JP3607644B2 - Print head temperature control system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a temperature control system for a print head, and more particularly, to a temperature control system and a temperature control method that can detect a concentrated overheating of a predetermined coil in a print head without the help of a thermistor.
[0002]
[Prior art]
Generally, a print head, particularly a print head of a dot impact type serial printer, includes an armature that repeats reciprocating motion, a wire brazed to the tip of the armature, a cylindrical magnetic material yoke that serves as a core for an electromagnetic coil, The coil spool is wound around the yoke. The wire sandwiches an ink ribbon and printing paper between the platen as printing pins and prints dots on the printing paper. The two terminals of the coil are soldered on the substrate and connected to the head control circuit by a connector. A thermistor is mounted on the substrate as a temperature detection element for detecting the ambient temperature. In the print head having such a configuration, in the temperature control system that controls the temperature at the time of abnormal overheating due to heat generation of the coil, the above-described thermistor measures the ambient temperature in the print head. That is, abnormal overheating due to a plurality of coils driving each of a plurality of pins in the print head was detected at a temperature near the thermistor, but the thermistor is usually on the printed circuit board even when 24 electromagnetic coils are connected. Only one was mounted, and the temperature corresponding to each coil was not detected from the positional relationship with the coil.
[0003]
[Problems to be solved by the invention]
However, as described above, even when 24 electromagnetic coils are connected, usually only one thermistor is mounted on the printed circuit board, and the temperature corresponding to each coil can be detected from the positional relationship. Because there was no pin, when only pins corresponding to some coils were driven in a concentrated manner, for example, specific pins could be printed by continuous horizontal ruled line printing using only the pin corresponding to the coil farthest from the thermistor position. Even if only the heat is abnormally overheated, the thermistor does not detect it, and the coil temperature and the coil spool temperature may exceed the limits before the thermistor temperature is sufficiently raised. In addition, even if it is possible to detect abnormal overheating of the coil after a lapse of time, it is impossible to measure a rapid temperature rise in a short time due to a specific single pin or two pins being concentrated and continuously energized. Already, there was a case where damage due to printing concentration of a specific pin was caused.
[0004]
For this reason, conventionally, an expensive liquid crystal polymer is used as the material of the coil spool, or the printing speed is lowered from the relatively low thermistor detection temperature, the waiting time between lines is inserted, and the like, thereby preventing the burnout indirectly. However, the original throughput could not be demonstrated. Moreover, if such protection was not implemented, smoke and burning accidents were caused, resulting in loss of customer trust.
[0005]
The present invention has been made in view of the above circumstances, and can detect the concentrated overheating of a predetermined coil in a print head without the help of a thermistor, thereby improving the overall throughput. It is an object of the present invention to provide a temperature control system and a temperature control method capable of performing the above.
[0006]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the invention according to claim 1 is a temperature detection means for detecting abnormal overheating by a plurality of coils driving each of a plurality of pins in the print head, and controls the temperature in the print head. And a temperature control system for the print head, the temperature detection means comprising:A temperature detection element for detecting the temperature of the print head, and a first detection means for detecting normal overheating in the print head;Grouping means for dividing the plurality of pins into a plurality of groups, and counting means for counting the number of print dots for each group of the plurality of groups and obtaining a print dot ratio for the total number of dots of the print dots in each group And comparing the print dot ratio with a certain threshold value,Concentrated overheatingDetermining means for determining a group of coilsSecond detection means for estimating partial overheating in the print headIt is characterized by consisting of.
[0007]
According to a second aspect of the present invention, there is provided the temperature control system for a print head according to the first aspect, wherein the grouping means divides the plurality of groups into groups by overlapping adjacent pins one by one. It is characterized by that.
[0008]
According to a third aspect of the present invention, there is provided the printhead temperature control system according to the first aspect, wherein the counting means has counters corresponding to the number of the plurality of groups.
[0009]
According to a fourth aspect of the present invention, there is provided the printhead temperature control system according to the third aspect, wherein the counting means reads one byte for counting dots from the image development buffer memory, and each group is read for each byte. The number of print dots is counted.
[0010]
According to a fifth aspect of the present invention, there is provided the temperature control system for a print head according to the fourth aspect, wherein the counting means applies a mask by AND to a certain portion of the print dots, and the result corresponds to a predetermined number of dots. The number of print dots is obtained by conversion using a table.
[0011]
According to a sixth aspect of the present invention, there is provided the print head temperature control system according to the fifth aspect, wherein the counting means is performed every time one line is printed.
[0012]
According to a seventh aspect of the present invention, there is provided the print head temperature control system according to the sixth aspect, wherein the counting means counts the number of print dots after one dot row (for 3 bytes) and then prints the print width. It is characterized by repeating minutes.
[0013]
The invention according to claim 8 relates to the temperature control system for a print head according to claim 7, wherein the counting means calculates the total number of dots by a product of the print width and the number of print pins in each group. It is characterized by seeking.
[0014]
According to a ninth aspect of the present invention, there is provided the printhead temperature control system according to the eighth aspect, wherein the determination means is an upper threshold value that is a reference for the print dot ratio and a reference value that is a lower reference. It is characterized by defining a lower threshold value.
[0015]
A tenth aspect of the present invention relates to the printhead temperature control system according to the ninth aspect, wherein the determination means includes the number of print dots of each group, the upper threshold value, and the lower limit value. Comparing means for comparing the threshold value with the result of the comparing means,Central heatingThe present invention is characterized in that a group of coils is determined.
[0016]
11. Claims
An eleventh aspect of the present invention relates to the temperature control system for a print head according to the tenth aspect, wherein the determination unit is configured such that one predetermined group exceeds the upper threshold and the other group is the lower control. The predetermined group is said to beCentral heatingIt is characterized in that it is determined that it is a group of coils.
[0017]
According to a twelfth aspect of the present invention, there is provided the printhead temperature control system according to the first, ninth, tenth, or eleventh aspect of the present invention.Central heatingThe control means reduces the printing speed when a group of coils is determined.
[0018]
A thirteenth aspect of the present invention relates to the printhead temperature control system according to the first, ninth, tenth, or eleventh aspect of the present invention.Central heatingIn the case where a group of coils is determined, the control means is characterized in that a printing waiting time is inserted between printing lines or the printing waiting time is lengthened.
[0019]
According to a fourteenth aspect of the present invention, there is provided the printhead temperature control system according to the first, ninth, tenth, or eleventh aspect of the present invention.Central heatingIn the case where a group of coils is determined, the control means changes from bidirectional printing to unidirectional printing. The temperature control system of a print head according to any one of claims 1 to 11.
[0020]
A fifteenth aspect of the present invention relates to the print head temperature control system according to any one of the first to fourteenth aspects, wherein the print head is a print head of a dot impact serial printer. .
[0021]
A sixteenth aspect of the present invention relates to the printhead temperature control system according to the first aspect, whereinThe temperature detection element consists of a thermistorIt is characterized by that.
[0038]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described in detail with reference to the drawings. The description will be made specifically using examples. The print head temperature control system of the present invention can be applied to the print head of any printer. Here, the print head temperature control system of a dot impact serial printer will be described.
[0039]
FIG. 1 is a cross-sectional view showing a configuration of a print head of a dot impact serial printer to which a temperature control system according to an embodiment of the present invention is applied.
The print head of the dot impact serial printer of this example includes an armature 1 that repeats reciprocating motion, a wire 2 brazed to the tip of the armature 1, a cylindrical magnetic material yoke 3 that serves as a core for an electromagnetic coil, a yoke It consists of a coil 4 wound on top. The armature 1 and the wire 2 constitute an armature assembly, and the yoke 3 and the coil 4 constitute a yoke assembly. The wire 2 sandwiches an ink ribbon and printing paper between a platen (not shown) as printing pins and prints dots on the printing paper. Two terminals of the coil 4 are soldered on the substrate 5 and connected to the head control circuit by a connector (not shown). A thermistor 6 is mounted on the substrate 5 as a temperature detection element for detecting the ambient temperature.
[0040]
FIG. 2 is a diagram showing a head control circuit in a print head of a dot impact serial printer to which the temperature control system of the present invention is applied.
As described above, the head control circuit of this example is a representative circuit for one coil among the coils 4 connected by the connector. Usually, there are 24 such circuits. Coil L₁ One end of the transistor is directly connected to the power supply voltage VDD, and the other end of the switching sink transistor Tr₂ Connected to the collector terminal. Sink side transistor Tr₂ Are connected to GND, and the base terminal is connected to the drive signal S through a resistor.₁ It is connected to the. Coil L₁ At both ends of the common transistor Tr₁Is connected to the coil L₁ Loop current (I₂ ) Is configured. This common transistor Tr₁The Zener diode ZD₁ Is built-in, coil L₁ Transistor Tr from₁When the voltage on the collector terminal side of the transistor exceeds the zener voltage, the common transistor Tr₂ A base current is passed through the transistor Tr₁Turn on the coil L₁ Loop current (I₂ ). Transistor Tr₁ If the voltage on the collector terminal side of the₁ Becomes OFF, and the current from the power supply voltage VDD₁ Passing through GND and flowing to GND as it is (I₁ ).
[0041]
FIG. 3 is a diagram illustrating a relationship between a timing chart and a waveform of a current flowing through the coil. TP₁ In the interval, the sink side transistor Tr₂ Is turned on and current is passed through the coil. The current increases with time according to the time constant. TP₂ In the interval, the sink side transistor Tr₂ Turns off and the common transistor Tr₁Is turned on, and a loop current is passed through the coil by the electromotive force in the coil. In this section, the current gradually decreases. TP₂  At the end of the section, a control signal is applied so that both the two transistors are turned off, but the flyback voltage is zener diode ZD.₁ Via the common transistor Tr₁Until the voltage drops below the zener voltage, the transistor Tr₁Turns on. However, as shown in the figure, it turns off in a short time and TP₃  TP again₁ Transition to the section.
[0042]
Next, the operation of the print head to which the temperature control system according to the embodiment of the present invention is applied will be described in detail with reference to FIGS.
Print head (hereinafter referred to as print head) of dot impact serial printer, electromagnetic coil L₁ By energizing the armature, the armature assembly composed of the wire 2 and the armature 1 is pushed forward by the generated electromagnetic force. This operation is performed by the current waveform TP shown in FIG.₁ It is a part called. The wire 2 at the tip of the armature 1 is gradually accelerated by an increase in current. During this time, the sink transistor Tr₂ Is turned on, but after a certain time has elapsed, the sink transistor Tr₂ Is turned off, and then the common transistor Tr₁Turns on and coil L₁ A loop current is passed through. This operation is performed by the current waveform TP.₂ It is a part called. This operation suppresses the peak current and creates a state where the armature assembly is pushed out for a while, that is, a state where the wire tip continues to impact the ink ribbon or paper. After that, the common transistor Tr₁Is also turned off, but for a very short time coil L₁ Zener diode ZD by flyback voltage generated in₁  The base current is supplied from and absorbs this generated energy. By repeating this, the tip of the wire 2 reciprocates to perform printing. For example, a 24-pin Japanese Kanji printer has a configuration of 24 circuits.
[0043]
Due to the above energization, the electromagnetic coil L₁ Repeats fever. The temperature inside the print head rises due to energization and printing of each of the 24 pins. As a result, a resistance change also appears in the thermistor 6 on the substrate 5, and the temperature in the head is measured from the change in resistance value to prevent overheating of the head coil and control of applied pulses according to temperature.
[0044]
As shown in FIGS. 1 and 5C, the arrangement of the coils 4 arranged on the yoke 3 is arranged in a circle from the center. When the coil corresponding to the pin farthest from the thermistor 6 generates heat intensively and the other pins hardly generate heat, it is necessary to perform control so that the corresponding coil does not cause abnormal heat generation.
[0045]
FIG. 4 is a schematic diagram showing grouping of pins according to a temperature control system for a print head according to an embodiment of the present invention.
In the pin arrangement according to the temperature control system of this example, the pin number is simply shown in the column and the group number is shown in the row. The black circles in the figure are the pins that belong to the group. In this way, the 24 pins of the print head are divided into 8 groups for every 4 pins including the adjacent overlap, and the ratio of the printing dots in the printing width of each group is obtained. If it is simply divided into 6 groups of 4 pins without overlapping, it is not possible to sufficiently grasp the heat generation of the adjacent coils grouped together. The reason for making groups of four pins is that the concentrated printing of one single pin and the concentrated printing of two adjacent pins are targeted for abnormal heat generation. In addition, when the number of grouping is small and the number is small, it is difficult to detect intensive heat generation. Conversely, when the number of grouping is large and the number of groups is large, the load on the CPU to be calculated increases too much. There are concerns. Since this selection depends on the characteristics of the print head, the optimal combination should be selected.
[0046]
FIG. 5 is a schematic diagram specifically showing an example of pin grouping according to a temperature control system for a print head according to an embodiment of the present invention. The pin arrangement at the wire tip of the print head in this example shows an example in which the number of pins is 24. FIG. 5A shows an array of print head tips, FIG. 5B shows a staggered array of print head tips, and FIG. 5C shows a circular arrangement of coils.
[0047]
In the columnar arrangement shown in FIG. 5A, the 24 pins are divided into an even column and an odd column, and in order, the first pin of the odd column is the pin number 1, the first pin of the even column is the pin number 2, and the odd number. The second pin in the row is pin number 3,..., The last pin in the even row is pin number 24, and grouping is performed by grouping odd-numbered pin numbers 1, 3, 5 and 7 into group 1, odd rows. Pin number 7, 9, 11, 13 of group 2, group number 3, 15, 17, and 19 of odd column are group number 3, pin number 19, 21, 23 of odd column, and pin number 24 of even column are group 4, even number pin numbers 24, 22, 20, 18 are group 5, even number pin numbers 18, 16, 14, 12 are group 6, even number pin numbers 12, 10, 8, 6 are group 7, Even number pin number 6, 4, 2, odd number pin number 1 is group 8 That. By the way, the wire wire tip (pin) diameter is about 0.2 mm, the 1/2 pitch A between the pins is about 1/160 inch (0.159 mm), and the interval B between the pin rows is about 7,5 / 160 inch ( 1.192 mm).
[0048]
In the distributed staggered arrangement shown in FIG. 5B, 24 pins are divided into even columns and odd columns, and even columns and odd columns are further divided into 3 pins. The pin numbers are the same as in the above-described row arrangement, the first pin of the odd row is pin number 1, the first pin of the even row is pin number 2, the second pin of the odd row is pin number 3,. The last pin in the even-numbered column is pin number 24. As for grouping, odd-numbered pin numbers 1, 3, 5, and 7 are group 1, odd-numbered pin numbers 7, 9, 11, and 13 are group 2, and odd-numbered pin numbers 13, 15, 17, and 19 are grouped. Number 3, odd number pin number 19, 21, 23, even number pin number 24 is group 4, even number pin number 24, 22, 20, 18 is group 5, even number pin number 18, 16, 14 , 12 are group 6, pin numbers 12, 10, 8, and 6 of even columns are group 7, and pin numbers 6, 4, 2, and odd columns of even columns are group 8. Thus, each group includes a pin that is one pin apart. By the way, the wire tip (pin) diameter is about 0.2 mm, the 1/2 pitch A between the pins is about 1/160 inch (0.159 mm), and the interval B between the pin rows is about 7,5 / 160 inch ( 1.192 mm), which is similar to the array of rows, but in particular, in this distributed staggered array, three pins are dispersed for each row, and the dispersion interval C is about 1 / (160 × 8). ) Inches (0.020 mm).
[0049]
The circular arrangement shown in FIG. 5 (c) shows the arrangement of the coil spools, in which 24 pins are arranged in a circle and the pin numbers are set to 1, 3, 5, 7,. .., 23, 24, 22, 20,..., 6, 2, 2, and grouping is performed by using adjacent pins 1, 3, 5, and 7 as group (GRP) 1 and adjacent pin numbers 7, 9, and so on. 11 and 13 are group 2, adjacent pin numbers 13, 15, 17, and 19 are group number 3, adjacent pin numbers 19, 21, 23, and 24 are group 4, and adjacent pin numbers 24, 22, 20, and 18 are Group 5, adjacent pin numbers 18, 16, 14, and 12 are group 6, adjacent pin numbers 12, 10, 8, and 6 are group 7, and adjacent pin numbers 6, 4, 2, and 1 are group 8.
[0050]
In this way, the 24 pins are divided into a plurality of groups, and each group forms a group that overlaps the adjacent group by one pin, and then the number of printed dots in one line of this group is counted to obtain one line. A ratio for all dots is obtained, and it is detected that one group has a particularly high print dot ratio with respect to another group. If one group meets a predetermined condition, the printing speed is slightly reduced and temperature control is performed. Specifically, the drive frequency of printing is reduced by about 10 to 20%, a waiting time for printing is inserted between each line, or bi-directional printing is changed to uni-directional printing. Control so that the limit is not exceeded. In this way, the specific pin printing concentration that cannot be detected only by the temperature detection element thermistor, that is, the coil overheating of the specific pin by one or two horizontal ruled line printing is detected without using the temperature detection element, Overheating can be prevented. Further, by performing in combination with the thermistor, the detection processing load of the present invention can be minimized and reliable overheat detection can be performed.
[0051]
FIG. 6 is a flowchart showing a temperature control method for a print head according to an embodiment of the present invention.
First, when the printing width is less than half of full printing (13.6 inches), the amount of heat generation is small and there is no fear of overheating of the coil, so the processing is unnecessary, and the following processing is not performed.
[0052]
As a processing flow, first, one byte for counting dots is read from the image development buffer memory (step A1), and black dots are counted for each group (step A2). Eight counters are required for each group. The count is obtained by applying an AND mask to the portion of the group where the dot of the group is located in one byte and converting the result using a 256-dot number correspondence table to obtain the number of dots (step A3). Depending on the group, since it extends over 2 bytes, it is necessary to count 12 times for one dot row, that is, one vertical dot (3 bytes) in terms of characters. This is repeated for the printing width (step A4). However, if a more severe printing speed limit condition is satisfied during the process, the process is terminated. Next, the dot ratio is obtained (step A5). Since one group is every 4 dots, the total number of dots in one line group is print width × 4. For example, the lower (low) threshold value and the upper (high) threshold value are multiplied by 10% and 37% to obtain the reference dot number.
[0053]
Upper threshold = print width × 4 × 37 ÷ 100
Lower threshold = print width × 4 × 10 ÷ 100
[0054]
Since the criterion is when one group exceeds the upper threshold value and the other group falls below the lower threshold value, “whether one group exceeds the upper threshold value” (step A6a). ), “Are other than one group not exceeding the lower threshold” (step A6b) (step A6).
[0055]
In the two-stage determination, first, one work area is prepared for checking how many groups exceed the lower threshold. A determination is made as to whether the lower threshold is exceeded for each group, and if so, a bit corresponding to the group is set. Since the number of bits is 8 groups, 8 bits are required. When the value of this workpiece is 1H, 2H, 4H, 8H, 10H, 20H, 40H, or 80H, “the lower threshold is not exceeded except for one group”. If one group exceeds the lower threshold, a check is made to see if the group exceeds the upper threshold. Here, if the upper threshold value is exceeded, it is determined that the determination criterion is satisfied.
[0056]
As described above, when it is found that there is a coil that is abnormally heated, control such as reducing the printing speed is performed (step A7). In order to reduce the speed, the following designation flag is set on the control program. If there is no abnormally heated coil, normal printing is performed.
[0057]
As described above, there is a combination in which the proportion of the total number of dots in one line of any one group exceeds 37%, for example, and the ratio of all other groups is less than 10%. In this case, for example, the printing speed is reduced to unidirectional printing at a speed of 80%. That is, it is detected that the print DUTY (dot density or row dot density) is high only in a specific group and the print DUTY is relatively low in other groups. This mode will not be entered if there are two or more groups exceeding 37%, or if any other group is 10% or more DUTY. This is because when the overall printing DUTY is high, a normal thermistor can sufficiently detect it. If the print width is less than half of the maximum print width (13.6 inches), this process is not performed. This is due to the determination that the number of printed dots itself is small. Further, the ratio of the number of printed dots is determined by an experimental evaluation, instead of the head structure or each constant.
[0058]
FIG. 7 is a flowchart showing the flow of the counting process in the print head temperature control method according to the embodiment of the present invention.
First, the values of the print left end and the print right end set in the image development process are read and the difference between these values is obtained to obtain the print width from the print right end to the print left end (step B1). For example, if the print width is a maximum of 2176 dot rows, one dot row is composed of 24 dots = 24 pins = 3 bytes, 1 to 8 pins are in the first byte, 9 to 16 pins are in the second byte, Since the 17th to 24th pins are arranged in the third byte, the image development buffer is composed of this 24 dots (= 1 dot row) × 2176 dot rows.
[0059]
Next, the first byte (pins 1 to 8) of the dot row is read from the image development buffer (step B2).
[0060]
Next, in order to count the dots of the grouped group 1 (for example, 1, 3, 5, and 7 pins), AND is performed at 55H, and the dot number correspondence table (256 bytes in which the number of dots of 1 byte is set) The number of dots is extracted using the (array), and the group 1 counter is updated with the number of dots (step B3).
[0061]
Next, among grouped group 2 (for example, pins 7, 9, 11, and 13), since pin 7 is in the first byte, AND is performed at 40H, and the number of dots is extracted using the dot number correspondence table. The counter for group 2 is updated with the number of dots (step B4).
[0062]
Next, among grouped groups 7 (for example, 6, 8, 10, 12 pins), since pins 6 and 8 are in the first byte, AND is performed with A0H, and the number of dots is determined using the dot number correspondence table. And the counter for group 7 is updated with the number of dots (step B5).
[0063]
Next, in order to count the dots of the grouped group 8 (for example, 1, 2, 4, 6 pins), AND is performed with 2BH, and the number of dots is extracted using the dot number correspondence table. The counter is updated (step B6).
[0064]
Next, the second byte (9 to 16 pins) of the dot row is read from the image development buffer (step B7).
[0065]
Next, in group 2 (for example, pins 7, 9, 11, and 13), since pins 9, 11, and 13 are in the second byte, AND is performed at 15H, and the dot number correspondence table is used. The number of dots is taken out and the group 2 counter is updated with the number of dots (step B8).
[0066]
Next, among grouped group 2 (for example, pins 7, 9, 11, and 13), since pin 7 is in the first byte, AND is performed at 40H, and the number of dots is extracted using the dot number correspondence table. The counter for group 2 is updated with the number of dots (step B9).
[0067]
Next, in group 3 (for example, 13, 15, 17, and 19 pins), since the 13 and 15 pins are in the second byte, AND is performed at 50H, and the number of dots is determined using the dot number correspondence table. And the counter for group 3 is updated with the number of dots (step B10).
[0068]
Next, among the grouped groups 6 (for example, 12, 14, 16, 18 pins), since the 12, 14, 16 pins are in the second byte, AND is performed with A8H, and the dot number correspondence table is used. The number of dots is taken out and the counter for group 6 is updated with the number of dots (step B11).
[0069]
Next, among the grouped groups 7 (for example, 6, 8, 10, 12 pins), since the 10th and 12th pins are in the second byte, AND is performed with 0AH, and the number of dots is calculated using the dot number correspondence table. And the counter for group 7 is updated with the number of dots (step B12).
[0070]
Next, the third byte (17-24 pins) of the dot row is read from the image development buffer (step B13).
[0071]
Next, in group 3 (for example, 13, 15, 17, and 19 pins), since pins 17 and 19 are in the third byte, AND is performed with 05H, and the number of dots is determined using the dot number correspondence table. And the counter for group 3 is updated with the number of dots (step B14).
[0072]
Next, in order to count the dots of the grouped group 4 (for example, 19, 21, 23, 24 pins), AND is performed with D4H, the number of dots is extracted using the dot number correspondence table, and the number of dots is used for group 4 The counter is updated (step B15).
[0073]
Next, in order to count the number of dots of the grouped group 5 (for example, 18, 20, 22, 24 pins), AND is performed with AAH, the number of dots is extracted using the dot number correspondence table, and the group is determined by the number of dots. The counter for 5 is updated (step B16).
[0074]
Next, among the grouped groups 6 (for example, 12, 14, 16, 18 pins), since 18 pins are in the second byte, AND is performed at 02H, and the number of dots is extracted using the dot number correspondence table. Then, the counter for group 6 is updated with the number of dots (step B17).
[0075]
Next, the dot widths 3 to 16 for the print width are repeated (step B18).
Next, a threshold value is obtained from the print width. Since each group consists of 4 pins,
High threshold = print width × 4 × high threshold ratio (37%)
Low threshold = print width × 4 × low threshold ratio (10%)
Calculate with
[0076]
For example, when the maximum print width is 13.6 inches (2176 dot rows),
High threshold = 2176 × 4 × 37/100 = 3220
Low threshold = 2176 × 4 × 10/100 = 870
Thus, 3220 and 870 are the upper and lower threshold values of the counter of each group.
[0077]
FIGS. 8 to 10 are flowcharts showing a determination process in the print head temperature control method according to the embodiment of the present invention.
In FIG. 8, first, it is determined whether or not only group 1 exceeds the high threshold (step C1). If it exceeds, whether or not all of groups 3 to 7 are below the low threshold is determined. If it is determined (step C2) and all are below a low threshold, temperature control is performed. If the group 1 does not exceed the high threshold value, or if any of the groups 3 to 7 is equal to or higher than the low threshold value even if it exceeds, the process proceeds to step C3. Next, it is determined whether or not only the group 2 exceeds the high threshold value (step C3). Step C4), if all are below a low threshold, temperature control is performed. If the group 2 does not exceed the high threshold value, or if any of the groups 4 to 8 is equal to or higher than the low threshold value even if it exceeds, the process proceeds to step C5. Next, it is determined whether or not only the group 3 exceeds the high threshold value (step C5). (Step C6), if all are below the lower threshold, temperature control is performed. If the group 3 does not exceed the high threshold value, or if any of the groups 1, 5 to 8 is equal to or higher than the low threshold value even if it exceeds, the process proceeds to step C7. Next, it is determined whether or not only the group 4 exceeds the high threshold value (step C7). If it exceeds the threshold value, whether or not the groups 1, 2, 6 to 8 are all below the low threshold value. (Step C8), and if all are below a low threshold, temperature control is performed. If the group 2 does not exceed the high threshold value, or if any of the groups 1, 2, 6 to 8 is equal to or higher than the low threshold value even if it exceeds, the process proceeds to FIG.
[0078]
In FIG. 9, next, it is determined whether or not only the group 5 exceeds the high threshold value (step C9), and if it exceeds, all the groups 1 to 3, 7, and 8 are below the low threshold value. It is determined whether or not there is (step C10). If the group 5 does not exceed the high threshold value, or if any of the groups 1 to 3, 7, and 8 is equal to or higher than the low threshold value even if the group 5 is exceeded, the process proceeds to step C11. Next, it is determined whether or not only the group 6 exceeds the high threshold value (step C11). (Step C12), if all are below a low threshold, temperature control is performed. If the group 6 does not exceed the high threshold value, or if any of the groups 1 to 4 and 8 is equal to or higher than the low threshold value even if it exceeds, the process proceeds to step C13. Next, it is determined whether or not only the group 7 exceeds the high threshold value (step C13). Step C14), if all are below a low threshold, temperature control is performed. If the group 7 does not exceed the high threshold value, or if any of the groups 1 to 5 is equal to or higher than the low threshold value even if the group 7 is exceeded, the process proceeds to step C15. Next, it is determined whether or not only the group 8 exceeds the high threshold (step C15), and if it exceeds, it is determined whether or not the groups 2 to 6 are all below the low threshold ( Step C16) If all are below a low threshold, temperature control is performed. If the group 8 does not exceed the high threshold value, or if any of the groups 2 to 6 is equal to or higher than the low threshold value even if it exceeds, the process proceeds to FIG.
[0079]
In FIG. 10, since the groups 1, 8, 4, and 5 are not particularly durable and often generate abnormal heat, the following processing is performed. First, it is determined whether or not only the groups 1 and 8 exceed the high threshold (step C17), and if they exceed, it is determined whether or not the groups 3 to 6 are all below the low threshold. (Step C18) If all are below a low threshold, temperature control is performed. If the groups 1 and 8 do not exceed the high threshold value, or if any of the groups 3 to 6 is equal to or higher than the low threshold value even if it exceeds, the process proceeds to step C19. Next, it is determined whether or not only the groups 4 and 5 exceed the high threshold value (step C19). If the threshold values are exceeded, are all the groups 1, 2, 7, and 8 below the low threshold value? It is determined whether or not (step C20), and if all are below a low threshold, temperature control is performed. If the groups 4 and 5 do not exceed the high threshold value, or if any of the groups 1, 2, 7, and 8 is greater than or equal to the low threshold value, normal temperature control is performed. That is,in this caseIt can be detected with a thermistor.
[0080]
Next, another embodiment of the present invention will be described.
In the above-described embodiment, the coil heat generation of the print head is targeted. However, this embodiment is an embodiment for preventing damage to the transistor that drives the print head by applying the temperature control system to the transistor. Usually, a common or sink side transistor often uses a built-in transistor array. These transistors generate the most heat when they are driven at the same time, but under normal usage conditions, the usage rate is 1/3 or less, and an expensive transistor is selected for the design considering heat generation at the maximum load. It will be. Therefore, the 24 pins of the print head are divided into 6 groups for every 4 pins, which is the distribution unit of the transistor array, and the ratio of the print dots in the print width for each group is obtained. Heat generation is suppressed by reducing the printing speed. When there is even one group in which the proportion of print dots exceeds 70%, unidirectional printing is performed. However, when printing by thinning, the determination is made with the threshold set to 35%.
[0081]
The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and there are design changes and the like without departing from the gist of the present invention. Are also included in the present invention.
[0082]
For example, in the above-described embodiments, the temperature control system and the temperature control method of the print head of the dot impact serial printer have been described. However, the present invention is not limited to this. Applicable.
[0083]
In the above-described embodiments, the case of 24 pins has been described as an example. However, the number of pins is not limited to this, and if grouping according to the present invention is possible, 12 pins and 48 pins are possible. Any number of pins such as pins and 64 pins can be targeted.
[0084]
In the above-described embodiments, the pin array has been described with reference to the example of the row-like and distributed staggered array shown in FIG. 5, but the present invention is not limited to this and can be applied to various arrays.
[0085]
In the above-described embodiment, the grouping is performed by overlapping one pin at a time. However, the present invention is not limited to this, and it is possible to perform the grouping without overlapping. It can also be grouped by overlapping one by one.
[0086]
In the above-described embodiment, the lower threshold value and the upper threshold value are set at the time of the counting process, and each group determines the coil that is abnormally overheated based on these. The determination is not limited to this, and the determination can be made with a single threshold value, or more detailed determination can be made by setting a larger number of threshold values.
[0087]
【The invention's effect】
As described above, according to the configuration of the present invention, even when only the electromagnetic coil corresponding to a specific pin out of 24 pins is concentrated and generates heat, the printing is concentrated only on the specified pin, and the others. Since it is possible to detect that the pins are relatively lightly printed, it is possible to prevent abnormal heat generation and smoke burning due to concentration of horizontal ruled line printing.
[0088]
Conventionally, in order to prevent this risk, it has been necessary to apply printing restrictions by the thermistor, that is, speed reduction, insertion of waiting time between lines, and one-way coil printing, etc. from a low thermistor temperature. According to the configuration, it is not necessary to limit printing from a low thermist temperature and the like, and it is possible to improve the throughput as a whole.
[0089]
Further, in addition to preventing an excessive temperature rise of the coil, as described in other embodiments, the transistor array can be applied to prevent overheating due to the concentration of the transistor array in one array. Can be used to reduce costs.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a configuration of a print head to which a temperature control system according to an embodiment of the present invention is applied.
FIG. 2 is a head control circuit of a print head to which a temperature control system according to an embodiment of the present invention is applied.
FIG. 3 is a diagram showing a relationship between a drive timing of a printhead coil to which a temperature control system according to an embodiment of the present invention is applied and a current waveform;
FIG. 4 is a schematic view showing pin grouping of a print head to which a temperature control system according to an embodiment of the present invention is applied.
FIG. 5 is a schematic view specifically showing grouping of pins of a print head to which a temperature control system according to an embodiment of the present invention is applied. (A) An array of print head tips, (b) is a staggered arrangement of print head tips, and (c) is a diagram showing a circular arrangement of coils.
FIG. 6 is a flowchart showing a temperature control method according to an embodiment of the present invention.
FIG. 7 is a flowchart showing a counting process in the temperature control method according to the embodiment of the present invention.
FIG. 8 is a flowchart showing determination processing in the temperature control method according to the embodiment of the present invention.
FIG. 9 is a flowchart showing determination processing in the temperature control method according to the embodiment of the present invention.
FIG. 10 is a flowchart showing determination processing in the temperature control method according to the embodiment of the present invention.
[Explanation of symbols]
1 Armature
2 wires
3 York
4 Coils
5 Substrate
6 Thermistor

Claims (16)

A temperature control system for a print head, comprising: temperature detection means for detecting abnormal overheating by a plurality of coils that drive each of a plurality of pins in the print head; and control means for controlling the temperature in the print head. ,
The temperature detecting means includes
A temperature detection element for detecting the temperature of the print head, and a first detection means for detecting normal overheating in the print head;
Grouping means for dividing the plurality of pins into a plurality of groups;
Counting means for counting the number of print dots in each group of the plurality of groups, and obtaining a print dot ratio with respect to the total number of dots of the print dots in each group;
Determining means for comparing the print dot ratio with a certain threshold value and determining a group of coils that are concentrated and overheated, and a second detection means for estimating partial overheating in the print head ; A print head temperature control system comprising: 2. The temperature control system for a print head according to claim 1, wherein the grouping means overlaps adjacent pins of the plurality of groups one by one and divides the group into groups. The counting means, the temperature control system of the print head according to claim 1, characterized in that it comprises a counter for the number of the plurality of groups. 4. A temperature control system for a print head according to claim 3, wherein said counting means reads one byte counting dots from the image development buffer memory and counts the number of print dots of each group for each byte. 5. The print head according to claim 4, wherein the counting means applies an AND mask to a portion where the print dots are present, and converts the result using a predetermined dot number correspondence table to obtain the print dot number. Temperature control system. 6. The temperature control system for a print head according to claim 5, wherein the counting means is performed every time one line is printed. 7. The temperature control system for a print head according to claim 6, wherein the counting means repeats the print dot number after performing the dot width (for 3 bytes) for the print width. 8. The print head temperature control system according to claim 7, wherein the counting means obtains the total number of dots by a product of the printing width and the number of printing pins of each group. 9. The print head according to claim 8, wherein the determination unit defines an upper threshold value that is a reference above the print dot ratio and a lower threshold value that is a lower reference. Temperature control system. The determination unit includes a comparison unit that compares the number of print dots of each group with the upper threshold value and the lower threshold value, and performs the concentrated heating according to a result of the comparison unit. The printhead temperature control system according to claim 9, wherein a group of coils is determined. In the determination means, when the predetermined one group exceeds the upper threshold value and the other group is lower than the lower threshold value, the predetermined one group performs the concentrated heating . The print head temperature control system according to claim 10, wherein the print head temperature control system is determined to be a group of coils. 12. The temperature control of a print head according to claim 1, wherein when the determination unit determines a group of coils that are centrally heated , the control unit decreases a printing speed. system. The control means inserts a printing waiting time between each printing line or lengthens the printing waiting time when the determining means determines the group of coils that are performing the central heating. The print head temperature control system according to claim 1, 9, 10 or 11. 12. The control unit according to claim 1, wherein the control unit changes from bidirectional printing to unidirectional printing when the determination unit determines the group of coils that are intensively heated . Print head temperature control system. 15. The print head temperature control system according to claim 1, wherein the print head is a print head of a dot impact serial printer. 16. The printhead temperature control system according to claim 1 , wherein the temperature detection element is a thermistor .

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