JPH1097158A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inhibit the vibration of an image carrying drum caused by the vibration of an image forming element coming into press-contact with the image carrier drum, for suppressing an abnormal sound generated from the image carrying drum by fixedly arranging a weight in the image carrying drum and setting the weight of the image carrying drum and the weight, so as to satisfy specific conditions. SOLUTION: The weight 26 whose outside diameter is slightly smaller than the inside diameter of a photoreceptor drum 7 is used and fixed on the inner periphery of the drum 7 by an adhesive 27. The weight 26 is fixedly arranged in the image carrier drum of such a drum 7. When the weight of the image carrying drum is defined as W1 and the weight 26 is defined as W2 , the weight W1 and the weight W2 are set to satisfy W2 /W1 >=1. Thus, the vibration is transmitted from a cleaning blade, but the total weight is increased by the weight 26 and the rigidity of the whole is increased as well, so that the vibration occurring in the drum 7 is suppressed to stop the generation of the abnormal sound.

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 for forming a toner image on an outer peripheral surface of a rotating image bearing drum by a plurality of image forming elements and transferring the toner image to a transfer material. The present invention relates to an image forming apparatus in which at least one of the plurality of image forming elements is in pressure contact with an outer peripheral surface of an image bearing drum.

[0002]

2. Description of the Related Art In an image forming apparatus of the above-mentioned type constituted as a copying machine, a printer, a facsimile or a multifunction machine having at least two functions thereof, at least one image forming device is formed on an outer peripheral surface of a rotating image bearing drum. Since the elements are pressed against each other, the pressed image forming elements vibrate with a small amplitude, and the vibration is transmitted to the image bearing drum. As a result, abnormal noise is generated from the image bearing drum, which may cause discomfort to the operator of the image forming apparatus.

In order to prevent the generation of such abnormal noise, there has been proposed a configuration in which the weight ratio between the charging roller and the image bearing drum which presses against the outer peripheral surface of the image bearing drum is set within a predetermined range (Japanese Patent Laid-Open No. Hei 5 (1994)). -333668). However,
According to this configuration, the weight of the image bearing drum must be set according to the weight of the charging roller, and the degree of freedom in designing the image forming apparatus is reduced. Further, it is difficult to prevent generation of abnormal noise caused by an image forming element other than the charging roller.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus of the type described at the beginning, which can effectively suppress the generation of abnormal noise without being subjected to the above-mentioned restrictions.

[0005]

According to the present invention, in order to achieve the above object, in an image forming apparatus of the type described at the beginning, a weight is fixedly arranged inside an image bearing drum, and the weight of the image bearing drum is reduced. W ₁ , where W ₂ is the weight of the weight, each weight W ₁ , W ₂ is set such that W ₂ / W ₁ ≧ 1 is proposed.

At this time, in the above configuration, it is advantageous that the weight of the image bearing drum is 150 gf or less.

In each of the above structures, it is advantageous that the thickness of the image bearing drum is 1.5 mm or less.

Further, in each of the above structures, when the image bearing drum is stopped, it is further advantageous that the time from the start of deceleration of the image bearing drum to the stop is 0.3 seconds or more.

In each of the above configurations, a mode is provided in which the image bearing drum rotates in a direction opposite to the direction in which the image bearing drum rotates during image formation for forming a toner image on the peripheral surface of the image bearing drum. It is advantageous.

Further, in each of the above structures, it is advantageous that the weight is disposed only in a part of the longitudinal direction of the image bearing drum.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a cross-sectional view showing the inside of an image forming apparatus according to an embodiment of the present invention from the front side. This image forming apparatus is configured as a copier, and the copier has functions such as a printer and a facsimile. Can be provided.
As shown in FIG. 1, an image forming unit 1 is detachably mounted on the image forming apparatus main body 100.

FIG. 2 is a vertical sectional view of the image forming unit 1 mounted on the image forming apparatus main body 100 as shown in FIG. 1, and FIG. 3 is an external perspective view of the image forming unit 1. The image forming unit 1 is pushed into the image forming apparatus main body 100 in a direction indicated by an arrow A in FIG. 3 (a direction perpendicular to the sheet of FIG. 1), so that the image forming unit 1 is moved to FIGS. The image forming unit 1 can be taken out from the image forming apparatus main body 100 by loading and setting it at a predetermined position in the image forming apparatus main body shown in the figure and pulling out the image forming unit 1 in the direction opposite to the arrow A.

As shown in FIGS. 2 and 3, the image forming unit 1 has a unit case 2 and various image forming elements described later incorporated therein, and the unit case 2 includes a plurality of case members. It is configured to be detachably assembled. The opening 16 (FIG. 3) formed in the unit case 2 is covered by a developer cartridge 43 (FIG. 2).

A photosensitive drum 7 as an example of an image bearing drum and a charging roller 8 as an example of a charging device are rotatably mounted in the unit case 2.
The charging roller 8 extends parallel to the photosensitive drum 7 and is in pressure contact with the outer peripheral surface of the photosensitive drum 7.

As shown in FIG. 4, the photosensitive drum 7 has a cylindrical tube 3 made of a conductive material such as aluminum.
And end pieces 5 and 6 fitted to respective longitudinal ends of the photosensitive layer 4 applied to the outer peripheral surface thereof, and are rotatably supported by the unit case 2. A gear 25 is formed on the outer peripheral surface of one end piece 6, and another gear (not shown) is meshed with this gear, and these gears are driven by the operation of a drive motor (not shown). 7 is driven to rotate about its central axis.

During the image forming operation, the photosensitive drum 7 is
In this case, the charge removing light L1 from the charge removing device (not shown) supported by the image forming apparatus main body 100 enters the unit case 2 through the opening 34 formed in the unit case 2 at this time. Then, the surface of the photoconductor 7 is irradiated. As a result, the surface potential of the photoconductor 7 is averaged to a reference potential of, for example, 0 to -150V.

On the other hand, the charging roller 8 is in pressure contact with the outer peripheral surface of the photosensitive drum 7, and is driven to rotate by the rotation of the photosensitive drum 7, so that the surface potential of the photosensitive drum 7 becomes, for example, about -1100V. As described above. During the charging operation, a voltage is applied to the charging roller 8 from a power supply (not shown).

The exposed portion 9 irradiates the light-modulated laser beam L2 to the surface portion of the photosensitive drum 7 charged to a predetermined polarity as described above. This laser beam L2
Is emitted from the exposure optical system unit 32 (FIG. 1) supported by the image forming apparatus main body 100, and enters through the opening 35 of the unit case 2. With this exposure, a predetermined electrostatic latent image is formed on the photosensitive drum 7.
For example, the photoconductor portion (image portion) irradiated with the laser beam L2 has a surface potential of 0 to -290 V, and the photoconductor portion (background portion) not irradiated with the laser beam L2 has the surface potential of -1100 V described above. Maintain around the front and back. An original (not shown) is illuminated, and the reflected light image is
To form an electrostatic latent image.

On the other hand, a developing sleeve 11 of a developing device 10 is rotatably supported on the unit case 2 as shown in FIG. The developing sleeve 11 is made of a non-magnetic material, and is driven to rotate counterclockwise in FIG. 2 during an image forming operation. The unit case 2 allows the developing device 1
A two-component developer D having a toner and a carrier is accommodated in a developer chamber 90 of the developer case 12. Are immovably arranged. A doctor blade 14 is fixed to the upper portion of the developer case 12 so as to face the developing sleeve 11 and to be spaced from the surface of the sleeve 11 by a predetermined gap G. The toner and the carrier of the developer D are agitated, whereby the toner and the carrier are frictionally charged to polarities opposite to each other. In this example, the toner is negatively charged and the carrier is positively charged. A one-component developer containing no carrier may be used.

By the rotation of the developing sleeve 11 as described above, the developer D in the developer case 12 is transported while being carried on the developing sleeve 11 by the magnetic force of the magnet 13, and the developer D The amount is regulated by the scraping action of the doctor blade 14. The regulated developer is
Developing area D between developing sleeve 11 and photosensitive drum 7
A, and at this time, for example,-
Since a developing bias voltage of about 800 V is applied, the negative polarity toner in the developer transported to the developing area DA is electrostatically transferred to and adheres to the image area on the photosensitive drum 7, A predetermined toner image is formed on the outer peripheral surface of the body drum 7. The electrostatic latent image formed on the photosensitive drum 7 is visualized as a toner image.

As shown in FIG. 2, in the developer chamber 90 of the developer case 12, two agitating members 44 and 45 are disposed, and these agitating members 44 and 45 have their shafts 63 and 6 respectively.
4 and stirring blades 65 and 66 fixed thereto. The shafts 63 and 64 are rotatably supported by the unit case 2, and are driven to rotate, so that the development in the developer chamber 90 is performed. The agent D is stirred while being conveyed. Due to such a stirring action, the toner and the carrier are frictionally charged to opposite polarities as described above. When the toner concentration of the developer D decreases, the toner case 67 set in the image forming apparatus main body 100 passes through the toner supply port 30 (FIG.
The toner is replenished to the developer chamber 90 in the inside.

On the other hand, FIG.
As shown in FIG. 2, a transfer roller 15 as an example of a transfer device is rotatably supported so as to face the photosensitive drum 7.

As shown in FIG. 1, an appropriate number of paper feeders 33, 33a, 3b, 33c are provided on the main body of the image forming apparatus. Transfer paper P, which is an example of the material, is transported toward a transfer unit 22 (FIG. 2) between the photosensitive drum 7 and the transfer roller 15.

Each paper feeder 33, 33a, 33b, 33c
Are paper feed cassettes 36 containing transfer paper P of each size,
36a, 36b, 36c and paper feed rollers 37, 37a,
The paper feed rollers of the selected paper feeder are driven to rotate, and the transfer paper in the paper feed cassette is fed one by one. For example, the lowest paper feeder 33
When c is selected, the paper feed roller 37c rotates to transfer the transfer paper P stored in the paper feed cassette 36c in a direction indicated by an arrow B in a transfer paper transport path 39 by a series of transport roller pairs 38.
Is transported to the transfer unit 22 by the registration roller pair 40 at a predetermined timing.

The transfer paper P fed as described above is aligned with the photosensitive drum 7 and the transfer roller as shown in FIG. 2 in a state where the leading end of the transfer paper P matches the leading end of the toner image formed on the photosensitive drum 7. 15 through the transfer section 22. At this time,
The transfer roller 15 rotates counterclockwise in FIG. 2 while pressing against the outer peripheral surface of the photosensitive drum 7 via the transfer paper P, and since a transfer voltage is applied to the transfer roller 15, The toner image on the drum 7 is transferred to the transfer paper P.

The transfer paper P leaving the photosensitive drum 7 is shown in FIG.
Then, the toner image is conveyed to the fixing device 41 as indicated by an arrow B1 in FIG. 2, where the toner image is fused and fixed on the transfer paper P by the action of heat and pressure. The transfer paper P that has passed through the fixing device 41 is used as a copy paper as the image forming apparatus main body 100.
The sheet is discharged outside and stacked on the sheet discharge tray 42.

In this embodiment, a transfer sheet P is used as a transfer material, and the toner image on the photosensitive drum 7 is transferred to the transfer sheet P. The image may be primary-transferred to the intermediate transfer member, and then the toner image on the intermediate transfer member may be secondarily transferred to a transfer paper as a final transfer material.

The residual toner adhering to the photosensitive drum 7 after the transfer of the toner image is scraped off the surface of the photosensitive drum 7 by the cleaning blade 18 of the cleaning device 17 shown in FIG. In this way, the surface of the photosensitive drum 7 is cleaned, and the process proceeds to the next image forming operation again.
The cleaning device 17 has a cleaning case 19 formed by a part of the unit case 2, and the toner T (FIG. 2) scraped off by the cleaning blade 18 removes toner T Is discharged out of the cleaning device 17 by the rotation of.

The cleaning blade 18 is an example of a cleaning member for cleaning the surface of the photosensitive drum 7, and has a base end fixedly held in the unit case 2 and a leading end edge formed on the photosensitive drum 7. Is in pressure contact with the outer peripheral surface. The cleaning blade 18 is made of, for example, an elastic body such as rubber.

As described above, the illustrated image forming apparatus includes:
It has an image bearing drum composed of a photoreceptor drum 7, around which image forming elements such as a charging roller 8, a developing sleeve 11, a transfer roller 15 and a cleaning blade 18 are arranged. A toner image is formed on the outer peripheral surface of the image bearing drum composed of the rotating photosensitive drum 7, and the toner image is transferred to a transfer material composed of transfer paper P. At this time, at least one of the plurality of image forming elements, in this example, the charging roller 8 and the transfer roller 15
The cleaning blade 18 is in pressure contact with the outer peripheral surface of the image bearing drum.

When the photosensitive drum 7 rotates with the image forming element pressed against the outer peripheral surface of the photosensitive drum 7, the image forming element pressed against the photosensitive drum vibrates in the conventional image forming apparatus. This may be transmitted to the photosensitive drum to cause abnormal noise.

The transfer roller 15 of the image forming apparatus shown in FIGS. 1 to 3 can be substantially prevented from generating abnormal noise caused by the roller 15 by forming it from a soft material such as foam. However, since the cleaning blade 18 pressed against the outer peripheral surface of the photosensitive drum 7 is a blade made of an elastic body, the image forming operation is particularly continuously performed.
As a result, when the temperature of the cleaning blade 18 rises as the temperature inside the apparatus main body 100 rises, the cleaning blade 18 is moved by the external force received from the photosensitive drum 7 at the leading edge of the cleaning blade 18 as shown in FIG. It vibrates with a small amplitude in the direction shown by the arrow S.

FIG. 5 is an explanatory view schematically showing a state where the cleaning blade 18 vibrates. The leading edge of the cleaning blade 18 is in pressure contact with the outer peripheral surface of the photosensitive drum 7. First, the cleaning blade 18 that has been in pressure contact with the photosensitive drum 7 in a solid line state is rotated by the rotation of the photosensitive drum 7. And is deformed as shown by the dashed line. However, the base end of the cleaning blade 18 is fixedly supported by the unit case 2 (FIG. 2), and the cleaning blade 18 is made of an elastic material. Return to the state. By repeating such an operation, the cleaning blade 18 vibrates in the direction of arrow S.

In the conventional image forming apparatus, when the cleaning blade 18 vibrates as described above, the vibration is transmitted to the photosensitive drum 7, whereby the photosensitive drum 7 vibrates and abnormal noise is generated. It is. It is considered that the cleaning blade 18 vibrated so as to strike the outer peripheral surface of the photosensitive drum 7, which caused abnormal noise. Such behavior of the cleaning blade 18 is also called “stick slip”.

It has been experimentally confirmed that the stick-slip phenomenon described above becomes more conspicuous as the weight of the photosensitive drum 7 decreases and as the thickness of the photosensitive drum 7 decreases. Therefore, when the photosensitive drum 7 is stopped, the speed of the photosensitive drum 7 is reduced from the time when the photosensitive drum 7 is stopped to immediately before the photosensitive drum 7 is stopped, compared to when the photosensitive drum 7 is rotating at a high speed during the image forming operation. During that time, the stick-slip phenomenon became remarkable, and in the conventional image forming apparatus, relatively large abnormal noise occurred at this time.

The noise may be caused not only by the stick-slip between the cleaning blade 18 and the photosensitive drum 7 but also by the charging roller 8 made of an elastic material such as rubber pressed against the photosensitive drum 7. . In particular, when a DC and AC superimposed voltage is applied to the charging roller 8 to charge the rotating photosensitive drum 7, abnormal noise is generated due to the application of the AC voltage.

As described above, a configuration has been proposed in which the weight ratio between the charging roller and the photosensitive drum is set within a predetermined range in order to prevent the occurrence of abnormal noise as described above. However, in this configuration, the weight of the photosensitive drum must be set according to the weight of the charging roller, and the disadvantage that the degree of freedom in designing the image forming apparatus is reduced is unavoidable. Further, generation of abnormal noise due to stick-slip of the cleaning blade cannot be prevented.

Therefore, in the image forming apparatus of this embodiment,
As shown in FIG. 4, a weight 26 is fixedly arranged inside the photosensitive drum 7. As the weight 26, a rigid body such as a metal, a synthetic resin, rubber, or oily clay, an elastic body, a plastic body, or a combination thereof can be used as appropriate. And
Weight 26 having an outer diameter slightly smaller than the inner diameter of photoconductor drum 7
May be inserted into the photosensitive drum 7 and the weight 26 may be fixed to the inner peripheral surface of the photosensitive drum 7 with an adhesive 27 or may be slightly larger than the inner diameter of the photosensitive drum 7. A weight 26 having an outer diameter may be pressed into the photosensitive drum 7 and the weight 26 may be fixed to the photosensitive drum 7. When using clay, it is also possible to fix the clay to the photosensitive drum 7 without using an adhesive simply by packing the clay inside the photosensitive drum 7.

The use of the photosensitive drum 7 having the above-described weight 26 contained therein increases the overall weight of the photosensitive drum 7 and increases its rigidity.
The photosensitive drum 7 rotates in a state where the image forming elements such as the charging roller 8 and the cleaning blade 18 are pressed against the outer peripheral surface of the photosensitive drum as shown in FIG. Even if vibrations are transmitted from the elements to the photosensitive drum 7, generation of abnormal noise due to the vibration can be suppressed.
For example, the cleaning blade 1 is
Vibration is transmitted from the photosensitive drum 8, but the weight 26 loaded inside the photosensitive drum 7 increases the overall weight and rigidity of the photosensitive drum 7. As a result, vibration generated in the photosensitive drum 7 is suppressed, and abnormal noise is generated. Is suppressed.

Since the abnormal noise is generated by the vibration of the photosensitive drum surface, the weight 26 is fixed to the inner peripheral surface of the photosensitive drum 7 via an adhesive 27 having a predetermined viscosity and spring property. Then, the weight 26 functions as an additional mass of the dynamic damper, and the vibration of the photosensitive drum surface can be more effectively suppressed. For the same reason, it is also advantageous to use an elastic body such as rubber or clay as the weight 26.

As described above, by arranging the weight 26 inside the photosensitive drum 7, the noise generated from the photosensitive drum 7 when the photosensitive drum 7 rotates can be suppressed. However, according to the study of the present inventor, simply adding the weight 26 to the photoreceptor drum 7 is insufficient in the effect of suppressing the generation of abnormal noise, or the weight of the weight 26 increases. It has been found that there is a disadvantage that the weight of the image forming apparatus main body increases.
Hereinafter, this point will be clarified while explaining the progress of the experiment performed by the inventor.

First, an aluminum cylindrical body having a diameter of 30 mm, a length of 340 mm, and a thickness of 0.75 mm was prepared as the raw tube 3 of the photosensitive drum 7, and the photosensitive layer 4 was applied to the outer peripheral surface thereof. The photosensitive drum 7 was used. At this time, the weight of the photosensitive drum 7 was 65 gf. Inside the photosensitive drum 7, a metal weight 2 having a diameter slightly smaller than its inner diameter is provided.
6 and the adhesive 2 previously applied inside the photosensitive drum.
7, the weight 26 was fixed to the inner peripheral surface of the photosensitive drum 7. Then, a number of weights having various weights are prepared, and each of them is assembled into the unit case 2 of the imaging unit 1 via the end pieces 5 and 6 as shown in FIGS. Then, the above-described image forming operation was performed, and the occurrence of abnormal noise at this time was confirmed. In this experiment, the transfer paper P is continuously fed for 30 minutes, and after the temperature in the image forming apparatus main body is increased, the photosensitive drum 7 is decelerated to stop it, and immediately before the stop. The occurrence of abnormal noise was examined. The abnormal noise was observed outside the image forming apparatus, and an experiment was performed in a general office environment. After the photosensitive drum 7 starts to decelerate,
The time before this stopped was 0.7-0.8 seconds.

As a result, as the weight of the weight 26 increases, the volume of the abnormal noise decreases, and when the weight reaches about 50 gf, the effect of suppressing the generation of the abnormal noise starts to appear, and the weight of the weight becomes 65 gf.
As described above, the generation of abnormal noise is sharply reduced, and when the external noise is observed from outside the image forming apparatus, the abnormal noise can hardly be heard. The results are shown in Table 1 below. In this table, W ₁ is the weight of the photosensitive drum 7 (the tube 3
And the weight including the photosensitive layer 4) (gf), and W ₂ is the weight (gf) of the weight 26. In addition, “x” indicates a situation where abnormal noise is certainly recognized by the ear, and “○” indicates that almost no abnormal noise is transmitted to the outside of the image forming apparatus main body, and substantially no abnormal noise is generated. It is not shown.

[0045]

[Table 1]

As can be seen from Table 1, the weight W _{2 of the} weight 26
Is 65 gf, that is, when the weight is equal to or more than the weight of the photosensitive drum 7, the generation of abnormal noise is sharply reduced and becomes almost inaudible.

Next, a photosensitive layer 4 is formed on the outer peripheral surface of an aluminum tube 3 having a diameter of 60 mm, a length of 340 mm and a thickness of 1 mm.
The photosensitive drum 7 weight W ₁ of 150gf coated with, a variety of weight of the weight 26 provides a number of those fixedly arranged therein, the same experiment was performed as was described above. The results are as shown in Table 2.

[0048]

[Table 2]

As can be seen from Table 2, the weight W _{2 of the} weight 26
Is greater than 150 gf, that is, the same weight or more as the photosensitive drum 7, the occurrence of abnormal noise sharply decreases and becomes almost inaudible.

As described above, two typical experimental examples have been described. As shown by these experimental results, if the weight W _{2 of the} weight 26 is set to be equal to or larger than the weight W ₁ of the photosensitive drum 7, abnormal noise is generated. Can be effectively suppressed. From this fact, in the image forming apparatus of the present embodiment, the weight 26 is fixedly arranged inside the image bearing drum composed of the photosensitive drum 7 and
When the weight of the image bearing drum is W ₁ and the weight of the weight 26 is W ₂ , the weights W ₁ and W ₂ are set so as to satisfy W ₂ / W ₁ ≧ 1. This is a configuration corresponding to claim 1.

With this configuration, it is possible to reliably reduce the generation of abnormal noise due to the vibration of the image bearing drum surface, and to prevent a problem that gives an unpleasant feeling to the operator of the image forming apparatus.
Moreover, it is not necessary to set the weight of the photosensitive drum 7 according to the charging roller 8, and the degree of freedom in designing the image forming apparatus is not narrowed. Further, generation of abnormal noise due to vibration of the image forming element other than the charging roller 8 such as the cleaning blade 18 can also be prevented.

By the way, as described above, the weight 2
In the conventional image forming apparatus using no 6, the smaller the weight W ₁ of the photosensitive drum 7 and thinner if the thickness is thin, the surface of the photosensitive drum tends to vibrate,
Therefore, abnormal noise was easily generated. The weight and thickness of the photosensitive drum in the conventional image forming apparatus by the inventor,
When the correlation with the generation of abnormal noise was examined through various experiments, the weight of the photosensitive drum was 150 gf (1.47
N) and below, the generation of abnormal noise became remarkable, and when the thickness became 1.5 mm or less, the generation of abnormal noise became clear.

From such facts, when the weight is fixedly arranged inside the image bearing drum, and the weight of the image bearing drum is W ₁ and the weight of the weight is W ₂ , W ₂ / W ₁ ≧ 1 is satisfied. The configuration according to claim 1, wherein each weight is set, when the weight of the image bearing drum is 150 gf or less, when the thickness of the image bearing drum is 1.5 mm or less, If the weight of the drum is 150gf or less,
When the thickness is 1.5 mm or less, it can be particularly advantageously employed. This is a configuration corresponding to claims 2 and 3. Although an image bearing drum having a small weight and thickness is low in cost, conventionally, when such an image bearing drum was used, abnormal noise was easily generated. By adopting the corresponding configuration, the generation of the abnormal noise can be effectively suppressed.

In the image forming apparatus shown in FIGS. 1 to 4, the photosensitive drum 7 and the cleaning blade 18 are assembled to the unit case 2 to form the image forming unit 1. In the case of an image forming apparatus in which an image forming unit is configured by integrally assembling a carrier drum and a cleaning blade that cleans the transfer residual toner, the unit is detachable from the image forming apparatus main body. Conventionally, it is necessary to reduce the size and weight of the image bearing drum, and to set the weight and the thickness of the drum small. Therefore, in the related art, such an image forming apparatus is particularly likely to generate abnormal noise. Therefore, the respective configurations corresponding to the first to third aspects can be particularly advantageously applied to such an image forming unit type image forming apparatus. Conventionally, it is possible to effectively reduce the occurrence of abnormal noise of the image forming apparatus, which is likely to generate abnormal noise.

The noise from the photosensitive drum 7 is more likely to occur as the temperature of the cleaning blade 18 is higher and as the rotational speed of the photosensitive drum 7 is lower. The temperature inside the main body 100 rises,
In addition, as described above, abnormal noise is likely to be generated immediately before the photosensitive drum 7 stops rotating or immediately after the rotation of the photosensitive drum 7 becomes slow. The abnormal noise is likely to occur due to unstable stick-slip of the image forming element such as the cleaning blade 18 at the time of low-speed rotation immediately before the stop of the photosensitive drum 7 or the like. Therefore, the shorter the time from the start of deceleration to the stop of the photosensitive drum 7 until it stops, the shorter the time of occurrence of abnormal noise, and the more difficult it is to recognize the abnormal noise.

FIG. 6 shows an experimental result obtained by examining the relationship between the time and the abnormal noise using a conventional image forming apparatus. The horizontal axis is
When the photosensitive drum 7 stops, the time t (second) from when the photosensitive drum 7 starts to decelerate to when the photosensitive drum 7 stops, the vertical axis indicates the noise generation level at that time, and “○” indicates almost The level at which abnormal noise cannot be recognized by the ear, the level “x” indicates a level at which abnormal noise is remarkable, and the level “△” indicates an intermediate level. When the time t becomes 0.3 seconds or less, abnormal noise is generated. Is almost inaudible.

Therefore, even in the conventional image forming apparatus,
If the time T from when the photosensitive drum is decelerated and accelerated to when it stops can be made 0.3 seconds or less, it is possible to substantially eliminate abnormal noise. However, it is generally difficult to stop the photosensitive drum suddenly in this way, or a braking device for suddenly stopping the motor for the photosensitive drum must be provided. However, such a braking device is expensive,
In addition, when this device is provided, a large load is applied to the drive system, and the life of transmission elements such as gears is shortened. Therefore,
Normally, such a braking device is not provided, and therefore, it takes 0.5 seconds or more from the start of deceleration to the stop of the photosensitive drum 7. As described above, it requires 0.7 to 0.8 seconds. In the conventional image forming apparatus having such a configuration, as shown in FIG. 6, a large noise is generated from the photosensitive drum. However, by employing the above-described configuration in such a device, it is possible to effectively suppress the generation of abnormal noise. Therefore,
The image forming apparatus according to any one of claims 1 to 3, wherein the time from the start of deceleration of the image bearing drum to the stop thereof is 0.3 seconds or more when the image bearing drum is stopped. It can be applied particularly advantageously to devices. Conventionally, abnormal noise of the image forming apparatus, which is likely to generate abnormal noise, can be effectively reduced. This is a configuration corresponding to claim 4.

Incidentally, in the image forming apparatus shown in FIGS. 1 to 4, the photosensitive drum 7 is moved during the image forming operation.
Although it rotates clockwise in FIG. 2, it is configured to rotate counterclockwise by a predetermined angle after the photosensitive drum 7 stops after the end of the image forming operation. This is to prevent a foreign matter such as paper dust entering between the leading edge portion of the cleaning blade 18 and the photosensitive drum 7 from being taken out from the leading edge portion, and to prevent a defect that a toner image to be formed next becomes streaked. However, in the conventional image forming apparatus, a loud noise is generated both when the photoreceptor drum 7 starts the reverse rotation and when it stops. The generation of such abnormal noise can be suppressed without any trouble by the above-described configuration. Therefore, in each configuration corresponding to the above-described claims 1 to 4, the image bearing drum rotates in a direction opposite to the direction in which the image bearing drum rotates at the time of image formation for forming a toner image on the peripheral surface of the image bearing drum. The present invention can be applied particularly advantageously to an image forming apparatus having a mode. In the conventional image forming apparatus, abnormal noise is likely to be generated when the image bearing drum rotates in the reverse direction. However, the above-described configuration can effectively suppress such abnormal noise. This is a configuration corresponding to claim 5.

The weight 26 shown in FIG. 4 is disposed only in a part of the photosensitive drum 7 in the longitudinal direction.
The weight 26 may be arranged over the entire length of the photosensitive drum 7. However, if the weight 26 is provided over the entire length of the photosensitive drum 7, the operation of loading the weight 26 into the photosensitive drum 7 and fixing the same becomes complicated. For example, weight 2
When fixing the photosensitive drum 7 to the photosensitive drum 7 with the adhesive 27, the adhesive 27 is applied to the inner peripheral surface of the photosensitive drum 7 over its entire length, and the long weight 26 is attached to the photosensitive drum 7 Must be inserted into the inside of the device, which reduces the workability.

On the other hand, as shown in FIG. 4, if the weight is arranged only in a partial range in the longitudinal direction of the image bearing drum, the adhesive is applied to the inner peripheral surface of the image bearing drum. This can also be done easily when applying. Moreover, when the weight is inserted into the image bearing drum, this can be easily performed, and workability at the time of loading the weight can be improved. Such a configuration can be applied to any of the configurations according to claims 1 to 5 described above, and this is a configuration corresponding to claim 6.

The present invention can be widely applied to various types of image forming apparatuses other than those shown in FIGS. Also, the image bearing drum is not a photosensitive drum,
The present invention can be applied to a dielectric drum formed by laminating a dielectric layer on the outer peripheral surface of a base tube without any trouble.

[0062]

According to the image forming apparatus of the present invention, the vibration of the image bearing drum caused by the vibration of the image forming element pressed against the image bearing drum is suppressed by a simple configuration, and the image is generated from the image bearing drum. Abnormal noise can be suppressed or substantially eliminated.

According to the image forming apparatus of the second aspect,
Even when the weight of the image bearing drum is small, generation of abnormal noise can be effectively suppressed.

According to the image forming apparatus of the third aspect,
Even when the thickness of the image bearing drum is thin, generation of abnormal noise can be effectively suppressed.

According to the image forming apparatus of the fourth aspect,
The time from the start of deceleration of the image bearing drum to the stop is 0.
Even when the time is 3 seconds or longer, generation of abnormal noise can be effectively suppressed.

According to the image forming apparatus of the fifth aspect,
Even after the image bearing drum is stopped, when the drum is reversed, generation of abnormal noise can be effectively suppressed.

According to the image forming apparatus of the sixth aspect,
The size of the weight can be reduced, and workability when loading the weight on the image bearing drum can be improved.

[Brief description of the drawings]

FIG. 1 is a front sectional view showing the inside of an image forming apparatus.

FIG. 2 is a vertical sectional view of the image forming unit mounted on the image forming apparatus main body.

FIG. 3 is an external perspective view showing an image forming unit without a developer cartridge and a toner bottle.

FIG. 4 is a longitudinal sectional view of a photosensitive drum rotatably supported by a unit case.

FIG. 5 is a diagram illustrating a stick-slip phenomenon of a cleaning blade.

FIG. 6 is a graph showing the time from when the photosensitive drum starts to decelerate to when it stops, and the noise generation level at this time.

[Explanation of symbols]

 26 Weight

Continued on the front page (72) Inventor Takero Kurenuma 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd.

Claims (6)

[Claims] 1. An image forming apparatus for forming a toner image on an outer peripheral surface of a rotating image bearing drum by a plurality of image forming elements and transferring the toner image to a transfer material, wherein the plurality of image forming elements are Wherein at least one of the image bearing drums is pressed against the outer peripheral surface of the image bearing drum, wherein a weight is fixedly arranged inside the image bearing drum, the weight of the image bearing drum is W ₁ , and the weight of the weight is when set to W _2, so as to satisfy the W ₂ / W ₁ ≧ _1, the image forming apparatus characterized by setting each weight W _1, W _2. 2. The image forming apparatus according to claim 1, wherein the weight of the image bearing drum is 150 gf or less. 3. The image forming apparatus according to claim 1, wherein the thickness of the image bearing drum is 1.5 mm or less. 4. When the image bearing drum stops, the time from when the image bearing drum starts to decelerate to when it stops is set to 0.
The image forming apparatus according to claim 1, wherein the time is three seconds or more. 5. A mode for rotating an image bearing drum in a direction opposite to a direction in which the image bearing drum rotates when forming a toner image on a peripheral surface of the image bearing drum.
The image forming apparatus according to any one of claims 1 to 4. 6. The image forming apparatus according to claim 1, wherein the weight is disposed only in a part of the image bearing drum in a longitudinal direction.