JP2017013910A - Image generating apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect overload of sheets more accurately than conventional method.SOLUTION: An image generating apparatus counts transportation time from start of transportation of sheets to the timing where the sheets reach a predetermined position on a transportation path. The image generating apparatus determines whether the transportation time exceeds overload threshold Tk for detecting overload. The image generating apparatus determines that there is no overload of the sheets in a case where transportation time does not exceed the overload threshold Tk. On the other hand, the image generating apparatus does not determine that there is no overload in a case where the transportation time exceeds the threshold Tk.SELECTED DRAWING: Figure 13

Description

  The present invention relates to an image forming apparatus.

  The image forming apparatus has a stacking unit for stacking sheets. Examples of the stacking unit include a paper feed cassette and a manual feed tray provided inside the image forming apparatus. When sheets exceeding the number of sheets assumed in the design are stacked on these stacking units, a feeding failure such as a conveyance delay or a jam may occur. According to Patent Document 1, an image forming apparatus that detects an overload by measuring the height of a sheet bundle described in a cassette in an analog manner using a sensor is proposed.

JP 05-278896 A

  However, in the technique described in Patent Document 1, if the sheet is wavy, the height of the sheet bundle is erroneously measured, and thus an erroneous determination of overloading may occur. Accordingly, an object of the present invention is to detect sheet overloading more accurately than in the past.

According to the present invention, for example,
A housing,
Stacking means for stacking sheets, and stacking means that can be inserted into and removed from the housing;
Insertion / removal detection means for detecting insertion / removal of the loading means;
Conveying means for conveying the sheet;
Timing means for timing the conveyance time from when the conveyance means starts conveying the sheet until the sheet arrives at a predetermined position in the conveyance path;
Whether or not sheets are overloaded on the stacking means based on whether or not the transport time of the first transported sheet after the removal / insertion detecting means detects the insertion / removal of the stacking means exceeds the overload threshold. An overload judging means for judging;
An image forming apparatus is provided.

  According to the present invention, it is possible to detect sheet overloading more accurately than in the past by paying attention to the sheet conveyance time.

Schematic sectional view of the image forming apparatus Diagram showing control system Diagram showing sheet feeding from the paper cassette The figure which shows the relationship between the detection signal output from a sheet sensor, and conveyance time The figure which shows an example of the conveyance time and conveyance delay about the sheet | seat bundle which is not overloaded Perspective view of paper cassette Cross section of paper cassette Perspective view showing side regulating plate, middle plate, rear end regulating plate and locking claw Diagram showing an example of overloading Diagram showing the behavior of overloaded sheets The figure which shows an example of the conveyance time of the sheet | seat with which it overloaded Diagram showing the behavior of overloaded sheets Diagram showing the relationship between overload threshold and transport time Diagram showing the behavior of overloaded sheets Flow chart showing overload determination Diagram explaining cancellation of overload notification The figure which shows the overload judgment method when jam occurs Flow chart showing overload determination Diagram illustrating double feeding of overloaded sheets Diagram illustrating double feeding of overloaded sheets The figure which shows an example of the measurement result of the sheet size in double feed The figure explaining the function of CPU

<Example 1>
[Configuration of Image Forming Apparatus]
The image forming apparatus 100 will be described with reference to FIG. The image forming apparatus 100 in this embodiment is an electrophotographic printer, but an image forming apparatus to which the present invention can be applied may employ other image forming methods such as an ink jet method and a thermal transfer method. The image forming apparatus 100 may be realized as a copying machine, a multifunction machine, or a facsimile machine. The image forming apparatus 100 includes four image forming units (stations), and forms yellow (Y), magenta (M), cyan (C), and black (K) toner images. In FIG. 1, the four image forming units are assigned Y, M, C, and K, which are reference symbols associated with colors, respectively. The photosensitive drum 1 is a photosensitive member and an image carrier, and rotates clockwise at a predetermined peripheral speed (process speed). The charging roller 2 uniformly charges the surface of the photosensitive drum 1. The optical scanning device 9 outputs a light beam corresponding to the image signal. The light beam is applied to the surface of the photosensitive drum 1 to form an electrostatic latent image. The developing roller 6 attaches toner and develops the electrostatic latent image to form a toner image. The YMCK toner images are transferred onto the intermediate transfer belt 12 in a superimposed manner by the primary transfer roller 11 to form a multicolor image.

  The sheet feeding cassette 23 is an example of a stacking unit that stacks sheets and can be inserted into and removed from the casing 101 of the image forming apparatus 100. The sheet S accommodated in the paper feed cassette 23 is picked up by the pickup roller 35 and sent out to the conveyance path by the feed roller 24. The pickup roller 35 and the feed roller 24 are examples of a conveying unit that conveys a sheet. The skew correction is executed when the leading edge of the sheet S hits the registration roller 17. The sheet S is conveyed to the secondary transfer unit by the registration roller 17. The toner image conveyed by the intermediate transfer belt 12 is secondarily transferred to the sheet S by the secondary transfer roller 16 of the secondary transfer portion. The fixing device 18 fixes the toner image on the sheet S and discharges it to the outside of the image forming apparatus 100.

  The manual feed tray 38 is an example of a stacking unit that stacks sheets. By rotating the manual feed tray 38 around the fulcrum 37, the manual feed tray 38 is switched between a storage state in which the manual tray 38 is stored in the image forming apparatus 100 and a use state in which the sheets S can be stacked. The sheet S stacked on the manual feed tray 38 is picked up by the paper feed roller 36, sent out to the transport path by the transport roller 39, and heads toward the registration roller 17. The sheet feeding roller 36 and the conveying roller 39 are examples of a conveying unit that conveys a sheet.

  The controller 50 is a control unit that comprehensively controls the entire image forming apparatus 100. The operation unit 59 has a display device and an input device. The controller 50 uses the sheet sensor 52 to determine whether a conveyance delay or a jam has occurred. Since the sheet sensor 52 is disposed near the registration roller 17, it may be referred to as a registration sensor. The sheet sensor 52 is used to detect the leading edge and trailing edge of the sheet S, and to detect the conveyance time of the sheet S and the size in the conveyance direction.

[Controller functions]
The function of the controller 50 will be described with reference to FIG. By executing a control program stored in the CPU 51 or the storage device 55, the entire image forming apparatus 100 is controlled in an integrated manner. The storage device 55 has a memory such as a ROM or a RAM. The controller 50 sets image forming conditions according to the image forming mode designated from the operation unit 59. The image forming conditions are, for example, the conveyance speed of the sheet S and the fixing temperature of the fixing device 18. The image forming mode may include, for example, a plain paper mode for forming an image on plain paper, a thick paper mode for forming an image on thick paper, and an envelope mode for forming characters on an envelope. The controller 50 holds the image forming conditions for each image forming mode in the storage device 55 and reads out the image forming conditions corresponding to the designated image forming mode.

  The CPU 51 measures the conveyance time T using a sheet sensor 52 that determines whether a conveyance delay or a jam has occurred. When the sheet S causes conveyance delay or jam in the conveyance path, the CPU 51 displays a message indicating that the conveyance delay or jam has occurred on the display unit of the operation unit 59. When the CPU 51 detects overloading of sheets S on the paper feed cassette 23 or the manual feed tray 38, the CPU 51 displays a message indicating that overloading has occurred on the display unit of the operation unit 59. The conveyance delay is a phenomenon in which the conveyance time T of the sheet S becomes so long that the accuracy of the image forming position cannot be guaranteed, and may be called a conveyance error or a conveyance error. In a narrow sense, the jam is a phenomenon in which the sheets S are stacked or jammed in the conveyance path. A phenomenon in which a large conveyance resistance is imparted to the sheet S due to overloading in the sheet feeding cassette 23 and no sheet S can be conveyed is a kind of jam. As described above, overloading may cause a case in which the sheet S is successfully fed from the sheet feeding cassette 23 but the transport time T is too long or the feeding is failed.

  The CPU 51 uses the surface sensor 53 to lift up (raise) the surface of the uppermost sheet S of the plurality of sheets S stacked in the sheet feeding cassette 23 to a predetermined height H. Detect whether or not. That is, the surface sensor 53 is an example of a surface detection unit that detects whether the surface of the sheet S stacked on the intermediate plate 43 has been raised to a predetermined height by the motor 60. The CPU 51 uses the position sensor 54 to detect the position of the trailing edge regulating plate 41 (FIG. 6) that regulates the position of the trailing edge of the sheets S stacked in the sheet feeding cassette 23. The position sensor 54 is an example of a position detection unit that detects the position of the rear end regulating plate 41.

  The motor 57 is a drive source that drives conveying rollers such as the pickup roller 35 and the feed roller 24. The CPU 51 outputs a paper feed start signal to the drive circuit 56 that drives the motor 57. When the drive circuit 56 receives the paper feed start signal, the drive circuit 56 starts driving the motor 57. The CPU 51 sets the conveyance speed corresponding to the image forming mode in the drive circuit 56 in advance. The motor 57 rotates at a rotation speed corresponding to the set conveyance speed. The motor 60 is a so-called lift-up motor, and is a motor that lifts up the intermediate plate on which the sheet S is placed in the paper feed cassette 23. The motor 60 is an example of a raising unit that raises the middle plate so that the sheet S stacked on the middle plate, which is a plate member, comes into contact with the pickup roller 35. The CPU 51 drives the motor 60 so that the uppermost sheet Sa of the surface sensor 53 becomes the height H. The cassette sensor 61 is an example of an insertion / removal detection unit that detects that the paper feed cassette 23 has been inserted / removed from the housing 101 of the image forming apparatus 100. The paper feed cassette 23 is, for example, a drawer-shaped cassette. When the operator stores the sheet S, the paper feed cassette 23 is pulled out from the housing 101. When the storage of the sheet S is completed, the paper feed cassette 23 is inserted into the housing 101. The CPU 51 detects the insertion / removal of the paper feed cassette 23 using the paper feed cassette 23.

  As shown in FIG. 3, when the leading edge of the sheet S tilts a flag 49 provided near the registration roller 17, the sheet sensor 52 outputs a detection signal indicating that the leading edge of the sheet S has been detected to the controller 50. The CPU 51 uses a timer or a counter to measure the conveyance time from the timing when the conveyance of the sheet S is started to the timing when the sheet sensor 52 detects the leading edge of the sheet S. The CPU 51 may obtain a difference between time data acquired from a real time clock (RTC) in order to measure the conveyance time.

  FIG. 4 is a diagram illustrating an example of a detection signal of the sheet sensor 52. The horizontal axis indicates time, and the vertical axis indicates the level of the detection signal. Conveyance of the first sheet S is started at time t1. At time t2, the leading edge of the sheet S arrives at the sheet sensor 52, and the detection signal changes from OFF to ON. The CPU 51 determines the time from time t1 to time t2 as the conveyance time T1 of the first sheet S. At time t3, the trailing edge of the first sheet S passes through the sheet sensor 52, and the level of the detection signal is switched from ON to OFF. At time t4, conveyance of the second sheet S is started. At time t5, the leading edge of the second sheet S arrives at the sheet sensor 52, and the detection signal changes from OFF to ON. The CPU 51 determines the time from time t4 to time t5 as the conveyance time T2 for the second sheet S. At time t6, the trailing edge of the second sheet S passes through the sheet sensor 52, and the level of the detection signal is switched from ON to OFF.

  FIG. 5A shows an example of the conveyance time when a plurality of sheets S are continuously fed. The conveyance time T may vary slightly depending on the state of wear of the pickup roller 35 and the type of sheet S (thickness, basis weight, bag shape, presence or absence of a surface coat, etc.). However, if a plurality of sheets S are normally stacked on the sheet feeding cassette 23 and no jam occurs, the conveyance time of each sheet S falls within the allowable range X.

  FIG. 5B shows an example of the conveyance time when a plurality of sheets S are continuously fed. In particular, a conveyance delay (conveyance error) occurs in the fifth sheet S. As shown in FIG. 5B, a conveyance delay may occur in the second and subsequent sheets S after the job is started. The CPU 51 monitors the conveyance time T of each sheet S, and determines whether or not the conveyance time T exceeds the delay threshold Tm. When the conveyance time T exceeds the delay threshold Tm, the CPU 51 determines that a conveyance delay has occurred, discharges all sheets S remaining in the conveyance path, and stops the motor 57. The delay threshold Tm for determining the conveyance delay is set to a value that deviates from the allowable range X and is larger than the upper limit value of the allowable range X. If the conveyance time exceeds the delay threshold value Tm, the accuracy of image formation on the sheet S is not guaranteed, and the CPU 51 stops image formation.

  The CPU 51 may feed the first sheet S in advance, and wait the first sheet S by the registration roller 17 until the image forming unit is ready. In this case, even if the conveyance time T of the first sheet S exceeds the delay threshold Tm, the CPU 51 does not have to determine the conveyance delay for the first sheet S. That is, for the first sheet S, the conveyance delay determination process may be skipped. The time from the start of the job until the image forming unit is ready is the general transport time T (the transport distance from the position of the leading edge of the sheet S stored in the paper feed cassette 23 to the sheet sensor 52 is transport speed. Longer than the conveyance time obtained by dividing by. Therefore, the tolerance for the conveyance delay of the first sheet S is large. As described above, in this embodiment, the conveyance delay determination is applied to the second and subsequent sheets S.

  However, the first sheet S may not reach the flag 49 even if the conveyance time T when the first sheet feeding operation is performed for the first sheet S greatly exceeds the threshold value Tm. That is, the CPU 51 may not be able to detect the leading edge of the sheet S even if the count value of the timer exceeds the retry threshold Tr (the threshold Tm may be adopted as the retry threshold Tr). In this case, the CPU 51 instructs the drive circuit 56 to perform a second paper feeding operation (retry). Note that the CPU 51 may continue to count the conveyance time T from the first paper feeding operation even during the retry. If the first sheet S does not reach the flag 49 even when the transport time T exceeds the jam threshold Tj, the CPU 51 determines that a jam has occurred. When the CPU 51 detects a jam, the CPU 51 displays a message indicating that a jam has occurred on the operation unit 59 or transmits the message to the address of the person in charge of maintenance via the communication device 58. The message can be delivered by e-mail, for example.

[Structure of paper cassette]
The configuration of the paper feed cassette 23 will be described with reference to FIGS. As described above, the paper feed cassette 23 can be inserted into and removed from the casing 101 of the image forming apparatus 100. As shown in FIG. 6, the paper feed cassette 23 has a cassette basket 40. A rear end regulating plate 41 that is movable in both directions (which may be referred to as the front-rear direction) of the conveying direction of the sheet S and the opposite direction thereof is provided on the bottom surface inside the cassette bag 40. The operator moves the trailing edge regulating plate 41 according to the size of the sheet S. The rear end regulating plate 41 is an example of a regulating unit that regulates and aligns the position of the rear end of the sheet S. As a result, the conveyance of the plurality of sheets S is started from substantially the same position. The position of the rear end regulating plate 41 is detected by the position sensor 54 described above. Two side regulating plates 42 that are movable in a direction (also referred to as a left-right direction or a width direction) orthogonal to the conveyance direction of the sheet S are provided on the bottom surface of the cassette basket 40. The two side regulating plates 42 regulate and align the positions of both ends of the sheet S. The intermediate plate 43 is a plate member that is provided in the paper feed cassette 23 and on which the sheets S are stacked, and rotates about a fulcrum 44.

  As shown in FIG. 7A, when the paper feed cassette 23 is pulled out of the housing 101, the intermediate plate 43 is positioned near the bottom surface of the cassette basket 40. The operator stacks a bundle of sheets S on the sheet feeding cassette 23 and manually moves the rear end regulating plate 41 so that the rear end regulating plate 41 abuts on the rear end of the sheet S stacked on the middle plate 43. Similarly, the operator manually moves the side regulating plate 42 so that the side regulating plate 42 abuts against the left end and the right end of the sheets S stacked on the middle plate 43. Thereby, the bundle of sheets S stacked on the intermediate plate 43 is aligned in both the front-rear direction and the left-right direction.

  As shown in FIG. 7B, when the CPU 51 detects that the paper feed cassette 23 has been inserted into the housing 101 by the cassette sensor 61, the CPU 51 drives the lift-up motor 60 to raise the intermediate plate 43. . As a result, the intermediate plate 43 rotates around the fulcrum 44. When the uppermost sheet S pushes up the surface flag 46, the surface sensor 53 outputs a detection signal indicating that the sheet S has been detected to the CPU 51. For example, as shown in FIG. 7B, when the surface of the sheet S reaches the height H, the surface sensor 53 outputs a detection signal. The CPU 51 recognizes that the surface of the sheet S has reached the height H based on the detection signal, and stops the motor 60. Note that the lower the number of sheets S stacked on the intermediate plate 43, the more the intermediate plate 43 is raised and the longer the operation time of the motor 60 is. On the contrary, as the number of stacked sheets S increases, the rising amount of the middle plate 43 decreases, and the operation time of the motor 60 decreases. That is, the CPU 51 can estimate the number of sheets S stacked on the intermediate plate 43 by measuring the operating time of the motor 60 with a timer or a counter. Each time the sheet S is fed to the conveyance path, the position of the surface of the uppermost sheet S stacked on the intermediate plate 43 is lowered. When the surface sensor 53 no longer detects the surface of the sheet S, the CPU 51 drives the motor 60 again to lift up the sheet S.

  In this way, by providing the rear end regulating plate 41 and the like, the sheets S stacked in the sheet feeding cassette 23 are always fed from the same position in the transport direction without depending on the number of stacked sheets. Further, the pressure applied to the sheets S by the pickup roller 35 by the lift-up of the intermediate plate 43 is always kept constant without depending on the number of stacked sheets.

  The sheet feed cassette 23 is provided with an upper limit value (upper limit number of sheets) for the height of the bundle of sheets S. If the height of the bundle of sheets S is equal to or less than the upper limit value, it is guaranteed by design that the image forming apparatus 100 can form an image normally. As shown in FIG. 8, a mark 72 indicating an upper limit value is provided on the side surface of the side regulating plate 42. The mark 72 may be affixed or a groove.

  As shown in FIG. 8, the rear end regulating plate 41 is provided with two locking claws 47. The locking claw 47 prevents the sheet S from riding on the rear end regulating plate 41. When the sheet S rides on the rear end regulating plate 41, the carried sheet S is shifted to the upstream side (rear) in the transport direction. As a result, the conveyance time T measured by the sheet sensor 52 becomes longer than the normal conveyance time of the sheet S. This causes an error in detecting overloading based on the conveyance time T or measuring the length of the sheet S in the conveyance direction based on the conveyance time T. Therefore, the latching claw 47 is provided on the rear end regulating plate 41. The height of the surface of the locking claw 47 facing the surface of the sheet S is substantially the same as the upper limit value of the height of the bundle of sheets S.

  As described above, the position sensor 54 is provided in order to detect which sheet S the rear end regulating plate 41 is arranged at a position corresponding to the size. The CPU 51 determines the size of the sheets S stacked on the paper feed cassette 23 based on the position of the trailing edge regulating plate 41 detected by the position sensor 54. However, when the trailing edge regulating plate 41 is correctly positioned according to the sheet size, the sheet size discrimination accuracy is high, but when the trailing edge regulating plate 41 is positioned away from the trailing edge of the sheet S, the discrimination result is obtained. Is wrong. Therefore, the CPU 51 uses the sheet size information input from the input device of the operation unit 59, the sheet size information received from the host computer through the communication device 58, the sheet size information obtained from the conveyance time T, and the like. Thus, the sheet size may be determined.

[Overloading in paper cassette]
A state in which the sheets S are overloaded on the sheet feeding cassette 23 will be described in detail. Here, an overloading case in which sheets S are stacked on the locking claws 47 and an overloading case in which the sheets S are forcibly stacked under the locking claws 47 will be described (stacking on the locking claws 47). Case)
As shown in FIG. 9, when a large number of sheets S are stacked up to a height exceeding the design upper limit value, some sheets S run on the locking claws 47. The upper limit number corresponding to the upper limit value varies depending on the thickness of the sheet S. Since some of the sheets S that have run on the locking claws 47 are not restricted in position in the conveyance direction by the trailing edge regulating plate 41, they are located upstream in the conveyance direction (that is, in a direction opposite to the conveyance direction). It will shift.

  10A to 10D show the behavior of the sheet S when a small amount of the sheet S is overloaded on the locking claw 47. FIG. As shown in FIG. 10A, the leading edge of the sheet Sa that is overloaded so as to ride on the locking claw 47 is shifted in the opposite direction to the conveying direction. Note that the pickup roller 35 is not in contact with the sheet Sa at a time before the start of conveyance. As shown in FIG. 10B, the CPU 51 raises the intermediate plate 43 or lowers the pickup roller 35 to bring the pickup roller 35 into contact with the overloaded sheet Sa. The pickup roller 35 is raised and lowered by a drive source driven by the CPU 51 such as a motor or a solenoid. As shown in FIG. 10B, since the amount of deviation in the transport direction of the overloaded sheets S is small, the pickup roller 35 is placed on the sheet Sa positioned at the top of the bundle of sheets S. Can touch. Therefore, as shown in FIG. 10C, the sheet S fed by the pickup roller 35 is the uppermost sheet Sa. As shown in FIG. 10D, the leading edge of the fed sheet Sa pushes down the flag 49 and further strikes the nip portion of the registration roller 17.

  At the timing when the CPU 51 outputs a control signal for instructing the sheet feeding to the drive circuit 56, the leading edge position of the sheets Sa is upstream from the leading edge position of the normally stacked sheets S. That is, the conveyance distance from the leading edge position of the sheet Sa to the flag 49 is longer than the conveyance distance from the leading edge position of the normally stacked sheets S to the flag 49. That is, the conveyance time T of the sheet Sa is longer than the conveyance time of the normally stacked sheets S. The normally stacked sheets S are sheets S constituting a sheet bundle having a height equal to or lower than the upper limit value. That is, the normally stacked sheets S are the sheets S stacked at positions assumed by design in both the transport direction and the height direction.

  As shown in FIG. 11A, the transport time T of the five overloaded sheets Sa exceeds the upper limit value of the allowable range X, but does not exceed the delay threshold value Tm for determining the transport delay. Not in. Since the sixth and subsequent sheets S are normally stacked, the transport time T falls within the allowable range X. However, as shown in FIG. 11B, when the transport time T deviates from the allowable range X and further exceeds the delay threshold value Tm, the CPU 51 determines that a transport delay (transport error) has occurred, and transport path After all the sheets S existing in the sheet are discharged, the image formation is stopped.

  On the other hand, as illustrated in FIG. 12A, the overloading amount of the sheets S may further increase, and the overloaded sheets Sa may be further shifted and stacked on the downstream side. As shown in FIG. 12B, even if the pickup roller 35 is lowered, the sheet Sa cannot be contacted, and contacts the sheet Sb stacked below the sheet Sa. Since the sheets Sb are stacked below the locking claws 47, they are stacked at a normal position in the transport direction. For this reason, the sheet picked up when the pickup roller 35 begins to rotate is the sheet Sb. When the sheet Sb starts to move, the overloaded sheet Sa stacked on the sheet Sb is conveyed together with the sheet Sb while being on the sheet Sb.

  As shown in FIG. 12C, when the overloaded sheet Sa contacts the pickup roller 35, the sheet Sb loses contact with the pickup roller 35 even though the sheet Sb has not yet reached the feed roller 24. Stops on the spot. As shown in FIG. 12D, only the sheet Sa is conveyed by the pickup roller 35 by the pickup roller 35 and reaches the flag 49. Note that the second and subsequent sheets Sa that are overloaded are conveyed to a position where they can contact the pickup roller 35 as shown in FIGS. That is, the subsequent behavior is the same as the behavior of the sheet Sa described with reference to FIGS. 10 (A) to 10 (D).

  As shown in FIG. 12A, the leading edge position of the uppermost sheet Sa among the overloaded sheets Sa is upstream of the leading edge position of the normally stacked sheets Sb. It is shifted to. Therefore, the conveyance time T of the sheet Sa is longer than the conveyance time T of the sheet Sb. Therefore, the CPU 51 can determine whether or not overloading has occurred based on the conveyance time T of the sheet Sa.

[Judgment of overloading]
A procedure for determining overloading in the paper feed cassette 23 will be described in detail. As described above, the transport time T of the overloaded sheets Sa is longer than the transport time T of the normally stacked sheets S, but does not exceed the delay threshold Tm. Therefore, as shown in FIG. 13, an overload threshold Tk is defined. The overload threshold Tk is not less than the upper limit value of the allowable range X and is less than the delay threshold Tm. The CPU 51 determines the presence / absence of overloading by comparing the transport time T of the sheet S detected using the sheet sensor 52 with the overload threshold Tk. That is, when the conveyance time T of the sheet S exceeds the overload threshold Tk, the CPU 51 determines that the sheet S is an overloaded sheet. Further, if the transport time T of the sheet S does not exceed the overload threshold Tk, the CPU 51 determines that the sheet S is a normally stacked sheet. As described above, the CPU 51 can detect the sheet S which is not delayed as much as the conveyance delay as an overloaded sheet. Note that when the transport time T of the sheet S transported from the second sheet onward after the start of the image forming job exceeds the delay threshold Tm, the CPU 51 determines a transport delay and an overload.

(Execution conditions for overload detection)
(1) The CPU 51 may execute overloading when the execution condition is satisfied without always executing overloading determination. There are several possible execution conditions. In order to load the sheet S on the paper feed cassette 23, the operator needs to insert and remove the paper feed cassette 23 from the housing of the image forming apparatus 100. Therefore, after the cassette sensor 61 detects insertion / removal of the paper feed cassette 23, the CPU 51 executes overload determination for the first sheet S to be fed. That is, the execution condition is that the sheet S is the first sheet S that is fed after detecting the insertion / removal of the sheet feeding cassette 23. This is because, when sheets S are overloaded, overloading is always detected with the first sheet S, and overloading is not detected with the first sheet S, but for the first time with the second and subsequent sheets S. This is because overloading is not detected. As described above, the overload determination accuracy is improved only by applying the overload determination to the first sheet S after the paper feed cassette 23 is inserted. For example, in the control that always performs the overload determination, the overload may be erroneously detected even though the conveyance delay is caused by another factor. Therefore, if the overload determination is executed only when the execution condition is satisfied, the overload can be detected with higher accuracy.

  (2) As an execution condition, it may be adopted that the difference between the height of the seat S estimated from the operating time of the lift-up motor 60 and the upper limit value of the operation guarantee is equal to or less than a predetermined threshold value. When overloading occurs, the height of the sheet S is close to the upper limit value. Therefore, in the case where the height of the sheet S is significantly below the upper limit value, the possibility of overloading is low. In addition, if overload determination is performed in such a situation, it may be determined that overloading has occurred even though a transport delay is caused by another factor. Therefore, if the execution condition is that the height of the sheet S is close to the upper limit value, overloading can be detected with higher accuracy.

  (3) As shown in FIG. 14A, when the trailing edge regulating plate 41 is disposed at a position away from the trailing edge of the sheet S, the sheet S is disposed at a position shifted in the direction opposite to the conveying direction. End up. As a result, even for a sheet S that is not overloaded, the transport time T exceeds the overload threshold Tk. Therefore, it may be adopted that the rear end regulating plate 41 is in a correct position as an execution condition. As a result, the conveyance time T becomes longer due to the rear end restricting plate 41 being placed at the wrong position, and the possibility of erroneous detection of overloading can be reduced. The following method can be considered as a method for determining whether or not the rear end regulating plate 41 is in the correct position.

  As shown in FIG. 14B, the CPU 51 determines the time Tp from the time when the leading edge of the sheet S reaches the flag 49 to the time when the trailing edge of the sheet S leaves the flag 49, the size of the sheet S (length in the transport direction). Convert to. A length L in the transport direction is calculated by multiplying the transport speed v of the sheet S by the time Tp. On the other hand, the CPU 51 detects the position of the trailing edge regulating plate 41 by the position sensor 54 and converts the position into the size of the sheet S. The CPU 51 compares the size acquired using the sheet sensor 52 with the size acquired using the position sensor 54. If the size acquired using the sheet sensor 52 is smaller than the size acquired using the position sensor 54, the CPU 51 determines that the rear end regulating plate 41 is disposed at an incorrect position. Alternatively, the CPU 51 may compare the size specified by the operation unit 59 or the host computer with the size acquired using the position sensor 54. If the size specified by the operation unit 59 or the host computer is smaller than the size acquired using the position sensor 54, the CPU 51 determines that the rear end regulating plate 41 is disposed at an incorrect position.

(4) As the number of sheets S on which an image is formed increases, the roller surfaces of the pickup roller 35 and the feed roller 24 are worn, the roller diameter decreases, and the frictional resistance with the sheet S decreases. As the wear of the roller progresses, the conveyance distance of the sheet S conveyed by rotating the roller once decreases. Therefore, even for the sheets S of the same size, the conveyance time T gradually increases. That is, the smaller the wear of the contact member forming the surface of the roller, the higher the accuracy of the overload determination based on the transport time T. Therefore, it may be adopted that the roller wear is small as an execution condition. Only when the wear of the roller is not progressing, the accuracy of the overload judgment will be improved by executing the overload judgment.
In the image forming apparatus according to the present exemplary embodiment, when the roller (contact member) is worn to cause a conveyance delay, the conveyance time of the sheet S among 500 sheets (one cassette in the present exemplary embodiment) is not overloaded. The event that the overload threshold value Tk is exceeded even once occurs continuously for 5 times or more.

  Therefore, in the present embodiment, the CPU 51 continues the event that the conveyance time of the sheet S exceeds the overload threshold Tk even once in M sheets (for example, 500 sheets) N times (for example, 5 times) or more. If this occurs, it is determined that the wear of the pickup roller 35 and the feed roller 24 has exceeded the allowable range. The allowable range of wear is determined from the viewpoint of the accuracy of overload determination. As described above, when the wear exceeds the allowable range, the CPU 51 interrupts the overload determination. N and M are determined in advance by experiments.

  When the pickup roller 35 and the feed roller 24 are replaced, the CPU 51 may resume the overload determination. If the pickup roller 35 and the feed roller 24 are not worn so as to cause a conveyance delay, one of the K sheets (for example, 4000 sheets) S is not erroneously detected as being overloaded. In other words, none of the conveyance times of the K sheets S exceeds the overload threshold Tk. Therefore, when the CPU 51 interrupts the overload determination because it is determined that the wear has occurred, the pick-up roller 35 is based on whether or not each of the continuous conveyance times of the K sheets S exceeds the overload threshold Tk. Alternatively, it may be determined whether the feed roller 24 has been replaced with a new one. The CPU 51 restarts the overload determination if any of the conveyance times of the continuous K sheets S does not exceed the overload threshold Tk. When information indicating that the pickup roller 35 or the feed roller 24 has been replaced with a new one is input through the operation unit 59, the CPU 51 may resume the overload determination. K is determined in advance by simulation.

(flowchart)
FIG. 15 is a flowchart showing overload determination. When an image formation instruction is input from the operation unit 59 or the host computer, the CPU 51 executes the following processing.

  In S1, the CPU 51 starts feeding the sheet S. For example, the CPU 51 outputs a control signal (paper feed start signal) for causing the drive circuit 56 to start driving the motor 57. The drive circuit 56 starts driving the motor 57 based on the control signal. Note that the sheet S is fed from the paper feed port (the paper feed cassette 23 or the manual feed tray 38) designated by the job. In S2, the CPU 51 starts measuring the conveyance time T using a timer or a counter.

  In S3, the CPU 51 determines whether to execute the overload determination based on whether the overload determination execution condition is satisfied. Several conditions are listed as execution conditions, but when all the above conditions are satisfied, the CPU 51 determines to execute overload determination. Alternatively, the CPU 51 may determine that the overload determination is to be performed when any one or a plurality of conditions are satisfied. If it is determined not to execute the overload determination, the CPU 51 causes the image forming unit to form an image unless a conveyance delay is detected based on the delay threshold Tm or a jam is detected based on the jam threshold Tj. When detecting the conveyance delay, the CPU 51 stops the image formation after all the sheets S in the conveyance path are discharged from the image forming apparatus 100. Further, when the CPU 51 detects a jam, the CPU 51 stops image formation. The CPU 51 may also output a message regarding conveyance delay or jam to the operation unit 59. The CPU 51 may output a message that advises about the upper limit stacking amount of sheets S and the correct stacking method to the operation unit 59. If the overload determination execution condition is not satisfied in S3, the CPU 51 ends this process. On the other hand, if the overload determination execution condition is satisfied in S3, the CPU 51 proceeds to S4. In S4, the CPU 51 determines whether or not the sheet S is overloaded in the sheet feeding cassette 23 based on whether or not the conveyance time T exceeds the overload threshold Tk. If overloading is not detected in S4, the CPU 51 ends this process. That is, the CPU 51 continues image formation. On the other hand, if the CPU 51 determines that the transport time T exceeds the overload threshold Tk, the process proceeds to S5. In S5, the CPU 51 outputs an overload message. The CPU 51 stops the image formation after all the sheets S existing in the conveyance path are discharged. For example, the CPU 51 can detect that all the sheets S existing in the conveyance path have been discharged by a sheet sensor (not shown) installed in the discharge section of the conveyance path.

(Overload information)
A message regarding overloading may be output to the operation unit 59 or may be transmitted to a computer (such as a server of a maintenance company) on a network via the communication device 58. For example, the CPU 51 may send an overloading message indicating that overloading has occurred as an e-mail to the address of a maintenance person (maintenance company) that has a maintenance contract for the image forming apparatus 100. Note that the overload message may be transmitted to the maintenance company server using a communication protocol other than electronic mail. When a message regarding overloading is transmitted to the maintenance company, it may not be output to the operation unit 59. The maintenance company may notify the user of the image forming apparatus 100 that an overload has occurred as part of the maintenance contract by e-mail or verbally. In addition, the maintenance company may give advice on the upper limit stacking amount of the sheets S, the correct stacking method, the precautions for envelope printing, and the like.

  As described above, the CPU 51 can warn of overloading when the transport time T exceeds the overload threshold value Tk but no transport delay or jam is detected. Overloading can result in transport delays and jams. Therefore, by notifying overloading, the operator will recognize the correct loading amount and reduce the occurrence of conveyance delay and jam.

  By sending the overload message to the maintenance company, the operator can save the trouble of contacting the maintenance company. The maintenance company will be able to give appropriate advice to the operator based on the overload message received from the image forming apparatus 100.

(Delete overload message)
When the overload state is eliminated, the CPU 51 stops or deletes the output of the overload message. The condition for stopping or deleting the output of the overloading message is called a cancellation condition. Alternatively, the CPU 51 displays a cancellation message indicating that the overloading state has been canceled on the operation unit 59 or transmits it via the communication device 58. The cancellation condition may be that the cassette sensor 61 has detected that the paper cassette 23 has been inserted or removed. Further, as shown in FIG. 16, when the overloading message (overloading information) is output and the transport time T of the sheet S becomes equal to or shorter than the overload threshold Tk, the CPU 51 stops outputting the overload message. May be. The degree of overloading decreases as the sheet S is conveyed. Therefore, if the conveyance time T of the sheet S is less than the overload threshold Tk, the possibility that the overload state has been resolved is high. Thus, the fact that the conveyance time T of the sheet S is less than the overload threshold value Tk may be adopted as a cancellation condition.

<Example 2>
According to the first embodiment, when the transport time T exceeds the overload threshold Tk, the CPU 51 determines that overload has occurred. By the way, even if the sheets S are stacked under the locking claws 47, overloading may occur. As shown in FIG. 17A, when the sheet S exceeding the upper limit is forcibly pushed under the locking claw 47, the rear end portion of the sheet S is strongly pressed by the locking claw 47. For this reason, the conveyance resistance acting on the sheets S is larger than the conveyance resistance acting on the sheets S that are not overloaded. In particular, the conveyance resistance may increase as the pickup roller 35 cannot convey the sheet S. The CPU 51 determines that a jam has occurred if the leading edge of the sheet S is not detected by the sheet sensor 52 even if the elapsed time from the start of feeding exceeds the jam threshold Tj.

  It is also possible to design so that the conveyance time T is not completed unless the leading edge of the sheet S reaches the flag 49. In this case, when no sheet S can be fed, the conveyance time T cannot be measured, and the CPU 51 cannot determine overloading. Therefore, this embodiment introduces the following overload determination method.

[Judgment method of overloading]
The overload determination method according to the second embodiment will be described with reference to the flowchart of FIG. Compared to FIG. 15, in FIG. 18, S10 and S11 are inserted between S2 and S3.

  In S10, the CPU 51 determines whether or not a jam has occurred. For example, the CPU 51 determines that a jam has occurred when the leading edge of the sheet S cannot be detected by the sheet sensor 52 even after retrying J times. If a jam has not occurred, the CPU 51 proceeds to S3. On the other hand, if a jam is detected, the CPU 51 proceeds to S11.

  In S11, the CPU 51 forcibly substitutes the predetermined value Tk3 for the transport time T. As shown in FIG. 17B, the predetermined value Tk3 is smaller than the delay threshold Tm for detecting a transport error and larger than the overload threshold Tk. Thereby, even if the sheet S does not reach the flag 49, the conveyance time T is determined. Moreover, since a predetermined value Tk3 larger than the overload threshold value Tk is substituted for the transport time T, overload is detected in S4. As described above, in the second exemplary embodiment, even when a jam occurs in the first sheet S, overloading can be detected.

<Example 3>
As shown in FIG. 19A, at least a part of the overloaded sheet S may ride on the locking claw 47, and may deviate greatly in the direction opposite to the conveying direction. As shown in FIG. 19B, since the pickup roller 35 is not in contact with the uppermost sheet Sa, the sheet Sb is fed by the pickup roller 35. As shown in FIG. 19C, the sheet Sa is also transported together with the sheet Sb, and the sheet Sa reaches the paper feed position of the pickup roller 35. At this time, the sheet Sb has already reached the nip portion of the feed roller 24. Therefore, as shown in FIG. 19D, the sheet Sa and the sheet Sb continue to be conveyed thereafter. This phenomenon is called double feed. The conveyance time T timed by the CPU 51 is the time from when the sheet feeding starts to when the sheet Sb reaches the flag 49. Therefore, the transport time T may be within the allowable range X. This is because the sheet Sb is conveyed from the regular position. Therefore, in the case where double feeding occurs, overloading cannot be accurately determined based on the conveyance time T.

[Judgment of overloading]
The CPU 51 can determine that double feeding has occurred when the size designated in advance and the size actually measured using the sheet sensor 52 are different. Therefore, the CPU 51 causes overloading when the size of the sheet S acquired using the sheet sensor 52 is larger than the size corresponding to the position of the trailing edge regulating plate 41 detected by the position sensor 54. It is determined that

  As described above, the CPU 51 can detect the size in the transport direction from the elapsed time from the timing when the sheet sensor 52 detects the leading edge of the sheet S to the timing when the trailing edge is detected. As shown in FIG. 20A, the CPU 51 starts timing for obtaining the sheet size at the timing when the leading edge of the sheet Sb reaches the flag 49. As shown in FIG. 20B, the timing is stopped at the timing when the sheet Sa passes through the flag 49, and the measured elapsed time Tp is converted into the sheet size. Conversion formulas, conversion tables, and the like may be stored in the storage device 55.

  As shown in FIG. 21A, the sheet size obtained by the CPU 51 using the sheet sensor 52 is La. The sheet size obtained by the CPU 51 using the position sensor 54 is Lb. In FIG. 21A, since La> Lb is established, the CPU 51 determines that overloading has occurred. As described above, when the sheet size mismatch (La> Lb) occurs, the CPU 51 stops the image formation after discharging all the sheets S existing in the conveyance path. Further, the CPU 51 outputs information indicating that the sheet sizes do not match and information indicating that overloading has occurred to the operation unit 59 and the communication device 58.

(Execution conditions for overload detection)
As shown in FIG. 21B, when the rear end regulating plate 41 is positioned behind the rear end of the sheet S and positioned, the sheet size La and the position sensor 54 obtained using the sheet sensor 52 are used. The sheet size Lb obtained in this way may match. In this case, the CPU 51 cannot detect overloading from the sheet sizes La and Lb.

  Therefore, it may be adopted that the rear end regulating plate 41 is in a correct position as an execution condition for the overload determination. As described above, the CPU 51 acquires sheet size information designated by the operator through the operation unit 59 and the communication device 58. Therefore, if the sheet size specified by the operator matches the sheet size Lb obtained using the position sensor 54, the CPU 51 executes overload determination. On the other hand, if the sheet size designated by the operator and the sheet size Lb obtained using the position sensor 54 do not match, the CPU 51 skips overload determination. As a result, even if double feeding and overloading occur simultaneously, overloading will be detected with high accuracy.

<Summary>
The function of the CPU 51 will be described with reference to FIG. As described with reference to FIG. 4 and S2, the timing unit 70 measures the conveyance time T from when the motor 57 and the pickup roller 35 start conveying the sheet S until the sheet S arrives at a predetermined position on the conveyance path. To do. As described in S4 and the like, the determination unit 62 determines whether the transport time T of the sheet S that is transported first after the cassette sensor 61 detects the insertion / removal of the paper feed cassette 23 exceeds the overload threshold Tk. May be. The determination unit 62 determines whether or not the sheet S is overloaded in the sheet feeding cassette 23 based on whether or not the conveyance time T exceeds the overload threshold Tk. If the conveyance time T does not exceed the overload threshold Tk, the image formation control unit 63 controls the image formation unit to form an image on the sheet S. If the conveyance time T of the sheet S exceeds the overload threshold Tk, the image formation control unit 63 controls the image formation unit and does not form an image on the sheet S. In this way, it is possible to detect overloading of sheets more accurately than in the past by focusing on the sheet conveyance time without using a sensor for measuring the height of the bundle of sheets S.

  The jam detection unit 64 may detect the conveyance delay described above. That is, the jam detection unit 64 is an example of a detection unit that detects that a conveyance delay has occurred in the sheet S based on whether or not the conveyance time of the sheet S exceeds the conveyance delay threshold. The overload threshold may be the same as the transport delay threshold.

  In the image forming apparatus, the maximum stacking height or the number of stacked sheets that guarantees normal operation may be defined by design. Further, the CPU 51 may function as a stacking degree determination unit for sheets stacked in the sheet feeding cassette 23. If the CPU 51 determines that the stacking degree is a stacking capacity within a predetermined range with respect to the stacking height or the number of stacked sheets, the CPU 51 may determine whether the stacking unit 62 is overloaded. The range within a predetermined range with respect to the stacking height or the number of stacked sheets is, for example, within an accuracy variation range in which the stacking degree determination unit can determine the stacking height or the number of stacked sheets.

  As described for the execution condition of the overload determination, the ascending time required to raise the middle plate 43 may be adopted as the execution condition. The intermediate plate 43 is a plate member that descends to the lowest part when the paper feed cassette 23 is pulled out of the image forming apparatus. The raising control unit 68 controls the motor 60 through the drive circuit 56 so that the sheet S stacked on the middle plate 43 comes into contact with the pickup roller 35 to raise the middle plate 43. The measuring unit 66 measures the rising time required for raising the middle plate 43. When the rising time is less than the rising threshold, the CPU 51 determines that the loading degree is a loading capacity that is within a predetermined range with respect to the loading height or the number of loaded sheets. As described above, the determination unit 62 determines whether or not the sheet S is overloaded in the sheet feeding cassette 23 when the rising time is less than the rising threshold. Overloading can occur when the number of sheets S stacked is close to the upper limit number. Therefore, enabling the overload determination in a situation where overload is likely to occur will increase the accuracy of overload determination. Further, the determination unit 62 does not determine whether or not the sheets S are overloaded in the sheet feeding cassette 23 when the rising time is not less than the rising threshold. As a result, it is possible to suppress erroneous detection of overloading in a situation where there is a high possibility that overloading has not occurred.

  The image forming apparatus 100 may further include a surface sensor 53 that detects whether the surface of the sheet S stacked on the intermediate plate 43 has been raised to a predetermined height H by the motor 60. When the surface of the sheet S stacked on the intermediate plate 43 rises to a predetermined height H, the rise control unit 68 stops the motor 60 through the drive circuit 56. Thereby, the raising of the intermediate plate 43 is stopped. Accordingly, the position of the leading edge of the sheet S can always be maintained at the same position, and the measurement accuracy of the conveyance time T is improved. That is, the overload determination accuracy based on the conveyance time T is also improved. Further, the pressure exerted on the sheet S by the pickup roller 35 can be kept constant.

  As described for the execution condition of the overload determination, the position of the rear end regulating plate 41 may be adopted as the execution condition. The determination unit 62 determines whether or not the trailing edge regulating plate 41 is correctly positioned with respect to the size of the sheet S stacked on the sheet feeding cassette 23. For example, the determination unit 62 determines whether the position of the trailing edge regulating plate 41 detected by the position sensor 54 corresponds to the size of the sheet S stacked on the sheet feeding cassette 23. If the detected position of the trailing edge regulating plate 41 corresponds to the size of the sheet S, the determination unit 62 performs overload determination. On the other hand, the determination unit 62 does not perform the overload determination unless the detected position of the trailing edge regulating plate 41 corresponds to the size of the sheet S. The determination unit 62 stacks the position of the trailing edge regulating plate 41 on the sheet feeding cassette 23 when the size of the sheet S to be conveyed and the size of the sheet S obtained from the position of the trailing edge regulating plate 41 match. It may be determined that the size corresponds to the size of the sheet S. The determination unit 62 determines that the position of the trailing edge regulating plate 41 is in the sheet feeding cassette 23 when the size of the conveyed sheet S and the size of the sheet S obtained from the position of the trailing edge regulating plate 41 do not match. It may be determined that it does not correspond to the size of the stacked sheets S. More specifically, the size of the sheet S conveyed by the pickup roller 35 can be measured by the size measuring unit 71. Further, the conversion unit 69 converts the position of the trailing edge regulating plate 41 detected by the position sensor 54 into the size of the sheet S (eg, length in the conveyance direction). The determination unit 62 overloads the sheet S in the sheet feeding cassette 23 when the size of the sheet S conveyed by the pickup roller 35 matches the size of the sheet S obtained from the position of the trailing edge regulating plate 41. Determine whether it has been. On the other hand, when the size of the sheet S conveyed by the pickup roller 35 and the size of the sheet S obtained from the position of the trailing edge regulating plate 41 do not match, the determination unit 62 stores the sheet S in the sheet feeding cassette 23. It is not necessary to determine whether the is overloaded. As a result, overload determination is executed in a situation where overload is likely to occur, so the determination accuracy of overload will be improved. The image forming apparatus 100 may further include a size measuring unit 71 that measures the size of the sheet S conveyed by the pickup roller 35. The determination unit 62 determines whether or not the execution condition is satisfied by comparing the size of the sheet S measured by the size measurement unit 71 and the size of the sheet S obtained from the position of the trailing edge regulating plate 41. May be. The operation unit 59 and the communication device 58 may function as an input unit that inputs the size of the sheet S conveyed by the pickup roller 35. The determination unit 62 may determine whether or not the execution condition is satisfied by comparing the input size of the sheet S and the size of the sheet S obtained from the position of the trailing edge regulating plate 41.

  The image forming apparatus 100 may further include a jam detection unit 64 that determines whether or not a jam of the sheet S has occurred based on an elapsed time after the pickup roller 35 starts conveying the sheet S. As described with reference to FIG. 18 and the like, the determination unit 62 may determine that the sheet S is overloaded in the sheet feeding cassette 23 when the sheet S is jammed. In addition, if the sheet does not arrive at a predetermined position on the conveyance path after the time when the timing unit 70 finishes measuring a predetermined time after the conveyance of the sheet is started, the determination unit 62 determines that the sheet is overloaded. You may judge. As described with reference to FIG. 18 and the like, when the sheet S is jammed, the substitution unit 65 substitutes a predetermined value Tk3 larger than the overload threshold value Tk for the conveyance time T, whereby the sheet cassette 23 receives the sheet. The determination unit 62 may determine that S is overloaded. As a result, overloading can be determined even in a situation where the conveyance time T is not fixed due to the occurrence of a jam. Similarly, if the sheet does not arrive at a predetermined position on the conveyance path between the start of conveyance of the sheet and the time measurement unit 70 measuring the predetermined time, the substitution unit 65 sets a predetermined value Tk3 at the conveyance time T. May be substituted.

  As described with reference to the third embodiment, when the double feed occurs, the size of the sheet S conveyed by the pickup roller 35 does not match the size of the sheet S obtained from the position of the trailing edge regulating plate 41. There is. The determination unit 62 determines whether the size of the sheet S estimated by the position sensor 54 and the conversion unit 69 matches the size of the sheet S input by the operation unit 59 or the host computer. If the rear end regulating plate 41 is correctly positioned with respect to the sheet S, the estimated size and the input size should match. Therefore, the determination unit 62 may determine whether or not the rear end regulating plate 41 is correctly positioned with respect to the sheet S based on the determination result. In the determination unit 62, the rear end regulating plate 41 is correctly positioned, and the size of the sheet S measured by the size measurement unit 71 is the size obtained by the position sensor 54 or the size designated by the operation unit 59 or the like. To determine if it is greater than. When the rear end regulating plate 41 is correctly positioned and the measured size is larger than the estimated or designated size, the determination unit 62 can determine whether the transport time T does not exceed the overload threshold Tk. Alternatively, it may be determined that the sheets S are overloaded in the sheet feeding cassette 23. For example, as described with reference to FIG. 21A, when the sheets S are overloaded on the locking claws 47, the sheet sizes are likely to be mismatched. Therefore, the determination unit 62 may determine the presence / absence of overload based on the match / mismatch of the sheet sizes.

  As described regarding the execution condition, a determination unit 73 may be further provided for determining whether the pickup roller 35 has deteriorated. If the pickup roller 35 is not deteriorated, the determination unit 62 determines whether or not the sheet S is overloaded in the sheet feeding cassette 23. On the other hand, if the pickup roller 35 is deteriorated, the determination unit 62 does not determine whether or not the sheet S is overloaded in the sheet feeding cassette 23. When the pickup roller 35 and the feed roller 24 deteriorate, the conveyance time T becomes longer. Therefore, the accuracy of overload determination based on the conveyance time T can be reduced. Therefore, the determination unit 62 may improve the determination accuracy by executing the overload determination only when the pickup roller 35 or the like is not deteriorated. The discriminating unit 73 picks up when an event that the conveyance time of the sheet S exceeds the overload threshold value Tk even once in M sheets (for example, 500 sheets) continuously occurs N times (for example, 5 times) or more. It may be determined that the roller 35 has deteriorated. In other words, it is determined whether or not an event in which the transport time exceeds the overload threshold even within one occurrence of the first predetermined number of sheets has occurred continuously a predetermined number of times. In addition, the determination unit 73 may determine that the pickup roller 35 has not deteriorated unless any of the conveyance times of the predetermined number of consecutive sheets S exceeds the overload threshold Tk. In addition, the determination unit 73 determines that the sheet S is loaded in the sheet feeding cassette 23 if none of the transport times of the sheet S that is larger than the continuous predetermined number (for example, 4000 sheets) exceeds the overload threshold Tk. The determination of whether the vehicle is overloaded may be resumed. That is, after it is determined that the pickup roller 35 has deteriorated, the overload determination may be resumed when the transport time does not exceed the overload threshold continuously over the second predetermined number of sheets. In this way, when it is estimated that the pickup roller 35 or the like has been replaced with a new one, the determination of overloading may be resumed.

  The execution condition is that the roller is not worn, the first sheet after the sheet feeding cassette 23 is inserted and removed, the estimated stacking capacity of the sheet S is close to the upper limit stacking capacity, and the trailing edge The position of the regulation plate 41 may be correct.

  When the determination unit 62 determines that the sheet S is overloaded in the paper feed cassette 23, the output unit 67 may output overload information indicating that the sheet S is overloaded. This will make it easier for operators and maintenance companies to recognize overloading. If the determination unit 62 determines that the sheet S is overloaded in the sheet cassette 23 after determining that the sheet S has been overloaded, the output unit 67 displays the overload information. The output may be stopped. This will make it easier for operators and maintenance companies to recognize that overloading has been resolved. When the determination unit 62 determines that the sheet S is overloaded in the sheet feeding cassette 23 and the cassette sensor 61 detects insertion / removal of the sheet feeding cassette 23, the output unit 67 outputs the overloading information. You may stop. This is because when the paper cassette 23 is inserted and removed, the operator may have removed the overloaded sheets S. Further, after the determination unit 62 determines that sheets are overloaded, the output unit 67 may stop outputting the overload information when the conveyance time does not exceed the overload threshold.

  The output unit 67 may display the overload information on the display device of the operation unit 59. This would allow the operator to be notified visually of overloading. The output unit 67 may use the communication device 58 as a transmission unit that transmits a message including overload information. The overload message may be transmitted to an address of a maintenance person (maintenance company) of the image forming apparatus 100. This would allow the maintenance company to inform the customer how to eliminate the overload as part of the maintenance service.

  DESCRIPTION OF SYMBOLS 100 ... Image forming apparatus, 23 ... Paper feed cassette, 52 ... Sheet sensor, 35 ... Pick-up roller, 24 ... Feed roller

Claims (26)

A housing,
Stacking means for stacking sheets, and stacking means that can be inserted into and removed from the housing;
Insertion / removal detection means for detecting insertion / removal of the loading means;
Conveying means for conveying the sheet;
Timing means for timing the conveyance time from when the conveyance means starts conveying the sheet until the sheet arrives at a predetermined position in the conveyance path;
Whether or not sheets are overloaded on the stacking means based on whether or not the transport time of the first transported sheet after the removal / insertion detecting means detects the insertion / removal of the stacking means exceeds the overload threshold. An overload judging means for judging;
An image forming apparatus comprising: Further comprising detection means for detecting that a conveyance delay has occurred in the sheet based on whether the conveyance time of the sheet exceeds a conveyance delay threshold;
The image forming apparatus according to claim 1, wherein the overload threshold is the same as the conveyance delay threshold. The image forming apparatus has a maximum loading height or number of sheets that guarantees normal operation,
Furthermore, it has a stacking degree determination means for the sheets stacked on the stacking means,
If it is determined that the loading degree determined by the loading degree determination unit is a loading capacity within a predetermined range with respect to the loading height or the number of stacked sheets, whether the overloading unit is overloaded or not The image forming apparatus according to claim 1, wherein the determination is performed. 4. The predetermined range with respect to the stacking height or the number of stacked sheets is within an accuracy variation range in which the stacking degree determining means can determine the stacking height or the number of stacked sheets. Image forming apparatus. A plate member provided in the stacking means and on which the sheets are stacked;
Raising means for raising the plate member so that the sheets stacked on the plate member come into contact with the conveying means;
A measuring means for measuring a rising time required for lifting the plate member;
Have
The plate member descends to the lowest part when the stacking means is pulled out of the image forming apparatus.
The loading degree determining means determines that the loading degree is a loading capacity within a predetermined range with respect to the loading height or the number of loaded sheets when the rising time is less than a rising threshold, and the overloading 5. The image forming apparatus according to claim 3, wherein the determination unit determines whether sheets are overloaded on the stacking unit. A surface detecting means for detecting whether or not the surface of the sheet stacked on the plate member has been raised to a predetermined height by the raising means;
The image forming apparatus according to claim 5, wherein the raising unit stops the raising of the plate member when a surface of the sheet stacked on the plate member rises to the predetermined height.   If the sheet does not arrive at a predetermined position in the conveyance path after the conveying unit starts conveying the sheet and until the timing unit finishes measuring a predetermined time, the overload determination unit 7. The image forming apparatus according to claim 1, wherein it is determined that sheets are overloaded on the means.   If the sheet does not arrive at a predetermined position in the conveyance path after the conveyance unit starts conveying the sheet and until the time measuring unit finishes measuring the predetermined time, the conveyance time is less than the overload threshold value. 7. The apparatus according to claim 1, further comprising: a substituting unit that causes the overloading determination unit to determine that a sheet is overloaded on the stacking unit by substituting a larger value. The image forming apparatus described. A restricting means that is movable in a conveying direction of the sheets stacked on the stacking means and restricts the position of the trailing edge of the sheet in the conveying direction;
Position detecting means for detecting the position of the regulating means;
Further comprising
If the position of the restricting means detected by the position detecting means corresponds to the size of the sheets stacked on the stacking means, the overload determining means determines whether the sheets are loaded on the stacking means by the overload determining means. If the position of the regulating means detected by the position detecting means does not correspond to the size of the sheets stacked on the stacking means, the stacking means by the overload determining means is determined. 9. The image forming apparatus according to claim 1, wherein it is not determined whether or not sheets are overloaded. Further comprising conversion means for converting the position of the restriction means detected by the position detection means into a sheet size;
The overload determination unit is configured to detect the restriction unit detected by the position detection unit when the size of the sheet conveyed by the conveyance unit matches the size of the sheet obtained from the position of the restriction unit. It is determined that the position corresponds to the size of the sheet stacked on the stacking unit, and the size of the sheet conveyed by the conveying unit does not match the size of the sheet obtained from the position of the regulating unit The image forming apparatus according to claim 9, wherein the position of the restricting unit detected by the position detecting unit is determined not to correspond to a size of a sheet stacked on the stacking unit. A measuring unit that measures a size of the sheet conveyed by the conveying unit;
The image forming apparatus according to claim 10, wherein the overload determination unit compares the size of the sheet measured by the measurement unit with the size of the sheet obtained from the position of the regulation unit. An input unit that inputs a size of a sheet conveyed by the conveying unit;
The image forming apparatus according to claim 10, wherein the overload determination unit compares a sheet size input by the input unit with a sheet size obtained from a position of the restriction unit. A restricting means that is movable in a conveying direction of the sheets stacked on the stacking means and restricts the position of the trailing edge of the sheet in the conveying direction;
Position detecting means for detecting the position of the regulating means;
Conversion means for converting the position of the restriction means detected by the position detection means into a sheet size;
Further comprising
The overload determination unit is configured such that when the size of the sheet conveyed by the conveyance unit is larger than the size of the sheet obtained by the conversion unit from the position of the regulation unit, the conveyance time does not exceed the overload threshold. 7. The image forming apparatus according to claim 1, wherein it is determined that sheets are overloaded on the stacking unit. Measuring means for measuring the size of the sheet conveyed by the conveying means;
Further comprising
When the sheet size measured by the measuring unit is larger than the sheet size obtained by the converting unit from the position of the regulating unit, the overload determination unit does not exceed the overload threshold. The image forming apparatus according to claim 13, wherein it is determined that sheets are overloaded on the stacking unit.   The image forming apparatus according to any one of claims 1 to 14, wherein the restricting means is provided with a locking claw for restricting a height of the sheet bundle. It further has a determination means for determining whether or not the transport means has deteriorated,
The overload determination unit determines whether or not a sheet is overloaded on the stacking unit if the conveyance unit is not deteriorated. If the conveyance unit is deteriorated, the sheet is overloaded on the stacking unit. The image forming apparatus according to claim 1, wherein it is not determined whether or not the image forming apparatus is on.   The discriminating means is deteriorated when an event in which the transport time exceeds the overloading threshold value even in the first predetermined number of sheets occurs continuously a predetermined number of times. The image forming apparatus according to claim 16, wherein the image forming apparatus is determined.   The overload determination unit determines that the stacking unit does not exceed the overload threshold continuously after the determination unit determines that the transfer unit has deteriorated for a second predetermined number of sheets or more. 18. The image forming apparatus according to claim 16, wherein the determination as to whether or not sheets are overloaded on the means is resumed.   2. The apparatus according to claim 1, further comprising output means for outputting overload information indicating that sheets are overloaded when the overload determination means determines that sheets are overloaded on the stacking means. 19. The image forming apparatus according to any one of items 18 to 18.   If the overload determination unit determines that the sheets are overloaded on the stacking unit and then determines that the sheet overloading has been eliminated, the output unit stops outputting the overload information. The image forming apparatus according to claim 19, wherein the image forming apparatus is configured to do so.   After the overload determination unit determines that sheets are overloaded on the stacking unit, the output unit outputs the overload information when the insertion / removal detection unit detects insertion / removal of the stacking unit. The image forming apparatus according to claim 19, wherein the image forming apparatus is configured to stop.   After the overload determination unit determines that sheets are overloaded on the stacking unit, the output unit stops outputting the overload information when the transport time does not exceed the overload threshold. The image forming apparatus according to claim 19, configured as described above.   The image forming apparatus according to claim 19, wherein the output unit is a display unit that displays the overload information.   The image forming apparatus according to claim 19, wherein the output unit is a transmission unit that transmits a message including the overload information.   25. The image forming apparatus according to claim 24, wherein the transmission unit is configured to transmit the message to an address of a maintenance person of the image forming apparatus. A housing,
Stacking means for stacking sheets, and stacking means that can be inserted into and removed from the housing;
Insertion / removal detection means for detecting insertion / removal of the loading means;
Conveying means for conveying the sheet;
Timing means for timing the conveyance time from when the conveyance means starts conveying the sheet until the sheet arrives at a predetermined position in the conveyance path;
Whether or not sheets are overloaded on the stacking means based on whether or not the transport time of the first transported sheet after the removal / insertion detecting means detects the insertion / removal of the stacking means exceeds the overload threshold. An overload judging means for judging;
If the overload determination unit does not determine that the sheet is overloaded on the stacking unit, an image is formed on the sheet, and the overload determination unit determines that the sheet is overloaded on the stacking unit. An image forming apparatus comprising: an image forming unit that does not form an image on the sheet.

Images