JP4202627B2 - Inkjet printer head driver IC temperature detection device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a temperature detection technique for a head driver IC of an ink jet printer that detects that a head driver IC has reached a predetermined temperature or higher in a head of the ink jet printer.
[0002]
[Prior art]
2. Description of the Related Art Inkjet color printers that eject several colors of ink from a recording head have been widely used as computer output devices, and are widely used to print images processed by computers and the like with multi-color and multi-tone. It has been. For example, in an ink jet printer using a piezoelectric element as a drive element for ejecting ink, each piezoelectric element is selectively driven by driving a plurality of piezoelectric elements respectively corresponding to a plurality of nozzles of a print head. The ink droplets are ejected from the nozzles based on the dynamic pressure of the element, and the ink droplets are adhered to the printing paper, whereby dots are formed on the printing paper and printing is performed.
[0003]
Here, each piezoelectric element is provided corresponding to a nozzle for ejecting ink droplets, and is driven by a drive signal supplied from at least one head driver IC mounted in the print head. Is to be discharged.
[0004]
By the way, each head driver IC generates heat by driving, and the heat is radiated by ejected ink droplets. However, due to continuous driving or the like, sufficient heat radiation may not be performed by ink droplets. is there. If printing is continued in such a state, the temperature of each head driver IC may further increase, and each head driver IC may be thermally destroyed.
[0005]
Therefore, in the conventional ink jet printer, focusing on the fact that the anode voltage of the diode provided in each head driver IC varies depending on the ambient temperature, as shown in FIG. The anode voltage of the diode in each of the head driver ICs 1a, 1b, 1c, and 1d is output to the control unit 4 configured by, for example, an ASIC in the printer main body 3 via the cables 2a, 2b, 2c, and 2d, respectively.
[0006]
Then, it is converted into a digital value by the AD converter 5 in the control unit 4, and the anode voltage of the diode of each head driver IC is detected. Based on these anode voltages, each head driver IC 1a, 1b, 1c, 1d is detected. The temperature is detected. Here, when the temperature of any one of the head driver ICs 1a, 1b, 1c, or 1d becomes equal to or higher than a predetermined temperature, the control unit 4 temporarily stops the printing operation, and the head driver ICs 1a, 1b, 1c, The temperature of 1d is lowered.
[0007]
[Problems to be solved by the invention]
However, in such a temperature detection method for the head driver ICs 1a, 1b, 1c, and 1d, the cables 2a, 2b, 2c, and 2d from the head driver ICs 1a, 1b, 1c, and 1d to the control unit 4 are relatively long. At the same time, analog signals pass through these cables 2a, 2b, 2c, and 2d, so that they are susceptible to noise and the detection accuracy is lowered.
[0008]
Further, since the anode voltage from each head driver IC 1a, 1b, 1c, 1d is converted into a digital signal by the AD converter in the control unit 4, the detection time becomes long and the AD in the control unit 4 becomes AD. Converter 5 is required. Therefore, for example, the control unit 4 composed of ASIC is increased in size.
[0009]
Further, signals are output from the head driver ICs 1a, 1b, 1c, and 1d to the control unit 4 via the cables 2a, 2b, 2c, and 2d, respectively, and also to the AD converter 5 in the control unit 4 of the printer body 3. Signals are input from the head driver ICs 1a, 1b, 1c, and 1d via the cables 2a, 2b, 2c, and 2d, respectively. For this reason, the number of cables 2a, 2b, 2c, and 2d is required to be the same as the number of head driver ICs, the number of input pins of the control unit 4 is increased, and the cost is increased. This is contrary to the trend of reducing the number of pins.
[0010]
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a head driver IC temperature detection device for an ink jet printer that has a simple configuration and is not affected by noise and has a simplified configuration of a control unit.
[0011]
[Means for Solving the Problems]
In order to solve the above-described problems, in the present invention, the anode voltage of the diode of each head driver IC is compared with a reference voltage in the head driver IC, and when the voltage drops below a predetermined voltage, a digital signal is sent to the control unit. I did it.
[0012]
That is, in the head driver IC temperature detecting device for an ink jet printer according to claim 1, the head driver IC is controlled by the control unit of the printer body based on the anode voltage of the diode provided in the head driver IC of the ink jet printer. A head driver IC temperature detection device for an ink jet printer that detects the level of a temperature relative to a predetermined temperature, a temperature setting unit that sets a digital reference value corresponding to a reference temperature for temperature detection, and a temperature setting unit The DA converter that converts the digital reference value into the analog reference value, the anode voltage of the diode, and the analog reference value from the DA converter are compared, and the level of the anode voltage of the diode with respect to the analog reference value is Output as a digital signal to the controller Characterized in that the comparator, the contains in each head driver IC.
[0013]
According to this configuration, after the ink jet printer is turned on, the digital reference value is set by the temperature setting unit, so that the DA converter converts the digital reference value into an analog reference value in the head driver IC. , Input to one input terminal of the comparator.
[0014]
In this state, the comparator compares the anode voltage of the diode provided in the head driver IC with the analog reference value from the DA converter, and the comparator determines that the diode anode voltage is higher than the analog reference value. The digital signal is made inactive, and the digital signal is made active when the anode voltage of the diode becomes lower than the analog reference value.
[0015]
During the printing operation, the control unit of the printer body can detect that each head driver IC has become higher than a predetermined temperature by monitoring a digital signal from a comparator provided in each head driver IC. . Furthermore, when the control unit of the printer main body detects that each head driver IC has become higher than the predetermined temperature as described above, the control unit temporarily stops the printing operation or forcibly terminates the printing operation in some cases, It is possible to prevent thermal destruction due to temperature rise of the head driver IC.
[0016]
Therefore, since the temperature detection signal output from each head driver IC to the control unit of the printer body is a digital signal, even if the cable from the head driver IC to the control unit is long, it is affected by noise. It is difficult to improve the detection accuracy. In addition, since an AD converter is not required in the control unit of the printer main body, the detection time is short, and the temperature of each head driver IC can be reliably detected even in a short time between printing operations.
[0017]
The head driver IC temperature detection device according to claim 2 is characterized in that the digital signals output from the comparators of the head driver ICs are output to the control unit of the printer main body independently of each other. According to this configuration, since the digital signals from the comparators of the head driver ICs are independently output to the control unit of the printer main body, one cable from each head driver IC to the control unit of the printer main body. Even if a fault such as a disconnection occurs in the part, it is impossible to detect only the temperature of the head driver IC that uses the faulty cable, but it is possible to detect the temperature of the head driver IC that uses other cables. is there.
[0018]
4. The head driver IC temperature detecting device according to claim 3, further comprising a FET for each head driver IC, wherein the digital signal output from each comparator is input to the gate and the output is an open drain. And According to this configuration, the FET is turned on / off by the digital signal from each comparator, and the output of the open drain is input to the control unit of the printer main body.
[0019]
5. The head driver IC temperature detecting device according to claim 4, wherein the digital signals output from the open drains of the FETs of the head driver ICs are output to the control unit of the printer body independently of each other. Features. According to this configuration, since the digital signals from the FETs of the head driver ICs are independently output to the control unit of the printer main body, one cable from each head driver IC to the control unit of the printer main body. Even if a fault such as a disconnection occurs in the part, it is impossible to detect only the temperature of the head driver IC that uses the faulty cable, but it is possible to detect the temperature of the head driver IC that uses other cables. is there.
[0020]
6. The head driver IC temperature detecting device according to claim 5, wherein digital signals output from the open drains of the FETs of the head driver ICs are wired and connected to each other, and the printer body is controlled by a single cable. Output to the unit. According to this configuration, since the digital signal from the FET of each head driver IC is output by the open drain, even if the output of the open drain of each FET is wired and connected to each other, the digital output signal of each FET is output. The signals are output to the control unit of the printer main body by one cable without interfering with each other.
[0021]
Therefore, only one cable for temperature detection from a plurality of head driver ICs is required, the cost is reduced, and the input pins of the control unit of the printer main body are reduced, and the pins of the ASIC constituting the control unit It can contribute to the reduction of.
[0022]
7. The head driver IC temperature detection device for an ink jet printer according to claim 6, further comprising a bipolar transistor for each head driver IC, wherein a digital signal output from each comparator is input to a base and an output is an open collector. It is characterized by. According to this configuration, the bipolar transistor is turned on / off by the digital signal from each comparator, and the output of the open collector is input to the control unit of the printer main body.
[0023]
8. A head driver IC temperature detecting device for an ink jet printer according to claim 7, wherein digital signals output from the open collector of the bipolar transistor of each head driver IC are output to the control unit of the printer body independently of each other. It is characterized by being. According to this configuration, since the digital signals from the bipolar transistors of each head driver IC are independently output to the control unit of the printer main body, the cable from each head driver IC to the control unit of the printer main body. Even if a failure such as disconnection occurs in a part of the cable, only the temperature detection of the head driver IC using the cable in which the failure has occurred becomes impossible. However, the temperature detection of the head driver IC using another cable is not possible. Is possible.
[0024]
9. A head driver IC temperature detecting device for an ink jet printer according to claim 8, wherein the digital signals output from the open collectors of the bipolar transistors of each of the head driver ICs are wired and connected to each other, so that one cable is connected. Is output to the control unit of the printer main body. According to this configuration, since the digital signal from the bipolar transistor of each head driver IC is output from the open collector, even if the outputs of the open collector of each bipolar transistor are wired and connected to each other, The digital output signals of the transistors are output to the control unit of the printer body through a single cable without interfering with each other.
[0025]
Therefore, only one cable for temperature detection from a plurality of head driver ICs is required, the cost is reduced, and the input pins of the control unit of the printer main body are reduced, and the pins of the ASIC constituting the control unit It can contribute to the reduction of.
The head driver IC temperature detection device according to claim 1, wherein the temperature setting unit sets a digital reference value corresponding to an upper limit temperature set slightly lower than a guaranteed temperature of the head driver IC. .
Further, in the head driver IC temperature detecting device according to the claim, the temperature setting unit is configured such that the diode indicating the anode voltage measured at room temperature is an upper limit temperature set slightly lower than the guaranteed temperature of the head driver IC. A digital reference value corresponding to an upper limit anode voltage that may be output is set.
[0026]
In the head driver IC temperature detection device according to the claims, the temperature setting unit of each head driver IC is independently set corresponding to individual conditions such as heat generation conditions and heat dissipation conditions of the head driver IC. It is characterized by. According to this configuration, the digital reference value of the temperature setting unit can be set for each head driver IC in accordance with the individual conditions of each head driver IC and the variation in characteristics of the diodes provided in the head driver IC. it can.
[0027]
6. The head driver IC temperature detecting device for an ink jet printer according to claim 1, wherein the temperature setting unit of each head driver IC includes digital data storage means having a predetermined number of bits, and the digital reference is within the range of the number of bits. It is characterized in that the value can be set freely. According to this configuration, the printer designer can freely set the digital reference value within the range of the number of bits while referring to individual conditions and the like found by prior measurement for each head driver IC.
[0028]
DETAILED DESCRIPTION OF THE INVENTION
A head driver IC provided with a head driver IC temperature detection device according to an embodiment of the present invention will be described with reference to the drawings. The embodiments described below are preferable specific examples of the present invention, and thus various technically preferable limitations are given. However, the scope of the present invention particularly limits the present invention in the following description. As long as there is no description of the effect, it is not restricted to these aspects.
[0029]
FIG. 1 shows the configuration of a first embodiment of a head driver IC temperature detection device according to the present invention. The head driver IC temperature detection device 10 includes an anode voltage of a diode provided in each of a plurality (four in the illustrated example) of head driver ICs 11a, 11b, 11c, and 11d provided in a printer head of an ink jet printer. Is compared with a reference voltage, and the comparison result is digitized and output to the control unit 14 of the printer main body 13 via a single cable 12.
[0030]
Here, each of the head driver ICs 11a, 11b, 11c, and 11d has the same configuration, and is configured as a head driver IC for driving a head nozzle portion corresponding to each color of yellow, magenta, cyan, and black, for example. . Therefore, the configuration of the head driver IC 11a will be described below.
[0031]
FIG. 2 is a block diagram showing a configuration of a portion related to temperature detection of the head driver IC 11a. In FIG. 2, the head driver IC 11 a includes a temperature setting unit 21, a DA converter 22, a diode 23, a comparator 24, and an FET 25.
[0032]
The temperature setting unit 21 includes, for example, a register, and sets a digital reference value Vd corresponding to the reference temperature Tref for temperature detection. The DA converter 22 converts the digital reference value Vd from the temperature setting unit 21 into an analog reference value Va. The diode 23 is provided in the head driver IC 11a, and the anode side is connected to the constant voltage power supply Vdd1 via the resistor R1, and the cathode side is connected to the ground.
[0033]
In the case shown in the figure, the diode 23 is configured by connecting a plurality of (for example, four) diodes in series with each other. Here, as will be described later, the anode voltage of the diode 23 has a characteristic of decreasing as the temperature of the head driver IC increases.
[0034]
The comparator 24 receives the anode voltage V of the diode 23 at the inverting input terminal and the analog reference value Va from the DA converter 22 at the non-inverting input terminal, so that these anode voltage V and analog The reference value Va is compared. When the anode voltage V of the diode 23 is higher than the analog reference value Va, the comparator 24 outputs an L level digital signal and the anode voltage V of the diode 23 is lower than the analog reference value Va. At this time, an H level digital signal is output.
[0035]
The FET 25 has a gate connected to the output terminal of the comparator 24, a source connected to the ground, a drain connected to the constant voltage power supply Vdd2 via the resistor R2, and a digital signal output from the drain as an open drain. It has become so. Thereby, when the output signal from the comparator 24 is at L level, the FET 25 is off and its drain is held at the voltage of the constant voltage power supply Vdd2, but the output signal from the comparator 24 is at H level. Turns on and its drain is pulled to ground potential.
[0036]
FIG. 3 shows a specific configuration example of the head driver IC 11a. 3, the head driver IC 11a has the same configuration as the head driver IC 11a of FIG. 2, and includes a plurality of flip-flop circuits 26 and a resistor group 27 instead of the voltage setting unit 21 and the DA converter 22. ing.
[0037]
In the illustrated case, the flip-flop circuit 26 is composed of eight flip-flop circuits 26a. In each of these flip-flop circuits 26a, a latch signal is input to the clock terminal CLK, a setting signal is input to the D terminal, and a reference voltage Vref is input to the Vref terminal.
[0038]
When H is set in the flip-flop, the output becomes Vref, and when L is set, it becomes GND. The head driver IC sends data for nozzle selection, for example, serially, but this data may be used for the inputs D0 to D7 of the D terminal. In this case, serial data is input to the shift register. For example, the last data sent is D0 to D7, and the latch signal LAT dedicated to the temperature detection circuit is used to store the data in the flip-flop.
[0039]
The resistor group 27 includes seven resistors 1R and one resistor 2R connected in series between the non-inverting input terminal + of the comparator 24 and the ground, the anode side of each resistor 1R, and each flip-flop circuit 26a. And 8 resistors 2R respectively connected to the output terminal Q.
[0040]
As a result, the analog reference value Va input to the non-inverting input terminal + of the comparator 24 is reduced from the voltage 0 to a voltage slightly lower than Vref by the combination of the setting signals input to the D terminal of each flip-flop circuit 26a. 256 levels can be set.
[0041]
Here, the analog reference value Va input to the non-inverting input terminal + of the comparator 24 is a guaranteed temperature T1 of the head driver ICs 11a to 11d in consideration of characteristic variations of the diodes 23 incorporated in the head driver ICs 11a to 11d. The head driver ICs 11a to 11d are set before shipment so that the voltage corresponds to the upper limit temperature T2 set slightly lower than the upper limit temperature T2.
[0042]
The head driver IC temperature detection device 10 according to the embodiment of the present invention is configured as described above and operates as follows. First, the setting of the analog reference value Va will be described.
[0043]
As shown in FIG. 4, the diode 23 incorporated in the head driver ICs 11a to 11d has a temperature-voltage characteristic width as indicated by the straight line P and the straight line Q due to individual differences in individual characteristic variations. Variations in this characteristic include variation in inclination and variation in offset, but the adverse effect due to variation in inclination is great. That is, the offset variation can be corrected by measuring the voltage at a certain temperature at the time of factory shipment.
[0044]
First, consider the case where the initial measurement is not performed. Each diode 23 has a characteristic between the straight line P and the straight line Q. As a result, the voltage Vb giving the intersection A between the straight line P indicating the upper limit of the characteristic and the slightly lower upper limit temperature T2 with a margin with respect to the guaranteed temperature T1 of the head driver IC is the anode of the diode when the initial measurement is not performed. As a voltage threshold value, an intersection B (temperature T3, voltage Vb) with the threshold value straight line Q is obtained.
[0045]
In this way, when the initial measurement of the diode 23 is not performed, the anode voltage threshold Vb set in consideration of the characteristic variation of each diode 23 is a temperature range between points A and B, that is, T3 to T3. It will have a temperature range of T2.
[0046]
For this reason, depending on the characteristic variation of the diode 23, an increase in the temperature of the head driver IC is detected even at a temperature T3 that is significantly lower than the upper limit temperature T2.
[0047]
On the other hand, the anode voltage of the diode 23 is actually measured at room temperature T0, and this anode voltage is measured voltage V0, and a point C is plotted on the temperature-voltage graph as shown in FIG. Then, a straight line R parallel to a gradual straight line P (the sign of the inclination is negative), which is the upper limit of the variation in inclination, is drawn from this point C to obtain an intersection D (temperature T2, voltage Vc) with the upper limit temperature T2. .
[0048]
At this time, a straight line S parallel to the steep straight line Q which is the lower limit of the variation in inclination is drawn from the point C to obtain an intersection E (temperature T4, voltage Vc) with the voltage Vc. In this case, when an initial measurement of the diode 23 is performed, the threshold value of the anode voltage at the intersection D is a temperature range between the points D and E, that is, a relatively narrow temperature range of T4 to T2, and the temperature detection accuracy is high. Will improve.
[0049]
When the threshold voltage Vc (= analog reference value Va) of the anode voltage of the diode 23 is determined in this way, a digital reference value Vd (for example, represented by [01001100]) corresponding to the analog reference value Va is obtained. Therefore, the digital reference value Vd is input to the temperature setting unit 21. Thereby, the accuracy of temperature detection is improved by absorbing the characteristic variation of the individual diodes 23.
[0050]
Next, the temperature detection operation of the head driver IC temperature detection device 10 will be described. When the power of the ink jet printer is turned on, in each head driver IC 11a to 11d as an initialization operation, each voltage setting unit 21 is initially measured and determined in advance in a factory or the like and stored in a nonvolatile RAM or the like. A reference value Vd is set, and the DA converter 22 converts this digital reference value Vd into an analog reference value Va and inputs it to the non-inverting input terminal of the comparator 24.
[0051]
On the other hand, an anode voltage V corresponding to the temperature of the head driver ICs 11a to 11d is generated in the diode 23. Thereby, the comparator 24 compares the analog reference value Va with the anode voltage V, and outputs an L level signal when the anode voltage V is higher than the analog reference value Va, so that the FET 25 remains off. The voltage from the constant voltage power supply Vdd2 is applied to the output terminal 28, and an H level signal is output from the output terminal 28.
[0052]
On the other hand, when the temperature of the head driver ICs 11a to 11d rises with the printing operation and the anode voltage V of the diode 23 falls and becomes lower than the analog reference value Va, the comparator 24 outputs an H level signal. Since the output is performed and the FET 25 is turned on, the output terminal 28 is grounded, so that an L level signal is output from the output terminal 28.
[0053]
Here, as shown in FIG. 2, since the outputs of the output terminals 28 of the FETs 25 are open drains, the head driver ICs 11a to 11d interfere with each other even if the output terminals 28 are AND-connected to each other. If any one of the FETs 25 of the head driver ICs 11a to 11d is turned on, the signal is output to the ground via the FET 25, so that the signal from the output terminal 28 is an L level digital signal. .
[0054]
In this way, when the temperature of any of the head driver ICs 11a to 11d may exceed the upper limit temperature T2 (which may be lower than T2 due to variation in inclination, but higher than T4), the output of the comparator 24 Becomes the H level, the digital signal input from the open drain of the FET 25 to the control unit 14 changes from the H level to the L level, and the control unit 14 detects that the temperature of any of the head driver ICs exceeds the upper limit temperature T2. It can be detected that there is a possibility.
[0055]
In this case, since the digital signals are input to the control unit 14 from the head driver ICs 11a to 1d via the single cable 12, it is not necessary to AD-convert the anode voltage from the diode 23 as in the prior art. Therefore, it is not necessary to provide an AD converter, and it is not necessary to provide a cable and an input pin for each head driver IC 11a to 11d. Therefore, the control unit 14 can be made small and configured with a small number of input pins, and the temperature detection cable can be a single core, so that the cost can be reduced.
[0056]
The control unit 14 operates as shown in FIG. 5, for example, in response to the input of a digital signal for temperature detection from the head driver IC. In the flowchart of FIG. 5, first, in step ST1, the control unit 14 outputs a temperature detection command to each head driver IC 11a. The output of the temperature detection command is performed, for example, when printing for each page or each line is completed.
[0057]
In step ST2, when the digital signal XHOT input from the head driver ICs 11a to 11d via the cable 12 is at the H level, the control unit 14 determines that each of the head driver ICs 11a to 11d has an upper limit temperature T2. Therefore, in step ST3, the count CNT = 0 (CNT is a variable indicating the number of times XHOT has been continuously L), the printing operation is continued in step ST4, and then the process returns to step ST1.
[0058]
If the digital signal XHOT is at the L level in step ST2, the control unit 14 checks the count CNT in step ST5. If CNT ≦ 5, the control unit 14 counts the CNT in step ST6. = CNT + 1, and after stopping the printing operation for a predetermined pause time in step ST7, the printing operation is resumed in step ST8 and the process returns to step ST1. Note that the pause time in step ST7 may be constant, or may be set to increase as the value of CNT increases.
[0059]
On the other hand, when CNT> 5 in step ST5, the control unit 14 determines that a fatal error has occurred in step ST9, and performs a shear error process including forced printing termination in step ST10. Then, the operation of the ink jet printer is stopped and the process is terminated.
[0060]
FIG. 6 shows a second embodiment of the head driver IC temperature detection device according to the present invention. In FIG. 6, a head driver IC temperature detection device 30 has the same configuration as the head driver IC temperature detection device 10 of FIG. 1, but differs only in the following points.
[0061]
In other words, in the head driver IC temperature detection device 30, the temperature detection output signals of the head driver ICs 11a to 11d are sent to the control unit 14 of the printer main body 13 via the cables 12a, 12b, 12c, and 12d, which are independent of each other. To be input.
[0062]
According to the head driver IC temperature detection device 30 having such a configuration, the head driver IC temperature detection device 10 operates in the same manner as the head driver IC temperature detection device 10 in FIG. 1, and the cables from the head driver ICs 11a to 11d are connected to the individual head drivers 11a to 11d. For example, when a failure such as disconnection occurs in any of the cables 12a, 12b, 12c, or 12d, only the temperature detection of the head driver IC that uses the failed cable cannot be performed. It is possible to detect the temperature of the head driver IC using other cables.
[0063]
FIG. 7 shows a third embodiment of a head driver IC temperature detection device according to the present invention. In FIG. 7, the head driver IC temperature detection device 40 has the same configuration as the head driver IC temperature detection device 10 of FIG. 6, but differs only in the following points.
[0064]
That is, in the head driver IC temperature detection device 40, the output of the comparator 24 of each head driver IC 11a to 11d is not directly passed through the FET 25 but directly through the cables 12a, 12b, 12c, and 12d that are independent of each other. It is input to the control unit 14 of the main body 13.
[0065]
According to the head driver IC temperature detection device 30 configured as described above, the operation is the same as that of the head driver IC temperature detection device 30 of FIG. 6, and the FET 25 is omitted, so that the number of parts can be reduced and the cost can be reduced. It can be reduced.
[0066]
In the embodiment described above, each of the head driver IC temperature detection devices 10 and 30 includes four head driver ICs 11a to 11d. However, the present invention is not limited to this. For example, the head driver IC temperature detection devices 10 and 30 have seven color drivers including seven head driver ICs. It is obvious that the present invention can be applied to an ink jet printer or a monochrome ink jet printer having only one head driver IC.
[0067]
In the above-described embodiment, the characteristic variation of the diode 23 is taken into account when setting the analog reference value Va. However, the present invention is not limited to this, and it depends on the arrangement of the individual head driver ICs 11a to 11d. Individual conditions such as heat generation conditions and heat dissipation conditions may also be considered.
[0068]
For example, when a plurality of head driver ICs are arranged side by side, the head driver ICs on both sides have relatively good heat dissipation conditions, but the inner head driver ICs have relatively poor heat dissipation conditions. In such a case, the analog reference value Va relating to the inner head driver IC may be set lower.
[0069]
In this way, the analog reference value Va of each head driver IC may be set so that each head driver IC does not exceed the upper limit temperature T2 during the printing operation until the next temperature detection.
[0070]
【The invention's effect】
As described above, according to the present invention, since the temperature detection signal output from each head driver IC to the control unit of the printer body is a digital signal, the cable from the head driver IC to the control unit. Even if it is long, it is difficult to be influenced by noise, and the detection accuracy is improved.
[0071]
In addition, since an AD converter is not required in the control unit of the printer main body, the detection time is short, and the temperature of each head driver IC can be reliably detected even in a short time between printing operations.
[0072]
Further, when the FET is turned on / off by the digital signal from each comparator, and the output of the open drain is connected to each other and output to the control unit of the printer main body by one cable, Since the digital signal from the FET of the head driver IC is output by the open drain, even if the output of the open drain of each FET is AND-connected to each other, the digital output signals of the FETs do not interfere with each other. The data is output to the control unit of the printer body through a cable.
[0073]
Accordingly, since only one cable for detecting the temperature from the plurality of head driver ICs is required, the cost is reduced and the number of input pins of the control unit of the printer main body can be reduced, and the ASIC constituting the control unit can be reduced. This can contribute to reduction of pins.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a first embodiment of a head driver IC temperature detection device according to the present invention.
2 is a block diagram showing a main part of each head driver IC in the head driver IC temperature detection device of FIG. 1; FIG.
3 is a diagram illustrating a specific configuration example of a main part of each head driver IC in FIG. 2;
4 is a graph showing an analog reference value setting procedure in the head driver IC temperature detection device of FIG. 1; FIG.
FIG. 5 is a flowchart showing an example of control by a control unit in the head driver IC temperature detection device of FIG. 1;
FIG. 6 is a block diagram showing a configuration of a second embodiment of a head driver IC temperature detection device according to the present invention.
FIG. 7 is a block diagram showing a main part of each head driver IC in a third embodiment of the head driver IC temperature detecting device according to the present invention.
FIG. 8 is a block diagram showing a configuration of an example of a conventional head driver IC temperature detection device.
[Explanation of symbols]
10, 30, 40 Head driver IC temperature detection device
11a, 11b, 11c, 11d Head driver IC
12, 12a, 12b, 12c, 12d cable
13 Printer body
14 Control unit
21 Temperature setting part
22 DA converter
23 Diode
24 Comparator
25 FET
26 Flip-flop circuit
27 resistance group
28 Output terminal

Claims (11)

Ink jet printer head driver IC temperature detection based on the anode voltage of the diode provided in the head driver IC of the ink jet printer, and detecting the level of the head driver IC temperature with respect to a predetermined temperature at the control unit of the printer body. A device,
A temperature setting unit for setting a digital reference value corresponding to a reference temperature for temperature detection;
A DA converter that converts a digital reference value from the temperature setting unit into an analog reference value;
A comparator that compares the anode voltage of the diode with the analog reference value from the DA converter, and outputs the level of the anode voltage of the diode with respect to the analog reference value as a digital signal to the control unit of the printer body;
In each head driver IC,
The head driver IC temperature of the ink jet printer, wherein the temperature setting unit of each head driver IC is independently set corresponding to individual conditions such as heat generation conditions and heat dissipation conditions of the head driver IC. Detection device.   2. The head driver IC temperature of an ink jet printer according to claim 1, wherein digital signals output from the comparators of the head driver ICs are output to the control unit of the printer main body independently of each other. Detection device.   3. The ink jet printer according to claim 1, further comprising a FET for each head driver IC, wherein each of the head driver ICs is provided with an FET whose digital signal output from each comparator is input to a gate and whose output is an open drain. Head driver IC temperature detection device.   4. The ink jet printer according to claim 3, wherein the digital signals output from the open drain of the FET of each head driver IC are output to the control unit of the printer main body independently of each other. Head driver IC temperature detection device.   The digital signals output from the open drains of the FETs of the head driver ICs are wired and connected to each other, and are output to the control unit of the printer main body through a single cable. Item 4. A head driver IC temperature detection device for an inkjet printer according to Item 3.   The ink jet printer according to claim 1 or 2, further comprising a bipolar transistor for each head driver IC, wherein a digital signal output from each comparator is input to a base and an output is an open collector. -Type printer head driver IC temperature detection device.   7. The ink jet type according to claim 6, wherein the digital signals output from the open collector of the bipolar transistor of each head driver IC are output to the control unit of the printer main body independently of each other. Printer head driver IC temperature detection device.   The digital signals output from the open collectors of the bipolar transistors of the head driver ICs are wired and connected to each other, and are output to the control unit of the printer main body through a single cable. A head driver IC temperature detection device for an ink jet printer according to claim 6.   9. The ink jet printer head according to claim 1, wherein the temperature setting unit sets a digital reference value corresponding to an upper limit temperature set slightly lower than a guaranteed temperature of the head driver IC. Driver IC temperature detection device.   The temperature setting unit includes a digital reference corresponding to an upper limit anode voltage that may be output at an upper limit temperature set slightly lower than a guaranteed temperature of the head driver IC by a diode indicating an anode voltage measured at room temperature. 9. A head driver IC temperature detecting device for an ink jet printer according to claim 1, wherein a value is set.   2. The temperature setting unit of each head driver IC includes digital data storage means having a predetermined number of bits, and the digital reference value can be freely set within the range of the number of bits. 11. A head driver IC temperature detection device for an ink jet printer according to any one of items 10 to 10.

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