JP4483484B2 - Sheet transport device - Google Patents

Description

  The present invention relates to a sheet conveying apparatus that feeds recording sheets stored in a sheet feeding tray, and more particularly to a sheet conveying apparatus having a sheet sensor that detects the presence or absence of a recording sheet in a sheet feeding tray.

In a conventional image forming apparatus such as a FAX, a printer, or a copier, a sheet sensor that detects the presence or absence of a recording sheet is provided in a sheet conveying apparatus that conveys a recording sheet stored in a sheet feeding tray. The presence or absence of a recording sheet in the tray is detected.
The following technique (J01) is conventionally known as a sheet feeding device having a sheet sensor.

(J01) Technology described in Patent Document 1 (Japanese Patent Application Laid-Open No. 2000-327175) Patent Document 1 describes a bottom plate that supports the lower surface of a recording sheet bundle and raises the recording sheet (P) to an upper sheet feeding position. In the paper feed tray (32) having 33), before the bottom plate (33) is raised, the presence or absence of the recording sheet (P) is detected by the no paper sensor (56) disposed on the bottom plate (33), and the sheet is conveyed. A technique is described in which the presence or absence of a recording sheet is detected by an upper paper sensor (58) disposed in the vicinity of the nudger roll (35).

JP 2000-327175 A (“0027” to “0038”, FIG. 4)

(Problems of conventional technology)
FIG. 13 is an explanatory diagram of a state in which a recording sheet cannot be detected by a conventional sheet sensor.
In the prior art (J01), the presence or absence of a recording sheet is detected based on the detection result of one of the two sheet sensors, and a sensor (no paper) detects the lower surface of the recording sheet at the start of a job. The presence or absence of the recording sheet is detected only by the sensor). However, as shown in FIG. 13, the front end portion of the recording sheet 01 in the sheet conveyance direction gets on the sheet feeding side upper portion 02a of the sheet feeding tray 02 or is sandwiched between the separation rolls 03 that prevent the recording sheet 01 from being double-fed. Then, the recording sheet 01 may not be detected by the sensor 04 that detects the lower surface of the recording sheet. Therefore, in the technique of detecting the presence or absence of the recording sheet 01 only by the sensor 04 that detects the lower surface before the start of paper feeding as in the prior art (J01), the recording is performed even if the recording sheet 01 remains in the paper feeding tray 02. There is a problem of detecting no sheet. In particular, in the large-capacity paper feed tray 02 having a large storage capacity of the recording sheet 01, when the front end of the recording sheet S is caught by the paper feed side upper portion 02a of the paper feed tray 02, the recording sheet 01 is bent and the paper feed side It is easy to get on the upper portion 02a.

In view of the above circumstances, the present invention has the following description (O01) as a technical problem.
(O01) To accurately detect the presence or absence of a recording sheet in the paper feed tray.

(Invention)
Next, the present invention that has solved the above problems will be described. In order to facilitate the correspondence between the elements of the present invention and elements of specific examples (examples) of the embodiments described later, Add the code enclosed in parentheses. The reason why the present invention is described in correspondence with the reference numerals of the embodiments described later is to facilitate understanding of the present invention, and not to limit the scope of the present invention to the embodiments.

(First invention)
In order to solve the technical problem, the sheet conveying apparatus of the first invention is characterized by comprising the following structural requirements (A01) to (A07).
(A01) Paper feed trays (TR1 to TR4) for storing recording sheets (S) on which images are recorded,
(A02) A paper feed member (K) that is disposed above the paper feed trays (TR1 to TR4) and feeds the recording sheets (S) stored in the paper feed trays (TR1 to TR4).
(A03) An upper sheet feeding position where the recording sheet (S) in the sheet feeding tray (TR1 to TR4) is supported and the recording sheet (S) is fed, and the recording sheet (S) A sheet elevating member (6) capable of elevating to and from a lower standby position where paper feeding is not performed,
(A04) Sheet elevating member operating means (C6) for operating the sheet elevating member (6) between the paper feeding position and the standby position,
(A05) A bottom sheet sensor (SN1) that is disposed below the sheet feed trays (TR1 to TR4) and that can detect the presence or absence of a recording sheet (S) in a state where the sheet elevating member (6) is in a standby position. ),
(A06) A sheet feeding sheet sensor (SN2) disposed in the vicinity of the sheet feeding member (K) and capable of detecting the presence or absence of a recording sheet (S) in the vicinity of the sheet feeding member (K);
(A07) Sheet presence / absence determining means (C7) for determining that there is no recording sheet (S) when both the bottom sheet sensor (SN1) and the sheet feeding sheet sensor (SN2) detect the absence of the recording sheet (S). , C7 ′, C7 ″).

(Operation of the first invention)
In the sheet conveying apparatus according to the first aspect of the present invention having the structural requirements (A01) to (A07), the sheet feeding device (TR1 to TR4) disposed above the sheet feeding trays (TR1 to TR4) for storing recording sheets (S) on which images are recorded. The paper member (K) feeds the recording sheets (S) stored in the paper feed trays (TR1 to TR4). The sheet elevating member (6) that supports the recording sheet (S) in the sheet feeding trays (TR1 to TR4) includes an upper sheet feeding position where the sheet feeding of the recording sheet (S) is performed, and the recording sheet It is possible to move up and down with the lower standby position where the paper feed of (S) is not executed. The sheet elevating member operating means (C6) operates the sheet elevating member (6) between the paper feeding position and the standby position.

The bottom sheet sensor (SN1) disposed below the sheet feeding trays (TR1 to TR4) can detect the presence or absence of the recording sheet (S) in a state where the sheet elevating member (6) is at the standby position. A paper feed sheet sensor (SN2) disposed in the vicinity of the paper feed member (K) can detect the presence or absence of a recording sheet (S) in the vicinity of the paper feed member (K). The sheet presence / absence discriminating means (C7, C7 ′, C7 ″) detects the recording sheet (S) when both the bottom sheet sensor (SN1) and the sheet feeding sheet sensor (SN2) detect the absence of the recording sheet (S). S) It is determined that there is none.
Accordingly, in the sheet conveying apparatus of the first invention, for example, the front end of the recording sheet (S) is placed on the sheet feeding tray (TR1 to TR4), and the recording sheet (S) cannot be detected by the bottom sheet sensor (SN1). Even in this case, when the recording sheet (S) is detected by the sheet feeding sheet sensor (SN2), it can be determined that the recording sheet (S) is present. As a result, it is possible to accurately detect the presence or absence of the recording sheet (S) in the paper feed trays (TR1 to TR4).

(First Embodiment 1)
A sheet conveying apparatus according to a first aspect of the present invention is characterized in that, in the first aspect, the following structural requirements (A08) to (A011) are provided.
(A08) It moves between the upper feed standby position where the recording sheet (S) is not fed and the feeding execution position where the recording sheet (S) is brought into contact with the uppermost surface of the recording sheet (S). Possible said paper feeding member (K),
(A09) Paper feed member operating means (C5 ′) for moving the paper feed member (K) between the paper feed standby position and the paper feed execution position;
(A010) When both the bottom sheet sensor (SN1) and the paper feed sheet sensor (SN2) detect the absence of the recording sheet (S) before the paper feed is started, the paper feed member (K) is fed. Sheet-less sheet feeding member actuating means (C5A) to be moved to the paper execution position,
(A011) With the sheet feeding member (K) moved to the sheet feeding execution position, both the bottom sheet sensor (SN1) and the sheet feeding sheet sensor (SN2) indicate that there is no recording sheet (S). The sheet presence / absence discriminating means (C7 ′, C7 ″) for discriminating that there is no recording sheet (S) when detected.

(Operation of Form 1 of the First Invention)
In the sheet conveying apparatus according to the first aspect of the first invention having the configuration requirements (A08) to (A011), the sheet feeding member (K) is an upper sheet feeding that does not feed the recording sheet (S). It is possible to move between a standby position and a paper feed execution position where the uppermost surface of the recording sheet (S) is brought into contact with and is fed. The paper feed member actuating means (C5 ′) moves the paper feed member (K) between the paper feed standby position and the paper feed execution position. When no sheet is fed, the sheet feeding member actuating means (C5A) detects the absence of a recording sheet (S) when both the bottom sheet sensor (SN1) and the sheet feeding sheet sensor (SN2) detect the absence of a recording sheet (S) before starting feeding. The paper feed member (K) is moved to the paper feed execution position. The sheet presence / absence discriminating means (C7 ′, C7 ″) has the bottom sheet sensor (SN1) and the sheet feeding sheet sensor (SN2) in a state where the sheet feeding member (K) is moved to the sheet feeding execution position. In any case, when no recording sheet (S) is detected, it is determined that there is no recording sheet (S).

  Therefore, in the sheet conveying apparatus according to the first aspect of the present invention, the bottom sheet sensor (SN1) and the sheet feeding sheet sensor (SN2) are left in a state where the recording sheet (S) remains in the sheet feeding trays (TR1 to TR4). ) Cannot detect the recording sheet (S), the recording sheet (S) may move to a detectable position by the movement of the sheet feeding member (K) to the sheet feeding execution position. As a result, the recording sheet (S) can be detected, and the presence or absence of the recording sheet (S) in the paper feed trays (TR1 to TR4) can be detected more accurately than in the past.

(First Embodiment 2)
A sheet conveying apparatus according to a second aspect of the first invention is characterized in that, in the first invention or the first aspect of the first invention, the following structural requirements (A012) to (A014) are provided.
(A012) At the end of a job as an image forming operation, if any of the bottom sheet sensor (SN1) and the paper feed sheet sensor (SN2) detects the presence of a recording sheet (S), the recording sheet (S) is present Sheet detection result storage means (C31) for storing
(A013) Before feeding at the start of the job, both the bottom sheet sensor (SN1) and the feeding sheet sensor (SN2) detect the absence of the recording sheet (S) and the sheet detection result storage means (C31) ) Detection failure determination means (C32) for determining a sensor detection failure when the presence of sheet is stored in
(A014) Before feeding at the start of the job, both the bottom sheet sensor (SN1) and the sheet feeding sheet sensor (SN2) detect the absence of the recording sheet (S) and the sheet detection result storage means (C31) The sheet presence / absence discriminating means (C7 ″) for discriminating that there is no recording sheet (S) when no sheet is stored in ().

(Operation of the second aspect of the first invention)
In the sheet conveying apparatus according to the second aspect of the first invention having the structural requirements (A012) to (A014), the sheet detection result storage means (C31) is configured to detect the bottom sheet sensor (SN1) at the end of a job as an image forming operation. ) And the sheet feeding sheet sensor (SN2), the presence of the recording sheet (S) is stored when the presence of the recording sheet (S) is detected. The detection failure determination means (C32) detects that the bottom sheet sensor (SN1) and the sheet feeding sheet sensor (SN2) are both out of the recording sheet (S) before feeding at the start of the job and the sheet. When the detection result storage means (C31) stores the presence of the sheet, it is determined that the sensor is defective. The sheet presence / absence judging means (C7 ″) detects that the bottom sheet sensor (SN1) and the sheet feeding sheet sensor (SN2) are both free of recording sheets (S) before feeding at the start of a job, and If no sheet is stored in the sheet detection result storage means (C31), it is determined that there is no recording sheet (S).

  Therefore, in the sheet conveying apparatus according to the second aspect of the first invention, it is stored that there is a recording sheet (S) at the end of the previous job, and it is determined that there is no recording sheet (S) at the start of the next job. Then, it is determined that the recording sheet (S) could not be detected by the bottom sheet sensor (SN1) and the sheet feeding sheet sensor (SN2). As a result, for example, there is a possibility that the posture of the recording sheet (S) is shifted and the recording sheet (S) cannot be detected because the user replenishes or removes the recording sheet (S) during the job. Can be determined.

(Embodiment 3 of the first invention)
A sheet conveying apparatus according to a third aspect of the first invention is characterized in that, in any one of the first invention and the first and second aspects of the first invention, the following structural requirement (A015) is provided.
(A015) A sheet presence / absence notification member (UI1) for notifying the user that there is no sheet when the sheet presence / absence determining means (C7, C7 ′, C7 ″) determines that there is no sheet.

(Operation of the third aspect of the first invention)
In the sheet conveying apparatus according to the third aspect of the first invention having the above-described configuration requirement (A015), the sheet presence / absence notification member (UI1) is determined to have no sheet by the sheet presence / absence determining means (C7, C7 ′, C7 ″). In this case, the user is notified that there is no sheet, so that the user can recognize that there is no sheet.

The above-described present invention has the following effect (E01).
(E01) The presence or absence of a recording sheet in the paper feed tray can be accurately detected.

Next, specific examples (examples) of the embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to the following examples.
In order to facilitate understanding of the following description, in the drawings, the front-rear direction is the X-axis direction, the left-right direction is the Y-axis direction, the up-down direction is the Z-axis direction, and arrows X, -X, Y, -Y, The direction indicated by Z and -Z or the indicated side is defined as the front side, the rear side, the right side, the left side, the upper side, the lower side, or the front side, the rear side, the right side, the left side, the upper side, and the lower side, respectively.
In the figure, “•” in “○” means an arrow heading from the back of the page to the front, and “×” in “○” is the front of the page. It means an arrow pointing from the back to the back.

FIG. 1 is an overall explanatory view of an image forming apparatus according to an embodiment of the present invention.
In FIG. 1, an image forming apparatus (digital copying machine) U of the embodiment has an image forming apparatus main body U1 and an automatic document feeder U2. The image forming apparatus main body U1 includes an IOT (image output terminal) and an IIT (image input terminal, that is, an image reading unit).
The automatic document feeder U2 is supported on the platen glass PG on the top surface of the IIT.
A sheet discharge tray TRh is provided between the upper surface of the IOT and the upper IIT.

In FIG. 1, the automatic document feeder U2 has a document feed tray TG1 on which a plurality of documents Gi to be copied are stacked. Each of the plurality of documents Gi placed on the document feed tray TG1 is sequentially passed through a copy position on the platen glass PG and discharged to the document discharge tray TG2. The automatic document feeder U2 can be rotated with respect to the upper surface of the platen glass PG by a hinge shaft (not shown) provided in the rear end portion (−X end portion) extending in the left-right direction. When a person puts it on the platen glass PG by hand, it is rotated upward.
The image forming apparatus main body U1 has a UI (user interface) through which a user inputs an operation command signal such as copy start.

An exposure optical system A for reading a document image is disposed below the transparent platen glass PG.
Reflected light from a document conveyed on the upper surface of the platen glass PG by the automatic document feeder U2 or a document (not shown) manually placed on the platen glass PG is passed through the exposure optical system A to a CCD ( It is converted into an electrical signal by a solid-state imaging device).
The IPS (image processing system) converts RGB electrical signals input from the CCD into image data and temporarily stores them, and the image data is used as laser drive circuit DL as image data for forming a latent image at a predetermined timing. Output to.
The laser drive circuit DL outputs a laser drive signal to the ROS (latent image forming apparatus) according to the input image data. The operation of the UI (user interface), IPS and laser drive signal output device DL, and a power supply circuit E for applying a bias voltage to the developing roll Ga and transfer roll Rt, which will be described later, are controlled by a control C.

The image carrier PR constituted by the photosensitive drum rotates integrally with its axis PRa in the direction of the arrow (clockwise in FIG. 1), and its surface is uniformly charged by the charging roll CR. At the latent image writing position, exposure scanning is performed with a laser beam L of the ROS (latent image forming apparatus) to form an electrostatic latent image.
The surface of the image carrier PR on which the electrostatic latent image is formed rotates and sequentially passes through a developing area (area facing the developing roll Ga) and a transfer area (area facing the transfer roll Rt) Q1.

The developing device G includes a developing container V that rotatably supports the developing roll Ga and the developer stirring members Gb, Gc, and Gd and that stores the developer, and is on the image carrier PR that passes through the developing region. The electrostatic latent image is developed into a toner image.
A plurality of paper feed trays TR1 to TR4 (see FIG. 1) contain recording sheets S to be transported to the transfer area Q1, and in the front-rear direction (in FIG. 1) on the left and right sides (Y-axis direction both sides). It is supported so as to be movable along a pair of rails RL1 and RL1 arranged along a direction perpendicular to the paper surface.

FIG. 2 is an enlarged explanatory view of a main part of a sheet feeding member of the image forming apparatus according to the present embodiment.
1 and 2, a sheet feeding device (sheet feeding member) K provided on the sheet feeding side upper portion of each of the sheet feeding trays TR1 to TR4 includes a pickup roll Rp, a feed roll Rs1, a retard roll Rs2, and the like. And a member (not shown) for rotationally driving. The recording sheet S taken out by the pickup roll Rp of the paper feeding device K is separated one by one by the separating roll Rs having the feed roll Rs1 and the retard roll Rs2, and is conveyed to the sheet conveyance path SH. The recording sheet S on the sheet conveyance path SH is conveyed to the registration roll Rr by a plurality of sheet conveyance rolls Ra arranged along the sheet conveyance path SH. The registration roll Rr (see FIG. 1) conveys the recording sheet S to the transfer area Q1 at a predetermined timing.
The recording sheet S fed from the manual feed tray TR0 is also transported to the transfer region Q1 by the sheet transport roll Ra and the registration roll Rr arranged along the sheet transport path SH.

In FIG. 1, a transfer roll Rt to which a transfer bias is applied is disposed in the transfer region Q1. The transfer roll Rt is in pressure contact with the image carrier PR in the transfer region Q1, and transfers the toner image on the image carrier PR to the recording sheet S passing through the transfer region Q1.
After the toner image on the surface of the image carrier PR is transferred to the recording sheet S in the transfer region Q1, the residual toner attached to the surface of the image carrier PR is collected by the cleaner CL. The image carrier PR from which the residual toner adhering to the surface is collected by the cleaner CL is charged by the charging roll CR.

  The recording sheet S on which the unfixed toner image is transferred in the transfer area Q1 is conveyed to the fixing area Q2 in a state where the toner image is not fixed, and a pair of fixing rolls Fh of the fixing device F disposed in the fixing area Q2 , Fp fix the toner image. The recording sheet S on which the fixing toner image has been formed is guided by the sheet guide and conveyed to the sheet discharge roll R1, and is discharged from the sheet discharge port Ha to the sheet discharge tray TRh.

Inside the printer U, a main body sheet reversing path SH3 connected to the sheet discharge port Ha is provided. A sheet reversing device U3 is mounted on the manual feed tray TR0. An optional sheet reversing path SH4 connected to the main body sheet reversing path SH3 is formed inside the sheet reversing device U3. Therefore, at the time of duplex printing, the sheet S on which the toner image is fixed in the fixing area Q2 passes through the main body sheet reversing path SH3 and the option sheet reversing path SH4 and is conveyed to the registration roll Rr. In the reversed state, the image is retransmitted to the transfer area Q1.
The main body sheet reversing path SH3 and the option sheet reversing path SH4 constitute a sheet reversing path (SH3 + SH4).

(Paper feeder)
2, the ascending rotary shaft 2 is disposed outside the sheet front end support wall 1 at the front end (left end in FIG. 2) of the paper feed trays TR1 and TR2 arranged in multiple stages of the image forming apparatus according to the first embodiment. Is arranged. One end of a plate-like lift lever 3 having an L-shaped cross section is fixed to the lift rotary shaft 2. The other end of the raising lever 3 is in contact with the lower surface of the bottom plate 4, and a bundle of recording sheets S is placed on the upper surface of the bottom plate 4.

The bottom plate 4 and the raising lever 3 are held at a standby position shown in the lower sheet feeding tray TR2 in FIG. When feeding the recording sheets S stored in the paper feed trays TR1 and TR2, the raising rotary shaft 2 is rotated by a bottom plate raising / lowering motor (not shown), and the raising lever 3 is placed on the sheet. The placement plate 4 is lifted, and the sheet upper surface position of the bundle of recording sheets S is held at an appropriate position where the sheet can be fed (feed position, see the upper sheet feed tray TR1 in FIG. 2).
A sheet elevating member 6 is constituted by the bottom plate elevating motor, the elevating rotary shaft 2, the elevating lever 3, the sheet placing plate 4, and the like.

  In FIG. 2, a sensor placement recess 11a is formed at the front of the bottom wall 11 of each of the paper feed trays TR1 and TR2 in the paper feed direction. A bottom sheet sensor SN1 is arranged in the sensor arrangement recess 11a. The bottom sheet sensor SN1 includes a detection bar 12 and an optical sensor 13. The lower end of the detection bar 12 is rotatably supported by the sensor placement recess 11a, and the tip thereof is positioned above (see the bottom sheet sensor SN1 of the upper sheet feed tray TR1 in FIG. 2) by a spring (not shown). Is being energized. Therefore, when the seat elevating member 6 is in the standby position, the leading end of the detection bar 12 protrudes upward through the bar through holes 3a and 4a formed in the ascending lever 3 and the bottom plate 4, respectively. When there is a recording sheet S placed on the bottom plate 4, the detection bar 12 protruding upward rotates in contact with the lower surface of the recording sheet S (see the bottom sheet sensor SN 1 in the lower stage of FIG. 2). The detection light of the sensor 13 is shielded to detect the presence of a sheet.

A sheet feeding device (sheet feeding member) K above each sheet feeding tray TR1, TR2 has a sheet feeding frame 21 that rotatably supports a pickup roll Rp to which driving force is transmitted by a gear train (not shown). Yes. The paper feed frame 21 is supported by the image forming apparatus main body U1 so as to be rotatable about the same axis as the rotation axis of the feed roll Rs1. Accordingly, the sheet feeding device K has an upper sheet feeding standby position (see the sheet feeding device K in the lower stage in FIG. 2) when the sheet feeding is not performed by on / off control of a pickup roll Rp lowering solenoid (not shown). ) And a paper feed execution position (see the upper paper feed device K in FIG. 2) that contacts the uppermost surface of the bundle of recording sheets S with a predetermined pressing force.
Between the pickup roll Rp and the feed roll, a no-paper sensor (paper feed sheet sensor) SN2 near the paper feed unit supported by the image forming apparatus body U1 is disposed. The paper feed unit vicinity no paper sensor SN2 includes a detection bar 22 configured in the same manner as the bottom sheet sensor SN1 and a light sensor (not shown).

When the recording sheet S is fed, the sheet feeding device K moves to the sheet feeding execution position, and the pickup roll Rp is driven to convey the uppermost recording sheet S to the separation roll Rs. A rotational driving force that rotates in the sheet conveying direction is transmitted to the feed roll Rs1 of the separating roll Rs, and a rotational driving that rotates in the direction opposite to the sheet conveying direction via a torque limiter (not shown) to the retard roll Rs2. Power is transmitted. Therefore, in a state where the sheet S is not conveyed to the press contact portion of the feed roll Rs1 and the retard roll Rs2, or in a state where only one recording sheet S is conveyed, the retard roll Rs2 rotates following the feed roll Rs1. . On the other hand, when a plurality of sheets S are simultaneously taken out from the paper feed tray by the pickup roll Rp, the uppermost recording sheet S is conveyed by the feed roll Rs1, while the lower sheet S is fed by the retard roll Rs2. Returned to the trays TR1 and TR2.
A sheet conveying device 26 is constituted by the sheet feeding device K, the sheet feeding trays TR1 to TR4, the sheet elevating member 6, the bottom sheet sensor SN1, the sheet feeding unit vicinity no-paper sensor SN2, and the like.

(Description of the control part of Example 1)
FIG. 3 is a block diagram (functional block diagram) illustrating each function provided in the control portion of the image forming apparatus according to the first exemplary embodiment.
In FIG. 3, the controller C stores an I / O (input / output interface) that performs input / output of signals to / from the outside and adjustment of input / output signal levels, programs and data for performing necessary processing, and the like. ROM (read-only memory), hard disk, RAM (random access memory) for temporarily storing necessary data, CPU (central processing unit) that performs processing according to programs stored in the ROM, etc., and It is constituted by a microcomputer having a clock oscillator or the like, and various functions can be realized by executing a program stored in the ROM or the like.

(Signal input element connected to the controller C)
The controller C receives signals from signal input elements such as a UI (user interface), a bottom sheet sensor SN1, and a no-paper sensor SN2 near the paper feed unit.
The UI includes a plurality of input keys such as a display unit (sheet presence / absence notification member) UI1, a copy start key UI2, a numeric keypad UI3, and the like. input.
The bottom sheet sensor SN1 detects the presence or absence of the recording sheet S in a state where the sheet elevating member 6 is in the standby position (see the lower stage in FIG. 2), and inputs the detection signal to the controller C.
The paper feeding unit vicinity no-paper sensor SN2 detects the presence or absence of the recording sheet S in the vicinity of the paper feeding device K, and inputs the detection signal to the controller C.

(Control element connected to the controller C)
The controller C is connected to a main motor driving circuit D1, a sheet conveying motor driving circuit D2, a pickup roll lowering solenoid driving circuit D3, a bottom plate lifting motor driving circuit D4, a power supply circuit E, and other control elements. These operation control signals are output.
The power supply circuit E includes a development power supply circuit E1, a charging power supply circuit E2, a transfer power supply circuit E3, a fixing power supply circuit E4, and the like.

The developing power supply circuit E1 applies a developing bias to the developing roll Ga of the developing device G.
The charging power supply circuit E2 applies a charging bias to the charging roll CR.
The transfer power supply circuit E3 applies a transfer bias to the transfer roll Rt.
The fixing power supply circuit E4 supplies a heater heating current to the heater of the heating roll Fh of the fixing device F.

The main motor drive circuit D1 rotationally drives the image carrier PR, the developing roll Ga of the developing device G, the fixing device F, and the like via the main motor M1.
The sheet conveying motor drive circuit D2 rotationally drives the pickup roll Rp, the separating roll Rs, and the like of the sheet feeding device K via the sheet conveying motor M2.
The pickup roll lowering solenoid driving circuit D3 drives (on / off) the pickup roll lowering solenoid S1 to move the paper feeding device K between the paper feeding execution position and the paper feeding standby position.
The bottom plate lifting / lowering motor drive circuit D4 drives the bottom plate lifting / lowering motor M3 to lift and lower the bottom plate 4. That is, the sheet elevating member 6 is moved between the paper feeding position and the standby position.

(Function of the controller C)
The controller C has a function (control means) for executing a process according to an output signal from each signal output element and outputting a control signal to each control element. The function (control means) of the controller C will be described next.
C1: Job control means The job control means C1 controls the operations of the ROS, the image carrier PR, the transfer device Rt, the fixing device F, etc. according to the input of the copy start key UI2, and is a job that is an image recording operation. (Print operation, copy operation) is executed.

C2: Main motor rotation control means The main motor rotation control means C2 controls the main motor drive circuit D1 to control the driving of the image carrier PR, the developing device G, the fixing device F, and the like.
C3: Power supply circuit control means The power supply circuit control means C3 includes a development power supply control means C3A, a charging power supply control means C3B, a transfer power supply control means C3C, and a fixing power supply control means C3D, and controls the power supply circuit E. The power supply to each member of the image forming apparatus U is controlled.

C3A: Development power supply control means The development power supply control means C3A controls the development power supply circuit E1 to control the development bias.
C3B: Charging power supply control means The charging power supply control means C3B controls the charging power supply circuit E2 to control the charging bias.
C3C: Transfer power supply control means The transfer power supply control means C3C controls the transfer power supply circuit E3 to control the transfer bias.
C3D: Fixing power supply control means The fixing power supply control means C3D controls the fixing power supply circuit E4 to control the fixing temperature of the heating roll Fh.

C4: Sheet conveying device control means The sheet conveying device control means C4 controls the rotation driving of the pickup roll Rp and the separating roll Rs by controlling the sheet conveying motor drive circuit D2.
C5: Paper feeding device operating means (paper feeding member operating means)
The sheet feeding device actuating means C5 controls the pickup roll lowering solenoid drive circuit D3 to move the sheet feeding device K to the sheet feeding standby position (see the lower part of FIG. 2) and the sheet feeding execution position (see the upper part of FIG. 2). Move between.
C6: Seat Elevating Member Actuating Means The sheet elevating member actuating means C6 controls the bottom plate elevating motor drive circuit D4 to move the sheet elevating member 6 to the sheet feeding position (see the upper part of FIG. 2) and the standby position (FIG. 2). (See the lower row).

C7: Sheet presence / absence determination unit The sheet presence / absence determination unit C7 includes a bottom sensor unit sheet presence / absence determination unit C7A and a sheet feeding unit vicinity no paper sensor unit sheet presence / absence determination unit C7B, and includes a bottom sheet sensor SN1 and a sheet feeding unit vicinity. If none of the no-paper sensors SN2 detects the absence of a recording sheet, it is determined that there is no recording sheet.
C7A: Bottom sensor section sheet presence / absence determination means The bottom sensor section sheet presence / absence determination means C7A determines whether or not a recording sheet is detected by the bottom sheet sensor SN1 based on the detection signal of the bottom sheet sensor SN1, that is, the bottom plate 4 It is determined whether or not the recording sheet S is present.

C7B: No-paper sensor unit sheet presence / absence determining unit in the vicinity of the paper feeding unit No-paper sensor unit in the vicinity of the paper feeding unit C7B is based on a detection signal from the no-paper sensor SN2 in the vicinity of the paper feeding unit. It is determined whether or not the recording sheet S is detected by the sensor SN2, that is, whether or not the recording sheet S is present near the no-paper sensor SN2 in the vicinity of the paper feed unit.
C8: Notification member control means The notification member control means C8 displays no recording sheet on the display UI1 of the user interface UI when it is determined that there is no recording sheet, and notifies the user of the recording sheets in the paper feed trays TR1 to TR4. Announce that S is gone.

(Description of Flowchart of Example 1)
(Description of main flowchart of sheet presence / absence determination processing)
FIG. 4 is a main flowchart of the sheet presence / absence determination process of the image forming apparatus according to the first exemplary embodiment.
The processing of each ST (step) in the flowchart of FIG. 4 is performed according to a program stored in the ROM or hard disk of the controller C. This process is executed in a multitasking manner in parallel with other various processes of the image forming apparatus U.
The flowchart shown in FIG. 4 is started when the image forming apparatus U is powered on.

In ST1 of FIG. 4, it is determined whether or not the copy start key UI2 is input, that is, whether or not the job is started. If yes (Y), the process proceeds to ST2, and if no (N), ST1 is repeated.
In ST2, it is determined whether or not the bottom sheet sensor SN1 detects the presence of a sheet. If yes (Y), the process proceeds to ST5, and, if no (N), the process proceeds to ST3.
In ST3, it is determined whether or not the no-paper sensor SN2 in the vicinity of the sheet feeding unit detects the presence of a sheet. If yes (Y), the process proceeds to ST5, and, if no (N), the process proceeds to ST4.
In ST4, the absence of the recording sheet S is displayed on the UI display UI2. Then, the process returns to ST1.

In ST5, the following processes (1) to (3) are executed, and the process proceeds to ST6.
(1) The sheet elevating member 6 is moved to the sheet feeding position.
(2) Move the paper feeder K to the paper feed execution position.
(3) The pickup roll Rp and the separation roll Rs are driven at a predetermined timing to execute paper feeding.
In ST6, it is determined whether or not the job is finished. If yes (Y), the process proceeds to ST7, and, if no (N), ST6 is repeated.
In ST7, the following processes (1) and (2) are executed, and the process returns to ST1.
(1) The paper feeding device K is moved to the paper feed standby position.
(2) The seat elevating member 6 is moved to the standby position.

(Operation of Example 1)
FIG. 5 is an explanatory diagram showing a state in which there is no recording sheet in the paper feed tray.
In FIG. 5, in the image forming apparatus U including the sheet conveying apparatus 26 according to the first embodiment having the above-described configuration, any of the bottom sheet sensor SN1 and the no-paper sensor SN2 in the vicinity of the sheet feeding unit at the start of the job and before the sheet feeding is performed. If no sheet is detected, it is determined that there is no recording sheet (see ST4). That is, when one or both of the bottom sheet sensor SN1 and the no-paper sensor SN2 in the vicinity of the paper feeding unit detect the presence of a sheet, it is determined that there is a recording sheet, and paper feeding is executed (see ST5).

FIG. 6 is an explanatory diagram showing a state in which the recording sheet in the paper feed tray cannot be detected by the bottom sheet sensor.
In FIG. 6, at the end of the previous job, the recording sheet S that has been separated (separated) by the separation roll Rs and has not returned to the paper feed tray side is sandwiched by the separation roll Rs, or the recording sheet S is fed. When the front end portion in the paper direction is caught by the upper end of the sheet front end support wall 1 of the paper feed tray TR1, the recording sheet S is curved. Depending on the orientation of the recording sheet S at this time, the bottom sheet sensor SN1 may not be detected. However, in the sheet conveying device 26 according to the first embodiment, even if the recording sheet S cannot be detected by the bottom sheet sensor SN1, it is determined that there is a sheet when the recording sheet S is detected by the no-paper sensor SN2 in the vicinity of the sheet feeding unit. Then, paper feeding is executed. As a result, the presence / absence of the recording sheet S in the sheet feeding trays TR1 to TR4 can be accurately detected as compared with the conventional technique in which the recording sheet S is detected only by the bottom sheet sensor SN1 before the sheet feeding is started.

  In the prior art, the absence of a recording sheet is detected in the state shown in FIG. 6, and the user notified of the absence of the recording sheet pulls out the paper feed tray TR1 from the image forming apparatus main body U1 in order to replenish the recording sheet S. At this time, a sheet jam occurs in which the recording sheet S is sandwiched between the sheet feeding tray TR1 and the image forming apparatus main body U1 to be in an accordion shape or torn. However, in the sheet conveying apparatus 26 according to the first embodiment, the presence of a recording sheet is detected, and the job is executed without notifying the user that there is no sheet, so that the occurrence of a jam can be prevented.

  Next, a second embodiment of the present invention will be described. In the description of the second embodiment, components corresponding to those of the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted. To do. The second embodiment is different from the first embodiment in the following points, but is configured in the same manner as the first embodiment in other points.

(Description of Control Unit of Example 2)
FIG. 7 is a block diagram (functional block diagram) illustrating functions provided in the control unit of the image forming apparatus according to the second embodiment, and corresponds to FIG. 3 according to the first embodiment.
(Function of the controller C of the second embodiment)
The controller C according to the second embodiment replaces the sheet feeding member operating unit C5, the bottom sensor unit sheet presence / absence determination unit C7A, and the paper feeding unit vicinity no paper sensor unit sheet presence / absence determination unit C7B with the following functions (control). Means).

C5 ': Paper feeding device operating means (paper feeding member operating means)
The sheet feeding device actuating means C5 ′ has a sheet feeding device actuating means when no sheet (sheet feeding member actuating means when no sheet exists) C5A and controls the pickup roll lowering solenoid driving circuit D3 to feed the sheet feeding device K. Move between the standby position and the paper feed execution position.
C5A: Sheet feeding device operating means when no sheet exists Sheet feeding device operating means C5A when there is no sheet is detected when both the bottom sheet sensor SN1 and the no-paper sensor SN2 near the sheet feeding unit detect the absence of a recording sheet before starting feeding. The paper feeding device K is moved to the paper feeding execution position.

C7 ': Sheet presence / absence determination means The sheet presence / absence determination means C7' includes a bottom sensor portion sheet presence / absence determination means C7A 'and a sheet feeding portion vicinity no paper sensor portion sheet presence / absence determination means C7B'. After the sheet feeding device K is lowered, if both the bottom sheet sensor SN1 and the no-paper sensor SN2 near the sheet feeding unit detect the absence of the recording sheet, it is determined that there is no recording sheet.
C7A ′: Bottom sensor unit sheet presence / absence determination unit The bottom sensor unit sheet presence / absence determination unit C7A ′ includes a bottom sensor unit determination unit C7A1 before the sheet feeding device descends and a bottom sensor unit discrimination unit C7A2 after the sheet feeding device descends, Based on the detection signal of the bottom sheet sensor SN1, it is determined whether or not the recording sheet S is detected by the bottom sheet sensor SN1.

C7A1: Bottom sensor unit discriminating means before lowering the paper feeding device The bottom sensor unit discriminating unit C7A1 before lowering the paper feeding device uses the bottom sheet sensor SN1 to record sheets before the paper feeding device K moves (lowers) to the paper feeding execution position. It is determined whether or not S is detected, that is, whether or not the recording sheet S is present at the bottom sheet sensor SN1.
C7A2: Bottom sensor section discriminating means after lowering of paper feeding device Bottom sensor section discriminating means C7A2 after lowering of paper feeding device is used to record sheet S by bottom sheet sensor SN1 after paper feeding device K has moved (lowered) to the paper feeding execution position. Is detected, that is, whether or not the recording sheet S is present at the bottom sheet sensor SN1.

C7B ': Near-paper sensor unit sheet presence / absence discriminating means in the vicinity of the paper feed unit No-paper sensor unit sheet presence / absence discriminating means in the vicinity of the paper feed unit C7B' A paper-sheet-near-no-paper sensor section discriminating means C7B2 after the paper apparatus is lowered, and the recording sheet S is detected by the paper-sheet-near-no-paper sensor SN2 based on the detection signal from the paper-sheet-near no-paper sensor SN2. It is determined whether or not.
C7B1: Near-paper sensor portion discriminating means in the vicinity of the paper feeding unit before lowering the paper feeding device The no-paper sensor portion discriminating means C7B1 in the vicinity of the paper feeding unit before lowering the paper feeding device moves (lowers) the paper feeding device K to the paper feeding execution position. Prior to this, it is determined whether or not the recording sheet S is detected by the no-paper sensor SN2 in the vicinity of the paper feeding unit, that is, whether or not the recording sheet S exists in the portion of the no-paper sensor SN2 in the vicinity of the paper feeding unit.
C7B2: No-paper sensor portion discriminating means in the vicinity of the paper feeding unit after lowering the paper feeding device The no-paper sensor SN2 portion discriminating means C7B2 in the vicinity of the paper feeding portion after lowering the paper feeding device moves (lowers) the paper feeding device K to the paper feeding execution position. After that, it is determined whether or not the recording sheet S is detected by the no-paper sensor SN2 in the vicinity of the paper feeding unit, that is, whether or not the recording sheet S exists in the portion of the no-paper sensor SN2 in the vicinity of the paper feeding unit.

(Explanation of flowchart of embodiment 2)
(Description of main flowchart of sheet presence / absence determination processing)
FIG. 8 is a main flowchart of the sheet presence / absence determination process of the image forming apparatus according to the second embodiment, and corresponds to FIG. 4 according to the first embodiment.
In FIG. 8, in the sheet presence / absence determination process of the second embodiment, the same processes as ST1 to ST3 are executed in ST1 to ST3, and when the determination is NO (N) in ST3, the process proceeds to ST11.

In ST11, the sheet feeding device K is moved (lowered) to the sheet feeding execution position, and the pickup roll Rp is lowered. Then, the process proceeds to ST12.
In ST12, it is determined whether or not the bottom sheet sensor SN1 detects the presence of a sheet. If yes (Y), the process proceeds to ST5, and, if no (N), the process proceeds to ST13.
In ST13, it is determined whether or not the no-paper sensor SN2 in the vicinity of the sheet feeding unit detects the presence of a sheet. If yes (Y), the process proceeds to ST5, and, if no (N), the process proceeds to ST4.
Next, processing similar to ST4 to ST7 of the sheet presence / absence determination processing of the first embodiment is executed, and the process returns to ST1.

(Operation of Example 2)
In the image forming apparatus U having the sheet conveying apparatus 26 according to the second embodiment having the above-described configuration, both the bottom sheet sensor SN1 and the no-paper sensor SN2 in the vicinity of the sheet feeding unit record at the start of the job and before the sheet feeding is performed. When it is detected that there is no sheet, the sheet feeding device K is moved to the sheet feeding execution position (see ST11). Then, even after the sheet feeding device K is moved to the sheet feeding execution position, when both the bottom sheet sensor SN1 and the no-paper sensor SN2 near the sheet feeding unit do not detect the presence of the recording sheet, it is determined that there is no recording sheet ( (Refer to ST4).

FIG. 9 is an explanatory diagram of a state in which neither the bottom sheet sensor SN1 nor the no-paper sensor SN2 in the vicinity of the sheet feeding unit can detect the recording sheet.
In FIG. 9, both the bottom sheet sensor SN1 and the no-paper sensor SN2 in the vicinity of the sheet feeding unit detect the recording sheet S in a state in which the sheet feeding direction front end of the recording sheet S is caught on the upper end of the sheet front end support wall 1. There are cases where it is not possible (see the solid line in FIG. 9). In the sheet conveying device 26 according to the second exemplary embodiment, when both the bottom sheet sensor SN1 and the no-paper sensor SN2 in the vicinity of the sheet feeding unit detect the absence of a recording sheet, the sheet feeding device K is moved to the sheet feeding execution position (see FIG. (See dotted line 9). When the paper feeding device K moves to the paper feeding execution position, the recording sheet S may come into contact with the pickup roll Rp, or vibration may occur when the paper feeding device K is moved, so that the recording sheet S that has been caught may fall. Yes (see dotted line in FIG. 9). When the recording sheet S that has been caught falls, the recording sheet S can be detected by the bottom sheet sensor SN1. As a result, the presence / absence of the recording sheet S in the paper feed trays TR1 to TR4 can be detected more accurately as compared with the case where the paper feed device K is not moved.

  Next, a third embodiment of the present invention will be described. In the description of the third embodiment, the same reference numerals are given to the components corresponding to the components of the first and second embodiments, and a detailed description thereof will be given. Is omitted. The third embodiment is different from the first and second embodiments in the following points, but is configured in the same manner as the first and second embodiments in other points.

(Description of Control Unit of Example 3)
FIG. 10 is a block diagram (functional block diagram) illustrating the functions of the control unit of the image forming apparatus according to the third embodiment, and corresponds to FIG. 7 according to the second embodiment.
(Function of the controller C of the third embodiment)
The controller C of the third embodiment has the following functions (control means) in addition to the functions (control means) of the controller C of the second embodiment.

C31: Sheet detection result storage unit The sheet detection result storage unit C31 stores the presence of a recording sheet when any of the bottom sheet sensor SN1 and the no-paper sensor SN2 in the vicinity of the sheet feeding unit detects the presence of a recording sheet at the end of the job. . Therefore, the sheet detection result storage unit C31 stores the absence of a recording sheet as the detection result when both the bottom sheet sensor SN1 and the no-paper sensor SN2 near the sheet feeding unit detect the absence of the recording sheet.
C32: Detection failure determination unit The detection failure determination unit C32 detects that there is no recording sheet in both the bottom sheet sensor SN1 and the no-paper sensor SN2 in the vicinity of the sheet feeding unit before feeding at the start of the job, and the sheet detection result. When the presence of a sheet is stored in the storage unit C31, it is determined that the sensor detection is defective.

C7 ″: Sheet presence / absence determination means The sheet presence / absence determination means C7 ″ includes a bottom sensor section sheet presence / absence determination means C7A ′ and a sheet feeding portion vicinity no paper sensor section sheet presence / absence determination means C7B ′. The sheet presence / absence discriminating means C7 ″ of the third embodiment detects the absence of a recording sheet by the bottom sheet sensor SN1 and the no-paper sensor SN2 in the vicinity of the sheet feeding unit after the sheet feeding device K is lowered before sheet feeding is started. When there is no sheet stored in the sheet detection result storage unit C31, it is determined that there is no recording sheet, and the bottom sensor unit sheet presence / absence determination unit C7A 'or the paper feed unit vicinity no paper sensor unit sheet presence / absence determination unit. Since the function of C7B ′ is the same as that of the second embodiment, detailed description thereof is omitted.

C8 ': Notification member control means The notification member control means C8' includes a no-sheet notification control means C8A and a detection failure notification control means C8B. The determination result of the sheet presence / absence determination means C7 and the detection failure determination means C32 Is displayed on the display unit UI1 of the user interface UI and notified to the user.
C8A: Notification control means when no sheet is present The notification control means C8A when there is no sheet displays that the recording sheet S is no longer displayed on the display UI1 when the recording presence / absence determination means C7 determines that there is no recording sheet. To announce.
C8B: Detection failure notification control means The detection failure notification control means C8B urges the recording sheet S to be set correctly or replenished when the detection failure determination means C32 determines that the sensor detection is defective. A display for informing the sensor detection failure is displayed on the display UI1 to notify the user.

(Description of Flowchart of Example 3)
(Description of main flowchart of sheet presence / absence determination processing)
FIG. 11 is a main flowchart of the sheet presence / absence determination process of the image forming apparatus according to the third embodiment, and corresponds to FIG. 8 according to the second embodiment.
In FIG. 11, in the sheet presence / absence determination process according to the third embodiment, processes similar to the sheet presence / absence determination process according to the second embodiment are executed in ST1 to ST3 and ST11 to ST13. Then, in the sheet presence / absence determination processing of the third embodiment, if NO (N) in ST13, the process proceeds to ST21, and if YES (Y) in ST2, ST3, ST12, ST13, the process proceeds to ST23.

In ST21, it is determined whether or not a sheet presence is stored as a sheet detection result in the sheet detection result storage unit C31. If yes (Y), the process proceeds to ST22, and, if no (N), the process proceeds to ST4.
In ST22, the following processes (1) and (2) are executed, and the process returns to ST1.
(1) The sensor detection failure notification display is displayed on the display UI1.
(2) The absence of sheet is stored as the sheet detection result in the sheet detection result storage means C31.
In ST23, the presence of a sheet is stored as a sheet detection result in the sheet detection result storage means C31. Then, the process proceeds to ST5.
Next, in the sheet presence / absence determination process of the third embodiment, the processes of ST5 to ST7 of the first embodiment are executed, and the process proceeds to ST24.

In ST24, it is determined whether or not the bottom sheet sensor SN1 detects the presence of a sheet. If yes (Y), the process proceeds to ST26, and, if no (N), the process proceeds to ST25.
In ST25, it is determined whether or not the no-paper sensor SN2 in the vicinity of the sheet feeding unit detects the presence of a sheet. If yes (Y), the process proceeds to ST26, and, if no (N), the process proceeds to ST27.
In ST26, the presence of a sheet is stored as a sheet detection result in the sheet detection result storage means C31. Then, the process returns to ST1.
In ST27, no sheet is stored as the sheet detection result in the sheet detection result storage unit C31. Then, the process returns to ST1.

(Operation of Example 3)
In the image forming apparatus U having the sheet conveying apparatus 26 according to the third embodiment having the above-described configuration, it is determined whether or not the recording sheet S is present in the sheet feeding trays TR1 to TR4 when the job is finished (ST24). To ST27). When both a bottom sheet sensor SN1 and a no-paper sensor SN2 in the vicinity of the paper feed unit detect that there is a recording sheet even after the paper feed device K has moved to the paper feed execution position when a new job is started, The sheet detection result stored in the sheet detection result storage unit C31 is referred to. Then, according to the stored sheet detection result, it is determined whether there is no recording sheet or a sensor detection failure.

FIG. 12 is an explanatory diagram of a state in which the recording sheet in the paper feed tray cannot be detected by the sensor due to the posture of the paper feed tray.
In FIG. 12, for example, when the user replenishes, replaces, removes, partially removes or resets the recording sheet S in the paper feed trays TR1 to TR4 during a job, depending on the orientation of the recording sheet S The bottom sheet sensor SN1 and the no-paper sensor SN2 in the vicinity of the sheet feeding unit may not be able to detect the recording sheet S.
In the sheet conveying device 26 according to the third exemplary embodiment, when the presence of a sheet is stored at the end of the job, the recording sheet S may not actually exist in the sheet feeding trays TR1 to TR4. It is determined that the recording sheet S in the paper tray may not be detected by the sensors SN1 and SN2. In this case, a sensor detection failure notification prompting to set the recording sheet S correctly or to replenish the recording sheet S is displayed. Therefore, in the sheet conveying device 26 according to the third embodiment, it is possible to determine that there is a possibility that the recording sheet S cannot be detected due to the posture of the recording sheet S, and it is possible to perform display according to the possibility.

(Example of change)
As mentioned above, although the Example of this invention was explained in full detail, this invention is not limited to the said Example, A various change is performed within the range of the summary of this invention described in the claim. It is possible. Modification examples (H01) to (H012) of the present invention are exemplified below.
(H01) The present invention is not limited to a copying machine, but can be applied to an image forming apparatus such as a printer, a FAX, or a multifunction machine. Further, the present invention is not limited to a monochrome image forming apparatus, and can be applied to a color image forming apparatus. Furthermore, the present invention is not limited to an electrophotographic image forming apparatus, and can be applied to an image forming apparatus of another recording system such as an ink jet recording system.

(H02) In each of the above embodiments, the indicator UI1 is used as a sheet presence / absence notification member. However, the present invention is not limited to this, and a notification sound generating member for generating a notification sound, a notification lamp, voice guidance, or a combination thereof is optional. It is possible to use a sheet presence / absence notification member.
(H03) In each of the above embodiments, the bottom sheet sensor SN1 is provided on the bottom wall 11 of the paper feed trays TR1 to TR4. However, the present invention is not limited to this, and the bottom sheet sensor is disposed on the bottom plate 4 or the raising lever 3. Is also possible. It is also possible to dispose the no-paper sensor SN2 in the vicinity of the paper feed unit in the paper feed frame 21.

(H04) In each of the above embodiments, the sheet feeding device K as the sheet feeding member has the separation roll Rs. However, the separation roll Rs is omitted, and recording is performed using a retard pad that contacts the pickup roll Rp. It is also possible to separate and feed the sheets S one by one.
(H05) In the first exemplary embodiment, the paper feeding device K is configured to be movable between the paper feeding execution position and the paper feeding standby position. However, the paper feeding device K may be configured to be immovable.
(H06) In each of the above embodiments, the contact type sensor in which the detection lever contacts the recording sheet S is used as the bottom sheet sensor SN1 and the no-paper sensor SN2 in the vicinity of the paper feed unit. It is also possible to use an optical sensor or the like.

(H07) In each of the above-described embodiments, the position where the bottom sheet sensor SN1 and the no-paper sensor SN2 near the sheet feeding unit are arranged can be changed according to the design or the like. Note that, as in the above-described embodiments, the arrangement positions of the bottom sheet sensor SN1 and the no-paper sensor SN2 in the vicinity of the sheet feeding unit are shifted with respect to the sheet feeding direction of the recording sheet S. However, both the sensors SN1 and SN2 may not be able to detect, but the paper sheet vicinity no-paper sensor SN2 and the bottom sheet sensor SN1 are arranged above and below the same position with respect to the paper feeding direction to feed the recording sheet. The recording sheet S can be easily detected by detecting the same position in the two sensors SN1 and SN2.
(H08) In each of the above embodiments, the sheet elevating member 6 has the bottom plate 4 and the ascending lever 3 and raises the front end of the recording sheet S in the paper feeding direction. In addition, it is possible to use a sheet elevating member (for example, see FIG. 5 of Patent Document 1) that raises both ends of the recording sheet S in the sheet feeding direction.

(H09) In each of the embodiments described above, the sheet elevating member 6 is lowered every time the job is finished. However, the sheet elevating member 6 may be controlled so as not to be lowered even when the job is finished and to be held at the paper feed position. In this case, the bottom sheet sensor SN1 needs to be disposed on the bottom plate 4.
(H010) In the second and third embodiments, when both the bottom sheet sensor SN1 and the no-paper sensor SN2 in the vicinity of the sheet feeding unit have no sheet, the sheet feeding device K is lowered, but the bottom sheet sensor SN1 and the sheet feeding unit It is also possible to lower the paper feeding device K before performing detection by the paper portion vicinity no paper sensor SN2.

(H011) In each of the embodiments, the bottom sheet sensor SN1 and the no-paper sensor SN2 in the vicinity of the sheet feeding unit are disposed one by one. However, a plurality of sheets are disposed along the sheet width direction or a plurality along the sheet feeding direction. It is also possible to arrange.
(H012) In each of the above embodiments, the sheet feeding device K is held in the state where it is lowered to the sheet feeding execution position during the execution of the job. However, it may be controlled to return to the sheet feeding standby position each time one sheet is fed. Is possible.

FIG. 1 is an overall explanatory view of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is an enlarged explanatory view of a main part of a sheet feeding member of the image forming apparatus according to the present embodiment. FIG. 3 is a block diagram (function block diagram) illustrating each function provided in the control unit of the image forming apparatus according to the first exemplary embodiment. FIG. 4 is a main flowchart of the sheet presence / absence determination process of the image forming apparatus according to the first exemplary embodiment. FIG. 5 is an explanatory diagram showing a state in which there is no recording sheet in the paper feed tray. FIG. 6 is an explanatory diagram of a state in which the recording sheet in the paper feed tray cannot be detected by the bottom sheet sensor. FIG. 7 is a block diagram (functional block diagram) illustrating functions provided in the control unit of the image forming apparatus according to the second embodiment, and corresponds to FIG. 3 according to the first embodiment. FIG. 8 is a main flowchart of the sheet presence / absence determination process of the image forming apparatus according to the second embodiment, and corresponds to FIG. 4 according to the first embodiment. FIG. 9 is an explanatory diagram of a state in which neither the bottom sheet sensor SN1 nor the no-paper sensor SN2 in the vicinity of the sheet feeding unit can detect the recording sheet. FIG. 10 is a block diagram (functional block diagram) illustrating the functions of the control unit of the image forming apparatus according to the third embodiment, and corresponds to FIG. 7 according to the second embodiment. FIG. 11 is a main flowchart of the sheet presence / absence determination process of the image forming apparatus according to the third embodiment, and corresponds to FIG. 8 according to the second embodiment. FIG. 12 is an explanatory diagram of a state in which the recording sheet of the paper feed tray cannot be detected by the sensor due to the posture of the paper feed tray. FIG. 13 is an explanatory diagram of a state in which a recording sheet cannot be detected by a conventional sheet sensor.

Explanation of symbols

6 ... Seat lifting member,
C5 '... paper feeding member operating means,
C5A: Sheet feeding member operating means when no sheet is present,
C6: Seat elevating member operating means,
C7, C7 ', C7 "... sheet presence / absence discriminating means,
C31: Sheet detection result storage means,
C32 ... detection failure discrimination means,
K: Paper feeding member,
S ... Recording sheet,
SN1 ... bottom sheet sensor,
SN2: paper feed sheet sensor,
TR1 to TR4 ... paper feed tray,
UI1: Sheet presence / absence notification member.

Claims (4)

A sheet conveying apparatus comprising the following constituent elements (A01) to (A07):
(A01) A paper feed tray for storing recording sheets on which images are recorded,
(A02) a paper feed member that is disposed above the paper feed tray and feeds a recording sheet stored in the paper feed tray;
(A03) The recording sheet in the sheet feeding tray is supported and moved up and down between an upper sheet feeding position where the recording sheet is fed and a lower standby position where the recording sheet is not fed Possible seat lifting member,
(A04) Sheet elevating member operating means for operating the sheet elevating member between the paper feeding position and the standby position;
(A05) a bottom sheet sensor that is disposed below the sheet feed tray and that can detect the presence or absence of a recording sheet in a state where the sheet elevating member is in a standby position;
(A06) a paper feed sheet sensor disposed in the vicinity of the paper feed member and capable of detecting the presence or absence of a recording sheet in the vicinity of the paper feed member;
(A07) Sheet presence / absence discriminating means for discriminating that there is no recording sheet when both the bottom sheet sensor and the sheet feeding sheet sensor detect the absence of the recording sheet. The sheet conveying apparatus according to claim 1, comprising the following constituent elements (A08) to (A011):
(A08) The paper feed member movable between an upper paper feed standby position where the recording sheet is not fed and a paper feed execution position where the recording sheet is brought into contact with the uppermost surface of the recording sheet ,
(A09) Paper feed member operating means for moving the paper feed member between the paper feed standby position and the paper feed execution position;
(A010) When the bottom sheet sensor and the paper feed sheet sensor detect the absence of a recording sheet before the paper feed is started, the paper feed member operation without a sheet is moved to move the paper feed member to the paper feed execution position. means,
(A011) When both the bottom sheet sensor and the paper feed sheet sensor detect that there is no recording sheet in a state where the paper feeding member is moved to the paper feeding execution position, it is determined that there is no recording sheet. Sheet presence / absence discriminating means. The sheet conveying apparatus according to claim 1 or 2, comprising the following constituent elements (A012) to (A014):
(A012) a sheet detection result storage means for storing the presence of a recording sheet when any of the bottom sheet sensor and the paper feed sheet sensor detects the presence of a recording sheet at the end of a job as an image forming operation;
(A013) Before feeding at the start of a job, when both the bottom sheet sensor and the feeding sheet sensor detect the absence of a recording sheet, and the presence of a sheet is stored in the sheet detection result storage unit, A detection failure determination means for determining a sensor detection failure;
(A014) When both the bottom sheet sensor and the sheet feeding sheet sensor detect the absence of a recording sheet and the absence of sheet is stored in the sheet detection result storage unit before feeding at the start of a job, The sheet presence / absence determining means for determining that there is no recording sheet. The sheet conveying apparatus according to any one of claims 1 to 3, further comprising the following constituent (A015):
(A015) A sheet presence / absence notification member for notifying the user that there is no sheet when the sheet presence / absence determination unit determines that there is no sheet.

Images