JP2009255404A - Position detection device and printer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a printer that does not require a home position during an initializing operation or occurrence of an error and can be controlled by an inexpensive motor. <P>SOLUTION: This printer is equipped with a position detection device. The printer comprises a gear 6 as a shade plate of which transmittance is varied depending on its position, a photosensor 14 for detecting the transmittance of the gear 6, and a detection section for detecting a position of an object to be detected moving in association with the gear 6 on the basis of the transmittance detected by the photosensor 14. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a position detection apparatus, and more particularly to a position detection apparatus suitable for position detection of a thermal transfer type printer apparatus.

  The conventional thermal transfer type printer device moves the thermal head upward during conveyance and standby of printing paper, keeps the platen roller and thermal head separated, and moves the thermal head downward during printing, Printing was performed with the head in a pressure-bonded state. Therefore, it is necessary to detect the position of the thermal head in order to move the thermal head to the correct position.

  As this detection method, there is a method in which a shielding plate attached to a cam for driving a thermal head up and down is read by a transmission type photosensor (see, for example, Patent Document 1). In some cases, the home position is detected by a reflective photosensor, and the amount of movement from the home position is controlled by the number of pulses of the stepping motor (for example, see Patent Document 2).

JP 2002-254385 A JP 2001-088395 A

  However, in the position detection method of Patent Document 1, in order to know the current thermal head position at the time of initialization operation or error, it is necessary to first search for the home position, and the current thermal head position becomes the target position. Even in the near case, it was necessary to rotate the cam more than necessary.

  Further, the position detection method of Patent Document 2 uses an expensive stepping motor to perform pulse control in order to control the amount of movement from the home position.

  The present invention has been made to solve such a problem, and an object of the present invention is to obtain a position detection device that does not require a home position and can be controlled by an inexpensive motor, and a printer device using the position detection device.

  A position detection device according to the subject of the present invention includes a light-shielding plate whose transmittance varies depending on a position, a photosensor that detects the transmittance of the light-shielding plate, and a detection target that interlocks with the light-shielding plate from the transmittance detected by the photosensor. A detection unit for detecting the position of the object.

  According to the present invention, the transmittance of the light-shielding plate changes depending on the position, and the position of the detection target interlocked with the light-shielding plate is detected from the transmittance detected by the photosensor. Moreover, it can be controlled by an inexpensive motor.

(Embodiment 1)
A printer apparatus including a position detection apparatus according to the present embodiment will be specifically described with reference to the drawings. However, the detection target of the printer device is a thermal head or a platen roller. Here, for convenience of description, a thermal head will be described. The procedure is the same for detecting the position of the platen roller.

  FIG. 1 shows a thermal head driving unit during printing, and FIG. 2 shows a thermal head driving unit during standby. The thermal head drive unit rotates a thermal head 1 that prints ink on an ink ribbon (not shown) on printing paper (not shown), a platen roller 11 that presses the ink ribbon and printing paper against the thermal head 1, and a worm 3. DC motor 2, the worm 3 fixed to the shaft of the DC motor 2, the worm wheel 4 meshing with the worm 3, the rotation shaft 5 of the worm wheel 4, and the rotation from the worm wheel 4 is transmitted around the shaft 8. A rotating gear 6, a cam 7 that is fixed to the gear 6 and drives the thermal head 1, a shaft 8 of the cam 7, and a roller 9 that is fixed to the thermal head 1.

  Next, the operation will be described. The thermal head 1 and the platen roller 11 energize the thermal head 1 by energizing the thermal head 1 while sandwiching and pressing an ink ribbon and printing paper (not shown) between them, and form an image on the printing paper. The printing is done.

  At the time of printing, the thermal head 1 is in a lowered position as shown in FIG. However, at the time of standby, the thermal head 1 is in a raised position as shown in FIG. 2, that is, a position away from the ink ribbon. This is to prevent the ink ribbon from coloring due to the residual heat of the thermal head 1 during non-printing.

  The mechanism of the thermal head 1 at this time will be described in detail. First, the DC motor 2 rotates the worm 3, and the rotation is transmitted to the worm wheel 4 through the worm 3. Then, the rotation from the worm wheel 4 is transmitted to the gear 6, and the gear 6 rotates about the shaft 8. The cam 7 is fixed to the gear 6, and the cam 7 also rotates about the shaft 8. The roller 9 is fixed to the thermal head 1, and the roller 9 rolls on the outer periphery of the cam 7 as the cam 7 rotates. When the roller 9 is closest to the shaft 8 of the cam 7, the thermal head 1 is lowered as shown in FIG. 1, and when the roller 9 is farthest from the shaft 8 of the cam 7, the thermal head 1 is moved as shown in FIG. The position will be raised.

  FIG. 3 is a view of the gear 6 portion of FIG. 1 as viewed from above. In FIG. 1, a photosensor 14 (not shown) is installed so as to sandwich the gear 6 as shown in FIG.

  FIG. 4 is an explanatory diagram showing the position detection device according to the present embodiment. The position detection device is interlocked with the thermal head 1 and has a gear 6 that also functions as a light shielding plate whose transmittance changes according to the rotation angle, a photo sensor 14 that detects the transmittance of the gear 6, and the transmission detected by the photo sensor 14. It comprises a detector (not shown) that detects the position of the thermal head 1 from the rate.

  By the way, the gear 6 has innumerable holes, and the density of the holes changes depending on the angle. A cam 7 is fixed to the gear 6, and the thermal head 1 is driven up and down around the shaft 10 by rotating the cam 7 around the shaft 8. The photosensor 14 is installed so as to sandwich the gear 6 and detects the transmittance of the gear 6. The photosensor 14 may be either a transmission type or a reflection type as long as the transmittance of the gear 6 is known.

  In the position detection method, first, the transmittance of the gear 6 is detected by the photosensor 14. Next, the detected transmittance is sent to the detection unit. Further, the detection unit detects the position of the thermal head 1 to be detected linked to the gear 6 from the transmitted transmittance.

  The lower graph of FIG. 4 shows the output of the photosensor 14 with respect to the rotation angle when the gear 6 is used. In this way, since the density of the hole of the gear 6 changes depending on the rotation angle, the conventional apparatus only detects binary values of H or L, whereas in the present invention, from H Continuous analog output values up to L can be detected. Therefore, if the analog output value of the photosensor 14 with respect to the rotation angle of the gear 6 is measured in advance, the rotation angle of the gear 6, that is, the position of the thermal head 1 can be detected from the output value of the photosensor 14.

In the lower graph of FIG. 4, the output value V _{0 °} when the thermal head 1 is in the lowered position and the thermal head 1 when the gear 6 is rotated 45 degrees from the position of the output value V _{0 °} are raised. The position output value V _{45 °} is shown.

  In the conventional apparatus, the detectable rotation angle is limited by the number of windows of the light shielding plate and the installation location of the windows. However, since the apparatus of the present invention can obtain a continuous analog output value corresponding to the rotation angle, an arbitrary rotation angle can be detected. Thus, since the gear 6 also serves as a light shielding plate, there is an advantage that the number of parts can be reduced as compared with the conventional device.

  The gear 6 may have any form as long as the transmittance changes according to the rotation angle. For example, instead of the hole, the thickness of the gear 6 may be changed according to the rotation angle. FIG. 5 shows an example in which a filter having a different transmittance depending on the rotation angle is attached to the gear 6.

  In this embodiment, the platen roller 11 is fixed and the thermal head driving unit that moves the thermal head 1 up and down is described. However, the thermal head 1 is fixed and the platen roller 11 is moved up and down. It can also be used for a roller drive unit.

  In this way, with the gear 6 as a light shielding plate, the transmittance changes in accordance with the rotation angle in conjunction with the thermal head 1 or the platen roller 11, and the rotation angle of the gear 6, that is, the current rotation angle, that is, the current output value of the photosensor. Since the position of the thermal head or the platen roller can be detected, a home position is not required and control can be performed with an inexpensive motor.

(Embodiment 2)
FIG. 6 is a diagram showing a control method of the position detection apparatus according to the embodiment of the present invention. In general, it is known that the photosensor 14 has a large variation in output level due to individual variation and aging. Therefore, in FIG. 4, the output value of the photosensor 14 with respect to the rotation angle of the gear 6 differs for each printer device, and even with the same printer device, it changes due to aging. It is possible.

  The present embodiment is characterized in that the detection unit rotates the gear 6 one or more times at the initial setting of the printer device, and measures the maximum value and the minimum value of the output value of the photosensor 14 at that time.

In FIG. 6, V _max is the maximum output value of the photo sensor 14, and V _min is the minimum output value of the photo sensor 14. An output value V _max when the thermal head 1 is lowered (head down) and an output value (V _max −V _min ) / 4 when the thermal head 1 is raised (head up) are shown. If the transmission of the gear 6 and the output value of the photosensor 14 are designed to be linear, for example, depending on the rotation angle of the gear 6, the rotation angle of the gear 6 is uniquely determined by the ratio of V _max and V _min. Can do.

  In this manner, the detection unit calibrates the output value of the photosensor 14 by rotating the light shielding plate one or more times and measuring the maximum value and the minimum value of the output value of the photosensor 14 at the initial setting of the printer apparatus. Therefore, the position of the thermal head can be detected without being affected by the variation in the output value of the photosensor 14 and the variation due to aging.

  As an application example of the present invention, the present invention can be applied to position detection of a thermal head or a platen roller of any position detection apparatus or thermal transfer type printer apparatus.

It is a figure which shows the thermal head drive part at the time of the printing of the printer apparatus which concerns on this Embodiment. It is a figure which shows the thermal head drive part at the time of standby of the printer apparatus which concerns on this Embodiment. It is the figure which looked at the gear part of FIG. 1 from the top. It is explanatory drawing of the position detection apparatus which concerns on Embodiment 1 of this invention. It is a figure which shows the example which affixed the filter on the gear which concerns on Embodiment 1 of this invention. It is a figure which shows the control method of the position detection apparatus which concerns on Embodiment 2 of this invention.

Explanation of symbols

  1 thermal head, 6 gears, 11 platen roller, 14 photo sensor.

Claims (4)

A shading plate whose transmittance varies depending on the position;
A photosensor for detecting the transmittance of the light shielding plate;
A detection unit that detects a position of a detection target interlocked with the light shielding plate from the transmittance detected by the photosensor;
Position detection device. The light-shielding plate changes the transmittance according to a rotation angle.
The position detection device according to claim 1. A printer device comprising the position detection device according to claim 2,
The detection object of the printer device is a thermal head or a platen roller,
The printer device includes a gear whose transmittance changes according to a rotation angle in conjunction with the thermal head or the platen roller as the light shielding plate.
Printer device. The detection unit calibrates the output value of the photosensor by rotating the light shielding plate at least once and measuring the maximum value and the minimum value of the output value of the photosensor when the printer apparatus is initially set. It is characterized by
The printer device according to claim 3.