JP2003324982A - Printer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To learn the state of a printing medium, such as the presence or absence of a loaded tape cassette, with relatively high accuracy and reduction in the number of revolutions of a DC motor suppressed. <P>SOLUTION: The voltage between the terminals T1 and T2 of a tape transfer motor 34 which is the DC motor whose number of revolutions is kept constant by an electronic governor circuit 36 is divided through resistors and converted into digital signals through A-D converters 46 and 47. The digital signals are then supplied to CPU 40. Based on the voltages, the CPU 40 judges in what state a tape is. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printing apparatus in which a DC motor is used as a print medium conveyance drive source.

[0002]

2. Description of the Related Art In a small printing apparatus such as a tape printer, a DC motor is often used as a drive source for transporting a print medium. In order to obtain a high quality print result in which the dot interval is kept constant, it is necessary to keep the number of rotations of the DC motor constant. As a result, when the load torque on the DC motor changes, the voltage applied to the DC motor also changes accordingly, so that the DC voltage is changed by the electronic governor circuit.
Motors are often controlled.

Utilizing the fact that the above control is performed, there is a technique for determining whether or not a tape cassette, in which a tape, which is a print medium, is wound, is mounted at a predetermined position. It is disclosed in Japanese Patent Laid-Open No. 6-191126. According to this publication, a resistor is prepared between the electronic governor circuit and the ground at a position where all the current flowing in the DC motor flows, and the voltage applied to the DC motor is detected by measuring the voltage at one end of the resistor. Then
Based on the detected voltage value, it is possible to determine whether or not the tape cassette is mounted at a predetermined position.

[0004]

However, in the technique of the above publication, a large detection voltage cannot be obtained unless a resistor having a large resistance value is prepared because the current value flowing through the DC motor is relatively small. As a result, it becomes impossible to know with sufficient accuracy whether or not the tape cassette is mounted at a predetermined position. However, when a resistor having a large resistance value is used, the required voltage cannot be applied to the DC motor, and the DC motor cannot rotate at a desired rotation speed.

Therefore, an object of the present invention is to obtain a state relating to the print medium from the voltage applied to the DC motor used as a conveyance drive source of the print medium with relatively high accuracy and to suppress a decrease in the rotation speed of the DC motor. It is to provide a printing device that can be known.

[0006]

In order to achieve the above object, a printing apparatus according to a first aspect of the present invention is a printing apparatus in which a DC motor is used as a drive source for transporting a printing medium, the reference voltage generating circuit and the reference voltage. An electronic governor circuit that controls the rotation speed of the DC motor using a comparison circuit that compares a counter voltage of the DC motor with a reference voltage generated by a generation circuit, and a voltage at both terminal positions of the DC motor is detected. And a detection means for

According to the first aspect of the present invention, since a relatively large detection voltage can be obtained by detecting the voltage at both terminal positions of the DC motor having a relatively large internal resistance value, it can be kept constant in the electronic governor circuit. It is possible to know the state of the print medium with high accuracy from the voltage applied to the DC motor while suppressing the decrease in the rotation speed of the DC motor. Further, since it is not necessary to separately use a resistor having a large resistance value, cost and heat generation amount can be suppressed and the mounting area can be reduced.

The printing apparatus according to a second aspect of the invention is characterized in that the detecting means includes two AD converters respectively connected to both terminal positions of the DC motor.

According to the second aspect, since the detected voltage between the terminals of the DC motor is converted into a digital signal by the AD converter, it is possible to easily control the printing apparatus.

Further, the printing apparatus of claim 3 is characterized in that a wound long tape-shaped printing medium is used as the printing medium.

According to the third aspect of the present invention, the state relating to the tape can be discriminated in detail on the basis of the detected voltage across the terminals of the DC motor, and the state, such as the normal state, can be determined with high accuracy.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a front view of a tape printer which is a printing apparatus according to an embodiment of the present invention. As shown in FIG. 1, on a housing surface of a tape printer 1, a keyboard 11 including a large number of character keys and a liquid crystal display (LCD) for displaying print contents and the like.
play) 12 and a manual cutter button 13 for cutting a tape (not shown) as a printing medium are arranged. Inside the housing of the tape printer 1, a long tape wound and housed in a cassette and a tape transport motor 34 (see FIG. 2) which is a DC motor are housed.

The LCD 12 is controlled by a signal given from a liquid crystal display controller (LCDC) 14 (see FIG. 2) having a display RAM for outputting display data to the LCD 12. The keyboard 11 includes character keys for inputting kana and alphabets, kanji conversion keys, katakana conversion keys, lowercase input keys, cursor movement keys, a power key for switching the tape printer 1 on and off, and a built-in line thermal head. 31 (Fig. 2
The print key etc. that gives the print trigger to the tape by the reference) are included.

Next, the control system of the tape printer 1 will be described with reference to FIG. 2, which is a block diagram of the tape printer shown in FIG.

As shown in FIG. 2, the tape printer 1 is
In addition to the keyboard 11, the LCDC 14, the LCD 12, etc., the line thermal head 31 and its driver 32, the tape transport motor 34 and its driver 35, the CPU 40 including the ROM 38 and the RAM 39, the CG-ROM 42, the buffer RAM 43, the general-purpose personal computer 44.
Connection interface 45 with two analog-digital converters (ADC: AD converter) 46, 47
have.

In the line thermal head 31 of the tape printer 1, a large number of heating elements, each corresponding to one printing dot, are arranged in one row. The tape transport motor 34 transports a tape, which is a print medium, by rotationally driving a rotation shaft of a pressure bonding roller that applies a transport force to the tape. In the present embodiment, the driver 35 of the tape transport motor 34 has an electronic governor circuit 36, as will be described later.
(See FIG. 3 and FIG. 4). Therefore, the number of rotations of the tape feeding motor 34 is kept at a set constant number of rotations, and as a result, the tape feeding speed is also kept constant. Be drunk

The ROM 38 stores various programs for controlling the operation of the tape printer 1, such as programs for controlling the LCD 12 and energizing the heating elements in the line thermal head 31, and data tables. The RAM 39 stores print data such as character data input from the keyboard 11 and image data supplied from the personal computer 44 via the connection interface 45, and stores calculation results in the CPU 40. In the CG-ROM 42, dot pattern data of many characters to be printed or displayed is stored in association with the code data of the characters. The buffer RAM 43 is the line thermal head 31.
When the printing is performed, the print data stored in the RAM 39 is stored in a state of being expanded into a bitmap.
As will be described later, the AD converters 46 and 47 convert a signal obtained by dividing the voltage at both terminal positions of the tape transport motor 34 from analog into digital and give it to the CPU 40.

In the tape printer 1 thus constructed, for example, when the print key is pressed after the user inputs a character to be printed from the keyboard 11, the keyboard 1
The character data input from 1 and stored in the RAM 39 is converted into bitmap data according to the dot pattern stored in the CG-ROM 42, which is the buffer R.
It is stored in AM43. Then, the tape transport motor 34
While the tape is being conveyed at a constant speed, the line thermal head 31 is driven in accordance with the bitmap data in synchronization with the tape conveying speed, whereby desired characters are thermally printed in a dot pattern on the tape.

The CPU 40 has the AD converters 46 and 47.
Based on the voltage signal given from the tape printer 1
However, the cassette containing the tape is not installed in the specified position (no cassette), the cassette is installed but the tape is full (tape end state), and the cassette is installed but it is dust. It is determined whether the motor 34 is in a locked state (motor locked state) or in a normal state (a state in which the tape is normally conveyed in none of the above) due to some reason such as being caught. When it is determined that the state is other than the normal state, the alarm information is displayed on the LCD 12 or the printing is prohibited. As a result, it is possible to call the user's attention and prompt the user to replace the cassette, and it is possible to prevent the platen roller made of rubber from being melted by heat.

Next, the driver 3 of the tape feeding motor 34
5 will be described in detail with reference to FIGS. 3 and 4.
FIG. 3 is a circuit diagram around the electronic governor circuit included in the driver of the tape transport motor. As shown in FIG. 3, the electronic governor circuit 36 includes one governor IC chip 51 and a rotational speed adjusting resistor R of the tape transport motor 34, which is a variable resistor.
v and a resistor R connected in series with the rotation speed adjusting resistor Rv
1 and.

The governor IC chip 51 has Vcc, Vref,
It has four terminals V0 and Vss. Vcc is one terminal T1 of the tape transport motor 34 and the input voltage Vin terminal, Vref is an intermediate point between the rotation speed adjusting resistors Rv and R1, and V0 is Vss is connected to the connection point between the other terminal T2 of the tape transport motor 34 and the rotation speed adjusting resistor Rv, and to the ground. Governor IC chip 51
Is the tape transport motor 3 taken out at the terminals Vref and V0.
The proportional current control is performed so that the counter electromotive voltage of No. 4 is maintained at a desired value regardless of the fluctuation of the load, and the voltage supplied from the terminal Vcc to the tape feeding motor 34 is controlled. Since the counter electromotive voltage of the tape transport motor 34 is proportional to the rotation speed of the tape transport motor 34, if the counter electromotive voltage of the tape transport motor 34 is controlled to be constant, the tape transport motor 3
The rotational speed of 4 is kept constant. As will be described later,
In this embodiment, by changing the resistance value of the rotation speed adjusting resistor Rv, the back electromotive force of the tape transport motor 34, and thus the rotation speed thereof, can be adjusted to a desired value.

Further, the terminal T1 of the tape feeding motor 34
Is connected to the ground via two resistors Ra and Rb. An AD converter 46 is connected between the resistors Ra and Rb. On the other hand, the terminal T2 of the tape transport motor 34 is connected to the ground via the two resistors Rc and Rd. Then, the resistance Rc and the resistance Rd
An AD converter 47 is connected between and. Therefore, the voltages at both terminals T1 and T2 of the tape transport motor 34 are divided and then digitally converted and supplied to the CPU 40. In this way, the tape transport motor 34
The voltage at both terminals T1 and T2 of the two resistors Ra and Rb:
The reason why the voltage is divided by Rc and Rd and then converted by the AD converters 46 and 47 is that it is not preferable to directly input large voltage data to the CPU 40. The resistors Ra, R
b: The resistance values of Rc and Rd may be large in order to increase the detected voltage value, but even if these resistance values are increased, the required voltage is applied to the tape transport motor 34 as in the above publication. It will not be given away.

FIG. 4 is a partial equivalent circuit diagram of FIG. As shown in FIG. 4, the tape transport motor 34 can be replaced with a resistor R2 and a counter electromotive voltage Va in terms of a circuit. The resistance R2 of the tape transport motor 34 is the resistance R1, R
It constitutes a part of a bridge circuit in which four resistors including 3 and R4 are used as peripheral resistors. In this bridge circuit, 4
Each resistance value is adjusted so that the resistance value of one resistance is R1: R3 = R2: R4.

In this bridge circuit, the resistance R
A reference voltage generating circuit 53 that generates a reference voltage is connected to the intermediate point between 1 and R3. Reference voltage generation circuit 53
Is composed of a voltage source having a constant voltage Vb and a rotation speed adjusting resistor Rv connected in parallel with the voltage source. The reference voltage output by the reference voltage generating circuit 53 can be adjusted by changing the resistance value of the rotation speed adjusting resistor Rv. The rotation speed adjustment resistance Rv may be, for example, a rotation type whose resistance value is determined in proportion to the rotation angle of the knob, or may be a type whose resistance value can be changed stepwise.

The reference voltage generated by the reference voltage generation circuit 53 is supplied to the minus input terminal of the comparison circuit 54 including an operational amplifier. The positive input terminal of the comparison circuit 54 is connected to the midpoint between the resistors R2 and R4.
Accordingly, the comparison circuit 54 can compare the reference voltage generated by the reference voltage generation circuit 53 and the counter electromotive voltage of the tape transport motor 34.

The output signal of the comparison circuit 54 is supplied to the voltage adjustment circuit 55. As described above, in the present embodiment, since the resistance values of the four resistors have the relationship of R1: R3 = R2: R4, the voltage adjustment circuit 55 uses the comparison result of the comparison circuit 54. The output voltage of the terminal Vcc is automatically adjusted so that the difference between the two becomes zero (for example, when the counter electromotive voltage of the tape transport motor 34 is larger than the reference voltage generated by the reference voltage generation circuit 53, the output of the terminal Vcc is output). If the voltage is decreased and the output voltage of the terminal Vcc is increased in the opposite case, the back electromotive force Va of the tape transport motor 34 is always the reference voltage generated by the reference voltage generating circuit 53 (rotation speed adjusting resistor Rv). Is adjustable by a variable voltage).

As described above, by using the electronic governor circuit 36, the tape conveying motor 34 can be set at a desired rotation speed by appropriately adjusting the resistance value of the rotation speed adjusting resistor Rv.

Further, the tape printer 1 shown in FIG.
Since the tape transport motor 34 controlled by the electronic governor circuit 36 as described above is used as the tape transport drive source, the tape can be rotated at the desired constant rotation speed. Therefore, it is possible to obtain a good printing result with little variation in dot spacing.

The resistors R3 and R4, the reference voltage generating circuit 53, the comparing circuit 54 and the voltage adjusting circuit 55 shown in FIG.
Is configured within the governor IC chip 51 in the circuit diagram of FIG.

Returning to FIG. 3, AD converters 46 and 47.
When the CPU 40 receives the divided voltage values at the terminals T1 and T2 of the tape transport motor 34 from the CPU 40, the CPU 40 obtains the voltage difference between the terminals T1 and T2 from these two voltage values. The voltage difference between the terminals T1 and T2 thus obtained is detected as a relatively large value, for example, about 5V to 10V, because the resistance value of the resistor R2, which is the internal resistance of the tape transport motor 34, is relatively large. To be done.

Then, the CPU 40 determines the state regarding the tape based on the detected voltage difference between the terminals T1 and T2. This determination can be performed with high accuracy because the detected voltage value is relatively large. As an example, when the voltage difference is 10 V or less, it is determined as a normal state,
In the case of 10V to 11V, it is judged that there is no cassette,
In the case of 11V to 12V, it is judged as the tape end state,
When the voltage is 12 V or more, it is determined that the motor is locked. On the other hand, in the technique of the above-mentioned publication, since the voltage value detected is small, it is virtually impossible to distinguish the state relating to the tape into four states as in the present embodiment. The platen rubber (not shown) has a larger voltage difference than the normal state without the cassette.
This is because of the contact resistance between the line thermal head 31 and the line thermal head 31, and the voltage difference in the tape end state is smaller than that in the motor lock state because the clutch is slipping and the shaft is rotating at the tape end.

If it is determined that the CPU 40 is in a state other than the normal state, the CPU 40 causes the LC 40 to operate as described above.
Alarm information is displayed on D12, or printing is prohibited. According to the present embodiment, it is possible to judge the state of the tape with high accuracy.
The alarm display and the prohibition of printing are also less erroneous. Therefore, the probability of false alarm display is reduced.

As described above, in the tape printer 1 according to the present embodiment, a relatively large detection voltage can be obtained by detecting the voltage at both terminal positions of the tape transport motor 34 having a relatively large internal resistance value. Therefore, the tape feeding motor 3 which is to be kept constant by the electronic governor circuit 36
4 while suppressing the decrease in the number of rotations of the tape 4
The state of the tape can be known with high accuracy from the voltage applied to the tape. Further, since it is not necessary to separately use a resistor having a large resistance value, it is possible to obtain an advantage that cost and heat generation amount can be suppressed and a mounting area can be reduced.

Further, in the tape printer 1 of the present embodiment, the detected terminal voltage of the tape transport motor 34 is A
Since the digital signals are converted by the D converters 46 and 47, the tape printer 1 can be easily controlled by supplying the digital signals to the CPU 40.

Further, since the tape printer 1 uses a wound long tape as a printing medium, it is based on the detected terminal voltage of the tape transport motor 34 that the tape is in the normal state, the cassette-less state, and the tape. End state,
It is possible to accurately determine the motor lock state.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above-mentioned embodiments, and various design changes are possible within the scope of the claims. Is. For example, although the AD converter is used in the above-described embodiments, the AD converter does not necessarily have to be used. Further, the present invention can be applied to a printing apparatus other than a tape printer as long as the printing apparatus uses a DC motor as a drive source for conveying a print medium.

[0038]

As described above, according to the first aspect of the present invention, the print medium is changed from the voltage applied to the DC motor while suppressing the decrease in the rotation speed of the DC motor, which is kept constant by the electronic governor circuit. It is possible to know the state regarding to with high accuracy. Further, since it is not necessary to separately use a resistor having a large resistance value, cost and heat generation amount can be suppressed and the mounting area can be reduced.

According to the second aspect, since the detected voltage between the terminals of the DC motor is converted into a digital signal by the AD converter, it is possible to easily control the printing apparatus.
According to the third aspect, the state relating to the tape can be discriminated in detail on the basis of the detected inter-terminal voltage of the DC motor, and which state, such as the normal state, can be determined with high accuracy.

[Brief description of drawings]

FIG. 1 is a front view of a tape printer which is a printing device according to an embodiment of the present invention.

FIG. 2 is a block diagram of the tape printer shown in FIG.

FIG. 3 is a circuit diagram around an electronic governor circuit included in a driver of a tape transport motor included in the tape printer shown in FIG.

FIG. 4 is a partial equivalent circuit diagram of FIG.

[Explanation of symbols]

1 tape printer 31 line thermal head 34 Tape transport motor (DC motor) 35 driver 36 Electronic governor circuit 40 CPU 46, 47 AD converter 51 governor IC chip 53 Reference voltage generation circuit 54 Comparison circuit 55 Voltage adjustment circuit Rv speed adjustment resistor

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 2C058 AC04 AC06 AE04 GA05 GE04                       GE13                 2C060 BA01 CA11                 5H550 AA15 BB08 DD06 FF03 GG03                       HB12 LL15 LL16 LL23 LL24                       MM01

Claims (3)

[Claims] 1. A printing apparatus, in which a DC motor is used as a drive source for transporting a print medium, a comparison comparing a reference voltage generating circuit, a reference voltage generated by the reference voltage generating circuit, and a counter electromotive voltage of the DC motor. A printing apparatus comprising: an electronic governor circuit that controls the rotation speed of the DC motor using a circuit; and a detection unit that detects a voltage at both terminal positions of the DC motor. 2. The printing apparatus according to claim 1, wherein the detection unit includes two AD converters respectively connected to both terminal positions of the DC motor. 3. The printing apparatus according to claim 1, wherein a wound long tape-shaped printing medium is used as the printing medium.