JP2006126505A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To cause a rapid stop to be performed at the time a driving system including a driving motor is stopped. <P>SOLUTION: A paper sheet conveyance system has a register roller 13 for supplying a paper sheet fed from a paper sheet cassette 8 at a prescribed timing to an image recording section, and a register clutch 20 for selectively transmitting the driving force to the register roller 13. At the time of stopping the driving motor for driving the paper sheet conveyance system, a driving motor stop signal is generated and the register clutch 20 is turned on. An equally good alternative is to equip the apparatus with a measuring means for measuring the time before the stop of the driving motor and to drive the register clutch 20 in synchronization with the subsequent driving motor stop signal when the measured time becomes longer than the preset specified time. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus that forms an image on a recording material such as paper, and more particularly to stop control of a drive motor thereof.

  As such a conventional image forming apparatus, an apparatus employing an intermittent rotation system using a registration roller for correcting the front and rear position and timing of a sheet in front of an image recording unit is known. The registration roller is also referred to as a registration roller. For example, the connection with a drive source (such as a motor) is interrupted by operation of an electromagnetic clutch (registration clutch). The paper fed from the paper cassette is temporarily stopped by this registration roller before the image recording unit. In this stopped state, the sheet is fed by the transport roller before the registration roller until it is loosened (looped). As a result, the registration clutch is operated with the leading end position of the sheet being corrected, whereby the sheet is fed out in synchronism with the timing of the image recording unit.

  By the way, if the occurrence of a paper jam is detected during paper conveyance, a drive motor (main motor) that serves as a drive source for the photosensitive drum, various rollers, etc. in order to prevent further trouble from occurring. The drive is stopped. At this time, also with respect to the registration roller, power transmission is cut off by the operation of the clutch, and its rotation is stopped. A DC motor is often used as the drive motor.

Japanese Patent Application Laid-Open No. 2004-228561 discloses an image forming apparatus including a registration brake that forcibly stops rotation of a registration roller when an abnormality occurs during paper conveyance. Specifically, this brake locks a gear attached to a rotation shaft of a registration roller by an electromagnetically operated clutch. Accordingly, it is possible to prevent the paper from entering the cleaner or the like due to the overrun of the paper, or to prevent the paper from being pushed into the image recording unit.
JP-A-9-77307

  When stopping the drive motor, when a stop signal is output from a control unit such as a CPU or ASIC, the drive motor does not actually stop immediately, but it is stopped to some extent due to inertial force. After turning. For this reason, the power of the drive motor is transmitted to the load system during rotation by inertia, and the load driven by the drive motor operates.

  If the paper discharge sensor does not turn on after a certain period of time after the registration clutch is turned on, it is determined that a paper jam has occurred and the drive of the main body is turned off to stop the machine. However, as described above, even if the drive motor is stopped due to inertia around the drive, etc., there is a time lag in actually stopping the drive gear, and the load connected to the drive motor is only during the rotation time due to inertia. It will be driven similarly. That is, when the fixing roller of the fixing unit is a load of the driving motor, if the driving motor does not stop immediately when a jam occurs in the fixing unit, the sheet is likely to be completely wound around the fixing roller. In such a situation, the user cannot cope with the situation, and it is necessary to call a service person and take measures such as disassembling the fixing unit.

  Further, for example, since the driving force of the driving motor is always transmitted to the photosensitive drum, the photosensitive drum also rotates during rotation by inertia. Along with this, when the drive motor is stopped, an abnormal noise accompanying the cleaning blade called blade squeal sometimes occurs. The cause of this is not clear, but it is presumed that the absence of toner on the photosensitive drum and the change (decrease) in the rotational speed of the photosensitive drum at the time of emergency driving stop are affected.

  Such a phenomenon becomes prominent when the load on the drive motor becomes lighter with time. This is because as the image forming apparatus is used, the driving part gradually becomes familiar, and the load in the cartridge (for example, the toner agitation) becomes lighter as the toner in the cartridge is consumed. .

  The known technique described in Patent Document 1 forcibly stops the rotation of the registration roller when an abnormality occurs during paper conveyance, but does not attempt to stop the rotation of the drive motor itself.

  An object of the present invention is to provide an image forming apparatus capable of promptly stopping when a drive system including a drive motor is stopped.

  An image forming apparatus according to the present invention is an image forming apparatus for forming an image on a recording material, and selectively transmits a driving motor for driving a driven portion in the image forming apparatus and a driving force of the driving motor. And a control means for generating a drive motor stop signal and turning on the clutch when the drive motor is stopped.

  In the present invention, the load on the drive motor is increased by intentionally turning on a clutch for selectively transmitting the drive force of the drive motor when the drive motor is stopped. As a result, it is possible to stop the rotation of the drive motor that continues to rotate with the inertial force even after the output of the drive motor stop signal.

  When an abnormality detection unit that detects an abnormality in the image forming apparatus is provided, the control unit generates the drive motor stop signal and activates the clutch when an abnormality is detected by the abnormality detection unit.

  When a fixing unit that thermally fixes a toner image formed on a recording material conveyed in the image forming apparatus is provided and the driving motor is also used for driving the fixing unit, a sheet is wound around a fixing roller or the like. Even if the drive motor is stopped immediately, the winding can be stopped at a level that can be processed by the user.

  A measuring means for measuring the time until the drive motor stops; and when the measured time is longer than a preset specified time, the clutch is synchronized with the subsequent drive motor stop signal. You may make it drive. Thereby, if necessary, the clutch-on operation when the drive motor is stopped can be performed, and even when the stop time is short, the uniform operation of the clutch can be avoided.

  The driven unit to which the clutch selectively transmits the driving force of the drive motor is, for example, a registration roller that supplies the recording material to be conveyed to the image recording unit at a predetermined timing. The registration roller is a load for the driving motor to selectively transmit the driving force by the clutch. When the recording material conveyed in the image forming apparatus has been conveyed, the registration roller is turned off and the transmission of the driving force is stopped. Is. Further, even if the registration roller rotates in this way, it does not affect other parts at all, so there is no adverse effect on the processing of the apparatus.

  According to the present invention, when the drive motor is stopped, the clutch is turned on to intentionally increase the load of the drive motor, thereby rotating the drive motor including the influence of the inertial force after the drive motor stop signal is generated. It can be stopped quickly. As a result, it is possible to prevent deterioration of the situation such as when a paper jam occurs, or to prevent the generation of abnormal noise called blade squealing.

  Also, by measuring the actual stop time of the drive motor and selectively performing the clutch-on operation when the drive motor is stopped according to the measurement result, the clutch can be operated uniformly even when the stop time is short. This can be prevented. As a result, the life of the clutch and the registration roller is not unnecessarily reduced.

  The fact that the measured time is longer than a preset specified time is stored in a nonvolatile manner as a flag state, and the stop time is measured each time the drive motor stop signal is generated after the flag is turned on. No processing is required. As a result, the processing load is reduced.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the drawings.

  FIG. 1 is a cross-sectional view showing a mechanical schematic configuration of an image forming apparatus according to an embodiment of the present invention. Here, a printer is described as an example of the image forming apparatus, but the present invention can be applied to a facsimile, a copying machine, and the like in addition to the printer.

  In FIG. 1, a paper cassette 8 is detachably attached to the apparatus main body, and a paper 9 before image recording is accommodated therein. A paper feed roller 11 is provided at the end of the paper cassette 8, and the paper feed roller 11 rotates to feed the paper one by one to the conveyance path. The paper feed roller 11 is connected to a drive source (drive motor) by the operation of the paper feed clutch 21 and rotates by the driving force transmitted thereby.

  A registration sensor 12 for detecting the sheet position at the initial stage of conveyance is installed downstream of the sheet feed roller 11 in the conveyance direction. The paper fed out from the paper cassette 8 passes through the registration sensor 12 and reaches the registration roller 13. The registration roller 13 includes a pair of upper and lower rollers, and is connected to a registration clutch 20 for intermittently connecting to the drive source. On the downstream side of the registration roller 13 in the conveying direction, an image recording unit including a photosensitive drum 15 and a transfer roller 14 is formed. The paper that has reached the registration roller 13 is fed out so that the timing coincides with the developed image formed on the photosensitive drum 15. Although not described here, a cleaning unit, a charging unit, an exposure unit, and a developing unit are provided around the photosensitive drum 15.

  Further, a fixing unit is provided downstream of the image recording unit in the conveyance direction. The fixing unit includes a fixing roller 17 having a built-in heater and a pressure roller 16, and thermally fixes the toner image on the sheet conveyed from the image recording unit to the sheet. A paper discharge sensor 18 is downstream of the fixing roller 17 in the conveying direction, and detects the presence or absence of paper after passing through the fixing roller 17. A paper discharge roller 19 is provided on the most downstream side in the transport direction. The paper discharge roller 19 discharges the paper that has passed through the fixing roller 17 onto the main body paper discharge tray. In the present embodiment, the rotation driving of the fixing roller 17 and the rotation driving of the registration roller 13 are performed by the same driving motor.

  Next, the configuration of the control system of the image forming apparatus shown in FIG. 1 will be described. FIG. 2 is a functional block diagram thereof.

  2, the control unit 7 includes a control IC such as a CPU and an ASIC, a ROM storing a control program, and a RAM storing various control data. On the input side of the control unit 7, a paper feed sensor 10 that detects the presence or absence of paper 9 in the paper cassette 8, a registration sensor 12 that detects the paper position during paper feeding, and a paper discharge sensor 18 are provided.

  On the output side of the control unit 7, there are provided a drive motor 1, a registration clutch 20, and a paper feed clutch 21 which are drive sources for the apparatus main body. The control unit 7 performs ON / OFF control of the drive motor 1. At this time, when the drive signal for the drive motor 1 output from the control unit 7 is “H”, it means motor drive, and when it is “L”, it means motor stop.

  FIG. 3 shows a state in which the paper that has passed through the fixing unit is to be discharged by the paper discharge roller 19 and is wound around the fixing roller 17 and is jammed.

  Next, the operation procedure of the image forming apparatus according to the present embodiment will be described with reference to the flowchart of FIG. A program representing an execution procedure of the processes in this flowchart and the subsequent flowcharts is stored in a storage device such as the ROM, and this process is realized by the CPU interpreting and executing it. The same applies to the processing of other flowcharts.

  First, the drive motor 1 is turned on in accordance with a print request from the host PC (S1), and pre-multi-rotation is started for temperature control of the fixing unit before the image forming operation. Thereafter, the sheet feeding roller 11 is rotated by turning on the sheet feeding clutch 21 in order to feed the sheet to the conveyance path (S2). As a result, one sheet of paper is picked up from the paper cassette 8 and fed to the transport path.

  Next, it is monitored whether the paper advances along the conveyance path and reaches the position of the registration roller 13 and the registration sensor 12 is turned on (S3). At this time, it is determined that a paper jam (JAM) has occurred if the registration sensor 12 is not turned on even after a predetermined time has elapsed after paper feeding (S12).

  When the registration sensor 12 is turned on, the leading edge of the sheet hits the registration roller 13 and the sheet is conveyed until a predetermined loop is generated.

  Thereafter, in synchronization with the development on the image recording unit, the registration clutch 20 is turned on, the registration roller 13 is rotated, and the sheet is sent to the image recording unit (S4). After the registration sensor 12 is turned off (S5), the registration clutch 20 is turned off (S6).

  Thereafter, it is monitored whether the paper discharge sensor 18 is turned on at a predetermined timing (S7). Here, if the paper discharge sensor 18 is turned on and then turned off at a predetermined time set in accordance with each paper size, the process ends normally (S11).

  After the registration clutch 20 is turned on, if the paper discharge sensor 18 is not turned on within a predetermined time, it is determined that a jam has occurred (S12), and the drive motor 1 is braked (S8). Any known means can be used for applying the brake. For example, a motor drive winding short circuit or a mechanical brake can be used.

  If the registration clutch 20 is not on at the same time as the brake is applied (S9, No), the registration clutch 20 is immediately turned on (S10). The case where the registration clutch 20 is already on corresponds to the case where a long sheet such as A3 is being conveyed. By turning on the registration clutch 20, the registration roller 13 acts as a load on the drive motor 1, so that the drive motor can be rapidly stopped. This state is shown in FIG. 7 and FIG. 7 shows the stop time of the drive motor when the registration clutch drive is not performed when the drive motor is off, and FIG. 8 shows the stop time of the drive motor when the registration clutch drive is performed when the drive motor is off. Yes. In this way, a load is applied to the drive motor, and the rotation of the drive motor due to inertia stops rapidly.

  As a result, in the case where a jam occurs due to the winding of the paper around the fixing roller 17, the drive system can be stopped immediately after the jam detection, so that the complete winding of the paper around the fixing roller 17 can be avoided. It becomes possible.

  FIG. 6 shows a more detailed configuration around the photosensitive drum. Around the photosensitive drum 15, a developing unit 5, a transfer unit 4, and a cleaning unit 26 are arranged. A transfer roller 14 is provided in the transfer unit 4. A cleaning blade 27 for removing toner adhering to the surface of the photosensitive drum 15 is provided in the cleaning unit 26. In this embodiment, since the drive motor is shared for driving the photosensitive drum 15 and the registration roller 13, the above-described blade noise is suppressed by stopping the drive system in a short time by using the load of the registration roller 13. be able to.

  Next, a second embodiment will be described. FIG. 5 is a diagram showing a part of FIG. In the previous embodiment, the registration clutch 20 is always turned on when the drive motor 1 is in an emergency stop. However, the on / off control of the registration clutch 20 every time the drive motor 1 is stopped in an emergency means the life of the registration clutch 20. There is a problem that the life of the registration roller 13 is reduced. Therefore, in the present embodiment, the time from the generation of the stop signal of the drive motor 1 to the actual stop of the drive motor 1 is measured, and when that time is shorter than the predetermined time, the registration clutch when the drive motor is stopped 20 is not performed.

  As described above, the control unit 7 performs ON / OFF control of the drive motor 1. In this figure, an FG pulse is fed back from the drive motor 1 to the control unit 7. The FG pulse is a pulse synchronized with the rotation of the drive motor 1. Thereby, the control part 7 can detect the mode of rotation of the drive motor 1. As shown in FIG. 10, the time (t) from the time when the drive signal of the drive motor becomes L (stop signal) until the time when the rotation speed of the drive motor becomes 0 (the last falling edge of the FG pulse). taking measurement. The fact that the rotational speed of the drive motor has become zero can be detected by the fact that a predetermined time has passed without rising after the FG pulse has fallen.

  FIG. 11 is a flowchart showing the operation in the second embodiment.

  In the process of FIG. 11, first, after the apparatus is turned on, a drive signal is output to the drive motor (S21). Thereafter, a stop signal is output to the drive motor (S22). The stop time (t) from the output of the drive motor stop signal at this time until the drive motor stops completely is measured as described above (S23), and a predetermined time (T set in advance by the control unit) And comparison is made (S24).

  As a result of comparing the set specified time (T) with the stop time (t), if the stop time is longer than the specified time (FIG. 9), the process proceeds to step S25, and a special stop method is performed. As a result of the comparison, when the stop time is shorter than the specified time, the process returns to step S21 and the normal stop method is performed.

  In step S25, when a drive motor drive signal is output and then a drive motor stop signal is output (S26), the registration clutch is turned on for a predetermined time in synchronization with the stop signal output (S27). This certain time is preferably longer than the time during which the motor stops in the state where the registration clutch is on. Steps S25 to S27 are repeated until the apparatus is turned off.

  As a result, an additional load is applied to the drive motor, the rotation time due to inertia can be shortened, and control can be performed so as to always obtain the same or less stop time (FIG. 8).

  When the load on the drive motor is reduced to some extent, the stop time tends to increase, but in this embodiment, such a state can be detected and dealt with based on the stop time.

  In the process of FIG. 11, the time t until stopping is measured every time the driving motor stops. However, it is normally considered that the period from when the apparatus power is turned on to when it is turned off is a relatively short period (for example, less than one day), and the time t does not change so much within that period. FIG. 12 is a flowchart showing a flag setting process for switching the operation in the third embodiment.

  In the process of FIG. 12, the front multi-rotation is normally started when the apparatus power is turned on. Therefore, first, the flag is reset to OFF (S31). Next, it is checked whether or not the front multi-rotation has stopped (S32). When the front multi-rotation stops, the time (t) from the stop signal output to the complete stop is measured (S33). This time t is compared with a specified time (T) until stopping (S34). When t> T, the flag is turned on (S35). Otherwise, this process is terminated without turning on the flag. Note that the rotation speed of the motor at the time of multiple front rotations is not necessarily the same as the rotation speed of the motor at the time of image formation. The specified time (T) can be changed according to the rotation speed of the motor during the previous multiple rotations.

  FIG. 13 shows a flowchart of a stop process that actually uses the flag.

  As shown in FIG. 13, when the drive motor stop signal is output (S41, Yes), the state of the flag is checked. If the flag is on (S42, Yes), the registration clutch is driven for a certain period of time (S42, Yes). S43). If the flag is off, the operation in step S43 is omitted.

  In the processing of FIG. 12, after the power is turned on, the stop time is measured with the stop of the previous multi-rotation, and when the stop time exceeds the specified time, the registration clutch on operation is performed when the drive motor is stopped urgently. I made it. Even after the stop time exceeds the specified time, when the power is turned on again after the power is turned off, the stop time is measured again. However, generally, once the stop time exceeds a specified time, it is considered that the same state continues. Therefore, as a modification of the processing of FIG. 12, the flag is stored in a nonvolatile memory (in the control unit 7), and this value is maintained even after the power is turned off. That is, once the flag is turned on, the operation for measuring the stop time when the power is turned on is omitted.

  FIG. 14 shows a flag setting process for switching the operation.

  In the process of FIG. 14, first, the state of the flag is checked based on the stored contents (S51). The fact that this flag is in the on state means that t> T, and the operation mode for performing the registration clutch on operation is set when the drive motor is stopped. In this case, the process of FIG.

  If the flag is off, the stop time (t) is measured in accordance with the previous multi-rotation stop (S52) (S53). When the stop time exceeds the specified time (S54, Yes), the flag is turned on (S55). The state of this flag is stored in a nonvolatile memory so that it is maintained even when the power is turned off (S56).

  According to this modification, once the flag is turned on, it is not necessary to measure the stop time each time the apparatus power is turned on.

  Note that the flag once turned on can be reset to the off state in the following cases. For example, when a cartridge containing the photosensitive drum 15, the developing unit 5, the cleaning unit 26, etc. is replaced with a new one, the load usually becomes heavy. Therefore, the flag is reset to OFF when the cartridge is replaced. May be. Confirmation of cartridge replacement can be performed by using the detection result of the remaining amount of toner or by receiving a manual operation by the user.

  The preferred embodiments of the present invention have been described above, but various modifications and changes other than those mentioned above can be made.

  For example, in the above embodiment, the driving motor is stopped when a paper jam occurs during paper conveyance. However, the operation of the registration clutch is not limited to when a paper jam occurs. It can also be applied.

1 is a cross-sectional view illustrating a mechanical schematic configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a functional block diagram of the image forming apparatus illustrated in FIG. 1. FIG. 2 is a diagram illustrating a jam state at a fixing unit in the image forming apparatus illustrated in FIG. 1. 4 is a flowchart illustrating an operation procedure of the image forming apparatus according to the embodiment of the present invention. It is the figure which extracted and showed a part of FIG. 2 about the 2nd Embodiment of this invention. FIG. 6 is a diagram showing a more detailed configuration around the photosensitive drum shown in FIG. 5. It is a figure which shows the stop time of a drive motor when not performing a registration clutch drive at the time of the drive motor OFF in embodiment of this invention. It is a figure which shows the stop time of a drive motor at the time of performing a registration clutch drive at the time of the drive motor OFF in embodiment of this invention. In the 2nd Embodiment of this invention, it is explanatory drawing in case a stop time (t) is long with respect to regulation time (T). It is explanatory drawing about the measurement of the stop time of the drive motor in the 2nd Embodiment of this invention. FIG. 11 is a flowchart showing the operation in the second embodiment. It is a flowchart which shows the setting process of the flag for switching of operation | movement in the 3rd Embodiment of this invention. It is a flowchart which shows the stop process using the flag set by the process of FIG. It is a flowchart which shows the setting process of the flag for operation | movement switching in the modification of the 3rd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 4 ... Transfer unit 5 ... Development unit 7 ... Control part 8 ... Paper cassette 9 ... Paper 10 ... Paper feed sensor 11 ... Paper feed roller 12 ... Registration sensor 13 ... Registration roller 14 ... Transfer roller 15 ... Photosensitive drum 16 ... Pressure roller 17 ... Fixing roller 18 ... Discharge sensor 19 ... Discharge roller 20 ... Registration clutch 21 ... Feeding clutch 26 ... Cleaning unit 27 ... Cleaning blade

Claims (6)

An image forming apparatus for forming an image on a recording material, a drive motor for driving a driven portion in the image forming apparatus;
A clutch for selectively transmitting the driving force of the driving motor;
An image forming apparatus comprising: control means for generating a drive motor stop signal and turning on the clutch when the drive motor is stopped. Provided with an abnormality detection means for detecting an abnormality in the image forming apparatus,
The image forming apparatus according to claim 1, wherein the control unit generates the drive motor stop signal and activates the clutch when an abnormality is detected by the abnormality detection unit.   3. A fixing unit for thermally fixing a toner image formed on a recording material conveyed in an image forming apparatus, wherein the driving motor is also used for driving the fixing unit. The image forming apparatus described.   A measuring means for measuring a time until the drive motor stops; and when the measured time becomes longer than a predetermined time set in advance, the clutch is synchronized with a subsequent drive motor stop signal. The image forming apparatus according to claim 1, wherein the image forming apparatus is driven.   The control means stores, in a non-volatile manner, that the measured time is longer than a preset specified time as a flag state, and once the flag is turned on, the time by the measurement means The image forming apparatus according to claim 4, wherein the measurement is omitted, and the clutch is driven in synchronization with the drive motor stop signal.   6. The driven roller to which the clutch selectively transmits the driving force of the driving motor is a registration roller that supplies a recording material to be conveyed to the image recording unit at a predetermined timing. The image forming apparatus according to any one of the above.

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