JP3330225B2 - Printing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printing apparatus having an automatic gap setting function.

[0002]

2. Description of the Related Art In FIG. 8, a platen 2 is rotatably held by main body cases (1L, 1R) and rotated by a paper feed motor (not shown). The carrier 4 on which the print head 5 is mounted is slidably mounted on the shaft 3, and is reciprocated in the X direction by a carrier moving mechanism (not shown) including a carrier motor, a timing belt, a sprocket, and the like.

Here, the gap adjusting mechanism 10 includes an eccentric cam mechanism 11L. 11R, a driven gear 13 and a drive gear 14, a motor (stepping motor) 15, and a motor drive unit 20. The gap setting control means is formed by the control unit 40. When the motor 15 is rotated forward, the eccentric cam mechanism 11L. The shaft 3 moves forward in a direction approaching the platen 2 by 11R, and retreats in a direction away from the shaft 3 when the shaft 3 is rotated in the reverse direction. The movement amount detector 17 for detecting the forward / backward movement is formed of, for example, a slit disk 18 attached to the shaft 3 and an encoder 19.

In the case of a four-phase stepping motor (15) shown in FIG. 9, each phase coil 15CL is connected in series to each phase switching control element (transistor) 22Q. Each phase switching control element 22Q is provided with a phase switching signal generation circuit 2Q.
1 together with the motor drive unit 20. Reference numeral 25 in the drawing denotes a current detection resistor.

In a printing apparatus including the gap adjusting mechanism 10 and the gap setting control means (40), when a gap setting command is issued, a driving pulse signal is input from the control unit 40 to the motor drive unit 20, and the motor 1
5 rotates forward. Then, the eccentric cam mechanisms 11L and 11R
Works to move (forward) the shaft 3, that is, the print head 5, in a direction approaching the platen 2 (ST 2 in FIG. 10).
0).

[0006] Here, the control unit 40 outputs the moving amount detector 17 (1) despite outputting the moving pulse signal.
If the rotation signal of shaft 3 is not output from 9),
It is determined that the print head 5 is not moving. That is, when the stepping motor (15) steps out, it is determined that the print head 5 has contacted the platen 2 (YE in ST21).
S).

[0007] Then, the control unit 40 reads the set amount (ST22), and rotates the motor 15 in the reverse direction to retreat (retreat) the print head 5 by the set amount (ST2).
3, 24). Then, the motor 15 is stopped (ST2).
5). Therefore, an accurate gap can be automatically set.

[0008]

By the way, the motor 15
Is generated by the gap adjusting mechanism 10 (14, 13,
11L, 11R), the maximum value is set in consideration of the load variation over time, power supply fluctuation and low temperature environment. Also,
The generated torque may be reset by the user.
On the other hand, the platen 2 and its supporting shaft, and further the shaft 3 and the like are often limited in design because the apparatus is not exceptionally required to be compact and lightweight.

Thus, the deflection of the platen 2 and the shaft 3 when the print head 5 comes into contact with the platen 2 may increase as the printable range increases. Therefore, the setting accuracy of the gap is affected. That is,
High precision setting cannot be performed. Furthermore, depending on the structure,
The platen 2 or the like may be deformed. At worst, it can be damaged.

An object of the present invention is to provide a printing apparatus capable of automatically setting a gap with higher precision.

[0011]

A printing apparatus according to the present invention forms a gap adjusting mechanism formed so that a gap can be adjusted by moving a print head forward and backward with respect to a platen, and a part of the gap adjusting mechanism. And a gap setting control means for setting a gap by rotating the motor to rotate the print head until the print head contacts the platen and retreating the print head after contact by a preset set amount. A switching device for determining whether or not the print head advanced by the gap setting control device has reached a predetermined switching point before the platen; and a switching point. On the condition that it has been determined that the motor has reached And obtaining torque switch controller, the provided any switching point in front of said platen
Is determined .

[0012]

In the present invention having the above-mentioned structure, when the print head is moved in the direction approaching the platen by the gap setting control means, the switching point arrival determination means determines whether or not the switching point has been reached. When it is determined that the print head has reached the switching point, the generated torque switching control means switches the value of the generated torque of the motor to a value smaller than before.

Thus, the print head is further advanced with a small value of torque and is brought into contact with the platen, so that the platen or the like is not greatly bent. Therefore,
Thereafter, the gap can be automatically set with higher accuracy by retreating the print head by a preset amount by the gap setting control means.

Of course, the platen and the like are not deformed or damaged while the print head is in contact with or in contact with the platen. In addition, since the generated torque is set to a large value at the time of starting the movement, a smooth start is guaranteed.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. (First Embodiment) As shown in FIG. 1, this printing apparatus has the same basic structure as that of a conventional example (FIGS. 8 to 10), and has a switching point arrival determining means (41, 42) and a generated torque. Switching control means (41, 42), and when the print head 5 moving in the direction to approach the platen 2 by the gap setting control means (41, 42) reaches a predetermined switching point, the motor 15 Is automatically switched to a smaller value than before.

In FIG. 1, the control unit 40 comprises a CP
U41, ROM42, RAM43, input / output port 45
And drive control of the entire apparatus. In FIG. 1, the print head 5, the paper feed motor, the carrier motor and the like and the connection relation between them are not shown.

The gap setting control means includes a ROM 42 storing a gap setting control program and a CPU 41, and is the same as in the conventional example (ST20 to ST25 in FIG. 10) (ST11, ST14, ST16 to ST19 in FIG. 2). The gap is automatically set by driving and controlling the gap adjusting mechanism 10 to move the print head 5 forward and backward with respect to the platen 2.

Note that PLS in FIG. 1 is a pulse signal that defines the rotation direction and rotation angle of the stepping motor 15, and Sph is a phase switching signal based on this pulse signal.

Each of the phase coils 15CL of the stepping motor 15 has a normal DC power supply V2 (for example, 24 V) via a transistor 52Q and a DC power supply having a lower voltage (for example, 12V) than V2 via a diode 26. V1
And are connected.

Here, the switching point arrival discriminating means moves the print head 5 in a direction approaching the platen 2 by the gap setting control means (41, 42) (ST1 in FIG. 2).
1) a means for determining whether or not the print head 5 has reached a predetermined switching point before the platen 2 during the operation.
2 and the CPU 41, and is executed in ST12 of FIG.

In the case of this embodiment, the switching point is formed to be determined based on the movement amount detection signal from the movement amount detector 17. Therefore, if the number of reference pulses to be compared with the number of movement amount detection signals (pulse signals) is changed, the switching point before the platen 2 can be arbitrarily selected and determined.

Next, the generated torque switching control means sets the generated torque of the motor 15 to a value smaller than the value until the switching point is reached, on condition that it is determined that the switching point has been reached (YES in ST12). A switching means for storing a torque switching control program in a ROM 42 and a CPU;
41 and is executed in ST13 shown in FIG.

In the case of the first embodiment, the input / output port 4
5, the switching signal Stv shown in FIG. 1 is output (L level), the switching element (transistor) 51Q is turned off and the transistor 52Q is turned off, so that the DC power supply V2 (24V) for a large generated torque is cut off. A DC power supply V1 (12 V) for a small generated torque is applied to the motor 15 (15CL) through the diode 26. That is, FIG.
As shown in the figure, the current I (1 A) flowing to the motor 15 by the DC power supply (24 V) is changed to the DC power supply V1 (12 V).
To 0.5A to reduce the generated torque by half.

The switching element 51Q, the transistor 52Q, and the resistors R51 and R52 form a torque switching circuit 50.

In this embodiment, when the gap setting control is started (started), as shown in FIG.
The switching element 51Q and the transistor 52
Q is turned on and the DC power supply V2 is connected to the motor 15. That is, a large generated torque is set (ST10 in FIG. 2). Also, when the print head 5 contacts the platen 2 and the motor 15 steps out (YES in ST14 of FIG. 2), that is, when the print head 5 is retracted (ST17), the torque is switched to a large generated torque (ST15). Have been. Note that ST15 may be specified between ST16 and ST17.

According to the first embodiment having such a configuration, when a gap setting command is given, the CPU 41 sets the switching signal Stv shown in FIG. 1 to the H level as shown in FIG. 3 and sets the torque generated by the motor 15 to a large value. That is, the switching element 51Q
And the transistor 52Q is turned on, and the DC power supply V2
(24V) is connected to the motor 15, and the current I is switched to high torque by setting the current I to 1A (ST10 in FIG. 2).

Then, the gap setting control means (41, 4)
2) operates to rotate the motor 15 to advance the print head 5 via the gap adjusting mechanism 10 in a direction to approach the platen 2 (ST11). Since the generated torque is large, smooth startup is guaranteed.

The rotation angle amount of the shaft 3 during this time is detected by the movement amount detector 17 (18, 19), and the movement amount detection signal is input via the input / output port 46 shown in FIG. Have been.

Here, at time t1 when the advance time reaches T shown in FIG.
42) determines that the print head 5 has reached the switching point (YES in ST12). Then, the generated torque switching control means (41, 42) outputs the switching signal S shown in FIGS.
tv is output (L level).

Therefore, the switching element 51Q is turned off, and the DC power supply V2 (24V) is disconnected from the motor 15. A DC power supply V1 (12 V) is connected to the motor 15 through a diode 26. The motor current I is switched from 1A shown in FIG. 3 to 0.5A. That is,
The generated torque of the motor 15 is switched to a low torque having a smaller value than before (ST13).

When the gap setting control means (41, 42) further moves the print head 5, the print head 5 comes into contact with the platen 2. Contact at time t2 in FIG. 3 (ST1
4 YES). In this case, the motor 15 steps out. That is, the CPU 41 determines that the step-out occurs because the movement amount detection signal from the movement amount detector 17 is not stepped in spite of outputting the advance pulse signal PLS to the motor drive unit 20 (21).

However, since the generated torque is small, the platen 2 and the shaft 3 are not largely bent or broken. When it is determined that the contact has been made (YES in ST14), the gap setting control means (41, 42) outputs a reversing pulse signal PLS for reverse rotation to move the print head 5 away from the platen 2. Retreat (ST17).
At this time, the switching signal Stv is set to the H level and the motor 15
Is returned to a large value (ST15).

Thus, when the print head 5 is retracted by the set amount (ST16) (YES in ST18) and the motor 15 is stopped (ST19), the gap can be automatically set with high accuracy.

According to the first embodiment, the switching point arrival determining means (41, 42) and the generated torque switching control means (41, 42) are provided, and the gap setting control means (41, 42) is provided. When the print head 5 moving in the direction to approach the platen 2 reaches a predetermined switching point, the value of the torque generated by the motor 15 can be automatically switched to a smaller value than before. Therefore, when the print head 5 contacts the platen 2 and during the contact, the pressing force has a small value according to the torque generated by the motor 15. Therefore, a large deflection is not generated in the platen 2 and the like, so that the gap can be automatically set with higher accuracy, and the platen 2 and the like are not deformed or damaged. In addition, since the generated torque has a large value at the start of the movement, a smooth start is guaranteed.

The switching point arrival determining means (41, 41)
42) is formed to determine whether or not the print head 5 has reached the switching point using the movement amount detection signal output from the movement amount detector 17 including the slit disk 18 and the encoder 19. Therefore, the switching point can be accurately determined even if the distance from the platen 2 is extremely small.

The generated torque switching control means (41, 4)
Since 2) is configured to switch the DC power supplies V1 and V2, it is easy to select the torque at which the print head 5 comes into contact with the platen 2 to the minimum possible value, and the applicability is wide.

(Second Embodiment) This second embodiment is shown in FIG.
As shown in FIG. In the case of the second embodiment, the motor drive units 20 (21, 22Q) are the same as in the first embodiment, but a constant current control circuit 30 is provided. Therefore, the generated torque switching control means (41, 42) outputs the switching signal Sti from the output port 47 shown in FIG. 4 and switches the current I flowing through the motor 15 from 1 A to 0.5 A (ST13 in FIG. 2). Accordingly, the generated torque is switched to a small value.

That is, the constant current control circuit 30 includes the comparator 31 shown in FIG. Voltage setting circuits (resistors 32 and 33) for setting the
5 is formed by a feedback circuit (resistor 34) for feeding back the feedback signal detected at 5 and transistors 35Q and 36Q controlled by a current control signal Schg output from the comparator 31. Therefore, basically, as shown in FIG. 5, the current I flowing through the motor 15 is controlled to a constant current of 1 A. Diode 27, 2
8 forms a discharge circuit.

Here, the generated torque switching control means (41,
42), a torque switching circuit 50 is provided. This torque switching circuit 50 has a configuration in which the resistor 56 and the transistor 55Q shown in FIG. 4 are connected between the resistors 32 and 33 and the ground, and the inverter 57 is connected to the base of the transistor 55Q. Therefore, when the switching signal Sti is output (L level) at time t1 shown in FIG. 5, the transistor 55Q is turned on, and the reference signal Vref.
And the current control signal Schg output from the comparator 31 can be switched to the L level. That is, by changing the ON-OFF timing of the transistors 35Q and 36Q, the current I flowing through the motor 15 is set to 0.5 A, and the torque generated by the motor 15 can be switched to a small value.

The operation is the same as that of the first embodiment (FIG. 2).

Therefore, according to the second embodiment, it is possible to achieve the same effects as the first embodiment, such as the setting of a high-precision gap, and it is not necessary to provide another DC power supply V1. Realization becomes even easier in terms of cost.

(Third Embodiment) The third embodiment is an improvement of the second embodiment (FIG. 4). As shown in FIG. 6, a capacitor 59C is provided between a resistor 33 forming a voltage setting circuit and ground.
Are connected so that the torque generated by the motor 15 is gradually reduced as shown in FIG.

Therefore, in the case of the third embodiment, the same operation and effect as in the case of the second embodiment can be obtained, and the torque can be switched more smoothly.

[0044]

According to the present invention, a switching point arrival discriminating means and a generated torque switching control means are provided, and the print head moving in the direction approaching the platen is determined by the gap setting control means. When the print head reaches the point, the value of the generated torque of the motor can be automatically switched to a smaller value than before, so the pressing force when the print head comes into contact with the platen and while The value becomes small according to the generated torque. Therefore, a large deflection is not generated in the platen or the like, so that the gap can be automatically set with higher accuracy, and the platen or the like is not deformed or damaged. In addition, since the generated torque has a large value at the start of the movement, a smooth start is guaranteed.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a first embodiment of the present invention.

FIG. 2 is a flowchart for explaining the operation.

FIG. 3 is a timing chart for explaining a generated torque switching operation.

FIG. 4 is a circuit diagram showing a second embodiment.

FIG. 5 is a timing chart for explaining a generated torque switching operation.

FIG. 6 is a circuit diagram showing a third embodiment.

FIG. 7 is a timing chart for explaining the generated torque switching operation.

FIG. 8 is a view for explaining a gap adjusting mechanism of the present invention and a conventional example.

FIG. 9 is a circuit diagram for explaining a conventional example.

FIG. 10 is a flowchart for explaining the operation of the conventional example.

[Explanation of symbols]

1L, 1R Main frame 2 Platen 3 Shaft 4 Carrier 5 Print head 10 Gap adjusting mechanism 11L, 11R Eccentric cam mechanism 15 Motor 15CL Phase coil 17 Movement detector 20 Motor drive unit 21 Phase switching signal generation circuit 22Q Phase switching control element 30 Constant current control circuit 31 Comparator 40 Control unit 41 CPU (gap setting control means, switching point arrival determination means, generated torque switching control means) 42 ROM (gap setting control means, switching point arrival determination means, generated torque switching control means) 43 RAM 50 Torque switching circuit 51Q Switching element 52Q Transistor 55Q Transistor 56 Resistance 57 Inverter

──────────────────────────────────────────────────の Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B41J 25/308

Claims (1)

(57) [Claims] 1. A gap adjusting mechanism formed so that a gap can be adjusted by moving a print head forward and backward with respect to a platen, and a motor forming a part of the gap adjusting mechanism is rotated to cause the print head to contact the platen. A gap setting control means for moving the print head until contact and retreating the contacted print head by a preset amount only to set a gap, wherein the gap setting control means A switching point arrival determining means for determining whether or not the advancing print head has reached a predetermined switching point before the platen; and And a generated torque switching control means for switching the generated torque of the motor to a value smaller than the value before reaching the switching point. The switching point before the platen
A printing device characterized in that: