JP5693191B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to shortening of a first printout time in an electrophotographic image forming apparatus.

  In an image forming apparatus using an electrophotographic process, a plurality of image forming units are juxtaposed, and toner images are sequentially transferred onto an intermediate transfer belt disposed opposite to the plurality of image forming units, and the toner images are recorded on a recording sheet. A tandem type color image forming apparatus that performs batch transfer onto the top is widely known.

  In such a color image forming apparatus, the photosensitive drum and the intermediate transfer belt are often separated from each other when image formation is not performed. This is because, when the photosensitive drum and the intermediate transfer belt are always in contact with each other, the transfer roller disposed to face the photosensitive drum via the intermediate transfer belt is slightly deformed with time due to the contact pressure. When this deformation occurs, the toner image transfer conditions differ between the deformed portion and the non-deformed portion, and the difference in the transfer conditions affects the transferred image. For this reason, only when the image forming operation is performed, measures are taken to bring the photosensitive drum into contact with the intermediate transfer belt.

  At the time of image formation, transfer voltage control (hereinafter referred to as ATVC) is executed after a predetermined time from the end of the contact operation. This ATVC is performed because the resistance value of the transfer roller for transferring an image from the photosensitive drum to the intermediate transfer belt and the resistance value of the intermediate transfer belt largely change due to environmental factors and individual variation factors. That is, the ATVC is a control performed to grasp a resistance value that dynamically changes, set an appropriate transfer voltage, and transfer a toner image formed on the photosensitive drum onto a recording sheet. A technique related to the ATVC is disclosed in, for example, Japanese Patent Application Laid-Open No. 2003-149963.

JP 2003-149963 A

  In an image forming apparatus, there is a demand for shortening the time until the first page can be printed (first printout time: hereinafter abbreviated as FPOT). In order to shorten this FPOT, for example, a countermeasure may be considered in which the ATVC is operated in parallel with the contact operation in the latter half of the contact operation.

  However, ATVC applies a constant current to the transfer roller in advance, and determines the transfer bias based on the voltage determined from the resistance value of the transfer roller. Therefore, the transfer roller is driven stably during ATVC. It is desirable to have If the photosensitive drum and the transfer roller transition from the separated state to the contact state during ATVC execution, the current flowing to the transfer roller becomes unstable due to the impact at the time of contact, and the accuracy of ATVC is impaired. End up.

  Here, the contact operation between the photosensitive drum and the intermediate transfer belt varies in operation time due to individual differences in parts of the mechanical parts (solenoid, clutch, cam, gear, etc.) used for the contact / separation operation. For this reason, in the sequence processing of the image forming apparatus, the time for completing the operation of the mechanical parts is set to a time that can afford to absorb the individual variations of the mechanical parts. Transition.

  As described above, while it is desired to shorten the FPOT, it is unavoidable to lengthen the FPOT for a certain period of time in order to ensure the accuracy of ATVC. Further, the image sequence is not limited to ATVC, and the same problem as ATVC may occur if the image sequence has an effect on the operation accuracy due to the contact operation between the photosensitive drum and the intermediate transfer belt. In the above description, the photosensitive drum and the intermediate transfer belt have been described. However, the photosensitive drum and the transfer material carrier in the image forming apparatus that directly transfers the toner image from the photosensitive drum to the recording paper (recording material). The same problem arises for and. That is, the same problem may occur in an endless belt that rotates in contact with the photosensitive drum.

  The present invention has been made in view of the above problems, and an object thereof is to improve the FPOT while avoiding the influence of the contact operation between the photosensitive drum and the endless belt on the subsequent image sequence.

  The present invention has been made for the purpose of solving the above-described problems, and includes the following configuration as one means for achieving the object.

In other words, the image forming apparatus according to the present invention includes an image carrier, a forming unit that forms an image on the image carrier, an endless belt, and a contact that abuts and separates the image carrier and the endless belt. A recording paper that is provided with a separating unit and that conveys a toner image carried on the image carrier by the endless belt or the endless belt in a state where the image carrier and the endless belt are in contact with each other; In the image forming apparatus to be transferred to the image forming apparatus, an output signal from a driving unit that rotationally drives the image carrier or the endless belt in response to a load fluctuation at the time of contact between the image carrier and the endless belt Measuring means for detecting a change in an output signal when the load on the driving means increases, and measuring an actual operation time required for contact between the image carrier and the endless belt based on a detection result ; Total According actual operation time measured by the unit, and a control means for executing an image sequence of the next step, the said control means, when performing measurement by the measuring means, wherein the rotational speed of the image carrier endless the rotational speed difference between the rotational speed of the Jo belt, characterized that you control either the rotational speed of the image bearing member and said endless belt so as to be larger than during normal image formation.

  According to the present invention, since the actual time required for contact between the photosensitive drum and the endless belt is measured, the image sequence of the next process can be started early while avoiding the influence of the contact operation. As a result, FPOT can be shortened.

Schematic configuration diagram of an image forming apparatus The figure which shows the state of contact | abutting / separation of an image carrier and an intermediate transfer body Timing chart showing phase correction between image carriers, contact between image carrier and intermediate transfer member, and ATVC series of operations The figure which shows an example of structure and control of DC brushless motor The figure explaining the relationship between the control part 10 in Example 1 and another structure. Image diagram for explaining the operation of the first embodiment Enlarged view of drive current of intermediate transfer motor before contact Enlarged view of the drive current of the intermediate transfer motor after contact The flowchart which shows the process of the contact time measurement mode explaining operation | movement of Example 1. FIG. The figure explaining the relationship between the control part 10 in Example 2 and another structure. The flowchart which shows the process of the contact time measurement mode explaining operation | movement of Example 2. FIG. The figure explaining the relationship between the control part 10 in Example 3 and another structure. Image diagram for explaining the operation of the third embodiment The flowchart which shows the process of the contact time measurement mode explaining operation | movement of Example 3. FIG.

  Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. However, the constituent elements described in this embodiment are merely examples, and are not intended to limit the scope of the present invention only to them.

[Configuration example of image forming apparatus]
FIG. 1 is a diagram illustrating a configuration of the image forming apparatus 100. In the image forming apparatus 100 shown in FIG. 1, four image forming units are arranged for each color of yellow (Y), magenta (M), cyan (C), and black (Bk). Each image forming unit includes photosensitive drums 101Y, 101M, 101C, and 101Bk. Hereinafter, the photosensitive drum is referred to as an image carrier as an abstracted expression. Each image forming unit includes charging means 102Y, 102M, 102C, and 102Bk for uniformly charging the image carriers 101Y to 101Bk to a predetermined potential. Each of the image forming units irradiates laser beams 103Y to Bk corresponding to each color image data onto the charged image carriers 101Y to 101Bk to form electrostatic latent images, thereby forming laser latent images 104Y, 104M, 104C and 104Bk are provided. Each image forming unit includes developing means 105Y, 105M, 105C, and 105Bk for developing and developing the electrostatic latent images formed on the image carriers 101Y to 101Bk. Each of the image forming units includes sleeve rollers 106Y, 106M, 106C, and 106Bk for sending the color toners in the developing units 105Y to 105Bk to the image carriers 101Y to 101Bk. Each of the image forming units includes transfer units 108Y, 108M, 108C, and 108Bk for transferring the toner images (toner images) formed on the image carriers 101Y to 101Bk to the transfer belt 113. Each of the image forming units includes cleaning units 109Y, 109M, 109C, and 109Bk for removing the toner remaining on the image carriers 101Y to 101Bk after the transfer of the toner to the transfer belt 113. Reference numerals 110Y, 110M, 110C, and 110Bk denote waste toner units for storing waste toner.

  The image forming apparatus 100 has a paper feeding unit at the bottom, and a paper feeding cassette 111 in which the recording medium 107 is stored. In the transport path of the recording medium 107 from the paper feed cassette 111, a pickup roller 112 for feeding the recording medium, a feed roller 123 for feeding the recording medium into the transport path, and a retard roller 124 arranged to face the feed roller 123 are provided. Has been placed. In addition, a registration sensor 114 is provided for detecting the leading end of the recording medium 107 and measuring the transfer timing at the transfer position with the transfer belt 113. In addition, a registration roller 115 is provided for timing the secondary transfer of the toner image primarily transferred onto the transfer belt 113 onto the recording medium 107. The recording medium 107 fed from the paper feed cassette 111 is secondarily transferred with the toner image at the position of the secondary transfer roller 116. A fixing unit 117 melts and fixes the four color toner images transferred onto the recording medium 107. The fixed recording medium 107 is discharged outside the apparatus, and the image forming operation is finished.

[Configuration example of contact / separation of image carrier (photosensitive drum) and intermediate transfer member (endless belt)]
FIG. 2 shows the contact / separation state of the image carrier 101 and the intermediate transfer member 113 of the image forming apparatus. 2A shows a separated state between the image carrier 101 and the intermediate transfer member 113, and FIG. 2B shows a contact state between the image carrier 101 and the intermediate transfer member 113. FIG. 118 is a solenoid for contacting / separating the image carrier 101 and the intermediate transfer body 113 (referred to as a contact / separation solenoid), 119 is a connecting gear between the contact / separation solenoid and the contact / separation unit, 120 is a contact / separation drive cam, and 121 is a contact / separation unit.

  During the contact operation, when the contact / separation solenoid 118 is electromagnetically attracted by a control instruction from the control unit 10, the connection gear 119 rotates in the direction of the arrow (clockwise) in the figure, and the contact gear rotates per rotation. The contact / separation drive cam 120 is driven clockwise by 1/4 turn. When the abutment / separation drive cam 120 is driven by ¼ rotation, the abutment / separation unit 121 is pushed up together with the transfer roller 108 by the convex portion of the abutment / separation drive cam 120 to contact the image carrier 101.

  At the time of the separation operation, after the contact operation, when the contact / separation solenoid 118 is electromagnetically attracted, the connection gear 119 rotates in the direction of the arrow (clockwise) in the figure, and contact / separation per one rotation of the connection gear. The drive cam 120 is driven clockwise by 1/4 turn. When the contact / separation drive cam 120 is driven by a quarter rotation, the convex portion of the contact / separation drive cam 120 moves, so that the contact / separation unit 121 moves downward together with the transfer roller 108 and separates from the image carrier 101. To do.

  Before performing the next contact operation, the connecting gear 119 is moved by two rotations, and the contact / separation drive cam 120 is moved to the original position. By devising the shapes of the contact / separation drive cam 120 and the contact / separation unit 121, for example, only the Bk image carrier 101Bk corresponding to monochrome printing is brought into contact, and the image carriers 101Y to 101C are separated from each other. It is also possible to set another contact / separation pattern, such as placing it.

[Explanation of the timing of a series of operations from phase correction to ATVC published by the image carrier]
FIG. 3 is a timing chart showing a series of operations of phase correction between the image carriers 101Y, M, C, and Bk, contact between the image carrier 101 and the intermediate transfer member 113, and ATVC. In FIG. 3, reference numeral 1 denotes a timing as a starting point in the sequence, which corresponds to an initial sequence start timing after the image forming apparatus is turned on, a print start timing, and the like. Reference numeral 2 denotes a period in which the phase of the image carrier 101 (photosensitive drum 101) is corrected. As an example of the phase correction of the image carrier 101, a time of about 2.5 sec to 3 sec is required. The phase correction of the image carrier 101 will be described in more detail. For example, if the reference color is Y, another image is set so as to have a predetermined phase difference relative to the rotational phase of the image carrier 101Y. This refers to adjusting / controlling the rotational phase of the carrier. The phase difference relationship between the image carriers 101M, C, and Bk is determined by the arrangement interval of the image carriers. 3 is a period during which the image carrier 101 and the intermediate transfer body 113 are brought into contact with each other, and it takes about 1 sec. However, since the time required for the actual operation of the contact between the image carrier 101 and the intermediate transfer member 113 is unknown due to the solid variation of the mechanical parts, the intermediate between the image carrier 101 and the intermediate transfer member 113 is ensured with a margin for the operation variation. The time during which the contact with the transfer body 113 can be completed is set. 4 is a period during which ATVC is performed. As an example of ATVC, a time of about 4 sec to 5 sec is required. Reference numeral 5 denotes a signal indicating the operating state of the contact / separation solenoid 118. The contact / separation solenoid 118 is turned ON at the timing when it becomes Hi, and the drive is transmitted to the connecting gear 119. Even after the contact / separation solenoid 118 is turned off, the contact / separation drive cam 120 continues to be driven with a delay until the pawl of the contact / separation solenoid 118 is engaged with the connecting gear 119. For this reason, the OFF timing of the contact / separation solenoid 118 is different from the timing of completion of contact between the image carrier 101 and the intermediate transfer member 113. Therefore, in the sequence of the image forming apparatus, the entire contact period 3 between the image carrier 101 and the intermediate transfer body 113 is set as the time required for contact. Reference numerals 6 to 9 denote ATVC execution timings for Y, M, C, and Bk. The time required for the ATVC of each transfer portion alone is the timing when it becomes Hi of 6 to 9, and it takes about 1.5 sec.

[Configuration example of driving means for image carrier and intermediate transfer member]
Incidentally, a DC brushless motor is often used as the motor for driving the image carrier 101 and the intermediate transfer member 113 described above because it can generate high torque and has low vibration.

  Here, FIG. 4 shows an example of the structure and control circuit of a DC brushless motor. In FIG. 4, reference numeral 50 denotes an ASIC that performs drive control of each rotating body, and 51 denotes a motor control unit that performs position control and speed control of a motor provided in the ASIC 50. Reference numeral 52 denotes a driver for controlling electric power sent to the motor, which includes three high-side transistors and three low-side transistors, and is connected to U, V, and W of the coil 54, respectively. Reference numeral 53 denotes a DC brushless motor, and the DC brushless motor 53 includes a coil 54 and a rotor 55 that are three-phase star connection of U, V, and W. As the rotor position detecting means, three Hall elements 56a, 56b and 56c for detecting the magnetic poles of the rotor 55 are provided. Further, the DC brushless motor 53 is provided with a magnetic pattern 57 and a magnetic sensor 58 on the motor substrate on the outer periphery of the rotor 55. The magnetic sensor 58 detects an electromotive force generated in the magnetic pattern 57 as the rotor 55 rotates, and generates a pulse signal 59 (Frequency Generator Pulse: hereinafter referred to as FG pulse) corresponding to the rotational speed of the rotor 55. This FG pulse 59 (also referred to as a speed signal) is input to the motor control unit 51 and counted to calculate the rotational speed of the motor. The voltage conversion value of the motor drive current detected by the current detection resistor 60 is monitored to detect an abnormal state of the driver 52 and the DC brushless motor 53.

  The motor control unit 51 specifies the position of the rotor 55 based on the rotor position signals HU to W generated by the hall elements 56a to 56c, and generates a phase switching signal. The phase switching signals UU to UW and LU to LW sequentially switch the phases to be excited by ON / OFF control of the transistors of the driver 52 and rotate the rotor 55.

  Further, in order to perform speed control, the motor control unit 51 compares the rotation speed target value with the rotation speed information to obtain speed error information. Further, in order to perform position control, the position information of the rotor 55 integrated with the rotation speed information is compared with the position target value to obtain position error information. The motor operation amount is calculated from the speed error information and the position error information, and a PWM signal is generated and output based on the result. The PWM signal is 0 for duty 0%, and 255 for duty 100%. The PWM signal performs chopping processing of the drive current by phase switching signals UU to UW and a NAND gate to control the rotation speed of the motor. The motor can be braked by turning on all the phases of the low-side transistors.

  FIG. 5 is a diagram illustrating the configuration of the first embodiment. In the description of the present embodiment, the detailed description of the reference numerals described above is omitted. In FIG. 5, 10 is a control unit of the image forming apparatus. Reference numeral 11 denotes an operation signal for operating the contact / separation solenoid 118 in accordance with an instruction from the control unit 10. Reference numeral 12 denotes a control signal for driving the image carrier driving motor 13. An image carrier driving motor (13Y, 13M, 13C, 13Bk) is arranged on each of the image carriers 101Y to 101Bk of Y, M, C, and Bk, and a control signal ( 12Y, 12M, 12C, 12Bk) are connected. Reference numeral 14 denotes a control signal for driving the intermediate transfer member drive motor 15. Reference numeral 16 denotes a voltage conversion signal of the drive current of the intermediate transfer body drive motor 15 detected by the detection resistor 60. Note that the detection resistor 60 here corresponds to the detection resistor 60 described in FIG.

  FIG. 6 shows an example of the operation timing of the contact / separation solenoid 118 when the image carrier 101 and the intermediate transfer member 113 are in contact with each other from the separated state and finally separated, and the current waveform of the intermediate transfer member drive motor 15. Show. Here, the current waveform of the intermediate transfer member drive motor 15 is performed by detecting the voltage value of the current detection resistor 60.

  In FIG. 6, 17 indicates the operation timing of the contact / separation solenoid 118, and 18 indicates the drive current waveform of the intermediate transfer member drive motor 15. 19 is a timing at which the intermediate transfer body drive motor 15 starts to start, 20 is a timing at which the contact / separation solenoid 118 starts an operation at the time of contact by a drive signal, and 21 is a current change in the intermediate transfer body drive motor 15. It is timing. It can be seen that the load current applied to the intermediate transfer member driving motor 15 changes due to the contact between the image carrier 101 and the intermediate transfer member 113 at this timing 21. According to the measurement result of this example, the actual operation time from when the contact / separation solenoid 118 is turned on until the image carrier 101 and the intermediate transfer member 113 contact each other is about 500 msec. Reference numeral 22 denotes a timing at which the control unit 10 of the image forming apparatus presets a time required for the image carrier 101 and the intermediate transfer member 113 to contact each other. The estimated time from when the contact / separation solenoid 118 is turned on until the image carrier 101 and the intermediate transfer body 113 contact each other is set to about 950 msec. Reference numerals 23 and 24 denote timings at which the contact / separation solenoid 118 starts an operation at the time of separation by a drive signal. 23 is the first stage, among the Y, M, C, and Bk image carriers, only the Y, M, and C image carriers are separated (that is, only Bk abuts), and 24 is the second stage. This is the timing for separating the Bk image carrier, and all separation operations are completed.

  FIG. 7 shows an enlarged view of the drive current of the intermediate transfer member motor 15 at timings 20 to 21 (before the image carrier 101 and the intermediate transfer member 113 come into contact) in FIG. In FIG. 7, reference numeral 25 denotes an example of sampling when detecting the driving current of the intermediate transfer body motor 15 at timings 20 to 21. In this embodiment, one cycle of the drive current of the intermediate transfer body motor 15 is about 50 μsec. This is determined by the generation period of PWM output from the motor control unit 51 of the DC brushless motor. By measuring a plurality of points (4 points / cycle in the present embodiment) from one cycle of the driving current of the intermediate transfer body motor 15 and averaging the measurement results (measurement data) for about 500 μsec for 10 cycles, The current level of the intermediate transfer body motor 15 is calculated. Reference numeral 26 denotes an average current level at timings 20 to 21 (before the image carrier 101 and the intermediate transfer member 113 come into contact with each other). In addition, it is not limited to an average process about the measurement result of several points. For example, when measuring 5 points, the middle measurement result may be adopted.

  Next, FIG. 8 shows an enlarged view of the drive current of the intermediate transfer body drive motor 15 at timings 21 to 22 (after the image carrier 101 and the intermediate transfer body 113 are in contact) in FIG.

  In FIG. 8, reference numeral 27 denotes an example of sampling when detecting the drive current of the intermediate transfer member drive motor 15 at the timings 21 to 22. The current level of the intermediate transfer body motor 15 is calculated in the same manner as in timings 20 to 21. Reference numeral 28 denotes an average current level at timings 21 to 22 (after the image bearing member 101 and the intermediate transfer member 113 are in contact with each other).

  After the contact / separation solenoid 118 is turned on, this average current level measurement is performed every 10 cycles from timing 20 to 22. The timing at which the difference between the average current levels 26 and 28 before and after the contact between the image carrier 101 and the intermediate transfer member 113 is detected can be determined as the timing at which the image carrier 101 and the intermediate transfer member 113 are in contact.

  FIG. 9A is a flowchart for explaining the contact time measurement mode for measuring the contact time between the image carrier and the intermediate transfer member in the first embodiment. Note that the contact time measurement mode may be performed once when an image forming apparatus is newly purchased and when the image carrier and the intermediate transfer member are subsequently replaced, and the contact time information is updated.

  In FIG. 9A, when the contact time measurement mode starts, the image carrier 101 and the intermediate transfer member 113 start to drive (S101). The timing of this start substantially coincides with the timing of the starting point 1 in FIG. At this time, the image carrier 101 and the intermediate transfer member 113 are not in contact with each other.

  Next, the control unit 10 detects the voltage conversion signal 16 to start measuring the drive current of the intermediate transfer body drive motor 15 (S102). Here, in practice, the voltage change corresponding to the change in the current value as shown in FIG. 6 is detected by the control unit 10, but the detection of this voltage change will be described below. This is referred to as detecting (or measuring) current. Based on the measured current value, the control unit 10 calculates an average current before the image carrier 101 and the intermediate transfer member 113 come into contact with each other (S103). The drive current is measured while updating the average current value every predetermined time (for example, 10 cycles of the drive current described in FIG. 7 (approximately every 500 μsec)) until the contact time measurement mode ends. Continue measuring.

  In step S104, the control unit 10 instructs the contact / separation solenoid 118 to turn on and shifts to a contact operation. Then, the control unit 10 continues to measure the drive current of the intermediate transfer body drive motor 15 and sequentially calculates the average current value after the image carrier 101 and the intermediate transfer body 113 come into contact with each other (S105).

  Then, the control unit 10 recognizes that a level difference of a certain condition has occurred in the average drive current value of the intermediate transfer body drive motor 15 before and after the actual contact based on the detected current change (S106). The details of the level difference under certain conditions will be described in detail later. When the determination is YES in S106, the control unit 10 calculates the time from the timing when the contact / separation solenoid 118 is turned on to the timing until the level difference of the drive current average value is recognized (S107). This time is stored as a contact time between the image carrier 101 and the intermediate transfer member 113 in actual operation in a non-illustrated non-volatile storage unit, and the process is terminated (S108). As for the level difference of the drive current average value of the intermediate transfer member drive motor 15 before and after contact, a constant change in the drive current average value was recognized in the continuous measurement of the drive current of the intermediate transfer member drive motor 15. It can be judged with things. In the example shown in FIGS. 7 and 8, the difference in level of the average value of the drive current before and after contact is about 500 mA.

  On the other hand, the control unit 10 advances the process to S109 when the level difference in the average value of the drive current of the intermediate transfer body drive motor 15 cannot be recognized in S106 for a certain period. The initial set value is stored as a contact time between the image carrier 101 and the intermediate transfer member 113 in a non-volatile storage unit (not shown), and the process is terminated. Here, the initial setting value is a timing at which the control unit 10 of the image forming apparatus described above with reference to FIG. 6 estimates and sets in advance the time required for the image carrier 101 and the intermediate transfer body 113 to contact each other. is there. For example, it corresponds to a value stored as a default value in a factory. Further, separately from the factory, the value stored in the process of S <b> 108 in which the flowchart of FIG. 9 was previously executed may be used.

  Next, after the contact time measurement mode of FIG. 9A is completed and the actual operation time required for contact between the image carrier 101 and the intermediate transfer member 113 is stored in the storage means, FIG. The flowchart is executed. The flowchart of FIG. 9 shows a processing flowchart when the image forming apparatus receives a print signal.

  In FIG. 9B, when the image forming apparatus receives the print signal and the printing operation is started, the control unit 10 compares the image carrier 101 and the intermediate transfer member 113 stored in a storage unit (not shown). The contact time information is set as an actual operation time for contact (S110). Next, the phase relationship between the image carriers 101Y, 101M, 101C, and 101K is corrected under the control of the control unit 10 (S111). When the phase correction is completed, the control unit 10 turns on the contact / separation solenoid (S112).

  In step S113, the control unit 10 counts from the timing when the contact / separation solenoid is turned on until the time set as the actual operation time for contact between the image carrier 101 and the intermediate transfer member 113 is reached. When the set contact time elapses, the control unit 10 advances the process to S114, determines that the contact between the image carrier 101 and the intermediate transfer member 113 is completed, and starts ATVC. Then, after ATVC ends, the process proceeds to an image forming sequence.

  As described above, the current of the intermediate transfer member drive motor 15 is measured, and the change in current due to the load fluctuation at the time of contact between the image carrier 101 and the intermediate transfer member 113 is detected, so The contact time in actual operation with the transfer body 113 can be known. The FPOT can be shortened by applying the contact time in actual operation as the contact time between the image carrier 101 and the intermediate transfer member 113 in the subsequent pre-printing sequence.

  The contact time measurement mode described in this embodiment is performed once when the power is turned on when a new image forming apparatus is purchased and every time the image carrier or intermediate transfer member is replaced thereafter. It is assumed that the time information is updated.

  In the above description, ATVC has been described, but the present invention is not limited thereto. An image sequence other than ATVC can be applied as long as it is an image sequence in which the operation accuracy is affected by the contact operation between the photosensitive drum and the intermediate transfer belt, and the same effect as the ATVC in improving accuracy can be applied. Can be obtained.

  In the second embodiment, a case where a current change at the time of contact between the image carrier 101 and the intermediate transfer member 113 is detected by a current change of the image carrier drive motor 13 will be described.

  FIG. 10 is a diagram illustrating the relationship between the control unit 10 and other configurations in the second embodiment. In describing the configuration of the present embodiment, the detailed description of the above-described reference numerals will be omitted. In FIG. 10, reference numeral 29 denotes a detection resistor for detecting the drive current of the image carrier drive motor 13. The image carrier drive motor 13 is also provided with a control circuit similar to that described with reference to FIG. 4, and the detection resistor 29 corresponds to the detection resistor 60 described with reference to FIG. A voltage conversion signal 30 of the driving current of the image carrier driving motor 13 detected by the detection resistor 29 is input to the control unit 10. In this embodiment, only the detection resistor 29 for detecting the drive current of the image carrier drive motor 13 is connected to the image carrier drive motor 13Bk for driving the image carrier 101Bk. However, the same effect can be obtained even when the detection resistors for detecting the drive current are connected to the image carrier drive motors 13Y, 13M, and 13C that drive the other image carriers 101Y, 101M, and 101C.

  The state of the current waveform when the current change at the time of contact between the image carrier 101 and the intermediate transfer member 113 is detected by the current change of the image carrier drive motor 13 is the same as that of the intermediate transfer member drive motor 15 of the first embodiment. It can be explained in the same way as the case.

  FIG. 11 is a flowchart for explaining a contact time measurement mode for measuring the contact time between the image carrier and the intermediate transfer member in the second embodiment. In FIG. 11, when the contact time measurement mode is started, the image carrier 101 and the intermediate transfer member 113 start to be driven as in S101 described above (S201).

  Next, the control unit 10 detects the voltage conversion signal 39 to start measuring the drive current of the image carrier drive motor 13 (S202). Based on the measured current value, the control unit 10 calculates an average current before the image carrier 101 and the intermediate transfer member 113 come into contact with each other (S203). The measurement of the drive current is continued while updating the average current value every predetermined time (for example, 10 cycles described in FIG. 7 described above, approximately every 500 μsec) until the contact time measurement mode ends.

  In step S204, the control unit 10 instructs the contact / separation solenoid 118 to turn on and shifts to a contact operation. Then, the control unit 10 continues to measure the drive current of the image carrier drive motor 13 and sequentially calculates an average current value after the image carrier 101 and the intermediate transfer body 113 come into contact with each other (S205).

  Then, the control unit 10 recognizes that a level difference of a certain condition has occurred in the average driving current value of the image carrier driving motor 13 before and after the actual contact due to the detected current change (S206). Then, when the control unit 10 determines YES in S206, the control unit 10 calculates the time from the timing when the contact / separation solenoid 118 is turned on until the timing when the level difference of the drive current average value is recognized (S207). Then, this time is stored as a contact time between the image carrier 101 and the intermediate transfer member 113 in actual operation in a non-illustrated nonvolatile storage unit, and the paper processing is ended (S208). As for the level difference of the drive current average value of the image carrier drive motor 13 before and after contact, the average value of the drive current in the continuous measurement of the drive current of the image carrier drive motor 13 is the same as in the first embodiment. The determination can be made when a certain change is recognized.

  On the other hand, if the control unit 10 cannot recognize the level difference of the average drive current value of the image carrier drive motor 13 for a certain period in S206, the control unit 10 proceeds to S209. The initial set value is stored as a contact time between the image carrier 101 and the intermediate transfer member 113 in a non-volatile storage unit (not shown), and the process is terminated. Here, the initial set value is as described in the first embodiment.

  The processing when the image forming apparatus receives a print signal after the contact time measurement mode ends is performed in the same manner as described in the first embodiment.

  As described above, the current of the image carrier driving motor 13 is measured, and the change in current due to the load variation at the time of contact between the image carrier 101 and the intermediate transfer member 113 is detected. The contact time in actual operation with the transfer body 113 can be known. The FPOT can be shortened by applying the contact time in actual operation as the contact time between the image carrier 101 and the intermediate transfer member 113 in the subsequent pre-printing sequence.

  In the above description, ATVC has been described, but the present invention is not limited thereto. An image sequence other than ATVC can be applied as long as it is an image sequence in which the operation accuracy is affected by the contact operation between the photosensitive drum and the intermediate transfer belt, and the same effect as the ATVC in improving accuracy can be applied. Can be obtained.

  In the third embodiment, a case will be described in which a load fluctuation at the time of contact between the image carrier 101 and the intermediate transfer member 113 is detected by a change in an FG pulse signal (hereinafter referred to as an FG pulse) of the intermediate transfer member drive motor 15.

  FIG. 12 is a diagram illustrating the relationship between the control unit 10 and other configurations in the third embodiment. In the description of the present embodiment, the detailed description of the reference numerals described above is omitted. In FIG. 12, reference numeral 31 denotes an FG pulse output from the intermediate transfer body drive motor 15 and is input to the control unit 10. The rotation speed of the motor is calculated by counting the number of pulses from the FG pulse 31.

  FIG. 13 is a timing chart for explaining the operation of the third embodiment. In FIG. 13, 32 indicates the operation timing of the contact / separation solenoid 118, and 33 indicates the driving speed of the intermediate transfer member 113. Reference numeral 34 denotes an FG pulse output from the intermediate transfer member drive motor 15. Reference numeral 35 denotes an ON timing of the contact / separation solenoid 118. Reference numeral 36 denotes a period from when the contact / separation solenoid 118 is turned on to when the image carrier 101 and the intermediate transfer body 113 actually contact each other. 37 is the contact timing between the image carrier 101 and the intermediate transfer member 113, 38 is the contact speed between the image carrier 101 and the intermediate transfer member 113, and the drive speed of the intermediate transfer member 113 is changed. This is a period during which the speed fluctuation converges to the target speed by the speed control of the motor 15.

  If the speed of the intermediate transfer member 113 fluctuates due to the contact between the image carrier 101 and the intermediate transfer member 113 in the speed fluctuation period 38 of the intermediate transfer member 113, the intermediate transfer member 113 decreases with the decrease in the speed of the intermediate transfer member 113. The cycle of the FG pulse output from the drive motor 15 becomes longer. The control unit 10 detects the timing at which the count cycle of the FG pulse during this period 36 and the interval 38 fluctuates, and recognizes the contact timing between the image carrier 101 and the intermediate transfer member 113.

  FIG. 14 is a flowchart for explaining the contact time measurement mode for measuring the contact time between the image carrier and the intermediate transfer member in the third embodiment.

  In FIG. 14, when the contact time measurement mode is started, the image carrier 101 and the intermediate transfer body 113 start to be driven in the same manner as S101 described above (S301).

  Next, the control unit 10 starts measuring the FG pulse of the intermediate transfer body drive motor 15 (S302). Then, the control unit 10 calculates a driving speed before the image carrier 101 and the intermediate transfer body 113 come into contact with each other based on the measured (detected) FG pulse cycle (S303). While the pulse period of the FG pulse is constant, the measurement is continued with the driving speed being constant.

  Next, the control unit 10 proceeds to S304, instructs the contact / separation solenoid 118 to turn ON, and shifts to the contact operation. Then, the control unit 10 continues to measure the FG pulse of the intermediate transfer body drive motor 15 and calculates the drive speed from the periodic fluctuation of the FG pulse after the image carrier 101 and the intermediate transfer body 113 are sequentially brought into contact with each other ( S305).

  Then, the control unit 10 recognizes that the drive speed of the intermediate transfer member drive motor 15 has changed before and after the actual contact due to the detected change in the FG pulse cycle (S306). If the control unit 10 determines YES in S306, it calculates the time from the timing when the contact / separation solenoid 118 is turned on until the timing when the level difference of the drive current average value is recognized (S307). Then, this time is stored as a contact time between the image carrier 101 and the intermediate transfer member 113 in actual operation in a non-illustrated nonvolatile storage unit, and the process is terminated (S308). If the control unit 10 cannot recognize a change in the FG pulse of the intermediate transfer body drive motor 15 for a certain period in S306, the process proceeds to S309, and the initial set value is abutted between the image carrier 101 and the intermediate transfer body 113. The time is stored in a non-volatile storage unit (not shown) and the process ends. Here, the initial set value is as described in the first embodiment.

  The processing when the image forming apparatus receives a print signal after the contact time measurement mode ends is performed in the same manner as described in the first embodiment.

  As described above, the image carrier 101 and the intermediate transfer member are detected by detecting the speed fluctuation (FG pulse cycle) of the intermediate transfer member 113 due to the load fluctuation at the time of contact between the image carrier 101 and the intermediate transfer member 113. It is possible to know the contact time in actual operation with 113. The FPOT can be shortened by applying the contact time in actual operation as the contact time between the image carrier 101 and the intermediate transfer member 113 in the subsequent pre-printing sequence.

  In this embodiment, the FG pulse of the intermediate transfer member drive motor 15 is measured, and the contact timing between the image carrier 101 and the intermediate transfer member 113 is detected from the speed fluctuation of the intermediate transfer member 113. However, it is also possible to measure the FG pulse of the image carrier driving motor 13 and detect the contact timing between the image carrier 101 and the intermediate transfer member 113 from the speed fluctuation of the image carrier 101.

  In the above description, ATVC has been described, but the present invention is not limited thereto. An image sequence other than ATVC can be applied as long as it is an image sequence in which the operation accuracy is affected by the contact operation between the photosensitive drum and the intermediate transfer belt, and the same effect as the ATVC in improving accuracy can be applied. Can be obtained.

[Modification]
Note that the contact time measurement mode described in the above embodiment is assumed to be performed once when the image forming apparatus is newly purchased and every time the image carrier or intermediate transfer body is replaced. Is done. By updating the contact time information, the actual contact time between the image carrier 101 and the intermediate transfer member 113 can be applied to the pre-printing sequence, and the FPOT can be shortened.

  Further, by setting a larger peripheral speed difference (rotational speed difference) between the driving speed of the image carrier 101 and the driving speed of the intermediate transfer body 113, the load at the time of contact between the image carrier 101 and the intermediate transfer body 113 is increased. The fluctuation can be increased. That is, in the contact time measurement mode, the driving speed of the image carrier 101 and the driving speed of the intermediate transfer body 113 are set in advance so that at least the peripheral speed difference during normal image formation is larger. With this setting, the maximum drive current (I1b) before the contact between the image carrier 101 and the intermediate transfer member 113 and the minimum drive current after the contact between the image carrier 101 and the intermediate transfer member 113 are set. The relationship with the value (I1a) can be set to I1b <I1a with a larger difference. Thereby, in the contact time measurement mode, it is possible to more easily detect a point where the drive current of the intermediate transfer body drive motor 15 changes sharply, and this makes contact between the image carrier 101 and the intermediate transfer body 113. It becomes possible to distinguish it from points.

  In the second and third embodiments, the driving speed of the image carrier 101 and the driving speed of the intermediate transfer body 113 in the contact time measurement mode are set in advance to be larger than at least the peripheral speed difference during normal image formation. Is the same. In the case of the second embodiment, the calculation of the drive current of the intermediate transfer member drive motor 15 in the above description may be performed for the image carrier drive motor 13. In the case of the third embodiment, the change in the FG pulse signal may be detected as described above after setting the peripheral speed difference large. In setting the peripheral speed difference between the image carrier 101 and the intermediate transfer body 113 to be larger than at least the peripheral speed difference during normal image formation, the intermediate transfer body drive motor 15 and the image carrier drive motor 13 Either or both may be controlled.

  In the above description of each embodiment, the photosensitive drum and the intermediate transfer belt have been described. However, the present invention can also be applied to an image forming apparatus that directly transfers a toner image from a photosensitive drum to a recording sheet (recording material). is there.

DESCRIPTION OF SYMBOLS 10 Control part 11 Operation signal for operating contact / separation solenoid 12 Control signal for driving image carrier drive motor 13 Image carrier drive motor 14 Control signal for driving intermediate transfer member drive motor 15 Intermediate Transfer body drive motor 16 Signal for detecting drive current of intermediate transfer body drive motor 31 FG pulse of intermediate transfer body drive motor 50 ASIC
DESCRIPTION OF SYMBOLS 51 Motor control part 52 Motor driver 53 DC brushless motor 100 Image forming apparatus 101 Image carrier 108 Transfer roller 113 Intermediate transfer body 118 Contact / separation solenoid 120 Contact / separation drive cam 121 Contact / separation unit

Claims (6)

An image carrier, a forming unit that forms an image on the image carrier, an endless belt, and a contact / separation unit that contacts and separates the image carrier and the endless belt. In the image forming apparatus for transferring the toner image carried on the image carrier to the endless belt or the recording paper conveyed by the endless belt in a state where the carrier and the endless belt are in contact with each other,
In response to a load change at the time of contact between the image carrier and the endless belt, an output signal from a drive unit that rotationally drives the image carrier or the endless belt increases a load on the drive unit. Measuring means for measuring the actual operation time required to contact the image carrier and the endless belt based on the detection result,
In accordance with the actual operation time measured by the measuring means, the control means for executing the image sequence of the next process ,
The control means, when performing the measurement by the measurement means, makes the difference between the rotation speed of the image carrier and the rotation speed of the endless belt larger than that during normal image formation. an image forming apparatus comprising that you control either the rotational speed of the carrier and the endless belt.   The measuring means measures a plurality of points of output signals output from the driving means before and after the contact between the image carrier and the endless belt, and based on the plurality of measurement results, the output signals from the driving means are 2. The image forming apparatus according to claim 1, wherein a change in an output signal when a load on the driving unit is increased is detected. 3. The image according to claim 1, wherein the output signal is a signal indicating a current value for driving the driving unit, or a speed signal output in accordance with rotation driving of the driving unit. Forming equipment. Comprising a plurality of image carriers,
Said measuring means, an image forming apparatus according to any one of claims 1 to 3, characterized in that to measure the actual operation time required for contact of all said endless belt of said plurality of image bearing members . The image forming sequence in the next step is a sequence for controlling a transfer voltage when transferring the toner image carried on the image carrier onto the endless belt or the recording paper conveyed by the endless belt. the image forming apparatus according to any one of claims 1 to 4, characterized in. An image carrier;
An endless belt,
Contact / separation means for contacting and separating the image carrier and the endless belt, and a toner carried on the image carrier in a state where the image carrier and the endless belt are in contact with each other In an image forming apparatus for transferring an image onto the endless belt or a recording sheet conveyed by the endless belt,
Detecting means for detecting an output signal output from a driving means for rotationally driving the image carrier or the endless belt;
Measuring means for measuring the time until the image carrier and the endless belt are brought into contact with each other based on the detection result by the detection means;
When performing measurement by the measuring means, the image carrier and the endless so that the rotational speed difference between the rotational speed of the image carrier and the rotational speed of the endless belt is larger than that during normal image formation. An image forming apparatus comprising: a control unit that controls a rotational speed of any one of the belts .

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