JPS625861A - Printer - Google Patents

Abstract

PURPOSE:To inexpensively provide a printer having a function of resetting to an initial condition securely and forcibly, by providing a motor energization condition detecting circuit,a motor energization time detecting circuit and an output circuit, and inputting an output result to a resetting circuit. CONSTITUTION:The motor energization condition detecting circuit 11 detects the ON state of VP1 and VP2 by two input NANDs 23, 24. In normal operation of a microcomputer 3, a detection time determining capacitor 27 in the motor energization time detecting circuit 12 is electrically charged through a charging resistance 25 for a period of time t1. When a malfunction of the microcomputer 3 occurs and the charging time exceeds t1 to be t2, VPC becomes larger than VR, an output from a comparator 20 in an output circuit 9 is inverted, the microcomputer 3 and a programmable extension port 4 are reset by the resetting circuit 10, and continuous energization of a pulse motor 2 is stopped.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a printer used in various office automation equipment.

Conventional technology A printer controlled using a microcomputer has a significantly simpler hardware configuration than one that does not use a microcomputer. It has become impossible to commercialize products such as fine control of printer head color development time and motor control without the use of microcomputers. However, if a microcomputer goes out of control due to external noise, it becomes completely unpredictable how it will operate. Furthermore, depending on the operating mode when the runaway occurs, products such as the head and motor may be destroyed. For this reason, in the conventional technology, in order to prevent noise from entering during mounting, the control board is shielded or a noise filter is used to prevent noise from entering from the power supply.

Problems to be Solved by the Invention Although such a method would be ideal if it could completely suppress the runaway of the microcomputer, it is generally very difficult to analyze noise and it is difficult to take complete countermeasures. Furthermore, the cost is often high.

The present invention aims to inexpensively realize a printer that has the function of intensively monitoring aspects that could lead to fire or product destruction, and reliably and forcibly returning to the initial state if the microcomputer starts to run out of control in such a mode. It is something.

Means for Solving the Problems The present invention solves the above problems by connecting the head conduction state detection resistor to the common transistor of the transistor in the previous stage of the head drive transistor (usually there are the same number of transistors as the number of heads). A head color development state detection circuit is provided with a resistance value that can detect even one dot of color, and its output is input to a head color development time detection circuit, which is connected to an output circuit that outputs an output after a certain period of time. The results are input to the reset circuit, and for pulse motors, the motor signals are divided into two groups, which are then configured with a motor energization state detection circuit, a motor energization time detection circuit, and an output circuit, similar to the head, and the output results are sent to the reset circuit. The configuration is such that input is required.

Operation With the above configuration, even if the microcomputer goes out of control, safety can be ensured by intensively monitoring safety aspects that could lead to fire or product destruction and forcibly resetting the system.

EXAMPLE Hereinafter, a printer of the present invention will be explained using the drawings.

First, I will explain the basic idea.

The first idea is to monitor the energization state of the head for each dot of the head, but since each head develops color at the same timing, if you monitor the common part of the - spot, you can monitor the entire dot by attaching a detection resistor to one spot. You can monitor dots. When a detection resistor is attached to the head drive transistor common or the head common portion, the voltage drop across the detection resistor is different when one dot is colored and when a gold dot is colored, so the voltage applied to the head is different, causing density unevenness. In order to prevent density irregularities, the value of the detection resistor must be made small. However, if the value is made small, the detected value itself becomes small, making it difficult to detect.

Therefore, these problems can be solved by adding a detection resistor to the melangistor common section in front of the head drive transistor. The value of the detection resistor is set to such a value that it can be determined whether even one dot of color is higher or lower than the reference voltage of the comparator of the head color detection circuit.

The head energization time detection circuit is a charging/discharging circuit that monitors the output time of the comparator of the head color detection circuit. This charging/discharging circuit charges rapidly when the head is energized, but the malfunction of the microcomputer is not caused by continuous head energization.
Set a constant to charge even when over-duty current is applied. The charging result is determined by a comparator in the output circuit. If the output of the comparator of this output circuit determines that the head energization time is long, the reset circuit -\ is input and the microcomputer is reset.

Regarding the energization state of the pulse motor, it is necessary to monitor all signal lines because each phase of the pulse motor is not turned on at the same timing. When the pulse motor is rotating, which phase is always ON, so when monitoring the motor energization time, the ON and OFF states are always required.
Each requires two sets of energization state, energization time detection circuit, and output circuit. The operation of the energization state 2 energization time detection circuit and output circuit is the same as in the case of the head, and input is made to the reset circuit.

Next, specific examples will be described.

FIG. 1 is an electrical circuit diagram showing one embodiment of the present invention. Further, FIGS. 2 and 3 are timing charts of this embodiment. 1 is a thermal head, 2 is a pulse motor, which is controlled by a microcomputer 3 and a programmable expansion port 4. When the microcomputer 3 goes out of control and the thermal head 1 or pulse motor 2 becomes continuously energized, the reset circuit 1o controls the microcomputer 3 and the programmable expansion port 4. Continuous energization is prevented by setting and initializing the computer 3 and programmable expansion port 4.

The head color detection circuit 7 uses a comparator 14 to compare VD, which is varied by the head color state detection resistor 6 connected to the common portion of the front and rear transistors of the head drive transistor 5, and vr e f, which is determined by the reference voltage setting resistor 15.16. By doing so, the coloring state of the head is monitored.

As shown in Figure 2, if the head is in a colored state, vD and vr
ef, the level of the output terminal of the comparator 14 is reflected, and the detection time determining capacitor 19 is charged by the charging resistor 18 of the head color development time detection circuit 8.

Further, when the microcomputer 3 is in normal operation, the head coloring is stopped after this charging time T1, and the head is discharged by the discharge resistor 17. At this time, the charging/discharging voltage VC satisfies VC<VR, and the output circuit 9 does not change its operating state at all.

Microcomputer 3 malfunctions and the head color is 12.
When the time is exceeded and the current is continuously applied for a time T3, VC>vR, the output of the comparator 20 of the output circuit 9 is inverted, the reset circuit 1o resets the microcomputer 3 and the programmable expansion port 4, and stops energizing the thermal head 1. do. In addition, the reference voltage setting resistor 21.2
2 is for the comparator 2o. Pulse motor 2
can be divided into two groups as mentioned above. The motor energization state detection circuit 11 has two input NAND23.2J
? :J:, Detects the ON state of 9Vp1 and ■P2. When the microcomputer 3 is in normal operation, as shown in FIG. 3, the detection time determination capacitor 27 of the motor energization time detection circuit 12 is charged through the charging resistor 25 during tl. During this t1 period, the output of the comparator 33 of the output circuit 9 does not change due to ■Pc (V n ).The microcomputer 3 malfunctions and the charging time exceeds tl and t2
When Pc>vR, the output of the comparator 2o of the output circuit 9 is inverted, the reset circuit 10 resets the microcomputer 3 and the programmable expansion port 4, and stops the continuous energization of the pulse motor 2.

In the figure, 13 is an amplification circuit connected between the pulse motor 2 and the microcomputer 3, 34 is a comparator of the output circuit 9, 29.30 in the motor energization time detection circuit 12 is a discharge diode, 31. 32 is a discharging resistor, 26 is a charging resistor, and 28 is a detection time determining capacitor.

Effects of the Invention As described above, according to the present invention, if the microcomputer inside the printer goes out of control, the safety aspect that could lead to a fire or product destruction is intensively monitored, and when in such a mode, the Resetting the system can be done very reliably at a fixed price and is of industrial value.

[Brief explanation of the drawing]

Fig. 1 is an electrical circuit diagram showing an embodiment of the printer of the present invention, Fig. 2 is a waveform diagram of the main part when preventing continuous energization of the head, and Fig. 3 is a waveform of the main part when preventing continuous energization of the pulse motor. It is a diagram. 1...Thermal head, 2...Pulse motor, 3...Microcomputer, 4...
...Programmable expansion port, 5...Head drive transistor, 6...Head coloring state detection resistor, 7...Head coloring state detection circuit, 8... ...Head color development time detection circuit, 9...
...Output circuit, 1o...Reset circuit, 11
...Motor energization state detection circuit, 12...
・Motor energization time detection circuit, 13...Width increase circuit, 14...Comparator, 15.16...
...Reference voltage setting resistance, 17...Discharge resistance, 1
8...Charging resistor, 19...Detection time determining capacitor, 20...Comparator, 21.
22...Reference voltage setting resistor, 23°24...
...NANDI C126,26...Charging resistor, 27.28...Detection time determining capacitor,
29゜3o・・・Discharge diode, 31.32
・Old...Discharge resistance, 33...Comparator, 3
4...Mark Comparator, VD...Detection 11E
Voltage, VC...Comparator input voltage, vR・
...Comparator reference voltage, VC...
Output voltage, vPl, ■P2...Pulse motor control voltage, ■PC...Comparator input voltage.

Claims (1)

[Claims] It is equipped with a microcomputer that controls the thermal head and pulse motor, and a head coloring state detection circuit that has a head coloring state detection resistor that can detect even one dot of coloring in the common part of the transistor in the front stage of the head drive transistor. A head coloring time detection circuit whose constant is set to ignore a short head coloring OFF state, and an output circuit whose output is configured to input a reset signal to a microcomputer and other programmable expansion ports when a certain period of time is exceeded. , a printer having a circuit that divides the motor drive signal line into two sets, detects the energization state and energization time of the pulse motor, and resets input to the microcomputer and other programmable expansion ports when a certain period of time is exceeded.