JPH068048B2 - Inkjet recording device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an inkjet recording apparatus that records an image using a recording head that ejects an amount of ink according to a drive signal, and particularly has a temperature compensation function. The present invention relates to an inkjet recording device.

[Summary of Disclosure] This specification and the drawings show that in an ink jet recording apparatus, a head driving frequency is changed according to temperature, and density data is converted into an optimum head driving voltage according to temperature to determine any temperature state. Disclosed is a technique in which the ejection drive frequency and the drive voltage of the recording head are optimized even under the conditions described above, whereby high-quality recording can always be obtained, and variation in characteristics due to the temperature of the recording head is absorbed.

[Prior Art] Conventionally, a recording-type inkjet that already changes a drive voltage of an inkjet head to change an ink ejection amount, thereby changing a recording dot diameter on a recording paper to express a halftone. Recording devices have been proposed.

[Problems to be Solved by the Invention] However, in this type of apparatus, the physical properties of the ink, which is the recording liquid, that is, the viscosity and surface tension, change significantly with temperature, and the ejection of the head itself also changes with temperature. Has the temperature characteristic. Therefore, in general, the relationship between the optical density on the recording paper after recording and the voltage applied to the head changes depending on the temperature as shown in FIG. That is, the higher the temperature, the higher the optical density with the same head applied voltage.

For this reason, if the printing is performed at 10 ° C. using the density-voltage data of 25 ° C. as in the conventional case, the printing density becomes low, or the ink is not ejected in the low voltage range. Inconvenience occurs, and if you print at 40 ° C using 25 ° C density-voltage data, the amount of ejected ink will be too large and the recording paper will not be able to absorb the ink. There are various inconveniences such as bleeding, which is not only the change in density of the image reproduction range.

On the other hand, as a conventional temperature compensating method, there are a method of keeping the physical property value of ink constant by using a heater or the like, and a method of changing the voltage applied to the head according to the temperature. But,
In the former method of keeping the physical property values constant, the size of the device is increased, the power supply capacity is increased, the manufacturing cost is increased accordingly, and the improper printing due to the generation of dissolved gas in the ink accompanying the rapid heating. There are drawbacks.

The latter method of changing the applied voltage is effective only for a binary image, and when the halftone is expressed by changing the ink ejection amount by this method, it is possible to deal with nonlinear changes of various characteristics. There is a drawback that the circuit configuration becomes extremely complicated, resulting in high cost and difficulty in practical use. Furthermore, the latter method has a problem that the viscosity of the ink at a low temperature delays the recovery of the meniscus after ejection, lowers the response frequency, and requires compensation of the frequency characteristics of the head at each temperature. It was

Therefore, an object of the present invention is to eliminate the above-mentioned drawbacks and to provide an ink jet recording apparatus capable of always obtaining high-quality recording regardless of temperature change with a simple circuit configuration.

[Means for Solving the Problems] In order to achieve the above object, the present invention is an inkjet recording apparatus that records an image using a recording head that ejects an amount of ink ejected according to a drive signal. Detecting means for detecting as data, defining means for defining a drive frequency of the recording head according to temperature data detected by the detecting means, generating means for generating density data for recording an image, and the detecting means A conversion table for inputting the temperature data detected by the means and the density data generated by the generation means, converting the density data into discharge amount data according to the temperature data, and outputting the converted data, and outputting from the conversion table The drive signal corresponding to the discharged ejection amount data is supplied to the recording head at the drive frequency defined by the defining means. And a driving unit for driving the recording head.

Further, preferably, as one form thereof, the conversion table may be a ROM in which the temperature data and the density data are input to an address input, and the ejection amount data is output from a data output. .

[Operation] According to the present invention, the drive frequency of the recording head is defined by the defining means in accordance with the temperature data of the ambient temperature detected by the detecting means, and the temperature data and the density data generated by the generating means are converted into a conversion table. The density data is input, the density data is converted into ejection amount data according to the temperature data, and a drive signal corresponding to the ejection amount data is supplied to the recording head at the above-mentioned drive frequency defined by the defining means to be driven. Therefore, the drive frequency and drive signal of the recording head are optimized under any temperature condition, and thus high-quality recording can always be performed.

Embodiments Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a basic configuration example of the embodiment.

Here, a is a detection unit that detects the ambient temperature as temperature data, b is a definition unit that defines the drive frequency of the recording head f according to the temperature data detected by the detection unit a,
c is generation means for generating density data for recording an image, d is temperature data detected by the detection means a and density data generated by the generation means c are inputted,
It is a conversion table for converting density data into discharge amount data according to temperature data and outputting the data. Reference numeral e denotes a drive unit that supplies a drive signal corresponding to the ejection amount data output from the conversion table d to the recording head f at the drive frequency defined by the definition unit b to drive the recording head f. Records an image by ejecting an amount of ink corresponding to the drive signal.

FIG. 3 shows a circuit configuration example of the embodiment apparatus.

In the figure, reference numeral 1 is a sequence controller, which performs control operation of the entire apparatus based on a control procedure as shown in FIG. Reference numeral 2 is a temperature sensor as an ambient temperature detecting means such as a thermistor. The temperature detection signal 3 output from this temperature sensor is
It is converted into a 2-bit temperature signal 5 by the A / D (analog / digital) converter 4 and sent to the system controller 1.

An image processing unit 8 performs predetermined image processing on the image input signal 6 to convert it into density data 9, stores the density data 9 in an internal memory, and then outputs the data from the system controller 1. In response to the command signal 7, the internal memory sequentially outputs.

Reference numeral 11 denotes a data conversion table section as a discharge amount data output means, which inputs density data 9 from the image processing section 8 and temperature data 10 from the system controller 1
Converted to bit voltage value data 12. 14 shows this voltage value data 12 as the latch pulse 13 from the system controller 1.
It is a D / A converter that performs latching and D / A (digital / analog) conversion in synchronization with, and outputs converted analog data 15.

Reference numeral 17 denotes a motor driver that drives a head scanning motor 18 that reciprocates a recording head, which will be described later, in the scanning direction via a carriage (not shown), and is controlled by a control signal 16 from the sequence controller 1. Reference numeral 19 denotes an encoder unit that detects a position of a recording head described later and outputs a position signal 20, and is composed of a known optical sensor, a slit, and the like.

Reference numeral 22 denotes a head driver as a drive unit that drives the recording head 23, and an ejection command output from the sequence controller 1 by the analog voltage data 15 from the D / A conversion unit 14 and the position signal 20 from the encoder unit 19. The recording head 23 is driven according to the pulse 21. The recording head 23 ejects ink droplets toward a recording medium, which is a recording medium.

As will be described later, the sequence controller 1 has a configuration for defining the minimum time interval of the ejection command pulse 21, that is, the maximum frequency, according to the temperature signal 5.

Further, 24 is a pulse motor driver for driving a paper feed pulse motor 25 for feeding the recording paper, which is controlled by a control signal from the sequence controller 1.

The temperature sensor 2 and the head 23 are arranged near the scanning path or an ink tank (not shown) for supplying ink to the head 23.

FIG. 4 shows an example of the structure of the table unit 11 shown in FIG. As shown in the figure, the table unit 11 is composed of, for example, one ROM (read-on memory), the temperature data (temperature signal) 10 from the sequence controller 1 is input to the upper 2 bits of its input port, and its input By inputting the density data (density signal) 9 from the image processing unit 8 to the lower 6 bits of the port, the search address (reference address) is determined, and the 6-bit voltage value data (D ₀
~ D ₅ ) 12 is output.

FIG. 5 shows an example of the contents of the above-mentioned table section 11. As shown in the figure, as the temperature data _(A 6, A ₇₎ is changed, different voltage value data for the same density data _{(A 0 ~A 5) (D} 0 ~D 5) is output Like the contents are pre-assembled.

Here, in this embodiment, since the density data (000000) indicates that the ejection is not performed, the density data (000001) to (111111) indicating that the ejection is performed is converted according to the temperature data.
Is.

FIG. 6 shows a time chart regarding the regulation of the drive frequency of the recording head 23. Here, the timer 31 is an internal timer of the sequence controller 1, and the motor voltage 32 is a drive voltage of the head scanning motor 18.

Next, the operation of the apparatus having the above configuration is shown in FIGS. 7 (A) and 7 (B).
The flow chart will be described.

When the printing process is started (step S1), the output signal 3 of the temperature sensor 2 is first converted into a 2-bit temperature signal 5 by the A / D converter 4 and sent to the sequence controller 1 (step S2). Next, in response to the 2-bit temperature signal 5, the recording head is set in the sequence controller 1.
A time constant Tref for determining the driving frequency 1 / Tref of 23 is prepared in advance from among constants Tref ... Tref ₄ such as Tref ₁
Is selected (step S3). Further, the temperature data 10 corresponding to the 2-bit temperature signal 5 from the A / D converter 4 is output from the sequence controller 1 to the upper 2 bits (A ₇ , A ₆ ) of the input port of the table 11 and the temperature Data is latched during recording of one screen (one page) (step S4). This latch removes the instability near the temperature switching point, and the change in the temperature of the ejected ink is relatively gradual even when the ambient temperature changes suddenly. This is because there is no need to change it.

Next, when the image input signal 6 is input to the image processing unit 8,
After the input signal 6 is subjected to a predetermined image processing necessary for image reproduction in the image processing unit 8, it is converted into density data 9 and the converted density data 9 is stored in an internal memory (step S
Five). When the print execution preparation is completed, the sequence controller 1 outputs the data output command signal 7 to the image processing unit 8 to output the density data 9 for one pixel (first pixel) from the internal memory of the image processing unit 8 to the table unit 11. To (step S6). Next, in the sequence controller 1, the count value N is set in the internal counter (step S7), and the motor driver 17 is operated by the control signal 16. As a result, the motor 18 is activated and the scanning of the recording head 23 is started (step S8).

At the same time, the timer (see FIG. 6) in the sequence controller 1
31) is activated (step S9-1). The set value of the timer at this time is the constant Tref ₁ selected according to the temperature signal 5 in the above step S3. Next, the rising edge of the output signal 20 of the encoder section 19 is detected (steps S9-2, S9-3). If the rising edge of the encoder output signal 20 is input after the timer ends (step S9-4), it indicates that the moving speed of the recording head 23 is slow, and therefore the sequence controller 1 accelerates the head scanning motor 18 ( Step S9-5), and if the rise of the encoder output signal 20 described above indicates that the timer is operating, the sequence controller 1 indicates that the head scanning motor is moving fast.
Decelerate 18 (step S9-6). At the same time, the value of the timer is reset and the count value N is decremented by 1 (step S10), and if the value of N is not zero (step S11), the process returns to the timer start process of step S9-1 again. The processes of steps S9-1 to S9-6 are repeated. By repeating this operation sequentially, the moving speed of the recording head 23 becomes constant, and the recording head 23 changes the output pitch of the encoder unit 19 with time.
Move with Tref ₁ . Accordingly, by matching the output pitch of the encoder 19 with the output pitch of the image, the driving frequency of the recording head 23 is kept constant, and the driving frequency is changed by changing the constant Tref according to the cooling temperature signal 5. You can

Next, the value of the count value N of the encoder output signal 20 is set in advance so that the above-mentioned count value N becomes zero when the recording head 23 having the constant speed reaches the initial ejection position. Since it has been done, N in step S11
When = 0 is reached, the process moves to the next step S12 to start ejection. At this time, the 6-bit density data 9 corresponding to the fourth pixel has already been sent from the image processing unit 8 to the input ports A _{5 to} A ₀ of the table unit 11 by the processing in step S6.
Further, the temperature data 10 is sent to the input ports A ₇ and A ₆ of the table 11 by the processing in step S4. As described above, the table section 11 extracts the data 9 and 10 input to the input ports A _{7 to} A ₀ as addresses and outputs the 66-bit voltage value data 12 from the output ports D _{5 to} D _0. The data 12 is converted into an analog voltage value 15 by the D / A converter 14 and input to the head driver 22. At this time, when the encoder output 20 is input to the sequence controller 1, the ejection command pulse 21 is output from the sequence controller 1 to the head driver 22 (step S12), and the recording head 23 with the analog voltage value 15 in synchronization with the ejection command pulse 21. Is driven, and a predetermined amount of ink is ejected.

Next, the controller 1 sends the data output command signal 7 again to the image processing unit 8, and the density data corresponding to the next pixel is sent from the image processing unit 8 to the table unit 11 (step
S13). Then, the above-described steps S9-1 to S9-8 are performed (step S14), and the above-described processing operations of steps S12 to S14 are repeated until one line is printed (step S15).
After that, the image is recorded on the recording paper by repeating the above operation for one screen.

In this example, the case where the number of recording heads is one is described, but the present invention is not limited to this, and it is needless to say that the present invention is also applicable to a plurality of recording heads for color recording and line heads. In this case, it is also possible to change the address of the table unit (ROM) 11 so as to correspond to the temperature data of each recording head. It is also possible to obtain finer temperature compensation by further increasing the number of bits of the temperature data 10. Further, the method of controlling the moving speed of the recording head is not limited to that of this example, and it goes without saying that other known methods can be used.

[Effects of the Invention] As described above, according to the present invention, the drive signal of the print head with respect to the density data is adjusted according to the temperature data, and the drive frequency of the print head is changed. Inkjet recording apparatus in which the drive frequency and drive signal of the recording head are optimized under any temperature condition that occurs during the state, whereby high-quality recording can always be performed, and variations in characteristics due to the temperature of the recording head can be completely absorbed. Can be provided.

Further, according to the present invention, compared with the conventional technology using a heater or the like for temperature compensation, the power consumption is much lower and the cost is further reduced, and great advantages such as miniaturization, simplification of the equipment and improvement of reliability are obtained. To be

[Brief description of drawings]

FIG. 1 is a block diagram showing an example of the basic configuration of an embodiment of the present invention, FIG. 2 is a characteristic diagram showing the relationship between the head applied voltage and the optical density with respect to temperature, and FIG. 3 is a block showing the configuration of the embodiment apparatus. Fig. 4, Fig. 4 is a circuit diagram showing an example of the configuration of the table section in Fig. 3, Fig. 5 is an explanatory diagram showing the contents of the table in Fig. 4, and Fig. 6 shows an operation example of the device in Fig. 3. Signal timing charts, and FIGS. 7A and 7B are flowcharts showing an example of control operation by the sequence controller of FIG. 1 ... Sequence controller, 2 ... Temperature sensor, 4 ... A / D conversion unit, 8 ... Image processing unit, 11 ... Table unit, 14 ... D / A conversion unit, 17 ... Motor driver, 18 ...... Head scanning motor, 19 ...... Encoder part, 22 ...... Head driver, 23 ...... Recording head, 24 ...... Pulse motor driver, 25 ...... Pulse motor.

Claims (2)

[Claims] 1. An ink jet recording apparatus for recording an image using a recording head for ejecting an ink of an ejection amount according to a drive signal, and a detecting means for detecting an ambient temperature as temperature data, and the detecting means for detecting the ambient temperature. Defining means for defining the drive frequency of the recording head according to temperature data, generating means for generating density data for recording an image, temperature data detected by the detecting means and the generating means for generating the temperature data Density data is input, a conversion table that converts the density data into ejection amount data according to the temperature data and outputs the conversion table, and the drive signal that corresponds to the ejection amount data output from the conversion table Driving means for supplying the recording head with the driving frequency defined by the means and driving the recording head. An ink jet recording apparatus according to claim Rukoto. 2. The conversion table is a ROM in which the temperature data and the density data are input to an address input, and the discharge amount data is output from a data output. The inkjet recording device described.