JP7581010B2 - Recording device - Google Patents

Description

The present invention relates to a recording device.

For example, one type of recording device that ejects liquid (ink) to record an image on a recording medium is a thermal inkjet recording device equipped with a recording head for ejecting ink.

In a thermal inkjet recording device, a pulse voltage (hereafter referred to as a heat pulse) is applied to a heating resistor (hereafter referred to as an ejection heater), which is an energy generating element, and the ink in the ink chamber adjacent to the ejection heater is instantaneously boiled to generate bubbles. The expansion of the generated bubbles (film boiling) causes ink to be ejected from the ejection orifices and recorded on the recording medium. The recording head uses multiple ejection heaters arranged on a semiconductor substrate (hereafter referred to as a heater board), which is also formed with the drive circuits for each ejection heater.

In Patent Document 1, the number of simultaneous heating events is measured from the print data, the amount of voltage fluctuation is estimated, and the ejection heaters are driven with a heat pulse that takes the amount of voltage fluctuation into account.

On the other hand, it is known that ink can be indirectly heated by driving a heater (hereafter referred to as a sub-heater), which is a heating element provided separately from the ejection heater on the heater board, based on information from a temperature detection element (hereafter referred to as a diode temperature sensor).

Japanese Patent Application Publication No. 8-118645

However, if a configuration is adopted in which the power wiring for the sub-heater and the power wiring for the ejection heater are shared to prevent an increase in the board area, the following issues can be expected:

Control of the sub-heater is necessary even while ink is being ejected to record an image. Changes in the amount of current flowing through the sub-heater are reflected in changes in the voltage drop in the power supply wiring, and changes in the voltage applied to the ejection heater can cause changes in the ink ejection speed and ejection amount, which can affect image quality.

The present invention is a recording device that records using a printhead having a substrate on which a portion of the line supplying power to the recording elements and a portion of the line supplying power to the heating elements are common, the recording device comprising: a plurality of recording elements that are driven by applying a voltage and arranged in a plurality of groups for forming an image on a recording medium; and a plurality of heating elements that are arranged in each group for heating a substrate, the recording device further comprising: a plurality of temperature detection elements arranged in each group on the substrate ; an acquisition means for acquiring information regarding the number of recording elements and heating elements to which a voltage is simultaneously applied among the plurality of recording elements and the plurality of heating elements; and a control means for controlling the power applied to the recording elements based on the information, the control means changing settings regarding the time applied to the recording elements based on the average temperature or the minimum temperature of the plurality of temperature detection elements .

According to the present invention, it is possible to perform printing while suppressing the impact on image quality caused by driving the sub-heater of the print head.

1 is a perspective view of a recording section of an image recording apparatus to which the present invention can be applied; 1 is a block diagram of an image recording device to which the present invention can be applied; FIG. 2 is a detailed block diagram of a printhead drive signal generating circuit. FIG. 2 is a block diagram of a control circuit inside the printhead. 4 is a timing chart of signals for controlling the recording head. 4 is a flowchart showing a process in which a CPU controls a print head.

(First embodiment)
FIG. 1 is a perspective view showing the main part of an image recording apparatus equipped with a recording head for performing recording according to an ink jet method of this embodiment.

The carriage unit 2 carrying the recording head 1 is moved in the direction of the arrow M, and then the recording medium 3 is transported at a predetermined pitch in a transport direction (direction S in this case) that intersects with the direction of M, and this process is repeated. Ink is selectively ejected from the recording head 1 in synchronization with these movements, and is deposited on the recording medium 3 to form characters and images in this serial recording device. The carriage unit can move back and forth in the direction of the arrow M.

The carriage 2 is partially fixed to a timing belt 5 connected to a motor 4, and can move back and forth in the direction of arrow M in response to the rotation of the motor 4. The carriage 2 is also provided with an encoder 7 for reading position information from an encoder film 6. The motor 4 is controlled by the position information from the encoder 7, which in turn controls the direction, speed, and distance of movement of the carriage unit 2. It also has a recording head control unit that determines the timing of ink ejection from the recording head 1 based on the position information from the encoder 7.

Figure 2 is a block diagram showing the connections of the printhead control unit. The printhead control unit 8 is connected to the printhead 1 and encoder 7 in Figure 1, and is composed of a flexible flat cable (hereafter referred to as FFC) 9-a that supplies power to the printhead, and FFC 9-b through which printhead control signals pass.

The heater board, which is the substrate of the print head 1, is equipped with multiple ejection heaters and a heater drive circuit that generate thermal energy for ejecting ink, and multiple sub-heaters and a heater drive circuit that are heating elements for keeping the print head 1 warm. In addition, it is composed of a heater board on which multiple diode temperature sensors, which are temperature detection elements that detect the temperature of the print head 1, a control circuit, and an interface circuit are mounted, and an ink flow path forming member.

In this embodiment, an example will be described in which six nozzle rows, each with 640 ink ejection ports, are arranged on a heater board. This thermal energy causes the ink to instantly boil, creating bubbles that expand, causing ink to be ejected from the ejection ports and used to print on a print medium.

The printhead control unit 8 includes a CPU 80, a thermistor 81 that measures the temperature inside the printing device, a printhead drive signal generation circuit 82 that generates information and signals to drive the printhead 1, and a memory 83 that stores image data, etc.

Figure 3 is a block diagram explaining the details of the printhead drive signal generation circuit 82. It is provided with a diode temperature sensor selection register 821 for selecting one of the multiple diode temperature sensors on the heater board, and a sub-heater control register 822 for individually controlling the ON/OFF of the voltage application to the multiple sub-heaters.

The CPU 80 rewrites the diode temperature sensor number in the diode temperature sensor selection register 821 and reads out the temperature in order to switch the diode temperature sensor at regular intervals in order to raise the temperature of each part of the print head to the target value. It then determines whether or not to apply voltage to the sub-heater corresponding to the selected diode temperature sensor position, writes the result to the sub-heater control register 822, and performs heat retention control.

The recording head drive signal generating circuit 82 further includes an ejection data generating circuit 823 that reads image data from the memory 83 in synchronization with an ejection timing signal (hereinafter referred to as a latch signal or LT) coming from the encoder 7 and generates data to be recorded by the ejection heater. It also includes a heat pulse data generating circuit 824 for applying an optimal heat pulse to the ejection heater that performs the ejection.

The output data of the diode temperature sensor selection register 821, the sub-heater control register 822, the ejection data generation circuit 823, and the heat pulse data generation circuit 824 is input to the transfer data generation circuit 825. The image data and control code are then converted into serial data and transferred to the recording head 1.

Ejection of ink from each nozzle row of the print head 1 is controlled by capturing image data and control codes transmitted over data signal lines (Data1 to Data6) synchronized with a serial clock signal (CLK) using a latch signal (LT), which is an ink ejection timing signal.

The operation of the recording head 1 that receives the above signals is explained in detail using the block diagram of the control circuit inside the recording head in FIG. 4 and the timing chart of the control signals in FIG. 5.

In FIG. 4, inside the heater board of the print head 1, there are six common circuits 50-1, 50-2 to 50-6 that serve as the circuit block 50 that controls each nozzle row.

Each circuit block is connected to common control signals, such as a serial clock signal (CLK) and a latch signal (LT), independent control signals, such as data signals (Data1 to Data6), and common temperature status signals, such as diode temperature sensor signals (DiA, DiK).

The Data1 signal sent in synchronization with the serial clock signal (CLK) is stored in the data receiving circuit 101, which is composed of a 122-bit shift register. Then, the signal is held in data latch circuit 1, data latch circuit 2, data latch circuit 3, data latch circuit 4, and data latch circuit 5 at the timing of the latch signal (LT).

The 640 ejection heaters in each nozzle row are driven in 16 separate cycles, so data latch circuit 1 holds the 40-bit group data (GDT) to be recorded at one time, and data latch circuit 2 holds the 4-bit block data (BDT) that selects the block to be recorded this time from among the 16 blocks.

The position of the ejection heater to be printed is selected using the combined group data (GDT) and block data (BDT).

The data latch circuit 3 holds 32-bit heat pulse data (HPD) as information for generating a pulse waveform that controls the amount of power applied to the ejection heater with a pulse signal. The data latch circuit 4 holds 40-bit sub-heat enable data (SHE) as position information for the sub-heater that controls the heating of the heater board.

The data latch circuit 5 holds 6-bit diode temperature sensor selection data (DiSel) that indicates which one or none of the 40 temperature detection diode temperature sensors in the nozzle row should be selected.

The heat pulse generating circuit 104 is connected to the rear of the data latch circuit 3, and is internally composed of a counter, a comparison circuit, and a logic circuit.

The internal counter is reset to zero by the LT signal and counts up every time the CLK signal changes.

The counter value is connected to a circuit that compares it with the four 8-bit data inputs PT0, PT1, PT2, and PT3, and is equipped with a circuit that inverts and outputs a heat pulse signal (HP) when the values are equal.

The recording block selection circuit 106 is connected to the rear of the data latch circuit 2. This circuit inputs a 4-bit block signal and a heat pulse signal (HP) from the heat pulse generation circuit 104, and outputs the heat pulse signal input to one block heat pulse signal line selected by the 4 to 16 decoder.

The control signal that is output is a signal that bundles 16 block signals together and is output as 40 group heat pulses (G1HP to G40HP), and each signal line is connected to switching elements 108-1 to 108-40 that apply voltage to the ejection heaters.

The ejection heaters are also arranged in groups of 16 blocks, designated 109-1 to 109-40, and the image of the circuit diagram matches the image of the ejection heater arrangement. The ejection heaters are each connected to switching elements 108-1 to 108-40 and the power line (VH).

Diode temperature sensors 110-1 to 110-40 for measuring temperature are placed near each group of ejection heaters, and each diode temperature sensor is connected to a switching circuit 111.

The temperature sensor switching circuit 111 switches the connection based on the value of the diode temperature sensor selection data (DiSel). For example, when the diode temperature sensor selection data (DiSel) is 1, the following is done. The current of the constant current source (approximately 200 uA, not shown) connected to the terminal DiA of the heater board is switched to flow from the anode terminal of the diode temperature sensor 110-1 via the cathode terminal to the ground connected to the terminal DG of the heater board. This circuit is a circuit that flows current only to the selected diode temperature sensor. The voltage of the anode terminal of the selected diode temperature sensor 110-1 is switched to be output to the terminal MDiA of the heater board, and the voltage of the cathode terminal is switched to be output to the terminal MDiK of the heater board.

In addition, when the diode temperature sensor selection data (DiSel) is 0, switching is performed so that no current flows through any of the diode temperature sensors 110, and the MDiA terminal and MDiK terminal are switched to an electrically floating state.

The CPU 80 detects the voltage across both ends of the diode temperature sensor 110 (between MDiA and MDiK) and performs voltage-to-temperature conversion. Then, for locations where the temperature around the ejection heater group 111 has not yet reached the target temperature, data is transferred to apply voltage to each of the sub-heaters 513-1 to 513-40 located near each ejection heater group. The transferred data is held as 40-bit data (GSHE) in the data latch circuit 4.

Each bit of GSHE is input as a gate signal to switching elements 514-1 to 514-40, and the other terminal of the sub-heater 513 connected to the power supply line (VH) is connected to the drain terminal and the source terminal is connected to ground (GH). This controls the application of power to the sub-heater 513. In this way, the sub-heater and the ejection heater are connected to a common power supply line (VH).

Next, the relationship between the input and output signals is explained using the timing chart in Figure 5.

The signal is a latch signal (LT) from the top, and section A is an interval of approximately 3u seconds during which ink is ejected using 40 of the 640 nozzles in one row at a time. The next section X, from section B to section P, is a latch signal (LT) of 16 times, and an image is printed using all the nozzles in one row.

Next, group data (GDT) is transferred in the first 40-bit section 41 of the data signal (Data1) using the serial clock signal (CLK) and data signal (Data1). Block data (BDT) is transferred in the next 4-bit section 42, and heat pulse change point position data (PT0, PT1, PT2, PT3) is transferred in the next 32-bit section 43. Sub-heat enable data (SHE) is transferred in the next 40-bit section 44, and finally diode temperature sensor selection data (DiSel) is transferred in the last 6-bit section 44. The above is the input signal to the heater board 1, with one data signal assigned to each nozzle row and control data transferred individually, but the control signal for one nozzle row is explained in the timing chart of Figure 5.

The following signals are charts of the internal signals of heater board 1. PT0, PT1, PT2, and PT3 are the outputs of data latch circuit 3, which are the data sent to section 43 at the rising edge of the latch signal (LT) that has been latched.

The next heat pulse signal is generated by a circuit that compares the value of a counter that counts up with changes in the serial clock signal (CLK) in the heat pulse generating circuit 104 with the value of PT0, and rises if they match. It then compares the counter value with the value of PT1, and falls if they match, then compares the counter value with the value of PT2, and rises if they match, and then compares the counter value with the value of PT3, and falls if they match.

The next block data signal is the output of data latch circuit 2, which is the data sent to section 42 latched at the rising edge of the latch signal (LT).

The next block heat enable signals BHE0 to BHE15 are the outputs of the recording block selection circuit 106, which receives the previous heat pulse signal and the data block signal as input. It outputs a heat pulse to one of the 16 block heat enable signals selected by the data block signal.

The next heat data is the output of data latch circuit 1, which is the latched data sent to section 41 at the rising edge of the latch signal (LT).

The next sub-heat data is the output of data latch circuit 4, which is the data sent to section 44 latched at the rising edge of the latch signal (LT), and is the control signal 115-1 to 115-40 that controls the voltage application to the 40 sub-heaters 513-1 to 513-40.

The current flowing through each ejection heater is 34mA, and the current flowing through each sub-heater is 4.25mA. However, while the sub-heater is always ON during the LT interval (3uS), the ejection heater is controlled by HE. As a result, current only flows for about half the interval. Therefore, the average current flowing through each ejection heater is 17mA, and the current ratio of one ejection heater to one sub-heater is 4:1.

The value of the current flowing between LT is the sum of the number of bits whose heat data, which is the number of data discharged in the LT section, (minimum 0 to maximum 40) multiplied by a coefficient 1 (value 1 in this embodiment) and the number of bits whose sub-heat data is 1 (minimum 0 to maximum 40) multiplied by a coefficient 2 (value 0.25 in this embodiment). Therefore, the calculation result is a value between minimum 0 and maximum 50.

The block that implements this calculation is the calculation circuit 826 in Figure 3. The discharge heater current constant register 827 stores coefficient 1 of the current that flows through the discharge heater, and the sub-heater current constant register 828 stores coefficient 2 of the current that flows through the sub-heater.

The larger this value, the greater the current, and the voltage drop across the discharge heater is determined by the resistance value of 9-a of the FFC, the wiring resistance value of the heater board 1, and the current flowing there. Therefore, if the voltage drop is large with the pulse width of the block heat enable signal fixed, the amount of input energy decreases, making stable discharge impossible. In other words, the voltage drop is affected by the number of discharge heaters and sub-heaters to which voltage is applied simultaneously.

The conversion table for changing the pulse width of the block heat enable signal from the current that flows is shown in Table 1. The table is just an example, but it obtains the number of discharge data and the number of sub-heat data, and derives the change point position data of the block heat enable signal from the information on the current value calculated from them.

The operation of Table 1 is implemented as a circuit in the heat pulse data generation circuit 824 in Figure 3.

The printhead drive signal generation circuit 82 includes a circuit that calculates the number of ejection data and the number of heats of the sub-heater, and determines the values of PT0, PT1, PT2, and PT3 according to Table 1.

Control based on this table is applied to the timing chart in Figure 5. In section A, the number of heat data items is 40 (heat data = "FFFFFFFFFFFF"), the number of sub-heat data items is 10 (sub-heat data = "1111111111"), and the current calculation result is 42.5, so PT0 is 1, PT1 is 14, PT2 is 37, and PT3 is 120.

The values in this table are comparison values with the counter in the heat pulse generating circuit 104, and since a 50 MHz counter clock is used, there is 0.02 μsec per count, so the first voltage application pulse width is 13 clocks (0.26 μsec) from PT0 to PT1, the voltage application stop section is 23 clocks (0.46 μsec) from PT1 to PT2, and the second voltage application pulse width is 38 clocks (1.66 μsec) from PT2 to PT3.

Next, in section B, the number of heat data is 40, the number of sub-heats is 20, and the calculation result is 45, so PT0 is 1, PT1 is 15, PT2 is 36, and PT3 is 120.

Next, in section C, the number of heat data is 40, the number of sub-heats is 30, and the calculation result is 47.5, so PT0 is 1, PT1 is 15, PT2 is 35, and PT3 is 120.

Next, in section D, the number of heat data is 40, the number of sub-heats is 40, and the calculation result is 50, so PT0 is 1, PT1 is 15, PT2 is 33, and PT3 is 120.

Next, in section N, the number of heat data is 10, the number of sub-heats is 40, and the calculation result is 20, so PT0 is 1, PT1 is 12, PT2 is 44, and PT3 is 120.

Next, in section O, there are 10 heat data items and 30 sub-heat data items, and the calculation result is 17.5, so PT0 is 1, PT1 is 11, PT2 is 45, and PT3 is 120.

Next, in section P, there are 10 heat data items and 20 sub-heat data items, and the calculation result is 15, so PT0 is 1, PT1 is 11, PT2 is 46, and PT3 is 120.

The table reference circuit of the heat pulse data generation circuit 824 is rewritten by the CPU if the average temperature or minimum temperature of the heater board becomes higher than the target insulation temperature.

Specifically, by setting the value to shorten the time that the heat pulse is on, excess power is not applied to the discharge heater.

Figure 6 is a flowchart showing the sequence for rewriting the diode selection register, the sub-heater control register, and the table reference value of the heat pulse data generation circuit 824 by the CPU.

The sequence in this flowchart is a routine within an interrupt process that is executed at a set fixed time interval (for example, 1 ms).

First, in step S1, the value of the diode temperature sensor selected is read and temperature conversion is performed.

In step S2, the temperature is compared with the target temperature (e.g., 40°C), and if it has not been reached, proceed to step S3, where a setting to turn on the sub-heater corresponding to the currently selected diode temperature sensor position is written to the sub-heater control register. If it is equal to or higher than the target temperature, proceed to step S4, where a setting to turn off the sub-heater corresponding to the currently selected diode temperature sensor position is written to the sub-heater control register.

In step S5, the number of the diode temperature sensor to be read next is written to the diode selection register.

In step S6, the values of the 40 diode temperature sensors are temporarily stored and the lowest temperature is calculated from them.

In step S7, the minimum temperature is compared with the target temperature, and if it has not been reached, proceed to step S8 and write table setting 1 to the table reference register of the heat pulse data generation circuit 824. If it is equal to or higher than the target temperature, proceed to step S9 and write table setting 2 to the table reference register of the heat pulse data generation circuit 824.

After the above processing, the interrupt sequence will be exited and the program will wait for the next time interrupt.

Other Embodiments
In the above-described embodiment, an example has been given of a printing device that generates an image by serially scanning a print head that ejects ink from an ejection port to print on a print medium, but the embodiment may also be applied to a full-line type print head in which multiple printing elements are arranged over an area greater than the printing width of the print medium.

It may also be applied to a recording device that selectively heats the heating elements to cause the ink on an ink ribbon to record on a recording medium, or to a recording device that records on thermal paper that changes color when heated.

Claims (10)

A recording device that performs recording using a recording head having a substrate including a plurality of recording elements, which are divided into a plurality of groups and are driven by applying a voltage to form an image on a recording medium, and a plurality of heating elements, which are provided for each group and are used to heat a substrate, and in which a portion of a line for supplying power to the plurality of recording elements and a portion of a line for supplying power to the plurality of heating elements are common,
A plurality of temperature detection elements provided on the substrate for each group;
An acquisition means for acquiring information on the number of recording elements and heating elements to which a voltage is simultaneously applied among the plurality of recording elements and the plurality of heating elements;
and a control unit for controlling the power applied to the recording element based on the information ,
The recording apparatus according to claim 1, wherein the control means changes a setting relating to a time for which voltage is applied to the recording element based on an average temperature or a minimum temperature of the plurality of temperature detection elements and a target temperature . The recording device according to claim 1, characterized in that the heating element is controlled based on the temperature detected by the temperature detection element. The recording device according to claim 1, characterized in that the acquisition means includes an arithmetic circuit that adds values obtained by multiplying the number of recording elements to which voltage is applied simultaneously and the number of heating elements to which voltage is applied at that time by a coefficient. The recording device according to any one of claims 1 to 3, characterized in that the control means controls the voltage applied to the recording element based on the information. The recording device according to claim 3, characterized in that the control means controls the time applied to the recording element based on the information. A recording device according to any one of claims 1 to 5, characterized in that the recording head ejects ink from the ejection ports by expanding bubbles generated by instantaneously boiling ink in contact with the heating elements, which are the recording elements, to record on the recording medium. A recording device according to any one of claims 1 to 5, characterized in that the recording head selectively heats the heating elements, which are the recording elements, to cause the ink of the ink ribbon to record on the recording medium. A recording device according to any one of claims 1 to 5, characterized in that the recording head selectively heats the heating elements, which are the recording elements, to record on thermal paper that changes color when heat is applied. A recording device according to any one of claims 1 to 8, characterized in that it has a carriage that carries the recording head and moves back and forth in a direction intersecting the transport direction of the recording medium, and a means for detecting position information of the carriage, and determines the timing of ink ejection from the position information. A recording device according to any one of claims 1 to 8, characterized in that the recording head is a full-line type recording head in which the multiple recording elements are arranged over a width greater than or equal to the recording width of the recording medium, and an image is formed on the recording medium by recording using the multiple recording elements and transporting the recording medium.

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