JP2016185880A - Medium conveyance device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce multiple feed where a plurality of media are conveyed while guiding the media to a separation member even when a guide member having a small frictional resistance is used.SOLUTION: A medium conveyance device (1) is provided with a separation member (3) arranged so as to face a conveyance member (2); a holding member (4) for holding the separation member (3); and a guide member (11) which is supported astride the separation member (3) and the holding member (4), is arranged on the upstream side in the conveyance direction of a medium (S) to the separation member (3), guides the medium (S) toward the separation member (3), has a coefficient (μ3) of friction with the medium (S) smaller than a coefficient (μ2) of friction of the medium (S) and the separation member (3), where both ends (11a) in the width direction of the medium (S) extends to the downstream side of the conveyance direction of the medium (S) than the central portion (11b) in the width direction.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a medium conveying apparatus and an image forming apparatus.

  In a conventional image forming apparatus, a technique described in Patent Document 1 below is known regarding a medium conveying apparatus that conveys a medium.

  Japanese Patent Laid-Open No. 2002-326732 as Patent Document 1 discloses a first friction member (1) pressed against a paper feed roller (12) in a configuration for preventing multiple feeding of a plurality of media. However, a configuration is described in which the paper feed roller (12) has a width dimension (B) larger than the width dimension (A) in the paper width direction and is made of urethane rubber that is highly frictional with respect to the paper. Further, in the configuration described in Patent Document 1, a second friction member (1) is disposed between the first friction members (1) with respect to the plurality of first friction members (1) arranged at intervals in the paper width direction. The friction member (2) is disposed, and the second friction member (2) is made of high-friction urethane rubber, and is curved convexly toward the paper feed roller (12). Further, the guide shape (8) of the first holding member (14) is arranged on the upstream side in the paper feeding direction (X4) with respect to each friction member (1, 2), and is further made of sheet metal on the further upstream side. The paper guide plate (10) is arranged.

JP 2002-326732 A (“0048” to “0059”, FIG. 1, FIG. 6, FIG. 7)

  It is a technical object of the present invention to reduce double feeding in which a plurality of media are conveyed while guiding the media to the separation member even when a guide member having low frictional resistance is used.

In order to solve the technical problem, a medium conveying device according to claim 1 is provided.
A transport member for transporting the medium;
A separating member disposed to face the conveying member;
A holding member for holding the separating member;
A guide member that is supported across the separation member and the holding member, and is disposed upstream of the separation member in the medium conveyance direction, and guides the medium toward the separation member. The guide member that has a smaller coefficient of friction with the medium than the coefficient of friction with the separation member, and that both ends of the medium in the width direction extend further downstream in the medium conveying direction than the center in the width direction;
It is provided with.

The invention according to claim 2 is the medium conveying apparatus according to claim 1,
The both end portions extending downstream in the medium conveyance direction are arranged outside the both ends in the medium width direction of the conveyance member.

In order to solve the technical problem, an image forming apparatus according to claim 3 is provided.
An image reading apparatus comprising the medium conveying apparatus according to claim 1 for conveying an original as the medium, and reading an image of the original;
An image recording apparatus for recording an image read by the image reading apparatus on a medium;
It is provided with.

In order to solve the technical problem, an image forming apparatus according to a fourth aspect of the present invention provides:
An image recording apparatus comprising the medium conveying apparatus according to claim 1 or 2, which conveys a medium, and records an image on the medium conveyed by the medium conveying apparatus,
It is provided with.

According to the first, third, and fourth aspects of the present invention, when both ends of the medium in the width direction of the guide member having a small frictional resistance do not extend downstream in the conveyance direction of the medium from the center in the width direction. In comparison, it is possible to reduce the multi-feed in which a plurality of media are conveyed while guiding the media to the separation member.
According to the second aspect of the present invention, it is possible to reduce double feeding as compared with the case where both end portions are disposed inside both ends in the medium width direction of the conveying member.

FIG. 1 is an explanatory diagram of an image forming apparatus according to a first embodiment of the present invention. FIG. 2 is an explanatory diagram of a main part of the medium carrying device according to the first embodiment. 3 is a cross-sectional view taken along line III-III in FIG. FIG. 4 is an explanatory diagram illustrating the positional relationship between the conveying member, the separating member, and the guide member in the medium width direction according to the first exemplary embodiment. FIG. 5 is an operation explanatory view of the first embodiment, FIG. 5A is an explanatory view when the guide member does not reach the upper end of the inclined surface, and FIG. 5B is a case when the guide member reaches the upper end of the inclined surface. FIG. 5C is an explanatory diagram of the first embodiment.

Next, specific examples of embodiments of the present invention (hereinafter referred to as examples) 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 front, rear, right, left, upper, lower, or front, rear, right, left, upper, and lower, 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.
In the following description using the drawings, illustrations other than members necessary for the description are omitted as appropriate for easy understanding.

FIG. 1 is an explanatory diagram of an image forming apparatus according to a first embodiment of the present invention.
In FIG. 1, a copier U as an example of an image forming apparatus according to the first exemplary embodiment is an example of a recording unit, and includes a printer unit U1 as an example of an image recording apparatus. A scanner unit U2 as an example of a reading unit and an example of an image reading device is supported on the upper portion of the printer unit U1. An auto feeder U3 as an example of a medium transport device is supported on the upper portion of the scanner unit U2. The scanner unit U2 of the first embodiment supports a user interface U0 as an example of an input unit. The user interface U0 can be operated by the operator by inputting the user interface U0.

  A document tray TG1 as an example of a medium container is disposed on the upper part of the auto feeder U3. A plurality of documents Gi to be copied can be stacked and stored in the document tray TG1. A document discharge tray TG2 as an example of a document discharge unit is formed below the document tray TG1. A document transport roll U3b is disposed between the document tray TG1 and the document discharge tray TG2 along the document transport path U3a.

A platen glass PG as an example of a transparent document table is disposed on the upper surface of the scanner unit U2. In the scanner unit U2 of the first embodiment, a reading optical system A is disposed below the platen glass PG. The optical system A for reading in Example 1 is supported so as to be movable in the left-right direction along the lower surface of the platen glass PG. The reading optical system A is normally stopped at the initial position shown in FIG.
On the right side of the optical system A for reading, an imaging element CCD as an example of an imaging member is arranged. An image processing unit GS is electrically connected to the image sensor CCD.
The image processing unit GS is electrically connected to the writing circuit DL of the printer unit U1. The writing circuit DL is electrically connected to an exposure apparatus ROS as an example of a latent image forming apparatus.

In the printer unit U1, a photosensitive drum PR as an example of an image holding member is disposed. Around the photosensitive drum PR, a charging roll CR as an example of a charging member, a developing device G, a transfer unit TU as an example of a transfer device, and a drum cleaner CLp as an example of a cleaner are arranged.
On the right side of the developing device G, a cartridge K as an example of a developer container is disposed. The cartridge holder KS that supports the cartridge K and the developing device G are connected by a developer transport device GH having a reserve tank RT.

Below the transfer unit TU, paper feed trays TR1 to TR4 as examples of medium storage containers are arranged. A conveyance path SH1 extends from each of the paper feed trays TR1 to TR4. In the transport path SH1, a pick-up roll Rp as an example of a medium take-out member, a scoop roll Rs as an example of a scooping member, a transport roll Ra as an example of a transport member, and a registration roll Rr as an example of a delivery member are arranged. Yes.
A fixing device F having a heating roll Fh and a pressure roll Fp is disposed on the left side of the transfer unit TU. The fixing device F and the paper discharge tray TRh are connected by a discharge path SH2. The discharge path SH2 and the registration roll Rr are connected by an inversion path SH3. In the discharge path SH2, a transport roll Rb and a discharge roll Rh that can rotate in the forward and reverse directions are arranged.

(Description of image forming operation)
The plurality of documents Gi stored in the document tray TG1 sequentially passes through the document reading position on the platen glass PG and is discharged to the document discharge tray TG2.
When the automatic feeder U3 is used to automatically convey and copy a document, each document that sequentially passes through the reading position on the platen glass PG with the reading optical system A stopped at the initial position. Gi is exposed.
When the operator places the document Gi on the platen glass PG by hand, the optical system A for reading moves in the left-right direction, and the document on the platen glass PG is scanned while being exposed.
The reflected light from the original document Gi passes through the optical system A for reading and is condensed on the image sensor CCD. The image pickup device CCD converts the reflected light of the original collected on the image pickup surface into an electric signal.

The image processing unit GS converts the read signal input from the image sensor CCD into a digital image signal and outputs the digital image signal to the writing circuit DL of the printer unit U1. The writing circuit DL outputs a control signal corresponding to the input image writing signal to the exposure apparatus ROS.
The exposure apparatus ROS outputs a laser beam L and forms a latent image on the surface of the photosensitive drum PR charged by the charging roll CR. The latent image on the surface of the photosensitive drum PR is developed into a visible image by the developing device G. The transfer roll TR of the transfer unit TU transfers the visible image on the surface of the photosensitive drum PR to a recording sheet S as an example of a medium that has been transported through the transport path SH1. The visible image transferred to the recording sheet S is fixed by the fixing device F. The recording sheet S that has passed through the fixing device F is conveyed to the reverse path SH3 when duplex printing is performed, and is discharged by the discharge roll Rh when discharged to the discharge tray TRh.

(Description of paper feeder)
FIG. 2 is an explanatory diagram of a main part of the medium carrying device according to the first embodiment.
3 is a cross-sectional view taken along line III-III in FIG.
FIG. 4 is an explanatory diagram illustrating the positional relationship between the conveying member, the separating member, and the guide member in the medium width direction according to the first exemplary embodiment.
1 and 2, a sheet feeding device 1 as an example of a medium transport device according to the first embodiment includes the pickup roll Rp and the separating roll Rs. 2 and 3, the separating roll Rs has a driving roll 2 as an example of a conveying member. Drive is transmitted to the drive roll 2 from a drive motor (not shown) as an example of a drive source.

Below the drive roll 2, a separation pad 3 as an example of a separation member is disposed. The separation pad 3 has a separation surface 3 a that contacts the drive roll 2. On the upstream side in the conveyance direction of the recording sheet S with respect to the separation surface 3a, an inclined surface 3b that is inclined downward is formed.
In FIG. 4, the separation pad 3 according to the first embodiment is formed such that the length L <b> 2 in the width direction is longer than the length L <b> 1 in the width direction of the drive roll 2.
In Example 1, the separation pad 3 is made of urethane rubber as an example of a high friction material. The high friction material is not limited to urethane rubber, and a high friction material that can be used as a separation pad such as silicon rubber can be used.

The lower surface of the separation pad 3 is supported by a holder 4 as an example of a holding member. The holder 4 has a concave holding portion 4 a that supports the separation pad 3, and a second inclined surface 4 b that extends upward on the upstream side in the conveyance direction of the recording sheet S with respect to the inclined surface 3 b. The holder 4 is rotatably supported by a bearing portion 7 extending from the main body of the printer unit U1 around the rotation shaft 6 at the lower right.
In FIG. 3, the holder 4 is biased in a direction in which the separation pad 3 is pressed against the drive roll 2 by a spring 8 as an example of a biasing member.

2 and 3, a guide plate 11 as an example of a guide member is supported on the inclined surface 3b and the second inclined surface 4b. The guide plate 11 according to the first embodiment is supported so as to straddle the inclined surface 3b and the second inclined surface 4b. The guide plate 11 according to the first embodiment is made of sheet metal (stainless steel) as an example of a material having a lower friction than the separation pad 3.
2 and 4, the length L3 in the width direction of the guide plate 11 according to the first embodiment is configured in substantially the same manner as the width L2 of the separation pad 3. Therefore, the width L3 is formed longer than the length L1 of the drive roll 2 in the width direction. Further, in the guide plate 11 of the first embodiment, the upper end portion, which is the downstream end in the conveyance direction of the recording sheet S, has both end portions 11a outside the width L1 extending downstream from the central portion 11b. Therefore, in the first exemplary embodiment, as illustrated in FIG. 2, the inclined surface 3 b is exposed on the downstream side of the central portion 11 b with respect to the conveyance direction of the sheet S.

(Operation of Example 1)
FIG. 5 is an operation explanatory view of the first embodiment, FIG. 5A is an explanatory view when the guide member does not reach the upper end of the inclined surface, and FIG. 5B is a case when the guide member reaches the upper end of the inclined surface. FIG. 5C is an explanatory diagram of the first embodiment.
In the copying machine U of the first embodiment having the above-described configuration, when a plurality of recording sheets S are sent out from the pickup roll Rp, the recording sheets S are guided by the guide plate 11 and are driven by the driving roll 2 of the separating roll Rs. And the separation pad 3. In FIG. 5C, when two recording sheets S <b> 1 and S <b> 2 are conveyed, the upper sheet S <b> 1 in contact with the driving roll 2 is conveyed downstream as the driving roll 2 rotates. The lower sheet S2 in contact with the separation pad 3 is stopped by the frictional force received from the separation pad 3 and separated from the upper sheet S1 conveyed downstream.

  In FIG. 5A, let us consider a case where both end portions 11 a are not provided on the guide plate 11 in the guide plate 11 upstream of the drive roll 2. Consider a configuration in which the downstream end (upper end) of the guide plate 01 does not reach the upper end of the inclined surface 02, for example, a configuration in which the guide plate 01 exists only up to the position of the central portion 11b in the first embodiment. In this case, the sheet 03 guided by the guide plate 01 comes into contact with the inclined surface 02 of the separation pad 06 before reaching the drive roll 04. Therefore, before reaching the drive roll 04, there is a possibility that the front end of the sheet 03 is caught in the separation pad 06 having a high frictional resistance. Therefore, the guide plate 01 cannot guide the sheet 03 to the drive roll 04, and there is a possibility that a conveyance failure of the sheet 03, a so-called pickup failure may occur.

On the other hand, as shown in FIG. 5B, a configuration is conceivable in which the downstream end of the guide plate 01 ′ in which the both end portions 11 a of Example 1 are not provided reaches the upper end of the inclined surface 02. In this configuration, let us consider the force acting on the lower sheet 03B when the two recording sheets 03A and 03B are conveyed.
In the region sandwiched between the drive roll 04 and the separation pad 06, the force pushed by the spring is N1, the friction coefficient between the sheets 03A and 03B is μ1, and the friction coefficient between the sheet 03 and the separation pad 06 is μ2. To do. In addition, the thickness of the recording sheet 03B and the tension acting on the recording sheet 03B at a place other than the region sandwiched between the drive roll 04 and the separation pad 06, particularly at the corner position that is the boundary between the separation surface 07 and the inclined surface 02. When a force in the direction of compressing the spring is applied due to the rigidity of the recording sheet 03B, that is, so-called stiffness, a force corresponding to the vertical drag acts as a reaction. This force is N2, and the friction coefficient between the guide plate 01 ′ and the sheet 03 is μ3.

At this time, in the region sandwiched between the drive roll 04 and the separation pad 06, F1 = N1 × μ1 acts on the lower sheet 03B as the force F1 sent downstream by being dragged by the upper sheet 03A. To do. On the other hand, F2 = N1 × μ2 acts as the transport resistance F2 from the separation pad 06 on the lower sheet 03B.
Further, at the position of the upper end of the guide plate 01 ′, F3 = N2 × μ1 acts as the force F3 sent downstream, and F4 = N2 × μ3 acts as the frictional resistance F4.
Therefore, the force that the lower sheet 03B receives in the transport direction is expressed by the following equation (1).
(F1-F2) + (F3-F4)
= (N1 * [mu] 1-N1 * [mu] 2) + (N2 * [mu] 1-N2 * [mu] 3) (1)

Here, the separation pad 06 is made of a highly frictional material and is set to satisfy μ1 <μ2. Therefore, F1-F2 <0 is established, and the lower sheet 03B is not sent downstream. On the other hand, the guide plate 01 ′ is made of a low-friction material for smoothly guiding the sheet 03, and generally satisfies μ1> μ3. Therefore, F3-F4> 0, and the downstream conveying force acts on the lower sheet 03B. Therefore, there is a possibility that the recording sheet S is fed by this conveying force (F3-F4) and double feeding occurs.
Therefore, in the configuration shown in FIG. 5B, the guide member 01 ′ functions as a guide for the sheet S, but there is a possibility that double feeding may occur.

  In the configuration described in Patent Document 1, the guide shape on the upstream side of the friction member corresponds to the second inclined surface 4b of the first embodiment, and the friction coefficient of the guide shape is larger than that of the guide plate 11. As in FIG. 5A, there is a problem that the guide performance is low. When the friction coefficient of the guide shape is smaller than that of the guide plate, there is a risk of double feeding as in FIG. 5B.

On the other hand, in the configuration of Example 1, both end portions 11a of the guide plate 11 reach the upper end of the inclined surface 3b, and the central portion 11b is formed only to the upstream side of the both end portions 11a. The central portion of the surface 3b in the width direction is exposed.
Therefore, when the front end portion in the conveyance direction of the recording sheet S is sent out, the recording sheet S is guided to the upper end of the inclined surface 3b at both end portions 11a and sent to the drive roll 2. At this time, the exposed portion of the inclined surface 3b is in a position that is recessed by the thickness of the guide plate 11 with respect to both end portions 11a, and at the stage where the front end portion of the recording sheet S is conveyed, the recording sheet S is inclined surface 3b. It is hard to touch. Therefore, compared with the configuration shown in FIG. 5A, the performance of the guide plate 11 guiding the recording sheet S is improved.

  Further, as shown in FIG. 5C, when the recording sheet S is sandwiched between the drive roll 2 and the separation pad 3 when the two recording sheets S1 and S2 are sent out, the boundary between the inclined surface 3b and the separation surface 3a. The force N2 is likely to act on the position of the corner. At this time, the recording sheet S is easily brought into contact with the exposed portion of the inclined surface 3b by being pressed by the force N2. Therefore, in Example 1, not only the both ends 11b of the low friction guide plate 11 but also the inclined surface 3b of the high friction separation pad 3 is contacted. Therefore, in the configuration of the first embodiment, the resistance F4 ′ is larger than the resistance F4 in FIG. 5B. Therefore, as compared with the configuration shown in FIG. 5B, the force F3-F4 ′ for conveying the recording sheet S to the downstream side is reduced, and double feeding is less likely to occur.

  In particular, in the first embodiment, both end portions 11 a are disposed outside the width L <b> 1 of the drive roll 2. In a state where the sheet S is sandwiched between the drive roll 2 and the separation pad 3, the force sandwiched by the drive roll 2 that is in direct contact with the recording sheet S easily acts on the upstream side inside the width L 1 of the drive roll 2. On the other hand, outside the width L1, the recording sheet S is not in direct contact with the drive roll 2, and the recording sheet S can escape, to speak. Therefore, for the force N2 acting at the position of the upper end of the inclined surface 3b, the force acting at the position inside the width L1 tends to be larger than the force acting at the position outside the width L1. Therefore, when the low friction end portions 11a are provided inside the width L1, the entire frictional resistance F4 ′ is larger than when the exposed portion of the high friction separation pad 3 is provided inside the width L1. As a result, the conveyance force (F3-F4) tends to increase. Therefore, in Example 1, the both ends 11a are arrange | positioned on the outer side of the width | variety L1, and it is reduced that conveyance force (F3-F4) becomes large.

(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 made in the range of the summary of this invention described in the claim. Is possible. Modification examples (H01) to (H06) of the present invention are exemplified below.
(H01) In each of the above-described embodiments, the copying machine U as an example of the image forming apparatus is illustrated. However, the present invention is not limited to this, and can be applied to a printer, a FAX, or a multifunction machine having a plurality of functions. . Further, the image forming apparatus is not limited to a single-color developing image forming apparatus, and can be configured by a multi-color, so-called color image forming apparatus.
(H02) In the above-described embodiment, the paper feeding device 1 provided in the paper feeding trays TR1 to TR4 is exemplified as the medium transport device, but is not limited thereto. For example, the paper feeding device 1 can be applied to the auto feeder U3, or can be applied to a paper feeding unit of a manual feed tray.

(H03) In the above-described embodiment, the configuration including the pickup roll Rp and the separating roll Rs is exemplified as the paper feeding device 1, but the present invention is not limited to this. For example, it is also possible to apply to a configuration in which a pick-up roll and a roll are used as a single roll.
(H04) In the above-described embodiment, the both end portions 11a are preferably arranged outside the width L1, but can also be arranged inside.
(H05) In the above embodiment, the constituent materials of the separation pad 3 and the guide plate 11 are not limited to those illustrated. For example, a commercially available high-friction rubber material can be used for the separation pad 3, and the guide plate 11 is not limited to a sheet metal, and a resin material with good slipperiness such as another metal or polyacetal can also be used. It is. At this time, the friction coefficient of the guide plate 11 with respect to the medium needs to be smaller than the friction coefficient of the separation pad 3.

(H06) In the above-described embodiment, the guide plate 11 is provided on the inclined surface 3b. However, the present invention is not limited to this. For example, the both ends 11a of the guide plate 11 according to the embodiment are in a position where the force N2 is applied depending on the posture (curved state or the like) during conveyance of the recording sheet S due to the positional relationship between the pickup roll Rp and the separation roll Rs. It is possible to apply the configuration.

1, U3 ... medium conveying device,
2 ... conveying member,
3 ... separation member,
4 ... holding member,
11 ... guide member,
11a ... both ends,
11b ... central part,
Gi ... manuscript,
S ... medium
U: Image forming apparatus,
U1 ... Image recording device U2 ... Image reading device,
μ2: Coefficient of friction between the medium and the separating member,
μ3: Coefficient of friction between the medium and the guide member.

Claims (4)

A transport member for transporting the medium;
A separating member disposed to face the conveying member;
A holding member for holding the separating member;
A guide member that is supported across the separation member and the holding member, and is disposed upstream of the separation member in the medium conveyance direction, and guides the medium toward the separation member. The guide member that has a smaller coefficient of friction with the medium than the coefficient of friction with the separation member, and that both ends of the medium in the width direction extend further downstream in the medium conveying direction than the center in the width direction;
A medium carrying device comprising: The medium conveying apparatus according to claim 1, wherein the both end portions extending downstream in the medium conveying direction are disposed outside both ends of the conveying member in the medium width direction. An image reading apparatus comprising the medium conveying apparatus according to claim 1 for conveying an original as the medium, and reading an image of the original;
An image recording apparatus for recording an image read by the image reading apparatus on a medium;
An image forming apparatus comprising: An image recording apparatus comprising the medium conveying apparatus according to claim 1 or 2, which conveys a medium, and records an image on the medium conveyed by the medium conveying apparatus,
An image forming apparatus comprising:

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