JP2013209181A - Image recording apparatus and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance accuracy in detecting the upstream end of a recording medium in a conveyance direction.SOLUTION: First and second sheet sensors output ON when the intensity of the reflected light of incident light outputted to a sheet exceeds a predetermined threshold, and output OFF in other cases. The second threshold of the second sheet sensor is higher than the first threshold of the first sheet sensor 26a. When such a result is obtained that the output of the first sheet sensor is shifted from "ON" to "OFF", and also, the output of the second sheet sensor is shifted from "ON" to OFF" (S108), and when the output of the first sheet sensor is maintained in an OFF-state in a predetermined time after the result is obtained (S109, S110), the position is determined as the upstream end of the sheet in the sheet conveyance direction (S110).

Description

  The present invention relates to an image recording apparatus and a program for recording an image on a recording medium.

  In the printer, in order to prevent printing in a place other than the transported paper, it is necessary to grasp the paper position in the transport path, particularly the position of the upstream end (rear end) in the paper transport direction. An inexpensive reflective sensor may be used as a means for detecting the rear end position. However, when double-sided printing is performed or when printing is performed on the backing paper, a low-reflectance area is formed on the printed surface of the paper, such as when an image recorded on the back surface is shown on the front surface. May be. When such a sheet is conveyed, the reflective sensor may misrecognize a low-reflectance area as the trailing edge of the sheet. To prevent this, two reflective sensors that detect the front and back sides of the paper are arranged along the transport direction, and the rear edge of the paper is predetermined only when both reflective sensors detect the rear edge of the paper. A technique for determining that the position has been passed is known (see, for example, Patent Document 1).

  In addition, with respect to a reflection type sensor that detects a sheet to be conveyed, an analog signal detected by the reflection type sensor is input as a binary signal with a predetermined threshold as a reference to a control unit of the printer. A technique for simplifying the processing in the printer control unit is also known.

JP 2002-137847 A

  However, in the case of paper show-through in double-sided printing, an image printed on the back surface shows through on the front surface, so that a black region with low reflectivity may be formed at the same location on the front and back surfaces of the paper. . Therefore, there is still a possibility of erroneously detecting the trailing edge of the sheet. In the case of the back paper, if a black region having a low reflectance is formed at the same location on the front and back surfaces of the paper, the rear edge of the paper may be erroneously detected. It is also conceivable to lower the threshold value of one reflective sensor so that the difference between the state where no paper is present and the black area where the reflectance is low can be detected. There is a possibility that misdetection of the paper edge due to disturbance such as

  An object of the present invention is to provide an image recording apparatus and program capable of improving the detection accuracy of the upstream end in the conveyance direction of the recording medium.

  The image recording apparatus of the present invention includes a transport mechanism that transports a recording medium in a predetermined transport direction, and the intensity of reflected light with respect to incident light output to the surface of the recording medium transported by the transport mechanism has a first threshold value. A first sensor for detecting whether or not the light intensity exceeds a second threshold value that is higher than the first threshold value and the intensity of the reflected light with respect to the incident light that is output to the surface of the recording medium conveyed to the conveyance mechanism; From the detection result at the specific position related to the transport direction by the first sensor and the second sensor with respect to the recording medium transported by the transport mechanism, the second sensor for detecting the recording medium, and the transport direction of the recording medium End determination means for determining whether or not the specific position is an end. The edge determination means has a detection result at a specific position in the transport direction of the recording medium by the first sensor and the second sensor, and the intensity of reflected light with respect to the incident light according to the first sensor is the first. The state changes from the state exceeding the threshold to the state not exceeding the first threshold, and the intensity of the reflected light with respect to the incident light related to the second sensor exceeds the second threshold from the second. If the result changes to a state where the threshold value is not exceeded, the specific position is determined to be the upstream end of the recording medium in the transport direction.

  From another viewpoint, the image recording apparatus of the present invention includes a transport mechanism that transports a recording medium in a predetermined transport direction, and an output unit that outputs incident light to the surface of the recording medium transported by the transport mechanism. A first sensor having a first light receiving unit that receives reflected light with respect to incident light output by the output unit, and an output unit that outputs incident light to the surface of the recording medium transported to the transport mechanism; A second sensor having a second light receiving unit that receives reflected light with respect to the incident light output by the output unit; and a control unit. The control means includes a first detection function for detecting whether or not the light received by the first light receiving unit exceeds a first threshold, and a first detection function in which the light received by the second light receiving unit is higher than the first threshold. 2. Detection result at a specific position in the transport direction by the second detection function for detecting whether or not the threshold value is exceeded, and the first detection function and the second detection function for the recording medium transported by the transport mechanism. And an edge determination function for determining whether or not the specific position in the transport direction of the recording medium is an edge. The edge discrimination function is such that the detection result at a specific position in the transport direction of the recording medium by the first detection function and the second detection function is the intensity of light received by the first light receiving unit. From the state exceeding the first threshold, and the intensity of the light received by the second light receiving unit exceeds the second threshold from the state exceeding the second threshold In the case where the result is a change to a non-existing state, it is determined that the specific position is the upstream end of the recording medium in the transport direction.

  The program according to the present invention includes a transport mechanism that transports a recording medium in a predetermined transport direction, and whether the intensity of reflected light with respect to incident light output to the surface of the recording medium transported by the transport mechanism exceeds a first threshold value. A first sensor for detecting whether or not, and whether or not the intensity of reflected light with respect to incident light output to the surface of the recording medium conveyed to the conveying mechanism exceeds a second threshold value higher than the first threshold value. A program that causes a computer to function as a control unit that controls an image recording apparatus having a second sensor to be detected, and relates to the conveyance direction by the first sensor and the second sensor with respect to a recording medium conveyed by the conveyance mechanism. An end determination step for determining whether the specific position in the transport direction of the recording medium is an end from the detection result at the specific position; In the edge determination step, the detection result at the specific position in the transport direction of the recording medium by the first sensor and the second sensor indicates that the intensity of the reflected light with respect to the incident light according to the first sensor is the first sensor. The state changes from a state exceeding the first threshold to a state not exceeding the first threshold, and the intensity of the reflected light with respect to the incident light related to the second sensor exceeds the second threshold. 2 If the result changes to a state where the threshold value is not exceeded, it is determined that the specific position is the upstream end of the recording medium in the transport direction.

  According to the present invention, since the position where the first sensor having a low threshold and the second sensor having a high threshold both detect the presence of the edge are determined as the upstream edge in the conveyance direction of the recording medium, the detection of the edge is detected. Accuracy can be improved.

  In the present invention, it is preferable that the first and second sensors are different from each other in the transport direction and are arranged at the same position in a direction orthogonal to the transport direction. According to this, since the first and second sensors detect the same position with respect to the recording medium, even when a black region having a low reflectance is formed only on a part of the sheet, The upstream end in the transport direction can be detected more accurately.

  Further, in the present invention, the edge detection means is in a state where the intensity of reflected light with respect to the incident light related to the first sensor does not exceed the first threshold, and the incident light related to the second sensor. When the intensity of the reflected light with respect to the second sensor does not exceed the second threshold, the intensity of the reflected light with respect to the incident light according to the second sensor changes to a state exceeding the second threshold, It is preferable to detect the position as the downstream end of the recording medium in the transport direction. According to this, since the downstream end can be detected without referring to the detection result of the first sensor, detection processing can be reduced.

  At this time, it is more preferable that the second sensor is disposed upstream of the first sensor in the transport direction. According to this, since the downstream end (tip) of the sheet can be detected quickly, the subsequent image recording process and the like can be accelerated.

  In the present invention, it is preferable that the first and second sensors are the same with respect to the transport direction and are disposed at different positions with respect to a direction orthogonal to the transport direction. According to this, since the first and second sensors can simultaneously output a detection result with respect to the position in the conveyance direction of the recording medium, it is possible to quickly determine whether or not it is the upstream end in the conveyance direction of the recording medium. It can be carried out.

  Further, in the present invention, the edge detection means is in a state where the intensity of the reflected light with respect to the incident light related to the first sensor does not exceed the first threshold at the position in the transport direction of the recording medium. When the recording time is equal to or longer than the predetermined time, it is preferable that the position is detected as an upstream end in the transport direction of the recording medium. According to this, when the detection result of the first sensor with low sensitivity is determined to be noise, the detection result is excluded, so that it is possible to more accurately determine whether or not the end portion is on the upstream side with respect to the conveyance direction of the recording medium. It can be carried out.

  In addition, in the present invention, it further comprises a sensor abnormality detecting means for detecting an abnormality of the first sensor, the sensor abnormality detecting means is not transporting the recording medium by the conveying means, and It is preferable that an abnormality of the first sensor is detected when the intensity of reflected light with respect to the incident light according to the first sensor exceeds the first threshold. According to this, it is possible to quickly detect abnormality of the first sensor.

  According to the present invention, since the position where the first sensor having a low threshold and the second sensor having a high threshold both detect the presence of the edge are determined as the upstream edge in the conveyance direction of the recording medium, the detection of the edge is detected. Accuracy can be improved.

1 is a schematic side view of an ink jet printer according to a first embodiment. FIG. 2 is a plan view of an ink jet printer showing a positional relationship between first and second paper sensors shown in FIG. 1. It is a functional block diagram of the control part shown in FIG. It is a figure for demonstrating the edge part discrimination | determination part shown in FIG. FIG. 4 is a flowchart showing an operation related to edge determination of the printer shown in FIG. It is a top view of the inkjet printer which showed the positional relationship of the 1st and 2nd paper sensor which concerns on 2nd Embodiment. It is a functional block diagram of a control part concerning a modification.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

<First Embodiment>
First, with reference to FIG. 1, the overall configuration of an inkjet printer 1 according to the first embodiment of the present invention will be described.

  The printer 1 has a rectangular parallelepiped casing 1a. A paper discharge unit 4 is provided on the top of the casing 1a. The internal space of the housing 1a can be divided into spaces A, B, and C in order from the top. In the spaces A and B, a paper transport path from the first paper feed section 23 and the second paper feed section 17 to the paper discharge section 4, and a paper retransmission path from the downstream side to the upstream side with the paper transport path interposed therebetween Is formed. As shown in FIG. 1, the paper P is transported along a thick black arrow in the paper transport path, and is transported along a thick thick arrow in the paper retransmission path. In the space A, paper feed from the second paper feed unit 17 to the transport path, image formation on the paper P, transport of the paper P to the paper discharge unit 4, and retransmission of the paper P are performed. In the space B, paper is fed from the first paper feeding unit 23 to the transport path. From the space C, ink is supplied to the inkjet head 2 in the space A.

  In the space A, four inkjet heads 2 (hereinafter referred to as the head 2), a transport mechanism 40, two guide portions 10a and 10b for guiding the paper P, a retransmission mechanism 60, a second paper feed portion 17, and a control The part 100 and the like are arranged.

  From the four heads 2, ink droplets of any one of magenta, yellow, cyan, and black are ejected. These four heads 2 have a substantially rectangular parallelepiped shape elongated in the main scanning direction. The four heads 2 are arranged at a predetermined pitch in the sub-scanning direction, and are supported by the housing 1a via a head holder (not shown). By the head holder, a predetermined gap suitable for recording is formed between the lower surface of the head 2 and the conveyor belt 43 (conveying mechanism 40).

  Each head 2 is a laminated body in which an actuator unit 21, a reservoir unit, a flexible printed circuit board (FPC), a control board, and the like are laminated in addition to the head body 3. The lower surface of the head main body is an ejection surface 2a having an ejection port opened. The signal adjusted by the control board is converted into a drive signal by a driver IC on the FPC, and further output to an actuator unit (not shown). When the actuator unit is driven, the ink supplied from the reservoir unit is ejected from the ejection port.

  The transport mechanism 40 includes two belt rollers 41 and 42, a transport belt 43, a platen 46, a nip roller 47, and a peeling plate 45. The conveyor belt 43 is an endless belt wound between the rollers 41 and 42. The belt roller 42 is a driving roller and causes the transport belt 43 to travel. The belt roller 42 is rotated clockwise in FIG. 1 by a motor (not shown). The belt roller 41 is a driven roller and is rotated by the travel of the transport belt 43. A weak adhesive silicon layer is formed on the outer peripheral surface of the conveyor belt 43. Further, the outer peripheral surface of the conveyor belt 43 has a low reflectance. The nip roller 47 presses the sheet P conveyed from the first sheet feeding unit 23, the second sheet feeding unit 17, and the retransmission mechanism 60 against the outer peripheral surface of the conveyance belt 43. The pressed paper P is held on the conveyor belt 43 by the silicon layer and conveyed toward the head 2. The peeling plate 45 peels the conveyed paper P from the transport belt 43 and guides it to the paper discharge unit 4 on the downstream side.

  The two guide portions 10a and 10b are arranged with the transport mechanism 40 interposed therebetween. The guide unit 10a on the upstream side in the transport direction includes two guides 31a and 31b and a feed roller pair 32, and connects the first paper feed unit 23 and the transport mechanism 40. Further, a guide 18 is connected to an intermediate portion of the guide 31b, and the second paper feeding unit 17 and the transport mechanism 40 are also connected. The image forming paper P is transported toward the transport mechanism 40. The guide unit 10b on the downstream side in the transport direction has two guides 33a and 33b and two feed roller pairs 34 and 35, and connects the transport mechanism 40 and the paper discharge unit 4. The paper P after image formation is conveyed toward the paper discharge unit 4. Moreover, the guide part 10b switches a conveyance path | route by switchback operation | movement. When double-sided printing or maintenance operation is performed on the paper P, the guide unit 10 b transports the paper P transported toward the paper discharge unit 4 toward the retransmission mechanism 60.

  The retransmission mechanism 60 includes three feed roller pairs 61 to 63 and four guides 64 to 67 in addition to the above-described guide portion 10b. As shown in FIG. 1, four guides 64 to 67 are arranged in this order to form a paper retransmission path. The paper retransmission path is connected to the upstream vicinity of the feed roller pair 34 on the downstream side in the transport direction, and joins the downstream end of the guide 33a. The paper re-transmission path is connected to the vicinity of the upstream side of the feed roller pair 32 on the upstream side in the transport direction, and joins the downstream end of the guide 31a. The three feed roller pairs 61 to 63 are arranged in this order between the two adjacent guides 64 to 67. Such a retransmission mechanism 60 conveys the sheet P conveyed to the paper discharge unit 4 in the reverse direction, and retransmits it upstream of the head 2, that is, upstream of the conveyance mechanism 40 in the conveyance direction. At this time, the retransmitted paper P is supplied again to the transport mechanism 40 in a state where the front and back of the paper P are reversed.

  A first paper sensor (first sensor) 26 a and a second paper sensor (second sensor) 26 b are disposed above the transport belt 43 and upstream of the head 2 in the paper transport direction D. As shown in FIG. 2, the first and second paper sensors 26 a and 26 b are arranged along the paper transport direction D so as to face the central portion of the transport belt 43 in the main scanning direction. The second paper sensor 26b is located upstream of the first paper sensor 26a in the paper transport direction D. The first and second paper sensors 26a and 26b output ON when the intensity of reflected light with respect to incident light output toward the conveyor belt 43 exceeds a predetermined threshold value, and output OFF otherwise. To do. Here, the second threshold value, which is the threshold value determined by the second paper sensor 26b, is higher than the first threshold value, which is the threshold value determined by the first paper sensor 26a (see FIG. 4). As will be described later, the first and second paper sensors 26a and 26b detect the positions of the upstream end and the downstream end in the paper transport direction D of the paper P on the transport belt 43 being transported. Used.

  Returning to FIG. 1, the second paper feed unit 17 includes a manual feed tray 15 and a paper feed roller 16, and joins a midway portion of the guide 31 b via the guide 18. The manual feed tray 15 is a plate-like member that is rotatably supported by the housing 1a, on which a sheet P2 of a predetermined size (for example, B5 size) is placed. The paper feed roller 16 sends out the uppermost paper P2 on the tray 15 to the paper transport path under the control of the control unit 100. Here, the tray 15 can be accommodated in an opening formed in the housing 1a, and is accommodated in the opening to constitute a side wall of the housing 1a.

  In the space B, the first paper feeding unit 23 is arranged. The first paper feed unit 23 includes a paper feed tray 24 and a paper feed roller 25. Among these, the paper feed tray 24 is detachable from the housing 1a. The paper feed tray 24 is a box that opens upward, and can store a plurality of papers P1. In the present embodiment, A4 size paper P1 can be stored. The paper feed roller 25 sends out the uppermost paper P 1 in the paper feed tray 24.

  Here, the sub-scanning direction is a direction parallel to the paper transport direction D transported by the transport mechanism 40, and the main scanning direction is a direction parallel to the horizontal plane and perpendicular to the sub-scanning direction.

  In the space C, four cartridges 22 for storing ink are detachably attached to the housing 1a. The four cartridges 22 store magenta, cyan, yellow, and black inks and supply them to the corresponding heads 2.

  Next, the control unit 100 will be described with reference to FIG. The control unit 100 includes a CPU (Central Processing Unit), a program executed by the CPU, and an EEPROM (Electrically Erasable and Programmable Read Only Memory) that stores data used for the program in a rewritable manner. It includes RAM (Random Access Memory) for temporary storage. Each functional unit constituting the control unit 100 is constructed by cooperation of these hardware and software in the EEPROM. As illustrated in FIG. 3, the control unit 100 includes a print control unit 71, a conveyance control unit 72, an end determination unit 73, and an abnormality detection unit 74.

  The print control unit 71 controls the head 2 so that ink droplets are ejected onto the paper P at a desired timing based on the image data transmitted from the client. Therefore, the print control unit 71 needs to accurately grasp the positions of the conveyed paper P, particularly the positions of both ends of the paper P in the paper conveyance direction D.

  The conveyance control unit 72 controls the conveyance mechanism 40 so that the paper P is conveyed at a predetermined conveyance speed.

  The edge determination unit 73 determines the edge of the sheet P conveyed by the conveyance mechanism 40 in the sheet conveyance direction D based on the detection results of the first and second sheet sensors 26a and 26b.

  FIG. 4 shows an example of detection by the first and second paper sensors 26a and 26b. In FIG. 4, the reflected light intensity, the first paper sensor output, the second paper sensor output, and the edge determination unit output corresponding to the paper position shown in the upper part of the drawing are shown (first paper). (Equivalent to the case where the sensor 26a and the second paper sensor 26b are arranged in the same transport direction position) The edge determination unit 73 is at a specific position in the paper transport direction D of the paper P by the first and second paper sensors 26a and 26b. If the detection result is that the output of the first paper sensor 26a changes from ON to OFF and the output of the second paper sensor 26b changes from ON to OFF, then the detection of the first paper sensor 26a. When it is confirmed that the output is maintained OFF for a predetermined time, it is determined that the specific position is the upstream end of the paper P in the paper transport direction D. Further, the edge determination unit 73 changes the output of the second paper sensor 26b to ON while the detection result at the specific position indicates that both the outputs of the first and second paper sensors 26a and 26b are OFF. If the result is a result, it is determined that the specific position is the downstream end of the paper P in the paper transport direction D. In FIG. 4, the same specific position has a time width of rising and falling of the intensity of the reflected light. In addition, the hatched portion of the paper indicates that the area printed on the back surface is shown through. As described above, since the position where the first sheet sensor 26a having a low threshold and the second sheet sensor 26b having a high threshold both detect the presence of the edge is determined as the upstream edge, there is a show-through on the surface of the sheet. However, the show-through area is not mistaken as the upstream end.

  Returning to FIG. 3, the abnormality detection unit 74 detects an abnormality of the first sheet sensor 26 a when the first sheet sensor 26 a outputs ON, even though the conveyance mechanism 40 does not convey the sheet P. To do.

  Hereinafter, the operation related to the edge determination of the printer 1 will be described with reference to FIG. As shown in FIG. 5, when the printer 1 is powered on, does the abnormality detection unit 74 turn on the output of the first paper sensor 26a until the conveyance of the paper P is started (S102: NO)? It is determined whether or not (S101). When the output of the first paper sensor 26a is turned on (S101: YES), the abnormality detection unit 74 notifies the user by displaying on the display (not shown) that the first paper sensor 26a is abnormal (S103). ). Then, the flowchart of FIG. 5 ends.

  When the conveyance of the paper P is started (S102: YES), the edge determination unit 73 waits until both the outputs of the first and second paper sensors 26a and 26b are turned off (S104: NO). When both the outputs of the first and second paper sensors 26a and 26b are turned off (S104: YES), the edge determination unit 73 determines whether or not the output of the second paper sensor 26b is changed to ON (S104: YES). S105). If the output of the second paper sensor 26b does not change to ON (S105: NO), the edge determination unit 73 waits again until both the outputs of the first and second paper sensors 26a and 26b are turned off ( If it is changed to ON (S105: YES), the changed specific position is determined as the downstream end of the paper P (S106). And it waits until the output of the 1st paper sensor 26a turns ON (S107: NO).

  If the output of the first paper sensor 26a is turned on (S107: YES), then the edge determination unit 73 is at each specific position regarding the paper transport direction D of the paper P by the first and second paper sensors 26a and 26b. Is waited until the output of the first paper sensor 26a changes from ON to OFF and the output of the second paper sensor 26b changes from ON to OFF (S108: NO). If it is determined that the result has been obtained (S108: YES), the edge determination unit 73 determines whether or not the output of the first sheet sensor 26a is maintained OFF (S109).

  If the output of the first sheet sensor 26a is not maintained OFF (S109: NO), the edge determination unit 73 again detects the detection result at each specific position by the first and second sheet sensors 26a and 26b. The process waits until the output of the first paper sensor 26a changes from ON to OFF and the output of the second paper sensor 26b changes from ON to OFF (S108: NO). If the output of the first paper sensor 26a is kept OFF (S109: YES), the edge determination unit 73 determines whether a predetermined time has passed (S110). If the predetermined time has not elapsed (S110: NO), the edge determination unit 73 determines again whether or not the output of the first sheet sensor 26a is kept off (S109). If the predetermined time has elapsed (S110: YES), the edge determination unit 73 determines that the specific position is the upstream edge of the paper P (S111).

  The edge determination unit 73 determines whether or not the conveyance of the paper P has been completed (S112). If it is determined that the conveyance of the paper P has not ended (S112: NO), the edge determination unit 73 repeats the process immediately after the start of the conveyance of the paper P (S104) and determines that the conveyance of the paper P has been completed. If it is (S112: YES), the flowchart of FIG. 5 will be complete | finished.

  As described above, according to the ink jet printer 1 of the present embodiment, the position at which the first sheet sensor 26a having a low threshold and the second sheet sensor 26b having a high threshold both detect the presence of the edge is determined as the upstream edge. Therefore, even if there is a show-through on the surface of the paper, the show-through area is not mistaken for the upstream end.

  Further, since the first and second paper sensors 26a and 26b are different from each other in the paper transport direction D and are arranged at the same position in the main scanning direction, the first and second paper sensors 26a and 26b The same position with respect to P is detected, and even when a show-through black region with low reflectivity is formed on only a part of the paper P, the upstream end of the paper P is more accurately detected. Can be detected.

  Further, the edge determination unit 73 indicates that the output of the second sheet sensor 26b changes to ON while the detection result at the specific position indicates that both the outputs of the first and second sheet sensors 26a and 26b are OFF. If the result is a result, the downstream end is determined without referring to the output of the first sheet sensor 26a in order to determine that the specific position is the downstream end in the paper transport direction D of the paper P. Can do. As a result, the determination process can be reduced.

  At this time, since the second paper sensor 26b is disposed upstream of the first paper sensor 26a in the paper transport direction D, the downstream end of the paper P can be detected quickly, and the subsequent printing process Etc. can be made faster.

  In addition, the edge determination unit 73 indicates that the detection result at the specific position in the paper transport direction D of the paper P by the first and second paper sensors 26a and 26b changes the output of the first paper sensor 26a from ON to OFF. When the output of the second paper sensor 26b changes from ON to OFF, and when the output of the first paper sensor 26a is maintained OFF for a predetermined time after that, The position is determined to be the upstream end of the paper P in the paper transport direction D. Accordingly, when the output of the first paper sensor 26a having low sensitivity is determined to be noise, the detection result is excluded, so that it is possible to more accurately determine whether or not the upstream end of the paper P is present. .

  In addition, the abnormality detection unit 74 can quickly detect an abnormality in the first paper sensor 26a.

Second Embodiment
A second embodiment according to the present invention will be described. This embodiment is different from the first embodiment only in the arrangement positions of the first and second paper sensors 26a and 26b, and only this point will be described. About another member and a function part, the code | symbol same as 1st Embodiment is attached | subjected and description is abbreviate | omitted.

  As shown in FIG. 6, the first and second paper sensors 26 a and 26 b are disposed above the transport belt 43 and upstream of the head 2 in the paper transport direction D. The first and second paper sensors 26 a and 26 b are arranged along the main scanning direction so as to face the conveyor belt 43.

  As described above, according to the ink jet printer 1 of the present embodiment, the position at which the first sheet sensor 26a having a low threshold and the second sheet sensor 26b having a high threshold both detect the presence of the edge is determined as the upstream edge. Therefore, even if there is a show-through on the surface of the paper, the show-through area is not mistaken for the upstream end.

  Further, since the first and second paper sensors 26a and 26b are the same in the paper transport direction D and are arranged at different positions in the main scanning direction, the first and second paper sensors 26a and 26b are provided. The detection result can be output at the same time with respect to the position of the paper P in the paper transport direction D, and it can be quickly determined whether or not it is the upstream end of the paper P.

<Modification>
A modification according to the present invention will be described. In the above-described embodiment, the first and second paper sensors 26a and 26b are configured to determine whether or not the reflected light exceeds the threshold value. However, as shown in FIG. 7, the first and second paper sensors 326a and 326b each have an output unit 81 that outputs incident light and a light receiving unit 82 that receives reflected light with respect to the incident light output by the output unit 81, and the intensity of the reflected light from each light receiving unit 82 is increased. The signal which shows may be output. At this time, the control unit 300 includes first and second detection units 375 and 376 that receive signals from the light receiving units 82 and determine whether or not the reflected light exceeds the threshold value from the signals. .

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and various modifications can be made as long as they are described in the claims. In the first embodiment described above, the first and second paper sensors 26a and 26b are different from each other in the paper transport direction D and are arranged at the same position in the main scanning direction. The paper sensors 26a and 26b may be disposed at arbitrary positions. For example, the first and second paper sensors 26a and 26b may be arranged at different positions with respect to the paper transport direction D and the main scanning direction.

  Further, the edge determination unit 73 indicates that the output of the second sheet sensor 26b changes to ON while the detection result at the specific position indicates that both the outputs of the first and second sheet sensors 26a and 26b are OFF. If the result is a result, it is determined that it is the downstream end of the paper P, but the result of the output of the first paper sensor 26a changing to ON, or the first and second paper sensors 26a, 26b. It is also possible to determine whether or not the output of both is turned to the ON side on the downstream side of the paper P.

  In the above-described embodiment, the second paper sensor 26b is arranged upstream of the first paper sensor 26a in the paper conveyance direction D, but is arranged downstream of the first paper sensor 26a. May be.

  In the above-described embodiment, the edge determination unit 73 determines that the detection result of the first and second paper sensors 26a and 26b at the specific position in the paper transport direction D of the paper P is the output of the first paper sensor 26a. Is changed from ON to OFF and the output of the second paper sensor 26b is changed from ON to OFF. Thereafter, the output of the first paper sensor 26a is maintained OFF for a predetermined time. In some cases, the specific position is determined to be the upstream end of the paper P in the paper transport direction D. However, it is considered whether the output of the first paper sensor 26a is maintained OFF for a predetermined time. It does not have to be.

  In the above-described embodiment, the abnormality detection unit 74 is configured to detect an abnormality of the first paper sensor 26a, but the abnormality detection unit 74 may not be provided.

  In the above-described embodiment, the control unit 100 may be configured by a single CPU, or may be controlled by a plurality of CPUs, a specific application specific integrated circuit (ASIC), or a combination of a CPU and a specific ASIC. The unit 100 may be configured.

  The present invention is also applicable to a liquid ejecting apparatus that ejects liquid other than ink. It can also be applied to laser printers. Further, the present invention is not limited to a printer, and can be applied to a facsimile, a copier, and the like.

DESCRIPTION OF SYMBOLS 1 Inkjet printer 2 Head 26a, 26b Paper sensor 43 Conveyor belt 71 Print control part 72 Conveyance control part 73 End part discrimination | determination part 74 Abnormality detection part 100 Control part

Claims (9)

A transport mechanism for transporting the recording medium in a predetermined transport direction;
A first sensor that detects whether or not the intensity of reflected light with respect to incident light output to the surface of the recording medium transported to the transport mechanism exceeds a first threshold;
A second sensor for detecting whether or not the intensity of the reflected light with respect to the incident light output to the surface of the recording medium transported to the transport mechanism exceeds a second threshold higher than the first threshold;
Whether the specific position in the transport direction of the recording medium is an end from the detection result at the specific position in the transport direction by the first sensor and the second sensor for the recording medium transported by the transport mechanism. End determination means for determining whether or not,
The end discrimination means is
The detection result at the specific position in the transport direction of the recording medium by the first sensor and the second sensor indicates that the intensity of reflected light with respect to the incident light according to the first sensor exceeds the first threshold value. The state changes to a state where the first threshold value is not exceeded, and the state where the intensity of the reflected light with respect to the incident light related to the second sensor exceeds the second threshold value does not exceed the second threshold value. An image recording apparatus, wherein if the result is a change, the specific position is determined to be an upstream end of the recording medium in the transport direction.   The image recording apparatus according to claim 1, wherein the first and second sensors are different from each other in the transport direction and are arranged at the same position in a direction orthogonal to the transport direction.   The end detection unit is configured such that the intensity of reflected light with respect to the incident light according to the first sensor does not exceed the first threshold, and the intensity of reflected light with respect to the incident light according to the second sensor is In a state where the second threshold value is not exceeded, when the intensity of reflected light with respect to the incident light according to the second sensor changes to a state exceeding the second threshold value, the position of the recording medium is conveyed. The image recording apparatus according to claim 1, wherein the image recording apparatus is detected as an end portion on a downstream side with respect to a direction.   The image recording apparatus according to claim 3, wherein the second sensor is disposed upstream of the first sensor in the transport direction.   2. The image recording apparatus according to claim 1, wherein the first and second sensors are the same in the transport direction and are arranged at different positions with respect to a direction orthogonal to the transport direction.   The edge detection means has a time during which the intensity of the reflected light with respect to the incident light related to the first sensor does not exceed the first threshold at a predetermined time or more at a position in the transport direction of the recording medium. The image recording apparatus according to claim 1, wherein the position is detected as an end on the upstream side in the transport direction of the recording medium. Sensor abnormality detecting means for detecting an abnormality of the first sensor,
The sensor abnormality detecting means is in a state where the recording medium is not conveyed by the conveying means, and the intensity of reflected light with respect to the incident light related to the first sensor exceeds the first threshold. 7. The image recording apparatus according to claim 1, wherein an abnormality of the first sensor is detected when the image recording apparatus is in an abnormal state. A transport mechanism for transporting the recording medium in a predetermined transport direction;
A first sensor having an output unit that outputs incident light to the surface of the recording medium conveyed to the conveyance mechanism, and a first light receiving unit that receives reflected light with respect to the incident light output by the output unit;
A second sensor having an output unit that outputs incident light to the surface of the recording medium conveyed to the conveyance mechanism, and a second light receiving unit that receives reflected light with respect to the incident light output by the output unit;
Control means,
The control means includes
A first detection function for detecting whether the light received by the first light receiving unit exceeds a first threshold;
A second detection function for detecting whether the light received by the second light receiving unit exceeds a second threshold value higher than the first threshold value;
From the detection result at the specific position in the transport direction by the first detection function and the second detection function for the recording medium transported by the transport mechanism, the specific position in the transport direction of the recording medium is an end portion. It has an edge determination function to determine whether or not there is,
The end discrimination function is
The detection result at the specific position related to the transport direction of the recording medium by the first detection function and the second detection function indicates that the intensity of the light received by the first light receiving unit exceeds the first threshold value. Result that changes to a state that does not exceed the first threshold, and changes from a state where the intensity of light received by the second light receiving unit exceeds the second threshold to a state that does not exceed the second threshold In the case of the image recording apparatus, the specific position is determined to be an upstream end in the transport direction of the recording medium. A transport mechanism that transports the recording medium in a predetermined transport direction, and a first that detects whether or not the intensity of reflected light with respect to incident light output to the surface of the recording medium transported to the transport mechanism exceeds a first threshold value. A sensor and a second sensor for detecting whether the intensity of the reflected light with respect to the incident light output to the surface of the recording medium conveyed to the conveyance mechanism exceeds a second threshold value higher than the first threshold value; A program for causing a computer to function as control means for controlling an image recording apparatus having
Whether the specific position in the transport direction of the recording medium is an end from the detection result at the specific position in the transport direction by the first sensor and the second sensor for the recording medium transported by the transport mechanism. An edge determination step for determining whether or not,
In the edge determination step,
The detection result at the specific position in the transport direction of the recording medium by the first sensor and the second sensor indicates that the intensity of reflected light with respect to the incident light according to the first sensor exceeds the first threshold value. The state changes to a state where the first threshold value is not exceeded, and the state where the intensity of the reflected light with respect to the incident light related to the second sensor exceeds the second threshold value does not exceed the second threshold value. A program characterized in that, if the result is a change, the specific position is determined to be an upstream end of the recording medium in the transport direction.