JP2686840B2 - Contact detection circuit between platen and print head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a platen for automatically setting a distance between a print head and a printing paper in a printer to a predetermined amount according to the thickness of the paper, the printing speed, and the like. And a print head contact detection circuit.

(Prior Art) FIG. 2 is a perspective view showing a main part of a conventional printer device.

The illustrated apparatus includes a print head 11, a carriage 12, a protector 13, a stepping motor 17, a platen 20 and the like.

The print head 11 is a dot impact type print head, and performs printing by bringing the tip of the wire into contact with the paper 19 on the platen 20.

The carriage 12 carries the print head 11. The carriage 12 is supported by a shaft 18. The shaft 18 is provided with a preparation cam 22a and a gear 23 at one end, and an adjustment cam 22b and a slit disk 24 at the other end. The shaft 18 is moved toward the cam follower 26 by springs 25 attached to both ends.

A gear 23 provided on one side of the shaft 18 is adapted to transmit the rotation of the stepping motor 17 via gear trains 27a, 27b, 27c.

The protector 13 presses the paper 19 against the platen 20. The protector 13 is fixed to the carriage 12, and is located between the print head 11 and the platen 20.

 Next, the operation of the above-described device will be described.

When the stepping motor 17 is rotated counterclockwise,
The shaft 18 rotates via the gear trains 27a, 27b, 27c and the gear 23, and the carriage 12 moves in the A direction in the drawing. The position of the carriage 12 is monitored by counting the change in the slit signal of the sensor 28 sandwiching the slit disk 24 attached to the other end of the shaft 18 by a control unit (not shown), and when setting the paper in the printer. Moves the carriage 12 to a position (hereinafter referred to as a retreat position) where the distance between the protector 13 and the platen 20 is secured by a distance that does not hinder the setting of the paper 19.

 FIG. 3 is a diagram showing a retracted state of the carriage 12.

In the illustrated state, the paper 19 on the platen 20 and the protector are
It is sufficiently distant from the platen 13, and the platen 13 and the print head 11 have a constant space.

Next, when the stepping motor 17 is rotated clockwise, the carriage 12 moves in the B direction, and the protector 13 pushes the platen 20 via the paper 19. At this time, even though the control unit (not shown) tries to rotate the stepping motor 17 by a certain amount, the protector 13 detects that the change of the slit signal is no longer obtained, and the protector 13 moves the platen 20 to the platen 20 via the paper 19. Recognize that it has hit, and at the same time recognize the thickness of the paper set at this time.

In FIG. 4, the protector 13 of the print head 11 has the platen 20.
FIG. 6 is a diagram showing a state in which the upper sheet 19 is abutted.

In the state shown in the figure, protect the paper 19 on the platen 20 with the protector.
The protector 13 is deformed due to the contact of 13 and the gap between the protector 13 and the print head 11 is narrowed.

(Problems to be solved by the invention) However, the above-mentioned conventional technology has the following problems.

That is, the position where the protector 13 abuts against the sheet 19 on the platen 20 was a point where the torque of the stepping motor 17 and the load of the mechanical section were balanced. However, the force with which the protector 13 is pressed fluctuates due to fluctuations in the torque of the stepping motor 17 and fluctuations in the gear train load. Therefore,
The protector 13 as shown in FIG.
The position where the carriage 12 comes into contact with 19 and stops is changed. As a result, there is a problem in that the accuracy of detecting the thickness of the paper is reduced.

The present invention has been made in view of the above points. The contact between the platen and the print head is such that the contact position of the protector of the print head is always constant so that the paper thickness can be detected with high accuracy. It is intended to provide a detection circuit.

(Means for Solving Problems) The contact detection circuit between the platen and the print head of the present invention is
When the print head is apart from the platen, a predetermined inductance is output, and when the protector moving close to the platen and moving with the print head comes into contact with the platen, the inductance generating means and the inductance generating means change the inductance. An oscillating circuit that outputs an oscillating signal having a frequency corresponding to the output inductance, compares the frequency of the oscillating signal output by the oscillating circuit with a fixed frequency every time the print head is moved by a predetermined amount, and oscillates The contact between the print head and the platen is detected when the frequency of the oscillation signal output from the circuit changes with respect to the fixed frequency, or when the print head is first moved by a predetermined amount. The frequency of the oscillation signal output by the oscillation circuit is stored, and thereafter the print head is moved by a predetermined amount. The frequency of the oscillation signal output from the oscillation circuit is compared with the stored frequency every time the frequency of the oscillation signal output from the oscillation circuit changes with respect to the stored frequency. The contact between the platen and the platen is detected, or each time the print head is moved by a predetermined amount, the frequency of the oscillation signal output by the oscillation circuit before the movement and the oscillation output by the oscillation circuit after the movement. It is characterized in that the frequency of the signal is compared and the contact between the print head and the platen is detected when both frequencies change before and after the movement.

(Function) In the contact detection circuit between the platen and the print head of the present invention, the frequency of the oscillation signal output by the oscillation signal connected to the inductance generating means provided in the print head is detected. When the change in the frequency is detected, the interval adjusting means of the print head is stopped and the sheet thickness at that time is detected. Therefore, an accurate contact position can be detected without being affected by torque fluctuations and load fluctuations of the interval adjusting means. Thereby, for example, the sheet thickness and the like can be accurately detected. As a result, the printing pressure can always be made appropriate according to the paper thickness, and the printing quality can be improved.

(Embodiment) FIG. 1 is a block diagram showing a configuration of a printer device including a contact detection circuit between a platen and a print head according to the present invention.

The illustrated apparatus includes an inductance generating means 1, a space adjusting means 2, a capacitor 3, an oscillating circuit 4, an oscillating signal counting circuit 5, a paper thickness detecting means 6 and the like.

The inductance generating means 1 normally generates a constant inductance, and causes a change in inductance when the protector 13 of the print head 11 contacts the paper 19 on the platen 20. That is, the carriage 12 having the print head 11 has a protector 13 for holding the paper.

A magnetic body 14 is provided on a portion of the protector 13 located on the side surface of the print head 11. And this magnetic body 14
The magnetic body 15 is provided so as to face the. Magnetic material 15
Is fixed to the carriage 12 by a fixing member 21, and the coil 16 is wound.

FIG. 5 is a perspective view showing a detailed configuration of the inductance generating means.

In this figure, the inductance is changed by a distance l _2/2 between the magnetic body 14 and 15 is changed.

Magnetic path length l ₁ of the magnetic member 14 and 15 of the _{illustrated, l 1 = l 1 '+} l 1 ", the magnetic path length l ₂ of the gap _{portion, l 2 = (l 2/} 2) × 2, the magnetic The cross-sectional area is S, the magnetic permeability of the magnetic material is μ ₁ , the magnetic permeability of the void is μ ₂ , the number of turns of the coil is N, and the current of the coil is I.

At this time, the magnetic resistance R ₁ inside the magnetic material is R ₁ = l ₁ / μ ₁ S, and the magnetic resistance R _{2 in the} void portion is R ₂ = l ₂ / μ ₂ S.

Therefore, the total magnetic resistance R is R = R ₁ + R ₂ = l ₁ / μ ₁ S + l ₂ / μ ₂ S.

 The magnetomotive force F is F = NI.

On the other hand, the generated magnetic flux φ is φ = F / R = NI / (l ₁ / μ ₁ S + l ₂ / μ ₂ S).

Therefore, the inductance L is L = Nφ / I = N ² / (l ₁ / μ ₁ S + l ₂ / μ ₂ S).

At this time, the frequency f of the oscillator, the capacitor C provided separately, given by f = 1 / 2π (LC) 1/2. Therefore, the frequency f
By reading the change in
It can be determined _2/2.

The change in the frequency f is read by reading the oscillation frequency of the oscillation circuit as described below.

FIG. 6 is a circuit diagram showing a detailed configuration of the oscillator circuit 4 of FIG.

In the figure, the coil 16 and the capacitor 3 are connected in parallel. This parallel circuit is connected to the parallel circuit of the inverter 32 and the resistor 33 via the capacitor 31. This parallel circuit also includes an inverter 36 via a capacitor 34.
And resistor 37 connected in parallel. The output of this parallel circuit is connected to the capacitor 31 via the negative feedback resistor 39.
Has been returned to the input of. Inverter connected in this way
A signal obtained by extracting the output of 36 through the inverter 38 becomes an oscillation signal.

FIG. 7 is a graph showing the relationship between the distance between the magnetic bodies 14 and 15 and the oscillation frequency.

As shown in this figure, the frequency change rate varies depending on the distance between the magnetic bodies 14 and 15.Therefore, in order to improve the detection accuracy, the distance between the magnetic bodies 14 and 15 should be set to a distance at which the frequency change rate is as large as possible. Set.

For example, the initial value of the distance between the magnetic bodies 14 and 15 is 0.3 mm. At this time, the frequency of the oscillator is 160 KHz. When the distance between the magnetic bodies 14 and 15 changes to 0.2 mm, the frequency of the oscillator changes to 150 KHz.

Such a frequency change is detected by a change in the frequency detected by the oscillation signal counting circuit 5.

FIG. 8 is a diagram showing an input signal and an output signal of the oscillation signal counting circuit 5.

The input signals are the oscillation signal from the oscillation circuit 4, the read signal from the CPU, and the stepping motor drive signal from the CPU. The signal from the CPU is assumed to be low active.

 The output signal is the counter value of the oscillation signal.

 Here, the other components of FIG. 1 will be described.

The space adjusting means 2 includes a stepping motor, and the paper thickness detecting means 6 includes a slit disk or the like. These are the same as the conventional configuration, and the details are the same as those described in FIG.

Further, a CPU 30, a ROM 31, a RAM 32 and the like are provided for controlling the device.

The CPU 30 controls each unit according to the program read from the ROM 31 or the RAM 32.

The ROM 31 is a read-only memory and is connected to the data bus 34 and the address bus 33 of the CPU 30.

RAM32 is random access memory, CPU30
Are connected to the data bus 34 and the address bus 33.

FIG. 9 is a time chart showing the operation of the oscillation signal counting circuit.

The oscillation signal counting circuit 5 first receives a stepping motor drive signal. When receiving this drive signal, the counter
51 is reset. Then, the oscillation signal is counted. That is, the counter 51 is input every time one pulse of the oscillation signal is input.
Is counted up. Then, immediately before receiving the stepping motor drive signal, the read signal is input and the value of the counter is read by the CPU 30. After that, the counter 51 is reset by inputting the stepping motor drive signal. Then, similarly, the oscillation signals are counted. In this way, all oscillation signals generated during the stepping motor drive signal are read. Since the stepping motor drive signals are output at equal intervals, it is possible to detect the number of pulses of the oscillation signal per unit time, that is, the frequency.

When the stepping motor drive signal is output, the stepping motor phase signal is switched and output so as to drive the next phase of the stepping motor. As a result, the stepping motor rotates by a constant angle.

 Next, the operation of the above-described device will be described.

FIG. 10 is a flowchart showing a program executed by the CPU 30 of the apparatus shown in FIG.

First, in order to adjust the position of the print head 11, driving of the stepping motor is started (step S1), and a stepping motor drive signal is sent (step S2). Next, after waiting for a fixed time (step S3), the counter 51 of the oscillation signal counting circuit is read (step S3).
S4). The fixed time in this case is set such that the reading of the counter 51 is performed immediately before the generation of the next stepping motor drive signal.

Then, the frequency is obtained from the counter value of the counter 51, and it is determined whether or not the frequency has changed with respect to a fixed frequency (for example, 160 KHz) (step S5). If there is no change with respect to the fixed frequency, since the protector 13 is not in contact with the paper 19 on the platen 20, the protector 13 sends a stepping motor drive signal to further move the print head 11 (step S2).

When there is a change with respect to the fixed frequency, it is detected that the protector 13 has come into contact with the sheet 19 on the platen 20. The sheet thickness is obtained by reading the detection value of the sheet thickness detecting unit 6 at this time. Then, in order to set the printing pressure according to the sheet thickness, the stepping motor is driven in the reverse direction by a predetermined amount according to the sheet thickness (step S6).

FIG. 11 is a diagram showing another example of a program executed by the CPU of FIG.

First, driving of the stepping motor is started (step S21), and a stepping motor drive signal is sent (step S22). Then, after waiting for a certain period of time (step S23), it is determined whether or not the stepping motor drive signal is for the first step (step S2).
Four). If it is the first step, the value f ₀ read by the oscillation signal counting circuit is stored in a register (not shown) (step S25). This value f ₀ is the oscillation frequency of the oscillation circuit when the protector 13 is not deformed, and is therefore the oscillation frequency that is output when the protector 13 is not in contact with the paper 19 on the platen 20. On the other hand, if it is not the first step, the value f obtained by reading the oscillation signal is stored in the register (not shown) (step S26). This value f is equal to the value f ₀ while the protector 13 is not in contact with the sheet 19 on the platen 20.

Then, the values f ₀ and f are compared (step S27), and if the difference is larger than the predetermined value Δf, the paper 19 on the platen 20 is
It is detected that the print head 11 has come into contact with. At this time, the sheet thickness detecting means 6 detects the sheet thickness, and the stepping motor is driven in the reverse direction by a predetermined amount corresponding to the sheet thickness in order to set the printing pressure according to the sheet thickness (step S28).

According to such control, the following effects can be obtained.

FIG. 12 is a graph showing the relationship between the distance between the magnetic bodies shown in FIG. 5 and the oscillation frequency of the oscillation circuit.

The distance between the magnetic bodies and the oscillation frequency have a fixed relationship, but the inductance of the coil 16 changes due to temperature changes and the like. Therefore, the oscillation frequency f ₀ corresponding to the distance d ₁ between the magnetic bodies when the protector 13 is not in contact with the paper 19 is
It does not become a constant value, but becomes f ₀ ′ at high temperature. For this reason,
When the oscillation frequency reaches a constant value f ₁ , the distance between magnetic bodies becomes d ₂ as shown in the figure. That is, in the control of FIG. 10, even if the protector 13 is already in contact with the sheet 19 when the distance between the magnetic bodies is d ₁ , the contact cannot be detected.

On the other hand, in the control of FIG. 11, the initial value of the oscillation frequency is obtained before the detection of the paper thickness, and the contact of the print head is detected by the change Δf from this initial value, so that it is possible to detect it even in the high temperature state. , It is surely detected that the distance between the magnetic bodies reaches the predetermined value d ₁ .

In the embodiment described above, the value f ₀ read by the oscillation signal counting circuit when the stepping motor drive signal is the first step is compared with the value f ₀ read by the oscillation signal counting circuit at other times. However, the present invention is not limited to this, and the values f ₁ and f ₂ read by the oscillation signal counting circuit may be compared for successive steps of the stepping motor drive signal. The difference between these values is the predetermined value Δ
If it is larger than f, protect the paper 19 on the platen 20 with the protector.
The contact of 13 is detected.

As described above, according to the contact detection circuit of the platen and the print head of the present invention, the contact between the print head and the paper on the platen is oscillated by the inductance generating means and the capacitor. Detected by the change in the oscillation frequency of the circuit,
Since the printing pressure is adjusted by detecting the paper thickness at this time, the following effects can be obtained.

In other words, the contact of the print head with the paper on the platen can be detected before the torque of the stepping motor reaches the equilibrium state, and the stable contact position can be detected without depending on the change in the torque of the stepping motor. be able to. As a result, it is possible to perform stable detection of the paper thickness and the like. Therefore, it is possible to improve the accuracy of detection of the paper thickness and the like, and it is possible to set an appropriate printing pressure.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a printer device including a contact detection circuit between a platen and a print head according to the present invention, and FIG.
FIG. 3 is a perspective view showing the structure of a conventional apparatus, FIG. 3 is a view showing a state where the print head is not in contact, FIG. 4 is a view showing a state where the print head is in contact, and FIG. FIG. 6 is a perspective view of the oscillator circuit 4 of FIG. 1, and FIG.
FIG. 8 is a graph showing the relationship between the distance between magnetic materials and the oscillation circuit frequency. FIG. 8 is a diagram showing the input / output of the oscillation signal counting circuit.
The figure is a time chart showing the operation of the oscillation signal counting circuit.
FIG. 10 is a flowchart showing a program executed by the CPU of the apparatus shown in FIG. 1, and FIG. 11 is a flowchart showing another example of a program executed by the CPU of the apparatus shown in FIG.
The figure is a graph showing the temperature-dependent relationship between the distance between magnetic materials and the oscillation circuit frequency. 1 ... Inductance generating means, 2 ... Interval adjusting means,
3 ... Capacitor, 4 ... Oscillation circuit, 5 ... Oscillation signal counting circuit, 6 ... Paper thickness detecting means, 11 ... Print head, 12
...... Carriage, 13 ...... Protector, 14, 15 ...... Magnetic material, 16 ...... Coil, 19 ...... Paper, 20 ...... Platen.

Claims (4)

(57) [Claims] 1. Inductance generating means for outputting a predetermined inductance when the print head is separated from the platen, and changing the inductance in which a protector moving close to the platen and moving with the print head contacts the platen. An oscillation circuit that outputs an oscillation signal having a frequency corresponding to the inductance output by the inductance generating means, and compares the frequency of the oscillation signal output by the oscillation circuit with a fixed frequency every time the print head is moved by a predetermined amount. The contact between the print head and the platen is detected when the frequency of the oscillation signal output from the oscillation circuit changes with respect to the fixed frequency. Contact detection circuit. 2. Inductance generating means for outputting a predetermined inductance when the print head is separated from the platen, and changing the inductance when the protector moving close to the platen and moving with the print head contacts the platen. An oscillation circuit that outputs an oscillation signal having a frequency corresponding to the inductance output by the inductance generating means, and stores the frequency of the oscillation signal output by the oscillation circuit when the print head is first moved by a predetermined amount. Then, every time the print head is moved by a predetermined amount, the frequency of the oscillation signal output by the oscillation circuit is compared with the stored frequency, and the frequency of the oscillation signal output by the oscillation circuit is compared with the stored frequency. The contact between the print head and the platen is detected when there is a change in Contact detecting circuit of the print head and the platen to. 3. Inductance generating means for outputting a predetermined inductance when the print head is separated from the platen, and changing the inductance when the protector moving close to the platen and moving with the print head contacts the platen. An oscillation circuit that outputs an oscillation signal having a frequency corresponding to the inductance output by the inductance generating means, and each time the print head is moved by a predetermined amount, the frequency of the oscillation signal output by the oscillation circuit before the movement. After the movement, the frequency of the oscillation signal output from the oscillation circuit is compared, and if there is a change in both the frequencies before and after the movement, the contact between the print head and the platen is detected. A contact detection circuit between the platen and the print head. 4. A contact detecting circuit between a platen and a print head according to claim 1, wherein said inductance generating means is arranged on a protector on a carriage unit on which the print head is mounted. And a second magnetic body having a coil wound thereon, which is arranged at a position on the carriage facing the first magnetic body with a gap, and is arranged in a direction in which the print head approaches the platen. When moved, the protector comes into contact with the paper on the platen and bends toward the protector print head side, and the gap between the first magnetic body and the second magnetic body is narrowed, so that the generated inductance changes. Contact detection circuit between the and print head.