CN1031163A - Piezoelectric motors - Google Patents

Abstract

Piezoelectric motors comprise stator 1 and rotor 3.Stator 1 has shell 7 and the radial vibration piezoelectric vibrator 6 that is contained on the shell 7.Vibrator comprises piezoelectric element 9 and at least two push rods 10 of belt electrode 13.One end of each push rod 10 is fixed on the plane of piezoelectric element 9 with minimum degree, makes between piezoelectric element 9 and the push rod 10 and leaves gap 14, and the other end of each push rod 10 withstands on the rotor 3.

Description

Piezoelectric motors

The present invention relates to piezo-electric device, be specifically related to piezoelectric motors.

The present invention can be used as the motor of no deceleration device, carries out the rotation of continuous or discontinuous (stepping).These motor can be used in the actuator of automated system and replace electromagnet, also can be used as the basic driver device of recorder, phonograph, film camera equipment.

Known piezoelectric motors comprise stator and with the rotor of stator frictional fit.Stator has shell and is contained in the piezoelectric vibrator of radial vibration on the shell.Piezoelectric vibrator comprises electroded garden plate-like piezoelectric element (this garden dish is by these electrode perpendicular polarizations) and at least two push rods of installing with rotor coaxial, and an end of each push rod is fixed on the garden cylinder of piezoelectric element, and the other end withstands on the rotor.

In this piezoelectric motors, when needs change its nominal speed, must change the diameter of piezoelectric element.So just can not make piezoelectric element general, that can be used for any speed of piezo electric actuator machine rotor.Therefore, for given piezoelectric element, the speed scope of rotor is limited.

In addition, the firm degree of fixed mandril thickens and strengthens with piezoelectric element, and this has limited the possibility of (for example camera aperture use the power demand of piezoelectric motors when zero load) of reducing consumed power.

The objective of the invention is to make a kind of piezoelectric motors that enlarge rotor speed scope that provide for given piezoelectric element.

Another object of the present invention is to make a kind of piezoelectric motors that guarantee to enlarge its consumed power scope.

The problem that proposes is to solve like this: piezoelectric motors have stator and with the rotor of stator frictional fit, stator has shell and the radial vibration piezoelectric vibrator that is contained on the shell, vibrator comprises the electroded garden plate-like piezoelectric element of installing with rotor coaxial (coil by these electrode perpendicular polarizations in the garden), have two push rods at least, each push rod one end is fixed on the piezoelectric element, and the other end withstands on the rotor.According to the present invention, an end of each push rod is fixed on the plane of piezoelectric element with minimum degree, makes between piezoelectric element and the push rod and leaves the gap.

The present invention can make the piezoelectric motors of a series of consumed power wider range.

The present invention also can make and use the normalization piezoelectric element, and the piezoelectric motors of rotor speed scope and consumed power wide ranges.The present invention can reduce the price of piezoelectric motors, and therefore available its replacement electromagnet also can reduce the workload of making piezoelectric motors as final controlling element.

Set forth the present invention with instantiation and accompanying drawing below, wherein:

Fig. 1 is the sectional arrangement drawing that has the piezoelectric motors of garden cylindrical rotors according to invention, and this rotor is wrapping the push rod that nestles up it;

Fig. 2 represents the profile that piezoelectric motors of the present invention cut along Fig. 1 II-II line;

Fig. 3 a, 3b, 3c represent of the present invention have by push rod encase rotor piezoelectric motors piezoelectric element and be fixed on the push rod of piezoelectric element;

Fig. 3 d, 3e, 3g represent the push rod that has the piezoelectric element of the piezoelectric motors of configuration rotor between push rod and be fixed on piezoelectric element of the present invention;

Fig. 4 represents that the present invention has the piezoelectric motors schematic diagram of the push rod on two planes that are fixed on piezoelectric element, and its rotor is encased by push rod;

Fig. 5 represents to be used for the profile of the low speed piezoelectric motors of the present invention of final controlling element;

Fig. 6 represents to connect with contact method the profile of the high speed piezoelectric motors of the present invention of piezoelectric element;

Fig. 7 represents to have the profile of the piezoelectric motors of the present invention of atresia garden plate-like piezoelectric element.

Referring to Fig. 1, piezoelectric motors comprise on stator 1 and the lead-in wire 2(figure in order to the connection alternating voltage not shown).Stator 1 is the standing part of piezoelectric motors for the product (not shown) that it is installed.The rotor 3 of piezoelectric motors is contained on the stator 1, can rotate in bearing 4, and with detachable connection 5, for example lock washer is fixed on above it, in case its moving axially along oneself.

The stator 1 of piezoelectric motors comprises the piezoelectric vibrator 6 of radial vibration, and the shell 7 of it and stator 1 is a sound insulation, and is fixed on the shell 7.Shell 7 is used for preventing that the piezoelectric vibrator 6 of radial vibration is damaged, and also is for the piezo electric actuator function is fixed on the product by supported hole 8.

The piezoelectric vibrator 6 of radial vibration is an electro-mechanical devices, is used for electric energy is converted to the vibration of piezoelectric vibrator 6 solids, and this vibration mainly in the footpath of the piezoelectric element of rotary body shape upwards.Piezoelectric element is the active part of radial vibration piezoelectric vibrator 6.

The passive part of radial vibration piezoelectric vibrator 6 is different with active part, and it can not become another kind of form to energy from a kind of formal transformation.Push rod 10 and the sound-conducting body 11 that its piezoelectric element 9 is connected belong to the passive part of radial vibration piezoelectric vibrator 6.Four push rods 10 are arranged in this radial vibration device 6.As eliminate the active force of 3 pairs of stators 1 of rotor, push rod 10 is minimum will be with two.When the number of push rod 10 equals 2 and greater than 2 the time (evenly being provided with), make a concerted effort to be approximately equal to zero from what each push rod 10 acted on rotor 3.In this case, push rod 10 is many more, and the rotating torque of rotor 3 is big more, at this moment must increase the supply power voltage of piezoelectric motors simultaneously, and this is below 32 with regard to the quantity that limits push rod 10.Fixedly the one end is on a plane of piezoelectric element 9 with minimum degree for each push rod, and the other end withstands on the rotor 3.

Each push rod 10 is all used resilient the material of leading, and for example steel or bakelite are made, shape such as flat plate.Usually each push rod 10 is all made rectangle.The shape of push rod 10 is allowed change, for example they is made the shape that narrows down gradually to the on-fixed end, or makes them have protuberance, in order to fixed radial vibration piezoelectric vibrator 6, or fixed mandril 10.At this moment, the parameter of piezoelectric motors can not degenerate.

Push rod 10 is to be pressed on the rotor 3 by elasticity own.Therefore, when being installed to rotor 3 on the stator 1, be the not end bending of push rod 10.But, push rod 10 is pressed on the rotor 3, also can be to rotor 3 application of forces on axis direction, for example, utilize the weight of rotor 3 itself or use electromagnet, leaf spring or helical spring (Fig. 1 is not shown).The sound-conducting body 11 that push rod 10 and piezoelectric element 9 couple together, be scolder or the organic hard thing (for example epoxy resin after the polymerization) that has hardened.

In order to produce radial vibration in piezoelectric vibrator 6, piezoelectric element 9 is made the garden plate-like, on the plane of garden dish 12 electrode 13 is arranged.The garden panel surface is the thin topped thing of metal of one deck, and the method for its formation is spray metal, burning infiltration silver or metal is precipitated in chemical solution in a vacuum.Supply voltage (power supply does not draw among Fig. 1) 2 is delivered on the electrode 13 by going between, and lead-in wire 2 is welded on the electrode 13, as shown in Figure 1, perhaps links to each other with electrode with contact method.Push rod 10 is not connected to the part that sound-conducting body 11 hides, but is fixed on the plane of piezoelectric element 9, and push rod 10 can not contact with the electrode 13 of piezoelectric element 8 when gap length should be enough to guarantee to assemble piezoelectric motors.For example, if assembling the time has ten piezoelectric motors, wherein have the push rod 10 of a motor to run into electrode 13, that just should change the structure of this motor, the numerical value in gap 14 is increased be twice.Garden dish 12 is to make with the polycrystalline material with piezoelectric property.To manifest piezoelectric property in the polycrystalline material in order making, to make residual polarization, the process that obtains residual polarization is also named the polarization of material.The material of the piezoelectric element 9 of piezoelectric motors should use the titanate solid solution of lead zirconates to make matrix.

Electrode 13 is to make the material polarization necessary.On these two electrodes, add polarizing voltage.At this moment, the polarised direction of piezoelectric element 9 equates with polarization field intensity vector, promptly perpendicular to the surface of electrode 13.In order in the piezoelectric element of radial vibration piezoelectric vibrator 6, to obtain the radial vibration of piezoelectric motors operating frequency, be suitable for the maximum dimension D that makes piezoelectric element 9 ₁, perhaps diameter difference D ₁-D equals half of radially acoustic vibration wavelength X, and D is the bore dia of garden dish 12 here.Use formula for this reason:

(λ)/2 ≈ (N)/(f)

F is the resonance frequency of radial vibration in the formula; N is when the frequency constant of piezoelectric element 9 materials, and it is relevant with the velocity of sound in this material.

The rotor 3 of piezoelectric motors comprises three parts.First-friction portion 15, it is the ring with garden cylinder or garden conical surface, with push rod 10 frictional fit.Friction portion 15 should be made with the minimum high-abrasive material of surface roughness, to reduce the wearing and tearing of push rod 10.For the very long piezoelectric motors of working life, the mineral pottery that its friction portion aluminium oxide is a matrix, or heat cured plastics for example bakelite make.Friction portion 15 fixedly is fixed on the second portion-sleeve 16 of piezo electric actuator machine rotor 3.Third part-the rotating shaft 17 of piezo electric actuator machine rotor 3 is installed in 16 li in sleeve.Rotating shaft 17 can utilize the detachable connection 5 that tightly suppresses it to be fixed in 4 li rotations of bearing in the axial direction.For working life is not the piezoelectric motors of decisive parameter, the combination of three parts of all of rotor 3 or any two parts, with the material of monoblock for example steel make.

Radial vibration piezoelectric vibrator 6 is fixing by the groove on the shell 7 18 with respect to shell 7, and the end of push rod 10 presses closer in groove.As long as radial vibration piezoelectric vibrator 6 keeps sound insulation with shell 7, use other method, for example, do not change essence of the present invention with elastic gum fixed radial vibration piezoelectric vibrator.In the piezoelectric motors that this paper sets forth, the sound insulation between radial vibration piezoelectric vibrator 6 and the shell 7 is to realize by the packing ring 19 that rubber is done.Improve the working life of piezoelectric motors, damper 20 vibration dampings that push rod 10 utilizes rubber to do.The material of making damper 20 drips on the push rod 10 with liquid (before the polymerization reaction) drops, encases push rod 10, opens along the surface current of electrode 13, after this this material polymerization reaction take place again.

Fig. 2 illustrates the piezoelectric motors top view by II among Fig. 1-II line crosscut.Angle α (Fig. 2) is made of two tangent lines, and tangent line is the tangent line on the push rod surface done by the push rod 10 and the contact point of friction portion 15, and another is the tangent line of the friction portion 15 done by this contact point.If every α value is less than 45 °, decrease in efficiency then.If angle α value is greater than 85 °, the rotating torque of rotor 3 reduces, and this also will cause decrease in efficiency.Angle α should be in 85 ° to the 45 ° scopes less than 90 °.The relation of the speed ω of rotor 3 and rotating torque M and angle α is as follows:

ω～ 1/(cosα) （2）

M～cosα （3）

Angle β constitutes by the tangent line on push rod 10 surfaces of doing at the fixing point of push rod 10 with through the straight line of the rotating shaft of the stiff end of push rod 10 and rotor 3, and it seldom influences the speed ω and the rotating torque M of rotor 3.

At Fig. 3 a, 3b, 3c, 3d, 3e, 3g piezoelectric element is shown and coils the different various situations of 12 centre distances with the garden when the stiff end that be fixed on the push rod 10 above it, the thickness of the side-play amount h of 12 center lines greater than garden dish 12 is coiled in the relative garden of the center line of push rod 10, and this can make push rod 10 do radial displacement.In this case, can be fixed on push rod 10 on the edge of garden dish 12, shown in Fig. 3 a, 3b, 3c, 3g, also can be fixed on the middle body of garden dish 12, shown in Fig. 3 b, 3e.Fixed mandril 10 like this, no matter rotor 3 is encased radial vibration piezoelectric vibrator 6(Fig. 3 a, 3b, the 3c of the low speed piezoelectric motors of push rod 10), perhaps rotor 3 is positioned at radial vibration piezoelectric vibrator 6(Fig. 3 d, 3e, the 3g of the high speed piezoelectric motors in the middle of the push rod 10) all be feasible.When the skew of the fixing point of push rod 10, and the length of push rod 10 can change the diameter of rotor when changing, thereby for the piezoelectric element 9 of certain specification, the speed scope of expansion piezo electric actuator machine rotor 3.In this case, if push rod 10 obviously exceeds the edge of piezoelectric element 9, the damper 20 of available rubber case tubulose is enclosed within its damping of the terminal realization of push rod, shown in Fig. 3 a or 3g.

Fig. 4 illustrates two piezoelectric motors of showing on the planes that push rod 10 is fixed on piezoelectric element 9.This is equivalent to two same radial vibration devices of cutting apart by dotted line are linked together.Push rod 10 is fixed on two surfaces of piezoelectric element 9, is used for increasing the volume of radial vibration piezoelectric vibrator 6, goes up power with this axle that increases piezoelectric motors.

Fig. 5 illustrates the example of the low speed piezoelectric motors of finishing the electromagnet function.Here, by groove 18 and have decorative pattern pad 19 a fixed radial vibrations piezoelectric vibrator 6 of the flange 21 that is placed between the push rod.The removable section 22(of shell 7 is a bearing) rely on the detachable connector 5 of likeness in form nut that flange 21 is pressed onto on the piezoelectric element 9, fix the angle position of radial vibration piezoelectric vibrator 6.Close sleeve 16 and the axle 17 put in a part, the part as shell 7 is cast into plastics.This just might arrange the tooth 23 of gear simultaneously on sleeve 16, with make rotatablely move convert to straight-line eccentric cam 24 and with contact 26 interactional side flanges 25.Side flanges and the state sensor that contacts 26 composition rotors 3.

The example of the high speed piezoelectric motors of rotor 3 between push rod 10 is shown in Fig. 6.Here, shell 7 is surrounded by metallized bakelite dull and stereotyped 27 and metal lid 28 from both sides.The liner 19 that crown cap is done by elastic conducting material, and be electrically connected with an electrode 13 of piezoelectric element 9 by push rod 10.Another electrode 13 is to be pressed in dull and stereotyped 27 metalized surface with the way of contact.Lead-in wire 2 usefulness on dull and stereotyped 27 metalized surface are so that voltage inserts piezoelectric motors, and at this moment, metalized surface is electrically connected with lid 28 by welding.

Fig. 7 illustrates the piezoelectric motors of piezoelectric element 9 likeness in form atresia garden dishes 12.Here, lid 28 is connected with the flat board 27 of shell 7 by flange.Groove 18 on the lid 28 is from radially fixing radial vibration piezoelectric vibrator 6.In the axial direction, it is fixing that radial vibration piezoelectric vibrator 6 relies on the packing ring 19 of likeness in form elastic tape.For fixed rotor 3, prevent to move axially, the axle 17 of rotor 3 has ring-shaped groove, and the annular flange flange 30 of lid 28 is just embedding wherein.

The piezoelectric motors work that this paper proposes is as follows: the voltage of external ac power source 2 is fed to one of the vertical radial vibration resonance frequency of (the external power frequency should equal or approach radial vibration piezoelectric vibrator 6(Fig. 1) on the electrode of piezoelectric element 9 by going between), in piezoelectric element, encourage the radial vibration of indulging.These vibrations are passed to push rod 10 by acoustic conductor 11.Push rod 10 is shifted on the surface of piezoelectric element 9, and therefore, in the fixed point of push rod 10 with piezoelectric element 9, vertically acoustic vibration is converted to horizontal acoustic vibration earlier; Be subjected to the reflex time of push rod 10 ends, transverse vibration converts extensional vibration again to, gets up in 10 li propagation of push rod.(Fig. 3 a) with respect to the skew of the extensional vibration in the piezoelectric element 9 h value in these extensional vibrations.At this moment the part acoustic energy of having changed remains the transverse vibration energy, but most of acoustic energy has become the extensional vibration energy.Select the frequency of alternating-current voltage source, make it to approach the resonance frequency of extensional vibration, can eliminate the influence of transverse vibration piezoelectric motors.In the contact area of push rod 10 and rotor 3,, rotor is rotated in bearing 4 because angle α less than 90 °, can produce the tangential force with respect to rotor 3.This power is passed to axle 17 through sleeve 16.If piezoelectric motors are not fixed, then stator 1 and rotor 3 will move in the other direction.For stator 1 is not rotated, it is fixed on the product by hole 8.Issuable power relies on the element of fixed axis 17 on rotor 3 axis directions in the rotor 3, will rely on dismountable joint 5 equilibriums especially.The rotating torque of the rotor 3 that produces because of tangential force will make radial vibration piezoelectric vibrators 6 rotations in the shell 7, but this will be subjected to stopping of groove 18.In push rod 10 and zone that rotor 3 contacts, except tangential force, also produce alternating force, in push rod 10, encouraged the flexural vibrations of subharmonic formula, promptly frequency is lower than the vibration of piezoelectric motors supply voltage frequency.20 pairs of damping flexural vibrations of damper effect is very big, because the elasticity of push rod bending flexibility and damper 20 is comparable.Therefore, damper 20 does not counteract the extensional vibration of push rod 10, and but can eliminate had negative interaction and can add the self-excitation of the subharmonic of very noisy the piezoelectric motors life-span.When push rod 10 contacted with electrode 13, push rod 10 promptly took place intermittently to contact with piezoelectric element 9, and it is unstable that the extensional vibration in the push rod 10 becomes, and produced the parasitic subharmonic oscillation that causes efficient sharply to descend.In order to eliminate this phenomenon, when push rod 10 is installed, reserve gap 14 with respect to piezoelectric element 9 surfaces.When selecting gap 14 big or small, make that under bump and oscillating load effect and under Temperature Influence, the surface of push rod 10 and piezoelectric element 9 does not have Mechanical Contact.Usually gap 14 is taken in 0.2 millimeter to the 0.3 millimeter scope, and along with the size of radial vibration piezoelectric vibrator 6 strengthens and increases.If these gap 14 values are less than 0.2 millimeter, then piezoelectric motors are subjected to the extraneous vibration load and do the time spent, have Mechanical Contact between push rod 10 and the piezoelectric element 9, and this can make noise strengthen.If these gap 14 values are greater than 0.3 millimeter, then efficient will descend.

If the end of the fixing point of push rod 10 along radius from piezoelectric element shifted to the other end, the excitation mechanism of extensional vibration is constant in the push rod 10.At this moment, as push rod 10 around fixing point Rotate 180 °, the phase change of extensional vibration, but this does not influence, for example, the efficient of piezoelectric motors, if push rod 10 is contained in the two sides (Fig. 4) of piezoelectric element 9, the work of piezoelectric motors is constant.Push rod 10 is contained on two planes of piezoelectric element 9, and the volume of piezoelectric element 9 can increase to twice, and increases the power of piezoelectric motors thus, meanwhile, will enlarge the scope of its consumed power.

Push rod 10 is fixed on the plane of piezoelectric element 9, might change the diameter of rotor 3, and needn't change the size of piezoelectric element 9 on a large scale.This just might broadening uses the speed scope of the piezo electric actuator machine rotor 3 of given piezoelectric element 9.In this case, the fastness that push rod 10 is connected with piezoelectric element 9 and the thickness of piezoelectric element 9 are irrelevant, thus the desirable arbitrarily little value of the thickness of piezoelectric element 9.Can reduce the consumed power of supply power voltage and piezoelectric motors thus greatly, enlarge the scope of piezoelectric motors consumed power, thereby enlarge its application.When push rod 10 is installed, reserve gap 14, can ensure the ability to work of piezoelectric motors, eliminate noise and avoid decrease in efficiency with respect to piezoelectric element 9, thus the power bracket of guaranteeing to enlarge the speed scope of rotor 3 and enlarging piezoelectric motors.

Make the piezoelectric motors (Fig. 5) that have the external rotor 3 that encases push rod 10, can obtain sizable rotating torque, this moment will convert longitudinal force to by eccentric cam 24.This motor is the torque type piezoelectric motors, and they are equipped with the such end switch of side flange 25, interacts to 26 with contacting.This motor can be used to replace electromagnet.The piezoelectric motors that tooth 23 is housed can be used as the low speed transmission device.

The normal high speed piezoelectric motors that use in tape transport.In this motor, by lid 28(Fig. 6) and packing ring 19, and rely on electrode 13 to conduct electricity with direct contact of the coating metal layer of flat board 27.

Piezoelectric element 9 is the atresia garden and coils the piezoelectric motors of 12 shapes (Fig. 7) and can be used in the toy for children.Owing to have the shape of the lid 28 of flange 29 to be convenient to assemble rapidly stator 1 and rotor 3, also because annular ditch groove and collar flange 30 can make that the structure of motor is very simple along axis direction fixed rotor 3.

Therefore, the present invention gives regularly at piezoelectric element 9, can enlarge the speed scope of rotor 3, and can enlarge the consumed power scope of piezoelectric motors.

Claims (1)

1. Piezoelectric motors comprise stator 1 and with the rotor 3 of stator 1 frictional fit.Stator has shell 7, and the piezoelectric vibrator 6 of radial vibration is housed on shell 7.Piezoelectric vibrator comprises the piezoelectric element 9 and the electrode 13 of disk 12 shapes of installing with rotor coaxial, piezoelectric element is by electrode 13 perpendicular polarizations, also have two push rods 10 at least, one end of each push rod all is fixed on the piezoelectric element 9, and the other end withstands on the rotor 3, its characteristics are that an end of each push rod 10 is fixed on the plane of piezoelectric element 9 with minimum degree, makes between piezoelectric element 9 and the push rod 10 and leaves gap 14.

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