JPH05221080A - Automatic adjustment mechanism of printer head - Google Patents

Abstract

PURPOSE:To save the time and labor required for fine adjustment and at the same time, obtain the setting value of a highly stable gap. CONSTITUTION:A printing head is of such a structure that a distance between the head and a platen can be changed using a stepping motor 14, and is activated by a command from a motor rotation command part 20. In addition, a slit disc 7 and a slit sensor 8 determine whether the printing head comes in contact with the surface of a printing sheet. If the tip of the printing head comes in contact with the surface of the printing sheet 10 following the movement of the printing head 1 in a pressing direction using the stepping motor 14 and then the out-of-step state of the stepping motor 14 is detected, during a gap adjustment action, the stepping motor 14 is reversed by a constant number of steps SG+SO to fetch back the printing head. After that, the stepping motor 14 is rotated by SO step again in the pressing direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control method of a mechanism for keeping a distance between a print head tip and a print paper upper surface constant in a printer.

[0002]

2. Description of the Related Art A conventional apparatus, as described in Japanese Patent Laid-Open No. 59-153131, detects a contact of a print head with the surface of a printing sheet and then pulls back a certain amount.

[0003]

However, the above-described invention technique does not consider the backlash existing in each part of the drive mechanism. (1) Since the backlash is different for each unit, the pullback amount in the stepping motor is different. Even if they are the same, the actual gap setting amount will vary from unit to unit. Therefore, in order to eliminate this variation, the pullback amount is finely adjusted for each machine, and the adjustment requires a lot of time and labor.

(2) There is a clearance between the carrier and the support rail, and the print head and the carrier move by the clearance due to the reaction force when the print head operates. Therefore, an accurate gap amount cannot be maintained.

There was a problem.

It is an object of the present invention to eliminate the variation for each machine, to save the time and labor required for fine adjustment, and to obtain a stable gap setting amount even when the print head is operating.

[0007]

The object is to move the print head toward the print paper first, that is, in the pressing direction, and to move away from the print paper when it is detected that the print head contacts the surface of the print paper. That is, it is achieved by moving a certain amount in the pullback direction and then again moving in the pressing direction.

[0008]

[Function] First, the print head is moved toward the print paper, that is, in the pressing direction, and when it is detected that the print head contacts the surface of the print paper, the print head is moved away from the print paper, that is, the pullback direction by a certain amount. , And then move it again in the pushing direction. Then, the backlash of each part of the drive mechanism is crushed and the influence of the backlash disappears, the variation between machine numbers disappears, and the gap setting amount does not change due to the reaction force during printing.

[0009]

EXAMPLES The following is an example of the present invention.

First, the mechanism will be described with reference to FIGS. 1 and 2.

A left side frame 12a and a right side frame 12b are fixed to the underframe 13, and a fixed support rail 3 is provided between them.
The carrier 2 on which the print head 1 is placed is guided by the fixed support rail 3 and the eccentric support rail 4 and can move in the B direction. A platen 11 is rotatably supported on the left side frame 12a and the right side frame 12b, and the printing paper 10 is wrapped around this plate for about half a circumference. When the print head 1 is operated while moving the carrier 2 in the B direction, the ink of the ink ribbon 9 is transferred to the print paper 10, that is, printed.

The eccentric support rail 4 is rotatably supported by the left side frame 12a and the right side frame 12b, and a gear 5 is attached to the right end thereof. However, since the center axis of the eccentric support rail 4 is deviated from the rotation center axis of the gear 5, when the gear 5 rotates, the carrier 2 and the print head 1 move in the A direction. Since the gear 5 is driven by the pinion 6 attached to the shaft of the stepping motor 14, the tip of the print head 1 and the platen 1 are driven by the stepping motor 14.
It is possible to change the distance from 1. A slit disk 7 is also attached to the shaft of the stepping motor 14, and the rotation state can be known by the slit sensor 8. Although the head 1 is described as being of the wire dot type, the same applies to the case of a thermal type or an inkjet type.

Next, the control unit will be described with reference to FIG.

The motor rotation command unit 20 outputs a rotation command and a rotation direction command based on external conditions such as the presence or absence of printing paper and a step-out signal from the step-out determination unit 19. The oscillator 21 generates a phase advance timing pulse in response to this rotation command. In this embodiment, a stepping motor is used in a self-starting method to simplify control, and the advance pulse rate is constant at 300 pps. Needless to say
This advance pulse rate may be another value. The advance timing pulse and the rotation direction command are distributed to the signal for each phase by the pulse generator 16 and then input to the drive circuit 15. The driving method may be either constant voltage or constant current, or two-phase excitation or 1-2-phase excitation. Although the stepping motor is used as the power source in the present embodiment, it does not matter if a DC magnet motor or the like is used and the drive circuit is changed to a suitable one.

The voltage output from the drive circuit 15 is applied to and driven by the stepping motor 14. The rotation state of the stepping motor 14 is pulsed by the slit disk 7 and the slit sensor 8 and sent to the pulse interval t _f measuring unit 18. On the other hand, the advance timing pulse is also measured by the pulse interval t _c measuring unit 17, and t _f
If the difference t _d between t _c and t _c exceeds a certain ratio with respect to t _c , the step-out determination unit 19 determines that the step is out of step, that is, the print head 1 contacts the surface of the printing paper 10. In this embodiment, when | t _d / t _c |> 0.3, it is set to determine that the step is out of step. The optimum value of this judgment value changes depending on the mechanism of the printer, and the value of 0.3 is obtained experimentally. Note that the above control may be implemented by software or hardware. Further, the method of detecting that the print head 1 has come into contact with the surface of the printing paper 10 may be a method other than that shown in this embodiment, for example, a method using a dedicated contact sensor.

FIG. 4 is an overall operation diagram including the setting of the gap.

In the gap adjusting operation, first, the print head 1 is moved in the pressing direction by the stepping motor 14. As for the positional relationship between the eccentric support rail 4 and the carrier 2 at this time, as shown in FIG. 5, the platen side is in contact. Next, when it is detected that the tip of the print head 1 comes into contact with the surface of the print sheet 10 and the stepping motor 14 is out of step, the stepping motor 14 is reversed by a certain number of steps S _G + S _O and the print head 1 is pulled back. . At this time, the positional relationship between the eccentric support rail 4 and the carrier 2 has a clearance on the platen side as shown in FIG. Here, when the stepping motor 14 is further rotated in the pressing direction by S _O step, the state shown in FIG. 5 is obtained again, and the reaction force F at the time of printing can be reliably transmitted to the eccentric support rail 4 by the contact. it can. Therefore, the carrier 2 does not move due to the reaction force F, and the gap setting amount is maintained. At this time, the backlash between the gear 5 and the pinion 6 is also crushed, so that the backlash is not affected. Thus, the gap setting operation is completed and printing is started. The value of S _O should be larger than the value corresponding to the total of all the backlashes of the drive system, such as the backlash between the eccentric support rail 4 and the carrier 2 and the backlash between the gear 5 and the pinion 6. I have to keep it.

[0018] pullback during operation moves the print head 1 in the pull-back direction, the stepping motor 1 in the direction pressed only S _H step Once you have detected that hit the stopper
Rotate 4 to stop. The reason for moving only S _H steps is to prevent overloading the stopper.

Although the above description is for the case where the moving direction A of the print head 1 and the carrier 2 is horizontal, the inclination of the moving direction A becomes large, and the fixed support rail 3 is located at a position higher than the eccentric support rail 4. If the stepping motor 14 comes to the end, the print head 1 and the carrier 2 may slide down due to their own weight without rotating the stepping motor 14, and the state of FIG. 5 may naturally change to the state of FIG. In this case, there is no point in rotating the stepping motor 14 in the pressing direction again. Therefore, the moving direction A must be in the horizontal direction or a state close thereto.

[0020]

According to the present invention, since the backlash of each part of the drive mechanism is crushed at the end of the gap setting, there is no variation in the gap setting amount among the machines.
The gap setting amount does not change due to the reaction force during printing.

[Brief description of drawings]

FIG. 1 is a side view of a mechanism portion of the present invention.

FIG. 2 is a plan view of a mechanism portion of the present invention.

FIG. 3 is a control block diagram of the present invention.

FIG. 4 is an overall operation diagram of the present invention.

FIG. 5 is an explanatory diagram of a positional relationship between a carrier and an eccentric support rail when moving in a pressing direction.

FIG. 6 is an explanatory diagram of a positional relationship between a carrier and an eccentric support rail when moving in a pullback direction.

[Explanation of symbols]

7 ... Slit disk, 8 ... Slit sensor, 14 ... Stepping motor, 15 ... Drive circuit, 16 ... Pulse generating unit, 17 ... Pulse interval t _c measuring unit, 18 ... Pulse interval t
_f measurement unit, 19 ... step-out determination unit, 20 ... motor rotation command unit, 21 ... oscillation unit.

Claims (1)

[Claims] 1. A printer in which a printing paper having an arbitrary thickness is mounted on a platen, and printing is performed on the printing paper while moving the printing head in the axial direction of the platen, the printing head is perpendicular to the printing direction. A device for moving the print head toward the print sheet, and moving the print head away from the print sheet after detecting that the print head has come into contact with the surface of the print sheet, An automatic adjusting mechanism for a printer print head, wherein the print head is moved toward the print sheet again.