JP2018132628A - Image forming apparatus - Google Patents

Abstract

There is provided an image forming apparatus capable of efficiently collecting toner accumulated on a toner receiving member disposed in a developing device over an entire region in a longitudinal direction. An image forming apparatus includes an image carrier, a developing device, and a control unit. An electrostatic latent image is formed on the image carrier. The developing device includes a developing roller, a toner supply roller, a regulating blade, a casing, a toner receiving support member, a toner receiving member, and a vibration generator. The image forming apparatus can execute a toner collection mode in which a toner generating member is vibrated by a vibration generator during non-image formation to shake off toner accumulated on a toner receiving surface. The control unit changes the frequency of the vibration generator so that the amplitude of the toner receiving member during execution of the toner collection mode is equal to or greater than a predetermined value over the entire area in the longitudinal direction. [Selection diagram] FIG.

Description

  The present invention relates to an electrophotographic image forming apparatus including a developing device that supplies a developer to an image carrier.

  An electrophotographic image forming apparatus irradiates a peripheral surface of an image carrier (photosensitive drum) with light based on image information read from an original image or image information transmitted from an external device such as a computer. An electrostatic latent image is formed, toner is supplied from the developing device to the electrostatic latent image to form a toner image, and then the toner image is transferred to a sheet. The paper after the transfer process is subjected to a toner image fixing process and then discharged to the outside.

  By the way, in recent years, in the image forming apparatus, the configuration of the apparatus becomes complicated with the progress of color printing and high-speed processing, and the toner stirring member in the developing device is forced to rotate at high speed to cope with high-speed processing. . In particular, in a development method using a two-component developer including a magnetic carrier and a toner and using a magnetic roller (toner supply roller) that carries the developer and a development roller that carries only the toner, the development roller and the magnetic roller In the opposite portion, only the toner is carried on the developing roller by the magnetic brush formed on the magnetic roller, and the toner that has not been used for development is peeled off from the developing roller. Therefore, toner scattering is likely to occur in the vicinity of the facing portion between the developing roller and the magnetic roller, and the toner floating in the developing device accumulates around the earbrush blade (regulating blade), and the accumulated toner aggregates. If the toner adheres to the developing roller, the toner may be dropped and an image defect may occur.

  Therefore, for example, in Patent Documents 1 and 2, in a developing device using a two-component developer containing a magnetic carrier and toner, and using a magnetic roller carrying the developer and a developing roller carrying only the toner, the developing roller Alternatively, a toner receiving support member that faces the magnetic roller, a toner receiving member that is disposed along the longitudinal direction of the toner receiving support member and that receives toner falling from the developing roller, and a vibration generating unit that vibrates the toner receiving member are provided. A developing device is disclosed.

JP 2012-208469 A Japanese Patent Laying-Open No. 2014-6411

  When a plate-shaped toner receiving member having both ends free as in Patent Documents 1 and 2, the attachment position of a vibration motor having a large inertia weight becomes a node of amplitude and does not vibrate. Further, the end portion of the toner receiving member vibrates greatly as an antinode of amplitude. That is, the toner deposited on the end portion is easily dropped by vibration, but the toner deposited on the center portion cannot be dropped.

  In addition, a coil spring that is attached to make the vibration direction of the toner receiving member substantially vertical has an effect of constraining the vibration motion, and reduces the amplitude. When the natural frequency of the coil spring is the same as the natural frequency of the toner receiving member, the coil spring and the toner receiving member resonate at the same frequency, so that the amplitude increases. However, the amplitude of the portion to which the coil spring is attached increases excessively, resulting in a non-uniform amplitude distribution in the longitudinal direction of the toner receiving member.

  In view of the above problems, the present invention can efficiently collect toner deposited on a toner receiving member by vibrating the toner receiving member disposed in the developing device with a certain amplitude or more over the entire longitudinal direction. An object is to provide an image forming apparatus.

  In order to achieve the above object, a first configuration of the present invention is an image forming apparatus including an image carrier, a developing device, and a control unit. An electrostatic latent image is formed on the image carrier. The developing device includes a developing roller, a toner supply roller, a regulating blade, a casing, a toner receiving support member, a toner receiving member, and a vibration generating device, and includes an electrostatic latent image formed on the image carrier. Develop the image. The developing roller is disposed to face the image carrier on which the electrostatic latent image is formed, and supplies toner to the image carrier in a region facing the image carrier. The toner supply roller is disposed to face the developing roller, and supplies toner to the developing roller in a region facing the developing roller. The regulating blade is disposed to face the toner supply roller at a predetermined interval. The casing houses a developing roller, a toner supply roller, and a regulating blade. The toner receiving support member is disposed in the casing and faces the developing roller or the toner supply roller between the regulating blade and the image carrier. The toner receiving member has a toner receiving surface that is disposed along the longitudinal direction of the toner receiving support member and receives toner falling from the developing roller. The vibration generator vibrates the toner receiving member. The control unit controls driving of the developing device. The image forming apparatus can execute a toner recovery mode in which the toner receiving member is vibrated by the vibration generating device during non-image formation to shake off the toner accumulated on the toner receiving surface. The control unit changes the vibration frequency of the vibration generating device so that the amplitude of the toner receiving member during execution of the toner recovery mode is equal to or greater than a predetermined value over the entire longitudinal direction.

  According to the first configuration of the present invention, the frequency of the vibration generating device is changed so that the amplitude of the toner receiving member in the toner recovery mode is equal to or greater than a predetermined value over the entire area in the longitudinal direction. The amplitude can be set to a predetermined value or more over the entire area in the longitudinal direction. As a result, the toner deposited on the toner receiving surface can be efficiently shaken off over the entire region in the longitudinal direction, and the occurrence of toner dropping can be effectively suppressed.

Schematic configuration diagram of a color printer 100 equipped with the developing devices 3a to 3d of the present invention Side sectional view of the developing device 3a according to the embodiment of the present invention mounted on the color printer 100. A block diagram showing an example of a control path used in the color printer 100 The perspective view which looked at the toner receiving support member 35 used for the developing device 3a of this embodiment from the inside of the developing container 20. An exploded perspective view of the toner receiving support member 35 used in the developing device 3a of the present embodiment. An exploded perspective view of the vibration generator 42 Front view of vibration motor 43 Side view of the vibration motor 43 as seen from the side of the vibration weight 50 FIG. 4 is a side cross-sectional view of the vicinity of the toner receiving support member 35 in the developing device 3a of the present embodiment, showing a cross section near the vibration motor 43; FIG. 4 is a side sectional view of the periphery of the toner receiving support member 35 in the developing device 3a of the present embodiment, showing a section including a coil spring 40. A graph showing the amplitude distribution of the toner receiving member 37 when the vibration motor 43 is rotated at 80 Hz (4800 rpm). A graph showing the amplitude distribution of the toner receiving member 37 when the vibration motor 43 is rotated at 90 Hz (5400 rpm). A graph showing the amplitude distribution of the toner receiving member 37 when the vibration motor 43 is rotated at 100 Hz (6000 rpm). A graph showing the amplitude distribution of the toner receiving member 37 when the vibration motor 43 is rotated at 110 Hz (6600 rpm). A graph showing the amplitude distribution of the toner receiving member 37 when the vibration motor 43 is rotated at 120 Hz (7200 rpm). A graph showing the amplitude distribution of the toner receiving member 37 when the vibration motor 43 is rotated at 130 Hz (7800 rpm). A graph showing the amplitude distribution of the toner receiving member 37 when the vibration motor 43 is rotated at 135 Hz (8084 rpm). A graph showing the amplitude distribution of the toner receiving member 37 when the vibration motor 43 is rotated at 140 Hz (8400 rpm). The graph which shows an example of the fluctuation pattern of the rotation speed of the vibration motor 43 in toner collection mode The graph which shows the other example of the fluctuation pattern of the rotation speed of the vibration motor 43 in toner collection mode

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional view of an image forming apparatus on which developing devices 3a to 3d of the present invention are mounted. Here, a tandem color printer is shown. In the main body of the color printer 100, four image forming portions Pa, Pb, Pc, and Pd are sequentially arranged from the upstream side in the transport direction (the right side in FIG. 1). These image forming portions Pa to Pd are provided corresponding to images of four different colors (cyan, magenta, yellow, and black), and cyan, magenta, and yellow are respectively performed by charging, exposure, development, and transfer processes. And a black image are sequentially formed.

  These image forming portions Pa to Pd are provided with photosensitive drums 1a, 1b, 1c and 1d for carrying visible images (toner images) of the respective colors, and further rotate clockwise in FIG. An intermediate transfer belt 8 is provided adjacent to each of the image forming portions Pa to Pd.

  When image data is input from a host device such as a personal computer, first, the surfaces of the photosensitive drums 1a to 1d are uniformly charged by the chargers 2a to 2d. Next, light is irradiated by the exposure device 5 according to the image data, and electrostatic latent images corresponding to the image data are formed on the respective photosensitive drums 1a to 1d. The developing devices 3a to 3d are filled with a predetermined amount of a two-component developer (hereinafter, also simply referred to as a developer) containing toners of cyan, magenta, yellow, and black by toner containers 4a to 4d. The toner in the developer is supplied onto the photosensitive drums 1a to 1d by 3a to 3d and electrostatically adheres. Thereby, a toner image corresponding to the electrostatic latent image formed by exposure from the exposure device 5 is formed.

  The primary transfer rollers 6a to 6d apply an electric field at a predetermined transfer voltage between the primary transfer rollers 6a to 6d and the photosensitive drums 1a to 1d, and cyan, magenta, yellow, and yellow on the photosensitive drums 1a to 1d. A black toner image is primarily transferred onto the intermediate transfer belt 8. Toner remaining on the surfaces of the photosensitive drums 1a to 1d after the primary transfer is removed by the cleaning devices 7a to 7d.

  The transfer paper P to which the toner image is transferred is accommodated in a paper cassette 16 disposed in the lower part of the image forming apparatus 100. The transfer paper P is transferred to a predetermined position via a paper feed roller 12a and a resist roller pair 12b. At a timing, the sheet is conveyed to the nip portion (secondary transfer nip portion) between the secondary transfer roller 9 provided adjacent to the intermediate transfer belt 8 and the intermediate transfer belt 8. The transfer sheet P on which the toner image is secondarily transferred is conveyed to the fixing unit 13.

  The transfer paper P conveyed to the fixing unit 13 is heated and pressed by the fixing roller pair 13a to fix the toner image on the surface of the transfer paper P, and a predetermined full-color image is formed. The transfer paper P on which the full-color image is formed is discharged to the discharge tray 17 by the discharge roller pair 15 as it is (or after being distributed to the reverse conveyance path 18 by the branching unit 14 and the image is formed on both sides).

  FIG. 2 is a side sectional view of the developing device 3a according to the embodiment of the present invention mounted on the color printer 100. FIG. 2 shows a state viewed from the back side of FIG. 1, and the arrangement of each member in the developing device 3a is opposite to that in FIG. Further, in the following description, the developing device 3a disposed in the image forming unit Pa of FIG. 1 is illustrated, but the configuration of the developing devices 3b to 3d disposed in the image forming units Pb to Pd is basically the same. Therefore, explanation is omitted.

  As shown in FIG. 2, the developing device 3a includes a developing container (casing) 20 in which a two-component developer (hereinafter simply referred to as a developer) composed of toner and a magnetic carrier is stored. The partition wall 20a is divided into an agitating and conveying chamber 21 and a supply and conveying chamber 22. In the agitating / conveying chamber 21 and the supply / conveying chamber 22, the agitating / conveying screw 25 a for supplying toner (positively charged toner) supplied from the toner container 4 a (see FIG. 1) with the carrier, agitating and charging, and the supplying and conveying Each screw 25b is rotatably arranged.

  Then, the developer is agitated by the agitating / conveying screw 25a and the supply / conveying screw 25b and conveyed in the axial direction (perpendicular to the paper surface of FIG. 2) to pass through the developer (not shown) formed at both ends of the partition wall 20a. It circulates between the stirring and conveying chamber 21 and the supply and conveying chamber 22 through the path. That is, a developer circulation path is formed in the developer container 20 by the agitating / conveying chamber 21, the supply / conveying chamber 22, and the developer passage.

  The developing container 20 extends obliquely upward to the right in FIG. 2. A toner supply roller 30 (developer carrying member) is disposed above the supply / conveying screw 25 b in the developing container 20. A developing roller 31 is disposed diagonally upward. The developing roller 31 faces the photosensitive drum 1a (see FIG. 1) on the opening side (the right side in FIG. 2) of the developing container 20, and the toner supply roller 30 and the developing roller 31 are shown in FIG. 2 rotates counterclockwise.

  A toner concentration sensor 28 is disposed in the agitating and conveying chamber 21 so as to face the agitating and conveying screw 25a. The toner concentration sensor 28 detects the ratio (T / C) of the toner to the carrier in the developer. For example, a magnetic permeability sensor that detects the magnetic permeability of the developer in the developing container 20 is used. In the present embodiment, the toner density sensor 28 detects the magnetic permeability of the developer, and a voltage value corresponding to the detection result is output to a control unit (not shown) described later. The toner density is determined from the output value of the toner density sensor 28. The control unit transmits a control signal to a toner replenishing motor (not shown) according to the determined toner concentration, and a predetermined amount of toner is transferred from the toner container 4a to the stirring and conveying chamber 21 via a toner replenishing port (not shown). The toner is replenished.

  The toner supply roller 30 is composed of a non-magnetic rotating sleeve that rotates counterclockwise in FIG. 2 and a fixed magnet body having a plurality of magnetic poles contained in the rotating sleeve.

  The developing roller 31 includes a cylindrical developing sleeve that rotates counterclockwise in FIG. 2 and a developing roller side magnetic pole that is fixed in the developing sleeve. It faces with a predetermined gap at the facing position (facing position). The developing roller side magnetic pole has a different polarity from the opposing magnetic pole (main pole) of the fixed magnet body.

  Further, a spike cutting blade 33 is attached to the developing container 20 along the longitudinal direction of the toner supply roller 30 (a direction perpendicular to the paper surface of FIG. 2), and the spike cutting blade 33 rotates in the rotation direction of the toner supply roller 30. In the counterclockwise direction in FIG. 2, the developing roller 31 and the toner supply roller 30 are positioned on the upstream side. A slight gap (gap) is formed between the tip of the ear cutting blade 33 and the surface of the toner supply roller 30.

  A DC voltage (hereinafter referred to as Vslv (DC)) and an AC voltage (hereinafter referred to as Vslv (AC)) are applied to the developing roller 31, and a DC voltage (hereinafter referred to as Vmag (DC)) is applied to the toner supply roller 30. ) And an alternating voltage (hereinafter referred to as Vmag (AC)). These DC voltage and AC voltage are applied from the developing bias power source to the developing roller 31 and the toner supply roller 30 via a bias control circuit (both not shown).

  As described above, the developer is agitated by the agitating / conveying screw 25a and the supply / conveying screw 25b, and the toner is charged by circulating through the agitating / conveying chamber 21 and the supplying / conveying chamber 22 in the developing container 20, and the supply / conveying screw 25b. The developer is conveyed to the toner supply roller 30. Then, a magnetic brush (not shown) is formed on the toner supply roller 30. After the layer thickness of the magnetic brush on the toner supply roller 30 is regulated by the earbrushing blade 33, the toner supply roller 30 and the developing roller 31 are separated. A thin toner layer is formed on the developing roller 31 by a potential difference ΔV between Vmag (DC) applied to the toner supply roller 30 and Vslv (DC) applied to the developing roller 31 and a magnetic field.

  The toner thin layer formed on the developing roller 31 by contact with the magnetic brush on the toner supply roller 30 is conveyed to a facing portion (facing region) between the photosensitive drum 1 a and the developing roller 31 by the rotation of the developing roller 31. The Since Vslv (DC) and Vslv (AC) are applied to the developing roller 31, the toner flies due to a potential difference with the photosensitive drum 1a, and the electrostatic latent image on the photosensitive drum 1a is developed. .

  Remaining toner that is not used for development is conveyed again to the opposite portion between the developing roller 31 and the toner supply roller 30 and is collected by the magnetic brush on the toner supply roller 30. The magnetic brush is peeled off from the toner supply roller 30 at the same polarity portion of the fixed magnet body, and then falls into the supply conveyance chamber 22.

  Thereafter, a predetermined amount of toner is replenished from a toner replenishing port (not shown) based on the detection result of the toner concentration sensor 28, and is uniformed again at an appropriate toner concentration while circulating through the supply transport chamber 22 and the stirring transport chamber 21. It becomes a charged two-component developer. This developer is again supplied onto the toner supply roller 30 by the supply / conveyance screw 25 b to form a magnetic brush, and is conveyed to the ear cutting blade 33.

  A toner receiving and supporting member 35 having a triangular cross-section projecting inward of the developing container 20 is provided in the vicinity of the developing roller 31 on the right side wall in FIG. As shown in FIG. 2, the toner receiving support member 35 is disposed along the longitudinal direction of the developing container 20 (the direction perpendicular to the paper surface of FIG. 2). A wall portion that faces the developing roller 31 and is inclined downward from the developing roller 31 toward the toner supply roller 30 is configured. On the upper surface of the toner receiving support member 35, a toner receiving member 37 is attached along the longitudinal direction for receiving the toner that is peeled off from the developing roller 31 and falls.

  FIG. 3 is a block diagram illustrating an example of a control path used in the color printer 100 of the present invention. In addition, since various controls of each part of the apparatus are performed when the color printer 100 is used, the control path of the entire color printer 100 becomes complicated. Therefore, here, a portion of the control path that is necessary for the implementation of the present invention will be mainly described.

  The bias control circuit 55 is connected to the charging bias power source 52, the developing bias power source 53, and the transfer bias power source 54, and operates each of these power sources in accordance with an output signal from the control unit 90. In accordance with a control signal from the control circuit 55, the charging bias power source 52 is supplied to the charging rollers in the chargers 2a to 2d, and the developing bias power source 53 is transferred to the toner supply roller 30 and the developing roller 31 in the developing devices 3a to 3d. A predetermined bias 54 is applied to the primary transfer rollers 6a to 6d and the secondary transfer roller 9, respectively.

  The image input unit 60 is a receiving unit that receives image data transmitted to the color printer 100 from a personal computer or the like. The image signal input from the image input unit 60 is converted into a digital signal and then sent to the temporary storage unit 94.

  The operation unit 70 is provided with a liquid crystal display unit 71 and LEDs 72 indicating various states, and displays the state of the color printer 100 and displays the image forming status and the number of copies to be printed. Various settings of the color printer 100 are performed from a printer driver of a personal computer.

  In addition, the operation unit 70 includes a start button for instructing the user to start image formation, a stop / clear button used when the image formation is stopped, and various settings of the color printer 100 when making the default settings. A reset button or the like to be used is provided.

  The control unit 90 includes a central processing unit (CPU) 91 as a central processing unit, a read only memory (ROM) 92 that is a read-only storage unit, a random access memory (RAM) 93 that is a readable / writable storage unit, A plurality of (two in this case) that transmit control signals to and receive input signals from the operation unit 50, such as a temporary storage unit 94 for storing image data and the like, a counter 95, and each device in the color printer 100. At least an I / F (interface) 96 and a printing rate calculation unit 97 are provided. Further, the control unit 90 can be arranged at an arbitrary location inside the apparatus main body.

  The ROM 92 stores a program for controlling the color printer 100, numerical values necessary for control, and the like that are not changed during use of the color printer 100. The RAM 93 stores necessary data generated during control of the color printer 100, data temporarily required for control of the color printer 100, and the like. The RAM 93 (or ROM 92) also stores an operation pattern of the vibration motor 43 (see FIG. 5) when a toner recovery mode described later is executed. The temporary storage unit 94 temporarily stores an image signal input from the image input unit 60 that receives image data transmitted from a personal computer or the like and converted into a digital signal. The counter 95 counts the accumulated number of printed sheets.

  The printing rate calculation unit 97 calculates a printing rate for each image calculated based on the image signal stored in the primary storage unit 94, and calculates a cumulative printing rate obtained by integrating the printing rate. Further, the printing rate calculation unit 97 can calculate the cumulative printing rate by dividing it into a plurality of regions in the paper width direction.

  The control unit 90 transmits a control signal from the CPU 91 to the respective units and devices in the color printer 100 through the I / F 96. In addition, a signal indicating the state and an input signal are transmitted from each part or device to the CPU 91 through the I / F 96. Examples of the parts and devices controlled by the control unit 90 include, for example, the image forming units Pa to Pd, the exposure device 5, the intermediate transfer belt 8, the secondary transfer roller 9, the fixing unit 13, the bias control circuit 55, and the image input unit 60. And the operation unit 70 and the like.

  4 is a perspective view of the toner receiving support member 35 used in the developing devices 3a to 3d as viewed from the inside of the developing container 20 (left side in FIG. 2), and FIG. 5 is an exploded perspective view of the toner receiving support member 35. .

  The toner receiving member 37 is made of sheet metal and has a bent shape in which a bent portion 37a is formed along the longitudinal direction. The toner receiving surface 37b faces the developing roller 31 (see FIG. 2) across the bent portion 37a. And a substantially vertical toner dropping surface 37c facing the toner supply roller 30. The toner receiving member 37 is supported by a resin support member main body 36 via two coil springs 40. Specifically, an engagement portion 37d where one end of the coil spring 40 engages is formed at two locations on both ends of the toner receiving member 37, and a spring base 39 (see FIG. 10) is formed at the other end of the coil spring 40. Is installed. The spring pedestal 39 is held by the spring pedestal holding portion 36 a of the support member main body 36. In addition, a holder holding portion 37 e that supports the vibration generating device 42 is formed at a substantially central portion of the toner receiving member 37 by bending.

  A vibration motor 43 (see FIG. 6), a circuit for controlling the drive of the vibration motor 43, and an electronic component (not shown) are mounted in the vibration generator 42, and power is supplied to the vibration motor 43. Lead wire 45 is connected.

  Sheet members 41 a and 41 b (see FIG. 9) are attached to the surface of the toner receiving member 37. The sheet members 41 a and 41 b are formed of a material that prevents toner from adhering to the toner receiving member 37 in order to suppress toner adhesion to the toner receiving member 37. Examples of the material of the sheet members 41a and 41b include a fluororesin sheet.

  The sheet member 41 a is affixed so as to cover the surface (toner dropping surface 37 c) of the toner receiving member 37 including the boundary between the support member main body 36 and the toner receiving member 37 on the ear cutting blade 33 side. The sheet member 41b is attached so as to cover the entire boundary of the toner receiving surface 37b including the boundary between the support member main body 36 and the toner receiving member 37 on the seal member 44 side, the engaging portion 37d, and the holder holding portion 37e. Yes. The sheet members 41 a and 41 b prevent toner from adhering to the toner receiving surface 37 b and the toner dropping surface 37 c, and the toner from the boundary between the support member main body 36 and the toner receiving member 37 to the inside of the toner receiving support member 35. The malfunction of the vibration motor 43 due to the entry or toner entry is prevented.

  A film-like seal member 44 is provided at the upper end of the support member main body 36. The seal member 44 extends in the longitudinal direction (left-right direction in FIG. 4) of the support member main body 36 so that the tip portion contacts the surface of the photosensitive drum 1a, and the seal member 44 is in the developing container 20 (see FIG. 2). It has a function of shielding the toner from leaking outside.

  FIG. 6 is an exploded perspective view of the vibration generator 42 in FIG. The vibration generator 42 includes a vibration motor 43, a motor attachment plate 42 a to which the vibration motor 43 is fixed, and a cover member 42 b, and an excitation weight 50 is fixed to the output shaft 43 a of the vibration motor 43. . The vibration motor 43 is fixed so that the output shaft 43 a is along the longitudinal direction of the toner receiving member 37.

  FIG. 7 is a front view of the vibration motor 43, and FIG. 8 is a side view of the vibration motor 43 as viewed from the side of the vibration weight 50. When seen from the direction of the output shaft 43a of the vibration motor 43 (the right direction in FIG. 7), the vibration weight 50 has a cam shape in which a notch 50a is formed in a part of the disk as shown in FIG. Thus, the shape is asymmetric with respect to the output shaft 43a. When the output shaft 43a rotates at a speed higher than a predetermined speed, the centrifugal force acting on the notch 50a is smaller than that of the other portions, so that an uneven centrifugal force is applied to the vibration weight 50. As the centrifugal force is transmitted to the output shaft 43a, the vibration motor 43 vibrates. The shape of the vibration weight 50 is not limited to a cam shape, and may be an arbitrary shape that shifts the center of gravity with respect to the output shaft 43a.

  9 and 10 are side cross-sectional views showing the internal configuration of the toner receiving support member 35 used in the developing device 3a of this embodiment. 9 shows a cross section of the toner receiving support member 35 in the vicinity of the vibration motor 43 (cross section taken along the line XX ′ in FIG. 5), and FIG. 10 shows a cross section including the coil spring 40 of the toner receiving support member 35 (YY ′ in FIG. 5). (Arrow cross section).

  The toner receiving member 37 is inclined such that the toner receiving surface 37b facing the developing roller 31 is inclined upward from the toner supply roller 30 side toward the photosensitive drum 1a side, and the toner falling surface 37c facing the toner supply roller 30. Are arranged so as to be substantially vertical. In addition, the angle and surface roughness (friction coefficient) of the toner receiving surface 37b are adjusted so that the toner accumulated on the toner receiving surface 37b does not fall naturally due to gravity or vibration accompanying driving of the developing device 3a.

  As shown in FIGS. 9 and 10, only the edge 37f on the toner supply roller 30 side of the toner receiving member 37 is in contact with the support member main body 36, and the edge 37g on the opposite side (photosensitive drum 1a side) is It is a free end. The substantially central portion of the toner receiving surface 37b in the width direction (left-right direction in FIG. 9) is supported by the support member body 36 via the vibration generator 42. Thus, the toner receiving member 37 is configured to be swingable with the end edge 37f as a fulcrum. Further, the vibration motor 43 is disposed so that the output shaft 43 a is substantially parallel to the longitudinal direction of the toner receiving member 37.

  The color printer 100 according to the present embodiment can execute a toner recovery mode in which the toner receiving member 37 in the developing devices 3a to 3d is vibrated by the vibration generating device 40 during non-image formation to shake off the toner accumulated on the toner receiving surface 37b. It is. Specifically, when the output shaft 43a of the vibration motor 43 is rotated at a high speed (for example, about 10,000 rpm) during non-image formation, the excitation weight 50 also rotates at a high speed together with the output shaft 43a. At this time, since an uneven centrifugal force is applied to the vibration weight 50, the vibration generator 42 including the vibration motor 43 and the motor mounting holder 42 vibrates via the output shaft 43a. The toner receiving member 37 to which the vibration generating device 42 is attached also vibrates. Specifically, the toner receiving surface 37b of the toner receiving member 37 vibrates so that the amplitude increases toward the end edge 37g with the end edge 37f as a fulcrum. Due to the vibration of the toner receiving member 37, the toner accumulated on the edge 37g side of the toner receiving surface 37b is bounced up toward the edge 37f (in the direction of the white arrow) and gradually moves toward the edge 37f.

  Due to the vibration of the toner receiving surface 37b, as shown in FIG. 10, the toner T deposited on the toner receiving surface 37b slides downward (in the direction of the white arrow in FIG. 10) along the inclination of the toner receiving surface 37b, and is substantially vertical. The toner falls freely into a region R sandwiched between the toner dropping surface 37c and the toner supply roller 30. A portion of the toner that has fallen into the region R passes through the gap between the ear cutting blade 33 and the toner supply roller 30 and falls into the supply conveyance chamber 22 as it is.

  In the present embodiment, in order to return the toner that has fallen to the region R to the supply conveyance chamber 22, the developing roller 31 and the toner supply roller 30 are rotated in the opposite direction (clockwise direction in FIG. 9) during image formation. Rotate (reverse). By rotating the toner supply roller 30 in the reverse direction, the toner that has fallen into the region R and accumulated on the tip of the ear cutting blade 33 is scraped off by the magnetic brush of the toner supply roller 30, and is rotated around the surface of the toner supply roller 30. After passing through the gap between the toner supply roller 30 and the ear cutting blade 33 and being peeled off from the toner supply roller 30 at the same polarity part of the fixed magnet body, the toner is forcibly returned to the supply conveyance chamber 22.

  When the developing roller 31 and the toner supply roller 30 are rotated in the reverse direction, the magnetic force of the magnetic pole (regulatory pole) of the fixed magnet body facing the ear cutting blade 33 so that the ears of the magnetic brush formed on the toner supply roller 30 become long. By adjusting the arrangement, the effect of scraping off the toner deposited on the tip of the ear cutting blade 33 is enhanced. Further, when the developing roller 31 and the toner supply roller 30 are rotated in the reverse direction, the agitating and conveying screw 25a and the supply and conveying screw 25b are also rotated in the reverse direction, so that the developer in the developing container 20 overflows from the toner supply port or the developing container 20 In some cases, the developer may be biased and noise of the toner density sensor 28 may be generated. Therefore, after the developing roller 31 and the toner supply roller 30 are rotated in reverse, it is preferable to rotate the developing roller 31 and the toner supply roller 30 in order for a predetermined time.

  Note that when the toner receiving member 37 is vibrated, the toner supply roller 30 and the developing roller 31 can be rotated forward. By rotating the toner supply roller 30 forward, a part of the toner dropped from the toner receiving surface 37 b to the region R adheres to the magnetic brush on the toner supply roller 30. The remaining toner that has not adhered to the magnetic brush on the toner supply roller 30 passes through the gap between the toner supply roller 30 and the ear cutting blade 33 and falls into the supply conveyance chamber 22.

  In the toner recovery mode, the output shaft 43a of the vibration motor 43 and the outer peripheral surface of the output shaft 43a facing the toner receiving member 37 are supported from the free end (end edge 37e) of the toner receiving member 37 as a fulcrum (end edge 37d). In the direction of moving toward (counterclockwise in FIG. 9). By rotating the output shaft 43a in this direction, the toner receiving member 37 vibrates so as to move the toner accumulated on the toner receiving surface 37b from the end edge 37g side to the end edge 37f side.

  On the other hand, when the output shaft 43a is rotated in the reverse direction (clockwise direction in FIG. 9), the toner is moved up from the edge 37f side to the edge 37g side by the vibration of the toner receiving member 37. Therefore, the toner deposited on the toner receiving surface 37b does not slide down. Therefore, by rotating the output shaft 43a of the vibration motor 43 as in the present embodiment, the toner accumulated on the toner receiving surface 37b can be effectively dropped to the region R along a descending gradient.

  Further, since the sheet members 41 a and 41 b are attached to the surface of the toner receiving member 37, it is possible to suppress toner adhesion to the toner receiving member 37. Further, since the sheet members 41a and 41b are attached so as to cover the boundary between the support member main body 36 and the toner receiving member 37, the engaging portion 37d, and the holder holding portion 37e, the support member main body 36 and the toner receiving member It is also possible to prevent the toner from entering the inside of the toner receiving support member 35 from the boundary with the toner 37 and the malfunction of the vibration motor 43 due to the toner entering.

  The execution timing of the toner recovery mode may be performed every time the printing operation is completed, or at a predetermined timing such as when the number of printed sheets reaches a predetermined number or when the temperature in the developing device 3a exceeds a predetermined level. You may make it do. The timing for vibrating the toner receiving member 37 and the timing for rotating the developing roller 31 and the toner supply roller 30 in reverse (or forward) may be the same or different. Further, by vibrating the toner receiving member 37 every time the predetermined number of printed sheets is reached, the vibration of the toner receiving member 37 is automatically executed according to the number of printed sheets. Therefore, it is not necessary for the user himself to manually set the vibration of the toner receiving member 37, and it is possible to avoid setting mistakes, forgetting to set, or unnecessary vibration.

  By the way, the amplitude of the toner receiving member 37 is determined by the relationship between the resonance frequency of the toner receiving member 37 and the rotational speed (rotational frequency) of the vibration motor 43. The distribution of the amplitude of the toner receiving member 37 when the rotation frequency of the vibration motor 43 is changed is shown in FIGS. The toner receiving member 37 is formed by bending a stainless steel plate having a thickness of 0.2 mm. The length is 303 mm, the width of the toner receiving surface 37 b is 7.4 mm, and the width of the toner falling surface 37 c is 2.5 mm. The angle of the toner receiving surface 37b with respect to 37c is 120 °. Further, the vibration generating device 42 is mounted slightly closer to the rear end from the longitudinal center of the toner receiving member 37.

  FIG. 11 is a graph showing the amplitude distribution of the toner receiving member 37 when the vibration motor 43 is rotated at 80 Hz (4800 rpm). As shown in FIG. 11, at the resonance frequency of 80 Hz that appears first, the both end portions in the longitudinal direction of the toner receiving member 37 are small in the range of 0 to 2 μm even though they are free ends. The central portion of the toner receiving member 37 in the longitudinal direction has a relatively large amplitude of 15 to 18 μm.

  12 to 16 show the amplitude of the toner receiving member 37 when the vibration motor 43 is rotated at 90 Hz (5400 rpm), 100 Hz (6000 rpm), 110 Hz (6600 rpm), 120 Hz (7200 rpm), and 130 Hz (7800 rpm), respectively. It is a graph which shows distribution. As shown in FIGS. 12 to 16, when the vibration motor 43 is rotated in the range of 90 to 130 Hz, the amplitude is as small as 2 μm or less over the entire region in the longitudinal direction of the toner receiving member.

  FIG. 17 is a graph showing the amplitude distribution of the toner receiving member 37 when the vibration motor 43 is rotated at 135 Hz (8084 rpm). As shown in FIG. 17, at 135 Hz, which is the resonance frequency of the toner receiving member 37, both end portions and the central portion in the longitudinal direction of the toner receiving member become nodes of amplitude, and the amplitude becomes large at the intermediate portion between both end portions and the central portion. In the middle part from the center part to the front end part (end part far from the vibration generator 42), the amplitude is 40 μm, and in the middle part from the center part to the rear end part (end part close to the vibration generator 42) The amplitude is increased to 30 μm.

  FIG. 18 is a graph showing the amplitude distribution of the toner receiving member 37 when the vibration motor 43 is rotated at 140 Hz (8400 rpm). As shown in FIG. 18, at 140 Hz, the both ends and the center in the longitudinal direction of the toner receiving member become nodes of amplitude as in FIG. 17, but the amplitude is 2 μm or less over the entire length of the toner receiving member 37 in the longitudinal direction. small.

  It is sufficient that the amplitude of the toner receiving member 37 necessary for shaking off the toner deposited on the toner receiving surface 37b is about half (2 to 3 μm) of the particle diameter of the toner.

  Therefore, in the present embodiment, the operation frequency of the vibration motor 43 stored in the RAM 93 (or ROM 92) is read by the control unit 90, and the vibration frequency applied to the toner receiving member 37 in the toner recovery mode using the read operation pattern. That is, the rotation frequency of the vibration motor 43 is changed. As a result, as shown in FIGS. 11 to 18, the toner can be vibrated with an amplitude (2 μm or more) sufficient to shake the toner over the entire length of the toner receiving member 37, and the toner is shaken off. Therefore, it is possible to eliminate a portion where the amplitude is not sufficient. Therefore, the toner deposited on the toner receiving surface 37b can be efficiently shaken off over the entire area in the longitudinal direction.

  Specifically, as shown in FIG. 19, the rotational speed of the vibration motor 43 is raised from 0 to 4800 rpm (80 Hz). after that. The rotational speed is increased to 8400 rpm (140 Hz) over 10 seconds, lowered from 8400 rpm to 4800 rpm over 10 seconds, and then returned to 0 again.

  As a result, when the rotation frequency of the vibration motor 43 becomes 80 Hz, the amplitude near the central portion in the longitudinal direction of the toner receiving member 37 increases, and when the rotation frequency of the vibration motor 43 becomes 135 Hz, the toner receiving member 37. Since the amplitude in the vicinity of the intermediate portion from the central portion to both ends of the toner receiving member 37 increases, the toner receiving member 37 can be vibrated with sufficient amplitude to shake off the toner in the entire longitudinal direction.

  In this embodiment, since the amplitude of the toner receiving member 37 increases at the resonance frequencies of 80 Hz and 135 Hz, the rotation speed of the vibration motor 43 is increased from 0 to 8084 rpm (135 Hz) over 5 seconds as shown in FIG. It may be controlled to increase, hold at 135 Hz for 1 second, lower to 4800 rpm (80 Hz) over 5 seconds, hold at 80 Hz for 1 second, and then return to 0 again.

  In this case, since the vibration time at the resonance frequencies of 80 Hz and 135 Hz becomes long, the toner can be sufficiently shaken off even if the vibration time is 12 seconds. That is, the vibration time of the vibration motor 43 required to shake off the toner can be shortened as compared with the case where the rotation speed of the vibration motor 43 is not held at the resonance frequency (20 seconds).

  Note that the fluctuation pattern of the rotational speed of the vibration motor 43 is not limited to the patterns shown in FIGS. 19 and 20, and can be arbitrarily changed according to the distribution of the toner accumulation amount on the toner receiving surface 37a. Since it is difficult to directly measure the toner accumulation amount, the print rate calculation unit 97 (see FIG. 3) divides the cumulative print rate into a plurality of regions in the longitudinal direction of the toner receiving member 37 (paper width direction). calculate. Then, the distribution of the toner accumulation amount on the toner receiving surface 37a is estimated using the calculated cumulative printing rate.

  Generally, when the printing rate of the entire output image is high, that is, when the amount of toner replenished from the toner containers 4a to 4d to the developing devices 3a to 3d is large, the replenishment toner and the carrier in the developing devices 3a to 3d are mixed. It becomes insufficient and the charge amount of the toner decreases. In particular, since the toner charge amount (charge amount distribution) in the developing devices 3a to 3d is shifted in a high-humidity environment to a lower direction, the development is performed when an image with a high printing rate is continuously printed in a high-humidity environment. In the devices 3a to 3d, the ratio of toner with a low charge amount increases.

  On the other hand, at the time of image formation, the toner on the developing roller 31 that has not been used for development is peeled off by the toner supply roller 30, and new toner is resupplied from the toner supply roller 30 to the developing roller 31. When the amount of toner peeled off from the developing roller 31 by the toner supply roller 30 increases, the amount of toner scattered in the developing container 20 also increases. At this time, if there is a portion where the toner amount to be peeled off from the developing roller 31 in the longitudinal direction of the toner receiving member 37 is large, that is, a region where the cumulative print rate is a predetermined value or less (low print rate region), The amount of toner that scatters also increases. Therefore, the toner deposited on the portion corresponding to the low printing rate area in the longitudinal direction of the toner receiving member 37 increases.

  For example, when there are low print rate areas at both ends in the paper width direction, the toner receiving surface increases because the toner that is peeled off from the developing roller 31 to the toner supply roller 30 at both ends in the paper width direction increases. The amount of toner accumulation near both ends of 37a increases. Therefore, by increasing the vibration time in the vicinity of 8084 rpm (135 Hz) at the time of executing the toner recovery mode, the vibration in the state where both ends of the toner receiving member 37 are large as shown in FIG. 17 is maintained for a certain time. The toner deposited near the both ends of the toner receiving surface 37a can be shaken off with priority.

  On the other hand, when the low printing rate area exists in the central portion in the paper width direction, the toner receiving surface increases because the toner that is peeled off from the developing roller 31 to the toner supply roller 30 in the central portion in the paper width direction falls. The amount of toner accumulation near the center of 37a increases. Therefore, by increasing the vibration time in the vicinity of 4800 rpm (80 Hz) when executing the toner recovery mode, the vibration in the state where the amplitude of the central portion of the toner receiving member 37 is large as shown in FIG. The toner deposited near the center of the toner receiving surface 37a can be shaken off with priority.

  As a method of extending the vibration time while maintaining the rotation speed (rotation frequency) of the vibration motor 43 in the vicinity of a predetermined value, a method of stopping the fluctuation of the rotation speed of the vibration motor 43 at a predetermined value for a certain time, or the vibration motor 43 There is a method in which the fluctuation speed of the rotational speed is set to a predetermined speed or less near a predetermined value.

  In addition, this invention is not limited to the said embodiment, A various change is possible in the range which does not deviate from the meaning of this invention. For example, the shape and configuration of the toner receiving support member 35 and the toner receiving member 37 shown in the above embodiment are merely examples, and are not particularly limited to the above embodiment, and these are appropriately set according to the apparatus configuration and the like. be able to.

  The present invention can be used for an image forming apparatus including a developing device having a toner receiving member facing the developing roller between a region where the image carrier and the developing roller are opposed to each other and a regulating blade. By utilizing the present invention, it is possible to provide a developing device capable of efficiently collecting the deteriorated toner accumulated on the toner receiving member.

Pa to Pd Image forming section 1a to 1d Photosensitive drum (image carrier)
3a to 3d Developing device 4a to 4d Toner container 20 Developing container (casing)
30 Toner supply roller 31 Developing roller 33 Ear cutting blade (regulating blade)
35 toner receiving support member 35a tip portion 36 support member main body 37 toner receiving member 37a bent portion 37b toner receiving surface 37c toner falling surface 40 vibration generators 41a and 41b sheet member 90 control unit 97 print rate calculating unit 100 color printer (image forming) apparatus)

Claims (9)

An image carrier on which an electrostatic latent image is formed;
A developing roller that is disposed to face the image carrier and supplies toner to the image carrier in a region facing the image carrier;
A toner supply roller that is disposed to face the developing roller and supplies toner to the developing roller in a region facing the developing roller;
A regulating blade disposed opposite to the toner supply roller at a predetermined interval;
A casing that houses the developing roller, the toner supply roller, and the regulating blade;
A toner receiving support member disposed in the casing and facing the developing roller or the toner supply roller between the regulating blade and the image carrier;
A toner receiving member that has a toner receiving surface that is disposed along the longitudinal direction of the toner receiving support member so as to have a downward gradient from the image carrier side toward the toner supply roller side and that receives toner falling from the developing roller. When,
A vibration generator for vibrating the toner receiving member;
A developing device that develops an electrostatic latent image formed on the image carrier into a toner image;
A control unit for controlling driving of the developing device;
An image forming apparatus capable of executing a toner recovery mode in which the toner receiving member is vibrated by the vibration generating device during non-image formation to shake off the toner deposited on the toner receiving surface.
The image forming apparatus is characterized in that the control unit changes the frequency of the vibration generating device so that the amplitude of the toner receiving member during the execution of the toner recovery mode is equal to or greater than a predetermined value over the entire region in the longitudinal direction. apparatus. A printing rate calculation unit that calculates the cumulative printing rate of the toner image developed by the developing device by dividing the cumulative printing rate into a plurality of regions in the longitudinal direction of the toner receiving member;
When the toner collection mode is executed, the control unit responds to the low print rate area when there is a low print ratio area in which the cumulative print ratio is less than or equal to a predetermined value after the previous execution of the toner collection mode. 2. The image forming apparatus according to claim 1, wherein the vibration generating device is vibrated for a certain period of time at a frequency at which an amplitude of the toner receiving member in a portion to be a predetermined value or more.   The control unit stops a change in the frequency of the vibration generating device for a certain period of time at a frequency at which the amplitude of the toner receiving member in a portion corresponding to the low printing rate region is equal to or greater than a predetermined value, or the low printing rate 3. The image according to claim 2, wherein a fluctuation speed of the frequency of the vibration generating device in the vicinity of a frequency at which the amplitude of the toner receiving member in a portion corresponding to the region is equal to or higher than a predetermined value is set to be equal to or lower than a predetermined speed. Forming equipment.   The control unit stops the change in the frequency of the vibration generating device at a resonance frequency of the toner receiving member, and restarts the change in the frequency of the vibration generating device after a predetermined time has elapsed. The image forming apparatus according to claim 3. The vibration generating device has a vibration motor fixed to the back surface of the toner receiving member, and an excitation weight fixed so that the center of gravity is shifted with respect to the output shaft of the vibration motor.
5. The image forming apparatus according to claim 1, wherein the control unit changes a vibration frequency of the vibration generator by changing a rotation speed of the vibration motor. The vibration motor is fixed to a back surface of the toner receiving member so that an output shaft is substantially parallel to a longitudinal direction of the toner receiving member,
The toner receiving member is swingably supported with an edge on the toner supply roller side as a fulcrum and an edge on the image carrier side as a free end,
The output shaft of the vibration motor is rotated in a direction in which an outer peripheral surface of the output shaft of the vibration motor facing the toner receiving member moves from a free end side of the toner receiving member toward a fulcrum side. Item 6. The image forming apparatus according to Item 5.   The image forming apparatus according to claim 1, wherein the developing roller and the toner supply roller are rotated in a direction opposite to that at the time of image formation while the vibration generator is driven.   8. The image forming apparatus according to claim 7, wherein after the driving of the vibration generating device is finished, the developing roller and the toner supply roller are continuously rotated for a predetermined time in the same direction as in image formation.   7. The image forming apparatus according to claim 1, wherein the developing roller and the toner supply roller are rotated in the same direction as during image formation while the vibration generator is driven.

Images