JP5007408B2 - Printer and control method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a printer that is equipped with a print head having a plurality of heating resistor elements which are arranged in at least one line at a part of a heat radiation member and adapted to record an image on a recording medium by using the print head and to provide a method for controlling the printer capable of suppressing difference in density in the image recorded on the recording medium. <P>SOLUTION: This printer 1 is controlled by the method including a first process of supplying power to at least a part of the plurality of heating resistor elements in order to perform preheating, a second process of determining a first temperature of at least one position of the heat radiation member 11 and a second temperature of at least one of the heating resister elements in order to start recording of an image on a recording medium 40, and a third process of permitting the starting of the recording of the image on the recording medium 40 when the first temperature is higher than a prescribed temperature and the second temperature is higher than the first temperature. <P>COPYRIGHT: (C)2007,JPO&amp;INPIT

Description

  The present invention relates to a printer having a print head including a plurality of heating resistance elements and a control method thereof.

  There is known a method of printing an image on a recording paper by having a print head including a plurality of heating resistance elements and controlling thermal energy applied to these heating resistance elements. One of them is a thermal printer, which heats a thermal recording paper (thermal paper) with a plurality of heating elements provided in the thermal head, thereby printing an image on the recording paper. Another type of thermal printer is also called a sublimation type, which uses plain paper and heats an ink ribbon with a heating element of a thermal head, thereby transferring the ink onto plain paper and printing an image. In either case, the density of the image printed (recorded) on the recording paper depends on the temperature of the heating element of the thermal head.

  Patent Document 1 discloses a technique for correcting resistance unevenness, heat storage unevenness, heat storage of a head, and the like in order to prevent occurrence of density unevenness, blurring of an image outline, and the like. In the technique described in Patent Document 1, each heat generation data for one line to be printed is converted into time data for energizing the heat generating elements by a first LUT (lookup table). The correction processing circuit performs linear calculation based on variation in heat energy generated in the heat generating element due to heat storage of the heat generating element and the thermal head, and variation in resistance value of the heat generating element, and obtains each correction coefficient for each time data. Each conversion time data indicating the energization time corrected by the correction coefficient is converted into converted heat generation data by the second LUT.

In thermal printers, the thermal head is preheated to near the color temperature of the thermal recording paper or ink ribbon. Patent Document 2 discloses a technique related to preheating of the thermal head. The technique described in Patent Document 2 adds image information to the setting of the remaining heat time, and information on the number of lines is input from the line number control circuit to the preheating RAM, and image data is transmitted via the communication control circuit. The preheating history based on is supplied as an LUT. The preheating control circuit reads the preheating information of the heating elements from the preheating RAM and performs preheating.
Japanese Patent Laid-Open No. 10-804 JP 2004-160854 A

  As disclosed in Patent Document 1, density unevenness is suppressed by referring to the LUT based on heat storage of the head and correcting the heat generation data, and further preheating as shown in Patent Document 2. The amount of heat storage is also controlled by this. However, the image density or color tone may differ greatly for each recording sheet immediately after the power is turned on or when recording is resumed after the recording is once stopped. In recent years, a product group called a photo printer, which is often used to output images (images) from a digital camera, is not frequently used continuously. , Often print after a while. Therefore, if the density difference between the first and second photos to be output is large, the performance as a photo printer may be questioned even if the image quality of each print is good.

  Accordingly, the present invention provides a control method and a printer that are intended to suppress a density difference or a color tone difference immediately after the start of recording.

One aspect of the present invention is a printer control method that includes a print head including a plurality of heating resistance elements arranged in at least one row on a part of a heat dissipation member, and records an image on a recording medium by the print head. . This printer control method includes the following steps.
(A1) In order to preheat the print head, power is supplied to at least some of the plurality of heating resistance elements (first step).
(A2) In order to start recording an image on the recording medium, the first temperature is acquired from at least one location of the heat dissipation member, and the second temperature is acquired from at least one heating resistance element of the plurality of heating resistance elements. (Second step).
(A3) When the first temperature is higher than the predetermined temperature and the second temperature is higher than the first temperature, the start of image recording on the recording medium is permitted (third step).

  According to this printer control method, after preheating, in the second step, in order to start recording an image on a recording medium, for example, recording paper, only the first temperature is obtained from at least one location of the heat dissipation member. Instead, the second temperature is obtained from at least one of the plurality of heating resistance elements, and in the third step, it is determined whether recording can be started based on these temperatures. When a certain end condition is established during preheating before starting printing, it is the conventional control method to end preheating and start printing. Once it is determined that preheating has ended, the LUT and the like are later performed. Use this to print while correcting the amount of heat generation. On the other hand, in the printer control method included in the present invention, in the step of acquiring the temperature for starting the image recording, that is, in the step of acquiring the temperature in order to correct the heat generation amount of the heating resistor element, Whether or not recording can be started is determined using the temperature. Therefore, in this printer control method, after the preheat is determined to be completed, there is a choice not only to perform printing, but also to not perform printing or postpone if conditions are not met.

  As one of the factors of the density difference immediately after the start of recording, at the stage where it was determined that the preheating was completed, the preheating was completed even though it was determined that the conditions of the heat dissipation member were suitable for recording. It is expected that there is a possibility that the condition of the heat radiating member will rapidly shift to a state not suitable for recording later. By determining whether or not recording can be started in the temperature measurement for starting recording, it is possible to prevent recording from being started in a state where the conditions of the heat dissipation member are not suitable for recording.

  Furthermore, in the third step, recording is performed on the condition that, in addition to the first temperature of the heat radiating member being higher than a predetermined temperature, the second temperature obtained from the heating resistor element is higher than the first temperature. To start. The fact that the first temperature of the heat dissipating member is higher than a predetermined temperature is effective as a condition for terminating the preheating. Further, the first temperature is effective not only as an index indicating the heat storage state of the head but also as an index for correcting the amount of heat generated by the heating resistance element during recording.

  During preheating and recording, power is supplied to the heating resistor element, and the heating resistor element generates heat, so that the heat dissipation member is heated by the heat to promote heat dissipation. Therefore, the heating resistor element and its vicinity are usually at the highest temperature, and in such a state, the amount of heat generated by the heating resistor element is usually corrected based on the first temperature and recorded on the recording medium. is there. However, in a situation where the heat radiating member is not sufficiently heated, when the heating resistor element finishes generating heat, the second temperature in the heating resistor element and the vicinity thereof may decrease and become lower than the first temperature. is there. In such an unsteady state, if the heat generation amount is corrected based on the first temperature, the heat generation amount of the heat generation resistive element is insufficient. Therefore, after that, there is a possibility that an image having a density difference is recorded with respect to the density when the heat radiating member is in a steady state.

  In the third step, by permitting the start of recording in addition to the condition that the second temperature is higher than the first temperature, the temperature gradient inside the heat radiating member is substantially stable or approximated thereto. The image can be recorded on the recording medium in the state. For this reason, the density difference between the images recorded on each recording medium can be suppressed.

  Furthermore, in the printer control method included in the present invention, whether or not the temperature state of the heat radiating member is in a steady state or near in the second step of acquiring the temperature to start recording an image on the recording medium. The second temperature for determining whether or not is obtained by using the heating resistor element itself. The timing at which the temperature is sampled to start recording an image on the recording medium is before preheating to supply power to the heating resistor element and before recording is performed by supplying power to the heating resistor element. No electric power is supplied, and the heating resistor element can be used as a temperature measuring element. By sharing the heating resistance element as the temperature measuring element, the temperature at the optimum position for grasping the temperature state of the heat radiating member can be sampled with a very simple configuration.

  The first temperature and the second temperature may be temperatures measured at a single measurement point, and are values obtained by performing an appropriate statistical process such as an average or an intermediate temperature measured at a plurality of measurement points. Also good. In the second step, the temperature state of the heat dissipating member can be more accurately determined by sampling the temperature at a location away from the plurality of heating resistance elements as the first temperature.

  In order to use the heating resistance element as a temperature measurement element, a switching circuit may be provided. In the second step, the second temperature can be determined by switching the circuit of at least one heating resistance element. Furthermore, in the third step, since it is only necessary to determine that the heat dissipating member is in a steady state or a temperature state close thereto, the second temperature sampling point may be small. For example, one heating resistor of a plurality of heating resistor elements Satisfactory accuracy can be obtained simply by sampling the second temperature using the element.

  In the third step, when the start of recording cannot be permitted, the recording may be stopped, but it is not preferable that the job from the digital camera or personal computer as the host is canceled on the printer side. Therefore, in the third step, when image recording on the recording medium cannot be started, the first step, that is, preheating is restarted, and the second and third steps are used again to determine whether recording can be started. Is desirable.

  Another aspect of the present invention is a printer having a print head for recording an image on a recording medium. The printer includes a heat dissipating member, a plurality of heat generating resistive elements arranged in at least one row on a part of the heat dissipating member, and a first temperature attached to the heat dissipating member at a position away from the heat generating resistive elements A measurement element and a circuit for switching at least one heating resistance element of the plurality of heating resistance elements to be used as the second temperature measurement element are provided. In addition, the printer further supplies power to at least a part of the plurality of heating resistance elements for preheating, and then passes the first temperature measured by the first temperature measurement element and the switching circuit. And a controller having a function of starting recording by the print head with reference to the second temperature measured in this manner.

  According to this printer, the first temperature is acquired by the first temperature measurement element attached at a position distant from the plurality of heating resistance elements, and the second temperature is obtained from at least one heating resistance element of the plurality of heating resistance elements. You can get the temperature. Then, the controller supplies power to at least a part of the plurality of heating resistance elements for preheating, and then refers to the first temperature and the second temperature to determine whether the print head can start recording. Judgment can be made. Therefore, when the first temperature is higher than the predetermined temperature and the second temperature is higher than the first temperature, that is, a steady state in which the temperature gradient inside the heat radiating member is substantially stable or a state that approximates this. When it is confirmed that the image is recorded, the image recording on the recording medium can be started, and the second temperature for that purpose can be obtained using the heating resistor element. Therefore, this printer is one of the printers suitable for realizing the control method according to one aspect of the present invention, and is a sublimation printer that often prints a small amount of printed matter discontinuously. It is suitable as a photo printer for printing color photographs.

The controller of the printer preferably includes the following functions.
(B1) A first function for preheating the plurality of heating resistance elements by supplying power to at least a part of the plurality of heating resistance elements.
(B2) In order to start image recording on the recording medium, the first temperature is measured by the first temperature measuring element, and the second temperature is measured by at least one heating resistor element by the switching circuit. function.
(B3) A third function for starting image recording on the recording medium when the first temperature is higher than the predetermined temperature and the second temperature is higher than the first temperature.

  These functions can be provided as firmware for controlling the CPU, and the CPU can function as a controller.

  The printer also sets information for setting recording power to be supplied to the plurality of heating resistance elements based on the temperature information obtained by the first temperature measuring element, or temperature information obtained by the first temperature measuring element. It is preferable to further include a memory storing a function for setting recording power to be supplied to a plurality of heating resistance elements based on the above. When the first temperature is higher than the predetermined temperature and the second temperature is higher than the first temperature, the third function generates heat using information stored in the memory based on the first temperature. Appropriate power can be supplied to the resistance element, and high-quality image recording can be started.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a schematic configuration of a printer according to an embodiment of the present invention. FIG. 2 shows a part of the printer head control mechanism in a circuit form including a CPU. This printer 1 records a monochrome or color image on a recording paper by controlling the thermal energy applied to the recording paper or ink ribbon from the heating resistance element of the print head, and the entire printer is compact. Therefore, the line thermal printer is suitable when an individual user prints a color photograph.

  The printer 1 includes a print head 10 that records an image on a recording paper 40 via an ink ribbon 30, a platen roller feeder 20 that moves while the recording paper 40 is sandwiched between the print head 10, and the feeder. 20 includes a motor 21 that drives the motor 20, a controller 50 for controlling the elements constituting the printer 1, and a memory 60 that stores a program 61 of the controller 50, control data 62, and the like.

The print head 10 includes a plurality of heat generating resistors provided in a line in the width direction of the recording paper 40 on the heat radiating plate 11 and one surface (hereinafter referred to as a print surface) 11 a of the heat radiating plate 11 facing the recording paper 40. A temperature measurement element (temperature detection element) R attached to a heat generating resistor element group 13 composed of the elements R and the other surface (hereinafter referred to as a heat dissipation surface) 11b of the heat radiating plate 11 apart from the heat generating resistor element group 13. _THr . The heating resistance element group 13 includes a heating resistance element and an element R _THf that also functions as a temperature measurement element (temperature detection element). The head 10 uses the heating resistance element R _THf as a heating resistance element and a temperature measurement element. A circuit 15 for switching and using is provided. The switching of the circuit 15 is performed by a switch 15 a that operates under the control of the controller 50.

In the present embodiment, a thermistor (Thermally Sensitive Resister) having a negative temperature coefficient is employed as the first temperature measuring element R _THr . Further, the second temperature measuring element R _THf that is also used as the heating resistance element is also a heating resistance element / thermistor element having characteristics as a thermistor. Since a general heating resistance element also has a positive temperature coefficient, it may be necessary to improve the measurement accuracy, but it can be used as a second temperature measurement element by switching the circuit. These heating resistance elements R and R _THf are grouped into 10 IC1 to IC10, and are controlled by the controller 50 for printing. The second temperature measurement element R _THf is replaced with one of the plurality of heating resistance elements R of the IC 5 located in the central portion of the heating resistance element group 13. In the present embodiment, the plurality of heating resistor elements R, the heating resistor element and the thermistor R _THf also shows a heating resistor element group including, if not otherwise indicated, the heating resistance element and a thermistor element R _THf as heating elements This is the case when it is functioning.

  The feeder 20 is driven by a motor 21 and feeds the print head 10 while pressing the recording paper 40 through an ink ribbon (transfer sheet) 30 having a region divided for each color. Therefore, by supplying electric power to the desired heating resistance element R of the head 10 to generate heat, dots of a desired color can be formed on the recording paper 40 and a color image can be recorded on the recording paper 40.

  The controller 50 is an ASIC including a CPU 56 (embedded with the CPU 56), and includes a control mechanism unit 54 having a temperature control function 52, a print control function 53, and a preheat control function 51, an interface 55, and a memory 60. Yes. The interface 55 can connect a host 70 such as a personal computer or a digital camera and the control mechanism unit 54, and allows the printer 1 to acquire image information from the host 70 and print it. The memory 60 controls the CPU 56, a program 61 for realizing the functions as the preheat control function 51, the temperature control function 52 and the print control function 53 and other functions required as the printer 1 using the CPU 56, An LUT (Look Up Table) 62 in which a correction value or a corrected value of recording power supplied to the heating resistance element R is recorded is stored.

A preheat control function (first function) 51 included in the controller 50 controls the process of preheating the print head 10 by supplying power to the heating resistor element R when the printer 1 starts recording. The preheat control function 51 is the same as the print control function 53 described later in that power is supplied to the heating resistor element R. The preheat control function 51 performs voltage control for preheating, that is, an LUT 62 for correcting power for printing. In the circuit configuration shown in FIG. 2, the same circuit is assigned to these functions. The setting of the preheating time or the setting of power for preheating can be made variable by, for example, the temperature (first temperature) T _THr of the heat radiating plate 11, and an LUT for that purpose may be prepared in the memory 60.

The temperature control function (second function) 52 measures the first temperature T _THr of the heat radiating surface 11b by the first thermistor R _THr attached to the heat sink 11 and switches the circuit 15 of the header 10 to change the second temperature. The second temperature T _THf of the printing surface 11a is measured by the heating resistance element R _THf that also serves as the thermistor. The first temperature T _THr can be sampled (obtained) at an arbitrary timing. The second temperature T _THf can also be sampled (obtained) at any timing by switching the circuit 15 of the header 10 at any timing. Therefore, the second temperature T _THf can be measured even during preheating. However, in the situation where electric power is supplied to the surrounding heating resistor element R, it is substantially equivalent to measuring the heating temperature of the heating resistor element R, and the temperature of the heat radiating surface 11b of the heat sink 11 can be measured with high accuracy. I can't say that. At the timing when the temperature is measured in order to start recording an image on the recording paper 40 after the preheating process is finished, no heat is supplied to the surrounding heating resistor element R, and therefore heat generation also serving as the second thermistor. Using the resistance element R _THf , the temperature of the printed surface 11a of the heat sink 11 can be measured with relatively high accuracy. The temperature measured for starting the recording and the temperature measured at an appropriate timing after the start of recording, particularly the first temperature T _THr, are used to correct the amount of heat generated by the heating resistor element R. .

In the print control function (third function) 53, the first temperature T _THr measured for starting the image recording on the recording paper 40 in the temperature control function 52 is higher than the predetermined temperature Ta, and the second When the temperature T _THf is higher than the first temperature T _THr , image recording on the recording paper 40 is started. The print control function 53 sets recording power to be supplied to the heating resistor element R based on the first temperature T _THr . Further, the print control function 53 takes charge of other control necessary for recording an image on the recording paper 40 such as control of the motor 21 for driving the feeder 20.

FIG. 3 shows a control method of the printer 1 by the controller 50 using a flowchart. When there is an instruction to start printing from the host 70, first, in step 101, the temperature control function 52 _samples the first temperature T _THr by the first thermistor R _THr . Further, the switch 15a is turned on to switch the circuit 15, and the second temperature _TTHf is sampled using the heating resistor element _RTHf as the second thermistor. When sampling is completed, the circuit 15 is switched, and the heating resistor element R _THf is set to function as a heating resistor element. In step 101, the order of sampling the first temperature T _THr and the second temperature T _THf is arbitrary.

In step 102, if the first temperature T _THr is equal to or lower than the predetermined temperature Ta, preheating is set in step 105, and the preheating control function 51 supplies power to the heating resistor element R to start preheating (first heating). Step 1). Further, in step 102, also the first temperature _{T THr} is not reach the predetermined temperature Ta, at step 103, the second temperature _{T THf} is equal to or smaller than the first temperature _{T THr,} then pre-heat set preheat Start or continue.

_Preheating is performed. In step 102, when the first temperature T _THr is higher than the predetermined temperature Ta, and in step 103, the second temperature T _THf is higher than the first temperature T _THr . , Stop preheating and end preheating. A change in resistance value (actually a voltage value) corresponding to the first temperature T _THr can be read using the AD converter 57 of FIG. _Further , the comparison between the second temperature T _THf and the first temperature T _THr can be made by using the comparator 58 of FIG. 2 to determine the resistance value (actually, if the thermistor characteristics for obtaining the respective temperatures are the same). Can be performed according to the voltage value. However, the sampling method and the comparison method and circuit are not limited to these. Note that when printing is instructed from the host 70, printing is performed immediately before and the conditions of Steps 102 and 103 are satisfied, preheating is not performed.

When the preheating is stopped in step 104, the printing process can be started in step 106. In Step 107, in order to start recording an image on the recording paper 40, the first temperature T _THr is sampled by the first thermistor R _THr provided on the heat radiating surface 11b of the heat radiating plate 11. At the same time, the second temperature T _THf is sampled by the heating resistance element R _THf that also serves as the second thermistor (second step). The specific procedure is the same as that in step 101, and will be further described with reference to the circuit of FIG.

That is, in the circuit of FIG. 2, at the timing of step 107, the nVHOE (head power supply enable, active low) terminal is H, and the head voltage is not output. Also, a VCC-R terminal (a terminal for supplying the same voltage as VCC when measuring temperature at the heating resistor / thermistor _RTHf ) and a B terminal (a terminal to which a voltage dropped by the heating resistor / thermistor _RTHf is input) ) Is separated from the right circuit by Hi-Z. Further, during image recording, FET 15a for disconnecting the resistive element _{R PB} from the heating resistor element and the thermistor _{R THf} is in OFF state, DLOE terminal for ON / OFF control of the FET 15a is L. Further, at the timing of step 107, the voltage dropped by the first thermistor R _THr is input to the terminal A, converted into a digital signal by the AD converter 57, and transmitted to the CPU 56. The resistance element R _PA and the resistance element R _PB are selected so that the voltages at the A terminal and the B terminal at the same temperature are equal.

In step 108, the first temperature _{T THr} is higher than the predetermined temperature Ta, at step 109, the second temperature _{T THf} is higher than the first temperature _{T THr,} the print control function 53, in step 110 The LUT 62 is read, and printing is performed in step 111 (third step).

That is, in the circuit of FIG. 2, in step 108, when the first temperature T _THr is higher than the predetermined temperature Ta, the nVHOE terminal remains H, the VCC-R terminal and the DLOE terminal are activated, and the B terminal is activated. In Step 109, the comparator 58 performs temperature comparison (voltage comparison) between the first temperature T _THr and the second temperature T _THf . In step 109, when the second temperature T _THf is higher than the first temperature T _THr , the nVHOE terminal becomes L and outputs the head voltage. Further, the VCC-R terminal and the B terminal are separated from the right circuit by Hi-Z, and the DLOE terminal is L. In step 110, when the power value information for correcting the heat generation amount is obtained from the _{LUT 62} based on the first temperature T _THr obtained from the thermistor R _THr at the timing of step 107, the CPU 56 appropriately sets the value of the voltage control unit 59. set. The CPU 56 outputs DATA1 to DATA10, CLK, LATCH, and STB signals corresponding to the image, and the image is printed on the recording medium 40 in step 111.

On the other hand, when the first temperature T _THr is equal to or lower than the predetermined temperature Ta at step 108, or when the second temperature T _THf is _{equal to} or lower than the first temperature T _{THr at} step 109, step 112 is performed. , Preheating is resumed. Then, the process returns to step 101, and the print head 10 is preheated again until the condition for ending preheating is satisfied.

  In step 113, when the temperature measurement timing comes during printing periodically or due to the progress of printing, the process returns to step 107 to measure the temperature, and in step 110, the LUT 62 is used, and if necessary, the heating resistance The voltage supplied to the element R is reset. In step 114, the above processing is repeated until printing is completed.

FIG. 4 schematically shows changes in temperature measured with time on the printed surface 11a and the heat radiating surface 11b of the heat radiating plate 11. In FIG. At time t0, power is supplied to the heating resistor element R and preheating is started. The second temperature T2 (corresponding to the temperature _TTHf ) of the printed surface 11a in which the heating resistance elements R are arranged starts to rise immediately. On the other hand, the first temperature T1 (corresponding to the temperature _TTHr ) of the heat radiating surface 11b starts to rise at time t1 because there is a time lag due to heat transfer. When the first temperature T1 reaches the predetermined temperature Ta at time t2, the temperature T2 of the heated print surface 11a is higher than the temperature T1, so that the condition for terminating the preheating is satisfied, and the preheating is temporarily terminated. To do.

  As soon as the preheating is finished, the cooling of the heat sink 11 proceeds. Since the printed surface 11a is at a higher temperature than the heat radiating surface 11b, the amount of heat radiation is large and the possibility of rapid cooling is high. Further, the print surface 11a is formed with a heating resistor element R and a circuit for supplying electric power to them, and since it is necessary to determine the position of the print surface 11a with high precision in printing, the vicinity of the print surface 11a is present. It is often attached to the chassis of the printer 1. In the preheating stage, the temperature including the chassis and the like is rarely in a steady state, and the print surface 11a is more likely to be cooled more rapidly than the heat dissipation surface 11b due to the above factors. As a result, the temperature difference between the printed surface 11a and the heat radiating surface 11b disappears. In some cases, the second temperature T2 is expected to decrease to the first temperature T1 or less as after the time t3.

  For this reason, at the time t4 when printing is to be started after completion of preheating, there is a possibility that the temperature T2 of the print surface 11a is lower than the temperature T1 of the heat dissipation surface 11b. When printing is started in this state, the heat generation amount of the heating resistor element R is originally based on the information of the LUT 62 at the temperature T1 lower than the temperature T2 if the heat storage state of the heat sink 11 is steady when the print surface is at the temperature T2. Where correction should be made, at time t4, correction is made at temperature T1 that is higher than temperature T2 or almost unchanged from temperature T2. Therefore, if printing is started as it is at time t4, the density of the image recorded on the first or first few sheets of recording paper 40 printed before the temperature state of the heat sink 11 reaches the steady state is expected. Phenomenon that becomes thinner than what it was.

  As described above, when printing is started after a predetermined time or more (time t4) has elapsed after preheating, it is determined that the temperature of the heating resistor element group is higher than the actual temperature and is originally required. Read different LUTs. In such a case, as a result, it is substantially equivalent to the fact that the LUT is misread. The degree of such temperature misleading becomes smaller as the printer is operated continuously and the temperature gradient of the heat sink becomes substantially constant, but it appears significantly when the first sheet or the first few sheets are printed. There are many.

  In the printer control method described in FIG. 3, at time t4, since the temperature T2 of the print surface 11a is not higher than the temperature T1 of the heat dissipation surface 11b, the start of printing is not permitted and preheating is resumed. Due to the restarted preheating, at the time t5, the first temperature T1 reaches the predetermined temperature Ta, and at this time, if the second temperature T2 is higher than the first temperature T1, the preheating ends. Thereafter, at time t6, the temperatures T1 and T2 are sampled again to start printing. Due to the second preheating, the printer 1 is heated or heated not only in the print head 10 but also in the surrounding chassis and the like, and becomes close to a steady state. As a result, the relationship between the temperature T1 and the temperature T2 is reversed during the time t6 when the temperature is sampled in order to start printing from the end time t5 of the second preheating, or the temperature T1 is rapidly decreased to a predetermined value. The temperature Ta is not cut off. Therefore, the temperatures T1 and T2 sampled at time t6 satisfy the condition for starting printing, and printing is started based on the correction amount obtained from the LUT 62 by the temperature T1.

  At time t6, it is considered that the temperature gradient inside the heat radiating plate 11 is in a substantially stable steady state or a state close to this due to the relationship between the temperatures T1 and T2. , The density between the images recorded on the recording paper 40 is as planned, and the density difference or color tone difference between the images appearing on the first few sheets of recording paper can be suppressed.

As described above, according to the present embodiment, the heating resistor element _RTHf at the center of the heating resistor element group 13 is _used as a thermistor (Thermally Sensitive Resister), and an additional sampling point is provided at the center of the heating resistor element group 13, When the sampling temperature of the additional sampling point becomes higher than the sampling temperature of the heat sink 11, the start of image recording is permitted. In this state, it is considered that the temperature gradient of the heat radiating plate 11 is close to the normal use state, so that it is possible to record an image on the recording paper 40 with a substantially uniform density. In addition, according to the present embodiment, there is no cost increase as compared with the case where all of the plurality of heating resistance elements are thermistors. Moreover, since the temperature sample value of the heat sink 11 can be used for power control, an image can be recorded on the recording paper 40 at a stable density even in a normal use state.

Moreover, the heat sink 11 has both a function as a heat sink and a function as a mount for supporting the heating resistor element R. For this reason, if the first thermistor R _THr is close to the heating resistor element group 13, it may be difficult to determine the temperature gradient inside the heat sink 11 from the printed surface 11a to the heat sink 11b. On the other hand, according to the present embodiment, the first thermistor R _THr is provided on the heat radiating surface 11b away from the printed surface 11a. Therefore, it is possible to satisfactorily determine the temperature gradient inside the heat dissipation plate 11 from the printed surface 11a toward the heat dissipation surface 11b. In addition, since one heating resistor element located at the center of the plurality of heating resistors is the second thermistor _RTHf , the temperature of the heating resistor element group 13 is compared without using many thermistors. Can be accurately determined.

  In this embodiment, a thermal line printer having a print head in which a plurality of heating resistance elements are arranged in a row on one surface of the heat radiating plate is described as an example. The same operation and effect can be obtained in a printer having a print head in which resistance elements are arranged in two or more rows. Furthermore, the print head is not limited to a line head, and may be a carriage return type print head.

  Further, the shape of the heat radiating member is not limited to a flat plate shape, and may be arbitrary, and may be a finned one, a box-shaped one, or a one that also serves as a chassis. In the present embodiment, a printer that records an image on recording paper via the ink ribbon by heating the ink ribbon has been described as an example. However, a printer that heats thermal paper may be used. In the present embodiment, paper has been described as an example of the recording medium. However, the recording medium is not limited to paper, and may be a resin film, a recording medium rewritable by heating, or the like. .

  Furthermore, in the printer control method of the present embodiment, power is supplied to all the heating resistance elements R in order to preheat, but it is also possible to preheat by partially using the heating resistance elements R. is there.

In step 102, since the heating resistor elements R and R _THf are _preheated to generate heat, it is natural that the second temperature T _THf becomes higher than the first temperature T _THr . Accordingly, as a condition for stopping the preheating, the second temperature T _THf sets a condition that is higher than the first temperature T _THr is not absolutely necessary.

Furthermore, in this embodiment, the recording power supplied to the heating resistance elements R and R _THf is set by reading the _{LUT 62. However} , the recording power supplied to the heating resistance elements R and R _THf is set as follows: You may perform by the calculation by arbitrary functions.

FIG. 2 is a diagram illustrating a schematic configuration of a printer. The circuit diagram which shows a thermal control mechanism including CPU. 3 is a flowchart illustrating a printer control method. The figure which shows the time-dependent change of each temperature of a heating resistive element group and a heat sink.

Explanation of symbols

10 Print head, 11 Heat sink (Heat dissipation member)
15 circuits, 40 recording paper (recording medium)
50 controller, 60 memory R _THr first thermistor (first temperature measuring element)
R heating resistance element, R _THf heating resistance element that also serves as the second thermistor

Claims (6)

A printer control method comprising a print head comprising a plurality of heating resistance elements arranged in at least one row on a part of a heat dissipation member, and recording an image on a recording medium by the print head,
A first step of supplying power to at least some of the plurality of heating resistance elements to preheat the print head;
In order to start recording an image on the recording medium, a first temperature is acquired from at least one location of the heat radiating member, and a second temperature is acquired from at least one heating resistance element of the plurality of heating resistance elements. A second step;
A third step of permitting the start of image recording on the recording medium when the first temperature is higher than a predetermined temperature and the second temperature is higher than the first temperature. Control method.   2. The control method according to claim 1, wherein, in the second step, the temperature of the part of the heat radiating member away from the plurality of heating resistance elements is sampled as the first temperature.   3. The control method according to claim 1, wherein, in the second step, the second temperature is sampled by switching a circuit of the at least one heating resistor element.   2. The control method according to claim 1, wherein, in the third step, the first step is resumed when it is impossible to start recording an image on the recording medium. A printer having a print head for recording an image on a recording medium,
The print head is a heat dissipation member,
A plurality of heating resistance elements arranged in at least one row on a part of the heat dissipation member;
A first temperature measuring element attached to the heat dissipating member at a position away from the plurality of heating resistance elements;
A circuit that switches at least one of the plurality of heating resistance elements to be used as a second temperature measurement element,
The printer further includes
Power is supplied to at least some of the plurality of heating resistance elements for preheating, and then a first temperature measured by the first temperature measurement element and a second temperature measured via the switching circuit. Referring to the temperature of, we have a controller with a function of starting the recording by said print head,
The controller supplies a power to at least a part of the plurality of heating resistance elements to preheat the plurality of heating resistance elements;
In order to start recording an image on the recording medium, a first temperature is measured by the first temperature measuring element, and a second temperature is measured by the at least one heating resistor element by the switching circuit. Functions and
And a third function of starting image recording on the recording medium when the first temperature is higher than a predetermined temperature and the second temperature is higher than the first temperature . According to claim 5, for recording an image on the recording medium, the information for setting the recording power supplied to the plurality of heating elements based on the temperature information obtained by the first temperature measuring element Further having a stored memory;
The third function is a printer that sets the recording power to be supplied to a plurality of heating resistance elements based on the first temperature.

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