JP2001002261A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of saving labor of jam disposed by detecting the size difference and double feeding of transfer paper and preventing jam stopping even through the size is slight different. SOLUTION: A first threshold value for detecting a jam on a transfer paper conveying passage by a transfer paper detecting means 37 and a time measuring means and a second threshold value smaller than the first threshold value are prepared for each transfer paper size. When the transfer paper conveying time is not less than the first threshold value, a paper jam is judged, and the image forming operation is immediately stopped. When a state where the transfer paper conveying time is less than the first threshold value and not less than the second threshold value is continuously detected twice or more, it is judged that the transfer paper size is abnormal, paper feeding of the next transfer paper is prohibited, and the image forming operation is stopped at the time when discharging of the transfer paper on the way of the image formation is completed. When a state where the transfer paper conveying time is less than the first threshold value and not less than the second threshold value is detected once, the image forming operation is continued.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to paper jam detection in an image forming apparatus for forming an image on transfer paper by an electrophotographic process.

[0002]

2. Description of the Related Art Conventionally, one transfer paper (paper) is taken from a cassette.
2. Description of the Related Art An image forming apparatus that feeds a sheet at a time and forms an image detects a paper jam (jam) on a transport path based on size information from a transfer paper size detecting unit provided in a cassette. When the user sets the transfer paper in the cassette, the size detection means performs ON / OFF of a plurality of SWs (switches) by a dial method in accordance with the paper size, and a size code based on a combination of ON / OFF states of the SWs. And the output voltage from the slide resistor linked to the regulating plate that is moved according to the transfer paper to be set is A /
For example, there is one that converts the data and reads it.

For example, the transport speed of the apparatus is set to 100 mm / s
ec, the transfer paper size set in the cassette is A4
If the size is detected, A4 length in the transport direction = 210 m
m, the transfer time is 210 mm ÷ 100 mm / sec
= 2100 msec. 20mm allowance for jam detection
Assuming that ÷ 100 mm / sec = 200 msec, the time from the start of conveyance of the transfer paper to the detection of the jam is 2100 ms.
ec + 200 msec = 2300 msec. Similarly, if the size of the transfer paper set in the cassette is detected as B5 size, the length of B5 in the transport direction = 182 mm
And the transfer time is 182 mm ÷ 100 mm / sec = 18
20 msec, so the time from the start of conveyance to the detection of a jam is 1820 msec + 200 msec = 20
20 msec. Similarly, when the size of the transfer paper set in the cassette is detected as A3 size,
A3 length in the transport direction of A3 = 420 mm, transport time is 420
mm ÷ 100 mm / sec = 4200 msec,
Therefore, the time from the start of conveyance to the detection of a jam is 4200.
msec + 200 msec = 4400 msec.

[0004]

However, when the jam detection is performed based on the transfer paper size information from the cassette size detecting means as described above, the user may make a mistake in setting the cassette size detecting means, or perform the size detection. If the size is mistakenly read due to a failure of the means or the like, it is detected that a jam has occurred even though the jam has not actually occurred.

For example, if the transfer paper actually set in the cassette is A4 size and the information from the cassette size detection means is B5 size, the jam detection time for B5 size is 2100 msec for A4 size conveyance time. Since the transfer time of A4 size is longer than the jam detection time of B5 size, it is determined that the transfer paper is stagnant or delayed, and the jam is detected.

Further, even when double feeding occurs, a jam is detected when a plurality of transfer sheets are fed with a shift in the transport direction. For example, the transfer paper set in the cassette is B
The information from the cassette size detection means is the same for 5 sizes B
Even if it is 5 sizes, when the transfer papers are overlapped and fed in a state shifted by 24 mm in the transport direction, the transport time is 1820 msec + 24 mm２４100 mm / sec =
2060 msec, B5 size jam detection time 2
It takes 060 msec, causing a jam. Here, A4
A4 size: 210m when comparing size and B5 size
The size of B5 with respect to m: 182 mm is only a difference of about 28 mm, and does not mean that the transfer paper is actually jammed. Therefore, it is considered that even if the transfer paper is discharged as it is, the apparatus may be damaged. Absent. The same applies to the case where the transfer paper is slightly shifted due to the double feed.The double feed is basically known to easily occur between the books in which the transfer paper bundle is added to the transfer paper bundle. There is no. Nevertheless, if the operation is stopped due to the detection of the jam, the transfer paper remains in the apparatus, so it is necessary to perform the jam processing. This is a problem in view of the trouble of the user and the deterioration of the image of the product.

[0007] In addition, when a jam is detected due to a cassette size setting error, there is a problem that it is difficult for a user to understand why the jam has occurred. Therefore, it is conceivable to allow a difference between the B5 size and the A4 size to increase the jam detection allowance, and to allow the use of the A4 size even when the B5 size is set. There is a possibility that fixing failure may occur due to improper temperature control of the section.

In view of the above problems, the present invention detects a difference in transfer paper size and occurrence of double feeding, and does not stop jamming even if there is a slight difference in size. It is intended to provide a device.

Another object of the present invention is to provide an image forming apparatus capable of obtaining a stable operation with good operability by giving a warning of a difference in size of transfer paper.

[0010]

An image forming apparatus according to the present invention comprises an image carrier for forming an image by a series of electrophotographic processes, and an image carrier for fixing an image transferred from the image carrier to transfer paper. Fixing means; transfer paper bundle holding means for holding a transfer paper bundle on which an image is transferred; transfer paper size determination means for determining the size of the transfer paper held by the transfer paper bundle holding means; A transfer unit for feeding and transferring one transfer sheet of the bundle to an image transfer position, a fixing position, and a discharge position; a transfer sheet detection unit provided on a transfer sheet transfer path; and the transfer sheet detection unit. A time measuring unit for measuring a time during which paper is detected, an operation unit for performing a status display and an operation instruction of the apparatus, and a control unit for controlling each of the units and the operation unit; The control means includes the transfer paper detection means and A first threshold value for detecting a paper jam of the transfer paper conveying path by serial time measuring means, said first
And a second threshold value smaller than the threshold value is prepared for each transfer paper size. If the transfer paper transport time is equal to or greater than the first threshold value, it is determined that a paper jam has occurred, and the image forming operation is immediately stopped. If the state is less than the first threshold value and the state equal to or more than the second threshold value is detected twice or more consecutively, it is determined that the transfer paper size is abnormal, and the feeding and conveyance of the next transfer paper is prohibited. The image forming operation is stopped when the paper discharge is completed, and the image forming operation is stopped when the transfer paper transport time is less than the first threshold value and the state that the transfer paper is equal to or greater than the second threshold value is detected one by one. It is characterized by continuing.

If the transfer paper transport time is less than the first threshold value and the state of the second threshold value or more is not detected one by one, the image forming operation is continued in this case. Transfer paper is shifted in the transport direction (double feed)
Is determined to have been conveyed.

According to the present invention, the margin of the first threshold with respect to the conventional paper jam (jam) detection reference is increased from the second threshold, and the jam is stopped when the jam is detected within the expanded margin. Is performed, and if the cause is temporary, the image forming operation can be continued as it is. Further, even if the cause is continuous, the transfer sheet is discharged for the time being, and the trouble of the jam processing can be omitted.

Preferably, the control means includes a size error display means for displaying a notification of the size error on the operation unit when the transfer sheet size error is detected, and displays the size error and the following: The image forming operation is prohibited.

Further, two or more transfer paper bundle holding means, transfer paper size determination means for determining the size of the transfer paper held in each of the transfer paper bundle holding means, and the transfer paper size determination means are provided on the operation unit. The apparatus may further include initialization instruction means for initializing an operation mode of the apparatus, and paper feed stage selection means for selecting and instructing one of the plurality of transfer sheet bundle holding means. When the next image forming operation is prohibited by the detection of the transfer paper size abnormality, the transfer paper size detected by the transfer paper size determination unit changes, and the initialization of the operation mode is performed by the initialization unit. The prohibition of the image forming operation is released when the instruction for the image formation is given or when a different paper feed stage is selected by the paper feed stage selecting means. Thus, the image forming operation can be restarted.

Storage means for counting and storing the number of occurrences of double feed when the double feed is detected; a numerical value display unit provided on the operation unit; and the number of double feeds stored in the storage means May be provided. The value of the double feed detection counter can be used as maintenance information relating to an abnormality in the paper feeding unit, a paper setting method, and the like.

[0016]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a schematic diagram showing a paper cassette mounted on a copying machine which is an image forming apparatus according to the present invention. This copying machine forms an image by a series of electrophotographic processes such as charging, exposure, development, transfer, cleaning, and charge elimination. In this embodiment, two (cassette) paper cassettes 10 can be mounted on the copying machine main body.

The user sets a bundle of sheets in the cassette 10. The set sheet bundle is pushed up by a middle plate (not shown), and the leading end of the sheet in the sheet passing direction shown in FIG. 1 is pressed by the separation claw 11 on the side of the cassette. When the sheet is fed in the sheet passing direction by the roller, only the top sheet is separated and fed from the sheet bundle below it by the separation claw 11.
After setting the paper, the user sets the size by turning the cassette size setting dial 12 shown in FIG. 1 to a position corresponding to the set paper size. When the cassette size setting dial 12 is turned, a plurality of (four in this example) slide pieces 13 are individually driven by a link mechanism (not shown), and slide in the sliding direction shown in FIG. As a result, depending on the dial position, the slide piece 13 stops at the projected position or stops at the lowered position. After setting the paper and setting the dial, the user pushes the cassette in the cassette insertion direction shown in FIG. 1 to set the cassette in the copying machine main body.

FIG. 2 is a schematic diagram showing the configuration of the cassette size detecting mechanism provided on the inner wall of the cassette insertion slot of the copying machine main body. FIG. 2A is a plan view, and FIG. 2B is a front view. In this specification, the term “cassette size” indicates a paper size set for the cassette, and does not mean the size of the cassette itself.

The cassette size detecting mechanism shown in FIG. 2 is provided for each of a plurality of cassette insertion ports of the copying machine main body, and can individually detect the cassette size. That is, when the cassette is set in the copying machine main body by the user, FIG.
When each of the slide pieces 13 is in a protruding position, the leaf spring 15 at a position corresponding to each of the slide pieces 13 shown in FIG. 2 is pressed against the pressure. The pressed leaf springs 15 turn on the size detection SWs (switches) 14 that are respectively opposed to each other.
N. The slide piece in the retracted position is a leaf spring 15.
Is not pressed, the size detection SW 14 facing the leaf spring 15 remains OFF.

Note that the cassette size detecting mechanism shown in FIGS. 1 and 2 is merely an example of a paper size detecting means, and the present invention is not limited to this. it can.

FIG. 3 shows a schematic hardware configuration for controlling the copying machine. The copier control board 100 receives various input signals and generates various output signals. The operation unit 20 is connected to the copier control board 100. The operation unit 20 receives a copy mode setting instruction and a copy operation start instruction by a key input by the user, and displays various states of the copying machine.

The copying machine control board 100 stores a ROM 104 in which a copying machine control program is recorded, a RAM 105 for storing data used by the control program, and adjustment values and jam data even after the power is turned off. A backup power supply (battery) 106 for the RAM,
A CPU 101 for reading a control program from a ROM 104 and executing an instruction, and a reset circuit 10 for outputting a reset signal for a certain period to the CPU 101 when the power is turned on to operate the CPU 101 from the beginning of the control program
2. A plurality of timers 103 and the like for generating each control timing of the copying machine are provided.

The copier control board 100 receives various inputs from various sensors for determining the state of the copier, SW, thermistor, etc., various motors for driving the copier, and various SLs (solenoids). ), And generates output signals to various CLs (clutches), heaters, lamps, and the like.

The CPU 101 forms an image by performing a mode setting process and a display process according to a key input of the operation unit 20, a state determination / display process by each input signal, and a drive control of each output according to a control program. .
Further, the CPU 101 performs the size detection SW1 shown in FIG.
Based on the ON / OFF state of 4 (size code of 4 bits), the set paper size is determined.

FIG. 10 shows a table of paper sizes determined by the CPU 101. If the cassette is not inserted into the copier, all the size detection switches 14
Since the state is the FF state, it is possible to determine "cassette omission". If "Cassette missing" is recognized,
The copy operation is prohibited and the fact is displayed on the operation unit. Size detection SW1 not assigned to any size
Also in the case where the state of “no assignment” corresponding to the ON / OFF combination of No. 4 is determined, the same warning processing as the cassette missing is performed. “U1” and “U2” are prepared as special size codes when it is desired to handle paper of a special size other than a standard size such as A4 or A3. U1, U
The special size 2 is used when the user inputs an arbitrary width and length from the operation unit.

FIG. 4 is a diagram showing a schematic configuration of the operation unit. FIGS. 11 and 12 show reference numbers, names, and contents of various keys and displays on the operation unit in FIG.

When instructing the start of copying, the user presses the start key K12. D12 is the copy start key K
The indicator is provided in the unit 12. The indicator is lit in green when the copying is possible, and is lit in red when the copying is not possible such as when there is no paper or a jam occurs. The user uses the numeric keypad K10 to copy the number of copies (number of copies) and the fixed-size variable key K3.
To set a copy mode such as a copy magnification. The numerical display D11 displays numerical data such as the set number and magnification. Further, the user selects one of a plurality of cassettes (two stages in the embodiment) or the manual feed tray using the paper selection key K4. One of the cassette indicators D7 and D8 corresponding to the selected cassette is lit and displayed, and the paper size corresponding to the selected cassette detected by the cassette size detection is one of the paper size indicators D10.
One is illuminated. The set copy mode is cleared by the reset key K7, and the
1 ", magnification" 100% "(actual magnification), and paper selection are in the initial state of the" first cassette ".

FIG. 5 is a diagram showing a schematic configuration of a transport system of a copying machine according to the present embodiment, and FIG. 6 is a diagram showing a schematic configuration of each cassette sheet feeding stage.

When a copy start is instructed by the operation unit 20, a main motor (not shown) is turned on. The driving force of the main motor is directly transmitted to the drum 34, the fixing roller 33, and the paper discharge roller 32 shown in the figure, and rotates in synchronization with the main motor during driving of the main motor. The registration roller 36 and the vertical path rollers 38a and 38b are kept in a position until an electromagnetic clutch (registration roller clutch, vertical path roller clutch) (not shown) provided for each of them is turned on.
The driving force of the main motor is not transmitted. Further, the pickup rollers A of the cassettes 10a and 10b turn on the pickup solenoids (not shown) provided respectively.
As a result, the driving force of the main motor is not transmitted unless a spring clutch (not shown) is connected. The pickup roller A has a half-moon shape in cross section. When the roller is stopped, the circumferential surface of the roller faces upward, and the circumferential surface of the roller does not contact the sheet surface of the cassette.

At the start of the paper feeding operation, if the pickup solenoid of the selected cassette is turned on for 300 msec,
The release state of the spring clutch of the selected cassette is released, and the driving force of the main motor is transmitted to the pickup roller A of the selected cassette. The pickup roller A makes one revolution in about 600 msec, and the pickup solenoid is turned off 300 msec after being turned on. For this reason, when the big-up roller A makes one rotation, the spring clutch is again released, and the driving force of the main motor is not transmitted to the pickup roller A, so that the stop state is established. While the big-up roller A makes one rotation and the roller circumferential surface faces downward, the roller circumferential surface is brought into contact with the sheet surface of the cassette, picks up one sheet from the sheet bundle and sends it to the transport roller B.
The transport roller B operates following the pickup roller A, and feeds the sheet to the vertical path roller 38a or 38b of the selected cassette (hereinafter collectively referred to as 38; the same applies to other reference numerals). The drive of the vertical path roller 38 is started by turning on the vertical path roller clutch almost simultaneously with the pickup solenoid. Cassette 1
When 0b is selected, both clutches of the vertical pass rollers 38a and 38b are turned on, and when the cassette 10a is selected, only the clutch of the vertical pass roller 38a is turned on. The vertical pass rollers 38a,
When the paper is received from the transport roller B, a loop is formed so that the leading end of the paper abuts against the registration roller 36 to correct the skew of the paper, and then the clutch is turned off to stop the transport.

The above is the schematic operation from the start of the paper feeding operation to the completion of the paper feeding. FIGS. 13A and 13B respectively show:
The following table shows parameters indicating the timing from when the pickup solenoid of the cassette 10a is turned ON to when the sheet feeding operation is completed, and when the pickup solenoid of the cassette 10b is turned ON until the sheet feeding is completed. The time to reach the leading end of the sheet from the pickup solenoid ON to the pre-registration sensor 37 is T5 for the cassette 10a and T10 for the cassette 10b.
Assuming that the jam margin for the time when the leading edge of the paper reaches the pre-registration sensor 37 is 500 msec, the case of the cassette 10a is T
5 + 500 msec, T10 + 5 for cassette 10b
00 msec is the pre-registration sensor delay jam detection time. When the pickup solenoid is ON, the pre-registration sensor delay jam detection timer is started, and if the pre-registration sensor does not turn on (detects the presence of paper) even after the time has elapsed, a pre-registration sensor delay jam is determined.

When the paper feeding operation is completed normally without the sensor delay jam before the registration, the paper is transferred to the transfer position where the transfer charger 35 shown in FIG. Is sent to a fixing roller 33 for fixing the image transferred to the sheet. The driving of the registration roller 36 is started by turning on a registration roller clutch in synchronization with a document scan of a scanner provided in an optical system (not shown) for exposing and scanning a document. The document image exposed and scanned by the scanner is guided onto the surface of the drum 34 shown in FIG. 5 by reflection of a plurality of mirrors. The drum surface is charged in advance by a charger (not shown), and when the drum surface is irradiated with light, the charged charge is discharged. When the charged drum surface is illuminated with the light of the original image, the charge in the bright part where no characters or lines are placed is discharged, and the dark part where the characters or lines are placed remains, leaving the original on the drum surface. An electrostatic latent image corresponding to the image is formed. The electrostatic latent image formed on the drum surface is visualized by applying toner to a portion of the drum surface where the charge remains, by a developing device (not shown). When the toner image formed on the paper and the visible drum surface comes to the transfer position, the transfer charger 35 applies an electric charge from the back side of the paper, and the toner on the drum surface is transferred to the paper surface. You. The toner image transferred to the paper surface is fused by a fixing roller 33 having a heater controlled to a predetermined temperature inside. The sheet on which the image has been transferred and fixed from the leading edge to the trailing edge of the sheet is discharged through a sheet discharging roller 32, and one copy is completed. When the setting number of “2” or more is set by the operation unit 20, the operations from the sheet feeding operation to the transfer, fixing, and sheet discharging are continuously repeated for the set number.

The above is the outline of the operation from the registration roller 36 to the paper discharge. FIGS. 14A and 14B show the parameters representing the timing of the leading edge transport and the trailing edge transport from the ON of the resist roller clutch to the paper discharge. Show. The time from when the registration roller clutch is turned on to when the leading edge of the sheet reaches the sheet ejection sensor is T14, and the jam margin is 500 msec.
Then, T14 + 500 msec becomes the paper ejection sensor delay jam detection time. A discharge sensor delay jam detection timer is started at the same time as the registration roller clutch is turned on. If the discharge sensor is not turned on (detection of the presence of a sheet) even after the lapse of the time, a discharge sensor delay jam is determined.

The timing of the leading edge of the paper is the same regardless of the paper size, but the timing of the trailing edge of the paper differs depending on the paper size (feed length). As shown in FIG. 14B, the time from the ON of the registration roller clutch to the OFF of the pre-registration sensor is (paper feed length−L4) / V
It becomes 2. Here, L4 is a distance from the pre-registration sensor 37 to the registration roller 36 as shown in FIG.
The length of the trailing edge of the paper remaining upstream from the pre-registration sensor 37 is shorter than (paper feed length-L4) because a loop is formed immediately before the registration roller 36 during paper feeding. However, since the movement of the trailing end of the sheet is started after the registration roller clutch is turned ON after the formed loop is eliminated, the timing calculation may be maintained at (sheet feed length-L4). For example, V2 = 100 mm
/ Sec, L4 = 20 mm, and the feed length in the case of A4 size is 210 mm. Therefore, the time T15 from ON of the A4 size registration roller clutch to OFF of the pre-registration sensor is (210−20) / 100 = 1. 9 sec
= 1900 msec. In the case of the B5 size, since the feed length is 182 mm, T15 = (182-20) /
100 = 1.62 sec = 1620 msec. Here, assuming that the jam allowance is 200 msec, the A4 size before-registration sensor retention jam detection time of A4 size is 1900 + 200.
= 2100 msec, the B5 size pre-registration sensor retention jam detection time is 1620 + 200 = 1820 msec. The feed length for jam clearance is 0.2 (sec) x
100 (mm / sec) = 20 mm. However, if the user mistakenly sets the cassette size setting dial to the B5 size when setting A4 size paper in the cassette, or if the cassette size detection fails and the paper size is A4 size, the B5 size In such a case, since the CPU attempts to detect the jam in the B5 size, the A4 size pre-registration sensor OFF time of 1900 msec is longer than the B5 size pre-registration sensor staying jam detection time of 1820 msec. Will detect it. As described above, in the conventional machine, the jam margin is set so that the jam occurs even when the difference between the A4 size and the B5 size is about 210-182 = 28 mm. In the case of such a jam, it is difficult to understand why the jam has occurred simply by displaying the occurrence of the jam on the operation unit, and there is a problem that it is necessary to remove the jam paper from the inside of the machine.

Therefore, in the present embodiment, the jam margin is set larger so that the difference between the A4 size and the B5 size can be passed without change. In the present embodiment, if the jam margin is described as 500 msec, the B5 size pre-registration sensor stay jam detection time is 1620 + 500 = 2120 msec, and the A4 size pre-registration sensor OFF time of 1900 msec falls within the jam detection. The pre-registration sensor retention jam detection timer is activated at the same time as the registration roller clutch is turned on.

However, since it is not preferable to continue using the device with the wrong setting size, a threshold for detecting that the setting size is wrong is provided.

Therefore, as shown in FIG. 15, the (paper feed length-L4) / V2 + jam margin (500 msec) of the pre-registration sensor stay jam detection time of the present embodiment is the first.
The second threshold value is the threshold value of the sensor before jam and the jam detection time (paper feed length−L4) / V2 + the jam margin (200 msec) of the conventional machine used in the conventional machine. Also, if the pre-registration sensor is not turned off, a jam occurs. If the pre-registration sensor is turned off within the first threshold but the second threshold is passed, it is determined that the set size is wrong.

However, attention must be paid here. It is known that a double feed in which a sheet overlaps with a sheet and the sheet is fed is likely to occur between booklets in which a sheet bundle is added to the sheet bundle already set in the cassette. There is no problem if the leading edge and the trailing edge of the sheet are completely coincident. However, in the case of the double feeding in which the sheet edge is slightly shifted in the transport direction, the shift amount is equal to or more than the second threshold value and the first threshold value is set. If it is within the range, it is determined that the set size is different even if the set size is correct. As a countermeasure, double feed between books does not occur frequently,
When a state that is equal to or greater than the second threshold and less than the first threshold is detected twice consecutively, the difference in the set size is determined, and the copy operation is stopped after the discharge of the remaining paper in the apparatus is completed.
After the copy operation is stopped, the selected cassette display D7 or D8 shown in FIG. 4 is blinked to notify that there is an abnormality in the cassette size detection. Also, the selected cassette size is changed or the paper selection key K4
To select a different paper source, or press the reset key K7
Until the copy mode is cleared, the start of the next copy is prohibited, and the indicator D12 is lit red.

In the detection of the jam in the paper discharge sensor, the jam margin needs to be matched with the jam margin time of the jam detection of the sensor before the registration, so that the jam margin is set to 500 msec.
And Therefore, the paper discharge sensor retention jam detection time is the paper feed length / V2 + 500 msec.

FIGS. 7 to 9 are flow charts showing a transport sequence from the above-mentioned sheet feeding to sheet discharging.

Steps S1 to S20 indicate the sheet feeding operation, and steps S21 to S65 indicate the steps from ON of the registration roller clutch to sheet discharge.

In steps S1 to S3, it is determined whether or not the copy operation after the jam processing is to be resumed. If the copy operation after the jam processing is not to be resumed, the operation of the sheet feed counter and the discharge counter designated by the operation unit is performed. The number is set and initialized. The paper feed counter and the paper discharge counter are counted down each time the paper feed operation and the paper discharge operation are completed, and the transport sequence is executed until the value of the counter becomes “0”.

In steps S4 to S5, if the main motor has not been started, the main motor is started.
Wait for the motor rotation to stabilize for 00 msec.

In steps S7 and S8, the timing of starting the paper feeding operation is determined so that the leading edge of the second and subsequent sheets does not catch up with the trailing edge of the immediately preceding sheet.

In steps S9 and S10, the big-up solenoid and the vertical pass roller clutch are turned on to start the sheet feeding operation, and at the same time, the pre-registration sensor delay jam timer is started. Since the pickup roller only needs to make one round, the big-up solenoid is turned off after 300 msec in steps S11 and S12.

If the pre-registration sensor delay jam detection timer does not turn on the pre-registration sensor after a predetermined time has elapsed in steps S13 to S16, a pre-registration sensor delay jam is determined, and jamming is stopped in step S16 (all sequences are stopped and all Of the drive system is turned off), and the process is terminated.

If the paper has been normally fed, step S
After stopping the pre-registration sensor delay jam detection timer and forming a loop in 17 to S20, the vertical pass roller clutch is turned off.
The sheet feeding counter is counted down at the same time as the FF is performed to stop the sheet feeding operation.

Step S21 waits for the registration roller clutch to be turned on synchronously from the document exposure sequence of the optical system (not shown) so that the leading edge of the document coincides with the leading edge of the sheet. O of registration roller clutch
After the detection of N, in steps S22 to S23, the pre-registration sensor retention jam detection timer and the paper discharge sensor delay jam detection timer are started.

Turning to FIG. 8, steps S24 to S28
Then, check the value of the paper feed counter, and confirm that the paper feed counter is not "0" (paper feeding for the set number has not been completed), the cassette has paper, and there is no copy stop request. Then, the next sheet transport sequence is started.

Since the copier control program of this embodiment is executed by a known multitasking process, the same sequence can be executed simultaneously by a plurality of programs (tasks). Therefore, the next sheet transport sequence is executed from step S1 in a program (task) different from the program (task) executing the current sheet transport sequence.

In steps S29 and S30, a pre-registration sensor OFF waiting flag and a paper discharge sensor ON which are held until the pre-registration sensor OFF and the paper discharge sensor ON are detected.
The wait flag is turned on.

In steps S31 to S35, if the pre-registration sensor OFF waiting flag is ON, the pre-registration sensor stay jam detection timer is checked and a predetermined time (first threshold) is set.
If the pre-registration sensor remains ON even after the elapse, the jam is stopped as the pre-registration sensor stagnant jam. If the pre-registration sensor is turned off within the time-up of the pre-registration sensor stay jam detection timer, the process proceeds to S36 and subsequent steps.

In steps S36 to S40, it is checked whether or not the pre-registration sensor stay jam detection timer is within the second threshold value. If the timer is not less than the second threshold value, the size abnormality detection counter is counted up. If the value of the size abnormality detection counter is “2”, the size abnormality is determined by detecting the size abnormality twice consecutively, and the size abnormality detection flag and the copy stop request flag are turned ON. The size abnormality detection flag is used to indicate that the size abnormality detection has been activated in a display control sequence (not shown), and the copy stop request flag does not activate the next sheet conveyance sequence in steps S22 to S28 (the copy operation is not performed). Stop)
Used for

If the pre-registration sensor OFF timing is less than the second threshold, steps S43 to S45 are executed. In step S43, if the value of the size abnormality detection counter is "1", it is determined that the multi-feed is a state in which the sheet edge is slightly shifted because the size abnormality detection is not continuous, and the multi-feed is performed in step S44. The detection counter is counted up, and in step S45, the size abnormality detection counter is cleared in preparation for the next size abnormality detection. The value of the double feed detection counter is retained by the backup power supply even after the power is turned off, and can be displayed on the numerical display D11 on the operation unit. When displaying the double feed detection count value, for example, after entering the service mode with the service mode key K9, a mode number for displaying the double feed detection count value is designated with the ten keys K10. If the value of the double feed detection counter seems to be large, there is a problem with the paper feeding section such as a problem with the separation claw of the cassette, or the problem of how to set the paper such that the paper bundle is divided and added to the paper bundle. To be considered,
This can be used as maintenance information.

When the size abnormality detection counter is "0" in step S43 or after execution of steps S40 and S45, in steps S41 and S42, the stop of the pre-registration sensor stay jam detection timer and the OFF of the pre-registration sensor OFF wait flag are performed.
FF is performed, and the process proceeds to step S46 and subsequent steps. Also,
Also in step S31, if the OFF waiting of the pre-registration sensor has been completed, the process proceeds to step S46 and thereafter.

Referring to FIG. 9, in step S46, the check of the paper discharge sensor ON waiting flag in step S47 is performed first so that the paper discharge sensor is not repeatedly checked after detecting the ON of the paper discharge sensor. The sensor OFF waiting flag is checked. Until the paper ejection sensor is turned on, the paper ejection sensor OFF waiting flag is not turned on, so steps S47 to S55 are executed first.

In steps S47 to S51, the paper discharge sensor delay jam detection timer is checked, and if the paper discharge sensor is not turned on after a predetermined time has elapsed, the paper jam is stopped as the paper discharge sensor delay jam. If the paper discharge sensor delay jam detection timer has not expired, the pre-registration sensor is turned off and the paper discharge sensor is turned off depending on the paper size.
Since the timing at which N is detected first is different, the process returns to step S31 to check the pre-registration sensor OFF waiting flag.

If it is detected that the paper discharge sensor has been turned on within a predetermined time of the paper discharge sensor delay jam detection timer, the processing of steps S52 to S55 is executed. Step S52-
In step S55, the paper discharge sensor delay jam detection timer is stopped, and at the same time, the paper discharge sensor stay jam detection timer is started, the paper discharge sensor ON waiting flag is turned off, the paper discharge sensor OFF waiting flag is turned on, and the pre-registration sensor of step S31 is turned on. OF
The process returns to the check of the F wait flag.

When the waiting for the sheet ejection sensor ON is completed and the process is executed again from step 31, the processes of steps S47 to S55 are not executed, and the processes of steps S46 and S56 to S65 are executed. If the discharge sensor OFF waiting flag is ON in step S46, steps S56 and thereafter are executed.

In steps S56 to S59, the paper discharge sensor staying jam detection timer is checked. If the paper discharge sensor remains ON even after a predetermined time has elapsed, the jam is stopped as the paper staying jam. . If the paper discharge sensor stay jam detection timer is within the predetermined time, step S
The process returns to step 31 for checking the pre-register sensor OFF waiting flag. If it is detected that the discharge sensor is OFF, the process proceeds to step S
The processing after 60 is executed.

In steps S60 to S65, the paper discharge sensor staying jam detection timer is stopped, the paper discharge sensor OFF waiting flag is turned off, and the paper discharge counter is counted down. Since the copying operation has been completed, post-rotation processing such as drum cleaning is performed, and then the main motor is stopped.

Although the preferred embodiment of the present invention has been described above, various modifications and changes are possible.

[0064]

According to the present invention, when there is a slight difference between the set paper and the size detected by the cassette size detection, or when a double feed in which the paper end is slightly shifted occurs. In addition, since the jam is not stopped, and the size is different, this fact is indicated, so that an image forming apparatus with good operability can be provided. Further, when a double feed is detected, the number of times is counted and displayed, whereby an image forming apparatus having excellent maintainability can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a paper cassette mounted on a copying machine which is an image forming apparatus according to the present invention.

FIG. 2 is a schematic diagram showing a configuration of a cassette size detecting mechanism provided on an inner wall of a cassette insertion slot of a copying machine main body.

FIG. 3 is a block diagram showing a schematic hardware configuration for controlling the copying machine.

FIG. 4 is a diagram showing a schematic configuration of an operation unit of the copying machine.

FIG. 5 is a diagram illustrating a schematic configuration of a transport system of the copying machine according to the embodiment of the present invention.

FIG. 6 is a diagram illustrating a schematic configuration of a sheet feeding unit of the copying machine according to the embodiment of the present invention.

FIG. 7 is a flowchart illustrating a first part of a transport sequence from feeding to discharging of the copying machine according to the embodiment of the present invention.

FIG. 8 is a flowchart showing a second part of the transport sequence following FIG. 7;

FIG. 9 is a flowchart showing a third part of the transport sequence following FIG. 8;

FIG. 10 is a diagram illustrating a table of paper sizes determined by a CPU 101 in the copying machine.

11 is a diagram showing reference numbers and names of various keys on the operation unit in FIG. 4 and their contents.

12 is a diagram showing reference numbers, names, and contents of various displays on the operation unit in FIG. 4;

FIG. 13 shows a cassette 10 according to the embodiment of the present invention.
FIG. 7A is a diagram showing parameters indicating timings from the time when the pickup solenoid is turned ON to the completion of sheet feeding operation and the time from when the pickup solenoid of the cassette 10b is turned ON to time when sheet feeding is completed.

FIG. 14 is a diagram illustrating timings of leading edge transport and trailing edge transport from registration roller clutch ON to sheet ejection in the embodiment of the present invention.

FIG. 15 is a diagram for describing first and second threshold values for detecting a sensor jam before a registration in the embodiment of the present invention.

[Explanation of symbols]

 10 (10a, 10b) Cassette 11 Separation claw 12 Cassette size setting dial 13 Slide frame 14 Size detection switch 20 Operation unit 100 Copy machine control board 101 CPU 102 Reset circuit (RESET) 103 Timer 104 ROM 105 RAM 106 Backup power supply

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (reference) G03G 21/00 386 G03G 21/00 386 500 500 F term (reference) 2H027 DA38 DA47 DC03 DC14 DC19 EE08 EH10 EK01 EK03 EK04 EK07 EK10 EK11 FC07 GB01 GB08 2H072 AA02 AA04 AA23 AA29 AB25 AB27 BA02 EA05 JA02 3F048 AA02 AA05 AB01 BA07 BA13 BA14 BB02 BB05 CC01 CC17 DB13 DB15 EA15 EB12 3F343 FA02 FB02 FC30 HA33 MC17 MA03 KB03 MA30 KB MC28

Claims (4)

[Claims] An image carrier for forming an image by a series of electrophotographic processes, fixing means for fixing an image transferred from the image carrier to transfer paper, and a transfer paper bundle on which the image is transferred Transfer paper holding means for holding the transfer paper, transfer paper size determining means for determining the size of the transfer paper held in the transfer paper bundle holding means, and transferring one transfer paper of the transfer paper bundle to the image transfer position. , Fixing position,
Conveyance means for feeding and conveying the paper to the paper discharge position; transfer paper detection means provided on a transfer paper conveyance path; and time measurement means for measuring a time during which the transfer paper detection means detects the presence of paper. An operation unit for displaying a status of the apparatus and instructing an operation; and a control unit for controlling each of the units and the operation unit. The control unit is configured to perform transfer by the transfer paper detection unit and the time measurement unit. A first threshold value for detecting a paper jam on a paper transport path and a second threshold value smaller than the first threshold value are prepared for each transfer paper size, and the transfer paper transport time is equal to or greater than the first threshold value. In the case of, the image forming operation is immediately stopped by determining that the paper is jammed, and if the transfer paper transport time is shorter than the first threshold and the state equal to or higher than the second threshold is detected twice or more consecutively, the transfer paper size is abnormal. And transfer the next transfer paper Stop, stop the image forming operation at the place where the discharge of the transfer paper in the middle of image formation is completed, and transfer the transfer paper less than the first threshold and once more than the second threshold one by one. An image forming apparatus, wherein the image forming operation is continued when the image is detected. 2. An image forming apparatus according to claim 1, wherein said control means detects the transfer paper size abnormality.
An image forming apparatus, comprising: a size error display unit for displaying a notification of a size error on the operation unit; displaying the size error and prohibiting a next image forming operation. 3. An image forming apparatus according to claim 1, wherein two or more transfer paper bundle holding means, and a transfer paper size for determining the size of the transfer paper held by each of the transfer paper bundle holding means. Determination means, initialization instruction means for initializing an operation mode of the apparatus provided on the operation unit, and sheet feeding for selecting and instructing one of the plurality of transfer sheet bundle holding means A stage selection unit, wherein when the next image forming operation is prohibited by the detection of the transfer paper size abnormality, the transfer paper size detected by the transfer paper size determination unit changes; An image forming apparatus configured to release the prohibition of the image forming operation when an initialization of an operation mode is instructed by a unit or when a different sheet feeding stage is selected by the sheet feeding stage selecting unit. 4. The image forming apparatus according to claim 1, further comprising: storage means for counting and storing the number of occurrences of the double feed when the double feed is detected; and a numerical value display unit provided on the operation unit. An image forming apparatus comprising: a multi-feed count display instructing unit for instructing a display of the number of multi-feeds stored in the storage unit.