JP6273963B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus that forms an image on a sheet.

  For example, in the image forming apparatus described in Patent Document 1, a movable member such as an actuator that contacts a sheet positioned at the upper end in the stacking direction and a plurality of optical sensors that detect the position of the movable member are provided. When the remaining number of sheets remaining in a sheet tray such as a paper cassette decreases, and (b) when the remaining number of sheets becomes zero is detected.

JP-A-5-97278

In the image forming apparatus described in Patent Document 1, since a plurality of optical sensors are provided, the structure of the image forming apparatus is complicated, and it is difficult to reduce the number of assembly steps.
SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus capable of reducing the number of detection units such as optical sensors and proximity switches.

  In order to achieve the above object, according to the present invention, in an image forming apparatus for forming an image on a sheet, a plurality of sheets are placed in a stacked state and conveyed from the sheet tray (17). The image forming unit (5) that forms an image on the sheet and one or more sheets placed on the sheet tray (17) are contacted from above, and the sheet is supplied to the image forming unit (5) side. A plate-like pressing plate that lifts the sheet by making contact with the pickup roller (15A) and one or more sheets placed on the sheet tray (17) from below, and penetrates in the thickness direction. A pressing plate (23) having a hole (23A), and a displaceable movable member extending from the upper side of the sheet tray (17) toward the through hole (23A), the leading end (29A) in the extending direction of the sheet tray (17 When the sheet is placed in contact with the sheet tray and displaced, and when no sheet is present in the sheet tray (17), the leading end side detects the movable member (29) passing through the through hole (23A) and the detected part. In addition, a first movable object that has a detection part (35) that emits an ON signal indicating that it has been detected and a first detection part (31A) that forms a detection part and is displaced integrally with the movable member (29). A first movable detected member (a detection member) that is in a position where the first detected portion (31A) can be detected by the detecting portion (35) when the movable member (29) passes through the through hole (23A). 31) and a second movable detected member having a second detected portion (33A) forming a detected portion, and a movable member (23) when the pressing plate (23) is displaced upward from the lowest position. 29) is displaced integrally with the detection unit (35). The second movable detected member (33) passing through the position where the second detected portion (33A) can be detected and the pressing plate (23) rise from the lowest position toward the pickup roller (15A). A timer unit (40) that counts the elapsed time from the start to the time when the ON signal is issued from the detection unit (35), and the pressing plate (23) based on the elapsed time measured by the timer unit (40) And an arithmetic unit (40) for calculating the number of sheets placed thereon.

  Accordingly, in the present invention, (a) when the first detected part (31A) is detected by the detection part (35) when the movable member (29) passes through the through hole (23A), the remaining sheet is detected. It can be detected that the number of sheets has become zero. (B) Since the number of sheets is calculated based on the elapsed time from when the pressing plate (23) is in the lowest position to when the ON signal is issued, it can be estimated that the remaining number of sheets has decreased. obtain. Therefore, in the present invention, it is possible to detect when the remaining number of sheets remaining in the sheet tray (17) is reduced and when the remaining number of sheets is 0 by one detection unit (35).

  Incidentally, the reference numerals in parentheses for each of the above means are examples showing the correspondence with the specific means described in the embodiments described later, and the present invention is indicated by the reference numerals in the parentheses of the above respective means. It is not limited to specific means.

1 is a central sectional view of an image forming apparatus 1 according to an embodiment of the present invention. FIG. 3 is a top view of a paper feed tray 17 according to the first embodiment of the present invention. FIG. 3A is a side view of the paper feed tray 17 according to the first embodiment of the present invention. (B) is a figure which shows the vertical cross section parallel to the width direction of the paper feed tray 17 which concerns on 1st Embodiment of this invention. (A), (b) and (c) is a figure which shows the action | operation of the actuator 28 which concerns on 1st Embodiment of this invention. (A), (b) and (c) is a figure which shows the action | operation of the actuator 28 which concerns on 1st Embodiment of this invention. (A), (b) and (c) is a figure which shows the action | operation of the actuator 28 which concerns on 1st Embodiment of this invention. (A), (b) and (c) is a figure which shows the action | operation of the actuator 28 which concerns on 1st Embodiment of this invention. 2 is a control block diagram of the image forming apparatus 1 according to the embodiment of the present disclosure. FIG. It is a flowchart which shows the action | operation of the control part 40 which concerns on 1st Embodiment of this invention. It is a flowchart which shows the action | operation of the control part 40 which concerns on 1st Embodiment of this invention. (A), (b), (c) and (d) is a figure which shows the action | operation of the actuator 28 which concerns on 2nd Embodiment of this invention.

  The “embodiment of the invention” described below shows an example of the embodiment. In other words, the invention specific items described in the claims are not limited to the specific means and structures shown in the following embodiments.

  In this embodiment, the present invention is applied to a printer connected to a computer. Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, the arrow etc. which show the direction attached | subjected to each figure are described in order to make it easy to understand the relationship between each figure.

  That is, the present invention is not limited to the directions given in the drawings. At least one member or part described with at least a reference numeral is provided, except where “plurality”, “two or more”, and the like are omitted.

(First embodiment)
1. 1. Outline of Image Forming Apparatus 1.1 Schematic Structure As shown in FIG. 1, an image forming unit 5 for forming an image on a sheet is accommodated in a housing 3 of the image forming apparatus 1. The image forming unit 5 is an electrophotographic system having a developing cartridge 7, a photosensitive drum 8, an exposure device 9, a fixing device 11, and the like. In FIG. 1, a movable member 29 and the like which will be described later are not shown.

  A discharge port 3 </ b> A and a discharge tray 3 </ b> B are provided at the top of the housing 3. The discharge port 3A is a portion where a sheet on which an image is formed is discharged. The discharge tray 3B is a placement unit on which the sheet discharged from the discharge port 3A is placed.

  The developing cartridge 7 includes a developing roller 7A, a storage portion 7B, and the like. The photosensitive drum 8 carries a developer image. The charger 8A charges the photosensitive drum 8. The exposure device 9 exposes the charged photosensitive drum 8. Thereby, an electrostatic latent image is formed on the photosensitive drum 8.

  The developing roller 7A supplies the developer stored in the storage unit 7B to the photosensitive drum 8. As a result, a developer image is formed on the photosensitive drum 8. A transfer unit 13 is disposed at a position facing the photosensitive drum 8.

  The transfer unit 13 transfers the developer image carried on the photosensitive drum 8 to a sheet. The fixing device 11 directly or indirectly heats the developer transferred to the sheet, and fixes the developer image on the sheet. A feeder mechanism 15 is provided upstream of the image forming unit 5 such as the transfer unit 13 in the sheet conveyance direction.

  The feeder mechanism 15 conveys the sheets placed on the paper feed tray 17 one by one toward the image forming unit 5 side. The sheet feed tray 17 is a sheet tray on which one or more sheets can be stacked and is detachably attached to the apparatus main body.

  The apparatus main body refers to a portion that is not disassembled by the user when the housing 3 or the frame (not shown) is used. The user can attach / detach the paper feed tray 17 to / from the apparatus main body by moving the paper feed tray 17 in the front-rear direction.

  The feeder mechanism 15 includes a pickup roller 15A, a separation roller 15B, a separation pad 15C, and the like. The pickup roller 15 </ b> A comes into contact with one or more sheets placed on the paper feed tray 17 from above and supplies the sheets to the image forming unit 5 side.

  The pickup roller 15A can be displaced between the transport position and the separation position. The conveyance position is a position where the pickup roller 15A comes into contact with the sheet and applies a conveyance force to the sheet. The separation position is a position where the pickup roller 15A is separated from the sheet.

  The mechanism for displacing the pickup roller 15A is the same as the “vertical drive mechanism” described in, for example, Japanese Patent Application Laid-Open No. 2008-174390, and therefore the detailed structure and detailed operation description thereof are omitted.

  The separation roller 15B and the separation pad 15C constitute a separation mechanism that separates the sheets one by one and sends them to the image forming unit 5 side when two or more sheets fed by the pickup roller 15A overlap. .

  The sheet sent from the paper feed tray 17 by the feeder mechanism 15 is supplied to the image forming unit 5 by a pair of conveying rollers 19 and a pair of registration rollers 20. The pair of registration rollers 20 corrects the posture of the sheet supplied to the image forming unit 5 and adjusts the timing of supplying the sheet to the image forming unit 5.

  A movable body 21 is provided in the sheet conveyance path from the feeder mechanism 15 to the image forming unit 5. The movable body 21 is a member that is displaced in contact with the conveyed sheet and detects whether or not the sheet exists due to the displacement.

  Specifically, the movable body 21 is an oscillating body whose one end side is supported by the apparatus main body so as to be able to oscillate, and the other end side is located at a position where it can come into contact with the conveyed sheet. A plate-shaped shielding plate (not shown) that is displaced integrally with the movable body 21 is provided at the swing center of the movable body 21.

  The shielding plate is displaced between a position where light emitted from a light emitting unit of a photo interrupter (not shown) is blocked and a position shifted from the position. Then, whether or not a sheet exists is detected based on whether or not the light receiving unit of the photo interrupter has received light. Hereinafter, the movable body 21, the shielding plate, and the photo interrupter are collectively referred to as a rear end sensor S1.

1.2 Sheet Feed Tray and its Surrounding Structure A pressing plate 23 and a pair of guide walls 25 are provided at the bottom of the sheet feed tray 17, that is, the part on which the sheet is placed. The pressing plate 23 is a plate-like member that comes into contact with one or more sheets placed on the paper feed tray 17 from below and raises the sheets toward the pickup roller 15A.

  The pressing plate 23 is assembled to the paper feed tray 17 so as to be swingable, and is moved upwardly by the lifting mechanism 27. The raising mechanism 27 raises the pressing plate 23 so that the contact surface pressure between the pickup roller 15A and the sheet is within a predetermined range set in advance.

  Specifically, when the number of sheets placed decreases and the contact surface pressure decreases, the pressing plate 23 is displaced upward toward the pickup roller 15A to increase the contact surface pressure. Note that the pressing plate 23 that has been displaced upward will not be displaced downward unless the paper feed tray 17 is removed from the apparatus main body.

  That is, while the paper feed tray 17 is mounted on the apparatus main body, the pressing plate 23 is displaced upward as the remaining number of sheets decreases. When the paper feed tray 17 is removed from the apparatus main body, the pressing plate 23 is lowered to a horizontal state.

  Thereafter, when the paper feed tray 17 is attached to the apparatus main body, the pressing plate 23 rises to a position where the contact surface pressure is within a predetermined range. Incidentally, the specific structure of the raising mechanism 27 is the same as the pressure plate lift mechanism described in, for example, Japanese Patent No. 4888573.

  As shown in FIG. 2, the pressing plate 23 is provided with a through hole 23A penetrating in the thickness direction. As shown in FIGS. 3A and 3B, the through hole 23 </ b> A is a through portion through which the distal end side of the movable member 29 can penetrate.

  As shown in FIG. 3A, the movable member 29 is a displaceable movable member that extends from the upper side in the vertical direction of the paper feed tray 17 toward the through hole 23A. As shown in c), the extending direction leading end 29A is a member that contacts and displaces the sheet placed on the sheet feeding tray 17.

  When no sheet is present in the paper feed tray 17, the leading end 29A side of the movable member 29 penetrates the through hole 23A, so that the movable member 29 is pressed as shown in FIGS. 5 (a) to 5 (c). It is not displaced regardless of the position of the plate 23.

  The movable member 29 according to this embodiment is assembled to the apparatus main body so as to be swingable. The rotating shaft 29B of the movable member 29 is set on the backward side in the sheet conveying direction from the rotating shaft 15D of the pickup roller 15A. That is, the tip 29A of the movable member 29 is positioned on the forward side in the transport direction from the rotation shaft 29B.

  The detection unit 35 is a sensor that emits an ON signal indicating that it has been detected when the first detection unit 31A or the second detection unit 33A is detected. As shown in FIG. 3B, the detection unit 35 according to the present embodiment is a photointerrupter including a light emitting unit 35A that emits light, a light receiving unit 35B that receives light emitted from the light emitting unit 35A, and the like.

  The first detected part 31A and the second detected part 33A are light shielding plates capable of blocking the optical path from the light emitting part 35A to the light receiving part 35B. Then, the detection unit 35 issues an ON signal when the first detected unit 31A or the second detected unit 33A blocks the optical path. When the light receiving unit 35B receives light, the detection unit 35 issues an off signal.

  The first detected part 31A is provided on the first movable detected member 31 as shown in FIG. As shown in FIGS. 4A to 4C, the first movable member 31 is displaced integrally with the movable member 29, and the tip 29A of the movable member 29 passes through the through hole 23A. In addition, as shown in FIGS. 5A to 5C, the first detected part 31 </ b> A is connected to the movable member 29 so that the first detected part 31 </ b> A can be detected by the detecting part 35.

  In addition, the 1st movable to-be-detected member 31 is connected and integrated with the extending direction root side of the movable member 29. As shown in FIG. The rotating shaft 29 </ b> B is provided at a connecting portion 29 </ b> C between the first movable detected member 31 and the movable member 29.

  The second detected portion 33 </ b> A is provided on the second movable detected member 33. As shown in FIGS. 4A to 4C, the second movable member 33 is displaced integrally with the movable member 29 when the pressing plate 23 is displaced upward from the lowest position. Thus, the detection unit 35 is connected to the movable member 29 so as to pass through a position where the second detection target portion 33A can be detected.

  The second movable detected member 33 is connected to a connecting portion 29 </ b> C between the first movable detected member 31 and the movable member 29. The movable member 29, the first movable detected member 31, and the second movable detected member 33 are integrated to form one actuator 28. For this reason, the movable member 29, the first movable detected member 31, and the second movable detected member 33 rotate integrally around the rotation shaft 29B.

  Incidentally, when the paper feed tray 17 is removed from the apparatus main body, the actuator 28 is held in a state (hereinafter referred to as a locked state) displaced upward in the vertical direction by a holding mechanism (not shown). When the paper feed tray 17 is attached to the apparatus main body, the locked state is released.

  As shown in FIG. 2, the pair of guide walls 25 suppress the skew of the sheet conveyed while contacting the both ends in the width direction of the sheet placed on the sheet feeding tray 17. The width direction is a direction orthogonal to the sheet feeding direction and the sheet thickness direction.

  Of the pair of guide walls 25, at least the guide wall 25 located on the same side (left side in the present embodiment) as the movable member 29 with respect to the pickup roller 15A is displaceable in the width direction. This is because sheets of various sizes can be placed on the paper feed tray 17.

  As shown in FIG. 3B, the movable member 29 projected onto the virtual plane orthogonal to the sheet conveying direction always has the guide wall 25 projected onto the virtual plane regardless of the position of the guide wall 25. It is located between the pickup roller 15A projected on the virtual plane.

1.2 Operation of pressure plate and actuator <When no sheet is present in the paper feed tray>
When no sheet is present on the paper feed tray 17, that is, the pressing plate 23, as shown in FIGS. 5A to 5C, the tip 29A side of the movable member 29 penetrates the through hole 23A, and the tip 29A is It reaches the bottom 17A of the paper feed tray 17.

  For this reason, when there is no sheet on the pressing plate 23, the optical path of the detecting unit 35 is blocked by the first detected unit 31A regardless of the position of the pressing plate 23. Be emitted.

<When there are sheets in the paper feed tray>
When a sheet is present on the sheet feeding tray 17, that is, the pressing plate 23, the leading end 29A of the movable member 29 is in contact with the sheet, as shown in FIGS. The movable member 29 is also displaced according to the position of the sheet located at the upper end in the stacking direction among the plurality of sheets.

  For this reason, after the pressing plate 23 starts to rise from the lowermost position toward the pickup roller 15A, the second detecting portion 33A has the second detecting portion 35A until the raising of the pressing plate 23 stops. Passes a position where the detection unit 33A can be detected.

  In the above operation, the sheet feeding tray 17 is fully loaded with sheets (see FIGS. 6A to 6C), and only one sheet is placed on the sheet feeding tray 17 (see FIG. 6). 7 (a) to 7 (c)). That is, when there is a sheet in the sheet feeding tray 17, the detection unit 35 issues an ON signal once from when the pressing plate 23 starts to rise until when the raising stops.

2. 2.1 Control System of Image Forming Unit and the like 2.1 Control System A control unit 40 shown in FIG. 8 controls operations of the feeder mechanism 15, the image forming unit 5, the notification unit 41, and the like. The control unit 40 is configured by a microcomputer having a CPU, a RAM, a ROM, and the like. The control unit 40, that is, a control program for operating the microcomputer is stored in advance in a nonvolatile storage unit such as a ROM.

  The control unit 40 includes an electric motor (not shown) that supplies rotational force to the pickup roller 15A and the like, and a solenoid (not shown) that moves the pickup roller 15A away from and in contact with the sheet. The feeder mechanism 15 is controlled by controlling the operation. The control unit 40 controls the image forming unit 5 by controlling the operations of the exposure device 9 and the transfer unit 13.

  The alerting | reporting part 41 is for alerting | reporting information to a user. The notification unit 41 according to the present embodiment includes a display device that can notify character information or graphic information, a speaker that can notify sound information, and the like.

  The control unit 40 includes a detection signal generated from the rear end sensor S1, a detection signal generated from the detection unit 35 (light receiving unit 35B), and a mounting sensor that detects whether or not the paper feed tray 17 is mounted on the apparatus main body. The signal from S2 is input. The mounting sensor S2 according to the present embodiment includes a proximity switch, a limit switch, and the like.

  The mounting sensor S2 issues a “signal indicating that the paper feed tray 17 has been mounted (hereinafter, a mounting signal)”. When the mounting signal is input, the control unit 40 determines that the paper feed tray 17 is mounted on the apparatus main body. When the mounting signal is not input, the control unit 40 determines that the paper feed tray 17 is mounted on the apparatus main body. It is determined that it is not installed.

2.2 Control operation <Overview>
The control unit 40 according to the present embodiment can execute the following control operations.

  That is, the control unit 40 measures the elapsed time from when the pressing plate 23 starts to rise toward the pickup roller 15A from the lowest position until when the ON signal is issued from the detection unit 35. Next, the control unit 40 calculates the number of sheets (hereinafter referred to as the predicted number) placed on the pressing plate 23 based on the elapsed time (hereinafter referred to as the timed time).

  The control unit 40 counts the number of sheets on which image formation has been performed, and the number obtained by subtracting the counted number from the predicted number (hereinafter referred to as the remaining number) is equal to or less than a predetermined number. When this happens, the notification unit 41 is notified of this.

Note that the predicted number and the remaining number are stored in a rewritable nonvolatile storage unit (hereinafter, the storage unit is referred to as a number counter) provided in the control unit 40.
The control unit 40 calculates the predicted number of sheets by the following method. That is, the raising mechanism 27 raises the pressing plate 23 so that the contact surface pressure between the pickup roller 15A and the sheet is within a predetermined range set in advance.

  For this reason, as the number of sheets placed on the paper feed tray 17, that is, the pressing plate 23 increases, the time required for measurement decreases accordingly. On the contrary, when the number of sheets placed on the pressing plate 23 is reduced, the time is increased accordingly.

  In a non-volatile storage unit such as a ROM, a function expression indicating the relationship between the time measurement and the number of sheets is stored in advance. Then, the control unit 40 calculates the predicted number of sheets by substituting the actually measured time for the function equation.

  In the present embodiment, the timer unit that counts the time is realized by a program (software) that executes the above-described control operation and an operation control clock unit (not shown) of the CPU. The calculation unit that calculates the predicted number of sheets and the counting unit that counts the number of sheets on which image formation has been performed are realized by a program (software) that executes the above-described control operation.

<Details>
FIG. 9 is a flowchart illustrating an example of control executed by the control unit 40 when a print command (print job) is received from the computer. A program for executing the control shown in FIG. 9 and FIG. 10 described later is stored in advance in a nonvolatile storage unit such as a ROM.

  When receiving a print command (print job) from the computer, the control unit 40 executes the control shown in FIG. When this control is executed, the number counter update process is executed (S1). Details of the sheet counter updating process will be described later.

  Next, it is determined whether or not light is received by the detection unit 35 (light receiving unit 35B), that is, whether or not an off signal is emitted from the detection unit 35 (S3). If it is determined that no light is received, that is, an ON signal is generated (S3: ON signal), the number counter is reset to 0 (S5).

  At this time, the control unit 40 considers that the actuator 28 is in any of the states shown in FIGS. 5A to 5C, and displays on the notification unit 41 that the remaining number is 0 (“empty”). ) Is displayed (S7), this control is terminated.

  When it is determined in S3 that an off signal has been issued (S3: off signal), the feeder mechanism 15 is activated to perform the operation of feeding out the sheet placed on the paper feed tray 17 (pickup operation) ( S9).

  When the pickup roller 15A has a lowering displacement amount that is larger than a preset displacement amount during the pickup operation, the raising mechanism 27 is activated and the pressing plate 23 is displaced upward.

  Next, it is determined whether or not the pickup has been successful, that is, whether or not the presence of the sheet has been detected by the trailing edge sensor S1 before a predetermined time has elapsed since the pickup roller 15A was activated (S11).

  When it is determined that the pickup has not been successful, that is, the presence of the sheet has not been detected within a predetermined time (S11: NO), information indicating that “pickup has failed (pick miss)” is sent via the notification unit 41. (S13), the image forming process ends.

  If it is determined that the pickup has succeeded (S11: YES), after the image is formed on the sheet for one page and printing is completed (S15), the value stored in the number counter is only 1. The value is updated to the reduced value (S17).

  Next, it is determined whether or not the value stored in the updated number counter is equal to or less than a predetermined value (S19). If it is determined that the value is equal to or less than the predetermined value (S19: less than the predetermined value), information indicating that the number of sheets existing in the paper feed tray is small (near empty) is notified via the notification unit 41. (S21) and S23 are executed.

  If it is determined that the value stored in the updated number counter is not less than or equal to the predetermined value (S19: greater than the predetermined value), whether there is a next page on which an image is to be formed, that is, for all pages. It is determined whether or not image formation (printing) has been completed (S23).

  When it is determined that image formation (printing) has been completed for all pages (S23: YES), this control ends. If it is determined that image formation (printing) has not been completed for all pages (S23: NO), S3 is executed again.

<Number counter updating process (see FIG. 10)>
This control process includes (a) when a print command (print job) is received from the computer (S1), (b) when a power switch (not shown) of the image forming apparatus 1 is turned on, and (c) This process is executed when the paper feed tray 17 is mounted.

  Note that “when the paper feed tray 17 is mounted” refers to a time when a mounting signal is input from a state where no mounting signal is input from the mounting sensor S2, and a predetermined time from when the mounting signal is input. When it is within time.

  Then, when this control process is executed, the measurement of the time measurement is started (S31). That is, when this control process is executed, the control unit 40 considers that the pressing plate 23 has started to rise from the lowest position toward the pickup roller 15A (S33), and measures the timed time. Start.

  Next, it is determined whether or not the output signal of the detection unit 35 has changed, that is, whether or not the output signal has changed from an off signal to an on signal (S35). If it is determined that there is no change, that is, an off signal has been issued (S35: off signal), has a predetermined time (for example, ○ seconds) elapsed since the start of measurement of the timed time? It is determined whether or not (S37).

  If it is determined that the predetermined time has not elapsed (S37: NO), S35 is executed again. If it is determined that the predetermined time has elapsed (S37: YES), the measurement process is terminated after the measurement of the time measurement is stopped (S39). Note that the control unit 40 considers that the pressing plate 23 has already been raised when S39 is executed.

  When it is determined in S35 that the change has occurred, that is, the ON signal is issued (S35: ON signal), the measurement of the measured time is stopped (S41). Next, after the predicted number of sheets is calculated based on the timed time (S43), the value of the number counter is updated to the calculated expected number (S45), and this control process ends.

  In addition, although it is described as “pressing plate raising start” in S33 of FIG. 10, as described above, only “the control unit 40 considers that the raising of the pressing plate 23 has started”, and actually There is a case where the pressing plate 23 has not started to rise.

  That is, for example, in a case where a print command is continuously received from a computer, it is highly likely that the pressing plate 23 has already been raised when at least a second print command is received. Therefore, in this case, in reality, the pressing plate 23 has not started to rise.

  However, for example, “when the paper feed tray 17 is mounted”, the pressing plate 23 starts to rise from the lowest position toward the pickup roller 15A. Therefore, for example, when the print command is continuously received from the computer, the present embodiment is established even if S33 is deleted.

3. Features of the Image Forming Apparatus According to the Present Embodiment In this embodiment, (1) when the first detected part 31A is detected by the detecting part 35 when the movable member 29 passes through the through hole 23A, the sheet remains. It can be detected that the number of sheets has become zero. (2) Since the number of sheets is calculated based on the elapsed time from when the pressing plate 23 is in the lowest position to when the ON signal is issued, it can be estimated that the remaining number of sheets has decreased.

(Second Embodiment)
In the first embodiment, the actuator 28 swings and displaces. However, in the present embodiment, as shown in FIGS. 11A to 11D, the direction intersecting the horizontal direction (this embodiment). Then, the actuator 28 is displaced in the vertical direction). In the present embodiment, the first detected part 31A is arranged on the upper side in the vertical direction from the second detected part 33A.

  FIG. 11A shows a case where no sheet is present in the paper feed tray 17. In this case, the movable member 29 of the actuator 28 passes through the through hole 23A, and the first detected part 31A blocks the optical path of the detecting part 35.

  FIG. 11B shows a case where a sheet is present in the paper feed tray 17 and the pressing plate 23 is at the lowest position. In this state, the optical path of the detection unit 35 is not blocked by either the first detected unit 31A or the second detected unit 33A.

  When the pressing plate 23 is lifted from the lowest position, the actuator 28 is displaced upward in the vertical direction as shown in FIG. 11 (c) → FIG. 11 (e) in order, and the second detected portion 33A. Passes through the optical path.

(Other embodiments)
The image forming apparatus 1 according to the above-described embodiment is a monochrome electrophotographic system, but the present invention is not limited to this, and may be a color electrophotographic system or an inkjet system, for example.

  In the above-described embodiment, the movable member 29 projected onto the virtual plane orthogonal to the sheet conveyance direction is always projected onto the virtual plane and the guide wall 25 projected onto the virtual plane regardless of the position of the guide wall 25. Although it is located between the pickup roller 15A, the present invention is not limited to this.

That is, for example, when only the guide wall 25 on one side in the width direction of the pair of guide walls 25 is movable, the movable member 29 may be positioned on the guide wall 25 on the other side in the width direction.
In the above-described embodiment, the movable member 29, the first movable detected member 31, and the second movable detected member 33 are integrated to form one actuator 28. However, the present invention is limited to this. Instead, it is sufficient that the movable member 29, the first movable detected member 31 and the second movable detected member 33 are displaced together in an integrated manner.

  In the above-described embodiment, the timer unit and the calculation unit are realized by software. However, the present invention is not limited to this, and the timer unit and the calculation unit may be realized by using dedicated hardware. . Note that the hardware in this case may be either electrical hardware or mechanical hardware.

  Further, the present invention is not limited to the above-described embodiment as long as it matches the gist of the invention described in the claims.

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus 3 ... Housing | casing 3A ... Discharge port 3B ... Discharge tray 5 ... Image formation part 7 ... Developing cartridge 7A ... Developing roller 7B ... Storage part 8 ... Photosensitive drum 8A ... Charger 9 ... Exposing device 11 ... Fixing device DESCRIPTION OF SYMBOLS 13 ... Transfer part 15 ... Feeder mechanism 15A ... Pickup roller 15B ... Separation roller 15C ... Separation pad 15D ... Rotating shaft 17 ... Paper feed tray 19 ... Conveyance roller 20 ... Registration roller 21 ... Movable body 23 ... Pressing plate 23A ... Through-hole 25 ... guide wall 27 ... ascending mechanism 28 ... actuator 29 ... movable member 31 ... first movable detected member 31A ... first detected portion 33 ... second movable detected member 33A ... second detected portion 35 ... detecting portion 40 ... Control unit 41 ... Notification unit S1 ... Rear end sensor S2 ... Wear sensor

Claims (6)

In an image forming apparatus for forming an image on a sheet,
A sheet tray on which a plurality of sheets are stacked, and
An image forming unit that forms an image on a sheet conveyed from the sheet tray;
A pickup roller that comes into contact with the one or more sheets placed on the sheet tray from above and supplies the sheet to the image forming unit side;
A plate-like pressing plate that contacts the one or more sheets placed on the sheet tray from below to raise the sheet, and has a through-hole penetrating in the thickness direction; and
A displaceable movable member extending from the upper side of the sheet tray toward the through-hole, the front end of the extending direction being in contact with the sheet placed on the sheet tray and being displaced, and the sheet on the sheet tray When there is not, a movable member whose tip side penetrates the through hole,
A detection unit that emits an ON signal indicating the detection when detecting the detected unit;
A first movable detected member having a first detected portion that constitutes the detected portion and displaced integrally with the movable member, wherein the movable member passes through the through hole. A first movable member to be detected at which the detection unit can be detected by the detection unit;
A second movable detected member having a second detected portion that constitutes the detected portion, wherein the second movable detected member is integrally displaced with the movable member when the pressing plate is displaced upward from the lowest position. A second movable detected member that passes through a position where the second detected portion can be detected by the detecting portion;
A timer unit that counts an elapsed time from the time when the pressing plate starts to rise toward the pickup roller from the lowest position until the time when the ON signal is issued from the detection unit;
An image forming apparatus, comprising: an arithmetic unit that calculates the number of sheets placed on the pressing plate based on an elapsed time measured by the timer unit. The sheet tray is detachably attached to the apparatus main body,
A tray detector that emits a mounting signal indicating that the sheet tray is mounted when the sheet tray is mounted on the apparatus body;
The control unit for controlling the operation of the timer unit and the calculation unit, comprising: a control unit that operates the timer unit and the calculation unit when the mounting signal is issued. The image forming apparatus described. An informing unit for informing the user of information;
A counting unit that counts the number of sheets on which image formation has been performed in the image forming unit,
When the number obtained by subtracting the number counted by the counting unit from the number calculated by the calculation unit becomes equal to or less than a predetermined number, the control unit notifies the fact through the notification unit. The image forming apparatus according to claim 2, wherein: Wherein relative to the seat tray a displaceable guide wall in the width direction, a guide wall for guiding the conveyance of the sheet in contact with the widthwise end portion of the sheet placed on the sheet tray,
The movable member projected on the virtual plane orthogonal to the sheet conveying direction is always between the guide wall projected on the virtual plane and the pickup roller projected on the virtual plane, regardless of the position of the guide wall. 4. The image forming apparatus according to claim 1, wherein the image forming apparatus is located in a position. The movable member, the first movable detected member, and the second movable detected member are integrated to form one actuator,
The image forming apparatus according to claim 1, wherein the actuator is held so as to be rotatable around a predetermined rotation axis. The first movable member to be detected is coupled to the movable member;
The second movable detected member is connected to a connecting portion between the first movable detected member and the movable member,
The image forming apparatus according to claim 5, wherein the rotation shaft is provided in the connecting portion.

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