JPH10315559A - Apparatus for controlling position of print head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To elaborately control a position of a print head by a low-resolution encoder fence. SOLUTION: A plurality of encoder sensors 13a-13c are mounted to face an encoder fence 14 of a print head 11. A signal acquisition timing of each encoder sensor is set to be a (m-a/n) pitch multiple of a resolution of the head when (m) is an arbitrary positive integer, (n) is a count of set encoders, and (a) is a positive integer smaller than (n).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an on-demand type print head, and more particularly to a print head position control suitably applied to an ink jet printer.

[0002]

2. Description of the Related Art Conventional on-demand print heads,
In particular, the print head position control device of the ink jet printer forms a slit of the encoder fence in accordance with the resolution of the head, and determines the position with one pitch of the slit as a minimum control dimension. Normally, a head resolution up to 300 dots / inch (300 dpi) can be dealt with by existing technologies and products for both the encoder fence and the encoder sensor. However, when a resolution exceeding 300 dpi is required, the production capacity of the encoder fence is exceeded ( Since the pitch of the slits is extremely small and cannot be manufactured), a corresponding solution is used in which one pitch of the encoder is time-divided. However, in this solution, the control of the integer pitch is the control of the position, but the control of less than one pitch is a control of time, and the essential condition is that the speed between the pitches is constant. For example, if a servo motor is used as the print head drive motor, it is easy to control and the price is low, but it is difficult to make the head speed uniform, so that the printing accuracy is poor and moire is generated on the print sample. there were. If a stepping motor is used as the drive motor for the print head, the speed within one pitch can be made fairly uniform by controlling the phases, but the motor control becomes complicated and a high-resolution stepping motor is required, which is expensive. There was a problem.

[0003]

In the conventional print head position control apparatus, problems in print quality such as poor printing dot placement accuracy and moiré of a print sample occur in high-resolution position control of 300 dpi or more. was there.

[0004] It is an object of the present invention to provide a print head position control device capable of handling high resolution.

[0005]

In order to achieve the above object, an on-demand print head, a shaft slidably supporting the print head, a fixing plate for fixing the shaft, and a shaft parallel to the shaft are provided. An ink jet printer comprising a stretched encoder fence, an encoder sensor fixed to the print head, and print head sliding means, wherein a plurality of the encoder sensors are attached to the print head, and each encoder sensor Is obtained at the head resolution (m
−a / n) It is set to be a pitch multiple.

Here, m: an arbitrary positive integer n: the number of encoder sensors installed a: a positive integer smaller than n The print head sliding means drives a timing belt attached to the print head and the timing belt. And a motor that performs the operation.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention has been devised with an encoder sensor and an encoder fence for detecting the operation and position of a print head in order to adapt to the high resolution of the print head. For example, in order to perform 900 dpi position control using a 300 dpi encoder fence, it is possible to divide the interval between signals read from the encoder sensor into three by interpolation. However, position control does not work well because unevenness occurs in the motor feed or the head feed speed is not uniform during the print head acceleration / deceleration stage. Therefore, by reading one pitch of the encoder fence by dividing it by a plurality of encoder sensors, for example, 900 dpi position control is enabled.

Hereinafter, the present invention will be described with reference to the drawings.
FIG. 1 is a perspective view of a main part of an on-demand type ink jet printer to which the present invention is applied. The inkjet printer 1 includes a print head 11, a shaft 15 slidably supporting the print head, and a rear shaft 16.
A fixing plate 20 for fixing the shafts 15 and 16, an encoder fence 14 stretched in parallel with the shafts, and a plurality of encoder sensors 13 a, 13 b, and 13 c fixed to the print head 11. I have. The print head sliding means includes a timing belt 18 and a drive motor 19. Reference numeral 21 denotes a fastener for attaching the encoder fence 14 to the fixing plate 20. Reference numeral 12 denotes an orifice hole.

FIG. 2 is a diagram schematically showing the positional relationship between the encoder fence 14 and a plurality of encoder sensors 13a, 13b, 13c attached to the print head 11. As shown in FIG. In the encoder fence 14, black and white stripes are formed at equal intervals for each pitch. When the signal sensing position of the encoder sensor 13a comes to the black / white boundary position of the encoder fence, the signal sensing position of the second encoder sensor 13b is set to (4-1 / 3) pitch, and the signal of the third encoder sensor is changed. 13a from the sensing position (7-2 / 3)
They are arranged to have a pitch.

FIGS. 3 and 4 show examples of an embodiment for newly generating a high-density signal from the signals of the three encoder sensors shown in FIG. 2. FIG. 3 is a block diagram and FIG. 4
Is a timing chart. In FIG. 3, the position sensing signal from the encoder sensor 13a is connected to the line a, the position sensing signal 13b is connected to the line b, the position sensing signal 13c is connected to the line c, and the output signal is d.
Take out. FIG. 4 is a timing chart showing the signals a, b, c, and d. The signal a is generated at intervals when the signal moves by one pitch. The signal b is shifted from the signal a by 1/3 pitch to generate a signal, and the signal c is shifted from the signal a by 2/3 pitch to generate a signal. Next, the output signal d is obtained by taking the sum of the generated signals,
A signal is generated every three pitches.

The operation of the above embodiment will be described below. When a control signal is input to the drive motor 19, the motor rotates and the print head 11 attached to a part of the timing belt 18 can be moved along the shafts 15, 16. In the case of one encoder fence and one encoder sensor 13a, one of the encoder fences
Although it can only take in signals for each pitch, the signal sensing position of the encoder sensor 13b is
3 (a) is arranged at a pitch of (4-1 / 3) with respect to the signal sensing position, and the signal sensing position of the encoder sensor 13c is (7-2 / 3) with respect to the signal sensing position of the encoder sensor 13a.
If the head is moved along the encoder fence, the encoder sensor 13
After the position sensing signal a is generated, the next position sensing signal can be generated from the encoder sensor 13b when the head moves 1/3 pitch. Hereinafter, when the head further moves by 1/3 pitch, a position sensing signal is generated from the encoder sensor 13c, and high-definition control can be performed as if it were controlled by a 900 dpi encoder fence. Similarly, the number of encoder sensors is n, and the signal generation distance between adjacent encoder sensors is (m-1 / n).
If the pitch is (m: any positive integer), (300 ·
n) It is possible to control the position of the print head with high definition of dpi.

[0012]

As described above, according to the present invention,
High resolution printhead position control is possible with a low resolution encoder fence.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an embodiment of an ink jet printer to which the present invention is applied.

FIG. 2 is a schematic diagram showing a positional relationship between the print head and an encoder fence.

FIG. 3 is a block diagram of the same input / output signal formation.

FIG. 4 is a timing chart of the same.

[Explanation of symbols]

11 is a print head, 13a, 13b and 13c are encoder sensors, 14 is an encoder fence, 15 is a shaft, 18 is a timing belt, 19 is a motor, and 20 is a fixed plate.

Claims (1)

[Claims] 1. An on-demand printhead, a shaft slidably supporting the printhead, a fixing plate for fixing the shaft, an encoder fence stretched parallel to the shaft, and fixed to the printhead. An ink jet printer comprising an encoder sensor provided and a print head sliding means, wherein a plurality of the encoder sensors are attached to the print head, and the signal acquisition timing of each encoder sensor is set to (m- a / n) pitch times where m: any positive integer n: number of encoder sensors installed a: a positive integer smaller than n