JPH01101164A - Driving method for printer head - Google Patents

Abstract

PURPOSE:To obtain a stable printing quality for varying voltage, by controlling the width of a energy controlling pulse according to a head driving voltage and varying a full conduction time. CONSTITUTION:A full conduction pulse generator circuit 8 generates a pulse P1 with a fixed width T1. By triggering the rise of the pulse P1 an energy control pulse generator circuit 10 generates an energy control pulse P2 with a variable pulse width T2. The pulse width T2 is varied by the control signal S2 of a voltage detector circuit 11 according to a head drive voltage V so as to keep a printing energy constant. By triggering the fall of a pulse P2 a chopping pulse generator circuit 9 generate a chopping pulse P3. The frequency and duty of the pulse P3 is constant. A synthetic pulse P4 is applied to the base of a transistor 1 by an AND gate 6 and NOR gate 5, and T'2 varies with a drive voltage V. To the base of a transistor 2 a full conduction pulse P1 is applied.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnet coil drive circuit for a dot printer.

[Conventional technology]

An example of a conventional magnet coil driving method is shown in FIG.

P5 in FIG. 6 is a drive pulse, 15 is a magnet coil current waveform, and d5 is a wire displacement waveform. In this method, the pulse width P5 is set to 13.13'' according to the head drive voltage so that the printing energy remains constant even when the head drive voltage fluctuates.
It is controlled like.

[Problem that the invention seeks to solve]

Therefore, if the head drive voltage is low, the pulse width should be set to 13
It is necessary to make the length longer as shown in 15'', and since the energization is not finished when the wire returns, an attractive force remains in the direction opposite to the wire return, resulting in a delay in wire return as shown in 15''. As a result, the response range to voltage fluctuations is narrow, and attempts to widen the response range result in poor response, resulting in printing defects such as print shading and dot pitch unevenness.

Another method is to detect the current value of a magnet coil, as in Japanese Patent Publication No. 61-58315, and repeat the opening and closing of the current so that the current value remains constant, and then use an integral circuit to make the total input energy a predetermined value. This is a method of stopping electricity supply at a certain point. In the case of this method as well, as shown in FIG. 7, the same problem as in the example of FIG. 6 occurs.

The present invention has been made in view of this problem, and its object is to provide a dot printer that can obtain stable printing quality over a wide range of voltage fluctuations.

[Means for solving problems]

That is, in order to achieve such an object, the present invention provides a method for energizing a magnet coil for a predetermined period of time (total energizing pulse generating means for generating a pulse having a fixed pulse width, and a range shorter than the fixed pulse width). energy control pulse generating means for generating a pulse having a variable pulse width and synchronized with the total energization pulse; and voltage detecting means for detecting fluctuations in head drive voltage; The printer head drive circuit controls the pulse width of the energy control pulse in accordance with the value of the drive voltage to vary the complete energization time.

〔Example〕

Therefore, details of the present invention will be explained below based on illustrated embodiments.

FIG. 1 is a schematic diagram of a circuit showing an embodiment of the present invention, and FIG. 2 is a time chart showing pulse waveforms at various parts. The total energization pulse generation circuit 8 generates a total energization pulse P1 having a fixed pulse width Tl at the timing of the print signal t1.

Using the rise of the total energization pulse P1 as a trigger t2, the energy control pulse generation circuit 10 generates an energy control pulse P2 having a variable pulse width T2. Variable pulse width T2
is varied by the control signal S2 of the voltage detection circuit 11 in accordance with the head drive voltage (2) so that the printing energy remains constant. Furthermore, the chipping pulse generation circuit 9 generates a chopping pulse P3 using the fall of the energy control pulse P2 as a trigger T3. The number of cycles and duty of the chopping pulse P3 are fixed. The AND gate 6 and the NOR gate 5 connect the base of the transistor 1 with the second
A composite pulse P4 shown in the figure is obtained. Here, T''2, like T2, varies depending on the value of the head drive voltage V.The time from the start of 0 energization, when the total energization pulse P1 is applied to the base of transistor 2, to T'2 is Both transistors 1 and 2 are turned on, and the magnet coil 4 is directly connected to the power source, and current flows through the magnet coil 4 along a time constant curve determined by the inductance, internal resistance, and head drive voltage V of the magnet coil 4.T°
When the time period 2 has elapsed, only the transistor 1 is turned off, so that a back electromotive force is generated in the magnet coil 4. This is fed back to the magnet coil via the diode 3 and the transistor 2. Transistor 1 is further turned on and off according to the frequency and duty of chopping pulse P3. When time T1 has elapsed, both transistors 1 and 2 are turned off, and the back electromotive force generated in magnet coil 4 is transferred to the power source via diode 3.3°. will be returned to. The waveform of the current flowing through the magnet coil 4 due to the above operation is shown in FIG. obtain. In other words, the time T"2, T"2 during which both the transistor 1 and the transistor 2 are in the on state (completely energized time) changes in accordance with the fluctuation of the head drive voltage V. The resulting wire displacements d are 12 and 12”
Figure 4.1.
Since the phenomenon of wire return delay as shown in 5'' does not occur, poor response does not occur even if the head drive voltage fluctuates.

Further, FIGS. 4 and 5 show an embodiment in which the present invention is applied to a blister wheel type driver. As shown in FIG. 4, when pulses P6 and P7 are applied to the transistor 17 and 1, respectively, a magnet coil current as shown in FIG. 5 is obtained. Here, if the pulse width Tll of P7 is fixed and the pulse width TI2 of P6 is varied according to the head drive voltage V, the same effect as in the above embodiment can be obtained.

〔Effect of the invention〕

As described above, according to the present invention, the total energization pulse width that determines the entire energization time is fixed, and the pulse width of the energy control pulse, which is shorter than the total energization pulse width, is used to compensate for printing energy due to fluctuations in head drive voltage. Since this is done through control, it is possible to obtain the same printing energy without changing the entire energization time even if the head drive voltage fluctuates.

Therefore, even when the head drive voltage is low, the phenomenon of wire return delay does not occur, and it is possible to cope with a wide range of drive voltages without causing poor response, and it is possible to stably obtain high-quality printing.

[Brief explanation of the drawing]

FIG. 1 is a schematic circuit diagram showing an embodiment of the present invention. FIG. 2 is a timing chart showing pulse waveforms at various parts in FIG. 1. FIG. 3 is an operation diagram showing voltage and current waveforms applied between magnet coils, and FIGS. 4(a) and 4(b) are circuit schematic diagrams and waveform diagrams showing an embodiment in which the present invention is applied to a flywheel type driver. FIG. 5 is a current waveform diagram in FIG. 4. FIG. 6 and FIG. 7 are diagrams showing a method of driving a magnet coil according to the prior art. 1, -------PNP switching transistor 2, ---NPN switching transistor 3.3°, --- Diode 4, ---1 --- −... Magnet coil 5, −
-----------NOR gate 6, ----1----
---AND gate 7, --------Inverter and above Applicant Seiko Epson Co., Ltd. Agent Patent attorney Tsutomu Mogami (and 1 other person) Figure 1 Figure 2 Figure 6 Figure 11-T Figure 7

Claims (1)

[Scope of Claims] A method for driving a magnet coil for a dot printer, in which a magnet coil is provided corresponding to each of a plurality of printing wires, and the magnet coil is selectively energized to print, comprising: energizing the magnet coil for a predetermined period of time. total energization pulse generation means for generating a pulse having a fixed pulse width to perform the above, and energy control for generating a pulse having a variable pulse width within a range shorter than the fixed pulse width and synchronized with the total energization pulse. A pulse generating means and a voltage detecting means for detecting fluctuations in the head driving voltage are provided, and the pulse width of the energy control pulse is controlled in accordance with the value of the head driving voltage detected by the voltage detecting means, so that the pulse width of the energy control pulse is completely energized. A method for driving a printer head characterized by varying time.