JPH05124287A - Serial printer - Google Patents

Abstract

PURPOSE:To construct a printer of a low-cost motor by a method where in heat generation is limited by switching a control method of a carriage motor. CONSTITUTION:In controlling operation with a carriage motor 8 of a serial printer equipped with a carriage, a carriage motor 8, a switching means connected in an H bridge type to both terminals of the carriage motor, a drive means 6 which operates regularly or reversely and stop the carriage motor by turning ON and OFF selectively the switching means, a mode wherein damping is performed by reversely applying electricity and a mode wherein damping is performed by short-cutting both terminals, are provided. Then, a heating state of the carriage motor 8 is detected with a temperature-detecting means 13 and a damping mode of the motor is selected according to the result. The heating value of the carriage motor is restrained to construct a low-cost printer.

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 In a serial printer, a carriage having a print head is reciprocated in a platen axis direction by a carriage motor through a timing belt or the like based on print data to perform recording. In recent years, the printing speed of printers has been increasing, and an example of using a DC motor as a carriage motor is increasing due to its good responsiveness and controllability. In the case of a DC motor, due to its characteristics, the energizing current is the largest in the acceleration / deceleration state (the effective torque is large), and the energizing current is small in the constant speed (printing) (the effective torque is small). Therefore, the larger the number of print digits of the printer, the smaller the energizing current of the motor per line. FIG. 7 shows the operation of the carriage. Further, FIG. 8 shows a current flowing through the carriage motor at this time. Here, the drive circuit of the carriage motor is the circuit shown in FIG. 3, and has a configuration including a drive unit that can select forward / reverse rotation and a current limiting unit. When decelerating, braking is performed by reverse energization (reverse braking) to accelerate braking. As shown in FIG. 8, the current supplied to the carriage motor is large during acceleration and deceleration and small during constant speed control. Therefore, the average value of the energizing current per line becomes larger as the printing area becomes shorter (the carriage moving distance becomes shorter). However, the movement distance of the printer carriage in the print digit direction greatly varies depending on the print data sent from the host device, and the energizing current of the carriage motor changes accordingly, and the heat generation amount of the motor varies greatly depending on the print data. Becomes In other words, when the number of print digits is small, the amount of heat generated increases, and the coil of the motor heats up and the armature resistance increases due to long-term use, which lowers the output and interferes with printer operation, resulting in poor print quality. descend. Further, if the amount of heat generation increases and exceeds the allowable temperature, the motor may be burned. In a conventional printer, a large output carriage motor is used in consideration of the case where the number of print digits is small in order to prevent the above problems.

[0003]

However, the number of print digits of a printer is generally several tens, and printing with a small number of digits rarely lasts for a long time. Therefore, assuming these special situations. If a carriage motor is selected, there is a problem that the cost of the printer becomes extremely high. In addition, the large output motor has a large size, which causes a problem of arrangement in the printer.

An object of the present invention is to solve the above-mentioned conventional problems and to provide at low cost a serial printer in which heat generation of a carriage motor is suppressed.

[0005]

According to the present invention, there is provided a print head, a carriage which reciprocates with respect to a recording medium on a platen based on print data, a DC motor for driving the carriage, and both terminals of the DC motor. In a serial printer having switching means connected to the H-bridge type and driving means for selectively turning on / off the switching means to normally / reversely rotate and stop the DC motor,
At the time of stopping operation of the carriage, a means for applying a reverse current to the DC motor for braking and a means for short-circuiting both terminals of the DC motor for braking are provided, and a temperature detecting means is provided in the vicinity of the DC motor. The braking means of the DC motor is selected according to the detection result.

[0006]

The temperature detected by the temperature detecting means is monitored, and when the amount of heat generated by the carriage motor is small and the temperature detection result is less than the predetermined temperature, the braking mode by reverse energization is selected and the amount of heat generated by the carriage motor is detected. It is possible to suppress the heat generation amount of the carriage motor by selecting the braking control mode according to the detection result of the temperature detecting means, such as selecting the braking mode by shorting both terminals when the result exceeds the predetermined temperature. Therefore, it is only necessary to select the motor assuming printing of a digit number that is frequently used, so that an inexpensive printer can be configured.

[0007]

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

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a structural diagram of a printer showing an embodiment of the present invention. Reference numeral 1 in FIG. 1 denotes a CPU which is a control unit of the printer, and is provided with a ROM 2 which stores control programs and the like and a RAM 3 which temporarily stores various data. The print data from the host device 4 is sent to the CPU 1 via the I / F unit (interface unit) 5. Reference numeral 13 in FIG. 1 is a thermosensitive element which constitutes a temperature detecting means, and a thermistor is used in this embodiment. FIG. 13 shows a circuit diagram of the temperature detecting means. 2 is a carriage drive circuit,
Reference numeral 8 is a carriage motor, and 13 is a thermosensitive element (thermistor). In the present embodiment, the heat sensitive element 13 is installed on the side surface of the carriage motor 8 so as to be thermally dense. If more accurate temperature detection is required, it can be installed in the motor. 2 is a carriage,
It is driven by the carriage motor 8. Reference numeral 12 is a platen, 9 is a recording medium, and 11 is a print head. Here, the carriage motor 8 is a DC motor, and the output shaft thereof is provided with an encoder 7 for position detection. The position management of the carriage 10 is performed by counting the output signal of this encoder.

The operation of one embodiment of the present invention will be described with reference to FIGS. The CPU 1 expands the head drive data in the RAM 3 according to the print data from the host device 4, calculates the print area according to the print data, drives the carriage motor 8, and starts the movement of the carriage 10. The carriage motor 8 starts acceleration from the stopped state toward the set speed, and after reaching the set speed, the carriage motor 8 is controlled to a constant speed and reaches 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 the printing corresponding to the print data is completed, the carriage motor 8 is in deceleration control. Here, the CPU 1 is the temperature detecting means 13
The carriage 10 is stopped after the carriage motor 8 is braked by selecting the braking mode according to the detected temperature, which will be described later, by detecting the detection result of.

FIG. 3 is a carriage motor drive circuit diagram showing an embodiment of the present invention. The carriage motor drive circuit of the present invention is the same in structure as the conventional one, and the braking method is different. Here, the operation of each braking mode will be described with reference to FIGS. 3, 4, 5, and 6.
In FIG. 3, the carriage motor 8 includes transistors Q1 to Q1.
Connected to Q4 and H bridge type, ON / O of Q1 to Q4
The current supply direction is determined and the rotation direction is determined according to the FF state. Now, assuming that the printing direction of the printer is the forward path and Q1 and Q4 are in the ON state, the carriage motor 8 is started and then controlled at a constant speed, the carriage 10 is driven, and printing is performed at a predetermined position according to the print data. When the printing of one line is completed, the carriage motor 8 is brake-controlled. 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. 5 (equivalent to the H bridge portion in FIG. 3), Q1 and Q4 are in the ON state from the start to the constant speed running, and current flows through the route. In braking control, Q1 and Q4 are O
A current flows through the path in which the FF state is entered and Q2 and Q3 are also turned on, and the carriage motor 8 enters the reverse braking state and is rapidly decelerated. After a lapse of a predetermined time, Q2 and Q3 are turned off, and the carriage motor 8 is stopped. Next, the operation of the second braking mode for braking by short-circuiting both terminals of the motor (hereinafter referred to as short brake) will be described. In FIG. 6, Q1 and Q4 are in the ON state from the startup to the constant speed running, which is the same as described above, and the current flows through the route. Q1 is O in braking control
A current flows through the path in which the FF state is set and the Q3 is turned on, and the carriage motor 8 is in the dynamic braking state and decelerated. In other words, the counter electromotive voltage corresponding to the rotation speed of the carriage motor 8 causes a circulating current to flow through the motor winding and Q3 and D4 (equivalent to short-circuiting both terminals of the carriage motor 8), which causes braking torque. Is. However, the braking force in the second braking mode is small because the current flowing through the motor is small. Therefore, the braking time and the braking distance increase. The above is the operation in the two braking modes. For the operation on the return path, the ON / OFF relationship of the paired transistors may be reversed. 3 in FIG.
The relationship between the switching element and the operation mode in FIG.
The applied current in each braking mode is shown in FIGS.
Shown in.

Now, the setting of the braking mode according to the detection result of the temperature detecting means will be described. As described above, the current supplied to the carriage motor 8 is large during acceleration and deceleration and small during constant speed control. Therefore, the average value of the energizing current per line becomes larger as the number of print digits becomes shorter and becomes smaller as the number of print digits becomes longer. That is, the heat generation temperature of the motor also changes depending on the size of the movement distance of the carriage accompanying the printing operation. Further, the energizing current greatly changes depending on the braking mode during deceleration. 11 and 12 show the relationship between the number of print digits in continuous printing and the saturation temperature of the motor armature portion after heat generation in the 136-digit printer to which this embodiment is applied. FIG. 11 shows the case of the reverse energization brake, and FIG. 12 shows the case of the short brake. 11 and 12
The environmental temperature in is the upper limit of the operation guarantee temperature of the printer to which the present embodiment is applied, which is 35 ° C. Here, assuming that the allowable temperature of the motor armature is 120 ° C., there is a risk that the motor will burn due to heat generation in the 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, if the heat detection state of the carriage motor is monitored by the temperature detecting means, the reverse energization brake is selected when the temperature does not reach the predetermined temperature, and the short brake is selected when the temperature exceeds the predetermined temperature. 8
The calorific value of will fall within the allowable temperature range. When the short brake is selected when the temperature exceeds the predetermined temperature, the heat generation amount of the carriage motor 8 starts to decrease. When the temperature falls below the detected temperature, the reverse energization brake is selected again. Thereafter, similar temperature detection and selection of the braking mode are repeated, and the heat generation amount of the carriage motor 8 is limited. That is, by selecting the braking mode according to the heat generation state of the carriage motor 8, the heat generation amount of the carriage motor 8 can be suppressed to a certain value or less.

The predetermined temperature is set in consideration of the correlation between the installation location of the heat sensitive element and the temperature in the carriage motor, and the variation in detection accuracy. In the present embodiment, the allowable temperature in the carriage motor is 120 ° C. and the temperature difference from the installation location of the heat sensitive element is 30 ° C., and the set temperature is set to 80 ° C. in consideration of the variation in detection accuracy and the margin. In the circuit diagram of FIG. 13, each resistance element is set so that the output Vo is inverted at the boundary of 80 ° C., and the braking mode is switched according to the output state.

By setting the braking mode to the short brake, the actual printing speed of the printer is slowed down. However, in order to reach the predetermined temperature, it is only necessary to continue printing with a short number of digits for a certain length of time. Yes,
In normal use such as intermittent use or a large number of print digits, the print speed can be reduced. Further, when higher speed printing is required, a carriage motor may be appropriately selected as needed.

[0014]

As described above, according to the present invention, it is possible to suppress the heat generation amount of the carriage drive motor by simple control, and it is possible to achieve high reliability without deterioration of print quality and burnout of the motor. The printer can be provided at a low cost.

[Brief description of drawings]

FIG. 1 is a block diagram showing an 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 carriage motor drive circuit diagram.

FIG. 4 is a diagram showing a relationship between a switching element and an operation.

FIG. 5 is a diagram illustrating a first braking mode according to an embodiment of the present invention.

FIG. 6 is a diagram illustrating a second braking mode according to an 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 the second braking mode according to the 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 an embodiment of the present invention.

FIG. 11 is a diagram showing the amount of heat generated by the carriage motor during reverse energization braking.

FIG. 12 is a diagram showing a heat generation amount of a carriage motor at the time of short brake.

FIG. 13 is a circuit diagram showing a temperature detecting means of an embodiment of the present invention.

[Explanation of symbols]

 1 CPU 2 ROM 3 RAM 4 Host device 5 I / F section 6 Carriage motor drive section 7 Encoder 8 Carriage motor 9 Recording medium 10 Carriage 11 Print head 12 Platen 13 Thermal element Q1 to Q7 Transistor R1 to R15 Resistive element Rth Thermistor OP1 operational amplifier CP1 Comparator D1 to D5 Diode ZD1 to ZD2 Zener diode

Claims (1)

[Claims] 1. A carriage that mounts a print head and reciprocates relative to a recording medium on a platen based on print data, a DC motor that drives the carriage, and both terminals of the DC motor are connected in an H-bridge type. Switching means and selectively turning on / off the switching means
In a serial printer equipped with a driving means for causing the DC motor to rotate in the forward / reverse direction and to stop the DC motor, a means for reversely energizing and braking the DC motor when the carriage is stopped, and both terminals of the DC motor are provided. A serial printer characterized in that a means for short-circuiting and braking is provided, temperature detecting means is provided in the vicinity of the DC motor, and the braking means for the DC motor is selected according to the detection result of the temperature detecting means.