JP2007271757A - Image forming apparatus and method for detecting mounting of process cartridge - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of detecting the respective mounting states of a plurality of process cartridges which can be attached/detached to/from an apparatus body even in constitution reducing the cost of the apparatus body. <P>SOLUTION: The image forming apparatus is provided with a control means for controlling the drive of the plurality of process cartridges by a single driving means, a load detection means for detecting load during the drive control by the driving means, and a blocking member for blocking a beam optical path of a beam to be irradiated for each process cartridge in response to the attaching/detaching operation of the process cartridge to/from the apparatus body. Further, the image forming apparatus is provided with a process cartridge existence detection means for detecting the existence of mounting of the process cartridge on the basis of a signal expressing the existence of a beam in the beam optical path blocked by the blocking member and a process cartridge state discrimination means for discriminating respective mounting states of the process cartridges on the basis of the detected load and the detection result of the process cartridge existence detection means. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus and a cartridge mounting detection method, and more particularly, an image forming apparatus in which a plurality of process cartridges are detachably mounted, and the plurality of cartridges are driven and controlled by a single driving unit, and the same The present invention relates to a mounting detection method for each cartridge.

  First, a configuration of a known electrophotographic image forming apparatus in which a plurality of process cartridges are detachably mounted will be described.

  FIG. 1 is a diagram showing a color image forming apparatus provided with image forming means for four colors, that is, yellow Y, magenta M, cyan C, and black K. In the figure, the portions indicated by reference numerals 1Y, 1C, 1M, and 1K are process cartridges. The process cartridge is a unit of image forming process devices such as the photosensitive drums 1aY, 1aM, 1aC, and 1aK that form an electrostatic latent image, and is configured to be detachable from the main body. This includes a primary charging device (not shown), a developing device (not shown) for developing an electrostatic latent image, a cleaning device (not shown), and the like. The portions indicated by the reference numerals 6Y, 6M, 6C, and 6K are motors that drive the process cartridges. The portions denoted by reference numerals 3Y, 3M, 3C, and 3K are transfer rollers for transferring the electrostatic latent images formed on the photosensitive drums 1aY, 1aM, 1aC, and 1aK to a recording medium. The portions indicated by reference numerals 2Y, 2M, 2C, and 2K are laser scanner units that perform exposure according to image signals and form electrostatic latent images on the photosensitive drums 1aY, 1aM, 1aC, and 1aK, respectively. Reference numeral 5 denotes a fixing device for fixing the toner image transferred onto the recording medium onto the recording paper as a permanent image. The fixing device 5 includes a fixing roller 5a and a pressure roller 5b. Reference numeral 7 denotes a conveying belt for conveying the recording medium.

  Further, the image forming apparatus 100 feeds the recording medium from the cassette 4 by a paper feed motor (not shown). Then, the fed recording medium is conveyed by driving a conveying belt by a belt drive motor (not shown), and the toner images on the photosensitive drums 1aY, 1aM, 1aC, 1aK are transferred to the recording medium, respectively. Thereafter, the fixing roller 5a is driven by a fixing drive motor (not shown) to heat the toner image transferred onto the recording medium at a predetermined temperature, and pressurize the pressing roller 5b to fix the toner image on the recording medium. Then eject the recording medium out of the device.

  In the above-described symbols, Y, M, C, and K represent yellow, magenta, cyan, and black, respectively, thereby indicating that the portions represented by numbers are for these colors.

  The transfer operation and the fixing operation are performed under optimum transfer conditions and fixing conditions according to the type of recording medium (plain paper, cardboard, OHT, etc.), for example. Further, the current flowing through the transfer rollers 3Y, 3M, 3C, and 3K and the fixing roller 5a can be measured, and based on the result, the transfer and fixing conditions can be optimized.

  The photosensitive drum, the conveyance belt, the fixing roller, and the like are consumable members that deteriorate as the image forming apparatus is used. It is necessary to replace the photosensitive drum, the conveyance belt, and the fixing roller when they reach the end of their lifetimes. For this reason, a unit that is detachable from the main body of the image forming apparatus is generally used so that the user can easily replace it.

  For example, a developing unit (so-called process cartridge) in which a photosensitive drum and a developing device are unitized, a belt unit in which a conveyance belt is unitized, a fixing unit in which a fixing device is unitized, and the like.

  However, since these units are exchangeable, the influence on the image due to individual differences for each unit becomes a problem. In other words, since the units are freely exchanged, the deteriorated conditions are different in each exchanged unit, and thus there is a difference in image density formed due to individual differences. For this reason, a storage unit such as a memory for storing predetermined information is provided in the unit, and characteristic information unique to the unit is stored. At the time of image formation, image formation control suitable for the characteristics of the unit is executed based on the information. Thereby, a stable image can be obtained.

  In addition, a predetermined time immediately after the start of the image forming apparatus is operated with a setting different from the predetermined time, thereby obtaining a stable image.

  Therefore, since the unit is replaced, a means for determining the presence or absence of the replaceable unit is required. In addition, since the color image forming apparatus has a plurality of process cartridges, a means for determining the presence or absence of each of the plurality of process cartridges is also required. This is caused by the necessity of obtaining various triggers for error processing, various control for obtaining a more stable image, and changing the setting.

  As a method for determining the presence or absence of a process cartridge, for example, as described in Patent Document 1, a technique for determining the presence or absence of a process cartridge by measuring the load torque of a motor for driving the process cartridge Has been proposed. Patent Document 2 discloses a configuration in which image light is blocked by a shutter member arranged in the middle of the image light in conjunction with the attachment / detachment of the process cartridge to / from the apparatus main body. There has been proposed a technique for detecting the absence of a process cartridge in the apparatus main body when no image light is detected by a detection sensor disposed in the optical path where the image light is blocked.

  Patent Document 3 describes the replacement of a process cartridge and the formation of a stable image related thereto.

JP 2002-072773 A Japanese Patent Laid-Open No. 03-084562 JP-A-2002-49225

  In recent years, a single drive motor has been used to drive one process cartridge, but a single motor is used to drive all of the multiple process cartridges. Cost reduction. In addition, a conventional laser scanner unit irradiates a single photosensitive drum with a laser, but a single laser scanner unit irradiates a plurality of photosensitive drums with a laser to reduce costs. Realized. According to this configuration, it is possible to reduce the number of BD (Beam Detect) sensors, polygon mirrors, and scanners / motors for detecting image writing timing, thereby realizing cost reduction.

  However, adoption of such a cost-reduced configuration has caused the following problems. Conventionally, since one process cartridge is driven by one drive motor, the presence or absence of each of the plurality of cartridges can be determined by the torque of each drive motor. However, since a plurality of process cartridges are driven by a single drive motor, it is impossible to determine which process cartridge of a plurality of process cartridges is mounted only by detecting torque.

  Further, as in the above-described prior art, a sensor (BD sensor) for detecting image light provided for each process cartridge is also mounted only on a specific cartridge. For example, one polygon mirror corresponds to a plurality of process cartridges and one BD sensor is provided for each polygon mirror. In this case, when the polygon mirror is shared for two colors, it is mounted only for one of the colors. With this, it is possible to determine whether or not the process cartridge is attached / detached (presence / absence) only for a color cartridge not equipped with a BD sensor.

  In order to prevent such a situation, it is conceivable to use a detection sensor such as a dedicated photo sensor for detecting whether a cartridge is mounted or not. However, if a dedicated sensor is provided, the number of sensors increases, which increases the cost of the apparatus main body and increases power consumption.

  However, even if the dedicated sensor as described above is used, the printing operation may not be performed depending on the specification of the error processing. For example, when a dedicated sensor for detecting the presence / absence of each unit fails, it is determined that there is no unit and error processing is executed even though the unit is mounted. As described above, it is not preferable from the viewpoint of usability that the printing operation cannot be performed although it is not a fatal failure for the printer.

  Knowing the mounting status of each cartridge, in other words, detecting the replacement of each cartridge is an indispensable matter for the subsequent stable image formation.

  SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and image formation capable of detecting the mounting states of a plurality of process cartridges that can be attached to and detached from the apparatus main body even when the apparatus main body is reduced in cost. An object is to provide a device, a unit detection device, and a unit detection method. Specifically, an object of the present invention is to provide an image forming apparatus, a unit detection apparatus, and a unit detection method capable of effectively and efficiently detecting the presence / absence of replacement of a plurality of process cartridges by respective users. And

  In order to achieve the above object, the present invention provides an image forming apparatus in which a plurality of process cartridges are detachably mounted, and the control means controls driving of the plurality of process cartridges by a single driving means. And a load detecting means for detecting a load at the time of drive control by the drive means, and a cutoff for interrupting a beam optical path irradiated for the process cartridge in conjunction with an attaching / detaching operation of the process cartridge to the apparatus main body. A plurality of members, a beam detecting means for detecting the presence or absence of a beam in a beam optical path blocked by the blocking member, a load detected by the load detecting means, and a detection result of the beam detecting means. And a process cartridge state discriminating means for discriminating each mounting state of the process cartridge. It is intended.

  An image forming apparatus in which a plurality of process cartridges are detachably mounted, wherein the plurality of process cartridges are driven and controlled by a single driving means, and a load during drive control by the driving means is set. A load detecting means for detecting; a measuring means for measuring a current flowing through each process cartridge when the plurality of process cartridges are mounted; a load detected by the load detecting means; and a measurement result of the measuring means And a process cartridge state determining means for determining the mounting state of each of the plurality of process cartridges.

  According to the present invention, even when the apparatus configuration is reduced in cost, it is configured to detect the operation status from the signal originally provided as the image forming apparatus, thereby reliably detecting the mounting state of each process cartridge. It becomes possible. This makes it possible to execute a process for forming a stable image over a long period of time.

  Hereinafter, several preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings, particularly a motor drive of a process cartridge and a laser scanner unit including a polygon mirror and a BD sensor.

(First embodiment)
The configuration of the image forming apparatus according to the first embodiment of the present invention will be described with reference to FIGS. 2, 3, 6, and 7. The description of the same parts as those of the apparatus configuration and operation described in FIG. 1 is omitted.

  FIG. 2 is a diagram showing the configuration of the image forming apparatus according to the first embodiment of the present invention. In FIG. 2, there are two differences from the conventional example of FIG. 1, one of which is that three process cartridges 1Y, 1M, 1C are driven by one motor 6YMC. That is, the three process cartridges 1Y, 1M, and 1C photosensitive drums 1aY, 1aM, and 1aK are driven by one motor 6YMC. The process cartridge 1K is driven by a motor 6K. Another point is that there are two laser scanner units, one for 1Y and 1M, and one for 1C and 1K process cartridges. The configuration of FIG. 2 uses only one motor and one laser scanner unit in monochrome mode, and uses two motors and two laser scanner units in color mode. Therefore, the operation in the monochrome mode is made efficient.

(About process cartridge motor drive)
DC brushless motors are used for the 6YMC and 6K motors in FIG. FIG. 3 is a diagram showing a configuration example of this DC brushless motor. The DC brushless motor 50 has a coil 51 and a rotor 52 that are U-phase, V-, and W-phase star connections. Further, three Hall elements 53 for detecting the magnetic poles of the rotor are provided as rotor position detection means, and the output is amplified by an amplifier 54. In addition, it has means for detecting the rotational speed composed of a magnetic pattern 55 and a magnetic sensor 56 provided on the outer periphery of the rotor, and its output is amplified by an amplifier 57 and input to the speed controller 60.

  Reference numeral 70 denotes a driver circuit for driving a DC brushless motor, which includes three high-side transistors 71 and three low-side transistors 72, which are connected to U, V, and W of the coil 51, respectively. Reference numeral 58 denotes an energization logic circuit that controls energization. Reference numeral 80 denotes a current limiter circuit unit.

  The energization logic circuit specifies the position of the rotor based on the rotor position signals HU, HV, and HW generated by the hall element 53, and generates a phase switching signal. The phase switching signals UU, UV, UW, LU, LV, and LW rotate the rotor by sequentially switching the phases to be excited by on / off controlling each transistor of the driver circuit.

  The speed control unit 60 generates a voltage proportional to the motor rotation speed by the F / V converter 61 and then compares the voltage generated by the comparator 62 with the reference voltage to obtain a differential output. Further, the PLL unit 63 compares the phase of the motor rotation frequency signal and the reference frequency signal, and obtains an output corresponding to the phase shift. Further, the two outputs are mixed by a mixer 64 and a PWM signal generator 65 generates a PWM signal. The PWM signal is input to the energization logic circuit, and the energization logic circuit controls the rotation speed (torque in another expression) of the motor based on the PWM signal.

  The current limiter circuit unit converts the drive current into a voltage by the detection resistor 81, and compares the voltage converted by the comparator 82 with the reference voltage. As a result of the comparison, if the converted voltage is greater than the reference voltage, a signal is output to the energization logic circuit so as to stop the driving of the motor.

  As is apparent from FIG. 3, this motor drive has a loop that feeds back a signal representing the rotational speed to the drive unit, so that the phase of the motor is within a predetermined load range at a predetermined rotational speed. The configuration is such that a predetermined phase is obtained. In general, such a drive circuit also has a function of opening a feedback loop, and can be controlled in various ways from the outside by various methods.

  In this embodiment, a function (not shown) for detecting the rotational speed of the motor is provided. This function performs A / D conversion on the output of the F / V converter in FIG. It can also be realized by counting for a predetermined time. In this case, the value after A / D conversion or the counter value can be used by a microprocessor or the like as a value representing the rotational speed of the motor or a value proportional to the rotational speed.

  Next, the cartridge mounting state detection sequence in this embodiment will be described with reference to FIGS. FIG. 4 is a diagram showing attenuation of the rotation speed of the motor due to the load torque, and FIG. 5 is a flowchart for determining the number of process cartridges mounted from the detected motor load torque in the first embodiment. . Here, a case will be described in which the magnitude of the load of the motor 6YMC that drives the three process cartridges 1Y, 1M, and 1C of yellow, magenta, and cyan is detected, and the mounting state of the cartridge, that is, the number of mounted cartridges is detected. Note that this sequence is a CPU that controls each device in the image forming apparatus (for example, various settings such as the motor drive unit in FIG. 3, the setting of the high-voltage power supply, the conveyance motor, and the laser scanner unit). (Engine controller).

  When the process cartridge mounting state detection sequence starts, first, in step T1, a PWM value is set so that the motor 6YMC is driven with a constant input power. In the present embodiment, for example, PWM value = 100 is set. Thereafter, after the driving of the motor 6YMC is started and the motor 6YMC is in a steady rotation, the PWM value (= 0) is set so as to stop the driving. In step T2, a predetermined time is waited. During this time, drive transmission to the process cartridge is interrupted, and the DC brushless motor rotates by inertia and the rotational speed decreases.

  Next, in step T3, after waiting for a predetermined time, the speed of the motor 6YMC is detected. At this time, as shown in FIG. 4, the load applied to the motor 6YMC differs depending on the number of mounted process cartridges. Therefore, the speed attenuation curve of the motor 6YMC from a predetermined rotational speed varies. FIG. 4 shows the degree of motor speed attenuation, and shows the relationship between the passage of time after the motor stops driving and the motor speed at that time. The speed of the motor 6YMC after waiting for a predetermined time is detected. If the detected speed is lower than the preset threshold value 1, three process cartridges, that is, three process cartridges 1Y, 1M, and 1C of yellow, magenta, and cyan are all mounted. Judge that it has been.

  If the motor speed is higher than the threshold value 1 in step T3, it is determined whether or not the motor speed is lower than the threshold value 2 in step T4. When the motor speed is lower than the threshold 2, there are two process cartridges, that is, at least two process cartridges of yellow, magenta, and cyan (any two of 1Y, 1M, and 1C). Is determined to be installed.

  If the motor speed is higher than the threshold value 2 at step T4, it is determined whether the motor speed is lower than the threshold value 3 at step T5. When the motor speed is lower than the threshold value 3 in FIG. 4, one process cartridge, that is, at least one process cartridge (1Y, 1M, 1C) of yellow, magenta, and cyan is selected. 1) is installed.

  If the motor speed is higher than the threshold value 3 in step T5, it is determined that no process cartridge is mounted.

  As described above, it is possible to determine the number of process cartridges mounted by detecting the motor speed after a predetermined time from stopping the driving of the motor 6YMC.

  Similarly, by detecting the motor speed after a predetermined time from stopping the driving of the motor 6K, it is possible to determine the number of mounted process cartridges, that is, the mounting status of the process cartridge 1K. is there.

(Configuration of laser scanner unit)
Since the laser scanner units 2YM and 2CK in FIG. 2 have the same configuration, the configuration of one scanner unit 2CK will be described in detail, and the scanner unit 2YM will be described supplementarily.

  FIG. 6 is a diagram showing the configuration of the scanner unit 2CK of this embodiment. In FIG. 6, reference numerals 101 and 102 denote laser diodes, which scan the photosensitive drums 1aK and 1aC with laser light based on the video signal generated by the engine controller. Here, 101 is a first laser diode (LD1), and 102 is a second laser diode (LD2).

  Reference numeral 103 denotes a polygon mirror as a means for deflecting and scanning the laser beam. The polygon mirror 103 is controlled by a motor (not shown) so as to rotate at a constant speed in the direction of arrow A in FIG. Scan with reflection. The motor rotates at a constant speed according to the acceleration signal and deceleration signal of the speed control signal from the engine controller.

  Reference numeral 106 denotes another sensor that is on the scanning path of the laser diode LD2 (102) and generates a horizontal synchronization signal that serves as a reference for the exposure start position (image writing position) of the laser beam on the photosensitive drum. This sensor is an optical sensor that generates a signal when a laser beam is incident, and is hereinafter referred to as a BD (Beam Detect) sensor. As can be seen from the figure, this BD sensor is present in a region to be scanned prior to the scanning portion for image formation. In this figure, the BD sensor is only on the scanning path of the laser diode LD2 (102), and is not provided on the scanning path of the other laser diode LD1 (101). In other words, the beam emitted from the laser diode LD 1 is not reflected by the polygon mirror 103 and reaches the BD sensor 106.

  The laser beam emitted from the laser diode LD2 (102) is scanned while being reflected by the polygon mirror 103, further reflected by the folding mirror 105, and scanned on the photosensitive drum 1aC from right to left in the figure.

  In practice, the laser beam passes through various lens groups (not shown) in order to focus on the photosensitive drum or to convert the laser beam from diffused light to parallel light. Because of this configuration, the description is omitted.

  The image forming apparatus has a function of receiving image data from a host computer and converting the received data, and a video controller (not shown) that issues a print command. Further, it has an engine controller (not shown) that receives a print command from the video controller and executes and controls a printing operation.

  This video controller transmits a video signal based on image data to be printed to the engine controller after a predetermined time from detecting the output signal of the BD sensor 106. The engine controller emits a laser beam based on the video signal and scans the photosensitive drum with the laser beam. By emitting a laser beam based on the output signal from the BD sensor, the writing position of the image in the main scanning direction always matches.

  On the other hand, similarly to the laser diode LD2 (102), the laser diode LD1 (101) forms an electrostatic latent image on the photosensitive drum 1aK.

  Here, since the BD sensor is not provided on the scanning path of the laser diode LD1 (101) with respect to the output of the horizontal synchronization signal, the engine controller can simulate the horizontal synchronization signal for the laser diode LD1 (101). To generate.

A signal obtained by delaying the horizontal synchronizing signal from the BD sensor for the laser diode LD2 (102) by a predetermined time is generated. In the following description, this signal is referred to as a pseudo horizontal synchronization signal.
Generation of the pseudo horizontal synchronizing signal will be described with reference to FIG. FIG. 7 is a diagram for explaining that the image writing is started by delaying the horizontal synchronization signal from the BD sensor for a predetermined time in the configuration shown in FIG.

  The scanner unit 2YM has the same configuration except that the photosensitive drum 1ak in FIG. 6 becomes the photosensitive drum 1aM and the photosensitive drum 1aC becomes the photosensitive drum 1aY. Therefore, the BD sensor is provided only for 1C and 1Y.

  In FIG. 7, reference numeral 701 denotes a position where the BD sensor for LD1 according to the conventional method is arranged. Originally, if a BD sensor is arranged at this position and an image is written after a predetermined timing tc from the output signal of this BD sensor, the image is written from the correct position.

  Light emitted from the laser diodes LD1 and LD2 is reflected by the polygon mirror and applied to the photosensitive drum. In this embodiment, a polygon mirror having four reflecting surfaces is used.

  In the case where the BD sensor for LD1 is not provided, if the horizontal synchronizing signal of LD2 is simply used as the horizontal synchronizing signal for LD1, the image writing position of LD2 in the main scanning direction becomes the image writing position of LD1 in the main scanning direction. It will shift every time. Furthermore, this deviation is usually different for each surface (four surfaces) of the polygon mirror.

  Therefore, a signal obtained by delaying the horizontal synchronizing signal of LD2 by one BD period is generated and used as the horizontal synchronizing signal of LD1. Here, the BD cycle is an average cycle of the generation cycles of the horizontal synchronization signal of LD1. By writing the image at a timing delayed by tc from the horizontal synchronization signal for LD1 generated in this way, the image can be written at the correct position. Here, the 1BD period means that the LD1 generates a horizontal synchronizing signal for the LD1 from the BD signal generated on the LD2 side on the same polygonal surface as the polygonal surface that scans the photosensitive drum. This procedure is because the polygon mirror is not an exact quadrilateral and its center of rotation is not the exact center of this quadrilateral, but if the number of revolutions is constant, the BD period in the figure. Takes the same value every four cycles.

  In this manner, an image corresponding to cyan is formed on the photosensitive drum 1aC by the laser diode LD2 (102) on the side having the BD sensor 106. Further, an image corresponding to the black color is formed on the photosensitive drum 1aK by the laser diode LD1 (101) on the side not having the BD sensor 106. In the present embodiment, the cyan color has a BD sensor and the black color has no BD sensor. However, conversely, the cyan color may not have a BD sensor, and the black color may have a BD sensor.

  The scanner unit 2YM having the same configuration as the scanner unit 2CK205 has a configuration in which the magenta color has no BD sensor and the yellow color has a BD sensor. However, conversely, the yellow color may have no BD sensor, and the magenta color may have a BD sensor.

  In the present embodiment, as described above, among yellow, magenta and cyan process cartridges driven by the motor 6YMC, yellow and cyan have BD sensors, and magenta has a BD sensor. It has no configuration.

  In addition, a shutter member that blocks the optical path of the BD sensor is attached in conjunction with the attachment and detachment of the process cartridge. When there is no process cartridge, no laser light is incident on the BD sensor. Yes. In this embodiment, since BD sensors are provided for yellow and cyan, laser light does not enter the BD sensor when there are no yellow and cyan process cartridges.

  Based on such a configuration, after the drive of the motor 6YMC is stopped, the motor speed after a predetermined time is detected and the number of process cartridges mounted is determined, and then a non-mounted process cartridge is specified. The sequence will be described with reference to FIGS.

  FIG. 8 is a sequence when the speed of the motor 6YMC is detected and it is determined that one process cartridge is not mounted (two process cartridges are mounted).

  Control starts when there is only one process cartridge not mounted, and in step S1, the scanner motor is driven to wait for a predetermined time. In step S2, the horizontal synchronization signal is monitored by the BD sensor during this predetermined time. Here, if the horizontal synchronizing signal in the scanner unit 2YM cannot be monitored, the horizontal synchronizing signal by the laser beam for yellow of the scanner unit 2YM cannot be detected, so the yellow process cartridge is not mounted. Judge.

  If the horizontal synchronization signal in the scanner unit 2YM can be monitored in step S3 and the horizontal synchronization signal in the scanner unit 2CK cannot be monitored, it can be determined that the cyan process cartridge is not installed.

  In step S4, since the horizontal synchronization signals in the scanner units 2YM and 2CK can be monitored, it is determined that the magenta process cartridge is not installed because the yellow and cyan process cartridges are installed. it can.

  FIG. 9 is a sequence in a case where the torque of the motor is detected and it is determined that there are two process cartridges that are not mounted (one process cartridge is mounted). Control starts when there is one process cartridge not mounted, and in step V1, the scanner motor is driven to drive the scanner motor. In step V2, the horizontal synchronizing signal is monitored by the BD sensor during this predetermined time. Here, when the horizontal synchronizing signal in the scanner unit 2YM can be monitored, the process cartridge for yellow is mounted. That is, it is determined that the magenta and cyan process cartridges are not mounted.

  If the horizontal synchronization signal in the scanner unit 2YM cannot be monitored in step V3, if the horizontal synchronization signal in the scanner unit 2CK can be monitored in step V4, a cyan process cartridge is installed. . That is, it is determined that the yellow and magenta process cartridges are not mounted.

  If the horizontal synchronization signal in the scanner unit 2CK cannot be monitored in step V4, it is determined that the yellow and cyan process cartridges are not mounted.

  As described above, the number of process cartridges mounted can be specified by the process cartridge mounting state detection sequence for detecting the speed of the motor. Further, by monitoring the horizontal synchronizing signal, it is possible to specify which process cartridge is mounted.

  The result of the determination is output to an operation provided on the image forming apparatus, a panel (not shown), a computer (not shown) connected to the image forming apparatus, or the like, and notified to the user.

  In the present embodiment, the process / cartridge mounting state detection sequence for detecting the motor speed is performed first, and then the control for monitoring the horizontal synchronization signal has been described. However, these two detection sequences may be performed simultaneously, or after monitoring the BD signal, a process / cartridge mounting state detection sequence for detecting the speed of the motor may be performed.

  In this embodiment, a process cartridge for yellow, magenta, and cyan is driven by a single motor 6YMC, and a BD sensor for monitoring horizontal sync signals for yellow and cyan is provided. However, if the number of process cartridges driven by one motor is n (n> = 2) and the number of BD sensors for monitoring horizontal synchronization signals is n-1, this embodiment can be applied. It is.

  As described above, according to the present embodiment, even in the main body configuration in which the number of BD sensors is reduced to realize cost reduction, it is possible to detect in detail the mounting states (presence / absence of mounting) of a plurality of process cartridges.

(Second Embodiment)
Next, the configuration of the image forming apparatus according to the second embodiment of the present invention will be described.

  Note that the configuration of the image forming apparatus and the schematic configuration of the control system in the present embodiment are the same as those in the first embodiment, and a description thereof will be omitted. In the present embodiment, the process cartridge mounting state detection sequence using the motor described in the first embodiment is the same, and the description thereof is omitted.

  The second embodiment of the present invention will be described in detail based on FIGS.

  FIG. 10 is a schematic wiring diagram of a pre-transfer charging bias circuit and a transfer bias circuit used in a laser printer as an example of a color image forming apparatus according to this embodiment. FIG. 11 is a schematic wiring diagram focusing on one image forming unit in FIG. FIG. 12 is an explanatory diagram of a circuit for detecting a transfer current. FIGS. 13 and 14 are flowcharts relating to the procedure for detecting the state of the process cartridge by detecting the transfer current.

  Reference numeral 30 (30a, 30b, 30c, 30d) in FIG. 10 is a transfer positive bias circuit provided for each image forming unit of four colors (yellow, magenta, cyan, black). By this circuit, a transfer voltage is applied to each transfer roller 3 in order to sequentially superimpose and transfer the respective color toner images formed on the photosensitive drums 1aY, 1aM, 1aC, and 1aK onto the recording medium.

  These transfer positive bias circuits can variably output a high voltage corresponding to the ON width of the PWM clock signal S28 (28a, 28b, 28c, 28d) from the control circuit 28. The control circuit 28 controls these output voltages to predetermined values according to the environmental state in which the printer is used, the paper type, the printing timing, and the like.

When a predetermined high voltage is output from the transfer negative bias circuit 32a of the first color yellow image forming unit, most of the first color transfer current I28a is transferred from the transfer roller 4a as the transfer load 29a. It flows to the paper 14 and the photosensitive drum 1aY and flows to the ground.
The transfer current I28a of the first color (yellow) flowing to the ground follows a current loop that returns to the transfer positive bias circuit 30a via the current detection circuit 31a and the transfer negative bias circuit 32a.
Similarly, transfer currents I28b, I28c, and I28d also flow in the second to fourth image forming units (magenta, cyan, and black). In this embodiment, current detection circuits 31a and 31b are provided in the yellow image forming unit and the cyan image forming unit.

  Reference numeral 32 (32a, 32c) denotes a transfer negative bias circuit, which can be variably controlled by the PWM signal S29 (S29a, S29c) of the control circuit 28 in the same manner as the positive bias. Used to clean waste toner).

  The operation of the transfer current detection circuit 31a using the OP-AMP 41 will be described below with reference to FIG.

The transfer current I28a flows from the ground of the OP-AMP 41 of the current detection circuit as shown by the output terminal, the protective resistor 43, the resistor 39 and the arrow in the figure. The + terminal of the OP-AMP 41 is connected to the ground by the impedance matching resistor 42. Since the + terminal and the − terminal of the OP-AMP 41 are generally considered as imaginary shorts (virtual shorts), the − terminal can also be considered as a ground potential (plus terminal potential). When the transfer current I28a flows, a voltage of Vi is generated with reference to the virtual ground of the negative terminal of the OP-AMP. This Vi is expressed by the following equation when the transfer current is Itr and the resistance 39 is Ra.
Vi≈Itr × Ra

  Therefore, the value of the output signal S30 from the current detection circuit 31a is Vi, and as a result, the current detection circuit converts the magnitude of the transfer current I28a flowing through the first image forming unit into an analog voltage.

  The output signal S32 output from the transfer current detector 31a is transmitted to the A / D port in the control circuit 28. The control circuit 28 performs digital conversion based on the output signal S30 and calculates a transfer current value.

  The case where the yellow process cartridge is not attached is the case where the photosensitive drum 1aY for 29a among the transfer loads 29a, 29b, 29c, and 29d in FIG. 10 is not attached. That is, the transfer current I28a hardly flows, and the current value is smaller than that in the state where the yellow process cartridge is mounted.

  A sequence for detecting the motor speed after a predetermined time after the driving of the motor 6YMC is stopped and discriminating the number of non-mounted cartridges after identifying the transfer current detection method. Will be described with reference to FIGS. 13 and 14.

  FIG. 13 is a sequence when it is determined that the number of process cartridges that are not attached is one (two process cartridges that are attached) as a result of detecting the speed of the motor.

  Control in the case where there is one process cartridge not mounted (control for determining whether one CRG is present) starts, a transfer voltage is applied in step W1, and a wait is performed for a predetermined time in step W2. The transfer voltage applied during the predetermined time waits for a sufficient time until the transfer current flows to the transfer load. In step W3, if the transfer current value flowing from the yellow transfer roller (3Y) to the photosensitive drum (1aY) is not a predetermined value or more, it is determined that the yellow process cartridge is not mounted. In step W3, if the transfer current value is a predetermined value or more, whether or not the transfer current value flowing from the cyan transfer roller (3C) to the photosensitive drum (1aC) is a predetermined value or more in step W4. Determine. If the transfer current value is not greater than or equal to the predetermined value in step W4, it is determined that no cyan process cartridge is installed. In step W4, if the transfer current value is equal to or greater than the predetermined value, it is determined that the magenta process cartridge is not mounted.

  FIG. 14 is a sequence when the motor speed is detected and it is determined that there are two unmounted process cartridges (one mounted process cartridge).

  Control in the case where there are two process cartridges not mounted (control for determining whether or not there are two CRGs) is started, a transfer voltage is applied in step X1, and a wait is performed for a predetermined time in step X2. The transfer voltage applied during the predetermined time waits for a sufficient time until the transfer current flows to the transfer load. In step X3, if the transfer current value flowing from the yellow transfer roller (3Y) to the photosensitive drum (1aY) is equal to or greater than a predetermined value, the magenta and cyan process cartridges are not mounted. to decide. In step X3, if the transfer current value is not a predetermined value or more, whether or not the transfer current value flowing from the cyan transfer roller (3C) to the photosensitive drum (1aC) is a predetermined value or more in step X4. Determine. In step X4, if the transfer current value is equal to or larger than the predetermined position, it is determined that the yellow and magenta process cartridges are not mounted. In step X4, if the transfer current value is not equal to or greater than the predetermined value, it is determined that the yellow and cyan process cartridges are not installed.

  As described above, the number of mounted process cartridges can be specified by the process cartridge mounting state detection sequence in which the motor speed is detected. By detecting the transfer current, it is possible to specify which process cartridge is mounted.

  In the present embodiment, the process cartridge detection state detection sequence in which the motor speed is detected is performed first, and then the control for detecting the transfer current has been described. However, these two sequences may be performed simultaneously, or after detecting the transfer current, a process cartridge mounting state detection sequence in which the motor speed is detected may be performed.

  Further, the present embodiment has described the configuration in which yellow, magenta, and cyan process cartridges are driven by one motor 6YMC to detect transfer currents in the yellow and cyan image forming units. However, the present embodiment can be applied to any configuration in which the number of process cartridges driven by one motor is n (n> = 2) and the number of stations for detecting the transfer current is n-1.

  As described above, according to the present embodiment, even in a main body configuration in which the number of BD sensors is reduced to realize cost reduction, it is possible to detect in detail the mounting states (presence / absence of mounting) of a plurality of process cartridges.

(Third embodiment)
Next, the configuration of the image forming apparatus according to the third embodiment of the present invention will be described.

  Note that the configuration of the image forming apparatus and the schematic configuration of the control system in the present embodiment are the same as those in the first embodiment, and a description thereof will be omitted.

  In the first and second embodiments, the motor speed (the number of revolutions per unit time) is detected in order to detect the motor load torque. In the present embodiment, the motor is controlled in a closed loop, that is, in a form having a signal line from the magnetic sensor 56 to the speed control unit 60, and from the signal indicating the magnitude of the input power when driving at a constant rotational speed, Detect the load torque. The signal representing the input power uses a PWM signal output from the speed control unit, and detects the magnitude of the input power from this PWM value.

  However, the load usually fluctuates according to the structural rotational position of the driven load side. Therefore, the following processing is performed to average the fluctuations, in other words, the sampled PWM value. A value indicating the average value or a value indicating the integrated value is calculated.

  A specific process cartridge mounting state detection sequence will be described with reference to FIG.

  When the process cartridge mounting state detection sequence starts, in step Y1, the final target rotational speed is set in the speed controller so that the motor 6YMC is driven at a constant rotational speed. Then, after the motor 6YMC has made steady rotation, in step X2, a predetermined count value is set in the counter and the PWM value addition variable α is cleared to zero. Here, α is also a place for storing the integration result of the sampled PWM values. Thereafter, in step Y3, the PWM value is added to the PWM value addition variable α at regular intervals. In step Y4, the count value of the counter is subtracted. In step Y5, it is determined whether or not the count value has become 0 by subtraction. If it is not 0, the processes of Y3 and Y4 are repeated. When the count value becomes 0, the addition of the PWM value is finished. At this time, although the variable α is an integrated value, a value proportional to the power consumed in a predetermined time can be obtained by changing the time average and view of the driving power. This value is also a value proportional to the magnitude of the load torque.

  Next, in step Y6, after the addition of the PWM value is completed, the total sum α of the calculated PWM values is compared with a threshold value serving as a predetermined reference value to determine the number of cartridges mounted. If the total sum α of the calculated PWM values is larger than the threshold value that is the reference value, the load torque is large, and if the total sum α of the calculated PWM values is smaller than the threshold value that is the reference value, the load torque is small.

  In step Y6, when the total sum α of the PWM values calculated is larger than the threshold value 1, it is determined that all three process cartridges for yellow, magenta, and cyan are mounted. If the total PWM value α is not greater than or equal to the threshold value 1 in step Y6, it is determined in step Y7 whether the total PWM value α is greater than or equal to the threshold value 2. In step Y7, when the total sum α of the PWM values calculated is larger than the threshold value 2, it is determined that at least two process cartridges are installed in yellow, magenta, and cyan. If the total PWM value α is not greater than or equal to the threshold value 2 in step Y7, it is determined in step Y8 whether the total PWM value α is greater than or equal to the threshold value 3. If the total sum α of PWM values calculated in step Y8 is larger than the threshold 3, it is determined that at least one process cartridge is mounted among yellow, magenta, and cyan. . If the total sum α of the PWM values is not equal to or greater than the threshold value 3, it is determined that no process cartridge is mounted.

  The magnitude relationship between threshold values 1, 2, and 3 is such that threshold value 1> threshold value 2> threshold value 3.

  As described above, it is possible to determine the number of mounted process cartridges from the signal indicating the magnitude of the input power when the motor 6YMC is driven at a constant rotational speed. If the load-side torque is constant regardless of the load-side rotational position or is a change that can be ignored for such processing, the loop processing from Y3 to Y5 is stopped and the processing from Y3 to Y6 is stopped. It is possible to proceed to processing.

  It should be noted that when the motor is driven with a constant power in an open loop, that is, without a signal line from the magnetic sensor 56 to the speed control unit 60, a process that is mounted from a signal that represents the number of rotations. It is also possible to determine the number of cartridges. Also in this case, depending on the fluctuation of the load torque in that case, it is possible to execute the averaging process described above or to perform the process without executing it.

  Further, it is possible to detect the load torque from the magnitude of the input power when the motor is accelerated from a certain speed to a certain speed, and determine the presence or absence of the cartridge in the same manner as described above. For example, the motor is accelerated from the rotational speed = 0 rpm to the final target rotational speed, the PWM value is detected at a constant period during the motor acceleration, and the PWM value is added. By stopping this addition when the motor reaches the final target rotational speed, a value proportional to the electric power required for the acceleration can be obtained from the integrated value of PWM. This integrated value also represents the magnitude of the load torque. When the load is heavy, if the acceleration is constant, the power required for the acceleration becomes large, and if the driving for acceleration and the increase in power for acceleration are constant, the power reaches a constant speed. Will require a lot of time to complete.

  Further, even when the motor is decelerated from a certain speed to a certain speed, the PWM can be integrated by a similar method to obtain a value proportional to the electric power during that period. In this case, when the load is heavy, the obtained value becomes small. Conversely, when the load is light, the obtained value becomes large. This tendency is opposite to the case shown in FIG. 15, but the threshold processing is executed, and the same result as shown in FIG. 15 can be obtained.

  In addition, the magnitude of the load can be detected from a value representing the rotation speed when the motor drive is controlled in an open loop and a constant input power is applied. In this case, the value representing the rotational speed is inversely proportional to the magnitude of the load.

  Further, the magnitude of the load can be detected from the change in the rotational speed of the motor at that time by changing the input power. When changing in the increasing direction, the amount of change in rotational speed is inversely proportional to the magnitude of the load, and when changing in the direction of decreasing, the amount of change in rotational speed is proportional to the magnitude of the load. become. In this case, the averaging process performed in Y3 to Y5 in FIG. 15 is substantially performed on the assumption that the rotation speed is obtained by performing signal processing from the magnetic sensor. By processing the signal from the magnetic sensor, a broad rotation angle of the motor for a predetermined time period can be obtained.

  The process cartridge mounting state detection sequence described in this embodiment is used in place of the detection sequence based on the motor speed detection described in the first and second embodiments, and the process cartridge mounting state is detailed. Can be detected.

  As shown in FIGS. 2, 6, and 7, in the above-described embodiment, a BD sensor is provided for Y and C for each of Y, M, C, and BK cartridges. Yes. If only the BD sensor is considered, it can be provided in M and BK instead of Y and C, but in this case, as described above, it is impossible to detect the mounting state of each cartridge. . Therefore, the present invention is based on the premise that two of Y, M, and C are provided with BD sensors when the monochrome and color cartridges are driven by two dedicated motors. ing.

It is a figure which shows the general structure of the color image forming apparatus in the past. 1 is a diagram illustrating a configuration of an image forming apparatus according to a first embodiment of the present invention. It is a figure explaining the motor shown in FIG. 2, and its drive structure. It is a figure which shows attenuation | damping of the rotational speed of the motor by load torque. 4 is a flowchart for determining the number of process cartridges mounted from detected motor load torque in the first embodiment of the present invention. It is a figure explaining the structure of the scanner unit 2CK of FIG. FIG. 7 is a diagram for explaining starting image writing by delaying a horizontal synchronization signal from a BD sensor by a predetermined time in the configuration shown in FIG. 6. FIG. 2 is a diagram illustrating a configuration example of the transfer bias circuit. In the first embodiment of the present invention, a method of identifying a removed process cartridge from the presence or absence of a horizontal synchronization signal when it is determined that there are two process cartridges from the detected load torque is illustrated. It is a flowchart. It is a figure which shows the structural example of the pre-transfer charging bias circuit and transfer bias circuit in the 2nd Embodiment of this invention. FIG. 11 is a diagram illustrating a current path of the transfer bias circuit of FIG. 10. It is a figure which shows the circuit example of the electric current detection part of FIG. In the second embodiment of the present invention, a method for identifying a removed process cartridge from the presence or absence of a horizontal synchronization signal when it is determined that there is one process cartridge from the detected load torque is illustrated. It is a flowchart. In the second embodiment of the present invention, a method of identifying a removed process cartridge from the presence or absence of a horizontal synchronization signal when it is determined that there are two process cartridges from the detected load torque is illustrated. It is a flowchart. It is a flowchart explaining 2nd Embodiment. 12 is a flowchart for determining the number of process cartridges mounted from detected motor driving power in the third embodiment of the present invention.

Explanation of symbols

100 Image forming apparatus 1 (Y to K) Process cartridge 1a (Y to K) Photosensitive drum (latent image carrier)
2 Laser scanner unit 3 (Y to K) Transfer roller 4 Paper feed cassette 5 Fixing unit (fixing device)
6 drive motor 28 control circuit 29 transfer load 30 transfer bias circuit 31 transfer current detector 32 transfer negative bias circuit 33 on-off signal 34 pre-transfer charging load 35 pre-transfer charge bias circuit 36 current detection circuit 37 pre-transfer negative charge bias circuit 38 Capacitor 39 Resistor 40 Resistor 41 OP-AMP
42 impedance matching resistor 43 protective resistor 44 voltage 50 DC brushless motor 51 coil 52 rotor 53 hall element 54 amplifier 55 magnetic pattern 56 magnetic sensor 57 amplifier 58 energization logic circuit 60 speed control unit 61 F / V converter 62 comparator 63 PLL
64 Mixer 65 PWM signal generator 70 Driver 71 High side transistor 72 Low side transistor 80 Current limiter 81 Current detection resistor 82 Comparator 101, 102 Laser diode 103 Polygon mirror 104, 105 Folding mirror 106 BD sensor

Claims (11)

An image forming apparatus in which a plurality of process cartridges are detachably mounted,
Control means for driving and controlling the plurality of process cartridges by a single drive means;
Load detection means for detecting a load during drive control by the drive means;
A blocking member that blocks a beam optical path irradiated for the process cartridge in conjunction with an attaching / detaching operation of the process cartridge to the apparatus main body,
Beam detecting means for detecting the presence or absence of a beam in a beam optical path blocked by the blocking member;
And a process cartridge state determining unit that determines a mounting state of each of the plurality of process cartridges based on a load detected by the load detecting unit and a detection result of the beam detecting unit. Image forming apparatus. An image forming apparatus in which a plurality of process cartridges are detachably mounted,
Control means for driving and controlling the plurality of process cartridges by a single drive means;
Load detection means for detecting a load during drive control by the drive means;
Measuring means for measuring a current flowing in each process cartridge when the plurality of process cartridges are mounted;
An image comprising: a process cartridge state determining unit that determines a mounting state of each of the plurality of process cartridges based on a load detected by the load detecting unit and a measurement result of the measuring unit. Forming equipment. The driving means includes a motor;
The load detection means detects the magnitude of a load based on a change in a signal representing the number of rotations of the motor after the motor is driven at a constant number of rotations. Image forming apparatus. The driving means includes a motor;
3. The image according to claim 1, wherein the load detection unit detects the magnitude of the load based on a signal representing the number of rotations of the motor when the motor is driven with a constant input power. 4. Forming equipment. The driving means includes a motor;
The load detection means detects the magnitude of the load based on a signal representing the magnitude of the input power when the motor is driven at a constant rotational speed. Image forming apparatus. The driving means includes a motor;
The image according to claim 1, wherein the load detection unit detects the magnitude of the load based on a change in a signal indicating the magnitude of input power when the motor is accelerated or decelerated. Forming equipment. The driving means includes a motor;
The load detection means detects the magnitude of the load based on a change in a signal representing the number of rotations of the motor when the input power to the motor is changed. Image forming apparatus.   The image forming apparatus according to claim 2, wherein the motor is a DC motor. The plurality of cartridges are yellow, magenta, cyan, black process cartridges;
The control means includes a single drive means for driving and controlling the yellow, magenta and cyan color process cartridges, and a single drive means for driving and controlling the black color process cartridges. Including
The image forming apparatus according to claim 1, wherein the blocking member and the beam detecting unit are provided for at least two process cartridges of yellow, magenta, and cyan. apparatus. A method for detecting attachment of each process cartridge of an image forming apparatus, comprising: a plurality of process cartridges detachably mounted; and a control unit that drives and controls the plurality of process cartridges by a single driving unit.
A load detection step of detecting a load during drive control by the drive means;
A beam detection step of detecting the presence or absence of a beam irradiated to form an image on the process cartridge;
A determination step of determining a detection result of the load detection step, a detection result of the beam detection step, and a mounting state of each of the plurality of process cartridges;
A method for detecting attachment of each process cartridge of the image forming apparatus. A method for detecting attachment of each process cartridge of an image forming apparatus, comprising: a plurality of process cartridges detachably mounted; and a control unit that drives and controls the plurality of process cartridges by a single driving unit.
A load detection step of detecting a load during drive control by the drive means;
A current measuring step for measuring a current value of a current path flowing through each process cartridge;
A determination step of determining the mounting state of each of the plurality of process cartridges based on the detection result of the load detection step and the measurement result of the current measurement step;
A method for detecting attachment of each process cartridge of the image forming apparatus.

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