JPH0356188B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for detecting overload in a dot matrix print head.

A dot matrix print head has a large number of dot forming means (for example, needle pins), and forms characters or figures on the paper by individually driving these dot forming means. It is. Therefore, each dot forming means is not always driven during the printing operation, and there is an average operating rate (duty) of each dot forming means during general use. The allowable usage conditions of the print head are regulated by the duty of the dot forming means at a certain printing speed.

Conventionally, it has been detected whether the duty of the dot forming means is within a permissible value by detecting the temperature rise of the entire printing head. When the temperature of the print head reaches a permissible temperature or higher, the printing speed is reduced to prevent the print head from burning out due to overload. However, with this method, when only the duty of a certain dot forming means increases, for example when printing ruled lines, it is not possible to effectively detect the overload of the dot forming means, and printing Unable to prevent head damage.

In order to avoid this problem, it is possible to adopt a method of measuring the duty for each dot forming means, but this method of simply setting a certain measurement interval and measuring the duty within that interval is The problem is how to determine the measurement interval. In other words, if the measurement interval is short, the printing device will frequently be switched to low-speed operation due to a temporary increase in the operating rate, and if the measurement interval is long, the duty of a certain dot forming means will increase over two measurement intervals. If this happens again, it will not be possible to detect it effectively.

The present invention was made in order to solve the above-mentioned problems, and provides a method for detecting overload of each dot forming means without setting a specific duty measurement section. Using a hammer strobe pulse as an input signal, generating subtraction information related to the allowable duty of the dot forming means, and detecting overload for each dot forming means by comparing the subtraction information with the hammer data. It was made so that it could be done.

FIG. 1 shows an example of a printing apparatus embodying the present invention. In the figure, 1 is a platen, 2 is a printing paper, 3 is an ink ribbon, 4 is a dot matrix type printing head, and 5 is a printing head 4. Spiral rod to traverse, 6 is spiral rod 5
7 is a slit disk fixed to the spiral rod 5, and 8 is a sensor for detecting the slit in the slit disk 7. The slit disk 7 and the sensor 8 are provided to detect the rotation angle of the spiral rod 6 and provide timing for printing dots. 9 is a control device for controlling this printing device, 10 is a print head drive device, 11 is a motor drive device, 1
2 is an amplification device for amplifying the signal from the sensor 8; a is a hammer strobe signal given from the control device 9 to the print head drive device 10; b
are hammer data for each dot forming means of the print head 4.

Reference numeral 13 is an overload detection device using the method of the present invention, which detects overload of the print head from hammer data b for each dot forming means when a hammer strobe signal a is applied, and outputs the necessary output. The signal c is given to the control device 9. The overload detection device 13 is constructed by implementing the method of the present invention using hard logic or soft logic.

FIG. 2 shows an embodiment in which the present invention is implemented using hard logic. In the illustrated embodiment, the allowable duty for the print head is
33.33%, and the hammer data exceeding this allowable duty is
The configuration is such that an overload detection signal is output when the signal is integrated 330 times. In the figure, 14 is a subtraction information generator that generates one pulse d every three hammer strobe pulses (1/0.3333 hammer strobe pulses), 15 is a counter, and 16 is an upper limit value that detects the upper limit value of counter 15. A setting device 17 is a counter 15 using hammer data b and subtraction information d.
This is a count signal generator that outputs signals e and f for incrementing by +1 or -1. Here, 18 to 21 are Nand gates, 22, 2
3 is an AND gate, 24 to 26 are inverters, 27 is a decimal counter, and 28 to 30 are decimal up/down counters. In the counters 27 to 30, CK is the clock pulse input terminal, Qa or Qd is the output terminal of the binary count value,
Qa is the lowest rank and Qd is the highest rank. UP is addition pulse input terminal, DW is subtraction pulse input terminal, CRY is upper digit pulse output terminal, BOR is lower digit pulse output terminal,
CLR is the clear pulse input terminal. In addition, the third
In the figure, the state of signals in each circuit portion of FIG. 2 is shown by a timing chart. Here, M is the count value of the counter 15.

In the above configuration, the subtraction information generator 14 is
When the count value of the counter 27 reaches 2, subtraction information d is output until the next hammer strobe pulse a is input. That is, one subtraction information d is output for every three hammer strobe pulses. The count signal generator 17 generates hammer data b when the hammer strobe pulse a is applied.
exists and the subtraction information d does not exist, outputs an addition count pulse e and outputs the addition count pulse e to the counter 15.
, and on condition that subtraction information d exists and hammer data b does not exist, a subtraction count pulse f is output and the counter 15 is decremented by 1. If both the hammer data b and the subtraction information d are present or absent, the count signal generator 17 outputs nothing. counter 15
is configured as a 3-digit decimal up-down counter, and the count value of counter 15 is
When the value reaches 330, the upper limit value setter 16 outputs an overload detection signal c and the counter 15 is cleared. Since this counter 15 cannot count negative numbers, the lower limit setting value of this counter is 0, and the subtraction count pulse f applied to the DW terminal when the count value is 0 is ignored. It turns out. Note that the count signal generator 17, counter 15, and upper limit setter 16 configured as described above must be provided for each dot forming means of the print head 4.

In the above configuration, if the hammer data b given to each dot forming means of the print head 4 is maintained at an allowable duty of 33.33% or less, more subtraction count pulses f are output than addition count pulses e. Therefore, counter 1
The count value of 5 is maintained approximately near 0. When hammer data b is given to a certain dot forming means in an amount exceeding the allowable duty, the counter 15 sequentially adds up the hammer data b exceeding the allowable duty, and when this exceeds the upper limit value, the upper limit value setter An overload detection signal c is generated from 16. For example, in the illustrated embodiment, if a certain dot forming means prints ruled lines and the duty of the dot forming means is 100%, the count value of the counter 15 corresponding to the dot forming means will change every three hammer strobe pulses. The count value is added up by 2, and when this count value reaches 330, the overload detection signal c is output. Also,
The duty for a certain dot forming means is 66.66
%, the counter 15 corresponding to this dot forming means is incremented by 1 for every three hammer strobe pulses, and when this count value reaches 330, an overload detection signal c is output. Ru. That is, according to the overload detection method of the present invention, the counter 15 starts counting when the duty of a certain dot forming means begins to exceed the allowable duty, and the product of the excess from the allowable duty and its duration is set. An overload signal is generated when the upper limit value is reached.

FIG. 4 is a flowchart showing an embodiment in which the same operation as the hard logic shown in FIG. 2 is performed using soft logic. In the figure, STB is a hammer strobe pulse, CD is a carrier of subtraction information, and CD=3 means that subtraction information has occurred. N is the number of the dot forming means, and in this embodiment, a case is described in which there are 24 dot forming means. HDT(N) is the hammer data for the Nth dot forming means, and CT(N) is the count value of hammer data exceeding the allowable value for the Nth dot forming means.

When the program starts, all count values CD and CT(N) (N=1 to 24) are cleared to give initial values, and then, in step 31, a hammer strobe pulse is detected. When a hammer strobe pulse is detected, 1 is added to CD, and when this CD becomes 3, step 32 is executed.
It is determined that there is subtraction information and the CD is cleared, and the first
Read whether the hammer data HDT (N) is 1 or 0 for each of the 24th dot forming means from the dot forming means, and if this is 1, the count value is
CT(N) is not changed, and when it is 0, 1 is subtracted from the count value CT(N). When the count value CT(N) becomes negative, a procedure is carried out to maintain it at the lower limit set value of 0 in step 33. When all the procedures for the 24 dot forming means are completed, the program returns to step 31, the hammer strobe pulse detection step. If it is determined in step 32 that CD≠3, that is, if the subtraction information is not output,
When the hammer data for each dot forming means is read and the hammer data is 1, 1 is added to the count value CT(N) for that dot forming means, and when the hammer data is 0, the count value is not changed. Then, the count value CT(N) for any dot forming means is the upper limit setting value.
330, this is detected in step 34, the control program of the control device 9 is interrupted, and a procedure is taken to reduce the duty of the dot forming means.

As can be understood from the above description, the print head overload detection method of the present invention calculates one subtraction information d for every n hammer strobe pulses, where n is the reciprocal of the duty allowed for the print head 4.
CD = 3, and the subtraction information is set to 0 on the condition that the subtraction information and the hammer data b, HDT (N) both exist or do not exist when each hammer strobe pulse a, STB is given. -1 is counted for each dot forming means on the condition that the hammer data is present and no subtraction information is present, and 1 is counted on the condition that the hammer data is present and no subtraction information is present, and this count value is set as the lower limit setting value (in the above implementation). In the example, when the count value exceeds 0), the count value is maintained at the lower limit set value, and when this count value exceeds the upper limit set value (330 in the above example), an overload detection signal is issued and the above count value is cleared. When the duty of the dot forming means is less than the allowable duty, the count value is maintained at the lower limit set value, and when the duty exceeds the allowable duty, the hammer data exceeding the allowable duty is counted. ,
An overload detection signal is generated when this count value reaches the upper limit setting value.

Therefore, by appropriately setting the value of n and the difference between the lower limit set value and the upper limit set value of the counter, it is possible to prevent the dot forming means from operating unnecessarily due to a temporary increase in duty, and to reduce the duty. It is possible to detect an overload by detecting data from the point when the increase in dots starts, and also to detect overloads on the printing head for each dot forming means. Therefore, print head overload can be effectively detected under any usage conditions.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the flow of control signals of a printing device implementing this method, Fig. 2 is an electric circuit diagram showing an embodiment of the method of the present invention implemented using hard logic, and Fig. 3 2 is a timing chart showing the state of signals at each connection point over time in FIG. 2, and FIG. 4 is a flow chart showing an embodiment of the method of the present invention implemented by software logic. In the figure, 1 is a platen, 2 is a printing paper, 4 is a print head, 5 is a spiral rod, 6 is a motor, and 9
10 is a control device, 10 is a print head drive device, 11 is a motor drive device, 13 is an overload detection device, a is a hammer strobe signal, b is hammer data, c is an overload detection signal, d is subtraction information, and e is addition. Count pulse, f is subtraction count pulse, 1
4 is a subtraction information generator, 15 is a counter, 16 is an upper limit value setter, 17 is a count signal generator, STB
is hammer strobe pulse, CD=3 is subtraction information,
HDT(N) is the hammer data for the Nth dot forming means, and CT(N) is the count value of the hammer data exceeding the allowable duty.

Claims (1)

[Claims] 1 One subtraction information is generated for every n hammer strobe pulses, and 0 on the condition that both subtraction information and hammer data are present or absent when each hammer strobe pulse is given.
, -1 on the condition that subtraction information exists and hammer data does not exist, and 1 on the condition that hammer data exists and subtraction information does not exist, are counted for each dot forming means, and this count value is the lower limit. This is a dot matrix type print head which is characterized in that when the count value exceeds the set value, it maintains the lower limit set value, and when the count value exceeds the upper set value, it issues an output signal to clear the counter. Load detection method (where n is the reciprocal of the operating rate allowed by the print head and is not necessarily an integer).