JP4343612B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to a color image forming apparatus using an electrophotographic recording system such as a laser printer, a copying machine, a facsimile machine, etc., comprising a plurality of image carriers, and images formed on each image carrier are sequentially transferred. The present invention relates to an image forming apparatus that forms images of a plurality of colors by superimposing them.

  Various color image forming apparatuses for forming a color image on a transfer material using an electrophotographic recording system have been devised, and some of them have been put into practical use.

  As a typical example, the electrostatic latent image on the photosensitive drum can be sequentially developed by using each developing device containing a plurality of color developers for the photosensitive drum as one image carrier. A rotating developing device that is integrally provided with four color developing devices of yellow, magenta, cyan, and black is provided in the vicinity of one photosensitive drum and formed on a common photosensitive drum. Each electrostatic latent image of each color is visualized as a toner image at the development position reached by the rotation of each developing device, and is transferred onto a transfer material which is a sheet-like recording medium such as paper each time the toner image is obtained. However, there is an image forming apparatus of a type that forms a multicolor image by repeating a process in which residual toner on the photosensitive drum is removed by a cleaning device.

  Also, an apparatus has been devised that selectively superimposes each color toner image on the surface of the photosensitive drum, forms a multicolor toner image on the surface of the photosensitive drum, and then collectively transfers the image onto a transfer material.

  Here, as another method, a plurality of photosensitive drums are used as an image carrier, and each color toner image is separately formed by each color developing device provided facing each photosensitive drum. There has been proposed an in-line image forming apparatus in which a transfer material is conveyed to form a multicolor image while transferring sequentially from the drum onto the transfer material, and residual toner on each photosensitive drum is removed by a cleaning device. Image forming means such as each photosensitive drum, developing device, charger, cleaning device, etc. are integrated for each color to form image forming means (hereinafter referred to as “process station”), and transfer material that conveys the transfer material They are sequentially arranged according to the moving direction of the carrier. In order to adopt another transfer method for such an image forming apparatus, a multicolor toner image is formed by superimposing toner images of respective colors sequentially on an intermediate transfer member, not directly on a transfer material, and then collectively transferred to the transfer material. Then, the toner remaining on the intermediate transfer material is removed by an intermediate transfer member cleaning member, or the electrical characteristics of the residual toner are charged to a reverse characteristic by a charger, and the toner is reversed on the photosensitive drum of the first color process station. There is also a type that is removed by a photosensitive drum cleaning device by copying. Each process station is often detachable from the image forming apparatus as a process cartridge.

  The cleaning device uses a cleaning blade that contacts the photosensitive drum and scrapes off the transfer residual toner on the photosensitive drum to clean the photosensitive drum.

  As this cleaning blade, a flexible one such as urethane rubber is generally used. Normally, the cleaning blade is optimized for conditions such as rubber hardness, thickness, elastic modulus, protrusion amount, etc., so that the frictional resistance between the photosensitive drum and the cleaning blade increases during image formation. Chatter (stick slip) occurs on the photosensitive drum, and a slight squeak noise is generated between the photosensitive drum and the cleaning blade. This slight squeak noise is amplified in resonance with the photosensitive drum and becomes abnormal noise. Is preventing.

  In addition, there is a description that a slight squeak noise generated between the cleaning blade and the photosensitive drum is prevented from resonating with the photosensitive drum by adding a damping material or the like in the photosensitive drum (Patent Document 1). 2, 3).

  In addition, abnormal noise generated between the cleaning blade and the photosensitive drum by supplying toner onto the photosensitive drum by the developing unit and using the toner as a lubricant while the photosensitive drum is stopped after image formation. The thing which prevents this is also described (refer patent document 4).

However, in order to prevent noise on each photosensitive drum in the inline type color image forming apparatus, as described above, toner is supplied onto the photosensitive drum by the developing means while the image carrier is stopped after the image formation. There is no technical disclosure about the method, and when used as it is, for example, there is a photosensitive drum in which toner is excessively supplied by each of the following image forming process stations. Excessive toner supply not only shortens the life of the process station, but in some cases, excess waste developer is generated, resulting in puncture of the waste developer container or a large amount of supplied toner. In some cases, the cleaning unit cannot remove the cleaning image, causing a defective cleaning, and the output image may be soiled.
Japanese Patent Laid-Open No. 2-118684 JP-A-3-44689 JP-A-3-45981 Japanese Patent Laid-Open No. 10-161426

  The present invention has been proposed in view of the above-described problems. In an image forming apparatus having a plurality of image carriers, there is an adverse effect caused by excessive developer consumption when preventing the generation of abnormal noise in the cleaning unit. An object of the present invention is to provide an image forming apparatus that suppresses the above.

In order to achieve the above object, the present invention provides a plurality of image carriers that carry electrostatic latent images, and a developer image that is visualized based on the electrostatic latent images on the plurality of image carriers. In an image forming apparatus, the image forming apparatus includes: transfer means for sequentially transferring the image to the intermediate transfer body; and a plurality of cleaning blades for cleaning the developer remaining on the plurality of image carriers.
A developing agent supply means capable of supplying the developer to the non-image forming region on said plurality of image carriers,
A developer charging roller for charging the developer remaining on the intermediate transfer member;
Have
The intermediate transfer member is cleaned by collecting the developer charged by the developer charging roller with an electric field on the collecting image carrier among the plurality of image carriers.
The amount of developer supplied to the non-image forming area on the recovery image carrier by the developer supply means is greater than the amount of developer supplied to the non-image formation area on the image carrier other than the recovery image carrier. The image forming apparatus is also characterized by a small amount.
Another aspect of the present invention is to transfer a plurality of image carriers carrying electrostatic latent images and a developer image visualized based on the electrostatic latent images on the plurality of image carriers. Transfer means for sequentially transferring to the member;
An image forming apparatus comprising: a conveying member that carries and conveys the transferred member to a transfer position of the plurality of image carriers; and a plurality of cleaning blades that clean the developer remaining on the plurality of image carriers.
Developer supply means capable of supplying a developer to non-image forming areas on the plurality of image carriers;
A developer charging roller for charging the developer adhering to the conveying member;
Have
The developer charged by the developer charging roller is recovered by an electric field on a recovery image carrier among the plurality of image carriers, whereby the transport member is cleaned,
The amount of developer supplied to the non-image forming area on the recovery image carrier by the developer supply means is more than the amount of developer supplied to the non-image formation area on the image carrier other than the recovery image carrier. This is an image forming apparatus characterized by a small amount.

As an effect of the present invention, since the minimum amount of supplied developer necessary for preventing the generation of abnormal noise in the cleaning blade portion can be set, the generation of abnormal noise is prevented without causing excessive toner consumption. be able to.

  As another effect of the present invention, by sharing the developer supplying unit and the developing unit, it is possible to supply the developer without providing a special member, and it is possible to prevent the cost of the image forming apparatus from being increased.

  As another effect of the present invention, it is possible to reliably prevent the generation of abnormal noise without causing excessive toner consumption according to the environment in which the image forming apparatus is placed.

  As another effect of the present invention, it is possible to reliably prevent the generation of abnormal noise without causing excessive toner consumption according to the degree of use of the developing means.

Another effect of the present invention is that the image carrier and the cleaning blade are process cartridges that can be attached to and detached from the image forming apparatus main body, so that a plurality of consumables can be replaced simply by replacing the process cartridge. The maintenance of the forming apparatus is simplified. In addition, stable image quality can be easily maintained.

  As another effect of the present invention, various settings of the image forming apparatus main body can be performed simply by changing information for determining the amount of developer to be supplied in the storage medium incorporated in the process cartridge in accordance with the characteristics of the process cartridge. Is to change the environment in which the amount of developer to be supplied is changed and the timing of the degree of use of the developing means. For example, when the durability of the developing unit is improved and a process cartridge that does not deteriorate the developer can be provided even in the same usage, the user of the image forming apparatus can perform the above-described convenience without complicated operation. Can be enjoyed.

  As another effect of the present invention, the relationship between the amount of the developer supplied to the image carrier and the temperature or humidity is included in the information of the storage medium, so that it can be adapted to the characteristics of the developing means incorporated in the process cartridge. Similarly, the determination for changing the amount of toner to be supplied can be changed without changing various settings of the main body of the image forming apparatus only by changing the value in the storage medium incorporated in the process cartridge.

  As another effect of the present invention, the number of prints representing the degree of use of the developing means and the operation of the developing means are included in the process cartridge itself as the detected member by including the usage of the developing means in the information of the storage medium. Accumulated values such as time can be stored, and even if the process cartridge is attached or detached, it can be detected with reference to the information stored in the storage medium of the process cartridge, thereby accurately detecting the usage level of the developing means. The amount of developer to be supplied can be changed. An identification number is assigned to the storage medium of the process cartridge, and when the process cartridge is replaced before the life of the image carrier is reached, the main body of the image forming apparatus can be notified that a new process cartridge has started to be used.

[ Reference Example 1]
The configuration of an image forming apparatus which is an example of a color image forming apparatus according to the present invention will be described with reference to FIG. The image forming apparatus shown in the figure includes four first, second, third, and fourth image forming units that are independent of yellow (Y), magenta (M), cyan (C), and black (Bk). From the upstream to the downstream in the moving direction (rotating direction, arrow direction) of the transfer belt 10 as a conveying member that conveys the transfer material P that is a transferred member to the transfer position. Different colors formed in the first to fourth process stations Y, M, C, and Bk on the transfer material P that is arranged in a horizontal row and adsorbed on the surface of the transfer belt 10 (from right to left in the figure). The developer image (toner image) is sequentially transferred by a transfer member, which is a transfer unit, to form a four-color full-color image, which is a so-called in-line image forming apparatus.

  Further, as shown in FIG. 2, in order to improve maintainability, the first to fourth process stations Y, M, C, and Bk that are image forming units are photosensitive drums 1a to 1d that are image carriers, and charging units. The charging rollers 2a to 2d, developing devices 4a to 4d which are developer supplying means and developing means, photosensitive drum cleaning means 6a to 6d which are cleaning means, and storage media 46a to 46d are integrated into an image forming apparatus. The process cartridges 20a, 20b, 20c, and 20d are detachable.

In the image forming apparatus of this reference example, information on the process cartridges 20a, 20b, 20c, and 20d when the process cartridges 20a, 20b, 20c, and 20d are attached to and detached from the main body of the image forming apparatus or at the end of the printing operation. Are read from and written to the storage media 46a to 46d via a reading / writing means (not shown) provided in the apparatus.

In this reference example , an NV-RAM (Non Volatile-RAM) having a storage capacity of 2 kbytes is used as the storage media 46a to 46d. However, this is a storage medium such as a magnetic storage medium or an optical storage medium. There may be.

In this reference example , the photosensitive drums 1a to 1d, which are electrostatic latent image carriers, use OPC (organic photo semiconductor) photosensitive drums having a negative charging characteristic with a diameter of 20 mm. An arrow R1 is used when each image is formed. It is rotationally driven with a peripheral speed (process speed) of 200 mm / sec in the direction.

  Around each of the photosensitive drums 1a to 1d, primary chargers 2a, 2b, 2c, and 2d, exposure devices 3a, 3b, 3c, and 3d, which are information writing devices, and a developing device 4a are arranged almost in order along the rotation direction. 4b, 4c, 4d, transfer members 8a, 8b, 8c, 8d, and cleaning blades (electrostatic latent image carrier cleaning means) 6a, 6b, 6c, 6d are disposed.

  The photosensitive drums 1a to 1d are uniformly charged to a predetermined polarity and potential by primary charging rollers 2a, 2b, 2c, and 2d, which are primary chargers, in a rotating process, and then exposed to exposure apparatuses 3a, 3b, 3c, and 3d. By receiving image exposure by the group, electrostatic latent images corresponding to the first to fourth color component images (yellow, magenta, cyan, and black component images) of the target color image are formed. The primary charging rollers 2a to 2d are rollers having an actual resistance of 1 × 10 6 Ω to which a DC voltage of −1.2 kV is applied, and are in contact with the photosensitive drums 1a to 1d with a total pressure of 9.8 N (Newton). The drum 1a to 1d rotates following the rotation. By applying this voltage, the surfaces of the photosensitive drums 1a to 1d are charged to -600V.

The exposure apparatuses 3a to 3d used in the present reference example are polygon scanners using laser diodes, and image a laser beam modulated by an image signal on the photosensitive drums 1a to 1d to form an electrostatic latent image. Form. The surface of the photosensitive drum in the exposed portion becomes −200V. The laser exposure is written from the position signal in the polygon scanner called BD for each scanning line in the main scanning direction (direction perpendicular to the moving direction of the transfer material), and in the sub-scanning direction (transfer material moving direction). By delaying a predetermined time from a TOP signal starting from a switch (not shown) in the road, the photosensitive drums 1a to 1d are always used in the first to fourth process stations Y, M, C, and Bk. The exposure can be performed at the same upper position.

Next, the electrostatic latent image is developed by the developing devices 4a, 4b, 4c, and 4d of the first to fourth process stations Y, M, C, and Bk. In the developing devices 4 a to 4 d, a developing sleeve 41, which is an elastic roller as a developer carrying member, is disposed at the opening portion of the developing container 43 so as to be opposed to the photosensitive drums 1 a to 1 d, and the developing sleeve 41 is interposed therebetween. Each color toner is attached to the electrostatic latent images on the photosensitive drums 1a to 1d and developed as toner images. The developer in each of the developing devices 4a to 4d is a negatively charged nonmagnetic one-component toner, and the development of the electrostatic latent image is performed by a nonmagnetic one-component contact development method. In this reference example , as a means for regulating the layer thickness of the developer that adheres to the developing sleeve 41 of the developing devices 4a to 4d, it is attached to the opening portion of the developing container 43 upstream of the developing position of the developing sleeve 41 in the rotation direction. A layer thickness regulating blade 42 is used.

At this time, each developing sleeve 41 rotates in a forward direction with respect to the photosensitive drums 1a to 1d at a constant value, a process speed of 170% in this reference example , and can be changed by a controller signal (this reference example). Then, −350 V) is applied, and development is performed.

Transfer belt 10 as a transfer material carrying member, the driving roller 7 and are passed over the driven roller 9, the counterclockwise rotation of the drive roller 7, the reference example in the time of development of the direction of the arrow photosensitive drum 1a~1d Is driven at the same process speed. The transfer belt is a 100 μm thick PVDF single-layer resin belt with resistance adjusted to 1 × 10 10 Ωcm. The transfer belt has an endless shape, and ribs for preventing meandering and biasing of the belt are provided at both ends on the back side. Is provided.

  As the transfer member, transfer rollers 8a, 8b, 8c, and 8d adjusted to a volume resistivity of 1 × 10 5 Ωcm are used, and the transfer belt 10 is pressed from the back surface to be pressed against the photosensitive drums 1a to 1d. Yes. By applying a positive transfer bias to the transfer rollers 8a to 8d by a transfer bias power source (not shown), the toner images on the photosensitive drums 1a to 1d are sequentially transferred onto the surface of the transfer material P.

  The photosensitive drum cleaning blades 6a, 6b, 6c, and 6d, which are cleaning means for the photosensitive drums 1a to 1d, remove toner (transfer residual toner) that is not transferred to the transfer material P and remains on the surfaces of the photosensitive drums 1a to 1d.

  In the image forming apparatus having the above-described configuration, the transfer material P is fed from a paper feed cassette (not shown), passes through a registration roller (not shown), and then passes through a transfer inlet guide (not shown). 10 to come into contact.

  In the image forming apparatus configured as described above, the transfer material P needs to be sufficiently adsorbed to the transfer belt 10.

  The transfer material P passes through the transfer entrance guide and comes into contact with the transfer belt 10. At this time, an adsorption roller 11 as an adsorption member is disposed in the vicinity of the contact point. The suction roller 11 is disposed so as to sandwich the transfer belt 10 with the driven roller 9 which is one of the rollers around which the transfer belt 10 is stretched, and +1 kV during the image forming operation. Is applied to the transfer material P to generate an attracting force. Due to the suction force of the suction roller 11, the transfer material P is sucked onto the surface of the transfer belt 10.

The transfer material P to which the suction force with the transfer belt 10 is applied enters the first process station Y. In this transfer material P, a yellow toner image of the first color is transferred from the photosensitive drum 1a by a transfer roller 8a provided on the back surface of the transfer belt 10 in the transfer portion. The transfer roller 8a used in this reference example is a transfer roller 8a having a resistance value adjusted to 1 × 10 5 Ωcm. Under this condition, the contact nip width between the transfer roller 8a and the transfer belt 10 along the rotation direction (arrow direction) of the transfer belt 10 is 1.5 mm. A DC bias of +2 kV is applied to the transfer roller 8a from a high voltage power source.

  Thereafter, a toner image of a different color is transferred from each of the photosensitive drums 1b, 1c, and 1d each time it passes through each of the process stations M, C, and Bk as the transfer belt 10 rotates in the arrow direction. Four color toner images are superimposed.

In the present reference example , the transfer bias applied to the transfer material P on the transfer belt 10 in the first to fourth process stations Y, M, C, and Bk is absorbed in order to absorb the influence on the transfer contrast. Is increased by 300V as it goes to the downstream process station, and the fourth process station Bk is set to 2.9 kV, thereby preventing transfer defects.

  After the transfer of the four color toner images to the transfer material P is completed, the transfer material P separated by the curvature from the most downstream side (rear end) of the transfer belt 10 is then transferred to the four colors of the surface by a fixing device (not shown). The toner image is fixed by heating and pressing. Thus, the formation of the four-color full-color image is completed, and the transfer material P is discharged outside the image forming apparatus main body.

  In the image forming apparatus having such a transfer belt 10, if toner remains on both surfaces of the belt 10, the transfer material P may become dirty on the back side or the image may be stained. Specifically, the residual toner is transferred from the photosensitive drums 1a to 1d for detection of color misalignment for paper jam, fog toner adhesion to a non-image portion, or color misregistration control or toner image density control. Color misregistration detection toner images and the like.

  The toner remaining and attached to the transfer belt 10 is removed by a transfer belt cleaning means (cleaning blade) 12.

Further, the image forming apparatus of the present reference example has an environment detecting unit 45 capable of detecting temperature and humidity. Further, in this reference example , values (temperature 30 ° C., humidity 40% described below) are stored in the storage media 46a to 46d for determining the amount of toner to be supplied based on the temperature / humidity detected by the environment detection means 45, respectively.

Next, a toner image creation method for preventing abnormal noise in the cleaning unit (cleaning blades 6a to 6d) will be described. FIG. 3 is a timing chart showing timings for operating the charging bias, writing (exposure), and developing bias in order to create a toner image. Here, the horizontal axis in the figure represents time, and the vertical axis represents a state in which each bias is ON or OFF. Image formation is performed by performing exposure in accordance with an image corresponding to a document image or an image signal from the outside and making the image developed by a developing unit. A toner image is created to prevent abnormal noise in the non-image forming area after image formation. Specifically, in the reference example , when the post-rotation operation is performed, a short horizontal band-shaped image is exposed again in the entire width direction in the rotation direction (circumferential direction) of the photosensitive drum, and developed by the developing unit. A toner image is created. In addition, the length of the photosensitive drum in the rotation direction (circumferential direction) can be changed by increasing or decreasing the time during which the exposure is turned on during the post-rotation operation. In this reference example , the toner supply amount in this method was set to 0.4 mg / cm ² .

  Apart from this method, toner image creation can also be performed as shown in the timing chart of FIG. When exposure is performed and image formation is completed by developing means and image formation is completed and the post-rotation operation is performed, exposure is not performed and the development bias remains on and the charging bias is turned off for a certain period of time. The potential of the photosensitive drum in that portion becomes 0 V, and the effect is the same as the formation of an electrostatic latent image. Therefore, negatively charged toner is developed on the photosensitive drum and a toner image is created. At this time, the toner image becomes a horizontal band-like image in the entire width direction. Further, the length of the photosensitive drum in the rotation direction (circumferential direction) can be changed by increasing or decreasing the time during which the charging bias is turned off for the predetermined period.

As another method, it can be performed as shown in the timing chart of FIG. When exposure is performed and image formation is completed by developing means, and after image formation is completed and the post-rotation operation is performed, after the development bias is turned off and the charging bias is also turned off, the development bias is turned on for a certain period. In the portion, a developing bias is applied to the portion where the potential of the photosensitive drum is 0 V, so that the negatively charged toner is developed on the photosensitive drum and a toner image is formed. At this time, the toner image becomes a horizontal band-like image in the entire width direction. In addition, the length of the photosensitive drum in the rotation direction (circumferential direction) can be changed by increasing or decreasing the time for which the developing bias is turned on for the predetermined period. As a means for supplying toner to the photosensitive drum, any supply means may be used as long as it can supply a predetermined amount of toner in addition to a means for utilizing the potential difference between the photosensitive drum and the developing means as in this reference example .

  The horizontal belt-like toner image created in this way moves to the cleaning position between the photosensitive drum and the cleaning blade as the photosensitive drum rotates, and the coefficient of friction between the photosensitive drum and the cleaning blade is lowered. As a result, chattering (stick slip) of the cleaning blade with respect to the photosensitive drum does not occur, and generation of abnormal noise can be prevented. At this time, it is preferable that the bias applied to the transfer roller 8 is lower than the bias during normal transfer so that the toner image created on the photosensitive drum is not completely transferred to the transfer belt 10.

Next, in the inline image forming apparatus of this reference example , the relationship between the toner supply amount and the generation of abnormal noise was examined. As the toner supply method, the method shown in the timing chart of FIG. 4 was used. The environment at this time was a temperature of 23 ° C., a humidity of 60% (normal temperature and normal humidity), and each process cartridge used was equivalent to 5000 sheets with a lifetime of 10,000 sheets.

  First, as a comparative example (1.1), during the post-rotation operation in all the process stations, the toner bias of 20 mm was supplied in the photosensitive drum rotating direction by turning off the charging bias for 0.1 second. No abnormal noise was generated at the cleaning blade.

  Next, as a comparative example (1.2), when the charging bias is turned off in all process stations for 0.05 seconds and the length of toner supplied in the photosensitive drum rotation direction is 10 mm, the yellow station There was an abnormal noise only in

Next, in this reference example (1), the time for turning off the charging bias of the yellow station is set to 0.07 seconds, the length of the supplied toner in the rotating direction of the photosensitive drum is 14 mm, and the charging bias of other process stations is set. When the OFF time was set to 0.05 seconds and the length of the supplied toner in the photosensitive drum rotating direction was set to 10 mm, no abnormal noise was generated in all the process stations.

  This is because there is almost no toner remaining on the transfer belt because of the transfer belt cleaning member 12. Therefore, the toner that comes to the photosensitive drum cleaning unit in the process station is only residual toner that could not be transferred from the photosensitive drum to the transfer material, and toner that moved from the image transferred to the transfer material to the photosensitive drum by reverse transfer. In the process station for the first color, only the remaining toner is transferred to the cleaning blade portion without being transferred to the transfer material. However, in the process stations for the second and subsequent colors, in addition to the transfer residual toner, the image transferred onto the transfer member. Since toner generated by reverse transfer of toner (so-called retransfer toner) also comes to the cleaning blade portion, the process station for the second and subsequent colors has a larger amount of toner coming to the photosensitive drum cleaning portion than the process station for the first color, and the cleaning blade This is because abnormal noise is hardly generated at the part. That is, the photosensitive drum of the second color process station, which is the second image carrier, is transferred after the first image carrier, rather than the photosensitive drum of the first color process station, which is the first image carrier. This increases the amount of toner that comes to the cleaning section of the process station. Therefore, in order to prevent abnormal noise from the cleaning blade, the amount of toner supplied to the image carrier needs to be larger in the first image carrier than in the second image carrier.

As described above, when the same amount of toner is supplied to all the process stations as in the prior art, in the comparative example (1.1), although the noise of the cleaning blade can be prevented, excessive toner is consumed. Therefore, in the comparative example (1.2), even when the toner is supplied, the noise of the cleaning blade is generated. By supplying an appropriate toner to each process station as in this reference example (1), it was possible to prevent noise from the cleaning blade and to reduce toner consumption.

[ Reference Example 2]
Under normal circumstances, the toner supply amount to the photosensitive drum may be set as described above. However, since the viscoelasticity of the cleaning blade may change due to environmental changes or the charge amount of the toner may change greatly, As described above, it is preferable to set the toner supply amount according to the environment. First, the relationship between the toner supply amount and the generation of abnormal noise was examined using an environment where the temperature is 35 ° C., humidity is 60% (high temperature / normal humidity), and each process cartridge has a life equivalent to 10,000 sheets for 10,000 sheets. The other conditions are the same as in Reference Example 1. As the toner supply method, the method shown in the timing chart of FIG. 4 was used.

  First, as Comparative Example (2.1), when the toner supply amount determined in an environment of a temperature of 23 ° C. and a humidity of 60% (normal temperature / normal humidity) was used, abnormal noise was generated at all stations.

This is because, in an environment at a temperature of 35 ° C., as compared with an environment at a temperature of 23 ° C., the viscoelasticity of the cleaning blade is high, and the cleaning blade tends to chatter against the photosensitive drum and noise is likely to occur. This is because. Therefore, when the temperature changes, it is necessary to correct the supplied toner amount. As a reference example (2.1), the amount of toner to be supplied was corrected by adding a time for turning off the charging bias in all process stations for 0.05 seconds. When the length of the supplied toner in the direction of rotation of the photosensitive drum was 24 mm at the yellow station and 20 mm at the other stations, no abnormal noise was generated at all the process stations.

  Next, the relationship between the toner supply amount and the generation of abnormal noise was examined using an environment with a temperature of 23 ° C., a humidity of 25% (normal temperature / low humidity), and each process cartridge having a life of 10,000 sheets corresponding to 10,000 sheets. As the toner supply method, the method shown in the timing chart of FIG. 4 was used.

  First, when the toner supply amount determined in an environment of a temperature of 23 ° C. and a humidity of 60% as Comparative Example (2.2) was made, abnormal noise was generated at all stations.

This is because in a 25% humidity (low humidity) environment where the humidity is 60% (normal humidity), the toner charge is higher than when the humidity is high, and the toner polarity is opposite to the normal polarity (reversal toner). This is considered to be because the amount of toner to be transferred to the non-exposed portion on the photosensitive drum is reduced, so that sticking slip of the cleaning blade is likely to occur. Therefore, when the humidity changes, it is necessary to correct the amount of toner to be supplied. Therefore, as a reference example (2.2), the time to turn off the charging bias in all process stations is added for 0.05 seconds, the length of the supplied toner in the photosensitive drum rotation direction is 24 mm in the yellow station, and other stations. No noise was generated in all process stations.

  As described above, in the inline type image forming apparatus, the toner supply amount necessary for preventing the abnormal noise generated in the cleaning blade portion by supplying the toner is different in each process station, and the image forming apparatus is provided. It was found that it varies depending on the environment (temperature and humidity). Therefore, it is preferable to correct the amount of toner supplied depending on the environment where the image forming apparatus is placed.

In this reference example , the correction values for the amount of toner supplied to the process station are all the same, but the appropriate correction values may differ slightly depending on the characteristics of the toner of each color. For example, since the toner is charged by frictional charging, the toner charge amount decreases as the toner is left. At this time, how the toner charge amount drops depends on the color of the toner. Therefore, the susceptibility of the cleaning blade in each process station when left under high humidity may change. Therefore, it is preferable to change the correction value for each process station.

Based on the above, the final toner supply amount determination in the image forming apparatus of this reference example was performed according to the procedure shown in the flowchart of FIG. The control described in this flowchart is the same for each process cartridge. The storage medium provided in each process cartridge stores temperature / humidity values (30 ° C., 40%) for switching the supplied toner amount. In this reference example , the temperature is set to 30 ° C. and the humidity is set to 40% as environmental conditions for switching the amount of supplied toner. However, the present invention is not limited to this, and it depends on the cleaning blade material, the contact condition with respect to the photosensitive drum, and the like. Can be set arbitrarily.

  When image formation is started (S11), it is determined whether or not the temperature detected by the environment detection means 45 is 30 ° C. or higher (S12). If it is 30 ° C. or higher, the temperature is first determined in an environment of 23 ° C. and humidity 60%. Add 0.05 seconds to the time to turn off the charging bias (0.07 seconds for yellow station, 0.05 seconds for other stations) (S13). Further, it is determined whether or not the humidity detected by the environment detection means 45 is 40% or less (S14). If it is 40% or less, the time for further turning off the charging bias (0.07 seconds for the yellow station, 0 for other stations). .05 seconds) is added for 0.05 seconds (S15). When increasing or decreasing the amount of toner supplied based on temperature and humidity, the amount supplied by each process station may be increased or decreased, or the same amount supplied by all process stations may be increased. You may make it increase / decrease. Normally, the supply amount may be changed for each process station only when the same amount of toner is supplied and the environment changes.

  Based on these determinations, the time for turning off the final charging bias is determined (S16), toner supply is executed during the post-rotation (S17), and the process ends (S18).

  By using the above-mentioned means, the temperature of the environment in which the image forming apparatus is placed becomes high, the viscoelasticity is high as the rubber characteristic of the cleaning blade, and the cleaning blade is easily struck against the photosensitive drum. Abnormal noise generation at the blade portion can be prevented. In addition, the humidity in the environment where the image forming apparatus is placed becomes lower, the amount of charge of the toner becomes higher than when the humidity is high, and the amount of toner whose polarity is opposite to that of normal (reverse toner) is high. Therefore, it is possible to prevent noise from being generated at the cleaning blade portion when the amount of fog toner is reduced. Further, a value for determining the amount of toner to be supplied to each image carrier on the storage medium based on the temperature and humidity detected by the environment detection means, for example, temperature or humidity, and an image determined according to the temperature or humidity. Since the relationship with the amount of toner supplied to the carrier is stored, the image forming apparatus can be changed by simply changing the value in the storage medium incorporated in the process cartridge according to the characteristics of the developing means incorporated in the process cartridge. The judgment for changing the amount of toner to be supplied can be changed without changing various settings of the main body.

In this reference example , since the amount of supplied toner could be reduced except for the yellow station, the toner life could be extended accordingly.

The developer in this reference example is a non-magnetic one-component developer, but the present invention can also be applied using a magnetic one-component developer or a two-component developer. In addition, a non-contact development method can also be adopted as a development method.

In addition to this reference example , in addition to the above-described one, the inline type color image forming apparatus superimposes the toner images of each color on the intermediate transfer body as a transfer material, not directly on the transfer material. The same reason is applied to an image forming apparatus in which a multicolor toner image is formed by the above, and then transferred onto a transfer material at a time, and the toner remaining on the intermediate transfer member is removed by an intermediate transfer member cleaning member which is a transfer cleaning member. Thus, the amount of toner coming to the photosensitive drum cleaning unit is larger in the second, third, and fourth color process stations than in the first color process station, and abnormal noise is less likely to occur in the cleaning blade unit. Accordingly, similarly, the photosensitive drum of the second color process station, which is the second image carrier, is transferred after the first image carrier, rather than the photosensitive drum of the first color, which is the first image carrier. The drum has a larger amount of toner coming to the cleaning part of the process station. Therefore, in order to prevent abnormal noise from the cleaning blade, it is necessary to increase the amount of the lateral belt-like toner supplied to the image carrier in the first image carrier over the second image carrier.

[ Example 1 ]
FIG. 7 is a configuration diagram of a multicolor image forming apparatus such as a color laser printer which is an embodiment of the present invention.

  The transfer form of the image forming apparatus is not limited to the structure of the image forming apparatus shown in FIG. 1, and as in the image forming apparatus of FIG. 7, a toner image is primarily transferred onto an intermediate transfer member as a transfer member and superimposed. Accordingly, the present invention can also be applied to a type in which a multicolor toner image is formed and then secondarily transferred onto the transfer material P at once.

A color electrophotographic apparatus, which is an image forming apparatus using an intermediate transfer body, does not require any processing or control (for example, gripping by a gripper, adsorbing, giving a curvature, etc.) to a transfer material, and an image from an intermediate transfer belt. Can be transferred from thin paper (40 g / m ² paper) to thick paper (200 g / m ² paper), such as envelopes, postcards, and label papers. Regardless of thickness, there is an advantage that a wide variety of transfer materials can be selected, and various products have been put to practical use by this method.

  With reference to FIG. 7, a configuration example of an inline image forming apparatus using an intermediate transfer member will be described. In FIG. 7, as color image forming apparatuses, photosensitive drums 1a to 1d, which are electrostatic latent image carriers arranged to be opposed to developing apparatuses 4a to 4d containing developers of yellow, magenta, cyan, and black. Are sequentially disposed in the moving direction of the intermediate transfer belt 10 ′, which is an intermediate transfer member, and the toner images of the respective colors developed on the drums 1a to 1d by the developers of the developing devices 4a to 4d are transferred to the intermediate transfer belt. A four-drum image forming apparatus (hereinafter referred to as an in-line color printer) that obtains a full-color image with four colors of toner including yellow, magenta, and cyan plus black on the intermediate transfer belt 10 'while transferring images onto the intermediate transfer belt 10'. ) Is a schematic cross-sectional view.

  In FIG. 7, an endless intermediate transfer belt 10 ′ is suspended by a driving roller 7 and a driven roller 9, and rotates in a direction opposite to the rotating direction of the rotating drums 1a to 1d (the counterclockwise direction of the arrow in the figure). The four photosensitive drums 1a to 1d are arranged in series facing the intermediate transfer belt 10 '. The process stations Y, M, C, and Bk of the image forming units for each color are composed of photosensitive drums 1a to 1d, charging units 2a to 2d, exposure units 3a to 3d, and developing units 4a to 4d, which are respectively photosensitive. Arranged around the drums 1a to 1d.

  That is, in the image forming apparatus shown in FIG. 7, four independent second colors of yellow (Y), magenta (M), cyan (C), and black (Bk) are arranged along the moving direction of the intermediate transfer belt 10 ′. Process stations Y, M, C, and Bk, which are first, second, third, and fourth image forming units, are provided. The process stations Y, M, C, and Bk for the respective colors are photosensitive drums 1a to 1d that are photosensitive drums, developing devices 4a to 4d, charging units 2a to 2d, exposure units 3a to 3d, and cleaning blades that are photosensitive drum cleaning units. 6a to 6d.

Further, in the image forming apparatus of the present embodiment as well, in the same manner as in Reference Example 1, the first to fourth process stations are process cartridges that are detachable from the image forming apparatus and have a storage medium as shown in FIG. It is.

  Here, the image forming operation will be described below. The surfaces of the photosensitive drums 1a to 1d that are uniformly charged by the charging rollers 2a to 2d, which are the respective charging means, are irradiated from the exposure means 3a to 3d with laser beams modulated according to image data from a host such as a personal computer. A desired electrostatic latent image is obtained for each color. The latent image is reversely developed at the development site and visualized as a toner image by the developing devices 4a to 4d including the toners of the respective colors arranged opposite to the latent image. The toner images are sequentially primary-transferred onto the intermediate transfer belt 10 ′, and the combined toner images of the respective colors formed on the intermediate transfer belt 10 ′ are fed by a sheet feeding unit (not shown) and conveyed by a conveying unit. 2 is a secondary transfer member that is in contact with the transfer material P at a position downstream of the process stations Y, M, C, and Bk in the moving direction of the intermediate transfer belt 10 ′ and sandwiches and conveys the transfer material P. Transfer is performed by a secondary transfer bias applied to the next transfer roller 13. This color toner image is melted and fixed by a fixing device (not shown), and is permanently fixed on the transfer material P to obtain a desired color print image. Further, the secondary transfer residual toner is moved to the opposite surface between the photosensitive drum and the intermediate transfer belt 10 ′ by charging the toner polarity to the opposite polarity by the secondary transfer residual toner charging roller 44. A method in which the toner disposed at the most upstream in the direction is recovered by being reversely transferred by the electric field to the photosensitive drum 1a of the first process station, which is a recovery image carrier for recovering by the electric field, and removed by the photosensitive drum cleaning unit. I'm taking it. The electric field for recovery from the intermediate transfer belt is not formed on the photosensitive drums of other process stations. Here, it is more advantageous during maintenance that the image carrier for collection is arranged at the most upstream position because the secondary transfer residual toner is not collected by an image carrier other than the image carrier for collection.

Also, in this embodiment, as in Reference Example 1, the environment detection unit 45 capable of detecting temperature and humidity is provided, and the toner supplied to the storage medium based on the temperature and humidity detected by the environment detection unit 45 A value is stored to make a decision to change the amount.

In each process station Y, M, C, and Bk, the toner image creation method for preventing abnormal noise in the cleaning unit is the same as that described in Reference Example 1.

  Next, in the inline type image forming apparatus of this embodiment, the relationship between the toner supply amount and the generation of abnormal noise was examined. As the toner supply method, the method shown in the timing chart of FIG. 4 was used. The environment at this time was a temperature of 23 ° C., a humidity of 60%, and each process cartridge had a lifespan corresponding to 5000 sheets with respect to 10,000 sheets.

  First, as a comparative example (3.1), after image formation is completed in all process stations, toner charging of 20 mm is performed in the photosensitive drum rotation direction by turning off the charging bias for 0.1 second. No abnormal noise was generated at the cleaning blade part even at the station.

  Next, as a comparative example (3.2), when the length of the supplied toner in the photosensitive drum rotating direction was set to 8 mm for 0.04 seconds for turning off the charging bias in all process stations, magenta, cyan There was an abnormal noise at the black station.

  Next, the time for turning off the charging bias of the yellow station is set to 0.04 seconds, the length of the supplied toner in the photosensitive drum rotating direction is set to 8 mm, and the time for turning off the charging bias of the other process stations is set to 0.05 seconds. When the length of the supplied toner in the rotating direction of the photosensitive drum was set to 10 mm, no abnormal noise was generated in all the process stations.

  This is because the secondary transfer residual toner is collected by the electric field at the process station for the first color, so that the secondary transfer is performed in addition to the primary transfer residual toner remaining on the cleaning blade portion without being transferred to the intermediate transfer member. A large amount of secondary transfer residual toner charged with the reverse polarity of the toner polarity by the residual toner charging roller 44 is reversely transferred and collected, so that the first color process station comes to the photosensitive drum cleaning unit from the second color and subsequent process stations. This is because the amount is so large that abnormal noise is hardly generated at the cleaning blade portion.

When the same amount of toner is supplied to all the process stations as in the past, in the comparative example (3.1), although the noise of the cleaning blade can be prevented, excessive toner is consumed. In (3.2), the noise of the cleaning blade is generated even when the toner is supplied. By supplying an appropriate toner to each process station as in this embodiment ( 1.1 ), it was possible to prevent abnormal noise from the cleaning blade and to suppress toner consumption.

Next, the environment is 35 ° C. and the humidity is 60%, and each process cartridge has a lifetime equivalent to 5,000 sheets, and the environment is 23 ° C. and the humidity is 25%. Each process cartridge has a lifetime of 10,000 sheets and 5,000 sheets. When the relationship between the toner supply amount and the occurrence of abnormal noise was examined using a sheet equivalent, it was necessary to add a time for turning off the charging bias in each environment in the same manner as in Reference Example 1. .

  As described above, in the image forming apparatus having the configuration described in this embodiment, the toner supply amount necessary for preventing the abnormal noise generated in the cleaning blade portion by the toner supply is the same as that in the process station where the secondary transfer residual toner is returned. It has been found that the amount is small and varies depending on the environment (temperature / humidity) in which the image forming apparatus is placed.

Based on the above, the flowchart up to the final determination of the toner supply amount and the effect in the image forming apparatus of the present embodiment are the same as those described in Reference Example 1.

  In this embodiment, since the amount of toner supplied can be reduced at the yellow station, the toner life can be extended accordingly.

  In addition to this embodiment, in addition to the above-described color image forming apparatus of an inline system, the transfer material is not an intermediate transfer body, but a transfer belt that is a transfer member is used to transfer a paper that is a transfer material to a transfer position, Even in an image forming apparatus of a type that directly transfers to paper, if toner remains on the transfer belt surface, it becomes a cause of dirt on the back side of the paper or the like, and a photosensitive drum that collects toner is required. . When there is such a photosensitive drum for collecting toner, for the same reason, in the process station where the residual toner on the transfer belt is collected, the transfer residue remaining on the cleaning blade portion without being transferred to paper or the like. In addition to the toner, a large amount of residual toner on the transfer belt is reversely transferred and recovered, so that the amount of toner to be supplied can be reduced in a process station having a recovery photosensitive drum.

[Example 2]
The present embodiment is characterized in that the amount of toner to be supplied is changed in order to prevent abnormal noise generated in the cleaning blade portion depending on the degree of use of the process cartridge of the image forming apparatus. Configuration of the image forming apparatus of this embodiment will be described in what in Figures 1 and 2 used in the description of Example 1 not equipped with environment detecting means 45.
In the storage medium provided in each process cartridge, information on the degree of use of the developing means (number of printed sheets) and a value for determining the amount of toner to be supplied depending on the degree of use of the developing means (1000 sheets in this embodiment) , Etc. are stored.

In each process station Y, M, C, and Bk, the toner image creation method for preventing abnormal noise in the cleaning unit is the same as that described in Reference Example 1.

  When each process cartridge is at the beginning of its life and the toner is in its initial state, an appropriate amount of external additive is adhered compared to the toner at the end of its life, and good charging and fluidity can be obtained, resulting in good transfer efficiency. There may be a small amount of toner remaining on the cleaning portion due to a small amount of toner remaining after transfer, and abnormal noise is likely to occur.

In the example ( 2 ), each process cartridge has an unused life with respect to 10,000 sheets at a temperature of 23 ° C. and a humidity of 60% (normal temperature and normal humidity). To prevent abnormal noise in the cleaning blade, supply the toner in the rotating direction of the photosensitive drum to a length of 24 mm at the yellow station and 20 mm at the other stations. Abnormal noise is eliminated.

  As described above, in the in-line image forming apparatus, the toner supply amount necessary for preventing the abnormal noise generated in the cleaning blade portion by supplying the toner differs in each process station and also according to the degree of toner use. I understood it. Therefore, it is preferable to correct the amount of toner supplied according to the amount of toner used. In this embodiment, the correction value of the toner amount supplied at each process station is the same, but it is preferable that the correction value is changed for each process station according to the characteristics of the toner of each color as described above.

  Based on the above, the final toner supply amount determination in the image forming apparatus of this embodiment was performed according to the procedure shown in the flowchart of FIG. The control described in this flowchart is the same for each process cartridge. In addition, the storage medium provided in each process cartridge stores information on the degree of use of the process cartridge (number of printed sheets) necessary for switching the amount of supplied toner, the number of printed sheets 1000 when switching, and the like. In the present embodiment, the number of printed sheets for switching the amount of supplied toner is set to 1000. However, the number of prints is not limited to this, and may be arbitrarily set according to the material of the cleaning blade, the contact condition with the photosensitive drum, the toner prescription, and the like. Can be set.

  When image formation starts (S21), it is determined whether the number of printed sheets read from the storage medium provided in the process cartridge is 1000 or less (S22). If it is 1000 sheets or less, the time to turn off the charging bias previously determined when the temperature is 23 ° C., the humidity is 60%, and the number of printed sheets is 5000 sheets (0.07 seconds for the yellow station, 0.05 seconds for the other stations) ) For 0.05 seconds (S23). It is also possible to change this time for each station (for example, 0.07 seconds for the yellow station and 0.05 seconds for the other stations).

  Based on this determination, the time for turning off the final charging bias is determined (S24), toner supply is executed during post-rotation (S25), and the process ends (S26).

  By using the above-mentioned means, an appropriate amount of external additive is attached in the initial state of the toner, and good toner chargeability and fluidity can be obtained. It is possible to reliably prevent the generation of noise in the cleaning blade when there is little. In addition, since the storage medium stores a value for determining the amount of toner to be supplied based on the number of prints, the storage medium is also incorporated in the process cartridge in accordance with the characteristics of the developing means incorporated in the process cartridge. It is possible to change the judgment for changing the amount of toner to be supplied without changing various settings of the main body of the image forming apparatus simply by changing the value in the image.

  In this embodiment, it is determined whether to increase the time for turning off the charging bias according to the number of printed sheets. However, this may be performed by counting the pixel count or the exposure time. Further, in this embodiment, it is determined whether or not the time for turning off the charging bias is increased based on whether or not the number of printed sheets is within 1000 sheets. However, as more detailed control, a plurality of toner supply amount change timings are provided and gradually increased. Control may be performed so as to reduce the time for turning off the charging bias depending on the number of printed sheets.

Further, as in the present embodiment, the change in the toner supply amount is not limited to the number of printed sheets, but the environment detection means is provided as described in Reference Example 1 and can be used to change the toner supply amount together with the temperature and humidity. Easy to guess.

In this embodiment, a cleaning blade is used as a cleaning unit. However, the present invention can be applied to all cleaning units that can reduce noise between the image carrier and the cleaning unit by supplying toner to prevent noise. It is.
In the embodiment, the developing devices 4a to 4d are used as the developer supply means. However, an original developer supply means may be provided.

1 is a configuration diagram of a multicolor image forming apparatus of Reference Example 1. FIG. 4 is a cross-sectional view of a process cartridge that is detachable from the multicolor image forming apparatus of Reference Example 1. FIG. 6 is a timing chart showing operation timing of Reference Example 1. 6 is a timing chart showing operation timing of Reference Example 1. 6 is a timing chart showing operation timing of Reference Example 1. 6 is a flowchart showing a flow until a toner supply amount determination in Reference Example 1; 1 is a configuration diagram of a multicolor image forming apparatus according to Embodiment 1 of the present invention. FIG. 3 is a flowchart illustrating a flow up to determination of a toner supply amount according to the first exemplary embodiment.

1a to 1d Photosensitive drum 2a to 2d Charger 3a to 3d Writing device (exposure device)
4a to 4d Developing device 6a to 6d Photosensitive drum cleaning blade 8a to 8d Transfer roller 10 Transfer belt (transfer material carrier)
10 'Intermediate transfer belt (intermediate transfer member)
12 Transfer belt cleaning blade 20a to 20d Process cartridge 44 Secondary transfer toner charging roller 45 Environment detection means 46a to 46d Storage medium P Transfer material Y, M, C, Bk Process station (image forming means)

Claims (12)

Transfer that sequentially transfers a plurality of image carriers carrying electrostatic latent images and a developer image visualized based on the electrostatic latent images on the plurality of image carriers to an intermediate transfer member And an image forming apparatus having a plurality of cleaning blades for cleaning the developer remaining on the plurality of image carriers.
A developing agent supply means capable of supplying the developer to the non-image forming region on said plurality of image carriers,
A developer charging roller for charging the developer remaining on the intermediate transfer member;
Have
The intermediate transfer member is cleaned by collecting the developer charged by the developer charging roller with an electric field on the collecting image carrier among the plurality of image carriers.
The amount of developer supplied to the non-image forming area on the recovery image carrier by the developer supply means is greater than the amount of developer supplied to the non-image formation area on the image carrier other than the recovery image carrier. An image forming apparatus characterized by having a small amount. Transfer that sequentially transfers a plurality of image carriers carrying electrostatic latent images and a developer image visualized based on the electrostatic latent images on the plurality of image carriers to a member to be transferred Means,
An image forming apparatus comprising: a conveying member that carries and conveys the transferred member to a transfer position of the plurality of image carriers; and a plurality of cleaning blades that clean the developer remaining on the plurality of image carriers.
Developer supply means capable of supplying a developer to non-image forming areas on the plurality of image carriers;
A developer charging roller for charging the developer adhering to the conveying member;
Have
The developer charged by the developer charging roller is recovered by an electric field on a recovery image carrier among the plurality of image carriers, whereby the transport member is cleaned,
The amount of developer supplied to the non-image forming area on the recovery image carrier by the developer supply means is more than the amount of developer supplied to the non-image formation area on the image carrier other than the recovery image carrier. An image forming apparatus characterized by a small amount. The recovery image bearing member, according to claim 1, characterized in that disposed the most upstream with respect to the moving direction of the transfer member in a surface facing the transfer member and the plurality of image bearing members Or the image forming apparatus according to 2; It said developer supply means, the image forming apparatus according to any one of claims 1 to 3, characterized in that the developing means for visualizing the developer image on the basis of the electrostatic latent image. Claims wherein having an environment detecting means for detecting an environment where the image forming apparatus is placed, characterized in that the detection based on the result of the developer supply means a developing agent amount correction supplied by the environment detecting means Item 5. The image forming apparatus according to any one of Items 1 to 4 . The image forming apparatus according to claim 5 , wherein the environment is humidity. Any of claims 1 to 6, characterized in that said developer supply means based on the degree of use of a developing means for visualizing the original developer image an electrostatic latent image is a developer amount correction supplies The image forming apparatus according to claim 1. The developer supplied to the non-image forming area on the image carrier is a developer supplied from the developer supply unit by an electric field between the developer supply unit and the image carrier. the image forming apparatus according to any one of claims 1 to 7. Integrating at least said image bearing member and the cleaning means, the image forming apparatus according to any one of claims 1 to 8 to the image forming apparatus main body and a process cartridge detachably mountable. The image forming apparatus according to claim 9 , wherein the process cartridge includes a storage medium storing information for determining a developer amount to be supplied to the image carrier. The image forming apparatus according to claim 10, wherein the information is a relationship between temperature or humidity and an amount of the developer supplied to the image carrier determined according to the temperature or humidity. The process cartridge includes a developing unit that visualizes a developer image based on an electrostatic latent image, and the information includes at least one of a usage of the developing unit and an identification number of the cartridge. The image forming apparatus according to claim 10 or 11 .