JPH09239966A - Recording device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid the occurrence of a white line or a black line by changing a dot diameter or a dot forming position firstly or finally formed in an each line direction independently against another dot in a recording device. SOLUTION: A constant voltage driving circuit of a piezoelectric element corresponding to a tip nozzle is independent of another constant voltage driving circuit of a piezoelectric element corresponding to another nozzle. For example, a voltage Vp is set to a voltage Vp1 by arranging a variable resistance r3 of the constant voltage driving circuit of the piezoelectric element, and the voltage Vp is set to a voltage Vp2 by arranging the variable resistance r3 of the constant voltage driving circuit of another piezoelectric element. In this manner, when an input signal IN is provided, to the piezoelectric element a driving wave form of the driving voltage Vp1 is applied and to the other piezoelectric element a driving wave form of the driving voltage Vp2 is applied. As Vp1 >Vp2 , an ink discharge from a tip nozzle corresponding to the piezoelectric element becomes larger than an ink discharge from other tip nozzles corresponding to other piezoelectric elements and a dot diameter can be made larger.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording apparatus, and more particularly to a recording apparatus for forming dots on a recording medium to record an image.

[0002]

2. Description of the Related Art As a recording apparatus, for example, an inkjet recording apparatus for recording an image by forming dots on the recording medium by the recording head while moving the recording head in the main scanning direction and feeding the recording medium in the sub scanning direction, Thermal (thermal transfer)
Recording devices and the like are known.

In such a recording apparatus, when the feeding amount (line feed amount) of the recording medium is larger than the image width in one spacing, the trailing edge of the image recorded before the line feed and after the line feed. So-called white streaks are generated between the front end of the recorded images, and when the line feed amount is small, the images overlap and black streaks occur.

Therefore, as a conventional ink jet recording apparatus, as described in, for example, Japanese Patent Laid-Open No. 4-189143, only the diameter of the first nozzle in the line feed direction among the plurality of nozzles of the recording head is changed to another. By making it larger than the nozzle diameter and making the amount of ink ejected from the first nozzle larger than the amount of ink ejected from other nozzles, it is possible to prevent white or black streaks caused by variations in the line feed amount. There is something to do.

On the other hand, in a recording apparatus using a recording head in which a plurality of head units having a plurality of dot forming means (for example, nozzles, heating elements, etc.) are arranged, the dot forming means located at the joint of each head unit is used. When the distance between the head units is narrower than a specified value, the overlapping of adjacent dots becomes large and a black streak occurs, and when the distance between the adjacent head units is larger than the specified value, the images are adjacent to each other. White stripes occur because the overlap between dots is small or there is no overlap.

Therefore, as a conventional ink jet recording apparatus, as described in, for example, Japanese Patent Laid-Open No. 6-255098, a plurality of print areas of the head unit are overlapped by at least one orifice (one nozzle). There is one that attempts to prevent white or black streaks caused by the mounting error of each head unit by mounting the head unit.

[0007]

However, by making only the diameter of the first nozzle of the former in the line feed direction larger than the diameters of the other nozzles, white stripes and black stripes caused by variations in the line feed amount are generated. In the inkjet recording device to be prevented, when the nozzle diameter is made larger than the others, the ink ejection amount increases, but since the ejection speed decreases, it deviates from the regular landing position on the recording medium. When a straight line is drawn in the line feed direction, only the dots of the first nozzle are displaced from the straight line, and the image quality is degraded. In addition, the nozzle diameter cannot be easily adjusted at the time of factory shipment or on the user side.

Further, by mounting a plurality of head units so that the printing areas of the latter adjacent head units overlap by at least one orifice,
In an ink jet recording apparatus that attempts to prevent white streaks and black streaks caused by the mounting error of each head unit, it is difficult to prevent the white streaks and black streaks from occurring once the head unit is mounted. However, it cannot be easily adjusted at the time of factory shipment or on the user side.

The present invention has been made in view of the above points, and an object thereof is to improve image quality.

[0010]

In order to solve the above-mentioned problems, a recording apparatus according to a first aspect of the invention moves the recording head in the main scanning direction and feeds the recording medium in the sub-scanning direction while the recording head is operated by the recording head. In a recording device that forms dots on a recording medium to record an image, the dot diameter or dot forming position of the first or last dot formed in the column direction of each row by the recording head is independent of other dots. Equipped with means to change.

A recording apparatus according to a second aspect is the recording apparatus according to the first aspect, wherein the recording head has a plurality of nozzles for ejecting ink droplets, and a plurality of liquid chambers communicating with the nozzles.
A plurality of actuator means for pressurizing each liquid chamber, and another actuator means for ejecting an ink droplet that forms a dot formed first or last in the column direction of each row in the plurality of actuator means. Means for driving independently of the actuator means were provided.

According to a third aspect of the present invention, a recording head for ejecting ink droplets of each color is moved in the main scanning direction to feed the recording medium in the sub-scanning direction, and the recording head is used to form dots of each color on the recording medium. In the recording apparatus for forming a color image by forming a dot diameter or a dot forming position independently of other dots depending on the color of the dot formed first or last in the column direction of each row by the recording head. Equipped with means to change.

According to a fourth aspect of the present invention, there is provided a recording device including a recording head in which a plurality of independent head units are arranged, and the recording head forms dots on the recording medium to record an image. A means for independently changing the area or diameter or the formation position of the dots located near the joint of each head unit is provided for other pixels or dots.

According to a fifth aspect of the present invention, in the recording apparatus according to the fourth aspect, the head unit includes a plurality of nozzles for ejecting ink droplets, a plurality of liquid chambers communicating with the respective nozzles, and respective liquid chambers. A plurality of actuator means for pressurizing, and an actuator means for ejecting ink droplets forming dots located in the vicinity of the joint of the recording head among the plurality of actuator means independently of other actuator means. It was made possible to drive.

[0015]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a schematic perspective view of a mechanism portion of an inkjet recording apparatus to which the present invention is applied, and FIG. 2 is a schematic perspective view of a recording head.

In this ink jet recording apparatus, a carriage 4 is movably mounted on guide rails 2 and 3 extending horizontally on a frame 1, a recording head 5 is mounted on the carriage 4, and the carriage is mounted on a rotary shaft of a motor (not shown). A timing belt is stretched between the driving pulley and the driven pulley, the carriage is connected to the timing belt, and the motor is rotated to move the carriage 4 in the direction A (in the main scanning direction). There is. On the other hand, the sheet 7 as the recording medium set on the guide plate 6 is taken in by the platen 10 provided with the feed knob 10a rotated by the drive source (not shown) via the drive gear 8 and the sprocket gear 9, and the platen 10 The peripheral surface and the pressure roller 11 that is in pressure contact with the peripheral surface enable conveyance in the arrow B direction (sub-scanning direction).

In this ink jet recording apparatus, the recording head 5 (carriage 4) is moved and scanned in the main scanning direction (arrow A direction) while the paper 7 is conveyed in the sub scanning direction (arrow B direction). A desired image is recorded on the paper 7 by ejecting ink droplets from the recording head 5 according to the image data.

Here, as shown in FIG. 2, the recording head 5 includes a piezoelectric element 16 which is an actuator means provided on a substrate 15, and a flow path plate 17 which forms an ink flow path.
A liquid chamber member 18 that forms a liquid chamber that communicates with each ink flow path, and a nozzle plate 19 that has a plurality of nozzles 20 that communicate with each ink flow path and eject ink droplets are provided. ing. The recording head 5 is attached to the carriage 4 so that the plurality of nozzles 20 of the nozzle plate 19 are arranged in the sub-scanning direction. Then, the recording head 5 supplies ink from the direction of the arrow and drives the piezoelectric element 16 in accordance with image data to eject ink droplets from the nozzle 20.

Next, a head drive circuit for driving the recording head of this ink jet recording apparatus will be described with reference to FIGS.
This will be described with reference to FIG. The head drive circuit includes a constant voltage drive circuit 21 that applies a drive waveform to a common electrode COM to which a plurality of actuator elements (piezoelectric elements 16) of the recording head 5 are commonly connected, and a plurality of piezoelectric elements 16 of the recording head 5. And a selection circuit 22 for giving a selection signal to The constant voltage drive circuit 21 generates a drive voltage having a predetermined voltage waveform when ink is pressurized from a rectangular pulse, and a waveform generation circuit 23 outputs the waveform generation circuit 23 as a common electrode of the recording head 5 including an inkjet head. COM
And a low impedance output circuit 24 for outputting

Waveform generation circuit 23 of constant voltage drive circuit 21
Can be composed of a ROM, a D / A converter or other pulse generating circuit and a waveform modifying circuit such as a calculus integrating circuit, a clipping circuit, and a clamping circuit. Further, the low impedance output circuit 24 is a buffer amplifier, SEPP (single end device).
It consists of a low impedance amplifier composed of d push pull) or the like. By using the low impedance output circuit, the output of the drive voltage waveform becomes a low impedance output to the piezoelectric element, and the waveform is not distorted due to the variation of the piezoelectric element and the number of drive channels.

On the other hand, the selection circuit 22 includes a shift register circuit, a latch circuit, and each piezoelectric element 16 of the recording head 5 (a channel, where a channel includes one nozzle, an ink flow path or a liquid chamber, and a piezoelectric element). It is used in the sense of a part.) It consists of a transistor and die array corresponding to.

Here, a specific example of the constant voltage drive circuit 21 will be described with reference to FIG. This constant voltage drive circuit 21
Is connected to the base of the transistor Tr1 via the buffer B and the base of the transistor Tr2 via the inverter I, respectively.
The collector of these transistors Tr1 is supplied with the voltage Vs, and the emitter of the transistor Tr2 is grounded.

Between the emitter of the transistor Tr1 and the collector of the transistor Tr2, a series circuit of a resistor ra and a diode D1 and a parallel circuit of a series circuit of a resistor rb and a diode D2 are connected, and the diode D is connected.
1 and D2 are connected to a point, a capacitor Ck is connected between the a point and the ground, and a time constant circuit for charging with a resistor ra and a capacitor Ck and a time constant circuit for discharging with a resistor rb and a capacitor Ck. Are configured.

A series circuit of a resistor r1, a variable resistor r3 and a resistor r2 is connected between the voltage Vs and the ground, and the point a connected between the capacitor Ck and the resistor ra and the resistor rb is connected via a diode Dk. The resistor r1 and the variable resistor r3 are connected to a connection point b, and an electric field capacitor C for current compensation is connected between the connection point b and the ground.

The point a is set to the transistors Tr3 to Tr.
A low-impedance output circuit 24 consisting of 6 is connected between the base of the transistor Tr3 on the input side and the base of the transistor Tr4, and is on the output side of the transistor Tr3.
The common electrode COM of the plurality of piezoelectric elements 16 of the recording head 5 is connected between the emitter of the transistor 5 and the collector of the transistor Tr6.

In this constant voltage drive circuit, when a pulsed input signal is input to the input terminal IN, the transistor Tr1 is turned on via the buffer B, the transistor Tr2 is turned off via the inverter I, and the voltage is lowered. Vs
By this, charging of the capacitor Ck is started with a time constant determined by the resistor ra and the capacitor Ck. At this time, since the voltage Vs is connected to the point a via the diode Dk (falling voltage Vd), the voltage Vs is connected to the voltage dividing point b where the resistance ratio is divided by the resistor r1 and the series circuit of the variable resistor r3 and the resistor r2. The charging voltage of Ck is clipped to the voltage Vp. That is,
Vp = Vs * {(r2 + r3) / (r1 + r2 + r
3)}-Vd is charged, and this voltage becomes the maximum value of the drive voltage Vp.

When the pulsed input signal is not input to the input terminal IN, the transistor Tr1 is turned off via the buffer B, the transistor Tr2 is turned on via the inverter I, and is determined by the resistor rb and the capacitor Ck. The capacitor Ck is discharged with a time constant.

Next, a specific configuration including the selection circuit 22 will be described with reference to FIG. The select electrodes SEG of the plurality (16) of piezoelectric elements PZT1 to PZT16 of the recording head 5 are connected to NPN type transistors Tr11 to Tr.
It is connected to the collector side of 16. On the other hand, the piezoelectric element PZ
Of the T1 to PZT16, the common electrode COM of the piezoelectric element PZT1 of the nozzle 20 that forms the first dot in the column direction of each row of the recording medium is made independent as the common electrode Coma.
It is connected to one constant voltage drive circuit 21 shown in FIG. In addition, the common electrodes COM of the other piezoelectric elements PZT2 to PZT16 are all connected in common and are connected to the common electrode Co.
mb, and is connected to another constant voltage drive circuit 21 shown in FIG.

Further, diodes D1 to D16 are connected between the common electrode COM side of each of the piezoelectric elements PZT1 to PZT16 and the emitters of the transistors Tr11 to Tr16,
The piezoelectric elements PZT1 to PZT16 are selected by applying a selection signal to the terminals 1 to 16 connected to the bases of the transistors Tr11 to Tr16.
It should be noted that the shift register and the latch circuit forming the selection circuit are not shown.

Next, the operation of the ink jet recording apparatus thus constructed will be described. First, when the ink droplets are ejected from all the nozzles of the recording head at the same timing, the n-th line on the m-th line and the (m + 1) -th line from the print start position.
The dots in the row are as shown in FIG. Since the line feed amount (line feed amount) in this case is an ideal value (specified value),
Pitch (inter-line pitch) P'between the trailing (last) dot of the m-th row and the leading (first) dot of the (m + 1) -th row
Is equal to the dot pitch P formed by the adjacent nozzles. Further, the line feed amount Wc at this time is equal to (the number of nozzles N) × (inter-dot pitch P) = Wco.

However, since the line feed amount has an error depending on the feeding accuracy of the recording medium, when the line feed amount Wc becomes larger than a desired value, the line pitch P'is set to a dot as shown in FIG. 7A. The pitch becomes larger than the inter-pit pitch P (P '> P), and as a result, white lines are generated between the rows. In this case, if the diameter of the dots forming the inter-row spacing is made larger than the other dot diameters, white streaks can be filled, and the nozzle forming the inter-row dots is the first or last nozzle of the nozzle row. FIG. 2B shows a case where only the dot diameter of the first nozzle (tip nozzle) is increased.

Therefore, in this ink jet recording apparatus, since the recording head using the piezoelectric element is used, the drive waveform of the piezoelectric element corresponding to the tip nozzle is controlled independently of the drive waveforms of the other piezoelectric elements. I am trying.
Here, in the recording head using the piezoelectric element, in order to increase the dot diameter, the ink ejection amount Mj may be increased. The ink ejection amount Mj largely depends on the drive waveform, and the drive voltage Vp is increased. Alternatively, the ink ejection amount Mj can be increased by increasing the voltage application time (pulse width Pw) or shortening the charging time constant tr corresponding to the ink ejection timing.

In the head drive circuit of this recording apparatus, as described above, the piezoelectric element P corresponding to the tip nozzle.
Since the constant voltage drive circuit of ZT1 and the constant voltage drive circuits of the piezoelectric elements PZT2 to PZT16 corresponding to the other nozzles are independent, they are applied to the piezoelectric element PZT1 by adjusting the respective variable resistors r3. The drive voltage of the drive waveform and the drive voltage of the drive waveform applied to the piezoelectric elements PZT2 to PZT16 can be adjusted independently.

Therefore, for example, the variable resistor r3 of the constant voltage drive circuit of the piezoelectric element PZT1 is adjusted to change the voltage Vp to the voltage Vp.
1 and adjusting the variable resistance r3 of the constant voltage drive circuit of the piezoelectric elements PZT2 to 16 to change the voltage Vp to the voltage Vp2 (Vp
2 <Vp1). As a result, when the input signal IN is given as shown in FIG.
A drive waveform of the drive voltage Vp1 is applied to ZT1 as shown in FIG. 7A, and a drive waveform of the drive voltage Vp2 is applied to piezoelectric elements PZT2 to PZT2-16 as shown in FIG. Since it is Vp2, the amount of ink ejected from the tip nozzle corresponding to the piezoelectric element PZT1 is equal to that of the other piezoelectric element P.
The amount of ink ejected from other nozzles corresponding to ZT2 to 16 becomes larger, and the dot diameter can be increased.

When the line feed amount Wc is smaller than the desired value, the line pitch P'is set as shown in FIG. 9 (a).
Is smaller than the dot pitch P (P '<P), and as a result, black streaks occur between the rows. In this case,
As shown in FIG. 6B, it is possible to reduce the diameter of only the dot formed by the tip nozzle. Therefore, in this case, in the head drive circuit described above, the drive voltage Vp1 of the drive waveform applied to the piezoelectric element PZT1 is applied to the other piezoelectric elements PZT2 to PZT2-16.
It may be adjusted so as to be smaller than p (Vp1 <Vp2).

Further, in the above description, the dot diameter of the front end nozzle is made variable, but the dot diameter at the rear end nozzle may be changed instead of the front end nozzle or together with the front end nozzle. Further, as shown in FIG. 9C, the leading dot of the next row is increased only when the trailing edge dot of the preceding row is present, and the leading edge of the next row is increased when there is no trailing edge dot of the preceding row. The dots may have the same diameter as other dots. Furthermore, when the nozzle that forms the dots between the rows is not the front end nozzle or the rear end nozzle of the nozzle row, similarly, it is possible to control the drive waveform of the piezoelectric element corresponding to the nozzle that forms the dots that form the inter-row. Good. Further, although the dot diameter is made variable, the dot formation position may be made variable.

Next, another example of the recording head is shown in FIG.
This will be described with reference to FIGS. The recording head shown in FIG. 3 of the above embodiment is an edge shooter type recording head which ejects ink droplets in a direction orthogonal to the displacement direction of the piezoelectric element. The recording head of this embodiment is the displacement direction of the piezoelectric element. It is a side shooter type recording head that ejects ink droplets in the same direction as.

The recording head comprises an actuator unit 31 and a liquid chamber unit 32 joined on the actuator unit 31. The actuator unit 31 includes two rows of piezoelectric element rows 34 and 34 in which a plurality of laminated piezoelectric elements are arranged in rows on a head substrate 33 made of ceramic, glass epoxy resin or the like, and these two rows. A frame member 35 that surrounds the piezoelectric element rows 34, 34 is bonded by a bonding agent 36. The piezoelectric element array 34 includes a plurality of piezoelectric elements (hereinafter referred to as “driving section piezoelectric elements”) 37, 37, ... To which a driving pulse is applied to make the ink droplets and fly, and the driving section piezoelectric element 3.
A structure in which a plurality of piezoelectric elements (which are referred to as “fixed portion piezoelectric elements”) 38, 38, which are located between Nos. 7 and 37 and serve only as liquid chamber unit fixing members without being given a drive pulse, are arranged alternately. I am trying.

The liquid chamber unit 32 includes a diaphragm portion 41.
A liquid chamber flow path forming member 45 including two photosensitive resin films (dry film resists) 43 and 44 forming a pressure liquid chamber, a common ink flow path, etc.
And a nozzle plate 47 having a plurality of nozzles 46 formed thereon is bonded onto the liquid chamber flow path forming member 45. By the vibrating plate 42, the liquid chamber flow path forming member 45, and the nozzle plate 47, a plurality of pressurizing liquid chambers each having a diaphragm portion 41 facing each driving portion piezoelectric element 37, 37 of the piezoelectric element array 34 are provided. 48, the fluid resistance parts 49, 49 are formed on both sides of the pressurized liquid chamber 48, and the common liquid chamber 5 is formed outside the fluid resistance parts 49, 49.
0 and 50 are formed respectively.

In this recording head, the driving piezoelectric elements 37, 37 of the piezoelectric element rows 34, 34 are selectively driven to cause the driving piezoelectric elements 37, 37 to expand in the stacking direction. The ink in the pressurizing liquid chamber 48 is pressurized by the nozzle 46, and is made into droplets from the nozzle 46 to be ejected as ink droplets.

In the above example, a piezoelectric element is used as an actuator element as a recording head, but a recording head having a heating element as an actuator element can also be used. An example of such a recording head will be described with reference to FIGS. 13 and 14.

In this recording head, a plate 61 is joined to the surface of a substrate 60, and a plurality of grooves 63 having an orifice 62 at the tip and a liquid chamber 64 communicating with each groove 63 are formed in the plate 61, and one substrate Heat generating elements (heat generating resistors) 65 are respectively formed on the plurality of grooves 63 corresponding to the plurality of grooves 63, and a pattern of a common electrode 66 and a selection electrode 67 connected to each heat generating element 65 is formed. FIG.
As shown in FIG. 7, an ink supply pipe 69 is connected to the ink introduction port 68 provided in the plate 61 to supply the ink to the liquid chamber 64, and the common electrode 66 and the selection electrode 67 are provided in the central portion of the substrate 60. It is connected to the control unit via a diode array 70 provided in the vicinity.

In this recording head, the heating element 6
By supplying power to No. 5, it is possible to boil the ink in the vicinity of the element and eject the ink droplet from the orifice 62 at the tip of the groove 63 by the force.

Next, application to a color ink jet recording apparatus will be described. When recording a color image, a recording head in which a head unit having a plurality of nozzles or the like is combined for each color is used, or a plurality of nozzle rows is formed in one recording head and each nozzle row is formed for each color. Use the assigned recording head. When a color image is recorded using such a recording head, when colors of dots between lines are different, it is necessary to consider color mixture and bleeding between the respective colors.

Therefore, for example, in FIG. 9A described above, at least the trailing edge dot of the m-th row is black (B
In k), if at least the leading dot of the next (m + 1) th row is any of yellow (Y), magenta (M), and cyan (C) other than black, the (m + 1) th row is Bk.
The drive voltage Vp1c is set to be higher so that the front dot diameter is larger than that in the above case. When at least the trailing edge dot of the m-th row is any of Y, M, and C other than Bk, and at least the leading edge dot of the next (m + 1) -th row is Bk, compared to when the m-th row is Bk. Drive voltage Vp1k is lowered (Vp2 <Vp1k) so that the tip dot diameter becomes smaller.
<Vp1) Set.

On the other hand, in FIG. 9B, at least the trailing edge dot on the m-th row is Bk, and at least the leading edge dot on the next (m + 1) -th row is any of Y, M, and C other than black. , The drive voltage is set so that the leading dot diameter is larger than that in the case of Bk in the (m + 1) th row (however, it is smaller than at least the trailing end dot in the mth row). When at least the trailing edge dot of the m-th row is any of Y, M, and C other than Bk, and at least the leading edge dot of the next (m + 1) -th row is Bk, compared to when the m-th row is Bk. Also, the drive voltage is set so that the tip dot diameter becomes smaller.

As described above, in the recording apparatus for recording a color image, the dot diameter or the dot forming position is independent of the other dots depending on the color of the dot formed first or last in the column direction of each row by the recording head. By changing the values in this manner, it is possible to record a high-quality image with less blurring of boundaries between different inks.

Next, in the case of a recording head using a piezoelectric element as an actuator element, when the driving voltage is increased, the ink ejection amount Mj increases, so that the dot diameter formed on the recording medium becomes large. However, since the ink ejection speed Vj also increases at the same time, the ink landing position on the recording medium may shift in the carriage traveling direction. In such a case, by controlling both the drive voltage Vp and the time constant at the ink ejection timing (the charging time constant tr of the head drive circuit (the rising time Tr of the drive waveform) described above), such an impact is achieved. Positional deviation can be corrected.

That is, when the drive voltage is increased according to the desired dot diameter, the time constant tr is set to be longer than a predetermined time so that the ink ejection blocking degree Vj is constant, and V is set to V.
When p is set low, the time constant tr may be set to be shorter than a predetermined time. The time constant tr can be set by the head drive circuit of FIG. 4 by variably adjusting the resistance ra.

Next, FIG. 15 shows the second embodiment of the present invention.
A description will be given with reference to the following. FIG. 15 is a perspective view showing an example of a line type recording head to which the present invention is applied, and FIG. 16 is a front view showing the arrangement of the head unit.

In this recording head, a plurality of head units 71, 71, ... Same in structure as the recording heads shown in FIGS. 13 and 14 are mounted on a common support plate 72 up and down (sub scanning direction) and left and right (main scanning). Direction). M nozzles 62 are formed in each head unit, and the interval between adjacent nozzles 62, 62 is set to Q. Further, between the pair of upper and lower head units 71, 71 adjacent to each other along the arrangement direction of the head units 71, the distance between the left end nozzle 62 of one head unit 71 and the right end nozzle 62 of the other head unit 71 is equal. It is set to Q. Here, the number of head units 71 is N from the first head unit to the Nth head unit, and the number of nozzles 65 of the head unit 71 is M from the first nozzle on the left end side to the Mth nozzle on the right end side.

When a plurality of head units are arranged vertically like this recording head, the distance between the first nozzle and the Mth nozzle at the ends of the pair of adjoining head units is Q with high accuracy. It is not easy to attach the head to the support plate, and this spacing tends to vary.

FIG. 1 shows the joint between two adjacent head units when front surface printing is performed by ejecting ink droplets from all the nozzles of such a recording head.
7 and FIG.

First, FIG. 17 shows a case where the distance between the first nozzle of one head unit and the Mth nozzle of the other head of two adjacent head units becomes a distance Q'wider than the set nozzle distance Q. Is. In this case, if the dots formed by the first nozzle and the Mth nozzle have the same size, the dots do not overlap at the interval Q ′ as shown in FIG. To do.

Therefore, the diameter of the dot corresponding to the joint of each head unit is made larger than the diameters of the other dots.
For example, as shown in FIG. 2B, the dot formed by the first nozzle of one head unit of two adjacent head units and the Mth nozzle of the other head unit has a larger diameter than the other dots. . As a result, white stripes do not occur between adjacent dot rows corresponding to the joints.

Further, as shown in FIG. 6C, when the dot formed by the first nozzle of one head unit and the Mth nozzle of the other head unit is made larger in diameter than the other dots, The dots formed by the nozzles and the Mth nozzle are alternately enlarged in the sub-scanning direction. Even in this case, white stripes do not occur between adjacent dot rows corresponding to the joints. Further, the first nozzle and the Mth
It is also possible to make the dots formed by the nozzles larger in a random order in the sub-scanning direction. By doing so, the moire pattern becomes inconspicuous and the image quality is further improved.

Next, in FIG. 18, the distance between the first nozzle of one head unit and the M-th nozzle of the other head unit of two adjacent head units is a distance Q ″ which is narrower than the set nozzle distance Q. In this case,
If the dots formed by the first nozzle and the M-th nozzle have the same size, the dot overlap becomes too large at the interval Q ″ as shown in FIG. .

Therefore, the diameter of the dot corresponding to the joint between the head units is made smaller than that of the other dots. For example, as shown in FIG. 2B, the dot formed by the first nozzle of one head unit of two adjacent head units and the Mth nozzle of the other head unit has a smaller diameter than the other dots. . As a result, black stripes do not occur between adjacent dot rows corresponding to the joints.

Further, as shown in FIG. 7C, when the dot formed by the first nozzle of one head unit and the Mth nozzle of the other head unit is made smaller in diameter than the other dots, The dots formed by the nozzles and the Mth nozzle are alternately made smaller in the sub-scanning direction. Even in this case, white stripes do not occur between adjacent dot rows corresponding to the joints. Further, the first nozzle and the Mth
It is also possible to make the dots formed by the nozzles smaller in a random order in the sub-scanning direction. By doing so, the moire pattern becomes inconspicuous and the image quality is further improved.

An example of a head drive circuit for performing such drive control will be described with reference to FIGS. 19 and 20.
In this head drive circuit, a diode 73 is connected in series with a heating element (heating resistor) 65 corresponding to each nozzle 62 of each head unit 71, and one head unit 71 is provided.
The anode side of the diode 73 connected to the M number of heat generating elements 65 is commonly connected to the electrodes Com1 to ComN. On the other hand, the other side of the heating element 65 of each of the N head units 71 has a nozzle 62 having the same nozzle number (first to Mth nozzles) of each head unit 71.
Are commonly connected to the electrodes Seg1 to SegM, and a switching element (not shown) such as an NPN transistor is connected to the electrodes Seg1 to SegM.

In this head drive circuit, N blocks (Com1 to ComN) * M segments (S
Driving is performed separately for eg1 to SegM). In this drive mode, as shown in FIG. 20, time division drive is performed in block units. That is, as shown in FIG.
A pulse having a drive voltage Vp and a pulse width T0 is applied to the electrode Com1 at a repetition duty of 1 / N, and the electrode Com2
The same drive waveform is applied with a delay time of T0 to .about.ComN.

Then, as shown in FIG. 9B, the heating element 65 corresponding to the first nozzle of the first head unit.
Is the electrode S at the same timing as the drive waveform of the electrode Com1.
The energization is performed only while the transistor base input (not shown) of eg1 is at "H". Similarly, the second, third ...
Heating element 65, 6 of the first nozzle of the Nth head unit
5 ... also synchronize with the electrodes Com2, 3 ... M and the electrodes Se.
g2,3 ... M is energized only while the input level of M is "H".

Therefore, the energization time of the heating element 65 corresponding to the first nozzle of each of the first to Nth head units is time T1 (T1 <T0). Further, the energization time of the heating element 65 corresponding to the second nozzle to the Mth nozzle of each of the first to Nth head units is time T2 (T2 <T1). As a result, only the dots formed by the first nozzle are larger than the dots formed by the other nozzles.

As described above, when the heating element of each head unit is sequentially energized in a time-divisional manner and the first nozzle of the first head unit is driven again, the electrode Seg1
Since the input signal width of is changed from T1 to T2, the energization time is time T2. Similarly, the second of each head unit
Heater element 6 corresponding to nozzle (M-1) th nozzle
The energization time of 5 is T2. Since the input signal width of the electrode SegM changes from T2 to T1, only the dots formed by the M-th nozzle of each head unit are larger than the dots formed by the other nozzles.

In this way, the dot diameters formed by the nozzles at both ends corresponding to the joints of the head units can be alternately made larger than the dot diameters formed by the other nozzles. In a recording head using a heating element as an actuator element, the dot diameter can be changed by changing the number of driving pulses instead of changing the energization time (driving pulse width) to the heating element. it can. Further, instead of the dot diameter, the dot area or the dot landing position can be changed.

Next, another example of the head drive circuit will be described with reference to FIGS. This example is a head drive circuit when a piezoelectric element is used as an actuator element. Each of the N first to Nth head units has M piezoelectric elements PZT corresponding to M first to Mth nozzles, and one of the piezoelectric elements PZT corresponding to the first nozzle of each head unit. The electrode of the electrode Com
Connected to 1. Further, one electrode of the piezoelectric element PZT corresponding to the M-th nozzle of each head unit is the electrode Com.
Connected to 2. Further, one electrode of the piezoelectric element PZT corresponding to the other nozzles of each head unit is connected to the electrode Com3.

Further, the piezoelectric element PZT of each head unit
The other electrode is connected to the collector of the NPN transistor Tr, and the electrode Seg1 is connected to the base of each transistor Tr.
-1 to 1-M to M-1 to NM are connected to select each piezoelectric element PZT of each head unit driven by the base input of the transistor Tr. The electrode Com1
The drive voltage Vp of the output waveform (drive waveform) can be arbitrarily changed by connecting each of the constant voltage drive circuits shown in FIG. 4 described above to Com3 and changing the resistance value of the variable resistor r3. Further, the diode D is connected in parallel with the piezoelectric element PZT and the transistor Tr.

In this head drive circuit, as shown in FIG. 22, the drive voltage Vp2 applied to the electrode Com2 is kept constant, and only the drive voltages of the electrodes Com1 and Com3 are sequentially applied to the drive voltages Vp1 and Vp2 (Vp2 <Vp1). By switching to, the driving voltage corresponding to the first nozzle to the Mth nozzle of each head unit can be alternately driven at a higher voltage than the other piezoelectric elements, and the dot diameter can be increased as in the first embodiment. can do.

In this way, the dot diameter formed by the nozzles at both ends corresponding to the joint of the heads can be alternately made larger than the dot diameter formed by the other nozzles.

In this head drive circuit, when the dot diameter is changed by the pulse width instead of the drive voltage,
In the circuit shown in FIG. 4, the pulse width of the input signal (timing signal) applied to the input terminal IN may be varied, and the dot rise may be varied by controlling the waveform rise time corresponding to the ink ejection timing. For this purpose, the resistance ra may be varied. Further, the dot position accuracy can be improved by controlling the drive voltage or voltage application time and the rise time at the same time.

Further, in each of the above-mentioned embodiments, the present invention has been described with respect to the case where the recording head is an ink jet head, but the present invention is not limited to this, and when the present invention is applied to another head using an energy conversion element, for example, a thermal head. However, similar effects can be obtained by controlling the injected electric energy.

[0072]

As described above, according to the recording apparatus of the first aspect, while the recording head is moved in the main scanning direction and the recording medium is fed in the sub scanning direction, the recording head forms dots on the recording medium. In the recording device for forming and recording an image, since the dot diameter or the dot forming position of the first or last dot formed in the column direction of each row by the recording head is changed independently of other dots, The occurrence of white stripes or black stripes between lines is reduced, and the image quality is improved.

According to a recording apparatus of a second aspect, in the recording apparatus of the first aspect, the recording head has a plurality of nozzles for ejecting ink droplets, a plurality of liquid chambers communicating with each nozzle, and each liquid chamber. A plurality of actuator means for pressurizing, and an actuator means for ejecting an ink droplet that forms a dot formed first or last in the column direction of each row of the plurality of actuator means is independent of other actuator means. Since it is provided with a means for driving, it is possible to easily reduce the occurrence of white streaks and black streaks between lines at the time of factory shipment or user use.

According to the recording apparatus of the third aspect, in the recording apparatus for recording a color image, the dot diameter or the dot forming position is changed depending on the color of the dot formed first or last in the column direction of each row by the recording head. Since the dots are changed independently, it is possible to reduce the boundary bleeding between inks of different colors and improve the image quality.

According to a fourth aspect of the present invention, there is provided a recording apparatus including a recording head in which a plurality of independent head units are arranged, and the recording head records dots by forming dots on a recording medium. Since the area or diameter of the dots located near the joint of each head unit or the formation position is changed independently with respect to other pixels or dots, it is possible to compensate the mounting position error of the head unit. , The image quality is improved.

According to a recording apparatus of a fifth aspect, in the recording apparatus of the fourth aspect, the head unit has a plurality of nozzles for ejecting ink droplets, a plurality of liquid chambers communicating with each nozzle, and each liquid chamber. A plurality of actuator means for pressurizing, and an actuator means for ejecting ink droplets forming dots located in the vicinity of the joint of the recording head among the plurality of actuator means independently of other actuator means. Since it can be driven by the above, it is possible to easily reduce the occurrence of white stripes and black stripes between lines at the time of factory shipment or user use.

[Brief description of drawings]

FIG. 1 is a schematic perspective view of a mechanism portion of an inkjet recording apparatus according to a first embodiment of the invention.

FIG. 2 is a perspective view showing an example of a recording head of the recording apparatus.

FIG. 3 is a block diagram of a head drive circuit used in the recording apparatus.

FIG. 4 is a circuit diagram of a constant voltage drive circuit of the head drive circuit.

FIG. 5 is a circuit diagram of a main part of a head drive circuit of the recording apparatus.

FIG. 6 is an explanatory diagram for explaining the operation of the recording apparatus.

FIG. 7 is an explanatory diagram for explaining the operation of the recording apparatus.

FIG. 8 is a waveform diagram for explaining the operation of the head drive circuit.

FIG. 9 is an explanatory diagram for explaining the operation of the recording apparatus.

FIG. 10 is a perspective view showing another example of the recording head of the recording apparatus.

11 is a sectional view taken along the line AA of FIG.

12 is a sectional view taken along the line BB of FIG.

FIG. 13 is a perspective view showing still another example of the recording head of the recording apparatus.

FIG. 14 is an overall perspective view of the recording head.

FIG. 15 is a perspective view of a recording head showing a second embodiment of the invention.

FIG. 16 is a front explanatory view of the recording head.

FIG. 17 is an explanatory diagram for explaining the operation of the embodiment.

FIG. 18 is an explanatory diagram for explaining the operation of the embodiment.

FIG. 19 is a circuit diagram showing an example of a head drive circuit of the same embodiment.

FIG. 20 is a waveform diagram for explaining the operation of the head drive circuit.

FIG. 21 is a circuit diagram showing another example of the head drive circuit of the same embodiment.

FIG. 22 is a waveform diagram for explaining the operation of the head drive circuit.

[Explanation of symbols]

4 ... Carriage, 5 ... Recording head, 16 ... Piezoelectric element, 1
7 ... Flow path plate, 18 ... Liquid chamber member, 19 ... Nozzle plate, 20 ...
Nozzle, 21 ... Constant voltage drive circuit, 22 ... Selection circuit, 31
... actuator unit, 32 ... liquid chamber unit, 37
... Drive portion piezoelectric element, 42 ... Vibration plate, 46 ... Nozzle, 48
... Pressurized liquid chamber, 60 ... Substrate, 61 ... Plate, 62 ... Nozzle, 65 ... Heating element, 71 ... Head unit.

Front page continued (72) Inventor Yoshihisa Ota 1-3-6 Nakamagome, Ota-ku, Tokyo In Ricoh Co., Ltd. (72) Inventor Taeko Murai 1-3-6 Nakamagome, Ota-ku, Tokyo In Ricoh, Inc.

Claims (5)

[Claims] 1. A recording apparatus for recording an image by forming dots on the recording medium by the recording head while moving the recording head in the main scanning direction and feeding the recording medium in the sub scanning direction. 2. A recording apparatus comprising means for independently changing a dot diameter or a dot forming position of a dot formed first or last in the column direction of each row with respect to other dots. 2. The recording apparatus according to claim 1, wherein the recording head includes a plurality of nozzles for ejecting ink droplets,
A plurality of liquid chambers communicating with each nozzle and a plurality of actuator means for pressurizing the respective liquid chambers are provided, and dots to be formed first or last in the column direction of each row of the plurality of actuator means are generated. A recording apparatus, which is provided with a means for driving an actuator means for ejecting an ink droplet to be driven independently of other actuator means. 3. A color image in which dots of each color are formed on the recording medium by the recording head while moving the recording head ejecting ink droplets of each color in the main scanning direction and feeding the recording medium in the sub scanning direction. In the recording apparatus for recording, the recording head is provided with means for independently changing the dot diameter or the dot formation position with respect to other dots in accordance with the color of the dot formed first or last in the column direction of each row. A recording device characterized by the above. 4. A recording apparatus, comprising: a recording head having a plurality of independent head units arranged therein, wherein dots are formed on the recording medium by the recording head to record an image. A recording apparatus comprising means for independently changing the area or diameter of a dot located in the vicinity of, or the formation position with respect to other pixels or dots. 5. The recording apparatus according to claim 4, wherein the head unit has a plurality of nozzles for ejecting ink droplets, a plurality of liquid chambers communicating with each nozzle, and a plurality of pressurizing each liquid chamber. Actuator means for ejecting ink droplets forming dots located in the vicinity of the joint of the recording head among the plurality of actuator means can be driven independently of other actuator means. A recording device characterized by the above.