JPS61262161A - Mechanism for automatically adjusting printing head of printer - Google Patents

Abstract

PURPOSE:To make it possible to stably set the gap of a printing head to a predetermined amount, by constituting the titled mechanism from a stepping motor for moving a carriage forwardly and rearwardly, a detection element for detecting an initial position and generating a feedback pulse with the movement of the carriage from said position and a control part for processing a signal. CONSTITUTION:When printing data is received, a microprocessor 27 rotates a stepping motor 22 and a carriage 2 is stopped at an initial position where a feedback pulse is not outputted from a slit detection element 25. Next, the stepping motor 22 is reversely rotated and the judgement is performed on the basis of the difference between the number of forward signals and the increase amount of the number of the feedback pulses from the slit detection element 25 to stop the stepping motor 22. The total of the feedback pulses from the initial position to the stop position is compared with the memory of a feedback pulse-paper thickness memory part 28b to judge the absolute thickness of paper. Next, the carriage is moved so as to adjust a printing head gap optimum to paper to be used on the basis of the information from a paper thickness- carriage position memory part 28c before printing operation is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an automatic adjustment mechanism for the distance between a print head tip and a platen.

(Prior Art) As is well known, the printing operation of a wire dot print head is performed by driving a p-dot wire by a drive mechanism within the print head in response to a print signal, and causing the tip of the p-dot wire to protrude from the front end surface of the print head. The paper on the platen is struck through the ink ribbon and the ink ribbon, thereby printing characters, symbols, etc. in the form of dots on the paper.

Therefore this kind of in/? In print printers, in order to increase the printing speed, it is necessary to make the dot wire operating stroker as small as possible. However, there are many different types of paper used in printers, and the paper thickness is also 0.
．． There is a wide range of paper thickness, from as thin as 0.5W to over 0.6wm, and printers adjust the distance between the platen and the tip of the print head (
After that, it is necessary to adjust the printing bed gap). As a technique for automatically adjusting the rad gap for printing on various thicknesses of printing paper, for example, there is
No. 153131, a stepper motor is used to move the print head to the paper placed on the platen, the print head is brought into contact with the paper to cause the stepping motor to step out, and then the stepper monitor is ignored and the step is set in advance. After continuing to send a certain input pulse to the stepping motor, a certain input pulse that causes the stepping motor to rotate in the reverse direction is given to set the rad gap for printing to a predetermined JiK.

(Problem to be Solved by the Invention) However, in such a conventional configuration, even after the stepping motor contacts the print head, constant input pulses are continued to be sent, ignoring step-out of the stepping motor. Therefore, the paper pressing force of the print head becomes unstable due to the severe vibration phenomenon that occurs when the stepping motor goes out of step. As a result, the print head presses the paper further than the position at which it first contacted the paper, causing the guide shafts of the platen and carriage to change, resulting in a change in the contact position of the print head. In this way, with the conventional method of ignoring step-out of the pulse motor and sending constant input pulses, the contact position of the print head may not be stable between two positions: the position at the start of step-out and the final position of adjustment. It became clear. Therefore, if the paper thickness used is different, it is input after the stepping motor tax adjustment is started. p'l? Since the number of pulses is not constant, there is a drawback that the position where the print head finally contacts the paper is not stable. That is, even if a constant input pulse that causes the stepping motor to rotate in reverse is applied to the stepping motor, it is difficult to stably set the rad gap for printing to a predetermined amount.

The present invention aims to solve such problems.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention includes a stepping motor that moves a carriage on which a print head is mounted back and forth in a direction perpendicular to the platen axis, and detects the initial position of the carriage. It is composed of a detection element that generates a feedback pulse generated as the carriage moves from its initial position, and a control section that processes the signal from the detection element.

(Function) According to the present invention having the above-described means, it is possible to perform control to detect the position where the print head first contacts the paper by the feedback pulse when the stepping motor starts adjusting the paper, and therefore, the paper thickness used by the printer can be controlled. Since the absolute thickness of paper can always be detected stably even over a wide range of thickness, the above-mentioned problem can be eliminated.

(Example) Examples will be described below with reference to the drawings.

FIG. 1 is a left side view of the printer according to the present invention, FIG. 2 is a right side view of the printer according to the present invention, FIG. 3 is a plan view of the printer according to the present invention, and FIG. 4 is a block diagram of the control unit. It is.

In the figure, 1 is a print head, 2 is a carriage on which the print head 1 is mounted, and 3 is a protector. It protrudes slightly from the tip of the print head 1 to prevent the paper from being stained by the print head 4. 5 is a platen, 6 is a platen shaft, and both ends of this platen shaft are side frames 7.
．． It is rotatably supported by 8. Reference numeral 9 designates a guide shaft that penetrates and engages the front portion of the carriage 2, and 10 designates a slide beam that engages with a bearing 11 and a guide 12 provided at the rear portion of the carriage 2. Both ends of the guide shaft 9 are slidably and rotatably fitted into elongated holes 12.13 provided in the side frame 7.8, and both ends of the slide beam 10 are fixed to the side frame 7.8. The carriage 2 is supported so that it can move parallel to the platen 5 and can also move in a direction perpendicular to the platen axis 6 together with a guide shaft 9. The tab carriage 2 is movable in the direction of arrow A shown in FIG. 3 by a drive source and a power transmission mechanism (not shown).
The guide shaft 9 also moves in the direction of arrow B.
is supported by

14 and 15 are cams fixed to both ends of the guide shaft, respectively. 16.17 is a cam follower rotatably supported by the side frame 7.8. 18.19
from both ends of the guide shaft to the side frame 7.8
A spring tensioned in the guide shaft 9 biases the guide shaft 9 in one direction to move the carriage 2 in one direction.

20 is a driven gear fixed to the left end of the guide shaft 9. Reference numeral 21 denotes an idle gear provided substantially directly below the driven gear 20, and is rotatably supported by the side frame 7. 22 is a stepping motor that engages with an idle gear, and a motor gear 23 is fixed to the motor shaft. A slit disk 24 is fixed to the right end of the guide shaft 9 and has a slit portion 24a and a non-slit portion 24b. , 25 is a slit disk 24
This is a slit detection element arranged at the bottom of the .

26 is paper, and the carriage 2 rotates the platen 50 times.
It moves in a direction perpendicular to the spacing direction.

Next, a control section that controls the above-mentioned mechanism will be explained.

The same parts as mentioned above will be indicated by the same reference numerals as shown above. Reference numeral 26 denotes a drive circuit for driving the stepping motor, which operates the stepping motor 22 in accordance with an input arm command from the microprocessor 27.

28 is a control graph 28m for operating the microprocessor, a feedback pulse for determining the paper thickness according to the number of feed pack pulses from the slit detection element 25, and a paper thickness storage section 28b, which is most suitable for the paper thickness. The paper thickness/carriage position storage section 28c stores the position of the carriage in the B direction.

The operation of the embodiment with the above-described configuration will be explained.

When the paper 26 is mounted on the platen 5 and print data is transmitted from a host computer (not shown), the microprocessor 22 sends a reverse signal to the stepping motor drive circuit 2 to rotate the stepping motor 22 to the left.
6 and is fed back from the slit detection element 25, pJ? The stepping motor 22 rotates until the position where no pulse is output (carriage initial position) and then stops. When the tipping motor 22 rotates to the left, the drive gear 21, driven gear 20. The carriage 2 moves in a direction to widen the rad gap for printing via the cams 14, 15 and the guide shaft 9, and the carriage 2 stops at the initial position. Next, the microprocessor 27 outputs a forward signal to the stepping motor drive circuit 26 to rotate the stepping motor 22 clockwise. In other words, the stepping motor 22 moves the carriage 2 from the initial position toward the platen S. As the forward signal continues to be sent, the paper 26 becomes stuck to the carriage 2, and the distance between the gongro protector 3 and the paper 26 becomes narrower, and finally, 9. The roller protector 3 and the paper 26 come into contact. As the forward signal continues to be sent, the load on the stepping motor 22 gradually increases, but as long as the rotational force of the stepping motor 220 is greater than the load, the carry and tsuji 2 continue to push the platen 5 through the paper 26, and the platen 5 and guide The shaft 9 is elastically deformed. When the carriage 2 moves forward to a position where the total load of the forward force of the carriage 2 due to 220 rotations of the stepping motor, the friction load of the carriage longitudinal movement mechanism, and the load due to elastic deformation of the platen 5 and guide shaft 90 is combined, the stepping motor 22 starts to lose synchronization from time to time. (At the initial stage of step-out
.

Becomes constantly out of step. The adjustment torque of the stepping motor generated by the vibration during this step-out is larger than the normal rotational torque, so the cam J4.15 rotates further and the carriage 2 gradually moves to a position further advanced than the initial position of the adjustment. Eventually, it will stop (at the end of the tax adjustment period). In the present invention, the microprocessor 27 constantly counts the number of forward signals output to the stepping motor drive circuit 26 and the number of feedback pulses from the slit detection element 25, and compares the amount of increase in the two.

Therefore, the number of forward signals to the stepping motor drive circuit 26 is determined by setting the initial position of the adjustment as a decrease in the rotational speed of the cam, rather than the final adjustment position where the stepping motor 22 violently vibrates during step-out and the rotation of the cam 14.15 stops. The rotation of the stepping motor 220 is stopped based on the difference in the amount of increase in the number of feedback pulses from the slit detection element 25.

As an example, the amount of carriage advance corresponding to the forward signal l pulse to the stepping motor drive circuit 26 is 0.
003125m, the method of the present invention has an accuracy of 0.07-0.07 mm compared to the conventional method that ignores the tax adjustment and continues to send the forward signal to the stepping motor 22.
It has been experimentally confirmed that the degree of improvement (equivalent to the thickness of a single sheet of ordinary paper) has been improved. On the other hand, in the control section, the total number of feedback pulses from the initial position of the carriage 2 to the stopping position of the stepping motor is counted by the microprocessor 27, and is stored in advance in the feedback pulse-paper thickness storage section 28b. The absolute paper thickness corresponding to the paper thickness is read out to determine the absolute thickness of the paper. Next, based on the information from the paper thickness/carriage position storage section 28c, the carriage 2 is moved so that the rad gap is optimal for printing on the paper being used, and then the printing operation is performed.

(Effects of the Invention) As explained in detail above, the present invention detects the position where the print head contacts the paper using feedback pulses from the slit disk fixed to the cam and the slit detection element, causing the stepping motor to step out of step. Since the detection can be performed at the early stage of tax adjustment before the vibration occurs, there is an advantage that the contact between the print head and paper can always be detected stably regardless of the thickness of the paper.

In addition, since the slit disk has a slit section and a non-slit section, there is no need to return the carriage to the initial position after the paper comes into contact with the glue protector in order to detect the absolute thickness of the paper. Therefore, the paper thickness detection time can be significantly shortened.

Further, since there is no clutch in the carriage moving mechanism from the stepping motor to the carriage, there is no fear that the print head gap will change due to vibrations caused by horizontal movement of the carriage or printing operations of the print head.

In addition, since the absolute thickness of the paper is determined based on the number of feedback pulses from the slit detection element, depending on the number of stacked sheets of paper used, for example, if there are many stacked sheets, the stacking of paper such as paper stapler etc. In consideration of the fact that the total thickness of the paper is thicker than the total thickness of the paper, the distance between the print head and the paper may be set slightly wider depending on the total thickness of the paper.

[Brief explanation of the drawing]

FIG. 1 is a left side view of the printer according to the present invention, FIG. 2 is a right side view of the printer according to the present invention, FIG. 3 is a plan view of the printer according to the present invention, and FIG. 4 is a printer according to the present invention. It is a block diagram of the control part of. 1: Print head, 2: Carriage, 3: Rizan protector, 5 Ni platen, 9 Ni guide shaft, 12: Long hole,
13: Long hole, 14: Cam, 15: Cam, 16: Cam follower, 17: Cam follower, 2o drive gear, 21
22 Ni dripping motor, 24 Ni slit disk, 25 Ni slit detection element, 27: Microprocessor, 28: Storage section.

Claims (1)

[Claims] In a printer in which paper of any thickness is mounted on a platen and the print head is moved along the axis of the platen to print on the paper, the carriage carrying the print head is set perpendicular to the axis of the platen. a stepping motor that moves the carriage back and forth in the direction; a detection element that detects feedback pulses generated as the carriage moves from the initial position; and a control unit that processes the feedback pulses from the detection element; The carriage moves from the initial position to the platen side, the carriage comes into contact with the paper, and detects that the stepping motor has started to step out by a change in the amount of increase in feedback pulses from the slit detection element; An automatic printing head of a printer characterized in that the absolute thickness of the paper is determined based on the number of feedback pulses from the position to the position where it contacts the paper, and the carriage is moved to the optimal position for the thickness of the paper used. Adjustment mechanism.