JP2004108987A - Head driver ic temperature detection device of ink jet printer, and anode voltage specification method of its diode - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To specify an anode voltage of a diode in a head driver IC temperature detection circuit utilizing temperature dependence of the anode voltage of the diode. <P>SOLUTION: In the temperature detection circuit of the head driver IC for comparing the anode voltage of the diode in the head driver IC with an output voltage of a DA converter, for example, in the case where digital temperature reference values of 256 steps can be set on an 8-bit DA converter, first of all, the reference value is set at a median ([01111111]=127), and it is determined that on which side of the higher and lower sides the anode voltage exists. In this case, if the anode voltage is higher, the reference value is set at ([11000000]=192) which is an intermediate value between the median ([01111111]=127) and the maximum value ([11111111]=256), and it is determined that on which side of the higher and lower sides the anode voltage exists. Such an operation is repeated, and the anode voltage of the diode can be specified by the determination in 8 times. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a temperature detection circuit for a head driver IC of an ink jet printer, which detects that a head driver IC has reached a predetermined temperature or higher by utilizing a change in an anode voltage of a diode with temperature in a head of the ink jet printer. In particular, the present invention relates to a technique for specifying an anode voltage of a diode in the temperature detection circuit.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, as an output device of a computer, an ink jet type color printer of a type in which several colors of ink are ejected from a recording head has been widely used, and is widely used for printing an image processed by a computer or the like in multiple colors and multiple gradations. Has been. For example, in an ink jet printer using a piezoelectric element as a driving element for discharging ink, a plurality of piezoelectric elements provided corresponding to a plurality of nozzles of a print head are selectively driven so that each piezoelectric element is driven. Ink droplets are ejected from the nozzles based on the dynamic pressure of the element, and the ink droplets are attached to the printing paper, thereby forming dots on the printing paper and performing printing.
[0003]
Here, each piezoelectric element is provided corresponding to a nozzle for ejecting an ink droplet, and is driven by a drive signal supplied from at least one head driver IC mounted in the print head, and the ink droplet is ejected. Is discharged.
[0004]
By the way, each head driver IC generates heat by driving, and the heat is radiated by the ejected ink droplets. However, if continuous printing is performed in a state of extremely high load, the heat radiation capability may be insufficient. Further, in a state where ink is not normally ejected due to lack of ink or clogging of nozzles, sufficient heat radiation is not performed. If printing is continued in such a state, the temperature of each head driver IC may further increase, and the life of each head driver IC may be shortened.
[0005]
For this reason, in a conventional ink jet printer, focusing on the fact that the anode voltage of the diode provided in each head driver IC changes depending on the ambient temperature, for example, four The anode voltage of the diode in the provided head driver IC is output to a control unit constituted by, for example, an ASIC in the printer main body via a signal line in an FFC (flexible flat cable).
[0006]
In the control unit, the data is converted into a digital value by an AD converter, the anode voltage of the diode of each head driver IC is detected, and the temperature of each head driver IC is detected based on these anode voltages. . Here, when the temperature of any one of the head driver ICs becomes equal to or higher than the predetermined temperature, the control unit temporarily stops the printing operation and lowers the temperature of the head driver IC.
[0007]
[Problems to be solved by the invention]
However, in such a method for detecting the temperature of the head driver IC, since the analog signal passes through a relatively long signal line in the FFC extending from the printer head to the printer main body, it is easily affected by noise, and the detection accuracy is low. There was a problem that it would decrease.
[0008]
In addition, since the anode voltage from each head driver IC is converted into a digital signal by the AD converter in the control unit, the detection time becomes long and an AD converter is required in the control unit. Therefore, for example, the control unit constituted by the ASIC becomes large.
[0009]
Further, the number of signal lines in the FFC is required to be equal to the number of head driver ICs, and the number of input pins of the control unit is increased, resulting in an increase in cost.
[0010]
In view of this, the applicant of the present application disclosed in Japanese Patent Application No. 2001-262363 a comparator that compares the anode voltage of a diode provided inside each head driver IC of a printer head with the output voltage of a DA converter that has set a digital temperature reference value. A head driver IC temperature detecting device for an ink jet printer that detects the temperature inside the head driver IC by comparison is proposed. According to this head driver IC temperature detection device, the anode voltage of the diode is compared with a reference voltage, and when the anode voltage inside one or more ICs becomes equal to or lower than a predetermined voltage, a digital signal is generated. The temperature detection output is sent to a control unit in the printer body. Therefore, since the temperature detection signal output from the comparator in each head driver IC to the control unit of the printer main body is a digital signal, it is hardly affected by noise, and the detection accuracy is improved. Further, since an AD converter is not required in the control unit of the printer body, the detection time is short, and the temperature rise of each head driver IC can be reliably detected even during a short time during the printing operation.
[0011]
However, even in the head driver IC temperature detecting device described in Japanese Patent Application No. 2001-262363, it is determined whether the temperature of any one or more head driver ICs is higher or lower than a predetermined temperature set by the above-described digital temperature reference value. Although it can be detected, the anode voltage of the above-described diode inside a certain head driver IC cannot be specified. If the anode voltage can be specified, more precise control can be performed more easily than in the past. For example, in the conventional example described at the beginning, the control for temporarily stopping the printing operation when the temperature of any one of the head driver ICs becomes equal to or higher than a predetermined temperature is performed. When the voltage drops to the predetermined voltage, the printing speed is reduced by 10% to suppress the heat generation of the IC, and when the anode voltage rises to the predetermined voltage (returns), the printing speed is returned to the original value. It becomes possible.
[0012]
Accordingly, an object of the present invention is to provide a head driver IC temperature detection circuit of an ink jet printer that can specify the diode anode voltage in a head driver IC temperature detection circuit of an ink jet printer utilizing the temperature dependency of the anode voltage of the diode. It is to provide a detection device and a method.
[0013]
[Means for Solving the Problems]
In order to solve the above problem, according to the present invention, in a temperature detection circuit of a head driver IC that compares an anode voltage of a diode in a head driver IC with an output voltage of a DA converter, a digital temperature reference value set in the DA converter is sequentially determined. By changing, the anode voltage of the diode in the head driver IC is specified.
[0014]
That is, according to the present invention, the anode voltage of the diode in the head driver IC is compared with the output voltage of the DA converter, and the temperature detection output is detected when the anode voltage is higher or lower than the output voltage of the DA converter. In the head driver IC temperature detecting device to be transmitted, the operation of judging the temperature detection output while sequentially changing the digital temperature reference value set in the DA converter is repeated, thereby specifying the anode voltage corresponding to the digital temperature reference value. Thus, a head driver IC temperature detecting device for an ink jet printer can be obtained.
[0015]
For example, in the case of a temperature detection circuit capable of setting a 256-step digital temperature reference value using an 8-bit DA converter, the digital temperature reference value of the DA converter of the head driver IC is first set to the median value ([01111111] = 127) to determine whether the anode voltage is higher or lower. Here, when the anode voltage is higher, the anode value is set to an intermediate value ([11000000] = 192) between the median value ([01111111] = 127) and the maximum value ([111111111] = 256). It is determined whether the voltage is higher or lower. By repeating this operation, the anode voltage of the diode can be specified by eight determinations.
[0016]
Further, according to the present invention, the anode voltage of each diode in the plurality of head driver ICs is compared with the output voltage of the DA converter, and the anode voltage in any one or more head driver ICs is output from the DA converter. In a head driver IC temperature detection device that sends out a temperature detection output when a voltage level is changed, a digital temperature reference value set in each of the DA converters of all head driver ICs except one head driver IC is set. By repeating the operation of setting the minimum value (0) and determining the temperature detection output while sequentially changing only the digital temperature reference value set in the DA converter of the one head driver IC, An anode voltage corresponding to the digital temperature reference value is specified. Head driver IC temperature detector of Formula printer is obtained.
[0017]
As described above, in a configuration in which the temperature detection output is sent out when the anode voltage inside any one or more of the plurality of head driver ICs becomes higher or lower than the output voltage of the DA converter, the anode voltage is reduced. The digital temperature reference value to be set in the DA converters of all the other head driver ICs except the head driver IC to be specified is set to the minimum value ([00000000] = 0), and only the head driver IC for which the anode voltage is to be specified By sequentially changing the digital temperature reference value in the same manner as described above, the anode voltage can be specified.
[0018]
Furthermore, according to the present invention, in the head driver IC temperature detecting device having the above configuration, the anode voltage of the head driver IC is predicted with reference to the specified result of the anode voltage of the adjacent head driver IC. A head driver IC temperature detecting device for an ink jet printer, wherein the determination operation is started from a section close to the anode voltage, is obtained. Further, the head driver IC temperature detecting device having the above configuration further includes temperature detecting means for detecting a temperature near the head, and refers to a detection result by the temperature detecting means to determine an anode voltage in the head driver IC. A head driver IC temperature detecting device for an ink-jet printer is provided, in which the operation is predicted from the section close to the predicted anode voltage and the determination operation is started.
[0019]
As described above, based on a detection result of a head driver IC that is close (for example, adjacent), a measurement result of a head environment temperature by a thermistor provided on a head substrate, and a detection result by other temperature detecting means, etc. If the approximate value of the anode voltage in the head driver IC whose voltage is to be specified can be predicted, the number of determinations can be further reduced from eight by starting the determination from a section near the anode voltage.
[0020]
On the other hand, according to the present invention, the anode voltage of the diode in the head driver IC is compared with the output voltage of the DA converter, and the temperature detection output is detected when the anode voltage is higher or lower than the output voltage of the DA converter. In the method of specifying the anode voltage of the diode in the head driver IC temperature detecting device for transmitting, at least
Setting a first digital temperature reference value in the DA converter;
Determining the temperature detection output based on the level of the anode voltage with respect to the output voltage of the DA converter;
Setting a second digital temperature reference value different from the first digital temperature reference value based on the determination result;
Determining the temperature detection output based on the level of the anode voltage with respect to the output voltage of the DA converter,
The anode voltage specifying method for the diode, wherein the step of setting the digital temperature reference value and the step of determining the temperature detection output are repeated to specify an anode voltage corresponding to the digital temperature reference value. can get.
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION
A head driver IC temperature detecting device according to an embodiment of the present invention will be described with reference to the drawings. The embodiment described below is a preferred specific example 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. The embodiments are not limited to these embodiments unless otherwise described.
[0022]
FIG. 1 shows a configuration of a head driver IC temperature detecting device according to an embodiment of the present invention. Note that the ink jet printer including the head driver IC temperature detecting device of the present embodiment includes cyan (C), magenta (M), yellow (Y), black (K), light cyan (LC), light magenta (LM), The printer is a color printer of seven colors of dark yellow (DY). The printer head includes two nozzle rows for black (K) and one nozzle row for a total of eight nozzle rows.
[0023]
The head driver IC temperature detecting device 10 of the present embodiment includes a plurality (eight) of head driver ICs 11a, 11b, 11c, 11d, provided for each nozzle row in the printer head 15 of the above-described ink jet printer. 11e, 11f, 11g, and 11h, the anode voltage of each of the diodes is compared with a reference voltage, the comparison result is digitized, and the signal in the printer body 13 through one signal line 12 in the FFC 16 is obtained. It is configured to output to the control unit 14.
[0024]
Here, each of the head driver ICs 11a to 11h has the same configuration, and is used to turn on / off a switch circuit for controlling the ejection / non-ejection of ink from a plurality of nozzles in the eight nozzle rows of each color. (Integrated Circuit [Integrated Circuit]) that constitutes the transmission gate (TG).
[0025]
FIG. 2 is a diagram showing a configuration of a portion related to temperature detection of each of the head driver ICs 11a to 11h and a connection method of each temperature detection output. 2, each of the head driver ICs 11a to 11h includes a temperature setting unit 21, a DA converter 22, a diode 23, a comparator 24, and an FET 25.
[0026]
The temperature setting unit 21 includes, for example, a register, and sets a digital reference value Vd corresponding to a 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. It should be noted that the DA converter 22 is an 8-bit DA converter, and therefore, the temperature setting unit 21 can set the digital reference value Vd in 256 steps of 8 bits. The diode 23 is provided in the head driver IC 11a, and has an anode connected to the constant voltage power supply Vdd1 via the resistor R1, and a cathode connected to the ground.
[0027]
In the illustrated case, 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 that it decreases as the temperature of the head driver IC increases.
[0028]
The comparator 24 receives the anode voltage V of the diode 23 at an inverting input terminal and receives the analog reference value Va from the DA converter 22 at a non-inverting input terminal. Compare with the reference value Va. 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 becomes lower than the analog reference value Va. At this time, an H level digital signal is output.
[0029]
The FET 25 has a gate connected to the output terminal of the comparator 24, a source connected to ground, a drain connected to a constant voltage power supply Vdd2 via a resistor R2, and a digital signal output from the drain as an open drain. It has become so. Thus, when the output signal from the comparator 24 is at the L level, the FET 25 is off and the drain is held at the voltage (H level) of the constant voltage power supply Vdd2. Is turned on, the drain thereof is dropped to the ground potential (L level).
[0030]
In FIG. 2, each of the temperature detection units of the head driver ICs 11a to 11h configured as described above is wired and connected to an output terminal 28 having a common open drain output of each FET 25. Accordingly, if the temperature detection outputs of all the head driver ICs 11a to 11h are held at the voltage (H level) of the constant voltage power supply Vdd2, the temperature detection signal XHOT from the output terminal 28 maintains the H level, When the temperature detection output of any one of the head driver ICs 11a to 11h becomes the ground potential (L level), the temperature detection signal XHOT from the output terminal 28 becomes L. When the temperature detection output of any one of the head driver ICs 11a to 11h becomes the ground potential (L level), the output of the open drain of each FET 25 is changed so that the temperature detection signal XHOT from the output terminal 28 becomes L. The common output terminal 28 may be connected to a wired OR connection.
[0031]
FIG. 3 shows an example of the temperature detection unit of the head driver IC 11a as a specific configuration example of the temperature detection unit of each head driver IC. 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. I have.
[0032]
The flip-flop circuit 26 is composed of eight flip-flop circuits 26a in the case shown. In each of these flip-flop circuits 26a, a latch signal is input to a clock terminal CLK, a setting signal is input to a D terminal, and a reference voltage Vref is input to a Vref terminal.
[0033]
When H is set to the flip-flop, the output becomes Vref, and when L is set, it becomes GND. The head driver IC converts the data for nozzle selection (data for turning on / off a switch circuit for controlling the discharge / non-discharge of ink from a plurality of nozzles in each nozzle row described above) as, for example, serial data. This data is preferably used for the inputs D0 to D7 of the D terminal. In this case, the serial data is input to the shift register. For example, the last transmitted data is D0 to D7, and the data is stored in the flip-flop using the latch signal LAT dedicated to the temperature detection circuit.
[0034]
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 eight resistors 2R respectively connected between the output terminal Q and the output terminal Q.
[0035]
Thereby, the analog reference value Va input to the non-inverting input terminal + of the comparator 24 is changed 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. It can be set to 256 levels.
[0036]
Here, the analog reference value Va input to the non-inverting input terminal + of the comparator 24 is determined based on the guaranteed temperature T1 of the head driver ICs 11a to 11h in consideration of the characteristic variation of the diode 23 incorporated in the head driver ICs 11a to 11h. Is set before shipment from the factory for each of the head driver ICs 11a to 11h so as to have a voltage corresponding to the upper limit temperature T2 set slightly lower than.
[0037]
The head driver IC temperature detecting device 10 according to the present embodiment is configured as described above, and operates as follows. First, the setting of the analog reference value Va will be described.
[0038]
As shown in FIG. 4, the diodes 23 incorporated in the head driver ICs 11a to 11h have the width of the temperature-voltage characteristic as shown by the straight line P and the straight line Q due to individual differences in individual characteristic variations. The variation in the characteristics includes the variation in the inclination and the variation in the offset. Among them, the variation in the offset can be corrected by measuring the voltage at a certain temperature at the time of factory shipment or the like.
[0039]
First, the case where the initial measurement is not performed will be considered. Each diode 23 has a characteristic between the straight line P and the straight line Q. Thus, 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 for the guaranteed temperature T1 of the head driver IC is set to the anode of the diode when the initial measurement is not performed. The intersection B (temperature T3, voltage Vb) of the threshold with the straight line Q is determined as the threshold of the voltage.
[0040]
Thus, when the initial measurement of the diode 23 is not performed, the threshold value Vb of the anode voltage set in consideration of the characteristic variation of each diode 23 is in the temperature range between the points A and B, that is, T3 to T3. It will have a temperature range of T2.
[0041]
For this reason, depending on the characteristic variation of the diode 23, even if the temperature T3 is significantly lower than the upper limit temperature T2, the temperature rise of the head driver IC will be detected.
[0042]
On the other hand, for example, the anode voltage of the diode 23 is detected at the room temperature T0, and the point C is plotted on the temperature-voltage graph as shown in FIG. Then, from this point C, a straight line R parallel to a straight line P having a gentle slope (the sign of the slope is negative), which is the upper limit of the variation of the slope, is drawn, and an intersection D (temperature T2, voltage Vc) with the upper limit temperature T2 is obtained. .
[0043]
At this time, a straight line S parallel to the steep straight line Q which is the lower limit of the slope variation is drawn from the point C, and an intersection E (temperature T4, voltage Vc) with the voltage Vc is obtained. In this case, when the initial measurement of the diode 23 is performed, the threshold value of the anode voltage at the intersection D becomes 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 becomes low. Will be improved.
[0044]
When the threshold value Vc (= analog reference value Va) of the anode voltage of the diode 23 is determined in this manner, a digital reference value Vd (for example, represented by [010011100]) corresponding to the analog reference value Va is obtained. Since it is determined, 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 each diode 23.
[0045]
By the way, in the first embodiment of the present invention, for example, when the anode voltage of the diode 23 is detected at the above-mentioned room temperature T0, it is not necessary to directly measure the anode voltage in an analog manner. An A / D converter for converting a voltage into a digital value is unnecessary. Hereinafter, a method for digitally specifying the anode voltage according to the first embodiment of the present invention will be described in detail with reference to FIG.
[0046]
For example, in the DA converter 22 or the flip-flop circuit 26 described above, an 8-bit digital temperature reference value can be set in 256 steps, that is, first, if the head driver IC whose anode voltage is to be specified is the head driver IC 11c, First, the digital reference value Vd (DAC value) set in the DA converter 22 of the head driver IC 11c is set to the median value ([01111111] = 127) (step S1), and the anode voltage is higher or lower, that is, Then, it is determined whether or not the temperature detection signal XHOT is at the L level (step S2). If XHOT does not become L level (if H level is maintained), the anode voltage is higher, so that the intermediate value between the central value ([01111111] = 127) and the maximum value ([11111111] = 255) Value ([10111111] = 191, the display of the binary number is omitted hereafter) (step S3), and it is determined again whether the anode voltage is higher or lower (step S4). If XHOT does not become L level (if H level is maintained), since the anode voltage is higher, it is set to (223) which is an intermediate value between the value (191) and the maximum value (255). (Step S5) It is determined again whether the anode voltage is higher or lower (Step S6). If XHOT does not become L level (if H level is maintained), the anode voltage is higher, so that it is set to (239) which is an intermediate value between the value (223) and the maximum value (255). (Step S7) It is determined again whether the anode voltage is higher or lower (Step S8). If XHOT does not become L level (if H level is maintained), since the anode voltage is higher, it is set to (247) which is an intermediate value between the value (239) and the maximum value (255). (Step S9) It is determined again whether the anode voltage is higher or lower (Step S10). If XHOT does not become L level (if H level is maintained), the anode voltage is higher, so that it is set to (251) which is an intermediate value between the value (247) and the maximum value (255). (Step S11) It is determined again whether the anode voltage is higher or lower (Step S12). If XHOT does not become L level (if H level is maintained), since the anode voltage is higher, it is set to (253) which is an intermediate value between the value (251) and the maximum value (255). (Step S13) It is determined again whether the anode voltage is higher or lower (Step S14). If XHOT does not become L level (if H level is maintained), the anode voltage is higher, so that it is set to (254) which is an intermediate value between the value (253) and the maximum value (255). (Step S15), it is determined again whether the anode voltage is higher or lower (Step S16). If XHOT does not become L level (maintain H level), the anode voltage is determined to be the maximum value (255) because the anode voltage is higher (step S17). Conversely, if XHOT goes low, it means that the anode voltage is not higher, so the anode voltage is determined to be this value (254) (step S18). If the XHOT goes low in step S14, it means that the anode voltage is not higher, so that the intermediate value between the set value (253) and the previous set value (251) is (252). It is set (step S19), and it is determined again whether the anode voltage is higher or lower (step S20). If XHOT does not become L level (if H level is maintained), the anode voltage is determined to be a value (253) because the anode voltage is higher (step S21). Conversely, if XHOT goes low, it means that the anode voltage is not higher, so the anode voltage is determined to be a value (252) (step S22). In addition, in step S12, if XHOT goes to L level, the anode voltage is not higher, so that (249) which is an intermediate value between the set value (251) and the previous set value (247) It is set (step S23), and it is determined again whether the anode voltage is higher or lower (step S24). If XHOT does not become L level (if H level is maintained), it is set to (250) which is an intermediate value between the set value (249) and the previous set value (251) (step S25). It is determined whether the anode voltage is higher or lower (step S26). If XHOT does not become L level (if H level is maintained), the anode voltage is determined to be a value (251) because the anode voltage is higher (step S27). Conversely, if XHOT goes low, it means that the anode voltage is not higher, so the anode voltage is determined to be a value (250) (step S28). If the XHOT goes low in step S24, this indicates that the anode voltage is not higher, so the value is set to (248) (step S29), and it is determined again whether the anode voltage is higher or lower. (Step S30). If XHOT does not become L level (if H level is maintained), the anode voltage is determined to be a value (249) because the anode voltage is higher (step S31). Conversely, if XHOT goes low, it means that the anode voltage is not higher, so the anode voltage is determined to be a value (248) (step S32). On the other hand, in step S10, if XHOT goes to the L level, it means that the anode voltage is not higher, so that the value (243) which is an intermediate value between the set value (247) and the previous set value (239) is set. It is set (step S33), and it is determined again whether the anode voltage is higher or lower (step S34). Thereafter, the same determination is repeated. Also, in step S8, if XHOT goes to the L level, it means that the anode voltage is not higher. It is set (step S35), and it is determined again whether the anode voltage is higher or lower (step S36). Thereafter, the same determination is repeated. In step S6, if XHOT goes to L level, it means that the anode voltage is not higher, so that (207) which is an intermediate value between the set value (223) and the previous set value (191) is set. It is set (step S37), and it is determined again whether the anode voltage is higher or lower (step S38). Thereafter, the same determination is repeated. In step S4, if XHOT goes to L level, it means that the anode voltage is not higher, so that (159) which is an intermediate value between the set value (191) and the previous set value (127) It is set (step S39), and it is determined again whether the anode voltage is higher or lower (step S40). Thereafter, the same determination is repeated. Furthermore, in step S2, if XHOT goes to the L level, it means that the anode voltage is not higher, so that it is set to (63) which is an intermediate value between the set value (127) and the minimum value (0). (Step S41) It is determined again whether the anode voltage is higher or lower (Step S42), and thereafter, the same determination is repeated.
[0047]
As described above, the anode voltage of the diode at a certain temperature, for example, the room temperature T0, can be digitally specified. Therefore, based on such a temperature, for example, the anode voltage of the diode at room temperature T0, it is possible to control the temperature of the head driver IC when performing the initial measurement of the diode shown in FIG.
[0048]
As described above, according to the present embodiment, the variation in the anode voltage characteristics can be corrected by specifying the anode voltage of the diode in the head driver IC at a certain temperature.
[0049]
Next, a description will be given of a second embodiment of the present invention in which an anode voltage of a diode in a head driver IC is digitally specified in an ink jet printer including the head driver IC temperature detecting device shown in FIGS. .
[0050]
That is, in the ink jet printer including the head driver IC temperature detecting device shown in FIGS. 1 to 3, each temperature detecting unit of the head driver ICs 11a to 11h has the open drain of each FET 25 as shown in FIG. The output is connected to the output terminal 28 having a common output by a wired AND connection. Therefore, when the temperature detection output of any one of the head driver ICs 11a to 11h becomes the ground potential (L level), the output terminal 28 Is set to L, the digital temperature reference value set in the DA converters of all the other head driver ICs except the head driver IC whose anode voltage is to be specified is set to the minimum value ([00000000] ] = 0), and set the head drive to specify the anode voltage. The anode voltage is specified by sequentially changing the digital temperature reference value of only the IC in the same manner as in the first embodiment described above.
[0051]
As described above, in a configuration in which the temperature detection output is sent out when the anode voltage inside any one or more of the plurality of head driver ICs becomes higher or lower than the output voltage of the DA converter, the anode voltage is reduced. The digital temperature reference value to be set in the DA converters of all the other head driver ICs except the head driver IC to be specified is set to the minimum value ([00000000] = 0), and only the head driver IC for which the anode voltage is to be specified By sequentially changing the digital temperature reference value in the same manner as described above, the anode voltage can be specified.
[0052]
If the anode voltage can be specified, more precise control can be performed more easily than in the past. For example, in the conventional example described at the beginning, the control for temporarily stopping the printing operation when the temperature of any one of the head driver ICs becomes equal to or higher than a predetermined temperature is performed. When the voltage drops to the predetermined voltage, the printing speed is reduced by 10% to suppress the heat generation of the IC, and when the anode voltage rises to the predetermined voltage (returns), the printing speed is returned to the original value. It becomes possible.
[0053]
Further, in the configuration of the first and second embodiments, when a rough value of the anode voltage in the head driver IC whose anode voltage is desired to be specified can be predicted from the detection result of the adjacent (for example, adjacent) head driver IC. The determination can be further reduced from eight times by starting the determination from a section in the vicinity. For example, in the example shown in FIG. 5, when the detection result of the anode voltage of the head driver IC 11c is a voltage (step S22) corresponding to the digital temperature reference value (252), the head driver IC 11d adjacent to the head driver IC 11c If it is intended to specify the anode voltage of the head driver IC, it is assumed that the temperature is relatively close in the case of the adjacent head driver IC. Therefore, at least steps S1 to S4 are omitted and the digital temperature reference value ( It is sufficient to start from step S5 which sets 223). Therefore, in this case, the number of determinations can be reduced to six.
[0054]
Further, for example, a case where a rough value of the anode voltage in the head driver IC for which the anode voltage is to be specified can be predicted from a result of measurement of the head environment temperature by a thermistor provided on the head substrate or a result of detection by other temperature detecting means or the like. In addition, by starting the determination from a section near the temperature, the number of determinations can be reduced to less than eight.
[0055]
In the second embodiment described above, the result obtained by comparing the anode voltage of the diode provided in each of the plurality of head driver ICs 11a to 11h provided in the printer head 15 of the ink jet printer with the reference voltage is a digital value. And the anode voltage is specified by the control unit 14 in the printer main body 13. However, the present invention is not limited to this configuration. A configuration in which the driver IC receives the temperature detection command and sequentially changes the digital temperature reference value (DAC value) to specify the anode voltage and output the result as parallel or serial multi-bit data, as described above.
[0056]
The present invention is not limited to the method of specifying the anode voltage of the head driver IC temperature detecting diode shown in the flowchart of FIG. 5, but a computer-readable recording medium recording these processes and the computer program itself for executing these processes. Of course, it can be applied to
[0057]
【The invention's effect】
According to the present invention, in the temperature detection circuit provided in each of the plurality of head driver ICs of the ink jet printer, the anode voltage of the temperature detection diode is changed by sequentially changing the digital reference value set in the DA converter. Can be identified. By specifying the anode voltage at a certain temperature, it is possible to correct the variation in the anode voltage characteristics of the diode.
[0058]
In a configuration in which a temperature detection output is sent when an anode voltage inside one or more ICs of a plurality of head driver ICs is higher or lower than an output voltage of a DA converter, a head whose anode voltage is desired to be specified The digital temperature reference values set in the DA converters of all the other head driver ICs except the driver IC are set to the minimum value, and the digital temperature reference values of the head driver ICs whose anode voltage is to be specified are sequentially increased in the same manner as described above. By changing, the anode voltage can be specified.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of an embodiment of a head driver IC temperature detecting device according to the present invention.
FIG. 2 is a block diagram showing a main part of each head driver IC in the head driver IC temperature detecting device of FIG. 1;
FIG. 3 is a diagram showing a specific configuration example of a main part of each head driver IC of FIG. 2;
FIG. 4 is a graph showing a procedure for setting a temperature limit reference value in the head driver IC temperature detecting device of FIG. 1;
FIG. 5 is a flowchart illustrating a method of specifying an anode voltage of a head driver IC temperature detecting diode according to an embodiment of the present invention.
[Explanation of symbols]
10 Head driver IC temperature detector
11a-11h Head driver IC
12 signal line (cable)
13 Printer body
14 Control unit
21 Temperature setting section
22 DA converter
23 Diode
24 Comparator
25 FET
26 flip-flop circuit
27 Resistance group
28 output terminal

Claims (5)

A head driver IC temperature detecting device that compares an anode voltage of a diode in a head driver IC with an output voltage of a DA converter and sends out a temperature detection output when the anode voltage is higher or lower than the output voltage of the DA converter. An ink jet printer characterized by specifying an anode voltage corresponding to the digital temperature reference value by repeating an operation of judging the temperature detection output while sequentially changing a digital temperature reference value set in the DA converter. Head driver IC temperature detecting device. The anode voltage of each diode in the plurality of head driver ICs is compared with the output voltage of the DA converter, and when the anode voltage in any one or more head driver ICs is higher or lower than the output voltage of the DA converter, In a head driver IC temperature detecting device for transmitting a temperature detection output, a digital temperature reference value set in each of the D / A converters of all head driver ICs except one head driver IC is set to a minimum value (0). By repeating the operation of judging the temperature detection output while sequentially changing only the digital temperature reference value set in the DA converter of the one head driver IC, the digital temperature reference value of the one head driver IC corresponds to the digital temperature reference value. Heading of an ink jet printer characterized by specifying an anode voltage to be changed Driver IC temperature sensing device. 3. The head driver IC temperature detecting device according to claim 1, wherein the anode voltage of the head driver IC is predicted with reference to the specified result of the anode voltage of the adjacent head driver IC, and from the section close to the predicted anode voltage. A head driver IC temperature detecting device for an ink jet printer, wherein the operation for determining is started. 3. The head driver IC temperature detecting device according to claim 1, further comprising a temperature detecting means for detecting a temperature in the vicinity of the head, and referring to a detection result by the temperature detecting means to determine an anode voltage in the head driver IC. A head driver IC temperature detecting device for an ink jet printer, which predicts and starts the determination operation from a section close to the predicted anode voltage. A head driver IC temperature detecting device that compares an anode voltage of a diode in a head driver IC with an output voltage of a DA converter and sends out a temperature detection output when the anode voltage is higher or lower than the output voltage of the DA converter. Setting the first digital temperature reference value in at least the DA converter in the method of specifying the anode voltage of the diode in;
Determining the temperature detection output based on the level of the anode voltage with respect to the output voltage of the DA converter;
Setting a second digital temperature reference value different from the first digital temperature reference value based on the determination result;
Determining the temperature detection output based on the level of the anode voltage with respect to the output voltage of the DA converter,
An anode voltage specifying method for the diode, wherein an anode voltage corresponding to the digital temperature reference value is specified by repeating a step of setting the digital temperature reference value and a step of determining the temperature detection output.

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