JPH07137396A - Impact type serial printer - Google Patents

Abstract

PURPOSE:To contrive to raise a quality of a printing by regulating a parallelism of a printing head and a platen on the basis of a printing pressure automatically and with high accuracy. CONSTITUTION:A printing head 1 is conveyed along a platen 6 by means of a guide shaft 5 arranged on base plates 3, 4. An eccentric shaft 5a is set with its projecting state on a left edge section of the guide shaft 5, a coaxial thin shaft 5b is set with its projection on its right edge section and a shaft engagement in a bearing is executed freely to rotate through both base plates. A gear 8d is fixed on a projecting edge from a base plate 3 of the eccentric shaft 5. A driving motor 8a is fixed on a base plate 3 and a rotation of a driving gear 8b of this motor is transferred to the gear 8d through a transmission gear 8c. In a face 6a opposing the printing head 1 of the platen 6, four sensors 9a, 9b and 9d are built in with a space so as to form the same face as the face 6a. A printing pressure of the printing head 1 is detected by the sensors 9a, 9b, 9c and 9d, their detection signals are supplied to a control circuit, a guide shaft 5 is rotated by controlling a driving of the motor 8a and a parallelism of the printing head 1 and the platen 6 is regulated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an impact type serial printer which prints on a sheet by moving an impact type print head in a direction orthogonal to a paper feed direction in parallel with a platen.

[0002]

2. Description of the Related Art In this type of printer, when the parallelism between the print head and the platen is low, the print pressure varies greatly depending on the position where the print head moves, and the print density becomes uneven. There is. To solve this problem,
In the conventional structure, the parallelism between the platen and the print head can be adjusted as needed.

For example, in the technique disclosed in Japanese Utility Model Laid-Open No. 4-60449, one end of a pair of guide shafts for guiding the print head is eccentrically supported, and the parallelism is adjusted at one end thereof. A plate, a parallelism adjusting lever, and a connecting means for connecting the two are provided, and the parallelism between the platen and the print head can be adjusted by manually operating the parallelism adjusting lever to rotate the parallelism adjusting plate. Has become.

[0004]

However, in the above conventional structure, since the parallelism between the platen and the print head is manually adjusted, it takes time and effort to adjust the parallelism between the platen and the print head. There is a problem that the parallelism between the platen and the print head cannot be adjusted with high accuracy.

Therefore, an object of the present invention is to provide an impact type serial printer capable of automatically and highly accurately adjusting the parallelism between the platen and the print head.

[0006]

In order to achieve the above object, the present invention is an impact type serial printer which prints on a sheet by moving an impact type print head parallel to a platen in a direction orthogonal to a paper feeding direction. A guide shaft that guides the print head along the platen and is rotatably supported at both ends, and a guide shaft that has an eccentric shaft at one end on the bearing side and a drive that drives the guide shaft to rotate. Means, a plurality of sensors that face the print head via the paper and detect the printing pressure of the print head, and drive the drive means based on the detection signals from the sensors to rotate the guide shaft, And a control means for adjusting the platen in parallel.

When the above platen is fixed,
A plurality of sensors may be fixedly provided at intervals on the platen.

A plurality of sensors may be fixedly provided outside the printing area adjacent to the platen.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. As shown in FIGS. 1 and 2, the impact-type print head 1 is mounted on a carriage 2 and guided by a guide shaft 5 erected by base plates 3 and 4 to move right and left along a platen 6. It is to be transported. That is, the guide hole 2a is formed in the carriage 2, and the guide shaft 5 is slidably passed through the guide hole 2a. Behind the guide shaft 5, the fixed guide 7 is provided with the main plates 3 and 4.
A guide piece 2b provided at the rear end of the carriage 2 is slidably received on the fixed guide 7.

The structure for rotatably bearing the guide shaft 5 on the base plates 3 and 4 will be described below. An eccentric shaft 5a is projectingly provided at one end (left end) of the guide shaft 5, and the eccentric shaft 5a rotatably penetrates the main plate 3 and projects to the outside of the main plate. A concentric thin shaft 5b is provided at the other end (right end) of the guide shaft 5, and the thin shaft 5b rotatably penetrates the main plate 4 and projects outward.

The guide shaft 5 is rotationally driven by the driving means 8. That is, the drive motor 8a is fixed to the main plate 3,
The rotation of the drive gear 8b of this motor is transmitted to the gear 8d provided on the eccentric shaft 5a via the transmission gear 8c, and the guide shaft 5
I am trying to rotate. Therefore, since the guide shaft 5 rotates about the eccentric shaft 5a, the left end portion of the guide shaft 5 approaches and separates toward the platen 6, and the distance between the guide shaft 5 and the platen 6 can be delicately changed.

The platen 6 is fixedly installed on the base plates 3 and 4 and has a square cross section. The surface 6a facing the print head 1 is provided with a plurality of (four in this example) sensors 9a at intervals. , 9b, 9c, 9d are buried so as to be flush with the surface 6a of the platen 6.

A ribbon cassette 10 is set behind the print head 1 on the carriage 2, and an ink ribbon 10a pulled out from the ribbon cassette 10 passes between the print head 1 and the platen 6 and is wound around. .

Each of the sensors 9a, 9b, 9c, 9d faces the print head 1 via the paper which is conveyed between the ink ribbon 10a and the platen 6 in the direction perpendicular to the paper surface of FIG. The printing pressure of 1 is detected.

As shown in FIG. 3, the sensors 9a, 9b, 9
The printing pressure detected by c and 9d is converted into a current / voltage, and the detection signal thereof forms a control circuit 11 which constitutes a control means.
Sent to. The control circuit 11 calculates the parallelism between the print head 1 and the platen 6 based on the supplied detection signal, and controls the rotation of the motor 8 a via the motor drive circuit 12.

Next, the operation of the present invention will be described with reference to FIGS.
Will be described with reference to. First, after a sheet is set between the platen 6 and the ink ribbon 10a, the print head 1 is driven to perform a printing operation as usual. Sensors 9a, 9b embedded in the platen 6 by the print head 1,
When printing is performed on 9c and 9d, the pressure applied to each sensor is converted into a current / voltage, and the detection signal thereof is sent to the control circuit 11. In the control circuit 11, the comparison circuit in the control circuit calculates at which position of the platen 6 the largest printing pressure was detected based on the supplied detection signal, and the motor drive is performed based on the calculated data. A drive signal is supplied to the circuit 12. The motor 8a is driven by this drive signal, and the gear 8 is driven from the drive gear 8b through the transmission gear 8c.
Rotate d. Since the eccentric shaft 5a rotates due to the rotation of the gear 8d, the guide shaft 5 rotates about the eccentric shaft 5a. By this rotation, the left end of the guide shaft 5 is moved toward or away from the platen 6 while the right end of the guide shaft 5 is kept in a fixed position, and the printing pressure on the sensors 9a, 9b, 9c, 9d is made uniform. So that the parallelism between the guide shaft 5 and the platen 6 is automatically adjusted. By adjusting the parallelism, the parallelism between the print head 1 and the platen 6 is automatically and highly accurately adjusted. After that, if the printing operation is performed as usual, the print head 1 and the platen 6 are separated from each other. High-precision adjustment of parallelism prevents uneven printing density,
Uniform and good quality printing is possible.

Even if the parallelism between the print head 1 and the platen 6 changes due to some reason during the printing operation, the printing pressure is applied by the sensors 9a, 9b, 9c and 9d during the printing operation. It is also possible to detect and readjust the parallelism between the print head 1 and the platen 6.

Further, when the print head 1 generates heat due to continuous printing and the printing ability is deteriorated, or the paper is not fed correctly, the printing pressure detected by each of the sensors 9a, 9b, 9c, 9d is changed. Since the value is abnormal, it is possible to notify the abnormality.

Further, it is possible to simultaneously inspect whether or not the print pin of the print head 1 is damaged from the print pressure detection data.

As another embodiment of the present invention, sensors are fixedly provided adjacent to the platen outside the left and right sides of the print area, and the print head is moved to the left and right sides of the print area prior to the printing operation. It is also possible to print on both sensors, detect the printing pressure by both sensors, adjust the parallelism between the guide shaft and the platen by the control means in the same manner as described above, and then print. In this case, not only the type in which the platen is fixed, but also the type in which the platen rotates when the sheet is fed is applicable.

[0021]

As described above, according to the present invention,
A plurality of sensors for detecting the printing pressure of the print head are provided in opposition to the print head, and the rotation of the guide shaft is controlled by the control means based on the detection signal from each sensor so that the guide shaft and the platen become parallel. The platen and print head parallelism can be adjusted automatically and with high accuracy based on the printing pressure, which simplifies the parallelism between the platen and print head and improves the print quality. There is a remarkable effect of improving.

[Brief description of drawings]

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

FIG. 2 is an enlarged sectional view taken along the line AA of FIG.

FIG. 3 is a block diagram of a drive circuit of the present invention.

[Explanation of symbols]

 1 impact type print head 5 guide shaft 5a eccentric shaft 6 platen 8 driving means 9a, 9b sensor 9c, 9d sensor 11 control means

Claims (3)

[Claims] 1. An impact type serial printer which prints on a sheet by moving an impact type print head in a direction orthogonal to a paper feed direction in parallel with a platen, wherein the print head is guided along the platen, and A guide shaft that is rotatably supported at both ends and that has an eccentric shaft at one end on the bearing side; drive means that drives the guide shaft to rotate; and the print head through the paper. A plurality of sensors that face each other and detect the printing pressure of the print head, and the driving means are driven to rotate the guide shaft based on the detection signals from the sensors, and the guide shaft and the platen are parallel to each other. An impact type serial printer, comprising: 2. The impact serial printer according to claim 1, wherein the platen is fixed, and the plurality of sensors are fixedly provided on the platen at intervals. 3. The impact serial printer according to claim 1, wherein the plurality of sensors are fixedly provided outside the printing area adjacent to the platen.