JP2006072210A - Image forming apparatus and control method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem that it takes a longer time than in normal activation since the rotating speed of a motor does not converge while a target speed changes in steps. <P>SOLUTION: A PLL circuit detects a motor rotation and outputs a motor lock signal showing whether its revolution is in a prescribed revolution range; when the motor lock signal is turned into a high level after it is discriminated that a prescribed time (ΔTon) has passed after the activation of the motor, recording paper is conveyed and image forming operation is started. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus that forms an image on a recording medium by, for example, an electrophotographic method, and a control method thereof.

  In an electrophotographic printer, a sheet stored in a sheet cassette is fed by a rotation drive of a conveyance motor, conveyed to an image forming unit, and an image is formed on the conveyed sheet. In the image formation, the electrostatic latent image formed on the photosensitive drum is developed with toner, the toner image is transferred onto a sheet, and the toner image on the sheet is fixed with a fixing device. A motor used for paper feeding at the time of image formation is called a main motor, and is commonly used for driving a photosensitive drum, a fixing device, and a paper discharging mechanism in addition to a paper feeding mechanism.

  Conventionally, there has been a case where such a rotational speed of a motor is monitored, and when the rotational speed is out of a predetermined rotational speed range, a motor rotation failure is caused to be in an error state. This is to prevent the electrostatic latent image formed on the photosensitive drum from expanding and contracting in the drum rotating direction due to the rotation speed of the photosensitive drum changing due to the rotational fluctuation of the motor.

  In general, when the motor starts rotating from a stopped state, the rotational speed does not become a constant rotational speed until a certain time elapses, and gradually converges to a predetermined rotational speed while increasing or decreasing the rotational speed. Go. In the conventional printing apparatus, the number of rotations of the motor is monitored, and the latent image forming and paper feeding operations are started after the region where the rotation is unstable is completed and the rotation is stabilized. Also, in order to shorten the time from when the copy start button is pressed to when the copy paper is discharged (First Copy Out Time: hereinafter referred to as FCOT), the paper transport speed to the image transfer unit is increased. The method is adopted.

However, when the latent image formation and paper feeding operation is started after the motor rotation is stabilized, the time until the motor rotation passes through the unstable region is added to the FCOT. As a method for solving this, it is monitored whether or not the rotation speed of the motor is within a normal rotation range, and the rotation of the motor deviates from the normal rotation speed range within a predetermined time from the start of rotation of the motor. Even if a signal indicating this is generated, the signal is ignored. Specifically, the paper conveyed from the paper tray is once transported to a predetermined position on the transport path, and then waits at the predetermined position. Then, the sheet is conveyed from the standby position toward the image forming unit at a predetermined timing. In this way, paper is transported from the paper tray to the standby position in an area where the initial rotation of the motor is unstable. In other words, a paper feeding operation that does not greatly depend on the driving speed should be performed while ignoring fluctuations in the rotation of the transport motor. Has been proposed (Patent Document 1).
JP 2000-118749 A

  However, in recent printing apparatuses, depending on the type of paper to be printed (thick paper, envelope paper, OHP sheet, etc.), the image forming speed is reduced to half the normal speed due to problems such as fixing properties, and the image forming operation is performed. There is. In this case, a speed change operation of the motor (deceleration operation from normal speed to half speed) is required, and during that time, as in the case of start-up, the motor rotation speed starts to decelerate for a certain period of time. Until the time elapses, the speed does not become constant, but converges to half speed while increasing or decreasing the speed. Furthermore, when the recording paper is returned to plain paper from thick paper or envelopes, it is necessary to accelerate the transport speed from half speed to normal speed. In this case as well, the recording paper is rotated until a certain time elapses. The number is not constant. Here, it is generally known that the time required for a motor to converge to a certain number of revolutions varies depending on the acceleration / deceleration driving conditions, the load to be driven at that time, and the like.

  Therefore, even when the paper feeding operation as in the conventional technique is performed in an unstable region, the paper transported from the paper tray is once transported to a predetermined position on the transport path, and then at that position. It is necessary to wait and transport the sheet from the standby position toward the image forming unit at a predetermined timing. This predetermined timing includes an operation of waiting from the time when the rotation of the motor starts to a time until the motor converges to the normal speed.

  However, in the case of a copy or print job in which printing using thick paper or plain paper occurs alternately, it is necessary to change the rotational speed of the motor itself as needed. In this case, the drive conditions differ depending on the acceleration and deceleration of the motor, and the time for the motor rotation speed to converge to the target rotation speed also varies. For this reason, the time for which the paper waits increases, and there is a problem that in the above-described jobs in which printing using thick paper or plain paper is alternately generated, the time until all jobs are completed becomes long.

  Recently, a fixing device using a fixing film has been used. In such a fixing device, the fixing film is heated and the toner on the paper is fixed by the heat. In such a fixing method using a fixing film, when the conveyance of the fixing film is started, the fixing film is shifted depending on the temperature of the fixing film. For this purpose, the fixing film is transported by a step acceleration operation in which the speed is changed step by step by a predetermined step up to the final target speed, thereby starting up the rotation of the fixing motor more slowly than normal startup. There is a method to prevent the film from shifting. While the target speed is changed stepwise in this way, the rotation speed of the fixing motor does not converge, so that it takes more time than during normal startup. Therefore, when image formation is performed while waiting for conveyance in the same manner as in normal startup, the rotation of the motor does not converge and an error due to motor rotation failure occurs.

  The present invention has been made in view of the above problems, and the feature of the present invention is that after a predetermined time elapses until the rotation is substantially stabilized according to the driving state of the motor, the rotation speed of the motor reaches the target rotation. An image forming apparatus capable of shortening the waiting time until the rotation of the motor is stabilized by accurately starting the image forming operation according to whether or not the number is within a range, and accurately determining the number of rotations of the motor and forming an image It is in providing the control method.

  Further, the present invention is characterized in that the predetermined time until the rotation is substantially stabilized is set to be different for each driving state according to the driving state of the motor, and after the predetermined time has elapsed, the rotational speed of the motor is By starting the image forming operation according to whether or not the rotation speed is within the target range, the waiting time until the motor rotation is stabilized can be shortened, and the image can be formed by accurately grasping the rotation speed of the motor. It is to provide a forming apparatus and a control method thereof.

An image forming apparatus according to an aspect of the present invention has the following configuration. That is,
Drive means for rotationally driving the motor;
PLL means for detecting rotation of the motor and generating a signal indicating whether the rotation speed is in a predetermined rotation speed range;
Discriminating means for discriminating whether or not a predetermined time has elapsed since the start of the motor by the driving means;
And a control unit that controls to start an image forming operation in response to the signal from the PLL unit after the determination unit determines that the predetermined time has elapsed.

An image forming apparatus according to an aspect of the present invention has the following configuration. That is,
Drive means for rotationally driving the motor;
PLL means for detecting rotation of the motor and generating a signal indicating whether the rotation speed is in a predetermined rotation speed range;
Discriminating means for discriminating whether or not a predetermined time has elapsed from the time when the driving rotational speed of the motor by the driving means is changed;
And a control unit that controls to start an image forming operation in response to the signal from the PLL unit after the determination unit determines that the predetermined time has elapsed.

An image forming apparatus control method according to an aspect of the present invention includes the following steps. That is,
A driving process for rotationally driving the motor;
An identification step of detecting rotation of the motor and identifying whether the rotation speed is in a predetermined rotation speed region;
A determination step of determining whether a predetermined time has elapsed since the start of the motor by the driving step;
And a control step of controlling to start an image forming operation when it is determined in the determination step that the predetermined time has elapsed and then the identification step is determined to be in the predetermined rotation speed region. Features.

An image forming apparatus control method according to an aspect of the present invention includes the following steps. That is,
A driving process for rotationally driving the motor;
An identification step of detecting rotation of the motor and identifying whether the rotation speed is in a predetermined rotation speed region;
A determination step of determining whether or not a predetermined time has elapsed since the time when the drive rotation speed of the motor was changed by the drive step;
And a control step of controlling to start an image forming operation when it is determined in the determination step that the predetermined time has elapsed and then the identification step is determined to be in the predetermined rotation speed region. Features.

  According to the present invention, at the time of starting the motor, the rotation of the motor is normal by determining whether or not the rotation speed of the motor is within a predetermined region after a predetermined time has elapsed until the rotation of the motor is stabilized. Nevertheless, it is possible to prevent the problem of erroneously determining that the rotation of the motor is defective.

  In addition, a predetermined time until the rotation of the motor is stabilized is set according to each driving state of the motor, and after the predetermined time has elapsed, it is determined whether or not the number of rotations of the motor is within a predetermined region. This makes it possible to shorten the waiting time until the rotation of the motor becomes stable and to prevent the motor from being erroneously determined to be defective in spite of the normal rotation of the motor.

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

[Embodiment 1]
FIG. 1 is a block diagram showing the internal structure of an image forming apparatus (a multi-function device that functions as a copying machine, a printer device, and a facsimile device) according to an embodiment of the present invention. The image forming apparatus includes a scanner unit B, an image forming unit C, and a sheet deck D in each unit of the image forming apparatus main body A. The image forming apparatus main body A has a scanner unit B as image reading means for reading image information of a book document at the upper part thereof, an image forming part C as image forming means at the lower part thereof, and further at the lower part thereof. The seat deck D is assembled.

  More specifically, the scanner unit B includes a scanning light source 201, a platen glass 202, a document pressure plate 203 that can be opened and closed with respect to the image forming apparatus main body A, a mirror 204, a lens 205, a light receiving element (photoelectric conversion element) 206, And an image processing unit. Then, a book document such as a book / thick paper / curl paper or a sheet-like document is placed on the platen glass 202 with the document surface facing downward, and the document pressure plate 203 presses the back surface to set the document stationary. When the start key is pressed, the scanning light source 201 scans the lower part of the platen glass 202 in the direction of arrow a to read image information on the document surface. The image information of the original read in this way is processed by the image processing unit, converted into an electric signal, and transmitted to the laser scanner 111 of the image forming unit C.

  Here, the image forming apparatus main body A functions as a copying machine when the processing signal of the image processing unit is input to the laser scanner 111 of the image forming unit C, and functions as a printer when the output signal of the external device (computer) is input. . The image forming apparatus main body A also functions as a facsimile apparatus if it receives a signal from another facsimile apparatus or transmits a signal from the image processing unit to another facsimile apparatus.

  On the other hand, a sheet cassette 1 is mounted at the lower part of the image forming unit C. The sheet cassette 1 is configured as one feeding unit with two cassettes, a lower cassette 1a and an upper cassette 1b. In the present embodiment, two cassettes U1 and U2 can be mounted and four cassettes can be mounted. One feeding unit U1 positioned above is detachably attached to the image forming apparatus main body A, and the lower feeding unit U2 is detachably attached to the sheet deck D.

  The sheets (recording materials) accommodated in the lower cassette 1a and the upper cassette 1b are fed out by a pickup roller 3 serving as a feeding rotating body as will be described later, and the feed roller 4 and the retard roller 5 cooperate with each other. After being separated and fed one by one by the action, the sheet is conveyed by the conveying rollers 104 and 105, guided by the registration roller 106, and fed to the image forming unit C by the registration roller 106 in synchronization with the image forming operation. .

  In addition to the sheet cassette 1 described above, a manual feed tray 10 is disposed on the side surface of the image forming apparatus main body A, and the sheet S on the manual feed tray 10 is fed to the registration roller 106 by the rotation of the manual feed roller 11. .

  The image forming unit C includes a photosensitive drum 112, an image writing optical system 113, a developing device 114, a transfer charger 115, and the like. The surface of the photosensitive drum 112 uniformly charged by the transfer charger 115 is scanned with laser light corresponding to the image information emitted from the laser scanner 111 by the image writing optical system 113 to form an electrostatic latent image. A toner image is formed on the electrostatic latent image by the developing device 114, and the toner image is transferred by the transfer charger 115 to the first surface of the sheet conveyed in synchronization with the rotation of the photosensitive drum 112 by the registration roller 106. .

  Reference numeral 117 denotes a conveyance unit that conveys a sheet on which a toner image is formed, 118 denotes a fixing unit, and 119 denotes a discharge roller. The sheet on which the toner image is formed is conveyed to the fixing device 118 by the conveying unit 117, and is heated and pressed to fix the toner image on the sheet surface. The sheet on which the image is fixed in this manner is discharged and stacked on the sorter 120 disposed outside the apparatus by the rotation of the discharge roller 119.

  When images are printed on both sides of the sheet, the sheet discharged from the fixing device 118 is held between the discharge rollers 119, and the discharge roller 119 is reversed when the trailing edge of the sheet passes the branch point 207. . As a result, the sheet is fed onto the sheet double-sided tray 121 and once placed on the tray 121, and then conveyed by the rotation of the conveying rollers 104 and 105 to reach the registration roller 106. An image is formed in the same manner as described above on the second side (the back side printed last time) of the sheet thus reversed, and then discharged onto the sorter 120 and stacked.

  Next, a configuration according to Embodiment 1 of the present invention will be described with reference to FIG.

  FIG. 2 is a diagram illustrating motor control of the image forming apparatus according to Embodiment 1 of the present invention.

  The CPU 21 of the control unit 20 controls the entire image forming apparatus based on a program stored in the ROM 22. The RAM 23 temporarily stores calculation values and the like processed by the CPU 21 and performs reading and writing via the bus. The CPU 21 transmits a CLK signal and a motor-on (ON) signal to a motor drive circuit 27 to be described later in order to cause the main motor 28 that is a drive source of the photosensitive drum 112 to perform a drive operation. The CLK signal is a synchronization signal for operating the main motor 28 at the target rotational speed. When the rotational speed is increased, the rotational speed can be increased by increasing the frequency of the CLK signal. The motor-on signal is a signal for starting the rotation of the main motor 28. By enabling the motor-on signal, the motor-on signal of the main motor 28 is set to the rotation speed based on the frequency of the CLK signal. Start the startup operation. In addition, the control unit 20 outputs a paper feed on signal for starting paper feeding on the sheet cassette 1 to turn on a paper feeding clutch (not shown), and starts a paper feeding operation.

  Further, the control unit 20 receives an input signal of a registration sensor provided in front of the registration roller 106. The output of the registration sensor becomes a high level when a sheet arrives at the registration roller 106. Thereby, it can be detected that the sheet has arrived at the registration roller 106. In the present embodiment, for example, a DC brushless motor is used as the main motor 28. The operation unit 29 includes a display unit that displays messages and errors to the user in addition to switches and buttons operated by the user. The timer 30 is used for measuring time described later.

  The rotation of the registration roller 106 can be controlled by outputting a registration-on signal from the CPU 21 to the clutch drive circuit 24, turning on the registration clutch (CL) 25, and rotating the registration roller 106.

  FIG. 3 is a diagram illustrating the configuration of a DC brushless motor that is the main motor 28 according to the present embodiment.

  In the figure, 51 is a coil, 52 is a rotor, 53 is a Hall element, 54 is an amplifier, 55 is a magnetic pattern, 56 is a magnetic sensor, 57 is an amplifier, 58 is an energization logic circuit for controlling energization, and 60 is a speed control unit. , 61 is an F / V converter, 62 is a comparator, 63 is a PLL, 64 is a mixer, 65 is a PWM signal generator, 70 is a driver, 71 is a high side transistor, 72 is a low side transistor, 80 is a current limiter, 81 is a current detection resistor, 82 is a comparator, HU, HV, and HW are rotor position signals, and UU, UV, UW, LU, LV, and LW are phase switching signals.

  The DC brushless motor 50 includes a coil 51 and a rotor 52 that are three-phase star connection of U, V, and W. Further, three Hall elements 53 for detecting the magnetic poles of the rotor are provided as position detecting means for the rotor 52, and outputs thereof are amplified by the amplifier 54 and input to the energization logic circuit 58. Further, it has a rotational speed detecting means comprising a magnetic pattern 55 and a magnetic sensor 56 provided on the outer periphery of the rotor 52, and its output is amplified by an amplifier 57 and input to the speed control unit 60. The driver 70 is a circuit that rotationally drives the DC brushless motor 50, and 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.

  The energization logic circuit 58 receives the motor-on signal transmitted from the CPU 21, identifies the position of the rotor 52 by the rotor position signals HU to HW generated by the hall element 53, and generates phase switching signals UU to UW and LU to LW. To do. These phase switching signals UU to UW and LU to LW rotate the rotor 52 by sequentially switching the phases to be excited by on / off control of the transistors 71 and 72 of the driver 70.

  The speed controller 60 generates a voltage proportional to the rotation speed of the motor 28 by the F / V converter 61, and then compares the voltage with a reference voltage by the comparator 62 to obtain a differential output. Further, the PLL 63 compares the rotation frequency signal of the motor 28 with the phase of the CLK signal transmitted from the CPU 21 to obtain an output corresponding to the phase shift. Further, these two outputs are mixed by a mixer 64 and a PWM signal generator 65 generates a PWM signal. This PWM signal is input to the energization logic circuit 58 to control the rotational speed of the motor 28. When the rotational frequency of the motor 28 falls within a predetermined range, the motor lock signal is changed from the mixer 64 to a level (in this embodiment, a high level) indicating that the motor lock signal has entered the predetermined rotational speed. Then, the data is transmitted from the motor drive circuit 27 to the CPU 21.

  Next, operations and effects according to the present embodiment in the image forming apparatus having the above-described configuration will be described in detail.

  FIG. 4 is a timing chart showing changes in the rotational speed of the main motor 28 according to the first embodiment, together with signal waveforms at various parts.

  “Motor rotation speed” in the figure represents a change in the rotation speed of the motor 28 until the rotation speed of the motor 28 starts from a stopped state and falls within a specified rotation speed range. As can be seen from the figure, it takes a certain time after the rotational driving of the motor 28 is started until the rotational speed of the motor 28 falls within the range of the normal rotational speed.

  2 is a signal for starting a paper feeding operation, which is output from the control unit 20, and the paper feeding mechanism starts to operate by this signal and starts transporting the paper. In the present embodiment, a motor that drives the paper feed mechanism uses a stepping motor that is different from the main motor that drives the photosensitive drum and the like described above. Specifically, when this paper feed on signal is turned on, a paper feed clutch (not shown) is turned on. When the paper supply clutch is turned on, the paper is pulled out from the sheet cassette 1 and its conveyance is started. Then, after the feeding of the one sheet is completed, the feeding on signal is turned off.

  The motor lock signal is output from the mixer 64. As described above, the motor lock signal is a signal indicating whether or not the rotational speed of the motor 28 is in the normal rotational speed region. In the present embodiment, the motor lock signal is at a high level if the rotational speed is in the normal rotational speed region. If it is outside the area, the level is low.

  In the example of FIG. 4, even after the rotational speed of the motor 28 once enters the normal rotational speed region, the rotational speed rises from the upper limit of the normal rotational speed region during the time t3 to t4, and from the time t5 to During t6, it is lower than the lower limit of the normal rotational speed region. For this reason, the motor lock signal is at a low level in each of these periods.

  The motor-on signal is a control signal for driving the motor supplied from the control unit 20 to the driver 70, and is turned on at time t1 in FIG. The registration sensor signal is a detection signal at the leading edge of the paper output from the registration sensor. When this signal becomes high level, it is detected that the paper has reached the registration roller 106. In the example of FIG. 4, when the position of the registration sensor is reached after paper feeding is started, the registration sensor signal becomes high level at that time. The sheet waits at this position. The control unit 20 can recognize that the sheet is in the standby position based on the registration sensor signal.

  The clutch-on signal is a signal for driving the registration roller 26 output from the control unit 20 to the clutch drive circuit 24. The sheet is conveyed toward the transfer portion by driving the registration roller 26. Therefore, the time from when the registration sensor signal becomes high level to when the clutch-on signal becomes on (high level) is the waiting time.

  ΔTon is a non-detection period in which the CPU 21 stops detecting whether or not the rotation of the motor 28 has entered a predetermined number of rotations based on the motor lock signal since the rotation of the motor 28 is started. In FIG. 4, ΔTon is set as a non-detection period when the motor is started. Accordingly, this period ΔTon is an empirical period after the main motor 28 is started until the rotation speed converges within the target rotation speed range.

  In this way, when the user first changes the paper feed setting to the manual feed tray and sets the paper type to thick paper or envelope while a print job for printing on plain paper is being executed. The operation will be further described with reference to FIG.

  When the print job is changed at time t9, the number of rotations of the main motor 28 in the previous print job for printing on plain paper was the normal speed (hereinafter referred to as constant speed). (T9). At this time, the target rotational speed of the main motor 28 is changed to ½ of the normal rotational speed by changing the frequency of the CLK signal output from the CPU 21 from f to f / 2. At this time, the detection stop period of the motor lock signal is changed to a value ΔTdec that is different from ΔTon at the time of activation in the case of printing on plain paper (ΔTdec> ΔTon in this embodiment).

  Here, after the start of deceleration of the motor 28 and after the ΔTdec period elapses, lock detection as to whether the rotation speed of the motor 28 is within the normal rotation range is started by monitoring the motor lock signal. If the motor lock signal is at a high level for a predetermined time, it is determined that the rotation of the motor 28 is in a normal rotation state (motor lock state). At this time, the CPU 21 outputs a clutch-on signal to the clutch drive circuit 24, turns on the registration clutch 25, and rotationally drives the registration roller 106. As a result, the thick paper or envelope paper loaded on the manual feed tray 10 and fed to the registration roller 106 and waiting is conveyed to the photosensitive drum 112. As a result, the toner image is transferred from the photosensitive drum 112 to the thick paper or envelope paper, and the image is fixed by the fixing device 118 and discharged.

  Also, the motor lock signal is monitored, and if the motor lock signal is at a low level for a predetermined time, it is determined that the rotation of the motor 28 is not in a normal rotation state, an error due to a motor rotation failure is generated, and an error code is displayed on the operation unit 29. Display with

  With the above operation, when the main motor is started from a stopped state, it is possible to start the image formation by shortening the waiting time of the recording paper on the registration roller, and further, the image formation is instructed on the cardboard or envelope paper. Even when the speed decreases, image formation can be performed while waiting for an appropriate period according to the rotational characteristics of the motor. As a result, image formation can be performed without causing a rotation error of the main motor 28.

  In addition to the present embodiment, when a print job for printing on plain paper is followed by a print job for which printing on cardboard or envelope paper is designated, unlike the present embodiment, The rotation speed of the main motor 28 is accelerated from half speed to constant speed. In this case, the target rotational speed of the main motor 28 can be changed to the normal rotational speed by changing the frequency of the CLK signal output from the CPU 21 from f / 2 to f. Here, the detection stop period of the motor lock signal is changed to a value ΔTacc further different from ΔTon at the time of startup and ΔTdec at the time of deceleration (ΔTon <ΔTacc <ΔTdec). Thereafter, as in the above-described embodiment at the time of deceleration, after the time ΔTacc has elapsed after the start of acceleration of the motor 28, a lock detection as to whether the rotational speed of the motor 28 is in the normal rotation region is detected. Start by monitoring Here, if the motor lock signal is at a high level for a predetermined time, it is determined that the rotation of the motor 28 is in a normal rotation state (motor lock state), and the CPU 21 outputs a resion signal to the clutch drive circuit 24. As a result, the registration clutch 25 is turned on and the registration roller 106 is driven to rotate. In this way, the plain paper waiting on the registration roller 106 is conveyed to the photosensitive drum 112, the toner image is transferred from the photosensitive drum 112, and the image is fixed and discharged by the fixing device 118. Further, when the motor lock signal is monitored, if the motor lock signal is at a low level for a predetermined time, it is determined that the rotation of the motor 28 is not in a normal rotation state, a motor rotation failure error is generated, and the operation unit 29 With error code.

  FIG. 5 is a flowchart for explaining the rotation control of the main motor 28 by the control unit 20 of the image forming apparatus according to the present embodiment. This processing is the number of rotations of the main motor 28 for executing a print job on plain paper or the like. Is a process for increasing to a normal rotational speed. It is stored in the ROM 22 that executes this process, and is executed under the control of the CPU 21.

  First, in step S1, the frequency of CLK is set to a normal frequency f. Next, in step S2, the motor-on signal is turned on (high level), and the rotation of the main motor 28 is started. Next, in step S3, time measurement by the timer 30 is started. In step S4, the paper feed clutch is turned on to start feeding plain paper from the paper cassette 1. Next, in step S4, it is checked whether the output of the registration sensor has become a high level and the plain paper has been conveyed to the position of the registration roller 106. When the plain paper is conveyed to the position of the registration roller 106, the paper feeding clutch is turned off in step S6 to stop the paper feeding operation. In step S7, the rotation of the motor 28 is started based on the time measured by the timer 30. Check whether the time ΔTon has elapsed. This corresponds to the motor lock detection stop period of FIG. When the time ΔTon elapses, the process proceeds to step S8, where it is determined whether the motor lock signal is on, that is, whether the rotation speed of the main motor 28 is in the normal rotation speed region. Then, the rotation of the registration roller 106 is started, and the conveyance of the plain paper at the position of the registration roller 106 is started. As a result, the plain paper is sent to the position of the photosensitive drum 112, and the toner image is transferred (step S10). On the other hand, if the motor lock signal is not on in step S8 even though the time ΔTon has elapsed, the process proceeds to step S11, an error is displayed on the operation unit 29, and the process is terminated.

  Next, a process for reducing the rotation speed of the main motor 29 from a normal rotation speed to a half rotation speed will be described.

  FIG. 6 is a flowchart for explaining the rotation control of the main motor 28 by the control unit 20 of the image forming apparatus according to the first embodiment. This processing is switched to a print job for thick paper after a print job for plain paper. In this case, the processing is performed when the rotational speed of the main motor 28 is reduced from the normal rotational speed to half the rotational speed. It is stored in the ROM 22 that executes this process, and is executed under the control of the CPU 21.

  First, in step S21, the frequency of CLK is set to f / 2 that is half of the normal frequency f. Next, in step S22, time measurement by the timer 30 is started. In step S23, the paper feeding clutch is turned on to start feeding thick paper from the manual feed tray 10, for example. Next, in step S24, it is checked whether the output of the registration sensor has become a high level and the thick paper has been conveyed to the position of the registration roller 106. When the thick paper is conveyed to the position of the registration roller 106, the paper feeding clutch is turned off in step S25 to stop the paper feeding operation. In step S26, the time from the start of the rotation of the motor 28 based on the time measured by the timer 30 is reached. Check if ΔTdec has elapsed. This corresponds to the motor lock detection stop period at half speed shown in FIG. When the time ΔTdec elapses, the process proceeds to step S27, where it is determined whether the motor lock signal is on, that is, whether the rotation speed of the main motor 28 is in a rotation speed region that is half the normal rotation speed. In step S28, the rotation of the registration roller 106 is started, and the transport of the thick paper at the position of the registration roller 106 is started. As a result, the thick paper is sent to the position of the photosensitive drum 112, and the toner image is transferred (step S29). On the other hand, if the motor lock signal is not on in step S8 even though the time ΔTdec has elapsed, the process proceeds to step S30, an error is displayed on the operation unit 29, and the process is terminated.

  When the rotational speed of the main motor 28 is increased from a half speed to a normal speed, the CLK frequency is set from f / 2 to f in step S21 in the flowchart of FIG. 6, and the time ΔTacc is set in step S26. 6 can be executed in the same manner as the flowchart of FIG.

  As described above, according to the first embodiment, the period during which the motor clock is not detected (ΔTon, ΔTdec, ΔTacc) is set to a period during which the rotational speed of the motor is substantially stabilized by the inertia of the motor. By determining whether the motor rotation is stable at the desired rotation speed after the elapse of time, based on the motor lock signal, it is possible to perform proper image formation without making a mistake in determining whether the motor rotation speed is stable. It can be carried out.

[Embodiment 2]
The configuration of the image forming apparatus according to the embodiment of the present invention will be described. Note that the overall configuration of the image forming apparatus according to the second embodiment is the same as that of the first embodiment, and a description thereof will be omitted.

  FIG. 7 is a diagram for explaining motor control of the image forming apparatus according to the second embodiment of the present invention. Portions that are the same as those in FIG.

  The CPU 21 of the control unit 20 outputs a CLK signal and a motor-on signal to the motor driving circuit 97 in order to cause the fixing motor 98 that is a driving source of the fixing film driving roller 99 to perform a driving operation. The CLK signal is a synchronization signal for causing the fixing motor 98 to operate at the target rotational speed. When the rotational speed is increased, the rotational speed can be increased by increasing the frequency of the CLK signal. The motor-on signal is a signal for starting the rotation of the fixing motor 98. By setting the motor-on signal to an enable state (high level), the fixing motor 98 has a rotational speed corresponding to the frequency of the CLK signal. It is activated. In addition, the control unit 20 outputs a paper feed on signal for starting the paper feeding of the paper loaded in the paper cassette 1, turns on a paper feeding clutch (not shown), and starts a paper feeding operation. . Further, the control unit 20 inputs a signal from a registration sensor provided in front of the registration roller 106, and can detect that the sheet has arrived at the registration roller 106 when the signal becomes a high level.

  In the second embodiment, the output signal of the fixing thermistor 901 is further input to the control unit 20. As a result, the CPU 21 can detect the temperature of the fixing heater of the fixing device.

  FIG. 8 is a timing chart showing changes in the rotation speed of the fixing motor 98 according to the second embodiment together with signal waveforms.

  When a copy or print job start signal is input, the motor starts. Here, based on the signal from the fixing thermistor 901 in FIG. 7, the CPU 21 calculates the temperature of the fixing heater. Here, when the temperature of the fixing heater is lower than a predetermined value, if the fixing film constituting the fixing device is driven steeply before being sufficiently heated as described above, the fixing film tends to be shifted. . In order to prevent this, a roller for driving the fixing film (fixing film driving roller 99) is accelerated stepwise.

  In the second embodiment, the target speed of the fixing motor 98 is specifically set to 1/4 of the normal speed → 1/2 speed → normal speed (constant speed) (that is, the rotational speed is gradually increased). In this way, it accelerates step by step every predetermined time. Thus, the fixing film is slowly driven until the fixing film is sufficiently heated.

  “Motor rotational speed” in FIG. 8 indicates that the rotational speed of the fixing motor 98 is started when the fixing heater is at a predetermined temperature or less and when the fixing film is stepped, and the rotational speed is a target rotational speed region. 3 shows a change in the rotation speed of the fixing motor 98 until it falls within the range. As shown in the figure, after the rotation of the fixing motor 98 is started, the target speed is increased stepwise from the normal speed 1/4 speed → 1/2 speed → normal speed (constant speed). As described above, the speed increases in accordance with the rotational speed of the fixing motor 98. Then, a predetermined time is required from the start of rotation driving of the fixing motor 98 until it falls within the normal rotation speed region that is the final target speed.

  Here again, as in the first embodiment, the paper feed on signal is a signal for starting the paper feed operation output from the control unit 20, and the paper feed mechanism starts operating in response to this signal. Start transporting.

  In the second embodiment, the motor that drives the paper feeding mechanism is driven by using a stepping motor that is a driving source different from the fixing motor 98 that drives the fixing film described above. Specifically, when this paper feed on signal is turned on, a paper feed clutch (not shown) is turned on. When the paper supply clutch is turned on, the paper is picked up from the sheet tray 1 and its conveyance is started. The feed-on signal is turned off after the completion of feeding one sheet.

  The motor lock signal is output from the mixer 64. As described above, it is a signal indicating whether or not the rotation speed of the fixing motor 98 is in the normal rotation speed region. In the second embodiment as well, a high level is obtained if it is in the normal rotation region, and a low level if it is outside this region. The signal is output.

  In the example of FIG. 8, the rotation speed of the fixing motor 98 is changed so that the rotation speed becomes 1/4 rotation speed → 1/2 rotation speed → normal rotation speed at predetermined time intervals. Even after entering the area, for example, in the case of 1/4 rotation speed, the rotation speed of the fixing motor 98 rises from the upper limit of the normal rotation speed area between time t3 and t4, and between time t5 and t6. It is lower than the lower limit of the normal rotation speed range. For this reason, the lock signal is at a low level in each period.

  The motor-on signal is a control signal for rotational driving of the fixing motor 98 given from the control unit 20 to the driver 70, and is turned on at time t1 in FIG. The registration sensor signal is a detection signal at the leading edge of the paper output from the registration sensor. In the example of FIG. 8, when the leading edge of the paper reaches the position of the registration sensor after the paper feeding is started, the registration sensor signal becomes high level at this time. The paper waits at this position. The control unit 20 recognizes that the sheet is in the standby position based on the registration sensor signal. The clutch-on signal is a signal output from the control unit 20 for driving the registration roller 106. By the rotational driving of the registration roller 106, the sheet at the position of the registration roller 106 is conveyed toward the transfer unit. Therefore, the waiting time is from when the registration sensor signal becomes high level until when the clutch-on signal becomes high level.

  ΔTstep is a non-detection period in which detection of whether or not the rotation of the fixing motor 98 has entered a predetermined number of rotations is stopped based on the motor lock signal after the rotation of the fixing motor 98 is started.

  In FIG. 8, when the fixing thermistor 901 determines that the temperature of the fixing heater is equal to or lower than a predetermined temperature, the length of the period during which the rotation speed of the fixing motor 98 is not detected is changed. Specifically, as shown in the figure, the rotation speed of the fixing motor 98 is not detected until the rotation speed becomes 1/4 speed → 1/2 speed → constant speed from the time when the rotation of the fixing motor 98 is started. A set value is ΔTstep in which the period until the rotation speed of (normal rotation speed) converges to the non-detection period. Therefore, the motor lock detection stop period is changed to ΔTstep which is different from the non-detection period ΔTon at the time of startup and the non-detection period ΔTdec at the time of deceleration set in the first embodiment (in the first embodiment, ΔTon <ΔTdec <ΔTstep relationship).

  The lock detection of whether the rotation of the fixing motor 98 is in the normal rotation region after the lapse of ΔTstep period after the rotation start of the fixing motor 98 is started by monitoring the motor lock signal, and the motor lock signal is at a high level for a predetermined time. If it is, it is determined that the motor is in a normal rotation state (motor lock state). In this case, the CPU 21 outputs a registration-on signal to the clutch drive circuit 94 to turn on the registration clutch 95 and rotationally drive the registration roller 106. As a result, the paper that has been fed to the registration roller 106 and has been waiting is conveyed to the photosensitive drum 112, the toner image is transferred, fixed by the fixing device 118, and discharged.

  Also, the motor lock signal is monitored, and if the motor lock signal is at a low level for a predetermined time, it is determined that the rotation of the fixing motor 98 is not in a normal rotation state, and a rotation failure error of the fixing motor 98 is generated, causing an error in the operation unit 29. Display with code.

  FIG. 9 is a flowchart for explaining processing according to Embodiment 2 of the present invention. It is stored in the ROM 22 that executes this process, and is executed under the control of the CPU 21.

  First, in step S41, the temperature of the fixing heater is detected by the fixing thermistor 901, and it is determined whether or not the temperature is lower than a predetermined value. If not lower, the process proceeds to step S55, where the fixing motor 98 starts to rotate and the fixing film drive roller 99 moves the fixing film. On the other hand, when the temperature of the fixing heater is lower than the predetermined value, the process proceeds to step S42, and time measurement by the timer 30 is started. In step S43, the frequency of CLK is set to (f / 4) which is 1/4 of the normal frequency f. In step S44, the paper feed clutch is turned on to start feeding the recording paper from the paper cassette 1. Next, in step S45, it is checked whether the output of the registration sensor has become a high level and the recording paper has been conveyed to the position of the registration roller 106. When the recording paper is conveyed to the position of the registration roller 106 and inside the residence, the process proceeds to step S46. However, when the recording paper is conveyed to the position of the registration roller 106, the paper feeding operation is stopped by turning off the paper feeding clutch in step S49. Proceed to S46.

  In step S46, it is determined whether or not the fixing motor 98 has been rotated by a predetermined amount at the current CLK frequency. If not, the process returns to step S45. Here, f / 2). In step S48, it is checked whether the frequency of CLK is the normal frequency f. If not, the process returns to step S45 to execute the above-described processing.

  In step S48, if the frequency of CLK is f, the process proceeds to step S50, and it is checked whether the time ΔTstep (see FIG. 8) has elapsed since the rotation of the fixing motor 98 is started based on the time measured by the timer 30. This corresponds to the motor lock detection stop period in FIG. When the time ΔTstep elapses, the process proceeds to step S51, where it is determined whether the motor lock signal is on, that is, whether the rotation speed of the fixing motor 98 is in the normal rotation speed region. Then, the rotation of the registration roller 106 is started, and the conveyance of the recording paper at the position of the registration roller 106 is started. As a result, the recording paper is sent to the position of the photosensitive drum 112, and the toner image is transferred (step S53). On the other hand, if the motor lock signal is not on in step S51 even though the time ΔTstep has elapsed, the process proceeds to step S54, an error is displayed on the operation unit 29, and the process is terminated.

  As described above, according to the second embodiment, even when the fixing motor 98 is activated in a special rotational drive mode, the timing for detecting whether the rotation speed of the fixing motor 98 is in the normal range is controlled by mistake. The risk of determining that a rotation failure of the fixing motor 98 has occurred can be reduced.

  As described above, according to the present embodiment, even when the rotation of the motor starts or when the image forming speed of cardboard, envelope paper, or the like is slow, after the period corresponding to the characteristics of the motor has elapsed, By determining whether or not the rotational speed is in the normal range, the risk of a motor rotation error occurring can be reduced.

  Furthermore, according to the present embodiment, even when the motor is started in a special drive mode, it is erroneously determined that the rotational speed of the motor is abnormal by detecting the rotational speed of the motor at an appropriate timing. Risk can be reduced.

1 is a cross-sectional view illustrating a schematic configuration of an image forming apparatus unit according to an embodiment of the present invention. It is a block diagram explaining the structure of the drive part of the main motor which concerns on Embodiment 1 of this invention. It is a figure explaining the structure of the DC brushless motor which is the main motor which concerns on this Embodiment. It is a timing chart which shows the change of the rotation speed of the motor which concerns on Embodiment 1 of this invention with the signal waveform of each part. 4 is a flowchart illustrating rotation control of a main motor by a control unit of the image forming apparatus according to the first embodiment. 4 is a flowchart illustrating rotation control of a main motor by a control unit of the image forming apparatus according to the first embodiment. It is a figure explaining the motor control of the image forming apparatus which concerns on Embodiment 2 of this invention. 6 is a timing chart showing a change in the rotation speed of the fixing motor according to the second embodiment together with a signal waveform. It is a flowchart explaining the process which concerns on Embodiment 2 of this invention.

Claims (16)

Drive means for rotationally driving the motor;
PLL means for detecting rotation of the motor and generating a signal indicating whether the rotation speed is in a predetermined rotation speed range;
Discriminating means for discriminating whether or not a predetermined time has elapsed since the start of the motor by the driving means;
Control means for controlling the image forming operation to start in accordance with the signal from the PLL means after the determining means determines that the predetermined time has elapsed;
An image forming apparatus comprising:   2. The image forming apparatus according to claim 1, wherein the predetermined time corresponds to a time when the rotational speed of the motor is gradually increased by the driving unit to approach the target rotational speed. Drive means for rotationally driving the motor;
PLL means for detecting rotation of the motor and generating a signal indicating whether the rotation speed is in a predetermined rotation speed range;
Discriminating means for discriminating whether or not a predetermined time has elapsed from the time when the driving rotational speed of the motor by the driving means is changed;
Control means for controlling the image forming operation to start in accordance with the signal from the PLL means after the determining means determines that the predetermined time has elapsed;
An image forming apparatus comprising:   The image forming apparatus according to claim 1, wherein the motor is a recording sheet conveyance motor.   The image forming apparatus according to claim 1, wherein the motor is a motor for conveying a fixing film of a fixing device.   6. The image forming apparatus according to claim 2, wherein the predetermined time is different at startup, acceleration, and deceleration of the motor.   The image forming apparatus according to claim 6, wherein the predetermined time is longer when decelerating than when accelerating. A driving process for rotationally driving the motor;
An identification step of detecting rotation of the motor and identifying whether the rotation speed is in a predetermined rotation speed region;
A determination step of determining whether a predetermined time has elapsed since the start of the motor by the driving step;
A control step for controlling to start an image forming operation when it is discriminated that the predetermined time has elapsed in the discrimination step, and it is discriminated that the predetermined rotation speed region is in the discrimination step;
A control method for an image forming apparatus, comprising:   The control method according to claim 8, wherein the predetermined time corresponds to a time for gradually increasing the rotation speed of the motor in the driving step so as to approach the target rotation speed. A driving process for rotationally driving the motor;
An identification step of detecting rotation of the motor and identifying whether the rotation speed is in a predetermined rotation speed region;
A determination step of determining whether or not a predetermined time has elapsed since the time when the drive rotation speed of the motor was changed by the drive step;
A control step for controlling to start an image forming operation when it is discriminated that the predetermined time has elapsed in the discrimination step, and it is discriminated that the predetermined rotation speed region is in the discrimination step;
A control method for an image forming apparatus, comprising:   The control method according to claim 8, wherein the motor is a recording sheet conveyance motor.   The control method according to claim 8, wherein the motor is a conveyance motor for a fixing film of a fixing device.   The control method according to any one of claims 10 to 12, wherein the predetermined time is different when the motor is started, when the motor is accelerated, and when the motor is decelerated.   The control method according to claim 13, wherein the predetermined time is longer during deceleration than during acceleration. Drive means for rotationally driving the motor;
PLL means for detecting rotation of the motor and generating a signal indicating whether the rotation speed is in a predetermined rotation speed range;
A discriminating means for discriminating whether or not a predetermined time has elapsed since the driving by the driving means, according to the driving state of the motor by the driving means;
Control means for controlling the image forming operation to start in accordance with the signal from the PLL means after the determining means determines that the predetermined time has elapsed;
An image forming apparatus comprising: A driving process for rotationally driving the motor;
An identification step of detecting rotation of the motor and identifying whether the rotation speed is in a predetermined rotation speed region;
A determination step of determining whether a predetermined time has elapsed since the driving of the motor according to the driving state of the motor by the driving step;
A control step for controlling to start an image forming operation when it is discriminated that the predetermined time has elapsed in the discrimination step, and it is discriminated that the predetermined rotation speed region is in the discrimination step;
A control method for an image forming apparatus, comprising:

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