JPH09150507A - Ink jet recording apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To always keep the consumption quantity of ink for recording an image constant even if the kind of a recording medium is different by providing a drive signal selection means keeping the emitting amt. of ink droplets almost constant and capable of selecting the waveform shape of a drive signal making an ink emitting speed variable corresponding to the kind of a recording medium. SOLUTION: A carriage 1 is supported by a guide member 2 and connected to a pulse motor 23 through a timing belt 3 and reciprocally moved in parallel to a heat conductive member 5 also used as a platen. Further, the carriage 1 is loaded with a recording head and further loaded with an ink cartridge 9 in a freely detachable manner. In this constitution, by changing a pulse width signal applying the drive voltage signal corresponding to the kind of a recording medium 6, an ink emitting speed is made high in the recording medium 6 hard to spread ink droplets and made low in the recording medium 6 easy to spread ink droplets without changing the amt. of ink droplets. By this constitution, proper recording corresponding to the kind of the recording medium 6 is performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention forms a recording dot on a recording medium by ejecting ink droplets by utilizing pressure vibration generated by a vibration source according to image information, and an image is formed by the structure of the recording dot. More particularly, the present invention relates to an inkjet recording apparatus having a drying unit for promoting drying and fixing of recording dots attached to a recording medium.

[0002]

2. Description of the Related Art In an inkjet recording apparatus that forms recording dots by ink droplets ejected from an inkjet recording head onto a recording medium in accordance with image information, since the recording dots are liquid, they are fixed on the recording medium. Requires drying time. The drying time has a great influence on the recording quality. If the drying time is too long, the recording dots may bleed on the recording medium, impairing the recording quality. In particular, when colorization is performed by an inkjet recording apparatus, blurring between C (cyan), M (magenta), Y (yellow), and K (black) becomes severe, and a clear image cannot be obtained.

Various proposals have heretofore been made in order to solve the problem that the drying time of recording dots largely depends on the recording quality as described above.

For example, Japanese Laid-Open Patent Publication No. 1-113249,
JP-A-1-290430, JP-A-3-21457
Japanese Patent Laid-Open No. 3-83647,
A fixing heater is provided in the recording head or the recording device to control the temperature. The temperature control is ON / OFF of the fixing heater.
This is an inkjet recording apparatus that is turned off so that the drying time is optimized according to the recording density of the image.

According to this method, it is possible to control the fixing heater so that the optimum drying time is obtained even if the recording density of the image is different. For this reason, the power consumption of the inkjet recording apparatus main body can be minimized, and high recording quality can be ensured.

The ink jet recording apparatus uses, as a recording medium, coated paper having a recording surface coated, plain paper generally used in offices, OHP sheets and the like.

One of the purposes of coating coated paper is to obtain uniform print quality by making the spread, penetration and bleeding of print dots on the print medium uniform for each print dot. Another reason is that the permeation is quick and the drying time is short. It prevents unnecessary bleeding.
The OHP sheet is also coated with some kind of coating for the same purpose.

On such a recording medium, the ejected ink droplets spread on the recording surface by the ejection energy according to the ejection speed or the ejection amount, and then penetrate into the inside of the recording medium.
Alternatively, bleeding and recording dots are formed after the drying time has elapsed.

In a general ink jet recording apparatus, the ejection energy of ink droplets is set so as to obtain an image of high recording quality on the recording surface of coated paper or OHP sheet. However, plain paper does not have a coating like coated paper, and therefore spreads, penetrates, and bleeds ink droplets differently from coated paper and OHP sheets. Therefore, in the case of plain paper, it is difficult to obtain proper recording quality such as coated paper or OHP sheet.

There are various types of plain paper such as high-quality paper, copy paper, recycled paper, etc., and the spread, penetration, and bleeding of ink droplets differ depending on the type of plain paper.

Generally, a manufacturer that provides an ink jet recording apparatus recommends a coated paper and an OHP sheet dedicated to the apparatus as dedicated paper. However, coated paper is more expensive than plain paper, and there is a demand for an inkjet recording apparatus that can achieve high recording quality on plain paper.

In order to realize such a demand, Japanese Patent Laid-Open No.
In Japanese Patent No. 142251, the management temperature of the recording head is made variable by a variable means, and the management temperature is controlled according to the type of recording medium to control the ink droplet amount.

Further, in Japanese Patent Laid-Open No. 1-290440, a plurality of recording heads having different ejection amounts of ejected ink droplets are provided, and the recording head to be used is selected according to the recording medium to determine the ink droplet amount. Have control.

Further, in Japanese Patent Laid-Open No. 1-290439, a plurality of recording heads having the same ejected ink droplet amount are provided,
The amount of the ink droplet is controlled by forming one dot recorded on the recording medium or the recording medium according to the image information by a plurality of ink droplets.

Further, as an apparatus which obtains an appropriate recording quality by varying the ejection speed of ink drops for each recording medium.
There are techniques such as 6359, JP-A-5-318766, and JP-A-5-338165. In all of them, the ejection speed of an ink drop is determined by utilizing the residual pressure wave in the pressure chamber after the ink drop is ejected. Is variable.

[0016]

However, the proposal of the above publication has the following problems.

Japanese Unexamined Patent Publication Nos. 1-113249 and 1
-290430, JP-A-3-21457,
In JP-A-3-83647, a fixing heater is used to accelerate the drying time, and means for detecting the image density is required for temperature control as described above according to the image density. Therefore, the device becomes large and expensive.

Further, in order to carry out the temperature control as in JP-A-3-142251, a device such as a temperature control means is required and the ink jet recording apparatus becomes large.
Further, since the ejection amount of ink droplets ejected from the recording head is changed depending on the type of recording medium, the amount of ink droplets differs for each recording medium when an image of proper recording quality is obtained for each recording medium. That is, in the case of a recording medium in which the ink droplets are difficult to spread, the amount of the ink droplets must be increased in order to obtain a recording dot equivalent to that in the recording medium in which the ink droplets are likely to spread, which results in poor quick-drying of the ink, and There is a problem that the consumption of ink becomes severe and the running cost becomes high.

Further, both Japanese Patent Laid-Open Nos. 1-290440 and 1-290439 have a plurality of recording heads, so that the ink jet recording apparatus becomes large. Further, since the amount of ink droplets that form one dot is changed, the amount of ink consumed differs for each recording medium, and the above problem occurs.

Also, when ink droplets are ejected using the residual pressure in the pressure chamber as in JP-A-5-16359, JP-A-5-318766, and JP-A-5-338165, ink droplets are also ejected. The discharge amount also increases with the increase of the discharge speed of. Further, if the residual vibration characteristics are subtly different, the ejection speeds of the ink droplets are greatly different, which is very unstable.

The present invention has been made in view of the above problems, and an object of the present invention is to accelerate the drying of recording dots on a conventional recording medium and quickly fix the recording dots. Equipped with a recording dot fixing unit that replaces a fixing heater to obtain proper recording quality regardless of the type of recording medium used in the device, and the ink consumption for recording an image is always constant regardless of the type of recording medium. It can be provided at a low price.

[0022]

In order to solve such a problem, the present invention is provided with a drive signal selection means capable of selecting a waveform shape of a drive signal according to the type of recording medium, and the ejection amount of ink droplets is recorded. The ejection speed of the ink droplets can be selected according to the type of the recording medium while keeping it substantially constant regardless of the type of the medium.

A non-recording surface side of the recording medium is provided with a heat conducting member arranged in a direction perpendicular to the conveying direction of the recording medium and parallel to the recording medium, and the heat conducting member conveys the recording medium. And a carriage motor for scanning the recording head in a direction perpendicular to the conveying direction of the recording medium, and the heat conducting member generates the drive signal to the drive signal generating means. For this reason, a structure was adopted in which elements with heat loss that perform switching operation are joined.

Further, in the stand-by state in which the recording is not performed, an excitation signal having a voltage lower than the rated voltage of the both motors is input to the carry motor and the carriage motor to cause heat conduction to the heat conducting member. Let

The drive signal generating means includes a charge / discharge circuit for a capacitor, and a first region in which the drive voltage is raised at a constant gradient to expand the volume of the pressure chamber and supply ink to the pressure chamber. Switching the switching operation from a first region to a third region that descends at a constant gradient in order to contract the volume of the pressure chamber and eject the ink droplets from the nozzle. for,
A second region for maintaining the driving voltage is formed in the trapezoidal driving signal portion.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION The details of the present invention will be described below based on illustrated embodiments.

FIG. 1 shows an outline of an ink jet recording apparatus according to the present invention. In the figure, reference numeral 1 denotes a carriage, which is supported by a guide member 2 and is connected to a pulse motor 23, which is a carriage motor, via a timing belt 3 and can reciprocate in parallel with a heat conduction member 5 also serving as a platen. Is configured. For the heat conducting member 5, a metal having a high heat conductivity such as aluminum or copper, or a heat pipe is used.

An ink droplet 80, which will be described later, is applied to the carriage 1 by directing a nozzle 27, which will be described later, toward the recording medium 6.
The recording head 4 that discharges from the
An ink cartridge 9 is detachably mounted on the upper part of the.

Reference numeral 11 is a flexible cable for transmitting a driving voltage signal and recording data from a driving signal generating circuit 43, which will be described later, which is a driving signal generating means, to a driving circuit mounted on the recording head 4. Ink from the ink cartridge 9 flows into the recording head 4 to form an image on the recording medium 6.

When temperature control is performed, the temperature detecting sensor 10 is bonded to the surface of the heat conducting member 5 opposite to the side where the recording medium 6 is conveyed, and the output of the temperature detecting sensor 10 is used.

A gear (not shown) fixed to one end of the rotary shaft of the paper feed roller 21 is connected to the pulse motor 20 which is a paper feed / pump motor to convey the recording medium 6 in accordance with the recording process. Reference numeral 12 in the figure is a recovery mechanism installed outside the recording area of the movement path of the carriage 1. The heat conduction member 5 includes a pulse motor 23 and a pulse motor 2
0. The pulse motor 23 and the pulse motor 20 are arranged at both ends of the heat conducting member 5 as shown in the figure.

Pulse motor 23 and pulse motor 2
Reference numeral 0 is a stepping motor having a four-phase structure, and each phase is made of a material with heat loss such as a nichrome wire.

FIG. 2 is an explanatory view showing the structure of the peripheral portion of the heat conducting member 5 of the ink jet recording apparatus of the present invention, which is a sectional view parallel to the conveying direction of the recording medium 6.

As described above, the recording medium 6 is conveyed by the pulse motor 20 through the conveying roller 21 to the gap between the heat conducting member 5 and the recording head 4 by the paper guide mechanism (not shown).

Ink droplets 80 are ejected from the recording head 4 to form an image on the recording medium 6. A board 7 on which a drive signal generating circuit 43, which will be described later, is mounted is arranged below the heat conducting member 5. An NPN type transistor 107 and a PNP type transistor 108, which are elements accompanied by heat loss and constitute a power amplification circuit described later provided in the drive signal generation circuit 43, are joined to the heat conduction member 5.

FIG. 3 is a timing chart showing an outline of input signals to the pulse motor 23 and the pulse motor 20.

At the time of recording during the above-described recording, a motor drive signal is input to the pulse motor 23 and the pulse motor 20. In addition, during standby when no recording is performed, the excitation signal is input to two of the four phases of each pulse motor. When the motor drive signal is input, the rated voltage of each pulse motor is applied (35 V in this embodiment), and when the excitation signal is input, an input voltage equal to or less than the rated voltage is applied.

FIG. 4 is an explanatory view showing the internal structure of the recording head 4 according to the present invention. Reference numeral 27 in the drawing denotes a nozzle, and a plurality of nozzle plates 28 are formed in the nozzle plate 28. A pressure chamber 29 communicates with each nozzle 27. A reservoir 31 communicates with the pressure chamber 29 via a supply port 30. A supply pipe 32 communicates with the reservoir 31. The ink is filled from the supply pipe 32 into the reservoir 31, the supply port 30, the pressure chamber 29, and the nozzle 27. The vibration plate 3 is provided above the pressure chamber 29.
3 is provided. An electromechanical conversion element 34, which is a pressure generating element, is connected to the diaphragm 33. Each of the plurality of electromechanical conversion elements 34 has substantially the same capacitance. As the electromechanical conversion element 34, a piezoelectric vibrator in which piezoelectric materials and electrodes are alternately laminated can be used.

FIG. 5 is an embodiment showing the configuration of a recording head drive circuit which is a drive signal selecting means. A drive signal is selectively supplied from the drive signal generating circuit 43, which will be described later, to the electromechanical conversion element 34 as a recording signal. Then, the ink droplet 80 is ejected.

Reference numeral 35 in the drawing denotes a recording control circuit for storing a predetermined number of recording data serially transferred to the terminal 37 in the first shift register composed of flip-flop circuits 41, 41, 41. , And the shift lock signal is alternately output to the terminal 40 and the recording data whose voltage level is converted to the terminal 39. After that, when a timing signal generated each time the carriage 1 moves by a predetermined distance is input to the terminal 36, the recording control circuit 35 further causes the recording data stored in the first shift register to be flip-flop circuits 42 and 4.
A latch signal is output to the terminal 38 to be latched by the second flip-flop circuit composed of 2, 42, ..., And the record data is stored in the second shift register all together.
This turns on the transistors 45, 45, 45 ...
/ OFF and the drive signal is selectively applied to the electromechanical conversion element 34. A diode D is connected in parallel with each transistor 45.

The timing signal at the terminal 36 is also input to the pulse width generation circuit indicated by the reference numeral 46, and the timing voltage is used as a trigger to output from the pulse width generation circuit 46 a drive voltage signal corresponding to the type of the recording medium 6. The two pulse width signals and the reference voltage signal for obtaining are output to the drive signal generating circuit 43.

In the figure, reference numeral 53 is a selector, which is a terminal 55.
The drive signal generating circuit 43 depends on the presence / absence of a recording signal to be input.
Drive signals output from the electromechanical conversion elements 34, 3
4 or 34 ... or the capacitor 54 is selected. The electromechanical conversion elements 34, 34, 34, ... Are selected during recording with a recording signal. Further, the capacitor 54 is selected in the standby state in which there is no recording signal and recording is not performed.

FIG. 6 shows the details of the pulse width generation circuit 46. In the figure, reference numeral 201 is an oscillator, and the output of the oscillator 201 is frequency-divided by a frequency divider 202 into a predetermined frequency (for example, 1 MHz) and a counter having a reset function. It serves as a clock signal of 203, and the time output of the counter 203 is input to one input group of the comparator 204. The reset terminal of the counter 203 is connected to the output Q of the flip-flop 208.

When the output Q of the flip-flop 208 becomes HIGH level due to the timing signal input to the terminal 209, the counter 203 starts counting time. When the data value of the other input group of the comparator 204, which will be described later, coincides with the data value of the other input group, the coincidence signal resets the flip-flop 208, clears the count data of the counter 203, and stops clocking. As a result, a pulse signal having a predetermined width is output to the terminal 210 in synchronization with the timing signal of the terminal 209, and the rising time of the drive voltage signal described later is determined. Further, the pulse signal of a predetermined width from the output Q of the flip-flop 208 is the one-shot multivibrator 2
11 is also input, is triggered by the falling edge of the pulse signal having the predetermined width, outputs a pulse signal having a constant time width t, and further, from the one-shot multivibrator 211 with the falling edge signal of the constant time t, which will be described later. The pulse width signal that determines the fall time of the drive voltage signal
6 is output. That is, a delay time of a fixed time t is taken from the fall of the pulse width signal at the terminal 210 and the terminal 216 is taken.
From the pulse width signal that determines the fall time of the drive voltage signal.

Reference numeral 207 is a memory that stores drive conditions corresponding to the type of the recording medium 6, and the type of the recording medium 6 input from the operation panel of the host device or the printer is used as an address input, and the corresponding recording medium 6 is used. Is output to the data terminal, and the condition regarding the time is stored in the latch 205 and input to the other input group of the comparator 204. Further, the information on the voltage from the memory 207 is input to the D / A converter 213, converted into an analog value, and the voltage VH is supplied to the drive voltage generation circuit 43 via the voltage amplification circuit 214.

Next, the drive signal generation circuit 43 for generating a drive signal will be described.

FIG. 7A shows an embodiment of the drive signal generation circuit 43, and the charging pulse output from the pulse width generation circuit 46 is input to the terminal of the reference numeral 47 in the figure. The discharge pulse output from the pulse width generation circuit 46 is input to the terminal 48. Reference numerals 300 and 301 represent
It is a constant current source of a flow type and a sink type in which complementary transistor pairs are cascaded with an emitter follower. The flow type constant current source 300 has a PNP transistor 10 having an NPN transistor 101 and an emitter resistor 122 with a voltage V1 obtained by dividing the voltage VH by a ladder resistor as an input voltage.
The main part is composed of 2 and operates by turning on the transistor 103 by a charging pulse input to the terminal 47. Further, the sink type constant current source 301 is mainly composed of a PNP type transistor 104 and a transistor 105 having an emitter resistance 124 with the voltage V2 as an input voltage, and a discharge pulse inputted to the terminal 48 causes a transistor 106 to be discharged. It works by turning off. This flow type constant current source 300 and sink type constant current source 30
1 is alternately operated by the above-mentioned charging pulse and discharging pulse with a delay time t, and the capacitor 50 connected to the output terminals of the constant current sources 300 and 301 is charged and discharged. As a result, a trapezoidal voltage waveform is obtained in the capacitor 50. The terminal voltage of the capacitor 50 is power-amplified by a power amplifier circuit of an emitter-follower configuration in which Darlington connection is made using the NPN type transistor 107 and the PNP type transistor 108, and a drive signal is output to the terminal 49.

Here, assuming that the transistors 101, 102, 104, and 105 that constitute the constant current sources 300 and 301 are the voltages generated in the resistors 122 and 124, respectively, are V1.
22 and 124, V122 = V1-VBE101 + VBE102 V124 = V2 + VBE104-VBE105, but since the base-emitter saturation voltage of the transistor is almost the same including the temperature characteristics regardless of polarity,
The above equations are V1≈V3 and V4≈V2, respectively, regardless of temperature.

Therefore, the flow current i1 = V1 / (resistor 122) from the flow type constant current source, and the sink current i2 of the sink type constant current source is i2 = V2 / (resistor 124), The resistance is determined only by the resistance accuracy regardless of the temperature, and the resistance can be obtained at low cost even with the accuracy of 0.5% or more. Therefore, the desired constant current sources can be designed at low cost. Moreover, if the voltage V1 and the voltage V2 are 0.3 V or more, the capacitor 50 operates accurately, so that the final charging voltage of the capacitor 50 can be set to the value of the voltage VH and the final discharging voltage can be set to the GND level.

When it is necessary to adjust the rising slope of the drive voltage signal waveform by the recording medium 6 as well, FIG.
The circuit shown in (b) is added instead of the resistor 122. In this case, the terminal 53 is connected to the terminal 51 and the terminal 54 is connected to the terminal 52 for use. Incidentally, reference numeral 55 is a data selector, and the resistors 122a and 122a are set according to the recording medium information of the memory 207.
One of b, 122c ... Is selected.

Since the drive voltage signal is output in synchronization with the timing signal input to the terminal 36, the transistors 45, 45 which are turned on by the recording data signal.
A drive signal is applied to the electromechanical conversion element 34 connected to 45 ... That is, during the fall of the drive voltage signal waveform, the electromechanical conversion elements 34, 34,
34 ... contracts, whereby the pressure generating chamber expands, and ink is sucked from the reservoir. Then, the electromechanical conversion elements 34, 34, 34, ... Extend due to the fall of the drive voltage signal waveform after a time (delay time t) during which the meniscus 81 described later is settled, and the pressure is thereby increased. The generation chamber contracts and the ink droplets 80 are ejected from the nozzle 27.

FIGS. 8A to 8F show the process of ejecting the ink droplets. Incidentally, reference numeral 82 is
The satellite ink particles are slower in ejection speed than the main ink droplet 80.

FIG. 9 is a timing chart showing the operation of the drive signal generating circuit 43 shown in FIG. In the figure, the charge pulse refers to the pulse width signal input from the pulse width generation circuit 46 to the terminal 47, and the discharge pulse refers to the pulse width signal input to the terminal 48. Further, each signal waveform shown by a solid line in the figure is a signal waveform when recording is performed on the recording medium 6 on which ink droplets easily spread, and each signal waveform shown by a broken line is recorded on the recording medium 6 on which ink droplets hardly spread. It is a signal waveform in the case of making it.

As can be seen from the figure, for the recording medium 6 in which the ink droplets 80 are difficult to spread, the voltage VH2 supplied from the pulse width generating circuit 46 is set higher than the voltage VH1 for the recording medium 6 in which the ink droplets easily spread. There is. This allows
Since the current value i2 of the sink type constant current source becomes large and the falling gradient of the drive voltage signal becomes steep, the ink droplet ejection speed becomes high.

By the way, when the voltage VH is changed, the trailing slope of the driving voltage signal is also changed, the retreat speed of the meniscus 81 is changed, and when the ink droplets 80 are ejected at the same timing, the position of the meniscus 81 changes the ink. The size of the drop 80 changes. Therefore, in this embodiment, the width of the charge pulse is also changed so that the discharge pulse is output when the position of the meniscus 81 reaches the set value. As a result, only the ejection speed can be adjusted without changing the ejection amount of the ink droplet 80.

That is, without changing the amount of the ink droplets 80, the ejection speed can be increased in the recording medium 6 in which the ink droplets 80 are difficult to spread, and can be slowed in the recording medium 6 in which the ink droplets 80 are easily spread. Proper recording can be performed according to the six types.

The drive signal 51 is the pulse width generation circuit 4 described above.
The width of the charging pulse from 6 is t1, and the value of the driving voltage VH is V
The drive signal at the time of H1 is shown. Further, the drive signal 52 indicates a drive signal when the width of the charging pulse is t2 and the value of the drive voltage VH is VH2. The drive signal 74 has a charging pulse width of t
1, the drive signal charging pulse t2 when the value of the drive voltage VH is VH7, the drive signal 75 when the value of the drive voltage VH is VH8
Can be obtained.

The drive signal 51 and the drive signal 52 are waveforms necessary for ejecting the ink droplets 80 required for recording an image from the nozzles 27. In addition, the drive signal 74 is the nozzle 2
7, the waveform is insufficient to eject the ink droplet 80. The relationship between VH1 and VH7 and VH2 and VH8 is approximately VH2 ≦ 0.25 × VH1.

Next, the flow of processing performed by the ink jet recording apparatus of the present invention will be described with reference to FIG.

First, after the power is turned on, the type of the recording medium 6 is specified from the host device or the operation panel. Hereinafter, the drive conditions of the specified recording medium 6 will be set.
Since the ink jet recording apparatus of the present invention also has a density adjusting function, it is judged whether the density is changed from the standard value, and the driving condition is set according to the judgment result, and then the image recording is performed. The driving condition is stored in the memory 207 described above, and can be set by inputting address information in which the corresponding driving condition is stored into the memory 207.

By the way, after the ink droplet 80 is ejected from the nozzle 27, the meniscus 81 repeats the residual vibration of moving in and out of the nozzle 27. This residual vibration has its amplitude as the ejection speed of the ink droplet 80 is higher. Becomes large and it takes time to settle. This residual vibration limits the repetition rate of the ink droplet 80.

Another embodiment of the present invention capable of suppressing the above residual vibration will be described below with reference to FIG.

Also in FIG. 11, the solid line shows the signal waveform when recording is performed on the recording medium 6 where the ink droplets 80 are likely to spread, and the broken line is the signal waveform when recording is performed on the recording medium 6 where the ink droplets 80 are difficult to spread. It is a waveform.

In this embodiment, in the process in which the meniscus 81 after ejecting the ink droplet 80 is directed to the opening side of the nozzle 27, an auxiliary pulse is input and the electromechanical conversion elements 34, 34, 34 ...
By contracting again, the meniscus 81 is pulled back to the pressure generating chamber side to cancel the residual vibration, so that the ejection repetition speed of the ink droplet 80 is not affected by the residual vibration.

This auxiliary pulse is obtained by cascading two other one-shot multi-vibrators to the output of the one-shot multi-vibrator 212 of the pulse width generating circuit 46 described above, and acts on the flow type constant current source 300. For the auxiliary pulse and the flip-flop 20
8 is output to the terminal 210 via the OR gate.

FIG. 12 is a further improvement of the driving method shown in FIG. 9, in which the slope of the falling voltage waveform of the driving voltage signal is changed in the middle of the process of ejecting the ink droplet 80 (reference numeral in the drawing). 72, 73). In the embodiment of FIG. 11, the gradient of the trailing edge of the drive voltage signal in the latter half is made larger than the gradient of the trailing edge in the first half to suppress the generation of the satellite particles 82 shown in FIG. The falling slope can be changed by temporarily changing the voltage VH of the drive signal generating circuit 43. If such a driving method is adopted, the satellite particles 82 become very small, the recording dots on the recording medium 6 by the main ink droplets 80 become close to a perfect circle, and the recording quality is further improved. In addition, since the amount of satellite particles 82 overlaid on the main ink droplets 80 on the recording medium 6 is extremely small, the drying time required for forming recording dots is shortened.

FIG. 13 is an explanatory diagram showing the temperature rise of the heat conducting member 5 in the ink jet recording apparatus of the present invention. The horizontal axis shows the recording density according to the image at the time of recording, and the vertical axis shows the reached temperature of the heat conductive member 5.

As described above, by inputting the excitation signal to the pulse motor 23 and the pulse motor 20, the heat conducting member 5
Becomes temperature T1. In this embodiment, the thermal resistance of the heat conducting member 5 is set to about 5 ° C./W, and when 5 V is applied to the pulse motor 23 and the pulse motor 20, the temperature T1 is about 40 ° C. in an environment of room temperature of about 25 ° C. Further, when the motor driving signal is input, the temperature of the heat conducting member 5 becomes T3. Rated voltage (35V) for pulse motor 23 and pulse motor 20
Is applied, the temperature T3 becomes about 65 ° C.

Since the recording medium 6 is conveyed on the heat conducting member 5 in accordance with the recording process as described above, the temperature is close to the temperature T1 in the standby state where the recording is not performed, and is close to the temperature T2 in the recording state where the recording is performed. Be warmed. Then, the recording dots during recording are quickly dried and fixed, and bleeding between the recording dots does not occur, so that an image of high recording quality can be obtained.

As described above, each phase of the pulse motor 23 and the pulse motor 20 is made of a material with heat loss. Therefore, the electric resistance value of the material changes according to the change of the environmental temperature. In the present embodiment, since the pulse motor 23 and the pulse motor 20 have already become higher than the environmental temperature due to the excitation signal, it is possible to suppress the characteristic variation of the pulse motor 23 and the pulse motor 20 due to the environmental temperature due to the change in the electric resistance.

Further, since the temperature of the pulse motor 23 and the pulse motor 20 rises irrespective of the recording density, an image of high recording quality can be formed regardless of the recording density.

By setting the voltage at the time of inputting the excitation signal to be higher in the range of the rated voltage or less, the temperature difference between the standby state and the recording state can be further reduced, and an image of higher recording quality can be obtained. It will be possible.

Further, the ink jet recording apparatus of the present invention does not use a heater as in the prior art, but positively utilizes the heat generation of the pulse motor 23 and the pulse motor 20 necessary for recording, so that the apparatus itself is simple. It is possible to obtain an image of high recording quality which is economical and inexpensive.

Next, the effect of inputting the drive signal 51 and the drive signal 52 to the electromechanical conversion element 34 will be described with reference to FIG.

The electromechanical conversion element 34 is selected by the drive signal selection circuit, and the drive signal 51 or the drive signal 52 is selected.
Drive. As described above, the plurality of electromechanical conversion elements 34
The respective capacitances are substantially equal. Therefore, the drive signal generation circuit 43
The NPN type transistor 107 and the PNP type transistor 108 cause heat loss in approximately proportion to the number of electromechanical conversion elements 34 driven.

Further, as described above, the NPN transistor 1
07 and the PNP transistor 108 are joined to the heat conducting member 5. Therefore, by driving the electromechanical conversion element 34, the heat conducting member 5 also conducts heat. At this time,
The number of selected electromechanical conversion elements 34 and the temperature of the heat conducting member 5 change substantially in proportion.

When all the electromechanical conversion elements 34 are driven, a temperature increase of T4 is obtained by the drive signal 51, a temperature T5 is obtained by the drive signal 52, and a temperature increase of T2 is obtained by the drive signal 53.

In the drive signal 52, the charging pulse t1 and the charging pulse t2 are shorter than the driving signal 51. Further drive voltage V
2 is also higher than the drive voltage V1. Therefore, the drive signal 51
From the electromechanical conversion element 34, 3
4, 34 ... Drive the above flow current i1,
Since the sink current i2 increases, the NPN transistor 1
07, the heat loss amount of the PNP type transistor 108 increases. Therefore, the temperature T5 is higher than the temperature T4. In this embodiment, the temperature T4 is about 20 ° C, the temperature T5 is about 25 ° C, and the temperature T2 is about 5 ° C.

During recording, the temperature of the heat conducting member 5 changes according to the recording density. Then, of course, at a low recording density, it is possible to easily and quickly dry and fix even at a high recording density which is difficult to dry and fix. Also, drive waveform 51 and drive waveform 5
2 makes it possible to easily obtain higher recording quality. In addition, since the recording medium 6 is warmed even when recording is started due to the temperature rise of the heat conductive member 5 even during standby, it is possible to obtain higher recording quality.

Further, as described above, when the recording medium 6 is easily blurred, the drive waveform 51. The drive waveform 52 is used when the recording medium 6 is difficult to bleed. As a result, the recording medium 6 is warmed to a higher temperature when the recording medium 6 is less likely to bleed. Therefore, it is possible to obtain high recording quality regardless of the easiness of bleeding of the recording medium 6.

The temperature of the recording medium 6 which is less likely to bleed rises faster than that of the recording medium 6 which is more likely to bleed. Therefore, the recording medium 6 that hardly bleeds even after the start of recording can obtain the same high recording quality as the recording medium 6 that easily bleeds. That is, it becomes possible to use the recording medium 6 regardless of the ease of bleeding.

By inputting the drive signal 74 described above into the electromechanical conversion element 34 during standby, the following effects are also exhibited. However, in this case, the configuration of the recording head drive circuit of FIG. 5 does not include the selector 53 and the capacitor 54, and the output of the drive signal generation circuit 43 directly outputs the electromechanical conversion element 34,
34, 34 ...

As described above, in the drive signal 74, VH2 is V
Since it is lower than H1, ink droplets 80 from the nozzle 27
There is no discharge. However, the drive signal 52 causes the electromechanical conversion element 34 to expand and contract as the capacitor 50 is charged and discharged. Therefore, minute vibration is applied to the meniscus 81 formed on the nozzle 27. As a result, it is possible to suppress the phenomenon that the nozzles 27 are clogged due to ink drying and the like, and it is possible to stably eject recording dots, and it is possible to always obtain high recording quality.

Needless to say, the same effects are exhibited in FIGS. 11 and 12.

Further, as shown in FIG. 5, the following effects can be obtained by making the selector 54 selectable for the capacitor 54. This will be described using the drive signal 51 and the drive signal 52 in FIG.

The drive signal 51 or the drive signal 52 is input in synchronism with the timing signal input to the terminal 36 during the standby state where recording is not performed. At this time, the recording signal is the terminal 55
Is not input to the capacitor 54, the output of the drive signal generation circuit 43 is output to the capacitor 54. Then, the NPN-type transistor 107 and the PNP-type transistor 108 in FIG. 5 cause heat loss that is substantially proportional to the capacitance of the capacitor 54 provided.

That is, even in the standby state, the same NPN type transistor 107 and PNP type transistor 1 as those at the time of recording are used.
The recording medium 6 when the recording was started with the heat loss of 08 was obtained.
It is possible to easily improve the effect of drying and fixing the recording dots on the recording dots.

However, when the effect of drying and fixing can be sufficiently obtained by the temperature rise in the pulse motor 23 and the pulse motor 20, the heat conducting member 5 and the NPN transistor 1 are used.
07 and the PNP transistor 108 may not be joined. Further, when the effect of drying and fixing can be sufficiently obtained by increasing the temperature of either the pulse motor 23 or the pulse motor 20, the pulse motor 2 is attached to the heat conducting member 5.
The structure may be such that only one of the three or the pulse motor 20 is joined.

Further, the pulse motor 23 and the pulse motor 20 are controlled by the output of the temperature detecting sensor 10 shown in FIG.
Vary the input voltage when the excitation signal is input. By doing so, the temperature of the heat conducting member 5 can be easily controlled, and the accuracy of drying and fixing on the recording medium 6 can be made constant. Therefore, it is possible to always obtain a uniform image of high recording quality.

Further, by varying the number of the electromechanical conversion elements 34 driven in the standby state to be driven according to the output of the temperature detection sensor 10, the NPN transistor 107 and the PNP are connected.
The amount of heat loss in the mold transistor 108 changes.
This allows delicate temperature control. By using this method, an image with higher recording quality can be obtained.

As described above, according to the present invention, it is possible to facilitate the drying of the recording dots on the recording medium 6 and to quickly fix the recording dots. Ink bleeding (color mixing bleeding) can be prevented, and when applied to color printing, color dullness disappears and an image of high recording quality can be obtained.

In the above embodiment, an ink jet recording head using a piezoelectric vibrator that contracts when charged and expands when discharged from a charged state has been described as an example. Further, it is apparent that the same effect can be obtained even when applied to a recording head using a piezoelectric vibrator that contracts by being discharged from a charged state.

[0093]

As described above, in the present invention,
Since the ejection speed of ink droplets is selected according to the type of recording medium having different bleeding characteristics, it is possible to make the recording dot diameter landed and recorded on the recording medium uniform regardless of the recording medium. You can

Further, by providing a heat conducting member and joining a pulse motor and an element with heat loss to the heat conducting member,
It is possible to inexpensively provide a recording dot fixing unit that replaces the conventional fixing heater. Especially in color printing,
Ink bleeding between recording dots can be prevented, and when applied to color printing, dullness of color disappears and an image of high recording quality can be obtained.

Further, by making the pulse motor higher than the ambient temperature in advance by the excitation signal, it is possible to suppress the characteristic variation due to the temperature change, and it is possible to form a high quality image regardless of the recording density.

Further, by selecting the drive signal according to the type of the recording medium and driving the electromechanical conversion element, a high recording quality can be obtained regardless of the easiness of bleeding of the recording medium 6.

Further, by applying a minute vibration to the meniscus formed on the nozzle, it is possible to suppress the phenomenon that the nozzle is clogged due to ink drying and the like, and it is possible to stably eject recording dots, and always obtain a high recording quality. It becomes possible.

By selecting a capacitor with the selector during standby and inputting a drive signal to the capacitor, it is possible to further improve the effect of drying and fixing recording dots on the recording medium when recording is started. .

By varying the input voltage during excitation of the pulse motor according to the output of the temperature detection sensor, the temperature of the heat conducting member can be easily controlled, and the accuracy of drying and fixing on the recording medium can be improved. Can always be made constant, and an image of high recording quality that is always uniform can be obtained.

Further, by varying the number of driven electromechanical conversion elements to be driven during standby in accordance with the output of the temperature detection sensor, delicate temperature control becomes possible, and ink jet recording with which an image of higher recording quality can be obtained. A device can be provided.

Further, by selecting the drive signal according to the type of recording medium, it is possible to provide an inexpensive ink jet recording apparatus capable of making the ink consumption for recording an image substantially constant even if the recording medium is different.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a structure around a recording mechanism of an inkjet recording apparatus according to the present invention.

FIG. 2 is an explanatory diagram showing the periphery of a heat loss member.

FIG. 3 is a timing chart showing an input signal of a pulse motor.

FIG. 4 is a perspective view showing an internal structure of a recording head.

FIG. 5 is a circuit diagram showing an embodiment of a recording head drive circuit.

FIG. 6 is a circuit diagram showing an embodiment of a pulse width generation circuit.

FIG. 7 is a circuit diagram showing an embodiment of a drive signal generation circuit.

FIG. 8 is a state diagram showing a process of ejecting ink droplets from a nozzle.

FIG. 9 is a timing chart showing an example of drive signals.

FIG. 10 is a flowchart showing a control flow of the inkjet recording apparatus of the present invention.

FIG. 11 is a timing chart showing an example of drive signals.

FIG. 12 is a timing chart showing an example of drive signals.

FIG. 13 is a graph showing the relationship between the recording density and the temperature reached by the heat conducting member.

[Explanation of symbols]

 1 Carriage 4 Recording Head 5 Thermal Conductive Member 6 Recording Medium 10 Temperature Detection Sensor 20, 23 Pulse Motor 27 Nozzle 34 Electromechanical Converter 35 Recording Control Circuit 43 Drive Signal Generation Circuit 46 Pulse Width Generation Circuit 51, 52 Drive Signal 300 Flow Type Constant current source 301 Sink type constant current source

Claims (15)

[Claims] 1. A pressure chamber is provided with a plurality of nozzles for ejecting ink droplets, receiving ink supply from a reservoir and inputting a drive signal generated by a drive signal generating means to a pressure generating element, to the pressure chamber. An inkjet recording apparatus that includes a recording head that generates a change, ejects ink droplets from the nozzles selected by a drive signal selection unit to form an image on a recording medium, and a conveyance motor that conveys the recording medium. A carriage motor for scanning the recording head in a direction perpendicular to the direction of conveyance of the recording medium, and a device with heat loss for performing a switching operation to generate the drive signal in the drive signal generating means. A heat-conducting member on the non-recording surface side of the recording medium, perpendicular to the conveying direction of the recording medium, and parallel to the recording medium. And a drive signal selection unit that selects a waveform shape of the drive signal for varying the ink ejection speed with the ejection amount of the ink droplets being substantially constant according to the type of the recording medium. Inkjet recording device. 2. An image density selecting means for selecting a plurality of image densities is provided, and the drive signal according to the image density selected by the image density selecting means can be selected by the drive signal selecting means. The inkjet recording apparatus according to claim 1. 3. A drive signal including a trapezoidal drive signal portion in the waveform is generated from the drive signal generating means in synchronization with a timing signal from the outside, and the drive signal is generated by a recording signal from the outside. The inkjet recording apparatus according to claim 1, comprising switching means for outputting to the vibration source, and control means for generating a pulse signal for turning on the switching means. 4. The heat loss amount of the element accompanied by the heat loss is substantially proportional to the number of pressure generating elements which are selected and driven by the drive signal selecting means in accordance with an image. Inkjet recording device. 5. The ink jet recording apparatus according to claim 1, wherein the heat conduction amount of the heat conduction member is substantially proportional to the number of the pressure generating elements to be selectively driven. 6. In a standby state where the recording is not performed, a voltage equal to or lower than a rated voltage of the both motors is input to the transport motor and the carriage motor by an excitation signal to cause heat conduction to the heat conduction member. The ink jet recording apparatus according to claim 1, wherein 7. A temperature detecting sensor is arranged on the heat conducting member, and the temperature of the heat conducting member is controlled by controlling an input voltage of the excitation signal according to an output result of the temperature detecting sensor. The ink jet recording apparatus according to claim 6, 8. The drive signal generating means comprises a capacitor charging / discharging circuit, and a first region for increasing the drive voltage at a constant gradient in order to expand the volume of the pressure chamber and supply ink to the pressure chamber. Switching the switching operation from a first region to a third region that descends at a constant gradient in order to contract the volume of the pressure chamber and eject the ink droplets from the nozzle. The ink jet recording apparatus according to claim 3, wherein a second region for maintaining the drive voltage is formed in the trapezoidal drive signal portion. 9. The operation time of the first region is a constant current source operated by a charging pulse generated by a pulse width generating means provided outside the drive signal generating means, and a drive voltage applied to the drive signal generating means. 9. The ink jet recording apparatus according to claim 8, wherein the pulse width generating means generates the charging pulse in synchronization with the timing signal. 10. The operating time of the third region is determined by a constant current source operated by a discharge pulse by a pulse width generating means for generating a pulse at fixed intervals after the charging pulse is output, and the driving voltage. The inkjet recording device according to claim 8, wherein 11. The pulse width generating means forms the charging pulse based on an output pulse from an oscillator, and the driving signal selecting means determines the width of the charging pulse and the value of the driving voltage. The inkjet recording device according to claim 9. 12. In the standby mode, a drive signal having a voltage lower than the drive voltage for generating only the ink droplets from the nozzles is generated, and a drive signal having a voltage lower than the drive voltage is input to the pressure generating element. The inkjet recording apparatus according to claim 8, wherein 13. The temperature control of the heat conducting member is performed by controlling the number of the pressure generating elements selected by the drive signal selecting means according to the output result of the temperature detecting sensor. Inkjet recording device. 14. An excitation signal input to both of the motors and a drive signal of a voltage lower than the drive voltage are input to the pressure generating element according to an output result of the heat detection sensor. The inkjet recording apparatus according to claim 8. 15. The drive signal from the drive signal generating circuit is input to a capacitor in the standby state when an electromechanical conversion element is used for a plurality of the pressure generating elements. Inkjet recording device.