JP3726869B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus such as a printer, a facsimile, or a copying machine that forms an image using electrophotographic technology. In particular, the present invention relates to a cleaning technique for the photosensitive member and the intermediate transfer member.
[0002]
[Prior art]
In general, an image forming apparatus using an electrophotographic technique is a rotationally driven photosensitive member having a photosensitive layer on an outer peripheral surface (surface), a charging unit that uniformly charges the outer peripheral surface of the photosensitive member, and the charging unit. An exposure unit that selectively exposes the outer peripheral surface charged uniformly by the above-described method to form an electrostatic latent image, and toner that is a developer may be applied to the electrostatic latent image formed by the exposure unit. The image forming apparatus includes a developing unit that forms a visual image (toner image) and a transfer device that transfers the toner image developed by the developing unit to a recording medium such as paper.
[0003]
Then, in order to transfer the toner image developed on the photosensitive member to a recording medium such as a sheet to be transferred, the toner image formed on the photosensitive member is transferred (primary transfer), and this toner image is further recorded. One having an intermediate transfer body that transfers (secondary transfer) to a medium is known.
[0004]
In such an image forming apparatus, the primary transfer and the secondary transfer are not completely performed (the toner is not 100% transferred), and some untransferred toner remains on the surface of the photoreceptor after the primary transfer. However, after the secondary transfer, some untransferred toner remains on the surface of the intermediate transfer body (this is referred to as the secondary residual toner). If these residual toners are left unattended, the image quality deteriorates. Therefore, the primary residual toner is removed by scraping the photosensitive member surface with a photosensitive blade, and the intermediate transfer member surface has an intermediate portion. In general, secondary residual toner is removed by bringing a transfer member blade into contact therewith.
[0005]
As a conventional technique, Japanese Patent Publication No. 7-19115 discloses the following technique.
[0006]
That is, in this publication, if the contact pressure of the intermediate transfer member blade to the intermediate transfer member is the same as the contact pressure of the photosensitive member blade to the photosensitive member, residual toner (secondary residual toner) on the intermediate transfer member is obtained. There is a description that the cleaning performance of the toner is significantly reduced. In order to improve this, a technique has been disclosed in which the contact pressure of the intermediate transfer member blade with respect to the intermediate transfer member is set larger than the contact pressure of the photosensitive member blade with respect to the photosensitive member.
[0007]
[Problems to be solved by the invention]
The inventor of the present application actually forms an image using an image forming apparatus having a photosensitive member and an intermediate transfer member, and in this case, the distribution of the particle size of toner existing on the photosensitive member before primary transfer, Distribution of the particle size of toner (primary residual toner) remaining on the photoreceptor after primary transfer, and particle size of toner (secondary residual toner) remaining on the intermediate transfer member after secondary transfer The distribution of was observed. Such experiments were conducted many times and the results were summarized.
[0008]
The results are shown in FIGS. 4 (a), (b) and (c).
[0009]
4A, 4B, and 4C, the horizontal axis represents the toner particle size, and the vertical axis represents the frequency (the amount of toner having the particle size). Curve A in FIG. 1A is a distribution curve of the particle diameter of toner existing on the photoreceptor before primary transfer, and curve B in FIG. 2B is toner remaining on the photoreceptor after primary transfer. The distribution curve of the particle size of (primary residual toner) and the curve C of FIG. (C) show the distribution curve of the particle size of the toner (secondary residual toner) remaining on the intermediate transfer body after the secondary transfer. Show.
[0010]
From the experimental results, the following was found.
[0011]
A: As can be seen from the distribution curve A in FIG. 1A, the distribution of the particle size of the toner existing on the photoconductor before the primary transfer is generally a normal distribution state.
[0012]
B: As can be seen from the distribution curve B in FIG. 5B, the toner (primary residual toner) remaining on the photoconductor after the primary transfer is often relatively small in particle size and has a relatively small particle size. There are few big ones. This is because toner having a large particle diameter is easily transferred, and toner having a small particle diameter is difficult to transfer.
[0013]
C: As can be seen from the distribution curve C in FIG. 5C, the toner remaining on the intermediate transfer body after the secondary transfer (secondary residual toner) is relatively small in particle size, and relatively Many have a large particle size. This is because the toner having a relatively small particle diameter has not been transferred to the intermediate transfer member so much at the time of primary transfer, and has remained as a residual toner on the photosensitive member.
[0014]
The present invention has been made on the basis of the above experimental results, and provides an image forming apparatus capable of satisfactorily removing the residual toner on the photosensitive member and the intermediate transfer member.
[0015]
[Means for Solving the Problems]
In order to achieve the above object, an image forming apparatus according to claim 1 is rotationally driven to form a toner image on a surface thereof, and is rotationally driven to primarily transfer the toner image on the photoreceptor. An intermediate transfer belt for secondary transfer of a toner image to a transfer target; a photoconductor blade that contacts the surface of the photoconductor to remove primary residual toner remaining on the surface of the photoconductor after the primary transfer; and the intermediate An intermediate transfer belt blade that is in contact with the transfer belt surface and removes secondary residual toner remaining on the surface of the intermediate transfer body after the secondary transfer;
The photosensitive member has a thin cylindrical shape having flexibility, and the intermediate transfer belt is attached to the photosensitive member by the tension of the intermediate transfer belt itself between the rollers that stretch the intermediate transfer belt. An electrode roller is formed on the driving roller of the intermediate transfer belt via an intermediate transfer belt, and a primary transfer voltage is applied to the intermediate transfer belt via the electrode roller.
The contact pressure of the photoreceptor blade with respect to the photoreceptor is set to be larger than the contact pressure of the intermediate transfer belt blade with respect to the intermediate transfer belt. At the same time, the contact pressure of the photoconductor blade against the photoconductor is such that the contact pressure when the photoconductor is stopped is smaller than the contact pressure when the photoconductor is rotating. The contact pressure of the intermediate transfer belt blade to the intermediate transfer belt is configured to decrease as the friction with the intermediate transfer belt surface increases. It is characterized by that.
[0018]
[Function and effect]
According to the first aspect of the present invention, a toner image is formed on the surface of the rotationally driven photoreceptor, and the toner image on the photoreceptor is primarily transferred to the rotationally driven intermediate transfer body. The image is further secondarily transferred to the transfer target. Further, the primary residual toner remaining on the surface of the photoconductor after the primary transfer is removed by a photoconductor blade in contact with the surface of the photoconductor, and remains on the surface of the intermediate transfer body after the secondary transfer. The secondary residual toner is removed by the intermediate transfer member blade that is in contact with the surface of the intermediate transfer member.
[0019]
The contact pressure of the photosensitive member blade with respect to the photosensitive member is set to be larger than the contact pressure of the intermediate transfer member blade with respect to the intermediate transfer member, in other words, the intermediate transfer member of the intermediate transfer member blade. Since the contact pressure with respect to the photosensitive member blade is set to be smaller than the contact pressure with respect to the photosensitive member of the photosensitive member blade, the residual toner on the photosensitive member and the intermediate transfer member is removed well.
[0020]
As described above, the toner remaining on the photoreceptor after primary transfer (primary residual toner) is often a toner having a relatively small particle diameter, but the contact pressure of the photoreceptor blade to the photoreceptor is relatively low. Since it is set to be large, the primary residual toner is removed well.
[0021]
Further, the toner remaining on the intermediate transfer body after the secondary transfer (secondary residual toner) has a relatively small particle size as described above, and a relatively large particle size. Even if the contact pressure of the blade for the intermediate transfer member with respect to the intermediate transfer member is set to be relatively small, the secondary residual toner can be satisfactorily removed.
[0022]
In addition, scratches on the surface of the intermediate transfer member due to sliding contact with the intermediate transfer member blade are also reduced.
[0023]
Further, in the case of superimposing a plurality of color toner images on the intermediate transfer member, the intermediate transfer member blade needs to be configured to be separable from the intermediate transfer member. In the apparatus, since the contact pressure of the intermediate transfer member blade with respect to the intermediate transfer member is set to be relatively small, a force for separating the intermediate transfer member blade from the intermediate transfer member is small, and therefore the separation mechanism It is also possible to reduce the size.
[0024]
That is, according to the image forming apparatus of the first aspect, the primary and secondary residual toners can be removed well without increasing the blade contact pressure more than necessary, and the intermediate transfer member is scratched. It is possible to reduce sticking, and it is possible to reduce the size of the intermediate transfer member blade separation mechanism when a plurality of color toner images are superimposed on the intermediate transfer member.
[0025]
According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the contact pressure of the photoconductor blade against the photoconductor is higher than the contact pressure when the photoconductor is rotating. Since the contact pressure when the photosensitive member is stopped is smaller, the following effects can be obtained.
[0026]
If the contact pressure of the photoconductor blade to the photoconductor is set to be relatively large as in the image forming apparatus according to claim 1, the frictional force between the photoconductor blade and the photoconductor becomes large at the start of rotation of the photoconductor. As a result, there is a risk that blade curling is likely to occur.
[0027]
On the other hand, according to the image forming apparatus of the second aspect, the contact pressure of the photoconductor blade to the photoconductor is stopped compared with the contact pressure when the photoconductor is rotating. Since the contact pressure during the rotation of the photosensitive member is smaller, the frictional force between the photosensitive member blade and the photosensitive member acting at the start of the rotation of the photosensitive member is reduced, resulting in blade curl. It becomes difficult to occur.
[0028]
In addition, after the photosensitive member starts rotating, the photosensitive member blade comes into contact with the photosensitive member with a contact pressure larger than that at the start of rotation, so that it remains on the photosensitive member after the primary transfer. The primary residual toner that is present will be removed well.
[0029]
That is, according to the image forming apparatus of the second aspect, it is possible to remove the primary residual toner satisfactorily and to prevent the occurrence of blade curl.
[0030]
According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, the contact pressure of the intermediate transfer member blade against the intermediate transfer member increases friction with the surface of the intermediate transfer member. In other words, it is configured to increase as the friction with the surface of the intermediate transfer member decreases, so that the following effects can be obtained.
[0031]
As described above, the secondary residual toner remaining on the intermediate transfer body after the secondary transfer does not contain many small particles.
[0032]
When a toner having a small particle diameter, especially a finely powdered toner, is interposed between the blade and the intermediate transfer member (or the photosensitive member), it will act as a lubricant, but on the intermediate transfer member after the secondary transfer. Since the remaining secondary residual toner does not contain many particles having a small particle size, the toner acts as a lubricant in the initial contact between the intermediate transfer member blade and the intermediate transfer member. Can not expect.
[0033]
In such a situation, the intermediate transfer member blade is brought into contact with the intermediate transfer member with a large contact force from the beginning of contact (however, a contact force smaller than the contact pressure of the photosensitive member blade with respect to the photosensitive member). As a result, the intermediate transfer member is easily damaged. Further, depending on how the intermediate transfer member blade is brought into contact with the intermediate transfer member, there is a possibility that the blade may be bent.
[0034]
On the other hand, according to the image forming apparatus of the third aspect, the intermediate transfer member is configured such that the contact pressure of the intermediate transfer member blade with the intermediate transfer member decreases as the friction with the intermediate transfer member surface increases. Since it is configured to increase as the friction with the body surface decreases, in the initial contact between the intermediate transfer body blade and the intermediate transfer body, where the toner cannot be expected to act as a lubricant, the intermediate transfer body The blade comes into contact with the intermediate transfer member with a relatively small contact pressure. Therefore, the intermediate transfer member is hardly scratched, and at the same time, it is difficult to cause blade curl.
[0035]
Further, when the contact time between the intermediate transfer member blade and the intermediate transfer member has passed to some extent, although the toner having a small particle size remaining on the intermediate transfer member after the secondary transfer is small, the toner gradually increases. It accumulates at the contact portion between the intermediate transfer member blade and the intermediate transfer member and acts as the lubricant, and the friction between the intermediate transfer member blade and the intermediate transfer member surface gradually decreases. As the friction between the intermediate transfer member blade and the surface of the intermediate transfer member gradually decreases, the intermediate transfer member blade comes into contact with the intermediate transfer member with a gradually increasing contact pressure. Will be removed.
[0036]
That is, according to the image forming apparatus of the third aspect, the secondary residual toner can be removed satisfactorily, and the occurrence of scratches on the intermediate transfer member and blade curl can be reduced.
[0037]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0038]
FIG. 1 is a schematic front view showing a main part of an embodiment of an image forming apparatus according to the present invention, FIG. 2 is an operation explanatory view of a photoreceptor blade, and (a) is an operation explanatory view of the present embodiment. FIG. 3B is an explanatory view of a comparative example, and FIG. 3 is a rear view mainly showing the periphery of the intermediate transfer member blade.
[0039]
This image forming apparatus is an apparatus that can form a full-color image using a developing device using toner of four colors of yellow (Y), cyan (C), magenta (M), and black (K).
[0040]
In FIG. 1, reference numeral 10 denotes a photoconductor, which is rotationally driven in a direction indicated by an arrow by an appropriate driving means (not shown). The photoconductor 10 has a thin cylindrical shape having flexibility, and a backup drum 11 is disposed inside the photoconductor 10. The backup drum 11 has a rotational center that is eccentric (eccentric to the right in the drawing) with respect to the rotational center of the photosensitive member 10, and is partially driven from the inside while rotating following the photosensitive member 10. (At least a contact portion with the photosensitive member blade 21 and a contact portion with the charging roller 12 described later) are supported.
[0041]
A charging roller 12 as a charging unit, a developing roller 13 (Y, M, C, K) as a developing unit, an intermediate transfer device 30, and a cleaning unit 20 are arranged around the photosensitive member 10 along the rotation direction. Has been placed.
[0042]
The charging roller 11 is in contact with the outer peripheral surface of the photoconductor 10 to uniformly charge the outer peripheral surface. On the outer peripheral surface of the uniformly charged photoconductor 10, selective exposure L corresponding to desired image information is performed by an exposure unit (not shown), and an electrostatic latent image is formed on the photoconductor 10 by this exposure L. The
[0043]
This electrostatic latent image is developed with toner applied by the developing roller 13.
[0044]
In this embodiment, a developing roller 13Y for yellow, a developing roller 13C for cyan, a developing roller 13M for magenta, and a developing roller 13K for black are provided as developing rollers. These developing rollers 13Y, 13C, 13M, and 13K can selectively come into contact with the photosensitive member 10, and when contacted, toner of any one of yellow, cyan, magenta, and black is supplied to the photosensitive member. The electrostatic latent image on the photoconductor 10 is developed by applying to the surface 10.
[0045]
The developed toner image is transferred (see primary transfer portion T1) onto an intermediate transfer belt 36 as an intermediate transfer member described later.
[0046]
After the transfer, the cleaning unit 20 scrapes the toner (primary residual toner) remaining on and adhered to the outer peripheral surface of the photoconductor 10 with a photoconductor blade (cleaning blade) 21 and the photoconductor blade 21. A receiving portion 22 that receives the dropped toner, a scooping sheet 23 that scoops off the toner to be scraped off, a screw 24 that conveys the toner in the receiving portion 22 to a waste toner bottle (not shown), and a case 25 are provided.
[0047]
The upper portion of the photoreceptor blade 21 is fixed to a blade holder 26. The blade holder 26 swings with respect to the side portions 25a and 25a (only one shown) of the case 25 by shafts 26b and 26b (only one shown) via arm portions 26a and 26a (only one shown) provided at both ends thereof. It is mounted movably. A blade urging spring (compression coil spring) 27 is provided between the case 25 and the blade holder 26, and the tip of the photoreceptor blade 21 is urged by the urging force of the blade urging spring 27 and the elastic force of the blade itself. The portion (edge) is brought into contact with the surface of the photoreceptor 10. This contact pressure is set to be larger than the contact pressure of an intermediate transfer member blade, which will be described later, with respect to the intermediate transfer member.
[0048]
Further, the contact pressure of the photoconductor blade 21 with respect to the photoconductor 10 is smaller when the photoconductor is stopped than when the photoconductor 10 is rotating. It is configured as follows.
[0049]
Specifically, the axis 26b, which is the center of oscillation of the photosensitive member blade 21, is set to be more than the normal N (see FIG. 2A) at the contact portion 10a of the photosensitive member 10 with the photosensitive member blade 21. The photoconductor 10 is disposed on the downstream side in the rotation direction.
[0050]
The operation will be described with reference to FIG.
[0051]
The blade holder 26 shown in FIG. 2 (a) has a slightly different shape from that shown in FIG. 1 in order to make the comparison with the holder 26 ′ of FIG. There is no change in the principle of action.
[0052]
Now, as shown in FIG. 5B, the shaft 26b ′ of the holder 26 ′, which is the center of swinging of the photoreceptor blade 21, is placed in the contact portion 10a of the photoreceptor 10 with the photoreceptor blade 21. It is assumed that it is arranged upstream of the normal line N with respect to the rotation direction of the photoconductor 10. Assuming that the photoconductor 10 rotates in the direction of the arrow in this state, the blade holder 26 ′ and the photoconductor blade 21 are separated from the photoconductor 10 by the frictional force acting on the photoconductor blade 21 from the photoconductor 10. It tries to turn in the direction to do.
[0053]
Therefore, in the configuration as shown in FIG. 2B, the contact pressure of the photoconductor blade 21 with respect to the photoconductor 10 is smaller than the contact pressure when the photoconductor 10 is rotating. The abutting pressure during the operation is larger.
[0054]
On the other hand, as in this embodiment (as shown in FIG. 1A), the shaft 26b, which is the swing center of the photoreceptor blade 21, is brought into contact with the photoreceptor blade 21 of the photoreceptor 10. When arranged on the downstream side of the normal line N in the portion 10a with respect to the rotation direction of the photoconductor 10, when the photoconductor 10 rotates in the direction of the arrow in the figure, the frictional force acting on the photoconductor blade 21 from the photoconductor 10 The blade holder 26 and the photoreceptor blade 21 tend to rotate in a direction approaching the photoreceptor 10.
[0055]
Therefore, the contact pressure of the photoconductor blade 21 with respect to the photoconductor 10 is smaller when the photoconductor is stopped than when the photoconductor 10 is rotating. .
[0056]
As described above, the contact pressure of the photoreceptor blade 21 with respect to the photoreceptor 10 is the contact pressure when the photoreceptor is stopped compared to the contact pressure when the photoreceptor 10 is rotating. Is configured to be small.
[0057]
The intermediate transfer device 30 includes a driving roller 31, four driven rollers 32, 33, 34, and 35, an endless intermediate transfer belt 36 as an intermediate transfer member stretched between these rollers, and a secondary transfer. A roller 37 and a cleaning means 40 are provided.
[0058]
The drive roller 31 is rotationally driven at substantially the same peripheral speed as that of the photoconductor 10 when a gear (not shown) fixed to the end of the drive roller 31 meshes with a drive gear (not shown) of the photoconductor 10, and therefore is intermediate. The transfer belt 36 is circulated and driven in the direction indicated by the arrow at substantially the same peripheral speed as that of the photoreceptor 10.
[0059]
The driven roller 35 is disposed at a position where the intermediate transfer belt 36 is pressed against the photoconductor 10 by its own tension with the drive roller 31 when the intermediate transfer belt 36 is driven to circulate. A primary transfer portion T1 is formed at the pressure contact portion between the intermediate transfer belt 36 and the intermediate transfer belt 36.
[0060]
An electrode roller (not shown) is disposed on the drive roller 31 via an intermediate transfer belt 36, and a primary transfer voltage is applied to the intermediate transfer belt 36 via the electrode roller.
[0061]
The driven roller 32 is a tension roller, and urges the intermediate transfer belt 36 in the tension direction by urging means (not shown).
[0062]
The driven roller 33 is a backup roller that forms the secondary transfer portion T2. A secondary transfer roller 37 is disposed opposite to the backup roller 33 via an intermediate transfer belt 36. The secondary transfer roller 37 can be brought into and out of contact with the intermediate transfer belt 36 by a contact and separation mechanism (not shown). A secondary transfer voltage is applied to the secondary transfer roller 37.
[0063]
The driven roller 34 is a backup roller for the cleaning means 40.
[0064]
As shown in FIG. 3, the cleaning unit 40 also has an intermediate transfer member blade (cleaning blade) 41 that contacts the intermediate transfer belt 36 and scrapes off the toner remaining on the outer peripheral surface thereof, and the intermediate transfer belt 41. A receiving portion 42 that receives the toner scraped off by the body blade 41, a screw 43 that conveys the toner dropped on the receiving portion 42 toward a waste toner bottle (not shown), and a case 44 are provided.
[0065]
The intermediate transfer member blade 41 is fixed to the case 44 via an L-shaped blade holder 46 in the front view.
[0066]
The case 44 is swingably attached to a side plate of a frame (not shown) by a shaft 43a of the screw 43 or a shaft concentric with the shaft 43a. Pins 44a and 44a (only one is shown) are provided on the upper ends of both ends of the case 44. These pins 44a and 44a and spring hooks 45 and 45 (only one shown) provided on a side plate of a frame (not shown). Between them, tension springs 47 (only one is shown) are stretched. Due to the urging force of the spring 47, the case 44 is constantly urged in the direction in which the intermediate transfer body blade 41 is pressed against the intermediate transfer belt 36 (counterclockwise in FIG. 3). The pressure contact with the intermediate transfer belt 36 is regulated by a contact / separation mechanism (separation mechanism).
[0067]
The contact / separation mechanism includes an eccentric cam 48 that is rotatably provided with respect to a frame (not shown), a contact portion 44b of a case 44 that contacts the cam 48, and the spring 47.
[0068]
The cam 48 is rotationally driven by a driving means (not shown) provided on the image forming apparatus main body side. As shown in FIG. 3, the small diameter portion 48 a is in contact with the contact portion 44 b of the case 44. When facing each other without abutting, the case 44 is rotated counterclockwise by the biasing force of the spring 47 around the shaft (the shaft 43a of the screw 43 or a concentric shaft), and the biasing force of the spring 47 and the blade The intermediate transfer body blade 41 is pressed against the intermediate transfer belt 36 by its own elastic force as shown in the figure.
[0069]
Further, when the cam 48 rotates about 120 ° in the clockwise direction from the state shown in FIG. 3 and the large diameter portion 48b comes into contact with the contact portion 44b of the case 44, the case 44 is attached with the spring 47 around its axis. The intermediate transfer member blade 41 is separated from the intermediate transfer belt 36 by rotating clockwise against the force (the separated state is not shown).
[0070]
The contact pressure when the intermediate transfer blade 41 is pressed against the intermediate transfer belt 36 by the biasing force of the spring 47 and the elastic force of the blade itself is as shown in FIG. It is set smaller than the contact pressure with respect to the photoconductor 10.
[0071]
Further, the contact pressure of the intermediate transfer body blade 41 against the intermediate transfer belt 36 is configured to decrease as the friction with the surface of the intermediate transfer belt 36 increases.
[0072]
Specifically, a shaft 43a (or a concentric shaft) that is the center of oscillation of the intermediate transfer member blade 41 is a normal line at a contact portion 36a of the intermediate transfer belt 36 with the intermediate transfer member blade 41. It is arranged upstream of N ′ with respect to the rotation direction (circulation direction) of the intermediate transfer belt 36.
[0073]
With this configuration, as described above with reference to FIG. 2B, when the intermediate transfer belt 36 rotates in the direction of the arrow shown in FIG. 2, the friction acting on the intermediate transfer member blade 41 from the intermediate transfer belt 36 is achieved. Due to the force, the blade holder 46 and the intermediate transfer member blade 41 try to rotate in a direction away from the intermediate transfer belt 36.
[0074]
Therefore, the contact pressure of the intermediate transfer body blade 41 against the intermediate transfer belt 36 decreases as the friction with the surface of the intermediate transfer belt 36 increases.
[0075]
As described above, the contact pressure of the intermediate transfer body blade 41 against the intermediate transfer belt 36 is configured to decrease as the friction with the surface of the intermediate transfer belt 36 increases.
[0076]
In the process in which the intermediate transfer belt 36 is circulated, the toner image on the photoconductor 10 is transferred onto the intermediate transfer belt 36 and transferred onto the intermediate transfer belt 36 in the primary transfer portion T1 (see FIG. 1). The image is transferred to the recording medium S such as a sheet to be transferred supplied between the image and the secondary transfer roller 37 in the secondary transfer portion T2 (see FIG. 1). The recording medium S is fed from a paper feeder (not shown) and is supplied to the secondary transfer unit T2 at a predetermined timing.
[0077]
The operation of the entire image forming apparatus as described above is as follows.
[0078]
(I) When a print command signal (image formation signal) from a host computer (not shown) (personal computer or the like) is input to the control unit of the image forming apparatus, the intermediate transfer belt 36 is stretched by the operation of the tension roller 32. Thus, the photosensitive member 10, the developing roller 13, and the intermediate transfer belt 36 are rotationally driven by a driving unit (not shown).
[0079]
(Ii) The outer peripheral surface of the photoconductor 10 is uniformly charged by the charging roller 11.
[0080]
(Iii) On the outer peripheral surface of the uniformly charged photoreceptor 10, selective exposure L corresponding to image information of the first color (for example, yellow) is performed by an exposure unit (not shown), and an electrostatic latent image for yellow is formed. It is formed.
[0081]
(Iv) Only the developing roller 13Y for the first color (for example, yellow) is in contact with the photosensitive member 10, whereby the electrostatic latent image is developed, and the first color (for example, yellow) toner image is transferred to the photosensitive member. 10 is formed.
[0082]
(V) A primary transfer voltage having a polarity opposite to the charging polarity of the toner is applied to the intermediate transfer belt 36, and the toner image formed on the photoreceptor 10 is transferred to the primary transfer portion T1, that is, the photoreceptor 10 and the intermediate transfer belt. The toner image is transferred onto the intermediate transfer belt 36 at a pressure contact portion T1 with the roller 36. At this time, the secondary transfer roller 37 and the cleaning unit 40 (therefore, the intermediate transfer member blade 41) are separated from the intermediate transfer belt.
[0083]
(Vi) After the toner (primary residual toner) remaining on the photoconductor 10 is removed by the photoconductor blade 21, the photoconductor 10 is neutralized by a neutralizing light from a neutralizing unit (not shown).
[0084]
(Vii) The operations (ii) to (vi) are repeated as necessary. That is, the second color, the third color, and the fourth color are repeated according to the contents of the print command signal, and the toner images according to the contents of the print command signal are superimposed on the intermediate transfer belt 36 to be intermediate. It is formed on the transfer belt 36.
[0085]
(Viii) The recording medium S is supplied at a predetermined timing, immediately before or after the leading end of the recording medium S reaches the secondary transfer portion T2 (in short, on the intermediate transfer belt 36 at a desired position on the recording medium S). The secondary transfer roller 37 is pressed against the intermediate transfer belt 36 and a secondary transfer voltage is applied to the toner image (basically a full color image) on the intermediate transfer belt 36 (at the timing when the toner image is transferred). Transferred onto the recording medium S. Further, the operation of the cam 48 causes the intermediate transfer member blade 41 to contact the intermediate transfer belt 36, and the toner (secondary residual toner) remaining on the intermediate transfer belt 36 after the secondary transfer is removed.
[0086]
(Ix) When the recording medium S passes through a fixing device (not shown), the toner image is fixed on the recording medium S, and then the recording medium S is discharged out of the apparatus.
[0087]
(X) After the above operations (i) to (ix) have been completed, if the image forming signal is not input for a predetermined time or the apparatus is turned off, the tension roller is operated to stretch the intermediate transfer belt 36. Is released.
[0088]
According to the image forming apparatus as described above, the following effects can be obtained.
[0089]
(A) A toner image is formed on the surface of the photoconductor 10 that is rotationally driven, and the toner image on the photoconductor 10 is primarily transferred (T1) to the intermediate transfer body 36 that is rotationally driven. Secondary transfer (T2) is performed on the transfer target S. The primary residual toner remaining on the surface of the photoconductor 10 after the primary transfer (T1) is removed by the photoconductor blade 21 in contact with the surface of the photoconductor 10, and the intermediate transfer is performed after the secondary transfer (T2). The secondary residual toner remaining on the surface of the body 36 is removed by the intermediate transfer body blade 41 in contact with the surface of the intermediate transfer body 36.
[0090]
The contact pressure of the photoreceptor blade 21 with respect to the photoreceptor 10 is set larger than the contact pressure of the intermediate transfer body blade 41 with respect to the intermediate transfer body 36. In other words, the intermediate transfer body blade 41 is set. Since the contact pressure with respect to the intermediate transfer body 36 is set to be smaller than the contact pressure with respect to the photoreceptor 10 of the photoreceptor blade 21, the residual toner on the photoreceptor 10 and the intermediate transfer body 36 is satisfactorily removed. It will be.
[0091]
As described above, the toner (primary residual toner) remaining on the photoconductor 10 after the primary transfer (T1) has a relatively small particle size. Since the contact pressure is set to be relatively large, the primary residual toner is removed well.
[0092]
Further, as described above, the toner (secondary residual toner) remaining on the intermediate transfer member 36 after the secondary transfer (T2) has a relatively small particle size and a relatively large particle size. Therefore, even if the contact pressure of the intermediate transfer body blade 41 with respect to the intermediate transfer body 36 is set to be relatively small, the secondary residual toner can be satisfactorily removed.
[0093]
In addition, scratches on the surface of the intermediate transfer member 36 due to sliding contact with the intermediate transfer member blade 41 are also reduced.
[0094]
Further, when a plurality of color toner images are superimposed on the intermediate transfer member 36 as in this embodiment, the intermediate transfer member blade 41 needs to be configured to be separable from the intermediate transfer member 36. However, in the image forming apparatus of this embodiment, since the contact pressure of the intermediate transfer body blade 41 against the intermediate transfer body 36 is set to be relatively small, the intermediate transfer body blade 41 is removed from the intermediate transfer body 36. The force for separating (in this embodiment, the driving force of the cam 48 for rotating the case 44 in the clockwise direction in FIG. 3 against the urging force of the springs 47, 47) is small. Also, it is possible to reduce the size of the separation mechanism (for example, the size of the drive motor).
[0095]
That is, according to the image forming apparatus of this embodiment, the primary and secondary residual toners can be removed well without increasing the contact pressure of the blades 21 and 41 (particularly, the intermediate transfer member blade 41) more than necessary. In addition, the scratch on the intermediate transfer member 36 can be reduced, and the separation mechanism of the intermediate transfer member blade 41 when the toner images of a plurality of colors are superimposed on the intermediate transfer member 36 can be reduced in size. Is possible.
[0096]
(B) The contact pressure of the photoconductor blade 21 with respect to the photoconductor 10 is higher when the photoconductor 10 is stopped than when the photoconductor 10 is rotating. Since it is configured to be small, the following effects can be obtained.
[0097]
As in this embodiment, when the contact pressure of the photoconductor blade 21 with respect to the photoconductor 10 is set to be relatively large, the frictional force between the photoconductor blade 21 and the photoconductor 10 becomes large at the start of rotation of the photoconductor 10. As a result, there is a risk that blade curling is likely to occur.
[0098]
On the other hand, according to the image forming apparatus of this embodiment, the contact pressure of the photoreceptor blade 21 with respect to the photoreceptor 10 is higher than the contact pressure when the photoreceptor 10 is rotating. Since the contact pressure is smaller when the photosensitive member 10 is stopped, the frictional force between the photosensitive member blade 21 and the photosensitive member 10 acting at the start of rotation of the photosensitive member 10 is reduced. As a result, blade curling is less likely to occur.
[0099]
Further, after the photosensitive member 10 starts to rotate, the photosensitive member blade 21 comes into contact with the photosensitive member 10 with a contact pressure larger than that at the time of starting rotation, so that the photosensitive member after the primary transfer (T1). The primary residual toner remaining on the body 10 is favorably removed.
[0100]
That is, according to the image forming apparatus of this embodiment, it is possible to remove the primary residual toner satisfactorily and to prevent the occurrence of blade curl.
[0101]
(C) In other words, the contact pressure between the intermediate transfer member blade 41 and the intermediate transfer member 36 decreases as the friction with the intermediate transfer member 36 increases. In other words, the friction with the intermediate transfer member 36 surface. Since it is configured to become larger as the value becomes smaller, the following effects can be obtained.
[0102]
As described above, the secondary residual toner remaining on the intermediate transfer body 36 after the secondary transfer (T2) does not include many small particles.
[0103]
When a toner having a small particle diameter, particularly a finely powdered toner, is interposed between the blade and the intermediate transfer member (or the photoreceptor), it acts as a lubricant, but the intermediate transfer after the secondary transfer (T2). The secondary residual toner remaining on the body 36 does not contain many particles having a small particle diameter, so that the action of the toner as a lubricant acts as the intermediate transfer body blade 41 and the intermediate transfer body 36. It cannot be expected in the initial stage of contact.
[0104]
In such a situation, the intermediate transfer member blade 41 is contacted with the intermediate transfer member 36 by a large contact force from the beginning (however, a contact force smaller than the contact pressure of the photosensitive member blade 21 with respect to the photosensitive member 10). If the contact is made, the intermediate transfer member 36 is easily damaged. Further, depending on how the intermediate transfer member blade 41 is brought into contact with the intermediate transfer member, there is a possibility that the blade may be bent.
[0105]
On the other hand, according to the image forming apparatus of this embodiment, the contact pressure of the intermediate transfer member blade 41 against the intermediate transfer member 36 is reduced as the friction with the surface of the intermediate transfer member 36 increases. Since it is configured to increase as the friction with the surface of the intermediate transfer member 36 becomes smaller, at the initial contact between the intermediate transfer member blade 41 and the intermediate transfer member 36 where the above-described action of the toner as a lubricant cannot be expected. The intermediate transfer body blade 41 comes into contact with the intermediate transfer body 36 with a relatively small contact pressure. Therefore, the intermediate transfer member 36 is hardly scratched, and at the same time, it is difficult to cause blade curl.
[0106]
In addition, when a certain amount of contact time between the intermediate transfer member blade 41 and the intermediate transfer member 36 elapses, there is little toner having a small particle size remaining on the intermediate transfer member 36 after the secondary transfer (T2). No, the toner gradually accumulates at the contact portion between the intermediate transfer member blade 41 and the intermediate transfer member 36 and acts as the lubricant, and the friction between the intermediate transfer member blade 41 and the surface of the intermediate transfer member 36 also occurs. It will gradually become smaller. As the friction between the intermediate transfer member blade 41 and the surface of the intermediate transfer member 36 gradually decreases, the intermediate transfer member blade 41 gradually contacts the intermediate transfer member 36 with a large contact pressure. Residual toner will be removed satisfactorily.
[0107]
That is, according to the image forming apparatus of this embodiment, it is possible to remove the secondary residual toner satisfactorily, and to reduce the occurrence of scratches on the intermediate transfer member 36 and blade curl.
[0108]
Although one embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment, and can be appropriately modified within the scope of the gist of the present invention.
[0110]
【The invention's effect】
The image forming apparatus according to any one of claims 1 to 3 can satisfactorily remove the primary and secondary residual toners without increasing the contact pressure of the blade more than necessary, and can damage the intermediate transfer member. It is possible to reduce sticking, and it is possible to reduce the size of the intermediate transfer member blade separation mechanism when a plurality of color toner images are superimposed on the intermediate transfer member.
[0111]
further,
According to the image forming apparatus of the second aspect, it is possible to satisfactorily remove the primary residual toner and to prevent occurrence of blade curl.
[0112]
According to the image forming apparatus of the third aspect, it is possible to satisfactorily remove the secondary residual toner, and it is possible to reduce the occurrence of scratches on the intermediate transfer member and blade curl.
[0113]
[Brief description of the drawings]
FIG. 1 is a schematic front view showing a main part of an embodiment of an image forming apparatus according to the present invention.
FIGS. 2A and 2B are operation explanatory views of the photosensitive member blade, in which FIG. 2A is an operation explanatory view of the present embodiment, and FIG.
FIG. 3 is a rear view mainly showing the periphery of an intermediate transfer member blade;
4A, 4B, and 4C are diagrams showing experimental results, respectively.
[Explanation of symbols]
10 photoconductor
21 Blade for photoconductor
T1 Primary transfer part
36 Intermediate transfer belt (intermediate transfer member)
T2 Secondary transfer section
S Recording material (transfer target)
41 Blade for intermediate transfer member

Claims (1)

A photosensitive member that is rotationally driven to form a toner image on the surface thereof, an intermediate transfer belt that is rotationally driven to primarily transfer the toner image on the photosensitive member, and secondarily transfers the toner image to a transfer target; and the photosensitive member A photosensitive blade for removing primary residual toner remaining on the surface of the photoreceptor after the primary transfer by contacting the surface of the body, and an intermediate transfer body surface after the secondary transfer by contacting the intermediate transfer belt surface An intermediate transfer belt blade for removing secondary residual toner remaining in
The photosensitive member has a thin cylindrical shape having flexibility, and the intermediate transfer belt is attached to the photosensitive member by the tension of the intermediate transfer belt itself between the rollers that stretch the intermediate transfer belt. An electrode roller is formed on the driving roller of the intermediate transfer belt via an intermediate transfer belt, and a primary transfer voltage is applied to the intermediate transfer belt via the electrode roller.
Wherein with contact pressure against the photoconductor photosensitive member blade is set to be larger than the contact pressure to the intermediate transfer belt of the intermediate transfer belt blade contact pressure against the photosensitive member of the photosensitive-body blade, the photosensitive The contact pressure when the photosensitive member is stopped is smaller than the contact pressure when the member is rotating, and the contact force of the intermediate transfer belt blade against the intermediate transfer belt is reduced. An image forming apparatus , wherein the contact pressure is configured to decrease as the friction with the surface of the intermediate transfer belt increases .

Images