JP4852966B2 - Image forming apparatus and state determination method - Google Patents

Description

  The present invention relates to an image forming apparatus that performs image formation, and a state determination method that determines the state of a unit mounted on the image forming apparatus.

  Conventionally, a charged photoreceptor is exposed based on image data, a toner image is formed on the photoreceptor by development processing, the toner image is transferred to a recording medium, and then the toner image on the recording medium is fixed by a fixing device. An image forming apparatus that forms an image on a recording medium by fixing the image is known.

  In such an image forming apparatus, the life of the fixing device is short, and it is difficult to design a fixing device having a life equivalent to the life of the entire image forming apparatus. Normally, the fixing device is a replacement part in the image forming apparatus. ing. Further, not only the fixing device but also other devices such as a developing device constituting the image forming apparatus have different lifetimes and are replaced parts. In recent years, a fixing device or the like has been unitized so that a user can attach or detach the fixing device or the like with respect to the image forming apparatus. These units are provided with a rotating body such as a fixing roller and a developing roller. In the image forming apparatus, an image is formed by driving these rotating bodies with a motor.

  Against this background, whether each unit is installed in the image forming apparatus, whether each unit has reached the end of its life (whether it has been time to replace the unit), or whether each unit has an abnormality There is an increasing demand for quickly and easily grasping the state of units such as, etc. and responding quickly.

On the other hand, there is known an image forming apparatus that determines whether a unit is mounted / not mounted by measuring the driving power of a motor (see, for example, Patent Document 1).
JP 2002-72773 A

  However, in the above conventional image forming apparatus, it is only possible to determine whether or not the unit is mounted on the main body of the image forming apparatus, and it is possible to determine the state of other units, for example, the life or abnormality of the unit. I couldn't. In addition, when a dedicated circuit for measuring power is provided, there is a problem that a dedicated interface with the MCU is required and the cost is increased.

  SUMMARY An advantage of some aspects of the invention is that it provides a highly reliable image forming apparatus and state determination method that can easily determine the state of a unit at low cost. .

In order to achieve the above object, an image forming apparatus according to the present invention is a unit for forming an image, and a motor for driving a rotating body provided in a unit detachable from the apparatus main body; A pulse generating means for generating a pulse in accordance with the rotation of the motor; a detecting means for detecting the rotational speed of the motor based on the pulse generated by the pulse generating means; the rotational speed detected by the detecting means; Difference calculation means for calculating a difference from the target rotation speed of the motor, modulation pulse generation means for generating a pulse having a pulse width modulated based on the difference calculated by the difference calculation means, and generation by the modulation pulse generation means on the basis of the pulse, a driving means for driving the motor, a pulse width data indicating the pulse width of the generated by the modulation pulse generation means pulses, a first threshold value, before When the same comparison result is repeated a predetermined number of times by comparing each of the second threshold value greater than the first threshold value and the third threshold value greater than the second threshold value, or the same comparison result appears during the predetermined period In the case where the number of performed times exceeds a predetermined number, when the same comparison result indicates that the pulse width data is less than or equal to the first threshold, it is determined that the unit is not installed, and the same comparison result is When the pulse width data is greater than the second threshold and less than or equal to the third threshold, it is determined that the unit has a lifetime, and the same comparison result indicates that the pulse width data is greater than the third threshold. when large, viewed contains a determination unit, a determining that an abnormality has occurred in the unit, at least one of the predetermined period and a predetermined number of times, the accumulated use time of the motor, the species of the motor , And it is capable of changing in response to at least one type of the unit.

As described above, the unit state is judged by comparing the pulse width data indicating the pulse width of the pulse generated by the modulation pulse generating means with each of the plurality of threshold values, and thus dedicated to measuring power. Therefore, the state of the unit can be easily determined at low cost by using the pulses generated for driving the motor. Furthermore, it is possible to determine the state of the unit in more detail and with high reliability by using a plurality of threshold values. In this way, when comparing the pulse width data and each of the plurality of threshold values, when the same comparison result continues for a predetermined number of times, instead of judging the state of the unit by only one comparison result, Alternatively, when the same comparison result appears many times during the predetermined period, the unit state can be determined with higher reliability by determining the unit state based on the comparison result. In addition, if any of the accumulated motor usage time, motor type, or unit type changes, the motor rotation may be affected (the load state changes). Is changed, the state of the unit can be determined with high accuracy.

  The detection means may detect, for example, a count value obtained by counting the pulse width in synchronization with the clock signal as the rotation speed, or a value obtained by performing a predetermined calculation on the counted count value as the rotation speed. It may be detected.

  The detection unit may detect at least one of a pulse width and a pulse interval of the pulse generated by the pulse generation unit as the rotation speed.

  If both the pulse width and the pulse interval are detected as the number of rotations, the rotation of the motor can be accurately controlled even when the number of pulses generated by the pulse generating means with the rotation of the motor is small.

  In addition, the detection means includes an average value or moving average value of a plurality of pulses generated by the pulse generating means, and an average value or moving average value of pulse intervals of the plurality of pulses generated by the pulse generating means, At least one of these may be detected as the rotation speed.

  By controlling using the averaged or moving averaged in this way, even if a variation (mechanical error) occurs in the pulse generated by the pulse generating means, the variation can be reduced. In addition, the unit state can be determined with higher accuracy by using the pulse generated by the modulation pulse generating means using such data for the unit state determination.

Further, the three threshold values, device environment, and images changeably can be isosamples according to at least one type of recording medium formed.

  For example, the load on the rotating body may become heavier as the environment of the apparatus is higher in temperature and humidity. Therefore, the state of the unit can be determined with high accuracy by changing the threshold in consideration of the influence of temperature and humidity. Further, when the recording medium is an OHP sheet, a paper medium, or a paper medium, a load fluctuation may occur depending on the type of the recording medium such as the paper quality. Therefore, the state of the unit can be determined with high accuracy by changing the threshold depending on the type of the recording medium. Note that the environment of the apparatus may be an environment inside the apparatus or an environment around the apparatus main body.

  In addition, when the determination unit determines that the state of the unit is not mounted, life, or abnormality, a processing unit that performs at least one of notification of the determination result and rotation stop of the motor Can be further provided.

  By notifying the determination result, the user can easily grasp the state of the unit and can take an appropriate response.

  In addition, if the unit is abnormal, if the motor is automatically stopped, a fire due to heat generation can be quickly prevented. If the unit is at the end of its life, image formation is stopped by stopping the motor rotation. Image quality deterioration can be prevented.

The state determination method of the present invention is based on pulses generated in accordance with the rotation of a motor for driving a rotating body provided in a unit that forms an image and is detachable from the apparatus main body. , Detecting the rotational speed of the motor, calculating a difference between the detected rotational speed and the target rotational speed of the motor, generating a pulse having a pulse width modulated based on the calculated difference, and generating the generated pulse And a pulse width data indicating a pulse width of the generated pulse, a first threshold value, a second threshold value greater than the first threshold value, And when the same comparison result continues for a predetermined number of times by comparing each of the third threshold values greater than the second threshold value, or when the number of times that the same comparison result appears during the predetermined period exceeds the predetermined number of times When the same comparison result indicates that the pulse width data is less than or equal to the first threshold value, it is determined that the unit is not attached, and the same comparison result indicates that the pulse width data indicates the second threshold value. If it is larger and less than or equal to the third threshold value, it is determined that the unit is at the end of its life, and if the same comparison result indicates that the pulse width data is greater than the third threshold value, an abnormality has occurred in the unit. And at least one of the predetermined period and the predetermined number of times can be changed according to at least one of the cumulative use time of the motor, the type of the motor, and the type of the unit .

  Since the state determination method of the present invention also operates in the same manner as the image forming apparatus of the present invention, the state of the unit can be easily determined at low cost.

  As described above, according to the present invention, there is an excellent effect that the state of the unit can be easily determined at low cost.

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

  FIG. 1 is a cross-sectional view showing the configuration of the image forming apparatus according to the present embodiment. A photosensitive drum 2 is rotatably disposed inside the housing 1 of the image forming apparatus. For example, the photosensitive drum 2 is formed of a conductive cylinder having a surface coated with a photosensitive layer made of OPC or the like. The photosensitive drum 2 is rotationally driven at a predetermined process speed along the arrow direction by a corresponding DC motor (hereinafter referred to as a motor).

  The surface of the photosensitive drum 2 is charged to a predetermined potential by a charging roll 3 serving as a charger disposed almost immediately below the photosensitive drum 2, and then a laser beam (LB) is output by a ROS (Raster Output Scanner) 4. Image exposure is performed. Thereby, an electrostatic latent image is formed on the surface of the photosensitive drum 2.

  The developing device 5 includes developing devices 5Y, 5M, 5C, and 5K for each color of yellow (Y), magenta (M), cyan (C), and black (K), which are arranged along the circumferential direction. . The electrostatic latent image formed on the photosensitive drum 2 is developed by the developing devices 5Y, 5M, 5C, and 5K for each color when the developing device 5 is driven and rotated by a motor to form a toner image of a predetermined color. Is done.

  In the case of printing a color image, charging, exposure, and development processes are repeated four times on the surface of the photosensitive drum 2 corresponding to each color of YMCK. As a result, toner images corresponding to the respective colors of YMCK are sequentially formed on the surface of the photosensitive drum 2.

  When the series of steps for one color is completed, the developing device 5 is rotationally driven at a predetermined timing, and the developing devices 5Y, 5M, 5C, and 5K corresponding to the color to be developed are opposed to the photosensitive drum 2. Move to.

  The toner images sequentially formed on the photosensitive drum 2 are superposed on each other on the intermediate transfer belt 6 at the primary transfer position where the intermediate transfer belt 6 as an intermediate transfer member is wound around the outer periphery of the photosensitive drum 2. Thus, primary transfer is performed by the primary transfer roll 7. The YMCK toner images transferred in multiple onto the intermediate transfer belt 6 are secondarily transferred collectively onto the recording paper 9 fed at a predetermined timing by the secondary transfer roll 8.

  The secondary transfer roll 8 as a load unit is disposed at a position where the distance on the circumference of the intermediate transfer belt 6 is close to the downstream side of the photosensitive drum 2, and the secondary transfer roll 8 is the intermediate transfer belt. 6 is configured to reduce or increase the driving speed of the photosensitive drum 2 in response to the timing of contact with the photosensitive drum 6.

  Further, the intermediate transfer belt 6 is stretched by a plurality of rolls, is configured to circulate and move at a predetermined process speed, and to be driven and rotated by the photosensitive drum 2. The intermediate transfer belt 6 includes a wrap-in roll 15 that specifies the wrap position of the intermediate transfer belt 6 on the upstream side in the rotational direction of the photosensitive drum 2 and a toner image formed on the photosensitive drum 2 as an intermediate transfer belt. A primary transfer roll 7 to be transferred onto 6, a wrap-out roll 16 for specifying the wrap position of the intermediate transfer belt 6 on the downstream side of the wrap position, and a backup that contacts the secondary transfer roll 8 via the intermediate transfer belt 6. The roll 17, the first cleaning backup roll 19 facing the cleaning device 18 of the intermediate transfer belt 6, and the second cleaning backup roll 20 are stretched with a predetermined tension. The intermediate transfer belt 6 is stretched by these plural rolls 7, 15 to 17, 19, and 20. In this embodiment, the cross-sectional shape of the intermediate transfer belt 6 is stretched to reduce the size of the image forming apparatus. However, it is comprised so that it may become a flat and elongate substantially trapezoid shape.

  The recording paper 9 is fed from a paper feeding unit 10 disposed at the lower part of the housing 1 by a pickup roll 11 and is fed in a state of being fed one by one by a feed roll 12 and a retard roll 13, and a registration roll. 14 is conveyed to the secondary transfer position of the intermediate transfer belt 6 while being synchronized with the toner image transferred onto the intermediate transfer belt 6. The secondary transfer roll 8 is configured to come in contact with and separate from the surface of the intermediate transfer belt 6 at a predetermined timing.

  Further, the cleaning device 18 for the intermediate transfer belt 6 includes a scraper 24 disposed so as to contact the surface of the intermediate transfer belt 6 stretched by the first cleaning backup roll 19 and a second cleaning backup roll 20. And a cleaning brush 25 disposed so as to be in pressure contact with the surface of the stretched intermediate transfer belt 6. Residual toner and paper dust removed by the scraper 24 and the cleaning brush 25 are collected inside the cleaning device 18. The cleaning device 18 is supported so as to be able to swing counterclockwise in the figure about the swing shaft 26, and is retracted to a position spaced from the surface of the intermediate transfer belt 6, and is also predetermined. At this timing, it is configured to abut on the surface of the intermediate transfer belt 6.

  Further, the recording paper 9 on which the toner image is transferred from the intermediate transfer belt 6 is conveyed to the fixing device 27, and the toner image is applied onto the recording paper 9 by heat and pressure by the heating roll and pressure roll of the fixing device 27. It is fixed. In the case of single-sided printing, the recording paper 9 is discharged as it is onto a discharge tray 29 provided on the top of the housing 1 by a discharge roll 28.

  On the other hand, in the case of double-sided printing, the recording paper 9 on which the toner image has been fixed by the fixing device 27 is not discharged as it is onto the discharge tray 29 by the discharge roll 28, but the rear end of the recording paper 9 by the discharge roll 28 The discharge roll 28 is reversely rotated in a state in which is held. At this time, the conveyance path of the recording paper 9 is switched to the double-sided paper conveyance path 30, and again with the conveyance roll 31 disposed in the double-sided paper conveyance path 30, the recording paper 9 is turned upside down. The sheet is conveyed to the secondary transfer position of the intermediate transfer belt 6 and an image is formed on the back surface of the recording paper 9.

  Further, in this image forming apparatus, a manual feed tray 32 can be attached to the side surface of the housing 1 so as to be freely opened and closed. An arbitrary size and type of recording paper 9 placed on the manual feed tray 32 is fed by the paper feed roll 33 and is transferred to the secondary transfer position of the intermediate transfer belt 6 via the transport roll 31 and the registration roll 14. By being conveyed, it is possible to form an image on the recording paper 9 of any size and type.

  It should be noted that the surface of the photosensitive drum 2 after the toner image transfer process is completed is cleaned by a cleaning blade 35 of a cleaning device 34 disposed obliquely below the photosensitive drum 2 every time the photosensitive drum 2 rotates once. As a result, residual toner and the like are removed to prepare for the next image forming process.

  Further, in this image forming apparatus, an ADC sensor 23 including a reflective photosensor for detecting the density of a patch formed on the intermediate transfer belt 6 is disposed on the intermediate transfer belt 6. Based on the patch density and position detected by the ADC sensor 23, the toner density is controlled and the positional deviation is controlled.

  Further, the image forming apparatus is provided with an environment sensor 44 that measures the temperature and humidity inside the image forming apparatus. A PWM threshold, which will be described later, is set according to the temperature and humidity detected by the environmental sensor 44. The environment sensor 44 may be provided outside the apparatus.

  In this image forming apparatus, each function of the photosensitive drum 2, the developing device 5, the cleaning device 18, the fixing device 27, etc. is unitized so as to improve the maintainability while achieving the downsizing of the device. Yes. Thus, each unit can be easily attached to and detached from the image forming apparatus main body by opening the upper cover 22 of the image forming apparatus.

  FIG. 2 is a block diagram showing the configuration of the motor control system in this image forming apparatus.

  Inside the image forming apparatus, there is provided a control unit 50 that controls each unit constituting the image forming apparatus. The control unit 50 also includes a photosensitive unit including the photosensitive drum 2, a recording medium transport unit including a feed roll 12, a retard roll 13, a resist roll 14, and the like, and a developing device having developing units 5Y, 5M, 5C, and 5K. DC motor that applies rotational force to the rotating body of each unit such as a developing unit such as 5, a cleaner unit having cleaning backup rolls 19 and 20, and a fixing device 27 (fixing device unit) having a heating roll and a pressure roll. (Motor) The rotational speed of 60a-60d is controlled. In FIG. 2, only four motors 60a to 60d are shown, but actually, a motor corresponding to each unit is installed.

  The control unit 50 includes a CPU 52, a clock generation unit 54, and a processing unit 56. The clock generator 54 generates a 10 MHz clock signal, for example, and outputs it to the CPU 52 and the processor 56. The CPU 52 is bus-connected to the processing unit 56 and the like, and controls the processing unit 56 and the like in synchronization with the clock signal input from the clock generation unit 54. The processing unit 56 has a plurality of digital processing circuits (in FIG. 2, four digital processing circuits 58a to 58d are shown in accordance with the motors 60a to 60d) according to each unit, and an ASIC (Application Specific Integrated Circuit). ) As one chip.

  Each of the digital processing circuits 58a to 58d is the same circuit, operates in synchronization with a clock signal input from the clock generation unit 54 to the processing unit 56, and each has a pulse generator (FG = Function Generator) 62a to 62d. In accordance with the pulses output from 62d, the motors 60a to 60d are controlled by PWM (Pulse Width Modulation) via the drivers 64a to 64d.

  The drivers 64a to 64d supply current to the motors 60a to 60d under the control of the digital processing circuits 58a to 58d, and the motors 60a to 60d rotate according to the current supplied from the drivers 64a to 64d. The pulse generators 62a to 62d include, for example, a Hall element (see, for example, FIG. 9) that rotates coaxially with the rotation axis of the motors 60a to 60d, a light emitting element and a light receiving element (not shown), and the like. A pulse is generated according to the rotation of 60d and output to the digital processing circuits 58a to 58d.

  Hereinafter, in the case where any one of a plurality of components such as the motors 60a to 60d is indicated without being specified, the suffixes a to d at the end are omitted, and are simply abbreviated as “motor 60” or the like.

  FIG. 3 is a block diagram showing a detailed configuration of the digital processing circuit 58.

  The digital processing circuit 58 includes a counter 70, a register 72, a difference calculation unit 74, an addition unit 76, a multiplication unit 78, and a modulation pulse generation unit 80.

  The counter 70 measures the pulse input from the pulse generator 62 by counting the pulse width in synchronization with the clock signal, and uses the count value (digital data) as the detected number of rotations to calculate a difference. And output to the CPU 52. For example, as shown in FIG. 4, a pulse generator 62 generates a pulse having a frequency of 500 Hz and a duty ratio of 50% in synchronization with the rotation of the motor, and a clock signal of 10 MHz is sent from the clock generator 54 to the digital processing circuit 58. When input, the counter 70 counts the pulse width of 1 mS (half cycle) in synchronization with the 10 MHz clock signal, and the count value 10000 (1 [mS] ÷ (1/10 [MHz] = 10000, where (10000 is a decimal number) is output to the CPU 52 and the difference calculation unit 74. At this time, the counter 70 converts the count value into, for example, 16-bit digital data and outputs it.

  The register 72 stores an initial value, a set value, and the like input via a user interface (not shown) and the CPU 52, and outputs a predetermined value to each unit constituting the digital processing circuit 58. The values stored in the register 72 include a target frequency (target rotational speed) of the motor 60, a start signal that defines a pulse at the start of the motor 60, a feedback rate (FB rate) described later, and a setting value for the modulation pulse generator 80. There is.

Specifically, the register 72 outputs a pulse width value (count value) corresponding to the target frequency of the motor 60 to the difference calculation unit 74 as 16-bit data, or defines a pulse when the motor 60 is started. The start signal to be output is output to the adder 76, the set value for the modulation pulse generator 80 is output to the modulation pulse generator 80 by the setting control signal, and the FB rate is output to the multiplier 78. Or Note that the FB rate is a rate used for rounding an output value of an adder 76, which will be described later, by multiplication in order to suppress motor shake (wah flutter). Here, 1/2 ⁿ (n is 1 to 16) Integer).

  The value stored in the register 72 can be changed via a user interface (not shown) or the counter 70 and the CPU 52.

  The difference calculation unit 74 compares the count value input from the counter 70 with the pulse width value (count value) corresponding to the target frequency input from the register 72, and the rotation frequency detected by the pulse generator 62. The difference between the (rotational speed) and the target frequency is calculated and output to the adding unit 76. The difference between the detected rotation frequency and the target frequency is a difference indicating that the detected rotation frequency is slower than the target frequency (a difference on the plus side) and a difference indicating that the detected rotation frequency is faster than the target frequency. (Difference on the minus side) and output to the adder 76 as 18-bit data.

  The plus side difference is a value of 0 or more, and the minus side difference is a value of 0 or less. That is, when the detected rotation frequency is slower than the target frequency, the minus side difference is 0, and when the detected rotation frequency is faster than the target frequency, the plus side difference is 0.

  When the plus side difference and the minus side difference are input from the difference calculating unit 74, the adding unit 76 cumulatively adds the plus side difference and the minus side difference together, and adds it to the multiplying unit 78 as 24-bit data. Output. However, when the start signal is input from the register 72, that is, in a predetermined period (initial control period) when the motor 60 is started, the addition unit 76 and the difference on the plus side input from the difference calculation unit 74 and A predetermined value corresponding to the activation signal is output to the multiplier 78 instead of the result of cumulative addition of the minus side difference.

The multiplier 78 multiplies the 24-bit data input from the adder 76 and the FB rate (1/2 ⁿ ) input from the register 72 and outputs the data to the modulation pulse generator 80 as 20-bit data, for example. To do.

  The modulation pulse generation unit 80 generates a pulse width-modulated pulse based on the 20-bit data input from the multiplication unit 78 and the setting control signal (a signal indicating a predetermined setting value) input from the register 72, and the driver 64 Output for. However, when the motor 60 is started, a predetermined pulse may be output in a predetermined period (initial control period) by a setting control signal input from the register 72. For example, during the initial control period, the modulation pulse generator 80 outputs a pulse having a duty ratio of less than 50% at least once, thereby reducing the overshoot of the rotation frequency with respect to the target frequency of the motor 60.

  Note that the registers 72 of the digital processing circuits 58a to 58d store individual initial values and set values under the control of the CPU 52. By individually changing the values stored in the individual registers 72, the control unit 50 can perform different controls on the motors 60a to 60d.

  The digital processing circuit 58 further includes a comparator 82, a threshold table 84, and a comparison result register 86.

  Data indicating the pulse width of the pulse generated by the modulation pulse generation unit 80 (hereinafter referred to as pulse width data) is input to the comparator 82 from the modulation pulse generation unit 80. Each time the pulse width data is input, the comparator 82 compares the input pulse width data with a plurality of threshold values set in the threshold value table 84 and outputs the comparison result to the comparison result register 86. . The pulse width data may be indicated by time or may be indicated by a duty ratio.

  The plurality of threshold values set in the threshold value table 84 are based on whether or not a unit including a rotating body to be driven by the motor 100 is mounted on the image forming apparatus, whether the unit life has occurred, or whether an abnormality has occurred in the unit. In this embodiment, three threshold values TH1, TH2, and TH3 are set. However, the magnitude relationship among the thresholds TH1, TH3, and TH3 is TH1 <TH2 <TH3 here. This is because the motor 60 has a tendency that the pulse width of the pulse to the motor 60 becomes larger as the load becomes heavier. Here, the threshold is set stepwise to detect the load state applied to the motor 60. , So as to determine the state of the unit.

  The three threshold values TH1, TH2, and TH3 are appropriately set by the CPU 52 according to the environment (temperature and humidity) information of the image forming apparatus output from the environment sensor 44. Specifically, a memory (not shown) that stores a table defining threshold values to be used according to temperature and humidity is connected to the CPU 52 via a bus, and the CPU 52 reads the corresponding threshold values from this table, The threshold value table 84 of the digital processing circuit 58 is set.

  FIG. 5 is an example of a plurality of predetermined threshold tables and a selection table for selecting which threshold table to use among the plurality of threshold tables according to temperature and humidity. For example, when the temperature is not less than 0 degrees and less than 5 degrees and the humidity is less than 70%, the threshold table A is designated in the selection table, so the CPU 52 refers to the threshold table A and designates the threshold table A. Each of the threshold values a, b, c is set in the threshold value table 84 of the digital processing circuit 58. That is, a is set as the threshold TH1, b is set as the threshold TH2, and c is set as the threshold TH3 in the threshold table 84. Similarly, when the temperature is 5 degrees or more and less than 10 degrees and the humidity is less than 80%, each of the threshold values d, e, and f specified in the threshold value table B is set in the threshold value table 84.

  For example, a motor that rotates the photosensitive drum causes a load fluctuation due to a change in temperature and humidity of the toner in the developing device. That is, the load tends to increase as the environment inside the apparatus is higher in temperature and humidity. Therefore, it is preferable to set a threshold in consideration of the influence of temperature and humidity. In addition, the load variation due to temperature and humidity is not a variation that is represented by a simple linear function, but tends to increase exponentially. Therefore, in the present embodiment, as shown in FIG. 5, combinations of a plurality of threshold values are stored in a table according to the temperature and humidity, and the threshold values are set according to the detection result of the environmental sensor 44. Like that.

  In addition, since the threshold value is different for each unit, the selection table and the threshold value table are determined and stored for each unit.

  The comparison result register 86 has a 3-bit area (bit0, bit1, bit2), and a comparison result compared with the above three threshold values is stored in the 3-bit area. Specifically, when the pulse width data is equal to or less than the threshold value TH1, the flag (1) is set in the first bit (bit0) of the comparison result register, and the other two bits are not set (set to 0). When the pulse width data exceeds the threshold value TH2 and is equal to or less than the threshold value TH3, a flag is set for the second bit (bit1) of the comparison result register, and the other two bits are not set. When the pulse width data exceeds the threshold value TH3, the third bit (bit 2) of the comparison result register is flagged, and the other two bits are not flagged. With this comparison result register 86, the level of the pulse width of the pulse generated by the modulation pulse generator 80 can be grasped. The CPU 52 determines the state of the unit based on the state of the flag in the comparison result register 86.

  Next, the PWM control operation of the digital processing circuit 58 will be described.

  When the motor 60 rotates, the pulse generator 62 generates a pulse corresponding to the rotation of the motor 60 and outputs it to the counter 70. The counter 70 counts a count value corresponding to the pulse width of the pulse input from the pulse generator 62 and outputs the count value to the difference calculation unit 74. The difference calculation unit 74 compares the count value input from the counter 70 with the count value corresponding to the target frequency of the motor 60 input from the register 72, and calculates a plus-side difference and a minus-side difference.

  For example, the count value 10000dec (2710hex) is assumed to be a count value corresponding to the target frequency, and the count value counted from the pulse output from the pulse generator 62 according to the rotation of the motor is 11111dec (2B67hex). In this case, since the detected rotation frequency is slower than the target frequency, 2B67hex-2710hex = 457hex is calculated as a positive side difference, and 0 is calculated as a negative side difference. This difference is used as follows and fed back as a pulse width.

  The adding unit 76 cumulatively adds the plus side difference and the minus side difference calculated by the difference calculating unit 74 to calculate 24 bit data, and outputs the data to the multiplying unit 78. The multiplier 78 rounds the 24-bit data input from the adder 76 with the FB rate input from the register 72 and outputs the data to the modulation pulse generator 80 as 20-bit data so that a motor waffle does not occur.

  The modulation pulse generation unit 80 generates a pulse width modulated pulse based on the 20-bit data input from the multiplication unit 78 and the setting control signal input from the register 72, and outputs the pulse to the driver 64. The driver 64 drives the motor 60 according to the pulse input from the modulation pulse generator 80.

  As a result, when the rotation speed of the motor is slow, a pulse with the pulse width increased by the difference is output, and when the rotation speed of the motor is fast, a pulse minus the difference by the pulse width is output. .

  However, when the motor 60 is started, the register 72 outputs a start signal to the adder 76, a predetermined pulse is output from the modulation pulse generator 80 to the driver 64, and the motor 60 is driven.

  Next, a process for determining the state of the unit that is the target of driving the motor based on the pulse generated by the modulation pulse generator 80 will be described.

  6 and 7 are flowcharts showing the flow of the unit state determination processing routine executed by the CPU 52. FIG.

  In step 100, the temperature level is acquired from the environment sensor 44, and in step 102, the humidity level is acquired from the environment sensor 44.

  In step 104, thresholds TH1, TH2, and TH3 for the corresponding motor 60 are obtained from the acquired temperature and humidity level. Specifically, the threshold value table is selected from the selection table shown in FIG. 5, and the threshold values TH1, TH2, and TH3 specified in the selected threshold value table are read.

  In step 106, the threshold values TH 1, TH 2, TH 3 obtained above are set in the threshold value table 84 of the digital processing circuit 58.

  In step 108, the number of times X determined to be abnormal is set in a register (not shown) in the CPU 52 in accordance with the life (cumulative usage time) of the corresponding motor 60. Here, PV (Print Volume), which is always counted by the image forming apparatus, may be used as the accumulated usage time. In the present embodiment, the comparison result between the above three threshold values and the pulse width data indicating the pulse width of the pulse generated by the modulation pulse generator 80 is sampled ten times continuously, and the pulse indicated by each sampled comparison result When the same pulse width level among the width levels exceeds the set number of times X, the unit state is determined based on the pulse width level. This number X depends on the life of the motor 60. The CPU 52 may calculate the number of times X according to the life, or may store the number of times X according to the life in a predetermined memory, and read and set it. Here, since the number of times of sampling is 10, X is an integer of 10 or less.

  In step 110, the driving of the DC motor is started.

  In step 112, four variables ctr1, ctr2, ctr3, and Samp ctr are set to zero. Here, the variable ctr1 is a variable for counting the number of times that the pulse width data is equal to or less than the threshold value TH1. The variable ctr2 is a variable for counting the number of times that the pulse width data exceeds the threshold value TH2 and becomes equal to or less than the threshold value TH3. The variable crt3 is a variable for counting the number of times that the pulse width data exceeds the threshold value TH3. The variable “Samp ctr” is a variable for counting the number of times of sampling.

  In step 114, it is determined whether or not Nms has elapsed since the start of driving of the DC motor. If Nms has elapsed, the process proceeds to step 116. Here, Nms is a time equal to or longer than the initial control time.

  In steps 116, 120, and 124, the state of the flag in the comparison result register 86 is determined. As described above, the three bits of the comparison result register 86 include the latest comparison between the pulse width data input from the modulation pulse generator 80 by the comparator 82 and the three threshold values TH1, TH2, and TH3 set as described above. The result is stored. In step 116, it is determined whether or not a flag is set in bit 0 of the comparison result register 86. If it is determined that the flag 0 is set in bit 0 of the comparison result register 86, the pulse width data is equal to or less than the threshold value TH1, and therefore, 1 is added to the variable ctr1 in step 118.

  If it is determined in step 116 that no flag is set in bit 0 of the comparison result register 86, the process proceeds to step 120 and it is determined whether or not a flag is set in bit 1 of the comparison result register 86. Here, if it is determined that the flag is set in bit 1 of the comparison result register 86, the pulse width data exceeds the threshold value TH2 and is equal to or less than the threshold value TH3. Therefore, in step 122, 1 is added to the variable ctr2. To do.

  If it is determined in step 120 that no flag is set in bit 1 of the comparison result register 86, the process proceeds to step 124, and it is determined whether or not a flag is set in bit 2 of the comparison result register 86. If it is determined that the flag is set in bit 2 of the comparison result register 86, the pulse width data exceeds the threshold value TH3, and 1 is added to the variable ctr3 in step 126.

  If it is determined in step 124 that no flag is set in bit 2 of the comparison result register 86, the pulse width data exceeds the threshold value TH1 and is equal to or less than the threshold value TH2 (the unit is normally mounted and has reached the end of its life. The values of the variables of ctr1 to ctr3 are not updated.

  After incrementing the variable in steps 118, 122, 126, or if a negative determination is made in step 124, the process proceeds to step 128 and the variable Samp Ctr is incremented by one.

  In step 130, it is determined whether or not the variable Samp Crt is 10 or more. If it is determined that the variable Samp Crt is less than 10, the process returns to step 114 and the above process is repeated. That is, the CPU 52 samples the comparison result of the comparator 82 ten times.

  If it is determined in step 130 that the variable Samp Crt has become 10 or more, the process proceeds to step 132 (FIG. 7). In step 132, it is determined whether or not the variable ctr1 exceeds the number of times X. If it is determined that the variable ctr1 exceeds X, it is determined that the unit is not attached to the image forming apparatus because the pulse width is too small, that is, the load on the motor 60 is too light. Then, a message indicating that the unit is not mounted is displayed on a user interface (not shown) such as a touch panel display.

  If it is determined in step 132 that the variable ctr1 does not exceed X, the process proceeds to step 136, and it is determined whether or not the variable ctr2 exceeds X. Here, if it is determined that the variable ctr2 exceeds the number of times X, it is determined that the pulse width is large, that is, the load of the motor 60 is getting heavier and the life of the unit is approaching. A warning message is displayed on the user interface indicating that the unit is approaching the end of its life.

  If it is determined in step 136 that the variable ctr2 does not exceed X, the process proceeds to step 140, and it is determined whether or not the variable ctr3 exceeds X. Here, if it is determined that the variable ctr3 exceeds the number X, it is determined that an abnormality has occurred in the unit because the pulse width is too large, that is, the load on the motor 60 is abnormally heavy, and the process proceeds to step 142. Display a message to the user interface that an error has occurred in the unit.

  If it is determined in step 140 that the variable ctr3 does not exceed X, none of the variables ctr1 to ctr3 exceeds X times, that is, the pulse width data exceeds the threshold TH1 and is equal to or less than the threshold TH2. Accordingly, the unit is normally mounted and is considered to be operating normally without reaching the end of its life, and no message is displayed, and the image forming operation is continued.

  After displaying a message in steps 134, 138, 142, or if a negative determination is made in step 140, the process proceeds to step 144, and 0 is set to variables ctr1, ctr2, ctr3, and Samp ctr.

  In step 146, it is determined whether or not the motor 60 is kept on. While the image forming operation is not completed, a negative determination is made here, and the routine proceeds to step 148.

  In step 148, as in step 108, the number of times X determined to be abnormal is set in a register (not shown) in the CPU 52 according to the life (use period) of the corresponding motor 60. That is, after the ten times of sampling, since the life of the motor has also changed, the value of X is newly set accordingly.

  After setting X, the process proceeds to step 114 and the same processing as described above is repeated.

  Here, it is considered that there is no significant change in temperature and humidity during one image forming operation period, and the thresholds TH1, TH2, and TH3 are not changed after step 146, but the present invention is not limited to this. For example, assuming that the temperature and humidity change greatly, after affirmative determination is made in step 146, the process may return to step 100 to newly set a threshold value.

  If the image forming operation is completed in step 146, a negative determination is made to turn off the motor 60, and this processing routine ends.

  In the above description, the number of times the same comparison result (same pulse width level) appears during the sampling period of 10 times, and the unit state is determined based on the comparison result. When the same comparison result continues for a predetermined number of times without being limited to the period, the state of the unit may be determined based on the comparison result.

  Here, specific numerical values will be described as examples.

  For example, assume that the motor rotation is 500 Hz, and the PWM frequency is PWM controlled at 4 KHz, which is 8 times the motor rotation basic frequency. At this time, one cycle is 250 μS. Three types of threshold values, threshold value TH1 = 20 μS, threshold value TH2 = 125 μS, and threshold value TH3 = 200 μS, are set in threshold value table 84 for the pulse width in one cycle.

  When the pulse width data equal to or smaller than the threshold TH1 is detected a predetermined number of times or more in the sampling period, or continuously detected a predetermined number of times, it is determined that the motor drive unit is unloaded (not mounted).

  When the pulse width data exceeding the threshold TH2 and not exceeding the threshold TH3 is detected a predetermined number of times in the sampling period or continuously detected a predetermined number of times, the load unit driven by the motor 60 has a large torque. Therefore, it is determined that the load life is approaching (it is time for replacement).

  Further, when the pulse width data exceeding the threshold value TH3 is detected a predetermined number of times or more in the sampling period, or continuously detected a predetermined number of times, it can be determined that the load unit driven by the motor 60 is abnormal.

  When the state where the pulse width data exceeds the threshold value TH3 continues for a predetermined period or longer, abnormal heat generation of the motor 60 may occur. Therefore, in order to prevent a secondary failure, the digital processing circuit 58 uses a command ( The motor 60 may be stopped regardless of the command. Or you may issue the command which stops the motor 60 from CPU52.

  As described above, the pulse width data indicating the pulse width of the pulse generated by the modulation pulse generator 80 is compared with a plurality of threshold values, and the unit state is determined based on the comparison result. The unit status can be easily determined at a low cost.

  In the above embodiment, since the comparison unit 82 for comparing the thresholds is provided in the digital processing circuit 58 (ASIC), it is more expensive to stabilize the detection circuit than when an analog element is used. It is not necessary to provide a separate circuit, and it is not necessary to provide a completely separate control circuit. That is, in the above embodiment, the circuit provided in the digital processing circuit 58 can make a determination by comparing the pulse width data with a plurality of threshold values, so that the cost can be reduced. Moreover, since it is a digital process, it can process with high precision. Furthermore, even when different units are driven by the same motor, a threshold value can be set individually for each unit (depending on usage), and the state of the unit can be determined with high accuracy.

  In addition, since it is possible to determine the life of the unit based on the actual rotation detection result, it is possible to extend the replacement display, which has conventionally relied on predictive control, to the actual life.

  Even if an abnormality occurs in the unit, it is possible to take appropriate measures such as stopping the motor or replacing the unit before damaging the protection circuit such as the fuse.

  In the above embodiment, the example in which the threshold value is changed according to the temperature and humidity detected by the environment sensor 44 has been described. However, when the variation due to the environment is small, the temperature and humidity are not considered and It is possible to determine the state of the unit only by setting a threshold value determined in (1).

  In addition, when the torque of the rotating body of the unit changes according to the type (paper quality) of the recording paper, the threshold value may be changed for each type of recording paper.

  In the above embodiment, the pulse width data indicating the pulse width is compared with a plurality of threshold values, and the unit state is determined based only on the comparison result. The state of the unit may be determined in consideration of each actual use period.

  In the above-described embodiment, an example in which the number of times X determined to be abnormal is set according to the life (cumulative usage time) of the motor 60 has been described. However, the present invention is not limited to this. The number of times X may be determined and set according to the type of unit to be driven.

  In the above-described embodiment, the example in which the comparison result sampling period (number) is set to 10 has been described. However, the present invention is not limited to this. Can do.

  In the above-described embodiment, the example in which each of the unit mounting state, the unit lifetime, and the unit abnormal state is determined by comparing with a plurality of threshold values has been described. Only one or any two of the state, the unit life, and the unit abnormal state may be compared with a plurality of threshold values. Further, when determining in more detail about the abnormal state, it is also possible to determine by setting a plurality of thresholds for determining the abnormal level (mild, moderate, severe, etc.). With regard to the lifetime, the lifetime level such as whether the lifetime has not yet been reached, is approaching the lifetime, or has reached the lifetime can be determined based on a plurality of threshold values.

  In the above embodiment, in the PWM control, the counter 70 measures the pulse input from the pulse generator 62 by counting the pulse width in synchronization with the clock signal. However, the present invention is not limited to this. For example, the count value can be calculated and output to the difference calculation unit 74 as follows.

  For example, as shown in FIG. 8, for a pulse with a duty ratio of 50% output from the pulse generator 62, the counter 70 measures the pulse width and pulse interval by counting them in synchronization with the clock signal, Each count value (digital data) is output to the difference calculation unit 74. Thus, the counter 70 can count two types of count values for the pulses output from the pulse generator 62 by counting the data x from the pulse width and counting the data y from the pulse interval. The data twice as many as the number of pulses can be counted. By using each of the two types of count values to generate a pulse in the modulation pulse generation unit 80, the control unit 50 can be used even when the number of pulses from the pulse generator 62 accompanying the rotation of the motor 60 is small. The rotation of 60 can be accurately controlled. In addition, the unit state can be determined with higher accuracy by using the pulse generated by the modulation pulse generation unit 80 using such rotation speed data for unit state determination. Note that these two types of count values may be used individually in the modulation pulse generator 80, or both may be averaged.

  As shown in FIG. 9, when the Hall element 90 having three holes is provided in the pulse generator 62, the rotating shaft 92 of the Hall element 90 rotates together with the rotating shaft of the motor 60. When rotating, the pulse generator 62 outputs three pulses. Here, as shown in FIG. 8, when the counter 70 counts the pulse width and the pulse interval in synchronization with the clock signal with respect to the pulses output from the pulse generator 62, the number of rotations relative to the rotation of the motor 60 is obtained. Six data can be counted.

  As described above, the data indicating the number of rotations of the motor 60 can be increased more than the number of pulses. Therefore, even when the number of pulses from the pulse generator 62 accompanying the rotation of the motor 60 is small, the control unit 50 can Can be accurately controlled.

  Further, each of the value obtained by averaging the pulse widths of the three pulses by the Hall element 90 and the value obtained by averaging the pulse intervals of the three pulses may be used in the modulation pulse generation unit 80. By performing PWM control using the averaged values in this way, even if variations (mechanical errors) occur in the pulses generated by the pulse generator 62, the variations can be reduced. Further, the unit state can be determined with higher accuracy by using the pulse generated by the modulation pulse generation unit 80 based on the average value of the pulse width and the pulse interval in this way for the unit state determination.

  Furthermore, as shown in FIG. 10, for the pulses output from the pulse generator 62, the counter 70 counts the count value for the pulse width by, for example, moving average the pulse width every three pulses, A mechanical error may be diffused. Similarly, for the pulses output from the pulse generator 62, the counter 70 may count the count value for the pulse interval by, for example, moving average the pulse interval for every three pulses. Furthermore, the count value may be counted by combining moving averages of the pulse width and the pulse interval. By controlling using the moving average value in this way, even if variations (mechanical errors) occur in the pulses generated by the pulse generator 62, the variations can be reduced.

  Further, the unit state can be determined with higher accuracy by using the pulse generated by the modulation pulse generation unit 80 based on the moving average value of the pulse width and the pulse interval in this way for the unit state determination. .

1 is a cross-sectional view illustrating a configuration of an image forming apparatus according to an exemplary embodiment. 2 is a block diagram illustrating a configuration of a motor control system in the image forming apparatus. FIG. It is the block diagram which showed the detailed structure of the digital processing circuit. It is explanatory drawing explaining measurement of the count value by a counter. It is an example of a selection table for selecting which threshold value table to use from a plurality of predetermined threshold value tables according to temperature and humidity, and a plurality of predetermined threshold value tables. It is the flowchart which showed the flow of the determination processing routine of the unit state performed with CPU. FIG. 7 is a flowchart showing the flow of a unit state determination processing routine executed by the CPU, and is a continuation of FIG. It is explanatory drawing explaining the method for a counter to measure two types of count values from one pulse. It is a front view of the Hall element which has three holes. It is explanatory drawing explaining the method of counting a count value by moving average a pulse width and a pulse interval for every three pulses with respect to the pulse output from a pulse generator.

Explanation of symbols

2 Photosensitive drum 3 Charging roll 5 Developing device 6 Intermediate transfer belt 7 Primary transfer roll 8 Secondary transfer roll 9 Recording paper 18 Cleaning device 27 Fixing device 44 Environmental sensor 50 Control unit 52 CPU
54 clock generation unit 58 digital processing circuit 60 motor 62 pulse generator 64 driver 70 counter 72 register 74 difference calculation unit 76 addition unit 78 multiplication unit 80 modulation pulse generation unit 82 comparator 84 threshold table 86 comparison result register

Claims (6)

A motor for driving a rotating body provided in a unit for forming an image and detachable from the apparatus main body;
Pulse generating means for generating a pulse in accordance with rotation of the motor;
Detecting means for detecting the rotational speed of the motor based on the pulse generated by the pulse generating means;
Difference calculation means for calculating a difference between the rotation speed detected by the detection means and the target rotation speed of the motor;
Modulated pulse generating means for generating a pulse having a pulse width modulated based on the difference calculated by the difference calculating means;
Driving means for driving the motor based on the pulses generated by the modulation pulse generating means;
Pulse width data indicating the pulse width of the pulse generated by the modulation pulse generating means, a first threshold value, a second threshold value greater than the first threshold value, and a third threshold value greater than the second threshold value. When the same comparison result continues for a predetermined number of times compared with each other, or when the same comparison result appears within a predetermined period exceeds the predetermined number of times, the same comparison result indicates that the pulse width data is When the threshold is equal to or less than 1, the unit is determined not to be mounted, and when the same comparison result indicates that the pulse width data is greater than the second threshold and equal to or less than the third threshold, Determining means for determining that the unit is at the end of life, and when the same comparison result indicates that the pulse width data is greater than the third threshold value, an abnormality has occurred in the unit;
Only including,
An image forming apparatus in which at least one of the predetermined period and the predetermined number of times can be changed according to at least one of an accumulated usage time of the motor, a type of the motor, and a type of the unit.   The image forming apparatus according to claim 1, wherein the detection unit detects at least one of a pulse width and a pulse interval of a pulse generated by the pulse generation unit as the rotation speed.   The detection means includes at least an average value or moving average value of pulse widths of a plurality of pulses generated by the pulse generation means, and an average value or moving average value of pulse intervals of the plurality of pulses generated by the pulse generation means. The image forming apparatus according to claim 1, wherein one is detected as the rotation speed. The image forming apparatus according to claim 1, wherein the three threshold values can be changed according to at least one of an environment of the apparatus and a type of a recording medium on which an image is formed. Processing means for performing at least one of notification of the determination result and stop of rotation of the motor when the determination means determines that the state of the unit is not installed, life, or abnormality; the image forming apparatus according to any one of claims 1 to 4 is provided. The number of rotations of the motor is detected based on pulses generated according to the rotation of a motor for driving a rotating body provided in a unit that forms an image and is detachable from the apparatus main body. And calculating a difference between the detected rotation speed and the target rotation speed of the motor, generating a pulse having a pulse width modulated based on the calculated difference, and driving the motor based on the generated pulse. A state determination method in an image forming apparatus,
The pulse width data indicating the pulse width of the generated pulse is compared with each of the first threshold value, the second threshold value greater than the first threshold value, and the third threshold value greater than the second threshold value. When the same comparison result continues for a predetermined number of times, or when the same comparison result appears within a predetermined period exceeds the predetermined number of times, the same comparison result indicates that the pulse width data is less than or equal to the first threshold value. Sometimes it is determined that the unit is not installed, and the same comparison result indicates that the unit is at the end of its life when the pulse width data is greater than the second threshold and less than or equal to the third threshold. And when the same comparison result indicates that the pulse width data is greater than the third threshold, it is determined that an abnormality has occurred in the unit ;
A state determination method in which at least one of the predetermined period and the predetermined number of times can be changed according to at least one of the accumulated usage time of the motor, the type of the motor, and the type of the unit .

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