CN114291506A - Workpiece conveying device - Google Patents

Abstract

The invention provides an unprecedented workpiece conveying device, namely a workpiece conveying device which can realize stable conveying with small amplitude unevenness and can restrain jumping of workpieces. The workpiece conveying device comprises: a vibrating body (3A) including a conveying surface (31) on which a workpiece is conveyed in a state in which the workpiece is placed; and a vibration generating unit (3B) that generates a dilatational wave containing a compressive strain and a tensile strain in a direction along the workpiece conveying direction to the vibrator (3A) in at least two modes, thereby generating vibration that describes an elliptical orbit to the conveying unit (31), wherein the vibration generating unit (3B) is configured such that the piezoelectric element (36) is disposed at a position that is substantially physically symmetrical with respect to the upper surface side and the lower surface side of the vibrator (3A).

Description

Workpiece conveying device

Technical Field

The present invention relates to a workpiece conveying apparatus for conveying a workpiece by generating a traveling wave on a conveying surface.

Background

In recent years, electronic devices such as chip capacitors have been increasingly miniaturized, and demands for high-speed processing of production facilities have been increased. The parts feeder is also required to convey the workpiece at a high speed, but if the amplitude is increased for high speed, a problem such as dropping and clogging of the workpiece occurs in a portion abutting on the next process equipment. Therefore, although studies have been made to increase the frequency of the driving device, reduce the displacement amplitude, and increase the transport speed, noise is generated because the sensitivity is close to 1kHz to 4kHz, which is high in human ear sensitivity. Further, if the frequency is increased, the conveyance path and the like are easily elastically deformed, which may hinder the normal conveyance of the workpiece. Therefore, the conventional structure utilizing the resonance of the leaf spring is limited in increasing the conveying speed.

Therefore, as shown in patent document 1 (japanese patent application laid-open No. 2017-043431), the following parts feeder is proposed: a flexural traveling wave in an ultrasonic region is generated in the conveying section, and the conveying surface is elliptically vibrated to convey the workpiece.

The workpiece conveying apparatus described in patent document 1 includes a conveying surface having a rail shape and on which a workpiece is placed, and a traveling wave generating mechanism for generating a traveling wave rotating around the conveying surface, and conveys the workpiece on the conveying surface by the traveling wave generated by the traveling wave generating mechanism.

In such a workpiece conveying device, the traveling wave becomes a traveling bending wave by bending the conveying surface. When the traveling flexural wave is generated, an elliptical motion in a side view with respect to the conveyance direction is generated at each position of the conveyance surface, and the workpiece placed on the conveyance surface is conveyed in a direction opposite to the traveling direction of the traveling wave due to a horizontal direction velocity component in the elliptical motion.

Patent document 1 also proposes the following structure: a plurality of slits extending in the width direction are formed in the conveying surface in the circumferential direction (fig. 11 and 12 of patent document 1). By forming the slits on the conveying surface in this way, the horizontal velocity component of the elliptical motion generated on the conveying surface by the traveling flexural wave can be increased.

However, in the conventional work conveying apparatus using the traveling flexural wave, jumping of the work occurs due to vibration in the vertical direction of the elliptical motion on the conveying surface. Therefore, in order to suppress the jumping of the workpiece, it is desirable to increase the amplitude in the horizontal direction with respect to the amplitude in the vertical direction in the elliptical motion. In the case of using the slit structure, although the effect of increasing the amplitude in the horizontal direction is obtained, it is still insufficient, and a new problem such as disturbance of the posture of the workpiece occurs in the slit portion.

In order to generate vibration having a large amplitude in the horizontal direction, it is considered to use a longitudinal wave traveling wave. If a dilatational wave containing a compressive strain and a tensile strain in a direction along the conveying direction of a workpiece is generated in at least two modes for a vibrator including a conveying surface, vibration can be generated in which one point on the conveying surface describes an elliptical orbit having a major axis in the conveying direction of the workpiece when viewed from the side. The workpiece conveying direction is the traveling direction of the traveling wave, and the bowl feeder and the linear feeder are circular and long circular directions.

In the parts feeder using such a longitudinal traveling wave, since the horizontal component of the elliptical vibration of the conveying surface can be increased, it is expected that the workpiece can be conveyed at high speed while suppressing the vibration amplitude in the vertical direction, which causes the workpiece to jump.

In this case, the following configuration is considered: as in the case of the device using the flexural traveling wave, an excitation source (piezoelectric element) for generating the longitudinal traveling wave is attached to the bottom surface (the surface on the opposite side from the conveying surface) or the side surface of the vibrating body.

However, when a compressional/tensile compressional/extensional compressional/extensional wave is generated in the vibrator by the expansion/contraction operation of the piezoelectric element from such a position, as will be described later with reference to fig. 5, a force (bending moment) is applied to the vibrator to generate a bending, and in addition to a desired longitudinal wave, an undesired vibration accompanying the bending may be excited. In particular, in the structure in which the excitation element is attached to the bottom surface of the vibrating body, the vibration mode itself of the longitudinal wave may have a distorted shape as will be described later with reference to fig. 8(b) because the structure is vertically asymmetric.

As a result, the workpiece conveying speed is not uniform, and the workpiece jumps. Such a problem is a problem specific to longitudinal waves, and is not generated in a device using flexural traveling waves which are transverse waves.

Disclosure of Invention

An object of the present invention is to provide an unprecedented workpiece conveying apparatus that can realize stable conveyance with little variation in amplitude while suppressing jumping of workpieces, in a workpiece conveying apparatus that conveys workpieces by generating a traveling wave on a conveying surface.

In order to achieve the above object, the present invention adopts the following aspects.

That is, the workpiece conveying apparatus of the present invention includes: a vibrating body including a conveying section for conveying the workpiece in a state where the workpiece is placed; and a vibration generating unit that generates a dilatational wave including a compressive strain and a tensile strain in a direction along a conveying direction of the workpiece with respect to the vibrator in at least two modes, thereby generating vibration that describes an elliptical orbit with respect to the conveying surface, wherein the vibration generating unit is disposed at a position that is substantially physically symmetrical with respect to an upper surface side and a lower surface side of the vibrator.

Here, "physical symmetry" refers to the following structure: the excitation source is disposed so that an excitation force acts on the neutral axis, and the action point of the elastic force and the inertia force at the time of generating the longitudinal vibration is substantially coincident with the neutral axis. The "neutral axis" means an axis in which tension and compression are balanced with respect to bending without generating stress when the vibrating body is viewed from the thickness direction. Such a shaft-connected surface is also referred to as a neutral surface.

Thus, the occurrence of unnecessary vibration can be suppressed without generating a moment that causes the vibrating body to bend. As a result, stable conveyance with less variation in amplitude, an improved traveling wave ratio, and less variation in speed can be achieved. In the structure in which the vibration generating portion is disposed on the bottom surface, the asymmetry is further increased depending on the shape such as the thickness of the excitation source, and thus it is difficult to freely design the shape of the excitation source. Therefore, for example, it is also easy to design the excitation source to be thick to increase the capacitance.

In this case, the excitation source is preferably disposed along the neutral axis of the vibrator within the thickness of the vibrator. In the case where the upper side and the lower side are the same single material, the vicinity of the center in the thickness direction is a neutral axis, and if an excitation source is arranged here, physical symmetry can be obtained. In addition, even if slightly asymmetric, physical symmetry can be obtained if the position of the neutral axis is shifted in the thickness direction. Further, since the vibration source is disposed within the thickness, both sides of the vibration source are sandwiched by the vibrating body, and thus, a failure such as a crack is not likely to occur.

Preferably, the vibrator includes an upper vibrator and a lower vibrator, and the upper vibrator and the lower vibrator are arranged so as to sandwich the excitation source. With this structure, the electrode can be easily manufactured with a half-divided structure, and the electrode can be easily drawn out.

Preferably, the upper vibrator and the lower vibrator are made of the same material or have the same shape as a main portion, and the excitation source is disposed substantially on the neutral axis. In this case, if the upper side and the lower side are made of the same single material, the vicinity of the center in the thickness direction is a neutral axis, and if an excitation source is disposed therein, physical symmetry can be obtained, so that an appropriate configuration can be easily realized.

Preferably, the physical asymmetry between the upper vibrator and the lower vibrator is corrected by giving one of the upper vibrator and the lower vibrator a different shape from the other. Even if the upper vibrator and the lower vibrator have different shapes or different materials and thicknesses, the physical symmetry can be relatively easily and appropriately secured by correcting the shapes.

Preferably, the vibration sources are arranged in pairs at positions displaced toward the upper surface side and positions displaced toward the lower surface side in the vibrator. In this way, the synthesized excitation force acts on the neutral axis, and thus, physical symmetry can be ensured, and an increase in excitation force and the like can be achieved.

The effects of the present invention are as follows.

According to the present invention described above, since the traveling wave based on the uniform elliptical vibration with the conveying direction as the major axis is generated on the conveying surface by the compressional wave, stable conveyance can be realized in which the jumping of the workpiece is suppressed and the variation in amplitude is small.

Drawings

Fig. 1 is a perspective view showing a schematic configuration of a workpiece conveying device according to the present embodiment.

Fig. 2 is a view showing the conveying unit in fig. 1.

Fig. 3 is a schematic diagram showing a structure for exciting a vibrating body in the workpiece conveying device.

Fig. 4 is a diagram showing an arrangement structure of piezoelectric elements as an excitation source.

Fig. 5 is a diagram showing a comparative example of fig. 4.

Fig. 6 is a diagram illustrating generation of longitudinal waves from compressional waves.

Fig. 7 is a diagram showing a state in which a traveling wave generated by a longitudinal wave propagates.

Fig. 8 is a diagram showing a state of deformation occurring in the vibrator in the excitation source configuration of fig. 4 and 5.

Fig. 9 is a view illustrating physical symmetry with the neutral axis in the case of the bowl feeder.

Fig. 10 is a diagram illustrating a configuration in which physical symmetry is corrected by a shape.

Fig. 11 is a view corresponding to fig. 4 showing a modification of the present invention.

Fig. 12 is a view corresponding to fig. 4 showing another modification of the present invention.

In the figure:

3A, 4A vibrators, 31, 41 carriers, 3B, 4B vibrators (traveling wave generators), 3A1, 4A1 upper vibrators, 3A2, 4A2 lower vibrators, 36, 46 excitation sources (piezoelectric elements), and N neutral axes.

Detailed Description

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

A workpiece transfer device (parts feeder) 1 of the present embodiment shown in fig. 1 includes a disc-shaped bowl feeder 3 and a linear feeder 4 connected to each other so as to extend in a tangential direction of the bowl feeder 3 on a base portion 2.

The bowl feeder 3 includes a bowl feeder side conveying part 31 as a disk-shaped member. The bowl feeder side conveying unit 31 is fixed to the base unit 2 by a fixing unit 32 located at the center. As shown in the drawing, the upper surface of the bowl feeder side conveying portion 31 includes a concave portion 33 into which the workpiece is input on the center side, a mortar-shaped inclined surface 34 around the concave portion 33, and a spiral track 35 serving as a conveying track for conveying the workpiece is formed from the peripheral edge of the concave portion 33 to the upper edge of the inclined surface 34. The spiral track 35 includes a groove that rises while describing a spiral, and the bottom of the groove serves as a conveying surface 351. The conveying surface 351 conveys the workpiece by being deformed in an undulating manner by a vibration generating portion (traveling wave generating portion) 3B (see fig. 3).

The linear feeder 4 includes a linear feeder side conveying portion 41 having an oval shape in plan view. The linear feeder side conveying portion 41 is fixed to the base portion 2 by a fixing portion 42 located at the center in the width direction. The carrying rail in the linear feeder 4 includes a main rail 43 and a return rail 44. The main rail 43 includes a linear groove extending in the longitudinal direction on the upper surface of the linear feeder side conveying portion 41, and the bottom of the groove serves as a conveying surface 431. The return rail 44 includes an oblong groove located on the inner side in the width direction of the main rail 43 on the upper surface of the linear feeder side conveying portion 41, and the bottom of the groove is a conveying surface 441. These conveying surfaces 431 and 441 convey the workpiece by being deformed in an undulating manner by a vibration generating portion (traveling wave generating portion) 4B (the same configuration as the vibration generating portion 3B of the bowl feeder 3 of fig. 3, see fig. 2).

In each of the feeders 3 and 4, a plurality of workpieces can be conveyed on the conveying surfaces 351, 431, and 441 in a state of being arranged adjacent to each other, and also can be conveyed with a space.

A workpiece having an inappropriate posture or the like among the workpieces on the main rail 43 is moved from the main rail 43 to the return rail 44 by a movement mechanism (air nozzle or the like) not shown. In the schematic illustration of the drawings, the return track 44 is depicted as circulating, but in practice the following suitable arrangement may be employed: the workpiece moved to the return rail 44 is returned to the bowl feeder 3, or is again merged with the main rail 43, or the like.

Since the mechanism for conveying the workpiece is common to the bowl feeder 3 and the linear feeder 4, the configuration of the present embodiment will be described below by taking either the bowl feeder 3 or the linear feeder 4 as an example.

First, a basic configuration will be described by taking the bowl feeder 3 as an example, and as shown in fig. 1 to 3, the bowl feeder 3 includes a vibration body 3A and a vibration generating portion 3B. The vibrating body 3A is a part of the bowl-type feeder side conveying portion 31, and is an annular member. The vibrator 3A is an elastic body and is formed of a material that serves as a medium for transmitting waves. The vibrator 3A of the present embodiment has a structure in which the piezoelectric element 36 as an excitation source is embedded inside, and is not a solid metal member to which the excitation source is attached on the lower surface or the side surface. As will be described later.

In order to generate a dilatational wave in the vibrator 3A, the vibration generating unit 3B applies an ac voltage from the exciting unit 37 to the piezoelectric element 36 as an excitation source, and causes the piezoelectric element 36 to perform an expansion operation and a contraction operation in the circumferential direction (the workpiece conveying direction and the traveling direction of the traveling wave), as shown in fig. 3. The dilatational wave causes, as shown in fig. 4, a tensile strain indicated by an arrow (solid line) a1 and a compressive strain indicated by an arrow (broken line) a2 in the drawing to proceed in a direction (circumferential direction) along the conveying direction of the workpiece by the poisson effect of the vibrator 3A, and causes a displacement B1 for contracting and a displacement B2 for expanding in the thickness direction orthogonal to the conveying direction.

As shown in fig. 6, the vibrator 3A includes a plurality of standing wave modes (natural modes) of longitudinal waves as dilatational waves, which alternately generate tensile strain and compressive strain in the circumferential direction. In the present embodiment, a 0 ° mode standing wave and a 90 ° mode standing wave, which are two standing waves having substantially the same natural frequency and spatially shifted by 90 °, are synthesized to form a traveling wave in which peaks and valleys shown in fig. 7 travel in, for example, the clockwise direction indicated by an arrow. Further, the "standing wave" refers to a wave (longitudinal wave) generated at a constant position in the circumferential direction of the vibrator 3A.

Since the mechanism of the medium movement itself in the standing wave of the longitudinal wave is known, a detailed description thereof will be omitted.

In the medium, in each of fig. 6(a) and 6(b), the upper diagram shows the case where the vibrating body 3A is deformed by a compressional wave, and the lower diagram is a diagram in which the hydrophobic state is recorded side by side using a vertical line indicating hydrophobic for easy understanding. As is clear from these drawings, in fig. 6(a) and 6(b), sparse portions and dense portions are periodically replaced with time in the circumferential direction. In fig. 6(a), the positions a and B are positions of "antinodes" in the displacement distribution of the longitudinal wave, and the positions C and D are positions of "nodes". The position C causes tensile strain to make the medium "sparse", and the position D causes compressive strain to make the medium "dense". When fig. 6(a) and 6(b) are compared, the strain state at the position of the anti-node A, B is unchanged and the node C, D is inverted in the hydrophobic state.

The vibrator 3A expands or contracts in the thickness direction by a change amount corresponding to the poisson's ratio as it expands or contracts in the circumferential direction. The poisson's ratio defines that the strain in the thickness direction and the strain in the circumferential direction are in an inverse relationship. That is, the vibrator 3A contracts in the thickness direction at the tension position C and expands in the thickness direction at the compression position D. By generating displacements having phases different by 90 ° at the positions of the 0 ° mode and the 90 ° mode, a flat elliptical vibration R having the traveling direction as the major axis is formed as shown in fig. 6 (b).

At the upper portion of the elliptical vibration R, the workpiece W contacts the conveying surface to generate a conveying force M. Since the longitudinal wave has a longer axis of the ellipse and a smaller vertical displacement in the conveying direction than the transverse wave, the workpiece W has a smaller jump, and an effective conveying force M can be realized.

As shown in fig. 3, the vibration generating section 3B includes a piezoelectric element 36 serving as a plurality of excitation sources, and applies the compressive strain and the tensile strain to the vibrator 3A. In the present embodiment, the vibrator a is configured by disposing the piezoelectric element 36 within the thickness of the vibrator 3A as shown in fig. 4, and the piezoelectric element 36 is not attached to the lower surface (or the side surface) of the vibrator 3A as shown in fig. 5. As shown in fig. 3, each piezoelectric element 36 includes: a first group (first piezoelectric element group) 36A configured to exchange polarization directions ("+", "-") with a pitch of 1/2(λ/2) of the wavelength of the standing wave pattern; and a second group (second piezoelectric element group) 36B which is arranged at a position shifted from the first group 36A by 1/4 wavelengths (λ/4) in the circumferential direction and which is arranged so as to reverse the polarization direction at a pitch of 1/2 of the wavelength of the standing wave pattern, similarly to the first group 36A. That is, the plurality of piezoelectric elements 36 are respectively grouped into the groups 36A, 36B of the number corresponding to the number of the above-described modes (two in the present embodiment).

As shown in fig. 3, the excitation unit 37 includes a control unit 371 for applying a sinusoidal wave having a frequency corresponding to a natural mode for generating a compressional wave to the piezoelectric element 36, and the control unit 371 is connected to the piezoelectric element 36. The control unit 371 inputs sine waves of different phases to the piezoelectric elements 36 by the groups 36A and 36B. Specifically, the sine wave of the alternating voltage is divided into two systems, and one system is shifted in phase in time by the phase shifter 371 d. Although not shown, the control unit 371 can adjust the frequency of the sine wave to increase or decrease. The original sine wave and the phase-shifted sine wave 371a are amplified by amplifiers 371B and 371c, respectively, and applied to the piezoelectric elements 36 belonging to the groups 36A and 36B via the current-carrying terminals 37a and 37B. In the present embodiment, a sinusoidal wave having a temporal phase difference is applied to the phase shifter 371d so that the frequency substantially coincides with the natural frequency in the 0 ° mode and the 90 ° mode and the standing wave phases of the 0 ° mode and the 90 ° mode are shifted by 90 ° in time with respect to the piezoelectric elements 36 belonging to the respective groups 36A and 36B.

Each piezoelectric element 36 is disposed at an antinode position in the displacement distribution of the longitudinal wave standing wave mode. One of the two standing wave patterns spatially shifted in phase by 90 ° is excited by one piezoelectric element group 36A and the other of the two standing wave patterns spatially shifted in phase by 90 ° is excited by the other piezoelectric element group 36B by a sine wave applied to the piezoelectric elements 36 from the control section 371 so as to be temporally shifted in phase by 90 °.

As a result, as shown in fig. 6 and 7, a standing wave of a longitudinal wave is generated in the vibrator 3A instead of a transverse wave (in the case of a flexural traveling wave). Then, by generating a standing wave in a plurality of (two in the present embodiment) standing wave patterns whose phases are spatially and temporally shifted, the traveling wave can be made to travel in the circumferential direction.

In the present embodiment, as shown in fig. 4, the piezoelectric element 36 as an excitation source is disposed in the thickness of the vibrator 3A in order to make the position of the piezoelectric element 36 substantially physically symmetrical with respect to the upper surface side and the lower surface side of the vibrator 3A. That is, this arrangement is intended to substantially match the point of action of the elastic force and the inertial force with the neutral axis N when the vertical vibration occurs. As mentioned above, the neutral axis N refers to the axis: when the vibrator 3A is observed from the thickness direction (longitudinal cross-sectional direction), the tension and compression are balanced with respect to the bending, and no stress is generated. Specifically, in the present embodiment, the upper vibrator 3A1 and the lower vibrator 3A2 are arranged so as to sandwich the piezoelectric element 36 as an excitation source, and preferably have a half-divided sandwich structure, and the upper vibrator 3A1 and the lower vibrator 3A2 are made of the same material and have substantially the same shape such as thickness, and the piezoelectric element 36 as an excitation source is arranged along the neutral axis N of the vibrator 3A.

In the configuration of fig. 5, compared to fig. 4, since the piezoelectric element 36 is extended and contracted on the lower surface (or side surface) of the vibrator 3A, and the entire vibrator 3A is compressed and extended in the conveying direction from this position, displacement in the bending direction of the vibrator 3A due to the bending moment is increased at a position farther from the piezoelectric element 36 as indicated by an arrow in the drawing.

Fig. 8(a) is a diagram showing a deformed state of the vibrator 3A in the arrangement of the piezoelectric elements shown in fig. 4, and fig. 8(b) is a diagram showing a deformed state of the vibrator 3A in the arrangement of the piezoelectric elements shown in fig. 5.

In fig. 8(a), the compression and tension states in the horizontal direction are shown at intervals indicating a longitudinal line that is hydrophobic. The part indicated by the symbol P is a part with a small displacement in the horizontal direction, and the part indicated by the symbol Q is a part with a large displacement in the horizontal direction. The displacement in the thickness direction is conversely increased at the portion P where the displacement in the horizontal direction is small, and the displacement in the thickness direction is decreased at the portion Q where the displacement in the horizontal direction is large. At these P, Q positions, when the interval of the vertical line representing the hydrophobization, the shape of the vertical line, and the direction of extension are observed, in the vicinity of P, Q, a line representing the hydrophobization drawn across the vertical line above the neutral axis N and passing through the upper and lower vertical lines extends substantially orthogonal and symmetrical to the neutral axis N. When the upper conveying surface 351 is observed, the positions of the mountain portions and the positions of the valley portions are smoothly continued at a predetermined cycle, and an ideal longitudinal wave traveling wave is formed on the conveying surface 351 by uniform elliptical vibration.

In contrast, in fig. 8(b), at positions P 'and Q' corresponding to the position P, Q, lines indicating hydrophobicity, which are drawn through vertical lines extending over the neutral axis N and passing through the upper and lower sides, extend in a direction asymmetrically curved from the direction perpendicular to the neutral axis N due to a bending moment and are irregularly distorted, and when the upper conveying surface 351 'is observed, the positions of the peaks and the positions of the valleys are distorted and discontinuous, and a smooth traveling wave cannot be formed on the conveying surface 351'.

As can be seen from this, fig. 8(a) can realize stable conveyance with less variation in amplitude while suppressing jumping of the workpiece, as compared with fig. 8 (b).

In the bowl feeder 3 and the line feeder 4, although the vibrating body is described as a ring shape in fig. 2, physical symmetry can be ensured by appropriately adopting the following form: when the neutral axis N is present in a mortar shape at a substantially central position of the upper surface and the lower surface as necessary as shown in fig. 9(a), a piezoelectric element is disposed along the neutral axis N; alternatively, when a virtual recess 34' physically equivalent to the recess 34 of the bowl feeder 3 is formed on the lower surface side as shown in fig. 9(b), a piezoelectric element or the like is arranged along the neutral axis N of planarity.

Further, if necessary, a virtual rail 35 'can be secured on the lower surface side of the lower vibrator 3a2, and the virtual rail 35' can be physically symmetrical with the rail 35 of the upper vibrator 3a1 as shown in fig. 10, for example. That is, including the case of fig. 9(b), it is possible to correct the physical asymmetry between the upper vibrator 3a1 and the lower vibrator 3a2 by giving a shape different from one of the upper vibrator 3a1 or the lower vibrator 3a2 to the other one as necessary. Therefore, even if the upper vibrator 3a1 and the lower vibrator 3a2 are different in shape or material or thickness, physical symmetry can be ensured by utilizing the correction in shape. This also means that, as shown in fig. 10, the shape of the virtual rail 35' is not necessarily the same as the rail 35 of the conveying unit.

The measures shown in fig. 9(a), 9(b), and 10 can be similarly applied to the linear feeder 4.

As described above, the workpiece conveying apparatus according to the present embodiment includes: vibrators 3A, 4A including conveying sections 31, 41 for conveying the workpiece in a state where the workpiece is placed; and vibration generating units 3B and 4B for generating dilatational waves including compressive strain and tensile strain in a direction along the workpiece conveying direction to the vibrators 3A and 4A in at least two modes to generate vibrations describing an elliptical orbit to the conveying units 31 and 41, wherein the vibration generating units 3B and 4B are configured such that piezoelectric elements 36 and 46 as excitation sources of the vibration generating units 3B and 4B are disposed at positions physically substantially symmetrical with respect to the upper surface side and the lower surface side of the vibrators 3A and 4A.

Thus, since no moment is generated to bend the vibrators 3A, 4A, it is possible to suppress the generation of unnecessary vibration. As a result, stable conveyance with less variation in amplitude, an improved traveling wave ratio, and less variation in speed can be achieved.

In the configuration in which the piezoelectric element 36 as the excitation source is disposed on the bottom surface, the asymmetry is further increased depending on the shape such as the thickness of the piezoelectric element 36, and thus it is difficult to freely design the shape of the piezoelectric element 36. Therefore, for example, it is also easy to design the piezoelectric element 36 to be thick to increase the capacitance.

Further, a piezoelectric element 36 as an excitation source is disposed along the neutral axis N of the vibrators 3A, 4A within the thickness of the vibrators 3A, 4A. Therefore, since the piezoelectric element 36 is disposed within the thickness, both sides thereof are sandwiched by the vibrator, and a failure such as a crack is not easily generated.

The vibrators 3A and 4A include an upper vibrator 3A1(4A1) and a lower vibrator 3A2(4A2), and the upper vibrator 3A1(4A1) and the lower vibrator 3A2(4A2) are arranged so as to sandwich the piezoelectric elements 36 and 46 as excitation sources. Therefore, the electrode can be easily manufactured by the half-divided structure, and the electrode can be easily drawn out.

The upper vibrator 3a1(4a1) and the lower vibrator 3a2(4a2) are made of the same material or have the same shape, and the excitation source is disposed substantially on the neutral axis N. Therefore, physical symmetry can be obtained with a simple configuration.

Further, the physical asymmetry between the upper vibrator 3a1(4a1) and the lower vibrator 3a2(4a2) can be corrected by giving one of the upper vibrator 3a1(4a1) and the lower vibrator 3a2(4a2) a shape different from the other. Accordingly, even if the upper vibrator 3a1(4a1) and the lower vibrator 3a2(4a2) have different shapes or different materials and thicknesses, the shapes can be corrected relatively easily, and physical symmetry can be appropriately secured.

As described above, the workpiece conveying apparatus according to the present embodiment can generate traveling waves based on elliptical vibration with the conveying direction as the major axis on the conveying surface by the dilatational wave, and can realize stable conveyance with small variations in amplitude while suppressing jumping of workpieces.

While one embodiment of the present invention has been described above, the specific configuration of each part is not limited to the above embodiment.

For example, in the case where the upper side and the lower side of the vibrating body are made of a single material, the vicinity of the center in the thickness direction is the neutral axis, and if the excitation source is arranged here, physical symmetry can be obtained, but even if it is slightly asymmetric, the physical symmetry can be obtained by adjusting the position of the neutral axis by shifting it in the thickness direction.

As shown in fig. 11, even if the surface layer 30 made of a material having sufficiently low density and young's modulus such as resin or a thin material such as a coating is provided on the surface of either the upper vibrator 3a1 or the lower vibrator 3a2, physical symmetry can be secured when the position of the neutral axis N, the elastic force, and the inertial force are not substantially applied. Of course, as described above, the physical symmetry may be improved by offsetting the neutral axis N as necessary, or by modifying the shape of the lower vibrator 3a2(4a2) or the like.

As shown in fig. 12, the piezoelectric element 36 as the excitation source may be disposed in pairs at a position displaced toward the upper surface side and a position displaced toward the lower surface side in the vibrator 3A in a vertically symmetrical positional relationship. Since the synthesized excitation force acts on the neutral axis N in this way, it is possible to increase the excitation force while ensuring physical symmetry.

In addition, the piezoelectric element may be formed in a multilayer structure, or the excitation source may be formed by an element other than the piezoelectric element, and various modifications may be made without departing from the scope of the present invention.

Further, even if the upper elastic body and the lower elastic body have slightly different thicknesses due to characteristics such as rigidity, imbalance in physical symmetry can be absorbed by making the upper elastic body and the lower elastic body different in material.

Claims (3)

1. A workpiece conveying apparatus, comprising:

a vibrating body including a conveying surface on which a workpiece is conveyed in a state where the workpiece is placed; and

a vibration generating unit that generates a dilatational wave including a compressive strain and a tensile strain in a direction along a conveying direction of the workpiece to the vibrator in at least two modes to generate vibration that describes an elliptical orbit on the conveying surface,

the vibration generating portion is disposed at a position substantially symmetrical in physical relation to an upper surface side and a lower surface side of the vibrating body.

2. The workpiece handling device of claim 1,

an excitation source is disposed along a neutral axis of the vibrating body within a wall thickness of the vibrating body.

3. The workpiece handling device of claim 2,

the vibrator includes an upper vibrator and a lower vibrator, and the upper vibrator and the lower vibrator are arranged so as to sandwich the excitation source.

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