Patent Application
20060022401
The present invention relates to: a control device that controls a driving device to move an object for a predetermined distance; a conveyance control device that controls a conveyance device to convey an object along a conveyance path; a conveyance system with the conveyance control device; and an image forming system that forms an image at a conveyance destination on an object conveyed by the conveyance system.
Conventionally, an inkjet image forming system is known wherein an image is formed on an image forming medium, such as paper. In this type of image forming system, ink is jetted out from a recording head that serves as an image forming device, and an image is formed on an image forming medium based upon image data. Consequently, the above-described system is provided with a mechanism (conveyance device) for conveying an image forming medium, e.g. paper, to an image formation point wherein image formation is conducted by the image forming device, and a conveyance control device.
A conventional conveyance device that conveys an object, such as paper, is provided with one pair of conveyance rollers that are disposed along a conveyance path and respectively rotate on rotational axis perpendicular to a conveyance direction of an object to be conveyed. In this type of conveyance device, an object is held by the above-described pair of conveyance rollers that are facing to each other, driving force (frictional force) in a rotational direction of the conveyance rollers is applied thereon, and conveyed in the rotational direction by the conveyance rollers being rotated while the object is held therebetween.
As for a control device, a control device having two functions: feedback control function and feedforward control function, is conventionally known.
The control device according to one aspect of the present invention is connected to a driving device that is operated according to a control signal inputted therein and moves a driving object by applying a driving force corresponding to the operation amount of the driving device. By controlling the driving device, the control device moves the driving object for a predetermined distance. The control device includes: a detector that detects travel distance of the driving object; a target setter that sets the target travel distance of the driving object in every predetermined period when the driving object is moved; an operation amount calculator that calculates an operation amount of the driving device that is necessary to attain the target travel distance set by the target setter based on a detection result of the detector; a controller for the driving device to move the driving object for a predetermined distance by sequentially inputting a control signal into the driving device corresponding to the operation amount calculated by the operation amount calculator; and an operation amount determiner that determines whether or not the operation amount calculated by the operation amount calculator is equal to or more than a predetermined upper limit. The target setter sets the target travel distance according to a first rule when the operation amount is determined by the operation amount determiner to be less than the upper limit. When the operation amount is determined to be equal to or more than the upper limit by the operation amount determiner, the target setter sets the travel distance according to a second rule.
The control device according to one aspect of the present invention is capable of conducting the most suitable control even when the operation amount becomes equal to or more than the upper limit,
The invention will now be described below, by way of example, with reference to the accompanying drawings.
Referring to
The feed cassette 3 is constituted to be able to store a plurality of paper P, for example, in A4 or legal sizes. The narrow side of each paper P is placed in parallel to a direction (corresponding to a main scanning direction and Y-axis) orthogonal to a paper conveyance direction (corresponding to a sub-scanning direction and the X-axis).
On the front end of the feed cassette 3, a support member 3a, movable in the X-axis direction, is attached to support the rear end portion of paper P having a long length (such as in legal-size).
On the rear side of the feed cassette 3, a bank 5 is provided to separate the sheets of paper P. On the bottom plate of a box-shaped metal mainframe 7 of the MFD 1, the rear end of a feed arm 9a of a feed unit 9 is attached so as to be rotatable in the vertical direction. Paper P stored in the feed cassette 3 in layers are fed separately in a sheet-by-sheet manner by a feed roller 9b provided at the bottom end of the feed arm 9a and the bank 5. A sheet of paper P, separated as above, is conveyed to an image forming unit 13 disposed above (at a higher position) the feed cassette 3 via a U-turn path 11 constituting a conveyance path in a U shape.
The image forming unit 13 comprises a carriage 17 which carries an inkjet recording head 15 thereto, and can reciprocate in the main scanning direction. The carriage 17 is controlled by CPU 51 that is to be described later, and moves the recording head 15 in the main scanning direction. The recording head 15 ejects ink while scanning and forms an image on stationary paper P, which is placed under the recording head 16. During image formation, paper P is supported from below by a platen 19 constituting a conveyance path. That is, the recording head 15 is located over the platen 19. Image formation on paper P by the recording head 15 is conducted over the platen 19.
Paper P is discharged to a discharge unit 21 after image formation is conducted thereon by the image forming unit 13. The discharge unit 21 is formed on the upper side of the feed cassette 3. A discharge outlet communicating with the discharge unit 21 has an opening that forms one portion of the opening 2a on the front surface of the housing 2.
On the housing 2, an image reading device 23 is disposed to be used for reading an original image. A bottom wall 23a of this image reading device 23 is disposed overlapping an upper cover 25 almost without any interspace therebetween. The image reading device 23 is turnable around one end of the housing 2 via a pivot (not shown) so as to be opened and closed. The rear end of a cover 27 covering the upper surface of the image reading device 23 is attached to the rear end of the image reading device 23 so as to be vertically turnable around the pivot 23b.
In front of the image reading device 23, there is an operation panel unit 29 comprising various operation buttons and a LCD. On the upper surface of the image reading device 23, a glass plate 31 is provided for an original to be placed thereon when the cover 27 is opened upward. Under the glass plate 31, an image scanner (CIS: Contact Image Sensor) 33 for reading an original is provided reciprocatably along a guide shaft 35 extending in the main scanning direction (the Y-axis direction).
In the front portion of the housing 2 covered by the imaged reading device 23, an ink storage unit (not shown) is provided to be opened upward. In this ink storage unit, ink cartridges respectively storing one of four colors (black, cyan, magenta and yellow) for full-color printing are removably installed from above. In the MFD 1 of the present embodiment, ink stored in the ink cartridges is supplied to the recording head 15 through a plurality of ink supply tubes 37 connecting respective ink cartridges and the recording head 15.
The following describes a paper conveyance system of the MFD 1.
As shown in
The upstream portion of the conveyance path constituted with the bank 5 and the U-turn path 11 limits the movement of paper P fed by the feed roller 9b, and guides the paper P to the contact point of the conveyance roller 41 and the pinch roller 42. Under the downstream portion (in regard to the conveyance direction of paper P) of the U-turn path 11, there is an assistant unit 11a provided to guide paper P to the contact point of the conveyance roller 41 and the pinch roller 42.
Accordingly, paper P fed from the feed cassette 3 is guided to the contact point between the conveyance roller 41 and the pinch roller 42 by the bank 5, U-turn path 11 and the assistant unit 11a. When paper P is guided to the contact point and the conveyance roller 41 makes a regular rotation in regard to the conveyance direction (counterclockwise rotation in
The platen 19 constitutes the downstream portion of the conveyance path connecting the conveyance roller 41 and the discharge roller 43, and is disposed between the conveyance roller 41 and the discharge roller 43 along a line connecting these rollers. The platen 19 guides paper P sent from the conveyance roller 41 to an area wherein an image is formed by the recording head 15, and guides paper P, on which an image is formed, by the recording head 15 to a contact point between the discharge roller 43 and the pinch roller 44. Hereinafter, the end point in the downstream side of an image formation area RG, wherein image formation is conducted with various colors of ink, is referred to as an image formation point GP, and a point in the vicinity of the end point in the upstream side of the image formation area RG is referred to as a conveyance start point GS.
Paper P is conveyed toward the discharge roller 43 along the platen 19. When the leading end (the edge in the downstream side) of paper P reaches the contact point between the discharge roller 43 and the pinch roller 44, corresponding to the rotation of the discharge roller 43, paper P is drawn between the discharge roller 43 and the pinch roller 44 and held by these two rollers. Subsequently, corresponding to the further rotation of the discharge roller 43, paper P is conveyed in the conveyance direction toward the discharge unit 21 for a distance corresponding to the amount of rotation of the discharge roller 43 (the same amount as in the rotation of the conveyance roller 41). The above-described conveyance roller 41, discharge roller 43, pinch rollers 42 and 44, are all rotators respectively having a rotational axis in a direction perpendicular to the conveyance direction (main scanning direction). Paper P receives a driving force generated corresponding to the rotations of the conveyance roller 41 and the discharge roller 43 at the respective contact points with these two rollers. Paper P is conveyed in the conveyance direction along the conveyance path (i.e. from the upstream to downstream of the conveyance path) as described above.
The above-mentioned motor 45 is constituted with a DC motor and is driven by the driving circuit 47. The motor 45 provides rotational force thereof to the conveyance roller 41 via the transmission mechanism BL1 provided between the motor 45 and the conveyance roller 41. Consequently, the conveyance roller 41 is rotated. The rotational force transmitted to the conveyance roller 41 is furthermore transmitted to the discharge roller 43 via the transmission mechanism BL2 provided between the conveyance roller 41 and the discharge roller 43. Thus, the discharge roller 43 is rotated together with the conveyance roller 41 in the same direction. Still furthermore, the rotational force generated from the motor 45 is transmitted to the feed roller 9b via a transmission mechanism BL3 and the feed roller 9b is rotated thereby.
However, the feed roller 9b rotates in the conveyance direction of paper P only during a feeding process of feeding paper P toward the conveyance roller 41. During an image formation process, the feed roller 9b does not receive a rotational force from the motor 45 and therefore is idle. In other words, the transmission mechanism BL3 connecting the feed roller 9b and the motor 45 only transmits a rotational force to the feed roller 9b during the feeding process, but disengages gears installed therein and does not transmit the rotational force to the feed roller 9b during the image formation process.
When the feed roller 9b is rotated in the conveyance direction, the conveyance roller 41 and the discharge roller 43 are rotated in the opposite direction to the conveyance direction. That is, the transmission mechanism BL3 connecting the feed roller 9b and the motor 45 does not transmit the rotational force to the feed roller 9b when the motor 45 is regularly rotated. When the motor 45 is reversely rotated, the transmission mechanism BL3 converts the rotational force into a rotational force in the regular direction by the installed gears, and transmits the converted rotational force to the feed roller 9b.
It should be noted that the feed process mentioned herein indicates a process to rotate the feed roller 9b while being pressed against paper P, and to convey the leading end of paper P to a resist position that is the contact point with the conveyance roller 41 and the pinch roller 42. The image formation process herein indicates a process comprising: an initial conveyance process to convey the leading end of a drawing area of paper P placed at the resist position to the image formation point GP; and a subsequent main process to sequentially convey paper P so as to move a reference point, located at the conveyance start point GS, to the image formation point GP in every interval corresponding to the width of the image formation area RG in the conveyance direction, and to form an image on paper P by ejecting ink from the recording head 15 in conjunction with the conveyance of paper P. It is to be noted that the reference point of an object simply indicates a point on an object located at a position corresponding to the conveyance start point, but this does not mean that an object to be conveyed has a structure formed to be indicating this reference point.
The above-described conveyance unit 40 is provided with a rotary encoder 49 that outputs pulse signals every time the conveyance roller 41 rotates through a predetermined amount. Output signals from the rotary encoder 49 are inputted into the ASIC 53 of the conveyance control unit 50. In the present embodiment, the conveyance roller 41 and the discharge roller 43 are rotated by the motor 45, and the rotation of the motor 45 is also transmitted to the feed roller 9b. Consequently, in the MFD 1, it is possible to detect the rotational amount of the motor 45, conveyance roller 41, discharge roller 43, and the feed roller 9b, and to detect the travel distance (conveyance distance) of paper P conveyed by each roller (41, 43 and 9b) by detecting and counting the pulse signals from the encoder 49.
The conveyance control unit 50 connected to the driving circuit 47 of the conveyance unit 40 provides the driving circuit 47 with a command for the motor 45, and controls the rotation of the motor 45 constituting the conveyance unit 40. Additionally, the conveyance control unit 50 indirectly controls paper conveyance with the feed roller 9b, conveyance roller 41 and discharge roller 43. The conveyance control unit 50 mainly comprises the CPU 51 that controls the overall operation of the MFD 1, and the ASIC (Application Specific Integrated Circuit) 53 that controls the rotational speed and rotational direction of the motor 45.
As described above, the paper conveyance during the image formation process is attained by paper P being sequentially conveyed for a predetermined distance in the sub-scanning direction (paper conveyance direction). Specifically, recording for one path of an image is conducted by the reciprocating recording head 15 in the main scanning direction. For further recording of subsequent paths, paper P is conveyed in the sub-scanning direction for a predetermined distance (conveyance distance Ds to convey paper P for one path that is the distance corresponding to the width of the image formation area RG in the conveyance direction shown in
In the following, first, the structure of the driving circuit 47, which receives various commands from a drive signal generator 55 provided in the ASIC 53 of the conveyance control unit 50, is described and then the structure of the conveyance control unit 50 (especially the ASIC 53) is described based on
The structure of the driving circuit 47 is as shown in
The drive signals generator 55 provided in the ASIC 53 provides the driving circuit 47 constituted as above with a drive command and a direction command, based on a preset value in the start-up setting register RS1. The drive signal generator 55 generates a target current command (control signal) based on an operation amount u (the target current value in the present embodiment) generated in the control unit 60 within the ASIC 53, and provides the command for the driving circuit 47.
Respective parts in the ASIC 53, such as the above-described drive signal generator 55, an encoder edge detection unit 56, a position counter 57, a cycle counter 58, a signal process unit 59, and the control unit 60, operate based on a clock signal with a cycle that is sufficiently shorter than the cycle of a pulse signal from the encoder 49 generated by a clock generator CLK of the ASIC 53.
The encoder edge detection unit 56 obtains pulse signals from the encoder 49 and detects edges of the pulse signals (for example, either or both of a leading edge or/and a trailing edge). The position counter 57 detects the rotation amount of the conveyance roller 41 as a count value y by counting the edges detected by the encoder edge detection unit 56.
The cycle counter 58 counts time (cycle length) between edges detected by the encoder edge detection unit 56. The signal process unit 59 conducts error handling and outputs interrupt signals to the CPU 51. The control unit 60 calculates an operation amount u to be inputted into the drive signal generator 55 based on various values of operation mode setting registers RS in the ASIC 53 and a count value y of the position counter 57, and conducts feedback control of the motor 45 for paper conveyance.
The position counter 57 provided in the ASIC 53 is constituted to clear the count value y every time paper conveyance (the conveyance process) to convey paper P for one path is initiated. Consequently, the rotation amount of the conveyance roller 41 during conveyance control for one path can be obtained from the count value y in the position counter 57. The rotation amount of the conveyance roller 41 during the conveyance control for one path generally corresponds to the travel distance of paper P during the conveyance control for one path. Therefore, the count value y can be interpreted as a value indicating the conveyance distance (position) of a point of reference in paper P from the conveyance start point GS. The reference point is initially located at the conveyance start point GS when the conveyance control for one path is started.
The target conveyance speed setting unit 607 constituting the feedback calculation process unit 60a provides the target position calculation unit 601 and the feedforward control unit 603 with a target conveyance speed v(t) for conveyance control for one path based on a first target conveyance speed v1 and a second target conveyance speed v2 (cf.
The target position calculation unit 601 sets the target position x(t) based on the above-described target conveyance speed v(t) every time calculation timing comes. The calculation timing is determined from a value of a calculation cycle Ts stored in a calculation timing setting register RS10. The target position x(t) indicates target rotation amount of the conveyance roller 41 and the discharge roller 43, and generally corresponds to the target conveyance position of paper P.
In case the conveyance unit 40 operates according to a design value based on the target conveyance speed v(t) set in the target conveyance speed setting unit 607, at every calculation timing, the feedforward control unit 603 successively calculates an operation amount u1(t) of the motor 45 in order to rotate the conveyance roller 41 and the discharge roller 43 so as to convey the paper P to the target position x(t), until the paper P is conveyed for a conveyance distance Ds and the conveyance (motor driving) is finished.
For example, when the relationship between the target conveyance speed v(t), and the target position x(t) calculated in the target position calculation unit 601, is expressed with a transfer function F1(s), and the relationship between the operation amount u1(t) and the rotation amount x(t), in case the conveyance unit 40 operates according to a design value, is expressed with a transfer function P(s), the operation amount u1(t) is obtained in the feedforward control unit 603 with a transfer function F2(s)=F1(s)/P(s) using the target conveyance speed v(t).
In the ASIC 53, a target locus setting register RS6 is provided in order to store a value of parameter a, constituting an arithmetic expression for extracting the target position x(t) from the target conveyance speed v(t). When the feedback calculation process unit 60a is operated, the value in the target locus setting register RS6 is extracted, and according to this value, transmission characteristics in the target position calculation unit 601 are determined.
Moreover, in the ASIC 53, a feedforward control setting register RS7 is provided in order to store a value of parameter B constituting an arithmetic expression for extracting the operation amount u1(t) from the target conveyance speed v(t). When the feedback calculation process unit 60a is operated, the value in the feedforward control setting register RS7 is extracted, and according to this value and the value in the target locus setting register RS6, transmission characteristics in the feedforward control unit 603 are determined.
The above-described first adder ADD1 obtains an error Θ between the target position x(t) calculated in the above-described target position calculation unit 601 and the count value y in the position counter 57 from Θ=x·y, and provides this value Θ for the feedback control unit 605. The feedback control unit 605 calculates the correction amount u2(t) of an operation amount based on the error Θ calculated in the first adder ADD1, and provides the correction amount u2(t) for the second adder ADD2. The transmission characteristics are determined, in the same way as in the above-described target position calculation unit 601 and the feedforward control unit 603, by a value in a feedback control setting register RSS that stores the value of parameter γ constituting a arithmetic expression for extracting the operation amount u2(t) from the error Θ provided by the ASIC 53.
The second adder ADD2 adds the operation amount u1(t) outputted from the feed forward control unit 603 and the operation amount u2(t) outputted from the feedback control unit 605. Subsequently, the second adder ADD2 generates the operation amount u(t) that is necessary for the conveyance roller 41 and the discharge roller 43 to move paper P to the target position x(t), and provides the operation amount u(t) for the drive signal generator 55. The operation amount u(t) mentioned herein represents a target current value that should be applied to the motor 45.
Conveyance control to convey paper P for one path is attained as described above. That is, conveyance for one path is controlled: first, by the operation amount u calculated as above being inputted into the drive signal generator 55 at every calculation timing; second, by a target current command being regularly inputted into the driving circuit 47 based on this operation amount u; third, by the conveyance unit 40 being operated and the conveyance roller 41 and the discharge roller 43 being rotated for predetermined amount; and then, paper P is conveyed for one path. Correspondingly, a reference point of paper P located at the conveyance start point GS is conveyed to the image formation point GP.
The following describes various responses produced when the motor 45 is driven and the conveyance roller 41 is rotated by the feedback calculation process unit 60a.
As shown in
In the driving circuit 47, there is a limit to an attainable current value. Therefore, even when the operation amount u exceeding a predetermined upper limit is inputted from the feedback calculation process unit 60a, the target current value does not exceed the upper limit. In other words, when the operation amount u exceeds the upper limit, the current value attained in the driving circuit 47 is saturated at the upper limit as shown in
Accordingly, when a load on paper P is large and the operation amount U exceeds the upper limit, continuing the operation of the feedback calculation process unit 60a results in the error Θ between the target position x(t), calculated by the target position calculation unit 601, and the count value y in the position counter 57 being enlarged to make the operation amount u2(t) larger. This results in a status wherein the operation amount u exceeding the upper limit (i.e. status wherein current value is saturated) is continued.
In this kind of case, since the rotational speed of the conveyance roller 41 and the discharge roller 43 and the conveyance speed of paper P in the vicinity of the image formation point GP is too high, despite the motor 45 being short-circuited to finish the conveyance operation (despite the stopping of the driving of the conveyance roller 41 and the discharge roller 43), the amount of rotation of the conveyance roller 41 and the discharge roller 43 through inertia is large. Hence, the conveyance roller 41 and the discharge roller 43 are rotated more than necessary and then stopped. Moreover, paper P is moved to a large extent by inertia and stopped at a position more toward the downstream than the image formation point GP.
That is to say, in a conveyance system of the MFD 1, when the load applied to paper P (rotational load on the motor 45) is large, if the status wherein the operation amount u exceeds the upper limit is not promptly resolved, then the paper P cannot be accurately conveyed to the image formation point GP.
Additionally, there are some cases wherein the operation amount u naturally falls below the upper limit when a load on a paper P is decreased. In this case, at the moment when the load on the paper P decreases, the driving force works more than necessary on the conveyance roller 41, the discharge roller 43 and paper P, and rotates the conveyance roller 41 and the discharge roller 43 so as to convey the paper P beyond the target position x(t). Consequently, as shown in
In order to solve problems like these, the control unit 60 of the MFD 1 is provided with a switching process unit 61 that switches control methods based on a value in an upper limit setting register RS11 that stores the value for the upper limit of operation amount u, and based on a value of the operation amount u outputted from the second adder ADD2.
As shown in
Accordingly, when conveyance control is initiated, the feedback calculation process unit 60a calculates the operation amount u1(t) and the target position x(t) based on the target conveyance speed v(t), and calculates the operation amount u based on the result of the above-described calculation and the count value y in the position counter 57.
In case the load is large and the operation amount u reaches the upper limit and goes beyond the limit as time passes, the operation of the target position calculation unit 601, the feedforward control unit 603, and the target conveyance speed setting unit 607, are switched off.
When a calculation timing comes while these units are in an off-status, the first adder ADD1 of the feedback calculation process unit 60a obtains the error Θ between a value x(Tb) calculated and maintained by the target position calculation unit 601 at a calculation timing immediately before the switch-off, and the current count value y in the position counter 57 (i.e. Θ=x(Tb)·y). The feedback control unit 605 calculates the operation amount u2(t) based on this error E). The second adder ADD2 adds the value u1(Tb) calculated and maintained by the feedforward control unit 603 at the calculation timing immediately before the switch-off and the above-described operation amount u2(t) calculated by the feedback control unit 605, generates the operation amount u(t)=u1(Tb)+u2(t), and provides the operation amount u2(t) for the drive signal generator 55.
In conducting control with this status, as the error becomes smaller and the operation amount u(t) falls below the upper limit, at a calculation timing subsequent to the calculation timing wherein the operation amount u(t) becomes below the upper limit (time t=Tc), the operation of the target position calculation unit 601, the feedforward control unit 603, and the target conveyance speed setting unit 607, are once again switched on. In the feedback calculation process unit 60a, the operation amount u1(t-(Tc-Tb)) and the target position x(t-(Tc-Tb)) based on the target conveyance speed v(t-(Tc-Tb)) are calculated. Based on the result of this calculation and the count value y in the position counter 57, the operation amount u(t) is calculated. In other words, the target position calculation unit 601 and the feedforward control unit 603 calculate the target position x and the operation amount u1 after the delay for the length of time in the off-status of theses units, The second adder ADD2 calculates the operation amount u with these values, and outputs the operation amount u.
The above has described the operation of the ASIC 53 in conveyance control so as to convey paper P for one path. In the present MFD 1, main control, such as feed process, image formation process, and discharge process, is conducted in the CPU 51.
When the main control process is initiated, in S100, register setting in connection with feed operation is conducted on the ASIC 53 by the CPU 51. Consequently, in the ASIC 53, processes in connection with feed operation are conducted, and in the conveyance unit 40, the paper P is conveyed to the resist position (feed process). When this feed process is finished in S200, the image formation process is subsequently conducted.
When the image formation process is initiated, in S210 the initial conveyance process is conducted by the CPU 51 and based on control by the ASIC 53, the start point of the drawing area in paper P is conveyed to the image formation point GP. When this process is finished, in S220, the image formation process for one path of an image is conducted by the CPU 51. The image for one path is formed on the paper P by the carriage 17 moving in the main scanning direction, and ink being ejected from the recording head 15.
When this process is over, in S230, a determination is made by the CPU 51 as to whether or not image formation is finished up to the end point of paper P. When the CPU 51 determines that image formation is not yet finished (S230:NO), the process proceeds to S240 and the conveyance process is conducted by the CPU 51 (S240). A recording area for next path is conveyed to the image formation area RG (i.e. the reference point of paper P located at the conveyance start point GS is conveyed to the image formation point GP). Subsequently, the process goes back to S220 and the image formation process for another path is conducted.
On the other hand, when it is determined that image formation is finished up to the end point of the paper P (S230:YES), the process proceeds to S300 wherein the discharge process is conducted by the CPU 51 and, based on control by the ASIC 53, the paper P is discharged to the discharge unit 21.
Upon receiving the allowance for stop interrupt, the ASIC 53 detects, using the signal process unit 59, every status wherein paper P reaches the target stop position r set in the target stop position setting register RS 9 (i.e. every time the count value y in the position counter 67 becomes equal to or more than the value for the target stop position r), and provides a stop interrupt signal for the CPU 51. Even when the count value y in the position counter 57 does not go beyond the count value for the target stop position r, if the count value y in the position counter 57 does not change for certain period of time the ASIC 53 also provides a stop interrupt signal for the CPU 51. The target stop position r set in the target stop position setting register RS9 represents a point wherein the driving of the motor 45 is stopped.
When the process in S243 is finished, in S245, start-up setting on the ASIC 53 is conducted by the CPU 51. That is, the setting in the start-up setting register RS1 by the CPU 51 triggers the initiation of calculations for the operation amount u in the ASIC 53. The driving of the motor 45 and the corresponding paper conveyance for one path conducted by the rotation of the conveyance roller 41 and the discharge roller 43 are subsequently initiated. The motor control of the motor 45, initiated after the start-up setting (conveyance control for one path: c.f.
When a stop interrupt signal is inputted from the ASIC 53, the CPU 51 clears the stop interrupt flag. Additionally, a masking process against the stop interrupt is conducted so as to block further stop interrupt signals. Subsequent to receipt of the interrupt signal, the process proceeds to S220 and the image formation process for one path is conducted as described above.
When start-up setting is done and conveyance control for one path is initiated, in S510, the ASIC 53 initiates driving control for the motor 45. In this step, calculation for the operation amount u by the feedback calculation process unit 60a and motor control on the motor 45 based thereon are repeated until conveyance termination timing T2 to convey paper P for one path comes and the motor 45 is short-circuited.
Subsequently, when paper P reaches the target stop position r that is before the conveyance destination (image formation point GP) for predetermined distance, the conveyance termination timing T2 cones (S520:YES). The motor 45 is short-circuited, the rotation thereof is braked, and the rotation of the motor 45 is stopped. Consequently, paper P is moved for the conveyance distance Ds for one path, and the reference point of paper P, located at the conveyance start point GS previous to conveyance control, reaches the image formation point GP.
When the rotation of the conveyance roller 41 and the discharge roller 43 as well as the rotation of the motor 45 is stopped, in S530, the ASIC 53 provides a stop interrupt signal for the CPU 51. Subsequently, the ASIC 53 terminates conveyance control to convey paper P for one path.
In S510, the target conveyance speed v(t) is determined based on a first target conveyance speed v1 maintained in a first target speed setting register RS3 and a second target conveyance speed v2 maintained in a second target speed setting register RS4. In S512, the target position x(t) corresponding the obtained target conveyance speed v(t) is set by the target position calculation unit 601. In S513, the operation amount u1(t) corresponding to the above-described target conveyance speed v(t) is calculated by the feedfoward control unit 603.
In S514, the first adder ADD1 calculates the error Θ based on the target position x(t) calculated by the target position calculation unit 601 in S512 and the count value y in the position counter 57. In S516, the feedback control unit 605 calculates the operation amount u2(t) based on the error Θ. In S517, the second adder ADD2 calculates the operation amount u(t) based on the operation amount u1(t) calculated in S513 and the operation amount u2(t) calculated in S516. The obtained operation amount u(t) is outputted to the drive signal generator 55. Consequently, the conveyance roller 41 and the discharge roller 43 are rotated at a rotational speed corresponding to the operation amount u. Paper P is conveyed at a speed corresponding to the rotational speed.
However, the above-described processes in S512 to S517 are conducted only when the comparator 611 outputs an on-command, that is when the operation amount u(t) from a previous output is less than the upper limit and only at the first calculation timing after conveyance control is initiated.
If the operation amount u is equal to or more than the upper limit (S511:YES), the comparator 611 outputs an off-command. Thus, the processes in S512 to 514 are not conducted at next calculation timing (i.e. the setting of the operation amount u1, the setting of the target position x, and the calculation of the error Θ, which are usually conducted as routine, are not conducted). In S515, the position obtained from the previous calculation in S512 is used as the target position x. Based on the value of this target position x and the current count value y in the position counter 57, the error Θ is obtained. Subsequently, in S516, the operation amount u2 is obtained in the feedback control unit 605 based on the error Θ. In S517, the operation amount u for this time is determined based on the operation amount u2 obtained in S516 and the latest operation amount u1 calculated in S513. The operation amount u is inputted into the drive signal generator 55.
In the present embodiment, speed in the positive direction is set for the target conveyance speed v(t), but speed is not set in the negative direction. The target position x(t) is set in the target position calculation unit 601 according to the inclination corresponding to the target conveyance speed v(t) (the variation of the target conveyance speed v(t)). Thus, the target position x(t) is set more toward the downstream than the previously set target position. In case a previous operation amount u is equal to or more than the upper limit (S511:YES), the target position x(t) is set more toward the upstream in the conveyance direction than a usual case (wherein the operation amount u is less than the upper limit).
Accordingly, in the MFD 1 of the present embodiment, it is possible to resolve the status wherein the drive circuit 47 is more promptly operated with the maximum current, as compared to a case wherein an on-off control is not conducted in the switching process unit 61. Consequently, it is possible to inhibit unnecessary driving force from being applied to the conveyance roller 41, discharge roller 43 and paper P, and to conduct highly accurate conveyance (rotation) control.
According to the present embodiment, paper P is conveyed for a predetermined conveyance distance Ds, and a reference point thereof can be conveyed to a target position (image formation point GP). Hence, in a series of image formation attained on a paper P by paper conveyance, it is possible to conduct image formation at predetermined positions with high levels of accuracy, and therefore inhibit the deterioration in image quality that could be caused in the form of lines of print gaps or overlapping of ink.
The above has described an example to resolve the status wherein the operation amount u exceeds the upper limit by temporarily stopping calculations in the target position calculation unit 601 and the feedforward control unit 603. It goes without saying that the above-described method can be applied to a case wherein the operation amount u is saturated at the upper limit. The status wherein the operation amount u exceeds the upper limit may be also resolved by decreasing the target conveyance speed.
In addition to the constituents of the ASIC 53, the ASIC 70 shown in
Moreover, the ASIC 70 is provided with a control unit 71 having a feedback calculation process unit 71a as shown in
As shown in
This target conveyance speed setting unit 711 comprises a speed output unit 712, a speed switching unit 713, a third target speed selector 714, a saturation counter 715, and a comparator 716.
The speed output unit 712 outputs a value of speed outputted from the speed switching unit 713 as the target conveyance speed v(t) during the period between conveyance initiation and time T1 that is when predetermined switching time comes, and outputs the second target conveyance speed v2 stored in the second target speed setting register RS4 as the target conveyance speed v(t) during the period after time T1 passes until the conveyance termination timing T2 comes. The switching timing comes when the count value y in the position counter 57 becomes equal to or more than a predetermined value. The target conveyance speed v(t), outputted from the speed output unit 712, is inputted into the target position calculation unit 601 and the feedforward control unit 603 constituted as described above.
the speed switching unit 713 is constituted to provide either of the speed values between the first target conveyance speed v1 stored in the first target speed setting register RS3 and the speed value outputted from the third target speed selector 714 for the speed output unit 712. Specifically, when a command to select the first target conveyance speed v1 is inputted from the comparator 716, the speed switching unit 713 provides the first target conveyance speed v1 for the speed output unit 712. When a command to select the third target conveyance speed is inputted from the comparator 716, the speed switching unit 713 provides the speed value outputted from the third target speed selector 714 for the speed output unit 712.
The comparator 716 compares the upper limit maintained in the upper limit setting register RS11 and the operation amount u outputted from the second adder ADD2 every time a calculation timing comes. When the operation amount u is less than the upper limit, the comparator 716 provides a command to select the first target conveyance speed v1 for the speed switching unit 713. When the operation amount u is equal to or more than the upper limit, the comparator 716 provides a command to select the third target conveyance speed for the speed switching unit 713. At the time to initiate conveyance control, the comparator 716 inputs a command to select the first target conveyance speed v1.
When the operation amount u is equal to or more than the upper limit, the comparator 716 increments (counts up) a count value CN by one in the saturation counter 715 at every calculation timing. When the operation amount u is less than the upper limit, the comparator 716 clears the counter value of the saturation counter 715 and sets the count value CN to “0”. In other words, in the saturation counter 715, the number of determination, which is made when the comparator 716 determines the operation amount u is equal to or more than the upper limit, is stored.
The third target speed selector 714 selects one of the values amongst v31, v32, and v33, stored in the third target speed setting register RS5 corresponding to the count value CN in the saturation counter 715, and provides the selected value for the speed switching unit 713.
Specifically, when the count value CN satisfies the relational expression 0≦CN<m (m: natural number), the third target speed selector 714 provides the speed value v31 for the speed switching unit 713. When the count value CN satisfies the relational expression m≦CN<n (n: natural number that satisfies n>m), the third target speed selector 714 provides the speed value v32 for the speed switching unit 713. When the count value CN satisfies the relational expression n≦CN, the third target speed selector 714 provides the speed value v33 for the speed switching unit 713. As described above, since the values v31, v32, and v33, satisfy the relational expression v31>v32>v33, a lower speed value is selected and inputted into the speed switching unit 713 as the count value CN becomes larger (i.e. as the period wherein the operation amount u is equal to or more than the upper limit becomes longer).
In the feedback calculation unit 71a, the following process takes place. When a calculation timing comes, if a switching timing for switching into the second target conveyance speed v2 has already come (S610:YES), the process proceeds to S615 and the second target conveyance speed v2 stored in the second target speed setting register RS4 is outputted from the speed output unit 712 as the target conveyance speed v(t).
On the other hand, if the switching timing for switching into the second target conveyance speed v2 has not yet come (S610:NO), the process proceeds to S620, and the comparator 716 determines whether or not the operation amount u is equal to or more than the upper limit. If the operation amount u is less than the upper limit (S620:NO), in S630 the count value in the saturation counter 715 is cleared. In this case, the process proceeds to S640 and a command to select the first target conveyance speed v1, is inputted into the speed switching unit 713 from the comparator 716. Thus, the first target conveyance speed v1 stored in the first target speed setting register RS3, is outputted from the speed output unit 712 as the target conveyance speed v(t).
Alternatively, if the operation amount u is equal to or more than the upper limit (S620:YES), in S621 the third target speed selector 714 refers to the count value CN in the saturation counter 715. Subsequently, a speed value corresponding to the count value CN is outputted from the speed switching unit 713 and one of the third target conveyance speed corresponding to the count value CN is outputted as the target conveyance speed v(t) from the speed output unit 712 (in one of S623, S625 or S627). Specifically, when the count value CN satisfies the relational expression 0≦CN<m, the process proceeds to S623, and the speed value V31 is outputted as the target conveyance speed v(t) from the speed output unit 712.
When the count value CN satisfies the relational expression m≦CN<n, the process proceeds to S625, and the speed value v32 is outputted as the target conveyance speed v(t) from the speed output unit 712. When the count value CN satisfies the relational expression n≦CN, the process proceeds to S627, and the speed value v33 is outputted as the target conveyance speed v(t) from the speed output unit 712. In case one of the third target conveyance speeds is set as the target conveyance speed v(t), in S629 “1” is added to the count value CN in the saturation counter 715.
In S650 of the operation amount calculation process, in the target position calculation unit 601 that receives the target conveyance speed v(t) outputted from the target conveyance speed setting unit 711, a value which is larger than a previous value and corresponds to the outputted target conveyance speed v(t) is calculated as a value for the target position x(t). That is, when the third target conveyance speed is inputted as the target conveyance speed v(t), the target position x(t) is located more toward the upstream in the conveyance direction as compared to a target position located in a case in which the first target conveyance speed v1 is inputted.
Subsequently, in S660, the operation amount u1(t), corresponding to the above-described target conveyance speed v(t), is calculated in the feedfoward control unit 603. In a case in which the third target conveyance speed is inputted as the target conveyance speed v(t), a smaller operation amount u1(t) is calculated as the target conveyance speed v(t) as compared to a case wherein the first target conveyance speed v1 is inputted.
In S670, the error Θ is calculated in the first adder ADD1 based on the target position x(t) calculated by the target position calculation unit 601 in S650 and the count value y in the position counter 57. In S680, the operation amount u2(t) is calculated by the feedback control unit 605 based on the error Θ. When the third target conveyance speed is inputted as the target conveyance speed v(t), a smaller operation amount u2(t) is calculated as compared to a case wherein the first target conveyance speed v1 is inputted as the target conveyance speed v(t).
In S690, the operation amount u(t) is calculated in the second adder ADD2 based on the operation amount u1(t) obtained in S660 and the operation amount u2 obtained in S680 and inputted into the drive signal generator 55.
In the ASIC 70, if the operation amount u exceeds the upper limit, the target position x(t) is set at a position more toward the upstream in the conveyance direction than usual by temporarily decreasing the target conveyance speed v(t) (i.e. the target traveling amount is set smaller than usual). Therefore, as well as in the ASIC 53, it is possible to shorten the period SP wherein the operation amount u exceeds the upper limit. Consequently, with MFD 1 in which the method of this embodiment is used, it is also possible to appropriately convey the paper P with a large load, and to accurately convey the paper P so as to move the reference point to the image formation point GP. As a result of accurate conveyance of paper P, it is possible to form an image on one surface of paper P without displacement, and to inhibit lines of gaps that may otherwise be created from a failure in image formation.
The above has described an example to resolve the status wherein the operation amount u exceeds the upper limit by decreasing target conveyance speed. It is also possible to resolve the status wherein the operation amount u exceeds the upper limit for a long period of time by switching the value of the parameter a, which constitutes an arithmetic expression for extracting the target position x(t) from the target conveyance speed v(t).
As shown in
As shown in
When a command to select the first value is inputted from the comparator 811, the parameter switching unit 813 sets the value a1 stored in the target locus setting register RS6′ into the target position calculation unit 601 and the feedforward control unit 603. When a command to select the second value is inputted from the comparator 811, the parameter switching unit 813 sets the value a2 stored in the target locus setting register RS6′ into the target position calculation unit 601 and the feedfoward control unit 603.
The values a1 and a2, registered in the target locus setting register RS6′, are values that satisfy a relational expression δ1>δ2 wherein δ1 represents the inclination of the target position x(t) when the value al is set as the parameter a for the arithmetic expression for extracting the target position x(t) from the target conveyance speed v(t), (i.e. δ1=dx(t,a1)/dt), and δ2 represents the inclination of the target position x(t) when the value a2 is set as the parameter a (i.e. δ2=dx(t,a2)/dt).
The target position calculation unit 601 and the feedfoward control unit 603 are constituted to obtain variation by a predetermined calculation with the target conveyance speed v(t) and the parameter a, to add the variation to a previous calculation result (i.e. to conduct integration), and to obtain the target position x(t) and the operation amount u1(t) corresponding to the target conveyance speed v(t). Thus, when the value of the parameter a is changed from a1 to a2 during conveyance control, the target position x(t) is set more toward the upstream in the conveyance direction as compared to a case wherein the parameter a=a1.
When a calculation timing comes, in S710 it is determined whether or not switching timing into the second target conveyance speed v2 has come. When it is determined that the switching timing has come (S710:YES), the process proceeds to S715 and the second target conveyance speed v2 stored in the second target speed setting register RS4 is outputted as the target conveyance speed v(t) from the target conveyance speed setting unit 607.
On the other hand, when it is determined that the switching timing has not yet come (S710:NO), the process proceeds to S717 and the first target conveyance speed v1 stored in the first target speed setting register RS3 is outputted as the target conveyance speed v(t) from the target conveyance speed setting unit 607.
Subsequent to the process in S717, for the process in S720 the comparator 811 determines whether or not the operation amount u is equal to or more than the upper limit. When the operation amount u is less than the upper limit (S720:NO), the process proceeds to S730. In S730, the comparator 811 provides a command for the parameter switching unit 813 to select the first value, and the parameter a=a1 is set in the target position calculation unit 601 and the feedforward control unit 603. When the operation amount u is equal to or more than the upper limit (S720:YES), the process proceeds to S740 wherein the comparator 811 provides a command for the parameter switching unit 813 to select the second value, and the parameter a=a2 is set in the target position calculation unit 601 and the feedforward control unit 603.
In S750, a calculation is conducted in the target position calculation unit 601, which receives the target conveyance speed v(t) outputted from the target conveyance speed setting unit 711, in order to obtain the target position x(t) corresponding to the target conveyance speed v(t). When the operation amount u is less than the upper limit, the parameter a=a1 is used in the calculation. When the operation amount is equal to or more than the upper limit, the parameter a=a2 is used. In a case where the parameter a=a2, the target position x(t) is calculated to be located more toward the upstream in the conveyance direction as compared to a case wherein the target position x(t) is calculated with the parameter a=a1.
In S760, the above-described target conveyance speed v(t) and the operation amount u1(t) corresponding to the value of the parameter a are calculated in the feedforward control unit 603. In S770, the error Θ is calculated in the first adder ADD1 based on the target position calculated by the target position calculation unit 601 in S750 and the count value y in the position counter 57. In S780, the operation amount u2(t) is calculated by the feedback control unit 605 based on the calculation result in S770. In a case in which the parameter a=a2, a smaller value is obtained for the operation amount u2(t) as compare to a case wherein the parameter a=a1.
In S790, the operation amount u(t) is calculated in the second adder ADD2 based on the operation amount u1(t) obtained in S760 and the operation amount u2(t) calculated in S780, and is inputted into the drive signal generator 65. Consequently, in a case in which the parameter a=a2, a smaller value is obtained for the operation amount u(t) as compared to a case wherein the parameter a=a1.
As described above, when the operation amount u is equal to or more than the upper limit, in the ASIC 80 the target position x(t) is set at a position more toward the upstream in the conveyance direction than usual by switching the parameter a that relates to the inclination of the target position x(t) (i.e. the target travel distance is set to be smaller than usual). Hence, according to the third embodiment, it is possible to shorten the period SP wherein the operation amount u exceeds the upper limit as well as in other embodiments described above.
Therefore, in the MFD 1 wherein the method of the present embodiment is used, it is also possible to appropriately convey paper P with a large load and to accurately convey the paper P so as to move a reference point to the image formation point GP. As a result of the accurate conveyance of paper P, it is also possible to form an image on one surface of paper P without displacement and to inhibit lines of gaps, which may be created from a failure in image formation.
The control device, the conveyance control device, the conveyance system and the image forming system of the present invention are not limited to the above-described embodiments. Variations and modifications are possible within the scope of the present invention.
For example, if the status wherein the operation amount u exceeds the upper limit is not so promptly resolved even when the device is constituted to resolve this status, it is possible to reconstitute the device to change the value of the parameter a so that the inclination of the target position x(t) becomes furthermore smaller by switching the parameter a.
The present invention can be also applied to a driving system 100 for a cam 101 that rotates together with the conveyance roller 41,
In the driving system 100 of the cam 101 shown in
Specifically, the small-diameter bevel gear 109 is engaged with the deceleration gear 111, and the deceleration gear 111 is engaged with the sun gear 113. The sun gear 113 is engaged with the planet gear 115 provided on an end portion of a swing arm 177 that is rotatable about the sun gear 113. When the sun gear 113 rotates in the counterclockwise direction in
In a case in which a cam 101 is constituted as above, the cam 101 cannot be reversely rotated unless the cam 101 stops at a target rotational angle. Thus, rotational control on the cam 101 needs to be conducted several times so as to rotate the cam 101 more than one time and to stop the cam 101 at the target rotational angle. However, since the same control is conducted as the above-described conveyance control, it is possible to stop the cam 101 accurately and promptly at a target rotational angle. The rotational amount of the cam 101 can be detected with the encoder 49 provided on the conveyance roller 41.
In a conventional conveyance device wherein an object is conveyed by driving force being applied thereto, an object is still moved slightly toward the downstream side of a conveyance path by inertia even when the driving of the conveyance rollers is stopped. For this reason, in this type of conveyance device, the movement of an object to be conveyed toward the downstream of a conveyance path by inertia even after the driving of the conveyance rollers is stopped is already expected. Therefore, the conveyance device is controlled in a manner so that an object stops at a target point (conveyance destination).
In a conventional conveyance device, due to a large load on an object generated by the influence from the material of an object and the interference between an object and conveyance path, a target set by the conveyance control device may be largely different from the actual conveyance distance.. In this case, conveyance with the maximum capacity of the conveyance device is continued up to the vicinity of the conveyance destination. If conveyance with the maximum capacity of the conveyance device is continued, a more than necessary driving force is applied to an object when the load on the object is reduced, and a feedback control may not be able to function appropriately.
In this kind of situation, even when the driving of the conveyance rollers is stopped, the distance the object is moved by inertia is large and the object may be moved more than expected. In other words, in a conventional conveyance control device, an object cannot be accurately conveyed to a conveyance destination when a large load is applied to the object.
According to the embodiments described above, the following effects can be attained. One of the effects is that a skill is provided wherein a driving object can be moved for a predetermined distance with high accuracy irrespective of a large load generated on the driving object. Another effect is that a skill is provided wherein an object can be accurately to a conveyance destination irrespective of a large load generated on the object. Still another effect is that an image forming system can be provided wherein an image can be formed at a predetermined position of an image forming medium.
A control device according to the above-described embodiment, the above and other issues can be solved.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2004-219052 | Jul 2004 | JP | national |
This application claims the benefit of Japanese Patent Application No. 2004-219052 filed on Jul. 27, 2004 in the Japanese Patent Office, the disclosure of which is incorporated herein by reference.
