JP2002001949A - Ink jet printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To excellently control an ink ejection not influenced by change of environmental temperature without providing a special memory device in an ink jet printer driven in contact upon printing operation. SOLUTION: An ink jet printer is provided with a pressurizing chamber formed by a vibration plate 34 of which a part can bend outward, a nozzle connecting the pressurizing chamber with the outside, and an electrode 35 arranged in opposition to the vibration plate 34 with a gap G of a predetermined distance. In printing, a driving voltage obtained by addition of a zero voltage to be charged between the vibration plate 34 and the electrode 35 when the contact between the vibration plate 34 and the electrode 35 is detected and a predetermined ejecting voltage is applied between the vibration plate 34 and the electrode 35.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an ink jet printer.

[0002]

2. Description of the Related Art Conventionally, a plurality of pressurizing chambers, each of which is formed by a vibrating plate partially bent outward, a nozzle formed in the pressurizing chamber, and a vibrating plate having a predetermined gap. There is an ink-jet printer having an ink-jet head having electrodes arranged opposite to each other.

In such an ink jet printer,
A voltage is applied between the diaphragm and the electrode while the ink is supplied to the pressurizing chamber. As a result, an electrostatic force acts between the diaphragm and the electrode, and the diaphragm bends in a direction to increase the volume of the pressurizing chamber. When the application of the voltage to the electrodes is stopped, the diaphragm rapidly returns to the initial position. When the support returns to the initial position, the volume in the pressurizing chamber contracts, and the ink in the pressurizing chamber is pressurized. Thereby, a part of the ink in the pressurized chamber is ejected from the nozzle as an ink droplet.

[0004] The diaphragm forming a part of the pressurizing chamber gradually bends outward according to the voltage applied to the electrode. When the applied voltage exceeds a predetermined value, the diaphragm rapidly bends to a position where it contacts the electrode due to the balance between the mechanical force acting on the diaphragm and the electrostatic force generated in the gap. Hereinafter, the printing operation performed by applying a voltage to the electrode such that the diaphragm is brought into contact with the electrode is referred to as contact driving, and the printing operation performed by applying a voltage to the electrode so that the diaphragm is not brought into contact with the electrode is not performed. It is called contact drive.

Japanese Patent Application Laid-Open No. Hei 7-132598 discloses that, in an ink jet printer that performs a printing operation by non-contact driving, in order to stabilize the print density, the charge rate of the charge near the electrode of the diaphragm is determined by the charge rate. There has been disclosed a technique in which the operation speed of an electrostatic actuator is controlled so that the operation speed is in a range sufficiently smaller than the discharge speed when discharging. According to the technology disclosed in the publication, the suction speed of the ink into the pressurized chamber is made smaller than the discharge speed of the ink out of the pressurized chamber, and the difference in the flow path impedance at the nozzle or the like is used. Thus, stable ink ejection can be realized.

Japanese Patent Application Laid-Open No. 10-202883 discloses a temperature detecting means for detecting the ambient temperature of the ink jet head in order to perform temperature compensation control of the ink discharge characteristics, and based on the detected ambient temperature. A drive control device for an inkjet head that corrects a pulse width of a voltage applied to an electrostatic actuator is disclosed. According to the technique disclosed in the publication, a correction pulse width is calculated in accordance with the ambient environment temperature detected by the temperature detection means, and the calculated correction pulse width is added to a preset pulse width. By applying a drive voltage having a pulse width to the electrostatic actuator, it becomes possible to perform temperature compensation control of ink ejection characteristics. According to the technology disclosed in the publication, a correction table in which a drive voltage is associated with each ambient environment temperature is stored in advance,
It is possible to improve the processing speed by omitting the arithmetic processing for adding the correction pulse width.

Further, in the above-described ink jet printer, regardless of the contact driving or the non-contact driving, if the diaphragm is bent outward by applying a voltage, the shape of the pressurizing chamber and the flow of the ink are reduced. The ink in the pressurized chamber vibrates due to the above. As a result, the ink level at the nozzle (hereinafter,
Meniscus vibration occurs in which the meniscus is displaced.

FIG. 12 is a correlation diagram showing the relationship between the amount of meniscus displacement at the nozzles and the time during printing of a conventional ink jet printer. In FIG. 12, the horizontal axis represents the passage of time, and the vertical axis represents the amount of meniscus displacement based on a certain position in the nozzle.
When voltage application between the diaphragm and the electrode is started (FIG. 1)
2a), the meniscus displacement amount sharply decreases. When the diaphragm comes into contact with the electrode (a ′ in FIG. 12), the meniscus displacement starts to increase. When the application of the voltage to the electrodes is stopped (FIG. 12B), ink is ejected from the nozzles (FIG. 12B '), and the meniscus displacement thereafter sharply decreases again.

In ejecting ink, it has been conventionally practiced to improve the driving efficiency by utilizing the behavior of ink observed in meniscus vibration.

[0010]

However, Japanese Patent Application Laid-Open No.
According to the technology disclosed in Japanese Patent Application Laid-Open No. 132598, it is possible to realize stable ink ejection with respect to an ink jet printer that performs a printing operation by non-contact driving, but a voltage sufficient to bring the diaphragm into contact with the electrode. However, it is difficult to apply the present invention to an ink jet printer that performs a printing operation by a contact drive in which is applied to an electrode.

In the technique disclosed in Japanese Patent Application Laid-Open No. 10-202888, every time the ambient temperature is detected, the corresponding correction value and the pulse width of the target voltage are calculated. Processing becomes complicated. Further, in the technology disclosed in the publication, a storage device having a large capacity for storing a correction table must be provided in order to improve a processing speed without performing an arithmetic process.
There is a concern that the cost of the device will increase.

In addition, in general, the viscosity of the ink used in an ink jet printer depends on the environmental temperature,
At an ambient temperature of 40 ° C. to 40 ° C., it is expressed by the following equation. η = α (1 / T) + β In the formula, η is the viscosity of the ink, α and β are constants, and T is the absolute temperature.

As can be seen from the equation, the viscosity of the ink is
It changes according to the change of environmental temperature. On the other hand, in the above-described ink jet printer, viscosity of the ink is one of the factors in determining the vibration characteristics of the ink system in the pressurizing chamber and the ink flow path. When the viscosity of the ink changes due to a change in the environmental temperature, the vibration characteristics of the ink system change. As a result, the ejection speed Vj of the ink droplets ejected from the nozzles changes, making it difficult to perform a stable printing operation.

Further, in the conventional technique, the time for applying a voltage to the electrode is considered as the time from the start of the voltage application. For this reason, from when the diaphragm abuts on the electrodes until the application of the voltage is stopped (between a ′ and b ′ in FIG. 10).
Causes a variation in time. That is, a variation occurs in the meniscus displacement amount at the time when the application of the voltage is stopped. For this reason, variations occur in the ink ejection speed,
Problems such as unevenness occur in the print result.

The present invention relates to an ink-jet printer which performs a contact drive during a printing operation and can perform good ink discharge control without being affected by a change in environmental temperature without providing a special storage device. The purpose is to obtain.

According to the present invention, an ink jet printer that performs a contact driving during a printing operation is provided at low cost.
An object of the present invention is to provide an ink jet printer capable of obtaining a good print result without being affected by a change in ink viscosity.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an ink jet printer which performs a contact drive during a printing operation and which can perform stable ink ejection control without being affected by a change in environmental temperature.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an ink-jet printer which performs a contact driving at the time of a printing operation and can obtain a good print result without being affected by a change in environmental temperature.

[0019]

According to the first aspect of the present invention, there is provided an ink jet printer for performing a printing operation on a recording material by an ink jet method using an ink jet head. A pressure chamber formed by a diaphragm that can bend in a direction, a nozzle that communicates the pressure chamber with the outside, an electrode having a gap at a predetermined interval, and an electrode disposed opposite to the diaphragm, Voltage applying means for applying a voltage between the diaphragm and the electrode, and contacting the diaphragm and the electrode by applying a voltage between the diaphragm and the electrode by the voltage applying means. Contact detecting means for detecting the contact between the diaphragm and the electrode when the contact detecting means detects the contact between the diaphragm and the electrode; Configured and voltage acquiring means for acquiring a voltage by, when printing was to apply a drive voltage obtained by adding the said zero voltage with a preset discharge voltage by the voltage applying means to the electrodes.

Therefore, in the ink-jet head, the driving voltage obtained by adding the voltage acquired by the voltage acquiring means and the ejection voltage when the contact between the diaphragm and the electrode is detected by the contact detecting means is used for printing. The voltage is applied to the electrodes by the voltage applying means. by this,
A voltage that brings the diaphragm and the electrode into contact with each other and sets the discharge speed of the ink discharged from the nozzles to zero is set to zero voltage, and the desired discharge speed can be obtained by adding to this zero voltage. By obtaining the voltage as the ejection voltage in advance through experiments or the like, it becomes possible to obtain the target ejection speed based on the gradient of the ink ejection speed. Further, since it is only necessary to store the ejection voltage, it is not necessary to separately provide a storage device having a particularly large storage capacity.

According to a second aspect of the present invention, in the ink jet printer according to the first aspect, the voltage obtaining means includes:
The zero voltage is acquired at every predetermined timing.

Therefore, the drive voltage is updated at every predetermined timing. This makes it possible to minimize the update of the drive voltage without acquiring a zero voltage every time ink is ejected.

According to a third aspect of the present invention, there is provided an ink jet printer for performing a printing operation on a recording material by an ink jet method using an ink jet head, wherein the ink jet head is capable of partially bending outward. A pressurizing chamber formed by a diaphragm, a nozzle for communicating the pressurizing chamber with the outside, an electrode having a gap at a predetermined interval, disposed opposite to the diaphragm, and the diaphragm and the electrode Voltage applying means for applying a voltage therebetween, and contact detecting means for detecting contact between the diaphragm and the electrode by applying a voltage between the diaphragm and the electrode by the voltage applying means. And a timer for measuring a predetermined time after detecting the contact between the diaphragm and the electrode by the contact detection means, and It was set to apply a voltage only to the electrodes while the predetermined time is measured by the time measuring means from the detection of the contact between the electrode and the vibrating plate by the abutment detection means by pressurizing means.

Therefore, during printing, a voltage is applied to the electrodes by the voltage applying means only during a predetermined period of time measured by the timing means after the contact between the diaphragm and the electrodes is detected by the contact detecting means. You. This makes it possible to obtain the target discharge speed based on the meniscus vibration by previously acquiring the time until a meniscus occurs at which the target discharge speed can be obtained by an experiment or the like.

According to a fourth aspect of the present invention, in the ink jet printer according to the third aspect, the voltage applying means includes:
A rectangular wave voltage is applied.

Therefore, a rectangular voltage is applied to the electrodes. This makes it possible to prevent the vibration of the diaphragm from occurring.

The invention described in claim 5 is the invention according to claims 1, 2, and 3.
5. The ink jet printer according to claim 4, wherein a plurality of the pressure chambers are provided, and the contact detection unit detects contact between the diaphragm and the electrode in one of the pressure chambers.

Therefore, only the contact between the diaphragm and the electrode in one pressure chamber is detected. This makes it possible to apply an appropriate drive voltage to all the diaphragms and electrodes with a simple circuit configuration even when a plurality of pressurizing chambers are provided.

According to a sixth aspect of the present invention, in the ink jet printer according to the fifth aspect, the voltage applying means applies the voltage to the diaphragm and the electrode, to which a voltage is applied by the contact detecting means, other than during printing. A collecting member is provided for applying a voltage and collecting ink ejected from the pressurizing chamber corresponding to the diaphragm and the electrode.

Therefore, a driving voltage is obtained based on the contact between the diaphragm and the electrode to which no voltage is applied during printing, and the ink ejected at this time is collected by the collecting member. As a result, it is possible to acquire the drive voltage without performing the printing operation using the paper.

[0031]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to FIGS. The present invention shows an example of application to an ink jet printer which is used by being connected to a personal computer or the like and performs a printing operation in accordance with print data transmitted from the personal computer.
The inkjet printer according to the present embodiment performs monochrome printing.

FIG. 1 is a perspective view showing an ink jet printer according to a first embodiment of the present invention, and FIG. 2 is a longitudinal sectional side view thereof. In a casing 2 of the inkjet printer 1, a paper feed port 4 in which a paper feed cassette 3 for holding and stacking sheets is mounted, a manual feed tray 5 for stacking and holding sheets by manual feeding, and a sheet ejection for discharging printed sheets. A tray 6 is provided. FIG. 1 shows a paper cassette 3
Is in a state of being mounted.

An upper cover 8 is provided above the casing 2 so as to be rotatable in a direction away from the casing 2 about a support shaft 7 provided above the paper discharge tray 6. The casing 2 is opened by rotating the upper cover 8 in a direction away from the casing 2 around the pivot 7. The upper cover 8 is opened, for example, when exchanging an ink cartridge 19 described later.

Although not shown, the casing 2 is provided with various operation keys such as a power switch and a key for declaring execution of a drive voltage setting process described later.

In the casing 2, a paper transport path 10 is formed from the paper feed cassette 3 or the manual feed tray 5 to the paper discharge tray 6 via the printing mechanism 9.

A paper feed mechanism 11 of a friction pad type is provided at the end of the paper feed path 10 on the paper feed cassette 3 side. The paper feed mechanism 11 includes a paper feed roller 12 and a friction pad 13, and separates the sheets stacked and held in the paper feed cassette 3 by the paper feed roller 12 and the friction pad 13. Paper is fed to the paper transport path 10.

A paper feed roller 14 is provided at the end of the paper transport path 10 on the manual tray 5 side. Paper feed roller 1
4 separates the sheets stacked and held on the manual feed tray 5 one by one and feeds them to the sheet transport path 10.

In the paper transport path 10, a transport roller 15 and a plurality of pairs of transport rollers 16 are provided. Transport roller 1
5 and a plurality of pairs of transport rollers 16 are rotationally driven by a drive motor (not shown), and transport the paper in the paper transport path 10.

The printing mechanism 9 includes a carriage 17 slidable in the main scanning direction, an inkjet head 18 mounted on the carriage 17, and an inkjet head 18.
Is formed by an ink cartridge 19 and the like which hold ink to be supplied to the printer.

The carriage 17 is slidably supported in the main scanning direction by a main guide rod 20 provided in the casing 2 and extending in the main scanning direction, and a sub guide rod 21 parallel to the main guide rod 20. ing. A driving pulley 22 and a driven pulley 23 are provided in the casing 2.
And a timing belt 24 that is wound around the main guide rod 20 and is rotated along the direction in which the main guide rod 20 extends.
The drive pulley 22 is driven to rotate by a main scanning motor 25. The carriage 17 is attached to a part of the timing belt 24. Thus, the carriage 17 can be slid in the main scanning direction by driving the main scanning motor 25 to rotate the timing belt 24.

The ink jet head 18 is mounted on the carriage 17 such that the nozzles (see FIG. 3) 26 face the lower side (toward the paper transport path 10). In the inkjet head 18 of the present embodiment, the diaphragm 34 is
This is an inkjet head 18 that performs a contact drive to bend until it comes into contact with both (described later).

The ink cartridge 19 is provided with an air port communicating with the outside and an ink supply port (both not shown) communicating with the ink jet head 18, and a porous body (not shown) filled with ink. Is built-in. The ink cartridge 19 is provided detachably with respect to the carriage 17. Thus, when the ink runs out, the ink can be refilled by replacing the ink cartridge 19.

In addition, a recovery device 27 is provided in the casing 2 at a standby position of the carriage 17 at one end of the main guide rod 20. Although illustration and detailed description of each part are omitted because of the known technique, the recovery device 27
Includes a capping mechanism that caps the nozzle 26 of the inkjet head 18, a suction mechanism that suctions the nozzle 26 of the capped inkjet head 18, and a cleaning mechanism that cleans the nozzle 26 and the vicinity of the nozzle 26. The recovery device 27 is operated only when the carriage 17 is at the standby position.

The capping mechanism caps the nozzle 26 while the carriage 17 is at the standby position, and maintains the vicinity of the nozzle 26 in a wet state.

The suction mechanism is driven in a state where the nozzle 26 is capped by the capping mechanism, and generates a negative pressure in a state where a tube or the like is communicated with the nozzle 26, so that the suction mechanism and the ink inside the pressure chamber 44 which will be described later. Are sucked from the nozzle 26. The suction mechanism has a waste ink reservoir for collecting the sucked ink. The waste ink reservoir includes an ink absorber (not shown) formed of a porous body in a waste ink case (not shown).

The cleaning mechanism wipes the nozzle 26 and the vicinity of the nozzle 26 with, for example, a wiper (not shown), thereby removing ink, dust and the like adhering to the periphery of the nozzle 26 and preventing the nozzle 26 from being clogged.

Next, the ink jet head 18 will be described. FIG. 3 is an exploded perspective view showing the inkjet head 18, and FIG. 4 is a longitudinal sectional view thereof. The ink jet head 18 includes a liquid chamber substrate 28, an electrode substrate 36, a nozzle plate 30, and the like.

The liquid chamber substrate 28 is formed of a silicon substrate such as a single-crystal silicon substrate, a polycrystalline silicon substrate, or an SOI substrate, and has two rows of recesses 32 in which a plurality of recesses 31 extend parallel to one end surface. Is formed. Each recess 31
The inner part of the concave row 32 is formed to be shallower than the outer part. Further, a rectangular through hole 33 is formed in the liquid chamber substrate 28 so as to be sandwiched between the concave row 32.

On the bottom surface of each recess 31 of the liquid chamber substrate 28, there is provided a diaphragm 34 having an elastic force capable of bending downward in FIG. In a normal state, the vibration plate 34
It has a planar shape as shown in FIG. A conductive substance is diffused in the vibration plate 34, whereby the vibration plate 34 itself has conductivity. Further, an electrode film having conductivity may be laminated on the vibration plate 34.

Although a detailed description is omitted because it is a known technique, the diaphragm 34 is formed by, for example, etching a liquid chamber substrate 28 on which a high-concentration boron layer which is not eroded by an etchant is formed. 31 can be formed. Further, the diaphragm 34 can be formed by attaching a polycrystalline silicon thin film to the liquid chamber substrate 28 in which the holes are already formed.

On the vibration plate 34 side of the liquid chamber substrate 28, there is provided an electrode substrate 36 on which a plurality of electrodes 35 corresponding to the respective recesses 31 are formed. The electrode substrate 36 is joined to the liquid chamber substrate 28 such that a predetermined gap G is formed between the electrode 35 and the vibration plate 34. The electrode substrate 36 has a through hole 33 in a state of being joined to the liquid chamber substrate 28.
A rectangular through-hole 37 is formed at a position overlapping with. In a state where the liquid chamber substrate 28 and the electrode substrate 36 are joined, a common liquid chamber flow path 38 is formed by the through holes 33 and 37. The surface of the electrode 35 facing the liquid chamber substrate 28 is covered with a protective film (not shown). The electrode 35
Are connected via a FPC cable 39 to a driver IC 40 for applying a voltage to each electrode 35.

On the surface of the electrode substrate 36 opposite to the surface on which the electrodes 35 are formed, ink supply holes 41 are formed at positions overlapping the through holes 33 and 37 in a state of being joined to the electrode substrate 36. , A joint member 42 are provided. The ink supply hole 41 communicates with the ink supply port of the ink cartridge 19 via another joint member (not shown), a filter, or the like.

A nozzle plate 30 is provided on the opening side of the concave portion 31 of the liquid chamber substrate 28. The nozzle plate 30 is provided with the nozzles 2 associated with the respective recesses 31.
6 are formed. The nozzle plate 30 has an insulating adhesive 43 applied so as to cover the outside of the end of the liquid chamber substrate 28 and the connection between the electrode 35 and the FPC cable 39.
Thereby, it is joined to the electrode substrate 36 and the liquid chamber substrate 28. In addition, the nozzle plate 30 includes the liquid chamber substrate 28,
It is fixed to a frame F arranged beside the electrode substrate 36 and the joint member 42 by an insulating adhesive 43.

A plurality of pressurizing chambers 44 are formed by closing the opening of the recess 31 with the nozzle plate 30. Each of the pressure chambers 44 is communicated with the outside by the nozzle 26. Each recess 31 is formed by a recess row 32.
Are formed to be shallower on the inner side than on the outer side. Therefore, even when the opening of the concave portion 31 is closed by the nozzle plate 30, each pressurizing chamber 44 is connected to the common liquid chamber flow path 38.
Is communicated to. At this time, each of the pressurizing chambers 44 and the common liquid chamber flow path 38 communicate with each other via a fluid resistance portion 45 which is a wall surface of the concave portion 31 formed shallower than the outside. By providing the fluid resistance portion 45, the ink in the pressurizing chamber 44 can be satisfactorily pressurized.

The ink jet head 18 of the present embodiment
Are the dimensions of the diaphragm 34 and the electrodes 35 in each pressure chamber 44.
When a voltage is applied between the diaphragm 34 and the electrode 35 in a printing operation or a drive voltage setting process, which will be described later, by adjusting the gap G and the like of the gap G between the diaphragm 34 and the diaphragm 34. Until the electrode 35 contacts the diaphragm 34
Is formed to be equal to a voltage for making the ejection speed of the ink ejected from the nozzle 26 zero. That is, ink is not ejected from the nozzle 26 until the vibration plate 34 contacts the electrode 35.

Next, a control system provided in the ink jet printer 1 will be described with reference to FIG. FIG. 5 is a block diagram schematically showing a control system related to printing among the control systems provided in the inkjet printer 1. The inkjet printer 1 has a control device 46 that centrally drives and controls each unit in the inkjet printer 1.

Although not shown, the control device 46 is provided with a storage device for storing an ejection voltage used in a drive voltage setting process described later. The ejection voltage is
This voltage is such that a desired ejection speed can be obtained at the time of a printing operation by adding to a zero voltage described later.

Here, FIG. 6 is a correlation diagram showing the relationship between the drive voltage and the ink ejection speed obtained by experiments. As can be seen from FIG. 6, it is known that the slope of the ink ejection speed is not affected by the change in the viscosity of the ink within the temperature range (5 ° C. to 40 ° C.) which is a practical problem. In the present embodiment, the target ejection speed is obtained by applying a voltage between the diaphragm 34 and the electrode 35 based on the gradient of the ejection speed of the ink, which is known not to be affected by the change in the viscosity of the ink. The voltage obtained by subtracting the zero voltage that makes the discharge speed 0 by applying the voltage between the diaphragm 34 and the electrode 35 from the applied voltage was used as the discharge voltage.

Although not particularly shown, the control device 46 includes a diaphragm 34 during a drive voltage setting process described later.
Various storage areas for temporarily storing the drive voltage applied between the electrode and the electrode 35 and the detected zero voltage are secured.

In addition, a charge / discharge circuit 47 as a voltage applying means for applying a voltage between the diaphragm 34 and each electrode 35 is connected to the control device 46. The diaphragm 34 and each electrode 35 are connected to the charge / discharge circuit 47, respectively.

A current detection circuit 48 is connected between one electrode 35a of the plurality of electrodes 35 and the charge / discharge circuit 47 (see FIG. 7). To the current detection circuit 48, a comparison circuit 49 for detecting contact between the diaphragm 34 and the electrode 35 when setting a drive voltage described later is connected.

The current detecting circuit 48 has a known resistance 50 provided between one electrode 35a of the plurality of electrodes 35 and the charging / discharging circuit 47, and amplifies the voltage value of the resistance 50. It is formed by the differential amplifier circuit 51. The current detection circuit 48 detects the current value of the resistor 50 based on the detected voltage value obtained by amplifying the voltage value of the resistor 50 by the differential amplifier circuit 51.

The comparison circuit 49 determines whether the diaphragm 34 contacts the electrode 35 based on the reference voltage value input from the reference voltage signal source 52 and the detected voltage value input from the differential amplifier circuit 51. To detect.

In this embodiment, no voltage is applied to the electrode 35a during the printing operation. That is, the ink ejected from the pressure chamber 44 corresponding to the vibration plate 34 facing the electrode 35a does not participate in printing.

Next, the operation of each part of the ink jet head 18 when performing a printing operation in the ink jet printer 1 will be described. In the printing operation, by receiving the print data transmitted from the personal computer, the control device 46 declares the start of driving to the charge / discharge circuit 47.

When the drive start is declared, the charge / discharge circuit 47
Applies a voltage between the vibration plate 34 and the electrode 35 facing the pressure chamber 44 for discharging ink. Thereby, an electrostatic force acts between the diaphragm 34 and the electrode 35. Due to this electrostatic force, the diaphragm 34 bends in a direction to increase the volume of the pressurizing chamber 44.

When the application of the voltage between the diaphragm 34 and the electrode 35 is stopped, the flexed diaphragm 34 suddenly returns to the initial position. Since the ink is supplied to the pressurizing chamber 44 via the common liquid chamber flow path 38, the volume of the pressurizing chamber 44 contracts due to the column returning to the initial position, thereby reducing the volume of the pressurizing chamber 44. The ink is pressurized, and a part of the ink in the pressurizing chamber 44 is ejected from the nozzle 26 as an ink droplet. Thus, a printing operation is performed.

Next, a process of setting a drive voltage to be applied to the electrode 35 during the above-described printing operation will be described with reference to FIG. FIG. 8 is a timing chart showing the relationship between the current and voltage in the inkjet head 18 and the displacement of the diaphragm 34.

The drive voltage setting processing is executed when the start is declared by an operator's key operation or the like, or every time print data is transmitted a predetermined number of times from a personal computer.

In the drive voltage setting process, first, the main scanning motor 25 is driven to slide the carriage 17 to the standby position, and the nozzle 26 is capped by the capping mechanism.

Next, between the diaphragm 34 and the electrode 35a,
Apply drive voltage. When the application of a voltage between the diaphragm 34 and the electrode 35 is started (FIG. 8A), a peak current called a charging current is generated in the ink jet head 18 (FIG. 8B). ).

Thereafter, the displacement of the diaphragm 34 in the direction of the electrode 35 gradually increases in accordance with the voltage applied between the diaphragm 34 and the electrode 35 (see FIG. 8C). The diaphragm 34 is
Due to the balance between the mechanical force acting on the diaphragm 34 and the electrostatic force, when the amount of displacement of the diaphragm 34 with respect to the gap G exceeds a predetermined amount, the diaphragm 34 rapidly bends to a position where it contacts the electrode 35, and the amount of displacement is reduced. It becomes the maximum value at a stretch (FIG. 8 (c) B). The maximum value of the amount of displacement of the diaphragm 34 is determined by the size of the gap G until the diaphragm 34 contacts the electrode 35.

When the vibration plate 34 and the electrode 35 come into contact with each other, a capacitive peak current called a contact current is generated in the ink jet head 18 (FIG. 8B). The generated contact current is amplified by the differential amplifier circuit 51 and
Is input to the comparator C. In the comparison circuit 49,
The detection voltage from the differential amplifier circuit 51 input to the comparator C is compared with the reference voltage from the reference voltage signal source, and when the voltage input from the differential amplifier circuit 51 exceeds the reference voltage, Only, it outputs a contact current detection signal indicating that it has exceeded the threshold value to the control device 46. Here, the contact detecting means is realized.

In the contact between the diaphragm 34 and the electrode 35, it is not necessary to obtain an accurate value of the contact current, and it is possible to detect the peak position due to the occurrence of the contact current. I just need. In the present embodiment, the voltage value at the resistor 50 is directly input to the differential amplifier circuit. Thus, the circuit can be simplified.

In this embodiment, the contact between the diaphragm 34 and the electrode 35 is detected by the generation of a contact current.
However, the present invention is not limited to this. For example, the contact between the diaphragm 34 and the electrode 35 may be detected by a transmission optical sensor or the like.

When the contact current detection signal is input from comparison circuit 49, control device 46 obtains the voltage at this time as zero voltage based on the detection voltage output from differential amplifier circuit 51. The acquired zero voltage is temporarily stored in a storage area of the storage device. Here, a voltage acquisition unit is realized.

When the zero voltage is obtained, the control device 46 outputs a stop signal to the charge / discharge circuit 47 to stop applying the voltage. The charging / discharging circuit 47 stops applying a voltage between the diaphragm 34 and the electrode 35a in response to the stop signal (FIG. 8 (A) C). When the application of the voltage between the diaphragm 34 and the electrode 35a is stopped, the electric charge charged in the pressurizing chamber 44 is released, and the voltage at the electrode 35 is reduced at once (FIG. 8).
(a) C), the displacement of the diaphragm 34 returns to the initial value (FIG. 8).
(c) C). At this time, a bottom current called a discharge current in the direction opposite to the contact current is detected (C in FIG. 8B).

When the diaphragm 34 returns, the pressure chamber 44 corresponding to the diaphragm 34 to which the electrode 35 is applied and the electrode 35 is applied.
The ink droplets are ejected from the nozzles 26 of. Since the drive voltage setting process is executed with the carriage 17 at the standby position, the ejected ink droplets are collected in the waste ink reservoir via the capping mechanism. Here, a collecting member is constituted by the capping mechanism and the waste ink reservoir.

In this way, the drive voltage can be set without unnecessary consumption of paper in the drive voltage setting process.

Further, conventionally, the ink jet printer 1
By collecting the ink ejected in the drive voltage setting process by using the capping mechanism and the waste ink reservoir generally provided, the ink ejected in the drive voltage setting process can be collected without increasing the number of parts. Can be.

In this embodiment, the positions of the capping mechanism, which is a collection member, and the waste ink reservoir are fixed.
With the carriage 17 slid to the standby position,
The processing for setting the drive voltage is performed. However, the present invention is not limited to this. For example, the vibration plate 34 facing the electrode 35a may be used.
And a capping member (not shown) that slides the nozzle 26 of the pressurizing chamber 44 corresponding to the carriage 17 in accordance with the slide of the carriage 17.
By capping 6, the drive voltage setting process may be performed at an arbitrary position regardless of the position of the carriage in the main scanning direction. In this case, the waste ink reservoir may be a mechanism in which the waste ink case slides together with the capping member, or the capping member and the waste ink case may be communicated with a tube or the like with the waste ink reservoir fixed. Good.

In the printing operation performed after the above-described drive voltage setting process, the drive voltage is obtained by adding the zero voltage stored in the storage area and the ejection voltage stored in the storage device in advance in the above-described drive voltage setting process. A voltage is applied to the electrode 35.

Here, the diaphragm 34 is operated by the comparing circuit 49.
Amplifying circuit 5 when the contact between electrode and electrode 35 is detected.
The driving voltage obtained by adding the zero voltage and the ejection voltage obtained based on the first voltage to the charging / discharging circuit 47 during the printing operation is used.
Is applied to the electrode 35.

As a result, a voltage that causes the vibration plate 34 and the electrode 35 to come into contact with each other and makes the discharge speed of the ink discharged from the nozzle 26 zero is set to zero voltage. By obtaining a voltage capable of obtaining the ejection speed as the ejection voltage in advance by an experiment or the like, the target ejection speed can be obtained based on the gradient of the ink ejection speed.
Good printing results can be obtained without being affected by changes in the viscosity of the ink.

Further, by setting the drive voltage based on the zero voltage detected from the pressurizing chamber 44 of the ink jet head 18 actually used, a good drive voltage suitable for actual use can be obtained.

Further, in the present embodiment, the drive voltage setting process is executed when the start is declared by an operator's key operation or the like, or every time print data is transmitted a predetermined number of times from a personal computer. . That is, the drive voltage is set at a predetermined or arbitrary timing.

As a result, the drive voltage is updated at each predetermined timing, so that it is not necessary to acquire a zero voltage every print operation, and the update of the drive voltage can be minimized.

Further, since the current detecting circuit 48 is provided between one of the plurality of electrodes 35 a 35 a and the charging / discharging circuit 47, the current detecting circuit 48 is compared with the case where zero voltage is obtained for each pressurizing chamber 44. Thus, a zero voltage can be obtained with a simple circuit configuration.

Thus, even when a plurality of pressurizing chambers 44 are provided, a good print result can be obtained without greatly increasing the manufacturing cost and without being influenced by the change in the viscosity of the ink.

In addition, the storage device only needs to store one ejection voltage, and there is no need to separately provide a storage device having a particularly large capacity.

Thus, the ink jet printer 1 which can obtain a good print result without being influenced by the change in the viscosity of the ink can be obtained at low cost.

Next, FIG. 9 exemplifies an experimental result in a case where a printing operation is actually performed under various environmental temperatures using the driving voltage set under the above-described control. FIG.
FIG. 5 is a correlation diagram showing the relationship between the environmental temperature and the ejection speed when a printing operation is actually performed at various environmental temperatures using the drive voltage set under the above control.
Numerical values given in the vicinity of each plot in FIG. 9 are actual drive voltages applied to the electrodes 35 when the above-described control is performed.

In the printing operation, the voltage is set to zero voltage.
A drive voltage to which a discharge voltage of 5 V was applied was applied between the diaphragm 34 and each electrode 35. As a result, the diaphragm 34 is actually
There was a slight difference in the drive voltage applied between the electrode and each electrode 35.
It can be seen from FIG. 9 that the ejection speed can be stably obtained within a practically allowable range without being influenced by the change in the viscosity of the ink due to the environmental temperature.

In the present embodiment, the driving voltage applied between the diaphragm 34 and each electrode 35 is such that a zero voltage and a discharge voltage are added each time a voltage is applied to each electrode 35 during a printing operation. However, the present invention is not limited to this, and the drive voltage may be calculated when the zero voltage is obtained, and the drive voltage may be stored in the storage device. In this case,
At the time of the printing operation, the drive voltage can be acquired with reference to the storage device. At this time, the drive voltage is updated and stored every time the zero voltage is obtained.

As a result, it is not necessary to perform the addition process of the zero voltage and the ejection voltage for each printing operation, and the processing speed for obtaining the driving voltage at the time of the printing operation can be improved.

Further, in this embodiment, the application to the ink jet printer 1 for performing monochrome printing has been described. However, the present invention is not limited to this, and full-color printing can be performed using four color inks of yellow, cyan, magenta, and black. The present invention may be applied to a color ink-jet printer that performs the operation. Although not particularly shown, the color ink jet printer has an ink jet head corresponding to the number of colors of ink generally used. For this reason, when setting the drive voltage, it is possible to set the drive voltage for each inkjet head, but the inkjet heads used are generally manufactured in the same lot. Therefore, the drive voltage may be set based on the zero voltage of any one of the inkjet heads serving as a reference.

Thus, even in a color ink jet printer having a plurality of ink jet heads,
With a simple circuit configuration, it is possible to satisfactorily control the ejection speed in all the ink jet heads.

Next, a second embodiment of the present invention will be described with reference to FIGS. The ink jet printer 1 according to the second embodiment is different from the first embodiment in that the time for applying a voltage to the electrode 35 is corrected.

FIG. 10 is a block diagram schematically showing a control system of the ink jet printer 1 according to the second embodiment of the present invention. Inkjet printer 1 of the present embodiment
In the embodiment, a delay circuit 53 is provided between the comparison circuit 49 and the control device 46. The delay circuit 53 starts driving by detecting the contact current, and outputs a contact current detection signal to the control device 46 a predetermined time after the start of driving.

In the above-described ink jet printer 1, at the time of a printing operation, a driving voltage is first applied to the electrode 35 by receiving a driving start signal. The drive voltage at this time is a voltage stored in the storage device in advance, and has a rectangular waveform.

Although a detailed description is omitted because it is a known technique, there is a method using a clipper circuit for shaping a sine wave into a rectangular wave, for example, in order to apply a rectangular wave voltage. In the clipper circuit, a rectangular wave voltage can be applied by clipping a part of an alternating current waveform given as a sine wave using a diode and a transistor and applying a constant level of current.

When the diaphragm 34 contacts the electrode 35, the contact current detection signal output from the comparison circuit 49 is
The signal is input to the delay circuit 53. The delay circuit 53 starts driving when the contact current detection signal is input, and outputs a contact current detection signal to the control device 46 a predetermined time after the start of driving. Here, a function as a timing unit is executed.

In the control device 46, when the contact current detection signal output from the delay circuit 53 is input, the charge / discharge circuit 4
7, a stop signal for stopping the application of the voltage is output.
The charge / discharge circuit 47 stops applying a voltage between the diaphragm 34 and the electrode 35 in response to the stop signal.

Here, FIG. 11 shows the relationship between the environmental temperature and the ejection speed when the printing operation is actually performed at various environmental temperatures using the drive voltage set under the above control. It is a correlation diagram. Numerical values given near each plot in FIG. 11 are actual voltages at the electrodes 35 when the above-described control is performed. As a result, the electrode 35 is actually
Although a slight difference occurred in the voltage applied to the ink, the desired ejection speed of 7 m / s was stably obtained within a practically allowable range without being affected by the change in the viscosity of the ink due to the environmental temperature. .

At the time of printing, the comparison circuit 4
The voltage is applied to the electrodes by the charge / discharge circuit 47 only while the predetermined time is measured by the delay circuit 53 after the contact between the diaphragm 34 and the electrode 35 is detected by 9.
This makes it possible to obtain the target discharge speed based on the meniscus vibration by previously acquiring the time until a meniscus occurs at which the target discharge speed can be obtained by an experiment or the like.

As a result, the desired ejection speed can be obtained satisfactorily without being affected by the change in the viscosity of the ink, and a good print result can be obtained.

Further, by applying a rectangular wave voltage between the diaphragm 34 and the electrode 35 to the electrode 35, the time during which the amount of voltage fluctuates can be shortened, and the vibration of the diaphragm 34 can be prevented. In addition, the vibration of the ink in the pressurizing chamber 44 due to the change in the displacement of the vibration plate 34 can be suppressed to a necessary minimum.

Thus, the ink ejection timing can be controlled based on the previously obtained meniscus displacement amount.

[0109]

According to the ink jet printer of the first aspect of the invention, in the ink jet head, the driving voltage obtained by adding the zero voltage and the ejection voltage when the contact between the diaphragm and the electrode is detected is used for printing. By applying a voltage to the electrode, a voltage is applied to bring the diaphragm and the electrode into contact with each other and the discharge speed of the ink discharged from the nozzle is set to zero. By obtaining in advance by experiment or the like a voltage that can obtain
Since the desired ejection speed can be obtained based on the gradient of the ink ejection speed, the desired ejection speed can be obtained satisfactorily irrespective of the change in the viscosity of the ink. As a result, a good print result can be obtained without being affected by the change in the viscosity of the ink. In addition, since it is only necessary to store the ejection voltage, it is not necessary to separately provide a storage device having a particularly large storage capacity, and a desired ejection speed can be obtained satisfactorily without being affected by a change in ink viscosity. This makes it possible to obtain a low-cost inkjet printer that can obtain a good print result without being affected by a change in the viscosity of the ink.

According to the second aspect of the present invention, in the ink jet printer according to the first aspect, by updating the drive voltage at each predetermined timing, a zero voltage is not acquired every time ink is ejected. Since the updating can be minimized, the effect described in claim 1 can be obtained without unnecessarily updating the driving voltage.

According to the ink jet printer of the third aspect of the present invention, upon printing, a voltage is applied to the electrodes only for a predetermined time after detecting the contact between the diaphragm and the electrodes. By acquiring in advance the time until a meniscus is generated such that a desired ejection speed is obtained by an experiment or the like, the desired ejection speed can be obtained based on the meniscus vibration.
The desired ejection speed can be obtained satisfactorily irrespective of the change in the viscosity of the ink. As a result, a good print result can be obtained without being affected by the change in the viscosity of the ink.

According to the fourth aspect of the invention, in the ink jet printer according to the third aspect, it is possible to prevent the vibration of the diaphragm from occurring by applying a rectangular wave voltage to the electrodes. The effect described in claim 3 can be obtained more reliably.

According to the invention set forth in claim 5, claim 1,
In the ink-jet printer described in 2, 3 or 4, by detecting only the contact between the diaphragm and the electrode in one pressurizing chamber, even if it has a plurality of pressurizing chambers, it is possible to use a simple circuit configuration. Since it becomes possible to apply an appropriate drive voltage to the diaphragm and the electrode, it is possible to simplify the control in the case where a plurality of pressure chambers are provided.
As a result, it is possible to suppress an increase in the manufacturing cost of the device when a plurality of pressurizing chambers are provided.

According to the sixth aspect of the present invention, in the ink jet printer according to the fifth aspect, a driving voltage is obtained based on the contact between the diaphragm and the electrode to which no voltage is applied at the time of printing, and ejection is performed when the driving voltage is obtained. By collecting the ink collected by the collecting member, it is possible to acquire the drive voltage without performing printing using the paper, and thus to acquire the drive voltage without unnecessary consumption of the paper. Can be.

[Brief description of the drawings]

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

FIG. 2 is a vertical sectional side view thereof.

FIG. 3 is an exploded perspective view showing the inkjet head 18. FIG.

FIG. 4 is a longitudinal sectional view thereof.

FIG. 5 is a block diagram schematically showing a control system related to printing among control systems provided in the inkjet printer.

FIG. 6 is a correlation diagram showing a relationship between a driving voltage and an ink ejection speed.

FIG. 7 is a block diagram schematically showing a current detection circuit.

FIG. 8 is a timing chart illustrating a relationship between a current, a voltage, and a displacement amount of a diaphragm in the inkjet head.

FIG. 9 is a correlation diagram showing a relationship between an environmental temperature and a discharge speed.

FIG. 10 is a block diagram schematically showing a control system of an ink jet printer according to a second embodiment of the present invention.

FIG. 11 is a correlation diagram showing a relationship between an environmental temperature and a discharge speed.

FIG. 12 is a correlation diagram showing a relationship between a displacement amount of a meniscus in a nozzle at the time of printing of a conventional inkjet printer and time.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Inkjet printer 18 Inkjet head 26 Nozzle 34 Vibration plate 35 Electrode 44 Pressurization room 47 Voltage application means G gap

Claims (6)

[Claims] 1. An ink-jet printer which performs a printing operation on a recording material by an ink-jet method using an ink-jet head, wherein the ink-jet head has a pressurizing chamber partially formed by a vibrating plate capable of flexing outward. A nozzle for communicating the pressurizing chamber with the outside, an electrode having a gap at a predetermined interval and opposed to the diaphragm, and applying a voltage between the diaphragm and the electrode. Means, contact detecting means for detecting contact between the diaphragm and the electrode by applying a voltage between the diaphragm and the electrode by the voltage applying means, and the contact detecting means Voltage acquiring means for acquiring a zero voltage applied between the diaphragm and the electrode when contact between the diaphragm and the electrode is detected. Inkjet printer is characterized in that so as to apply a driving voltage obtained by adding the said zero voltage with a preset discharge voltage by the voltage applying means to the electrodes Te. 2. The apparatus according to claim 1, wherein the voltage acquiring means acquires the zero voltage at every predetermined timing.
The ink-jet printer as described. 3. An ink-jet printer which performs a printing operation on a recording material by an ink-jet method using an ink-jet head, wherein the ink-jet head has a pressurizing chamber partially formed by a vibrating plate capable of flexing outward. A nozzle for communicating the pressurizing chamber with the outside, an electrode having a gap at a predetermined interval and opposed to the diaphragm, and applying a voltage between the diaphragm and the electrode. Means, contact detecting means for detecting contact between the diaphragm and the electrode by applying a voltage between the diaphragm and the electrode by the voltage applying means, and the contact detecting means A time measuring means for measuring a predetermined time after detecting contact between the diaphragm and the electrode, wherein the vibration is detected by the contact detecting means by the voltage applying means. Jet printer, characterized in that the predetermined time by the time counting means from the detection of the contact between the plate-electrodes so as to apply a voltage only to the electrodes while being measured. 4. The ink jet printer according to claim 3, wherein said voltage applying means applies a rectangular wave voltage. 5. The apparatus according to claim 1, wherein a plurality of said pressure chambers are provided, and said contact detection means detects contact between said diaphragm and said electrode in one of said pressure chambers. ,
The inkjet printer according to 2, 3 or 4. 6. The voltage applying means applies a voltage to the diaphragm and the electrode to which a voltage is applied by the contact detecting means other than at the time of printing, and applies a voltage to the diaphragm and the electrode. 6. The ink jet printer according to claim 5, further comprising a collecting member for collecting ink discharged from the pressurizing chamber.