JPH0360316B2 - - 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 in particular, relates to a shuttle type serial line printer that uses a magnetic linear scale and a magnetoresistive effect element as a means to create print drive timing, and in particular, to This is to obtain stable timing.

(Prior Art) In a shuttle type serial line printer, as shown in FIG.
The printer is equipped with a head bank 1 in which a large number of print elements (dot impact type printing hammers in Fig. 8) Di are attached in an array at a constant pitch in the A' direction. Each printing element Di is driven to print at a plurality of predetermined dot positions while being linearly moved back and forth in the directions A and A' through the dots. In the figure, 3a and 3b
are rails for guiding the head bank 1 in directions A and A'. The movement of head bank 1 is the 9th
As shown in the figure, it becomes approximately sinusoidal, and the printing period C
1, relatively slow near the beginning and end of C1';
Fastest at the halfway 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. 11 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. 14. magnetic linear scale 1
When the MR element mounting body 20 moves in directions A and A' with respect to 0, the output terminal 21 of the sensor circuit shown in FIG.
A sinusoidal sensor output signal is obtained from a and 21b. In other words, a magnetic field parallel to the film is applied to each MR element Fi, and the direction of this magnetic field is determined by the MR element Fi.
When it moves one pitch H with respect to the magnetic linear scale 10, it rotates once. 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, the first
In the sensor circuit shown in Figure 4, the resistance values of MR elements F1 and F3 change in a sinusoidal waveform in the same phase, and the resistance values of MR elements F2 and F4 change in phase in a sinusoidal waveform with a phase difference of 180 degrees from these. As a result, the output terminal 21a,
From 21b, a multiplied sinusoidal sensor output signal S ₀ is taken out as shown in FIG. 15a.

The magnetic linear scale 10 is integrally attached to the lower part of the head bank 1, as shown in FIG. 16, for example, and the MR element mounting body 20 faces the magnetic linear scale 10 in the arrangement relationship 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 15th 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 12 and 13,
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. 12 (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. 13 (printing suspension period C0'), and then the state shown in FIG. C ₀ ) and repeat the cycle.

(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 periods C0, C0', the waveform of the sensor output signal _S0 is disturbed as shown in FIGS.
An error occurred in the start and end timing of 1'. In FIG. 17, ta is the starting point of the predetermined (original) printing period C1, but printing is actually started at the wrong time ta' due to the undesired position detection pulse _P0 .

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 caused by sensing.

The present invention has been made in view of the above-mentioned problems of the prior art, and it is an object of the present invention to provide a shuttle type serial line printer that uses an improved magnetic linear scale to obtain accurate and stable print start timing. purpose.

(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 portion in which poles and S poles are 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, produces a magnetoresistive effect. In a shuttle-type serial line printer that obtains the timing for printing the print element based on the sensor output signal of the element, the magnetic field is effectively applied to both ends of the magnetized part of the magnetic linear scale by the magnetoresistive element. The present invention is characterized in that an auxiliary magnetized portion is provided in which N poles and S poles are arranged at such a small pitch that they cannot be sensed.

(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 part of the magnetic linear scale, N
A periodic waveform sensor output signal is generated in response to the periodic magnetic field of the pole and south pole.

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.

(Example) An example of the present invention will be described with reference to FIGS. 1 to 7. Note that the configuration shown in FIG. 8 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 set, for example, from 2 to
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 approximately 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 disturbed 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
A second sensor output signal Sb having a waveform similar to that of the sensor output signal Sa shown in FIG. That is, when the head bank 1 moves in the direction A, the phase of the second sensor output signal Sb lags the first sensor output signal Sa by 90 degrees, as shown in FIG. 5a.
However, when the head bank 1 moves in the direction A', the phase of the second sensor output signal Sb advances by 90 degrees with respect to the first sensor output signal Sa, as shown in FIG. 5b.

FIG. 6 shows a signal processing circuit that receives the first and second sensor output signals Sa and Sb and generates a position detection pulse Pi. This signal processing circuit includes first and second signal processing sections 300A having the same configuration,
It consists of 300B and an or gate 340.

In the first signal processing section 300A, the input terminals 302a and 304a are connected to the first sensor output circuit 2.
02 output terminals 210 and 212 (connected to FIG. 3a, respectively, and receive the first sensor output signal Sa.
Figure a) is amplified by an operational amplifier 312a that operates as a differential amplifier circuit using resistors 306a, 308a and a feedback resistor 310a, and then is amplified by a resistor 314.
a to the inverting input terminal of operational amplifier 316a. The power supply voltage +Vcc is connected to the non-inverting input terminal of the operational amplifier 316a through resistors 318a and 320a.
A comparison reference voltage VRE obtained by dividing the voltage is applied via the resistor 322a.
The level of this comparison reference voltage VRE is selected to correspond to the vicinity of the zero-crossing point of the first sensor output signal Sa supplied to the inverting input terminal. Also,
A feedback resistor 324a is connected between the inverting input terminal and the output terminal of the operational amplifier 316a, and the output terminal is connected to the power supply voltage +Vcc via a pull-up resistor 326a. As a result, the operational amplifier 316a operates as a comparator or a waveform shaping circuit, and a rectangular wave signal Ea as shown in FIG. 7b is obtained at its output terminal. This square wave signal Ea
is Ex-OR (exclusive or) gate 3
is supplied to one input terminal of 28a, and
Inverter buffer 330a, CR delay circuit 33
2a, 334a and inverter buffer 336
a, it is delayed by a predetermined time Td as shown in FIG. 7c, and the delayed rectangular wave signal Ea' is supplied to the other input terminal of the Ex-OR gate 328a. Therefore, Ex−OR gate 3
At the output terminal of 30a, an exclusive OR signal Ka as shown in FIG. Supplied.

Note that the second signal processing section 300B performs the same signal processing as the first signal processing section 300A described above on the second sensor output signal Sb, so that
A signal Kb (FIG. 7e) having a phase difference of 90 degrees from the signal Ka is generated, and this signal Kb is mixed with the signal Ka in an OR gate 340 and supplied to the print element drive circuit as a position detection pulse Pi.

As described above, in this embodiment, the waveforms of the sensor output signals Sa and Sb are not disturbed at the start and end of the printing periods C1 and C1' due to the action of the auxiliary magnetic pole 100a' of the magnetic linear scale 100, so that position detection is possible. The generation of the pulse Pi starts and ends at predetermined timings, so printing starts and ends at accurate timings. In addition, the first and second sensor output signals whose phases are different from each other by 90°
Since Sa and Sb are generated and then a double-precision position detection pulse Pi is obtained, double-density printing is possible.

(Effects of the Invention) As described above, in the present invention, the N pole and the S pole are formed at both ends of the magnetized part of the magnetic linear scale with extremely small bits such that the magnetic field is not substantially sensed by the magnetoresistive element. By providing the auxiliary magnetization section formed by arranging the sensor output signal, the sensor output signal instantly appears in a regular waveform at the beginning of the printing period, so printing can be started at accurate 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 first and second
FIG. 7 is a timing diagram showing the signals of each part to explain the operation of the signal processing circuit, and FIG. , a schematic perspective view showing the head bank of the shuttle type serial line printer, FIG. 9 is a diagram showing the movement characteristics of the head bank, and FIG. 10 is a diagram showing the predetermined dot position Qi and position detection pulse in the serial line printer.
Diagram showing the timing relationship with Pi, Figure 11, Figure 1
Figures 2 and 13 are diagrams showing the relative positional relationship between the magnetic linear scale and the magnetoresistive element (MR element), Figure 14 is a circuit diagram of a sensor circuit consisting of the magnetoresistive element, and Figure 15. 16 is a waveform diagram of the sensor output signal generated by the sensor circuit, FIG. 16 is a perspective view showing the mounting positional relationship between the magnetic linear scale and the MR element mounting body in the serial line printer, and FIG. 17 is FIG. 2 is a signal waveform diagram showing a problem in a 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, 340...OR 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. In a shuttle type serial line printer, the other is fixedly arranged, and the timing for driving the printing element to print is obtained based on the sensor output signal of the magnetoresistive element, wherein both ends of the magnetized part of the magnetic linear scale are fixedly arranged. A shuttle type serial line printer is provided with an auxiliary magnetizing section in which N poles and S poles are arranged at such a small pitch that the magnetic field is not substantially detected by a magnetoresistive element.