Image forming apparatus

Abstract

The objective of this technology is to provide an image forming apparatus that enables efficient detection of sheets. [Solution] An image forming apparatus according to one embodiment of this technology comprises a transport guide and a detection unit. The transport guide is provided along the curved portion of the sheet transport path, has a curved shape, and has an opening. The detection unit is provided on the opposite side of the curved portion from the transport guide, and detects the edge of the sheet in the scanning direction. In this image forming apparatus, the edge of the sheet in the scanning direction is detected by the detection unit through the transport guide, which has a curved shape and an opening. This makes it possible to efficiently detect the sheet.

Description

Technical Field

[0001] The present technology relates to an image forming apparatus applicable to a printer or the like.

Background Art

[0002] Patent Document 1 discloses a recording apparatus in which a light-transmitting member that transmits light is arranged along the vertical direction, and a sheet is detected through the light-transmitting member by an optical sensor. In this recording apparatus, since foreign matter attached to the light-transmitting member is likely to fall downward due to gravity, it is possible to suppress a decrease in detection accuracy due to foreign matter adhering to the surface of the light-transmitting member.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Thus, there is a need for a technology that enables efficient detection of a sheet.

[0005] In view of the above circumstances, an object of the present technology is to provide an image forming apparatus that enables efficient detection of a sheet.

Means for Solving the Problems

[0006] To achieve the above object, an image forming apparatus according to one embodiment of the present technology includes a conveyance guide and a detection unit. The conveyance guide is provided along a curved portion of a conveyance path of a sheet, has a curved shape, and has an opening. The detection unit is provided on the side opposite to the curved portion with respect to the conveyance guide, and detects an end portion of the sheet in the scanning direction.

[0007] In this image forming apparatus, the edges of the sheet in the scanning direction are detected by a detection unit through a curved transport guide with an opening. This makes it possible to efficiently detect the sheet.

[0008] The detection unit may detect the edge of the sheet by scanning in the scanning direction.

[0009] The opening may be a plurality of openings arranged along the scanning direction.

[0010] The widths of the ribs between the openings in the scanning direction may all be the same. In this case, if the detection unit detects an object with a length exceeding the width of the ribs, it may determine that the end of the object is the end of the sheet.

[0011] The image forming apparatus may further include a first pair of rollers and a second pair of rollers, each positioned on the transport path, which feed the sheet by gripping it. In this case, the first pair of rollers may be provided upstream of the detection unit on the transport path. The second pair of rollers may be provided downstream of the detection unit on the transport path.

[0012] The scanning direction may be perpendicular to the conveying direction of the sheet in the curved portion. [Brief explanation of the drawing]

[0013] [Figure 1] This is a schematic diagram showing an example of the configuration of an image forming apparatus according to one embodiment of this technology. [Figure 2] This is a perspective view showing an example configuration of a transport guide. [Figure 3] This is a schematic diagram showing an example of a sensor configuration. [Figure 4] This is a schematic diagram illustrating the detection operation by the sensor. [Modes for carrying out the invention]

[0014] The embodiments of this technology will be described below with reference to the drawings.

[0015] [Image forming apparatus] Figure 1 is a schematic diagram showing an example of the configuration of an image forming apparatus 1 according to one embodiment of this technology. Figure 1 shows the interior of the image forming apparatus 1. The image forming apparatus 1 is a printer that forms a color image on paper 2 using an inkjet method. The image forming apparatus 1 may be other types of printers, fax machines, copiers, or multifunction devices.

[0016] For convenience, an XYZ coordinate system is defined for the drawing. This coordinate system is such that, when viewed from a direction where the positive Z-axis is at the top and the positive X-axis is to the right, the positive Y-axis is at the back (i.e., a right-handed coordinate system). In this embodiment, the Z-direction is the vertical direction (direction of gravity), and the X and Y directions are the horizontal directions, and the image forming apparatus 1 is arranged as shown in Figure 1. It should be noted that the orientation in which the image forming apparatus 1 is used is not limited to the application of this technology.

[0017] The image forming apparatus 1 includes a paper feed cassette 3 (3a, 3b), pick rollers 4 (4a, 4b), roller pairs 5 (5a to 5n), transport guide 6, sensor 7, pulleys 8 (8a, 8b), transport belt 9, line head 10, ink storage section 11, flaps 12 (12a, 12b), and discharge trays 13 (13a, 13b).

[0018] The paper feed cassette 3 is a cassette that holds the paper 2. The paper 2 is a sheet of paper that has been pre-cut into a rectangular shape. In this embodiment, multiple sheets of paper 2 are placed horizontally and parallel to each other inside the paper feed cassette 3.

[0019] The specific shape of paper 2 is not limited, and its shape may be changed as appropriate within the scope of what is feasible for this technology. Alternatively, any type of sheet capable of forming an image on its surface may be used instead of paper 2. For example, a film, cloth, or other medium may be used as the sheet. The sheet 2 corresponds to an embodiment of the sheet according to the present technology.

[0020] In this embodiment, two paper feed cassettes 3a and 3b are provided, and sheets 2 of different sizes are accommodated therein. Of course, only one or three or more paper feed cassettes 3 may be provided. Also, different types of sheets may be accommodated in the plurality of paper feed cassettes 3.

[0021] The pick-up roller 4a is rotated by a drive source such as a motor to send out the uppermost sheet 2 in the paper feed cassette 3a to the conveyance path 14. The conveyance path 14 is shown by a broken line in FIG. 1. Note that the conveyance path 14 in FIG. 1 is merely an example, and its specific path is not limited.

[0022] The roller pair 5 consists of two rollers, and one or both of them are rotated by a drive source to send out the sheet 2 by sandwiching it. Since the conveyance path 14 through which the sheet 2 passes is formed between the roller pair 5, it can be said that the roller pair 5 is arranged along the conveyance path 14. Note that the specific number and position of the roller pair 5 are not limited.

[0023] Hereinafter, the side of the conveyance path 14 through which the sheet 2 passes first is referred to as the upstream side, and the side through which it passes later is referred to as the downstream side. As shown in the figure, the sheet 2 sent out by the pick-up roller 4a first passes through the roller pair 5a, is conveyed along the conveyance path 14, and then passes through the downstream roller pair 5f. Although not shown in the figure, conveyance guides for guiding the sheet 2 along the conveyance path 14 are appropriately provided between the roller pairs 5a and 5f. The same applies to the other roller pairs 5.

[0024] The pick-up roller 4b is rotated by a drive source to send out the uppermost sheet 2 in the paper feed cassette 3b to the conveyance path 14. The sheet 2 passes through the roller pairs 5b, 5c, 5e, 5f in this order.

[0025] In this embodiment, paper 2 fed from an expansion unit (not shown) is transported along transport path 14a and merges into transport path 14 between roller pairs 5c and 5e. Paper 2 fed from a manual feed tray is transported along transport path 14b, passes through roller pair 5d, and reaches roller pair 5e. The expansion unit, manual feed tray, transport paths 14a and 14b, and roller pair 5d are not required to be configured.

[0026] The transport path 14c between roller pairs 5f and 5g is curved. The transport guide 6 has a curved shape similar to that of the transport path 14c and is provided along the transport path 14c. In this embodiment, the transport guide 6 is provided on the left side (negative side in the X direction) of the transport path 14c.

[0027] A sensor 7 is located further to the left of the transport guide 6. That is, the sensor 7 is located on the opposite side of the transport path 14c from the transport guide 6. When the paper 2 passes through the transport path 14c, the edge of the paper 2 is detected by the sensor 7. The detailed configuration and operation of the transport guide 6 and sensor 7 will be described later.

[0028] Sensor 7 corresponds to one embodiment of the detection unit related to this technology. Roller pair 5f corresponds to the first roller pair located upstream of sensor 7 in the transport path 14. The roller pair 5g corresponds to a second roller pair located downstream of the sensor 7 in the transport path 14.

[0029] The pulley 8, conveyor belt 9, and line head 10 are positioned between roller pairs 5g and 5h. The conveyor belt 9 is an endless belt, wrapped around and held by pulleys 8a and 8b. When one or both of the pulleys 8a and 8b are rotated by a drive source, the conveyor belt 9 also rotates. The surface of the conveyor belt 9 (the upper left side) is part of the conveyor path 14, and as the conveyor belt 9 rotates, the paper 2 also moves from the upstream side to the downstream side. In order to fix the paper 2 to the surface of the conveyor belt 9, holes are provided in the surface of the conveyor belt 9, and the paper 2 is attracted by negative pressure through these holes.

[0030] The line head 10 is positioned opposite the surface of the conveyor belt 9 and ejects black, cyan, magenta, and yellow ink onto the paper 2 at predetermined timings. This forms a color image on the paper 2. The ink ejected from the line head 10 is supplied from the ink storage unit 11 via tubes or the like (not shown).

[0031] If double-sided printing is not performed after paper 2 has passed roller pair 5h, flap 12a transports paper 2 to the left. Next, flap 12b transports paper 2 in either the direction of roller pair 5i or 5j. Paper 2 transported to roller pair 5i is discharged to output tray 13a. Paper 2 transported to roller pair 5j passes through roller pair 5k and is then discharged to output tray 13b. In this example, two output trays 13 are provided, making it possible to separate the output destination of printed materials for each person who performed the printing. Alternatively, only one output tray 13 may be provided.

[0032] After the paper 2 passes roller pair 5h, if double-sided printing is to be performed, the flap 12a transports the paper 2 in the direction of roller pair 5l. The paper 2 then switches back and passes roller pairs 5m and 5n to reach roller pair 5e. Similarly, the line head 10 then forms an image on the unprinted side of the paper 2, and it is discharged into the output tray 13a or 13b.

[0033] Furthermore, the specific configuration of the image forming apparatus 1 is not limited. For example, it may include a drying mechanism for drying the ink adhering to the paper 2, or an inspection device for inspecting the formed image.

[0034] [Conveyor guides and sensors] Figure 2 is a perspective view showing an example configuration of the transport guide 6. Figure 2 shows the transport guide 6 and the paper 2 in the process of passing through the transport path 14c. The paper 2 is shown transparently to make the shape of the transport guide 6 easier to see. The sensor 7 is not shown.

[0035] The transport guide 6 is roughly rectangular when viewed from the X direction, but slightly curved towards the negative side of the X direction when viewed from the Y direction. Hereafter, the positive side in the X direction will be referred to as the front surface 17, and the negative side as the back surface 18. The paper 2 is transported so as to be in contact with the front surface 17.

[0036] The transport guide 6 has multiple openings 19. Each opening 19 is generally rectangular in shape and is arranged along the Y-direction on the upper part of the transport guide 6. A rib 20 is located between two openings 19. In Figure 2, only two openings 19 and one rib 20 are represented by reference numerals. The shape, number, and arrangement of the openings 19 are not limited and may be modified as appropriate within the scope of the feasibility of this technology.

[0037] In this embodiment, the width of the ribs 20 in the Y direction is the same for all of them. Note that "same" does not mean exactly the same, but also includes cases where there are slight differences.

[0038] Figure 3 is a schematic diagram showing an example configuration of sensor 7. Figure 3 schematically illustrates the sensor 7, as well as the carriage 23, timing belt 24, pulleys 25 (25a, 25b), and motor 26. Figure 3 shows these components viewed from the positive side in the X direction. That is, the transport guide 6 and paper 2 are located on the near side of the page in Figure 3.

[0039] Sensor 7 is mounted on the positive X-side surface of carriage 23, and carriage 23 is connected to the upper surface of timing belt 24. When pulleys 25a and 25b rotate due to the drive of motor 26, the upper surface of timing belt 24 moves left and right (positive and negative Y-side), and consequently carriage 23 and sensor 7 also move left and right.

[0040] Here, the vertical position of the sensor 7 is the same as the position of the opening 19 and rib 20 of the transport guide 6. In other words, regardless of the horizontal position of the sensor 7, either the opening 19 or the rib 20 is always present on the front side of the sensor 7 in Figure 3.

[0041] Sensor 7 can detect objects located directly in front of it (the positive side in the X direction). For example, an optical sensor may be used as sensor 7. In this case, a separate reflective element is provided in front of the paper 2. The light emitted by sensor 7 is blocked and not reflected when an object is present in front of it, and reflected by the reflective element when no object is present. By detecting the state of the reflected light, sensor 7 can determine whether or not an object is present in front of it. The specific configuration of sensor 7 is not limited to this.

[0042] As the sensor 7 continues its detection operation and moves in the left-right direction, it is determined whether or not an object is present in front of it at each position in the left-right direction. In other words, the scanning direction of the sensor 7 is the Y direction. In this embodiment, since the transport direction of the paper 2 at the position of the opening 19 is the Z direction, the transport direction and the scanning direction are orthogonal. However, the scanning direction may be any direction as long as this technology is feasible.

[0043] Figure 4 is a schematic diagram illustrating the detection operation by sensor 7. Sensor 7 scans in the Y direction to detect the edges 27 of the paper 2 in the Y direction. Specifically, the left edge 27a, which is the left side in the Y direction, and the right edge 27b, which is the right side, are detected by sensor 7. The specific detection method will be explained below.

[0044] Figure 4 shows a cross-sectional view of the paper 2, transport guide 6, and sensor 7 when cut along the XY plane at the height of the center of the opening 19 and rib 20 in Figure 2. For the sake of clarity, the position, number, and width of the opening 19 and rib 20 are different from those in Figure 2. In this example, the width of all ribs 20 is the same in d (mm).

[0045] Sensor 7 begins scanning from its initial position A toward the right (positive side in the Y direction). Position A is the same as the left edge of the leftmost opening 19a in the Y direction. Now, let's consider a case where, if sensor 7 detects an object, it is immediately determined to be the left edge 27a of paper 2. In this case, an object is detected when sensor 7 reaches the left edge of the leftmost rib 20a, and sensor 7 will determine that the object is the left edge 27a of paper 2. However, in reality, the object is the left edge of rib 20a.

[0046] In this embodiment, to prevent such false detections, the sensor 7 is controlled to determine the left edge of an object with a length exceeding the width d (mm) of the rib 20 as the left edge 27a of the paper 2. In other words, the sensor 7 is set to ignore the detection of a length of d (mm).

[0047] In this example, when sensor 7 reaches position B, an object with a width of exactly d (mm) (actually rib 20a) is detected, but since it does not exceed d (mm), the left edge of rib 20a is not identified as the left edge 27a of paper 2. Subsequently, no object is detected until sensor 7 reaches the left edge 27a of paper 2.

[0048] Then, when the sensor 7 reaches the left edge 27a of the paper 2, the object (actually the paper 2) is detected again, and when it exceeds d (mm) from that point (position C), it is determined that the left edge of the object is the left edge 27a of the paper 2. Since the object is indeed the paper 2, this determination is correct. More specifically, the sensor 7 calculates the Y-direction position of the left edge 27a of the paper 2 by offsetting d (mm) from its Y-direction position at position C.

[0049] Similarly, the sensor 7 detects the right edge 27b of the paper 2 by scanning from the right side. Alternatively, if the size of the paper 2 is known in advance, the position of the right edge 27b may be calculated based on the position and size of the left edge 27a.

[0050] Furthermore, if the edge 27 of the paper 2 overlaps with the rib 20, the sensor 7 will also detect the portion of the rib 20 that does not overlap with the paper 2 as part of d(mm). Therefore, when the position of the edge 27 of the paper 2 is calculated by offsetting d(mm), there may be a discrepancy of up to d(mm) between the calculated position and the actual position of the edge 27. For this reason, it is desirable to set d(mm) to a value that is acceptable for such a discrepancy. For example, d=1.5(mm) is suitable.

[0051] In the image forming apparatus 1 according to this embodiment, the edge 27 of the paper 2 in the Y direction, which is the scanning direction, is detected by the sensor 7 through the transport guide 6, which has a curved shape and an opening 19. This makes it possible to efficiently detect the paper 2.

[0052] If the actual paper width is smaller than the width set by the user, ink will be ejected onto the part of the conveyor belt opposite the line head where no paper is present, potentially contaminating the conveyor belt. To prevent this, the paper width is detected in the conveyor path prior to the line head.

[0053] One possible detection method is to use a reflective sensor to detect the paper through a light-transmitting member, but this method has the problem that false detections can occur if foreign objects such as paper fragments adhere to the light-transmitting member.

[0054] Another approach is to arrange the light-transmitting members vertically, which would allow foreign objects adhering to them to fall off more easily due to gravity. However, this would still not completely prevent foreign objects from adhering, and a tray would need to be placed to collect the foreign objects that fall off due to gravity. There is also the problem of the high cost of the light-transmitting members themselves. Furthermore, if the light-transmitting members are curved, the sensor light from the reflective sensor will be refracted, preventing the sensor's light-receiving part from detecting the reflected light. Therefore, the light-transmitting members must be constructed as straight members. This imposes constraints on the shape of the transport path.

[0055] This technology employs a configuration in which an opening 19 for detection by a sensor 7 is provided in the transport guide 6, thereby achieving cost reduction and easing of design constraints on the transport path. Furthermore, since sensing is performed through the opening 19, foreign matter cannot adhere to the sensing path, making it possible to detect the position of the edge 27 of the paper 2 with high precision.

[0056] Furthermore, in this technology, the sensor 7 performs scanning in the Y direction, which is the scanning direction, and the edge 27 of the paper 2 is detected. This makes it possible to detect the edge 27 of the paper 2 with even greater accuracy.

[0057] Furthermore, in this technology, multiple apertures 19 are arranged along the scanning direction. This makes it possible to detect the edges 27 of the paper 2 with even greater accuracy.

[0058] Furthermore, in this technology, the width of the ribs 20 between the openings 19 is the same, and when the sensor 7 detects an object whose length exceeds the width of the ribs 20, it is determined that the end of that object is the end 27 of the paper 2. This makes it possible to prevent false detections, such as detecting the ribs 20 as the paper 2.

[0059] Furthermore, this technology provides roller pairs 5f and 5g positioned on the transport path 14 to feed the paper 2 by gripping it. Roller pair 5f is positioned upstream of sensor 7, and roller pair 5g is positioned downstream of sensor 7. This makes it possible to detect the edges 27 of the paper 2 with even greater accuracy.

[0060] Furthermore, in this technology, the scanning direction, the Y direction, is perpendicular to the Z direction, which is the transport direction of the paper 2 in the curved transport path 14c. This makes it possible to detect the edges 27 of the paper 2 with even greater accuracy. [Explanation of symbols]

[0061] 1…Image forming apparatus 2… Paper 5... Roller vs. 6…Conveyor Guide 7...Sensor 14…Conveyor Route 19...Aperture 20... Ribs 27…End

Claims

1. A conveying guide is provided along the curved portion of the sheet conveying path, has a curved shape, and has an opening. A detection unit is provided on the opposite side of the curved portion from the transport guide, and detects the edge of the sheet in the scanning direction. An image forming apparatus comprising the following:

2. An image forming apparatus according to claim 1, The detection unit detects the edge of the sheet by scanning in the scanning direction. Image forming apparatus.

3. An image forming apparatus according to claim 2, The aforementioned openings are a plurality of openings arranged along the scanning direction. Image forming apparatus.

4. An image forming apparatus according to claim 3, The width of the ribs between the openings is the same in the scanning direction. When the detection unit detects an object whose length exceeds the width of the rib, it determines that the end of the object is the end of the sheet. Image forming apparatus.

5. An image forming apparatus according to any one of claims 1 to 4, further comprising: Each comprises a first pair of rollers and a second pair of rollers, each positioned on the transport path, which feed out the sheet by gripping it. The first pair of rollers is provided upstream of the detection unit in the transport path. The second pair of rollers is provided downstream of the detection unit in the transport path. Image forming apparatus.

6. An image forming apparatus according to any one of claims 1 to 4, The scanning direction is perpendicular to the conveying direction of the sheet in the curved portion. Image forming apparatus.

Images