JPH07117880A - Sheet material supply device and image forming device - Google Patents

Abstract

PURPOSE:To provide a sheet material supply device of retard separation type which can improve separation performance and durability. CONSTITUTION:Since a sponge retard roller 51 is formed by a material having smaller hardness than that of a feed roller 6 and the shape of a nip section becomes a recessed shape on the sponge retard roller 51 side when the feed roller 6 is pressure-contacted with the sponge retard roller 51, tips of transfer paper sheet 2 are shifted in the shape of tiles when a plurality of transfer paper sheets 2 are fed into the nip section by a pick-up roller so that the tips of all the transfer paper sheets 2 which are fed in can come into contact with the sponge retard roller 51 directly. Consequently, it is possible to separate various transfer paper sheets 2 having different thickness and friction coefficient securely by the sponge retard roller 51.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet material supplying device for supplying a sheet material to an apparatus main body, and more specifically, a sheet suitable for supplying a transfer sheet as a sheet material into the image forming apparatus main body. Material supply device.

[0002]

2. Description of the Related Art FIG. 9 shows a conventional sheet material feeding device 1. The sheet material feeding device 1 feeds a transfer paper 2 which is a sheet material to an image forming apparatus (not shown) (arranged on the left side of the paper surface in FIG. 9). As shown in FIG. 9, the sheet material supply device 1 feeds the uppermost transfer papers 2 one by one from the sheet material storage device 3 in which a plurality of transfer papers 2 are stacked and stored on a stacking base (not shown). The pickup roller 5, a feed roller 6 that conveys the transfer sheet 2 fed from the sheet material storage device 3 by the pickup roller 5 into the main body of the image forming apparatus (not shown) (direction of arrow b in the figure), and the feed roller 6 When there are a plurality of transfer papers 2 which are arranged facing each other and are fed from the sheet material storage device 3, the retard roller is rotated in the direction opposite to the rotation direction of the feed roller 6 and separated into one transfer paper 2. 7 and a pair of conveying rollers 9 arranged in front of the main body of the image forming apparatus.

A guide 11 is arranged in a sheet material passing region 10 between the pickup roller 5, the feed roller 6 and the retard roller 7, and between the feed roller 6 and the retard roller 7 and the conveying roller pair 9, and Guides 12 are arranged between the pair of conveying rollers 9 and the main body of the image forming apparatus so that the transfer paper 2 is guided and conveyed.

The feed roller 6 and the retard roller 7 are driven by a drive transmission device 13 shown in FIG. As shown in FIG. 10, the drive transmission device 13 includes a feed roller shaft 15 for supporting the feed roller 6, a retard roller shaft 16 for supporting the retard roller 7, and a retard roller connected to the retard roller shaft 16. The drive shaft 17 is provided substantially in parallel.

The retard roller shaft 16 is supported by a swingable support member (not shown) so that it can come into contact with and separate from the feed roller shaft 15 in parallel.

A coupling 19 and a torque limiter 20 are arranged between the retard roller shaft 16 and the retard roller drive shaft 17. Further, an electromagnetic clutch 22 is provided at the end of the feed roller shaft 15 for transmitting the driving force transmitted from the main driving means (not shown) of the main body of the image forming apparatus via the drive input belt 21 to the feed roller shaft 15. There is. Further, between the feed roller shaft 15 and the retard roller drive shaft 17, the rotational driving force transmitted to the feed roller shaft 9 is applied to the retard roller drive shaft 1.
The retard drive belt 23, which transmits to 7, is wound around.

The coupling 19 is for transmitting drive from the retard roller drive shaft 17 to the retard roller shaft 16 even if the retard roller 7 is displaced.

The driving of the feed roller 6 and the retard roller 7 by the drive transmission device 13 will be described.

The rotational driving force given from the main driving means of the image forming apparatus main body (not shown) is applied to the driving input belt 21.
And is input to the pulley 25 provided in the armature part of the electromagnetic clutch 22 which is ON / OFF controlled according to the sheet feed timing.

Here, since the feed roller shaft 15, which rotates integrally with the rotor portion of the electromagnetic clutch 22, the retard roller drive shaft 17 and the retard roller shaft 16 are connected by the retard drive belt 23, the feed roller shaft 15 and the retard roller are connected. The roller shaft 16 and the retard roller drive shaft 17 rotate in the same direction, and the feed roller 6 and the retard roller 7 are rotationally driven in synchronization with the feed timing being ON.

By the drive transmission device 13, the transfer paper 2 is fed in the paper feeding direction (direction of arrow b shown in FIGS. 9, 10 and 12).
When the sheets are fed one by one, the torque limiter 20 idles in the retard roller 7 due to the frictional force between the feed roller 6 and the transfer sheet 2, and the retard roller 7 rotates in the direction opposite to the drive rotation direction of the retard roller drive shaft 17.

When a plurality of transfer papers 2 are fed, the frictional force between the plurality of transfer papers 2 is smaller than the frictional force between the retard roller 7 and the transfer paper 2. The torque limiter 20 does not idle, and the retard roller 7 rotates in the same direction as the rotation driving direction of the retard roller driving shaft 17.

As a result, the transfer paper 2 on the feed roller 6 side, that is, the uppermost transfer paper 2 and the other transfer papers 2 among the plurality of transfer papers 2 are separated, and the transfer papers 2 into the main body of the image forming apparatus. It is designed to prevent double feeding.

In the following description, a phenomenon in which a plurality of transfer sheets 2 are sent from the sheet material storage device 3 to the retard roller 7 is referred to as "bundle conveyance", and a plurality of sheets of the transfer paper 2 cannot be separated by the retard roller 7 into the main body of the image forming apparatus. A phenomenon in which the transfer paper 2 is fed is referred to as “double feeding”.

Next, a theoretical formula for satisfying the conditions for feeding and separating the transfer sheet 2 by the sheet material feeding apparatus 1 having the above-mentioned configuration will be described.

N> T / rμ _BP + (μ _APP −μ _AP ) W / μ _BP (1) N <T / rμ _BPP -2 μ _APP W / μ _BPP (2) N> T / r μ _CP ( 3) where μ _AP : coefficient of friction between pickup roller 5 and transfer paper 2 μ _BP : coefficient of friction between feed roller 6 and transfer paper 2 μ _CP : coefficient of friction between retard roller 7 and transfer paper 2 μ _APP : pickup Friction coefficient between transfer paper 2 under pressure portion of roller 5 μ _BPP : Coefficient of friction between transfer paper 2 at nip portion between feed roller 6 and retard roller N: Pressing force of retard roller 7 T: Torque limiter 20 idling Torque r: radius of retard roller 7 W: pressure of pickup roller 5

The above formula (1) is a formula that satisfies the paper feed condition, (2) is the separation condition, and (3) is the formula that satisfies the retard roller spiraling condition. Note that if the same transfer paper is used in the above formula, the friction coefficient of each roller pressing part will not vary so much, so if μ _APP ≈ μ _BPP = μ _PP , replace (1) and (2) below. Equations (4) and (5) are obtained.

N> T / r μ _BP + (μ _PP −μ _AP ) W / μ _BP (4) N <T / r μ _PP -2W (5) The above formulas (3), (4) and (5) FIG. 11 is a graph showing the relationship using the pressing force N of the retard roller 7 and the idling torque T of the torque limiter 20 as parameters.

In the figure, the shaded area is the feeding area.
That is, in order to enlarge the shaded area, the friction coefficient between each roller and the transfer paper is increased or the pickup roller 5 is used.
It is necessary to reduce the pressing force of the sheet feeding condition, and the feeding condition is set under the condition of increasing both the pressing force N of the retard roller 7 and the idling torque T of the torque limiter 20 (the upper right direction in the figure). It can be understood that the feeding area is wider.

[0020]

However, the conventional sheet material feeding device 1 has the following problems.

Among the transfer papers 2 that are usually used, even if the same kind is used, the coefficient of friction between papers varies,
Further, depending on the user, there are many cases in which different types of transfer paper are separately loaded on the loading table of the sheet material storage device 3. In such a case, the coefficient of friction between the transfer paper 2a in the plurality of transfer papers 2 stacked in the sheet material storage device 3 and the transfer paper 2b immediately below (see FIG. 11) is the transfer paper 2 in the periphery thereof. If the friction coefficient is significantly smaller than the coefficient of friction between them, bundle conveyance as shown in FIG. 12 occurs (in FIG. 11, three transfer sheets 2 are bundled).

In this case, the bundle of transfer sheets 2 is conveyed to the nip portion between the feed roller 6 and the retard roller 7 and separated and conveyed into the main body of the image forming apparatus.

However, the transfer sheets 2 conveyed in a bundle may not be separated even if the setting of sheet feeding conditions is changed, and double feeding may occur. FIG. 13 shows a schematic diagram when the transfer sheet bundle is conveyed (the figure shows a bundle of three sheets).

Here, when the transfer paper friction coefficients μ _PP are all equal, or when the transfer paper NO. 1 and NO. 2 friction coefficient μ _BPP1 is the transfer paper NO. 2 and NO. If μ _BPP1 <μ _BPP2 with respect to the friction coefficient μ _BPP2 between _No. 3 and _No. 3, the transfer paper conveyed in a bundle is transferred by the retard roller 7 to NO. 3, NO. It is separated in the order of 2 and double feeding does not occur.

However, when the condition of μ _BPP1 > μ _BPP2 occurs, the transfer paper NO. No. 3 is separated by the retard roller 7, and the transfer sheet No. 3 is fed until it passes through the nip portion of the feed / retard roller pair 6, 7. 2 is a transfer paper No.
It is dragged to 1 and fed into the device by a predetermined distance. The transfer paper NO. Transfer paper No. 3 before all 3 are separated. If 2 rushes into the conveyance roller 9, a double feed will result.

That is, the behavior of the transfer sheet in the middle other than the uppermost part and the lowermost part conveyed in the bundle is the pressure of the retard roller 7, the idling torque of the torque limiter 20 and the feeding coefficient such as the friction coefficient between each roller and the transfer sheet. No matter how the parameter for determining the condition is changed, it is determined by the friction coefficient between the transfer sheets 2 conveyed in a bundle.

Further, the schematic diagram of the bundle conveyance shown in FIG. 13 shows the conveyance of three sheets, but in a situation where the types of transfer papers are diversified as in recent years, it is unusual to convey a bundle of about 5 to 10 sheets. Needless to say, the fact that the number of sheets conveyed in a bundle increases makes the separation situation more severe.

Further, regarding the separating behavior of the transfer papers conveyed in a bundle at the retard roller portion, the transfer paper front end feeds and the rush separation is repeated into the retard roller pairs 6 and 7, and the retard roller 7 makes small forward and reverse rotations. Since this is done, the problem of vibration of the retard roller 7 occurs. Here, the vibration of the retard roller 7 induces the misalignment of the transfer sheet 2 conveyed in a bundle, and also contributes to the large fluctuation of the retard pressure.

Conventionally, in order to prevent the occurrence of bundle conveyance as against the above problems, the pressure W of the pickup roller 5 is reduced, or the pre-discriminating means is provided on the paper path portion in the upstream region of the feed / retard roller pair 6, 7. As a method, a baffle board is used. Further, in order to improve the separation performance under the sheet feeding condition as much as possible, a means for increasing the idling torque of the torque limiter 20 and reducing the pressing force of the retard roller 7 is also implemented.

However, in the former case, the pickup roller 5 is used in consideration of the occurrence of a pickup defect when the thick paper having a basis weight of about 150 to 200 g / m ² used for the cover mode is conveyed.
Of the pressing force W of the sheet and the amount U of the baffle that penetrates into the paper path U
P naturally has its limits.

In the latter case, the durability of the retard roller 7 is remarkably deteriorated because the latter is a paper feeding condition that facilitates the abrasion of the retard roller 7 by the transfer paper 2.

Further, the above-mentioned bundle conveyance becomes more noticeable in a high-speed machine which requires durability of the apparatus and parts, and the setting of the sheet feeding condition that lowers the durability of the roller is in the direction of the product. It becomes a measure against the sex.

Further, the above-mentioned vibration phenomenon of the retard roller 7 remains as a difficult problem in which the retard separating mechanism using the rubber roller does not have such a measure.

The present invention has been made in view of the above problems, and it is an object of the present invention to provide a retard separation type sheet material supply device capable of improving separation performance and durability.

[0035]

According to the present invention, there is provided a sheet material accommodating means for accommodating and supporting a sheet, a feeding means for feeding a sheet material from the sheet material accommodating means, and a sheet material fed from the delivering means. And a retard separating mechanism for separating and conveying the sheets one by one, the retard separating mechanism includes a feeding rotating unit that rotates in a sheet feeding direction, and the feeding rotating body. Separating rotation means for pressing the sheet material to rotate in a direction to return the sheet material to the sheet storing means, and the separating rotation means is formed of a material having a hardness lower than that of the feeding rotation means. Is.

[0036]

With the above construction, since the hardness of the feeding / rotating means is smaller than the hardness of the separating / rotating means, the nip shape becomes concave toward the separating / rotating means when pressed, and the sheet is fed to this nip portion by the feeding means. When a plurality of materials are fed in a bundle, the leading ends of the sheets are displaced in a straw shape due to the concave shape, and the leading ends of all the fed sheet materials can directly contact the separating / rotating means. Therefore, various sheet materials having different thicknesses and friction coefficients can be reliably separated by the separating and rotating means.

[0037]

1 shows a first embodiment of the present invention.

Reference numeral 51 in the drawing denotes a retard roller 51 made of sponge. Sponge has Asker hardness (C) of 7
Polyurethane foam of about °. As shown,
Regarding the nip shape between the feed roller 6 and the sponge retard roller 51, the feed roller 6 is the sponge retard roller 5
1 It has a recessed shape that is difficult to insert.

Further, the sponge retard roller 51 has an outer peripheral surface provided with a coating portion 52 which is uniformly spray-coated with a urethane liquid of the same material as the base material. The coating 52 is provided in order to prevent the surface of the sponge from being rusted and scraped, and to improve the durability of the roller.

The structure relating to the drive transmission of the feed roller 6 and the retard roller 7 is the same as the conventional structure, and the description thereof will be omitted.

The superiority of the present invention will be described with reference to FIGS.

FIG. 2 shows a situation in which the transfer paper 2 bundle-conveyed into the nip portion between the feed roller 6 and the sponge retard roller 51 made of rubber similar to the conventional system. As shown in the figure, the nip shape is concave in the direction of the sponge retard roller 51 as compared with the conventional rubber retard roller method, so that the front end of the transfer sheet 2 that has been conveyed in a bundle is displaced like a rock and is conveyed in a bundle. Since transfer papers other than the lowermost transfer paper can also be directly contacted with the sponge retard roller 51, all but the uppermost transfer paper can be separated by the sponge retard roller 51. And it is possible to prevent the double feeding of the transfer paper other than the lowermost part.

Further, since the rubber retard roller method described in the prior art cannot form a large concave nip as in the present embodiment, the transfer sheets 2 conveyed in a bundle are repeatedly gripped or skipped by the nip. However, in the present embodiment, since the bundle-conveying transfer paper having a staggered shape as described above continues to be reliably gripped at the nip portion during the separating operation, the transfer paper 2 is a sheet material. Stable separation is possible without being skipped to the rear of the storage device (upstream side of paper feeding).

Further, since the hardness of the sponge itself is much smaller than that of the conventional rubber roller (Asker hardness (A) 20 to 30 °), the base material itself absorbs the vibration of the sponge retard roller 51 during the separating operation. It can be said that there is almost no fluctuation in the pressure applied to the sponge retard roller.

Next, the fluctuation of the feeding area when the sponge retard roller 51 is used will be described.

FIG. 3 is an explanatory view of the mechanical balance of the sponge retard roller system. The pickup roller is omitted for the sake of explanation. In the figure, h is the amount of collapse of the sponge retard roller 51 in the radial direction, f is the stress at the nip portion,
θ is the turning angle of the nip, rt is the torque working radius,
R is the feed roller radius.

Here, since the sponge retard roller 51 has a larger amount of crushing in the radial direction than the rubber retard roller, it is replaced with a virtual retard roller whose original radius r is reduced to r−h. It becomes the formula of.

Μ _PP N (r−h) <T (6) However, since the actual sponge retard roller 51 is in contact with the feed roller 6 over the entire concave nip portion, the nip portion is subdivided in the circumferential direction. In that case, the stress actually applied to each contact surface and the torque operating radius that is the radius from the retard roller center on each contact surface fluctuate.

Specifically, the torque operating radius and the stress variation in the nip portion with the turning angle θ as a parameter are as shown in the graphs of FIGS. 4 and 5.

Here, N = Σf ... (7) rt = (R + r−h) cos θ−R ... (8)

That is, the true condition of separation of the sponge retard roller 51 is that the circumferential frictional force μ _PP f applied to each contact surface obtained by subdividing the nip portion in the circumferential direction and the torque at each contact surface. Operating torque μ which is the product of operating radius rt
The sum of _PP frt μ _PP Σ frt is less than the torque limiter idling torque T, and the equation is μ _PP Σ frt <T (9).

Here, μ _PP Nr = T ₁ (10) μ _PP N (r−h) = T ₂ (11) μ _PP Σfrt = T ₃ (12) T ₁ : in a rubber retard roller of radius r the balance torque T _2: the radius (r-h) of the virtual retarding torque balance in roller T _3: When the torque balance in the sponge retard roller 51 Figure 4, T ₁ as apparent from Figure _{5> T 2> T 3 ...} ( 13). In other words, in contrast to the rubber retard roller method, the sponge retard roller method can reduce the idling torque of the torque limiter 20 that satisfies the separation condition under the same retard roller pressure.

FIG. 6 is a graph showing the feeding area in each roller system based on the above data, using the pressing force N of the retard roller and the idling torque T of the torque limiter 20 as parameters.

As concrete data of this embodiment, the feed roller 6 radius R = 16 mm, the sponge retard roller 5
1 radius r = 16.5 mm, feed, retard roller inner diameter φ20 mm, sponge hardness Asker (C) 7 ° roller is used, and the radial direction collapse amount h of the sponge retard roller 51 is 2.5 mm, 3.3 mm, 4 mm Table 1 shows the results of the balancing torques T ₁ , T ₂ , and T ₃ below.

[0055]

[Table 1]

As described above, the sponge retard method can reduce the idling torque of the torque limiter 20 which satisfies the separation condition, so that the stress caused by the separation operation on the transfer paper 2 at the time of paper feeding can be reduced and the feeding such as skewing can be reduced. Not only paper defects can be reduced, but also damage to the sponge retard roller 51 is reduced and durability is greatly improved.

Since the idling torque of the torque limiter 20 is reduced, the driving torque is also reduced. Therefore, the allowable torque of the drive motor, the clutch, etc. can be reduced, and the cost of the driving means can be greatly reduced.

Next, FIG. 7 shows an example of an image forming apparatus (copying machine) equipped with the sheet material feeding device of the present invention.

The apparatus main body 200 includes a document table 206,
A light source 207, a lens system 208, a paper feeding unit 209, an image forming unit 202 and the like are provided. The paper feeding unit 209 accommodates the transfer paper and is detachably attached to the apparatus main body 200.
11 and a pedestal 212 are provided with a paper deck 213, and the present invention is applied to the supply of transfer paper from the cassettes 210, 211 and the paper deck 213. The image forming unit 202 includes a cylindrical photoconductor 21.
4. Developing device 215 containing toner, transfer charger 21
6, separation charger 217, cleaner 218, primary charger 2
19 and the like are provided respectively. The conveying device 220, the fixing device 204, and the discharge roller 2 are provided on the downstream side of the image forming unit.
05 and the like are provided.

The operation of this image forming apparatus will be described.

When a paper feed signal is output from a controller (not shown) provided on the apparatus main body side 200, the cassette 2
Transfer paper 2 from 10, 211 or paper deck 213
Is supplied. On the other hand, from the light source 207 to the document table 206
Light reflected by the document D placed on the document D is applied to the photoconductor 214 via the lens system 208. The photoconductor 214 is previously charged by the primary charger 219, and an electrostatic latent image is formed by being irradiated with light, and then a toner image is formed by the developing device 215.

The transfer sheet 2 fed from the sheet feeding section 209 is corrected by the registration roller 201 for skewing, and is further sent to the image forming section 202 at a timed timing. In the image forming unit 202, the toner image on the photoconductor 214 is transferred onto the transfer paper 2 sent by the transfer charger 216, and the transferred transfer paper 2 has a polarity opposite to that of the transfer charger 216 by the separation charger 217. And is separated from the photoconductor 214.

Then, the separated transfer paper 2 is conveyed to the fixing device 204 by the conveying device 220, and the fixing device 2
By 04, the unfixed transfer image is permanently fixed on the transfer paper 2. The transfer paper 2 on which the image is fixed is discharged from the apparatus main body 200 by the discharge roller 205.

In this way, the transfer sheet 2 fed from the sheet feeding section 209 is formed with an image and is discharged.

[Other Embodiments] FIG. 8 shows a second embodiment of the present invention.

Reference numeral 53 in the figure denotes an elastic retard belt. The elastic retard belt 53 is configured to separate and convey the transfer paper 2 by the retard driving means similar to the conventional one.

In this system, the predetermined nip area determined by the hardness and outer shape of the sponge retard roller 51 is set in the first embodiment, whereas the belt hardness, tension and feed roller 6 are set. The predetermined nip area can be set by changing the conditions such as the relative position of the belt with respect to.

As an advantage of this method, since the belt has a large peripheral area relative to the roller, the contact frequency between the transfer paper and the belt is reduced, and the durability of the retarding means can be further improved.

[0069]

As described in detail above, the present invention is
The hardness of the separating and rotating means in the retard separating mechanism is made smaller than the hardness of the feeding and rotating means so that the nip portion has a concave shape on the separating and rotating means side. Even so, the separating and rotating means can reliably separate and feed the sheet material, so that the feeding stability of the sheet material can be improved, and the durability of the feeding and rotating means and the separating and rotating means can be improved.

[Brief description of drawings]

FIG. 1 is a side view of a transfer paper material feeding device according to a first embodiment of the present invention.

FIG. 2 is an enlarged view of a nip portion of the apparatus shown in FIG.

FIG. 3 is a diagram illustrating a function of a main part of the apparatus shown in FIG.

FIG. 4 is a diagram showing a relationship between a winding angle and a torque working radius in a main part of the apparatus shown in FIG.

5 is a diagram showing a relationship between a winding angle and a nip stress in a main part of the apparatus shown in FIG.

FIG. 6 is a diagram showing a relationship between idling torque of a torque limiter in a retard roller and applied pressure.

FIG. 7 is a cross-sectional view showing an example of a copying machine provided with the transfer paper material supply device of the present invention.

FIG. 8 is a side view of the essential portions of a second embodiment of the transfer paper material feeding device of the present invention.

FIG. 9 is a side view showing an example of a conventional transfer paper material supply device.

10 is a perspective view showing a drive transmission mechanism in the apparatus shown in FIG.

FIG. 11 is a diagram showing a relationship between idling torque of a torque limiter and a pressing force in a conventional retard roller.

FIG. 12 is a side view showing a state in which a bundle of transfer sheets is conveyed in the conventional apparatus shown in FIG.

FIG. 13 is a schematic diagram showing a state of the bundle conveyance shown in FIG.

[Explanation of symbols]

 1 Transfer Paper Material Supply Device 2 Transfer Paper (Sheet Material) 3 Transfer Paper Material Storage Device (Transfer Paper Material Storage Means) 5 Pickup Roller (Feeding Means) 6 Feed Roller (Feeding Rotation Means) 51 Sponge Retard Roller (Separation Rotation Means) ) 52 coating layer 53 elastic retard belt

Claims (8)

[Claims] 1. A sheet material accommodating means for accommodating and supporting a sheet, a delivering means for delivering a sheet material from the sheet material accommodating means, and a sheet material for separately conveying the sheet material delivered from the delivering means. In the sheet material supply device including a retard separating mechanism, the retard separating mechanism presses the sheet feeding material into a sheet feeding rotating means that rotates in a sheet feeding direction and presses the sheet material into the sheet. And a separating and rotating means that rotates in a direction of returning to the storing means, wherein the separating and rotating means is formed of a material having a hardness smaller than that of the feeding and rotating means. 2. The sheet material feeding device according to claim 1, wherein the feeding rotation means is a rubber roller, and the separation rotation means is a sponge roller. 3. The sheet according to claim 2, wherein the sponge roller is composed of a sponge base material disposed inside and a coating layer of a material similar to the sponge base material disposed on an outer peripheral side. Material supply device. 4. A sheet material accommodating means for accommodating and supporting a sheet, a feeding means for feeding a sheet material from the sheet material accommodating means, and a sheet material fed separately from the feeding means for separate conveyance. In the sheet material supply device including the retard separating mechanism, the retard separating mechanism presses the sheet rotating member to rotate in a feeding direction of the sheet material and the sheet feeding rotating means. Separating rotation means that rotates in the direction of returning to the sheet storage means, and the feeding is performed such that the nip shape of the pressure contact portion between the separating rotation means and the feeding rotation means is a concave shape on the separating rotation means side. A sheet material supply device comprising a rotating body and the separating rotating body. 5. The feeding rotation means is a rubber roller, the separation rotation means is a sponge roller, the sponge roller is formed, and a concave shape is formed by pressing the sponge roller against the rubber roller. Sheet material supply device described. 6. The sheet according to claim 4, wherein the feeding rotating means is a rubber roller, the separating rotating means is a belt-shaped member, and the belt-shaped member is pressed against the rubber roller to form a concave shape. Material supply device. 7. A sheet material accommodating means for accommodating and supporting a sheet, a delivering means for delivering a sheet material from the sheet material accommodating means, and a sheet material fed from the delivering means are separately conveyed one by one. In the image forming apparatus provided with the retard separating mechanism, and the image forming means for forming an image on the sheet material separated by the retard separating mechanism, the retard separating mechanism is arranged in the sheet feeding direction. And a separating and rotating unit that rotates in a direction in which the sheet material is returned to the sheet storing unit, the separating and rotating unit being in pressure contact with the feeding rotating body. An image forming apparatus, which is formed of a material having low hardness. 8. A sheet material accommodating means for accommodating and supporting a sheet, a feeding means for feeding a sheet material from the sheet material accommodating means, and a sheet material fed separately from the feeding means for separate conveyance. In the image forming apparatus, the retard separating mechanism includes an image forming unit for forming an image on the sheet material separated by the retard separating mechanism, wherein the retard separating mechanism rotates in a sheet feeding direction. And a separating and rotating unit that presses against the supplying and rotating unit and rotates the sheet material in a direction to return the sheet material to the sheet storing unit, and presses the separating and rotating unit and the supplying and rotating unit. The image forming apparatus is characterized in that the feeding rotating body and the separating rotating body are configured such that the nip shape of the portion is concave toward the separating rotating means side.