Sheet stacking device, image forming apparatus, and image forming method

Abstract

To provide a paper stacking device, and an image forming device and method, for preventing unevenness of stacked printed matter.SOLUTION: This paper stacking device 150 for stacking paper includes a paper attitude detecting part 340 for detecting an attitude for delivering the paper, and an attitude control part 350 for controlling the attitude of the paper based on a result detected by the paper attitude detecting part 340.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a paper stacking device, an image forming apparatus, and a method for preventing misalignment of loaded paper. [Background technology]

[0002] Image forming apparatuses that process large volumes of printed materials are equipped with a paper stacking device as a paper output unit. When printed materials are stacked, they may become misaligned due to misalignment of the stacking position or curling of the printed materials. In particular, if a large volume of paper is stacked and the paper becomes misaligned, this may cause defects in subsequent processing steps.

[0003] In this regard, Japanese Patent Laid-Open No. 2015-036331 (Patent Document 1) discloses a configuration including a discharge section that discharges paper, a stacking section that stacks the paper discharged from the discharge section, a first air blowing device that blows air onto the upper side of the paper when the paper is discharged from the discharge section, a second air blowing device that blows air onto the lower side of the paper when the paper is discharged from the discharge section, and a control section that controls the operation of the first air blowing device and the second air blowing device. According to Patent Document 1, it is possible to stabilize the posture of the paper when it is discharged.

[0004] However, the technology in Patent Document 1 controls the airflow volume according to the thickness and basis weight of the paper. Therefore, the configuration in Patent Document 1 cannot prevent misalignment of the loaded paper, which occurs depending on the environment in which the device is used and the condition of each individual sheet of paper. Therefore, there is a need for a new technology to prevent misalignment of the loaded paper. Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention has been made in view of the above-mentioned problems in the prior art, and has an object to provide a paper stacking device, an image forming apparatus, and a method that prevent misalignment of stacked printed materials. [Means for solving the problem]

[0006] That is, according to the present invention, A paper stacking device for stacking paper, a detection means for detecting the orientation of the paper when it is discharged; a control means for controlling the attitude of the paper based on the result detected by the detection means; A sheet loading device is provided, including: [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a paper stacking device, an image forming apparatus, and a method for preventing misalignment of stacked printed materials. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram showing a schematic configuration of the overall hardware of an image forming apparatus according to an embodiment of the present invention; [Figure 2] FIG. 2 is a diagram showing the hardware configuration included in the image forming apparatus of the present embodiment. [Figure 3] FIG. 2 is a block diagram of software included in the image forming apparatus of the present embodiment. [Figure 4] FIG. 2 is a diagram illustrating the configuration of a paper stacking device according to a first example of the present embodiment. [Figure 5] 6 is a flowchart showing an example of the operation of a tray of the paper stacking device of the present embodiment. [Figure 6] 6 is a timing chart showing an example of a tray operation process according to the present embodiment. [Figure 7] 10 is a flowchart showing another example of the operation of the tray of the paper stacking device of the present embodiment. [Figure 8] 10 is a timing chart showing another example of the tray operation process of the present embodiment. [Figure 9] 6A to 6C are diagrams showing an example of detection of the falling attitude of paper in the embodiment. [Figure 10] 6 is a flowchart showing a process for adjusting the air volume in the present embodiment. [Figure 11] FIG. 10 is a diagram illustrating the configuration of a paper stacking device in a second example of the present embodiment. [Figure 12]FIG. 10 is a diagram illustrating the configuration of a paper stacking device in a third example of the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] The present invention will be described below with reference to embodiments, but the present invention is not limited to the embodiments described below. In the drawings referred to below, the same reference numerals will be used for common elements, and their description will be omitted as appropriate.

[0010] 1 is a diagram showing a schematic configuration of the overall hardware of an image forming apparatus 100 according to this embodiment. As shown in FIG. 1, the image forming apparatus 100 according to this embodiment is configured by connecting a paper feeder 110, a conveying device 120, a printing device 130, a drying device 140, and a paper stacking device 150.

[0011] The paper feeder 110 is a device that feeds paper sheets on which an image is to be formed. The paper feeder 110 can also be configured as a paper storage unit. Note that, although the embodiment described shows an example in which an image is formed on paper, this is not intended to be a limitation of the embodiment. Therefore, the object on which an image is to be formed can be various sheet materials other than paper (for example, film, OHP sheets, etc.).

[0012] The transport device 120 is a device that transports paper. The transport device 120 can transport paper placed in the paper feed device 110 to the printing device 130.

[0013] The printing device 130 is a device that prints an image on paper. The printing device 130 of this embodiment can be, for example, an inkjet device, and can form an image on paper by ejecting ink onto the paper at a predetermined timing. Note that in the embodiment described below, the printing method of the printing device 130 is inkjet type, but this is not particularly limited to this embodiment. Therefore, for example, the printing device 130 may be a laser type that forms an image by fixing toner attached to paper with heat.

[0014] The drying device 140 is a device that dries the ink ejected onto the paper. The paper on which an image has been formed by the printing device 130 is transported to the drying device 140, where the water in the ink is evaporated. The paper is then transported from the drying device 140 to the paper stacking device 150.

[0015] The paper stacking device 150 is a device that stacks paper sheets. The paper stacking device 150 of this embodiment can stack paper sheets that have been transported and discharged from the drying device 140, for example. The paper stacking device 150 of this embodiment is equipped with a configuration that controls the posture of the paper sheets to be stacked. Therefore, the paper stacking device 150 can prevent the paper sheets from becoming misaligned even when a large amount of paper sheets is stacked. By preventing the stacked paper sheets from becoming misaligned, it is possible to prevent problems from occurring in subsequent processing steps (such as bookbinding).

[0016] The configuration of image forming apparatus 100 shown in Fig. 1 is an example in the embodiment to be described and does not particularly limit the embodiment. Therefore, image forming apparatus 100 may be configured without any of the devices shown in Fig. 1, or may be configured with devices not shown in Fig. 1. Furthermore, for example, several devices shown in Fig. 1 may be configured as a single device.

[0017] Next, the hardware configuration of image forming apparatus 100 will be described. Fig. 2 is a diagram showing the hardware configuration included in image forming apparatus 100 of this embodiment. Image forming apparatus 100 is configured to include a CPU 210, RAM 220, ROM 230, storage device 240, paper feeder 110, conveying device 120, printing device 130, drying device 140, and paper stacking device 150. Note that since paper feeder 110, conveying device 120, printing device 130, and drying device 140 have been described in Fig. 1, detailed description thereof will be omitted here.

[0018] The CPU 210 is a device that executes programs that control the operation of the image forming apparatus 100 and performs predetermined processing. The RAM 220 is a volatile storage device that provides an execution space for the programs executed by the CPU 210, and is used for storing and expanding programs and data. The ROM 230 is a non-volatile storage device that stores the programs executed by the CPU 210, firmware, etc.

[0019] The storage device 240 is a readable / writable non-volatile storage device that stores an OS, various software, setting information, various data, etc. that operate the image forming apparatus 100. Examples of the storage device 240 include a hard disk drive (HDD) and a solid state drive (SSD).

[0020] The CPU 210, RAM 220, ROM 230, and storage device 240 may be included in each of the paper feed device 110, conveying device 120, printing device 130, drying device 140, and paper stacking device 150, or may be included in any one of the devices.

[0021] The paper stacking device 150 includes a sensor 151 , a fan 152 , a lifting mechanism 153 , and a transport mechanism 154 .

[0022] The sensor 151 is a device that detects the posture of the paper. The sensor 151 in this embodiment constitutes a detection means. The paper stacking device 150 can be equipped with multiple sensors 151, and can be, for example, optical sensors. The sensor 151 can detect, for example, whether or not the paper falling onto the tray has passed through the detection range of the sensor 151. Furthermore, by providing multiple sensors 151, it is possible to detect the time difference between when the paper passes through the detection range of each sensor 151. The posture of the paper can be detected based on the detection results of such multiple sensors 151. Furthermore, the sensor 151 in this embodiment can detect the height of the paper stacked on the tray.

[0023] The fan 152 is a device that controls the posture of the paper by blowing air onto the paper. In this embodiment, the fan 152 constitutes a control means. The paper stacking device 150 can be equipped with multiple fans 152. The fan 152 can control the posture of the paper being discharged by adjusting the air volume based on the detection result of the sensor 151. For example, if the paper is not being discharged in the proper posture (for example, if the paper does not fall horizontally), the air volume of the fan 152 can be adjusted to control the paper so that it is discharged properly.

[0024] The lifting mechanism 153 is a device that raises or lowers a tray on which paper sheets are stacked. The lifting mechanism 153 of this embodiment can adjust the height of the tray based on the height of the paper sheets detected by the sensor 151.

[0025] The transport mechanism 154 is a device that transports the paper sheets dried by the drying device 140 to the paper stacking device 150 and stacks them at a predetermined position. The transport mechanism 154 of this embodiment can be composed of, for example, a belt to which clips for holding the paper sheets are attached, and a motor for driving the belt.

[0026] The hardware configuration included in the image forming apparatus 100 of this embodiment has been described above. Next, the functional means executed by each piece of hardware in this embodiment will be described with reference to Fig. 3. Fig. 3 is a software block diagram included in the image forming apparatus 100 of this embodiment.

[0027] The image forming apparatus 100 includes the following functional units: a printing unit 310, a tray position detection unit 320, a tray position adjustment unit 330, a paper attitude detection unit 340, and an attitude control unit 350. Each functional unit will be described below.

[0028] The printing unit 310 is a means for controlling the operation of the printing device 130 and performing printing. The printing unit 310 constitutes the printing means in this embodiment. The printing unit 310 in this embodiment can form an image on paper using an inkjet method.

[0029] The tray position detection unit 320 is a means for detecting the position of a tray on which paper sheets are stacked based on the output of the sensor 151. The tray position detection unit 320 constitutes the detection means in this embodiment. The tray position detection unit 320 in this embodiment can detect the position of the tray by, for example, using the sensor 151 to detect paper sheets stacked on the tray.

[0030] The tray position adjustment unit 330 is a means for adjusting the position of the tray by operating the lifting mechanism 153. The tray position adjustment unit 330 constitutes the adjustment means in this embodiment. The tray position adjustment unit 330 in this embodiment can control the height of the tray on which paper is stacked, based on the result of detection by the tray position detection unit 320. In other words, the tray position adjustment unit 330 in this embodiment can raise and lower the tray.

[0031] The paper orientation detection unit 340 is a means for detecting the orientation of the paper being discharged based on the output of the sensor 151. The paper orientation detection unit 340 constitutes the detection means in this embodiment. The paper orientation detection unit 340 in this embodiment can detect the orientation of the paper, for example, while it is falling toward the tray. Here, the orientation of the paper refers to the inclination of the paper in the horizontal or vertical direction. Therefore, an example of an appropriate paper orientation is one in which the paper is parallel to the sides of the tray and parallel to the tray's loading surface.

[0032] The attitude control unit 350 is a means for controlling the operation of the fan 152 and controlling the attitude of the paper. The attitude control unit 350 constitutes the control means in this embodiment. The attitude control unit 350 in this embodiment can control the attitude of the paper by controlling the air volume of each of the multiple fans 152. By having the attitude control unit 350 control the attitude of the paper, it is possible to prevent the paper loaded on the tray of the paper loading device 150 from shifting. Note that the control of the attitude of the paper may be performed by a device other than the fan 152.

[0033] The software blocks described above correspond to functional means realized by causing each piece of hardware to function by executing the program of this embodiment by the CPU 210. The functional means shown in each embodiment may be realized entirely by software, or some or all of them may be implemented as hardware that provides equivalent functions.

[0034] Furthermore, all of the above-described functional units do not necessarily have to be included in the configuration shown in Fig. 3. For example, in other embodiments, one or more of the functional units, tray position detection unit 320, tray position adjustment unit 330, paper attitude detection unit 340, and attitude control unit 350, may be included in paper stacking device 150.

[0035] Next, a detailed configuration of the paper stacking device 150 of this embodiment will be described with reference to FIG. 4. FIG. 4 is a diagram illustrating the configuration of the paper stacking device 150 in a first example of this embodiment. FIG. 4(a) is a perspective view illustrating the configuration of the paper stacking device 150, and FIG. 4(b) is a side view illustrating the configuration of the paper stacking device 150. In the following description, for convenience, the direction in which the paper on which an image is formed is transported and moved (i.e., the sub-scanning direction) is defined as the x-axis, the direction perpendicular to the x-axis with respect to the horizontal plane is defined as the y-axis, and the height direction of the paper stacking device 150 is defined as the z-axis. Therefore, the side view of FIG. 4(b) is a view of the side of the paper stacking device 150 in the zx plane as viewed along the y-axis. Note that FIG. 4 only illustrates the configuration necessary for explaining the embodiment, and other configurations are omitted as appropriate.

[0036] As shown in FIG. 4(a), the paper stacking device 150 includes multiple sensors. The multiple sensors include sensors (e.g., sensors 151a and 151b) that detect excessive elevation of the tray and the passage of ejected paper, and sensors (e.g., sensors 151c and 151d) that detect the top surface of paper stacked on the tray. Here, sensors 151a and 151b are sensors that detect the orientation of paper and are arranged along the x-axis direction. As shown in FIG. 4(a), by arranging multiple sensors along the x-axis, it is possible to detect whether paper is falling horizontally. Furthermore, sensors 151c and 151d are sensors that detect paper stacked on the tray. In the embodiment described below, sensor 151 can be configured as a light transmission sensor, with a light emitting unit and a light receiving unit installed opposite each other.

[0037] As shown in FIG. 4(a), a plurality of fans 152 are provided above the paper stacking device 150 as means for controlling the attitude of the paper being discharged. In the example of FIG. 4(a), six fans 152a to 152f are provided, three in the x-axis direction and two in the y-axis direction. The number of fans 152 is not limited to the number shown in FIG. 4, and any number can be used. In this embodiment, the attitude of the paper being dropped can be controlled by adjusting the airflow rate of the fans 152.

[0038] As shown in FIG. 4(a), paper stacking section 155 is configured integrally with lifting mechanism 153. In this embodiment, paper stacking section 155 may also be referred to as a tray. As shown in FIG. 4(a), paper stacking section 155 is loaded with paper sheets P on which images have been formed and which have been transported. When multiple sheets of paper are loaded on paper stacking section 155 and the height of paper sheets P reaches a predetermined height, lifting mechanism 153 lowers paper stacking section 155.

[0039] As shown in FIG. 4B, the paper is transported by a transport mechanism 154. The transport mechanism 154 is composed of, for example, a belt to which a clip for holding the paper is attached and a motor for driving the belt. The paper P' is held by the clip, and the clip moves along the x-axis direction as the belt is driven by the motor. When the clip reaches a predetermined position, it releases its grip and allows the paper P' to fall. Thus, the paper P' is stacked on top of the paper P stacked in the paper stacking unit 155. At this time, sensors 151a and 151b detect the falling paper P', thereby detecting the orientation of the paper P'. If the orientation of the paper P' is not appropriate, the stack of paper will be misaligned (the paper will be stacked out of alignment). Therefore, the airflow of the fan 152 is adjusted according to the orientation of the falling paper P'. This allows the paper stacking device 150 of this embodiment to prevent the stacked paper from becoming misaligned.

[0040] Here, the process of lowering the tray in this embodiment will be described with reference to Fig. 5. Fig. 5 is a flowchart showing an example of the operation of the tray of the paper stacking device 150 in this embodiment.

[0041] In this embodiment, paper stacking device 150 starts processing at step S1000. In step S1001, processing branches depending on whether paper has been detected for a predetermined time or longer. The detection in step S1001 can be performed by sensors 151c and 151d in FIG. 4, for example. In step S1001, if paper has been detected for a predetermined time or longer, it can be determined that the paper has reached the height of sensors 151c and 151d. On the other hand, if paper detection is not performed for the predetermined time or shorter, it can be determined that the paper has simply passed sensors 151c and 151d while falling. Therefore, in step S1001, if paper has been detected for a predetermined time or longer, the height of the tray is adjusted.

[0042] In step S1001, if paper has not been detected for a predetermined time or longer (NO), the process returns to step S1001 and waits for paper detection. In step S1001, if paper has been detected for a predetermined time or longer (YES), the process proceeds to step S1002. In step S1002, the tray position adjustment unit 330 controls the lifting mechanism 153 to lower the tray by a predetermined amount.

[0043] Next, in step S1003, the process branches depending on whether the tray has reached its lowest position. If the tray has not reached its lowest position (NO), the process returns to step S1001 and waits for paper detection again. If the tray has reached its lowest position (YES), the process proceeds to step S1004.

[0044] If the tray reaches its lowest position, the tray cannot be lowered even if more paper is loaded, so it is determined that the tray is full, i.e., the amount of paper on the tray has reached its upper limit. Therefore, in step S1004, the user is notified that the amount of paper has reached its upper limit. Then, in step S1005, the process ends.

[0045] The flowchart in FIG. 5 performs processing according to the timing chart shown in FIG. 6. FIG. 6 is a timing chart showing an example of tray operation processing in this embodiment. FIG. 6(a) shows the output of sensor 151 that detects paper. FIG. 6(b) shows a command from tray position adjustment unit 330 to raise or lower the tray, showing three states: raised, stopped, and lowered. FIG. 6(c) shows a determination of abnormal paper loading, showing two states: normal and abnormal. An abnormal paper loading is determined to be a possible paper jam, for example, when sensors 151a and 151b that detect paper passage continue to detect paper for a long period of time.

[0046] In Fig. 6(a), when paper is detected, the output of sensor 151 is turned ON, and when paper is not detected, the output of sensor 151 is turned OFF. The circled numbers in Fig. 6(a) indicate the number of times paper has been detected. The predetermined threshold in Fig. 6(a) corresponds to the predetermined time for determining whether paper has been detected in step S1001 in Fig. 5.

[0047] As shown in Figure 6(a), the time taken for the first and second paper detections is shorter than the predetermined threshold, so it can be determined that the detection was due to a fallen paper. Therefore, at this time, the tray is stopped as shown in Figure 6(b).

[0048] 6(a), since the time taken for the third paper detection is longer than the predetermined threshold, it can be determined that the paper has reached the height of sensors 151c and 151d (YES in step S1001 in FIG. 5). Therefore, tray position adjustment unit 330 controls the tray to be lowered by a predetermined amount (predetermined time) as shown in FIG. 6(b).

[0049] Thereafter, similarly, the time for the fourth paper detection is shorter than the predetermined threshold, so the tray remains stopped, and the time for the fifth paper detection is longer than the predetermined threshold, so the tray is controlled to lower.

[0050] By the processes shown in FIGS. 5 and 6, the paper stacking device 150 of this embodiment can appropriately control the position of the tray.

[0051] The tray does not have to be lowered by a predetermined amount as shown in Figures 5 and 6. For example, as shown in Figure 7, the tray may be lowered while the sensors 151c and 151d detect paper. Figure 7 is a flowchart showing another example of the operation of the tray of the paper stacking device 150 of this embodiment. In the flowchart shown in Figure 7, explanations of processes common to the flowchart in Figure 5 will be omitted as appropriate.

[0052] The paper stacking device 150 starts processing from step S2000. In step S2001, the processing branches depending on whether or not paper has been detected for a predetermined time or longer. The processing in step S2001 is the same as the processing in step S1001. If paper has not been detected for a predetermined time or longer in step S2001 (NO), the processing returns to step S2001 and waits for paper detection. If paper has been detected for a predetermined time or longer in step S2001 (YES), the processing proceeds to step S2002.

[0053] In step S1002, the tray position adjustment unit 330 lowers the tray by controlling the lifting mechanism 153. At this time, the sensors 151c and 151d continue to detect the presence or absence of paper, as in step S2002.

[0054] Next, in step S2003, the process branches depending on whether the tray has reached the lower limit position. If the tray has not reached the lower limit position (NO), the process proceeds to step S2004.

[0055] In step S2004, the process branches depending on whether sensors 151c and 151d still detect paper. If sensors 151c and 151d detect paper (YES), the process returns to step S2002 and repeats the above process, continuing to lower the tray. If sensors 151c and 151d do not detect paper (NO), the process proceeds to step S2005.

[0056] In step S2005, the tray position adjustment unit 330 stops the tray from descending. The fact that no paper is detected in step S2004 means that the tray has been lowered sufficiently. Therefore, in step S2005, the tray stops descending. Then, the process proceeds to step S2007, where the process ends.

[0057] On the other hand, if the tray has reached the lower limit position in step S2003 (YES), the process proceeds to step S2006. In step S2006, the user is notified that the amount of paper on the tray has reached the upper limit. Note that the process in step S2006 is the same as the process in step S1004. Thereafter, the process ends in step S2007.

[0058] In the flowchart in FIG. 7, processing is performed according to the timing chart shown in FIG. 8. FIG. 8 is a timing chart showing another example of tray operation processing in this embodiment. FIG. 8(a) shows the output of the sensor 151 that detects paper. FIG. 8(b) shows a command from the tray position adjustment unit 330 to raise or lower the tray, and shows three states: raised, stopped, and lowered. FIG. 8(c) shows a determination of a paper stacking abnormality, and shows two states: normal and abnormal. Note that the circled numbers in FIG. 8(a) are the same as those shown in FIG. 6(a).

[0059] As shown in Figure 8(a), the time taken for the first and second paper detections is shorter than a predetermined threshold, so it can be determined that the detection was due to a fallen paper. Therefore, at this time, the tray is stopped as shown in Figure 8(b).

[0060] 8(a), the time taken for the third paper detection is longer than the predetermined threshold, so it can be determined that the paper has reached the height of sensors 151c and 151d (YES in step S2001 in FIG. 7). Therefore, tray position adjustment unit 330 controls the tray to lower as shown in FIG. 8(b).

[0061] At this time, the sensors 151c and 151d detect the paper and output ON as shown in Fig. 8(a). Then, when the tray is lowered and the outputs of the sensors 151c and 151d turn OFF, the tray position adjustment unit 330 stops the control of lowering the tray (YES in step S2004, step S2005 in Fig. 7).

[0062] Thereafter, similarly, the time taken for the fourth and fifth sheet detections is shorter than the predetermined threshold value, so the tray remains stopped.

[0063] By the processes shown in FIGS. 7 and 8, similarly to the examples of FIGS. 5 and 6, the paper stacking device 150 of this embodiment can appropriately control the position of the tray.

[0064] So far, the process of lowering the tray in this embodiment has been described. Next, the control of the posture of stacked paper in this embodiment will be described. FIG. 9 is a diagram showing an example of detecting the posture of paper being discharged in this embodiment. FIG. 9(a) shows an example of paper falling horizontally, FIG. 9(b) shows an example of paper falling with the rear side in the paper transport direction tilted downward, and FIG. 9(c) shows an example of paper falling with the front side in the paper transport direction tilted downward. Note that in the following description, for convenience, the rear side in the paper transport direction will be referred to as the rear end side of the paper, and the front side in the paper transport direction will be referred to as the leading end side of the paper. Also, the first example shown in FIG. 9 is a configuration that detects the tilt of the leading and trailing ends of the paper, but this is not a limitation of this embodiment. Therefore, a configuration may be used in which the posture of the paper is adjusted by detecting the tilt in the left-right direction (using multiple sensors 151 arranged along the y-axis), or a configuration may be used in which the posture is adjusted by detecting the tilt in both the front-rear and left-right directions.

[0065] As shown in FIG. 9(a), when a sheet of paper falls almost horizontally, sensors 151a and 151b can detect the sheet almost simultaneously. Here, if the time between when one sensor 151 detects the sheet and when the other sensor 151 detects the sheet is equal to or less than a predetermined threshold, it can be determined that the sheet of paper is falling horizontally. The sheet of paper falls freely due to gravity, and is discharged onto the tray by an airflow from the top to the bottom of sheet stacking device 150 generated by fan 152. Therefore, by appropriately adjusting the airflow of the multiple fans 152 provided in sheet stacking device 150, the sheet of paper can be allowed to fall horizontally.

[0066] An example in which a sheet of paper does not fall horizontally will be described. As shown in FIG. 9B, when a sheet of paper falls with its trailing edge tilted downward, sensor 151b first detects the sheet, and then sensor 151a detects the sheet. If the time between when sensor 151b detects the sheet and when sensor 151a detects the sheet is equal to or greater than a predetermined threshold, it can be determined that the sheet is falling at an angle. Since falling sheets at an angle can cause misalignment of the stacked sheets, in this embodiment, the posture control unit 350 controls the operation of fan 152 so that the sheets fall horizontally. In the example of FIG. 9B, the trailing edge of the sheet is tilted downward, so the posture control unit 350 controls the operation of fan 152 so that the leading edge of the sheet is tilted downward. For example, the posture control unit 350 controls the fan 152 to increase the airflow rate of fan 152a near the leading edge of the sheet, or to decrease the airflow rate of fan 152c near the trailing edge of the sheet, or both. This allows the sheet of paper to fall horizontally, as shown in FIG. 9A.

[0067] Another example of a case where the paper does not fall horizontally will be described. As shown in FIG. 9(c), when the leading edge of the paper falls tilted downward, sensor 151a first detects the paper, and then sensor 151b detects the paper. At this time, if the time between when sensor 151a detects the paper and when sensor 151b detects the paper is equal to or greater than a predetermined threshold, it can be determined that the paper is falling tilted. When it is determined that the paper is falling tilted, posture control unit 350 controls the operation of fan 152 so that the paper falls horizontally. In the example of FIG. 9(c), the trailing edge of the paper is tilted downward, so posture control unit 350 controls the operation of fan 152 so that the trailing edge of the paper falls tilted downward. For example, posture control unit 350 controls the fan 152 to increase the airflow rate of fan 152c near the trailing edge of the paper, or to decrease the airflow rate of fan 152a near the leading edge of the paper, or both. This allows the paper to fall horizontally, as shown in FIG. 9(a).

[0068] The process of adjusting the air volume as shown in Fig. 9 will now be described with reference to Fig. 10. Fig. 10 is a flowchart showing the process of adjusting the air volume in this embodiment.

[0069] Paper stacking device 150 starts processing from step S3000. In step S3001, processing branches depending on whether one of multiple sensors 151 has detected paper. If sensor 151 has not detected paper (NO), processing returns to step S3001 and waits for paper detection. If sensor 151 has detected paper (YES), processing proceeds to step S3002.

[0070] In step S3002, the process starts counting the time difference Ts between when the two sensors 151 detect the paper. That is, the time difference Ts is the time from when one sensor 151 detects the paper to when the other sensor 151 detects the paper. The time difference Ts can be counted by, for example, the paper orientation detection unit 340.

[0071] After starting counting the time difference Ts in step S3002, in step S3003, the process branches depending on whether the other sensor 151 (different from the sensor 151 that detected the paper in step S3001) has detected the paper. If the other sensor 151 has not detected the paper (NO), the process returns to step S3003 and waits for the other sensor 151 to detect the paper. If the other sensor 151 has detected the paper (YES), the process proceeds to step S3004.

[0072] In step S3004, paper orientation detection unit 340 stops counting the time difference Ts, which enables paper orientation detection unit 340 to measure the time difference Ts from when one sensor 151 detects the paper in step S3001 to when the other sensor 151 detects the paper in step S3003.

[0073] Next, in step S3005, the process branches depending on whether the value of Ts is greater than a predetermined threshold. If Ts is less than the threshold (NO), the orientation of the falling paper is deemed to be approximately parallel (see FIG. 9(a)), and the air volume is not adjusted. Therefore, the process proceeds to step S3007, where it ends.

[0074] If Ts is greater than the threshold value in step S3005 (YES), the process proceeds to step S3006. In this case, it is assumed that the falling paper is tilted (see FIGS. 9(b) and 9(c)), and in step S3006, the posture control unit 350 adjusts the airflow rate of the fan 152. In step S3006, the posture control unit 350 performs, for example, control to reduce the airflow rate of the fan 152 located closer to the sensor 151 that detected the paper in step S3001, control to increase the airflow rate of the fan 152 located closer to the sensor 151 that detected the paper in step S3003, or both. Note that the adjustment of the fan airflow rate may be performed based on, for example, the speed at which the paper is falling. The speed at which the paper is falling can be calculated, for example, from the time difference Ts between when the multiple sensors 151 detect the paper.

[0075] After adjusting the airflow rate of the fan 152 in step S3006, the process proceeds to step S3007, where the process ends.

[0076] By performing the process shown in FIG. 10, the paper stacking device 150 of this embodiment can stabilize the posture of the paper and prevent the loaded paper from becoming misaligned.

[0077] So far, the configuration for detecting and controlling the posture of discharged paper has been described. Below, other configuration examples of this embodiment will be described with reference to Figs. 11 and 12. Fig. 11 is a diagram illustrating the configuration of paper stacking device 150 in a second example of this embodiment. Also, Fig. 12 is a diagram illustrating the configuration of paper stacking device 150 in a third example of this embodiment.

[0078] First, the second example will be described with reference to Fig. 11. As shown in Fig. 11(a), paper sheet stacking device 150 of the second example has sensors 151e and 151f on its sides that detect the horizontal orientation of paper sheets (i.e., the inclination of paper sheets in the xy plane), in addition to the configuration of paper sheet stacking device 150 shown in Fig. 4(a). As shown in Fig. 11(a), sensor 151e can detect paper sheets along the y-axis, and sensor 151f can detect paper sheets along the x-axis.

[0079] Figures 11(b) and (c) are top views of a tray with paper stacked on it. The dashed lines in Figures 11(b) and (c) indicate the optical axes of the light-emitting elements of sensors 151e and 151f. Figure 11(b) shows an example where the paper is not tilted, while Figure 11(c) shows an example where the paper is tilted.

[0080] When the paper is not tilted horizontally, as shown in FIG. 11(b), the paper does not intersect with the optical axes of sensors 151e and 151f. That is, sensors 151e and 151f do not output a detection signal for the paper. On the other hand, when the paper is tilted horizontally, as shown in FIG. 11(c), the paper intersects with the optical axes of sensors 151e and 151f. That is, sensors 151e and 151f output a detection signal for the paper. Therefore, the attitude control unit 350 adjusts the airflow of fan 152 so that the paper is in the orientation shown in FIG. 11(b). Alternatively, the attitude control unit 350 may control the orientation of the paper by adjusting the direction of airflow from fan 152.

[0081] Next, a third example will be described with reference to Fig. 12. As shown in Fig. 12(a), paper stacking device 150 of the third example includes, in addition to the configuration of paper stacking device 150 shown in Fig. 4(a), a sensor 151g on the top that detects the horizontal orientation of paper (i.e., the inclination of paper in the xy plane). Sensor 151g can be configured as a surface photoelectric sensor that can detect the orientation of paper on a tray.

[0082] 12(b) and 12(c) are top views of a tray loaded with paper sheets. Fig. 12(b) shows an example where the paper sheets are not tilted, and Fig. 12(c) shows an example where the paper sheets are tilted.

[0083] As shown in FIG. 12(b), if the paper is not tilted horizontally (or if the amount of tilt is equal to or less than a predetermined threshold), the paper orientation is deemed to be appropriate, and the orientation control unit 350 maintains the airflow of the fan 152. On the other hand, as shown in FIG. 12(c), if the paper is tilted horizontally (if the amount of tilt is equal to or greater than a predetermined threshold), the orientation control unit 350 adjusts the airflow of the fan 152 so that the paper orientation becomes as shown in FIG. 12(b). Alternatively, the orientation control unit 350 may control the paper orientation by adjusting the air direction of the fan 152.

[0084] According to the second example shown in FIG. 11 and the third example shown in FIG. 12, it is possible to adjust not only the vertical misalignment as in the first example, but also the horizontal tilt of the paper, thereby more appropriately preventing misalignment of the paper.

[0085] According to the embodiments of the present invention described above, it is possible to provide a paper stacking device, an image forming apparatus, and a method for preventing misalignment of stacked printed materials.

[0086] Each function of the above-described embodiments of the present invention can be realized by a device-executable program written in C, C++, C#, Java (registered trademark), etc., and the program of this embodiment can be stored and distributed on a device-readable recording medium such as a hard disk drive, CD-ROM, MO, DVD, flexible disk, EEPROM (registered trademark), EPROM, etc., and can also be transmitted over a network in a format that can be used by other devices.

[0087] Each function of the above-described embodiments can be realized by one or more processing circuits. Here, the term "processing circuit" in this specification includes a processor programmed to perform each function by software, such as a processor implemented by electronic circuits, as well as devices such as an ASIC (Application Specific Integrated Circuit), a DSP (Digital Signal Processor), an FPGA (Field Programmable Gate Array), or a conventional circuit module designed to perform each of the above-described functions.

[0088] Although the present invention has been described above with reference to embodiments, the present invention is not limited to the above-described embodiments, and any embodiment that can be conceived by a person skilled in the art is included in the scope of the present invention as long as it exhibits the functions and effects of the present invention. [Explanation of symbols]

[0089] 100...image forming apparatus, 110...paper feeding device, 120...conveying device, 130...printing device, 140...drying device, 150...paper stacking device, 151...sensor, 152...fan, 153...elevating mechanism, 154...conveying mechanism, 155...paper stacking section, 210...CPU, 220...RAM, 230...ROM, 240...storage device, 310...printing section, 320...tray position detection section, 330...tray position adjustment section, 340...paper attitude detection section, 350...attitude control section [Prior art documents] [Patent documents]

[0090] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-036331

Claims

1. A paper stacking device for stacking paper, a detection means for detecting the orientation of the paper when it is discharged; a control means for controlling the attitude of the paper based on the result detected by the detection means; a paper loading device including:

2. the control means includes a fan that blows air onto the paper, The air volume of the fan is controlled to control the attitude of the paper. The paper stacking device according to claim 1 .

3. a plurality of the detecting means and a plurality of the fans; the plurality of detection means detect the skew of the paper; the control means controls the airflow rate of at least one of the plurality of fans in accordance with the tilt. The paper stacking device according to claim 2 .

4. the detecting means detects the tilt of the paper in the horizontal direction. The paper stacking device according to claim 1 .

5. the detecting means includes means for detecting the presence or absence of paper in a first horizontal direction, and means for detecting the presence or absence of paper in a second horizontal direction perpendicular to the first horizontal direction. The paper stacking device according to claim 4.

6. The detection means is disposed above a stacking section on which the paper is stacked. The paper stacking device according to claim 4.

7. The detection means detects the posture of the paper as it falls. The paper stacking device according to claim 1 .

8. An image forming apparatus comprising the paper stacking device according to any one of claims 1 to 7.

9. 1. A method of loading paper, comprising: detecting the posture of the paper when it is discharged; a step of controlling the attitude of the paper based on the result detected in the detection step; A method comprising:

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