JP5867702B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus, and more particularly to an improvement in a recording material feeding method.

  2. Description of the Related Art Conventionally, there is an image forming apparatus in which the rotational speed of the outer periphery of a roller disposed between a paper feeding unit and a forming unit (transfer unit) is set to be equal to the rotational speed of the outer periphery of a photosensitive drum. Known (for example, Patent Document 1).

  Also known is an image forming apparatus that can adjust the paper speed by adjusting the rotation speed of the registration roller and, as a result, match the exposure start position of the photosensitive drum with the transfer start position of the paper. (For example, Patent Document 2).

Japanese Patent Application Laid-Open No. 09-311606 JP-A-2005-352448

  Here, as one of the methods for reducing the distance between the paper feeding unit and the forming unit (transfer unit), for example, a method of omitting the registration roller from between the paper feeding unit and the forming unit (transfer unit). Conceivable.

  However, if the registration roller is omitted, the paper feed roller of the paper feed unit realizes not only the function of feeding the recording material to the forming unit side but also the function of adjusting the timing of supplying the recording material to the transfer position. It is also required to do. As a result, there arises a problem that the accuracy of positioning between the toner image formed on the outer peripheral surface of the photosensitive drum and the recording material to be fed is lowered.

  Accordingly, an object of the present invention is to provide an image forming apparatus that can feed a recording material satisfactorily toward a forming unit.

In order to solve the above-described problems, the invention of claim 1 includes a mounting portion on which a plurality of recording materials are mounted, a photosensitive drum, and a transfer roller, and each of the plurality of recording materials includes the photosensitive member. A forming unit that transfers a toner image formed on the outer peripheral surface of the body drum, and rotating according to a driving force from a driving source, so that the uppermost layer of the plurality of recording materials mounted on the mounting unit The recording material of interest is fed to a transfer position sandwiched between the photosensitive drum and the transfer roller, and a laser beam is emitted toward the exposure position of the photosensitive drum to be rotated. The target recording material, which is provided between the exposure unit that forms an electrostatic latent image on the outer peripheral surface of the photosensitive drum, the paper feed roller, and the transfer roller, and is transported along the transport path is a detection position. Reached A detection unit for detecting whether the recording material reaches the detection unit, based on the timing at which the output value is changed is output from the detecting unit, and a control unit which makes starting the emission of the laser beam The second distance along the conveyance path of the recording material from the detection position to the transfer position is shorter than the first distance along the outer peripheral surface of the photosensitive drum from the exposure position to the transfer position. and has, wherein, a first time and taken to the photosensitive drum is rotated by said first distance, and a second time required for conveying the recording material by the second distance, the equivalent Preferably , the driving of the photosensitive drum and the paper feed roller is controlled so that the rotational speed of the photosensitive drum is larger than the conveyance speed of the recording material from the detection position to the transfer position. Do

  According to a second aspect of the present invention, in the image forming apparatus according to the first aspect of the present invention, the separation is provided so as to face the paper feed roller and separates the target recording material one by one from the plurality of recording materials. And a feeding position for feeding the recording material of interest to the forming section side by applying the driving force from the driving source and a retreating position separated from the feeding roller. And when the target recording material is fed by a unit feed amount by the paper feed roller, the separation unit moves to the paper feed roller side, and At the time before the feeding of the material is started and the time after the feeding of the recording material of interest by the unit feed amount is completed, the separation unit is separated from the paper feeding roller, The unit feed by the paper feed roller Is a third distance being greater than between the conveying path the transfer position and the sheet feeding position along the.

According to a third aspect of the present invention, in the image forming apparatus according to the second aspect of the present invention, the image forming apparatus further includes a swinging portion that swings the push-up plate by rotating according to the driving force from the driving source. The push-up plate is moved from the retracted position to the paper feed position while the swinging part makes one rotation, thereby bringing the pressed recording material into contact with the paper feed roller and the paper feed. When the recording material is moved from the position to the retracted position, the recording material other than the recording material of interest is separated from the paper feeding roller.

  According to a fourth aspect of the present invention, in the image forming apparatus according to the third aspect of the present invention, the paper feed roller is configured to be the recording material of interest while the oscillating portion is rotated once by applying the driving force. Is fed by the unit feed amount.

  Further, the invention of claim 5 is the image forming apparatus according to any one of claims 1 to 4, further comprising an advancing / retreating part for moving the transfer roller toward or away from the photosensitive drum, After the leading edge of the recording material of interest has reached the transfer position, the control unit causes the transfer roller to approach the photosensitive drum by the advance / retreat section, and causes the recording material of interest to move between the photosensitive drum and the transfer roller. It is characterized by being sandwiched between.

  According to a sixth aspect of the present invention, in the image forming apparatus according to any one of the first to fifth aspects, the toner image defect distance along the outer peripheral surface of the photosensitive drum is determined by the photosensitive drum. The length of the nip range of the recording material of interest along the outer peripheral surface of the recording medium is larger.

  According to a seventh aspect of the present invention, in the image forming apparatus according to any one of the first to sixth aspects, the paper feed roller is a rotating shaft that receives the driving force applied from the driving source. It is characterized by a gap fit.

  According to the first to seventh aspects of the present invention, the first time required to move the first distance from the exposure position to the transfer position along the outer peripheral surface of the photosensitive drum, and the conveyance path. The rotational speeds of the photosensitive drum and the paper feed roller can be set so that the second time required to move the second distance from the detection position of the detection unit to the transfer position is equivalent.

  Accordingly, even when a roller (for example, a registration roller) for adjusting the conveyance timing is not arranged between the paper feeding roller and the transfer roller, the transferred toner image is accurately placed on the recording material of interest. Can be positioned. That is, in order to accurately position the toner image with respect to the recording material of interest, it is not necessary to further provide a component such as a registration roller. Therefore, the distance between the paper feed roller and the transfer roller can be reduced, and the apparatus can be miniaturized.

  Further, by adjusting the rotation speeds of the paper feed roller and the transfer roller, the second distance can be set to be smaller than the first distance, and the length of the conveyance path can be further reduced. Therefore, the device can be further reduced in size.

  In particular, according to the second aspect of the present invention, the recording material of interest is fed to the transfer position separated by the third distance from the feeding position by the feeding operation of the unit feed amount by the feeding roller.

The separation part
When the recording material of interest is fed by the feed roller by the unit feed amount, it moves to the feed roller side,
At a time before feeding of the recording material of interest starts, and after completion of feeding the recording material of interest by the unit feed amount, the recording material is separated from the paper feed roller.

  As a result, at the time after the recording material of interest reaches the transfer position, the photosensitive drum and the transfer roller receive the recording material of interest without receiving the frictional resistance caused by being sandwiched between the paper feed roller and the separation unit. Can be transported. Therefore, the recording material can be transported satisfactorily only by the photosensitive drum and the transfer roller.

  In particular, in the invention according to claim 3, the push-up plate brings the recording material of interest into contact with the paper feed roller and feeds the recording material of interest to the forming portion side while the swinging portion makes one rotation. Subsequently, the push-up plate separates a plurality of recording materials other than the fed recording material of interest from the paper feeding roller. Thus, the recording material of interest can be easily fed to the forming portion side by one rotation of the swinging portion.

  In particular, according to the invention described in claim 4, by the same driving force applied from the same driving source, the unit feeding amount by the sheet feeding roller, the swing of the push-up plate by the swinging portion, Are executed simultaneously. That is, it is possible to realize the sheet feeding operation of the sheet feeding roller and the swinging movement of the push-up plate by a single drive source. Therefore, the number of parts required for the paper feeding operation and the swinging operation can be reduced, and the manufacturing cost of the entire apparatus can be reduced.

  In particular, according to the fifth aspect of the present invention, after the leading end of the recording material of interest reaches the transfer position, the recording material of interest can be sandwiched between the photosensitive drum and the transfer roller. For this reason, it is possible to suppress image disturbance due to the difference between the rotational speed of the outer periphery of the photosensitive drum and the conveyance speed of the recording material of interest without increasing the nip range between the photosensitive drum and the transfer roller.

  In particular, according to the sixth aspect of the invention, the missing distance of the toner image along the outer peripheral surface of the photosensitive drum is set to be larger than the nip distance of the recording material of interest along the outer peripheral surface of the photosensitive drum. Has been. Thus, when the leading edge of the recording material of interest reaches the nip range, the leading edge of the recording material of interest does not collide with the toner image formed on the outer peripheral surface of the photosensitive drum. Therefore, image disturbance in the nip range can be suppressed.

  In particular, according to the seventh aspect of the present invention, the paper feed roller is fitted in the gap with respect to the rotation shaft, and the rotation of the rotation shaft is transmitted with a delay to the paper feed roller. Similarly, when the conveyance speed of the recording material of interest fed by the paper feed roller increases and the rotation speed of the paper feed roller increases, this increase in the rotation speed of the paper feed roller is reflected behind the rotation axis. Is done.

  As a result, the recording material of interest is sandwiched between the photosensitive drum and the transfer roller whose rotational speed is faster than that of the paper feed roller, so that even if the transport speed of the recording material of interest increases, As a result, this increase is transmitted late. Therefore, image disturbance due to the difference between the rotation speed of the outer periphery of the photosensitive drum and the conveyance speed of the recording material of interest can be suppressed.

1 is a front view illustrating an example of a configuration of an image forming apparatus according to first and second embodiments of the present invention. FIG. 3 is a front view for explaining the positional relationship between a photosensitive drum and a transfer roller, and a paper feed roller in the first embodiment. It is a side perspective view which shows an example of a structure of the paper feed part in 1st and 2nd embodiment. It is a rear view which shows an example of a structure of the rocking | swiveling part vicinity in 1st and 2nd embodiment. It is a front view for demonstrating operation | movement of the isolation | separation part and the raising board in 1st and 2nd embodiment. It is a front view for demonstrating operation | movement of the isolation | separation part and the raising board in 1st and 2nd embodiment. It is a skeleton figure of the power transmission system in the paper feed unit of the first and second embodiments. It is a front perspective view for demonstrating operation | movement of the paper feed part at the time of paper feed of 1st and 2nd embodiment. It is a front perspective view for demonstrating operation | movement of the paper feed part at the time of paper feed of 1st and 2nd embodiment. It is a front perspective view for demonstrating operation | movement of the paper feed part at the time of paper feed of 1st and 2nd embodiment. 6 is a timing chart for explaining sheet feeding timing and exposure timing in the first embodiment. It is a side perspective view for demonstrating the delay amount of the paper feed roller with respect to a rotating shaft. It is a front view for demonstrating arrangement | positioning relationship with the photoconductor drum and transfer roller in 2nd Embodiment, and a paper feed roller. It is a front view for demonstrating the other example of arrangement | positioning relationship with the photoconductive drum and transfer roller in embodiment of this invention, and a paper feed roller.

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

<1. First Embodiment>
<1.1. Configuration of image forming apparatus>
FIG. 1 is a front view showing an example of the configuration of the image forming apparatus 1 according to the first embodiment of the present invention. Here, the image forming apparatus 1 prints the toner image on the recording material P by electrophotography. As shown in FIG. 1, the image forming apparatus 1 mainly includes a forming unit 10, a fixing unit 20, a paper feeding unit 30, a paper discharging unit 50, and a control unit 90. In FIG. 1 and the subsequent drawings, an XYZ orthogonal coordinate system in which the Z-axis direction is the vertical direction and the XY plane is the horizontal plane is appropriately attached as necessary.

  The forming unit 10 transfers the toner image to the recording material P. As shown in FIG. 1, it mainly includes a photosensitive drum 13, a developing unit 16, a transfer roller 18, and an exposure unit 19.

  The photosensitive drum 13 has a cylindrical shape or a columnar shape, and is disposed to face the transfer roller 18. A photoconductive film is provided on the outer peripheral surface 13 a of the photosensitive drum 13. Therefore, light is irradiated from the exposure unit 19 to the outer peripheral surface 13a of the photoconductive drum 13, and the electrostatic charge image is formed on the outer peripheral surface 13a of the photoconductive drum 13 by removing the charge of the irradiated portion. .

  The developing unit 16 supplies a developer (including toner) to the photosensitive drum 13 on which the electrostatic latent image has been formed, thereby generating a toner image based on the electrostatic latent image on the outer peripheral surface 13a of the photosensitive drum 13. Form. As shown in FIG. 1, the developing unit 16 has a developing roller 17.

  The developer supplied from the developing unit 16 to the photosensitive drum 13 may be a one-component developer that does not use a carrier, or a two-component developer that includes toner and a carrier. Also good.

  Similar to the photosensitive drum 13, the transfer roller 18 has a cylindrical shape or a columnar shape. A charge having a polarity opposite to that of the outer peripheral surface 13 a of the photosensitive drum 13 is applied to the outer peripheral surface of the transfer roller 18. Thus, when the recording material P is sandwiched between the photosensitive drum 13 and the transfer roller 18 while the photosensitive drum 13 and the transfer roller 18 are rotating, the recording material P is placed on the outer peripheral surface 13 a of the photosensitive drum 13. The formed toner image is transferred.

  The exposure unit 19 emits a laser beam 19a toward the exposure position PE (see FIG. 2) of the photosensitive drum 13 to be rotated, thereby forming an electrostatic latent image on the outer peripheral surface 13a of the photosensitive drum 13.

  The fixing unit 20 fixes the toner image transferred onto the recording material P. As shown in FIG. 1, the fixing unit 20 is disposed on the downstream side of the transfer roller 18 in the conveyance direction of the recording material P (corresponding to the arrow AR1 direction: hereinafter, also simply referred to as “conveyance direction”). .

  The paper feed unit 30 is used as a supply unit that supplies the recording material P to the forming unit 10. The detailed configuration of the paper feeding unit 30 will be described later.

  The paper discharge unit 50 is provided on the downstream side of the fixing unit 20 in the transport direction, and discharges the recording material P on which the toner image is fixed to the outside of the apparatus. As shown in FIG. 1, the paper discharge unit 50 mainly includes a paper discharge roller 51 and a paper discharge tray 52.

  As shown in FIG. 1, the control unit 90 is provided below the forming unit 10 and the fixing unit 20. The control unit 90 realizes operation control of each element of the image forming apparatus 1 and data calculation. For example, the control unit 90 receives an image signal from an external terminal (not shown), converts it into digitized image data, and controls the operations of the forming unit 10 and the paper feeding unit 30 to record the image signal. The printing process on the material P is executed.

<1.2. Configuration of paper feed unit>
FIG. 2 is a front view for explaining the positional relationship between the photosensitive drum 13 and the transfer roller 18 and the paper feed roller 32. FIG. 3 is a side perspective view illustrating an example of the configuration of the paper feeding unit 30. FIG. 4 is a rear view showing an example of the configuration in the vicinity of the swinging portion 40. 5 and 6 are front views for explaining the operation of the separating portion 33 and the push-up plate 36. FIG. FIG. 7 is a skeleton diagram of a power transmission system in the paper feeding unit 30. As shown in FIGS. 3 and 7, the paper feed unit 30 mainly includes a paper feed roller 32, a separation unit 33, a detection unit 34, a placement unit 35, a push-up plate 36, and a swinging unit 40. ,have.

  The paper feed roller 32 rotates according to the driving force from the motor 47 (see FIG. 7), thereby sandwiching a plurality of recording materials P placed on the placement unit 35 between the photosensitive drum 13 and the transfer roller 18. The paper is fed to the transfer position PT (see FIG. 2).

  As shown in FIG. 1, the detection unit 34 is provided between the paper feed roller 32 and the transfer roller 18. The detection unit 34 detects whether or not the leading end of the recording material P conveyed along the conveyance path Ra has reached the detection position PS (see FIG. 2).

  Then, the control unit 90 controls the rotation operation of the photosensitive drum 13 and the transfer roller 18 and the timing of the laser light 19a emitted from the exposure unit 19 based on the detection result of the detection unit 34.

For example, the control unit 90 opens the laser beam 19a based on the timing when the recording material P reaches the detection unit 34 and the output value output from the detection unit 34 transitions from “Low” to “High”. Let it begin.

  The separation unit 33 is provided to face the paper feed roller 32 and separates a plurality of recording materials P fed by the paper feed roller 32 one by one. The arm 33a and the urging member 33b interlock the swinging motions of the separation portion 33 and the push-up plate 36.

  Specifically, when the push-up plate 36 is at the paper feed position PF, one end of the arm 33a and the lower portion of the push-up plate 36 are separated from each other, and the separation unit 33 is urged by the urging member 33b to feed the paper. Approach the roller 32.

  On the other hand, when the push-up plate 36 is at the retracted position PL, the arm 33a and the lower portion of the push-up plate 36 are in contact with each other, and the separation unit 33 is moved downward. As a result, the separation unit 33 is separated from the paper feed roller 32.

  The placement unit 35 places a plurality of recording materials P as shown in FIG. The push-up plate 36 is supplied with a driving force from a motor 47, so that a paper feed position PF (see FIG. 5) for feeding the recording material P to the forming unit 10 side and a retreat position separated from the paper feed roller 32. It swings between PL (see FIG. 6).

  The swinging portion 40 swings the push-up plate 36 up and down by rotating according to the driving force from the motor 47. As shown in FIGS. 3 and 4, the swinging portion 40 mainly includes a one-rotation clutch 41, a plurality of cams 42 (42 a and 42 b), a locking portion 45, and a solenoid 46. .

  The one-rotation clutch 41 is a mechanical element that switches between transmission and interruption of driving force for each rotation. As shown in FIG. 3, it has the load side gear 41a and the continuous rotation gear 41b. For example, as shown in FIG. 4, a missing portion 41c having no teeth is formed on the outer periphery of the load side gear 41a.

  The locking portion 45 swings around the rotation shaft 45a in accordance with the rotational movement of the load side gear 41a and the forward / backward movement of the solenoid 46. Specifically, one end of the locking portion 45 moves along the original node portion 41d formed near the center of the load side gear 41a. The other end of the locking portion 45 is in contact with the plunger 46a of the solenoid 46 and is biased by the biasing member 46b.

  Therefore, when the original node portion 41d is engaged with the locking portion 45, the driving force from the motor 47 is interrupted in the one-rotation clutch 41, and the rotation of the cam 42 is stopped. Further, after the driving force is interrupted, the plunger 46a of the solenoid 46 is retracted, so that the engagement between the original node portion 41d and the locking portion 45 is released, and the driving force from the motor 47 is transmitted to the rotating shaft 40a. .

  The cam 42 (42a, 42b) converts the rotary motion transmitted to the rotary shafts 40a, 40b into a swing motion of the push-up plate 36. As shown in FIG. 3, docking gears 43a and 43b are formed on the outer circumferences of the cams 42a and 42b, respectively.

  The protrusions 44 (44a, 44b) are formed on the main surfaces of the corresponding cams 42 (42a, 42b). Each protrusion 44 (44a, 44b) is movable along the outer periphery of the corresponding follower 37 (37a, 37b).

  Therefore, when the cam 42 (42a, 42b) is rotated by the driving force from the motor 47, the push-up plate 36 swings about the swinging shaft 36a while being biased upward by the biasing member 36b. .

  Here, the power transmission system in the paper feeding unit 30 will be described. The drive gear 47 a is attached to the shaft center of the motor 47. As shown in FIG. 7, the drive gear 47a is meshed with each of the load side gear 41a and the continuous rotation gear 41b of the one-rotation clutch 41.

  Further, as shown in FIG. 7, the load side gear 41a and the continuous rotation gear 41b of the one-rotation clutch 41 and the docking gear 43a of the cam 42a are attached to the same rotation shaft 40a. The docking gears 38a and 38b are attached to one end and the other end of the rotation shaft 32a of the paper feed roller 32, respectively. Furthermore, the docking gear 43b of the cam 42b is attached to the rotating shaft 40b. The docking gear 38a meshes with the docking gear 43a, and the docking gear 38b meshes with the docking gear 43b.

  Therefore, the driving force from the motor 47 is transmitted to the load side gear 41a and the continuous rotation gear 41b, and the cam 42a is rotated by rotating the rotating shaft 40a. Further, when the driving force is transmitted from the docking gear 43a to the docking gear 38a and the rotating shaft 32a is rotated, the driving force is transmitted from the docking gear 38b to the docking gear 43b and the rotating shaft 40b is rotated. The cam 42b is rotated.

  That is, the driving force from the motor 47 is transmitted to the paper feed roller 32 via the swinging portion 40 and the docking gear 38a attached to the rotating shaft 32a. Therefore, the rotation of the swinging portion 40 (more specifically, the cam 42 (42a, 42b)) and the rotation of the paper feed roller 32 can be easily synchronized.

  Here, in the present embodiment, the driving force from the motor 47 is applied, and the feed roller 32 is placed on the placement unit 35 while the cam 42 (42a, 42b) of the swinging unit 40 rotates once. Among the plurality of recording materials P, the uppermost recording material (hereinafter also simply referred to as “target recording material”) is fed by a unit feed amount. As a result, by the same driving force applied from the same motor 47, the feeding of the unit feed amount by the paper feed roller 32 and the swinging of the push-up plate 36 by the swinging unit 40 are executed simultaneously. That is, the single motor 47 can realize the paper feeding operation of the paper feeding roller 32 and the swinging motion of the push-up plate 36.

  In this embodiment, the unit feed amount is the distance L3 along the conveyance path Ra between the transfer position PT of the photosensitive drum 13 and the transfer roller 18 and the paper feed position PF (FIGS. 2 and 2). 5)).

  As described above, in the present embodiment, it is not necessary to prepare a plurality of motors corresponding to each of the paper feed roller 32 and the swinging unit 40, and a separate transport roller is provided to transport the recording material P. There is no need. Therefore, the number of parts required for the paper feeding operation and the swinging operation can be reduced, and the manufacturing cost of the entire apparatus can be reduced.

<1.3. Operation of paper feed unit during paper feed>
Each of FIGS. 8 to 10 is a front perspective view for explaining the operation of the sheet feeding unit 30 during sheet feeding. Here, the feeding operation of the recording material P will be described with reference to FIGS.

  Note that, before the recording material P is fed (see FIG. 8), one end of the locking portion 45 is engaged with the original joint portion 41d (see FIG. 4), and the push-up plate 36 is And stopped at the retreat position PL (see FIG. 6). Further, the separation unit 33 is separated from the paper feed roller 32.

  First, when the plunger 46a of the solenoid 46 is retracted, the engagement between the original node portion 41d of the load side gear 41a and the locking portion 45 is released, and the driving force from the motor 47 is transmitted to the rotating shaft 40a.

  Thereby, the cam 42 (42a, 42b) is rotated, and the protrusion 44 (44a, 44b) is separated from the corresponding follower 37 (37a, 37b). Then, the push-up plate 36 is urged upward by the urging member 36b, and the push-up plate 36 is swung upward. When the push-up plate 36 is swung upward, the separating portion 33 is swung upward by the urging member 33b.

  Therefore, the recording material of interest comes into contact with the paper feed roller 32, the separation unit 33 approaches the paper feed roller 32, and the paper feed roller 32 and the separation unit 33 feed a plurality of recording materials P one by one. Yes (see FIG. 9).

  Subsequently, when the cam 42 (42a, 42b) is further rotated, the protrusion 44 (44a, 44b) re-contacts with the corresponding follower 37 (37a, 37b) (see FIG. 10). As a result, the push-up plate 36 is swung downward, and the separation portion 33 is swung downward.

  Then, at the point after the feeding of the recording material of interest by the unit feed amount is completed, the separation unit 33 is separated from the paper feed roller 32 and the rotation of the paper feed roller 32 and the swing of the push-up plate 36 are stopped. To do. Thus, the photosensitive drum 13 and the transfer roller 18 can transport the recording material P without receiving frictional resistance between the paper feed roller 32 and the separation unit 33.

  Here, in the present embodiment, the transfer roller 18 is formed of a soft material such as urethane, and the nip force between the photosensitive drum 13 and the transfer roller 18 is between the paper feed roller 32 and the separation unit 33. Less than nip force. Further, the separation unit 33 is separated from the above-described paper feed roller 32 in a state where the paper feed operation of the unit feed amount by the paper feed roller 32 is finished and the rotation of the paper feed roller 32 is stopped.

  Thereby, the photosensitive drum 13 and the transfer roller 18 can convey the recording material of interest without receiving a frictional resistance caused by being sandwiched between the paper feeding roller 32 and the separation unit 33. Therefore, the recording material of interest can also be transported satisfactorily by the photosensitive drum 13 and the transfer roller 18 having a weak nip force.

  In this way, the push-up plate 36 is moved from the retracted position PL (see FIG. 6) to the paper feeding position PF (see FIG. 5) while the cam 42 (42a, 42b) of the swinging portion 40 makes one rotation. . As a result, the pressed recording material is brought into contact with the paper feed roller 32 and fed to the forming unit 10 side.

  Further, while the cam 42 (42a, 42b) of the swinging portion 40 makes one rotation, the push-up plate 36 is moved from the paper feed position PF to the retreat position PL. As a result, among the plurality of recording materials P placed on the placement unit 35, those other than the recording material of interest are separated from the paper feed roller 32.

  In this way, the recording material of interest can be easily fed to the forming unit 10 side by one rotation of the swinging unit 40.

<1.4. Feeding and exposure timing>
FIG. 11 is a timing chart for explaining sheet feeding timing and exposure timing. FIG. 12 is a side perspective view for explaining a delay amount DL of the paper feed roller 32 with respect to the rotation shaft 32a.

  Here, with reference to FIGS. 2, 11, and 12, the feeding timing of the recording material P fed from the feeding device 30 and the exposure timing at which the photosensitive drum 13 is exposed by the laser light 19a. Explain the relationship.

  First, when a driving force is applied from the motor 47 at time t1, the paper feed roller 32 starts to rotate and the push-up plate 36 is moved to the paper feed position PF. As a result, the recording material of interest comes into contact with the paper feed roller 32 and is fed into the transport path Ra.

Then, at time t2, the tip of the target recording material reaches the detection position PS, the output value outputted from the detector 34, for example, when a transition from "Low" to "High", the photosensitive from dew optical unit 19 A laser beam 19 a is irradiated toward the outer peripheral surface 13 a of the body drum 13.

Here, as shown in FIG.
(1) Time T1 (s) required for the photosensitive drum 13 to rotate by a distance L1 (m) (first distance) between the exposure position PE and the transfer position PT along the outer peripheral surface 13a (first time) )When,
(2) Time T2 (s) (second time) required for the recording material P to be transported by a distance L2 (m) (second distance) between the detection position PS and the transfer position PT along the transport path Ra ), The photosensitive drum 13, the transfer roller 18, and the paper feed roller 32 are rotated.

  That is, when the rotation speed of the outer periphery of the photosensitive drum 13 is V1 (m / s) and the rotation speed of the outer periphery of the paper feed roller 32 is V2 (m / s), the distances L1, L2 and the rotation speeds V1, V2 This relationship can be expressed as in equation (1).

V1 = V2 × (L1 / L2) (1)
By setting the distances L1 and L2 and the rotation speeds V1 and V2 so as to satisfy the expression (1), the position of the outer toner image at the transfer position PT and the position of the recording material P can be accurately positioned. it can.

  Further, as can be seen from the equation (1), the length of the transport path Ra can be further reduced as the value of (L1 / L2) is larger. Therefore, the image forming apparatus 1 can be further downsized.

  Further, in the present embodiment, the paper feed roller 32 is fitted in a gap with respect to the rotating shaft 32 a that receives the driving force applied from the motor 47. That is, the inner diameter of the paper feed roller 32 is larger than the outer diameter of the rotating shaft 32a.

  Thereby, the rotation of the rotating shaft 32a is transmitted to the paper feed roller 32 with a delay (delayed by the delay amount DL). Similarly, when the conveyance speed of the recording material of interest fed by the paper feed roller 32 increases and the rotation speed of the paper feed roller increases, the increase in the rotation speed of the paper feed roller 32 is applied to the rotary shaft 32a. Reflected late.

  For example, when the recording material of interest reaches the transfer position PT and the recording material of interest is sandwiched between the photosensitive drum 13 and the transfer roller 18 whose rotational speed is faster than that of the paper feed roller 32, the conveyance speed of the recording material of interest increases. To do. On the other hand, the increase in the conveyance speed is transmitted to the rotating shaft 40a with a delay.

  As described above, when the paper feed roller 32 is fitted into the clearance with respect to the rotation shaft 32a, it is possible to prevent a sudden load from being applied to the rotation shaft 40a. Therefore, it is possible to suppress the occurrence of image disturbance due to the difference between the rotation speed of the outer periphery of the photosensitive drum 13 and the conveyance speed of the recording material of interest.

<1.5. Advantages of Image Forming Apparatus in Present Embodiment>
As described above, in the image forming apparatus 1 according to the present embodiment, the time T1 required to move the distance L1 from the exposure position PE to the transfer position PT along the outer peripheral surface 13a of the photosensitive drum 13, and the conveyance path. The rotational speeds of the photosensitive drum 13 and the transfer roller 18 are set so that the time T2 required to move the distance L2 from the detection position PS of the detection unit 34 to the transfer position PT along Ra is equal. The rotation speed of the paper roller 32 can be set.

  Thereby, even when a roller (for example, a registration roller) for adjusting the conveyance timing is not arranged between the paper feed roller 32 and the transfer roller 18, the transferred toner image is placed on the recording material of interest. Accurate positioning is possible. That is, in order to accurately position the toner image with respect to the recording material of interest, it is not necessary to further provide a component such as a registration roller. Therefore, the distance L3 between the paper feed roller 32 and the transfer roller 18 can be reduced, and the image forming apparatus 1 can be downsized.

  Further, by adjusting the rotation speeds of the paper feed roller 32 and the transfer roller 18, the distance L2 can be set smaller than the distance L1, and the length of the transport path Ra can be further reduced. Therefore, the image forming apparatus 1 can be further downsized.

<2. Second Embodiment>
Next, a second embodiment of the present invention will be described. The image forming apparatuses 1 and 100 of the first and second embodiments have the same configuration except that the configurations of the corresponding forming units 10 and 110 are different. Therefore, in the following, this difference will be mainly described.

  It should be noted that the same constituent elements in the image forming apparatuses 1 and 100 are denoted by the same reference numerals, and the constituent elements having the same reference numerals have been described in the first embodiment. Therefore, description is abbreviate | omitted in this Embodiment.

  FIG. 13 is a front view for explaining the arrangement relationship between the photosensitive drum 13 and the transfer roller 118 and the paper feed roller 32 in the present embodiment. The transfer roller 118 has the same configuration as the transfer roller 18, and a charge having a polarity opposite to that of the outer peripheral surface 13 a of the photosensitive drum 13 is applied to the outer peripheral surface of the transfer roller 118.

  The advance / retreat unit 125 moves the transfer roller 118 closer to or away from the photosensitive drum 13. For example, the advance / retreat unit 125 separates the transfer roller 118 from the photosensitive drum 13 at a time before the recording material P reaches the transfer position PT. On the other hand, when the recording material P reaches the transfer position PT, the advance / retreat unit 125 brings the transfer roller 118 into contact with the photosensitive drum 13.

  As a result, the control unit 90 brings the transfer roller 118 closer to the photosensitive drum 13 at a time after the leading edge of the recording material of interest has reached the transfer position PT, and causes the recording material of interest to move to the photosensitive drum 13 and the transfer roller 18. Can be sandwiched between. That is, it is possible to prevent the leading end of the recording material P from colliding with the outer peripheral surfaces of the photosensitive drum 13 and the transfer roller transfer roller 118.

  Therefore, it is possible to suppress image disturbance due to the difference between the rotational speed of the outer periphery of the photosensitive drum 13 and the conveyance speed of the recording material of interest without increasing the nip range between the photosensitive drum 13 and the transfer roller 118. .

<3. Modification>
Although the recording material P has been described as being supplied to the transfer position PT in the first embodiment, the method of supplying the recording material P to the photosensitive drum 13 and the transfer roller 18 is limited to this. Not.

  FIG. 14 is a front view for explaining another example of the arrangement relationship between the photosensitive drum 13 and the transfer roller 18 and the paper feed roller 32 in the embodiment of the present invention. As shown in FIG. 14, the recording material P is supplied to a nip range (length LN) defined by the collision position PC and the transfer position PT.

  In this case, the missing distance LL of the toner image along the outer peripheral surface 13a of the photosensitive drum 13 is set to be larger than the length LN of the nip range of the recording material of interest along the outer peripheral surface 13a of the photosensitive drum 13. May be. Thereby, even if the leading edge of the recording material of interest reaches the nip range, the leading edge of the recording material of interest does not collide with the toner image formed on the outer peripheral surface 13 a of the photosensitive drum 13. Therefore, image disturbance in the nip range can be suppressed.

DESCRIPTION OF SYMBOLS 1,100 Image forming apparatus 10,110 Forming part 13 Photoconductor drum 13a Outer peripheral surface 18, 118 Transfer roller 19 Exposure part 19a Laser beam 20 Fixing part 30 Paper feed part 32 Paper feed roller 32a Rotating shaft 32a
33 Separating section 34 Detection section 35 Placement section 36 Push-up plate 40 Oscillating section 40a, 40b Rotating shaft 47 Motor 50 Paper discharge section 90 Control section 125 Advance / retreat section 125 Noun DL Delay amount P Recording material PF Feeding position PL Retraction position PT Transfer position L1 distance (first distance)
L2 distance (second distance)

Claims (7)

(a) a placement unit for placing a plurality of recording materials;
(b) a photosensitive drum and a transfer roller, and a forming portion that transfers a toner image formed on the outer peripheral surface of the photosensitive drum to each of the plurality of recording materials;
(c) By rotating according to the driving force from the driving source, the uppermost recording material of the plurality of recording materials placed on the placement portion is sandwiched between the photosensitive drum and the transfer roller. A paper feed roller that feeds to the designated transfer position,
(d) an exposure unit that forms an electrostatic latent image on the outer peripheral surface of the photosensitive drum by emitting laser light toward the exposure position of the rotated photosensitive drum;
(e) a detection unit that is provided between the paper feed roller and the transfer roller and detects whether or not the target recording material conveyed along a conveyance path has reached a detection position;
(f) a control unit that starts emission of the laser light based on the timing at which the recording material reaches the detection unit and the output value output from the detection unit transitions;
With
The second distance along the conveyance path of the recording material from the detection position to the transfer position is shorter than the first distance along the outer peripheral surface of the photosensitive drum from the exposure position to the transfer position. And
The controller is
The photosensitive member and the first time the drum is required to rotate only the first distance, prior Symbol a second time requiring the recording material to carry only the second distance, the order to equal, the photosensitive drum The image forming apparatus controls the drive of the photosensitive drum and the paper feed roller so that the rotation speed of the photosensitive drum is higher than the conveyance speed of the recording material from the detection position to the transfer position . The image forming apparatus according to claim 1.
(g) a separation unit that is provided facing the paper feed roller and separates the recording material of interest from the plurality of recording materials one by one;
(h) By applying the driving force from the driving source,
A paper feeding position for feeding the recording material of interest to the forming unit;
A retreat position separated from the paper feed roller;
A push-up plate that swings between
Further comprising
When the recording material of interest is fed by a unit feed amount by the paper feed roller, the separation unit moves to the paper feed roller side,
At the time before the feeding of the recording material of interest starts, and the time after the feeding of the recording material of interest by the unit feed amount is completed, the separation unit is separated from the paper feeding roller. And
The image forming apparatus according to claim 1, wherein the unit feed amount by the paper feed roller is larger than a third distance between the transfer position and the paper feed position along the transport path. The image forming apparatus according to claim 2 .
(i) a swinging part that swings the push-up plate by rotating according to the driving force from the drive source;
Further comprising
While the push-up plate rotates the swinging part once,
As the recording material pushed up is brought into contact with the paper feed roller by being moved from the retracted position to the paper feed position,
An image forming apparatus characterized in that, by being moved from the paper feed position to the retreat position, a plurality of recording materials other than the recording material of interest are separated from the paper feed roller. The image forming apparatus according to claim 3.
While the swinging portion makes one rotation by applying the driving force,
The image forming apparatus, wherein the sheet feeding roller feeds the recording material of interest by the unit feeding amount. 5. The image forming apparatus according to claim 1, wherein:
(j) an advancing / retreating part for moving the transfer roller toward or away from the photosensitive drum;
Further comprising
After the leading edge of the recording material of interest has reached the transfer position, the control unit causes the transfer roller to approach the photosensitive drum by the advance / retreat section, and causes the recording material of interest to move between the photosensitive drum and the transfer roller. An image forming apparatus sandwiched between the image forming apparatuses. The image forming apparatus according to claim 1, wherein:
2. An image forming apparatus according to claim 1, wherein a missing distance of the toner image along the outer peripheral surface of the photosensitive drum is larger than a length of a nip range of the recording material of interest along the outer peripheral surface of the photosensitive drum. The image forming apparatus according to any one of claims 1 to 6,
The image forming apparatus, wherein the paper feed roller is fitted in a gap with respect to a rotating shaft that receives the driving force applied from the driving source.

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