JP2020086094A - Image forming apparatus - Google Patents

Abstract

To provide an image forming apparatus that comprises a function to diagnose whether or not a control board for controlling an optical sensor which detects a toner image formed on an image carrier fails.SOLUTION: An image forming apparatus sets a control signal 506 that supplies current to a sensor 601 to 0 V to sample (step S103) a forward voltage signal 505 and a current detection signal 507 respectively, then sets the control signal 506 to 3.3 V to sample (step S103) the forward voltage signal 505 and the current detection signal 507 respectively, diagnoses (step S105) which diagnostic pattern of a failure mode of components of the sensor 601 and the control board 500 a combination of a sampling result corresponds to, and determines (step S107) that the control board 500 fails when it is determined that a Tr 510 or an OPAMP 509 of an LED driving circuit 502 is not normal.SELECTED DRAWING: Figure 6

Description

The present invention relates to an image forming apparatus, and more particularly to a copier, a printer, and a printing machine having a function of detecting a toner image of a predetermined pattern formed on an endless belt and adjusting toner density or color misregistration. And an image forming apparatus.

Conventionally, an electrophotographic apparatus such as a copying machine or a printer uses an optical sensor having a light emitting unit and a light receiving unit to detect a toner image of a predetermined pattern formed on a belt-shaped image carrier to determine the toner density. It has a function to properly adjust. Further, for example, there is also known an image forming apparatus having a function of detecting a positional deviation of an image composed of four colors of yellow, magenta, cyan and black from a toner image of a predetermined pattern formed on an image carrier and adjusting the positional deviation. Has been.

An optical sensor that detects a toner image formed on an image carrier may have a low SN ratio (signal, noise ratio) due to toner stains or a decrease in reflectance of the image carrier that is an object to be monitored. . Therefore, the output value of the optical sensor when the image carrier to be monitored is detected is constant within a predetermined range by periodically adjusting the drive current of the light emitting component, for example, every predetermined number of prints or every power-on. The light amount adjustment control is performed so as to achieve the following (Patent Document 1). In such light amount adjustment control, if the output value of the sensor cannot be adjusted within a predetermined range due to severe dirt, failure of the optical sensor, or the like, it is determined that the sensor is abnormal.

JP, 2017-146352, A

However, in the above-mentioned conventional technique, when it is determined that the sensor is abnormal, there is a problem in that the apparatus itself cannot determine whether the abnormality has occurred on the optical sensor side or the control board side controlling the optical sensor has failed.

Generally, various semiconductor components are used for a control board that controls an optical sensor, and the semiconductor components may accidentally fail due to overstress such as static electricity. Even if the semiconductor component accidentally fails, the sensor output cannot be adjusted within the predetermined range in the light amount adjustment control of the sensor, and thus it is determined that the sensor is abnormal. When it is determined that the sensor is abnormal, the maintenance worker needs to specify the failure portion while replacing the semiconductor parts one by one, and thus it takes a long time to restore the device.

Therefore, there is a demand for a technique capable of separately diagnosing a failure on the side of the optical sensor or a failure on the side of the control board for controlling the optical sensor, in order to recover the device determined to be the sensor abnormality in a short time. In particular, there is a demand for the development of a technique that can detect a failure of a control board that uses a semiconductor component that may accidentally fail due to overstress such as static electricity, separately from a failure of an optical sensor.

In view of the above situation, the present invention provides an image forming apparatus having a function of diagnosing whether or not a control board for controlling an optical sensor that detects a toner image formed on an image carrier has a failure. The purpose is to

In order to solve the above problems, an image forming apparatus according to claim 1, wherein an image carrier on which an image formed by the image forming unit is transferred, and a detecting unit for detecting the image transferred on the image carrier. Drive means for supplying power to the detection means, current detection means for detecting a current flowing through the detection means, voltage detection means for detecting a voltage applied to one end of the detection means, and the detection means by the drive means. A determination unit that determines whether or not there is a failure in the drive unit using the detection results of the current detection unit and the voltage detection unit when the current value supplied to the drive unit is changed.

According to the present invention, the presence/absence of a failure of the drive unit is determined using the current value flowing through the detection unit and the voltage value applied to the detection unit when the current value supplied to the detection unit is changed. It is possible to determine whether or not the control board has a failure by separating it from the side failure.

FIG. 1 is a vertical sectional view showing a schematic configuration of an image forming apparatus according to an embodiment. FIG. 2 is a vertical sectional view showing the intermediate transfer belt and a sensor when viewed from the upstream side with respect to the conveyance direction of the intermediate transfer belt in FIG. 1. It is a figure which shows the circuit structure of the control board in which the sensor and the circuit which drives a sensor were mounted. FIG. 6 is a diagram showing an example of a relationship between a toner pattern and a sensor output waveform applied when measuring the toner density of a toner image on an intermediate transfer belt by a sensor. It is a figure which shows an example of the relationship between a toner pattern and a sensor output waveform at the time of measuring the color gap between 4-color images with a sensor. It is a flow chart which shows the procedure of the sensor control board diagnostic processing which diagnoses whether the control board which drives a sensor is out of order. 6 is a table showing failure modes of components constituting the sensor and the control circuit, and corresponding forward voltage signals and current detection signals. 7 is a flowchart showing a procedure of sensor diagnosis processing executed in step S109 of FIG. 6.

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

FIG. 1 is a vertical sectional view showing a schematic configuration of an image forming apparatus according to an embodiment. In FIG. 1, an image forming apparatus 300 is a color electrophotographic apparatus adopting an intermediate transfer system. The image forming apparatus 300 includes a document reading unit 200 that reads a document image and a printer unit 100 that prints the read image on a sheet as a transfer material. An operation display unit 600 (not shown) for operating the image forming apparatus 300 is provided on the front surface of the document reading unit 200.

The printer unit 100 includes an image forming unit 10, a paper feeding unit 20, an intermediate transfer unit 30, and a fixing unit 40.

The image forming unit 10 includes four image forming stations (image forming units) 10a, 10b, 10c and 10d. The image forming stations 10a to 10d have the same configuration. The image forming stations 10a to 10d are provided with photosensitive drums 11a, 11b, 11c, and 11d as image carriers, and the photosensitive drums 11a to 11d are rotatably supported in the arrow direction in FIG. The photosensitive drums 11a to 11d are cylindrical photoconductors for electrophotography.

The primary charging devices 12a to 12d, the optical systems 13a to 13d, the folding mirrors 16a to 16d, the developing devices 14a to 14d, and the cleaning devices 15a to 11d are arranged along the rotation direction of the photosensitive drums 11a to 11d so as to face the outer peripheral surfaces thereof. 15d is arranged.

The primary charging devices 12a to 12d give a uniform amount of charge to the surfaces of the photosensitive drums 11a to 11d. The optical systems 13a to 13d emit a laser beam based on a signal modulated according to an image signal from the document reading unit 200, and expose the photosensitive drums 11a to 11d through the folding mirrors 16a to 16d to expose the laser beams. Form a latent image. The developing devices 14a to 14d respectively contain black, cyan, magenta, and yellow developers (hereinafter, referred to as "toners"), and apply high developing pressure to the developing sleeves to cause the corresponding photosensitive drums 11a to 11d to develop. Toner is supplied to visualize the electrostatic latent image.

An intermediate transfer belt 31 as an image carrier is arranged below the photosensitive drums 11a to 11d of the image forming stations 10a to 10d so as to be in sliding contact therewith. The intermediate transfer belt 31 is rotatably supported by a plurality of rollers 32 to 34. The intermediate transfer belt 31, which is an intermediate transfer member, constitutes the intermediate transfer unit 30. Primary transfer chargers 35a to 35d are arranged to face the photosensitive drums 11a to 11d via the intermediate transfer belt 31, respectively. The contact portions of the photosensitive drums 11a to 11d and the primary transfer chargers 35a to 35d are image transfer areas (primary transfer portions) Ta to Td, respectively.

The visible images visualized on the photosensitive drums 11a to 11d are transferred onto the intermediate transfer belt 31 at the primary transfer portions Ta to Td by applying transfer high voltage to the primary transfer chargers 35a to 35d, respectively. , Are superimposed to form a multi-color image. The cleaning devices 15a to 15d scrape off the toner remaining on the photosensitive drums 11a to 11d without being transferred to the intermediate transfer belt 31 to clean the surfaces of the photosensitive drums 11a to 11d.

A secondary transfer roller 36 is arranged so as to face a support roller 34 that supports the intermediate transfer belt 31. The contact portion between the support roller 34 and the secondary transfer roller 36 serves as the secondary transfer portion Te. On the downstream side of the secondary transfer portion Te on the intermediate transfer belt 31, a cleaning device 50 is arranged so as to face the support roller 33. The cleaning device 50 includes a cleaning blade 51 and a recovery toner box 52. The cleaning blade 51 is a blade for collecting the toner remaining on the intermediate transfer belt 31 after the image transfer. The collected toner box 52 is a storage box that stores the collected toner collected by the cleaning blade 51.

The sheet feeding unit 20 that supplies the sheet P to the secondary transfer unit Te includes cassettes 21a and 21b that store the sheet P, and a manual feed tray 27 provided on the side surface of the apparatus body. The sheet feeding unit 20 functions as a sheet conveying device. The paper feeding unit 20 has a conveyance path 24 that conveys the sheet P fed by the pickup rollers 22a, 22b, or 26 to the secondary transfer portion Te. In the vertical path portion of the transport path 24, a plurality of transport roller pairs 23 for transporting the sheet P sent from the pickup rollers 22a and 22b are arranged. Further, at the manual feed path portion for conveying the sheet P paid out from the pick-up roller 26 of the manual feed tray 27, a pair of paper feed conveyance rollers 23 is also arranged.

A pair of registration rollers (registration rollers) 25a and 25b are arranged on the downstream side of the junction of the vertical path portion and the manual feed path portion in the transport path 24. The pair of registration rollers 25a and 25b send the sheet P to the secondary transfer portion Te at the image forming timing of the image forming unit 10. A fixing unit 40 and a conveyance guide 43 for guiding the sheet P to the nip portion of the fixing unit 40 are provided on the downstream side of the secondary transfer unit Te. The fixing unit 40 includes a fixing roller 41a and a pressure roller 41b. The fixing roller 41a includes a heat source such as a halogen heater inside. The pressure roller 41b is a roller that is pressed by the fixing roller 41a. A paper discharge roller pair 44 and 45 for discharging the sheet P discharged from the fixing unit 40 to the outside of the apparatus is arranged in the transport path on the downstream side of the fixing unit 40.

The sensor 60 (61) is arranged so as to face the image transfer surface (outer surface) of the intermediate transfer belt 31. The sensor 60 (61) detects the toner image formed on the intermediate transfer belt 31 and detects the presence or absence of toner density or color misregistration.

Next, the operation of the image forming apparatus 300 having such a configuration will be described.

When an image forming operation start signal is issued from the operation display unit 600 (not shown) due to a user operation or the like, for example, the pickup roller 22a feeds the sheets P one by one from the cassette 21a. The sent-out sheet P is guided along the transport path 24 by the transport roller pairs 23, 23 and is transported to the registration roller pair 25a, 25b. At this time, the pair of registration rollers 25a and 25b are stopped, and the leading edge of the sheet P hits the nip portion. After that, the pair of registration rollers 25a and 25b start rotating at the timing when the image forming unit 10 starts forming an image. The rotation start timing of the pair of registration rollers 25a and 25b is set so that the sheet P and the toner image transferred onto the intermediate transfer belt 31 from the image forming unit 10 coincide with each other in the secondary transfer area Te. ..

On the other hand, in the image forming unit 10, when an image forming operation start signal is issued from the operation display unit 600, a toner image of each color is formed on the photosensitive drums 11a to 11d according to each process. After that, the toner image formed on the photosensitive drum 11d on the most upstream side in the rotation direction of the intermediate transfer belt 31 is transferred to the intermediate transfer belt 31 in the primary transfer area Td by the primary transfer charger 35d to which a high voltage is applied. Transcribed. The transferred toner image is conveyed to the next primary transfer area Tc as the intermediate transfer belt 31 rotates. At this time, the image forming operation is executed in each image forming station with a delay of the time during which the toner image is conveyed between the image forming stations, the resist is aligned on the previous toner image, and the next toner image is formed. Is transcribed.

Thereafter, the same steps are repeated, and finally the toner images of four colors are transferred and superposed on the intermediate transfer belt 31. After that, when the sheet P enters the secondary transfer area Te and comes into contact with the intermediate transfer belt 31, a high voltage is applied to the secondary transfer roller 36 in synchronization with the passage timing of the sheet P. As a result, the multi-color image formed on the intermediate transfer belt 31 is transferred to the surface of the sheet P. The sheet P to which the toner image is transferred is guided to the nip portion of the fixing roller along the conveyance guide 43. The transferred image on the sheet P guided to the nip portion of the fixing roller is heated and pressed to be fixed on the surface of the sheet P. The sheet P on which the image is fixed is conveyed by the action of the inner paper discharge roller pair 44 and the outer paper discharge roller pair 45 and is discharged to the outside of the machine.

Next, a schematic configuration of the sensor 60 (61) arranged to face the outer peripheral surface which is the image bearing surface of the intermediate transfer belt 31 will be described. The sensor 60 (61) diagnoses the toner density of the toner image transferred to the intermediate transfer belt 31 and the presence or absence of color misregistration between multicolor images.

2 is a vertical cross-sectional view of the intermediate transfer belt 31 and the sensor when viewed from the upstream side with respect to the conveyance direction of the intermediate transfer belt 31 in FIG.

In FIG. 2, a sensor 60 (61) is an optical sensor, and includes a light emitting diode (hereinafter referred to as “LED”) 601 as a light emitting element, a phototransistor (hereinafter referred to as “Ptr”) 602 as a light receiving element, And a lens unit 603. The LED 601 is arranged so as to irradiate the intermediate transfer belt 31 with infrared rays at an incident angle of about 15°. The Ptr 602 receives the reflected light of the light emitted from the LED 601 to the intermediate transfer belt 31 and the toner image 70 at the position of the regular reflection angle.

Next, a circuit configuration of the sensor 60 (61) and a control board on which a circuit for driving the sensor 60 (61) is mounted will be described.

FIG. 3 is a diagram showing a circuit configuration of the sensor 60 (61) and a control board 500 on which a circuit for driving the sensor 60 (61) is mounted.

In FIG. 3, the sensor 60 (61) includes an LED 601, a Ptr 602, an amplifier circuit 603, and a voltage conversion element 604. The voltage conversion element 604 converts the received light current flowing through the Ptr 602 into a voltage. The amplifier circuit 603 amplifies the output voltage according to the amount of light received by the Ptr 602.

The control board 500 that drives the sensor 60 (61) includes a CPU 501, an LED drive unit 502, and a current detection unit 503. The control board 500 functions as a light emitting element drive unit that drives the LED 601 which is the light emitting element of the sensor 60 (61). The CPU 501 of the control board 500 incorporates an internal ROM and an AD conversion unit (not shown). The CPU 501 controls various loads based on a program stored in advance in the internal ROM, samples signals, and executes arithmetic processing.

The LED drive unit 502 is a circuit for supplying a current to the LED 601 of the sensor 60 (61). The LED drive unit 502 includes a transistor Tr510 that drives the LED 601 and an OPAMP 509 that controls the Tr510. The OPAMP 509 functions as a control unit of the Tr 510.

The power supply voltage supplied from the control board 500 to the sensor 60 (61) is, for example, 5V. On the other hand, the allowable voltage of the CPU 501 is, for example, 3.3V. Therefore, a resistor for dividing the sensor power supply 5V into about 3V is arranged on the sensor power supply inspection signal line, and the sensor power supply inspection signal 504 divided into about 3V by the resistance is input to the CPU 501. Is configured. The AD conversion unit of the CPU 501 measures the voltage level of the sensor power supply inspection signal 504.

The current detector 503 is a resistance element (about 75Ω) for converting the current flowing through the LED 601 and the LED driver 502 into a voltage. The drive current of the LED 601 can be variably controlled by giving the control signal 506 from the CPU 501 to the LED drive unit 502. The current value detected by the current detection unit 503 is fed back from the current detection unit 503 to the OPAMP 509 for feedback control so that the current value of the LED 601 is kept constant. The sensor output signal 508 is an output signal of the sensor 60 (61) and is input to the AD input terminal of the CPU 501.

The control board 500 includes a comparator circuit (not shown), and the comparator circuit binarizes the sensor output signal 508 of the sensor 60 (61) which is an analog signal. The binarized signal is input to an ASIC (highly integrated circuit) (not shown) and used for color misregistration measurement.

In FIG. 3, the current detection signal 507 of the current detection signal line connected to the feedback signal line of the OPAMP 509 and the forward voltage signal 505 of the forward voltage signal line connected to the cathode side of the LED 601 are input to the CPU 501. ing. Thus, when an abnormality is found in the output waveform of the sensor 60 (61), it is possible to determine whether the sensor 60 (61) is out of order or the control board 500 that drives the sensor 60 (61) is out of order. A method for diagnosing the failure state of the LED 601 and the failure state of the Tr 510 or the OPAMP 509 for diagnosing the failure of the control board 500 will be described later.

A voltage dividing resistor (about 1 M, 1.5 MΩ) is connected to the voltage detection signal line that inputs the forward voltage signal 505 to the CPU 501. The voltage dividing resistor suppresses the voltage to about 60%. As a result, the power supply voltage exceeding 3.3V, for example, 5V is not directly applied to the CPU 501.

As described above, in the sensor 60 (61), specularly reflected light mainly from the intermediate transfer belt 31 enters the Ptr 602. For this reason, when the toner image 70 is formed on the intermediate transfer belt 31, the incident light reaching the surface of the intermediate transfer belt 31 and the reflected light reflected by the surface decrease, so that the amount of light received by the Ptr 602 decreases. Based on this principle, the density of the toner image 70 can be grasped from the output level of the sensor 60 (61).

FIG. 4 is a diagram showing an example of a relationship between a toner pattern and a sensor output waveform applied when the toner density of the toner image on the intermediate transfer belt 31 is measured by the sensor 60 (61). In FIG. 4, when the toner patterns D1 to D5 formed on the intermediate transfer belt 31 and having different densities are read by the sensor 60 (61) along the arrow direction, the sensor output gradually increases as the toner pattern density increases. A decreasing signal waveform is obtained.

Further, FIG. 5 is a diagram showing an example of the relationship between the toner pattern and the sensor output waveform when the color shift between the four-color images is measured by the sensor 60 (61). In FIG. 5, Y, M, C, and K are yellow, magenta, cyan, and black toner patterns formed on the intermediate transfer belt 31 at a relatively high density. The sensor output waveform when the toner pattern is sequentially read by the sensor 60 (61) along the arrow direction is the sensor output waveform (upper waveform) in FIG. A digital waveform obtained by binarizing the obtained output waveform by a comparator circuit (not shown) is the binarized output waveform (lower waveform) in FIG. By measuring the time between the centers of gravity of the binarized output waveforms, it is possible to grasp the relative positional deviation of the Y, M, C, and K images. In FIG. 5, when there is no displacement of the image, the binarized output waveforms are exactly overlapped.

Next, a sensor control board diagnosis process for diagnosing whether or not the control board 500 in FIG. 3 is out of order will be described.

FIG. 6 is a flowchart showing a procedure of a sensor control board diagnostic process for diagnosing whether or not the control board 500 that drives the sensor 60 (61) is out of order. The sensor control board diagnostic processing is executed by the CPU 501 of the control board 500 according to the sensor control board diagnostic processing program stored in an internal ROM (not shown). This sensor control board diagnosis processing is for diagnosing whether or not there is a failure in the control board 500 using the detection signal of the current flowing through the LED 601 of the sensor 60 (61) and the detection signal of the forward voltage applied to one end of the LED 601.

The sensor control board diagnosis processing is executed when it is determined that some abnormality has occurred from the primary analysis of the output waveform of the sensor 60 (61) during the toner density measurement control and the color shift measurement control. For example, when adjusting the current of the LED 601 in order to adjust the reflected output from the intermediate transfer belt 31 to a predetermined level, even if the maximum current is set and the reflected output from the intermediate transfer belt 31 does not rise to the predetermined level, The sensor control board diagnosis process is executed. In the sensor control board diagnosis process, the binarized waveform obtained at the time of measuring the color shift (see FIG. 5) is counted by using the ASIC or the CPU 501 (not shown), and the count does not reach the predetermined count within the predetermined time. And so on.

In FIG. 6, when the sensor control board diagnosis processing is started, the CPU 501 first applies the power supply voltage 5V to the LED 601 and the sensor power supply inspection signal 504 input to the CPU 501 is 2.5 to 3.5V. It is determined whether it is within the range (step S101). If the result of determination in step S101 is that the sensor power supply inspection signal 504 is within the range of 2.5 to 3.5 V (“YES” in step S101), the CPU 501 advances the processing to step S103. In this case, it is considered that the voltage is properly applied to the sensor 60 (61).

In step S103, the CPU 501 sets the control signal 506 to 0V, supplies a control current corresponding to 0V to the LED 601, and after 50 msec has elapsed, samples the forward voltage signal 505 and the current detection signal 507 10 times at 10 msec intervals. .. The forward voltage signal 505 is a detection signal of a forward voltage applied to one end of the LED 601, and the current detection signal 507 is a detection signal of a current flowing through the LED 601. Next, the CPU 501 obtains the average values of the sampled forward voltage signal 505 and the current detection signal 507, and sets them as A0 and B0 (step S103).

Next, the CPU 501 sets the control signal 506 to 3.3 V, supplies a control current corresponding to 3.3 V to the LED 601, and similarly, after 50 msec has elapsed, the forward voltage signal 505 and the current detection signal 507 are each 10 msec. Sample 10 times at intervals. Next, the CPU 501 obtains the average values of the forward voltage signal 505 and the current detection signal 507, which are sampled, and sets them as A3 and B3 (step S104).

After setting the control signal 506 in two ways and sampling the forward voltage signal 505 and the current detection signal 507, respectively, the CPU 501 advances the process to step S105. That is, the CPU 501 collates with which diagnostic pattern of the failure mode of each component the average value of the detection results of the forward voltage signal 505 and the current detection signal 507 obtained in steps S103 and S104 applies (step S105). ..

FIG. 7 is a table showing the failure modes of the components forming the sensor 60 (61) and the control board 500, and the corresponding forward voltage signals and current detection signals. In FIG. 7, each of the failure modes of the OPAMP 509 and Tr 510 on the control board 500 side, the LED 601 on the sensor 60 (61) side, the voltage level of the corresponding current detection signal 507 and forward voltage signal 505, and the control signal 506 is 0V. It is shown under two conditions of 3.3V.

In addition, in FIG. 7, the current detection signal 507 is represented as a voltage value corresponding to the current value. Further, the circuit failure in the present embodiment assumes a case where an active component such as OPAMP 509 or Tr 510 accidentally fails due to overstress such as static electricity, and a passive component such as a resistor or a capacitor does not fail. Not targeted.

In FIG. 7, when the LED 601 fails in the open mode, no current flows in the LED drive unit 502. Therefore, the current detection signal 507 is 0. Both when the control signal 506 is 0V and when it is 3.3V. It becomes smaller than 5V. Further, since the forward voltage signal 505 is also pulled down by the resistor, it becomes smaller than 0.5 V regardless of the control signal 506. This state is called a diagnostic pattern (A). In the present embodiment, the failure in the open mode means that the target component has a failure in a state where a circuit that does not conduct electricity is open.

Next, when the LED 601 fails in the short mode and the control signal 506 is 0V, the LED drive unit 502 works to stop the current, and the current detection signal 507 becomes smaller than 0.5V. At this time, the forward voltage signal 505 has a value obtained by dividing the power source 5V applied to the LED 601 and is larger than 2.0V (5×1.5÷2.5=3.0V). On the other hand, when the control signal 506 is 3.3 V, the maximum current of about 35 mA flows in the LED drive unit 502 within the control range, so that the current detection signal 507 is larger than 2.0 V (75Ω×35 mA≈2.6 V). ). Then, the forward voltage signal 505 becomes larger than 2.0 V because the power supply 5 V applied to the LED 601 has a divided voltage as in the case where the control signal 506 is 0 V. This state is called a diagnostic pattern (B). In the present embodiment, the failure in the short mode means that the target component fails in a short-circuited state in which electricity is conducted.

Next, when a failure occurs in the open mode between the collector and the emitter of the Tr 510 of the LED driving unit 502, no current flows in the Tr 510 and the current detection signal line. Therefore, the current detection signal 507 becomes smaller than 0.5 V regardless of whether the control signal 506 is 0 V or 3.3 V. Further, regardless of the control signal 506, that is, in the case where the control signal 506 is 0V and 3.3V, the forward voltage signal 505 is a value obtained by dividing the value of the applied power source 5V by the forward voltage of the LED 601. It becomes the pressed value. When the forward voltage of the LED 601 is 0.7 V and the voltage dividing resistors connected to the voltage detection signal line are 1 MΩ and 1.5 MΩ, the forward voltage signal 505 is (5.0−0.7)×1.5÷( 1.0+1.5)=2.58V. That is, the forward voltage signal 505 becomes larger than 2.0V. This state is called a diagnostic pattern (C).

Next, when a failure occurs between the collector and the emitter of the Tr 510 in the short mode, regardless of the control signal 506, that is, when the voltage is 0 V or 3.3 V, the current continues to flow to the LED 601. The detection signal 507 becomes larger than 2.0V. In addition, the forward voltage signal is in the same state regardless of the control signal 506, and when the control signal 506 is 0V or 3.3V, the power supply 5V applied to the LED 601 is a divided value (3.0v). Is a value further reduced by the forward voltage of the LED 601. When the forward voltage of the LED 601 in the present embodiment is 0.7V, the forward voltage signal 505 becomes larger than 2.0V (3.0-0.7=2.3V). This state is called a diagnostic pattern (D).

Next, when the OPAMP 509 of the LED drive unit 502 fails due to the output open, the control signal is not transmitted from the OPAMP 509 to the Tr 510, so that the Tr 510 does not operate. That is, since no current flows through the Tr 510 and the current detection signal line, the current detection signal 507 becomes smaller than 0.5 V when the control signal 506 is 0V or 3.3V. Further, in this case, since the LED 601 is assumed to be normal, the forward voltage signal 505 is a value obtained by dividing the applied power source 5V both when the control signal 506 is 0V and 3.3V. It becomes larger than 0V. This state is similar to the diagnostic pattern (C).

Next, in the failure mode in which the power supply of the OPAMP 509 and the output of the OPAMP 509 are internally short-circuited (power supply short-circuit), the control signal is continuously transmitted from the OPAMP 509 to the Tr 510, so that the Tr 510 remains ON. In this case, when the control signal 506 is 0V or 3.3V, the current continues to flow to the LED 601, so that the current detection signal 507 becomes larger than 2.0V. Further, the forward voltage signal is not related to the control signal 506, that is, when the control signal 506 is 0V or 3.3V, the power supply 5V applied to the LED 601 is divided from the divided value (3.0v). Further, it becomes a value (2.3 V) lowered by the forward voltage of the LED 601. This state is similar to the diagnosis pattern (D).

Next, in the failure mode in which the GND and the OPAMP 509 outputs are internally short-circuited (GND short), all the outputs of the OPAMP 509 flow to the GND, and the control signal is not transmitted from the OPAMP 509 to the Tr 510, so the Tr 510 is not driven. Therefore, the current detection signal 507 becomes smaller than 0.5 V when the control signal 506 is 0 V or 3.3 V. Further, in this case, the forward voltage signal 505 is 2.0 V or more because the applied power source 5 V is divided even when the control signal 506 is 0 V and 3.3 V. This state is similar to the diagnostic pattern (C).

Finally, in the failure mode in which the output of the OPAMP 509 of the LED driving unit 502 remains at the intermediate potential (failure at the output intermediate potential), current flows in the LED 601 or does not flow. Therefore, regardless of whether the control signal 506 is 0 V or 3.3 V, if no current flows in the current detection signal line, the current detection signal 507 becomes smaller than 0.5 V, and current flows in the current detection signal line. For example, the current detection signal 507 becomes larger than 2.0V. Further, both when the control signal 506 is 0 V and when it is 3.3 V, the forward voltage signal 505 is a value obtained by dividing the value obtained by reducing the forward voltage of the LED 601 by 5 V from the applied power source 5 V. The forward voltage signal 505 of this embodiment is 2.0 V or higher. That is, when the OPAMP 509 fails at the output intermediate potential, the diagnostic pattern (C) or diagnostic pattern (D) is obtained.

Returning to FIG. 6, when the result of the determination in step S105 is to compare with the diagnostic pattern (A) or (B), the LED 601 is defective, so the CPU 501 determines that the sensor 60 or the sensor 61 is defective, and the main diagnosis is performed. The process ends (step S106). At this time, the CPU 501 displays information indicating the failure point on the operation display unit 600 to notify the user.

When the result of the determination in step S105 is to match the diagnostic pattern (C) or (D), the CPU 501 determines that the Tr 510 or the OPAMP 509 of the LED drive unit 502 is abnormal, and determines that the control board 500 has a failure. The process ends (step S107). At this time, the CPU 501 displays information indicating the failure point on the operation display unit 600 to notify the user.

On the other hand, as a result of the determination in step S105, when none of the diagnostic patterns (A) to (D) is collated, the CPU 501 determines that the control board 500 is normal without any failure (step S108). After determining that the control board 500 is normal (step S108), the CPU 501 executes sensor diagnosis processing for determining whether the sensor 60 (61) is normal (step S109). Details of the sensor diagnosis process will be described later with reference to FIG.

On the other hand, if the result of determination in step S101 is that the sensor power supply inspection signal 504 is outside the range of 2.5 to 3.5 V (“NO” in step S101), the CPU 501 advances the processing to step S102. That is, the CPU 501 determines that the control board 500 has a failure because the power supply voltage is not normally supplied from the control board 500 to the sensor 60 (61) (step S102). Then, after that, the CPU 501 displays information indicating the failure point on the operation display unit 600 to notify the user, and ends the present process.

According to the processing of FIG. 6, a failure of the sensor 60 (61) and a failure of the Tr 510 or OPAMP 509 according to the detected values of the forward voltage signal 505 and the current detection signal 507 when the control signal 506 supplied to the LED 601 is changed. Are distinguished and detected (step S105). With this, it is possible to determine whether or not the control board 500 including the Tr 510 and the OPAMP 509 has a failure.

In the present embodiment, when it is determined that the control board 500 has not failed (step S108), subsequently, the sensor diagnosis process of determining whether or not the sensor 60 (61) has failed is executed ( Step S109). In this case, the failure of the sensor 60 (61) is due to the failure of components other than the LED 601.

In the present embodiment, the sensor 60 (61) is a sensor that diagnoses and determines the density or color misregistration of the image transferred to the intermediate transfer belt 31. Further, in the present embodiment, the current detection signal 507 indicating the value of the current flowing through the sensor 60 (61) is output as the voltage value corresponding to the current value.

In the present embodiment, when the power supply voltage is not normally supplied from the control board 500 to the sensor 60 (61), it is determined that the control board 500 has a failure (step S102). In this case, the control board 500 is considered to have failed due to a failure of a component other than the Tr 510 or OPAMP 509.

The present invention that distinguishes between a sensor failure and a control board failure according to the detected values of the forward voltage signal 505 and the current detection signal 507 when the control signal 506 supplied to the LED 601 is changed is shown in FIG. It can be widely applied to the technical field in which the combination of the above diagnostic patterns is applied. That is, the present invention can be applied in a wide field including a sensor and a control board that drives the sensor.

Next, the sensor diagnosis processing executed in step S109 of FIG. 6 will be described. FIG. 8 is a flowchart showing the procedure of the sensor diagnosis processing executed in step S109 of FIG. The sensor diagnosis processing is executed by the CPU 501 of the control board 500 according to the sensor diagnosis processing program stored in an internal ROM (not shown), as in the sensor board diagnosis processing.

In FIG. 8, when the sensor diagnosis control is started, the CPU 501 first sets the control signal 506 to 0 V, and after 50 msec has elapsed, samples the sensor output signal 508 10 times at 10 msec intervals. Then, the average value of the detection values of 10 times is calculated and set as C0 (step S201). After sampling the sensor output signal 508 with the control signal 506 set to 0V, the CPU 501 sets the control signal 506 to 3.3V, measures the sensor output signal 508 similarly to step S201, and averages it to C3 (step S202). Next, the CPU 501 determines whether the ratio C3/C0 of C3 to C0 is larger than 1.2 (step S203).

If the result of determination in step S203 is that C3/C0 is greater than 1.2 (“YES” in step S203), the CPU 501 changes the output in response to the change in the control signal, so the sensor 60 (61). Is determined to be normal (step S205). At this time, the CPU 501 ends the sensor diagnosis process without displaying a message indicating the failure location.

On the other hand, if the result of determination in step S203 is that C3/C0 is smaller than 1.2 (“NO” in step S203), the CPU 501 changes the output of the sensor 60 (61) in response to the change in the control signal. Judge that it has not. Then, the CPU 501 determines that the sensor 60 (61) has failed (step S204). Next, the CPU 501 displays information indicating the failure location on the operation display unit 600, and ends this sensor diagnosis processing.

According to the process of FIG. 8, in the normal state of the control board 500, the control signal 506 of the sensor 60 (61) is changed from 0V to 3.3V and the sensor output signal 508 is measured (step S202). Then, when the sensor output signal 508 changes in accordance with the change of the control signal 506, the sensor is determined to be normal (step S205), and when it does not change, it is determined that the sensor has failed (step S206). This makes it possible to determine whether or not the sensor 60 (61) has a failure due to an abnormality in a component other than the LED 601.

31 intermediate transfer belt 60 (61) sensor 300 image forming apparatus 500 control board 501 CPU
502 LED drive unit 503 Current detection unit 504 Sensor power supply inspection signal 505 Forward voltage signal 507 Current detection signal 508 Sensor output signal 509 Operational amplifier element (OPAMP)
510 Transistor element (Tr)
601 light emitting diode (LED)
602 Phototransistor (Ptr)
603 Amplifier circuit 604 Voltage conversion element

Claims (12)

An image carrier to which the image formed by the image forming means is transferred,
Detection means for detecting the image transferred to the image carrier,
Drive means for supplying power to the detection means,
Current detecting means for detecting a current flowing through the detecting means,
Voltage detection means for detecting a voltage applied to one end of the detection means,
Using the detection results of the current detection means and the voltage detection means when changing the current value supplied to the detection means by the drive means, the determination means for determining the presence or absence of failure of the drive means,
An image forming apparatus comprising: The image forming apparatus according to claim 1, wherein the determination unit distinguishes a failure of the drive unit from a failure of the detection unit by using a combination of detection results of the current detection unit and the voltage detection unit. 3. The image forming apparatus according to claim 1, wherein the determining unit determines whether the detecting unit is out of order when it is determined that the driving unit is out of order. The image forming apparatus according to claim 1, wherein the current detecting unit outputs a current value flowing through the detecting unit as a voltage value corresponding to the current value. The image forming apparatus according to claim 1, wherein the detection unit is an optical sensor having a light emitting element and a light receiving element. The image forming apparatus according to claim 5, wherein the driving unit includes a light emitting element driving section that supplies a current to the light emitting element, and a control section that controls the light emitting element driving section. 7. The image forming apparatus according to claim 5, wherein the current detecting unit detects a current flowing through the light emitting element, and the voltage detecting unit detects a voltage applied to one end of the light emitting element. Equipped with an operation display unit that informs information,
The image according to any one of claims 1 to 7, wherein when the determination unit determines that the drive unit is out of order, the determination unit displays the fact on the operation display unit to notify the fact. Forming equipment. The image forming unit has a plurality of image forming units, forms a plurality of images of different colors, and transfers the plurality of images to the image carrier to form a multi-color image. Item 9. The image forming apparatus according to any one of items 1 to 8. The image forming apparatus according to claim 9, wherein the image carrier is an intermediate transfer body onto which the images of the plurality of colors are transferred. The image transferred to the image carrier is a toner pattern for diagnosing the presence or absence of density or color shift in the image transferred to the image carrier. The image forming apparatus according to item 1. The image forming apparatus according to claim 11, wherein the detection unit detects the toner pattern and determines whether there is a density or color shift of the image.