JP5937037B2 - Remaining amount detection device - Google Patents

Description

  The present invention relates to a remaining amount detection device that detects the remaining amount of recording paper placed on a lift plate as a laminate.

  In an image forming apparatus represented by a copying machine or a multifunction peripheral, recording sheets are placed on a sheet feeding tray such as a sheet feeding cassette as a stack, and the recording sheets are separated and supplied one by one from the top of the stack. In many cases, an image is formed on the fed recording paper, and the remaining amount of the recording paper placed as a stack on the paper feed tray is detected.

As a method for detecting the remaining amount of recording paper, an instruction means including a coil and a capacitor is attached to the tray on which the recording paper is placed, and a signal is sent to a plurality of coils provided along the movement path of the tray and received. There has been proposed a technique for detecting the position of the coil closest to the instruction means from the change in the signal (for example, see Patent Document 1).
In addition, a technique has been proposed in which a magnet is disposed in a movable portion of a paper feed tray on which recording paper is placed, and the remaining amount of recording paper is detected by detecting the amount of movement or tilt of the magnet with a magnetic sensor. (For example, refer to Patent Document 2).
Further, the lift plate on which the recording paper is placed is provided with a conductor plate, and an eddy current is generated in the conductor plate by a remaining amount sensor arranged so as to face the lift plate, and the magnetic flux generated by the eddy current is used as a basis. In addition, a technique for detecting the remaining amount of recording paper by detecting the distance between the remaining amount sensor and the conductor plate has also been proposed (see, for example, Patent Document 3).

JP 2008-1501 A JP 2007-302443 A JP 2005-343583 A

However, in the technique of Patent Document 1, it is necessary to provide a plurality of coils along the movement path of the tray. In particular, in order to increase detection accuracy, it is necessary to increase the number of coils to be closely packed. There was a problem that the cost would be high.
Further, in the technique of Patent Document 2, a Hall sensor is used as a magnetic sensor, and the magnetic flux of the magnet is detected. Therefore, within a circular range centered on a magnet having a radius of the maximum distance between the magnet and the Hall sensor, Since the magnetic flux to the Hall sensor is disturbed, there is a problem in that metal cannot be installed and design restrictions are increased.
Furthermore, in the technique of Patent Document 3, as a restriction for installing the drive coil, the reference coil, the detection coil, and the metal plate that constitute the remaining amount sensor, the drive coil and the reference coil are installed on the opposite side and are detected. It is necessary to install the coil and the metal plate on the opposite side. However, the reference coil and the detection coil are coils for detection, and the detection voltage will be distorted if affected by other magnetic fluxes. There is a design constraint. In particular, as the paper runs out, these coils and the like become closer to each other, and care must be taken regarding the reference coil, the detection coil, and the installation. Therefore, in order to mount the remaining amount sensor disclosed in Patent Document 3, a large space is required, which causes a problem that the apparatus itself becomes large.

  The present invention has been made in view of the above situation, solves the above problems, can detect the remaining amount of recording paper placed as a laminate on a lift plate with a small number of parts, and is designed. The above limitation is to provide a remaining amount detection device that is very light.

The remaining amount detection device of the present invention is a remaining amount detection device that detects the remaining amount of recording paper stored in a paper feeding unit of an image forming apparatus, and is disposed in the paper feeding unit, A lift plate that moves according to the amount; a coil spring that expands and contracts according to the position of the lift plate; an oscillation circuit that applies a predetermined alternating voltage to the coil spring; a core around which the coil spring is wound; A detection coil wound around a core; and a detection circuit for detecting a voltage of the detection coil. The lift plate extends to a region where the maximum size recording paper is not placed, and the core penetrates the lift plate. An extension part in which a through hole is formed is formed, and the coil spring expands and contracts according to the position of the extension part .
Further, in the remaining amount detection device of the present invention, the coil spring may be used as an elastic member that biases the lift plate toward a paper feed roller that feeds the recording paper placed on the lift plate. good.

  According to the present invention, the remaining amount of the recording paper P placed as a laminate on the lift plate can be detected with a small number of parts including two coils and a core. Furthermore, since the detection is performed by the induced electromotive force using the core, there is little influence even if the metal parts are arranged in the immediate vicinity, and the design restrictions are very light.

1 is a schematic cross-sectional view illustrating a configuration of an embodiment of an image forming apparatus on which an embodiment of a remaining amount detection device according to the invention is mounted. It is a perspective view which shows the structure of the paper feed cassette shown in FIG. It is a side view which shows the structure of embodiment of the residual amount detection apparatus which concerns on this invention. It is a side view which shows the structure of other embodiment of the residual amount detection apparatus which concerns on this invention.

Next, embodiments of the present invention will be specifically described with reference to the drawings.
The image forming apparatus 1 on which the remaining amount detection device 90 according to the present embodiment is mounted is a copier. Referring to FIG. 1, the image forming apparatus 1 includes a document reading unit 20, a document feeding unit 30, and a recording unit 40. ing. The document reading unit 20 is disposed above the recording unit 40, and the document feeding unit 30 is disposed above the document reading unit 20. Although the image forming apparatus 1 of the present embodiment has been described with reference to a copying machine, it is needless to say that a scanner, a multifunction machine, and the like are included.

  On the front side of the image forming apparatus 1, a touch panel device 10 for setting the image forming apparatus 1 and instructing operation is disposed. The touch panel device 10 has a numeric keypad for inputting a numerical value such as the number of printed sheets, a reset key for inputting an instruction for initializing setting information, a copy operation to be stopped, and an input numerical value to be erased. Various operation keys such as a stop key and a start key for inputting an output instruction for starting a printing operation are provided. The touch panel device 10 is provided with a display area for notifying the state of the image forming apparatus 1 and displays the remaining amount of recording paper detected by the remaining amount detecting device 90.

  Referring to FIG. 1, the document reading unit 20 includes a scanner 21, a platen glass 22, and a document reading slit 23. The scanner 21 includes an exposure lamp, a CCD (Charge Coupled Device) sensor, and the like, and is configured to be movable in the direction in which the document MS is transported by the document feeding unit 30. The platen glass 22 is an original table made of a transparent member such as glass. The document reading slit 23 has a slit formed in a direction orthogonal to the direction in which the document MS is conveyed by the document feeding unit 30.

  When reading the document MS placed on the platen glass 22, the scanner 21 is moved to a position facing the platen glass 22 and reads the document MS while scanning the document MS placed on the platen glass 22. Image data is acquired, and the acquired image data is output to the recording unit 40. When reading the document MS conveyed by the document feeding unit 30, the scanner 21 is moved to a position facing the document reading slit 23, and the document MS by the document feeding unit 30 is passed through the document reading slit 23. The document MS is read in synchronism with the conveying operation to acquire image data, and the acquired image data is output to the recording unit 40.

  The document feeding unit 30 includes a document placement unit 31, a document discharge unit 32, and a document transport mechanism 33. The documents MS placed on the document placement unit 31 are sequentially fed out one by one by the document conveyance mechanism 33 and conveyed to a position facing the document reading slit 23 of the document reading unit 20, and then the document discharge unit. 32 is discharged. The document feeding unit 30 is configured to be retractable, and the upper surface of the platen glass 22 can be opened by lifting the document feeding unit 30 upward.

  The recording unit 40 includes an image forming unit 50, and includes a paper feeding unit 60, a conveyance path 70, a conveyance roller 81, a discharge roller 82, and a discharge tray 83.

  The paper feeding unit 60 includes a paper feeding cassette 61 that stores recording paper P stacked thereon, and a paper feeding roller 62 that feeds the recording paper P from the paper feeding cassette 61 to the transport path 70 one by one. The paper feed roller 62, the transport roller 81, and the discharge roller 82 function as a transport unit, and the recording paper P is transported. The recording paper P fed to the conveyance path 70 by the paper feed roller 62 is conveyed to the image forming unit 50 by the conveyance roller 81. Then, the recording paper P on which recording is performed by the image forming unit 50 is output to the outside by the discharge roller 82. The recording sheet P on which recording has been performed is guided to the discharge roller 82 and output to the discharge tray 83.

  The image forming unit 50 includes a photosensitive drum 51, a charging unit 52, an exposure unit 53, a developing unit 54, a transfer unit 55, a cleaning unit 56, and a fixing unit 57. The exposure unit 53 is an optical unit including a laser device, a mirror, and the like. The exposure unit 53 outputs a laser beam based on image data, exposes the photosensitive drum 51 charged by the exposure unit 53, and An electrostatic latent image is formed on the surface. The developing unit 54 is a developing unit that develops the electrostatic latent image formed on the photosensitive drum 51 using toner, and forms a toner image based on the electrostatic latent image on the photosensitive drum 51. The transfer unit 55 transfers the toner image formed on the photosensitive drum 51 by the developing unit 54 to the recording paper P. The fixing unit 57 heats the recording paper P onto which the toner image has been transferred by the transfer unit 55 to fix the toner image on the recording paper P.

Next, the configuration of the paper feed cassette 61 will be described in detail with reference to FIGS.
The main body of the paper feed cassette 61 is composed of a cassette frame 610 and is slid horizontally in the direction of arrow A shown in FIG. 2 and inserted into the image forming apparatus 1. The cassette frame 610 is configured in a flat box shape with an open top surface, and a lift plate 611 is provided on the bottom surface of the cassette frame 610. The recording paper P is stacked on the lift plate 611 and supplied in the direction of arrow B shown in FIG. The lift plate 611 is configured such that the upstream end of the recording paper P in the paper supply direction is supported by the bottom surface of the cassette frame 610 and can swing around the fulcrum as the center and the downstream end as a free end.
When the paper feed cassette 61 is inserted and stored in the image forming apparatus 1, the motor coupling portion 612 is connected to a lift motor (not shown) provided in the image forming apparatus 1, so that the downstream end of the lift plate 611 is lifted. When the uppermost layer of the recording paper P loaded on the lift plate 611 comes into contact with the paper feed roller, the paper feed preparation is completed.

  At the downstream end of the lift plate 611, an extension portion 613 is formed that extends in a direction (for example, a direction perpendicular to the sheet feeding direction) that intersects the sheet feeding direction up to a region where the maximum size recording sheet P is not placed. The extending portion 613 adjusts the remaining amount of the recording paper P loaded in a state where the paper feeding preparation is completed, that is, the uppermost layer of the recording paper P stacked on the lift plate 611 is in contact with the paper feeding roller. Accordingly, the height from the bottom surface of the cassette frame 610 is displaced. A remaining amount detecting device 90 for detecting the displacement of the extending portion 613 is provided.

  Referring to FIG. 3, the remaining amount detection device 90 includes a coil spring 91 that expands and contracts according to the position of the extending portion 613 formed on the lift plate 611, and an oscillation circuit 92 that applies a predetermined AC voltage to the coil spring 91. The detection coil 93 that receives the magnetic flux from the coil spring 91, and the core used to generate a mutual induction electromotive force between the coil spring 91 and the detection coil 93 are wound around the coil spring 91 and the detection coil 93. 94) and a detection circuit 95 for detecting the voltage of the detection coil 93. The core 94 is a metal core such as an iron core having a large relative permeability, and is attached to the cassette frame 610 perpendicular to the bottom surface of the cassette frame 610. A through hole 614 (see FIG. 2) through which the core 94 passes is formed in the extending portion 613, and the coil spring 91 wound around the core 94 is between the extending portion 613 and the bottom surface of the cassette frame 610. Is intervened. The core 94 extends downward through the bottom surface of the cassette frame 610, and a detection coil 93 is wound around the extended portion.

The inductance L of the coil spring 91 can be expressed as L = k * μ ₁ * π * a ² * n ² / b, where μ ₁ is the magnetic permeability of the core 94. Here, k is the Nagaoka coefficient, a is the radius of the coil spring 91, b is the length of the coil spring 91, and n is the number of turns of the coil spring 91. The Nagaoka coefficient k, the radius a of the coil spring 91, and the number of turns n of the coil spring 91 are fixed values, and only the length b of the coil spring 91 changes according to the position of the extending portion 613.
Further, the magnetic flux Φ generated by the current flowing through the coil spring 91 can be expressed by Φ = L * (di / dt). The inductance L of the coil spring 91 and the time change of the current i flowing through the coil spring 91 are expressed as follows. Each is proportional.
Furthermore, the electromotive force ε generated in the detection coil 93 can be expressed by ε = −N * (dΦ / dt). Here, N is the number of turns of the detection coil 93.

  Therefore, the electromotive force ε generated in the detection coil 93 is proportional to the inductance L of the coil spring 91, and the inductance L of the coil spring 91 is inversely proportional to the length b of the coil spring 91. It can be seen that the electric power ε is inversely proportional to the length b of the coil spring 91. Thus, the length b of the coil spring 91 can be obtained by detecting the electromotive force ε generated in the detection coil 93 by the detection circuit 95.

That is, as shown in FIG. 3A, the length of the coil spring 91 when the lift plate 611 is swung in a state where the recording paper P is not placed on the lift plate 611 and the paper feed preparation is completed. and L _0, length receiving the magnetic flux of the coil spring 91 of the L _0, the voltage sensing coil 93 is detected by the detection circuit 95 outputs a V ₀ [V]. Then, as shown in FIG. 3B, the lift plate 611 is swung while the recording paper P is placed on the lift plate 611, and is detected by the detection circuit 95 when the paper feed preparation is ready. when voltage is the _{V 1 [V], L 1} the length of the coil spring 91 at this _time, L ₁ = L ₀ it can be determined by _(V 0 / V _1), stacked on the lift plate 611 The remaining amount of the recording paper P can be detected.

  In the present embodiment, as shown in FIG. 3, the extending portion 613 is formed at the downstream end of the lift plate 611 so that the expansion / contraction stroke of the coil spring 91 is increased. By taking a large expansion / contraction stroke of the coil spring 91, the detection accuracy can be improved. On the other hand, since the detection coil 93 needs to be disposed outside the movement range of the extending portion 613, the detection coil 93 is disposed so as to protrude downward from the bottom surface of the cassette frame 610.

  Therefore, as shown in FIG. 4, between the upstream end and the downstream end of the lift plate 611, it extends in a direction (for example, a direction perpendicular to the sheet feeding direction) to a region where the maximum size recording sheet P is not placed. An extension portion 613a may be formed, and a remaining amount detection device 90a that detects the displacement of the extension portion 613a may be provided. In the remaining amount detection device 90a, the core 94 is attached perpendicularly to the bottom surface of the cassette frame 610 through a through-hole formed in the extending portion 613a. The coil spring 91 wound around the core 94 is interposed between the extending portion 613a and the bottom surface of the cassette frame 610. And the detection coil 93 is wound out of the movement range of the extension part 613a of the core 94 which penetrated the extension part 613a and protruded upwards. In this case, the expansion / contraction stroke of the coil spring 91 is reduced, but the remaining amount detection device 90a can be arranged without protruding downward from the bottom surface of the cassette frame 610.

  In the present embodiment, the lift plate 611 is swung by a lift motor (not shown) so that the uppermost layer of the recording paper P stacked on the lift plate 611 is brought into contact with the paper feed roller. Even if the sheet feeding cassette is of a type in which the lift plate 611 is swung by the urging force of an elastic member such as a spring without using a lift motor, the same operation and effect as described above can be obtained. Note that it is preferable to use an elastic member that urges toward the paper feed roller 62 as the coil spring 91 that expands and contracts according to the position of the lift plate 611 because the number of parts of the paper feed unit 60 can be reduced. .

As described above, in the present embodiment, the remaining amount detection device 90 that detects the remaining amount of the recording paper P stored in the sheet feeding unit 60 of the image forming apparatus 1 is provided in the sheet feeding unit 60. A lift plate 611 that moves according to the remaining amount of the recording paper P, a coil spring 91 that expands and contracts according to the position of the lift plate 611, an oscillation circuit 92 that applies a predetermined AC voltage to the coil spring 91, and a coil spring A core 94 around which 91 is wound, a detection coil 93 wound around the core 94, and a detection circuit 95 that detects the voltage of the detection coil 93 are provided.
With this configuration, the remaining amount of the recording paper P placed as a laminate on the lift plate 611 can be detected with a small number of components including two coils (the coil spring 91 and the detection coil 93) and the core 94. Furthermore, since the detection is performed by the induced electromotive force using the core 94, there is little influence even if the metal parts are arranged in the immediate vicinity, and the design restrictions are very light.

  Further, in the present embodiment, the lift plate 11 is formed with an extending portion 613 that extends to an area where the maximum size recording paper P is not placed and is formed with a through hole 614 through which the core 94 passes. The spring 91 is configured to expand and contract according to the position of the extending portion 913.

Further, in the present embodiment, the coil spring 91 can be used as an elastic member that urges the lift plate 611 toward the paper feed roller 62 that feeds the recording paper P placed on the lift plate 611. .
With this configuration, it is possible to reduce the number of parts of the paper feed unit 60.

  Note that the present invention is not limited to the above-described embodiments, and it is obvious that the embodiments can be appropriately changed within the scope of the technical idea of the present invention. In addition, the number, position, shape, and the like of the constituent members are not limited to the above-described embodiment, and can be set to a suitable number, position, shape, and the like in practicing the present invention. In each figure, the same numerals are given to the same component.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 10 Touch panel apparatus 20 Original reading part 21 Scanner 22 Platen glass 23 Original reading slit 30 Original feeding part 31 Original placing part 32 Original discharge part 33 Original conveyance mechanism 40 Recording part 50 Image forming part 51 Photosensitive drum 52 Charging unit 53 Exposure unit 54 Development unit 55 Transfer unit 56 Cleaning unit 57 Fixing unit 60 Paper feed unit 61 Paper feed cassette 62 Paper feed roller 70 Carriage path 81 Carrying roller 82 Ejection roller 83 Ejection tray 90, 90a Remaining amount detection device 91 Coil Spring 92 Oscillation circuit 93 Detection coil 94 Core 95 Detection circuit 610 Cassette frame 611 Lift plate 612 Motor joint portion 613, 613a Extension portion 614 Through hole

Claims (2)

A remaining amount detecting device for detecting the remaining amount of recording paper stored in a paper feeding unit of an image forming apparatus,
A lift plate disposed in the paper feeding unit and moving according to the remaining amount of the recording paper;
A coil spring that expands and contracts depending on the position of the lift plate;
An oscillation circuit for applying a predetermined alternating voltage to the coil spring;
A core around which the coil spring is wound;
A detection coil wound around the core;
A detection circuit for detecting the voltage of the detection coil ;
The lift plate is extended to an area where the maximum size recording paper is not placed, and an extension part is formed in which a through hole is formed through which the core passes.
The said coil spring expands / contracts according to the position of the said extension part, The residual amount detection apparatus characterized by the above-mentioned . The coil spring is, the remaining amount detection according to claim 1, wherein a toward the paper feed roller for feeding the recording paper placed on the lifting plate is an elastic member that urges the lifting plate apparatus.

Images