs, for example, a tandem system in which an image forming process is performed using four color toners (developer) of yellow (Y), magenta (M), cyan (C), and black (K). There is. In addition, in the following description, only when the color is specifically designated, the reference numeral of each arithmetic numeral is given in parentheses with a color of (Y, M, C, K). Description will be given with reference numerals.

The image forming unit 15 corresponds to each color (Y, M, C, K) and a plurality of toner containers 19 containing replenishment toner and print data (image data) transmitted from an externally connected device such as a personal computer. ), a plurality of photoconductor drums 20 for forming toner images of respective colors, a plurality of developing devices 21 for supplying toner to the photoconductor drums 20, and a toner image formed on the photoconductor drums 20. The endless intermediate transfer belt 22 that is primarily transferred, and the residual toner that is disposed on the upstream side of the photoconductor drum 20 on the most upstream side in the rotational movement direction of the intermediate transfer belt 22 and adheres to the surface of the intermediate transfer belt 22 are removed. A belt cleaning device 24 for removing and an exposure unit 25 for emitting a beam of light to each photoconductor drum 20 are provided.

The photoconductor drum 20 has a photosensitive layer formed on the surface of a support (base). Here, the photoconductor drum 20 is composed of a cylindrical metal tube and a photosensitive layer formed on the surface of the tube. Aluminum, iron, titanium, magnesium, etc. are mentioned as a metal which forms a shell. As the photosensitive layer, an organic photosensitive layer using an organic photoconductor or an inorganic photosensitive layer using an inorganic photoconductor can be used, but amorphous silicon photosensitive film formed by vapor deposition of silane gas etc. due to its high durability. Layers are preferred. Each of the photoconductor drums 20 carries a toner image of each color on the surface thereof based on the light beam emitted from the exposure unit 25, and transfers the toner image to the intermediate transfer belt 22, as shown in FIG. Thus, it is arranged below the intermediate transfer belt 22 together with the developing device 21.

Further, as shown in FIGS. 1 and 2, a charging roller (charging member) 26, an exposure unit 25, a developing device 21, a cleaning device 28, and a charge removing device 29 are arranged around the photosensitive drum 20, and an intermediate portion is provided. A primary transfer roller 27 is arranged to face the photoconductor drum 20 with the transfer belt 22 interposed therebetween.

The toner image transferred onto the intermediate transfer belt 22 at each primary transfer portion configured by the photoconductor drum 20 and the primary transfer roller 27 is transported from the paper feed cassette 13 or the manual feed tray through the recording paper transport path 16. The secondary transfer unit 17 transfers the received recording paper.

The developing devices 21 having basically the same configuration are arranged below the intermediate transfer belt 22 along the rotational movement direction. The developing device 21 is a two-component developer including a developer container 31 that stores a two-component developer (hereinafter, also simply referred to as a developer), two stirring screws 32 a and 32 b, a magnetic roller 34, and a developing roller 35. It is a developing type, a thin toner layer is formed on the developing roller 35 by using a magnetic brush standing upright on the surface of the magnetic roller 34, and a developing bias having the same polarity (positive) as the toner is applied to the developing roller 35 to form a photosensitive drum. Toner is ejected onto the surface of 20. As a result, the electrostatic latent image on the surface of the photoconductor drum 20 is developed into a toner image.

The developing device 21 can supply (discharge) the toner on the developing roller 35 to the photoconductor drum 20 side during non-image formation. This makes it possible to supply toner to the periphery of the edge of the cleaning blade 42 for the purpose of reducing the frictional force between the photosensitive drum 20 and the cleaning blade 42 and preventing the external additive from slipping through. The toner is supplied after printing a predetermined number of sheets (for example, 100 sheets). The toner supplied to the photoconductor drum 20 side is removed by the cleaning blade 42 of the cleaning device 28. The toner contains a toner external additive (abrasive particles) made of metal particles such as titanium oxide.

The developing container 31 is partitioned by a partition wall 31a, and the first stirring chamber 31b and the second stirring chamber 31c are provided with a first stirring screw 32a and a second stirring screw 32b. The first stirring screw 32a and the second stirring screw 32b mix the toner (positively-charged toner) supplied from the toner container 19 with the carrier, stir the mixture, and charge the mixture. The developer in the first stirring chamber 31b and the second stirring chamber 31c is conveyed in the axial direction while being stirred by the first stirring screw 32a and the second stirring screw 32b, and the first stirring chamber 31b and the second stirring chamber 31b are conveyed. It circulates between 31c.

A magnetic roller 34 is arranged in the developing container 31 at a position facing the second stirring screw 32b, and a developing roller 35 is arranged on the opposite side of the second stirring screw 32b with the magnetic roller 34 in between. The developing roller 35 faces the photoconductor drum 20.

The magnetic roller 34 is composed of a non-magnetic rotating sleeve 36 and a fixed magnet body 37 having a plurality of magnetic poles arranged in the rotating sleeve 36. The magnetic poles of the fixed magnet body 37 have a five-pole structure including a main pole 37a, a regulation pole 37b, a carrier pole 37c, a peeling pole 37d, and a pumping pole 37e.

A regulation blade 38 is attached to the developing container 31 along the longitudinal direction of the magnetic roller 34 (direction perpendicular to the paper surface of FIG. 2). The regulation blade 38 is provided on the upstream side of the facing position (proximity position) between the developing roller 35 and the magnetic roller 34 in the rotation direction of the magnetic roller 34.

The developing roller 35 includes a cylindrical developing sleeve 35a and a magnet member 35b fixed inside the developing sleeve 35a. The magnet member 35b has a different polarity from the facing magnetic pole (main pole 37a) of the fixed magnet body 37.

The developer circulating in the developing container 31 is conveyed to the magnetic roller 34 by the second stirring screw 32b. By restricting the restricting blade 38 and the restricting pole 37b of the fixed magnet body 37 and using a non-magnetic material or a magnetic material as the restricting blade 38, a magnetic field in a direction attracting a gap between the tip of the restricting blade 38 and the rotary sleeve 36 is generated. appear. This magnetic field forms a magnetic brush between the regulation blade 38 and the rotating sleeve 36.

When the magnetic brush on the magnetic roller 34 is moved to a position facing the developing roller 35 after the layer thickness is regulated by the regulating blade 38, a magnetic field attracted by the main pole 37a of the fixed magnet body 37 and the magnet member 35b on the developing roller 35 side. Is imparted, the magnetic brush contacts the surface of the developing roller 35. Then, a toner thin layer is formed on the developing roller 35 by the potential difference ΔV between Vmag (DC) applied to the magnetic roller 34 and Vslv (DC) applied to the developing roller 35 and the magnetic field. The thickness of the toner layer on the developing roller 35 changes depending on the resistance of the developer, the rotational speed difference between the magnetic roller 34 and the developing roller 35, and the like, but can be controlled by ΔV. Specifically, when ΔV is increased, the toner layer on the developing roller 35 becomes thicker, and when ΔV is decreased, the toner layer becomes thinner. The developing device 21 is not limited to the above-mentioned configuration, and a conventionally known device can be used.

The intermediate transfer belt 22 is an endless belt horizontally stretched between a driving roller and a driven roller in the printer body 12, and is accompanied by rotation of the driving roller by a belt driving motor (not shown) and image forming operation. It is driven by circulation.

The toner density detection sensor 23 measures the reflection density of the toner image primarily transferred to the intermediate transfer belt 22, and outputs the detection value to the CPU 51 (see FIG. 3). It should be noted that the toner concentration detection sensor 23 can be provided at a plurality of locations along the rotational movement direction of the intermediate transfer belt 22 and the width direction orthogonal to the rotational movement direction. At this time, if the toner concentration detection sensor 23 detects the toner concentration on only one side in the width direction of the intermediate transfer belt 22, for example, a phenomenon in which a density difference occurs at both ends in the width direction of the intermediate transfer belt 22 (side burning phenomenon). Since it is not possible to deal with the occurrence of, it is preferable to dispose near both ends in the width direction.

The charging roller 26 is formed of, for example, conductive rubber, and is arranged so as to contact the photosensitive drum 20. Then, as shown in FIG. 2, when the photoconductor drum 20 rotates in the clockwise direction, the charging roller 26 contacting the surface of the photoconductor drum 20 is driven to rotate in the counterclockwise direction. At this time, by applying a predetermined voltage to the charging roller 26, the surface of the photoconductor drum 20 is uniformly charged. Further, as the charging roller 26 rotates, a charging cleaning roller (not shown) contacting the charging roller 26 is driven to rotate in a clockwise direction to remove foreign matters attached to the surface of the charging roller 26.

The cleaning device 28 is disposed in the cleaning housing 40 having a depth in the recording paper width direction (direction orthogonal to the recording paper conveyance direction), and is disposed near the lower inside of the cleaning housing 40 and rotates in the clockwise direction in FIG. A collecting spiral 41 that conveys the collected toner to one side in the paper width direction and sends it to a waste toner container (not shown), a cleaning blade 42 that is attached to the outer lower side of the cleaning housing 40, and an inner upper side of the cleaning housing 40. And a scraping roller (cleaning roller) 43 that is in contact with the surface of the photosensitive drum 20 and a scraper 44 that is disposed above the sliding roller 43 and is in contact with the surface of the sliding roller 43.

The cleaning blade 42 is formed of a high hardness and low repulsion material such as urethane rubber. The impact resilience of the cleaning blade 42 is preferably 30% or less at 25[deg.] C., and 25% to 28% is used. The impact resilience is an index that represents the energy absorbed by the material when the object collides, and the energy that the object has when colliding or bouncing when colliding an object with a prescribed mass from a prescribed height with a test piece. Refers to the ratio of.

The cleaning blade 42 is arranged so that its tip contacts the surface of the photoconductor drum 20 from below the rotation axis of the photoconductor drum 20. At this time, the tip of the cleaning blade 42 is in contact with the rotation direction of the photoconductor drum 20 (see the arrow in FIG. 2) in the counter direction. The contact portion between the end of the cleaning blade 42 and the surface of the photosensitive drum 20 is a “blade edge” described later.

The rubbing roller 43 collects the waste toner from the surface of the photoconductor drum 20 and polishes the surface of the photoconductor drum 20 with the waste toner attached to the surface of the rubbing roller 43. For this reason, the rubbing roller 43 is formed into a cylindrical shape extending in the recording paper width direction by using foamed rubber (for example, carbon-containing conductive foamed EPDM) in order to maintain the waste toner retention at a high level. It is arranged on the upstream side in the rotation direction of the photoconductor drum 20 with respect to the tip. The rotation direction of the rubbing roller 43 is opposite to the rotation direction of the photoconductor drum 20. The scraper 44 is made of a durable thin sheet metal, and in order to make the amount of the toner adhering to the surface of the rubbing roller 43 uniform, the scraper 44 is arranged in the counter direction on the downstream side in the rotation direction of the rubbing roller 43. The tip is in contact with.

The static eliminator 29 is arranged downstream of the cleaning device 28 along the rotation direction of the photosensitive drum 20. An LED (light emitting diode) is used for the static eliminator 29, and a reflector is provided as necessary. The static eliminator 29 irradiates the photoconductor drum 20 with static elimination light (erase light) to remove the charged charges on the surface of the photoconductor drum 20, and prepares for the charging step in the next image forming operation.

The cooling fan 45 is arranged between the cleaning device 28 and the static eliminator 29 so as to face the cleaning blade 42. The cooling fan 45 cools the cleaning blade 42 by blowing an air flow on the cleaning blade 42.

Next, the control of the image forming apparatus 11 of this embodiment will be described. FIG. 3 is a block diagram showing a control path of the image forming apparatus 11. In the image forming apparatus 11, various controls of each device are performed, so that control of the entire device becomes complicated. Therefore, here, of the control path, a portion necessary for implementing the present invention will be mainly described.

The control unit 50 includes a CPU 51 as a central processing unit, a ROM 52 that is a read-only storage unit, a RAM 53 that is a readable/writable storage unit, a HDD 54 that temporarily stores image data and the like, a counter 55, a photosensitive drum 20, and the like. The motor drive driver 56 for driving and controlling the drive motor 48, the torque detector 57 for detecting the torque of the drive motor 48, the developing bias circuit 58 for applying the developing bias to the developing device 21, and the charging roller 26. And a transfer bias circuit 59 for applying a transfer bias to the primary transfer roller 27 and the secondary transfer portion 17, and the like.

The ROM 52 stores a control program for the image forming apparatus 11, numeric values and data necessary for control. The RAM 53 stores necessary data generated during the control of the image forming apparatus 11, data temporarily necessary for controlling the image forming apparatus 11, and the like.

The control unit 50 mainly controls the rotational drive of each photoconductor drum 20, a developing bias applied to the developing device 21, a primary transfer bias applied to the primary transfer roller 27, and a charging bias applied to the charging roller 26. It controls the light amount of the laser light P (see FIG. 1) emitted from the exposure unit 25, and controls the erase light amount of the static eliminator 29.

The control unit 50 also controls the cooling of the cleaning blade 42 by the cooling fan 45 as described later. Specifically, when the variation cycle of the torque of the drive motor 48 detected by the torque detection unit 57 becomes smaller than a predetermined value, the cooling fan 45 is rotated to cool the cleaning blade 42. Hereinafter, the cooling control of the cleaning blade 42 will be referred to as “blade cooling control”.

Next, the image forming procedure of the image forming apparatus 11 will be described. When image data is input from an external connection device such as a personal computer, the CPU 51 first applies a charging bias to the charging roller 26 via the charging bias circuit 59, and the charging roller 26 cleans the surface of the photosensitive drum 20. To charge. Next, the exposure unit 25 irradiates the surface of the photosensitive drum 20 with the laser light P. As a result, an electrostatic latent image corresponding to the image data of the received job is formed on each photoconductor drum 20.

The CPU 51 applies a bias voltage having a potential difference to the magnetic roller 34 and the developing roller 35 via the developing bias circuit 58. As a result, a thin toner layer is formed on the developing roller 35. Then, due to the potential difference between the developing roller 35 and the photosensitive drum 20, the toner on the developing roller 35 flies to the photosensitive drum 20 side, and a toner image corresponding to the electrostatic latent image is formed on the surface of the photosensitive drum 20. .. The developing device 21 is filled with a predetermined amount of developer containing toner of each color of yellow, magenta, cyan and black. When the ratio of the toner in the developer filled in each developing device 21 is below a specified value due to the formation of a toner image, which will be described later, the toner is supplied from the toner container 19 to each developing device 21.

On the other hand, the recording paper is fed from the paper feed cassette 13 (or the manual feed tray) at the timing of forming the toner image in the image forming unit 15, and is conveyed to the registration roller pair 30 a through the recording paper conveyance path 16.

Then, the CPU 51 applies a transfer bias having a polarity opposite to that of the toner (negative polarity when positively charged toner is used) to the primary transfer roller 27 via the transfer bias circuit 60. As a result, a predetermined electric field is applied between the primary transfer roller 27 and each photoconductor drum 20, and the yellow, magenta, cyan, and black toner images on each photoconductor drum 20 are primarily transferred onto the intermediate transfer belt 22. To be done. These four-color images are formed in a predetermined positional relationship that is predetermined for forming a predetermined full-color image. Next, the CPU 51 applies a negative transfer bias to the secondary transfer unit 17 via the transfer bias circuit 60. As a result, the toner image on the intermediate transfer belt 22 is transferred onto the recording paper conveyed from the registration roller pair 30a. After that, the toner and the like remaining on the surface of the photoconductor drum 20 after the primary transfer are removed by the cleaning device 28 in preparation for the subsequent formation of a new electrostatic latent image. Further, the residual charge on the surface of the photoconductor drum 20 is removed by the static eliminator 29.

When the intermediate transfer belt 22 starts rotating in the counterclockwise direction in FIG. 1, the recording paper is conveyed from the registration roller pair 30a to the secondary transfer portion 17 provided adjacent to the intermediate transfer belt 22 at a predetermined timing, The full-color image on the intermediate transfer belt 22 is secondarily transferred onto the recording paper. The recording paper on which the toner image is secondarily transferred is conveyed to the fixing unit 18. The residual toner and the like attached to the surface of the intermediate transfer belt 22 are removed by the belt cleaning device 24.

The recording paper conveyed to the fixing unit 18 is heated and pressed to fix the toner image on the surface of the recording paper, and a predetermined full-color image is formed. The recording paper on which the full-color image is formed is guided to the end portion of the recording paper conveyance path 16 and discharged onto the discharge tray 12a which also serves as the upper surface of the printer body 12 by the discharge roller pair 30b.

The image forming apparatus 11 of the present invention cools the cleaning blade 42 by the cooling fan 45 when the elastic deformation amount of the cleaning blade 42 becomes large and the stick-slip operation is performed, such as when printing is performed in a high temperature environment. By reducing the elastic deformation amount of the cleaning blade 42 and stabilizing the edge, it is possible to execute blade cooling control that suppresses the stick-slip operation. Hereinafter, the blade cooling control of the image forming apparatus 11 according to the present exemplary embodiment and the control related thereto will be described.

(1) Detection of Driving Torque of Photosensitive Drum 20 The CPU 51 controls the driving motor (driving device) 48 that rotates the photosensitive drum 20 via the motor driving driver 56, and detects the torque of the driving motor 48. The detection value from the unit 57 is acquired. In the present embodiment, the torque detection unit 57 detects the output current value of the drive motor 48. That is, the output current value of the drive motor 48 is used as an index of torque. The means for detecting the torque of the drive motor 48 is usually provided in the image forming apparatus 11 in order to prevent the drive motor 48 from being damaged due to an excessive load applied to the drive motor 48.

(2) Driving of Cooling Fan In the present embodiment, the CPU 51 determines whether or not the cooling fan 45 needs to be cooled by the cooling fan 45 according to the elastic deformation amount of the cleaning blade 42. The elastic deformation amount of the cleaning blade 42 is estimated based on the fluctuation cycle of the torque of the drive motor 48 detected by the torque detection unit 57.

FIG. 4 is a graph showing the relationship between the environmental temperature and the impact resilience of the cleaning blade 42 used in this embodiment. The repulsion elastic modulus of a general rubber material has a correlation with the environmental temperature, and the repulsive elastic modulus of the cleaning blade 42 also increases as the environmental temperature rises. As shown in FIG. 4, the impact resilience of the cleaning blade 42 at 25° C. is 28%, but at 40° C., the impact resilience increases to 45%. When the impact resilience increases, the elastic deformation amount of the cleaning blade 42 increases and the edge easily sticks.

FIG. 5 is a graph showing the fluctuation cycle of the torque of the drive motor 48 when the temperature of the cleaning blade 42 having the repulsion elastic modulus shown in FIG. 4 is 25° C. Since the cleaning blade 42 slowly stick-slips with the rotation of the photosensitive drum 20, the torque of the drive motor 48 fluctuates in a predetermined cycle T1 as shown in FIG.

FIG. 6 is a graph showing the fluctuation cycle of the torque of the drive motor 48 when the temperature of the cleaning blade 42 having the repulsion elastic modulus shown in FIG. 4 is 40° C. As the temperature of the cleaning blade 42 increases, the elastic deformation amount of the cleaning blade 42 increases. As a result, as shown in FIG. 6, the torque of the drive motor 48 becomes large and the stick-slip becomes severe, so that the fluctuation cycle of the torque becomes T2, which is shorter than T1. It has been found that in such a state, the external additive easily slips through the gap between the photoconductor drum 20 and the cleaning blade 42.

Therefore, in the present embodiment, when the fluctuation cycle of the torque of the drive motor 48 becomes shorter than the preset cycle T0, it is determined that the temperature of the cleaning blade 42 is high and the elastic deformation amount is large, and the cooling is performed. The fan 45 is driven to cool the cleaning blade 42. As a result, the amount of elastic deformation of the cleaning blade 42 returns to the state of FIG. 4 and the external additive can be prevented from slipping through.

The cycle T0 is set according to the hardness of the cleaning blade 42, the impact resilience, and the properties of the photosensitive drum 20. For example, when the cleaning blade 42 is made of urethane rubber having an Asker hardness of 72° and a repulsion elastic modulus of 24% at 25° C., and the photosensitive drum 20 is an organic (OPC) photosensitive member having a diameter of 30 mm, the cycle T0 is 0.1 sec. Becomes

FIG. 7 is a flowchart showing an example of blade cooling control in the image forming apparatus 11 of this embodiment. There is a main routine (not shown) that controls the entire image forming apparatus 11, and the flow shown in FIG. 7 is a subroutine of the main routine. The blade cooling control subroutine shown in FIG. 7 starts when the image forming apparatus 11 is powered on.

The CPU 51 monitors whether a print job has been accepted (step S1). The print job is accepted by an input from a user via the operation panel of the image forming apparatus 11 or an input from a personal computer or the like connected via a communication line such as a LAN or the Internet. If the print job is not accepted (No in step S1), the monitoring is continued.

When the print job is accepted (Yes in step S1), the drive motor 48 starts the rotational driving of the photosensitive drum 20. The CPU 51 starts acquiring the torque fluctuation period Ts of the drive motor 48 that drives the photoconductor drum 20 from the torque detection unit 57 (step S2).

Next, the CPU 51 determines whether or not the fluctuation period Ts of the acquired torque is less than T0 (for example, 0.1 sec) (step S3). When the fluctuation cycle Ts is less than T0 (Yes in step S3), the CPU 51 drives the cooling fan 45 (step S4). Next, the CPU 51 determines whether or not the print job is completed (step S5). When the print job is completed (Yes in step S5), the rotation of the photosensitive drum 20 is stopped, and the cleaning blade 42 is stopped. It is determined whether the ambient temperature t has become lower than t0 (for example, 25° C.) (step S6). When t<t0 is satisfied (Yes in step S6), the driving of the cooling fan 45 is stopped (step S7), and the process is ended.

On the other hand, if the fluctuation cycle Ts is not less than T0 in step S3 (No in step S3), the CPU 51 determines whether the print job is completed (step S8), and if the print job is completed ( Yes in step S8), the rotation of the photoconductor drum 20 is stopped without driving the cooling fan 45, and the process is ended. In addition, in the flow of FIG. 7, step S3 to step S7 can be regarded as blade cooling control.

As described above, in the image forming apparatus 11 according to the present exemplary embodiment, the necessity of cooling the cleaning blade 42 and the cooling time for cooling the cleaning blade 42 are determined according to the elastic deformation amount of the cleaning blade 42. Specifically, when the torque fluctuation cycle Ts is less than the predetermined value T0, the cooling fan 45 is rotated to cool the cleaning blade 42.

As a result, the cooling fan 45 can be driven for the minimum drive time required to reduce the elastic deformation amount of the cleaning blade 42. That is, since the cooling fan 45 is driven only when the stick-slip is intense and the fluctuation cycle of the torque becomes short, the stick-slip of the cleaning blade 42 is suppressed without driving the cooling fan 45 unnecessarily, and the photosensitive drum 20 and It is possible to effectively prevent the external additive from slipping through the gap between the cleaning blade 42 and the charging failure caused by the external additive adhering to the charging roller 26. Further, since the cooling fan 45 is driven only when necessary, it is possible to suppress toner scattering inside the image forming apparatus 11.

Further, in the present embodiment, a method of driving the cooling fan 45 based on the temperature inside the machine by estimating the elastic deformation amount of the cleaning blade 42 by using the fluctuation cycle of the torque of the drive motor 48 that drives the photosensitive drum 20. The elastic deformation amount of the cleaning blade 42 can be estimated more accurately than the above, and the drive timing of the cooling fan 45 can be easily set according to the decrease in the elastic deformation amount of the cleaning blade 42. Further, the elastic deformation amount of the cleaning blade 42 can be estimated without providing a new device, which also contributes to cost reduction.

Besides, the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, the method of detecting the torque of the drive motor 48 is not limited to the detection of the output current value of the drive motor 48, and the torque of the rotating shaft of the drive motor 48 may be directly detected by the torque sensor.

Further, the image carrier is not limited to the photoconductor drum 20 in which the photosensitive layer is formed on the surface of the cylindrical material tube, and for example, the one in which the photosensitive layer is formed on the surface of the plate-shaped support body. Can also be used. Further, the cleaning member is not limited to the flat plate-shaped cleaning blade 42, and may have a columnar shape, for example. Further, the charging member is not limited to the charging roller 26, and may be, for example, a charging brush.

Further, in the above-described embodiment, a tandem type color printer is described as an example of the image forming apparatus 11, but the present invention can be applied to, for example, monochrome and color copying machines, digital multi-function peripherals, monochrome printers and facsimiles. Of course.

INDUSTRIAL APPLICABILITY The present invention is applicable to an image forming apparatus including an image carrier on which a toner image is formed and a cleaning blade for cleaning the surface of the image carrier. By utilizing the present invention, it is possible to provide an image forming apparatus capable of suppressing the damage and stick-slip of the cleaning blade and suppressing the slipping of the external additive from the gap between the image carrier and the cleaning blade for a long period of time.

11 image forming apparatus 20 photoconductor drum (image carrier)
21 developing device 26 charging roller (charging member)
28 Cleaning Device 42 Cleaning Blade 43 Rubbing Roller 45 Cooling Fan 48 Drive Motor (Drive Device)
50 control unit 52 ROM
54 HDD
57 Torque detector

Claims (6)

An image carrier on which an electrostatic latent image is formed,
A drive device for rotationally driving the image carrier,
A developing device for developing the electrostatic latent image formed on the surface of the image carrier into a toner image,
A cleaning blade disposed so as to contact the surface of the image carrier, for cleaning the surface of the image carrier,
A cooling fan for cooling the cleaning blade,
A torque detection unit that detects the torque when the image carrier is driven to rotate,
A control unit for controlling the drive of the cooling fan,
Equipped with
The image forming apparatus, wherein the control unit drives the cooling fan when the fluctuation cycle of the torque detected by the torque detection unit is less than a predetermined value. A temperature detection device for detecting the temperature around the cleaning blade,
The image forming apparatus according to claim 1, wherein the control unit continues driving the cooling fan until the temperature detected by the temperature detection device becomes equal to or lower than a predetermined value. The image forming apparatus according to claim 1 or 2, wherein the cleaning blade has a repulsion elastic modulus at 25°C of 30% or less. The torque detection unit detects a torque when the image carrier is rotationally driven by detecting an output current value of the drive device. Image forming apparatus. The image forming apparatus according to claim 1, further comprising a charging member that is arranged in contact with or close to the surface of the image carrier to charge the image carrier. The image forming apparatus according to claim 1, wherein an amorphous silicon photosensitive layer is formed on the surface of the image carrier.

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