JP3479544B2 - Printing device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printing apparatus for performing a desired printing by printing with a print head, and more particularly to an optical paper detecting sensor for detecting a paper. The present invention relates to a device capable of detecting a sheet for a long time with high accuracy by devising the arrangement of the sheets. 2. Description of the Related Art In a printing apparatus of a type which performs desired printing by printing with a print head, paper is detected by a configuration as shown in FIG. Paper stacked and held on a paper stocker (not shown) (in this case, cut-sheet paper)
1 is by pressing rollers (pinch rollers) 3 and 5
The sheet is conveyed in the direction indicated by the arrow a in the figure and is wound around the platen 7. Then, the sheet is conveyed in the direction of the print head 9, where desired printing is performed by stamping with the print head 9. Further, between the pressing rollers 3 and 5 in FIG. 4, a reflection type photo sensor 11 for detecting the sheet 1 is provided. Then, as shown in FIG. 5, the detection signal from the reflection type photosensor 11 is input to the A / D converter 13, where it is converted from analog data to digital data. Then, the digital data is input to the microprocessor unit (MPU) 15. The microprocessor unit 15 stores the input data and the ROM 17
The presence or absence of the sheet 1 is determined from the data stored in the. The determination of the presence or absence of the sheet 1 will be described in detail. First, if you are sheet 1 is wound around the platen 7, the light emitted from the photosensor 11,
The light is reflected by the sheet 1 and received by the reflection type photosensor 11. On the other hand, when the paper 1 is not wound, the light emitted from the reflective photosensor 11 is reflected by the platen 7 and received by the reflective photosensor 11. At that time, the sheet 1 and the platen 7 have different reflectances. Further, a preset reference value is stored in the ROM 17, and this reference value is set as an intermediate value between the measured values when the sheet 1 is present and when the sheet 1 is not present. If the measured value is lower than the reference value, it is determined that there is no paper 1, and if the measured value exceeds the reference value, it is determined that the paper 1 is present. Although the above description has been made with reference to a cut sheet as an example of the sheet 1, the same applies to a continuous sheet. FIG. 6 shows a configuration when the continuous paper 1 is used.
First, a push tractor 21 as a sheet transport means is arranged, and the push tractor 21 sends out the sheet 1. The push tractor 21 includes a driving pulley 23, a driven pulley 25, and a belt 27 wound around the driving pulley 23 and the driven pulley 25. The belt 27 has a plurality of pins 29 projecting at a predetermined pitch. A rotational force from a stepping motor (not shown) is transmitted to the drive pulley 23. The continuous paper 1 is formed by connecting and folding a predetermined length of paper through a perforation, and has holes formed on both sides thereof for fitting the pins 29. The other structure is the same as that of the cut sheet described above, and the same parts as those shown in FIG. In FIG. 6, reference numeral 31 denotes a guide, 33 denotes a bail roller, and 35 denotes a carriage. Also in this case, the presence or absence of the sheet 1 is detected by the reflection type photosensor 11, and the determination method is the same as that described above. The reflection type photo sensor 11 is as shown in FIGS. 7 and 8. As shown in FIG. 7, first, there is a substrate 41, on which an LED (light emitting diode) 43 as a light emitting element is provided on one side, and a phototransistor 45 as a light receiving element on the other side. is set up. And L
The light output from the ED 43 collides with the sheet 1 (or the platen 7), is reflected, and is received by the phototransistor 45. The light reflected from the paper 1 has a high reflectance because the paper 1 is close to white, but one platen 7 is usually formed of a black rubber-based material, and the reflectance is extremely low. The presence or absence of the sheet 1 is determined by comparing the data indicating the amount of received reflected light with a reference value. FIG. 8 shows the reflection type photosensor 1 shown in FIG.
1 is a diagram showing a circuit diagram of No. 1 and reference numerals (1), (2), (3),
(4) indicates terminals. [0007] According to the above-described conventional configuration, there are the following problems. First, when the mounting position of the conventional reflective photosensor 11 is viewed in relation to the printing area of the paper 1, the result is as shown in FIG. That is,
The reflection type photo sensor 11 is mounted in the print area 1 a of the paper 1. Although the difference in reflectance (difference between the sheet 1 and the platen 7) is large at the beginning of use as described above, it is convenient.
While the platen 7 has been used for a long period of time, the surface of the platen 7 is smoothed by printing with the print head 9 during printing, and the reflectance thereof gradually increases. As a result, the output value from the reflective photosensor 11 when the sheet 1 is not present gradually increases, and the difference between the output value and the reference value becomes small. Therefore, there is a problem that the detection accuracy of the sheet 1 gradually decreases, and for example, a situation occurs in which the sheet 1 is determined to be present even though the sheet 1 is not present. An object of the present invention is to provide a printing apparatus provided with a paper detecting means capable of detecting a paper with high accuracy for a long period of time. It is in. In order to achieve the above object, a printing apparatus according to the present invention feeds a sheet in the direction of a platen by a sheet conveying means and winds the sheet around a platen. In a printing device that performs desired printing by stamping with an impact head, it is the area where the paper passes through the reflective photo sensor and
Platen in a region where the platen surface condition does not change over time due to
And the presence or absence of a sheet is determined based on the difference in the amount of reflected light between the sheet and the platen. In other words, the optical paper detection sensor is installed in a region where the paper passes and which is outside the printing region of the paper, so that it is not affected by the smoothing of the platen surface due to long-term use. In addition, paper detection can be performed with high accuracy over a long period of time. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIGS.
An embodiment will be described. The same parts as those in the related art are denoted by the same reference numerals, and description thereof is omitted. Also, shown in FIGS.
The configuration is the same in the present embodiment, and has already been described.
It is on the street. As shown in FIG. 1, in the case of this embodiment,
Up the reflective photosensor 11, a region where the sheet 1 passes, in a region 1b deviates from the printing area 1a of the paper 1
Installed facing Latin . With this configuration, the paper 1 can be detected with high accuracy over a long period of time. That is, in the region 1b,
This is because the platen 7 is not stamped by the print head 9, and therefore, the surface thereof is not smoothed and the reflectance is not increased. In this embodiment, a single sheet is used as an example of the sheet 1. As shown in FIG. 2, a printer using A4 sheet usually has a print width of 8 inches. In general, the width (c) of the area 1b is about 3 mm (in this case, slightly different depending on the type of the printer). Therefore, the distance (d) between the center position of the reflective photosensor 11 and the edge of the sheet 1 is set to about 1.5 mm, and the reflective photosensor 11 is mounted. Next, a case where continuous paper is used as the paper 1 will be described with reference to FIG. In the case of the continuous paper 1, holes 13 are formed on both sides at a predetermined pitch.
The holes 13 correspond to a plurality of pins provided on a belt of a push tractor as a transport means.
The paper 1 is transported by fitting the pins into the holes 13. Reference numeral 15 in the drawing indicates a perforation. In the case of this type of continuous paper 1, the width (e) of the area 1b is usually 12.7 mm or more.
The distance (g) from the end of the sheet 1 to the position where the hole 13 is formed is defined as 6.35 mm, and the diameter of the hole 13 is 4 mm. Therefore, the distance (f) from the position of the hole 13 to the printing area 1a is 6.35 mm, and from that value, it is half the diameter of the sprocket hole 13 2
When mm is subtracted, it becomes 4.35 mm, which is the distance (h) from the right end of the sprocket hole 13 to the left end of the print area 1a. And 1 of this distance (h)
The reflection type photosensor 11 is installed at a distance of / 2. The present invention is not limited to the above embodiments. The dimensions of each part are shown only as an example, and may be appropriately changed depending on the type of the printer and the like. In addition, the basic configuration and the like of the printer are not particularly limited. As described above in detail, according to the printing apparatus of the present invention, the optical paper detection sensor is set in the area where the paper passes and which is outside the printing area of the paper. Thus, the paper can be detected with high accuracy for a long period of time without being affected by a change in the surface state of the platen due to the stamping.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view showing a first embodiment of the present invention and is a view showing a mounting position of a reflection type photosensor. FIG. 2 is a diagram illustrating the first embodiment of the present invention, and is a diagram illustrating an example of a mounting position of a reflection type photosensor on a cut sheet. FIG. 3 is a diagram illustrating a second embodiment of the present invention, and is a diagram illustrating an example of a mounting position of a reflective photosensor on continuous paper. FIG. 4 is a diagram used to explain a conventional example and is a diagram showing a partial configuration of a printing apparatus. FIG. 5 is a block diagram showing a configuration for determining the presence or absence of a sheet in the diagram used for explaining the conventional example. FIG. 6 is a diagram used to explain a conventional example and is a diagram showing a partial configuration of a printing apparatus. FIG. 7 is a diagram used for explaining a conventional example and is a diagram showing a configuration of a reflection type photosensor. FIG. 8 is a circuit diagram of a reflection type photosensor used for explaining a conventional example. FIG. 9 is a view showing a conventional example, and is a view showing a mounting position of a reflection type photosensor. [Description of Signs] 1 Paper 1b An area through which the paper passes and which deviates from the printing area of the paper 1a Printing area 5 Pressing roller 7 Platen 11 Reflection type photo sensor (optical paper detection sensor)

Claims (1)

(57) [Claims 1] A sheet is fed in the direction of a platen by a sheet conveying means and wound around the platen, and at that time, desired printing is performed by stamping with an impact head arranged opposite to the platen. In the printing device, the area where the paper passes the reflection type photo sensor
Platen in an area where the platen surface condition does not change over time due to
A printing apparatus which is installed to face the printer and determines the presence or absence of a sheet based on a difference in the amount of reflected light between the sheet and the platen.