JP2000238921A - Sheet conveyance device and image forming device equipped therewith - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce occurrence of delayed jams. SOLUTION: This sheet conveyance device 104 is equipped with a sheet conveyance means 3 operating for a predetermined time and conveying sheets, a sheet conveyance path 27 for guiding the sheets conveyed by the sheet conveyance means 3, a passing required time measuring means for measuring the time required per passing sheet for a sheet to pass a predetermined distance of the sheet conveyance path 27, and a controller 40 for storing measurement results per sheet by the passing required time measuring means and extending the operation time of the sheet conveyance means 3 when a ratio of a number of sheets conveyed other than a predetermined passing time and a number of sheets in the predetermined passing time exceeds a predetermined ratio.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet conveying apparatus for conveying a sheet, and an image forming apparatus including the sheet conveying apparatus, such as a copying machine, a printer, a facsimile, and a composite device thereof.

[0002]

2. Description of the Related Art Conventionally, a sheet conveying device provided in a main body of an image forming apparatus feeds sheets one by one by a rotating body (roller or paddle) that comes into contact with the uppermost sheet among the stacked sheets. It is designed to be sent.

FIG. 6 shows a conventional sheet conveying apparatus. The sheet conveying device is provided, for example, in a main body of an image forming apparatus (not shown), and supplies a large amount of sheets S stacked on the sheet stacking table 1 to image forming means of the image forming apparatus. ing.

[0004] The sheet conveying device is arranged above the sheet stacking table 1, and is arranged at a pickup roller 2 for feeding the uppermost sheet one by one, and is arranged at the front of the sheet stacking table 1 and fed by the pickup roller 2. And a separation roller pair 3 that separates the plurality of sheets S into a single sheet and conveys the sheet downstream.

The pickup roller 2 is attached to a tilting end of an arm 6 rotatably attached to a drive shaft 5 attached to the main body of the image forming apparatus.
The rotational force of the drive shaft 5 is transmitted via an endless belt 10 wound around 9.

The pickup roller 2 is pressed against the uppermost sheet by a pressing force (contact pressure) W generated by the weight of the pickup roller 2, the weight of the arm 6, the weight of the weight 11 attached to the tip of the arm 6, and the like. The conveying force required to convey the sheet S is obtained by the pressing force W. When a rotational force from a power source (not shown) is input to the drive shaft 5, the pickup roller 2 rotates in the direction of the arrow to feed the uppermost sheet.

On the other hand, the separation roller pair 3 includes a feed roller 12 and a retard roller 13. The separation roller pair 3 separates a plurality of sheets S fed by the pickup roller 2, feeds one sheet, and returns the remaining sheets S to the sheet stacking table 1.

The feed roller 12 is rotatably and non-movably provided in the main body of the image forming apparatus, and is rotated in the direction of an arrow by a rotational force transmitted from a power source (not shown). The retard roller 13 is movably attached to a support member 15 fixed to the image forming apparatus main body, and is pressed by the pressure roller 16 to be pressed by the feed roller 12 at a predetermined pressure P. ing.

The pressure roller 16 is provided at one end of a tilt link 21 that tilts about a rotation center shaft 20, and is connected to the retard roller 13 by a tension spring 22 stretched between the other end and the support member 15. It is pressed against the coaxial intermediate roller 19.

The sheet S having passed through the separation roller pair 3 is sent to an image forming means (not shown) through a sheet conveying path 27. At this time, the sheet S that has passed through the separation roller pair 3 is
It is detected by a first sheet detection sensor 28 and a second sheet detection sensor 29 installed in the sheet transport path 27.

Here, the conveyance timing t required from when the sheet S is detected by the first sheet detection sensor 28 to when the sheet S is detected by the second sheet detection sensor 29 on the downstream side is determined by the conveyance force of the feed roller 12 and the like. It is determined. When the transport timing t exceeds the predetermined time Tjam, it is conceivable that some abnormality has occurred on the way.

Therefore, in general, when the transport timing t exceeds Tjam, the sheet supply operation is interrupted and a delay jam of the sheet S is reported to urge the user to clear the jam.

On the other hand, the feed roller 12 has a reduced conveying force due to wear of the outer peripheral surface (surface) for conveying the sheet, adhesion of the sheet powder, or deposition of foreign matter contained in the roller. I do. According to the experiments so far, as the wear of the feed roller 12 progresses, the frequency distribution of the sheet passing timing t gradually changes from the initial state shown by the curve b in the direction a as shown in FIG. Are known.

The distribution indicated by the curve d in the figure shows a distribution in a state where the durability of the feed roller 12 is considerably advanced. In such a distribution, a hatched portion in the figure indicates a delay jam. Will happen.

The sheets include plain paper, thin resin sheets which are substitutes for plain paper, postcards, cardboard,
There are sealed letters and plastic thin plates.

[0016]

Problems to be solved by the invention
In the conventional sheet conveying apparatus, when the conveying force of the feed roller 12 is reduced, and the sheet passing timing t exceeds a predetermined time Tjam, a delay jam frequently occurs.

When the delay jam occurs frequently, the user contacts the manufacturer for the first time, and a service person or the like replaces the parts or cleans the feed roller 12 and the retard roller 13. Was normal.

However, when parts are replaced as described above,
During the cleaning of the feed roller 12 and the retard roller 13, the user cannot use the image forming apparatus, so that the user loses time and cannot perform cleaning processing or component replacement at an optimal time.

Further, the image forming apparatus having such a sheet conveying device cannot form a high quality image on a sheet because the sheet cannot be reliably sent to the image forming means.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a sheet conveying apparatus capable of reducing occurrence of a delay jam and an image forming apparatus provided with the sheet conveying apparatus.

[0021]

According to the present invention, there is provided a sheet conveying apparatus for operating a sheet for a predetermined time to convey a sheet, a sheet conveying path for guiding a sheet conveyed by the sheet conveying means, and A time required for the sheet to pass a predetermined distance in the sheet conveying path, a passage required time measuring means for measuring for each sheet to be passed, and a measurement result for each sheet by the required passage time measuring means are stored, and a predetermined time is stored. When the ratio between the number of sheets conveyed other than the passing time and the number of sheets within the predetermined passing time exceeds a predetermined ratio, a control device for extending the operation time of the sheet conveying means is provided. ing.

In the above-mentioned sheet conveying apparatus, the sheet is conveyed on the sheet conveying path by the sheet conveying means. The sheet conveying means stops after operating for a predetermined time. At this time, the required passage time measuring means measures the time required for the sheet to pass a predetermined distance in the sheet conveying path for each sheet passing therethrough. The control device stores the measurement result of each sheet by the required passage time measuring means, and determines that the ratio of the number of sheets conveyed outside the predetermined passage time to the number of sheets within the predetermined passage time is a predetermined value. Is exceeded, the operating time of the sheet conveying means is extended.

Accordingly, it is possible to cope with an increase in the time required to convey the sheet due to abrasion or the like, and the sheet conveying means does not stop before the conveyance of the sheet is completed. To prevent the occurrence of

[0024] The sheet conveying apparatus of the present invention is characterized in that the passage required time measuring means is provided in a sheet conveying area in which the sheet conveying means is provided.

In the above-mentioned sheet conveying apparatus, the passage time measuring means is provided in the area where the sheet conveying means conveys the sheet. Therefore, even if the sheet conveying time by the sheet conveying means becomes long, the sheet is reliably detected. it can.

The sheet conveying device according to the present invention is characterized in that the sheet conveying means rotates in a direction in which the sheet is conveyed, and that the sheet conveying means rotates following the feed roller when one sheet is fed. And a separation roller that rotates in a direction to reverse the sheet when the sheets are double-fed, and the passing time measuring means includes a pair of sheet detection sensors arranged apart from the sheet conveyance path. , Is characterized by.

The sheet conveying device conveys a sheet by sandwiching the sheet between a feed roller and a separation roller. When the feed roller is worn and the sheet conveyance time is longer than a predetermined time, the pair of detection sensors detects that the required passage time is longer than the predetermined time.

[0028] The image forming apparatus of the present invention may include any one of the above.
And an image forming unit for forming an image on a sheet conveyed by the sheet conveying device.

[0029]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A sheet conveying apparatus according to an embodiment of the present invention and a copying machine which is an image forming apparatus provided with the sheet conveying apparatus in a main body will be described with reference to FIGS.

As shown in FIG. 1, a sheet conveying device 104 according to an embodiment of the present invention includes a copying machine 10 as an image forming apparatus.
0 and constitutes a part of the copying machine 100. In addition to the copying machine, the present sheet conveying apparatus can be provided in a main body of a facsimile, a printer, or a composite device thereof.

Since the mechanical portion of the sheet conveying device 104 is the same as that of the conventional sheet conveying device 4, the same portions are denoted by the same reference numerals.

The sheet transporting device 104 includes the sheet loading table 1
02, a large number of sheets S stacked on the image forming unit 11
8.

The copying machine 100 includes a sheet stacking table 102 in which a large number of sheets S are stacked and stored on one side of the copying machine body 101.
A plurality of sheet supply cassettes 1 each having a predetermined amount of sheets S stacked and stored in a lower portion inside the copying machine main body 101;
1 is provided.

Near the sheet stacking table 102 and the sheet supply cassettes 1, 1, separation roller pairs (sheet conveying means) 3, 3, 3 of retard separation type are provided, respectively. The separation roller pair 3 includes a feed roller 12
And a retard roller 13.

The sheet S in the sheet stacking table 102 and the sheet S in the sheet supply cassettes 1 and 1 are fed by a pickup roller 2, separated and conveyed by respective separation roller pairs 3, 3, and rotated. It is sent to the stopped registration roller pair 110, where the skewed state is corrected.

Next, a pair of registration rollers 110 rotating at a timing with respect to the latent image formed on the photosensitive drum 111 causes the transfer between the photosensitive drum 111 and the transfer charger 112 constituting the image forming means 118. The toner image on the photosensitive drum 111 is transferred here.

Thereafter, the sheet S is sent to a fixing unit (fixing roller pair) 115 by a conveyor belt 113. The transferred toner image is fixed on the sheet.

The copying machine 100 has a duplex copying mode for performing duplex copying on the sheet S and a multiplex copying mode for performing multiple copying. In the case of the normal copy mode, the sheet S after the fixing process is transferred to the main body 10 by the outer sheet discharge roller pair 117.
The sheet is discharged onto the outside sheet discharge tray 119.

In the case of the duplex copying mode and the multiple copying mode, the sheet S after the fixing process is passed through the re-sheet supply path 120 and the duplex transport path 126 by the inner sheet discharge roller pair 116 or the switchback roller pair 127. And is temporarily loaded and stored on the intermediate tray 121.

Sheets S stored on the intermediate tray 121
Is conveyed to the registration roller pair 110 for image formation again by the sheet re-supply roller pair 130, and thereafter discharged out of the main body 101 through the same process as for one-sided copying.

FIG. 2 is a block diagram of the control device 40 for the sheet conveying device provided in the main body 101 of the copying machine 100. The control device 40 receives a detection signal from the first and second sheet detection sensors 28 and 29 that have detected each sheet fed by the pickup roller 2 and passed through the separation roller pair 3 when the copying operation has started. Input sequentially. The first and second sheet detection sensors 28 and 29 constitute required time measuring means 43. The first and second sheet detection sensors 28 and 29 are provided in an area where the separation roller pair 3 can convey a sheet.

Then, the control device 40 calculates a transport timing t until each sheet reaches the second sheet detection sensor 29 from the first sheet detection sensor 28 based on this signal. Then, the sensor storage timing t for the predetermined number n is stored by the timing storage unit 41. further,
The transfer timing t sent by the ratio calculating means 42 every n sheets is out of the range of the predetermined numerical values L and M, that is, L <
Calculate the ratio k that is not t <M.

According to the experiments so far, when a large number of sheets are conveyed and the number of conveyed sheets is small, the frequency distribution of the sheet passing timing is drawn, and as shown in FIG. 7, the conveyance timing t is distributed like a normal distribution. It has been known.
Further, when the number of sheets conveyed increases and the conveying force decreases, the distribution state gradually moves from the state shown by the curve b to the direction a, and as the endurance advances, it becomes the state shown by the curve d, causing a delay jam. Was.

Therefore, as shown in FIG. 5, the values of L and M are set so that, for example, the average value of the transfer timing t of a predetermined number of sheets among the small number of sheets is interposed, and L <t <M
By calculating the probability K other than the above, it is possible to know a decrease in the conveying force of the roller.

Here, when the ratio K in which the transport timing t is other than L <t <M becomes larger than the predetermined value R, Tjam is delayed by a predetermined time S [ms] as shown in FIG. By doing so, even when the conveyance force is reduced and the distribution of the sheet passage timing becomes like the curve d, the jam is prevented because the Tjam is delayed by S as shown in FIG. it can.

Here, n = 500, L is the average value of t of 500 sheets of initial passing sheets−10 ms (average value−10 m
s), M is the average value of t of 500 sheets that passed the initial time +10
ms (average value +10 ms), R is 5%, and S is 5 ms, the following operation is performed.

That is, the sheet passing timing t of the 500 initial passing sheets is measured, stored, and the average value is calculated. Thereafter, the probability K of a sheet that has passed a value other than the average value −10 ms <t <average value + 10 ms is calculated every 500 sheets. If K is less than 5%, no special action takes place, but if K exceeds 5%, Tjam is delayed by 5 ms.

Here, 8000 K sheets before a jam occurs
3 is shown in FIG. The left end is before jam occurs 80
The number of K is 00, and the right end is K when a jam occurs (L indicates an average value of −10 ms for 500 sheets of initial paper passing, and M indicates an average value of +10 ms). Here, if R is set to 5%, K exceeds 4% before 4,500 sheets. At this time, by delaying Tjam by 5 ms, it is possible to prevent the occurrence of a jam at the right end.

Next, the Tjam changing operation of the sheet conveying device 104 thus configured will be described with reference to the flowchart shown in FIG.

The copying operation of the copying machine is started, and the sheet S fed by the pickup roller 2 is detected by the first and second sheet detecting sensors 28 and 29 and conveyed. Then, the first and second sheet detection sensors 28 and 29 detect the passage of the sheet S (step 1). Then, the detection signals are sequentially input to the control device 40, and the control device 40 calculates the conveyance timing t for each sheet conveyed based on the detection signals. The storage unit 41 stores a predetermined number (n) of t (step 2), and the ratio calculation unit 42 calculates a ratio K where t is out of the range of the predetermined numerical values L and M (step 3). If it is less than R (step 4), the jam detection timing control means 31 does not operate, and the feed roller 12 continues normal sheet conveyance.

On the other hand, when the number of conveyed sheets increases and the durability of the feed roller 12 advances, and the friction coefficient μ of the outer peripheral surface of the feed roller 12 decreases due to the accumulation of sheet powder or foreign matter,
The probability K gradually increases, and eventually becomes larger than the predetermined value R.

When the probability K exceeds the predetermined value R (step 4), the ratio calculating means 42 sends a signal to the jam detection timing control means 31, and the jam detection timing control means 31 delays Tjam by a predetermined time S (step 5). ).

As described above, the predetermined number n of t is stored,
Calculate the probability K that t is out of the range between the predetermined values L and M,
When K is larger than the predetermined value R, the occurrence of a delay jam can be prevented by delaying Tjam by a predetermined time.

However, if K repeatedly becomes larger than the predetermined value R, the jam detection timing may be infinitely delayed. In such a case, a part of the copying machine may be damaged. Therefore, the maximum jam detection timing (TMax) may be set, and if Tjam becomes longer than that, an abnormality may be displayed on the operation unit.

The Tjam control can be applied not only to the sheet supply unit but also to any part of the sheet conveyance unit where jam detection is performed.

[0056]

According to the sheet conveying apparatus of the present invention, when the conveying force of the sheet conveying means decreases, the conveying time of the sheet conveying means can be lengthened to prevent the occurrence of a jam.

In the sheet conveying apparatus according to the present invention, the passage time measuring means is provided in the area where the sheet conveying means conveys the sheet. Can be detected.

Since the image forming apparatus of the present invention is provided with the sheet conveying device in which the occurrence of a jam is prevented, an image can be accurately formed on a sheet.

[Brief description of the drawings]

FIG. 1 is a schematic front sectional view of a copying machine which is an image forming apparatus provided with a sheet conveying device according to an embodiment of the present invention.

FIG. 2 is a block diagram of a control circuit of the sheet conveying device of FIG.

FIG. 3 is a graph showing the behavior of 8,000 K sheets before a jam occurs.

FIG. 4 is a flowchart illustrating jam detection timing control in the sheet conveying apparatus of FIG. 1;

FIG. 5 is a diagram of a frequency distribution of transport timing according to the embodiment of the present invention.

FIG. 6 is a front sectional view of a conventional sheet conveying apparatus.

FIG. 7 is a diagram illustrating a transition of a frequency distribution of conveyance timing in the sheet conveying apparatus.

[Explanation of symbols]

 S sheet 1 sheet supply cassette 3 separation roller pair (sheet conveying means) 12 feed roller 13 retard roller 27 sheet conveying path 28 first sheet detection sensor 29 second sheet detection sensor 31 jam detection timing control means 40 control device 41 timing storage means 42 Ratio Calculation Means 43 Required Time Measurement Means 100 Copying Machine (Image Forming Apparatus) 101 Copying Machine Main Body 102 Sheet Loading Table 104 Sheet Conveying Device 111 Photosensitive Drum 112 Transfer Charger 118 Image Forming Means

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3F048 AA02 AA04 AA05 AB01 BA05 BB02 CA04 CC01 CC11 DA06 3F049 AA01 LA02 LA05 LA07 3F343 FA02 FB02 FB03 FB04 FC03 GA01 GB01 GC01 GD01 MA03 MA15 MA44 MB03 MB15 MC04 MC08

Claims (4)

[Claims] A sheet conveyance unit that operates for a predetermined time to convey a sheet; a sheet conveyance path that guides a sheet conveyed by the sheet conveyance unit; and a sheet conveyance path that passes a predetermined distance of the sheet conveyance path. The time required for the passing required time measuring means to measure each passing sheet, and stores the measurement result for each sheet by the required passing time measuring means, the number of sheets conveyed other than a predetermined passing time, A control device for extending an operation time of the sheet conveying means when a ratio of the number of sheets within the predetermined passage time to the number of sheets exceeds a predetermined ratio. 2. A sheet conveying apparatus according to claim 1, wherein said passage time measuring means is provided in a sheet conveying area of said sheet conveying means. 3. A feed roller rotating in a direction in which a sheet is transported, wherein the sheet transport means rotates following the feed roller when one sheet is fed.
A separation roller that rotates in a direction to reverse the sheet when the sheet is multi-fed; and a pair of sheet detection sensors arranged so as to be separated from the sheet conveyance path by the passage required time measurement unit. The sheet conveying device according to claim 1, further comprising: 4. The sheet conveying device according to claim 1, further comprising: an image forming unit configured to form an image on a sheet conveyed by the sheet conveying device. An image forming apparatus comprising: