JP5031676B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as a copying machine, a facsimile, or a printer including an endless belt member that moves endlessly so as to repeatedly pass through a transfer portion where a visible image transfer process is performed.

  In this type of image forming apparatus, a recording paper as a recording member is held on the surface of a paper conveying belt as a belt member, and the recording paper comes into contact with an image carrier such as a photosensitive member as the paper conveying belt moves endlessly. What is conveyed to a transfer part is known. In addition, there is also known a technique in which a toner image on an intermediate transfer belt is transferred onto a recording sheet when the recording sheet is passed through a transfer unit that contacts the surface of the intermediate transfer belt as a belt member. In any of the image forming apparatuses, a conveying unit that conveys the recording paper toward the belt member or conveys the recording paper received from the belt member to the next process is provided in the vicinity of the belt member. For example, a registration roller pair that feeds a recording sheet toward a belt member at a predetermined timing after sandwiching a recording sheet in a registration nip formed by a pair of rollers that rotate while being in contact with each other is one type of the above-described conveying means. Also, for example, a fixing device that fixes a toner image on the surface of the recording paper in the fixing nip while the recording paper fed from the belt member is sandwiched and conveyed by a fixing nip formed by a pair of rollers that rotate while contacting each other. Is also a kind of the transport means described above.

  In an image forming apparatus including such a conveying unit, the distance between the belt member and the conveying unit may be set to be relatively small in order to save space. In such a setting, if there is a linear speed difference between the endless moving speed of the belt member (hereinafter referred to as belt traveling speed) and the conveyance speed of the recording paper by the conveying means, the toner image at the time of transfer onto the recording paper is disturbed. Resulting in. Specifically, the recording paper fed out from the pair of registration rollers as the conveying means will eventually have its own rear end positioned within the registration nip of the pair of registration rollers while closely contacting its leading end to the belt member. It will be in the state. In this state, if the conveyance speed of the recording paper by the registration roller pair is faster than the belt traveling speed, the registration roller pair applies a force to push the belt member in the traveling direction via the recording paper. Increase speed. As a result, when the belt running speed becomes faster than the normal standard speed, the toner image being transferred onto the recording paper by the transfer unit is slightly extended in the belt running direction. Conversely, if the recording paper transport speed by the registration roller pair is slower than the belt running speed, the registration roller pair applies a force in the direction (pulling direction) to the belt member through the recording paper to prevent the running. To do. As a result, when the belt running speed becomes slower than the standard speed, the shape of the toner image is slightly shortened in the belt running direction.

  As described above, if there is a linear speed difference between the conveyance speed of the recording paper by the registration roller pair serving as the conveyance means and the belt traveling speed, the registration roller pair pushes or pulls the belt member through the recording paper. As a result, the belt traveling speed deviates from the design speed, and the image is disturbed. In addition, although the image disturbance due to the linear speed difference between the conveying speed by the registration roller pair and the belt traveling speed has been described, there is a linear speed difference between the conveying speed by the fixing device as the conveying means and the belt traveling speed. In the same manner, the image is disturbed. An image forming apparatus that stabilizes the belt traveling speed by detecting the belt traveling speed and feeding back the result to the control of the belt driving speed is known. It will be difficult to stabilize the belt running speed.

  Assume that in a monochrome image, the shape of the image is slightly disturbed due to the above-described difference in linear velocity. If the disturbance is such that it can only be seen with close eyes, the image quality will not be significantly impaired. However, in the method of obtaining a full color image by superimposing and transferring the yellow, magenta, cyan, and black toner images onto the recording paper on the belt member, the image quality can be improved even with the slight disturbance as described above. It will be significantly reduced. This is because even if the shape of the toner image of each color is slightly disturbed, the slight disturbance is easily recognized as a color shift.

  2. Description of the Related Art Conventionally, an image forming apparatus described in Patent Document 1 is known as an image forming apparatus that can suppress image disturbance caused by a difference in linear velocity between a conveying speed of a conveying unit and a belt traveling speed. The image forming apparatus includes a belt traveling speed detection unit that detects the traveling speed of the belt member, and a paper conveyance speed detection unit that detects the conveyance speed of the recording paper by the registration roller pair. As the belt running speed detecting means, a photo sensor or an encoder is employed. The above-described photosensor detects a plurality of marks provided at a predetermined pitch over the entire circumferential direction of the belt member at a predetermined position. The encoder detects a rotational angular displacement or a rotational angular velocity of a driven roller that is driven to rotate as the belt travels while the belt member is stretched. As the paper conveyance speed detecting means, one that detects the leading edge of the recording paper by two photo sensors arranged in the paper conveyance direction between the registration roller pair and the belt member is used. If the detection result by the paper conveyance speed detection means does not match the detection means by the belt running speed detection means, the difference between the two linear speeds can be determined by adjusting the drive speed of the registration drive motor that is the drive source of the registration roller pair. Reduce. Thereby, it is possible to suppress image disturbance due to a linear speed difference between the belt traveling speed and the paper conveyance speed by the registration roller pair.

  However, in this image forming apparatus, there is a problem that the cost increases because the paper transport speed detecting means is provided in addition to the belt running speed detecting means. If the paper conveyance speed detection means is not provided, the linear velocity difference between the belt traveling speed and the paper conveyance speed by the registration roller pair cannot be reduced satisfactorily for the reason described below. That is, the relationship between the drive speed of the registration drive motor and the paper conveyance speed is such that the diameter changes with time due to wear of the registration rollers, the change of the registration roller due to environmental changes, the change of the transfer speed with time due to wear of the drive transmission diameter, etc. Will fluctuate. For this reason, the actual paper transport speed cannot be accurately grasped based on the drive speed of the registration drive motor.

  On the other hand, Patent Document 2 describes the following image forming apparatus. That is, this image forming apparatus is also provided with belt running speed detecting means similar to that of the image forming apparatus described in Patent Document 1. Then, when the recording paper is not fed out from the registration roller pair, the belt driving speed at which the belt member can run at a predetermined standard speed is specified while detecting the belt running speed by the belt speed detecting means. Next, a test sheet is passed to identify the optimum driving speed of the registration roller pair. Specifically, a plurality of recording sheets are continuously passed while the belt member is running at a standard speed, and the driving speed of the registration roller pair (hereinafter referred to as the registration driving speed) is changed step by step for each sheet passing. I will let you. Then, based on the belt traveling speed detected under the conditions of the respective resist driving speeds, a registration driving speed that can bring the belt traveling speed closest to the standard speed is specified. After that, at the time of a print job, the registration roller pair is driven at the registration driving speed, thereby suppressing an increase in the linear velocity difference caused by pushing or pulling the belt member with the registration roller pair via the recording paper when the paper is passed. . According to this configuration, it is possible to satisfactorily reduce the linear speed difference between the belt traveling speed and the paper transport speed by the registration roller pair without using the paper transport speed detection means.

JP 2004-151382 A JP 2006-195016 A

  However, in this image forming apparatus, it is necessary to perform the above-described test paper feeding at a certain frequency in order to quickly cope with the inappropriateness of the resist driving speed due to the change in the diameter of the registration roller accompanying the environmental change. . During the test paper passing, a print job based on a print command from the user cannot be executed, which causes a problem that the downtime of the apparatus is relatively increased.

  The present invention has been made in view of the above background, and an object thereof is to provide the following image forming apparatus. That is, the image forming apparatus can satisfactorily suppress image disturbance due to a difference in linear velocity between the conveying speed of the conveying means and the belt traveling speed without causing a downtime of the apparatus due to test paper passing.

In order to achieve the above object, the invention of claim 1 is directed to transferring a visible image carried on its surface to a recording member, or to displaying a visible image carried on the surface of an image carrier on its surface. An endless belt member that moves endlessly so as to repeatedly pass through a transfer portion for transferring to the recording member held on the recording member, and the belt member as it is driven to rotate while stretching the belt member A driving roller that moves the belt member in an endless manner, a driven roller that stretches the belt member so that the belt member rotates following the endless movement of the belt member, a motor that exerts a driving force that rotates the driving roller, Belt drive control means for controlling the driving speed and conveying means for transferring the recording member being conveyed to the belt member or conveying the recording member received from the belt member to the next process And an image forming apparatus including a conveyance drive control unit that controls a drive speed of the conveyance unit, motor control information transmitted from the belt drive control unit to the motor, and a rotational angular displacement or a rotational angular velocity of the motor. Motor rotation information which is information on the above, driving roller rotation information which is information on the rotational angular displacement or rotational angular velocity of the driving roller, and driven roller rotational information which is information on the rotational angular displacement or rotational angular velocity of the driven roller The information acquisition means for acquiring at least two pieces of information is provided, and the recording member being conveyed by the conveying means is not in contact with the belt member being endlessly moved while the belt member is moved endlessly. 1 state, while the belt member is moved endlessly, the leading end side of the recording member being conveyed by the conveying means or Based on the information acquired by the information acquisition means in the second state where the end side is in contact with the belt member that is moving endlessly, respectively, through the drive roller and the belt member from the motor While grasping the characteristic value of the output side driving amount with respect to the input side driving amount in a predetermined section in the drive transmission system leading to the driven roller, and grasping the characteristic value in the second state, The transport drive is calculated so that a difference from the characteristic value grasped in advance in the first state is calculated, and the drive speed of the transport means after the difference calculation in the second state is adjusted based on the calculation result. The control means is configured.
According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the conveyance drive control unit is configured to drive the conveyance unit at a predetermined driving speed in the first state. Is.
According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, in the second state, at least two of the motor control information, motor rotation information, drive roller rotation information, and driven roller rotation information. The information acquisition unit is configured to acquire two pieces of information at a predetermined cycle, and the characteristic value and the difference are calculated every time the cycle arrives in the second state, and the transport unit after calculating the difference The conveyance drive control means is configured so as to adjust the drive speed.
According to a fourth aspect of the present invention, in the image forming apparatus according to the third aspect, as the information acquisition unit, one that acquires at least one of the driving roller rotation information and the driven roller rotation information is used. The belt drive control means is configured to control the drive speed of the motor based on the acquisition result of the drive roller rotation information or the driven roller rotation information.
According to a fifth aspect of the present invention, in the image forming apparatus of the third or fourth aspect, at least one of the rotational angular velocity of the motor, the rotational angular velocity of the driving roller, and the rotational angular velocity of the driven roller is the above. The information acquisition means is configured to acquire at a cycle, and an average value of the characteristic values is calculated based on the one rotational angular velocity when the belt member is continuously driven for a predetermined time in the first state. The transport drive control means is configured to obtain the difference between the average value and the characteristic value based on the one rotational angular velocity acquired every time the period arrives in the second state as the difference. It is characterized by that.
According to a sixth aspect of the present invention, in the image forming apparatus according to the third or fourth aspect, at least one of the rotational angular displacement of the motor, the rotational angular displacement of the driving roller, and the rotational angular displacement of the driven roller. The information acquisition means is configured to acquire one at the cycle, and the characteristic value with respect to the one rotational angular displacement when the belt member is continuously driven for a predetermined time in the first state. A change equation is obtained, and as the difference, based on the amount of change over time of the characteristic value obtained based on the change equation over time and the one rotational angular displacement obtained each time the period arrives in the second state. The conveyance drive control means is configured to calculate a difference from the characteristic value obtained in this way.
According to a seventh aspect of the present invention, in the image forming apparatus according to the fifth or sixth aspect, at least one of the rotational angular velocity of the motor, the rotational angular velocity of the driving roller, and the rotational angular velocity of the driven roller, or Low-pass filter means for performing low-pass filter processing on the acquisition result of at least one of the rotational angular displacement of the motor, the rotational angular displacement of the driving roller, and the rotational angular displacement of the driven roller; The conveyance drive control unit is configured to calculate the characteristic value in the first state or the second state based on information after processing by the low-pass filter unit.
The invention according to claim 8 is a recording member for transferring a visible image carried on its surface to a recording member, or for holding a visible image carried on the surface of an image carrier on its surface. An endless belt member that moves endlessly so as to repeatedly pass through a transfer portion for transferring, and a drive roller that moves the belt member endlessly as the belt member is driven to rotate while stretching the belt member A driven roller that stretches the belt member to rotate following the endless movement of the belt member, a motor that exerts a driving force that rotates the driving roller, and a belt that controls the driving speed of the motor Drive control means, conveyance means for delivering the recording member being conveyed to the belt member, or conveying the recording member received from the belt member to the next process, and driving of the conveyance means In the image forming apparatus comprising a conveyance drive control means for controlling the degree, a mark for detecting, at a predetermined position, a plurality of marks attached to the belt member at a predetermined pitch over the entire circumference in the endless movement direction. Motor detection information obtained from the belt drive control means and transmitted to the motor by the detection means, and motor rotation information that is information on the rotation angular displacement or rotation angular speed of the motor; Information that also acquires at least one of the driving roller rotation information that is information on the rotation angle displacement or rotation angular velocity of the driving roller and the driven roller rotation information that is information on the rotation angle displacement or rotation angular velocity of the driven roller. An acquisition unit is provided and the recording member being conveyed by the conveying unit is moved endlessly while the belt member is moved endlessly. The first state that is not in contact with the belt member, and the belt member that is moving endlessly on the leading end side or the trailing end side of the recording member that is being conveyed by the conveying means while the belt member is moved endlessly. In the second state, which is a contact state, based on the information acquired by the information acquisition unit, in the drive transmission system from the motor to the driven roller through the drive roller and belt member While grasping the characteristic value of the output side driving amount with respect to the input side driving amount in the predetermined section and grasping the characteristic value in the second state, the characteristic value and the characteristic previously grasped in the first state The conveyance drive control means is configured to calculate a difference from the value and adjust the driving speed of the conveyance means after the difference calculation in the second state based on the calculation result. It is a sign.

In these inventions, with all of the invention specific matters of claim 1, the characteristic value of the output side drive amount with respect to the input side drive amount in the first state and the output side drive amount with respect to the input side drive amount in the second state Based on the difference from the characteristic value, it is grasped how much the conveying means pushes the belt member through the recording member or how much the belt member is pulled in the second state. For example, the information acquisition means acquires two of the motor rotation information and the driven roller rotation information among the four information of the motor control information, the motor rotation information, the drive roller rotation information, and the driven roller rotation information. To do. In this case, in the first state in which the recording member being conveyed is not brought into contact with the belt member being moved endlessly by the conveying means while the belt member is moved endlessly, it is on the output side with respect to the drive amount of the motor on the input side. The characteristic value of the driven amount of the driven roller is obtained. Examples of such characteristic values include the driving amount of the driven roller (output side driving amount) obtained per unit driving amount of the input side motor. Further, it may be a difference between the driving amount of the motor and the driving amount of the driven roller obtained thereby. At any characteristic value, it is possible to grasp what drive amount the output side is driven with respect to the drive amount on the input side. Such a characteristic value is grasped in a first state in which the conveying means does not push or pull the belt member through the recording member. Then, a difference from the characteristic value grasped in advance in the first state is obtained while grasping the same characteristic value in the second state. If this difference is not zero, it is considered that there is a difference in the characteristic value between the first state and the second state because the conveying means pushes or pulls the belt member through the recording member in the second state. It does not matter. The difference in the characteristic values indicates how much the belt speed is pushed through the recording member and how much the belt member is pulled in the second state. Of the four pieces of information described above, the case where the characteristic value is obtained using two of the motor rotation information and the driven roller rotation information has been described as an example. However, even when other information is used, the difference in the characteristic value is used. Indicates how much the belt speed is pushed in through the recording member and how much the belt member is pulled in the second state. In the second state, the difference in linear velocity between the transport speed of the transport means and the belt traveling speed is reduced by adjusting the drive speed of the transport means after the difference calculation based on the difference between the characteristic values.
In such a configuration, if the following settings are made, it is possible to satisfactorily suppress image disturbance due to a difference in linear velocity regardless of changes in the diameter of the registration roller. That is, immediately after grasping the above characteristic value in the first state at the start of the print job, the second state is established by passing the paper, and the timing of grasping the above characteristic value in the first state condition and the condition in the second state The time difference from the timing for adjusting the driving speed of the conveying means is set to be relatively short. In such a setting, the characteristic value in the first state and the characteristic value in the second state are grasped under conditions of substantially the same roller diameter, and the driving speed of the conveying unit suitable for the roller diameter is specified. Therefore, it is possible to satisfactorily suppress the image disturbance due to the linear velocity difference regardless of the fluctuation of the roller diameter.
Further, when the second state is created by passing a print job without performing the test paper passing, the above-mentioned difference is obtained while grasping the above characteristic value in the second state, and the transport of the transport unit is performed. Since the speed can be adjusted, it is possible to avoid the occurrence of downtime of the apparatus due to the test paper passing.
Therefore, it is possible to satisfactorily suppress image distortion due to a difference in linear velocity between the conveying speed of the conveying unit and the belt traveling speed without causing a downtime of the apparatus due to test paper passing.

  In addition, according to the ninth aspect of the invention, the input side drive amount or the output is based on at least one of motor control information, motor rotation information, drive roller rotation information, and driven roller rotation information. While grasping the side drive amount, the output side drive amount or the input side drive amount is grasped based on the belt traveling speed information acquired by the mark detection means. And after calculating | requiring the said characteristic value in a 1st state or a 2nd state based on the input side drive amount and the output side drive amount, it adjusts the drive speed of a conveyance means based on those differences, and is conveyed The linear speed difference between the conveying speed of the means and the belt running speed is reduced. Even in such a configuration, similarly to the first aspect of the invention, image disturbance due to a difference in linear velocity between the conveying speed of the conveying means and the belt traveling speed can be satisfactorily suppressed without causing downtime of the apparatus due to test paper passing. be able to.

  Hereinafter, as an embodiment of an image forming apparatus to which the present invention is applied, a tandem type color image in which toner images of different colors formed on respective photoconductors in four image forming stations (image forming means) are transferred in a superimposed manner. A laser printer (hereinafter simply referred to as a printer) will be described. The embodiment is merely an example of a form to which the present invention is suitably applied, and the embodiment of the present invention is not limited to this embodiment.

First, a basic configuration of the printer according to the embodiment will be described.
FIG. 1 is a schematic configuration diagram illustrating a printer according to an embodiment. The printer includes an image forming unit 1, paper feed trays 3 and 4, a paper feed unit 5, a transfer unit 6, a fixing device 7, and the like. Then, an image is formed on a recording sheet as a recording member taken out from the sheet feeding trays 3 and 4, and the image is discharged onto a sheet discharge tray 8 provided at the upper part of the casing.

  The image forming unit 1 includes four image forming stations for individually forming magenta (M), cyan (C), yellow (Y), and black (K) toner images. In addition, the optical writing apparatus 2 that individually exposes and scans the photosensitive members (11M, C, Y, and K) in the respective image forming stations is also provided. The image forming stations for M, C, Y, and K are each configured to be easily detachable from the printer body by the user.

  FIG. 2 is an enlarged configuration diagram showing the image forming station for Y together with the paper conveying belt 60 of the transfer means 6. In FIG. 2, the Y image forming station holds a charging / cleaning unit 10Y and a developing unit 20Y as developing means around a photoconductor 11Y as an image carrier. Laser light L emitted from an optical writing device (not shown in FIG. 1) for optical writing passes between the charging / cleaning unit 10Y and the developing unit 20Y and scans the surface of the photoreceptor 11Y. .

  The charging / cleaning unit 10Y includes a charging roller 15Y as a uniform charging unit, a cleaning brush 12Y as a cleaning unit, and a cleaning blade 13Y. The charging roller 15Y uniformly charges the surface of the photoconductor 11Y by generating a discharge between itself and the surface of the photoconductor 11Y while a charging bias is applied by a power source (not shown). Also, the cleaning brush 12Y scrapes off the transfer residual toner on the surface of the photoreceptor 11Y by sliding the brush tip against the surface of the photoreceptor 11Y while being driven to rotate. The transfer residual toner that cannot be completely removed by the cleaning brush 12Y is removed from the surface of the photoconductor 11Y by a cleaning blade that has a free end abutting the surface of the photoconductor 11Y while being cantilevered.

  The developing unit 20Y includes a developing sleeve 22Y as a developer carrying member, a stirring roller 23Y, a conveying roller 24Y, a doctor blade 25Y, a toner concentration sensor 26Y, a toner bottle 27Y, and the like. Among the members described above, those other than the toner bottle 27Y are accommodated in the developing casing 21Y. The Y toner supplied from the toner bottle 27Y into the developing casing 21Y is sent to the stirring roller 23Y while being stirred by the transport roller 24Y, and is further stirred by the stirring roller 23. By the stirring, the Y toner moves to the developing sleeve 22Y side in a state where it is triboelectrically charged and a potential is applied. The Y toner that has migrated to the surface of the developing sleeve 22Y is regulated to a predetermined layer thickness by the doctor blade 25Y, and moves to the developing region facing the photoreceptor 11Y as the developing sleeve 22Y rotates. In this development area, the latent image formed by the optical writing is developed with toner to become a Y toner image. The Y toner image formed on the surface of the photoreceptor in this way is a primary transfer nip (transfer section) for Y formed by contact between the photoreceptor 11Y and an endless paper transport belt 60 as a belt member. ) On the recording paper P adsorbed on the surface of the paper conveying belt 60.

  Untransferred toner that has not been transferred onto the recording paper P and remains on the surface of the photoreceptor 11Y is removed from the surface of the photoreceptor 11Y by the cleaning brush 12Y or the cleaning blade 13Y. Although the image forming station for Y has been described, the image forming stations for M, C, and K shown in FIG. 1 are similarly provided with M, C on the photoconductors 11M, C, K. , K toner images are formed.

  The paper feed unit 5 includes paper feed rollers 5a and 5b that pick up the recording paper P from the paper feed trays 3 and 4, paper feed rollers 5c provided along the paper feed path 5e, and the image forming unit 1 in the paper transport path. A registration roller pair 5d provided immediately before is provided. Each roller in the registration roller pair 5d is rotationally driven by a registration motor (not shown). The driving of the registration motor is controlled by a controller (not shown). The registration roller pair 5d is rotationally driven at a predetermined timing to send the recording paper toward the paper transport belt 60. The fed recording paper is adsorbed on the front surface (outer loop surface) of the paper conveying belt 60 and then moves together with the belt and sequentially passes through the primary transfer nips for M, C, Y, and K. At the primary transfer nips, the M, C, Y, and K toner images are sequentially superimposed and transferred. A full color image is formed on the recording paper by such superposition transfer.

  The recording paper on which the full-color image is formed after passing through the primary transfer nip for K is separated from the front surface of the paper conveying belt 60 and delivered to the fixing device 7. The fixing device 7 forms a fixing nip by contact between a heating roller 7a including a heat source (not shown) and a fixing belt 7b. Then, the recording paper received from the paper conveying belt 60 is sandwiched in the fixing nip and conveyed, and a fixing process of a full color image is performed on the recording paper. The recording sheet on which the full-color image is fixed by the fixing device 7 is discharged onto the discharge tray 8 through the discharge path 8a.

  FIG. 3 is a perspective view showing the transfer unit 6 together with the belt drive control unit 70. In the drawing, for convenience, various members disposed in the belt loop are drawn through the paper conveying belt 60. The paper transport belt 60 is endlessly moved by the rotational drive of a driving roller 65 that is one of the stretching rollers while being stretched by a plurality of stretching rollers disposed in the belt loop. The entrance roller 61, which is one of the plurality of stretching rollers, is disposed at a position closest to the pair of registration rollers (not shown) among the plurality of stretching rollers. In addition, the tension roller denoted by reference numeral 62 in the drawing is an exit roller. Of the entire area in the circumferential direction of the paper transport belt 61, the positions before passing the position where the paper is fed to the entrance roller 61 and before entering the position where the paper is fed to the exit roller 62 are M, C, Y, K (not shown). A primary transfer nip for M, C, Y, and K is formed in contact with the photosensitive member. The transfer rollers 64M, C, Y, and K are in contact with the positions where the primary transfer nips for M, C, Y, and K are formed on the paper transport belt from the back side of the belt. By applying a transfer bias to the transfer rollers 64M, C, Y, and K by a power source (not shown), a transfer electric field is formed between the belt and the photosensitive member in the primary transfer nip of each color.

  Below the entrance roller 61, an encoder roller 63, which is one of the stretching rollers, is disposed. This is a driven roller that is driven to rotate as the paper conveying belt 60 moves endlessly. Further, below the outlet roller 62, a driving roller 65, which is one of the stretching rollers, is disposed. The driving roller 65 is a roller that moves the paper transport belt 60 endlessly with its own rotational driving, and is connected to a belt driving motor 67 as a driving source via a speed reduction mechanism 66. The speed reduction mechanism 66 has a configuration in which a drive belt 66c is stretched between a small pulley 66a and a large pulley 66b.

  An adsorption roller that contacts the front surface of the paper conveyance belt 60 at a position facing the entrance roller 61 is disposed outside the belt loop, and the front surface of the paper conveyance belt 60 is arranged by this adsorption roller. By applying an electric charge to the surface, the recording paper is adsorbed to the front surface. A belt cleaning device (not shown) disposed outside the belt roll is in contact with the cleaning backup roller 69 disposed on the side of the drive roller 65 inside the belt loop via the belt. The belt cleaning device collects foreign matters such as toner adhering to the front surface of the belt from the belt surface by a potential difference between itself and the cleaning backup roller 69.

  A rotary encoder 68 is attached to the rotation shaft of the encoder roller 63 as a driven roller. The rotary encoder 68 outputs a pulse signal that reflects the rotational angular displacement amount and rotational angular velocity of the encoder roller 63.

  FIG. 4 is an explanatory diagram for explaining the drive control system of the paper transport belt 60 and the registration roller pair 5d. In the drawing, a belt drive motor 67 that is a drive source of a drive roller 65 that moves the paper transport belt 60 endlessly is controlled by a belt drive control unit 70. The registration roller pair 5 d is connected to a registration drive motor 87 via a speed reducer 86. The registration drive motor 87 that is a drive source of the registration roller pair 5 d is controlled by the registration drive control unit 80. The belt drive control unit 70 and the registration drive control unit 80 are communicably connected. These control units (70, 80) can communicate with a main control unit 88 that controls the entire printer. The main control unit 88 includes a CPU (Central Processing Unit) (not shown), a ROM (Read Only Memory) that stores control programs and various data, a RAM (Random Access Memory) that temporarily stores various data, and the like. ing. Based on the control program and various input information, the entire printer is controlled.

  The belt drive motor 67 is feedback-controlled by a belt drive control unit 70. Specifically, the belt drive control unit 70 calculates the rotational angular velocity of the encoder roller 63 based on the pulse signal from the rotary encoder 68, and compares the result with a predetermined target value at a cycle of 1 [msec]. carry out. Here, if the calculated rotational angular velocity matches the target value, the paper transport belt 60 is traveling at a predetermined target speed. If the rotational angular velocity does not match the target value, the belt drive control unit 70 adjusts the drive speed by increasing or decreasing the number of output pulses to the belt drive motor 67 according to the magnitude relationship or difference between the two. Is carried out. By such feedback control, even if the drive roller 65 is rotationally driven in an eccentric state, the paper transport belt 60 can be stably driven at a substantially target speed (for example, 125 mm / sec).

  FIG. 5 is a block diagram illustrating a circuit configuration of the belt drive control unit 70. In the figure, the belt drive control unit 70 includes an input processing circuit 71, a first calculation circuit 72, an output adjustment unit 73, a second calculation circuit 74, a pulse drive circuit 75, an amplification circuit 76, and the like.

  When a pulse signal from the rotary encoder 68 that reflects the belt traveling speed is input to the belt drive control unit 70, it is first processed by the input processing circuit 71. The input processing circuit 71 calculates the rotational angular velocity of the encoder roller (63) based on the number of pulses per 1 [msec] in the input pulse signal, and outputs the calculation result as digital data. In this way, digital data of the rotational angular velocity of the encoder roller (63) is output from the input processing circuit 71 every 1 [msec]. The rotation angular velocity digital data output from the input processing circuit 71 is input to the first arithmetic circuit 72. In addition, the target value (Ref (i)) of the rotational angular velocity of the encoder roller (63) is input from the main control unit 88 to the first arithmetic processing circuit 72. The first arithmetic processing circuit 72 calculates the difference (difference e (i)) between the rotational angular velocity data sent from the input processing circuit 71 and the target value of the rotational angular velocity sent from the main control unit 88. Output to the output adjustment unit 73. The output adjustment unit 73 includes a low pass filter circuit 73a for removing high frequency noise and a gain adjustment circuit 73a. The output adjustment unit 73 obtains a correction control amount for the standard drive frequency used for drive control of the belt drive motor 67 and outputs the correction control amount to the second arithmetic circuit 74. The second arithmetic circuit 74 adds the above-described correction control amount to the predetermined standard drive frequency Refp_c to obtain the drive frequency u (i), and then outputs it to the pulse generation circuit 75. The pulse generation circuit 75 generates a pulsed motor control signal based on the input drive frequency u (i). The motor control signal is amplified by the amplifier circuit 76 and then input to the belt drive motor 67. The motor control signal input to the belt drive motor 67 in this way is such that the drive frequency u (i) is adjusted at intervals of 1 [msec] according to the belt running speed, and the belt running speed is adjusted by the adjustment. Is feedback controlled to the driving speed.

  Although the output adjustment unit 73 uses the gain adjustment circuit 73a to adjust the output value by extending the input signal by a predetermined coefficient, it is not limited to this. The standard drive frequency Refp_c described above is the number of pulses uniquely determined based on the rotational angular velocity of the drive roller 65, the reduction ratio of the reduction system, and the like. Further, the drive frequency u (i) can be limited to a range in which a step-out phenomenon does not occur during motor driving.

  Next, a characteristic configuration of the printer according to the embodiment will be described. In FIG. 4 described above, the driving speed of the registration driving motor 87 is controlled by a registration driving control unit 80 serving as a conveyance driving control unit. As described above, the driving force of the registration driving motor 87 is transmitted to the registration roller pair 5d via the speed reducer 86. The driving force may be transmitted to the paper feed roller (5c) or the like by the speed reducer 86 formed of a gear train. The driving speed of the registration driving motor 87 is controlled by the registration driving control unit 80 so that the surface moving speed (roller linear speed) of the registration roller pair 5d is substantially the same as the belt traveling speed (for example, 125 mm / sec). .

  The registration drive control unit 80 is supplied with information on the drive start (paper feed start) timing and drive stop timing of the registration roller pair 5d from the main control unit 88, and based on this information, the registration drive control unit 80 The drive of the drive motor 87 is turned on / off. The aforementioned drive start timing is important for synchronizing the recording paper with the toner images on the photoconductors 11M, C, Y, and K of the respective colors.

  The main controller 88 determines the drive start timing of the registration roller pair 5d based on the timing at which the paper detection sensor 81 disposed in the vicinity of the registration roller 5d detects the leading edge of the recording paper. The drive stop timing of the registration roller pair 5d is determined based on the fact that the paper detection sensor 81 no longer detects the trailing edge of the recording paper.

  When the registration drive motor 87 is used as a drive source for the registration roller pair 5d and also as a drive source for the paper feed roller 5c, a clutch mechanism is provided in the drive transmission system. Then, the driving force of the registration drive motor 87 can be individually turned on and off by the clutch mechanism with respect to the registration roller pair 5d and the paper feed roller 5c.

  The pulse signal output from the rotary encoder 68 attached to the encoder roller 63 is input to the belt drive control unit 70 and also to the registration drive control unit 80. The motor control signal (drive frequency u (i)) output from the belt drive control unit 70 to the belt drive motor 67 is also input to the registration drive control unit 80. The registration drive control unit 80 sets the frequency of the motor control signal output to the registration drive motor 87 based on the pulse signal sent from the rotary encoder 68 and the motor control signal sent from the belt drive control unit 70. Feedback control. As a result, the recording paper conveyance speed by the registration roller pair 5d is feedback-controlled.

  The inventors have noted that the following phenomenon occurs when the pair of registration rollers 5d changes the belt traveling speed by pushing or pulling the paper conveying belt 60 through the recording paper. That is, in the predetermined section in the drive transmission system from when the motor control signal is sent to the belt drive motor 67 until the drive force finally reaches the paper conveyance belt 60, the output side drive with respect to the input side drive amount. The characteristic value of the quantity changes. As this characteristic value, an output side driving amount per unit driving amount on the input side can be exemplified. Further, it may be a difference between the input side driving amount and the output side driving amount obtained by the input side driving amount. At any characteristic value, it is possible to grasp what drive amount the output side is driven by the drive amount on the input side. These characteristic values change when the registration roller pair 5d pushes or pulls the paper transport belt 60 through the recording paper.

  The members constituting the drive transmission system described above are listed from the input side as follows. That is, the rotating shaft of the belt drive motor 67, the speed reducer 66, the drive roller 65, the paper transport belt 60, and the encoder roller 63 are arranged in this order from the input side. In such a drive transmission system, a unit drive amount of a member disposed on the input side is set as a unit drive amount on the input side. The drive amount obtained by the unit drive amount described above is set as the output side drive amount in the member disposed on the output side. In the drive transmission system, when the load on each member is stable, the output side drive amount with respect to the unit drive amount on the input side is stable. However, when the load on the output member increases, the output drive amount decreases. Conversely, when the load on the output side member becomes light, the output side drive amount increases. Based on such an increase / decrease in the output side driving amount, it is possible to detect that the registration roller pair 5d pushes or pulls the paper transport belt 60 via the recording paper. The case where the output side drive amount with respect to the input side unit drive amount is used as the characteristic value has been described as an example, but the difference between the input side drive amount and the output side drive amount obtained thereby is used as the characteristic value. The same detection is possible. Further, the drive amount based on the motor control signal for the belt drive motor 67 can be used as the unit drive amount on the input side.

  The difference between the input side drive amount and the output side drive amount is due to the reason described below. That is, various rotation shafts in the drive transmission system are twisted, coupling to connect the roller rotation shaft and the speed reducer, torsion of the pulley shaft, deformation of gear gears, expansion and contraction of the belt, and the like. It is assumed that a motor control signal for rotating the encoder roller 63 by a rotation angle of 100 radians is sent to the belt drive motor 67 at a certain time. On the other hand, it is assumed that the rotational angular displacement based on the pulse signal from the rotary encoder 68 attached to the encoder roller 63 is 95 radians. In this case, the driving amount is reduced by 5 radians on the output side due to the twist, deformation, belt expansion and contraction, etc. listed above. Such a drive change amount on the output side varies in accordance with a variation in load torque applied to the paper transport belt 60.

  Hereinafter, an example in which an input / output drive difference that is a difference between the input side drive amount and the output side drive amount is used as the characteristic value will be described. Hereinafter, a state in which the recording paper being conveyed is not in contact with the traveling paper conveyance belt 60 by the registration roller pair 5d while the paper conveyance belt 60 is running (whether the paper is conveyed or not conveyed) is first. It is called a state. A state in which the leading end side of the recording paper being conveyed by the registration roller pair 5d is in contact with the traveling paper conveyance belt 60 is referred to as a second state.

  In the first state, since the recording paper is not interposed between the registration roller pair 5d and the paper conveyance belt 60, the registration roller pair 5d pushes or pulls the paper conveyance belt 60 through the recording paper. Does not occur. Therefore, the above-described input / output drive difference detected in the first state is when the force of the registration roller pair 5d via the recording paper is not applied to the paper transport belt 60, and the force is It can be used as a reference value for determining whether or not it has been assigned. On the other hand, in the second state, if there is a linear speed difference between the belt running speed of the paper conveyance belt 60 and the paper conveyance speed by the registration roller pair 5d, the registration roller pair 5d causes the paper conveyance belt 60 to move through the recording paper. It will push and pull. For this reason, based on the difference between the input / output driving difference detected in the first state and the input / output driving difference detected in the second state, the registration roller pair 5d passes the paper through the recording paper in the second state. It is possible to grasp how much the conveying belt 60 is pushed or pulled.

  Therefore, the belt drive control unit 80 feedback-controls the drive speed of the registration drive motor 87 in the second state based on the difference between the input / output drive difference in the first state and the input / output drive difference in the second state. It has become. At this time, the drive frequency u (i) of the motor control signal transmitted from the belt drive control unit 70 to the belt drive motor 67 is used as the input side drive amount. Further, as the output side drive amount, the rotational angular velocity of the encoder roller 63 based on the pulse signal output from the rotary encoder 68 is used.

  FIG. 6 is a block diagram showing a circuit configuration of the registration drive control unit 80. In the figure, a registration drive control unit 80 includes a first input processing circuit 80a, a second input processing circuit 80b, a multiplication circuit 80c, a first arithmetic circuit 80d, a second arithmetic circuit 80e, a switch SW1r, an output adjustment unit 80f, 3 arithmetic circuit 80i, pulse generation circuit 80j, amplification circuit 80k, zero signal generation circuit 80n, switch control circuit 80m and the like.

  The pulse signal output from the rotary encoder 68 reflects the traveling speed of the paper transport belt (60), and is input to the first input processing circuit 80a of the registration drive controller 80. The first input processing circuit 80a calculates the rotational angular velocity of the encoder roller (63) based on the number of pulses per 1 [msec] in the pulse signal, and outputs the calculated rotational angular velocity data P every 1 [msec]. Output as (i-1). The rotational angular velocity data P (i−1) is input to the first arithmetic circuit 80d.

  On the other hand, in addition to the pulse signal output from the rotary encoder 68, the registration drive control unit 80 also receives a motor control signal output from the belt drive control unit 70 for driving control of a belt drive motor (not shown). . This motor control signal is input to the second input processing circuit 80b in the registration drive control unit 80, where it is converted from analog data to digital data to become drive frequency data. The drive frequency data is converted into rotational angular velocity data Pf (i-1) of the belt drive motor (67) by being multiplied by a predetermined coefficient by the multiplication circuit 80c, and then input to the first arithmetic circuit 80d. .

  The first arithmetic circuit 80d is based on the rotational angular velocity data P (i-1) input from the first input processing circuit 80a and the rotational angular velocity data Pf (i-1) input from the multiplier circuit 80c. An input / output drive difference Er (i) that is a difference between the two is calculated. And it outputs to the 2nd arithmetic circuit 80e. The second arithmetic circuit 80e is configured to perform different processes in the first state and the second state described above. Specifically, in the first state, the input / output drive difference Er (i) as the characteristic value sent from the first arithmetic circuit 80d is set every 1 [msec] within the period from the start to the end. I will remember it temporarily. When the first state ends, the average value of the input / output drive difference Er (i) from the start to the end is calculated, and the result is calculated as the input / output drive difference Er (i) in the first state. The offset value Os, which is a reference value, is stored in a data storage means (not shown) composed of a nonvolatile RAM or IC. On the other hand, in the second state, the difference between the input drive difference Er (i) sent from the first arithmetic circuit 80d and the offset value Os read from the data storage means is calculated as a load fluctuation amount (Er (i ) -Os). When the load fluctuation amount is zero, the registration roller pair 5d does not push or pull the paper transport belt 60 via the recording member. On the other hand, when the load fluctuation amount is a positive value, the registration roller pair 5d pushes the paper conveying belt 60 through the recording member, thereby increasing the output side driving amount. When the load fluctuation amount is a negative value, the output roller driving amount is reduced by the registration roller pair 5d pulling the paper conveyance belt 60 through the recording member.

  In the second state, the load fluctuation amount calculated by the second arithmetic circuit 80e is sent to the output adjustment unit 80f via the switch Sw1r described later. The output adjustment unit 80f includes a low-pass filter circuit 80g and a gain adjustment circuit 80h. The low-pass filter circuit 80g removes high-frequency noise in the load fluctuation amount data sent from the second arithmetic circuit 80e. The frequency pass threshold value by the low-pass filter circuit 80g is preferably set to a value that can eliminate periodic transmission errors caused by component errors of pulleys and drive belts in the drive transmission system. However, when such a setting is made, it is necessary to add a compensator for the phase delay generated by the low-pass filter circuit 80g. The gain adjustment circuit 80h calculates a drive frequency change amount that is a drive change amount corresponding to the load fluctuation amount by multiplying the data that has passed through the low-pass filter circuit 80g by a predetermined minus sign coefficient. By reducing the sign of the coefficient, if the output drive amount is increasing, the registration drive amount is decreased to reduce the paper transport speed, while the output drive amount is decreasing. Can increase the paper driving speed by increasing the resist driving amount.

  The drive frequency variation data output from the output adjustment unit 80f is input to the third arithmetic circuit 80i. The third arithmetic circuit 80i adds the drive frequency change amount input from the output adjustment unit 80f to the predetermined standard drive frequency Refrp_c for driving the registration drive motor 87 at the standard drive speed, and thereby the drive frequency Find Ur (i). Then, the result is input to the pulse generation circuit 80j. The pulse generation circuit 80j generates a pulsed motor control signal based on the input drive frequency ur (i). This motor control signal is amplified by the amplifier circuit 80 k and then input to the registration drive motor 87. The motor control signal input to the registration drive motor 87 in this way is such that the drive frequency ur (i) is adjusted at intervals of 1 [msec] according to the load fluctuation amount. The paper conveyance speed by the pair 5d is feedback controlled.

  The standard drive frequency Refrp_c is a pulse number uniquely determined based on the angular velocity of the registration roller pair 5d, the reduction ratio of the reduction system, and the like. The standard drive frequency Refrp_c may be finely adjusted by an external operation. Further, the drive frequency Ur (i) can be limited to a range in which a step-out phenomenon does not occur during motor driving.

  In this printer, the period from when the drive of the paper transport belt 60 is started until the leading edge of the recording paper reaches the paper transport belt 60 is in the first state. At a predetermined time in the period, the registration drive controller 80 obtains the above-described offset value Os based on the encoder pulse signal and the motor control signal for the belt drive motor, and stores it in the data storage means. After this storage, a few seconds at the latest, the recording paper is sent out from the registration roller pair 5d to obtain the second state. That is, the time from when the offset value Os is obtained in the first state to when the registration drive motor 87 is feedback-controlled in the second state is very short. In such a setting, the input / output drive difference Er (i), which is a characteristic value in the first state, and the input / output drive difference Er (i), which is a characteristic value in the second state, are approximately the same roller diameter. To grasp. Since a registration driving speed suitable for the roller diameter is specified and used for feedback control, an image caused by a linear speed difference between the belt running speed and the paper conveyance speed by the registration roller pair 5d is used regardless of the fluctuation of the roller diameter. Can be satisfactorily suppressed. Further, even when the test paper is not executed, when the second state is created by actually passing the paper during the print job, the input / output drive difference Er (i) in the second state is grasped and the above-mentioned. Since the registration driving speed can be adjusted by obtaining the load fluctuation amount, it is possible to avoid downtime of the apparatus due to the test paper passing.

  Although the example in which the input / output drive difference Er (i) is obtained as the characteristic value in the first state or the second state has been described, the output side driving amount with respect to the input side unit driving amount may be obtained as the characteristic value.

  The example using the motor control signal for the belt drive motor 67, which is motor control information, and the pulse signal from the rotary encoder 68, which is driven rotation information, has been described as information used for calculating the characteristic value. May be used. For example, when the belt drive motor 67 uses a built-in encoder, motor rotation information that is a pulse signal from the encoder may be used as information used to calculate the characteristic value. Further, driving roller rotation information that is a pulse signal from a rotary encoder provided on the driving roller 65 may be used as information used for calculating the characteristic value. In addition, a detection result by a mark sensor that detects scale marks provided at a predetermined pitch on the entire area in the circumferential direction of the paper transport belt 60 may be used as information used for calculating the characteristic value. If any information is two pieces of information different from each other, one of them indicates the driving amount on the input side, while the other indicates the driving amount on the output side. For example, it is assumed that the motor rotation information described above is used as one information, and the pulse signal from the rotary encoder 68 is used as the other information. Then, since this pulse signal is information on the input side rather than the motor rotation information, the motor rotation information can be used as information on the drive amount on the output side. Further, as the other information, it is assumed that a pulse signal from an encoder that detects the rotational angular displacement and rotational angular velocity of the driving roller is used instead of the above-described pulse signal. In this case, since the pulse signal is more information on the output side than the motor rotation information, the motor rotation information can be used as information on the drive amount on the input side.

  In FIG. 6, the output from the paper detection sensor 81 disposed in the vicinity of the registration roller pair (5d) is input to the switch control circuit 80m of the registration drive control unit 80. Based on the output from the paper detection sensor 81, the switch control circuit 80 specifies the timing when the paper detection sensor detects the leading edge of the recording paper and the timing when the paper detection sensor 81 no longer detects the trailing edge of the recording paper. . And based on those timings and the signal sent from the main control part which is not shown in figure, it is determined whether it is a 2nd state about the present condition. In the second state, the switch SW1r is turned on. When the switch SW1r is turned on, as shown by a solid line in the figure, the second arithmetic circuit 80e and the output adjustment unit 80f are brought into conduction, and communication between them is performed. Thereby, the feedback control of the registration driving speed based on the load fluctuation amount described above is executed. On the other hand, when shifting from the second state to another state, the switch control circuit 80m turns off the switch SW1r. Then, as indicated by a dotted line in the figure, the zero signal generation circuit 80n and the output adjustment unit 80f are brought into conduction instead of the second arithmetic circuit 80e and the output adjustment unit 80f being cut off. The zero signal generation circuit 80n outputs a signal indicating that the load fluctuation amount is zero at intervals of 1 [msec]. As a result, it is assumed that there is no load fluctuation, and a motor control signal having a standard drive frequency Refrp_c is output from the registration drive control unit 80 to the registration drive motor 87, and the registration roller pair 5d has a standard linear velocity. At a constant drive.

  FIG. 7 is a flowchart showing a control flow executed by the registration drive control unit 80. In the figure, when the driving of the paper conveying belt 60 is started at the start of a print job, the registration drive control unit 80 starts the paper feed by the registration roller pair 5d before the offset value Os described above. Is calculated and stored in the data storage means (step 1: hereinafter, step is denoted as S). Naturally, it is in the first state from the start of driving of the paper conveying belt 60 to the start of paper feeding by the registration roller pair 5d. The on / off of the driving of the registration roller pair 5d is also executed at a timing different from the on / off of the paper feed. Specifically, the registration roller pair 5d stops driving with the leading end of the recording paper sandwiched between the rollers prior to starting the feeding of the recording paper. In this way, the registration roller pair 5d is driven on and off before the recording paper is fed in order to put the leading end of the recording paper between the rollers. The driving of the registration roller pair 5d at the start of paper feeding does not include the aforementioned driving ON. The start of paper feeding means turning on the driving of the registration roller pair 5d in a state where the leading end portion of the recording paper is sandwiched between the rollers.

  After storing the offset value Os in the first state, the registration drive control unit 80 outputs a motor control signal of the standard drive frequency Refrp_c to the registration drive motor 87 when the paper feed start timing arrives (Y in S2) ( S3). As a result, paper feeding is started while the registration roller pair 5d is driven at a constant standard speed. At this time, the switch SW1r remains OFF. Next, based on the elapsed time from the paper feed start timing, it is determined whether or not the state has shifted to the second state. When the state has shifted to the second state (Y in S4), the switch SW1r is turned on (S5). ) The drive control method of the resist drive motor 87 is switched from the constant speed control method to the feedback control method based on the load fluctuation amount described above. Thereafter, when the second state is shifted to another state (Y in S6), the switch SW1r is turned off (S7), and the drive control system of the resist drive motor 87 is returned to the constant speed control system. When the registration stop timing comes (Y in S8), the registration drive motor 87 is finally stopped while the drive frequency is lowered (S9).

  In the above control flow, in the first state in which the offset value Os is calculated and stored, the registration drive motor 87 is driven at a constant speed, so that the calculation process of the offset value Os is complicated by changing the drive speed. It can be avoided.

  As the belt drive motor 67 and the resist drive motor 87, a DC servo motor can be adopted instead of the stepping motor. The DC servo motor incorporates a printed coil frequency generator (FG) as a speed sensor with a built-in motor, or an MR sensor as a built-in encoder, and the rotation detected by the rotational speed detector. The speed information is compared with external target rotational speed information, and a PWM signal is generated and output so that the detected rotational speed of the motor shaft becomes the target rotational speed. Based on the PWM signal, the drive circuit chops the drive current and controls the rotational speed of the drive motor. That is, it can be used as a drive motor that realizes a desired rotational speed by giving drive speed information in the same manner as a pulse motor.

  The example of adjusting the paper conveyance speed by the registration roller pair 5d as the conveyance means by adjusting the drive speed of the registration drive motor 87 which is the drive source of the registration roller pair 5d has been described. However, the paper by the fixing device 7 as the conveyance means has been described. The conveyance speed may be adjusted similarly. In addition, the method of directly transferring each color toner image on the photoconductor to the recording paper held on the surface of the paper conveyance belt 60 has been described. After transferring each color toner image on the photoconductor to the intermediate transfer belt, The present invention can also be applied to an image forming apparatus that transfers to recording paper.

Next, modifications of the printer according to the embodiment will be described. Unless otherwise specified, the configuration of the printer according to each modification is the same as that of the embodiment.
[First Modification]
The registration drive control unit 80 of the printer according to the first modified example obtains the rotation angle displacement amount instead of the rotation angular velocity as the drive amount information. Specifically, in FIG. 6 shown above, the first input processing circuit 80a is configured to change the rotational angular displacement of the encoder roller (63) based on the pulse signal from the rotary encoder 68 within a predetermined period of the first state. The amount (accumulation from the start of rotation) is obtained, and the result is output as digital data to the first arithmetic circuit 80d. In addition, the second input processing circuit 80b, based on the motor control signal output from the belt drive control unit 70 to the belt drive motor 67 within the above-described predetermined period, (Accumulation from) and output the result. This result is multiplied by a predetermined coefficient by the multiplication circuit 80c to be converted into a rotational angular displacement amount of the encoder roller (63), and then input to the first arithmetic circuit 80d.

  In the first state, the first arithmetic circuit 80d has a rotation angle displacement amount (output side) of the encoder roller (63) sent from the first input processing circuit 80a and an encoder roller (from the multiplication circuit 80c). 63) is obtained as an input / output displacement difference. Then, based on the input / output displacement difference as the characteristic value and the elapsed time in the predetermined period, a time-dependent change equation of the input / output displacement difference in the predetermined period is obtained. This time-varying equation is a linear equation that indicates how the input / output displacement difference changes with time in the first state. When such a time-varying equation is obtained in the first state, the result is stored in the data storage means.

  Further, in the second state, the first arithmetic circuit 80d is a first state that is an input / output displacement difference corresponding to the same elapsed time in the first state based on the above-described temporal change equation and the elapsed time so far. The input / output displacement difference is obtained every 1 [msec]. At the same time, the rotation angle displacement amount (output side) of the encoder roller (63) sent from the first input processing circuit 80a and the rotation angle displacement amount (input side) of the encoder roller (63) sent from the multiplication circuit 80c. ) And the input / output displacement difference in the second state every 1 [msec], and the difference from the first state input / output displacement difference is obtained every 1 [msec] as the load fluctuation amount. Then, the result is output to the output adjustment unit 80f.

  By using the above-mentioned time-varying equation, the load fluctuation amount per 1 [msec] can be appropriately obtained even when the rotational angular displacement amount in which the numerical value increases cumulatively with the passage of time is obtained. Can do.

[Second Modification]
FIG. 8 is a configuration diagram illustrating a main configuration of a printer according to a second modification. This printer includes an intermediate transfer belt 160 as a belt member. The intermediate transfer belt 160 is endlessly moved in the counterclockwise direction in the drawing by the rotational drive of the driving roller 165 that is one of the stretching rollers while being wound around the plurality of stretching rollers.

  Below the intermediate transfer belt 160, the photoreceptors 11Y, 11C, 11M, and 11K are in contact with the intermediate transfer belt 160 while being aligned along the belt moving direction, thereby forming primary transfer nips for Y, C, M, and K. is doing. In the loop of the intermediate transfer belt 160, primary transfer rollers 164Y, C, M, and K for Y, C, M, and K are disposed, and primary transfer nips for Y, C, M, and K are disposed. The intermediate transfer belt 160 is pressed toward the photoconductors 11Y, 11C, 11M, and 11K. A primary transfer bias is applied to these primary transfer rollers 164Y by a power source (not shown). As a result, in the primary transfer nips for Y, C, M, and K, primary transfer electric fields are formed between the intermediate transfer belt 160 and the photoconductors 11Y, C, M, and K. The Y, C, M, and K toner images on the photoconductors 11Y, 11C, 11M, and 11K are superimposed on the front surface of the intermediate transfer belt 160 by the primary transfer electric field and the nip pressure to perform primary transfer. Is done. As a result, a four-color superimposed toner image is formed on the front surface of the intermediate transfer belt 160.

  Below the photoconductors 11Y, 11C, 11M, and 11K of each color, an optical writing device 2 for writing an electrostatic latent image by optical scanning is disposed.

  A secondary transfer roller 166 disposed on the outer side of the belt loop is in contact with a portion of the intermediate transfer belt 160 in the circumferential direction around the drive roller 165. Thus, a secondary transfer nip is formed in which the front surface of the intermediate transfer belt 160 and the secondary transfer roller 166 to which a secondary transfer bias is applied by a power source (not shown) are in contact.

  The registration roller pair 5d disposed below the secondary transfer roller 166 in the drawing sends out the recording paper P at a timing at which the recording paper P can be superimposed on the four-color superimposed toner image on the intermediate transfer belt 160 at the secondary transfer nip. The fed recording paper P enters the secondary transfer nip, and a four-color superimposed toner image on the belt is collectively secondary transferred by the action of the secondary transfer electric field and nip pressure. As a result, a full-color image is formed on the recording paper P.

  The recording paper P that has passed through the secondary transfer nip is fed into the fixing device 107 while being separated from the intermediate transfer belt 160 and the secondary transfer roller 166. The fixing device 107 forms a fixing nip by contact between a fixing roller 107a containing a heat source (not shown) and a pressure roller 107b pressed toward the fixing roller 107a. The recording paper P delivered from the secondary transfer nip to the fixing device 107 is sandwiched in the fixing nip and subjected to a fixing process for a full-color image. Thereafter, the recording paper P exits the fixing nip and is discharged out of the apparatus.

  The belt drive controller 70 stabilizes the running speed of the intermediate transfer belt 160 by feedback controlling the drive speed of the belt drive motor 67 in the same manner as in the embodiment.

  In addition, the registration drive control unit 80 feedback-controls the drive speed of the registration drive motor 87 in the same manner as in the embodiment, so that the registration roller pair 5d passes the recording paper P in the second state and the intermediate transfer belt 160. This reduces the pressing force and attractive force that would be applied. As a result, the intermediate transfer belt 160 is indirectly stabilized.

  Further, the fixing drive control unit 90 performs the same feedback control as the registration drive control unit 80 on the fixing drive motor 97, so that the fixing device 107 in the second state passes the recording paper P through the intermediate transfer belt 160. This reduces the pressing force and attractive force that would be applied. This indirectly stabilizes the intermediate transfer belt 160, but the second state targeted by the fixing drive control unit 90 is different from the second state targeted by the registration drive control unit 80. . Specifically, the fixing drive control unit 90 sets the second state when the fixing device 107 is in contact with the running intermediate transfer belt 160 at the rear end side of the recording paper P being conveyed. Only in this second state, the point where the switch SW1r is turned on to perform feedback control is the same as in the embodiment.

  FIG. 9 is a graph showing the relationship between the load fluctuation amount in the second state of the registration drive motor 87 and the elapsed time. As shown in the figure, when feedback control is performed in the second state, the load fluctuation amount, which is the difference of the input / output drive difference Er (i) between the first state and the second state, is almost constant and stable. I understand. This indicates that the feedback control of the registration drive motor 87 described above is very effective in stabilizing the belt traveling speed. As the recording paper P, a paper having a length in the transport direction of 420 [mm] is used, and the paper is continuously fed at an interval of about 100 [mm] between the papers. For the intermediate transfer belt 160, the belt drive motor 67 is feedback-controlled so that the average traveling speed is 60 [mm / sec]. The passing period of the recording paper is 8.6 seconds.

  On the other hand, when feedback control is not performed in the second state and the paper conveyance speed by the registration roller pair 5d is increased by 3 [%] or 3 [%] slower than the belt traveling speed, As shown in the figure, it can be seen that a very large load fluctuation amount occurs. When the linear speed of the registration roller pair 5d is made 3% lower than the belt traveling speed, a large load fluctuation occurs on the minus side every time the recording paper passes. This is because the registration roller pair 5d pulls the intermediate transfer belt 160 through the recording paper P. On the other hand, when the linear speed of the registration roller pair 5d is set 3% higher than the belt running speed, a large load fluctuation occurs on the plus side after passing the recording paper. This is because the registration roller pair 5d pushes the intermediate transfer belt 160 through the recording paper P in the running direction.

  FIG. 10 is a graph showing the relationship between the load fluctuation amount in the second state and the elapsed time for the fixing drive motor 97. As shown in the figure, when feedback control is performed with the fixing drive motor 97 in the second state, there is almost no load fluctuation amount that is the difference of the input / output drive difference Er (i) between the first state and the second state. It turns out that it is stable. This indicates that the feedback control of the fixing drive motor 97 is very effective in stabilizing the belt traveling speed.

  As an example of using the pulse signal from the rotary encoder 68 as information reflecting the traveling speed of the paper transport belt 60 and the intermediate transfer belt 160, the output signal from the mark detection sensor may be used. This mark detection sensor detects a plurality of scale marks attached to the belt member at a predetermined pitch over the entire area in the circumferential direction at a predetermined position, and may be constituted by, for example, a reflective photosensor. Is possible.

  In the feedback control of the driving source of the conveying means, information reflecting the belt traveling speed (pulse signal from the rotary encoder 68 or a mark detection sensor is used as one of at least two pieces of information for calculating the specific value. Signal) is desirable. This is because the actual increase / decrease in belt running speed can be reflected in the specific value.

  As described above, in the printer according to the embodiment and each modification, in the first state, the registration drive control unit 80 serving as the conveyance drive control unit 80 drives the registration roller pair 5d serving as the conveyance unit and the fixing device 107 at a predetermined driving speed. The fixing drive control unit 90 is configured. In this configuration, as already described, it is possible to avoid complication of calculation processing of the offset value Os due to changing the driving speed in the first state.

  In the printer according to the embodiment or each modification, in the second state, an encoder pulse signal that is at least two pieces of information among motor control information, motor rotation information, drive roller rotation information, and driven roller rotation information. And the drive motor control signal are configured with an information acquisition means including a belt drive control unit 70, a rotary encoder 68, a registration drive control unit 80, and the like so as to be acquired at a predetermined cycle of 1 [msec]. . Then, every time the predetermined period arrives in the second state, the input / output drive difference Er (i) as the characteristic value and the load fluctuation amount as the difference are calculated, and the registration drive speed after the difference calculation The registration driving control unit 80 and the fixing driving control unit 90 are configured to adjust the fixing driving speed (driving unit driving speed). In this configuration, the resist driving speed and the fixing driving speed can be finely adjusted for each period by feedback control.

  In the printer according to the embodiment, as the information acquisition unit, one that acquires an encoder pulse signal is used as at least one of driving roller rotation information and driven roller rotation information. And the belt drive control part 70 which is a belt drive control means is comprised so that a belt drive speed may be controlled based on the acquisition result of the encoder pulse signal. In such a configuration, the belt traveling speed can be further stabilized by feedback control of the registration driving speed and the fixing driving speed while the belt traveling speed is stabilized by the feedback control of the belt driving motor 67.

  In the printer according to the embodiment, information is obtained so that an encoder pulse signal that is at least one of the rotational angular velocity of the motor, the rotational angular velocity of the driving roller, and the rotational angular velocity of the driven roller is acquired at a predetermined period. It constitutes acquisition means. Then, in the first state, an average value of the input / output drive difference Er (i), which is a characteristic value, is obtained based on the encoder pulse signal when the paper transport belt 60 is continuously driven for a predetermined time. A register serving as a conveyance drive control means so as to obtain a load fluctuation amount which is a difference between the average value and an input / output drive difference Er (i) based on an encoder pulse signal acquired every time a predetermined period arrives in the second state. A drive control unit 80 is configured. In such a configuration, it is possible to grasp the load fluctuation amount based on the rotational angular velocity of the encoder roller (63).

  In the first modification, an encoder pulse signal that is at least one of the rotational angular displacement of the motor, the rotational angular displacement of the driving roller, and the rotational angular displacement of the driven roller is acquired at a predetermined cycle. Constitutes information acquisition means. Then, in the first state, a time-dependent change equation of the input / output displacement difference, which is a characteristic value for the rotational angular displacement based on the encoder pulse signal when the paper transport belt 60 is continuously driven for a predetermined time, is obtained. The amount of change over time of the input / output displacement difference obtained based on the time change equation, and the input / output displacement difference obtained using the rotational angular displacement based on the encoder pulse signal obtained every time the predetermined period arrives in the second state, The registration drive control unit 80 serving as a conveyance drive control unit is configured to calculate the difference between the two as a load fluctuation amount. In such a configuration, by using the time-varying equation, the load fluctuation amount per 1 [msec] is appropriately set even when the rotational angular displacement amount in which the numerical value increases cumulatively with the passage of time is obtained. Can be sought.

1 is a schematic configuration diagram illustrating a printer according to an embodiment. FIG. 3 is an enlarged configuration diagram illustrating a Y image forming station of the printer together with a paper conveyance belt 60 of a transfer unit. The perspective view which shows the transfer means with a belt drive control part. FIG. 3 is an explanatory diagram for explaining a drive control system for a paper conveyance belt and a registration roller pair of the printer. The block diagram which shows the circuit structure of the belt drive control part. FIG. 3 is a block diagram showing a circuit configuration of a registration drive control unit of the printer. 6 is a flowchart showing a control flow executed by the registration drive control unit. FIG. 9 is a configuration diagram illustrating a main configuration of a printer according to a second modification. The graph which shows the relationship between the load fluctuation amount in the 2nd state about the registration drive motor of the printer, and elapsed time. The graph which shows the relationship between the amount of load fluctuations in the 2nd state about the fixing drive motor of the printer, and elapsed time.

Explanation of symbols

P: Recording paper (recording member)
5d: Registration roller pair (conveying means)
11M, C, Y, K: photoconductor (image carrier)
60: Paper transport belt (belt member)
63: Encoder roller (driven roller)
65: Drive roller 67: Belt drive motor 68: Rotary encoder (part of information acquisition means)
70: Belt drive control unit (belt drive control means)
80: Registration drive control unit (conveyance drive control means)
90: Fixing drive control unit (conveyance drive control unit)
107: Fixing device (conveying means)
160: Intermediate transfer belt (belt member)
163: Encoder roller (driven roller)
165: Driving roller

Claims (8)

In order to transfer the visible image carried on its surface to the recording member, or to transfer the visible image carried on the surface of the image carrier to the recording member held on its surface, a transfer portion for An endless belt member that moves endlessly so as to repeatedly pass through, a driving roller that moves the belt member endlessly as the belt member is driven to rotate while stretching the belt member, and endless movement of the belt member A driven roller that stretches the belt member so that the belt member rotates along with the motor, a motor that exerts a driving force that rotates the driving roller, a belt drive control unit that controls the driving speed of the motor, The recording member being transferred to the belt member, or a conveying means for conveying the recording member received from the belt member to the next process, and a conveyance driving control for controlling the driving speed of the conveying means. In the image forming apparatus and means,
Motor control information transmitted from the belt drive control means to the motor, motor rotation information that is information on the rotation angle displacement or rotation speed of the motor, and information on rotation angle displacement or rotation angle speed of the drive roller. Provided is an information acquisition means for acquiring at least two pieces of information among the drive roller rotation information and the driven roller rotation information which is information of the rotation angle displacement or rotation angular velocity of the driven roller,
A first state in which the recording member being conveyed by the conveying means is not in contact with the belt member being moved endlessly while the belt member is moved endlessly, and the belt member is moved endlessly while the belt member is moved endlessly. Based on the information acquired by the information acquisition means, respectively, in the second state in which the front end side or the rear end side of the recording member being conveyed by the means is in contact with the belt member being moved endlessly, The characteristic value of the output side drive amount with respect to the input side drive amount in a predetermined section in the drive transmission system from the motor through the drive roller and the belt member to the driven roller is grasped, and in the second state, While grasping the characteristic value, the difference between the characteristic value and the characteristic value grasped in the first state in advance is calculated, and the difference in the second state is calculated based on the calculation result. So as to adjust the driving speed of the conveying means after the difference calculation, the image forming apparatus being characterized in that constitute the conveyor drive control means. The image forming apparatus according to claim 1.
The image forming apparatus according to claim 1, wherein the conveyance drive control unit is configured to drive the conveyance unit at a predetermined driving speed in the first state. The image forming apparatus according to claim 1 or 2,
In the second state, the information acquisition means is configured to acquire at least two pieces of information out of the motor control information, motor rotation information, drive roller rotation information, and driven roller rotation information at a predetermined period,
In the second state, the conveyance drive control unit is configured to calculate the characteristic value and the difference each time the period arrives and adjust the driving speed of the conveyance unit after the difference is calculated. An image forming apparatus. The image forming apparatus according to claim 3.
As the information acquisition means, a device that acquires at least one of the driving roller rotation information and the driven roller rotation information is used.
An image forming apparatus comprising: a belt drive control unit configured to control a drive speed of the motor based on an acquisition result of the drive roller rotation information or the driven roller rotation information. The image forming apparatus according to claim 3 or 4,
The information acquisition means is configured to acquire at least one of the rotational angular velocity of the motor, the rotational angular velocity of the driving roller, and the rotational angular velocity of the driven roller in the cycle, and
In the first state, an average value of the characteristic values is obtained based on the one rotational angular velocity when the belt member is continuously driven for a predetermined time, and the average value and the second state are obtained as the difference. The image forming apparatus, wherein the conveyance drive control unit is configured to obtain a difference from the characteristic value based on the one rotation angular velocity acquired every time the period arrives. The image forming apparatus according to claim 3 or 4,
The information acquisition means is configured to acquire at least one of the rotation angle displacement of the motor, the rotation angle displacement of the driving roller, and the rotation angle displacement of the driven roller in the cycle,
In the first state, a time change equation of the characteristic value with respect to the one rotational angular displacement when the belt member is continuously driven for a predetermined time is obtained, and the difference is obtained based on the time change equation. The conveyance drive so as to calculate a difference between the amount of change of the characteristic value with time and the characteristic value obtained based on the one rotational angular displacement acquired every time the period arrives in the second state. An image forming apparatus comprising a control means. The image forming apparatus according to claim 5 or 6,
At least one of the rotational angular velocity of the motor, the rotational angular velocity of the driving roller, and the rotational angular velocity of the driven roller, or the rotational angular displacement of the motor, the rotational angular displacement of the driving roller, and the driven roller Low pass filter means for performing low pass filter processing on the acquisition result of at least one of the rotational angular displacements of
An image forming apparatus comprising: the conveyance drive control unit configured to calculate the characteristic value in the first state or the second state based on information after processing by the low-pass filter unit. In order to transfer the visible image carried on its surface to the recording member, or to transfer the visible image carried on the surface of the image carrier to the recording member held on its surface, a transfer portion for An endless belt member that moves endlessly so as to repeatedly pass through, a driving roller that moves the belt member endlessly as the belt member is driven to rotate while stretching the belt member, and endless movement of the belt member A driven roller that stretches the belt member so that the belt member rotates along with the motor, a motor that exerts a driving force that rotates the driving roller, a belt drive control unit that controls the driving speed of the motor, The recording member being transferred to the belt member, or a conveying means for conveying the recording member received from the belt member to the next process, and a conveyance driving control for controlling the driving speed of the conveying means. In the image forming apparatus and means,
Belt travel speed information is acquired by mark detection means for detecting a plurality of marks attached at a predetermined pitch over the entire circumference in the endless movement direction of the belt member at a predetermined position, and the belt drive Motor control information transmitted from the control means to the motor, motor rotation information that is information on the rotational angular displacement or rotational angular velocity of the motor, and driving roller that is information on the rotational angular displacement or rotational angular velocity of the driving roller Provided with information acquisition means for acquiring at least one of the rotation information and the driven roller rotation information which is information of the rotation angle displacement or rotation angular velocity of the driven roller;
A first state in which the recording member being conveyed by the conveying means is not in contact with the belt member being moved endlessly while the belt member is moved endlessly, and the belt member is moved endlessly while the belt member is moved endlessly. Based on the information acquired by the information acquisition means, respectively, in the second state in which the front end side or the rear end side of the recording member being conveyed by the means is in contact with the belt member being moved endlessly, The characteristic value of the output side drive amount with respect to the input side drive amount in a predetermined section in the drive transmission system from the motor through the drive roller and belt member to the driven roller is grasped, and the characteristic is obtained in the second state. While grasping the value, the difference between the characteristic value and the characteristic value previously grasped in the first state is calculated, and the difference in the second state is calculated based on the calculation result. Driving speed of the conveying means after calculating so as to adjust the image forming apparatus being characterized in that constitute the conveyor drive control means.

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