JP3098121B2 - Serial printer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a serial printer, and more particularly to a serial printer having a synchronizing signal generating circuit for synchronizing the movement of a carriage having a print head and the printing operation of a print head.

[0002]

2. Description of the Related Art In a serial printer, printing (printing) is performed while scanning a carriage on which a printing head of a printing means is mounted in a horizontal direction with respect to a printing medium. Then, density unevenness of the recording result occurs. In particular, in a color printer, a shift in color registration occurs, which is a problem.

Conventionally, as one method for solving these problems, a configuration in which the amount of movement of a carriage equipped with recording means with respect to the apparatus main body is detected, and the recording operation is performed by the recording means while synchronizing with the detection result. It has been known.

That is, a scale section of a linear encoder is fixed on a main body side, and a detection section of a linear encoder is mounted on a carriage which moves relatively to the scale section, and an output signal from the detection section is amplified. Then, the recording signal is taken out of the carriage and a recording signal is generated in synchronization with the amplified signal, thereby preventing print density unevenness and color registration deviation.

FIG. 4 is a perspective view of a main part of the serial printer shown together with the recording medium. In FIG. 1, a carriage 1 indicated by an alternate long and short dash line has a recording unit 2 such as an ink jet recording system mounted thereon, and is guided by a guide shaft 3 having a spiral groove formed on an outer peripheral surface thereof, and is locked by the rotation of the guide shaft 3. A portion (not shown) is driven along the spiral groove, and is reciprocally driven in a direction indicated by an arrow in the drawing with respect to the recording sheet 5 wound on the outer peripheral surface of the platen 4, and a recording sheet (recording medium) A so-called serial printer that forms dots and images by printing dots D at a pitch P on the print head 5 is formed.

[0006] The carriage 1 constructed as described above is provided with an encoder for obtaining a synchronization signal. This encoder is a magnetic linear encoder, and a scale part 6 of the linear encoder in which a magnetic pattern is recorded on a magnetic material formed on the surface of the wire at a print pitch density equivalent to, for example, 180 dots / inch (dpi) or 360 dpi. A magnetic head main body 101 composed of an MR element or the like is fixed inside the carriage 1 while being fixed to the apparatus main body 7, and enables position detection by movement of the carriage 1.

Further, a flexible printed circuit board 8 for extracting an output signal from the MR element in the magnetic head to the outside is connected to the detecting section 101, and a contact section 9 is connected to a connector (not shown). Thus, the carriage substrate 104 (shown by a broken line) mounted on the carriage 1
To connect to.

The carriage substrate 104 and the recording section 2
Is a flexible cable 10 attached to a printer control circuit board 109 fixed on the main body 7 (shown schematically).
Are electrically connected via

FIG. 5 is a block diagram showing an example of a circuit configuration of the serial printer shown in FIG. In FIG.
The detection unit 101 of the magnetic linear encoder which detects the magnetized information on the scale unit of the magnetic linear encoder mounted on the carriage and fixed to the main body side and detects the relative movement position of the carriage has a magnetic resistance. Magnetic sensing elements 102, 10 each composed of an MR element operating based on the effect
3 built-in. The detection unit 101 is connected to a carriage substrate 104 (shown by a broken line in FIG. 4) mounted on the carriage. This carriage substrate 104
It has constant current circuits 105 and 106, and a differential amplifier 107 that differentially amplifies each signal detected by each detection element, and outputs an output signal A ₀ (or 10
8) is output.

[0010] The printer control circuit board 109, generates an output signal A ₀ and A / D converter 112 for converting A / D, the counter pulse A pulse waveform by comparing the reference voltage and the output signal A ₀ (or 111) Comparator 110
A D / A converter 114 for generating a reference voltage V _ref (or 120) as an input signal of one terminal of the comparator 110, a counter / timer 113 for counting a counter pulse A, and a CPU 11 for controlling the system
5 and storage devices such as EEPROM 116 and ROM 11
7, a RAM 118, and a CPU bus 119 which is a bus for data, addresses, and control signals of the CPU 115. Note that some or all of the components shown in the broken lines may be incorporated in the CPU 115.

Next, the operation of the above circuit configuration will be described. Each of the magnetic detection elements 102 and 103 has a constant current circuit 105,
A constant current is supplied through the sensor 106, and the detection unit 101 is moved along the scale unit 6 (see FIG. 4) of the magnetic linear encoder fixed to the main body side in which the magnetic pattern is magnetized in advance at regular intervals. When moved, the magnetic sensing element 102,
The resistance value of the resistor 103 changes, and the amount of change in the resistance value is detected as a voltage change, amplified by the differential amplifier 107, and then the amplified signal is input to one input terminal of the comparator 110.

The output signal A ₀ from the differential amplifier 107 is a pseudo sine wave.
Reference voltage V _ref output from D / A converter 114
And a counter pulse A is obtained as a synchronization signal. The counter pulse A is input to the counter / timer 113 and counted, and the count value indicates the position of the carriage. The CPU 115 controls the system.
It transfers data to and from the ROM 116, the ROM 117, and the RAM 118, controls the A / D converter 112, the counter / timer 113, and the D / A converter 114. Other functions as a serial printer (for example, interface with a host) Function, control of various motors, printing operation, etc.).

As described above, since the output signal A ₀ obtained from the detector of the magnetic linear encoder is a pseudo sine wave, the converter 110 converts the output signal A ₀ into a counter pulse A represented by a digital signal (pulse waveform). Need to convert. On the other hand, it is desirable reference voltage V _ref to be compared is input to the comparator to be used in the conversion and the output signal A ₀ is an average value of the output signal A _0, Therefore,
As the reference voltage V _ref is an average value of the output signal A ₀ is necessary to initially adjust.

The procedure for initial adjustment of the reference voltage _Vref will be described below with reference to the flowchart shown in FIG. FIG.
(A) is a main routine for initial adjustment of the reference voltage _{Vref in} the conventional example. In FIG. 6A, the movement of the carriage is started (step S1). At this time, since the counter pulse from the linear encoder has not yet been correctly output, the moving speed is not known. For this reason, the minimum torque that can move the load based on the mechanical components such as the carriage and the guide shaft is obtained in advance, and the CPU instructs the carriage to move at a speed that is not too fast. Next, the output signal A ₀ from the differential amplifier 107 is detected, and a digital value whose average value of A ₀ becomes the reference voltage _Vref is output to the D / A converter 114 (step S).
2). Next, the carriage is returned to the initial position (step S
3).

[0015] Next, with reference to FIG. 6 (b) will be explained in detail the contents of the aforementioned step S2, first, as initial setting, A ₀ predetermined number n (1 or more integer number of measurements ) Is set in the counter, and at the same time, the addition area A _sum of A ₀ is cleared (step S11). Next, A / D
After A / D conversion of the data of A ₀ using the converter 112, the data is taken into the RAM 118 (step S12). Next, the counter is decremented and A ₀ is added to A _SUM.
Is added (step S13). Next, it is determined whether or not the counter is 0 (step S14). If it is not 0, the process returns to step S12, and if it is 0, the process proceeds to step S15. That is, until the counter becomes 0, Step S12,
Repeat step 13. When the counter reaches 0 in step S14, the carriage is stopped (step S15). Next, the average value A _ave of A ₀ is obtained by dividing A _SUM by the number of measurements n (step S16). Next, a digital value such that V _ref = A _ave is set in the D / A converter 114 (step S17). Finally, the EEPROM 116
To store the digital value set in step S17.

[0016] Note that the sequence of V _ref initial adjustment described above, usually a serial printer is performed only once before being shipped from the factory, when time course of A ₀ output is large, for example, the power at the time of use After turning on, the sequence of _Vref initial adjustment may be incorporated in the initialization sequence. As described above, the digital value stored in the EEPROM is set in the D / A converter in the initialization sequence after the power of the serial printer is turned on.

[0017]

However, the above conventional example has the following disadvantages. As aforementioned,
Since the moving speed of the carriage is unknown at the time of the initial adjustment of the reference voltage V _ref , the sampling period of the A / D conversion of A ₀ is A
_{In the} case where the period becomes an integral multiple of the period T _A0 of the pseudo sine wave of _0, the average value A _ave and the ideal reference voltage V _ref , that is, A ₀
Error with the DC component may increase. FIG. 7 shows such a case. If the average value A _ave having a large error is set in the D / A converter as the reference voltage V _ref , a counter pulse having a duty ratio greatly deviated from 50% will be output.

The reference voltage V _ref is an ideal reference voltage V _ref
FIG. 8 shows a case where the relative deviation ΔV occurs between the average value A ₀ and the reference voltage V _ref in the case of the case of FIG. The relative displacement occurs due to a temperature change, a temporal change in a gap between the scale unit and the detection unit of the linear encoder, and the like. Paying attention to the falling edge of the converter output, it can be seen that Δt ′ in the case of the reference voltage _{Vref having} a large error is larger than the edge fluctuation Δt in the case of the ideal _Vref .

Accordingly, it is an object of the present invention to provide a serial printer capable of initially adjusting a reference voltage so as to obtain an ideal reference voltage.

[0020]

SUMMARY OF THE INVENTION In order to achieve the above-mentioned object, the present invention provides a recording apparatus which performs reciprocating motion on an apparatus main body and performs recording by a recording means while synchronizing the movement of a carriage on which the recording means is mounted. In the serial printer device to be performed, a scale section of a linear encoder provided on the apparatus main body, a detection section of a linear encoder mounted on the carriage to detect the position of the scale section,
Synchronizing signal generating circuit means for receiving a signal output from the detection unit as an input signal and comparing the signal with a reference voltage to generate an output signal having a pulse waveform as a synchronizing signal; and the reference voltage input to the synchronizing signal generating circuit means Reference voltage initial adjusting means for initial adjusting the speed, the reference voltage initial adjusting means includes a speed synchronizing means for synchronizing the moving speed of the carriage and a sampling period for sampling the output signal, and the speed synchronizing means. Measuring means for measuring the value of the output signal a predetermined number of times based on the sampling, after synchronizing the moving speed of the carriage and a sampling cycle for sampling the output signal by the means, and obtained from the measuring means. Means for obtaining a reference voltage by averaging the values.

[0021]

Next, a preferred embodiment of the present invention will be described with reference to FIGS. Note that the hardware of these embodiments has the same configuration as the conventional example already described with reference to FIGS. 4 and 5, and a description of the hardware will be omitted. FIG. 1 is a flowchart showing a sequence of the initial adjustment of the reference voltage Vref of the comparator.

In FIG. 1, steps S21 to S23
Are the same as steps S1 to S3 of the conventional example shown in FIG. These steps S21 to S23, normal values can be obtained to some extent as a counter pulse A _0.

Next, the carriage is moved again (step S24). Next, steps S25 to S27 are performed, and these steps are a carriage speed control loop. That is, the speed of the carriage is detected (step S2).
5) It is determined whether or not the carriage speeds are synchronized (step S26). If not, the carriage speed is adjusted (step S27), the process returns to step S25, and the carriage speed is detected again, and again. It is determined whether or not the carriage speeds are synchronized, and steps S25 to S27 are repeated until the carriage speeds are synchronized. When the carriage speeds are synchronized, the process proceeds to the next step, step S28.

[0024] Here, the speed adjustment of the carriage in step S27 reads the count value of the counter pulse A counter / timer, the period of the output A ₀ of the MR element with respect to the A / D converter sampling period T _S is This is performed by adjusting the speed of the carriage so that the following relational expression 1 holds. T _S = T _A0 / 2 ^m (m is an integer of 1 or more) (1) An example in which the relational expression 1 holds is shown in FIG.

[0025] If this time, T _S is variable, without changing the T _A0, i.e. without changing the moving speed of the carriage may be changed so that only the T _s equation 1 is satisfied.

Next, in step S28, by measuring n times A ₀ at intervals of T _s and calculates an average value A _ave. Step S28 is the same as steps S11 to S18 of the conventional example already described with reference to FIG. However, the number of measurements n must satisfy the following relational expression 2. n = k · 2 ^m (2) (where m is the same as m in the relational expression 1, and k is an integer of 1 or more). An example in which relational expression 2 holds is also shown in FIG. In the example of FIG. 2, m = 2, k = 2, n
= 8.

In order for the average value A _ave of the n times of measurement to be equal to the DC component of A ₀ , it is sufficient to perform sampling at a point where the phase of A ₀ is shifted by 180 °, and in the example of FIG. , Points 201 and 203, points 202 and 204, point 2
It can be seen that the values at points 05 and 207 and the points 206 and 208 cancel out the error with the DC level of A ₀ , respectively.

Finally, the carriage is returned (step S29), and the initial adjustment of _Vref is completed.

Next, another embodiment will be described with reference to FIG. The sequence of the initial adjustment of the reference voltage is the same as in FIG. This embodiment, when the sampling period T _s can not be shorter than the period T _A0 output A ₀ of the MR element, i.e., can be applied if it can not slow down the moving speed of the carriage.
That is, if the above-mentioned relational expressions 1 and 2 are changed to the following relational expressions (1 ′) and (2 ′), the average value A _{ave of the} measurement is obtained.
Can be reduced. T _S = T _A0 (1/2 + m) (m is an integer of 1 or more) (1 ′) n = 2 ^k (k is an integer of 1 or more) (2 ′) An example where m = 1, k = 2, and n = 4 is shown, and the values of points 301 and 302 and the values of points 303 and 304 cancel each other.

[0030]

As described above, the sequence of synchronizing the moving speed of the carriage with the sampling period of the output of the MR element by the A / D converter and sampling the number of times obtained from the moving speed of the carriage and the sampling period is V _ref. By adding to the initial adjustment sequence, a counter pulse with a duty ratio close to 50% can be obtained, and a change in the waveform of the counter pulse due to a temporal change in the output of the MR element is suppressed. Density unevenness can be reduced.

[Brief description of the drawings]

FIG. 1 is a flowchart of an initial adjustment sequence of a comparator reference voltage in a first embodiment of a serial printer of the present invention.

FIG. 2 is a waveform diagram of a comparator input for explaining a synchronization timing according to the first embodiment.

FIG. 3 is a waveform diagram of a comparator input for explaining a synchronization timing according to the second embodiment.

FIG. 4 is a perspective view of a main part of the serial printer.

FIG. 5 is a block diagram illustrating an example of a circuit configuration of FIG. 4;

FIG. 6 is a flowchart of a conventional reference initial adjustment sequence of a comparator reference voltage.

FIG. 7 is a waveform diagram of a counter pulse when a sampling cycle is an integral multiple of a cycle of a comparator input.

FIG. 8 is a waveform diagram showing a change in a duty ratio and an edge position of a counter pulse when a relative shift occurs between a comparator input and a reference voltage.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Carriage 2 Recording part 3 Guide shaft 4 Platen 5 Recording sheet 6 Magnetic linear encoder scale part 7 Main body 8 Flexible substrate 9 Contact part 10 Flexible cable 101 Detecting part 102, 103 MR element 104 Carriage substrate 105, 106 Constant current circuit 107 Differential amplifier 108 Output signal A ₀ 109 Printer control circuit board 110 Comparator 111 Counter pulse 112 A / D converter 113 Counter / timer 114 D / A converter 115 CPU 116 EEPROM 117 ROM 118 RAM 119 CPU bus 120 Reference voltage V _ref

Claims (4)

(57) [Claims] 1. A serial printer device which reciprocates on an apparatus main body and performs recording by a recording unit while synchronizing with movement of a carriage on which the recording unit is mounted, wherein a scale of a linear encoder provided on the apparatus main body is provided. And a detection unit of a linear encoder mounted on the carriage to detect the position of the scale unit. A signal output from the detection unit is received as an input signal, compared with a reference voltage, and pulsed as a synchronization signal. Synchronous signal generating circuit means for generating a waveform output signal, and reference voltage initial adjusting means for initially adjusting the reference voltage input to the synchronous signal generating circuit means, wherein the reference voltage initial adjusting means comprises: Speed synchronizing means for synchronizing the moving speed of the carriage and a sampling cycle for sampling the output signal; Measuring means for measuring the value of the output signal a predetermined number of times based on the sampling, after synchronizing the moving speed of the carriage and a sampling cycle for sampling the output signal by the means, and obtained from the measuring means. Means for averaging values to obtain a reference voltage. 2. The serial printer according to claim 1, wherein said speed synchronizing means _sets T _S = T _S0 between a period T _A0 , a sampling period T _S , and the number of measurements n of said output signal.
T _A0 / 2 ^m (m is an integer of 1 or more), n = k · 2 ^m (where m is the same as m in the preceding expression, and k is an integer of 1 or more). A serial printer, comprising: 3. The serial printer according to claim 1, wherein said speed synchronizing means _sets T _S = T _S0 between the output signal period T _A0 , the sampling period T _S , and the number of measurements n.
T _A0 (1/2 + m) (m is an integer of 1 or more), n = 2
A serial printer characterized in that a relational expression of ^k (k is an integer of 1 or more) is satisfied. 4. A serial printer according to claim 1, wherein said reference voltage obtained from said reference voltage initial adjusting means is D / A converted and input to a comparing means of said synchronization signal generating circuit. A serial printer further comprising a converter.