JP2988069B2 - Serial printer - Google Patents

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 carriage reciprocating with respect to a recording medium is driven by a DC motor.

[0002]

2. Description of the Related Art In a serial printer, a carriage on which a print head is mounted is reciprocated in a platen axis direction based on print data by a carriage motor via a timing belt or the like for recording. 2. Description of the Related Art In recent years, the printing speed of a printer has been increased, and examples of using a DC motor as a carriage motor have been increasing due to good responsiveness and good controllability. In the case of a DC motor, due to its characteristics, the energizing current is the largest in the acceleration / deceleration state (effective torque is large), and at a constant speed (during printing), the energizing current is small (effective torque is small). Therefore, as the number of print digits of the printer increases, the current supplied to the motor per line decreases. FIG. 7 shows the operation of the carriage. FIG. 8 shows the current supplied to the carriage motor at this time. Here, the drive circuit of the carriage motor is the circuit shown in FIG. 1 and includes a drive unit capable of selecting normal rotation and reverse rotation, and a current limiting unit. Also, during deceleration, braking by reverse energization (reverse rotation braking) is applied to accelerate braking. As shown in FIG. 8, the current supplied to the carriage motor increases during acceleration and deceleration, and decreases during constant speed control. Therefore, the average value of the energizing current per line increases as the printing area becomes shorter (as the moving distance of the carriage becomes shorter). However, the moving distance of the carriage of the printer in the printing digit direction greatly depends on the print data sent from the host device, and accordingly the current supplied to the carriage motor changes, and the heat generated by the motor greatly changes depending on the print data. Becomes In other words, when the number of printed digits is small (for example, when the number of printed digits is less than 20 digits), the amount of heat generated is large. The operation is hindered and the print quality is reduced. Further, if the heat generation increases and exceeds the allowable temperature, the motor may be burned. Conventional printers use a high-output carriage motor in consideration of the case where the number of print digits is small in order to prevent the above-described problem.

[0003]

However, the number of printing digits of a printer is generally about several tens of digits, and printing with a small number of digits rarely lasts for a long time. If the carriage motor is selected, there is a problem that the printer becomes extremely expensive. In addition, a large-output motor has a large size, and thus has a problem of arrangement in a printer.

An object of the present invention is to solve the above-mentioned conventional problems and provide an inexpensive serial printer which suppresses heat generation of a carriage motor.

[0005]

SUMMARY OF THE INVENTION A serial printer according to the present invention includes a DC motor for driving a carriage on which a head is mounted, and a motor control for providing a plurality of braking modes by changing the control mode of the DC motor. Means,
Data generating means for generating head drive data in print line units from print data from the host, print area calculating means for calculating a print area of each print line from the generated head drive data, and a print area for each print line. Printing means for printing on a recording medium based on the head drive data while driving the carriage by the DC motor based on the print data, wherein the printing means calculates the calculated print every time the carriage is driven for each print line. One of the plurality of braking modes is selected based on the length of the region, and the DC motor is braked in the braking mode. Here, the motor control means typically supplies H terminals to both terminals of the DC motor.
It has switching means connected in a bridge type, and provides a plurality of braking modes by selectively turning on and off the switching means.

[0006]

As described above, when the number of digits to be printed is large (the moving distance is large) and the calorific value of the carriage motor is small, the braking mode by reverse energization is selected, and the number of digits to be printed is small (the moving distance is small). If the heat generation amount of the carriage is large, it is possible to suppress the heat generation amount of the carriage motor by selecting the braking control mode according to the moving distance of the carriage in the printing operation, such as selecting the braking mode due to shorting of both terminals. It is only necessary to select a motor assuming printing of a frequently used number of digits, so that an inexpensive printer can be configured.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the embodiments shown in the drawings.

FIG. 1 is a carriage motor drive circuit diagram showing one embodiment of the present invention. The carriage motor drive circuit of the present invention is not different in configuration from the conventional one, and there is a difference in the braking method. FIG. 5 is a block diagram showing one embodiment of the present invention, and FIG. 6 is a structural diagram of a printer showing one embodiment of the present invention. Reference numeral 1 in FIG. 5 denotes a CPU which is a control unit of the printer, and stores a control program and the like.
An OM 2 and a RAM 3 for temporarily storing various data are provided. The print data from the host device 4 is an I / F
The data is sent to the CPU 1 via the interface (interface) 5. In FIG. 5, reference numeral 6 denotes a carriage drive circuit, and reference numeral 8 denotes a carriage motor. 6 is a carriage, which is driven by a carriage motor 8. Reference numeral 12 denotes a platen, 9 denotes a recording medium, and 11 denotes a print head.
Here, the carriage motor 8 is a DC motor, and its output shaft is provided with an encoder 7 for position detection. The position of the carriage 10 is managed by counting output signals of the encoder.

The operation of one embodiment of the present invention will be described with reference to FIGS. The CPU 1 develops the head drive data in the RAM 3 according to the print data from the host device 4, calculates a print area corresponding to the print data, drives the carriage motor 8, and starts the movement of the carriage 10. The carriage motor 8 starts accelerating from the stopped state toward the set speed, and after reaching the set speed, is controlled at a constant speed to reach the print 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 in accordance with the print data is completed, the carriage motor 8 starts deceleration control. Here, the CPU 1 selects a braking mode according to the number of print digits, which will be described later, brakes the carriage motor 8, and then stops the carriage 10.

The operation of each braking mode will be described with reference to FIGS. 1, 2, 3 and 4. In FIG. 1, the carriage motor 8 is connected to transistors Q1 to Q4 in an H-bridge type, and the current supply direction is determined according to the ON / OFF state of Q1 to Q4, and the rotation direction is determined. Now, assuming that the printing direction of the printer is the outward path and Q1 and Q4 are in the ON state, the carriage motor 8 is controlled at a constant speed after starting, and the carriage 10 is driven to perform printing at a predetermined position according to the print data. When printing of one line is completed, the carriage motor 8 is braked. Here, the operation of braking by reverse energization (hereinafter referred to as reverse energization brake) which is the first braking mode will be described. In FIG. 3 (equivalent to the H-bridge portion in FIG. 1), from the start to the constant speed traveling, current flows through the path in which Q1 and Q4 are in the ON state. In the braking control, a current flows through a path in which Q1 and Q4 are turned off and Q2 and Q3 are turned on, and the carriage motor 8 enters a reverse rotation braking state and rapidly decelerates. After a lapse of a predetermined time, Q2 and Q3 are turned off, and the carriage motor 8 stops. Next, a description will be given of the operation of braking (hereinafter, referred to as a short brake) by short-circuiting both terminals of the motor in the second braking mode. In FIG. 4, Q1 and Q4 are in the ON state from the start to the cruising at the same speed as described above, and the current flows through the same route. In the braking control, a current flows through a path in which Q1 is turned off and Q3 is turned on, so that the carriage motor 8 is in a power generation braking state and decelerated. That is, a circulating current flows through the motor windings and Q3 and D4 due to the back electromotive voltage according to the rotation speed of the carriage motor 8 (equivalent to short-circuiting both terminals of the carriage motor 8), and a braking torque is generated. It is. However, the braking force in the second braking mode is smaller as the current flowing through the motor is smaller. Therefore, the braking time and the braking distance become longer. The above is the operation in the two braking modes. In the operation in the return path, the ON / OFF relationship of the paired transistors may be reversed. FIG. 2 shows the relationship between the switching elements and the operation modes in FIG. 8 and 10 show the energizing current in each braking mode.

Now, the setting of the braking mode according to the number of printing digits will be described. As described above, the carriage motor 8
Is larger during acceleration and deceleration and smaller during constant speed control. Therefore, the average value per line of the energizing current increases as the number of print digits decreases, and decreases as the number of print digits increases. That is, the heat generation temperature of the motor changes depending on the magnitude of the movement distance of the carriage accompanying the printing operation.
FIGS. 11 and 12 show the relationship between the number of print digits in continuous printing in a 136-digit printer to which this embodiment is applied and the saturation temperature of the motor armature after heat generation. FIG. 11 shows the case of the reverse brake, and FIG. 12 shows the case of the short brake. The environmental temperature in FIGS. 11 and 12 is 35 ° C., which is the upper limit of the operation guarantee temperature of the printer to which the present embodiment is applied. Here, assuming that the allowable temperature of the motor armature is 120 ° C., in a printing operation of 20 digits or less in FIG. On the other hand, in FIG. 12, the heat generation in the printing operation of 20 digits or less is within the allowable temperature. Therefore, in a printing operation of 20 digits or more, the amount of heat generated by the carriage motor 8 is within the allowable temperature range of the carriage motor 8 even when braking is performed by the reverse energizing brake. Therefore, when the moving distance of the carriage 10 is equal to or more than 20 digits, the reverse energizing brake is selected, and when the moving distance is less than 20 digits, the short brake is selected. Become. That is, by selecting the braking mode in accordance with the moving distance of the carriage 10 based on the print data, the heat generation amount of the carriage motor 8 can be suppressed to a certain value or less. By setting the braking mode to the short brake mode, the actual printing speed of the printer is reduced. However, for printing of 20 digits or more, the braking by the reverse energizing brake becomes possible. Can be configured without reducing the printing speed. When higher-speed printing is required, a carriage motor may be appropriately selected as needed.

In general, a printer has a plurality of printing modes, and the printing resolution and printing speed (carriage speed) differ depending on each printing mode. Accordingly, the current supplied to the carriage motor varies depending on the printing mode. However, a printer having a plurality of printing modes can be handled by providing a plurality of thresholds for selecting the braking mode in accordance with the printing mode. Also, for special carriage drive operation such as logical seek,
The same effect can be obtained by setting a threshold value for selecting the braking mode according to the moving distance. In the above description, the number of print digits is the number of digits at a 1/10 inch pitch which is the standard of this printer. However, printing at a pitch of 1/12 inch or the like can be easily applied by converting the moving distance of the carriage. it can.

[0013]

As described above, according to the present invention, the amount of heat generated by the carriage drive motor can be suppressed by a simple control, and a highly reliable printer which does not cause deterioration in print quality or burnout of the motor. Can be provided at low cost.

[Brief description of the drawings]

FIG. 1 is a carriage motor drive circuit diagram according to one embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between a switching element and an operation according to an embodiment of the present invention.

FIG. 3 is a diagram illustrating a first braking mode according to one embodiment of the present invention.

FIG. 4 is a diagram illustrating a second braking mode according to one embodiment of the present invention.

FIG. 5 is a block diagram showing one embodiment of the present invention.

FIG. 6 is a structural diagram of a printer showing one embodiment of the present invention.

FIG. 7 is a diagram illustrating the operation of the carriage.

FIG. 8 is a diagram showing a current supplied to a carriage motor.

FIG. 9 is a diagram illustrating the operation of the carriage in a second braking mode according to one embodiment of the present invention.

FIG. 10 is a diagram showing a current supplied to a carriage motor in a second braking mode according to one embodiment of the present invention.

FIG. 11 is a diagram illustrating a calorific value of a carriage motor at the time of reverse energization braking.

FIG. 12 is a diagram showing a calorific value of a carriage motor at the time of short brake.

FIG. 13 is a diagram showing a calorific value of a carriage motor according to one embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 CPU 2 ROM 3 RAM 4 Host device 5 I / F part 6 Carriage motor drive part 7 Encoder 8 Carriage motor 9 Recording medium 10 Carriage 11 Print head 12 Platen Q1-Q7 Transistor R1-R11 Resistance element OP1 Operational amplifier D1-D5 Diode ZD1 Zener diode

Claims (2)

(57) [Claims] 1. A DC motor for driving a carriage having a head mounted thereon, a motor control means for providing a plurality of braking modes by changing a control mode of the DC motor, and a head drive based on print data from a host. Data generating means for generating data in print print line units; print area calculating means for calculating a print area of each print line from the generated head drive data; and a carriage by the DC motor based on the print area of each print line. After reaching the set speed,
In line printing on a recording medium based on the head drive data
And a printing means for stopping the brake by applying a brake thereafter , wherein the printing means is configured such that each time the carriage is driven at each of the printing lines at the constant speed, the plurality of brakes are determined based on the calculated print area length. A serial printer that selects one of the modes and brakes the DC motor in the braking mode. 2. The serial printer according to claim 1, wherein said printing means selects the braking by the reverse energization if the length of the printing area is equal to or more than a predetermined value, and selects the braking by the short circuit if the length is less than the predetermined value.