JP2004025632A - Thermal head controller and printer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To control the conduction time such that the conduction amount of a heating element approaches the actually required conduction amount furthermore. <P>SOLUTION: Conduction time of a heating element is determined according to formula (1), t<SB>k</SB>(v)=t0<SB>k</SB>(v)×(a(v)/AD(temp.)+b(v)). The t0<SB>k</SB>(v) on the right side of the formula (1) is a main factor determining the conduction time and depends on the head voltage. The right side of the formula (1) other than the t0<SB>k</SB>(v) represents the temperature correction factor for the main factor. In the temperature correction factor, a(v) and b(v) other than AD (temperature) dependent on the environmental temperature of the heating element are correction coefficients being determined depending on the machine type of a printer and they are functions of the head voltage. <P>COPYRIGHT: (C)2004,JPO

Description

【００３８】
式（１）において、ｔ０_ｋ（ｖ）は通電時間を決定する主因子であって、ヘッド電圧の大きさに応じた値を持っている。ｔ０_ｋ（ｖ）の値は、所定範囲に区切られたヘッド電圧とそれぞれ対応させたテーブルに記憶されている。そして、ｔ値算出部３２は、ヘッド電圧記憶部３６に記憶されたヘッド電圧に対応したｔ０_ｋ（ｖ）をテーブルから読み出す。或いは、ｔ値算出部３２は、所定の演算式に基づいてヘッド電圧記憶部３６に記憶されたヘッド電圧からｔ０_ｋ（ｖ）を算出してもよい。
【００３９】
式（１）の右辺内のｔ０_ｋ（ｖ）以外の部分は、主因子に対する温度補正因子である。ＡＤ（温度）は、サーミスタ２７から制御部３１に与えられて環境温度記憶部３７に記憶された電圧であって発熱素子２８の環境温度を表しており、温度が上昇するに連れて小さくなる。
【００４０】
ａ（ｖ）及びｂ（ｖ）は共にプリンタ機種に応じて定められる補正係数であって、ヘッド電圧の大きさに応じた値を持っている。ａ（ｖ）及びｂ（ｖ）の値は、所定範囲に区切られたヘッド電圧とそれぞれ対応させたテーブルに記憶されている。そして、ｔ値算出部３２は、ヘッド電圧記憶部３６に記憶されたヘッド電圧に対応したａ（ｖ）及びｂ（ｖ）をテーブルから読み出す。或いは、ｔ値算出部３２は、所定の演算式に基づいてヘッド電圧記憶部３６に記憶されたヘッド電圧からａ（ｖ）及びｂ（ｖ）を算出してもよい。
【００４１】
ｔ値算出部３２は、上述したｔ０_ｋ（ｖ）、ＡＤ（温度）、ａ（ｖ）及びｂ（ｖ）の値から、式（１）に基づいてｔ_ｋ（ｖ）を算出する。或いは、温度及びヘッド電圧の異なる組み合わせごとにｔ_ｋ（ｖ）の値がテーブルに記憶されており、ｔ値算出部３２がｔ_ｋ（ｖ）をテーブルから読み出してもよい。
【００４２】
このようにして算出されたｔ_ｋ（ｖ）の値は、その時点での発熱素子の環境温度及びヘッド電圧を考慮したものとなっている。なお、ｔ値算出部３２は、所定温度制御範囲（例えば１０℃〜３５℃）内においてのみｔ値を算出し、それ以外の温度範囲では所定温度制御範囲の下限又は上限での値（例えば１０℃未満では１０℃でのｔ値、３５℃を超える場合は３５℃でのｔ値）を与えるものであってよい。
【００４３】
ｆ値算出部３３は、ｔ値が算出されるごとに、以下に示す式（２）にしたがってｆ（ｎ）値を算出する。判断部３４は、ｆ値算出部３３がｆ（ｎ）値を算出した直後に、ｆ（ｎ）値がゼロ以下（ｆ（ｎ）≦０）となったかどうか（通電終了条件）を判断する。なお、式（２）において、Ｃはプリンタの機種など様々な条件に基づいて定められた定数である。
【００４４】
【数２】

【００４５】
信号生成部３５は、印刷データのオンドットに対応した通電すべき発熱素子に適切なタイミングでヘッド電圧の印加が開始されるような、印刷データに相当する制御信号を生成してヘッドドライバ２６に与える。また、信号生成部３５は、判断部３４によって通電中の発熱素子に関して通電終了条件が満たされたと判断されると、制御信号の生成を中止する。つまり、発熱素子は、信号生成部３５が制御信号をヘッドドライバ２６に供給している間だけ通電されることになる。
【００４６】
このように、本実施の形態においては、ｆ（ｎ）値がゼロ以下になった時点でのｋをｎとしたとき、以下に示す式（３）にしたがって決定される時間が発熱素子への通電時間Ｔｏｎとされる。なお、式（３）において、ｓは上述した所定の温度測定間隔を表している。タイマー３８は、この所定の温度測定間隔を測定するために設けられたものである。
【００４７】
【数３】

【００４８】
次に、本実施の形態に基づいた通電時間制御を含む印刷手順を説明する。まず、図６のステップＳ１において、サーミスタ２７を用いて発熱素子２８の環境温度を読み取り、環境温度記憶部３７に格納する。そして、ステップＳ２において、信号生成部３５から１ライン分の印刷データがヘッドドライバ２６を介してサーマルヘッド１５へ転送され、これにより、ステップＳ３においてサーマルヘッド１５への通電が開始される。そして、ステップＳ４において、タイマー３８が２５０μｓの計測を開始する。
【００４９】
ステップＳ５では、タイマー３８の計測開始時刻から２５０μｓが経過したかどうかが繰り返して判断される。そして、２５０μｓ経過した場合（Ｓ５：ＹＥＳ）、ステップＳ６に進んで、ヘッドドライバ２６からヘッド電圧を読み取り、ヘッド電圧記憶部３６に格納する。なお、すでにヘッド電圧記憶部３６にヘッド電圧が記憶されている場合には、その値が最新の値に書き換えられる。
【００５０】
続いて、ステップＳ７では、ヘッド電圧記憶部３６に記憶されたヘッド電圧に応じたｔ０_ｋ（ｖ）、ａ（ｖ）及びｂ（ｖ）の値を、ｔ値算出部３２が上述したテーブルから読み出す。そして、ステップＳ８において、ｔ値算出部３２が、ステップＳ７で読み出したｔ０_ｋ（ｖ）、ａ（ｖ）及びｂ（ｖ）の値と、環境温度記憶部３７に記憶されたＡＤ（温度）とを用いて、式（１）に基づいてｔ_ｋ（ｖ）を算出する。
【００５１】
次に、ステップＳ９では、ｆ値算出部３３によって式（２）にしたがってｆ（ｎ）値が算出される。続いて、ステップＳ１０では、ｆ（ｎ）値がゼロ以下となったかどうかが判断部３４によって判断される。ｆ（ｎ）＞０と判断された場合（Ｓ１０：ＮＯ）、ステップＳ４に戻って、ステップＳ４からステップＳ１０にかけての動作を再度行う。
【００５２】
一方、ステップＳ１０でｆ（ｎ）≦０と判断された場合（Ｓ１０：ＹＥＳ）、ステップＳ１１に進んで、発熱素子への通電終了処理が行われる。つまり、信号生成部３５が制御信号をヘッドドライバ２６に供給するのを停止する。これにより、当該発熱素子への駆動信号の供給は停止されて通電が終了する。
【００５３】
引き続き、ステップＳ１２では、１ライン分の所定印刷周期が終了したかどうかが繰り返して判断される。そして、所定印刷周期が終了した場合（Ｓ１２：ＹＥＳ）、ステップＳ１３に進む。ステップＳ１３では、全ラインの印刷が終了したかどうかが判断される。そして、全ラインの印刷が終了していないと判断された場合には（Ｓ１３：ＮＯ）、ステップＳ２に戻って、ステップＳ４からステップＳ１３にかけての動作を再度行う。一方、全ラインの印刷が終了したと判断された場合には（Ｓ１３：ＹＥＳ）、本実施の形態に係る印刷動作を終了する。
【００５４】
このように、本実施の形態では、温度補正因子（式（１）右辺においてｔ０_ｋ（ｖ）以外の部分）の補正係数ａ（ｖ）、ｂ（ｖ）がそれぞれヘッド電圧の関数になっている。つまり、温度補正因子が発熱素子の環境温度（式（１）右辺においてＡＤ（温度）で表される）とヘッド電圧との関数として決定される。従って、主因子ｔ０_ｋ（ｖ）だけにおいてヘッド電圧を考慮して通電時間を決定している場合よりもヘッド電圧の変動が十分に考慮されることになって小さな誤差で通電時間を決定することができる。従って、今までよりも通電時間を短めに設定してもカスレた画像が印刷されることが少なくなり高品質の画像が得られるようになる。そのため、電力消費量を抑制することが可能となって、電源としてバッテリが用いられた場合であっても、比較的長い総印刷可能時間が得られる。
【００５５】
特に、本実施の形態では、温度補正因子の２つの項（つまり、ａ（ｖ）／ＡＤ（温度）と、ｂ（ｖ））がともにヘッド電圧の関数である。そして、前者は発熱素子の環境温度及びヘッド電圧の両方の関数であり、後者はヘッド電圧だけの関数である。そのために、発熱素子への通電量をさらに実際の所要通電量に近づけることが可能となっており、従って、電力消費量の一層の低減化によってさらに長い総印刷可能時間が得られる。
【００５６】
また、上述したような通電時間制御は、発熱素子の環境温度及びヘッド電圧の変化履歴を考慮してこれらが急激に変動した場合にも対応可能であるために、電源としてバッテリが用いられた場合のようにヘッド電圧の変動が大きく、またこれを印刷開始前にあらかじめ予測しておくことが困難であるときに有効である。
【００５７】
以上、本発明の好適な実施の形態について説明したが、本発明は上述の実施の形態に限られるものではなく、特許請求の範囲に記載した限りにおいて様々な設計変更が可能なものである。例えば、上述の実施の形態において２つの補正係数ａ（ｖ）、ｂ（ｖ）がともにヘッド電圧の関数であるが、いずれか一方だけがヘッド電圧の関数で、他方は単なる定数であってもよい。通電時間制御に関する具体的な式の形は上述した式（１）〜式（３）に限られるものではなく、様々な形とすることが可能である。また、発熱素子の環境温度を検出するための環境温度検出手段やヘッド電圧を検出するためのヘッド電圧検出手段としては、上述したようなものに限らず、公知の技術をいずれも使用することが可能である。また、上述した実施の形態では、発熱素子への通電時間を制御する制御部３１がプリンタ１内に配置されているが、制御部３１は必ずしもプリンタ１内に配置されていなくてもよく、例えばこれと接続されたコンピュータ内に設けられていてもよい。
【００５８】
【発明の効果】
以上説明したように、本発明によると、通電時間内での発熱素子への通電量を今までよりもさらに所要通電量に近づけることができるので、今までよりも通電時間を短めに設定してもカスレた画像が印刷されることが少ない高品質の画像が得られるようになる。そのため、電力消費量を抑制することが可能となって、電源としてバッテリが用いられた場合であっても、比較的長い総印刷可能時間が得られる。
【図面の簡単な説明】
【図１】本発明のサーマルヘッド制御装置の一実施の形態である制御部が含まれたプリンタの斜視図である。
【図２】図１に示されたプリンタの側面断面図である。
【図３】図１に示されたプリンタの用紙収容部に用紙をセットした状態を示した図である。
【図４】図１に示されたプリンタの用紙分離部及び印刷機構部の詳細を示した拡大断面図である。
【図５】図１に示されたプリンタにおける通電時間制御に関連したブロック図である。
【図６】図１に示されたプリンタにおける通電時間制御を含む印刷動作を説明するためのフローチャートである。
【符号の説明】
１　プリンタ
１５　サーマルヘッド
１６　プラテンローラ
１７　ペーパーガイド
２６　ヘッドドライバ
２７　サーミスタ
２８　発熱素子
３１　制御部
３２　ｔ値算出部
３３　ｆ値算出部
３４　判断部
３５　信号生成部
３６　ヘッド電圧記憶部
３７　環境温度記憶部
３８　タイマー[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a thermal head control device for controlling a thermal head included in a thermal printer and a printer including the same.
[0002]
[Prior art]
The thermal printer has a thermal head on which a number of heating elements are arranged. When power is supplied to the heating element corresponding to the on-dot of the print data among these many heating elements, the ink of the ink ribbon is transferred to the paper (thermal transfer method) or the paper itself develops a color (thermal recording method). ), An image based on the print data is formed on a sheet.
[0003]
In such a thermal printer, in order to obtain an image having a density equal to or higher than a desired density without blur, the amount of current supplied to the heating element (defined by the driving voltage (head voltage) supplied to the heating element and the current supply time) Must be more than a certain amount. On the other hand, even if the amount of current supplied to the heating element is larger than the above-mentioned fixed amount, the density of the printed image is not substantially changed only by increasing the power consumption. For this reason, it is preferable that the amount of current supplied to the heating element is set to a necessary minimum as long as the image is not blurred.
[0004]
The required minimum amount of current depends on the environmental temperature of the heating element. Normally, the required minimum amount of power supply decreases when the environmental temperature is high, and the required minimum amount of power supply increases when the environmental temperature is low. Therefore, in controlling the amount of power supply to the heating element, the power supply time is controlled based on the environmental temperature detected by the sensor while taking into account the head voltage.
[0005]
[Problems to be solved by the invention]
However, the energization time determined based on the above-described environmental temperature is based on a power supply that is maintained at a substantially constant voltage such as a commercial power supply, and the voltage greatly fluctuates as time passes, such as a battery. The fact is that power supplies are not sufficiently considered and errors are large. Therefore, when a battery is used as a power source, the energization time to the heating element is set to be longer so that the energization amount always exceeds the minimum necessary energization amount in order to prevent a printed image from being blurred. There is a need. Therefore, a situation has occurred in which the battery is quickly consumed and the total printable time with the battery is shortened, and a solution is desired. Further, even when a commercial power supply is used as the power supply, by controlling the energization time to the heating element to a time as short as possible within a range in which a necessary minimum energization amount for obtaining a blur-free image is secured. It is desired to further reduce power consumption. In order to satisfy these demands, the error between the amount of current supplied to the heating element and the actual required amount of current (for example, the minimum amount of current required to obtain an image without blurring) should be reduced more than ever. It is necessary to control the energization time more precisely.
[0006]
Therefore, an object of the present invention is to provide a thermal head control device capable of controlling the energization time so that the amount of energization to the heating element approaches the actual required amount of energization more than ever, and a printer including the same. It is to be.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a thermal head control device for controlling an energizing time to a heating element corresponding to an on-dot among a large number of heating elements included in a thermal head. The energization time is determined based on a main factor that is a function of the head voltage applied to the heating element and its temperature correction factor, and the temperature correction factor is a function of the ambient temperature of the heating element and the head voltage. It is a variable to be determined (claim 1).
[0008]
According to the present invention, the temperature correction factor that determines the energizing time to the heating element together with the main factor is determined not as a function of only the environmental temperature of the heating element but as a function of the environmental temperature and the head voltage. Can be made closer to the required amount of power (for example, the minimum amount of power required to obtain a printed image without blurring) than before. Therefore, even if the power-on time is set shorter than before, a high-quality image in which a blurred image is hardly printed can be obtained. Therefore, power consumption can be suppressed, and a relatively long total printable time can be obtained even when a battery is used as a power supply.
[0009]
In the present invention, the temperature correction factor has a plurality of terms each of which is a function of a head voltage, and the plurality of terms are a function of both the environmental temperature of the heating element and the head voltage. There may be a term and a term that is a function of only the head voltage (claim 2).
[0010]
According to this configuration, it is possible to make the amount of current supplied to the heating element closer to the actual required amount of current. Accordingly, a longer total printable time can be obtained by further reducing the power consumption.
[0011]
According to another aspect of the present invention, there is provided a thermal head control device according to claim 1 or 2, a thermal head, a head voltage detecting means for detecting a head voltage, and an environmental temperature of the heating element. The printer is provided with an environmental temperature detecting means for detecting.
[0012]
According to this configuration, it is possible to obtain a printer having excellent characteristics and exhibiting the above-described effects.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
[0014]
First, a schematic structure of a printer including a thermal head control device according to an embodiment of the present invention will be described with reference to FIGS. The printer 1 whose perspective view is shown in FIG. 1 is of a thermal printing type, and is designed on the assumption that it is carried around and used with a portable personal computer. The printer 1 has a configuration in which the size in a plan view is approximately A6 size or A7 size and the thickness is approximately 2 cm or less, and the compactness is particularly emphasized.
[0015]
The printer 1 is connected to a computer via a cable (not shown). When the user instructs a computer program to print, the program generates a print command, and the printer 1 receives the print command from the computer and performs a printing operation. The power for printing is supplied from a rechargeable battery (not shown) provided inside the printer 1.
[0016]
The main body case 2 of the printer 1 is formed by covering the lower surface of the frame 3 with the lower cover 4 and partially covering the upper surface with the upper cover 5. In the remaining portion of the upper surface of the frame body 3 except for the portion covered by the upper cover 5, a paper storage portion (paper feed portion) 6 is formed as shown in FIG. As shown in FIG. 3, a plurality of A6-A7 size cut sheet-shaped thermal papers (recording media; hereinafter, referred to as “papers”) 7 are stored in the paper storage unit 6 in the paper storage unit 6. The paper package 9 can be set. A control unit 31 (see FIG. 5) for controlling the operation of each unit of the printer 1 is disposed below the horizontally extending frame 3 below the paper storage unit 6. The control unit 31 is an embodiment of the thermal head control device according to the present invention.
[0017]
As shown in FIG. 2, four reflection type package detection sensors 23 are embedded in the end portion of the bottom plate portion of the sheet storage portion 6 with their light receiving portions facing upward. On the other hand, in the package material 8 of the paper package 9, an identification mark indicating information on the type of paper is attached at a position facing the position of the sensor 23 (not shown). The identification marks are arranged in four places corresponding to the number of the package detection sensors 23, and 0 to 3 places are colored black while the remaining places are not colored, and the remaining places are not colored. The color (white) remains. This black-and-white pattern corresponds to the type of paper stored in the package material 8 (for example, a normal type thermal paper, a thermal paper capable of two-color development, a label paper, a copy paper capable of simultaneously printing two sheets, etc.). Is predetermined in accordance with. The printer 1 reads the pattern with the package detection sensor 23 to automatically identify the type of paper.
[0018]
The pattern of the four black and white combinations is 2 ⁴ = 16 patterns are possible, but as a result of not using a pattern colored black at all four places, the number of types of paper that can be represented is 16-1 = 15. The reason why a pattern in which all four portions are colored black is not attached to the package material 8 is that when the paper package 9 is not set in the paper storage unit 6 in the first place, the package detection sensors 23 emit reflected light. In order to make it possible for the printer to determine that the paper package 9 is not set in the paper storage unit 6 when all of the package detection sensors 23 detect black using the detection of black without detection. It is.
[0019]
The upper part of the paper storage unit 6 is covered with a lid 10, and the lid 10 is rotatable as shown in FIG. A lock mechanism (not shown) is provided on the main body case 2 side. With the paper package 9 set in the paper storage section 6 as described above, the lid 10 can be closed and locked as shown in FIG. Has become.
[0020]
At one end of the sheet storage unit 6, a pickup roller 12 as a sheet separation unit 11, a separation block 13, and the like are arranged. Below the upper cover 5, a thermal head 15, a platen roller 16, and a paper guide 17 as a printing mechanism (printing unit) 14, which will be described in detail later, are arranged.
[0021]
The details of the sheet separating unit 11 will be described. A pickup roller 12 and a separation block 13 are provided at an end of the paper storage unit 6 on the side close to the printing mechanism unit 14. On the pickup roller 12 side of the separation block 13 disposed close to the pickup roller 12, a separation guide surface 13a inclined with respect to the sheet feeding direction of the pickup roller 12 is provided. A pressing plate 18 is rotatably supported on the inner surface of the lid 10 facing the paper storage unit 6 side. A coil-shaped urging spring 19 is interposed between the pressing plate 18 and the lid 10. The urging spring 19 constantly applies an urging force to the pressing plate 18 in a direction for rotating the pressing plate 18 downward.
[0022]
The paper package 9 is a state in which the lower surface of the lowermost paper 7 among the papers 7 housed inside in a stacked state with the printing surface facing downward is partially exposed from the package material 8. Is set in the sheet storage unit 6. When the lid 10 is closed and locked, the pressing plate 18 urged downward by the urging spring 19 presses the exposed portion of the paper 7 toward the pickup roller 12 via the package material 8. Then, the lower surface of the paper 7 is brought into contact with the pickup roller 12.
[0023]
Therefore, when the pickup roller 12 is rotationally driven, a conveying force is applied to the lowermost sheet 7 that comes into contact with the pickup roller 12. Then, in combination with the separation action of the separation guide surface 13a of the separation block 13, only one sheet 7 located at the lowermost layer is separated and sent out.
[0024]
Details of the printing mechanism unit 14 will be described. At a position adjacent to the separation block 13, a platen roller 16 is rotatably mounted. A paper guide 17 is arranged at a position close to the outer peripheral surface of the platen roller 16. As shown in the enlarged view of FIG. 4, the paper guide 17 has a concave curved sliding contact surface 17 a having a substantially U-shaped cross section along the outer peripheral surface of the platen roller 16. Have been. A pressing coil spring 20 is provided between the paper guide 17 and the main body case 2, and urges the sliding contact surface 17 a toward the outer peripheral surface of the platen roller 16.
[0025]
In this configuration, the sheet 7 separated by the above-described sheet separation unit 11 is conveyed by the pickup roller 12, and forms the lower end of the separation block 13 with the guide plate 21 for directing the sheet to the platen roller 16 side. Pass through. The paper 7 is guided by the guide plate 21, and is fed between the platen roller 16 and the paper guide 17 from the lower surface side of the platen roller 16. The paper 7 is conveyed while being held between the outer peripheral surface of the platen roller 16 and the sliding contact surface 17a of the paper guide 17 while being inverted in a horizontal U-shape by the rotation of the platen roller 16, and the printing surface is turned upward. While reaching the upper surface of the platen roller 16.
[0026]
The thermal head 15 located on the upper surface side of the platen roller 16 has a heating element 15a serving as a printing section, and a large number of small heating elements 28 (see FIG. 5) are arranged in the heating element section 15a in the paper width direction. . The thermal head 15 is provided so as to be rotatable around a rotation shaft 15 b, and the heating element 15 a can be brought into contact with and separated from the upper surface of the platen roller 16. The reason why the thermal head 15 is configured to be rotatable in this manner is that the thermal head 15 hinders the work in the jam paper removal operation when the paper 7 is jammed between the platen roller 16 and the paper guide 17. This is so as not to be.
[0027]
One end of a torsion coil spring type spring 22 is locked to the thermal head 15, and the heating element 15 a of the thermal head 15 constantly applies a biasing force in a direction approaching the upper surface of the platen roller 16. With this configuration, as described above, the heating element 15a of the thermal head 15 contacts the upper surface of the paper 7 sent by the platen roller 16 with the print surface facing upward, and printing is performed on the paper 7 at the contacting point. Done.
[0028]
The thermal head 15 is of a line head type, and can print arbitrary characters and images on the heat-sensitive paper 7 being conveyed for each line extending in a direction perpendicular to the conveyance direction of the paper 7. The printing width when printing per line is set substantially equal to the width of the paper 7 to be printed.
[0029]
The use of the thermal head 15 as a print head in this manner can eliminate the need for consumables such as ink and an ink ribbon by using thermal paper as a recording medium, and can omit a mechanism for supplying ink. This is because the printer 1 can be made compact.
[0030]
As the thermal paper, various types such as a thermal coloring type having a coloring layer that develops a color by heating the thermal head 15 and a thermal piercing type in which a piercing layer pierced by heating is laminated on a substrate layer are available. Can be used.
[0031]
As shown in FIG. 4, a head driver 26 and a thermistor 27 are arranged on the lower surface of the thermal head 15. The head driver 26 receives a command from the control unit 31 described above, generates a drive signal for the heating element 28, and supplies it to the heating unit 15a. The thermistor 27 functions as a sensor for detecting the environmental temperature of the heating element 28.
[0032]
The separation block 13 has a paper discharge guide surface 13b that is inclined with respect to the paper feeding direction of the platen roller 16. The paper 7 on which printing has been performed by the heating element portion 15a of the thermal head 15 is guided by a paper discharge guide surface 13b, and as shown in FIG. The paper is discharged to the upper side of the lid 10 from the gap formed.
[0033]
Next, details of the power-on time control in the printer 1 will be described with further reference to FIGS. FIG. 5 is a block diagram of the printer 1 related to the energization time control, and FIG. 6 is a flowchart for explaining the operation of the printer 1 regarding the energization time control. In FIG. 5, members that are less relevant to the control of the power distribution time, such as a motor for rotating the pickup roller 12, are omitted.
[0034]
As shown in FIG. 5, the control unit 31 of the printer 1 includes a t value calculation unit 32, an f value calculation unit 33, a determination unit 34, a signal generation unit 35, a head voltage storage unit 36, an environmental temperature storage unit 37, a timer 38 are provided. These are constructed by combining hardware such as a CPU and a RAM arranged in the control unit 31 with software such as a control program of the printer 1.
[0035]
The controller 31 receives a signal indicating the ambient temperature of the heating element from the thermistor 27 and a signal indicating the head voltage from the head driver 26. For example, the signal indicating the head voltage may be a signal obtained by dividing the head voltage by a resistor connected in series. The signal indicating the head voltage and the signal indicating the environmental temperature of the heating element are directly supplied to, for example, an analog input port of the CPU. Then, the signal indicating the head voltage and the signal indicating the environmental temperature of the heating element are stored as digital signals in the head voltage storage unit 36 and the environmental temperature storage unit 37, respectively.
[0036]
The t-value calculating unit 32 calculates the value of t until the power supply termination condition described later is satisfied at a predetermined temperature measurement interval (250 μs in the present embodiment) from the start of power supply to the heating element according to the following equation (1). Value (= t _k (V)) is sequentially calculated. k is a natural number, and increases by one each time the t value is calculated from the start time of energization of the heating element. That is, the initially calculated t value is t ₁ (V) The t value calculated 250 μs after that is t ₂ (V) The t value calculated 250 μs after that is t ₃ (V).
[0037]
(Equation 1)

[0038]
In equation (1), t0 _k (V) is a main factor for determining the energization time, and has a value corresponding to the magnitude of the head voltage. t0 _k The value of (v) is stored in a table corresponding to each of the head voltages divided into a predetermined range. Then, the t value calculation unit 32 calculates t0 corresponding to the head voltage stored in the head voltage storage unit 36. _k (V) is read from the table. Alternatively, the t-value calculation unit 32 calculates t0 from the head voltage stored in the head voltage storage unit 36 based on a predetermined arithmetic expression. _k (V) may be calculated.
[0039]
T0 in the right side of equation (1) _k The part other than (v) is a temperature correction factor for the main factor. AD (temperature) is a voltage supplied from the thermistor 27 to the control unit 31 and stored in the environmental temperature storage unit 37 and represents the environmental temperature of the heating element 28, and decreases as the temperature rises.
[0040]
Both a (v) and b (v) are correction coefficients determined according to the printer model, and have values corresponding to the magnitude of the head voltage. The values of a (v) and b (v) are stored in a table corresponding to each of the head voltages divided into a predetermined range. Then, the t value calculation unit 32 reads a (v) and b (v) corresponding to the head voltage stored in the head voltage storage unit 36 from the table. Alternatively, the t value calculation unit 32 may calculate a (v) and b (v) from the head voltage stored in the head voltage storage unit 36 based on a predetermined arithmetic expression.
[0041]
The t value calculation unit 32 calculates the value of t0 described above. _k From the values of (v), AD (temperature), a (v) and b (v), t _k (V) is calculated. Alternatively, t for each different combination of temperature and head voltage. _k The value of (v) is stored in the table, and the t value calculation unit 32 _k (V) may be read from the table.
[0042]
The t calculated in this way _k The value of (v) takes into account the environmental temperature of the heating element and the head voltage at that time. The t value calculation unit 32 calculates the t value only within a predetermined temperature control range (for example, 10 ° C. to 35 ° C.), and in the other temperature range, the value at the lower limit or the upper limit (for example, 10 ° C.) of the predetermined temperature control range. If it is less than 0 ° C, the t value at 10 ° C, and if it exceeds 35 ° C, the t value at 35 ° C) may be given.
[0043]
Each time the t value is calculated, the f value calculation unit 33 calculates the f (n) value according to the following equation (2). The determination unit 34 determines whether or not the f (n) value has become equal to or less than zero (f (n) ≦ 0) immediately after the f-value calculation unit 33 calculates the f (n) value (energization termination condition). . In the equation (2), C is a constant determined based on various conditions such as a printer model.
[0044]
(Equation 2)

[0045]
The signal generation unit 35 generates a control signal corresponding to the print data so that the application of the head voltage is started at an appropriate timing to the heating element to be energized corresponding to the on-dot of the print data, and sends the control signal to the head driver 26. give. In addition, the signal generation unit 35 stops generating the control signal when the determination unit 34 determines that the energization termination condition is satisfied for the heating element that is energized. That is, the heating element is energized only while the signal generation unit 35 supplies the control signal to the head driver 26.
[0046]
As described above, in the present embodiment, when k at the time when the f (n) value becomes equal to or less than zero is set to n, the time determined according to the following expression (3) is applied to the heating element. The energization time is Ton. In the equation (3), s represents the above-mentioned predetermined temperature measurement interval. The timer 38 is provided for measuring the predetermined temperature measurement interval.
[0047]
[Equation 3]

[0048]
Next, a printing procedure including power-on time control based on the present embodiment will be described. First, in step S <b> 1 of FIG. 6, the environmental temperature of the heating element 28 is read using the thermistor 27 and stored in the environmental temperature storage unit 37. Then, in step S2, the print data for one line is transferred from the signal generation unit 35 to the thermal head 15 via the head driver 26, whereby the energization of the thermal head 15 is started in step S3. Then, in step S4, the timer 38 starts measuring 250 μs.
[0049]
In step S5, it is repeatedly determined whether 250 μs has elapsed from the measurement start time of the timer 38. When 250 μs has elapsed (S5: YES), the process proceeds to step S6, where the head voltage is read from the head driver 26 and stored in the head voltage storage unit 36. If the head voltage has already been stored in the head voltage storage unit 36, that value is rewritten to the latest value.
[0050]
Subsequently, in step S7, t0 according to the head voltage stored in the head voltage storage unit 36 is set. _k The values of (v), a (v), and b (v) are read from the above-described table by the t-value calculator 32. Then, in step S8, the t value calculation unit 32 reads out the t0 read in step S7. _k Using the values of (v), a (v) and b (v) and the AD (temperature) stored in the environmental temperature storage unit 37, t _k (V) is calculated.
[0051]
Next, in step S9, the f (n) value is calculated by the f value calculation unit 33 according to equation (2). Subsequently, in step S10, the determination unit 34 determines whether the f (n) value has become zero or less. When it is determined that f (n)> 0 (S10: NO), the process returns to step S4, and the operation from step S4 to step S10 is performed again.
[0052]
On the other hand, if it is determined in step S10 that f (n) ≦ 0 (S10: YES), the process proceeds to step S11, and a process of terminating the power supply to the heating element is performed. That is, the signal generation unit 35 stops supplying the control signal to the head driver 26. Thus, the supply of the drive signal to the heating element is stopped, and the energization ends.
[0053]
Subsequently, in step S12, it is repeatedly determined whether or not the predetermined printing cycle for one line has ended. Then, when the predetermined printing cycle has ended (S12: YES), the process proceeds to step S13. In step S13, it is determined whether printing of all lines has been completed. If it is determined that printing of all the lines has not been completed (S13: NO), the process returns to step S2, and the operation from step S4 to step S13 is performed again. On the other hand, if it is determined that the printing of all lines has been completed (S13: YES), the printing operation according to the present embodiment ends.
[0054]
As described above, in the present embodiment, the temperature correction factor (t0 on the right side of Equation (1)) _k The correction coefficients a (v) and b (v) of (parts other than (v)) are functions of the head voltage. That is, the temperature correction factor is determined as a function of the ambient temperature of the heating element (represented by AD (temperature) on the right side of Equation (1)) and the head voltage. Therefore, the main factor t0 _k In the case of (v) only, the fluctuation of the head voltage is sufficiently considered as compared with the case where the energizing time is determined in consideration of the head voltage, so that the energizing time can be determined with a small error. Therefore, even if the energization time is set shorter than before, a blurred image is less likely to be printed, and a high-quality image can be obtained. Therefore, power consumption can be suppressed, and a relatively long total printable time can be obtained even when a battery is used as a power supply.
[0055]
In particular, in the present embodiment, the two terms of the temperature correction factor (that is, a (v) / AD (temperature) and b (v)) are both functions of the head voltage. The former is a function of both the ambient temperature of the heating element and the head voltage, and the latter is a function of only the head voltage. For this reason, the amount of current supplied to the heating element can be made closer to the actual required amount of current supplied. Therefore, a longer total printable time can be obtained by further reducing the power consumption.
[0056]
In addition, since the energization time control as described above can cope with a sudden change in the environmental temperature of the heating element and the change history of the head voltage in consideration of the change history, when a battery is used as a power supply, This is effective when the fluctuation of the head voltage is large and it is difficult to predict this before starting printing.
[0057]
The preferred embodiment of the present invention has been described above. However, the present invention is not limited to the above-described embodiment, and various design changes can be made within the scope of the appended claims. For example, in the above-described embodiment, the two correction coefficients a (v) and b (v) are both functions of the head voltage, but only one of them is a function of the head voltage and the other is a simple constant. Good. The specific form of the equation regarding the energization time control is not limited to the above-described equations (1) to (3), but may be various forms. Further, the environmental temperature detecting means for detecting the environmental temperature of the heating element and the head voltage detecting means for detecting the head voltage are not limited to those described above, and any known technique may be used. It is possible. Further, in the above-described embodiment, the control unit 31 that controls the energization time to the heating element is disposed in the printer 1, but the control unit 31 may not necessarily be disposed in the printer 1, for example, It may be provided in a computer connected to this.
[0058]
【The invention's effect】
As described above, according to the present invention, the energization amount to the heating element within the energization time can be closer to the required energization amount than before, so that the energization time is set shorter than before. Also, a high-quality image in which a blurred image is hardly printed can be obtained. Therefore, power consumption can be suppressed, and a relatively long total printable time can be obtained even when a battery is used as a power supply.
[Brief description of the drawings]
FIG. 1 is a perspective view of a printer including a control unit which is an embodiment of a thermal head control device of the present invention.
FIG. 2 is a side sectional view of the printer shown in FIG.
FIG. 3 is a diagram illustrating a state in which paper is set in a paper storage unit of the printer illustrated in FIG. 1;
FIG. 4 is an enlarged cross-sectional view illustrating details of a sheet separating unit and a printing mechanism unit of the printer illustrated in FIG. 1;
FIG. 5 is a block diagram related to power-on time control in the printer shown in FIG. 1;
FIG. 6 is a flowchart for explaining a printing operation including power-on time control in the printer shown in FIG. 1;
[Explanation of symbols]
1 Printer
15 Thermal head
16 Platen roller
17 Paper Guide
26 Head Driver
27 Thermistor
28 Heating element
31 Control unit
32 t value calculation unit
33 f-value calculator
34 Judgment Department
35 signal generator
36 Head voltage storage
37 Environmental temperature storage
38 timer

Claims (3)

In a thermal head control device for controlling an energizing time to a heating element corresponding to an on-dot among a large number of heating elements included in a thermal head,
The energization time to the heating element is determined based on a main factor that is a function of a head voltage applied to the heating element and a temperature correction factor thereof, and the temperature correction factor is determined based on an ambient temperature of the heating element and A thermal head controller, wherein the variable is determined as a function of a head voltage. The temperature correction factor has a plurality of terms, each of which is a function of the head voltage. 2. The thermal head control device according to claim 1, wherein a term that is a function of the following exists. A thermal head control device according to claim 1 or 2,
Thermal head,
Head voltage detecting means for detecting a head voltage,
A printer comprising: an environmental temperature detecting unit configured to detect an environmental temperature of the heating element.

Images