JP6131580B2 - Printing device - Google Patents

Description

  The present invention relates to a printing apparatus that forms an image on a printing surface of a printing medium by moving a carriage on which printing means is mounted in a main scanning direction.

  As a representative example of this type of printing apparatus, an ink jet type printing apparatus is well known. In this printing apparatus, a print head moves in a main scanning direction orthogonal to the so-called sub-scanning direction of the printing medium at a position spaced upward from the surface of the printing medium (printed surface), and ink droplets are printed on the printing medium. While discharging toward the surface, the print medium is sequentially conveyed in the sub-scanning direction. Thus, images, characters, etc. are printed on the print medium.

  In this printing apparatus, wrinkles may occur in the print medium due to conveyance deviation during conveyance of the print medium. In addition, so-called cockling, in which the print medium undulates due to ink absorption of the print medium or elongation due to heating of the print medium, may occur. When these phenomena occur, the print medium partially floats and the print head may rub or collide with the print medium surface during the printing operation.

  In order to suppress such problems, for example, an apparatus described in Patent Document 1 has been proposed. This apparatus is provided with a sensor for detecting a gap (interval) between the print medium and the print head, and when the detection result by the sensor deviates from a specified amount, it is determined that the print medium is lifted, and the carriage Stop moving. As a result, the apparatus suppresses rubbing and collision of the print head against the surface of the print medium.

JP-A-5-262019 (paragraph [0035]) JP 2006-168138 A (FIG. 12)

  By the way, in order to suppress the rubbing and collision of the print head, it is important to detect the lift of the print medium. Therefore, conventionally, for example, a technique described in Patent Document 2 has been proposed in order to detect a gap between the print medium and the print head. The apparatus described in Patent Document 2 irradiates a print medium with light, receives regular reflection light from the surface of the print medium with a line sensor, and based on the output from the line sensor, the distance from the print head to the print medium The so-called print medium distance is calculated.

  However, since the print medium distance is obtained using specular reflection light, the specular reflection angle changes depending on the surface condition of the surface to be printed, particularly whether the print medium is raised, and accurate printing is performed. It may be difficult to calculate the medium distance. Therefore, when the invention described in Patent Document 2 is applied to the apparatus described in Patent Document 1 as means for detecting the floating of the print medium, it is impossible to avoid rubbing or collision of the print head against the surface of the print medium (printed surface). Alternatively, even if rubbing or collision does not occur, there is a possibility that the movement of the carriage may be stopped, and the effect of suppressing rubbing or the like may not be sufficiently exhibited.

  The present invention has been made in view of the above problems, and provides a printing apparatus that can accurately detect the floating of a print medium and can effectively suppress rubbing and collision of a print head against a print surface of the print medium. The purpose is to provide.

  A printing apparatus according to the present invention is a printing apparatus that forms an image on a printing surface of a printing medium by moving a carriage on which printing means is mounted in the main scanning direction, and includes an optical element and a light source configured by a diaphragm or a lens. And a light receiving element that irradiates light from the light source and reflects diffused reflected light from the light receiving surface through the optical element and reflects the light from the light source. A light source, an optical element, and a light receiving element, comprising: a position detection unit that outputs position information from the light receiving element; and a controller that stops the movement of the carriage when the lift of the print medium is detected based on the position information output from the light receiving element. Is characterized in that the virtual plane including is inclined in the main scanning direction with respect to the normal line of the printing surface.

  In the printing apparatus configured as described above, diffuse reflected light out of the reflected light reflected by the printing surface enters the light receiving element through the optical element. Here, when the virtual plane including the light source, the optical element, and the light receiving element is arranged so as to be parallel to the normal line of the printing surface, specularly reflected light enters the light receiving element through the optical element depending on the surface state of the printing surface. Sometimes. On the other hand, in the present invention, the virtual plane is inclined in the main scanning direction with respect to the normal line of the printing surface. Even if the light is incident, the specularly reflected light that has been specularly reflected always travels away from the optical element and the light receiving element. Therefore, it is possible to prevent the regular reflection light from entering the light receiving element regardless of whether the printing surface is lifted or not, and only the diffuse reflection light is incident on the light receiving element, and the distance to the printing surface can be accurately detected. . In addition, the detection resolution of the print medium distance increases as the virtual plane is inclined with respect to the normal of the printing surface. For example, when the inclination angle is θ, the resolution of the light receiving element is a value obtained by multiplying cos θ, and the detection resolution is improved as compared with the case where the virtual plane is arranged in parallel with the normal of the printing surface. Therefore, the print medium distance can be obtained with high resolution without being affected by the surface condition of the printing surface, and the lift of the print medium can be accurately detected. As a result, it is possible to effectively suppress rubbing and collision of the print head against the printing surface of the print medium.

  Here, in order to accurately detect the lift of the print medium and appropriately stop the movement of the carriage, for example, the controller determines the print medium distance from the printing unit to the printing surface based on the position information output from the light receiving element. A distance deriving unit that detects the lift of the print medium based on the print medium distance obtained by the distance deriving unit, and a carriage movement when the lift detecting unit detects the lift of the print medium. A movement stop unit for stopping the movement may be provided.

  In addition, a position detection unit may be attached to the carriage so that the light from the light source is reflected at a position away from the printing unit in the main scanning direction, thereby positioning the front side of the printing surface in front of the carriage in the main scanning direction. It is possible to detect whether or not the surface portion to be printed, that is, the surface portion in the pre-printing stage, is raised. In this way, it is possible to start stopping the carriage movement before the printing means arrives at the floating portion. In other words, the allowable time required for stopping the carriage movement, that is, the stop margin is increased. As a result, rubbing and collision of the print head can be more effectively suppressed.

1 is a diagram illustrating an embodiment of a printing apparatus according to the present invention. The figure which shows typically the attachment state of the position detection part to a carriage. The figure which shows the internal structure of a position detection part. 2 is a flowchart showing the operation of the printing apparatus shown in FIG. 6 is a graph illustrating an example of a change in a print medium distance with respect to a carriage position and an operation of the printing apparatus.

  FIG. 1 is a diagram illustrating an outline of a configuration of an ink jet printer which is an embodiment of a printing apparatus according to the present invention. The ink-jet printer 1 is a print medium P such as plain paper, coated paper, or film based on print data sent from a user / personal computer (hereinafter referred to as “user PC”) 100 configured as a known general-purpose computer. It is a device that prints images and characters on the surface. As shown in FIG. 1, the inkjet printer 1 includes a paper feed mechanism 2 that transports a print medium P in a transport direction, that is, a sub-scanning direction Y by driving a paper feed roller 22 by a print medium feed motor 21, and a paper A printer mechanism 3 that performs printing by ejecting ink droplets from a print head 32 onto the surface of the print medium P that is conveyed onto the platen 31 by the feed mechanism 2 and a controller 4 that controls the entire inkjet printer 1 are provided.

  The printer mechanism 3 has a carriage motor 34a disposed at one end (the right hand end in the figure) of the mechanical frame 33 and a driven roller 34b disposed at the other end (the left hand end in the figure). doing. A carriage belt 35 is provided between the carriage motor 34a and the driven roller 34b. A carriage 36 is connected to a part of the carriage belt 35. For this reason, when the carriage motor 34 a is operated based on the operation command from the controller 4, the carriage 36 reciprocates in the main scanning direction (left-right direction in the figure) X along the carriage shaft 37. Further, a linear encoder (not shown) that outputs a pulse signal to the controller 4 as the carriage 36 moves is disposed on the rear surface of the carriage 36, and the controller 4 is based on the signal from the linear encoder. Manages the position of the carriage 36 in the main scanning direction X.

  A print head 32, an ink cartridge 38, and a position detection unit 5 are mounted on the carriage 36 and move in the main scanning direction X integrally with the carriage 36. The ink cartridge 38 individually accommodates CMYK inks of cyan (C), magenta (M), yellow (Y), and black (K), each containing a dye or pigment as a colorant in water as a solvent. ing. Then, the print head 32 receives ink supplied from the ink cartridge 38 and ejects ink droplets. The position detection unit 5 is attached to the side surface of the carriage 36 on the (+ X) direction side, and controls a signal related to the distance from the print head 32 to the print medium P on the platen 31 (hereinafter referred to as “print medium distance”). 4 is output. The configuration of the position detection unit 5 will be described in detail later.

  As shown in FIG. 1, the controller 4 is configured as a microprocessor centered on a CPU (Central Processing Unit) 41. In addition to the CPU 41, a ROM (Read Only Memory) 42 that stores various processing programs, a temporary memory, and the like. A random access memory (RAM) 43 for storing data, a flash memory 44 capable of writing / erasing data, an interface (I / F) 45 for exchanging information with an external device, an input / output port (not shown), etc. I have. The RAM 43 is provided with a print buffer area, and print data sent from the user PC 100 via the interface (I / F) 45 is stored in the print buffer area. Each time the CPU 41 outputs a drive signal to the print medium feed motor 21 and sequentially conveys the print medium P in the sub-scanning direction Y, the CPU 41 outputs a drive signal to the carriage motor 34a to move the carriage 36 in the main scanning direction X. Reciprocate. Further, the CPU 41 discharges ink droplets from the print head 32 by giving a drive signal to the print head 32 corresponding to the conveyance of the print medium P and the reciprocation of the carriage 36. As a result, an image or a character corresponding to the print data is printed on the surface of the print medium P, that is, the print surface PS (see FIG. 3).

  During printing on the print medium P in this way, the CPU 41 exchanges various signals with the position detection unit 5 configured as described below, and derives the print medium distance. When the CPU 41 detects the lift of the printing surface PS based on the print medium distance, the CPU 41 rapidly stops the carriage 36. Hereinafter, after describing the configuration of the position detection unit 5, the above operation will be described in detail with reference to FIGS.

  FIG. 2 is a diagram showing the configuration of the position detection unit and the state of attachment to the carriage. FIG. 2 (a) is a perspective view showing the attachment structure, and FIG. 2 (b) is a diagram of each component constituting the position detection unit. It is a figure which shows arrangement | positioning relationship. FIG. 3 shows the internal structure of the position detection unit. The position detection unit 5 includes a light source 52, a diaphragm 53, and a light receiving element 54 arranged inside a housing 51, and the position of the print medium P in the height direction Z perpendicular to the main scanning direction X and the sub-scanning direction Y is determined. The surface, that is, the position of the printing surface PS is detected, and position information related to the position is output. More specifically, as shown in FIG. 3, the housing 51 has a box structure in which a space for arranging the light source 52, the diaphragm 53, and the light receiving element 54 is formed. Moreover, the bottom part of the housing 51 is comprised with the transparent member with respect to the light beam L1 of the light sources 52, such as resin and a glass plate. Then, the transparent member is inclined in the (+ X) direction by a predetermined inclination angle θ with respect to the normal line N of the printing surface PS so that the lower end portion of the housing 51 is located on the (+ X) direction side of the upper end portion. The housing 51 is attached to the (+ X) side surface of the carriage 36 by a housing fixture (not shown) while facing the measurement area RX positioned on the (+ X) direction side of the carriage 36 in the printing surface PS. Yes. The normal line N is a normal line in which the print medium P is placed so that there is no wrinkle or float during printing and the printing surface PS is flat.

  In the internal space of the housing 51, as shown in FIG. 2A, the light source 52 and the light receiving element 54 are arranged apart from each other in the sub-scanning direction Y. Among these, the light source 52 is fixed on the (+ Y) direction side with respect to the light receiving element 54 with the light emitting surface 52a facing the measurement region RX. For this reason, the light beam L1 generated by the light source 52 is emitted by being inclined in the (+ X) direction with respect to the normal line N of the printing surface PS by an angle θ, as in the housing 51, and is measured through the transparent member. RX is irradiated. Then, the light beam L1 is reflected by the measurement region RX, and the specularly reflected light L2 of the reflected light travels away from the carriage 36 and the housing 51, that is, in the (+ X) direction, as indicated by a two-dot chain line in FIG. . On the other hand, part of the diffusely reflected light passes through the opening 53 a of the diaphragm 53 arranged as follows and enters the light receiving element 54. In this embodiment, an infrared or red light beam L1 is used, and the beam diameter is set to 2 to 10 [mm].

  The light receiving element 54 includes a PSD (Position Sensitive Detector) extending in the vertical direction, a line sensor, a photodiode array, and the like, and the light receiving surface 54 a faces the light source 52. However, in the present embodiment, this corresponds to the fact that the optical axis of the light beam L1 is inclined by the angle θ in the (+ X) direction with respect to the normal line N, and the long side of the light receiving surface 54a is angled similarly to the housing 51. It is inclined in the (+ X) direction with respect to the normal line N of the printing surface PS by θ, and the light receiving surface 54a is inclined so as to be substantially perpendicular to the optical axis of the light beam L1.

  The diaphragm 53 is arranged on the upper surface of the transparent member so that the opening 53a is positioned on a virtual plane VP including the light emitting surface 52a of the light source 52 and the light receiving surface 54a of the light receiving element 54 as shown in FIG. Yes. Since the light source 52, the diaphragm 53, and the light receiving element 54 are fixed to the housing 51, for example, as shown by a dotted line in FIG. The angle of the diffusely reflected light L3 that passes through 53a and enters the light receiving element 54 is different from that before rising, and as a result, the position at which the diffusely reflected light L3 is received by the light receiving surface 54a also changes. Specifically, when the lift does not occur, that is, when the measurement region RX is located at a height position sufficiently away from the print head 32, the light receiving element 54 serves as a light source of the light receiving surface 54a. The diffuse reflected light L3 is received on the near side (+ Y direction side). On the other hand, when the lift occurs, the measurement area RX approaches the print head 32, and accordingly, the light receiving element 54 receives the diffuse reflected light L3 on the side farther from the light source (−Y direction side) of the light receiving surface 54a. . In the present embodiment, the position where the diffusely reflected light L3 is received using this, that is, the position where the amount of received light is maximized is set as the height position of the region to be measured RX, and the light receiving element 54 receives a signal related thereto as a measurement target. The position information indicating the height position of the region RX is output to the controller 4.

  In the controller 4, the CPU 41 calculates the print medium distance based on the position information in accordance with the processing program stored in the ROM 42 and uses it as a measurement value (measurement of the print medium distance). Further, the CPU 41 detects whether or not the print medium P is lifted based on the measured value, and stops the movement of the carriage 36 in the main scanning direction X when the lift is detected. Thus, in this embodiment, the CPU 41 functions as the “distance deriving unit”, “lifting detection unit”, and “movement stop unit” of the present invention, and controls the respective units to perform the operations shown in FIG. Run.

  FIG. 4 is a flowchart showing the operation of the printing apparatus shown in FIG. In the present embodiment, during the printing operation, the print medium distance measurement process described above is repeatedly executed (step S1). By repeating the measurement process, for example, a change in the print medium distance with respect to the carriage position as shown in FIG. 5 is obtained. For example, in the figure, the print medium P is lifted near the carriage position 200 [mm], the print medium distance is greatly reduced, and the print surface PS of the print medium P (see FIG. 3) becomes the print head 32. collide. Therefore, in the present embodiment, a value of about 10% to 30% of the distance between the platen 31 and the print head 32 is set as the “threshold value”, and while the measured value is equal to or greater than the threshold value (“ NO ") continuously measures the print medium distance while moving the carriage 36 in the main scanning direction X. On the other hand, when the measured value is less than the threshold value (“YES” in step S2), the movement of the carriage 36 is forcibly stopped in response to a movement stop command from the CPU 41 (step S3). As a result, it is possible to effectively suppress rubbing and collision of the print head 32 against the print medium P.

  As described above, according to the present embodiment, the light source 52, the virtual plane VP including the light source 52, the diaphragm 53, and the light receiving element 54 is inclined in the (+ X) direction with respect to the normal line N of the printing surface PS. Since the diaphragm 53 and the light receiving element 54 are disposed, the following effects can be obtained. That is, the specularly reflected light L2 specularly reflected by the printing surface PS travels away from the diaphragm 53 and the light receiving element 54 as indicated by a two-dot chain line in FIG. Accordingly, it is possible to reliably prevent the regular reflection light L2 from entering the light receiving element 54 regardless of the surface state of the printing surface PS, and only the diffuse reflection light L3 enters the light receiving element 54. Moreover, the detection resolution of the print medium distance is increased by an amount inclined with respect to the normal line N of the printing surface PS. That is, the resolution of the light receiving element 54 is a value obtained by multiplying the resolution when the virtual plane VP is arranged parallel to the normal line N by cos θ, and when the virtual plane VP is arranged parallel to the normal line of the printing surface PS. In comparison, the detection resolution can be improved. Thus, the print medium distance can be obtained with high resolution without being affected by the surface state of the printing surface PS, and the rising of the print medium P can be accurately detected. As a result, it is possible to effectively suppress rubbing and collision of the print head 32 against the printing surface PS of the print medium P.

  In the present embodiment, the position detector 5 is attached to the carriage 36 so that the light beam L1 from the light source 52 is incident on the measurement region RX away from the print head 32 in the main scanning direction (+ X). By adopting such a configuration, it is possible to detect whether or not a lift has occurred in the measurement target area RX in the pre-printing stage. As a result, an allowable time (stop margin) required for stopping the carriage movement is widened, and it is possible to more effectively suppress rubbing and collision of the print head 32 against the printing surface PS.

  Thus, in the present embodiment, the print head 32 corresponds to an example of the “printing unit” of the present invention. Further, the position of the measurement region RX in the direction Z, that is, the height position corresponds to “the position of the printing surface where the light from the light source is reflected”. Further, the diaphragm 53 corresponds to an example of the “optical element” of the present invention.

  The present invention is not limited to the above-described embodiment, and various modifications other than those described above can be made without departing from the spirit of the present invention. For example, in the above embodiment, the diffuse reflected light L3 is configured to enter the light receiving surface 54a of the light receiving element 54 through the diaphragm 53. However, a lens may be used instead of the diaphragm 53. It functions as the “optical element” of the present invention.

  In the above embodiment, the position detection unit 5 is attached to the (+ X) direction side of the carriage 36, but the virtual plane VP is in the (−X) direction with respect to the normal N instead of the position detection unit 5. A position detection unit configured to incline may be attached to the (−X) direction side of the carriage 36. Further, the position detection unit 5 may be attached to the (+ X) direction side and the (−X) direction side. In this case, the position detection unit 5 on the (+ X) direction side while the carriage 36 moves in the (+ X) direction. , While the carriage 36 moves in the (−X) direction, the position detection unit 5 on the (−X) direction side detects the floating of the print medium P. May be.

  DESCRIPTION OF SYMBOLS 1 ... Inkjet printer (printing apparatus), 4 ... Controller, 5 ... Position detection part, 32 ... Print head (printing means), 36 ... Carriage, 41 ... CPU (Distance deriving part, Lifting detection part, Movement stop part), 52: Light source, 53: Diaphragm (optical element), 54: Light receiving element, L1: Light beam, L2: Regular reflection light, L3: Diffuse reflection light, N: Normal, P: Print medium, PS: Printed surface, RX: measurement area, VP: virtual plane, X: main scanning direction

Claims (3)

A printing apparatus that forms an image on a printing surface of a printing medium by moving a carriage loaded with printing means in a main scanning direction,
It has an optical element composed of a diaphragm or a lens, a light source and a light receiving element, and irradiates light from the light source and makes diffuse reflected light incident on the light receiving element through the optical element. A position detector that outputs position information about the position of the printed surface from which light from the light source is reflected, from the light receiving element;
A controller that stops the movement of the carriage when the floating of the print medium is detected based on position information output from the light receiving element, a virtual plane including the light source, the optical element, and the light receiving element, A printing apparatus, wherein the printing apparatus is inclined with respect to the normal line of the printing surface in the main scanning direction. The printing apparatus according to claim 1,
The controller is
A distance deriving unit for obtaining a print medium distance from the printing unit to the printing surface based on position information output from the light receiving element;
A lift detection unit that detects the lift of the print medium based on the print medium distance obtained by the distance deriving unit;
A printing apparatus comprising: a movement stop unit that stops the movement of the carriage when the lift detection unit detects a lift of the print medium. The printing apparatus according to claim 1, wherein:
The position detection unit is a printing apparatus attached to the carriage so that light from the light source is reflected at a position away from the printing unit in the main scanning direction.

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