JPH0340608Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a drive circuit for a wire dot print head used in a printer or the like.

[Prior art]

FIG. 1 is a side view of one half of a wire dot printing head used in printers, etc., taken in cross section. In the figure, 1 is a first yoke, 2 is a core provided inside the first yoke 1, and 3 is a A core piece 4 adhered to a notch provided at a corner of the front end face of the core 2 is an electromagnetic coil attached to the outer periphery of the core 2.

A permanent magnet 5 and a second yoke 6 are superimposed and fixed on the first yoke 1, and the second yoke 6 is also fixed to the first yoke 1.
A third yoke 7, a fourth yoke 8, a fifth yoke 9, and a head frame 10 are stacked on top and fixed with screws or the like.

11 is an armature with a printing wire 12 at one end.
The other end is supported by one end of the leaf spring 13. The other end of the leaf spring 13 is fixed between the third yoke 7 and the fourth yoke 8, and the armature 11 supported at one end is fixed.
is deformed so that it is always biased toward the core 2 located on the back side.

Reference numeral 14 denotes a rangeable sheet disposed between the core 2 and the armature 11, 15 a limit guide provided inside the head frame 10 for guiding the printing wire 12 and limiting lateral vibration, and 16 the same. This is a guide for the printing wire 12 and a tip guide for determining the position at the tip of the head.

One printing drive element is constituted by the parts 1 to 16 explained above.

FIG. 2 is a sectional view taken along line A-A in FIG. 1, and 2 ₁ ,
2 ₂ , 2 _{3 .} . . 2 ₂₄ indicate cores arranged in a circular manner. In other words, the wire print head in Figure 1 has a total
It has a structure in which 24 print drive elements are arranged in a circle, and the decimal numbers attached to the core 2 represent the number of each print drive element.

In this configuration, the printing core 2, core piece 3, electromagnetic coil 4, armature 11, printing wire 12, and leaf spring 13 are 24 individual parts, and the others are one common part.

FIG. 3 is an enlarged view of the tip of the wire print head, with 24 print wires 1 as shown.
2 ₁ to 12 ₂₄ are arranged and positioned in two rows divided into odd numbers and even numbers by holes provided in the tip guide 16.

FIG. 4 shows dots printed continuously by the printing wires 12 ₁ to 12 ₂₄ , where P is the pitch between adjacent dots. Here, the printing wires 12 ₁ , 12 ₃ , 12 ₅ in the first row in FIG.
...12 ₂₃ and the second row printing wires 12 ₂ , 12
₄ , 12 ₆ . . . 12 ₂₄ are spaced apart by (n+1/2)P (n is a positive integer) in order to reduce magnetic interference of the print drive elements or peak currents during simultaneous operation.

FIG. 5 is a diagram showing a conventional drive circuit for driving the above-mentioned wire print head. The circuit for operating one print drive element is, for example, connected to the electromagnetic coil 4 ₁ attached to the core 2 ₁ in FIG. On the other hand, drive transistors 17 ₁ , 20 ₁ , reset transistors 18 ₁ , 19 ₁ and diodes 21 ₁ , 22
₁ , ₂₃₁ , and ₂₄₁ , and for this unit circuit and each unit circuit, a drive transistor ₁₇₁ , a reset transistor ₁₉₁ , and an equivalent drive transistor ₁₇₂ of each unit circuit. It is composed of drive transistors 25 ₁ , 25 ₂ and the like that drive the reset transistor 19 ₂ and the like.

Next, a case will be described in which one print drive element is driven by the conventional drive circuit described above.

First, in FIG. 5, when the electromagnetic coil 4 ₁ is not energized, the magnetic flux of the permanent magnet 5 shown in FIGS. _{1 and} 2 is 4 yoke 8 - third yoke 7 - second yoke 6, thereby the core 2
₁ and the armature 11, the leaf spring 13 is deformed into an S-shape and strain energy is stored.

In this state, the driving transistor 25 in FIG.
₁ and the drive transistor 20 ₁ are made conductive at the same time, and the electromagnetic coil 4 ₁ is energized via the drive transistor 17 ₁ . This current drives the current
id, and is shown as id in FIG. 6A. When the electromagnetic coil ₄₁ is energized as described above, the magnetic flux generated thereby cancels the magnetic flux of the permanent magnet 5 in the space between the core ₂₁ and the armature 11, so that the armature 11 is released from the core _21. .
At this time, the strain energy stored in the leaf spring 13 is released, the armature 11 begins to rotate about the corner of the core piece 3, and the printing wire 12 ₁ begins to operate accordingly.

Thereafter, the drive transistor 20 ₁ is made non-conductive. At this time, the back electromotive force generated in the electromagnetic coil 4 ₁ forms a closed loop passing through the diode 23 ₁ and the drive transistor 17 ₁ , current flows through the electromagnetic coil 4 ₁ , and the printing wire 12 ₁ is accelerated. Then, the driving transistor 25 ₁ is also made non-conductive for a time when the required printing force is obtained.

On the other hand, the printing wire ₁₂₁ collides with a medium set on a platen (not shown) via a ribbon to print, and after printing is completed, the armature 11 rotates in the direction of the core ₂₁ , that is, counterclockwise, due to the repulsive force. Exercise. At about the same time, the drive transistor 26 ₁ and the reset transistor 18 ₁ are turned on simultaneously, and the electromagnetic coil 4 ₁ is energized via the reset transistor 19 ₁ . This current is called a reset current and is shown as ir in FIG. 6A. As a result, the electromagnetic coil 4 ₁ is energized in the opposite direction to the above, and the magnetic flux of the electromagnetic coil 4 ₁ increases the magnetic flux of the permanent magnet in the space between the core 2 ₁ and the armature 11. The total amount of magnetic flux increases compared to when no current is passed in the opposite direction through ₁ , and the attraction force that attracts the armature 11 to the core ₂₁ increases.

When the reset transistor 18 ₁ is made non-conductive when appropriate acceleration is obtained, the back electromotive force generated in the electromagnetic coil 4 ₁ forms a closed loop passing through the diode 21 ₁ and the reset transistor 19 ₁ , and the electromagnetic coil A current flows through 4 ₁ and the core 2 ₁ is further accelerated in the direction. After that, printing wire 12 ₁
The driving transistor 26 ₁ is also rendered non-conductive during the time it takes for the transistor 26 to return to its original position. This allows the first part of the printing operation to be
Complete the journey.

The above description has been made by taking as an example the driving of one print driving element by the conventional driving circuit, but this driving circuit drives the driving transistor 25 ₁ and the reset transistor 18 ₁ as described above, and sends the electromagnetic coil 4 ₁ in the opposite direction. By supplying a _{current of}
Achieves faster printing speed.

Next, the drawbacks of this conventional drive circuit will be explained.

Now, there are 12 odd-numbered print driving elements, corresponding to the cores 2 ₁ , 2 ₃ , 2 ₅ ...2 ₂₃ and print wires 12 ₁ , 12 ₃ , 12 ₅ ...12 ₂₃ in FIGS. 2 and 3. Let us consider a case where the print drive elements of 1 are driven, and the other 12 even-numbered print drive elements are not driven.

Here, FIG. 6A shows the waveform of the current flowing through the electromagnetic coils 4 ₁ , 4 ₃ , . . . 4 ₂₃ of the odd-numbered print driving elements, and To represents the repetition period. In addition, FIG. B shows the timing for turning on the driving transistor 25 ₁ that drives the printing driving element of the parsimonious number,
C in the figure shows the timing at which the driving transistors 26 ₁ that drive the even-numbered print driving elements are made conductive. Furthermore, T ₂ in C of the same figure is the third
Since the printing pitch between the printing wires in the first and second rows in the figure is (n+1/2)P, T ₂ = To/2, and the printing wires 12 in each row are driven alternately. shall be.

Therefore, we will now particularly describe the operation at time T in FIG. 6A.

FIG. 7A shows the direction of the magnetic flux φ ₁ when the reset current ir flows through the electromagnetic coil 4 of the odd-numbered printing drive element, and the armature 11 is attracted to the core 2 by this magnetic flux φ ₁ . In the case of a magnetic flux in the opposite direction, the armature 11 moves in the direction in which it is released from the core 2, that is, in the direction of the printing operation.

FIG. 7B shows the direction of magnetic flux flowing into the electromagnetic coil 4 of the even-numbered print drive element due to current flowing through the electromagnetic coil 4 of the odd-number print drive element, and this inflow magnetic flux is defined as φ ₂ .

During the time T in FIG. 6A, the current decreases, so the inflow magnetic flux φ ₂ decreases with time. Therefore, according to the law of electromagnetic induction, the electromagnetic coil 4 in the even-numbered print drive element has e=-
A voltage of N ^d 〓 ² /dt (N is the number of turns of the electromagnetic coil 4) is induced. At the time T when this voltage is induced, the drive transistor 1 drives the even-numbered print drive elements at the timing shown in FIG. 6C.
7 ₂ , 17 ₄ . . . 17 ₂₄ are conductive, so that in _{FIG .}
- A closed loop consisting of the drive transistor 17 ₂ is formed, and the current at this time generates an induced magnetic flux φ ₃ in the direction shown in FIG. 7C. The direction of this induced magnetic flux φ ₃ is the direction of the magnetic flux φ ₁ shown in figure A,
In other words, this is the same direction as the direction in which the armature 11 is released from the core 2.

FIG. 8 is a graph showing the results of measuring the magnetic flux amount of the induced magnetic flux φ ₃ induced in each of the even-numbered printing drive elements that are not driven when 12 odd-numbered printing drive elements are driven at the same time. 2, 4, 6 on the axis
...24, the numbers of the print driving elements correspond to each other, and the distribution of the induced magnetic flux φ ₃ is plotted on the vertical axis.

The inflow magnetic flux φ ₂ is larger in even-numbered print drive elements that are closer to odd-numbered print drive elements (see the arrangement of core 2 shown in FIG. 2 for the arrangement of print drive elements), so it can be seen in this figure. As such, the amount of induced magnetic flux φ ₃ also increases.

The print drive element is the armature 1 as described above.
The armature 11 is released from the core 2 by canceling the magnetic flux of the permanent magnet 5 in the space between the core 1 and the core 2. However, in order to increase the stability of printing operation, the magnetic flux of the permanent magnet 5 is canceled by a certain amount. The armature 11 is set to be released from the core 2 when canceled. Therefore, when the induced magnetic flux φ ₃ is small, the armature 11 in the even-numbered printing driving elements does not move quickly, but when the induced magnetic flux φ ₃ reaches a certain amount, the armature 11 is released from the core 2. Printing will occur as a malfunction.

φ ₄ shown in FIG. 8 is the limit induced magnetic flux that causes this malfunction, and the print drive element whose induced magnetic flux φ ₃ exceeds the limit induced magnetic flux φ ₄ malfunctions. That is, the cores 2 ₁ , 2 ₃ , 2 ₂₁ , 2 ₂₃ shown in FIG.
The print drive elements including cores 2 ₂ , 2 ₄ , 2 22 , and 2 24 close to the print drive elements numbered 1, 3, ₂₁ , and ₂₄ , including the cores 2 2 , 2 4 , 2 22 , and 2 24 including the When driven, the above 1, 3, 21, 24
This method has the disadvantage that the printing drive element of the number 200 may perform erroneous printing operations.

Further, the induced magnetic flux φ ₃ , the limit induced magnetic flux φ ₄ , and the number of print drive elements that perform erroneous printing operations vary depending on the configuration, shape, dimensions, etc. of the print drive elements, but generally they are as shown in FIG. A print drive element group corresponding to the first row of print wires 12 ₁ , 12 ₃ , _{12 5} ... _{12 23} shown in FIG.
The effect is strong in the vicinity of the boundary with the print drive element group corresponding to 12 ₆ ...12 ₂₄ , and the print drive elements near this boundary perform erroneous printing operations.

However, there is a method to eliminate the above-mentioned drawbacks in constructing a wire print head. That is the first
The first yoke 1, permanent magnet 5, second yoke 6, third yoke 7, fourth yoke 8, fifth yoke 9, etc. shown in the figure are not common parts of each printing drive element,
The present invention is to configure an independent magnetic circuit corresponding to each printing drive element. By doing so, the inflow magnetic flux φ ₂ becomes small, the printing operation of each printing drive element becomes stable, and it becomes possible to prevent erroneous printing operations.

However, in this case, the number of parts increases significantly, the structure becomes complicated, and the wire print head becomes expensive.

On the other hand, there is also a method of eliminating the above-mentioned drawbacks in configuring the drive circuit. That is, when the print drive element is not driven, the signal shown in FIG. 6A is not input. That is, in FIG. 5, drive transistors 17 ₁ , 17 ₂ , 17
₃ ...17 Make sure that ₂₄ is not conductive. In other words, drive transistors 17 ₁ , 17 ₂ , 17 ₃ ...1
The driving transistor 25 ₁ that drives the transistor 7 ₂₄ is connected to each of the driving transistors 17 ₁ , 17 ₂ ,
17 ₃ ... 17 ₂₄ and are configured to be driven individually, even if a voltage is induced in the electromagnetic coil 4 by the inflow magnetic flux φ ₂ in FIG.
Since no closed loop is formed on the circuit, no current flows and no induced magnetic flux φ ₃ is generated.

Therefore, the printing operation of the printing drive element is stabilized, and it is possible to prevent erroneous printing operations.

However, this case has the disadvantage that the number of transistors used increases and the cost increases.

[Purpose of invention]

The present invention has been made to solve the above-mentioned drawbacks of the conventional technology, and allows each print drive element to perform stable printing operations without erroneous printing operations, as well as to provide an inexpensive and highly stable drive. The purpose is to realize a circuit.

[Structure of the idea]

In order to achieve the above-mentioned object, the present invention includes a permanent magnet that attracts the wire printing head shown in FIGS. 1 to 3, that is, an armature supported by a leaf spring to a core located on the back side of the armature, and A plurality of printing drive elements each having an electromagnetic coil released from the core are arranged in a circle, and printing wires attached to each armature are arranged in two rows at the tip of the head, and the process of releasing and attracting the armature is arranged in a circle. In the drive circuit of the wire print head, which alternately drives the electromagnetic coils corresponding to each row of print wires, a diode group consisting of two diodes connected in series in a direction that is non-conductive to the power supply, and a switching element are used. Two switching element groups each connected in series are connected in parallel to a power supply, and the midpoint of one diode group and the midpoint of the switching element group are connected to one end of the electromagnetic coil, and the other It has one unit circuit for each printing drive element, which is formed by connecting the midpoint of the group of diodes and the midpoint of the switching element group to the other end of the electromagnetic coil, and also corresponds to one row of printing wires. For the print drive elements near the boundary between the print drive element group corresponding to the print wire of the second column and the print drive element group corresponding to the print wire of the second column, the three switching elements of each unit circuit are each independently driven. a drive element group;
1 that commonly drives the remaining one switching element
drive elements. For the other printing drive elements, there is a drive element group that independently drives the two switching elements of each unit circuit, and two drive elements that commonly drive the remaining two switching elements. By providing a printing drive element group corresponding to the first row of printing wires and a second row of printing wires,
A circuit in which the current induced by the inflow magnetic flux generated when driving the print drive element of the paired column does not flow into the circuit of the print drive element near the boundary with the print drive element group corresponding to the print wire of the column. It is.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

First, FIG. 9 is a diagram showing a first embodiment of the wire print head drive circuit according to the present invention, and the wire print head applied here is the wire print head having the configuration shown in FIGS. 1 to 3. The electromagnetic coils 4 ₂ , 4 ₄ , 4 ₆ ... 4 ₂₄ in the figure are those attached to the cores 2 ₂ , 2 ₄ , 2 ₆ ... 2 ₂₄ (see Fig. 2) of the even-numbered print drive elements. It is.

The electromagnetic coils of one printing drive element are each driven by a set of unit circuits. For example, the unit circuit that drives the electromagnetic coil 4 ₂ includes drive transistors (switching elements) 27 ₂ , 30 ₂ , and reset transistors. Transistor (switching element) 28 ₂ ,
29 ₂ , and diodes 31 ₂ , 32 ₂ , 33 ₂ , 3
Equipped with 4 ₂ .

Here, the drive transistor 27 ₂ and the reset transistor 28 ₂ are connected in series, and the reset transistor 29 ₂ and the drive transistor 30 ₂ are also connected in series to form two transistor groups.

On the other hand, diodes 31 ₂ and 32 ₂ , 33 ₂ and 34 ₂
are connected in series in a direction that makes them non-conductive with respect to the power supply, thereby forming two diode groups.

Then, connect the midpoint of one diode group and the midpoint of the transistor group to one end of the electromagnetic coil ₄₂ ,
The configuration is such that the midpoint of the other diode group and the midpoint of the transistor group are connected to the other end of the electromagnetic coil ₄₂ .

Similarly, unit circuits for driving the electromagnetic coils 4 ₄ , _{4 6} , 4 ₈ .

For the circuit corresponding to the total of four print drive elements near the boundary with the odd numbered print drive element group, drive transistors 27 ₂ , 27
Driving transistors (driving elements) 35 ₂ , 35 ₄ , _{35 6} , which independently drive 4 , 27 ₂₂ , 27 ₂₄ ,
The other drive transistors _{27 6 ,} 27 ₈ . . . 27 ₂₀ are driven in common by a drive transistor (drive element) 35 ₁₀ .

Furthermore, reset transistors 29 ₂ , 29 ₄ ...2
9 ₂₄ are commonly driven by a driving transistor (drive element) 36 ₂ , which is the same as the conventional configuration.

Although not shown, circuits for driving odd-numbered print drive elements are similarly configured.

Furthermore, since the method of driving the print drive element by these circuits is the same as the conventional method, the explanation thereof will be omitted here.

Now, when 12 odd-numbered print drive elements are driven at the same time and even-numbered print drive elements are not driven, the magnetic flux that affects each even-numbered print drive element is as explained in the prior art. According to this, regarding the print drive elements No. 6, 8, 10, . . . 20, even if the drive circuit has the same configuration as the conventional one, the printing operation as a malfunction will not occur.

On the other hand, print drive elements No. 2, 4, 22, and 24,
In other words, in order to prevent the above-mentioned induced magnetic flux φ ₃ shown in FIG. 7C from being emitted from the print drive elements near the boundary with the odd-numbered print drive element groups, in this embodiment, each unit is divided as shown in FIG. The circuit drive transistors 27 ₂ , 27 ₄ , 27 ₂₂ , 27 ₂₄ are replaced by independent transistors 35 ₂ , 35 ₄ , 35 ₆ , 3
5 to ₈ , and if you do not drive the printing drive element, these drive transistors 2
7 ₂ , 27 ₄ , 27 ₂₂ , and 27 ₂₄ are made non-conductive. Therefore, even if the odd-numbered print drive elements are driven, the 2nd, 4th, 22nd, and 24th print drive elements will not malfunction and perform a printing operation.

The same can be said of the odd-numbered print drive elements.

Next, a second embodiment of the present invention will be described.

Although the first embodiment described above uses a drive transistor and a reset transistor as switching elements, it is also possible to use, for example, a thyristor as a switching element instead of these transistors.

FIG. 10 is a diagram showing a unit circuit using such a thyristor, and for one electromagnetic coil 4,
Diodes D ₁ , D ₂ , D ₃ , D ₄ and thyristor
It has a unit circuit consisting of _SCR1 , _SCR2 , _SCR3 , and _SCR4 .

This unit circuit has the same structure as the unit circuit shown in FIG. That is, diodes D ₁ and D ₂ ,
and D ₃ and D ₄ are each connected in series in a direction in which they are non-conductive to the power supply, forming two groups of diodes, and the thyristors SCR ₁ and SCR ₂ and
SCR ₃ and SCR ₄ are also connected in series, forming two thyristor groups. These are connected in parallel to the power supply, and the midpoint of one diode group and the midpoint of the thyristor group are connected to one end of the electromagnetic coil 4, and the midpoint of the other diode group and the midpoint of the thyristor group are connected to one end of the electromagnetic coil 4. It is connected to the other end of the electromagnetic coil 4, and one circuit is provided for each printing drive element. Incidentally, the drive element is the same as in the case of FIG. 9.

FIG. 11 is a diagram showing the waveforms of the pulses that drive the unit circuit of FIG. 10 mentioned above and the current i flowing through the electromagnetic coil 4. By driving in this way, the same function can be obtained.

[Effect of idea]

As explained above, the present invention provides printing drive elements near the boundary between the print drive element group corresponding to the first row of print wires of the wire print head and the print drive element group corresponding to the second row of print wires. Since the circuit is configured in such a way that the current induced by the inflow magnetic flux generated when driving the print drive elements in the parallel column does not flow, the print drive elements other than the print drive elements that should be driven will It is possible to prevent printing operations and ensure stable printing operations, and because only the minimum number of transistors is required, an inexpensive and highly stable drive circuit can be realized. be.

[Brief explanation of drawings]

Fig. 1 is a side view of the wire print head with half of one side cut away, Fig. 2 is a sectional view taken along the line A-A in Fig. 1, Fig. 3 is an enlarged view of the tip of the wire print head, and Fig. 4 is an explanatory diagram showing the pitch of continuously printed dots, Fig. 5 is a circuit diagram showing the drive circuit of a conventional wire print head, and Fig. 6 is a diagram showing the current flowing through the electromagnetic coil in the drive circuit of a conventional wire print head. A waveform diagram showing the timing of conduction of the drive transistor that drives the print drive element and the print drive element, seventh waveform diagram.
Figure 8 is an explanatory diagram showing the direction of magnetic flux, Figure 8 is a graph showing the amount of magnetic flux of induced magnetic flux, Figure 9 is a circuit diagram showing the first embodiment of the wire print head drive circuit according to the present invention, and Figure 10. is a circuit diagram showing a second embodiment,
FIG. 11 is a waveform diagram of pulses and current that drive the unit circuit of FIG. 10. 2, _{2 1} ~ 2 ₂₄ ... Core, 4, 4 ₁ ~ 4 ₂₄ ... Electromagnetic coil, 5 ... Permanent magnet, 11 ... Armature, 1
2, 12 ₁ to 12 ₂₄ ...printing wire, 27 ₂ , 27 ₄ ,
...27 ₂₄ ...drive transistor, 28 ₂ ,2
8 ₄ ...28 ₂₄ ...Reset transistor, 29 ₂ ,
29 ₄ ...29 ₂₄ ...Reset transistor, 30
₂ , 30 ₄ ... 30 ₂₄ ... Drive transistor, 3
1 ₂ , 31 ₄ ... 31 ₂₄ ... diode, 32 ₂ , 32 ₄
...32 ₂₄ ...diode, 33 ₂ ,33 ₄ ...33 ₂₄ ...
Diode, 34 ₂ , 34 ₄ ... 34 ₂₄ ... Diode, 35 ₂ , 35 ₄ , 35 ₈ , 35 ₁₀ ... Drive transistor, 36 ² ... Drive transistor, D ₁ to _{D 4} ...
Diode, SCR ₁ to _{SCR 4} ...Thyristor.

Claims (1)

[Scope of utility model registration request] A plurality of armatures each having a printing wire attached to its tip and whose rear end is supported by a leaf spring, a permanent magnet that attracts the armature to a core located on the back side of the armature, and an electromagnetic coil that releases the armature from the core. The printing drive elements are arranged in a circle, and the printing wires attached to each armature are arranged in two rows at the tip of the head, and in the process of armature release and suction, an electromagnetic pulse is generated corresponding to each row of printing wires. A drive circuit for a wire printing head that alternately drives coils, consisting of a diode group consisting of two diodes connected in series in a direction that is non-conductive to the power supply, and a switching element group consisting of two switching elements connected in series. Two sets of each are connected in parallel to a power supply, and the midpoint of one diode group and the midpoint of the switching element group are connected to one end of the electromagnetic coil, and the midpoint of the other diode group and the switching element group are connected to one end of the electromagnetic coil. There is one unit circuit for each print drive element, in which the midpoint of the group is connected to the other end of the electromagnetic coil, and the print drive element group corresponding to the print wire of the first row and the second For print drive elements near the boundary with the print drive element group corresponding to the print wire of the column, there is a drive element group that independently drives the three switching elements of each unit circuit, and a drive element group that independently drives the three switching elements of each unit circuit, and a drive element group that independently drives the three switching elements of each unit circuit. For the other print drive elements, there is a drive element group that drives the two switching elements of each unit circuit independently, and a drive element group that drives the two switching elements of each unit circuit independently. 1. A drive circuit for a wire print head, comprising two drive elements that commonly drive two switching elements.