JPH07276737A - Device for regulating head gap of wire dot printing head - Google Patents

Abstract

PURPOSE:To accurately regulate a head gap even when a carriage route is changed by measuring electrostatic capacity between an armature and a core by an electrostatic capacity sensor and calculating sensor output from the measured electrostatic capacity and slicing the sensor output by a slice level and obtaining sensor output information. CONSTITUTION:An armature 35 is displaced by supplying driving current to an electromagnet 30. Printing is performed by a printing wire 36 fixed to the tip of the armature 35. At this time, electrostatic capacity between the armature 35 and a core 28 is measured by a sensor electrode 40 being an electrostatic capacity sensor fitted to a sensor substrate 26. Sensor output is calculated from the measured electrostatic capacity. The sensor output is sliced by a preset slice level and sensor output information is obtained. Thereby the head gap of the printing wire 36 and a printing medium is accurately regulated even when the carriage route of a printing medium is changed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a head gap adjusting device for a wire dot print head.

[0002]

2. Description of the Related Art Conventionally, an impact printer has a wire dot print head, and a print wire is driven by the wire dot print head to strongly press an ink ribbon and a print medium against a platen for printing. ing. In a spring-charged wire dot print head, for example, a plate spring for biasing supports the armature swingably, and the armature is attracted to the core by a permanent magnet against the restoring force of the plate spring. When printing, the coil wound around the core is excited to generate a magnetic flux in the direction opposite to the magnetic flux of the permanent magnet to release the armature.

FIG. 2 is a sectional view of a wire dot print head. In the drawing, 11 is a base, and the base 11
A lower yoke 12, a permanent magnet 13, an upper yoke 14, a spacer 15, a leaf spring 21, an armature yoke 22, a stopper 23, a sensor substrate 24, and a guide frame 25 are sequentially stacked on the peripheral portion of, and clamped and fixed by a clamp 26.

Further, 28 is a core attached to the base 11, 29 is a coil wound around the outer periphery of the core 28, and the electromagnet 30 is composed of the core 28 and the coil 29.
Is formed. Reference numeral 32 is a cover that protects the coil substrate 33 that energizes the coil 29. An armature 35 is attached to the flexible portion of the leaf spring 21 adjacent to the armature yoke 22, and a printing wire 36 is fixed to the tip of the armature 35. The printing wire 36 is guided by a wire guide 39 fixed to a guide nose 38 at the tip of the guide frame 25.

In the wire dot print head having the above-described structure, when the coil 29 is not energized, the armature 35 is caused to move to the core 28 by the magnetic flux generated by the permanent magnet 13.
Is sucked into. In this case, the printing wire 36 does not protrude from the wire guide 39. On the other hand, the coil 29
When the current is applied to the print wire 36, a magnetic flux is generated in a direction in which the magnetic field of the permanent magnet 13 is canceled, and the restoring force of the leaf spring 21 causes the printing wire 36 to project from the wire guide 39. The printing wire 36 thus projected strongly presses the ink ribbon (not shown) and the print medium, which are arranged so as to face the wire dot print head, against the platen (not shown) for printing.

A sensor electrode 40 is mounted on the sensor substrate 24 (lower surface in the figure). The sensor electrode 40 is opposed to each armature 35 with a slight space to form a capacitance sensor, and the capacitance sensor can measure the capacitance between the two. Then, the measured capacitance is output from the capacitance sensor as a sensor output.

By the way, in the conventional wire dot print head, the operation of each armature 35 can be detected by measuring the capacitance. Then, the energization time to the coil 29, that is, the driving time is controlled in accordance with the operation of the armature 35 so that optimum printing can be performed or the thickness of the print medium is detected to detect the print medium. The head gap corresponding to is formed.

FIG. 3 is an operation waveform diagram of a print wire in a head gap adjusting device for a conventional wire dot print head. In the figure, the horizontal axis represents time, and the vertical axis represents values of print wire speed, sensor output, drive current, print wire displacement, and impact. In the figure, L1 is the waveform of the print wire speed, L2 is the waveform of the sensor output, L3 is the waveform of the drive current, L4 is the waveform of the print wire displacement, and L5 is the impact waveform.

As shown in the figure, due to the displacement of the print wire, the waveform L1 of the print wire speed and the waveform L of the sensor output
2 is uniquely determined, and both are similar to each other. Therefore, the print wire displacement can be detected based on the sensor output. FIG. 4 is a conceptual diagram of a sensor output waveform and sensor output information in a conventional head gap adjusting device for a wire dot print head. In the figure, the horizontal axis represents time, and the vertical axis represents sensor output and drive current values.

In the figure, L2 is the waveform of the sensor output, L
3 is the waveform of the drive current. As shown, when the sensor output is sliced by the high-side slice level V _REF1 and the low-side slice level V _REF2 , the coil 29
Release time T ₁ until the armature 35 is released from the core 28 after supplying the drive current to (FIG. 2), until the print wire 36 collides with a print medium (not shown) after the armature 35 is released from the core 28. The print time T ₂ and the armature 3 after the print wire 36 collides with the print medium.
It is possible to obtain the sensor output information of the return time T ₃ until the core 5 is again attracted to the core 28. The release time T ₁ , the print time T _2, and the return time T ₃ for each print wire 36 are stored in a memory (not shown), and the head gap adjusting device of the wire dot print head uses the release time T ₁ , the print time T 3. _The head gap can be adjusted and the drive time of the print wire 36 can be controlled based on ₂ and the return time T ₃ .

[0011]

However, in the above-mentioned head gap adjusting device for a wire dot print head, the sensor output changes when the paper feed route is changed. Therefore, the head gap is adjusted accurately. In addition, the drive time of the print wire 36 cannot be controlled accurately.

Here, the change in the sensor output due to the change of the paper feed route will be described. FIG. 5 is a state diagram of the head gap at the time of rear feeding in the conventional impact printer, and FIG. 6 is a state diagram of the head gap at the time of top feeding in the conventional impact printer. In the figure, reference numeral 51 denotes a platen rotatably arranged in the direction of arrow A, and a wire dot print head 52 is arranged to face the platen 51. Further, a pinch roller 53 is arranged on the upstream side of the wire dot print head 52 in the rotation direction of the platen 51 so as to face the platen 51.
It is rotatably supported.

The impact printer has a paper feed mechanism, and the paper feed mechanism can convey the print medium 54 to the printing section between the platen 51 and the wire dot print head 52. There is. in this case,
The paper feeding mechanism includes a rear feed device for feeding the print medium 54 from the rear of the platen 51, a top feed device for feeding the print medium 54 from above the platen 51, and a print medium 54 of the platen 51. It has a bottom feed device for feeding from below and can selectively operate them.

At the time of rear feed, as shown in FIG.
As shown in FIG.
The paper is fed by a tractor 55, which is a rear feed device, disposed behind the platen 51 and the pinch roller 5
It is conveyed through the space between 3 and the printing section. At this time, the pinch roller 53 is separated from the platen 51. On the other hand, at the time of top feed, as shown in FIG.
The pinch roller 53 is pressed against the platen 51 in the direction of arrow B, and along a guide 57 as a top feed device disposed above the back surface of the platen 51,
The print medium 54 is fed. Then, the print medium 54
Passes through the platen 51 and the pinch roller 53 and is conveyed to the printing section.

During bottom feeding, the pinch roller 53 is separated from the platen 51 and is fed by a bottom feeding device (not shown) arranged below the platen 51. By the way, when the head gap is x _R during rear feed and bottom feed, the pinch roller 53 is pressed against the platen 51 during top feed, and the pressure of the pinch roller 53 causes the center of the platen 51 to move. The position P moves to the position P ′, and the head gap becomes x _{T accordingly.}
Will change to. When the head gap changes, the sensor output also changes accordingly, so that the head gap cannot be adjusted accurately.
Further, the drive time of the print wire 36 (FIG. 2) cannot be controlled accurately.

The present invention solves the problems of the conventional head gap adjusting device for a wire dot print head, and can accurately adjust the head gap even if the feed route of the print medium is changed. An object of the present invention is to provide a head gap adjusting device for a wire dot print head that can accurately control the drive time of the wire.

[0017]

Therefore, in a head gap adjusting device for a wire dot print head according to the present invention, a drive current is supplied to an electromagnet to displace the armature, and the print wire fixed to the tip of the armature. And a capacitance sensor for measuring the capacitance between the armature and the core,
It has a means for obtaining a sensor output from the measured capacitance, and a means for obtaining sensor output information by slicing the sensor output at a preset slice level.

Further, a paper feed route discriminating means for discriminating the paper feed route, a means for correcting the sensor output information corresponding to the paper feed route, and an appropriate head gap is calculated based on the corrected sensor output information. And a gap changing device that moves the wire dot print head so that the proper head gap is formed.

[0019]

According to the present invention, in the head gap adjusting device for the wire dot print head, a driving current is supplied to the electromagnet to displace the armature, and printing is performed by the print wire fixed to the tip of the armature. And a capacitance sensor for measuring the capacitance between the armature and the core, a means for obtaining a sensor output from the measured capacitance, and slicing the sensor output with a preset slice level. , And means for obtaining sensor output information.

Therefore, by setting the print medium in the print section between the platen and the wire dot print head and performing trial printing, the sensor output information corresponding to the thickness of the print medium currently set is obtained. be able to.
Further, a sheet feeding route determining unit that determines a sheet feeding route, a unit that corrects the sensor output information corresponding to the sheet feeding route, and a unit that calculates an appropriate head gap based on the corrected sensor output information. And a gap changing device for moving the wire dot print head so that the proper head gap is formed.

Therefore, when the paper feed route is changed,
The sensor output information is corrected according to the paper feed route, and the appropriate head gap is calculated based on the corrected sensor output information. Then, the gap changing device is actuated so that the proper head gap is formed, and the wire dot print head is moved.

[0022]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 7 is a block diagram of a head gap adjusting device for a wire dot print head according to the first embodiment of the present invention. In the figure, 29 is a coil, 4
0 is a sensor electrode, 52 is a wire dot print head, 61
Is an interface (I / F) for inputting print data to the impact printer, 62 is a control circuit for controlling the operation of the entire impact printer, 63 is a head driver,
64 is a spacing motor driver, 65 is a line feed motor driver, 66 is a pulse motor driver, 6
7 is a spacing motor, 68 is a line feed motor, 69 is an operation switch, 71 is a sensor circuit, 74 is a pulse motor, and 75 is a pulse motor 74. By driving the pulse motor 74, the print wire 36 (see FIG. 2) and the print medium 54
(See FIG. 5) A gap changing device for changing the head gap between the sheet feeding device and the sheet feeding device is shown. Reference numeral 77 is a sheet feeding route discriminating means including a micro switch for discriminating the selected sheet feeding route when the sheet feeding mechanism is switched. is there.

The control circuit 62 stores the input / output interface LSI 81, LSI 82, the CPU 83 for performing various processes such as a process for calculating the head gap based on the detected sensor output information, print data, internal data and the like. RAM84 and control program for
It has a ROM 85 for storing print font data and the like.

By the way, when the impact printer is assembled and adjusted, the wire dot print head 52 is set so that the reference gap (for example, 0.5 [mm]) is formed between the platen 51 and the print wire 36. Then, a standard print medium (not shown) of which thickness is known is inserted between the platen 51 and the print wire 36 by, for example, the feed route of the rear feed, and at that time, formed between the standard print medium and the print wire 36. All the print wires 36 (for example, 9 or 24 wires) are driven with the standard gaps respectively, and the release time T ₁ (see FIG. 4), the print time T ₂ , and the return from the waveform of the sensor output by the displacement of the armature The standard sensor output information such as time T ₃ is calculated, and the standard sensor output information is stored in the ROM 85 as self-adjustment data.

Therefore, when using the impact printer, the wire dot print head 52 is set so that the reference gap is formed between the platen 51 and the print wire 36. Then, a predetermined print medium 54 is inserted between the platen 51 and the print wire 36, test printing is performed on the print medium 54, and the sensor output information obtained by the test printing, the standard sensor output information, and the standard gap are recorded. Based on this, the proper head gap is calculated, and the gap changing device 75 is operated to move the wire dot print head 52 so that the proper head gap is formed.

However, when performing the test printing, when the print medium 54 is inserted between the platen 51 and the print wire 36 by a paper feeding route different from that at the time of assembling and adjusting the impact printer, the sensor output information obtained by the test printing Will change. FIG. 8 is a diagram showing a change in the waveform of the sensor output due to the change of the paper feed route. In the figure, the horizontal axis represents time t, the vertical axis represents sensor output during rear feed, sensor output during top feed,
And the value of the drive current.

In the figure, S _R is the sensor output waveform during rear feed, S _T is the sensor output waveform during top feed, and I _P is the drive current waveform. As described above, the pinch roller 53 (see FIG.
And 6), the center P of the platen 51 moves. As a result, the actual head gap changes even when the head gap range of the impact printer is set to the same value.

The sensor output during rear feed
Force waveform S_RHigh side slice level V_REF1And low side
Slice level V_REF2When sliced by and released
Interval T ₁, Printing time T₂And return time T₃To get
On the other hand, the waveform S of the sensor output during top feed
_THigh side slice level V_REF1And low-side slice
Bell V_REF2When sliced by, release time T₁,mark
Letter time T₂′ And return time T₃'Is obtained and the sensor output
Information changes.

In this case, the release time T ₁ and the printing times T ₂ and T ₂ ′ are obtained by slicing the waveforms S _R and S _T with the high-side slice level V _REF1 to obtain the return time T 1.
₃ , T ₃ ′ is obtained by slicing the waveforms S _R and S _T with the high-side slice level V _REF1 and the low-side slice level V _REF2 , respectively. Therefore, it is determined whether the rear feed paper feed route or the top feed paper feed route has been selected.
(FIG. 7), it is possible to make a distinction. Then, when it is determined that the top feed sheet feeding route is selected, the control circuit 62 corrects the printing time T ₂ ′ and the return time T ₃ ′ obtained by the trial printing, and the rear feed It is set to the same value as the print time T ₂ and the return time T ₃ when the trial printing is performed by the paper feed route.

In this way, when the head gap range of the impact printer is set to the same value, the same sensor output information can always be obtained.
In the present embodiment, the case where the sensor output information changes between the rear feed and the top feed has been described, but the same applies to the case where the sensor output information changes between the bottom feed and the top feed. It is possible to perform various processing. That is, during bottom feed, the same sensor output information as during rear feed can be obtained.

Next, the wire dot printing head having the above construction
The operation of the head gap adjusting device will be described. Figure
1 is the wire dot printing in the first embodiment of the present invention.
Flow chart showing the operation of the head gap adjustment device
It is Step S1 Turn on the power supply (not shown) of the impact printer
turn on. Steps S2 and S3 Is it a host computer not shown
It waits to receive the print data from them. Step S4 Print with platen 51 (see FIGS. 5 and 6)
There will be a reference gap between the wire 36 (see Fig. 2)
The wire dot print head 52 is set. That
The predetermined print medium 54 to the platen 51 and the print wire 3.
6 and insert it between the first and the second print data.
Perform trial printing of several to several tens of dots on the line where characters are written,
The sensor output information at that time is detected. In step S5, the paper feed route determination means 77 (FIG. 7) is used.
To determine the paper feed route. Top feed paper feed route
If is selected, the rear feed (or
Bottom feed) is selected when the paper feed route is selected.
Go to step S7. Step S6 Sensor output information obtained by trial printing
The printing time T which is a report ₂′ And return time T₃′ Is corrected
The rear feed (or bottom feed)
Printing time T when test printing is performed₂And return
Time T₃Same value as. Step S7: Self-adjustment stored in ROM85
Read the test data, and obtain the
Sensor output information and self-adjustment data
The proper head gap corresponding to the print medium 54 is calculated.
Ask for.

In this case, the difference between the reference head gap and the actual head gap is calculated based on the sensor output information obtained by the test printing and the standard sensor output information stored in the ROM 85, and the difference is calculated from the difference. The thickness of the set print medium 51 is calculated. Step S8: The head gap is automatically adjusted. That is, the amount of movement of the wire dot print head 52 required to form an appropriate head gap corresponding to the thickness of the print medium 54 is calculated, and the gap changing device 75 is operated to move the platen 51. Step S9 Normal printing is performed.

By the way, in the first embodiment of the present invention, when the paper feed route is changed, the sensor output information obtained by the test printing is corrected, and the head gap of the head gap is corrected based on the corrected sensor output information. Although automatic adjustment is performed, the value of drive current cannot be changed for each paper feed route. Therefore, the drive current is set to a large value in anticipation of the change in the head gap due to the automatic adjustment, and a sufficient impact force is secured to improve the print quality. Therefore, extra energy is consumed depending on the paper feeding route, and the thermal efficiency is reduced.

Therefore, in the second embodiment of the present invention, the setting of the drive current can be changed for each sheet feeding route. In this case, the setting of the drive current is changed by changing the pulse width of the drive signal. FIG. 9 is a flowchart showing the operation of the head gap adjusting device for the wire dot print head according to the second embodiment of the present invention. Step S11: Turn on the power source (not shown) of the impact printer. Steps S12 and S13 stand by for receiving print data from a host computer (not shown). Step S14 The wire dot print head 52 is set so that the reference gap is provided between the platen 51 (see FIGS. 5 and 6) and the print wire 36 (see FIG. 2). Then, a predetermined print medium 54 is inserted between the platen 51 and the print wire 36, and a test print of several to several tens of dots is performed on the line to be printed first by the print data, and the sensor output information at that time is displayed. To detect. Step S15 The paper feed route is determined by the paper feed route determination means 77 (FIG. 7). When the top feed sheet feed route is selected, the process proceeds to step S16, and when the rear feed (or bottom feed) sheet feed route is selected, the process proceeds to step S17. Step S16 wherein the printing time is a sensor output information obtained by test printing T ₂ 'and return time T _3' to correct the printing in the case of performing test printing by the sheet feeding route in the rear feed (or bottom feed) The values are the same as the time T ₂ and the return time T ₃ . In step S17, the self-adjustment data stored in the ROM 85 is read, the sensor output information obtained by the test printing is compared with the self-adjustment data, and the calculation is performed to obtain the proper head gap corresponding to the print medium 54. Step S18 The head gap is automatically adjusted. That is, the amount of movement of the wire dot print head 52 required to form an appropriate head gap corresponding to the thickness of the print medium 54 is calculated, and the gap changing device 75 is operated to move the platen 51. In step S19, the paper feed route determination means 77 determines the paper feed route. When the top feed sheet feed route is selected, the process proceeds to step S20, and when the rear feed (or bottom feed) sheet feed route is selected, the process proceeds to step S21. In step S20, the drive current for top feed is set. Step S21 Rear feed (or bottom feed)
Set the drive current for. Step S22 Normal printing is performed.

In this embodiment, since the optimum setting of the drive current can be changed for each paper feed route, not only the printing quality can be improved but also the thermal efficiency can be improved. It should be noted that the present invention is not limited to the above-described embodiments, and various modifications can be made based on the spirit of the present invention, and they are not excluded from the scope of the present invention.

[0036]

As described in detail above, according to the present invention, in the head gap adjusting device for the wire dot printing head, the driving current is supplied to the electromagnet to displace the armature and fix it to the tip of the armature. Printing is performed by the printed wire, a capacitance sensor for measuring the capacitance between the armature and the core, a means for obtaining a sensor output from the measured capacitance, and the sensor output. With a slice level set in advance to obtain sensor output information.

Further, a paper feed route discriminating means for discriminating a paper feed route, a means for correcting the sensor output information corresponding to the paper feed route, and an appropriate head gap is calculated based on the corrected sensor output information. And a gap changing device that moves the wire dot print head so that the proper head gap is formed. Therefore, when the paper feed route is changed, the sensor output information is corrected corresponding to the paper feed route, and the proper head gap is calculated based on the corrected sensor output information. Even if the head gap changes due to a problem, the head gap can be adjusted accurately. Further, the drive time of the print wire can be controlled accurately.

[Brief description of drawings]

FIG. 1 is a flowchart showing an operation of a head gap adjusting device for a wire dot print head according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of a wire dot print head.

FIG. 3 is an operation waveform diagram of a print wire in a head gap adjusting device for a conventional wire dot print head.

FIG. 4 is a conceptual diagram of a sensor output waveform and sensor output information in a head gap adjusting device for a conventional wire dot print head.

FIG. 5 is a state diagram of a head gap at the time of rear feeding in a conventional impact printer.

FIG. 6 is a state diagram of a head gap at the time of top feed in a conventional impact printer.

FIG. 7 is a block diagram of a head gap adjusting device for a wire dot print head according to the first embodiment of the present invention.

FIG. 8 is a diagram showing a change in a waveform of a sensor output due to a change in a paper feed route.

FIG. 9 is a flowchart showing an operation of a head gap adjusting device for a wire dot print head according to a second embodiment of the present invention.

[Explanation of symbols]

40 sensor electrode 52 wire dot print head 62 control circuit 75 gap changing device 77 paper feed route determination means 83 CPU V _REF1 , V _REF2 slice level

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mitsuru Kishimoto 1-7-12 Toranomon, Minato-ku, Tokyo Oki Electric Industry Co., Ltd.

Claims (2)

[Claims] 1. A head gap adjusting device for a wire dot printing head, wherein a driving current is supplied to an electromagnet to displace the armature, and printing is performed by a printing wire fixed to a tip of the armature, wherein (a) the armature and the core. A capacitance sensor for measuring a capacitance between the sensor and (b) means for obtaining a sensor output from the measured capacitance; and (c) slicing the sensor output with a preset slice level to obtain a sensor. Output means for obtaining output information; (d) paper feed route determination means for determining a paper feed route; (e) means for correcting the sensor output information in correspondence with the paper feed route; and (f) corrected A means for calculating an appropriate head gap based on sensor output information; and (g) a wire dot printing head for forming the appropriate head gap. A head gap adjusting device for a wire dot print head, comprising: 2. The head gap adjusting device for a wire dot print head according to claim 1, further comprising means for changing the setting of the drive current corresponding to the sheet feeding route.