JPH06255810A - Sheet feeder - Google Patents

Abstract

PURPOSE:To provide a front loading sheet feeder excellent in fitting/removing operability by providing a sheet feed roller, a separating roller, a guide member on the sheet feed side of a tray inclined with a sheet stacking face downward on a sheet feed face, and pushing up a bottom plate so that the upper face of a sheet bundle is brought into pressure contact with the sheet feed roller. CONSTITUTION:A sheet feed tray 20 is provided with front/rear side fences 10, 11 and an end fence 12 restricting the stacking of a sheet bundle 19, a moving bottom plate 21 rocked while a rotating fulcrum 23 near the rear end serves as the axis and movable in the vertical direction, a sheet feed roller 51 feeding the uppermost sheet of the sheet bundle 19 mounted on the bottom plate 21 in the sheet feeding direction, a separating roller holding a shaft 53, pressed to the sheet feed roller 51 across an upper guide member guiding the upper face of the fed sheet and a feed path, and rotatable only in the opposite direction to the sheet feeding direction, and a housing 81 holding it, guiding it in the approaching/separating direction from the sheet feed roller 51, and having a lower guide section 13 of sheets. No electric parts are provided on the tray 20.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet feeding device of an image forming apparatus having a front loading type sheet feeding tray for inserting / removing a sheet feeding tray from the front side of an operation side of an image forming apparatus main body and attaching / detaching it at a predetermined position. Regarding

[0002]

2. Description of the Related Art Conventionally, a paper feed tray of an image forming apparatus such as an electrophotographic copying machine, a facsimile machine or a printer is detachably attached from a side surface of an operation side of the apparatus main body, and is attached to the paper feeding tray provided in the main body of the apparatus. The rollers are pressed against the upper surface of the sheet bundle placed in the paper tray, and the paper feed roller rotates in response to the paper feed signal. The side loading type is widely adopted.

However, recently, there is an advantage that a paper feed tray can be easily attached and detached without requiring a space on the side of the main body of the image forming apparatus. 2. Description of the Related Art Paper feeding apparatuses having a so-called front loading type paper feeding tray in which a paper tray is inserted / removed, mounted at a predetermined position, and ejected are in widespread use. In this method, the attaching / detaching direction of the paper feed tray and the paper feed direction are at right angles to each other.

In the conventional paper feeding apparatus using the front loading type paper feeding tray, as in the case of the side loading type, the paper feeding roller is provided in the main body of the apparatus, and as a multi-feed separating means, it is separated by pressing against the paper feeding roller. When a roller, a separation pad or the like is used, it is usual that these separation means are also provided in the apparatus main body. Therefore, the conventional front-loading type paper feed tray has only a function of stacking a sheet bundle, has a low height and low rigidity strength, is easily bent when the sheet bundle is fully loaded, and has improved operability of insertion and removal. It is common practice to add rolling rollers to both sides in order to make them work. Therefore, since rails for supporting the above-mentioned rolling rollers and supporting the tray are attached to both sides (upstream side and downstream side in the sheet feeding direction) of the sheet bundle stacking range, there is a drawback that the width becomes wide.

By the way, as a double feed separating means for separating and feeding the sheets one by one from the sheet bundle stacked in the paper feed tray, conventionally, there are corner claw separation (CS separation) and friction pad separation (CS separation). FP separation), friction roller separation (FR separation), return roller separation (FRR)
Separation) has been commonly adopted.

[0006] Corner claw separation (CS separation) has a simple structure and is low in cost, but since the rigidity of the paper is used, the paper types that can be passed are as narrow as 50K to 70K and the separation performance is high. Since it is easily affected by the usage environment, there are many limitations to the user.

Friction pad separation (FP separation) is, for example, as disclosed in Japanese Patent Laid-Open No. 4-39226, only a simple mechanism of providing a friction pad (friction member) which is in pressure contact with a sheet feeding roller as a separating member. ,
The paper types that can be passed are wide, from 45K to 111K, and it has been considered that the separation method has a good balance between cost and quality, except for the occurrence of abnormal noise. The cost of the device has increased due to the positional relationship of the separating member and the pressure releasing mechanism. Further, in recent years, high durability is desired, and it is becoming technically difficult in terms of the material of the friction pad.

Friction roller separation (FR separation) is
For example, JP-A-63-267626 and JP-A-63-263626
As disclosed in Japanese Patent No. 295341, etc., the friction pad is used as a friction roller, and the friction roller is rotated so that the contact position with respect to the paper feed roller is sequentially changed.
Although it has higher durability than friction pad separation, it requires a one-way clutch and ratchet mechanism to control the rotation of the separation roller, which increases the cost by that amount, and cost performance cannot be balanced. The position of the advantageous image processing number (the number of copies per minute, the number of prints per minute, etc.) was in a floating state.

In the return roller separation (FRR separation), the paper feed path is sandwiched between the paper feed rollers and the return roller rotatable in either forward or reverse directions is brought into pressure contact with the paper feed roller. When one sheet of paper is passed through, the return roller rotates with the sheet against the torque in the direction opposite to the paper feeding direction, and when two or more sheets are fed, the return roller Due to the difference between the coefficient of friction between the roller and the sheet and the coefficient of friction between the sheets, the return roller rotates in the direction opposite to the sheet feeding direction due to the torque in the direction opposite to the sheet feeding direction, and the second sheet or less from the sheet feeding roller side. I tried to bring it back,
It is excellent in that there is no sliding between the sheet and the roller, there is little fluffing of the sheet, and there is little wear of the roller, and it can handle a wide range of paper types that can be passed, approximately 45k to 200k, but the mechanism is complicated and cost is low. Is also significantly higher than other separation methods,
It is not suitable for popular machines and can only be used for high-speed machines (high-production machines).

Corner claw separation, friction pad separation,
In either the friction roller separation method or the return roller separation method, since the consumable rollers and pads are mounted inside the image forming apparatus main body, the workability for replacement is not good, and therefore maintenance is not performed by a service person. I had to leave it to my hand.

A separation method which is an intermediate position in terms of cost between the friction pad separation and the return roller separation,
A separation method called a separate friction separation (RF separation) method has been proposed. This separation method has a range of quality and paper types that can be passed over the return roller separation method. One of the features of this method is that the separation roller having a high friction coefficient is used, so that the sheet is not bent at the leading edge. It has occurred and its solution is one of the technical problems.

The separation roller used in the friction roller separation system or the separate friction separation system is supposed to be rotatable only in the non-feeding direction, but conventionally, the roller can be rotated in one direction and in the other direction. In order to prevent rotation, for example, a one-way clutch and a shaft having high hardness are used as disclosed in JP-A-63-295341 and JP-A-63-190142. However, there was a drawback that the cost was abnormally high despite the simple configuration.

Further, as means for reversing in order to sequentially change the contact position of the separation roller to the paper feed roller, conventionally,
A transmission mechanism for transmitting drive from a drive unit via a gear train, a shaft, etc., and an interlocking mechanism including levers, arms, springs, etc. interlocked with the attachment / detachment operation of the paper feed cassette to the apparatus main body (Japanese Patent Laid-Open No. 61-90943). ), A dedicated mechanism consisting of a solenoid, a lever, and a spring was used, so a mechanism composed of dedicated parts only for that purpose is required, and the structure is complicated and costly for performing simple operation. There was a flaw.

When the shafts of the paper feed roller and the separation roller are held in the middle of the housing by molding, conventionally, a slide type is used to form a hole, but two U-shaped grooves are formed in which the openings are oriented in different directions when pressed. Since it was installed on the surface, the molding die became complicated and high precision was required, so a large amount of capital investment was forced.

Further, as a means for stopping the movement of the roller shaft in the thrust direction, an annular groove is generally formed in the shaft to form E.
A retainer ring called E-ring, which has teeth inside a ring that opens a single part of the mold or C-shape, and an S-shape without internal teeth, or a push nut, has been used, but the former costs to cut the groove. However, the latter is difficult to disassemble once assembled, and the shaft cannot be reused, so the overall cost was high.

[0016]

SUMMARY OF THE INVENTION In view of the above problems of the conventional sheet feeding device of the image forming apparatus using the front loading type sheet feeding tray, the present invention has the rigidity of the front loading type sheet feeding tray. Even when loading and unloading the stack of sheets to and from the main body of the device, the paper tray does not bend, and the width of the paper tray does not become wider in the direction perpendicular to the insertion direction. The main problem is to provide a paper feeding device.

With respect to the paper feed roller and the separation roller which are in pressure contact with the paper feed device and are rotatable only in the direction opposite to the paper feed direction, they are related to the drive of these rollers and the pivotal support of the conventional paper feed device. By improving the above-mentioned drawbacks, the range of paper types that can be passed through, the separation quality is the same as that of the conventional separate friction (RF) separation, the durability is the same as that of the friction roller (FR) separation, and the cost is the corner claw ( (CS) Separation is almost the same, and some consumable parts can be replaced even by the user's hand, and although the quality is high, total cost is low when considering the unit price of parts, assembly cost, service cost, etc. It is an object of the present invention to provide a sheet feeding device that becomes

[0018]

According to the present invention for solving the above-mentioned main problems, the paper feed tray is mounted on the apparatus body by inserting / removing it into / from the apparatus body from the front side of the operation side of the apparatus body. In a sheet feeding device that feeds one sheet at a time from a sheet feeding tray in a direction perpendicular to the attaching / detaching direction by a sheet feeding roller and a separating roller in pressure contact with the sheet feeding tray, the sheet separating roller and the sheet holding roller, The upper and lower guide members for guiding the
The paper feed tray is provided so as to be inclined such that the sheet bundle mounting surface is lowered on the paper feed side, and the upper surface of the sheet bundle placed on the sheet bundle mounting surface when the paper feeding tray is mounted on the main body. Has a bottom plate which is pushed up by a bottom plate raising member provided in the main body of the apparatus so as to come into pressure contact with the sheet feeding roller.

[0019]

In the paper feeding apparatus of the present invention, as described above, the paper feeding tray is provided with the paper feeding roller, the separating roller, and the upper and lower guide members for respectively holding these, so that the guide member reinforces the paper feeding tray. As a member, the rigidity of the paper feed tray is improved, the paper feed tray does not bend even when a stack of sheets is loaded in the main body of the device, and the attachment / detachment operation is easy without adding auxiliary means such as guide rollers. , Be sure.

Further, since the sheet mounting surface of the paper feed tray is formed as an inclined surface such that the paper feed side provided with the paper feed roller goes down, the rail opposite to the paper feed side of the guide rail when the paper feed tray is attached or detached is It is possible to make it slide under the sheet stacking surface, and the width in the direction perpendicular to the insertion direction of the paper feed tray can be reduced, and the increased height increases the rigidity of the paper feed tray. Operability is improved.

Further, since the paper feed tray and the separation roller are provided in the paper feed tray, it is not necessary to mount electrical parts on the paper feed tray, and the material of the paper feed tray can be a low-priced material with a safety standard of V2. Therefore, the cost can be reduced.

Further, since the upper guide is attached to the paper feeding tray, the curl pressing of the paper end portion, which is required in the conventional front loading paper feeding tray, becomes unnecessary. Further, since the sheet bundle is placed on the sheet feed tray, when the sheet feed tray is pulled out from the apparatus body, the bottom plate raising member provided on the apparatus body does not work and the bottom plate goes down, so that the sheet bundle is placed. Since a sufficient gap is formed between the placing surface and the sheet feeding roller, the setability of the sheet bundle is improved.

Drive of the above-mentioned paper feed roller and separation roller,
The structure and operation of each of the inventions subordinate to the above-mentioned main invention for solving various problems related to the shaft support etc. will be clarified by the description of the embodiments described in detail below with reference to the drawings. Will

[0024]

Embodiments of the present invention will be described below in detail with reference to the drawings.

<Overall Structure> FIG. 1 is a perspective view showing a paper feed tray of a paper feed device according to an embodiment of the present invention and the tray mounting portion of an image forming apparatus main body to which the paper feed tray is mounted. FIG. FIG. 4 is a cross-sectional view of the paper tray mounted at right angles to the attachment / detachment direction.

The paper feed tray 20 is slidable on a pair of left and right rails 3 provided in the image forming apparatus 1 by rails 22 provided on the left and right side surfaces of the paper feed tray 20 from the front side of the operating side. The image forming apparatus 1 can be inserted / removed in a direction indicated by a thick arrow to be attached / detached at a predetermined position in the main body of the image forming apparatus 1. Such a paper feed tray attachment / detachment method is generally called a front loading paper feed tray method.

The paper feed tray 20 swings around a front and rear side fences 10 and 11 and an end fence 12 that regulate the placement position of the sheet bundle 19 and a pivot fulcrum 23 near the rear end, and can move up and down in the vertical direction. A movable bottom plate 21, a paper feed roller 51 for feeding the uppermost sheet of the sheet bundle 19 placed on the bottom plate to the downstream side in the paper feed direction (to the right in FIG. 2), and a shaft 53 of the paper feed roller 51. And an upper guide member 25 that holds the sheet being fed and guides the upper surface of the sheet to be fed, and a separation roller 71 that is sandwiched in the sheet feeding path and comes into pressure contact with the sheet feeding roller 51 by means to be described later, and is rotatable only in the opposite sheet feeding direction.
And a housing 81 having a lower guide portion 13 for the sheet, which holds the sheet, guides it in the direction toward and away from the sheet feeding roller 51, and a leading end reference wall 24 of the sheet bundle.
When the friction coefficient of the paper feed roller 51 with respect to paper is μ _R , the friction coefficient of the separation roller 71 with respect to paper is μ _S , and the friction coefficient between them is μ _P , μ _P <μ _S <μ _R is set. ing. As shown in FIG. 15, the lower guide portion 13 cooperates with the paper feed roller 51 to guide the leading end of the sheet sent out by the paper feed roller 51 to the vicinity of the nip portion between the paper feed roller 51 and the separation roller 71. A guide 83 is provided.

Further, on both sides of the paper feed roller 51 in the axial direction, as shown in FIG.
As shown in FIG. 13, the end of the sheet fed by the paper feed roller 51 is received at an interval of 10 to 20 mm from the end surface of the paper feed roller 51, and the amount of bite into the range of the cross section of the paper feed roller is received. The blocking member 84 is provided on the lower guide portion 13 so that the maximum value is 0.9 mm to 2.0 mm. The friction coefficient μ _B of the blocking member 84 against the paper is determined by the separation roller 71.
It is said to be about the same as the friction coefficient against paper μ _S.

<Separator Roller Reversing Mechanism> As shown in FIGS. 7 and 8, a ratchet tooth 73 is provided on the outer periphery of a hub 72 provided at one end of the separator roller 71, and is engaged with this tooth. A lever 77 having a ratchet pawl 78 at its tip and a tail 79 at the bottom for receiving upward pushing force.
Is a guide portion 82 formed integrally with the housing 81.
It is held slidably inside. As shown in FIGS. 9 and 10, a strong compression spring 85 is stretched between the upper end of the lever 77 and the upper end of the guide portion 82, and the urging force of the compression spring 85 causes the positioning portion of the lever 77 to move to the guide portion 82. The lever 77 contacts the stopper 86 formed at the lower end and is positioned at a fixed position with respect to the housing 81 when the sheet cassette is mounted.

<Apparatus Main Body> The image forming apparatus 1 is provided with a pair of left and right rails 3 for attaching and detaching the paper feed tray 20 from the front side of the operation side as described above, and also FIG. 11 and FIG.
As shown in FIG. 6, in the passage of the tail 79 at the lower end of the lever 77 having the ratchet claw 78 described above, the convex portion 2 having a gently inclined surface before and after the loading direction of the paper feeding tray and the driving portion (not shown) are provided. The output joint 5 (see FIGS. 1 and 3) for transmitting power to the shaft 53 of the paper feed roller 51 and the movable bottom plate 21 of the paper feed tray mounted at a predetermined position are pushed up so that the sheet upper surface on the bottom plate is fed by the paper feed roller. It has a bottom plate raising member (not shown) that is brought into pressure contact with 51, and a conveyance member and a conveyance guide plate (not shown) that guide the fed and separated sheets to the image forming unit.

<Paper Feed Unit> In the paper feed unit of the paper feed tray 20, as shown in FIG. 3, a paper feed roller 51 is provided in the center on the right side as seen from the tray loading / unloading side, and its shaft 53 is fed from the back side. It is past the paper roller 51, the front end of the shaft is tapered so that it can be easily inserted into the hole of the roller, and the rear end is integrally connected with a bearing and joint 55 which is a separate member. There is. The joint 55 is adapted to be coupled to the output joint 5 at the engaging portion 57.

The shaft 53 has a U-shaped groove 15 having a width in which the upper guide member 25 passes through a round hole on the rear side, the sheet mounting surface side is released on the front side as shown in FIG. 6, and the shaft 53 is loosely fitted. And when the shaft is pushed all the way to the bottom of the U-shaped groove 15, the lower end of the shaft and 1-3 m
It is held by the fall prevention member 16 fixed to the upper guide member 25 so that the upper ends thereof face each other at an interval of m.

When the paper feed tray 20 is mounted in the apparatus, as shown in FIG. 4, the paper feed roller 51 is normally applied with the paper feed pressure P and the separation pressure Q from below, and the paper feed roller 51 Axis 53
Is held at a position where it comes into contact with the bottom of the U-shaped groove 15. Even when the paper feed tray 20 is taken out from the apparatus, the separation pressure Q is applied, so the position of the paper feed roller 51 does not always change.

When the shaft 53 is passed through the center hole of the paper feed roller 51, the paper feed roller 51 is first supported by the edge of the paper feed roller clearance hole provided in the lower portion of the upper guide portion 25. From the viewpoint of sheet conveyance quality and strength of the guide portion, the clearance hole is opened with a slight gap from the peripheral surface of the paper feeding roller at the regular position. When it is placed on the upper side, the position of the shaft center comes to a position several mm lower than the normal position. Next, when the tip of the shaft 53 is moved toward the sheet feeding roller 51 through the round hole on the back side, the tip of the shaft 53 is lowered by its own weight as shown by the chain line in FIG. The penetration portion on the front side of the upper guide portion 25 has a lower limit of 1 to 3 held by the upper end of the fall prevention member 16.
Since there is a margin of mm, it is easy to pass through. Also, since the paper feed roller 51 is supported below the regular position, the shaft 53 can be easily passed through the central hole of the paper feed roller 51.

As shown in FIG. 3 and FIG. 5, the shaft 53 is elastically pressed laterally in the middle of the above-mentioned two supporting portions for supporting the immediate vicinity of the paper feeding roller 51 and the rear end portion of the shaft 53. The pushing member 17 is fixed to the upper guide member 25. Therefore, when the shaft 53 is passed through, the pushing member 17 makes sliding contact with the shaft in a state of being pushed laterally by the shaft 53 against its resilience, but the shaft 53 is penetrated by the pushing member 17 in a mounted state. Since it is pressed against the side surface of the hole or U-shaped groove 15, the shaft 5
3 is difficult to slip out in the axial direction. Further, since the clutch of the sheet feeding roller engages with the shaft, the shaft 53 is more difficult to slip out. Since almost no force is applied to the shaft 53 of the paper feed roller in the axial direction, this degree of retaining is sufficient, and the above-mentioned problems that occur when retaining means such as a retainer ring is eliminated. To be done. When the paper feed tray is mounted in the main body of the apparatus, the paper feed roller shaft 53 is sandwiched between the output joint 5 and the upper guide member 25 of the paper feed tray 20, so that the paper feed roller shaft 53 should move in the axial direction. There is no.

<Sheet stacking section and its operation> Paper feed tray 2
The sheet placing portion including the sheet placing surface of the movable bottom plate 21 inside 0 is inclined by about 4 ° so that the sheet feeding side provided with the sheet feeding roller 51 and the separation roller 71 is lowered, and The functional part is provided in accordance with this inclination.

At the side end on the side opposite to the sheet feeding side, which is on the slope, there is a margin at the bottom of the sheet placing surface, so that the rail 22 that engages with the rail 3 in the apparatus main body for front loading is that portion. It fits in. Therefore, unlike the conventional paper feeding tray, the end surface of the paper feeding tray 20 on the side opposite to the paper feeding side does not protrude to the outside of the sheet stacking portion such as the rail, and the width of the paper feeding tray can be narrowed.

On the sheet feeding side, a sheet feeding roller 51 is provided above the end portion of the sheet stacking portion, and the sheet feeding roller 5 is sandwiched in the sheet feeding path at a position immediately downstream of the sheet mounting surface range.
A separation roller 71 is provided at a position where it comes into pressure contact with 1.
A sheet fed by the sheet feeding roller 51 is guided to a nip portion between the sheet feeding roller 51 and the separation roller 71 and fed in the front of the sheet bundle mounting surface range about 30 mm in front of the sheet feeding direction. An upper guide 25 that covers the front and rear portions of the roller 51 in the sheet feeding direction and both ends in the axial direction, is open at the upper portion, and has an escape hole at the lower portion for allowing the lower portion of the sheet feeding roller 51 to face the sheet bundle and the separation roller 71. Paper feed tray 2
It is fixed at 0.

In order to supply the sheet bundle into the paper feed tray 20, the rail 22 of the paper feed tray 20 is replaced with the rail 3 of the apparatus main body.
When the paper feed tray 20 is pulled out from the apparatus main body 1 by sliding it to, the movable bottom plate 21 is disengaged from the above-described bottom plate raising member provided in the apparatus main body, and is rotated about the rear end shaft fulcrum 23. The paper side edge is lowered, and as shown in FIG. 2, between the surface corresponding to the upper surface of the sheet bundle when the maximum allowable number of sheet bundles 19 is placed on the bottom plate 21 and the lower end of the paper feed roller 51, α mm
Gaps are formed.

Therefore, the paper feed tray 20 is attached to the main body 1 of the apparatus.
If the sheet bundle of the maximum allowable number is inserted on the bottom plate 21 from the side opposite to the paper feed side, the upper face of the bottom plate and the paper feed roller 51 are pulled out.
Since there is a gap larger than the maximum allowable number of sheets by .alpha.mm, the sheet is smoothly inserted until the front end abuts against the front reference wall without being obstructed or broken by the supply roller 51. To be done. At this time, the upper guide member 25 also plays a role of curl pressing of the supplied sheet.

<Reverse operation of separation roller> Separation roller 71
2 is held in a U-shaped housing 81 so as to be slidable in a direction toward and away from the paper feed roller 51 and rotatable about a shaft 74, and a paper feed tray is mounted in the main body. In the opened state, as shown in FIGS.
The ratchet teeth 73 provided around the hub 72 provided at one end of the first end of the arm 87 cantilevered to the tail portion of the lever 77 that is positioned and fixed by abutting the lower end against the stopper 86 by the spring 85. Ratchet claw 78 provided
And the shape of the ratchet teeth engages the separating roller 71
When the paper is about to rotate around the paper feed roller 51, the rotation is blocked, and when the separation roller 71 is about to rotate in the opposite paper feed direction (indicated by an arrow in FIG. 10), the arm 87 that supports the ratchet pawl 78. Bends to allow rotation of the separation roller. Therefore, the separation roller 71 cannot rotate in the sheet feeding direction, but can rotate in the counter sheet feeding direction.

A tail 79 is formed at the lower end of the lever 77,
When the lever 77 is attached to the guide portion 82 of the housing 81, the tail 79 projects from the housing 81 and pushes the tail 79 upward from the outside, so that the lever 77 slides vertically along the guide portion 82. be able to. Therefore, as shown in FIG. 16, during the front loading of the paper feed tray 20 with respect to the apparatus body, the apparatus body 1
11, the lever 77 is pushed up against the force of the spring 85 when the lever tail 79 crosses over the above-mentioned projection 2 having a gentle slope on both sides, and as shown in FIG. As shown, the ratchet pawl 78 of the lever 77
Is pushed up until it is engaged with the ratchet teeth 73 of the hub, so that the separation roller 71 is rotated in the reverse direction. When the lever tail 79 passes over the pass of the convex portion 2, the lever 77 is pushed down by the force of the spring 85. At this time, the ratchet pawl 7 of the lever 77 is pressed.
Since the arm 87 bends and slides down the slope of the ratchet teeth, the separation roller 71 does not rotate in the sheet feeding direction.

<Sheet Feed Separation Operation> The rotation drive generated by the drive source in the main body 1 of the image forming apparatus feeds the sheet in the sheet feed tray 20 through the output joint 5 and the input joint 55 coupled to each other. The roller 51 is rotated.

Since the upper surface of the sheet bundle 19 is pressed against the sheet feeding roller 51 by the bottom plate raising member 6 via the bottom plate 21 with a predetermined pressing force, a conveying force is generated between the sheet feeding roller 51 and the sheets 18. The uppermost sheet 18 is conveyed in the downstream direction as the sheet feeding roller 51 rotates. The conveyed sheet 1
8 is a sheet feeding roller at the front end of the sheet by being blocked by the blocking member 84 provided on both sides of the sheet feeding roller 51 in the axial direction, and the blocking member biting into the cross section of the sheet feeding roller. The left and right outer parts are buckled upward from the central part. Due to the strength of the strained sheet, a restoring force to return to the original flat state is generated in the buckled sheet, and this restoring force becomes a low separation pressure to the blocking member 84, and the sheet 18 and the blocking member 84 A blocking force is generated between the sheets, and the sheets that have been double-fed as a block are separated. At this time, the larger the number of double-fed sheets, the greater the restoring force and the higher the separation pressure.

This is the blocking member 8 for the paper feed roller 51.
The position setting of No. 4 is shown in FIG.
14 is 0.9 mm to 2.0 mm, and the distance between the edge of the blocking member 84 and both end surfaces of the paper feed roller 51 is 10 mm to 20 mm as shown in FIG. 14, a sheet of 45K to 90K is obtained. Up to 3 sheets can be separated without damage.

Next, the sheet 18 separated into three or less sheets
Is guided by the tip guide 83 to the front of the nip between the paper feed roller 51 and the separation roller 71 shown in FIG. At the tip of the tip guide 83, the separation roller 71 has three sheets 1
Since the separation margin that enables separation of 8 is extended to the vicinity of the nip, the contact angle when the sheet 18 hits the separation roller 71 can be reduced, and the leading edge of the sheet is not supported by the separation roller 71. "Feed""Bend"
Can be prevented.

From the above, the sheet 18 which has been double-fed as a block by the low-pressure pre-separation by the blocking member 84 and the main separation by the separation roller 71 is only the uppermost one sheet without damage. It can be separated and conveyed downstream.

[0048]

As described above, according to the first aspect of the invention, the paper feed tray is provided with the paper feed roller, the separation roller, and the guide member that holds these rollers integrally. The rigidity of the sheet bundle is improved, and the sheet bundle loading surface is inclined so that the sheet feeding side is lowered, so that the guide rails for inserting and removing the tray are slid below the sheet bundle loading surface at the end opposite to the sheet feeding side. In addition, the height can be increased, the rigidity can be improved, the width of the paper feed tray can be reduced, and the operability of attachment / detachment can be improved.

Further, since it is not necessary to provide electrical components in the paper feed tray, the material of the paper feed tray can be made cheaper in accordance with the safety standard V2, and the cost can be reduced.

Further, since the upper feed guide is attached to the paper feed tray itself, the curl pressing of the paper end portion, which is required in the conventional apparatus main body, is unnecessary, and the paper feed tray is removed from the main body for replenishing the sheet bundle. In the removed state, the movable bottom plate descends.Therefore, even if the maximum allowable number of sheet bundles are slid on the bottom plate and inserted, a sufficient margin can be created between the upper surface of the sheet bundle and the paper feed roller. Workability is improved.

According to the second aspect of the present invention, the U-shaped groove having a play in which the hole for holding the shaft of the paper feed roller at the back side of the paper feed roller is opened downward, and the shaft in the regular position. Since it is composed of the lower end of the roller and the fall prevention member with the upper end facing each other with a gap of approximately 1 to 3 mm, when the shaft is passed through the hole of the roller, the paper feed roller is placed on the clearance hole of the upper guide section. By placing it, you do not have to support the paper feed roller,
Assembly workability improves. Further, the configuration of the fitting hole formed by the U-shaped groove and the fall-off preventing member has a better positional accuracy than that of the conventionally used combination of two U-shaped grooves, and is effective in reducing the cost.

According to the third aspect of the present invention, since no retainer ring or the like is required to hold the shaft of the paper feed roller in the thrust direction with respect to the upper conveyance guide member, the paper feed roller is assembled and replaced. Occasionally, the work time is short and the work process is simple, so work mistakes are less likely to occur, and it is possible to reduce the cost by reducing the number of parts and the ideal combination of parts.

According to the fourth aspect of the invention, it is possible to prevent the separation roller from rotating in the conveying direction following the rotation of the sheet feeding roller at low cost.

According to the fifth aspect of the present invention, when the paper feed cassette is attached to or detached from the main body of the apparatus, the separation roller can be reversed by a predetermined amount in association with the attachment / detachment operation, and the life of the separation roller is improved. be able to.

Finally, according to the sixth and seventh aspects of the present invention, in addition to the friction roller separation that enables high durability, the sheets fed in blocks are pre-loaded up to 3 sheets or less. After separation, the tip guide guides the sheet to the nip portion between the paper feed roller and the separation roller, so that the contact angle of the sheet with the separation roller can be reduced and the diameter of the separation roller can be reduced. It is possible to reduce "double feed", "tip break", and "non-feed" and save space.

[Brief description of drawings]

FIG. 1 is a perspective view showing a configuration of a paper feed tray of a paper feed device according to an embodiment of the present invention and a paper feed tray mounting portion of an image forming apparatus to which the paper feed tray is mounted.

FIG. 2 is a cross-sectional view of the paper feed tray mounted at right angles to the mounting direction.

FIG. 3 is a cross-sectional view illustrating a method of supporting the paper feed roller of the paper feed tray on the upper conveyance guide member.

FIG. 4 is a cross-sectional view of a sheet feeding / separating unit of the embodiment.

FIG. 5 is a cross-sectional view showing a pushing member for preventing movement of the paper feed roller shaft in the thrust direction.

FIG. 6 is a front view showing a configuration of a through hole of a sheet feeding roller side support portion of a sheet feeding roller shaft.

FIG. 7 is a front view showing ratchet teeth formed around a hub provided at one end of the separation roller and ratchet pawls that engage with the ratchet teeth.

FIG. 8 is a side view thereof.

FIG. 9 is a side view showing a mechanism for holding and moving the ratchet pawl.

FIG. 10 is a front view thereof.

FIG. 11 is an explanatory diagram illustrating an operation of the ratchet pawl moving mechanism.

FIG. 12 is an explanatory diagram illustrating a pattern of engagement and disengagement of a ratchet pawl and a ratchet tooth due to movement of the ratchet pawl.

FIG. 13 is a cross-sectional view showing a blocking member for pre-separation of a block-shaped multi-feed sheet according to the present invention together with a paper feed / separation roller.

FIG. 14 is a top view thereof.

FIG. 15 is a cross-sectional view showing a front end guide that guides the front ends of two or three sheets that have been pre-separated to a nip portion between the paper feed roller and the separation roller, together with the paper feed roller.

FIG. 16 is an explanatory diagram illustrating that the ratchet pawl moves up and down when the paper feed tray is attached and detached, and the separation roller reverses a certain amount.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Convex part 3 Rail 5 Output joint 10, 11 Side fence 12 End fence 13 Lower guide member 14 Hole (supporting part) 15 U-shaped groove 16 Fall prevention member 17 Push member 18 Sheet 19 Sheet bundle 20 Paper feed tray 21 movable bottom plate 22 rail 23 bottom plate rotation fulcrum 24 tip reference wall 25 upper guide member 51 paper feed roller 53 shaft 55 bearing and input joint 57 engagement part 71 separation roller 72 hub 73 ratchet tooth 74 shaft 77 lever 78 ratchet claw 79 tail 81 Housing 82 Guide Part 83 Tip Guide 84 Blocking Material 85 Spring 86 Stopper

Claims (7)

[Claims] 1. A paper feed tray is inserted into and removed from the apparatus main body from the front side of the operation side of the apparatus main body, and is attached / detached. In a sheet feeding device that feeds the sheets one by one by a separating roller that is pressed against the sheet, the sheet feeding roller, the separating roller, and the upper and lower guide members that respectively hold these and guide the sheet are provided on the sheet feeding side of the sheet feeding tray. The sheet feeding tray is provided so as to be inclined such that the sheet bundle mounting surface is lowered on the sheet feeding side, and when the sheet feeding tray is mounted on the main body, the sheet bundle mounted on the sheet bundle mounting surface is A sheet feeding device having a bottom plate which is pushed up by a bottom plate raising member provided in the main body of the apparatus so that the upper surface of the sheet feeding roller is pressed against the sheet feeding roller. 2. The shaft of the paper feed roller is connectable to the drive shaft on the back side, the paper feed roller is fixed to the front end, and the sheet is provided at a position near the back side of the paper feed roller support. The stopper member fitted in the U-shaped groove having a play with respect to the shaft whose transfer surface side is open, and the upper surface of which is opposed to the lower end of the shaft at the regular position with a gap of about 1 to 3 mm is provided. The sheet feeding device according to claim 1, wherein the sheet feeding device is provided on the guide member. 3. The shaft of the paper feed roller is connected to a drive shaft on the back side, and the paper feed roller is fixed to the front end of the shaft.
A member integrally molded from another member having both a bearing and a joint is fixed to the back side, and the front end portion is formed into a substantially conical tapered shape, and the bearing portion of the shaft and the feed roller mounting portion are provided. The sheet feeding device according to claim 1, wherein a pressing member, which receives a light pressing force from the side, is fixed to the upper guide member at an intermediate portion between the two. 4. The hub of the separation roller is provided with ratchet teeth, and a lever having ratchet pawls engaging with the ratchet teeth is provided so as to be movable in the vertical direction until it abuts against a stopper fixed to a lower guide member. The sheet feeding device according to claim 1, wherein the sheet feeding device is provided. 5. A spring for urging the lever in the direction of abutting against the stopper is provided, and the lower end of the lever is inserted and removed from the front of the image forming apparatus main body to attach and detach it. 5. The sheet feeding device according to claim 4, wherein the image forming apparatus main body is provided with a convex portion having two inclined surfaces that gently fall toward the front side and the back side, respectively, at a position where the image forming apparatus main body interferes with. 6. A leading end guide member is provided to face the above-mentioned paper feed roller with a paper feed path sandwiched therebetween and to guide a sheet to a nip portion between the paper feed roller and the separation roller in cooperation with the paper feed roller. On both sides in the axial direction of the paper feeding roller, the friction coefficient is similar to that of the separating roller, and the trailing end of the sheet in the sheet conveying direction receives the leading end of the fed sheet thereon, and the leading end of the cross section of the separating roller. The sheet feeding device according to claim 1, further comprising a flat blocking member that is inclined so as to bite into the range. 7. The tip position of the blocking member has a maximum bite amount of 0.9 mm to 2.0 in the range of the cross section of the feed roller.
The sheet feeding device according to claim 6, wherein the sheet feeding device is set to have a width of 10 mm to 20 mm, and the edge of the blocking member in the sheet feeding width direction is set to be 10 mm to 20 mm apart from the end surface of the sheet feeding roller.