JP2005275202A - Image forming apparatus and its control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide control technique that is used to appropriately cope with the situation in which abnormality has occurred in an image forming apparatus that forms an image by using toner and to provide its control method. <P>SOLUTION: In a first condition of an engine section in which degree of degradation is less and toner is sufficiently stored, a relatively narrow appropriate range of R1min and R1max is set for the density of a patch image (a). When the density detection result of the patch image is out of the appropriate range, it is judged that abnormality has occurred in the apparatus and the abnormality of the apparatus is accurately detected. On the other hand, in a second condition of the engine section in which constituting parts are deteriorated or the toner is insufficiently stored, the lower limit value of the appropriate range is lowered to expand the appropriate range (b). Thus, even though the apparatus is in a condition that image quality is slightly deteriorated, it is not judged that abnormality has occurred and the image is continuously formed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus that forms an image using toner and a control method thereof.

  In an image forming apparatus that forms an image using toner, such as a printer, a copier, and a facsimile machine, as the apparatus is used, image quality deterioration due to, for example, deterioration of the apparatus or a change in the state of the toner such as a decrease in the remaining amount of toner Will occur. In such a case, if image formation is prohibited immediately, further deterioration in image quality can be prevented. However, even when the image quality is somewhat deteriorated, the user may want to continue image formation. Therefore, for example, in the printing apparatus described in Patent Document 1, when the remaining amount of toner falls below the first predetermined value, a warning is given to the user by displaying a message that the printed matter may be faded. At least print job data currently being processed can be output as a printed matter in accordance with a user operation. In this way, it is possible to meet the user's request and to improve the convenience for the user.

JP 2002-196628 (for example, paragraph 0033)

  In this type of image forming apparatus, the formed toner image may exhibit an abnormal image density due to a malfunction of the apparatus. That is, if the density detection result of the formed toner image is significantly different from the assumed image density, it can be determined that some malfunction has occurred in the apparatus. However, it is difficult to judge in an apparatus that recognizes image formation in a state where image quality may be deteriorated as in the above-described conventional technology. This is because it is assumed to some extent that a density abnormality will occur in an image formed in such a state, and it cannot be determined that the cause of the density abnormality is generally a malfunction of the apparatus. For this reason, there is a problem in terms of maintainability that an abnormality in the apparatus can be surely detected and a necessary treatment can be performed promptly.

  As described above, in order to provide excellent convenience to the user, in an apparatus that allows image formation in a state where image quality may be slightly deteriorated, special consideration is given to handling when an abnormality occurs in the apparatus. is required. However, no proposal has been made for a control technique considering such points.

  SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and provides an image forming apparatus that forms an image using toner and a control method thereof that can appropriately cope with a case where an abnormality occurs in the apparatus. The purpose is to do.

  In order to achieve the above object, the image forming apparatus according to the present invention executes an image forming operation to form a toner image, and the state of the image forming unit is the best image quality of the toner image. A state in which the first state and the second state in which the image quality of the toner image may be inferior to that in the first state are determined based on index information indicating the use history of the image forming unit Determining the state of the appropriate range as the toner amount constituting the patch image and the toner amount detecting unit for detecting the toner amount constituting the toner image as the patch image formed by the image forming unit; And a control method for determining that there is an abnormality in the apparatus when the detection result of the toner amount detection unit for the patch image is not within the appropriate range. It is characterized in that it comprises and.

  Further, in order to achieve the above object, the control method for the image forming apparatus according to the present invention is such that the state of the image forming means for executing the image forming operation to form the toner image has the best image quality of the toner image. State determination for determining which of the first state and the second state in which the image quality of the toner image may be inferior to that of the first state is based on index information indicating the use history of the image forming unit A setting step for setting an appropriate range as a toner amount constituting the toner image as a patch image according to a determination result in the state determination step, and a patch image for forming the patch image by the image forming unit An abnormality determination step of detecting a toner amount for the formed patch image and determining that the apparatus is abnormal when the detection result is not within the appropriate range; It is characterized in that it comprises.

  In these inventions, the toner amount constituting the patch image is detected as a value corresponding to the image density of the toner image actually formed as the patch image, and the presence or absence of abnormality of the apparatus is determined based on the detection result. By so doing, it is possible to appropriately detect an abnormality in the apparatus that causes an abnormality in image density and an abnormality in the toner amount detection process.

  In these inventions, the state of the apparatus is divided into a first state in which image formation can be performed with good image quality and a second state in which image quality may be deteriorated. Here, since the constant image quality is guaranteed when the apparatus is in the first state, the density of the patch image is relatively stable, and the amount of toner constituting the patch image should substantially match the expected value. It is. On the other hand, when the apparatus is in the second state, the density of the patch image may be different from the expected density. For example, even if there is no abnormality in the operation of the apparatus, the patch image may run out of toner due to a decrease in the remaining amount of toner. Thus, in the second state, the amount of toner constituting the patch image tends to become unstable.

  As described above, the stability of the toner amount constituting the patch image to be formed is greatly different between the first state and the second state. Therefore, as in the present invention, the appropriate range of the toner amount is changed depending on whether the image forming unit is in the first state or the second state, and whether or not the toner amount detection result in the patch image is in the appropriate range. By determining whether or not there is an abnormality in the apparatus, it is possible to appropriately determine whether or not there is an abnormality in the apparatus regardless of the case of the apparatus, and the maintainability of the apparatus is improved.

  For example, when the image forming unit is in the second state, the variation in the amount of toner constituting the patch image is large even if there is no abnormality in the apparatus, so that the appropriate range is wider than in the first state. It is preferable to set the appropriate range. By doing so, the following effects can be obtained. First, when the image forming unit is in the first state, the amount of toner constituting the patch image is considered to be relatively stable. Therefore, by setting the appropriate range relatively narrow and determining that the measured toner amount deviates from this, it is possible to more reliably grasp the abnormality of the apparatus. On the other hand, the toner amount varies when the image forming unit is in the second state, which is a phenomenon that is assumed in advance, and this cannot be said to be an unexpected device abnormality. Therefore, if a relatively wide appropriate range is provided, a certain amount of toner amount variation is allowed, but if the toner amount detection result deviates greatly from the expected result, it is determined that there is an abnormality.

  In addition, a decrease in the remaining amount of toner or a natural deterioration associated with the use of the apparatus generally causes a decrease in the amount of toner constituting the image, such as an insufficient image density or a blurred image. Therefore, for example, when the apparatus is in the second state, the appropriate range may be set such that the lower limit value of the appropriate range is on the low toner amount side than when the apparatus is in the first state.

  Further, the image forming apparatus configured as described above may further include a notifying unit that notifies that when the image forming unit is determined to be in the second state. As a result, the user can know that there is a possibility that the image quality may be deteriorated, so that it is possible to prevent the formation of a useless image that does not reach the quality desired by the user. Further, the user can know that the maintenance work of the apparatus is necessary. Moreover, you may provide the alerting | reporting means which alert | reports that when it determines with an apparatus having abnormality. As a result, the user can know the occurrence of an abnormality and take appropriate measures to eliminate it.

  According to another aspect of the image forming apparatus of the present invention, in order to achieve the above object, an image forming unit that executes an image forming operation to form a toner image, and the state of the image forming unit is the toner image. Index information for indexing the use history of the image forming means to indicate which of the first state where the image quality of the image is the best and the second state where the image quality of the toner image may be inferior to the first state A state determination unit for determining based on the toner image, a toner amount detection unit for detecting a toner amount constituting the toner image as a patch image formed by the image forming unit, and the toner amount detection unit for the patch image Control means for executing an abnormality processing operation when the detection result is not within a predetermined appropriate range, and the control means performs processing of the abnormality processing operation according to a determination result by the state determination means. It is characterized by varying the contents.

  In order to achieve the above object, the image forming apparatus control method according to the present invention performs the image forming operation to form the toner image, and the state of the image forming unit is the best image quality of the toner image. State determination for determining which of the first state and the second state in which the image quality of the toner image may be inferior to that of the first state is based on index information indicating the use history of the image forming unit A detection step of detecting a toner amount for the formed patch image, a detection result in the detection step is a predetermined value, a patch image forming step of forming the toner image as a patch image by the image forming means, An abnormality processing step executed when not in the proper range, and the processing content of the abnormality processing step differs depending on the determination result in the state determination step It is. Note that the state determination step may be performed as part of the abnormality processing step.

  In these inventions, the operation when the toner amount detection result for the patch image is not within the proper range differs depending on the state of the image forming unit. That is, the reason that the toner amount detection result is out of the proper range even though the image forming unit is in the first state in which a good image can be formed is considered to be due to an abnormality in the apparatus. On the other hand, in the second state, the toner amount variation in the patch image is a phenomenon that is expected to some extent. Therefore, the abnormality in the toner amount detection result is not necessarily due to an accidental abnormality of the apparatus. Therefore, if the content of the post-processing when the toner amount detection result is not within the proper range, that is, the abnormal process is changed according to the state of the apparatus, an appropriate process according to the state of the apparatus can be performed. It is possible to improve user convenience.

  The contents of the abnormal processing according to the state of the image forming means can be as follows, for example. That is, when the image forming unit is in the first state, execution of the image forming operation by the image forming unit is prohibited. On the other hand, when the image forming unit is in the second state, the image forming unit by the image forming unit. Allows execution of an action. By doing so, in the first state, it is possible to prevent an image from being formed with poor image quality due to an abnormality of the apparatus. Further, in the second state, although image quality may be inferior, it is possible to form an image once, so that convenience for the user is improved.

  Here, even when the image forming unit is in the second state, it may be better to prohibit the image forming operation. As described above, the natural degradation of the apparatus often appears as a decrease in the toner amount, and it is unlikely that the toner amount will increase due to such degradation. That is, if an abnormally high toner amount is detected in the second state, there is a high possibility that some abnormality has occurred in the apparatus. Therefore, when the toner amount detection result deviates from the proper range to the high toner amount side, execution of the image forming operation by the image forming unit is prohibited, while the toner amount detection result deviates from the proper range to the low toner amount side. The image forming unit may allow the image forming operation to be performed when the image forming unit is in the open state. By so doing, it is possible to more reliably detect the occurrence of abnormality while allowing image formation in the second state.

  This image forming apparatus may further include notifying means for notifying the user of the state of the apparatus to the user when necessary when abnormality processing is executed. In particular, when the image forming unit is in the second state and image formation is permitted, it is desirable to notify the user in advance that the desired image quality may not be obtained.

  In the second state, the image forming operation may be permitted only when the user performs a predetermined operation. In other words, a wasteful image that does not meet the user's wishes can be formed by performing image formation only when the user expresses an intention to acknowledge that there is a possibility of image quality degradation. Is prevented.

  Further, in each image forming apparatus configured as described above, the following information can be used as index information for determining the state of the image forming unit. For example, when the image forming means has a latent image carrier capable of carrying an electrostatic latent image, the operating amount of the latent image carrier can be used as the index information. As the operation amount here, the operation time of the latent image carrier or the number of rotations of the latent image carrier when the latent image carrier is configured as a rotating body can be used.

  When the image forming unit is configured to store toner, the remaining amount of toner can be used as the index information. Of course, the remaining toner amount may be calculated from the initial toner amount and the toner consumption amount. When the image forming unit has a toner carrier that carries toner, the operation amount of the toner carrier can be used as the index information. Also in this case, the operation time of the toner carrier and the number of rotations thereof can be used. These pieces of information are information whose values gradually change as the image forming unit is used, and can be used as index information for estimating the state of the image forming unit.

  In the apparatus for determining the state of the image forming unit based on the index information about the toner, when the image forming unit is configured to be able to form a color image with a plurality of toner colors, it corresponds to each of the plurality of toner colors. When all of the index information to be satisfied satisfies a predetermined image quality maintenance condition, the apparatus is determined to be in the first state. On the other hand, when at least one of the index information does not satisfy the image quality maintenance condition, the apparatus is in the second state. You may make it determine with there. It is important to balance each toner color in order to form a color image with good image quality. If good image quality cannot be maintained even with a single toner color, good image quality can be achieved for the color image. I can't hope. Therefore, when a condition necessary for maintaining a good image quality for any one of the toner colors is not satisfied, the image forming unit is in the second state even if the conditions for the other toner colors are satisfied. It is desirable to be determined.

  Hereinafter, two embodiments of an image forming apparatus to which the present invention is applied will be sequentially described. Each of these embodiments has the same apparatus configuration, and some of the operation contents are different from each other. Therefore, first, the configuration of the apparatus will be described, and then the operation in each embodiment will be described.

(Device configuration)
FIG. 1 is a diagram showing the configuration of an image forming apparatus according to the present invention. FIG. 2 is a block diagram showing an electrical configuration of the image forming apparatus of FIG. This apparatus 1 forms a full color image by superposing four color toners (developers) of yellow (Y), cyan (C), magenta (M), and black (K), or black (K) toner. This is an image forming apparatus that forms a monochrome image using only the image forming apparatus. In the image forming apparatus 1, when an image signal is given to the main controller 11 from an external device such as a host computer, the engine controller 10 controls each part of the engine unit EG in accordance with a command from the main controller 11 to obtain a predetermined image. The forming operation is executed, and an image corresponding to the image signal is formed on the sheet S.

  In the engine unit EG, the photosensitive member 22 is provided to be rotatable in the arrow direction D1 in FIG. A charging unit 23, a rotary developing unit 4 and a cleaning unit 25 are arranged around the photosensitive member 22 along the rotation direction D1. The charging unit 23 is applied with a predetermined charging bias, and uniformly charges the outer peripheral surface of the photoconductor 22 to a predetermined surface potential. The cleaning unit 25 removes the toner remaining on the surface of the photosensitive member 22 after the primary transfer, and collects it in a waste toner tank provided inside. The photosensitive member 22, the charging unit 23, and the cleaning unit 25 integrally constitute the photosensitive member cartridge 2, and this photosensitive member cartridge 2 is detachably attached to the main body of the apparatus 1 as a whole.

  Then, the light beam L is irradiated from the exposure unit 6 toward the outer peripheral surface of the photosensitive member 22 charged by the charging unit 23. The exposure unit 6 exposes the light beam L onto the photosensitive member 22 in accordance with an image signal given from an external device, and forms an electrostatic latent image corresponding to the image signal.

  The electrostatic latent image thus formed is developed with toner by the developing unit 4. That is, in this embodiment, the developing unit 4 is configured as a support frame 40 that is rotatably provided about a rotation axis center orthogonal to the paper surface of FIG. A yellow developing device 4Y, a cyan developing device 4C, a magenta developing device 4M, and a black developing device 4K are provided. The developing unit 4 is controlled by the engine controller 10. Based on the control command from the engine controller 10, the developing unit 4 is driven to rotate, and the developing units 4Y, 4C, 4M, and 4K are selectively positioned at predetermined developing positions facing the photoconductor 22. Then, the toner is applied to the surface of the photosensitive member 22 from the developing roller 44 which is provided in the developing unit and carries the charged toner of the selected color and to which a predetermined developing bias is applied. As a result, the electrostatic latent image on the photosensitive member 22 is visualized with the selected toner color.

  Each of the developing devices 4Y, 4C, 4M, and 4K is provided with non-volatile memories 91 to 94 for storing information related to the developing devices. One of the connectors 49Y, 49C, 49M, and 49K provided in each developing device is selected as necessary, and the connector 109 provided on the main body side is connected to each other, and the CPU 101 of the engine controller 10 and the memory Communication is performed with 91-94. In this way, information about each developing device is transmitted to the CPU 101, and information in each of the memories 91 to 94 is updated and stored.

  The toner image developed by the developing unit 4 as described above is primarily transferred onto the intermediate transfer belt 71 of the transfer unit 7 in the primary transfer region TR1. The transfer unit 7 includes an intermediate transfer belt 71 stretched between a plurality of rollers 72 to 75, and a drive unit (not shown) that rotates the intermediate transfer belt 71 in a predetermined rotation direction D2 by rotationally driving the roller 73. It has. When a color image is transferred to the sheet S, each color toner image formed on the photosensitive member 22 is superimposed on the intermediate transfer belt 71 to form a color image and taken out from the cassette 8 one by one. The color image is secondarily transferred onto the sheet S conveyed to the secondary transfer region TR2 along the conveyance path F.

  At this time, in order to correctly transfer the image on the intermediate transfer belt 71 to a predetermined position on the sheet S, the timing of feeding the sheet S to the secondary transfer region TR2 is managed. Specifically, a gate roller 81 is provided on the transport path F on the front side of the secondary transfer region TR2, and the gate roller 81 rotates in accordance with the timing of the circumferential movement of the intermediate transfer belt 71. S is sent to the secondary transfer region TR2 at a predetermined timing.

  Further, the sheet S on which the color image is thus formed is conveyed to the discharge tray portion 89 provided on the upper surface portion of the apparatus main body via the fixing unit 9, the pre-discharge roller 82 and the discharge roller 83. Further, when images are formed on both sides of the sheet S, when the rear end portion of the sheet S on which the image is formed on one side as described above is conveyed to the reversal position PR behind the pre-discharge roller 82. The rotation direction of the discharge roller 83 is reversed, whereby the sheet S is conveyed in the direction of the arrow D3 along the reverse conveyance path FR. Then, the sheet is again placed on the transport path F before the gate roller 81. At this time, the surface of the sheet S to which the image is transferred by contacting the intermediate transfer belt 71 in the secondary transfer region TR2 is first transferred. It is the opposite surface. In this way, images can be formed on both sides of the sheet S.

  Further, a density sensor 60 and a cleaner 76 are provided in the vicinity of the roller 75. The density sensor 60 optically detects the amount of toner constituting the toner image formed on the intermediate transfer belt 71 as necessary. That is, the density sensor 60 irradiates light toward the toner image, receives reflected light from the toner image, and outputs a signal corresponding to the reflected light amount. Since the amount of reflected light varies depending on the amount of toner on the intermediate transfer belt 71, the level of the output signal from the density sensor 60 eventually corresponds to the density of the toner image. The cleaner 76 is configured to be able to come into contact with and separate from the intermediate transfer belt 71, and scrapes the residual toner on the belt 71 by contacting the intermediate transfer belt 71 as necessary.

  In addition, the apparatus 1 includes a display unit 12 controlled by the CPU 111 of the main controller 11 as shown in FIG. The display unit 12 is constituted by, for example, a liquid crystal display, and in accordance with a control command from the CPU 111, the operation guidance to the user, the progress of the image forming operation, the occurrence of an abnormality in the apparatus, the replacement timing of any unit, etc. A predetermined message for notification is displayed.

  In FIG. 2, reference numeral 113 denotes an image memory provided in the main controller 11 for storing an image given from an external device such as a host computer via the interface 112. Reference numeral 106 is a ROM for storing a calculation program executed by the CPU 101, control data for controlling the engine unit EG, and the like. Reference numeral 107 is a RAM for temporarily storing calculation results in the CPU 101 and other data. is there.

  In the image forming apparatus 1 configured as described above, a toner image as a patch image is formed at a predetermined timing such as immediately after the apparatus is turned on or when the number of formed images reaches a predetermined number. Based on the density detection result, the engine controller 10, more specifically the CPU 101, performs an adjustment operation for adjusting the developing bias of the apparatus, and controls the image density to a predetermined target density. In this way, an image can be stably formed with a predetermined image quality.

  Since the image pattern of the patch image is known, the image density can be predicted to some extent, and as long as the apparatus is operating normally, the image density of the patch image that is actually formed will be close to the predicted value. . On the other hand, a detection result greatly different from the predicted value may be obtained due to a malfunction of the apparatus. In this apparatus 1, a range that can be regarded as appropriate for the patch image density is determined in advance, and the subsequent operation contents differ depending on whether or not the actual density detection result is within the appropriate range. The specific operation will be described by exemplifying two embodiments below. In the following, the scale of the density of the patch image is represented by the image density converted from the output signal of the density sensor 60. Since the density of the patch image reflects the amount of toner constituting the patch image, the patch image The principle is the same even if the amount of toner constituting the image is used as a scale.

(First embodiment)
FIG. 3 is a flowchart showing the first embodiment of the adjustment operation in the present invention. In this adjustment operation, first, it is determined what state the engine unit EG is currently in (step S101).

  When each component constituting the engine unit EG maintains a predetermined performance and a sufficient amount of toner is stored in each developing device, it is determined that the engine unit EG is in the first state. To do. In this first state, as long as no sudden abnormality occurs, image formation can be performed with image quality that satisfies the specifications of the apparatus.

  On the other hand, if any of the components of the engine unit EG deteriorates in performance or if the remaining amount of toner in any of the developing devices decreases, an image can be formed with image quality that satisfies the specifications of the apparatus. It may not be possible. In such a case, it is determined that the engine unit EG is in the second state. Note that the performance of components and the remaining amount of stored toner gradually decrease, and the image quality gradually decreases accordingly. Therefore, just because the engine unit EG is in the second state does not mean that the image quality of the formed image is always poor. However, while a constant image quality is always guaranteed in the first state, there is no such guarantee in the second state.

  Examples of the index information that indicates the state of the engine unit EG include the remaining amount of toner (or toner consumption) in each developing device, the operation amount (rotation time or rotation speed) of the photosensitive member 22, and the operation amount of the developing roller 44. (Rotation time or number of rotations) can be used. As shown below, these values affect the quality of the formed image. Note that the state of the engine unit EG can be determined based on any one of these pieces of index information or an appropriate combination thereof.

  When the toner in the developing device becomes low, a sufficient amount of toner is not supplied to the developing roller 44, resulting in insufficient image density. The amount of consumed toner or the amount of toner remaining in the developing device can be determined by directly measuring the amount of toner in the developing device, for example. Further, the toner consumption amount for each color can be estimated based on the toner count value calculated based on the image signal given from the external device.

  Even if toner remains in the developing device, its characteristics may be deteriorated. The degree of this degradation also affects the image quality. For example, in the case of toner that has been repeatedly adhered to and peeled from the developing roller 44 in the developing unit, the charging efficiency is lowered, and thus the developing efficiency is lowered. The degree of toner deterioration can be estimated not only from the remaining amount of toner but also from the total rotation time or rotation speed of the developing roller 44.

  Further, the photoconductor 22 is worn and thin as it is used, and the performance thereof is also reduced. Generally, when the photosensitive member 22 is worn, an electrostatic latent image having a sufficient contrast cannot be formed, and as a result, the density of the formed toner image is lowered. That is, when the total operation amount of the photosensitive member 22 becomes large, sufficient image quality may not be obtained. The degree of wear of the photosensitive member 22 can be estimated from the total rotation time or rotation speed.

  When the state determination is performed based on the index information related to the developing device or the toner, the index information exists for each toner color. In this case, the engine unit EG is in the first state when all the index information indicates that a condition for enabling image formation with good image quality (hereinafter referred to as “image quality maintenance condition”) is satisfied. It is determined that On the other hand, when at least one toner color has index information that does not satisfy the image quality maintenance condition, the engine unit EG determines that the engine state is in the second state. This is because the image quality of a color image cannot be maintained if there is even one toner color for which sufficient image quality cannot be obtained.

  However, the black color (K) that is the toner color corresponding to the monochrome image may be specially handled. In other words, there is no need to consider the balance with other colors in a monochrome image, and the mainly formed image is a character image or line drawing that does not require relatively high gradation reproducibility. May be. Therefore, if only the index information for the black color does not satisfy the image quality maintenance condition and all the index information for the other toner colors satisfies this condition, it may be determined that the engine unit EG is in the first state. it can.

  Of course, since the performance of the photoconductor 22 affects all toner colors, it is not appropriate to treat the index information regarding the photoconductor 22 in this way. That is, it is desirable to determine the first state when the index information regarding the photoconductor 22 satisfies the image quality maintenance condition, and the second state when the index information does not satisfy the image quality maintenance condition.

Examples of image quality maintenance conditions are shown below (the number of sheets formed is equivalent to Japanese Industrial Standard A4 version):
The operating amount of the photoreceptor 22 is equal to or less than 16000 sheets formed;
For toner consumption, a toner count value of 12000000 or less;
The operating amount of the developing roller 44 is less than or equal to 6000 sheets.

  Further, in this image forming apparatus, since the density sensor 60 detects the density of the patch image transferred to the intermediate transfer belt 71, the toner image visualized on the photosensitive member 22 is applied to the intermediate transfer belt 71. There is also a possibility that density changes occur during the transfer process. Since such a change depends on the degree of wear of the intermediate transfer belt 71, the image quality maintaining condition may be set for the operation amount of the transfer unit 7.

  By defining the image quality maintenance condition in this way, it is determined as the first state when the engine unit EG is new and the toner remaining amount is sufficient. Then, as the use progresses, each operation information is also updated, and the engine unit EG shifts to the second state at a certain time. The fact that the engine unit EG is in the second state indicates that it is time to replace the unit of the photosensitive member 22 or the developing devices 4Y, 4M, 4C, and 4K.

  When performing the state determination of the engine unit EG, it is also possible to refer to the result of the state determination performed previously. That is, once the engine unit EG shifts to the second state, it does not return to the first state unless the unit that has been replenished with toner or is exhausted is replaced. Therefore, when it is determined that the engine unit EG is in the second state in the adjustment operation performed earlier and there is no fact that necessary unit replacement has been performed thereafter, the CPU 101 does not need to refer to each index information. It can be determined that the engine unit EG is still in the second state.

  When the engine unit EG is in the second state and there is a request for image formation from a user or an external device, the desired image quality may not be obtained if image formation is performed as it is. Therefore, generally prohibiting image formation in such a state. However, in this case, the following problems occur. That is, even if the engine unit EG shifts to the second state, it does not immediately cause noticeable image quality degradation. Nevertheless, if the image formation cannot be performed, the apparatus cannot be used effectively. In addition, since the user does not always prepare a replacement unit, the apparatus cannot be used until a new unit is obtained. In addition, some users want to use up the unit to the end of its service life with a view to cost merit, and knowing that the image quality is somewhat deteriorated. However, such a request cannot be met.

  In this embodiment, these problems are solved by performing the adjustment operation as follows. That is, after determining the state of the engine unit EG as described above, an appropriate range for the patch image density is determined according to the determination result (steps S102 and S103). As will be described later, in the adjustment operation in this embodiment, the development bias Vb is changed and set in a plurality of stages to form a patch image. Then, an appropriate range is typically determined for each of the patch images at the minimum value Vbmin and the maximum value Vbmax, and whether or not there is an abnormality is determined by comparing the actually detected density with the appropriate range. To do.

  FIG. 4 is a diagram showing an example of setting an appropriate range of patch image density in this embodiment. First, a case where the state of the engine unit EG is the first state will be described with reference to FIG. In this case, appropriate ranges R1min and R1max are determined for patch images corresponding to the development bias Vbmin at which the patch image is expected to have the lowest density and the development bias Vbmax at which the highest density is expected, respectively. . This appropriate range corresponds to a range of density variation assumed when an image is formed using the engine unit EG in the first state. In FIG. 3, the appropriate ranges R1min and R1max are collectively referred to as “first range”.

  Here, for the appropriate range R1min, it is desirable to set the target density Dt for the patch image as its upper limit, and for the appropriate range R1max, the target density Dt as its lower limit. By doing so, the following effects can be obtained. As long as the density detection results of the patch images corresponding to the development biases Vbmin and Vbmax are in the appropriate ranges R1min and R1max, respectively, as shown by the white circles in FIG. An optimum value Vbopt of the developing bias that coincides with the target density Dt always exists between Vbmin and Vbmax. Therefore, in this case, in this image forming apparatus, a desired image density can be obtained by setting the developing bias Vb to the optimum value Vbopt.

  On the other hand, as shown by the black circles in FIG. 4A, the patch image density may be out of the proper range. In this first state, each index information indicates that the apparatus should be in a state where image formation can be performed with good image quality. Nevertheless, if the patch image density is out of the proper range, it can be considered that some abnormality has occurred in the apparatus. Thus, by determining whether the density detection result of the patch image is within an appropriate range, it is possible to detect an abnormality of the apparatus.

  Next, a case where the state of the engine unit EG is the second state will be described with reference to FIG. In this state, the density variation of the patch image is larger than that in the first state even if there is no problem in the apparatus itself. Therefore, appropriate ranges R2min and R2max that are wider than the appropriate range in the first state are set in correspondence with the developing biases Vbmin and Vbmax, respectively. In particular, since the image density often decreases in the second state, it is preferable to extend the appropriate range to the low density side. In FIG. 3, the appropriate ranges R2min and R2max are collectively referred to as “second range”.

  Returning to FIG. 3, the description of the adjustment operation will be continued. As described above, in this adjustment operation, the state of the engine unit EG is determined, and an appropriate range for the patch image density is determined based on the result (steps S101 to S103). Here, when the engine unit EG is in the second state, since it is almost time to replace any unit, a message to that effect is displayed on the display unit 12 (step S104). Thereby, the user can prepare a new unit before image formation becomes impossible. Although the operation for one toner color will be described below, the following operation is actually executed for each toner color.

  Next, a patch image of a predetermined pattern is formed with each bias value while changing and setting the developing bias Vb in a plurality of stages within the variable range (Vbmin to Vbmax) (step S105). Subsequently, the image density is detected by the density sensor 60 (step S106). Then, for each patch image formed with the minimum development bias Vbmin and the maximum development bias Vbmax, it is determined whether or not the density detection result is within the predetermined appropriate range (step S107).

  At this time, if the density detection results for the two patch images are both within the appropriate range, the apparatus can be regarded as operating normally. Therefore, the optimum value or suboptimal value of the developing bias Vb is calculated based on the density detection result of each formed patch image (step S108). Here, if the engine unit EG is in the first state, there is a bias value Vbopt in which the image density coincides with the target density Dt within the variable range of the developing bias Vb, so that value is the optimum value of the developing bias Vb. It can be.

  Further, when the engine unit EG is in the second state, there is not always a bias value in which the image density matches the target density Dt. If there is such a value, it is a matter of course that the value may be set as an optimum value. If not, the bias value at which the image density is closest to the target density can be used as the next best value. In the example of FIG. 4B, if the developing bias Vb is the maximum value Vbmax in the variable range, an image density closest to the target density can be obtained.

  By performing the image forming operation with the developing bias Vb set to the optimum value or the suboptimal value thus obtained, the following effects can be obtained. First, when the engine unit EG is in the first state, an image with a desired image density Dt can be stably obtained. Since the image density of each toner color is appropriately controlled, the balance between the toner colors is not lost, and a color image with good image quality can be stably formed. Further, even when the engine unit EG is in the second state, an image forming operation can be performed, and the development bias Vb is adjusted so as to be as close to the optimum state as possible, so that deterioration in image quality can be suppressed.

  On the other hand, if at least one of the density detection results for the two patch images is out of the appropriate range, the CPU 101 executes the following error processing. That is, it is determined that there is an abnormality in the apparatus (step S109), an error message indicating that there is an abnormality is displayed on the display unit 12 (step S110), and the subsequent image forming operation by the engine unit EG is prohibited. (Step S111). This prevents an image from being formed while the apparatus is in an abnormal state. Also, the user can know the occurrence of an abnormality and take necessary measures.

  The device abnormality referred to here includes not only the case where the density of the formed image is far from the original density due to the abnormality of the engine unit EG, but also that which occurs in the process of density detection. For example, due to relatively minor problems such as contamination of the density sensor 60 and the intermediate transfer belt 71 and poor contact of the wiring, the actual patch image has a correct density, but the detection result may be incorrect. is there. Therefore, the adjustment operation may be executed again after the cleaning work is completed, with the message to the user prompting the cleaning work of the apparatus. Then, if the abnormality is not solved by this, it is considered that the abnormality is more serious, and therefore a message prompting a serviceman to check may be displayed.

  As described above, in this embodiment, the appropriate range for the patch image density for determining whether or not there is an abnormality in the apparatus differs depending on the state of the engine unit EG. More specifically, when the engine unit EG is in the first state in which an image can be formed with good image quality, a relatively narrow appropriate range is determined. On the other hand, when the engine unit EG is in the second state in which the image quality may deteriorate, an appropriate range wider than this is determined. If the density detection result of the patch image is out of the appropriate range, it is determined that the apparatus is abnormal and the image forming operation is prohibited. By doing so, the following effects can be obtained.

  When the engine unit EG is in the first state, an image can be stably formed with good image quality. Further, even a minor abnormality can be reliably detected with respect to what appears as a change in patch image density. Therefore, there is no problem that an image having a reduced image quality due to an abnormality in the apparatus is wasted. In addition, since the user can recognize the abnormality at an early stage and take appropriate measures to eliminate it, the maintenance is excellent.

  Further, when the engine unit EG is in the second state, the image quality may be lowered, but the image formation can be continuously performed according to the user's request, so that the apparatus is convenient for the user. . In particular, by extending the appropriate range to the low density (low toner amount) side, the density reduction due to the natural performance degradation of the apparatus is allowed, so that the life of the photoreceptor 22 and the developing device 4Y etc. is full. It can respond to the user's request to use up. Also in this case, when the patch image density is out of the appropriate range, it is determined that there is an abnormality. Therefore, even when an abnormality occurs in the apparatus, appropriate measures can be taken.

  In addition, when the engine unit EG is in the second state, a message indicating that fact is displayed on the display unit 12. Therefore, even if some quality degradation is seen in the image formed in this state, the user can You can know that it is due to natural deterioration. If the image quality reaches the required level, the user can continue to use the device as it is. If the image quality is unsatisfactory, the user performs necessary maintenance work (for example, unit replacement) according to the message. Just do it.

(Second Embodiment)
FIG. 5 is a flowchart showing a second embodiment of the adjusting operation in the present invention. In the adjustment operation of the second embodiment, the appropriate range for the density detection result of the patch image is fixed. That is, the same appropriate range is applied regardless of whether the engine unit EG is in the first state or the second state. However, the content of post-processing when the patch image density is out of the appropriate range varies depending on the state of the engine unit EG.

  In this embodiment, a patch image is first formed (step S201). The method is the same as in the first embodiment, and a patch image is formed with each bias value while changing and setting the development bias Vb in multiple stages within the variable range (Vbmin to Vbmax). And also in the point which detects the density of those image densities, it is the same as 1st Embodiment (step S202). Subsequently, the density detection results of two patch images formed with the minimum bias value Vbmin and the maximum bias value Vbmax among these patch images are compared with a predetermined appropriate range.

  FIG. 6 is a diagram showing an example of setting an appropriate range of patch image density in this embodiment. In this embodiment, there are provided appropriate ranges of a range Rmin for the patch image density at the minimum bias value Vbmin and a range Rmax for the patch image density at the maximum bias value Vbmax. This is the state of the engine unit EG. Regardless of, it is determined in one way. In addition, each appropriate range can be determined based on the same idea as the appropriate range corresponding to the first state of the engine unit EG in the first embodiment.

  Returning to FIG. 5, the description of the adjustment operation will be continued. In step S203, it is determined whether or not the density detection results of the two patch images exceed the appropriate range. If at least one of the two patch images deviates from the appropriate range to a higher density side as indicated by the black circles in FIG. 6, it is not a natural change of the apparatus, and the toner adhesion amount is more than necessary. It is suspected that there is an abnormality in the apparatus such as an increase in the output signal of the concentration sensor 60 or an abnormality. Therefore, in such a case, error processing in steps S209 to S211 is performed. The content of this error process is the same as the error process in the first embodiment (steps S109 to S111 in FIG. 3).

  If not, step S204 is executed to determine whether each density detection result is below the lower limit value of the appropriate range. If all of these determination results are NO, that is, if the concentration detection result is equal to or greater than the lower limit value of the appropriate range, it is understood that the concentration detection result is within the appropriate range as shown by the white circles in FIG. In this case, since there is always an optimum value Vbopt that can control the image density to the target density Dt within the variable range of the developing bias Vb, a process for calculating this optimum value is performed as in the first embodiment. (Step S205).

  On the other hand, if the determination result in step S204 is YES, that is, if either concentration detection result is below the lower limit value of the appropriate range as indicated by the triangular mark in FIG. 6, first, the state determination for the engine unit EG is performed. (Step S206), and the subsequent operation changes depending on the determination result. The state determination in this embodiment can be performed in the same manner as the state determination in the first embodiment.

  If the engine unit EG is in the first state, it is highly possible that the insufficient concentration is due to an abnormality in the apparatus. Therefore, in this case, the process proceeds to step S209 to perform error processing. If the engine unit EG is in the second state, it is difficult to determine whether the insufficient density is due to an abnormality in the apparatus, or due to an insufficient amount of remaining toner or natural deterioration of the apparatus. Therefore, in such a case, the apparatus is not regarded as abnormal, and the apparatus is put in a state where image formation is possible. That is, the optimum value of the developing bias Vb for obtaining the target density Dt or the suboptimal value of the developing bias Vb for obtaining the image density as close as possible to the target density Dt is calculated from the density detection result of each patch image (step S208). ), By enabling the image forming operation with this bias value, deterioration of image quality is suppressed. Also in this case, as in the first embodiment, a message for notifying the user that the engine unit EG is in the second state is displayed on the display unit 12 (step S207).

  FIG. 7 is a diagram showing the result of the adjustment operation in this embodiment. In FIG. 7, “excess density” and “insufficient density” in the density detection results respectively indicate that “at least one of the density detection results for the two patch images deviates to a higher density side than the appropriate range”, “two patches”. "At least one of the density detection results for the image is out of the low density side from the appropriate range". The “optimum condition” represents a state in which the development bias Vb is set to the optimum value Vbopt for all toner colors. Further, the “condition according to the optimum condition” refers to a state in which the development bias Vb is set to the sub-optimal value for at least one of the toner colors and the other is set to the optimum value Vbopt. This includes a state in which a suboptimal value is set for the toner color.

  As shown in FIG. 7, the result of the adjustment operation as described above is as follows. When the density of the patch image is within an appropriate range, there is no abnormality in the apparatus, and image formation can be performed under optimal image formation conditions. Thereby, an image with good image quality can be stably formed. Further, when at least one of the two patch images has an excessive density, image formation is prohibited. On the other hand, when the density of the patch image is insufficient, image formation is prohibited if the engine unit EG at that time is in the first state, but image formation is possible if the engine unit EG is in the second state. is there.

  As described above, in this embodiment, an appropriate range in which the apparatus can be regarded as normal with respect to the density of the formed patch image is provided in advance. When the density detection result is within the appropriate range, it is assumed that the apparatus is operating normally, and the optimum value Vbopt of the developing bias Vb is calculated based on the density detection result. By performing the image forming operation with the developing bias Vb set to the optimum value Vbopt, the image forming apparatus can stably form an image with a desired image density. This is the same regardless of whether the engine unit EG is in the first state or the second state.

  On the other hand, when the density detection result is out of the appropriate range, the following processing is performed as an abnormal processing operation. If the engine unit EG is in the first state, it is considered that the concentration detection result is out of the proper range because an abnormality has occurred in the apparatus, and error processing is executed. This prevents the image forming operation from being performed in an abnormal state and an image having inferior image quality from being formed. Further, by displaying an error message indicating that an abnormality has occurred, it is possible to prompt the user to take necessary measures.

  In addition, when the engine unit EG is in the second state, it can be assumed in advance that an image density shortage due to toner shortage, device deterioration, or the like will occur. That is, in this state, it is a “predicted abnormality” that the density detection result of the patch image deviates from the appropriate range to the low density side. Accordingly, in this case, the image forming operation is maintained in a state where it can be temporarily used. This is convenient for the user who is not ready for the unit to be replaced or who wants to use up the entire life of the photosensitive member 22 and the developing device 4Y. This is an excellent device. On the other hand, the fact that the concentration detection result deviates to the high concentration side is considered to indicate that an “unexpected abnormality” has occurred in the apparatus. In this case, therefore, error processing is executed to prohibit image formation.

(Other)
As described above, in each of the above embodiments, the engine unit EG functions as the “image forming unit” of the present invention. Further, the engine controller 10, particularly the CPU 101, functions as the “state determination unit” and “control unit” of the present invention. Further, the density sensor 60, the photosensitive member 22, and the developing roller 44 function as the “toner amount detection means”, “latent image carrier”, and “toner carrier” of the present invention, respectively. The display unit 12 functions as the “notification unit” of the present invention. Furthermore, in the second embodiment, the process (steps S206 to S211) executed when the patch image density is out of the appropriate range corresponds to the “abnormal process” of the present invention.

  The present invention is not limited to the above-described embodiment, and various modifications other than those described above can be made without departing from the spirit of the present invention. For example, in the first embodiment, the appropriate range is expanded by lowering the lower limit value of the appropriate range of patch image density according to the state of the engine unit EG, while the upper limit value of the appropriate range is unchanged. However, the upper limit value may be changed.

  Further, in each of the above embodiments, the upper limit value or lower limit value of the appropriate range is made to coincide with the target density Dt, but this is not necessarily required. In short, the range of the density of the toner image (or the amount of toner constituting the toner image) that can be regarded as the apparatus operating normally with respect to the given development bias value may be set to an appropriate range.

  In each of the above embodiments, the image density is controlled by adjusting the developing bias Vb, so that patch images are formed with different developing bias values. An appropriate density range is determined for each patch image formed with two types of bias values, the minimum development bias Vbmin and the maximum development bias Vbmax. The number of patch images to be formed and the number of patch images among them to be provided with an appropriate density range may be arbitrary. Further, the developing bias Vb is not necessarily variable, and other operation parameters may be variable.

  In each of the above embodiments, the upper limit value and the lower limit value of the appropriate range for the patch image density are both provided, but only one of them may be provided. For example, the appropriate range may be set such that the patch image with the minimum development bias Vbmin is equal to or lower than the target density Dt and the patch image with the maximum development bias Vbmax is equal to or higher than the target density Dt. Even in this case, as long as the densities of both patch images are within the appropriate range, there exists an optimum bias value Vbopt that can control the image density to the target density Dt within the variable range (Vbmin to Vbmax) of the developing bias. This is because it is guaranteed.

  In the second embodiment, when the engine unit EG is in the second state, the insufficient density of the patch image is not handled as an abnormality of the apparatus. However, when the density is extremely insufficient, it may be treated as abnormal. Further, in this embodiment, the state determination of the engine unit EG is performed only when the density of the patch image is insufficient. However, even if the state determination is performed before the density of the patch image is compared with the appropriate range, the same is performed. That is.

  Further, in each of the above-described embodiments, when the engine unit EG is in the second state, an image forming operation can be performed after a message indicating that the unit replacement time is near is displayed on the display unit 12. Instead of this, for example, the following may be used. That is, a message indicating that there is a possibility that the image quality may be deteriorated is displayed, and if the user wishes to form an image with the knowledge, a specific operation input is performed. Only when the user performs the operation, a certain number of images are allowed to be formed. In this way, the image is formed using the engine unit EG in the second state only when the user specifically desires, and formation of useless images with image quality that does not satisfy the user's request is prevented. Is done. Here, the number of images that can be formed may be a fixed number such as 1 or 10, for example, or may be a number specified in the job.

  In each of the above embodiments, the present invention is applied to an apparatus that forms an image using toners of four colors, yellow, magenta, cyan, and black. However, the types and number of toner colors are limited to those described above. It is optional. In addition to the rotary development type apparatus as in the present invention, the so-called tandem type image forming apparatus in which developing units corresponding to the respective toner colors are arranged in a line along the sheet conveying direction. The present invention is also applicable. Furthermore, the present invention is not limited to the electrophotographic apparatus as in the above embodiment, but can be applied to all image forming apparatuses.

1 is a diagram showing a configuration of an image forming apparatus according to the present invention. FIG. 2 is a block diagram illustrating an electrical configuration of the image forming apparatus in FIG. 1. It is a flowchart which shows 1st Embodiment of adjustment operation in this invention. It is a figure which shows the example of a setting of the appropriate range of the patch image density in 1st Embodiment. It is a flowchart which shows 2nd Embodiment of adjustment operation | movement in this invention. It is a figure which shows the example of a setting of the appropriate range of the patch image density in 2nd Embodiment. It is a figure which shows the result of adjustment operation | movement in 2nd Embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 12 ... Display part (notification means), 22 ... Photoconductor (latent image carrier), 44 ... Developing roller (toner carrier), 60 ... Density sensor (toner amount detection means), 101 ... CPU (state determination means, control) Means), EG ... Engine (image forming means)

Claims (14)

An image forming means for performing an image forming operation to form a toner image;
Whether the state of the image forming means is a first state where the image quality of the toner image is the best or a second state where the image quality of the toner image may be inferior to the first state, State determination means for determining based on index information indicating the use history of the image forming means;
A toner amount detecting means for detecting a toner amount constituting the toner image as a patch image formed by the image forming means;
An appropriate range as the amount of toner constituting the patch image is set according to the determination result by the state determination unit, and when the detection result by the toner amount detection unit for the patch image is not within the appropriate range, An image forming apparatus comprising: a control unit that determines that there is an abnormality.   2. The control unit according to claim 1, wherein when the determination result by the state determination unit is the second state, the control unit sets the appropriate range so that the appropriate range is wider than when the determination result is the first state. The image forming apparatus described.   When the determination result by the state determination unit is in the second state, the control unit is configured so that the lower limit value of the appropriate range is on the lower toner amount side than when the determination result is in the first state. The image forming apparatus according to claim 1, wherein the range is set.   The information processing device according to claim 1, further comprising: a notification unit that notifies the user of the state of the device when the determination result by the state determination unit is in the second state and / or when the control unit determines that the device is abnormal. The image forming apparatus according to claim 3. An image forming means for performing an image forming operation to form a toner image;
Whether the state of the image forming means is a first state where the image quality of the toner image is the best or a second state where the image quality of the toner image may be inferior to the first state, State determination means for determining based on index information indicating the use history of the image forming means;
A toner amount detecting means for detecting a toner amount constituting the toner image as a patch image formed by the image forming means;
Control means for executing an abnormal processing operation when a detection result of the toner amount detection means for the patch image is not within a predetermined appropriate range;
The image forming apparatus according to claim 1, wherein the control unit varies processing contents of the abnormal processing operation in accordance with a determination result by the state determination unit. The control unit prohibits execution of the image forming operation by the image forming unit in the abnormality processing operation when the determination result by the state determining unit is the first state.
The image forming apparatus according to claim 5, wherein the image forming operation can be performed by the image forming unit in the abnormality processing operation when the determination result by the state determining unit is in the second state.   In the abnormal processing operation in which the determination result by the state determination unit is in the second state, the control unit is configured to output the image when the detection result by the toner amount detection unit deviates from the appropriate range to the high toner amount side. While the execution of the image forming operation by the forming unit is prohibited, when the detection result by the toner amount detecting unit deviates from the appropriate range to the low toner amount side, the execution of the image forming operation by the image forming unit is performed. 7. The image forming apparatus according to claim 6, wherein the image forming apparatus is permitted.   The image forming apparatus according to claim 5, further comprising an informing unit that informs a user of a state of the apparatus when necessary when the abnormality processing operation is performed. The image forming means has a latent image carrier capable of carrying an electrostatic latent image, and
The image forming apparatus according to claim 1, wherein the state determination unit uses an operation amount of the latent image carrier as the index information. The image forming means is configured to store toner, and
The image forming apparatus according to claim 1, wherein the state determination unit uses the remaining amount of toner in the image forming unit as the index information. The image forming means has a toner carrier for carrying toner, and
The image forming apparatus according to claim 1, wherein the state determination unit uses an operation amount of the toner carrier as the index information. The image forming means is configured to be capable of forming a color image with a plurality of toner colors, and
The state determination means determines that the apparatus is in the first state when all of the index information corresponding to each of the plurality of toner colors satisfies a predetermined image quality maintenance condition, while at least one of the index information 12. The image forming apparatus according to claim 10, wherein the image forming apparatus determines that the apparatus is in the second state when the image quality maintaining condition is not satisfied. There is a possibility that the state of the image forming unit that executes the image forming operation to form the toner image is the first state in which the image quality of the toner image is the best and the image quality of the toner image is inferior to the first state. A state determination step of determining which of the second states is based on index information indicating a use history of the image forming unit;
A setting step for setting an appropriate range as a toner amount constituting the toner image as a patch image according to a determination result in the state determination step;
A patch image forming step of forming the patch image by the image forming means;
An image forming apparatus control method comprising: detecting an amount of toner for the formed patch image, and determining that the apparatus is abnormal when the detection result is not within the proper range. . There is a possibility that the state of the image forming unit that executes the image forming operation to form the toner image is the first state in which the image quality of the toner image is the best and the image quality of the toner image is inferior to the first state. A state determination step of determining which of the second states is based on index information indicating a use history of the image forming unit;
A patch image forming step of forming the toner image as a patch image by the image forming means;
A detection step of detecting a toner amount for the formed patch image;
An abnormality processing step that is executed when the detection result in the detection step is not within a predetermined appropriate range, and
A control method for an image forming apparatus, wherein the processing contents of the abnormality processing step differ according to the determination result in the state determination step.

Images