JPS60230884A - Printer - Google Patents

Abstract

PURPOSE:To prevent controlling efficiency from being lowered and enhance printing quality, by providing a carriage-controlling part which is provided additionally with a mode-selecting circuit for changing over a voltage impressed on a DC motor, and a part which generates a printing timing. CONSTITUTION:When the speed of the motor 4 is lowered below a preset speed, a phase advance signal 8 is outputted, and the mode-selecvting circuit 19 is changed over, thereby returning to a controlling operation conducted before braking. In this controlling circuit, a brake by passing a reverse current is applied at the time of deceleration, so that response as high as that at the time of of acceleration can be obtained. According to an output 20 from the circuit 19, the current-passing direction and curring-passing time for the motor 4 are varied by a switching-type driver 3 consisting of four transistors. A programmable phase-dividing circuit 50 subjects an encoder signal 7 to 1/N phase division by a phase division value signal 52, and a programmable phase-dividing circuit 51 subjects an output signal 56 of a voltage-controlled type variable frequency oscillator 55 to 1/N phase division on the basis of the phase division signal 52. The phase difference between output signals 57, 57 thus obtained by phase division is outputted as a pulse width signal 59 by a phase difference detector 53.

Description

[Detailed description of the invention] Technical fields> The present invention relates to a serial dot printer device.

<Prior Art> Conventionally, step motors have been widely used in the carriage drive systems of serial printers because of their ease of control.

However, as the performance of printers has improved, Do motors have begun to be used as drive sources.

Furthermore, as the number of dots forming a character increases, it is becoming possible to obtain print quality close to that of boat-shaped printing, and at the same time, there is an increasing demand for printers with a variety of fonts and character pitches similar to boat-shaped printing printers.

The present invention is a low-cost, high-performance, high-precision carriage control device that uses a DC motor in the carriage drive system of a serial dot printer, and a phase-locked loop control system that uses print timing signals at fixed intervals generated as the carriage moves. This invention relates to a serial dot link printing control device comprised of a printing timing generation circuit that generates printing timing at arbitrary intervals and enables printing using all character generators with the same arbitrary character pitch. It is.

Conventionally, analog type carriage control devices using tacho generator sound have been widely used as carriage control devices for serial dot printers using Do motors. In recent years, digital detectors such as rotary encoders and linear encoders have become easily available, and digital control systems using them have come into use. In particular, due to its high control accuracy and simple control circuit configuration, the speed is controlled by detecting the phase difference signal between the reference oscillator signal and the encoder corresponding to the set speed, and directly switching the voltage applied to the motor using this digital signal. Phase-locked loop type digital control devices are often used.

FIG. 1 shows a basic block diagram of this conventional control device. The phase comparator 2 detects the position difference between the reference speed signal oscillated by the reference oscillator 1 and the pulse train corresponding to the speed from the encoder 5 attached to the motor, and the pulse signal 8 changes the duty depending on the phase difference. The DQ motor 4 is driven via the switching circuit 5 to perform speed control.

In such a control system, the reference oscillator 1 and phase comparator 2 are commercially available as integrated circuits, and the switching circuit 5 can be easily constructed using transistors, so it is often used in control systems of consumer equipment. The characteristics of this control system are that the speed accuracy is determined by the safety of the reference oscillator 1, so it has advantages such as extremely high control accuracy and low heat generation in the circuit and motor. Because it is expensive and cannot be changed easily,
It has the disadvantage of being prone to oscillation and having poor stability. In particular, when used in serial printer carriage control devices that require high-speed response, the frictional load and
Since the design is such that both inertial loads are small, this drawback becomes noticeable. In serial-type high-dot-density dot impact printers and inkjet printers aimed at high print quality, the dot spacing is not constant due to the imaging phenomenon caused by this defect, resulting in a decrease in print quality.

In order to eliminate this drawback, a method of lowering the gain of the control loop has been considered, but the circuit becomes complicated and the control accuracy decreases.

<Objects> The entire object of the present invention is to provide a printer device that eliminates the above drawbacks of the conventional printers.

<Configuration> The serial dot printer device of the present invention uses a DC motor in the carriage drive system of the device, and has phase-locked loop speed control with a frequency modulation feedback loop of a reference oscillator consisting of a low-pass filter and a differential circuit. The print timing is generated by the carriage control section with all the circuits and mode selection circuit that switches the voltage applied to the DC motor, reference encoder, frequency divider circuit, phase difference detection circuit, filter and ridge pressure control generator. The printer has a print control section configured by a print timing generation section.

<Embodiment> The serial dot printer device of the present invention employs a method of improving the stability of the carriage control device and suppressing oscillation by adding a simple circuit without reducing the loop gain. FIG. 2 is a block diagram of this method. The phase difference signal 8 detected by the phase comparator 2 is converted into an analog speed signal 11 via a low-pass filter 9, and further converted into a pseudo acceleration signal 12 by a differentiating circuit 10. This signal 12 frequency-modulates the output signal of the reference oscillator 1. This control system achieves the same effect as adding an acceleration history feedback loop to a speed control device composed of analog circuits, and has the same quick response as a phase-locked loop control device.

It has the effect of completely improving stability without reducing high accuracy. FIG. 3(a) shows the response 16 of the phase-locked loop control device shown in FIG. 1, and FIG. 3(b) shows the response 17 of the control device of the type shown in FIG. 18F in the diagram
i Set speed kyr indicates a state where a signal of set speed 18 is applied from a stopped state at time 0.

In the carriage control of a serial printer, it is possible to skip non-printing sections at high speed, or move at high speed to the next printing start position after printing one line (substantive printing speed can be improved).

In view of the above points, the present invention provides a method for improving responsiveness when completely reducing the set speed using a simple circuit without adding a special mechanical brake device.
This example will be explained using the block diagram shown in the figure. Fourth
The diagram shows the system shown in Figure 2 with all mode 4 selection circuits 19 added. 24 is an input signal that changes the entire frequency of the reference oscillation 51 to change the set speed. When a certain set speed signal 24 is input, the oscillator 1's output frequency 6 changes. At this time,
When the input fcG constant speed is larger than the set speed before changing, the 6γ phase advance signal 8 of the phase detector 2 (when the oscillator output signal is ahead compared to the encoder output signal 7 VC) is This output signal is the mode selection circuit 1.
9. A force 11 is applied to the dryer 4 through the driver circuit 3, allowing it to load at full speed. The control method Fi is the same as that shown in FIG. On the other hand, if the input set speed width is smaller than the previous set speed, a speed reduction signal 25 is applied to the brake flip-flop 25 at the same time as the set speed signal 24 changes, and this flip-flop 23 is set. The output signal 21 of this flip-flop 23 is converted into a control signal by the mode selection IC!1 path 19 to a phase delayed signal 22 (
When the phase of the oscillator output signal is delayed compared to the encoder output signal 7), the current direction is changed and the current is output to the driver 5, and the brake is applied. When the speed of the motor decreases below the set speed, the phase advance signal 8 is output, so the brake flip-flop 23 is reset and the mode selection circuit 19 is completely switched to return to the control operation before braking. This control circuit applies reverse energization to the brakes during deceleration, providing the same level of responsiveness as during acceleration. Fifth
The figure shows an example of the response when the set speed is completely changed. Time 31
When the set speed 24 is changed from 0 to the value shown at 28 at time 26, the speed of this control device increases from O to the value 30 as shown at 26, and when the set speed 24 is further increased to the value 27 at time 32, the speed 26 increases to a value of 29. Time 33
Conversely, when the set speed 24 decreases to the original value of 28, the speed 26 is decelerated to the value of 30. Break #r shown in 34,
J This circuit shows the characteristics of the car seat when it is not fitted with metal.

FIG. 6 shows a concrete diagram of the embodiment shown in FIG. 4. 1
01 is an integrated circuit capable of frequency modulation with the acceleration signal 12, and its output signal 68 is divided into a frequency corresponding to the full speed setting signal 14 by a 7 programmable frequency divider 57, and the phase of this output signal 6 and encoder signal 7 is shifted. Detected by phase difference detector 2. 6
Reference numeral 9 denotes a circuit called a photodischarge pump, which is combined with an operational amplifier 4o to convert the phase difference signal into an analog velocity signal 11 by a low-pass filter 9, which is then converted into an analog velocity signal 11 by a differentiating circuit 10. Changed to 12th.

The part within the dotted line 47 is a part built into a commercially available integrated circuit for controlling the phase linear loop. On the other hand, the signal 35 is a signal that completely determines the advancing direction of the carriage shown in 13 in FIG. The circuit is mode selection circuit 1
It is 9.

Mode 1@The output 2o of the selection circuit 19 changes the direction and time of energization of the motor 4 by the switching type driver 3 made up of four transistors. A current limiting circuit is used to control the large current that flows during reverse energization and startup of the 36id motor, allowing the DC motor to be started like the carriage drive system of a serial printer. Prevents a significant reduction in service life when used in equipment that frequently stops and reverses.

The bandwidth of the low-pass filter 9 is determined by the resistor 44 and the capacitor 43, but this value is sufficiently lower than the frequency of the encoder signal corresponding to the set speed, and the specific frequency of the control system can be obtained by actual measurement or measurement. Set the bandwidth to be sufficient to pass through.

The value of the resistor 42 that performs high frequency correction of this low-pass filter is selected to be sufficiently smaller than that of the resistor 44. Further, the ratio between the resistor 41 and the resistor 44 becomes an adjustment parameter for the damping ratio of this control system. Also, the resistor 45 and capacitor 46 of the differentiating circuit 1o
The time constant is determined by the product of , and this value is set to a value that has a differential effect on the specific number of motions of the control system.

Next, the print timing generation circuit will be explained.

Generally, serial dot printers use a printing pitch of 10 characters/inch, but as printing quality has improved, the printing pitch has changed to 12 characters/inch, which is used in boat-type printers, and 15 characters/inch. is required. A simple method is to have as many character generators as there are printing pitches, but this is expensive as it requires a large amount of memory for the character generators. By generating print timing at different pinches, the same character generator can be used for characters with different pinches. In the present invention, this print timing generation circuit has been devised. The details are given below.

Generally, a rotary encoder or a linear encoder is used to generate print timing. These encoders output print timing at fixed intervals of 11" when the carriage moves. Conventionally, in order to feel the change in the printing pinch of dots, the encoder's inch is set finely compared to the actual printing pinch, and the printing signal of the predetermined printing pitch is generated by dividing the output printing timing. There are methods to obtain the print timing signal, and methods to divide the print timing signal using an open timer with several pulses. However, these methods require a commercially priced high-resolution encoder, accumulate errors, and have the disadvantage that the error in the printing pinch at the end of the divided section increases. In order to eliminate such drawbacks, the present invention has devised a printing timing generation circuit using a phase-locked loop. The present invention will be explained using FIG. 50 is a programmable frequency dividing circuit which divides the encoder signal 7 by 100 based on a frequency dividing value signal 52 from a microprocessor which mainly controls the printer. Similarly, the programmable frequency divider circuit 51 receives the frequency division value signal 5.
2, the output signal 56 of the voltage controlled variable frequency oscillator 55 is frequency-divided by −. Divided output signal 57.58
The total phase difference detector 53 determines the phase difference of the phase difference.
Output as .

54 is a filter circuit for converting the pulse width signal to the all analog voltage signal 6 (1 m), and is a low-pass type filter.

An analog voltage proportional to this phase difference is applied to the pressure-controlled variable frequency oscillator 55 and sent as a print timing signal 56 to the main control microprocessor.

The encoder signal 7 is output as the printer carriage moves, and the print timing signal is VC locked to the negative frequency (M, N are integers) of the encoder signal frequency, and follows the frequency change of the encoder signal. For example, when the encoder print pitch is set to 10 characters/inch, the value of - is set to -2 for printing of 12 characters/inch, and - for 15 characters/inch. Furthermore, the bandwidth of the filter circuit 54 is at least twice the response frequency of the carriage drive system to ensure stability of the print timing circuit. Determine by considering tracking accuracy.

<Effects> As described above, the present invention relates to a print control device for a serial dot printer, and in a carriage control device that uses a DC motor in its carriage drive system, it has the following advantages: By adding a simple acceleration signal detection circuit and a circuit that frequency modulates the reference excavator with this signal, stability is increased without reducing control accuracy, and excavation can be prevented. In addition, the mode selection circuit applies a reverse energization brake from the time the speed is changed until the phase difference signal is detected, making it possible to shorten the time required to change the speed. As a result, it is possible to improve the printing quality during high dot density printing and to increase the apparent printing speed W.

In addition, in the print timing generation circuit, the print timing signal from the reference encoder is all-phase locked loop 1.
By arbitrarily dividing the characters using the circuit, it becomes possible to print any character with a pinch using the same character generator.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a conventional Phazron rad-loop type control device, in which 15r represents a printer carriage, 14 represents a belt pulley, and 15 represents printing paper. FIG. 2 is a block diagram of the control device when an acceleration feedback loop is added to the phase-locked loop control device. Fig. 3 σ is a comparative diagram of response example 16 of the conventional phase-locked loop control device 6 shown in Fig. 1 and response example 17 of the control device added with the force-a-velocity feedback loop shown in Fig. 2. . l! J] 41〆1-゛Shows a block diagram of Yumei Moto's carriage control device. No. 5121 is a response example of the gear ridge control device of the present invention. 1)-- indicates the state of each signal at this time. 61z1 is shown in the circuit diagram embodiment of the carriage control device of the printer device of the present invention shown in No. 41z1. FIG. 7 is a block diagram of the print timing generator circuit of the printer device of the present invention. Applicant: Epson Corporation Agent Patent Attorney Mogami

Claims (1)

[Claims] In a serial dot printer device, a DC motor is used in the carriage drive system of the device, and a phase-locked loop type speed control circuit is added with a frequency modulation type feedback loop of a reference oscillator consisting of a low-pass filter and a differentiation circuit, and a DC motor is used. A carriage control unit with a mode selection circuit that switches the voltage applied to the
What is claimed is: 1. A printer device comprising: a print control section including a print timing generation section that generates print timing using a voltage controlled oscillator.