JP2017005901A - Motor drive device, image forming apparatus, and motor drive method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a motor drive device that drives a conveyance roller by means of a DC motor.SOLUTION: A motor drive device controls rotation of an IBLDC motor 160. The motor drive device comprises: a speed detector 105 that detects rotation speed of the IBLDC motor 160; a memory 103 that stores a plurality of correction values αi corresponding to time from the startup of the IBLDC motor 160; a filter 102 that calculates a correction value αi' on the basis of a speed detection value Vsns and a speed target value Vtar; a first adder 108 that adds the correction value αi and the correction value αi' and outputs a correction value (αi'+αi); and a controller 104 that controls the IBLDC motor 160 on the basis of the speed target value Vtar and the correction value (αi'+αi). The motor drive device updates the correction value αi stored in the memory 103, to the correction value (αi'+αi).SELECTED DRAWING: Figure 3

Description

  The present invention relates to a drive control technology for a conveyance roller for conveying a recording material such as paper in an image forming apparatus such as a copying machine or a printer.

  An image forming apparatus using an electrophotographic method forms an image on a recording material by forming a toner image on an image carrier such as a photosensitive drum or an intermediate transfer belt, and transferring the toner image to the recording material. The recording material is stored in a paper feed cassette, picked up one by one at a predetermined timing, and conveyed through a conveyance path by a plurality of conveyance rollers. The conveyance speed of the recording material is adjusted by the rotational speed of the drive motor that drives the conveyance roller and the timing of start and stop of the drive according to the position of the recording material being conveyed and the timing deviation with respect to the sequence of the image forming process.

  The timing deviation with respect to the sequence of the image forming process includes a case where the conveyance of the recording material is slow and a case where it is early. The conveyance delay of the recording material causes a decrease in productivity (number of output sheets per unit time). Conversely, if the recording material is transported quickly, it may collide with the preceding recording material or overlap the preceding recording material. Therefore, adjustment of the recording material conveyance speed is important.

  In many cases, an image forming apparatus includes a registration roller (hereinafter referred to as “registration roller”) on a conveyance path immediately before a transfer position for transferring a toner image onto a recording material. The recording material is conveyed in the conveyance path and hits the stopped registration roller to bend and stop in a loop shape. As a result, the skew of the recording material is corrected. The registration roller adjusts the timing so that the toner image is accurately transferred to a predetermined position on the recording material, and conveys the recording material to the transfer position. In order to accurately adjust the transfer position of the toner image onto the recording material, it is necessary for the driving motor of the registration roller to adjust the rotational speed and the conveyance distance of the recording material with high accuracy.

  A stepping motor is often used as a drive motor for driving the registration roller and other transport rollers. The stepping motor does not require feedback control of the rotational speed and rotational position, and rotates at an angle determined by the motor structure in accordance with the current flowing through the winding. The stepping motor is suitable for controlling the registration roller because the accuracy of the rotation angle is guaranteed. Actually, a controller having a stepping motor driver outputs a pulse signal for a desired rotation angle at a predetermined frequency, so that the rotation speed and the rotation position of the stepping motor are accurately controlled.

  Stepping motors can cause “step-out”. The step-out is a phenomenon that the rotation stops when the load torque exceeds the output torque of the stepping motor, and should not occur as a motor used in the image forming apparatus. Therefore, the current passed through the stepping motor is determined so that an output torque having a margin with respect to the maximum load torque can be obtained. This causes an excess current to flow when the load torque is small, causing power loss. The higher the possibility of step-out during actual operation, the less the load torque increases. For many periods, the load torque is sufficiently smaller than the output torque. Therefore, the stepping motor has a problem in terms of power consumption.

  Patent Document 1 proposes an image forming apparatus using a brushless DC motor that is advantageous in terms of power consumption instead of a stepping motor. In Patent Document 1, a speed or position detection sensor such as an encoder is provided on a rotating shaft of a brushless DC motor, and the brushless DC motor is feedback-controlled. The inner brushless DC motor in which the rotor is disposed inside the stator is excellent in transient response due to the small inertia of the rotor, and is supposed to be capable of acceleration / deceleration response equivalent to a conventional stepping motor.

JP 2012-213308 A

  However, even if the brushless DC motor has the performance that can obtain the desired acceleration / deceleration response as a specification, it is difficult to reduce the error with respect to the target speed when starting up the speed to the same extent as the stepping motor when performing feedback control. It is. Specifically, since the brushless DC motor cannot rotate at a very low speed, the behavior varies at the timing of starting movement, and overshoot occurs during the transition from acceleration to constant speed. If acceleration is reduced by overshoot countermeasures, productivity decreases.

  FIG. 8 is a time transition diagram of the recording material conveyance speed when the conveyance roller is driven by the brushless DC motor. FIG. 8A shows a time transition of the conveyance speed for 2 seconds from the start of rotation of the brushless DC motor. The conveyance speed follows the rotation speed of the brushless DC motor. FIG. 8B is an enlarged view of the waveform within the dotted line frame in FIG. 8A (0.1 second from the start of rotation). The broken line in FIG. 8B represents the target speed. FIG. 8 shows that the deviation of the rotational speed when the brushless DC motor starts to move and the overshoot when shifting to the constant speed are large with respect to the target speed. FIG. 9 shows the difference between the target speed and the conveyance speed, and FIG. 10 shows the integrated amount of the difference. FIG. 10 shows that the transport distance has advanced by about 0.4 [mm] with respect to the target before the transport speed becomes constant. That is, the recording material is conveyed in a state of being advanced from the target. The deviation of the conveyance distance is just an example. The characteristics of the brushless DC motor, the assembly error of the conveyance roller, the sleeve bearing deterioration and the change in the temperature of the drive transmission body from the motor to the conveyance roller due to the environmental temperature change (motor characteristics, expansion, etc.) Changes in the torque of the rotating part). Further, depending on the basis weight of the recording material, the thickness, and the load on the registration roller according to the conditions of the conveyance path, the rising method differs and a difference in the conveyance distance is generated.

  As described above, when feedback control is performed by the inner brushless DC motor, it is difficult to obtain acceleration / deceleration followability equivalent to that of the stepping motor. In addition, the speed deviation at the time of rising is not uniform, and errors caused by the speed deviation also vary.

  In view of the above problems, it is a main object of the present invention to provide a motor driving device that drives a conveyance roller by a DC motor.

  A motor driving device of the present invention that solves the above-described problem is a motor driving device that controls the rotation of a DC motor, and includes a detection unit that detects the rotation speed of the DC motor, Storage means for storing a plurality of first correction values corresponding to the time from the start of raising, calculation means for calculating a second correction value based on the detected rotational speed and target speed, and the first correction value Stored in the storage means, the adding means for adding the second correction value and the third correction value, the control means for controlling the DC motor based on the target speed and the third correction value, and the storage means. Updating means for updating the first correction value to the third correction value.

  According to the present invention, in order to correct the rotational speed of the DC motor with the new correction value calculated by adding the correction value to the difference between the target value and the detected value, the error caused by the speed deviation is reduced. Variation can be reduced.

1 is a schematic configuration diagram of an image forming apparatus. The schematic block diagram of a registration roller drive part. The circuit block diagram of a drive circuit board. The flowchart showing the operation control process of an IBLDC motor. (A)-(d) is an illustration figure showing the speed change of an IBLDC motor. The circuit block diagram of a drive circuit board. The flowchart showing the operation control process of an IBLDC motor. (A), (b) is a time transition figure of conveyance speed. The figure showing the difference of target speed and conveyance speed. The figure showing the integrated amount of a difference.

  Hereinafter, embodiments will be described in detail with reference to the drawings.

<First Embodiment>
FIG. 1 is a schematic configuration diagram of an image forming apparatus using an electrophotographic system. The image forming apparatus includes an image reading device 25, and performs an image forming process according to an image read from the original by the image reading device 25. The image forming apparatus includes four image forming units for forming images of four colors of yellow, magenta, cyan, and black. By superimposing the images of the respective colors, the color image is applied to a recording material such as paper. Form. Each image forming unit has the same configuration. For example, the yellow image forming unit includes a photosensitive drum 1a which is an image carrier, a charging roller 2a, an exposure device 3a, a developing device 4a incorporating a developing sleeve 41a, a primary transfer roller 5a, and a photosensitive cleaner 6a. “A” added after the symbol indicates that it corresponds to yellow. “B” for magenta, “c” for cyan, and “d” for black are added after the code. In addition, when it is not necessary to divide and explain colors, a to d will be omitted.

  In the yellow image forming unit, a yellow toner image is formed on the photosensitive drum 1a. In the magenta image forming unit, a magenta toner image is formed on the photosensitive drum 1b. In the cyan image forming unit, a cyan toner image is formed on the photosensitive drum 1c. In the black image forming portion, a black toner image is formed on the photosensitive drum 1d.

  The image forming apparatus includes each intermediate transfer belt 7, intermediate transfer belt drive roller 8, secondary transfer roller pair 9, and intermediate transfer belt cleaner 10. The intermediate transfer belt 7 is sandwiched between the photosensitive drum 1 and the primary transfer roller 5 and is driven to rotate by the intermediate transfer belt drive roller 8. Since the intermediate transfer belt 7 is sandwiched between the photosensitive drum 1 and the primary transfer roller 5, a toner image formed on the photosensitive drum 1 is transferred. The intermediate transfer belt 7 is transferred with the toner images formed at the respective image forming portions being superimposed. The intermediate transfer belt 7 is also sandwiched between the secondary transfer roller pair 9.

  The image forming apparatus includes a plurality of paper feed cassettes 11e to 11h that accommodate the recording material P. In each of the paper feed cassettes 11e to 11h, the recording material P is picked up one by one by the corresponding pickup rollers 12e to 12h. The recording material P is conveyed to the registration roller pair (registration roller pair) 16 through the conveyance path by the paper feed roller pairs 13e to 13h and the vertical path conveyance roller pairs 14e to 14h after being picked up. The sheet feeding cassettes 11e to 11h can accommodate recording materials P of different sizes and types. “E to h” added after the reference numerals respectively correspond to the “first to fourth stage” paper feed cassettes 11. If there is no need to separately explain the paper feed cassettes, explanation will be made with e to h omitted. The recording material P can be supplied from the external paper feed tray 24 in addition to the paper feed cassette 11. The recording material P placed on the external paper feed tray 24 is conveyed to the registration roller pair 16 by the multi-roller pair 15.

  The registration roller pair 16 temporarily stops the conveyance of the recording material P, and at the timing when the toner image transferred to the intermediate transfer belt 7 is conveyed to the position of the secondary transfer roller pair 9, the registration material pair 16 transfers the recording material P to the secondary transfer roller pair. Transport to 9. The recording material P is sandwiched between the secondary transfer roller pair 9 together with the intermediate transfer belt 7 to transfer the toner image. A fixing roller pair 17, a paper discharge flapper 18, and a paper discharge roller pair 19 are provided on the downstream side of the conveyance path of the secondary transfer roller pair 9. The fixing roller pair 17 fixes the transferred toner image on the recording material P. The paper discharge flapper 18 distributes the recording material P to the paper discharge roller pair 19 side and the double-sided path side. The paper discharge roller pair 19 discharges the recording material P out of the image forming apparatus. The double-sided path includes a reversing roller pair 20 and double-sided roller pairs 21, 22, and 23, reverses the recording material P having an image formed on one side, and conveys it to the registration roller pair 16.

  The image forming apparatus performs image forming processing under the control of a controller (not shown) having a CPU (Central Processing Unit). For example, when the controller receives an image forming command for the recording material P from an input device (not shown), the controller starts an image forming process. At the start of the image forming process, the controller first rotates the photosensitive drum 1, the intermediate transfer belt 7, the charging roller 2, the developing sleeve 41, the primary transfer roller 5, the secondary transfer roller pair 9, and the fixing roller pair 17. Start.

  The charging roller 2 is connected to a high voltage power supply (not shown), and is applied with a high voltage in which a sine wave voltage is superimposed on a DC voltage. The charging roller 2 charges the surface of the photosensitive drum 1 to the same potential as the applied high voltage DC voltage. The surface of the photosensitive drum 1 is irradiated with a laser beam E emitted from the exposure device 3 to form an electrostatic latent image. For example, the exposure device 3 emits a laser beam E in accordance with an image signal generated when the image reading device 25 reads an image of a document. As a result, the electrostatic latent image corresponds to the image of the document. The developing sleeve 41 of the developing device 4 is connected to a high voltage power supply (not shown), and a high voltage in which a sine wave voltage is superimposed on a DC voltage is applied. The developing sleeve 41 develops an electrostatic latent image by supplying toner to the surface of the photosensitive drum 1 by applying a high voltage. By developing the electrostatic latent image, a toner image is formed on the photosensitive drum 1.

  As the photosensitive drum 1 rotates, the toner image is transferred to the intermediate transfer belt 7 by the primary transfer roller 5. The toner images on the photosensitive drums 1 a to 1 d are transferred on the intermediate transfer belt 7 in a superimposed manner. As a result, a full-color toner image is formed on the intermediate transfer belt 7. The toner image is conveyed to the secondary transfer roller pair 9 by the rotation of the intermediate transfer belt 7.

  Meanwhile, the recording material P is picked up by the pickup roller 12 from the paper feed cassette 11 and conveyed to the paper feed roller pair 13. The pickup roller 12 can move up and down with respect to the paper feed cassette 11, approaches the paper feed cassette 11 when the recording material P is picked up, and when the recording material P reaches the paper feed roller pair 13, the paper feed cassette 11. It is designed to be separated from The pair of paper feed rollers 13 is driven so that the upper roller rotates in a direction in which the recording material P is conveyed, and the lower roller rotates in a direction in which the recording material P is returned to the paper feed cassette 11. The lower roller contains a torque limiter. When one recording material P is conveyed, the lower roller rotates in a direction corresponding to the rotation of the upper roller by friction. When two or more recording materials P are conveyed, the lower roller rotates in a direction to push the recording material P back toward the paper feed cassette 11 because the frictional force of the recording material P becomes small. With such a configuration, it is possible to prevent two or more recording materials P from being supplied to the conveyance path at a time.

  The paper feed roller pair 13 transports the recording material P to the vertical path transport roller pair 14. The longitudinal path transport roller pair 14 transports the recording material P to the stopped registration roller pair 16 through the transport path. The recording material P is abutted against the pair of registration rollers 16 to be stopped, and temporarily stops in a bent state. Since the recording material P is abutted against the registration roller pair 16 and bends, the skew is corrected. The registration roller pair 16 is rotationally driven so that the recording material P reaches the secondary transfer roller pair 9 at a timing when the toner image transferred to the intermediate transfer belt 7 reaches the secondary transfer roller pair 9. The secondary transfer roller pair 9 is applied with a DC high voltage from a high voltage power source (not shown), and transfers the toner image on the intermediate transfer belt 7 to the recording material P.

  The recording material P onto which the toner image has been transferred is thermocompression bonded by the fixing roller pair 17. As a result, the color image is fixed on the recording material P. When the image formation on one side or the image formation on both sides is completed, the recording material P is guided to the discharge roller pair 19 side by the discharge flapper 18 and discharged out of the image forming apparatus. When the image formation on both sides is instructed and the image formation on one side is finished, the recording material P is guided to the reverse roller pair 20 side by the paper discharge flapper 18. The reverse roller pair 20 stops in a state where the recording material P is sandwiched, and rotates in the reverse direction to convey the recording material P to the double-sided roller pair 21. The double-sided roller pairs 21, 22, and 23 convey the recording material P to the registration roller pair 16. As a result, the surface of the recording material P on which the image is formed is reversed, and an image is formed on both sides.

  As described above, the image forming apparatus receives an image forming command from the controller to the recording material P, and executes an image forming process. When the recording material P is supplied from the external paper feed tray 24, the same processing is performed after the registration roller pair 16 except for the conveyance path of the recording material P to the registration roller pair 16.

  FIG. 2 is a schematic configuration diagram of a registration roller driving unit that drives the registration roller pair 16. The registration roller driving unit includes an inner brushless DC motor (hereinafter referred to as “IBLDC motor”) 160 as a driving source. The IBLDC motor 160 has a drive circuit board 161 built therein. The drive circuit board 161 is a motor drive device that controls the rotation of the IBLDC motor 160 by a signal input from the controller. The signals input from the controller include a rotation direction signal that determines the rotation direction, a drive signal that instructs the start and end of driving of the IBLDC motor 160, and a control signal that controls the amount of current flowing through the IBLDC motor 160. The control signal is, for example, a PWM (Pulse Width Modulation) signal. In the present embodiment, a target value (steady speed target value) of the rotational speed (steady speed) during steady operation of the IBLDC motor 160 is also input from the controller to the drive circuit board 161. An encoder 162 is provided on the rotating shaft of the IBLDC motor 160. The encoder 162 outputs an A phase signal and a B phase signal, which are pulse signals that are 90 ° out of phase according to the amount of rotation of the IBLDC motor 160. The drive circuit board 161 detects the rotational speed of the IBLDC motor 160 based on the pulse signal output from the encoder 162.

  A pinion gear 163 is provided on the rotating shaft of the IBLDC motor 160. The pinion gear 163 transmits the rotation to the step gear 165 by the gear belt 164. The gear 166 is connected to the step gear 165. The gear 166 is connected to the metal roller 169. With such a structure, the IBLDC motor 160 rotationally drives the metal roller 169. A gear 167 is attached to the metal roller 169. Gear 167 is coupled to gear 168. Gear 168 is connected to roller 170. The rotation of the metal roller 169 is transmitted to the roller 170 by the gears 167 and 168. The metal roller 169 and the roller 170 constitute a registration roller pair 16, and when the recording material P is conveyed, the metal roller 169 and the roller 170 convey the recording material P in the conveying direction. The roller 170 is provided with a plurality of rubber rollers on a metal shaft.

  FIG. 3 is a circuit configuration diagram of the drive circuit board 161. The drive circuit board 161 includes a CPU 100. The CPU 100 generates a PWM signal for controlling the operation of the IBLDC motor 160 based on a signal acquired from the controller 200 that controls the operation of the image forming apparatus and a pulse signal output from the encoder 162. The drive circuit board 161 controls the rotation of the IBLDC motor 160 by supplying the PWM signal generated by the CPU 100 to the IBLDC motor 160. The CPU 100 and the controller 200 perform serial communication. The CPU 100 includes a target speed calculator 101, a filter 102, a memory 103, a controller 104, a speed detector 105, a first subtractor 106, a second subtracter 107, a first adder 108, a second adder 109, a first A switch SW1 and a second switch SW2 are provided.

  The target speed calculator 101 receives a drive signal and a steady speed target value from the external controller 200, outputs a drive signal to the IBLDC motor 160, and based on a predetermined acceleration, a target speed speed target value Vtar. Is calculated. The acceleration is set in advance according to the characteristics of the IBLDC motor 160, for example. The speed target value Vtar is determined according to the steady speed target value, the acceleration of the IBLDC motor 160, and the time from the start of driving the IBLDC motor 160 (the timing at which a drive signal indicating the start of driving is received). The speed target value Vtar is a value that changes according to acceleration during the acceleration period of the IBLDC motor 160. The speed when the IBLDC motor 160 is ideally accelerated becomes the speed target value Vtar. The speed target value Vtar during steady operation after the acceleration period is the same as the steady speed target value acquired from the controller 200.

  The filter 102 detects the difference between the speed target value Vtar and the speed detection value Vsns every predetermined sampling period ts in a period T including a predetermined start-up period (acceleration period of the IBLDC motor 160) from the start of driving. A filter operation is performed to calculate a correction value αi ′. For this purpose, a first subtractor 106 that calculates the difference between the target speed value Vtar and the detected speed value Vsns is provided between the target speed calculator 101 and the filter 102. The speed detection value Vsns is the rotational speed of the IBLDC motor 160 obtained from the detection result of the encoder 162. The filter 102 uses a low-pass filter for attenuating a high-frequency signal with low reproducibility. However, the filter 102 may be a constant only for gain adjustment, or may be a controller configuration adjusted to improve controllability.

The memory 103 stores correction values α i (i = 1, 2, 3,..., T / ts) for each sampling period ts in the period T. The correction value αi is set corresponding to the time from the start of the start of the IBLDC motor 160, and represents a correction amount for bringing the speed detection value Vsns closer to the speed target value Vtar. The correction value α i stored in the memory 103 is updated every time the IBLDC motor 160 is started up.
The first adder 108 adds the correction value αi previously stored in the memory 103 to the correction value αi ′ output from the filter 102, and outputs a correction value (αi ′ + αi). The correction value (αi ′ + αi) is output to the second adder 109 via the second switch SW2. Further, the correction value (αi ′ + αi) is stored in the memory 103 as a new correction value αi. That is, the correction value αi in the memory 103 is updated to the correction value (αi ′ + αi).
The second adder 109 adds the speed target value Vtar to the correction value (αi ′ + αi) to generate a correction target value Vcor. The corrected target value Vcor is calculated every sampling period ts.

  The controller 104 is a feedback controller having a difference between the correction target value Vvor and the speed detection value Vsns, and is a PI (Proportional-Integral) controller in this embodiment. The controller 104 generates a PWM signal according to the difference between the correction target value Vvor and the speed detection value Vsns and transmits the PWM signal to the IBLDC motor 160. The rotation of the IBLDC motor 160 is controlled by a PWM signal. The second subtracter 107 calculates the difference between the correction target value Vvor and the speed detection value Vsns.

  The speed detector 105 counts the time width between the pulse edges of the A-phase signal and the B-phase signal, which are pulse signals output from the encoder 162, with an internal clock, and derives the time between pulses for each pulse edge. The speed detector 105 divides a predetermined constant by the time between pulses to derive a speed detection value Vsns. Further, the speed detector 105 performs low-pass filter processing for cutting high-precision low-frequency and sampling processing for each sampling time ts.

  The first switch SW1 and the second switch SW2 are switched on and off at the same time. During the period T, the first switch SW1 and the second switch SW2 are in a conducting state, and after the period T has elapsed, the first switch SW1 and the second switch SW2 are in a non-conducting state. When the first switch SW1 and the second switch SW2 are turned off, the filter 102, the memory 103, and the first adder 108 are disconnected from the configuration of the drive circuit board 161. Therefore, the speed target value Vtar becomes the correction target value Vcor as it is without adding the correction value αi. When the period T elapses, the IBLDC motor 160 operates in a steady state and it is not necessary to correct the speed target value Vtar, so the first switch SW1 and the second switch SW2 are in a non-conductive state. Thereby, power consumption by the filter 102, the memory 103, and the first adder 108 during steady operation can be reduced.

  FIG. 4 is a flowchart showing the operation control process of the IBLDC motor 160 by the CPU 100. The CPU 100 executes the processing shown in FIG. 4 using a RAM (not shown) as a work memory based on a program stored in a ROM (not shown).

  The CPU 100 receives from the controller 200 a drive signal indicating a drive start and a steady speed target value (S1). The CPU 100 transmits the received drive signal to the IBLDC motor 160 (S2). The IBLDC motor 160 receives the drive signal, and starts rotating at a rotation speed corresponding to the PWM signal output from the controller 104 at that time.

  The target speed calculator 101 of the CPU 100 derives a speed target value Vtar based on a predetermined acceleration (S3). The target speed calculator 101 sequentially derives the speed target value Vtar for each sampling period ts within the period T in which the drive start timing based on the drive signal is the start time.

  If the drive time t from the start time is less than the period T (S4: Y), the CPU 100 corrects the correction value αi ′ output from the filter 102 by the first adder 108 and stored in the memory 103. The correction value (αi ′ + αi) is calculated by adding the value αi. The correction value (αi ′ + αi) becomes a new correction value αi. The new correction value αi (correction value (αi ′ + αi)) is stored in the memory 103, and the old correction value αi is updated. The second adder 109 derives a correction target value Vcor by adding the new correction value αi (correction value (αi ′ + αi)) calculated by the first adder 108 to the speed target value Vtar (S5). . The controller 104 generates a PWM signal using the corrected target value Vcor as a feedback target value, and performs feedback control of the rotational speed of the IBLDC motor 160 (S6).

  If the drive time t from the start time is equal to or longer than the period T (S4: N), the CPU 100 determines that the startup period of the IBLDC motor 160 has ended and the steady state has been reached. The CPU 100 turns off the first switch SW1 and the second switch SW2. The controller 104 generates a PWM signal using the speed target value Vtar as a feedback target value, and performs feedback control of the rotational speed of the IBLDC motor 160 (S7). Since the startup period of the IBLDC motor 160 ends, the rotational speed of the IBLDC motor 160 becomes a steady speed target value.

  The CPU 100 repeats the processes of steps S4 to S7 until it receives a drive signal indicating drive stop (S8: N). When the drive signal indicating the drive stop is received (S8: Y), the CPU 100 stops the rotation of the IBLDC motor 160 according to the received drive signal (S9). A period T is from the reception of the drive signal indicating the start of driving to the reception of the drive signal indicating the stop of driving. The CPU 100 stops the IBLDC motor 160 by inputting a drive signal indicating the stop of driving to the IBLDC motor 160 or by feedback control in which the speed target value Vtar is set to “0”. When the sensor provided downstream of the registration roller pair 16 in the transport path detects the passage of the recording material P, the controller 200 transmits a drive signal indicating the stop of driving to the CPU 100 to stop the next recording material P. .

  FIG. 5 is an exemplary diagram showing a change in the speed of the IBLDC motor 160 due to the above processing. In the initial state, the correction values α i stored in the memory 103 are all “0”, and feedback control is not performed in the first operation. FIG. 5A shows the speed change in this state. In FIG. 5A, the solid line represents the speed detection value Vsns, and the chain line represents the speed target value Vtar. The speed target value Vtar is equal to the correction target value Vcor because the correction value αi is “0”.

  In the second operation, the correction value α i stored in the memory 103 is updated by the first operation. FIG. 5B shows the correction value α i stored in the memory 103 after the first operation. Therefore, in the second and subsequent operations, the speed deviation is improved by the correction target value Vcor calculated from the speed target value Vtar and the correction value αi. FIG. 5C shows the speed change in the second operation. In FIG. 5C, the solid line represents the speed detection value Vsns, the chain line represents the speed target value Vtar, and the alternate long and short dash line represents the correction target value Vcor. FIG. 5D shows the correction value α i stored in the memory 103 after the second operation.

  Since the correction value αi is updated by each operation, the variation amount of the correction value αi decreases as the operation is repeated. That is, the error converges. By repeating the image forming process, the rotational speed error of the IBLDC motor 160 converges, and the deviation of the conveyance distance of the recording material P by the registration roller pair 16 is reduced. Note that the memory 103 is nonvolatile and keeps the latest correction value αi even when the power supply voltage is not supplied to the image forming apparatus.

  In such an image forming apparatus, the deviation of the rise time is sufficiently corrected by the image forming process in the shipping inspection stage at the time of production, and the front end position deviation of the image with respect to the recording material P is corrected well. Furthermore, even after shipment, the correction value αi for each image forming process can be updated for deterioration of the sleeve bearing, wear of each driving member, environmental change, the number of image formations, changes with time, etc. The response of the speed at the start-up can be corrected for a long time. Therefore, it is possible to keep the position of the leading end of the image tip relative to the recording material P with good accuracy.

  In the present embodiment, the example applied to the registration roller driving unit has been described. However, the present invention is not limited thereto, and is effective for a driving device that has a problem of speed deviation at the time of acceleration and a rotation amount error caused thereby. Moreover, although the case where the shape of the change of the speed target value is a trapezoid has been shown, it can be applied regardless of the shape of the acceleration curve.

Second Embodiment
The image forming apparatus of the second embodiment is different from the image forming apparatus of the first embodiment only in the configuration of the drive circuit board 161, and the other configurations are the same. Here, different configurations will be described, and description of the same configurations will be omitted.

  FIG. 6 is a circuit configuration diagram of the drive circuit board 161 according to the second embodiment. In the second embodiment, the controller 400 that controls the image forming apparatus transmits paper feed information to the CPU 300 in addition to the drive signal and the steady speed target value. In the present embodiment, the paper feed information represents a path when the recording material P is conveyed to the registration roller pair 16. The components of the drive circuit board 161 of the second embodiment are the same as those of the drive circuit board 161 of the first embodiment, but the processing of the memory 303 to which paper feed information is input from the controller 400 is different. Components other than the memory 303 that perform the same processing with the same configuration are denoted by the same reference numerals and description thereof is omitted.

  The memory 303 receives a steady speed target value and paper feed information from the controller 400. The memory 103 corresponds to the time from the start of startup of the IBLDC motor 160, and the correction value αij (i = 1, 2, 3,..., T / ts) (j) generated for each sampling period ts in the period T. = 1, 2, 3,..., N). “N” is a number determined by the steady speed target value and the paper feed information.

  The image forming apparatus according to the present exemplary embodiment includes a plurality of, for example, three types of steady speeds during conveyance of the recording material P in the conveyance path from the registration roller pair 16 to the fixing roller pair 17. Therefore, three kinds of steady speed target values can be input to the CPU 300. This is because the amount of heat necessary for fixing varies depending on the basis weight of the recording material P. For example, when the basis weight is large, the amount of heat taken away by the recording material P during image fixing is large, so it is necessary to reduce the conveying speed and increase the time for passing the fixing roller pair 17. The basis weight of the recording material P is set by the user via the user interface. The controller 400 determines the steady speed according to the set basis weight of the recording material P, and inputs the steady speed target value to the CPU 300.

  Further, there are six conveyance paths to the registration roller pair 16 including four sheet feeding cassettes 11e to 11h, an external sheet feeding tray 24, and a duplex roller pair 23. The curvatures of the paths leading to the registration roller pair 16 are different, and particularly when the basis weight of the recording material P is large, the load torque applied to the registration roller pair 16 is greatly different. Therefore, it is necessary to provide these six conditions for the paper feeding place to the registration roller pair 16.

  Thus, there are three steady speed target values and there are six conveyance paths as the paper feed information. Therefore, in this embodiment, N is set to “18 (= 3 × 6)” to satisfy these conditions. The The memory 303 stores N (18) T / ts data groups as the correction value αij in the period T corresponding to the time from the start of the start of the IBLDC motor 160. From the memory 303, the correction value αij corresponding to “i” determined by the sampling period is read out to the first adder 108 from the data group corresponding to “j” determined by the steady speed target value and the paper feed information.

  The correction value αij stored in the memory 303 is updated every time the IBLDC motor 160 is started up. The first adder 108 adds the correction value αij stored in the memory 303 in advance to the correction value αij ′ output from the filter 102 and outputs a correction value (αij ′ + αij). The correction value (αij ′ + αij) is output to the second adder 109 via the second switch SW2. Further, the correction value (αij ′ + αij) is stored in the memory 303 as a new correction value αij. That is, the correction value αij in the memory 303 is updated to the correction value (αij ′ + αij). The second adder 109 adds the speed target value Vtar to the correction value (αji ′ + αij) to generate a correction target value Vcor. The corrected target value Vcor is calculated every sampling period ts.

  FIG. 7 is a flowchart showing operation control processing of the IBLDC motor 160 by the CPU 300.

  The CPU 300 receives from the controller 400 a drive signal indicating the start of driving, a steady speed target value, and paper feed information (S10). The CPU 300 determines a data group of correction values αij used for feedback control according to “j” determined by the received steady speed target value and paper feed information (S11). The CPU 300 transmits the received drive signal to the IBLDC motor 160 (S12). The IBLDC motor 160 receives the drive signal, and starts rotating at a rotation speed corresponding to the PWM signal output from the controller 104 at that time.

  The target speed calculator 101 of the CPU 100 derives a speed target value Vtar based on a predetermined acceleration (S13). The target speed calculator 101 sequentially derives the speed target value Vtar for each sampling period ts within the period T in which the drive start timing based on the drive signal is the start time.

  If the drive time t from the start time is less than the period T (S14: Y), the CPU 100 stores the correction value αij ′ output from the filter 102 in the memory 103 in advance by the first adder 108. The correction value αij is added. Thereby, the first adder 108 calculates a correction value (αij ′ + αij). The correction value (αij ′ + αij) becomes a new correction value αji. The new correction value αij (correction value (αij ′ + αij)) is stored in the memory 303, and the old correction value αij is updated. The second adder 109 derives a correction target value Vcor by adding the new correction value αij (correction value (αij ′ + αij)) calculated by the first adder 108 to the speed target value Vtar (S15). . The controller 104 generates a PWM signal using the corrected target value Vcor as a feedback target value, and performs feedback control of the rotational speed of the IBLDC motor 160 (S16).

  If the drive time t from the start time is equal to or longer than the period T (S14: N), the CPU 100 determines that the startup period of the IBLDC motor 160 has ended and the steady state has been reached. The CPU 100 turns off the first switch SW1 and the second switch SW2. The controller 104 generates a PWM signal using the speed target value Vtar as a feedback target value, and performs feedback control of the rotational speed of the IBLDC motor 160 (S17). Since the startup period of the IBLDC motor 160 ends, the rotational speed of the IBLDC motor 160 becomes a steady speed target value.

  The CPU 100 repeats the processes of steps S14 to S17 until it receives a drive signal indicating drive stop (S18: N). When the drive signal indicating the drive stop is received (S18: Y), the CPU 100 stops the rotation of the IBLDC motor 160 according to the received drive signal (S19). A period T is from the reception of the drive signal indicating the start of driving to the reception of the drive signal indicating the stop of driving. Note that the controller 200 determines the passage of the recording material P by a sensor provided downstream of the registration roller pair 16 in the conveyance path, and transmits a drive signal indicating driving stop to the CPU 100 to stop the next recording material P.

  In such an image forming apparatus, in addition to the same effects as those of the image forming apparatus of the first embodiment, it is possible to correct an image forming position shift in accordance with a target steady speed and paper feed information regarding the recording material P. it can. In addition to the conveyance path of the recording material P to the registration roller pair 16, the size of the recording material P may be used as the paper feed information. In addition, it is possible to set the conditions more finely and to divide the correction values.

  100, 300 ... CPU, 160 ... IBLDC motor, 162 ... encoder, 200,400 ... controller

Claims (13)

A motor driving device for controlling the rotation of a DC motor,
Detecting means for detecting the rotational speed of the DC motor;
In the startup process of the DC motor, storage means for storing a plurality of first correction values corresponding to the time from the start of startup,
Calculating means for calculating a second correction value based on the detected rotational speed and target speed;
Adding means for adding the first correction value and the second correction value and outputting a third correction value;
Control means for controlling the DC motor based on the target speed and the third correction value;
Update means for updating the first correction value stored in the storage means to the third correction value,
Motor drive device. A steady speed target value representing the steady state rotational speed of the DC motor is received from an external device, and the received steady speed target value, the acceleration of the DC motor, and the time from the start of driving of the DC motor are received. It comprises a target speed calculation means for calculating the target speed,
The motor drive device according to claim 1. The target speed calculation means receives a drive signal for instructing the DC motor to start rotation together with the steady speed target value from the external device, and instructs the DC motor to start rotation. ,
The motor drive device according to claim 2. The control means controls the DC motor based on a difference between a sum of the target speed and the third correction value and a detection value by the detection means.
The motor drive device of any one of Claims 1-3. The calculation means calculates the second correction value at a predetermined cycle during a period including an acceleration period from the start of driving of the DC motor,
The storage means stores the third correction value calculated during the period as a data group.
The motor drive device of any one of Claims 1-4. The DC motor drives a roller that conveys a predetermined recording material,
The storage means stores a plurality of the data groups corresponding to the basis weight of the recording material,
The motor drive device according to claim 5. The DC motor drives a roller that conveys a predetermined recording material,
The storage means stores a plurality of the data groups corresponding to a conveyance speed of the recording material,
The motor drive device according to claim 5. The DC motor drives a roller that conveys a predetermined recording material,
The storage unit stores a plurality of the data groups corresponding to a conveyance path of the recording material.
The motor drive device according to claim 5. The detection means detects the rotational speed of the DC motor from a pulse signal corresponding to the amount of rotation of the DC motor output by an encoder provided in the DC motor.
The motor drive device of any one of Claims 1-8. The motor drive device according to any one of claims 1 to 9,
An image carrier on which a toner image is formed;
Transfer means for transferring the toner image to a recording material;
A roller driven by the DC motor to convey the recording material to the transfer means;
Fixing means for fixing the transferred toner image onto the recording material onto which the toner image has been transferred by the transfer means;
Image forming apparatus. The roller temporarily stops the conveyance of the recording material, and conveys the recording material to the transfer unit at a timing when the toner image formed on the image carrier is conveyed to the position of the transfer unit. And
The image forming apparatus according to claim 10. The roller is characterized in that the recording material is abutted in a stopped state, and the recording material is temporarily stopped in a bent state to correct skewing.
The image forming apparatus according to claim 11. A method that is executed by a motor driving device that includes a storage unit that stores a plurality of first correction values corresponding to the time from the start of startup of a DC motor,
Detecting the rotational speed of the DC motor,
Calculating a second correction value based on the detected rotation speed and a target speed of the rotation speed;
Adding the first correction value and the second correction value to calculate a third correction value;
Controlling the DC motor based on the target speed and the third correction value;
Updating the first correction value stored in the storage means to the third correction value,
Motor drive method.