1. Technical Field
The present invention relates to a printing apparatus which forms an image on a printing surface of a printing medium which is transported in the sub-scanning direction by causing a carriage with a printing unit mounted thereon to move in the main scanning direction.
2. Related Art
An ink jet printing apparatus is a well-known representative example of such a printing apparatus. In the printing apparatus, a printing unit such as a print head discharges ink droplets toward a printing medium surface while moving in a transport direction of the printing medium, that is, the main scanning direction which orthogonally intersects the so-called sub-scanning direction, in a position of being distanced upward from the printing medium surface (the printing surface), and the printing medium is sequentially transported in the sub-scanning direction. In this manner, images, characters and the like are printed onto the printing medium.
In the printing apparatus, there is a case in which wrinkling occurs in the printing medium due to transport shifting during the transporting of the printing medium. In addition, there is a case in which so-called cockling occurs in which the printing medium forms waves due to stretching or the like caused by ink absorption of the printing medium or heating of the printing medium. When these phenomena occur, there is a case in which the printing medium lifts up partially and the print head rubs against or collides with the printing medium surface during a printing operation.
Therefore, in order to suppress such problems, an apparatus disclosed in JP-A-5-262019 (paragraph [0035]) is proposed, for example. The apparatus is provided with a sensor which detects a gap (an interval) between a printing medium and a print head, and when a detection result according to the sensor deviates from a stipulated amount, it is determined that lifting up of the printing medium has occurred and the movement of the carriage is stopped. Accordingly, in the apparatus, rubbing and collision of the print head in relation to the printing medium surface is suppressed.
Incidentally, in order to suppress the rubbing and the collision of the print head, it is important to detect the lifting up of the printing medium. Therefore, in the related art, in order to detect the gap between the printing medium and the print head, the technology disclosed in JP-A-2006-168138 (
However, since the printing medium distance is obtained using regular reflection light, there is a case in which the printing medium is inclined according to the surface state of the printing surface, in particular, whether or not the lifting up occurs in the printing medium, the angle of the regular reflection changes, and it is difficult to accurately calculate the printing medium distance. Therefore, when the invention disclosed in JP-A-2006-168138 (
An advantage of some aspects of the invention is that a printing apparatus is provided which can accurately detect the lifting up of the printing medium and can effectively suppress the rubbing and the collision of the printing unit in relation to the printing surface of the printing medium.
According to an aspect of the invention, there is provided a printing apparatus that forms an image on a printing surface of a printing medium which is transported in a sub-scanning direction by causing a carriage with a printing unit mounted thereon to move in a main scanning direction, that includes a position detection unit which includes an optical element configured by an aperture or a lens, a light source and a light receiving element, irradiates the printing surface with light from the light source, causes diffused reflection light of reflection light which is reflected by the printing surface to be incident to the light receiving element through the optical element and outputs positional information relating to a position of the printing surface at which the light from the light source reflects, from the light receiving element, and a controller which causes movement of the carriage to stop when lifting up of the printing medium is detected on a basis of the positional information output from the light receiving element, in which a virtual plane which contains the light source, the optical element and the light receiving element is in a state of being inclined in relation to a normal line of the printing surface.
In the printing apparatus configured in this manner, the diffused reflection light of the reflection light which is reflected by the printing surface is incident to the light receiving element through the optical element. Here, when the virtual plane which contains the light source the optical element and the light receiving element is disposed so as to be parallel with the normal line of the printing surface, the diffused reflection light decreases when the printing surface is subjected to printing and the printing concentration increases. However, since the regular reflection light does not decrease, when the regular reflection light and the diffused reflection light are incident to the light receiving element at the same time, the influence of the regular reflection light is greater. In addition, according to the surface state of the printing surface, there is a case in which the regular reflection light is incident to the light receiving element through the optical element. In contrast, in the present invention, since the virtual plane is inclined in relation to the normal line of the printing surface, even if lifting up occurs in the printing surface and the light from the light source is incident to the lifted up portion, the regular reflection light, which reflects regularly, always proceeds in a moving-away direction from the optical element and the light receiving element. Therefore, incidence of the regular reflection light to the light receiving element is prevented regardless of the presence or absence of lifting up in the printing surface, only diffused reflection light is incident to the light receiving element, and the distance to the printing surface can be accurately detected. Moreover, the detection resolution of the printing medium distance increases by the amount by which the virtual plane is inclined in relation to the normal line of the printing surface. For example, when the inclination angle is θ, the resolution of the light receiving element is a value which is multiplied by cosθ, and the detection resolution improves in comparison to a case in which the virtual plane is disposed parallel to the normal line of the printing surface. Therefore, the printing medium distance can be obtained at a high resolution without receiving the influence of the printing state or the surface state of the printing surface, and the lifting up of the printing medium can be accurately detected. As a result, the rubbing and the collision of the printing unit in relation to the printing surface of the printing medium can be effectively suppressed.
Here, the virtual plane is in a state of being inclined in the sub-scanning direction in relation to the normal line of the printing surface.
In addition, the virtual plane is in a state of being inclined in the main scanning direction in relation to the normal line of the printing surface.
Furthermore, the position detection unit may be installed in the carriage such that the light from the light source reflects at a position distanced from the printing unit in the main scanning direction, and it is therefore possible to detect whether or not lifting up is occurring in the surface part which is positioned closer to the front in the main scanning direction within the printing surface than the carriage, that is, the surface part of the previous stage of the printing. In this manner, it is possible to start the movement stopping of the carriage before the arrival of the printing unit at the portion which is lifting up. In other words, the allowable time necessary to stop the carriage movement, that is, the stopping margin, is expanded. As a result, the rubbing or the collision of the print head can be more effectively suppressed.
Here, a configuration may also be adopted in which the position detection unit includes a housing which accommodates the optical element, the light source and the light receiving element, and a shielding member configured by a material which is non-transmissive in relation to regular reflection light of reflection light which is reflected by the printing surface, and in which the shielding member is provided to extend from the housing in a direction in which the regular reflection light proceeds, and blocks the regular reflection light. In this manner, the regular reflection light can be prevented from returning to the housing side by providing the shielding member, and the occurrence of stray light can be suppressed. Furthermore, the influence of the light from outside can also be suppressed by the shielding member. As a result, it is possible to more accurately detect the printing medium distance.
In addition, when a reflection prevention member is provided on the incidence surface of the shielding member to which the regular reflection light is incident, the reflection of the regular reflection light in the incidence surface is prevented by the reflection prevention member and the occurrence of stray light and the influence of external light can be further suppressed. Therefore, it is possible to more accurately detect the printing medium distance.
In addition, in order to accurately detect the lifting up of the printing medium and appropriately stop the movement of the carriage, for example, a configuration may also be adopted in which the controller is provided with a distance derivation unit which obtains a printing medium distance from the printing unit to the printing surface on a basis of positional information which is output from the light receiving element; a lifting up detection unit which detects lifting up of the printing medium on the basis of the printing medium distance obtained by the distance derivation unit, and a movement stopping unit which causes movement of the carriage to stop when the lifting up detection unit detects the lifting up of the printing medium.
A configuration such as the following may also be adopted for the detection of the lifting up of the printing medium. For example, a configuration may be adopted in which the lifting up detection unit detects the lifting up of the printing medium on the basis of whether or not the printing medium distance is shorter than a threshold value which is set in advance. Accordingly, the movement of the carriage is stopped at the point in time at which the printing unit approaches and reaches the printing medium, and the rubbing or the collision of the printing unit in relation to the printing surface of the printing medium is suppressed.
Furthermore, as another configuration, a configuration may be adopted in which the lifting up detection unit obtains the printing medium distance when the carriage is assumed to have moved only a distance which is set in advance, that is, an estimated distance, and the lifting up detection unit detects the lifting up of the printing medium on the basis of whether or not the estimated distance is shorter than a threshold value which is set in advance. By estimating the approach of the printing unit to the printing medium in this manner, a movement stopping operation of the carriage can be started before the printing unit approaches and reaches the distance indicated by the threshold value, and the suppression of the rubbing or the collision of the printing unit in relation to the printing surface of the printing medium can be rendered more reliable. Furthermore, when performing such estimation control, it is favorable to obtain the estimated distance at a high precision, and for example, it is possible to adopt a configuration in which a change in the printing medium distance which accompanies movement of the carriage is obtained, and the estimated distance is obtained on the basis of the change.
The invention will be described with reference to the accompanying drawings, wherein like numbers reference like elements.
The printer mechanism 3 includes a carriage motor 34a which is disposed on one end (the right end of the diagram) of a mechanical frame 33 and a driven roller 34b which is disposed on the other end (the left end of the diagram) of the mechanical frame 33. Furthermore, a carriage belt 35 bridges the carriage motor 34a and the driven roller 34b. A portion of the carriage belt 35 is linked to a carriage 36. Therefore, when the carriage motor 34a operates on the basis of an operation command from the controller 4, the carriage 36 moves reciprocally in the main scanning direction (the left-right direction in the diagram) X along a carriage shaft 37. Furthermore, a linear encoder (omitted from the drawing), which outputs a pulse-shaped signal to the controller 4 together with the movement of the carriage 36, is disposed on the rear surface of the carriage 36. The controller 4 manages the position of the carriage 36, that is, the carriage position in the main scanning direction X on the basis of the signal from the linear encoder.
The 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 inks of each color of CMYK of cyan (C), magenta (M), yellow (Y) and black (K) in which, a coloring agent such as a dye or a pigment is contained in a solvent such as water. Furthermore, the print head 32 receives a supply of an ink from the ink cartridge 38 and discharges ink droplets. Furthermore, the position detection unit 5 is installed on the side surface of the (+X) direction side of the carriage 36 and outputs a signal relating to the distance (hereinafter referred to as the “printing medium distance”) from the print head 32 to the printing medium P on the platen 31 to the controller 4. Description will be given of the configuration of the position detection unit 5 later.
As shown in
While the printing onto the printing medium P is being performed, the CPU 41 exchanges various signals with the position detection unit 5, which is configured as described next, and derives the printing medium distance. Furthermore, when the CPU 41 detects the lifting up of the printing surface PS on the basis of the printing medium distance, the CPU 41 causes the carriage 36 to stop rapidly. Hereinafter, after describing the configuration of the position detection unit 5 with reference to
As shown in
The light receiving element 54 is configured by a position sensitive detector (PSD) which extends in the up-down direction, a line sensor, a photodiode array or the like, and a light receiving surface 54a is disposed facing the light source 52. However, in the embodiment, corresponding to the fact that the light axis of the light beam L1 is inclined by the angle θ to the (+Y) direction in relation to the normal line N, as shown in
As shown in
In the controller 4, the CPU 41 calculates the printing medium distance on the basis of the positional information according to the processing program which is stored in the ROM 42, and the printing medium distance is used as the measured value (the measurement of the printing medium distance). In addition, the CPU 41 detects the presence or absence of the lifting up of the printing medium P on the basis of the measured value and stops the movement of the carriage 36 in the main scanning direction X when the lifting up is detected. In this manner, in the embodiment, the CPU 41 functions as the “distance derivation unit”, the “lifting up detection unit” and the “movement stopping unit” of the invention and controls each portion of the apparatus to execute the operations shown in
As described above, according to the embodiment, the light source 52, the aperture 53 and the light receiving element 54 are disposed so that the virtual plane VP which contains the light source 52, the aperture 53 and the light receiving element 54 is inclined to the (+Y) direction in relation to the normal line N of the printing surface PS. Therefore, the following effects can be obtained. In other words, the regular reflection light L2, which is regularly reflected at the printing surface PS, proceeds in a moving-away direction from the aperture 53 and the light receiving element 54 as shown by the two-dot line in
In this manner in the embodiment, the print head 32 is equivalent to an example of the “printing unit” of the invention. In addition, the position of the measured region RX in the direction Z, that is, the height position is equivalent to “the position of the printing surface at which the light from the light source reflects”. Furthermore, the aperture 53 is equivalent to an example of the “optical element” of the invention.
In addition, as shown in
Furthermore, in the light receiving element 54 of the modification example, corresponding to the fact that the light axis of the light beam L1 is inclined by the angle θ to the (+X) direction in relation to the normal line N, the long edge of the light receiving surface 54a is inclined to the (+X) direction in relation to the normal line N of the printing surface PS by the angle θ in the same manner as the housing 51, and the light receiving surface 54a is inclined so as to be substantially perpendicular to the light axis of the light beam L1. As shown by the dotted line in
As described above, according to the modification example, the light source 52, the aperture 53 and the light receiving element 54 are disposed so that the virtual plane VP which contains the light source 52, the aperture 53 and the light receiving element 54 is inclined to the (+X) direction in relation to the normal line N of the printing surface PS. In addition, the position detection unit 5 is installed in the carriage 36 such that the light beam L1 from the light source 52 is incident at the measured region RX which is separated from the print head 32 in the main scanning direction (+X). By adopting such a configuration, it is possible to detect whether or not the lifting up occurs at the measured region RX in the previous stage of the printing. As a result, the allowable time necessary to stop the carriage movement (the stopping margin) is expanded and the rubbing and the collision of the print head 32 in relation to the printing surface PS can be effectively suppressed.
In addition, in the modification example, the position detection unit 5 is installed on the (+X) direction side of the carriage 36. However, the position detection unit, which is configured such that the virtual plane VP is inclined to the (−X) direction in relation to the normal line N, may also be installed on the (−X) direction side of the carriage 36.
The shielding member 55 is provided to extend from the lower end portion of the (+Y) side of the housing 51 in the (+Y) direction and partially covers the printing surface PS from above. More specifically, as shown in
In addition, the reflection prevention member 56 such as matting or electrostatic flocking is provided on the incidence surface of the shielding member 55 to which the regular reflection light L2 is incident, that is, the lower surface of the horizontal part 552. Therefore, the regular reflection light L2 is prevented from reflecting at the lower surface of the horizontal part 552 by the reflection prevention member 56 and the occurrence of stray light can be further suppressed. Furthermore, in the embodiment, the reflection prevention member 56 is provided not only in relation to the horizontal part 552, but also in relation to the surface which faces the printing surface PS within the inclined part 551. Therefore, the reflection prevention member 56 reliably prevents the occurrence of stray light due to light reflection at the inclined part 551. Furthermore, even the influence of the light from outside can be suppressed by the shielding member 55 and the reflection prevention member 56.
As described above, according to the second embodiment, it is possible to suppress the occurrence of stray light and the influence of external light by adding the shielding member 55, and to increase the detection precision of the printing medium distance. In addition, since the reflection prevention member 56 is provided in addition to the shielding member 55, the occurrence of stray light and the influence of external light can be more effectively suppressed and the printing medium distance can be more accurately detected. Therefore, the rubbing and the collision of the print head 32 to the printing surface PS of the printing medium P can be suppressed with a higher precision.
During the printing operation, the measurement process of the printing medium distance described above is repeatedly executed (step S1). Furthermore, every time the printing medium distance is measured, the CPU 41 determines whether or not the measured value is less than the threshold value (step S2), and when step 2 is determined to be “YES”, in the same manner as in the first embodiment, the movement of the carriage 36 is forcibly caused to stop (step S3).
Meanwhile, when step S2 is determined to be “NO”, the CPU 41 newly adds the measured value of the printing medium distance to the array of the RAM 43 (step S4). Furthermore, the oldest measured value of the measured values stored in the array is deleted from the RAM 43 corresponding to the addition of a measured value. In this manner, after executing the measurement of the printing medium distance N times, the newest N measured values are stored in the array of the RAM 43.
In the next step S5, the CPU 41 determines whether or not the newest measured value is less than the estimated calculated distance. The “estimated calculated distance” is used as the standard for starting the execution of the estimation operation of the printing medium distance, and unnecessary estimation calculations (steps S6 and S7) are omitted by setting the estimated calculated distance. In other words, as long as the printing medium distance is sufficiently great, the lifting up does not occur or the lifting up amount is negligible (“NO” in step S5), the process returns to step S1 and measurement of the printing medium distance is performed without performing the estimation calculation processing (steps S6 and S7) described next. Furthermore, in the embodiment, as shown in
Meanwhile, when step S5 is determined to be “YES”, the CPU 41 reads out N measured values from the array of the RAM 43 and derives the change in the printing medium distance which accompanies the movement of the carriage on the basis of the N measured values as an estimation calculation formula (step S6). In the embodiment, as shown by the dotted line in
In the next step S7, the CPU 41 calculates the printing medium distance at a position in front of the carriage position at the time of measurement, for example, a position 5 mm in front of the carriage position (hereinafter referred to as the “estimated distance”) on the basis of the estimation calculation formula. Furthermore, as long as the estimated distance is the threshold value or more (“NO” in step S8), the CPU 41 returns to step S1 and continually performs measurement of the printing medium distance while causing the carriage 36 to move in the main scanning direction X. Meanwhile, when the estimated distance is less than the threshold value (“YES” in step S8), the CPU 41 forcibly stops the movement of the carriage 36 (step S3).
As described above, in the third embodiment, since lifting up of the printing medium P is detected in the same manner as in the first embodiment, the same effects can be gained as in the first embodiment. In addition, in the third embodiment, the lifting up is detected by estimating the change in the printing medium distance, and the lifting up of the printing medium P can be detected earlier in comparison with the first embodiment. Therefore, the third embodiment can further reinforce the effects of the first embodiment. In other words, according to the third embodiment, the carriage 36 can be forcibly stopped with a leeway by performing estimation detection, and the effect of suppressing the rubbing or the collision of the print head 32 with the printing surface PS can be further increased.
Furthermore, the invention is not limited to the embodiments described above, and various modifications other than those described above can be made without departing from the spirit of the invention. For example, in the configuration according to the embodiments, the diffused reflection light L3 is incident to the light receiving surface 54a of the light receiving element 54 through the aperture 53. However, a lens may also be used instead of the aperture 53, and in this case, the lens functions as the “optical element” of the invention.
In addition, in the embodiments, the virtual plane VP is configured so as to be inclined to the (+Y) direction in relation to the normal line N. However, the inclination direction of the virtual plane VP is not limited thereto, for example, a configuration may also be adopted in which the virtual plane VP is inclined to the (−Y) direction in relation to the normal line N. In addition, the position detection unit 5 is installed on the (+X) direction side of the carriage 36. However, instead of the position detection unit 5, the position detection unit may also be installed on the (−X) direction side of the carriage 36. In addition, the position detection unit 5 may be installed on the (+X) direction side and the (−X) direction side, and in this case, a configuration may be adopted in which the lifting up of the printing medium P is detected by the position detection unit 5 of the (+X) direction side while the carriage 36 moves in the (+X) direction, and the lifting up of the printing medium P is detected by the position detection unit 5 of the (−X) direction side while the carriage 36 moves in the (−X) direction.
In addition, without being limited to the embodiments, an image can be formed on the printing surface PS of the printing medium P by causing the carriage 36 to move in the main scanning direction X and the sub-scanning direction Y, and an image can also be formed on the printing surface PS of the printing medium P by causing the printing medium P to be transported in the main scanning direction X and the sub-scanning direction Y. In any of the modes described above, it is preferable that the position detection unit 5 be installed in the carriage 36 on at least one of the relative movement directions of the carriage 36 and the printing medium P, and the position detection unit 5 may also be installed on at least one of the (+Y) direction side and the (−Y) direction side of the carriage 36.
In addition, in the embodiments, the light receiving element 54 is disposed such that the light receiving surface 54a is substantially perpendicular to the light axis of the light beam L1. However, the disposition mode of the light receiving element 54 is not limited thereto, for example, the light receiving element 54 may also be disposed such that the light receiving surface 54a is substantially parallel to the light axis of the light beam L1. In this case, when the lifting up does not occur, that is, when the measured region RX is positioned at a height position which is sufficiently separated from the print head 32, the light receiving element 54 receives the diffused reflection light L3 at the side separated from the printing surface PS of the light receiving surface 54a. In contrast, when the lifting up occurs, the measured region RX approaches the print head 32 and the light receiving element 54 receives the diffused reflection light L3 at the side which is close to the printing surface PS of the light receiving surface 54a.
The entire disclosure of Japanese Patent Application No. 2012-262117, filed Nov. 30, 2012 and 2012-276559, filed Dec. 19, 2012 are expressly incorporated by reference herein.
Number | Date | Country | Kind |
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2012-262117 | Nov 2012 | JP | national |
2012-276559 | Dec 2012 | JP | national |