JPH07196206A - Method for monitoring conveyance condition of medium - Google Patents

Abstract

PURPOSE:To achieve high-speed printing by minimizing the dispersion of time required for the medium detection 2 a medium detector. CONSTITUTION:A passing time measuring part 21 measures plural times the time T1 from the time when a first detector PS3 detects a medium to the time when a second detector PS4 detects it, and when the maximum value of the measured time is represented by T1max and the margin is represented by alphaand the maximum allowable time T2 is represented by T1mx+alpha and the minimum value of the measured time is represented by T1min and the margin is represent by beta and the minimum allowable time T3 is represented by T1min--beta, a maximum and minimum passing time setting part stores those into a memory 23. After that, a transfer condition judgement part 24 monitors whether the passing time T1 is not less than the maximum allowable time T2 or not andn also whether the passing time T1 is not more than the minimum allowable time T3 or not, and the transfer condition judgement part 24 stops the transfer of the medium and generates an alarm signal when T1>T2 or T1<T3. The maximum and minimum passing time setting part 22 renews the maximum allowable time T2 and the minimum allowable time T3 by a similar method every time when a fixed number of sheets pass.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a medium conveyance state monitoring method, and more particularly to a medium conveyance state monitoring method in an image forming apparatus such as an electrophotographic printer.

[0002]

2. Description of the Related Art In a recording device such as an electrophotographic printer,
A toner image is formed on the photosensitive drum, and the toner image is transferred to the paper sent from the hopper through the medium carrying path. After that, the paper is further carried to fix the toner image in the fixing unit, and the fixing is performed. After that, the paper is ejected to the stacker. FIG. 11 is an overall configuration diagram of an electrophotographic printer that uses laser light as an exposure source. Reference numeral 1 denotes a photosensitive drum having a photoconductor (photoconductor) on its surface, which rotates in the direction of arrow A at a constant speed.
Is a pre-charger for uniformly charging the surface of the photosensitive drum, 3 is an exposure optical unit for irradiating an optical image on the photosensitive drum to form an electrostatic latent image, and 4 is a toner image corresponding to the electrostatic latent image. Of the toner supply section 4a and the developing section 4b.
Is equipped with. Reference numeral 5 is a transfer charger for transferring the toner image onto the paper CP, 6 is an optical static eliminator for irradiating light to remove the electrostatic charge on the photosensitive drum, and 7 is a cleaner for removing and cleaning the toner remaining on the photosensitive drum. , A brush 7a and a blade 7b. Numerals 8 and 8'are rollers for conveying the paper, and numeral 9 is a fixing unit for fixing the toner image transferred on the paper, which is composed of, for example, a heat fixing roller 9a. CP is a sheet of paper (cut sheet), 1 from the hopper on the right (not shown)
The sheets are delivered one by one, conveyed in the direction of arrow B, and discharged to a stacker (not shown) on the left side via the transfer charger 5 and the fixing unit 9.

When the surface of the photosensitive drum 1 which has been positively charged uniformly by the pre-charger 2 is irradiated with an optical image, the potential of the portion exposed to the light is lowered and an electrostatic latent image is formed. Next, in the developing unit 4, when the magnet roll MGR biased with a predetermined developing voltage V _B is rotated to rub the positively charged toner on the surface of the photosensitive drum, the toner moves to the electrostatic latent image and the toner is moved. An image is formed. Then, if corona discharge is generated from the back surface of the paper CP in the transfer charger 5 at a potential having a polarity (minus) opposite to the charging potential of the toner image, the paper is negatively charged, whereby the toner image is attracted to the paper CP. Is transcribed. The paper CP on which the toner image has been transferred by the transfer charger 5 is conveyed and reaches the fixing unit 9, where it is thermally fixed and discharged to a stacker (not shown) on the left side. After the toner image is transferred to the paper, the photosensitive drum 1 is further rotated, the charge is removed by the optical charge eliminator 6, the residual toner is removed by the cleaner 7, and the next electrostatic latent image is prepared.

In such an electrophotographic printer, medium detecting portions PS1 and PS2 (only two of which are shown in FIG. 11) are provided at a plurality of points on the medium conveying path in order to monitor the sheet conveying state. . Specifically, there are a method of monitoring the sheet conveyance state using two detectors and a method of monitoring the sheet conveyance state using a single detector. -When using two detectors The time T1 from when the paper is detected by the first detector PS1 to when it is detected by the second detector PS2 is measured,
The measurement time T1 is compared with predetermined allowable maximum time and allowable minimum time. When the measurement time is within the predetermined time range, it is determined that the medium is normally conveyed, and when it is out of the range, it is determined that the medium is abnormal, the medium conveyance is stopped, and an alarm is output. -When using one detector: The time T4 during which the paper passes a predetermined detector is measured, and the measured time T4 is compared with a predetermined allowable maximum time and allowable minimum time. When the measurement time is within the predetermined time range, it is determined that the medium is normally conveyed, and when it is out of the range, it is determined that the medium is abnormal, the medium conveyance is stopped, and an alarm is output.

By the way, the allowable maximum / minimum times Tmax and Tmin which are predetermined for detecting the transport state are the variations in the mounting position of the detector, the variations in the operation of the detector,
Since there are variations in medium transportability, variations between apparatuses, etc., these variations are set in consideration. However, since the value of ~ is the sum of the maximum value / minimum value of all the devices, the values of the set times Tmin and Tmax are generally considerably longer / shorter than the actual transit time. FIG. 12 is an explanatory diagram of such a situation. CP is a sheet (medium), PS1 and PS2 are first and second medium detectors,
PSD1 and PSD2 are output signals of the first and second medium detectors, which become high level when the leading edge of the paper is detected, and become low level when the paper passes. In the ideal case where the sheet is fed at the speed v ₁ and the distance between the detectors is d ₁ , the time T1 from when the sheet is detected by the first detector PS1 to when it is detected by the second detector PS2 Becomes d ₁ / v ₁ .

However, as mentioned above, the first detector PS
1 operation variation t ₁ , 2nd detector PS2 operation variation t ₂ , 1st and 2nd detector mounting position variation t ₃ , medium transportability variation t ₄ , device-to-device variation t ₅
Exists. Therefore, the maximum allowable time T of the passage time T1
max and allowable minimum time Tmin are Tmax = MAX (d ₁ / v ₁ + t ₁ + t ₂ + t ₃ + t ₄ + t ₅ + margin) Tmin = MIN (d ₁ / v ₁ + t ₁ + t ₂ + t ₃ + t ₄ + t ₅ − Margin). Further, when the length of the paper is L ₁ , the maximum times Tmax and Tm of the time T4 in which the paper passes a predetermined detector are similarly set.
in each _{Tmax = MAX (L 1 / v} 1 + t 1 + t 2 + t 3 + t 4 + t 5 + _{margin) Tmin = MIN (L 1 /} v 1 + t 1 + t 2 + t 3 + t 4 + t 5 - margin) become.

[0007]

It is necessary to set the distance between the media continuously fed from the hopper in consideration of the maximum time Tmax, and the distance between the media is increased as the total sum Σti of the variation times is increased. There is a need. If the variation time is zero, the mediums do not interfere with each other even if the distance between the mediums is small, and desired printing can be performed on each medium and high-speed printing is possible (see FIG. 13A). But,
In reality, since there is a variation time, if the interval Δd _ps (see FIG. 13 (b)) corresponding to the variation time is not set, the adjacent sheets interfere with each other and it is impossible to print on each sheet correctly. . Actually, since the margin distance d _ps is set between the respective media, it is necessary to provide a space of (Δd _ps + d _ps ) between the media as shown in FIG. If the distance between the media becomes large, the interval at which the media are sent out becomes long, the number of sheets sent out per predetermined time becomes small, and high-speed printing becomes impossible. That is, in order to perform high-speed printing, it is necessary to shorten the distance between the media, but in the past, the variation time becomes long, which is an obstacle to high-speed printing.

If the mounting position of the detector is changed or the detector is changed due to a design change, the set time T
It is necessary to change the values of min and Tmax, which causes a problem that compatibility between devices is lost. Further, conventionally, the type of medium is determined by measuring the passage time of each medium detector to confirm that the wrong medium is not used. However, if the variation time is large, A4 size (210 There is a problem that the distinction between x297) and letter size (215.9 x 279.4) cannot be made. In addition, when the device is used for a long period of time, the operating characteristics of the transport system and the detector change, and there is a problem that an abnormality is erroneously reported.

In view of the above, it is an object of the present invention to provide a method for monitoring a medium transporting state in which variation time is minimized and high speed printing is possible. Another object of the present invention is to provide a medium transport state monitoring method capable of correctly detecting a medium having a size different from a predetermined size. It is still another object of the present invention to provide a medium transport state monitoring method capable of correctly detecting an abnormality in the transport system and the type of medium even if the operating characteristics of the transport system and the detector change over time. Another object of the present invention is to provide a medium conveyance state monitoring method which is compatible even if the mounting position of the detector is changed by changing the design or the detector is changed.

[0010]

FIG. 1 is a diagram for explaining the principle of the present invention. Reference numeral 10 denotes an image forming unit for forming an image on a recording carrier with a transfer material (toner), 10a denotes a recording carrier (photosensitive drum), 10b denotes a pre-charger for uniformly charging the surface of the photosensitive drum, and 10c denotes An exposure optical unit for irradiating an optical image on the photosensitive drum to form an electrostatic latent image, a developing unit 10d for forming a toner image corresponding to the electrostatic latent image, 10e.
Is a transfer charger for transferring the toner image onto the paper CP, 10f ₁
Is an optical static eliminator that irradiates light to remove the electrostatic charge on the photosensitive drum, and 10f ₂ removes the toner remaining on the photosensitive drum.
It is a blade to be cleaned. Reference numeral 11d is a fixing device for fixing the material to be transferred onto the transfer medium, 12 is a hopper for supplying the medium (paper) one by one, 13 is a stacker for storing the medium on which the toner is fixed, and 14 is a medium for transporting the medium from the hopper to the stacker. The medium transport paths, PS3 and PS4, are the medium detectors provided in the medium transport path.

Reference numeral 20 denotes a medium transport monitor / control unit, which is 2
1 is a passage time measuring unit for measuring the time T1 from when the medium is detected by the first detector PS3 to when it is detected by the second detector PS4, and 22 is a passage time measured a plurality of times (= N times). Where T1max is the maximum value and α is the margin, T1max + α is set as the allowable maximum time T2, and the minimum value of the measured time is T1min and the margin is β.
, T1min-β is set as the allowable minimum time T3, the maximum / minimum time setting unit 23 is a memory for storing the maximum allowable time T2 and the minimum allowable time T3, and 24 is the actual minimum time T1 during the actual printing. A conveyance state determination unit that monitors whether the maximum allowable time T2 or more and the minimum allowable time T3 or less are detected, and when T1> T2 or T1 <T3, stops the medium transportation and generates an alarm signal ALM. Is.

[0012]

The passage time measuring unit 21 has the first detector PS as the medium.
When the time T1 from the time when it is detected by 3 to the time when it is detected by the second detector PS4 is measured multiple times, and the passing maximum / minimum time setting unit 22 sets the maximum value of the measured time to T1max and the margin is α. , T1max + α is the maximum allowable time T2
When the minimum value of the measured time is T1min and the margin is β, T1min−β is the allowable minimum time T3.
Stored in the memory 23 as
Monitors whether the passage time T1 is equal to or longer than the maximum allowable time T2 and / or is equal to or smaller than the minimum allowable time T3.
When> T2 or T1 <T3, the conveyance of the medium is stopped and an alarm signal is generated. Further, the maximum / minimum passage time setting unit 22 updates the maximum allowable time T2 and the minimum allowable time T3 in the same manner for each fixed number of sheets.

Further, the passage time measuring unit 21 measures a plurality of times T4 during which the medium passes the predetermined detector PS3, and the passage maximum / minimum time setting unit 22 sets the maximum value of the measured time to T4.
When max and margin are γ, T4max + γ is the maximum allowable time T5, and the minimum value of the measured time is T4mi
When n and the margin are δ, T4min−δ is stored in the memory 23 as the allowable minimum time T6, and thereafter, the transport state determination unit 24 determines whether the passing time T4 is the allowable maximum time T5 or more and / or the allowable minimum time. It is monitored whether the time is T6 or less, and when T4> T5 or T4 <T6, the conveyance of the medium is stopped and an alarm signal is generated. Also, the maximum passing
The minimum time setting unit 22 updates the permissible maximum time T5 and the permissible minimum time T6 by a similar method for each fixed number of sheets passed.

As described above, the medium is actually conveyed and the maximum and minimum times of passage are obtained by the latest N measurements,
Since the allowable maximum time and the allowable minimum time are set by adding a margin to these, the variation time can be suppressed to the minimum, the distance between the media can be shortened, and the printing speed can be increased. Further, since the variation time can be suppressed to the minimum, the misuse of the medium can be surely detected. Furthermore, since the maximum and minimum allowable times are set by actually moving the medium, it is possible to relax the fluctuations in the mounting position accuracy of the detector and the operating time of the detector, and to change the detector. There is no need to maintain compatibility between devices for changes in mounting positions, etc., and device design can be facilitated. Moreover, the maximum transit time is obtained by actually carrying the medium and measuring the latest N times.
Since the minimum time is obtained and the margin is added to these to set the maximum allowable time and the minimum allowable time, the medium transport state can be correctly detected even when the detector and the transport system time-change.

[0015]

【Example】

(a) Overall Configuration of Printing Mechanism FIG. 2 is an overall configuration diagram of a printing mechanism to which the present invention can be applied. The printing mechanism is composed of a process system and a transport system. As shown in FIG. 2, the process system irradiates a photosensitive drum 10a, a pre-charger 10b that uniformly charges the photosensitive drum 10a, and an optical image on the photosensitive drum 10a. And an exposure optical unit 10c that forms an electrostatic latent image, and a developing unit 10d that develops the electrostatic latent image formed on the photosensitive drum with toner to form a toner image.
A transfer / separation unit 10e for transferring the toner image to the conveyed paper and separating the paper from the photosensitive drum, and a cleaner for removing the electrostatic charge of the photosensitive drum and removing the toner remaining on the photosensitive drum. It is provided with a static elimination / cleaning section 10f. The developing unit 10d includes a cartridge 10d-1 for supplying toner, and a developing unit 10d-2 for charging the toner and rubbing the toner with a developing roller against the photosensitive drum to develop the electrostatic latent image with the toner. The transfer / separation unit 10e includes a transfer charger and a separation charger, and the transfer charger generates corona discharge from the back surface of the paper to charge the paper to the opposite polarity to the toner image and transfer the toner image to the paper.

The paper transport system includes a pick roller 11a for picking cut paper from the paper hoppers 12a-12b, a standby roller 11b, a transport roller 11c for transporting the picked paper to the standby roller 11b, and the transferred toner image on the paper. A heat roller fixing device 11d for heat fixing to the back side, a back side printing conveyance path 11e for conveying the reversed sheet for back side printing to the standby roller 11b, and a back side printing conveyance path for the rear end of the sheet from the heat roller fixing device. An impeller 11f directed to 11e, a switchback roller 11g that conveys the paper from the heat roller fixing device 11d in the discharge direction and then sends the paper to the backside printing conveyance path 11e, and a guide roller 11h that guides the discharge of the paper. , A discharge roller 11i, a stacker 11j for storing discharged paper, and a purge tray 11k for discharging misprinted paper. It is provided.

The paper is picked from the paper hoppers 12a to 12b by the pick roller 11a and sent to the standby roller 11b by the conveying roller 11c. The standby roller 11b synchronizes the toner image and the printing paper so that they arrive at the transfer charger at the same time, and conveys the printing paper to the transfer charger at a predetermined timing. In parallel with the above, the photosensitive drum 10a is charged by the pre-charger 10b and is irradiated with a light image by the optical unit 10c to form an electrostatic latent image.
Thus, a toner image is formed. The paper is sent to the transfer / separation unit 10e in synchronism with the standby roller 11b, the toner image is transferred there, and is separated from the photosensitive drum and sent to the heat roller fixing device 11d to heat-fix the toner image. To be done. Then, it is sent in the direction of the switchback roller 11g and is conveyed in the direction of the stacker 11j by the switchback roller.

In the case of single-sided printing, the paper is further conveyed by the guide roller 11h and the discharge roller 11i and discharged to the stacker 11j. On the other hand, in the case of double-sided printing, when the trailing edge of the sheet reaches the impeller 11f, the switchback roller 11g stops the conveying operation to stop the sheet, and the trailing edge of the sheet moves in the counterclockwise direction of the impeller 11f. By the rotation, the trailing edge of the paper is sent to the standby roller 11b by the carrying roller of the backside printing carrying path 11e. After that, as with surface printing,
The paper sent by the standby roller 11b is transferred / separated by the transfer / separation unit 10e.
Then, the toner image is transferred to the back surface and is fixed by the heat roller fixing device 11d. Then, the paper is fed toward the switchback roller 11g, and the stacker 1 is fed by the switchback roller 11d.
The sheet is conveyed in the 1j direction, discharged by the discharge roller 11i to the stacker 11j, and double-sided printing is performed.

(B) Description of Arrangement Position of Medium Detector FIG. 3 is an explanatory view of the arrangement position of the medium detector in the printing mechanism shown in FIG. 2, and is a medium detector for detecting the sheet conveyance state and the sheet size. Are provided at various places in the medium transport system 14. In the figure, PS1-1 and PS1-2 are paper feeding units (hopper 12a,
12b; a medium detector disposed behind the pick roller 11a), PS2 is a medium detector disposed behind the transport roller 11c, PS3 is a medium detector disposed before the standby roller 11b, and PS4. Is a medium detector provided behind the fixing device 11d, PS5 is a medium detector provided on the back side printing conveyance path 11e, PS6 is a medium detector provided behind the guide roller 11h, and PS7, PS8. Is a medium detector provided in front of the stacker 11j and the purge tray 11k.

The time taken to pass between two adjacent detectors or the time taken to pass each single detector is monitored, and it is checked whether the passing time is within a specified time range. It is determined that the medium is well conveyed at the position where the medium is conveyed, and if it is outside the specified time, it is judged that an abnormality has occurred in the medium conveyance (for example, a jam etc.), and the medium conveyance is stopped, Raise an alarm. FIG. 4 is a state display explanatory diagram of the display unit DPL that displays various states, in which a red blinking mark is displayed at a position (portion indicated by ... In the figure) corresponding to the location of the abnormality. In addition, HPS is a hopper selection display section, S
KS is a stacker selection display part, PRQ is a remaining paper amount display part,
EXP is a consumables position display unit.

(C) Configuration of Printing Device FIG. 5 is an overall configuration diagram of the printing device. Reference numeral 51 is a print control device, 52 is the printing mechanism described in FIGS. 2 and 3, and 53 is a host device. In the print control device 51, 51a is a microprocessor (MPU), 51b is an interface unit with a higher-level device, a command analysis unit for analyzing commands from the higher-level device, and a status processing unit for notifying the higher-level device of the state of the printing mechanism. have. Reference numeral 51c is a memory (program memory) for storing a program for controlling the medium conveyance state monitoring and various operations of the printer, 51d is a work memory, and 51e is a medium conveyance state monitoring device for jams and the like, and a passage time of the paper size detection control party. A timer unit 51f for measuring the time, various parameters used for carrying state monitoring control and the like (for example, an allowable maximum time T2 and an allowable minimum time T3 of the passage time between two adjacent medium detectors; passage allowance for each medium detector) Maximum time T5, allowable minimum time T6, etc.)
Is a non-volatile memory for storing the media, 51g is an I / O port for the printing mechanism 52,
It has an input port for S8 (FIG. 3) and an output port for outputting various motor drive signals for the paper feed unit, the photosensitive drum, the standby roller, the fixing roller, and the like. Reference numeral 51h is an operation panel including a display unit 51h-1 and various keys 51h-2.

(D) Medium Transport Monitoring Method of the Present Invention FIG. 6 is an explanatory diagram of the medium transport monitoring method of the present invention.
A and PSB are two adjacent medium detectors, CP is a medium (cut paper), RL1 to RL3 are paper feed rollers, PSA
S and PSBS are output signals of each medium detector. As the medium detectors PSA and PSB, any combination of two adjacent detectors in FIG. 3 can be adopted. (d-1) Medium conveyance monitoring using the passage time between two adjacent medium detectors The microcomputer 51a of the print control device 51 (Fig. 5) is
An allowable maximum time T2 and an allowable minimum time T3 for passing between two adjacent medium detectors PSA and PSB are set according to a program for setting the allowable maximum / minimum time. That is, the time T1 from when the medium (paper) CP is detected by the first medium detector PSA to when it is detected by the second medium detector PSB is measured a plurality of times, and the maximum value of the measured time is T1max ( 6B), when the margin is α, T1max + α is registered in the non-volatile memory 51f as the allowable maximum time T2. In addition, the minimum value of the measured time is T
When 1 min and the margin are β, T1min−β is similarly registered in the nonvolatile memory 51f as the allowable minimum time T3.

After that, during printing, the microcomputer 51a follows the conveyance state monitoring program, and after the medium CP is detected by the first medium detector PSA, the second medium detector P is detected.
The time T1 until the detection by the SB is measured, and the time T1
1 is the allowable maximum time T2 or more and the allowable minimum time T3 or less, and when T3 <T1 <T2, the transport state is determined to be normal, and T1> T2 or T1.
When 1 <T3, the medium conveyance state is determined to be abnormal, the medium conveyance is stopped, and an alarm signal is generated. or,
In parallel with the above-mentioned conveyance state monitoring, the microcomputer 51a follows the allowable maximum / minimum time update program, and registers the allowable maximum time T2 and the allowable minimum time T registered in the nonvolatile memory 51f.
3 is updated every time a fixed number of sheets (= M sheets) are passed, and thereafter, the conveyance state is monitored using the updated maximum allowable time T2 and minimum allowable time T3.

Setting of T2 and T3 FIG. 7 is a flow chart of processing for setting allowable maximum and minimum times T2 and T3. A command for setting T2 and T3 is input from the operation panel 51h or the time setting key is pressed to enter the allowable maximum / minimum time setting mode. In this state, the medium is conveyed and printing is actually performed (step 101). The microcomputer 51a uses the time T1 (detection signal PSA) from when the paper CP is detected by the first medium detector PSA to when it is detected by the second medium detector PSB.
The time from when S goes to high level until the detection signal PSBS goes to high level) is measured using the timer 51e,
The time T1 is stored in the work memory 51d (step 102). Then, the number m (the initial value is 0) is counted up and it is checked whether m = M (step 10
3) If m <M, the operation after step 101 is repeated.

When m = M, the maximum value T1max and the minimum value T1min of the M measurement times stored in the work memory 51d are obtained (step 104), and the maximum time margin is α, and the following equation T2 = The maximum allowable time T2 is calculated by T1max + α and the nonvolatile memory 51
It is stored in f (step 105). Next, when the minimum time margin β is set, the allowable minimum time T3 is calculated by the following equation T3 = T1min−β to calculate the non-volatile memory 51.
If it is registered in f (step 106), the process of setting the allowable maximum / minimum times T2 and T3 is completed. The setting control of the allowable maximum / minimum times T2 and T3 is mainly performed by the printer manufacturer at the time of shipping or maintenance.

Medium Transport State Monitoring FIG. 8 is a flow chart of the medium transport state monitoring process. During printing, the microcomputer 51a operates the second medium detector PS after the medium CP is detected by the first medium detector PSA.
The time T1 until it is detected by B is measured (step 2
01), it is monitored whether the time T1 is equal to or longer than the maximum permissible time T2 or equal to or smaller than the minimum permissible time T3 (step 202). If T3 <T1 <T2, the transport state is determined to be normal (step 202). Step 203). However, T1>
When T2 or T1 <T3, it is determined that the medium transport state is abnormal (occurrence of a jam or the like), the medium transport is stopped, and an alarm signal is generated (step 204).

Update of Allowable Maximum / Minimum Times T2 and T3 FIG. 9 is a flow chart of update processing of the allowable maximum / minimum times T2 and T3. During printing, the paper CP is first in the microcomputer 51a.
The time T1 from the time when it is detected by the second medium detector PSA to the time when it is detected by the second medium detector PSB is measured, and the time T1 is stored in the work memory 51d (step 3).
01, 302). The work memory 51d has the latest N
Data for each piece shall be stored. Next, the number m of sheets that have passed through the medium detectors PSA and PSB (initial value is 0)
Is counted up to check if m = M (step 303), and if m <M, the operation from step 302 is repeated. On the other hand, if m = M, the maximum value T of the N measurement times stored in the work memory 51d is obtained.
1maxp, minimum value T1minp is calculated (step 304), T
1maxp is T1max and the minimum value T1minp is T1min (step 305).

After that, the allowable maximum time T2 is calculated by the following formula T2 = T1max + α with the maximum time margin α, and the allowable maximum time registered in the nonvolatile memory 51f is updated by the time T2. Also, as the minimum time margin β, the allowable minimum time T3 is calculated by the following formula T3 = T1min−β, and the allowable minimum time registered in the nonvolatile memory 51f is updated by the time T3 (step 306). After that, when the printing is not stopped (step 307), the processing from step 302 onward is repeated. On the other hand, when the printing is stopped, the latest N pieces of data and m are stored in the non-volatile memory 51d, and the above processing is ended. The stored data is restored to the work memory when printing is started.

(D-2) Conveyance state monitoring using the passage time of one medium detector The microcomputer 51a of the printing control device 51 previously detects the detector PSA for which the medium is predetermined according to the program for setting the allowable maximum / minimum time. The passing time T4 is measured a plurality of times, and when the maximum value of the measured time is T4max (see FIG. 6B) and the margin is γ, T4max + γ is registered in the nonvolatile memory 51f as the allowable maximum time T5. When the minimum value of the measured time is T4min and the margin is δ, T4min-
Similarly, the non-volatile memory 51 is set with δ being the allowable minimum time T6.
Register in f. After that, during printing, the microcomputer 51a measures the time T4 during which the medium CP passes through the first medium detector PSA according to the transport state monitoring program, and the time T4 is measured.
4 is monitored to see if it is equal to or longer than the allowable maximum time T5 or equal to or smaller than the allowable minimum time T6. If T6 <T4 <T5, it is determined that the transport state is normal, and T4> T5 or T4.
When <T6, the medium conveyance state is determined to be abnormal, the medium conveyance is stopped, and an alarm signal is generated.

Further, in parallel with the above-mentioned conveyance state monitoring, the microcomputer 51a registers the maximum allowable time T5 registered in the non-volatile memory 51f according to the maximum allowable / minimum time update program.
The allowable minimum time T6 is updated every time a fixed number of sheets (= M sheets) are passed, and thereafter, the conveyance state is monitored using the updated maximum allowable time T5 and minimum allowable time T6. Note that the setting control of the allowable maximum / minimum times T5 and T6, the monitoring control of the medium conveyance state, and the update control of the allowable maximum / minimum times T5 and T6 should be performed based on almost the same flow as the flow charts of FIGS. You can

(E) Comparison between the present invention and the conventional example As described above, in the present invention, the passing time between the adjacent medium detectors or the passing time of a single medium detector is measured, and the latest N Since the maximum and minimum times of the transit time obtained by the measurement of the times are calculated and the margin is added to these, the maximum allowable time and the minimum allowable time are set.
It is not necessary to consider the variation between devices and the variation due to the time change, and therefore the variation time Δt can be minimized and can be made smaller than the conventional variation time.
It should be noted that the above is the case of focusing on a set of adjacent medium detectors or a single medium detector, but in reality, as shown in FIG. 3, there are a plurality of medium detectors on the transport path.
Then, the variation time of each portion is accumulated as it goes backward (in the stacker direction). In the conventional method, since the individual variation time is large, the cumulative variation time is considerably long, and as a result, the medium interval cannot be shortened and high-speed printing cannot be performed. On the other hand, in the present invention, since the individual variation time can be minimized, the cumulative variation time does not become so large, the medium interval can be reduced, and high-speed printing becomes possible.

FIG. 10 shows a case in which attention is paid to the three detectors PS3, PS4 and PS7 in the printing mechanism of FIG.
FIG. 9 is an explanatory diagram for comparing (a) the variation time of the present invention and (b) the variation time of the conventional example. In the figure, T6 is the paper passage time of the detector PS3, and in the case of A4 size (210 × 297), it is 1.579 sec when the paper conveyance speed is 133 mm / s. T
7 is a medium interval time obtained by dividing the medium interval by the velocity.

Conventional variation time (see FIG. 10 (b)) T1 is from the detection of the leading edge of the paper by the detector PS3 to the detector PS
4 is the time until the leading edge of the sheet is detected, and T2 is the time when the sheet passes the detector PS4. T2 is the detector PS
4 is longer than the actual passage time of the paper due to the variation in operation and the variation in mounting position. T1 ′ and T2 ′ represent the variation time, T1 ′ = 10 to 30 msec, T2 ′ =
It will be 20-60 msec. T3 is the time from the detection of the trailing edge of the sheet by the detector PS4 to the detection of the leading edge of the sheet by the detector PS7, and T3 'represents the variation in the sheet detection time, and T3'.
= 30 to 90 msec. T4 is the time for the sheet to pass the detector PS7, T4 'is the variation in the detection time, and T4' = 40 to 120 msec. T5 is a value that guarantees a margin against variations in the paper detection time, 200 m
Expecting sec. Therefore, in the conventional case, in order to prevent the front and back sheets from interfering with each other, the time T7 for guaranteeing the sheet interval is set to 320 msec. At this time, the printing speed is 3
1.5 sheets / minute.

Variation time of the present invention (see FIG. 10 (a)) In the case of the conventional example, T1 'to T4' are values including variations between devices and variations due to aging. Therefore, the variation time is considerably long. According to the present invention, T1 'to T4' can be determined so as not to include variations between these devices and variations due to aging. In fact, in the present invention, T1 '= 3-5 msec, T2' =
6-10 msec, T3 '= 9-15 msec, T4' = 12-20 msec. In addition, we expect a margin of 100 msec. Therefore, T7 = 112 to 120 msec, and the printing speed is 35.
It becomes 3 to 35.4 sheets / minute, and an extra 4 sheets can be printed per minute in A4 size. Although the case where the present invention is applied to the electrophotographic printer has been described above, the present invention can be applied to an apparatus including an image forming unit such as a copying machine and a facsimile apparatus. Although the present invention has been described above with reference to the embodiments, the present invention can be variously modified according to the gist of the present invention described in the claims, and the present invention does not exclude these.

[0035]

As described above, according to the present invention, the maximum and minimum times of transit time are obtained by actually transporting the medium and measuring the latest N times, and the allowable maximum time and allowable minimum time are added by adding a margin to them. Since it is set, it is not necessary to consider the variation between devices and the variation due to time change, the variation time can be minimized, the distance between media can be shortened, and the printing speed can be increased. Further, since the variation time can be suppressed to the minimum, the misuse of the medium can be surely detected. Furthermore, according to the present invention, since the medium is actually moved to set the allowable maximum time and the allowable minimum time, it is possible to loosen the fluctuation limit of the mounting position accuracy of the detector and the operating time of the detector. Moreover, it is not necessary to maintain compatibility between devices for changes in detectors, changes in mounting position, etc., and device design can be facilitated. Further, according to the present invention,
Since the maximum and minimum transit times are found by actually transporting the medium and measuring the latest N times, and the allowable maximum and minimum times are set by adding a margin to these, the detector and transport system are set. It is possible to correctly detect the medium transport state even if the time changes.

[Brief description of drawings]

FIG. 1 is a diagram illustrating the principle of the present invention.

FIG. 2 is an overall configuration diagram of a printing mechanism.

FIG. 3 is an explanatory view of the arrangement position of a medium detector.

FIG. 4 is an explanatory diagram of various status displays.

FIG. 5 is a configuration diagram of a print control apparatus.

FIG. 6 is an explanatory diagram of a medium transport monitoring method of the present invention.

FIG. 7 is a flowchart of a setting process of allowable maximum / minimum times T2 and T3.

FIG. 8 is a flowchart of a transport state monitoring process.

FIG. 9 is a flowchart of update processing of allowable maximum / minimum times T2 and T3.

FIG. 10 is an explanatory diagram comparing the present invention with a conventional variation time.

FIG. 11 is an overall configuration diagram of an electrophotographic printer.

FIG. 12 is an explanatory diagram of a detection unit passage time in consideration of variations.

FIG. 13 is an explanatory diagram of sheet intervals.

[Explanation of symbols]

 10: Image forming unit 10a: Recording carrier (photosensitive drum) 10e: Transfer charger 11d: Fixing device 12: Hopper 13: Stacker 14: Medium transport path 20: Medium transport monitoring unit 21.・ Passing time measuring unit 22 ・ ・ Passing maximum / minimum time setting unit 23 ・ ・ Memory for storing allowable maximum time and allowable minimum time 24 ・ ・ Conveyance state determination unit PS3, PS4 ・ ・ Media detector

Claims (12)

[Claims] 1. An image forming means for forming an image on a recording medium with a transfer material, a medium supply means for supplying a medium, and a transfer means for transferring the transfer material onto the medium fed from the medium supply means. Fixing means for fixing the transferred material to the transfer medium, medium storing means for storing the medium on which the transferred material is fixed, medium conveying path for conveying the medium from the medium supplying means to the medium storing means, and medium conveying path In the method of monitoring the medium transport state in the image forming apparatus including the plurality of medium detecting means provided in the above, a plurality of times T1 from when the medium is detected by the first detecting means to when the medium is detected by the second detecting means are set. When the maximum value of the measured time is T1max and the margin is α, T1max + α is set as the allowable maximum time T2, and thereafter, it is monitored whether the time T1 is the allowable maximum time T2 or more, and T1> T2 To Lever, the medium conveying state monitoring method for generating an alarm signal to stop the conveyance of the medium. 2. The medium conveyance state monitoring method according to claim 1, wherein the allowable maximum time T2 is updated every time a fixed number of sheets are passed. 3. An image forming means for forming an image on a recording carrier with a material to be transferred, a medium supplying means for supplying a medium, and a transfer means for transferring the material to be transferred onto the medium fed from the medium supplying means. Fixing means for fixing the transferred material to the transfer medium, medium storing means for storing the medium on which the transferred material is fixed, medium conveying path for conveying the medium from the medium supplying means to the medium storing means, and medium conveying path In the method of monitoring the medium transport state in the image forming apparatus including the plurality of medium detecting means provided in the above, a plurality of times T1 from when the medium is detected by the first detecting means to when the medium is detected by the second detecting means are set. When the minimum value of the measured time is T1min and the margin is β, T1min-β is set as the allowable minimum time T3, and thereafter, it is monitored whether the time T1 is equal to or less than the allowable minimum time T3. <To T3 Lever, the medium conveying state monitoring method for generating an alarm signal to stop the conveyance of the medium. 4. The medium conveyance state monitoring method according to claim 3, wherein the allowable minimum time T3 is updated every time a fixed number of sheets have passed. 5. An image forming means for forming an image on a recording carrier with a material to be transferred, a medium supplying means for supplying a medium, and a transfer means for transferring the material to be transferred onto the medium fed from the medium supplying means. Fixing means for fixing the transferred material to the transfer medium, medium storing means for storing the medium on which the transferred material is fixed, medium conveying path for conveying the medium from the medium supplying means to the medium storing means, and medium conveying path In the method of monitoring the medium transport state in the image forming apparatus including the plurality of medium detecting means provided in the above, a plurality of times T1 from when the medium is detected by the first detecting means to when the medium is detected by the second detecting means are set. When the maximum value of the measured time is T1max and the margin is α, T1max + α is set as the allowable maximum time T2, and the minimum value of the measured time is T1min and the margin is β. It is set as the allowable minimum time T3, and thereafter, it is monitored whether the time T1 is the allowable maximum time T2 or more and the allowable minimum time T3 or less. If T1> T2 or T1 <T3, the medium is transported. A method for monitoring the state of medium conveyance, which stops the alarm and generates an alarm signal. 6. The medium conveyance state monitoring method according to claim 5, wherein the allowable maximum time T2 and the allowable minimum time T3 are updated every time a fixed number of sheets are passed. 7. An image forming means for forming an image on a recording carrier with a material to be transferred, a medium supply means for supplying a medium, and a transfer means for transferring the material to be transferred onto the medium fed from the medium supply means. Fixing means for fixing the transferred material to the transfer medium, medium storing means for storing the medium on which the transferred material is fixed, medium conveying path for conveying the medium from the medium supplying means to the medium storing means, and medium conveying path In a method for monitoring a medium transport state in an image forming apparatus including a plurality of medium detecting means provided in, a time T4 during which a medium passes a predetermined detecting means is measured a plurality of times, and a maximum value of the measured time is T4max, a margin. Is set as γ, and T4max + γ is set as the allowable maximum time T5, and thereafter, it is monitored whether the passing time T4 is the allowable maximum time T5 or more. If T4> T5, the medium conveyance is stopped and the alarm signal is output. Medium conveyance condition monitoring method for generating. 8. The medium conveyance state monitoring method according to claim 7, wherein the allowable maximum time T5 is updated every time a fixed number of sheets are passed. 9. An image forming means for forming an image on a recording carrier with a material to be transferred, a medium supplying means for supplying a medium, and a transfer means for transferring the material to be transferred onto the medium fed from the medium supplying means. Fixing means for fixing the transferred material to the transfer medium, medium storing means for storing the medium on which the transferred material is fixed, medium conveying path for conveying the medium from the medium supplying means to the medium storing means, and medium conveying path In a method of monitoring a medium transport state in an image forming apparatus having a plurality of medium detecting means provided in, a time T4 during which a medium passes a predetermined detecting means is measured a plurality of times, and a minimum value of the measured time is T4min, a margin. Is set as δ, and T4min−δ is set as the allowable minimum time T6, and thereafter, it is monitored whether the passing time T4 is the allowable minimum time T6 or less, and when T4 <T6, the medium conveyance is stopped. Alarm signal Medium conveyance condition monitoring method for generating. 10. The medium conveyance state monitoring method according to claim 9, wherein the allowable minimum time T6 is updated every time a fixed number of sheets are passed. 11. An image forming means for forming an image on a recording carrier with a material to be transferred, a medium supplying means for supplying a medium, and a transfer means for transferring the material to be transferred onto the medium fed from the medium supplying means. A fixing means for fixing the transfer material to the transfer medium,
Medium storing means for storing the medium on which the material to be transferred is fixed;
In a medium transport state monitoring method in an image forming apparatus including a medium transport path for transporting a medium from a medium supply means to a medium storage means, and a plurality of medium detection means provided in the medium transport path, the medium is a predetermined detection means. When the passing time T4 is measured multiple times and the maximum value of the measured time is T4max and the margin is γ, T4max + γ is set as the allowable maximum time T5, and the minimum value of the measured time is T4min and the margin is δ. At this time, T4min-δ is set as the allowable minimum time T6, and thereafter, it is monitored whether the passing time T4 is the allowable maximum time T5 or more and the allowable minimum time T6 or less, and T4> T5 or T4 <T6. If so, a method of monitoring the medium transportation state in which the medium transportation is stopped and an alarm signal is generated. 12. The medium conveyance state monitoring method according to claim 11, wherein the allowable maximum time T5 and the allowable minimum time T6 are updated every time a fixed number of sheets are passed.