JPS5948175A - Printer - Google Patents

Abstract

PURPOSE:To prevent the occurrence of trouble with heating by a method in which the exciting time of a hammer is watched, and excitation exceeding a give time is forcibly prohibited. CONSTITUTION:From a comparator 8, a pulse similar to the pulse of exciting time. The pulse is delayed by an oscillating circuit 10 and a delay circuit 11. The delay time is set in such a way that it becomes longer than the width of the longest time pulse T1 at which excitation is made as in the timing chart. The delay time is also set in such a way that the delay pulse DT1 is trailed before leading of the next exciting pulse T2. The output signal 13 of the delay circuit 11 and the signal 12 showing the exciting pulse are applied to AND gate A. In case where excitation as in abnormal pulse E is made, the output 14 of the AND gate A rises to interrupt the power source + or -Vop.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field] The present invention relates to a printing device which monitors the excitation time of an impact printer and prohibits excitation for longer than a predetermined time to prevent heat generation accidents.

[Conventional contact]

For some reason, an accident may occur in a low-resistance inductive load drive system such as a hammer excitation circuit where the drive system is excited for more than a predetermined period of time.

In this case, the coil generates a large amount of heat, which may destroy the coil itself or cause a dangerous situation such as a fire. For this reason, methods of monitoring the amount of current and methods of monitoring temperature have been considered.

However, in both cases, groove formation becomes complicated.

〔the purpose〕

In order to solve these problems, the present invention monitors the excitation time of the hammer and forcibly prohibits excitation if the excitation exceeds a predetermined time.

〔Example〕

An embodiment of the present invention will be described below.

FIG. 1 shows an example of a circuit for driving the hammer of the present invention. 1
is the input terminal to which the hammer drive signal is input. This is a certain predetermined time pulse. This input turns on the transistor 2, and current flows through the inductive load 6, such as a coil, to excite a magnet (not shown). During this time, a current set by &J1 and the variable resistor 5 flows through the current detection resistor 4, and is output as a voltage to the output terminal B of the differential amplifier. This output of B is separately input to the comparator 7 side and the excitation time monitoring side (comparator 8). 1,2゜3.
4,5. <S, 7 is a well-known constant current drive circuit, and its details will be omitted. The other input of the comparator 8 is inputted with a setting signal 9 for the lowest detectable current value of the excitation current. From this K, the comparator 8 generates a pulse similar to the current excitation time pulse. This is delayed by an oscillation circuit 10 and a delay circuit 11. As shown in the timing chart shown in FIG. 2, the delay time is set to be longer than the width of the longest pulse T1 during which excitation is performed, and the delay pulse DT is set before the rise of the next excitation pulse T2.
Set so that 1 falls.

The output signal 1 of this delay circuit 11 and the signal 12 indicating the current excitation pulse are applied to the AND gate A.

If excitation like the abnormal pulse E in FIG. 2 is performed, the output 14 of the AND gate A rises.

Therefore, this signal is input to the power supply circuit, and the power supply ±Vop
cut.

〔effect〕

The above operation can prevent an accident in which the hammer continues to be energized for more than a predetermined period of time.

Also, since the delay time was set as described above, the excitation pulses TI, T2 . Even when a T error (set for various printing pressures) occurs, the AND gate A does not open at all during normal operation, making it possible to reliably detect only abnormal conditions.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of an example of the present invention, and FIG. 2 is a waveform diagram for explaining its operation. 3...Load 11...Delay circuit A...And gate agent Gi Marushima -゛ ξ L, I, Nagi 5

Claims (2)

[Claims] (1) A printing device characterized by comprising means for monitoring hammer excitation time and means for forcibly prohibiting non-hammer excitation when the means detects that a predetermined hammer excitation time has been exceeded. . (2) The monitoring means includes a delay circuit for one hammer excitation pulse, the delay time of which is set longer than the longest pulse width of the one hammer excitation pulse, and the falling edge of the delayed pulse is used for the next hammer excitation. The printing device according to item (1), wherein the printing device is set before the start-up of the Hals.