JP4501751B2 - Conveying apparatus and image forming apparatus - Google Patents

Description

The present invention includes a conveyance roller that is rotationally driven by a motor, and a conveyance device that conveys a recording medium that is a conveyance target to a predetermined conveyance position by the conveyance roller, and the conveyance device for conveying a recording medium. The present invention relates to an image forming apparatus provided as a conveying unit.

  2. Description of the Related Art Conventionally, for example, in a serial type ink jet printer, an operation of stopping a recording sheet after it has been conveyed to an image forming position via a conveying roller that is rotationally driven by a motor, and a conveying direction of the recording sheet at this image forming position The head is configured to form an image on the recording paper by repeating the operation of ejecting ink from the recording head to the recording paper based on the recording data while moving the recording head in the main scanning direction orthogonal to the recording data. .

  In such an image forming position, it is necessary to transport and stop the recording paper for each scan of the recording head. However, if the stop position of the recording paper after the transport is deviated from the target stop position, white streak or color A dark streak occurs and a clear image cannot be formed.

Therefore, in an ink jet printer, the conveyance roller is usually controlled as indicated by a solid line in FIG. 12B while monitoring the conveyance position of the recording sheet by the conveyance roller via an encoder for each scan of the recording head . Yes.

In other words, conventionally, the motor is accelerated once and then gradually decelerated, so that the rotation of the conveyance roller is reduced to a sufficiently small speed in the vicinity of the target stop position, and the conveyance position of the recording paper is a predetermined amount from the target stop position. When the motor OFF position just before α is reached, the conveyance roller is driven and controlled by a procedure such as turning off the energization of the motor and stopping the conveyance roller after it is inertial. It stops at the stop position. (For example, refer patent document 1 etc.).
JP 2002-128313 A

However, in this method, if the conveyance speed at the motor OFF position is controlled to a predetermined speed, the conveyance amount due to inertia after that becomes constant, so that the conveyance roller is set to the target as shown by the solid line in FIG. Although it can be stopped at the stop position, the energization to the motor is interrupted to stop the conveyance roller. Therefore, when an external force is applied to the recording paper, the motor and the conveyance roller move.

  That is, for example, in a printer, the resistance caused by friction or deformation of the paper, the resistance due to the paper feed roller, and the like return the recording paper in the direction opposite to the paper feeding direction in the paper feeding device that feeds the recording paper from the storage unit. As the back tension is applied to the recording paper, if the back tension is large, the recording paper is returned to the paper feeding device after the motor is turned off as indicated by the dotted line in FIG. This causes a problem that an image cannot be formed at a desired position on the recording paper.

  On the other hand, if the return amount of the recording paper due to back tension is constant, this problem can be solved by setting the motor OFF position in anticipation of the return amount. In this case, the dotted line in FIG. As shown in FIG. 3, since it is necessary to transport the recording paper once to a position that takes the return amount into account, the recording paper needs to be returned, so that there is a delay in the transportation of the recording paper and the image formation time cannot be shortened. The problem arises.

In addition, a DC motor is usually used as a motor for driving the conveyance roller. Due to the structure of the DC motor, even if the drive current and the drive voltage are constant, the motor shaft rotates once. Since the torque is not uniform and a periodic torque fluctuation (refer to FIG. 13A) called a cogging cycle occurs, when the motor OFF position overlaps this torque fluctuation position, the return amount of the recording paper due to the back tension changes. thus, a sometimes stop position error as shown in FIG. 12 (b) is generated.

In this case, not only a stop position error occurs, but an unstoppable region in which the transport roller cannot be stopped may occur.
That is, as shown in FIG. 13A, when a periodic torque fluctuation occurs in the conveyance roller due to cogging of the motor or the like, the rotation speed of the conveyance roller also periodically decreases. In the vicinity of the position, when the motor OFF position (in other words, the phase of the periodic torque fluctuation at the motor OFF position) is in front of the center position of the torque fluctuation (region A shown in FIG. 13B), the conveyance is performed. When the roller is affected by torque fluctuation and the return amount from the motor OFF position increases, conversely, when the motor OFF position exceeds the center position of torque fluctuation (region B shown in FIG. 13B). The transport roller is returned to the center position of the torque fluctuation and stops at that position.

As a result, in the state where torque is applied from the recording medium such as recording paper to the conveyance roller in the direction opposite to the conveyance direction of the recording medium , the power supply to the motor is cut off in a region near the center position of the torque fluctuation. the time, as apparent from the solid line shown in FIG. 13 (c), be adjusted motor OFF position, (and thus the transport rollers) motor stop impossible region that can not be stopped is generated, the recording In some cases, the medium cannot be conveyed to a desired image forming position .

  In Patent Document 1, the minimum transport amount of the transport roller that can be controlled when transporting the recording paper is an integral multiple of the cogging cycle of the motor so that periodic torque fluctuations do not occur near the motor OFF position. In addition, it is described that the gear ratio for transmitting power from the motor to the conveying roller is set so that the time α from when the power supply to the motor is cut off until the conveying roller stops is always a fixed time.

  However, in such measures, the dimensional accuracy of the gears and belts constituting the power transmission system from the motor to the conveyance roller so that the minimum conveyance amount of the conveyance roller is an integral multiple of the cogging cycle of the motor, or There is a problem that it is necessary to manage the roller diameter and the like of the conveying roller with high accuracy, and the cost of the apparatus is increased.

The present invention has been made in view of these problems, conveyed from a recording medium such as a recording sheet even when the conveying roller such as the power of such back tension is applied, the recording medium to a desired image forming position It is an object of the present invention to provide a transfer device that can be used and an image forming apparatus including the transfer device.

The invention according to claim 1 which has been made in order to achieve the object,
A conveying unit that conveys a recording medium that is an object of image formation to an image forming position, an image forming unit that forms an image on a recording medium conveyed to the image forming position by the conveying unit, the conveying unit, and the An image forming apparatus comprising: an image forming control unit that forms an image on the entire recording medium by alternately operating the image forming unit; and a transport device used as the transport unit,
A conveyance roller which is rotationally driven by a motor and conveys the recording medium in a predetermined direction;
A rotation amount detecting means for detecting a rotation amount from a reference rotation position of the conveying roller;
When a conveyance command from the image formation control unit to the target stop position of the recording medium is input, the conveyance position of the recording medium is monitored based on the rotation amount detected by the rotation amount detection unit. by performing energization control on the motor, the rotating driving the conveying roller to the recording medium reaches the control end position before than the target stop position, when the recording medium reaches the control end position , Conveying control means for ending energization control to the motor and stopping the conveying roller at the target stop position ;
From the end of the energization control to the motor until the conveyance control unit starts energization control next, a holding current energization unit that supplies a holding current for stopping the conveyance roller to the motor;
When the holding current energizing unit supplies a holding current to the motor, the stop position of the recording medium is detected from the rotation amount detected by the rotation amount detecting unit, and the stop position and the target stop position are detected. Based on the deviation of the holding current update means for setting the holding current that the holding current energization means will flow to the motor next time, so that the deviation is reduced,
It is provided with.

As described above, the conveyance device of the present invention rotates the conveyance roller by energization control to the motor by the conveyance control means, and then does not interrupt the energization to the motor, unlike the conventional device, Each time a holding current for stopping the roller is supplied and the energization control to the motor by the conveyance control unit is completed, the deviation between the stop position of the recording medium and the target stop position is obtained, and the deviation is reduced. In addition, the holding current is updated (see FIG. 14A).

Therefore, according to the present invention, the conveying roller from the recording medium, even if external force is applied in the direction opposite to the conveying direction of the recording medium, without returning the recording medium by the external force, the recording medium will be capable of carrying a desired position, it is possible to rapidly convey and accurately the recording medium to the target stop position.

By the way, in the present invention, since the holding current is supplied to the motor even after the energization control to the motor by the conveyance control unit is completed, the torque from the recording medium to the conveyance roller is applied to the motor by the conveyance control unit. Even if the end timing of the energization control overlaps the region where the periodic torque fluctuation generated in the drive system of the transport roller is maximized, as shown in FIG. 14B, the recording medium is stopped near the target stop position. I can. That is, according to the present invention, to prevent the stop impossible region as shown in FIG. 13 (c) occurs, conveying the recording medium to the desired position can.

In this case, however, merely has to flow a holding current to the motor, the transport rollers, since the influence of rotation variation occurring in the drive system, as shown in FIG. 14 (b), the target stop position It cannot be stopped accurately.

Therefore, in order to reliably stop the transport roller (and hence the recording medium ) at the target stop position, as described in claim 2, the transport device according to claim 1,
The period of the periodic torque fluctuation generated in the driving system of the conveying roller including the motor is stored in association with the rotation amount of the conveying roller, and the phase of the maximum point of the periodic torque fluctuation is the reference of the conveying roller. Periodic fluctuation characteristic storage means stored as a rotation amount from the rotation position;
When the conveyance command is input from the image formation control unit, based on the period and phase of the periodic torque variation stored in the periodic variation characteristic storage unit and the rotation amount detected by the rotation amount detection unit. A phase difference calculating means for obtaining a phase of a periodic torque fluctuation at a control end position set based on the conveyance command and calculating a phase difference between this phase and a phase at a maximum point of the periodic torque fluctuation;
Based on the phase difference calculated by the phase difference calculating means, a control position correcting means for correcting the control end position so that the end of the energization control is delayed as the phase difference is smaller;
It is good to provide.

In other words, the phase difference calculated by the phase difference calculating means represents a deviation from the maximum torque fluctuation position at the timing when the conveyance control means finishes energization control to the motor (motor OFF position), and this deviation is small. Since the force applied to the transport roller due to the periodic torque fluctuation of the drive system becomes larger, the transport control means in the invention according to claim 2 can apply torque to the transport roller against this force. Corrects the control end position used for control. As a result, according to the transport apparatus of the second aspect, the transport roller (and hence the recording medium ) can be more reliably controlled to the target stop position.

  Further, in the transport apparatus according to claim 2, the period of the periodic torque fluctuation stored in the periodic fluctuation characteristic storage means and the phase of the maximum point thereof are determined by the rotation amount of the transport roller at the time of shipment of the transport apparatus from the factory. Of these, in particular, the phase of the maximum point of the periodic torque fluctuation is defined by the amount of conveyance from the reference rotation position of the conveyance roller. If the detection result by the rotation amount detection means disappears when the power is turned off, or if the rotation amount detection means cannot detect the rotation amount accurately due to manual rotation of the transport roller, the phase difference calculation means In this case, the phase difference between the phase of the periodic torque fluctuation at the control end position and the phase at the maximum point of the periodic torque fluctuation cannot be accurately calculated.

  For this reason, in the transport apparatus according to claim 2, as described in claim 3, when the transport apparatus is activated, the transport roller is rotationally driven via the motor to thereby rotate the periodic device. The rotation position of the conveyance roller that maximizes the torque fluctuation is detected, and the maximum torque having the current conveyance roller stop position as the reference rotation position from the detected maximum torque fluctuation rotation position and the period of the periodic torque fluctuation. It is preferable to provide period fluctuation phase detecting means for obtaining the phase of the fluctuation rotation position and storing the phase in the period fluctuation characteristic storage means.

  In other words, in this way, when the transport device is started up, the transport roller is actually rotationally driven via a motor to detect periodic torque fluctuations applied to the transport roller, and the phase of the maximum point is transported. The rotation amount from the reference rotation position of the roller can be stored in the periodic fluctuation characteristic storage means, and in the phase difference calculation means, the phase of the periodic torque fluctuation at the control end position and the maximum point of the periodic torque fluctuation are determined. The phase difference from the phase can always be accurately calculated.

According to a fourth aspect of the present invention, there is provided a conveying unit that conveys a recording medium that is an object of image formation to an image forming position, and an image on the recording medium that is conveyed to the image forming position by the conveying unit. An image forming apparatus comprising: an image forming unit to form; and an image forming control unit that forms an image on the entire recording medium by alternately operating the transport unit and the image forming unit. As a feature of the present invention, the conveyance apparatus according to any one of claims 1 to 3 is provided.

  Therefore, according to this image forming apparatus, the conveyance amount of the storage medium with respect to the image forming position can be accurately controlled, and the periodic torque is generated in the power transmission system from the motor and the motor to the conveyance roller constituting the conveyance unit. Even in the case where the fluctuation occurs, the image forming unit can form an image at a desired position on the storage medium. Therefore, according to the present invention, it is possible to provide an image forming apparatus that can always form a clear image.

Embodiments to which the present invention is applied will be described below with reference to the drawings.
FIG. 1 is a perspective view of a multi-function device (MFD) 1 according to the embodiment, and FIG. 2 is a side sectional view thereof.

  The multi-function device 1 has a printer function, a copy function, a scanner function, and a facsimile function. As shown in FIGS. 1 and 2, the multi-function device 1 is used for reading an original on a synthetic resin housing 2. An image reading device 12 is provided.

  The image reading device 12 is configured to be vertically openable and closable with respect to the housing 2 around a pivot (not shown) provided at the left end thereof, and further, a document cover body 13 that covers the upper surface of the image reading device 12. However, it is attached to the image reading device 12 so as to be able to open and close up and down around a pivot 12a (see FIG. 2) provided at the rear end thereof.

  As shown in FIG. 2, a placement glass plate 16 is provided on the upper surface of the image reading device 12 for placing the document for reading by opening the document cover 13 upward. A contact image sensor (CIS: Contact Image Sensor) 17 for reading a document is provided so as to be reciprocally movable along a guide shaft 44 extending in a direction (main scanning direction, left-right direction) perpendicular to the paper surface of FIG. ing.

  As shown in FIGS. 1 and 2, an operation including an operation button group 14a for performing an input operation and a liquid crystal display unit (LCD) 14b for displaying various types of information is provided in front of the image reading device 12. A panel portion 14 is provided.

On the other hand, at the bottom of the housing 2, a paper feeding unit 11 for feeding recording paper P as a recording medium ( recording medium ) is provided. In the paper feeding unit 11, a paper feeding cassette 3 that accommodates recording paper P in a stacked (stacked) state is attached to and detached from the housing 2 in the front-rear direction via an opening 2 a formed on the front side of the housing 2. It is provided as possible. In the present embodiment, the paper feed cassette 3 is a recording paper P of A4 size, letter size, legal size, postcard size, etc., whose short side (width) is in the paper feed direction (sub-scanning direction, front-rear direction, arrow A direction). A plurality of sheets can be stacked (stacked) in a direction extending in a direction (main scanning direction, left-right direction) orthogonal to the direction of storage.

  As shown in FIG. 2, an inclined separation plate 8 for separating recording paper is disposed on the back side (rear end side) of the paper feed cassette 3. The inclined separation plate 8 is formed in a convex curved shape in plan view so as to protrude at the center in the width direction (left-right direction) of the recording paper P and to recede toward the left and right ends in the width direction of the recording paper P. In addition, a serrated elastic separation pad for abutting the leading edge of the recording paper P to promote separation is provided at the center in the width direction of the recording paper P.

  Further, in the paper feed unit 11, a base end portion of a paper feed arm 6a for feeding the recording paper P from the paper feed cassette 3 is mounted on the housing 2 side so as to be rotatable in the vertical direction. The rotational driving force from the LF (conveyance) motor 54 (see FIG. 4) is transmitted to the paper feed roller 6b provided at the tip of the arm 6a by the gear transmission mechanism 6c provided in the paper feed arm 6a. The Then, the recording paper P accumulated in the paper feed cassette 3 is separated and conveyed one by one by the paper feed roller 6b and the elastic separation pad of the inclined separation plate 8 described above. The recording paper P separated in this manner so as to proceed along the paper feeding direction (arrow A direction) passes through a laterally U-shaped path formed in the gap between the first conveyance path body 53 and the second conveyance path body 52. The paper is fed to the recording unit 7 provided above (high position) of the paper feed cassette 3 through the feed path 9 including the feed path 9. The recording unit 7 corresponds to the image forming unit of the present invention.

FIG. 3 is a partial plan view of the multi-function device 1 with the image reading device 12 removed.
As shown in the figure, the recording unit 7 is supported by a main frame 21 formed in an upwardly open box shape and a pair of left and right side plates 21a and extends in a horizontally long plate shape extending in the left-right direction (main scanning direction). An ink jet recording head 4 (see FIG. 2) that is provided between the first guide member 22 and the second guide member 23 and records an image on the recording paper P by ejecting ink from the lower surface thereof. And a carriage 5 on which the head 4 is mounted.

  The carriage 5 is slidably supported across the first guide member 22 on the upstream side in the paper discharge direction (arrow B direction) and the second guide member 23 on the downstream side, and can reciprocate in the left-right direction. Yes. A timing belt 24 extends on the upper surface of the second guide member 23 arranged downstream in the paper discharge direction (arrow B direction) so as to extend in the main scanning direction (left-right direction) in order to reciprocate the carriage 5. A CR (carriage) motor (not shown) that is wound and drives the timing belt 24 is fixed to the lower surface of the second guide member 23.

  On the other hand, in the recording unit 7, a flat platen 26 extending in the left-right direction facing the recording head 4 is provided on the lower surface of the recording head 4 in the carriage 5 between the guide members 22 and 23. 21 is fixed.

  As shown in FIG. 2, on the upstream side of the platen 26 in the paper discharge direction (arrow B direction), a conveyance roller 50 for conveying the recording paper P to the lower surface of the recording head 4 and a conveyance roller 50 opposed thereto are conveyed. A nip roller 51 biased toward the roller 50 is provided. Further, on the downstream side of the platen 26 in the paper discharge direction (arrow B direction), the recording paper P that has passed through the recording unit 7 is driven so as to be conveyed to the paper discharge unit 10 along the paper discharge direction (arrow B direction). A paper discharge roller 28 and a spur roller (not shown) biased toward the paper discharge roller 28 are disposed opposite to the paper discharge roller 28.

  The paper discharge unit 10 on which the recording paper P recorded by the recording unit 7 is discharged with its recording surface facing upward is disposed above the paper supply unit 11, and the paper discharge port 10 a is an opening on the front surface of the housing 2. Opened in common with 2a. Then, the recording paper P discharged from the paper discharge unit 10 in the paper discharge direction (arrow B direction) is accumulated and accommodated on a paper discharge tray 10b located inside the opening 2a.

  An ink storage unit (not shown) is provided at the front right end position of the housing 2 covered with the image reading device 12. In this ink storage unit, four ink cartridges each containing ink of four colors (black (Bk), cyan (C), magenta (M), and yellow (Y)) for full-color recording are stored in the image reading apparatus. It is mounted so that it can be attached and detached with 12 open upward.

  The ink cartridges of each color and the recording head 4 described above are connected by four flexible ink supply tubes, and the ink stored in each ink cartridge is recorded via each ink supply tube. It is supplied to the head 4.

  Next, the control system of the multi-function device 1 is composed of a CPU, a ROM, a RAM, and the like, and a microcomputer that comprehensively controls the entire device 1 (hereinafter simply referred to as a CPU 100 shown in FIG. 4) and the CPU 100 ASIC (Application Specific Integrated Circuit) for driving and controlling each of the above parts (LF motor 54, CR motor, recording head 4, CIS 17, etc.).

  In this ASIC, information from a user input via the operation button group 14 a of the operation panel unit 14 is captured and input to the CPU 100, or various information is input to the liquid crystal display unit 14 b of the operation panel unit 14 in accordance with a display command from the CPU 100. Communicates via a panel interface for displaying messages, etc., a parallel interface for communicating with external devices such as a personal computer via a parallel cable or USB cable, a USB interface, or a PSTN (Public Switched Telephone Network). An NCU (Network Control Unit) is also connected to this NCU. Further, the NCU demodulates a communication signal input from the PSTN to the NCU, and transmits data transmitted from the NCU to the outside by facsimile transmission or the like. To modulate Modem is connected.

  That is, in the multi-function device 1 of the present embodiment, the printer function, the copy function, the scanner function, and the facsimile function are realized by the operation of the CPU 100 and the ASIC connected thereto.

  However, since the panel interface, the parallel interface, the USB interface, the NCU, the modem, and the like are not necessary in describing this embodiment, the description and illustration thereof are omitted here.

  For example, when an image is recorded on the recording paper P in the printer function, copy function, and facsimile function, the CPU 100 first drives the LF motor 54 to rotate in a preset direction via the ASIC. As a result, the sheet feeding roller 6 b is rotated in the sheet feeding direction, and the recording sheet P is fed from the sheet feeding cassette 3 toward the conveying roller 50. Thereafter, by rotating the LF motor 54 by a predetermined amount in the reverse direction, the conveying roller 50 and the paper discharge roller 28 are rotated by the predetermined amount in the feeding direction of the recording paper P, and the recording paper P is moved on the platen 26. Move in stages. Further, the CPU 100 moves the recording paper P stepwise, so that when the recording paper P temporarily stops on the platen 26, the CPU 100 drives the CR motor to move the carriage 5 in the main scanning direction. Then, ink is ejected from the recording head 4 based on the recording data.

As a result, an image for one scan is formed on the recording paper P. The CPU 100 repeatedly executes a series of controls such as driving of the LF motor 54 (movement of the recording paper P), driving of the CR motor (movement of the carriage 5), and driving of the recording head 4 through the ASIC. Thus, an image is formed on the entire area of the recording paper P. That is, the CPU 100 functions as an image formation control unit of the present invention.

Note that the CPU 100 switches the rotation direction of the LF motor 54 when the recording paper P is transported from the paper feed cassette 3 to the recording unit 7 for the following reason.
That is, in the present embodiment, the paper feed roller 6b, the transport roller 50, and the paper discharge roller 28 rotate all at once by the rotational driving force transmitted from the LF motor 54, but the paper feed roller 6b feeds paper. In a state where the recording paper P is rotated in the direction in which the recording paper P is fed from the cassette 3, the transport roller 50 and the paper discharge roller 28 are transported in the direction in which the recording paper P is transported to the paper discharge side (hereinafter referred to as “transport rotation direction”). , The leading edge of the recording paper P fed from the paper feed cassette 3 abuts against the transport roller 50 and the nip roller 51 to correct the skew, and then the rotation direction of the LF motor 54 Thus, the recording roller P is transported from the recording unit 7 to the paper discharge unit 10 by rotating the transport roller 50 and the paper discharge roller 28 in the transport rotation direction.

  And in order to convey the recording paper P in this way, the rotational driving force transmission path from the LF motor 54 to the paper feed roller 6b has a transmission state in which the rotational driving force is transmitted and a non-transmission state in which the rotational driving force is not transmitted. The rotation driving force is transmitted from the LF motor 54 to the paper feed roller 6b only when the recording paper P is fed.

Next, FIG. 4 shows an LF motor drive system used for driving the LF motor 54 in accordance with a command from the CPU 100 as the image formation control means in order to convey the recording paper P as described above (that is, the present invention). It is a block diagram showing the structure of a conveyance apparatus or a conveyance means) .

  The LF motor 54 of the present embodiment is configured by a DC brush motor, and as shown in FIG. 4, the rotation amount of the LF motor 54 (and hence the rotation amount of the transport roller 50) is applied to the rotation shaft thereof. A rotary encoder 58 is provided for detection.

  The rotary encoder 58 is provided, for example, on a rotating shaft of the LF motor 54 and has a rotating plate having slits formed at predetermined angular intervals around the shaft, and the light emitting element and the light receiving element face each other across the slit of the rotating plate. In order to make it possible to easily detect the rotation direction of the LF motor 54 from the output detection signal, the detection unit is configured to have a fixed period (for example, 1). / 4 period) Two kinds of encoder signals ENC1 and ENC2 which are shifted are outputted.

  That is, the two types of encoder signals ENC1 and ENC2, for example, when the LF motor 54 rotationally drives the transport roller 50 and the paper discharge roller 28 in the transport rotation direction, the phase of ENC1 advances by a certain period with respect to ENC2. When the LF motor 54 rotates the paper feed roller 6b in the paper feed direction, the phase of ENC1 is set to be delayed by a certain period with respect to ENC2.

The two types of encoder signals ENC1 and ENC2 thus output from the rotary encoder 58 are input to the paper transport control device 70 provided in the ASIC.
The sheet conveyance control device 70 is for controlling the LF motor 54 in response to a command from the CPU 100, generates a PWM signal for controlling the rotation speed, the rotation direction, and the like of the LF motor 54, and outputs the LF signal. By outputting to the drive circuit 56, the LF motor 54 is driven via the LF drive circuit 56.

For this reason, the sheet conveyance control device 70 has a register group 72 for storing various parameters used for controlling the LF motor 54, and the encoder signals ENC1 and ENC2 fetched from the rotary encoder 58, so that the LF motor 54 (and hence the conveyance roller 50). From the motor rotation positioning unit 74 that calculates the rotation speed and rotation position (and hence the conveyance position of the recording paper P), the drive control unit 76 that generates a command signal for driving the LF motor 54, and the drive control unit 76 A PWM generator 78 that generates a PWM signal for duty driving the LF motor 54 in accordance with the command signal is provided. The drive control unit 76, the PWM generation unit 78, and the LF drive circuit 56 correspond to the conveyance control unit and the holding current energization unit of the present invention.

  Here, based on the encoder signals ENC1 and ENC2 from the rotary encoder 58, the motor rotation positioning unit 74 detects an edge detection signal indicating the start / end of each cycle of the encoder signal ENC1 (for example, when ENC2 is at a high level, Edge detection unit 91 and edge detection unit 91 that detect the rotation direction of the LF motor 54 (for example, the forward direction if the edge detection signal is the falling edge of ENC1, and the reverse direction if the edge detection signal is the rising edge). When the conveyance roller 50 is rotated in the conveyance rotation direction according to the detected rotation direction of the LF motor 54 (in other words, the rotation direction of the conveyance roller 50) (that is, when the recording paper P is conveyed), an edge detection signal is detected. Is counted up and the rotation direction is opposite (that is, when the recording paper P is fed by the paper feed roller 6b). In this case, the edge detection signal is counted down to detect the rotation amount (rotation position) of the LF motor 54 (and hence the conveyance roller 50). The interval from when the detection signal is input to when it is input next is counted by the internal clock CK having a constant pulse width, and the LF motor 54 (and hence the conveying roller 50 is extended) based on the count value and the cycle of the internal clock CK. ), And the like.

  Further, the register group 72 includes various control gains (proportional gain,...) Necessary for feedback control (FB control) of the rotation speed of the LF motor 54 in addition to the activation setting register 80 of the paper conveyance control device 70. The register 81 for setting the FB control parameter including the integral gain and the like, and the drive control of the LF motor 54 are stopped, and then the LF motor 54 (and hence the conveyance roller 50) is actually stopped by energizing a holding current described later. The register 82 for setting the stop braking distance until the start, the register 83 for setting the stop holding current to be passed to the LF motor 54 when the LF motor 54 is stopped, and the targets of the LF motor 54 (and hence the transport roller 50) A register 8 for setting a stop position (specifically, a conveyance count number representing the rotation amount after the driving of the LF motor 54 is started) , A register 85 for setting a current FB coefficient for feedback control of the holding current at the stop according to the deviation from the target stop position that occurs when the LF motor 54 is stopped, and a periodic torque fluctuation generated in the drive system of the transport roller 50 A register 86 for setting a correction amount calculation function necessary for calculating a correction amount for correcting a deviation of the conveyance roller 50 from the target stop position caused by (such as torque fluctuation due to cogging of the LF motor 54), the conveyance roller A register 87 for setting a periodic fluctuation phase center value representing a phase having the largest fluctuation amount among periodic torque fluctuations (hereinafter also simply referred to as periodic fluctuations) generated in 50 drive systems, and one of the periodic fluctuations A register 88 or the like for setting a period variation period length representing the length of the period is provided.

  Of the various parameters set in the register group 72, all parameters except the holding current at stop set in the register 83 and the period fluctuation phase center value set in the register 87 are set by the CPU 100 and stopped. The current holding current is updated every time the LF motor 54 is driven during image formation by the operation of the holding current setting device 120 provided in the ASIC separately from the paper conveyance control device 70, and the period variation phase center value is Similarly, it is initialized immediately after activation of the multi-function device 1 by the operation of the period fluctuation phase calculation device 110 provided in the ASIC separately from the paper conveyance control device 70.

  Further, the periodic fluctuation phase center value is obtained by rotating the LF motor 54 in the conveyance rotation direction from the reference position where the position count value C of the position counting unit 92 is the initial value “0” to the position where the periodic fluctuation is the largest. Represents the number of counts of the position count unit 92 when the position count unit 92 is reset to the initial value “0” after the multi-function device 1 is activated. Therefore, when the position count unit 92 is reset at the start of conveyance of the recording paper P, the paper conveyance control device 70 determines the period based on the position count value C before the reset. A periodic fluctuation phase center value updating unit 94 that updates the fluctuation phase center value is also provided.

Note that the register 87 the periodic fluctuation phase center value is set to, and registers 88 which periodic fluctuation period length is set by the CPU 100, and CPU 100 cycle variation period length is stored to be set in the register 88 (details The internal ROM) corresponds to the periodic fluctuation characteristic storage means of the present invention, and the periodic fluctuation phase calculation device 110 corresponds to the periodic fluctuation phase detection means of the present invention.
Further, the holding current setting device 120 that updates the holding current at stop in the register 83 every time the LF motor 54 is driven during image formation corresponds to the holding current update unit of the present invention.

  Further, the sheet conveyance control device 70 sets the correction amount calculation function, the period variation phase center value, and the period variation period length set in the registers 86, 87, and 88 during image formation in which the conveyance roller 50 is repeatedly driven and stopped. Based on the correction amount setting unit 96 for calculating a correction amount for correcting the target stop position set in the register 84, and the correction amount set in the correction amount setting unit 96 is set in the register 84. A stop position correction unit 98 that corrects the target stop position and inputs it to the drive control unit 76 is also provided. The correction amount setting unit 96 and the stop position correcting unit 98 correspond to the phase difference calculating unit and the control position correcting unit of the present invention.

  The target stop position corrected by the stop position correction unit 98 is input to the drive control unit 76 together with the FB control parameter, stop braking distance, stop holding current, and the like. The drive control unit 76 sets these parameters. The LF motor 54 is driven and controlled.

Hereinafter, among the drive system of the LF motor 54 configured as described above, the main part related to the present invention is the periodic fluctuation phase calculation device 110 as the periodic fluctuation phase detection means , the transport control means, and the holding current energization means. Along with the counter reset of the drive control unit 76, the holding current setting device 120 as the holding current updating unit, the correction amount setting unit 96 and the stop position correcting unit 98 as the phase difference calculating unit and the control position correcting unit, and the position counting unit 92 The operation of the period variation phase center value update unit 94 that updates the period variation phase center value in the register 87 and associates it with the position count value C will be described.
Each of these units is provided in the ASIC, but can be realized as a microcomputer process. Here, in order to explain the operation of each unit in an easy-to-understand manner, a flowchart is used to describe the operation. And

First, FIG. 5 is a flowchart showing a period variation phase calculation process executed by the period variation phase calculation device 110.
The period fluctuation phase calculation device 110 is activated only once immediately after the power is turned on to the multi-function device 1 of the present embodiment, and executes this period fluctuation phase calculation processing. In the cycle variation phase calculation process, first, the cycle variation cycle length “B” set by the CPU 100 in the register 88 is read in S110 (S represents a step). The period variation period length “B” is defined by the number of edge detection signals output from the edge detection unit 91.

  In the subsequent S120, the number of data (acquired data) K to be sampled to detect the period variation and its phase is obtained by multiplying the period variation period length “B” by a preset coefficient n, and then continues. In S130, a drive command for the LF motor 54 is output to the CPU 100, so that the LF motor 54 is rotated at a constant speed in the conveying rotation direction of the conveying roller 50. In S140, a speed calculation is performed in synchronization with the rotation. The K rotation speeds V output from the unit 93 are sampled.

  In the subsequent S150, the position count unit 92 is reset by the CPU 100 to initialize the position count value C to a value of 0. In the subsequent S160, from the K rotational speeds V sampled in S140, The average speed Vav during the sampling period is obtained, and the rotational speed fluctuation υ is calculated by calculating the difference from the average speed Vav for each K rotational speeds V sampled in S170. (See FIG. 6).

  Next, in S180, an initial value “0” is set as the phase D of the reference signal S, and in S190, the current period of the LF motor 54 is the same as the period variation period length “B” in the same period and the same resolution. A rectangular wave having a phase of “D” at the rotation stop position is generated for n wavelengths (see FIG. 6). This rectangular wave is a data string that periodically changes with a high level as a value 1 and a low level as a value −1, and is used as a reference signal S for detecting a period variation phase. In subsequent S200, a product-sum operation (σd ← υ1 · S1 + υ2 · S2 +... + ΥK · SK) of the generated rectangular wave (that is, reference signal S) and the rotational speed fluctuation υ obtained in S190 is performed.

  Next, in S210, the value of the phase D is incremented, and in the subsequent S220, it is determined whether or not the phase D has reached the number of data per one period fluctuation period (that is, the period fluctuation period length “B”). Thus, it is determined whether or not the generation of the reference signal S in S190 and the product-sum operation in S200 have been executed for one period variation.

  In S220, if it is determined that the generation of the reference signal S and the product-sum operation cannot be performed for one period variation, the process proceeds to S190 again, and the phase D of the reference signal S is shifted by the value 1. In S200, a product-sum operation is performed on the reference signal S and the rotational speed fluctuation υ.

  On the other hand, when it is determined in S220 that the generation of the reference signal S and the product-sum operation have been executed for one period variation, the process proceeds to S230, and the product-sum operation result for each reference signal S obtained in S200 is obtained. The product-sum operation result having the maximum absolute value is selected from among them. In subsequent S240, the phase D of the reference signal S of the selected product-sum operation result is obtained. In S250, the obtained phase D is obtained. This is set as the period variation phase center value D and written to the register 87.

  That is, the periodic fluctuation phase calculation device 110 detects the rotational speed fluctuation υ of the LF motor 54 (it is preferable that the detection period is at least twice the period of the periodic torque fluctuation), and the internally generated reference signal S. Is repeatedly performed while sequentially shifting the phase of the reference signal S with the resolution of the edge detection unit 91 as the minimum unit, so that the product-sum operation is performed for one period of the periodic torque fluctuation. The position count value C of the position count unit 92 when the LF motor 54 is rotated in the conveyance rotation direction with the current stop position of the LF motor 54 as a reference position is determined, and the value is calculated as It is initially set as the period variation phase center value D.

  This is so that the phase of the maximum point of the periodic torque fluctuation generated in the LF motor 54 can be easily detected in association with the position count value C of the position count unit 92 without performing complicated calculations such as FFT. It is to do.

Next, FIG. 7 is a flowchart showing a motor drive control process executed by the drive control unit 76 when an image is formed on the recording paper P.
As shown in FIG. 7, the drive control unit 76 first rotates the target stop position corrected by the stop position correction unit 98 (specifically, how much the LF motor 54 is rotated from the current stop position in S300). LF motor 54 by reading the conveyance count number Cf), which is expressed by the count number of the position count unit 92, and adding the conveyance count number Cf to the current position count value C of the position count unit 92 in subsequent S310. A target stop position count value Ct for stopping (in other words, the conveyance roller 50) is calculated.

  In subsequent S320, as shown in FIG. 12A, the LF motor 54 is driven in the conveyance rotation direction of the conveyance roller 50, and the position stop value C of the position count unit 92 is set in S310. Until the position count value Ct is reached, drive control of the LF motor 54 is executed to decelerate the LF motor 54 to an extremely low speed before stopping.

  Further, during the drive control of the LF motor 54, after obtaining the position count value C from the position count unit 92 in S330, the process proceeds to S340, where the position count value C is obtained from the target stop position count value Ct. It is determined whether or not the rotation position of the LF motor 54 has reached the control end position by determining whether or not the reduced value (Ct−C) has become equal to or less than the stop braking distance α set in the register 82. To do.

If the rotational position of the LF motor 54 has not reached the control end position, the drive control of the LF motor 54 in S320 is continued. If the rotational position of the LF motor 54 has reached the control end position, in S350, The energizing current amount to the LF motor 54 is switched to the holding current I at the time of stop set in the register 83, and the transport control for one scan by the LF motor 54 is once ended.
In addition, the process of S300-S340 functions as a conveyance control unit of the present invention, and the process of S350 functions as a holding current energizing unit of the present invention.

Next, FIG. 8 is a flowchart showing a holding current setting process executed by the holding current setting device 120 as a holding current update unit . The holding current setting device 120 executes the holding current setting process every time the drive control unit 76 transports the recording paper P by the motor drive control process shown in FIG.

In this holding current setting process , first, in S360, the drive control unit 76 acquires the target stop position count value Ct set when the motor drive control process of FIG. 7 is executed, and in S370, the position count is counted. The current position count value C is read from the unit 92 as a stop position count value Cs representing the actual stop position of the LF motor 54.

  In subsequent S380, the current FB coefficient k is read from the register 85, the current FB coefficient k, the stop-time holding current I currently set in the register 83, the target stop position count value Ct, and the actual stop position. Using the following equation (1) with the count value Cs as a parameter, the stop holding current I is updated, and in the subsequent S390, the updated stop holding current I is written to the register 83, and the processing ends. To do.

I = I−k · (Cs−Ct) (1)
As a result, the holding current I at the time of stop is feedback-controlled so that the stop position when the drive controller 76 drives the LF motor 54 at the time of image formation becomes the target stop position commanded from the CPU 100. The current value is optimal for controlling the image forming position on the recording paper P by the recording head 4 to the target position by stopping the LF motor 54 (and hence the conveying roller 50) at the target stop position during image formation. The current value is updated.

Next, FIG. 9 is a flowchart showing the operations of the correction amount setting unit 96 and the stop position correction unit 98 as stop position correction processing.
As shown in FIG. 9, in this stop position correction process, first, in S410, the conveyance count number Cf representing the target stop position of the LF motor 54 is read from the register 84, and in the subsequent S420, the current count of the position count unit 92 is read. Based on the position count value C, the conveyance count number Cf, and the stop braking distance α set in the register 82, the drive control unit 76 executes the motor drive control process of FIG. An energization control end position count value Cc (= C + Cf−α) is calculated.

  In subsequent S430, the phase variation phase Dc at the energization control end position is calculated using the following equation (2) using the energization control end position count value Cc and the cycle variation cycle length “B” as parameters.

Dc = mod (Cc, B) (2)
In the above equation, mod represents obtaining a remainder obtained by dividing the former value (here, Cc) in parentheses by the latter value (here, B).

  Next, in subsequent S440, using the following equation (3) whose parameters are the period fluctuation phase Dc and the period fluctuation period length “B” obtained in S430, the period fluctuation phase Dc at the energization control end position is A phase difference Cdd with respect to the period variation phase center value D is calculated.

Cdd = mod (D−Dc + B · 3/2, B) −B / 2 (3)
As a result, the phase difference Cdd is obtained as a value within a range of 1/2 period before and after the period fluctuation phase center value D as a reference (phase difference 0).

  In subsequent S450, the correction amount calculation function f (x) is read from the register 86, and the stop position correction amount F is calculated by substituting the phase difference Cdd obtained in S440 for the variable x of the correction amount calculation function. {F = f (Cdd)}.

  As shown in FIG. 10, the correction amount calculation function f (x) has a smaller stop phase correction as the phase difference Cdd is smaller and the cycle variation phase Dc at the energization control end position is closer to the cycle variation phase center value D. The amount F is set to be large.

  This is because, as shown in FIG. 14C, the closer to the torque fluctuation maximum position the energization control end position, the more the actual stop position deviates from the target stop position. In the present embodiment, the subsequent processing is performed. Thus, the LF motor 54 (and hence the conveying roller 50) is stopped at the target stop position designated by the CPU 100 by delaying the energization control end position by the positional deviation.

  That is, in the subsequent S460, when the drive control unit 76 executes the motor drive control process shown in FIG. 7 by adding the stop position correction amount F to the conveyance count number Cf that is the target stop position designated by the CPU 100. Then, the energization control end position is delayed by the stop position correction amount F, and then the drive controller 76 starts driving the LF motor 54 in S470.

  Therefore, according to the present embodiment, even if periodic torque fluctuations occur in the drive system of the transport roller 50 due to cogging of the LF motor 54, the recording paper P is not affected by the periodic torque fluctuations. It can be transported to the image forming position and stopped reliably.

In FIG. 9, the processing of S410 to S440 corresponds to the phase difference calculation means of the present invention, and the processing of S450 and S460 corresponds to the control position correction means of the present invention.
Next, FIG. 11 is a flowchart showing a periodic variation phase center value update process executed by the periodic variation phase center value update unit 94.

  This process is executed simultaneously when the position count unit 92 is reset by a command from the CPU 100. When the process is started, first, in S510, the current position count value C of the position count unit 92 is set. (Value before reset) is read and set as the operation value N.

Next, in S520, the period variation phase center value D is read from the register 87 and set as the operation value M.
Then, in the subsequent S530, using the following equation (4) with the calculation values N and M set in S510 and S520 and the period variation period length “B” as parameters, the position count unit 92 is reset. The period fluctuation phase center value D is calculated, and the calculation result is written in the register 87 in the subsequent S540, thereby updating the period fluctuation phase center value D.

D = mod {M-mod (N, B) + B, B} (4)
As a result, even if the position count unit 92 is reset and the position count value C is returned to the initial value (0), the period variation phase center value D in the register 87 is always the position count of the position count unit 92. The value corresponds to the value C, and the phase of the periodic fluctuation can always be monitored.

  As described above, in the multi-function device 1 of the present embodiment, when an image is formed on the recording paper P, the energization to the LF motor 54 is not interrupted every time the recording paper P is conveyed, but the recording paper P Even when the conveyance of the LF motor 54 is completed (that is, the drive control of the LF motor 54 is completed), the LF motor 54 is supplied with the holding current I at the time of stoppage. By constantly feeding back the control error of the stop position that occurs, it is constantly updated to the optimum value.

  Therefore, according to the multi-function device 1 of the present embodiment, the recording paper P is transported to the transport roller 50 (and thus the LF motor 54) due to friction generated in the paper feed roller 6b and the recording paper P feed system. Even if a torque in the direction opposite to the direction is applied, it is possible to prevent the recording paper P from being returned by causing the LF motor 54 to generate a torque that opposes the torque. It becomes possible to accurately and promptly transport to the image forming position.

  In the present embodiment, a period variation phase center value D representing a phase in which the periodical torque variation applied to the conveying roller 50, such as cogging torque of the LF motor 54, is stored in the register 87, and image formation is performed. Therefore, when the recording paper P is repeatedly conveyed for each scanning of the recording head 4, the phase variation phase Dc and the cycle variation phase center value D at the LF energization control end position at which the energization control to the LF motor 54 is terminated. And the energization control end position is corrected so as to be delayed as the phase difference Cdd is smaller.

  Therefore, according to the present embodiment, the recording paper P can be transported to a predetermined image forming position and stopped without being affected by periodic torque fluctuations generated in the drive system of the transport roller 50.

  In this embodiment, every time the multifunction device 1 is turned on and its control system is activated, the periodic fluctuation phase calculation device 110 actually drives the LF motor 54 to obtain the periodic fluctuation phase center value. In addition, during the operation of the multi-function device 1, the period variation phase center value update unit 94 causes the position variation unit 94 to always correspond to the count value of the position count unit 92. Since the periodic fluctuation phase center value D is updated every time is reset, the phase of the periodic fluctuation can be always accurately grasped from the count value of the position counting unit 92, and the control accuracy can be improved.

As mentioned above, although one Embodiment of this invention was described, this invention is not limited to the said embodiment, A various aspect can be taken in the range which does not deviate from the summary of this invention.
For example, in the above-described embodiment, the case where the present invention is applied to the drive control of the LF motor 54 in the multi-function device having the ink jet recording unit 7 is described. However, the present invention rotates the transport roller by the motor. Therefore, the present invention can be applied to any conveyance device that sequentially conveys a recording medium by a predetermined amount.

It is a perspective view of the multi-function device of an embodiment. It is a sectional side view of the multifunctional device of an embodiment. It is a partial top view of a multi-function device in a state where an image reading device is removed. FIG. 3 is a block diagram illustrating a configuration of a control system that performs recording sheet conveyance control in a multi-function device. It is a flowchart showing a period fluctuation | variation phase calculation process. It is explanatory drawing showing the rotational speed fluctuation | variation and reference signal which are used by a period fluctuation | variation phase calculation process. It is a flowchart showing the motor drive control process performed at the time of image formation. It is a flowchart showing a holding current setting process. It is a flowchart showing a stop position correction process. It is explanatory drawing showing the correction amount calculation function used by a stop position correction process. It is a flowchart showing a period fluctuation | variation phase center value update process. FIG. 10 is an explanatory diagram illustrating a problem caused by back tension of a recording sheet in a conventional image forming apparatus. FIG. 10 is an explanatory diagram for explaining a control error caused by a periodic torque fluctuation in a conveyance roller drive system in a conventional image forming apparatus. It is explanatory drawing explaining operation | movement of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Multifunctional device, 2 ... Housing, 3 ... Paper feed cassette, 4 ... Recording head, 5 ... Carriage, 6b ... Paper feed roller, 7 ... Recording part, 9 ... Feed path, 10 ... Paper discharge part, 11 ... Paper feeding unit, 12 ... Image reading device, 13 ... Document cover, 14 ... Operation panel unit, 16 ... Placing glass plate, 26 ... Platen, 28 ... Paper discharge roller, 50 ... Conveying roller, 51 ... Nip roller, 52 2nd transport path body, 53 ... 1st transport path body, 54 ... LF motor, 56 ... LF drive circuit, 58 ... Rotary encoder, 70 ... Paper transport control device, 72 ... Register group, 74 ... Motor rotation positioning part, 76 ... Drive control unit, 78 ... PWM generation unit, 80 to 88 ... Register, 91 ... Edge detection unit, 92 ... Position count unit, 93 ... Speed calculation unit, 94 ... Cycle variation phase center value update unit, 96 ... Correction amount Setting unit, 98 ... stop position correction , 110 ... period fluctuation phase calculating unit, 120 ... holding current setting device.

Claims (4)

A conveying unit that conveys a recording medium that is an object of image formation to an image forming position, an image forming unit that forms an image on a recording medium conveyed to the image forming position by the conveying unit, the conveying unit, and the An image forming apparatus comprising: an image forming control unit that forms an image on the entire recording medium by alternately operating the image forming unit; and a transport device used as the transport unit,
Is driven to rotate by the motor, a conveying roller for conveying the recording medium in a predetermined direction,
A rotation amount detecting means for detecting a rotation amount from a reference rotation position of the conveying roller;
When a conveyance command from the image formation control unit to the target stop position of the recording medium is input, the conveyance position of the recording medium is monitored based on the rotation amount detected by the rotation amount detection unit. by performing energization control on the motor, the rotating driving the conveying roller to the recording medium reaches the control end position before than the target stop position, when the recording medium reaches the control end position , Conveying control means for ending energization control to the motor and stopping the conveying roller at the target stop position ;
From the end of the energization control to the motor until the conveyance control unit starts energization control next, a holding current energization unit that supplies a holding current for stopping the conveyance roller to the motor;
When the holding current energizing unit supplies a holding current to the motor, the stop position of the recording medium is detected from the rotation amount detected by the rotation amount detecting unit, and the stop position and the target stop position are detected. Based on the deviation of the holding current update means for setting the holding current that the holding current energization means will flow to the motor next time, so that the deviation is reduced,
A conveying apparatus comprising: The period of the periodic torque fluctuation generated in the driving system of the conveying roller including the motor is stored in association with the rotation amount of the conveying roller, and the phase of the maximum point of the periodic torque fluctuation is the reference of the conveying roller. Periodic fluctuation characteristic storage means stored as a rotation amount from the rotation position;
When the conveyance command is input from the image formation control unit, based on the period and phase of the periodic torque variation stored in the periodic variation characteristic storage unit and the rotation amount detected by the rotation amount detection unit. A phase difference calculating means for obtaining a phase of a periodic torque fluctuation at a control end position set based on the conveyance command and calculating a phase difference between this phase and a phase at a maximum point of the periodic torque fluctuation;
Based on the phase difference calculated by the phase difference calculating means, a control position correcting means for correcting the control end position so that the end of the energization control is delayed as the phase difference is smaller;
The transport apparatus according to claim 1, further comprising:   When the transport device is started, the transport roller is rotationally driven via the motor to detect the rotational position of the transport roller at which the periodic torque variation is maximum, and the detected maximum torque variation rotational position and A period fluctuation phase detecting means for obtaining a phase of a maximum torque fluctuation rotation position with a current rotation position of the conveying roller as a reference rotation position from the period of the periodic torque fluctuation and storing the phase in the period fluctuation characteristic storage means. The transport apparatus according to claim 2, further comprising: A conveying unit that conveys a recording medium that is an object of image formation to an image forming position, an image forming unit that forms an image on a recording medium conveyed to the image forming position by the conveying unit, the conveying unit, and the An image forming apparatus comprising: image forming control means for forming an image on the entire recording medium by operating image forming means alternately ;
An image forming apparatus comprising the transport device according to claim 1 as the transport unit.