Ink Jet Recording With Character Distortion Compensation

Abstract

Ink jet type recording apparatus comprising means for continuously jetting droplets of ink; an ink jet recording head provided with vertical and horizontal deflection means for vertically and horizontally deflecting the jetted ink droplet; driving means for driving the recording head, in plural steps corresponding to clock pulses and in a horizontal direction defined by the deflection means, across a recording paper during the time period in which one character is recorded; and means for sequentially generating vertical and horizontal deflection signals for respectively determining vertical and horizontal deflection amounts, in an attempt to define a character consisting of a plurality of ink droplets jetted according to the clock pulse, and supplying to the vertical and horizontal deflection means a character signal set in synchronism with the horizontal movement of the recording head.

Description

This invention relates to an improved ink jet type recording apparatus capable of correcting any character distortion caused when a recording head is moved across a recording paper so as to effect a printing.

An ink jet type recording apparatus has an ink jet recording head 11 as schematically illustrated in FIG. 1. The recording head 11 is provided with a nozzle 12 for jetting an ink droplet and an acceleration electrode 13 for accelerating the jetted ink droplet. Ink is supplied by means of an ink pump (not shown) to the nozzle 12 from the mouth of which ink droplet 14 is jetted in the particle form under an electrical field from the acceleration electrode 13. The jetted ink droplet 14 is deflection-controlled by a vertical and horizontal system 15 so that a predetermined character, figure etc. are recorded on a recording paper. In a case where characters are continuously recorded on a recording paper using the single ink jet recording head 11 the arrangement is as shown in FIGS. 2 and 3. That is, guide rails 17 are arranged opposite to and parallel to a recording paper 16. Along the guide rail 17 the recording head 11 is moved in a direction as indicated by arrows. To the deflection system 15 of the recording head 11 are fed deflection voltages corresponding to a character signal, and characters are continuously recorded horizontally across the recording paper.

In a case where characters [2] and [3] are recorded on the recording paper as shown in FIG. 4A a deflection signal corresponding to the character [2] is applied from a character signal generating circuit to the deflection system 15 during the time period in which the recording head 11 is moved over the range indicated by L.sub.1, and then a deflection signal corresponding to the character [3] is applied to the deflection system 15 during the time period in which the recording head is moved over the range indicated by L.sub.2. However, when the deflection signals corresponding to the characters [2] and [3] are applied to the deflection system 15 during the time period in which the recording head 11 is moved over the range indicated by L.sub.1 and L.sub.2, then distorted characters as shown in FIG. 4B are actually recorded on the recording paper, since the recording head is continuously moved even during the time period in which the deflection signal is generated. To avoid such a drawback, a saw-tooth signal repeated for each character is applied to the horizontal deflection system so that the amount of movement of the recording head 11 is compensated. That is, use is made of a saw tooth wave oscillator so designed that the time for the recording head to be moved an amount corresponding to one character is taken as one cycle. However, it is very difficult to make an oscillation frequency completely in synchronism with the movement of the recording head. Even if synchronism is attained at the stage of adjustment, it is often affected due to the influence of the temperature etc. Furthermore, even if the `rise` phase of the saw-tooth wave oscillator is set, for example, in synchronism with the generation of a character signal, it would be very difficult to make the `fall` phase of the oscillator correspond to the moving speed of the recording head, and it would be actually impossible to record a character and figure in substantially correct or undistorted form on a recording paper.

The object of the invention is to provide an ink jet type recording apparatus capable of recording undistorted characters on a recording paper even when a recording head is continuously moved to effect a recording. According to this invention the above-mentioned drawbacks can be overcome.

To attain such object, this invention is to provide a simplified ink jet type recording apparatus capable of driving a recording head in a manner to control the position of the recording head according to clock pulses; capable of sequentially generating a vertical and horizontal deflection signals for determining respectively vertical and horizontal deflection amounts, in an attempt to define a character consisting of a plurality of ink droplets jetted according to the clock pulse, and supplying to vertical and horizontal means a character signal set in synchronism with the horizontal movement of the recording head; and capable of causing the feed speed of the recording head and the driving of a character generating circuit to be synchronized in a predetermined relationship.

The present invention can be more fully understood from the following detailed description when taken in connection with reference to the accompanying drawings, in which:

FIG. 1 is a schematic diagram for explaining an ink jet type recording head;

FIG. 2 is a view for showing the manner in which the recording head is located;

FIG. 3 is a side view of FIG. 2;

FIGS. 4A to 4C are illustrative representations of characters recorded;

FIG. 5 is a block diagram for explaining an ink jet type recording apparatus according to one embodiment of this invention;

FIG. 6 is a graphical representation of a character for explaining the above embodiment; and

FIGS. 7A to 7D are signal waveforms for explaining the above embodiment.

There will now be described one embodiment of this invention by reference to the accompanying drawings. In FIG. 5 reference numeral 21 shows a character selecting circuit. A character signal obtained from the character selecting circuit 21 is fed to a memory circuit 22. To the memory circuit 22 is supplied a count signal, for example, from a scale-of-24 counter 24 which is counted by a signal from a clock pulse generating circuit 23. By the count signal supplied to the memory circuit 22 character signals are read out, and driven as coordinate signals in the vertical and horizontal directions, from the memory circuit 22. In a case where a figure [2] is described by a plurality of dots d.sub.1, d.sub.2 ..., for example, as shown in FIG. 6 X- and Y-axis positions of the dot d.sub.1 are firstly read out, as digital values, from the memory circuit 22 by a count signal, corresponding to a counting value (1), from the counter 24. That is, signals of Y = 20, X = 0 are derived by the counting value (1) of the counter 24. These signals are coupled to up-down counters 25 and 26 corresponding to the Y- and X-directions, respectively, where a count setting is effected. Thereafter, an output deviation from a preceding dot is obtained from the memory circuit 22. When the counting value of the counter 24 is (2) signals Y = +4, X = +4 are obtained. When the counting value of the counter 24 is (3), then signals Y = 0, X = +4 are obtained. The up-down counters 25 and 26 are count-controlled by these signals. That is, the counting value of the up-down counters 25 and 26 are varied as shown in FIGS. 7B and 7C. Digital outputs from the up-down counters 25 and 26 are supplied to D-A converters 27 and 28 corresponding to Y and X respectively. In other words, stepwise varying analog signals are obtained, as shown in FIGS. 7B and 7C, from the D-A converters 27 and 28. These analog signals are fed to differential amplifiers 29 and 30 from which Y- and X-direction differential deflection voltages 29 and 30 are supplied to paired Y deflection plates 31A, 31B and paired X deflection plates 32A, 32B.

A clock pulse from the clock pulse generating circuit 23 is applied, for example, to a ternary or scale-of-three counter 33. A carrier signal, as shown in FIG. 7A, from the ternary counter 33 is applied as a driving signal to a pulse motor 34. The pulse motor 34 is so controlled in its rotation that it advances one step for each three clock pulses. By this pulse motor 34 an ink jet type recording head is driven in a direction horizontal to a recording paper. When the pulse motor 34 is advanced eight steps the recording head is driven an amount corresponding to one character including a space. That is, ink droplets from a nozzle of the recording head are deflected at the Y- and X-deflection plates 31A, 31B and 32A, 32B so that characters are recorded on a recording paper. In this case, however, the recording head is continuously moved while character signals are successively read out. As a result, a distorted character as shown in FIG. 4B is obtained.

To avoid such a situation a counting signal is further fed to the up-down counter 26. That is, a stepwise varying digital signal as shown in FIG. 7D is derived from the counter 24 and the counting value of the up-down counter 26 is controlled. The counting value of the up-down counter 26 is so subtracted for each clock pulse that the amount of movement of the recording head is cancelled, and deflection signals from the differential amplifiers 29 and 30 cause the character to be as shown in FIG. 4C. As a result, an undistorted character is recorded on a recording paper.

With the above recording apparatus, character signals are read out by reference clock pulses and then diflection signals for recording are obtained. The movement of the recording head is effected by the clock pulse. Therefore, the character signal completly synchronizes with the movement of the recording head with the result that a character can be recorded on a predetermined area of a recording head. What is most important here is: the character signal corresponding to FIG. 4A is caused to be distorted, as shown in FIG. 4C, by the clock pulse as a reference for reading out the character signal and as a reference for moving the recording head, and is also synchronously associated with the movement of the recording head with the result that an undistorted, accurate character can be recorded on a recording paper.

According to this invention the readout of the character signal is synchronously associated with the movement of the recording head. As a result, a character deformation caused by the movement of the recording head can be corrected easily and with accuracy. Since the correction of a character, per se, the oscillation of saw-tooth waves and so on are not involved in this case, a very simplified construction results. Furthermore, there is no influence from the ambient temperature etc. and a very stable operation characteristic is also obtained.

A signal, as shown in FIG. 7D, applied to the up-down counter 26 is necessary to exist only during the time period in which a character signal is present, i.e., in a case where a character [2] is recorded, to exist until a counting value (4) is encountered. Therefore, said signal effectively works only over the range corresponding to that hatched area as shown in FIG. 7D. In those signal-free states as shown in FIGS. 7B and 7C, unnecessary ink droplets may be effectively collected in an ink collector by cutting out a supply of a signal from the counter 24 to the up-down counter 26. Though the movement of the recording head is explained as corrected by a subtractive method, it is needless to say that it may also be corrected by an additive method using a coordinate setting method.

Since a character is recorded in a distorted form due to a continuous movement of the recording head even during the deflection signal generating period, if the distorted character is stored, from the outset, in the memory circuit, then an undistorted character can be recorded on a recording paper during the movement of the recording head.

Claims

1. An ink jet type recording apparatus comprising an ink jet type recording head having means for continuously jetting droplets of ink and vertical and horizontal deflecting means arranged opposite to a recording medium for deflecting the ink droplet in vertical and horizontal directions and adapted to be movable in the horizontal direction defined by the deflecting means; means for moving the recording head in the horizontal direction; means for generating clock pulses; means set in synchronism with the clock pulse and adapted to drive said head moving means in plural steps in recording one character on the recording medium; a deflection signal supplying means set in synchronism with the clock pulse and adapted to sequentially generate vertical and horizontal signals for determining vertical and horizontal deflection amounts respectively, in an attempt to define a character consisting of a plurality of jetted ink droplets, and supply to said vertical and horizontal deflection means a character signal set completely in synchronism with the horizontal movement of the recording head, said vertical and horizontal signals being corrected

2. An ink jet type recording apparatus as claimed in claim 1 in which said deflection signal supplying means has a counter connected to the clock pulse generating means for counting in accordance with the clock pulse and adapted to sequentially generate an output signal in synchronism with the clock pulse; a memory storage connected to said counter, having signals corresponding to desired characters stored therein, and adapted to generate in synchronism with the output signal of the counter vertical and horizontal deflection digital signals for respectively determining vertical and horizontal deflection amounts so as to define a desired character consisting of a plurality of jetted ink droplets; a first D-A converter connected to the memory storage for converting the vertical deflection digital signal to an analog signal for supply to the vertical deflection means; and a second D-A converter connected to the memory storage for converting the horizontal deflection digital signal into an

3. An ink jet type recording apparatus as claimed in claim 1 in which said deflection signal supplying means has a counter connected to the clock pulse generating means for counting in accordance with the clock pulse and adapted to sequentially generate an output signal in synchronism with the clock pulse; a memory storage connected to the counter, having signals corresponding to desired characters stored therein, and adapted to generate in synchronism with the output signal of the counter vertical and horizontal signals for respectively determining vertical and horizontal deflection amounts so as to define a desired character consisting of jetted ink droplets; a first up-down counter connected to said memory storage and said counter for generating in synchronism with the output signal a vertical deflection digital signal for determining a vertical deflection amount of ink droplets; a second up-down counter connected to said memory storage and said counter for generating in synchronism with the output signal a horizontal deflection digital signal for determining a horizontal deflection amount of ink droplets; a first D-A converter connected to the first up-down counter for converting the vertical deflection digital signal to an analog signal for supply to the vertical deflection means; a second D-A converter connected to the second up-down counter for converting the horizontal deflection digital signal to an analog signal for supplying to the horizonatal deflection means.