DE102014225584A1 - Piezoelectric linear motor - Google Patents

Abstract

The invention relates to a piezoelectric linear motor and a method for operating such a linear motor. The piezoelectric linear motor (01) comprises an axially extending support (02) with two opposite ends, wherein at a first end a fastening ring (03) is arranged. It further comprises a first and a second elastic claw (04, 05) each having an annular base body (07) with an opening (08) in the periphery, a piezo stack (10, 11), which at electrical activation at the ends of the body ( 07) imprint tangential forces. The first elastic claw (04) is arranged at the second end of the carrier (02) axially immovable to this and the second elastic claw (05) is axially slidably positioned between the fastening ring (03) and the first elastic claw (04). A rod (14) which extends through the annular base body (07 ) of the first and / or second elastic claw (04, 05) is held. A group of third piezo stacks (15) is disposed between first and second elastic claws (04, 05) and when actuated electrically generates an axial displacement force between the two jaws.

Description

The present invention relates to a piezoelectric linear motor.

The motor according to the invention can be used for example in leveling systems for motor vehicles. Leveling systems are used to adjust the vehicle floor clearance and to compensate for different loading situations.

From the prior art piezoelectric linear motors for various applications are known, in particular for the realization of small adjustment paths and when exposed to small loads. The previously known motors are usually relatively expensive, because of the time-consuming production technologies required for their production.

In the US 8,217,553 is a linear motor with a threaded passage element, a threaded shaft and a drive system described. The drive system includes at least two components with piezoelectric layers that vibrate the element, allowing the threaded shaft to rotate and translate along the axis of rotation and apply an axial force to a load. Areas of application are autofocus systems for cameras.

The DE 10 2008 041 452 A1 relates to a piezoelectric drive device for adjusting a vehicle component, such as a vehicle window. The drive device comprises at least two effective masses, which are associated with friction means. About the friction means, the masses are based on a guide rail. The two masses are connected to one another via a piezo actuator designed as a piezo stack and can be adjusted relative to one another by means of a piezoactuator along the guide rail.

The DE 44 08 618 B4 shows an adjustment with a piezo drive especially for precision mechanical-optical devices. The adjusting device comprises at least one piezoelectric vibrator, which undergoes a change in length by applying differently controlled electrical voltages and alternately passes through its free end with an output element in operative connection. With existing active connection, a motion is transmitted to the output element. The piezoelectric vibrator has two actuators, which are arranged in parallel next to one another and behind one another in the drive direction and are fixedly connected to one another to form a bimorph element.

From the prior art leveling systems for adjusting the ground clearance in motor vehicles are known. The EP 0 616 412 A1 shows a vehicle comprising a sprung mass and an unsprung mass interconnected via a suspension and a controllable electromechanical transducer for movement along a path for providing a controllable force between the sprung and unsprung masses and a controller for controlling the transducer in response to a control signal. With a constant control signal, a constant force is maintained between the unsprung and sprung mass, which is independent of position or velocity. The electromechanical converter may be a multi-pole motor.

The WO 2012/024596 A1 describes a mechanical actuator comprising a motor, a screw assembly having a housing, a threaded spindle shaft disposed in the housing and rotatable by the motor by means of a threaded nut, and an extension tube connected to the threaded spindle shaft which are moved by rotation of the threaded spindle shaft between an extended and a retracted position can. The actuator further comprises a bearing assembly for supporting the threaded spindle shaft and a lubrication system for lubricating the screw assembly and bearing assembly.

The object of the present invention is to provide a piezoelectric linear motor which can be locked in intermediate positions, has a compact design and operates reliably under severe conditions such as high temperature fluctuations, dust, water, vibration, impact. Furthermore, a method for operating such a linear motor is to be made available.

To achieve the object according to the invention is a piezoelectric linear motor according to the appended claim. 1

The piezoelectric linear motor according to the invention comprises a support with angled ends. At one end of the carrier, a fastening ring is arranged. The piezoelectric linear motor further comprises a first and a second elastic claw. Both jaws each have an annular body not closed in the circumferential direction with a slot or an opening. In the opening, a piezo stack is arranged, which bears against the ends of the base body, wherein the first elastic claw, a first piezo stack and the second elastic claw, a second piezo stack is associated. The claws furthermore have a first spring element for preloading the basic body with a spring force. The first elastic claw is disposed at the second end of the carrier. The second elastic claw is located between the fastening ring and the first elastic claw. Between the fastening ring and the second elastic claw, a second spring element for preloading the second elastic claw is arranged with a spring force. By fastening ring, elastic claws and second spring element extends a rod which is supported in the de-energized state of the first and / or second piezo stack by the annular base body of the first and / or second elastic claw. The mounting ring has a slightly larger diameter than the rod and serves to guide the rod. Between the first and second elastic claws, a group of third piezo stacks are mounted, which are supported on the first elastic claw and abut the second elastic claw. An energy source serves to supply the first and second piezoelectric stacks with electrical energy.

The piezoelectric linear motor according to the invention is characterized by a simple and compact design, whereby it has a high reliability even under harsh environmental conditions. It can be easily positioned away from the power source. For power supply of the piezo stack only appropriate cables are needed.

In the de-energized state of the first and second piezo stack is due to the mechanical bias an interference fit between the elastic claws and the rod, d. H. The rod is held securely by the elastic claws. By energizing the piezoelectric stack arranged in the opening of the elastic claws, the piezoelectric stacks expand, whereby a force is exerted on the ends of the annular basic body, which expands the basic body and thus releases the press fit between the elastic claws and the rod. In modified versions, of course, the reverse operation would be conceivable d. H. in the de-energized state, the claws are widened and in the energized state, the press fit is made to the rod.

To move the rod, the first and second piezo stacks are alternately energized. In addition, the third piezo stack must also be energized at the appropriate time. The distance traveled during a lifting displacement of the rod is determined by the stroke of the third piezo stack. When lowering the distance traveled displacement of the rod is also determined by the stroke of the third piezo stack in a force acting against the lowering direction. By lowering the voltage used to charge the third piezo stack, the displacement travel of the rod that is traveled during a single lifting or lowering operation can be reduced, thereby requiring more lifting or lowering operations to fully raise or lower the rod. Adequately, the voltage used to charge the third piezo stack can be increased, thereby requiring less lifting or lowering operations. Thus, with the piezoelectric linear motor according to the invention, multi-stage lifting or lowering operations can be realized with little effort.

According to an advantageous embodiment, fastening ring and first elastic claw are integrally formed on the ends of the carrier, whereby a low-cost production is made possible.

In an advantageous embodiment extends from the opening of the main body of the elastic claws on both sides in each case an edge to the outside. The first spring element acts on the edges to fix the elastic claws on the rod.

For the first spring element has a training as horseshoe spring proved to be advantageous. The second spring element is preferably a spiral spring.

It has proved to be advantageous if the piezoelectric linear motor comprises a microcontroller for controlling the current supplied to the piezo stack. In this way, the current supplied to the piezo stack can be adjusted with little effort, depending on the respective requirements.

The piezoelectric linear motor according to the invention is preferably part of a leveling system for adjusting the vehicle floor clearance of a motor vehicle. However, it can readily be used in other fields of application. It would be conceivable, for example, the application in mining, where the linear motor could be used in chassis of drilling equipment.

A method for operating a piezoelectric linear motor according to claim 8 or 9 is also used to achieve the object according to the invention. The method according to claim 8 serves for carrying out a lifting operation and comprises the following steps. First, a release of the first elastic claw from the rod by energizing the first piezo stack occurs. Subsequently, the third piezo stacks are energized. As a result, the third piezoelectric stacks expand and thus exert a force acting against the spring force of the second spring element on the second elastic claw. Since a press fit exists between the second elastic claw and the rod, the second elastic claw and the rod move together against the direction of action of the spring force of the second spring member. The distance traveled by the rod and the second elastic claw displacement depends on the stroke the third piezostack. Subsequently, the first elastic claw is fixed to the rod by the energization of the first piezo stack is terminated. There is now a release of the second elastic claw of the rod by energizing the second piezo stack. The energization of the third piezo stack is then terminated, whereby the second elastic claw is returned by means of second spring element to its original position. Finally, the interference fit between the second elastic claw and rod is restored by the energization of the second piezo stack is terminated. The described steps can be repeated several times to allow a stepwise and complete lifting of the rod.

The method according to claim 9 is used to perform a lowering operation, wherein a release force acting in the lowering direction, the first and second elastic claw of the rod is carried out by energizing the first and second piezo stack. The rod would in this case completely lower due to the force acting. If there is a force acting counter to the lowering direction, the steps described below are performed during the lowering process. In a first step, the second elastic claw is released by energizing the second piezo stack from the rod. Subsequently, the third piezo stack are energized, whereby the second elastic claw is moved against the spring force of the second spring element. The second elastic claw is then determined by the energization of the associated second piezo stack is terminated. There is now a release of the first elastic claw of the rod by energizing the first piezo stack. The energization of the third piezo stack is then terminated, whereby the rod is moved together with the second elastic claw due to the force acting by the second spring element spring force. Finally, the press fit between the first elastic claw and rod is restored by the energization of the first piezo stack is terminated. The described steps can be repeated several times to allow a gradual and complete lowering of the rod.

Preferred embodiments of the invention will be explained in more detail with reference to the accompanying figures. Show it:

1 a perspective view of a piezoelectric linear motor according to the invention;

2 a perspective view of a carrier with elastic claws and mounting ring;

3 a tabular overview with a Bestromungsschema the piezo stack during a lifting operation;

4 a tabular overview with a Bestromungsschema the piezo stack during a lowering process;

5 a schematic diagram of an electrical supply circuit for the piezoelectric linear motor according to the invention.

The structure of the piezoelectric linear motor according to the invention will be described below with reference to FIG 1 and 2 described. An inventive piezoelectric linear motor 01 includes a carrier 02 with angled ends. At a first end of the carrier 02 is a fixing ring 03 arranged. The second end of the carrier 02 has a first elastic claw 04 on. The fastening ring 03 and the first elastic claw are immovably positioned relative to each other, preferably integral with the carrier 02 educated. A second elastic claw 05 is between mounting ring 03 and first elastic claw 04 arranged, but without firm connection with the carrier. The fastening ring 03 and the claws 04 . 05 are aligned axially to each other, so that their centers lie on a common longitudinal axis.

Both elastic claws 04 . 05 are adequately structured. They have an annular body 07 Made of elastic material with an opening 08 , By impressing a tangential adjusting force, the width of the opening can be changed in an elastic range, whereby the clear cross section of the annular claw changes. If the impressed adjusting force is omitted, the claw returns to its resting form due to an inherent or impressed spring force.

In the illustrated embodiment extend from the opening 08 edges on both sides 09 outward. In the opening 08 a piezo stack is arranged, wherein the first elastic claw 04 a first piezo stack 10 and the second elastic claw 05 a second piezo stack 11 assigned. This piezostack 10 . 11 lies on the edges 09 of the basic body 07 at. With the edges 09 is a first spring element 12 operatively connected. The first spring element 12 is designed as a horseshoe spring and imprints a likewise tangentially attacking restoring force.

Between mounting ring 03 and second elastic claw 05 is a second, designed as a spiral spring spring element 13 arranged. The second spring element 13 is used to preload the second elastic claw 05 with a spring force in the axial direction. By fastening ring 03 . elastic claws 04 . 05 and second spring element 13 extends in the axial direction of a rod 14 , In the de-energized state of the first and second piezo stack 10 . 11 There is a press connection between the elastic claws 04 . 05 and the pole 14 , The fastening ring 03 has a slightly larger inner diameter than the rod 14 on and serves to guide the rod 14 ,

Between first and second elastic claw 04 . 05 is a group of third piezostacks 15 arranged. The third piezostack 15 are arranged circumferentially distributed. They are at the first elastic claw 04 held and lie on the second elastic claw 05 at. For energy supply of the piezo stack 10 . 11 . 15 serves an energy source 17 (please refer 5 ). The entire assembly may be enclosed by a housing (not shown).

The piezoelectric linear motor according to the invention works as follows. First, the running during a lifting process steps are explained. The first piezostack 10 is energized. As a result, the first piezo stack expands 10 out, whereby a force against the force of the first spring element 12 on the edges 09 of the annular base body 07 the first elastic claw 04 is exercised. The main body 07 Expands, causing the previously existing interference fit between rod 14 and basic body 07 will be annulled. The first elastic claw 04 is now solved. The pole 14 only becomes of the second elastic claw 05 held.

In a second step, the third piezostack becomes 15 energized. The third piezostack 15 expand. As a result, a force which counteracts the spring force of the second spring element 13 acts on the second elastic claw 05 exercised. Because second elastic claw 05 and rod 14 are firmly connected to each other, move second elastic claw 05 and rod 14 together against the spring force of the second spring element 13 up. The distance traveled thereby corresponds to the stroke of the third piezo stack 15 ,

In the next step, the first elastic claw becomes 04 At the rod 14 set by the energization of the first piezo stack 10 is ended. As a result, the first piezo stack stretches 10 together again. The annular body 07 the first elastic claw 04 is by means of the first spring element 12 , which at the edges 09 of the basic body 07 attacks, to the pole 14 pressed. The first elastic claw 04 is now fixed again, ie axially immovable on the rod 14 created. The pole 14 is made by first and second elastic claw 04 . 05 held.

Hereinafter, the second elastic claw becomes 05 by energizing the second piezo stack 11 off the rack 14 solved. The pole 14 only becomes of the first elastic claw 04 held. Thereafter, the energization of the third piezo stack 15 completed. This pulls the third piezo stack 15 together again. The second elastic claw 05 is by means of the second spring element 13 led back to their starting position. Finally, the second elastic claw 05 back on the pole 14 set by the energization of the second piezo stack 11 is ended. The pole 14 gets back from both elastic claws 04 . 05 held.

By repeatedly repeating the described method steps, the rod 14 be raised gradually. By lowering the to load the third piezo stack 15 Serving voltage can be reduced during each stroke covered displacement, creating more lifting operations for complete lifting of the rod 14 needed. Conversely, by lifting the to load the third piezo stack 15 serving voltage of the opposite effect can be achieved, ie the distance traveled during a stroke displacement of the rod 14 would increase.

The lowering process will be explained below. First of all, a distinction must be made as to whether a force acting in the lowering direction is present, for example a weight force in leveling systems. In this case, first and second elastic claws become 04 . 05 solved, whereupon the pole 14 completely lowered as a result of the external force acting on it.

If there is a force acting counter to the desired lowering direction, the steps described below are carried out. In a first step, the second piezostack becomes 11 the second elastic claw 05 energized, causing the second elastic claw 05 off the rack 14 solves. The pole 14 only becomes of the first elastic claw 04 held. The third piezostack 15 are now energized and expand as a result. As a result, the second elastic claw moves 05 against the spring force of the second spring element 13 , The second elastic claw 05 is terminated by termination of the energization of the second piezo stack 11 back on the pole 14 established. The pole 14 is thus again from both elastic claws 04 . 05 held. Following this, the first elastic claw becomes 04 by energizing the first piezo stack 10 off the rack 14 solved. The pole 14 Now only the second elastic claw becomes 05 held. There is now a termination of the energization of the third piezo stack 15 , This causes the rod to move 14 together with the second elastic claw 05 due to the second spring element 13 acting spring force down. Below is the energization of the first piezo stack 10 the first elastic claw 04 finished, making this back on the pole 14 is applied. The pole 14 gets back from both elastic claws 04 . 05 held.

By repeatedly repeating the described method steps, the rod 14 gradually lowered. Of course, also applies to the lowering process, that by lowering the loading of the third piezo stack 15 serving voltage of the distance traveled during the individual lowering operations displacement can be reduced, whereby more lowering operations for complete lowering of the rod 14 needed. Conversely, by lifting the to load the third piezo stack 15 serving voltage of the opposite effect can be achieved, ie the distance traveled during a lowering operation displacement of the rod 14 would increase.

3 shows a tabular overview with a Bestromungsschema the piezo stack during a lifting process. While status "0" no energization of the respective piezo stack 10 . 11 . 15 takes place, the current status is "1".

4 shows a tabular overview with a Bestromungsschema the piezo stack during a lowering process.

5 shows an electrical supply circuit for the piezoelectric linear motor according to the invention. The piezostacks 10 . 11 . 15 be from an energy source 17 supplied with electrical energy. Because the piezostack 10 . 11 . 15 need high voltages is to the power source 17 a voltage amplifier 18 connected. The power is through a microcontroller 19 and a series of gateways a, b, c controlled.

LIST OF REFERENCE NUMBERS

01

 piezoelectric linear motor

02

 carrier

03

 fixing ring

04

 first elastic claw

05

 second elastic claw

06

07

 annular body

08

 opening

09

 edge

10

 first piezo stack of the first elastic claw

11

 second piezo stack of the second elastic claw

12

 first spring element

13

 second spring element

14

 pole

15

 third piezo stack

16

17

 energy

18

 voltage amplifier

19

 microcontroller

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 8217553 [0004]
• DE 102008041452 A1 [0005]
• DE 4408618 B4 [0006]
• EP 0616412 A1 [0007]
• WO 2012/024596 A1 [0008]

Claims (10)

Piezoelectric linear motor ( 01 ) comprising: an axially extending support ( 02 ) having two opposite ends, wherein at a first end a fastening ring ( 03 ), a first and a second elastic claw ( 04 . 05 ) each having - an annular body ( 07 ) with an opening ( 08 ) in scope, - a piezo stack ( 10 . 11 ), which upon electrical activation to the ends of the body ( 07 ) imprinting tangential forces, wherein the first elastic claw ( 04 ) a first piezo stack ( 10 ) and the second elastic claw ( 05 ) is assigned a second piezo stack, - a first spring element ( 12 ) for preloading the basic body ( 07 ) with a tangential spring force, wherein the first elastic claw ( 04 ) at the second end of the carrier ( 02 ) is arranged axially immovable to this and the second elastic claw ( 05 ) between mounting ring ( 03 ) and first elastic claw ( 04 ) is positioned axially displaceable; • one between mounting ring ( 03 ) and second elastic claw ( 05 ) arranged second spring element ( 13 ) for preloading the second elastic claw ( 05 ) with a spring force in the axial direction; • a through fastening ring ( 03 ), elastic claws ( 04 . 05 ) and second spring element ( 13 ) extending rod ( 14 ), which in a first energizing state of the first and / or second piezo stack ( 10 . 11 ) through the annular body ( 07 ) of the first and / or second elastic claw ( 04 . 05 ) is held; A group of third piezo stacks ( 15 ), which between first and second elastic claw ( 04 . 05 ) are arranged and generate an axial displacement force between the two jaws when electrically activated. Piezoelectric linear motor ( 01 ) according to claim 1, characterized in that the fastening ring ( 03 ) and the first elastic claw ( 04 ) at the opposite ends of the carrier ( 02 ) are formed. Piezoelectric linear motor ( 01 ) according to claim 1 or 2, characterized in that from the opening ( 08 ) of the basic body ( 07 ) of the elastic and second claws ( 04 . 05 ) on both sides in each case an edge ( 09 ) extends outwardly, wherein the first spring element ( 12 ) at these edges ( 09 ) attacks. Piezoelectric linear motor ( 01 ) according to one of claims 1 to 3, characterized in that the first spring element ( 12 ) is a horseshoe spring. Piezoelectric linear motor ( 01 ) according to one of claims 1 to 4, characterized in that the second spring element ( 13 ) is a coil spring. Piezoelectric linear motor ( 01 ) according to one of claims 1 to 5, characterized in that it comprises an electrical energy source ( 17 ) and a microcontroller ( 19 ) for controlling the piezo stacks ( 10 . 11 . 15 ) supplied stream. Piezoelectric linear motor ( 01 ) according to one of claims 1 to 6, characterized in that it is part of a leveling system for adjusting the vehicle floor clearance of a motor vehicle. Method for operating a piezoelectric linear motor ( 01 ) according to any one of claims 1 to 7, comprising the following steps for performing a lifting operation: • releasing the first elastic claw ( 04 ) off the rack ( 14 ) by energizing the first piezo stack ( 10 ); • energizing the third piezo stack ( 15 ), causing the rod ( 14 ) together with the second elastic claw ( 05 ) against the spring force of the second spring element ( 13 ) is moved; • fixing the first elastic claw ( 04 ) At the rod ( 14 ) by terminating the energization of the first piezo stack ( 10 ); • release the second elastic claw ( 05 ) off the rack ( 14 ) by energizing the second piezo stack ( 11 ); • Terminating the energization of the third piezo stack ( 15 ) and returning the second elastic claw ( 05 ) in its initial position by means of the second spring element ( 13 ); • fixing the second elastic claw ( 05 ) At the rod ( 14 ) by terminating the energization of the second piezo stack ( 11 ). Method for operating a piezoelectric linear motor ( 01 ) according to one of claims 1 to 7 for performing a lowering operation, wherein in a lowering force acting on a release of the first and second elastic claw ( 04 . 05 ) off the rack ( 14 ) by energizing the first and second piezo stack ( 10 . 11 ) and in the case of a force acting counter to the lowering direction, the following steps are performed: detaching the second elastic claw (FIG. 05 ) off the rack ( 14 ) by energizing the second piezo stack ( 11 ); • energizing the third piezo stack ( 15 ), whereby the second elastic claw ( 05 ) against the spring force of the second spring element ( 13 ) is moved; • fixing the second elastic claw ( 05 ) At the rod ( 14 ) by terminating the energization of the second piezo stack ( 11 ); • releasing the first elastic claw ( 04 ) off the rack ( 14 ) by energizing the first piezo stack ( 10 ); • Terminating the energization of the third piezo stack ( 15 ), causing the rod ( 14 ) together with the second elastic claw ( 05 ) due to the second spring element ( 13 ) acting spring force is moved; • fixing the first elastic claw ( 04 ) At the rod ( 14 ) by terminating the energization of the first piezo stack ( 10 ). Method according to claim 8 or 9, characterized in that it is necessary to fully raise or lower the rod ( 14 ) - is repeated several times with a force acting in the lowering direction.

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