JPH04312858A - Wire dot printing head - Google Patents

Abstract

PURPOSE:To prevent a thermal throughput from becoming deteriorated without suspending a printing process by providing a device to detect the temperature of each coil sequentially. CONSTITUTION:If temperature detection data which is output from a buffer is received, a temperature detection device runs an electric current for temperature detection to each coil 13 to detect the coil temperature sequentially. If there is any pin which reaches the level where a detected temperature is equal to the limits of heat resistance, the temperature detection device stops the drive of the pin only without suspending a printing process, and prints a single line of data based on buffer printing data. Further, the device feeds a line and prints the line again by driving another coil 13 at low temperature. During this period, the temperature drops as the coil 13 which reaches the limits of heat resistance remains undriven. Thus the thermal throughput increases significantly due to the continuation of a printing process using a pin at low temperature.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to wire dot printheads.

0002

[Prior Art] Conventionally, impact printers drive a printing wire, strike the printing medium through an ink ribbon, and print using the striking force. It is used in many fields including output devices for information processing systems and the like.

The above-mentioned impact printers are classified into plunger type, spring charge type, and clapper type based on the type of wire dot print head. Among these, the spring-charged type supports an armature to which a printing wire is fixed so that it can swing freely by a leaf spring for bias, and the armature is placed in advance by a permanent magnet against the elastic force of the leaf spring. When printing, a coil wound around the core is energized to generate a magnetic flux in the opposite direction to the permanent magnet, and the armature is released. There is a demand for higher speeds, and this spring-charged wire dot print head, which has good high-speed response, is being widely used.

FIG. 2 is a sectional view of a conventional spring-charged wire dot print head. In the figure, between the guide frame 1 and the cap 2, there is a base 3, a permanent magnet 4,
A base plate 5, a spacer 6, a bias plate spring 7, and a yoke 8 are laminated in order with a clamp 9 interposed therebetween. An armature 10 is attached to the flexible part of the leaf spring 7, and the base of a printing wire 11 is fixed to the tip of the armature 10, and the tip of the printing wire 11 is guided toward the platen by a guide 1a so that it can freely protrude. It has become. A core 12 is provided in the center of the base 3, and a coil 13 is wound around the core 12.

For example, nine to twenty-four assemblies consisting of an armature 10, a core 12, and a coil 13 to which the printing wire 11 is fixed are provided in the print head, and they are arranged in a substantially circular shape. Note that 14 is a board for energizing the coil 13, and 15 is a space sheet for positioning the board 14. Further, 16 is a thermistor for temperature detection, and 17 is a filler material with good thermal conductivity that covers the coil 13 and the thermistor 16. The filler material transfers the heat generated by the coil 13 to the outside to dissipate the heat, and also fixes the core 13.

In the wire dot print head configured as described above, the magnetic flux of the permanent magnet 4 is distributed between the base plate 5, the spacer 6, and the yoke 8.
, a magnetic circuit is formed that passes through the armature 10, core 12 and base 3 and returns to the permanent magnet 4, and the armature 10 is attracted to the core 12 by this magnetic circuit, and strain energy is accumulated in the leaf spring 7, causing it to be biased. placed in In this biased state, when the coil 13 is excited to generate a magnetic flux in the opposite direction to the magnetic circuit, the force attracting the armature 10 is reduced. As a result, the strain energy accumulated in the leaf spring 7 is released, and the leaf spring 7 returns to its original position, causing the printing wire 11 attached to the tip of the armature 10 to protrude from the guide 1a, thereby transferring the ink ribbon and printing medium (not shown) to the platen. to press against.

[0007] Thereby, characters and graphic patterns can be printed. In addition, since heat is generated by energizing the coil 13 during printing, the thermistor 16 is provided in the center of the print head as described above, and the heat is transferred via the filler 17 such as epoxy resin with good thermal conductivity. Detects the heat generated. By monitoring the temperature rise inside the print head, the temperature of the coil 13 is maintained below the heat-resistant temperature and burnout is prevented. The installation work for the thermistor 16 is cumbersome, and only one thermistor 16 is installed at the center of the print head. Therefore, it is not possible to monitor the temperatures of all the plurality of coils 13.

[0008] Therefore, the coil heat resistance temperature is determined experimentally and used as the thermal monitoring temperature, and control is performed such as stopping printing when the temperature detected by the thermistor 16 reaches the thermal monitoring temperature.

[0009]

[Problems to be Solved by the Invention] However, in the wire dot print head having the above structure, due to the need to increase the printing speed and to reduce the size and weight of the print head, if the energization cycle of the coil 13 is shortened, the coil 13 Not only does the amount of heat generated increase, but the heat dissipation performance deteriorates, causing the temperature inside the print head to quickly reach the thermal monitoring temperature. In that case, control such as interrupting printing must be performed, resulting in a decrease in the number of characters printed per unit time and a decrease in thermal throughput.

Further, since only one thermistor is provided at the center of the print head and detects the average temperature within the print head, it does not detect the temperature of all the coils. Therefore, printing may be stopped even though there are coils that have not reached the allowable temperature limit, and the driving efficiency of the coils decreases, resulting in a decrease in thermal throughput.

[0011] The present invention solves the problems of the conventional wire dot print head and prevents the thermal throughput from decreasing when the print speed is increased or the print head is made smaller and lighter. The purpose is to provide a wire dot print head that can

0012

[Means for Solving the Problems] To achieve this, the wire dot print head of the present invention includes an armature with a printing wire attached to its tip, a core provided opposite to the armature, and a bias for supporting the armature. It has a leaf spring, and a coil that is wound around the core and generates magnetic flux when excited to swing the armature.

[0013] Furthermore, it has a buffer for storing data for temperature detection, and coil temperature detection means for sequentially detecting the temperature of each coil. Upon receiving the temperature detection data output from the buffer, the coil temperature detection means causes a temperature detection current to flow through each coil and sequentially detects the coil temperature. Then, the drive of the pin whose detected coil temperature has reached the heat-resistant temperature is stopped to continue printing that line, and after a line feed, other pins are driven to print the unprinted part of the same line. have the means to do so.

[0014]

[Operation] According to the present invention, there is provided an armature having a printing wire attached to its tip as described above, a core provided opposite to the armature, a bias plate spring supporting the armature, and a leaf spring wound around the core. The armature is equipped with a coil that generates magnetic flux when excited to swing the armature. Therefore, when a drive current flows through each coil based on print data, the corresponding armature swings, and the print wire strikes the print medium via the ink ribbon.

The present invention also includes a buffer for storing data for temperature detection, and coil temperature detection means for sequentially detecting the temperature of each coil, and the coil temperature detection means uses the data for temperature detection outputted from the buffer. Upon receiving the data, a temperature detection current is passed through each coil to sequentially detect the coil temperature. If there is a pin whose detected coil temperature has reached the heat-resistant temperature, the drive of that pin is stopped and printing continues on that line, and after a line feed, other pins are driven to print on the same line. conduct. At this time, only the portions that were not printed are printed.

[0016]

Embodiments Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a sectional view of a wire dot print head showing an embodiment of the present invention, FIG. 3 is a partial cross sectional view of the wire dot print head of the invention, and FIG. 4 is a diagram showing an example of printing by the wire dot print head.

In the figure, a base 3, a permanent magnet 4, a base plate 5, a spacer 6, a bias plate spring 7, and a yoke 8 are stacked in order between a guide frame 1 and a cap 2 via a clamp 9. There is. An armature 10 is attached to the flexible portion of the leaf spring 7, and the armature 10
The base of the printing wire 11 is fixed to the tip of the printing wire 11, and the tip of the printing wire 11 is guided toward the platen by a guide 1a so that it can protrude freely. A core 12 is provided in the center of the base 3, and a coil 1 is attached to the core 12.
3 is wrapped.

Note that 14 is a board for energizing the coil 13, and 15 is a space sheet for positioning the board 14. Further, 16 is a filling material with good thermal conductivity that covers the coil 13, and radiates the heat generated by the coil 13 and fixes the coil 13. In the wire dot print head having the above configuration, the magnetic flux of the permanent magnet 4 is transferred to the base plate 5.
, spacer 6, yoke 8, armature 10, core 12
A magnetic circuit is formed which passes through the base 3 and returns to the permanent magnet 4, which attracts the armature 10 to the core 12, stores strain energy in the leaf spring 7, and places it in a biased state. In this biased state, when the coil 13 is excited to generate a magnetic flux in the opposite direction to the magnetic circuit, the force attracting the armature 10 is reduced. As a result, the strain energy accumulated in the leaf spring 7 is released and the leaf spring 7 returns to its original position, causing the printing wire 11 attached to the tip of the armature 10 to protrude from the guide 1a.
An ink ribbon and print medium (not shown) are pressed against the platen.

[0019] Thereby, characters and graphic patterns can be printed. In the above-described printing operation, when the printing wire 11 is composed of pins a1 to a7, there is a difference in the driving frequency of each pin a1 to a7, for example, "H" as shown in FIG. ”
When printing characters, the frequency of pin a4 is higher than that of other pin a1.
~a3, higher than a5 ~a7. Therefore, the driving frequency of each coil 13 corresponding to each pin a1 to a7 is different, and the coil temperature is different for each coil 13. Therefore, the temperature of each coil 13 can be detected.

FIG. 5 is a driving circuit diagram of the wire dot print head of the present invention. In the figure, 31 is a CPU, 32 is a buffer that receives print data from the CPU 31 and temporarily holds it, C1, C2, . . . are coils of the wire dot print head, and Tr0, Tr1, . . . are driving transistors. The transistor Tr0 receives a signal from the CPU 31, and the transistors Tr1, Tr2, . . . receive a signal from the buffer 32 and become conductive. D0, D1
,... are diodes for feedback of back electromotive force, R0 is a voltage dividing resistor for dividing the power supply voltage VC with each coil resistance value, S
w1, Sw2, ... are switches that selectively connect each coil C1, C2, ... and the voltage dividing resistor R0, and 33 is a comparator that compares the voltage VP at point P with the comparison voltage VR for each coil C1, C2, ... It is. The output of the comparator 33 is connected to the CPU 31, and the CPU 31 controls the drive of the print head based on the information.

In the wire dot print head configured as described above, when starting printing with the print head, the switch S is pressed.
w1, Sw2, . . . are connected to terminals A1, A2, . . . and each coil C1, C2, . . . is energized. For example, at the time of line feed, the switches Sw1 and Sw2 are sequentially connected to the terminals B1, B2, . . . , and at that time, the CPU 3
1 and the buffer 32, temperature detection data is output from the transistor Tr0 and each switch Sw1, Sw2,
The transistors Tr1, Tr2, . . . corresponding to the transistors Tr1, Tr2, . . . are turned on in sequence. As a result, each coil C1
, C2, . . . are connected, and the voltage VP at point P and the comparison voltage VR are compared.

Here, the voltage VP at point P is
, C2, . . . and the resistance value of the voltage dividing resistor R0. Therefore, when the temperature of each coil C1, C2, . . . changes, the resistance value of each coil changes accordingly, and the voltage VP at the above-mentioned point P also changes. On the other hand, the comparison voltage VR is a partial voltage based on the coil resistance value at the allowable temperature. Therefore, by comparing the two, each coil C1, C
2. The temperature of... can be detected. Note that since the resistance value of the voltage dividing resistor R0 is high, each coil C1, C2
, . . . becomes small, and the printing wire 11 is not driven when detecting the coil temperature. Further, temperature detection data output at the time of line feed to detect the coil temperature is stored in the buffer 32 in advance.

Next, the operation when printing the character "H" using the wire dot print head of the present invention will be explained. FIG. 6 is a diagram showing a printing state when printing is performed by the wire dot print head of the present invention. The circle mark in (a) in the figure is “H”.
" character dot pattern is shown. The ○ mark in (b) indicates the pattern printed at the first timing when the temperature of the coil rises, and the ● mark in (c) indicates the pattern printed at the next timing.

[0024] When printing is performed continuously and as a result of detecting the temperature of each coil at the time of a line feed, if the coil 13 corresponding to pin A4 reaches the heat-resistant temperature, instead of stopping printing, the process shown in (b) In this way, driving of only pin a4 is stopped and printing for one line is directly performed based on the print data in the buffer 32. Then, continue with a new line on the same line, (c)
As shown in , the pins of other coils 13 having lower temperatures, for example pin a1, are driven to print the same line again. During this time, the coil 13, which has reached the allowable temperature limit, is not driven, so the temperature decreases.

[0025] In this way, since the low temperature pins are used to continue, the thermal throughput is greatly improved. FIG. 7 is an operation flowchart of the wire dot print head of the present invention. Step S1 Printing is performed. Step S2: Perform line feed. Step S3 Switches Sw1, Sw2,... are connected to terminal B
n (B1, B2,...). Step S4 Print data is sequentially output from the buffer 32. Step S5: The temperature of each coil C1, C2, . . . is sequentially detected. Step S6: Determine whether the heat resistant temperature has been reached. Step S7: When the heat-resistant temperature is reached, printing is continued without driving that pin, and then the line is returned to the same line and printing is performed using other pins. Step S8 If the heat-resistant temperature has not been reached, switch switches Sw1, Sw2, ... are connected to terminals An (A1, A2
,…).

It should be noted that the present invention is not limited to the above-mentioned embodiments, and various modifications can be made based on the spirit of the present invention, and these are not excluded from the scope of the present invention. For example, in the above embodiment, the coil temperature is detected by dividing the voltage between the coil and the voltage dividing resistor, but it may also be detected by the peak current value of the current flowing through the coil.

[0027]

As described above in detail, the present invention includes a buffer for storing data for temperature detection, and coil temperature detection means for sequentially detecting the temperature of each coil. Upon receiving the temperature detection data output from the buffer, the detection means passes a temperature detection current through each coil, sequentially detects the coil temperature, and detects the pin whose detected coil temperature has reached the heat-resistant temperature. If so, stop driving that pin, continue printing on that line, start a new line on the same line, and then drive other pins to print only the part that was not printed.

[0028] Therefore, printing is continued without stopping, the number of characters that can be printed per unit time increases, and thermal throughput can be improved.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a wire dot print head showing an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a conventional spring-charged wire dot print head.

FIG. 3 is a partial cross-sectional view of the wire dot print head of the present invention.

FIG. 4 is a diagram showing an example of printing by a wire dot print head.

FIG. 5 is a drive circuit diagram of the wire dot print head of the present invention.

FIG. 6 is a diagram showing a printing state when printing is performed by the wire dot print head of the present invention.

FIG. 7 is an operation flowchart of the wire dot print head of the present invention.

[Explanation of symbols]

3 Base 4 Permanent magnet 6 Groove 8 York 10 Armature 11 Printing wire 12 core 13 Coil 17 Filling material

Claims (1)

[Claims] 1. An armature with a printing wire attached to its tip, a core provided opposite to the armature, and a bias plate spring supporting the armature.
A wire dot print head consisting of a coil that is wound around the core and that generates magnetic flux when excited to swing the armature, includes (a) a buffer that stores data for temperature detection, and (b) output from the buffer. (c) coil temperature detection means that sequentially detects the temperature of each coil in response to the detected temperature detection data; and (c) stopping the drive of the pin whose detected coil temperature has reached the heat-resistant temperature and continuing printing that line. A wire dot print head characterized in that the wire dot print head has means for printing an unprinted portion of the same line by driving another pin after a line break.