JPH031261Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to printers, and more particularly to a printer that improves the energization time of a pulsed current applied to a latching solenoid that controls a print head.

<Prior Art> Until now, the pulse width of the pulse current applied to the latching type solenoid that controls the print head of a printer has been a certain fixed value, and the width has been changed by changing the software of the microcomputer.

The configuration of the drive unit of this type of conventional printer is
As shown in the figure. Reference numeral 1 denotes a platen which rotates around an axis P. Recording paper 2 is placed on the cylindrical surface of platen 1, and the recording paper is fed thereby. The print head 3 is fixed to one end of an arm 4 which rotates about a fulcrum Q. The other end R of arm 4 is rod 5
is rotatably fixed in any position. One end of the rod 5 is pulled in the axial direction of the rod 5 by a spring 6 and fixed to a base 7. The other end of the rod 5 is fixed to a plunger 9 of a latching solenoid 8. The plunger 9 is made of a magnetic material. The latch type solenoid 8 is covered with a frame 10 made of magnetic material, and the frame 10 is cylindrical and has a through hole in the center of its bottom 11 so that the plunger 9 can move in its axial direction. There is. The other open end of the frame 10 is closed with a disk-shaped permanent magnet 12 with a hole in the center. The permanent magnet 12 has, for example, a south pole on the circumferential surface of the central hole and a north pole on the outer circumferential surface. Permanent magnet 1
The hole in the center of 2 is closed by a stopper 13 made of rubber, and the other end of the plunger 9 comes into contact with this part. The reason why the stopper 13 is made of rubber is to obtain a sound deadening effect. Inside the frame 10 surrounded by the bottom 11 and the permanent magnet 12, two types of cylindrical solenoids are arranged coaxially along the cylindrical inner surface of the frame 10. One is an attraction coil 14 that creates a magnetic field that attracts the plunger 9 toward the permanent magnet 12, and the other is a return coil 15 that creates a magnetic field that pulls the plunger 9 away from the permanent magnet 12. A stopper 16 is provided outside the frame 10 so as to define the position of the plunger 9 when it is pulled out. Terminal T ₁ is the terminal for the attraction coil, terminal T ₂ is the terminal for the return coil, terminal T ₃
is a common terminal common to these.

In the above configuration, when a pulse current of a predetermined width is passed between the terminals T ₁ and T ₃ , the plunger 9 is attracted toward the permanent magnet 12 against the force of the spring 6 .
Once the plunger 9 is attracted by the permanent magnet 12, it is self-held by the permanent magnet 12 even if the pulse current between the terminals _T1 and _T3 disappears. While the plunger 9 is held by the permanent magnet 12, the arm 4 rotates about the fulcrum Q to press the print head 3 against the recording paper 2, making it ready for recording. On the other hand, in order to raise the print head 3 above the recording paper 2, a pulsed current is passed between the terminals T ₂ and T ₃ to generate a magnetic field in the return coil 15 to pull out the plunger 9. Release self-holding. Therefore, the plunger 9 is pulled out by the elastic force of the spring 6 and is stopped at the stopper 16.

FIG. 2 shows a circuit for passing current through the solenoid coil described above. In FIG. 2, the emitter of a transistor Q ₁ is connected in series with the terminal T ₁ of the attraction coil 14, the transistor Q ₂ is connected in series with the terminal T ₂ of the return coil 15, and these transistors Q ₁ , A power supply E _B is applied between the collector of Q ₂ and the common terminal T ₃ . Diodes D ₁ and D ₂ are connected between the terminals T ₁ and T ₂ and the terminal T ₃ , respectively, so that the common terminal T ₃ side serves as an anode. These diodes D ₁ and D ₂ are for dissipating the electromagnetic energy in the attraction coil 14 and the return coil 15, respectively. The bases of transistors Q ₁ and Q ₂ are connected to output ports P ₁ and P ₂ of a microcomputer (hereinafter abbreviated as CPU) 17, respectively.

In the above configuration, when a pulse voltage that is made positive by the time width prestored in the CPU 17 is applied to the base of the transistor _Q1 via the output port _P1 , the transistor _Q1 becomes conductive and the time width of the corresponding positive pulse is changed. A current flows through the attraction coil 14 to attract the plunger 9. In order to cause current to flow through the return coil 15, a pulse voltage is applied to the output port _P2 to make it positive for a time width stored in advance in the CPU 17.

In this way, in conventional printers, the pulse width applied to the attraction coil and return coil is constant, so
In order to take into account variations in the spring constant of the springs and fluctuations in the power supply voltage, a pulse with a width longer than necessary must be applied to provide a margin, which has the drawback of causing unnecessary heat generation. In particular, thermal transfer printers are susceptible to the effects of ambient temperature, so an increase in the internal temperature of the printer due to unnecessary heat generation poses a problem. It is also unfavorable from the point of view of power saving.

<Purpose of the invention> In view of the above-mentioned conventional technology, the object of the present invention is to provide a printer that can minimize heat generation by passing current with an optimal pulse width through the attraction coil and the return coil. .

<Structure of the invention> The structure of the invention that achieves this object is to control the movement of the plunger of a latch type solenoid having an attraction coil and a return coil by means of a current flowing through the attraction coil and the return coil, and record the print head by this movement. Relating to a printer that records by pressing onto paper, the first current supply means causes current to flow through the attraction coil, and the time detection means detects the attraction time from when the current flows through the attraction coil until the plunger reaches a predetermined position. and a calculation means for calculating the return time by multiplying the suction time by a predetermined coefficient, and a second current supply means for supplying current to the return coil based on the calculation result of the calculation means. It is.

<Example> Hereinafter, an example of the present invention will be described based on the drawings. Note that parts having the same functions as those in the prior art are denoted by the same reference numerals, and redundant explanations will be omitted.

FIG. 3 is a block diagram showing an embodiment of the present invention. A terminal T ₂ of the return coil 15 is connected to an inverting input terminal of a comparator 19 via a resistor 18 . A parallel circuit including a resistor 20 and a diode 21 is connected between the inverting input terminal of the comparator 19 and the power supply E _B '. The polarity of diode 21 is the power supply
It is connected so that the E _B ′ side becomes the cathode side.
A reference power source E _S is connected between the non-inverting input terminal of the comparator 19 and the common C, and a voltage of _−ES is applied to the non-inverting input terminal of the comparator 19 . The output terminal of the comparator 19 is connected to the input port P ₃ of the CPU 22 and at the same time to the power supply E _B ' through a resistor 23. Comparator 19 is an open collector output, and the output amplitude takes a value between O volts and + _EB ' volts.

Next, the operation of the embodiment of FIG. 3 constructed as above will be explained using the waveform diagram shown in FIG. 4. When the output port P ₁ of the CPU 22 is set to a high level H (FIG. 4A) and the transistor Q ₁ is turned on, a current flows through the attraction coil 14 and generates a magnetic field in the axial direction of the attraction coil 14 that attracts the plunger 9.
The plunger 9 is attracted toward the permanent magnet 12 by this magnetic field, and approaches the permanent magnet 12. Permanent magnet 12
As you get closer to the side, the plunger 9 and permanent magnet 12
As the magnetic resistance of the magnetic path connecting the frame 10 decreases, the magnetic flux density begins to increase, and a back electromotive force is generated in the return coil 15, increasing to the clamp voltage E _C that is clamped by the diode D ₂ . (Figure 4b). This increase in back electromotive force stops at the peak of the waveform shown by the dotted line. This apex is the point when the plunger 9 comes into contact with the stopper 13,
After this, the plunger 9 is held and fixed by the permanent magnet 12, and the back electromotive force decreases (FIG. 4b).
Comparator 19 compares the voltage across return coil 15 with reference voltage _ES . As a result of the comparison, when the voltage at the non-inverting input terminal of the comparator 19 exceeds the reference voltage _ES , the potential at the output terminal becomes a high level H, and when it further falls below the reference voltage _ES , the pulse voltage becomes a low level L. This occurs at the output terminal of (Fig. 4 C). The CPU 22 detects the rise of the voltage at the output end of the comparator 19 at the input port _P3 ,
From this point, the output port
Control the output of _P1 to low level L. The suction time T ₁ (fourth
A) is determined and stored in the memory of the CPU 22.

A calculation procedure for multiplying this suction time T ₁ by a predetermined coefficient R is stored in the memory of the CPU 22, and the pulse width of the current flowing through the return coil 5 is calculated according to this calculation procedure. The coefficient R is a proportionality constant determined by the type of spring and the characteristics of the solenoid. Upon completion of recording on the recording paper 2, a pulse is output from the output port _P2 of the CPU 22 to turn on the transistor _Q2 based on the calculation result _RT1 (Fig. 4D), and the print head 3 is moved from the recording paper 2. Let go.

In the embodiment shown in FIG. 3, the timing for setting the output of output port P ₁ to a low level is determined after detecting the rising edge of input port P ₃ and waiting for a margin time α, but when the falling edge of input port P ₃ is detected. It is also possible to set the output of output port _P1 to a low level. However, if the spring is sufficiently smaller than the unexcited attraction force near zero stroke (the state in which the plunger is held by a permanent magnet), the rise of output port P ₃ will be detected and the output of output port P ₁ will be set to low level L. There is no problem.

In addition, when detecting the comparator output,
By setting a time limit in the CPU 22, disconnection of the solenoid can be detected, and operation with the print head left open can be prevented.

<Effects of the invention> As explained above in detail with the embodiments, according to the invention, the current flowing to the solenoid is turned off after confirming that the stroke of the plunger has become zero, so that the solenoid and mechanical Current can always flow through the solenoid for the optimum amount of time without being affected by variations in power supply voltage or variations in power supply voltage. Therefore, unnecessary heat generation can be prevented, which is useful when applied to thermal transfer printers that are easily affected by ambient temperature.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a drive unit of a conventional printer, FIG. 2 is a block diagram of a circuit that passes current through the coil in FIG. 1, and FIG. 3 is a block diagram showing an embodiment of the present invention. FIG. 4 is a waveform diagram illustrating the operation of the embodiment of FIG. 3. 1... Platen, 2... Recording paper, 3... Print head, 4... Arm, 5... Rod, 6... Spring, 8... Latch type solenoid, 9... Plunger, 10... Frame, 12 ...Permanent magnet, 14
...Attraction coil, 15...Return coil, 17,2
2...CPU, 19...Comparator, _T1 ...Suction time, E _S ...Reference voltage.

Claims (1)

[Scope of utility model registration request] In a printer in which the movement of a plunger of a latch type solenoid having an attraction coil and a return coil is controlled by a current flowing through the attraction coil and the return coil, and the movement presses a print head against a recording paper to record, the attraction coil The first point that passes current
a current supply means; a time detection means for detecting a suction time from when current is applied to the suction coil until the plunger reaches a predetermined position; and a return time is calculated by multiplying the suction time by a predetermined coefficient. A printer comprising a calculation means and a second current supply means for supplying current to the return coil based on the calculation result of the calculation means.