JP2543149B2 - Ultrasonic linear motor - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic linear motor that generates a driving force by using elastic vibration of a piezoelectric body.

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

Hereinafter, a conventional technique of an ultrasonic linear motor will be described with reference to the drawings.

FIG. 6 is a schematic view of a conventional ultrasonic linear motor. The vibrating body 5 is constructed by sandwiching and fixing the disk-shaped piezoelectric bodies 1 and 2 between the cylindrical elastic bodies 3 and 4. . When an AC electric field in the vicinity of the resonance frequency of the vibrating body 5 is applied to the piezoelectric bodies 1 and 2, the vibrating body 5 vibrates vertically in the longitudinal vibration mode as indicated by the arrow in the figure.

The mechanical impedance of the vibrating body 5 viewed from the vibrating surface is impedance-converted by the horn 6 to match the mechanical impedance with respect to the bending vibration of the transmission rod 7. The tip of the horn 6 is acoustically coupled to a portion of the transmission rod 7 near one end. Therefore, the vertical vibration of the vibrating body 5 is efficiently transmitted to the transmission rod 7 by the horn 6, and the transmission rod 7 flexurally vibrates. This flexural vibration proceeds from one end of the transmission rod 7 toward the other end.

At a portion near the other end of the transmission rod 7, the tip of the horn 8 is acoustically coupled like the one end. The disk-shaped piezoelectric bodies 9 and 10 are sandwiched and fixed by the cylindrical elastic bodies 11 and 12, so that the same vibrating body 13 as the vibrating body 5 is constituted. The vibrating body 13 is connected to the horn 8. Therefore, the flexural vibration that has progressed from one end of the transmission rod to the other end is transmitted to the vibrating body 13 by the horn 8,
Converted to 13 vertical vibrations. An impedance-matched load R is connected to the piezoelectric bodies 9 and 10, and the above-described vertical vibration is consumed by the load R. Therefore, bending vibration exists only on the transmission rod 7 as a traveling wave.

Reference numeral 14 denotes a moving body, which is driven by the bending vibration traveling on the transmission rod 7 and is interlocked with the direction opposite to the traveling direction of the traveling wave. In the above description, the moving direction of the moving body 14 is one direction, but if the driving end is reversed, the moving body 14 also moves in the opposite direction.

FIG. 7 shows the principle by which a flexural elastic traveling wave drives a moving body. Due to the bending vibration of the transmission rod 7, the transmission rod 7
A point on the surface of (i.e., point A) draws an elliptical locus in the vertical direction w and the horizontal direction u. The velocity at the apex of this elliptical trajectory is opposite to the traveling direction of the wave. When the moving body 14 is installed under pressure on the transmission rod 7, the moving body 14 contacts the transmission rod 7 only near the apex of the wave. Therefore, the frictional force between the transmission rod 7 and the moving body 14,
The lateral velocity of the elliptical locus drives the moving body 14 in the direction opposite to the traveling direction of the wave. Further, reference numeral 15 in the figure is a wear resistant friction material for efficiently extracting the lateral component of the elliptical locus.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention The above-described conventional ultrasonic linear motor excites a Langevin structure vibrating body in a longitudinal vibration mode, and vibrates the vibration surface of the vibrating body into a transmission rod by a horn to excite vibration. Therefore, it is necessary to accurately match the mechanical impedance between the vibrating surface and the horn and between the horn and the transmission rod. In reality, this is very difficult and results in some loss.

Further, in order to excite only the traveling wave in the transmission rod, the vibration energy input from one side must be completely lost on the other side.

In addition, in order to move a relatively small moving body, the vibrating body and the transmission rod must be vibrated. Therefore, there are problems of low efficiency and large size.

Means for Solving the Problems In order to solve the above problems, an ultrasonic linear motor of the present invention has a vibrating body formed by fixing piezoelectric bodies to two adjacent rectangular surfaces of an elastic prism having a square cross section. Comprising, the both ends of the elastic prism, or the vicinity corresponding to 0.22 of the length of the prism from both ends is processed into a circular cross section, and the vibration is achieved by fixing the circular cross section in a circumferential shape. A body is supported and fixed, and an AC electric field having a predetermined phase difference is applied to each of the two piezoelectric bodies to simultaneously excite two flexural vibrations having different vibration displacement directions in the vibrating body. In this configuration, the vibrating body is moved along the rail by pressurizing the substantially central portion of one of the two non-fixed rectangular surfaces on the rail.

Action By applying an alternating electric field to the above two piezoelectric bodies,
Two flexural vibrations with spatially 90 degrees different phases are excited in the vibrating body, and one of the two rectangular planes without the piezoelectric body of the vibrating body is pressure-installed on the rail to direct the vibrating body By moving, the ratio of the vibration energy of the vibrating body to the mechanical output can be reduced, the size can be reduced, the weight can be reduced, and the efficiency can be improved.

By processing both ends of the above-mentioned elastic prism, or the vicinity from both ends corresponding to the length 0.22 of the prism to have a circular section, and supporting and fixing the circular section, the above-mentioned 2
The vibrating body can be supported and fixed so that the two flexural vibrations are affected to the same degree.
Two flexural vibrations can be excited.

Embodiment Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a perspective view of a vibrating body used in an ultrasonic linear motor according to an embodiment of the present invention. In the elastic prism 16 having a square cross section, the slits 19 are processed so as to have a circular cross section in the vicinity of the length of 0.22 from both ends. Then, on the two adjacent rectangular surfaces of the elastic body 16, the piezoelectric body 17
The vibrating body 20 is configured by bonding 18 to each other. When an AC electric field near the resonance frequency is applied to the piezoelectric body 17, the vibrating body 20 flexurally vibrates in the direction of arrow B. When an AC electric field is applied to the piezoelectric body 18, the vibrating body 20 flexurally vibrates in the direction of arrow C.

FIG. 2 is a displacement distribution diagram in the longitudinal direction when only one piezoelectric body of the vibrating body of FIG. 1 is driven. Since the two flexural vibrations are spatially 90 degrees out of phase, the two piezoelectric elements 17
When an alternating electric field 90 degrees out of phase is applied to and 18, the rectangular surface of the vibrating body 20 makes a rotational motion in a plane perpendicular to the rectangular surface. Rotational movement is based on the displacement distribution shown in FIG.
Maximum at the center of 20.

The positions of the slits 20 correspond to the positions of the nodes of the displacement distribution shown in FIG. As shown in FIG.
Supports A21 and 22 with semi-circular holes and slit 20
B23 with two semi-circular holes corresponding to the position of
Thus, by supporting and fixing via the slit 20, it is possible to fix the position with a small loss and the same effect on the two flexural vibrations. As a result, the impedance characteristics of the two vibrations match and the control of the rotary motion is simplified.

If the rail 24 is configured to hit the central portion of the rectangular surface of the vibrating body 20 to which the piezoelectric body is not adhered, the vibrating body itself is applied to the rail 24 by applying an AC voltage to each of the two piezoelectric bodies. Move at maximum speed along. Although one vibrating body is used in this embodiment, the same movement can be realized by arranging a plurality of vibrating bodies in parallel.

FIG. 4 is a perspective view of a vibrating body used in an ultrasonic linear motor according to another embodiment of the present invention. Reference numeral 25 is an elastic prism having a square cross section, and piezoelectric bodies 26 and 27 are bonded to two adjacent rectangular surfaces to form a vibrating body 28. Elastic body
Both ends of 25 are processed to have a circular cross section. When an AC electric field near the resonance frequency is applied to the piezoelectric body 26, the vibrating body 28 flexurally vibrates in the direction of arrow D. Also, piezoelectric
When an alternating electric field is applied to 27, the vibrating body 28 flexurally vibrates in the direction of arrow E.

FIG. 5 is a displacement distribution in the lengthwise direction when one piezoelectric body of the vibrating body of FIG. 4 is driven. Similar to the flexural vibration of the vibrating body 20 shown in FIG. 1, the two flexural vibrations are spatially 90
Since the phases are out of phase with each other, if an alternating electric field with a phase out of 90 degrees is applied to the two piezoelectric bodies 26 and 27, the rectangular surface of the vibrating body 28 makes a rotational motion in a plane perpendicular to the rectangular surface. . The rotational movement is maximum at the center of the vibrating body 28 according to the displacement distribution of FIG.

As shown in FIG. 3, by supporting and fixing the vibrating body 28 with two supports having semi-circular holes so as to sandwich the circular cross section at both ends, a small loss and two flexural vibrations are prevented. It is possible to fix the position with the same influence. As a result, the impedance characteristics of the two vibrations match and the control of the rotary motion is simplified.

Further, as in the case shown in FIG. 3, if the rail is configured to hit the central portion of the rectangular surface of the vibrating body 28 where the piezoelectric body is not adhered, an AC voltage is applied to each of the two piezoelectric bodies. By doing so, the vibrating body itself moves at the maximum speed along the rail.

EFFECTS OF THE INVENTION According to the present invention, by moving the vibrating body, an ultrasonic linear motor can be realized with small vibration energy. That is, it is possible to provide an ultrasonic linear motor having a small size, a small weight, and a high efficiency with a simple structure.

[Brief description of drawings]

FIG. 1 is a perspective view of a vibrating body used in an ultrasonic linear motor according to an embodiment of the present invention, FIG. 2 is a displacement distribution diagram in the longitudinal direction of flexural vibration of the vibrating body of FIG. 1, and FIG. FIG. 1 is a perspective view showing the structure for supporting and fixing the vibrating body and the ultrasonic linear motor in FIG. 1, FIG. 4 is a perspective view of the vibrating body used in the ultrasonic linear motor in another embodiment, and FIG. FIG. 6 is a displacement distribution diagram of flexural vibration of the vibrating body in the longitudinal direction, FIG. 6 is a general view of a conventional ultrasonic linear motor, and FIG. 7 is an explanatory diagram showing a driving principle of the ultrasonic linear motor. 16 …… elastic body, 17,18 …… piezoelectric body, 19 …… slit, 20
…… Vibrator, 21, 22 …… Support A, 23 …… Support B, 24
...... Rail, 25 …… Elastic body, 26,27 …… Piezoelectric body, 28 ……
Vibrating body.

Claims (1)

(57) [Claims] 1. A vibrating body is formed by adhering piezoelectric bodies to two adjacent rectangular surfaces of an elastic prism having a square cross-section, and the vibrating body is constituted by both ends of the elastic prism or the length of the prism from both ends. Of 0.22 is processed into a circular cross section, and the circular cross section is circumferentially fixed to support and fix the vibrating body, and the two piezoelectric bodies have an alternating current of a predetermined phase difference. Two flexural vibrations having different vibration displacement directions are simultaneously applied to the vibrating body by applying an electric field, respectively, and the piezoelectric body of the vibrating body is not fixed.
An ultrasonic linear motor characterized in that the vibrating body is moved along the rail by pressure-installing a substantially central portion of one of the two rectangular surfaces on the rail.