JPH0943992A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To constitute the driving system of a developing roller in high degree of freedom with simple mechanism in a developing method capable of using a drum-shaped photoreceptor by using the flexible developing roller. SOLUTION: A developing roller 49 and a toner regulating means are constituted so that no trouble generates even if the linear velocity ratio of the developing roller 49 to a photoreceptor 32 is reduced to about two times or less, and a photoreceptor gear 61 arranged on the shaft of a photoreceptor 32 is meshed with a developing gear 62 arranged on the shaft of the developing roller 49 to rotate and drive the developing roller 49.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a laser printer, a copying machine or a facsimile which develops an electrostatic latent image on a photoconductor using a one-component magnetic toner.

[0002]

2. Description of the Related Art In an image forming apparatus for forming an image using an electrophotographic process, there are various methods for each process. When attention is paid to the developing system, one of them is a one-component magnetic toner developing system as shown in FIG. First, the developing roller 2 rotatably arranged in the developing device 1 is a rigid roller having a magnetic field generating layer 4 in which N and S poles are alternately formed on an outer peripheral portion of a cored bar 3. The one-component magnetic toner 6 in the toner hopper 5 is replenished to the surface of the developing roller 2 via the replenishing roller 7 by the magnetic force of the magnetic field generating layer 4, and is held in a state of forming a brush. Downstream of the replenishing roller 7 of the developing roller 2, a leading edge 8 of a developing blade 8 made of elastic and magnetic thin plate metal.
The toner a held in contact with the magnetic field generating layer 4 of the developing roller 2 and conveyed is cut off by the tip edge 8 a of the developing blade 8 and thinned to a uniform toner layer thickness to form a photosensitive member 9. Be transported to the side. As a result, the electrostatic latent image on the photoconductor 9 is developed. At this time, since it is necessary to form a predetermined contact nip for development, in the development method shown in FIG. 6, the base material of the photoconductor 9 is formed into a belt shape with respect to the rigid development roller 2. A contact nip is secured by pressing the developing roller 2 into contact with the developing roller 9. Therefore, the photoconductor 9 is, for example, three rollers 10 to 10.
It is configured to be held by 12 and driven to rotate. A developing bias is appropriately applied to the developing roller 2 by a developing bias power source 13.

However, in the case of the developing system shown in FIG.
Since it is necessary to use the belt-shaped photosensitive member 9, a driving mechanism for the photosensitive member 9 and a belt deviation preventing mechanism are required, and there is a drawback that the cost is high and the apparatus becomes large in terms of layout.

Further, the magnetic field generation layer 4 of the actual developing roller 2
Has a magnetic pole pitch of 1.3 mm and a magnetic flux density of 25 mT (250 gauss). Since the magnetic pole pitch is relatively large and the magnetic force (surface magnetic flux density) is also relatively large, basically, on the surface of this magnetic field generation layer 4. Can hold a sufficient amount of toner. However, when the linear velocity of the developing roller 2 relative to the photoconductor 9 is slow, the toner is transferred to the photoconductor 9 at a pitch obtained by dividing the pitch of the toner layer corresponding to a large magnetic pole pitch by the linear velocity ratio, and a stripe pattern is formed on the image. Will appear in. From this, in order to uniformly output a solid black image or a halftone image, the linear velocity of the developing roller 2 relative to the linear velocity of the photoconductor 9 is set to 3 to 4.
The speed is doubled to make the magnetic pole pitch inconspicuous. For example, the linear velocity of the developing roller 2 is set to 4 times the linear velocity of the photoconductor 9.
If doubled, the effective pitch of the magnetic poles of the magnetic field generation layer 4 is 0.3.
It becomes 25 mm and the striped pattern becomes inconspicuous.

However, since the developing roller 2 is rotated at a high speed for development, the vertical line near the intersection of the vertical and horizontal fine lines becomes thin, and the trailing edge of the solid image is extremely emphasized. As a result, the image is adversely affected and the image quality is impaired. At the same time, since the developing roller 2 is rotated at a high speed, the load on the motor side also increases.

Further, since the developing roller 2 is rotated at a high speed, the degree of freedom in designing the gear trains for the driving roller 10 and the developing roller 2 for rotating the photosensitive member 9 is reduced. That is, if the gear for the drive roller 10 of the photoconductor 9 and the gear for the developing roller 2 are to be directly connected, it is necessary to dispose the gears relatively close to each other, and the rollers 10 and 2 have the same diameter. Drive roller 10 if any
It is necessary to make the gear diameter on the side of the developing roller 3 to 3 to 4 times the diameter of the gear on the developing roller 2 side, which causes a restriction on the layout inside the machine. That is,
Either reduce the pitch circle diameter of the gear for the developing roller 2 (however, if it is made too small, the tooth tip of one gear may come into contact with the tooth root of the other gear to cause "tooth interference" and prevent the rotation). You must make your diameter very large. Therefore, at present, in order to avoid such complication, as shown in FIG. 6, the gear 14 for the drive roller 10 is engaged with the drive gear 15, and the gear 16 for the developing roller 2 is driven differently. By engaging the gear 17, the photoconductor 9 and the developing roller 2 are driven separately. As a result, in order to allow the user or the service person to replace the photoconductor 9 and the developing unit for maintenance, the gears 14, 15, 16 are provided at two positions on the main body side and the photoconductor side, and on the main body side and the developing unit side. The connection of 17 must be configured so that it can be released and reconnected, which not only complicates the mechanism, but also severely limits the operability of the user or service person.

On the other hand, according to JP-A-3-259278, JP-A-4-21881 and JP-A-4-181970, an elastic layer (for example, rubber equivalent hardness 7
A developing method using a flexible developing roller having a magnetic field generating layer on the surface layer is described. Especially,
According to Japanese Patent Laid-Open No. 4-21881, the minimum magnetization reversal pitch (magnetic pole pitch) is reduced to 100 μm or less, and a developing blade that has elasticity and magnetism and is pressed against the surface of the developing roller is provided to provide a toner layer. It is also described to homogenize. Further, JP-A-4-181970 discloses that the magnetic pole pitch is made finer to 100 μm or less.

[0008]

By using the developing roller having elasticity and magnetism as described in these publications, a drum-shaped photosensitive member can be used as a photosensitive member, and a belt-shaped photosensitive member can be used. The disadvantages of using can be eliminated. Further, by making the magnetic pole pitch of the magnetic field generating layer on the surface layer of the developing roller finer, basically, the magnetic pole pitch becomes inconspicuous even if the linear velocity ratio of the developing roller to the photoconductor is lowered.

However, according to the stabilization of the thin toner layer by miniaturizing the magnetic pole pitch of the magnetic field generating layer described in these publications, the multi-layered thin toner layer is not considered, and in reality, the developing roller is not considered. Retaining toner on the surface
It is not suitable for reducing the rotation speed of the developing roller because the amount of conveyance is too small. Even if one intends to further increase the number of layers by these publication methods, the developing blade having the soft magnetic property for controlling the toner layer thickness is the same as the developing blade 8 shown in FIG. Since the operation of being magnetically attracted to the magnetic field generating layer is repeatedly oscillated at the magnetic pole pitch, the toner layer thickness becomes uneven even if the magnetic pole pitch is fine. As a result, the uniformity of the toner layer thickness conveyed by the developing roller cannot be ensured, and unevenness of the toner layer thickness appears on the image. From this point as well, it is not suitable for reducing the rotation speed of the developing roller. .

Therefore, even in the system in which the drum-shaped photosensitive member can be used by using the developing roller having flexibility, the rotating speed of the developing roller with respect to the photosensitive member is increased after all. However, there is still a problem in that the drive system for these photoconductors and the developing roller must adopt another drive system as described with reference to FIG. 6, and the mechanism becomes complicated.

[0011]

According to a first aspect of the present invention, there is provided an image forming apparatus, wherein a drum-shaped photosensitive member on which an electrostatic latent image is formed, and the surface of the photosensitive member are pressed and brought into contact with each other by a single-component magnetic toner. A developing roller that develops the electrostatic latent image, and a toner regulating unit that regulates the toner layer thickness by elastically contacting the developing roller surface at a position upstream of the contact portion between the developing roller and the photoconductor in the rotational direction. The developing roller includes an elastic layer having a rubber equivalent hardness of 70 ° or less, and a magnetic field generation layer formed on the surface of the elastic layer and having a fine magnetic pole pitch for holding the one-component magnetic toner. The means is formed by a sheet material having elastic and non-magnetic properties. This allows
The toner regulating means forms a toner layer having a uniform layer thickness without vibrating in accordance with the magnetic pole pitch of the magnetic field generating layer on the surface layer of the developing roller. Even if the toner layer thickness is made uniform, the toner layer may be multi-layered. Therefore, there is no problem even if the linear velocity of the developing roller is lowered, and the problem of toner deviation is solved. Under such a structure, by engaging the photoconductor gear provided on the shaft of the photoconductor with the development gear provided on the shaft of the developing roller, complexity of the mechanism and restrictions on layout are involved. In addition, the rotation driving system of the developing roller is simply configured.

An image forming apparatus according to a second aspect is the image forming apparatus according to the first aspect.
In the configuration of the image forming apparatus described above, the module between the photoconductor gear and the developing gear is set to 1.0 or less, and even when the linear velocity ratio of the developing roller to the photoconductor is reduced to nearly 1 time, The minimum number of teeth never falls below 18.

An image forming apparatus according to a third aspect is the image forming apparatus according to the first aspect.
In the configuration of the image forming apparatus described above, the diameter ratio of the developing roller to the photoconductor is set to 2/3 or less, and the developing apparatus is prevented from becoming large due to the increase in the diameter of the developing roller.

An image forming apparatus according to a fourth aspect is the image forming apparatus according to the first aspect.
In the configuration of the image forming apparatus described above, the number of teeth of the developing gear is a value that does not have a common divisor with respect to the number of magnetic poles of the magnetic field generating layer of the developing roller surface layer, and the least common multiple of both is (the number of teeth) ×
Since it becomes (the number of magnetic poles), there is no inconvenience on the image such that the pitch density fluctuation caused by the minute rotation unevenness caused by the backlash of the developing gear and the density fluctuation caused by the magnetic pole pitch are overlapped and emphasized.

An image forming apparatus according to a fifth aspect is the image forming apparatus according to the first aspect.
In addition to the configuration of the image forming apparatus described above, a supply member that is disposed on the upstream side in the rotation direction of the contact portion between the developing roller and the toner regulating unit and that replenishes the developing roller with the one-component magnetic toner by rotation is provided. In addition to a supply member drive gear provided on the shaft for rotationally driving the supply member, the number of teeth of the supply member drive gear has a common divisor with respect to the number of magnetic poles of the magnetic field generating layer on the surface layer of the developing roller. Since the minimum common multiple of both is (the number of teeth) x (the number of magnetic poles), the pitch density fluctuation due to minute rotation unevenness caused by the backlash of the supply member drive gear and the density fluctuation caused by the magnetic pole pitch are There is no inconvenience on the image such as overlapping and emphasis.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIGS. The image forming apparatus of the present invention includes:
As one embodiment, for example, the present invention is applied to an electrophotographic recording device 31 whose outline is shown in FIG.

The electrophotographic recording device 31 is mainly composed of a drum-shaped photosensitive member 32, and around the photosensitive member 32, a charging unit 33, an optical writing unit 34, a developing unit 35, and a transfer unit according to an electrophotographic process. Means 36 and cleaning means 37 are arranged in order. Further, between the paper feed cassette 38 and the paper discharge tray 39, there is formed a conveyance path that passes through the transfer position for the photoconductor 32, and along this conveyance path the paper feed roller 40, the registration means 41, and the fixing unit. The means 42 and the paper discharge roller 43 are arranged in this order. Here, the photosensitive member 32 having a small diameter of about 30 mm is used, and the entire electrophotographic recording device 31 is downsized.

As a result, the transfer paper (not shown) fed from the paper feed cassette 38 by the paper feed roller 40 is conveyed toward the transfer position of the photoconductor 32 in synchronism with the registration means 41. . On the other hand, the surface of the photoconductor 32 is uniformly charged by the charging unit 33 while being rotated in the clockwise direction, and the laser light is emitted from the optical writing unit 34, whereby an electrostatic latent image is formed on the surface. This electrostatic latent image is developed with toner when passing through the developing means 35 to be visualized. The visualized toner image is transferred to the transfer position on the transfer paper conveyed by the registration unit 41 by the transfer action of the transfer unit 36. The transferred transfer paper is fixed by the fixing means 42,
The paper is discharged onto the paper discharge tray 39 by the paper discharge roller 43.

In such an electrophotographic recording apparatus 31, the structure of the developing means 35, which is the main part of the present invention, will be described with reference to FIG. The developing means 35 is for developing an electrostatic latent image on the photoconductor 32 using a one-component magnetic toner (not shown), and is provided in a developing container 47 communicating with a toner hopper (not shown) through an opening 46. The photoconductor 3
2 and the developing roller 49 located in the opening 48 close to
Is provided. The developing roller 49 is a metal core 50.
Is a roller formed by a thick elastic layer 51 covering the outer peripheral surface of the elastic layer 51 and a thin magnetic field generating layer 52 covering the surface layer of the elastic layer 51 to have flexibility, A contact portion 53, which is a developing nip portion, is formed by pressing and contacting the surface of the photoconductor 32. The contact portion 53 is set, for example, at an obliquely lower position with respect to the photoconductor 32. The developing roller 49 is rotatably supported by the side plates on both sides, and is rotationally driven counterclockwise by a drive transmission system described later. The elastic layer 51 is made of a material having elasticity of rubber equivalent (JIS A hardness) of 70 ° or less. Further, the magnetic field generation layer 52 is formed by magnetizing a plurality of stripe-shaped magnetic poles of N and S poles parallel to each other in parallel with a fine magnetic pole pitch (preferably 0.3 to 0.65 mm). FIG. 4 schematically shows a state where a large number of stripe-shaped magnetic poles 52a having N and S poles are formed in parallel along the axis, and both end regions 52 are formed.
The region excluding b functions as the magnetic field generation layer 52.

The developing roller 49 has a metal core 5
A predetermined developing bias (a value approximately halfway between the charging potential and the exposure potential of the photoconductor 32) is applied through 0.

A developing blade 54 is provided which is in contact with the surface of the developing roller 49 at a position upstream of the contact portion 53 in the rotational direction. The developing blade 54 serves as a toner regulating means for regulating the toner layer thickness on the surface of the developing roller 49, and is formed of a metal or resin thin plate material having elasticity and non-magnetic characteristics, preferably a metal thin plate spring material. Has been done. Specifically, the thickness is 0.1 to 0.15
It is formed of a thin metal plate material such as SUS301 or 304-CSP of mm. The developing blade 54 has its lower end side elastically abutted against the surface of the developing roller 49 in the counter direction (meaning a direction in which the developing roller 54 bites from the opposite direction to the rotation direction), and is provided on the upper side of the opening 48. And is supported by a part of the developing container 47 obliquely downward. More specifically, on the lower end side of the developing blade 54, a bent portion 55 of, for example, about 2 mm is formed to be bent outward at about 90 °, and the outer peripheral surface of the bent portion 55 is in contact with the developing roller 49. 56 are formed.

The radius of curvature of the bent portion 55 is 0.3 mm or more (preferably about 0.3 to 0.5 mm).
The bending angle of the bent portion 55 is not particularly limited, but is 90 °.
It is desirable that the angle is acute or less. In any case, it is difficult to bend the magnetic thin metal plate material, but in the case of the non-magnetic thin metal plate material forming the developing blade 54, the bent portion 55 is formed by bending. Is easy.

Further, in the developing container 47, a contact portion 5 between the developing roller 49 and the developing blade 54.
A toner replenishing plate 57 serving as a supply member is provided at a position immediately upstream of the rotational direction of 6, specifically, at a position substantially below the developing roller 49. An agitator 58 is provided between the toner supply plate 57 and the opening 46. The toner supply plate 57 and the agitator 58 have a length over the entire area of the developing roller 49 in the longitudinal direction, and are rotatably supported by the side plates on both sides of the developing container 47.
The toner replenishing plate 57 may be formed of sheet metal or the like, or may be formed of resin or the like, but here, for example, a molded product of sheet metal or the like is used. This toner supply plate 57
As shown in FIG. 1, the effective stirring portion 57a is formed by appropriately forming openings 57b in the plate material portion.
Is longer than the length of the effective image area. Further, the toner replenishing plate 57 is rotationally driven in the opposite direction to the developing roller 49 by a rotary driving system described later, and at this time, the outer circumference of the effective stirring portion 57a is the developing roller 49.
Of the toner replenishment plate 5 without touching the outer periphery of
7 is disposed close to the developing roller 49. Specifically, the rotation outer circumference of the effective stirring unit 57a and the developing roller 49
It is set so that the gap d between it and the outer circumference is 2 mm or less. Further, the rotation peripheral speed of the developing roller 49 is Vd,
When the peripheral speed of rotation of the effective stirring portion 57a of the toner replenishing plate 57 is Vs, the speed relationship between the two is set so that Vd ≦ Vs.

In such a basic structure, the one-component magnetic toner is supplied from the toner hopper to the agitator 58 side through the opening 46. 1 supplied to the agitator 58 side
The component magnetic toner is rotatably driven by an agitator 58,
The replenishing plate 57 sequentially stirs and conveys the toner to the developing roller 49 side, and adheres onto the developing roller 49. This adhesive force is due to the magnetism of the magnetic field generating layer 52 on the surface layer of the developing roller 49. When the developing roller 49 rotates clockwise, it is elastically pressed against the surface of the developing roller 49 with a predetermined pressure. When passing through the contact portion 56 with the developing blade 54, the toner layer is regulated to have an appropriate layer thickness. Developing roller 4
The toner layer formed on the surface layer 9 is conveyed to the contact portion 53 with the photoconductor 32 as the developing roller 49 rotates, and develops the electrostatic latent image on the photoconductor 32 formed by the optical writing unit 34.

At this time, the toner development amount required to obtain the image density on the transfer paper of 1.4 or more by the Macbeth densitometer is, for example, 0.8 mg / in the case of the one-component magnetic toner used here.
cm ² or more. As described above, when the toner layer thickness is regulated by the bent portion 55 of the developing blade 54 having elasticity and non-magnetic characteristics as shown in the present embodiment with respect to the toner amount required on the photoconductor 32, It was found that the amount of toner held on the surface layer of the roller 49 was stable at 0.6 to 1.0 mg / cm ² . That is, although the magnetic field generating layer 52 on the surface layer of the developing roller 49 has a fine magnetic pole pitch, the toner layers are formed in a multi-layered state. This means that the developing roller 49 can supply a necessary / sufficient amount of toner to the photoconductor 32 side, and the linear velocity of the developing roller 49 is reduced to 1.5 times or less the linear velocity of the photoconductor 32. However, it is possible to develop with a sufficient toner density. More specifically, the magnetic flux density of the magnetic poles of the magnetic field generation layer 52 is 5 mT and the magnetic pole pitch is 0.63.
mm (developing roller 49 having a diameter of 20 mm, the number of magnetic poles is 100), and the linear velocity ratio of the developing roller 49 to the photoconductor 32 is set to 1.5 times, and development is performed, and a substantially uniform black solid image is obtained. I was able to confirm. In this way, the developing roller 4
By lowering the linear velocity of 9, the problem of toner deviation can be basically solved.

Further, the toner magnetically adhered to the developing roller 49 needs to be charged before being conveyed to the photosensitive member 32 side, and is triboelectrically charged when passing through the developing blade 54. Here, the abutting portion 56 between the developing blade 54 and the developing roller 49 is formed not by the tip edge of the developing blade 54 but by a bent portion 55 bent at about 90 °, and its radius of curvature is set to 0.3 mm or more. By doing so, it was found that the amount of toner held on the developing roller 49 and its charge amount were stable.

Incidentally, the toner replenishing plate 57 also greatly contributes to the multi-layering of the toner layer and the uniformization of the layer thickness in the developing roller 49. First, the one-component magnetic toner is supplied from the toner hopper to the surface of the developing roller 49 after being agitated by the agitator 58. The toner replenishing plate 57 is provided immediately upstream of the contact portion 56 between the developing roller 49 and the developing blade 54. Since it also receives the action of stirring and replenishing toner,
Sufficient toner is supplied to the abutting portion 56, so that the multi-layering is effectively performed. Further, in consideration of time, toner agglomerates may be generated in the developing container 47, and if such toner agglomerates are sent to the contact portion 56 as they are, the effect of the developing blade 54 cannot be expected, When the toner layer thickness becomes uneven, such toner aggregates may be sent to the developing position of the photoconductor 32 as they are and used for development. In this respect, the toner replenishing plate 57 is rotationally driven immediately upstream of the contact portion 56 in the rotational direction, and even if toner agglomerates exist, the toner replenishing plate 57 and the developing roller 49 are agitated by the toner replenishing plate 57 while stirring. Since the toner is pulverized in a small gap between the toner and the toner, it is possible to stably replenish the toner without aggregation. In particular, since the effective stirring portion 57a of the toner replenishing plate 57 is longer than the effective image area, it is possible to uniformly replenish the toner over the entire axial length of the developing roller 49 without toner aggregation, and the toner layer thickness by the developing blade 54. It is possible to maximize the homogenizing ability of. This is the rotation peripheral speed Vd of the developing roller 49.
On the other hand, since the rotation peripheral speed Vs of the effective stirring portion 57a of the toner supply plate 57 is higher than the same speed, the crushing effect of toner aggregates can be expected. At the same time, effective stirring unit 5
Since 7a does not contact the developing roller 49, the toner replenishing plate 57 does not damage the developing roller 49. However, since d = 2 mm or less is approached, the ability of finely pulverizing toner aggregates is high.

Next, the developing roller 49 and the toner supply plate 5
The rotary drive system 7 will be described. First, the photoconductor gear 61 is provided on the shaft of the photoconductor 32 which is rotationally driven in the clockwise direction, and the photoconductor gear 61 is provided on the shaft of the developing roller 49.
There is provided a developing gear 62 that meshes with. A drive gear 63 serving as a supply member drive gear is provided on the other end side of the developing roller 49 on the shaft, and a driven gear 64 meshing with the drive gear 63 is provided on the shaft of the toner supply plate 57. ing.

Here, the linear velocity of the developing roller 49 is the photosensitive member 3
The developing gear 62 has a diameter smaller than that of the photoconductor gear 61. However, the module m between the photoconductor gear 61 and the developing gear 62
Is set to 1.0 or less. As a result, the photoconductor 3
Even if the linear velocity ratio of the developing roller 49 to 2 is reduced to about 1, the minimum number of teeth of the developing gear 62 is 1.
Since it does not fall below eight, inconvenience such as "tooth interference" does not occur. That is, the minimum number of teeth Zg that does not cause tooth interference is generally given by Zg = 2 / sin ² α ₀ , and α ₀ is a tool pressure angle at gear cutting, which is usually 20 °, so Zg = This is because it is 17.09, and if the minimum number of teeth is less than 18, tooth interference occurs.

The same applies to the toner replenishing plate 57 that rotates at a higher speed than the developing roller 49, and the driven gear 64 has a smaller diameter than the drive gear 63. However, between the drive gear 63 and the driven gear 64. Module m is 1.0
It is as follows.

By the way, D ₁ is the diameter of the photoconductor 32 D _{2 is} the diameter of the developing roller 49 D _{3 is} the diameter of the toner replenishing plate 57 (the width of the effective stirring portion 57a) Z _{1 is the} number of teeth of the photoconductor gear 61 Z ₂ The number of teeth Z ₃ of the developing gear 62; the number of teeth Z ₄ of the drive gear 63; the number of teeth L ₁ of the driven gear 64; the center distance L ₂ between the photoconductor 32 and the developing roller 49; the developing roller 49 and the toner supply plate 57 The distance between the centers of Then, the pitch circle diameter of the photosensitive member gear 61; Z ₁ · m The pitch circle diameter of the developing gear 62; Z ₂ · m The pitch circle diameter of the drive gear 63; Z ₃ · m The pitch circle diameter of the driven gear 64; Z ₄ · m center-to-center distance L ₁ = (Z ₁ + Z ₂ ) · m / 2 center-to-center distance L ₂ = (Z ₃ + Z ₄ ) · m / 2 The amount of biting of the developing roller 49 with respect to the photoreceptor 32; {(D
₁ + D ₂ ) / 2} -L ₁ Developing roller 4 for photoreceptor 32
Linear velocity ratio of 9; Z ₁ · D ₂ / Z ₂ · D ₁ developing roller 49
Linear velocity ratio of the toner replenishing plate 57 with respect to: Z ₃ D ₄ / Z ₄
It becomes D ₃ .

Under these conditions, three samples A, B and C having the following specifications were prepared and subjected to development processing, and all of them produced good images. is there. Note that, as an example, the elastic layer 5 of the developing roller 49 is
1 is BR rubber with JIS A hardness of 30 °, magnetic field generation layer 5
2 is made of flexible EPDM rubber.

<Sample A> In Sample A, each element is the diameter D ₁ of the photoconductor 32; 30 mm, the diameter D ₂ of the developing roller 49; 20 mm module m; 0.8 the number of teeth Z ₁ of the photoconductor gear 61; 43 sheets Number of teeth Z ₂ of developing gear 62; 19 sheets Pitch circle diameter of photoconductor gear 61; 34.4 mm Pitch circle diameter of developing gear 62; 15.2 mm Center distance L ₁ ; 24.8 mm Biting amount; 0.2 mm Photosensitive Linear velocity ratio of developing roller 49 to body 32; 1.52
The number of magnetic poles of the developing roller 49 is 100.

In sample A, the module m is 0.8 and 1.0 or less, and the number of teeth Z ₂ of the developing gear 62 is 19
Sheets are reserved. The diameter ratio of the developing roller 49 to the photoconductor 32 is D ₂ / D ₁ = 20/30 = 2/3. As a result, the diameter of the developing roller 49 does not increase so much, and the developing means 35 does not increase in size. Further, when the number of magnetic poles of the developing roller 49 and the number of teeth Z ₂ of the developing gear 62 are compared, Z ₂ = 19 with respect to 100 of magnetic poles, and the number of teeth Z ₂ is set to a value having no common divisor. There is. As a result, the least common multiple of them is (the number of magnetic poles) × (the number of teeth Z ₂ ) = 100 × 19 = 1900. Therefore, there is no inconvenience on the image such that the pitch density fluctuation caused by the minute rotation unevenness caused by the backlash of the developing gear 62 and the density fluctuation caused by the magnetic pole pitch of the surface layer of the developing roller 49 are overlapped and emphasized.

<Sample B> In Sample B, each element is the diameter D ₁ of the photoconductor 32; 30 mm, the diameter D ₂ of the developing roller 49; 15 mm module m; 0.6 the number of teeth Z ₁ of the photoconductor gear 61; 64 sheets Number of teeth Z ₂ of developing gear 62; 19 sheets Pitch circle diameter of photoconductor gear 61; 38.4 mm Pitch circle diameter of developing gear 62; 11.4 mm Center distance L ₁ ; 24.9 mm Biting amount; 0.1 mm exposure Linear velocity ratio of developing roller 49 to body 32; 1.61
The number of magnetic poles of the developing roller 49 is 100.

In sample B, the module m is 0.6 and 1.0 or less, and the number of teeth Z ₂ of the developing gear 62 is 19
Sheets are reserved. Further, the diameter ratio of the developing roller 49 to the photoconductor 32 is D ₂ / D ₁ = 15/30 = 0.5 <2
/ 3. As a result, the diameter of the developing roller 49 does not increase so much, and the developing means 35 does not increase in size. Further, when the number of magnetic poles of the developing roller 49 and the number of teeth Z ₂ of the developing gear 62 are compared, as with the sample A, Z ₂ = 19 with respect to 100 of magnetic poles,
The number of teeth Z ₂ is set to a value having no common divisor. As a result, the least common multiple of both is (the number of magnetic poles) × (the number of teeth Z ₂ )
= 100 × 19 = 1900. Therefore, the developing gear 6
There is no inconvenience on the image such that the pitch density fluctuation caused by the minute rotation unevenness caused by the backlash of No. 2 and the density fluctuation caused by the magnetic pole pitch on the surface layer of the developing roller 49 are overlapped and emphasized.

<Sample C> In the sample C, the relationship between the developing roller 49 and the toner replenishing plate 57 is taken into consideration. Each element has a diameter D ₁ of the photoconductor 32; 30 mm, a diameter D _{2 of the} developing roller 49; 20 mm. Toner supply plate 57 diameter D ₃ ; 12 mm Module 63 between gears 63 and 64; 0.5 Number of teeth of drive gear 63 Z ₃ ; 47 sheets Number of teeth of driven gear 64 Z ₄ ; 19 sheets Pitch circle of drive gear 63 Diameter: 23.5 mm Pitch circle diameter of the driven gear 64; 9.5 mm Center-to-center distance L ₂ ; 16.5 mm Gap d; 0.5 mm Linear velocity ratio of the developing roller 49 to the photoconductor 32; 1.61
The number of magnetic poles of the developing roller 49 is 100.

In sample C, when the number of magnetic poles of the developing roller 49 and the number of teeth Z ₃ of the drive gear 63 are compared, the number of magnetic poles is 10
For 0, Z ₃ = 47, and the number of teeth Z ₃ is set to a value having no common divisor. Thus, the least common multiple of both is (the number of magnetic poles) × (the number of teeth Z ₃ ) = 100 × 47 = 470
It becomes 0. Therefore, there is no inconvenience on the image such that the pitch density fluctuation caused by the minute rotation unevenness caused by the backlash of the drive gear 63 and the density fluctuation caused by the magnetic pole pitch of the surface layer of the developing roller 49 are overlapped and emphasized.

As the gears such as the photoconductor gear 61 described above, spur gears are used for simplifying the calculation and the like, but helical gears, helical gears and the like may be used.

[0040]

According to the first aspect of the present invention, the structure is provided with the developing roller and the toner regulating means so that the linear velocity ratio of the developing roller to the photoconductor may be reduced to about 2 times or less. In addition, since the photoconductor gear provided on the shaft of the photoconductor meshes with the development gear provided on the shaft of the developing roller to rotate and drive the developing roller, the complexity of the mechanism and restrictions on layout, etc. The rotation drive system of the developing roller can be simply configured without involving, and as a result, the maintainability can be improved.

According to the invention of claim 2, the module between the photoconductor gear and the developing gear is set to 1.0 or less. Therefore, in addition to the effect of the invention of claim 1, the line of the developing roller to the photoconductor is Even when the speed ratio is reduced to nearly 1 time, the minimum number of teeth does not become less than 18, and tooth interference can be prevented.

According to the third aspect of the invention, the diameter ratio of the developing roller to the photosensitive member is set to 2/3 or less. Therefore, in addition to the effect of the first aspect of the invention, the diameter of the developing roller becomes large. Therefore, it is possible to prevent the developing device from becoming large, and it is advantageous in achieving the intended purpose of reducing the size and cost of the entire device.

According to the invention of claim 4, the number of teeth of the developing gear is set to a value having no common divisor with respect to the number of magnetic poles of the magnetic field generating layer on the surface layer of the developing roller. Therefore, the effect of the invention of claim 1 is obtained. In addition, the least common multiple of both is (number of teeth) x (number of magnetic poles)
Therefore, it is possible to prevent an inconvenience on the image such that the pitch density fluctuation caused by the minute rotation unevenness caused by the backlash of the developing gear and the density fluctuation caused by the magnetic pole pitch are overlapped and emphasized. .

According to the fifth aspect of the invention, the supply member disposed upstream of the contact portion between the developing roller and the toner regulating means and replenishing the developing roller with the one-component magnetic toner by rotation, and the developing roller. In addition to a supply member drive gear provided on the shaft for rotationally driving the supply member, the number of teeth of the supply member drive gear has a common divisor with respect to the number of magnetic poles of the magnetic field generating layer on the surface layer of the developing roller. In addition to the effect of the invention described in claim 1, the least common multiple of both can be increased to (the number of teeth) × (the number of magnetic poles), so that the fineness caused by the backlash of the supply member drive gear can be achieved. It is possible to prevent an inconvenience on the image such that the pitch density fluctuation caused by the uneven rotation and the density fluctuation caused by the magnetic pole pitch are overlapped and emphasized.

[Brief description of drawings]

FIG. 1 is a cross-sectional structural view near a developing unit showing an embodiment of the present invention.

FIG. 2 is a schematic front view showing the layout configuration of the entire electrophotographic recording apparatus.

FIG. 3 is a schematic front view showing a configuration near a developing unit.

FIG. 4 is a perspective view showing a developing roller.

FIG. 5 is a schematic front view of the vicinity of a developing unit including a gear.

FIG. 6 is a schematic front view showing a conventional example using a developing roller having flexibility.

[Explanation of symbols]

 32 Photoreceptor 49 Developing Roller 51 Elastic Layer 52 Magnetic Field Generating Layer 53 Contact Part 54 Toner Regulation Means 57 Supply Member 61 Photoreceptor Gear 62 Development Gear 63 Supply Member Drive Gear

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Hiroshi Hosokawa 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd.

Claims (5)

[Claims] 1. A drum-shaped photosensitive member on which an electrostatic latent image is formed, an elastic layer having a rubber-equivalent hardness of 70 ° or less, and a one-component magnetic toner formed on the surface of the elastic layer to hold a one-component magnetic toner. A developing roller that has a magnetic field generating layer with a fine magnetic pole pitch, press-contacts with the surface of the photoconductor to develop the electrostatic latent image with one-component magnetic toner, and a thin plate material having elasticity and non-magnetic characteristics. A toner regulating means for elastically contacting the surface of the developing roller at a position upstream of the contact portion between the developing roller and the photoconductor in the rotational direction to regulate the toner layer thickness; and a toner regulating means provided on the shaft of the photoconductor. An image forming apparatus comprising: a photosensitive member gear; and a developing gear that is provided on the shaft of the developing roller and meshes with the photosensitive member gear. 2. The image forming apparatus according to claim 1, wherein the module between the photoconductor gear and the developing gear is 1.0 or less. 3. The diameter ratio of the developing roller to the photosensitive member is 2
The image forming apparatus according to claim 1, wherein the image forming apparatus has a thickness of / 3 or less. 4. The image forming apparatus according to claim 1, wherein the number of teeth of the developing gear is set to a value having no common divisor with respect to the number of magnetic poles of the magnetic field generating layer on the surface layer of the developing roller. 5. A supply member, which is arranged on the upstream side in the rotation direction of the contact portion between the developing roller and the toner regulating means and supplies the one-component magnetic toner to the developing roller by rotation, and a supply member provided on the shaft of the developing roller. And a feed member drive gear for rotating the feed member, wherein the number of teeth of the feed member drive gear is a value that does not have a common divisor with respect to the number of magnetic poles of the magnetic field generating layer of the developing roller surface layer. The image forming apparatus according to claim 1, wherein: