JPH059960U - Automatic gear adjustment mechanism - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a mechanism for accurately adjusting a gap between a print surface of a paper and a print head with a simple structure by a non-contact method. A carriage driven by a pulse motor through a gear so as to move forward and backward with respect to a platen, a print head mounted on the carriage, and a print head mounted on the carriage in the vicinity of the print head. It is composed of a reflection type photo sensor, a paper pressing plate arranged along the platen, and a gap detecting protrusion provided on the paper pressing plate. [Effect] The gap can be adjusted without bringing the paper and the print head into contact with each other.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an automatic adjustment mechanism of a gap between a print surface of a paper and a print head in a printer having a paper transport function in which a print head mounted on a carriage prints by printing or ejecting ink.

[0002]

[Prior Art]

 As a conventional method for adjusting the gap between the print surface of the paper and the print head, for example, as disclosed in Japanese Patent Publication No. 2-6169, printing is performed by controlling the rotation speed of a motor for moving the print head. There is a method of adjusting the gap by making the force with which the tip of the head hits the paper constant. Further, as disclosed in Japanese Patent Laid-Open No. 62-44480, there is also a method of adjusting the gap by using a slip clutch to make the force with which the tip of the print head abuts on the paper to be constant. Further, as disclosed in Japanese Patent Laid-Open No. 61-199969, a detection piece at the rear of the carriage, which is moved by advancing a platen sandwiching a sheet toward a print head and pushing up the print head, is an interrupt type. There is a method of adjusting the gap by detecting the paper thickness by detecting with a photo sensor.

[0003]

[Problems to be solved by the device]

 However, the above-mentioned conventional method has a drawback in that the print head comes into contact with the paper, so that the paper is contaminated, and in the case of copying paper, the second and subsequent papers are also contaminated. Further, since the sheet thickness is converted into force or the amount of rotation of the carriage for detection, a large number of gears, clutches or movable parts are required, which complicates the structure. Therefore, there have been problems such as detection error and poor reliability.

In order to solve the above problems, an object of the present invention is to provide a mechanism for accurately adjusting the gap between the print surface of the paper and the print head with a simple structure by a non-contact method.

[0005]

[Means for Solving the Problems]

 In order to achieve the above object, the present invention provides a print head mounted on a carriage that can move forward and backward, a reflection type photosensor disposed near the print head on the carriage, a paper pressing plate, and a paper sheet. It consists of a protrusion for gap detection provided on the pressing plate.

[0006]

[Action]

 When the carriage is moved perpendicularly to the printing surface from a position sufficiently behind the printing surface of the paper to the vicinity of the printing surface, there is a position where the output of the reflection type photosensor to the protrusion for gap detection becomes maximum. When the thickness of the paper changes, the protrusion for gap detection provided on the paper pressing plate moves by the change, but the position where the output of the reflection type photo sensor becomes maximum also moves by the same amount. The position of the protrusion for gap detection can be confirmed, and the optimum amount of print head movement can be obtained.

[0007]

【Example】

 FIG. 1 shows an embodiment of the present invention. The carriage 6 is moved forward and backward by rotating the eccentric guide shaft 11 with the pulse motor 8 via the gears 9 and 10. A reflection type photosensor-4 in which a light emitting element and a light receiving element are integrated is arranged near the tip of the print head 5 on the carriage 6 so as to face the platen 1. The gap detecting protrusion 3a provided on the paper pressing plate 3 is always provided on the path through which the paper passes, and is configured to press the paper with a weak force that does not cause a problem in conveying the paper. The gap detection protrusion 3a has a uniform surface roughness so that an output sufficiently higher than the output from the reflection type photosensor-detection surface on the platen 1 can be obtained. It is necessary to design thin so that the gap between the print surface and the print head 5 does not become too wide. In the embodiment, a metal plate having a thickness about twice the thickness of the paper is used, but plastic, polyester or the like may be used.

FIG. 2 is a diagram for explaining the gap detection principle of the present invention. The output state of the reflection type photosensor-4 to the gap detecting protrusion 3a while the carriage 6 is moving from the rearmost A to the frontmost B is shown for a thin sheet 2a and a thick sheet 2b. Are the curves 13a and 13b, respectively. For thin paper 2a, the maximum output of the reflective photosensor-4 appears at the position 131 near the platen 1, and for thick paper 2b, the maximum output of the reflective photosensor-4 is as much as the thicker paper 2b. Also appears at a position 132 away from the platen 1. That is, it is possible to keep the gap between the print surface of the paper 2 and the print head 5 constant by detecting the maximum output position of the paper of any thickness.

FIG. 3 is a flowchart of the operation of automatic gap adjustment provided by the present invention. Before the start of the gap adjustment, the carriage 6 is moved along the eccentric guide shaft 11 and the guide rail 7 so that the reflective photosensor 4 comes to a position facing the gap detecting projection 3a to be detected in advance. And move it in the direction perpendicular to the plane of the drawing. First, the output of the reflective photosensor-4 at the initial position is set to V (0), and then the output of the reflective photosensor-4 when the carriage 6 advances by one pulse of the pulse motor 8 is output. Let V (1). In order to detect the maximum output, it is necessary to move the carriage 6 in the direction in which the output increases. Therefore, if V (1)> V (0), move forward, and if V (1) <V (0), move forward. The backward movement is performed one pulse at a time, and the output of the reflection-type photosensor-4 at the Nth pulse is V (N), and the reflection-type photosensor-4 at the position of this V (N) and the immediately preceding pulse. The output V (N-1) of each is compared, and the position of the (N-1) th pulse when V (N) <V (N-1) is set as the maximum output position of the reflective photosensor-4. , And then move the carriage 6 by the designated pulse. The designated pulse here means that the control unit (not shown) provided in the printer moves the print head 5 from the position at the (N-1) th pulse to a position optimum for printing. It is the number of feed pulses given to the controller 8.

[0010]

[Effect of the device]

 In the automatic gap adjustment according to the present invention, a reflective photosensor is used for gap detection, and the gap is detected by obtaining an output from a stable surface of the protrusion for gap detection provided on the paper pressing plate. Since it is not necessary to make contact with the print head, the paper can be kept clean and the gap can be adjusted accurately and stably. Further, the drive for the automatic gap adjustment can be realized with an extremely simple structure because it is sufficient to rotate the eccentric guide shaft by the pulse motor via the gear to move the carriage forward and backward.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a diagram illustrating a gap detection principle of the present invention.

FIG. 3 is a flowchart of the operation of automatic gap adjustment provided by the present invention.

[Explanation of symbols]

 1 Platen 2 Paper 2a Thin Paper 2b Thick Paper 3 Paper Press Plate 3a Gap Detection Protrusion 4 Reflective Photo Sensor-5 Print Head 6 Carriage 7 Guide Rail 8 Pulse Motor 9 Gear 10 Gear 11 Eccentric Guide Shaft 13a Thin Paper Curve of sensor output of sensor 13b Curve of sensor output of thick paper

Claims (1)

Claims for utility model registration: Claims: 1. A carriage driven by a pulse motor through a gear so as to move forward and backward with respect to a platen, a print head mounted on the carriage, and also on the carriage. And a reflection type photosensor disposed in the vicinity of the print head, a sheet pressing plate disposed along the platen, a gap detecting protrusion provided on the sheet pressing plate, and the gap detecting protrusion. The maximum output position of the reflection type photosensor with respect to is detected by advancing and retreating the carriage, and by applying a predetermined pulse to the pulse motor with this position as a reference to move the carriage, the print head and the printing surface of the paper. An automatic gap adjustment mechanism for the printer, which consists of a means for adjusting the distance to the printer.