JPH09141849A - Ink-jet recording apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To complete the start-up of an apparatus in a short time even when the heat capacity of a front heater is small. SOLUTION: A recording head 12 is equipped with a front heater 26 for heat-melting hotmelt ink, a piezoelectric element member 24 for discharging the hotmelt ink by the expansion/contraction by applying driving voltage, and a voltage control part 54 for driving the piezoelectric element member 24 to melt the hotmelt ink by heating with the front heater 26 and the heat generation by the piezoelectric element member 24 at the start up of an apparatus.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording apparatus for spraying hot melt ink on a sheet for printing.

[0002]

2. Description of the Related Art A communication device such as a facsimile device and an information processing device such as a personal computer usually have a recording device capable of recording data consisting of characters and figures as visual information so that the data can be recorded on paper. Have. This recording device employs various printing methods such as impact method, heat-sensitive method, inkjet method, etc., but in recent years, it is excellent in quietness and can print on paper of various materials and has clear image quality. Attention has been paid to an inkjet type inkjet recording apparatus using a hot melt ink capable of obtaining the above.

The above-mentioned ink jet recording apparatus has hitherto been known.
The hot-melt ink that solidifies at room temperature is heated and melted by a heater, and the hot-melt ink is ejected from the nozzles and sprayed onto the paper while the main scanning of the recording head having a large number of nozzles is performed. ing.
Then, according to this configuration, when the hot-melt ink is sprayed onto the paper, the hot-melt ink in the molten state is rapidly cooled and changes to the solid state, so that bleeding of the paper such as liquid ink does not occur, A very good image quality can be obtained.

[0004]

However, in the above-mentioned conventional structure, since the hot melt ink is melted only by using the heater, the heat capacity of the heater is set to such an extent that the molten state of the hot melt ink is maintained. In this case, when the power of the recording apparatus is turned on and started up, there is a problem that a long waiting time occurs until the hot melt ink changes from the solid state at room temperature to the molten state due to the heating of the heater. .

Therefore, it is conceivable to employ a heater having a large heat capacity so as to shorten the waiting time when the apparatus is started up. In this case, a heater having a heat capacity necessary to keep the molten hot melt ink warm is used. In comparison, an expensive heater is required, and there is a problem that the cost of parts is excessive if it is used only when the apparatus is started up.

Therefore, the present invention is intended to provide an ink jet recording apparatus capable of completing the startup of the apparatus in a short time even with a heater having a small heat capacity.

[0007]

In order to solve the above-mentioned problems, the invention of claim 1 is directed to heating means for heating and melting the hot-melt ink, and expansion and contraction of the hot-melt ink upon application of a drive voltage. In an inkjet recording apparatus including a piezoelectric element for discharging and a recording head, when the apparatus is started up, the piezoelectric element is set so that the hot melt ink is melted by heating by the heating unit and heat generated by driving the piezoelectric element. It is characterized by having drive control means for driving. As a result, when the apparatus is started up, the hot melt ink is melted by the heating by the heating means and the heat generated by driving the piezoelectric element. Therefore, even if the heater has a small heat capacity, the apparatus can be started up in a short time. Can be completed.

According to a second aspect of the present invention, there is provided a temperature detecting means for detecting the temperature of the hot melt ink, and the drive control means comprises the piezoelectric element in a temperature range below the softening point of the hot melt ink. The element is driven at the maximum frequency and the maximum voltage, and in the temperature range where the hot melt ink is at or above the softening point, the drive voltage is reduced to such an extent that the hot melt ink is not ejected, and the piezoelectric element is driven. It has a feature. With this,
The piezoelectric element is driven at the maximum frequency and maximum voltage in the temperature range below the softening point, and at a drive voltage that does not eject hot melt ink in the temperature range above the softening point. No leakage will occur.

According to a third aspect of the present invention, the drive control means according to the second aspect reduces the drive voltage to about ½ of the maximum voltage in the temperature range above the softening point of the hot melt ink. Then, the piezoelectric element is driven. Accordingly, by further reducing the drive voltage to about ½ of the maximum voltage, it is possible to more reliably prevent ink leakage of the melted ink by easy control.

According to a fourth aspect of the present invention, the drive control means according to any one of the first to third aspects is characterized in that the pulse having a wave shape different from the drive pulse applied to the piezoelectric element during printing is used. It is characterized by driving a piezoelectric element. As a result, the piezoelectric element is driven by the drive pulse having a wave shape different from the drive pulse used for printing, so that ink leakage can be prevented more reliably.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to FIGS. As shown in FIG. 2, the ink jet recording apparatus according to the present embodiment includes a lower cover 1 and an upper cover 2 which are casings. On the rear side of the upper cover 2, there are provided front and rear sheet feeding mechanisms 3 and 4 capable of stacking and accommodating a large number of sheets 20. Paper feed rollers 5 and 6 are provided near the lower ends of the paper feed mechanisms 3 and 4, respectively.
The paper 20 stored in 4 is sent out to the transport path 7.

The carrying path 7 has a first carrying roller 8, a second carrying roller 9, a paper discharge tray portion 10 and a paper discharge port 1a in this order from the paper feed mechanism 3 and 4 side. While the sheet 20 is quantitatively or continuously moved in the arrow direction (sub-operation direction) by the first and second conveying rollers 8 and 9, the sheet 20 is ejected from the ejection port 1a to the outside of the machine. There is.

A printing mechanism main body 11 is arranged on the side of the upper cover 2 of the transport path 7. Printing mechanism body 11
Is a recording head 12, a carriage 13 joined to the recording head 12, a guide member 14 for movably supporting the carriage 13 in a main scanning direction perpendicular to the sub-scanning direction, and a carriage 13 for the guide member 14. And a traveling mechanism (not shown) that reciprocates in the main scanning direction (main scanning).

As shown in FIG. 3, the recording head 12 has a head portion 15 for ejecting hot melt ink,
It is composed of a tank portion 16 for containing the hot melt ink supplied to the head portion 15. The hot melt ink used in the ink jet recording apparatus is solidified at room temperature, has a softening point of 40 to 140 ° C. and a melting point of 50 to 15
At 0 ° C, the ink viscosity when ejected from the ink is 3 to 50
It is a general term for inks having a property of cps, preferably 30-90% wax, 5-70% resin,
It is composed of 0.1 to 10% of colorant and other additives (thickener, surface active agent, solubilizer, etc.).

As shown in FIG. 4, the head portion 15 is opposed to the sheet 20 and has a large number of nozzles 2 in the sub-scanning direction.
It has a nozzle plate 21 on which 1a is formed. The nozzle plate 21 is joined to the cavity plate 22, and each of the nozzles 21 is attached to the cavity plate 22.
A large number of ink ejection grooves 22a and ink chamber grooves 22b formed corresponding to a, and an ink supply groove 22c connected to all the ink chamber grooves 22b are formed.

A diaphragm 23 is bonded to the entire surface of the cavity plate 22. The diaphragm 23 has the grooves 22a to 22c of the cavity plate 22.
By closing the upper surface of the nozzle chamber 27 and the ink chamber 2
8 and the ink supply chamber 29 are formed. The diaphragm 23 has a base plate 2
A large number of piezoelectric element members 24 supported by 5 are joined, and each piezoelectric element member 24 is arranged so as to be located above the ink chamber 28 via the diaphragm 23.

The piezoelectric element member 24 is made of a material such as lead zircon titanate (PZT), and when the recording head 12 is manufactured, a predetermined voltage (eg, 80 V) is applied at a predetermined temperature (eg, 130 ° C.). It is polarized by being applied. Further, each of the piezoelectric element members 24 of this embodiment is provided with at least a pair of electrodes (driving voltage generating means) so that a driving voltage having the same polarity as the polarization direction thereof is applied. In general, piezoelectric elements
When an electric field that is the same as the polarization direction is applied, it exhibits a characteristic that it extends in the parallel direction of the electrodes and contracts in the vertical direction. When a voltage is applied to the piezoelectric element member 24 via the electrodes, the piezoelectric element member 24 expands and contracts by an expansion and contraction amount according to the applied drive voltage, and the diaphragm 23 is displaced up and down to change the volume of the ink chamber 28. The ink in the ink chamber 28 is ejected in the direction of the paper 20 through the nozzle chamber 27 and the nozzle 21a by increasing or decreasing the.

A flat plate-shaped front heater 26 (heating means) is joined to a base plate 25 that supports the piezoelectric element member 24 in a planar shape. The front heater 26 is arranged from the base plate 25 to the ink supply passage 16a of the tank portion 16, heats the hot melt ink in the piezoelectric element member 24 and the ink supply chamber 29 via the base plate 25, and at the same time, supplies the ink supply passage 16a. It is designed to heat the hot melt ink.

The ink supply passage 16a is provided in the tank portion 1
6 is connected to the ink containing chambers 16b, and the hot melt ink contained in the ink containing chambers 16b is made to flow to the ink supply chamber 29. Ink chamber 1
A tank heater 31 is attached to the bottom wall of 6b, and the tank heater 31 heats and melts the hot-melt ink contained in the ink containing chamber 16b.

The printing mechanism body 11 provided with the front heater 26, the tank heater 31, the piezoelectric element member 24, etc.
Is controlled by a recording device control system 40 as shown in FIG. The recording device control system 40 includes a CPU 42, a ROM 43, and an RA connected via a bus 46.
It has an M45, a timer 44, an interface 49, a mechanical control unit 47, a heater control unit 53, and a voltage control unit 54.

The ROM 43 has various printing routines such as a printing routine for printing the dot data in the output data storage area, and an ink heating routine for driving the piezoelectric element member 24 so as to heat the hot melt ink when the apparatus is started up. Contains the control program. In the RAM 45, an output data storage area for storing dot data is formed in a matrix-shaped data table composed of main scanning direction addresses and sub scanning direction addresses. Also,
The timer 44 outputs time data indicating the current time, and the interface 49 is connected to an information processing device such as a personal computer (not shown) and receives information data such as image data from the information processing device. It is adapted to be input to the recording device control system 40.

Further, the mechanical control unit 47 is provided for the recording head 12
Are connected to a CR motor 55 for main scanning and a PF motor 56 for sub-scanning the paper 20. The heater control unit 48 is connected to the front heater 26 and the tank heater 31 of FIG. 3, and obtains the heat generation temperature from the thermistors 50 and 50 provided in these heaters 26 and 31, respectively, and thereby the heaters 26 and 31 are controlled. The temperature is adjusted to a predetermined temperature. Further, the voltage controller 54 is configured to generate a drive voltage applied to the piezoelectric element member 24 of the recording head 12. Furthermore, the recording head 12
Is provided with an ink temperature detecting sensor 51 (temperature detecting means) for detecting the temperature of the hot melt ink of the head portion 15. The ink temperature detecting sensor 51 detects the temperature of the hot melt ink, The temperature data is output to the bus 46.

Then, the recording apparatus control system 40 having such a configuration has the front heater 2 at the time of printing operation.
6 and the tank heater 31 are maintained at a temperature slightly higher than the melting point of the hot melt ink to melt the hot melt ink, and the motors 55 and 56 operate to perform main scanning of the recording head 12 and sub scanning of the paper 20. By repeating this, the dot data stored in the output data storage area of the RAM 45 is printed on the paper 20 in units of one band. Further, when the power is turned on, the head unit 15 is turned on by the front heater 26 and the tank heater 31.
By heating the hot melt ink in the tank portion 16 and heating the hot melt ink in the head portion 15 by the heat generated by driving the piezoelectric element member 24 based on the ink temperature data, the hot melt ink in the solid state is formed. It is designed to melt.

The operation of the ink jet recording apparatus having the above structure will be described. When the power of the recording apparatus is turned on, the CPU 42 reads out and executes the ink heating routine of FIG. 5 stored in the ROM 43. When the ink heating routine is executed, first, the front heater 2
The energization of 6 and the tank heater 31 is started, and the hot melt ink is heated by these heaters 26 and 31 (S1). Thereafter, the ink temperature data output to the bus 46 from the ink temperature detection sensor 51 that detects the temperature of the hot melt ink is sent to the CPU 42.
Is read (S2), and the ink temperature data and the softening point data are compared to determine whether the temperature of the hot melt ink is lower than the softening point (S3).

When it is determined that the temperature of the hot melt ink is lower than the softening point (S3, YES), the hot melt ink is in a solid state and is not ejected from the recording head 12. Therefore, as shown in FIG. All the piezoelectric element members 24 of the recording head 12 are driven with the maximum drive voltage and frequency. As a result, the piezoelectric element member 24 is heated by self-heating, and the amount of heat of the piezoelectric element member 24 is applied to the hot melt ink existing in the nozzle chamber 27, the ink chamber 28, and the ink supply chamber 29, as shown in FIG. As a result, the hot melt ink is transferred to the front heater 26.
And the piezoelectric element member 24 are heated (S
4).

Thereafter, the process is re-executed from the above S2, the ink temperature data is read (S2), and it is determined whether the temperature of the hot melt ink is lower than the softening point (S3).
The heating (S4) of the hot melt ink is repeated.

When it is determined in S3 that the temperature of the hot melt ink is not lower than the softening point (S
3, NO), and subsequently, by comparing the ink temperature data with the melting point data, it is determined whether or not the temperature of the hot melt ink is lower than the melting point (S5). When it is determined that the temperature of the hot melt ink is lower than the melting point (S5, YES), since the hot melt ink has changed from the solid state to the melted state,
As shown in FIG. 6, the hot melt ink is used for the recording head 1.
The hot melt ink is heated while the piezoelectric element member 24 is driven by the drive voltage corresponding to the temperature (viscosity) of the hot melt ink so as not to be ejected (ink leakage) from 2 (S6). As described above, the drive voltage is reduced to the extent that hot melt ink is not ejected, and the pulse shape of the drive voltage, such as a wave-shaped drive pulse in which the rise time of the pulse is set to be long, is used when printing. It is desirable that ink leakage can be further suppressed by making the shape different from the drive pulse.

Thereafter, the process is re-executed from the above S2, the ink temperature data is read (S2), and it is determined whether the temperature of the hot melt ink is lower than the softening point (S3).
The determination of whether the temperature of the hot melt ink is lower than the melting point (S5) and the heating of the hot melt ink (S6) are repeated.

When it is determined in S5 that the temperature of the hot melt ink is not lower than the softening point (S5)
5, NO), as shown in FIG. 1, after the driving of the piezoelectric element member 24 is stopped (S7), the voltage generated by the voltage controller 54 is set so as to generate the driving voltage during the printing operation. (S8). Thereafter, the front heater 26 and the tank heater 31 are adjusted to predetermined temperatures so that the hot melt ink is maintained in a molten state (S9),
The ink heating routine is ended.

Next, when the print routine is executed, as shown in FIG.
As shown in FIG. 4, when the paper 20 is fed from the paper feed mechanism 3 or 4 to the conveyance path 7 and reaches a predetermined position facing the recording head 12, the paper 20 is stopped and the printing operation is started. Will be. That is, the mechanical control unit 52 main-scans the recording head 12 via the CR motor 55, and at the same time, the drive voltage is generated from the drive voltage generation unit 54 based on the dot data stored in the output data storage area of the RAM 45. Will be applied to. As a result, as shown in FIGS. 3 and 4, the piezoelectric element member 24 expands and contracts by the expansion and contraction amount according to the drive voltage, and the diaphragm 23 is displaced up and down to increase or decrease the volume of the ink chamber 28. 28 ink is ejected toward the paper 20 through the nozzle chamber 27 and the nozzle 21a. When printing for one band is performed by the main scanning of the recording head 12, the PF motor 56 causes the paper 20
Is sub-scanned by the paper feed amount for one band, and then the printing of the next stage is started. After this, when printing on the paper 20 is completed, the paper 20 is discharged from the transport path 7 to the outside of the machine via the paper discharge port 1a.

[0031]

According to the first aspect of the present invention, an ink jet recording head is provided with a heating means for heating and melting the hot melt ink and a piezoelectric element which expands and contracts by the application of a driving voltage to discharge the hot melt ink. The recording apparatus has a drive control means for driving the piezoelectric element so that the hot melt ink is melted by heating by the heating means and heat generated by driving the piezoelectric element when the apparatus is started up. is there. As a result, when the apparatus is started up, the hot melt ink is melted by the heating by the heating means and the heat generated by driving the piezoelectric element. Therefore, even if the heater has a small heat capacity, the apparatus can be started up in a short time. There is an effect that it can be completed.

According to a second aspect of the present invention, there is provided temperature detection means for detecting the temperature of the hot melt ink, and the drive control means includes the piezoelectric element in a temperature range below the softening point of the hot melt ink. The element is driven at the maximum frequency and the maximum voltage, and in the temperature range of the hot melt ink above the softening point, the drive voltage is reduced to such an extent that the hot melt ink is not ejected, and the piezoelectric element is driven. is there. As a result, it is driven at the maximum frequency and maximum voltage in the temperature range below the softening point,
Since the piezoelectric element is driven with a drive voltage that does not eject hot melt ink in the temperature range above the softening point, there is an effect that ink leakage does not occur when the hot melt ink is melted.

According to a third aspect of the present invention, the drive control means according to the second aspect reduces the drive voltage to about ½ of the maximum voltage in the temperature range above the softening point of the hot melt ink. Then, the piezoelectric element is driven. As a result, the drive voltage can be further reduced to 1 / maximum
By reducing the amount to about 2, it is possible to more reliably prevent ink leakage of the melted ink by easy control.

According to a fourth aspect of the present invention, the drive control means according to any one of the first to third aspects uses a pulse having a waveform different from that of the drive pulse applied to the piezoelectric element at the time of printing. This is a configuration for driving the piezoelectric element. As a result, the piezoelectric element is driven by the drive pulse having a wave shape different from the drive pulse used for printing, so that it is possible to more reliably prevent ink leakage.

[Brief description of the drawings]

FIG. 1 is a block diagram of a recording device control system.

FIG. 2 is a schematic configuration diagram of an inkjet recording apparatus.

FIG. 3 is an explanatory diagram showing an internal structure of a recording head.

4A and 4B are explanatory views showing the internal structure of the head portion of the recording head, in which FIG. 4A is a front view and FIG. 4B is a side view.

FIG. 5 is a flowchart of an ink heating routine.

FIG. 6 is a graph showing the relationship between drive voltage and ink temperature.

[Explanation of symbols]

 11 Printing Mechanism Main Body 12 Recording Head 15 Head Section 16 Tank Section 20 Paper 21 Nozzle Plate 22 Cavity Plate 23 Diaphragm 24 Piezoelectric Element Member 25 Base Plate 26 Front Heater 27 Nozzle Chamber 28 Ink Chamber 29 Ink Supply Chamber 31 Tank Heater 53 Heater Control Unit 54 Voltage controller 55 CR motor 56 PF motor

Claims (4)

[Claims] 1. An inkjet recording apparatus comprising a heating unit for heating and melting hot melt ink and a piezoelectric element for expanding and contracting by applying a drive voltage to eject the hot melt ink in an inkjet recording apparatus. At the same time, the ink jet recording apparatus is characterized by further comprising drive control means for driving the piezoelectric element so that the hot melt ink is melted by heating by the heating means and heat generated by driving the piezoelectric element. 2. A temperature detection unit for detecting the temperature of the hot melt ink, wherein the drive control unit controls the piezoelectric element to have a maximum frequency in a temperature range below the softening point of the hot melt ink. The piezoelectric element is driven by driving at the maximum voltage, and reducing the drive voltage to such an extent that the hot melt ink is not ejected in a temperature range above the softening point of the hot melt ink. 1. The inkjet recording device according to 1. 3. The drive control means drives the piezoelectric element by reducing the drive voltage to about ½ of the maximum voltage in the temperature range of the hot melt ink above the softening point. The ink jet recording apparatus according to claim 2, which is characterized in that. 4. The drive control means drives the piezoelectric element with a pulse having a wave shape different from that of a drive pulse applied to the piezoelectric element during printing. The ink jet recording apparatus according to any one of claims.