JPH08149860A - Driver using electromechanical converting element - Google Patents

Abstract

PURPOSE: To provide a driver using an electromechanical converting element which can be driven stably at high speed, without an elastic member to give frictional force being elastically transformed in the shifting direction, even if a drive member reciprocates at different speeds in positive and negative directions. CONSTITUTION: A driver is composed of a static member 1, a piezoelectric element 2, a drive shaft 3, and a slider 4. The slider 4 is equipped with a main body part 4a in frictional contact with the drive shaft 3, and a mount 4e for a member to be driven such as a lens retaining frame, etc. The drive shaft 3 pierces the cut 4b of the main body 4a, and a catch member 5 engages with right and left wall faces without slack, and it contacts with approximately upper half of the drive shaft 3. The catch member 5 contacts by friction with the drive shaft 3 by the plate spring 6 fixed to the main body 4a, being pressed against it, and the pressing force is adjusted by the extent of the fastening of a screw 8. Since the plate spring 6 to give frictional force contacts with the drive shaft 3 through the catch member 5, even by the motion of the drive shaft, it is not elastically transformed in the shifting direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive device using an electromechanical conversion element.

[0002]

2. Description of the Related Art A sawtooth wave drive pulse is supplied to an electromechanical conversion element coupled to a drive shaft to displace the drive shaft in the axial direction, and a moving member frictionally coupled to the drive shaft is moved in the axial direction. An actuator is known (hereinafter, such an actuator is referred to as an "impact type actuator").
Called).

FIG. 8 is a perspective view showing an example in which such an impact type actuator is applied to drive a lens of a camera, in which a support 72 for supporting a lens barrel 71 of a lens which is a moving member slides. The fitting portions 72a and 72b are the drive shaft 73.
Is slidably frictionally contacted with and fitted. The drive shaft 73 is supported by the support portions 75 and 76 of the frame 77 so as to be displaceable in the axial direction. One end of the piezoelectric element 78 that is displaced in the thickness direction is fixed to the axial end of the drive shaft 73,
The other end of the piezoelectric element 78 is fixed to the frame 77, and the displacement of the piezoelectric element 78 in the thickness direction causes the drive shaft 73 to move.
Is displaced in the axial direction.

A leaf spring 74 is attached to the sliding fitting portions 72a and 72b of the support body 72 by means of a small screw (not shown).
It is fixed from below. A bent portion 74a that is bent upward is formed in the central portion of the leaf spring 74. This is for the bent portion 74a to press against the drive shaft 73 and to generate an appropriate frictional force at the contact portion. .

In the drive mechanism shown in FIG. 8, when a drive pulse having a waveform consisting of a gentle rising portion as shown in FIG. 9A and a rapid falling portion following it is applied to the piezoelectric element 78, the driving pulse is generated. In the gradual rising portion of the piezoelectric element 78, the piezoelectric element 78 gradually expands and displaces in the thickness direction, and the drive shaft 73 moves axially in the direction of arrow a.

At this time, the frictional force between the drive shaft 73 and the sliding fitting portions 72a and 72b of the support 72 and the frictional force between the drive shaft 73 and the bent portion 74a of the leaf spring 74 are driven by the piezoelectric element 78. If it is less than the force applied to the shaft 73, the support 7
Reference numeral 2 moves in the direction of arrow a together with the drive shaft 73 while being frictionally coupled to the drive shaft 73, and the lens barrel 71 moves in the direction indicated by the arrow a.

On the other hand, at the rapid falling edge of the drive pulse, the piezoelectric element 78 rapidly undergoes contraction displacement in the thickness direction, so that the drive shaft 73 rapidly moves in the direction opposite to the arrow a in the axial direction.

At this time, the sliding fitting portion 72 is attached to the drive shaft 73.
The support body 72 supported by a and 72b has a sliding fitting portion 72a, 7a between the drive shaft 73 and the support body 72 due to its inertial force.
The lens barrel 71 does not move because it overcomes the frictional force with 2b and the frictional force between the drive shaft 73 and the bent portion 74a of the leaf spring 74 and substantially stays at that position.

By continuously applying the drive pulse having the above waveform to the piezoelectric element 78, the piezoelectric element 78 expands and contracts in the thickness direction at different speeds, and the lens barrel 71 is continuously moved in the direction indicated by the arrow a. be able to. Lens barrel 71
Is moved in the direction opposite to the arrow a by applying to the piezoelectric element 78 a drive pulse having a waveform having a rapid rising portion and a gentle falling portion following the rising portion as shown in FIG. 9B. Can be achieved.

[0010]

By the way, in the above drive device, since frictional force is generated in the contact portion,
Since the leaf spring is in direct pressure contact with the drive shaft, when the drive shaft reciprocates at different speeds in the positive and negative directions in the axial direction, the leaf spring also elastically deforms in the movement direction, and the leaf spring and the drive shaft The contact portion is relatively displaced with respect to the support body, and the displacement due to the reciprocating motion of the drive shaft cannot be accurately transmitted to the support body. As a result, the support body, which is a moving member, can be sufficiently moved. There are inconveniences such as not being possible. The present invention aims to solve the above problems.

[0011]

SUMMARY OF THE INVENTION The present invention is to solve the above-mentioned problems, and includes a stationary member, an electromechanical conversion element having one end in the expansion / contraction direction fixed to the stationary member, and expansion / contraction of the electromechanical conversion element. A driving member coupled to the other end of the electromechanical conversion element and supported so as to be movable in the expansion / contraction direction of the electromechanical conversion element, and frictionally coupled to the driving member so as to be movable in the expansion / contraction direction of the electromechanical conversion element. A supported moving member, a frictional force adding means for generating a frictional force between the driving member and the moving member, and an electromechanical conversion element for performing expansion and contraction of the electromechanical conversion element at different speeds. In a drive device using an electromechanical conversion element composed of an electric circuit capable of supplying an electric current, the frictional force applying means is an elastic member fixed to the moving member to generate a pressing force,
The elastic member is disposed between the elastic member and the driving member to transmit the pressing force generated by the elastic member to the driving member, and the frictional force generated by the movement of the pressing force and the driving member is transmitted in the moving direction. On the other hand, it is characterized in that it is composed of a sandwiching member fitted to the moving member without loosening.

The contact portion between the sandwiching member and the moving member and the driving member may be made of a material having an elastic modulus of 500 kgf / mm ² or more.

Further, the contact portion between the sandwiching member and the moving member and the driving member may be made of a material different from that of the driving member. The driving member is made of a polymer fiber reinforced composite, and the sandwiching member and the moving member are driven. The contact portion of the member may be made of a metal material or a metal compound material.

Further, a discharge groove for discharging abrasion powder generated at the contact portion between the sandwiching member and the moving member and the driving member can be provided at the contact portion between the sandwiching member and the moving member and the driving member. In this case, the contact portion between the moving member and the driving member and the contact portion between the sandwiching members may have a V-shaped cross section.

Further, the driving member contact portion of the moving member can be constructed separately from the moving member.

[0016]

The sandwiching member forming the frictional force adding means is fitted to the moving member in the moving direction of the driving member without loosening. As a result, the pressing force generated by the elastic member is transmitted to the driving member via the sandwiching member that does not displace with respect to the moving member, so that the elastic member is able to move even if the driving member moves in the axial direction at different speeds in the positive and negative directions. The moving member can be stably driven at high speed without elastic deformation.

[0017]

Embodiments of the present invention will be described below.
In this embodiment, the drive shaft contact surface of the moving body is formed by a separate component, and the shape of the drive shaft contact portion and the material can be freely selected.

1 and 2 are perspective views for explaining the structure of a driving device using an electromechanical conversion element according to the present invention.
FIG. 1 shows a disassembled state, and FIG. 2 shows an assembled state. The drive device 10 is composed of a stationary member 1, a piezoelectric element 2, a drive shaft 3, a slider 4, and the like.

The stationary member 1 has a substantially cylindrical shape, and one end portion 1a thereof is a mounting portion for a device (not shown). The stationary member 1 has a hole 1b for accommodating the piezoelectric element 2 and a slider 4
Is formed with a partition plate 1g between the holes 1b and 1c, and an end plate 1h is formed at the end of the stationary member 1 on the hole 1c side.

The piezoelectric element 2 is housed in the hole 1c of the stationary member 1, one end of which is adhered and fixed to one wall surface 1f of the hole 1c of the stationary member 1, and the other end is connected to the end 3a of the drive shaft 3. Adhesively fixed.

The drive shaft 3 is axially movably supported by a bearing hole 1d provided in the partition plate 1g of the stationary member 1 and a bearing hole 1e provided in the end plate 1h, and the piezoelectric element 2 expands and contracts in the thickness direction. The drive shaft 3 reciprocates in the axial direction.

A leaf spring 7 is fixed to the end plate 1h of the stationary member 1 by a screw 9 so as to press the drive shaft 3 slightly protruding from the bearing hole 1e at one end of the stationary member 1 in the axial direction. There is. As a result, the drive shaft 3 is pressed against the piezoelectric element 2 with a predetermined force, and the pressing force can be adjusted by tightening or tightening the screw 9.

The slider 4 is provided with a main body portion 4a that makes frictional contact with the drive shaft 3 and a mounting portion 4e for fixing a member to be driven, for example, a lens holding frame. A notch 4b is formed in the central portion of the main body 4a, and holes 4 through which the drive shaft 3 penetrates are formed in the left and right wall surfaces of the notch 4b.
d is provided. Further, a groove 4c having a semicircular cross section is formed in the notch portion 4b so as to contact the substantially lower half of the drive shaft 3. The mounting portion 4e is provided with a mounting hole 4f on the lower surface thereof, through which a screw for mounting a member to be driven such as a lens holding frame penetrates.

The notch 4b is fitted with a sandwiching member 5 which comes into contact with the drive shaft 3 penetrating the hole 4d from above, and the lower surface of the sandwiching member 5 contacts substantially the upper half of the drive shaft 3. A groove 5a having a semicircular cross section is formed. The sandwiching member 5 is configured to be fitted to the left and right wall surfaces of the cutout portion 4b without looseness.

Further, the sandwiching member 5 is pressed against the drive shaft 3 by a leaf spring 6 fixed to the main body 4a of the slider 4 by a screw 8 to make a frictional contact, and the pressing force depends on how much the screw 8 is tightened. Can be adjusted.

FIG. 3 is a sectional view showing the structure of the contact portion between the drive shaft 3 and the main body portion 4a of the slider 4 and the sandwiching member 5. The cutout portion 4b formed in the main body portion 4a of the slider 4 is shown in FIG. The sandwiching member 5 is inserted in the. The ridge 5a provided on the upper surface of the sandwiching member 5 is pressed downward by the leaf spring 6 fixed to the main body 4a by the screw 8, and the sandwiching member 5 makes frictional contact with the drive shaft 3 with an appropriate pressing force.

FIG. 4 is a perspective view showing an example in which the driving device 10 shown in FIGS. 1 and 2 is applied to the movement of the lens holding frame. The same members of the driving device 10 are designated by the same reference numerals as those in FIG. However, detailed explanation is omitted.

Reference numeral 20 is a lens stand, 21 is a stand,
The column 23 is fixed to the base 21 with screws 22. An arm member 24 is fixed to the pillar 23 with a screw 25. In the drive unit 10, the mounting portion 1 a at one end of the stationary member 1 is mounted on the arm member 24 and fixed by the screw 26.

The holding frame 12 of the lens L is attached by screws 13 to the lower surface of the attachment portion 4e of the slider 4 of the drive unit 10.

The drive of the drive unit 10 in the above embodiment is similar to the conventional drive shown in FIG. 8, and is composed of a gradual rising portion and a rapid falling portion following it as shown in FIG. 9 (a). When a drive pulse having a waveform is applied to the piezoelectric element 2, the piezoelectric element 2 gradually expands in the thickness direction at the gently rising portion of the drive pulse, and the drive shaft 3
Is axially displaced in the direction of arrow a. Therefore, the drive shaft 3
Since the slider 4 frictionally coupled to the slider 4 also moves in the arrow a direction, the holding frame 12 of the lens L attached to the slider 4 can be moved in the arrow a direction.

At the rapid falling edge of the drive pulse, the piezoelectric element 2 rapidly undergoes contraction displacement in the thickness direction, and the drive shaft 3
Is also displaced in the direction opposite to the arrow a in the axial direction. At this time, the slider 4, which is frictionally coupled to the drive shaft 3, overcomes the frictional coupling force between the slider 4 and the drive shaft 3 due to its inertial force, substantially stays at that position, and does not move.

The term "substantially" as used herein means that the slider 4 and the drive shaft 3 follow each other in the direction of the arrow a and in the opposite direction, causing slippage, and are caused by a difference in drive time. It also means that it includes the one that moves in the direction of arrow a as a whole. The form of movement is determined according to the given friction conditions.

By continuously applying the drive pulse having the above waveform to the piezoelectric element 2, the holding frame 12 of the lens L can be continuously moved in the direction indicated by the arrow a.

When the lens holding frame 12 is moved in the direction opposite to the arrow a, a piezoelectric element is applied with a drive pulse having a waveform consisting of a rapid rising portion and a gentle falling portion as shown in FIG. 9B. It can be achieved by applying a voltage of 2.

In the drive device described above, a sandwiching member for generating a frictional force is provided between the drive shaft 3 and the slider 4, and the sandwiching member 5 is a leaf spring fixed to the main body portion 4a of the slider 4 by the screw 8. 6 is pressed against the drive shaft 3 by frictional contact, and the sandwiching member is fitted into the slider 4 without loosening and is not displaced with respect to the slider 4. Since the leaf spring 6 contacts the drive shaft 3 via the sandwiching member that does not displace with respect to the slider 4 and transmits the pressing force, the drive shaft 3 is reciprocated by the piezoelectric element 2 at different speeds in the positive and negative directions in the axial direction. Even when driven, the leaf spring 6 does not elastically deform in the moving direction of the drive shaft 3.

Next, the relationship between the elastic modulus of the material of the slider and the sandwiching member and the driving speed will be described. FIG. 5 shows, as materials for the slider and the sandwiching member, stainless steel (SUS), phosphor bronze, zinc (Zn), which have different elastic moduli,
Aluminum (Al), P which is a polymer fiber reinforced composite
PS (containing 40% GF (glass fiber)), PC (GF (glass fiber)) which is a polymer fiber reinforced composite
20% content), PC (polycarbonate), PE (polyethylene) are selected, and the moving speed is measured under the condition of a drive pulse frequency of 25 kHz applied to the piezoelectric element.

From this result, when the elastic modulus of the material of the slider and the sandwiching member is low, the slider and the sandwiching member frictionally contacting the drive shaft elastically deforms in the movement direction of the drive shaft, and the moving speed decreases. Judged as something. According to this experimental result, it is desirable that the material of the slider and the sandwiching member has an elastic modulus of 500 kgf / mm ² or more.

If the slider and the sandwiching member are made of metal or a metal compound and the drive shaft is made of a metal or a metal compound, seizure occurs on the contact surface (a phenomenon in which the drive shaft, the slider and the sandwiching member are caught). . However, when the slider and the sandwiching member were made of metal or a metal compound and the drive shaft was made of a polymer fiber reinforced composite, seizure did not occur. When this configuration is reversed and the slider and the sandwiching member are made of a polymer composite material and the drive shaft is made of a metal or a metal compound, the weight of the drive shaft is larger than that of a polymer fiber reinforced composite body. It became heavy, the resonance frequency of the drive system decreased, and the moving speed decreased.

From the results of this experiment, it is desirable that the drive shaft is made of a polymer fiber reinforced composite body and the slider and the sandwiching member are made of a metal or a metal compound.

Next, the shapes of the slider and the sandwiching member will be described. When the drive mechanism of the present invention is used for a long period of time, the contact surfaces of the drive shaft, the slider, and the sandwiching member are worn by sliding, and the generated abrasion powder is clogged with the contact surfaces to deteriorate the operating performance. As a countermeasure against this, a groove 4c having a semicircular cross section, which is formed in the cutout portion 4b of the slider 4 in the embodiment shown in FIG.
As shown in FIGS. 6 and 7, instead of the groove 5a having a semicircular cross section, which is formed on the lower surface of the sandwiching member 5 and contacts the upper half of the drive shaft 3, each groove has a V-shaped cross section. A modified example is proposed.

FIG. 6 shows a groove 4c formed in the notch 4b of the slider and a groove 5a formed in the lower surface of the sandwiching member 5 in the embodiment shown in FIG. 4m and 5m, wear powder generated by sliding of the contact surfaces of the drive shaft, the slider, and the sandwiching member is pushed out to the troughs of the V-shaped grooves 4m and 5m (not in contact with the drive shaft). Are discharged.

In the structure shown in FIG. 7, a notch 4n having a groove having a V-shaped cross section is formed along the drive shaft 3 in the central portion of the main body 4a of the slider. A groove 5n having a V-shaped cross section is formed on the lower surface, and the sandwiching member 5 is fitted into the notch 4n of the main body 4a of the slider from above and brought into contact with the drive shaft. Protrusions 4p that come into contact with the periphery of the end surface of the sandwiching member 5 are provided on the left and right of the cutout portion 4n of the body portion 4a. It is configured not to move in the direction. According to this configuration,
By removing the sandwiching member 5, the upper part of the slider in the drawing can be opened, and the slider can be attached and detached from a direction other than the axial direction of the drive shaft.

Although not shown in FIGS. 6 and 7,
Also in the above-described two modified examples, the sandwiching member is pressed against the drive shaft by a leaf spring fixed to the main body of the slider by a screw and makes frictional contact, and the pressing force can be adjusted by tightening or tightening the screw. Is exactly the same as the embodiment shown in FIG.

[0044]

As described above, in the driving device using the electromechanical conversion element of the present invention, the frictional force adding means for generating the frictional force between the driving member and the moving member is fixed to the moving member. It is composed of an elastic member that generates a pressing force and a sandwiching member that transmits the pressing force generated by the elastic member to the drive member. Since the sandwiching member is fitted into the moving member without loosening in the moving direction of the driving member, the sandwiching member does not displace with respect to the moving member.

With this configuration, the pressing force generated by the elastic member is transmitted to the driving member via the sandwiching member that does not displace with respect to the moving member, so that the driving member has different axial speeds in the positive and negative directions. When driven reciprocally, the elastic member is not elastically deformed in the moving direction of the driving member, and the moving member can be stably driven at high speed.

If the moving member and the sandwiching member are made of a material having an elastic modulus of 500 kgf / mm ² or more, they will not be elastically deformed in the movement direction of the drive shaft.

When the driving member is made of a polymer fiber reinforced composite material and the moving member and the sandwiching member are made of a metal or a metal compound, it is possible to stably drive without causing seizure on the contact surface. .

Further, when the contact surfaces of the driving member, the moving member and the sandwiching member are formed by grooves having a V-shaped cross section, abrasion powder generated by sliding of the contact surfaces can be efficiently discharged. It is possible to drive stably for a long period of time without deteriorating the operating performance.

[Brief description of drawings]

FIG. 1 is a perspective view in a disassembled state illustrating a configuration of a drive device using an electro-mechanical conversion element of the present invention.

FIG. 2 is a perspective view showing an assembled state of the drive device shown in FIG.

FIG. 3 is a cross-sectional view showing a configuration of a contact portion between a drive shaft of the drive device shown in FIG. 1 and a slider main body and a sandwiching member.

FIG. 4 is a perspective view showing an example in which the drive device shown in FIG. 1 is applied to the movement of a lens holding frame.

FIG. 5 is a diagram showing the relationship between the elastic modulus of the material of the slider and the sandwiching member and the moving speed.

FIG. 6 is a perspective view showing a first modification of the shapes of the slider and the sandwiching member.

FIG. 7 is a perspective view showing a second modification of the shapes of the slider and the sandwiching member.

FIG. 8 is a perspective view showing a configuration of a drive device using a conventional electromechanical conversion element.

FIG. 9 is a diagram showing an example of a waveform of a drive pulse applied to the electromechanical conversion element.

[Explanation of symbols]

 1 stationary member 2 piezoelectric element 3 drive shaft 4 slider 5 sandwiching member 6 leaf spring 7 leaf spring

Claims (8)

[Claims] 1. A stationary member, an electromechanical conversion element having one end in the expansion and contraction direction fixed to the stationary member, and another end in the expansion and contraction direction of the electromechanical conversion element, A drive member supported so as to be movable in the extension / contraction direction, a moving member frictionally coupled to the drive member, and supported so as to be movable in the extension / contraction direction of the electromechanical conversion element; and the drive member and the movement member. An electromechanical conversion element comprising: a frictional force applying means for generating a frictional force between the electromechanical conversion element and an electric circuit capable of supplying a current to the electromechanical conversion element so as to expand and contract the electromechanical conversion element at different speeds. In the drive device used, the frictional force applying means includes an elastic member that is fixed to the moving member and generates a pressing force, and the elastic member that transmits the pressing force generated by the elastic member to the driving member. A sandwiching member which is arranged between the member and the driving member, and which is fitted loosely to the moving member in the moving direction so as to transmit the pressing force and the frictional force generated by the movement of the driving member to the moving member. A drive device using an electromechanical conversion element characterized by being configured. 2. The drive using the electromechanical conversion element according to claim 1, wherein a contact portion between the sandwiching member and the moving member and the driving member is made of a material having an elastic modulus of 500 kgf / mm ² or more. apparatus. 3. The drive device using the electromechanical conversion element according to claim 1, wherein a contact portion between the sandwiching member and the moving member and the drive member is made of a material different from that of the drive member. 4. The electric machine according to claim 3, wherein the drive member is made of a polymer fiber reinforced composite body, and a contact portion between the sandwiching member and the moving member and the drive member is made of a metal material. Drive device using a conversion element. 5. The electric device according to claim 3, wherein the driving member is made of a polymer fiber reinforced composite material, and a contact portion between the sandwiching member and the moving member and the driving member is made of a metal compound material. Drive device using mechanical conversion element. 6. A discharge groove for discharging abrasion powder generated at a contact portion between the sandwiching member and the moving member and the driving member is provided at a contact portion between the sandwiching member and the moving member and the driving member. A drive device using the electromechanical conversion element described. 7. The driving device using the electromechanical conversion element according to claim 6, wherein the contact portion between the moving member and the driving member and the contact portion between the sandwiching members have a V-shaped cross section. 8. The driving device using the electromechanical conversion element according to claim 1, wherein the driving member contact portion of the moving member is separate from the moving member.