JPH0477552B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to linear motors. More specifically, the present invention relates to a step-type linear motor that utilizes piezoelectric elements as a drive source and is capable of precise positioning.

BACKGROUND ART Conventionally, among the widely known linear motors are those that utilize electromagnetic force. Such linear motors utilize electromagnetic force by combining electromagnets and coils, and can be realized relatively easily and inexpensively, but on the other hand, the power consumption is extremely large compared to the driving force. Disadvantages include that it is difficult to precisely control the amount of displacement of the actuator. In particular, in controlling the amount of displacement, that is, positioning the actuator, due to the limitations of the processing accuracy of electromagnets, even with a step-type linear motor designed with emphasis on controlling the amount of displacement, the actuator positioning accuracy that can be achieved is only 0.1. mm step was the limit.

On the other hand, step-type linear motors have been realized that utilize piezoelectric elements as drive sources for actuators for applications that sometimes require precise position control. An example of a linear motor using such a piezoelectric element is shown in a schematic diagram in FIG. a pair of annular clamp elements 42a, 42b configured to penetrate inside;
A telescopic element 4 connects these pair of clamp elements 42a, 42b via connecting members 43a, 43b.
The actuator is composed of 4 actuators. Clamp elements 42a, 42b and expansion and contraction element 4
4 is made of a material having a piezoelectric effect, and the clamp elements 42a and 42b are configured to reduce their inner diameters when a voltage is applied, and the expansion and contraction element 44 is configured to expand and contract in parallel to the direction of movement of the actuator. Furthermore, each element is configured to individually control the applied voltage.

To briefly explain the operation of such a linear motor, first, one of the clamp elements 42, for example 4
When a voltage is applied to 2a, the inner diameter of the clamp element 42a becomes smaller, and the actuator 45 is fixed on the shaft 41 by tightening the shaft 41. Next, a voltage is applied to the elastic element 44 to bring it into an expanded state. Next, a voltage is applied to the other clamp element 42b to bring it into a fastened state, and then the clamp element 4
After stopping the voltage application to the elastic element 2a to release the fastened state, the voltage application to the elastic element 44 is stopped and the extended state is released.

Through this series of operations, the actuator 45 moves from the side of the clamp element 42a toward the side of the clamp element 42b by a distance corresponding to the extension of the expandable element 44. By repeating this operation, the actuator 45 can be moved by a desired amount.

A step-type linear motor using a piezoelectric element as described above can control the amount of movement of its actuator extremely precisely compared to one using electromagnetic force. In other words, the amount of one expansion of the telescopic element that defines the amount of movement of the actuator is several μ.
This is because by counting the number of the above-mentioned operation cycles, it is possible to control the movement amount on the order of μm. In addition, since the operation process always includes the tightening of the guide means by the clamp means,
Displacement errors due to friction are also extremely small.

Problems to be Solved by the Invention The fastening of the guide means by the clamping means of a linear motor using a piezoelectric element as described above depends exclusively on the deformation of the piezoelectric material constituting the clamping means. The deformation is extremely small; for example, in the actual example of the conventional linear motor mentioned above, the change in the inner diameter of the clamping means was about 5 μm for an applied voltage of 400V.

Therefore, in order to ensure that the actuator can move freely without applying voltage to the clamping means, the shaft serving as the guiding means is required to have extremely high dimensional accuracy. That is, in the above example, since the change in the inner diameter of the clamping means due to voltage application is about 5 μm, the dimensional accuracy of the shaft surface must be 2.5 μm or less or smooth movement of the actuator will be hindered.

For this reason, when manufacturing a linear motor using piezoelectric elements, it is extremely complicated to precisely finish the shaft surface while matching the actual clamp element and shaft. The linear motor used was an extremely expensive product, and as a result, despite its excellent displacement control performance, it was not possible to replace it with a linear motor that uses electromagnetic force.

An object of the present invention is to provide a linear motor that can be manufactured relatively easily and retains the advantages of conventional linear motors using piezoelectric elements, while eliminating the above-mentioned drawbacks.

Means for solving the problem The problem with the conventional linear motor using piezoelectric elements mentioned above is that the deformation of the piezoelectric material is extremely small, ensuring free movement of the actuator when the clamping means is released. This required extremely high machining precision. Therefore, the present inventors adopted a structure that mechanically amplifies the displacement of the piezoelectric element provided in the clamping means to ensure free movement of the actuator when the clamping means is released. The present invention has been completed by making it possible to reduce the requirement for machining accuracy, reduce manufacturing costs while maintaining high displacement control ability, and at the same time make the operation even more reliable.

That is, according to the present invention, the first piezoelectric effect element;
A U-shaped fixing member is rigidly connected to one end of the first piezoelectric effect element, and a U-shaped fixing member is attached to the legs of the fixing member so as to be tiltable. A pair of clamping means respectively constituted by a pair of abutting members connected to the ends, and a second piezoelectric effect element to which the pair of clamping means are symmetrically connected to both ends, A piezoelectric linear movable element is provided, wherein the contact member contacts a pair of surfaces of a pair of guide members having a pair of opposing surfaces at a uniform interval.

Operation The operation of the piezoelectric linear mover according to the present invention as described above will be explained. The first piezoelectric effect element pushes one end of the abutting member by expanding due to the application of a voltage, and this action causes the other end of the abutting member to be correspondingly displaced. At this time, the distance j from the tilting axis of the abutment member to the connection part of the member with the piezoelectric effect element, and the distance L from the tilting axis to the part where the abutment member abuts the guide member, satisfy l<L. If so, the displacement at the contact portion of the contact member with the guide member is the first
is expanded to L/l times the displacement of the length of the piezoelectric effect element. Therefore, when the clamping means is released, the distance between the guide member and the abutting member is easily secured, so when manufacturing the piezoelectric linear mover according to the present invention, it is possible to easily maintain the distance between the guide member and the abutting member. Machining accuracy is not required.

The operation of the piezoelectric linear mover according to the present invention having such characteristics will be described in more detail below with reference to Examples.

Embodiment FIG. 1 is a diagram schematically showing an example of a piezoelectric linear mover according to the present invention.

The piezoelectric effect elements 1 (1a, 1b, 1c) utilize a laminated piezoelectric element in which a ceramic piezoelectric material made of lead zirconate titanate or the like and an internal electrode made of silver, palladium alloy, etc. are layered and integrated. be. Moreover, this piezoelectric effect element 1
The length in the direction of expansion and contraction is 9 mm, and the DC voltage is 100 V.
The elongation displacement when applying the voltage is 6.5μm, and the generated force at that time is 13Kg.

The clamping means 6a, 6b are connected to the hinges 2a to 2.
h, fixing members 3a, 3b, contact members 4a to 4d, and other functional members, but in this embodiment, they are manufactured as a single piece from a metal plate by electric discharge machining. The piezoelectric effect elements 1a, 1b and the thermal dilatometer are made of Invar material, which is almost the same material, and the thickness is 2 mm.

Piezoelectric effect elements 1a to 1c and fixing members 3a and 3b
And the contact members 4a to 4d can be connected with an adhesive such as epoxy resin. Further, guide members 5a and 5b serving as guide means were produced by cutting a metal rod.

First, a mechanism for mechanically amplifying the displacement generated in the piezoelectric effect elements 1a and 1b using the lever principle will be described. When a voltage is applied to the piezoelectric effect element 1a, the displacement is caused by the contact member 4 via the hinge 2a.
Move in the direction of pushing up a. The contact member 4a tilts about the hinge 2a. The displacement amplification factor n at this time is the distance l between the hinge 2a and the hinge 2b and the first
With the length of the abutment member 4a represented by L shown in the figure, it can be expressed as n=L/l. With the above-mentioned mechanism, the contact members 4a, 4b spread outward from the contact portions of the contact members 4a, 4b, and the corresponding contact members 4a, 4b are guided by the guide members 5a, 5b.
Fix it by touching it. The same holds true when a voltage is applied to the piezoelectric effect element 1b.

Next, the operation of the piezoelectric linear mover according to the present invention having the above-described structure will be explained.
Incidentally, graphs showing the timing of applying voltage to each of the piezoelectric effect elements 1a to 1c in FIG. 2 are shown in FIGS. Refer to and explain.

First, a voltage is applied to the piezoelectric effect element 1a as shown in FIG.
a, 5b to fix the clamping means 6a. The voltage applied to each element at this time corresponds to α to β on the time axis (horizontal axis) of the graph in FIG.

Next, as shown in FIG. 3b, a voltage is applied to the piezoelectric effect element 1c, and the width of the piezoelectric effect element 1c is 6.5 μm from side to side.
As the clamping means 6b extends, the clamping means 6b moves to the left. The voltage applied to each element at this time corresponds to between β and γ on the time axis (horizontal axis) of the graph in FIG.

Next, a voltage is applied to the piezoelectric effect element 1b as shown in FIG.
5b to fix the clamping means 6b. The voltage applied to each element at this time corresponds to the range between γ and δ on the time axis (horizontal axis) of the graph in FIG.

Next, when the voltage of the piezoelectric effect element 1a is made zero as shown in FIG.
5b leave. The voltage applied to each element at this time corresponds to a period between δ and ε on the time axis (horizontal axis) of the graph in FIG.

Next, as shown in Figure 3e, when the voltage across the piezoelectric effect element 1c is reduced to zero, the width of the piezoelectric effect element 1c shrinks by 6.5 μm.
Along with this, the clamping means 6a moves to the left. The voltage applied to each element at this time corresponds to ε to ζ on the time axis (horizontal axis) of the graph in FIG.

The piezoelectric linear mover moves 6.5 .mu.m from right to left in the plane of the drawing, with the series of operations shown in FIGS. 3a to 3e as one stroke.

The performance of this piezoelectric linear mover is voltage 100V,
When driven by applying a pulse voltage with a frequency of 2.5 KHz, the speed was 12 mm/sec and the traction force was 10 Kg. Further, the positioning error was 2 μm for a movement amount of 100 mm.

Effects of the Invention As detailed above, the piezoelectric linear mover according to the present invention is equipped with a mechanism that mechanically amplifies the displacement of the length of the piezoelectric effect element, which is the driving source for the operation of the clamping means. The displacement of the clamping means at the contact portion with the guide member is large, facilitating movement of the movable element when the clamping means is released. Therefore, the machining accuracy required to manufacture this piezoelectric linear mover is that of ordinary machining, and the manufacturing cost of the piezoelectric linear mover is comparable to that of a conventional electromagnetic linear motor. It is quite comparable. In addition, the driving force as a motor has a sufficiently low loss compared to the power consumed, and at the same time, the precision of displacement control as a linear movable element that uses piezoelectric effect elements is higher than that of conventional piezoelectric effect elements. It is guaranteed to be equivalent to that of

In this way, piezoelectric linear movers whose displacement can be precisely controlled require precise positioning in computer external storage devices using magnetic disks, printer head drive devices, XY plotters, camera autofocus mechanisms, etc. It can be used in many types of equipment, and has an extremely wide range of industrial applications.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view schematically showing one embodiment of a piezoelectric linear mover according to the present invention, and FIG. 2 is a timing diagram for applying voltage to the piezoelectric effect element of the piezoelectric linear mover according to the present invention. FIG. 3 is a time chart showing the operation of the piezoelectric linear mover shown in FIG. 1, and FIG. FIG. 2 is a cross-sectional view of one example. (Main reference numbers), 1 (1a-1c)...Piezoelectric effect element, 2a-2h...Hinge, 3a, 3b...
...Fixing member, 4a to 4d...Abutting member, 5a, 5
b...Guiding member, 6a, 6b...Clamping means,
41...shaft, 42a, 42b...clamp element, 43...coupling member, 44...extensible element.

Claims (1)

[Claims] 1. First piezoelectric effect elements 1a, 1b; U-shaped fixing members 3a, 3b rigidly connected to one end of the first piezoelectric effect elements 1a, 1b; a pair of abutting members 4a, 4b, 4c, 4 which are tiltably attached to the legs of the fixed members 3a, 3b and connected to the other end of the first piezoelectric effect element;
a pair of clamping means 6 each consisting of
a, 6b, and a second piezoelectric effect element 1c to which the pair of clamping means 6a, 6b are symmetrically connected at both ends, and the abutting members 4a, 4b, 4c, 4d are arranged at uniform intervals. A piezoelectric linear movable element, characterized in that it comes into contact with a pair of surfaces of a pair of guide members 5a, 5b having a pair of opposing surfaces.