RU2440660C2 - Exciter of mechanical oscillations - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: vibration generator comprises a step motor, to phase windings of which control pulses are supplied. A yoke with a lever and an impact tool at the yoke's end is rigidly installed onto the shaft of the step motor. The longitudinal axis of the yoke is perpendicular to the axis of shaft rotation. It is equipped with levers, ends of which are connected to springs that in the end connect the shaft and the body. The yoke and levers are made with the possibility to make angular oscillating movements relative to the axis of the shaft rotation. As control signals are sent to the step motor stator windings, the impact tool makes angular oscillating movements relative to the axis of the shaft rotation. The moment of time for supply of control signals is determined using readings of the shaft angular position sensor.

EFFECT: increased reliability, efficiency factor, specific impact energy at minimum consumption and optimal dimensions.

2 cl, 7 dwg

Description

The invention relates to the field of electromechanics and can be used in vibration and vibration-shock devices for obtaining mechanical vibrations used in various vibration technologies, for example, for applying images to solid surfaces by means of program-controlled directed destruction of the surface by the impact method.

A device is known - an electromagnetic vibrator ([1] patent SU 1040573 dated 05/23/1986), comprising a stator with an alternating current winding, placed on poles that are clearly symmetrically spaced around the circumference, and an explicit pole armature, the pole division of which is equal to the pole division of the stator , the anchor poles are made in the form of two groups shifted in opposite directions relative to the axis of symmetry by half the width of the pole. The stator and the armature are interconnected by rolling bearings, as well as by elastic elements, which, when the stator windings are deenergized, lead to a neutral position a lever rigidly mounted on the rotor shaft.

Known electromagnetic vibrator ([2] patent SU 1469532 dated 30/03/1989), containing a symmetrical explicit pole stator with a pole winding, consisting of two parallel branches, inside of which there is a four-pole armature, the armature poles are displaced around the circumference by half the width of the pole the stator in pairs clockwise and counterclockwise and carry parallel branches of the stator winding, the pulsating current to which is supplied from the AC source through rectifier elements. In the yoke between its poles connected to the rectifier elements, additional gaps filled with non-magnetic material are made, which will eliminate the scattering fluxes in the magnetic circuit. The stator and the armature are interconnected by rolling bearings, as well as by elastic elements that, when the stator winding branches are de-energized, are switched to the neutral position and the lever is rigidly fixed to the rotor shaft.

Known electromagnetic vibrator ([3] patent SU 1820460 dated 07/06/1993), containing a stator with eight poles uniformly distributed around the circumference and equipped with winding coils of an alternating current winding consisting of two parallel branches that are connected to to the power source using rectifier elements, and the rectifier elements are turned on in opposite directions, and through them a pulsating current is supplied to the parallel branches of the stator winding. Inside the stator on the shaft with the help of a key an anchor is made, made explicitly polar, and the number of poles of the armature is equal to the number of poles of the stator. The pole of the armature is made in the form of two groups shifted in opposite directions by half the width of the pole relative to the axis of symmetry, passing in its neutral position in the middle of non-magnetic gaps made in the yoke of the stator between the poles, the coils of which belong to different parallel branches of the AC winding. The stator and the armature are interconnected by bearings, as well as by elastic elements, which, when the parallel branches of the stator winding are de-energized, turn the lever and, accordingly, the armature into neutral position; the lever is rigidly fixed to the vibrator shaft, and the working element, depending on the required linear amplitude of the vibrations, can be fixed both on the vibrator shaft and on the lever at an appropriate distance from the shaft. Between adjacent poles of the stator, the coils of which belong to different parallel branches, additional gaps are made in the stator yoke, filled with non-magnetic material.

A device is also known - an oscillatory stepper motor ([4] patent US 5,126,605 "Oscillating Stepper Motor" from 06/30/1992), including:

(a) a single-phase annular stator coil defining a central cylindrical cavity, said annular stator coil creates a magnetic field of a first polarity when an electric current passes through it in a first direction;

(b) a cylindrical rotor comprising a rotor magnet located for rotational motion relative to the specified annular stator coil in the specified Central cylindrical cavity and coaxially indicated by the annular stator coil; the specified cylindrical rotor, depending on the specified magnetic field of the first polarity created in the specified annular coil of the stator, can rotate less than 180 degrees from the lock position to the first position defined by the specified magnetic field of the specified first polarity; and

(c) a locking magnet, fixing located in view of said stator coil in said cylindrical cavity to rotate said rotor to said locked position, whenever said stator ring coil is de-energized

A device is known as a rotary drive ([5] patent US 4,795,929 "Rotary Actuator" dated 01/03/1989), having a permanent magnetic armature with diametrically opposite poles of different polarity, mounted between a pair of stator elements, at least one of which is an electromagnet, so that it can rotate between the first and second positions when creating the selected flow distribution in at least one electromagnetic stator element. The electromagnetic stator element is designed so that it creates an asymmetric magnetic field that is larger near one of the opposite fields of the armature than in the other. The electromagnetic stator consists of a core of soft iron material and the inner surface is turned towards the rotor. The coil is wound on the core so as to create magnetic force fields on the core on each surface of the core. An asymmetric flow field is created by providing the inside of the core of a larger segment, increasing the flow field and density at a given location and smaller fields for the rest of the core. Preferably, a larger segment of the surface of the core is elongated outward and closely located to the surface of the armature for a selected arc distance.

In particular, the drive includes a pair of electromagnetic stators, each of which has a non-magnetically conducting core and coil, interacting to create the first and second poles. The stators are fixed fixed at a distance against each other, their poles lie on the common axis of magnetization, and have an asymmetric shape to provide a larger force field to one side of the magnetization than the other. An anchor consisting of a cylindrical permanent magnet having opposite first and second poles lying along the diametrical pole axis is rotatably fixed between opposite stators so that the diametrical pole axis initially runs transversely to the magnetization axis of the stators. The electric circuit selectively supplies voltage to the electromagnetic stators so as to induce controlled stators on the first and second poles, directly and vice versa, to force the power zero to attract or repel the pole of the aforementioned cylindrical magnet lying on the same side of the magnetization axis to make the armature rotate.

Distinctive features of the object protected in the application and prototype devices will become apparent after the following description and the main features of the industrial stepper motor, which is used in the proposed application ([6] Kenio T. Stepper motors and their microprocessor control systems. - M.: Mir , 1987; [7] Andreev V.P., Sabinin Yu.A. Fundamentals of an electric drive. - M .; L .: Gosenergoizdat, 1963. - 772 p .; [8] Gulin V.F., Kalitinskaya T.V. Tracking electric stepper drive. - L .: Energia, 1980. - 168 p .; [9] Karpenko B.K., Larchenko V.I., Prokofiev Yu.A. Stepper electric motor Teli -. K .: Tehnika, 1972. - 216 c)..

There are three main types of stepper motors:

- motors with variable magnetic resistance,

- permanent magnet motors,

- hybrid engines.

We give a brief description of each of them.

Variable magnetic resistance stepper motors have a stator with several poles and a gear rotor made of soft magnetic material (Fig. 1). Rotor magnetization is absent. For ease of consideration, in FIG. 1, the rotor has 4 teeth, and the stator has 6 poles. The motor has 3 independent phase windings, each of which is wound on two opposite poles of the stator. The pitch of such an engine is 30 °.

When the current is turned on in one of the coils, the rotor tends to take a position when the magnetic flux is closed, i.e. the teeth of the rotor will be opposite those poles, the winding of which is under current. If then turn off this winding and turn on the next, the rotor will change its angular position, again closing the magnetic flux with its teeth. Thus, in order to carry out continuous rotation, it is necessary to include phases alternately. The motor is not sensitive to the direction of the current in the windings. A real motor can have a larger number of stator poles and rotor teeth, which corresponds to more steps per revolution. Sometimes the surface of each pole of the stator is toothed, which together with the corresponding teeth of the rotor provides a very small value of the pitch angle (of the order of several degrees).

Motors with permanent magnets consist of a stator, which has windings, and a rotor containing permanent magnets (figure 2). Alternating rotor poles have a rectilinear shape and are parallel to the axis of the motor. Due to the magnetization of the rotor, such magnetic motors provide a greater magnetic flux and, as a result, a greater moment than motors with variable magnetic resistance.

The motor shown in FIG. 2 has 3 pairs of rotor poles and 2 pairs of stator poles. Each of the independent windings is wound on two opposite poles of the stator. Such an engine, as well as the previously considered engine with variable magnetic resistance, has a step value of 30 °. When the current is turned on in one of the coils, the rotor tends to take such a position when the opposite poles of the rotor and stator are opposite each other. For continuous rotation, the phases must be switched on alternately. In practice, permanent magnet motors typically have 48-24 steps per revolution (pitch angle 7.5 ° -15 °).

Permanent magnet motors are affected by the back emf of the rotor, which limits its maximum speed. To operate at high speeds, motors with variable magnetic resistance are used.

Hybrid stepper motors are more expensive than permanent magnet motors, but they provide lower pitch, higher torque and higher speed. The typical number of steps per revolution for hybrid ballasts is from 100 to 400 (pitch angle 3.6 ° -0.9 °). Hybrid stepper motors combine the best properties of variable magnetic resistance motors and permanent magnet motors. The rotor of the hybrid SD has teeth located in the axial direction (figure 3).

The rotor is divided into two parts, between which is located a cylindrical permanent magnet. Thus, the teeth of the upper half of the rotor are the north poles, and the teeth of the lower half are the south. In addition, the upper and lower halves of the rotor are rotated relative to each other by half the pitch angle of the teeth. The number of pairs of rotor poles is equal to the number of teeth on one of its halves. Toothed pole tips of the rotor, like the stator, are assembled from separate plates to reduce eddy current losses. The hybrid stator stator also has teeth, providing a large number of equivalent poles, unlike the main poles on which the windings are located. Usually 4 main poles are used for 3.6 ° motors and 8 main poles for 1.8 ° and 0.9 ° motors. The teeth of the rotor provide less resistance to the magnetic circuit in certain positions of the rotor, which improves the static and dynamic moment. This is ensured by the appropriate arrangement of the teeth, when part of the teeth of the rotor is strictly opposite the teeth of the stator, and part - between them. The relationship between the number of rotor poles, the number of equivalent stator poles and the number of phases determines the pitch angle S of the motor

S = 360 / (Nph * Ph) = 360 / N,

where Nph is the number of equivalent poles per phase = the number of poles of the rotor,

Ph is the number of phases

N is the total number of poles for all phases together.

The rotor of the motor shown in FIG. 3 has 100 poles (50 pairs), the motor has 2 phases, so the total number of poles is 200, and the pitch, respectively, is 1.8 °.

Most modern industrial stepper motors are hybrid. In essence, a hybrid motor is a permanent magnet motor, but with a large number of poles. By the control method, such engines are the same. Most often they have 100 or 200 steps per revolution, respectively, the step is 3.6 ° or 1.8 °.

Depending on the configuration of the windings, industrial high voltage motors are divided into bipolar and unipolar. A bipolar motor has one winding in each phase, which must be reversed by the driver to change the direction of the magnetic field. This type of motor requires a bridge driver or half-bridge with bipolar power. In total, a bipolar SD has two windings and, accordingly, four outputs (figa).

Unipolar SD also has one winding in each phase, but a conclusion is drawn from the middle of the winding. This allows you to change the direction of the magnetic field created by the corresponding winding, by simply switching the halves of the winding. Thus, in a unipolar motor, another method is used to change the direction of the magnetic field. The average terminals of the windings can be combined inside the SD, so such an engine can have 5 or 6 conclusions (figb). Sometimes unipolar motor drives have separate 4 windings, for this reason they are erroneously called 4-phase motors. Each winding has separate conclusions, therefore, such an SD has only 8 conclusions (Fig. 4c). With the appropriate connection of the windings, such a motor can be used as a unipolar or bipolar motor. A unipolar motor drive with two windings and leads can also be used in bipolar mode, if the leads are left unconnected.

There are several ways to control the phases of a stepper motor. The first method is provided by alternating switching of phases, while they do not overlap, only one phase is turned on at a time (Fig. 5a). The equilibrium points of the rotor for each step coincide with the "natural" equilibrium points of the rotor in an uncharged SD.

The second method is phase control with overlap: two phases are included at the same time. With this control method, the rotor is fixed in intermediate positions between the poles of the stator (Fig.5b), and provides approximately 40% more torque than in the case of one switched on phase. This control method provides the same step size as the first method, but the position of the equilibrium points of the rotor is shifted by half a step.

The third method is a combination of the first two and is called a half-step mode when the stepper motor takes a step equal to half the main one (Fig. 5c).

Thus, the main features of a stepper motor used in the application as a pathogen, are the following:

1. The angle of rotation of the rotor is proportional to the number of input control pulses, and the angular velocity of rotation of the rotor shaft is proportional to the repetition rate of the control pulses.

2. The torque required to rotate the rotor shaft of the stepper motor is created by switching the phase windings. A stepper motor has at least two phase windings.

3. The stepper motor in stop mode, when the windings are not energized, provides a small momentum, called the holding moment, and in the case when the windings are energized, it provides maximum torque, precise positioning and repeatability, that is, it has an unambiguous dependence of the rotor position on input pulses.

In a stepper motor, torque is generated by the magnetic fluxes of the stator and rotor, which are suitably oriented relative to each other. The reverse of the ШД can be carried out at any step by changing the sign of the torque. The stator is made of a material with high magnetic permeability and has several poles. The pole can be defined as some region of a magnetized body where the magnetic field is concentrated. Both the stator and the rotor have poles. To reduce eddy current losses, the magnetic cores are assembled from separate plates, like a transformer core. The torque is proportional to the magnitude of the magnetic field, which depends on the current in the winding and the number of turns. If at least one winding of the stepper motor is energized, the rotor assumes a certain stable position, it will remain in this position until the external applied moment exceeds a certain value, called the holding moment. After that, the rotor will turn and take one of the next nearest equilibrium positions.

In the description of the prototype devices [1] - [3] it is not mentioned anywhere that the oscillation pathogen is a stepper motor; the devices themselves do not have the features of a stepper motor and are not stepper motors - these are typical electromagnetic vibrators that look like stepper motors, but they cannot be controlled and work like stepper motors. The given electromagnetic vibrator is a special electric single-phase synchronous AC motor of industrial frequency with an asymmetric rotor and a symmetric stator, the windings of which are connected according to the half-wave rectification scheme. Such an electric motor does not have the main features of the stepper motor listed above. From the design point of view, the device [4], although outwardly similar to a serial stepper motor with a magnetic rotor, is not a stepper motor and cannot operate as a stepper motor. Unlike a stepper motor, an oscillatory stepper motor has only one phase of the stator, and oscillatory movements are made only by changing the direction of the current in this phase winding. In addition, a fundamental feature of the oscillatory stepper motor, which does not allow it to be a classic stepper motor, is the presence, in addition to a single-phase stator and a permanent magnetic rotor, fixing a permanent magnet. The rotor in this design cannot continuously rotate at an infinite number of revolutions as in a classic stepper motor, but can only be rotated by a certain angle, the magnitude of which is proportional to the current supplied to the single-phase stator winding.

In addition, a significant drawback of all prototype devices is that they do not have the ability to adjust the position of the rotor relative to the stator - this stable position is initially set, determined by the relative position of the magnetic rotor and stator elements, and to adjust the position of the axis it is necessary to apply voltage or select a new magnet . In many applications, for example, when engraving, it is necessary to periodically adjust the initial stable position of the axis of the rocker arm, and therefore the working tool, in the plane of its oscillations.

It should also be noted that the inventive device using a stepper motor is a percussion device, and prototypes for their functionality do not apply to such devices.

Therefore, the author is not aware of the use of a stepper motor with the above signs in the role of the causative agent of oscillations in mechanical systems.

The aim of the invention is the construction of a simple in design, reliable electromechanical vibration generator of minimum cost, providing the highest possible coefficient of efficiency, specific impact energy and minimum consumption with optimal dimensions.

This goal is achieved by the fact that as the causative agent of mechanical vibrations, a step-by-step motor (ШД), commercially manufactured by the industry, is used, which has the following advantages, which determine, first of all, the quality of the oscillator:

- providing the required moment in vibration mode;

- the ability to quickly start, stop, reverse;

- high reliability associated with the absence of brushes;

- long service life;

- low cost;

- the possibility of obtaining a high value of the torque on the motor shaft without an intermediate gear;

- a large range of speeds, the speed is proportional to the frequency of the input control pulses.

Figure 1 shows a stepper motor with variable magnetic resistance.

Figure 2 shows a stepper motor with permanent magnets.

Figure 3 shows a hybrid stepper motor.

Figure 4 shows the phases of the windings of a bipolar (a) and unipolar (b), (c) stepper motor.

Figure 5 shows various methods of controlling a stepper motor - a full-step mode with the inclusion of one phase (a), a full-step mode with the inclusion of two phases (b) and a half-step mode (c).

Figure 6 presents a diagram of an electromechanical vibration generator using a serial industrial stepper motor.

Figure 7 shows the option of connecting the phase windings AB and LED of a hybrid stepper motor used as an exciter.

The proposed device is as follows. The electromechanical vibration generator (Fig. 6) contains a stepper motor 1, to the phase windings AB and LED of which control pulses 2 are received. Levers 7, 8, 9 are mounted on the shaft 3 of the motor drive 1 using fasteners, for example, a beam 4, rigidly connected to the motor shaft 3 1, The upper parts of the levers 7, 8, 9 interact with the springs 10, 11, 12, 13. The other ends of the springs are connected to the main body or to an additional body 6, rigidly connected to the main body. ShD 1 shaft, as well as levers 7, 8, 9, are made with the possibility of angular oscillatory movements together with ShD 1 shaft relative to its axis of rotation. The springs 10, 11, 12, 13 are selected for stiffness and are adjusted in length so as to ensure optimal amplitude and frequency of the SH shaft oscillations. This can be done, for example, using the adjusting screws 16, 17, 18, 19. One of such optimal positions is when the amplitude of the rocker arm oscillations is maximum, which corresponds to position 2-2, rotated relative to the initial position 1-1 (Fig. 7 ) The operation of the system with one lever 7 and springs 10 and 11 in pair or levers 8, 9 and springs 12 and 13 in pair, or with other combinations of levers and springs, is not ruled out.

Electromechanical vibration generator operates as follows. When you turn on the SH shaft takes position 1-1 (Fig.7), due to the moment of retention. Using the adjusting screws 16, 17, 18, 19, a new position 2-2 of the shaft is adjusted, corresponding to its rotation by an angle α ₀ , relative to the axis 1-1 (Fig. 7), which provides the maximum amplitude of the rocker arm vibration 4. On the phase windings AB and LED SD 1 receives a control signal 2 in the form of voltage pulses u _AC (t) (Fig. 7), as a result of which, under the influence of changes in the electromagnetic field fluxes Ф _АВ (t) and Ф _СД (t), rotor 15 (Fig. 6) rigidly connected with the shaft 3 ШД, begins a rotational movement around its axis. To control the current position of the ШД shaft, if the control algorithm requires it, a sensor of its angular displacement is used 14. The shaft 3 ШД 1 drives the beam 4 with the levers 7, 8, 9 connected with it. The angular movement of the beam 4 relative to the axis of rotation of the shaft 3 ШД limited by the action of the springs 10, 11, 12, 13, connecting the levers 7, 8, 9 with the housing 6 SH. Under the action of a pulse of the control signal 2, the shaft 3 of the motor drive rotates through an angle α _slave (Fig. 7), deforming the springs 10, 11, 12, 13 (Fig. 6). From the moment the pulse ends to the receipt of a new control signal, the SM rotor under the action of the elastic forces of the springs 10, 11, 12, 13 and the control moment caused by a change in the phase rotation of the stator windings SH 1, if this requires a control algorithm, starts moving in the opposite direction. The moment of completion of the reverse stroke of the shaft 3 ШД 1 and the supply of the next control signal to the phase windings of the stator ШД is determined, if the control algorithm requires it, using the angular position sensor 14 of the shaft 3 ШД 1. Thus, the shaft 3 ШД 1 together with the beam 4 starts make oscillatory movements around its axis. The dynamics of the oscillatory motion of an electromechanical vibration generator depends on the geometric arrangement of the levers 7, 8, 9 and the springs 10, 11, 12, 13 relative to the longitudinal axis 5 of the rocker arm 4 and the axis of rotation of the shaft 3 ШД 1, the stiffness of these springs, as well as the geometric and mass parameters of the elements, associated with the shaft 3 SHD 1, which affect the durability of the nodes SHD 1, and consequently, the entire electromechanical vibration generator.

Claims (2)

1. The causative agent of mechanical vibrations, including a stepper motor, characterized in that the stepper motor is equipped with springs that limit the angle of rotation of the stepper motor under the action of a control pulse supplied to the phase windings of the stepper motor, and return the stepper motor shaft in the opposite direction in the interval between two consecutive control pulses entering the phase windings of the stepper motor. 2. The causative agent of mechanical vibrations according to claim 1, characterized in that it further includes a rocker with a working tool mounted on the shaft of a stepper motor, and a sensor for the angular position of the shaft.

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