JP2000098679A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a driving device light in weight, compact in size, low in cost, hardly being affected by disturbance, etc., reduced in the gain of transfer function, capable of highly precisely driving a photoreceptor drum. SOLUTION: This image forming device is provided with a drive transfer means, which has a rotary body having an image forming body, driving body for driving the rotary body, and an elastic member and transmits the driving force of the driving body to the rotary body via the elastic member. In this case, inclination prevention members 36 for preventing the inclination of the driving body are provided between the rotary body and the driving body.

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 in which a driving device for rotating an image forming body is improved.

[0002]

2. Description of the Related Art In a copying machine or a printer for forming an image by an electrophotographic system, an electrostatic latent image is formed on a surface of a rotating cylindrical photoreceptor or a belt-shaped photoreceptor by moving the surface of the photoreceptor. Is formed, toner is adhered to the formed electrostatic latent image and developed to form a toner image, and the toner image is transferred and fixed on recording paper to obtain an image.

When a speed fluctuation (rotation unevenness) occurs on a photosensitive member which is an image forming member to be rotated at a uniform speed, a phenomenon called small pitch banding occurs.
Jitter and image unevenness occur in the output image. This is particularly noticeable in a digital electrophotographic technique in which writing on a photoconductor is performed by scanning a semiconductor laser. Fluctuations in the rotation speed of the photoconductor cause fluctuations in the sub-scanning direction of the writing system, resulting in a writing line. Causes a slight shift in the distance between the images, causing a significant reduction in image quality.

Although there are many proposals for a technique for improving the driving accuracy of an image forming body to be rotated at a uniform rotation speed, the following two main flows are seen.

[0005] One is to incorporate a flywheel into the drive system. Conventionally, a flywheel that is easily attached and detached is found in JP-A-7-281500 and JP-A-8-202205. Japanese Patent Application Laid-Open Nos. Hei 6-130872 and 6
-130874, 7-302020, 8-20
See, for example, the specification of No. 2206. Further, Japanese Patent Application Laid-Open No. H08-08204 discloses an apparatus that detects the frequency characteristics of an image forming body and optimizes the moment of inertia of a flywheel in relation to an excitation frequency.
No. 63041, No. 8-115041, No. 8-2209
See No. 66.

As another major flow, the use of a gear or a timing belt pulley incorporating an elastic member in the middle of the image forming body drive system absorbs the rotational vibration of the drive transmission system. . Specifically, JP-A-6-249321 and JP-A-6-294453.
And JP-A-7-325445, JP-A-7-325446 and JP-A-8-54047.

As described above, in the prior art, the use of a flywheel was the most effective technical means for improving the driving accuracy of an image forming body. There is a fundamental problem of requiring torque. In addition, since the flywheel itself reduces rotational vibrations due to the kinetic energy of rotation, when the image forming body is rotated at a low speed, a large diameter compared to the image forming body is required for the effect to be recognized. It is necessary to adopt a flywheel. Therefore, in order to avoid an increase in the size of the apparatus, functional limitations must be recognized even when a flywheel is provided in the image forming body.

In recent years, the natural frequency of the drive system of the image forming body has been determined, the drive system has been designed in consideration of the relationship with the excitation frequency, and the frequency of the rotation system centered on the natural frequency has been determined. The concept of optimizing the drive system by changing the shape of the frequency characteristic, that is, the shape of the transfer function by changing the shape of the frequency characteristic by designing the inertia amount by obtaining the response has been generalized. The biggest problem in this case is that in consideration of shifting the natural frequency to a low frequency region in one image forming body driving system, the flywheel diameter is inevitably increased or its weight is increased. . This means that the natural frequency f of the fundamental frequency is

[0009]

(Equation 1)

[0010] In this case, increasing the inertia moment I corresponds to decreasing the value of the natural frequency f.

On the other hand, improving the driving accuracy by providing an elastic member in the middle of the drive system involves converting a rotational vibration component generated in the drive system into heat in the elastic member and dissipating the heat. is there. Since the concept such as the frequency characteristic and the transfer function of the drive system is not included here, the effect cannot be predicted depending on the excitation frequency of the generated vibration and the configuration of the drive system, and the level of the effect varies.

[0012]

However, in the development of a digital image forming apparatus, as the performance is improved, the reproducibility of one dot line by writing with a laser is strictly required, and the accuracy required for a drive system is required. Quickly became tougher. The accuracy required here is a level at which the uniformity of the writing by the laser in the sub-scanning direction is guaranteed in relation to the visual sensitivity of the visual system, and the recording density is 60%.
With the increase in recording density from 0 dpi to 2400 dpi, it is required to drive an image forming body with high precision and without rotation unevenness that satisfies a high level in which small pitch banding cannot be recognized by humans.

For this reason, in the range of the prior art, high-precision gears, dedicated driving, and use of a large flywheel are generally used to increase the driving accuracy of the image forming body. However, the adoption of the flywheel inevitably increases the weight and the device as described above. Furthermore, in order to provide an electrophotographic printer, a light, compact, low-cost, high-precision drive is required, and the gear driving force is applied to a rotating body such as a photosensitive drum via an elastic member. A transmission structure and the like have been proposed. However, in this technology, the elastic member alone has a large effect of reducing the speed unevenness at a natural frequency or higher, but the gain in the resonance region increases, and the banding is greatly affected by speed unevenness near the resonance region and load fluctuation. There was a problem that got worse.

The present invention achieves high-quality image output by achieving a high-precision drive by achieving a lightweight, compact, low-cost, less susceptible to disturbances and the like by a new structure that solves these problems. The purpose of the present invention is to provide an image forming apparatus.

[0015]

The above-described image forming apparatus has a rotating body having an image forming body, a driving body for driving the rotating body, and an elastic member. An image forming apparatus provided with a drive transmitting means for transmitting a driving force of the driving body to the rotating body, wherein a fall prevention member for preventing the falling of the driving body is provided between the rotating body and the driving body. This is achieved by an image forming apparatus characterized in that:

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An image forming apparatus according to an embodiment of the present invention described below has the following two major differences from the prior art.

1. The embodiment of the present invention is different from the principle in which the shape of the transfer function in the frequency characteristic is changed by the flywheel, and enables the frequency characteristic to be controlled with a very simple configuration. That is,
In contrast to the conventional technique in which the inertia moment I is changed to change the natural frequency f (see FIG. 13A),
The torsional stiffness K of the driving system is changed to enable control of frequency characteristics.

2. The embodiment of the present invention can not only control the frequency characteristic by changing the peak position of the frequency characteristic, but also can freely reduce the magnitude of the frequency characteristic, that is, the magnitude of the gain of the transfer function. It is. This corresponds to not only moving the peak of the transfer function in parallel with the frequency axis, but also moving it in the size direction to lower the height of the transfer function (see FIG. 13B).

This has the effect of significantly reducing the absolute value of the vibration in the rotation direction in the corresponding frequency range.

(Embodiment 1) Next, the structure and operation of a color image forming apparatus according to Embodiment 1 of the present invention will be described with reference to FIG.
This will be described with reference to a cross-sectional view of FIG.

This color image forming apparatus forms a color image by superimposing toner images of respective colors sequentially formed on a photosensitive drum, which is an image forming body, and transferring the color toner images onto recording paper once at a transfer section. Then, a color image forming apparatus of a system of separating from the surface of the image carrier by a separating unit.

In FIG. 1, reference numeral 10 denotes a cylindrical photoconductor drum having a diameter of 120 mm, which is formed by coating an OPC photoconductor (organic photoconductor) on a drum base, and is grounded and has a linear velocity in a clockwise direction shown in the figure. At 100 mm / sec, it is driven and rotated by a driving source described later. Reference numeral 11 denotes a scorotron charger, which applies a constant charging potential to the photosensitive drum 10 by corona discharge from a grid and a corona discharge wire that are maintained at a constant voltage on the peripheral surface of the photosensitive drum 10. Prior to the charging by the scorotron charger 11, in order to eliminate the history of the photoconductor up to the previous print, exposure is performed by a pre-charging static eliminator (PCL) 12 using a light emitting diode or the like, and the peripheral surface of the photoconductor is neutralized. deep.

In the present embodiment, negative uniform charging is performed. In the following description, the magnitude and magnitude of a voltage and a potential refer to the magnitude and magnitude of an absolute value.

After the photosensitive drum 10 is uniformly charged, the image exposure means 13 performs image exposure based on the image signal. The image exposure means 13 scans the optical path by using a semiconductor laser (not shown) as a light emitting light source, the optical path of which is bent by a reflecting mirror via a polygon mirror, an fθ lens, and a cylindrical lens which rotate. It is formed. In the present embodiment, a character portion is exposed, and a latent image is formed such that the exposed portion potential is lower in absolute value than the charged potential.

Around the periphery of the photosensitive drum 10, a developing device 14Y containing a two-component developer including a toner such as yellow (Y), magenta (M), cyan (C), and black (K) and a carrier. , 14M, 14C, and 14K are provided. Each developing unit 14Y, 1
4M, 14C, and 14K each have a rotary developing sleeve 141 in which a fixed magnet is disposed (in the figure, reference numerals are assigned only to the yellow developing device 14Y, but the same applies to other developing devices).

First, development with the first color yellow toner is performed by the developing unit 14Y. The developer used in each developing unit is a carrier with ferrite as the core and an insulating resin coated around it, and a toner with polyester as the main material and a pigment according to the color, a charge control agent, silica, titanium oxide, etc. The developer is conveyed to the developing area while being regulated to a developer layer thickness of 100 to 600 μm on the developing sleeve 141 by a developer layer forming means described later.

The gap between the developing sleeve 141 and the photosensitive drum 10 in the developing area is larger than the developer layer thickness.
As 2～1.0Mm, AC bias V _AC and the DC bias V _DC is applied to overlap therebetween. Since direct-current region and the DC bias V _DC and the photosensitive member charge potential V _H of the voltage, the charging of the toner the same polarity, the toner given the opportunity to leave from the carrier by the AC bias V _AC is during positive charging DC bias V _It does not adhere to the portion of the photoreceptor charging potential V _H higher in potential than _DC, but adheres to the exposed portion potential _VL lower in potential than the DC bias _VDC to perform visualization (reversal development).

After the visualization of the first color is completed, the magenta image forming process of the second color is started, and the scorotron charger 1 is again activated.
1 is performed, and a latent image based on the image data of the second color is formed by the image exposure unit 13. At this time 1
The charge elimination by the PCL 12 performed in the color image forming process is not performed because the toner attached to the image portion of the first color scatters due to a sharp drop in the surrounding potential.

Again, of the photoreceptor uniformly charged over the entire peripheral surface of the photoreceptor drum 10, a latent image similar to that of the first color is formed on a portion having no image of the first color, and development is performed. However, in the portion where the image of the first color is developed again in the portion where the image of the first color is present, the exposure potential of the first color V
_L latent image slightly higher voltage V _M is formed than, developed in accordance with the voltage of the DC bias V _DC and the potential V _M is performed.

For the third color cyan and the fourth color black, an image forming process similar to that for the second color magenta is performed, and a visible image of four colors is formed on the peripheral surface of the photosensitive drum 10.

Each of the developing units 14Y, 14M, 14C, 1
A toner supply device for controlling and replenishing each new color toner in 4K includes a plurality of detachable toner cartridges 15.
(Y, M, C, K), toner storage means 16 (Y, M,
C, K) and toner transport means 161 (Y, M, C, K).

On the other hand, the half-moon roller 2
One transfer material (transfer paper or the like) P carried out through 1 is
The sheet is temporarily stopped near the registration sensor position via the intermediate sheet feeding roller pairs 22A and 22B, and is fed to the transfer area by the rotation operation of the registration roller pair 23 of the sheet feeding unit when the transfer timing is adjusted.

In the transfer area, transfer means 17 for applying a voltage for transferring a toner image to the peripheral surface of the photosensitive drum 10 is pressed against the peripheral surface of the photosensitive drum 10 in synchronization with the transfer timing, and the fed transfer material is pinched. The multicolor image is transferred at a time.

Next, the transfer material is separated by a separating means 1 such as a sawtooth electrode.
, And is conveyed to the fixing device 24 by being separated from the peripheral surface of the photosensitive drum 10, where the heat roller (upper roller) 2
After the toner is fused by heating and pressing of the pressure roller 41 and the pressure roller (lower roller) 242, the discharge roller pair 25A, 25
B and 25C, and are discharged onto a discharge tray 26 outside the apparatus. Note that the transfer unit 17 is retracted and separated from the peripheral surface of the photosensitive drum 10 after passing the transfer material to prepare for the formation of the next toner image.

On the other hand, the photosensitive drum 1 from which the transfer material has been separated
In the case of No. 0, the residual toner is removed and cleaned by the pressure contact of the blade 191 of the cleaning device 19, and the charge is removed by the PCL 12 and charged by the scorotron charger 11 again to start the next image forming process. The blade 191
Moves immediately after the cleaning of the surface of the photoconductor and retreats from the peripheral surface of the photoconductor drum 10. The waste toner scraped into the cleaning device 19 by the blade 191 is
After being discharged by the screw 192, it is stored in a waste toner collecting container (not shown).

The cleaning device 19 and the scorotron charger 11 centered on the photosensitive drum 10 are mounted in the photosensitive cartridge 10A. Further, since the developing unit for accommodating the plurality of developing units 14 is located near the operation side, it is possible to adopt a structure that can be pulled out to the front of the apparatus by a simple operation, and further, the upper part of the apparatus main body can be opened. The photosensitive member cartridge 1
It is also possible to take OA out of the device.

FIG. 2 is a cross-sectional view of the photoreceptor cartridge 10A. The photoreceptor drum 10 is driven and rotated by a driving mechanism 30 around a drum shaft 100 as a rotation axis. The drive mechanism 30 includes a drive motor (drive source) M1 such as a pulse motor or a DC motor provided on the apparatus body side, and gear trains 31 to 33 connected thereto. The final gear 33 of the gear trains 31 to 33 meshes with a drive gear (drive transmission member) 34 which is rotatably provided coaxially with the photosensitive drum 10 and has a pitch circle similar to that of the photosensitive drum 10.

The image forming body driving apparatus of the present invention has succeeded in minimizing the effects of load fluctuations and speed fluctuations of the driving system when transmitting the rotation from the driving gear 34 to the photosensitive drum 10. One embodiment will be described.

FIG. 3 is a side sectional view of the cartridge section showing the first embodiment of the present invention. A drum shaft 100 is fixedly supported between both side plates 101A and 102A of a cartridge 10A having a U-shaped cross section. The driving gear 34 as a driving body is, for example, an oilless bearing 34.
1 and is fitted to the drum shaft 100. The flanges 101 and 102 are fitted on the drum shaft 100 via bearings 103, respectively. In this embodiment, the drum shaft 10
0 is fixed, but the drum shaft 100 is
A configuration in which the photosensitive drum 10 is fixed to the drum shaft 100 by being rotatably supported by both side plates 101A and 102A of the 0A may be used.

In this embodiment, a drive transmitting section 35 as a drive transmitting means is provided between the side surface of the drive gear 34 and the flange 101 of the photosensitive drum 10 so as to suppress the influence of load fluctuations and speed unevenness of the drive system. And flange 10
The sliding member 110 is provided between the side surface of the cartridge 2 and the inner wall surface of the side plate 102A of the cartridge 10A to stabilize the thrust load. Further, a fall prevention member 36 is provided between the side surface of the flange 101 on the opposite side of the photosensitive drum 10 and the inner wall surface of the drive gear 34 to stabilize the thrust load and to prevent the drive gear 34 from falling. ing.

The drive transmitting section 35 and the fall prevention member 36 will be described below.

In the present embodiment, the side surface of the flange 101 and the side surface of the drive gear 34 are positioned at a predetermined distance, in this embodiment, at an interval of about 10 mm. The driving force of the driving motor 31 is transmitted to the photosensitive drum 10.

FIG. 4A is an exploded perspective view showing the structure of the drive transmission unit 35. FIG.

As the drive transmission portion 35 for transmitting drive between the drive gear 34 and the flange 101 of the photosensitive drum 10, a beam-shaped elastic body 351 having a beam portion 351A is used as the drive gear 34 as the drive member. A beam portion 3 is fixed to the end face and radially extends on the end face of the flange 101 which is an inertial rotating body.
A rod-shaped, rigid drive connection projection 352 is fixedly provided corresponding to 51A. Then, in the assembled state, as shown in FIG. 4B, the drive connection projection 352 abuts substantially at the center of the beam portion 351A of the beam-shaped elastic body 351.
With the rotation of the drive gear 34, the drive connection projection 352 is pushed in the direction of the arrow via the beam portion 351A, and the photosensitive drum 10
Is transmitted to the motor.

In the drive transmission unit 35 of the present embodiment, the beam 3
A viscoelastic body 353 is provided on the opposite side of the drive connection projection 352 of the 51A from the contact point, while being deformed at a constant compression ratio and making surface contact. According to the present invention, a first elastic member (beam portion 351A) that determines a natural frequency of a drive system including an image forming body and a drive source by an elastic deformation behavior, and acts on the elastic behavior of the first elastic member. Then, a second elastic member (viscoelastic body 353) for increasing the damping characteristic is provided in the drive transmission unit, and this will be described in detail below.

The beam-shaped elastic body 351 of this embodiment is a resin molded member made of polyacetal (POM).
For example, it is firmly fixed to the drive gear 34 by three screws. The beam portion 351A has a thickness of 1.8 mm and a length of 35 mm.
mm, which is fixed at both ends, whereby the natural frequency is determined. As the material of the beam-shaped elastic body 351, besides the above, an ABS resin (ABS), a SUS alloy, a galvanized steel sheet (SECC-C-20 / 20), an industrial resin material having elastic properties such as an aluminum alloy, or a metal Materials can be used selectively. Further, in the embodiment, a form of a cantilever is used, but a form of a cantilever as shown in FIG. 4C may be used.

The viscoelastic body 353 of this embodiment includes chloroprene rubber (CR) and ethylene propylene rubber (EPD).
M), silicone rubber, oil-impregnated porous rubber, butyl rubber, thermoplastic elastomer, and a highly functional material obtained by adding high vibration absorption performance to a thermoplastic resin. The viscoelastic body 353 is an elastic body having a JIS rubber hardness of 20 to 100 degrees, preferably 40 to 80 degrees, and a mechanical loss coefficient tan δ representing the magnitude of internal friction in the elastic body.
A viscoelastic body having a ratio of 0.3 or more, preferably 0.5 or more and 3 or less is used. As shown in FIG. 4B, the viscoelastic body 353 having such a characteristic is opposite to the contact point of the drive connection projection 352 of the beam portion 351A in a state where the compression ratio is 1% to 15% in advance. There is surface contact with a certain area on the side.

With this configuration, the viscoelastic body 353 can control the damping coefficient very effectively and freely. In this embodiment, FIG.
As shown in the figure, the viscoelastic body 353 is in contact with the side opposite to the side in contact with the drive connection projection 352 of the beam portion 351A.
As shown in FIG. 5A, the viscoelastic body 353 is a beam 351A.
May be configured to abut on the same side as the side that abuts on the drive connection protrusion 352.

Further, as shown in FIG. 5B, the viscoelastic body 353 may be configured to abut on the side surface of the beam portion 351A on the side that abuts on the drive connection projection 352. The position of the viscoelastic body 353 in contact with the beam 351A is not limited to one location. For example, as shown in FIG. 5C, the position of the viscoelastic body 353 in contact with the beam 351A is driven. It may be configured to abut on the same side as the side abutting on the connection protrusion 352 and on the opposite side.

The viscoelastic body 353 contacts the beam 351A in a pre-compressed state of between 1% and 15%.
As shown in (d), the beam portion 3 is provided separately from the beam-shaped elastic body 351.
A configuration may be adopted in which a pressing member 354 that allows fine adjustment of the interval with 51A is provided, and an optimal compression ratio of the viscoelastic body 353 inserted therebetween is determined and set.

The drive transmission unit 3 of the embodiment described above
Reference numeral 5 denotes a beam-like elastic body 351 fixed to the end face of the drive gear 34, and a drive connection projection 352 on the end face of the flange 101.
Is fixed, the beam portion 351A of the beam-shaped elastic body 351 is brought into contact with the drive connection protrusion 352, and the drive rotation of the drive gear 34 is transmitted to the drive connection protrusion 352 via the beam portion 351A (see FIG. 4). ), But the exact same effect can be obtained by adopting a completely opposite configuration.

FIG. 6 shows the structure of the drive transmission section 35 of this embodiment.

As shown in an exploded perspective view of FIG. 6A, a beam-like elastic body 351 having a beam portion 351A is provided on an end surface of a flange 101 which is an inertial rotating body. It is fixed in a positional relationship in the radial direction. The beam portion 351A is provided with a viscoelastic body 353 in contact therewith. Also, a rod-shaped, rigid drive connection projection 352 is fixed to the end face of the drive gear 34, and in the assembled state, as shown in FIG. 6B, the drive connection projection 352 is located substantially at the center of the beam portion 351A. The drive connection protrusion 352 comes into contact with the rotation of the drive gear 34 and the beam portion 351 is formed.
When A is pushed in the direction of the arrow, drive transmission to the photosensitive drum 10 is performed.

The present inventors have determined that the moment of inertia is 27000 g.
For the photosensitive drum 10 of cm ² , a compression ratio of 1 was used by using a viscoelastic body 353 made of CR rubber having a rubber hardness of 61 degrees.
The viscoelastic body 353 is in contact with the beam portion 351A having a natural frequency of 25 Hz so that the natural frequency is 15H.
z, it is possible to reduce the gain of the transfer coefficient and reduce the speed unevenness.

By providing the drive transmission unit 35 described above between the drive gear 34 and the photosensitive drum 10 or an inertia member integrally connected to the photosensitive drum 10, a first elastic member (beam part) is provided. Thereby, the natural frequency of the torsion of the inertial rotating body can be dominantly controlled by the second elastic member (viscoelastic body), so that the damping coefficient can be controlled freely and the degree of freedom of design is remarkably improved. The fact that the natural frequency and damping coefficient of the inertial rotating body drive system can be set freely is, as a specific effect, that the gain of the transfer function is in the region where the gain of the transfer function is inherently lower in the region higher than the natural frequency. Thereby, the speed unevenness is reduced, and the gain of the transfer function itself is reduced by the effect of the damping member.
Appears as an effect that the resonance level near the natural frequency decreases, and as a whole, it is possible to obtain an effect that the speed unevenness relating to the driving of the inertial rotating body is efficiently reduced and the driving accuracy of the inertial rotating body is significantly improved.

As a result, load fluctuations such as speed unevenness in the vicinity of the resonance area, vibration from the developing drive unit in the case of the image forming apparatus, or a cleaning blade, a transfer roller, and a transfer material entering and leaving the transfer area which come and go. And a stable drive system that is strong against disturbances such as

FIG. 7 is an exploded perspective view showing one embodiment of the sliding member 110. Flange 10 of photoconductor drum 10
A viscoelastic member fixed on one side and made of a material having good slidability is provided between the side surface of the second member 2 and the inner wall surface of the side plate 102A of the cartridge 10A.
Reference numeral 10 has a function of receiving a thrust load while being constantly compressed between the side surface of the flange 102 and the inner wall surface of the side plate 102A. As the viscoelastic member used for the sliding member 110, foamed EPDM, silicone gel, oil-impregnated porous rubber, butyl rubber, thermoplastic elastomer, and a high-functional material obtained by adding high vibration absorbing performance to a thermoplastic resin are used. Teflon or PET film having good slidability is used in a portion corresponding to a sliding surface on the surface of the elastic member, which is attached to the viscoelastic member. In the present embodiment, a ring-shaped viscoelastic member having a thickness of about 3 mm and a diameter of about 40 mm is attached to the side plate 102A using a double-sided adhesive tape, and 700 g
It is used in a form compressed to about 1.5 mm under a thrust load of f.

In this embodiment, as shown in FIG. 3, a fall prevention member 36 is provided between the side surface of the driving gear 34 as a driving body and the side surface of the flange 101 of the photosensitive drum 10.

As shown in FIG. 8 which is an exploded perspective view, the fall prevention member 36 is fixed to the three sides of the flange 101 with screws or the like. In the assembled state of FIG. 3, the fall prevention member 36 is provided. The tip of the drive gear 36 is provided in contact with the side surface of the drive gear 34 so as to make frictional contact.

Incidentally, the fall prevention member 36 may be fixedly provided on the side surface of the drive gear 34, and in this case, the tip is provided so as to make frictional contact with the side surface of the flange 101. As the fall prevention member 36, a POM (polyacetal) resin material, an ABS resin, a SUS alloy, SECC (galvanized steel plate), aluminum, or the like can be used.

(Embodiment 2) FIG. 9 is a side sectional view of a cartridge section showing Embodiment 2 of the present invention. Embodiment 2
Is a rotation prevention member formed of a rotating member between the side surface of the drive gear 34 and the side surface of the flange 101 of the photosensitive drum 10 instead of the prevention member 36 in the first embodiment described with reference to FIGS. A member 36A is provided. Less than,
A description will be given only of a portion different from the first embodiment.

As shown in FIG. 10 which is an enlarged side view of the fall prevention member 36A, and FIG. 11 which is an exploded perspective view of the flange 101 and the drive gear 34, the fall prevention member 36A is shown.
Is composed of a rotatable roller 361A, a support arm 362A that supports the roller 361A, and a screw 363A that fixes the support arm 362A to the flange 101. The roller 361 </ b> A contacts both side surfaces of the flange 101 and the drive gear 34.

Incidentally, the fall prevention member 36A is connected to the drive gear 34.
In this case, in this case, the tip is the flange 1
01 is provided so as to be in contact with the side surface.

The fall prevention member 36A may be made of a resin material such as POM or ABS, or a metal material such as stainless steel or galvanized steel plate, like the fall prevention member 36.

In the first and second embodiments, in transmitting power from the drive gear 34 to the photosensitive drum 10, the following two items are particularly effective for performing good power transmission.

The clearance c for fitting between the hole diameter of the drive gear 34 and the diameter d of the drum shaft 100 is set to 50 μm or less. When the clearance c is 50 μm or more, the influence of the falling down and rattling of the driving gear 34 appears, and for example, when the load fluctuates, for example, when the transfer material enters the transfer area, the speed unevenness appears. As a result of many experiments, it is desirable that the clearance c of the fitting be 35 μm or less and the clearance ratio (c / d) be 0.002 or less.

The drive gear 34 is formed of a molded resin member. At the time of molding, it is preferable to form a uniform thin wall from the viewpoint of ubiquity (shrinkage during solidification), and a rib or the like is provided to provide strong reinforcement. However, according to the study of the present inventors, the provision of radial ribs for reinforcement on such a drive gear has room for further improvement, particularly in order to obtain high-precision rotation characteristics. This is because a slight difference occurs between the gear pitch near the rib portion and the gear pitch at a portion other than the rib portion, which causes speed unevenness. FIG.
The cross-sectional view of the drive gear 34 shown in FIG. 1 shows a solution to this problem. For example, a metal disk 342 such as a SUS material is fixed to a thin flat portion of the gear using rivets or small screws. Reinforced. By providing the metal disk 342 in place of the rib, the above-mentioned uneven speed can be eliminated. When the metal disk 342 is omitted, in the drive gear 34 having a thrust load on the side surface, a natural vibration is generated from a thin flat portion at the time of driving transmission, and the influence of the natural vibration is recognized.

(Comparative Study) The excellent effects of the present invention have already been described with reference to FIG. Further, the fall prevention member 3
A comparison was made between a drive system without the 6,36A and a drive system with these components.

FIG. 14 illustrates this. FIG.
(A) is a graph showing the transfer function of the photoconductor drive system, in which the horizontal axis indicates frequency (Hz) and the vertical axis indicates the gain of the transfer function.

FIG. 14B is a graph showing a comparison of speed unevenness when a load changes.

The power transmission characteristics of the first embodiment in which the fall prevention member 36 is provided and the second embodiment in which the fall prevention member 36A is provided are shown by using a drive system without the fall prevention members 36 and 36A as a comparative example. In the case of Embodiment 1 with respect to the comparative example,
The speed unevenness at the time of the load change is reduced to about half, but the gain of the transfer function is increased and is increased on a part of the frequency side, and the speed unevenness is increased on the contrary. In the first embodiment, the excitation frequency is suppressed to a low level which does not cause any problem.

As described above, the gain can be changed with respect to the vibration frequency by providing the fall prevention members 36 and 36A.

On the other hand, in the second embodiment, the speed unevenness at the time of a load change is further reduced, and is at a level where there is almost no problem in image formation.
Is smaller than that in the first embodiment and slightly increased in the excitation frequency, but at a level that does not cause any problem in image formation. By such measures, the steady speed unevenness during image formation and the speed unevenness during load fluctuation are improved as compared with the comparative example, and the image quality is further improved.

[0074]

According to the present invention, the effects of load fluctuations and unevenness in the speed of the drive system can be minimized, and the rotation speed of the photosensitive member can be easily controlled, so that unevenness in the speed can be suppressed.

As a result, in the image forming apparatus, small-pitch banding, which is a major image trouble caused by unevenness in the speed of the photosensitive member, is significantly reduced to a level that cannot be recognized by humans, and a high-quality image is formed. Can be stably provided.

[Brief description of the drawings]

FIG. 1 is a sectional view of an image forming apparatus according to Embodiment 1 of the present invention.

FIG. 2 is a sectional view of the photosensitive member cartridge according to the first embodiment.

FIG. 3 is a side sectional view of the photoreceptor cartridge according to the first embodiment.

FIG. 4 is an explanatory diagram of a drive transmission unit according to the first embodiment.

FIG. 5 is an explanatory diagram showing an example of installation of a viscoelastic body in a drive transmission unit.

FIG. 6 is an explanatory diagram showing another example of the drive transmission unit.

FIG. 7 is an exploded perspective view of a sliding member according to the first embodiment.

FIG. 8 is an exploded perspective view of a flange provided with a fall prevention member and a drive gear according to the first embodiment.

FIG. 9 is a side sectional view of a cartridge unit according to the second embodiment.

FIG. 10 is an enlarged side view illustrating a fall prevention member according to the second embodiment.

FIG. 11 is an exploded perspective view of a flange and a drive gear according to the second embodiment.

FIG. 12 is a cross-sectional view of the drive gear according to the first embodiment.

FIG. 13 is an explanatory diagram relating to control of frequency characteristics.

FIG. 14 is a graph showing a comparison of speed unevenness during a load change.

DESCRIPTION OF SYMBOLS 10 Photoconductor drum 10A (Photoconductor) cartridge 30 Drive mechanism 34 Drive gear 35 Drive transmission unit 36, 36A Fall prevention member 100 Drum shaft 101, 102 Flange 101A, 102A Side plate 110 Sliding member

Claims (4)

[Claims] A rotating body having an image forming body, a driving body for driving the rotating body, and an elastic member;
An image forming apparatus comprising a drive transmitting unit that transmits a driving force of the driving body to the rotating body via the elastic member, wherein the falling of the driving body is prevented between the rotating body and the driving body. An image forming apparatus comprising a fall prevention member. 2. The apparatus according to claim 1, wherein the fall prevention member has a member fixed to one of the rotating body and the driving body and in frictional contact with the other.
An image forming apparatus according to claim 1. 3. The method according to claim 2, wherein the fall prevention member is the rotating body, or
2. The image forming apparatus according to claim 1, further comprising: the rotating body attached to one of the driving bodies, and a rotating member that contacts the driving body. 3. 4. The image forming apparatus according to claim 1, wherein said drive transmitting means has a viscoelastic member involved in driving force transmission.