JPH0360317B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a shuttle type serial line printer that uses a magnetic linear scale and a magnetoresistive effect element as a means for creating print drive timing, and particularly relates to a shuttle type serial line printer that uses a magnetic linear scale and a magnetoresistive effect element as a means for creating print drive timing, and in particular, This is to obtain accurate and stable printing timing at the edge.

(Prior Art) In a shuttle type serial line printer, as shown in Fig. 10, a large number of print elements (in Fig. 8, dot impact type printing Hammer) Di
Equipped with a head bank 1 in which are attached in an array,
While this head bank 1 is linearly moved back and forth in directions A and A' via an eccentric disk 2 by a drive motor (not shown), each print element Di is driven to print at a plurality of predetermined dot positions. In the figure, 3a and 3
b is a rail for guiding the head bank 1 in directions A and A'. The movement of the head bank 1 is approximately sinusoidal as shown in FIG. 11, and is relatively slow near the beginning and end of the printing period C1, C1' and fastest at the middle point. The instantaneous position of the head bank 1 is detected at regular distance intervals by a position detection device, and as shown in FIG. A position detection pulse Pi indicating timing is generated based on a position detection signal from the position detection device. The print element drive device is excited in response to this position detection pulse Pi and selectively prints each print element at a dot position Qi (that is, selectively since there are dot positions in the character that are not printed).

Conventionally, a rotary encoder has been known as such a position detection device, but recently, a combination of a magnetic linear scale and a magnetoresistive element (MR element) has been used in this type of printer.

FIG. 13 shows a position detection device consisting of a magnetic linear scale and an MR element. The magnetic linear scale 10 has N poles and S poles arranged alternately at a constant pitch H (for example, 423 μm) in directions A and A' substantially perpendicular to the paper feeding direction B, that is, in the direction of reciprocating linear movement of the head bank 1. The MR element mounting body 20 supports the MR elements F1 to F4, which are arranged in directions A and A' facing the magnetic linear scale 10. These MR elements F1 to F4 may be formed as vapor deposited or sputtered films on a Si substrate or a glass substrate, arranged at intervals of 0.5H, and bridge-connected as shown in FIG. 16. magnetic linear scale 1
When the MR element mounting body 20 moves in the directions A and A' with respect to 0, the output terminals 21a and 21b of the sensor circuit
A sinusoidal sensor output signal is obtained from. That is, a magnetic field parallel to the film is applied to each MR element Fi, and the direction of this magnetic field changes by 1 when the MR element Fi moves by 1 pitch H with respect to the magnetic linear scale 10.
Rotate. In response to changes in the direction of the magnetic field, the resistance value of the MR element changes sinusoidally, and the periodic speed appears to double. Therefore, in the sensor circuit shown in Fig. 16, the resistance values of MR elements F1 and F3 change sinusoidally in the same phase, and change in phase by 180° from these.
The resistance values of the MR elements F2 and F4 change to a sinusoidal wave in the same phase, and as a result, a multiplied sinusoidal wave sensor output signal _S0 is taken out from the output terminals 21a and 21b as shown in FIG. 17a. It will be done.

The magnetic linear scale 10 is integrally attached to the lower part of the head bank 1 as shown in FIG. 18, for example, and the MR element mounting body 20 is arranged so as to face the magnetic linear scale 10 as shown in FIG. and is fixed to the chassis base 11. Therefore, when the head bank 1 moves linearly in directions A and A', the magnetic linear scale 10 also moves together, and each MR element of the MR element mounting body 20 moves in the longitudinal direction, that is, A', with respect to the magnetic linear scale 10. , A′ direction, and as described above, a sinusoidal sensor output signal S ₀ is obtained as a position detection signal from the output terminals 21a and 21b of the sensor circuit, and this sensor output signal S ₀ is a rectangular The 17th waveform is shaped into a waveform and then differentiated.
A position detection pulse Pi as shown in FIG. b is generated.

The position detection pulse Pi is generated when the MR elements F1 to F4 face the magnetized portion 10a of the magnetic linear scale 10, and the period corresponds to the printing period C1, C1'. Also, as shown in Figures 14 and 15,
When the MR elements F1 to F4 face the non-magnetized portion 10b, the position detection pulse Pi is not generated, and this period is a printing pause period or movement direction switching period C0, C.
It becomes 0'. When the head bank 1 moves linearly back and forth in the directions A and A', the relative positional relationship between the magnetic linear scale 10 and the MR elements F1 to F4 changes from the state shown in FIG. 14 (printing pause period C0) to the state shown in FIG. The state shown in the figure (printing period C1) is reached to the state shown in FIG. 15 (printing suspension period C0'), and then the state shown in FIG. 13 (printing period C1') is reached, and the state shown in FIG. The cycle of returning to C0) is repeated.

(Problems to be Solved by the Invention) However, when the MR elements F1 to F4 pass through both ends of the magnetized section 10a, that is, during the printing period C1, C
1' and the printing pause period C0, C0', the waveform of the sensor output signal _S0 is transiently disturbed as shown in FIG.
1, an error occurred in the printing timing at the start and end of C1'. In FIG. 19, ta is the start point of the predetermined (original) printing period C1;
Due to the undesired position detection pulse _P0 , printing is actually started at the wrong time ta'.

The disturbance in the waveform of the sensor output signal _S0 as described above is caused by the hysteresis characteristics of the magnetic head for magnetization during the manufacturing stage of the magnetic linear scale.
MR elements F1 to F
4 is thought to be caused by sensing.

The present invention has been made in view of the above problems of the prior art, and provides a shuttle type serial line printer that uses an improved magnetic linear scale and signal processing technology to obtain accurate and stable printing timing. The purpose is to

(Means for Solving the Problems) The structure of the present invention that achieves the above object is to move a head bank, which is formed by mounting a plurality of print elements in an array in a predetermined direction substantially perpendicular to the paper feeding direction, in a reciprocating linear motion in a predetermined direction. While printing, each print element is driven to print at a plurality of predetermined dot positions, and N is printed in the predetermined direction.
A magnetic linear scale having a magnetized part consisting of poles and S poles arranged alternately at a constant pitch, and a magnetoresistive element facing the scale, one of which is moved integrally with the head bank while the other is fixedly arranged, creates a magnetoresistive scale. In a shuttle type serial line printer that obtains the timing for printing the print element based on the sensor output signal of the effect element, the magnetic field is applied to both ends of the magnetized part of the magnetic linear scale by the magnetoresistive element. an auxiliary magnetization section having N and S poles arranged in extremely small pits that are virtually undetectable; a first reference voltage set near the center level of the sensor output signal;
a reference voltage generating means for generating a second reference voltage somewhat higher than the first reference voltage and a third reference voltage somewhat lower than the first reference voltage; The position detection pulse is generated by setting the pulse width to a period from the first reference voltage to the second reference voltage and a period from the first reference voltage to the third reference voltage, respectively. and generating means.

(Function) When the head bank makes a reciprocating linear movement in a predetermined direction, the magnetoresistive element makes a reciprocating linear movement relative to the magnetic linear scale.

When the magnetoresistive element passes through the magnetized portion of the magnetic linear scale, a periodic waveform sensor output signal is generated in response to a periodic magnetic field of north and south poles arranged at a constant pitch.

Further, when the magnetoresistive element passes through a portion of the magnetic linear scale that is not magnetized, that is, a non-magnetized portion, there is no magnetic field large enough to be sensed, so no sensor output signal is generated.

When the magnetoresistive element passes both ends of the magnetized part of the magnetic linear scale, it faces the auxiliary magnetized part, but here the N and S poles are arranged at an extremely small pitch, and the magnetic field is applied to the magnetic linear scale. Moreover, since the undesired magnetic domains based on the magnetic hysteresis characteristics of the magnetic head are canceled out during the formation of the magnetized portion, there is no magnetic field sufficient to generate a sensor output signal.

Therefore, when the magnetoresistive element passes from the non-magnetized part of the magnetic linear scale, passes through the auxiliary magnetized part, and comes to face the magnetized part, the sensor output instantly has a normal (undisturbed) waveform. A signal is generated,
As a result, printing is started at a predetermined timing. In addition, the sensor output signal that was continuously generated with a normal waveform when the magnetoresistive element passes through the magnetized part changes instantly when the magnetoresistive element comes to face the auxiliary magnetized part. The waveform stops without any disturbance.

A position detection pulse is generated by subjecting the sensor output signal obtained in this way to signal processing. In the present invention, the sensor output signal not only cuts (exceeds or divides) the first reference voltage, but also 2
Since the position detection pulse will not be generated unless the reference voltage of the second reference voltage or the third reference voltage is also turned off, the level of the sensor output signal varies between the second reference voltage and the third reference voltage due to, for example, an offset. does not affect the timing at which the position detection pulse is generated.
Therefore, stable and constant printing timing can be obtained at the beginning and end of each printing period.

(Example) An example of the present invention will be described with reference to FIGS. 1 to 9. Note that the configuration shown in FIG. 10 is also used in this embodiment.

FIG. 1 shows a magnetic linear scale 100 according to this embodiment.

The magnetized portion 100a for obtaining a position detection signal of the magnetic linear scale 100 has a structure in which N poles and S poles are alternately arranged at a pitch Pa of 423 μm, for example.

Both ends of the magnetized part 100a, that is, the non-magnetized part 10
An auxiliary magnetic pole 100a' according to this embodiment is provided in a portion adjacent to 0b. This auxiliary magnetic pole 10
0a' is such that the magnetoresistive element (MR element) does not substantially detect the north pole and the south pole, for example 2~
It has a structure in which they are arranged alternately with an extremely small pitch Pa' of 3 μm. The length or extension range L of these auxiliary magnetic poles 100a is selected to be about 1 pitch Pa (423 μm).

FIG. 2 shows the MR element mounting body 20 according to this embodiment.
Indicates 0.

In this MR element mounting body 200, first MR elements F1 to F4 and second MR elements G1 to G4 are arranged in directions A and A' at a pitch of 0.5H, respectively.
Bridge-connected first and second sensor circuits 202 and 204 are formed as shown in FIGS. 3a and 3b.

Magnetic linear scale 100 is head bank 1
(not shown) integrally attached to the lower portion;
The MR element mounting body 200 may be fixed to a chassis base (not shown). Therefore, when the head bank 1 moves linearly in the directions A and A', the magnetic linear scale 100 also moves together, and each MR element of the MR element mounting body 200 moves linearly in the directions A and A'.
0, the first sensor circuit 20
A first sensor output signal Sa having a periodic waveform (more precisely, a sine wave shape) as shown in FIG. 4 is obtained from the second output terminals 210 and 212.

According to this embodiment, when the MR element mounting body 200 passes the auxiliary magnetized part 100a' of the magnetic linear scale 100, that is, during the period Ta in FIG. 4, the waveform of the sensor output signal Sa is particularly disturbed (pulsates). Never. This is the auxiliary magnetic pole 10
This is because 0a' cancels out the disordered magnetic domain at the end of the magnetized portion 100a, and the pitch of the auxiliary magnetic pole 100a' itself is extremely small, so that its magnetic field is not detected by the MR element.

Note that the output terminal 21 of the second sensor circuit 204
4,216 also provides a sensor output signal Sb with a waveform similar to the sensor output signal Sa in FIG.
However, the phase differs by 90°. That is, when the head bank 1 moves in the direction A, the second sensor output signal Sa is changed as shown in FIG.
The phase of the sensor output signal Sb is delayed by 90°. but,
When head bank 1 moves in direction A',
As shown in Figure 5b, the first sensor output signal Sa
The phase of the second sensor output signal Sb advances by 90° relative to the second sensor output signal Sb.

By the way, the sinusoidal sensor output signals Sa and Sb obtained as described above are shaped into rectangular wave pulses as in the conventional method, and the position detection pulse Pi is generated at the timing of the rise and fall of the rectangular wave pulses. Then, the problem remains that position detection pulses may or may not be output at the beginning and end of the printing periods C1, C1' depending on the offset levels of the sensor output signals Sa, Sb during the printing pause periods Co, Co'.

The situation is shown in FIG. Printing suspension period Co,
There is no problem if the levels of the sensor output signals Sa and Sb at Co' match the center level, that is, the zero cross level VC, but in reality, due to variations in the MR element and other circuit elements, as shown by the solid line in Figure 6a, The zero cross level is higher than VC and lower than it as shown by the dotted line.

Then, at the start and end of the printing period C1, C1', if the level is the solid line, the zero cross level VC is not crossed, so the position detection pulse Pi
However, in the case of the level indicated by the dotted line, the zero cross level VC is cut, so a position detection pulse Pi′ is generated, and as a result, the printing operation becomes uncertain and the printing quality deteriorates.

However, in this embodiment, the above-mentioned problem is solved by the signal processing circuit shown in FIG.

This signal processing circuit includes first and second signal processing sections 300A, 300B and an AND gate 360 having the same configuration.

In the first signal processing unit 300A, the input terminals 302a and 304a are connected to the first sensor circuit 202.
are connected to output terminals 210 and 212 (FIG. 3a), respectively, of the sensors, and receive the first sensor output signal Sa. The input first sensor output signal Sa is input to an operational amplifier 314a that operates as a differential amplifier using resistors 306a, 308a, 310a, and 312a.
After the signal is amplified into a signal waveform as shown in FIG.
is supplied to the inverting input terminal of a. First, second, and third reference voltages V1, V2, and V3 are supplied from a reference voltage generation circuit 340a to non-inverting input terminals of these operational amplifiers 320a, 328a, and 336a, respectively. The first reference voltage V1 is set to approximately the center level VC of the first sensor output signal Sa,
The second reference voltage V2 is set somewhat higher than the first reference voltage V1 (higher than the offset level), and the third reference voltage V3 is set to be higher than the first reference voltage V1.
It is set somewhat lower than the offset level (lower than the offset level). Operational amplifiers 320a, 328
Feedback resistors 318a, 326a, and 334a are connected between the inverting input terminals and output terminals of the transistors a and 336a, and each output terminal is connected to a pull-up resistor 3.
Supply voltage + via 22a, 330a, 338a
Vcc (“1”), thereby each operational amplifier 320a, 328a, 336a is connected to the first, second and third reference voltage V1, V2, V3, respectively.
It operates as a converter or waveform shaping circuit. Therefore, operational amplifiers 320a, 32
The output terminals of 8a and 336a are shown in Fig. 8b, c,
A square wave signal or pulse Ea1 as shown in d
Ea2 and Ea3 are obtained respectively. Pulse Ea1
is supplied to the clock input terminal CL of the D-type flip-flop 346a via an inverting circuit 344a, and directly to the clock input terminal CL of the D-type flip-flop 348a. Also pulse
Ea2 is supplied to the reset terminal R of the D-type flip-flop 346a via the inverting circuit 342a,
Pulse Ea3 is applied directly to reset terminal R of D-type flip-flop 348a. Data input terminals D of these D-type flip-flops 346a and 348a always receive power supply voltage +Vcc ("1"). Therefore, the D-type flip-flop 346a
takes in data "1" at the falling edge of pulse Ea1 (that is, at the rising edge of the output voltage of the inverting circuit 344a), thereby causing the output voltage of the inverting output terminal to fall to "0". Further, the D-type flip-flop 346a is reset at the rising edge of the pulse Ea2, thereby causing the output voltage at its inverting output terminal to fall to "1". Thus, a pulse Ja1 as shown in FIG. 8e is applied from the D-type flip-flop 346a to one input terminal of the AND gate 350a. On the other hand, the D-type flip-flop 348a takes in data of "1" at the rising edge of pulse Ea1, thereby causing the output voltage of its inverted output terminal to fall to "0", and the D-type flip-flop 348a takes in the data of "1" at the rising edge of pulse Ea3. This causes the output voltage of the inverting output terminal to rise to "1". Therefore, the D-type flip-flop 348
A pulse Ja2 as shown in FIG. 8f is applied to the other input terminal of the AND gate 350a.
As a result, a pulse Ja as shown in FIG. 8g is obtained at the output terminal of AND gate 350a, which is supplied to one input terminal of AND gate 360.

The second signal processing unit 300B inputs the second sensor signal Sb and performs the same signal processing on it.
A pulse Jb having a phase difference of 90° from the pulse Ja is obtained at the output terminal of the AND gate 350b, and is supplied to the other input terminal of the AND gate 360. Therefore, the output terminal of the AND gate 360 receives a position detection pulse Pi as shown in FIG.
is obtained. Note that the second sensor output signal Sb is different from the first sensor output signal Sa during the printing period C.
At 1', the phase advances by 90 degrees, and during the printing period C1, the phase advances by 90 degrees.
Delayed by 90°. Therefore, the first sensor output signal
Pulses from AND gate 350a based on Sa
Ja becomes the last position detection pulse Pie at the end of the printing period C1', and becomes the first position detection pulse Pis at the beginning of the printing period C1.

By the way, during the printing pause period Co, the level of the sensor output signal Sa from the operational amplifier 314a reaches the zero cross level as shown by the solid line in FIG. 8a.
When higher than VC, the sensor output signal at the end of the printing period C1' and the beginning of the printing period C1
Since Sa does not cross the zero cross level VC, the output voltage Ea1 of the operational amplifier 320a maintains the "0" level. As a result, the flip-flop 34
6a output voltage Ja1, flip-flop 348
a's output voltage Ja2 and AND gate 350a
The output voltages Ja are as shown by the solid lines in FIG. 8c, d, and e, respectively. Therefore, at the end of the printing period C1', the last position detection pulse is emitted at time te.
Pie is generated, and the first position detection pulse Pis is generated at time ts at the beginning of the printing period C1.

Also, during the printing pause period Co, the operational amplifier 3
The level of the sensor output signal Sa from 14a is 8th
As shown by the dotted line in Figure a, when the sensor output signal Sa is lower than the zero cross level VC at the end of the printing period C1' and the beginning of the printing period C1,
cuts the zero cross level VC. As a result, the output voltage Ea1 of the operational amplifier 320a becomes "0" at the end of the printing period C1', as shown by the dotted line in Figure 8b.
Changes from level to “1” level, printing pause period
It maintains the "1" level during Co, and changes from the "1" level to the "0" level at the beginning of the printing period C1. As a result, the output voltage Ja1 of the flip-flop 346a, the output voltage of the flip-flop 348a, and the output voltage of the AND gate 350a become as shown by the dotted lines in FIG. 8c, d, and e, respectively.
At the beginning of the printing period C1, the flip-flop 346a
However, since the output voltage of the flip-flop 348a is "0", the pulse [Ja1] does not appear at the output terminal of the AND gate 350a, and as a result, the first position is detected at time ts. Pulse Pis is generated.

In this way, even if the level of the sensor output signal Sa (and Sb) is offset and becomes higher or lower than the zero cross level VC during the printing pause period Co, the last position detection pulse Pie of the printing period C1' and the printing The first position detection pulse Pis in the period C1 is always generated at constant timings te and ts.

In this embodiment, the print drive is triggered by the rise of the position detection pulse Pi, so even if the output voltage of the AND gate 360 falls, no print timing is given.

Figure 9 shows the end of the printing period C1 and the printing pause period.
FIG. 6 is a timing chart for explaining the operation at the beginning of Co' and the printing period C1'. Even in this case, when the level of the sensor output signal Sa becomes higher or lower than the zero cross level VC during the printing pause period Co', the operational amplifier 320a, flip-flops 346a, 348
a, the output voltages of the AND gates 350a and 360 fluctuate as shown by the solid and dotted lines in the figure, but at the end of the printing period C1, the last position detection pulse Pie is generated at a constant timing te', and the printing is completed. At the beginning of period C1', the first position detection pulse Pis is generated at a constant timing ts'. In this case, contrary to FIG. 8, the pulse Jb from the AND gate 350b based on the second sensor output signal Sb becomes the final position detection pulse Pie at the end of the printing period C1, and the printing period C1' becomes the first position detection pulse Pis at the starting edge of .

(Effects of the Invention) As described above, in the present invention, the N and S poles are placed at both ends of the magnetized portion of the magnetic linear scale at such a small pitch that the magnetic field is not substantially sensed by the magnetoresistive element. By providing an auxiliary magnetized section consisting of an array of Since position detection pulses are formed using the first, second, and third reference voltages as comparison reference voltages, stable and constant printing can be achieved at the beginning and end of the printing period even if the level of the sensor output signal is offset during the printing pause period. You get the timing.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing the configuration of a magnetic linear scale 100 according to an embodiment of the present invention, and FIG.
Magnetoresistive elements F1 to F in the above embodiments
4. A perspective view showing the arrangement configuration of G1 to G4, FIG. 3 is a circuit diagram showing the connection configuration of the first and second sensor circuits 202, 204 in the above embodiment, and FIG. 4 is a perspective view showing the arrangement configuration of G1 to G4. First sensor circuit 2
FIG. 5 is a signal waveform diagram of the first sensor output signal Sa obtained from the output terminal 02. Figure 6 shows the sensor output signal
A timing diagram for explaining the inconvenience caused by the offset levels of Sa and Sb, FIG. 7 shows a signal processing circuit that inputs the first and second sensor output signals Sa and Sb and generates the position detection pulse Pi. , FIGS. 8 and 9 are timing diagrams showing signals of each part to explain the operation of the signal processing circuit, and FIGS.
Figure 0 is a schematic perspective view showing the head bank of a shuttle type serial line printer, Figure 11 is a diagram showing the movement characteristics of the head bank, and Figure 12 is a diagram showing the movement characteristics of the head bank.
Figures 13, 14, and 15, which show the timing relationship between the predetermined dot position Qi and the position detection pulse Pi in the above serial line printer, show the relative relationship between the magnetic linear scale and the magnetoresistive element (MR element). Diagram showing the positional relationship of the targets, 1st
Figure 6 is a circuit diagram of a sensor circuit consisting of a magnetoresistive element, Figure 17 is a waveform diagram of a sensor output signal generated by the sensor circuit, and Figure 18 is a diagram of the magnetic linear scale and MR in the serial line printer. A perspective view showing the mounting positional relationship with the element mounting body and FIG. 19 are signal waveform diagrams showing problems in the conventional serial line printer. 1...Head bank, D1~D _o ...Print element,
100...Magnetic linear scale, 100a...Magnetized part, 100a'...Auxiliary magnetized part, 100b...Non-magnetized part, F1-F4, G1-G4...Magnetoresistive effect element (MR element), 200...MR element mounting body ,202,
204...Sensor circuit, 300A, 300B...Signal processing unit, 322a, 322b, 328a, 328
b, 336a, 336b... operational amplifier, 340
a, 340b...Reference voltage generator, 346a, 34
6b, 348a, 348b...D flip-flop, 360...AND gate.

Claims (1)

[Scope of Claims] 1. A head bank in which a plurality of print elements are mounted in an array in a predetermined direction substantially perpendicular to the paper feeding direction is moved linearly back and forth in the predetermined direction, while each print element is placed at a plurality of predetermined dot positions. Printing is driven, and a magnetic linear scale having a magnetized portion in which N poles and S poles are alternately arranged at a constant pitch in the predetermined direction and one of the magnetoresistive elements facing the scale are moved integrally with the head bank. and the other fixedly arranged, and a shuttle system obtains a position detection pulse that provides timing for driving a print element for printing based on a periodic waveform sensor output signal obtained from the magnetoresistive element when the head bank moves. In a serial line printer, auxiliary magnetization is provided by arranging N and S poles at both ends of the magnetized portion of the magnetic linear scale at such a small pitch that the magnetic field is not substantially detected by the magnetoresistive element. a first reference voltage set near the center level of the sensor output signal, a second reference voltage somewhat higher than the first reference voltage, and a second reference voltage set somewhat higher than the first reference voltage; a reference voltage generating means for generating a low third reference voltage; a period during which the sensor output signal reaches the second reference voltage from the first reference voltage; and a period during which the sensor output signal reaches the second reference voltage; A shuttle type serial line printer comprising: means for generating position detection pulses each having a pulse width corresponding to a period from the voltage to the third reference voltage.