JP2008250152A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce manufacturing cost and size of an image forming apparatus. <P>SOLUTION: When a printing instruction is given, a CPU 13 drives a developing unit by a stepping motor M before executing a printing action and a value of load on the stepping motor M is calculated. Then, the CPU 13 judges whether or not the value of the load is within a prescribed range which is stored beforehand. Then, when the value of the load is not in the prescribed range, the CPU 13 makes a display part 50 display an error message. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus in which a stepping motor is used as a drive mechanism.

  In image forming apparatuses such as copiers, printers, and MFPs (Multi Function Peripheral) which are multifunctional devices of these, a stepping motor may be used as a drive source. In many cases, such an image forming apparatus employs a constant current driving method as a stepping motor control method. In the constant current method, a relatively high voltage is applied to the stepping motor at the start of driving until the target current flows, and after the current flowing through the stepping motor reaches the target current, PWM (Pulse Width Modulation) control is performed. This is a method for maintaining the target current. In other words, after the current flowing through the stepping motor reaches the target current, the current flowing through the stepping motor is continuously monitored, and a switching method that repeats ON / OFF of voltage application at high speed is adopted, so that the target current is reduced. Control to keep is realized.

  The stepping motor driven by the constant current method employed in the image forming apparatus is operated without causing the motor to step out even when the load on the part where the stepping motor is used in the apparatus is maximized. The current assumed when the load on the part is maximum is set as the target current. Note that step-out is a phenomenon in which when the period of the pulse signal of the drive voltage applied to the stepping motor becomes too short, the operation of the rotor of the stepping motor cannot be followed and the motor does not rotate normally. To tell.

Various techniques have been disclosed for such image forming apparatuses.
For example, Japanese Laid-Open Patent Publication No. 7-67016 discloses a technique for calibrating the rotational torque of the motor to an optimum state using the rotational speed and direction of the motor as parameters in the image processing apparatus.

  Further, in the cited document 2 (Japanese Patent Laid-Open No. 11-180003), the image forming apparatus detects a change in the rising edge of the driving current of the motor or counts the number of times of chopping of the driving current. A technique for detecting the state of rotation and controlling the drive current according to the detected state is disclosed.

In the image forming apparatus, in addition to such a motor, various sensors are provided to detect the occurrence of a jam in the paper feed mechanism, whether or not an ink cartridge is mounted in the image forming unit, and the like.
Japanese Patent Laid-Open No. 7-67016 Japanese Patent Laid-Open No. 11-180003

  In the image forming apparatus as described above, as in the case of a general apparatus, reduction of manufacturing cost is regarded as important, and there has been a demand for further miniaturization by reducing the number of components of the image forming apparatus as much as possible. .

  The present invention has been made in view of such problems, and an object of the present invention is to reduce the manufacturing cost and reduce the size of the image forming apparatus.

  An image forming apparatus according to one aspect of the present invention is an image forming apparatus that forms an image on a sheet, a member that is driven during image formation, a stepping motor that drives the member, The stepping motor includes control means for controlling and controlling supply of electric power for driving the member, storage means for storing information relating to the load of the stepping motor, and display means for displaying information, the control means comprising: The load for driving the member of the stepping motor is calculated based on the drive current waveform for the stepping motor, and the display based on the comparison result between the calculated load and the information stored in the storage unit The means is controlled.

  An image forming apparatus according to another aspect of the present invention is an image forming apparatus that forms an image on a sheet, a member that is driven during image formation, a stepping motor that drives the member, Control means for controlling the supply of electric power for driving the member to the stepping motor, storage means for storing information relating to the load of the stepping motor, and the control means for driving the member Power is supplied to the stepping motor, a load for driving the member of the stepping motor is calculated based on a drive current waveform for the stepping motor, the calculated load, and information stored in the storage means The state of the member is determined based on the comparison result.

  The image forming apparatus further includes a detection unit that detects a voltage value corresponding to a current value supplied to the stepping motor, and the control unit is based on a change in the voltage value detected by the detection unit. Thus, it is preferable to calculate a load for driving the member of the stepping motor.

  In the above image forming apparatus, it is preferable that the control unit calculates the load based on a current value at an inflection point in a rising region in the drive current waveform for the stepping motor.

  The image forming apparatus also fixes an image on a transfer sheet by sandwiching and conveying the sheet on which the developer has been transferred and an image forming unit that forms the image on the sheet by transferring the developer onto the sheet. It is preferable that the fixing member further includes a fixing unit, and the member is a roller for nipping and conveying the transfer sheet in the fixing unit.

  The image forming apparatus further includes display means for displaying information, and the control means supplies power to the stepping motor during a period when the image forming operation is not performed in the image forming means, It is preferable to execute a load calculation and control of the display unit based on the comparison result.

  The image forming apparatus according to the first aspect preferably further includes an intermediate transfer member, and the member is a developing device for transferring the developer onto a sheet.

  In the above image forming apparatus, the developing unit is configured to be able to mount a cartridge for storing a developer, the storage unit stores an upper limit value and a lower limit value related to the load of the stepping motor, and the control unit When the load on the stepping motor is equal to or higher than the upper limit value, the first information is displayed on the display unit, and when the load on the stepping motor is equal to or lower than the lower limit value, the first information is displayed. It is preferable to display the second information different from.

  In the image forming apparatus, the member is preferably a roller for nipping and conveying a sheet on which an image is formed.

  The image forming apparatus further includes display means for displaying information, a paper feed cassette for storing the paper, and a paper discharge roller for discharging the paper on which the image has been formed to the outside of the image forming apparatus, The storage means stores information relating to the load of the stepping motor corresponding to the time from when the paper is discharged from the paper feed cassette to the outside of the image forming apparatus via the paper discharge roller. The load of the stepping motor until the paper is discharged from the paper feed cassette to the outside of the image forming apparatus via the paper discharge roller is calculated and stored in the storage and the calculated load. It is preferable to control the display means based on a comparison result with information.

  According to the present invention, in the image forming apparatus, a load required to drive a member driven during image formation is calculated, and the display content of the display unit is based on the calculated load value. Can be

  In other words, according to the present invention, when an error occurs in the member as described above and a load more than usual is required to drive the member, this is the stepping motor that drives the member. If this load is calculated, it is reflected in an error display or the like on the display unit without installing a separate sensor or the like.

  Therefore, the number of parts required in the image forming apparatus can be suppressed, and the cost and size of the apparatus can be reduced.

  Embodiments of the present invention will be described below with reference to the drawings. In the following description, the same parts and components are denoted by the same reference numerals. Their names and functions are also the same unless otherwise noted.

[First Embodiment]
In the present embodiment, a case where the image forming apparatus according to the present invention is applied to a tandem digital color copying machine (hereinafter referred to as a copying machine) will be described. However, the image forming apparatus according to the present invention is not limited to a copying machine, and may be a printer, a facsimile machine, an MFP that is a complex machine thereof, or the like as long as the image forming apparatus uses a stepping motor as a drive mechanism. . Further, the printing method is not limited to the tandem method, and is not limited to the digital method. Furthermore, it may be a monochrome machine instead of a color machine.

  In a color tandem type image forming apparatus, four color image forming sections each including a developing device are arranged along an intermediate transfer belt (which is an intermediate transfer member carrying a toner image formed by the image forming section). It is installed and configured. Then, each color toner image formed in each image forming unit is transferred to the intermediate transfer belt (primary transfer), and a multicolor image is formed by superimposing the respective color toners. Further, the image superimposed on the intermediate transfer belt is transferred onto a sheet as a printing medium (secondary transfer), and output through a fixing process.

  FIG. 1 is a schematic cross-sectional view showing an outline of a hardware configuration of a copying machine 1 according to the present embodiment to which the image forming apparatus according to the present invention is applied. The copier 1 is a tandem digital color copier, and sequentially superimposes four color toners of yellow (Y), magenta (M), cyan (C), and black (K) to form a color image. Form.

  Referring to FIG. 1, the copying machine 1 according to the present embodiment includes an image reading unit 10, a paper transport unit 20, an image forming unit 30, and a paper storage unit 40.

  The image reading unit 10 includes a loading table 3 for setting a document, a document table glass 11, a conveyance unit 2 that automatically conveys documents set on the loading table 3 one by one to the document table glass 11, And a discharge table 4 for discharging the read document. Further, the document reading unit 10 includes a scanner (not shown). The scanner moves parallel to the platen glass 11 by a scan motor. The scanner has an exposure lamp that illuminates the document, a reflection mirror that changes the direction of the reflected light from the document, a mirror that changes the optical path from the reflection mirror, a lens that collects the reflected light, and an electrical signal depending on the received reflected light A photoelectric conversion element such as a three-row (R, G, B) CCD (Charge Coupled Device) is included.

  The document transported by the transport unit 2 is set on the document table glass 11 and is exposed and scanned when the scanner moves in parallel with the document table glass 11. The reflected light from the document is converted into an electrical signal by the photoelectric conversion element and input to the image forming unit 30.

  The image forming unit 30 is suspended by a plurality of rollers 32, 33, and 34 so as not to be loosened, and these rollers rotate counterclockwise (in the direction of arrow A in FIG. 1) in FIG. And an intermediate transfer belt 31 that is an endless belt rotating in the same direction, and yellow (Y), magenta (M), cyan (C), and black (K) colors arranged along the intermediate transfer belt 31 at predetermined intervals. Image forming units 21Y, 21M, 21C, and 21K (denoting these as representative image forming units 21) corresponding to toner and including developing units, developing units included in the respective image forming units 21, a photoconductor, After the transfer rollers 25Y, 25M, 25C, and 25K paired via the intermediate transfer belt 31 (representatively referred to as transfer rollers 25) and the toner image transferred to the intermediate transfer belt 31 are transferred to the sheet Fix Including a fixing device 36, a controller 100, including CPU (Central Processing Unit) 13 (see FIG. 3), and a memory 101 for storing data and the like used in the execution of the program or programs executed by the controller 100. The image forming units 21Y, 21M, 21C, and 21K are configured so that cartridges that store toners corresponding to the respective colors can be mounted.

  The paper storage unit 40 includes a paper feed cassette 41 that stores the paper S, which is a printing medium, and the paper transport unit 20 includes rollers 42, 43, 35, 37 for transporting the paper S from the paper feed cassette 41, and A paper discharge tray 38 for discharging printed paper is included.

  The controller 100 reads out and executes a program from the memory 101 based on an instruction signal input from an operation panel (not shown) or the like, and controls the above-described units. Further, the controller 100 may be provided with a timer such as a timer, and execute the program when a predetermined time is measured. The controller 100 and the memory 101 may be provided in the image reading unit 10 or the paper transport unit 20 other than the image forming unit 30.

  The controller 100 executes the above-described program, performs predetermined image processing on the image signal input from the image reading unit 10 or an external device, and performs color conversion to each color of yellow, magenta, cyan, and black. Create a signal. The image color data for cyan, the image color data for magenta, the image color data for yellow, and the image color data for black created by the controller 100 for each color are the controller 100 to the exposure unit of the image forming unit 21.

  The exposure device outputs a laser beam to the photoconductor based on the image data input from the controller 100, so that the surface of the uniformly charged photoconductor is exposed according to the image data, and the electrostatic latent image is generated. It is formed. A developing bias voltage is applied to the developing roller, and a potential difference is generated between the developing roller and the latent image potential of the photoreceptor. In this state, charged toner is supplied to form a toner image on the surface of the photoreceptor. The toner image formed on the surface of the photosensitive member is transferred to the intermediate transfer belt 31 as an image carrier by a constant voltage or constant current transfer roller 25. This is called primary transfer.

  The toner image primarily transferred to the intermediate transfer belt 31 is transferred onto the paper S conveyed from the paper feed cassette 41 by the roller 34. This is called secondary transfer. The toner image secondarily transferred to the paper is fixed on the paper by the fixing device 36 and is discharged to the paper discharge tray 38 as an electrophotographic image.

  Of the above-described configuration of the copying machine 1, as a driving mechanism, a mechanism for driving the image forming unit 21, particularly a photosensitive member (hereinafter referred to as a PC (Photo Conductor) driving unit), or a mechanism for driving the fixing device 36 (hereinafter, referred to as a driving unit). The toner is supplied to a mechanism that drives the rollers 42, 43, 35, and 37 of the paper transport unit 20 and a mechanism that supplies toner of the image forming unit 21 from the toner unit to the photosensitive member. A stepping motor can be used as a mechanism for this purpose (hereinafter referred to as a toner replenishing drive unit). In FIG. 1, one specific example of the stepping motor in which the stepping motor M1 is used for the fixing drive unit, one specific example of the stepping motor in which the stepping motor M2 is used in the PC drive unit, and the stepping motor M3 is the toner replenishment drive unit. One specific example of the stepping motor used in the above. In the present invention, the drive mechanism in which the stepping motor is used is not limited to the above mechanism, and may be used in another mechanism. Further, any one or two of the above mechanisms may be used. In the present embodiment, it is assumed that the stepping motor used is a two-phase bipolar type.

Here, the driving of the stepping motor will be described.
FIG. 2 is a diagram for explaining a relationship between a change in load torque necessary for driving the stepping motor with time and a constant current value (the above target current) to be set. In FIG. 2, the former load torque is indicated by “A”, and the torque corresponding to the latter constant current value is indicated by “B”.

  Referring to FIG. 2, the load torque indicated by A increases along with the passage of time, and the load on the apparatus main body becomes maximum depending on the conditions in the use environment or the like (the right end of A in the figure). Therefore, in general, in the constant current drive method, even if the usage environment is such a condition and the load torque becomes maximum, a sudden change occurs and the load torque temporarily increases. Even in such a case, a constant current value is set so that the motor can be driven with a torque corresponding to the maximum load torque (with a certain margin added) in order to operate the motor reliably without stepping out. (See B in FIG. 2).

  In the copying machine 1 according to the present embodiment, the driving of the stepping motor is controlled by the constant current driving method described above. FIG. 3 is a specific example of an equivalent circuit diagram of a drive circuit for controlling the driving of a stepping motor, and is a diagram showing a specific example of a circuit diagram of a drive circuit of a two-phase bipolar type stepping motor.

  Referring to FIG. 3, in the stepping motor drive circuit according to the present embodiment, the CPU 13 is connected to the input terminal of the motor driver circuit 12 connected to the stepping motor M (the general term for the above stepping motors M1 to M3). Is done. The motor driver circuit 12 outputs an excitation signal to the stepping motor M in accordance with a control signal from the CPU 13 and controls driving (rotation) of the stepping motor M. The CPU 13 controls the torque of the stepping motor M by changing the voltage at the Vref terminal of the motor driver circuit 12. In FIG. 3, the circuit configuration in which the voltage at the Vref terminal of the motor driver circuit 12 is set by a control signal from the CPU 13 is shown, but it may be set by dividing the resistance.

  Further, one end of the output terminal of the motor driver circuit 12 is grounded (GND), and the sense terminal which is the other end is connected to the CPU 13 via the current detection resistor 14 and the amplifier circuit 15. With this circuit configuration, a current corresponding to the voltage difference (Vref potential) between the voltage at the Vref terminal and the grounded terminal is supplied to the stepping motor M. Further, the CPU 13 detects the voltage between the sense terminal and the grounded terminal obtained by the current flowing out from the sense terminal and the current detection resistor 14, that is, the potential of the sense terminal. By detecting a change in the potential at the sense terminal in the CPU 13, a change in the current flowing through the stepping motor M can be detected.

  The CPU 13 is connected to a display unit 50 (not shown in FIG. 1) provided in the copying machine 1. As will be described later, the CPU 13 displays information based on the value of the current flowing through the stepping motor M on the display unit 50.

  Next, with reference to FIG. 4, the change of the increase / decrease rate of the current (referred to as motor current) flowing through the stepping motor M will be described. FIG. 4 shows changes in the motor current value in the four types shown as (A) to (D).

  First, referring to FIG. 4A, when a new excitation signal is input from the motor driver circuit 12 to the stepping motor M, or an excitation signal is input by switching from the currently excited phase to another phase. Then, current starts to flow through the motor coil, and the motor current value increases (corresponding to the “rising region” in FIG. 4).

  When detecting that the motor current has increased to the set current (target current), the CPU 13 outputs a control signal to the motor driver circuit 12 to output an excitation signal that repeats ON / OFF of the motor current. As a result, the motor current is maintained at the set current as shown as “constant current control region” in FIG.

  In the motor current waveform, the point where the excitation value is newly input or the excitation value is input after switching from the currently excited phase to another phase and the current value starts to rise is called the `` rising point '' A region that rises from the rising point to the set current (target current) is referred to as a “rising region”, and a region in which the set current is maintained is referred to as a “constant current control region”.

  In the rising region, immediately after the excitation signal is input, the increase / decrease rate (increase rate) of the motor current is low, and the increase / decrease rate gradually increases. And as the constant current control region is approached, the increase / decrease rate tends to decrease. In each example shown in FIGS. 4A to 4D, the increase / decrease rate is shown to have a positive increase rate. However, the characteristics of the stepping motor M and the stepping motor M Depending on the load torque required to drive the, the increase / decrease rate may be a negative value, resulting in a decrease rate.

  Furthermore, FIG. 4 shows the relationship between the point at which the increasing / decreasing rate decreases and the motor output at the constant current value currently set for the load torque necessary for driving the stepping motor in the apparatus. A description will be given with reference to FIGS. The point at which the rate of increase / decrease changes in the rising region (the rate of increase / decrease temporarily decreases in FIGS. 4A to 4D) is referred to as an “inflection point”.

  When the motor output at the constant current value that is currently set is large with respect to the load torque required to drive the stepping motor in the copying machine 1, in other words, the motor output at the constant current value that is currently set. On the other hand, when the required load torque is light, as shown in FIG. 4C, the inflection point is closer to the rising point than the constant current control region (at the start of driving and at the start of the constant current control region). Occurs closer to the driving start side than the middle).

  When the motor output at the currently set constant current value is appropriate for the required load torque in the copying machine 1, in other words, the load necessary for the motor output at the currently set constant current value. When the torque becomes heavier, as shown in FIG. 4B, the inflection point occurs closer to the constant current control region than the time when the inflection point appears in FIG. 4C.

  When the motor output at the constant current value currently set is small with respect to the load torque required for the copying machine 1, that is, the load torque required for the motor output at the currently set constant current value is heavier. Then, the inflection point becomes closer to the constant current control region than the position shown in FIG. 4B (becomes appearing at a later time), and if it becomes too heavy, it is shown in FIG. 4A. Thus, it does not occur before reaching the constant current control region.

  Note that when the motor output at the currently set constant current value is extremely small with respect to the load torque required for the copying machine 1, that is, the load torque required for the motor output at the currently set constant current value. If it becomes heavier (than the state shown in FIG. 4A), as shown in FIG. 4D, the time from the rising of the current waveform until reaching the constant current control region is shortened. This is because the motor output at the constant current value currently set with respect to the required load torque in the copying machine 1 is too small, that is, when the current constant current value is set to the required load torque, This indicates that the output is not driven. This can be said to be a motor drive in an unreliable state.

  In the copying machine 1 of the present embodiment, the position of the inflection point of the motor current at the start of motor driving (the time at which the inflection point occurs from the start of motor driving or the motor current value at the time of occurrence). Thus, the driving state (driving environment) of the stepping motor is determined, and a message is displayed or the target current value for the motor current is determined accordingly.

  FIG. 5 is a block diagram showing a specific example of a functional configuration for determining the state of each stepping motor in copying machine 1 of the present embodiment. The functions shown in FIG. 5 are functions mainly formed in the CPU 13 when the CPU 13 reads out and executes the program from the memory 101, and at least a part of them is based on the hardware configuration shown in FIG. It may be formed. Further, it is assumed that the functions shown in FIG. 5 are installed in the copying machine 1 so that the states of the stepping motors can be determined independently of each other.

  Referring to FIG. 5, the function for determining the state of the stepping motor includes control unit 1310, motor current detection unit 1311, inflection point detection unit 1312, first determination unit 1313, and first threshold value storage unit 1314. , Second determination unit 1315, third determination unit 1316, history storage unit 1317, control unit 1318, signal output unit 1319, second threshold value storage unit 1320, and third threshold value storage unit 1330. The

  The motor current detection unit 1311 is configured to be connected to the sense terminal of the motor driver circuit 12 and the amplifier circuit 15 shown in FIG. The potential of the sense terminal is detected. The detected voltage is input to the inflection point detector 1312 and the inflection point of the voltage waveform is detected. As shown in FIG. 3, since the current flowing out from the sense terminal of the motor driver circuit 12 corresponds to the current supplied to the stepping motor M, the voltage waveform due to the potential change at the sense terminal is the current of the motor current. The shape is almost the same as the waveform. The detection result of the inflection point is input to the first determination unit 1313 and the control unit 1318 or the third determination unit 1316.

  The first threshold value storage unit 1314 and the second threshold value storage unit 1320 are mainly configured in the memory 101 and the like, and are used to determine whether or not the position of the inflection point is an appropriate position. Memorize the threshold value. For example, each of the first threshold value storage unit 1314 and the second threshold value storage unit 1320 includes an upper limit value CU and a lower limit related to the load converted from the current value (or voltage value) at the inflection point for each motor. The value CD is stored. Since a method for converting the current value (or voltage value) in the stepping motor at the inflection point into the load of the stepping motor is well known, the description thereof will not be repeated here.

  When the inflection point is detected from the voltage waveform corresponding to the current waveform of the motor current in the inflection point detection unit 1312, the first determination unit 1313 uses the voltage value corresponding to the inflection point as the load of the stepping motor. Conversion is performed to determine whether or not the threshold value is less than the threshold value (CU) stored in the first threshold value storage unit 1314, and the result is output to the control unit 1318. Further, second determination unit 1315 converts the voltage value corresponding to the inflection point into the load of the stepping motor, and exceeds the threshold value (CD) stored in second threshold value storage unit 1320. It is determined whether or not, and the result is output to the control unit 1318. The threshold values CU and CD may be stored in advance in the first threshold value storage unit 1314 and the second threshold value storage unit 1320, or a setting operation is received on an operation panel (not shown), May be stored in the first threshold storage unit 1314 and the second threshold storage unit 1320 based on the operation signal.

  Note that the control unit 1318 determines that the load of the stepping motor obtained from the inflection point as described above is outside the range defined by the threshold values CU and CD (the threshold value CU or more or the threshold value) The current value of the target current can be set in the case of CD or less. Here, the set current value is referred to as “target position NA”.

  Specifically, the target position NA is, for example, a set value (target current) of a constant current that is currently set is a value Is, and a safety factor for a load required in the copying machine 1 is a safety factor H1 (for example, 10%). ), It can be determined as the position of the inflection point in the current waveform such that the current value in the constant current control region is Is / H1 (H1 = 1.1 when the safety factor is 10%). An operation for setting the position of the inflection point calculated in this way as a target position NA in an operation panel (not shown) is received and stored in the first threshold value storage unit 1314 based on an operation signal from the operation panel. Alternatively, an operation for setting the safety factor H1 is accepted, and a target position NA is calculated using necessary parameters stored in advance based on the safety factor H1, and the first threshold value storage unit 1314 is obtained. May be stored. Where the inflection point is located relative to the load required by the copying machine 1, the stepping motor M can be stably driven (rotated) by the motor output of the voltage waveform. The designer can design appropriately according to whether or not the configuration is such that it can cope with a case where the load is suddenly changed while the motor M is driven at a constant speed.

  The history storage unit 1317 is mainly configured in the memory 101 and the like, and stores a history of changes in the set value of the constant current in the constant current driving method described later. The third threshold value storage unit 1330 is mainly configured in the memory 101 and the like, and stores a threshold value used for determining whether or not step-out has occurred. When the inflection point detection unit 1312 does not detect the inflection point from the motor current, the third determination unit 1316 refers to the history stored in the history storage unit 1317 and increases the set value in the past. If there is no history, the determination result is input to the control unit 1318. The third determination unit 1316 includes a time measuring unit 1309. When there is a history of increasing the set value in the past, the current waveform of the motor current obtained by the time inflection point detecting unit 1312 in the time measuring unit 1309. Is measured from the rising point to the constant current control region, and it is determined whether or not the time exceeds the threshold value stored in the third threshold value storage unit 1330. . If it exceeds, the determination result is input to the control unit 1318, and if it does not exceed, it is determined that the step is out of step, and the determination result is input to the control unit 1310.

  The control unit 1318 includes a signal generation unit 1318A, and a signal for specifying a message to be displayed on the display unit 50 based on the determination results input from the first determination unit 1313, the second determination unit 1315, and the third determination unit 1316. The signal generation unit 1318A generates the signal, and the signal is input to the signal output unit 1319. The signal output unit 1319 outputs, to the motor driver circuit 12, a control signal for changing the set value in accordance with the input calculation result. In addition, the change in the setting value is stored in the history storage unit 1317 as a history.

  The control unit 1310 includes a signal generation unit 1308. Based on the determination result that the step-out is input from the third determination unit 1316, the signal generation unit 1308 is used according to the part where the target stepping motor is used. Then, a control signal is generated in order to output a control signal from the signal output unit 1319 to each necessary unit, and is input to the signal output unit 1319.

  FIG. 6 is a block diagram showing a specific example of a more detailed configuration of the inflection point detection unit 1312. FIG. 7 is a diagram for explaining a method of detecting an inflection point and is a diagram illustrating a specific example of a voltage waveform.

  Referring to FIG. 6, the inflection point detection unit 1312 includes a sampling unit 1321, a function setting unit 1322, a difference calculation unit 1323, and an inflection point recognition unit 1324.

  The function setting unit 1322 sets the constant current value (target current) and the time stored in the history storage unit 1317 to reach the constant current control region from the rising point detected in the previous motor current detection. Is used to calculate a linear function coefficient A (slope) until reaching the constant current control region at a constant current value set from the rising point, and the linear function Y1 (n) = A * shown in FIG. t (n) is set. Note that t (n) indicates the time from the rising point to the constant current control region.

  The sampling unit 1321 calculates the voltage between the sense terminal of the rising region from the rising point of the voltage waveform to the arrival of the constant current control region and the ground point n times at predetermined time intervals from the voltage detected by the motor current detecting unit 1311. Sampling is performed, and the sampled voltage value is defined as Y2 (n).

  The difference calculation unit 1323 calculates the difference D (n) between the voltage value Y2 (n) sampled by the sampling unit 1321 and the linear function Y1 (n) set by the function setting unit 1322, and the result is Input to the inflection point recognition unit 1324. The inflection point recognition unit 1324 compares the difference D (n) for n times and changes the point where the difference D (n) is 0 or the point where the difference D (n) changes from + to − or − to +. The position NB of the inflection point B recognized as the music point B is input to the first determination unit 1313 and the control unit 1318. Alternatively, if the difference D (n) is always 0, or if the difference D (n) does not change, the fact is input to the third determination unit 1316.

  FIG. 8 is a block diagram showing a specific example of a more detailed configuration of the control unit 1318. Referring to FIG. 8, control unit 1318 includes a determination unit 1331, a determination width storage unit 1332, a calculation unit 1333, a first coefficient storage unit 1334, and a second coefficient storage unit 1335.

  The determination width storage unit 1332 is mainly configured in the memory 101 and the like, and when the voltage value corresponding to the motor current is sampled a plurality of times, the difference between the maximum value and the minimum value of the detected inflection point is predetermined. The determination width as a threshold value used for determining whether or not the value is within the range is stored. This determination width may be stored in the determination width storage unit 1332 in advance. Further, it may be obtained by experiment, and in that case, a setting operation may be accepted on an operation panel (not shown) and stored in the determination width storage unit 1332 based on an operation signal from the operation panel.

  The determination unit 1331 calculates a difference H2 between the maximum value and the minimum value of the voltage value at the inflection point detected from the sampling results input a plurality of times input from the inflection point detection unit 1312, and determines the difference H2 and the above determination. By comparing with the width, it is determined whether or not the difference H2 is within the determination width. The determination result is input to the calculation unit 1333.

  The first coefficient storage unit 1334 and the second coefficient storage unit 1335 are mainly configured in the memory 101 and the like, and store a first coefficient K1 and a second coefficient K2 used for calculation in a calculation unit 1333 described later. The first coefficient K1 is an increase / decrease coefficient and is a coefficient determined from the safety factor H1 described above. The coefficient K1 may be stored in the first coefficient storage unit 1334 in advance, or may be stored in the first coefficient storage unit 1334 based on an operation signal from the operation panel after receiving a setting operation on an operation panel (not shown). Good. Alternatively, the correspondence relationship between the safety factor H1 and the coefficient K1 is stored, and may be automatically set from the safety factor H1. The second coefficient K2 is an increase / decrease coefficient, and is a coefficient used in accordance with the change when the required change in the copying machine 1 is large, that is, a coefficient determined from the difference H2. The coefficient K2 may also be stored in advance in the second coefficient storage unit 1335, or a setting operation is accepted on an operation panel (not shown) and stored in the second coefficient storage unit 1335 based on an operation signal from the operation panel. May be. Alternatively, the correspondence relationship between the difference H2 and the coefficient K2 is stored, and may be automatically set from the difference H2.

  The calculation unit 1333 calculates the set value I to be changed from the currently set constant current value Is according to the determination result input from the determination unit 1331. As specific examples of the arithmetic expressions used in the arithmetic unit 1333, the following arithmetic expressions (1) and (2) are given.

That is, when the determination unit 1331 determines that the difference H2 is within the determination range,
I = Is− (VA−VB) × K1 (1)
When the determination unit 1331 determines that the difference H2 is not within the determination range,
I = Is− (VA−VB) × K1 × K2... (2)
Is used. However,
Is is the constant current value currently set,
VA is the voltage value at the inflection point A, which is the target position NA,
VB indicates a voltage value at the inflection point B which is the position NB, and K1 and K2 indicate increase / decrease coefficients.

  Hereinafter, in the copying machine 1, a process (printing process) when an image is formed on a sheet in accordance with an image read by a scanner or an instruction from an external device (a device connected to the copying machine 1 such as a personal computer). Will be described with reference to FIG. 9 which is a flowchart of the processing.

  Referring to FIG. 9, in the printing process, controller 100 first determines in step S100 whether or not an instruction to form an image on a sheet (print instruction) has been issued. This instruction is issued by the controller 100 itself when the copying of the image in the copying machine 1 (processing for forming the image read by the scanner on the paper) is completed and the reading of the image by the scanner is completed. In some cases, it may be transmitted together with image data from an external device.

  Next, the controller 100 executes an error detection process in step S200. The contents of this process will be described with reference to FIG. 10 which is a flowchart of the subroutine of the process. In the following description, the image forming units 21Y, 21M, 21C, and 21K in FIG. 1 each form a unit together with the toner cartridge for each color, and each image forming unit 21 together with each toner cartridge at the time of toner empty. Explains the types to be exchanged.

  Referring to FIG. 10, in the error detection process, first, in step S201, the controller 100 reads from the first threshold value storage unit 1314 the upper limit value (threshold value) of the stepping motor (M2) that drives the photosensitive member. Value CU), and the lower limit value (threshold value CD) of the load for the stepping motor is read from the second threshold value storage unit 1320 and stored in a RAM (Random Access Memory) or the like in the controller 100. Write and proceed to step S202.

  In step S202, the controller 100 corrects and updates the upper limit value and the lower limit value read in step S201 based on the environmental temperature of the image forming unit 21 (temperature around the photoreceptor) and the like. The corrected upper limit value is referred to as an upper limit value CUA, and the corrected lower limit value is referred to as a lower limit value CDA.

  Next, in step S203, the controller 100 drives the photoconductor by energizing the stepping motor.

  Then, as described with reference to FIGS. 4A to 4D and the like in step S204, the controller 100 determines the stepping from the “inflection point” when the stepping motor is energized in step S203. The motor load (CX) is calculated.

  Next, in step S205, the controller 100 determines whether or not the load calculated in step S204 is smaller than the upper limit value CUA obtained in step S202. If so, the controller 100 proceeds to step S207. If not, the process proceeds to step S206.

  In step S206, the controller 100 determines that an abnormal load is applied to the photoconductor, displays an error message to that effect on the display unit 50, stops the operation, and ends the process.

  On the other hand, in step S207, the controller 100 determines whether or not the load calculated in step S204 is larger than the lower limit value CDA obtained in step S202. If so, the process proceeds to step S209. If determined, the process proceeds to step S208.

  In step S208, the controller 100 determines that the unit of the image forming unit 21 is not attached, displays an error message to that effect on the display unit 50, stops the operation, and ends the process.

  On the other hand, in step S209, the controller 100 updates the upper limit value and the lower limit value corrected in step S204 after returning them, and returns the process to the flowchart shown in FIG.

  Referring to FIG. 9 again, after step S200, controller 100 starts processing for printing an image on a sheet by appropriately controlling sheet conveying unit 20 and image forming unit 30 in step S300, and If the end of printing is detected in step S400, the process is terminated.

  In the printing process described above with reference to FIGS. 9 and 10, when printing is instructed, the image forming unit 21 including the photosensitive member is driven, the load of the stepping motor used for the driving is calculated, and It is then determined whether or not the load value is within a predetermined range (a range defined by the upper limit value and the lower limit value). When it is determined that the load value is within the range, printing is performed. When it is determined that the load value is not present, an error message is displayed on the display unit 50, and the process ends. Note that when the error message is displayed, the copier 1 causes the controller 100 to restart the copying machine 1 by taking a countermeasure (such as mounting the image forming unit including the photoconductor) by the user. From step S100, the process returns to the state in which the process is executed.

  In the printing process described above, it is mentioned that error processing is performed on the entire image forming unit including the photoconductor. Actually, however, an error is detected for each of the image forming units 21Y, 21M, 21C, and 21K. Detection processing is performed. In other words, in the actual processing, first, error processing (calling and correction of the upper limit value and lower limit value, driving by the stepping motor, calculation of the load, comparison of the upper limit value and lower limit value, and if necessary, for the image forming unit 21Y. If no error is displayed, error processing is executed for the image forming unit 21M. If no error is displayed for the image forming unit 21M, error processing is executed for the image forming unit 21C. If error processing is not executed for the image forming unit 21C, error processing is executed for the image forming unit 21K. If no error is displayed in the error process for the image forming unit 21K, printing is started.

  Note that the copying machine 1 executes error processing for all of the image forming units 21Y, 21M, 21C, and 21K even if an error is displayed in any of the error processing for the image forming units 21Y, 21M, 21C, and 21K. It may be configured. In this case, the printing operation is executed only when no error is displayed in any of the error processes of the image forming units 21Y, 21M, 21C, and 21K. In other words, the printing operation is an operation for transferring a developer (in this embodiment, toner is exemplified) to a sheet.

  In the present embodiment described above, when a printing instruction is given, the image forming unit including the photosensitive member is driven by the stepping motor before the actual printing operation is executed, and the load value of the stepping motor is calculated. If the load value is not within the predetermined range, an error is displayed. In other words, in the present embodiment, the load value of the stepping motor is detected, so that the state of the image forming unit including the photosensitive member (the load for driving due to the presence of foreign matter or the like around it is abnormally large). Or a state in which the cartridge is not attached can be detected without providing a special sensor. Therefore, the number of members constituting the copying machine 1 can be reduced, which can contribute to low cost and downsizing.

  Note that the state can be detected by detecting the load value of the stepping motor is not limited to the state of the image forming unit 21 including the photoconductor. For example, it is considered that the state of the heating roller can be detected by detecting the load value of the stepping motor that drives the heating roller provided in the fixing device 36. Further, by detecting the load value of the stepping motor that drives the mechanism that drives the rollers 42, 43, 35, and 37 of the paper transport unit 20, the state of the roller (the occurrence of JAM, etc.) can also be detected. it is conceivable that. In the above description, the type in which each image forming unit 21 is replaced together with each toner cartridge has been described. However, in the type in which only the toner cartridge is replaced, each image forming unit 21Y, 21M, 21C,. The removal of 21K can also be detected with the same configuration.

[Second Embodiment]
FIG. 11 is a diagram schematically showing a longitudinal section of a color printer which is the second embodiment of the image forming apparatus of the present invention.

  The color printer 200 includes a controller 201 that generally controls the operation of the color printer 200, a memory 202 that stores programs executed by the controller 201 and various data, and a display unit 203. The display content of the display unit 203 is controlled by the controller 201.

  The color printer 200 includes a photoconductor unit including a photoconductor drum 227 and a charger 212, a developing unit including a developing rack 99, an intermediate transfer unit including an intermediate transfer belt 221, and a laser scanning unit including an exposure device 240. And a fixing unit including a fixing device 244.

  In the photosensitive unit, the photosensitive drum 227 is charged by the charger 212 and rotated in the direction of arrow X in FIG. 11 by a driving device (not shown).

  The developing rack 99 is provided with developing devices 99K, 99C, 99M, and 99Y for black, cyan, magenta, and yellow, and these can be integrally and rotated around the support shaft in the developing rack 99. is set up. The developing devices 99K, 99C, 99M, and 99Y are configured to be detachable from the developing rack 99 together with the toner cartridges that store the respective color toners.

  The intermediate transfer belt 221 is suspended by a cleaner opposing roller 222, a primary transfer winding roller 223, a primary transfer roller 224, a secondary opposing transfer roller 225, and a tension roller 226, that is, five rollers. . Then, the primary transfer winding roller 223 is driven to rotate, so that the intermediate transfer belt 221 is driven to rotate in the arrow Y direction.

  In the color printer 200, the photosensitive drum 227 is exposed by the exposure device 240, so that an electrostatic latent image is formed on the photosensitive drum 227. The electrostatic latent image is developed (toner image) by the developing devices 99K, 99C, 99M, and 99Y of the developing rack 99. Then, the toner image is transferred to the intermediate transfer belt 221. In the color printer 200, a secondary transfer roller 243 is installed at a position facing the secondary transfer counter roller 225. Then, the sheet P as a transfer material is conveyed to a nip portion formed by the intermediate transfer belt 221 and the secondary transfer roller 243 supported by the secondary transfer counter roller 225, where the toner image on the intermediate transfer belt 221 is transferred. Is transcribed. The paper P to which the toner image has been transferred is sent to the fixing device 244 to fix the toner image, and then is discharged out of the color printer 200 by the paper discharge roller 251 and sent onto the paper discharge tray 252. .

  In this embodiment, transfer from the photosensitive drum 227 to the intermediate transfer belt 221 is referred to as primary transfer, and transfer from the intermediate transfer belt 221 to the paper P is referred to as secondary transfer.

  In the color printer 200, cleaner blades 232 and 218 for removing unnecessary substances such as toner remaining on the surfaces of the intermediate transfer belt 221 and the photosensitive drum 227 are installed.

FIG. 12 is an enlarged view of the fixing device 244 of the color printer 200.
Referring to FIG. 12, fixing device 244 includes a thermistor 291, a thermostat 292, a paper discharge sensor 293, a pressure roller 294, a heating roller 295, a heater lamp 296, and a cleaning roller 297.

  The pressure roller 294 applies pressure to the toner on the paper sent to the fixing device 244 to fix the toner on the paper.

  The heating roller 295 applies heat and pressure to the toner on the paper, and fixes the toner on the paper together with the pressure roller 294. The heating roller 295 generates heat when electric power is supplied via the controller 201, and is driven to rotate by a motor (not shown) (a fixing motor 298 described later).

  The thermistor 291 detects the temperature of the heating roller 295. The detection output of the thermistor 291 is input to the controller 201.

  The thermostat 292 adjusts the temperature of the heating roller 295 by cutting off the power supply to the heating roller 295 when the temperature of the heating roller 295 exceeds a predetermined temperature.

  The paper discharge sensor 293 detects the paper conveyed from the pressure roller 294 and the heating roller 295. The detection output of the paper discharge sensor 293 is input to the controller 201.

  The controller 201 turns on the heater lamp 296 during the heating period of the heating roller 295. The cleaning roller 297 is provided to remove paper dust attached to the heating roller 295.

FIG. 13 is an enlarged view of the vicinity of the heating roller 295 of FIG.
Referring to FIG. 13, in the color printer 200, a fixing motor 298 for rotating the heating roller 295 is installed in the vicinity of the heating roller 295. The fixing motor 298 is configured by a stepping motor. As described as the operation of the controller 100 (CPU 13) in the first embodiment, the controller 201 detects the change in the current value (or voltage value) when power is supplied to the fixing motor 298. The load on the fixing motor 298 can be calculated.

  In the memory 202 of the color printer 200 according to the present embodiment, information regarding an ideal value range is stored for the load of the fixing motor 298. Then, the controller 201 compares the load of the fixing motor 298 with the ideal value range. If the controller 201 is out of the range, an error message is displayed indicating that there is an abnormality in the operation state of the fixing motor 298. It is displayed on the display unit 203.

Hereinafter, display of an error message by the controller 201 will be described.
FIG. 14 is a diagram illustrating an example of an ideal value range for the load of the fixing motor 298 and an actual load of the fixing motor 298 from the start of power supply to the fixing motor 298.

  Referring to FIG. 14, the three types of areas V <b> 1 to V <b> 3 indicated by hatching are ideal fixing motors when power is supplied to fixing motor 298 from time T <b> 0. This is an area indicating a range of load values of 298. Information specifying the areas V1 to V3 is stored in the memory 202, for example. The region V1 is a region where the paper printed by the color printer 200 is plain paper, that is, a paper having an average thickness generally used, and the region V2 is a paper to be printed. The region is thicker than plain paper such as an envelope, and the region V3 is a region when operated in the JAM processing mode. The JAM processing mode refers to a state in which it is easy to remove a sheet sandwiched between the heating roller 295 and the pressure roller 294 by widening the gap or decreasing the contact pressure. Each of the region V1, the region V2, and the region V3 means that there is a range in load values that are considered to be ideal for a certain time. Information specifying the areas V1 to V3 may be stored in the memory 202 in advance, or a setting operation is accepted on an operation panel (not shown) and stored in the memory 202 based on an operation signal from the operation panel. May be.

  Note that the load is higher in the order of the region V1, the region V2, and the region V3. This means that the nip pressure between the pressure roller 294 and the heating roller 295 is high in this order.

Further, the solid line in FIG. 14 is an example of an actual measurement value of a change in load of the fixing motor 298 over time.
The controller 201 preliminarily supplies power to the fixing motor 298 for a predetermined period during a period in which the printing operation as described in the first embodiment is not performed and a printing instruction is not received. By doing so, a load indicated by a solid line in FIG. 14 is obtained. Then, the controller 201 determines whether or not the load indicated by the solid line is included in the above-described range. If it is determined that the load is included, the controller 201 ends the supply of the preliminary power as it is and performs the printing operation. Prepare. On the other hand, when the load indicated by the solid line is included in the above-described range, the preliminary power supply is stopped and an error message is displayed.

  Further, as shown in FIG. 14, when there are a plurality of ideal regions, the controller 201 determines which region is to be determined before supplying preliminary power. The setting contents stored in the memory 202 are confirmed. Specifically, the controller 201 determines information stored in the memory 202 regarding the current operation mode of the color printer 200 before supplying preliminary power, and relates to setting of a sheet to be printed. As information, it is determined whether information corresponding to “plain paper” is stored or information corresponding to “envelope” is stored. When the controller 201 determines that the former is the former, the controller 201 determines the region V1 as a target of determination. When the controller 201 determines that the latter is the latter, the controller 201 determines the region V2 as a target of determination.

  In the case as shown in FIG. 14, the solid line is included in the region V2. Therefore, when the region V2 is determined as a determination target, the controller 201 waits for the printing operation without causing the display unit 203 to display an error message. On the other hand, when it is determined that the region V1 is determined as a determination target, that is, it is found that the load torque corresponding to the envelope is actually generated even though the plain paper is set to be used. In this case, since the used paper (transfer material) and the setting are different (incorrect), an error message is displayed on the display unit 203. When the load torque is in the region V3, the printing operation is performed in the JAM processing mode, so the operation is stopped and an error message is displayed on the display unit 203.

  In the present embodiment described above, in the color printer 200, the controller 201 can detect information on the environment of the heating roller 295 of the fixing device 244 based on the load of the fixing motor 298 without providing a special sensor. .

  The driving of the heating roller 295 for such detection is preferably performed during warm-up before the printing operation is performed.

  In this embodiment, whether or not an error message is displayed, that is, whether or not the state of the heating roller 295 is in a basic state, is a load on the fixing motor 298 that drives the heating roller 295 is a region. Although it is determined by whether or not it is within the range of the region such as V1 to V3, an ideal curve, not an ideal region, is stored in the memory 202, and the load at that time is on the curve It may be determined by whether or not a corresponding time value is within a certain error.

  In the present embodiment, an ideal region is set for the entire preliminary drive time. However, the present invention is not limited to this, and only a part of the preliminary drive time is concerned. The area may be set. In this case, the controller 100 determines whether or not to display an error message by determining whether or not the motor load is within the range of the region only for the part of the time.

  In this embodiment, the target of the error message is not limited to the state of the heating roller 295 of the fixing device 244. In addition, the developing rack 99 may be targeted. The display of the error message in such a case will be described below.

  In FIG. 15, the load from the start of driving (time T0) of the developing device drive motor 990 for rotating the developing device, which is indicated by regions V11 to V14, during the period during which the developing rack 99 is rotated by one rotation. The ideal region for the change in the load and the change in the actual load shown by the solid line are shown.

  In FIG. 15, a period Y is indicated as a period Y in which the developing device (developing roller) 99Y is rotated in a state where yellow toner is supplied from the developing device 99Y to the photoconductor 227, and magenta toner is supplied from the developing device 99M to the photoconductor 227. The period during which the developing device 99M is rotated in a state where the developing device 99M is rotated is indicated by a period M, and the period during which the developing device 99C is rotated while the cyan toner is supplied from the developing device 99C to the photosensitive member 227 is indicated by a period C. A period K is shown as a period during which the developing device 99K is rotated in a state where black toner is supplied from 99K to the photosensitive member 227. The region V11 corresponds to the period Y, the region V12 corresponds to the period M, the region V13 corresponds to the period C, and the region V14 corresponds to the period K. In practice, there is a section corresponding to the time for which the developing rack 99 is rotated by a quarter turn between the sections of YMCK, but this is omitted in FIG.

  As understood from FIG. 15, the load of the developing device drive motor 990 includes values outside the region V12 and the region V13 in the period M and the period C, respectively. That is, it is determined that the developing device 99M is not installed in the period M because the load torque is extremely low, and it is determined that the magenta toner is exhausted because the load torque is low in the period C. The Therefore, the controller 201 causes the display unit 203 to display error messages for the developing devices 99M and 99C. That is, the controller 201 outputs an error message regarding the developing device corresponding to the region where the load value of the developing device drive motor 990 protrudes among the regions V11 to V14 in the developing devices 99Y, 99M, 99C, and 99K. It is displayed on the display unit 203. Although not shown, a motor (development rack motor 99A) that rotates the development rack 99 in a section in which the development rack 99 existing between the YMCK sections is rotated by a quarter is similarly ideal. The load can be compared with the actual load. In that case, for example, when any of the developing units is not mounted, the unmounted developing unit moves to a position corresponding to the photosensitive member 227 (a position where the developing unit 99Y exists in FIG. 11). It becomes possible to know that it is not mounted before being driven.

  The display of the error message based on the load of the developing device driving motor 990 may be, for example, at the time when the execution of the printing process is instructed and before the printing operation is performed, or the printing operation It may be a point in time when no printing is performed and no instruction is given to execute the printing process.

  In this embodiment, an error message is displayed on a roller that conveys a sheet from a sheet feeding cassette 241 to a sheet discharge tray 252 during a printing operation (conveying roller 242, secondary transfer roller 243, heating). The roller 295, the pressure roller 294, and the paper discharge roller 251) may be used. The display of the error message in such a case will be described below.

  In FIG. 16, an ideal conveyance motor load value region V21 and graphs G1, G2, and G3 for a period in which one sheet is conveyed from the paper feed cassette 241 to the paper discharge tray 252 are shown by graphs G1, G2, and G3. The example of the change of the load of the stepping motor which drives the said conveyance roller is shown. Graphs G1, G2, and G3 are graphs obtained separately when the printing operation is actually performed.

  In FIG. 16, six types of periods of “activation”, “paper feeding”, “image formation”, “fixing”, “paper ejection”, and “stop” are defined with respect to the time on the horizontal axis. “Activation” corresponds to a period from when the power supply to the motor is started until the motor actually starts driving the roller. “Paper feeding” refers to the time when the paper exits the paper feed cassette 241 and “Image formation” corresponds to a period until the trailing edge passes through the conveyance roller 242, and “image formation” corresponds to a period until the trailing edge of the paper passes through the conveyance roller 242 and then passes through the secondary transfer roller 243. , “Fixing” corresponds to a period from when the trailing edge of the sheet passes through the secondary transfer roller 243 to when it passes through the nip portion between the pressure roller 294 and the heating roller 295 of the fixing device 244. "Corresponds to the period from when the trailing edge of the paper passes through the nip portion to the time when it passes through the paper discharge roller 251, and" stop "means that the power supply to the stepping motor is stopped and In the period until the rotation of the roller stops To respond.

  In FIG. 16, the graph G1 protrudes outside the area V21 for the first time during the “paper discharge” period. The graph G2 protrudes outside the region V21 for the first time during the “fixing” period. Further, the graph G3 protrudes outside the area V21 for the first time during the “paper feeding” period.

  In each graph, the controller 201 causes the display unit 203 to display an error message corresponding to the period that has first protruded from the region V21. In other words, if the period when the graph protrudes for the first time is “paper feeding”, it means that JAM has occurred in the paper feed tray 241, and if “image formation”, it means that JAM has occurred in the secondary transfer roller 243. If it is “fixed”, it is determined that the JAM has occurred in the fixing device 244, so that the conveying operation is stopped, and if it is “discharge”, that the JAM has occurred in the paper discharge roller 251. Each error message is displayed on the display unit 203.

  In each embodiment described above, the control unit for controlling the display unit according to the present invention is configured by the controller 100 or 201.

  Further, in each of the embodiments described above, an apparatus using an intermediate transfer member (intermediate transfer belt) has been exemplified. However, even if the transfer is performed directly on a sheet by a photosensitive member, the present invention is exactly the same. It can be a mobile of implementation.

  Each embodiment disclosed this time must be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims. Moreover, it is intended that the techniques shown in the respective embodiments are realized in combination as much as possible.

1 is a schematic cross-sectional view showing an outline of a hardware configuration of a copier that is a first embodiment of an image forming apparatus of the present invention. FIG. 2 is a diagram for explaining a relationship between a change with time in load torque necessary for driving a stepping motor in the copier of FIG. 1 and a constant current value to be set. FIG. 2 is a diagram showing a specific example of an equivalent circuit diagram of a drive circuit for controlling driving of a stepping motor in the copying machine of FIG. 1. The relationship between the inflection point in the voltage waveform of the stepping motor in the copying machine of FIG. 1 and the motor output at the currently set constant current value with respect to the load torque necessary for driving the stepping motor in the copying machine will be described. FIG. FIG. 2 is a block diagram illustrating a specific example of a functional configuration for changing a constant current set value in the copier of FIG. 1. It is a block diagram which shows the specific example of a structure of the inflection point detection part of FIG. It is a block diagram which shows the specific example of a structure of the control part of FIG. FIG. 2 is a diagram for explaining a method of detecting an inflection point in the copying machine of FIG. 1. 2 is a flowchart of print processing executed in the copier of FIG. 10 is a flowchart of a subroutine of error detection processing in FIG. 9. FIG. 3 is a diagram schematically showing a longitudinal section of a color printer which is a second embodiment of the image forming apparatus of the present invention. It is an enlarged view of the fixing device of the color printer of FIG. FIG. 13 is an enlarged view of the vicinity of the heating roller in FIG. 12. FIG. 12 is a diagram illustrating values relating to the load of the fixing motor stored in the memory of the color printer of FIG. 11. It is a figure which shows the value regarding the load of a developing device motor memorize | stored in memory of the color printer of FIG. It is a figure which shows the value regarding the load of a conveyance motor memorize | stored in memory of the color printer of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Copier, 3 Loading stand, 2 Conveyance part, 4 Discharge stand, 10 Image reading part, 11 Document glass, 12 Motor driver circuit, 13 CPU, 14 Current detection resistor, 15 Amplification circuit, 20 Paper conveyance part, 21 21Y, 21M, 21C, 21K Image forming section, 25, 25Y, 25M, 25C, 25K Transfer roller, 30 Image forming section, 31 Intermediate transfer belt, 32, 33, 34, 35, 37, 42, 43 Roller, 38 Paper tray, 40 Paper storage unit, 41 Paper cassette, 50 Display unit, 100 Controller, 101 Memory, 1308, 1318A Signal generation unit, 1309 Timing unit, 1310, 1318 Control unit, 1311 Motor current detection unit, 1312 Inflection check Output unit, 1313 first determination unit, 1314 first threshold value storage unit, 1315 second determination unit, 1316 third determination unit, 131 7 History storage unit, 1319 Signal output unit, 1320 Second threshold storage unit, 1321 Sampling unit, 1322 Function setting unit, 1323 Difference calculation unit, 1324 Inflection point recognition unit, 1330
Third threshold storage unit, 1331 determination unit, 1332 determination width storage unit, 1333 calculation unit, 1334 first coefficient storage unit, 1335 second coefficient storage unit.

Claims (10)

An image forming apparatus for forming an image on paper,
A member driven during image formation;
A stepping motor for driving the member;
Control means for controlling supply of electric power for driving the member to the stepping motor;
Storage means for storing information relating to the load of the stepping motor;
Display means for displaying information,
The control means includes
Supplying power to the stepping motor to drive the member;
Based on the drive current waveform for the stepping motor, the load for driving the member of the stepping motor is calculated,
An image forming apparatus that controls the display unit based on a comparison result between the calculated load and information stored in the storage unit. An image forming apparatus for forming an image on paper,
A member driven during image formation;
A stepping motor for driving the member;
Control means for controlling supply of electric power for driving the member to the stepping motor;
Storage means for storing information relating to the load of the stepping motor;
The control means includes
Supplying power to the stepping motor to drive the member;
Based on the drive current waveform for the stepping motor, the load for driving the member of the stepping motor is calculated,
An image forming apparatus that determines a state of the member based on a comparison result between the calculated load and information stored in the storage unit. And further comprising detection means for detecting a voltage value corresponding to a current value supplied to the stepping motor,
The image forming according to claim 1, wherein the control unit calculates a load for driving the member of the stepping motor based on a change in the voltage value detected by the detection unit. apparatus.   4. The image forming apparatus according to claim 1, wherein the control unit calculates the load based on a current value at an inflection point in a rising region of the drive current waveform with respect to the stepping motor. 5. . Image forming means for forming an image on the paper by transferring the developer to the paper;
A fixing means for fixing and fixing the image on the transfer paper by nipping and conveying the paper on which the developer has been transferred;
The image forming apparatus according to claim 1, wherein the member is a roller that sandwiches and conveys a transfer sheet in the fixing unit. A display means for displaying information;
The control means controls power supply to the stepping motor, calculation of the load, and control of the display means based on the comparison result during a period when the image forming operation in the image forming means is not executed. The image forming apparatus according to claim 5, wherein the image forming apparatus is executed. Further comprising an intermediate transfer member,
The image forming apparatus according to claim 1, wherein the member is a developing device for transferring a developer to a sheet or the intermediate transfer member. The developing device is configured to be capable of mounting a cartridge containing a developer,
The storage means stores an upper limit value and a lower limit value regarding the load of the stepping motor,
The control means displays first information on the display unit when the load of the stepping motor is equal to or higher than the upper limit value, and when the load of the stepping motor is equal to or lower than the lower limit value, The image forming apparatus according to claim 7, wherein second information different from the first information is displayed.   The image forming apparatus according to claim 1, wherein the member is a roller that sandwiches and conveys a sheet on which an image is formed. Display means for displaying information;
A paper feed cassette for containing the paper;
A paper discharge roller for discharging the image-formed paper to the outside of the image forming apparatus,
The storage means stores information relating to the load of the stepping motor corresponding to the time from when the paper is discharged from the paper feed cassette to the outside of the image forming apparatus via the paper discharge roller,
The control unit calculates a load of the stepping motor until the sheet is discharged from the sheet feeding cassette to the outside of the image forming apparatus via the sheet discharge roller, and the calculated load and the storage are calculated. The image forming apparatus according to claim 9, wherein the display unit is controlled based on a result of comparison with information stored in the unit.

Images