JP7732199B2 - Sheet stacking device and image forming system - Google Patents

Description

The present invention relates to a sheet stacking device for stacking discharged sheets and an image forming system.

Sheet stacking devices are known that stack sheets on which images have been formed by an image forming device. Sheet stacking devices include, for example, a discharge section (discharge rollers, etc.) that discharges sheets, a stacking tray on which the discharged sheets are stacked, and a lifting mechanism that raises and lowers the stacking tray depending on the amount of sheets stacked. Post-processing devices are also known that include a post-processing section that performs post-processing on sheets on which images have been formed, and the above-mentioned sheet stacking device on which the post-processed sheets are stacked.

In such sheet stacking devices, if the top surfaces of the stacked sheets are too low relative to the discharge section, the position and posture of the discharged sheets will be disturbed, making it difficult for the user to align the documents they remove from the discharge tray. On the other hand, if the top surfaces of the sheets are too close to the discharge section, the stacked sheets and the discharged sheets will interfere with each other. Therefore, technologies for maintaining the appropriate height for the stacking tray have been studied.

For example, Patent Document 1 describes a system in which a swingable detection lever detects the height of the topmost sheet of paper when it comes into contact with the surface, and then drives a tray lifting device to displace the paper output tray so that the tray is kept at a constant height. Patent Document 2 describes a system in which a motor rotation speed detection means is attached to the output shaft of the motor that serves as the drive source for the tray lifting mechanism, and the amount of paper loaded on the tray is detected based on the rotation speed detection result, and the tray position is set based on the amount of paper loaded.

Japanese Patent Application Publication No. 6-9137 Japanese Patent Application Publication No. 9-255212

However, with the configuration described in Patent Document 1, the detection lever can get in the way or be damaged when the user removes paper from the tray. With the configuration described in Patent Document 2, the tray repeatedly rises and falls during actual operation, which complicates control and raises the risk of falsely detecting the load amount, making it impossible to improve the accuracy of stack tray height adjustment. Furthermore, if the power is turned on with sheets stacked on it, the position of the stack tray cannot be recognized, and the stack tray height cannot be adjusted.

The amount of sheets that can be loaded without compromising alignment (the alignment of the sheet position and posture) varies depending on the conditions of the print job. For example, when comparing large and small sheets, even if the number of sheets is the same, the smaller size is more likely to be unstable. Also, because the thickness of the sheet stack increases near stapled sections and folds, the tilt of the sheet stack increases as the load increases. Furthermore, when sheets of different sizes are mixed, the thickness of the sheet stack varies depending on the location, causing tilt. In these cases, as the load increases, sheet alignment decreases, and sheets may collapse and fall.

In consideration of the above circumstances, the present invention aims to provide a sheet stacking device and image forming system that can improve the accuracy of stacking tray height adjustment.

To solve the above problems, the sheet stacking device of the present invention is characterized by comprising a discharge unit that discharges sheets, a stacking tray on which the sheets discharged by the discharge unit are stacked, a lifting mechanism that raises and lowers the stacking tray, a first detection unit that can continuously detect the height of the stacking tray throughout the entire lifting range of the stacking tray, and a control unit that controls the lifting and lowering of the stacking tray based on the detection results of the first detection unit.

The first detection unit may be a contact image sensor in which multiple photoelectric conversion elements are arranged in the direction in which the loading tray is raised and lowered.

The sheet stacking device may further include a second detection unit that detects whether the loading surface of the loading tray on which the sheets are loaded is positioned at a receiving position for receiving the sheets, and the control unit may be configured to lower the loading tray according to the amount of sheets loaded and position the loading surface at the receiving position based on the detection result of the loading surface by the second detection unit, detect the height of the loading tray with the loading surface positioned at the receiving position using the first detection unit, and execute full-load control to stop raising or lowering the loading tray when the height of the loading tray reaches a predetermined lower limit position.

The image forming system according to the present invention includes an image forming device that accepts a print job and forms an image on the sheet; a sheet stacking device as described in claim 3 that stacks the sheets discharged from the image forming device; and a storage unit that stores condition data indicating the conditions included in the print job and the lowest height limit position of the stacking tray in association with each other, and the control unit is characterized in that, during the full-fill control, when the stacking tray reaches the lowest limit position associated with the condition data corresponding to the print job being processed, it stops raising or lowering the stacking tray and interrupts the print job.

When the condition data included in the print job being processed matches the condition data stored in the storage unit at a certain percentage, the control unit may interrupt the print job using the lower limit position associated with the stored condition data.

The image forming system may include an operation unit that accepts operations, and the control unit may be configured to, when the operation unit accepts an operation to store the lower limit position of the stacking tray height, associate condition data indicating the conditions included in the print job being processed with the stacking tray height detected by the first detection unit and store them in the storage unit.

If condition data corresponding to the print job being processed is not stored in the memory unit, the control unit may notify the operation unit that it is recommended to set the lower limit position of the height of the stacking tray.

The control unit may interrupt the print job using the lower limit position only when a load limit mode that limits the sheet load capacity is set.

The image forming system may include a post-processing unit that performs one or more of the following post-processing steps on the sheets on which images have been formed: stapling, shifting, and center-folding. The conditions included in the print job may include one or more of the presence or absence and number of staples, the presence or absence of shifting, the presence or absence of center-folding, and the number of sheets that make up a single sheet stack.

The conditions included in the print job may include one or more of the sheet size and whether or not mixed sizes are included.

This invention allows for increased accuracy in adjusting the height of the loading tray.

1 is a perspective view showing the appearance of an image forming system according to an embodiment of the present invention; 1 is a front view schematically illustrating an internal configuration of a post-processing device according to an embodiment of the present invention. FIG. 2 is a perspective view of a lifting mechanism according to an embodiment of the present invention. FIG. 2 is a front view of the lifting mechanism according to the embodiment of the present invention. 1 is a block diagram showing an electrical configuration of an image forming system according to an embodiment of the present invention. 4 is a flowchart showing the operation of the sheet stacking device according to the embodiment of the present invention. FIG. 10 is a diagram showing a tray height setting screen according to an embodiment of the present invention.

The following describes an image forming system 100 according to one embodiment of the present invention, with reference to the drawings.

First, the overall configuration of image forming system 100 will be described. Figure 1 is a perspective view showing the appearance of image forming system 100. In the following description, the Fr side in Figure 1 is the front side (front side) of image forming system 100, and left and right directions will be described based on the direction when image forming system 100 is viewed from the front. In each figure, U, Lo, L, R, Fr, and Rr represent top, bottom, left, right, front, and rear, respectively.

The image forming system 100 includes an image forming device 1 and a post-processing device 110. The image forming device 1 is, for example, a multifunction device including a printer, a scanner, and a document transport device. The document transport device transports documents along a transport path that passes through the scanner's reading position. The scanner is a flatbed image scanner that reads documents and generates image data. The printer forms images on sheets using inkjet or electrophotography methods, for example. The post-processing device 110 performs post-processing on sheets transported from the printer and discharges them.

Next, the configuration of the post-processing device 110 will be described (see Figures 1 and 2). Figure 2 is a front view showing a schematic internal configuration of the post-processing device 110. The post-processing device 110 has a roughly rectangular parallelepiped housing 21. An inlet 22 is provided at the top of the right side panel of the housing 21, through which sheets transported from the image forming device 1 are received.

The left side plate of the housing 21 has a recess 23 recessed to the right. When viewed from the left, the recess 23 is roughly rectangular with a long side running vertically and a short side running front-to-rear. The recess 23 comprises a bottom 23B formed to the right of the left side plate, front and rear side walls 23S formed between the front and rear ends of the bottom 23B and the left side plate, an upper wall 23U formed between the upper end of the bottom 23B and the left side plate, and a lower wall 23L formed between the lower end of the bottom 23B and the left side plate.

A discharge section 31 for discharging sheets is provided above the recess 23. A sheet stacking device 120, described below, is provided below the discharge section 31. An upper discharge section 44 is provided on the top plate of the housing 21. A transport path 41 is provided inside the housing 21, running from the receiving opening 22 to the discharge section 31, and a branch path 42 is provided that branches off from the transport path 41 and leads to the upper discharge section 44. A transport roller 43 is provided on the transport path 41.

The upper discharge section 44 is equipped with discharge rollers and a discharge port. A fixed-position stacking tray 45 is provided to the left of the upper discharge section 44.

The discharge section 31 includes a discharge opening 32 and a discharge roller 33 located to the right of the discharge opening 32. The discharge roller 33 includes a drive roller 33D driven by a motor (not shown) and a driven roller 33N that drives the drive roller 33D. The drive roller 33D can be pressed against and separated from the driven roller 33N.

A processing tray 51 (an example of a post-processing section) and a stapler 54 (an example of a post-processing section) are provided below the conveying path 41. The processing tray 51 is provided so as to slope downward toward the right from the discharge opening 32, and is loaded with a sheet stack to be stapled by the stapler 54. The left end of the processing tray 51 rotatably supports the driven roller 33N of the discharge roller 33. The stapler 54 is provided to the right of the processing tray 51, and staples the right end of the sheet stack loaded on the processing tray 51 (stapling process). The post-processing section 110 may also be provided with a center-folding device (an example of a post-processing section) that folds sheets in the middle (not shown).

The processing tray 51 is provided with a pair of side fences 52 facing each other in the front-to-rear direction. The pair of side fences 52 are movable along the sheet width direction (a direction intersecting the discharge direction Y). The pair of side fences 52 move synchronously toward each other, aligning the sheets on the processing tray 51 in the width direction. The pair of side fences 52 also move together in the width direction, shifting the sheet stack in the width direction (shift processing). A sheet receiving plate 53 is provided at the right end of the processing tray 51. When the right end of the sheet stack loaded on the processing tray 51 abuts against the sheet receiving plate 53, the sheets are aligned in the discharge direction Y.

[Sheet stacking device]
Next, a description will be given of the configuration of the sheet stacking device 120. Fig. 3 is a perspective view of the lifting mechanism 63. Fig. 4 is a front view of the lifting mechanism 63.

The sheet stacking device 120 includes a discharge section 31 that discharges sheets, a stacking tray 61 on which the sheets discharged by the discharge section 31 are stacked, a lifting mechanism 63 that raises and lowers the stacking tray 61, a tray detection section 71 that can continuously detect the height of the stacking tray 61 throughout the entire lifting range of the stacking tray 61, and a control section 2 that controls the lifting and lowering of the stacking tray 61 based on the detection results of the tray detection section 71.

[Loading tray]
The top surface of the stacking tray 61 is inclined upward toward the downstream side in the sheet discharge direction Y. The stacking tray 61 is provided to the left of the recess 23. Brackets 62 that connect the stacking tray 61 to a belt 66 (described later) are provided at the right ends of the front and rear side surfaces of the stacking tray 61 (see FIGS. 3 and 4). Slits (not shown) are formed in the vertical direction at locations corresponding to the brackets 62 on the bottom 23B or side wall 23S of the recess 23, and the brackets 62 pass through the slits.

[Lifting mechanism]
The lifting mechanism 63 (see FIGS. 3 and 4 ) includes a drive shaft 64, a driven shaft 65 provided below the drive shaft 64, and belts 66 provided at two locations, front and rear. The lifting mechanism 63 is provided to the right of the recess 23. Sprockets 64S are provided at two locations, front and rear, of the drive shaft 64, and a drive gear 64G is provided at one end of the drive shaft 64. Driving force is transmitted to the drive gear 64G via a motor and a reduction gear train (not shown). Sprockets 65S are provided at two locations on the driven shaft 65 corresponding to the sprockets 64S of the drive shaft 64. An endless belt 66 with teeth formed on its inner circumferential surface is wound around the sprockets 64S of the drive shaft 64 and the sprockets 65S of the driven shaft 65. The bracket 62 of the stacking tray 61 is fixed to the outer circumferential surface of the belt 66. When a driving force is transmitted to the driving gear 64G, the front and rear belts 66 circulate in the same direction in synchronization, and the loading tray 61 moves up and down as the belts 66 move.

[Upper surface detection unit (second detection unit)]
An upper surface detector 68 (an example of a second detector) is provided on the upper portion of the recess 23 of the housing 21 (see FIG. 2). The upper surface detector 68 is, for example, a transmission-type or reflection-type optical sensor. In the transmission-type detector, a light-emitting unit is provided on one of the front and rear side walls 23S of the recess 23, and a light-receiving unit is provided on the other side wall 23S (not shown). In the reflection-type detector, a light-emitting unit and a light-receiving unit are provided on one side wall 23S, and a reflector is provided on the other side wall 23S (not shown).

The top surface detection unit 68 detects whether the stacking surface on which sheets are stacked is positioned at a receiving position for receiving sheets. Specifically, the stacking surface refers to the top surface of sheets stacked on the stacking tray 61 (the top surface of the uppermost sheet), or the top surface of the stacking tray 61 when no sheets are stacked. If the height of the stacking surface is equal to or greater than the height of the light path of the light-emitting unit, the light is blocked by the sheets or stacking tray 61, preventing the light receiving unit from receiving the light. In this case, the top surface detection unit 68 outputs a first-level signal (hereinafter referred to as a light-blocking signal). On the other hand, if the height of the stacking surface is less than the height of the light path of the light-emitting unit, the light is not blocked by the sheets or stacking tray 61, allowing the light receiving unit to receive the light. In this case, the top surface detection unit 68 outputs a second-level signal (hereinafter referred to as a light-receiving signal).

The receiving position is a position where the right edge of the stacking surface is a predetermined distance below the discharge opening 32 of the discharge section 31. This distance is set to minimize interference between the discharged sheets and the stacking surface, as well as problems such as loss of alignment of the discharged sheets. The control section 2, which will be described later, performs top surface height control at a predetermined timing using the detection results of the stacking surface by the top surface detection section 68. Top surface height control will be described in detail later.

[Tray detection unit (first detection unit)]
A tray detector 71 (an example of a first detector) capable of continuously detecting the height of the loading tray 61 throughout the entire lifting range of the loading tray 61 is provided to the right of either the front or rear belt 66 (see FIG. 4 ). A detector piece 72 protruding to the right is provided on the bracket 62 of the loading tray 61. The tray detector 71 is a line sensor including multiple photoelectric conversion elements aligned in the lifting direction of the loading tray 61. The tray detector 71 is, for example, a contact image sensor (CIS) including a light source, a rod lens array, and a complementary metal-oxide-semiconductor field-effect transistor (CMOS) image sensor (not shown). Multiple CMOS image sensors are aligned throughout the entire lifting range of the loading tray 61. The light source includes a light-emitting diode (LED) provided at the upper or lower end of the lifting range of the loading tray 61 and a light guide that guides the LED light to the detector piece 72. In other words, the range in which the first detection unit can detect the height of the stacking tray 61 is continuous throughout the entire range in which the stacking tray 61 can be raised and lowered.

[Electrical configuration]
5 is a block diagram showing the electrical configuration of the image forming system 100. The image forming apparatus 1 is provided with a control unit 2. The control unit 2 includes a calculation unit 2P and a storage unit 2M. The calculation unit 2P is, for example, a central processing unit (CPU). The storage unit 2M includes storage media such as a read-only memory (ROM), a random access memory (RAM), and an electrically erasable programmable read-only memory (EEPROM). The calculation unit 2P performs various processes by reading and executing control programs stored in the storage unit 2M. Note that the control unit 2 may be realized by an integrated circuit without using software.

The control unit 2 is connected to the top surface detection unit 68, tray detection unit 71, lifting mechanism 63, and operation unit 19. The operation unit 19 is provided at the top of the front side of the image forming apparatus 1 (see Figure 1). The operation unit 19 includes a display panel, a touch panel provided on top of the display surface of the display panel, and a keypad adjacent to the display panel (not shown). The control unit 2 displays a screen showing operation menus for the image forming apparatus 1 and post-processing device 110 on the display panel, and controls each part of the image forming apparatus 1 and post-processing device 110 in response to operations detected on the touch panel and keypad.

Here, we will explain the load amount limit mode. The load amount limit mode is a mode that prevents the integrity of the stacked sheets from deteriorating by limiting the load amount according to the conditions of the print job. Specifically, condition data indicating the conditions included in the print job and the lowest height limit of the stacking tray 61 at which sheets can be stacked without deteriorating integrity are associated and stored in the memory unit 2M. The condition data includes, for example, six items: sheet size, whether or not mixed sizes are used, whether and how many sheets are stapled, whether or not shift processing is used, whether or not center folding is used, and the number of sheets that make up one sheet bundle.

The sheet size can be set to one of four types: A4 or Letter, A4R or LetterR, B4 or Legal, and Ledger or A3. Of these, A4R or LetterR means that the long side of the A4 or Letter is transported parallel to the transport direction. The other three types all mean that the short side is transported parallel to the transport direction.

Mixed size loading means transporting multiple types of sheets of different sizes in a single print job, and can be set to yes or no.

Stapling refers to binding multiple sheets together using the staple device 54. The number of staples refers to the number of locations where staples are applied to a single sheet stack. The presence or absence of staples and the number of locations can be set to two, one, or none.

Shift processing refers to the process of moving a pair of side fences 52 together in the width direction, thereby shifting the sheet stack alternately in the width direction, one copy at a time, and can be set to either enabled or disabled.

Center-folding refers to the process of center-folding a sheet stack using a center-folding device, and can be set to ON or OFF.

The number of sheets that make up one set of sheets refers to the number of sheets that make up the set of sheets used in staple processing, shift processing, and center folding processing, and can be set to 1, 2, 3 to 10, or 11 or more.

The memory unit 2M stores a data table that associates this condition data with the lowest height position of the stacking tray 61 at which sheets can be stacked without compromising consistency. The data table is stored, for example, by the manufacturer before shipping from the factory. The manufacturer conducts experiments using the sheet stacking device 120 with various combinations of the above condition data items to determine the lowest height position of the stacking tray 61 at which sheets can be stacked without compromising consistency. The degree of consistency corresponding to the lowest position is, for example, a level at which the tilt of the stacked sheets cannot be visually confirmed. The manufacturer writes the lowest position determined through the experiment into the memory unit 2M in association with the condition data. In this case, it is desirable to store multiple sets of condition data and lowest position combinations that are expected to be used relatively frequently.

Also, the condition data and lower limit position may be stored by the user. This will be discussed later.

The load limit mode can be set and canceled at any time. When the operation menu for the post-processing device 110 is called up on the operation unit 19, a selection button for selecting the load limit mode and a cancellation button for canceling the load limit mode are displayed in one corner of the screen (not shown). By default, the load limit mode is canceled.

Next, the operation of the sheet stacking device 120 will be described. Figure 6 is a flow chart showing the operation of the sheet stacking device 120. When the image forming system 100 is powered on, the control unit 2 executes full-load control according to the flow chart in Figure 6.

First, the control unit 2 determines whether a print job has started (step S01). If it determines that a print job has not started (step S01: NO), the control unit 2 repeats the process of step S01. On the other hand, if it determines that a print job has started (step S01: YES), the control unit 2 determines whether the load amount limit mode has been selected (step S03). If the load amount selection mode has been selected (step S03: YES), the control unit 2 proceeds to the process of step S05. If the load amount selection mode has not been selected (step S03: NO), the control unit 2 proceeds to the process of step S09. In this case, the lower limit position of the height of the stacking tray 61 for the print job being processed is set to the initial value. The initial value is the lowest height to which the stacking tray 61 can be lowered by the lifting mechanism 63.

In step S05, the control unit 2 determines whether condition data corresponding to the print job is stored in the memory unit 2M. Specifically, the control unit 2 compares the conditions included in the print job being processed with the condition data stored in the memory unit 2M, and extracts condition data for which a predetermined number or a predetermined percentage or more of the conditions included in the print job being processed match. Here, the predetermined number is, for example, five of the six conditions mentioned above. The predetermined percentage is, for example, 80%.

If condition data that matches a predetermined number or a predetermined percentage of the conditions included in the print job being processed is stored in storage unit 2M, control unit 2 determines that condition data corresponding to the print job is stored in storage unit 2M (step S05: YES) and proceeds to processing in step S07. On the other hand, if condition data that matches a predetermined number or a predetermined percentage of the conditions is not stored in storage unit 2M, control unit 2 determines that condition data corresponding to the print job is not stored in storage unit 2M (step S05: NO) and proceeds to processing in step S21.

In step S07, the control unit 2 sets the lower limit position associated with the condition data. Specifically, the control unit 2 sets the lower limit position associated with the condition data extracted in step S05 as the lower limit position for the height of the stack tray 61 for the print job being processed.

Next, the control unit 2 starts top surface height control (step S09). Specifically, the control unit 2 checks the output of the top surface detection unit 68 each time a predetermined number of sheets are discharged by the discharge unit 31. If the height of the stacking surface is equal to or greater than the height of the optical path of the top surface detection unit 68, the top surface detection unit 68 outputs a light-blocking signal. On the other hand, if the height of the stacking surface is less than the height of the optical path of the top surface detection unit 68, the top surface detection unit 68 outputs a light-receiving signal. As sheets are repeatedly discharged, the height of the stacking surface gradually increases, and the light-receiving signal switches to a light-blocking signal. When the light-receiving signal switches to a light-blocking signal, the control unit 2 lowers the stacking tray 61 until the top surface detection unit 68 outputs a light-receiving signal, and then raises the stacking tray 61 until the top surface detection unit 68 outputs a light-blocking signal. This process maintains the height of the stacking surface within a predetermined range that includes the receiving position, thereby maintaining the distance between the discharge opening 32 of the discharge section 31 and the stacking surface within an appropriate range. The control section 2 continues to control the top surface height while sheets are being discharged by the discharge section 31.

Next, the control unit 2 determines whether the print job has ended (step S11). If it determines that the print job has ended (step S11: YES), the control unit 2 repeats the processes from step S01 onwards. On the other hand, if it determines that the print job has not ended (step S11: NO), the control unit 2 determines whether the height of the stacking tray 61 has reached the lower limit position (step S13). Specifically, the control unit 2 determines whether the height of the stacking tray 61 detected by the tray detection unit 71 has reached the lower limit position set in step S07. If it determines that the height of the stacking tray 61 has not reached the lower limit position (step S13: NO), the control unit 2 repeats the processes from step S11 onwards.

On the other hand, if it is determined that the height of the stacking tray 61 has reached the lower limit position (step S13: YES), the control unit 2 stops the lifting and lowering of the stacking tray, suspends the print job (step S15), and causes the operation unit 19 to display a message urging the user to remove the printed materials and a resume button for resuming the print job. The resume button can only be operated when the upper surface detection unit 68 is outputting a light reception signal.

Next, the control unit 2 determines whether the print job has been resumed (step S17). Specifically, if the resume button has not been operated, the control unit 2 determines that the print job has not been resumed (step S17: NO) and repeats the processing of step S17. On the other hand, if the resume button has been operated, the control unit 2 determines that the print job has been resumed (step S17: YES) and repeats the processing from step S09 onwards.

Next, the processing from step S21 onwards will be described. In step S21, the control unit 2 causes the operation unit 19 to display a tray height setting screen. Figure 7 shows the tray height setting screen. The tray height setting screen includes the above six conditions included in the print job and a tray height setting button for setting the height of the stacking tray 61. In this example, the sheet size is A4 or Letter. Mixed size loading, shift processing, and center folding processing are performed. Stapling is performed in two places. The number of sheets that make up one sheet stack is 3 to 10.

The tray height setting screen may also include a message recommending that you set the lower limit of the height of the stacking tray 61 (for example, "Please use the tray height setting button to set the lower limit of the tray corresponding to the print job being processed").

Next, the control unit 2 starts upper surface height control (step S23), similar to step S09. Next, the control unit 2 determines whether the print job has ended (step S25), similar to step S11.

Next, the control unit 2 determines whether the lower limit position for the height of the stacking tray 61 has been set (step S27). Specifically, the user observes the state of the sheets stacked on the stacking tray 61, and if they detect signs of a decrease in alignment, they operate the tray height setting button. If the setting button on the tray height setting screen has not been operated, the control unit 2 determines that the lower limit position has not been set (step S27: NO) and repeats the processing from step S25 onwards. On the other hand, if the setting button on the tray height setting screen has been operated, the control unit 2 determines that the lower limit position has been set (step S27: NO) and interrupts the print job (step S29). At this time, the control unit 2 associates the height of the stacking tray 61 detected by the tray detection unit 71 with condition data indicating the conditions included in the print job being processed and stores it in the memory unit 2M.

Next, the control unit 2 determines whether the print job has been resumed (step S31). Specifically, if the resume button has not been operated, the control unit 2 determines that the print job has not been resumed (step S31: NO) and repeats the processing of step S31. On the other hand, if the resume button has been operated, the control unit 2 determines that the print job has been resumed (step S31: YES) and repeats the processing from step S23 onwards.

The sheet stacking device 120 according to the present embodiment described above includes a discharge section 31 that discharges sheets, a stacking tray 61 on which the sheets discharged by the discharge section 31 are stacked, a lifting mechanism 63 that raises and lowers the stacking tray 61, a first detection section (tray detection section 71) that can continuously detect the height of the stacking tray 61 throughout the entire lifting range of the stacking tray 61, and a control section 2 that controls the lifting and lowering of the stacking tray 61 based on the detection results of the first detection section, thereby improving the accuracy of height adjustment of the stacking tray 61.

Furthermore, according to the sheet stacking device 120 of this embodiment, the first detection unit is a contact image sensor in which multiple photoelectric conversion elements are arranged in the lifting and lowering direction of the stacking tray 61, so the height of the stacking tray 61 can be quickly detected when the power is turned on or when returning from power saving mode.

In addition, the sheet stacking device 120 according to this embodiment is further equipped with a second detection unit (upper surface detection unit 68) that detects whether the stacking surface of the stacking tray 61, on which sheets are stacked, is positioned in the receiving position for receiving sheets. Based on the detection result of the stacking surface by the second detection unit, the control unit 2 lowers the stacking tray 61 in accordance with the amount of sheets loaded to position the stacking surface at the receiving position. The control unit 2 detects the height of the stacking tray 61 when the stacking surface is positioned at the receiving position using the first detection unit. If the height of the stacking tray 61 reaches a predetermined lower limit position, full-load control is executed to stop the lifting and lowering of the stacking tray 61, so that the stacking surface can always be positioned at the receiving position.

The image forming system 100 according to this embodiment includes an image forming device 1 that accepts print jobs and forms images on sheets, a sheet stacking device 120 that stacks sheets discharged from the image forming device 1, and a memory unit 2M that stores condition data indicating the conditions included in the print job and the lowest height position of the stacking tray 61 in association with each other. During full-stack control, the control unit 2 stops the lifting and lowering of the stacking tray 61 and interrupts the print job when the stacking tray 61 reaches the lowest position associated with the condition data corresponding to the print job being processed. This allows the print job to be interrupted before the integrity of the stacked sheets deteriorates. As a result, the maximum number of sheets can be stacked without deteriorating the integrity. It also prevents sheets from falling off the stacking tray 61. It also reduces the effort required to align sheets removed from the stacking tray 61.

Furthermore, according to the image forming system 100 of this embodiment, when the condition data included in the print job being processed matches the condition data stored in the memory unit 2M to a certain extent, the control unit 2 interrupts the print job using the lower limit position associated with the stored condition data. Therefore, even if there is no condition data stored that exactly matches the conditions included in the print job being processed, the load amount can be limited using the lower limit position associated with condition data that is close to the conditions included in the print job.

In addition, the image forming system 100 according to this embodiment is equipped with an operation unit 19 that accepts operations. When the operation unit 19 accepts an operation to store the lower limit position of the height of the stacking tray 61, the control unit 2 associates condition data indicating the conditions included in the print job being processed with the height of the stacking tray 61 detected by the first detection unit and stores them in the memory unit 2M. This allows the lower limit position to be stored based on the user's judgment when observing the stacking situation.

Furthermore, according to the image forming system 100 of this embodiment, if the condition data corresponding to the print job being processed is not stored in the memory unit 2M, the control unit 2 notifies the user that it is recommended to set the lower limit position of the height of the stacking tray 61 relative to the operation unit 19, thereby making the user aware of the need to store the lower limit position.

Furthermore, according to the image forming system 100 of this embodiment, the control unit 2 interrupts the print job using the lower limit position only when a load capacity limit mode that limits the sheet load capacity is set, so the load capacity can be limited only when the user determines that a load capacity limit is necessary.

In addition, the image forming system 100 according to this embodiment is equipped with a post-processing device 110 that performs post-processing on sheets on which images have been formed, including one or more of stapling, shifting, and center-folding. The conditions included in the print job include one or more of the presence or absence and number of staples, presence or absence of shifting, presence or absence of center-folding, and the number of sheets that make up a bundle of sheets. Therefore, the load capacity can be limited depending on the post-processing conditions.

Furthermore, according to the image forming system 100 of this embodiment, the conditions included in the print job include one or more of the sheet size and whether or not mixed sizes are used, so the load amount can be limited depending on the sheet size and whether or not mixed sizes are used.

The above embodiment may be modified as follows:

In the above embodiment, an example was shown in which the control unit 2 suspends the print job (step S29) when it is determined that the lower limit position of the stacking tray 61 height has been set (step S27: YES). However, in addition to this, the system may be configured to allow the user to suspend the print job using the operation unit 19 and then set the lower limit position. This configuration is also suitable for cases in which the user is slow to detect signs of a decrease in alignment. For example, if the stack of sheets becomes too tilted or the top sheet falls, the user may suspend the print job, remove sheets until the tilt is resolved, and then operate the tray height setting button.

The functions of the control unit 2, memory unit 2M, and operation unit 19 of the image forming apparatus 1 according to the above embodiment may be provided in the sheet stacking device 120 or post-processing device 110.

In the above embodiment, an example was shown in which a CIS was used as the tray detection unit 71, but instead of a CIS, the height of the loading tray 61 may be detected by a sensor that irradiates light onto the detection piece 72 from above or below and detects the distance to the detection piece 72 from the phase shift of the light reflected from the detection piece 72.

100 Image forming system 1 Image forming apparatus 120 Sheet stacking device 2 Control unit 2M Memory unit 19 Operation unit 31 Discharge unit 51 Processing tray (post-processing unit)
54 Stapling device (post-processing section)
61: Loading tray 63: Lifting mechanism 68: Upper surface detector (second detector)
71 Tray detection unit (first detection unit)

Claims (7)

an image forming device that receives a print job and forms an image on a sheet;
a discharge section for discharging the sheet;
a stacking tray on which the sheets discharged by the discharge unit are stacked;
a lifting mechanism for lifting and lowering the loading tray;
a first detection unit capable of continuously detecting the height of the loading tray throughout the entire lifting range of the loading tray;
a control unit that controls the lifting and lowering of the stacking tray based on a detection result of the first detection unit;
a second detection unit that detects whether a loading surface of the loading tray on which the sheets are loaded is positioned at a receiving position for receiving the sheets;
a storage unit that stores condition data indicating conditions included in the print job and a lower limit position of the height of the stacking tray in association with each other;
an operation unit that accepts an operation,
The control unit
based on a detection result of the loading surface by the second detection unit, the loading tray is lowered in accordance with the loading amount of the sheets, and the loading surface is disposed at the receiving position;
a first detection unit detecting a height of the loading tray when the loading surface is placed at the receiving position, and when the height of the loading tray reaches the lower limit position, executing a full-load control to stop lifting and lowering of the loading tray;
In the full-fill control, when the stacking tray reaches the lower limit position associated with the condition data corresponding to the print job being processed, the lifting and lowering of the stacking tray is stopped, and the print job is interrupted;
An image forming system characterized in that when the operation unit receives an operation to store the lower limit position of the height of the loading tray while the loading tray is being lowered during processing of the print job, the condition data indicating the conditions included in the print job being processed and the height of the loading tray detected by the first detection unit are associated and stored in the memory unit. 2. The image forming system according to claim 1, wherein the first detection unit is a contact image sensor in which a plurality of photoelectric conversion elements are arranged in the direction in which the stacking tray is raised and lowered. The image forming system described in claim 1 or 2, characterized in that the control unit interrupts the print job using the lower limit position associated with the stored condition data when the condition data included in the print job being processed matches the condition data stored in the storage unit at a certain rate. The image forming system of any one of claims 1 to 3, characterized in that when the condition data corresponding to the print job being processed is not stored in the memory unit, the control unit notifies the user that it is recommended to perform an operation to set the lower limit position of the height of the loading tray relative to the operation unit. The image forming system according to any one of claims 1 to 4, characterized in that the control unit interrupts the print job using the lower limit position only when a load limit mode that limits the load amount of the sheets is set. a post-processing unit that performs one or more of a staple process, a shift process, and a center-fold process on the sheet on which the image has been formed,
An image forming system according to any one of claims 1 to 5, characterized in that the conditions included in the print job include one or more of the presence or absence and number of staple processing, the presence or absence of shift processing, the presence or absence of center folding processing, and the number of sheets constituting a copy of the sheet stack. An image forming system according to any one of claims 1 to 6, wherein the conditions included in the print job include one or more of the sheet size and whether or not mixed sizes are used.