JP5164661B2 - Sheet conveying apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to a sheet conveying apparatus provided in an image forming apparatus such as a transfer type or direct type printer such as an electrophotographic system or an ink jet system, a facsimile machine, or a copying machine.

  Conventionally, in a feeding section of this type of sheet conveying apparatus, a feeding roller which is an upstream conveying means and a separation pad are pressed against each other, and the angle of the separation pad with respect to the sheet is constant, or a sheet collision input or sheet It is held so as to be able to swing according to the number of sheets. The sheet is a sheet of paper such as transfer paper, photosensitive paper, thermal paper, electrostatic sheet, printing paper, document, card, envelope, postcard, and the material is not limited to paper quality.

  When the first sheet enters during sheet feeding, the sheet is fed by the difference between the frictional force between the feeding roller and the sheet and the frictional force between the separation pad and the sheet. When two or more sheets enter at the same time, the uppermost sheet is separated and fed by the difference between the frictional force between the feeding roller and the sheet and the frictional force between the sheets.

  In the sheet feeding unit shown in FIGS. 13 to 15, the plurality of sheets 108 stacked on the feeding tray 105 are fed by the feeding roller 102. Since the frictional force between the separation pad 103 and the sheet 108 is set higher than the frictional force between the sheets 108, only the uppermost sheet 108 is conveyed downstream in the conveying direction by the feeding roller 102.

  The uppermost sheet 108 is fed by the feeding roller 102 and then conveyed downstream in the conveying direction, the leading end of the sheet 108 is guided by the guide 106 (see FIG. 14), and further conveyed downstream in the conveying direction. Is done.

  A bent guide 106 that guides the lower surface of the sheet 108, a bent 107 that guides the upper surface of the sheet 108, and a drawing roller pair 101 that is a downstream conveying means are disposed on the downstream side in the conveying direction. Then, after the leading end of the sheet 108 reaches the pulling roller pair 101, the trailing end of the sheet 108 is pulled out from the nip portion between the separation pad 103 and the feeding roller 102 (see FIG. 15). At this time, the sheet 108 is pulled out with the entire sheet bent as shown in FIG.

  At this time, since the number of sheets 108 is large and multiple feeds are likely to occur, the tilt angle of the separation pad 103 is held swingably according to the number of sheets 108 to prevent double feed. (See Patent Document 1).

  In addition, there is one that prevents the occurrence of double feeding in the case where the inclination angle of the separation pad 103 is changed by the collision input at the leading end of the sheet and the frictional force between the sheets is large (see Patent Document 2).

JP 09-150979 A Japanese Unexamined Patent Publication No. 01-321229

  In the conventional sheet conveying apparatus, after the sheet 108 is separated and fed by the feeding roller 102 and the separation pad 103 which are upstream conveying means, a sound is generated when the leading edge of the sheet comes into contact with the bent guide 106.

  Further, when the sheet 108 is pulled out from the separation pad 103 by the pulling roller pair 101 which is the downstream side conveying means, the separation pad 103 and the sheet 108 are rubbed to generate a sound.

  Generally, in order to reduce the size of the apparatus, the fed sheet 108 is often bent and conveyed. For this reason, the contact angle between the sheet leading end and the bent guide 106 becomes larger as the device is downsized.

  Therefore, the contact angle when the sheet 108 contacts the bent guide 106 is larger than the inclination angle of the separation pad 103. Further, since the drawing roller pair 101 is provided on the curved downstream portion side, the sheet shape when the sheet 108 is pulled out is a greatly curved shape.

  Also, as in Patent Documents 1 and 2, even when the inclination angle of the separation pad 103 is variable, after the sheet 108 is separated and fed by the separation pad 103, the contact angle with the bent guide 106 is Become bigger. Further, when the sheet 108 is pulled out by the pair of pulling rollers 101, the sheet 108 is pulled out in a more bent state.

  When the contact angle between the bent guide 106 and the sheet tip increases, the speed component in the guide normal direction of the sheet 108 increases, so the contact force increases when the sheet tip contacts the guide 106, The generated sound is also louder.

  Further, since the pressing force of the sheet leading edge against the guide 106 increases, the sound generated when the sheet leading edge rubs against the guide 106 also increases.

  On the other hand, when an excitation force due to friction or the like acts on the sheet 108 in a largely bent shape, vibration in the normal (out-of-plane) direction of the sheet 108 occurs due to a tangential excitation force component with respect to the sheet 108. It becomes easy. Therefore, the sound due to the friction between the separation pad 103 and the sheet 108 tends to increase.

  In general, in order to accurately separate and convey the sheet 108, the rotation speed of the feeding roller 102 is driven at a lower speed than the rotation speed of the pulling roller pair 101.

  Therefore, when the trailing edge of the sheet is pulled out from the separation pad 103 by the pulling roller pair 101, the separation pad 103 and the sheet 108 are rubbed due to the speed difference between the sheet 108 and the feeding roller 102. A large excitation force due to friction has been generated in the feeding unit having the separation pad 103. As a result, a loud noise was generated when the trailing edge of the sheet was pulled out from the separation pad 103.

  As described above, in any of the conventional techniques, the contact noise generated when the bent guide 106 and the sheet tip contact each other and the friction sound generated when the sheet tip and the bent guide 106 rub are increased. I have.

  Further, when the sheet 108 is pulled out by the pulling roller pair 101, the sheet 108 is pulled out in a greatly curved state, so that the noise due to the friction between the separation pad 103 and the sheet 108 increases, and the sound at the feeding unit increases. It was. These sounds were noise.

  The technical problem of the present invention has been made in view of the circumstances as described above, and an object of the invention is to provide a sheet conveying apparatus capable of reducing the sound generated from the sheet without impairing the sheet conveying property, and An image forming apparatus is provided.

In order to achieve the above object, a sheet conveying apparatus of the present invention is arranged on an upstream side conveying means for nipping and conveying a sheet, and on the downstream side in the sheet conveying direction in the upstream side conveying means, and the upstream conveying means A downstream conveying means for nipping and conveying the conveyed sheet on the downstream side in the conveying direction; a bent conveying guide member arranged between the upstream conveying means and the downstream conveying means for guiding the sheet; In order to change the tangent angle formed by the nip tangent of the nip portion of the upstream conveying means and the nip tangent of the nip portion of the downstream conveying means, the nip tangent of the upstream conveying means The angle changing means can change the acute angle of the tangential angle, and the leading edge of the sheet passes through the nip portion of the upstream conveying means. The tip of the conveying guide member to the sheet is changed so as to decrease until contact later, to maintain the nip of the upstream conveying means to a small state the tangent angle to the rear end of the sheet passes It is characterized by that.

  According to the present invention, it is possible to reduce the impact sound of the sheet against the bent conveyance guide member and the sound generated when the sheet is pulled out from the upstream conveyance unit without impairing the conveyance of the sheet.

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

Embodiment 1

  FIG. 1 is a schematic diagram of a sheet conveying apparatus according to the first embodiment of the present invention, and FIGS. 2 and 3 are schematic diagrams when the separation pad holder of the sheet conveying apparatus of FIG. 1 is rotated. FIG. 16 is a sectional view showing an example of an image forming apparatus to which the present invention is applied.

  First, a laser beam printer (hereinafter simply referred to as “printer”) as an example of an image forming apparatus will be described with reference to FIG.

  In the printer 200, the sheet S before image formation is stacked on the intermediate plate 203 urged toward the supply roller 10 by the intermediate plate spring 201 and the supply tray 209. The middle leaf spring 201 is provided on the feeding tray 30.

  A rotating shaft 204 rotatably supported by the apparatus main body 222 of the printer 200 is rotated by a driving source (not shown), and the feeding roller 10 fixed to the rotating shaft 204 is also rotated. As a result, the sheet S pressed by the intermediate leaf spring 201 and pressed by the feeding roller 10 is sent out.

  The drawing roller pair 20 feeds the sheet S between the photosensitive drum 207 as an image forming unit and the transfer roller 214. A toner image is formed in advance on the photosensitive drum 207 by a laser scanner 208, a developing roller 220, and the like.

  The transfer roller 214 transfers the toner image from the photosensitive drum 207 to the sheet S. Thereafter, the fixing device 221 heats and presses the sheet S to fix the toner image on the sheet S. Then, the sheet S is discharged to the discharge tray 211 by the discharge roller 216.

  The sheet conveying apparatus 1 shown in FIGS. 1 to 3 is configured to hold a feeding roller 10, a feeding tray 30 that accommodates a plurality of sheets S, a separation pad 40 that constitutes upstream-side conveying means, a separation pad holder 50, and a separation pad 40. The cam 60 is an angle changing means for changing the angle.

  Further, it is constituted by a bent guide member 71 for guiding the lower surface of the sheet S and a bent guide member 72 for guiding the upper surface of the sheet S. The guide member 71 is formed in a curved shape having two straight portions or U-shaped portions.

  The sheet S is nipped and fed between the feeding roller 10 and the separation pad 40, and is then conveyed downstream in the conveying direction by the drawing roller pair 20 serving as a downstream conveying unit. In other words, the plurality of sheets S stacked on the feeding tray 30 are fed by the feeding roller 10 until the leading end contacts the separation pad 40.

  At this time, the separation pad 40 is made of a material having a friction coefficient larger than the friction coefficient between the sheets S. For this reason, when a plurality of sheets S are fed to the separation pad portion, the sheet S below the uppermost position is stopped by the separation pad 40, and only the uppermost sheet S is fed by the feeding roller 10. The

  After feeding by the feeding roller 10 and the separation pad 40, the leading end of the sheet arrives at the drawing roller pair 20, and is pulled out from the nip portion between the separation pad 40 and the feeding roller 10 by the drawing roller pair 20. At this time, in order to increase the sheet conveying speed after feeding, the sheet conveying speed of the drawing roller pair 20 is set to be higher than the sheet conveying speed of the feeding roller 10.

  The configuration of the holding unit for holding the separation pad 40 will be described. The separation pad holder 50 that holds the separation pad 40 is attached to the swing member 80 via a spring 51, and the swing member 80 is rotatably held on the same axis as the rotation shaft of the feeding roller 10.

  The swing member 80 is in contact with the cam 60 via the connecting pin 82. The cam 60 can be connected and rotated by a power transmission mechanism (not shown), and the swinging member 80 can follow the movement of the cam 60 and rotate around the rotation axis of the feeding roller 10.

  FIG. 4 is a schematic view of the swinging member 80, the feeding roller 10, the separation pad holder 50, and the cam 60, which constitute the angle changing means, constituting the holding unit, as viewed from the sheet conveying direction.

  In FIG. 4, the swing member 80 is connected to the rotating shaft 81 of the feed roller 10 via a bearing (not shown). The connecting pin 82 fixed to the swing member 80 and the cam 60 are in contact with each other, and the swing member 80 can rotate around the rotation shaft 81 of the feeding roller 10 following the movement of the cam 60.

  The feeding roller 10 can be rotated by a driving force from a driving source (not shown) via a gear 11. Further, the cam 60 can also be rotated by a driving force from a driving source (not shown) via the gear 62. It is also possible to use the driving force of the cam 60 from the driving force of the feeding roller 10 via a gear or the like. Instead of the cam 60, a mechanism using a solenoid or the like can be used.

  The cam 60 is held in the position shown in FIG. 1 until the sheet S is conveyed by a certain amount by the separation pad 40 and the feeding roller 10, that is, until the leading end of the sheet passes through the nip portion between the separation pad 40 and the feeding roller 10. Yes. After the leading edge of the sheet passes through the nip portion between the separation pad 40 and the feeding roller 10 by the feeding roller 10 and before the leading edge of the sheet comes into contact with the guide member 71, the cam 60 receives a driving force (not shown) and rotates. Move to the position.

  Here, it is desirable that the angle when the leading edge of the sheet S abuts on the guide member 71 is small, and it is necessary to set the angle when abutting in consideration of the conveyance speed, the paper type, and the like.

  For this reason, the tangent angle formed between the nip tangent of the drawing roller pair 20 and the nip tangent of the feed roller 10 and the separation pad 40 is made smaller when changing from the state of FIG. 1 to the state of FIG. 2 (θ> θ ') The optimum angle when the leading end of the sheet comes into contact with the guide member 71 is set by the tangent angle θ' after the change. The nip tangent of the drawing roller pair 20 is a tangent of each roller passing through the nip portion of the drawing roller pair, and the nip tangent of the feeding roller 10 and separation pad 40 is the nip tangent of the feeding roller 10 and separation pad 40. This is a tangent line of the feeding roller 10 passing through the nip portion.

  The tangent angle is an angle on the acute angle side at the intersection of each nip tangent. Since the rotation center of the separation pad holder 50 is the same as the rotation center of the feeding roller 10, even if the separation pad holder 50 rotates from the position of FIG. 1 to the position of FIG. It does not change.

  As described above, since the tangential angle is small before the leading edge of the sheet S comes into contact with the guide member 71, the speed in the normal direction of the sheet S with respect to the guide member 71 is small. Therefore, the contact force between the guide member 71 and the leading edge of the sheet S is reduced, and the contact sound between the guide member 71 and the sheet S is reduced. Further, since the contact force of the sheet S to the guide member 71 is suppressed, it is possible to reduce the frictional noise between the guide member 71 and the sheet leading end.

  Thereafter, the sheet S is conveyed by the feeding roller 10 and pulled out by the pulling roller pair 20. At this time, the sheet S is pulled closer to the straight line state and pulled out by the pulling roller pair 20, so that the sound at that time is reduced.

  As shown in FIG. 3, since the sheet S is pulled out, the excitation force component in the tangential direction of the sheet S is reduced, and vibration in the normal direction (out-of-plane direction) of the sheet S is less likely to occur. Therefore, the sound emitted from the sheet S to the outside of the paper surface is reduced, and the sound due to friction with the separation pad 40 can be reduced.

  Until the trailing edge of the sheet passes through the nip portion between the separation pad 40 and the feeding roller 10, the tangential angle is maintained at a small angle, and when the trailing edge of the sheet passes through the nip portion, it jumps with the rigidity of the sheet. Thus, the contact force when contacting the guide member 71 is kept small, and the generation of sound is also suppressed.

  After the trailing edge of the sheet is pulled out from the nip portion between the separation pad 40 and the feeding roller 10, the cam 60 rotates and returns to the tangential angle state shown in FIG. Do.

  FIG. 5 is a result of simulating the impact sound of the guide member 71 and the sheet tip with respect to the tangential angle. FIG. 5 shows a calculation result when a sheet having a basis weight of 209 g / m 2 and a thickness of 0.2 mm is brought into contact with the guide member 71 at a conveyance speed of 500 mm / s. As shown in FIG. 5, it can be seen that the larger the tangent angle, the greater the generated contact sound.

  FIG. 6 shows the result of simulating the sound generated when the separation pad 40 and the sheet trailing edge are rubbed in the present embodiment. The horizontal axis is the tangent angle, and the vertical axis is the sound volume when the tangent angle is 5 degrees.

  The result of FIG. 6 is a result of noise simulation (overall value of frequency response) when an excitation force is applied to one end of the paper model having a shape corresponding to the tangent angle. As shown in FIG. 6, it can be seen that the larger the tangent angle, the larger the generated sound. The tangent angle in FIGS. 5 and 6 has the same meaning as θ or θ ′.

  Further, FIG. 7 shows that a member (friction member) having a certain surface roughness is pressed against one end of the curved sheet S with a certain load, and the deformation of the sheet S is gradually loosened by conveying the sheet S with a roller. It is the experimental result of the noise generated when it goes. In addition, it is the experimental result which conveyed the sheet | seat S of basic weight 64g / m2, thickness 0.1mm, and A4 size to a longitudinal direction.

  The initial shape of the sheet S has a tangent angle of about 30 degrees, and is a result of time-sound pressure (dB) when the sheet S is changed to 0 degree by feeding the sheet S with a roller. This is a result of calculating an overall value after performing FFT processing on data sampled at 51.2 kHz every 0.01 s and correcting with A characteristics.

  Since the conveyance speed is 150 mm / s, the sheet S is conveyed by 30 mm from the tangential angle of 30 degrees to the tangential angle of 0 degrees. Since the total length of the sheet S is 300 mm, it is considered that the influence of the position of the friction member and the sheet position due to the conveyance of the sheet S is slight.

  As can be seen from FIG. 7, when the sheet S is curved and an excitation force due to friction or the like acts on the sheet S, it can be seen that the generated sound becomes extremely loud. This tendency agrees with the simulation result of FIG. 6 although the ratio to the tangent angle is different.

  As described above, it can be seen that by reducing the tangent angle, it is possible to reduce the contact sound between the sheet front end and the guide member 71 and the friction sound between the sheet rear end and the separation pad 40.

  Next, a case where the friction coefficient between the sheets of the sheet S becomes larger than the frictional force between the separation pad 40 and the paper, and the sheet S is not separated and fed by the separation pad 40 but is double fed. 8 will be used for explanation.

  Here, FIG. 8 is an enlarged view of the vicinity of the feeding roller 10. In FIG. 8, the separation pad holder 50 is fixed to the swing member 80 via a spring 51. The separation pad holder 50 is pressed against the feeding roller 10 by a spring 51 with a predetermined pressure, and is rotatable in the direction of the arrow in FIG.

  As shown in FIG. 8, when the sheet S is double fed, the separation pad holder 50 is tilted in the direction of the arrow shown in FIG. By tilting the separation pad holder 50, the adhesion between the plurality of sheets S is reduced, the frictional force between the plurality of sheets is reduced, and only the uppermost sheet S is fed.

  Even in the case where a plurality of sheets S are double-fed, it is possible to achieve a reduction in sound without impairing the feeding property. Although FIG. 8 shows an embodiment in which the angle of the separation pad holder 50 changes when the spring 51 is bent, the same effect can be obtained even when the swinging member 80 itself is slightly rotated instead of the spring 51. .

  In this embodiment, the angle formed by the nip tangent is reduced to θ ′ before the leading edge of the sheet S contacts the guide member 71, and the trailing edge of the sheet is pulled out from the nip portion between the separation pad 40 and the feeding roller 10. Until it is held at θ ′.

  However, after the sheet S is separated and fed by the feeding roller 10, the sheet S may be continuously decreased until the trailing edge of the sheet comes off. In that case, it is possible to further reduce the frictional noise generated when the trailing edge of the sheet is pulled out from the nip portion between the separation pad 40 and the feeding roller 10.

  As mentioned above, although Embodiment 1 of this invention was explained in full detail, this invention is not limited to description of the said Embodiment 1, and does not deviate from the mind of the invention described in the claim of this invention. Various changes can be made within the range.

Embodiment 2

  For example, FIG. 9 shows Embodiment 2 of the present invention. In the second embodiment, a sensor 73 for detecting the position of the sheet S is provided on the back side of the guide member 71, and other configurations are the same as those in the first embodiment. 10 and 11 are time charts related to the detection output signal from the sensor 73 and the driving timing of the feeding roller 10 and the cam 60. FIG.

  That is, after the leading edge of the sheet S is detected by the sensor 73 which is a reflection type photosensor, before the leading edge of the sheet S comes into contact with the guide member 71, the cam 60 is driven to the holding angle of FIG. It is possible to reduce the contact angle between the sheet front end and the guide member 71.

  In FIG. 10, when the feeding roller 10 starts to be driven, the cam 60 is stopped and kept at the tangential angle θ (T1). When the feeding roller 10 starts rotating and the sheet S is fed by a certain amount, the leading edge of the sheet reaches the sensor 73, and the output of the sensor 73 is generated (T2).

  With this output as a trigger, the cam 60 starts rotating and is held at the tangential angle θ ′. When the front end of the sheet comes into contact with the guide member 71, the tangential angle θ ′ is obtained, and it is possible to reduce the sound generated when the front end of the sheet comes into contact with the guide member 71.

  When the trailing edge of the sheet is pulled out from the nip portion of the separation pad 40 and the feeding roller 10, the feeding roller 10 stops rotating. Since the tangential angle θ ′ is maintained even when the trailing edge of the sheet is pulled out from the nip portion, the frictional noise between the separation pad 40 and the sheet S generated when the trailing edge of the sheet is pulled out from the nip portion can be reduced. It becomes possible.

  Thereafter, the cam 60 rotates again (T3), and the tangent angle is maintained at θ at time T4 at which the second sheet S starts to be fed, and the second sheet S is fed. Since the tangent angle θ is set when the second sheet S is fed, even when the second sheet S is attached, it is possible to stably separate and feed.

  Note that T3 can be set after a certain period of time has elapsed after the rotation of the feeding roller 10 is stopped, and if the trailing edge of the paper can be detected by the sensor 73, the time is used as a reference. Is also possible.

  In FIG. 11, the cam 60 does not stop the tangent angle at a constant θ ′, but performs a driving pattern in which the tangential angle continuously changes after T2. A similar effect can be obtained with such a drive pattern, and if the tangent angle can be made smaller than θ ′, the trailing edge of the sheet is pulled out from the nip portion between the feeding roller 10 and the separation pad 40. It is possible to further reduce the generated frictional noise.

  The drive patterns in FIGS. 10 and 11 can be appropriately changed. For example, in combination with a paper type sensor, the drive patterns as shown in FIGS. 8 and 9 can be changed for each paper type.

  In this way, by determining the timing for rotating the cam 60 from the output timing of the sensor 73 and the conveyance speed of the feed roller 10, the angle of the separation pad 40 can be changed stably regardless of the conveyance speed. It becomes.

  As a result, even when the size or the conveyance speed of the sheet S is different, the shape when the trailing edge of the sheet is pulled out can be surely made into a linear shape, so that it is possible to prevent the generation of a loud sound.

Embodiment 3

  FIG. 12 shows a third embodiment of the present invention. In the third embodiment, the shape of the cam is changed, and the other configuration is the same as that of the first embodiment.

  That is, the cam 61 has a shape including a part of concentric arcs having different radii with respect to the rotation axis. When such a cam shape is used, the inclination angle of the separation pad holder 50 does not change in the two concentric circular arc portions, so that the separation pad holder 50 can be held at the two angles for a predetermined time.

  The cam 61 is connected to driving means (not shown) via a gear or the like. By changing the position of the separation pad holder 50 with the cam 61, the separation pad holder 50 can be held at two holding angles before and after the separation feeding. S can be conveyed stably.

It is a schematic diagram of the sheet conveying apparatus which concerns on Embodiment 1 of this invention. FIG. 2 is a schematic diagram when a separation pad holder of the sheet conveying apparatus in FIG. 1 is rotated. FIG. 2 is a schematic diagram when a separation pad holder of the sheet conveying apparatus in FIG. 1 is rotated. FIG. 2 is a schematic view of the sheet conveying apparatus of FIG. 1 as viewed from the sheet conveying direction. FIG. 6 is a characteristic diagram illustrating a simulation result of noise of the sheet conveying device of FIG. 1. FIG. 6 is a characteristic diagram illustrating a simulation result of noise of the sheet conveying device of FIG. 1. It is explanatory drawing which shows the experimental result regarding the sound of the sheet conveying apparatus of FIG. FIG. 2 is an enlarged view of a feeding roller unit of the sheet conveying apparatus in FIG. 1. It is a schematic diagram of the sheet conveying apparatus which concerns on Embodiment 2 of this invention. 10 is a time chart regarding drive timing of the sheet conveying apparatus of FIG. 9. 10 is a time chart regarding drive timing of the sheet conveying apparatus of FIG. 9. It is a schematic diagram of the sheet conveying apparatus which concerns on Embodiment 3 of this invention. FIG. 10 is a schematic diagram illustrating an operation of a conventional sheet conveying apparatus. FIG. 10 is a schematic diagram illustrating an operation of a conventional sheet conveying apparatus. FIG. 10 is a schematic diagram illustrating an operation of a conventional sheet conveying apparatus. 1 is a cross-sectional view illustrating an example of an image forming apparatus to which the present invention is applied.

Explanation of symbols

1 Sheet transport device
10 Feed roller
20 Pulling roller pair
30 Feed tray
40 separation pad
50 separation pad holder
51 Spring
60, 61 cam
71, 72 Guide member
73 Sensor S sheet θ, θ 'Tangent angle

Claims (6)

An upstream conveying unit that sandwiches and conveys a sheet, and a sheet that is disposed downstream of the upstream conveying unit in the sheet conveying direction and that conveys the sheet conveyed by the upstream conveying unit to the downstream side in the conveying direction. A sheet conveying apparatus comprising: a downstream conveying unit; and a bent conveying guide member that is disposed between the upstream conveying unit and the downstream conveying unit and guides the sheet.
Angle changing means capable of changing the angle of the nip tangent of the upstream conveying means in order to change the tangential angle formed by the nip tangent of the nip of the upstream conveying means and the nip tangent of the nip of the downstream conveying means. Have
The angle changing means reduces the acute angle of the tangential angle between the time when the leading edge of the sheet passes through the nip portion of the upstream conveying means and the time when the leading edge of the sheet contacts the conveyance guide member. The sheet conveying apparatus is characterized in that the tangential angle is kept small until the trailing edge of the sheet passes through the nip portion of the upstream conveying unit. 2. The sheet conveying apparatus according to claim 1 , wherein the angle changing unit returns the changed tangential angle to a base angle after a rear end of the sheet passes through a nip portion of the upstream conveying unit. A sensor for detecting a position of a sheet to be conveyed is provided between the upstream conveying unit and the downstream conveying unit, and the upstream conveying unit is configured to detect the upstream conveying unit according to a detection output of the sensor. sheet conveying apparatus according to claim 1 or claim 2, characterized in that to change the nip tangent angle. The upstream conveying unit includes a feeding roller and a separation pad for separating and feeding the sheet, and the angle changing unit is configured to change a holding angle for holding the separation pad, thereby the upstream conveying unit. sheet conveying device according to any one of claims 1 to 3, characterized in that to change the nip tangent angle. A holding portion for holding the separation pad and pivotable axis of rotation coaxial with said feed roller, by swinging the holding portion, to claim 4, characterized in that for changing the holding angle The sheet conveying apparatus according to the description. The sheet conveying device according to any one of claims 1 to 5 ,
An image forming unit that forms an image on a sheet conveyed by the sheet conveying device;
An image forming apparatus comprising:

Images