JP2007011184A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus that satisfies color registration performance (restraining of color shift), obtains an image of stable image quality, and contributes to the extension of the life of developer. <P>SOLUTION: The image forming apparatus with a tandem configuration forms a full color image in such a manner that an exposure means conduct exposure corresponding to image data onto the surfaces of image carriers charged by a charging means, thereby forming electrostatic latent images, the electrostatic latent images are turned into toner images by a developing means, subsequently the toner images are transferred onto a transfer body, and the plurality of toner images are superposed one on another on the body. The image forming apparatus includes a first mode and a second mode that can be selectively used. In the first mode, rotation bodies disposed in contact with the image carriers, other than the transfer body, are driven during the transfer process. In the second mode, the rotation bodies are turned on or off during the transfer process. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine and a printer, and more particularly to a tandem image forming apparatus capable of forming a full-color image.

  It has a plurality of image forming means such as an image carrier, charging means, exposure means, developing means, transfer means and the like, and is provided with an intermediate transfer body composed of, for example, an intermediate transfer belt. For image formation, yellow (Y), cyan (C) Magenta and black (BK) toner images are formed on the corresponding image carrier, and then sequentially superimposed on the intermediate transfer member to form a full-color image, which is then transferred onto, for example, transfer paper An image forming apparatus having a tandem configuration that can obtain a final image is well known.

  In such an image forming apparatus, a rotating body that comes into contact with the image carrier, for example, developing means (specifically, development that is carried on its own surface and in contact with the image carrier via another developer). Sleeve), a charging roller as a charging means, a cleaning brush, or the like. When these rotating bodies are turned on and off during the transfer process, the rotational angular velocity (agrees with the peripheral speed) of the image carrier. As a result, there is a problem that color misregistration occurs in superposition of toner images and image quality is deteriorated.

  On the other hand, there is a high demand for a long life of the developer and the apparatus.

  In order to extend the life of the developer and the device, the image forming apparatus of single color recording detects the presence / absence of image writing and defers the driving of the developing means until the image writing occurs. Proposals have been made to make it as short as possible (see, for example, Patent Document 1).

  In addition to prolonging the life of the developer and the apparatus, the following proposal has been made as a countermeasure for color misregistration caused by slip between the intermediate transfer member and the drum-shaped image bearing member. Yes.

That is, after all of the plurality of developing units start driving the photosensitive member and the transfer belt and from the development timing of the photosensitive member where the transfer target reaches the earliest, the transfer belt is moved from the developing nip position of the photosensitive member. This is a control method in which the developing clutch is turned on before the time of the movement time of the photosensitive member to the pressure contact portion and the suction time of the developing clutch connecting the developing means to the system for transmitting the power of the electric motor. (For example, refer to Patent Document 2).
JP-A-5-134529 However, when the technology of Patent Document 1 is applied to an image forming apparatus having a tandem configuration, the life of the developer can be expected, but the developing means is turned on and off during image formation, so that the image bearing There was a problem that color misregistration occurred with changes in the peripheral speed of the body.

  In addition, the technique disclosed in Patent Document 2 can contribute to the improvement of color misregistration, but when a function such as one intermittent printing, double-sided printing, or cover insertion mode is used. Since the idling time of the developing means is increased as compared with a conventionally known method, it works disadvantageously for extending the life of the developer, and further tends to cause deterioration in image quality such as fogging and image distortion. Had.

  The present invention has been made in view of the above-described problems. An object of the present invention is an image forming apparatus having a tandem configuration, which satisfies color resist performance (suppression of color misregistration) and performs one intermittent printing or Therefore, an object of the present invention is to provide an image forming apparatus capable of obtaining a stable image quality with reduced fog and image distortion as much as possible even when performing double-sided printing, etc., and contributing to a long life of the developer.

The object of the present invention can be achieved by the following constitution.
(Claim 1)
The surface of the image carrier charged by the charging unit is exposed according to the image data by the exposure unit to create an electrostatic latent image, and the electrostatic latent image is converted into a toner image by the developing unit. In an image forming apparatus having a tandem configuration that can transfer a toner image onto a transfer target and superimpose a plurality of toner images on the transfer member to form a full color image.
A first mode for driving a rotating body that is in contact with the image carrier other than the transfer target during execution of the transfer process, and a second mode for turning on and off the rotating body during execution of the transfer process. And an image forming apparatus characterized by being selectively usable.
(Claim 2)
The rotating body includes a powder supply unit that supplies powder onto the image carrier, a developer carrier that carries a developer, a charging roller that charges the surface of the image carrier, and a surface of the image carrier. The image forming apparatus according to claim 1, further comprising a cleaning brush for cleaning.
(Claim 3)
The image forming apparatus according to claim 1, wherein the selection between the first mode and the second mode is automatically switched according to a use situation.
(Claim 4)
The image forming apparatus according to claim 1, wherein the selection between the first mode and the second mode is automatically switched based on an image formation history.
(Claim 5)
The surface of the image carrier charged by the charging unit is exposed according to the image data by the exposure unit to create an electrostatic latent image, and the electrostatic latent image is converted into a toner image by the developing unit. In an image forming apparatus having a tandem configuration that can transfer a toner image onto a transfer target body and superimpose a plurality of toner images on the transfer body to form a full color image.
During the transfer process, a first mode for driving a rotating body that is in contact with the image carrier other than the transfer object, and a second mode for turning the rotating body ON and OFF during the transfer process. The mode can be selected and used via the switching means, and
Periodically forming a resist patch on the transferred material,
Read the resist patch with an optical sensor,
An image forming apparatus having a configuration in which switching control between the first mode and the second mode is performed according to a reading result.
(Claim 6)
The surface of the image carrier charged by the charging unit is exposed according to the image data by the exposure unit to create an electrostatic latent image, and the electrostatic latent image is converted into a toner image by the developing unit. In an image forming apparatus having a tandem configuration that can transfer a toner image onto a transfer target body and superimpose a plurality of toner images on the transfer body to form a full color image.
During the transfer process, a first mode for driving a rotating body that is in contact with the image carrier other than the transfer object, and a second mode for turning the rotating body ON and OFF during the transfer process. A mode can be selected and used, and
The image forming apparatus is characterized in that the mode is selected and used by a switching means that can be manually operated.
(Claim 7)
The image forming apparatus according to claim 1, wherein the transfer target to which the toner image formed on the image carrier is transferred is an intermediate transfer member.

  The invention according to claim 1 includes a color resist priority control mode (corresponding to the first mode) with emphasis on the color resist and image quality stability, in other words, a material durability priority control mode (corresponding to the second mode). Therefore, it is possible to appropriately cope with a reduction in color misregistration and, for example, a longer life of the developer.

  In the invention according to claim 5, since the resist patch is periodically created and the first mode and the second mode can be switched according to the result, the time point can be obtained without bothering the customer. Therefore, the apparatus can be set in the most suitable state, and the convenience is high.

  In the invention according to claim 6, since the first mode and the second mode can be manually switched, it is possible to create and provide an image according to the customer's request.

  Next, a first embodiment according to the present invention will be described in detail with reference to the drawings.

  FIG. 1 is an overall view of an image forming apparatus having a tandem configuration capable of creating a full-color image. An image forming apparatus main body GH includes a plurality of sets of image forming units 10Y, 10M, 10C, and 10K, a belt-shaped intermediate transfer member 6, and the like. , Sheet feeding and conveying means, fixing means 24 and the like.

  The image forming unit 10Y that forms a yellow image includes an image carrier (Y) formed of a drum-type photoconductor, a charging unit 2Y, an exposure unit 3Y, and a developing unit disposed around the image carrier. Means 4Y and cleaning means 8Y comprising a blade are provided.

  The image forming unit 10M that forms a magenta image includes an image carrier 1M made of a drum-type photoconductor, a charging unit 2M, an exposure unit 3M, a developing unit 4M, and a cleaning unit 8M made of a blade.

  The image forming unit 10C that forms a cyan image includes an image carrier 1C made of a drum-type photoconductor, a charging unit 2C, an exposure unit 3C, a developing unit 4C, and a cleaning unit 8C made of a blade.

  The image forming unit 10K that forms a black image includes an image carrier 1K made of a drum-type photosensitive member, a charging unit 2K, an exposure unit 3K, a developing unit 4K, and a cleaning unit 8K made of a blade.

  The above-mentioned image carrier for each color, charging means, exposure means, and developing means constitute an image forming means, and the charging means and exposure means for each color constitute a latent image forming means.

  Each of the exposure means described above comprises a semiconductor laser exposure apparatus equipped with a laser light source, an fθ lens, a collimator lens, a polygon mirror, and the like.

  Each of the developing means described above includes, for example, a developer carrier S composed of a sleeve capable of carrying a two-component developer mainly composed of toner and a carrier on its surface and transporting it to the development area, and the developer carrying member. The developing device includes a magnet (not shown) provided in a fixed position inside the body S.

  The magnet is disposed so as to perform a function of attracting and holding the developer on the developer carrier S and a function of automatically removing the developer after the development processing from the developer carrier S. However, the configuration is well known and will be omitted.

  The intermediate transfer body 6 is rotatably supported by a plurality of rollers.

  In the present embodiment, the toner image formed on the image carrier is transferred onto the intermediate transfer member 6 and then transferred onto the final transfer material, for example, transfer paper. Although the intermediate transfer member can be said to be a transfer target like the transfer paper, the intermediate transfer member is hereinafter referred to as an intermediate transfer member and the final transfer material is referred to as a sheet in order to avoid confusion in expression.

  First transfer means 7Y, 7M, 7C, and 7K made of conductive rollers are disposed inside the intermediate transfer body 6 and at positions facing the above-described image carriers.

  Further, for example, a predetermined current value is selected and applied to the conductive roller from a current value table in which a matrix is formed with temperature and humidity and a counter.

  Reference numeral 8A denotes a cleaning means comprising a blade for keeping the surface of the intermediate transfer member 6 clean.

  The first transfer means is biased by a spring so as to press the intermediate transfer body 6 against the image carrier.

  The fixing unit 24 includes a roller-type fixing device having a first heating roller and a second heating roller or a second roller provided so as to be capable of rotating in pressure contact with the first heating roller.

  In the figure, reference numerals 5Y, 5M, 5C, and 5K denote toner replenishing means for replenishing the corresponding color toner to the developing means for each color.

  An image reading device YS is shown in the upper part of the image forming apparatus main body GH, and includes an automatic document feeder 210 and a document image scanning exposure device 220.

  d is a document, which is placed on a document placing table 211 provided in the automatic document feeder 210, separated one by one by a separating means without reference numerals, and a conveying means comprising rollers and a rotatable drum 212. Etc., and is read by the original image scanning exposure apparatus 220.

  The document image scanning exposure apparatus 220 includes a first block 221 integrally including an irradiation lamp and a first mirror, a second block 223 integrally including a second mirror and a third mirror, and imaging. Lens 225 and a line image sensor CCD.

  In other words, the image of the document d in the transported state is irradiated by the irradiation lamp at the reading position, reaches the imaging lens 225 via the three mirrors described above, and the line is sequentially formed by the action of the imaging lens 225. The image is formed on the image sensor CCD and read.

  The image information (analog signal) read by the line image sensor CCD is converted into analog processing, A / D conversion, shading correction, in an image processing unit provided in a control means (hereinafter also referred to as a control unit) SG. After appropriate processing such as image compression processing, it is stored in the storage means in the control means SG.

  The image data stored in the storage means is read in accordance with an image forming process and sent to exposure means (3Y, 3M, 3C, 3K) as image writing unit means.

  The exposure means irradiates the surface of the image carrier (1Y, 1M, 1C, 1K) with a laser beam modulated in accordance with image data, so that an electrostatic latent image corresponding to the image data is formed on the image carrier. To create.

  The automatic document feeder 210 is provided with an automatic double-sided document conveying means, and reads the contents of a large number of documents d fed from the document table 211 at a time and stores them in the storage means. Therefore, it can be conveniently used when copying the contents of a large number of originals with the copying function or when transmitting a large number of originals d with the facsimile function.

  In the figure, SG is a control means (hereinafter also referred to as a control unit) including a computer, and outputs information of sensors (actuators) such as sequence control for image formation, conveyance control of paper P, heating control of fixing means, and the like. Substantially all of the control can be executed, such as taking in motor drive control.

  Further, the control means SG sets the drive control mode of the rotating body in contact with the image carrier to the usage environment (synonymous with usage status: temperature / humidity, internal temperature, etc.) and usage history (synonymous with image formation history: number of prints). Or the sliding movement of the developer, or the drive control of the rotating body is performed according to the selection of a mode setting button that can be manually selected by the user as required. However, details will be described later.

  Next, the overall operation associated with the image forming process will be briefly described, including members or means not described.

  For convenience, when there is no need to classify a plurality of means such as an exposure means or an image carrier, they are simply referred to as an exposure means 3 and an image carrier 1.

  When the original is read by the line image sensor CCD as described above, and the exposure unit 3 performs exposure according to the image data generated by the image processing unit, an electrostatic latent image is created on the image carrier 1. The

  The exposure is performed for each color at an appropriate timing, and the created latent image is converted into a toner image for each color by the developing means 4.

  These toner images are sequentially transferred to the intermediate transfer member 6 under the action of the first transfer means 7 and are superimposed on the intermediate transfer member 6 to form a full-color image.

  The surface of the image carrier 1 that has passed through the transfer region is cleaned by the cleaning means 8 and is prepared for the next image creation.

  On the other hand, according to the image forming process, the paper P stored in the paper feeding cassette 20 is fed by the paper feeding means 21 and passes through the conveying means 22A, 22B, 22C comprising a pair of conveying rollers to the registration roller 23. The color image area on the intermediate transfer body 6 and the paper P are conveyed toward the transfer area with the start of rotation of the registration roller 23 driven at the timing when the sheet P overlaps.

  In the transfer area for the sheet P, a transfer roller 7A that is pressed against a backup roller (not shown) located in the intermediate transfer body 6 with a belt interposed therebetween is prepared as a second transfer means. For example, a predetermined current value selected from a current value table in which a matrix is formed by temperature and humidity and a counter is applied.

  The color image formed on the intermediate transfer body 6 is transferred to the paper P by the action of the second transfer means 7A.

  Thereafter, the paper P is heated and pressed by the fixing means 24, and the toner image is fixed on the paper P and discharged to the paper discharge tray 26 by the paper discharge roller 25.

  The intermediate transfer body 6 after the image is transferred onto the paper P by the transfer roller 7A as the second transfer means is cleaned by the cleaning means 8A and prepared so as to function as a new intermediate transfer body.

  Such an operation is repeated as many times as necessary, and the toner for each color consumed during this period depends on the output of a sensor provided in relation to each developing device, for example, a toner concentration sensor capable of detecting magnetic permeability. New toner is replenished from the toner replenishing means 5 and the development processing function is maintained.

  Incidentally, the developer carrier S constituting the developing means 4 is a rotating body that rotates while contacting the image carrier 1 through the developer. In the present embodiment, two drive control modes are used. It is configured so that it can be selected.

  In the first mode, driving of all developing means is started (ON) from a time before all color toner images are transferred to the intermediate transfer body 6, and all color toner images are transferred to the intermediate transfer body 6. This is a drive control mode in which the driving of all the developing means is stopped (OFF) after complete transfer.

  In other words, as viewed from the overall operation of the apparatus for image formation, during the transfer process, the drive of the rotating body (in this case, the developer carrying body) in contact with the image carrying body 1 is turned on. It is a mode to keep in.

  In this mode, the rotation (peripheral speed: synonymous with angular velocity) of the image carrier 1 can be made constant at all times, so that the color toner images can be well superimposed (color resist) (color resist priority control). Mode).

  The second mode is a drive control mode in which the driving of the developing means for each color is kept ON for a time necessary for developing the latent image for each color, and the driving is turned OFF when the time has passed.

  In other words, even while any one color toner image is being transferred to the intermediate transfer body 6, the rotating body (in this case, the developer carrying body) that is in contact with the image carrier 1. In this mode, the drive is turned on and off.

  In this mode, since the target developing means is not driven in a time zone that is not necessary for the development processing, the life of the developer can be extended, and as a result, a stable image quality can be provided. (Material durability priority control mode: image quality priority mode).

  For the drive control of the rotating body as described above, the drive control mode is automatically switched according to the usage environment (temperature / humidity, internal temperature, etc.) and usage history (number of prints, developer sliding distance, etc.). As described above, it can be controlled or selected by selecting a mode setting button.

  Regarding automatic switching (selection), data that has been confirmed by experiments is tabulated, and color misregistration (color resist) is likely to occur due to changes in temperature and humidity and the relationship between the number of prints and developer sag. If the control unit SG detects (determines) a condition or a condition that is a problem for extending the life of the developer, it can be achieved by appropriately changing the selected first mode and second mode. .

  For example, when image formation is performed in the second mode, a resist patch is produced on the intermediate transfer member periodically, for example, every 1000 prints, and when the controller detects that the color resist has deteriorated, This can be achieved by changing the second mode to the first mode.

  Then, the mode of subsequent image formation is that the mode in which the idling time of the developing means (substantially the developer carrying member) increases as in the case of one intermittent printing or double-sided printing has continued a predetermined number of times. When detected by the control unit SG, the first mode is switched to the second mode again, thereby making it possible to achieve both color resist performance and image quality stability (which also extends the life of the developer).

  For switching between the first and second modes by the user, for example, a mode setting button (including a mode selection setting means touch panel type) is prepared on an operation panel provided in the apparatus body. When the control unit SG detects a state in which the mode setting button is operated / selected by the user, the mode setting button may be forcibly switched to the first mode or the second mode corresponding thereto.

  In the present embodiment, the driving timing of the developing means is determined as follows.

  That is, even in the second mode in which the driving time is short, the developing means is driven (ON) earlier by that amount in consideration of the time when the output of the toner density sensor is stabilized, and the developing by the developing means is performed. The processing time is set so that a stable output of the toner density sensor can be secured.

  Here, the driving time (drive ON / OFF) of the developing means (meaning the rotating body) in the first mode and the second mode described above, and the time during which the transfer from the image carrier to the intermediate transfer body is performed. The relationship is shown in FIG. 2 and FIG.

  FIG. 2 shows the driving time of the developing means for each color in the first mode (color resist priority control mode), and the transfer time for transferring the toner image on the image carrier formed for each color to the intermediate transfer member. FIG. 3 is a diagram illustrating the relationship between the developing unit drive time for each color in the second mode (material durability priority control mode: image quality priority mode) and the toner on the image carrier formed for each color. It is a figure which shows the relationship with the transfer time which is transferring the image to an intermediate transfer body.

  First, in FIG. 2, when the image carriers Y, M, C, and K for each color start to rotate at a predetermined timing, the developing unit starts driving at substantially the same timing.

  Next, when exposure Y, M, C, K for each color is performed, a latent image is sequentially formed on the image carrier already charged by a charging unit (not shown), and the latent image is The toner image is formed by the developing means, and then sequentially transferred onto the intermediate transfer member by the action of the first transfer means (transfer process).

  After the transfer to the intermediate transfer member is completely completed, the drive for the image carrier and the developing means is turned off.

  As understood from this, since the developing means (rotating body) that contacts the image carrier through the developer layer is continuously driven until the primary transfer is completed, the load on the image carrier is always constant. Therefore, smooth rotation of the image carrier is guaranteed.

  In FIG. 3, the driving time of the developing means is turned on only during the time zone required for development, and is turned off immediately after that, similarly to the driving time of the exposure means and the first transfer means.

  For example, the black developing unit is turned on while the yellow image is being transferred, and the yellow developing unit is powered off during the magenta image transfer (during the transfer process).

  In this way, if any developing means is turned on or off while any color image (color toner) is being transferred onto the intermediate transfer body (transfer body), depending on the case, The color resist may be affected considerably.

  Next, a second embodiment according to the present invention will be described with reference to FIG.

  Since the image forming apparatus according to the second embodiment is based on the configuration shown in FIG. 1, FIG. 4 shows only the main part around the image carrier.

  In the first embodiment described above, the rotating member that contacts the image carrier is only the developing means. However, in the second embodiment, the powder supply means for supplying the powder onto the image carrier, the charging The configuration has three rotating bodies of a roller and developing means.

  In addition, about the powder supply means etc. concerning 2nd Embodiment including the various basic composition omitted in description of 1st Embodiment, it arranges here again and supplements.

  Image carrier: produced by applying a 60 mm diameter, organic semiconductor layer in which a phthalocyanine pigment is dispersed in polycarbonate.

            The film thickness of the photoreceptor layer including the charge transport layer is 25 μm.

      Exposure: Laser scanning method, semiconductor laser (LD) power is 300 μW.

  Developing means: A magnetic brush type configuration using a two-component developer mainly composed of an emulsion polymerization toner and a resin coating carrier.

            The development bias voltage for the developer carrying member (sleeve) was superimposed with direct current (-200 V to -700 V) and alternating current (0.5 kVp-p to 2.0 kVp-p, 2 kHz to 7 kHz).

  Intermediate transfer body: Consists of a seamless semiconductive resin belt. (Material is polyimide, surface resistivity 1E + 11Ω / □, volume resistivity 1E + 8Ω / cm), tension 5kg f.

  First transfer means: a conductive roller made of a foam roller having a diameter of 20 mm. Roller pressing 500g f. Select and apply a predetermined current value from a current value table that is a matrix of temperature and humidity and a counter.

Second transfer means: conductive roller (resistance value 1 × 10 ⁻⁷ Ω). Select and apply a specified current value from a current value table that is a matrix of temperature and humidity and a counter.

  In FIG. 4, 2 (2Y, 2M, 2C, 2K) is a charging roller as a charging means, and a known charging roller can be used. At the time of charging, power is supplied from a power source (not shown), and the image carrier A predetermined potential is applied to the surface. The charging roller is always in contact with the surface of the image carrier, and potential application (charging) is applied in a rotating state.

  Since the construction of the developing means 4 (4Y, 4M, 4C, 4K) has been described above, it will be omitted.

  Reference numeral KB indicates a powder supply means. The powder supply means KB is a means for supplying a lubricant onto the image carrier after the color toner image is transferred to the intermediate transfer body and cleaned by the cleaning means. Between.

  Further, the form of the powder supply means is a structure in which hair is planted around a cylindrical support member such as a fur brush (hereinafter, for convenience of explanation, the powder supply means is referred to as a lubricant application brush), and the length of the brush portion is It is 332 mm and is supported so as to be rotatable with an appropriate holder.

  Further, the drive source of the lubricant application brush is the same as the drive source of the developing means, and the drive (ON, OFF) of both is interlocked.

  In other words, if the driving of the developing unit is turned on, the driving of the lubricant applying brush is also turned on. If the driving of the developing unit is turned off, the driving of the lubricant applying brush is also turned off.

In addition, although the fiber diameter of the fiber which comprises the said application brush was 6.25d, the density was 100k piece / 2.54cm < ² > and the outer diameter was 12 mm, these conditions can be determined suitably.

  The rotation direction of the lubricant application brush is a counter direction with respect to the rotation direction of the image carrier.

  Incidentally, the lubricant supplied to the image carrier via the lubricant application brush is, for example, zinc stearate, and the lubricant is formed in a block shape.

  As is well known, the role of the lubricant is to improve transferability (slow-out) and to ensure cleaning performance.

  In addition to the zinc stearate, magnesium stearate, strontium stearate, or the like can be used and is not limited as long as it can perform the above function.

  And it is urged | biased by the direction of the lubricant application brush with a suitable spring so that it may always contact with the outer peripheral part of the said lubricant application brush.

  Therefore, when the lubricant application brush starts to rotate, the tip of the brush scrapes the surface of the block lubricant, bringing the powder held in the powder state onto the surface of the image carrier, causing collision and rubbing with the image carrier, etc. Then, the lubricant is adhered to the image carrier.

  The block-like lubricant has a size of 8 mm in width, 5 mm in height, and 332 mm in length, and the hardness is equivalent to F to HB of pencil hardness.

  Naturally, each of the charging roller, the developing means, and the lubricant application brush is prepared in an image forming section for each color.

  Assuming the configuration of the image forming apparatus of FIG. 1, the operation of the image forming apparatus having image forming means arranged around the image carrier as shown in FIG. 4 will be briefly described.

  Under the control of the control unit SG, when the image carriers in the image forming units 10Y, 10M, 10C, and 10K start to rotate, a predetermined driving voltage is applied to the charging roller accordingly, thereby the image carrier. The surface is uniformly charged.

  Next, when exposure according to image data is performed for each color at a predetermined timing, an electrostatic latent image is formed on the charged surface.

  The electrostatic latent image is visualized by the developing unit, and sequentially transferred onto the intermediate transfer member by the action of the first transfer unit, and a superimposed color image is produced on the intermediate transfer member.

  The subsequent processes until the image is formed on the paper P are the same as those in the first embodiment.

  A lubricant is applied to the image carrier having undergone the transfer process on the intermediate transfer member via a lubricant application brush.

  As a result, the toner particles remaining on the image carrier are weakened in adhesion and easily removed by the cleaning means, and the surface of the image carrier is prepared for the next image formation.

  The drive control of the three rotating bodies described above can be selectively switched between the first mode and the second mode automatically or by manual operation, as described in connection with the first embodiment. Can do.

  Here, the relationship between the driving time of the rotating body (driving ON / OFF) in the first mode and the second mode described above and the time during which the transfer from the image carrier to the intermediate transfer body is shown in FIG. As shown in FIG.

  FIG. 5 shows the relationship between the driving time of the developing means and the lubricant application brush for each color in the first mode and the transfer time for transferring the toner image on the image carrier formed for each color to the intermediate transfer member. FIG. 6 is a diagram showing the driving time of the developing means and lubricant application brush for each color in the second mode, and the transfer in which the toner image on the image carrier formed for each color is transferred to the intermediate transfer body It is a figure which shows the relationship with time, and respond | corresponds to FIG. 2, FIG.

  The reason why the driving time of the charging roller is not shown in the drawing is that the rotation is turned on and off in conjunction with the image carrier.

  However, this does not exclude the fact that the charging roller is controlled to be turned on and off at the time of charging.

  By the way, when the image formation is not performed, stopping the driving of the rotating body as described above to extend the life of these replacement parts not only lowers the running cost but also reduces the image quality due to the deterioration of the replacement parts as much as possible. This makes it possible to provide images with stable image quality at a low cost.

  The deterioration in image quality due to the deterioration of the rotating body is, for example, uneven image density due to uneven charging if the charging roller is deteriorated, and if the deterioration of the lubricant application brush, the lubricant is applied to the image carrier. This is due to a decrease in cleaning performance due to a decrease in performance and a transfer failure called “missing”.

  Further, in the developing means, it is considered that there is almost no deterioration of the rotating body. However, as described in the first embodiment, the developer is deteriorated depending on the driving time and the image quality is lowered.

  As described above, when image formation is not performed, it is possible to maintain stable image quality by stopping the driving of the rotating body that is in contact with the image carrier. Impact becomes a problem.

  Reference is now made to FIG. 6 relating to the second mode. The developing means 4 (4Y, 4M, 4C, 4K) for each color and the lubricant application brush KB are turned on almost simultaneously at a predetermined timing from the start of the image forming process, and are driven almost simultaneously when the time necessary for processing has passed. It is turned off.

  In the figure, two wavy lines (vertical lines) indicate the time from the start of transfer to the end of transfer when all color toners are transferred from the image carrier to the intermediate transfer member.

  (1), (2), (3), and (4) shown on the lower side of the figure show the driving of any developing means and lubricant application brush while any other color toner image is being transferred. Indicates the point at which control occurs.

  For example, (1) shows a point (timing) when driving of the developing means 4K and the lubricant application brush 4 relating to black toner image formation is turned on during transfer of the yellow toner image, and (2) is magenta. Points when the driving of the developing means 4Y and the lubricant coating brush related to yellow toner image formation are turned off during the transfer of cyan, black toner images are shown.

  Similarly, (3) shows a point at which the driving of the developing means 4M and the lubricant application brush related to magenta toner image formation are turned off during the transfer of cyan and black toner images, and (4) A point at which driving of the developing unit 4C and the lubricant applying brush related to the cyan toner image formation is turned off during the transfer of the black toner image is shown.

  FIG. 7 (7a, 7b, 7c, 7d) shows the color resist performance of the points (1) to (4).

  This is the color resist performance when measured with a dedicated chart for measuring A3 size color resist.

  FIG. 7A relates to a yellow toner image, (b) relates to a magenta toner image, (c) relates to a cyan toner image, and (d) relates to a black toner image.

  In the figure, the vertical axis represents the amount of positional deviation from the average reference (unit μm: synonymous with the amount of color deviation), and the horizontal axis represents the distance (unit: mm) in the sub-scanning direction of A3 size.

  Also, (1) to (4) in the figure indicate positions on the image corresponding to the points (1) to (4), and the wavy line in each figure indicates the allowable range of positional deviation (in the final image). When viewed, it indicates the range where color misregistration is not visible.

  As described above, the second mode is the image quality priority mode, but it can be seen that registration shift (position shift) occurs at the position corresponding to the point.

  As described above, in the second mode, it is possible to provide a stable image without extending the durability of replacement parts and causing defects related to image quality such as density unevenness, cleaning failure, and transfer failure. The performance may be adversely affected.

  This is because when the rotating member in contact with the image carrier is transferring the toner image on the image carrier onto the intermediate transfer member (transfer material) and the drive is turned ON / OFF, This is thought to be because the vibration generated in the image propagates to the image carrier and the toner image on the image carrier is not properly transferred onto the intermediate transfer member.

  This tendency can also be seen in the first embodiment when the rotating member that contacts the image carrier is only the developing means, but the positional shift amount is smaller than that in the present embodiment.

  FIG. 8 shown in the same manner as FIG. 7 is used to see the amount of positional deviation during the drive control (see FIG. 5) of the rotating body in the first mode, in the portion corresponding to the points (1) to (4). However, the positional deviation is greatly improved and is almost within the allowable range, and no positional deviation (color deviation) is felt even when the superimposed full-color image is visually recognized.

  Although the automatic switching control between the first mode and the second mode has been described in the first embodiment, an example will be described more specifically.

  When high temperature and high humidity environment is more likely to cause color shift due to the environment dependence of the intermediate transfer body, the first mode is prioritized in the high temperature and high humidity environment, the second mode is prioritized in the low temperature and low humidity environment, and the normal temperature is normal. In a wet environment, when the developer / material deteriorates, the image quality deteriorates. Therefore, the second mode is given priority when the predetermined number of image forming sheets has passed, and the first mode is given priority before the developer deterioration occurs. That is how to do it.

  For example, assuming an apparatus in which the developer needs to be replaced for image formation of 100,000 sheets, the first mode is given priority up to 70,000 image formations in the room temperature and humidity environment, and thereafter, 100,100 The second mode is given priority up to 10 million sheets.

  In order to achieve the above control, a temperature / humidity sensor and a counter for counting the number of image formations are provided, and their outputs are taken into the control unit SG. It can achieve by comparing and performing control by a control part.

  In addition, as the regular drive control, the second mode is given priority to suppress material deterioration, while the color registration adjustment performed periodically (for example, when the power is turned on in the morning or when environmental changes are detected, or In the above-described color registration adjustment performed every 1,000 prints), when the control unit SG detects a registration shift (color shift), it automatically switches to the first mode, and then the color registration adjustment executed at the next timing. If no color misregistration is detected at this time, it is possible to automatically switch to the second mode again to produce a good image and suppress deterioration of the material.

  Since the mode selection by the user is as described above, a duplicate description is omitted.

  In the first and second embodiments, the intermediate transfer member is interposed. However, the color toner image formed on the image carrier for each color is conveyed at a constant speed by the conveyance belt P. The image may be transferred (first transfer) sequentially and a superimposed color toner image may be produced on the paper P (transfer object), and the present invention is also applicable to an image forming apparatus having such a configuration. Applicable.

  Further, the developer may be a one-component developer instead of a two-component developer. However, in this case, it is not necessary to consider the deterioration of the developer, and it is important to keep the toner image density constant (for maintaining the image density).

  Further, a cleaning brush is considered as a rotating body that contacts the image carrier.

  Furthermore, modifications and applications can be made as appropriate to the configuration exemplified as the present embodiment, and such an aspect is included in the technical idea of the present invention.

1 is an overall view of an image forming apparatus having a tandem configuration capable of creating a full color image. The relationship between the drive time of the developing means for each color in the first mode (color resist priority control mode) and the transfer time for transferring the toner image on the image carrier formed for each color to the intermediate transfer member is shown. FIG. Driving time of the developing means for each color in the second mode (material durability priority control mode: image quality priority mode), and transfer time for transferring the toner image on the image carrier formed for each color to the intermediate transfer member It is a figure which shows the relationship. It is a fragmentary figure which shows 2nd embodiment concerning this invention. FIG. 6 is a diagram illustrating a relationship between a driving time of developing means and a lubricant application brush for each color in a first mode and a transfer time for transferring a toner image on an image carrier formed for each color to an intermediate transfer member. . FIG. 6 is a diagram illustrating a relationship between a driving time of a developing unit and a lubricant application brush for each color in a second mode and a transfer time for transferring a toner image on an image carrier formed for each color to an intermediate transfer member. . It is a figure which shows a color resist performance. It is a figure which shows a color resist performance.

Explanation of symbols

1 Image bearing member 6 Intermediate transfer member (transferred member)
10Y, 10M, 10C, 10K Image forming part KB Powder supply means (lubricant application brush)
S developer carrier SG control unit

Claims (7)

The surface of the image carrier charged by the charging unit is exposed according to the image data by the exposure unit to create an electrostatic latent image, and the electrostatic latent image is converted into a toner image by the developing unit. In an image forming apparatus having a tandem configuration that can transfer a toner image onto a transfer target and superimpose a plurality of toner images on the transfer member to form a full color image.
A first mode for driving a rotating body that is in contact with the image carrier other than the transfer target during execution of the transfer process, and a second mode for turning on and off the rotating body during execution of the transfer process. And an image forming apparatus characterized by being selectively usable. The rotating body includes a powder supply unit that supplies powder onto the image carrier, a developer carrier that carries a developer, a charging roller that charges the surface of the image carrier, and a surface of the image carrier. The image forming apparatus according to claim 1, further comprising a cleaning brush for cleaning. The image forming apparatus according to claim 1, wherein the selection between the first mode and the second mode is automatically switched according to a use situation. The image forming apparatus according to claim 1, wherein the selection between the first mode and the second mode is automatically switched based on an image formation history. The surface of the image carrier charged by the charging unit is exposed according to the image data by the exposure unit to create an electrostatic latent image, and the electrostatic latent image is converted into a toner image by the developing unit. In an image forming apparatus having a tandem configuration that can transfer a toner image onto a transfer target and superimpose a plurality of toner images on the transfer member to form a full color image.
During the transfer process, a first mode for driving a rotating body that is in contact with the image carrier other than the transfer object, and a second mode for turning the rotating body ON and OFF during the transfer process. The mode can be selected and used via the switching means, and
Periodically forming a resist patch on the transferred material,
Read the resist patch with an optical sensor,
An image forming apparatus having a configuration in which switching control between the first mode and the second mode is performed according to a reading result. The surface of the image carrier charged by the charging unit is exposed according to the image data by the exposure unit to create an electrostatic latent image, and the electrostatic latent image is converted into a toner image by the developing unit. In an image forming apparatus having a tandem configuration that can transfer a toner image onto a transfer target and superimpose a plurality of toner images on the transfer member to form a full color image.
During the transfer process, a first mode for driving a rotating body that is in contact with the image carrier other than the transfer object, and a second mode for turning the rotating body ON and OFF during the transfer process. A mode can be selected and used, and
The image forming apparatus according to claim 1, wherein the mode is selected and used by a switching unit that can be manually operated. The image forming apparatus according to claim 1, wherein the transfer target to which the toner image formed on the image carrier is transferred is an intermediate transfer member.

Images