JP2013182056A - Image forming apparatus and drive source control program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress resonance even when a resonance frequency to which a housing resonates is changed due to a placed object or an installation object, for example.SOLUTION: A printer 1 includes motors M1 and M2 in a casing 2, a mark sensor 8 that outputs a detection signal SG1 according to fluctuations in a resonance frequency to which the casing resonates, and a controller 30. When the controller determines that the resonance frequency of the casing fluctuated from a reference value on the basis of the detection signal SG1, it changes rotation speed of the motors M1 and M2, and performs changing processing for separating a frequency of an exciting force applied to the casing by the rotation of the motors M1 and M2 from the resonance frequency after the fluctuation.

Description

  The invention disclosed in this specification relates to a technique for controlling the driving speed of a driving source provided in a housing of an image forming apparatus that forms an image on an object.

  An image forming apparatus that forms an image on an object, such as an optical scanning device or a printer, has a configuration in which, for example, various rollers, a belt, a polarizing member, and the like are rotated by driving a driving source such as a motor provided in a housing. . Here, when the natural frequency of the housing and the frequency of the excitation force applied to the housing by driving the motor are close, the top surface side of the housing, particularly away from the installation surface, is greatly shaken to the object. There is a risk of adversely affecting image formation, such as fluctuations in the image forming position. For this reason, in general, at the design stage of the image forming apparatus, the rigidity and weight of the casing and the rotation speed of the motor are set so that the natural frequency of the casing and the frequency of the excitation force by the motor do not approach each other. .

  Conventionally, there has been an optical scanning device that can drive a polygon motor at different predetermined rotational speeds according to the resolution. In this optical scanning device, the polygon mirror is rotated at each rotational speed. In order to prevent resonance, the natural frequency of the housing changes to each value determined in advance in the manufacturing stage (Patent Document 1). Specifically, in this optical scanning device, a laser scanning unit is fixed to the main body via a support, an electromagnet is attached to the bottom surface of the laser scanning unit, and a ring-shaped member is attached to the main body frame. Then, by changing the amount of current flowing through the electromagnet, the attractive force between the electromagnet and the ring-shaped member is changed, and the natural frequency of the casing of the optical scanning device can be changed to each predetermined value.

JP-A-9-54265

  By the way, even if the natural frequency of the casing can be set or changed to a value determined in the manufacturing stage as in the conventional image forming apparatus such as the optical scanning device, for example, Resonance may occur due to a change in the weight of the casing due to an installation placed on the casing. For example, in a printer in which a plurality of output trays are arranged on a housing, a large amount of paper is discharged to the discharge tray by continuous printing and the weight on the upper surface side of the housing increases, resulting in resonance that the housing resonates. The frequency fluctuates and as a result, resonance may occur.

  The present specification discloses a technique capable of suppressing resonance even when the resonance frequency at which the casing resonates changes due to, for example, a mounted object or an installed object.

  The image forming apparatus disclosed in this specification includes a housing, a drive source provided in the housing, an image forming unit that operates by driving the drive source, and forms an image on an object, and the drive A drive unit that drives a source and changes a drive speed of the drive source, a detection unit that outputs a detection signal according to a change in a resonance frequency at which the housing resonates, and a control unit, and the control The determination unit determines whether the resonance frequency at which the casing resonates fluctuates from a reference value based on the detection signal of the detection unit, and determines that the resonance frequency fluctuates in the determination process. A change process of causing the drive unit to change the drive speed of the drive source, and separating the frequency of the excitation force applied to the housing by driving the drive source from the resonance frequency after the change; , To execute.

  For example, the resonance frequency at which the housing resonates may fluctuate due to the placement object or the installation object arranged on the upper surface. According to this image forming apparatus, it is determined whether or not the resonance frequency has fluctuated from the reference value. If it is determined that the resonance frequency has fluctuated, the drive speed of the drive source is changed and the drive source is driven to the housing. The frequency of the applied excitation force is separated from the changed resonance frequency. Thereby, even if the resonance frequency at which the casing resonates varies, it is possible to suppress the resonance.

  In the image forming apparatus, the image forming unit is configured to move relative to the object to form an image, and the detection unit outputs a signal corresponding to the position of the image formed on the object. The sensor outputs as the detection signal, and the control unit performs a mark formation process in which the image forming unit sequentially forms a plurality of marks along the relative movement direction on the object. In the determination process, when there is a periodic variation in the shift amount of each mark, which is a difference between the mark detection position based on the detection signal of the sensor and a predetermined reference position of the mark, It may be determined that the resonance frequency has fluctuated.

  According to this image forming apparatus, a plurality of marks are sequentially formed on the object along the direction of relative movement, the mark detection position based on the detection signal of the sensor, and a predetermined reference position of the mark It is determined whether or not there is a periodic variation in the shift amount of each mark, which is the difference between the two. Here, when the resonance frequency at which the housing resonates fluctuates and resonance occurs, the amount of deviation of each mark, which is the difference between the mark detection position and a predetermined mark reference position, is accordingly accompanied. Periodic fluctuations will appear. Therefore, as in the present image forming apparatus, it is possible to indirectly determine whether or not the resonance frequency at which the casing resonates has changed by determining whether or not the shift amount is periodically changed.

  In the image forming apparatus, each of the marks may have a linear portion inclined obliquely with respect to the direction of relative movement.

  According to this image forming apparatus, each mark has a linear portion inclined obliquely with respect to the direction of relative movement. For this reason, the detection position periodically fluctuates with respect to the reference position of the mark regardless of whether the resonance vibration direction is the direction of relative movement or the direction orthogonal to the direction of relative movement. Therefore, it can be determined whether the resonance frequency at which the housing resonates fluctuates regardless of which of the two vibration directions.

  In the image forming apparatus, an angle formed between the direction of the relative movement and the linear portion may be 45 degrees.

  According to this image forming apparatus, the angle formed between the direction of relative movement and the straight line portion of each mark is 45 degrees. Therefore, it is possible to determine whether the resonance frequency at which the casing resonates fluctuates with equal accuracy without any deviation regardless of the resonance vibration direction.

  In the image forming apparatus, the image forming unit forms an image on a sheet, and a discharge tray for discharging the sheet on which the image is formed by the image forming unit is provided on an upper surface of the housing. The detection unit is a sensor that outputs a signal corresponding to the number of sheets discharged to the discharge tray as the detection signal, and the control unit detects the detection signal of the sensor in the determination process. If the number of sheets changes based on the above, it may be determined that the resonance frequency has changed.

  According to this image forming apparatus, the discharge tray is provided on the upper surface of the housing. In such a configuration, the weight on the upper surface side of the casing increases in accordance with the number of sheets discharged to the discharge tray, and as a result, the resonance frequency at which the casing resonates varies. Therefore, based on whether or not the number of sheets discharged to the discharge tray has changed, it can be determined whether or not the resonance frequency at which the casing resonates has changed.

  In the image forming apparatus, the detection unit is a sensor that outputs a signal corresponding to the weight of the mounted object on the housing as the detection signal, and the control unit is configured to output the signal of the sensor in the determination process. It may be determined that the resonance frequency has changed when the weight changes based on the detection signal.

  When there is an object to be placed on the upper surface of the housing, the resonance frequency at which the housing resonates varies according to the weight of the object. Therefore, according to this image forming apparatus, the weight of the object placed on the casing is detected, and whether or not the fixed frequency of the casing has changed is determined based on whether or not the detected weight has changed. Can do.

  The present invention can be realized in various modes such as an image forming apparatus, a motor control method, a computer program for realizing the functions of these methods or apparatuses, and a recording medium on which the computer program is recorded.

  According to the invention disclosed in this specification, it is possible to suppress resonance even when the resonance frequency at which the casing resonates due to, for example, a mounted object or an installed object changes.

1 is a side sectional view showing a schematic configuration of a printer according to a first embodiment. Block diagram schematically showing the electrical configuration of the printer Graph showing the relationship between the resonance frequency of the casing and the vibration frequency of the motor Schematic diagram of a printer with the upper surface of the casing shaking in the main scanning direction Flow chart showing motor control processing Time chart showing the relationship between mark, detection position, reference position and deviation FIG. 4 is a side sectional view showing a schematic configuration of a printer according to a second embodiment. Block diagram schematically showing the electrical configuration of the printer Flow chart showing motor control processing Illustration of correspondence table

<Embodiment 1>
The printer 1 according to the first embodiment will be described with reference to FIGS. In the following description, the left side of FIG. 1 is the rear side (B) of the printer 1 and the sub-scanning direction, and the back side of the paper is the right side (R) of the printer 1 and the main scanning direction. Is the upper side (U) of the printer 1. The printer 1 is an example of an image forming apparatus.

(Entire printer configuration)
As shown in FIG. 1, the printer 1 of this embodiment is an example of an image forming apparatus. For example, multiple transfer that forms a color image using toners of four colors of black K, yellow Y, magenta M, and cyan C. This is a tandem color printer. In the following description, when each component or term of the printer 1 is distinguished for each color, K (black), C (cyan), M (magenta), Y (meaning each color at the end of the code of the component, etc. Yellow).

  The printer 1 includes a casing 2 that is an example of a housing, and a tray 4 on which a plurality of sheets 3 can be stacked is provided at the bottom of the casing 2. The sheet 3 is an example of an object, and includes a sheet and an OHP sheet. The sheets 3 stacked in the tray 4 are conveyed onto the belt unit 6 by the rotational drive of the conveying roller 5 provided above the front end of the tray 4.

  The belt unit 6 has a configuration in which an annular belt 7 is stretched between a pair of support rollers 6A and 6B. The belt 7 is an example of an object. The belt 7 circulates counterclockwise when the rear support roller 6A is driven to rotate, and conveys the sheet 3 placed on the upper surface thereof to the rear.

  A mark sensor 8 for detecting each mark Q (see FIG. 6) of the pattern P formed on the belt 7 is provided on the rear end side of the belt 7. The mark sensor 8 is an example of a sensor, and is a known optical sensor having a light emitting element that emits light to the detection area E on the belt 7 and a light receiving element that receives reflected light from the detection area E. The mark sensor 8 outputs the detection signal SG1 that changes in accordance with the position of each mark on the belt 7 in synchronism with the timing at which each mark Q enters the detection region E by the belt 7. A cleaning unit 9 having a cleaning roller 9A for removing deposits on the surface of the belt 7 is provided below the belt unit 6. The deposit includes toner (including pattern P), paper dust, and the like.

  A process unit 10 is provided above the belt unit 6. In the process section, for example, four sets of process cartridges corresponding to each color of black, yellow, magenta, and cyan are provided in the front-rear direction. Each process cartridge includes a toner storage chamber that stores toner of each color as a colorant, a developing roller, a photosensitive drum 11, a charger, and the like, and only the photosensitive drum 11 is illustrated in FIG.

  An exposure unit 12 is provided above the process unit 10. The exposure unit 12 includes a polygon mirror 13, a light source (for example, a laser diode not shown) corresponding to each color of black, cyan, magenta, and yellow, and optical components such as a reflecting mirror. Each laser beam L emitted from each light source is deflected by a polygon mirror 13, changed in direction by an optical component, and irradiated on the surface of each photosensitive drum 11 </ b> K to 11 </ b> C by high-speed scanning as shown in FIG. 1. Thereby, electrostatic latent images are formed on the respective photosensitive drums 11K to 11C.

  The electrostatic latent image on each photosensitive drum 11 is converted into a toner image by being supplied with toner by a developing roller, and transferred onto the surface of the belt 7 or the surface of the sheet 3 conveyed to the belt 7. The sheet 3 to which the toner image has been transferred is then conveyed to the fixing device 14, where the toner image is thermally fixed by the heating roller 14A and the fixing roller 14B. The heat-fixed sheet 3 is conveyed upward and discharged onto the upper surface of the casing 2 by the discharge roller 15.

  Further, a sorter unit 20 is mounted as an option on the upper surface of the casing 2. The sorter unit 20 includes a plurality of discharge trays 21 arranged in a vertical direction. With this sorter unit 20, the printer 1 can sort the printed sheets 3 into a different discharge tray 21 for each user, for example, and discharge a large amount.

  As shown in FIG. 1, a process motor M1, a fixing motor M2, and a polygon motor M3 are installed in the casing 2 as an example of a drive source. The process motor M1 is disposed in the vicinity of the process cartridge, and is driven to rotate about a rotation axis extending in the left-right direction, whereby the rollers 5 and 15, the support roller 6A of the belt unit 6 and the photosensitive of the process unit 10 are detected. The drum 11 and the like, and the cleaning roller 9A of the cleaning unit 9 are rotated.

  The fixing motor M2 is disposed in the vicinity of the fixing device 14, and rotates the heating roller 14A by being driven to rotate about a rotation axis along the left-right direction. The polygon motor M3 is built in the exposure unit 12, and rotates the polygon mirror 13 by being driven to rotate about a rotation axis along the vertical direction. Accordingly, each of the rollers 5 and 15, the belt unit 6, the cleaning unit 9, the process unit 10, the fixing device 14, and the exposure unit 12 is an example of an image forming unit.

(Electrical configuration of printer)
As illustrated in FIG. 2, the printer 1 includes a controller 30 that is an example of a control unit. The controller 30 is connected to the mark sensor 8, the cleaning unit 9, the process unit 10, the motor driver 31, the communication unit 32, the operation unit 33, and the display unit 34 so that data communication is possible. The controller 30 includes a central processing unit (hereinafter referred to as CPU) 30A, a ROM 30B, and a RAM 30C.

  The ROM 30B stores a program for executing various operations of the printer 1 such as a motor control process described later, and the CPU 30A controls each unit according to the program read from the ROM 30B. This program includes a motor control program which is an example of a drive source control program. The RAM 30C is used as a buffer for storing image data received by the communication unit 32, a work area for performing motor control processing described later, and the like. The medium for storing the various programs may be a non-volatile memory such as a CD-ROM, a hard disk device, or a flash memory in addition to the ROM 30B.

  The motor driver 31 is an example of a drive unit, and can drive the process motor M1, the fixing motor M2, and the polygon motor M3, and can individually change the rotation speeds of the motors M1 to M3 upon receiving an instruction from the controller 30. Is possible. In this embodiment, the process motor M1 and the fixing motor M2 are changed to the same rotational speed so that the sheet 3 can be conveyed at the same speed, while the polygon motor M3 is changed to the other motors M1 and M2. It is controlled at a very high speed compared to Note that the motor rotation speeds of the process motor M1 and the fixing motor M2 may be different.

  The communication unit 32 can receive a print job or image data by performing data communication with an external device such as a personal computer or an external memory (not shown) wirelessly or by wire. The operation unit 33 includes a plurality of buttons, and various input operations can be performed by the user. The display unit 34 includes a liquid crystal display, a lamp, and the like, and can display various setting screens and operation states of the apparatus.

(Regarding fluctuations in resonance frequency at which the housing resonates)
FIG. 3 shows the frequency at which the casing 2 resonates (hereinafter simply referred to as “resonance frequency”) and the frequency of the excitation force applied to the casing 2 by the rotation of the motors M1 and M2 (hereinafter simply referred to as “excitation”). A graph showing the relationship with "frequency" is shown. The vertical axis of this graph is the vibration amplitude and transfer function, and the horizontal axis is the vibration frequency. FC0 in the figure is the value of the natural frequency of the casing 2, and FM0 is the value of the vibration frequency when the rotational speeds of the motors M1 and M2 are the reference speed V0. In this embodiment, The reference speed V0 and the weight and rigidity of the casing 2 are set so that FC0 is larger than FM0.

  However, for example, when a large amount of paper is discharged to the discharge tray 21 by continuous printing and the weight on the upper surface side of the casing 2 is increased, the resonance frequency of the casing 2 fluctuates as shown in FIG. As the vibration frequency FM0 is approached, resonance may occur. Then, in particular, the upper surface side of the casing 2 away from the installation surface is greatly shaken, and, for example, a linear electrostatic latent image should be formed on the photosensitive drum 11 by the exposure unit 12, but a wave-like electrostatic latent image is formed. The image quality will deteriorate. FIG. 4 illustrates a case where the upper surface side of the casing 2 is shaken in the main scanning direction due to resonance. In this case, the exposure position on the photosensitive drum 11 from the exposure unit 12 is the original position due to resonance. It is shifted from X0 to position X1.

  Since the printer 1 employs the laser exposure method as described above, the exposure distance from the exposure unit 12 to the photosensitive drum 11 is longer than that of, for example, the LED exposure method. Tends to decrease. Further, as described above, the polygon motor M3 is controlled at an extremely high speed as compared with the other motors M1 and M2. Therefore, the excitation force due to the rotation of the polygon motor M3 depends on whether or not resonance of the casing 2 occurs. Almost no effect.

(Motor control processing)
For example, when the communication unit 32 receives a print job or image data from an external device, the controller 30 executes a motor control process shown in FIG. Specifically, the CPU 30A reads the motor control program from the ROM 30B and first controls the motor driver 31 to rotate the polygon motor M3, and the process motor M1 and the fixing motor M2 at the reference speed V0. Rotate (S1).

  Next, the CPU 30A reads the data of the pattern P from, for example, the RAM 30C, controls the process unit 10, and starts a mark forming process for sequentially forming the marks Q of the pattern P on the belt 7 (S2). Specifically, the process unit 10 sequentially forms the marks Q on the belt 7 at predetermined time intervals using only one process cartridge. Here, as shown on the left side of FIG. 6, each mark Q has a linear shape, and an angle formed with the main scanning direction is 45 degrees.

  The time interval is preferably uniform. Further, the one process cartridge is, for example, a process cartridge of toner having the largest difference in light reflectance from the belt 7, for example, black toner, thereby improving the detection accuracy of the position of the mark Q by the mark sensor 8. But you can. The one process cartridge is the most downstream process cartridge in the sub-scanning direction, so that the time from mark formation to detection by the mark sensor 8 is shortened, and the time required for the entire motor control processing is shortened. It may be configured.

  After starting the mark formation process, the CPU 30A starts reading the detection signal SG1 from the mark sensor 8 (S3). Here, when resonance does not occur, as shown in black on the left side of FIG. 6, the plurality of marks Q1 formed on the belt 7 are arranged at regular intervals in a line along the sub-scanning direction. . The alternate long and short dash line in the figure indicates the detection area E of the mark sensor 8, and the position where the mark Q1 and the detection area E overlap is the position of each mark Q1 detected by the mark sensor 8 (FIG. 6). (See the time chart in the middle). Hereinafter, this position is particularly referred to as a reference position X0, and information on the reference position X0 is stored in the RAM 30C in advance. In the example of FIG. 6, the arrangement interval between the reference positions X0, in other words, the detection time interval T1 of each mark Q1 is uniform.

  On the other hand, when resonance occurs in the main scanning direction, for example, as indicated by the hatched lines in the figure, the plurality of marks Q2 formed on the belt 7 form a row that periodically swings to the left and right according to the resonance. The position where the mark Q2 and the detection area E overlap is the position of each mark Q2 detected by the mark sensor 8 (see the central time chart in FIG. 6). Hereinafter, this position is particularly referred to as a detection position X1. In the example of FIG. 6, the arrangement interval between the detection positions X1, in other words, the detection time interval T2 of each mark Q2 is non-uniform and varies periodically. For this reason, when resonance occurs, as shown on the right side of FIG. 6, the shift amount D of each mark Q, which is the difference between the detection position X1 and the reference position X0, is periodically changed according to the resonance period T3. Changes appear.

  Therefore, the CPU 30A executes determination processing (S4, S5) for determining whether or not the resonance frequency of the casing 2 has changed from the reference value based on the detection signal SG1 from the mark sensor 8. Examples of the reference value include a value of the natural frequency of the casing 2 and a value of the natural frequency including the casing 2 and the sorter unit 20 when the sheet 3 is not discharged to the sorter unit 20. Specifically, the CPU 30A calculates the shift amount D sequentially from the head mark Q2 in the sub-scanning direction based on the detection signal from the mark sensor 8 and the information on the reference position X0 (S4), and on the right side of FIG. As shown in the figure, it is determined whether or not the deviation amount D calculated sequentially has a periodic variation with time (S5).

  For example, if there is no periodic fluctuation such as the deviation amount D of each mark Q2 is uniform, the fluctuation is not due to resonance. For this reason, the CPU 30A determines that there is no periodic variation in the deviation amount D, that is, the resonance frequency of the casing 2 does not vary from the reference value (S5: NO), and the rotational speeds of the motors M1 to M3. This motor control process is terminated without changing the above.

  On the other hand, when the CPU 30A determines that the deviation amount D has a periodic fluctuation, that is, the resonance frequency of the casing 2 has fluctuated from the reference value (S5: YES), the degree of the periodic deviation amount is large. Determine whether it is below a predetermined level. Specifically, the CPU 30A determines the periodic deviation amount such as the maximum value of the deviation amount D within the half cycle (= T3 / 2), the center value of the maximum and minimum values, or the average value of the deviation amounts D. It is determined whether or not a value corresponding to the degree (hereinafter referred to as period shift amount) is equal to or less than a specified value (S6). The specified value is, for example, a periodic shift amount that does not substantially affect the image quality, and is obtained in advance through experiments or the like and stored in the RAM 30C.

  CPU30A complete | finishes this motor control process, without changing the rotational speed of each motor M1-M3, when it is judged that the amount of period deviation is below a regulation value (S6: YES). As a result, even when the resonance is small and does not affect the image quality, it is possible to uniformly suppress the image forming operation from being slowed by the rotation speeds of the motors M1 to M3 being lowered.

  When the CPU 30A determines that the amount of period deviation is larger than the specified value (S6: NO), the CPU 30A controls the motor driver 31 to change the rotational speeds of the process motor M1 and the fixing motor M2, thereby changing the excitation frequency. A change process for separating from the changed resonance frequency is executed (S7). Specifically, the CPU 30A changes the rotational speeds of the process motor M1 and the fixing motor M2 to a speed that is slower than the reference speed V0 by a predetermined speed. If there is a margin between the reference speed V0 and the maximum settable speed, the rotational speed of the process motor M1 and the fixing motor M2 may be changed to a speed higher than the reference speed V0. Further, the rotational speed of the polygon motor M3 is also changed according to the rotational speeds of the process motor M1 and the fixing motor M2. CPU30A may display on the display part 34, when the said change process is performed.

  CPU30A returns to S2 again after execution of a change process, and repeats the process from S2-S5. As a result, the influence of resonance can be suppressed and the motor control process can be terminated to the extent that the amount of period deviation becomes equal to or less than the specified value (S6: YES). The determinations in S5 and S6 may be made from the detection signal SG1 having only one cycle T3, but the determination accuracy may be improved by making the determination from the detection signals SG1 having a plurality of cycles T3.

(Effect of this embodiment)
As the sheet 3 is discharged to the sorter unit 20, the resonance frequency at which the casing 2 resonates may fluctuate. On the other hand, according to the present embodiment, it is determined whether or not the resonance frequency has changed from the reference value. If it is determined that the resonance frequency has changed, the rotational speeds of the motors M1 and M2 are changed, and the motors M1 and M2 are changed. The frequency of the excitation force applied to the casing 2 by the rotation of M2 is separated from the changed resonance frequency. Thereby, even if the resonant frequency of the casing 2 fluctuates, it is possible to suppress the resonance.

  Further, a plurality of marks Q are sequentially formed on the belt 7 or the like, and each mark is a difference between a mark detection position X1 based on the detection signal SG1 of the mark sensor 8 and a predetermined mark reference position X0. It is determined whether or not there is a periodic variation in the deviation amount D. Here, when the resonance frequency of the casing 2 fluctuates and resonance occurs, a periodic fluctuation appears in the shift amount D of each mark Q accordingly. Therefore, as in the present embodiment, it is possible to indirectly determine whether or not the resonance frequency of the casing 2 has changed by determining whether or not the deviation amount D is periodically changed. Moreover, the existing mark sensor 8 used for color misregistration correction can be used.

  Furthermore, each mark Q of the pattern P has an angle of 45 degrees with the sub-scanning direction. Therefore, it can be determined whether the resonance frequency at which the casing resonates fluctuates with the same accuracy without deviation, regardless of whether the resonance vibration direction is the main scanning direction or the sub-scanning direction.

<Embodiment 2>
7 to 10 show the second embodiment. The difference from the first embodiment is the configuration of the printer and sorter unit and the contents of the motor control process, and the other points are the same as in the first embodiment. Therefore, the same reference numerals as those in the first embodiment are given and the redundant description is omitted, and only different points will be described next.

(Printer configuration)
As shown in FIGS. 7 and 8, the printer 40 of this embodiment does not include the mark sensor 8 and the cleaning unit 9. The sorter unit 41 has a plurality of discharge trays 42 arranged in a vertical direction, and a sheet sensor 43 is provided for each discharge tray 42. The sheet sensor 43 is provided with, for example, an arm whose angle changes in accordance with the number of discharged sheets 3 on the corresponding discharge tray 42, and provides the controller 30 with a detection signal SG2 corresponding to the angle of the arm. The sheet sensor 43 is an example of a detection unit.

(Motor control processing)
For example, when the communication unit 32 receives a print job or image data from an external device, the controller 30 executes a motor control process shown in FIG. Specifically, the CPU 30A reads the motor control program from the ROM 30B, and first measures the total number of sheets 3 discharged to the discharge tray 42 based on the detection signal SG2 from the sheet sensor 43 (S11). Next, the CPU 30A reads the corresponding table shown in FIG. 10 (S12).

  This correspondence table is information indicating the correspondence between the number rank and the rotation speeds of the motors M1 and M2. The number of sheets in the correspondence table is obtained by ranking the total number of sheets 3 discharged to the sorter unit 41 for each predetermined number of sheets. Each time the number rank to which the total number belongs differs, the weight of the sorter unit 41 changes, and accordingly, the resonance frequency of the casing 2 changes. The vibration frequency of the motors M1 and M2 depending on the rotation speed of the corresponding table and the resonance frequency corresponding to the number of corresponding ranks do not coincide with each other and do not resonate. . In addition, the magnitude relationship of each rotational speed is V0> V1> V2.

  Based on the read correspondence table, the CPU 30A selects a rotation speed corresponding to the number rank to which the measured number of S11 belongs (S13), and controls the motor driver 31 to rotate the motors M1 and M2 at the selected rotation speed. (S14), and the motor control process is terminated. As a result, the weight on the upper surface side of the casing 2 increases in accordance with the number of sheets 3 discharged to the sorter unit 41. As a result, even when the resonance frequency of the casing 2 fluctuates, the rotation of the motors M1 and M2 The speed is changed according to the number of measured sheets, and the excitation frequency can be separated from the changed resonance frequency. In addition, when the rotational speed is lower than the reference speed V0 by a predetermined speed or more, and when the number of measured sheets increases, the rotational speed may be returned to the reference speed V0 or higher.

(Effect of this embodiment)
In accordance with the number of sheets 3 discharged to the discharge tray 42, the weight on the upper surface side of the casing 2 increases, and as a result, the resonance frequency at which the casing 2 resonates varies. Therefore, according to the present embodiment, it is possible to determine whether or not the resonance frequency at which the casing 2 resonates fluctuates based on whether or not the number of sheets 3 discharged to the discharge tray 42 has changed.

<Other embodiments>
The present invention is not limited to the embodiments described with reference to the above description and the drawings, and for example, the following various aspects are also included in the technical scope of the present invention.

  In the above embodiment, as an example of the image forming apparatus, a multiple transfer tandem printer is used. However, the image forming apparatus is not limited to this, and may be a multiple development type (multi-rotation type, single-pass type) printer. Further, the image forming apparatus is not limited to the laser exposure method, but may be an LED method or a monochrome printer. Further, the image forming apparatus is not limited to the electrophotographic system, but may be an ink jet system or a dot marking system in which the image forming unit side moves. The image forming apparatus is not limited to a printer, and may be a multifunction machine having a plurality of functions such as a scanner function, a facsimile machine, or the like. In short, the image forming apparatus may be an image forming apparatus that includes a drive source and that may cause the casing to resonate due to the rotation of the drive source.

  In the above-described embodiment, the controller 30 that executes each process by the CPU 30A is taken as an example of the control unit. However, the control unit is not limited to this, and a configuration in which each process of motor control processing is executed by a plurality of CPUs, a configuration in which each process is executed only by a hardware circuit such as an ASIC (Application Specific Integrated Circuit), or a hardware circuit In addition, the configuration may be such that each process is executed by both the CPU and the CPU. For example, a configuration in which part or all of the motor control processing is executed by a separate CPU or hardware circuit may be used.

  In the first embodiment, the case where the resonance frequency of the casing 2 fluctuates as a result of discharging a large amount of the sheet 3 to the sorter unit 20 mounted on the upper surface of the casing 2 has been described as an example. However, the present invention is not limited to this. For example, even when a sorter unit 20 is not mounted, when a heavy object such as a dictionary is placed on the upper surface of the casing 2, the resonance frequency of the casing 2 varies. There is.

  In the first embodiment, the CPU 30A causes the process unit 10 to form each mark Q using only one process cartridge. However, the present invention is not limited to this, and the CPU 30 </ b> A may be configured such that the process unit 10 sequentially forms the marks Q by using a plurality of process cartridges. With this configuration, the mark formation process can be executed using the color misregistration correction pattern as it is. However, in this configuration, since the detection signal SG1 may include an influence due to so-called color misregistration, such as misalignment between process cartridges, motor control processing is performed after performing known color misregistration correction in advance. Is preferably performed.

  In the first embodiment, the mark Q has a linear shape with an angle of 45 degrees with the sub-scanning direction. However, the mark Q is not limited to this, and may be an angle other than 45 degrees, for example, an angle formed with the sub-scanning direction is 90 degrees. However, if the mark Q has a straight line portion inclined obliquely with respect to the sub-scanning direction, the resonance of the casing 2 is not only in the case where the resonance vibration direction is in the sub-scanning direction but also in the main scanning direction. It can be determined whether the frequency has fluctuated.

  In the said Embodiment 2, the sheet | seat sensor 43 was mentioned as an example as an example of a detection part. However, the detection unit is not limited to this, and may be, for example, a counter that counts the number of discharged sheets 3. Further, as shown by a one-dot chain line in FIG. 7, a weight sensor 50 that outputs a detection signal corresponding to a change in the weight of the sorter unit 40 that changes in accordance with the discharge amount of the sheet 3 may be used. Specifically, a load cell or a strain gauge may be used. In addition, the configuration may be such that the weight sensor 50 is provided on the upper surface of the printer 1 without providing the sorter unit 41 and a detection signal corresponding to the weight of the object placed on the upper surface is given to the controller 30.

  DESCRIPTION OF SYMBOLS 1,40: Printer 2: Casing 5,15: Roller 6: Belt unit 8: Mark sensor 9: Cleaning part, 10: Process part 12: Exposure part 14: Fixing device 30: Controller 31: Motor driver 43: Sheet sensor M1 : Process motor M2: Fixing motor Q: Mark SG1, SG2: Detection signal

Claims (7)

A housing,
A drive source provided in the housing;
An image forming unit that operates by driving the drive source to form an image on an object;
A drive unit that drives the drive source and changes the drive speed of the drive source;
A detection unit that outputs a detection signal according to a change in a resonance frequency at which the housing resonates;
A control unit,
The control unit, based on a detection signal of the detection unit, a determination process for determining whether or not the resonance frequency at which the housing resonates has fluctuated from a reference value;
When it is determined in the determination process that the resonance frequency has fluctuated, the drive unit is caused to change the drive speed of the drive source, and the vibration frequency applied to the housing by the drive source is changed. An image forming apparatus having a configuration for executing a change process for separating the fluctuation frequency from the resonance frequency after the fluctuation. The image forming apparatus according to claim 1,
The image forming unit is configured to form an image by moving relative to the object,
The detection unit is a sensor that outputs a signal corresponding to a position of an image formed on the object as the detection signal,
The controller is
Causing the image forming unit to perform a mark forming process for sequentially forming a plurality of marks along the direction of relative movement on the object;
In the determination process, if there is a periodic variation in the shift amount of each mark, which is a difference between the mark detection position based on the detection signal of the sensor and a predetermined reference position of the mark, the resonance An image forming apparatus that determines that the frequency has fluctuated. The image forming apparatus according to claim 1, wherein:
Each of the marks is an image forming apparatus having a straight line portion inclined obliquely with respect to the relative movement direction. The image forming apparatus according to any one of claims 1 to 3,
An image forming apparatus, wherein an angle formed between the direction of relative movement and the straight line portion is 45 degrees. The image forming apparatus according to claim 1,
The image forming unit is configured to form an image on a sheet,
On the upper surface of the housing, a discharge tray for discharging a sheet on which an image is formed by the image forming unit is provided,
The detection unit is a sensor that outputs a signal corresponding to the number of sheets discharged to the discharge tray as the detection signal,
The image forming apparatus, wherein the control unit determines that the resonance frequency has fluctuated when the number of sheets has changed based on the detection signal of the sensor. The image forming apparatus according to claim 1,
The detection unit is a sensor that outputs, as the detection signal, a signal corresponding to the weight of the mounted object on the housing,
The image forming apparatus, wherein the control unit determines that the resonance frequency has changed when the weight is changed based on the detection signal of the sensor by the determination process. An image forming unit that operates by driving a driving source provided in a housing to form an image on an object, a driving unit that drives the driving source and changes a driving speed of the driving source, and the housing A computer having an image forming apparatus comprising: a detection unit that outputs a detection signal according to a change in a resonant frequency that resonates;
Based on a detection signal of the detection unit, a determination process for determining whether a resonance frequency at which the casing resonates has fluctuated from a reference value;
When it is determined in the determination process that the resonance frequency has fluctuated, the drive unit is caused to change the drive speed of the drive source, and the vibration frequency applied to the housing by the drive source is changed. A drive source control program for executing a change process for separating the fluctuation frequency from the changed resonance frequency.

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