JP2018028582A - Image formation device and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image formation device that can correctly operate a banding suppression function compared to a case in which a vibration pattern of an endless belt is not used.SOLUTION: An image formation device comprises an endless belt on which a toner image to be transferred on a medium is formed, suppression means that suppresses deviation of the toner image to be primarily transferred on the endless belt, control means that controls the suppression means, and a plurality of pieces of detection means that are provided on a path of the endless belt, and that detect a position of the endless belt. The control means comprises measurement means that measures a vibration pattern of the endless belt based on information obtained from the plurality of pieces of detection means, and storage means that stores the vibration pattern when the deviation of the toner image occurs, and when the vibration pattern stored in the storage means occurs, the suppression means is operated.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an image forming apparatus and a program.

  In Patent Document 1, the speed of the belt body is made constant by giving the belt body driving source in advance a speed increase amount that corrects the speed reduction of the belt body that occurs when the cardboard enters the transfer section. An image forming apparatus is disclosed.

JP-A-2005-107118

  An object of the present invention is to provide an image forming apparatus capable of correctly operating a banding suppression function as compared with a case where a vibration pattern of an endless belt is not used.

  The image forming apparatus according to claim 1 includes: an endless belt on which a toner image to be transferred to a medium is formed; a suppression unit that suppresses deviation of a toner image that is primarily transferred to the endless belt; and the suppression unit. Control means for controlling, and a plurality of detection means provided on a path of the endless belt for detecting the position of the endless belt, wherein the control means is information from the plurality of detection means. A measuring means for measuring the vibration pattern of the endless belt, and a storage means for storing the vibration pattern when the toner image shifts, and the vibration pattern stored in the storage means is generated. If so, the suppression means is activated.

  In the image forming apparatus according to claim 2, the storage unit is a case where a deviation of the toner image has occurred, and a vibration pattern different from the vibration pattern already stored by the measurement unit is measured. Update the vibration pattern already stored.

  4. The image forming apparatus according to claim 3, further comprising detection means for detecting occurrence of deviation of the toner image by comparing the toner image transferred to the medium and image information as a basis of the toner image. The means updates the vibration pattern based on information from the detection means.

  5. The image forming apparatus according to claim 4, wherein the detection unit includes a pair of first detection units provided along a circumferential direction of the endless belt and a pair of units provided apart from each other in the width direction of the endless belt. Second detection means.

  A program according to a fifth aspect causes a computer to function as a control unit included in the image forming apparatus according to any one of the first to fourth aspects.

  According to the first aspect of the present invention, the banding suppression function can be operated correctly as compared with the case where the vibration pattern of the endless belt is not used.

  According to the invention of claim 2, the activation condition of the banding suppression function is changed according to the state of consumables such as a belt.

  According to the invention of claim 3, the activation condition of the banding suppression function is changed while printing.

  According to the invention of claim 4, the banding suppression function can be appropriately activated as compared with the case where the vibration state of the endless belt is measured from one direction.

  According to the fifth aspect of the present invention, there is provided software capable of correctly executing the banding suppression function even if the type of paper that the user has placed in the tray and the type of paper instructed to be printed are different. be able to.

1 is a schematic view illustrating an entire configuration of an image forming apparatus according to an exemplary embodiment viewed from the front side (front side) in the apparatus depth direction. FIG. 2 is a schematic view of an image forming unit constituting the image forming apparatus according to the present embodiment as viewed from the front side. 2 is a block diagram of a control device that controls the image forming apparatus according to the present embodiment. FIG. FIG. 4 is a diagram showing (A) pitch pattern and (B) roll pattern as vibration patterns of the transfer belt in the present embodiment. It is a figure which shows the pattern for an update as a vibration pattern of the transfer belt in this Embodiment. It is a flowchart which concerns on the vibration pattern registration process in this Embodiment. It is a flowchart which concerns on the vibration pattern update process in this Embodiment. It is a flowchart which concerns on the banding suppression process in this Embodiment.

  An example of this embodiment will be described with reference to the drawings. In the following description, the direction indicated by the arrow Y in the drawings is the device height direction, and the direction indicated by the arrow X is the device width direction. In addition, a direction (indicated by an arrow Z) orthogonal to each of the apparatus height direction and the apparatus width direction is defined as an apparatus depth direction. In FIG. 1, the front side of the image forming apparatus 10 is the front side in the apparatus depth direction.

<Configuration of image forming apparatus>
As shown in FIG. 1, the image forming apparatus 10 includes an image forming unit 12 that forms an image on a medium P by an electrophotographic method, a fixing device 40 that fixes a toner image transferred to the medium P to the medium P, A medium transport unit 50 that transports the medium P and a post-processing unit 60 that performs post-processing and the like on the medium P on which an image is formed are configured. Further, the image forming apparatus 10 includes a control unit 70 that controls the above-described units and a toner replenishing device 80 that replenishes the toner image forming unit 20 with toner.

(Image forming part)
As shown in FIGS. 1 and 2, the image forming unit 12 includes a toner image forming unit 20 that forms a toner image, a transfer device 30 that transfers an image formed by the toner image forming unit 20 to a medium P, and It is comprised including.

(Toner image forming unit)
A plurality of toner image forming units 20 are provided so as to form a toner image for each color. In the present exemplary embodiment, toner image forming units 20Y, 20M, 20C, and 20K having a total of four colors of yellow (Y), magenta (M), cyan (C), and black (K) are provided. In addition, Y, M, C, and K shown in FIGS. 1 and 2 indicate the colors described above. In the above description, the toner image forming units 20Y, 20M, 20C, and 20K are described as the toner image forming unit 20.

  The toner image forming units 20Y, 20M, 20C, and 20K have substantially the same configuration except for the toner to be used. In the following description, the subscripts Y, M, C, and K are omitted for the toner image forming units 20Y, 20M, 20C, and 20K and the members constituting the toner image forming portions when the toner colors need not be distinguished.

  The toner image forming unit 20 includes a photosensitive drum unit 22, a charging device 24, an exposure device 26, and a developing device 28.

(Photosensitive drum unit)
The photosensitive drum unit 22 includes a photosensitive drum 90 shown in FIG. The photosensitive drum 90 is a cylindrical member and is driven to rotate around its own axis by a driving device (not shown). As an example, a photosensitive layer having a negative charging polarity is formed on the outer peripheral surface of the photosensitive drum 90. An electrostatic latent image is formed on the outer peripheral surface of the photosensitive drum 90 by an exposure device 26 described later. The electrostatic latent image formed on the outer peripheral surface of the photosensitive drum 90 is developed as a toner image by a developing device 28 described later. In other words, the photosensitive drum 90 is configured to hold a toner image. Here, the photosensitive drum 90 is an example of an image carrier.

  The photosensitive drums 90 (or photosensitive drum units 22) of the respective colors are arranged in a straight line along the apparatus width direction when viewed from the front side (see FIGS. 1 and 2). Further, the photosensitive drums 90 (or the photosensitive drum units 22) of the respective colors are arranged along the apparatus depth direction when viewed from the apparatus height direction.

(Charging device)
The charging device 24 charges the outer peripheral surface (photosensitive layer) of the photosensitive drum 90 to a negative polarity. In the present embodiment, the charging device 24 is a charging roll that is performed by bringing a roll into contact with the outer peripheral surface of the photosensitive drum 90. The charging device 24 for each color is disposed on the upper side in the device height direction of the photosensitive drum 90 for each color.

(Exposure equipment)
The exposure device 26 forms an electrostatic latent image on the outer peripheral surface of the photosensitive drum 90 charged by the charging device 24. Specifically, the exposure light modulated according to the image data received from the image signal processing unit 101 (see FIG. 3) constituting the control unit 70 is applied to the outer peripheral surface of the photosensitive drum 90 charged by the charging device 24. It comes to irradiate. An electrostatic latent image is formed on the outer peripheral surface of the photosensitive drum 90 by irradiation of exposure light from the exposure device 26. In the present embodiment, the exposure device 26 uses a light beam (an arrow from the exposure device 26 in FIG. 1 to the photosensitive drum 90) irradiated from a light source (not shown) as an optical scanning unit (not shown) including a polygon mirror. The surface of the photosensitive drum 90 is exposed while scanning. Further, the exposure devices 26 for the respective colors are arranged on the upper side in the apparatus height direction of the photosensitive drums 90 for the respective colors.

(Developer)
The developing device 28 develops the electrostatic latent image formed on the outer peripheral surface of the photosensitive drum 90 with a developer including toner and carrier as a toner image. The developing device 28 includes an accommodating portion 28A (see FIG. 2) for accommodating the developer, a developing roll 28B (see FIG. 2) for supplying the developer accommodated in the accommodating portion 28A to the photosensitive drum 90 while rotating. It is comprised including. The developing devices 28 for the respective colors are disposed on the right side in the apparatus width direction when viewed from the front side with respect to the photosensitive drums 90 for the respective colors.

  In the developing device 28, the toner inside the developing device 28 is consumed as the electrostatic latent image formed on the outer peripheral surface of the photosensitive drum 90 is developed as a toner image. Then, the toner contained in the toner replenishing device 80 is replenished to the developing device 28.

  The developing device 28 is provided with a toner concentration sensor (not shown) that measures the amount (remaining amount) of toner accommodated therein based on the relationship with the amount of carrier accommodated. The toner density sensor measures the amount (remaining amount) of toner inside the developing device 28 at a predetermined timing, and the control unit 70 to which the result is transmitted causes the toner to be supplied from the toner replenishing device 80 to the developing device 28. It is to be replenished.

(Transfer device)
As shown in FIGS. 1 and 2, the transfer device 30 performs primary transfer by superimposing the toner images formed on the photosensitive drums 90 of the respective colors on the transfer belt 36, and further, transferring the superimposed toner images to the medium. Secondary transfer to P is performed. 1 and 2, the transfer device 30 includes a transfer belt 36, a plurality of rolls 32, 32B, 32D, and 32T, a motor 32M, and a secondary transfer roll 34. . 1 and 2, the transfer device 30 includes a pair of light shielding sensors 35 (first light shielding sensor 35A and second light shielding sensor 35B) provided along the circumferential direction of the transfer belt 36, and A pair of transmission sensors 37 (a first transmission sensor 37A and a second transmission sensor 37B) provided apart from each other in the width direction of the transfer belt 36 are configured.

  The transfer belt 36 has an endless shape and is wound around a plurality of rolls 32, 32B, 32D, and 32T to determine the posture. The transfer belt 36 has an inverted obtuse triangular posture that is long in the apparatus width direction when viewed from the front side. The roll 32D functions as a drive roll that drives the transfer belt 36 so that the transfer belt 36 rotates in the direction of arrow A by the power of the motor 32M. The roll 32T functions as a tension applying roll that applies tension to the transfer belt. The roll 32 </ b> B functions as a counter roll of the secondary transfer roll 34.

  The transfer belt 36 is in contact with the photosensitive drum 90 of each color from the lower side in the apparatus height direction at the upper side extending in the apparatus width direction with the above-described posture. Then, the toner image held on each photosensitive drum 90 is primarily transferred to the transfer belt 36 by an electric field between the primary transfer roll 38 to which the primary transfer bias voltage is applied and the outer peripheral surface of the photosensitive drum 90. It has become so.

  Further, the transfer belt 36 is configured such that a transfer nip NT is formed by contacting the secondary transfer roll 34 at the apex on the lower side in the apparatus height direction that forms an obtuse angle. The transfer belt 36 passes through the transfer nip NT by the electric field between the roll 32 </ b> B to which the secondary transfer bias voltage is applied and the secondary transfer roll 34 after the toner image that has been primarily transferred while being superimposed on the transfer belt 36. Is transferred to the medium P.

  Here, in the transfer belt 36 that circulates, the transfer belt 36 rotates in the circumferential direction of the transfer belt 36 upstream of the portion 72 wound around the roll 32D and from the portion wound around the roll 32B. The downstream region is referred to as an upstream region 74 (see FIG. 2). Further, in the circumferentially moving transfer belt 36, the transfer belt 36 is disposed downstream of the portion 72 wound around the roll 32 </ b> D in the circumferential movement direction of the transfer belt 36 and from the portion wound around the roll 32 </ b> T in the circumferential movement direction. The upstream area is referred to as a downstream area 76 (see FIG. 2). A portion wound around the roll 32B corresponds to the transfer nip NT.

  For this reason, the tension in the upstream region 74 is larger than the tension in the downstream region 76 in a state where the transfer belt 36 is rotating.

  Here, when vibration occurs in the transfer belt 36 in the upstream region 74, banding tends to occur in the image transferred to the transfer belt 36. Here, “banding” is a deviation of the toner image, and appears on the medium P as streaks or color unevenness.

  In the present embodiment, four sensors (an example of detection means) are formed in the upstream region 74 of the transfer belt 36 in order to grasp the occurrence of banding. Specifically, a pair of light shielding sensors 35 (a first light shielding sensor 35A and a second light shielding sensor 35B) are formed on the front side of the transfer belt 36 and in the circumferential direction. The light shielding sensor 35 is formed so that light can be emitted from the light emitting portion to the transfer belt 36 and the reflected light can be received by the light receiving portion. Normally, in the light shielding sensor 35, the light reflected from the transfer belt 36 is received by the light receiving portion (signal ON state). However, if the distance between the light shielding sensor 35 and the transfer belt 36 is increased due to vibration in the thickness direction of the transfer belt 36 (hereinafter referred to as “pitch”), the light receiving portion of the light shielding sensor 35 is separated from the transfer belt 36. There is a case where the reflected light is not received more than a certain amount (signal OFF state).

A pair of transmission sensors 37 (first transmission sensor 37 </ b> A and second transmission sensor 37 </ b> B) are formed on the downstream side of the light shielding sensor 35 and in the width direction of the transfer belt 36.
This transmission sensor 37 irradiates light to the light receiving portion located across the transfer belt 36 from the light emitting portion, and can receive this irradiation light when there is no obstacle between the light emitting portion and the light receiving portion. Is formed. Usually, in the transmission sensor 37, since the transfer belt 36 does not exist between the light emitting unit and the light receiving unit, irradiation light is received by the light receiving unit (signal ON state). However, if the transfer belt 36 enters between the light emitting portion and the light receiving portion of the light shielding sensor 35 due to vibration in the width direction of the transfer belt 36 (hereinafter referred to as “rolling”), the irradiation light is not received (signal). OFF state) occurs.

  Here, the transfer belt 36 is an example of an endless belt. The light shielding sensor 35 is an example of a first detection unit. The transmission sensor 37 is an example of a second detection unit.

(Fixing device)
The fixing device 40 fixes the toner image onto the medium P on which the toner image has been transferred by the transfer device 30 (see FIG. 1). In the present embodiment, the fixing device 40 is configured to fix the toner image on the medium P by applying pressure while heating the toner image in the fixing nip NF.

(Toner replenisher)
The toner replenishing device 80 has a function of replenishing toner to the developing device 28. The toner replenishing device 80 replenishes the toner contained in the toner containing portion 82 to the developing device 28 via the reserve tank 84 and the toner transporting portion 86.

  The toner replenishment is performed under the control of the control unit 70 when the toner amount (remaining amount) inside the developing device 28 measured by the toner density sensor is less than a predetermined toner amount (remaining amount). It is like that.

(Media transport section)
The medium transport unit 50 includes a medium supply unit 52 that supplies the medium P to the image forming unit 12 and a medium discharge unit 54 that discharges the medium P on which the image is formed. Further, the medium transport unit 50 includes a medium return unit 58 that is used when images are formed on both sides of the medium P, and an intermediate transport unit 56 that transports the medium P from the transfer device 30 to the fixing device 40. Has been.

  The medium supply unit 52 supplies the medium P one by one to the transfer nip NT of the image forming unit 12 in accordance with the transfer timing of the secondary transfer. The medium discharge unit 54 discharges the medium P on which the toner image has been fixed by the fixing device 40 and formed an image from the medium discharge unit 54 to the outside of the apparatus. When an image is formed on the other side of the medium P on which an image is formed on one side, the medium return unit 58 reverses the front and back of the medium P and conveys it again to the image forming unit 12 (medium supply unit 52). It is supposed to let you.

(Post-processing section)
The post-processing unit 60 includes a medium cooling unit 62, a correction device 64, and an image inspection unit 66. The medium cooling unit 62 cools the medium P on which the image is formed by the image forming unit 12. The correcting device 64 corrects the curvature of the medium P cooled by the medium cooling unit 62. The image inspection unit 66 inspects the image formed on the medium P after the correction device 64 forces the curvature of the medium P.

<Operation of Image Forming Apparatus>
An outline of an image forming process (printing process) on the medium P by the image forming apparatus 10 and a post-processing process performed thereafter will be described.

  Upon receiving the image formation command (print instruction), the control unit 70 operates the toner image forming unit 20, the transfer device 30, and the fixing device 40. As a result, the photosensitive drum 90 and the developing roll 28B of the developing device 28 are rotated, and the transfer belt 36 is moved around. Further, the pressure roll 40A is rotated and the fixing belt 40B is rotated (see FIG. 1). Further, in synchronization with these operations, the control unit 70 operates the medium conveyance unit 50 and the like.

  As a result, the photosensitive drum 90 for each color is charged by the charging device 24 while being rotated. Further, the control unit 70 sends the image data subjected to the image processing by the image signal processing unit 101 (see FIG. 3) to the exposure device 26 for each color. The exposure device 26 emits exposure light L according to the image data, and exposes the charged photosensitive drum 90. As a result, an electrostatic latent image is formed on the outer peripheral surface of the photosensitive drum 90. The electrostatic latent image formed on the photosensitive drum 90 is developed as a toner image by the developer supplied from the developing device 28. As a result, toner images of corresponding colors among yellow (Y), magenta (M), cyan (C), and black (K) are formed on the photosensitive drums 90 of the respective colors.

  The toner images of the respective colors formed on the photoconductive drums 90 of the respective colors are sequentially primary-transferred sequentially to the transfer belt 36 that moves around by the application of the primary transfer bias voltage through the primary transfer rolls 38 of the respective colors. As a result, a toner image in which toner images for four colors are superimposed is formed on the transfer belt 36. This toner image is conveyed to the transfer nip NT by the circular movement of the transfer belt 36. A medium P is supplied to the transfer nip NT by the medium supply unit 52 so as to synchronize the timing of the toner image conveyance. By applying a secondary transfer bias voltage at the transfer nip NT, the toner image is secondarily transferred from the transfer belt 36 to the medium P.

  The medium P on which the toner image has been secondarily transferred is conveyed by the intermediate conveyance unit 56 from the transfer nip NT of the transfer device 30 toward the fixing nip NF of the fixing device 40 while being sucked with negative pressure. Thereafter, heat and pressure (fixing energy) are applied to the medium P on which the toner image has been transferred while passing through the fixing nip NF of the fixing device 40. As a result, the toner image secondarily transferred to the medium P is fixed to the medium P.

  The medium P discharged from the fixing device 40 is processed by the post-processing unit 60 while being conveyed by the medium discharge unit 54 toward the discharge medium receiving unit outside the apparatus. The medium P heated in the fixing process is first cooled in the medium cooling unit 62. Next, the curvature of the medium P is corrected by the correction device 64. Further, the toner image fixed on the medium P is detected by the image inspection unit 66 for the presence or absence of toner density defects, image defects, image position defects, and the like. Then, the medium P is discharged to the medium discharge unit 54.

  On the other hand, when an image is formed on the non-image surface of the medium P on which no image is formed (in the case of double-sided printing), the control unit 70 uses the medium discharge path to the transport path of the medium P after passing through the image inspection unit 66. The unit 54 is switched to the medium return unit 58. As a result, the medium P is returned to the medium supply unit 52 with its front and back reversed. An image is formed on the back surface of the medium P in the same process as the image forming process on the front surface. The medium P is discharged from the medium discharge unit 54 to the outside through the same process as the post-processing process after the image formation on the surface described above.

(Control part)
Next, the configuration of the control system of the image forming apparatus 10 according to the present embodiment will be described. FIG. 3 is a block diagram showing an example of the configuration of the control system of the image forming apparatus 10 according to the present embodiment.

  The control unit 70 (an example of control means) includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), a storage device, and the like, and controls the entire device and performs various calculations. It is configured as a computer to do. In the present embodiment, the CPU reads a processing program related to the banding suppression function stored in a storage device such as a ROM, and executes the processing program using the RAM as a work area.

  Various drives may be connected to the control unit 70. Each type of drive is a device that reads data from a computer-readable portable recording medium such as a flexible disk, a magneto-optical disk, or a CD-ROM, and writes data to the recording medium. When various drives are provided, the processing program may be recorded on a portable recording medium, and read and executed by a corresponding drive. The processing program may be provided via a network.

  Each component of the image forming apparatus 10 is connected to the control unit 70. For example, as shown in FIG. 3, a first light shielding sensor 35A, a second light shielding sensor 35B, a first transmission sensor 37A, a second transmission sensor 37B, and an image inspection unit 66 are connected to the input side. Further, an exposure device 26 and a motor 32M are connected on the output side.

  On the other hand, the control unit 70 includes an image signal processing unit 101, a vibration measurement unit 102, a storage unit 103, a suppression processing unit 104, and a detection unit 105.

  The image signal processing unit 101 has a function of processing image data that is a source of exposure light emitted from the exposure device 26. That is, the image data can be said to be image information that is a basis of the toner image. The image data includes data received from an image reading device (not shown) provided adjacent to the image forming apparatus 10, or data sent from a user PC or the like and received via a communication means (not shown).

  When receiving a print instruction from the user, the image signal processing unit 101 outputs image data to the exposure device 26. In addition, the image signal processing unit 101 can provide image data to the detection unit 105 described later in order to detect the occurrence of banding.

The vibration measuring unit 102 (an example of a measuring unit) measures the vibration pattern of the transfer belt 36 based on information from the first light shielding sensor 35A, the second light shielding sensor 35B, the first transmission sensor 37A, and the second transmission sensor 37B. To do.
4A and 4B are examples of vibration patterns of the transfer belt 36 registered in a vibration pattern registration process described later, and FIG. 5 is a transfer belt 36 updated in a vibration pattern update process described later. It is an example of a vibration pattern.

  Specifically, the vibration measurement unit 102 measures a vibration pattern based on signals from the first light shielding sensor 35A and the second light shielding sensor 35B at a predetermined time (for example, 4 ms). For example, as shown in FIGS. 4A and 5, the vibration pattern is measured based on the signal pattern generated in the first light shielding sensor 35 </ b> A and the second light shielding sensor 35 </ b> B as the transfer belt 36 is pitched. . As shown in FIGS. 4A and 5, even when the signal from the first light shielding sensor 35A and the signal from the second light shielding sensor 35B are ON and OFF are opposite (FIG. 4A ) And the pattern on the left side and the pattern on the right side in FIG.

  Further, the vibration pattern is measured based on signals from the first transmission sensor 37A and the second transmission sensor 37B at a predetermined time (for example, 4 ms). For example, as shown in FIG. 4B, the vibration pattern is measured based on the signal pattern generated in the first transmission sensor 37A and the second transmission sensor 37B as the transfer belt 36 rolls. Note that, as shown in FIG. 4B, even if the signal from the first transmission sensor 37A and the signal from the second transmission sensor 37B are opposite to each other (on the left side in FIG. 4B). , And the pattern on the right side) are measured as the same vibration pattern.

  The storage unit 103 (an example of a storage unit) stores a vibration pattern when banding that is a shift of a toner image primarily transferred to the transfer belt 36 occurs.

  For example, when banding occurs, as shown in FIG. 5, if there is a signal pattern repeatedly generated in the first light shielding sensor 35 </ b> A and the second light shielding sensor 35 </ b> B, in other words, a vibration pattern exists, this is stored in the RAM or the like. .

  Further, there are “temporary registration” and “registration” as vibration pattern storage modes in the storage unit 103. “Temporary registration” stores a vibration pattern generated in the transfer belt 36 regardless of the occurrence of banding. On the other hand, “registration” stores a vibration pattern when banding occurs.

  The suppression processing unit 104 (an example of a suppression unit) controls a banding suppression function that suppresses banding, which is a shift of a toner image primarily transferred to the transfer belt 36.

  Here, banding occurs when the speed of the transfer belt 36 decreases when thick paper enters the transfer nip NT. Therefore, in the banding suppression function of the present embodiment, banding is suppressed by increasing the rotational speed of the motor 32M so as to keep the speed of the transfer belt 36 constant in order to correct the decrease in the speed of the transfer belt 36. doing.

  On the other hand, the operation method of the banding suppression function is controlled by whether or not a vibration pattern in which banding occurs is detected by paying attention to the vibration of the transfer belt 36 when banding occurs. Specifically, the suppression processing unit 104 according to the present embodiment compares the vibration pattern measured by the vibration measurement unit 102 with the vibration pattern stored in the storage unit 103, that is, when the two match, that is, measurement. The banding suppression function is activated when the generated vibration pattern is a vibration pattern in which banding occurs. When the banding suppression function operates, the suppression processing unit 104 outputs a drive signal corresponding to the speed increase to be corrected to the motor 32M in order to correct the speed decrease of the transfer belt 36.

  The detection unit 105 (an example of a detection unit) detects the occurrence of banding by comparing the toner image transferred to the medium P with the image data that is the basis of the toner image. Here, the image inspection unit 66 scans the image forming surface of the medium P and converts the transferred toner image into data. The detection unit 105 acquires data relating to the toner image from the image inspection unit 66 and image data from the image signal processing unit 101, and detects the occurrence of banding when the two do not match. It should be noted that the case where “the two do not match” in the detection process does not include the case where the difference between the image data and the toner image transferred to the medium P is merely a difference in contrast and contrast of the entire image. In the detection unit 105, when a streak or color unevenness is generated in the toner image transferred to the medium P, it is determined that “the two do not match”.

<About banding suppression function>
The banding suppression function of this embodiment will be described in detail below. First, the banding suppression function of this embodiment includes three processes: (1) vibration pattern registration process, (2) vibration pattern update process, and (3) banding suppression process. In the following description, the term “print” is treated as synonymous with the term “image formation”.

(1) Vibration Pattern Registration Processing FIG. 6 is a flowchart showing the flow of vibration pattern registration processing. This process is executed in the printing standby state of the device in order to recognize individual differences between devices in the image forming apparatus 10.

  First, in step S <b> 100, sampling of the sheet conveyance sensor is started as the image forming apparatus 10 is turned on. Here, the paper transport sensor is a sensor (not shown) provided on the transport path of the medium P, and detects whether the transport of the medium P is started. Then, the process proceeds to next Step S101.

  In step S101, sampling of the light shielding sensor 35 and the transmission sensor 37 is started. That is, the vibration measurement unit 102 measures the vibration pattern of the transfer belt 36. For example, in a state where the medium P is not conveyed, the vibration pattern of the pattern 1 in FIG. Then, the process proceeds to next Step S102.

  In step S102, the vibration pattern measured in step S101 is provisionally registered as a vibration pattern of banding occurrence. Specifically, it is temporarily stored in the storage unit 103. In the above example, the vibration pattern of pattern 1 is temporarily registered. Then, the process proceeds to next Step S103.

  In step S103, a test chart is printed. For example, printing is executed based on image data for a print test prepared in advance. Then, the process proceeds to next Step S104.

  In step S104, the presence / absence of banding is measured. As described above, the detection unit 105 compares the data relating to the toner image acquired from the image inspection unit 66 with the image data acquired from the image signal processing unit 101 to measure the presence / absence of banding. Then, the process proceeds to next Step S105.

  In step S105, it is determined whether or not the detection unit 105 has detected the occurrence of banding. If it is determined that the occurrence of banding has been detected, the process proceeds to the next step S106. On the other hand, if it is determined that the occurrence of banding has not been detected, the process proceeds to step S107.

  In step S106, the vibration pattern temporarily registered in step S102 is held as a vibration pattern when banding occurs. That is, it is registered as a vibration pattern when banding occurs. In the case of the example of steps S101 and S102 described above, “pattern 1” that is measured and temporarily registered is stored in the storage unit 103 as a vibration pattern in which banding occurs. Then, the vibration pattern registration process ends.

  In step S107, the vibration pattern temporarily registered in step S102 is deleted. In the case of the example of steps S101 and S102 described above, “pattern 1” that is measured and temporarily registered is not a vibration pattern in which banding occurs, and thus is deleted in the storage unit 103. Then, the vibration pattern registration process ends.

  As described above, the vibration pattern registration process is repeatedly executed in the print standby state. Taking FIG. 4A as an example, not only pattern 1 but also pattern 2 and pattern 3 are temporarily registered, and registration or deletion is performed depending on whether or not actual banding occurs.

(2) Vibration Pattern Update Processing FIG. 7 is a flowchart showing the flow of vibration pattern update processing. This process updates the vibration pattern at the time of occurrence of banding that changes while the image forming apparatus 10 is moving.

  First, in step S200, sampling of the sheet conveyance sensor is started with the printing operation. The paper transport sensor is as described above. Then, the process proceeds to next Step S201.

  In step S201, sampling of the light shielding sensor 35 and the transmission sensor 37 is started. That is, the vibration measurement unit 102 measures the vibration pattern of the transfer belt 36. For example, when the medium P is conveyed during normal printing, the vibration pattern of the pattern 4 in FIG. 5 is measured. Then, the process proceeds to next Step S202.

  In step S202, normal printing is performed. Specifically, printing based on image data designated by the user is executed. Then, the process proceeds to next Step S203.

  In step S203, the presence / absence of banding is measured. As described above, the detection unit 105 compares the data relating to the toner image acquired from the image inspection unit 66 with the image data acquired from the image signal processing unit 101 to measure the presence / absence of banding. Then, the process proceeds to next Step S204.

  In step S204, it is determined whether or not the detection unit 105 has detected the occurrence of banding. If it is determined that the occurrence of banding has been detected, the process proceeds to the next step S205. On the other hand, if it is determined that the occurrence of banding has not been detected, the vibration pattern update process is terminated.

  In step S205, the vibration pattern measured in step S201 is updated as a vibration pattern when banding occurs. That is, a new vibration pattern is registered instead of the already registered vibration pattern. In the case of the example of step S201 described above, when “pattern 2” is registered in the vibration pattern registration process, the pattern 4 is stored in the storage unit 103 as a vibration pattern in which banding occurs instead of the pattern 2. . And a vibration pattern update process is complete | finished.

  As described above, the vibration pattern update process is repeatedly executed in the normal printing state. Taking FIG. 5 as an example, not only the pattern 4 but also the pattern 5 or the pattern 6 is updated as a new vibration pattern if banding has occurred.

(3) Banding Suppression Processing FIG. 8 is a flowchart showing the flow of banding suppression processing. This process performs a banding suppression function during printing.

  First, in step S300, sampling of the paper conveyance sensor is started with the printing operation. The paper transport sensor is as described above. Then, the process proceeds to next Step S301.

  In step S301, sampling of the light shielding sensor 35 and the transmission sensor 37 is started. That is, the vibration measurement unit 102 measures the vibration pattern of the transfer belt 36. Then, the process proceeds to next Step S302.

  In step S302, it is determined whether or not the vibration pattern of the transfer belt 36 measured based on the signal from the transmission sensor 37 matches the roll pattern already registered. That is, it is determined whether or not banding occurs. If it is determined that the vibration pattern matches the already registered roll pattern, the process proceeds to step S304. On the other hand, if it is determined that the vibration pattern does not match the registered roll pattern, the process proceeds to the next step S303.

  In step S <b> 303, it is determined whether or not the vibration pattern of the transfer belt 36 measured based on the signal from the light shielding sensor 35 matches the already registered pitch pattern. That is, it is determined whether or not banding occurs. If it is determined that the vibration pattern matches the registered pitch pattern, the process proceeds to step S304. On the other hand, if it is determined that the vibration pattern does not match the registered pitch pattern, the banding suppression process is terminated as it is.

  In step S304, the banding suppression function is activated. The details of the banding suppression function are as described above. Then, the banding suppression process is terminated.

  As described above, the banding suppression process is repeatedly executed in the normal printing state. In other words, the banding suppression function is realized by monitoring the occurrence of vibrations in the transfer belt 36.

<Summary>
The present embodiment has the following features.

  The first feature is as follows. That is, on the path of the transfer belt 36, detection means (for example, a light shielding sensor 35 and a transmission sensor 37) for detecting the position of the transfer belt 36 is provided. Here, the vibration pattern of the transfer belt 36 is measured based on the information from the detection means, and the vibration pattern when banding occurs is stored. The banding suppressing function is activated when the measured vibration pattern is a vibration pattern in which banding occurs.

  By using the vibration pattern of the transfer belt 36 for the operation of the banding suppression function as described above, the banding suppression function can be correctly operated compared to the case where the vibration pattern is not used. Even if the sheet placed in the tray by the user is different from the type of sheet for which printing is instructed, the banding suppression function operates correctly. For example, even when the user designates plain paper, even when thick paper thicker than plain paper is set in the paper tray, the occurrence of banding is suppressed.

  The second feature is as follows. That is, in the storage unit 103 provided in the control unit 70, a vibration pattern different from the vibration pattern already stored by the vibration measurement unit 102 is measured when banding that is a deviation of the toner image occurs. In this case, the already stored vibration pattern is updated.

  According to the above feature, the activation condition of the banding suppression function is changed according to the state of the consumables such as the transfer belt 36. For example, by periodically executing the vibration pattern registration process described above, banding is suppressed in response to changes such as when the transfer belt 36 extends or when the tension of the roll 32T, which is a tension applying roll, changes. The function is activated. As described above, since the activation threshold of the banding suppression function can be periodically changed, the banding suppression function is not performed wastefully.

  The third feature is as follows. In other words, the detection unit 105 that detects the occurrence of deviation of the toner image by comparing the toner image transferred to the medium P with the image information that is the basis of the toner image is provided. The vibration pattern is updated based on the information from

  According to the above feature, the activation condition of the banding suppression function is changed while printing. For example, even if banding occurs on the first printed sheet, printing without banding is executed on the second and subsequent sheets. That is, the triggering condition for the banding suppression function is dynamically changed. Therefore, the banding suppression function operates correctly even when printing is performed in a state where the paper setting is incorrect, or when printing is performed by mixing sheets having different thicknesses.

  The fourth feature is as follows. That is, the detection means includes a pair of light shielding sensors 35 provided along the circumferential direction of the transfer belt 36 and a pair of transmission sensors 37 provided apart in the width direction of the transfer belt 36. Features.

  According to the above feature, the vibration state of the transfer belt 36 can be measured from a plurality of directions, and the banding suppression function is appropriately activated as compared with the case of measuring from one direction. In addition, by adding four sensors to the existing image forming apparatus 10 and performing control by a program, the banding suppression function can be controlled according to individual differences and dynamic changes of the apparatus. Compared with control by a physical mechanism, it is realized at a low cost.

  In this embodiment, as shown in FIG. 4B, only one pattern is registered for rolling, but a plurality of types of patterns may be registered in the same manner as the pitching pattern. Needless to say, the vibration pattern update process may be performed for rolling.

  In addition, the sensor provided as a detection means is not limited to the above-mentioned four pieces, You may add a sensor further. Further, only the light blocking sensor 35 for pitching, that is, only two sensors may be provided without providing the transmission sensor 37 for rolling. The sensor provided as the detection means is not limited to the optical type as in the present embodiment, and may be a capacitance type. Further, the state of the transfer belt 36 may be photographed with a video camera, and the occurrence of vibration may be detected by image analysis.

  As described above, in the present embodiment, the banding suppression function is activated by paying attention to the vibration of the transfer belt 36. Here, as a factor causing banding, as described above, there is a change in the speed of the transfer belt 36 when a thick sheet enters the transfer nip NT, but there are other factors. For example, the vibration caused by the operation of the post-processing unit 60 or the vibration caused by the vertical movement of the bottom plate when a large-capacity tray (not shown) is adopted as the paper tray for storing the medium P becomes a cause of banding. There is. In the present embodiment, even when the vibration accompanying the operation of the post-processing unit 60 and the large capacity tray propagates to the transfer belt 36, the occurrence of banding is suppressed.

10 image forming apparatus 35 light shielding sensor (an example of first detecting means (detecting means))
36 Transfer belt (an example of an endless belt)
37 Transmission sensor (an example of second detection means (detection means))
70 Control unit (an example of control means)
102 Vibration measurement unit (an example of measurement means)
103 storage unit (an example of storage means)
104 Suppression processing unit (an example of suppression means)
105 Detection unit (an example of detection means)

Claims (5)

An endless belt on which a toner image to be transferred to a medium is formed;
Suppression means for suppressing deviation of a toner image primarily transferred to the endless belt;
Control means for controlling the suppression means;
A plurality of detecting means provided on a path of the endless belt and detecting the position of the endless belt;
The control means includes
Measuring means for measuring a vibration pattern of the endless belt based on information from the plurality of detecting means;
Storage means for storing a vibration pattern when the toner image shift occurs,
An image forming apparatus that activates the suppression unit when a vibration pattern stored in the storage unit is generated.   The storage unit updates the vibration pattern already stored when a deviation of the toner image has occurred and a vibration pattern different from the vibration pattern already stored by the measurement unit is measured. The image forming apparatus according to claim 1. Detecting means for detecting occurrence of deviation of the toner image by comparing the toner image transferred to the medium and image information which is a basis of the toner image;
The image forming apparatus according to claim 2, wherein the storage unit updates a vibration pattern based on information from the detection unit. The detection means includes
A pair of first detection means provided along the circumferential direction of the endless belt;
The image forming apparatus according to any one of claims 1 to 3, further comprising a pair of second detection units provided apart from each other in a width direction of the endless belt. Computer
The program for functioning as a control means contained in the image forming apparatus of any one of Claims 1-4.