RU2295396C2 - Electromechanical adjustable vibrator - Google Patents

Abstract

FIELD: vibrating technology; electromechanical adjustable vibrators (vibration exciters) used in construction engineering, manufacture of building material.

SUBSTANCE: proposed electromechanical adjustable vibrator with two magnitudes of static moment which may be changed over in the course of operation is provided with drive shaft at variable rotational frequency, unbalance secured on this shaft, movable unbalance mounted eccentrically relative to shaft and limiting stop. Vibrator is supplied with power through frequency converter. Angle between straight line drawn through axis of rotation of eccentric and geometric axis of shaft and straight line connecting the axis of rotation of eccentric and center of gravity of movable unbalance ranges from 5° to 10° opposite to direction of shaft rotation. Shift to any magnitude of static moment by operator's command or by programmer's command is performed due to forces of inertia (dynamic moment) arising due to abrupt acceleration and deceleration of drive shaft.

EFFECT: extended capabilities of control of production process; enhanced reliability.

3 cl, 7 dwg

Description

The invention relates to vibration technology, namely to electromechanical centrifugal inertial vibrators (vibration exciters) used in construction, in the production of building materials and other industries.

Inertial centrifugal vibrators with unbalances are simple, reliable, relatively inexpensive and are widely used for vibration processing.

We agree to consider the device as a whole as an adjustable vibrator, including the electric motor and the frequency converter, when it is available, and the vibration exciter as part of a vibrator with rotating unbalances that directly creates vibrations; the electric motor, if the unbalances are fixed on its shaft, can be structurally attributed to the vibration exciter.

Centrifugal driving (disturbing) force F _in = k · m · R · n ² = k · M _st · n ² , where k is the coefficient of proportionality, depending on the choice of units; m is the mass of unbalance; R is the radius of the center of gravity of the unbalance; n is the rotation frequency; M _article = m · R is the static moment of unbalance.

For a vibration exciter with a continuous unbalance M _st = Const, the characteristic F _in (n) = k · m · R · n ^{2 is} represented by a parabola, the maximum speed and driving force are limited by the combination (n _max , F _{in max} ) according to the conditions of bearing durability.

In recent decades, the requirements for vibrators have increased; From the point of view of vibration processing efficiency, a vibrator (vibration exciter) with smooth independent adjustment of the rotational speed and driving force (or static moment) within the required technological limits could be considered ideal according to the optimal program.

With the advent of semiconductor frequency converters on the market, speed adjustment is not difficult and corresponds to the state of the art.

Separate partial solutions to the problem of regulating the static moment are known, for example, some vibrators of the Yaroslavl factory “Red Mayak” and foreign firms are equipped with composite unbalances; in them the value of the static moment is set by a preliminary rearrangement of the stops (analog).

The advantage of this solution should be attributed to almost the previous dimensions of the unbalance, which allows you to upgrade existing types of vibrators and adapt them to work with frequency converters.

Disadvantages - minimal adjusting capabilities, as the work takes place on one characteristic F _in (n), in addition, the rearrangement of the stops requires stopping and partial disassembly of the vibrator, which increases labor costs and reduces productivity.

Known electromechanical adjustable vibration exciter according to JP 2311619, an abstract (prototype), comprising a variable speed drive shaft fixed on the shaft (fixed) unbalance, movable unbalance mounted eccentrically relative to the shaft, counteracting spring and adjustable stops.

In this vibration exciter, when the set rotation frequency is reached, the eccentric component of the centrifugal force overcomes the spring counteraction force and puts the movable unbalance into the mismatched position, thereby reducing the value of the static moment. Adjustment of the force of operation of the spring is carried out by preliminary rearrangement of the stops in the off state.

The characteristic F _in (n) for such a vibration exciter consists of two adjacent parabolic sections F _in1 (n) and F _in2 (n):

where n is the current value of the speed;

n _lane - speed when switching;

n _max - the maximum allowable speed;

M _st1 - large static moment;

M _st2 - small static moment.

Work at low speed n <n _lane with low M _st2 and at high speed n> n _lane with large M _st1 for the prototype is fundamentally impossible. The first circumstance, apparently, does not matter, the second circumstance is a functional disadvantage of the prototype because for technological reasons it often requires a forced mode with short-term overload of bearings, which is unattainable in the prototype.

The main structural drawback of the prototype is the presence of a spring:

- the spring is an unstable and unreliable link in conditions of vibration alternating loads;

- improving the reliability of the spring is possible due to the reduction of mechanical stresses in it, but at the same time the dimensions and metal consumption of the structure increase;

- in the unbalanced compartment of mass-produced vibrators, for example, type IV, there is no free space for installing an opposing spring between unbalances, and the spring version requires an increase in size, which does not allow upgrading existing vibrators and does not suit a number of consumers, thereby reducing competitiveness.

The task of creating the invention can be divided into two parts: functional and design.

The functionally claimed vibrator has expanded process control capabilities compared to the prototype, namely it provides the option of working with any of two, large or small, static moment value, regardless of the rotational speed, and translating the moving unbalance in the process of working on command operator or software device at the desired point in time, i.e. flexible management.

Structurally, the problem is solved in the dimensions of serial vibrators without increasing their metal consumption and without the use of springs that reduce reliability due to the use of inertia forces (dynamic moment) arising from sudden acceleration and braking of the motor shaft, i.e. in principle, the position of the moving unbalance is controlled by pulses of positive and negative angular acceleration of the shaft.

The implementation of the principle required the mutual constructive adaptation of the links of the vibrator for their coordinated joint work; The problem was solved without major alterations on the basis of serial vibrators, which creates favorable conditions for the modernization of manufactured and in-service unregulated vibrators by adding frequency converters and replacing unbalanced units.

The essence of the invention lies in the fact that inertial forces (dynamic moment) arising from a sharp acceleration and braking of the motor shaft are used to transfer the moving unbalance from a position with a large static moment (agreed) to a position with a small static moment (inconsistent) e. switching is controlled by pulses of positive and negative angular acceleration of the shaft.

To obtain impulses of angular acceleration of the shaft, the asynchronous drive electric motor is powered from an adjustable frequency converter, made with the possibility of a sharp change in the frequency and amplitude of the output voltage, the frequency converter is controlled by an operator or a software device.

The vibrator operation cycle consists of the following phases:

- “easy” start-up, when only a fixed unbalance comes into motion and, having made more than half a revolution, comes into contact with a moving unbalance;

- fixing the moving unbalance in an agreed position;

- work with a large static moment;

- transfer of the moving unbalance to the mismatched position by a pulse of negative acceleration;

- keeping it in this state;

- work with a small static moment;

- braking by a pulse of negative angular acceleration;

- transfer of the moving unbalance to the position for "easy" start;

- stop.

It is known from the prior art (see Pat. RU 2184623) that during rotation an eccentric develops a setting moment M _ue , which tends to set the center of gravity of the eccentric in a position with a radius R _max farthest from the axis of rotation.

The theoretical analysis performed by the authors revealed some features of the eccentric mechanism, which, according to the applicant, do not follow from the prior art:

- at the smallest distance of the center of gravity of the eccentric from the axis of rotation O equal to R _min , the eccentric moment setting is zero;

- the state of the eccentric at R _min is unstable, the slightest deviation from it causes the appearance of M _ue , aimed at a further increase in this deviation;

- when the center of gravity passes through a straight line connecting the axis of the eccentric O _e and the axis of rotation of the shaft O (neutral NN ′), the moment M _ue changes sign; the direction of rotation of the shaft is taken as positive, and the opposite - as negative.

The identified features of the eccentric are the basis of the controlled locking unit that holds the movable unbalance in the combined position.

When starting, the emphasis on the fixed unbalance comes into contact with the movable unbalance with a negative mismatch angle of 5 ° ... 10 °, negative M _ue presses the movable unbalance against the emphasis.

Under the influence of a negative acceleration command pulse, the fixed unbalance together with the motor shaft is braked, the mobile unbalance by inertia goes over the neutral NN ′, the setting moment M _u changes its sign from negative to positive, and the mobile unbalance rushes to a steady state with R _max , reaches it; in this position, work is carried out with a small value of M _st2 until the next command pulse for braking, which translates the moving unbalance to the position of preparation for an “easy” start, then the engine stops.

The invention is illustrated by drawings, where Fig. 1 shows a functional structural diagram of a vibrator, Fig. 2 shows a longitudinal section of a vibration exciter, in Fig. 3 - unbalances are in a coordinated position (large static moment), in Fig. 4 - unbalances are mismatched ( small static moment), figure 5 illustrates the change in speed over time, figure 6 shows the pulses of positive and negative acceleration during the cycle, figure 7 shows a cyclogram of the vibrator in the coordinates "speed" - "forced the power of it. "

The vibrator comprises a program-command device 1, a controlled frequency converter 2, an electric motor 3 with a shaft 4, to which, for example, a keyed unbalance is connected via keyway 5. The end of the drive shaft 4 has an eccentric shank 8 on which a movable unbalance 6 is mounted, for example, using a needle bearing 9. On the flat surface of the fixed unbalance 5, a composite stop (7, 10, 12) is fixed, consisting of a pin (stud) 12, a shock-absorbing element 10 and the outer sleeve 7.

The outer radius of the sleeve 7 and the depth of the curvilinear recess on the side surface of the unbalance 6 in contact with the abutment are selected in such a way (distance O ₃ -CT ₂ ) so that at the beginning of the joint movement of the unbalances a mismatch angle of 5 ° ... 10 ° against the direction of rotation is established.

The software-command device (PCU) 1 issues real-time commands for all phases of the vibrator operation: start-up, acceleration, operation with a large value of the static moment, translation and operation of the moving unbalance in the position of a small static moment, braking with preparation of the subsequent “easy” start-up, engine stop 3.

PKU can be mounted in a separate case, or be combined with a frequency converter 2.

Adjustable frequency converter (RPC) 2 is powered from an AC network with voltage U ₁ and frequency f ₁ ; the converter is capable of drastically changing the output frequency (f ₂ ± Δf ₂ ) and voltage (U ₂ ± ΔfU ₂ ) due to which the asynchronous drive motor 3 generates control pulses of positive and negative angular acceleration of the shaft 4 in the form (n ₂ ± Δn), which used to translate a moving unbalance from one position to another.

The vibrator works on the next cycle. After turning on the RFC at the command of the operator or the control panel, the voltage U ₂ appears at the RPC output with a frequency of f ₂ , the engine starts rotation with positive acceleration, (see section o-a in FIGS. 5, 6, 7). The fixed eccentric weight 5 stop 7 in contact with the recess in the side surface of the movable unbalanced mass 6 and brings it in the joint motion, the angle between a straight line drawn through the center of gravity TST2 movable unbalanced mass and the axis O _e of the eccentric, and a straight line passing through the axis O of the drive shaft 4 and the axis O _{e of the} eccentric 8, is 5 ° ... 10 ° (mismatch angle). The dynamic moment generated as a result of acceleration presses the moving unbalance 6 against the stop 7, as the rotational speed increases, the centrifugal force develops, the eccentric component of which, due to the mismatch angle of 5 ° ... 10 ° (setting the eccentric moment), also presses the moving unbalance 6 against the stop 7 ; after the acceleration is completed, the angular acceleration is zero (point a of FIGS. 5, 6, 7), the dynamic moment disappears, but the setting eccentric moment continues to hold the unbalances 5, 6 in a combined state.

The next phase (section a-b of FIGS. 5, 6, 7) is work with a large value of the static moment in accordance with the technological program.

To translate the moving unbalance into an inconsistent position (small static moment) at the command of the operator or the control panel, the output frequency of the converter f ₂ and voltage U _{2 are} sharply reduced, the negative angular acceleration pulse slows down the rotation of the shaft, the moving unbalance by inertia passes through the neutral O-O _e , which sets the eccentric the moment changes sign and advances the moving unbalance to a stable state at the greatest distance from the axis of rotation (bc in Figs. 5, 6, 7).

This is followed by acceleration to the required speed (section c-d), and the phase of operation with a small static moment (section d-e).

Engine braking (efgo section) at the command of the control panel is due to a decrease in the output voltage U ₂ and frequency f _{2 of} converter 2.

Due to negative acceleration, the rotation frequency will drop, at the point f the dynamic moment overcomes the setting eccentric moment, the inertia of the moving unbalance 6 is pushed by its front face on the stop 7 from the side opposite to the one from which the movement began, point g. After stopping by gravity, both unbalances 5, 6 occupy the lowest position for an “easy” start, point o.

The next cycle begins with the fact that only a fixed unbalance begins to rotate (the so-called “easy” start).

Having made about 3/4 of a revolution, the fixed unbalance 5 with its emphasis enters the recess on the moving unbalance, and then the cycle discussed above occurs. To mitigate shock loads emphasis 7 is equipped with a shock absorbing element 10.

Vibrators of the proposed design are made at the Yaroslavl factory “Red Mayak”, have been tested, a small series is in operation at one of the concrete products plants; Thus, the industrial applicability of this technical solution is obvious.

Claims (3)

1. Electromechanical adjustable vibrator with two values of the static moment and the ability to switch them during operation, comprising a drive shaft with a variable speed, an unbalance fixed to the drive shaft, a movable unbalance eccentrically relative to the shaft and a limit stop, characterized in that the vibrator is powered through the frequency converter, the moving unbalance is made with the possibility of translating into any of two values of the static moment at the command of the operator or frame device due to inertia forces (dynamic moment) arising due to sharp acceleration and braking of the drive shaft, as well as with the possibility of holding in the position of a large static moment by contact with the stop mounted on a fixed unbalance, and the possibility of holding in the position of a small static moment only centrifugal force, the angle between the straight line drawn through the axis of rotation of the eccentric and the geometric axis of the shaft, and the straight line connecting the axis of rotation of the eccentric and the center the gravity of the moving unbalance is 5 ... 10 ° against the direction of rotation of the shaft. 2. Electromechanical adjustable vibrator according to claim 1, characterized in that the emphasis is equipped with a shock absorbing element. 3. Electromechanical adjustable vibrator according to claim 1 or 2, characterized in that the static moment of the moving unbalance is less than the static moment of the fixed unbalance by 1.5-3 times.

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