JP2024065300A - Image forming device - Google Patents

Abstract

[Problem] To distinguish more sheet states with one sensor. [Solution] A lift plate 20 has a falling opening 20a. A first swinging member 51 has a first arm portion 512 and a first flange portion 513. A second swinging member 52 has a second arm portion 522 and a second flange portion 523. A discrimination unit 8c discriminates a plurality of sheet states based on a change in a detection signal of an object detection sensor 53. A first contact portion 516a of the first arm portion 512 falls into the falling opening 20a in a sheet-free state. A first detection target portion 513a, a first opening 513b, a second detection target portion 513c, and a second opening 513d of the first flange portion 513 selectively move to a detection area 530 when the first swinging member 51 swings. The second arm portion 522 moves from a closed position to an open position by contacting the target sheet 9a. When the second arm portion 522 is in the open position, the second flange portion 523 is located in the detection area 530. (FIG. 1)

Description

The present invention relates to an image forming device that can distinguish between multiple states of a sheet sent out from a lift plate that rises and falls.

In an image forming device, a print unit forms an image on a sheet transported by a sheet transport unit. The sheet transport unit may include a lift plate on which one or more sheets are placed, and a sheet feeding unit.

The lift plate rises from the initial position until the uppermost target sheet of the one or more sheets reaches the delivery position. The sheet feeding unit feeds the target sheet that has reached the delivery position to the transport path.

The image forming device also includes a number of sensors that detect the state of the sheets on the lift plate. For example, it is known that the image forming device includes a paper-out sensor that detects when the paper on the lift plate runs out and a remaining amount sensor that detects the amount of paper remaining (see, for example, Patent Document 1).

JP 2019-206417 A

However, in the image forming device, it is desirable to be able to determine more sheet conditions using one sensor in order to reduce costs.

The object of the present invention is to provide an image forming device that can determine more sheet conditions using a single sensor.

An image forming apparatus according to one aspect of the present invention includes a lift plate, a sheet feeding unit, a printing unit, and a sheet condition discrimination unit. The lift plate has one or more sheets placed thereon, and rises from an initial position until the uppermost target sheet among the one or more sheets reaches a sending position, and then descends to the initial position. The sheet feeding unit feeds the target sheet that has reached the sending position from on the lift plate to a conveying path. The printing unit forms an image on the target sheet fed to the conveying path. The sheet condition discrimination unit discriminates a plurality of sheet conditions. The lift plate has a fall opening that is an opening that is blocked by the one or more sheets placed on the lift plate. The sheet condition discrimination unit includes an object detection sensor, a first swinging member, a second swinging member, and a discrimination unit. The object detection sensor detects an object present in a detection area. The first swinging member has a rotatably supported first shaft portion, a first arm portion formed by extending from the first shaft portion to the lift plate, and a plate-shaped first flange portion formed by extending from the first shaft portion and traversing the detection area. The second swinging member has a rotatably supported second shaft portion, a second arm portion formed by extending from the second shaft portion to an introduction portion of the transport path, and a plate-shaped second flange portion formed in parallel with the first flange portion by extending from the second shaft portion. The discrimination unit discriminates the presence or absence of a sheet on the lift plate and the success or failure of feeding of the target sheet based on a change in the detection signal of the object detection sensor according to the movement of the lift plate. The first arm portion has a first contact portion that abuts against the target sheet when the lift plate is in a sheet-present state and falls into the fall-in opening when the lift plate is in a sheet-free state. The first flange has a first detectable portion, a first opening, a second detectable portion, and a second opening that selectively move to the detection area when the first swinging member swings around the first shaft portion. When the lift plate is in the initial position with the first contact portion falling into the fall opening, the first detectable portion is located in the detection area. When the lift plate is in the initial position with the first contact portion abutting against the target sheet, the first opening is located in the detection area. When the lift plate rises from the initial position, the second detectable portion passes through the detection area before the target sheet reaches the discharge position. When the target sheet reaches the discharge position, the second opening is located in the detection area. When the target sheet is not present in the introduction section, the second arm portion is located in a closed position that blocks the introduction section. When the target sheet passes through the introduction section, the second arm portion moves from the closed position to an open position that opens the introduction section by abutting against the target sheet. When the second arm portion is in the closed position, the second flange portion is located in an area outside the detection area. When the second arm portion is in the open position, the second flange portion is located in the detection area.

The present invention makes it possible to provide an image forming device that can determine more sheet conditions using a single sensor.

FIG. 1 is a diagram showing the configuration of an image forming apparatus according to an embodiment. FIG. 2 is a block diagram showing the configuration of a control device in the image forming apparatus according to the embodiment. FIG. 3 is an exploded perspective view of a state detection device in the image forming apparatus according to the embodiment. 4 is a first side view of the state detection device in the image forming apparatus according to the embodiment, in which the lift plate on which no sheet is placed is in the initial position. 5 is a second side view of the state detection device in the image forming apparatus according to the embodiment, in which the lift plate with one sheet placed thereon is in the initial position. 6 is a third side view of the state detection device in the image forming apparatus according to the embodiment, in which the lift plate loaded with sheets is in the initial position. 7 is a fourth side view of the state detection device in the image forming apparatus according to the embodiment, in which the lift plate with one sheet placed thereon is in the operating position. 8 is a fifth side view of the state detection device in the image forming apparatus according to the embodiment, in which the lift plate loaded with sheets is in the operating position. 9 is a sixth side view of the state detection device in the image forming apparatus according to the embodiment, in which the target sheet is fed to the conveying path. FIG. 10 is a diagram showing an example of a time chart of a detection signal of the state detection device of the image forming apparatus according to the embodiment.

Below, an embodiment of the present invention will be described with reference to the drawings. Note that the following embodiment is an example of the present invention and does not limit the technical scope of the present invention.

[Configuration of Image Forming Apparatus 10]
The image forming apparatus 10 according to the embodiment includes a sheet storage unit 2, a sheet conveying unit 3, and a printing unit 4. The image forming apparatus 10 further includes an operation device 801, a display device 802, and a control device 8.

The transport path 30, the sheet transport unit 3, the print unit 4, and the control device 8 are housed in the main body 1. The main body 1 is a housing that contains the main components of the image forming device 10.

The sheet storage section 2 can store one or more sheets 9. The sheets 9 are image forming media such as paper or resin sheets.

The sheet storage section 2 includes a lift plate 20 and a drive device 21. The sheet transport section 3 includes a sheet feeding mechanism 31 and multiple pairs of transport rollers 32.

The lift plate 20 is supported so that it can be raised and lowered. One or more sheets 9 are placed on the lift plate 20. In the following description, the uppermost sheet of the one or more sheets 9 placed on the lift plate 20 is referred to as the target sheet 9a.

The drive device 21 raises and lowers the lift plate 20. Driven by the drive device 21, the lift plate 20 rises from the initial position to the operating position and then descends to the initial position.

The initial position is the lower end of the lift range of the lift plate 20. Figures 4 to 6 show the lift plate 20 in the initial position.

The position of the lift plate 20 when the target sheet 9a reaches the delivery position is the operating position. Figures 7 to 9 show the state in which the lift plate 20 is in the operating position. The operating position varies depending on the number of sheets 9 on the lift plate 20 and the thickness of each sheet 9.

Figures 5 and 7 show a state where one sheet 9 is placed on the lift plate 20. Figures 6 and 8 show a state where multiple sheets 9 are fully loaded on the lift plate 20.

The sheet feeding mechanism 31 feeds the target sheet 9a that has reached the delivery position from the lift plate 20 to the transport path 30. The sheet feeding mechanism 31 is an example of a sheet feeding section.

The sheet feeding mechanism 31 includes a pickup roller 311, a feeding roller 312, and a separating member 313. The separating member 313 is in contact with the feeding roller 312.

The pickup roller 311 rotates and contacts the target sheet 9a, sending the target sheet 9a between the feed roller 312 and the separation member 313.

The position of the target sheet 9a when it contacts the pickup roller 311 is the delivery position. Figures 7 and 8 show the state when the target sheet 9a reaches the delivery position.

The feed roller 312 takes over the transport of the target sheet 9a from the pickup roller 311. The feed roller 312 feeds the target sheet 9a to the transport path 30.

When multiple sheets 9 are sent out by the pickup roller 311, the separation member 313 blocks all of the multiple sheets 9 except the target sheet 9a.

As described above, the sheet feeding mechanism 31 feeds the target sheet 9a that has reached the delivery position from the lift plate 20 to the conveying path 30.

The multiple pairs of transport rollers 32 transport the target sheet 9a fed to the transport path 30 along the transport path 30. The final pair of the multiple pairs of transport rollers 32 discharges the target sheet 9a from the transport path 30 onto the discharge tray 101.

The printing unit 4 executes a printing process. The printing process is a process of forming an image on a target sheet 9a conveyed along the conveying path 30. That is, the printing unit 4 forms an image on the target sheet 9a fed to the conveying path 30.

In the example shown in FIG. 1, the printing unit 4 performs the printing process by electrophotography. In this case, the printing unit 4 includes an optical scanning device 40, a photoconductor 41, a charging device 42, a developing device 43, a transfer device 44, a cleaning device 45, and a fixing device 46.

The charging device 42 charges the surface of the drum-shaped photoconductor 41. The optical scanning device 40 forms an electrostatic latent image on the charged surface of the photoconductor 41. The developing device 43 develops the electrostatic latent image into a toner image.

The transfer device 44 transfers the toner image from the surface of the photoreceptor 41 to the target sheet 9a. The cleaning device 45 removes the remaining toner that has not been transferred to the target sheet 9a from the surface of the photoreceptor 41.

The fixing device 46 applies heat and pressure to the toner image on the target sheet 9a. This causes the fixing device 46 to fix the toner image to the target sheet 9a.

The printing unit 4 may be a device that performs the printing process using a method other than the electrophotographic method. For example, the printing unit 4 may be a device that performs the printing process using an inkjet method.

The operation device 801 is a device that accepts operations by a person. For example, the operation device 801 includes an operation button and a touch panel.

The display device 802 is a device that displays information. For example, the display device 802 includes a panel display device such as a liquid crystal display unit.

As shown in FIG. 2, the control device 8 includes a CPU (Central Processing Unit) 81, a RAM (Random Access Memory) 82, a secondary storage device 83, a signal interface 84, and a communication device 85.

The secondary storage device 83 is a computer-readable, non-volatile storage device. The secondary storage device 83 is capable of storing and updating computer programs and various data. For example, one or both of a flash memory and a hard disk drive are employed as the secondary storage device 83.

The signal interface 84 converts the signals output by the various sensors into digital data and transmits the converted digital data to the CPU 81. Furthermore, the signal interface 84 converts the control commands output by the CPU 81 into control signals and transmits the control signals to the devices to be controlled.

The communication device 85 communicates with other devices, such as a host device (not shown). The CPU 81 communicates with the other devices through the communication device 85.

The CPU 81 is a processor that executes various data processing and control by executing the computer program. The CPU 81 controls the sheet conveying unit 3, the printing unit 4, the display device 802, the communication device 85, etc.

RAM 82 is a computer-readable volatile storage device. RAM 82 temporarily stores the computer programs executed by CPU 81 and data output and referenced by CPU 81 in the course of executing various processes.

The CPU 81 includes a number of processing modules that are realized by executing the computer program. The processing modules include a main processing unit 8a, a print control unit 8b, and a discrimination unit 8c.

The main processing unit 8a executes processes such as starting various processes in response to operations on the operation device 801 and controlling the display device 802.

The print control unit 8b controls the sheet transport unit 3. As a result, the print control unit 8b controls the feeding of the target sheet 9a from the sheet storage unit 2 to the transport path 30, and the transport of the target sheet 9a in the transport path 30.

The print control unit 8b controls the drive device 21 to raise the lift plate 20 from the initial position to the operating position, and further lowers the lift plate 20 from the operating position to the initial position.

The print control unit 8b raises and lowers the lift plate 20 while operating the sheet feeding mechanism 31. This causes the target sheet 9a to be fed from the lift plate 20 to the transport path 30.

Furthermore, the print control unit 8b controls the print unit 4. The print control unit 8b causes the print unit 4 to execute the print process in synchronization with the conveyance of the sheet 9 by the sheet conveyance unit 3.

When the print control unit 8b receives a print request via the operation device 801 or the communication device 85, it causes the sheet conveying unit 3 to convey the sheet 9 and causes the printing unit 4 to execute the print process.

In the printing process, the printing unit 4 forms the electrostatic latent image on the surface of the photoconductor 41 using the optical scanning device 40, and then develops the electrostatic latent image into the toner image using the developing device 43.

Furthermore, in the printing process, the printing unit 4 transfers the toner image on the surface of the photoreceptor 41 to the sheet 9 by the transfer device 44. Furthermore, in the printing process, the printing unit 4 removes the residual toner that has not been transferred to the sheet 9 from the surface of the photoreceptor 41 by the cleaning device 45.

The discrimination unit 8c performs processing to discriminate various conditions based on the detection signals of various sensors equipped in the image forming device 10 and other data.

However, in order to reduce costs, it is desirable for the image forming device 10 to be able to detect as many sheet conditions as possible using one sensor. For example, the sheet conditions include the presence or absence of a sheet on the lift plate 20 and whether the target sheet 9a has been fed successfully.

The image forming apparatus 10 further includes a state detection device 5 that detects information used to determine the sheet state (see FIGS. 1, 3, and 4). The discrimination unit 8c discriminates the multiple sheet states based on a detection signal from a sensor included in the state detection device 5. The state detection device 5 and the discrimination unit 8c are an example of a sheet state discrimination unit.

The lift plate 20 has a drop opening 20a (see Figures 3 to 6). The drop opening 20a is an opening that is blocked by one or more sheets 9 placed on the lift plate 20. In this embodiment, the drop opening 20a is a slit formed by cutting inward from the tip of the lift plate 20 (see Figure 3).

[Configuration of state detection device 5]
The state detection device 5 includes a first swinging member 51, a second swinging member 52, and a photosensor 53 (see FIGS. 3 to 6).

The photosensor 53 detects an object present in the detection area 530. The photosensor 53 is fixed inside the main body 1. In this embodiment, the photosensor 53 is a transmission type sensor. Note that the photosensor 53 may also be a reflection type sensor.

The photosensor 53 is an example of a non-contact object detection sensor. Note that a contact object detection sensor may be used instead of the photosensor 53.

The first oscillating member 51 and the second oscillating member 52 are each supported so that they can oscillate. Hereinafter, the initial position of the first oscillating member 51 will be referred to as the first initial position, and the initial position of the second oscillating member 52 will be referred to as the second initial position.

Figure 4 shows the state in which the first oscillating member 51 is in the first initial position and the second oscillating member 52 is in the second initial position.

The first oscillating member 51 has a first shaft portion 511, a first arm portion 512, and a first flange portion 513 (see FIG. 3). The second oscillating member 52 has a second shaft portion 521, a second arm portion 522, and a second flange portion 523 (see FIG. 3).

[Configuration of the first pivot member 51]
The first shaft portion 511 is rotatably supported. The first swinging member 51 is swingable about the first shaft portion 511. The first shaft portion 511 is disposed along the width direction intersecting with the sheet feeding direction.

The first arm portion 512 is formed to extend from the first shaft portion 511 to the lift plate 20. The first arm portion 512 has a link portion 514, a parallel shaft portion 515, an action portion 516, and a guide portion 517 (see FIG. 3).

The link portion 514 is formed by extending from the first shaft portion 511 in a direction intersecting the width direction. The link portion 514 connects the first shaft portion 511 and the parallel shaft portion 515.

The parallel shaft portion 515 is formed parallel to the first shaft portion 511. The first shaft portion 511, the link portion 514, and the parallel shaft portion 515 form a gap 510. That is, the first oscillating member 51 forms a gap 510 between the first shaft portion 511 and the first arm portion 512.

The action portion 516 is formed by extending from the parallel shaft portion 515 to the lift plate 20. The end of the action portion 516 is a first contact portion 516a that abuts against the target sheet 9a.

The first contact portion 516a comes into contact with the target sheet 9a when there is a sheet on the lift plate 20 (see Figures 5 to 9). The sheet-present state is a state in which one or more sheets 9 are placed on the lift plate 20.

The first contact portion 516a falls into the fall opening 20a when there is no sheet on the lift plate 20 (see Figures 3 and 4).

The first oscillating member 51 is in the first initial position when the first contact portion 516a falls into the fall opening 20a. In this embodiment, the first spring 54 holds the first oscillating member 51 in the first initial position (see FIG. 3). The first spring 54 is a part of the state detection device 5.

The first oscillating member 51 may be held in the first initial position by balancing the moment loads of the parts extending from the first shaft portion 511, such as the first arm portion 512 and the first flange portion 513.

The guide portion 517 is formed extending from the first contact portion 516a. The guide portion 517 catches on the edge of the fall-in opening 20a when the first contact portion 516a falls into the fall-in opening 20a. In this way, the guide portion 517 limits the depth to which the first contact portion 516a falls into the fall-in opening 20a.

Furthermore, the guide portion 517 slides against the leading edge of the sheet 9 when one or more sheets 9 are placed on the lift plate 20. As a result, the guide portion 517 transmits the force received from the sheet 9 to the first swinging member 51 as a force for lifting the first arm portion 512.

When the sheet state on the lift plate 20 changes from the sheet-present state to the sheet-absent state, the first contact portion 516a falls into the fall opening 20a, causing the first oscillating member 51 to oscillate in the first direction.

On the other hand, when the sheet state on the lift plate 20 changes from the sheet-free state to the sheet-present state, the first contact portion 516a rises from the position where it fell into the fall opening 20a to above the target sheet 9a, causing the first oscillating member 51 to oscillate in a second direction. The second direction is the oscillating direction opposite to the first direction.

The first oscillating member 51 also oscillates in the second direction when a sheet 9 is added onto the lift plate 20 and when the lift plate 20 is raised.

The first flange 513 is a plate-shaped portion that extends from the first shaft 511 and crosses the detection area 530. The first flange 513 has a first detectable portion 513a, a first opening 513b, a second detectable portion 513c, and a second opening 513d (see FIG. 3).

When the first oscillating member 51 oscillates around the first shaft portion 511, the first detectable portion 513a, the first opening 513b, the second detectable portion 513c, and the second opening 513d selectively move to the detection area 530. That is, any one of the first detectable portion 513a, the first opening 513b, the second detectable portion 513c, and the second opening 513d is located in the detection area 530.

When the lift plate 20 is in the initial position with the first contact portion 516a falling into the fall opening 20a, the first detectable portion 513a is located in the detection area 530 (see FIG. 3). When the first detectable portion 513a is located in the detection area 530, the first opening 513b, the second detectable portion 513c, and the second opening 513d are located in an area outside the detection area 530 (see FIG. 3).

When the lift plate 20 is in the initial position with the first contact portion 516a in contact with the target sheet 9a, the first opening 513b is located in the detection area 530 (see Figures 5 and 6). That is, when the lift plate 20 is in the initial position with the sheet in the sheet-present state, the first opening 513b is located in the detection area 530.

When the first opening 513b is located in the detection area 530, the first detectable portion 513a, the second opening 513d, and the second detectable portion 513c are located in an area outside the detection area 530 (see Figures 5 and 6).

When the lift plate 20 rises from the initial position, before the target sheet 9a reaches the delivery position, the first opening 513b moves to an area outside the detection area 530, and the second detectable portion 513c passes through the detection area 530.

When the target sheet 9a reaches the delivery position, the second opening 513d is located in the detection area 530 (see Figures 7 and 8). When the target sheet 9a reaches the delivery position, the first detected portion 513a, the first opening 513b, and the second detected portion 513c are located in an area outside the detection area 530 (see Figures 7 and 8).

That is, when the lift plate 20 rises from the initial position to the operating position under the condition that the seat state is the seat-present state, the first opening 513b moves from the detection area 530 to an area outside the detection area 530, and the second detected portion 513c passes through the detection area 530. Furthermore, the second opening 513d moves from an area outside the detection area 530 to the detection area 530.

The target sheet 9a being fed from the lift plate 20 to the introduction section 30a passes through the gap 510 formed by the first shaft section 511 and the first arm section 512 (see Figure 9).

On the other hand, when the lift plate 20 descends from the operating position to the initial position, the second opening 513d moves from the detection area 530 to an area outside the detection area 530, and the second detected portion 513c passes through the detection area 530. Furthermore, the first opening 513b moves from an area outside the detection area 530 to the detection area 530.

In addition, when the lift plate 20 returns to the initial position, the sheet state may be the sheet-free state. In this case, the first opening 513b further moves from the detection area 530 to an area outside the detection area 530, and the first detectable portion 513a moves from an area outside the detection area 530 to the detection area 530.

[Configuration of the second pivot member 52]
The second shaft portion 521 is rotatably supported. The second swinging member 52 is swingable about the second shaft portion 521. The second shaft portion 521 is disposed along the width direction. In this embodiment, the second shaft portion 521 is disposed coaxially with the first shaft portion 511.

The second arm portion 522 is formed to extend from the second shaft portion 521 to the introduction portion 30a of the transport path 30. When the second swinging member 52 is in the second initial position, the second arm portion 522 is in a closed position that blocks the introduction portion 30a of the transport path 30 (see Figures 4 to 7).

The second initial position is the position of the second oscillating member 52 when the second arm portion 522 is in the closed position. In this embodiment, the second spring 55 holds the second oscillating member 52 in the second initial position (see FIG. 3). The second spring 55 is a part of the state detection device 5.

The second oscillating member 52 may be held in the second initial position by balancing the moment loads of the parts extending from the second shaft portion 521, such as the second arm portion 522 and the second flange portion 523.

When the target sheet 9a is not present in the introduction section 30a, the second arm portion 522 is located in the closed position. When the target sheet 9a passes through the introduction section 30a of the conveying path 30, the second arm portion 522 moves from the closed position to the open position by contacting the target sheet 9a (see FIG. 9). The open position is a position that opens the introduction section 30a of the conveying path 30.

When the target sheet 9a passes through the introduction section 30a, the second arm section 522 is held in the open position by the force it receives from the target sheet 9a.

When the second arm portion 522 moves from the closed position to the open position, the second oscillating member 52 swings about the second shaft portion 521 (see Figures 8 and 9). At this time, the second oscillating member 52 swings from the second initial position to the retracted position.

The second flange 523 is a plate-like portion extending from the second shaft 521 and formed in parallel with the first flange 513. When the second oscillating member 52 is in the second initial position, the second flange 523 is in a position extending from the second shaft 521 into an area outside the detection area 530 (see Figures 4 to 8).

That is, when the second arm portion 522 is in the closed position, the second flange portion 523 is located in an area outside the detection area 530. In other words, when the target sheet 9a is not present in the introduction portion 30a, the second flange portion 523 is located in an area outside the detection area 530.

When the second arm portion 522 moves from the closed position to the open position, the second flange portion 523 moves from an area outside the detection area 530 into the detection area 530 (see FIG. 9).

That is, when the second arm portion 522 is in the open position, the second flange portion 523 is located in the detection area 530. In other words, when the target sheet 9a passes through the introduction portion 30a, the second flange portion 523 is located in the detection area 530.

The discrimination unit 8c determines whether or not a sheet is present on the lift plate 20 and whether the target sheet 9a has been fed successfully based on the change in the detection signal of the photosensor 53 in response to the movement of the lift plate 20.

Figure 10 shows an example of a time chart of the detection signal of the photosensor 53. In Figure 10, when the detection signal is at the first level L1, the photosensor 53 is not detecting an object in the detection area 530. When the detection signal is at the second level L2, the photosensor 53 is detecting an object in the detection area 530.

When the first opening 513b or the second opening 513d is located in the detection area 530, the photosensor 53 outputs the detection signal at the first level L1. On the other hand, when the first detectable portion 513a, the second detectable portion 513c, or the second flange portion 523 is located in the detection area 530, the photosensor 53 outputs the detection signal at the second level L2.

In FIG. 10, the first point P1 is the point at which the lift plate 20 starts to rise from the initial position. The second point P2 is the point at which the target sheet 9a reaches the delivery position and the lift plate 20 reaches the operating position.

The third point P3 is the point at which the leading edge of the target sheet 9a begins to pass through the introduction section 30a of the conveying path 30. The fourth point P4 is the point at which the leading edge of the target sheet 9a passes through the introduction section 30a of the conveying path 30.

The fifth point P5 is the point at which the lift plate 20 starts to descend from the operating position. The sixth point P6 is the point at which the lift plate 20 descends and reaches the initial position.

When one or more sheets 9 are placed on the lift plate 20, the first opening 513b is located in the detection area 530 when the lift plate 20 is in the initial position (see Figures 5 and 6). At this time, the detection signal is in the first signal state S1 indicating the first level L1.

On the other hand, when the sheet 9 is not placed on the lift plate 20, the first detected portion 513a is located in the detection area 530 when the lift plate 20 is in the initial position (see FIG. 4). At this time, the detection signal is in the reference signal state S0 indicating the second level L2. In FIG. 10, the dashed line in the time chart indicates the reference signal state S0.

When one or more sheets 9 are placed on the lift plate 20 and the lift plate 20 rises from the initial position to the operating position, the detection signal changes from the first signal state S1 to the second signal state S2 and then to the third signal state S3.

The second signal state S2 is the state of the detection signal when the second detectable portion 513c passes through the detection area 530. Therefore, the second signal state S2 is a state in which the detection signal indicates the second level L2.

The third signal state S3 is the state of the detection signal when the second opening 513d is located in the detection area 530 (see Figures 7 and 8). Therefore, the third signal state S3 is a state in which the detection signal indicates the first level L1.

When the target sheet 9a reaches the delivery position due to the lift plate 20 rising, the target sheet 9a is delivered by the sheet feeding mechanism 31 toward the introduction portion 30a of the conveying path 30 (see FIG. 9). As a result, the second arm portion 522 moves from the closed position to the open position, and the detection signal changes from the third signal state S3 to the fourth signal state S4.

The fourth signal state S4 is the state of the detection signal when the second opening 513d and the second flange 523 are located in the detection area 530. Therefore, the fourth signal state S4 is a state in which the detection signal indicates the second level L2.

When the target sheet 9a passes through the introduction section 30a of the conveying path 30 by the sheet feeding mechanism 31, the second arm portion 522 returns from the open position to the closed position. This causes the detection signal to change from the fourth signal state S4 to the fifth signal state S5.

The fifth signal state S5 is the state of the detection signal when the second flange 523 moves to an area outside the detection area 530 so that only the second opening 513d is located in the detection area 530.

After the target sheet 9a passes through the introduction section 30a, when the lift plate 20 descends from the operating position to the initial position, the detection signal changes from the fifth signal state S5 to the sixth signal state S6, and then to the seventh signal state S7.

The sixth signal state S6 is the state of the detection signal when the second detectable portion 513c passes through the detection area 530. Therefore, the sixth signal state S6 is a state in which the detection signal indicates the second level L2.

The seventh signal state S7 is the state of the detection signal when only the first opening 513b is located in the detection region 530. Therefore, the seventh signal state S7 is the state in which the detection signal indicates the first level L1.

If one or more sheets 9 remain on the lift plate 20, the detection signal remains in the seventh signal state S7 even after the lift plate 20 returns to the initial position.

However, if the target sheet 9a is fed so that there is no sheet on the lift plate 20, when the lift plate 20 reaches the initial position, the detection signal changes from the seventh signal state S7 to the reference signal state S0.

When the lift plate 20 is in the initial position and the detection signal is in the reference signal state S0, the discrimination unit 8c discriminates that the seat state is the no-seat state. For example, when the lift plate 20 starts to rise or when the lift plate 20 stops to fall, the discrimination unit 8c discriminates between the seat-present state and the no-seat state based on the state of the detection signal.

The image forming device 10 also includes an initial position sensor (not shown). The initial position sensor detects that the lift plate 20 is in the initial position. The discrimination unit 8c may discriminate between the sheet-present state and the sheet-absent state when the initial position sensor detects that the lift plate 20 is in the initial position.

If the discrimination unit 8c determines that the sheet state is the no-sheet state, the print control unit 8b does not raise the lift plate 20. In this case, the main processing unit 8a outputs paper-out notification information through the display device 802.

Furthermore, the discrimination unit 8c determines that a rise failure has occurred if the detection signal does not show a change from the first signal state S1 through the second signal state S2 to the third signal state S3 within the time period from the first point in time P1 until the first set time has elapsed.

The failure to rise is a failure in the lifting operation of the lift plate 20. The failure to rise is an example of a state in which the target sheet 9a fails to be fed. The state in which the target sheet 9a fails to be fed is an example of the sheet state.

If the discrimination unit 8c determines that the above-mentioned lifting failure has occurred, the print control unit 8b stops the lifting of the lift plate 20. Furthermore, the main processing unit 8a outputs notification information that the above-mentioned lifting failure has occurred through the display device 802.

The discrimination unit 8c also measures the feed detection time T1 when the detection signal changes from the first signal state S1 through the second signal state S2 and the third signal state S3 to the fourth signal state S4 (see FIG. 10). The feed detection time T1 is the time from the first point P1 to when the detection signal changes to the fourth signal state S4.

The discrimination unit 8c can determine the amount of sheets loaded on the lift plate 20 based on a change in the detection signal in response to the movement of the lift plate 20. Specifically, the discrimination unit 8c can determine the amount of sheets loaded based on the feed detection time T1. The shorter the feed detection time T1, the greater the amount of sheets loaded. The main processing unit 8a outputs information on the amount of sheets loaded via the display device 802.

In addition, when the detection signal changes from the first signal state S1 through the second signal state S2 and the third signal state S3 to the fourth signal state S4, the discrimination unit 8c measures the duration T2 of the fourth signal state S4.

When the duration T2 of the fourth signal state S4 exceeds the second set time, the discrimination unit 8c discriminates that a jam of the target sheet 9a has occurred. A jam of the target sheet 9a is an example of a state in which feeding of the target sheet 9a has failed.

Furthermore, when the duration T2 of the fourth signal state S4 is shorter than the second set time, the discrimination unit 8c measures the fall time. The fall time is the elapsed time from the time when the detection signal changes from the fourth signal state S4 to the fifth signal state S5.

The discrimination unit 8c discriminates that a fall failure has occurred if the signal state does not show a change from the fifth signal state S5 through the sixth signal state S6 to the seventh signal state S7 before the fall time exceeds the third set time.

The descent failure is a failure in the descent operation of the lift plate 20. When the discrimination unit 8c determines that the descent failure has occurred, the print control unit 8b stops the descent of the lift plate 20. Furthermore, the main processing unit 8a outputs notification information that the descent failure has occurred through the display device 802.

As described above, by adopting the image forming device 10, many of the above sheet states can be detected using a single photosensor 53.

When a continuous printing process is performed, the print control unit 8b corrects the timing for lifting the lift plate 20 from the initial position in accordance with the feed detection time T1. The continuous printing process is a process for forming images continuously on multiple sheets 9.

In the image forming device 10, the multiple pairs of transport rollers 32 include one pair of registration rollers 32a (see FIG. 1). The registration roller pair 32a temporarily stops the sheet 9 and then transports it to the printing position.

When the continuous printing process is performed, the print control unit 8b starts lifting the lift plate 20 when the transport adjustment time has elapsed since the registration roller pair 32a started transporting the previous target sheet 9a. The transport adjustment time is set according to the length of the sheet 9.

As mentioned above, the greater the sheet load, the shorter the feeding detection time T1. Also, the shorter the feeding detection time T1, the shorter the time from when the lift plate 20 starts to rise to when the next target sheet 9a is sent out.

Therefore, the print control unit 8b corrects the transport adjustment time for starting the current operation of the lift plate 20 according to the feed detection time T1 during the previous operation of the lift plate 20. The print control unit 8b corrects the transport adjustment time to be longer as the feed detection time T1 is shorter.

[Notes on the invention]
The following will provide an overview of the invention extracted from the above-described embodiment. Note that the configurations and processing functions described in the following supplementary notes can be selected and combined as desired.

<Appendix 1>
a lift plate on which one or more sheets are placed, which rises from an initial position until a top target sheet among the one or more sheets reaches a delivery position, and then descends to the initial position;
a sheet feeding section that feeds the target sheet that has reached the delivery position from above the lift plate to a conveyance path;
a print unit that forms an image on the target sheet fed to the conveying path;
A seat state discrimination unit that discriminates between a plurality of seat states,
the lift plate has a drop opening that is an opening that is blocked by the one or more sheets placed on the lift plate;
The seat state determination unit is
an object detection sensor that detects an object present in a detection area;
a first swinging member having a rotatably supported first shaft portion, a first arm portion formed by extending from the first shaft portion to the lift plate, and a plate-shaped first flange portion formed by extending from the first shaft portion and traversing the detection area;
a second swinging member having a rotatably supported second shaft portion, a second arm portion formed by extending from the second shaft portion to an introduction portion of the conveying path, and a plate-like second flange portion extending from the second shaft portion and formed in parallel with the first flange portion;
a discrimination unit that discriminates whether a sheet is present on the lift plate and whether the target sheet has been fed successfully based on a change in a detection signal from the object detection sensor in response to the movement of the lift plate,
the first arm portion has a first contact portion that contacts the target sheet when the lift plate has a sheet thereon and falls into the fall opening when the lift plate has no sheet thereon;
the first flange portion has a first detectable portion, a first opening, a second detectable portion, and a second opening that selectively move to the detection area when the first swing member swings around the first shaft portion;
When the lift plate is in the initial position under a condition in which the first contact portion falls into the fall opening, the first detected portion is located in the detection area,
When the lift plate is in the initial position under a condition in which the first contact portion is in contact with the target sheet, the first opening is located in the detection area,
When the lift plate rises from the initial position, the second detected portion passes through the detection area before the target sheet reaches the delivery position,
When the target sheet reaches the delivery position, the second opening is located in the detection area,
When the target sheet is not present in the introduction portion, the second arm portion is located at a closed position that blocks the introduction portion,
when the target sheet passes through the introduction section, the second arm portion is brought into contact with the target sheet and moves from the closed position to an open position to open the introduction section;
When the second arm portion is in the closed position, the second flange portion is located in a region outside the detection region,
When the second arm portion is in the open position, the second flange portion is located in the detection area.

<Appendix 2>
2. The image forming apparatus according to claim 1, wherein the first swinging member forms the introduction portion of the transport path between the first shaft portion and the first arm portion.

<Appendix 3>
The image forming apparatus according to claim 1 or 2, wherein the discrimination unit discriminates between a malfunction of the lift plate's lifting operation and a jam of the target sheet as a state of failure in feeding the target sheet.

<Appendix 4>
The image forming apparatus according to any one of claims 1 to 3, wherein the discrimination unit determines the amount of sheets loaded on the lift plate based on a change in the detection signal of the object detection sensor in response to the movement of the lift plate.

10: Image forming apparatus 20: Lift plate 20a: Falling opening 21: Drive device 30: Transport path 30a: Introduction section 31: Sheet feeding mechanism 51: First swinging member 52: Second swinging member 53: Photo sensor 54: First spring 55: Second spring 510: Gap 511: First shaft portion 512: First arm portion 513: First flange portion 513a: First detected portion 513b: First opening 513c: Second detected portion 513d: Second opening 514: Link portion 515: Parallel shaft portion 516: Action portion 516a: First contact portion 517: Guide portion 521: Second shaft portion 522: Second arm portion 523: Second flange portion 530: Detection area

Claims (4)

a lift plate on which one or more sheets are placed, which rises from an initial position until a top target sheet among the one or more sheets reaches a delivery position, and then descends to the initial position;
a sheet feeding section that feeds the target sheet that has reached the delivery position from above the lift plate to a conveying path;
a print unit that forms an image on the target sheet fed to the conveying path;
A seat state discrimination unit that discriminates between a plurality of seat states,
the lift plate has a drop opening that is an opening that is blocked by the one or more sheets placed on the lift plate;
The seat state determination unit is
an object detection sensor that detects an object present in a detection area;
a first swinging member having a rotatably supported first shaft portion, a first arm portion formed by extending from the first shaft portion to the lift plate, and a plate-shaped first flange portion formed by extending from the first shaft portion and traversing the detection area;
a second swinging member having a rotatably supported second shaft portion, a second arm portion formed by extending from the second shaft portion to an introduction portion of the conveying path, and a plate-like second flange portion extending from the second shaft portion and formed in parallel with the first flange portion;
a discrimination unit that discriminates whether a sheet is present on the lift plate and whether the target sheet has been fed successfully based on a change in a detection signal from the object detection sensor in response to the movement of the lift plate,
the first arm portion has a first contact portion that contacts the target sheet when the lift plate has a sheet thereon and falls into the fall opening when the lift plate has no sheet thereon;
the first flange portion has a first detectable portion, a first opening, a second detectable portion, and a second opening that selectively move to the detection area when the first swing member swings around the first shaft portion;
When the lift plate is in the initial position under a condition in which the first contact portion falls into the fall opening, the first detected portion is located in the detection area,
When the lift plate is in the initial position under a condition in which the first contact portion is in contact with the target sheet, the first opening is located in the detection area,
When the lift plate rises from the initial position, the second detected portion passes through the detection area before the target sheet reaches the delivery position,
When the target sheet reaches the delivery position, the second opening is located in the detection area,
When the target sheet is not present in the introduction portion, the second arm portion is located at a closed position that blocks the introduction portion,
when the target sheet passes through the introduction section, the second arm portion is brought into contact with the target sheet and moves from the closed position to an open position to open the introduction section;
When the second arm portion is in the closed position, the second flange portion is located in a region outside the detection region,
When the second arm portion is in the open position, the second flange portion is located in the detection area. The image forming device according to claim 1, wherein the first swinging member forms a gap between the first shaft portion and the first arm portion through which the target sheet can pass. The image forming device according to claim 1 or 2, wherein the discrimination unit discriminates between a failure in the lifting operation of the lift plate and a jam of the target sheet as a state of failure in feeding the target sheet. The image forming apparatus according to claim 1 or 2, wherein the discrimination unit determines the amount of sheets loaded on the lift plate based on a change in the detection signal of the object detection sensor in response to the movement of the lift plate.