JP2002019100A - Image forming device - Google Patents

Abstract

(57) Abstract: An image forming apparatus having a print mode capable of executing a plurality of resolutions without increasing the type of moving speed of a carriage. SOLUTION: The driving waveform 10 has a maximum driving frequency at which stable ejection can be performed at 7500 (Hz), and the ejection ink droplet volume is 60 pl. The drive waveform 20 has a maximum drive frequency of 15000 (Hz) for stable ejection and an ejected ink droplet volume of 15 pl. Drive waveform 10 at 300 dpi
By using the driving waveform 20 in the 600 dpi mode and the driving waveform 20 in the 600 dpi mode, the moving speed of the carriage at the time of image formation is 7500/300 = 2 in the 300 dpi mode.
The speed becomes 5.0 (IPS), and in the 600 dpi mode, the speed becomes 15000/600 = 25.0 (IPS), and the carriage speed becomes the same.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image forming apparatus using an ink jet system.

[0002]

2. Description of the Related Art Conventionally, as an image forming apparatus, FIG.
As shown in FIG.
In some cases, the carriage 100 is mounted on the carriage 100 and scans in parallel with the print medium 700. The carriage 100 is slidably supported by guide bars 110 and 120 and reciprocates along the guide bars by a belt 140 driven by a motor 37. A tank 150 containing ink to be supplied to the head unit 600 is detachably mounted on the carriage 100. Printing medium 700
Is held in parallel with the scanning direction of the head unit 600 by the transport rollers 160 and 170 and is transported in a direction perpendicular to the scanning direction.

[0003] The ink ejecting apparatus 600 uses piezoelectric ceramics or electrostatic force as an actuator to deform the wall surface of an ink flow path to eject ink in the ink flow path from a nozzle as droplets, and a heater as an actuator. There is known a method in which ink in an ink flow path is locally boiled and ink droplets are ejected by the pressure, and a print pattern is represented by dots landed on a print medium. As an example of the former, there is a shear mode type using a piezoelectric material as disclosed in Japanese Patent Application Laid-Open No. 63-247051. An example is shown in FIG. The ink ejecting apparatus 600 includes an actuator substrate 601 in which a plurality of elongated groove-shaped ink flow paths 613 extending in the thickness direction of the print medium surface and a space 615 in which ink does not enter are arranged with a side wall 617 interposed therebetween, and a cover plate 602. The lower side of the side wall 617 has an arrow P
The lower wall 611 polarized in one direction and the upper half are indicated by an arrow P2.
The upper wall 609 is polarized in the direction. One end of each ink channel 613 has a nozzle 618, and the other end has a manifold (not shown) for supplying ink. The end of the space 615 on the manifold side is closed so that ink does not enter. Electrodes 619 and 621 are provided on both sides of each side wall 617 as a metallized layer. Specifically, the side wall 617 on the ink flow path 613 side
Is provided with a flow path electrode 619, and a space 615 side wall 617 is provided with a space electrode 621. In-space electrode 621 facing in the same space 615
Are insulated from each other.

Then, ink is ejected using a pair of side walls 617 sandwiching one ink flow path 613 as one actuator. For example, as shown in FIG.
3b, all the electrodes 619 in the flow path are grounded, and the voltage E is applied to the space electrodes 621c, d on both outer sides of the flow path.
When (V) is applied, an electric field is generated in the side wall 617c, d in the direction of arrow E perpendicular to the direction of polarization, and the upper and lower portions of the side wall 617c, d are each subjected to piezoelectric thickness sliding in the direction of increasing the volume of the ink flow path 613b. Deform. At this time, the nozzle 6
The pressure in the ink flow path 613b including around 18b decreases. This state is maintained for the one-way propagation time T of the pressure wave in the ink flow path 613. Then, ink is supplied from a manifold (not shown) during that time.

[0005] The one-way propagation time T corresponds to the ink flow path 6
13 is the time required for the pressure wave in the ink channel 613 to propagate in the longitudinal direction of the ink channel 613, and the length L of the ink channel 613
And T = L / a according to the sound velocity a in the ink inside the ink flow path 613. According to the pressure wave propagation theory, the pressure in the ink flow path 613 reverses and changes to a positive pressure just after T time has elapsed from the application of the voltage, but is applied to the space electrodes 621c and d in accordance with this timing. The returned voltage is returned to 0 (V).

Then, the side walls 617c and 617d return to the state before deformation (FIG. 6), and pressure is applied to the ink. At this time, the pressure that has turned positive and the pressure generated when the side walls 617 c and d return to the state before deformation are added, and a relatively high pressure is applied to the nozzle 61 of the ink flow path 613 b.
An ink drop is generated in a portion near 8b, and is ejected from the nozzle 618b.

More specifically, if the time from the application of the voltage to the return of the voltage to 0 (V) deviates from the one-way propagation time T, the energy efficiency drops because the ink drops are ejected, and the one-way propagation Injection is not performed at all when the time T is almost even number times. Therefore, in general, when it is desired to increase the energy efficiency, for example, when driving at a voltage as low as possible, the voltage is reduced from the application of the voltage to 0.
It is desirable that the time until returning to (V) be equal to the one-way propagation time T or at least approximately an odd multiple.

An example of specific dimensions of the conventional ink droplet ejecting apparatus 600 will be described. The length L of the ink chamber 613 is 12.
0 mm. The nozzle 618 has a diameter of 32 μm or 26 μm on the ink droplet ejection side and a diameter of 40 μm on the ink chamber 613 side.
It is a μm taper type and has a length of 75 μm. The viscosity of the ink used in the experiment at 25 ° C. was about 2 mPa ·
s, surface tension is 30 mN / m. This ink chamber 61
The ratio L / a of the sound velocity a to the above-mentioned L in the ink in No. 3
(= T) was 12.0 μsec.

[0009] Using the image forming apparatus having such a configuration,
The printing resolution in the moving direction of the carriage is, for example, 3
A conventional image forming method when there are a plurality of modes such as 60 dpi (dot / inch) and 720 dpi will be described. The first conventional example is 360 dpi and 72 dpi.
This is a method using the same drive waveform for 0 dpi. The higher the printing resolution, the smaller the volume of the ink droplet to be ejected is. Therefore, it is necessary to eject the ink at a lower drive voltage in the 720 dpi mode than in the 360 dpi mode. FIG. 4A shows an example of the driving waveform.
Shown in The number attached to the drive waveform 20 is the ratio of the time length to the one-way propagation time T of the pressure wave in the ink flow path 613. Injection pulse F for ejecting ink droplets
5 and an ejection stabilizing pulse S3 for suppressing residual vibration generated by the ejection pulse F5 and stopping unnecessary ink ejection. The peak values (voltage values) of all the pulses are the same. As shown in FIG. 5, the length L of the ink flow path 613 is 12.0 mm, and the emission diameter of the nozzle 618 is φ
When a driving voltage of 20 (V) is applied at a time of 32 μm, the volume of a droplet to be ejected is 35 pl (picoliter),
When a driving voltage of 15 (V) is applied, the voltage becomes 25 pl. Therefore, the former is used in a 360 dpi mode, and the latter is used in a 72 dpi mode.
Used in 0 dpi mode.

It is known from experiments that the maximum driving frequency at which the driving waveform 20 can be stably ejected is 10800 (Hz).
The maximum driving frequency is common to 10800 (Hz) in both the Pi mode and the 720 dpi mode.

Therefore, as shown in FIG. 3A, the moving speed of the carriage during image formation is 10800/360 = 30.0 (inch / se) in the 360 dpi mode.
c. The speed will be referred to as IPS hereinafter) and 720 dp
In the i-mode, 10800/720 = 15.0 (IP
S), which requires two carriage speeds. The minimum dot interval in the carriage movement direction in each mode is determined by the resolution H, 360 dp
i and the reciprocal 1 / H of 720 dpi.

In order to further improve the printing quality, a second conventional method uses a different driving waveform for both 360 dpi and 720 dpi in order to increase the difference between the ink droplet volumes in the low resolution mode and the high resolution mode. An example of the drive waveform is shown in FIG. The driving waveform 30 is a driving waveform for 360 dpi.
Is the ratio of the length of time to the one-way propagation time T of the pressure wave inside. Two ejection pulses F for ejecting ink droplets
6, F7 and an injection stabilizing pulse S4 for suppressing the residual vibration of the injection pulses F6, F7. The peak values (voltage values) of all the pulses are the same. The drive waveform for 720 dpi is the drive waveform 20 used in the first conventional example.
Is the same as As shown in FIG.
When the length L is 12.0 mm and the emission diameter of the nozzle 618 is φ26 μm, when the driving waveform 30 of the driving voltage of 18 (V) is applied, the volume of the ejected ink droplet becomes 4
When a drive waveform 20 of a drive voltage of 0 pl and 16 (V) is applied, the drive waveform becomes 20 pl, and the ink drop volume difference between the modes is larger than in the first conventional example, so that good print image quality can be obtained.

According to experiments, the maximum driving frequency at which the driving waveform 30 can be jetted stably is 13000 (Hz), and the driving waveform 20
The maximum driving frequency that can stably inject is 16000 (H
z) and therefore FIG.
As shown in (b), the moving speed of the carriage during image formation is 13000/360 = 360 dpi mode.
The speed is 36.1 (IPS), and the speed is 16000/720 = 22.2 (IPS) in the 720 dpi mode. In this case, two carriage speeds are required.

[0014]

As described in the above-mentioned prior art, when increasing the resolution in the carriage movement direction, some new carriage movement speeds have to be prepared in accordance with the resolution in the slower one. Must.

In general, in a serial type image forming apparatus, a carriage is driven by a stepping motor or a DC motor. In order to maintain a maximum printing speed and realize various resolutions, a repetitive driving frequency of an ink ejecting apparatus is set to a maximum possible frequency. And changing the moving speed of the carriage according to the resolution to be realized. Usually, it is designed so that three to four moving speeds can be selected. When the moving speed changes, a change in the motor drive system, a change in the motor drive current value, a change in the parameters of the acceleration / deceleration sequence, and the like are performed for the motor control. Further, in the ink jet type image forming apparatus, when printing is performed while the carriage reciprocates, the dot position shifts depending on the printing direction and further shifts depending on the moving speed, so that it is necessary to change parameters for dot position adjustment. For this purpose, the print control means stores all the above parameters and uses them properly. Further, when there is a possibility that the current value or the driving method may be changed, hardware having a function capable of realizing them is required.

Further, a stepping motor is often used to drive the carriage. In the case of the stepping motor, in addition to the above-described problems, vibrations are a problem with respect to the movement of the carriage. The vibration of the carriage becomes more problematic as the rotational speed range of the motor is widened, and adding a low speed greatly increases the rotational speed range of the motor.

As described above, the addition of the carriage speed has many problems such as storage of parameters, improvement of hardware functions, and problems of carriage vibration.

Accordingly, the present invention is to solve such a problem. An object of the present invention is to provide an image forming apparatus having a print mode capable of executing a plurality of resolutions without increasing the type of moving speed of a carriage. To provide.

[0019]

According to the first aspect of the present invention, there is provided an ink for ejecting ink filled in an ink chamber as droplets by applying an ejection pulse signal to an actuator. The ejecting device is mounted on a carriage that moves along the print medium, and the ink ejecting device ejects ink droplets while moving along the print medium, and expresses a print pattern by dots composed of ink droplets that land on the print medium. In the image forming apparatus, a plurality of printing modes for executing printing at each printing resolution having a different dot diameter are provided, and in at least two of the plurality of printing modes, the minimum dot in the moving direction of the carriage is set. The forming interval 1 / H is determined from the repetitive drive frequency F of the actuator of the ink ejecting apparatus,
The moving speed F / H of the carriage is the same.

By setting the minimum dot formation interval of each resolution and the repetition drive frequency of the actuator to predetermined values in at least two print modes, the carriage speed can be made the same regardless of the resolution, and the carriage movement There is no need to increase the type of speed.

According to a second aspect of the present invention, there are provided a plurality of printing modes for executing printing based on data of different printing resolutions, and the carriage is provided in at least two of the plurality of printing modes. The moving speed of the same, the actuator of the ink ejection device,
It is characterized by driving at a repetitive drive frequency according to each resolution and the moving speed of the carriage. Each print mode of a plurality of resolutions can be executed at the same carriage speed.

According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, a driving waveform applied to the actuator in a high resolution printing mode is lower than that in a lower resolution printing mode. The number of ejection pulses per dot is smaller than the drive waveform applied to the actuator.

As described above, since the number of ejection pulses is small at a high resolution, it is possible to increase the maximum repetition drive frequency of the ink ejection means, and to clarify the difference in the dot size between each resolution. Becomes possible.

According to a fourth aspect of the present invention, in the image forming apparatus according to the first or second aspect, the repetitive drive frequency in each of the print modes is a drive waveform for obtaining the dot diameter at each resolution. And the actuator has a substantially highest repetition drive frequency at which the actuator can stably eject. As described above, since the repetition drive frequency is almost the highest repetition drive frequency at which stable ejection can be performed, printing at each resolution can be stably realized at high speed.

According to a fifth aspect of the present invention, in the image forming apparatus according to the first or second aspect, the ink ejecting apparatus changes the volume of the ink chamber by the operation of the actuator. A pressure wave is generated to eject ink droplets.
As described above, in a device that generates a pressure wave, by associating the drive waveform with the propagation time of the pressure wave, it is possible to effectively realize the configurations of the above-described claims.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings.

The mechanical structure of the image forming apparatus and the ink ejecting apparatus according to the present embodiment is the same as the conventional structure described with reference to FIGS.

An example of specific dimensions of the ink droplet ejection device 600 will be described. The length L of the ink chamber 613 is 8.0 mm
It is. The size of the nozzle 618 was such that the diameter on the ink droplet ejection side was 26 μm, and the ratio L / a (= T) between the sound velocity a and the L in the ink in the ink chamber 613 was 8.0 μsec.

An image forming method according to the present embodiment will be described in the case where the ink jetting apparatus having such a configuration has a plurality of printing resolutions in the carriage moving direction, for example, 300 dpi and 600 dpi.

FIG. 2 shows an example of the driving waveform. Drive waveform 1
0 is a driving waveform for 300 dpi.
This is the ratio of the length of time to the one-way propagation time T of the pressure wave in the ink flow path 613. Two ejection pulses F1 and F2 for ejecting ink droplets and the ejection pulses F1 and F2
Injection stabilization pulse S1 for suppressing the residual vibration of
Two ejection pulses F3 for ejecting ink droplets again,
F4 and an injection stabilizing pulse S2 for suppressing the residual vibration of the injection pulses F3 and F4. The peak values (voltage values) of all the pulses are the same.

The driving waveform 20 is a driving waveform for 600 dpi, and is the same as that described with reference to FIG.

As shown in FIG.
Length L is 8.0 mm and the emission diameter of the nozzle 618 is φ
When the driving waveform 10 having a driving voltage of 17 (V) is applied at 26 μm, the volume of the ink droplet ejected is 60 p.
When a drive waveform 20 of a drive voltage of 1, 15 (V) is applied, the drive voltage becomes 15 pl. An ink droplet volume difference between the modes is larger than in the conventional example, and good print image quality can be obtained.

Experiments have shown that the maximum drive frequency at which the drive waveform 10 can be stably ejected is 7500 (Hz), and that the maximum drive frequency at which the drive waveform 20 can be stably ejected is 15000 (Hz). ing.

Therefore, as shown in FIG. 1, the moving speed of the carriage during image formation is 7 in the 300 dpi mode.
500/300 = 25.0 (IPS), and 15000/600 = 2 in the 600 dpi mode.
5.0 (IPS), in this case 1
Only one carriage speed is required.

FIG. 8 is a block diagram showing an electrical configuration of the image forming apparatus. The control system according to the present embodiment includes a microcomputer 41 having one chip, a ROM 42, and a RAM.
43. The microcomputer 41 drives the operation panel 14 for the user to give a print instruction and the like, a motor drive circuit 35 for driving a print medium conveyance motor 38, and a carriage moving motor 37 equipped with an ink ejecting device. And a motor drive circuit 36 are connected.

The ink ejection device 600 is driven by a drive circuit 21, which is controlled by a control circuit 22. That is, as shown in FIG. 6, the electrodes 619 and 621 provided in the respective ink flow paths 613 of the head unit 600 are connected to the drive circuit 21. The drive circuit 21 generates various pulse signals based on the control of the control circuit 22 and applies them to the ink ejecting apparatus.

A microcomputer 41 and a ROM 42,
The RAM 43 and the control circuit 22 are connected via an address bus 23 and a data bus 24. The microcomputer 41 generates a print timing signal TS and a control signal RS according to a program stored in the ROM 42 in advance, and transfers them to the control circuit 22.

The control circuit 22 is constituted by a gate array and prints the image data on a print medium based on the image data stored in the image memory 25 in accordance with the print timing signal TS and the control signal RS. Data DATA, a transfer clock TCK synchronized with the print data DATA, a strobe signal STB,
A print clock CLK is generated and transferred to the drive circuit 21.

The control circuit 22 converts image data transferred from an external device such as a personal computer 26 through the Centronics interface 27 into
It is stored in the image memory 25. And the control circuit 2
2 generates a Centronics data reception interrupt signal WS based on the Centronics data transferred from the external device via the Centronics interface 27, and transfers it to the microcomputer 41. In addition,
Each of the signals DATA, TCK, STB, and CLK is supplied to a harness cable 28 that connects the drive circuit 21 and the control circuit 22.
Forwarded over.

The microcomputer 41 determines the resolution of the image data transferred from the external device according to the program stored in the ROM 42, outputs a control signal RS corresponding to the resolution, and outputs a control signal RS corresponding to the resolution. The print clock CLK having the above-described highest drive frequency is output. The microcomputer 41 specifies the rotation speed of the carriage moving motor 37 to the drive circuit 35 according to the program stored in the ROM 42. The drive waveforms 10 and 2 are stored in a predetermined area of the ROM 42.
0 is stored in the microcomputer 4
Numeral 1 reads out the drive waveform data corresponding to the determined resolution and outputs it to the drive circuit via the control circuit 22. The resolution can be specified from the operation panel 44. That is, the microcomputer 41, the ROM 42, the RAM 4
3. The control circuit 22 constitutes means for determining the resolution, setting the print mode according to the resolution, setting the repetitive driving frequency of the ink ejecting device, setting the moving speed of the carriage, and the like.

[0041]

As described above, according to the image forming apparatus of the present invention, since the carriage moving speed is the same in a plurality of resolution printing modes, there is no need to increase the type of carriage moving speed. Unlike the related art, there is no need to store many parameters for changing the moving speed or to add hardware, and the problem of carriage vibration can be solved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a combination of a printing resolution and a driving frequency according to an embodiment of the present invention.

FIG. 2 is a diagram showing driving waveforms according to the embodiment of the present invention.

FIG. 3 is a diagram showing a combination of a conventional printing resolution and a driving frequency.

FIG. 4 is a diagram showing a driving waveform according to a conventional example.

FIG. 5 is a diagram illustrating a relationship between dimensions and ink droplet volumes of an ink ejecting apparatus according to an embodiment of the present invention and a conventional example.

FIG. 6 is a diagram illustrating an ink ejecting apparatus according to the embodiment of the present invention.

FIG. 7 is a diagram illustrating the operation of the ink ejecting apparatus according to the embodiment of the present invention.

FIG. 8 is a diagram illustrating an electrical control configuration of the image forming apparatus according to the embodiment of the present invention.

FIG. 9 is a diagram illustrating a structure of an image forming apparatus according to an embodiment of the present invention.

[Explanation of symbols]

 10 Drive Waveform 20 Drive Waveform 600 Ink Ejector 613 Ink Flow Path 618 Nozzle

Claims (5)

[Claims] An ink ejecting apparatus for ejecting ink filled in an ink chamber as droplets by applying an ejection pulse signal to an actuator is mounted on a carriage moving along a print medium, and the ink ejecting apparatus is provided with the ink ejecting apparatus. In an image forming apparatus which ejects ink droplets while moving along a print medium and expresses a print pattern by dots composed of ink droplets that have landed on the print medium, a plurality of dots having different dot diameters for printing at different print resolutions are provided. In at least two of the plurality of print modes, the minimum dot formation interval 1 / H in the moving direction of the carriage and the repetition drive frequency F of the actuator of the ink ejecting apparatus are determined. Wherein the moving speed F / H of the carriage is the same. 2. An ink ejection device that ejects ink filled in an ink chamber as droplets by applying an ejection pulse signal to an actuator is mounted on a carriage that moves along a print medium, and the ink ejection device includes An image forming apparatus that ejects ink droplets while moving along a print medium and expresses a print pattern by dots composed of ink droplets landed on the print medium, wherein a plurality of prints are executed based on the data of the different print resolutions. The printing mode has the same moving speed of the carriage in at least two of the plurality of printing modes, the actuator of the ink ejecting device, according to each resolution and the moving speed of the carriage. An image forming apparatus driven at a repetitive driving frequency. 3. A drive waveform applied to the actuator in a high-resolution print mode has a smaller number of ejection pulses per dot than a drive waveform applied to the actuator in a low-resolution print mode. The image forming apparatus according to claim 1 or 2, wherein 4. The repetitive drive frequency in each of the print modes is a drive waveform for obtaining the dot diameter at each resolution, and is substantially the highest repetitive drive frequency at which the actuator can stably eject. The image forming apparatus according to claim 1 or 2. 5. The ink jet apparatus according to claim 1, wherein the operation of the actuator changes the volume of the ink chamber to generate a pressure wave in the ink chamber, thereby jetting ink droplets. The image forming apparatus according to claim 1.