DRIVE UNIT AND METHOD FOR OPERATING A DRIVE UNIT

Abstract

An oscillating drive unit for driving a passive element relative to an active element includes a resonator with at least two arms extending in parallel to a reference plane, one of the arms including a contact element, movable by way of oscillating movements, for driving the passive element relative to the active element. Two of the arms extend in a substantially symmetric manner, and an other one of the arms is arranged not to come into contact with the passive element.

Claims

1. A drive unit for driving a passive element relative to an active element, wherein the active element comprises: resonator and at least one excitation means for exciting oscillations in the resonator, the resonator comprising at least two arms extending from a connection region of the resonator, the connection region and the arms extending in parallel to a reference plane, a first arm of the arms comprising, at an outer end of the arm, a contact element, the contact element being movable by way of oscillating movements of the first arm, the passive element being arranged to be driven and moved relative to the active element by way of these oscillating movements; the passive element comprises a first contact area, the first contact area being arranged to be in contact with the first contact element; wherein the at least two arms extend in a substantially symmetric manner from the connection region; wherein the resonator and its parts are integrally shaped as a single piece of material; wherein the second arm is arranged not to come into contact with the passive element.

2. The drive unit of claim 1, wherein the second arm is arranged to move with oscillating movements that balance the oscillating movement of the first arm.

3. The drive unit of claim 1, wherein the first arm and second arm are arranged in two-fold rotational symmetry to one another, with an axis of symmetry being normal to the reference plane.

4. The drive unit of claim 1, wherein the first arm and second arm are arranged in mirror symmetry to one another, with a mirror plane being normal to the reference plane, the first arm and second arm being arranged at opposite sides of the mirror plane and either the first arm and second arm extend in a direction normal to the mirror plane, or the first arm and second arm extend in a direction normal to the mirror plane.

5. The drive unit of claim 1, wherein the active element comprises, in addition to the first arm and second arm, a bearing arm, the bearing arm comprising a bearing region by means of which, in particular when the active element is not being excited, the bearing arm applies a pre-stress force on the passive element against the first arm, in particular the first contact element of the first arm.

6. The drive unit of claim 5, wherein, when the active element is excited, with a frequency for driving the passive element relative to the active element by means of the first arm, the bearing arm oscillates without imparting forces to the passive element that drive the passive element relative to the active element.

7. The drive unit of claim 6, wherein, when the active element is excited, with a frequency for driving the passive element relative to the active element by means of the first arm, a bearing region of the oscillating bearing arm alternatingly moves towards the passive element, thereby coming into contact with the passive element, and away from the passive element, thereby losing contact with the passive element and thus decreasing the friction force in the bearing region.

8. A method for operating a drive unit according to claim 5, comprising the steps of exciting the active element with a frequency: for driving the passive element relative to the active element by means of the first arm by performing an oscillating movement that, and for intermittently holding and releasing the passive element relative to the active element by means of the bearing arm.

9. A drive unit for driving a passive element relative to an active element, optionally according to claim 1, wherein the active element comprises: resonator and at least one excitation means for exciting oscillations in the resonator, the resonator comprising at least one arm extending from a connection region of the resonator, the connection region and the at least one arm extending in parallel to a reference plane, the at least one arm comprising, at an outer end of the arm, a contact element, the contact element being movable by way of oscillating movements of the at least one arm, the passive element being arranged to be driven and moved relative to the active element by way of these oscillating movements; the passive element comprises a first contact area, the first contact area being arranged to be in contact with the first contact element; wherein a resilient pre-stress element is arranged to apply a pre-stress force pushing, in particular when the active element is not being excited, at least the first contact element towards the first contact area, and in that the passive element is held in place against the active element by means of the pre-stress force.

10. The drive unit of claim 11, wherein the passive element and the active element are arranged to move a driven part relative to a base element, the driven part being partly constrained in its movement relative to the base element by means of a joint, and the passive element is held in the joint by means of the pre-stress force.

11. The drive unit of claim 10, wherein the joint is a rolling joint comprising rollers arranged between the base element and the driven part.

12. The drive unit of claim 9, wherein the joint allows for relative movement of the driven part relative to the base element along a linear axis or within a plane, and limits the relative movement in a direction that is normal to said linear axis or plane, and does not constrain the relative movement in the opposite direction, and wherein the pre-stress force constrains the relative movement in the opposite direction.

13. The drive unit of claim 9, wherein the joint allows for relative movement of the driven part relative to the base element around an axis of rotation, and limits the relative movement in a direction that is normal to said axis of rotation, and does not constrain the relative movement in the opposite direction, and wherein the pre-stress force constrains the relative movement in the opposite direction.

14. A drive unit for driving a passive element relative to an active element, wherein the active element comprises: a resonator and at least one excitation means for exciting oscillations in the resonator, the resonator comprising at least two arms extending from a connection region of the resonator, the connection region and the arms extending in parallel to a reference plane, each of the arms comprising, at an outer end of the arm, a respective contact element, the contact elements being movable by way of oscillating movements of the respective arm, the passive element being arranged to be driven and moved relative to the active element by way of these oscillating movements; the passive element comprises a first and a second contact area, each contact area being arranged to be in contact with a respective one of the first and second contact elements, wherein the resonator comprises: a pivot section about which the resonator is arranged to rotate relative to the base element, a counterforce section comprising a resilient part of the resonator, which when mounted on the base element is elastically deformed by a pre-stress torque around the pivot section, caused by a pre-stress force acting between the resonator and the passive element at the contact areas.

15. The drive unit of claim 14, wherein the counterforce section, in particular when not deformed, extends within the reference plane at the same side of the pivot section as the arms.

16. A drive unit for driving a passive element relative to an active element, wherein the active element comprises: a resonator and at least one excitation means for exciting oscillations in the resonator, the resonator comprising at least two arms extending from a connection region of the resonator, the connection region and the arms extending in parallel to a reference plane, at least one of the arms comprising, at an outer end of the arm, a contact element, the contact element being movable by way of oscillating movements of the at least one of the arms, the passive element being arranged to be driven and moved relative to the active element by way of these oscillating movements; the passive element comprises at least one contact area, the at least one contact area being arranged to be in contact with a respective contact element; wherein the at least one contact area has a concave shape, with two inner surfaces opposing one another, with the respective contact element being arranged to move between the two inner surfaces and make contact at the two inner surfaces.

17. The drive unit of claim 16, wherein the at least one contact area has a U-shape, with two arms, and wherein the respective contact element is arranged to move between the two arms of the U-shape and make contact at inner surfaces of the two arms of the U-shape, and in particular wherein the at least one contact area is manufactured in one piece as a bent piece of sheet metal.

18. The drive unit of claim 16, wherein the contact elements comprise flat contact surfaces.

19. The drive unit of claim 18, wherein a resonator length is defined as the dimension of the resonator along the resonator axis, from the ends of the arms to the opposing ends of their counterweight sections, and wherein the extension of each flat contact surface, projected onto the reference plane, is between one tenth and one hundredth of the resonator length, in particular between one twentieth and one eightieth of the resonator length.

20. The drive unit of claim 19, wherein the length of the resonator is between three and five millimetres, in particular four millimetres, and the extension of the flat region is between 0.05 millimetres and 0.15 millimetres, in particular between 0.08 millimetres and 0.12 millimetres, in particular 0.1 millimetres.

21. The drive unit of claim 16, wherein the surface of the resonator and/or the passive element is treated with high precision vibratory finishing or chemical polishing.

22. The drive unit of claim 16, wherein a wear suppressing element is arranged on the passive element in the contact areas.

23. The drive unit of claim 22, wherein the wear suppressing part is made of a material with a higher degree of hardness than a surrounding region of the passive element or is created by a hardening treatment of the material of the passive element.

24. The drive unit of claim 22, wherein the wear suppressing part is made of a ceramic material.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0114] The subject matter of the invention will be explained in more detail in the following text with reference to exemplary embodiments which are illustrated in the attached drawings, which schematically show:

[0115] FIG. 1 a drive with an active element including a resonator with a pair of arms, of which only one is in contact with and drives a passive element;

[0116] FIG. 2 a resonator with a pair of arms in a different arrangement;

[0117] FIG. 3 a drive with an additional arm acting as a bearing;

[0118] FIG. 4-6 different arrangements of arms for this type of drive;

[0119] FIG. 7-9 different arrangements with pre-stress elements;

[0120] FIG. 10-12 views of a drive unit in which a pre-stress force holds a base element and a driven part together;

[0121] FIG. 13 a resonator with an integral counterforce section for generating the pre-stress force;

[0122] FIG. 14-16 different configurations of the counterforce section;

[0123] FIG. 17 a drive unit in which the active element contacts and drives a concave region of the passive element;

[0124] FIG. 18 the same, in an exploded view;

[0125] FIG. 19 a detail of a contact element; and

[0126] FIG. 20-23 embodiments with rotating passive elements.

DETAILED DESCRIPTION OF THE INVENTION

[0127] In principle, identical or functionally identical parts are provided with the same reference symbols in the figures.

[0128] FIG. 1 shows a drive with an active element 1 including a resonator 2 with a pair of arms, a first arm 21 and a second arm 22, of which only the first arm 21 is in contact with and drives a passive element passive element 4. The arms 21, 22 and attachment regions 14 are attached to a connection region 20 of the resonator 2. The attachment regions 14 serve to mount the resonator 2 to another part, such as a base element 5 (illustrated in FIGS. 7 to 12) An excitation means 23, for example, a piezoelectric element, is arranged on the connection region 20. The excitation means 23 can include two separate elements, arranged on opposing sides of the excitation means 23 (visible in FIGS. 11, 13, 18). The resonator 2 and the excitation means 23 are flat elements, stacked onto one another and extending in parallel to a reference plane 28. Upon excitation by an alternating voltage with an excitation frequency, the arms 21, 22 oscillate and, depending on the frequency, a first contact element 31 of the first arm 21 is made to performs a roughly elliptical movement. Depending on the frequency, the movement can be clockwise (as illustrated by an arrow) or counter clockwise. Thereby, the first contact element 31 repeatedly contacts and drives a first contact area 41 of a passive element 4 relative to the active element 1. In this embodiment, the passive element 4, by bearing means not shown in the figure, can move along a linear movement axis 26.

[0129] The first arm 21 and second arm 22 extend from the connection region 20 in a substantially symmetric manner, and can differ in details of their shape, in particular their contour, if they are manufactured from a flat piece of material. A resonator axis 24 corresponds to an axis of symmetry at which the resonator 2, in particular the connection region 20 and the arms 21, 22, can be mirrored, except for the abovementioned details of the arms. Movement of the connection region 20 and the arms 21, 22, when excited by the excitation means 23, can be generally symmetric, with the same axis of symmetry. Nodes of this movement, that is, regions of minimal movement, can be located on the resonator axis 24. Attachment regions 14 for mounting the active element 1 on another element, can also be located on the resonator axis 24.

[0130] FIG. 2 shows a resonator with a pair of arms in a different arrangement: while in FIG. 1 the arms 21, 22 extend in parallel to the resonator axis 24, in FIG. 2 they extend at a right angle to the resonator axis 24. The resonator 2 can be arranged to drive only one passive element 4 (not shown in FIG. 2) with only the first arm 21, the second arm 22 serving to balance the movement of the first arm 21.

[0131] FIG. 3 shows a drive with, in addition to the elements already presented, a bearing arm 8 acting as a bearing, supporting a passive element 4 which in this case is arranged to rotate relative to the active element 1. Here too, driving the passive element 4 is effected by the first contact element 31 contacting and driving a first contact area 41 of the passive element 4 by oscillating movements. Simultaneously, a bearing region 81 of the bearing arm 8 oscillates towards and away from the passive element 4. In FIG. 3, this movement is represented by a double arrow. In this manner, the bearing arm 8 reduces contact forces acting on the passive element 4 while the first contact element 31 drives the passive element 4. Thereby, movement of the passive element 4 is facilitated.

[0132] The movement of the bearing arm 8 and thereby of the bearing region 81 can be synchronised with the movement of the first arm 21 by adjusting the length of the bearing arm 8. Given two oscillating frequencies for driving the first arm 21 to move the passive element 4 in the two opposite directions, the length of a bending section 84 of the bearing arm 8 can be chosen such that for both of these two frequencies the bending section 84 oscillates to move the bearing region 81 as described above. The two frequencies can be chosen close to one another, such that the first arm 21 oscillates in different directions according to the frequency, but the mode of oscillation of the bearing arm 8 is essentially the same for both frequencies.

[0133] Depending on the excitation frequency, the bearing arm 8 will exhibit corresponding modes of oscillation. Such a mode can be characterised by the location of nodes of the oscillation. For example, there can be at least three nodes: [0134] one near a point where the bearing arm 8 is attached to the connection region 20, for example at the C-shaped bend in FIG. 3; [0135] one near a point where the bearing arm 8 changes direction, for example at the L-shaped bend in FIG. 3; and [0136] one near the bearing region 81.

[0137] When the drive is not excited, the bearing arm 8 is at rest and exerts a pre-stress force that pushes the passive element 4 towards and against the first contact element 31, and thereby inhibits movement of the passive element 4.

[0138] FIGS. 4-6 show different arrangements of arms for this type of drive in a very schematic representation. FIG. 4 corresponds to the arrangement of FIG. 3, the arms running in parallel to the resonator axis 24. FIG. 5 represents an arrangement in which the arms running at right angles to the resonator axis 24. FIG. 5 represents an arrangement in which the arms are arranged in a point wise or 2-fold rotational symmetry. In these arrangements, the oscillations of the two arms can balance one another.

[0139] FIGS. 7-9 show different arrangements with pre-stress elements, in a highly schematic representation. Each shows a kinematic chain, from the active element 1 to the passive element 4, with the active element 1 being linked to a base element 5 and the passive element 4 being linked to a driven part 7 (Generally, this association is a matter of convention: depending on the point of view, the active element 1 can be considered to be linked to a driven part and the passive element 4 to a base element). The base element 5 and driven part 7 are linked by a joint such as a linear joint 52, or planar joint completing the chain. The same kinematic chain, but with a rotary joint 52′, is shown in FIGS. 21-23. The joint can be implemented with rollers 54 between the base element 5 and driven part 7. The chain includes a resilient pre-stress element 6 for exerting a force between the active element 1 and the passive element 4 and also on the joint. The pre-stress element 6 can be arranged at one of various locations along the chain. [0140] According to FIG. 7, the pre-stress element 6 is arranged between two parts of the base element 5, or between the base element 5 and the active element 1. [0141] According to FIGS. 8 and 9, it is arranged between two parts of the driven part 7, or between the driven part 7 and the passive element 4. In FIG. 8, the direction of movement or linear movement axis 26 of the passive element 4 relative to the active element 1 is normal to the active element's 1 resonator axis 24, in FIG. 9, it is parallel.

[0142] The pre-stress elements 6 not only exert a pre-stress force between the active element 1 and the passive element 4, but also on the joint between the driven part 7 and the base element 5. If rollers 54 are present in the joint, the pre-stress force also acts on them. The pre-stress force pushes the driven part 7 and base element 5 towards each other. This allows to simplify the construction of the joint, since elements that would otherwise be necessary to hold the driven part 7 and base element 5 in place against one another can be omitted.

[0143] In other embodiments there can be two or more pre-stress elements 6.

[0144] In other embodiments, a rotary or a spherical joint is present between the base element 5 and driven part 7, with a limited range of angular movement and with rollers on one side of the joint only. This corresponds to an arrangement as that of FIG. 7 but with facing sides of the driven part 7 and base element 5 forming concentric cylinders or spheres, separated by the rollers 54.

[0145] FIGS. 10-12 show views of a drive unit in which a pre-stress force holds a base element 5 and a driven part 7 together, as explained above with reference to FIGS. 7-9. A difference from these figures is that both arms of the resonator 2 contact the passive element 4, by means of a first contact element 31 on the first arm 21 and a second contact element 32 on the second arm 22. Two rollers 54 are shown in the exploded view of FIG. 11. Instead of a third roller, a sliding contact is present between the base element 5 and driven part 7.

[0146] FIG. 13 shows a resonator 2 with an integral counterforce section 62 for generating the pre-stress force, as used in the arrangement of FIGS. 10-12. In addition to the connection region 20 with arms 21, 23, the resonator 2 also includes counterforce sections 62, which can be integrally shaped with the other parts of the resonator 2. When mounted in the driven part 7, the resonator 2 is free to rotate—to a certain extent—around a pivot section 61 of the resonator 2. The resonator 2 and in particular the counterforce sections 62 and a pivot section 61 are elastically deformed, as shown in FIGS. 10 to 12, by forces acting on the contact elements 31 and 32 an on force application regions 63 at which the counterforce sections 62 are clamped under corresponding parts of the base element 5. This elastic deformation corresponds to the pre-stress force that is exerted, on the one hand, between the first contact element 31, second contact element 32 and the passive element 4. On the other hand the pre-stress force is exerted, by pressing the passive element 4 and the entire driven part 7 downward towards the base element 5, onto the rollers 54 of the joint between the driven part 7 and base element 5.

[0147] FIGS. 14-16 show different configurations of the counterforce section 62 in a schematic representation. FIG. 14 shows the configuration of FIG. 13, with the arms 21, 22 being parallel to the counterforce section 62 and the reference plane 28 when not loaded, and bent apart from one another at the pivot section 61 when loaded by the forces acting on the contact elements 31, 32 and the force application regions 63. FIG. 15 shows a configuration in which the counterforce section 62 extends upwards at an angle to the arms 21, 22. In another embodiment, it extends downwards at an angle. FIG. 15 shows a configuration in which the counterforce section 62 extends in parallel to the arms 21, 22 but in the opposite direction when not loaded.

[0148] FIG. 17 shows a drive unit in which the active element contacts and drives a concave region of the passive element, and FIG. 18 shows the same, in an exploded view. The active element 1 includes elements as already presented above. The passive element 4 includes a attachment sections and an attachment hole 47 for attaching it to, for example a driven part 7 or base element 5. A first attachment section 45 supports a first contact area 41 and a second attachment section 46 supports a second contact area 42. Each contact area 41, 42, and optionally the entire passive element 4 is manufactured from a flat part of a sheet material, for example, sheet metal. The contact areas 41, 42 are bent to form a concave shape, in particular a U-shape. Each contact element 31, 32 is arranged to contact a respective contact area 41, 42 by reaching into this concave shape. The passive element 4 can be driven to move along the linear movement axis 26. The attachment sections 45, 46 are relatively stiff in the movement direction and relatively elastic in directions normal to the linear movement axis 26. This allows the drive to absorb misalignment and movement in these directions. At the same time, the concave shape of the respective contact area 41, 42 keeps the contact elements 31, 32 within the contact area 41, 42.

[0149] FIG. 17 also shows a contact element 13 clamping two piezo plates constituting the excitation means 23 against the connection region 20. Electrical contacts for driving the piezo plates are constituted on the one hand by the contact element 13 and on the other hand by the resonator 2 and its attachment regions 14.

[0150] In other embodiments, not shown in the figures, the second arm 22 does not come into contact with a corresponding second contact area 42. The passive element 4 is thus driven only by the first arm 21.

[0151] FIG. 19 shows an extension d of a contact surface of a contact element 31 in the reference plane 28. The extension can be related to a resonator length, the resonator length being defined as the dimension of the resonator along the resonator axis 24, from the ends of the arms 21, 22 to the opposing ends of their counterweight sections (if present). In other words, the resonator length is the size of the resonator 2 in the direction along resonator axis 24, without fixation or support area(s) 27. The extension d of the flat contact surface is measured on a projection of the flat region projected onto the reference plane 28.

[0152] The contact surface includes the surface that intermittently comes into contact with the passive element 4. With its shape corresponding to the shape of the surface of the corresponding contact area on the passive element 4, contact forces are distributed over the contact surface and thereby wear of the contact element is reduced.

[0153] In the embodiment of FIG. 19, the contact surface is flat, and the location of the flat contact surface corresponds to the passive element 4 being arranged as in one of FIGS. 9 to 18. In the embodiments according to FIGS. 1, 7 and 8, the flat contact surface can be arranged on the respective contact element 31 facing the passive element 4.

[0154] In the embodiments according to FIGS. 3 and 20 to 23, the contact surface can be curved, according to an outer radius of the passive element 4, and arranged on the respective contact element 31 facing the passive element 4. The extension d of the contact surface is measured along the arc following the curve of the surface.

[0155] FIG. 20-23 show embodiments with rotating passive elements 4 and/or driven parts. The kinematic structure corresponds to that of FIGS. 1, 7, 8 and 9, respectively, but with a rotary joint 52′ instead of the linear joint 52. The remainder of the function and interaction of the active element 1 and passive element 4 are the same. [0156] According to FIG. 20, the passive element 4 of FIG. 1, instead of being linearly movable along the linear movement axis 26, is rotatable around a rotary movement axis 26′. [0157] According to FIG. 21, a pre-stress element 6 is arranged between two parts of the base element 5, or between the base element 5 and the active element 1. [0158] According to FIGS. 22 and 23, the pre-stress element 6 is arranged between two parts of the driven part 7, or between the driven part 7 and the passive element 4. In FIG. 22, the tangential direction of movement of the passive element 4 at the first contact area 41 is approximately normal to the active element's 1 resonator axis 24, in FIG. 23, it is parallel, or approximately parallel.

[0159] While the invention has been described in present embodiments, it is distinctly understood that the invention is not limited thereto, but may be otherwise variously embodied and practised within the scope of the claims.