JPH0622570A - Linear type actuator - Google Patents

Abstract

PURPOSE:To provide a linear type actuator having an excellent mass- productivity, wherein the moving speed of a moving substance can be varied without deteriorating the characteristic of the actuator, and the driving efficiency of the actuator can be improved by a simple circuit. CONSTITUTION:In the configuration of a linear type actuator, a moving substance 5 is contacted in a pressing way with the ridge line part of an elastic substance 1 having a square or triangular cross sectional shape, wherein first and second piezoelectric substances 2a, 2b are bonded to each other. Thereby, the restrictions relative to the plane accuracies and parallelisms of the elastic substance 1 and the moving substance 5 are eliminated completely, and the moving substance 5 is contacted stably with the elastic substance 1, and further, the moving speed of the moving substance 5 can be varied even at a low speed without deteriorating the characteristics of the actuator, by controlling arbitrarily the phase difference phi between the AC voltages applied to the respective piezoelectric substances 2a, 2b. Also, since a large vibrating displacement quantity can be obtained, the driving efficiency of the actuator can be improved, and since the drive controlling circuit of the actuator is configured simply, the mass-productivity of the actuator is excellent too.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a linear actuator for generating a driving force by using elastic vibration of a piezoelectric body.

[0002]

2. Description of the Related Art In recent years, attention has been paid to a linear actuator that excites elastic vibration in a vibrating body using a piezoelectric body such as a piezoelectric ceramic and uses this as a driving force.

A conventional linear actuator will be described below. FIG. 13 is a schematic view of a conventional linear actuator disclosed in Japanese Patent Laid-Open No. 63-283473. In FIG. 1, the vibrating body 11 is provided on three surfaces other than the base body 13 on which the driver element 12 is integrally projected and the driver element 11.
As shown in FIG. 4, the piezoelectric elements 14a, 14b and 14c are bonded together. By the parallel driving of the piezoelectric elements 14a and 14b and the parallel driving of 14a and 14c configured in this way, vibration is excited in the directions of the diagonal lines EF and GH of the vibrating body 11 of FIG. It is possible to move a slider (not shown) in pressure contact. Also,
As another driving method, a voltage v ₁ represented by (Equation 1) is applied to the piezoelectric element 14a as in the case of a disc type or an annular type ultrasonic motor.
Is applied, and a voltage v ₂ represented by (Equation 2) is applied to the piezoelectric elements 14b and 14c.

[0004]

[Equation 1]

[0005]

[Equation 2]

Here, V ₀ is the instantaneous value of the voltage, ω is the angular frequency, and t is the time. As a result, an elliptic bending vibration represented by (Equation 3) is excited in the driver element 12 of the vibrating body 11.

[0007]

[Equation 3]

Here, ξ is an amplitude value of bending vibration, and ξ ₀ is an instantaneous value of bending vibration. Due to the movement of the elliptical locus, the slider installed in pressure contact with the driver 12 of the vibrating body 11 is driven by the frictional force in the movement direction of the elliptical locus.

[0009]

However, in the above-mentioned conventional structure, the bending rigidity of the vibrating body driven by the piezoelectric body changes in the X and Y directions because the driving element is provided, and when the piezoelectric body 14a drives. The resonance frequencies and impedances when driven by the piezoelectric bodies 14b and 14c differ greatly. for that reason,
The drive circuit and control circuit are complicated. Further, the change in rigidity causes the displacement of the nodes in the displacement distribution in the X and Y directions, so that the vibration loss due to the supporting and fixing of the vibrating body is large and the driving efficiency is lowered. In addition, since the driver and the slider contact each other on a flat surface, if the plane accuracy or parallelism is poor,
Since the drive (contact) positions of the moving body and the vibrating body cannot be specified, there is a problem that the driving efficiency is lowered and noise is generated. On the other hand, improving the plane accuracy has a problem in that mass productivity is lowered and manufacturing cost is increased.

Further, when the moving speed of the moving body is made variable, (1) vibration in the X direction and Y are controlled by the same drive circuit.
Either the elliptical locus excited by the combined vibration in the direction must be made smaller, or in the control by separate drive circuits, either (2) the method of making only the vibration in the X direction, which is the moving direction of the moving body, smaller. I won't. However, in the case of (1), since the vibration in the Y direction is also reduced at the same time, the vibration of the vibrating body cannot be efficiently transmitted to the moving body when the plane accuracy of the moving body and the vibrating body is less than the plane accuracy (for example, swell). The drive of the body becomes unstable, and it becomes difficult to obtain the required torque. Further, in the case of (2), it is necessary to control the vibration displacement amounts in the X direction and the Y direction separately, which causes a problem that the cost is increased due to the increase in the number of circuit points.

An object of the present invention is to provide a linear actuator that solves the above problems.

[0012]

In order to achieve this object, a linear actuator of the present invention is constituted by sticking piezoelectric bodies on at least one set of intersecting planes on a rod-shaped elastic body having a rectangular or triangular cross section. By using a vibrating body, press the moving body against the ridge of the vibrating body, apply an AC voltage with an arbitrary phase difference to each piezoelectric body, and change the phase difference to make the moving speed of the moving body variable This is to solve the above problem.

[0013]

With this structure, since the pressure applied to the moving body and the vibrating body is not a surface but a point or a linear shape, the restrictions on the plane accuracy and parallelism of the moving body and the vibrating body are alleviated, improving the productivity and reducing the productivity. Cost can be easily obtained. Further, since it is not necessary to provide the vibrating body with a driver as in the conventional case, it is possible to prevent the resonance frequency and the impedance of the vibrating body from shifting in the X and Y directions due to the change in the rigidity of the elastic body.

Further, in the driving method of this structure, the moving body is brought into pressure contact with the ridge line portion of the vibrating body having a specific angle with respect to the vibration displacement in the X and Y directions, and the alternating current is applied in the X and Y directions. By changing only the phase difference of the voltage, the moving speed of the moving body can be arbitrarily driven at a variable speed.

[0015]

【Example】

(Embodiment 1) Hereinafter, Embodiment 1 of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view of a linear actuator according to a first embodiment of the present invention. In the figure, 1 is an elastic body having a rectangular cross section, 2a is a first piezoelectric body, 2b is a second piezoelectric body.
The first and second piezoelectric bodies 2a, 2b on the elastic body 1
The vibrating body 3 is formed by bonding the. Moreover, 4 is a support part, 5 is a moving body. FIG. 2 is a diagram showing the displacement distribution of the first-order free vibration of the rod. Reference numeral 6 is a node (node) corresponding to the position of the support portion 4. In the case of a vibrating body with both ends free, 0.224 l from both ends. The position is (l: vibrator length). From FIG. 1, the moving body 5 is in pressure contact with the ridge line portion of the vibrating body 3 in the vicinity of the maximum position of the vibration displacement amount at the center of the vibrating body 3. The vibrating body 3 is fixed to the supporting portion 4 using a material having a low Young's modulus such as a plastic pin or a material having a low sound velocity. At this time, the supporting part 4 is used for the vibrating body 3 in the X and Y directions.
It is preferable to provide them symmetrically in order to equalize their rigidity, but this is not the case if the influence on the vibration of the support portion 4 can be ignored.

Next, the driving principle will be described with reference to the operation explanatory view of FIG. In the figure, when the vibration ξ _{1 in the} X direction is excited by the _first piezoelectric body _{2 a} and the vibration ξ _{2 in the} Y direction is excited by the second piezoelectric body 2 b, the ridge line portion of the vibration body 3 is X- and Y-direction component moving direction components (ξ
_x1 and ξ _y1 ) vibration displacement ξ _x (Equation 4) and X and Y direction components vertical displacement component (ξ _x2 and ξ _y2 ) of the moving body ξ
_It shows how the elliptical motion that can be represented by the synthetic vibration displacement of _y (Equation 5) occurs.

[0018]

[Equation 4]

[0019]

[Equation 5]

Where φ is the phase difference between the X and Y vibrations, and θ
₁ and θ ₂ are inclination angles of the respective sides of the vibrating body with respect to the horizontal direction, and in the case of the first embodiment, both are π / 4. FIG. 4 shows how the moving speed of the moving body arbitrarily changes when the phase difference φ is changed to 30, 60, 90, 120, and 150 degrees. Of course, the moving direction of the moving body can be reversed by applying an AC voltage with a different sign of the phase difference φ.

As described above, according to the first embodiment of the present invention,
With the configuration in which the moving body 5 is brought into pressure contact with the ridge line portion of the vibrating body 3, there is no restriction on the parallelism between the moving body and the vibrating body and the plane accuracy, and the linear actuator is inexpensive, excellent in mass productivity, and highly reliable. Can be obtained.

By varying the phase of the AC voltage applied to the first and second piezoelectric bodies 2a and 2b, the moving body can be driven at an arbitrary moving speed. This means that, when the moving body is driven at a low speed, when the same driving circuit is used in the X direction and the Y direction as in the conventional case, the vibration displacement in the moving direction and the vertical direction of the moving body becomes small at the same time. The instability of the moving speed of the moving body due to the plane accuracy and undulation of the moving body is increased by increasing the vibration displacement in the vertical direction of the moving direction and decreasing the vibration displacement in the moving direction to reduce the moving speed during low-speed driving. It is possible to stabilize characteristics such as driving force.

Further, since the moving speed can be varied only by controlling the phase difference, it is not necessary to separately provide a control circuit for the X direction and the Y direction, and the circuit configuration is simple. Since it can be up to approximately √2 times larger than a single vibration displacement in the Y direction or the Y direction, it is possible to obtain a linear actuator in which the driving efficiency is significantly improved by the effect of expanding the vibration displacement even for the same input.

The first and second piezoelectric bodies 2a and 2b are not limited to the two planes orthogonal to each other as shown in FIG. 1, but the planes facing each other as shown in FIG. The piezoelectric body 2 is arranged so that the polarization direction is arranged as shown by the arrow.
By providing a'and 2b 'and driving with the combination of the piezoelectric bodies 2a, 2a' and the piezoelectric bodies 2b, 2b ', high driving efficiency due to low impedance and high coupling coefficient is obtained, and low voltage driving and load fluctuation. The advantage is that the control frequency of the control circuit that follows changes in the drive frequency can be lowered.

(Second Embodiment) A second embodiment of the present invention will be described below with reference to the drawings.

FIG. 6 is a sectional view of a linear actuator according to the second embodiment of the present invention. In the figure, 7 is an elastic body having a triangular cross section, 8a is a first piezoelectric body, and 8b is a second piezoelectric body.
Of the first piezoelectric body 8 and the second piezoelectric body 8 on the oblique plane of the elastic body 7.
The vibrating body 9 is formed by bonding a and 8b together, and the moving body 5 is brought into pressure contact with the ridge line portion of the triangular cross section sandwiched by the first and second piezoelectric bodies 8a and 8b. Further, since the displacement distribution of the first-order free vibration of the rod having the triangular cross section is also the same as that in FIG. 2, it can be supported and fixed by the vibration node 6 as in the first embodiment.

Next, the operating principle will be described with reference to FIG.
The basic operation is similar to that of the first embodiment. In FIG. 7, vibration ξ _{1 in the} X direction is excited by the first piezoelectric body 8a,
When the vibration ξ _{2 in the} Y direction is excited by the piezoelectric body 8 b of the above, the vibration displacement ξ _A of the moving direction components (ξ _A1 and ξ _B1 ) of the moving body in the X and Y direction components is applied to the ridge line portion of the vibrating body 7. (Equation 6) and X
And elliptical vibration that can be represented by the combined vibration displacement of the vibration displacement ξ _B (equation 7) of the vertical component (ξ _A2 and ξ _B2 ) of the moving body of the Y direction component.

[0028]

[Equation 6]

[0029]

[Equation 7]

Where φ is the phase difference between the X and Y direction vibrations, θ
₁ and θ ₂ are tilt angles of each side of the vibrating body with respect to the horizontal direction. At this time, as shown in FIG. 7, the moving speed of the moving body can be arbitrarily changed by making the phase difference φ and the tilt angle θ variable. For example, in FIG. 8, the tilt angle θ = 60
Phase difference φ = 30, 60, 90, 120, 1
FIG. 9 shows the relationship of the relative vibration displacement amount with respect to 50 degrees. In FIG. 9, when the phase difference φ = 90 degrees, the tilt angles θ = 10, 30, 4,
The relationship of the amount of relative vibration displacement with respect to 5, 60, and 80 degrees is shown. Of course, the moving direction of the moving body can be reversed by applying an AC voltage with a different sign of the phase difference φ.

As described above, according to the second embodiment of the present invention,
The same effect as that of the first embodiment can be obtained. Further, it is important to match the resonance frequencies of the piezoelectric bodies in order to simplify the driving efficiency and the circuit. However, in the square cross-section vibrating body of the first embodiment, the resonance frequencies cannot be adjusted independently because they are piezoelectrically coupled in the X direction and the Y direction, and the resonance frequencies must be the same because they affect each other. Is difficult. However, in the case of a vibrating body with a triangular cross section, the X and Y directions are not orthogonal to each other, and the resonance frequencies are given to each other, that is, even if the rigidity of the vibrating body is changed by chamfering in one direction, the rigidity in the other direction hardly changes. , Impact is small.
Therefore, since the resonance frequencies of the X and Y direction vibrations can be adjusted independently by processing such as chamfering the ridge portion facing each side, variations in the resonance frequency due to processing accuracy and the like can be easily matched.

Further, for example, when the vibrating body is an equilateral triangle,
The inclination angle θ = 60 degrees, and at that time, the vibration displacement amount can be further expanded up to about 1.2 times as much as that of the first embodiment by an arbitrary value of the phase angle φ, and a more efficient linear actuator Can be obtained.

The triangular shape of the vibrating body is preferably an equilateral triangle or an isosceles triangle in which the sides of the attachment surface of the piezoelectric body have the same length, but the invention is not limited to this.

(Third Embodiment) A third embodiment of the present invention will be described below with reference to the drawings.

In the third embodiment, in the structure of the first and second embodiments, at least the ridge line portion of the vibrating bodies 3 and 9 where the moving body 5 is in pressure contact with the vibrating body of FIGS. 10 (a) and 10 (b). As shown in the perspective view, this is a linear actuator in which a roundness 10 is formed and edges are eliminated, and the other configurations are the same as those in the first and second embodiments.

As described above, according to the third embodiment of the present invention,
Since the scratching wear of the moving body 5 due to the sticking effect at the edge of the vibrating body generated during driving of Examples 1 and 2 is extremely reduced, the life of the linear type actuator is remarkably improved, and the actuator having high long-term reliability is provided. Can be obtained, and the industrial merit is immeasurable.

In the first and second embodiments, the sectional shape of the vibrating body is quadrangular or triangular, but it goes without saying that it may be polygonal. In addition, except for the surface where the piezoelectric body is attached,
It is obvious that the same effect can be obtained with the arc shape as shown in FIG.

Further, as long as the supporting portion 4 can be supported and fixed in the vicinity of the center of the vibrating body, which is the position of the node 6 as shown in FIG. 12 (a), the vibrating body shown in the embodiment of the present invention can be used. Even if holes are provided at each ridge or each plane so as not to penetrate from the diagonal direction or the X and Y directions, the size in the vicinity of the node should be circular or have the same shape as the vibrating body, as shown in FIGS. It may be a reduced shape. Further, although FIG. 12 shows the quadrangular vibrator, it goes without saying that the present invention can be applied to other shapes.

[0039]

As described above, according to the present invention, the movable body is pressed and brought into contact with the ridge line portion of the vibrating body having a quadrangular or triangular cross section to drive the movable body, thereby eliminating any restrictions on the plane accuracy and the parallelism. Therefore, low cost and excellent mass productivity,
A linear actuator with stable characteristics can be realized.

Further, since the moving body is driven by the ridge of the vibrating body, the moving speed of the moving body can be changed only by changing the phase difference φ of the AC voltage applied to the piezoelectric body which excites the vibrations in the X and Y directions. Can be changed arbitrarily, so that the drive circuit and control circuit of each piezoelectric body that excites vibrations in the X and Y directions can be simplified.

Further, even when the moving body is driven at a low speed, the moving body can be driven at a low speed without reducing the vertical component of the vibration displacement amount with respect to the moving direction of the moving body. Since there is no transmission loss of
A linear actuator that does not generate noise and has stable and highly efficient characteristics can be easily realized with a simple configuration and driving principle.

[Brief description of drawings]

FIG. 1 is a sectional view of a linear actuator according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a first-order free vibration distribution of a rod.

FIG. 3 is an operation explanatory diagram of the embodiment.

FIG. 4 is a relationship diagram of relative vibration displacement amount with respect to phase difference in the example.

FIG. 5 is a view showing an arrangement example of piezoelectric bodies of the same embodiment.

FIG. 6 is a sectional view of a linear actuator according to a second embodiment of the present invention.

FIG. 7 is an operation explanatory diagram of the embodiment.

FIG. 8 is a relationship diagram of the vibration displacement amount with respect to the phase difference when the tilt angle is 60 degrees in the example.

FIG. 9 is a relationship diagram of the relative vibration displacement amount with respect to the tilt angle when the phase difference is 90 degrees in the example.

FIG. 10 is a sectional view of a vibrating body of a linear actuator according to a third embodiment of the present invention.

FIG. 11 is a sectional view showing an example of the shape of a vibrating body according to the present invention.

FIG. 12 is a cross-sectional view of a vibrating body showing an example of a supporting portion according to the present invention.

FIG. 13 is a schematic view of a vibrating body of a conventional linear actuator.

FIG. 14 is a diagram showing a conventional driving principle.

[Explanation of symbols]

 1, 7 Elastic body 2a, 8a First piezoelectric body 2b, 8b Second piezoelectric body 3, 9, 11 Vibrating body 4 Support part 5 Moving body 6 Node 10 Roundness 12 Driver 13 Base body 14a, 14b, 14c Piezoelectric element

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Katsushi Takeda 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Masanori Sumihara, 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. (72) Inventor Osamu Kawasaki 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (3)

[Claims] 1. A rod-shaped elastic body having a quadrangular cross section and at least one pair of orthogonal elastic bodies having first and second flat surfaces.
A piezoelectric body is provided to form a vibrating body, and a moving body is brought into pressure contact with at least one ridge line portion of a plane orthogonal to the vibrating body, and the first and second piezoelectric bodies are resonated with the vibrating body. A linear actuator characterized in that the moving speed of the moving body is driven at a variable speed by controlling and applying an AC voltage within a frequency range and an anti-resonance frequency range with an arbitrary phase difference. 2. A bar-shaped elastic body having a triangular cross section and first and second piezoelectric bodies provided on two hypotenuse planes of the elastic body to form a vibrating body. The moving body is brought into pressure contact with the ridge line portion sandwiched by the second piezoelectric body, and
And a second piezoelectric body, wherein the moving speed of the moving body is driven at a variable speed by controlling and applying an AC voltage within the resonance frequency and antiresonance frequency range of the vibrating body with an arbitrary phase difference. Linear actuator that does. 3. The linear actuator according to claim 1, wherein at least a portion of the ridgeline portion of the vibrating body that comes into contact with the moving body is rounded.