Paper transport device and inkjet recording device

Abstract

The aim is to improve the detection capabilities of thin paper and recycled paper on the conveyor belt. [Solution] The system comprises a transport belt 46 provided with first and second through holes 46a and 46b, and a sensor 49 for detecting paper on the transport belt 46. The sensor 49 includes a light-emitting part 101 located on one side of the transport belt 46, a first mirror surface 102 located on the other side of the transport belt 46 where the optical path between the light-emitting part 101 and the first through hole 46a crosses the optical path, and which reflects light from the light-emitting part 101, a second mirror surface 103 located on the other side of the transport belt 46 where the optical path between the first mirror surface 103 and the second mirror surface 103 crosses the optical path between the first through hole 46a and the first mirror surface 102, and which receives light from the second mirror surface 103.

Description

Technical Field

[0001] The present invention relates to a paper conveyance device and an inkjet recording device, and particularly to the detection of paper on a conveyance belt.

Background Art

[0002] A paper conveyance device includes, for example, a conveyance belt that conveys paper by circular movement and has suction holes that are covered by the paper and suck the paper when conveying the paper, and a sensor that detects the paper on the conveyance belt (see, for example, Patent Document 1). When the sensor is a reflection type photosensor, the detection of paper using the reflection type photosensor is performed by utilizing that the light emitted by the reflection type photosensor is received by the reflection type photosensor, and the intensity of the received light is different between the case where there is no paper on the conveyance belt and the case where there is paper.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the case of thin paper, the light emitted by the reflection type photosensor is not sufficiently reflected by the thin paper. Further, in the case of recycled paper having minute holes or transparent inclusions in the paper, if minute holes or transparent inclusions exist in the optical path of the light emitted by the reflection type photosensor, the light emitted by the reflection type photosensor is not sufficiently reflected by the recycled paper. For this reason, the difference in the intensity of the light received by the reflection type photosensor between the case where there is no paper on the conveyance belt and the case where there is paper is small, and it becomes difficult to detect the paper.

[0005] In addition, through-beam photosensors are sometimes used for paper detection. When using a through-beam photosensor, a light-emitting unit is placed on one side of the conveyor belt, and a light-receiving unit is placed on the other side of the conveyor belt. Paper detection using a through-beam photosensor is performed by the fact that the light-receiving unit receives the light emitted by the light-emitting unit, and the intensity of the received light differs depending on whether there is paper on the conveyor belt or not.

[0006] However, in the case of thin paper, the light emitted by the light-emitting unit is not sufficiently blocked by the thin paper and is transmitted through to the light-receiving unit. Also, in the case of recycled paper that has micro-pores or transparent inclusions, if micro-pores or transparent inclusions are present in the optical path of the light emitted by the light-emitting unit, the light emitted by the light-emitting unit is transmitted through the recycled paper with almost no obstruction and is transmitted to the light-receiving unit. For this reason, the difference in the intensity of light received by the reflective photosensor is small when there is no paper on the conveyor belt and when there is paper, making it difficult to detect the paper.

[0007] This invention has been made in view of the above circumstances, and aims to improve the detection capability of thin paper, recycled paper, and other materials on a conveyor belt. [Means for solving the problem]

[0008] A paper transport device according to one aspect of the present invention transports paper by moving in a circular motion and comprises a transport belt having a first through hole and a second through hole at positions that are simultaneously covered by the paper when transporting the paper, and a sensor for detecting the paper on the transport belt, wherein the sensor comprises a light-emitting part positioned at a first location facing one side of the transport belt and emitting light, a first mirror surface positioned at a second location facing the other side of the transport belt where light emitted by the light-emitting part reaches through the first through hole during the circular motion of the transport belt and reflects the light emitted by the light-emitting part, a second mirror surface positioned at a third location facing the other side of the transport belt and reflects the light reflected by the first mirror surface, and a light-receiving part positioned at a fourth location facing one side of the transport belt and receiving the light reflected by the second mirror surface through the second through hole during the circular motion of the transport belt.

[0009] An inkjet recording apparatus according to one aspect of the present invention comprises the above-mentioned paper transport device and an ink head that ejects ink onto the paper to form an image on the paper. [Effects of the Invention]

[0010] According to the present invention, when a first and second through-hole of the conveyor belt exist in the optical path from the light-emitting unit to the light-receiving unit, and there is paper on the first and second through-holes, there are two locations on the paper where the light emitted by the light-emitting unit may be blocked before it is received by the light-receiving unit. Therefore, even if the paper on the conveyor belt is thin, the light emitted by the light-emitting unit is blocked twice by the thin paper, thereby reducing the intensity of the light received by the light-receiving unit. Furthermore, if the paper on the conveyor belt is recycled paper with micro-pores or transparent inclusions, even if micro-pores or transparent inclusions are present at one of the two locations mentioned above, if they are not present at the other location, the light emitted by the light-emitting unit will be blocked at the other location, thereby reducing the intensity of the light received by the light-receiving unit. This increases the difference in the intensity of the light received by the light-receiving unit between the presence and absence of paper, thereby improving the detection capability of thin paper and recycled paper on the conveyor belt. [Brief explanation of the drawing]

[0011] [Figure 1] This is a schematic cross-sectional view showing an inkjet recording device to which a paper transport device according to one embodiment of the present invention is applied. [Figure 2] Figure 1 is a functional block diagram showing the main internal components of an inkjet recording device. [Figure 3] (A) is a schematic diagram showing the configuration of the paper detection sensor in the inkjet recording device shown in Figure 1, and (B) is a schematic diagram of the cross-section of line AA in (A). [Figure 4] (A) is a schematic diagram illustrating the function of the sensor in Figure 1 for recording paper of normal thickness, and (B) is a schematic diagram illustrating the function of the sensor in a comparative example for recording paper of normal thickness. [Figure 5] (A) is a schematic diagram illustrating the function of the sensor in Figure 1 for thin recording paper, and (B) is a schematic diagram illustrating the function of the sensor in the comparative example for thin recording paper. [Figure 6](A) is a schematic diagram illustrating the function of the sensor in Figure 1 for recording paper made from recycled paper that has micropores or transparent inclusions within the paper, and (B) is a schematic diagram illustrating the function of the sensor in a comparative example for recording paper made from recycled paper that has micropores or transparent inclusions within the paper. [Figure 7] This is an example of a timing chart used to explain the determination of whether there is no recording paper on the conveyor belt, using the detection results of the sensor in Figure 3 by the control unit in Figure 2. [Figure 8] This is an example of a timing chart used to explain the determination of the presence or absence of recording paper on the conveyor belt using the detection results of the sensor in Figure 3 by the control unit in Figure 2. [Modes for carrying out the invention]

[0012] One embodiment of the present invention will be described below with reference to the drawings.

[0013] First, the configuration of the inkjet recording device 1 to which the paper transport device according to one embodiment of the present invention is applied will be described with reference to Figures 1 and 2. Figure 1 is a schematic cross-sectional view of the inkjet recording device 1 to which the paper transport device according to one embodiment of the present invention is applied. Figure 2 is a functional block diagram showing the main internal configuration of the inkjet recording device of Figure 1.

[0014] The inkjet recording device 1 comprises an operation unit 11, a document reading unit 12, an image recording unit 13, a paper feeding unit 14, a transport unit 15, a transport belt unit (an example of a paper transport device) 16, and a cap unit 18.

[0015] The operation unit 11 is operated by the user to input instructions for various operations and processes performed by the inkjet recording device 1. For example, the operation unit 11 includes physical keys such as a numeric keypad, an enter key, and a start key, as well as a touch panel provided on the screen of the display unit 21.

[0016] In the original document reading unit 12, when the original document MS is placed on the original document tray 22, the original document MS is pulled out from the original document tray 22 and conveyed, and at the same time, the image of the original document MS is read by an image sensor. The analog output of this image sensor is converted into a digital signal, and image data indicating the image of the original document MS is generated.

[0017] The image recording unit 13 prints the image of the original document MS indicated by the above image data on the recording paper (an example of paper) P. Four-color (black, cyan, magenta, and yellow) ink droplets are ejected onto the recording paper P on the conveying belt 46 conveyed by the conveying belt 46 of the conveying belt unit 16 to form a color image on the recording paper P. Specifically, the image recording unit 13 has respective line heads (an example of an ink head) 23 corresponding to each of the colors black, cyan, magenta, and yellow. Therefore, the inkjet recording apparatus 1 is a line head type inkjet recording apparatus.

[0018] The above recording paper P is fed from the paper feeding unit 14, conveyed through the conveyance path 31 of the conveyance unit 15 to the conveying belt 46 of the conveying belt unit 16, and further discharged to the discharge tray 41 through the conveyance path 38 of the conveyance unit 15 from the conveying belt 46.

[0019] The paper feeding unit 14 includes a paper feeding cassette 27. A paper feeding roller 28 is provided in the paper feeding cassette 27, and the recording paper P accommodated in the paper feeding cassette 27 is pulled out by the paper feeding roller 28 and conveyed to the conveyance path 31.

[0020] Also, the paper feeding unit 14 includes a manual feed tray 32 provided on the wall surface of the apparatus main body. The recording paper P set on the manual feed tray 32 is pulled out by the paper feeding roller 33 and conveyed to the conveyance path 31.

[0021] The transport unit 15 includes a transport path 31 for transporting the recording paper P from the paper feeding unit 14, transport rollers 35 provided at appropriate locations in each transport path 31, 38, a registration roller 36 that corrects the diagonal feeding of the recording paper P and feeds the recording paper P onto the transport belt 46 of the belt unit 16, a transport path 38 for transporting the recording paper P that has been transported by the transport belt 46, and an discharge roller 42 that discharges the recording paper P that has been transported through the transport path 38 into the discharge tray 41.

[0022] The conveyor belt unit 16 comprises a drive roller 43, a driven roller 44, a tension roller 45, a conveyor belt 46, a fan 47, a sensor 49, and a workbench 50. As shown in Figure 3, the sensor 49 comprises a light-emitting section 101, a first mirrored surface section 102, a second mirrored surface section 103, and a light-receiving section 104. The conveyor belt 46 is an endless belt, stretched over the drive roller 43, the driven roller 44, and the tension roller 45, with the side of the conveyor belt 46 opposite to the side facing the image recording section 13 facing the upper surface of the workbench 50. The drive roller 43 is a roller that is driven to rotate counterclockwise by a motor (not shown). When the drive roller 43 is driven to rotate, the conveyor belt 46 rotates counterclockwise, and the driven roller 44 and tension roller 45 rotate counterclockwise in response.

[0023] The conveyor belt 46 transports the recording paper P from the conveyor path 31 of the conveyor unit 15 by placing the recording paper P on the conveyor belt 46 and moving it in a circular motion.

[0024] The tension roller 45 is a roller that maintains the tension of the conveyor belt 46 in an appropriate state.

[0025] The workbench 50 houses the first mirror surface 102 and the second mirror surface 103 of the fan 47 and the sensor 49, and is used when the image recording unit 13 records images on the recording paper P on the conveyor belt 46. As shown in Figure 3(A), the workbench 50 is provided with a first through hole 50a and a second through hole 50b in the portion of the workbench 50 facing the conveyor belt 46. In this embodiment, the first through hole 50a and the second through hole 50b are located on the same straight line parallel to the direction perpendicular to the circumferential direction of the conveyor belt 46, such that the distance between the first through hole 50a and the second through hole 50b in the direction perpendicular to the circumferential direction of the conveyor belt 46 is less than or equal to the distance between the two ends of the shortest recording paper P in the direction perpendicular to the circumferential direction of the conveyor belt 46. The recording paper P conveyed by the conveyor belt 46 passes through the first through hole 50a and the second through hole 50b simultaneously. Furthermore, this is not limited to cases where the first through-hole 50a and the second through-hole 50b are located on the same straight line parallel to the direction perpendicular to the circumferential direction of the conveyor belt 46.

[0026] As shown in Figure 3(A), the conveyor belt 46 has multiple first through holes 46a provided at equal intervals in the circumferential direction of the conveyor belt 46 at a predetermined position in a direction perpendicular to the circumferential direction of the conveyor belt 46, and multiple second through holes 46b provided at equal intervals in the circumferential direction of the conveyor belt 46 at a predetermined position other than the predetermined position in a direction perpendicular to the circumferential direction of the conveyor belt 46. The multiple first through holes 46a and the multiple second through holes 46b include suction holes for drawing in air to attract the recording paper P to the conveyor belt 46. The predetermined position is a position on the first through hole 50a of the workbench 50 (a position that coincides with the first through hole 50a of the workbench 50 in a plan view), and the predetermined other position is a position on the second through hole 50b of the workbench 50 (a position that coincides with the second through hole 50b of the workbench 50 in a plan view). In this embodiment, the multiple first through holes 46a and the multiple second through holes 46b are arranged one by one on multiple identical lines parallel to the direction perpendicular to the circumferential direction of the conveyor belt 46. In this embodiment, the distance between the first through holes 46a and the second through holes 46b in the direction perpendicular to the circumferential direction of the conveyor belt 46 is less than or equal to the distance between the two ends of the smallest recording paper P in the direction perpendicular to the circumferential direction of the conveyor belt 46.

[0027] The first through-hole 46a and the second through-hole 46b, which are located on the same straight line parallel to the direction perpendicular to the circumferential direction of the conveyor belt 46, simultaneously pass directly above the first through-hole 50a and the second through-hole 50b provided in the workbench 50.

[0028] The first through-hole 46a and the second through-hole 46b, which are located on the same straight line parallel to the direction perpendicular to the circumferential direction of the conveyor belt 46, are covered simultaneously by the recording paper P during the period when the conveyor belt 46 is conveying the recording paper P.

[0029] The fan 47 is positioned on the opposite side of the workbench 50 from the side where the conveyor belt 46 is located, relative to the portion of the workbench 50 where the first through-hole 50a and the second through-hole 50b are provided (the portion of the workbench 50 facing the conveyor belt 46). The fan 47 draws in air through the first through-hole 50a of the workbench 50 and the first through-hole 46a of the conveyor belt 46, which is used as a suction hole, and through the second through-hole 50b of the workbench 50 and the second through-hole 46b of the conveyor belt 46, which is used as a suction hole, causing the recording paper P to adhere to the conveyor belt 46 due to negative pressure.

[0030] Sensor 49 is a sensor that detects the recording paper P on the conveyor belt 46. The structure of sensor 49 will be described later with reference to Figure 3, etc.

[0031] The lifting mechanism 48 supports the conveyor belt unit 16 from below and moves the conveyor belt unit 16 up and down relative to each line head 23 of the image recording unit 13. In other words, the lifting mechanism 48 moves the conveyor belt unit 16 and each line head 23 apart and closer together by moving the conveyor belt unit 16 relative to each line head 23. Specifically, the lifting mechanism 48 moves the conveyor belt unit 16 between a recording position (the position shown in Figure 1) where printing by the image recording unit 13 is possible and a maintenance position located at a predetermined distance below this recording position.

[0032] When the conveyor belt unit 16 is lowered to the maintenance position by the lifting mechanism 48, an empty space is created below the image recording unit 13. In this state, the cap portion 18 is moved horizontally to the bottom of the image recording unit 13 by the moving mechanism 56 (shown in Figure 2), and then the cap portion 18 is moved upward by the moving mechanism 56 so that the nozzles of each line head 23 of the image recording unit 13 are covered by the cap portion 18, preventing the ink on the nozzles of each line head 23 of the image recording unit 13 from drying out.

[0033] The inkjet recording device 1 includes an operation unit 11, a document reading unit 12, an image recording unit 13, a paper feeding unit 14, a transport unit 15, a transport belt unit 16, a lifting mechanism 48, a moving mechanism 56 for moving the cap unit 18 horizontally and vertically as described above, an image memory 57, and a control unit 60.

[0034] The control unit 60 consists of a processor, RAM (Random Access Memory), ROM (Read Only Memory), and dedicated hardware circuits. The processor is, for example, a CPU (Central Processing Unit), an ASIC (Application Specific Integrated Circuit), or an MPU (Micro Processing Unit).

[0035] The control unit 60 functions as a control unit 61 when the processor executes various programs stored in non-volatile memory such as ROM. The control unit 61 is not limited to being realized by program execution, but can also be configured by various hardware circuits.

[0036] The control unit 61 is connected to the operation unit 11, the document reading unit 12, the image recording unit 13, the paper feeding unit 14, the transport unit 15, the transport belt unit 16, the lifting mechanism 48, the moving mechanism 56, and the image memory 57, and is responsible for the overall operation control of the inkjet recording device 1.

[0037] For example, the control unit 61 controls the motor for driving the transport roller 35 in the document reading unit 12, the image sensor, etc., to transport the document MS by the document reading unit 12, read the image of the document MS, and store the image data representing the image of the document MS in the image memory 57.

[0038] Furthermore, the control unit 61 controls the motors that rotate the paper feed rollers 33, transport rollers 35, and registration rollers 36 in the paper feed unit 14 and transport unit 15, the motor that rotates the drive rollers 43 of the transport belt 46 in the transport belt unit 16, the motor that rotates the fan 37, etc., to feed the recording paper P from the paper feed unit 14 and transport the recording paper P by the transport belt 46.

[0039] Then, the control unit 61 controls each line head 23 of the image recording unit 13 based on the image data representing the image of the original document MS in the image memory 57, causing each line head 23 to eject its respective ink, thereby forming the image of the original document MS on the recording paper P on the transport belt 46.

[0040] Furthermore, the control unit 61 controls the motors and actuators in the lifting mechanism 48 and the moving mechanism 56 to raise and lower the conveyor belt unit 16, and to move the cap portion 18 in the horizontal and vertical directions.

[0041] Based on the output of the sensor 49, the control unit 61 determines the presence or absence of recording paper P on the transport belt 46 using the sensor 49 just before ink ejection from each line head 23 begins. When the control unit 61 determines the presence or absence of recording paper P, it starts the ejection of ink from each line head 23 at a predetermined timing to form the image of the original document MS on the recording paper P.

[0042] Next, the sensor 49 provided in the inkjet recording device 1 shown in Figure 1 will be explained with reference to Figure 3. Figure 3(A) is a schematic diagram showing the configuration of the paper-detecting sensor 49 provided in the inkjet recording device 1 shown in Figure 1, and Figure 3(B) is a schematic diagram of the cross-section of line AA in Figure 3(A).

[0043] As shown in Figures 3(A) and (B), the sensor 49 comprises a light-emitting section 101, a first mirrored section 102, a second mirrored section 103, and a light-receiving section 104.

[0044] The light-emitting unit 101 is positioned at a first location facing one side of the conveyor belt 46. The light-emitting unit 101 is controlled by the control unit 61 to emit light of a predetermined intensity. In this embodiment, the light-emitting unit 101 is positioned directly above the first through-hole 50a of the workbench 50 (positioned where it overlaps with the first through-hole 50a of the workbench 50 in a plan view), and emits light in a downward direction (direction toward the first through-hole 50a of the workbench 50, and in the direction perpendicular to one side of the conveyor belt 46, from the light-emitting unit 101 toward the conveyor belt 46).

[0045] The first mirror surface 102 is positioned opposite the other surface of the conveyor belt 46 (the back surface of the conveyor belt 46 to the aforementioned surface), and is located at a second location separated from the conveyor belt 46 by the first through-hole 50a of the workbench 50, such that the optical path between it and the light-emitting unit 101 becomes the optical path through which the first through-hole 46a passes during the circumferential movement of the conveyor belt 46. In other words, the first mirror surface 46 is positioned opposite the other surface of the conveyor belt 46, and is located at a second location where light emitted by the light-emitting unit 101 reaches through the first through-hole 46a during the circumferential movement of the conveyor belt 46. The first mirror surface 102 reflects the light emitted by the light-emitting unit 102 toward the second mirror surface 103. In this embodiment, the first mirror surface 102 is positioned directly below the first through-hole 50a of the workbench 50 (positioned so as to overlap with the first through-hole 50a of the workbench 50 in a plan view), and reflects the light emitted by the light-emitting unit 101 in a downward direction in a direction parallel to the direction from the first through-hole 50a of the workbench 50 toward the second through-hole 50b of the workbench 50 (a direction perpendicular to the circumferential direction of the conveyor belt 46, and the direction from the first through-hole 46a toward the second through-hole 46b of the conveyor belt 46). In this embodiment, the light-emitting unit 101 and the first mirror surface 102 are positioned at the first and second locations on a straight line perpendicular to one of the surfaces of the conveyor belt 46.

[0046] The second mirror surface 103 is positioned at a third location on the conveyor belt 46 opposite the other surface, separated from the conveyor belt 46 by the second through-hole 50b of the workbench 50, and reflects the light reflected by the first mirror surface 102 toward the light receiving section 104. In this embodiment, the second mirror surface 103 is positioned directly below the second through-hole 50b of the workbench 50 (positioned where it overlaps with the second through-hole 50b of the workbench 50 in a plan view), and reflects light in an upward direction (direction toward the second through-hole 50b of the workbench 50, and in the direction perpendicular to one surface of the conveyor belt 46, from the second mirror surface 103 toward the conveyor belt 46).

[0047] The light receiving unit 104 is positioned at a fourth location on the conveyor belt 46 facing one of the aforementioned surfaces, such that the optical path between it and the second mirror surface 103 becomes the optical path crossed by the second through-hole 46b at the same time that the first through-hole 46a crosses the optical path between the light-emitting unit 101 and the first mirror surface 102 during the conveyor belt 46's circular movement. In other words, the light receiving unit 104 is positioned at a fourth location on the conveyor belt facing one of the aforementioned surfaces, so as the conveyor belt 46 moves around, it receives the light reflected by the second mirror surface through the second through-hole 46b. The light receiving unit 104 receives the light reflected by the second mirror surface 103 and outputs the intensity of the received light (hereinafter referred to as "received light intensity") to the control unit 61. In this embodiment, the light-receiving unit 104 is positioned directly above the second through-hole 50b of the workbench 50 (positioned so as to overlap with the second through-hole 50b of the workbench 50 in a plan view), and receives light reflected by the second mirror surface 103 from directly below (from the direction of the second through-hole 50b of the workbench 50, and from the direction perpendicular to one of the surfaces of the conveyor belt 46, specifically from the conveyor belt 46 toward the light-receiving unit 104). In this embodiment, the second mirror surface 103 and the light-receiving unit 104 are positioned at the third and fourth locations on a straight line other than the one straight line perpendicular to the one surface of the conveyor belt 46.

[0048] When the recording paper P is transported by the conveyor belt 46, there is a period during which the recording paper P simultaneously covers a first through-hole 46a that crosses the optical path between the light-emitting unit 101 and the first mirror surface unit 102, and a second through-hole 46b that crosses the optical path between the second mirror surface unit 103 and the light-receiving unit 104 at the same time that the first through-hole 46a crosses the optical path between the light-emitting unit 101 and the first mirror surface unit 102 (in this embodiment, the first through-hole 46a and the second through-hole 46b are on the same straight line parallel to the direction perpendicular to the circumferential direction of the conveyor belt 46). During this period, the optical path from the light-emitting unit 101 through the first mirror surface unit 102 and the second mirror surface unit 103 to the light-receiving unit 104 may be blocked by the recording paper P at two locations.

[0049] Next, the function of the sensor 49 in Figure 3 will be explained in comparison with the function of the comparative example sensor 49A. As shown in Figures 4 to 6, the comparative example sensor 49A comprises a light-emitting unit 101A and a light-receiving unit 104A. The light-emitting unit 101A is positioned opposite one side of the conveyor belt 46 and directly above the first through-hole 50a of the workbench 50, and emits light in a downward direction. The light-receiving unit 104A is positioned opposite the other side of the conveyor belt 46 and directly below the first through-hole 50a of the workbench 50, and receives the light emitted by the light-emitting unit 101 from directly above.

[0050] First, we will compare the function of the sensor 49 in Figure 1 with that of the comparative example sensor 49A for recording paper of normal thickness P, referring to Figure 4. Figure 4(A) is a schematic diagram illustrating the function of the sensor 49 in Figure 1 with respect to recording paper of normal thickness P, and Figure 4(B) is a schematic diagram illustrating the function of the comparative example sensor 49A for recording paper of normal thickness P.

[0051] In the comparative example sensor 49A, the light emitted by the light-emitting unit 101A is greatly attenuated in intensity by the recording paper P of normal thickness, passes through the recording paper P, passes through the first through-hole 46a of the conveyor belt 46 and the first through-hole 50a of the work table 50, and is received by the light-receiving unit 104A. In the case of recording paper P of normal thickness, the light emitted by the light-emitting unit 101A is blocked once by the recording paper P, so the intensity of the light received by the light-receiving unit 104A becomes small enough to detect the recording paper P.

[0052] In the sensor 49 shown in Figure 3, the light emitted by the light-emitting unit 101 is greatly attenuated by the recording paper P of normal thickness, passes through the recording paper P, passes through the first through-hole 46a of the conveyor belt 46 and the first through-hole 50a of the workbench 50, is reflected by the first mirror surface 102, and is further reflected by the second mirror surface 103. The light reflected by the second mirror surface 103 passes through the second through-hole 50b of the workbench 50 and the second through-hole 46b of the conveyor belt 46, is greatly attenuated by the recording paper P of normal thickness, passes through the recording paper P of normal thickness, and is received by the light-receiving unit 104. In the case of recording paper P of normal thickness, the light emitted by the light-emitting unit 101 is blocked twice by the recording paper P, so the intensity of the light received by the light-receiving unit 104 becomes even smaller, to the point where the recording paper P can be detected.

[0053] As described above, in the case of recording paper P of normal thickness, both the sensor 49A in the comparative example and the sensor 49 in Figure 3 can detect the recording paper P.

[0054] Next, we will compare the function of the sensor 49 in Figure 1 with that of the comparative example sensor 49A for thin recording paper P, referring to Figure 5. Figure 5(A) is a schematic diagram illustrating the function of the sensor 49 in Figure 1 with respect to thin recording paper P, and Figure 5(B) is a schematic diagram illustrating the function of the comparative example sensor 49A for thin recording paper P.

[0055] In the comparative example sensor 49A, the light emitted by the light-emitting unit 101A is attenuated by the thin recording paper P, passes through the thin recording paper P, passes through the first through-hole 46a of the conveyor belt 46 and the first through-hole 50a of the workbench 50, and is received by the light-receiving unit 104A. In the case of thin recording paper P, the light emitted by the light-emitting unit 101A is not blocked by the recording paper P even once, and the intensity of the light received by the light-receiving unit 104A does not decrease to a level where the recording paper P can be detected.

[0056] In the sensor 49 shown in Figure 3, the light emitted by the light-emitting part 101 is attenuated by the thin recording paper P, its intensity is reduced, and the light passes through the thin recording paper P, through the first through-hole 46a of the conveyor belt 46 and the first through-hole 50a of the workbench 50, reflected by the first mirror surface 102, and further reflected by the second mirror surface 103. The light reflected by the second mirror surface 103 passes through the second through-hole 50b of the workbench 50 and the first through-hole 46b of the conveyor belt 46, its intensity is reduced by the thin recording paper P, it passes through the thin recording paper P, and is received by the light-receiving part 104. In the case of thin recording paper P, if the light emitted by the light-emitting unit 101 is blocked by the recording paper P only once, the intensity of the light received by the light-receiving unit 104 will not decrease enough to detect the recording paper P. However, if the light is blocked by the recording paper P twice, the intensity of the light received by the light-receiving unit 104 will decrease enough to detect the recording paper P.

[0057] As mentioned above, in the case of thin recording paper P, the sensor 49A in the comparative example cannot detect the recording paper P, but the sensor 49 in Figure 3 can detect the recording paper P.

[0058] Next, we will compare the function of the sensor 49 in Figure 1 with that of the comparative example sensor 49A for recording paper P made from recycled paper that has micropores or transparent inclusions, with reference to Figure 6. Figure 6(A) is a schematic diagram illustrating the function of the sensor 49 in Figure 1 for recording paper P made from recycled paper that has micropores or transparent inclusions, and Figure 6(B) is a schematic diagram illustrating the function of the comparative example sensor 49A for recording paper P made from recycled paper that has micropores or transparent inclusions. Figure 6(A) is for the case where the optical path from the light-emitting part 101 to the first mirror part 102 contains a portion of the recording paper P with micropores P1, and the optical path from the second mirror part 103 to the light-receiving part 104 contains only a portion of the recording paper P without micropores, while Figure 6(B) is for the case where the optical path from the light-emitting part 101A to the light-receiving part 104A contains a portion of the recording paper P with micropores P1.

[0059] In the comparative example sensor 49A, the light emitted by the light-emitting unit 101A is attenuated around the micropores P1 of the recording paper P, and leaks out from the micropores P1, so as a whole, it does not attenuate significantly and passes through the recording paper P, passes through the first through-hole 46a of the conveyor belt 46 and the first through-hole 50a of the work table 50, and is received by the light-receiving unit 104A. In the case of recording paper P made of recycled paper that has micropores or transparent inclusions in the paper, when the light emitted by the light-emitting unit 101A passes through the recording paper P to the micropores P1 and the surrounding areas of the micropores P1, the intensity of the light received by the light-receiving unit 104A does not decrease to the point where the recording paper P can be detected.

[0060] In the sensor 49 shown in Figure 3, the light emitted by the light-emitting part 101 is attenuated in intensity by the area surrounding the micro-pores P1 of the recording paper P, and leaks out through the micro-pores P1. As a result, the overall intensity is not significantly attenuated, and the light passes through the recording paper P, passing through the first through-hole 46a of the conveyor belt 46 and the first through-hole 50a of the workbench 50, is reflected by the first mirror surface 102, and is further reflected by the second mirror surface 103. The light reflected by the second mirror surface 103 passes through the second through-hole 50b of the workbench 50 and the second through-hole 46b of the conveyor belt 46. When the light passes through only the area without micro-pores P1, the intensity is significantly attenuated by the recording paper P, and the light passes through the recording paper P and is received by the light-receiving part 104. In the case of recording paper P made from recycled paper that has micropores or transparent inclusions, when the light emitted by the light-emitting unit 101 passes through the recording paper P to the micropores P1 and the surrounding areas of the micropores P1, the overall intensity does not decrease significantly. However, when the light passes through only the areas without micropores P1, the intensity decreases significantly, so that the intensity of the light received by the light-receiving unit 104 becomes small enough to detect the recording paper P.

[0061] As described above, if there is a portion of the recording paper P with micropores P1 in the optical path from the light-emitting unit 101A to the light-receiving unit 104A, the comparative example sensor 49A cannot detect the recording paper P. However, even if there is a portion of the recording paper P with micropores P1 in the optical path from the light-emitting unit 101 to the first mirror surface unit 102, if there is only a portion of the recording paper P without micropores in the optical path from the second mirror surface unit 103 to the light-receiving unit 104, the light intensity will be greatly attenuated in that portion, and therefore the sensor 49 in Figure 3 can detect the recording paper P.

[0062] Next, we will explain how the control unit 61 in Figure 2 can determine the presence or absence of recording paper P on the transport belt 46 using the detection results of the sensor 49 in Figure 1.

[0063] First, the case where the recording paper P is not being transported on the transport belt 46 will be explained with reference to Figure 7. Figure 7 is an example of a timing chart for explaining the determination of the absence of recording paper P on the transport belt 46 using the detection result of the sensor 49 in Figure 3 by the control unit 61 in Figure 2.

[0064] The light-emitting unit 101 emits light under the control of the control unit 61 and continues to emit light.

[0065] In this embodiment, the multiple first through-holes 46a of the conveyor belt 46 are arranged at equal intervals in the circumferential direction of the conveyor belt 46, and each of the multiple first through-holes 46a crosses directly above the first through-hole 50a of the workbench 50 (the optical path from the light-emitting section 101 to the first mirrored section 102). In addition, the multiple second through-holes 46b of the conveyor belt 46 are arranged at equal intervals in the circumferential direction of the conveyor belt 46, and each of the multiple second through-holes 46b crosses directly above the second through-hole 50b of the workbench 50 (the optical path from the second mirrored section 103 to the light-receiving section 104). With respect to the first through-hole 46a and the second through-hole 46b of the conveyor belt 46, which are on the same straight line parallel to the direction perpendicular to the circumferential direction of the conveyor belt 46, the timing at which the first through-hole 46a crosses directly above the first through-hole 50a of the workbench 50 (the optical path from the light-emitting part 101 to the first mirror surface part 102) is the same as the timing at which the second through-hole 46b crosses directly above the second through-hole 50b of the workbench 50 (the optical path from the second mirror surface part 103 to the light-receiving part 104). Therefore, during the period when the conveyor belt 46 is rotating at a steady speed, if there is no recording paper P on the conveyor belt 46, the optical path from the light-emitting unit 101 to the light-receiving unit 104 via the first mirror surface 102 and the second mirror surface 103 is repeatedly blocked by parts of the conveyor belt 46 other than the first through-hole 46a and the second through-hole 46b, and connected through the first through-hole 46a and the second through-hole 46b of the conveyor belt 46 during the time period TB. While the conveyor belt 46 is moving in a steady speed, both time TA and time TB are constant.

[0066] At time T1, the first through-hole 46a and second through-hole 46b of the conveyor belt 46 begin to cross the optical path from the light-emitting unit 101 to the light-receiving unit 104, and the optical path from the light-emitting unit 101 to the light-receiving unit 104 is no longer obstructed by the conveyor belt 46. The light emitted by the light-emitting unit 101 passes through the first through-hole 46a of the conveyor belt 46 and the first through-hole 50a of the workbench 50, is reflected by the first mirror surface 102 and the second mirror surface 103 respectively, passes through the second through-hole 50b of the workbench 50 and the second through-hole 46b of the conveyor belt 46, is received by the light-receiving unit 104, and the light-receiving unit 104 outputs the intensity of the received light (received light intensity) to the control unit 61. At this time, the received light intensity exceeds a predetermined threshold (transmission), and the control unit 61 determines that there is no recording paper P based on the fact that the received light intensity input from the light-receiving unit 104 exceeds a predetermined threshold.

[0067] At time T2, the first through-hole 46a and the second through-hole 46b of the conveyor belt 46 have finished crossing the optical path from the light-emitting unit 101 to the light-receiving unit 104, and the light emitted from the light-emitting unit 101 is blocked by the conveyor belt 46 and does not reach the light-receiving unit 104 as much. The light-receiving unit 104 outputs the received light intensity to the control unit 61. At this time, the received light intensity is below a predetermined threshold (blocked light).

[0068] Even after time T3 has elapsed from time T2 to time TA, the rotational speed of the conveyor belt 46 is below the steady speed, so the next first through-hole 46a and the next second through-hole 46b of the conveyor belt 46 do not reach the optical path from the light-emitting unit 101 to the light-receiving unit 104, and the received light intensity output by the light-receiving unit 104 to the control unit 61 remains below a predetermined threshold (light shielding). The control unit 61 determines that there is recording paper P because the received light intensity below the predetermined threshold has continued beyond time TA.

[0069] As the rotational speed of the conveyor belt 46 increases and reaches a steady speed, the control unit 61 begins monitoring for the presence or absence of recording paper P, etc.

[0070] The control unit 61 determines that at time T4, the first through-hole 46a and the second through-hole 46b of the conveyor belt 46 begin to cross the optical path from the light-emitting unit 101 to the light-receiving unit 104, and the optical path from the light-emitting unit 101 to the light-receiving unit 104 is no longer obstructed by the conveyor belt 46. The light emitted by the light-emitting unit 101 passes through the first through-hole 46a of the conveyor belt 46 and the first through-hole 50a of the workbench 50, is reflected by the first mirror surface 102 and the second mirror surface 103 respectively, passes through the second through-hole 50b of the workbench 50 and the second through-hole 46b of the conveyor belt 46, and is received by the light-receiving unit 104, which outputs the received intensity of the received light to the control unit 61. At this time, the received light intensity exceeds a predetermined threshold (transmitted light), and the control unit 61 determines that there is no recording paper P based on the fact that the received light intensity input from the light receiving unit 104 exceeds a predetermined threshold.

[0071] At time T5, the first through-hole 46a and the second through-hole 46b of the conveyor belt 46 have finished crossing the optical path from the light-emitting unit 101 to the light-receiving unit 104, and the light emitted from the light-emitting unit 101 is blocked by the conveyor belt 46 and does not reach the light-receiving unit 104 as much. The light-receiving unit 104 outputs the received light intensity to the control unit 61. At this time, the received light intensity is below a predetermined threshold (blocked light).

[0072] When time T6 occurs, after time TA has elapsed from time T5, the first through-hole 46a and second through-hole 46b of the conveyor belt 46 begin to cross the optical path from the light-emitting unit 101 to the light-receiving unit 104, and the optical path from the light-emitting unit 101 to the light-receiving unit 104 is no longer obstructed by the conveyor belt 46. The light emitted by the light-emitting unit 101 passes through the first through-hole 46a of the conveyor belt 46 and the first through-hole 50a of the workbench 50, is reflected by the first mirror surface 102 and the second mirror surface 103 respectively, passes through the second through-hole 50b of the workbench 50 and the second through-hole 46b of the conveyor belt 46, and is received by the light-receiving unit 104, which outputs the received light intensity to the control unit 61. At this time, the received light intensity exceeds a predetermined threshold (transmission). The control unit 61 continues to determine that there is no recording paper P because the received light intensity has exceeded a predetermined threshold, before the duration of the received light intensity being below a predetermined threshold exceeds time TA.

[0073] At time T7, the first through-hole 46a and the second through-hole 46b of the conveyor belt 46 have finished crossing the optical path from the light-emitting unit 101 to the light-receiving unit 104, and the light emitted from the light-emitting unit 101 is blocked by the conveyor belt 46 and does not reach the light-receiving unit 104 as much. The light-receiving unit 104 outputs the received light intensity to the control unit 61. At this time, the received light intensity is below a predetermined threshold (blocked light).

[0074] When time T8 arrives, after time TA has elapsed from time T7, the first through-hole 46a and second through-hole 46b of the conveyor belt 46 begin to cross the optical path from the light-emitting unit 101 to the light-receiving unit 104, and the optical path from the light-emitting unit 101 to the light-receiving unit 104 is no longer obstructed by the conveyor belt 46. The light emitted by the light-emitting unit 101 passes through the first through-hole 46a of the conveyor belt 46 and the first through-hole 50a of the workbench 50, is reflected by the first mirror surface 102 and the second mirror surface 103 respectively, passes through the second through-hole 50b of the workbench 50 and the second through-hole 46b of the conveyor belt 46, and is received by the light-receiving unit 104, which outputs the received light intensity to the control unit 61. At this time, the received light intensity exceeds a predetermined threshold (transmission). The control unit 61 continues to determine that there is no recording paper P because the received light intensity has exceeded a predetermined threshold, before the duration of the received light intensity being below a predetermined threshold exceeds time TA.

[0075] Next, we will explain the case where the recording paper P is being transported on the transport belt 46 with reference to Figure 8. Figure 8 is an example of a timing chart for explaining the determination of the presence or absence of recording paper P on the transport belt 46 using the detection results of the sensor 49 in Figure 3 by the control unit 61 in Figure 2.

[0076] In the example timing chart shown in Figure 8, the same actions are taken from time T1 to time T8 as in the example timing chart shown in Figure 7.

[0077] When the first through-hole 46a and second through-hole 46b of the conveyor belt 46 are present in the optical path from the light-emitting unit 101 to the first mirror surface 102 and in the optical path from the second mirror surface 103 to the light-receiving unit 104, and at time T9, when the recording paper P begins to cross the optical path from the light-emitting unit 101 to the first mirror surface 102 and from the second mirror surface 103 to the light-receiving unit 104, the light emitted by the light-emitting unit 101 is blocked by the recording paper P at two points in the optical path from the light-emitting unit 101 to the light-receiving unit 104, and therefore does not reach the light-receiving unit 104 as much as it should. The light-receiving unit 104 outputs the received light intensity to the control unit 61. At this time, the received light intensity is below a predetermined threshold (light shielding).

[0078] Even after time T10 has elapsed from time T9 to time TA, the light emitted by the light-emitting unit 101 is blocked by the recording paper P at two points in the optical path from the light-emitting unit 101 to the light-receiving unit 104, and the received light intensity output by the light-receiving unit 104 to the control unit 61 remains below a predetermined threshold (blocked light). The control unit 61 determines that the recording paper P is present because the received light intensity remains below the predetermined threshold beyond time TA.

[0079] The recording paper P prevents two points in the optical path from the light-emitting unit 101 to the light-receiving unit 104 from being obstructed, and at time T11, when the first through-hole 46a and the second through-hole 46b of the conveyor belt 46 begin to cross the optical path from the light-emitting unit 101 to the light-receiving unit 104, the optical path from the light-emitting unit 101 to the light-receiving unit 104 is no longer obstructed by the conveyor belt 46. The light emitted by the light-emitting unit 101 passes through the first through-hole 46a of the conveyor belt 46 and the first through-hole 50a of the workbench 50, is reflected by the first mirror surface 102 and the second mirror surface 103 respectively, passes through the second through-hole 50b of the workbench 50 and the second through-hole 46b of the conveyor belt 46, and is received by the light-receiving unit 104, which outputs the received light intensity of the received light to the control unit 61. At this time, the received light intensity exceeds a predetermined threshold (transmitted light), and the control unit 61 determines that there is no recording paper P based on the fact that the received light intensity input from the light receiving unit 104 exceeds a predetermined threshold.

[0080] According to the above embodiment, when the first through-hole 46a and the second through-hole 46b of the transport belt 46 are present in the optical path from the light-emitting unit 101 to the light-receiving unit 104, and there is recording paper P on the first through-hole 46a and the second through-hole 46b, there are two locations on the recording paper P where the light emitted by the light-emitting unit 101 may be blocked before it is received by the light-receiving unit 104. Therefore, even if the recording paper P on the transport belt 46 is thin paper, the light emitted by the light-emitting unit 101 is blocked twice by the thin paper, thereby reducing the intensity of the light received by the light-receiving unit 104. Furthermore, if the recording paper on the transport belt 46 is recycled paper with micro-pores or transparent inclusions, even if micro-pores or transparent inclusions are present at one of the two locations mentioned above, if they are not present at the other location, the light emitted by the light-emitting unit 101 is blocked at the other location, thereby reducing the intensity of the light received by the light-receiving unit 104. This allows for a greater difference in the intensity of light received by the light receiving unit 104 between the presence and absence of recording paper P, thereby improving the detection capability of recording paper P, such as thin paper or recycled paper, on the transport belt 46.

[0081] Furthermore, the present invention is not limited to the configuration of the above-described embodiment, and various modifications are possible.

[0082] For example, in the above embodiment, the first through-hole 46a that crosses the optical path between the light-emitting part 101 and the first mirror surface part 102, and the second through-hole 46b that crosses the optical path between the second mirror surface 103 and the light-receiving part 104 at the same time that the first through-hole 46a crosses the optical path between the light-emitting part 101 and the first mirror surface part 102, are assumed to be on the same straight line parallel to the direction perpendicular to the circumferential direction of the conveyor belt 46. However, the embodiment is not limited to this, and for example, they may be on the same straight line inclined with respect to the direction perpendicular to the circumferential direction of the conveyor belt 46.

[0083] Furthermore, in the above embodiment, the light-emitting portion 101 and the first mirror portion 102 are positioned at the first and second locations on a straight line perpendicular to one of the surfaces of the conveyor belt 46, but the embodiment is not limited to this. For example, they may be positioned at the first and second locations on a straight line inclined with respect to the direction perpendicular to one of the surfaces of the conveyor belt 46.

[0084] Furthermore, in the above embodiment, the second mirror surface 103 and the light receiving portion 104 are positioned at the third and fourth locations on another straight line perpendicular to one of the surfaces of the conveyor belt 46, but the embodiment is not limited to this, and for example, they may be positioned at the third and fourth locations on another straight line inclined with respect to the direction perpendicular to one of the surfaces of the conveyor belt 46.

[0085] Furthermore, the configurations and processes shown in the above embodiments using Figures 1 to 8 are merely one embodiment of the present invention, and the present invention is not intended to be limited to these configurations and processes. [Explanation of Symbols]

[0086] 1. Inkjet recording device 16. Conveyor belt unit 46 Conveyor belt 46a 1st through hole 46b 2nd through hole 49 sensors 50 workbenches 50a 1st through hole 50b 2nd through hole 101 Light-emitting part 102 1st mirror surface section 103 2nd mirror surface section 104 Light receiving part

Claims

1. A conveyor belt that transports paper by moving in a circular motion, and has a first through-hole and a second through-hole provided at positions that are simultaneously covered by the paper as it is transported, The system includes a sensor for detecting the paper on the conveyor belt, The aforementioned sensor is A light-emitting part is positioned at a first location facing one side of the conveyor belt and emits light, A second location is provided opposite the other surface of the conveyor belt, where light emitted by the light-emitting unit reaches through the first through-hole during the conveyor belt's circumferential movement, and the first mirror surface reflects the light emitted by the light-emitting unit. A third mirror surface is positioned on the other side of the conveyor belt, and reflects the light reflected by the first mirror surface, A light receiving unit is positioned at a fourth location opposite to one of the surfaces of the conveyor belt, which receives the light reflected by the second mirror surface through the second through hole during the circumferential movement of the conveyor belt, A paper transport device equipped with the following features.

2. The paper transport device according to claim 1, wherein the first through hole and the second through hole are on the same line perpendicular to the circumferential direction of the transport belt.

3. The paper transport device according to claim 1 or claim 2, wherein the light-emitting portion and the first mirror portion are arranged at first and second locations on a straight line perpendicular to one surface of the transport belt, and the second mirror portion and the light-receiving portion are arranged at third and fourth locations on another straight line perpendicular to one surface of the transport belt.

4. A paper transport device according to any one of claims 1 to 3, An ink head that ejects ink onto the aforementioned paper to form an image on the paper, An inkjet recording device equipped with the following features.

Images