JPH04361061A - Impact dot head - Google Patents

Abstract

PURPOSE:To make high-speed printing possible without changing shape and size of an impact dot head. CONSTITUTION:In an impact dot head wherein strain energy is stored when printing is not in operation, in a spring 8 by attraction force of magnetic flux PHIA produced by a permanent magnet 2 and the spring is released when the printing is in operation by offsetting the attraction force acting on the spring by passage of an electric current to coils wound round cores 1-a and thereby a printing wire 10 connected to a lever 5 fixed to the spring is driven for formation of dots by impact force on a printing media, passage of the electric current to the coils is controlled after hitting of the printing wire against the printing media so that the attraction force by the permanent magnet can be increased.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an impact dot head.

0002

[Prior Art] In the conventional technology, as shown in Fig. 4(a), when a printing signal is issued, the current flowing through the coil is generally made to flow in only one direction to cancel the magnetic flux of the permanent magnet. Are known. The displacement waveform of the tip of the printing wire at that time is shown in FIG. 4(b).

0003

[Problems to be Solved by the Invention] However, when energizing the coil of an impact dot head as described above, in order to increase the speed, it is necessary to shorten the collision time until it collides with the print medium, and to reduce the collision time before colliding with the print medium. It is necessary to shorten the return time from the point to the standby position, and in order to shorten each time, the spring force must be increased, and the spring, armature, and core must be made larger to increase the magnetic flux that acts between the armature and the electromagnet. There is a problem in that the impact dot head becomes larger.

An object of the present invention is to compensate for these drawbacks and provide a compact and high-speed impact dot head.

[0005]

[Means for Solving the Problems] In order to solve the above problems, the impact dot head according to the present invention stores strain energy in a spring by the attractive force of magnetic flux generated from a permanent magnet when not printing, and stores strain energy in a core when printing. By energizing the coil wound on the spring, the attractive force acting on the spring is canceled and the spring is released, driving the printing wire that connects to the lever fixed to the spring, and printing dots on the printing medium by impact force. The impact dot head comprising the above-mentioned impact dot head is characterized in that after the printing wire collides with the printing medium, the coil is energized in a direction that increases the attractive force of the permanent magnet.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view of an impact dot head according to a first embodiment of the present invention.

An armature 6 is fixed to the tip of the spring 8, a lever 5 is fixed to the other end of the armature 6, a printing wire 10 is fixed to the tip of the lever 5, and the printing wire 10 is guided by a wire guide 12. Retained. The other end of the spring 8 is sandwiched and fixed between a spring pressing plate 9 and a side yoke 4, and is connected to the yoke plate 3, permanent magnet 2, and base plate 1.
are fixed in a stacked state. A plurality of cores 1-a are arranged substantially circumferentially on the base plate 1 and face the armature 6, and a magnet coil 7 is wound around the core 1-a to constitute an electromagnet. The armature 6 is attracted to the opposing core 1-a while distorting the fixed spring 8 due to the attractive force caused by the magnetic flux ΦΑ of the permanent magnet 2. Both ends of the winding of the magnet coil 7 are soldered to a substrate 17 through holes or slits provided in the base plate 1, and the other end of the substrate 17 is connected to a drive circuit.

FIG. 2(a) shows a drive circuit. The drive circuit is composed of a bridge circuit of two transistors, Tr1 and Tr2, and a power supply having two voltage levels of +V1 and -V2 so that the direction of the current flowing through the magnet coil 7 can be changed, and the transistor switching signal is S1,
By selecting S2, the direction of the current i flowing through the magnet coil 7 is switched, and a current waveform as shown in FIG. 2(b) is generated.

Next, the control and operation of the drive system will be explained. Figure 3
(a) is a diagram showing a control method according to an embodiment of the present invention. First, as shown in FIG. 1, the armature 6 has a permanent magnet 2.
An attractive force acts on the armature 6 and the core 1-a due to the magnetic flux ΦA, and the armature 6 is attracted to the core 1-a while distorting the spring 8 fixed to the armature 6. In this state, as shown in FIG. 3(a), a current i-1 generates a magnetic flux ΦB in the direction of canceling the magnetic flux ΦA due to the permanent magnet 2 in the magnet coil 7.
flow.

FIG. 3(b) is a diagram showing changes in the magnetic flux applied between the armature 6 and the core 1-a, with the direction in which the magnetic flux ΦB is generated being (+). amateur 6 and core 1-a
The magnetic flux between the armature 6 and the core 1 is the magnetic flux ΦA due to the permanent magnet 2 before the current i-1 flowing through the magnet coil 7 is applied, and the magnetic flux ΦB increases due to the current i-1 of the magnet coil 7. The magnetic flux between a gradually decreases, and as the magnetic flux changes, the attractive force due to the magnetic flux applied between the armature 6 and the core 1-a changes. Amateur 6 is spring 8
Since it is attracted to the core 1-a while being distorted, the magnetic flux decreases with the passage of time and current i-1, and it starts to move at time t1 when the spring force of the spring 8 becomes stronger. After that, the current i-1
While flowing, the difference between the spring force and the attractive force due to the magnetic flux acts as a force on the armature 6, lever 5, and printing wire 10, accelerating the printing wire 10 in the direction of protruding onto a printing medium (not shown).

FIG. 3(c) shows the force Fa which is the resultant force of the magnetic force and the spring force acting on the armature 6, the lever 5, and the printing wire 10. In the figure, the (+) direction is the direction in which the printing wire protrudes, and the (-) direction is the direction in which the armature 6 is attracted. Due to Fa shown in FIG. 3(c), the tip of the printing wire 10 draws a trajectory of Xa shown in FIG. 3(d), and as shown in FIG.
Near the apex of the middle trajectory Xa, the tip of the printing wire 10 collides with a ribbon and paper (not shown), forming dots on the paper surface. After the dots are formed, the armature 6 returns to the direction of the core 1-a again due to the resultant force of the repulsive force upon collision of the printing wire 10, the attractive force of the permanent magnet 2 acting on the armature 6, and the spring force of the spring 8. At this time, a current i-2 is passed through the magnet coil 7 in a direction to increase the magnetic flux caused by the permanent magnet 2 and further attract the armature 6, the armature 6, the lever 5, and the printing wire 10.
The armature 6 collides with the core 1-a, rebounds, and stops at the standby position, thus completing one printing process. In order to increase the speed of this printing process using the conventional control shown in FIG. In order to shorten the time the wire 10 collides with the print medium and shorten the time it takes to return to the standby position after dot formation, it is necessary to increase the spring force and further increase the suction force between the armature 6 and the core 1-a. , the impact dot head becomes large because the armature 6, core 1-a, spring 8, and permanent magnet 2 are made large.

However, in the impact dot head of the present invention, as described above, after the printing wire 10 collides with the printing medium, the armature 6, the lever 5, and the printing wire 10 are connected to the core 1-a by the magnetic flux of the permanent magnet by the current i-2. coil 7
By increasing the magnetic flux and increasing the attraction force, it is possible to forcefully return to the standby position and shorten the return time. Therefore, the speed of the impact dot head can be easily increased without changing the shapes and sizes of the spring 8, the armature 6, and the core 1-a.

When we actually compared the behavior waveform of the tip of the printing wire for one printing stroke, the trajectory of the printing wire 10 under conventional control shown in FIG. 4(a) becomes Xb in FIG. 3(d), and the time per one printing stroke is about 650 μsec in Figure 3 (a
), the control according to the embodiment of the present invention results in the trajectory Xa shown in FIG. 3(d), and the time per printing process is 580 μsec, which is a time reduction of 70 to 100 μsec per printing process, which is about 10% faster. This had the remarkable effect of achieving

[0014]

Effects of the Invention As described above, the impact dot head of the present invention is capable of controlling the power supply of the coil in the direction of increasing the attractive force of the permanent magnet after the printing wire collides with the printing medium. The wire can be forcibly returned to the standby position, making it possible to shorten the return time of the armature, lever, and printing wire without changing the spring force or the attraction force created by the permanent magnet between the armature and the core, and the impact dot head. A small, high-speed impact dot head can be realized without changing the size or shape of the head.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing a cross section of an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a drive circuit according to an embodiment of the present invention.

FIG. 3 is an explanatory diagram showing energization control of the electromagnet of the present invention.

FIG. 4 is an explanatory diagram showing energization control of an electromagnet in a conventional example.

[Explanation of symbols]

1 Base plate 1-a Core 2. Permanent magnet 3 Yoke plate 4 Side yoke 5 Lever 6 Amateur 7 Magnet coil 8 Spring 9 Spring pressing board 10 Printing wire 12 Wire guide 14 Nose 17 Board

Claims (1)

[Claims] Claim 1: When not printing, strain energy is stored in the spring by the attractive force of magnetic flux generated from a permanent magnet, and when printing, the attractive force acting on the spring is canceled by energizing a coil wound around the core. In an impact dot head that releases the spring and drives a printing wire connected to a lever fixed to the spring to form a dot by an impact force against a printing medium, after the printing wire collides with the printing medium, An impact dot head characterized in that energization of the coil is controlled in a direction that increases the attractive force of the permanent magnet.