JP2012177866A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the occurrence of a problem resulting from excess or insufficiency in applied lubricant, by appropriately maintaining an amount of lubricant on a charged photoreceptor even in a case where an amount of applied lublicant changes.SOLUTION: A power source device 123 for applying AC voltage to the charging roller 121 of an image forming unit 100 and AC peak-to-peak voltage alteration means 124 for altering an AC peak-to-peak voltage (Vp-p) applied by this power source device 123 are arranged. The AC peak-to-peak voltage alteration means 124 increases the AC peak-to-peak voltage (Vp-p) as the image area rate of a photoreceptor drum 110 decreases, and decreases the AC peak-to-peak voltage (Vp-p) as the image area rate increases.

Description

  The present invention relates to an image forming apparatus, and more particularly to an electrophotographic image forming apparatus equipped with a lubricant application mechanism.

  In recent years, quadruple tandem image forming apparatuses have become mainstream among electrophotographic image forming apparatuses as color copying machines, printers, high speed, and high image quality have progressed. In addition, with the growing awareness of the environment, there is an increasing demand for recycling, high reliability, and long life. In addition, due to consideration for the office environment, awareness of ozone generation and dust generation is increasing.

  Therefore, many image forming apparatuses as described above employ a charging roller that generates a small amount of ozone as the charging member. Furthermore, in order to extend the life of the apparatus, a charging roller that is arranged to face the photoconductor with a minute gap (gap) may be used. Also, due to the demand for higher image quality, there are an increasing number of cases where an AC voltage is applied to the charging roller so that the charging current flows sufficiently and the charging potential is stabilized.

  However, when an AC voltage is applied to the charging roller, the surface of the photoreceptor may be destroyed by the charging current. Therefore, in order to protect the surface of the photoconductor, a lubricant application device that applies a lubricant to the photoconductor may be employed. Further, when a lubricant is applied to the photoconductor, the coefficient of friction on the surface of the photoconductor can be lowered, the behavior of the cleaning blade edge can be stabilized, and the cleaning performance can be expected to be improved.

  As a lubricant application device, in general, a rod-shaped solid lubricant is pressed against a brush roller disposed upstream of the photosensitive member rotation direction of the photosensitive member cleaning member with a spring or the like, and the lubricant scraped by the brush roller is removed from the surface of the photosensitive member. A structure in which the film is applied to the film and further thinned with a photoconductor cleaning blade is employed.

  FIG. 12 is a cross-sectional view showing an image forming unit of a conventional image forming apparatus. The image forming unit 300 includes a photosensitive drum 310, a charging device 320, a lubricant applying device 330, a developing device 340, and a cleaning blade 350. A latent image created on the photosensitive drum 310 is developed by the developing device 340. The toner image is developed to create a toner image, and this toner image is transferred to the intermediate transfer belt 360. The charging device 320 is configured by disposing a charging roller 321 for applying an AC voltage spaced apart from the photosensitive drum 310 by a predetermined dimension (gap) in order to improve image quality and increase the life. The charging device 320 is provided with a cleaning roller 322 for cleaning the charging roller 321.

  The lubricant application device 330 is provided to prevent the surface of the photosensitive drum 310 from being damaged by an alternating current. The lubricant application device 330 presses the solid lubricant 332 against the brush roller 331 disposed on the upstream side of the cleaning blade 350 with respect to the rotation direction of the photosensitive drum 310 by the compression spring 333, and the lubricant 332 is brushed. The material is scraped off by a roller 331, and the lubricant thus shaved is applied to the photosensitive drum 310. The cleaning blade 350 removes residual toner from the photosensitive drum 310 and thins the applied lubricant. In the figure, reference numeral 351 denotes a waste toner conveying member that conveys waste toner.

  In such an image forming unit 300, on the downstream side of the charging device 320, the light beam LB for forming a latent image is incident on the photosensitive drum 310 from an exposure device (not shown), and the developing device 340 disposed downstream is exposed to light. The latent image formed on the body drum 310 is developed with toner and transferred to the intermediate transfer belt 360.

  In the conventional lubricant application device, the contact area between the photoreceptor surface and the lubricant application member varies depending on the size of the transfer residual image area on the photoreceptor drum 310, so that the amount of lubricant applied to the photoreceptor is adjusted. It varies depending on the image area ratio of the image being imaged. Here, the image area ratio refers to the ratio of the total image forming area to the image area where the toner is actually placed.

  FIG. 13 is a cross-sectional view showing a state where an appropriate amount of lubricant is applied in a conventional image forming unit, FIG. 14 is a cross-sectional view showing a state where the image area ratio is small and the lubricant is excessive, and FIG. FIG. 16 is a graph showing the relationship between the image area ratio and the amount of applied lubricant.

  That is, when the image area ratio is within the target setting range of the lubricant application amount, the residual toner T remains on the photosensitive drum 310 appropriately, and as shown in FIG. An appropriate amount is applied to the surface of the photosensitive drum 310 by the application member, that is, the brush roller 331, and is thinned by the cleaning blade 350. For this reason, the excessive lubricant L does not adhere to the charging roller 321, and the charging roller 321 operates properly. In FIG. 13, the residual toner T is indicated by a small black spot, and the lubricant L is indicated by a large black spot (the same applies hereinafter).

  When the image area ratio is small, particularly when non-image formation is performed, as shown in FIG. 14, the contact area between the surface of the photosensitive drum 310 and the lubricant application member, that is, the brush roller 331 increases. In such a case, the amount of the lubricant L applied by the brush roller 331 increases, and the lubricant L is in an excessively applied state. Then, the excessive lubrication agent L promotes the contamination of the charging roller 321. When this contamination accumulates, a vertical streak or the like due to a charging failure will eventually occur.

  Conversely, when the image area ratio is large, as shown in FIG. 15, the contact area between the surface of the photosensitive drum 310 and the brush roller 331 decreases, and the amount of lubricant L applied decreases. As described above, when the lubricant is insufficiently applied, the protective action of the photosensitive drum 310 becomes insufficient, the surface of the photosensitive member is destroyed due to the charging alternating current, and the problem of the photosensitive member filming occurs. The surface lubricity becomes poor, the behavior of the cleaning blade edge becomes unstable, and the problem of poor cleaning occurs.

  As shown in FIG. 16, the application amount of the normal lubricant is an appropriate amount when an image having an image area ratio of about 3% to 10%, which is a normal image for office use, is formed by the pressure of the compression spring 333. It is set. On the other hand, when the contact area between the lubricant application member, that is, the brush roller and the surface of the photoreceptor is large (that is, the image area ratio is small), the amount of lubricant applied increases and the contamination of the charging roller is promoted. On the other hand, if the contact area between the lubricant application member, i.e., the brush roller and the surface of the photoreceptor is small (that is, the image area ratio is large), the application of the lubricant is insufficient, and the photoreceptor filming due to insufficient photoreceptor protection action occurs.

  As an image forming apparatus including a lubricant application device, Patent Document 1 includes an image carrier and a charging unit that can be uniformly charged in a state of being in contact with or close to the image carrier, After the electrostatic latent image formed on the uniformly charged image carrier is subjected to visible image processing by a developing device, the visible toner image is transferred to the transfer target, and then the surface of the image carrier is transferred. Means for removing residual toner by a cleaning device, and means for supplying a lubricant to the image carrier, wherein the charging means counts the number of times of image formation or the rotation time of the image carrier. There is described an image forming apparatus having a counter and connected to a control means for controlling a ratio of an alternating voltage value applied during image formation and non-image formation according to the counter value.

  Similarly, in Patent Document 2, a charging unit that uniformly charges the surface of the image carrier and a surface of the image carrier that is uniformly charged by the charging unit are scanned and exposed based on image information to form an electrostatic latent image. Writing means, developing means for visualizing the electrostatic latent image formed by the writing means to form a toner image, transfer means for transferring the toner image formed by the developing means to the transfer target P, and transfer There is described an image forming apparatus comprising a lubricant supplying means for supplying a lubricant to the surface of the image carrier after transferring the toner image carried by the means in accordance with the amount of scumming toner on the surface of the image carrier.

  However, even in the conventional image forming apparatus, as described above, the contact area between the photosensitive member surface and the lubricant application member changes due to the fluctuation of the image area ratio, and charging due to charging roller contamination due to excessive lubricant application amount. There are problems such as the occurrence of vertical streaks due to defects, and photoreceptor filming and cleaning defects due to insufficient protection of the photoreceptor due to insufficient lubricant application amount.

  Therefore, the present invention can maintain the proper amount of lubricant on the photoreceptor after charging even if the amount of lubricant applied varies, and prevent occurrence of problems due to excessive or insufficient application of lubricant. An object is to provide a forming apparatus.

  The invention according to claim 1 that solves the above-described problems includes a charging member that charges the photosensitive member, a power supply device that applies an AC voltage to the charging member, and a lubricant application device that applies a lubricant to the photosensitive member. In the image forming apparatus, the AC peak-to-peak voltage that changes the AC peak-to-peak voltage (Vp-p) applied to the charging member by controlling the power supply device in accordance with the image area ratio of the toner image formed on the photoreceptor. An image forming apparatus including a changing unit.

  Similarly, according to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the alternating peak-to-peak voltage changing unit applies the alternating peak-to-peak voltage (Vp−) applied to the charging member as the image area ratio decreases. p) is increased.

  Similarly, according to a third aspect of the present invention, in the image forming apparatus according to the first aspect, the AC peak-to-peak voltage changing unit is configured to apply an AC peak-to-peak voltage (Vp-p) applied to the charging member as the image area ratio increases. ) Is made small.

  Similarly, according to a fourth aspect of the present invention, in the image forming apparatus according to any one of the first to third aspects, the lubricant application device scrapes off the rod-shaped solid lubricant with a brush roller and applies the solid lubricant to the surface of the photoreceptor. A structure is provided.

  Similarly, the invention according to claim 5 is the image forming apparatus according to claim 4, wherein the lubricant applying device is disposed upstream of the photoconductor cleaning device with respect to the rotation direction of the photoconductor. .

  Similarly, the invention of claim 6 is the image forming apparatus according to claim 4, wherein the lubricant applying device is mounted on the downstream side of the photoconductor cleaning device with respect to the rotation direction of the photoconductor.

  Similarly, the invention according to claim 7 is the image forming apparatus according to any one of claims 1 to 6, wherein the charging member includes a contact charging roller.

  Similarly, according to an eighth aspect of the present invention, in the image forming apparatus according to any one of the first to sixth aspects, the charging member includes a charging roller disposed opposite to the photosensitive member with a minute gap. And

  Similarly, the invention of claim 9 is the image forming apparatus according to any one of claims 1 to 8, wherein the lubricant contains at least a fatty acid metal salt (A) and an inorganic lubricant (B). Features.

  Similarly, the invention of claim 10 is the image forming apparatus according to claim 9, wherein the fatty acid metal salt (A) is zinc stearate and the inorganic lubricant (B) is boron nitride. And

  Similarly, the invention according to claim 11 is the image forming apparatus according to any one of claims 1 to 10, wherein the image forming unit includes the photoconductor, and at least of a charging device, a developing device, and a photoconductor cleaning device. It is a process cartridge including one.

  According to the present invention, the amount of lubricant remaining on the photoreceptor after passing through the charging member is set to an appropriate amount, and the charging roller becomes dirty due to excessive application of the lubricant, and the filming of the photoreceptor due to insufficient application of the lubricant, poor cleaning. Can be prevented.

1 is a sectional view conceptually showing an internal mechanism of an image forming apparatus according to Embodiment 1. FIG. It is sectional drawing which similarly shows an image forming apparatus. Similarly, it is a cross-sectional view showing a main part of the image forming apparatus in a state where the image area ratio is several percent. FIG. 6 is a cross-sectional view showing a main part of the image forming apparatus in a state where there is no transfer residual toner. It is sectional drawing which shows the principal part of an image creation apparatus in the state where an image area rate is large similarly. It is a graph which similarly shows the change state of the application amount of the lubricant with respect to the image area ratio and the AC peak-to-peak voltage value of the AC peak-to-peak voltage changing means. It is a graph which similarly shows the other change state of the application quantity of the lubrication agent with respect to the image area rate of an alternating peak voltage change means, and the alternating peak voltage value of an alternating peak voltage change means. 6 is a cross-sectional view illustrating an image forming apparatus according to Embodiment 2. FIG. It is sectional drawing which shows the principal part of an image forming apparatus in the state where the cleaning blade was similarly worn. It is sectional drawing which shows the principal part of an image forming apparatus in the state where the cleaning blade was similarly worn. FIG. 6 is a graph showing a change state of the amount of applied lubricant and the AC peak-to-peak voltage value of the AC peak-to-peak voltage changing means with respect to the image area ratio when the cleaning blade is worn. It is sectional drawing which shows the conventional image forming unit. Similarly, it is a cross-sectional view showing a state in which an appropriate amount of lubricant is applied in the image forming unit. Similarly, it is a cross-sectional view showing a state where the image area ratio is small and the lubricant is excessive. Similarly, it is a cross-sectional view showing a state where the image area ratio is large and the lubricant is insufficient. It is a graph which similarly shows the relationship between an image area ratio and a lubricant application amount.

  An image forming apparatus according to an embodiment includes: a charging member that charges a photosensitive member; a power supply device that applies an AC voltage to the charging member; and a lubricant application device that applies a lubricant to the photosensitive member. And an AC peak-to-peak voltage changing means for changing the AC peak-to-peak voltage (Vp-p) applied to the charging member by controlling the power supply device, and applying to the charging member as the image area ratio decreases. The AC peak voltage (Vp-p) is increased, and the AC peak voltage (Vp-p) applied to the charging member is decreased as the image area ratio increases. Thereby, the image forming apparatus sets the amount of lubricant remaining on the photosensitive member after passing through the charging member to an appropriate amount, contamination of the charging roller due to excessive application of lubricant, filming of the photosensitive member due to insufficient application of lubricant, It is possible to prevent the occurrence of defective cleaning.

  Hereinafter, an image forming apparatus according to an embodiment of the present invention (hereinafter simply referred to as an embodiment) will be described. Several examples will be described below, but the present invention is not limited to these examples, and many improvements, modifications, variations, substitutions and application examples are possible without departing from the true spirit and scope of the present invention. It will be possible for those skilled in the art to conceive.

<Example 1>
A four-tandem color copying apparatus will be described as an example of the image forming apparatus according to the first embodiment. FIG. 1 is a sectional view conceptually showing an internal mechanism of the image forming apparatus according to the first embodiment. As shown in FIG. 1, the image forming apparatus 1 forms a color image using toner of each color of yellow (Y), magenta (M), cyan (C), and black (K). The image forming apparatus 1 has a configuration in which a sheet feeding unit 10 in which sheet feeding cassettes 11 and 12 that store sheets as recording media are disposed is provided below, and an image forming unit 20 and a transfer unit 30 are disposed above the sheet feeding unit 10. .

  The image forming unit 20 includes photoconductor drums 110Y, 110M, 110C, and 110K (hereinafter referred to as the photoconductor drum 110 unless otherwise specified), which are image carriers. The image forming units 100Y, 100M, 100C, and 100K are provided. The transfer unit 30 includes an intermediate transfer belt 34 as an intermediate transfer member formed of a flexible endless belt wound around a plurality of rollers 31, 32, and 33, and photosensitive drums 110Y, 110M, 110C, and 110K. An optical writing unit 40 which is a latent image forming apparatus for forming a latent image, a fixing device 50 for fixing a toner image on a sheet, and the like are disposed. Further, a transport path 60 for transporting paper is formed between the paper feed cassettes 11 and 12 and the fixing device 50.

  Further, the intermediate transfer belt 34 is provided with a secondary transfer roller 35 serving as a secondary transfer device facing a conveyance path at a portion facing the roller 32, and a belt for cleaning the belt surface at a portion facing the roller 31. A cleaning device 37 is installed.

  The image forming unit 20 is disposed so as to face the lower belt running side of the intermediate transfer belt 34 disposed between the rollers 31 and 32 of the intermediate transfer belt 34. In each of the image forming units 100Y, 100M, 100C, and 100K, the photosensitive drums 110Y, 110M, 110C, and 110K are disposed so as to be in contact with the intermediate transfer belt 34. Transfer rollers 36Y, 36M, 36C, and 36K as transfer devices that perform primary transfer are provided inside the intermediate transfer belt 34 at positions where the photosensitive drums 110Y, 110M, 110C, and 110K are in contact with the intermediate transfer belt 34, respectively. It is. In the figure, reference numerals 70Y, 70M, 70C, and 70K denote toner bottles for storing replenishment toner.

  In the image forming apparatus 1 according to the first embodiment, the photosensitive drums 110Y, 110M, 110C, and 110K of the image forming units 100Y, 100M, 100C, and 100K are exposed in a predetermined pattern by the optical writing unit 40, and the photosensitive drums 110Y, 110Y, and 110K are exposed. In response to 110M, 110C, and 110K being developed by the developing unit, the transfer paper conveyed from the paper feed cassettes 11 and 12 is conveyed to the image forming unit 20, and the photoconductor drums 110Y and 110M are transferred by the transfer unit 30. , 110C, and 110K, the toner is sequentially transferred, fixed by the fixing device 50, and discharged.

  Next, the image forming unit 100 will be described. FIG. 2 is a cross-sectional view illustrating the image forming unit according to the embodiment. The image forming units 100Y, 100M, 100C, and 100K have the same structure as well as different toner colors. Therefore, the structure of one image forming unit 100 will be described without adding a suffix to the reference numerals. In the image forming unit 100, a charging unit 120, a developing device 130, a lubricant applying device 140, and a cleaning device 150 are arranged around the photosensitive drum 110.

  The charging unit 120 includes a charging roller 121 disposed with a gap (gap) in the photosensitive drum 110 and a cleaning roller 122 that removes dirt from the charging roller 121. The charging roller 121 is connected to a power supply device 123 that applies an AC voltage to the charging roller 121, and an AC peak-to-peak voltage that adjusts the peak-to-peak voltage (Vp−p) that the power supply device 123 applies to the charging roller 121. Changing means 124 is connected. In the image forming apparatus 1 according to the first embodiment, the AC peak-to-peak voltage changing unit 124 increases the AC peak-to-peak voltage (Vp−p) applied to the charging roller 121 as the image area ratio decreases, and the image area ratio. As the voltage increases, the power supply device 123 is controlled so as to reduce the AC peak-to-peak voltage (Vp-p) applied to the charging member. Here, the image area ratio is calculated based on the image data input to the optical writing unit 40.

  The developing device 130 includes a developing roller 131 and stirring rollers 132 and 133. Further, the lubricant application device 140 is disposed on the upstream side of the cleaning device 150 with respect to the rotation direction of the photosensitive drum 110, and the solid lubricant 141, the lubricant 141, and the photosensitive drum 110 are provided. A brush roller 142 that rotates by contact, scrapes the lubricant 141 and applies it to the photosensitive drum 110, and a compression spring 143 that presses the lubricant 141 against the brush roller 142 are provided.

  Further, the cleaning device 150 contacts the photoconductor drum 110 to remove residual toner on the photoconductor drum 110, and at the same time, a cleaning blade 151 that thins the lubricant applied by the lubricant application device 140, and the cleaning blade And a support member 152 that supports 151. Reference numeral 153 denotes a waste toner conveying member that conveys the removed waste toner.

  Hereinafter, control of the charging unit 120 in the image forming apparatus 1 according to the first embodiment will be described. FIG. 3 is a cross-sectional view illustrating a main part of the image forming apparatus in the state where the image area ratio is several percent in the image forming apparatus according to the first embodiment, and FIG. FIG. 5 is a cross-sectional view showing the main part of the image forming apparatus in a state where the image area ratio is large, and FIG. 6 is an alternating current of the lubricant application amount and the AC peak-to-peak voltage changing means with respect to the image area ratio. It is a graph which shows the change state of the voltage value between peaks.

  In the image forming apparatus according to the first embodiment, the basic structure of the image forming unit 100 is the same as that shown as the prior art. Therefore, the amount of the lubricant 141 applied to the photosensitive drum 110 is the same as that of the photosensitive drum 110. It changes depending on the size of the image area ratio (indicated by a one-dot chain line in FIG. 6). Further, the amount of the lubricant 141 applied is set when the compression spring 143 of the lubricant application device 140 is set to form an image having an image area ratio of about 3% to 10%, which is a normal image of office equipment. It is set to be an appropriate amount. In this case, as shown in FIG. 3, the amount of lubricant L applied to the surface of the photosensitive drum 110 becomes an appropriate amount, and there is no excess or deficiency of the lubricant application, and the contamination of the charging roller 121 is promoted. There is no progress of destruction or cleaning failure. This is indicated by the fact that the curve indicated by the alternate long and short dash line in FIG.

  When the image area ratio is small, particularly when the image forming apparatus 1 is not imaged, there is almost no residual toner T on the surface of the photosensitive drum 110 and the contact area between the photosensitive drum 110 and the brush roller 142 as shown in FIG. Increases and the amount of lubricant applied increases (see 3% or less of the lubricant application amount curve in FIG. 6). In such a case, in the image forming apparatus 1 according to the first embodiment, the AC peak-to-peak voltage changing unit 124 controls the power supply device 123 to increase the AC peak-to-peak voltage (Vp−p) of the AC voltage applied to the charging roller 121. Then, the charging current is increased (see Vp-p curve solid line 3% or less in FIG. 6).

  As a result, the amount of lubricant that is destroyed and consumed by the charging current from the charging roller 121 is increased, and the excessively applied lubricant is destroyed and consumed. Therefore, it is possible to prevent the excessive lubricant on the photosensitive member from adhering to the charging roller, and to suppress charging roller contamination, thereby preventing problems such as charging failure and streak image due to contamination. The amount of lubricant remaining on the photoreceptor after passing through the charged portion can be maintained appropriately. For example, when the lubricant application amount is about 1.2 times that during normal image formation, the charging AC peak-to-peak voltage is 1.9 kVp-p during normal image formation, while during non-image formation, 2.0 kVp-p, and the charging AC peak-to-peak voltage is increased.

  Further, when the image area ratio is large (the image area ratio is, for example, 10% or more), the residual toner T on the surface of the photosensitive drum 110 increases as shown in FIG. The contact area of 142 becomes small, and the application amount of the lubricant L decreases (see 10% or more of the lubricant application amount curve in FIG. 6). In such a case, in the image forming apparatus 1 according to the first embodiment, the AC peak-to-peak voltage changing unit 124 controls the power supply device 123 to reduce the AC peak-to-peak voltage (Vp−p) applied to the charging roller 121. The charging current is reduced (see 10% or more of the solid line of the Vp-p curve in FIG. 6), and the attacking action of the charging current on the photosensitive drum 110 is reduced.

  Thereby, in order to protect the photoconductor drum 110, the amount of lubricant consumed for destruction is reduced, and the surface of the photoconductor is broken due to insufficient application of the lubricant, resulting in photoconductor filming, and poor cleaning due to insufficient lubrication. Etc. are prevented. For example, when the application amount of the lubricant is about 0.5 times that at the time of normal image formation, the charging AC peak-to-peak voltage is 1.9 kVp-p at the time of normal image formation. .6 kVp-p and the charging AC peak-to-peak voltage is reduced.

  The change control of the AC peak-to-peak voltage (Vp-p) by the AC peak-to-peak voltage changing means 124 is summarized as follows. The curve drawn with a solid line in FIG. 6 shows an example of control of the AC peak-to-peak voltage (Vp-p) in the AC peak-to-peak voltage changing means 124 in the first embodiment, and the curve drawn with an alternate long and short dash line shows the lubricant application amount. It is shown.

  The AC peak-to-peak voltage changing means 124 is configured to cancel the change state of the lubricant application amount (a chain line in FIG. 6) accompanying the change in the image area ratio when the AC peak-to-peak voltage (Vp-p) is constant. (Vp-p) is continuously changed. Here, when the image area ratio is 3 to 10%, the lubricant application amount becomes an appropriate value. When the image area ratio is less than 3%, the lubricant application amount starts to increase, and the image area ratio is 10%. Above that, the lubricant begins to decrease.

  The AC peak-to-peak voltage changing means 124 increases the AC peak-to-peak voltage (Vp−p) when the image area ratio is small and the lubricant application amount increases, and conversely when the image area ratio is large and the lubricant application amount decreases. By reducing the AC peak voltage (Vp-p) and increasing or decreasing the amount of lubricant consumed and destroyed by the AC current, the amount of lubricant remaining on the photoreceptor after passing through the charging member is an appropriate amount. To prevent problems caused by excessive or insufficient lubricant application.

  Moreover, the change of the AC peak-to-peak voltage (Vp-p) of the power supply device 123 by the AC peak-to-peak voltage changing means 124 can be performed stepwise. FIG. 7 is a graph showing another change state of the AC peak-to-peak voltage value of the AC peak-to-peak voltage changing unit in the image forming apparatus according to the first embodiment. In this example, the AC peak-to-peak voltage (Vp-p) is changed in six steps corresponding to the change in the lubricant application amount.

<Example 2>
Next, an image forming apparatus according to Embodiment 2 will be described. FIG. 8 is a cross-sectional view showing the image forming apparatus according to the second embodiment, and FIGS. 9 and 10 are cross-sectional views showing the main parts of the image forming apparatus when the cleaning blade is worn. In the image forming apparatus according to the second embodiment, in order to prevent the contact area between the lubricant application member and the photoreceptor surface from fluctuating due to fluctuations in the image area ratio, As shown in FIG. 8, as the image forming unit 200, a lubricant application device 240 is disposed on the downstream side of the cleaning device 250 that removes the residual toner T from the photosensitive drum 110 with respect to the rotation direction of the photosensitive drum 110. The thing is adopted. In this image forming unit 200, a lubricant application blade 261 that contacts the photoconductor drum 110 downstream of the lubricant application device 240 and thins the lubricant applied by the lubricant application device 240 and applies it to the photoconductor drum 110 is provided. Deploy.

  The lubricant application device 240 includes a lubricant 241, a brush roller 242, and a compression spring 243. Further, the cleaning device 250 is arranged with the cleaning blade 251 supported by the support member 252. Further, the lubricant application blade 261 is supported by a support member 262.

  Even in such an image forming unit 200, when the edge of the cleaning blade 251 wears with time, the toner T1 that passes through the cleaning device 250 increases as shown in FIG. Then, when the wear of the edge of the cleaning blade 251 progresses, the cleaning slipping toner T1 changes due to the change in the image area ratio. In particular, in the case of an image having a large image area ratio, the slip-through toner T1 increases, the contact area between the brush roller 242 and the surface of the photoconductor drum 110 decreases, and the application of the lubricant is insufficient, and the photoconductor protection function is insufficient. As a result, destruction of the photoconductor progresses and a problem such as photoconductor filming occurs, or a cleaning failure occurs due to a lack of photoconductor lubricant.

  Therefore, the image forming unit 200 of the image forming apparatus according to the second embodiment records the usage time of the cleaning blade 251 and predicts the edge wear amount of the cleaning blade 251 based on the recorded usage time. The usage time of the cleaning blade 251 is to measure the usage time from when the cleaning blade 251 is replaced, and the measurement can be performed by the control unit of the image forming apparatus.

  In the image forming unit 200 according to the second embodiment, when the usage time of the cleaning blade 251 is the time that the edge wear proceeds and the slip-through toner increases, similarly to the image forming unit 100 according to the first embodiment. The AC peak-to-peak voltage (Vp-p) of the AC voltage applied to the charging roller 121 is controlled.

  That is, in the case of a high image area ratio, as shown in FIG. 10, the AC peak voltage (Vp-p) applied to the charging roller is reduced, the charging current is reduced, and the charging current is attacked by the photosensitive drum. Reduce action. Reduce the required amount of lubricant that is destroyed and consumed to protect the photoconductor to prevent the development of photoconductor surface destruction due to insufficient lubricant application, resulting in photoconductor filming, and poor cleaning due to insufficient lubrication. .

  FIG. 11 is a graph showing the change amount of the lubricant application amount and the AC peak-to-peak voltage value of the AC peak-to-peak voltage changing means with respect to the image area ratio in Example 2. A curve drawn with a solid line in FIG. 11 shows an example of control of the AC peak-to-peak voltage (Vp-p) in the AC peak-to-peak voltage changing means 124 in the second embodiment.

  The AC peak-to-peak voltage changing means 124 is configured to cancel the change state of the lubricant application amount (a chain line in FIG. 11) accompanying the change in the image area ratio when the AC peak-to-peak voltage (Vp-p) is constant. (Vp-p) is continuously changed. Here, when the image area ratio exceeds 20%, the lubricant application amount starts to decrease.

  In the second embodiment, the AC peak-to-peak voltage changing means 124 reduces the AC peak voltage (Vp-p) when the image area ratio is higher than 20%, and reduces the lubricant consumption due to the AC current. We try not to run out of lubricant.

  In the image forming apparatuses according to the first and second embodiments, the image forming unit is configured as a process cartridge in which a photosensitive member, a charging device, a photosensitive member cleaning device, and a lubricant applying device are integrated. The image forming apparatus main body is detachable as a unit, and the image forming unit can be replaced by replacing the process cartridge.

  According to this image forming apparatus, since the image forming unit is integrated into a process cartridge, it is possible to improve the installation and maintenance of each member on the image forming apparatus, and the position accuracy on the photosensitive drum. Can be improved.

  Further, the lubricant used in the lubricant application device of the image forming apparatus according to each of the embodiments contains a fatty acid metal salt (A) and an inorganic lubricant (B). The fatty acid metal salt is prevented from being destroyed by the charging current, and the surface of the photoconductor is prevented. At the same time, the inorganic lubricant that is not destroyed by the charging current provides a lubricating action (than the case where the lubricant is only the fatty acid metal salt). ) Since it is maintained in a better state, it becomes possible to maintain the photoconductor cleaning better.

  Examples of the fatty acid metal salt (A) include barium stearate, lead stearate, iron stearate, nickel stearate, cobalt stearate, copper stearate, strontium stearate, calcium stearate, cadmium stearate, magnesium stearate, Zinc stearate, zinc oleate, magnesium oleate, iron oleate, cobalt oleate, copper oleate, lead oleate, manganese oleate, zinc palmitate, cobalt palmitate, lead palmitate, magnesium palmitate, palmitate Aluminum, calcium palmitate, lead caprylate, lead caprate, zinc linolenate, cobalt linolenate, calcium linolenate, zinc ricinoleate, cadmium ricinoleate and mixtures thereof There, but is not limited to this. Moreover, you may mix and use these. In the present invention, zinc stearate is most preferably used since it is particularly excellent in film formability on an image carrier.

  The inorganic lubricant (B) refers to an inorganic compound that cleaves and lubricates itself or causes internal slip. Specific materials include talc, mica, boron nitride, molybdenum disulfide, tungsten disulfide, kaolin, smectite, hydrotalcite compound, calcium fluoride, graphite, plate-like alumina, sericite, and synthetic mica. However, it is not limited to this. Among these, boron nitride is most preferably used because hexagonal mesh surfaces in which atoms are firmly combined overlap with each other at a wide interval, and the force acting between the layers is only a weak van der Waals force.

  These inorganic lubricants may be surface-treated as necessary for the purpose of imparting hydrophobicity.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 10 Paper feed part 11,12 Paper feed cassette 20 Image forming part 30 Transfer part 31,32,33 Roller 34 Intermediate transfer belt 35 Secondary transfer roller 36Y, 36M, 36C, 36K Transfer roller 37 Belt cleaning device 40 Optical writing unit 50 Fixing device 60 Conveying path 100 Image forming units 100Y, 100M, 100C, 100K Image forming unit 110 Photosensitive drums 110Y, 110M, 110C, 110K Photosensitive drum 120 Charging means 121 Charging roller 121 Cleaning roller 123 Power supply device 124 AC peak-to-peak voltage changing means 130 Developing device 131 Developing roller 132, 133 Stirrer roller 140 Lubricant coating device 141 Lubricant 142 Brush roller 143 Compression spring 150 Cleaning device 151 Cleaning blade 152 Member 200 imaging unit 240 lubricant applying device 241 lubricant 242 brush roller 243 compression spring 250 cleaning device 251 cleaning blade 252 supporting member 261 lubricant application blade 262 supporting member

JP 2010-8998 A JP 2006-47517 A

Claims (11)

In an image forming apparatus comprising: a charging member that charges a photosensitive member; a power supply device that applies an alternating voltage to the charging member; and a lubricant application device that applies a lubricant to the photosensitive member.
AC peak-to-peak voltage changing means is provided for changing the AC peak-to-peak voltage (Vp-p) applied to the charging member by controlling the power supply device in accordance with the image area ratio of the toner image formed on the photoreceptor. An image forming apparatus.   2. The image forming apparatus according to claim 1, wherein the AC peak-to-peak voltage changing unit increases the AC peak-to-peak voltage (Vp-p) applied to the charging member as the image area ratio decreases. .   2. The image forming apparatus according to claim 1, wherein the AC peak-to-peak voltage changing unit reduces the AC peak-to-peak voltage (Vp−p) applied to the charging member as the image area ratio increases.   4. The image forming apparatus according to claim 1, wherein the lubricant application device has a structure in which a rod-shaped solid lubricant is scraped off by a brush roller and applied to the surface of the photoconductor. 5.   The image forming apparatus according to claim 4, wherein the lubricant application device is disposed upstream of the photosensitive member cleaning device with respect to the rotation direction of the photosensitive member.   The image forming apparatus according to claim 4, wherein the lubricant application device is mounted on the downstream side of the photoconductor cleaning device with respect to the rotation direction of the photoconductor.   The image forming apparatus according to claim 1, wherein the charging member includes a contact charging roller.   The image forming apparatus according to claim 1, wherein the charging member includes a charging roller disposed to face the photoconductor with a small gap.   The image forming apparatus according to claim 1, wherein the lubricant contains at least a fatty acid metal salt (A) and an inorganic lubricant (B).   The image forming apparatus according to claim 9, wherein the fatty acid metal salt (A) is zinc stearate and the inorganic lubricant (B) is boron nitride.   11. The process cartridge according to claim 1, wherein the image forming unit is a process cartridge including the photosensitive member and including at least one of a charging device, a developing device, and a photosensitive member cleaning device. Image forming apparatus.