JP2008176576A - Failure detection device and failure detection program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a versatile failure detection device and a failure detection program by which a failure is determined by an aggregate sum of the drive current of each driving mechanism without moving to a special mode, and in which the failure diagnosis time does not need specified, and a dedicated connection means is not needed. <P>SOLUTION: It is not necessary to recognize the time of taking in an actual current waveform required for the failure detection from a control part 100, etc. using a dedicated interface. Instead, for example, taking the operation instruction of a user interface as the starting point, a current waveform is taken in the range before the starting time and after the ending time of the actual current waveform. Then, by computing a cross-correlation coefficient r representing a degree of its agreement with the normal current waveform, the normal current waveform and the actual current waveform can be synchronized, thereby achieving highly precise failure detection functionality with versatility. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a failure detection apparatus and failure detection program for a mechanical drive mechanism that is driven by supplying a drive current.

  Mechanical drive mechanisms that are driven by a drive current being supplied include motors, solenoids, clutches, cooling fans, and the like, and a plurality of these drive mechanisms are provided in an image forming apparatus, a multifunction peripheral, or the like.

  When a failure occurs in these drive mechanisms, there is a problem that a favorable process cannot be performed. Therefore, it is necessary to detect a failure of each component provided in the apparatus.

  Conventionally, as a method of detecting a failure, a polygon motor, a solenoid, and a clutch are individually driven by a command from a CPU, and a current supplied to a drive mechanism such as each driver or motor is set to a potential difference between both ends of a resistor. It is proposed that the current value detected by the CPU is monitored, the current value detected by the CPU is monitored, and the fault diagnosis of the polygon motor, the solenoid, and the clutch is performed based on the input voltage value (see Patent Document 1).

  In addition, a reference current indicating that a specific component is functioning properly is stored in the computer memory, and only the specific component consumes current while the image is formed including the specific component. It has also been proposed to read the current supplied to the device, compare the read current value with the reference current stored in the memory, and detect the failure of the component depending on whether or not it matches the reference current. (See Patent Document 2).

Even when a plurality of components are operating simultaneously, a failure is detected by determining whether or not a failure has occurred based on the sum of the drive currents of each drive mechanism that is being driven. There has been proposed a failure detection device capable of detecting a failure without executing a special operation for the purpose (see Patent Document 3).
JP 2001-228056 A JP 2003-228419 A JP 2006-266844 A

  However, the failure detection itself in Patent Document 3 is a very excellent means that has never been used as a tool used in the field for maintenance by service personnel, and the total drive current (total current) Although it can be easily measured by using, it is necessary to synchronize the operation timing of each drive mechanism (component) by separately reading a signal from the controller.

  In order to achieve this synchronization, a dedicated connector and terminal (interface for connecting to the controller) had to be provided, and the versatility was poor.

  The present invention has been made in the background of such a background art, and when determining a failure based on the sum of drive currents of each drive mechanism, the failure diagnosis time is specified without shifting to a special mode. Without the need for dedicated connection means, such as providing a dedicated connector and terminal (interface for connection with the controller) for the operation timing of each drive mechanism (component), separately reading the signal from the controller, It is an object to obtain a failure detection device and a failure detection program that can be versatile.

  According to the first aspect of the present invention, the drive mechanism stores the drive current in the normal operation time range from the start to the end of the drive as a normal current waveform, and when the drive mechanism is actually driven. The actual current waveform capturing means for capturing the actual current waveform in a time range wider than the normal operation time, the normal current waveform, and the actual current waveform are repeatedly compared while moving the time axis. The degree of coincidence between the normal current waveform and the actual current waveform is the highest on the basis of the correlation information output means for outputting the correlation information as the respective comparison results and the correlation information output from the correlation information output means A synchronization timing selection means for selecting a timing as a synchronization time; and a failure based on a degree of coincidence between the normal current waveform and the actual current waveform at the synchronization timing selected by the synchronization timing selection means. And a, and failure determining means for determining whether or not it has none.

  According to the first aspect of the invention, since it is determined whether or not a failure has occurred based on the actual driving current of each driving mechanism that is being driven, a special mode or operating state for detecting the failure is determined. Failure detection can be performed without executing the operation in the above.

  Here, it is the failure detection time for comparing the actual drive current waveform and the normal current waveform. Conventionally, for example, information is obtained from a control program for controlling the drive mechanism, and synchronization is performed based on the information. I was taking it. For this reason, a special means for synchronizing (for example, a connection interface for obtaining information) is required.

  On the other hand, in the first aspect of the invention, the normal current waveform and the actual current waveform are repeatedly compared while moving the time axis, and correlation information that is a result of each comparison is output (correlation information output). means).

  Based on this correlation information, the time when the degree of coincidence between the normal current waveform and the actual current waveform is the highest is selected as the synchronization time (synchronization time selection means).

  It is determined whether or not a failure has occurred based on the degree of coincidence between the normal current waveform and the actual current waveform at the synchronization time (failure determination means).

  This eliminates the need for special means for synchronization, and provides a failure determination device with excellent versatility.

  According to a second aspect of the present invention, in the first aspect of the present invention, the actual current waveform capturing start time by the actual current waveform capturing unit is an arbitrary time after the actual operation instruction and before the actual operation. The uptake end time is an arbitrary time after actual operation.

  According to the second aspect of the present invention, the actual current waveform capturing start time by the actual current waveform capturing means is set to an arbitrary time after instructing the actual operation and before the actual operation, and the capture end time is actual. By setting an arbitrary time after the operation, it is possible to capture the entire current waveform of the actual current waveform without depending on the control program information of the drive system.

  The invention according to claim 3 is the invention according to claim 1 or 2, wherein the normal current waveform is a sum of drive currents when all the drive mechanisms are operating normally. It is said.

  According to the third aspect of the present invention, the correlation information for obtaining the synchronization time is clarified by setting the sum of the drive currents when all the drive mechanisms are operating normally as a normal current waveform.

  The invention according to claim 4 is the invention according to any one of claims 1 to 3, wherein the normal current waveform is a sum of drive currents when some drive mechanisms are operating normally. It is characterized by being.

  According to the fourth aspect of the present invention, the storage capacity can be reduced, and the control burden until the selection of the synchronization time based on the correlation information can be reduced.

  The invention according to claim 5 is the invention according to any one of claims 1 to 4, wherein the correlation information includes an average value of current values Xi at the time of comparison of the normal current waveform as Xave, When the average value of the current values Yi at the time of comparison of the actual current waveform is Yave, the cross-correlation coefficient r is calculated by the following equation (1), and the cross-correlation coefficient r is −1.0. <R <+1.0.

  According to the fifth aspect of the present invention, the cross-correlation coefficient is obtained by calculation as the correlation information. Thereby, since failure detection (determination) can be performed quantitatively, failure detection by fully automatic control can be easily performed.

  The invention according to claim 6 is a normal current waveform storage step in which the drive mechanism stores the drive current in the normal operation time range from the start to the end of the drive as a normal current waveform, and when the drive mechanism is actually driven. The actual current waveform capturing step for capturing the actual current waveform in a time range wider than the normal operation time, the normal current waveform, and the actual current waveform are repeatedly compared while moving the time axis. The degree of coincidence between the normal current waveform and the actual current waveform is the highest on the basis of the correlation information output step for outputting the correlation information as the respective comparison results and the correlation information output from the correlation information output step. Based on the degree of coincidence between the normal current waveform and the actual current waveform at the synchronization timing selection step for selecting the timing as the synchronization timing and the synchronization timing selected at the synchronization timing selection step. Failure detection program executed and determining whether or not failure determination process forms, the process comprising the computer.

  According to the sixth aspect of the invention, since it is determined whether or not a failure has occurred based on the actual drive current of each driving mechanism that is being driven, a special mode or operating state for detecting the failure is determined. Failure detection can be performed without executing the operation in the above.

  Here, it is the failure detection time for comparing the actual drive current waveform and the normal current waveform. Conventionally, for example, information is obtained from a control program for controlling the drive mechanism, and synchronization is performed based on the information. I was taking it. For this reason, a special means for synchronizing (for example, a connection interface for obtaining information) is required.

  On the other hand, in the invention of claim 6, the normal current waveform and the actual current waveform are repeatedly compared while moving the time axis, and correlation information that is a result of each comparison is output (correlation information output). Process).

  Based on this correlation information, the time when the degree of coincidence between the normal current waveform and the actual current waveform is the highest is selected as the synchronization time (synchronization time selection step).

  It is determined whether or not a failure has occurred based on the degree of matching between the normal current waveform and the actual current waveform at the synchronization time (failure determination step).

  This eliminates the need for special means for synchronization, and a fault determination program with excellent versatility can be obtained.

  As described above, in the present invention, a dedicated connection means is required when judging a failure based on the sum of drive currents of each drive mechanism without shifting to a special mode and without specifying a failure diagnosis time. However, it has an excellent effect that it can have versatility.

  FIG. 1 schematically shows a configuration of an image forming apparatus 10 according to the present embodiment. In this embodiment, an embodiment in which the present invention is applied to an image forming apparatus will be described.

  As shown in FIG. 1, the image forming apparatus 10 includes a conveyance unit 12 that conveys a sheet and an image formation unit 14 that forms an image.

  The transport unit 12 is provided with a paper feed tray 20, and sheets as recording media for forming images are stacked and stored. A pickup roll 22 and a paper feed roll 26 are provided on the upper surface side of the paper stacked on the paper feed tray 20. The pickup roll 22 is configured to be in contact with or separated from the sheet by the operation of the nudger solenoid 24 and to be rotatable.

  The paper feed roll 26 is also rotatable. When the pickup roll 22 is rotated in contact with the paper, the paper is taken out from the single paper feed tray 20. When the leading edge of the taken-out paper reaches the paper feed roll 26, the paper is fed onto the conveyance path to the image forming unit 14 by the rotation of the paper feed roll 26.

  A paper detection sensor 30 is provided on the downstream side of the paper feed direction of the paper feed roll 26 to detect the presence or absence of paper on the downstream side of the paper feed roll 26. Further, on the downstream side of the paper detection sensor 30, a plurality of transport rolls 28A are arranged along the paper transport path. The paper detection signal from the paper detection sensor 30 is used as a trigger for rotation control of the transport roll 28A.

  Further, a paper detection sensor 32 for detecting the presence or absence of paper at the position is disposed at a predetermined position in the vicinity of the image forming unit 14 on the paper transport path. A claw 36 is provided. The claw 36 is pushed out of the paper conveyance path or retracted from the conveyance path by the operation of the registration solenoid 38, and the claw 36 is conveyed on the conveyance path by being pushed out on the conveyance path. Stop the leading edge of the paper and adjust the transport timing. The registration loop solenoid 34 forms a loop so that the sheet whose conveyance is stopped by the claw 36 does not leave the conveyance path.

  The paper detection signal from the paper detection sensor 32 is used as a trigger for controlling the registration loop solenoid 34 and the registration gate solenoid 38.

  On the other hand, the image forming unit 14 includes a cylindrical photosensitive drum 50, and a transport roll 28B is disposed on the upstream side thereof. A sheet detection sensor 40 is disposed between the transport roll 28 </ b> B and the photosensitive drum 50.

  On the peripheral surface of the photosensitive drum 50, a cleaner roll 52, a lamp 54, a charger 56, a laser exposure device 58, a developing roll 60, and a transfer roll 62 are arranged in this order, and the photosensitive drum 50 has an axial center. It is fixed and rotated so that the surface sequentially faces each part.

  The cleaner roll 52 adsorbs and removes toner adhering to the surface of the photosensitive drum 50, and the lamp 54 neutralizes the surface of the photosensitive drum 50. The charger 56 charges the surface of the photosensitive drum 50 to a uniform potential.

  The laser exposure device 58 forms an electrostatic latent image on the surface of the photosensitive drum 50 by irradiating the uniformly charged surface of the photosensitive drum 50 with laser light based on image data to be image-formed. . Further, toner is uniformly attached to the circumferential surface of the developing roll 60 and rotated, and the electrostatic latent image formed on the surface of the photosensitive drum 50 is attached with toner and developed. A toner image is formed. The transfer roll 62 closely contacts the sheet conveyed to the photosensitive drum 50 and transfers the toner image on the surface of the photosensitive drum 50 to the sheet.

  A fixing roll 64 is provided on the downstream side of the photosensitive drum 50 and the transfer roll 62 in the paper conveyance path. The fixing roll 64 includes a heating roll and a pressure roll, and the toner on the surface of the paper is melted and pressure-bonded to be fixed on the paper while nipping and conveying the paper on which the toner has been transferred by these two rolls.

  A discharge roll 70 is provided on the downstream side in the conveyance direction of the fixing roll 64, and a sheet on which an image is formed is conveyed by the discharge roll 70 and discharged onto the discharge tray 16.

  FIG. 2 is a block diagram centering on a drive system for driving each part of the image forming apparatus 10 according to the present embodiment.

  As shown in FIG. 1, the image forming apparatus 10 includes a control unit 100 that controls the overall operation, a feed motor 140 that serves as a drive source for rotating the various rolls and drums, a pre-registration motor 142, and a drum. The motor 144 and the main motor 146, and a feed motor driver 110, a pre-registration motor driver 112, a drum motor driver 114, and a main motor driver 116 for driving each motor are configured. Each motor is connected to the control unit 100 via a corresponding motor driver, and each motor driver drives each motor so as to be in a driving state according to an instruction from the control unit 100. The control unit 100 includes an I / F (Interface) 130, a RAM (Random Access Memory) 132, a CPU (Central Processing Unit) 134, a ROM (Read Only Memory) 136, and an HDD (Hard Disk Drive) 138. (See FIG. 13). The ROM 136 is a non-writable nonvolatile storage device and stores a control program (for example, a program based on the flowcharts of FIGS. 5 and 12) (see FIG. 13). The HDD 138 is a readable / writable storage device and can store information such as various types of data and instructions. Therefore, the control program may be stored, but the control program is not stored in the HDD 138 but is stored in the ROM 136. It is better (see FIG. 13). Further, the RAM 132 is a readable / writable volatile storage device, and is a work area for processing data and the like according to instructions from the CPU 134. Also, the HDD 138 may be a storage device having a work area similar to the RAM 132 (see FIG. 13). Further, the CPU 134 is a central processing unit, and performs operations such as information processing such as data on the RAM 132 (or HDD 138) based on a control program stored in the ROM 136 (or HDD 138), and exchanges information such as data. Control and allow the I / F 130 to transmit and receive data and commands to control the entire control unit 100 (see FIG. 13). The I / F 130 inputs and outputs information such as commands and data transmitted and received from the CPU 134 and the outside (see FIG. 13).

  The driving force of the feed motor 140 is applied to the pickup roll 22 and the paper feed roll 26, the driving force of the pre-registration motor 142 is applied to the conveying roll 28A, and the driving force of the drum motor 144 is applied to the photosensitive drum 50, the cleaner roll 52, the conveying roll 28B, and the transfer roll. 62, the driving force of the main motor 146 is transmitted to the developing roll 60, the fixing roll 64, and the discharge roll 70, respectively, to rotate each roll and drum.

  As shown in the figure, the image forming apparatus 10 includes a nudger solenoid driver 118, a registration loop solenoid driver 120, and a registration loop solenoid driver 120 for operating the above-described nudger solenoid 24, registration loop solenoid 34, and registration gate solenoid 38, respectively. A registration gate solenoid driver 122 is included, and each solenoid driver is connected to the control unit 100. Each solenoid driver operates each solenoid in accordance with an instruction from the control unit 100.

  Further, the image forming apparatus 10 includes a DC power supply 102, and DC power is supplied to each motor driver and each solenoid driver that require DC power.

  By the way, in the present embodiment, the current value detection unit 160 for detecting the current value flowing through each driver and the current to be detected by the current value detection unit 160 when each driver is operating normally. A current value storage unit 162 in which values are stored in advance is provided, and each is connected to the control unit 100. The current value detector 160 includes a resistor for detecting the current value, a comparator, an A / D converter, and the like (similar to the current detection circuit of FIG. 6).

  In the control unit 100, a failure detection process for determining whether or not a failure has occurred in a part driven by each driver is performed by comparing the input detected current value with the stored current value.

  Here, in FIG. 3, a current value (hereinafter referred to as “normal current value”) to be detected by the current value detection unit 160 when each part operates normally is stored in the current value storage unit 162. The state is shown schematically. Since the normal current value generally changes with time, in this embodiment, the normal current waveform obtained by plotting the transition of the normal current value with the vertical axis representing the normal current value and the horizontal axis representing the time. Remember as.

  In addition, the normal current waveform differs depending on various conditions such as the paper size, the position of the paper feed tray, single-sided printing or double-sided printing, and the number of printed sheets. In this embodiment, the operating state of the image forming apparatus 10 The normal current waveform of each part is memorize | stored for every pattern (1-n) according to operation conditions.

  Further, in the control unit 100 according to the present embodiment, each time any part is turned ON / OFF, a current is compared to detect a failure, and each part is turned ON / OFF in each pattern ( A normal current waveform is stored for each detection period divided by A to J).

  FIG. 4 shows an example of a normal current waveform stored in the current value storage unit 162 as a timing chart. The example shown in the figure is a normal current waveform of each part when the paper size is A4, paper is fed from the paper feed tray 20 and single-sided printing is performed (pattern 1 in FIG. 3). Further, A to J shown in the figure are ON / OFF timings of the respective parts, and correspond to A to J in FIG.

  The normal current waveform of each part shown in the figure is combined (summed) to obtain the total current normal current waveform. When each part is operating normally, the actual current waveform is The waveform is as shown in FIG.

  In the control unit 100, when a failure has occurred, the absolute value of the difference between the input detected current value and the read normal current value is compared with the normal current value of each part, and the closest normal current value Is identified as the failed part.

  FIG. 6 shows an example of a circuit configuration for capturing a normal current waveform as a reference. As shown in the figure, the current supplied from the DC power supply 300 and passing through the motor driver circuit 302 and the solenoid driver circuit 304 is taken into the control circuit 308 via the current detection circuit 306. By operating each part independently in the circuit having such a configuration, the normal current waveform of each part is measured.

  Note that the current detection circuit 306 includes a load resistor 310, an operational amplifier 312, an A / D converter 314, and the like. In the current detection circuit, a current corresponding to a potential difference between both ends of the load resistor 310 by the operational amplifier 312. The value is input to the A / D converter 314 and digitized via the A / D converter 314.

  For example, when taking a normal current waveform of a nudger solenoid, since the pre-registration motor is ON between ON and OFF, it is divided into two, AB and BC. Therefore, the current waveform of 100 msec from the ON of the nudger solenoid is stored in the memory or the like as the normal current waveform of the nudger solenoid in the period AB. Next, a current waveform of 80 msec from 100 msec after the nudger solenoid is turned on is stored in a memory or the like as a normal current waveform of the nudger solenoid in the period CD.

  Further, when the normal current waveform of the feed motor is captured, the pre-registration motor is ON and the nudger solenoid is OFF during the period from ON to OFF. 100 msec from feed motor ON is stored in the memory as feed motor AB. A current waveform of 80 msec from the point of 100 msec after the feed motor is turned on is stored in a memory or the like as a normal current waveform of the feed motor in the period BC. A current waveform of 180 msec from the time point of 180 msec after the feed motor is turned on is stored in a memory or the like as a normal current waveform of the feed motor in the period CD.

  Similarly, other components store the current waveform in the memory in the division unit shown in FIG.

  With the above configuration, the normal current waveform stored in advance and the current waveform during actual driving (actual current waveform) are compared, and the operating state (normal or not) of each drive system is determined according to the degree of coincidence. (Details will be described later using the flowchart of FIG. 5).

  By the way, in this comparison, it is essential that the normal current waveform and the actual current waveform are synchronized on the time axis. Here, “synchronization” means that the drive start time and the drive end time are the same time.

  In order to achieve this synchronization, it is necessary to obtain the current operation state information of the image forming apparatus 10 from the control unit 100 shown in FIG. In other words, since it is essential to obtain this operation state information, a dedicated terminal and dedicated connector (dedicated interface) for outputting dedicated operation execution program simulation data must be prepared, which is convenient as a failure detection function. Even though the work efficiency was good, there was a problem in versatility.

  Therefore, in the present embodiment, a dedicated interface is not required and versatility is provided, and the improvement of the convenience of the failure detection function, which is one of the main objects of the present invention, is established.

  FIG. 7 shows only the full current waveform extracted from the normal current waveform shown in FIG.

  The normal current waveform is stored as described above, but when the target to be compared with the normal current waveform, that is, when the actual current waveform is captured, the capture is started before the actual operation is started, It is only necessary to end the capture after the actual operation is completed. In other words, in particular, precise capture accuracy is not required. For example, based on the user's image formation instruction signal (user interface start button operation, etc.), current waveform capture is started and the actual operation time is predicted to some extent. It is only necessary to end the capture after a lapse of a time obtained by adding a large amount of interval time before and after the actual operation.

  Specifically, the capture is performed in a time range that is twice or more the time from the start to the end of the normal current waveform (about 1450 msec in FIG. 7). As a result, in FIG. It is about 3600 msec.

  9 compares the actual current waveform captured in FIG. 8 with the normal current waveform of FIG. 7 while relatively shifting the time axis (here, comparing the normal current waveform with a shift of 1 msec). 3 is a timing chart showing the degree of coincidence (correlation information) quantitatively (numerically).

  As the correlation information, in this embodiment, a cross-correlation coefficient (or correlation coefficient) r is used. The cross-correlation coefficient r can be obtained by the following equation (1), and the range is −1.0 <r <+1.0, and +1.0 has the highest correlation (matches). Become.

  According to FIG. 9, it can be determined that the cross-correlation coefficient r is the highest (+1.0) and the degree of coincidence is highest when the normal current waveform advances 660 msec from the 0 msec position.

  The operation of this embodiment will be described below.

  When an image forming instruction is input in the image forming apparatus 10 according to the present embodiment, the nudger solenoid for feeding the paper and the feed motor are turned on to operate and feed the paper from the paper feed tray 20 onto the transport path. . At this time, the drum motor and the main motor are simultaneously turned on to start image formation, whereby a xerographic process such as exposure and development based on image data to be instructed to form an image on the photosensitive drum 50 is performed. Executed.

  When the paper passes through the paper feed roll, the preregistration motor, the registration loop solenoid, the registration gate solenoid, etc. are sequentially turned on to operate.

  FIG. 5 is a flowchart showing a flow of failure detection processing executed by the control unit 100 when an image formation instruction is input. Hereinafter, failure detection processing according to the present embodiment will be described with reference to FIG. To do.

  Here, in executing the failure detection process in FIG. 5, it is necessary to synchronize the normal current waveform and the actual current waveform in advance.

  FIG. 12 is a process for achieving this synchronization, which is performed before the execution of the failure detection process of FIG.

  In step 250 of FIG. 12, a normal current waveform (see FIG. 7) is read from the memory. In this normal current waveform, the time from the start to the end is 1450 msec.

  Next, in step 252, the acquisition of the actual current waveform is started from the start before actual operation (for example, image formation instruction operation of the user interface), and the actual operation time and the interval time (prediction) before and after that. After a longer time (as a guide, approximately twice the actual operation time), the capturing is finished. In the present embodiment, as shown in FIG. 8, an actual current waveform for 3600 msec is captured.

  In the next step 254, the variable k indicating the number of comparisons is cleared (initialized to k = 0), and the process proceeds to step 256. Note that the variable k depends on the processing time of the flowchart, and is preferably repeated at 5 msec to 10 msec.

  In step 256, a waveform in the period from 0 + k to 1450 + k is extracted from the actual current waveform in FIG. 8, and then the process proceeds to step 258 to compare with the reference waveform 0 to 1450 msec in FIG. The number r is calculated according to equation (1).

  In the next step 260, it is determined whether or not the variable k has reached a predetermined value (3600-1450). If a negative determination is made, the process proceeds to step 262 and the value of the variable k and the cross-correlation coefficient r. Then, in step 264, the variable k is incremented, the process returns to step 256, and the above process is repeated until an affirmative determination is made in step 260. The stored results are schematically shown in a graph with time on the horizontal axis and cross-correlation coefficient r on the vertical axis, as shown in FIG.

  If an affirmative determination is made in step 260, the process proceeds to step 266, and the maximum cross-correlation coefficient r and the value of k at that time are selected (extracted) from the stored data of the variable k and the cross-correlation coefficient r. Next, the routine proceeds to step 268, where it is determined whether or not the extracted cross-correlation coefficient r is a threshold value (that is, + 1.0−Δr: Δr indicates an allowable range of the degree of coincidence). In step 270, the variable k stored together with the cross-correlation coefficient r is set as the start time of the actual current waveform (time synchronized with the start time of the reference current waveform). finish.

  If a negative determination is made in step 268, the process proceeds to step 272, where the normal current waveform is changed (for example, changed to the normal current waveform of the registration solenoid shown in FIG. 10), the process returns to step 252, and again. Get the actual current waveform. In addition, you may make it apply the actual current waveform acquired last time. In this case, the process may be shifted from step 272 to step 254. In the case of passing through step 272, the previous characteristic results of the variable k and the cross-correlation coefficient r stored in step 262 are discarded, and new characteristic data as shown in FIG. 11 is stored. Become.

  That is, in the normal current waveform (see FIG. 7), which is the sum of all currents, when the actual operation is abnormal, the degree of coincidence is low. In such a case, the current waveform of any one or a combination of two or more of the individual drive systems may be used as the normal current waveform (here, the current waveform is used when the registration solenoid is driven). ).

  When the synchronization time is determined by the processing of FIG. 12, the failure detection processing of FIG. 5 is executed.

  First, in step 200, a detection period is set. In the next step 202, counting of the detection period is started, and then the process proceeds to step 204 to acquire a detected current value.

  The detection period is set according to the pattern (pattern 1 to pattern n) based on the paper size and printing conditions according to the image formation instruction and the current detection period. For example, in the period BC of pattern 1 If there is, 80 ms (see FIG. 4) is set.

  Further, the total current can be detected by installing a current sensor on the current line that has passed through the driver of each part. A resistor may be used to detect this current. However, if the resistor causes a voltage drop and hinders the operation of a component, a Hall element without a voltage drop may be used.

  In addition, current capture is usually digitized by an A / D converter and captured by a controller (see, for example, FIG. 6). The sampling frequency of the A / D converter is preferably the same sampling frequency as that for capturing a normal current waveform.

  In the next step 206, it is determined whether or not the set detection period has elapsed. If the determination is negative, the process returns to step 204 again. On the other hand, if an affirmative determination is made in step 206, it is determined that all the detected current values in the detection period have been acquired, the process proceeds to step 208, and a detected current waveform of all currents is generated. The detection current waveform is generated by taking the detection current value on the vertical axis and time on the horizontal axis, as in the normal current waveform.

  In the next step 210, the normal current waveform of each part is subtracted from the detected current waveform. For example, the normal current waveforms of the nudger solenoid, feed motor, drum motor, and main motor of the period AB are subtracted from the detected current waveform of the period AB. If each component operates normally during this detection period, the detected current waveform of period AB is the sum of the normal current waveforms of the nudger solenoid, feed motor, drum motor, and main motor of period AB. Therefore, the subtraction result is a waveform with current value = 0. In other words, it can be seen from the subtraction result whether a failure has occurred in the part.

  For example, assuming that the drive circuit of the feed motor driver is disconnected, the total current when the image forming apparatus 10 is operated is that the feed motor operates alone in the sections AB, BC, and CD. The current waveform is reduced by the amount of current.

  The subtraction of the current waveform may be performed in units of the number of samples of the normal current waveform, or a value obtained by previously averaging the waveform in units of divided sections or using a square average may be used. When using an average value or a mean square value, the current waveform may be taken in as an average value or a mean square value at the stage of waveform acquisition. When the average value or the mean square value is taken in, there is a merit that the memory is not consumed, rather than taking the waveform as it is.

  In the next step 212, it is determined whether or not the current value is 0 as a result of the subtraction. If the determination is affirmative, it is determined that each part is operating normally and the process proceeds to step 214. It shifts and it is determined whether the process of all the detection periods was complete | finished. If a negative determination is made in step 214, the process returns to step 200 again to execute processing for the next detection period. On the other hand, if the determination in step 214 is affirmative, the failure detection process ends.

  If the determination in step 212 is negative, it is determined that there is a part that is not operating normally, and the process proceeds to step 216, where the part of the normal current waveform whose absolute value is closest to the waveform after subtraction is determined. The failure is identified as a site where a failure has occurred, and then the failure detection process is terminated.

  As described in detail above, according to the present embodiment, power is supplied to each drive mechanism by the DC power supply 102 via a plurality of drive drivers for driving a plurality of drive mechanisms such as a motor and a solenoid, One of a plurality of preset operation patterns is selected, ON / OFF control of each drive mechanism is executed via each drive driver according to the selected operation pattern, and the ON / OFF control by the control means And detecting a sum of drive currents of the plurality of drive drivers at the time of executing a normal current waveform indicating a change over time in the sum of drive currents when the plurality of drive mechanisms are normally driven for each operation pattern. Is stored in the current value storage unit 162 in advance, and the actual current waveform indicating the change over time of the drive current detected by the current value detection unit 160 and the operation pattern Compared to the normal current waveform, if the actual current waveform and the normal current waveform are different from each other as a result of the comparison, it is determined that a failure has occurred in the drive mechanism. Even in the case of failure, failure detection can be performed without executing a special operation for detecting failure.

  Further, for example, the operation current waveform of the actual current waveform can be obtained from the operation instruction of the user interface as a starting point without recognizing the capture time of the actual current waveform necessary for the failure detection from the control unit 100 or the like using a dedicated interface. The normal current waveform and the actual operation are obtained by capturing the current waveform in a time range before the start time and after the end time and then calculating a cross-correlation coefficient r indicating the degree of coincidence with the normal current waveform. It can be synchronized with the current waveform, and the failure detection function with high accuracy can be made more versatile.

  Further, according to the present embodiment, the normal current waveform is stored in advance for each detection period divided by the timing (A to J) at which the driving of each part is turned ON / OFF according to the control state of each part. Since the failure determination is performed for each detection period, the failure detection can be accurately performed by paying attention to the change in the drive current of each part.

  Furthermore, in the present embodiment, the normal drive current for each drive mechanism is also stored in advance, and the location where the failure has occurred is specified, so that the operator identifies the location where the failure has occurred separately. It does not have to be.

  In this embodiment, the normal current waveform of each part is stored in advance. However, the present invention is not limited to this, only the normal current waveform of all currents is stored, It is also possible to adopt a form in which only the presence or absence of occurrence is detected.

  Further, in the present embodiment, only the failure detection process has been described, but when a failure is detected by the failure detection process, information indicating that may be notified. As a notification means for performing this notification, an operation panel or the like may be provided on the image forming apparatus and displayed on the operation panel, a buzzer or the like may be provided and a speaker or the like may be provided. Audio may be reproduced. Further, a separate communication unit or the like may be provided so that information indicating that a failure has occurred in the drive mechanism is output to an administrator outside the apparatus, a terminal such as a customer center, a computer, or the like.

  In this embodiment, the failure detection is performed using the detection result itself. However, the failure is detected using the cross-correlation coefficient between the total current derived based on the detection result and the current of each drive mechanism. Detection can also be performed.

  For example, the cross-correlation coefficient between the normal drive current waveform of each drive mechanism and the normal drive current waveform of each drive mechanism when each drive mechanism is driven normally is stored in advance. Deriving the cross-correlation coefficient between the detected drive current waveform and each normal drive current waveform, respectively, according to the derived cross-correlation coefficient and the control state (pattern) at the time of detecting the detected drive current waveform The cross-correlation coefficients are compared with each other, and it can be determined that a failure has occurred in the drive mechanisms that are different from each other.

  The cross-correlation coefficient for each drive mechanism indicates the correlation of the amount of change in the drive current of each drive mechanism with the amount of change in the total drive current of each drive mechanism, and when a failure occurs in any part The correlation coefficient between the detected drive current waveform and the normal drive current waveform of the faulty drive mechanism and the cross-correlation coefficient between the normal drive current waveform and the normal drive current waveform of the faulty drive mechanism There will be a difference. Note that there is no significant difference between the two regarding the normal drive mechanism.

  More specifically, the current waveform of each individual component is calculated in advance for each section and the total current and the cross-correlation coefficient are stored in a memory or the like together with the current waveform for that section. If the cross-correlation coefficient between the total current in the section to be examined and the waveform of the part is calculated and the result is different from the cross-correlation coefficient stored in advance, it can be determined that the part has failed. When this cross-correlation coefficient is used, it consumes a little more memory capacity than when subtraction is performed using the detection result itself as in the above-described embodiment, but overload at the time of overload where parts cannot be specified by subtraction. Also in the case of current, it is possible to detect which fault has failed. Furthermore, even if two or more parts operating in the same section have failed, it is possible to detect which and which have failed.

For example, if it is set that the pre-registration motor does not operate in the AB section of FIG. 4 but the pre-registration motor does not operate due to a failure, the cross-correlation coefficients are as follows.
Nager solenoid 0.66
Feed motor 0.84
Drum motor 0.1059074
Main motor 0.186037
Pre-registration motor -0.04321231
Thereby, it turns out that there is almost no correlation of a pre-registration motor. Nager solenoids and feed motors have large cross-correlation coefficients because of their relatively characteristic waveforms. On the other hand, since there is no feature of the drum motor and the main motor, the cross correlation coefficient is small. Therefore, it is possible to detect a failure by calculating a cross-correlation coefficient in a normal state in advance and determining whether the cross-correlation coefficient is small.

  Note that the configuration (see FIGS. 1 to 4) and the flow of processing (see FIG. 5) of the image forming apparatus 10 according to the present embodiment are merely examples, and needless to say, can be changed as appropriate.

  Further, the control unit 100 is configured as shown in FIG. 13 which is a detailed diagram of the control unit in FIG. 2, and the CPU 134 fails based on the actual drive current of each drive mechanism that is driven via the I / F 130. Therefore, it is possible to detect a failure without executing an operation in a special mode or operating state for detecting a failure.

  In the control unit 100, the normal current waveform stored in the ROM 136 (or the HDD 138) and the actual current waveform input from the outside are repeatedly compared while moving the time axis by the CPU 134, and the comparison results are obtained. The correlation information is output (stored) to the RAM 132 (or HDD 138). Based on this correlation information, the CPU 134 selects the time when the degree of coincidence between the normal current waveform and the actual current waveform is the highest as the synchronization time. The CPU 134 determines whether or not a failure has occurred based on the degree of coincidence between the normal current waveform and the actual current waveform at the synchronization time. This eliminates the need for special means for synchronization, and a fault determination program with excellent versatility can be obtained.

1 is a schematic diagram illustrating a configuration of an image forming apparatus according to an embodiment. 1 is a block diagram centering on a drive system for driving each part of an image forming apparatus according to an embodiment; FIG. It is a schematic diagram which shows the state by which the normal current waveform which concerns on embodiment was memorize | stored in the electric current value memory | storage part. It is a timing chart which shows an example of a normal current waveform. It is a flowchart which shows the flow of the failure detection process which concerns on embodiment. 2 shows an example of a circuit configuration for capturing a normal current waveform. 5 is a timing chart in which only normal current waveforms of all currents in FIG. 4 are extracted. It is a timing chart when an actual current waveform is taken. It is a timing chart of a cross correlation coefficient r value when a normal current waveform is shifted every 1 msec from an actual current waveform. It is a modification for obtaining a cross-correlation coefficient r value, and is a timing chart of a normal current waveform at the time of driving a registration solenoid when using a current waveform of a registration solenoid driven in the latter half of the operation. It is a timing chart of a cross-correlation coefficient r value when the normal current waveform of the registration gate solenoid is shifted by 1 msec with respect to the actual current waveform. It is a flowchart which shows the synchronous determination control routine for setting the synchronous time when comparing with a normal current waveform and an actual current waveform. FIG. 3 is a detailed view of a control unit in FIG. 2.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 20 Paper feed tray 22 Pickup roll 24 Nudge solenoid 26 Paper feed roll 28 Transport roll 34 Registration loop solenoid 38 Registration gate solenoid 50 Photosensitive drum 52 Cleaner roll 60 Development roll 62 Transfer roll 64 Fixing roll 70 Discharge roll 100 Control unit 102 DC power supply 110 Feed motor driver 112 Pre-registration motor driver 114 Drum motor driver 118 Nudge solenoid driver 120 Registration loop solenoid driver 122 Registration gate solenoid driver 140 Feed motor 142 Pre-registration motor 144 Drum motor 146 Main motor 160 Current value detection unit 162 Current value storage

Claims (6)

A normal current waveform storage means for storing a drive current in a normal operation time range from the start to the end of the drive as a normal current waveform;
When the drive mechanism is actually driven, an actual current waveform capturing means for capturing an actual current waveform in a time range wider than the normal operation time;
Correlation information output means for repeatedly comparing the normal current waveform and the actual current waveform while moving the time axis, and outputting correlation information as a result of each comparison;
Based on the correlation information output from the correlation information output means, the synchronization time selection means for selecting the time when the degree of coincidence between the normal current waveform and the actual current waveform is the highest as the synchronization time;
Failure determination means for determining whether or not a failure has occurred based on the degree of coincidence between the normal current waveform and the actual current waveform at the synchronization time selected by the synchronization time selection means;
A failure detection device having   The actual current waveform capturing start time by the actual current waveform capturing means is an arbitrary time after the actual instruction and before the actual operation, and the capture end time is an arbitrary time after the actual operation. The failure detection apparatus according to claim 1, wherein:   3. The failure detection apparatus according to claim 1, wherein the normal current waveform is a sum of drive currents when all drive mechanisms are operating normally.   4. The failure detection apparatus according to claim 1, wherein the normal current waveform is a sum of drive currents when some drive mechanisms are operating normally. When the correlation information is Xave as an average value of current values Xi at the time of comparison of the normal current waveform, and Yave as an average value of current values Yi at the time of comparison of the actual current waveform, the following (1) 5. The cross-correlation coefficient r calculated by the equation (1), wherein the cross-correlation coefficient r is -1.0 <r <+1.0. Failure detection device.

A normal current waveform storage step in which the drive mechanism stores a drive current in a normal operation time range from the start to the end of the drive as a normal current waveform;
When the drive mechanism is actually driven, an actual current waveform capturing step for capturing an actual current waveform in a time range wider than the normal operation time;
A correlation information output step of repeatedly comparing the normal current waveform and the actual current waveform while moving the time axis, and outputting correlation information as a result of each comparison;
Based on the correlation information output from the correlation information output step, a synchronization time selection step of selecting, as a synchronization time, a time when the degree of coincidence between the normal current waveform and the actual current waveform is the highest,
A failure determination step of determining whether or not a failure has occurred based on a degree of coincidence between the normal current waveform and the actual current waveform at the synchronization time selected in the synchronization time selection step;
A failure detection program for causing a computer to execute processing including

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