JP2011184169A - Image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming device which comprises a paper feed cassette the height of which is efficiently reduced by using a smaller number of structural members and in which the operability of restraining members such as side restraining plates is improved. <P>SOLUTION: The paper feed cassette 1 includes the side restraining plates 5L, 5R movable to respective restraining positions according to the size of sheets on a liftable center plate 2 and center plate pressing springs 24L, 24R for pressing the center plate to the feed roller 11 side while one ends thereof are supported on cassette frame side parts, respectively. The paper feed cassette further includes wires 22L, 22R one ends of which are connected to the side restraining plates, respectively, and the other ends of which are connected to the other ends of the center plate pressing springs, respectively. and a guide mechanism. The guide mechanism guides the wires so that the pressing force thereof against the feed roller is larger when the side restraining plates are aligned with the sheets of a large size than when aligned with the sheets of a small size. Consequently, the pressing force can be easily and reliably changed according to the loaded quantity and size of the sheets by merely moving the side restraining plates according to the size of the sheets. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image forming apparatus having a configuration in which sheets are sequentially fed from a sheet feeding cassette by a feeding roller.

  In recent years, image forming apparatuses such as laser beam printers and copiers have come to use large-capacity paper cassettes that store a large number of sheets of 250 to 500 sheets. As a result, the number of sheet replenishment by the user is reduced.

  FIG. 11A is a perspective view illustrating an example of a conventional sheet feeding apparatus including a sheet feeding cassette, and FIG. 11B is a schematic cross-sectional view taken along line AA in FIG. . As shown in both drawings, inside the sheet feeding cassette 41, a cassette frame is arranged so that an intermediate plate 42 as a sheet stacking plate can move up and down at one end (the left end portion in FIG. 11B). The shaft 41b of 41a is provided so as to be rotatable about a fulcrum. Two compression springs 46 for biasing the middle plate 42 upward are provided below the middle plate 42 in a state where the lower end is in contact with the bottom upper surface of the cassette frame 41a and the upper end is in contact with the bottom surface of the middle plate 42. Thus, the intermediate plate 42 is configured to be pressed upward. On the other hand, a feeding roller 44 having a D-cut section is disposed above the rotating front end side of the intermediate plate 42 in the copying machine main body. An abutting roller 45 is arranged on the same axis as the feeding roller 44.

  12A is a schematic cross-sectional view showing a state where sheets S are fully loaded (for example, 500 sheets) in the sheet feeding cassette 41, and FIG. 12B is a schematic sectional view showing a state where about 100 sheets are stacked. The position of the rear end (the right end surface in the drawing) of the sheet S is regulated by a rear end regulating plate 4 that is movably provided in the sheet conveyance direction (the direction of arrow B in FIG. 12B). Further, the position of the end portion in the width direction orthogonal to the sheet conveying direction is regulated by side regulating plates 43L and 43R that are provided so as to be movable in the same direction.

  Then, the feeding roller 44 is rotated in the clockwise direction in FIGS. 12A and 12B by a driving mechanism (not shown), and one sheet is separated by the separation pad 47 urged in the direction of the feeding roller 44 by the pressure spring 48. Separated one by one. Thereafter, the separated sheet S is pulled out by a pair of downstream conveyance rollers (not shown) and conveyed toward the image forming unit (not shown) while the feeding roller 44 rotates once.

  By the way, in this sheet feeding device, the sheet feeding pressure, that is, the sheet on the intermediate plate 42 to the feeding roller 44 in order to always perform stable sheet feeding regardless of the remaining amount of sheets in the sheet feeding cassette 41. It is necessary to make the pressure contact as constant as possible. The sheet feeding pressure Ff is determined by Ff = Fc−Fs, where Fc is the upward force from the two compression springs 46 and Fs is the weight of the sheet and the middle plate. Therefore, a compression spring that can reduce the difference between the upward force of the compression spring 46 when the amount of sheets in the sheet feeding cassette 41 is large and its own weight is large, and the force when the amount of sheets is small and its own weight is small. Should be set.

  However, when the sizes of the sheets stacked on the intermediate plate 42 are different, the sheet feeding pressure changes as follows. As an example of the case where the sheet sizes are different, consider an A4 size sheet and an A5 size sheet. In either size, since the length of the compression spring 46 when the sheets are full is equal, the upward pressure applied by the compression springs 46 × 2 is equal. However, since the A4 size is larger than the A5 size, there is a difference in the sheet feeding pressure between the A4 size and the A5 size when the A5 size is full. become.

  FIG. 13 is a graph showing this as a relationship between the number of loaded sheets and the load. In FIG. 13, the horizontal axis represents the number of stacked sheets (sheets), and the vertical axis represents the load (N). In the drawing, the pressing force of the spring is indicated by a black rhombus mark graph, the sheet's own weight (A4) is indicated by a black square mark, and the sheet's own weight (A5) is indicated by a black triangle mark. The hatched portion is the difference in sheet feeding pressure between the A4 size sheet and the A5 size sheet.

  Therefore, in order to suppress the change in the sheet feeding pressure due to the difference in sheet size, the following various methods have been conventionally employed. For example, in the paper feed cassette 49 shown in FIGS. 14A, 14 </ b> B, and 14 </ b> C, the middle plate 54 is pressed upward by three compression springs 72 a, 72 b, 72 c and provided on the side regulating plate 55. The compression spring 72c is maintained in a compressed state together with the intermediate plate pressure plate 71 by the regulating portion 55c. Thus, the upward pressing force of the intermediate plate 54 is changed according to the movement of the side regulating plate 55 in the directions of arrows A and B (see Patent Document 1). FIG. 14B is a cross-sectional view taken along line YY in FIG. Reference numeral 49a denotes a paper feed cassette frame, 49b denotes a shaft portion of the intermediate plate pressure plate 71a, and 70 denotes a feeding roller.

  Further, a paper feed cassette 19 shown in FIGS. 15A, 15B, and 15C has been proposed. As shown in the figure, the sheet feeding cassette 19 is disposed between the side regulating plates 17L, 17R, the middle plate 18, and the compression spring 26 that presses the middle plate 18 upward. A tension spring 29 is provided to press the intermediate plate 18 downward in accordance with the movement of 17R. In this technique, the downward pressing force is increased by the tension spring 29 as the sheet size is reduced, and the upward pressing force of the compression spring 26 is reduced (see Patent Document 2). In FIG. 15, reference numeral 19a denotes a paper feed cassette frame, 30 denotes a connecting member for connecting the intermediate plate 18 and the tension spring 29, and 31 denotes a feeding roller.

Japanese Utility Model Publication No. 2-135545 Japanese Patent Publication No. 5-49568

  However, the techniques described in Patent Documents 1 and 2 have the following problems. First, in any technique, since the compression springs 72 (72a, 72b, 72c), 26 are used below the middle plates 54, 18, when the middle plates 54, 18 are at the lowest position, at least the compression springs 72, A distance corresponding to 26 contact heights is required. For this reason, the distance from the bottom surface of the middle plates 54 and 18 to the bottom surface of the paper feed cassette frames 49a and 19a increases. Further, in Patent Document 1, since the regulating portion 55c that regulates the intermediate plate pressure plate 71 is provided on the side regulating plate 55, a dead space is created between the stacked sheets S and the bottom surface of the cassette frame 49a. As a result, the height direction size of the paper feed cassette 49 is increased.

  In Patent Document 2, since the side regulating plates 17L and 17R must be moved against the urging force of the tension spring 29 when operated, a large operating force is required and the operability is impaired. Further, since the upward pressing force by the compression spring 26 is canceled by the tension spring 29 connected to the side regulating plates 17L and 17R, two types of urging members are required, and the mechanical efficiency is not good. This causes problems such as an increase in the number of parts and a loss in assembly.

  SUMMARY OF THE INVENTION Accordingly, the present invention provides an image forming apparatus provided with a paper feed cassette that has fewer constituent members than conventional ones, efficiently reduces the height, and improves the operability of a regulating member such as a side regulating plate. It is an object.

  The present invention provides an image forming apparatus comprising: a sheet feeding cassette configured to be detachable from the apparatus main body; and a feeding roller that feeds a sheet accommodated in the sheet feeding cassette. A sheet stacking unit that is supported so that it can be moved up and down, a regulating member that can be moved to a regulating position according to the size of the sheets stacked on the sheet stacking unit, and one end supported on the side of the sheet feeding cassette body An elastic member that biases the sheet stacking portion toward the feeding roller in a state of being formed, a wire member having one end connected to the regulation member and the other end connected to the other end of the elastic member, When the restricting member is aligned with a small-sized sheet, when the elastic member is aligned with a large-sized sheet, the length of the elastic member that extends is increased to increase the pressure contact force to the feeding roller. It is characterized by comprising a guide mechanism for guiding the urchin the wire member.

  According to the present invention, it is possible to easily and reliably change the pressure contact force according to the number and size of sheets loaded by simply moving the regulating member in accordance with the size of the sheet on the sheet stacking unit. Feeding is possible. In addition, it is possible to obtain an image forming apparatus including a paper feeding cassette that efficiently reduces the height of the paper feeding cassette and improves the operability of the regulating member while using a small number of components. In addition, since the image forming apparatus includes such a sheet feeding cassette, it is possible to reduce the height of the apparatus main body.

1A and 1B show a paper feed cassette mounted on an image forming apparatus according to an embodiment of the present invention, in which FIG. FIG. 2A is a plan view of the sheet feeding cassette in the present embodiment, and FIG. FIG. 4 is a side view showing a state in which the paper feeding cassette is attached to and detached from the image forming apparatus main body according to the present embodiment, and FIGS. 1 shows a unique configuration of a paper feed cassette in the present embodiment, (a) is an upper perspective view, and (b) is a side view. 2A and 2B are diagrams illustrating a unique configuration of a sheet feeding cassette according to the present embodiment, in which FIG. FIG. 5A shows a state where a maximum size sheet is fully loaded in the paper feed cassette of the present embodiment, where FIG. FIG. 3A shows a state in which one maximum-size sheet is stacked in the paper feed cassette according to the present embodiment, where FIG. FIG. 5A shows a state in which a minimum size sheet is fully loaded in the paper feed cassette of the present embodiment, where FIG. The state which removed the paper feed cassette of this embodiment from the image forming apparatus is shown, (a) is a side view, (b) is a bottom view. 1 is a schematic sectional view showing a copying machine as an image forming apparatus according to the present invention. An example of the conventional sheet | seat feeding apparatus containing a paper feed cassette is shown, (a) is an upper perspective view, (b) is schematic sectional drawing cut | disconnected by the AA line in (a). FIG. 5A is a schematic cross-sectional view illustrating a state in which sheets are stacked on a conventional paper feed cassette, FIG. 5A is a schematic cross-sectional view illustrating a state in which sheets are fully loaded, and FIG. FIG. 9 is a graph showing the relationship between the number of loaded sheets and various loads in a conventional paper feed cassette. The structure of the paper feed cassette of patent document 1 as a prior art example is shown, (a) is a perspective view, (b) is sectional drawing, (c) is a perspective view of the principal part. Sectional drawing which shows the structure of the paper feeding cassette of patent document 2 as a prior art example, and (a), (b), (c) shows a different state, respectively.

  Hereinafter, embodiments according to the present invention will be described with reference to the drawings. First, a configuration of a copying machine as an image forming apparatus having a sheet feeding apparatus including a sheet feeding cassette according to the present invention will be described with reference to a schematic sectional view of FIG.

  As shown in FIG. 10, the copying machine includes a copying machine main body 100 as an apparatus main body. The copying machine main body 100 is moved in the direction of the arrow while irradiating light on the original platen glass 51 for placing the original provided on the upper surface thereof, and the original placed on the original platen glass 51, thereby moving the entire original surface. And an exposure device 52 for scanning. The reflected light obtained by irradiating the original with the exposure device 52 is imaged on the photosensitive drum 55 via the first mirror group 53a, the zoom lens 54, and further the second mirror group 53b, thereby electrostatically A latent image is formed. The photosensitive drum 55 is provided in a process cartridge 56 equipped with a plurality of process units contributing to image formation around the photosensitive drum 55, and a charging unit, a developing unit, a cleaning unit, and the like are disposed around the photosensitive drum 55. ing. The electrostatic latent image formed on the photosensitive drum 55 is developed by the developing unit to be visualized.

  At the bottom of the copying machine main body 100, a paper feed cassette 1 is detachably mounted. When the paper feed cassette 1 is mounted, the intermediate plate 2 is pushed up, and the sheet S stacked on the intermediate plate 2 is brought into pressure contact with the feeding roller 11 to obtain a predetermined paper supply pressure (pressure contact force). A sheet separating friction member 57 is pressed against and pressed against the feeding roller 11 that sequentially feeds the sheets stored in the sheet feeding cassette 1 by a pressing spring 57a. Then, the sheets S are fed one by one from the cassette 1 by a sheet feeding device having the feeding roller 11 and the friction member 57. The fed sheet is transported through a reverse transport path formed between the feed roller 11 and the reverse guide 59, and then passes through the pre-registration guide 60 to temporarily stop the registration roller pair 61. Led to. The registration roller pair 61 synchronizes with the developed image formed on the photosensitive drum 55 and conveys the sheet S to the transfer unit.

  A transfer roller 62 is in pressure contact with the photosensitive drum 55. The developed image is transferred when the sheet S conveyed by the registration roller pair 61 passes between the photosensitive drum 55 and the transfer roller 62. The sheet S after the image transfer is conveyed by the conveying device 63, and heat and pressure are applied when passing through the fixing device 65 to fix the transferred image. Then, the sheet S after image fixing is discharged out of the copying machine main body 100 by the discharge roller pair 66.

  Next, the basic configuration of the paper feed cassette 1 will be described. As shown in FIGS. 1 and 2, the sheet feeding cassette 1 has a middle plate 2 as a sheet stacking member supported so as to be able to move up and down in a state where sheets are stacked, and the size of the sheets stacked on the middle plate 2. Side restricting plates 5L and 5R as restricting members movable to the restricting positions. Further, the sheet feeding cassette 1 has a middle plate pressure spring 24L as an elastic member that urges the middle plate 2 toward the feeding roller in a state where one end is supported on the side of the cassette frame 1a which is a sheet feeding cassette body. , 24R and wires 22L, 22R as wire members. The wires 22L and 22R have one end connected to the side regulating plates 5L and 5R and the other end connected to the other ends of the middle plate pressure springs 24L and 24R.

  Further, the paper feed cassette 1 has a guide mechanism for guiding the wires 22L and 22R. This guide mechanism is a pressure contact force applied to the feeding roller 11 by the intermediate plate pressure springs 24L and 24R when the side regulating plates 5L and 5R are aligned with a sheet having a larger size than when the side regulating plates 5L and 5R are aligned with a small sheet. The wires 22L and 22R are guided so as to increase. The guide mechanism includes a first pulley 23a, a second pulley 23b, and a first pulley 23a, a second pulley 23b, which are rotatably supported by a first support shaft a1, a second support shaft a2, and a third support shaft a3, which will be described later. The third pulley 23c is used.

  In the paper feed cassette 1, the intermediate plate 2 is rotatably installed with the shaft portion 1b of the cassette frame 1a as a fulcrum. When the sheet feeding cassette 1 in a state in which no sheets are stored is mounted on the copying machine main body 100, the leading end 2 a of the intermediate plate 2 comes into contact with the abutting roller 12 provided on the same axis as the feeding roller 11. The upper limit position is determined. On the other hand, when the sheet is stored, the front end of the sheet similarly abuts against the abutting roller 12 to indirectly determine the position of the intermediate plate 2. Middle plate pressure springs 24L and 24R, which will be described later, are provided on the left and right sides of the cassette frame 1a.

  When removing the paper feed cassette 1 from the copying machine main body 100, as shown in FIGS. 3A and 3B, the cassette push-down cam 51 causes the cassette frame 1a side during the paper feed cassette 1 removal operation. The side end 2b of the intermediate plate 2 protruding slightly from the guide opening 18 is pushed down. As a result, the middle plate lock claw 9 provided on the side of the cassette frame 1a so as to face the guide opening 18 is engaged with the upper surface of the side end 2b, and the middle plate 2 is positioned in the state of FIG. To do. In this state, the sheet is supplied.

  Here, the positioning structure of the paper feed cassette 1 with respect to the copying machine main body 100 will be described. As shown in FIGS. 3A and 3B, the copying machine main body 100 is provided with a guide rail 52 for guiding the paper feed cassette 1 into the copying machine main body 100. The guide rail 52 positions the paper feeding cassette 1 in the width direction (front-back direction in the figure) and the height direction with respect to the copying machine main body 100. Further, in the insertion / extraction direction of the paper feed cassette 1 (left-right direction in the figure), the hook 15 rotatably supported by the cassette frame 1a is engaged with the hook receiving member 53 provided on the copying machine main body 100 side. Positioning is done.

  Further, as shown in FIG. 2A, side regulating plates 5L and 5R (see FIG. 1) as regulating members respectively provided on the left and right sides of the cassette frame 1a are screwed to the racks 6L and 6R, respectively. ing. The bosses 6Lb and 6Rb of the racks 6L and 6R are each guided by a groove 1c formed at the bottom of the cassette frame 1a, and the side regulating plates 5L and 5R and the racks 6L and 6R are shown in FIG. It is supported so that it can slide in the left-right direction. The racks 6L and 6R are composed of groove portions 6Lg and 6Rg guided by the hook portion 1d on the cassette frame side and hook portions 6Lf and 6Rf guided by the groove portion 1j on the cassette frame 1a side. (The front side in the middle) is secured.

  The left and right racks 6L and 6R are configured to move toward and away from each other via a pinion gear 7 rotatably supported at the bottom of the cassette frame 1a. As shown in FIG. 2 (b), the racks 6L and 6R have a sawtooth claw portion 6ac provided on the back surface of the side lever 6a rotatably provided on the side regulating plates 5L and 5R. The position is determined by engaging with the claw portion 1t on the 1a side. The side lever 6a is urged to the cassette frame 1a by an urging member (not shown), and when moving in the small size direction, the saw-type claw portion 6ac escapes from the claw portion 1t according to the direction of the claw and disengages. . When the side lever 6a moves in the large size direction, the user operates the lever to retract the saw-type claw portion 6ac from the claw portion 1t.

  The rear end regulating plate 8 disposed in the cassette frame 1a is supported by the rear hook portion 1e of the cassette frame 1a so as to be movable in the front-back direction of the paper feed cassette 1 (vertical direction in FIG. 2A). Similarly to the side restricting plates 5L and 5R, the rear end restricting plate 8 is engaged with a saw-like claw portion (not shown) provided on the rear lever 8a and a rear claw portion 1f provided on the cassette frame 1a. Alternatively, by retracting, the cassette frame 1a can be positioned and moved.

  Next, a characteristic configuration of the present invention will be described with reference to FIGS. 4A is a top perspective view in which the upper part of the cassette frame 1a is omitted, FIG. 4B is a right side view, and FIG. 5A is a diagram in which the bottom part of the cassette frame 1a is omitted. A lower perspective view and FIG. 5B are enlarged views of a portion D in FIG. 6A and 6B show a state in which the maximum size sheets are fully loaded in the paper feed cassette 1, wherein FIG. 6A is a side view and FIG. 6B is a bottom view.

  As shown in FIGS. 5 (a), 5 (b) and 6 (b), engagement members 21L and 21R are provided on the back side of the intermediate plate 2 to slide in conjunction with the side regulating plates 5L and 5R. It has been. As shown in FIG. 5B, the engaging member 21 </ b> R is attached so that the pair of arm portions 21 </ b> Ra can move up and down while sandwiching the side regulating plate 5 </ b> R. Furthermore, the engaging member 21R is supported so as to be movable in the direction of the arrow X in the figure via a mounting pin 21P slidably engaged with a slot 2c formed in the intermediate plate 2. Then, one end 22Ra of the wire 22R is hung on the engaging member 21R. Similarly, a pair of arm portions 21La of the engaging member 21L are attached with the side regulating plate 5L interposed therebetween, and one end portion 22La of the wire 22L (see FIG. 2A) is attached to the engaging member 21L. It is hung. Thus, the engaging members 21L and 21R can move in the width direction of the seat together with the side regulating plates 5L and 5R, and along the end portions of the side regulating plates 5L and 5R according to the raising and lowering of the middle plate 2. Can be moved up and down.

  A pair of left and right first pulleys 23a and 23a are rotatably supported on the back surface of the intermediate plate 2, and the side ends 2b of the left and right ends of the intermediate plate 2 are in the direction of the first support shaft a1 of the first pulley 23a. The second pulley 23b is rotatably supported by a second support shaft a2 in a direction orthogonal to the direction. Above the second pulley 23b on the side wall of the cassette frame 1a, a third pulley 23c is rotatably supported by a third support shaft a3 in a direction orthogonal to the direction of the second support shaft a2 of the second pulley 23b. .

  The wire 22R is wound around the first pulley 23a, is U-turned 180 degrees, is wound around the second pulley 23b, and is turned upward. Further, the other end portion 22Rb is connected to one end portion of the middle plate pressure spring 24R on one side surface of the cassette frame 1a by being wound around the third pulley 23c. Similarly, the wire 22L is also wound around the other first pulley 23a, is turned 180 degrees, is wound around the other second pulley 23b, and is turned upward. Further, as shown in FIG. 2A, the other end portion 22Lb is connected to one end portion of the intermediate plate pressure spring 24L on the other side surface of the cassette frame 1a by being hung around the other third pulley 23c. .

  The first support shaft a <b> 1 is attached at the bottom of the paper feed cassette 1 so as to face the front and back direction of the middle plate 2 (up and down direction of the paper feed cassette 1). The second support shaft a2 is attached so as to face in the front-rear direction (the front-rear direction of the paper feed cassette 1) of the side end 2b of the intermediate plate 2 (see FIGS. 2A and 5B). The third support shaft a3 is attached so as to face in the left-right direction (the left-right width direction of the paper feed cassette 1) at the side of the cassette frame 1a that is the paper feed cassette body (FIG. 2A). 5 (b)). The wires 22L and 22R receive the movement of the side regulating plates 5L and 5R approaching or separating in the left-right direction of the sheet cassette 1 at the one end portions 22La and 22Ra, and the first pulleys 23a and 23a at the center position of the intermediate plate 2 are used. Then, the direction of expansion and contraction is changed by folding back 180 degrees. Further, the wires 22L and 22R change directions by about 90 degrees between the second pulleys 23b and 23b and the third pulleys 23c and 23c positioned above in the up-and-down direction of the intermediate plate 2, respectively, and the intermediate plate pressure spring 24L , 24R are connected to the other end portions 22Rb, 22Lb, respectively.

  For this reason, when the side regulating plates 5L and 5R are aligned with the large size sheet on the middle plate 2 (on the sheet stacking portion), the wires 22L and 22R turned back by the first pulleys 23a and 23a are pulled, respectively. Thus, the working length of the intermediate plate pressure springs 24L and 24R is extended. Thus, the intermediate plate pressure springs 24L and 24R are extended so that the pressure contact force (sheet feeding pressure) of the sheet on the intermediate plate 2 to the feeding roller 11 is increased. On the other hand, when the side regulating plates 5L and 5R are aligned with the small-size sheet on the intermediate plate 2, the wires 22L and 22R turned back by the first pulleys 23a and 23a are loosened, thereby causing the intermediate plate pressure springs 24L and 24L, 24R is returned to a state close to the natural length. The intermediate plate pressure springs 24L and 24R are thus contracted, so that the pressure contact force (sheet feeding pressure) of the sheet on the intermediate plate 2 to the feeding roller 11 is set to be small. As described above, when the side regulating plates 5L and 5R are aligned with the large size sheet, when the side regulating plates 5L and 5R are aligned with the small size sheet, the extension length of the intermediate plate pressure springs 24L and 24R becomes longer. The paper feed pressure can be increased. Therefore, a mechanism that changes the pressure contact force of the middle plate 2 against the feeding roller 11 in conjunction with the adjustment operation of the side regulating plates 5L and 5R in the sheet feeding cassette 1 can be realized with a very simple structure. Furthermore, a mechanism with good operability can be obtained in which the sheet feeding pressure can be changed continuously (analog) simply by changing the pulling direction or the loosening direction of the intermediate plate pressure springs 24L, 24R with the pulleys 23a, 23b, 23c. .

  Next, the description will be continued with reference to FIGS. 3 (a) and 3 (b) and FIGS. 4 (a) and 4 (b). That is, the other end of the intermediate plate pressure spring 24R provided on the right side of the cassette frame 1a is hung on the shaft member 39. The shaft member 39 is slidably inserted into a groove portion 25a at one end portion of an arm member 25 that is rotatably supported with a shaft portion 1h provided on the right side portion of the cassette frame 1a as a fulcrum. Further, the shaft member 39 is slidably inserted into the groove portion 10 extending in the arrow A direction on the right side portion of the cassette frame 1a. Accordingly, the shaft portion 39 is freely moved in the direction of arrow A in FIG. 4B along the groove portion 10 in conjunction with the turning operation of the arm member 25. Note that the intermediate plate pressure spring 24L on the left side of the cassette frame 1a has the same configuration as that described above for the right side.

  On the side of the cassette frame (sheet feeding cassette body) 1a, there is a shaft as a support portion movable within a predetermined range (range within the groove portion 10) that supports one end of the intermediate plate pressure springs (elastic members) 24L and 24R. A portion 39 is provided. Further, an arm member 25 as a rotating arm that can be rotated along the surface of the side portion with a shaft portion 1h as a rotating shaft as a fulcrum is disposed on the side portion of the cassette frame 1a. The guide rail 52 of the copying machine main body 100 serves as an engaging portion that engages with the arm member 25 and rotates the arm member 25 in one direction when the paper feeding cassette 1 is mounted on the copying machine main body 100. The cam portion 52a is disposed. When the arm member 25 engages with the cam portion 52a and rotates in one direction (clockwise direction in FIG. 3), the arm member 25 pulls the intermediate plate pressure springs 24L and 24R by pulling the shaft portion 39. It functions to press the sheet on the intermediate plate 2 against the feeding roller 11.

  That is, when the paper feed cassette 1 is mounted on the copying machine main body 100, the arm member 25 engages with the cam portion 52a provided on the guide rail 52, so that FIG. It is turned to the turning position of (a). If there is no cam portion 52a of the guide rail 52 and the position of the arm member 25 is not changed, a state as shown in FIG. The intermediate plate pressure spring 24R has a length that applies an urging force capable of feeding a maximum number of sheets. Changing the position of the side restricting plates 5L, 5R in this state increases the operating force.

  Next, the operation state in each condition of the paper feed cassette 1 according to the present invention will be described.

(I) When the maximum size sheet is fully loaded FIG. 6A is a side view of a state where the maximum size sheet is fully loaded on the intermediate plate 2, and FIG. 6B is a bottom view thereof. Here, of the total weight of the sheet and the intermediate plate 2, the total force acting on the two second pulleys 23b is W1, and the force that pushes up the intermediate plate 2 by the two intermediate plate pressure springs 24L, 24R is F1, Each distance from the engaging members 21L and 21R to the first pulley 23a is L1l. Further, each distance from the first pulley 23a to the second pulley 23b is L21, a distance from the second pulley 23b to the third pulley 23c is L31, and a distance from the third pulley 23c to the shaft member 39 is L4. The sheet feeding pressure F1 ′ at this time is
F1 ′ = F1-W1 (1)
It is represented by

(Ii) When one maximum size sheet is stacked FIG. 7A is a side view showing a state in which one large size sheet remains on the intermediate plate 2, and FIG. 7B is a bottom portion of the cassette frame 1a. It is the bottom view which omitted illustration. Here, of the total weight of the sheet and the intermediate plate 2, the total force acting on the two second pulleys 23b is expressed as W2 = 0, and the force for pushing up the intermediate plate 2 by the two intermediate plate pressure springs 24L and 24R. F2, and the distance from the second pulley 23b to the third pulley 23c is L3s.

Here, the relationship between the intermediate plate pressing force in the states (i) and (ii) and the sheet feeding pressure F2 ′ are expressed as follows.
F2 = F1-2 * k * (L31-L3s)
Where k is the spring constant of the intermediate plate pressure springs 24L and 24R, and L3l-L3s is the maximum sheet stacking height.
F2 ′ = F2 = F1-2 × k × (L31-L3s) (2)

(Iii) When the minimum size sheets are fully loaded FIG. 8A is a side view showing a state where the minimum size sheets are fully loaded on the intermediate plate 2, and FIG. 8B is an illustration of the bottom portion of the cassette frame 1a omitted. FIG. Here, of the total weight of the sheet and the intermediate plate 2, the total amount acting on the two second pulleys 23b is W3, and the force that pushes up the intermediate plate 2 by the two intermediate plate pressure springs 24L and 24R is F3, The distance from the engaging members 21L and 21R to the first pulley 23a is L1s.

Here, the relationship between the intermediate plate pressing force in the states (i) and (iii) and the sheet feeding pressure F3 ′ are expressed as follows.
F3 = F1-2 × k × (L1l-L1s)
However, k: spring constant of the intermediate plate pressure springs 24L, 24R, L1l-L1s: (maximum sheet width-minimum sheet width) / 2.
F3 ′ = F3-W3 = F1-2 × k × (L1l-L1s) −W3 (3)
That is, the intermediate plate pressure springs 24L and 24R may be designed so that the calculated result value of the sheet feeding pressure F1 ′ to the sheet feeding pressure F3 ′ becomes a necessary sheet feeding pressure.

  For example, the required sheet feeding pressure is 1200 ± 120 [gf], the maximum sheet size is A4 (sheet width 210 mm), the minimum sheet size is A5 (sheet width 148.5 mm), and the maximum sheet stacking height is 50 mm (thickness 0. Tentatively determined that 1 mm / 1 sheet is 500 sheets). Furthermore, W1 = 500 [gf], W2 = 0 [gf], and W3 = 300 [gf] were provisionally determined, and the intermediate plate pressure springs 24L and 24R were designed. As a result, the above conditions can be satisfied by using a spring having a spring constant of about 5 to 7 [gf / mm].

Here, as shown in FIG. 12, the following can be cited regarding the required sheet feeding pressure at the time of maximum stacking and minimum stacking of sheets.
(1) The inclination of the uppermost sheet is different between the maximum stacking and the minimum stacking of the sheets with respect to the feeding direction by the feeding roller 11.
(2) The greater the difference between the inclination of the uppermost sheet and the inclination in the feeding direction, the greater the effect of curvature separation, and the easier the separation.
(3) On the contrary, the resistance when feeding the sheet is large.
For the reasons described above, it is preferable that the sheet feeding pressure at the maximum stacking of sheets can be set large and small at the minimum stacking. Of the above-described values, W1 and W3, that is, the load acting on the second pulley 23b when the maximum-size or minimum-size sheet is stacked is the position of the rotation center axis (shaft portion 1b) of the intermediate plate 2. Can be changed. The required paper feed pressure is a value that varies depending on the material of the separation pad.

(Iv) When the paper feed cassette 1 is removed from the copying machine main body 100 FIG. 9A shows the position of the side regulating plates 5L and 5R in the paper feed cassette 1 at the maximum size width and the middle plate 2 at the lowest position. FIG. 9B is a bottom view in which the bottom portion of the cassette frame 1a is omitted.

Here, if the distance from the third pulley 23c to the shaft member 39 is L4 ′, the force F4 required to move the side regulating plates 5L and 5R is:
F4 = F1 / 2−k × (L4−L4 ′) (4)
In other words, if the intermediate plate pressure springs 24L and 24R are determined to be L4 and L4 ′ so as to decrease the value of F4, the operability of the side regulating plates 5L and 5R when the sheet cassette 1 is removed and sheets are replenished. Can be made better.

  According to the copying machine of the present embodiment, stable feeding can be performed regardless of the size and number of stacked sheets stored in the sheet feeding cassette 1, and high reliability can be ensured. Further, since the middle plate pressure springs 24L and 24R are arranged on the side surface of the cassette frame 1a and the wire members 22L and 22R are wound along the side surface of the cassette frame 1a and the back surface of the middle plate 2, the conventional springs are separated. The dimension in the height direction can be reduced. Since the height of the paper feed cassette 1 can be reduced as compared with the conventional case, the height of the copying machine main body 100 can also be reduced.

DESCRIPTION OF SYMBOLS 1 ... Paper feed cassette, 1h ... Rotating shaft (shaft part), 2 ... Sheet stacking part (middle plate), 5L, 5R ... Restricting member (side restricting plate), 11 ... Feed roller, 22L, 22R ... Wire member (Wire), 23a, 23b, 23c ... guide mechanism (first pulley, second pulley, third pulley), 24L, 24R ... elastic member (medium plate pressure spring), 25 ... rotating arm (arm member), 39 ... support portion (shaft portion), 52a ... engagement portion (cam portion), 100 ... main body (copier main body), a1 ... first support shaft, a2 ... second support shaft, a3 ... third support shaft, S ... Sheet

Claims (3)

In an image forming apparatus comprising: a paper feed cassette configured to be detachable from the apparatus main body; and a feed roller that feeds a sheet stored in the paper feed cassette,
The paper cassette is
A sheet stacking unit supported so as to be able to move up and down by stacking sheets;
A restricting member movable to a restricting position according to the size of the sheets stacked on the sheet stacking unit;
An elastic member that urges the sheet stacking portion toward the feeding roller in a state where one end is supported on a side portion of the sheet feeding cassette body;
A wire member having one end connected to the restriction member and the other end connected to the other end of the elastic member;
When the restricting member is aligned with a small size sheet, when the elastic member is aligned with a large size sheet, the length of the elastic member to be extended is increased so that the pressure contact force to the feeding roller is increased. An image forming apparatus comprising: a guide mechanism for guiding the wire member. The guide mechanism includes a first pulley that is rotatably supported by a first support shaft provided on the sheet stacking portion so as to face the front and back sides of the sheet stacking portion, and a side end of the sheet stacking portion of the sheet feeding cassette. A second pulley rotatably supported by a second support shaft provided so as to face in the front-rear direction, and positioned above the sheet stacking portion in the up-and-down direction and on the side of the sheet feeding cassette body A third pulley rotatably supported by a third support shaft provided to face the left-right width direction of the paper cassette,
The wire member extends from the restricting member, is folded back by the first pulley, is further turned by the second and third pulleys, and is connected to the other end of the elastic member,
When the regulating member is aligned with a large-sized sheet, the working force of the elastic member is extended by pulling the wire member folded back by the first pulley to increase the pressure contact force, When the regulating member is aligned with the small-sized sheet, the elastic member is returned to a state close to a natural length by loosening the wire member folded by the first pulley, and the pressure contact force is reduced. The image forming apparatus according to claim 1. A support part movable in a predetermined range supporting the one end of the elastic member on the side part of the paper feed cassette body, and a turn capable of turning along the surface of the side part about a turning shaft An arm, and
The apparatus body includes an engaging portion that engages the rotating arm when the sheet feeding cassette is attached to the apparatus body to rotate the rotating arm in one direction.
The rotating arm pulls the support portion and pulls the elastic member when rotating in the one direction, and presses the sheet on the sheet stacking portion against the feeding roller. Item 3. The image forming apparatus according to Item 1 or 2.

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