JP7807896B2 - Sheet feeding device, manual feed tray device, document feeding device and image forming apparatus - Google Patents

Description

The present invention relates to sheet feeders, manual feed tray devices, document feeders, and image forming devices such as copiers, multifunction devices, printers, and facsimiles.

Sheet feeders equipped with a sheet tray on which sheets such as recording paper and originals are placed typically include a sheet size detection unit disposed on the sheet tray that detects the size of the sheets placed on the sheet tray (see Patent Document 1). Here, sheet feeders are provided, for example, in a manual feed tray device that is openably mounted on the side of the image forming device body, or in a document feeder that transports originals to a document reading position.

In such sheet feeders, the top surface of the sheet loading tray is often formed as a uniform plane (or approximately flat). As a result, deformation of the sheet (for example, Z-folding or curling of the sheet) can cause the detected portion of the sheet to move away from the sheet size detection unit, which can result in false detection by the sheet size detection unit depending on the degree of deformation of the sheet.

In addition, in order to place the sheet size detection unit on the sheet loading tray, a certain amount of space (thickness of the sheet loading tray) is required in the sheet loading tray, and if the top surface of the sheet loading tray is formed as a uniform plane (or approximately flat), the overall thickness of the sheet loading tray tends to increase.

Japanese Patent Application Publication No. 8-301457

The present invention aims to provide a sheet supply device, manual feed tray device, document feeder, and image forming device that can suppress erroneous detection by the sheet size detection unit even if the sheet is deformed, and that can reduce the overall thickness of the sheet loading tray.

In order to solve the above problem, the sheet supplying device of the present invention is a sheet supplying device comprising a sheet loading tray on which sheets are loaded, and a sheet size detection unit arranged on the sheet loading tray and detecting the size of the sheet loaded on the sheet loading tray, wherein the upper surface of the sheet loading tray has a first upper surface area including a detection portion of the sheet size detection unit that detects the sheet, and a second upper surface area other than the first upper surface area, the first upper surface area is formed convexly so as to be higher than the second upper surface area, the convex shape includes a curved shape, the convexly formed surface is composed of multiple surfaces, each of the multiple surfaces includes a convex curved surface, the multiple convex curved surfaces have different radii of curvature from each other, and the individual curved surfaces having the radii of curvature are combined and connected along the sheet supply direction, and when connected to each other, they form an overall smooth curved shape .

The manual feed tray device of the present invention is also characterized by being equipped with the sheet supply device of the present invention.

The document feeder of the present invention is characterized by including the sheet supply device of the present invention.

The image forming apparatus according to the present invention is characterized by being equipped with the manual feed tray device according to the present invention and/or the document feeder according to the present invention.

This invention makes it possible to prevent false detection by the sheet size detection unit even if the sheet is deformed, and also to reduce the overall thickness of the sheet loading tray.

1 is a perspective view showing an external appearance of an image forming apparatus according to an embodiment of the present invention; 1 is a perspective view of the front side of a document feeder according to an embodiment of the present invention, viewed obliquely from above; FIG. 2 is a perspective view of a sheet placement tray in the document feeder, viewed obliquely from above on the front side. FIG. 2 is a perspective view of a sheet placement tray in the document feeder, viewed obliquely from above on the rear side. FIG. 4 is a plan view showing a second tray portion of the sheet loading tray. 10 is a plan view showing a first upper surface area provided in a second tray portion of the sheet loading tray. FIG. 3 is an enlarged perspective view showing a first upper surface area portion on the upper surface of the sheet loading tray; FIG. FIG. 2 is an enlarged side view showing a first upper surface area portion on the upper surface of the sheet loading tray. 10 is a cross-sectional view showing a state in which both the first sheet size detection unit and the second sheet size detection unit in the first upper surface area detect the absence of a sheet; FIG. 10 is a cross-sectional view showing a state in which both the first sheet size detection unit and the second sheet size detection unit in the first upper surface area detect the presence of a sheet; FIG. FIG. 2 is a perspective view showing a sheet size detection unit. FIG. 2 is a perspective view showing an actuator that configures a sheet size detection unit. FIG. 10 is a plan view showing another example of the shape of the first upper surface region when viewed from above. FIG. 10 is a plan view showing yet another example of the shape of the first upper surface region when viewed from above.

Embodiments of the present invention will be described below with reference to the drawings. In the following description, identical components are designated by the same reference numerals. Their names and functions are also the same. Therefore, detailed descriptions thereof will not be repeated.

Figure 1 is a perspective view showing the appearance of an image forming apparatus 100 according to an embodiment of the present invention. The front side (front side, operation side) in the depth direction X of the image forming apparatus 100 is designated by the symbol X1, and the rear side (back side, back side) is designated by the symbol X2. In the left-right direction Y, which is perpendicular to both the depth direction X and the up-down direction Z of the image forming apparatus 100, one side (right side) is designated by the symbol Y1, and the other side (left side) is designated by the symbol Y2. The upper side in the up-down direction Z is designated by the symbol Z1, and the lower side is designated by the symbol Z2.

Image forming device 100 is a multifunction device with copy, scanner, facsimile, and printer functions. Image forming device 100 comprises an image forming device main body 110, a document feeder 200 equipped with a sheet feeder 201, and a manual feed tray device 120. Image forming device main body 110 comprises an image reading device 111, a paper feeder 112, an image forming unit 113, and an ejection unit 114. The manual feed tray device 120 is provided on the side of image forming device main body 110 (the side viewed from the front side X1) so as to be openable and closable.

The image reading device 111 reads images from documents and has a document reading unit (scanner) not shown. The image reading device 111 either reads images from documents using the document reading unit while the documents are transported by the document feeder 200, or scans and reads documents placed on the document reading unit's document placing table using the document reading unit.

The document feeder 200 is supported so as to be openable and closable relative to the image forming apparatus main body 110. When the document feeder 200 is opened relative to the image forming apparatus main body 110, the document placing tray of the image forming apparatus 100 is opened, allowing a document to be placed manually.

The paper feeder 112 stores sheets such as recording paper and supplies the stored sheets toward the image forming unit 113. The paper feeder 112 supplies sheets of various sizes using the center as a reference (center reference) in the width direction W, which is perpendicular to the supply direction H. The image forming unit 113 forms (prints) an image on the sheet sent from the paper feeder 112 based on image data. The discharge unit 114 discharges the sheet on which the image has been formed by the image forming unit 113.

[First embodiment]
FIG. 2 is a perspective view of the front side X1 of the document feeder 200 according to an embodiment of the present invention, viewed from diagonally above. FIGS. 3A and 3B are perspective views of the sheet loading tray 210 of the document feeder 200, viewed from diagonally above the front side X1 and the rear side X2, respectively. FIG. 4A is a plan view showing the second tray portion 212 of the sheet loading tray 210. FIG. 4B is a plan view showing a first upper surface area α1 portion provided on the second tray portion 212 of the sheet loading tray 210. FIGS. 5A and 5B are a perspective view and a side view, respectively, showing an enlarged view of the first upper surface area α1 portion of the upper surface 210a of the sheet loading tray 210. FIGS. 6A and 6B are cross-sectional views showing the first sheet size detection unit 220a and the second sheet size detection unit 220b in the first upper surface area α1 detecting the absence (OFF) and presence (ON) of a sheet (document G), respectively. 7A is a perspective view showing the sheet size detection unit 220. FIG. 7B is a perspective view showing an actuator 222 that constitutes the sheet size detection unit 220.

In this embodiment, the sheet supply device 201 includes a sheet loading tray 210 on which sheets (documents G in this example) are placed, and a sheet size detection unit 220 (document size detection unit) disposed on the sheet loading tray 210 and detecting the size of the sheets (G) placed on the sheet loading tray 210. The sheet supply device 201 supplies sheets (G) of each size using the center as a reference (center reference) in the width direction W perpendicular to the supply direction H.

Here, examples of sheet size detection units include those having an actuator that contacts the sheet (G) and rotates around a rotation axis along a transverse direction V that intersects with the sheet (G) supply direction H, and those having a light-reflection sensor equipped with a light-emitting unit and a light-receiving unit that detects the presence or absence of the sheet (G) by irradiating the sheet (G) with light emitted by the light-emitting unit and receiving light reflected from the sheet (G) with the light-receiving unit. A sheet size detection unit having an actuator can, for example, have one upper end of the actuator as the contact part with the sheet (G) and the other lower end of the actuator as the actuated part that activates the actuating part of the switch unit. Examples of switch units include a light-transmitting sensor switch that detects the interruption of light by the actuated part of the actuator, a reed switch that detects the presence or absence of a magnetic field by providing a permanent magnet in the actuated part of the actuator, and a mechanical microswitch that forms an actuator using a lever.

In this embodiment, the sheet size detection unit 220 is composed of multiple sheet size detection units. Specifically, the multiple sheet size detection units 220 detect the size of the sheet (G) in the supply direction H. In this example, the multiple sheet size detection units include a first sheet size detection unit 220a and a second sheet size detection unit 220b. Note that the first sheet size detection unit 220a and the second sheet size detection unit 220b have the same configuration, and are therefore shown in a single diagram in Figures 7A and 7B.

The first sheet size detection unit 220a and the second sheet size detection unit 220b detect the presence or absence of a sheet (G). The first sheet size detection unit 220a and the second sheet size detection unit 220b are electrically connected to an input system of the control unit (not shown). The control unit can detect the feed direction size of the sheet (G) in the feed direction H (e.g., A3 portrait, B4 portrait, A4 portrait, B5 portrait, A4 landscape, B5 landscape, etc.) by combining the on/off states of the first sheet size detection unit 220a and the second sheet size detection unit 220b.

As shown in Figures 7A and 7B, the sheet size detection unit 220 (220a, 220b) has an actuator 222 that abuts against the sheet (G) and rotates about a rotation axis β (rotation shaft 221) along a transverse direction V that intersects with the supply direction H of the sheet (G). In the sheet size detection unit 220, one upper end of the actuator 222 can be configured as a contact portion 222a that abuts against the sheet (G), and the other lower end of the contact portion 222a can be configured as an actuated portion 222b that actuates the actuating portion 223a of the switch unit 223. A through-hole 212a that penetrates the abutment portion 222a of the actuator 222 in the vertical direction Z is provided in the upper surface 210a (second tray portion 212) of the sheet loading tray 210. The through-hole 212a is slightly larger (by a predetermined dimension) than the size of the abutment portion 222a so that the abutment portion 222a can be inserted through the through-hole 212a when the actuator 222 rotates about the rotation axis β. In addition, a weight member 224 is provided on the opposite side of the actuator 222 from the abutment portion 222a across the rotation axis β. By providing the weight member 224 on the actuator 222 in this way, the abutment portion 222a of the actuator 222 can be reliably protruded from the through-hole 212a, and this can reliably operate the operating portion 223a of the switch portion 223 (turning it off in this example). When the contact portion 222a of the weight member 224 is not in contact with the sheet (G), the contact portion 222a protrudes from the upper surface 210a through the through-hole 212a, whereas when the contact portion 222a is in contact with the sheet (G), the weight member 224 has a weight such that the actuator 222 rotates and the contact portion 222a retracts into the sheet loading tray 210. In this example, the switch portion 223 is a light-transmitting sensor switch that detects the transmission and blocking of light L by the actuated portion 222b of the actuator 222. More specifically, the actuating portion 223a is composed of a light-emitting portion 223a1 and a light-receiving portion 223a2. The light-emitting portion 223a1 emits light toward the light-receiving portion 223a2. The light-receiving portion 223a2 receives the light L from the light-emitting portion 223a1. When the contact portion 222a of the actuator 222 is not in contact with the sheet (G), the actuated portion 222b blocks light L traveling from the light-emitting portion 223a1 to the light-receiving portion 223a2. On the other hand, when the contact portion 222a of the actuator 222 is in contact with the sheet (G), the actuated portion 222b allows light L to pass from the light-emitting portion 223a1 to the light-receiving portion 223a2.

As shown in Figures 3A to 6B, the upper surface 210a of the sheet loading tray 210 has a first upper surface area α1 including a detection portion γ (γa, γb) (see Figures 4B and 5B) that detects the sheet (G) of the sheet size detection unit 220 (220a, 220b), and a second upper surface area α2 other than the first upper surface area α1. The first upper surface area α1 is formed in a convex shape so that it is higher than the second upper surface area α2. In this example, the detection portion that detects the sheet (G) of the sheet size detection unit 220 is the portion where the actuator 222 comes into contact with at least the sheet (G).

According to this embodiment, the first upper surface region α1 is formed convexly so that it is higher than the second upper surface region α2, thereby increasing the height at which the sheet (G) can be detected by the sheet size detection unit 220 (220a, 220b). Therefore, even if the sheet (G) is deformed (e.g., Z-folding or curling), the detection margin for the deformed sheet (G) can be increased. In other words, the detected portion of the sheet (G) is less likely to separate from the sheet size detection unit 220, thereby reducing false detections by the sheet size detection unit 220. Furthermore, because only a portion of the upper surface 210a of the sheet loading tray 210 is formed convexly, the overall thickness of the sheet loading tray 210 can be reduced. This allows the sheet feeder 201 to be made thinner. Furthermore, because only a portion of the upper surface 210a of the sheet loading tray 210 is formed convexly, the ease of removing sheets (especially documents G) from the sheet loading tray 210 can be improved. Here, the greater the height of the first upper surface area α1, the more effective it is in suppressing false detection by the sheet size detection unit 220 and improving the ease of removing the sheet (G).

However, in this embodiment, the sheet size detection unit 220 (220a, 220b) having the actuator 222 is activated when the actuator 222 comes into contact with the sheet (G), making it prone to false detection.

In this regard, in this embodiment, the first upper surface region α1 is formed in a convex shape so that it is higher than the second upper surface region α2, so that erroneous detection by the sheet size detection unit 220 can be suppressed even if the sheet size detection unit 220 has an actuator 222.

The convex shape may also be rectangular, but in this case, unnecessary space is likely to be created for installing the sheet size detection unit 220.

In this regard, in this embodiment, the convex shape includes a curved shape. This reduces the number of angular portions, thereby reducing the space unnecessary for installing the sheet size detection unit 220.

In this embodiment, the convex surface is made up of multiple surfaces. This makes it easy to combine the individual surfaces of the convex surface, allowing the convex shape of the first upper surface region α1 to be flexibly formed to match the size and shape of the sheet size detection unit 220.

In this embodiment, the multiple surfaces include multiple convex curved surfaces α1(1) to α1(n) (n is an integer greater than or equal to 2; in this example, n=6) (see Figures 5A and 5B). This allows the first upper surface region α1 to have a smooth shape, and reduces the difference in level between the second upper surface region α2 and the first upper surface region α1. This in turn improves the detectability of the sheet size detection unit 220 (220a, 220b) for sheets (G), and also improves the ease with which sheets (particularly document G) can be removed from the sheet loading tray 210.

In this example, the multiple convex curved surfaces α1(1) to α1(n) have different radii of curvature. The multiple convex curved surfaces α1(1) to α1(n) are connected to each other and are formed into a smooth curved surface shape overall.

In this embodiment, the multiple convex curved surfaces α1(1) to α1(n) are connected along the feeding direction H of the sheet (G).

This allows the sheet (G) to be formed into a smooth curved shape along the supply direction H, thereby improving the design of the sheet loading tray 210 and the ease of removing the sheet (G).

In this embodiment, as shown in Figures 3A and 3B, the upstream region α2b of the second upper surface region α2, which extends from the upstream end α1a of the first upper surface region α1 to the upstream end α2a of the second upper surface region α2 in the supply direction H of the sheet (G), is lower than the first upper surface region α1.

This improves the ease of removing sheets (especially documents G) onto the sheet loading tray 210 on the upstream side of the second upper surface area α2 relative to the first upper surface area α1 in the sheet (G) supply direction H.

In this embodiment, the first upper surface region α1 is formed so that the convex apex Q (see Figure 5B) is located at the center of the sheet (G) in the supply direction H. Here, the concept of "center" includes not only the position halfway along the supply direction H from the first upper surface region α1 (the center position), but also the vicinity of the center position within a predetermined range in the supply direction H that includes the center position of the first upper surface region α1. The height of the apex Q from the second upper surface region α2 is not limited to this, but can be approximately 3 mm to 10 mm. In this example, the height of the apex Q from the second upper surface region α2 is approximately 3 mm.

This allows the sheet (G) to be reliably aligned from the center to the upstream and downstream sides of the convex supply direction H, thereby improving the detectability of the sheet size detection unit 220 (220a, 220b) for the sheet (G) and improving the ease of removal onto the sheet loading tray.

In this embodiment, the sheet loading tray 210 includes a first tray section 211 and a second tray section 212 connected to the first tray section 211 and located upstream of the first tray section 211 in the sheet (G) supply direction H. In this case, if the sheet size detection section 220 (220a, 220b) is provided in the first tray section 211 downstream of the second tray section 212 in the sheet supply direction H, size detection by the sheet size detection section 220 is likely to be restricted.

In this regard, in this embodiment, the first upper surface area α1 is provided in the second tray section 212. This allows the sheet size detection section 220 to be provided in the second tray section 212, which is upstream of the first tray section 211 in the supply direction H, thereby reducing the limitations on size detection by the sheet size detection section 220.

If the area of the first upper surface area α1 is too large relative to the area of the upper surface 210a of the second tray section 212, the proportion of the area of the upper surface 210a of the second tray section 212 that is occupied by the first upper surface area α1, which is higher than the second upper surface area α2, will increase accordingly. This will increase the overall thickness of the sheet loading tray 210, making it difficult to achieve a thin overall sheet supply device 201.

In this regard, in this embodiment, if the area of the second tray section 212 is Sa and the area of the first upper surface area α1 is Sb, the relationship (Sa - Sb) > Sb is satisfied. That is, the area Sb of the first upper surface area α1 may be smaller than 1/2, 1/3, 1/4, or 1/5 of the area Sa of the second tray section 212 (first upper surface area α1 and second upper surface area α2). The area Sb of the first upper surface area α1 can be set appropriately depending on the size and layout of the sheet size detection unit 220 (220a, 220b). For example, it can be set to an area that ensures the minimum space required to install the sheet size detection unit 220.

By doing this, the proportion of the first upper surface area α1 to the area of the upper surface 210a of the second tray section 212 can be reduced, which in turn reduces the overall thickness of the sheet loading tray 210 and makes it possible to make the sheet feeding device 201 thinner as a whole.

In this embodiment, the first upper surface area α1 is provided in the sheet (G) supply direction (H) of the second tray section 212 and in the center of the width direction W perpendicular to the sheet (G) supply direction (H). Here, the center not only refers to the position where the position (center position) of the first upper surface area α1 at half the maximum distance in the width direction W coincides with the position (center position) of the second tray section 212 at half the maximum distance in the width direction W, but also includes the vicinity of the center position where the center position of the first upper surface area α1 in the width direction W falls within a predetermined range in the width direction W that includes the center position of the second tray section 212.

In this way, by locating the first upper surface area α1 in the center of the second tray section 212 in the sheet (G) supply direction H and width direction W, it is possible to further improve size detection by the sheet size detection section 220 (220a, 220b) and the ease of removing sheets (especially original documents G) from the sheet loading tray 210.

In this embodiment, as shown in FIG. 5A, the second upper surface region α2 is flat. The upstream end α1a of the first upper surface region α1 in the sheet (G) supply direction H is at the same height as the flat second upper surface region α2, gradually increases in height from the upstream end α1a to the apex Q, and gradually decreases in height from the apex Q to the downstream end α1b in the sheet (G) supply direction H, with the downstream end α1b being at the same height as the second upper surface region α2. Here, "same height as the second upper surface region α2" not only means exactly the same height as the second upper surface region α2, but also encompasses a concept that includes substantially the same height as the second upper surface region α2, taking into account variations in parts and mounting errors during manufacturing.

This eliminates or nearly eliminates the step between the second upper surface region α2 and the first upper surface region α1, and allows the second upper surface region α2 and the first upper surface region α1 on the upper surface 210a to have a smooth shape.

However, if the number of different sheet (G) sizes increases, it will be necessary to provide multiple sheet size detection units 220.

In this regard, in this embodiment, multiple sheet size detection units 220 are arranged side by side along the sheet (G) supply direction H. The first upper surface region α1 includes detection portions (γa, γb) of the multiple sheet size detection units (220a, 220b) that detect the sheet (G).

In this way, by arranging multiple sheet size detection units 220 (220a, 220b) side by side along the sheet (G) supply direction H, it is possible to detect the size of the sheets (G) even if the number of different sizes of the sheets (G) is large. Furthermore, by including detection portions (γa, γb) that detect the sheets (G) of the multiple sheet size detection units (220a, 220b) in the first upper surface region α1, it is possible to suppress false detections by the multiple sheet size detection units (220a, 220b) and reduce the overall thickness of the sheet loading tray 210.

In this embodiment, the first upper surface region α1 is formed in a trapezoidal shape when viewed from a plane (top). More specifically, the trapezoidal shape of the first upper surface region α1 is an isosceles trapezoid extending in the supply direction H of the sheet (G), with the upstream side being the upper base and the downstream side being the lower base. In this example, as shown in FIG. 4B , the first upper surface region α1 is formed in a shape in which the distance d1 of the upper base is smaller than the distance d2 of the lower base, and the height h is greater than the distances d1 and d2 of the upper and lower bases.

Second Embodiment
FIG. 8 is a plan view showing another example of the shape of the first upper surface region α1 as viewed from above.

In the first embodiment, the shape of the first upper surface region α1 when viewed from above was trapezoidal, but in the second embodiment, the shape of the first upper surface region α1 when viewed from above is a shape consisting of an elliptical arc portion α1c and a linear portion α1d connecting both ends of the elliptical arc portion α1c. In this example, the first upper surface region α1 is formed in a shape such that the distance d3 of the elliptical arc portion α1c in the supply direction H is greater than the distance d4 of the linear portion α1d.

The second embodiment can also have the same configuration and effects as the first embodiment, except for the shape of the first upper surface region α1 when viewed from above.

[Third embodiment]
FIG. 9 is a plan view showing yet another example of the shape of the first upper surface region α1 as viewed from above.

In the third embodiment, the shape of the first upper surface region α1 when viewed from above is an ellipse extending in the supply direction H.

The second embodiment can also have the same configuration and effects as the first embodiment, except for the shape of the first upper surface region α1 when viewed from above.

[Other embodiments]
In the first to third embodiments, the sheet size detection unit 220 detects the size of the sheet (G) in the supply direction H, but it may also detect the size of the sheet in the width direction W perpendicular to the supply direction H. In this case, it can correspond to a sheet size detection unit that detects the size in the width direction W.

In addition, in the first to third embodiments, the first upper surface area α1 is provided in the center of the second tray section 212 in the width direction W, but it may also be provided on one side (front side X1) or the other side (rear side X2) in the width direction W. This is particularly effective when the sheet feeding device feeds sheets of various sizes based on one side or the other side in the width direction W, which is perpendicular to the feeding direction H.

In addition, in the first to third embodiments, the sheets are documents G and the sheet supply device 201 is provided in the document feeder 200, but the sheets may be recording materials such as recording paper, and the sheet supply device 201 may be provided in a manual feed tray device 120 that is openably and closably provided on the side of the image forming apparatus main body 110 (the side as viewed from the front side X1).

In addition, in the first to third embodiments, the sheet size detection unit 220 includes an actuator 222, but it may also include a light-reflection sensor equipped with a light-emitting unit and a light-receiving unit. In this case, the detection portion of the sheet size detection unit that detects the sheet (G) may be a light-passing portion (opening) that passes light emitted from the light-emitting unit and light reflected from the sheet (G), or the light-emitting element portion (sensor portion) of the light-emitting unit and the light-receiving element portion (sensor portion) of the light-receiving unit themselves.

The present invention is not limited to the embodiments described above, and can be embodied in various other forms. Therefore, the embodiments are merely illustrative in all respects and should not be interpreted as limiting. The scope of the present invention is defined by the claims and is not bound by the text of the specification. Furthermore, all modifications and variations that fall within the equivalent scope of the claims are within the scope of the present invention.

100 Image forming apparatus 120 Manual feed tray device 200 Document feeder 201 Sheet supply device 210 Sheet placement tray 210a Upper surface 211 First tray section 212 Second tray section 212a Through hole 220 Sheet size detection section 220a First sheet size detection section 220b Second sheet size detection section 221 Rotation shaft 222 Actuator 222a Contact section 222b Operated section 223 Switch section 223a Operated section 224 Weight member G Document H Supply direction Q Vertex Sa Area Sb Area V Intersecting direction W Width direction X Depth direction Y Left-right direction Z Up-down direction α1 First upper surface area α1a Upstream end α1b Downstream end α1c Elliptical arc section α1d Straight line section α2 Second upper surface area α2a Upstream end α2b Upstream area β Rotation axis γ Detection section

Claims (12)

A sheet feeding device including a sheet placement tray on which sheets are placed, and a sheet size detection unit disposed on the sheet placement tray and detecting the size of the sheets placed on the sheet placement tray,
an upper surface of the sheet loading tray has a first upper surface area including a detection portion of the sheet size detection unit that detects the sheet, and a second upper surface area other than the first upper surface area;
the first upper surface region is formed in a convex shape so as to be higher than the second upper surface region,
The convex shape includes a curved shape,
the convexly formed surface is made up of a plurality of surfaces,
each of the plurality of surfaces includes a convex curved surface;
A sheet feeding device characterized in that the multiple convex curved surfaces have different radii of curvature, and the individual curved surfaces having the radii of curvature are combined and connected along the sheet feed direction, and when connected to each other, they are formed into an overall smooth curved shape . 2. The sheet feeding device according to claim 1 ,
A sheet feeding device characterized in that the second upper surface area is lower than the first upper surface area in the sheet feeding direction from the upstream end of the first upper surface area to the upstream end of the second upper surface area. 3. The sheet feeding device according to claim 1 ,
The sheet feeding device according to claim 1, wherein the first upper surface area is formed so that the apex of the convex shape is positioned at the center in the feeding direction of the sheet. 4. The sheet feeding device according to claim 1,
the sheet placement tray includes a first tray portion and a second tray portion connected to the first tray portion and located upstream of the first tray portion in the sheet feeding direction,
The sheet feeding device, wherein the first upper surface area is provided in the second tray portion. 5. The sheet feeding device according to claim 4,
A sheet feeding device, characterized in that, when the area of the second tray portion is Sa and the area of the first upper surface region is Sb, the relationship (Sa-Sb)>Sb is satisfied. 6. The sheet feeding device according to claim 4, wherein:
The sheet feeding device according to claim 1, wherein the first upper surface area is provided at a center portion in a sheet feeding direction and a width direction orthogonal to the sheet feeding direction in the second tray portion. 7. The sheet feeding device according to claim 1,
A sheet supply device characterized in that the second upper surface area is a flat surface, and the first upper surface area has an upstream end in the supply direction of the sheet that is at the same height as the flat second upper surface area, gradually becomes higher from the upstream end to a peak, and gradually becomes lower from the peak to a downstream end in the supply direction of the sheet, and the downstream end is at the same height as the second upper surface area. 8. The sheet feeding device according to claim 1,
a plurality of the sheet size detection units are arranged in parallel along the sheet feeding direction,
The sheet feeding device according to claim 1, wherein the first upper surface area includes detection portions for detecting the sheets of the plurality of sheet size detection units. 9. The sheet feeding device according to claim 1,
The sheet feeding device according to claim 1, wherein the sheet size detection unit has an actuator that contacts the sheet and rotates about a rotation axis that extends in a direction intersecting the sheet feeding direction. 10. A manual feed tray device comprising the sheet feeding device according to claim 1. 10. A document feeding device comprising the sheet feeding device according to claim 1. An image forming apparatus comprising the manual feed tray device according to claim 10 and/or the document feeder according to claim 11 .