JPH04235073A - Serial printer - Google Patents

Abstract

PURPOSE:To prevent a carriage drive motor from heating and burning independently of the number of printing columns. CONSTITUTION:A CPU 1 develops head drive data on a RAM 4 in accordance with printing data transmitted to a host device 5 through an I/F part 6. Then, the CPU 1 arithmetically operates a printing area, drives a carriage motor 8, and moves a carriage 10. The CPU 1 reads a quiescent time in accordance with the number of printing columns from a table stored in a ROM 3 and actuates a timer 2 to count the quiescent time. Furthermore, paper is fed in accordance with the printing data. Upon completion of the paper feed action and the counting of the quiescent time, a printing for one line is finished, and printing shifts to a next line.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a serial printer, and more particularly to a serial printer in which a DC motor drives a carriage that reciprocates with respect to a recording medium.

0002

2. Description of the Related Art A serial printer performs recording by reciprocating a carriage carrying a print head in the direction of a platen axis based on print data using a carriage motor via a timing belt or the like. In recent years, the printing speed of printers has increased, and DC motors are increasingly being used as carriage motors due to their good responsiveness and controllability. In the case of a DC motor, due to its characteristics, the current flowing through the motor is greatest (the effective torque is large) during acceleration/deceleration, and the current flowing through the motor is small (the effective torque is small) when the motor is at constant speed (during printing). Therefore, the larger the number of digits printed by the printer, the smaller the current applied to the motor per line. Figure 3 shows the operation of the carriage. Further, FIG. 4 shows the current flowing through the carriage motor at this time.

Here, the carriage motor drive circuit is shown in FIG.
The circuit shown in FIG. 1 is composed of a driving section that can select between normal and reverse rotation, and a current limiting section. Also, during deceleration, braking is applied by reverse energization.

As shown in FIG. 4, the current flowing through the carriage motor is large during acceleration and deceleration, and becomes small during constant speed control. Therefore, the average value of the current per line increases as the print area becomes shorter (as the distance traveled by the carriage becomes shorter). However, the moving distance of the printer's carriage in the direction of the print digits varies greatly depending on the print data sent from the host device, and the current flowing through the carriage motor changes accordingly, and the amount of heat generated by the motor changes greatly depending on the print data. becomes. In other words, when the number of printed digits is small (for example, 10 digits or less), the amount of heat generated increases, and when used for a long time, the motor coil heats up and the armature resistance increases, resulting in lower output and the printer's This will interfere with operation and reduce print quality. Furthermore, if the amount of heat generated increases and exceeds the allowable temperature, there is a risk that the motor will burn out. In conventional printers, in order to prevent the above-mentioned problems, a high-output carriage motor is used, taking into consideration the case where the number of printed digits is small.

[0005]

[Problem to be Solved by the Invention] However, the number of digits printed by printers is generally around a few tens of digits, and it is rare for printing of less than ten digits to continue for a long time. If a carriage motor was selected, there was a problem in that the printer would be extremely expensive. In addition, the large-sized shape of a high-output motor created problems with its placement within the printer.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems and to provide an inexpensive serial printer in which the heat generation of the carriage motor is suppressed.

[0007]

[Means for Solving the Problems] The present invention provides a serial printer comprising a carriage mounted with a print head and reciprocated with respect to a recording medium on a platen based on print data, and a DC motor for driving the carriage. In the printer,
The present invention is characterized in that a timer is provided to set a time during which the printing operation is paused, and the timer sets the pause time in the drive operation of the DC motor according to the moving distance of the carriage that performs the printing operation based on print data.

[0008]

[Embodiments] The present invention will be specifically explained below with reference to embodiments shown in the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention, and FIG. 2 is a perspective view showing one embodiment of the present invention. 1 in FIG. 1 is a CPU which is a control unit of the printer, and is provided with a ROM 3 that stores control programs and the like, and a RAM 4 that temporarily stores various data. Print data from the host device 5 is sent to the CPU 1 via an I/F section (interface section) 6. 2 is a timer and CPU1
Timing is performed using the data set by . Note that the timer 2 can generally be easily configured with a programmable timer, a software timer, or the like. In this example, Figure 1
It is composed of a presettable up/down counter as shown in FIG.

7 in FIG. 1 is a carriage drive circuit, and 8
is the carriage motor. Reference numeral 10 in FIG. 2 is a carriage, which is driven by a carriage motor 8. As shown in FIG. 12 is a platen, 13 is a recording medium, and 11 is a print head. Here, the carriage motor 8 is a DC motor, and its output shaft is provided with an encoder 9 for position detection, and the position of the carriage 10 is controlled by counting the output signal of this encoder.

The operation of one embodiment of the present invention will be explained with reference to FIGS. 1 and 2. The CPU 1 develops head drive data in the RAM 4 according to the print data from the host device 5, calculates a print area according to the print data, drives the carriage motor 8, and starts moving the carriage 10. The carriage motor 8 starts accelerating toward a set speed from a stopped state, and after reaching the set speed, is controlled to a constant speed and reaches the printing area. When the print area is reached, the CPU 1 drives the print head based on the head drive data to perform printing. When printing according to the print data is completed, the carriage motor 8
will stop after deceleration control. Here, the CPU 1 reads a pause time corresponding to the number of printing digits, which will be described later, from a table stored in the ROM 3, activates a timer 2 to measure the pause time, and feeds the paper according to the print data. When both the paper feeding operation and the counting of the pause time are completed, one line of printing is completed, and the printing of the next line begins.

Now, the setting of the pause time of the printing operation will be described. As described above, the current flowing through the carriage motor 8 is large during acceleration and deceleration, and becomes small during constant speed control. Therefore, the average value of the current per line becomes larger as the number of printed digits becomes shorter, and becomes smaller as the number of printed digits becomes longer. In other words, the temperature of the heat generated by the motor changes depending on the distance traveled by the carriage during the printing operation.

FIG. 5 shows the relationship between the number of printed digits during continuous printing and the saturation temperature of the motor armature after heat generation in a 136-digit printer to which this embodiment is applied. FIG. 5 shows a case where the next printing operation is continued without a pause after the printing operation for one line is completed. Note that the environmental temperature in FIG. 5 is 35° C., which is the guaranteed operation temperature of the printer to which this embodiment is applied. Assuming that the permissible temperature of the motor armature is 120 DEG C., there is a danger that the motor will burn out due to heat generation in printing operations of 50 digits or less.

[0014] Therefore, the pause time that would keep the heat generation within the permissible temperature during printing operations of 50 digits or less was determined, as shown in Figure 6.
FIG. 7 shows the results of measuring the saturation temperature by applying the pause time. The pause time shown in the table of FIG. 6 is the printing operation pause time to be set. Although the printing speed of the printer will be slowed down by providing a pause time for the printing operation, as can be seen from the table in Figure 6, continuous operation is possible without any particular pause time when printing 50 digits or more. Therefore, the number of frequently used printing digits can be configured without reducing the printing speed.

By storing the down time shown in the table of FIG. 6 in the ROM 3, reading it out according to the number of printed digits, and operating the timer 2, it is possible to suppress the amount of heat generated by the carriage motor 8 to below a certain value. That's why.

[0016] Since printing one line requires the time required to feed the paper, the actual operation is the longer of the pause time measured by timer 2 and the time required to feed the paper (varies depending on print data from the host device). The time will determine the printing operation. This situation is shown in FIG.

Generally, a printer has a plurality of printing modes, and each printing mode has different printing resolution and printing speed (carriage speed). Therefore, the current applied to the carriage motor also varies depending on the print mode, but this can be handled by having a table for setting the pause time according to the print mode for a printer having multiple print modes. Further, for special carriage drive operations such as logical seek, the same effect can be obtained by providing a pause time that corresponds to the moving distance. In the above explanation, the number of printed digits was based on the standard 1/10 inch pitch for this printer, but it can also be easily applied to printing with a pitch of 1/12 inch, etc. by converting the distance traveled by the carriage. can.

[0018]

As explained above, according to the present invention, it is possible to suppress the amount of heat generated by the carriage drive motor through simple control, and a highly reliable printer without deterioration of print quality or burnout of the motor can be achieved. can be provided at low cost.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention.

FIG. 2 is a structural diagram of a printer showing an embodiment of the present invention.

FIG. 3 is a diagram illustrating the operation of the carriage.

FIG. 4 is a diagram showing the current flowing through the carriage motor.

FIG. 5 is a diagram illustrating the heat generation state of the carriage motor.

FIG. 6 is a diagram illustrating printing operation pause time according to an embodiment of the present invention.

FIG. 7 is a diagram illustrating a heat generation state in an embodiment of the present invention.

FIG. 8 is a diagram showing a carriage driving operation according to an embodiment of the present invention.

FIG. 9 is a circuit diagram showing a carriage motor drive circuit.

FIG. 10 is a circuit diagram showing the configuration of a timer according to an embodiment of the present invention.

[Explanation of symbols]

1 CPU 2 Timer 3 ROM 4 RAM 5 Host device 6 I/F section 7 Carriage motor drive section 8
Carriage motor 9 Encoder 10 Carriage 11 Print head 12 Platen 13 Storage medium Q1-Q5 Transistors R1-R7 Resistance element OP1 Operational amplifier D1 Diode ZD1 Zener diode

Claims (1)

[Claims] 1. In a serial printer equipped with a carriage mounted with a print head and reciprocated with respect to a recording medium on a platen based on print data, and a DC motor that drives the carriage, the printing operation is stopped. A serial printer characterized in that a timer is provided for setting a time for the drive operation of the DC motor to be set by the timer according to a moving distance of the carriage that performs a printing operation based on print data.