JPH04357049A - Printing wire driving apparatus - Google Patents

Abstract

PURPOSE:To feed back the electromagnetic energy accumulated in a coil to the input terminal of a constant voltage power supply when the supply of voltage is cut off by energizing the coil by the voltage supplied from a chopper type constant voltage power supply to drive a printing wire. CONSTITUTION:A printing wire driving apparatus is equipped with a chopper type constant voltage power supply 10, coils 18-1... 18-n receiving the voltage generated from the constant voltage power supply 10 to drive printing wires, a printing signal generating part 31 receiving printing data to generate a printing signal, a transistor 20 controlling the voltage given to the coils 18-1... 18-n corresponding to the printing signal and a diode 21 feeding back the electromagnetic energy accumulated in the coils 18-1... 18-n to the input terminal of the constant voltage power supply when the transistor 20 is turned OFF.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive device for efficiently and inexpensively controlling the print wire of a wire dot printer that prints characters and figures using dots.

0002

2. Description of the Related Art An example of a conventional print wire driving device will be explained with reference to FIG. This is a Japanese Patent Application Publication No. 62
This is a simplified embodiment of the invention disclosed in No.-161549.

A voltage V1 is supplied from a power supply input terminal 1 to a constant voltage power supply 3 via a capacitor 2 from a power supply (not shown). The constant voltage power supply 3 is provided with a control terminal 3a for opening and closing the generation of the output voltage Vp. A series circuit constituted by a coil 5 that drives a printed wire (not shown) via a diode 4 and a transistor 6 that controls energization from the constant voltage power source 3 to the coil 5 is connected in parallel to the constant voltage power source 3. ing. Print data is applied to the gate electrode 6a of the transistor 6. A diode 7 is connected to the connection point between the coil 5 and the transistor 6.

The diode 7 feeds back the current generated by the electromagnetic energy accumulated in the coil 5 to the capacitor 2 when the transistor 6 is off.

In the figure, i1 is a current flowing from the constant voltage power source 3 to the coil 5 when the constant voltage power source 3 and the transistor 6 are on. i2 is a current flowing through the diode 4, coil 5, and transistor 6 due to electromagnetic energy accumulated in the coil 5 when the constant voltage power supply 3 is off.

i3 is a current that flows due to electromagnetic energy accumulated in the coil 5 when the constant voltage power supply 3 is turned off and the transistor 6 is turned off.

[0007]

[Problems to be Solved by the Invention] In this conventional example, since the constant voltage power supply is usually of the dropper type, when the differential voltage V1 - Vp is large, the power consumption of the constant voltage power supply 3 itself increases, causing the overall as inefficient. In other words, when using the dropper method, (V1 - Vp) x i (current)
The problem is that a constant voltage power supply consumes a large amount of power.

The present invention is intended to solve these problems, and its purpose is to provide a print wire drive device that reduces the power consumption of the entire printer system by using a chopper type constant voltage power supply even when V1 is higher than Vp. Our goal is to provide the following. Still another object is to provide an inexpensive print wire drive device for serial printers in which components for supplying power to the coils are mounted on the carriage along with the print head.

[0009]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention provides a print wire drive device that drives a plurality of print wires mounted on a carriage of a printer in accordance with print data, in which a DC voltage is input. , a constant voltage power supply that outputs a DC voltage lower than the input DC voltage, and a plurality of drive coils each energized by the output voltage of the constant voltage power supply to drive each of the printed wires;
a plurality of switch means each provided between the output of the constant voltage power source and each of the drive coils to open and close each electric circuit between the output of the constant voltage power source and each of the drive coils, and receiving the print data; switch driving means for driving the switch means; and a unidirectional element for returning electromagnetic energy accumulated in each of the driving coils to the input side of the constant voltage power supply when each of the electric circuits is open. , the constant voltage power supply provides a printed wire drive device having chopper means for temporally chopping the input voltage to generate the output voltage.

0010

[Operation] According to the present invention, the chopper type constant voltage power supply outputs a DC voltage lower than the DC input voltage inputted thereto and supplies it to the drive coil, and the switch drive means drives the switch means according to the print data. The print wire is driven by controlling the supply of the output voltage. When the supply of the output voltage is cut off, the electromagnetic energy accumulated in the drive coil during the supply of the output voltage is returned to the input side of the constant voltage power supply via the unidirectional element.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of the present invention, and is a block diagram of a specific circuit and printer driving section.

The same numbers and symbols as in FIG. 5 have the same meanings.

A chopper type constant voltage power supply 10 is connected to the power supply input terminal 1 via a capacitor 2 . Constant voltage power supply 1
0 is composed of a control section 10a and a smoothing circuit section 10b. The control unit 10a includes a transistor 11 which is controlled to open and close, a transformer 13 which provides an intermittent high-frequency control signal to the transistor 11 via a bias resistor 12, and a transformer 13 which receives an output voltage Vp that is fed back via a wiring 14b. It is composed of a control circuit 14 that provides control signals. Although the transformer 13 may be removed and DC coupling may be used, the control power consumption increases. The smoothing circuit section 10b is a diode 1
5, a coil 17, and a capacitor 16.

The constant voltage power supply 10 has a series circuit of coils 18-1...18-n that drive printed wires (not shown) and coil drive circuits 19-1...19-n, and the output voltage of the constant voltage power supply 10 is connected to both ends of the series circuit. is connected so that it is given. Coils 18-1...18-n for n printed wires
n coil drive circuits 19-1...19-n are connected to each other. The coil drive circuits 19-1...19-n each include a transistor 20 and a diode 21. The cathodes of the n diodes 21 form a wired OR circuit and are connected to the capacitor 2 via wiring 22.

A system control section 30 is connected to the control circuit 14 via a wiring 14a, and a print signal generation section 31 is connected between the system control section 30 and the gate of each of the n transistors 20. The print signal generating section 31 includes a shift register 31a, a latch circuit 31b, and an enable circuit 31c.

The circuit of FIG. 1 is driven by a voltage VDD of approximately 5 volts. When a voltage V1 is supplied from a power supply (not shown) to the constant voltage power supply 10 from the power supply input terminal 1 via the capacitor 2, a voltage of several tens of KHz to
An output voltage with an intermittent waveform of several MHz appears. This output voltage is smoothed by the smoothing circuit section 10b and the output voltage Vp
becomes.

The output voltage Vp is fed back to the control circuit 14 via the wiring 14b, and the control circuit 14 provides a control signal to the transformer 13. When no output voltage appears at point A, the current due to the electromagnetic energy accumulated in coil 17 flows through coil 1.
8-1...18-n and coil drive circuit 19-1...19-n
It is smoothed by a series circuit with and a diode 15. Alternatively, the sawtooth waveform output voltage Vp is smoothed. This is the chopper method. In this case, the transistor 11 has a voltage drop of 0.5V or less when it is on, and the power loss is small.
In the case of the dropper type, power loss increases due to the voltage difference between voltages V1 and Vp. Normally, Vp = 20-3
5V, V1 = selected between 40 and 60V.

The operation of the constant voltage power supply 10 is briefly shown in FIG. 2, in which (a) shows the opening/closing signal given to the control circuit 14 from the system controller via the line 14a. (b) is an intermittent control signal given to the transistor 11; (c
) is the voltage waveform of the output voltage Vp. Rise time tr
, the fall time tf is required to be several μs. This is because the drive cycle of the print wire is about 200 μs, and it is necessary to make it sufficiently smaller than this.

When print data is given to the system control section 30 from the outside, the system control section 30 sends an open/close signal to the constant voltage power supply 10 via the wiring 14a, and then to the print signal generation section 31 via the wiring 30a. It sends out print data signals, shift clocks, latch pulses, and enable signals. The system control unit 30 also generates control signals for controlling other mechanisms of the printer (not shown).

When the above-mentioned signals are applied to the print signal generating section 31, the shift register 31a is placed under these signals.
The latch circuit 31 sequentially shifts and stores the print data.
The print data stored in b is latched and stored all at once.
Then, the print data latched and stored by the enable circuit 31c is given to the coil drive circuits 19-1...19-n via the wirings 31d-1...31d-n.

The method of driving the print wire will now be explained with reference to FIG. (a) is the output waveform of the constant voltage power supply 10, (
b) is the on-time of the transistor 20, (c) is the on-time of the coil 1
8-1...18-n, the print wire is driven to form dots on the recording paper at least before the current i2 ends. Current i1 is a current flowing from constant voltage power supply 10 to transistor 20.

Current i2 is due to electromagnetic energy stored in coil 17 and flows through a loop formed by transistor 20, diode 15, and coil 17. The current i3 is due to the electromagnetic energy of the coil 18 corresponding to the current at the end of the current i2 (when the transistor 20 is off), and flows through the loop formed by the diode 21, the capacitor 2, the diode 15, and the coil 17. Electromagnetic energy is fed back to the capacitor 2 to improve the driving efficiency of the printed wire.

Next, equations for the flow of currents i1, i2, and i3 will be derived. Letting the resistance and inductance of the coil 18 be R and L, respectively, and ignoring the voltage drop across the diodes 15 and 21 and the transistor 20, i1 = Vp /R・(1-EXP(-t/t
0)) ......(1) i2
=i20・EXP(-t/t0)
......(2) i3
=(i30+V1/R)・EXP(-t/t0)
-V1/R...(3).

[0024] However, t=time, i20 and i30 are i1
and the final current of i2, t0 = L/R.

According to such a printed wire driving method, the electromagnetic energy stored in the coil 18 is effectively utilized. Although not shown, the power supplied by the constant voltage power supply 10 can be reduced by 30 to 40% compared to other driving methods. Further, the current i3 needs to disappear quickly in order to improve the response frequency of the printed wire.

[0026] The time t3 at which i3 = 0 is determined from the previous equation,
t3 = -t0 ・log(V1 /(Ri3
0+V1 )) ......(4),
If V1 is increased, it becomes smaller. Keeping Vp constant,
Even if V1 is increased, the power consumption does not change much because the constant voltage power supply 10 is of a chopper type. In other words, the present invention is characterized in that power consumption is reduced and high-speed response characteristics are obtained.

Next, other driving methods shown in FIGS. 3(d), (e), and (f) will be explained. (d) is the output V of the constant voltage power supply 10
p and (e) indicate the on-time of the transistor 20, and the latter half is chopped under the control of the print signal generator 31. As a result, the current in the coil 18 becomes as shown in (f). In this case as well, the print wire can be efficiently driven. However, the number of turns of the coil 18 is reduced to reduce the inductance and the current rise is made faster.

The print wire drive device of the present invention is suitable for serial printers. The number of printed wires is n=
It is about 8 to 48. The response frequency is 1 to 4 KHz, and the peak of the current i1 is ii peak = 0.5 to 2 A. The driving energy for one cycle of the print wire is 3~
6 mJ is normal.

Next, FIG. 4 shows an example of a printer to which the print wire drive device of the present invention is applied. With this printer,
n printed wires and n coils 1 shown in Fig. 1
8-1...18-n are installed in the print head 42
is fixed on the carriage 43. Print data signals, shift clocks, latch pulses, and enable signals are sent from printer control board 47 to print head 42 via cable 46 . print head 4
2 is a belt pulley 45a and 45b when each of the above signals is given.
It moves left and right on the belt 44 and prints on the recording paper 41 provided on the platen 40. In addition, in FIG. 4, the ink ribbon, the motor for rotating the belt wheel, etc. are omitted.

The number of wires of the cable 46 is the sum of the number n of the coils 18-1...18-n shown in FIG. 1 and their common wires (
n+1) or more is normal. Coil 18-1...18-n
If the number of cables 46 is large, the cables 46 are divided into 2 to 4 cables. In this case, not only is it expensive, but it also becomes a load on the motor (not shown).

[0031] Therefore, the drive circuits 19-1...19-n,
The print signal generating section 31 is connected to at least the carriage 43.
to reduce the number of cables and wires.

In this way, as shown in FIG. 1, the number of wires in the cable 46 is the wires 30a and 22, the common wire of the coils 18-1...18-n, VDD, and GND. Since there are four lines 30a for the print data signal, shift clock, latch pulse, and enable signal, there are at least nine lines in total. When the number of coils 18-1...18-n is n=48, the number of wires is usually at least 49, but it can be improved to at least 9 wires.

To summarize the energy consumption of the drive device explained above, the copper loss of the coils 18-1...18-n is 60 to 8
0%, the iron loss of the magnetic circuit of coils 18-1...18-n is 5
-15%, energy converted into mechanical energy including dot formation energy is 5-10%, and energy consumption of circuit elements such as transistors is about 5%.

The iron loss of the magnetic circuit can be easily reduced by constructing the magnetic circuit using a laminated plate magnetic circuit or ferrite, and the printed wire drive efficiency can be further improved.

Furthermore, in carrying out the present invention, for example, if the number of printed wires is n=48 and i1 peak=1A, the total peak current reaches as much as 48A. In this case, stable switching characteristics of the constant voltage power supply 10 shown in FIG. 1 may not be obtained. In such a case, n=
Divide into 4 groups (48 = 4 x 12) and connect 10 constant voltage power supplies.
If you prepare 4 of them and drive them in time division, it will be 1/10 of the constant voltage power supply.
The peak current per unit can be reduced to 48A/4=12A. Controlling the peak current also reduces the load on a power source (not shown) on the input side of the constant voltage power source 10. Furthermore, line drops due to resistance and inductance on the wiring can actually be reduced, making it possible to provide stable driving force to the printed wire.

[0036] Here, specific numerical values and examples of setting conditions of the constituent elements of the present invention will be explained.

V1 = 60V, Vp = 20V, the inductance of the coil 17 is L1 = 10-4H, the capacitance of the capacitor 16 is C = 10-7F, the coil 18
-1...18-n equivalent inductance is L2 = 2.4
×10-3H, equivalent resistance R = 12Ω, coil 1
If VR1 and VR2 are the voltage rise formulas for the capacitor 16 when 1 and 12 8-1...18-n are energized, then VR1=174EXP(-3.71×105 t)+
EXP(-1.83×105t)×{-1.74CO
S (2.71 x 103 t) + 1.15 x 104 SI
N (1.44×103 t)} VR2=120EXP(-4.45×105 t)+E
XP(-2.21×105 t)×{-120COS(
1.44×103 t)+1.81×104 SIN(
1.44×103 t)}. From this, the rise time for the constant voltage power supply 10 to reach Vp = 20V is determined by numerical calculation for the coils 18-1...18.
It can be seen that the time is within several μs without being affected much by the number of −n.

On the other hand, if the falling voltage of the cutoff from the stable period of Vp = 20V is VF1 and VF2, the coil 18-1...
Assuming one initial current i0 = 1A of 18-n, VF1
=77.5EXP(-3.71×105t)+EXP
(-1.84×105 t)×{-57.5COS(2
．． 71×103 t)+1.29×103 SIN(2
．． 71×103 t)} VF2=77.9EXP(-4.45×105 t)+
EXP(-2.21×105t)+{-57.9CO
S (1.44 x 103 t) + 1.29 x 103 SI
N (2.71×10 3 t)}, which is almost the same and is not affected by the number of coils 18-1...18-n. In the above, t is time.

From the above, since the rise and fall characteristics of the constant voltage power supply 10 do not depend on the number of energizations of the coils 18-1...18-n,
High printing quality can be obtained without variations in the energy of wire dots.

In the above example, L1=10-4H<2.4
×10-3/12=2×10-4 and 1/2 CVp 2
=1/2 ×10-7×202 <1/2 L2 i
The values of the constituent elements are determined under the following conditions: 0 2 = 1/2 × 2.4 × 10 −3 × 12 . That is, the energy possessed by the smoothing circuit section 10b shown in FIG.
Energy required for energizing cycle of 18-n: 3 mJ to 5 m
The value is determined so that it is sufficiently smaller than J.

Next, the chopping frequency f will be explained. The emitted power of the constant voltage power supply 10 is Ps = 1/2 L1
i2 f, and the condition is that this is larger than the power consumption Vp i0 n of the coils 18-1...18-n. n=12, i0=1A, Vp=20V, L1=1
0-4H, i=ni0, then f>V from the above two equations
p i0 n/1/2 L1 i2 =34KHz (
Hertz) or higher is fine. On the other hand, the constant voltage power supply 1 described above
The conditions for the characteristic equation for the rise and fall of 0 must also be satisfied. In the equation, EXPONENTIAL damping term and SI
There is a product with the vibration term of NUSOIDAL, but EXP(-
1.83×105 t)=EXP(-t/τ0),
τ0 = 5.5 μs. It is attenuated by 63% at t=τ0. For 20% attenuation t=0.22τ0 =1.2μs
Therefore, f>1/1.2 μs=833 KHz. Therefore, for the component values mentioned above, the chopping frequency is f=1
It is desirable to set the frequency to about MHz, so that the start-up characteristics and flat characteristics in a steady state of a predetermined constant voltage power supply can be obtained.

Furthermore, by making the chopping frequency sufficiently high, the values of the coil 17 and capacitor 16 of the smoothing circuit section 10b can be made small, so that the space can be made smaller and the cost can be reduced. The present invention is also characterized by the settings between such constituent elements.

[0043]

According to the configuration of the present invention as described above, efficiency can be improved by using a highly efficient drive circuit to drive the printed wire and by using a chopper type constant voltage power supply that supplies power that can be opened and closed. Since the input of the constant voltage power supply can be set to a high voltage, the energy stored in the coil can be returned to the coil more quickly, which has an extremely large effect of providing high energy efficiency and high-speed response characteristics.

[Brief explanation of drawings]

FIG. 1 is a diagram showing one embodiment of a print wire driving device of the present invention.

FIG. 2 is a diagram showing operating waveforms of each part of the constant voltage power supply used in the present invention.

FIG. 3 is a diagram showing timing and current waveforms for driving the printed wire of the present invention.

FIG. 4 is a diagram showing an example of application of the present invention.

FIG. 5 is a diagram showing a conventional print wire driving device.

[Explanation of symbols]

1 Current input terminal 2, 16 Capacitor 3, 10 Constant voltage power supply 3a Control terminal 4, 7, 15 Diode 5, 17, 18-1...18-n Coil 6, 11
Transistor 6a Gate electrode 10a Control section 10b Smoothing circuit section 12 Bias resistor 13 Transformer 14 Control circuits 14a, 14b, 22, 31d-1...31d-n Wiring 19-1...19-n Coil drive circuit 30 System control section 31 Print signal Generating unit 31a Shift register 31b Latch circuit 31c Enable circuit 40 Platen 41 Recording paper 42 Print head 43 Carriage 44 Belts 45a, 45b Belt wheel 46 Cable 47 Printer control board

Claims (5)

[Claims] 1. A constant voltage power supply that inputs a DC voltage and outputs a DC voltage lower than the input DC voltage in a print wire drive device that drives a plurality of print wires mounted on a printer carriage according to print data. and a plurality of drive coils each energized by the output voltage of the constant voltage power supply to drive each of the printed wires;
a plurality of switch means each provided between the output of the constant voltage power source and each of the drive coils to open and close each electric circuit between the output of the constant voltage power source and each of the drive coils, and receiving the print data; switch driving means for driving the switch means; and a unidirectional element for feeding back the electromagnetic energy accumulated in each of the driving coils to the input side of the constant voltage power supply when each of the electric circuits is open. A printed wire drive device, wherein the constant voltage power supply has chopper means for temporally chopping the input voltage to generate the output voltage. 2. A printed wire driving device according to claim 1, wherein said constant voltage power source is driven at a predetermined timing to energize said driving coil. 3. The printed wire drive device according to claim 1, wherein the constant voltage power source includes a smoothing coil and a smoothing capacitor for smoothing the chopped voltage to obtain the output voltage, and the smoothing coil and the smoothing capacitor A printed wire drive device, wherein circuit constants of the smoothing coil and the smoothing capacitor are determined such that the energy stored in the drive coil is smaller than the electromagnetic energy stored in the drive coil. 4. The printed wire driving device according to claim 1, wherein when closing each of the electric circuits by each of the switch means, the switch driving means chops each of the switch means during a part of the time interval in which each of the electric circuits is to be closed. Printed wire drive device to operate. 5. The printed wire drive device according to claim 1, wherein at least the drive coil, the switch means,
A print wire driving device comprising: the switch driving means and the unidirectional element mounted on the carriage.