阅读说明：本技术 片材进给设备和成像设备 (Sheet feeding apparatus and image forming apparatus ) 是由 乾祐马 于 2019-05-31 设计创作，主要内容包括：本发明涉及片材进给设备和成像设备。片材进给设备包括传送辊、驱动输入轴、结合部、第一接合部分、第一被接合部分、第二接合部分和第二被接合部分。在所述结合部的轴向方向上观察时,由第一直线和第二直线形成的角度在大于或等于80度且小于或等于100度的范围内,所述第一直线穿过所述第一接合位置和所述驱动输入轴的旋转中心,所述第二直线穿过所述第二接合位置和所述延迟轴的旋转中心。(The invention relates to a sheet feeding apparatus and an image forming apparatus. The sheet feeding apparatus includes a conveying roller, a drive input shaft, a joining section, a first joining portion, a first joined portion, a second joining portion, and a second joined portion. An angle formed by a first straight line passing through the first engagement position and a rotation center of the drive input shaft and a second straight line passing through the second engagement position and a rotation center of the retard shaft is in a range of 80 degrees or more and 100 degrees or less as viewed in an axial direction of the coupling portion.)

1. A sheet feeding apparatus comprising:

A conveying roller configured to convey a sheet;

A retard roller configured to contact the conveying roller and separate sheets one by one;

a drive input shaft driven by a drive source;

a retard shaft configured to rotatably support the retard roller;

a coupling portion configured to transmit a rotational driving force of the driving input shaft to the delay shaft;

A first engaging portion provided on either one of the drive input shaft or the coupling portion;

A first engaged portion provided on the other of the drive input shaft or the coupling portion and configured to engage with the first engaging portion at a first engaging position in response to rotation of the drive input shaft;

a second engaging portion provided on either one of the delay shaft or the coupling portion;

A second engaged portion that is provided on the other of the delay shaft or the engaging portion and that is configured to engage with the second engaging portion at a second engaging position in response to rotation of the engaging portion;

Wherein an angle formed by a first straight line passing through the first engagement position and a rotation center of the drive input shaft and a second straight line passing through the second engagement position and a rotation center of the retard shaft is within a range of 80 degrees or more and 100 degrees or less as viewed in an axial direction of the coupling portion.

2. The sheet feeding apparatus according to claim 1, wherein the first engaging portion and the second engaging portion are a first pin and a second pin, respectively, extending in a direction intersecting with an axial direction of the joint,

the first engaged portion is a first groove portion engaged with the first pin, and

The second engaged portion is a second groove portion that engages with the second pin.

3. The sheet feeding apparatus according to claim 2, wherein the first pin is provided on the drive input shaft,

The second pin is disposed on the delay shaft, and

The first groove portion and the second groove portion are provided on a first end portion and a second end portion of the joint portion in the axial direction, respectively.

4. The sheet feeding apparatus according to claim 2, wherein each of the first pin and the second pin is formed in a cylindrical shape.

5. The sheet feeding apparatus according to claim 3, wherein the first groove portion includes a first surface and a second surface that extend in an axial direction of the joining portion and are opposed to each other with the first pin interposed therebetween,

The second groove portion includes a third surface and a fourth surface that extend in the axial direction of the joint portion and are opposed to each other with the second pin interposed therebetween,

The first surface is positioned downstream of the second surface in a rotational direction of the joint and is engaged with the first pin at the first engagement position, and

The third surface is positioned upstream of the fourth surface in a rotational direction of the joint and engages with the second pin at the second engagement position.

6. The sheet feeding apparatus according to claim 5, wherein the first engagement position is located at a boundary portion between the first surface and an outer peripheral surface of the bonding portion, and

The second engagement position is located at a boundary portion between the third surface and the outer peripheral surface of the joint portion.

7. The sheet feeding apparatus according to claim 5, wherein in a state in which the first pin and the second pin are engaged with the first surface and the third surface, respectively, the first pin and the second pin are arranged such that an angle formed by an axis of the first pin and an axis of the second pin is within a range of 50 degrees or more and 70 degrees or less as viewed in an axial direction of the joint.

8. The sheet feeding apparatus according to any one of claims 1 to 7, wherein the sheet feeding apparatus further comprises a torque limiter interposed between the retard roller and the retard shaft, and

the driving input shaft, the coupling part, and the delay shaft are rotated only in one direction by a driving force of the driving source.

9. The sheet feeding apparatus according to any one of claims 1 to 7, wherein an axial direction of the drive input shaft and an axial direction of the joining portion intersect with each other.

10. An image forming apparatus comprising:

The sheet feeding apparatus according to any one of claims 1 to 7; and

An image forming unit configured to form an image on a sheet fed from the sheet feeding apparatus.

11. A sheet feeding apparatus comprising:

A conveying roller configured to convey a sheet;

a retard roller configured to contact the conveying roller and separate sheets one by one;

A drive input shaft driven by a drive source;

A retard shaft configured to rotatably support the retard roller;

a coupling portion configured to transmit a rotational driving force of the driving input shaft to the delay shaft;

A first pin provided on either one of the drive input shaft or the coupling portion;

a first slot disposed on the other of the drive input shaft or the coupling and configured to engage the first pin at a first engagement position in response to rotation of the drive input shaft;

A second pin provided on either one of the delay shaft or the coupling portion; and

A second groove portion provided on the other of the delay shaft or the joint portion and configured to engage with the second pin at a second engagement position in response to rotation of the joint portion;

wherein, in a state in which the first pin and the second pin are engaged with the first groove portion and the second groove portion, respectively, the first pin and the second pin are arranged such that an angle formed by an axis of the first pin and an axis of the second pin is within a range of 50 degrees or more and 70 degrees or less as viewed in an axial direction of the joint portion.

12. the sheet feeding apparatus according to claim 11, wherein an angle formed by the first straight line and the second straight line is greater than or equal to 80 degrees and less than or equal to 100 degrees when viewed from an axial direction of the joining portion,

The first line passes through the first engagement position and a rotation center of the drive input shaft, and

the second line passes through the second engagement position and the center of rotation of the retard shaft.

13. The sheet feeding apparatus according to claim 11, wherein the first pin is provided on the drive input shaft,

the second pin is disposed on the delay shaft, and

The first groove portion and the second groove portion are provided on a first end portion and a second end portion of the joint portion in the axial direction, respectively.

14. The sheet feeding apparatus according to claim 11, wherein each of the first pin and the second pin is formed in a cylindrical shape.

15. the sheet feeding apparatus according to claim 13, wherein the first groove portion includes a first surface and a second surface that extend in an axial direction of the joining portion and are opposed to each other with the first pin interposed therebetween,

the second groove portion includes a third surface and a fourth surface that extend in the axial direction of the joint portion and are opposed to each other with the second pin interposed therebetween,

The first surface is positioned downstream of the second surface in a rotational direction of the joint and is engaged with the first pin at the first engagement position, and

The third surface is positioned upstream of the fourth surface in a rotational direction of the joint and engages with the second pin at the second engagement position.

16. The sheet feeding apparatus according to claim 15, wherein the first engagement position is located at a boundary portion between the first surface and an outer peripheral surface of the bonding portion, and

The second engagement position is located at a boundary portion between the third surface and the outer peripheral surface of the joint portion.

17. the sheet feeding apparatus according to any one of claims 11 to 16, wherein the sheet feeding apparatus further comprises a torque limiter interposed between the retard roller and the retard shaft, and

the driving input shaft, the coupling part, and the delay shaft are rotated only in one direction by a driving force of the driving source.

18. The sheet feeding apparatus according to any one of claims 11 to 16, wherein an axial direction of the drive input shaft and an axial direction of the joining portion intersect with each other.

19. An image forming apparatus comprising:

the sheet feeding apparatus according to any one of claims 11 to 16; and

An image forming unit configured to form an image on a sheet fed from the sheet feeding apparatus.

Technical Field

The present invention relates to a sheet feeding apparatus and an image forming apparatus equipped with the sheet feeding apparatus.

Background

Heretofore, japanese patent application laid-open No. h10-025034 discloses a sheet feeding apparatus configured to separate sheets fed from a cassette one by one using a feed roller and a retard roller. The retard roller is rotatably supported on the retard shaft by a torque limiter, and the retard shaft is connected to the drive shaft by a coupling.

the pins are press-fitted to the drive shaft and the delay shaft, respectively, with phases different by 90 degrees, and the two pins are passed through a long hole formed on the first end portion in the axial direction of the coupling and a notched groove formed on the second end, respectively. If the drive shaft is rotated in a state where the coupling is inclined with respect to the drive shaft and the retard shaft, the influence of friction caused between the two pins and the long hole or the second end portion will change the separation pressure applied from the retard roller to the feed roller. If the separation pressure fluctuates greatly, the occurrence probability of delay and jam of the sheet and conveyance failure such as sheet multi-feeding increases.

Disclosure of Invention

According to a first aspect of the present invention, a sheet feeding apparatus includes: a conveying roller configured to convey a sheet; a retard roller configured to contact the conveying roller and separate sheets one by one; a drive input shaft driven by a drive source; a retard shaft configured to rotatably support the retard roller; a coupling portion configured to transmit a rotational driving force of the driving input shaft to the delay shaft; a first engaging portion provided on either one of the drive input shaft or the coupling portion; a first engaged portion provided on the other of the drive input shaft or the coupling portion and configured to engage with the first engaging portion at a first engaging position in response to rotation of the drive input shaft; a second engaging portion provided on either one of the delay shaft or the coupling portion; a second engaged portion that is provided on the other of the delay shaft or the joint portion and is configured to engage with the second engaging portion at a second engaging position in response to rotation of the joint portion, wherein an angle formed by a first straight line that passes through the first engaging position and a rotation center of the drive input shaft and a second straight line that passes through the second engaging position and the rotation center of the delay shaft as viewed in an axial direction of the joint portion is in a range of greater than or equal to 80 degrees and less than or equal to 100 degrees.

According to a second aspect of the present invention, a sheet feeding apparatus includes: a conveying roller configured to convey a sheet; a retard roller configured to contact the conveying roller and separate sheets one by one; a drive input shaft driven by a drive source; a retard shaft configured to rotatably support the retard roller; a coupling portion configured to transmit a rotational driving force of the driving input shaft to the delay shaft; a first pin provided on either one of the drive input shaft or the coupling portion; a first slot disposed on the other of the drive input shaft or the coupling and configured to engage the first pin at a first engagement position in response to rotation of the drive input shaft; a second pin provided on either one of the delay shaft or the coupling portion; a second groove portion provided on the other of the delay shaft or the joint portion and configured to engage with the second pin at a second engagement position in response to rotation of the joint portion, wherein the first pin and the second pin are arranged such that an angle formed by an axis of the first pin and an axis of the second pin is within a range of 50 degrees or more and 70 degrees or less as viewed in an axial direction of the joint portion in a state in which the first pin and the second pin are engaged with the first groove portion and the second groove portion, respectively.

Further features of the invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.

drawings

Fig. 1 is a schematic diagram showing the configuration of an image forming apparatus according to an embodiment of the present invention.

Fig. 2 is a schematic diagram illustrating a configuration of a sheet feeding apparatus according to an embodiment of the present invention.

Fig. 3 is a perspective view showing the configurations of the retard roller, the retard shaft, the coupling member, and the drive shaft in a state where the drive shaft and the retard shaft are not deviated.

fig. 4 is a perspective view showing the connection portion and the coupling member in an enlarged view.

fig. 5 is an exploded view of the retard roller and the retard shaft.

Fig. 6 is a perspective view showing the configurations of the retard roller, the retard shaft, the coupling member, and the drive shaft in a state where the drive shaft and the retard shaft are not deviated.

fig. 7 is a perspective view showing a positional relationship of the first pin and the coupling member in a state where the swing resistance of the retard roller holder becomes maximum.

Fig. 8 is a perspective view showing a positional relationship of the first pin and the coupling member in a state where the swing resistance of the retard roller holder becomes minimum.

Fig. 9 is an explanatory view schematically showing a positional relationship of the first pin and the second pin when the first connecting portion and the second connecting portion are viewed from the second axial direction.

Fig. 10 is a graph showing a change in the delay pressure with respect to time in the case where θ is 0 °.

Fig. 11 is a graph showing a change in the delay pressure with respect to time in the case where θ is 90 °.

Fig. 12 is a graph showing the relationship between the angle θ formed by the first straight line and the second straight line and the fluctuation amplitude of the retard pressure.

Detailed Description

integral structure

Now, a sheet feeding apparatus and an image forming apparatus according to the present invention will be described with reference to the drawings. First, the printer 100 serving as the image forming apparatus according to the present embodiment will be described. The printer 100 is a full-color laser beam printer employing an electrophotographic system. As shown in the example in fig. 1, the printer 100 includes an image reading device 202 for reading image data from a document, the image reading device 202 being disposed above the apparatus main body 150 in a posture such that a loading surface of the document is disposed substantially horizontally. A discharge space where the sheet P is discharged is formed between the image reading apparatus 202 and the apparatus main body 150, and a sheet discharge tray 223 is arranged in the discharge space. Further, the printer 100 includes, inside the apparatus main body 150, an image forming unit 200 for forming an image on the sheet P, a sheet feeding portion 230 for feeding the sheet P toward the image forming unit 200, and a control unit 260 for controlling an image forming operation, a sheet feeding operation, and the like.

The image forming unit 200 constitutes an image forming unit employing a so-called four-drum full-color system, and includes a laser scanner 210, four process cartridges 211, and an intermediate transfer unit 201. The process cartridges 211 form toner images of respective colors of yellow (Y), magenta (M), cyan (C), and black (K), respectively. Each process cartridge 211 includes a photosensitive drum 212, a charging unit 213, a developing unit 214, a cleaner not shown, and the like. Toner cartridges 215 storing toner of respective colors are detachably attached to the apparatus main body 150 at positions above the image forming unit 200.

The intermediate transfer unit 201 is configured to have an intermediate transfer belt 216 serving as an intermediate transfer body wound on a driving roller 216a and a tension roller 216b, and is disposed above the four process cartridges 211, for example. The intermediate transfer belt 216 is arranged to contact the photosensitive drums 212 of the respective process cartridges 211, and is driven to rotate in the direction of an arrow D1, for example, by a driving roller 216 a. The intermediate transfer unit 201 includes primary transfer rollers 219 that contact the inner peripheral surface of the intermediate transfer belt 216 at positions opposed to the respective photosensitive drums 212, and a primary transfer portion serving as a nip portion is formed between the intermediate transfer belt 216 and the photosensitive drums 212. The image forming unit 200 includes a secondary transfer roller 217 which is in contact with the outer peripheral surface of the intermediate transfer belt 216 at a position opposite to the driving roller 216 a. A secondary transfer portion for transferring the toner image carried on the intermediate transfer belt 216 to the sheet P is formed as a nip portion between the secondary transfer roller 217 and the intermediate transfer belt 216.

the sheet feeding section 230 includes four sets of cassettes 1, a feeding roller 10, a conveying roller 11, and a retard roller 12. Each cassette 1 is arranged in such a manner as to be insertable into and removable from the apparatus main body 150, and stores sheets P in a stacked manner.

In a state where the printer 100 receives a command to start an image forming operation, the photosensitive drum 212 rotates and the surface of the photosensitive drum 212 is uniformly charged by the charging unit 213. Then, the laser scanner 210 modulates and outputs a laser beam based on image data input from an input interface or an external computer. The laser scanner 210 outputs a laser beam and scans the surface of each photosensitive drum 212, thereby forming an electrostatic latent image based on image data on the surface of each photosensitive drum 212. That is, yellow, magenta, cyan, and black electrostatic latent images are sequentially formed on the surfaces of the photosensitive drums 212 of the respective process cartridges 211. The formed electrostatic latent images for yellow, magenta, cyan, and black are visualized by the toners supplied from the developing unit 214, whereby yellow, magenta, cyan, and black toner images are developed. The yellow, magenta, cyan, and black toner images are sequentially transferred onto the intermediate transfer belt 216 and superimposed on the other toner images. Thereby, a full-color toner image is formed on the intermediate transfer belt 216.

Meanwhile, in the printer 100, the sheet feeding portion 230 feeds the sheet P toward the image forming unit 200 while performing an image forming operation. In the sheet feeding portion 230, first, for example, the sheets P stacked in the cassette 1 are sent out by the feeding roller 10. The sheet P having been fed out by the feed roller 10 is separated one by the conveying roller 11 and the retard roller 12, and is conveyed to the registration roller pair 240. The sheet P conveyed to the registration roller pair 240 is skew-corrected by the registration roller pair 240. After that, the sheet P is conveyed to the secondary transfer portion of the image forming unit 200 at a timing matching the toner image carried on the photosensitive drum 212. The toner images carried on the photosensitive drums 212 are collectively transferred to the sheet P by a secondary transfer bias applied to the secondary transfer roller 217. After the toner image is transferred, the toner remaining on the photosensitive drum 212 is collected by a cleaner. The sheet P to which the toner image has been transferred is heated and pressurized by the fixing unit 220, whereby the toner image transferred to the sheet P is fixed. The sheet P to which the toner image has been fixed is discharged to the sheet discharge tray 223 by the sheet discharge roller pair 225a or 225 b.

in order to form images on both sides of the sheet P, after fixing of the images to the surface of the sheet P is completed, the sheet is switched back by a reverse conveyance roller pair 222 provided in the reverse conveyance portion 205, which is rotatable in the forward and reverse directions. Then, the sheet P is re-conveyed to the image forming unit 200 through the re-conveying path 206, where an image is formed on the back side of the sheet P at the image forming unit 200.

Sheet feeding apparatus

next, the sheet feeding portion 230 serving as a sheet feeding apparatus will be described with reference to fig. 2 to 5. As described above, the sheet feeding portion 230 includes the feeding roller 10, the conveying roller 11, and the retard roller 12. As shown in fig. 2, the feed roller 10, the conveying roller 11, and the retard roller 12 are rotatably supported on a sheet feeding frame 6 fixed to an apparatus main body 150 (see fig. 1), respectively. Further, a swing shaft 18 that pivotably supports the retard roller 12 in the up-down direction is attached to the sheet feeding frame 6. The retard roller holder 14 is attached to the sheet feeding frame 6 by a swing shaft 18 in a manner swingable about the swing shaft 18. Further, the retard roller holder 14 holds a retard shaft 16 that rotatably supports the retard roller 12. Below the retard roller holder 14, a spring 15 is arranged that urges the retard roller holder 14 upward (i.e., toward the conveying roller 11).

Since the retard roller holder 14 is pivotably disposed in the up-down direction and is urged upward, the retard roller 12 can be brought into contact with the conveying roller 11 in a state of being urged toward the conveying roller 11. That is, the retard roller 12 is in pressure contact with the conveying roller 11 by the elastic force of the spring 15. Since the retard roller 12 is in pressure contact with the conveying roller 11, a separation nip portion N that separates the sheet P is formed between the retard roller 12 and the conveying roller 11.

meanwhile, the cartridge 1 can be inserted into and removed from the apparatus main body 150. Inside the cassette 2, there are provided a support plate 3 capable of supporting the sheets P in a stacked manner, a lift plate 4 capable of supporting the support plate 3 from below and pivotable in the up-down direction, and pivots 3a and 4a that respectively pivot the support plate 3 and the lift plate 4 in the up-down direction. The support plate 3 is pivotably attached to the pivot shaft 3a about the pivot shaft 3 a. Further, the elevating plate 4 is pivotably disposed about a pivot shaft 4a in the up-down direction below the support plate 3. The lifter plate 4 pivots by receiving a driving force supplied from a lifter motor, not shown, and lifts the support plate 3.

In a state where the sheet feeding portion 230 feeds the sheet P, the lifting plate 4 is pivoted in the upward direction about the pivot shaft 4a, whereby the support plate 3 is lifted to a position where the uppermost sheet P placed on the support plate 3 can be fed. The sheets P are fed by the feed roller 10, and the fed sheets P are separated one by the separation nip portion N.

drive transmission structure of delay roller

next, the drive transmission configuration of the retard roller 12 will be described with reference to fig. 3 and 4. As shown in fig. 3, a drive shaft 17 serving as a drive input shaft is rotatably supported on the sheet feeding frame 6 by a drive force transmitted from a motor 19 as a drive source. Further, as described above, the swing shaft 18 is attached to the sheet feeding frame 6. The drive shaft 17 and the retard shaft 16 are connected by a coupling member 30 serving as a coupling portion that transmits the rotational drive force of the drive shaft 17 to the retard shaft 16. The drive shaft 17 and the coupling member 30 are connected by a first connecting portion 25a that does not allow the drive shaft 17 and the coupling member 30 to rotate relative to each other. Further, the coupling member 30 and the delay shaft 16 are connected by a second connection portion 25b that does not allow the delay shaft 16 and the coupling member 30 to relatively rotate. The retard roller 12 is attached to an end of the retard shaft 16 on the side where the coupling member 30 is not connected in the axial direction via a torque limiter 13. In other words, the torque limiter 13 is interposed between the retard roller 12 and the retard shaft 16. The motor 19 rotates only in one direction, and the drive shaft 17, the coupling member 30, and the retard shaft 16 rotate only in one direction by the driving force of the motor 19.

The drive shaft 17, the coupling member 30, and the retard shaft 16 will be described in more detail with reference to fig. 4. The drive shaft 17 is formed to rotate in the direction of an arrow D2 and extend in the direction of an arrow D3 by being driven by a motor 19 (see fig. 3). In other words, the direction of the arrow D3 represents the axial direction of the drive shaft 17, hereinafter referred to as the "drive shaft direction". Further, the coupling member 30 connected to the drive shaft 17 via the first connecting portion 25a extends in the direction of the arrow D4 and is formed in a cylindrical shape. That is, an arrow D4 indicates an axial direction of the coupling member 30, hereinafter referred to as a "coupling axis direction". Further, the delay shaft 16 connected to the coupling member 30 via the second connecting portion 25b is formed to extend in the direction of the arrow D5. That is, the direction of the arrow D5 represents the retard axis direction in which the retard axis 16 extends. The retard axis direction is parallel to the drive axis direction.

The first connecting portion 25a includes a first pin 20a having a cylindrical shape provided on the drive shaft 17, and a pair of first groove portions 21a formed on the coupling member 30 and engaged with the first pin 20a in response to rotation of the drive shaft 17. The pair of first groove portions 21a are formed at positions of the coupling member 30 having a phase difference of 180 degrees in the rotational direction. A first pin 20a serving as a first engaging portion is arranged at an end portion of the drive shaft 17 as shown in fig. 5, and has a cylindrical shape. Further, the first pin 20a extends in a direction orthogonal to the drive shaft direction. The first pin does not necessarily extend in a direction orthogonal to the drive shaft direction, but it should extend only in a direction intersecting the coupling shaft direction. The first groove portions 21a serving as the first engaged portions are arranged at the first end portion 30b of the coupling member 30 in the coupling axis direction, and they extend in the coupling axis direction. The first pin 20a and the first groove portion 21a are engaged at a first contact portion 22a serving as a first engagement position.

the second connection portion 25b includes a second pin 20b having a cylindrical shape provided on the delay shaft 16, and a pair of second groove portions 21b formed on the coupling member 30 and engaged with the second pin 20b in response to rotation of the coupling member 30. The pair of second groove portions 21b are formed at positions of the coupling member 30 having a phase difference of 180 degrees in the rotational direction. A second pin 20b serving as a second engaging portion is arranged at an end of the delay shaft 16 as shown in fig. 5, and has a cylindrical shape. Further, the second pin 20b extends in a direction orthogonal to the retard axis direction. The second pin 20b does not necessarily extend in the direction orthogonal to the delay axis direction, but it should extend only in the direction intersecting the coupling axis direction. The second groove portions 21b serving as the second engaged portions are arranged at the second end portion 30c of the coupling member 30 in the coupling axis direction, and they extend in the coupling axis direction. The second pin 20b and the second groove portion 21b are engaged at a second contact portion 22b serving as a second engagement position.

delaying pressure fluctuations

With regard to the retard roller 12, the retard shaft 16 may be deviated with respect to the drive shaft 17 due to the influence of dimensional accuracy of parts, deformation and abrasion of the rubber roller, and the like. That is, as shown in fig. 6, the coupling member 30 may be inclined with respect to the drive shaft 17 and the retard shaft 16 such that the drive shaft direction indicated by the arrow D3 and the coupling shaft direction indicated by the arrow D4 intersect with each other. For example, as shown in fig. 6, if the retard shaft 16 is deviated toward the downstream side in the sheet conveying direction, the coupling member 30 rotates in an oblique manner with respect to the drive shaft 17 and the retard shaft 16 and transmits the driving force from the drive shaft 17 to the retard shaft 16. That is, the retard shaft 16 rotates eccentrically with respect to the drive shaft 17. In this state, a force that tries to rotate the drive shaft 17 and the retard shaft 16 while the joint member 30 maintains the inclined state is generated in both the first connection portion 25a and the second connection portion 25 b. Therefore, a fluctuation in the pressure contact force (hereinafter referred to as "retard pressure") is generated in which the retard roller 12 presses the conveying roller 11. As shown in fig. 6, in the retard roller 12 in which the retard shaft 16 is deviated toward the downstream side in the sheet conveying direction, the retard pressure is reduced.

In a state where the coupling member 30 rotates in the direction of the arrow D2 shown in fig. 6 when the coupling member 30 is tilted with respect to the drive shaft 17 and the retard shaft 16, the first pin 20a and the first groove portion 21a and the second pin 20b (refer to fig. 4) and the second groove portion 21b (refer to fig. 4) relatively move at the time of the sliding motion. As shown in fig. 7, the first groove portion 21a includes a first surface 23a and a second surface 24a that extend in the coupling axis direction and oppose each other with the first pin 20a interposed therebetween. The first surface 23a is located downstream of the second surface 24a in the rotational direction of the coupling member 30 (i.e., the arrow D2 direction). Similarly, the second groove portion 21b includes a third surface 23b and a fourth surface 24b that extend in the coupling axis direction and are opposed to each other with the second pin 20b interposed therebetween. The third surface 23b is located upstream of the fourth surface 24b in the rotation direction of the coupling member 30 (i.e., the direction of the arrow D2). If the coupling member 30 is rotated in a state of being inclined with respect to the driving shaft 17 and the retard shaft 16, the first pin 20a moves in a sliding motion in contact with the first surface 23a or the second surface 24a according to the rotation direction of the driving shaft 17. Like the first pin 20a, the second pin 20b also moves in a sliding motion in contact with the first surface 23a or the second surface 24a, depending on the direction of rotation of the drive shaft 17. During such relative sliding movement, the frictional force generated at the first and second connection portions 25a and 25b periodically changes according to the phase of the rotational direction of the first and second pins 20a and 20 b. The direction of the frictional force with respect to the delay pressure operation is changed according to the arrangement direction of the shafts of the first and second pins 20a and 20 b.

the direction of the arrow D6 and the direction of the arrow D7 shown in fig. 7 and 8 indicate the oscillating direction of the retard roller 12. For example, as shown in fig. 7, in a state where the axial direction of the first pin 20a is arranged in the swinging direction of the retard roller 12, the frictional force in the swinging direction generated at the first connection portion 25a becomes relatively large. Therefore, the amount of change in the retard pressure becomes large due to the frictional force generated at the first connection portion 25 a. Meanwhile, as shown in fig. 8, in a state where the axial direction of the first pin 20a is arranged orthogonal to the swinging direction of the retard roller 12, the frictional force in the swinging direction generated at the first connecting portion 25a becomes relatively small. Therefore, the amount of change in the retard pressure becomes small due to the frictional force at the first connection portion 25 a. Such periodic frictional force variation similarly occurs at the second connecting portion 25b, and the retard pressure periodically changes in response to the rotation of the drive shaft 17, the coupling member 30, and the retard shaft 16. As described above, if the delay pressure is unstable, the occurrence probability of conveyance failure such as delay and jam of the sheet or multi-feed increases.

Suppression of fluctuations in delay pressure

next, suppression of fluctuation of the retard pressure at the retard roller 12 will be described. As described above, in the state where the drive shaft 17 (refer to fig. 4) is rotated, the delay pressure fluctuates due to the influence of the frictional force occurring at both the first connecting portion 25a and the second connecting portion 25 b. Therefore, the final fluctuation of the retard pressure appears as a composite wave in which the waveform representing the fluctuation amount of the retard pressure caused by the friction force at the first connection portion 25a overlaps with the waveform representing the fluctuation amount of the retard pressure caused by the friction force at the second connection portion 25 b. The amplitude of the composite wave is determined by the positional relationship of the first pin 20a and the second pin 20b in the rotational direction of the coupling member 30.

Fig. 9 schematically shows the positional relationship of the first pin 20a and the second pin 20b as viewed in the second axial direction in which the coupling member 30 extends. As shown in fig. 9, in a state where the drive shaft 17 (refer to fig. 6) is rotated in the direction of the arrow D2, the drive force from the motor 19 (refer to fig. 3) is transmitted to the coupling member 30 and further to the delay shaft 16. In a state where the drive shaft 17 is rotated in the direction of the arrow D2, the first pin 20a contacts the downstream side surface of the first groove portion 21a in the direction of the arrow D2 between the first surface 23a and the second surface 24a, that is, the first surface 23a at the first contact portion 22 a. The first contact portion 22a is located at a boundary portion between the first surface 23a and the outer circumferential surface 30a of the coupling member 30.

Meanwhile, the retard roller 12 continuously receives the co-rotation force in the sheet conveyance direction when the driving force is input from the drive shaft 17. Therefore, the retard shaft 16 is driven by receiving resistance in a direction against the direction of the drive force transmission (i.e., resistance in the direction of the arrow D8, the direction of the arrow D8 being a rotational direction opposite to the rotational direction of the arrow D2). That is, the second pin 20b contacts the downstream side surface of the second groove portion 21b in the direction of the arrow D8, i.e., the second contact portion 22b of the third surface 23b, between the third surface 23b and the fourth surface 24 b. The second contact portion 22b is located at a boundary portion between the third surface 23b and the outer circumferential surface 30a of the coupling member 30.

If an angle formed by a first straight line L1 passing through the first contact portion 22a and the rotation center O and a second straight line L2 passing through the second contact portion 22b and the rotation center O is defined as the angle θ, the angle θ may be greater than or equal to 0 degree and less than 180 degrees. The fluctuation width of the delay pressure fluctuation (i.e., the amplitude of the composite wave) varies depending on the magnitude of the angle θ (refer to fig. 9).

Next, a change of the composite wave according to the angle θ will be described. In fig. 10 and 11, a wave C3 (a composite wave of a wave C1 representing the fluctuation of the delay pressure generated at the first connecting portion 25a and a wave C2 representing the fluctuation of the delay pressure generated at the second connecting portion 25 b) represents the final fluctuation of the delay pressure. As shown in fig. 10, if the angle θ is 0 degrees, the wave C1 and the wave C2 are in phase, that is, the wave C1 and the wave C2 become maximum and minimum at the same time. That is, in the case where θ is 0 ° shown in fig. 10, the wave C3 is a result of the waves C1 and C2 strengthening each other. When waves C1 and C2 become maximum, wave C3 takes a larger maximum, and when waves C1 and C2 become minimum, wave C3 takes a smaller maximuma minimum value. Therefore, the target value F of the retardation pressure with respect to the retardation pressure represented by the wave C3 when the waves C1 and C2 become minimum and maximum₀With a large amount of deviation.

In contrast, the retard roller 12 of the printer 100 (refer to fig. 1) is designed such that the angle θ is about 90 degrees. In the case where θ is 90 °, as shown in fig. 11, the waves C1 and C2 are opposite in phase, that is, the wave C2 becomes the smallest when the wave C1 becomes the largest, and the wave C2 becomes the largest when the wave C1 becomes the smallest. In other words, wave C3 is the result of wave C1 and wave C2 weakening each other. In the wave C3, the wave C2 becomes minimum when the wave C1 becomes maximum, and the wave C2 becomes maximum when the wave C1 becomes minimum. Therefore, the delay pressure represented by the wave C3 is generally close to the target value F₀relative to the target value F₀Is suppressed to a minimum.

As described above, the fluctuation width of the delay pressure fluctuation (hereinafter referred to as "fluctuation width") varies depending on the value of the angle θ (refer to fig. 9). Fig. 12 is a graph showing the relationship between the angle θ and the fluctuation amplitude of the retard pressure. As further detailed with reference to FIG. 12, the amplitude of the fluctuation of the retard pressure is a periodic function of the angle θ, where one period is 180 degrees. In the range of θ between-30 and 150 degrees shown in fig. 12, the fluctuation width becomes maximum when θ is 0 °, and becomes minimum when θ is 90 °. Further, a range R shown in fig. 12 indicates a range of the angle θ in which the value of the fluctuation amplitude is 5% or less with respect to the value of the fluctuation amplitude at 90 ° (position where the value of the fluctuation amplitude becomes the smallest). In other words, if the angle θ is in the range of 80 degrees or more and 100 degrees or less, i.e., 80 ° ≦ θ ≦ 100 °, the fluctuation width may be suppressed to 5% or less with respect to the minimum value.

If the fluctuation width exceeds 5% of the minimum value, the conveyance failure rate of the sheet increases, and if the fluctuation width is lower than 5% of the minimum value, the conveyance failure rate of the sheet can be suppressed. Therefore, according to the present embodiment, the first pin 20a, the second pin 20b, the first groove portion 21a, and the second groove portion 21b are arranged such that the angle θ is about 90 degrees, that is, the angle θ is 90 ° ± 10 °. This arrangement of the first pins 20a, the second pins 20b, the first groove portions 21a, and the second groove portions 21b makes it possible to sufficiently suppress fluctuations in the delay pressure and reduce conveyance failures of the sheet. Making the angle θ as close to 90 degrees as possible is effective to maximize the effect of suppressing the fluctuation of the retard pressure.

The effect of suppressing the fluctuation of the retard pressure has been described based on the angle θ formed by the first straight line L1 (refer to fig. 9) and the second straight line L2, but may also be based on the angle formed by the axis X1 and the axis X2 shown in fig. 9To describe this concept. Based on angleIf angle of the angleAbout 60 degrees, i.e. if the angle is such thatIs greater than or equal to 50 degrees and less than or equal to 70 degrees, that is,the fluctuation amplitude can be suppressed to 5% or less with respect to the minimum value. In this state, an angle formed by the center line of the first groove portion 21a and the center line of the first pin 20a in contact with the first contact portion 22a is 15 degrees, and an angle formed by the center line of the second groove portion 21b and the center line of the second pin 20b in contact with the second contact portion 22b is 15 degrees. Therefore, by arranging the first pin 20a and the second pin 20b so as to be angled in a state where the first pin 20a and the second pin 20b are engaged with the first surface 23a and the third surface 23b, respectivelyAbout 60 degrees, fluctuation of the delay pressure can be sufficiently suppressed, and conveyance failure of the sheet can be reduced. Make an angleapproaching 60 degrees as close as possible is effective to maximize the effect of suppressing fluctuations in the retard pressure.

The present invention is not limited to the above-described embodiments, and may be embodied in various forms other than the above-described examples. Various components may be omitted, replaced, or changed within the scope of the present invention. The size, materials, shape and relative arrangement of the components may be varied according to the configuration of the device or the conditions in which the invention is applied.

The above-described embodiment describes an example in which the first pin 20a (refer to fig. 4) is provided on the drive shaft 17 and the first groove portion 21a is formed on the coupling member 30, but the present invention is not limited to this example. The positional relationship of the first pin 20a and the first groove portion 21a may be reversed. That is, the first pin 20a may be provided on the coupling member 30, and the first groove portion 21a may be provided on the driving shaft 17. The same applies to the second pin 20b and the second groove portion 21 b. That is, the second pin 20b may be provided on the coupling member 30, and the second groove portion 21b may be provided on the delay shaft 16.

The above-described embodiment shows the case where the first pin 20a and the second pin 20b are cylindrical, but the present invention is not limited to this example. For example, a rib that extends in the axial direction of the drive shaft 17 and is engageable with the first groove portion 21a may be provided instead of the first pin 20 a. Further, a rib that extends in the axial direction of the delay shaft 16 and is engageable with the second groove portion 21b may be provided instead of the second pin 20 b.

The above-described embodiment also shows the case where the first groove portion 21a and the second groove portion 21b are groove shapes, but the present invention is not limited to this example. For example, the first groove portion 21a and the second groove portion 21b may be long holes extending in the second axial direction. Further, one of the first groove portion 21a and the second groove portion 21b may be a groove, and the other may be a long hole.

According to the above-described embodiment, the uppermost sheet P of the sheets P stacked inside the cassette 1 (refer to fig. 1) is fed by the feed roller 10, but the present invention is not limited to this example. The conveying roller 11 may also be used as the feed roller 10. That is, the printer 100 may be configured without the feeding roller 10 and such that the conveying roller 11 picks up the uppermost sheet P from the sheets P stacked inside the cassette 1 and conveys the sheets P toward the image forming unit 200.

according to the above-described embodiment, the printer 100 is described as an example of an image forming apparatus, but the present invention may also be applied to an inkjet type image forming apparatus in which an image is formed on a sheet by ejecting ink through nozzles.

other embodiments

while the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.