JP2016113295A - Image formation apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase printing productivity by making a paper interval smaller than a conventional one when conveying a plurality of sheets in an image formation apparatus which conveys the sheets by using synchronous motors and clutches.SOLUTION: Rollers 24, 25 for conveying sheets comprise: synchronous type motors M1, M2 for rotating the rollers 24, 25; clutches C1, C2 for transmitting rotational drive force to the rollers; control means 116; induction voltage detection means 112 for detecting an induction voltage Vk in the motors; and connection/opening completion timing detection means 114 for detecting connection completion timing, which is timing when the clutches C1, C2 have actually completed connection, and opening completion timing, which is timing when opening is actually completed, on the basis of the detected induction voltage Vk. The control means 116 determines command timing of giving commands to the clutches C1, C2 so as to perform connection operation or opening operation on the basis of the detected connection completion timing or opening completion timing.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an image forming apparatus that forms an image on a sheet.

  Image forming apparatuses such as printers, copiers, and multifunction machines take out paper from a paper storage unit and convey it, and perform printing at a predetermined position on the paper being conveyed. Rollers are arranged in the conveyance path inside the image forming apparatus at intervals shorter than the length in the vertical direction of the paper so that the paper can pass through each position on the conveyance path at a predetermined timing. Controls the rotational drive of the roller.

  A clutch is often used to turn on and off the rotational drive of the roller. By interposing a clutch that interrupts transmission of rotational driving force between the roller and the motor that is the driving source thereof, the roller can be stopped while the motor is rotating. The clutch is used, for example, when it is desired to use a single motor as a drive source for a plurality of rollers having different rotation timings.

  The clutch has a response delay with respect to the control signal. That is, there is a delay (connection delay) with respect to a switching command from the open state in which the roller and the motor are opened to a connected state in which the roller and the motor are connected, and a delay (open delay) with respect to the switching command from the connected state to the open state. . The connection delay and the release delay vary due to individual differences in the clutch. Also, if the thickness of the paper is different, the torque applied to the roller (load as viewed from the motor) will be different, resulting in variations in connection delay and release delay.

  Regarding the control of the clutch in the image forming apparatus, Patent Document 1 proposes a sheet conveying apparatus that stores data relating to the stop characteristics of the roller when the clutch is released, and controls the coupling timing of the clutch based on the stored data. Has been.

  In Patent Document 2, the connection time (connection delay) from the time when the clutch is connected to the time when the fluctuation in the rotation speed of the motor is within a predetermined range is measured, and after the connection is released, the clutch is instructed to be connected. It has been proposed to determine the timing to perform based on the connection time.

JP 2002-370845 A JP 2012-140212 A

  In a print job that continuously conveys a plurality of sheets, it is desired to reduce the interval between sheets (inter-sheet spacing) as much as possible in order to increase printing productivity.

  According to the prior art of Patent Document 1, since conveyance is controlled based on data relating to response delay stored in advance, the response delay varies due to machine differences in the image forming apparatus, load fluctuations, environmental changes, deterioration with time, and the like. Difficult to deal with. In other words, since the response delay is not measured, it is necessary to control the clutch at a timing that provides a margin so that the gap between the sheets is not too small even if the delay is the largest within the assumed range, assuming some variation in response delay. There is. For this reason, there has been a problem that the gap between the sheets cannot be minimized.

  On the other hand, according to the prior art of Patent Document 2, since the response delay is measured based on the number of rotations of the motor, it is theoretically possible to minimize the gap between the sheets.

  However, the method of detecting a change in the rotational speed of the motor is applicable only to a motor whose rotational speed varies according to torque, such as a DC brushless motor, and is not applicable to other motors. Therefore, when using a synchronous motor, such as a stepping motor, which does not vary in the number of rotations for transporting paper, there is a problem that the gap between papers cannot be minimized.

  SUMMARY An advantage of some aspects of the invention is that it improves printing productivity in an image forming apparatus that conveys paper using a synchronous motor and a clutch.

  An image forming apparatus according to an embodiment of the present invention includes a roller for conveying paper, a synchronous motor for rotationally driving the roller, a clutch for transmitting the rotational driving force of the motor to the roller, and a control unit. And an induced voltage detecting means for detecting an induced voltage Vk in the motor, and an induced voltage detected by the induced voltage detecting means. And a connection / release completion timing detection means for detecting a connection completion timing which is a timing when the clutch has actually completed the connection and a release completion timing which is a timing when the clutch is actually completed based on Vk. The control means determines a command timing for giving a command to perform a connection operation or a release operation on the clutch based on the connection completion timing or the release completion timing detected by the connection / release completion timing detection means. To do.

  According to the present invention, in an image forming apparatus that transports paper using a synchronous motor and a clutch, it is possible to increase the productivity of printing by reducing the paper spacing when transporting a plurality of paper sheets.

FIG. 3 is a diagram schematically illustrating a configuration of a main part related to sheet conveyance in the image forming apparatus according to the embodiment of the present disclosure. It is a figure which shows the MC structure, CM structure, and CC structure in connection with the roller drive mechanism for conveying a sheet | seat. 2 is a block diagram illustrating a hardware configuration of a control system of the image forming apparatus. FIG. It is a block diagram which shows the functional structure of CPU of a control system. It is a timing chart which shows the outline of the application of the drive voltage with respect to a motor. It is a figure which shows the example of the waveform of the coil voltage Ea and coil current Ia of a motor. It is a figure which shows the method of detecting the timing of the state transition of a clutch based on an induced voltage. 6 is a flowchart illustrating a schematic flow of paper feed control when a plurality of papers are conveyed. It is a figure which shows operation | movement and control of the roller drive mechanism of MC structure. FIG. 6 is a diagram illustrating an example of a position of a sheet that is temporarily stopped after sheet feeding. 6 is a flowchart illustrating a flow of sheet feeding control in the MC configuration. It is a flowchart of the timing setting process of MC configuration. It is a figure which shows the effect of the paper feed control in a MC structure. It is a figure which shows operation | movement and control of the roller drive mechanism of CM structure. 6 is a flowchart illustrating a flow of sheet feeding control in a CM configuration. It is a flowchart of the timing setting process of CM structure. It is a figure which shows the effect of the paper feed control in CM structure. It is a figure which shows operation | movement and control of the roller drive mechanism of CC structure. 6 is a flowchart illustrating a flow of sheet feeding control in a CC configuration. It is a flowchart of the timing setting process of CC structure. It is a figure which shows the effect of the paper feed control in CC structure.

  FIG. 1 schematically shows a configuration of a main part related to the conveyance of the paper 5 in the image forming apparatus 1 according to the embodiment of the present disclosure. The image forming apparatus 1 is a color printer including a tandem image forming unit 10 that forms an image by electrophotography. However, the present invention is not limited to this, and a monochrome printer, a copier, a multifunction machine, or a facsimile machine may be used.

  The image forming apparatus 1 forms an image on the paper 5 conveyed along the conveying path 20 by rotational driving of the rollers, and discharges the image. The image forming apparatus 1 includes a paper feed roller 24, a timing roller 25, a secondary transfer roller 26, a fixing roller 27, and a paper discharge roller 28.

  The paper feed roller 24 is a roller for sending the paper 5 stored in the paper feed cassette 30, which is a paper storage unit, one by one to the transport path 20. Hereinafter, sending out the paper 5 by the paper feed roller 24 may be referred to as “paper feed”. In addition, an operation of causing the paper 5 to enter the nip portion of the paper feeding roller 24 in a state stopped before paper feeding from the upstream side by, for example, a pickup roller (not shown) may be referred to as “paper feeding preparation”.

  The paper feed roller 24 is rotationally driven by a synchronous motor M1. The motor M <b> 1 is a stepping motor, and is provided in the image forming apparatus 1 as a drive source of the first roller drive mechanism 21.

  The timing roller 25 is a roller for sending the paper 5 sent out by the paper supply roller 24 to the transfer position along the transport path 20. The transfer position is a position where the transfer belt 15 of the image forming unit 10 and the secondary transfer roller 26 face each other and the image is transferred to the paper 5. The timing roller 25 temporarily stops the fed sheet 5 upstream of the transfer position, resumes conveyance at a predetermined timing for aligning the transfer of the toner image from the transfer belt 15 to the sheet 5, and transfers the sheet 5 to the transfer position. To send.

  The timing roller 25 is rotationally driven by a synchronous motor M2. The motor M <b> 2 is a stepping motor and is provided in the image forming apparatus 1 as a drive source of the second roller drive mechanism 22. The structure of the motor M2 is the same as that of the motor M1. However, it may be different.

  The secondary transfer roller 26 transfers the toner image from the transfer belt 15 to the paper 5. The fixing roller 27 is provided in the fixing device 18 and applies heat and pressure to the paper 5 on which the toner image is transferred. The paper discharge roller 28 discharges the image-formed paper 5 that has passed through the fixing unit 18 to the paper discharge tray 35.

  FIG. 2 shows an MC configuration, a CM configuration, and a CC configuration related to the first and second roller driving mechanisms 21 and 22.

  In manufacturing the image forming apparatus 1, a structure in which a clutch is interposed between the motor M <b> 1 and the paper feed roller 24 and a structure in which no clutch is interposed can be selected as the structure of the first roller driving mechanism 21. Similarly, as the structure of the second roller driving mechanism 22, a structure in which a clutch is interposed between the motor M2 and the timing roller 25 and a structure in which no clutch is interposed can be selected.

  Accordingly, when at least one clutch is used, the following three combinations of the structures of the first and second roller drive mechanisms 21 and 22 are provided.

  The configuration referred to as “MC configuration” shown in FIG. 2A is a combination of a first roller drive mechanism 21m that does not include a clutch and a second roller drive mechanism 22c that includes a clutch.

  The first roller driving mechanism 21 m includes a motor M 1 and one or more gears that transmit the rotational driving force of the motor M 1 to the paper feed roller 24. According to the first roller driving mechanism 21m, the paper feed roller 24 is connected to the motor M1 without a clutch.

  The second roller drive mechanism 22c includes a motor M2, one or more gears that transmit the rotational driving force of the motor M2 to the timing roller 25, and a timing clutch C2 that continuously transmits the rotational driving force. According to the second roller driving mechanism 22c, the timing roller 25 is connected to the motor M2 via the timing clutch C2.

  When the MC configuration is adopted, the motor M2 can be used not only for driving the timing roller 25 but also for driving the secondary transfer roller 26, for example. By sharing the motor M2 for a plurality of rotational drives having different timings, the number of motors mounted on the image forming apparatus 1 can be reduced and the component cost can be reduced.

  The configuration referred to as “CM configuration” shown in FIG. 2B is a combination of a first roller drive mechanism 21c that includes a clutch and a second roller drive mechanism 22m that does not include a clutch.

  The first roller driving mechanism 21c includes a motor M1, one or more gears that transmit the rotational driving force of the motor M1 to the paper feeding roller 24, and a paper feeding clutch C1 that intermittently transmits the rotational driving force. According to the first roller driving mechanism 21c, the paper feed roller 24 is connected to the motor M1 via the paper feed clutch C1.

  The second roller drive mechanism 22m is composed of a motor M2 and one or more gears that transmit the rotational driving force of the motor M2 to the timing roller 25. According to the second roller driving mechanism 22m, the timing roller 25 is connected to the motor M2 without a clutch.

  When the CM configuration is adopted, the motor M1 can be used not only for driving the paper feed roller 24 but also for driving a paper feed roller disposed at another paper feed port, for example. In other words, when the image forming apparatus 1 has the sheet feeding roller 24 and the other sheet feeding rollers because the sheet feeding cassette 30 is multi-staged or provided with a manual sheet feeding port, the motor M1 is rotated in the forward direction. It is possible to share the motor M1 by driving the other roller and rotating the other roller to drive the other roller.

  The configuration referred to as “CC configuration” shown in FIG. 2C is a combination of the first roller drive mechanism 21c including the paper feed clutch C1 and the second roller drive mechanism 22m including the timing clutch C2. It is. When the CC configuration is adopted, each of the motor M1 and the motor M2 can be shared by a plurality of rotational drives having different timings.

  FIG. 3 shows the hardware configuration of the control system of the image forming apparatus 1. The image forming apparatus 1 includes a control substrate 100 and a transport drive substrate 200.

  The control board 100 includes a CPU (Central Processing Unit) 101, a ROM (Read Only Memory) 102, a RAM (Random Access Memory) 103, an A / D converter 105, an interface element, and other peripheral elements.

  The CPU 101 is an example of a control unit of the image forming apparatus 1, and controls the overall operation of the image forming apparatus 1 including the conveyance of the paper 5 by executing a program stored in the ROM 102. The CPU 101 uses the RAM 103 as a work area for executing the program.

  The conveyance drive board 200 includes motor drivers 201 and 202 that drive the motors M1 and M2, respectively.

  The motor driver 201 applies an alternating voltage that periodically changes to the A-phase coil 42 and the B-phase coil 43 of the motor M1 to rotate the rotor 41 of the motor M1. A rectangular wave is usually used as the AC voltage. The rectangular wave is obtained by periodically turning on and off the output voltage of the constant voltage source, or by periodically inverting the sign of the output voltage. In addition, a rectangular wave can be synthesized by using an appropriate switching circuit and using a pulse train or PWM (pulse width modulation signal) having a higher frequency than the rectangular wave. If a pulse train or PWM is used, current control of the motor M1 can be performed.

  The motor driver 201 rotates or stops the motor M1 according to the motor control signal SM1 input from the control board 100.

  A voltage (coil voltage) Ea between both ends of the A-phase coil 42 is input to the A / D converter 105 of the control board 100 as a signal for detecting an induced voltage generated when the motor M1 is rotating. . The B-phase coil voltage Eb may be used as a signal for detecting the induced voltage.

  Similar to the case of the motor driver 201, the motor driver 202 applies an AC voltage that periodically changes to the motor M2 to rotate the motor M2. That is, similarly to the case of the motor driver 201, the motor driver 202 rotates or stops the motor M2 according to the motor control signal SM2.

  The A-phase coil voltage Ea of the motor M2 is input to the A / D converter 105 as a signal for detecting the induced voltage of the motor M2. The B-phase coil voltage Eb may be used as a signal for detecting the induced voltage.

  When the above-described CC configuration is employed, the sheet feeding clutch C1 and the timing clutch C2 are connected to the conveyance control board 200 as shown in the figure, and the clutch driver 203 that drives these clutches C1 and C2 is connected to the conveyance control board. 200. Then, the clutch driver 203 turns on / off (couples / releases) the paper feed clutch C1 according to the clutch control signal SC1 from the control board 100, and turns on / off the timing clutch C2 according to the clutch control signal SC2.

  When the M-C configuration is adopted, it is not necessary to connect the paper feed clutch C1 to the transport control board 200. When the CM configuration is adopted, the timing clutch C2 is connected to the transport control board 200. There is no need to connect to.

  FIG. 4 shows a functional configuration of the CPU 101 of the control system. In FIG. 4, a C-C configuration is assumed as an example, and the image forming apparatus 1 will be described as having both a paper feed clutch C1 and a timing clutch C2.

  The CPU 101 includes an induced voltage detection unit 112, a timing detection unit 114, and a conveyance control unit 116 as components related to paper conveyance control. These components are functional elements realized by the CPU 101 executing the above-described program.

  The induced voltage detector 112 detects the induced voltage Vk in the motors M1 and M2. The induced voltage detector 112 is an example of the “induced voltage detector” in the present invention. The induced voltage detector 112 monitors, for example, the A-phase coil voltage Ea of each of the motors M1 and M2, and the coil voltage Ea of the A-phase coil 42 when the current flowing through the A-phase coil 42 is 0 is induced voltage Vk. Detect as. The detection method will be described later.

  The timing detection unit 114, based on the induced voltage Vk detected by the induced voltage detection unit 112, completes the connection completion timing, which is the timing at which the paper feed clutch C1 and the timing clutch C2 have actually completed the connection, and the actual release. The opening completion timing that is the timing that has been detected is detected. The timing detection unit 114 is an example of the “connection / release completion timing detection unit” in the present invention. When the timing detection unit 114 detects the connection completion timing or the release completion timing, the timing detection unit 114 notifies the conveyance control unit 116 to that effect.

  The timing detection unit 114 is determined based on the magnitude of the induced voltage when the load applied to the motors M1 and M2 is the minimum load when the paper feed clutch C1 or the timing clutch C2 is connected. Using the threshold value Va, the timing at which the induced voltage Vk becomes smaller than the first threshold value Va is detected as the connection completion timing.

  Further, the timing detection unit 114 is determined based on the magnitude of the induced voltage when the load applied to the motors M1 and M2 is the maximum load with the paper feed clutch C1 or the timing clutch C2 connected. The timing at which the induced voltage Vk becomes larger than the second threshold value Vb is detected as the opening completion timing.

  The first threshold value Va or the second threshold value Vb may be changed according to the rotational speeds of the motors M1 and M2.

The conveyance control unit 116 controls the conveyance of the sheet 5 from the sheet feeding to the sheet ejection by the plurality of rollers including the sheet feeding roller 24 and the timing roller 25 described above. The conveyance control unit 116 is an example of the “control unit” in the present invention. The conveyance control unit 116 grasps the position of the sheet 5 based on the output of the timing detection unit 114 and the output of the sheet sensor included in the sensor group 50, and rotates or stops each roller at appropriate times. The conveyance control unit 116 uses a plurality of sheets 5 that give the motor control signals SM1 and SM2 to the motor drivers 201 and 202 and give the clutch control signals SC1 and SC2 to the sheet feeding clutch C1 and the timing clutch C2. In the print job, the conveyance control unit 116 issues a command to perform the connection operation or the release operation on the paper feed clutch C1 or the timing clutch C2 based on the connection completion timing or the release completion timing detected by the timing detection unit 114. Determine the command timing to be given. At this time, the interval between the two sheets 5 (the distance between the sheets) conveyed continuously by the sheet feeding roller 24 and the timing roller 25 is set to a predetermined range.

  Specifically, in the case of the MC configuration, the conveyance control unit 116 conveys the nth sheet 5 (n is an integer) by the paper feed roller 24 and the timing roller 25 and temporarily stops the nth sheet. When re-conveying the sheet 5 by the timing roller 25 and starting feeding the (n + 1) th sheet 5 by the sheet feeding roller 24, the time (T1) from the start timing of rotation of the motor M1 to the release completion timing in the timing clutch C2 ) To determine the rotation drive command timing for the motor M1 so that the (n + 1) th sheet 5 does not overlap the nth sheet 5 according to the stop position of the nth sheet obtained based on To do.

  In the case of the CM configuration, the transport control unit 116 transports the nth sheet 5 by the paper feed roller 24 and the timing roller 25 and pauses, and then restarts the nth sheet 5 by the timing roller 25. At the start of conveyance and delivery of the (n + 1) th sheet 5 by the sheet feed roller 24, n is obtained based on the time (T2) from the connection completion timing in the sheet feed clutch C1 to the rotation stop timing of the motor M2. According to the stop position of the sheet 5, the command timing for the coupling operation with respect to the sheet feeding clutch C1 is determined so that the (n + 1) th sheet 5 does not overlap the nth sheet 5.

  In the case of the CC configuration, the conveyance control unit 116 conveys the n-th sheet 5 by the paper feed roller 24 and the timing roller 25 and temporarily stops it, and then uses the timing roller 25 of the n-th sheet 5. When re-conveying and starting the feeding of the (n + 1) th sheet 5 by the paper feed roller 24, n is obtained based on the time (T3) from the connection completion timing in the paper feed clutch C1 to the release completion timing in the timing clutch C2. According to the stop position of the sheet 5, the command timing for the coupling operation with respect to the sheet feeding clutch C1 is determined so that the (n + 1) th sheet 5 does not overlap the nth sheet 5.

  FIG. 5 shows an outline of application of drive voltages to the motors M1 and M2, and FIG. 6 shows examples of waveforms of the coil voltage Ea and the coil current Ia of the motor.

  In this embodiment, the motors M1 and M2 that are stepping motors are driven by so-called two-phase excitation. That is, over the period when the motor control signals SM1 and SM2 are on, the A phase coil 42 and the B phase coil 43 of each of the motors M1 and M2 are shifted in phase by 90 ° as shown in FIG. , Eb) is applied. Since the rotor 41 has a permanent magnet, when the polarity of the voltage applied to each phase is switched and the direction of the coil current is reversed, the rotor 41 rotates in accordance with the change in the magnetic field. The motors M1 and M2 rotate by one step for every period of AC applied (8 clocks in the example in the figure). The rotation speed is determined by the clock frequency.

  When the motors M1 and M2 are rotating, the magnetic field for each coil changes, so that an induced voltage (counterelectromotive force) is generated in the A-phase coil 42 and the B-phase coil 43. That is, the rotating coil voltages Ea and Eb are voltages in which the induced voltage is superimposed on the voltage applied by the motor drivers 201 and 202.

  As shown in FIG. 6, the waveform of the coil voltage Ea is a waveform that is temporarily distorted from a rectangular shape during a period Tk in which the coil current Ia is zero. This waveform distortion is caused by the induced voltage Vk. For example, when the output of the motor driver 201 becomes high impedance in the period Tk, the voltage due to the output of the motor driver 201 becomes almost zero, and only the induced voltage Vk appears as the coil voltage Ea. Therefore, the magnitude of the induced voltage Vk can be determined by detecting the value (voltage level) of the coil voltage Ea in the period Tk.

  The induced voltage Vk is expressed by the following equation.

Vk = Ke · ω · cosθ
Ke: Induced voltage constant [V · s / rad]
ω: angular frequency [rad / s]
θ: Load angle (mechanical angle delay relative to electrical angle) [°]
When the load applied to the motors M1 and M2 is a large heavy load, the mechanical angle lag with respect to the electrical angle is large as compared with a light load with a small load. That is, the load angle θ2 in the case of a heavy load is larger than the load angle θ1 in the case of a light load. Since cos θ1> cos θ2 in the range of 0 ° <θ1, θ2 <90 °, the absolute value of the induced voltage Vk is larger in the heavy load than in the light load as shown by the broken line in FIG. small.

  FIG. 7 shows a method of detecting the timing of clutch state transition based on the induced voltage Vk.

  As shown in FIG. 7A, the above-described connection completion timing TA is a timing at which the induced voltage Vk changes from a state larger than the connection threshold value Va, which is the first threshold value. When the connection threshold Va is detected for the paper feed clutch C1, an experiment for feeding various types of paper 5 is performed in advance, and the load applied to the motor M1 with the paper feed clutch C1 connected is the lowest load. It is determined based on the result of examining the magnitude of the induced voltage Vk when (minimum load). In the case of detecting the timing clutch C2, a similar experiment is performed, based on the result of examining the magnitude of the induced voltage Vk when the load applied to the motor M2 is the minimum load while the timing clutch C2 is connected. Determined.

  As shown in FIG. 7B, a timing at which the induced voltage Vk is changed from a state smaller than the open threshold value Vb that is the second threshold value to a large state is set as the above-described open completion timing TB. When the release threshold value Vb is detected for the paper feed clutch C1, the above-described experiment is performed in advance, and the induced voltage when the load applied to the motor M1 is the maximum load with the paper feed clutch C1 connected. It is determined based on the result of examining the magnitude of Vk. In the case of detecting the timing clutch C2, a similar experiment is performed, based on the result of examining the magnitude of the induced voltage Vk when the load applied to the motor M2 is the maximum load with the timing clutch C2 connected. Determined.

  FIG. 8 shows a schematic flow of sheet feeding control when a plurality of sheets 5 are conveyed. This flow is common to the MC configuration, the CM configuration, and the CC configuration. In FIG. 8, it is assumed that the number N of sheets 5 is 3 or more. However, N may be 2 or more, and when N is 2, the sheet feeding control ends when re-transport of the second sheet 5 temporarily stopped is started.

  When a print job is given to the image forming apparatus 1, the CPU 101 starts feeding the first sheet 5 (# 11), and transfers the first sheet 5 being transported for transfer alignment. Temporarily stop the position upstream (# 12).

  The connection completion timing TA or the release completion timing TB is detected for the paper supply clutch C1 or the timing clutch C2 used in the stage from the paper supply to the temporary stop, and the distance moved by the paper 5 as described later based on the detection result Is detected (# 13).

  Subsequently, according to the detected error, the timings of the second sheet feeding and the first sheet transport resumption (re-carrying) are set so that the gap between the first sheet and the second sheet is optimized. Set (# 14).

  Then, the second sheet 5 is fed at the set timing, and the first sheet 5 is conveyed again at the set timing (# 15). The first sheet 5 that has been transported again is transported to the transfer position, the fixing device 18, and the paper discharge tray 35.

  The second sheet 5 that has been fed is temporarily stopped (# 16), and in the step (not shown), an error in the distance moved in the same manner as the first sheet is detected to optimize the gap between the third sheet and the third sheet. Set the timing. Then, the third sheet 5 is fed at the set timing, and the second sheet 5 is conveyed again at the set timing.

  The subsequent third to (N-1) th sheets are fed in the same procedure as before the second sheet, and the (N-1) th sheet 5 being conveyed is temporarily stopped upstream of the transfer position ( # 20). The error of the distance moved is detected (# 21), the timing for optimizing the gap between the last Nth sheet (# 22), the Nth sheet feeding and the (N-1) th sheet Re-conveyance is performed (# 23), and the paper feed control for the print job is completed.

Hereinafter, the operation and control of the image forming apparatus 1 will be described in more detail for each of the MC configuration, the CM configuration, and the CC configuration.
[MC configuration]
FIG. 9 shows the operation and control of the roller drive mechanism of the MC configuration. FIG. 9A shows the positions of the sheets 5a and 5b at a plurality of stages when the two sheets 5a and 5b are sequentially conveyed, and FIG. 9B shows the control timing.

  In FIG. 9A, odd-numbered sheets 5 including sheets 5a are represented by thick lines, and even-numbered sheets 5 including sheets 5b are represented by white thin bands. In addition, the stopped roller is represented by a white circle, and the rotating roller is represented by a hatched circle. The same applies to FIGS. 14A and 18A described later.

  In the case of the MC configuration, the progress of conveyance is detected using the three sensors A, B, and C. Sensors A, B, and C are paper sensors that output signals indicating the presence or absence of the paper 5 at the position where the sensors A, B, and C are arranged. The sensor A is disposed between the sheet feeding roller 24 and the timing roller 25 in the conveyance path 20, the sensor B is disposed near the downstream side of the timing roller 25, and the sensor C is disposed between the sensor B and the transfer position. Yes.

  Paper feeding is about to start at time t0. The paper feed preparation has already been completed, and the leading edge of one sheet 5 is sandwiched between the paper feed rollers 24. The motor M1 is stopped and the paper feed roller 24 is also stopped.

  When the motor control signal SM1 is switched from OFF (OFF) to ON (ON) at time t1 shown in FIG. 9B, the motor M1 rotates and the paper feed roller 24 rotates, and immediately the nth sheet 5a. Starts feeding.

  At time t2, when the sheet 5a arrives at the position of the sensor A and the sensor A is turned on, the clutch control signal SC2 is switched from off to on. This switching is a command to connect the timing clutch C2. The timing clutch C2 is connected at time t3 after receiving the connection command. The time point t3 is detected using the connection threshold value Va based on the induced voltage Vk of the motor M2 as described above. Time t3 is an example of connection completion timing TA.

  Note that the motor M2 has been rotating from time t2 or before, and the timing roller 25 is rotating at time t3. By rotating the timing roller 25 before the paper 5a arrives, the conveyance of the paper 5a can be taken over from the paper feeding roller 24 to the timing roller 25. The position of the sensor A is selected so that such preparation for conveyance can be performed in a timely manner. Since the sheet 5a has not arrived at the timing roller 25, the connection delay of the timing clutch C2 does not affect the conveyance of the sheet 5a.

  At time t4, when the paper 5a arrives at the position of the sensor B and the sensor B is turned on, the motor control signal SM1 is switched from on to off. The motor M1 stops and the paper feed roller 24 also stops. However, the conveyance of the sheet 5a by the timing roller 25 continues. In parallel with the conveyance of the sheet 5a, preparation for feeding the (n + 1) th sheet 5b is performed.

  At time t5, when the sheet 5a arrives at the position of the sensor C and the sensor C is turned on, the clutch control signal SC2 is switched from on to off. This switching is a release command for the timing clutch 24.

  The timing clutch C2 is released at time t6 after receiving the release command. The time point t6 is detected using the open threshold value Vb based on the induced voltage Vk of the motor M2 as described above. Time t6 is an example of the release completion timing TB.

  Since the timing clutch C2 has a release delay of time (opening operation time) from time t5 to time t6, when the paper 5a is temporarily stopped at time t6, the position P1 of the leading edge of the paper 5a is the position of the sensor C. It is a downstream position.

  The CPU 101 calculates a movement amount Da, which is the distance that the paper 5a has actually moved from the paper feed to the temporary stop from the transport speed V and the movement time T1 that is the time from the time t1 to the time t6. The movement amount Da is obtained by multiplying the movement time T1 and the conveyance speed V (Da = T1 · V). This movement amount Da is a value corresponding to the release delay of the timing clutch C2. Since there are variations in the release delay due to individual differences of the timing clutch C2, operating environment, secular change, etc., the movement amount Da varies.

  Next, the CPU 101 calculates a difference Dh (Dh = Da−D) between the calculated movement amount Da and the optimum movement amount D. The optimum movement amount D is the sum of the length L in the conveyance direction of the sheet 5a and the optimum sheet interval d. The length L of the paper 5a is determined by the paper size specified in the print job. The sheet interval d is a numerical value optimized according to the printing conditions such as the paper type, color / monochrome, single-sided printing / double-sided printing, and is determined by the setting of a plurality of items in the print job.

  Then, the CPU 101 starts the re-conveyance of the paper 5a at the time t9 when the re-conveyance for transfer is to be started, and provides the optimum paper interval d between the re-conveyed paper 5a and the next time. Time t8 and time t7 are set so that the paper 5b is conveyed.

  Time t8 is a timing at which a connection command is given to the timing clutch C2 for re-conveyance. The time point t7 is a timing at which the feeding of the (n + 1) th sheet 5b is started. These times t7 and t8 are examples of command timing.

  In the example of FIG. 9A, since the distance between the rear end position P2 of the sheet 5a and the sheet feed roller 24 is longer than the optimum sheet interval d at time t6, the next time before the sheet 5a is re-conveyed. The paper 5b is started to be fed. That is, a time point earlier than the time point t9 by the time Dh / V is set as the time point t7 so that the paper 5b advances downstream by the difference Dh between the time point t7 and the time point t9.

  Depending on the length L of the sheet 5a, as shown in FIG. 10, the distance between the rear end position P2 of the sheet 5a and the sheet feeding roller 24 becomes shorter than the optimum sheet interval d at time t6, and the movement amount Da And the difference Dh between the optimum movement amount D and a negative value. In this case, the time point t7 is set so as to start feeding the paper 5b after the re-conveyance of the paper 5a.

  FIG. 11 shows the flow of paper feed control in the MC configuration.

  The conveyance control unit 116 of the CPU 101 acquires a set value of the conveyance speed V (# 101). The conveyance control unit 116 turns on the motor control signal SM1 and starts feeding the nth sheet 5a as the preceding sheet (# 102), and starts counting the movement time T1 (# 103). Instead of timing, the current time may be taken from the system clock and stored as time t1.

  Waiting for sensor A to be turned on (# 104), and when sensor A is turned on, the conveyance control unit 116 turns on the clutch control signal SC2 in order to rotate the timing roller 25 in preparation for conveyance of the preceding paper. (# 105).

  Waiting for the sensor B to turn on (# 106), and when the sensor B is turned on, the conveyance control unit 116 prepares to feed the (n + 1) th sheet 5b, which is the subsequent sheet (# 107).

  Waiting for the sensor C to turn on (# 108), and when the sensor C is turned on, the transport control unit 116 switches the clutch control signal SC2 to off (# 109).

  Next, timing is set (# 110), and at the set timing, the conveyance control unit 116 turns on the clutch control signal SC2 to re-convey the preceding sheet (# 111).

  FIG. 12 is a flowchart of the timing setting process of the MC configuration in FIG.

  The timing detector 114 waits for the induced voltage Vk of the motor M2 periodically detected by the induced voltage detector 112 to become larger than the open threshold Vb (# 151). When the opening completion timing TB at which the induced voltage Vk becomes larger than the opening threshold value Vb is detected, the conveyance control unit 116 is notified of this.

  When the conveyance control unit 116 receives the notification that the opening completion timing TB has been detected, the conveyance control unit 116 ends the measurement of the movement time T1 (# 152). When the time point t1 is stored instead of the time measurement, the current time is fetched from the system clock as the time point t6, and the time from the time point t1 to the time point t6 is calculated as the movement time T1.

  Subsequently, the conveyance control unit 116 calculates the movement amount Da of the preceding sheet (# 153), and acquires the optimum movement amount D according to the setting contents of the print job from the control data stored in advance (#). 154).

  Then, the conveyance control unit 116 compares the calculated movement amount Da with the optimum movement amount D (# 155), and sets the sheet feeding timing of the subsequent sheet according to the magnitude relationship between the two as follows.

  If the movement amount Da is equal to the optimum movement amount D, the feeding timing of the succeeding sheet is kept at a predetermined reference timing (# 156). Further, the re-conveyance of the preceding sheet is earlier than the time t9 by the connection delay (difference between the time t2 and the time t3) when the timing clutch C2 is first connected at the time t2, as shown in FIG. 9B. The time point t8 is determined as a command timing for giving a command to perform the coupling operation on the timing clutch C2.

  When the movement amount Da is larger than the optimum movement amount D, the reference timing is set to a timing advanced by Th seconds as the feeding timing of the subsequent sheet (# 157). Th second is a time obtained by dividing the difference Dh between the movement amount Da and the optimum movement amount D by the conveyance speed V. Also in this case, for the re-conveyance of the preceding paper, the command timing is determined as in step # 156.

  When the movement amount Da is smaller than the optimum movement amount D, the reference timing is set to a timing delayed by Th seconds as the feeding timing of the subsequent sheet (# 158). Also in this case, for the re-conveyance of the preceding paper, the command timing is determined as in step # 156.

  As described above, the paper feeding timing of the succeeding sheet is advanced or delayed according to the movement amount Da, so that the optimum sheet spacing between the preceding sheet and the succeeding sheet is maintained regardless of variation in the release delay of the timing clutch C2. The interval d can be set, and the productivity of printing can be increased by minimizing the interval between sheets. The greater the number of sheets printed in a print job, the greater the effect of minimizing the gap between sheets.

  FIG. 13 shows the effect of sheet feeding control in the MC configuration. In FIG. 13, the transitions of the positions of the leading edge and the trailing edge of the preceding sheet and the succeeding sheet are depicted. The horizontal axis is time, and the vertical axis is the distance from the position of the paper feed roller 24. The same applies to FIGS. 17 and 21 described later.

  At time t1, the leading edge of the preceding sheet is at the position of the sheet feeding roller 24. The leading sheet moves at a constant speed from time t1 to time t5 when the timing clutch C2 is instructed to be released.

  In the ideal case where both the release delay and the connection delay of the timing clutch C2 are 0, as shown by the one-dot chain line in the figure, the preceding paper starts to be paused at the time t5, and then the connection is commanded from the time t8 when the connection is commanded. The paper starts moving again.

  When there is a certain release delay (for example, 7 ms) in the timing clutch C2, as shown by a solid line in the drawing, the actual pause of the preceding sheet starts at a time t6 delayed from the time t5, and then connected from the time t8. The preceding sheet starts to move again from time t9 later by the delay.

  When the release delay is the largest delay within the variation range (for example, 30 ms), as shown by a two-dot chain line in the figure, the actual pause of the preceding sheet starts at time t6 ′ delayed from time t6, and thereafter The preceding sheet starts to move again from time t9 ′ which is later than time t9.

  The trailing edge of the preceding sheet is always upstream of the leading edge of the preceding sheet by the length of the sheet.

  Now, paying attention to the feeding timing of the succeeding sheet, in this embodiment, as shown by the thick solid line in the figure, at the time t9 when the preceding sheet actually starts to move again, the trailing edge of the preceding sheet and the leading edge of the succeeding sheet are The feeding of the subsequent sheet is started at time t7 so that the distance becomes the optimum sheet interval d.

  On the other hand, conventionally, for example, feeding of the subsequent sheet is started at time t8. In this case, the gap between the sheets varies depending on variations in the opening delay and the connection delay. In the figure, the paper interval d1 when the opening delay and the connection delay are minimum and the paper interval d2 when it is the maximum are shown. These paper intervals d1 and d2 are both larger than the optimal paper interval d of this embodiment. In other words, conventionally, subsequent sheets are transported with an unnecessarily large sheet spacing d1, d2.

According to the present embodiment, the completion of paper discharge can be accelerated by time TS for each of the second and subsequent sheets.
[CM configuration]
FIG. 14 shows the operation and control of a roller driving mechanism having a CM configuration. FIG. 14A shows the positions of the sheets 5a and 5b at a plurality of stages when the two sheets 5a and 5b are sequentially conveyed, and FIG. 14B shows the timing of control.

  In the case of the MC configuration, only the sensor A of the three sensors A, B, and C is used, or none is used.

  At time t <b> 10, paper feed preparation has already been completed, and the leading edge of the nth paper 5 a that is the preceding paper is sandwiched between the paper feed rollers 24. The motor M1 is stopped and the paper feed roller 24 is also stopped.

  At time t11 shown in FIG. 14B, the clutch control signal SC1 is switched from off (OFF) to on (ON). This switching is a connection command for the paper feed clutch C1. The paper feed clutch C1 is in a connected state at time t12 after receiving a connection command. As a result, the paper feed roller 24 rotates to start feeding the paper 5a. The time point t12 is detected based on the induced voltage Vk of the motor M1 as described above. Time t12 is an example of connection completion timing TA.

  At time t13, when the sheet 5a arrives at the position of the sensor A and the sensor A is turned on, the motor control signal SM2 is switched from off to on. This switching is a rotation command for the motor M2. When the sensor A is not used, a time point at which a predetermined time a has elapsed from the time point t11 is set as a time point t13. When receiving the rotation command, the motor M2 starts rotating at a constant speed.

  At a time t14 when a predetermined time b has elapsed from the time t11, the clutch control signal SC1 is switched from on to off. At a time t15 delayed from the time t14, the paper feed clutch C1 is released and the paper feed roller 24 stops. However, the conveyance of the sheet 5a by the timing roller 25 continues. In parallel with the conveyance of the sheet 5a, preparation for feeding the (n + 1) th sheet 5b, which is a subsequent sheet, is performed.

  The time point t15 is detected using the open threshold Vb based on the induced voltage Vk of the motor M1 as described above. Time t15 is an example of the release completion timing TB.

  At a time t16 when a predetermined time c has elapsed from the time t13, the motor control signal SM2 is switched from on to off. The motor M2 stops and the timing roller 25 also stops. As a result, the temporary stop of the sheet 5a starts.

  Since there is a connection delay of time (connection operation time) from time t11 to time t12 in the paper feed clutch C1, when the paper 5a is temporarily stopped at time t16, the position P1 of the leading edge of the paper 5a is delayed in connection. Different positions depending on the variation.

  The CPU 101 calculates a movement amount Db, which is the distance that the paper 5a has actually moved from the paper feed to the temporary stop, from the transport speed V and the movement time T2 that is the time from the time t12 to the time t16. The movement amount Db is obtained by multiplying the movement time T2 and the conveyance speed V (Db = T2 · V). This movement amount Db is a value corresponding to the connection delay of the paper feed clutch C1. Since there is a variation in connection delay due to individual differences of the feed clutch C1, operating environment, secular change, etc., a variation occurs in the movement amount Db.

  Next, the CPU 101 calculates a difference Dh (Dh = Db−D) between the calculated movement amount Db and the optimum movement amount D. As described above, the optimum movement amount D is the sum of the length L in the conveyance direction of the sheet 5a and the optimum sheet interval d.

  Then, the CPU 101 actually starts the re-conveyance of the paper 5a at the time t17 when the re-conveyance for transfer is to be started, and provides the optimum paper interval d between the re-conveyed paper 5a and the next time. Time t18 and time t19 are set so that the paper 5b is fed.

  Time t18 is a timing at which a connection command is given to the paper feeding clutch C1 for feeding the paper 5b. The time point t19 is a timing at which the paper feed clutch C1 is engaged and the paper feed roller 24 actually starts feeding the (n + 1) th sheet 5b.

  In the example of FIG. 14A, since the distance between the rear end position P2 of the sheet 5a and the paper feed roller 24 is shorter than the optimal sheet interval d at time t16, the next time after the re-conveyance of the sheet 5a. Actual sheet feeding of the sheet 5b is started. In other words, the time point t19 is a time point later than the time point t17 by the time Dh / V so that the actual paper supply of the paper sheet 5b starts when the paper sheet 5a advances downstream by the difference Dh from the time point t17. The time point t18 is a time point earlier than the time point t19 by the connection delay.

  FIG. 15 shows the flow of paper feed control in the CM configuration.

  The conveyance control unit 116 of the CPU 101 acquires a set value of the conveyance speed V (# 201). The conveyance control unit 116 turns on the clutch control signal SC1 to feed the nth sheet 5a as the preceding sheet (# 202).

  The timing detection unit 114 waits for the induced voltage Vk of the motor M1 periodically detected by the induced voltage detection unit 112 to become smaller than the connection threshold value Va (# 203). When the connection completion timing TA at which the induced voltage Vk becomes smaller than the connection threshold value Va is detected, the transfer control unit 116 is notified accordingly.

  Upon receiving a notification that the connection completion timing TA has been detected, the transport control unit 116 starts counting the movement time T2 (# 204). The current time may be stored as in the above example.

  Waiting for sensor A to turn on (# 205), when sensor A is turned on, conveyance control unit 116 turns on motor control signal SM2 in order to rotate timing roller 25 in preparation for conveyance of the preceding paper. (# 206). When the sensor A is not used, it waits for the time a to elapse, and when the time a elapses, the motor control signal SM2 is turned on.

  Subsequently, the conveyance control unit 116 waits for the time c to elapse (# 207), and when the time c elapses, the motor control signal SM2 is turned off and the paper 5a is temporarily stopped (# 208). Preparation for feeding a certain (n + 1) th sheet 5b is performed (# 209).

  Next, timing setting processing is performed (# 210), and at the timing set thereby, the conveyance control unit 116 turns on the motor control signal SM2 to re-convey the preceding sheet (# 211).

  FIG. 16 is a flowchart of the timing setting process of the CM configuration in FIG.

  The conveyance control unit 116 acquires the movement time T2 (# 251). The moving amount Db of the preceding sheet is calculated (# 252), and the optimum moving amount D is acquired (# 253).

  Then, the conveyance control unit 116 compares the calculated movement amount Db with the optimum movement amount D (# 254), and sets the sheet feeding timing of the subsequent sheet according to the magnitude relationship between the two as follows.

  If the movement amount Db is equal to the optimum movement amount D, the feeding timing of the subsequent sheet is kept at the reference timing (# 255).

  When the movement amount Db is larger than the optimum movement amount D, the reference timing is set to a timing advanced by Th seconds as the feeding timing of the subsequent sheet (# 256). Th second is a time obtained by dividing the difference Dh between the movement amount Db and the optimum movement amount D by the conveyance speed V.

  If the movement amount Db is smaller than the optimum movement amount D, the reference timing is set to a timing delayed by Th seconds as the feeding timing of the subsequent sheet (# 158).

  As described above, the paper feeding timing of the succeeding paper is advanced or delayed in accordance with the movement amount Db, so that the optimum paper space between the preceding paper and the succeeding paper is optimized regardless of variations in the connection delay of the paper feeding latch C2. It is possible to set the gap between sheets d, and it is possible to increase the productivity of printing by minimizing the gap between sheets. The greater the number of sheets printed in a print job, the greater the effect of minimizing the gap between sheets.

  FIG. 17 shows the effect of sheet feeding control in the CM configuration.

  At time t11, the leading edge of the preceding sheet is at the position of the sheet feeding roller 24. As indicated by the alternate long and short dash line in the figure, when the connection delay of the paper feed clutch C1 is the minimum, the preceding paper moves at a constant speed from time t11 to time t16 when the motor M2 is instructed to stop. Then, after a temporary stop at time t16, the preceding sheet starts to move again from time t17 when rotation is commanded to the motor M2.

  When there is a certain connection delay in the paper feed clutch C1, the movement of the preceding paper starts from time t12 later than time t11 as shown by a solid line in the drawing. When the connection delay is the maximum, the movement of the preceding sheet starts at time t12 'delayed from time t12, as indicated by a two-dot chain line in the drawing. The time points t16 and t17 at which the temporary stop and re-conveyance start are the same regardless of the connection delay.

  When paying attention to the timing of feeding the succeeding sheet, in this embodiment, as indicated by a thick solid line in the drawing, after the preceding sheet starts moving again at time t17, the distance between the trailing end of the preceding sheet and the leading end of the succeeding sheet is The feeding of the subsequent sheet is actually started at time t19 so that the optimum sheet interval d is obtained.

  On the other hand, conventionally, for example, feeding of the succeeding sheet is started at time t17. In this case, the gap between the papers varies due to variations in connection delay. There was also a possibility that the sheets overlap each other because the distance between the sheets was too short. In the drawing, the sheet interval d1 when the connection delay is minimum is shown. These sheet intervals d1 are larger than the optimum sheet interval d of the present embodiment. In other words, conventionally, a subsequent sheet may be conveyed with an unnecessarily large sheet interval d1.

According to the present embodiment, the completion of paper discharge can be accelerated by time TS for each of the second and subsequent sheets.
[CC configuration]
FIG. 18 shows the operation and control of the roller drive mechanism of the CC configuration. In the CC configuration, only the sensor A of the three sensors A, B, and C is used, or all of them are used. I can't.

  At time t <b> 20, the paper feed preparation has already been completed, and the leading edge of the nth paper 5 a that is the preceding paper is sandwiched between the paper feed rollers 24. The motor M1 is stopped and the paper feed roller 24 is also stopped.

  At time t21 shown in FIG. 18, the clutch control signal SC1 is switched from OFF to ON. This switching is a connection command for the paper feed clutch C1. The paper feed clutch C1 is in a connected state at time t22 after receiving a connection command. As a result, the paper feed roller 24 rotates to start feeding the paper 5a. The time point t22 is detected using the connection threshold value Va based on the induced voltage Vk of the motor M1 as described above. Time t22 is an example of connection completion timing TA.

  At time t23, when the paper 5a arrives at the position of the sensor A and the sensor A is turned on, the clutch control signal SC2 is switched from off to on. This switching is a command to connect the timing clutch C2. When the sensor A is not used, a time point at which a predetermined time a has elapsed from the time point t21 is set as a time point t23.

  The timing clutch C2 enters the connected state at time t24 with a delay from the connection command. The time point t24 is detected using the connection threshold value Va based on the induced voltage Vk of the motor M2. Time t24 is an example of connection completion timing TA.

  At a time t25 when a predetermined time b has elapsed from the time t21, the clutch control signal SC1 is switched from on to off. At time t26 delayed from time t25, the paper feed clutch C1 is released and the paper feed roller 24 stops. However, the conveyance of the sheet 5a by the timing roller 25 continues. In parallel with the conveyance of the sheet 5a, preparation for feeding the (n + 1) th sheet 5b, which is a subsequent sheet, is performed.

  Time t26 is detected using the open threshold Vb based on the induced voltage Vk of the motor M1. Time t26 is an example of the release completion timing TB.

  At time t27 when a predetermined time c has elapsed from time t23, the clutch control signal SC2 is switched from on to off. At a time point t28 later than the time point t27, the timing clutch C2 is released, and the timing roller 25 stops. As a result, the temporary stop of the sheet 5a starts.

  The time point t28 is detected using the open threshold Vb based on the induced voltage Vk of the motor M2. Time t28 is an example of the release completion timing TB.

  When the paper 5a is temporarily stopped at the time t28, the position P1 of the leading edge of the paper 5a becomes a different position according to the variation in the connection delay of the paper feed clutch C1 and the variation in the release delay of the timing clutch C2.

  The CPU 101 calculates a movement amount Dc, which is the distance that the paper 5a has actually moved from the paper feeding to the temporary stop, from the transport speed V and the movement time T3 that is the time from the time t22 to the time t28. The movement amount Dc is obtained by multiplying the movement time T3 and the conveyance speed V (Dc = T3 · V).

  Next, the CPU 101 calculates a difference Dh (Dh = Dc−D) between the calculated movement amount Dc and the optimum movement amount D.

  Then, the CPU 101 actually starts the re-conveyance of the paper 5a at the time t32 when the re-conveyance for transfer is to be started, and provides the optimum paper interval d between the re-conveyed paper 5a and the next time. Time t29, time t30 and time t31 are set so that the paper 5b is fed.

  Time t29 is a timing at which a connection command is given to the paper feed clutch C1 to feed the paper 5b. The time point t30 is a timing at which the sheet feeding clutch C1 is engaged and the sheet feeding roller 24 actually starts feeding the (n + 1) th sheet 5b. Time point t31 is a timing at which a connection command is given to the timing clutch C2 for re-conveying the paper 5a.

  In the example of FIG. 18A, since the distance between the rear end position P2 of the paper 5a and the paper feed roller 24 is longer than the optimal paper interval d at time t28, before the re-conveyance of the paper 5a is started. Actual feeding of the next sheet 5b is started. That is, a time point earlier than the time point t32 by the time Dh / V is set as the time point t30 so that the sheet 5b advances downstream by the difference Dh between the time point t28 and the time point t32.

  FIG. 19 shows the flow of paper feed control in the CC configuration.

  The conveyance control unit 116 of the CPU 101 acquires a set value of the conveyance speed V (# 301). The conveyance control unit 116 turns on the clutch control signal SC1 to feed the nth sheet 5a as the preceding sheet (# 302).

  The timing detection unit 114 waits for the induced voltage Vk of the motor M1 periodically detected by the induced voltage detection unit 112 to become smaller than the connection threshold value Va (# 303). When the connection completion timing TA at which the induced voltage Vk becomes smaller than the connection threshold value Va is detected, the transfer control unit 116 is notified accordingly.

  Upon receiving notification that the connection completion timing TA has been detected, the transport control unit 116 starts measuring the movement time T3 (# 304). The current time may be stored as in the above example.

  Waiting for the sensor A to turn on (# 305), and when the sensor A is turned on, the conveyance control unit 116 turns on the clutch control signal SC2 in order to rotate the timing roller 25 in preparation for conveying the preceding paper. (# 306). When sensor A is not used, it waits for time a to elapse, and when time a elapses, clutch control signal SC2 is turned on.

  Subsequently, the conveyance control unit 116 waits for the time c to elapse (# 307). When the time c elapses, the conveyance control unit 116 turns off the clutch control signal SC2 and temporarily stops the paper 5a (# 308).

  Next, timing setting processing is performed (# 309), and at the timing set thereby, the conveyance control unit 116 turns on the clutch control signal SC2 to re-convey the preceding sheet (# 310).

  FIG. 20 is a flowchart of timing setting processing of the CC configuration in FIG.

  The timing detection unit 114 waits until the induced voltage Vk of the motor M2 periodically detected by the induced voltage detection unit 112 becomes larger than the open threshold value Vb (# 351). When the opening completion timing TB at which the induced voltage Vk becomes larger than the opening threshold value Vb is detected, the conveyance control unit 116 is notified of this.

  When the transfer control unit 116 receives a notification that the opening completion timing TB has been detected, the transfer control unit 116 ends the measurement of the movement time T3 (# 352). When the time point t22 is stored instead of the time measurement, the current time is fetched from the system clock as the time point t28, and the time from the time point t22 to the time point t28 is calculated as the movement time T3. Then, preparation for feeding the (n + 1) th sheet 5b, which is the subsequent sheet, is made (# 353).

  Next, the conveyance control unit 116 calculates the movement amount Dc of the preceding sheet (# 354), and acquires the optimum movement amount D (# 355).

  The conveyance control unit 116 compares the calculated movement amount Dc and the optimum movement amount D (# 356), and sets the sheet feeding timing of the subsequent sheet according to the magnitude relationship between the two as follows.

  If the movement amount Dc and the optimum movement amount D are equal, the feeding timing of the subsequent sheet is kept at a predetermined reference timing (# 357). For the re-conveyance of the preceding sheet, the timing clutch C2 is set at the timing t31 earlier than the timing t32 by the connection delay (difference between the timing t23 and the timing t24) when the timing clutch C2 is previously coupled at the timing t23. Is determined as a command timing for giving a command to perform a connecting operation.

  When the movement amount Dc is larger than the optimum movement amount D, the reference timing is set to a timing advanced by Th seconds as the feeding timing of the subsequent sheet (# 358). Th second is a time obtained by dividing the difference Dh between the movement amount Dc and the optimum movement amount D by the conveyance speed V. Also in this case, the command timing is determined in the same manner as in step # 357 for the re-conveyance of the preceding sheet.

  If the movement amount Dc is smaller than the optimum movement amount D, the reference timing is set to a timing delayed by Th seconds as the feeding timing of the subsequent sheet (# 359). Also in this case, the command timing is determined in the same manner as in step # 357 for the re-conveyance of the preceding sheet.

  In this way, by feeding the timing of feeding the succeeding paper in accordance with the movement amount Dc, the preceding paper and the preceding paper are controlled regardless of variations in the connection delay of the paper feed clutch C1 and the delay in opening of the timing clutch C2. It is possible to set the optimal gap between subsequent sheets to the gap d, and to improve the printing productivity by minimizing the gap between the sheets. The greater the number of sheets printed in a print job, the greater the effect of minimizing the gap between sheets.

  FIG. 21 shows the effect of sheet feeding control in the CC configuration.

  At time t21, the leading edge of the preceding sheet is at the position of the sheet feeding roller 24. As indicated by the alternate long and short dash line in the figure, when the connection delay of the paper feed clutch C1 is minimum, the preceding paper moves at a constant speed from time t21 to time t27 when the timing clutch C2 is instructed to be released. Then, after a temporary stop at time t27, the preceding paper starts to move again from time t31 when the connection is commanded to the timing clutch C2.

  When there is a certain connection delay in the paper feed clutch C1, the movement of the preceding paper starts from time t22 later than time t21 as indicated by a solid line in the drawing. When the release delay is the maximum, as shown by a two-dot chain line in the drawing, the movement of the preceding sheet starts at a time point t22 'later than the time point t22. In the subsequent pause, the timing clutch C2 release delay delays, and in the re-transfer, the timing clutch C2 connection delay delays the timing to complete the operation in response to the command.

  If attention is paid to the timing of feeding the succeeding sheet, in this embodiment, the distance between the trailing edge of the preceding sheet and the leading edge of the succeeding sheet when the preceding sheet starts to move again at time t32, as indicated by a thick solid line in the drawing. Is actually started at a time earlier than time t32 so that the optimal sheet spacing d is obtained.

  On the other hand, conventionally, for example, feeding of the succeeding sheet is started at time t31. In this case, the gap between the papers varies due to variations in connection delay. In the figure, paper intervals d0, d1, and d2 in three cases with different connection delays are shown. Among these, the paper gaps d1 and d2 are larger than the optimum paper gap d of the present embodiment. In other words, conventionally, there is a case where the following paper is transported with the paper gaps d1 and d2 larger than necessary.

  According to the present embodiment, the completion of paper discharge can be accelerated by time TS for each of the second and subsequent sheets.

  In the above embodiment, the timing for starting the feeding of the succeeding sheet 5b is advanced or delayed according to the shift of the temporary stop position of the preceding sheet 5a due to one or both of the connection delay and the release delay. However, in a print job that uses three or more sheets 5, the second and subsequent sheets of paper 5 (the subsequent sheet 5b viewed from the first sheet) are adjusted instead of adjusting the feeding timing of the second and subsequent sheets 5 5 (advanced sheet 5a viewed from the third sheet) may be adjusted. In that case, the conveyance control unit 116 stops the conveyance of the sheet according to the connection completion timing at the start of conveyance of the preceding sheet so that the stop position of the sheet 5 conveyed by the timing roller 25 falls within a predetermined range. The command timing of the releasing operation of the timing clutch C2 at the time is determined.

  The relationship between the magnitude of each of the connection threshold value Va and the release threshold value Vb and the induced voltage Vk and the clutch release / connection is not limited to the example, and the coil voltages Ea, Eb in the period for detecting the release / connection are not limited. Can be selected according to the polarity. For example, by controlling the output impedance of the motor drivers 201 and 202, the coil current Ia can be set to 0 at any time to detect the connection completion timing TA or the release completion timing TB.

  In addition, the entire or partial configuration of the image forming apparatus 1, the connection threshold value Va, the release threshold value Vb, the number of phases of the motors M1 and M2, the type of clutch, the arrangement of sensors, the control flow, etc. It can change suitably according to the meaning of invention.

  Although the image forming apparatus 1 has been described as a printer in the above-described embodiment, the image forming apparatus 1 may be any apparatus that transports the paper 5 in the apparatus, and may be a copier, a facsimile machine, or a multifunction machine. The image forming method is not limited to the electrophotographic method, and may be an ink jet method or other methods.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 5, 5a, 5b Paper 24 Paper feed roller 25 Timing roller 26 Secondary transfer roller 42 A phase coil 43 B phase coil C1 Paper feed clutch C2 Timing clutch d Paper gap (interval)
M1, M2 Motor Vk Induced voltage 112 Induced voltage detector (induced voltage detector)
114 Timing detection unit (connection / release completion timing detection means)
116 Transport control unit (control means)
TA connection completion timing TB release completion timing t8, t18, t29, t31 (command timing)
Va connection threshold (first threshold)
Vb open threshold (second threshold)

Claims (11)

A sheet having a roller for conveying the sheet, a synchronous motor for rotationally driving the roller, a clutch for transmitting the rotational driving force of the motor to the roller, and a control means, and the sheet conveyed by the roller In an image forming apparatus for forming an image on
Induced voltage detection means for detecting the induced voltage Vk in the motor;
Based on the induced voltage Vk detected by the induced voltage detecting means, a connection / release for detecting a connection completion timing which is a timing at which the clutch has actually completed a connection and a release completion timing which is a timing at which the clutch has actually been completed. Completion timing detection means,
The control means determines a command timing for giving a command to perform a connection operation or a release operation on the clutch based on the connection completion timing or the release completion timing detected by the connection / release completion timing detection means. To
An image forming apparatus. The motor is a stepping motor;
The induced voltage detection means detects the voltage of the phase coil when the current flowing through the phase coil of the stepping motor is 0 as the induced voltage Vk.
The image forming apparatus according to claim 1. The connection / release completion timing detection means uses a first threshold value Va determined based on the magnitude of the induced voltage when the load applied to the motor is the minimum load while the clutch is engaged. And detecting the timing at which the induced voltage Vk becomes smaller than the first threshold value Va as the connection completion timing.
The image forming apparatus according to claim 2. The connection / release completion timing detection means obtains a second threshold value Vb determined based on the magnitude of the induced voltage when the load applied to the motor is the maximum load with the clutch engaged. And detecting the timing at which the induced voltage Vk is larger than the second threshold value Vb as the opening completion timing.
The image forming apparatus according to claim 2. The first threshold value Va or the second threshold value Vb is changed according to the rotation speed of the motor.
The image forming apparatus according to claim 3 or 4. The control means determines the command timing so that an interval between two sheets continuously conveyed by the roller falls within a predetermined range.
The image forming apparatus according to claim 1. The control means opens the clutch when the paper conveyance is stopped according to the connection completion timing when the paper conveyance is started so that the stop position of the paper conveyed by the roller falls within a predetermined range. Determine the operation command timing,
The image forming apparatus according to claim 1. The roller is configured to transfer a sheet stored in the sheet storage unit to the conveyance path one sheet at a time, and to transfer an image onto the sheet along the conveyance path. Including a timing roller for feeding to the transfer position,
The image forming apparatus according to claim 1. The clutch includes a paper feed clutch and a timing clutch,
The paper feed roller is connected to the motor via the paper feed clutch, and the timing roller is connected to the motor via the timing clutch,
The control means transports and temporarily stops the nth sheet (n is an integer) by the paper feed roller and the timing roller, and then re-transports the nth sheet by the timing roller and (n + 1) According to the stop position of the nth sheet obtained based on the time from the connection completion timing in the sheet feeding clutch to the release completion timing in the timing clutch at the start of sending out the sheet by the sheet feeding roller. Determining a command timing for the coupling operation with respect to the paper feed clutch so that the (n + 1) th paper does not overlap the nth paper;
The image forming apparatus according to claim 8. The clutch includes a timing clutch;
The paper feed roller is connected to the motor without the clutch, and the timing roller is connected to the motor via the timing clutch,
The control means transports the nth sheet (n is an integer) by the sheet feeding roller and the timing roller and pauses, and then re-transports the nth sheet by the timing roller and (n + 1) sheets. When starting the feeding of the eye paper by the paper feed roller, according to the stop position of the nth paper obtained based on the time from the start timing of rotation of the motor to the release completion timing in the timing clutch, determining the rotation drive command timing for the motor so that the (n + 1) th sheet does not overlap the nth sheet;
The image forming apparatus according to claim 8. The clutch includes a paper feed clutch;
The paper feed roller is connected to the motor via the paper feed clutch, and the timing roller is connected to the motor without going through the clutch,
The control means transports the nth sheet (n is an integer) by the sheet feeding roller and the timing roller and pauses, and then re-transports the nth sheet by the timing roller and (n + 1) sheets. According to the stop position of the nth sheet obtained based on the time from the connection completion timing of the sheet feeding clutch to the stop timing of the rotation of the motor at the start of feeding of the eye sheet by the sheet feeding roller. Determining a command timing for the coupling operation with respect to the paper feed clutch so that the (n + 1) th paper does not overlap the nth paper;
The image forming apparatus according to claim 8.

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