JP5716334B2 - Developing device, cartridge, and image forming apparatus - Google Patents

Description

  The present invention relates to a developing device, a cartridge, and an image forming apparatus.

  A developing device main body provided with a rotating body inside, an input gear meshing with a driving gear driven to rotate by a driving motor, a shaft that can be engaged with and disengaged from the rotating body of the developing device main body, and a rotation integrally with the shaft The developing device has a gear that rotates in response to the rotation of the input gear and includes a drive module that is attached to a side surface of the developing device body. In order to provide a developing device mounting structure in which vibration of the driving gear is reduced, stopper means for prohibiting the drive module from moving to a deeper engagement than the optimal engagement position of the drive gear and the input gear, and the drive module is pressed against the stopper means There exists what is comprised with the biasing means to perform (refer patent document 1).

JP-A-7-199614

  An object of the present invention is to suppress unevenness in the density of a toner image caused by a resonance phenomenon of a magnet shaft portion used for development.

The invention of claim 1 wherein is a developing device for developing an electrostatic latent image formed on the image carrier, both end portions and containing body that forms the outer shape of the device, are housed in the housing body and by the housing body both ends but is rotatably supported, a cylindrical developer holder for holding a developer on the surface, by the inside of the developer holding portion exists along the axis of the developer holding portion and the housing body And a magnet shaft portion that attracts the developer by magnetic force, and is supported by the magnet shaft portion inside the developer holding portion and has a predetermined distance along the axis of the developer holding portion. spaced is provided, and a rotation support portion to which the developer holding portion is rotatably supporting the developer holding unit to rotate around the magnet shaft portion is connected to the developer holding unit, from a drive source Transmits driving force to the developer holder A that transmission unit, the magnet shaft portion is at a position the center of gravity is eccentric, the direction in which the natural frequency in the direction along the radial direction of the developer holding portion is centered on the axis of the developer holding portion The rotation support portion is a portion where the magnet shaft portion is supported by the container in a direction along the axis of the developer holding portion at the both end portions of the developer holding portion. The developer holding part is supported at a position closer to the center of the developer holding part than each of the above, the excitation frequency of the transmission part is specified based on the distance between the rotation support parts, and the developer The developing device is characterized in that the holding unit has a frequency different from the natural frequency of the magnet shaft in the direction toward the image holding member .
According to a second aspect of the present invention, the transmission unit includes a gear that transmits a driving force from the driving source to the developer holding unit at a frequency different from the natural frequency of the magnet shaft unit. The developing device according to claim 1 .
According to a third aspect of the present invention, a container having an outer shape that is detachable from the main body of the image forming apparatus, an image carrier that rotates while holding an electrostatic latent image on a surface, and the image carrier are provided side by side. A cylindrical developer holding portion that is housed in the container and is rotatably supported by the container, and that holds the developer on the surface thereof , and the development inside the developer holding portion. Both ends are supported by the container that exists along the axis of the developer holding portion , the magnet shaft portion attracts the developer by magnetic force, and is supported by the magnet shaft portion inside the developer holding portion. along the axis of the developer holding portion is provided at a predetermined distance, the rotation support portion in which the developer holding portion is rotatably supporting the developer holding unit to rotate around the magnet shaft And the developer holding part It is, and a transmission unit for transmitting a driving force from the driving source to the developer holding portion, said magnet shaft is unique in the direction along the radial direction of the developer holding portion is in a position where the center of gravity is decentered The frequency varies depending on the angle of the direction around the axis of the developer holding portion, and the rotation support portion is along the axis of the developer holding portion at the both ends of the developer holding portion. The developer holding part is supported at a position closer to the center of the developer holding part than each of the places where the magnet shaft part is supported by the container in the direction in which the vibration is applied. The cartridge is characterized in that the frequency is specified based on a distance between the rotation support portions and has a frequency different from a natural frequency of the magnet shaft portion in a direction in which the developer holding portion faces the image holding member .
According to a fourth aspect of the present invention, a container that forms the outer shape of the apparatus, an image carrier that rotates while holding an electrostatic latent image on the surface, and the image carrier are provided side by side, and are accommodated in the container. with both end portions by the housing body is rotatably supported, lies along a cylindrical developer holder for holding a developer on the surface, the axis of the said developer holding portion inside the developer holding section Both ends of the container are supported by the container, and a magnet shaft portion that attracts the developer by magnetic force, and is supported by the magnet shaft portion inside the developer holding portion and along the axis of the developer holding portion. provided at a predetermined distance, rotation and rotation support portion to which the developer holding portion is rotatably supporting the developer holding unit to rotate around the magnet shaft portion, said developer holding section A power source for supplying the power to be Connect the serial power source and said developer holding section, a driving force supplied from the power source and a transmission unit that transmits to the developer holding portion, said magnet shaft portion at a position where the center of gravity is decentered Yes, the natural frequency in the direction along the radial direction of the developer holding portion varies depending on the angle of the direction around the axis of the developer holding portion, and the rotation support portion is At both ends, the developer is held at positions closer to the center of the developer holding part than the portions where the magnet shaft is supported by the container in the direction along the axis of the developer holding part. The excitation frequency of the transmission unit is specified based on the distance between the rotation support units, and the natural frequency of the magnet shaft unit in the direction in which the developer holding unit faces the image holding body Features different frequencies That is an image forming apparatus.

According to the first aspect of the present invention, it is possible to further suppress unevenness in the density of the toner image due to the resonance phenomenon of the magnet shaft portion, as compared with the case where this configuration is not provided. Further, as compared with the case where the present configuration is not provided, for example, even when an eccentric magnet shaft portion is used, toner image density unevenness can be further suppressed.
According to the second aspect of the invention, as compared with the case not having the present structure, that the number of teeth of the selected gear, the density unevenness of a toner image can be suppressed in a more simple structure.
According to the third aspect of the present invention, it is possible to further suppress the unevenness in the density of the toner image due to the resonance phenomenon of the magnet shaft portion when mounted on the apparatus, as compared with the case where this configuration is not provided. A cartridge can be provided.
According to the fourth aspect of the present invention, it is possible to provide an image forming apparatus that can further suppress unevenness in the density of the toner image due to the resonance phenomenon of the magnet shaft portion as compared with the case where the present configuration is not provided.

1 is a schematic configuration diagram illustrating an image forming apparatus to which the exemplary embodiment is applied. It is sectional drawing along the axial direction of the developing device to which this Embodiment is applied. It is sectional drawing of the radial direction of the developing device to which this Embodiment is applied. It is a schematic diagram which shows that the mag roll in this Embodiment is brought close to one direction. It is explanatory drawing for demonstrating the support point in the measurement of the natural frequency of a mag roll shaft.

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
<Image forming apparatus 100>
FIG. 1 is a schematic configuration diagram illustrating an image forming apparatus 100 to which the exemplary embodiment is applied. An image forming apparatus 100 shown in FIG. 1 is a so-called tandem color printer. The image forming apparatus 100 includes an image forming unit 10 that forms an image corresponding to image data of each color, and a control unit 6 that controls the operation of the entire image forming apparatus 100. The image forming apparatus 100 is connected to an external device such as a personal computer (PC) 3 or an image reading device 4, and an image processing unit 5 that performs predetermined image processing on image data received from these devices. It has. Further, the image forming apparatus 100 includes a power supply unit 9 that supplies power to each unit, a paper stacking unit 40 that stacks the paper S supplied to the image forming unit 10, and a user who receives an instruction given by a user operation. And an interface 7. Furthermore, the image forming apparatus 100 includes a paper discharge stacking unit 49 that stacks sheets S on which images are formed by the image forming unit 10.
In the present embodiment, the image forming apparatus 100 is described as a so-called tandem color printer, but the present invention is not limited to this. For example, the toner images of the respective colors sequentially formed on a single photoconductor are primarily transferred in a state where they are superposed on the intermediate transfer member, and then transferred onto the intermediate transfer member in a multiple manner. A so-called multi-pass (4-cycle) type color printer may be used in which a color image is formed by secondary transfer onto a recording medium using a secondary transfer roll.

<Image forming unit 10>
The image forming unit 10 includes four image forming units 1Y, 1M, 1C, and 1K that are arranged in parallel at regular intervals. Each of the image forming units 1Y, 1M, 1C, and 1K uniformly charges the photosensitive drum 12 that forms an electrostatic latent image and holds the toner image, and the surface of the photosensitive drum 12 with a predetermined potential. Charging device 13. Each image forming unit 1Y, 1M, 1C, 1K has an exposure device 14 for exposing the photosensitive drum 12 charged by the charger 13 based on image data, and a photosensitive drum 12 on the photosensitive drum 12. And a developing device 20 that develops the formed electrostatic latent image using a developer. Further, each of the image forming units 1Y, 1M, 1C, and 1K includes a cleaner 16 that cleans the surface of the photosensitive drum 12 after transfer.
The image forming units 1Y, 1M, 1C, and 1K are configured in substantially the same manner except for the toner stored in the developing device 20. Each of the image forming units 1Y, 1M, 1C, and 1K forms yellow (Y), magenta (M), cyan (C), and black (K) toner images. For this reason, in the following description, the components of the image forming units 1Y, 1M, 1C, and 1K are distinguished from each other by adding “Y”, “M”, “C”, and “K”, respectively. However, when it is not necessary to distinguish, these symbols are not attached. For example, when the developing device of the image forming unit 1Y is meant, it is expressed as “developing device 20Y”, and when the developing devices 20Y, 20M, 20C, and 20K are not distinguished, they are expressed as “developing device 20”.

In the present embodiment, the developing device 20 and the photosensitive drum 12 are described as members configured independently of each other, but the present invention is not limited to this. The developing device 20 and the photosensitive drum 12 may be integrally formed and may be configured as a so-called cartridge that is detachably provided in the image forming apparatus 100.
Furthermore, in the present embodiment, a two-component developer including toner and carrier is used as the developer, but a one-component developer may be used. In the following description, the two-component developer is simply referred to as a developer.

The image forming unit 10 includes an intermediate transfer belt 18 to which the color toner images formed on the photosensitive drums 12 of the image forming units 1 are transferred in a multiple manner. Further, the image forming unit 10 includes a primary transfer roll 17 that sequentially transfers (primary transfer) each color toner image formed by each image forming unit 1 to the intermediate transfer belt 18. Further, the image forming unit 10 includes a secondary transfer roll 19 that collectively transfers (secondary transfer) each color toner image formed on the intermediate transfer belt 18 onto a sheet S that is a recording material (recording paper); And a fixing device 61 for fixing the second-transferred color toner images to the paper S.
In addition, the image forming unit 10 includes a pickup roller 68 that sequentially feeds the sheets S stacked on the sheet stacking unit 40, and a transport roll 69 that transports the sheets S sent by the pickup roller 68. Further, the image forming unit 10 includes an exit sensor 63 that detects passage of the paper S on which the toner image is fixed in the fixing device 61.

In the image forming apparatus 100 according to the present embodiment, the image data input from the PC 3 or the image reading apparatus 4 is subjected to predetermined image processing by the image processing unit 5, and then each image data is received via an interface (not shown). It is sent to the image forming unit 1. For example, in the image forming unit 1 </ b> K that forms a black (K) toner image, the photosensitive drum 12, which is an example of an image holding member, rotates at a predetermined potential by the charger 13 while rotating in the arrow A direction. The exposure device 14 scans and exposes the image data based on the image data transmitted from the image processing unit 5. Thereby, an electrostatic latent image related to a black (K) color image is formed on the photosensitive drum 12. The electrostatic latent image formed on the photosensitive drum 12 is an example of a developer supply unit, and is developed by the developing device 20 at a developing portion where the photosensitive drum 12 and the developing device 20 face each other. A black (K) toner image is formed on the photosensitive drum 12. Similarly, in the image forming units 1Y, 1M, 1C, and 1K, yellow (Y), magenta (M), cyan (C), and black (K) toner images are formed, respectively.
The toner images of the respective colors formed by the image forming units 1 are sequentially electrostatically attracted by the primary transfer roll 17 onto the intermediate transfer belt 18 that moves in the direction of arrow B, and the superimposed toner images on which the respective color toners are superimposed are formed. It is formed. The superimposed toner image on the intermediate transfer belt 18 is conveyed to a region (secondary transfer portion Tr) where the secondary transfer roll 19 is disposed as the intermediate transfer belt 18 moves.

  On the other hand, the paper S stacked on the paper stacking unit 40 is sent out by the pickup roller 68. The sheet S sent out by the pickup roller 68 is supplied to the secondary transfer unit Tr by the transport roll 69 in accordance with the timing at which the superimposed toner image is transported to the secondary transfer unit Tr. The superimposed toner image is collectively electrostatically transferred onto the paper S conveyed by the conveying roll 69 by the action of the transfer electric field formed by the secondary transfer roll 19 in the secondary transfer portion Tr.

Thereafter, the sheet S on which the superimposed toner image is electrostatically transferred is peeled from the intermediate transfer belt 18 and conveyed to the fixing device 61. The toner image on the paper S conveyed to the fixing device 61 is fixed on the paper S by being subjected to a fixing process by heat and pressure by the fixing device 61. The sheet S on which the fixed image is formed is further transported by the transport roll 69, detected by the exit sensor 63, and then stacked on the paper discharge stacking unit 49 provided in the discharge unit of the image forming apparatus 100.
On the other hand, toner (transfer residual toner) adhering to the intermediate transfer belt 18 after the secondary transfer is removed from the surface of the intermediate transfer belt 18 by the belt cleaner 15 after the completion of the secondary transfer to prepare for the next image forming cycle. It is done.
In this way, image formation in the image forming apparatus 100 is repeated for a cycle corresponding to the number of printed sheets.

<Structure of developing device 20>
Next, the structure of the developing device 20 will be described with reference to FIGS. FIG. 2 is a cross-sectional view along the axial direction of the developing device 20 to which the exemplary embodiment is applied. FIG. 3 is a cross-sectional view in the radial direction of the developing device 20 to which the exemplary embodiment is applied.
The developing device 20 is provided with a housing 21 that forms the outer shape of the device and accommodates the developer therein. Further, the developing device 20 includes a developing roll 22 that is accommodated in the housing 21 and is rotatably supported. Further, the developing device 20 includes a cover member 50 that is attached to the housing 21 in which a gear 47 that transmits a force from a motor (not shown) is accommodated.

The developing roll 22, which is an example of the developer holding portion, includes a mag roll shaft 31, a cylindrical sleeve 41 supported by the second bearing 24 so as to be rotatable around the mag roll shaft 31, and the sleeve And a support shaft 43 that supports 41.
A mag roll shaft 31, which is an example of a magnet shaft portion, has a magnet portion 32 having a magnetic pole on the surface and attracting developer, and is formed to protrude toward both ends of the magnet portion 32, and has a smaller diameter than the magnet portion 32. And an axial center portion 33. A flange portion 34 is formed between the magnet portion 32 and the shaft core portion 33. The mag roll shaft 31 has a natural frequency, but the value of the natural frequency of the eccentric mag roll shaft 31 differs depending on which radial frequency it is. The fact that the natural frequency differs depending on the radial direction of the mag roll shaft 31 makes the natural frequency of the developing roll 22 different depending on the radial direction of the developing roll 22.
In addition, the magnet part 32 with which the mag roll shaft 31 in this Embodiment is equipped may be comprised from the several magnet part 32 from which the material and weight provided in the circumferential direction of the mag roll shaft 31 differ.

The sleeve 41 is disposed so as to surround the outer periphery of the magnet portion 32 of the mag roll shaft 31 with a gap from the magnet portion 32.
At both ends of the sleeve 41, a stepped and cylindrical support shaft 43 that supports the sleeve 41 is provided so as to protrude in the axial direction of the sleeve 41. An outer peripheral annular step 45 is formed on the outer periphery of the support shaft 43, and an inner peripheral annular step 46 is provided on the inner periphery on the sleeve 41 side.

  A first bearing 23 is inserted into each mounting hole 21 </ b> B formed in the side surface 21 </ b> A of the housing 21. A support shaft 43 of a sleeve 41 is fitted inside the first bearing 23, and the first bearing 23 is positioned by an outer peripheral annular step 45. A gear 47, which is an example of a transmission unit, is fixed to the support shaft 43 provided at one end of the sleeve 41 so as not to rotate with respect to the support shaft 43. Note that the support shaft 43 provided at the other end of the sleeve 41 is not provided with the gear 47. Furthermore, the gear 47 of the present embodiment may be constituted by a plurality of gears.

  A second bearing 24, which is an example of a rotation support portion, is inserted into the inner circumferential annular step portion 46 of the sleeve 41, and the shaft core portion 33 is inserted inside the second bearing 24. The second bearing 24 is positioned by the flange portion 34 of the mag roll shaft 31. As shown in FIG. 2, the shaft core portion 33 projects from the side surface 21 </ b> A of the housing 21. The shaft core 33 may or may not protrude from the housing 21.

  A fixing hole 52 is formed in the cover member 50 which is an example of a container, and the shaft core portion 33 is inserted into the fixing hole 52. In addition, the holding member 60 is integrally formed with the cover member 50. The holding portion 60 has a shape protruding toward the photosensitive drum 12. Then, as shown in FIG. 3, the holding portions 60 integrally formed with the cover members 50 provided on both end sides of the sleeve 41 are pressed against the photosensitive drum 12, thereby developing the photosensitive drum 12 and the developing member. The roll 22 is held at a predetermined interval.

<Operation of Developing Device 20>
Here, the operation of the developing device 20 will be described with reference to FIGS. 1 and 2.
First, a motor (not shown) that receives an instruction from the controller 6 is driven, and a gear 47 that transmits the force from the motor to the developing roll 22 rotates. The rotating gear 47 rotates the support shaft 43 and the sleeve 41 supported by the support shaft 43 around the mag roll shaft 31. A developer attracted by the magnet portion 32 of the mag roll shaft 31 is held on the surface of the rotating sleeve 41.
In the developing device 20 of the present embodiment, the support shaft 43 and the sleeve 41 rotate when a motor (not shown) is driven, and the mag roll shaft 31, the housing 21, the cover member 50, and the like do not rotate.

When the gear 47 rotates, the sleeve 41 rotates and the driving reaction force received by the holding unit 60 may be directly transmitted to the mag roll shaft 31 or the sleeve 41. When the driving reaction force is transmitted to the mag roll shaft 31 and the sleeve 41, the mag roll shaft 31 and the sleeve 41 vibrate. When the mag roll shaft 31 or the sleeve 41 vibrates, the toner image formed by developing the electrostatic latent image held on the photosensitive drum 12 may have uneven density. Further, when the excitation frequency, which is the frequency transmitted to the developing roll 22 by the gear 47, matches the natural frequency of the developing roll 22, the vibration of the developing roll 22 is amplified by resonance. In this case, uneven density of the toner image formed on the photosensitive drum 12 is more likely to occur. In particular, when the natural frequency of the developing roller 22 in the direction toward the photosensitive drum 12 and the excitation frequency of the gear 47 coincide with each other, the gap between the photosensitive drum 12 and the developing roller 22 changes greatly, and the photosensitive drum 12 is changed. The density unevenness generated in the formed toner image is increased. The toner image density unevenness in the present embodiment refers to a state in which the toner image is disturbed in a band shape, and is an image defect called so-called banding.
Therefore, in the present embodiment, the natural frequency of the developing roll 22 and the excitation frequency of the gear 47 are made different. If the natural frequency of the developing roll 22 and the excitation frequency of the gear 47 are different, amplification of the vibration of the developing roll 22 due to resonance is suppressed, and as a result, uneven density of the toner image is suppressed.
Hereinafter, the natural frequency of the developing roll 22 will be described, and then the excitation frequency of the gear 47 will be described.

<Natural frequency of developing roll 22>
First, the natural frequency of the developing roll 22 is generally calculated as follows.
Considering the developing roll 22 as a beam supported at both ends, the natural frequency f (Hz) of the developing roll 22 is
f (Hz) = λ ² / 2πL ² × (EI / ρA) ^1/2
It is represented by Here, L: length of the beam, E: longitudinal elastic modulus of the beam material, I: secondary moment of section, ρ: density, A: sectional area, λ is the first order λ: π, second order λ : 2π, third-order λ: 3π.
Now, it was confirmed that the length L of the beam could be a problem when calculating the natural frequency of the developing roll 22 by the above formula. That is, assuming that the developing roll 22 is supported by the cover member 50, the length L of the beam in the above formula is obtained as a distance between the cover members 50 (see Lout in FIG. 2) and obtained by measurement. It was confirmed that the measured natural frequency did not match. The natural frequency obtained by the measurement is a value obtained by measuring the developing roll 22 in a state where the developing roll 22 is driven and the developer is held under a condition for actually developing.
On the other hand, the natural frequency calculated on the assumption that the developing roll 22 is supported by a support point separated from the length L of the beam in the above formula by the distance between the second bearings 24 (see Lin in FIG. 2), It was confirmed to be closer to the natural frequency obtained by the measurement. That is, the natural frequency of the developing roll 22 calculated considering the second bearing 24 positioned inside the developing roll 22 instead of the cover member 50 as a support point is the characteristic of the developing roll 22 in the state of holding the actual developer. It was confirmed that it was closer to the frequency.

Here, with reference to FIG. 4, it will be described that the beam length in the above equation is closer to the actual measurement result when the distance between the second bearings 24 is used. FIG. 4 is a schematic diagram showing that the mag roll shaft 31 in the present embodiment is moved in one direction. In FIG. 4, illustration of some members such as the magnet portion 32 is omitted for clarity.
The fact that the distance L between the second bearings 24 is closer to the actual measurement result than the distance between the cover members 50 in the above equation is considered to be due to the following reason. That is, under the actual use conditions of the developing roll 22, the developer is held on the surface of the sleeve 41 by the magnet portion 32 of the mag roll shaft 31 being attracted by the magnetic force. The developer held on the surface of the sleeve 41 and the magnet portion 32 provided in the mag roll shaft 31 are attracted to each other by magnetic force. Due to this pulling force, the central portion of the mag roll shaft 31 is moved in one direction (see the arrow in FIG. 4). In other words, the mag roll shaft 31 is bent as shown in FIG. As a result of the bending of the mag roll shaft 31 as described above, it is considered that the support point of the developing roll 22 is not the cover member 50 positioned on the outer side but the second bearing 24 positioned on the inner side.

<Experiment>
Now, an experimental result for confirming how the natural frequency of the mag roll shaft 31 changes depending on the support point will be described with reference to FIG.
Here, FIG. 5 is an explanatory diagram for explaining the support points in the measurement of the natural frequency of the mag roll shaft 31. In FIG. 5, members other than the mag roll shaft 31 are indicated by broken lines for explanation.

First, the experimental conditions will be described.
In this experiment, as shown in FIG. 5, the measurement was performed with the mag roll shaft 31 alone. The mag roll shaft 31 was measured without attracting the developer.
And the natural frequency of the mag roll shaft 31 was measured by oscillating the position (refer V of FIG. 5) where the gearwheel 47 is arrange | positioned with respect to the mag roll shaft 31 with a vibrator.
Further, in this experiment, the natural frequency of the developing roll 22 was measured while changing the position of the support point that supports the mag roll shaft 31. The support point of the mag roll shaft 31 was changed as follows. First, under the experimental condition (1), both ends of the mag roll shaft 31 are supported at the position of the cover member 50 as shown in FIG. In the experimental condition (2), one end of the mag roll shaft 31 is supported at the position of the second bearing 24 and the other end is supported at the position of the cover member 50 as shown in (2) of FIG. Is done. In the experimental condition (3), as shown in (3) of FIG. 5, both ends of the mag roll shaft 31 are supported at the position of the second bearing 24 provided with the magnet portion 32 interposed therebetween.

  As a result, the natural frequency of the developing roll 22 in each experimental condition was approximately 75 Hz in the experimental condition (1), approximately 90 Hz in the experimental condition (2), and approximately 110 Hz in the experimental condition (3). That is, it was confirmed that the natural frequency of the developing roll 22 increases as the distance between the support points becomes shorter. This result has the same tendency as the relation that the natural frequency of the developing roll 22 is inversely proportional to the square of the length of the beam in the above formula.

<Excitation frequency of gear 47>
Next, the excitation frequency of the gear 47 will be described.
The excitation frequency of the gear 47 that rotates the sleeve 41 is defined by the number of rotations and the number of teeth of the gear 47. More specifically, the product of the number of teeth of the gear 47 rotated by a motor (not shown) which is an example of a power source and the rotation number is the excitation frequency.

  Therefore, when making the excitation frequency of the gear 47 and the natural frequency of the mag roll shaft 31 different, a mode in which the excitation frequency of the gear 47 is changed can be considered. For example, there is a mode in which the number of teeth and the number of rotations are changed in order to change the excitation frequency of the gear 47 in accordance with the specification of the developing roll 22 having a certain natural frequency. Furthermore, in order to change the excitation frequency of the gear 47, a mode in which the module of the gear 47 is changed is also conceivable.

<Other aspects>
Now, by making the excitation frequency of the gear 47 different from the natural frequency of the developing roll 22 as described above, it is possible to avoid the vibration of the developing roll 22 from being amplified by resonance and to suppress unevenness in the density of the toner image. Is done. Here, as an aspect in which the excitation frequency of the gear 47 and the natural frequency of the developing roll 22 are made different, there is the following as well as changing the excitation frequency of the gear 47 as described above. That is, there are a mode in which the natural frequency of the developing roll 22 is changed instead of the vibration frequency of the gear 47, and a mode in which both the vibration frequency of the gear 47 and the natural frequency of the developing roll 22 are changed.
And as a mode of changing the natural frequency of the developing roll 22, changing the distance between the second bearings 24 is conceivable. Furthermore, a mode in which the natural frequency of the developing roll 22 is changed by changing the mass, length, diameter, material, and the like of the mag roll shaft 31, the magnet portion 32, the shaft core portion 33, the sleeve 41, and the like is also conceivable.

Here, in the present embodiment, the gear 47 has been described as a configuration for transmitting a force from a motor (not shown), but the present invention is not limited to this. For example, a force from a motor (not shown) may be transmitted by a timing belt or a coupling. The specifications of the timing belt, coupling, etc. are transmitted at a frequency different from the natural frequency of the developing roll 22 specified based on the distance between the second bearings 24 so as to transmit a force from a motor (not shown). A mode of setting may be used.
In the above formula, ρ: density is used. The density is calculated based on the mass of the developing roll 22. Here, in the developing device 20 under actual use conditions, the developer is held on the developing roll 22 as described above. Therefore, when the natural frequency of the developing roll 22 is grasped more accurately, the mass including the held developer is considered as the mass of the developing roll 22.

DESCRIPTION OF SYMBOLS 3 ... PC, 4 ... Image reading apparatus, 10 ... Image forming part, 12 ... Photoconductor drum, 13 ... Charger, 14 ... Exposure apparatus, 17 ... Primary transfer roll, 18 ... Intermediate transfer belt, 19 ... Secondary transfer roll , 20 ... developing device, 21 ... housing, 22 ... developing roll, 31 ... mag roll shaft, 41 ... sleeve, 61 ... fixing device, 100 ... image forming device, S ... paper

Claims (4)

A developing device for developing an electrostatic latent image formed on an image carrier,
A container forming the outer shape of the device;
A cylindrical developer holding portion that is housed in the housing and is rotatably supported by the housing, and that holds the developer on the surface thereof,
A magnet shaft portion that is present along the axis of the developer holding portion inside the developer holding portion and is supported at both ends by the container, and attracts the developer by magnetic force,
The developer holding part is supported by the magnet shaft part and provided at a predetermined distance along the axis of the developer holding part , and the developer holding part is provided on the magnet shaft part. a rotation support portion that rotatably supports the developer holding unit to rotate around,
A transmission unit connected to the developer holding unit and transmitting a driving force from a driving source to the developer holding unit;
The magnet shaft portion is at a position where the center of gravity is eccentric, and the natural frequency in the direction along the radial direction of the developer holding portion varies depending on the angle of the direction around the axis of the developer holding portion. ,
The rotation support portion holds the developer more than each of the portions where the magnet shaft portion is supported by the container in the direction along the axis of the developer holding portion at the both end portions of the developer holding portion. Supporting the developer holding part at a position on the center side of the part,
The excitation frequency of the transmission part is specified based on the distance between the rotation support parts and is different from the natural frequency of the magnet shaft part in the direction in which the developer holding part faces the image holding body. A developing device. The transmission unit is a frequency different from the natural frequency of the magnet shaft portion, the developing device according to claim 1, characterized in that it consists of gears for transmitting the driving force from the driving source to the developer holding unit . A container having an outer shape that is detachable from the main body of the image forming apparatus;
An image carrier that rotates by holding an electrostatic latent image on the surface;
A cylindrical developer holding portion which is provided side by side with the image holding body, is housed in the housing body and is rotatably supported by the housing body, and holds developer on the surface;
A magnet shaft portion that is present along the axis of the developer holding portion inside the developer holding portion and is supported at both ends by the container, and attracts the developer by magnetic force,
The developer holding part is supported by the magnet shaft part and provided at a predetermined distance along the axis of the developer holding part , and the developer holding part is provided on the magnet shaft part. a rotation support portion that rotatably supports the developer holding unit to rotate around,
A transmission unit connected to the developer holding unit and transmitting a driving force from a driving source to the developer holding unit;
With
The magnet shaft portion is located at a position where the center of gravity is eccentric, and the natural frequency in the direction along the radial direction of the developer holding portion varies depending on the angle of the direction around the axis of the developer holding portion,
The rotation support portion holds the developer more than each of the portions where the magnet shaft portion is supported by the container in the direction along the axis of the developer holding portion at the both end portions of the developer holding portion. Supporting the developer holding part at a position on the center side of the part,
The excitation frequency of the transmission part is specified based on the distance between the rotation support parts and is different from the natural frequency of the magnet shaft part in the direction in which the developer holding part faces the image holding body. A cartridge characterized by. A container forming the outer shape of the device;
An image carrier that rotates by holding an electrostatic latent image on the surface;
A cylindrical developer holding portion which is provided side by side with the image holding body, is housed in the housing body and is rotatably supported by the housing body, and holds developer on the surface;
A magnet shaft portion that is present along the axis of the developer holding portion inside the developer holding portion and is supported at both ends by the container, and attracts the developer by magnetic force,
The developer holding part is supported by the magnet shaft part and provided at a predetermined distance along the axis of the developer holding part , and the developer holding part is provided on the magnet shaft part. a rotation support portion that rotatably supports the developer holding unit to rotate around,
A power source for supplying power for rotating the developer holding unit;
A transmission unit that connects the power source and the developer holding unit, and transmits a driving force supplied from the power source to the developer holding unit;
The magnet shaft portion is located at a position where the center of gravity is eccentric, and the natural frequency in the direction along the radial direction of the developer holding portion varies depending on the angle of the direction around the axis of the developer holding portion,
The rotation support portion holds the developer more than each of the portions where the magnet shaft portion is supported by the container in the direction along the axis of the developer holding portion at the both end portions of the developer holding portion. Supporting the developer holding part at a position on the center side of the part,
The excitation frequency of the transmission part is specified based on the distance between the rotation support parts and is different from the natural frequency of the magnet shaft part in the direction in which the developer holding part faces the image holding body. An image forming apparatus.

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