Paper feeding device and image forming device

Abstract

To provide a paper feeding device and an image forming device with simplified configurations and thus cost benefits.SOLUTION: A paper feeding device 100 includes a lift plate 11 on which stacking sheets S are to be loaded, a displacement member 30 and a sensor 22. The displacement member 30 has an initial first form part 31, a second form part 32, and a next first form part 33. At a first stage of the sheet amount, the initial first form part 31 is displaced to a detection position D of the sensor 22 before and after lifting. In a second stage, the initial first form part 31 is displaced to the detection position D before lifting, and the second form part 32 is displaced to the detection position D after lifting. In a third stage, the initial first form part 31 is displaced to the detection position D before lifting, and the second form part 32 passes the detection position D during lifting, and the next first form part 33 is displaced to the detection position D after lifting. In a fourth stage, the second form part 32 is displaced to the detection position D before lifting, and the next first form part 33 is displaced to the detection position D after lifting.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present disclosure relates to a paper feeding device and an image forming apparatus. [Background technology]

[0002] 2. Description of the Related Art An image forming apparatus that forms an image on a sheet includes a sheet feeder that supplies sheets to an image forming unit, etc. A sheet feeder that is configured to be capable of determining the amount of sheets in the apparatus in multiple stages has been proposed.

[0003] The sheet feeding device described in Patent Document 1 determines the sheet amount in multiple stages by using two sensors that output ON or OFF depending on the position of a displacement member that blocks light to a detection unit.

[0004] Specifically, the paper feeding device changes the position of the displacement member in response to changes in the amount of sheets, and the combination of the two sensor outputs in response to this change in position changes gradually among four non-overlapping combinations, making it possible to determine the amount of sheets in four stages. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2016-124654 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, the paper feeder described in Patent Document 1 has a problem in that the configuration of the paper feeder becomes complicated and costly because two sensors are used.

[0007] The present disclosure has been made in consideration of the above-mentioned problems, and provides a paper feeder and an image forming apparatus that have a simplified configuration and are cost-effective. [Means for solving the problem]

[0008] A paper feeder according to an aspect of the present disclosure feeds sheets to the outside of the paper feeder. The paper feeder includes a cassette, a contact piece, a displacement member, a sensor, and a determination unit. The cassette has a lift plate on which a plurality of sheets are stacked and lifted. The contact piece comes into contact with the topmost sheet, which is the topmost sheet stacked on the lift plate, and displaces in response to an increase or decrease in the amount of sheets and a change in the position of the topmost sheet before and after the lift plate is lifted. The displacement unit is provided with a first form portion and a second form portion that are displaced in conjunction with the contact piece and have different forms. The sensor is provided at a position corresponding to the displacement member, and an output changes when the first form portion is displaced to a detection position and when the second form portion is displaced. The determination unit determines the sheet amount based on the respective changes in the output of the sensor. The displacement member is configured as follows. That is, the displacement member is provided with an initial first form portion which is a portion of the initial first form, a second form portion which is a portion of the second form, and a next first form portion which is a portion of the next first form, in this order, along a direction opposite to a direction in which the displacement member is displaced when the position of the topmost sheet is raised. In the first stage in which the sheet amount is minimum, the displacement member displaces the initial first form portion to the detection position of the sensor before lifting the lift plate, and the initial first form portion also displaces to the detection position after lifting. In the second stage in which the sheet amount is greater than in the first stage, the displacement member displaces the initial first form portion to the detection position before lifting, and the second form portion displaces to the detection position after lifting. In the third stage in which the sheet amount is greater than in the second stage, the displacement member displaces the initial first form portion to the detection position before lifting, and displaces the second form portion to pass the detection position during lifting, and the next first form portion displaces to the detection position after lifting.The displacement member is configured such that in a fourth stage in which the sheet amount is greater than the third stage, the second form portion is displaced to the detection position before lifting and the next first form portion is displaced to the detection position after lifting, and the determination unit determines which stage the sheet amount is in, from the first stage to the fourth stage, based on the respective changes in the output of the sensor before and after lifting of the lift plate described above.

[0009] According to one aspect of the present disclosure, there is provided an image forming apparatus including the sheet feeding device and an image forming section, the image forming section forming a toner image on the sheet. Effect of the Invention

[0010] According to the present disclosure, the paper feed device can be simplified in structure and configured to have cost benefits. [Brief description of the drawings]

[0011] [Figure 1] 1 is a diagram illustrating an example of an image forming apparatus including a paper feeder according to an embodiment of the present disclosure. [Diagram 2] FIG. 2 is a vertical cross-sectional view showing the configuration of the paper feeding device. [Diagram 3] 2 is a diagram showing the configuration of a contact piece, a displacement member, a sensor, and a control unit (an example of a "determination unit" in the present disclosure) in the paper feeding device. FIG. [Figure 4] 3A and 3B are a longitudinal sectional view and an enlarged view of a main portion of the sheet feeding device when the sheet amount is at a first stage. [Diagram 5] 4A and 4B are a longitudinal sectional view and an enlarged view of a main portion of the sheet feeding device when the sheet amount is at a second stage. [Figure 6] 13A and 13B are a longitudinal sectional view and an enlarged view of a main portion of the sheet feeding device when the sheet amount is at a third stage. [Figure 7] 13A and 13B are a vertical sectional view and an enlarged view of a main portion of the sheet feeding device when the sheet amount is at a fourth stage. [Figure 8] 13A and 13B are a vertical sectional view and an enlarged view of a main portion of the sheet feeding device when the sheet amount is at a fifth stage. [Figure 9]FIG. 11 is a diagram showing sensor outputs at various stages of sheet amount. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, a paper feeder 100 according to an embodiment of the present disclosure will be described with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference symbols and will not be described repeatedly. In the following description, terms that indicate positions or directions such as "upper", "lower", "horizontal" and "vertical" may be used. These terms are used for convenience to facilitate understanding of the embodiment, and are not limited to positions or directions when actually implemented.

[0013] An image forming apparatus 1 including a sheet feeding device 100 according to an embodiment of the present disclosure will be described with reference to Fig. 1. Fig. 1 is a diagram showing an example of an image forming apparatus 1 including a sheet feeding device 100 according to an embodiment of the present disclosure.

[0014] As shown in FIG. 1, the image forming apparatus 1 includes a paper feeding device 100 that supplies a sheet S, a transport path 2 along which the sheet S supplied from the paper feeding device 100 is transported, transport rollers 3 that transport the sheet S on the transport path 2, an image forming unit 4 provided midway along the transport path 2 that forms a toner image on the sheet S, a fixing unit 5 that fixes the toner image formed on the sheet S, and an output tray 6 onto which the sheet S with the fixed image is output.

[0015] The image forming apparatus 1 further includes an image reading unit 7 that optically reads image data from a document, an external communication unit 9 that receives image data from an external source, and a control unit 8 that controls devices within the apparatus.

[0016] The image forming unit 4 has a photoconductor drum 4b, an exposure unit (not shown), a development unit (not shown), and a transfer roller 4c. A toner image corresponding to image data is formed on the surface of the photoconductor drum 4b by the exposure unit and the development unit. The image data is image data read by the document reading unit or image data received by the external communication unit 9.

[0017] The transfer roller 4c is in pressure contact with the photoreceptor drum 4b, forming a transfer nip region N1 between the transfer roller 4c and the photoreceptor drum 4b. A transfer voltage is applied to the surface of the transfer roller 4c. When the toner image on the surface of the photoreceptor drum 4b passes through the transfer nip region N1 together with the sheet S, an image is formed on the sheet S by the electrostatic attraction of the transfer roller 4c. The sheet S on which the image has been formed is transported to the fixing unit 5.

[0018] The fixing unit 5 has a fixing roller 5b with a built-in heater, and a pressure roller 5c. The pressure roller 5c is in pressure contact with the fixing roller 5b, forming a fixing nip area N2 between the pressure roller 5c and the fixing roller 5b. When the sheet S on which an image has been formed passes through the fixing nip area N2, the image is fixed to the sheet S by the pressure and heat of the rollers 5b and 5c. The sheet S on which the image has been fixed is transported to a discharge tray 6.

[0019] Next, the configuration of the sheet feeding device 100 will be described with reference to Fig. 2. Fig. 2 is a vertical cross-sectional view showing the configuration of the sheet feeding device 100. 2, the paper feeder 100 has a frame 20 that is configured in a housing portion of the image forming apparatus 1 (see FIG. 1), and a cassette 10 that is inserted into the frame 20 from the upstream side of paper feed and accommodated therein.

[0020] The cassette 10 has a lift plate 11 on which the sheets S are stacked. The frame 20 has a contact piece 21 provided on the upper part of the uppermost sheet S (hereinafter referred to as the uppermost sheet TS) among the sheets S stacked on the lift plate 11, a displacement member 30 provided on the contact piece 21, a sensor 22 provided at a position corresponding to the displacement member 30, and a feed roller 23 that abuts against the downstream end of the uppermost sheet TS in the paper feed direction.

[0021] The cassette 10 is a box-shaped body with an open top and a lift plate 11 provided on the bottom. The upstream end of the lift plate 11 is rotatably supported on the bottom of the cassette 10, and the downstream side of the lift plate 11 is lifted with the upstream end as a fulcrum. The lift plate 11 has an opening 11b that opens in the vertical direction near the bottom of the contact piece 21.

[0022] The frame 20 has a lifting means (not shown) that uses a motor as a driving source to lift the lift plate 11, and a detection means (not shown) that detects that the topmost sheet TS on the lift plate 11 has come into contact with the feed roller 23. When the cassette 10 is inserted into the frame 20 from the upstream side of the feed and accommodated in the frame 20, the lifting means lifts the downstream end of the lift plate 11. When the detection means detects that the topmost sheet TS on the lift plate 11 has come into contact with the feed roller 23 as shown in FIG. 2 during the process of lifting the lift plate 11, the lifting means stops the motor to stop lifting, and the topmost sheet TS of the lift plate 11 becomes ready to be fed to the conveying path 2. That is, the lift plate 11 is lifted to a position where the topmost sheet TS can be fed outside the device. When the lift plate 11 without the sheet S is lifted, the contact piece 21 enters the opening 11b from above as shown in FIG. 4.

[0023] Although details of the contact piece 21 will be described later, a rotation shaft 21b provided at the downstream end of the contact piece 21 is rotatably supported by the frame 20, and an upstream end 21c of the contact piece 21 (hereinafter simply referred to as "contact piece end 21c") rotates and displaces in the vertical direction around the rotation shaft 21b. The contact piece end 21c abuts against the uppermost sheet TS on the lift plate 11 by the action of gravity. The contact piece end 21c abuts against the uppermost sheet TS upstream of the position where the feed roller 23 abuts against the uppermost sheet TS.

[0024] As the sheet amount increases, the distance between the topmost sheet TS and the feed roller 23 before lifting decreases, so the lift amount required by the lift plate 11 decreases, and the inclination of the topmost sheet TS along the feed direction approaches horizontal. Therefore, as the sheet amount increases, the position of the topmost sheet TS on the upstream side of the feed direction after lifting is displaced upward. At this time, the contact piece end 21c is pushed upward by the topmost sheet TS and rotated upward around the rotation shaft 21b. On the other hand, as the sheet amount decreases, the position of the topmost sheet TS is displaced downward, so that the contact piece 21 is rotated downward around the rotation shaft 21b by its own weight. That is, the contact piece end 21c is rotated upward and displaced according to the increase or decrease in the sheet amount and the change in the position of the topmost sheet TS before and after lifting the lift plate 11. The contact piece 21 may be biased against the lift plate 11 by a biasing member such as a spring.

[0025] The feed roller 23 is supported by the frame 20 above the cassette 10 and is brought into contact with the downstream end of the uppermost sheet TS on the lift plate 11. The feed roller 23 is rotated by an appropriate power to pick up the uppermost sheet TS from the lift plate 11 and feed it to the conveying path 2.

[0026] Next, the configurations of the contact piece 21, the displacement member 30, the sensor 22, and the control unit 40 of the paper feeder 100 will be described with reference to Fig. 3. Fig. 3 is a diagram showing the configurations of the contact piece 21, the displacement member 30, the sensor 22, and the control unit 40 in the paper feeder 100.

[0027] 3, the sheet feeding device 100 has a control unit 40 that determines the amount of sheets according to the output of the sensor 22, in addition to the contact piece 21, the displacement member 30, and the sensor 22.

[0028] The contact piece 21 is a long plate extending from the base 21d on which the rotating shaft 21b is provided along the radial direction of the rotating shaft 21b. As described above, the rotating shaft 21b of the contact piece 21 is rotatably supported by the frame 20 (see FIG. 2), and the contact piece end 21c is rotationally displaced in the vertical direction.

[0029] The displacement member 30 is a fan-shaped plate extending in the radial direction of the rotation shaft 21b of the contact piece 21, centered on the rotation shaft 21b of the contact piece 21, and is provided on the outer surface of the base 21d of the contact piece 21. The displacement member 30 is provided on the contact piece 21, and is displaced in rotation in conjunction with the contact piece 21 by making the contact piece 21 and the rotation shaft 21b the same.

[0030] The displacement member 30 has shielding portions 31 and 33 (examples of the "first form portion" of the present disclosure) and transmitting portions 32 and 34 (examples of the "second form portion" of the present disclosure) as portions with different forms. The transmitting portions 32 and 34 are configured as through holes that penetrate the displacement member 30 in the thickness direction, and the shielding portions 31 and 33 are configured as portions of the displacement member 30 that do not penetrate. The transmitting portions 32 and 34 penetrate the displacement member 30 and thereby transmit light L that illuminates the displacement member 30 from within the paper feeding device 100. The shielding portions 31 and 33 do not penetrate the displacement member 30 and therefore shield the light L.

[0031] The displacement member 30 is arranged in the opposite direction to the direction in which the displacement member 30 rotates and displaces in conjunction with the contact piece 21 when the position of the top sheet TS is raised, and includes a first shielding portion 31 (an example of a "first first form portion" in the present disclosure), a first transparent portion 32 (an example of a "second form portion" or "first second form portion" in the present disclosure), a second shielding portion 33 (an example of a "next first form portion" in the present disclosure), and a second transparent portion 34 (an example of a "next second form portion" in the present disclosure) arranged in this order.

[0032] The sensor 22 is typically an optical sensor whose output changes according to a change in the amount of light received by the light receiving section 22b (an example of a "detection section" in the present disclosure). The sensor 22 is disposed in a position where, when the displacement member 30 is rotationally displaced, the light L illuminating the light receiving section 22b from within the device is blocked by the blocking section or transmitted by the transmitting section. The sensor 22 outputs OFF when the blocking section is displaced to detection position D in the light receiving section 22b and blocks the light L to the light receiving section 22b, and outputs ON when the transmitting section is displaced to said detection position D and transmits the light L to the light receiving section 22b. In other words, the output of the sensor 22 changes between when the blocking section is displaced to detection position D and when the transmitting section is displaced.

[0033] With the above configuration, when the position of the topmost sheet TS (see FIG. 2) changes, the contact piece 21 rotates and displaces up and down in response to the change in position, and accordingly, the displacement member 30 rotates and displaces in the clockwise or counterclockwise direction in FIG. 3.

[0034] At this time, as the positional relationship between the sensor 22 and the displacement member 30 changes, either the shielding portions 31, 33 or the transmissive portions 32, 34 are displaced to the detection position D of the sensor 22, and the sensor 22 outputs ON or OFF in response to the displacement. In other words, the relationship between the position of the topmost sheet TS and the output of the sensor 22 in response to that position depends on how the shielding portions 31, 33 and the transmissive portions 32, 34 are arranged on the displacement member 30.

[0035] When the hierarchy of sheet amounts is divided into five stages, from stage 1 where the sheet amount is the smallest to stage 5 where the sheet amount is the largest, the displacement member 30 is configured with shielding sections 31, 33 and transparent sections 32, 34 so that the patterns of change in the output of the sensor 22 before and after lifting at each stage do not overlap at each stage (details will be described later).

[0036] The control unit 40 has a determination unit 41 and a storage unit 42. The determination unit 41 is a processor such as a CPU (Central Processing Unit) and an MPU (Micro Processing Unit). The storage unit 42 is a memory such as a ROM (Read Only Memory) and a RAM (Random Access Memory). Although details will be described later, the storage unit 42 stores, in a table or the like, the manner in which the output of the sensor 22 changes when the sheet amount is at each stage, and the determination unit 41 determines which stage the sheet amount is at, from the first stage to the fifth stage, by comparing the manner in which the output of the sensor 22 changes, input from the sensor 22 via an I / F 43 (Interface), with the table or the like in the storage unit 42 (an example of determination based on the change in the output of the sensor 22).

[0037] Each of the first shielding portion 31, the second shielding portion 33, the first transmitting portion 32, and the second transmitting portion 34 is configured such that the length in the displacement direction of the displacement member 30 is greater than the detectable length of the light receiving portion 22b of the sensor 22. This allows the displacement amount of the displacement member 30 that produces the same output from the sensor 22 to have a predetermined range. Thus, the sheet feeding device 100 can allow the number of sheets that are determined to be at the same stage to have a predetermined range.

[0038] As described above, in this embodiment, the contact piece 21 is configured such that the contact piece end 21c (an example of the "one end" in the present disclosure) comes into contact with the topmost sheet TS and rotates and displaces in response to a change in the position of the topmost sheet TS, and the displacement member 30 is provided on the base 21d, which is the other end of the contact piece 21 at a position farther from the one end 21c than the rotation center of the contact piece 21. That is, the contact piece 21 and the displacement member 30 are configured as an integrated member. As a result, the sheet feeding device 100 can be simplified in configuration by reducing the number of parts. However, the contact piece 21 and the displacement member 30 may be configured as separate members with an interlocking means for interlocking their displacements. As a result, the sheet feeding device 100 can be configured such that the contact piece 21 and the displacement member 30 are separate members and disposed separately using an interlocking means, in addition to configuring the contact piece 21 and the displacement member 30 as a single member, and thus improves the design freedom.

[0039] Furthermore, as described above, in this embodiment, the sensor 22 is configured as an optical sensor, and the transmitting parts 32, 34 and the shielding parts 31, 33 are configured as parts corresponding to the sensor 22. The optical sensor is a versatile and simply configured sensor, and the transmitting parts 32, 34 and the shielding parts 31, 33 can be simply configured by providing a through hole in the displacement member 30 or not. Therefore, the configuration of the sheet feeding device 100 can be simplified by minimizing the number of parts. However, the form of the sensor and the parts is not limited to this embodiment. The sheet feeding device 100 may be configured, for example, by configuring the sensor as an eddy current sensor, and arranging a plurality of parts made of different materials as parts of a form corresponding to the sensor.

[0040] Next, the configuration and operation of the displacement member 30 will be described with reference to Fig. 4 to Fig. 8. Fig. 4 to Fig. 8 are longitudinal sectional views and enlarged views of essential parts of the sheet feeding device 100 at each stage, showing the positional relationship between the sensor 22 and the displacement member 30 when the sheet amount is at each stage from the first stage to the fifth stage.

[0041] First, the operation of the displacement member 30 at the first stage when the sheet amount is minimum (in this embodiment, a state in which there is no sheet S) will be described with reference to Fig. 4. In Fig. 4, the state of the lift plate 11 before lifting is shown by a virtual line (two-dot chain line).

[0042] 4, before lifting, the upper surface of the lift plate 11 is below the contact piece end 21c, and the contact piece end 21c is not in contact with anything, so that the contact piece 21 is in a state where the contact piece end 21c hangs down and faces downward due to its own weight or the biasing force of the biasing member (hereinafter, this state is referred to as the "initial state"). At this time, the displacement member 30 displaces the first shielding portion 31 to the detection position D in the light receiving portion 22b (enlarged view of FIG. 4). That is, in the initial state, the first shielding portion 31 is displaced to the detection position D.

[0043] After the lift, since the sheet S is not present, the contact piece end 21c enters the opening 11b of the lift plate 11. As a result, the contact piece 21 does not come into contact with anything, so the contact piece 21 maintains its initial state. Therefore, even after the lift, the first shielding portion 31 remains in a position corresponding to the detection position D (enlarged view of FIG. 4). Therefore, in the first stage, the sensor 22 outputs OFF both before and after the lift plate 11 is lifted.

[0044] Next, the operation of the displacement member 30 in the second stage in which the amount of sheets is greater than that in the first stage will be described with reference to Fig. 5. In Fig. 5, the states of the sheet S, lift plate 11, contact piece 21, and displacement member 30 before lifting are shown by virtual lines (the same applies to Figs. 6 to 8 below). As can be seen from Fig. 5, before lifting, the contact piece 21 does not contact the uppermost sheet TS and maintains its initial state. Therefore, similar to the first stage, the first shielding portion 31 is displaced to the detection position D (left diagram of the enlarged view in Fig. 5).

[0045] On the other hand, after the lift, the sheet S covers the opening 11b of the lift portion from above, so that the contact piece end 21c does not enter the opening 11b of the lift plate 11, and the contact piece end 21c comes into contact with the uppermost sheet TS and is pushed upward. This causes the contact piece 21 to rotate upward, and the displacement member 30 to rotate clockwise in Fig. 5. At this time, the first transmission portion 32 of the displacement member 30 is displaced to the detection position (right side of the enlarged view in Fig. 5). As a result, the sensor 22 outputs OFF before the lift and outputs ON after the lift.

[0046] Next, the operation of the displacement member 30 in the third stage, in which the amount of sheets is greater than that in the second stage, will be described with reference to Fig. 6. As shown in Fig. 6, before lifting, the contact piece 21 does not contact the topmost sheet TS and maintains the initial state. Therefore, similar to the first and second stages, the first shielding portion 31 is displaced to the detection position D (left diagram of the enlarged view in Fig. 6).

[0047] On the other hand, after the lift, the amount of the sheet becomes greater than in the second stage, so that the contact piece 21 is rotationally displaced upward compared to in the second stage, and the displacement member 30 is rotationally displaced clockwise in Fig. 6. At this time, the first transmitting portion 32 of the displacement member 30 passes through the detection position D during the lift (the central view in the enlarged view of Fig. 6), and finally the second shielding portion 33 is displaced to the detection position D (the right view in the enlarged view of Fig. 6). As a result, the sensor 22 outputs OFF before the lift, outputs ON once during the lift, and then outputs OFF again after the lift.

[0048] Next, with reference to Fig. 7, the operation of the displacement member 30 in the fourth stage in which the sheet amount is greater than that in the third stage will be described. As can be seen from Fig. 7, when the sheet amount becomes greater than that in the third stage, the uppermost sheet TS comes into contact with the contact piece end 21c before being lifted, and pushes up the contact piece end 21c. This causes the contact piece 21 to be rotated upward, and the displacement member 30 to be rotated clockwise in Fig. 7. At this time, the first transmission portion 32 of the displacement member 30 is displaced to the detection position D (left view of the enlarged view in Fig. 7).

[0049] On the other hand, after the lift, the sheet amount becomes greater than in the third stage, so that the contact piece 21 is rotationally displaced upward compared to the third stage, and the displacement member 30 is rotationally displaced clockwise in Fig. 7. At this time, the second shielding portion 33 of the displacement member 30 is displaced to the detection position D. As a result, the sensor 22 outputs ON before the lift and outputs OFF after the lift.

[0050] Next, with reference to Fig. 8, the operation of the displacement member 30 in the fifth stage where the sheet amount is at its maximum will be described. As shown in Fig. 8, because the sheet amount is greater than in the fourth stage, the uppermost sheet TS comes into contact with the contact piece end 21c before being lifted, and pushes up the contact piece end 21c, as in the fourth stage. This causes the contact piece 21 to be rotationally displaced upward more than in the fourth stage, and the displacement member 30 to be rotationally displaced clockwise in Fig. 8. At this time, the second transmission portion 34 of the displacement member 30 is displaced to the detection position D (left view of the enlarged view in Fig. 8).

[0051] In the fifth stage, the sheet amount is at its maximum, and the position of the uppermost sheet TS is at its uppermost position. Therefore, the lift amount is small, and the position of the displacement member 30 remains almost the same before and after the lift, and the displacement member 30 is configured so that the second transmission portion 34 is displaced to the detection position D even after the lift. As a result, the sensor 22 outputs ON both before and after the lift.

[0052] The outputs of the sensor 22 when the sheet amount is at each of the first to fifth stages described above are shown in Fig. 9. Fig. 9 is a diagram showing the outputs of the sensor 22 when the sheet amount is at each stage.

[0053] 9, the output of the sensor 22 is checked within a range within a predetermined time (hereinafter, referred to as a checking range) to check the state before and after lifting of the lift plate 11. A feature quantity that indicates the feature of the output of the sensor 22 within the checking range is extracted.

[0054] For example, as shown in Fig. 9, the "initial output" in the confirmation range and the "number of switching times" of ON / OFF in the confirmation range are extracted. In this case, in the first stage, the initial output is OFF and the number of switching times is 0, in the second stage, the initial output is OFF and the number of switching times is 1, in the third stage, the initial output is OFF and the number of switching times is 2, in the fourth stage, the initial output is ON and the number of switching times is 1, and in the fifth stage, the initial output is ON and the number of switching times is 0. In this way, the feature amounts of the outputs of the sensors 22 do not overlap with each other in each stage.

[0055] Referring again to FIG. 3, the storage unit 42 of the control unit 40 stores in advance, for example, a feature table, the feature of the sensor 22 output when the sheet amount is at each stage. The determination unit 41 of the control unit 40 extracts the feature from the sensor 22 output input from the sensor 22 and compares it with the feature table stored in the storage unit 42. Specifically, the determination unit 41 searches the feature from the input sensor 22 output in the feature table. The determination unit 41 can determine which stage of the sheet amount is from the first stage to the fifth stage from the search result because the feature of each stage in the feature table does not overlap with each other. Therefore, the sheet feeder 100 and the image forming apparatus 1 including the sheet feeder 100 can determine the sheet amount at four or more stages using one sensor 22. As a result, the sheet feeder 100 can simplify the configuration by reducing the number of parts, etc., which has a cost advantage.

[0056] The embodiments of the present disclosure have been described above with reference to the drawings. However, the present invention is not limited to the above embodiments, and can be implemented in various forms without departing from the spirit of the present invention. The drawings are mainly schematic illustrations of each component for ease of understanding, and the thickness, length, number, spacing, etc. of each component shown in the drawings are different from the actual ones due to the convenience of drawing. In addition, the speed, material, shape, dimensions, etc. of each component shown in the above embodiments are examples and are not particularly limited, and various changes are possible within a range that does not substantially deviate from the configuration of the present invention. [Industrial Applicability]

[0057] The present disclosure provides a paper feeding device and an image forming apparatus, and has industrial applicability. [Explanation of symbols]

[0058] S Seat TS Top sheet D Detection position 1. Image forming device 2 Transport path 10 Cassettes 11 Lift Plate 20 Frames 21 Contact piece 21b Rotation axis 21c Contact piece end 21d base 22 Sensors 22b Light receiving part 30 Displacement member 31 1st shielding part 32 1st transparent part 33 Second shielding part 34 2nd transparent part 40 Control section 41 Judgment section 42 Storage section 100 Paper feeder

Claims

1. 1. A sheet feeder for feeding sheets out of a device, comprising: a cassette having a lift plate on which a plurality of the sheets are stacked and lifted; a contact piece that comes into contact with the topmost sheet, which is the topmost sheet loaded on the lift plate, and displaces in response to an increase or decrease in the amount of sheets and a change in the position of the topmost sheet before and after the lift plate is lifted; a displacement member that is displaced in conjunction with the contact piece and has a first shape portion and a second shape portion that are different in shape; a sensor provided at a position corresponding to the displacement member, the output of which changes depending on whether the portion of the first configuration is displaced to a detection position or the portion of the second configuration is displaced; a determination unit that determines the sheet amount based on each change in the output of the sensor; A paper feeder comprising: The displacement member is a first first form portion which is a first part of the first form, a second form portion which is a part of the second form, and a next first form portion which is a part of the next first form are provided in this order along a direction opposite to a direction in which the displacement member is displaced when the position of the topmost sheet is raised, In a first stage where the sheet amount is minimum, the initial first form portion is displaced to the detection position of the sensor before the lift plate is lifted, and the initial first form portion is also displaced to the detection position after the lift plate is lifted, In a second stage in which the sheet amount is greater than that in the first stage, the initial first form portion is displaced to the detection position before lifting, and the second form portion is displaced to the detection position after lifting, In a third stage in which the amount of the sheet is greater than that in the second stage, before lifting, the first first form portion is displaced to the detection position, and during lifting, the second form portion is displaced to pass through the detection position, and after lifting, the next first form portion is displaced to the detection position, In a fourth stage in which the amount of the sheet is greater than that in the third stage, the second form portion is displaced to the detection position before the sheet is lifted, and the next first form portion is displaced to the detection position after the sheet is lifted. The determination unit determines which stage, from the first stage to the fourth stage, the sheet amount is in based on the respective changes in the output of the sensor before and after the lifting of the lift plate described above.

2. The displacement member is when the position of the topmost sheet is raised, the initial first form portion, the initial second form portion which is a portion of the initial second form, the subsequent first form portion, and the subsequent second form portion which is a portion of the subsequent second form are provided in this order along the reverse direction; In a fifth stage in which the amount of the sheet is greater than that in the fourth stage, the next second form portion is located at the detection position before lifting, and the next second form portion is displaced to the detection position after lifting, The sheet feeding device according to claim 1 , wherein the determining unit determines which of the first to fifth stages the sheet amount is.

3. The sensor has a detection unit that detects the shape, 3. The paper feeding device according to claim 1, wherein the length of the initial first form portion and the subsequent first form portion, and the length of the second form portion or the length of the initial second form portion and the subsequent second form portion in the displacement direction of the displacement member is greater than the length of the detection portion of the sensor.

4. the contact piece has one end portion that comes into contact with the uppermost sheet and is rotationally displaced in response to a change in the position of the uppermost sheet, 3. The paper feeder according to claim 1, wherein the displacement member is provided at the other end of the contact piece at a position farther from the one end than a rotation center of the contact piece.

5. the first portion is one of a shielding portion that blocks light from inside the paper feeding device and a transmitting portion that transmits the light, the second form portion is the other of the shielding portion or the transmitting portion, 3. The paper feeding device according to claim 1, wherein the sensor is an optical sensor whose output changes in response to a change in the amount of received light between when the light is blocked by the blocking portion and when the light is transmitted by the transmitting portion.

6. The paper feed device according to claim 1 or 2, an image forming section for forming a toner image on the sheet; An image forming apparatus comprising:

Images