JPH0624018A - Impact dot printer - Google Patents

Abstract

(57) [Abstract] [Purpose] Regardless of the temperature of the impact dot head, the print wire operates properly to obtain print of constant quality. A spark killer circuit 33, whose conduction potential is controlled according to the temperature of a print head, is provided so as to compensate for a decrease in energy supplied to the drive coil 5 when the drive coil 5 becomes hot. The energy stored in the drive coil 5 is regenerated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an impact dot printer that prints characters and figures by hitting a printing wire at its tip onto a platen with a drive coil, and more particularly to a control circuit for the drive coil.

[0002]

2. Description of the Related Art An impact dot head prints by hitting a wire on a platen by a magnetic attraction force generated by a drive coil. At this time, printing is performed by driving the wire with a certain magnetic attraction force generated by inputting a certain input energy to the drive coil by a certain constant voltage and a constant energization time corresponding thereto in the drive coil. However, since the electric energy applied to the drive coil is regulated by a constant voltage and a constant energization time corresponding to it, when the data with high print density is printed or when it is printed continuously for a long time, the drive coil generates heat and the coil As a result, the resistance value increases, the flowing current decreases, and the input energy to the drive coil decreases. As a result, a predetermined magnetic attraction force cannot be obtained, the drive of the print wire becomes unstable, and normal printing cannot be performed.

In order to solve such a problem, Japanese Patent Laid-Open No. Sho 60
In No. 115477, when the temperature of the drive coil rises and it becomes difficult for the current to flow, the energization time to the drive coil is extended or the applied voltage is increased to compensate the energy amount input to the drive coil and print. The impact force of the wire is enhanced.

[0004]

However, in the case of trying to keep the printing cycle constant, in the above-mentioned conventional example, by extending the energization time, the non-energization time until the next printing timing is reduced, so that the printing wire is sufficiently supplied. There is a problem that the next printing operation is started without waiting for the attenuation, or a problem that the possibility of burnout of the drive coil is induced by increasing the applied voltage.

The present invention has been made in view of the above problems, and an object of the present invention is to sufficiently maintain the impact force on the printing wire and to provide an insufficient time until the next printing operation. It is to provide a novel method of always securing the necessary energy by securing the energization time so as not to cause the above and further securing a sufficient flyback current.

[0006]

In order to solve such a problem, in the impact dot printer of the present invention, in the drive circuit for driving the impact dot head, the conduction potential is controlled at least according to the temperature of the print head. The spark killer circuit has means for regenerating the energy stored in the drive coil so as to compensate for the decrease in the energy supplied to the drive coil when the temperature of the drive coil rises.

[0007]

The details of the present invention will be described below with reference to illustrated embodiments.

FIG. 1 shows a drive circuit for driving the impact dot head. One end of the drive coil 5 is a DC drive power supply circuit 30 and the other end is a switching transistor 32.
, But is also connected to the spark killer circuit 33 at the same time. In this spark killer circuit, three constant voltage diodes (34, 35, 3
6) are connected in series so that the direct-current drive power supply circuit side is in the forward direction, one end is connected to the direct-current drive power supply circuit 30, and the other end is connected to each drive coil 5 via a diode 37 that is in the reverse direction to the direct-current drive power supply circuit 30. Is connected to the connection point between the switching transistor 32 and
Switching transistors 38 and 39 are provided in parallel with 5 and 36.
Are connected. The spark killer voltage setting circuit 60 receives the signal from the temperature detecting element 8 and outputs no H level signal from either the first output terminal 60a or the second output terminal 60b when the temperature is within the normal range.
When the temperature deviates from the upper limit of the normal range, an H level signal is output from either one or both of the first output terminal 60a and the second output terminal 60b according to the deviated temperature. The first output terminal 60a is connected to the base electrode of the switching transistor 38, and the second output terminal 6a.
0b is connected to the base electrode of the switching transistor 39, and the temperature detection element 8 of the impact dot head is 7
When the temperature is 0 ° C. or higher, the first output terminal 60a outputs the H level signal, and when the temperature is 85 ° C. or higher, both the first and second output terminals output the H level signal.
The output terminal of the AND gate 40 is connected to each base electrode of the switching transistor 32. AND gate 4
For 0, print data is input to one input terminal and a signal from a reference timing signal generating circuit 50 described later is input to the other terminal. The reference timing signal generation circuit 50 includes a drive pulse signal generation circuit 51, an AND gate 52, a correction pulse signal generation circuit 54, and an OR gate 55. The drive pulse signal generating circuit 51 is configured to output a pulse signal of, for example, 250 μs, which is the time required to drive the print wire 7 when the print timing pulse (see A in FIG. 2) is received. A driving pulse signal is input to one input terminal of the AND gate 52, and a signal (see B in FIG. 2) described later is input to the other input terminal of the AND gate 52. It outputs the signal when the signal is input. The correction pulse signal generation circuit 54 is configured to be activated at the trailing edge of the pulse signal from the drive pulse signal generation circuit 51 and output a pulse of time T1. This time T1 is sufficient to drive the print wire normally even when the temperature of the impact dot head 23 (that is, the temperature of the drive coil 5) rises outside the set temperature range and the resistance value of the drive coil 5 increases. The pulse is set so that electric energy can be supplied (for example, 20 μs). The output terminals of the drive pulse signal generation circuit 51 and the correction pulse signal generation circuit 54 are connected to the output terminals via an OR gate 55. The temperature detection circuit 56 receives a signal from the temperature detector 8 which detects the temperature of the impact dot head 23, and outputs an L level signal in a temperature range lower than a set temperature range (eg 70 ° C.) and an H level signal in a temperature range higher than the set temperature range. Is set by the window comparator to output.

Next, the operation of the apparatus thus constructed will be described with reference to the timing chart of FIG. When the impact dot head 23 is maintained within the set temperature range (section A in FIG. 2), when the print timing pulse A is output, the drive signal generation circuit 51 causes the drive pulse having the pulse width set here. Output signal F, OR gate 55
The gate 40 of the output circuit 42 is opened via. On the other hand, the print data signal E for selecting the print wire 7 to be driven is output in synchronization with the output of the print timing pulse. As a result, the AND gate 40 associated with the printing wire 7 to be printed is driven by the drive pulse signal F.
A pulse synchronized with is output to turn on the switching transistor 32 connected thereto, thereby supplying a current from the DC drive power supply circuit 30 to the drive coil 5. This excites the drive coil, attracts the lever, and moves the print wire in the platen direction. On the other hand, the temperature of the impact dot head rises due to printing, and the temperature detection element 8
When the temperature exceeds the upper limit set value (for example, 72 ° C.) (section (a) in FIG. 2), the temperature detection circuit 56 outputs the H-level signal B. When the print timing pulse A is output in this state, the drive pulse signal generation circuit 51 outputs the drive pulse signal F, and similarly, a current is passed through the drive coil 5 to move the print wire 7 in the platen direction. The drive pulse signal F passes through the AND gate 52 opened by the H level signal from the temperature detection circuit 56 and the correction pulse signal generation circuit 5
It outputs to 4 and operates this. In this way, the correction pulse signal G is output from the correction pulse signal generation circuit 54 during the process in which the print wire 7 strikes the platen 16. Since the print data signal E is still held at this time, the switching transistor 32 related to the print wire that is performing printing is turned on again by the correction pulse signal G from the AND gate, and the DC drive power supply circuit 30 supplies the current. Drive coil 5 continuously
Will be excited. On the other hand, when the energization of the drive coil 5 is completed, the drive coil 5 releases its electromagnetic energy and generates a counter electromotive force.

When the impact dot head is below the normal set temperature range of 70 ° C., the counter electromotive force causes the flyback current Ib1 to be generated in the drive coil 5 because the potential of the counter electromotive force exceeds the conduction potential of the spark killer circuit 62. It will assist the movement of the platen toward the platen. In this way, the counter electromotive force becomes lower than the conduction potential V1 set in the spark killer circuit 33, and the flyback current Ib1
Will stop early. On the other hand, the detected temperature exceeds 70 ° C 7
In this case of 2 ℃, spark killer voltage setting circuit 60
Outputs an H level signal from the first output terminal 60a to make the switching transistor 38 conductive. This allows
The conduction potential V2 of the spark killer circuit 33 decreases by the Zener voltage of the constant voltage diode 34, and the flyback current Ib2 becomes longer than the flyback current Ib1 described above. As a result, the lever in the printing process is further attracted in the movement direction by the drive coil 5, and the printing wire is struck on the platen. Further, when the temperature of the impact dot head becomes 80 ° C. or higher (section C in FIG. 2), the correction pulse is supplied in the same manner as when the temperature is 70 ° C. or higher.
a, the switching transistors 38 and 39 are rendered conductive in order to output the H level signal from the second output terminal 60b.
As a result, the conduction potential V3 of the spark killer circuit 33 is reduced by the Zener voltage of the constant voltage diodes 34 and 35, so that the flyback current Ib3 becomes longer than the flyback current Ib2 described above, and the flyback current Ib3 becomes longer. It increases the role of assisting movement toward the platen. Therefore, even if the supply of electric energy to the drive coil 5 is lowered due to the rise in the temperature of the impact dot head, the correction pulse is further supplied, and the flyback current is supplied for a long time to supply the electric energy required for printing to the drive coil. 5, the printing wire can be stably driven, and normal printing can be performed.

FIG. 3 shows a second embodiment of the present invention.

Reference numeral 5 in FIG. 3 is a drive coil for operating the lever, one end of which is connected to the DC drive power supply circuit 60 and the other end of which is connected to the ground through the switching transistor 62. Each drive coil 5 is connected to the switching transistor 62, and the connected terminal is connected to the DC drive power supply circuit 30 via the spark killer circuit 33.

In the spark killer circuit 33, three constant voltage diodes 34, 35, 36 are connected in series so that the DC drive power supply circuit side is in the forward direction, and one end is DC drive power supply circuit 30 and the other end is DC drive. The power supply circuit 60 is connected to the connection point between each drive coil 5 and the switching transistor 62 via the diode 37 in the opposite direction, and the switching transistors 38 and 39 are connected in parallel to the two constant voltage diodes 35 and 36. ing. The spark killer voltage setting circuit 60 receives the signal from the temperature detecting element 8 and does not output an H level signal from either the first output terminal 60a or the second output terminal 60b when the temperature is within the normal range. When it deviates from the upper limit of the range, it is configured to output an H level signal from one or both of the first output terminal 60a and the second output terminal 60b according to the deviated temperature. The base electrode of the switching transistor 38 and the second output terminal 60b are connected to the base electrode of the switching transistor 39. In this embodiment, the first output terminal 60a outputs an H level signal when the temperature detecting element 8 of the impact dot head shows 70 ° C. or higher, and both the first and second output terminals when it shows 85 ° C. or higher. Is set to output an H level signal.

Each switching transistor 62 has its base electrode connected to the output terminal of an output circuit 67 formed of an AND gate 66. The print data is input to one input terminal of each AND gate 66, and the signal from the drive pulse signal generation circuit 61 is input to the other terminal. The drive pulse signal generation circuit 61 is configured to output a pulse signal of a time required to drive the print wire 7 when a print timing pulse is received. A signal from a temperature detection circuit 65, which will be described later, is also input to the drive pulse signal generation circuit 61, and the drive pulse signal generation circuit 61 drives the print wire according to the input signal by the signal from the temperature detection circuit 65. It is configured to output the pulse signal of the time required for the operation. The temperature detection circuit 65 outputs at least two or more different signals to the drive pulse signal generation circuit 61 according to the temperature information from the temperature detection element 8 which detects the temperature of the impact dot head. In the present embodiment, the temperature detection circuit 65 outputs different signals to the drive pulse signal generation circuit 61 in three stages of less than 70 ° C., 70 ° C. or higher, and 85 ° C. or higher.

Next, the operation of the apparatus thus constructed will be described with reference to the timing chart of FIG. When the print timing pulse K is output, the drive pulse signal generation circuit 61 outputs the drive pulse signal P having the time width set according to the signal L from the temperature detection circuit 65, and the gate 66 of the output circuit 67 is output. Open. The time width of the drive pulse in this case is set to 250 μs. On the other hand, the print data signal O for selecting the print wire to be driven is output in synchronism with the output of the print timing pulse. As a result, the AND gate 66 associated with the print wire to be printed outputs a pulse in synchronization with the drive pulse signal P, turns on the switching transistor 62 connected to this, and supplies a current from the DC drive power supply circuit 60 to the drive coil 5. To supply. As a result, the drive coil 5 is excited to attract the lever and move the print wire in the platen direction. On the other hand, the temperature of the impact dot head 23 rises due to printing, and the temperature detection element 8 is set to the upper limit set value or more,
For example, when the temperature reaches 72 ° C. (section (a) in FIG. 4), the temperature detection circuit 65 outputs a signal L different from that when the temperature is lower than 70 ° C. When the print timing pulse K is output in this state, the drive pulse signal generation circuit 61 receives the input signal and outputs 7
The drive pulse signal P that is longer than that at a temperature lower than 0 ° C. is output.
As an example, the drive pulse width in this case is 260 μs.

When the drive coil 5 is de-energized, the drive coil 5 releases its electromagnetic energy to generate a counter electromotive force. When the impact dot head 23 is below the normal set temperature range of 70 ° C., the counter electromotive force has a potential higher than the conduction potential of the spark killer circuit 33. Therefore, the flyback current Ic1 is generated in the drive coil 5 to cause the lever platen. Assist movement in the direction. Since the back electromotive force is below the conduction potential V1 set in the spark killer circuit 33, the flyback current Ib1 is stopped early. On the other hand, when the detected temperature is 72 ° C., the spark killer voltage setting circuit 60 outputs the H level signal from the first output terminal 60a and makes the switching transistor 38 conductive, so that the conduction potential V2 of the spark killer circuit 33 is constant. The time until the voltage drops by the Zener voltage of the voltage diode 34 and is stopped by the flyback current Ic2 becomes longer than in the case of the flyback current Ic1 described above. Therefore, as the temperature of the impact dot head 23 rises, the drive coil 5
Even when the supply of electric energy to the drive coil is reduced, by supplying a correction pulse further and by supplying a flyback current for a long time, the electric energy required for printing can be supplied to the drive coil 5, and the stable operation is possible. The printing wire is driven to enable normal printing. Temperature detection element 8 is 85 ℃
Then (section C in FIG. 4), the signal L is output from the temperature detection circuit 65.

When the print timing pulse K is output in this state, the drive pulse signal generation circuit 61 receives the input signal and outputs the drive pulse signal P which is longer than that at 70 ° C. or higher. As an example, the drive pulse width in this case is 2
70 μs. Further, the spark killer voltage setting circuit 60
Outputs an H level signal from the first output terminal 60a and the second output terminal 60b to output the switching transistors 38 and 39.
To conduct. As a result, the conduction potential V3 of the spark killer circuit 33 is lowered by the Zener voltage of the constant voltage diodes 34 and 35, and the time required to stop by the flyback current Ic3 is longer than that in the case of the flyback current Ic2 described above, and the lever platen Increases the role of assisting movement in 16 directions.

Thus, even if the temperature of the impact dot head rises and the supply of electric energy to the drive coil 5 decreases, the pulse time for energizing the drive coil 5 is lengthened to supply the electric energy required for printing. Therefore, the printing wire 7 can be stably driven, and a certain printing quality can be obtained.

[0019]

The spark killer circuit prevents the rebound when the current flowing through the drive coil changes from the increase to the decrease, and the necessary energy can be secured, so that the printing speed is not lowered and the printing wire is not used. It is possible to secure the energy required for printing without lowering the impact force of.

[Brief description of drawings]

FIG. 1 is an impact dot head drive circuit diagram of the present invention.

FIG. 2 is a timing diagram illustrating the operation of the drive circuit of FIG.

FIG. 3 is another impact dot head drive circuit diagram of the present invention.

FIG. 4 is a timing diagram illustrating the operation of the drive circuit of FIG.

[Explanation of Codes] 8 Temperature Detection Element 30 DC Drive Power Supply Circuit 32 Switching Transistor 33 Spark Killer Circuit 34 Constant Voltage Diode 35 Constant Voltage Diode 36 Constant Voltage Diode 37 Diode 38 Switching Transistor 39 for Changing Conduction Potential 39 To Change Conduction Potential Switching transistor 40 AND gate 41 Inverter 42 Inverter 50 Reference timing signal generation circuit 51 Drive pulse signal generation circuit 52 AND gate 54 Correction pulse signal generation circuit 55 OR gate 56 Temperature detection circuit 60 Spark killer potential setting circuit

Claims (1)

[Claims] 1. A drive circuit for driving an impact dot head, comprising a spark killer circuit whose conduction potential is controlled at least according to the temperature of the print head,
An impact dot printer comprising means for regenerating energy stored in the drive coil so as to compensate for a decrease in energy supplied to the drive coil when the drive coil becomes hot.