Conveyance device, image forming device and program

Abstract

To provide a conveyance device, an image forming device and a program capable of instantly adsorbing and conveying a recording medium with an appropriate suction force.SOLUTION: A conveyance device 22 includes: a conveyance part 221 that conveys a recording medium P; an air flow path W that connects a suction hole H provided in a conveyance surface F of the conveyance part 221 and a suction part 60 that sucks air;, a valve 51 that can divide the air flow path W into an open space OS on a suction hole H side and a closed space CS on the suction part 60 side; and a control part 40 that controls an adsorption of the recording medium P to the conveyance part 221, wherein the control part 40 opens the valve 51 when the recording medium P blocks the suction hole H.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a conveying device, an image forming apparatus, and a program. [Background technology]

[0002] Conventionally, there is known an image forming apparatus that forms an image on a recording medium transported by a transport unit. The transport unit includes, for example, a transport drum that rotates while adsorbing the recording medium to a transport surface. The transport drum is connected to a negative pressure source that sucks air, and adsorbs the recording medium to the transport surface by sucking air through suction holes provided on the transport surface.

[0003] In such a conveying unit, if the suction force is weak, the recording medium will float up, resulting in conveyance and printing defects. Therefore, for example, Patent Document 1 describes a configuration in which the connection to the negative pressure source is switched as the conveying drum rotates, thereby adsorbing the recording medium in order from the front end to the rear end. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-241272 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in this configuration, the suction holes are open to the atmosphere when no recording medium is placed on the conveyance surface, so the suction force is insufficient at the beginning of a print job. On the other hand, if the suction force is increased to prevent this problem, there is a risk of wrinkles forming on the recording medium.

[0006] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a conveying device, an image forming apparatus, and a program that can instantly attract and convey a recording medium with an appropriate suction force. [Means for solving the problem]

[0007] In order to solve the above problems, the invention described in claim 1 is a conveying device, a conveying unit that conveys the recording medium; an air flow path that communicates a suction hole provided on the conveying surface of the conveying unit with a suction unit that sucks air; a valve capable of dividing the air flow path into an open space on the suction hole side and a closed space on the suction part side; a control unit that controls the adsorption of the recording medium to the conveyance surface, The control unit opens the valve when the recording medium blocks the suction hole.

[0008] The invention described in claim 2 is the conveying device described in claim 1, the air flow path includes a flow path member that communicates the suction unit and the transport unit, The valve is provided in the flow path member.

[0009] The invention described in claim 3 is the conveying device described in claim 1, The valve is provided in the air flow path on a side closer to the transport unit than the suction unit.

[0010] The invention described in claim 4 is the conveying device described in claim 1, The air flow path includes a buffer tank in the closed space.

[0011] The invention described in claim 5 is the conveying device described in claim 1, The volume of the closed space is greater than the volume of the open space.

[0012] The invention described in claim 6 is the conveying device described in claim 5, The volume of the closed space is at least three times larger than the volume of the open space.

[0013] The invention described in claim 7 is the conveying device described in claim 1, The control unit opens the valve after the pressure in the closed space is saturated.

[0014] The invention described in claim 8 is the conveying device described in claim 1, The control unit opens the valve before the recording medium blocks the suction hole.

[0015] The invention described in claim 9 is the conveying device described in claim 8, The control unit closes the valve before the recording medium blocks the suction hole.

[0016] The invention described in claim 10 is the conveying device described in claim 1, an acquisition unit for acquiring information on a recording medium; The control unit controls the output of the suction unit in accordance with the information acquired by the acquisition unit.

[0017] The invention described in claim 11 is the conveying device described in claim 10, The control unit controls the timing at which the valve is opened in accordance with the output of the suction unit.

[0018] The invention described in claim 12 is the conveying device described in claim 1, the conveying surface has a plurality of regions; The air flow paths and the valves are provided corresponding to the plurality of regions, respectively.

[0019] The invention described in claim 13 is the conveying device described in claim 12, the conveying surface has a plurality of regions in a width direction, The control unit opens the valve corresponding to the region among the plurality of regions that corresponds to the center of the width of the recording medium to be placed before the valve corresponding to the region that corresponds to the end side of the width of the recording medium.

[0020] The invention described in claim 14 is the conveying device described in claim 1, the transport unit is a transport drum that rotates to transport the recording medium placed on the transport surface, The suction portion sucks air through the corresponding suction hole only at a predetermined rotation angle.

[0021] The invention described in claim 15 is an image forming apparatus, A conveying device according to any one of claims 1 to 14; and an image forming section that forms an image on a recording medium.

[0022] The invention described in claim 16 is a conveying unit that conveys the recording medium; an air flow path that communicates a suction hole provided on the conveying surface of the conveying unit with a suction unit that sucks air; a valve that separates the air flow path into an open space on the suction hole side and a closed space on the suction part side when closed, A program for causing the control unit to function as a control unit for controlling suction of the recording medium to the conveyance unit, The control unit opens the valve when the recording medium blocks the suction hole. [Effects of the Invention]

[0023] According to the present invention, the recording medium can be instantly attracted and transported with an appropriate suction force. [Brief explanation of the drawings]

[0024] [Figure 1] 2 is a schematic cross-sectional side view of each component of the image forming apparatus. FIG. [Figure 2] 1 is a block diagram of an image forming apparatus according to an embodiment of the present invention. [Figure 3] 3 is a cross-sectional view in the width direction illustrating the configuration of the inside and surrounding areas of a conveying unit according to the embodiment. FIG. [Figure 4] 3 is a cross-sectional view in the conveying direction illustrating the internal and peripheral configuration of a conveying unit according to the embodiment. FIG. [Figure 5] FIG. 2 is a perspective view illustrating a configuration around a transport unit according to the embodiment. [Figure 6] 10 is a graph summarizing the recording media placed on each conveying surface and the suction pressure from the start of single-sided printing in a conventional image forming apparatus. [Figure 7] 10 is a graph summarizing the recording media placed on each transport surface and the suction pressure from the start of single-sided printing in the image forming apparatus according to the present embodiment. [Figure 8] 10 is a graph summarizing the recording media placed on each conveying surface and the suction pressure from the start of double-sided printing in a conventional image forming apparatus. [Figure 9] 10 is a graph summarizing the recording media placed on each conveying surface and the suction pressure from the start of double-sided printing in the image forming apparatus according to the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0025] An image forming apparatus according to an embodiment of the present invention will be described in detail below with reference to the drawings. However, the scope of the invention is not limited to the illustrated examples. In the following description, components having the same functions and configurations are designated by the same reference numerals, and their description will be omitted.

[0026] [Overall configuration of image forming device] Fig. 1 is a diagram showing an example of a schematic configuration of an image forming apparatus 1. Fig. 2 is a block diagram showing a functional configuration of the image forming apparatus 1. The image forming apparatus 1 includes a paper feeder 10, an image forming apparatus main body 20, a paper discharge device 30, and a control unit 40.

[0027] In the following description, the X direction, Y direction, and Z direction are the directions shown in Fig. 1. In addition, in the following description, the X direction, Y direction, and Z direction are also referred to as the width direction, conveyance direction, and height direction, respectively.

[0028] (Paper feeder) The paper feed device 10 includes a paper feed tray 11 and a paper feed section 12. The paper feed tray 11 stores recording media P. The paper feed section 12 includes a roller and a belt. The belt is ring-shaped, and its inner side is supported by two rollers. The paper feed section 12 transports the recording media P in the transport direction by rotating the two rollers with the recording media P placed on the belt.

[0029] (Image forming device body) The image forming apparatus main body 20 includes a delivery roller 21 , a conveying device 22 , an image forming section 23 , a fixing section 24 , a conveying roller 25 , a belt conveying section 26 , and a swing arm section 27 .

[0030] {Transfer Roller} The delivery roller 21 is provided at a position between the paper feed unit 12 and the transport device 22. The delivery roller 21 has a claw portion 21a. The claw portion 21a is switched between an open and closed state under the control of the control unit 40. The delivery roller 21 holds the recording medium P on its transport surface by the claw portion 21a.

[0031] The delivery roller 21 delivers the recording medium P transported by the paper feed unit 12 to the transport device 22. In detail, the delivery roller 21 holds and picks up a first end of the recording medium P transported from the paper feed unit 12 with the swing arm portion 21b, and also holds it with the claw portion 21a. The delivery roller 21 then rotates clockwise as indicated by the arrow in FIG. 1, and delivers the recording medium P to one of the claw portions 222a to 222c of the transport device 22.

[0032] {Transportation equipment} FIG. 3 is a cross-sectional view in the width direction showing the internal and peripheral structure of the conveying device 22. FIG. 4 is a cross-sectional view in the transport direction showing the internal and peripheral structure of the conveying device 22. FIG. 5 is a perspective view showing the peripheral structure of the conveying device 22. Note that in FIG. 3, for convenience of illustration, the scale of the conveying device 22 is drawn larger than that of the delivery roller 21 and the transport roller 25. Also, in FIGS. 4 and 5, for simplicity, only air flow paths W (described below) corresponding to three regions in the width direction are drawn. The conveying device 22 conveys the recording medium P delivered from the delivery roller 21 in the transport direction indicated by the arrow in FIG. 1. The conveying device 22 includes a transport drum 221.

[0033] <Conveyor drum> The transport drum 221 is a transport unit that transports the recording medium P. The transport drum 221 has multiple transport surfaces F on its outer circumferential surface, on which one sheet of recording medium P is placed. The transport drum 221 has a cylindrical outer shape that extends in the width direction, and is connected to a transport drum motor (not shown). The control unit 40 drives the transport drum motor to rotate, thereby rotating the transport drum 221 by an angle proportional to the amount of rotation. Under the control of the control unit 40, the transport drum 221 transports the recording medium P in the transport direction while facing the image forming unit 23.

[0034] In this embodiment, the case where the transport drum 221 is a triple-sized drum is exemplified. A triple-sized drum means that the circumferential length of the transport drum 221 is large enough to simultaneously hold three recording media P having the maximum length usable in the image forming apparatus 1. That is, in this embodiment, the transport drum 221 has three transport surfaces F. Hereinafter, the three transport surfaces F will be referred to as surface A Fa, surface B Fb, and surface C Fc, respectively. Note that the transport drum 221 is not limited to a triple-sized drum. The transport drum 221 may be, for example, a quadruple-sized drum or a quintuple-sized drum.

[0035] <Claw part> The transport drum 221 has claw portions 222. The claw portions 222 are arranged on the A-side Fa, the B-side Fb, and the C-side Fc at intervals equal to the circumferential lengths of the delivery roller 21 and the transport roller 25. The claw portions 222 are switched between open and closed states under the control of the control unit 40. In the closed state, the claw portions 222 press a first end in the transport direction of the recording medium P delivered from the delivery roller 21 or the swing arm unit 27 with a predetermined pressing force, thereby holding the recording medium P on the transport surface F. In the open state, the claw portions 222 are released from the pressing state, and the recording medium P held on the transport surface F is delivered to the transport roller 25.

[0036] Chamber 3 and 4, the inside of the conveying drum 221 is hollow, and chambers 223 are formed below (inside) surfaces A Fa to C Fc. A sheet S forming the outer surface of the chamber 223 is placed on each conveying surface F. A plurality of suction holes H are formed in the sheet S.

[0037] 3, three chambers 223 (223a to 223c) are arranged between two claws 222 of the transport drum 221. Of these, the chamber 223a at the front in the transport direction has the longest length in the transport direction. The length of the chamber 223a in the transport direction corresponds to the length in the transport direction of the recording medium P that has the minimum length usable in the image forming apparatus 1.

[0038] As shown in Fig. 5, the chambers 223a to 223c are provided so as to divide each transport surface F into a plurality of regions in the width direction. Hereinafter, for convenience, of the chambers 223, the chamber 223 corresponding to the center in the width direction of the recording medium P to be placed will be referred to as the central chamber 2231, and the chambers 223 other than the central chamber 2231 will be referred to as the end chambers 2232 (see Fig. 4). Note that although Figs. 4 and 5 illustrate a case in which the central chamber 2231 is wider than the end chambers 2232, the central chamber 2231 and the end chambers 2232 may have the same width. Furthermore, the number of regions in the width direction of each transport surface F is not limited to three.

[0039] As described above, in this embodiment, the conveying drum 221 has (3 (number of double cylinders of the conveying drum 221) × 3 (conveying direction) × 3 (width direction) =) 27 chambers 223. The conveying surface F of the conveying drum 221 has 27 regions corresponding to these chambers 223.

[0040] <Rotating shaft, side plate, suction control plate> As shown in Fig. 4, side plates 225, 225 that hold a rotation shaft 224 of the transport drum 221 are provided on the front and rear sides of the transport drum 221 in the width direction. In addition, a substantially ring-shaped suction control plate 226 is configured to prevent rotation between the front side plate 225 and the transport drum 221. Specifically, for example, as shown in Fig. 4, the suction control plate 226 is biased toward the transport device 22 by a spring R provided between the suction control plate 226 and the side plate 225.

[0041] 3, arc-shaped groove-shaped openings 226a to 226c that form part of an air flow path W (described later) are provided in the suction control plate 226 at positions corresponding to a suction area A1 where the recording medium P is sucked by a suction device 60 (described later). Although not shown in FIG. 3, the openings 226a to 226c are provided in a number of rows (nine rows in this embodiment) equal to the number of divisions of each chamber 223 in the width direction and the transport direction.

[0042] <Connection holes, pipes> 4, connection holes 227 communicating with the openings 226a to 226c are provided on the surface of the transport drum 221 facing the suction control plate 226. Then, inside the transport device 22, pipes 228 are provided which have a plurality of flow paths and communicate with the chambers 223 in the areas corresponding to the connection holes 227.

[0043] (tube) 4 and 5, the tubes 50 are flow path members provided in plurality, each having a first end connected to the openings 226a to 226c and a second end connected to the suction device 60. The tubes 50 are provided with a valve 51 and a buffer tank 52.

[0044] <valve> Valve 51 is a solenoid valve that can be opened and closed under the control of control unit 40. Valve 51 is preferably provided at a position where the volume of the space from valve 51 to suction device 60 (hereinafter referred to as closed space CS) is larger than the volume of the space from valve 51 to suction hole H (hereinafter referred to as open space OS). Specifically, valve 51 is preferably provided at a position where the volume of closed space CS is at least three times the volume of open space OS. With this configuration, a sufficient negative pressure can be created in closed space CS during recording medium transport control, which will be described later.

[0045] It is also preferable to use a valve 51 that has sufficiently small flow path resistance when open. Using a valve 51 with small flow path resistance is preferable because, in recording medium conveyance control, the pressure in the air flow path W, which will be described later, can be quickly equalized after the valve 51 is opened.

[0046] <Buffer tank> The buffer tank 52 is provided in the tube 50 at a location that forms the closed space CS, i.e., between the valve 51 and the suction device 60. The buffer tank 52 is, for example, a rigid, sealed tank made of metal. If the volume of the closed space CS were to be secured using only the tube 50, the length of the tube 50 would need to be increased. This would increase the flow resistance within the tube 50, and it would take time for the pressure to equalize after the valve 51 is opened during recording medium transport control. Furthermore, if the tube 50 were made longer, it would be difficult to organize the tube 50. Therefore, in this embodiment, these problems are solved by providing the buffer tank 52.

[0047] (suction device) The suction device 60 is, for example, a pump equipped with a known fan and motor. The suction device 60 is driven under the control of the control unit 40 to suck air from the tube 50.

[0048] With the above configuration, one air flow path W is formed in the suction area A1, leading from the chamber 223 to the suction device 60. The suction pressure generated by driving the suction device 60 creates a negative pressure inside the chamber 223, the upper surface of which is covered by the recording medium P. As a result, the recording medium P is attracted to the conveying surface F, which has a plurality of suction holes H, and is held on the conveying surface F even when the conveying drum 221 rotates.

[0049] {Image forming section} Returning to FIG. 1, the image forming unit 23 forms an image on the recording medium P transported by the transport device 22. In this embodiment, the image forming unit 23 includes a plurality of head units, each consisting of a plurality of inkjet heads. Each head unit forms an image by ejecting ink of a corresponding color from a nozzle opening facing the transport surface F at an appropriate timing according to the rotation of the transport device 22 holding the recording medium P. The head unit is arranged so that the nozzle opening and the transport surface F are spaced a predetermined distance apart.

[0050] {Fixing part} The fixing unit 24 fixes the image formed on the recording medium P by the image forming unit 23. The fixing unit 24 is, for example, an energy beam irradiation unit. Specifically, the fixing unit 24 includes a light-emitting unit arranged across the width of the conveying device 22 in the perpendicular direction. Under the control of the control unit 40, the light-emitting unit irradiates the conveyed recording medium P with energy beams such as ultraviolet rays. This hardens and fixes the ink on the recording medium P.

[0051] {Transport roller} The transport rollers 25 transport the recording medium P that has passed through the image forming unit 23 and the fixing unit 24, being handed over from the transport device 22. As shown in FIG. 1 , the transport rollers 25 include, for example, a first transport roller 251, a second transport roller 252, a third transport roller 253, and a fourth transport roller 254.

[0052] The first transport roller 251 is disposed opposite the transport device 22. The second transport roller 252 is disposed opposite the first transport roller 251. The third transport roller 253 and the fourth transport roller 254 are disposed opposite the second transport roller 252. Of these, the first transport roller 251, the third transport roller 253, and the fourth transport roller 254 rotate in the direction opposite to the transport direction. The second transport roller 252 rotates in the transport direction.

[0053] The first transport roller 251 to the fourth transport roller 254 include claw portions 251a to 254a, respectively. The claw portions 251a to 254a open and close under the control of the control unit 40. In detail, the control unit 40 opens the claw portions 251a to 253a at the timing when the recording medium P is to be handed over to the downstream second transport roller 252 to the fourth transport roller 254, thereby handing over the first end of the recording medium P to the claw portions 252a to 254a. The control unit 40 also holds the first end of the recording medium P by closing the claw portions 252a to 254a at the timing when the first end of the recording medium P is handed over from the upstream claw portions 251a to 253a.

[0054] {Belt conveyor} The belt conveying unit 26 is disposed opposite the third conveying roller 253. The belt conveying unit 26 includes a loop-shaped conveying belt whose inner side is supported by a plurality of rollers. The belt conveying unit 26 conveys the recording medium P received from the third conveying roller 253 to the paper output tray 31.

[0055] {Swing arm section} The swing arm unit 27 is provided downstream of the fourth transport roller 254. When the image forming apparatus 1 performs double-sided printing, the fourth transport roller 254 and the swing arm unit 27 invert the first and second sides of the recording medium P and return it to the transport device 22.

[0056] Specifically, when image formation on the first side of the recording medium P is completed, the control unit 40 transfers the first end of the recording medium P to the first transport roller 251, the second transport roller 252, and the fourth transport roller 254 in that order. When the second end of the recording medium P reaches a position facing the swing arm unit 27, the control unit 40 transfers the recording medium P from the fourth transport roller 254 to the swing arm unit 27. Then, when any of the transport surfaces F reaches a position facing the swing arm unit 27, the control unit 40 transfers the recording medium P to the transport device 22.

[0057] It should be noted that the image forming apparatus main body 20 of the present invention performs so-called alternating circulation control when forming images on both the first and second sides of a recording medium P. Alternating circulation control is a control in which image formation on the second, third, etc. recording medium P is sandwiched between image formation on the first and second sides of a first recording medium P. When the image forming apparatus 1 employs alternating circulation control, the gap between sheets can be narrowed compared to the normal circulation method in which image formation on the first and second sides of a first recording medium P is performed consecutively, thereby improving the productivity of double-sided printing.

[0058] (Paper output device) The paper discharge device 30 stores the recording medium P discharged from the image forming apparatus main body 20 until the user collects it. The paper discharge device 30 includes a plate-shaped paper discharge tray 31.

[0059] (Control unit) The control unit 40 controls the operation of each device constituting the image forming apparatus 1. As shown in FIG. 2, the control unit 40 includes a CPU (Central Processing Unit) 41, a RAM (Random Access Memory) 42, and a ROM (Read Only Memory) 43.

[0060] The CPU 41 executes various types of arithmetic processing. The CPU 41 also performs overall control of the overall operation of the image forming apparatus 1. The RAM 42 provides the CPU 41 with a working memory space and stores temporary data. The ROM 43 is a storage device such as an HDD (Hard Disk Drive) or SSD (Solid State Drive), and stores various control programs and setting data executed by the CPU 41. Note that the ROM 43 may be replaced by a rewritable non-volatile memory such as an EEPROM (Electrically Erasable Programmable Read Only Memory) or flash memory.

[0061] (external device) The external device 2 is, for example, a personal computer. The external device 2 supplies the control unit 40 with image data of the image recorded by the image forming apparatus 1 and the like.

[0062] [Recording medium transport control; single-sided printing] A description will now be given of recording medium conveyance control in the image forming apparatus 1 configured as above. First, the description will be limited to the case of single-sided printing in which an image is formed only on the first surface of the recording medium P.

[0063] The control unit 40, which has received print job data from the external device 2, first causes the recording medium P to be transported from the paper feed device 10 to the image forming apparatus main body 20. The control unit 40 places the recording medium P on the transport surface F of the transport device 22 and causes the suction device 60 to suck the recording medium P.

[0064] FIG. 6 is a graph summarizing the measurement results of the recording medium P placed on each transport surface F and the suction pressure on each transport surface F in a conventional image forming apparatus 1 from the start of a print job. As described above, in the image forming apparatus 1, with the recording medium P placed on the transport surface F and an enclosed space formed in the chamber 223, the suction device 60 sucks air from the air flow path W, creating a negative pressure in the chamber 223 and adsorbing the recording medium P to the transport surface F. On the other hand, immediately after the start of a print job, no recording medium P is placed on the transport surface F, and the suction holes H are open. Therefore, as shown in FIG. 6, the negative pressure created in the chamber 223 is insufficient, and the suction pressure on the transport surface F increases (i.e., the adsorption force is weakened). Therefore, in conventional image forming apparatuses, immediately after the start of a print job, poor transport of the recording medium P and printing defects caused by the floating of the recording medium P are likely to occur.

[0065] Therefore, the control unit 40 according to this embodiment closes the valve 51 and then drives the suction device 60 to create a negative pressure in the closed space CS before the recording medium P starts to be conveyed. Then, by opening the valve 51 before (preferably just before) the recording medium P blocks the suction hole H on the leading edge of the conveyance surface F in the conveyance direction, an appropriate negative pressure is created in the chamber 223 immediately after the start of the print job. Then, by closing the valve 51 before (preferably just before) the recording medium P blocks the suction hole H on the leading edge of the conveyance surface F in the conveyance direction, the suction device 60 prevents the negative pressure in the air flow path W from further increasing. With this configuration according to this embodiment, the recording medium P can be conveyed while being sucked with an appropriate suction pressure from the start of the print job, as shown in FIG. 7 .

[0066] Furthermore, it is preferable that the negative pressure a [kPa] formed in the closed space CS is a value that satisfies a(c / b+c)=d, when the ratio of the volume of the open space OS to the volume of the closed space CS is b:c, and the appropriate negative pressure in the air flow path W when transporting the recording medium P is d [kPa].

[0067] For example, let us assume that the ratio of the volume of the open space OS (b) to the volume of the closed space CS (c) is 1:4. Furthermore, let us assume that the appropriate negative pressure (d) in the air flow path W when the recording medium P is being transported is -18 kPa. In this case, when the valve 51 is opened, the volume increases by 5 / 4 times as the open space OS is added to the closed space CS. Meanwhile, the pressure value in the open space OS increases by 4 / 5 times because the chamber 223 is connected to the atmosphere and is at atmospheric pressure. Therefore, after the valve 51 is opened, the pressure value in the air flow path W becomes a(4 / 5) = -18, and it is preferable to operate the suction device 60 so that the negative pressure a in the closed space CS becomes -22.5 kPa.

[0068] Furthermore, the timing at which the control unit 40 opens the valve 51 is preferably such that the time from when the valve 51 is opened until the recording medium P is placed on the conveyance surface F is approximately the same as the time from when the valve 51 is opened until the pressure value in the closed space CS is equalized. This is because if the valve 51 is opened too early, the recording medium P will be released to the atmosphere through the suction hole H, resulting in insufficient negative pressure in the closed space CS. Also, if the valve 51 is opened too late, the recording medium P will be conveyed with insufficient suction.

[0069] 3 and 5, in a configuration in which one conveying surface F has multiple regions, it is preferable that the control unit 40 controls the opening and closing of the valve 51 according to the size of the recording medium P. For example, if the size of the recording medium P in the width direction is small, opening the valve 51 corresponding to the end chamber 2232 opens the end chamber 2232 to the atmosphere.

[0070] In particular, when multiple valves 51 are opened, it is preferable that the control unit 40 opens the valve 51 corresponding to the central chamber 2231 at an earlier timing (for example, about 0.1 seconds earlier) than the valve 51 corresponding to the end chamber 2232. With this configuration, the recording medium P is attracted to the conveying surface F from the center, and the occurrence of wrinkles in the recording medium P can be suppressed.

[0071] [Recording medium transport control; double-sided printing] Next, a description will be given of the case where images are formed on both sides of the recording medium P. As described above, the image forming apparatus 1 according to this embodiment performs double-sided printing by so-called alternating circulation control.

[0072] 8 is a graph showing measurements of the recording media P placed on each transport surface F from the start of a print job and the suction pressure of each transport surface F in a conventional image forming apparatus 1. As shown in FIG. 8, in the following example, double-sided printing is performed on 10 sheets of recording media P.

[0073] In alternating circulation control, the second side of the inverted recording medium P is placed on a conveying surface F (for example, surface B Fb, surface A Fa, and surface C Fc, in that order) between conveying surfaces F, F on which the first side of the recording medium P is placed. Therefore, at the start of double-sided printing, it is necessary to provide a margin for the conveying surface F on which the second side of the inverted recording medium P is placed, and as shown in Figure 8, recording media P cannot be placed consecutively on consecutive conveying surfaces F. As a result, the suction pressure on the conveying surfaces F on which the recording medium P is not placed increases, and the suction pressure on the subsequent conveying surfaces F may not decrease completely.

[0074] 8, when double-sided printing is completed under alternating circulation control, the recording medium P is no longer transported. Therefore, it is not possible to continuously place recording media P on successive transport surfaces F. As a result, the suction pressure on the transport surfaces F on which the recording media P is not placed increases, and the suction pressure on the subsequent transport surfaces F may not decrease completely.

[0075] However, the control unit 40 according to this embodiment creates a negative pressure in the closed space CS until the recording medium P is transported to the transport surface F, and opens and closes the valve 51 before the recording medium P closes the suction hole H. Therefore, as shown in Fig. 9, even during double-sided printing, an appropriate suction pressure can be applied to the recording medium P at the timing when the recording medium P is placed on the transport surface F and transported.

[0076] [Other configurations] Although the present invention has been specifically described above based on the embodiments thereof, the present invention is not limited to the above-described embodiments. Of course, the present invention can be modified in various ways within the scope of the invention described in the claims and its equivalents.

[0077] For example, in the above example, the valve 51 is provided in the tube 50, but the present invention is not limited to this. The valve 51 can be opened and closed under the control of the control unit 40 in the air flow path W formed between the suction device 60 and the chamber 223, and it is sufficient that the valve 51 can create a predetermined negative pressure in the closed space CS until the recording medium P blocks the suction hole H and the valve 51 is opened. Therefore, the valve 51 may be provided in the conveying drum 221, for example.

[0078] Furthermore, the suction force required on the conveying surface F naturally differs depending on the characteristics of the recording medium P. Therefore, the control unit 40 may function as an acquisition unit that acquires information about the recording medium P. The control unit 40 may then adjust the output of the suction device 60 depending on the acquired information. For example, the control unit 40 acquires information such as the thickness and paper type of the recording medium P from a sensor provided upstream of the conveying device 22 in the conveying direction or from print job data acquired from the external device 2.

[0079] In addition, as the negative pressure formed in the closed space CS increases, the time required for the pressure value in the air flow path W to become uniform after the valve 51 is opened also increases. Therefore, when the control unit 40 adjusts the output of the suction device 60 in accordance with the information on the recording medium P acquired from the acquisition unit, the control unit 40 may also adjust the timing at which the valve 51 is opened.

[0080] In the above example, the transport surface F has a plurality of regions in the transport direction and the width direction, but the transport surface F is not limited to this. For example, the transport surface F may have a plurality of regions in the diagonal direction.

[0081] Also, while FIG. 1 illustrates one sheet feeding device 10 having one sheet feeding tray 11, this is not limiting. For example, one sheet feeding device 10 may be configured to have multiple sheet feeding trays 11. Furthermore, the image forming apparatus 1 may be configured to have multiple sheet feeding devices 10. Similarly, FIG. 1 illustrates one sheet discharging device 30 having one sheet discharging tray 31, but this is not limiting. In other words, the image forming apparatus 1 may be configured to have multiple sheet discharging trays 31.

[0082] In addition, in the above example, the conveying device 22 is provided with the conveying drum 221 having the conveying surface F in its specific region, but this is not limiting. For example, the configuration of the present invention is also applicable to a configuration in which the conveying device 22 is provided with an endless belt on the entire surface of which the recording medium P can be placed.

[0083] Although the above describes an example in which a hard disk or a semiconductor nonvolatile memory is used as a computer-readable medium for the program according to the present invention, the present invention is not limited to this example. Other computer-readable media include portable recording media such as CD-ROMs. Furthermore, a carrier wave can also be used as a medium for providing the program data according to the present invention via a communication line. [Explanation of symbols]

[0084] 1. Image forming device 22 Conveyor equipment 221 Conveyor drum (conveyor section) 23 Image forming unit 40 Control unit (acquisition unit) 50 Tube (flow path component) 51 Valve 52 Buffer Tank 60 Suction device (suction part) F Conveying surface H Suction hole P Recording medium W Air flow path OS open space CS closed space

Claims

1. a conveying unit that conveys the recording medium; an air flow path that communicates a suction hole provided on the conveying surface of the conveying unit with a suction unit that sucks air; a valve capable of dividing the air flow path into an open space on the suction hole side and a closed space on the suction part side; a control unit that controls the adsorption of the recording medium to the conveyance surface, The control unit opens the valve when the recording medium blocks the suction hole.

2. the air flow path includes a flow path member that connects the suction unit and the transport unit, The transport device according to claim 1 , wherein the valve is provided in the flow path member.

3. The transport device according to claim 1 , wherein the valve is provided in the air flow path on a side closer to the transport unit than the suction unit.

4. The conveying device according to claim 1 , wherein the air flow path includes a buffer tank in the closed space.

5. The transport device according to claim 1 , wherein the volume of the closed space is larger than the volume of the open space.

6. 6. The transport device according to claim 5, wherein the volume of the closed space is at least three times the volume of the open space.

7. The conveying device according to claim 1 , wherein the control unit opens the valve after the pressure in the closed space is saturated.

8. The conveying device according to claim 1 , wherein the control unit opens the valve before the recording medium blocks the suction hole.

9. The conveying device according to claim 8 , wherein the control unit closes the valve before the recording medium blocks the suction hole.

10. an acquisition unit for acquiring information on a recording medium; The transport device according to claim 1 , wherein the control unit controls an output of the suction unit in accordance with the information acquired by the acquisition unit.

11. The transport device according to claim 10 , wherein the control unit controls the timing at which the valve is opened in accordance with the output of the suction unit.

12. the conveying surface has a plurality of regions; The conveying device according to claim 1 , further comprising the air flow paths and the valves corresponding to the plurality of regions, respectively.

13. the conveying surface has a plurality of regions in a width direction, The conveying device described in claim 12, wherein the control unit opens the valve corresponding to the region among the plurality of regions that corresponds to the center of the width of the recording medium to be placed before the valve corresponding to the region that corresponds to the end side of the width of the recording medium.

14. the conveying unit is a conveying drum that rotates to convey the recording medium placed on the conveying surface, The conveying device according to claim 1 , wherein the suction unit sucks air from the corresponding suction hole only at a predetermined rotation angle.

15. A conveying device according to any one of claims 1 to 14; and an image forming unit that forms an image on a recording medium.

16. a conveying unit that conveys the recording medium; an air flow path that communicates a suction hole provided on the conveying surface of the conveying unit with a suction unit that sucks air; a valve that separates the air flow path into an open space on the suction hole side and a closed space on the suction part side when closed, A program for causing the control unit to function as a control unit for controlling suction of the recording medium to the conveyance unit, The control unit is a program that opens the valve when the recording medium closes the suction hole.

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