JPS5918845B2 - How to drive an electromagnet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of driving an electromagnet that is driven in a very short cycle, such as an electromagnet that operates a dot printer.

Figure 1 shows a conventional example of an electromagnet drive device. 1 is a monostable multipipulator (1) that is triggered by a drive command.
Reference numeral 2 (hereinafter abbreviated as "mono-multi") is a power transistor that conducts during the time T3 when the mono-multi 1 is triggered and returns to a stable state, and 3 is an electromagnetic coil that is energized when the power transistor 2 is conductive. If the electromagnetic coil 3 is energized in a very short cycle as described above, the magnetic flux generated during the first drive is stronger than the magnetic flux generated during the first drive due to the eddy current generated in the electromagnet core (not shown). As shown in FIG. 2, the magnetic flux generated increases.

For this reason, there is an inconvenience that the displacement of the armature of the electromagnet (not shown), for example, during the first drive is different from that during the second and subsequent drives. An object of the present invention is to eliminate the above-mentioned drawbacks of the prior art and to ensure stable and reliable operation of an electromagnet driven in such a short cycle.

FIG. 3 shows an embodiment of the present invention, in which reference numeral 11 denotes a monomultiplier triggered by a drive command, the output pulse width Ti of which is set to be shorter than the minimum period T of the drive command. .

Reference numeral 12 denotes a re-trigger monomulti that is triggered by the first output of the monomulti 11, and its output pulse width T2 is set longer than the minimum cycle T.

Reference numeral 13 denotes a monomulti that is triggered by the first output of the monomulti 11, and its output pulse width T3 is set to be shorter than the minimum period T.

Reference numeral 14 denotes an AND gate that performs the logical product of the 1 side output of the monomulti 11 and the o side output of the retrigger monomulti 12, 15 a power transistor that becomes conductive when the AND gate 14 opens its gate, and 16 a monomultiplier. 13 is a power transistor that becomes conductive when its first output becomes high level when triggered; 18 is an electromagnetic coil inserted between the collector of the power transistor 16 and the power supply; IT is an electromagnetic coil 18 inserted between the collector of the power transistor 15; This is a current limiting resistor inserted between the

As shown in the time chart of FIG. 4, when the drive command first comes and when the drive command comes more than time T2, the power transistor 15 becomes conductive immediately before the power transistor 16 becomes conductive, and the electromagnetic coil 18 A small current, which is limited by the limiting resistor IT, flows through it.

As a result, the influence of eddy current is reduced when the power transistor 16 is turned on and the electromagnet is driven for the first time, and the magnetic flux generated at that time becomes approximately the same magnitude as the magnetic flux generated during the second and subsequent drives. The small current that is limited by the limiting resistor IT and flows through the electromagnetic coil 18 may be of a magnitude that does not cause the electromagnet to operate.

According to the experimental results, when the minimum period T of the drive command is 1ms, T1=0.5ms, T222ms, T320.4
ms, the current flowing when the power transistor 16 conducts is 4 A, and the current flowing when the power transistor 15 conducts is approximately 0.8 A. As shown in the time chart of Fig. 4, for example, the displacement of mm is approximately be the same. As described above, according to the present invention, immediately before driving an electromagnet that has not been driven within a predetermined time, a small current that does not activate the electromagnet is passed through the electromagnet coil.
During this drive, the influence of the eddy current becomes smaller and the generated magnetic flux increases, and becomes approximately the same magnitude as the magnetic flux generated during the second and subsequent consecutive drives.

As a result of this Q, the displacements of the armatures, for example, 1 and 2, are almost the same, and it is possible to stably operate the electromagnet that is driven in a very short cycle. The present invention is not limited to the above configuration, and various modifications can be made to the VC within the scope of the claims. For example, as shown in FIG.
8 is the driving coil 181 and the pre-driving coil 182.
The pre-drive coil 182 can be energized with the small current immediately before the drive coil 181 is energized. Further, in the VC circuit shown in FIG. 3, the AND gate 14 can be omitted and the power transistor 15 can be made conductive by the O-side output of the retrigger monomulti 12.

[Brief explanation of the drawing]

Figure 1 is a connection circuit diagram showing a conventional example of an electromagnet drive device.
2 is a time chart for explaining the operation of FIG. 1, FIG. 3 is a connection circuit diagram showing an embodiment of the configuration for realizing the method of the present invention, FIG. 4 is a time chart for explaining the operation of FIG. FIG. 5 is a connection circuit diagram of a hair portion showing another embodiment of the configuration for realizing the method of the present invention. 11, 13... Mono multi, 12... Retrigger mono, multi, 14... AND gate, 15, 16...
・Power transistor, 17... Current limiting resistor, 18
...Electromagnetic coil.

Claims (1)

[Claims] 1. In an electromagnet that is driven at such a short period that the influence of eddy currents generated in its core cannot be ignored, the electromagnet is powered with a small current that does not activate the electromagnet immediately before driving the electromagnet that has not been driven within a predetermined time. A driving method characterized by passing current through a coil.