JPS6325163Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention provides a serial dot printer used as an output device of an information processing device, in which excessive current flows and overheats due to destruction of the drive transistor or short circuit of the excitation coil of the drive magnet.
The present invention relates to a malfunction detection circuit for preventing excitation coil burnout or fire. Furthermore, it is possible to reliably detect malfunctions even in a print head equipped with multiple rows of printing wires so as to be suitable for printing kanji characters, etc.

FIG. 1 is a plan view showing a wire-type serial printer as a dot printer, and FIG. 2 is a front perspective view of a print head. A printing paper 2 is wound around the platen 1, and a carrier 6 on which a printing head 5 is mounted is supported by a feed screw 3 and a guide rod 4 arranged parallel to the platen 1.
By rotationally driving the feed screw 3 by a space motor 8 via a timing belt 7, the print head 5 is transported at a constant speed in the space direction indicated by arrow a.

At the tip of the print head 5, as shown in FIG. 2, vertical lines of wires W _{1 ,} W ₂ .
While feeding the wires W 1 , W 2 ... by space at a constant speed, at each time t ₁ , t ₂ ... at a certain period, the wires W ₁ , W ₂ ...
By selectively driving and projecting the dots using a built-in magnet in the head, a character such as "A", for example, is formed on the paper 2 by a combination of dots 9 .
Note that if the printing paper 2 is pressure-sensitive paper, the wires W ₁ ,
When W ₂ ... is driven and the tip of the wire hits the paper 2, the impact causes the dot 9 to be recorded. However, in the case of plain paper, the impact occurs through the ink ribbon 10 as shown in Figure 1. Added.

However, due to destruction of the transistor that drives the magnet to operate the wires W ₁ , W ₂ , etc., or a short circuit due to peeling of the excitation coil of the magnet, an excessive current flows through the excitation coil, causing the coil to overheat and cause the coil to overheat. There is a risk of burnout or fire.

To prevent this, generally a fuse 13 for overcurrent prevention is connected in series with the excitation coil 11 and drive transistor 12 of the load, as shown in FIG.
A method is used to interrupt the circuit if an excessive current flows through the circuit. Alternatively, by using a circuit as shown in FIG. 4, the collector voltage of the transistor 14 that drives the excitation coil 11 and the drive signal
Compare with S ₁ and determine whether they match. That is, if the drive signal _S1 is now at logic "H", it is inverted by the inverter 15, the transistor 14 is turned off, and the excitation coil 1 of the magnet is turned off.
No current flows through the transistor 1, so the power supply voltage _V1 is applied to the collector of the transistor 14. Normally, the power supply voltage V ₁ in dot printers etc. is 24 [V], so it is divided by resistors 16 and 17 and converted to TTL level "H".
Input to OR circuit 18. On the other hand, the EX-OR circuit 1
A drive signal _S1 is also added to 8, and when the two match, the output of the EX-OR circuit 18 goes “L”.
becomes.

Further, when the drive signal _S1 is at logic "L", it is inverted by inverter 15 and its output becomes "H", turning on transistor 14. Therefore, an exciting current flows through the exciting coil 11 to drive the magnet, and the collector voltage of the transistor 14 becomes approximately the ground potential, and the terminal voltage of the resistor 17 also becomes zero. Therefore, the two input signals of the EX-OR circuit 18 are both logic "L" and match, and the output thereof becomes "L".

However, when the drive signal _S1 is "H", that is, a signal that does not drive the magnet, if a current flows due to destruction of the transistor 14, or if a current flows due to a short circuit in the excitation coil 11, the transistor 14 The collector voltage of becomes zero, and the voltage across the resistor 17 also becomes zero. Therefore, the input signals of the EX-OR circuit 18 do not match,
It can output "H" to notify the outside of a circuit abnormality.

However, these methods require one fuse or malfunction detection circuit for each magnet, which results in high costs and equipment complexity in devices that have a large number of magnets, such as the print head of a dot printer. There is a problem that the size of the image becomes large.

In order to solve this problem, the following method is adopted. That is, when printing simple characters with a small number of strokes such as alphanumeric characters, the print head is connected to the print wires W ₁ and W ₂ in a vertical line as shown in FIG. 5A.
. . , and as shown in FIG. Then, after leaving a space of, for example, three dots between the characters as Sp, the next character is printed. Therefore, during this space Sp,
Since none of the printing wires W ₁ , W ₂ , . . . W ₇ are driven, malfunction detection is performed using this idle time.

FIG. 6 shows its specific circuit configuration. _L1 ... _L7 are magnet excitation coils for driving the seven printing wires _W1 ... _W7 , and transistors _Tr1 ... _Tr7 drive the coils _L1 ... _L7, respectively.
The collector of each transistor Tr ₁ ... Tr ₇ is inserted between the power supply in series with the collector of the diode D ₁ ... D _7.
and is connected to a power supply via a resistor 20 to form a wired-OR circuit.

Now, at the timing of the space between characters, that is, in the section where none of the coils L ₁ ... L ₇ are excited, the voltage at the collector of each transistor Tr ₁ ... Tr ₇ is equal to the power supply voltage unless there is a faulty part. will be equal to V ₂ . Therefore, the diodes D ₁ ...D ₇
The voltage at the common point 19 on the anode side of is also equal to the power supply voltage V ₂ because no current flows through the resistor 20.
Generally, this voltage _V2 is as high as 24 [V], so it is converted to TTL level "H" by the level conversion circuit 21,
The signal is input to the AND circuit 22. This AND circuit 22
Then, the check timing signal T _S is set to logic “H”.
When inputted, both inputs match at "H", and the output of the AND circuit 22 becomes "H", informing the outside that there is no abnormality.

Transistor Tr ₁ ...Tr ₇ or excitation coil L ₁
... _L7 , for example, if a current flows through the coil _L1 due to destruction of the transistor _Tr1 or short circuit of the excitation coil L1, the collector voltage of _the transistor _Tr1 becomes zero even at the check timing, and the resistor 20, A current flows through the diode _D1 , and the potential of the common point 19 becomes approximately the ground potential.
Therefore, the input to the AND circuit 22 becomes the "L" output from the level conversion circuit 21 and the "H" level of the check timing signal, which do not match. As a result, the output of the AND circuit 22 becomes "L", which notifies the outside of the abnormality of the circuit or cuts off the power supply by a relay or the like.

However, in order to meet the recent demands for kanji printing, etc., it is necessary to increase the number of dots, that is, printing wires, but the minimum diameter of the printing wires W ₁ ... W ₇ is limited.
Furthermore, since the size of the characters is also limited, if it is desired to increase the number of dots to nine, for example, it is impossible to arrange them in a single vertical column as shown in FIG. 5A. Therefore, in such a case, as shown in Figure 7A,
A system is adopted in which the printing wires are arranged in two vertical rows and the printing wires W ₁ ... W ₉ are arranged in a bird-like pattern. In this case, odd wire
Rows of W ₁ , W ₃ , W ₅ , W ₇ , W ₉ and even wires W ₂ ,
Assuming that the spacing between the columns W ₄ , W ₆ , and W ₈ is 3 dots, and the character space spacing Sp is also 3 dots as shown in Figure 7B, when printing from the right side of the paper, First, odd wires W ₁ , K ₃ , W ₅ , W ₇ , W ₉
is printed, and after the printing head moves three dots to the right, even numbered wires W ₂ , W ₄ , W ₆ , and W ₈ are printed. Therefore, on paper, nine dots are printed overlappingly on the same vertical line, but as is clear from the timing chart in FIG. 8, the odd wire rows W ₁ , K ₃ , W ₅ , _W7 ,
After W ₉ has finished printing the last dot position of the first character and the inter-character space has been rested for 3 dots, the even wire rows W ₂ , W ₄ , W ₆ , W ₈ have finished printing the last dot position. Sometimes the odd wire row W ₁ ,
K ₃ , W ₅ , W ₇ , and W ₉ have already started typing their second letters. Therefore, there is no period during which all the printing wires W _{1 .} . . W ₉ can be stopped at the same time, and the conventional malfunction detection circuit using a wired OR circuit of the excitation coils of all the magnets cannot be used. Note that the dot pulse DP is obtained by the light receiving element 25 receiving the light transmitted through the slit array 24 formed in the circumferential direction in the slit disk 23 shown in FIG.

The present invention realizes a circuit that can reliably detect malfunctions even when serial printing is performed using a print head equipped with multiple rows of print wires. , a driving magnet is provided corresponding to each printing wire, and the printing wires are divided into N (N = an integer of 2 or more) sets of rows, and each set is arranged with an interval equal to or larger than the character space interval. In a serial dot printer, each set of print wires is driven at the same cycle to print characters while the print head moves relative to the platen. Each set is equipped with a malfunction detection circuit, and each malfunction detection circuit detects the transistors that drive each drive magnet in the set by a check timing signal that arrives when the print wire set corresponding to the circuit corresponds to the character space. The configuration includes means for detecting the state of the collector voltage.

In this way, the plurality of print wire sets are arranged with a spacing greater than the character space spacing Sp.
If the spacing between the printing wire sets is smaller than the character space spacing Sp, for example, if Sp is 3 dots and the spacing between the printing wire sets is 2 dots, there is a timing for one dot in which the printing wires are not driven at all, as shown in Figure 6. It is possible to check using the conventional method as shown in the example shown in FIG. However, if the spacing between the plurality of printing wire sets is larger than the character space spacing, it is impossible to check using the conventional method, and it becomes possible to check for the first time using the method of the present invention.

For example, one character is formed by 7 dots, there are 3 spaces, and the spacing between printing wire sets is 10.
Even in the case of dots, since the check timing for three dots can be determined, it is possible to check using the conventional method.

As described above, according to the present invention, even if the spacing between a plurality of printing wire sets is larger than the character space spacing, which cannot be checked using the conventional method, malfunction of the printing wire drive section can be reliably detected.

Next, details of the present invention will be explained based on illustrated embodiments. FIG. 9 shows an embodiment of the malfunction detection circuit, and an example in which there are nine printing wires will be described. In the same figure, between the collectors of the magnet drive transistors _Tr1 ... _Tr9 and the power supply _V3 ,
Excitation coil L ₁ of the printing wire drive magnet...
L ₉ is connected. Each collector is connected via a diode D ₁ ... D ₉ in parallel with an excitation coil L ₁ ... L ₉ .
Although connected to the power supply, the diodes D ₁ … D ₉
Diodes D ₁ , D ₃ , D ₅ , corresponding to odd wires,
Diodes for D ₇ , D ₉ and even wires
Divide into two groups D ₂ , D ₄ , D ₆ , D ₈ , connect the anodes of diodes in each group, and connect resistor 2
By connecting to the power supply V ₃ through 6, 27,
Forms a wired OR circuit.

Taking an example in which one character consists of 9 dots vertically, and the spacing between even and odd columns and the space between characters is 3 dots, the drive timing of printing wires W ₁ ... W ₉ is as shown in Figure 8. , for example odd wire W ₁ ,
K ₃ , W ₅ , W ₇ , W ₉ are driven from the first dot pulse DP to the ninth, and the even number wires W ₂ , W ₄ ,
W ₆ and W ₈ are printed at a period 3 dots later than these. Therefore, the odd wires W ₁ , K ₃ , W ₅ , W ₇ ,
W ₉ is not driven from the 10th to 12th dot pulse DP, and even wires W ₂ , W ₄ , W ₆ , W ₈
Regarding, since the first to third dot pulses DP are all non-driven, the transistor Tr ₁
...Taking into consideration the transition time of Tr ₉ , it is sufficient to set the check timing for the former at the 11th to 12th dot pulse DP, and for the latter at the 2nd to 3rd dot pulse DP. Assuming that the check timing is the dot timing in the middle of the empty period for taking space between characters, the odd wire timing signal TS ₁ of logic "H" is input to the AND circuit 29 when the dot pulse DP is the 11th. At this time, the transistor for odd wires
Tr ₁ , Tr ₃ , Tr ₅ , Tr ₇ , Tr ₉ and excitation coil L ₁ ,
If no accident occurs that causes excessive current to flow in any of L ₃ , L ₅ , L ₇ , and L ₉ , the diode
None of D ₁ , D ₃ , D ₅ , D ₇ , and D ₉ conducts, and the power supply voltage V ₃ appears as the potential at the common point 30. Then, it is converted to a TTL level "H" by the level conversion circuit 32 and inputted to the AND circuit 29, and when it matches the "H" of the odd wire timing signal TS ₁ , a logic "H" signal is output from the AND circuit 29. and notify outside parties that there have been no accidents. However, for example, if the transistor Tr ₁ is damaged or the excitation coil L ₁
When current flows through coil _L1 due to a short circuit, etc.,
The collector potential of the transistor Tr ₁ becomes the ground potential, the diode D ₁ also becomes conductive, and the potential of the common point 30 also becomes a value close to the ground potential. Since the signal converted to logic "L" by the level conversion circuit 32 does not match the odd wire timing signal TS ₁ , the output of the AND circuit 29 becomes a logic "L" alarm signal, notifying the outside of the failure and relaying Turn off the power. This operation is performed by the diodes D ₁ , D ₃ ,
Since D ₅ , D ₇ , and D ₉ are connected to wired OR, transistors Tr ₁ , Tr ₃ , Tr ₅ , Tr ₇ , and Tr ₉
Alternatively, if any one of the coils L ₁ , L ₃ , L ₅ , L ₇ , and L ₉ fails and excessive current flows, an alarm signal is generated by a similar operation. even wire
For W ₂ , W ₄ , W ₆ , and W ₈ , dot pulse DP
When the wire is fired for the second time, an even wire check timing signal TS ₂ is generated and inputted to the AND circuit 28, and the potential of the common point 31 is monitored to obtain an alarm signal in the same manner as in the case of the odd wire. I can do it.

The check timing signals TS ₁ and TS ₂ for odd wires and even wires can be controlled by software in a computer, but
It can also be obtained by hardware as shown in Figures A and B. In this case, one character consists of a total of 12 dots, including 9 dots required for printing and 3 dots for space between characters, so the 10th
As shown in the timing chart in Figure 9, one character pulse CHA is output every 12 dot pulses DP are output. This character pulse
After inputting CHA to the reset terminal R of the counter 37 in A of the same figure and resetting the counter 37, the dot pulse DP is input to the clock terminal CP.
count up. Among the output signals of the parallel output terminals O ₁ , O ₂ , O ₄ and O ₈ of the counter 37, only the signal of the output terminal O ₂ is sent to the inverter 33.
The output signals of the other output terminals O ₁ , O ₄ and O ₈ are input to the 4-input NOR circuit 34 as they are.
Further, only the signal from the output terminal O ₄ is inputted to the 4-input AND circuit 36 via the inverter 35, and the output signals from the other output terminals O ₁ , O ₂ and O ₈ are inputted as they are.
Now count up the dot pulse DP,
Output terminals O ₁ , O ₂ , when counting the second one
The states of O ₄ and O ₈ are logic “L”, “H”, and
"L", "L". However, the output terminal
Since the output signal of _O2 is inverted via the inverter 33, all the inputs of the NOR circuit 34 are in the logic "L" state, and the output is "H". When the count number is other than 2, the input logic of the NOR circuit 34 will not match, and its output will be “L”.
Therefore, the output of the NOR circuit 34 can be used as the even wire timing signal _TS2 . Also, the output terminal when counting 11 dot pulses DP.
The states of O ₁ , O ₂ , O ₄ and O ₈ are respectively logic “H” and
“H”, “L”, “H”. At this time, the output terminal
Since the output signal of _O4 is inverted via the inverter 35, all four inputs of the AND circuit 36 become "H", and its output also becomes "H". When the count number is other than 11, all four inputs of the AND circuit 36 do not become "H" and the output signal becomes "L", so the output of the AND circuit 36 is used as the odd wire check timing signal. Can be used as TS ₁ .

As described above, according to the present invention, the printing wires are divided into odd-numbered wires and even-numbered wires, and a check timing signal is generated independently for each set during the space operation period in which the printing wires are not driven. For each set, a circuit connects the collectors of the transistor group that drives the excitation coil by wire-OR, determines whether or not the collector voltage has reached a predetermined voltage in synchronization with the check timing signal, and outputs an alarm signal. It's structured well. Therefore, there are two or three rows of printing wires.
Even in serial printers that have print heads arranged in a bird-like pattern with more than one row, it is possible to notify failures such as short circuits for all print wires, and alarm signals are generated independently for each row. Since the column to which the faulty part belongs can be immediately known, it is easy to find the faulty part.

[Brief explanation of the drawing]

Figure 1 is a plan view of a wire-type serial printer, Figure 2 is a front perspective view of the printer's print head, Figures 3 and 4 are diagrams showing a conventional general malfunction detection circuit, and Figure 5. Figure 6 shows a malfunction detection circuit for the print head in Figure 5. Figure 8 shows a print head in which the print wires are arranged in two rows in a bird-like pattern, and the state of the characters printed by the print head. Figure 8 shows the operation timing chart of each print wire. Figure 9 shows the malfunction detection according to the present invention. FIGS. 10A and 10B are diagrams illustrating an example of a circuit and an operation timing chart of the circuit for obtaining a plurality of check timing signals. In the figure, 5 is the print head, W ₁ , W ₂ ... are print wires, Sp is the space between characters, L ₁ , L ₂ ... are exciting coils, Tr ₁ , Tr ₂ ... are coil drive transistors, and 32 is a level converter. The circuits 28 and 29 are AND circuits, DP is a dot pulse, _TS1 is an odd check timing signal, and _TS2 is an even check timing signal.

Claims (1)

[Scope of Claim for Utility Model Registration] A printer is equipped with a large number of printing wires, each printing wire is equipped with a corresponding driving magnet, and the printing wires are divided into N (N=an integer of 2 or more) sets of rows. , each set has print heads arranged at intervals equal to or greater than the character space spacing, and the print wires of each set are driven at the same period while the print heads move relative to the platen. In a serial type dot printer that prints characters, each set of print wires is equipped with a malfunction detection circuit, and each malfunction detection circuit detects a check timing that occurs when the set of print wires corresponding to that circuit corresponds to the character space. 1. A malfunction detection circuit for a dot printer, comprising means for detecting, based on a signal, the state of the collector voltage of a transistor that drives each drive magnet in the set.