JP2007297190A - Sheet material detecting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive sheet material detecting device capable of accurately detecting an edge of a sheet by eliminating chattering with simple machine structure. <P>SOLUTION: An abutment surface is provided to abut on a sheet material detecting lever in order to reset to the original position when resetting the sheet material detecting lever to the original position after a sheet material is passed, and the abutment surface is formed of a surface wherein a component force of reaction force when resetting is generated in the axial direction in relation to the turning direction of the sheet material detecting lever. The sheet material detecting lever is provided freely to move in the axial direction, and while a thrust receiver part is provided to limit the movement of the sheet material detecting lever so that the sheet material detecting lever is pushed to the thrust receiver part by an inclined surface and an energizing member when the sheet material detecting lever is reset. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to a sheet material detection device that detects an end portion of a sheet passing through a sheet conveyance path.

  2. Description of the Related Art Conventionally, for example, in an image forming apparatus, when a sheet material is conveyed to an image forming position, a detection device that detects the sheet material passing timing or the presence or absence of a sheet is provided. While controlling the image forming operation and the like by the detection device, it is possible to easily detect the sheet conveyance state in the conveyance system, for example, conveyance delay or jam.

  FIG. 6 shows an example of a sheet material detection apparatus that is provided in a conventional image forming apparatus and detects the leading edge and the trailing edge of a sheet conveyed through a sheet conveyance path.

This sheet material detection apparatus has a lever-like rotatable sheet detection flag 1 that rotates and retracts when the sheet passes. This sheet detection flag 1 is supported by a fixed part and is urged in the direction of contact with the sheet, and is rotated by passing the sheet to close or open the detection area of the sheet detection sensor 2 to detect the sheet. The sensor 2 is activated to detect the edge of the passing sheet.

However, the conventional sheet material detection apparatus as described above has the following problems.
When the sheet detection flag 1 rotated by the passage of the sheet returns to the standby position, the sheet detection flag 1 may come into contact with the receiving body 3 and bounce off as if jumping.

  That is, when the sheet detection flag 1 jumps from the standby position, the detection area of the sheet detection sensor 2 is crossed several times, and the detection signal from the sheet detection sensor 2 may be in a chattering state.

Such chattering can be electrically processed to prevent malfunction, but for example, it is conceivable to delay detection in consideration of the time when chattering occurs. However, this makes it impossible to accurately detect the trailing edge of the sheet.

In order to solve this problem, as in JP-A-6-94444, a shock absorber is provided on the abutting partner. Further, as disclosed in Japanese Patent Laid-Open No. 2000-335783, there is a method in which a leaf spring is provided integrally with the sheet detection flag so as to weaken the momentum that the sheet detection flag contacts the receiving body.
JP-A-6-94444 JP 2000-335783 A

  However, as in JP-A-6-94444, providing an impact absorber on the abutting partner also causes an increase in cost. In addition, as disclosed in Japanese Patent Laid-Open No. 2000-335783, there is a method in which a leaf spring is provided integrally with the sheet detection flag so as to weaken the momentum that the sheet detection flag contacts the receiving body, but this also increases the cost. .

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an inexpensive sheet material detection apparatus that can eliminate the chattering described above with a simple machine configuration and can accurately detect an end portion of a sheet.

  An image forming apparatus according to the present invention provides a sheet material detection device that detects a movement state of a sheet material by detecting a sheet material detection lever that swings about a rotation axis in accordance with the movement of the sheet material. It has a biasing member that returns the detection lever to the original position after passing the sheet material, and the sheet material detection lever includes a contact surface that comes into contact with the member to return to the original position when returning. The contact surface is an inclined surface, and is formed in a surface in which the component of the repulsive force when returning is axial with respect to the rotation direction of the sheet material detection lever. A thrust receiving portion is provided that is movable in the axial direction and restricts the movement. When the sheet material detecting lever returns, the sheet material detecting lever is pressed against the thrust receiving portion by the inclined surface and the biasing member. .

  According to the present invention, immediately before the sheet material P passes, the sheet detection lever rotates while contacting the stopper at the contact surface immediately before returning the sheet detection lever to the original position, and the thrust component Since it moves in the thrust direction by the force and returns to the original position, the sheet detection lever does not jump and the occurrence of chattering can be suppressed.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

Prior to that, a multi-function printer apparatus as an example of an image forming apparatus provided with a sheet material detection apparatus according to an embodiment of the present invention inside a main body will be described with reference to FIG.

  In the multi-function printer apparatus shown in FIG. 1, a paper feed cassette 10 is disposed on the lower side of the apparatus main body. The sheets P stacked in the sheet feeding cassette 10 are picked up by a half-moon-shaped sheet supply roller 11 and separated one by one by a pair of separation rollers 12, and only the uppermost sheet P is conveyed to a conveyance guide 13, The paper is conveyed to the registration roller pair 16 along the conveyance roller pair 14 and the pre-registration guide 15.

Thereafter, the sheet P is conveyed by the registration roller pair 16 in accordance with the rotation of the photosensitive drum 18 disposed in the process cartridge as the image forming means, and the toner on the photosensitive drum 18 is transferred onto the sheet P by the transfer roller 17. The image is transferred.

Then, the sheet P is guided by the conveyance guide 19 and is heated and pressed by a pair of the fixing roller 20 and the pressure roller 21. At this time, the toner image on the sheet P is fixed on the sheet as a permanent image.

Finally, the sheet P is transported along the transport guide rib 22 and is discharged onto the tray 24 and stacked by the transport roller pair 23.

On the other hand, on the left side of the apparatus main body, a multi-sheet feeding unit 30 that can feed sheets P having a size different from that of the sheet feeding cassette in addition to a recording medium having the same size as the sheet feeding cassette is provided. The multi-feed unit 30 is configured to be usable by opening the multi-tray 31, and the sheets P are stacked on the multi-tray 31 that is opened.

The multi-tray 31 extends toward the front side (the right side in the figure) in the paper feeding direction so as to be gently inclined, but is continuous with the extending direction of the multi-tray 31. A multi-middle plate 32 that can be rotated at a predetermined timing is disposed. A multi paper feed roller 33 formed of a cylindrical member is provided at the front end portion (the right end portion in the figure) of the multi intermediate plate 32. A drive source is connected to the rotating shaft of the multi-feed roller 33 via an electromagnetic clutch (not shown). Rotation control is performed so that the rotational driving force is intermittent at the timing.

  Further, a separation rocking base 34 to which a separation pad made of a thin plate member is adhered so as to be adjacent to the front side in the paper feed direction front edge (the right edge in the figure) of the multi-middle plate 32 described above is provided with the multi-feed plate. The paper roller 33 is disposed so as to come into pressure contact with the outer peripheral surface of the paper roller 33 from below. The separation oscillating base 34 is arranged to move up and down at a position directly below the multi-feed roller 33, and the separation oscillating base 34 is urged upward by a separation pressurizing spring. As a result, the separation oscillating base 34 is always kept in pressure contact with the lower surface side of the multi-feed roller 33 described above.

  When the sheet feeding is started, the above-described multi-middle plate 32 is swung at a predetermined timing by a control means including a cam, a missing gear, and a solenoid (not shown) to urge the middle plate spring. As a result, the multi-feed roller 33 approaches and rises. Therefore, the various sheets P stacked on the multi-tray 31 described above are pressed against the multi-feed roller by the pressurization of the rising intermediate plate 32. Then, by the rotation of the multi-feed roller 33, the sheet P passes through the nip portion between the separation pads and is separated one by one, and then along the conveyance guide 35, the aforementioned feed path 15 In the same way as when the paper is fed from the paper feed cassette 10 described above, it is abutted against the pair of registration rollers 16 and sent to the transfer area while taking an appropriate timing. It has come to go.

On the other hand, in the vicinity of the multi-feed roller 33, a sheet detection sensor unit 36 according to the embodiment of the present invention is provided.

Here, the details of the embodiment of the present invention will be described with reference to FIGS.
FIG. 2 is a perspective view showing an embodiment of the sheet material detection apparatus according to the present invention, and FIG. 3 is a front view showing the embodiment of FIG.
In the sheet material detection apparatus according to the present invention,

In order to be able to rotate, it has a rotating shaft 41a, a surface is perpendicular to the rotating shaft 41a, has a contact rib 41b extending downward, on the opposite side of the contact rib 41b across the rotation shaft 41a The sheet detection lever 41 includes a flag-shaped light shielding plate 41c that is perpendicular to the rotation shaft 41a and extends upward, and the sheet detection sensor 42 that detects that the sheet detection lever 41 is retracted.

Therefore, when there is no sheet material on the multi-tray 31 and in the sheet material conveyance path of the multi-feed unit 30, the contact rib 41b of the sheet detection lever 41 protrudes into the conveyance path ( This state is hereinafter referred to as the original position). In this state, the light shielding plate 41c is positioned in the slit portion of the sheet detection sensor.

On the other hand, when the sheet P is set on the multi-tray 31 of the multi-feed unit 30, or while the sheet material is being conveyed into the multi-feed unit 30, the contact rib 41b of the sheet detection lever 41 is used. Is brought into contact with the sheet to be rotated and retracted (this state is hereinafter referred to as a retracted position). In this state, the light shielding plate 41c is located outside the slit portion of the sheet detection sensor.

As described above, when setting the sheet P on the multi-tray 31 of the multi-sheet feeding unit 30 when starting the sheet feeding, the leading edge of the sheet abuts on the abutting rib 41b of the sheet detection lever 41, The contact rib 41b of the sheet detection lever 41 is rotated and retracted, and the light shielding plate 41c is also separated from the slit portion of the sheet detection sensor. Therefore, a signal from the sheet detection sensor is sent to a control circuit (not shown) to detect that the sheet P is set and to control the image forming process.

Furthermore, in the sheet material detection apparatus according to the present invention,

A stopper 43 that receives the sheet detection lever 41 and holds the contact rib 41b in a protruding state in the sheet conveyance path when the sheet detection lever 41 returns to its original position after the sheet material P has passed; I have. The sheet detection lever 41 is provided with a contact surface 41d so as to contact the stopper 43 when returning to the original position, and the contact surface 41d is inclined with respect to the rotation shaft 41a. The repulsive force P generated when contacting the stopper 43 decomposes the thrust component force P1 in the direction of the rotating shaft 41a. Further, the sheet detection lever 41 is provided so that the rotation shaft 41a is rotatable, and the rotation shaft 41a is provided so as to be movable by a predetermined movement amount S in the axial direction, and is returned to the original position. Immediately before starting (the position shown in FIGS. 2 and 3), the sheet detection lever 41 rotates while contacting the stopper 43 at the contact surface 41d, and the thrust component force P1 causes a predetermined direction in the thrust direction. The movement amount S is moved, and the position returns to the original position where it abuts against the thrust receiving portion 45. (Position shown in FIG. 4)

Furthermore, in the sheet material detection apparatus according to the present invention,
A torsion spring 44 is provided that rotates and biases the sheet detection lever 41 to return to the original position when the sheet detection lever 41 returns to the original position after the sheet P has passed.

The torsion spring 44 is provided at one end of the rotation shaft 41a of the sheet detection lever 41, and urges the sheet detection lever 41 to return to the original position, and the sheet P is moved according to the movement of the sheet P. When the sheet detection lever 41 is rotated to the retracted position, the sheet material detection lever 41 is moved and biased to a predetermined position in a direction opposite to the thrust component force P1 of the repulsive force P generated when returning. (State shown in FIG. 5)

Next, the operation of the sheet material detection device according to the present invention to eliminate the chattering described above will be described.

In the sheet material detection device of the present invention configured as described above,

Immediately before returning the sheet detection lever 41 to the original position after the sheet material P has passed, the sheet detection lever 41 rotates while contacting the stopper 43 at the contact surface 41d, and the thrust component force P1 As a result, the distance S is moved in the thrust direction and returned to the original position in contact with the thrust receiving portion 45, so that the sheet detection lever does not jump and the occurrence of chattering can be suppressed.

  The preferred embodiments of the present invention have been described above, but various modifications and changes other than those mentioned above can be made.

1 is a cross-sectional view of an image forming apparatus including a sheet material detection device according to an embodiment of the present invention inside a main body. It is a perspective view which shows one Embodiment in the sheet material detection apparatus by this invention. FIG. 4 is a front view showing the embodiment of FIG. It is sectional drawing which shows the original position of one Embodiment in the sheet | seat material detection apparatus by this invention. It is a perspective view which shows the retracted position of one Embodiment in the sheet | seat material detection apparatus by this invention. It is a perspective view which shows the conventional sheet | seat material detection apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Conventional sensor flag 2 ... Conventional sensor 3 ... Conventional stopper 30 ... Multi paper feed unit 31 ... Multi tray 32 ... Multi intermediate plate 33 ... Multi paper feed roller 34 ... Multi separation pad base 35 ... Multi sheet detection unit 41 ... sheet detecting lever 42 ... sheet detecting sensor 43 ... stopper 44 ... torsion coil spring 45 ... thrust receiving portion P ... repulsive force S received when the sheet detecting lever returns S ... movement amount of the sheet detecting lever in the thrust direction

Claims (1)

In the sheet material detection device that detects the movement state of the sheet material by detecting the sheet material detection lever that swings around the rotation axis according to the movement of the sheet material,
A biasing member for returning the sheet material detection lever to the original position after passing the sheet material;
The sheet material detection lever includes a contact surface that comes into contact with a member to return to the original position when returning.
The contact surface is an inclined surface, and is formed with a surface such that the component of the repulsive force when returning is axial with respect to the rotational direction of the sheet material detection lever,
The sheet material detection lever is provided so as to be movable in the axial direction, and a thrust receiving portion for restricting the movement is provided. When the sheet material detection lever returns, the sheet material detection lever is moved by the inclined surface and the biasing member. A sheet material detection device which is pressed against a thrust receiving portion.

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