JP4641404B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image of a copying machine, a printer, a recorded image display device, a facsimile machine or the like that develops an electrostatic latent image formed on an image carrier by an electrophotographic method, an electrostatic recording method, or the like to form a visible image. The present invention relates to a forming apparatus.

  Conventionally, a developing process for developing an electrostatic latent image in an image forming process using an electrophotographic method or an electrostatic recording method uses an electrostatic image of an electrostatic latent image to carry charged toner particles. This is a step of forming a developer image (toner image) by moving it on the electrostatic latent image of the body. Of the methods for developing such electrostatic latent images, the two-component development method employing a two-component developer containing toner and carrier as the developer is generally used for full-color copying machines and full-color printers that require high image quality. Is preferably used.

  As an embodiment of a developing apparatus employing this two-component developing method, as shown in FIG. 7, the developer supplied to the surface of the developing sleeve 41 which is a developer carrying member by the developer stirring members 43 and 44 is developed. The magnetic roller is held in the state of a magnetic brush by the magnetic force of a magnet roller (not shown) which is a cylindrical magnetic field generating means included in the sleeve 41, and this is held by the rotation of the developing sleeve 41 with the photosensitive drum 1 which is an image carrier. There is a developing device 4 that is configured to transport to the developing area of the opposing portion and to appropriately maintain the amount of developer transported to the developing area by cutting off the magnetic brush with a blade 42 that is a head height regulating member.

  In such a two-component developing device, the toner consumed by being subjected to the developing operation is appropriately replenished and controlled so that the ratio of the toner and the carrier is kept constant.

  More specifically, the inside of the developing container 40 containing the developer T of the developing device 4 is partitioned into a developing chamber 47 and a stirring chamber 48 by a partition wall 46 extending in the vertical direction. A two-component developer T containing a non-magnetic toner and a magnetic carrier is accommodated. Further, as described above, the screw type first and second developer agitating members 43 and 44 are arranged in the developing chamber 47 and the agitating chamber 48, respectively, and the developer T in the developing chamber 47 and the agitating chamber 48 is disposed. Is stirred and conveyed.

  The first agitating member 43 is disposed substantially parallel to the bottom of the developing chamber 47 along the axial direction of the developing sleeve 41, that is, along the developing width direction, and a blade member is provided in a spiral shape around the rotation axis. The screw structure is rotated and the developer in the developing chamber 47 is conveyed in one direction along the axial direction of the developing sleeve 41 at the bottom of the developing chamber 47.

  The second stirring member 44 has a screw structure in which a blade member is provided in a spiral shape around the rotation axis in a direction opposite to the first stirring member 43, and the first stirring member 43 is provided at the bottom of the stirring chamber 48. And is rotated in the same direction as the first stirring member 43 to transport the developer in the stirring chamber 48 in the direction opposite to the first stirring member 43.

  The second agitating member 44 is already in the agitating chamber 48 with the toner supplied from the toner supply tank 60 to the upstream side in the developer circulation direction in the second agitating member 44 under the developer concentration control. The developer is agitated and conveyed, and the developer concentration (toner concentration), which is the weight of the toner with respect to the total weight of the developer, is made uniform. By this stirring, the toner and the carrier are rubbed, and the toner retains an appropriate charge amount by frictional charging.

  A partition wall 46 exists between the first stirring member 43 and the second stirring member 44, and partitions the inside of the developing container 40 into a developing chamber 47 and a stirring chamber 48. However, as shown in FIG. 3, developer passages 46a and 46b are formed in the partition wall 46 at both ends so that the developing chamber 47 and the stirring chamber 48 communicate with each other. The developer in the developing chamber 47 in which the toner is consumed due to the conveying force of the second stirring members 43 and 44 and the toner concentration is reduced due to the use of the developing operation is transferred from the one passage 46b to the stirring chamber 48. Moving.

  As described above, the developer is circulated between the developing chamber 47 and the stirring chamber 48 by the rotation of the first and second stirring members 43 and 44.

  Conventionally, as a developer concentration detecting means for detecting a toner concentration in a circulating developer, an inductance sensor 45 for detecting a toner / carrier ratio as a toner concentration from a magnetic permeability of the developer is known.

  In the developing device having the above-described configuration, the inductance sensor 45 is provided in the upstream portion of the developer circulation in the stirring chamber 48 as shown in FIG. When it is determined that the toner density detected by the inductance sensor 45 is insufficient with respect to the originally determined target density, the toner replenishment port located immediately downstream of the toner density detection unit of the inductance sensor 45 is set as the insufficient toner amount. The toner is replenished from 6a (FIG. 7). As described above, the toner concentration in the developer is controlled to a constant level by detecting the toner concentration of the developer in the developing container 40 and replenishing the shortage from the toner replenishing means, so-called inductance ATR. .

  By the toner replenishment control as described above, the toner concentration (the ratio of the carrier and the toner) in the developing container 40 is always kept constant, and the toner can maintain an optimal charge amount when reaching the developing portion. It becomes possible. As a result, fogging and density reduction are suppressed.

  However, with the recent diversification of electrophotographic apparatuses, high-print images such as photographic images are frequently printed. In a high-print image, toner consumption associated with development is large. Therefore, a new toner is supplied into the developer in the developing container, and is agitated with the carrier, so that it takes a certain time for the toner to obtain a sufficient charge. In addition, when the stirring time is insufficient and the charge amount of the toner is insufficient, there is a problem that fog occurs and the image quality becomes unstable.

  In order to solve such a problem, a method has been proposed in which the charge amount of the toner is stabilized by rotating the stirring member in the developing container during non-image formation according to the image ratio (see Patent Document 1). ). This method makes it possible to maintain the image quality even when printing a high print image or the like.

However, in order to meet the recent diversification of users, the demand for higher image quality, and longer life, the above method sometimes cannot maintain the image quality in the latter half of the life of the developing device. In other words, in the above method, even if the carrier has a sufficient charge imparting ability at the beginning of the life and does not generate fog, when the toner is replenished in large quantities, the carrier is deteriorated by performing the stirring operation. In the latter half of the life, when the deterioration has progressed, the charge imparting power of the carriers has been reduced, which may cause fogging.
JP-A-4-136964

  An object of the present invention is to reduce the rotation time of the stirring member as much as possible by suppressing the deterioration of the carrier and performing an appropriate amount of stirring only when necessary, and even when a large amount of toner is replenished. It is an object of the present invention to provide an image forming apparatus that enables stable image formation over a long period of time without causing image defects.

The above object is achieved by the image forming apparatus according to the present invention. In summary, the present invention
An image forming apparatus for forming an image on a transfer material,
(A) an image carrier on which an electrostatic latent image is formed;
(B) a developer container containing a two-component developer containing toner and a carrier, a stirring member for stirring the toner replenished in the developer container and the developer in the developer container, and the developer A developer carrier for developing an electrostatic latent image on the image carrier by carrying and transporting the image carrier to the image carrier;
(C) toner replenishment control means for controlling the amount of toner replenished in the developing container;
(D) developing device usage amount detecting means for detecting the usage amount of the developing device;
(E) environmental detection means for detecting the temperature and humidity at which the image forming apparatus is used, and converting the absolute water content from the detected temperature and humidity;
In an image forming apparatus having
During the continuous image forming operation, it is detected that the absolute water content is less than a predetermined value, the usage amount of the developing device is larger than the predetermined value, and the amount of toner to be replenished is larger than the predetermined value. In this case, after the toner replenished in the developing container reaches the developer carrying member, the image forming operation is continued, and then the image forming operation is stopped and the stirring member is operated for a predetermined time. An image forming apparatus characterized by the above.

  The image forming apparatus of the present invention executes a toner agitation mode in which the toner and the carrier are mixed according to the amount of toner replenishment and the amount of use of the developing device, and the environment in which the image forming apparatus is used. It is possible to perform stirring for an appropriate time at a necessary timing while suppressing deterioration of the image, and it is possible to suppress the occurrence of image defects such as fogging. Further, by storing information on the usage amount of the developing device in a storage means provided in a detachable unit including the developing device, the usage information of the developing device can be obtained even when the developing device is removed from the main body and reattached. Therefore, it is possible to accurately determine whether the toner agitation mode is necessary.

  The image forming apparatus according to the present invention will be described below in more detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention only to those unless otherwise specified. Absent.

Example 1
An image forming apparatus to which the present invention can be applied, for example, forms an electrostatic latent image corresponding to an image information signal on an image carrier such as a photosensitive member or a dielectric by an electrophotographic method, an electrostatic recording method, or the like. Is developed with a developing device using a two-component developer mainly composed of toner particles and carrier particles to form a visible image, that is, a developer image (toner image), and the visible image is applied to a transfer material such as paper. Any structure may be used as long as it is transferred and made into a permanent image by a fixing means.

  First, an embodiment of an image forming apparatus according to the present invention will be described with reference to FIGS. In this embodiment, it is assumed that the image forming apparatus of the present invention is an electrophotographic full-color printer.

  Referring to FIG. 1, in the image forming apparatus of this embodiment, a desired image to be output is decomposed into a large number of pixels from an image reading apparatus or computer 33 through an image information processing apparatus 32 and sent to a printer. At this stage, the image information is converted into a pixel image signal that is image data corresponding to the density of each pixel.

  A drum-shaped electrophotographic photosensitive member (hereinafter referred to as “photosensitive drum”) 1 as an image bearing member has amorphous silicon, selenium, OPC or the like on its surface, rotates in the direction of the arrow, and is charged in the image forming process. The primary charging device 2 is uniformly charged in the process.

  A pixel image signal, which is image data, is input to a pulse width modulation circuit 31, and a laser drive pulse corresponding to the pixel image signal is supplied to a semiconductor laser 3 which is an exposure unit as a latent image forming unit, and its pulse width The light is emitted for the time corresponding to. On the photosensitive drum 1, a relatively long range is exposed for high density pixels in the main scanning direction, and a short range is exposed for low density pixels, and the area gradation corresponding to the image information signal is exposed. An electrostatic latent image having the following is formed (latent image forming step).

  This electrostatic latent image is developed by a developing device 4 using a two-component developer in which toner particles and carrier particles are mixed, and a visible image (toner image) is formed (developing step).

  The formed toner image is transferred to a transfer material 90 held on a transfer material carrier belt 91 as a transfer material carrier that is driven endlessly in the direction of the arrow by the action of a transfer roller 92 as a transfer means (transfer) Process). The toner image transferred to the transfer material 90 is fixed by a fixing unit (not shown) provided on the downstream side of the transfer material 90 to be a permanent image (fixing step), and a desired image formed product is provided. .

  The residual toner on the photosensitive drum 1 after the toner image is transferred is removed by the cleaning device 5 to prepare for the next image formation.

  In FIG. 1, for simplicity of explanation, one image forming station (photosensitive drum 1, exposure device 3, primary charging device 2) in which the above-described image forming process for one color of the image forming device is performed. Only the developing device 4, the cleaning device 5, etc.). As shown in FIG. 2, in the color image forming apparatus using a plurality of colors, for example, four image forming stations Y, M, C, and Bk for each color of cyan, magenta, yellow, and black are transferred. On the material carrying belt 91, it is arranged in order along the moving direction.

  The color separation toner images for each color of the original formed on the photosensitive drums 1 of the image forming stations Y, M, C, and Bk are sequentially superimposed on the transfer material 90 held and conveyed by the transfer material carrying belt 91. It is transferred and fixed in the same manner, resulting in a full color image. Note that the configurations of the image forming units in the stations Y, M, C, and Bk are the same except for the color of the developer.

  In this embodiment, the photosensitive drum 1, the primary charging device 2, the developing device 4, the cleaning device 5 and the like are integrated into each image forming station Y, M, C, and Bk for each color. It takes the form of a cartridge C which is a unit that can be detached from the main body. The cartridge C is provided with a storage means CM, and the storage means CM stores information relating to the image forming process.

  Next, details of the developing device 4 installed in the image forming apparatus will be described with reference to FIG.

  The developing device 4 has the same configuration as that shown in FIG. 7 described above except for the toner replenishing means.

  That is, in the present embodiment, the developing device 4 is disposed to face the photosensitive drum 1, and the inside of the developing container 40 in which the developer T is accommodated is first defined by the partition wall 46 extending in the vertical direction. The chamber is divided into a chamber (developing chamber) 47 and a second chamber (stirring chamber) 48. In the developing chamber 47, a non-magnetic developing sleeve 41, which is a hollow cylindrical body that rotates in the direction of the arrow, is disposed as a developer carrier, and a magnet (not shown) that is a magnetic field generating means is provided in the developing sleeve 41. Is fixedly arranged. The developing sleeve 41 carries and transports a layer of a two-component developer (including a magnetic carrier and non-magnetic toner) whose layer thickness is regulated by a blade 42 which is a developer regulating member, and in a development region facing the photosensitive drum 1. A developer is supplied to the photosensitive drum 1 to develop the electrostatic latent image.

  In order to improve the developing efficiency, that is, the application rate of toner to the electrostatic latent image, a developing bias voltage in which a DC voltage is superimposed on an AC voltage is applied to the developing sleeve 41 from a power source (not shown). .

  In the developing chamber 47 and the agitating chamber 48, first and second agitating members having a screw structure, that is, agitating screws 43 and 44 are arranged as developer agitating and conveying means, respectively. The first screw 43 stirs and conveys the developer in the developing chamber 47, and the second screw 44 already supplies the toner supplied from the toner supply tank 60 by the toner supply device 6 that is a toner supply means, and the developing device 4. The developer inside is agitated and conveyed to make the toner density uniform.

  In the partition wall 46 that partitions the developing chamber 47 and the stirring chamber 48, developer passages 46a and 46b that allow the developing chamber 47 and the stirring chamber 48 to communicate with each other on the front side and the rear side are formed by the developing container configuration shown in FIG. The developer in the developing chamber 47 in which the toner is consumed by the development due to the conveying force of the first and second screws 43 and 44 and the toner density is reduced is transferred from the one passage 46b to the stirring chamber 48. The developer whose toner density has been recovered in the stirring chamber 48 is moved from the other passage 46a into the developing chamber 47.

  In FIG. 1, a toner replenishing device 6 that is a toner replenishing means includes a toner replenishing tank 60 that contains toner as a replenishing developer, and a conveying screw 61 that communicates with a toner replenishing port 6a to the developing device 4. A driving motor 62 that drives the conveying screw 61 and a driving circuit 63 that controls the driving motor 62 are configured. In the toner replenishment control, the rotation time of the conveying screw 61 is calculated according to the toner replenishment amount determined from the detection result of the inductance sensor 45 as the density detection means by the CPU 67, and the motor drive circuit 63 is controlled. The motor 62 is driven to rotate for that time, and a predetermined amount of replenishment toner is replenished to the developing device 4. At this time, the developer stirring screw 61 and the developing sleeve 41 can be driven by a single driving source.

  In the toner replenishment control, an inductance detection ATR can be employed as a density detection means in order to detect a change in toner density in the developing device 4 and control the amount of replenished toner.

  The inductance ATR as a toner replenishment control method includes an inductance sensor 45 that detects an apparent permeability of a two-component developer including toner particles and carrier particles in the developing device 4. The toner density of the stored developer is detected, the toner supply amount is determined by the difference between the detection signal value (output value) based on the detection result and the reference value of the toner supply control, and the toner supply device 6 is operated. It is a control method.

  Next, the inductance ATR as the toner replenishment control means will be further described.

  In this embodiment, as shown in FIG. 3, the developing device 4 is provided with an inductance sensor 45 on the side wall of the upstream portion of the developer circulation in the stirring chamber 48. The output electric signal from the inductance sensor 45 changes substantially linearly according to the toner concentration.

  In the configuration shown in FIG. 1, detection data obtained by AD converting the electrical signal output from the inductance sensor 45 is sent to a CPU 67 that executes toner supply control. The CPU 67 is connected to a nonvolatile memory RAM 68 that is a storage means.

  The RAM 68 stores detection data (that is, “initial value”) corresponding to the specified toner density at the initial setting value from the inductance sensor 45 via the CPU 67, and preferably a predetermined “correction” corresponding to the temperature and humidity. A “value” table is also stored in advance.

  In this embodiment, the “correction value” and the “initial value” corresponding to the above temperature and humidity are read from the RAM 68 to the CPU 67 and added to obtain the “reference value”.

  Then, the CPU 67 compares the detection data newly obtained from the inductance sensor 45 with the “reference value”, and determines the insufficient toner amount corresponding to the difference as the toner replenishment amount. Then, the rotation time of the conveying screw 61 corresponding to the toner replenishment amount is calculated, the motor driving circuit 63 is controlled, and the motor 62 is rotated and driven for that time. The conveying screw 61 rotates for the above-described time, and supplies a shortage of toner from the toner supply tank 60 to the developing device 4. That is, the toner supply amount is controlled by controlling the driving time of the motor 62.

  The toner density here is a weight ratio (%) between the toner and the developer (toner and carrier), and is basically controlled to 8.0% in this embodiment.

  The toner concentration (the ratio of carrier to toner) in the developing container 40 is always kept constant, and the toner can hold an optimal charge amount when it reaches the developing portion. As a result, fogging and density reduction are suppressed. In a high-print image, since toner consumption during development is large, it is necessary to sufficiently agitate the agitation screws 43 and 44 to sufficiently charge the toner and maintain the charge amount with the above configuration. .

  However, the developer T in the two-component developing device 4 gradually deteriorates due to the compression between the developing blade 42 and the regulation sleeve 41 and the stirring operation by the stirring screws 43 and 44. In particular, since the carrier continues to be used without being replenished, it deteriorates and the charge imparting power tends to decrease. When a large amount of toner is replenished, deterioration of the carrier is accelerated by the stirring operation, and fogging may be caused in the latter half of the developing device life.

  Conventionally, a method of stirring the developer at the time of non-image formation according to the image ratio has been carried out. However, in this embodiment, when the replenishment operation is performed in order to maintain the image quality even in the latter half of the developing device life. In addition, toner that drives the agitating screws 43 and 44, which are agitating members, for a predetermined time inside the developing container 40 based on the amount of toner replenished, the amount of developing device used, and the absolute moisture content of the environment in which the toner is used. A feature is that the stirring mode is carried out.

  As described above, in the present embodiment, the storage unit CM is provided in the cartridge C in each of the image forming stations Y, M, C, and Bk, and the storage unit CM includes a part of information regarding the image forming process. Information regarding the use state of the developing device 4 is stored.

  Then, the image forming apparatus main body is provided with environment detecting means 100 (FIG. 2), and detects the temperature and humidity of the environment in which the image forming apparatus main body is used. From these temperatures and humidity, the absolute moisture content of the environment in which the main body is used is judged, and various process conditions relating to charging, development, etc. are determined according to the environment. The absolute water content detected here is an element for determining whether or not to execute the toner stirring mode.

  In this embodiment, the developing device usage amount detecting means is provided for the developing device 4 for each color. In this method, the amount of use of the developing device 4 is detected by integrating the rotation time of the developing sleeve 41, and the life is determined. The rotation time of the developing sleeve 41 is accumulated and stored in the storage means CM provided in the cartridge C as needed. In this embodiment, the usage amount of the developing device is detected based on the rotation time of the developing sleeve 41. However, for example, information that can determine the state of the developing device 4 such as the number of printed sheets can be substituted.

  Details of the toner stirring mode will be described below. The operation in the toner stirring mode is performed at the timing shown in the timing chart of FIG.

  First, as shown in FIG. 4, after the rotation of the photosensitive drum 1 is stopped, the toner agitation screws 43 and 44 are controlled while the toner replenishment control is performed with the inductance ATR for a time corresponding to the printing time of 6 sheets of A4 size. Rotate.

  The reason why this operation is performed can be understood with reference to FIG. 3. In the configuration of the developing device 4 of this embodiment, when the inductance sensor 45 detects it, the portion (developing portion) that already faces the photosensitive drum 1. Since the toner is consumed by the developing operation for the next image formation, the toner concentration is surely set to the reference value for the developer that has been consumed and has a low toner concentration after entering the toner stirring mode. This is because it is necessary to perform a toner supply operation for returning the toner. Here, if the toner density of the developer is surely returned to the reference value, stable and satisfactory image formation can be performed when image formation is resumed after the toner stirring mode.

  In the configuration of the present embodiment, it has been found that the toner concentration in the developing container 40 is almost restored to the reference value by performing the toner replenishment control for the time corresponding to the A4 size 6 sheet printing time. In this example, toner replenishment control is performed during this time.

  Next, the toner supply operation is stopped, and only the stirring operation is performed.

Here, the time of the stirring operation and the recovery state of the fogging are considered to be the most severe state of the fogging apparatus use amount 100%, toner replenishment amount maximum (0.45 g), absolute water content 0.5 (g / m Confirmed under the conditions of ³ ). The results are shown in Table 1.

  As shown in Table 1, when the stirring time is 20 seconds or more, no fog occurs at all, and at 15 seconds it is an acceptable level, but an extremely slight fog is generated. At 10 seconds, visible fogging has occurred. From the above results, it was found that in the configuration of this example, it takes 20 seconds or more to suppress fogging by the developer stirring operation.

  By increasing the stirring time, the fog is improved, but conversely, the carrier is deteriorated. For this reason, the agitation time without toner replenishment control is set to 20 seconds in order to obtain the minimum necessary agitation time.

  After the idle rotation of the developing sleeve 41 and the agitation screws 43 and 44 for 20 seconds, the toner agitation mode is terminated.

  As described above, in the toner agitation mode, after the operation of rotating the developing sleeve 41 and the agitation screws 43 and 44 while replenishing toner, the developing sleeve 41 and the agitation screws 43 and 44 are kept for a predetermined time without replenishing toner. The fog can be suppressed by idling.

  In this embodiment, this toner agitation mode is performed based on the amount of toner replenished when the replenishment operation is performed and the usage amount of the developing device. Further, whether or not to execute the toner stirring mode is determined according to the absolute moisture content of the environment in use. This operation will be described below using the flowchart shown in FIG.

  When image formation is started (S1), first, detection of the environment in which the main body of the image forming apparatus is used and development device usage at each station Y, M, C, Bk are detected (S2), and then toner supply control is performed. Is performed (S3).

  If the results of the environmental detection and the development device usage amount detection indicate that the absolute water content Z is equal to or greater than the threshold value C or the development device usage amount Y is equal to or less than the threshold value B (S4: No), toner replenishment control using a normal inductance ATR. The image formation is continued while performing (S10). That is, when the absolute water content Z is equal to or greater than the threshold C, the toner agitation mode is not executed, and even when the absolute water content Z is less than the threshold C, the toner replenishment mode is not executed as long as the developing device usage Y is equal to or less than the threshold B.

  On the contrary, if the absolute water content Z is less than the threshold value C, when the developing device usage amount Y is larger than the threshold value B (S4: Yes), the toner replenishment amount X per sheet replenished by the toner replenishment control is pulled out. Then, it is determined whether or not the replenishment amount X is larger than the threshold value A.

  That is, in the inductance ATR, the detection data from the inductance sensor 45 is newly compared with the reference value for each print, and the developing device 4 is supplied with a shortage of toner corresponding to the difference. The amount of toner replenished at this time is monitored, and it is determined whether or not the amount of toner X replenished in one sheet is greater than or equal to the threshold A (S5).

  At this time, if it is equal to or less than the threshold A (S5: No), the normal image forming operation is continued (S10), and if it is greater than the threshold A (S5: Yes), execution of the toner agitation mode is requested (S6).

  When entering the toner stirring mode, it is necessary to temporarily stop image formation. However, since fog does not occur until the replenished toner reaches the developing sleeve 41, it is possible to form an image. Therefore, during continuous printing, the image forming operation is continued until P sheets, and P sheets. After the end, it stops and enters the toner stirring mode. When the image forming operation is completed before the arrival of P sheets, the toner agitation mode is entered at that timing (S6 → S7).

  When the toner agitation mode ends, the next image formation can be started (S9).

The specific values used in this example are the threshold C of the absolute water content Z of 5.8 (g / m ³ ), the threshold B of the developing device usage Y is 75% of the lifetime, and the replenished toner amount X The threshold value A was 1.0 g.

  According to the above operation, in this embodiment, when the absolute water amount Z and the developing device usage amount Y are larger than the predetermined values, here, the threshold values C and B, the toner replenishment amount is detected, and the toner replenishment amount for each sheet. When X is larger than the predetermined value A, the toner agitation mode is executed during non-image formation.

  Here, conditions for determining thresholds for the absolute water amount, the developing device usage amount, and the toner replenishment amount will be described.

  The threshold of the absolute water content was determined by confirming the relationship between the main body use environment and the fog. Here, the relationship between the absolute moisture content and the fog when the toner replenishment amount is maximum and the developing device 4 is just before reaching the end of its life, in which the fog is the most severe, was confirmed. The toner replenishment amount at the time of confirmation is the amount of toner replenished in one A4 size sheet, and the maximum value is 0.45 g in the configuration of this embodiment. The results are shown in Table 2. As shown in Table 2, it can be seen that fog does not occur at all in an environment having a large amount of absolute moisture, and the fog level becomes worse as the humidity becomes lower.

In this example, 5.8 (g / m ³ ), which did not cause fogging that would affect the image at the time of maximum replenishment, was set as the absolute water content threshold. Therefore, in the toner replenishment control in this embodiment, since the toner agitation mode is not performed in an environment where the absolute water content is larger than 5.8 (g / m ³ ), the deterioration of the carrier may be promoted by unnecessary agitation. Disappear.

The threshold values A and B for the toner replenishment amount X and the developing device usage amount Y were determined by checking the fogging state with respect to them. Here, the examination was performed at an absolute water content of 0.5 (g / m ³ ), which is considered to be severe with respect to the fog from the relationship between the absolute water content and the fog. The results are shown in Table 3.

  From the results shown in Table 3, regarding the replenishment amount X, 0.25 g where no fogging occurred at any developing device usage (development life) was set as the threshold A. Further, the developing device usage amount Y was set to 75% of the threshold value B when fogging did not occur at any replenishment amount and the rotation speed reaching the end of life was set to 100%.

From the above results, the following three conditions were satisfied: the absolute water content was less than 0.5 (g / m ³ ), the toner replenishment amount was 0.25 g, and the developing device usage was greater than 75%. Only when the toner agitation mode is entered. By executing the toner agitation mode with the above settings, it is possible to suppress fogging in various environments, toner replenishment amounts, and the life of the developing device.

  In addition, useless stirring is eliminated, and stable image formation can be performed until the end of the development life.

  In addition, the first image is detected when the toner agitation mode is performed, and printing is possible up to the fifth sheet. That is, the predetermined number P is set to five. The number here is the number of A4 size sheets. (A3 size is converted into one A4 size.) This is about 6 sheets of time until the toner that has been replenished reaches the development area, that is, the development sleeve 41 is coated. This is because it takes.

  If the toner agitation mode can be executed before a large amount of toner is coated on the sleeve 41, no problem occurs on the image. However, when the post-rotation operation is performed by the fifth sheet and the image forming operation is temporarily stopped, the toner agitation mode is executed there.

  As a result, the image forming operation is not stopped immediately, so that the user is less likely to feel stress even when continuous printing is performed, for example.

As described above, it is possible to execute the toner agitation mode only when necessary by making a determination based on the usage amount of the developing device, the toner replenishment amount, and information on the environment in which the image forming apparatus main body is used. Become. As a result, the toner agitation mode is executed more than necessary, so that stable image formation can be performed over a long period without adversely affecting the deterioration of the carrier. Further, since image formation is not stopped uselessly, stress on the user is reduced.

  In the present embodiment, information on the usage amount of the developing device is stored in the storage means CM provided in the cartridge C. Therefore, even if the cartridge C is taken out and remounted, the usage amount Y of the developing device is not reset, so that it is possible to accurately determine whether or not to execute the toner stirring mode.

  In this embodiment, the threshold values of the absolute water amount, the toner replenishment amount, and the developing device usage amount are set to one value in order to simplify the control. However, the present invention is not limited to this. More detailed control is also possible by examining the three conditions of absolute water content, toner replenishment amount, developing device usage amount and the presence or absence of fogging to determine whether it is necessary to execute the stirring mode. It is.

For example, at an absolute water content of 2.5 (g / m ³ ), as shown in Table 4, the occurrence of fog is lighter than that at 0.5 (g / m ³ ). Therefore, it is possible to change the threshold values of the toner replenishment amount and the developing device usage amount in accordance with the absolute water amount. Here, when the absolute water content is in the range of 2.5 to 5.8 (g / m ³ ), the toner agitation mode is set when the toner replenishment amount is 0.3 g or more and the developing device usage amount (development life) is 80%. When the toner replenishing amount is less than 2.5 (g / m ³ ), the toner stirring mode is performed when the toner replenishing amount is 0.25 g or more and the developing device usage amount is 75% or more.

  As described above, by finely controlling the settings of the absolute water amount, the toner replenishment amount, and the developing device usage amount, it is possible to provide an image forming apparatus that is stable with higher image quality.

  In this embodiment, the inductance ATR is used for toner density control. However, the present invention is not limited to this, and as shown in FIG. 1, the accumulated value of the number of print pixels in the image information signal per page is obtained by the video counter 66. Alternatively, a control means (video count ATR) for determining toner consumption per page and supplying toner may be used.

  The video count ATR in this embodiment will be described below.

  As shown in FIG. 1, a laser drive pulse corresponding to a print pixel image signal transmitted from a pulse width modulation circuit 31 is supplied to one input of an AND gate 64, and the other input is supplied from a clock pulse oscillator 65. Supply clock pulses.

  The number of clock pulses corresponding to the pulse width of the laser drive pulse, that is, the number of clock pulses corresponding to the density of each pixel is output from the AND gate 64. The clock pulses are integrated for each image by the counter 66 to calculate the video count number.

  This video count number corresponds to the amount of toner consumed to form one toner image. The CPU 67 that performs toner replenishment control reads a conversion table indicating the correspondence between the video count number and the toner replenishment time provided in the RAM 68 from the video count number, and controls the driving time of the motor 62 as described above. The toner is replenished so as to compensate for the consumed toner amount.

  That is, in the inductance ATR, the density of the toner in the developing device 4 is directly detected by the inductance sensor 45 which is a density detection means, and the difference between the detected value and the reference value is used as the toner replenishment amount, whereas the video count ATR Then, the amount of toner consumed is calculated from the number of video counts and used as the replenishment amount.

  In the present embodiment described above, toner replenishment control is performed in the toner agitation mode. However, if a sufficient effect can be obtained with respect to fogging, only the developing sleeve and the agitation member are simply idled to achieve a simple configuration. Just fine.

  In the toner agitation mode of this embodiment, the developing sleeve is also rotated together with the agitating member. However, if the developer can be sufficiently agitated and the toner tribo can be sufficiently loaded, only the agitating member may be driven.

Example 2
The configuration of the present embodiment is basically the same as that of the first embodiment. The feature of the present embodiment is that, in the first embodiment, in the toner agitation mode, the agitation time while performing the toner replenishment operation and the agitation time after the toner replenishment operation is stopped are set to constant values. The time is variable according to the usage amount of the developing device, the environment in which it is used, and the toner replenishment amount.

  As shown in Table 3 above, there is a difference in the level of fog generation depending on the usage amount (development life) of the developing device and the toner replenishment amount. In Table 2, the Δ level part, that is, (a) when the toner replenishment amount per sheet is 0.3 g and the developing device usage amount is 80% to 90%, and (b) the developing device usage amount is 80% and When the toner replenishment amount per sheet is 0.3 g to 0.4 g, the x level portion in Table 3, that is, (c) when the usage amount of the developing device is at the end of the life, (d) per A4 sheet When the toner replenishing amount is 0.45 g or more, (e) fogging is lighter than when the developing device usage amount is 85% or more and the A4 toner replenishing amount is 0.35 g or more.

  In this Δ level situation, the occurrence of fog could be suppressed even when the stirring time after completion of the toner supply control in the toner stirring mode was 15 seconds.

  Therefore, when the development life is between 75% and 80% and the toner replenishment amount is between 0.25 g and 0.4 g, the stirring time is set to 15 seconds. The stirring time was also set to 15 seconds when the development life was between 80% and 90% and the toner replenishment amount was 0.25 g to 0.3 g. Other than the above, when the developing life was 75% or more and the toner replenishment amount was 0.25 g or more, the stirring time was 20 seconds.

  With the above configuration, it is possible to control more finely than in the first embodiment, thereby further suppressing the deterioration of the developer as well as the fogging. Therefore, it is possible to realize a further long life and high image quality.

  In this embodiment, the agitation time is changed depending on the usage amount (development life) of the developing device and the toner replenishment amount. However, finer control can be performed using environmental information.

  The overall configuration of the image forming apparatus described in the first and second embodiments is not necessarily limited to the above-described configuration, and a configuration in which a drum-shaped transfer material carrier is used instead of the transfer material carrier belt 91 is used. Alternatively, as in the image forming apparatus shown in FIG. 6, an intermediate transfer body 91 a is provided instead of the transfer material carrier, and toner images are superimposed on the intermediate transfer body 91 a from the plurality of photosensitive drums 1 to perform primary transfer. The secondary transfer unit 92a collectively performs secondary transfer from the intermediate transfer member 91a to the transfer material 90, and although not shown, a developing device is mounted on a rotating member and is sequentially placed on one photosensitive drum. The present invention can be applied to various image forming apparatuses such as a configuration facing each other.

  With respect to the cartridge, which has a developing device and is detachable from the image forming apparatus, the same operation and effect can be obtained by providing the above storage means and applying the present invention. it can.

1 is a partial schematic configuration diagram illustrating an embodiment of an image forming apparatus according to the present invention. 1 is a schematic configuration diagram illustrating an embodiment of an image forming apparatus according to the present invention. It is a top view which shows one Example of a developing device. 4 is a timing chart showing operation timings according to an embodiment of a toner agitation mode according to the present invention. 6 is a flowchart illustrating an embodiment of an image forming operation according to the present invention. It is a schematic block diagram which shows the other Example of the image forming apparatus which concerns on this invention. It is a schematic block diagram which shows an example of the conventional developing device and toner supply means.

Explanation of symbols

1 Photosensitive drum (image carrier)
4 Developing device 6 Toner supply device (toner supply means)
40 Developing container 41 Developing sleeve (developer carrier)
43, 44 Stir screw (stirring member)
45 Inductance sensor (concentration detection means)

Claims (6)

An image forming apparatus for forming an image on a transfer material,
(A) an image carrier on which an electrostatic latent image is formed;
(B) a developer container containing a two-component developer containing toner and a carrier, a stirring member for stirring the toner replenished in the developer container and the developer in the developer container, and the developer A developer carrier for developing an electrostatic latent image on the image carrier by carrying and transporting the image carrier to the image carrier;
(C) toner replenishment control means for controlling the amount of toner replenished in the developing container;
(D) developing device usage amount detecting means for detecting the usage amount of the developing device;
(E) environmental detection means for detecting the temperature and humidity at which the image forming apparatus is used, and converting the absolute water content from the detected temperature and humidity;
In an image forming apparatus having
During the continuous image forming operation, it is detected that the absolute water content is less than a predetermined value, the usage amount of the developing device is larger than the predetermined value, and the amount of toner to be replenished is larger than the predetermined value. In this case, after the toner replenished in the developing container reaches the developer carrying member, the image forming operation is continued, and then the image forming operation is stopped and the stirring member is operated for a predetermined time. An image forming apparatus. The amount of the developing apparatus, the image forming apparatus according to claim 1, wherein in which the rotation time of the developing agent carrier is accumulated. The amount of the developing apparatus, the image forming apparatus according to claim 1 or 2, characterized in that stored in the storage means provided in a cartridge having the image bearing member and said developing device. In the operation of the agitating member, a first operation for driving the agitating member in a state where the toner is replenished, and a second operation for driving the agitating member without replenishing the toner after the first operation. the image forming apparatus according to any one of claims 1-3, characterized in that to perform operation and, the. Wherein when performing the operation of the agitating member, the image forming apparatus according to any one of claims 1-4, characterized in that to also operate the developer carrier. The toner replenishment control means detects the ratio of toner and carrier from the magnetic permeability of the developer in the developer container and replenishes toner, or an image information signal for forming an electrostatic latent image on the image carrier the image forming apparatus according to determine the toner consumption to any one of claims 1-5, characterized in that performing the toner replenishment based on.

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