JPH0586341B2 - - Google Patents

Description

Detailed Description of the Invention (Technical Field) The present invention relates to a device that performs recording by ejecting recording droplets, such as an ink jet recording device, and in particular, the physical properties such as viscosity change depending on the environmental temperature. The present invention relates to a recording device that uses a recording liquid that varies depending on the situation.

(Prior Art) Ink jet recording devices are attracting attention as a new recording technology because they have advantages such as direct recording, easy colorization, and noiseless recording. In particular, on-demand type ink jet recording devices are becoming the centerpiece of full-color printer technology, which has recently been attracting attention, as they are inexpensive and compact.

Incidentally, the physical properties of the ink used as the recording liquid in these ink jet recording devices tend to change depending on the environmental temperature, such as its viscosity. Changes due to temperature will change the ink ejection characteristics, so some form of temperature compensation means is required to maintain good recording quality regardless of changes in environmental temperature. It was hot.

For example, as will be detailed later, in an on-demand ink jet recording device that uses a piezo vibrator (hereinafter referred to as a piezo element), which is an example of an electro-mechanical conversion element, as an energy source for ink ejection. After ejecting the required amount of ink once and before ejecting the required amount of ink again, the ink for the next ejection is loaded into the tip of the ink jet head, that is, the ink ejection orifice. It is necessary to refill the ink, and it takes a certain amount of time (refill time) to refill the ink. It is necessary to set the time interval of ink ejection by driving to be longer than this ink refill time. That is, unless
Ink is ejected before the required amount of ink is refilled in the ink ejection orifice, and the amount of ink ejected becomes less than the required amount, resulting in deterioration of recording quality or ink loss. This is because an undesirable situation such as non-ejection may occur.

Here, the refill time of the above-mentioned ink depends on physical property values such as the viscosity of the ink, and the higher the viscosity of the ink, the longer the time required for refilling becomes. On the other hand, the viscosity of ink depends on the environmental temperature and tends to increase as the temperature decreases. Therefore, the lower the environmental temperature, the longer the time required for refilling.

Therefore, in order to always guarantee high-quality and good recording regardless of changes in the environmental temperature, for example, the recording speed determined by the ink ejection frequency, which is the reciprocal of the ink ejection time interval, should be set. Measures for temperature compensation have been considered, such as setting the ink refill time in advance at the lowest temperature, or keeping the ink temperature constant using a heating device such as a heater. However, in the former method, the recording speed is uniquely determined to be suitable for use at the lowest expected temperature, so the recording time may be longer than necessary when used at room temperature or high temperature. In addition, in the latter method, the addition of a heating device increases the size of the recording device and increases the price.

(Purpose) The present invention was made in view of the above circumstances,
The main purpose of this invention is to provide a new liquid jet recording device that can eliminate all of the above-mentioned disadvantages as a recording device that performs recording using a recording liquid whose physical properties change depending on the environmental temperature. That is.

Another object of the present invention is to be able to maintain good recording quality irrespective of changes in environmental temperature, without causing an increase in the size of the device or a rise in price, and at the same time, without causing an increase in the size of the device or a rise in price. To provide a new recording device in which the recording time does not become longer than necessary under high temperature conditions.

Still another object of the present invention is to provide a recording device that can automatically realize a recording speed according to the environmental temperature, and thereby can always obtain high-quality recordings regardless of changes in the environmental temperature. It is about providing.

(Explanation based on Examples) Hereinafter, the means taken in the present invention to achieve the above object will be exemplified and explained using Examples shown in the accompanying drawings.

Note that in the present invention, the signal to be recorded may be a character signal or an image signal. In this specification, the term recording signal will be used to represent both. Therefore, a record means a record of characters and/or images.

Further, as an example of the present invention, the present invention is applied to an ink jet recording device that uses a piezo element, which is an example of an electro-mechanical conversion element, as an energy source for ejecting recording droplets. The energy source may be, for example, a means for ejecting the necessary amount of recording droplets by generating bubbles. Therefore,
It goes without saying that the present invention is not limited to the configurations shown in the embodiments, and the present invention is applicable to recording liquids whose physical properties change depending on the environmental temperature, as described at the beginning. It can be widely applied to recording devices that use the present invention to perform recording.

First, an ink jet head moving mechanism and a paper feeding mechanism in an example of an ink jet recording apparatus to which the present invention can be applied will be described with reference to FIG.

In the figure, 100 indicates at least one ink.
The ink jet head assembly includes jet head units 101, and although the illustrated example includes an array of eight head units 101, the number of head units 101 is not critical. Details of the structure of head unit 101 will be explained later with reference to FIGS. 3 and 3A. The head assembly 100 is supported by a head carriage 110, which is guided by two fixedly arranged parallel guide rods 113 and 114, as indicated by arrows A and B in the figure. As shown, it can be moved back and forth. Reference numeral 106 denotes a carriage moving motor as a head moving means, which has a first pulley 108 attached to its output shaft 106a and a position spaced a predetermined distance from the first pulley 108 along guide rods 113 and 114. A belt 107 is stretched between the second pulley 109 and a second pulley 109 which is rotatably provided in the second pulley 109, and the carriage 110 is connected to a part of this belt 107. Therefore, when the output shaft 106a of the motor 106 is rotated in the forward or reverse direction, the belt 107 reciprocates in the directions of arrows A and B, and the carriage 110 is guided.
The head assembly 100 is reciprocated in the directions of arrows A and B along the rods 113 and 114, and thus the recording position of the head assembly 100 with respect to the recording paper 102, which is the recording carrier, is changed.

112 is a recording position by the head assembly 100;
That is, the linear position encoder plate 111, which is fixedly arranged and has a plurality of marks 112a for indicating the ink ejection position, is connected to this encoder.
A discharge position detector for detecting the mark 112a on the plate 112, which is fixed to a part of the carriage 110 and is movable together with the carriage 110. Since the specific configuration of the position detector 111 is well known, detailed illustration will be omitted, but for example,
Mark 112a on encoder plate 112
A mark that looks like it is engraved in black on a transparent film,
Alternatively, if the mark is formed as a translucent slit on an opaque plate, the detector 1
11, this encoder plate 112
It includes a photo coupler or a photo interrupter consisting of a combination of a light emitting element and a light receiving element arranged in a sandwiching relationship, and outputs a pulse-like signal for instructing ink ejection every time the mark 112a is detected. It has a configuration that makes it possible to

It is obvious that instead of having the encoder plate 112 fixed and the detector 111 movable, the detector 111 may be fixedly arranged and the encoder plate 112 may be moved together with the carriage 110.

103 is a paper feeding mechanism including a pulse motor 103a and a gear train 103b;
4 is a paper feeding drum, and 105a is a paper pressing roller rotatably supported by a shaft 105. The recording paper 102 is held between the paper feed drum 104 and the paper pressing roller 105a, and the rotation of the pulse motor 103a is transmitted to the paper feed drum 104 via the gear train 103b, which rotates in the direction of the arrow in the figure. As a result, it is sent in the direction of arrow c.

Next, the control system of the ink jet recording apparatus having the above structure will be explained with reference to FIG.

In the figure, 201 is a head drive circuit that ejects ink by driving each head unit 101 in the head assembly 100; In response, the head unit 101 is selectively driven based on the recording signal that is being input at that time. In addition, 111, 112 and 201
A driving means for repeatedly driving the head unit 101 is constituted by the elements shown in .

202 is a motor control circuit that controls the head moving motor 106 through a motor drive circuit 204;
203a and 203b are an A-direction limit switch and a B-direction limit switch, respectively, which are configured to be closed, for example, by a portion thereof, when the head carriage 110 reaches its respective end position of movement in the directions of arrows A and B. The motor control circuit 202 switches the rotation of the motor 106 from, for example, forward rotation to reverse rotation in response to the turning on of the A direction limit switch 203a, and also switches the rotation of the motor 106 from forward rotation to reverse rotation in response to the turning on of the A direction limit switch 203b.
Switches from reverse rotation to forward rotation in response to turning on, and
During the rotation, the rotation of the motor 106 is controlled so that the rotation speed is constant.

In an ink jet recording apparatus having the configuration as described above, the head carriage 1
10 is moved at a constant speed by the motor 106, each time the ejection position is detected by the ejection position detector 111, the head drive circuit 201 detects the recording signal input to the head drive circuit 201 at that time. The head unit 101 in the head assembly 100 is selectively driven in accordance with the movement speed of the head carriage 110, and therefore the head assembly 100, to perform recording by ejecting ink. V (mm/sec), encoder plate 1
If the pitch of the mark 112a at 12, that is, the pitch of the ejection position, is P (mm), the ink ejection frequency by the head assembly 100 (or head unit 101) is V/P (Hz), and the ejection time is The interval is P/V (sec). Here, as will be described later, after each head unit 101 ejects ink once, it takes a certain amount of time to refill ink for the next ink ejection, that is, an ink refill time t (sec). In order to guarantee recording quality, the ejection time interval P/V needs to be greater than or equal to the refill time t.

In the apparatus configured as described above, recording may be performed only during the movement of the head carriage 110 in the direction of arrow A in FIG. It is also possible to perform recording during the movement process. In the former case, when the carriage 110 reaches the end position in the A direction and is moved back in the B direction, the paper feeding pulse motor 103a is activated to move the recording paper 10
The recording paper 102 may be fed by a predetermined amount in the direction of the arrow C. In the latter case, the pulse motor 103a is operated each time the carriage 110 reaches the end position in the A direction and the B direction to move the recording paper 102. It is sufficient to send a predetermined amount in the C direction.

The above ink jet head unit 10
1 has a configuration as shown in FIG.

In the figure, 1 is an ink sub-tank, and ink 2 as a recording liquid is supplied from an ink main tank (not shown) through an ink supply pipe 9 connected to an ink introduction port 1a of the ink sub-tank. , excess ink is discharged from overflow ink outlet 1
b and an overflow ink discharge pipe 10 connected thereto.

3 is a filter, 4 is an ink supply tube, and 5 is a glass tube, at one end of which there is an orifice 6 for discharging ink.
It is equipped with

7 is electricity as an energy source for ink ejection.
This is a cylindrical piezo element that is an example of a mechanical transducer. When the piezo element 7 is contracted by applying a voltage according to the recording signal by the head drive circuit 201 shown in FIG. One or more ink droplets 8 are ejected from the orifice 6. When the voltage is cut off, ink ejection ends, and the surface of the ink 2 in the glass tube 5 moves from the position of the tip D of the orifice 6 to E, as shown in FIG. 3A.
Move back to the position indicated by . Next, due to surface tension, the surface of the ink 2 moves from the position shown by E to the position shown by D, and at this time, the ink 2 is refilled into the glass tube 5 through the filter 3 and the ink supply pipe 4. . The time t required for this series of operations is the ink refill time.

When the piezo element 7 is repeatedly contracted at intervals longer than the refill time t described above, the amount of ink ejected corresponds to the amount of displacement of the piezo element 7 in an appropriate relationship, and an appropriate amount of ink can always be ejected. can.

On the other hand, if the piezo element 7 is contracted at a time interval shorter than the refill time t, the ink 2
Since the next ink ejection will be performed before the surface of the print head has completely returned to the position indicated by D in Figure 3A, an appropriate amount of ink cannot be ejected, resulting in a decrease in printing quality. It invites.

On the other hand, the refill time t largely depends on the physical properties of the ink, such as its surface tension and viscosity. To explain this based on Figure 4, Figure 4 shows temperature (in degrees Celsius) on the horizontal axis and viscosity (CP) on the vertical axis.
It shows the change characteristics of viscosity due to temperature change.
When the temperature drops from, for example, 10°C to 0°C, the fluidity of the ink decreases due to the increase in viscosity.
The ink refill time t at the ink jet head changes from t ₁ to t ₂ (>t ₁ ).

Therefore, in order to always guarantee high-quality recording regardless of temperature changes within the operating temperature range of the ink jet recording device, for example, (1) the ink jetting frequency should be - Make sure to set it in advance according to the refill time tmax.

(2) Keep the ink temperature constant using a heating device such as a heater.

Other methods have been considered.

However, the method described in (1) has the drawback that the recording time becomes unnecessarily long at room temperature or high temperature, and (2) the method described in the above method increases the cost and size of the ink jet device. It had drawbacks.

The present invention aims to eliminate such inconveniences, and embodiments thereof will be described below.

First, FIG. 5 shows a control system as an embodiment in which the present invention is applied to an ink jet recording apparatus as explained in FIGS. 1, 2, 3, and 3A. Elements designated by the same reference numerals in FIGS. 1 and 2 have the same configurations and functions as described above.

205 is an F that receives the detection pulse from the discharge position detector 111 and outputs a voltage according to its frequency.
-V conversion circuit, whose output is the differential amplifier circuit 210
is applied to the inverted input of That is, the ejection position detector 111 and the F-V conversion circuit constitute means for detecting the head movement speed. 206 is a predetermined temperature Tr
A first reference voltage generation circuit 207 generates a first reference voltage Vref.1 for defining a head movement speed suitable for recording at a temperature of (°C) or higher, and 207 is at a temperature lower than the predetermined temperature Tr. a second reference voltage to define a head movement speed suitable for recording under
A second reference voltage generation circuit that generates Vref.2, 208
is a switch for selectively applying the outputs of these reference voltage generation circuits 206 and 207 to the non-inverting input of the differential amplifier circuit 210;
8a and 208b, and one movable contact piece 208c located between them and having a self-closing behavior with respect to the fixed contact piece 208a.
7, and the movable contact piece 208c is connected to the non-inverting input of the differential amplifier circuit 210. 209
is a bimetallic temperature sensor, where:
If the environmental temperature is above the predetermined temperature, no action is taken on the switch 208, but if the environmental temperature becomes lower than the predetermined temperature,
By deforming in the direction of the arrow, the movable contact piece 208c of the switch 208 is moved from the fixed contact piece 208a side to the fixed contact piece 2 by the insulating switch operation part 209a at the tip.
Switch 2 so that it acts to switch to the 08b side.
It is placed against 08. Furthermore, bimetal 2
09 is preferably placed as close to the head assembly 100 as possible, but it does not necessarily need to be placed on the head carriage 110, and may be fixedly placed near the recording stage.

The output of the differential amplifier circuit 210 is the motor control circuit 2
02, and the motor control circuit 202 speeds up the motor 106 based on the output of the differential amplifier circuit 210 if the output is positive.
If it is negative, the motor 106 is controlled through the motor drive circuit 204 so that the output of the differential amplifier circuit 210 always approaches zero by decelerating it. That is, since feedback speed control is performed by the differential amplifier circuit 210, the moving speed of the head can be made stable and accurate.

Here, elements 202 and 205 to 210 control the head driving means 1 according to the environmental temperature.
Head unit 1 with 11, 112, 201
Means for controlling the drive frequency of 01 is configured.

Here, the first and second reference voltages Vref.1 and Vref.2 are determined as follows. That is, when the environmental temperature is the above-mentioned predetermined temperature Tr (°C), tr (sec) is required as the above-mentioned ink refill time t depending on the physical property value of the ink 2, and the environmental temperature is assumed. (minimum temperature within the operating temperature range of the device) Tmin (°C) (Tmin<Tr),
It is assumed that tmax (sec) (tmax>tr) is required as the ink refill time t depending on the physical property values of the ink 2, and that P and V are respectively set on the encoder plate 112 as described above. mark 11
2a and the moving speed of the head assembly 100, the first reference voltage Vref.1 is V=V ₁ ≦P/Tr for the head moving speed V, and the second reference voltage Vref.2 is V =V ₂ ≦P/tmax (however, V ₁ > V ₂ )
The voltage value is such that it gives

In this embodiment, when the environmental temperature is equal to or higher than the predetermined temperature Tr, the fixed contact piece 208c of the switch 208 is in contact with the fixed contact piece 208a, so that the non-inverting input of the differential amplifier circuit 210 is used as the non-inverting input. 1 reference voltage from the reference voltage generation circuit 206
Vref.1 is selected, which causes the differential amplifier circuit 2
Through the control of the head movement motor 106 by the motor control circuit 204 responsive to the output of the head movement speed V, the head movement speed V is controlled to the above-mentioned _V1 . Note that the ink ejection frequency, that is, the recording frequency in this case is V ₁ /P (Hz).

On the other hand, when the environmental temperature becomes lower than the predetermined temperature Tr, the bimetal 209 activates the switch 2.
Since the movable contact piece 208c of 08 is switched from the fixed contact piece 208a to the fixed contact piece 208b, the second reference voltage Vref.2 from the second reference voltage generation circuit 207 is now used as the non-inverting input of the differential amplifier circuit 210. is selected, and therefore the head movement speed V is the above-mentioned
It will be controlled by V ₂ . Incidentally, the ink ejection frequency in this case, that is, the recording frequency is V ₂ /P
(Hz).

Next, a modification of the control system shown in FIG. 5 will be described as another embodiment of the present invention.

FIG. 6 shows an example in which a temperature detection circuit including a thermal element is used in place of the bimetal 209 in FIG. 5. In the figure, the same reference numerals in FIGS. Elements denoted by have the same configurations or functions as those described above, and elements denoted by the same reference numerals with a dash are corresponding elements.

In the figure, 209' is the bimetal 20 in Figure 5.
Temperature detection circuit replacing 9, with resistors R ₁ and R ₂ placed between the power supply +Vcc and the circuit ground, respectively.
A series circuit of a resistor R ₃ and a thermistor R _TH , which is an example of a heat-sensitive resistance element, and a resistor R ₁
and _a voltage comparator CP connected to receive the potential at the connection point a of the resistor R 3 and the thermistor R _TH at its inverting input, and the potential at the connection point b of the resistor R ₃ and the thermistor R TH at its non-inverting input. Here, as is well known, the thermistor R _TH is an element that has a characteristic that its resistance value increases as the environmental temperature decreases, and here, if the environmental temperature is above the above-mentioned predetermined temperature Tr, The resistors R ₁ , R ₂ ,
Each resistance value of R ₃ is selected. Therefore, when the environmental temperature is above Tr, the output of the comparator CP, which is the output of the temperature detection circuit 209', is low, but when the environmental temperature is lower than Tr, the output becomes high.

211 latches the output of the temperature detection circuit 209' at that time in response to a latch pulse output from means not shown when the limit switches 203a and 203b described in FIG. 2 are turned on, for example. The latch circuit 208' is a switching circuit that replaces the switch 208 in FIG. 5, and the output of the latch circuit 211 is given as a control input.
is connected to input a, and if high, output c is connected to input b. This switching circuit 208'
has its input a connected to the output of the first reference voltage generation circuit 206, its input b connected to the output of the second reference voltage generation circuit 207, and its output c connected to the non-inverting input of the differential amplifier circuit 210.

Thus, in the configuration of this embodiment, when the environmental temperature is equal to or higher than Tr, the output of the temperature detection circuit 209' is low, so that the switching circuit 20
8' applies the first reference voltage Vref.1 from the first reference voltage generation circuit 206 to the non-inverting input of the differential amplifier circuit 210, thereby increasing the head movement speed V.
will be set to V ₁ above. On the other hand, when the environmental temperature becomes lower than Tr, the output of the temperature detection circuit 209' becomes high, so that the second reference voltage generation circuit 207 is output by the switching circuit 208'.
The second reference voltage Vref.2 from the differential amplifier circuit 21
0 is applied to the non-inverting input, thereby causing the head movement speed V to be set to the above-mentioned _V2 .

In this embodiment, the temperature detection circuit 209'
Since the output of the head is latched by the latch circuit 211, switching of the head movement speed V during recording of one line is prevented, and random fluctuations in the recording dot interval within one line are prevented.

In the embodiments shown in FIGS. 5 and 6, the head movement speed V is switched between two stages, high (V ₁ ) and low (V ₂ ), depending on the environmental temperature, but the number of speed control stages is two. Needless to say, the structure is not limited to just one stage, but may be even more multi-stage.

Alternatively, stepless control may be used as shown in the example of FIG. That is, in the figure, the thermistor _RTH forms a series circuit with the resistor _R4 ,
Provided between the power supply +Vcc and circuit ground,
The potential at the connection point c is applied to the non-inverting input of the differential amplifier circuit 210. Here, 202, 205,
Elements 210, R _TH and R ₄ constitute means for controlling the head drive frequency in response to the environmental temperature.

According to such a configuration, as the environmental temperature decreases, the potential at the connection point c decreases, so the head movement speed V also decreases, and the speed control in this case becomes stepless.

In order to prevent random fluctuations in the recording dot interval within one line, a sample-and-hold circuit (analog latch circuit) corresponding to the latch circuit 211 in FIG. between the non-inverting input of the amplifier circuit 210 or the output of the differential amplifier circuit 210 and the motor control circuit 202
It is possible to place it between the input of the

(Effects) As detailed above, according to the present invention, by controlling the drive frequency of the recording droplet ejecting head according to the environmental temperature, it is possible to control the recording droplet jetting head at any temperature within the operating temperature range of the device. To configure a liquid jet recording device that can always perform high-quality and good recording without unnecessarily lengthening the recording time even in such a case, and that is lower in cost and smaller than a temperature compensation means using a heater or the like. This provides many advantages, such as the ability to

Furthermore, since the moving speed of the recording head is controlled by feedback according to the environmental temperature,
The moving speed of the recording head can be made stable and accurate, and recording accuracy can also be improved.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of essential parts of an ink jet head moving mechanism and a paper feeding mechanism in an example of an ink jet recording apparatus to which the present invention can be applied;
The figure is a circuit block diagram showing an overview of the control system of the ink jet recording apparatus having the configuration shown in Figure 1.
Figure 1 is an enlarged cross-sectional view of one ink jet head unit in the illustrated device, Figure 3A is an enlarged cross-sectional view of the orifice portion in Figure 3, and Figure 4 is a diagram showing the relationship between temperature and ink viscosity. FIG. 5 is a diagram showing the relationship between the first, second, and third embodiments of the present invention.
6 and 7 are block diagrams showing an example of a control system when applied to an ink jet recording apparatus as explained in FIG. It is a block diagram. 101... Ink jet head unit, 2... Ink, 5... Glass tube, 6... Orifice, 7... Cylindrical piezo element, 8... Ink droplet, 106... Head moving motor, 111 ……
Discharge position detector, 112... Linear position encoder plate, 201... Head drive circuit, 20
2... Motor control circuit, 205... F-V conversion circuit, 206, 207... Reference voltage generation circuit, 20
8...Switch, 208'...Switching circuit,
209...Bimetal, 209'...Temperature detection circuit, 210...Differential amplifier circuit, _RTH ...Thermistor.

Claims (1)

[Scope of Claims] 1. The refill time required for refilling the ink ejection section with ink changes depending on the temperature, and the recording head that ejects the ink refilled in the ink ejection section onto the recording surface is controlled according to the temperature. a moving means for moving the recording head relative to the recording surface; a temperature detecting means for detecting environmental temperature; a speed detecting means for detecting the moving speed of the recording head; a movement control means for controlling the speed of the moving means to a speed that satisfies the refill time defined based on the detected temperature; and a movement control means for ejecting ink from the recording head at a frequency defined based on the detected temperature and satisfying the refill time. A recording device comprising a driving means. 2. The recording apparatus according to claim 1, wherein the recording head ejects ink by generating air bubbles.