JP2019189377A - Image forming apparatus - Google Patents

Abstract

To provide an image forming apparatus capable of simultaneously reducing a risk of malfunction due to an impact of a sheet cassette being pushed into a housing and improving operability of the sheet feed cassette.SOLUTION: A draw-in part (400) applies a force (FP) to a sheet feed cassette (11) in a housing in a direction of drawing to a sheet feed position (Xf). A driving member (601) can be displaced by a driving force of an actuator (600) installed in the housing. A driven member (244) can contact the driving member when the sheet feeding cassette is pushed into the housing and interlocked with a movable member (245) in the sheet feed cassette. An elastic member (602) applies forces (F1-F3) toward the other side of one of the driving member and the driven member. The driving member collides with the driven member at a first position (buffer position) and is moved to a second position (connection position) by the driving force of the actuator after the sheet feed cassette is stopped. At the first position, a force of the elastic member is stronger than a force of the draw-in part and is weaker after moving to the second position.SELECTED DRAWING: Figure 7

Description

  The present invention relates to a paper feed mechanism of an image forming apparatus, and more particularly, to a paper feed cassette positioning mechanism.

  “Feeding mechanism” refers to a mechanism that automatically feeds a sheet to a machine that processes the sheet, such as a printer, a copier, a scanner, a facsimile machine, or a finisher. And a pair of separating members. The paper feed cassette is a rectangular parallelepiped box that is housed in a housing of the image forming apparatus so as to be drawable, and generally has an open top surface and can stack sheets therein. The pair of the paper feed roller and the separating member forms a nip above the paper feed cassette. The sheet feeding roller rotates in contact with the leading edge of the sheet in the sheet feeding cassette, thereby feeding the sheet from the nip into the image forming apparatus. The separation member is a pad or a roller, and prevents the next sheet from being fed (multi-feed) by applying a frictional force to the back surface of the sheet passing through the nip.

  The sheet feeding mechanism is roughly classified into a type using a pickup roller and a type using a push-up mechanism when a sheet in a sheet feeding cassette is brought into contact with a sheet feeding roller. The pickup roller is a conveyance roller that is movable in the vertical direction, and is pressed against the upper surface of the sheet in the sheet feeding cassette from above and rotates to move the sheet to the sheet feeding roller. The push-up mechanism is a mechanism that raises and lowers at least a part of a sheet tray (hereinafter, referred to as “tray”) included in the sheet feeding cassette. By raising the tray, the leading end of the sheet on the tray is moved to the sheet feeding roller. Contact from below.

  In any type of paper feed mechanism, it is important to bring the sheet in the paper feed cassette into contact with the paper feed roller in the correct position and posture in order to improve the reliability. In order to accurately position the paper feed cassette with respect to the paper feed roller, the paper feed mechanism is generally provided with a drawing portion (see, for example, Patent Documents 1-5). The pull-in unit is coupled to the paper feed cassette when the paper feed cassette is pushed into the housing of the image forming apparatus, and applies a force in the direction of drawing to the paper feed position. The “paper feeding position” is a position where the paper feeding cassette should be stationary during the operation of the paper feeding roller, and particularly means a position in the sliding direction of the paper feeding cassette. Since the force of the user who pushes in the paper feed cassette is supplemented by the force of the pull-in portion, the paper feed cassette reaches the correct position even if a large number of sheets are stored. Thus, the operability of the paper feed cassette is improved. Furthermore, since the user does not need to accelerate the paper cassette excessively, the impact of the paper cassette on the housing of the image forming apparatus is reduced.

  As a drawing-in part, for example, an active type using an actuator such as a solenoid (for example, see Patent Documents 1 and 2) and a passive type using an elastic member such as a toggle spring (for example, see Patent Documents 3-5). Is known. A passive type in which a shock absorber (damper) is further incorporated is also known (see, for example, Patent Documents 4 and 5). The damper absorbs the force received by the drawing unit from the paper feed cassette when the paper feed cassette is pushed into the housing of the image forming apparatus. As a result, the speed of the paper feed cassette is suppressed, so that not only the positioning accuracy is improved, but also a defect caused by a collision with the housing, for example, a collapse of a sheet bundle, or between the paper feed cassette and the housing. Damage to the binding site is prevented.

JP 2005-178925 A JP 2005-263417 A JP 2006-151687 A JP 2011-037629 A JP 2012-148868 A

  Since the active pull-in unit requires a dedicated actuator and its control system, it is difficult to further reduce the manufacturing cost of the image forming apparatus. In this respect, the lead-in portion is preferably a passive type. However, it is difficult for the passive type to achieve both buffer performance and operability. In fact, the higher the performance of the damper, the more difficult the paper cassette is accelerated, and the impact of the paper cassette on the image forming device's housing is suppressed. Low risk. On the other hand, the pull-in force required to move the paper cassette to the paper feed position against the resistance of the damper is strong, so the user's power required to pull out the paper cassette against that force Tends to be excessive. Therefore, it is difficult to further improve the operability of the paper feed cassette.

  An object of the present invention is to solve the above-described problems, and in particular, further reduce the risk of malfunction due to the impact of the paper feed cassette that is pushed into the housing, and further improve the operability of the paper feed cassette. An object of the present invention is to provide an image forming apparatus capable of achieving both of the above.

  An image forming apparatus according to one aspect of the present invention takes a sheet from a paper feed cassette accommodated in a housing so as to be drawable, and forms an image on the sheet. The image forming apparatus is installed in the casing, and a drawing portion that couples with the paper feeding cassette when the paper feeding cassette is pushed into the casing and applies a force to the paper feeding cassette in the direction of drawing into the paper feeding position. The actuator, a drive member that can be displaced by the driving force of the actuator, and a drive member that is movable in the paper cassette so that the paper feed cassette can come into contact with the drive member when the paper cassette is pushed into the housing. A driven member that can be interlocked with the member, and an elastic member that applies a force toward the other to one of the drive member and the driven member. When the paper feeding cassette is pushed into the housing, the driving member collides with the driven member at the first position, and when the paper feeding cassette stops due to the collision, the driving member remains in contact with the driven member while driving the actuator. To move to the second position. While the driving member is in contact with the driven member at the first position, the force of the elastic member acting on the paper feed cassette in the sliding direction of the paper feed cassette is stronger than the force of the pull-in portion and moved to the second position. The shape of the contact portion between the driving member and the driven member is designed so as to be weak thereafter.

  In the second position, the driving member may be coupled to the driven member so that the driven member can be interlocked with the driving force of the actuator. Both the driving member and the driven member are rotating shafts, and may extend on the same straight line parallel to the sliding direction of the sheet feeding cassette. One of the drive member and the driven member includes a convex portion at an end portion that is a contact portion with the other, and the other is at an end portion that is a contact portion with the other, and a rotation angle with respect to one is within an allowable range. You may include the recessed part which a convex part can fit. The rotation angle of the drive member relative to the driven member may be out of the allowable range while the drive member is in contact with the driven member at the first position, and may be within the predetermined range after moving to the second position. The driving force transmitted to the driven member by the driving member does not substantially include a component in the sliding direction of the paper cassette when the driving member rotates forward with respect to the driven member, and the driving force of the paper feeding cassette when the driving member rotates reversely. The inner surface of the concave portion and the outer surface of the convex portion may be formed so as to include a component that keeps the driven member away in the sliding direction.

  The position where the sheet feeding cassette stops when the driving member collides with the driven member at the first position may be outside the sheet feeding position. The movable member in the paper feed cassette may be a push-up plate that pushes up the leading edge of the sheet from below. The drive member may be moved to the first position by the drive force of the actuator after the paper feed cassette is pulled out from the housing and the driven member is separated from the drive member. When the driving member collides with the driven member at the first position, when the deformation amount of the elastic member reaches a threshold value, the image forming apparatus fixes the elastic member to prevent further deformation, and receives a driving force from the actuator. A lock mechanism for releasing the elastic member may be further provided. The pull-in portion may include a shock absorber that absorbs a force received from the paper feed cassette when the paper feed cassette is pushed into the housing.

  In the image forming apparatus according to one aspect of the present invention, as described above, when the sheet feeding cassette is pushed into the housing, the driving member collides with the driven member at the first position. While the drive member is in contact with the driven member at the first position, the force of the elastic member acting on the paper feed cassette in the sliding direction of the paper feed cassette is stronger than the force of the retracting portion. Thereby, the impact of the sheet feeding cassette is mainly absorbed by the elastic member, not the drawing-in part. When the paper feeding cassette is stopped, the driving member moves to the second position by the driving force of the actuator while keeping contact with the driven member. After the drive member has moved to the second position, the force of the elastic member acting on the paper feed cassette in the sliding direction of the paper feed cassette is weaker than the force of the retracting portion. Thereby, the drawing-in part can make the paper feed cassette reach the paper feed position. Further, since the force required to pull out the paper cassette from the housing is determined by the force of the drawing-in part, it can be set independently of the force of the elastic member required for buffering the paper cassette. In this way, this image forming apparatus can achieve both a further reduction in the risk of malfunction due to the impact of the paper feed cassette that is pushed into the housing and a further improvement in the operability of the paper feed cassette.

FIG. 2A is a perspective view illustrating an external appearance of a multifunction peripheral according to an embodiment of the present invention. FIG. 2B is a front view schematically illustrating an internal structure of a printer included in the multifunction peripheral. (A), (b) is a perspective view which respectively shows the external appearance of the paper feed cassette seen from the upper direction and the downward direction. (A), (b) is a perspective view which shows the external appearance seen from the right front and the left front of the lower part which accommodates a paper feeding cassette among the chassis of a multifunctional device, respectively. (A) is an expansion perspective view of the range which (b) of Drawing 3 shows with a dashed-dotted line. (B), (c) is the perspective view and left view of a drawing-in part, respectively. (A) is a perspective view showing the appearance of the vicinity of the paper feeding side surface of the paper feeding cassette as seen from the rear. (B) is a schematic diagram which shows the structure of the raising mechanism with respect to a tray. (A), (b) is a perspective view which shows the external appearance which can each be seen from back and the downward direction of the connection part between the driven shaft of a paper feed cassette, and a raising / lowering motor. (C), (d) is a perspective view which shows the relationship between the connection end of a driven shaft and the rotation angle of the shaft of a raising / lowering motor. (E) is a top view of a lifting motor. (A)-(d) is a top view which shows typically operation | movement of a drawing-in part and a raising / lowering motor at the time of a paper feeding cassette being pushed in in the housing | casing of a printer. It is a block diagram which shows the structure of the electronic control system of a multifunctional machine. 6 is a timing chart showing control when a paper feed cassette is pushed into a housing of the printer and when it is pulled out from the housing. (A), (b) is a perspective view which shows the modification of the groove | channel of the shaft of a raising / lowering motor. (C), (d) is a schematic right side view showing the force that the groove applies to the pin at the connecting end of the driven shaft when the rotation of the shaft shown in (a) is normal rotation and reverse rotation, respectively. FIG. 11 is a timing chart showing control on a lifting motor including a groove shown in FIG. 10 when a paper feeding cassette is pushed into a housing of the printer and pulled out from the housing.

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

[Appearance of image forming apparatus]
FIG. 1A is a perspective view showing an appearance of an image forming apparatus according to an embodiment of the present invention. This image forming apparatus is a multi-function peripheral (MFP) 100 and has functions of a scanner, a copier, and a printer. An automatic document feeder (ADF) 110 is mounted on the upper surface of the casing of the MFP 100 so as to be openable and closable. A scanner 120 is built in the upper part of the casing located directly under the ADF 110, and a printer 130 is built in the lower part of the casing. In the main body of the printer 130, the paper feed cassette 11 is housed so as to be drawable.

  MFP 100 is an in-body discharge type. In other words, a paper discharge tray 44 is installed in the gap DSP between the scanner 120 and the printer 130, and sheets discharged from a paper discharge outlet (not shown) are stacked on the paper discharge tray 44. Is done. An operation panel 160 is attached to the front portion of the housing located beside the gap DSP. A touch panel is embedded in the front surface of the operation panel 160, and various mechanical push buttons are arranged around the touch panel.

[Printer structure]
FIG. 1B is a front view schematically showing the internal structure of the printer 130. In this figure, the elements of the printer 130 are depicted as if they were seen through the front of the housing. The printer 130 is an electrophotographic color printer, and includes a feeding unit 10, an image forming unit 20, a fixing unit 30, and a paper discharge unit 40. These functional units 10-40 cooperate to form an image on the sheet based on the image data while conveying the sheet within the housing of the printer 130.

  The feeding unit 10 is a paper feed mechanism mounted on the MFP 100, and a bundle of sheets SHT stored in the paper feed cassette 11 or the manual feed tray 16 using the transport roller groups 12F, 12R, 13, 15F, and 15R. The sheets are separated one by one and fed to the image forming unit 20. The paper feed cassette 11 is a so-called universal type and can accommodate a wide variety of sheets. The sheet material that can be stored includes paper and resin, and the paper types include plain paper, high-quality paper, color paper, and coated paper. The sheet size can be changed continuously both vertically and horizontally, and the range includes standard sizes defined by JIS standards such as A3 to A7 and B4 to B7, business cards, bookmarks, tickets, postcards, envelopes, and photographs. (L version) is included. The posture of the seat can be set either vertically or horizontally.

  The image forming unit 20 is, for example, an intermediate transfer tandem type, and forms a toner image on the sheet SH2 fed from the feeding unit 10. Specifically, first, the four image forming units 21Y, 21M, 21C, and 21K charge the surfaces of the photosensitive drums 25Y, 25M, 25C, and 25K, respectively, and are irradiated from the optical scanning unit 26. Exposure is performed with a different one of the laser beams. Each laser beam is modulated with image data of one different color among, for example, yellow (Y), magenta (M), cyan (C), and black (K). In this way, different monochromatic electrostatic latent images are created one by one on the charged portions of the photosensitive drums 25Y-25K. Next, the image forming units 21Y-21K develop their electrostatic latent images with toner colored in any one of Y, M, C, and K. Four single color toner images appearing on the surface of the photosensitive drums 25Y-25K are generated from the surface of the photosensitive drums 25Y-25K by the electric field between the primary transfer rollers 22Y, 22M, 22C, 22K and the photosensitive drums 25Y-25K. The images are sequentially transferred to the same position on the surface of the intermediate transfer belt 23. Thus, one color toner image is formed at that position. When the color toner image passes through the nip between the driving roller 23R and the secondary transfer roller 24 of the intermediate transfer belt 23, the sheet is simultaneously fed to the same nip by the electric field between the rollers 23R and 24. Transferred to the surface of SH2. The sheet SH <b> 2 is peeled off from the secondary transfer roller 24 and then sent out to the fixing unit 30.

  The fixing unit 30 heat-fixes the toner image on the sheet SH2 sent out from the image forming unit 20. Specifically, while the sheet SH2 is passed through the nip between the fixing roller 31 and the pressure roller 32, the fixing roller 31 applies heat from a built-in heater to the surface of the sheet SH2, and the pressure roller 32 applies pressure. The toner image is fixed on the surface of the sheet SH <b> 2 by the heat from the fixing roller 31 and the pressure from the pressure roller 32. Thereafter, the fixing unit 30 sends out the sheet SH2 from above.

  The paper discharge unit 40 discharges the sheet SH3 sent from the fixing unit 30 from the paper discharge port 42 by the paper discharge roller 43 and places it on the paper discharge tray 44.

[Paper cassette structure]
2A and 2B are perspective views showing the appearance of the paper feed cassette 11 that can be seen from above and below, respectively. The paper feed cassette 11 includes a main body 210, a tray (tray) 220, and an alignment plate 231-233.

  The main body 210 is a rectangular parallelepiped box, and the upper surface is opened. A front surface 211 (a surface located on the positive side of the X axis in the drawing) of the main body 210 forms a part of the front surface of the printer 130 when the paper feed cassette 11 is housed in the housing of the printer 130. The side surfaces 213 and 214 of the main body 210 extend from the front surface 211 in a direction in which the paper feed cassette 11 is pushed into the housing of the printer 130 (in the negative direction of the X axis in the figure). In a state where the paper feed cassette 11 is housed in the housing of the printer 130, one side 213 (positioned on the positive side of the Y axis in the figure, hereinafter referred to as “paper feed side”) is the upper end of the sheet conveyance. It is close to the starting end of the path, that is, the pair of the paper feed roller 12F and the separating roller 12R shown in FIG. End portions of the side surfaces 213 and 214 located on the opposite side of the front surface 211 include arm portions 217 and 218 that protrude rearward (in the drawing, in the negative direction of the X axis) from the back surface 215 of the main body 210. In particular, a thin pin 219 extends from the tip of the arm portion 217 of the paper feeding side surface 213 in the direction of the other arm portion 218 (the negative direction of the Y axis).

  The tray 220 is a thin plate member made of metal or hard resin having a substantially rectangular shape, and is placed on the bottom surface 216 of the main body 210 in parallel, and is fed in the paper feeding direction (sliding direction (X The sheet extends from the central portion in the horizontal direction (Y-axis direction) perpendicular to the axial direction) to the sheet feeding side surface 213. At the center portion of the bottom surface 216, the tray 220 is supported so as to be swingable around one side located there. By this swinging, the inclination angle of the tray 220 in the paper feeding direction (Y-axis direction) is variable. As shown in FIG. 2A by a two-dot chain line, a bundle of sheets SHT can be stacked on the tray 220. When the tray 220 is inclined, one side of the bundle SHT near the sheet feeding side surface 213 (hereinafter referred to as “tip”) is pushed up. The inclination angle of the tray 220 is controlled so that the leading edge of the uppermost sheet of the bundle SHT comes into contact with the paper feed roller 12F shown in FIG. 1B (details will be described later).

  Three alignment plates 231-233 surround three sides of the tray 220 on the bottom surface 216 of the main body 210. The first alignment plate 231 is located on the opposite side of the tray 220 from the sheet feeding side surface 213 and is supported on the bottom surface 216 of the main body 210 so as to be manually displaceable in the sheet feeding direction (Y-axis direction). . The first alignment plate 231 contacts the rear end of the sheet bundle SHT stacked on the tray 220 in the sheet feeding direction (Y-axis direction), and aligns the bundle SHT in the sheet feeding direction. The second alignment plate 232 and the third alignment plate 233 have the same shape and size, and are arranged one on each side of the tray 220 in the sliding direction (X-axis direction) of the paper feed cassette 11. Each of the second alignment plate 232 and the third alignment plate 233 rises from the bottom surface 216 of the main body 210 in the vertical direction (the positive direction of the Z axis) and extends in parallel to the paper feeding direction (Y axis direction). ing. Both the second alignment plate 232 and the third alignment plate 233 can be manually displaced on the tray 220 along the side surfaces 213 and 214 of the main body 210 (in the X-axis direction). It is supported by. The aligning plates 232 and 233 sandwich the bundle SHT of sheets stacked on the tray 220 from both sides in the longitudinal direction (X-axis direction) of the side surfaces 213 and 214 of the main body 210, and the bundle SHT is the longitudinal length of the side surfaces 213 and 214. Align in direction.

[Support structure of paper cassette]
FIGS. 3A and 3B are perspective views showing the appearance of the lower part of the chassis 300 of the MFP 100 that accommodates the paper feed cassette 11 as seen from the right front and the left front, respectively. The chassis 300 is a metal framework that supports the casing of the MFP 100 from the inside. The lower part shown in FIG. 3 of the chassis 300 is closed on both the left and right sides, the rear side, and the lower side with plate members 301-303 made of metal or hard resin, and a large cavity is formed inside (in the figure, The right side plate is removed so that the inside can be seen.) This cavity is used as a storage space for the paper feed cassette 11. The same number of rails 310 as the paper feed cassettes 11 are provided on the inner surfaces of the left and right side plates 301 and extend in the front-rear direction (X-axis direction in the figure). The right rail 311 has a lower end on the inner surface protruding inward to form a sliding surface 313, on which the lower end of the paper feeding side surface 213 of the paper feeding cassette 11 can slide along the longitudinal direction of the rail 311. Can be placed. On the upper surface of the left rail 312, the lower end of the left side surface 214 of the sheet cassette 11 is slidably mounted along the longitudinal direction of the rail 311. In the back plate 302 of the chassis 300, one through hole 304, 305 is opened near each rear end of the rails 311, 312. The arm portions 217 and 218 of the side surfaces 213 and 214 of the paper feed cassette 11 are inserted into the holes 304 and 305 when the paper feed cassette 11 is accommodated in the housing of the printer 130.

[Retraction part]
FIG. 4A is an enlarged perspective view of a range indicated by a one-dot chain line in FIG. In this figure, a part of the back plate 302 of the chassis 300 is removed, and the structure behind it can be seen. One retracting portion 400 is fixed near each rear end of the right rail 311 on the back surface of the back plate 302. The lead-in part 400 is a rectangular parallelepiped member that is long in the longitudinal direction of the rail 311 (X-axis direction in the figure), and the front end of the rail 311 protrudes ahead of the back plate 302 through the through hole 304 of the back plate 302. .

  FIGS. 4B and 4C are a perspective view and a left side view of the retracting portion 400, respectively. In FIG. 4C, the elements inside the lead-in portion 400 are depicted as if the left side surface of the housing 401 is seen through. The retracting unit 400 includes a sliding member 402, a rotary damper 403, and a coil spring 404 in the housing 401. The housing 401 is a rectangular plate-like housing that is long in one direction (X-axis direction in the figure), and is, for example, a resin molded product. A slit 411 in the longitudinal direction (X axis direction) is formed in one of the surfaces (upper surface in the figure) parallel to the longitudinal direction (X axis direction) and the thickness direction (Y axis direction in the figure) of the housing 401. A guide hole 412 in the longitudinal direction (X-axis direction) having a symmetrical shape is formed in the plate surface. The sliding member 402 is a small and thin resin piece having a uniform thickness (width in the Y-axis direction). From one side of the curved surface that spreads in the thickness direction (Y-axis direction) of the sliding member 402, the claw 421 projects outward (in the figure, the positive direction of the Z-axis), and on the opposite side, the rack gear 422 extends in the longitudinal direction (X-axis direction). ). Two pins 423 and 424 protrude from the flat surface of the sliding member 402 in the normal direction (Y-axis direction). The sliding member 402 is accommodated in the housing 401 in such a posture that the claw 421 protrudes outside from the slit 411 of the housing 401 and the pins 423 and 424 are fitted in the guide holes 412 of the housing 401, and the longitudinal direction is maintained. It can slide in the direction (X-axis direction). The rotary damper 403 includes a low-profile cylindrical container in which a highly viscous fluid such as silicon oil is confined, a shaft 431 and a toothless gear 432 that are coaxially and rotatably attached to the container. The rotary damper 403 is fixed in the housing 401 at a position where the toothless gear 432 can mesh with the rack gear 422 of the sliding member 402. When the missing gear 432 receives torque from the rack gear 422 as the sliding member 402 slides in the longitudinal direction (X-axis direction), the shaft 431 stirs the fluid in the rotary damper 403. Due to the high viscosity of the fluid, part of the energy received by the toothless gear 432 is dissipated to the outside as frictional heat. One end of the coil spring 404 is fixed in the housing 401, and the other end is fixed to the sliding member 402. In the longitudinal direction (X-axis direction) of the housing 401, the coil spring 404 is moved away from the predetermined position (the position indicated by the solid line in FIG. 4C). Since the elongation is long, the resilience is strong. When the sliding member 402 reaches the position farthest from the retracting end (the position indicated by the two-dot chain line in FIG. 4C, hereinafter referred to as “the retracting start end”), the front side of the sliding member 402 is reached. Since the pin 423 is hooked on the bent end 413 of the guide hole 412 of the housing 401 and the sliding member 402 stops, the extension of the coil spring 404 is fixed.

  Using these elements, the pull-in unit 400 is coupled to the arm portion 217 of the sheet feeding side surface 213 of the sheet feeding cassette 11 when the sheet feeding cassette 11 is pushed into the housing of the printer 130 as follows. A force is applied to the paper cassette 11 in the direction in which the paper cassette 11 is pulled into the paper feeding position. First, the pull-in portion 400 is arranged so that the track of the claw 421 of the sliding member 402 overlaps the track of the pin 219 of the arm portion 217 of the paper feed cassette 11. When the paper feed cassette 11 is pushed into the housing of the printer 130, the pin 219 of the arm portion 217 collides with the claw 421 of the sliding member 402 that is stationary at the drawing start end. Due to this impact, the sliding member 402 swings about the rear pin 424, so the front pin 423 is disengaged from the bent end 413 of the guide hole 412 of the housing 401, and the paper feed cassette 11 is inserted into the gap 425 of the claw 421. The pin 219 of the arm portion 217 is sandwiched. Thus, the sliding member 402 is coupled to the arm portion 217 of the paper feed cassette 11 and transmits the restoring force of the coil spring 404. As a result, the paper feed cassette 11 is pulled back (in the negative direction of the X axis) together with the sliding member 402. While the sliding member 402 moves rearward together with the paper feed cassette 11, the toothless gear 432 of the rotary damper 403 rotates while meshing with the rack gear 422, so a part of the kinetic energy of the paper feed cassette 11 is part of the rotary damper 403. To be absorbed. Thereby, the speed of the paper feed cassette 11 is suppressed. The pull-in portion 400 is designed so that the paper feed cassette 11 reaches the paper feed position when the sliding member 402 moves to the pull-in end.

[Tray lifting mechanism]
FIG. 5A is a perspective view showing the appearance of the vicinity of the paper feeding side surface 213 of the paper feeding cassette 11 seen from the rear. In this figure, the back surface 215 and bottom surface 216 of the main body 210 of the paper feed cassette 11, the second alignment plate 232, and a part of the tray 220 are removed, and the push-up mechanism hidden behind them can be seen. FIG. 5B is a schematic diagram showing the structure of the push-up mechanism for the tray 220. In this figure, the main body 210 of the paper feed cassette 11 is simplified to a rectangular parallelepiped (deformed), and only the tray 220 and the elements 244 to 246 of the push-up mechanism are simplified.

  One side of the rear end of the tray 220 is connected to the bottom surface 216 of the main body 210 so as to be able to swing around the tray 220. A push-up mechanism is installed immediately below the tray 220. The push-up mechanism is a mechanism (mechanism) that changes the inclination angle of the tray 220 with respect to the paper feeding direction (Y-axis direction), and includes a driven shaft 244 and a push-up plate 245. The driven shaft 244 is a rod-shaped member that extends in the sliding direction (X-axis direction) of the paper feed cassette 11 between the bottom surface 216 of the main body 210 and the tray 220, and both ends are connected to the back surface 215 and the bottom surface 216 of the main body 210. Is supported rotatably. One end of the driven shaft 244 protrudes backward through the back surface 215, and the tip of the driven shaft 244 is penetrated by a pin 246 perpendicular to the axial direction (hereinafter, the combination of the one end and the pin is referred to as a “connecting end”). The other end of the driven shaft 244 is fixed to the push-up plate 245. The push-up plate 245 is a thin plate member made of metal or hard resin that is substantially rectangular, has a smaller area than the tray 220, and is parallel to the gap between the bottom surface 216 of the main body 210 and the tray 220. Has been placed. Since the rear end of the push-up plate 245 in the paper feeding direction (X-axis direction) is connected to the other end of the driven shaft 244, the push-up plate 245 swings around the driven shaft 244 in conjunction with the rotation of the driven shaft 244. It is possible to move. In particular, since the push-up plate 245 is connected to the driven shaft 244 so as to be parallel to the pin of the connecting end 246 of the driven shaft 244, the inclination angle of the push-up plate 245 is relative to the horizontal direction of the pin of the connecting end 246 of the driven shaft 244. Equal to tilt angle. In FIG. 5, the inclination angle of the push-up plate 245 increases when the rotation of the coupling end 246 of the driven shaft 244 is clockwise, and decreases when the rotation is counterclockwise. Hereinafter, the rotation of the driven shaft 244 that increases the inclination angle of the push-up plate 245 is referred to as “forward rotation”, and the rotation that decreases is referred to as “reverse rotation”. When the push-up plate 245 increases the inclination angle, the tip of the push-up plate 245 pushes up the tray 220 from below (see the two-dot chain line in FIG. 5B). As a result, the sheet bundle SHT stacked on the tray 220 is applied with a force in the direction (Z-axis positive direction) in which the leading end in the sheet feeding direction (X-axis direction) approaches the sheet feeding roller 12F. The top sheet of the SHT is pressed against the paper feed roller 12F.

[Actuator and power transmission mechanism for push-up mechanism]
6A and 6B are perspective views showing the external appearance of the connecting portion between the driven shaft 244 of the paper feed cassette 11 and the lifting motor 600 as seen from the rear and the bottom. A drive shaft (shaft) 601 of the elevating motor 600 is disposed coaxially with the driven shaft 244 on the locus followed by the connecting end 246 of the driven shaft 244 as the paper feed cassette 11 slides. When the paper feed cassette 11 is pushed into the housing of the printer 130, the connecting end 246 of the driven shaft 244 contacts the shaft 601 of the lifting motor 600. The elevating motor 600 includes, for example, a stepping motor or a brushless direct current (BLDC) motor as a drive source, and rotates a shaft 601 connected to the drive source with a built-in gear (not shown) around a central axis. In particular, the shaft 601 can rotate in both forward and reverse directions. By rotating the connection end 246 of the driven shaft 244 following the rotation of the shaft 601, the lifting motor 600 functions as an actuator that supplies the tray 200 with a driving force required to push up the sheet bundle SHT. As shown in FIG. 3, one lift motor 600 is fixed to the back surface (the negative surface of the X axis) of the back plate 302 of the chassis 300 of the printer 130, one for each sheet feeding cassette 11. The shaft 601 of the lifting / lowering motor 600 protrudes forward (in the positive direction of the X axis) from the back plate 302 through a through hole 306 formed in the back plate 302.

  6C and 6D are perspective views showing the relationship between the connecting end 246 of the driven shaft 244 and the rotation angle of the shaft 601 of the lifting motor 600, and FIG. 6E is a perspective view of the lifting motor 600. It is a top view. In FIG. 6E, the elastic member 602 built in the lifting motor 600 is depicted as if the side of the shaft 601 is seen through. As shown in these drawings, the shaft 601 has a cylindrical shape, and has an outer diameter substantially equal to the entire width of the connecting end 246 of the driven shaft 244 and an inner diameter larger than the driven shaft 244. As shown in FIG. 6E, the base end of the shaft 601 is connected to the main body of the elevating motor 600 by an elastic member, for example, a coil spring 602, and the shaft 601 can be displaced in the axial direction due to its elasticity. The tip end of the shaft 601 (the contact portion with the driven shaft 244) is an open end, and a radial groove 603 is carved at 90 ° intervals around the central axis at the edge. The width of the groove 603 (inner method in the circumferential direction) is equal to or greater than the outer diameter of the pin of the connecting end 246 of the driven shaft 244. When the groove 603 of the shaft 601 rotates about 45 degrees around the central axis with respect to the pin 246, the pin 246 does not fit into any groove 603 as shown in FIG. , It contacts the tip surface 604 of the shaft 601. The rotation angle of the shaft 601 at this time is hereinafter referred to as a “buffer position” of the shaft 601. When the shaft 601 is stationary at the buffer position, the impact received by the tip surface 604 from the pin 246 is absorbed by the elastic member 602 of the lifting motor 600. On the other hand, when the rotation angle of any of the grooves 603 with respect to the pin 246 falls within an allowable range centered on 0 degree, the force of the elastic member 602 of the lift motor 600 causes the force as shown in FIG. The pin 246 fits in the groove 603 and the groove on the opposite side. The rotation angle of the shaft 601 in this case is hereinafter referred to as a “connection position” of the shaft 601. When the lifting / lowering motor 600 continues to rotate the shaft 601, the pin 246 of the driven shaft 244 continues to receive torque from the groove 603 after being inserted into the groove 603 at the connecting position of the shaft 601. As a result, the driven shaft 244 rotates following the shaft 601, and the push-up plate 245 is inclined by the same angle as the rotation angle.

[Buffer operation and pull-in operation for paper cassette]
7A to 7D are top views schematically showing the operation of the drawing unit 400 and the lifting motor 600 when the paper feed cassette 11 is pushed into the housing of the printer 130.

  As shown in FIG. 7A, when the paper feed cassette 11 is pulled out of the housing of the printer 130, the sliding member 402 is stopped at the pulling start end, that is, the front end of the slit 405 in the pulling portion 400. . On the other hand, the shaft 601 of the elevating motor 600 is stopped at the buffer position, that is, the rotation angle around the central axis is maintained around 45 degrees with respect to the pin of the connecting end 246 of the driven shaft 244. In this case, since the base end of the shaft 601 is pushed forward by the restoring force of the elastic member 602, the distal end surface 604 of the shaft 601 is stopped forward from the main body of the lift motor 600 (in the positive direction of the X axis) at the maximum distance D0. ing.

  When the paper feed cassette 11 is pushed into the housing of the printer 130, first, the pin 219 of the arm portion 217 of the paper feed cassette 11 collides with the claw 421 of the sliding member 402 and is caught in the gap 425 of the claw 421 (see FIG. 4). ). As a result, the arm portion 217 of the paper feed cassette 11 receives the force of the pull-in portion 400, that is, the restoring force FP of the coil spring 404, and the paper feed cassette 11 is drawn backward (in the negative direction of the X axis) together with the sliding member 402. . Next, as shown in FIG. 7B, the connecting end 246 of the driven shaft 244 of the sheet feeding cassette 11 collides with the front end surface 604 of the shaft 601. At this time, the elastic member 602 of the elevating motor 600 is shortened by the impact received by the front end surface 604 from the connecting end 246, so that the front end surface 604 moves forward (in the positive direction of the X axis) from the main body of the elevating motor 600 to the first distance D1. Retreat: D1 <D0. The retracting portion 400 and the lifting motor 600 are designed such that the restoring force F1 of the elastic member 602 of the lifting motor 600 is stronger than the force FP of the retracting portion 400 at the first distance D1: F1> FP. As a result, the kinetic energy of the paper feed cassette 11 is absorbed more greatly by the elastic member 602 of the elevating motor 600 than the rotary damper 403 of the retracting unit 400. As a result, the paper feed cassette 11 stops before the sliding member 402 of the drawing unit 400 reaches the drawing end. That is, the position in the sliding direction (X-axis direction) of the paper feed cassette 11, for example, the center position Xw of the tray 220 (hereinafter referred to as “standby position”) is ahead of the paper feed position Xf: Xw> Xf .

  After stopping the paper feed cassette 11, the elevating motor 600 rotates the shaft 601 from the buffer position (45 degrees) to the connection position (90 degrees). As a result, the pin 246 at the connecting end of the driven shaft 244 is displaced from the front end surface 604 into the groove 603. Since the drag from the pin 246 disappears, the elastic member 602 of the lifting motor 600 extends, and the tip surface 604 of the shaft 601 is moved forward from the main body of the lifting motor 600 (the positive X axis) as shown in FIG. Direction), advance to the second distance D2: D2> D1. That is, the pin 246 of the driven shaft 244 is fitted in the groove 603 of the shaft 601. At the second distance D2, the retracting portion 400 and the lifting motor 600 are designed so that the restoring force F2 is weaker than the force FP of the retracting portion 400 as the elastic member 602 of the lifting motor 600 extends: F2 <FP. Due to these force differences FP-F2, the paper feed cassette 11 together with the sliding member 402 starts to retract from the standby position Xw.

  When the sliding member 402 is retracted to the retracting end, the distal end surface 604 is retracted forward (in the positive direction of the X axis) from the main body of the elevating motor 600 to the third distance D3: D3 <D2. In the range from the second distance D2 to the third distance D3, in particular, the third distance D3 is larger than the first distance D1, so that the restoring force F3 of the elastic member 602 of the lifting motor 600 is weaker than the force FP of the retracting portion 400. Thus, the retracting part 400 and the lifting motor 600 are designed: F3 <FP, D3> D1. As a result, the sliding member 402 is reliably retracted to the retracting end, so that the sheet feeding cassette 11 is reliably retracted from the standby position Xw to the sheet feeding position Xf.

[Electronic control system of image forming apparatus]
FIG. 8 is a block diagram showing the configuration of the electronic control system of MFP 100. In this control system, in addition to the ADF 110, the scanner 120, and the printer 130, the operation unit 50 and the main control unit 60 are connected to each other through a bus 90 so as to communicate with each other.

-Printer-
Each of the functional units 10-40 of the printer 130 includes a dedicated actuator 10A-40A, a control circuit 10C-40C, and a drive circuit 10D-40D. Actuators 10A-40A include a stepping motor that is a driving source for various movable members such as a lifting motor 600 for the push-up plate 245, conveying rollers 12F, 12R, 13, 15F, 15R, and photosensitive drums 25Y-25K, BLDC Includes a motor or solenoid. The control circuit 10C-40C is an electronic circuit such as a microprocessor (MPU / CPU), an application specific integrated circuit (ASIC), or a programmable integrated circuit (FPGA), and an actuator belonging to the same functional unit 10-40 Control. Specifically, the control circuit 10C-40C determines the drive voltage and the like for the actuator based on the set value of the parameter instructed from the main control unit 60 and the measured value of the parameter fed back from the actuator to be controlled. A target amount is determined and directed to the drive circuit. Parameters for which setting values are instructed from the main control unit 60 include parameters relating to job processing such as sheet size, paper type, and conveyance speed. Parameters for which actual measurement values are fed back from the actuator include parameters representing the operating state of the actuator, such as the rotation speed, torque, and current amount. The drive circuit is a switching power supply, for example, and applies a drive voltage or drive current to the actuator using a switching element such as a power transistor (FET) and maintains the value at a target value instructed by the control circuit. .

  Further, the control circuit 10C-40C uses various sensors to monitor the operation state of the functional unit 10-40 of the printer 130 and the sheet conveyance state, and if a failure is detected from any of them, the failure is detected. Notify main controller 60. These sensors include a sheet passing sensor distributed along the sheet conveyance path, a position sensor for detecting the position or posture of a movable member such as the photosensitive drums 25Y-25K and the fixing roller 31, an actuator 10A-40A, or Temperature sensor for detecting overheating of drive circuits 10D-40D, cassette sensor for detecting paper feed cassette 11 pushed into the housing of printer 130, sensor for detecting paper out in paper feed cassette 11, image forming unit A sensor for detecting toner shortage at 21Y-21K is included.

-Operation part-
The operation unit 50 receives a job request and image data to be printed through a user operation or communication with an external electronic device, and transmits the information to the main control unit 60. The operation unit 50 includes an operation panel 51 and an external interface (I / F) 52. As shown in FIG. 1, the operation panel 51 includes a push button, a touch panel, and a display. The operation panel 51 displays on the display a graphic user interface (GUI) screen such as an operation screen or an input screen for various parameters. The operation panel 51 also identifies a push button pressed by the user or detects a position on the touch panel touched by the user, and transmits information related to the identification or detection to the main control unit 60 as operation information. In particular, when the input screen for the print job is displayed on the display, the operation panel 51 displays the sheet size, paper type, orientation (separately between portrait and landscape), the number of copies, color / monochrome, image quality, etc. Print conditions are received from the user, and items indicating these conditions are incorporated into the operation information. The external I / F 52 includes a USB port or a memory card slot, through which image data to be printed is taken directly from an external storage device such as a USB memory or a hard disk drive (HDD). The external I / F 52 is also connected to an external network by wire or wireless, and receives image data to be printed from other electronic devices on the network.

−Main control unit−
Main control unit 60 is an integrated circuit mounted on one printed circuit board installed inside MFP 100, and includes a CPU 61, a RAM 62, and a ROM 63. The CPU 61 is composed of one MPU, and implements various functions as a control subject for the other elements 50, 110, 120, and 130 of the MFP 100 by executing various firmware. For example, the CPU 61 displays a GUI screen such as an operation screen on the operation unit 50 to accept a user input operation. In response to this input operation, the CPU 61 determines an operation mode of the MFP 100 such as an operation mode, a standby (low power) mode, a sleep mode, and instructs the elements 110, 120, and 130 to perform processing corresponding to the operation mode. In particular, the CPU 61 selects a target value of the sheet conveyance speed according to the sheet type indicated by the operation information from the operation unit 50, and instructs the function unit 10-40 of the printer 130 about the target value. The RAM 62 is a volatile semiconductor memory device such as a DRAM or SRAM, and provides a work area for executing firmware to the CPU 61 and stores image data to be printed received by the operation unit 50. The ROM 63 is configured by a combination of a non-writable nonvolatile storage device and a rewritable nonvolatile storage device. The former stores firmware, and the latter includes a semiconductor memory device such as an EEPROM, flash memory, and SSD, or an HDD, and provides a storage area for environment variables and the like to the CPU 61.

[Controls for inserting and removing the paper cassette]
FIG. 9 is a timing chart showing control when the paper feed cassette 11 is pushed into the housing of the printer 130 and when it is pulled out from the housing.

-When the paper cassette is pushed into the printer-
When the paper feed cassette 11 is pulled out from the housing of the printer 130, the cassette sensor is in an off state (OFF). The cassette sensor is, for example, a mechanical switch (not shown in FIG. 3) installed on the back plate 302 (see FIG. 3) of the chassis 300 of the printer 130, and the sheet cassette 11 to be detected is in the standby position, for example. When it is retracted to Xw, it is fixed at a position in contact with the back surface 215 of the main body 210. The cassette sensor is turned on when the back surface 215 of the main body 210 of the paper feed cassette 11 comes into contact, and turned off when the back surface 215 leaves. While the cassette sensor is in the OFF state, the drive circuit 10D of the paper feed unit 10 maintains the lifting motor 600 in the stopped state. Therefore, the shaft 601 of the elevating motor 600 remains stationary at the buffer position (rotation angle = 45 degrees), and the push-up plate 245 maintains parallel to the bottom surface 216 of the main body 210 (inclination angle = 0 degrees) (FIG. 7). (See (a)).

  At a certain time T0 shown in FIG. 9, the paper feed cassette 11 starts to move toward the inside of the printer 130 (in the negative direction of the X axis) by the user's force. Thereafter, the arm portion 217 of the main body 210 of the sheet feeding cassette 11 is coupled to the drawing portion 400, and the connecting end 246 of the driven shaft 244 collides with the shaft 601 of the elevating motor 600. At this time, since the shaft 601 is stationary at the buffer position (rotation angle = 45 degrees), the connecting end 246 of the driven shaft 244 pushes the distal end surface 604 of the shaft 601 to shorten the elastic member 602 of the lifting motor 600 (see FIG. 7 (b)). In this way, the sheet feeding cassette 11 is buffered by the elastic member 602 of the elevating motor 600 in addition to the rotary damper 403 in the pull-in portion 400 and decelerates. When the paper feed cassette 11 reaches the standby position Xw at the first time T1, the back surface 215 of the main body 210 of the paper feed cassette 11 comes into contact with the cassette sensor, so that the cassette sensor is switched from the off state to the on state (ON). In response to this, the control circuit 10C of the paper feeding unit 10 causes the drive circuit 10D to activate the lifting motor 600 to cause the shaft 601 to rotate forward. The number of rotations of the lifting motor 600 is set to a value necessary for normal rotation of the shaft 601 from the buffer position (45 degrees) to the coupling position (90 degrees). During forward rotation of the shaft 601, the tip end surface 604 only slides on the surface of the coupling end 246 of the driven shaft 244, so that the driven shaft 244 cannot obtain a torque enough to incline the push-up plate 245. Therefore, the inclination angle of the push-up plate 245 is kept at 0 degree.

  Since the lifting motor 600 finishes rotating a predetermined number of times at the second time T2, the control circuit 10C of the sheet feeding unit 10 causes the driving circuit 10D to stop the lifting motor 600. At this time, since the shaft 601 stops at the coupling position, the elastic member 602 of the elevating motor 600 advances the distal end surface 604 of the shaft 601 to fit the pin 246 of the driven shaft 244 in the groove 603 of the shaft 601 ( (See (c) of FIG. 7). As a result, the elastic member 602 of the elevating motor 600 is extended and its restoring force F2 is weaker than the force FP of the retracting portion 400 (F2 <FP), so that the paper feed cassette 11 is retracted from the standby position Xw to the paper feed position Xf. .

  At a third time T3 when a time sufficiently longer than the time required for the backward movement has elapsed from the second time T2, the control circuit 10C of the paper feeding unit 10 causes the drive circuit 10D to activate the lifting motor 600 and to correct the shaft 601. Turn. At this time, the torque of the lifting motor 600 is transmitted from the shaft 601 to the push-up plate 245 through the driven shaft 244, so that the tilt angle of the push-up plate 245 increases from 0 degrees in accordance with the rotation angle of the shaft 601. While the elevating motor 600 is rotating, the control circuit 10C monitors, for example, with a dedicated sensor whether the upper surface of the sheet bundle accommodated in the sheet feeding cassette 11 has contacted the sheet feeding roller 15F. This sensor measures, for example, the height of a portion of the upper surface of the sheet bundle positioned above the push-up plate 245, the external pressure received by the paper feed roller 15F, or the output of the lifting motor 600.

  At the fourth time T4, the control circuit 10C of the sheet feeding unit 10 detects the contact of the upper surface of the sheet bundle with the sheet feeding roller 15F from the change in the output of the sensor, and causes the driving circuit 10D to stop the lifting motor 600. The control circuit 10C further sends a signal to the main control unit 60, confirms that the paper feed cassette 11 has been normally set at the paper feed position Xf, and the push-up plate 245 has successfully brought the leading edge of the sheet into contact with the paper feed roller 15F. The main control unit 60 is made to recognize.

-When the paper cassette is pulled out of the printer-
The main control unit 60 instructs the function unit 10-40 of the printer 130 to switch from the operation mode to the standby mode in response to the end of job processing, a stop instruction by the user, or detection of a malfunction such as a paper out or jam. In response to this instruction, the control circuit 10C of the paper feeding unit 10 causes the drive circuit 10D to activate the lifting motor 600 to reverse the shaft 601. After the fifth time T5, which is the activation time, the inclination angle of the push-up plate 245 decreases in accordance with the rotation angle of the shaft 601. While the elevating motor 600 is rotating, the control circuit 10C monitors, for example, with a dedicated sensor whether or not the inclination angle of the push-up plate 245 has reached 0 degrees. This sensor is the same as a sensor such as a rotary encoder used for normal feedback control with respect to the lifting motor 600, and measures, for example, the number of rotations (drive source) or output of the lifting motor 600.

  At the sixth time T6, the control circuit 10C of the paper feeding unit 10 detects the arrival at 0 degree due to the inclination angle of the push-up plate 245 from the change in the output of the sensor, and causes the drive circuit 10D to stop the lifting motor 600. The control circuit 10C further sends a signal to the main control unit 60 so that the main control unit 60 recognizes that the push-up plate 245 is completely collapsed and the paper feed cassette 11 can be pulled out.

  At the seventh time T7, the paper feed cassette 11 starts to move toward the outside of the printer 130 casing (in the positive direction of the X axis) with the help of the user. When the sheet feeding cassette 11 moves in the sliding direction (X-axis direction), the connecting end 246 of the driven shaft 244 receives almost no resistance force from the groove 603 of the shaft 601. Therefore, the resistance force against the drawer of the paper feed cassette 11 is mainly only the resistance force of the rotary damper 403 in the drawing-in part 400 in addition to the frictional force between the paper feed cassette 11 and the rail 310. When the paper feed cassette 11 moves forward beyond the standby position Xw at the eighth time T8, the back surface 215 of the main body 210 of the paper feed cassette 11 is separated from the cassette sensor, so that the cassette sensor is switched from the on state to the off state. In response to this, the control circuit 10C of the paper feeding unit 10 causes the drive circuit 10D to activate the elevating motor 600 to reverse the shaft 601. The number of rotations of the lifting motor 600 is set to a value necessary for reversing the shaft 601 from the coupling position (90 degrees) to the buffer position (45 degrees). At this time, since the connecting end 246 of the driven shaft 244 is already separated from the tip surface 604 of the shaft 601, the inclination angle of the push-up plate 245 is kept at 0 degree.

[Advantages of the embodiment]
As described above, in the paper feed mechanism according to the embodiment of the present invention, that is, the feeding unit 10 of the MFP 100, when the paper feed cassette 11 is pushed into the housing of the printer 130, the shaft 601 of the lift motor 600 is in the buffer position (rotation). Collide with the driven shaft 244 of the paper feed cassette 11 at an angle = 45 degrees. At this time, the elastic member 602 of the elevating motor 600 is shortened by the impact that the shaft 601 receives from the driven shaft 244. Since the shaft 601 is in contact with the connecting end 246 of the driven shaft 244 at the tip end surface 604 when the shaft 601 is stationary at the buffer position, the timing of the collision is earlier than in the case of contact with the groove 603. Thereby, the restoring force F1 of the elastic member 602 of the elevating motor 600 exceeds the force FP of the retracting part 400 before the sliding member 402 of the retracting part 400 reaches the retracting end. Thereby, the impact of the paper feed cassette 11 is mainly absorbed by the elastic member 602 of the elevating motor 600 instead of the pull-in portion 400. When the paper feed cassette 11 is stopped, the elevating motor 600 is activated to rotate the shaft 601 to the connection position (rotation angle = 0 degree). When the shaft 601 rotates to the coupling position, the pin 246 at the coupling end of the driven shaft 244 moves from the tip surface 604 into the groove 603, so that the elastic member 602 of the elevating motor 600 advances the tip surface 604 and enters the groove 603. The pin 246 of the driven shaft 244 is fitted. As the elastic member 602 of the elevating motor 600 is extended, the restoring force F2 is weaker than the force FP of the retracting unit 400, so that the retracting unit 400 retracts the sheet cassette 11 from the standby position Xw to the sheet feeding position Xf. it can. Furthermore, since the force required to pull out the paper feed cassette 11 out of the housing of the printer 130 is determined by the force FP of the pull-in portion 400, the restoring force F1 of the elastic member 602 of the lifting motor 600 required for buffering the paper feed cassette 11 Can be set independently. In other words, it is sufficient to increase the restoring force F1 of the elastic member 602 of the lifting motor 600 so as to be able to buffer the higher speed paper feeding cassette 11, and the resistance force of the rotary damper 403 of the retracting portion 400 is sufficient. It does not have to be strengthened. Thus, in the paper feed mechanism of the MFP 100, it is possible to further reduce the risk of malfunction due to the impact of the paper feed cassette 11 pushed into the housing and to further improve the operability of the paper feed cassette 11.

[Modification]
(A) The image forming apparatus 100 shown in FIG. 1 is an MFP. In addition, the sheet feeding mechanism according to the embodiment of the present invention is a sheet conveying device such as a single function image forming apparatus such as a printer, a copier, or a facsimile machine, or an ADF, finisher, or automatic sorting machine provided in an image reading device such as a scanner. It is possible to use either of them.

  (B) In the paper feed cassette 11 shown in FIG. 2, the push-up plate 245 presses the sheet against the paper feed roller 12 </ b> F through the tray 220. In addition, the paper feed cassette may include a pickup roller. In this case, the push-up plate 245 may press the sheet against the pickup roller through the tray 220, and the pickup roller may feed the sheet toward the sheet feeding roller 12F.

  (C) The drawing unit 400 shown in FIG. 4 is merely an example, and other equivalent known drawing devices may be used. For example, a cylinder type damper may be used instead of the rotary damper 403, and a plate spring, a torsion spring, or an elastomer may be used instead of the coil spring 404.

  (D) The push-up plate 245 shown in FIG. 5 is a separate member from the tray 220 and pushes up the tray 220 from below. In addition, the push-up plate may be a part of the tray. Furthermore, instead of the push-up plate, the driven shaft may apply torque directly to the tray to change the inclination angle.

  (E) As shown in FIGS. 6A and 6B, the connection between the driven shaft 244 and the shaft 601 of the lifting motor 600 is a shaft coupling. In addition, the gear connected to the driven shaft 244 and the gear connected to the shaft 601 of the lifting / lowering motor 600 may be separated from each other in accordance with the insertion / extraction of the paper feed cassette 11. Good. In this case, the driven shaft 244 or the shaft 601 may be arranged so as to intersect with the sliding direction of the paper feed cassette 11. Further, the movable member to which the driven shaft 244 is connected is not limited to the push-up plate 245. For example, the movement of the alignment plate may be automated by connecting the driven shaft 244 to any of the alignment plates 231-233.

  (F) The elastic member 602 of the lifting motor 600 shown in FIG. 6E is a coil spring. In addition, the elastic member may be any member that continuously changes the strength of the restoring force according to the relative displacement amount between both ends, and may be, for example, a leaf spring, a torsion spring, or an elastomer.

  (G) In FIG. 9, when the paper feed cassette 11 is pushed into the housing of the printer 130, the shaft 601 is moved to the buffer position (45) in response to the back surface 215 of the main body 210 of the paper feed cassette 11 contacting the cassette sensor. Forward) to the connecting position (90 degrees). When the paper feed cassette 11 is pulled out of the housing of the printer 130, the shaft 601 is moved from the coupling position (90 degrees) to the buffer position (45 degrees) as the back surface 215 of the main body 210 of the paper feed cassette 11 moves away from the cassette sensor. ). In addition, the control circuit 10C of the paper feeding unit 10 uses the rotation history of the lifting motor 600 as follows to make the shaft 601 stand still at the buffer position in the event of a collision with the driven shaft 244 of the paper feeding cassette 11. May be. First, when the MFP 100 is assembled, the shaft 601 is set to the buffer position. Thereafter, until the paper feed cassette 11 is pulled out, the control circuit 10C continues to record the rotation amount of the lifting motor 600 for each paper feed control, and when the paper feed cassette 11 is pulled out, the control circuit 10C counts the total rotation amount recorded. The lift motor 600 is reversely rotated by an equal rotation amount. As a result, the shaft 601 is returned to the buffer position before the paper feed cassette 11 is pulled out.

  (H) In FIG. 9, when the paper feed cassette 11 is pulled out of the casing of the printer 130, the control circuit 10C of the paper feed unit 10 is driven by the drive circuit on condition that the paper feed cassette 11 has advanced beyond the standby position. The lifting motor 600 is activated 10D, and the shaft 601 is rotated from the coupling position (90 degrees) to the buffer position (45 degrees). In addition, by deforming the groove 603 of the shaft 601, the sheet feeding cassette 11 is fed with a torque that the lifting motor 600 applies to the shaft 601 in the direction of rotating from the coupling position (90 degrees) to the buffer position (45 degrees). It is also possible to push out from the paper position to the standby position.

  10A and 10B are perspective views showing a modification of the groove 603 of the shaft 601 of the lifting motor 600. FIG. In FIG. 6, the inner surface of the groove 603 of the shaft 601 extends in parallel to the axial direction (X-axis direction). On the other hand, in FIG. 10A, among the inner surfaces of the groove 603 of the shaft 601, the one that precedes the forward rotation ND is the inclined surface 613 with respect to the axial direction (X-axis direction) of the shaft 601. The width of the groove 603 is narrowed as it advances from the open end to the back (in the negative direction of the X axis). In FIG. 10B, the inner surface of the groove 603 of the shaft 601 that follows the forward rotation ND includes a circumferential recess 623 at the rear end. The depth of the recess 623 (inner method in the X-axis direction) is equal to or greater than the outer diameter of the pin of the connecting end 246 of the driven shaft 244.

  10 (c) and 10 (d) show that the groove 603 is added to the pin 246 at the connecting end of the driven shaft 244 when the rotation of the shaft 601 shown in FIG. 10 (a) is forward rotation ND and reverse rotation RD, respectively. It is a typical right view which shows force. When the shaft 601 is stationary at the coupling position, the pin 246 is in contact with the innermost surface of the groove 603. When the shaft 601 rotates forward in this state (see the arrow ND shown in the figure), the direction of pushing the pin 246 (the lower side in FIG. 10C) on the inner surface of the groove 603 is the axial direction (X-axis direction). Therefore, the force FN that pushes the pin 246 is parallel to the circumferential direction of the shaft 601 (Z-axis direction in the figure) and does not substantially include the component in the axial direction (X-axis direction). Accordingly, the pin 246 rotates forward together with the shaft 601 without coming out of the groove 603. On the other hand, when the shaft 601 is reversed (see the arrow RD shown in the figure), the direction of pushing the pin 246 (upper side in FIG. 10D) on the inner surface of the groove 603 is relative to the axial direction (X-axis direction). Since it is inclined, the force FR pushing the pin 246 has a component Ff that moves the pin 246 away from the depth of the groove 603 in the axial direction (X-axis direction) in addition to the component Fr in the circumferential direction (Z-axis direction) of the shaft 601. Including. Since the inclination angle of the push-up plate 245 cannot be less than 0 degrees by being blocked by the bottom surface 216 of the main body 210 of the sheet cassette 11, the pin 246 cannot rotate in the reverse rotation direction RD beyond the rotation angle = 0 degrees. Therefore, when the shaft 601 is reversed, the pin 246 is pushed out from the groove 603 to the tip surface 604 (see the two-dot chain line shown in FIG. 10D). This means that the paper feed cassette 11 advances from the paper feed position Xf to the standby position Xw (see FIGS. 7B and 7C).

  Similarly, the shaft 601 shown in FIG. 10B continues to hold the pin 246 in the groove 603 when rotating forward, while pushing the pin 246 out of the groove 603 soon when rotating backward. In fact, when the shaft 601 rotates forward with the pin 246 in contact with the innermost inner surface of the groove 603 (see the arrow ND shown in the figure), the inner surface of the groove 603 is recessed in the direction of pushing the pin 246. Since there is 623, the pin 246 fits into the recess 623. Accordingly, the pin 246 rotates forward together with the shaft 601 without coming out of the groove 603. On the other hand, when the shaft 601 is reversed (refer to the arrow RD shown in the figure), the direction of pushing the pin 246 out of the inner surface of the groove 603 is flat, so that the flatness error or between the pin 246 and the groove 603 is flat. Due to the rattling of the rotating pin 246 due to the play of the pin 246, the force pushing the pin 246 easily generates a component Ff that moves the pin 246 away from the depth of the groove 603 in the axial direction of the shaft 601 (X-axis direction). obtain. The pin 246 cannot rotate in the reverse rotation direction RD beyond the rotation angle = 0 degree due to the resistance received by the push-up plate 245 from the bottom surface 216 of the main body 210 of the paper feed cassette 11, and therefore when the shaft 601 rotates in the reverse direction, the pin 246 rotates into the groove 603. From the paper feed position Xf to the standby position Xw.

  FIG. 11 is a timing chart showing control for the lifting motor 600 including the groove 603 shown in FIG. 10 in the shaft 601 when the paper feed cassette 11 is pushed into the housing of the printer 130 and when it is pulled out from the housing. is there. Since the control (time T0-T4) when the paper feed cassette 11 is pushed into the housing of the printer 130 is the same as the control shown in FIG. 9, the description of FIG. 9 is used for details thereof.

  In response to an instruction from the main control unit 60 to switch from the operation mode to the standby mode, the control circuit 10C of the sheet feeding unit 10 causes the drive circuit 10D to activate the lifting motor 600 at the fifth time T5 to cause the shaft 601. Reverse. Therefore, the inclination angle of the push-up plate 245 decreases in accordance with the rotation angle of the shaft 601. While the elevating motor 600 is rotating, the control circuit 10C monitors whether the paper feed cassette 11 has advanced from the paper feed position Xf to the standby position Xw through the output of the cassette sensor.

  Since the inclination angle of the push-up plate 245 reaches 0 degrees at the sixth time T6, the push-up plate 245 stops. At this point, since the pin 246 still remains in the groove 603 of the shaft 601, there is no change in the output of the cassette sensor. Therefore, the control circuit 10C of the sheet feeding unit 10 causes the drive circuit 10D to continue driving the lift motor 600 and continue to reverse the shaft 601.

  While the pin 246 cannot continue to reverse due to the resistance from the push-up plate 245, since the groove 603 has the shape shown in FIG. 10, the pin 246 is soon pushed out from the groove 603 to the tip surface 604. That is, at the tenth time TA, the paper feed cassette 11 moves forward from the paper feed position Xf to the standby position Xw, and the back surface 215 of the main body 210 of the paper feed cassette 11 is separated from the cassette sensor. Switch to. In response to this, the control circuit 10C of the paper feeding unit 10 causes the drive circuit 10D to stop the lifting motor 600. Here, the number of rotations of the lifting motor 600 during the period from the sixth time to the tenth time is set to a value necessary for reversing the shaft 601 from the coupling position (90 degrees) to the buffer position (45 degrees). . As a result, when the connecting end 246 of the driven shaft 244 is separated from the distal end surface 604 of the shaft 601, the shaft 601 stops at the buffer position (rotation angle = 45 degrees).

  As described above, the sheet feeding cassette 11 can be automatically pushed out of the sheet feeding position by using the torque when the elevating motor 600 rotates the shaft 601 from the coupling position to the buffering position. In this way, the torque of the lift motor 600 supplements the user's force to pull out the paper cassette 11, so that the operability of the paper cassette 11 is further improved.

  (I) When the paper feeding cassette 11 is pushed into the housing of the printer 130 and is excessively accelerated by the user, if the elastic member 602 of the lifting motor 600 cannot absorb the kinetic energy of the paper feeding cassette 11, Even if the paper cassette 11 reaches the standby position, there is a possibility that it will not stop. In this case, not only the elastic member 602 but also a portion of the back surface 302 (see FIG. 3) of the chassis 300 of the printer 130 that is not in contact with the paper feed cassette 11 is damaged due to an impact from the paper feed cassette 11. Such problems can occur.

  In order to prevent this problem, the lifting motor 600 may be provided with a lock mechanism for the elastic member 602 of the shaft 601. This locking mechanism may be a well-known mechanical mechanism for a movable member that reciprocates, such as a push lock / turn reset type push button. For example, a locking pin is embedded in the side surface of the shaft 601 so as to be radially expandable and contractable by a base end spring, and a region of the inner surface of the main body of the lifting motor 600 that faces the side surface of the shaft 601 A locking groove may be provided in a part of the direction. When the connecting end 246 of the driven shaft 244 of the paper feed cassette 11 collides with the shaft 601 at the buffer position, the elastic member 602 of the lifting motor 600 is shortened in the axial direction by the impact. If the paper feed cassette 11 does not stop even after the standby position, the amount of shortening of the elastic member 602 reaches a threshold value. In this case, the portion of the side surface of the shaft 601 where the locking pin is embedded reaches the locking groove of the lifting motor 600, so that the locking pin protrudes in the radial direction and the tip of the locking pin protrudes into the locking groove. . This prevents (locks) the movement of the shaft 601 in the axial direction, so that the elastic member 602 is fixed and further shortening is prevented. Thereafter, the impact of the paper feeding cassette 11 is surpassed by the rigidity of the main body of the shaft 601, the locking pin, and the lifting motor 600. After the sheet feeding cassette 11 is stopped in this way, the back surface 215 of the main body 210 is already in contact with the cassette sensor and the cassette sensor is turned on, so that the control circuit 10C of the sheet feeding unit 10 adds the lifting motor 600 to the drive circuit 10D. The shaft 601 is rotated forward by starting. At this time, before the shaft 601 reaches the coupling position (90 degrees) from the buffering position (45 degrees), the inner surface of the locking groove is pushed back into the side surface of the shaft 601 from the locking groove. The shape is designed. When the shaft 601 is unlocked and the elastic member 602 is released in this way, the restoring force is already stronger than the force FP of the retracting portion 400, so the connecting end 246 of the driven shaft 244 is pushed back through the front end surface 604 of the shaft 601. . As a result, the paper feed cassette 11 is pushed out to the standby position Xw (see FIG. 7B). When the shaft 601 reaches the connecting position (90 degrees) by the subsequent rotation of the lifting / lowering motor 600, the elastic member 602 advances the distal end surface 604 of the shaft 601, and the pin 246 of the driven shaft 244 in the groove 603 of the shaft 601. (See (c) of FIG. 7). As a result, the elastic member 602 of the lifting / lowering motor 600 is extended and its restoring force F2 is weaker than the force FP of the retracting portion 400, so that the paper feed cassette 11 is retracted from the standby position Xw to the paper feed position Xf.

  The present invention relates to a sheet feeding mechanism, and as described above, an elastic member incorporated in a connecting portion between an actuator in a housing of an image forming apparatus and a movable member in a sheet feeding cassette is used for buffering the sheet feeding cassette. Thus, the present invention is clearly industrially applicable.

100 MFP
130 Printer 11 Paper cassette 210 Main body of paper cassette 211 Front surface of main body 213 Feeding side surface of main body 214 Another side surface of main body 215 Rear surface of main body 216 Bottom surface of main body 217, 218 Arm portion on side surface of main body 219 Arm portion Tip pin 220 Tray 231-233 Alignment plate 244 Drive shaft 245 Push-up plate 246 Connection end of driven shaft or its pin 400 Pull-in portion 401 Pull-in housing 402 Slide member 403 Rotary damper 404 Pull-in coil spring 600 Lifting motor 601 Shaft 602 Elastic member 603 Shaft groove 604 Shaft end surface

Claims (9)

An image forming apparatus for taking a sheet from a paper feed cassette accommodated in a housing so as to be drawable and forming an image on the sheet,
A pull-in portion that couples with the paper feed cassette when the paper feed cassette is pushed into the housing and applies a force to the paper feed cassette into a paper feed position;
An actuator installed in the housing;
A driving member that can be displaced by the driving force of the actuator;
A follower member installed in the paper feed cassette so as to be able to come into contact with the drive member when the paper feed cassette is pushed into the housing, and being interlocked with a movable member in the paper feed cassette;
An elastic member that applies a force toward the other to one of the drive member and the driven member;
The drive member collides with the driven member at the first position when the paper feeding cassette is pushed into the housing, and contacts the driven member when the paper feeding cassette stops due to the collision. The actuator is moved to the second position by the driving force of the actuator,
While the drive member is in contact with the driven member at the first position, the force of the elastic member acting on the paper feed cassette in the sliding direction of the paper feed cassette is stronger than the force of the pull-in portion. The image forming apparatus is characterized in that a shape of a contact portion between the driving member and the driven member is designed so as to be weak after moving to the second position.   2. The image forming apparatus according to claim 1, wherein the driving member is connected to the driven member so that the driven member can be interlocked with the driving force of the actuator at the second position. The drive member and the driven member are both rotating shafts and extend on the same straight line parallel to the sliding direction of the paper feed cassette,
One of the driving member and the driven member includes a convex portion at an end portion that is a contact portion with the other, and the rotation angle with respect to the other is within an allowable range at the end portion that is a contact portion with the other. Including a recess into which the protrusion can be fitted,
The rotation angle of the driving member with respect to the driven member is out of the allowable range while the driving member is in contact with the driven member at the first position, and after the movement to the second position, the predetermined angle. The image forming apparatus according to claim 2, wherein the image forming apparatus falls within a range.   The driving force that the driving member transmits to the driven member does not substantially include a component in the sliding direction of the sheet feeding cassette when the driving member rotates forward with respect to the driven member, and when the driving member rotates in reverse. The image forming apparatus according to claim 3, wherein an inner surface of the concave portion and an outer surface of the convex portion are formed so as to include a component that moves the driven member away in the sliding direction of the paper feed cassette. apparatus.   The position at which the sheet feeding cassette stops when the driving member collides with the driven member at the first position is outside the sheet feeding position. The image forming apparatus according to any one of the above.   The image forming apparatus according to claim 1, wherein the movable member in the sheet feeding cassette is a push-up plate that pushes up the leading end of the sheet from below.   The drive member is moved to the first position by the drive force of the actuator after the paper feeding cassette is pulled out from the housing and the driven member is separated from the drive member. The image forming apparatus according to claim 6. When the driving member collides with the driven member at the first position, when the deformation amount of the elastic member reaches a threshold value, the elastic member is fixed to prevent further deformation, and when the driving force is received from the actuator The image forming apparatus according to claim 1, further comprising a lock mechanism that releases the elastic member. The pull-in part is
The image forming apparatus according to claim 1, further comprising a shock absorber that absorbs a force received from the paper feed cassette when the paper feed cassette is pushed into the housing.

Images