JP2019045643A - Image formation apparatus and leading end timing adjustment method - Google Patents

Abstract

To provide an image formation apparatus that can accurately perform sheet leading end timing adjustment.SOLUTION: An image formation apparatus comprises: a storage unit that stores a first profile describing a feed amount profile associated with a conveyance roller and a first driving mechanism component, and a second profile describing a feed amount profile associated with a second driving mechanism component; and a control unit that adjusts sheet leading end timing by controlling a driving speed of a first driving mechanism. The driving speed of the first driving mechanism for a period in which a sheet conveyed by the conveyance roller arrives to a transfer position is controlled on the basis of deviation of a feed amount of the sheet when the sheet arrives to the transfer position calculated from timing in which a sheet detection sensor detects a sheet leading end using the first profile of the first driving mechanism of a conveyance side, and deviation of a feed amount of an image when the sheet arrives to a transfer position calculated from timing in which the image arrives to an image formation position using the second profile of the image side.SELECTED DRAWING: Figure 9A

Description

  The present invention relates to an image forming apparatus and a tip timing adjustment method.

  In recent years, in the color commercial printing industry, electrophotographic image forming apparatuses are widely used in place of conventional offset printing apparatuses. In such commercial printing, front and back registration accuracy similar to that of the offset printing apparatus is required. One of the causes of variation in positional accuracy between the front and back surfaces is variation in the leading edge of the image. In commercial printing, the accuracy required for this leading edge variation is high, but achieving it by improving the component accuracy is not realistic from the viewpoint of manufacturing cost.

  Here, in the image forming apparatus, the toner images respectively formed on the surfaces of the plurality of photosensitive members are transferred to the intermediate transfer belt by the primary transfer unit and overlapped, and the sheet is conveyed by the secondary transfer unit. There is an intermediate transfer belt system for transferring to a belt. For example, in this intermediate transfer belt system, the error component of the feed amount on the intermediate transfer belt on the image side and the error component of the feed amount on the paper transport side are suppressed only by improving the component accuracy, and the leading edge position of the paper is highly accurate. It is difficult to align the image forming position with the paper transport timing at the time.

  In order to deal with such a problem, Patent Document 1 discloses that a first transport path from the registration roller to the secondary transfer roller and a dummy second transport path having the same configuration are located immediately upstream of the first transport path. The passage time of the second transport path is measured in advance by the paper detection sensor provided in the transport path and the leading edge timing is adjusted by accurately measuring the transit time of the first transport path. An image forming apparatus is disclosed.

  As another technique, in the image forming apparatus disclosed in Patent Document 2, a paper detection sensor that can move in the transport direction is provided between the registration roller and the transfer position of the secondary transfer unit, and the paper detection sensor detects this. The conveyance speed until the paper reaches the transfer position is increased / decreased according to the passage timing of the paper, and control is performed so that the front end of the paper reaches the transfer position in synchronization with the image. Then, the change in the conveyance speed due to the thermal expansion of the roller or the like is estimated based on the temperature change in the apparatus, and the position of the paper detection sensor is moved according to the change amount.

JP 2010-243650 A JP 2010-217789 A

  A plurality of gears are provided in the registration roller and the drive mechanism for driving the registration roller. These rotating members have deviations from the design value of the roller and uneven rotation according to the rotation period according to the tooth profile accuracy of the gear. There are not a few. The rotation unevenness causes periodic transport unevenness in the transport of the paper. Similar problems are inherent in the drive roller for driving the intermediate transfer belt and the drive mechanism for driving the intermediate transfer belt.

  However, the techniques disclosed in Patent Document 1 and Patent Document 2 do not consider these problems at all. For this reason, unevenness in conveyance due to the rotation cycle of the rotating member occurs, and it is difficult to suppress the tip variation at a high level.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide an image forming apparatus capable of performing paper leading edge timing adjustment with high accuracy.

  The above object of the present invention is achieved by the following means.

(1) a transport roller for transporting paper;
An image forming unit that has a first drive mechanism for driving the transport roller and an image carrier, and forms an image on the image carrier at an image forming position;
A second drive mechanism for driving the image carrier;
A transfer unit that transfers an image formed on the image carrier to a sheet conveyed by the conveyance roller at a transfer position;
A paper detection sensor that detects the paper that has been transported to a paper detection position between the transport roller and the transfer position;
A first profile describing a feed rate profile relating to the components of the transport roller and the first drive mechanism, and a second profile describing a feed rate profile relating to the components of the second drive mechanism A storage unit that stores
A control unit that adjusts the leading edge timing of the paper by controlling the driving speed of the first driving mechanism,
The controller is
Using the first profile, the shift of the sheet feed amount when reaching the transfer position calculated from the timing when the sheet detection sensor detects the leading edge of the sheet, and the second profile, Based on the shift of the image feed amount when reaching the transfer position calculated from the timing at which the image reaches the image forming position,
An image forming apparatus that adjusts a leading edge timing of a sheet by controlling a driving speed of the first driving mechanism in a period until the sheet conveyed by the conveying roller reaches the transfer position.

(2) comprising a plurality of HP detectors for detecting respective home positions of the transport roller, the constituent elements of the first drive mechanism, and the constituent elements of the second drive mechanism;
The image forming apparatus according to (1), wherein the control unit calculates the feed amount based on the first and second profiles and a detection output of the HP detection unit of each of the transport roller or the component. .

(3) The first profile is a profile of a feed deviation amount that is a deviation amount from an ideal feed amount in accordance with the rotation angle from the home position of each component of the first drive mechanism and the transport roller. Composed of data,
The second profile includes profile data of a feed deviation amount that is a deviation amount from an ideal feed amount according to a rotation angle from a home position of a component of the second drive mechanism. The image forming apparatus according to 2).

(4) The first profile is a composite profile obtained by synthesizing a feed amount profile with respect to a rotation angle of each of the components of the transport roller and the first drive mechanism,
The second profile is any one of the above (1) to (3), wherein the second profile is a combined profile obtained by combining profiles of feed amounts with respect to rotation angles of the respective components of the second drive mechanism. Image forming apparatus.

(5) The components of the first drive mechanism are:
The image according to any one of (1) to (4) above, which is a driven gear attached to a rotation shaft of the transport roller and a drive gear attached to a drive source and meshing with the driven gear. Forming equipment.

  (6) The first profile is created by synthesizing the outer profile of one rotation of the transport roller and the tooth profile of the driven gear and the driving gear of one rotation. Image forming apparatus.

  (7) The image carrier is an intermediate transfer belt on which a toner image is transferred at the image forming position and a toner image is formed on a surface thereof. The image forming apparatus described.

(8) The components of the second drive mechanism are:
A belt driving roller disposed on the inner peripheral side of the intermediate transfer belt and facing the transfer portion;
The image forming apparatus according to (7), wherein the image forming apparatus includes a driven gear attached to a rotation shaft of the belt driving roller, an idler gear meshing with the driven gear, and a driving gear attached to a driving source and meshing with the idler gear. .

  (9) The second profile is calculated by combining the outer profile of one rotation of the belt driving roller and the tooth profile of one rotation of each gear of the second driving mechanism, The image forming apparatus described.

(10) The image carrier is a photosensitive drum provided with a photosensitive layer on the surface of a cylindrical substrate,
The image forming apparatus according to any one of (1) to (6), wherein the second profile is a profile of a feed amount related to a component of the photosensitive drum and the second drive mechanism.

(11) A data acquisition unit that acquires data from the outside is further provided,
Each of the components of the first and second drive mechanisms and the profile of the transport roller are measured in advance, the data acquisition unit acquires and stores them in the storage unit, from (1) to above The image forming apparatus according to any one of (10).

(12) In the period, the control unit starts rotation of the first driving mechanism in a stopped state at a first driving speed, and then the paper detection sensor detects the paper and then the following equation (1) ) And the deceleration timing Tx represented by the equation (2), the driving speed is changed to a second driving speed that is slower than the first driving speed, according to any one of (1) to (11) above. Image forming apparatus.
Deceleration timing Tx = reference deceleration timing T1 + T profile (1)
T profile = (correction time for β mm) − (correction time for α mm) (2)
(However, the reference deceleration timing T1 is a predetermined set value,
α is calculated from the theoretical value when the first profile is an ideal shape at the rotational position at the timing when the leading edge of the paper is detected and the rotational position when reaching the transfer position, calculated from the first profile. It is the difference value of the deviation amount,
β is the amount of deviation from the theoretical value when the second profile is an ideal shape at the rotational position at the timing of image formation calculated from the second profile and at the rotational position when reaching the transfer position. Is the difference value. )
(13) a transport roller for transporting the paper;
An image forming unit that has a first drive mechanism for driving the transport roller and an image carrier, and forms an image on the image carrier at an image forming position;
A second drive mechanism for driving the image carrier;
A transfer unit that transfers an image formed on the image carrier to a sheet conveyed by the conveyance roller at a transfer position;
A paper detection sensor that detects the paper that has been transported to a paper detection position between the transport roller and the transfer position;
A first profile describing a feed rate profile relating to the components of the transport roller and the first drive mechanism, and a second profile describing a feed rate profile relating to the components of the second drive mechanism A leading end timing adjustment method for a sheet in an image forming apparatus comprising:
(A) starting to drive the first drive mechanism and starting transporting the paper by the transport roller;
(B) using the first profile, calculating a deviation of the sheet feed amount when the sheet detection sensor reaches the transfer position from the timing when the sheet detection sensor detects the leading edge of the sheet;
(C) using the second profile, calculating a shift in the image feed amount when reaching the transfer position from a timing when the image reaches the image forming position;
(D) Paper Based on the deviation of the feeding amount calculated in Step (b) and Step (c), the first paper in the period until the paper conveyed in Step (a) reaches the transfer position. Controlling the drive speed of the drive mechanism to adjust the leading edge timing of the paper;
Including a tip timing adjustment method.

(14) In the step (a), the stopped first driving mechanism is started to rotate at a first driving speed,
In the step (d), after the paper detection sensor detects the paper, at a deceleration timing Tx expressed by the following formulas (1) and (2), a second speed slower than the first driving speed is set. The tip timing adjustment method according to (13), wherein the tip speed is changed to a driving speed.
Deceleration timing Tx = reference deceleration timing T1 + T profile (1)
T profile = (correction time for β mm) − (correction time for α mm) (2)
(However, the reference deceleration timing T1 is a predetermined set value,
α is calculated from the theoretical value when the first profile is an ideal shape at the rotational position at the timing when the leading edge of the paper is detected and the rotational position when reaching the transfer position, calculated from the first profile. It is the difference value of the deviation amount,
β is the amount of deviation from the theoretical value when the second profile is an ideal shape at the rotational position at the timing of image formation calculated from the second profile and at the rotational position when reaching the transfer position. Is the difference value. )

According to the present invention, the shift of the sheet feed amount when the sheet detection sensor reaches the transfer position calculated from the timing when the sheet detection sensor detects the leading edge of the sheet using the first profile of the first drive mechanism on the transport side. Based on the shift of the image feed amount when reaching the transfer position calculated from the timing when the image reached the image forming position using the second profile on the image side,
By controlling the driving speed of the first drive mechanism during the period from the start of driving of the transport roller in the paused state until the paper transported by the transport roller reaches the transfer position, the leading edge timing of the paper Adjust. In this way, the leading edge timing between the paper and the image can be adjusted with high accuracy.

1 is a cross-sectional view illustrating a schematic configuration of an image forming apparatus according to an embodiment of the present invention. 1 is a block diagram of an image forming apparatus. It is a schematic diagram which shows the structure of a 1st drive mechanism. It is a schematic diagram which shows the structure of a 2nd drive mechanism. It is a figure which shows the profile of the feed amount of 1 rotation of a component. It is a figure which shows the synthetic | combination profile (1st profile) of the feeding amount of a registration roller and a 1st drive mechanism. It is a figure which shows the synthetic | combination profile (2nd profile) of the feed amount of a drive roller and a 2nd drive mechanism. It is a time chart which shows front-end | tip timing control. It is a flowchart which shows the procedure of the front-end | tip timing control performed by a control part. It is a flowchart which shows the procedure following FIG. 9A. It is a time chart which shows front-end | tip timing control.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. In addition, the dimensional ratios in the drawings are exaggerated for convenience of explanation, and may be different from the actual ratios.

  FIG. 1 is a sectional view showing a schematic configuration of an image forming apparatus 100 according to an embodiment of the present invention, and FIG. 2 is a block diagram of the image forming apparatus. As shown in FIGS. 1 and 2, the image forming apparatus 100 includes a control unit 10, a storage unit 20, an image forming unit 30, a paper feeding / conveying unit 40, an operation panel 50, paper detection sensors 61 and 62, first and second. Drive mechanisms 71 and 72, HP sensors 80 (811-812, 821-824), and a communication interface (I / F) 90.

  The control unit 10 is a CPU (Central Processing Unit), and controls the above-described units and performs various arithmetic processes according to a program.

  The storage unit 20 stores a ROM (Read Only Memory) that stores various programs and various data in advance, a RAM (Random Access Memory) that temporarily stores programs and data as a work area, and stores various programs and various data. It consists of a hard disk.

  The image forming unit 30 includes an intermediate transfer belt 31, a photosensitive drum 32, a developing unit 33, an exposure unit 34, a primary transfer unit 35, a secondary transfer roller 36, a fixing unit 37, and the like. Among these, the photosensitive drum 32, the developing unit 33, the exposure unit 34, and the primary transfer unit 35 are Y (yellow), M (magenta), C (cyan), and K (black) in order from the upstream side. A plurality are provided correspondingly. These components are the same except that the color of the toner stored in the developing unit 33 is different. In FIG. 1, the notation of symbols is omitted for some components of M, C, and K.

  In the present embodiment, the intermediate transfer belt 31 functions as an “image carrier”, and an image is formed on the intermediate transfer belt 31 at the primary transfer position p1 which is an “image forming position”, and 2 which is a “transfer position”. The image is transferred onto the sheet at the next transfer position p2.

  The photosensitive drum 32 is composed of an organic photosensitive member in which a photosensitive layer made of a resin containing an organic photoconductor is formed on the outer peripheral surface of a cylindrical metal base, for example, and rotates counterclockwise in FIG. .

  The photosensitive drum 32 charged to a uniform potential by a band electrode (not shown) is exposed by the exposure unit 34 based on the image data for printing, and an electrostatic latent image is formed. The electrostatic latent image is developed with toner of each color by the developing unit 33, and a toner image is formed on the surface of the photosensitive drum 32. The toner images are sequentially transferred onto the intermediate transfer belt 31 at the primary transfer position p1 of the primary transfer portion 35 of each color, and a full-color toner image is formed on the surface thereof.

  The secondary transfer roller 36 is urged with a predetermined pressure against the belt driving roller 311 disposed on the inner peripheral surface of the intermediate transfer belt with the intermediate transfer belt 31 interposed therebetween. At the secondary transfer position p2 (transfer nip) between the secondary transfer roller 36 and the belt drive roller 311, the toner image on the intermediate transfer belt 31 is on the sheet S conveyed by the paper feed conveyance unit 40 at the same timing. Is transcribed. Note that the interval between adjacent primary transfer positions p1 of each color, for example, the interval between the primary transfer position p1 (C) and the primary transfer position p1 (K) is made to coincide with the circumferential length of the belt driving roller 311. Designed. By doing in this way, the influence of the feed deviation amount by one rotation of the belt driving roller 311 becomes the same for all colors.

  The fixing unit 37 includes a fixing roller 371 in which a heater is disposed, and a pressure roller 372 urged by the fixing roller 371 with a predetermined pressure, and heats the sheet S conveyed to the fixing nip of both rollers. Then, the toner image on the paper S is melt-fixed on the surface thereof.

  The sheet feeding / conveying unit 40 includes a sheet feeding tray 41, a loop roller 42, a registration roller 43, a conveying path 44, a discharge tray 45, and the like. The sheets S stored in the sheet feed tray 41 are sent out to the transport path 44 one by one. The sheet S sent to the transport path 44 is transported downstream by the loop roller 42, the registration roller 43, and other transport rollers, which are transport rollers, and after the image is formed by the image forming unit 30, the discharge tray 45 is discharged. Further, the registration roller 43 performs leading edge timing adjustment (rough adjustment) and skew correction of the paper S to be conveyed. Specifically, the paper S sent out from the paper feed tray 41 to the conveyance path 44 is abutted against the registration roller 43 and stops. At this time, a paper loop (slack) is formed between the loop roller 42 and the registration roller 43 based on a signal from a paper detection sensor 61 (described later), and the leading edge of the paper runs along the axial direction of the registration roller 43. In this way, skew correction is performed. Further, the sheet S in a state of being stopped by hitting the registration roller 43 is re-conveyed and the leading edge timing is adjusted in synchronization with the image forming timing. The tip timing adjustment here is rough adjustment, and tip timing adjustment with higher accuracy is executed by tip timing control (FIGS. 9-10 and the like described later) described later.

  The operation panel 50 includes a touch panel, a numeric keypad, a start button, a stop button, and the like, and is used for inputting various settings regarding the apparatus, displaying the state of the apparatus, and inputting various instructions.

  The paper detection sensors 61 and 62 are configured by optical sensors, for example, and detect whether or not a paper is present at a paper detection position on the conveyance path 44. More specifically, the paper detection position of the paper detection sensor 61 is set to be between the loop roller 42 and the registration roller 43, and the paper detection position of the paper detection sensor 62 is the secondary transfer with the registration roller 43. It is set to be between the positions p2, and it is detected that the leading edge (leading edge) of the paper S has reached each paper detection position.

  The HP (home position) sensor 80 (811-812, 821-824) detects the home position of each component of the registration roller 43 and first and second drive mechanisms described later. Details of the HP sensor 80 will be described later.

  The communication I / F 90 is an interface for wired or wireless communication with an external device via a network, and standards such as Ethernet (registered trademark), FDDI, Bluetooth (registered trademark), IEEE 802.11, and the like are used. The communication I / F 90 also functions as a “data acquisition unit”, and the control unit 10 acquires profiles such as components to be described later from an external server via the communication I / F 90.

(First and second drive mechanisms)
Next, the first and second drive mechanisms 71 and 72 will be described with reference to FIGS. 3 and 4. FIG. 3 is a schematic diagram showing the configuration of the first drive mechanism 71, and FIG. 4 is a schematic diagram showing the configuration of the second drive mechanism 72.

  As shown in FIG. 3, the first drive mechanism 71 includes a drive motor 710, a drive gear 711 attached to the drive transmission shaft a <b> 1 of the drive motor 710, and a driven gear 712 that meshes with the drive gear 711. The drive motor 710 is, for example, a stepping motor.

  The registration roller 43 is a pair of conveyance rollers, and includes a driving roller 431 divided into a plurality of, for example, two or four in the axial direction, and a driven roller 432 that contacts the driving roller 431 with a predetermined urging force. The driving roller 431 is integrally formed with the shaft a2, and a driven gear 712 is attached to the shaft a2. The driving force of the driving motor 710 is transmitted to the driving roller 431 via the driven gear 712.

  Each of the drive gear 711 and the driven gear 712 is provided with an actuator for HP detection. This actuator is, for example, a disk in which a part of the periphery is cut out or provided with a protrusion. In the vicinity of these gears, HP sensors 811 and 812 are provided to detect the HP position of each gear. In addition, at the end of the axis a2 of the driving roller 431 of the registration roller 43, for example, a D-cut surface to be inserted into the driven gear 712 or an insertion hole for an insertion pin to be engaged with the driven gear 712 is provided. Thus, in the assembled and coupled state, the phase relationship between the driving roller 431 of the registration roller 43 and the driven gear 712 is uniquely determined.

  The control unit 10 can grasp the rotation angle from the HP position, that is, the rotation position, from the signal of the encoder built in the drive motor 710 and the signals of the HP sensors 811 and 812. In other words, the control unit 10 determines, based on these signals, the rotational positions (rotation phases) of the components of the first drive mechanism 71 and the registration rollers 43, that is, the drive gear 711, the driven gear 712, and the drive roller 731. ) And can be captured sequentially.

  As shown in FIG. 4, the second drive mechanism 72 includes a drive motor 720, a drive gear 721 provided on the drive shaft of the drive motor 720, idler gears 722 and 723 that mesh with the drive gear 721 in order, and a downstream side. A driven gear 724 that meshes with the idler gear 723 of the motor. The drive motor 720 is a stepping motor with a built-in encoder, for example.

  A belt driving roller 311 is disposed on the inner peripheral surface side of the intermediate transfer belt 31, and the intermediate transfer belt 31 rotates by the rotation of the belt driving roller 311. The belt driving roller 311 is configured integrally with the shaft a3, and a driven gear 724 is attached to the shaft a3. The driving force of the driving motor 720 is transmitted to the belt driving roller 311 via the driven gear 724 to drive the intermediate transfer belt 31.

  Each of the drive gear 721, the idler gears 722, 723, and the driven gear 724 is provided with an actuator for detecting HP. In the vicinity of these gears, HP sensors 821, 822, 823, and 824 are provided to detect the HP position of each gear. The phase relationship between the belt driving roller 311 and the driven gear 724 is also uniquely determined by the same coupling method as the driving roller 431 of the registration roller 43. In the examples shown in FIGS. 3 and 4, the HP sensor is provided for each gear. However, if the assembled state is such that the phase relationship with the adjacent gear is uniquely determined, the HP sensor The number can be reduced. For example, if all the gears of the second drive mechanism 72 are uniquely determined in the assembled coupled state, the number of HP sensors of the second drive mechanism 72 may be one.

(Feed profile)
FIG. 5 shows an example of the feed amount profile of the registration roller 43 and any one of the constituent elements of the first and second drive mechanisms. In the following, the registration rollers 43 are collectively referred to as “feed component” together with the components of the first and second drive mechanisms.

  A deviation occurs between the ideal feed amount (theoretical value when the ideal shape is designed) and the actual feed amount depending on the rotational position in one rotation. For example, if the profile of the feed amount is the registration roller 43, the average feed amount is shifted due to a deviation from the design center value of the average outer diameter. The amplitude of the waveform increases or decreases according to the deviation of the axial cross section from the perfect circle. In the case of a gear, the waveform is determined according to the outer peripheral shape of the tooth profile.

  This profile is measured in advance for each of the feed components, for example, on the production assembly line of the image forming apparatus or the production line of a component manufacturer such as a roller, and individually for each feed component together with a control number (eg serial number) Managed. The profile of each feed component is managed in a specific server database.

  For example, in the production line of the image forming apparatus 100, when the assembly is completed, the operator inputs the management number of each feeding component incorporated in the apparatus into the server management software, thereby acquiring the profile of each feeding component. can do. The acquired profile is stored in the storage unit 20 of the image forming apparatus 100. Similarly, when the feed component is exchanged at the office or print shop due to periodic maintenance, the operator inputs the management number of the feed component using the operation panel 50 or the like. The profile of the sending component can be obtained from the server via / F90. The acquired profile is stored in the storage unit 20.

  FIG. 6 is a diagram illustrating an example of a combined profile (hereinafter also referred to as “first profile”) of the feed amount of the registration roller 43 on the paper transport side and the first drive mechanism. The horizontal axis indicates the rotation angle (deg), and the vertical axis indicates the feed deviation amount. Here, the feed deviation amount is a deviation amount from a theoretical value when the ideal shape is designed. In the case of an ideal shape, it is always zero.

  In the figure, the profiles of other components are combined with the profile for one rotation with the HP position of the registration roller 43 as the base point (angle zero). This figure is an example when the least common multiple is 1 (one rotation of the registration roller 43), and when the cycle ratio (gear ratio) of the feed components does not correspond one-to-one, or other components Is not 1 / x (x is an integer) of the rotation period of the registration roller 43, it is necessary to use a composite profile corresponding to the least common multiple N (N is an integer greater than 1) rotation amount.

  FIG. 7 is a diagram illustrating an example of a combined profile of feed amounts of the second drive mechanism on the image side (hereinafter also referred to as “second profile”). In the figure, the profiles of other components are combined with the profile for one rotation with the HP position of the belt driving roller 311 as the base point (angle zero). Similar to the composite profile on the paper conveyance side in FIG. 6, this figure is an example in which the least common multiple is 1, and the least common multiple n (n is an integer greater than 1) depending on the period ratio of the feed components. It is necessary to use a synthesis profile. These first and second composite profiles are created in advance from the profiles of the respective feed components stored in the storage unit 20 and stored in the storage unit 20. It may be created by synthesizing from element profiles.

  The profile of the feed component, and the first and second profiles are composed of profile data of the feed deviation amount from the ideal feed amount according to the rotation angle. May be handled.

(Tip timing control by deceleration timing Tx)
Next, tip timing control based on the deceleration timing Tx will be described with reference to the time chart of FIG. The calculation procedure of the deceleration timing Tx will be described later.

  This figure shows the output of the sheet detection sensor 62 and the drive motor 710 for the registration roller 43, starting from the VTOP signal that is the image writing start trigger signal for each page (time t0).

  Image formation is started from the VTOP signal, and the image reaches the primary transfer position p1 at time t1. Further, the driving of the drive motor 710 is started at the rotation speed v1 at a time t2 when a predetermined time has elapsed from the VTOP signal. The paper S that has been temporarily stopped by being abutted against the registration roller 43 is transported again and transported toward the secondary transfer position p2.

  At time t3, as the leading edge of the conveyed paper S reaches the paper detection position of the paper detection sensor 62, the signal of the paper detection sensor 62 changes to ON.

  The controller 10 decelerates the rotational speed V1 of the drive motor 710 to the rotational speed V2 at time t4 when the deceleration timing Tx has elapsed from this time t3. At this rotational speed V2, the transport speed of the paper S transported by the registration rollers 43 is a so-called process speed (image forming speed). The time t4 is changed between the variable range tmin and tmax according to the setting of the deceleration timing Tx described later. This variable range is set in a range that does not hinder the conveyance of the preceding and following sheets when the sheet S is continuously conveyed.

  At time t5, the leading edge of the image formed on the intermediate transfer belt 31 reaches the secondary transfer position p2. For the sheet S, the sheet S is adjusted to reach the secondary transfer position p2 at time t5 in accordance with the setting of the deceleration timing Tx described above.

(Control flow)
Hereinafter, tip timing adjustment executed by the control unit 10 will be described with reference to FIGS. 9A to 10. FIG. 9A and FIG. 9B are flowcharts showing a method for adjusting the leading edge timing executed by the control unit 10, and FIG. 10 is a time chart for adjusting the leading edge timing when images are continuously formed on a plurality of sheets. The timing of each signal is shown. FIG. 9B is a diagram illustrating processing subsequent to FIG. 9A. The time chart shown in FIG. 8 is included in FIG. 10, and the times t1 to t5 in FIG. 8 correspond to the times t11 to t15 in FIG.

  The leading edge timing adjustment described below sets the deceleration timing Tx shown in FIG. 8 every time a sheet is conveyed using the conveyance side and image side profiles, and the leading edge timing of the sheet and the image is set according to this setting. Are the same. The algorithms shown in these flowcharts are stored as programs in the storage unit 20 and executed by the control unit 10.

(Step S101)
First, the control unit 10 receives a print job. This print job is received from a terminal device such as an external PC operated by a user connected via the communication I / F 90, for example. The print job includes print data and print settings such as paper size, basis weight, and paper type information of the paper type.

(Step S102)
The first profile on the conveyance side stored in the storage unit 20 and the second profile on the image side (intermediate transfer belt side) are called up.

(Step S103)
Here, driving of the photosensitive drum 32, the intermediate transfer belt 31, and the like is started, a preliminary rotation operation is performed, and the HP position of the feeding component on the image side is moved. In the time chart of FIG. 10, by starting the operation of the drive motor 720 at time t02, each component moves to the HP position, and the HP sensor 821-824 detects the timing at which the HP position is reached. At each detection timing of the HP sensor 821-824, the movement amount counter of each component is reset, and thereafter, the HP position information of each component, that is, the rotation position (encoder output) signal of the drive motor 720, that is, The rotation position (rotation phase) can be continuously captured. In FIG. 10, the HP position of each feed component is first detected, and the timing at which the HP position information starts to be captured is indicated by a flag mark (inverted triangle).

  Similarly, the HP position of the feeding component on the transport side is also moved. In the time chart of FIG. 10, the drive motor 710 is operated from the time t04 until the HP position is grasped. When both HP sensors 812 and 813 detect the HP position, the drive motor 710 is stopped. Thereafter, the control unit 10 grasps the rotation position (rotation phase) of the transport-side feed component in the stopped state.

(Step S104)
Here, the driving of the intermediate transfer belt 31 is started, and the movement amount is started to be counted. In the time chart of FIG. 10, after time t02, the drive motor 720 operates, and thereafter, the intermediate transfer belt 31 continues to rotate until the end of the print job.

(Step S105)
When the image processing unit of the image forming apparatus 100 has completed the rasterization process of the print data, the VTOP signal is transmitted when printing for one page is ready, the image correction calculation for one page, and the photoconductor Image formation on the drum 32 is started (time t10 in FIG. 10).

(Step S106)
The toner image formed on the photosensitive drum 32 reaches the primary transfer position p 1 and is transferred to the intermediate transfer belt 31. That is, an image is formed on the intermediate transfer belt 31 (time t11 in FIG. 10).

(Step S107)
Next, after a predetermined time has elapsed from the VTOP signal (time t12 in FIG. 10), the drive motor 710 is restarted at the rotation speed V1, and the re-conveyance of the sheet by the registration roller 43 is started.

(Step S108)
Here, it is determined whether or not the leading edge of the paper S conveyed by the registration roller 43 has reached the paper detection position. If the signal of the paper detection sensor 62 changes to ON and the leading edge of the paper S is detected, the process proceeds to step S109 (time t13 in FIG. 10).

(Step S109)
The control unit 10 uses the timing at which the paper detection sensor 62 detects the front edge of the paper, the HP position information of the conveyance component on the transport side, and the first profile, so that the front edge of the paper S reaches the secondary transfer position p2. A sheet feed deviation amount α at the time of arrival is calculated. This calculation is performed immediately after the timing when the leading edge of the sheet is detected (time t13).

  Specifically, as shown in FIG. 6, using the first profile, HP position information when the leading edge of the paper S is detected, that is, the feed deviation amount α1 at the rotational position at that time is obtained. . Next, the rotation position when the sheet S advances by the distance from the sheet detection position to the secondary transfer position p2 from the rotation position when the leading edge of the sheet S is detected is obtained, and the feed at the rotation position is obtained. The shift amount α2 is obtained. Then, α (= α2−α1) is obtained from the difference between both feed deviation amounts. In the example of FIG. 6, since α is negative, it is estimated that the paper S is delayed from the ideal timing by α.

(Step S110)
The control unit 10 includes the HP position information of the feeding component on the image side, together with the timing at which the image is formed on the intermediate transfer belt 31, that is, the timing at which the leading edge of the image reaches the primary transfer position p1 and begins to be transferred. Using the second profile, an image feed shift amount β when the leading edge of the image reaches the secondary transfer position p2 is calculated. This calculation can be performed after the timing of the VTOP signal (time t10).

  Specifically, as shown in FIG. 7, the second position is used to obtain HP position information when the image is first transferred, that is, the feed shift amount β1 at the rotational position at that time. The timing for starting the primary transfer is calculated from the VTOP signal.

  In the present embodiment, as described above, the interval between adjacent primary transfer positions p1 is designed to match the circumference of the belt drive roller 311 and the least common multiple of the second profile is Since 1 (one rotation of the belt driving roller 311), estimation may be performed at the primary transfer position p1 of any color. In this embodiment, the estimation is performed at the image formation timing of black (K).

  Next, the rotation position when the leading edge of the image is advanced by the distance from the primary transfer position p1 to the secondary transfer position p2 from the rotation position at the time of primary transfer is obtained, and the feed deviation amount β2 at that rotation position is obtained. Ask for. Then, β (= β2−β1) is obtained from the difference between both feed deviation amounts. In the example of FIG. 7, since β is negative, it is estimated that the image is delayed from the ideal timing by β.

(Step S111)
From the feed deviation amounts α and β calculated in steps S109 and S110, a T profile is calculated using the following equation (2).
T profile = (correction time for β mm) − (correction time for α mm) (2)
Then, the deceleration timing Tx is calculated from the calculated T profile using the following formula (1).
Deceleration timing Tx = reference deceleration timing T1 + T profile (1)
Here, the reference deceleration timing T1 is a timing preset from a theoretical value in design. For example, when it is estimated that the image is later than the paper, the T profile becomes negative, the deceleration timing TX becomes shorter, and the deceleration starts earlier than the reference deceleration timing T1. The conveyance timing to the next transfer position p2 is adjusted to be delayed.

  Next, a deceleration timer is set from the calculated deceleration timing Tx. The starting point of the timer is the leading edge detection timing of the paper (step S108, time t13).

(Step S121)
If the deceleration timing Tx elapses from the leading edge detection timing of the sheet and the deceleration timer counts up, the process proceeds to step S121.

(Step S122)
The control unit decelerates the drive motor 710 of the registration roller 43 from the rotation speed V1 to the rotation speed V2 (time t14 in FIG. 10).

(Step S123)
When the leading edge of the image and the leading edge of the paper S reach the secondary transfer position p2, the image is secondarily transferred to the paper S (time t15 in FIG. 10).

(Step S124)
When the image transfer is completed up to the rear end of the sheet S, the secondary transfer is completed. Thereafter, the drive motor 710 is stopped, the registration roller 43 is stopped, and preparation for receiving the next sheet S is made (time t16 in FIG. 10).

(Step S125)
If there is image formation on the next sheet S, the process returns to step S105 (symbol 20). On the other hand, if there is no image formation on the next sheet, the process ends (END).

  Thus, in the present embodiment, the sheet-side feed deviation amount α and the image-side feed deviation amount β are calculated using the first and second profiles. Then, the deceleration timing Tx is calculated from the feed deviation amounts α and β, and the driving speed of the first driving mechanism in the period from the deceleration timing Tx until the paper reaches the transfer position (time t12-t15 in FIG. 10) is calculated. By controlling, the leading edge timing of the paper is adjusted. Thereby, it is possible to suppress the leading edge variation due to the conveyance unevenness with the rotation period, and to adjust the leading edge timing between the sheet and the image with high accuracy.

(Other variations)
The configuration of the image forming apparatus described above is the main configuration for describing the features of the above-described embodiment, and is not limited to the above-described configuration, and can be variously modified within the scope of the claims. . Further, the configuration of a general image forming apparatus is not excluded.

  For example, in the embodiment shown in FIG. 1 and the like, an example in which an intermediate transfer belt is used as an image carrier is shown. However, the present invention is not limited to this, and a photosensitive drum is used as an image carrier without using an intermediate transfer belt. Alternatively, the image forming apparatus may be a transfer belt type in which each color toner is formed on a photosensitive drum, and this is held on a transfer belt and sequentially transferred onto a conveyed sheet. In this case, the rotation profile of the photosensitive drum is included in the second profile.

  The means and method for performing various processes in the image forming apparatus according to the above-described embodiments can be realized by either a dedicated hardware circuit or a programmed computer. The program may be provided by a computer-readable recording medium such as a CD (Compact Disc) -ROM, or may be provided online via a network such as the Internet. In this case, the program recorded on the computer-readable recording medium is usually transferred to and stored in a storage unit such as a hard disk. The program may be provided as a single application software, or may be incorporated in the software of the apparatus as a function of the image forming apparatus.

DESCRIPTION OF SYMBOLS 100 Image forming apparatus 10 Control part 20 Memory | storage part 30 Image forming part 31 Intermediate transfer belt 32 Photosensitive drum 33 Developing unit 34 Exposure part 35 Primary transfer roller 40 Paper feed conveyance part 41 Paper feed tray 42 Loop roller 43 Registration roller 50 Operation Panels 61 and 62 Paper detection sensor 71 First drive mechanism 710 Drive motor (registration motor)
711 Drive gear 712 Driven gear 72 Second drive mechanism 720 Drive motor 721 Drive gear 722, 723 Idler gear 724 Driven gear 80, 811, 812, 821, 822, 823, 824 HP sensor 90 Communication I / F

Claims (14)

A transport roller for transporting paper,
An image forming unit that has a first drive mechanism for driving the transport roller and an image carrier, and forms an image on the image carrier at an image forming position;
A second drive mechanism for driving the image carrier;
A transfer unit that transfers an image formed on the image carrier to a sheet conveyed by the conveyance roller at a transfer position;
A paper detection sensor that detects the paper that has been transported to a paper detection position between the transport roller and the transfer position;
A first profile describing a feed rate profile relating to the components of the transport roller and the first drive mechanism, and a second profile describing a feed rate profile relating to the components of the second drive mechanism A storage unit that stores
A control unit that adjusts the leading edge timing of the paper by controlling the driving speed of the first driving mechanism,
The controller is
Using the first profile, the shift of the sheet feed amount when reaching the transfer position calculated from the timing when the sheet detection sensor detects the leading edge of the sheet, and the second profile, Based on the shift of the image feed amount when reaching the transfer position calculated from the timing at which the image reaches the image forming position,
An image forming apparatus that adjusts a leading edge timing of a sheet by controlling a driving speed of the first driving mechanism in a period until the sheet conveyed by the conveying roller reaches the transfer position. A plurality of HP detectors for detecting the respective home positions of the transport roller, the first drive mechanism component, and the second drive mechanism component;
The image forming apparatus according to claim 1, wherein the control unit calculates the feed amount based on the first and second profiles and a detection output of the HP detection unit of each of the transport roller or the component. The first profile is constituted by profile data of a feed deviation amount that is a deviation amount from an ideal feed amount in accordance with a component of the first drive mechanism and a rotation angle of each of the transport rollers from a home position. And
The second profile is configured by feed deviation amount profile data, which is a deviation amount from an ideal feed amount, in accordance with a rotation angle from a home position of a component of the second drive mechanism. The image forming apparatus according to 2. The first profile is a composite profile obtained by synthesizing a feed amount profile with respect to a rotation angle of each of the components of the transport roller and the first drive mechanism,
The image according to any one of claims 1 to 3, wherein the second profile is a combined profile obtained by combining profiles of feed amounts with respect to rotation angles of the components of the second drive mechanism. Forming equipment. The components of the first drive mechanism are:
5. The image forming apparatus according to claim 1, wherein the image forming apparatus includes a driven gear attached to a rotation shaft of the transport roller and a drive gear attached to a driving source and meshing with the driven gear. 6. .   The image forming apparatus according to claim 5, wherein the first profile is created by synthesizing the outer profile of one rotation of the transport roller and the tooth profile of the driven gear and the driving gear of one rotation. .   The image forming apparatus according to claim 1, wherein the image carrier is an intermediate transfer belt on which a toner image is transferred at the image forming position to form a toner image on a surface. . The components of the second drive mechanism are:
A belt driving roller disposed inside the intermediate transfer belt and facing the transfer portion;
The image forming apparatus according to claim 7, wherein the driven gear is attached to a rotation shaft of the belt driving roller, the idler gear meshes with the driven gear, and the drive gear that is attached to a drive source and meshes with the idler gear.   The image formation according to claim 8, wherein the second profile is calculated by synthesizing the outer profile of one rotation of the belt driving roller and the tooth profile of one rotation of each gear of the second driving mechanism. apparatus. The image carrier is a photosensitive drum provided with a photosensitive layer on the surface of a cylindrical substrate,
7. The image forming apparatus according to claim 1, wherein the second profile is a profile of a feed amount related to components of the photosensitive drum and the second drive mechanism. It further comprises a data acquisition unit that acquires data from outside,
Each of the components of the first and second drive mechanisms and the profile of the transport roller are measured in advance, and the data acquisition unit acquires and stores them in the storage unit. The image forming apparatus according to any one of 10. The control unit starts rotation of the first drive mechanism in a stopped state at a first drive speed during the period, and then the following equation (1) and equation after the sheet detection sensor detects the sheet The image forming apparatus according to claim 1, wherein the image forming apparatus is changed to a second drive speed that is slower than the first drive speed at a deceleration timing Tx represented by (2).
Deceleration timing Tx = reference deceleration timing T1 + T profile (1)
T profile = (correction time for β mm) − (correction time for α mm) (2)
(However, the reference deceleration timing T1 is a predetermined set value,
α is calculated from the theoretical value when the first profile is an ideal shape at the rotational position at the timing when the leading edge of the paper is detected and the rotational position when reaching the transfer position, calculated from the first profile. It is the difference value of the deviation amount,
β is the amount of deviation from the theoretical value when the second profile is an ideal shape at the rotational position at the timing of image formation calculated from the second profile and at the rotational position when reaching the transfer position. Is the difference value. ) A transport roller for transporting paper,
An image forming unit that has a first drive mechanism for driving the transport roller and an image carrier, and forms an image on the image carrier at an image forming position;
A second drive mechanism for driving the image carrier;
A transfer unit that transfers an image formed on the image carrier to a sheet conveyed by the conveyance roller at a transfer position;
A paper detection sensor that detects the paper that has been transported to a paper detection position between the transport roller and the transfer position;
A first profile describing a feed rate profile relating to the components of the transport roller and the first drive mechanism, and a second profile describing a feed rate profile relating to the components of the second drive mechanism A leading end timing adjustment method for a sheet in an image forming apparatus comprising:
(A) starting to drive the first drive mechanism and starting transporting the paper by the transport roller;
(B) using the first profile, calculating a deviation of the sheet feed amount when the sheet detection sensor reaches the transfer position from the timing when the sheet detection sensor detects the leading edge of the sheet;
(C) using the second profile, calculating a shift in the image feed amount when reaching the transfer position from a timing when the image reaches the image forming position;
(D) Paper Based on the deviation of the feeding amount calculated in Step (b) and Step (c), the first paper in the period until the paper conveyed in Step (a) reaches the transfer position. Controlling the drive speed of the drive mechanism to adjust the leading edge timing of the paper;
Including a tip timing adjustment method. In the step (a), the rotation of the first drive mechanism in a stopped state is started at a first drive speed,
In the step (d), after the paper detection sensor detects the paper, at a deceleration timing Tx expressed by the following formulas (1) and (2), a second speed slower than the first driving speed is set. The tip timing adjustment method according to claim 13, wherein the tip timing is changed to a driving speed.
Deceleration timing Tx = reference deceleration timing T1 + T profile (1)
T profile = (correction time for β mm) − (correction time for α mm) (2)
(However, the reference deceleration timing T1 is a predetermined set value,
α is calculated from the theoretical value when the first profile is an ideal shape at the rotational position at the timing when the leading edge of the paper is detected and the rotational position when reaching the transfer position, calculated from the first profile. It is the difference value of the deviation amount,
β is the amount of deviation from the theoretical value when the second profile is an ideal shape at the rotational position at the timing of image formation calculated from the second profile and at the rotational position when reaching the transfer position. Is the difference value. )