JPH07274544A - Driving gear using electromechanical transducer - Google Patents

Abstract

PURPOSE:To drive a driven member at high speed by composing a driving member coupled to an electromechanical transducer and displaced together with the transducer of a fiber-reinforced resin composite body. CONSTITUTION:Gentle contraction displacement in the thickness direction are generated in a piezoelectric element 18 as an electromechanical transducer in the slow falling section of driving pulses, and a driving shaft 13 is moved gently in the axial direction (a). The driving shaft 13 is made of a fiber- reinforced resin composite body, and a contact surface, on which a zoom lens- barrel 11 as a driven member and a frictional plate 12 are brought into surface- contact, is moved smoothly. Accordingly, the response delay of the electromechanical transducer is reduced, thus driving the driven member at higher speed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving device using an electro-mechanical conversion element.

[0002]

2. Description of the Related Art A driving device using a piezoelectric element has been proposed for driving a camera and other members constituting precision equipment (Japanese Patent Laid-Open No. 4-69070 and Japanese Patent Laid-Open No. 63-110).
74 publication).

FIG. 4 shows an example of a driving device applied to drive a zoom lens mounted on a camera, which is a sliding fitting portion of a support body 72 for supporting a lens barrel 71 of a lens which is a driven member. 72a and 72b are slidably in frictional contact with and fitted to the drive shaft 73. Further, the drive shaft 73 has a frame 77.
It is supported by the support portions 75 and 76 of the above 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 portion of the drive shaft 73, and the other end portion of the piezoelectric element 78 is fixed to the frame 77, so that the piezoelectric element 78 is displaced in the thickness direction. As a result, the drive shaft 73 is displaced in the axial direction.

Reference numeral 74 is a leaf spring, which is attached to the sliding fitting portions 72a and 72b of the support 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. 4, when a drive pulse having a waveform consisting of a rapid rising portion and a subsequent gentle falling portion as shown in FIG. 5 is applied to the piezoelectric element 78, the driving pulse rapidly rises. In the portion, the piezoelectric element 78 rapidly undergoes extension displacement in the thickness direction, and the drive shaft 73 rapidly moves in the axial direction in the direction opposite to the arrow a.

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.
2b and the frictional force between the drive shaft 73 and the bent portion 74a of the leaf spring 74 are overcome to stay at that position.
The lens barrel 71 does not move.

On the other hand, at the gradual falling edge of the drive pulse, the piezoelectric element 78 gradually contracts in the thickness direction, so that the drive shaft 73 moves gently in the direction of arrow a.

At this time, the piezoelectric element 78 drives 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. 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.

The pulse having the above waveform is continuously applied to the piezoelectric element 78.
, The lens barrel 71 can be continuously moved in the direction indicated by the arrow a. Lens barrel 7
The movement of 1 in the direction opposite to the arrow a can be achieved by applying to the piezoelectric element 78 a drive pulse having a waveform consisting of a gentle rising portion and a subsequent rapid falling portion.

[0010]

By the way, in the driving apparatus using the electro-mechanical conversion element such as the piezoelectric element as described above, since the expansion and contraction of the electro-mechanical conversion element is utilized, the moving speed of the driven member is increased. Is related to the frequency of the drive pulse applied to the electro-mechanical conversion element and the displacement amount of the electro-mechanical conversion element caused by the applied drive pulse, and the displacement amount of the electro-mechanical conversion element with respect to the applied drive pulse. If is constant, it seems that the moving speed of the driven member can be increased by increasing the frequency of the driving pulse.

The electromechanical conversion element extends at the rising portion of the applied drive pulse and contracts at the falling portion of the pulse,
When the expansion / contraction speed ratio (expansion speed / contraction speed) is sufficiently large (2 to 3 or more in the experiment), the amount of movement of the driven member is equal to that of the electro-mechanical conversion element generated during one cycle of the applied drive pulse. The value is close to the displacement amount.

However, since the electro-mechanical conversion element has a physical characteristic called "response delay" in which displacement is delayed by a certain time after the drive pulse is applied, the electro-mechanical conversion element is applied to the electro-mechanical conversion element. When the frequency of the driving pulse to be increased is increased, the extension displacement and the contraction displacement overlap, and the expansion / contraction speed ratio gradually decreases. FIG. 2 shows the relationship between the frequency of the drive pulse applied to the electro-mechanical conversion element and the moving speed of the driven member. When the frequency of the applied drive pulse is increased, the moving speed of the driven member is initially increased. However, when the frequency exceeds a certain frequency, the moving speed of the driven member decreases, and when the expansion / contraction speed ratio becomes 1, the moving amount of the driven member that occurs during one cycle of the driving pulse becomes 0. Can not do.

The response delay, which is the physical characteristic of the electro-mechanical conversion element, is greatly influenced by the weight of the drive shaft fixed to the electro-mechanical conversion element, as shown in FIGS. The larger the weight of the drive shaft, the larger the response delay.

It was also confirmed by experiments that the response delay is small when the elastic modulus of the drive shaft is large, and the response delay becomes larger as the elastic modulus is smaller. In addition, even if the response delay of the electro-mechanical conversion element is small, if the elastic modulus of the drive shaft is small, the response delay occurs in the drive shaft itself, and the driven member causes speed fluctuation depending on the position on the drive shaft. It will not work.

A first object of the present invention is to provide a driving device using an electromechanical conversion element capable of driving a driven member at a higher speed.

A second object of the present invention is to reduce the response delay of the electro-mechanical conversion element including the drive shaft and to drive the driven member at a higher speed by using the electro-mechanical conversion element. To provide a device.

A third object of the present invention is to reduce the response delay of the electro-mechanical conversion element including the drive shaft by selecting the material of the driving member, so that the driven member can be driven at a higher speed. It is to provide a drive device using a mechanical conversion element.

[0018]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems by providing an electro-mechanical conversion element, a drive member coupled to the electro-mechanical conversion element and displaced together with the conversion element, and the drive member. The driven member is frictionally coupled to the drive member by providing a driven member frictionally coupled to the electro-mechanical transducer, and varying the speeds of expansion and contraction of the electro-mechanical transducer by a drive pulse applied to the electro-mechanical transducer. In the driving device using the electro-mechanical conversion element, the driven member can be moved substantially together with the driving member and the driven member can overcome the frictional coupling with the driving member so as not to move substantially. The drive member connected to the mechanical conversion element is made of a fiber-reinforced resin composite.

[0019]

When the driving member is gently displaced by the driving pulse applied to the electro-mechanical conversion element, the driven member frictionally coupled to the driving member substantially moves together with the driving member. Further, when the driving member is rapidly displaced by the driving pulse applied to the electro-mechanical conversion element, the driven member overcomes the frictional coupling with the driving member due to the inertial force and does not substantially move.

Since the driving member is composed of the fiber reinforced resin composite, it is possible to reduce the weight while maintaining the required elastic modulus as compared with the conventional driving member made of metal or the like, and to drive the driven member at a higher speed. You can

[0021]

Embodiments of the present invention will be described below.
FIG. 1 shows an embodiment of the present invention and shows a driving device using an electro-mechanical conversion element applied to a driving mechanism of a zoom lens.

In FIG. 1, 11 is a zoom lens barrel which is a driven member, 12 is a friction plate, 13 is a drive shaft, and 14 is a drive shaft.
Is a pressure contact spring, and the pressure contact spring 14 is displaced by a small screw 14a.
It is fixed to the mullens barrel 11, but at this time the pressure contact spring 1
The curved portion 14b provided at the center of the pressure plate 4 is configured to press the friction plate 12 downward. Reference numerals 15 and 16 denote pressing plates that prevent the friction plate 12 from shifting in the axial direction of the drive shaft 13, and are fixed to the zoom lens barrel 11 by machine screws 15a.

The drive shaft 13 penetrates between the zoom lens barrel 11 and the friction plate 12, and a direction in which the friction plate 12 sandwiches the drive shaft 13 with the zoom lens barrel 11 by the pressure contact spring 14. Since the drive shaft 13 is pressed against the surface of the zoom lens barrel 11 and the friction plate 12, the drive shaft 13 generates an appropriate frictional force on the contact surface. The drive shaft 13 is made of a fiber-reinforced resin composite, and has a smaller elastic modulus than the drive shaft made of metal or the like, but is lighter.

Reference numeral 21 is a frame, and 22 and 23 are support plates provided on the frame 21, which support the drive shaft 13 movably in the axial direction. Reference numeral 18 denotes a piezoelectric element that is displaced in the thickness direction, one end of which is fixed to the end of the drive shaft 13,
The other end is fixed to a support plate 24 provided on the frame 21.

The zoom lens barrel 11 has the drive shaft 13
In order to prevent the drive shaft 13 from rotating around, a support shaft (not shown) parallel to the drive shaft 13 may be provided so that the zoom lens barrel 11 is supported by the drive shaft 13 and the support shaft.

Next, the operation of the drive device will be described. First,
A case where the zoom lens barrel 11 is moved in the direction of arrow a will be described. When a drive pulse composed of a rapid rising portion and a gentle falling portion subsequent thereto as shown in FIG. 5 is applied to the piezoelectric element 18, the piezoelectric element 18 rapidly expands in the thickness direction at the rapid rising portion of the driving pulse. Due to the displacement, the drive shaft 13 rapidly moves in the axial direction in the direction opposite to the arrow a. At this time, the zoom lens barrel 11 and the friction plate 12 overcome the frictional force between the drive shaft 13 and the zoom lens barrel 11 and the friction plate 12 due to the inertial force thereof, and substantially remain at that position. , Don't move.

On the other hand, at the gradual fall portion of the drive pulse, the piezoelectric element 18 causes a gradual contraction displacement in the thickness direction, and the drive shaft 13 gently moves in the axial direction in the direction indicated by the arrow a. At this time, in the zoom lens barrel 11, the friction plate 12 is pressed by the pressure contact spring 14, and the zoom shaft is disengaged from the drive shaft 13.
Since the mullens lens barrel 11 and the friction plate 12 are in surface contact with each other and are coupled by the frictional force generated on the contact surface, they substantially move in the direction of the arrow a together with the drive shaft 13.

The term "substantially" means that the zoom lens barrel 11 and the friction plate 12 follow the drive shaft 13 while slipping in both the arrow a direction and the opposite direction. However, it is meant to include those that move in the direction of arrow a as a whole due to the difference in driving time. 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 18, the zoom lens barrel 11 can be continuously moved in the direction indicated by the arrow a.

The movement of the zoom lens barrel 11 in the direction opposite to the arrow a is achieved by applying to the piezoelectric element 18 a drive pulse having a waveform consisting of a gentle rising portion and a subsequent rapid falling portion. can do.

Next, the material of the drive shaft and the moving speed of the driven member will be described. Table 1 shows JIS as the material of the drive shaft.
Standard SUS304 stainless steel, ABS resin, and fiber reinforced epoxy resin containing carbon fiber 50 volume percent are selected as the fiber reinforced synthetic resin composite, and physical properties, weight, axial elasticity, and moving speed of driven member are selected for each. The results of tests conducted on the above are shown.

[0032]

[Table 1] It was impossible to move the driven member in the case where the stainless steel of JIS standard SUS304 was used as the material of the drive shaft and the case where the ABS resin was used. this is,
A shaft using JIS standard SUS304 stainless steel is too heavy and causes a large response delay in the displacement of the piezoelectric element, and ABS resin has a low elastic modulus and causes a large response delay in moving the driven member. It is presumed that it could not be done.

Since the fiber-reinforced epoxy resin is light in weight and has a large elastic modulus, the displacement of the piezoelectric element and the axis itself do not cause a large response delay. In addition, the fiber-reinforced epoxy resin has a self-lubricating property, so the movement is smooth and "squealing" occurs due to frictional vibration at the contact surface between the drive shaft and the driven member.
It never happened. In conclusion, the fiber reinforced epoxy resin containing carbon fiber 50 volume percent was the optimum material for the drive shaft.

Examples of synthetic resin materials that can be used for the fiber-reinforced synthetic resin composite include epoxy resins, unsaturated polyesters, polyimides, bismaleimides, polyamideimides, polyetherimides, polyetheretherketones, polyethersulfones, and fragrances. Group polyimide, polycarbonate, etc. can be used. Further, as the reinforcing fiber, in addition to carbon fiber, glass fiber,
Carbon whiskers, potassium titanate whiskers and the like can be used.

[0035]

As described above, according to the present invention, in the driving device using the electro-mechanical conversion element,
Since the drive member is made of a fiber-reinforced resin composite, it can be made lighter in weight while maintaining the required elastic modulus as compared to a conventional drive member made of metal or the like, and the response delay of the electromechanical conversion element can be reduced. Thus, the driven member can be driven at a higher speed.

[Brief description of drawings]

FIG. 1 is a perspective view showing the configuration of a drive device using an electro-mechanical conversion element to which the present invention is applied.

FIG. 2 is a diagram showing the relationship between the frequency of a drive pulse applied to an electro-mechanical conversion element and the moving speed of a driven member.

FIG. 3 is a diagram illustrating a response delay of an electro-mechanical conversion element including a drive shaft.

FIG. 4 is a perspective view showing a configuration of a drive device using a conventional electro-mechanical conversion element.

FIG. 5 is a diagram showing an example of a drive pulse waveform applied to an electro-mechanical conversion element.

[Explanation of symbols]

 11 zoom lens barrel 12 friction plate 13 drive shaft 14 pressure contact spring 18 piezoelectric element 21 frame 22, 23, 24 support plate

Claims (1)

[Claims] 1. An electro-mechanical conversion element, comprising: an electro-mechanical conversion element; a driving member coupled to the electro-mechanical conversion element and displaced together with the conversion element; and a driven member frictionally coupled to the driving member. A state in which the driven member substantially moves together with the driving member due to frictional coupling with the driving member by making the speed of expansion and contraction of the electro-mechanical conversion element different by the driving pulse applied to the driven member; In a drive device using an electro-mechanical conversion element, the drive member connected to the electro-mechanical conversion element is a fiber-reinforced resin composite. A driving device using an electro-mechanical conversion element.