JPS60247570A - Wire matrix printing head actuator - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a dot matrix print head, and more particularly to an actuator for such a print head. For example, the present invention relates to an actuator for a matrix printhead in which a plurality of actuators are supported within a body and are used to drive print wires extending from the body and contacting a print medium.

[Conventional technology]

Printing devices that use wire matrix printheads have the advantage that during each print cycle, the printing device does not print an entire character with each stroke (instead, it prints the entire character as the printhead is moved relative to the recording medium). Other printheads are characterized by the use of an array of wire needles that print selected combinations of dots in series on the recording medium to generate characters during the print cycle. It is common to use a separate electromagnetic actuator for each wire.

Clapper type printing generally includes a body containing a membrane actuator and a guide assembly that supports a wire needle. Each actuator supported within its body includes a magnetic yoke assembly. The magnetic yoke assembly has a coil and an armature assembly movable relative to the yoke assembly, the coil being wrapped around the yoke assembly, and the free end of the armature being coupled to a wire needle.

The coil is driven to actuate the lcl assembly to drive the associated wire needle to impinge on the print media. This type of printhead is listed in U.S. Patent No. 4,320,981, and other types of dot matrix actuators are listed in U.S. Patent No. 4,242.
,004-+, No. 4,109.776 and No. 3,96
No. 8,867. Electromagnetic actuators for other foods are disclosed in U.S. Pat. No. 2,998,553, No.
No. 98,810, No. 3.609.609. .

There are problems such as low speed, low magnetic efficiency, and high power consumption. The main factors limiting the design of these actuators are that they must pass enough magnetic flux to generate a large enough magnetic drive force, be robust enough to withstand the stresses of equilibrium, and be able to easily handle high accelerations. It must be light enough to achieve two goals:

SUMMARY OF THE INVENTION The present invention provides an improved dot matrix actuator having several design features to increase efficiency and speed of operation. The yoke assembly includes a base, a pair of legs, and an armature assembly pivotally connected to the force leg and extending beyond the other leg. The flexible element keeps the armature separated from the leg to eliminate friction between the armature and the leg.For maximum magnetic efficiency, the armature The joining surfaces between the '#L machine roots are rounded so that a constant minimum gap is maintained between the roots and the legs during rotation.

In order to optimize the magnetic properties and acceleration characteristics of the armature, the armature has a first magnetic seal extending between the two legs and an 11k loop with sufficient stiffness and high speed operation. ◇To maximize acceleration, the cross-sectional shape of the first part of the armature is
The ratio of magnetic flux and inertia is determined to be Itsukushima.

In order to improve efficiency, the drive circuit and magnetic path are made to have an operating magnetic flux level just below the saturation magnetic flux level.Also, while the 1iL machine is operating, the magnetic flux is The drive circuit provides a current waveform that keeps the yoke approximately constant during operation. This is accomplished by reducing the drive current as the object approaches the yoke during operation.

These features are added to the actuator in order to significantly improve the overall magnetic efficiency, reduce the driving power, shorten the time from when the actuator starts working to when it stops working, and increase the printing speed of the print head. and other features are adopted. [Examples] The present invention will be described in detail below with reference to the drawings.

First, refer to Figures 1 and 2. The actuator of the present invention includes a magnetic yoke assembly 1o.

The magnetic yoke assembly has a base 5ioa, a first leg 10b and a second leg 1oc. A second coil 12 is connected to a second coil 12 through which a driving current that generates a magnetic field is passed through the yoke.
wrapped around the legs of The driving circuit 6 is supplied with the driving circuit 14 and is applied to the first leg 10b by a pair of flexible elements 18. The armature extends over the second leg 10C. The appearance is the second leg 1
(Low inertia, high rigidity single machine extension part 16 extending above l)
The end i11 of this armature extension including a plastic tip 2o is fixed. This tip 20 strikes the hect 22a of the wire needle 22. The wire needle 22 is biased towards the armature by the spring 24. A plastic block 26 forming the contact surface with the adjusting screw 38 is placed towards the middle of the armature extension 16a. The 048 screw 28 is adjustable to adjust the armature distance.

In operation, yoke 10 and armature 16 form a magnetic circuit. When a current is passed through the coil lL/12, the armature 16
is rotated relative to the leg portion 10b, and the second leg s10
The flexure element 18 keeps the armature spaced apart from the first leg 10b to avoid zero friction pulling towards C. The flexible element pivots the armature and does not disturb the magnetic circuit between the armature and the yoke. In order to strictly control the magnetic efficiency, the upper surface of the first leg 10b is curved into a cylindrical shape, and the TIL machine root facing this cylindrical surface is also correspondingly curved into a cylindrical shape.

As a result, even if the armature rotates, the armature and yoke 0) I
A constant air gap is maintained at I (l). This is in contrast to conventional printheads that contact the armature or yoke and do not maintain a -tail air gap. No. 4,244°, 658. This U.S. patent discloses a rounded yoke extension. Therefore, the air gap is not maintained and friction is present.

The void size is on the order of approximately 0.0127+ll+m (half a mil). This narrow gap is obtained by first making the axle abutting the yoke extension μ. Then, their contact surfaces rub against each other,
i&i! during the break-in period so that eventually its contact surfaces wear out and create a void! Let me cry.

After they have worn away from each other, the flexure 18 functions to maintain the correct relative position of the armatures and prevent them from touching each other. In this way the air gap is self-formed and maintained at the required absolute minimum value, thereby maximizing the efficiency of the magnetic circuit.

In the embodiment described here, the deflection element 18
is made of stainless steel and is secured to the yoke extension or first leg 10b at point 30IC. For small rotation angles of the armature (less than about 5 degrees), the movement of the yoke resembles rotation about the center of the flexure element. The center of the flexure element is located at the center of the radius of the end of the first leg lOb. The use of flexure elements avoids the need for pivoting of the tool, thus eliminating friction and reducing wear on the actuator than traps. When the actuator is opened, the deflection element bends slightly to bias the machine towards the closed position. This biasing force is applied to the print wire spring 2.
This reduces the force required to operate the actuator against the spring force of 4. This makes it possible to use a spring with a somewhat stronger spring force, which is advantageous because the natural frequency of the spring is correspondingly higher. This also eliminates the overall vibration, which makes it possible to increase the operating speed of the actuator. Due to the torsional spring function of the flexible element, the force required for actuation remains small, and it is possible to Printed wire springs with relatively high natural frequencies can be employed.

Refer now to FIG. Armature assembly 16 is a two-part assembly whose magnetic circuit characteristics and inertial characteristics are optimized. This armature is made using metal strips 32 (FIG. 4). This metal piece is formed into a σ shape, and the armature body 34 is supported inside the metal piece. Metal strip 32 and armature body 34 are held together by pins 36 and 38.

In the detailed described embodiment of the invention, the armature body 34 is a laminated structure of magnetic materials. The laminated structure reduces eddy current inside the armature compared to traps. Since the armature extension 16a is hollow, it is very light. The edge of the metal strip 320 is also oriented to face the printing wire, giving the armature a stiffness of 8 m.

Since magnetic flux does not follow the armature extension 16a, it is optimized to have small inertia and sufficient stiffness so that high-speed operation can be performed. In contrast, the body parts are configured to optimize the properties of the magnetic circuit. In this regard, it should be noted that the body portion has a raised portion 34a (FIGS. 1 and 2). This raised portion is provided above the hole through which the pin 36 escapes, and functions to maintain the cross-sectional area of the body portion at one foot.

In the embodiment shown here, the deflection element 18
is formed integrally with the metal piece 32 of the armature. Since the flexure element is simply bent 90 degrees forward, there is no need to attach it separately to the root. By adopting this structure, the production of the actuator has become much easier.
Next, refer to FIGS. 5 and 6. Dimensions of armature body 34,
In particular, its cross-sectional area is selected such that the acceleration of the armature is maximum. As shown in FIG. 5, as the dimensions of the armature body increase, the magnetic force generated within the body also increases. However, as the dimensions increase, the mass also increases, so the inertia of the body also increases.

The angular acceleration of the armature increases as the magnetic force increases,
As inertia increases, it decreases, so it is proportional to magnetic force and inversely proportional to inertia.

FIG. 6 is a graph showing the relationship between changes in armature body dimensions and changes in angular acceleration. The dimensions of the armature body are chosen to optimize the angular acceleration of the armature, ie, so that the angular acceleration corresponds to point 40 of the curve in FIG. Their dimensions are determined by solid lines.

Refer now to FIGS. 7-9. When the actuator hits the extension 1oc of the yoke assembly, a reaction force is generated; the reaction force is perpendicular to the plane of the extension.

The reaction force is shown as arrow 42 in FIG.

This reaction force acts on armature 161C. What is the reaction force?

The zero component 44 can be divided into a component 44 perpendicular to the line 46 passing through the center of rotation 48 and the center of gravity 5o of the armature, and a component 52 parallel to the line 46.
The component 56 attempts to move the tiE machine root with respect to the rotation hollow 48. Since the rotation is a designed movement of the armature, it can be tolerated by the FF. However, the movement difference causes the IL armature rotation region 160 to move toward the first leg 1.
This movement is highly undesirable since it causes contact with the pace portion of 0b, prolonging the time between start and stop of actuator operation, and creates wear problems.

Those problems caused by reaction forces are eliminated by allowing reaction force 42 to cause only rotation. This is done by configuring the armature so that the line 46 is approximately perpendicular to the reaction force 42. Making the line 46 perpendicular to the reaction force 42 is the This is done by controlling the position.

In FIG. 8, the front end of the armature is lowered than shown in FIG. 7 to move the center of gravity.

Alternatively, as shown in FIG. 9, it is also possible to use the leg 10C of the tube 2 with a shorter length. Various other structures can also be adopted, but the basic design criteria is that the line 46 The aim is to locate the center of gravity of the armature to be perpendicular to the force. This must be done without adding unnecessary mass to the forward part of the armature.

Next, the B-■ curve of the armature (magnetic flux density vs. strength of magnetization)
□The strength of magnetization is proportional to the magnitude of the current applied to the armature coil.

In conventional actuators, the drive current is set so that the actuator is fully saturated, i.e., beyond point 54 on the curve shown at 1O1. Although this maximizes the strength of magnetization, it is insufficient because it uses a drive current that is higher than necessary. The magnetic and drive circuits are matched to provide a high operating flux, i.e., a single curved corner indicated by reference numeral 56 in FIG.

Furthermore, by controlling the current waveform provided by the drive circuit shown in FIG. 12, the magnetic flux level of the armature is maintained during forward motion.

The driving tm current is shown in Figure 11a. That drive wi J
The current is associated with the magnetic field shown in Figure 11b. When activated, the desired operating point 58 is reached; the machine begins to move.

As the armature continues to move, the reluctance of the magnetic circuit made up of the IE armature yoke IOK decreases, thereby reducing the drive current required to maintain the magnetic flux at the same level. Thus, the drive current is reduced at a necessary rate to maintain the magnetic flux level nearly constant until point 62, and the S drive current is then reduced to zero at a controlled decreasing rate. A @' drive circuit is shown in FIG. When an enabling pulse Fil is generated to activate the actuator, the control circuit 9o connects the drive coil 12 between the high voltage source HV and the sense resistor 96 which is grounded. Close f92.94. Current therefore flows through the coil. When the current reaches a predetermined value (2.5 A), the voltage across the sense resistor 96 is sufficient to operate the control circuit and the switch 92 is opened by operation of the 11FIJN circuit. This occurs at point 58 in Figure 11a. Then the current flowing through the coil is a low voltage tt source L
mouth sense resistor 96 to be controlled by V via diode 98, transistor 94, and coil 12.
By choosing the charge of the low voltage voltage @Ly to just cancel the resistance drop in the diode 98, the current flowing through the coil can be kept constant at a value that switches from the high voltage HV to the low voltage IIv.

In fact, the trap is that the low voltage LV is selected to a value lower than that value, so that the reduction in current begins at the time of switching. Most 'power efficiency selection' occurs in the magnetic circuit as the armature closes. The current decreases and remains approximately constant at a rate that corresponds to the rate at which the reluctance within the magnetoresistance decreases. This situation corresponds to the pulse RI
N lasts for about 250 microseconds. pulse]! When +N disappears (point 62
), switch 94 is turned off and the coil current flows through diode 1.
() so that it is discharged through 0.

The relationship between the current profile and the voltage LV of the low voltage '1 source is non-resonant due to the combination of the non-linear properties of the diode and the exponential decrease in current flowing through the inductive circuit. It was noted that there are no actuators (ゝO). Turning now to FIG. 13, several actuators are used to construct the matrix printhead.
Contains 4. The base portion 661C has a plurality of actuators 6
8 is installed. Usually, the actuators are arranged in a circular pattern on the same curve of the housing. Each actuator drives the print wire 70 with which it is associated. The print wire extends through printhead extension 72 and is supported by a plurality of print wire supports 74. As mentioned above,
A print wire spring 76 is associated with each print wire. A print wire tip extends from housing 72 and strikes inked ribbon 78 and print media 78 for printing.

Actuator 68 is molded into base portion 66 . The base portion is usually made of epoxy material. To reduce the noise generated by this printhead, a thin layer of Kg damping material can be provided between the actuator and the base.

This layer prevents noise from forming at the interface between the actuator and the N'70 portion of the printhead.

During operation, the print wire bends as it hits the ribbon and print media. This bending stores energy, which must be expended before another dot can be struck, i.e. the printing wire must return to its unbent state.In the present invention, the printing wire is The bend in the print wire itself is used to return to the point.

This is accomplished by positioning the print wire supports 74 such that they are relatively close together at the rear of the extension and leave a relatively long space at the front of the extension. This causes the print wire to bend in the area near the print medium. This bending of the print wire near the point of impact acts as a spring to return the rest of the print wire to its initial shape. This springing action of the print wire helps overcome the inertia of the rest of the print wire.

By bending the print wire near the print medium, the expiration recovery force is maximized. To further reduce the noise generated by the actuator, a damping means with a QIJ ring 84 is installed on the face of the yoke extension 10a. (Fig. 14). It is believed that most of the noise generated by the actuator is generated by the collision between the armature and the pole face of the second leg extension 10C. By placing the O-ring of the buffer means accurately around the magnetic pole surface, the actuator operates normally until just before it hits the magnetic pole surface of the second leg (the armature contacts the O-ring). The armature is prevented from closing the final approximately 0.0127 mm (approximately 0.5 mil), thereby eliminating metal-to-metal contact.

As explained above, the present invention provides a dot matrix actuator that has several characteristics to improve efficiency and operating speed, extend life, and reduce noise.

[Brief explanation of drawings]

1 is a perspective view of the actuator of the invention, FIG. 2 is a side view of the actuator of the invention, FIG. 3 is a top view of the armature of the actuator, and FIG. A plan view of the metal piece used; Figure 5 is a graph showing the variation of the inertia and magnetic force of the actuator as a function of the armature dimensions; Figure 6 shows the angular acceleration of the armature as a function of the armature dimensions. Graphs, Figures 7 to 9 are schematic diagrams of the actuator showing the reaction force generated by VC in the actuator, Figure 10 is B-1 of the magnetic circuit of the actuator.
The graph showing the first curve, aRlia, and xzb are graphs showing the drive current and magnetic field of the actuator, respectively.
Figure 2 is a circuit diagram of a drive circuit used in the actuator of the present invention, Figure 13 is a sectional view of a print head using the actuator of the present invention, Figure i14 is a schematic diagram showing the bending of the printing wire that occurs during impact. FIG. 15 is a plan view of an actuator including damping means to reduce noise generated by the actuator. 10-H-ku assembly, 10a, 66--Base part, 10--First leg part, 1oc--Second leg part, 1
2... Coil, 16... Armature, IIL... Armature extension, 18... Deflection element, 20... Plastic tip, 24... Spring, 64... Housing, 68 . . . actuator, 70 . . . printing wire, 72 . . . printing wire extension, 74 . . . printing wire support, 82 . February 22, 1985 2, Name of the invention A271-Rix printing head Akbu 11-ta 3, What is the relationship between the famous cases to be amended? 4';lf 'l Applicant Data Products,] - Boration 4, Agent

Claims (1)

Claims: (IJ) A yoke assembly having a pace portion, a first leg portion and a second leg portion extending from the base portion; an armature assembly extending beyond the leg; a drive coil surrounding a portion of the yoke assembly; and flexure means for pivoting the 11Lm child assembly with respect to the yoke assembly; The yoke assembly and the armature assembly are pivotable toward and away from the second leg, and the yoke assembly and the armature assembly form a magnetic circuit when the armature assembly is pivoted. The end of the first IlIIm and the armature assembly are configured such that a gap of - is maintained between the end of the first IlIIm and the coil is connected to the second leg. An actuator for wire matrix printing, characterized in that the actuator is for generating a magnetic field in a magnetic circuit in order to rotate the actuator toward the wire matrix. The means consists of a pair of flat metal flexure elements disposed on opposite sides of the first leg, one end of each flexure element being fixed to the root assembly, and the other end of each flexure element being fixed to the root assembly. An actuator fixed to a leg. (3) The actuator according to claim 2, wherein the end of the first leg has a cylindrical surface curved outward. (4) An actuator according to claim 2, wherein the actuator has a corresponding inwardly curved cylindrical surface. An actuator, characterized in that the deflection means is tensioned to bias the actuator towards the armature assembly. a print wire that is moved in a first direction when the child assembly is moved toward the second leg;
an actuator further comprising spring means for biasing the actuator in a direction opposite to that of the actuator, wherein the tension applied by the deflection means is less than the tension applied by the spring means. (6) a yoke assembly having a pace portion, a first ll11s and a second leg portion extending from one side of the pace portion, and extending across the legs to provide a magnetic circuit with the yoke assembly; The armature assembly, which is attached to the yoke assembly and the armature assembly,
deflecting means for pivoting the armature assembly with respect to the end of the first leg; and drive means for generating a magnetic field in the magnetic circuit that causes the armature to pivot with respect to the first leg;
Actuator of IJ Lux-shaped device, characterized in that a gap is maintained between the armature assembly and the first III41 section. (7) The actuator according to claim 6, wherein the m'' gap is maintained constant even if the armature rotates. (8) The actuator according to claim 7, wherein the end of the first leg is rounded, and the armature assembly is located close to the end of the first leg. (9) The actuator according to claim 6, wherein the deflection means includes a pair of pressure-connected portions on both sides of the first leg. An actuator comprising metal pieces, each metal piece extending up to and attached to the isogo assembly. (10) The actuator according to claim 6, wherein The Anekoburi includes a body portion made of a magnetic material and extending from a first leg to a second leg, and a relatively low-purchase root extension portion extending beyond the body portion. (11) The actuator according to claim 8g10, in which the armature extension portion is made of a metal piece, the gold piece is formed into a U shape, and one end of the metal piece is formed of a metal piece. is fixed to a first side of a body, the other end of the metal piece is fixed to a second side of the body, and the U-shaped metal piece includes a portion extending beyond a portion of the body. (12) The actuator according to claim 11 dd, characterized in that a part of the body is formed of a plurality of laminated members. (13) The actuator according to claim 6 4) The armature assembly is constructed so as to minimize the damage caused by the actuator generated within the armature assembly. An actuator characterized in that the angular acceleration of the child assembly is reduced to a certain angle.(14) A yoke assembly having a heel portion, a first leg portion and a second leg portion extending from one side of the pace portion; a t-root extending across the leg of the armature and rotatably supported with respect to the first leg and forming a magnetic circuit with said yoke assembly; A drive coil surrounding the yoke assembly to generate a magnetic field in the magnetic circuit to move the yoke assembly and a line passing through the center of gravity of the armature and the pivot point between the armature and the first leg or a second The A element and the yoke are constructed so as to be substantially parallel to the plane of the leg 91, so that the reaction force generated when the armature touches the second leg is directed to the bit point of the armature. 14. An actuator for a wire matrix printing device, characterized in that the actuator rotates almost simultaneously. (15) The actuator according to claim 14, wherein the actuator is supported with respect to the first leg by a deflection assembly, and a gap is maintained between the first armature and the first leg. An actuator characterized by: (16) a yoke assembly pivoted with respect to the yoke assembly with a variable gap therebetween; and M f
an armature assembly forming a magnetic circuit with the yoke assembly; coil means coupled to the yoke assembly for generating a magnetic field in the yoke assembly for causing the armature to rotate relative to the yoke assembly; and a coil for generating the magnetic field. The drive means is biased towards passing a drive current through the drive means, and the magnitude of the drive current is such that the number of magnetic fluxes in the magnetic circuit is slightly smaller than the number of saturation magnetic fluxes, which maximizes the efficiency of the actuator. Matrix print head actuator whose function is to (17) The actuator according to claim 16, wherein the driving means includes means for maintaining the number of magnetic fluxes in the magnetic circuit substantially constant after the magnetic flux in the magnetic circuit reaches a certain level. An actuator characterized by: (18) The actuator according to claim 17, characterized in that the front a pi drive means includes means for changing the drive current to change the width of the gap when the armature moves relative to the yoke. actuator. (19) The actuator according to claim 18, wherein the armature moves toward the actuator when a magnetic field is generated, the drive means generates a current, and the drive current increases to a predetermined level. and is then reduced in a controlled manner as the armature moves toward the yoke. (20) A yoke assembly having a pace part, a first leg part and a second leg part embedded in one part of the base part, and a first leg part extending from the legs; an armature assembly which is pivotally supported with respect to the yoke assembly and forms a K di air circuit with the yoke assembly; l! a drive coil coupled to the yoke assembly for generating a moving magnetic field in the magnetic circuit; an armature assembly disposed at the end of the second leg;
By preventing shocks to the surface of the legs,
An actuator for a matrix printhead, characterized in that it comprises a damping means that minimizes the amount of noise generated. (2. The device according to claim 20J:j4, wherein the damping means is made of an elastic material, the material surrounding the second leg and extending over the surface of the second leg. (22) a yoke assembly having a base portion and a first leg portion extending from one side of the base portion; The seed layer is applied to the leg of the second leg, pushing it beyond the second leg, creating a magnetic field in the magnetic path that attracts the armature around and around the plane of the second leg. a plurality of actuator assemblies including a drive coil surrounding the yoke assembly for the purpose of the present invention; a pace section surrounding the actuator assembly; and a pace section disposed between the base section and the actuator assembly for directing 'S movement from the actuator to the pace section. A matrix printhead, characterized in that it comprises: (2) an IJ Lux head, in which the armature is connected to a second characterized in that the length includes damping means disposed proximate the surface of the second leg to reduce the amount of noise generated by the printhead by preventing contact with the leg; (24) a wire guide housing including a plurality of print wires, including a plurality of actuator assemblies; and a wire guide housing disposed along the length of the wire guide housing for directing the print wires into the housing. a plurality of wire support means for supporting, each actuator having a yoke assembly and a s
1, a drive coil coupled to the yoke assembly for generating a magnetic field in the yoke assembly that attracts the armature of the on-board assembly armature, the end of each print wire being Proximate the armature assembly, the wire support means is moved by the armature assembly, bends when the print wire hits the print media, and then returns to an unstressed state, and the wire support means extends the length of the wire guide housing. is placed along the direction to cause the print wire to bend near its abutting end, such that the potential energy generated by the bend K quickly returns the print wire to its unstressed state. Features a wire matrix print head.