JPH05155048A - Circuit and method for driving impact head - Google Patents

Abstract

PURPOSE:To always stably perform printing operation without being affected by a temp. change and voltage fluctuations by detecting the driving current flowing to a solenoid to compare the same with a preset reference value and correcting a current supply time so that a proper driving current flows. CONSTITUTION:A microprocessor MPU controlling the driving operation of a head turns a measuring period signal MEAS being an output signal OFF. A current route is altered so that the driving currents of solenoids flow to a current detection circuit before printing is executed to select one of solenoids S1, S2... to drive the same. The current supply time until it is detected that the driving current of the selected solenoid reaches a preset value is measured with respect to each of the solenoid S1, S2... and, when printing executed, the current route is altered so that no driving current flows to the current detection circuit to drive the solenoid for the stored current supply time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving circuit and a driving method for an impact head of a printing apparatus.

[0002]

2. Description of the Related Art A conventional impact head drive circuit does not detect a drive current but simply controls the energization time of all solenoids according to a drive voltage value according to a preset energization time, or JP-B-59-. As shown in FIG. 45209 (shown in FIG. 8), all the wire driving solenoids are provided with the drive current value detection circuit 90, and the drive currents of the solenoids are individually controlled according to the output signal of the drive current value detection circuit 90.

[0003]

However, when the drive current is not detected, the drive current waveform fluctuates due to fluctuations in voltage, environmental temperature, or fluctuations in the resistance value of the solenoid due to heat generated by energizing the solenoid. As a result, fluctuations in print quality and the response capability of the wire when the solenoid is driven are unavoidable. Also, it goes without saying that individual solenoids can always be driven in an optimum state by detecting and controlling the drive currents of all solenoids, but all adjustment work of the circuit that determines the reference current value of the drive current detection circuit is required. However, it has a drawback that the adjustment becomes complicated because it is necessary for the solenoid.

The present invention solves such a problem. An object of the present invention is to optimize the drive current to the solenoid with a circuit configuration that facilitates the adjustment work of the circuit for determining the reference current value. It is to provide a driving circuit for controlling.

[0005]

In order to solve the above problems, the present invention provides a solenoid energizing means for receiving a solenoid selection command, selecting a solenoid indicated by the command from among a plurality of solenoids, and energizing the solenoid for a predetermined time. , A current detection means for detecting a value of a drive current flowing through the solenoid selected by the command, and outputting a detection signal when the value reaches a predetermined value at which desired print quality is obtained, and the detection signal is output. Switch means for disconnecting electrical connection between the solenoid selected by the command and the current detection means, and time measurement means for measuring the time from when the drive current starts to flow until the detection signal is output, A temporary storage unit that stores the measured time and updates the stored content each time the solenoid that is the target of detection of the drive current is selected; and the measured time. Wherein comprises a time changing means for changing the predetermined time, the energizing stop means for stopping the energization of the solenoid, which is selected by the instruction receiving said detection signal,
When the solenoid selected by the command and the current detection unit are not electrically connected to each other, the energizing unit receives the command for the predetermined time changed to the latest measurement time stored in the storage unit. The present invention provides an impact head drive circuit for a printing device that energizes a selected solenoid.

[0006]

According to the present invention, the drive current flowing through each of the plurality of solenoids is compared with a predetermined value that provides the desired print quality, and the energization time is corrected so that an appropriate drive current flows through each solenoid.

[0007]

1 is a block diagram showing the overall construction of a first embodiment of the present invention.

In the figure, S1 to SN are wire driving solenoids provided in the head (subscript N is the total number of solenoids, which will be described below).

The current i flowing through each solenoid is expressed by the following equation.

[0010]

[Equation 1] V1: Driving voltage R: Solenoid resistance L: Solenoid inductance t: Solenoid energizing time P: Magnetic circuit permeance T: Number of solenoid windings Solenoid due to variation of parameters V1, R, L, P, T in the above equation The value of the current that flows through changes. However, in one head, the magnetic circuit of each solenoid is mostly composed of a common member, and since the number of turns T is the same, the variation of the inductance L among the solenoids is very small. Further, since the number of turns of each solenoid is the same, the resistance R of the solenoid is almost equal under the same temperature. Therefore, most of the fluctuation of the current i flowing through the solenoid is due to the fluctuation of the resistance value R due to the temperature change and the fluctuation of the driving voltage V1.

The temperature change speed in the head due to the printing operation is relatively slow, and even if the drive current is controlled by detecting the current flowing in each solenoid at time intervals when the temperature change of the head is below a certain temperature, the solenoid No significant difference occurs as compared with the case where the drive current is controlled every time when driving. The present invention pays attention to this point, and reference numeral 4 in FIG. 1 denotes a current value detector provided in common to all solenoids which characterizes the present invention.

D1 to DN are diodes, ZD1 to ZDN
Is a Zener diode that constitutes a back electromotive force absorption circuit when the solenoid is off. An energization time measuring unit 1 measures an energization time for optimal solenoid driving. An energization time storage unit 2 temporarily stores the energization time. A current path changing unit 3 changes the current path so that the drive current is passed through the current value detecting unit 4 when the current value is detected, and is supplied to the ground otherwise. The current value detector 4 outputs a FULL signal when the current value flowing through the solenoids S1 to SN reaches a predetermined value that produces a predetermined optimum drive. This current value can be obtained, for example, by measuring the current value when the print quality becomes optimum.

An energization time control unit 5 terminates energization of the solenoid being driven when the FULL signal is output from the current value detection unit 4, and the drive is optimized in accordance with the temperature and the driving voltage at that time. Control the energization time of the solenoid. 6
Reference numeral 0 denotes an energization time application unit, which drives the solenoid with the energization time controlled by the energization time control unit 5 when measuring the energization time for optimum driving, and is set in the energization time storage unit 2 when the energization time is not measured. The solenoid is driven according to the energized time.

At the time of printing, a solenoid to be energized is selected by solenoid energization selection signals HD1 to HDN from an external control circuit (not shown). When the solenoid S1 is energized, the energization time measuring unit 1 measures the energization time t1 that provides the optimum driving according to the temperature and the driving voltage at that time, and is set in the energization time storage unit 2 in place of the initial value t0.

Further, the energization times t2 to tN are measured in the same manner as t1 for each of the solenoids S2 to SN and stored in the energization time storage unit 2. Thus the solenoid S1
The energization times t1 to tN, which are the optimum driving of the to SN, are measured and stored, and the solenoids S1 to SN are driven at the stored energization times t1 to tN during printing. After measuring the energization times t1 to tN, printing is continued for the stored energization times t1 to tN, and the temperature and drive voltage of the solenoids S1 to SN at that time are changed after an appropriate time when the temperature of the solenoid is expected to change to some extent. The energization time t is the optimum drive according to
1 ′ to tN ′ are measured again, and the solenoids S1 to SN are driven at the energization times t1 ′ to tN ′ until the energization time is measured next. After that, every time the set time elapses, the solenoid S1
~ Measures and stores the energization time for optimal SN drive,
All the solenoids selected by the energization solenoid selection signal are driven for the stored energization time.

In the present embodiment, the drive current is detected by only one current value detector 4 common to all the solenoids, but the solenoids may be divided into appropriate groups and a current value detector may be provided for each group. good.

Although the present invention has been described with reference to the block diagrams, each component will be described below in more detail with reference to the drawings.

FIG. 2 is a detailed circuit diagram of the block diagram of the first embodiment of the present invention shown in FIG. In FIG. 2, the energization time measuring unit 1 and the energization time recording unit 2 each include a counter 11 and latches LAT1 to LATN. The current path changing unit 3 is composed of a switching transistor QP.

The current detector 4 compares the resistance Rref for detecting the drive current of the solenoids S1 to SN with the detected drive current value Crnt and the set current value. When the drive current value reaches the set current value, the FULL signal is output. Comparator for outputting CMP
And a resistor RC and a variable resistor RD that divide the power supply voltage V2 to set the set current value to a current value that produces optimum driving,
It is composed of diodes DC and DD that hold the FULL signal output from the comparator CMP at the TTL level.

The energization time control section 5 is an AND gate AND which takes in a microprocessor MPU for controlling the drive of the head, a print timing signal PTS and a measurement period signal MEAS output by the microprocessor MPU. A and
AND gate AND The reset set flip-flop 9 is controlled by the A output signal to output the gate signal HON, and controlled by the FULL signal to stop the output of the gate signal HON.

The energization time application unit 60 supplies the energization time data t
While taking d1 to tdN from the latches LAT1 to LATN, timers TMR1 to TMRN outputting gate signals H02N1 to HONN and a measurement period signal MEAS, respectively.
Inverter INV whose output turns on when is off A and
Inverter INV Gate signal H when A output is on
AND gate ANDA that outputs ON1 to HONN respectively
1-ANDAN and gate signal HON or gate signal H
OR gates ORA1 to output ON1 to HONN respectively
According to the outputs of the ORAN and the OR gates ORA1 to ORAN, the solenoid energization selection signals are supplied to the energization signals H1 to HN, respectively.
AND gate AN given to solenoids S1 to SN as
It is composed of DB1 to ANDBN and OR gates ORB1 to ORBN that output energization signals H1 to HN as control signals of the latches LAT1 to LATN, respectively. In this embodiment, the current value detector 4 detects that the drive current value reaches a preset value.

The drive current of the solenoids S1 to SN is detected by the resistor Rref commonly connected in series to the drive elements Q1 to QN.

The operation of the circuit shown in FIG. 2 will be described below with reference to the timing chart of FIG. Reference symbols PTS and C in the figure
LKO is a print timing signal and a clock signal output from an external control circuit (not shown).

First, the energization operation in the period A for measuring the energization time which is the optimum driving before the printing is executed will be described.
In the period A, the microprocessor MPU which controls the driving operation of the head turns on the measurement period signal MEAS which is an output signal. At this time, the inverter INV The output of A turns off, and as a result, the outputs of the AND gates ANDA1 to ANDAN turn off. Also, the transistor Q of the current path changing unit 3
Since the base signal of P is turned off, the drive currents i1 to iN of the solenoids S1 to SN flow through the resistor Rref.

In order to measure the energization time t1, only the solenoid S1 energization selection signal HD1 is turned on and the signals HD2 to HD
When the print timing signal PTS is input with N turned off, the output of the flip-flop 9 in the energization time control unit 5 is turned on, and the energization signal H1 which is the base signal of the transistor Q1 is turned on, so that the solenoid S1 is energized. To start. At this time, only the drive current i1 of the solenoid S1 flows through the resistor Rref. The reference voltage V2 is adjusted by dividing the reference voltage V2 by the resistors RC and RD, the current corresponding to the set current value is input to the negative terminal of the comparator CMP, the drive current is input to the ten terminal of the comparator CMP, and the drive current value Crnt is input. Reaches the set current value, the FULL signal is output from the comparator CMP, as a result, the output of the flip-flop 9 is turned off, and the energization signal H1
Turns off.

The counter 11, which is the energization time measuring unit 1,
The period during which the energization signal H1 is on, that is, the solenoid S
When the energization signal H1 is turned off, the output of the OR gate ORB1 is also turned off when the clock signal counting operation is enabled and the clock signal CLKO is counted, and the latch LAT1 which is the energization time storage unit 2 is turned off. The count value of is stored as energization time data Td1.

In this way, the energization time t1 that provides an appropriate drive according to the temperature and drive voltage of the solenoid S1 at that time is measured, and the energization time data td1 corresponding to the energization time t1.
Are stored in the latch LAT1. Further solenoid S1
To SN, the energization time t2 to tN, which is the optimum driving according to the temperature and the driving voltage at that time, are sequentially measured, and the solenoid S
Similarly to the case of 1, the energization time data td2 to tdN corresponding to the energization times t2 to tN are respectively latches LAT2 to LA.
Stored in TN.

Next, the energization operation during the period for performing printing after the measurement of the energization time for the optimum driving is completed will be described.
During this period, the microprocessor MPU that controls the driving operation of the head turns off the measurement period signal MEAS that is an output signal. At this time, the inverter INV The output of A turns on, and as a result, the base signal of the transistor QP of the current path changing unit 3 turns on, so that the drive currents of the solenoids S1 to SN flow through the transistor QP and do not flow through the resistor Rref. Since the measurement period signal MEAS is off, AND gate AND The output of A is off, and as a result, the output of the flip-flop 9 is off. Timer TMR1 to T
When the print timing signal PTS is turned on, the MRN inputs the energization time data td1 to tdN output from the latches LAT2 to LATN, respectively, and outputs the gate signal HON1 during the period until the clock signal CLKO is input for the energization time data.
~ Turn ON each HONN. The energization selection signals HD1 to HDN of the solenoids S1 to SN are AND gates ANDA, respectively.
1-ANDAN and gate signals HON1-HONN arriving via OR gates ORA1-ORAN are output as energization signals H1-HN by AND gates ANDA1-ANDAN.

As described above, the current path is changed so that the drive current of the solenoid flows to the current detection circuit before printing is performed, and one of the solenoids S1 to SN is selected and driven. The energization time until detecting that the drive current value of the solenoid reaches a preset value is measured for each of the solenoids S1 to SN, and the current path is set so that the drive current does not flow to the current detection circuit when printing is performed. Is changed and the solenoid is driven for the stored energization time.

FIG. 4 is a detailed circuit diagram showing the second embodiment of the present invention. Its basic configuration is similar to that of the block diagram shown in FIG. In this embodiment, the current value detector 40 detects that the integrated value of the solenoid drive current reaches a preset value. In the second embodiment, the detection accuracy is improved by detecting the integrated value, whereas the first embodiment detects the current at a certain time.

In FIG. 4, the current detecting section 40 is composed of a current comparing circuit 40a, an integrating circuit 40b, and a switching circuit 40c for controlling switching of the integrating circuit 40b. The configuration and operation of the other parts are the same as the configuration and operation of the parts in the embodiment shown in FIG.
The description is omitted.

The current comparison circuit 40a includes solenoids S1 to S1.
A resistor Rref that detects the drive current of SN, a comparator CMP that compares the detected drive current value Crnt and the set current value, and outputs a FULL signal when the drive current value reaches the set current value, and a reference voltage -Vr. Resistor RC that divides the voltage to set the set current value to the integrated value of the current value that produces the optimum drive,
It is composed of a variable resistor RD and diodes Dc and Dd for holding the FULL signal at the TTL level.

The integrating circuit 40b comprises an operational amplifier OP, resistors R1 and R2 that determine the amplification degree of the operational amplifier OP, and an integrating capacitor C. Switching circuit 4
0c is a resistance R due to the energization signal H1 of the solenoid S1.
4, a transistor Qb that performs a switching operation between the positive and negative power supply voltages + Vx, -Vx via a resistor R5, and an OR gate OR Transistor Qa that supplies energization signals H1 to HN to transistor Qb via A and resistor R3, and the output voltage of transistor Qb is diode Da and capacitor Ca.
A switching element F1 for controlling switching of the integration circuit 40b by being supplied via
And a resistor Rgs for improving the switching speed of the.

When the energizing signals H1 to HN are turned on, the OR gate OR A base current flows through the transistor Qb through A, the resistor R3, and the transistor Qa. Then, the transistor Qb performs a switching operation between the positive and negative power supply voltages + Vx and -Vx, and its output voltage is given to the gate of the switching element F1 via the diode Da and the capacitor Ca. This causes the switching element F1 to perform a switching operation. Transistor Qb turns off and diode D
When a is reversely biased, the gate and source of the switching element F1 have the same potential via the resistor Rgs.

The operation of the current detector 40 will be described with reference to the timing chart of FIG. The operation of other members is shown in Fig. 3.
Since it is the same as that shown in the timing chart of FIG. When the energization signal H1 signal is turned on, the switching element F1 is turned off and the integrating circuit 40b operates,
The current value integration signal S by integrating the drive current of the solenoid S1
Output UM. The reference current -Vr is divided by resistors RC and RD to input the set current that is set to the + terminal of the comparator CMP, and the current value integration signal SUM is input to the-terminal of the CMP to set the integrated value of the drive current. FUL when the output value is reached
The L signal is output, and as a result, the flip-flop 9 is turned off and the energization signal H1 is turned off. When the energization signal H1 turns off, the switching element F1 turns on, and the output value of the integrating circuit 40b is reset to zero.

FIG. 6 is a block diagram showing an example of an impact head drive system using the impact head drive circuit of the present invention. Reference numeral 100 is a microprocessor for controlling the entire operation of the impact head printing apparatus, 101 is an impact head, 102 is the impact head drive circuit, 105 is a motor for retracting the ink ribbon, and 106 is an ink ribbon retract motor control circuit.

In this embodiment, the impact head drive circuit 1
The detailed circuit 02 is obtained by replacing the microprocessor MPU of the impact head drive circuit shown in FIG. 2 or 4 with the microprocessor 100. The microprocessor 100 retracts the ink ribbon by the ink ribbon retracting motor control circuit 106 and energizes the solenoid before printing is first performed after print data is sent from an external device such as immediately after powering on the printer. After the wire is not printed on the paper even after being driven, the measurement period signal MEAS and the energization selection signals HD1 to HD1 which are the preset measurement data at the timing shown in period A of FIG.
The HDN is output to the impact head drive circuit 102, the solenoid is energized to detect the current value, and the energization time is controlled, measured, and stored. After that, the ink ribbon withdrawal motor control circuit 106 finishes the withdrawal of the ink ribbon, and the ink is driven for the energization time stored in each solenoid to print on the paper.

Thereafter, the microprocessor 100 is instructed by an external device after a predetermined time has elapsed from the start of printing, after printing an appropriate number of characters from the start of printing, or after printing a plurality of lines including one line from the start of printing. During the printing operation of the print data, the ink ribbon retraction motor control circuit 106 retracts the ink ribbon so that the paper is not printed even when the solenoid is energized, and then the preset measurement data is driven by the impact head. Circuit 102
Then, the impact head is driven so that the solenoid is energized to detect the current value and the energization time is controlled, calculated and stored.

FIG. 7 is a block diagram showing another example of an impact head drive system using the impact head drive circuit of the present invention. Reference numeral 100 is a microprocessor for controlling the overall operation of the impact head printing apparatus, 101 is an impact head, 102 is an impact head drive circuit, 103 is a carriage motor for moving the impact head, and 104 is a carriage motor control circuit.

In this embodiment, the impact head drive circuit 1
The detailed circuit 02 is obtained by replacing the microprocessor MPU of the impact head drive circuit shown in FIG. 2 or 4 with the microprocessor 100. The microprocessor 100 causes the carriage motor control circuit 104 to move the print head to the outside of the print sheet area by the carriage motor control circuit 104 before the print data is sent from an external device such as immediately after the power supply of the print device is turned on, and then the solenoid is operated. After the wire is driven so that the paper is not printed, the measurement period signal MEA is output at the timing shown in period A of FIG.
S and the energization selection signals HD1 to HDN that are preset measurement data are set to the impact head drive circuit 102.
The current value is output to the solenoid, the current value is detected, the energization time is controlled, measured, and stored. After that, the carriage motor control circuit 104 moves the impact head to the print sheet, and each solenoid is driven for the stored energization time to print on the sheet.

Thereafter, the microprocessor 100 is instructed by an external device after a predetermined time has elapsed from the start of printing, after printing an appropriate number of characters from the start of printing, or after printing a plurality of lines including one line from the start of printing. Carriage motor control circuit 10 during the printing operation of the print data
After moving the print head to the outside of the print paper area by 4 so that the paper is not printed even when the solenoid is energized,
The preset measurement data is output to the impact head drive circuit 102, the solenoid is energized to detect the current value, and the impact time is controlled and measured, and the impact head is driven.

[0042]

As described above, according to the present invention, the driving current flowing through each solenoid is detected at a time interval where the temperature change of the impact head becomes a certain temperature or less, and the current value can obtain a desired print quality. The energization time is corrected so that an appropriate drive current flows by comparing with a preset reference value. Since at least one current detector is sufficient, the current detection value can be adjusted easily, and stable printing operation can always be performed without being affected by temperature changes and voltage changes.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention.

FIG. 2 is a diagram showing a detailed circuit of the first embodiment of the present invention shown in FIG.

FIG. 3 is a timing chart explaining the operation of the detailed circuit shown in FIG.

FIG. 4 is a diagram showing a detailed circuit showing a second embodiment of the present invention.

FIG. 5 is a timing chart explaining the operation of the detailed circuit shown in FIG.

FIG. 6 is a block diagram showing an example of an impact head drive system using the impact head drive circuit of the present invention.

FIG. 7 is a diagram showing another example of an impact head drive system using the impact head drive circuit of the present invention.

FIG. 8 is a diagram showing a conventional impact head drive circuit.

[Explanation of symbols]

1 energization time measurement unit 2 energization time storage unit 3 current path change unit 4 current value detection unit 5 energization time control unit LATN latch TMRN timer 9 reset set flip-flop 40 current value detection unit 40a comparison circuit 40b integration circuit 40c switching circuit 60 Energization time application section SN solenoid AND A AND GATE ANDAN AND GATE AND B AND gate ANDBN AND gate ORAN OR gate ORBN OR gate CMP comparator Rref resistance F1 switching element OP operational amplifier CL time constant correction unit MPU microprocessor

Claims (3)

[Claims] 1. A plurality of print wire driving solenoids selectively operated in response to a solenoid selection command,
In an impact head drive circuit of a printing device, a solenoid energizing unit that receives the solenoid selection command, selects a solenoid indicated by the command from among the plurality of solenoids, and energizes the solenoid for a predetermined time, and a solenoid selected by the command. A current detection unit that detects a value of a driving current that flows and outputs a detection signal when the value reaches a predetermined value at which desired print quality is obtained; and a solenoid selected by the command when the detection signal is output. First switching means for disconnecting electrical connection with the current detecting means, time measuring means for measuring the time from when the driving current starts to flow until the detection signal is output, and the measured time Temporary storage means for storing and updating the stored content each time the solenoid is selected by the command, and the predetermined time at the measured time. And a current stopping means for stopping the energization of the solenoid selected by the command in response to the detection signal, wherein the energizing means detects the solenoid selected by the command and the current detection. An impact head drive circuit for energizing a solenoid selected by the command for the predetermined time changed to the latest measurement time stored in the storage means when the means is not electrically connected. 2. The current detection means integrates the value of the detected drive current and outputs a current value integration signal, and the value of the current value integration signal provides a desired print quality. 2. A current comparison means for outputting a detection signal when a predetermined value is reached, and a second switch means for stopping the operation of the current integration means when the energization of the solenoid selected by the command is stopped. Impact head drive circuit. 3. A plurality of print wire driving solenoids selectively operated in response to a solenoid selection command,
In the method of driving an impact head of a printing apparatus, the solenoid selection command selects a solenoid indicated by the command from among the plurality of solenoids, energizes for a predetermined time, and a value of a drive current flowing through the solenoid selected by the command. Is detected, the detection signal is output when the value reaches a predetermined value at which desired print quality is obtained, and when the detection signal is output, the solenoid and the current detection are stopped, and the drive current starts to flow. To measure the time until the detection signal is output, store the measured time, update the stored contents every time the solenoid is selected by the command, and set the predetermined time to the measured time. Change, stop the energization of the solenoid that receives the detection signal to detect the drive current, and connect the solenoid selected by the command. Wherein when the current detection is not performed, the stored updated latest driving method of the impact head for energizing a selected solenoid by said predetermined time the command is changed to the measurement time.