JPH1023771A - Driver using electromechanical transducer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electromechanical transducer driver in which an inertia element is not used. SOLUTION: The holding frame 21 of a lens L is supported by a guide shaft 22 so as to be able to slide along the guide shaft 22 freely. One end of a piezoelectric device 23 is bonded and fixed to the holding frame 21 and one end of a spring 24 is fixed to the other end of the piezoelectric device 23. The neighborhood 24a of the end of the spring 24 is pressed against the guide shaft 22 with a suitable pressure to compose a friction coupling part Ma. Friction F2 produced in the friction coupling part Ma is so set as to be substantially larger than the friction F1 produced in a sliding part Mb composed of the lens holding frame 21 and the guide shaft 22 (F2>>F1). When a drive pulse is applied to the piezoelectric device 23, if the piezoelectric device 23 shows a gentle expansion displacement, the friction coupling state of the friction coupling part Ma is maintained and the lens holding frame 21 is moved in an arrow direction (a) and, if the piezoelectric device 23 shows a quick contraction displacement, the lens holding frame 21 tends to stay at the present position by inertia and repulsion inertia exceeds the friction F2 and the lens holding frame 21 is not moved practically.

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 electromechanical transducer, and more particularly to a XY moving stage for precise measurement, a photographing lens of a camera, a projection lens of an over head projector, and a binocular. The present invention relates to a driving device using an electromechanical transducer suitable for driving a lens or the like.

[0002]

2. Description of the Related Art When a drive pulse having a waveform consisting of a gentle rising portion and a rapid falling portion following the rising portion is applied to the piezoelectric element, the piezoelectric element gradually expands in the thickness direction at the gentle rising portion of the driving pulse. Displacement occurs, and at the rapidly falling part, contraction occurs rapidly. Therefore, by utilizing this characteristic, one end of the piezoelectric element is fixed to the frame, a driving member is bonded and fixed to the other end of the piezoelectric element, and a driving pulse having the above-described waveform is applied to the piezoelectric element to apply the same to the piezoelectric element. There is known a configuration in which generated vibrations having different speeds in the thickness direction are transmitted to a driving member to cause the driving member to reciprocate at different speeds, and to move a moving member frictionally coupled to the driving member in a predetermined direction.

However, in the driving device having this configuration, it is difficult to obtain a sufficient reciprocating displacement for moving the moving member due to the elastic deformation in the longitudinal direction as the length of the driving member increases. As a solution to this problem,
A configuration has been proposed in which one end of a piezoelectric element is not fixed to a frame but is fixed to an inertial body. In this configuration, one end of a piezoelectric element is fixed to an inertial body, and the other end is directly fixedly connected to a moving member. Can be moved in any direction.

FIG. 9 shows an example of a piezoelectric element driving device using the above inertial body. In FIG. 9, reference numeral 101 denotes a lens barrel, and 102 and 103, guide shafts for supporting the lens barrel 101 movably in the optical axis direction.
A guide shaft 102 penetrates the guide shafts 01a and 101b, and a central curved portion 114a of a leaf spring 114 fixed to the lower surfaces of the protrusions 101a and 101b with screws 104 and 105 is pressed against the guide shaft 102 with an appropriate pressure. . The tip of the projection 101c of the lens barrel is formed in a fork shape,
03. Reference numeral 115 denotes a piezoelectric element, one end of which is adhesively fixed to the lens barrel 101, and the other end of which is fixed to an inertial body (weight).

[0005] In the above configuration, the piezoelectric element shown in FIG.
When a drive pulse composed of a gentle rising portion and a rapid falling portion as shown in (1) is applied, the piezoelectric element causes a gradual extension displacement at the gentle rising portion of the driving pulse. At this time, since the lens barrel 101 is frictionally coupled to the guide shaft 102 by the leaf spring 114, it does not substantially move, and an inertial body (weight) 116 fixed to the end of the piezoelectric element is provided.
Only the displacement occurs in the direction of arrow a.

Next, at the rapid falling portion of the drive pulse, the piezoelectric element causes a rapid contraction displacement, but the inertial body (weight) 116 tries to stay at that position due to inertia. For this reason, the lens barrel 101 is provided with the guide shaft 1 by the leaf spring 114.
02, and substantially moves in the direction of arrow a with the contraction displacement of the piezoelectric element.

In the above description of the operation, it has been described that the lens barrel 101 does not substantially move when the piezoelectric element is slowly expanded and displaced substantially when the piezoelectric element is rapidly contracted. Means that the lens barrel 101 and the leaf spring 114 are both in the direction of the arrow a and in the opposite direction.
This means that the frictional coupling surface moves while generating a slip, and also moves in the direction of the arrow a as a whole due to a difference in driving time.

By continuously applying the driving pulse having the above-mentioned waveform to the piezoelectric element 115, the lens barrel 101 can be continuously moved in the direction indicated by the arrow a.

The movement of the lens barrel 101 in the direction opposite to the arrow a can be achieved by applying to the piezoelectric element 115 a drive pulse having a waveform consisting of a rapid rising portion followed by a gentle falling portion.

[0010]

In the driving device using the piezoelectric element described above, the moving body (the lens barrel in the above example) is driven by using the inertial force generated in the inertial body. FIG. 11 depends on the mass of
As shown in (1), the highest driving speed can be obtained when the ratio of the mass of the inertial body to the mass of the moving body is at an optimum value.
When the mass of the inertial body is smaller than the optimal value, the inertia force generated in the inertial body is reduced and the driving speed is reduced. When the mass of the inertial body is greater than the optimal value, the inertial force is large. In addition to this, a force in the direction opposite to the moving direction of the moving body will be generated, impeding the movement of the moving body, and increasing the driving pulse frequency because the resonance frequency of the mass system including the inertial body and the piezoelectric element will decrease. And the driving speed is reduced.

For this reason, in order to obtain a high driving speed, it is necessary to maintain the ratio between the mass of the inertial body and the mass of the moving body at an optimum value. Is very difficult. Further, when this type of driving device is applied to a driving device such as a moving stage, the mass of the moving object varies depending on the mass of the object placed on the table of the moving stage. It is almost impossible to set the ratio to the mass of the moving body to an optimum value, and there is a disadvantage that the driving speed varies depending on the mass of the object placed on the table.

[0012]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and is intended to move a moving body using an inertial force based on the mass of the moving body without using the above-described inertial body. An electromechanical transducer, a moving body fixedly coupled to one end of the electromechanical transducer and moving with the electromechanical transducer, a guide member for guiding the moving body in a predetermined direction, A frictional force coupled to the other end of the electromechanical transducer and frictionally coupled to the guide member to generate a frictional force at the frictionally coupled portion greater than a frictional force generated between the moving body and the guide member. It is characterized by comprising a generating member and drive control means for supplying electric power for expanding and contracting the electromechanical transducer.

When the mass of the moving body and the mass of the frictional force generating member are set in a relationship of (mass of the moving body) / 4 ≧ (mass of the frictional force generating member), the mass of the moving body increases. This can suppress a decrease in the moving speed of the moving body due to the above.

Further, if the mass of the electromechanical transducer and the mass of the frictional force generating member are set in a relationship of (mass of the electromechanical transducer) × 3/2 ≧ (mass of the frictional force generating member), By increasing the resonance frequency of the electromechanical transducer and the moving body, the frequency of the driving pulse can be increased, and the moving speed of the moving body can be increased.

Further, the drive control means generates a gradual expansion / contraction displacement of the electromechanical conversion element so as not to cause a slip at a frictional coupling portion between the guide member and the frictional force generating member, thereby providing an electromechanical conversion. Driving to move the moving body can be performed only by the amount of expansion and contraction generated in the element.

[0016]

Embodiments of the present invention will be described below. First, the relationship between the moving speed of the moving body, the mass of the moving body and the mass of the frictional force generating member, and the relationship between the driving speed of the electromechanical transducer and the mass of the frictional force generating member will be described.

FIG. 1 is a diagram schematically illustrating an example in which a piezoelectric element driving device using an inertial body described above with reference to FIG. 9 as a prior art is applied to a lens driving mechanism. The lens holding frame 11 holding the lens L is slidably supported by a guide shaft 12. One end of a piezoelectric element 13 is bonded and fixed to the lens holding frame 11, and an inertia body 14 is bonded and fixed to the other end of the piezoelectric element 13. One end of a spring 15 is fixed to the lens holding frame 11, and the other end 15a of the spring 15 is pressed against the guide shaft 12 with an appropriate pressing force, so that the spring 15 and the guide shaft 12 are frictionally connected. I have.

When a drive pulse consisting of a gentle rising portion and a rapid falling portion is applied to the piezoelectric element 13, the piezoelectric element 13 undergoes a gradual extension displacement at the gentle rising portion of the driving pulse, but the lens holding frame 11 Spring 1
5, the inertial body 14 adhered and fixed to one end of the piezoelectric element 13 because it is not substantially moved by being frictionally coupled to the guide shaft 12.
Only moves in the direction of arrow a.

At the rapid falling portion of the drive pulse, the piezoelectric element 13 causes a rapid contraction displacement, but the lens holding frame 11 and the lens L tend to stay at that position due to inertia. 13 is to be pulled in the direction opposite to the arrow a. At the same time, the inertial body 14 also tends to stay at that position due to inertia, so that the reaction force tends to pull the piezoelectric element 13 in the direction of arrow a. Therefore, each member fixed to both ends of the piezoelectric element 13 is drawn toward the piezoelectric element 13 side. At this time, if the frictional coupling force generated between the spring 15 and the guide shaft 12 is set to be weaker than the pulling force applied to the lens holding frame 11, the lens holding when the piezoelectric element 13 is rapidly contracted and displaced occurs. Frame 11
Moves in the direction of arrow a. Therefore, the driving speed of the moving body depends on the mass of each member such as the inertial body 14 and the lens holding frame 11 fixed to both ends of the piezoelectric element 13 and the frictional coupling force generated between the spring 15 and the guide shaft 12. Is determined.

FIG. 2 is a diagram schematically illustrating an example in which the piezoelectric element driving device according to the present invention is applied to a lens driving mechanism. The lens holding frame 21 holding the lens L is slidably supported on a guide shaft 22. Lens holding frame 2
One end of the piezoelectric element 23 is bonded and fixed to 1 and the piezoelectric element 2
One end of a spring 24 is fixed to the other end of the spring 3, and the other end 24a near the other end of the spring 24 is pressed against the guide shaft 22 with an appropriate pressure contact force, so that the spring 24 and the guide shaft 22 are frictionally coupled to each other. It constitutes the coupling part Ma. The frictional force F2 generated at the frictional coupling portion Ma formed by the spring 24 and the guide shaft 22 is significantly larger than the frictional force F1 generated at the sliding portion Mb formed by the lens holding frame 21 and the guide shaft 22. Value (F2 >> F1)
Set to be.

In this configuration, when a drive pulse including a gentle rising portion and a rapid falling portion is applied to the piezoelectric element 23, the piezoelectric element 23 undergoes a gradual extension displacement at the gentle rising portion of the driving pulse. At this time, since the frictional force F2 is significantly larger than the frictional force F1 as described above, the frictional coupling state is maintained at the frictional coupling portion Ma between the spring 24 and the guide shaft 22, so that the piezoelectric element 23
The lens holding frame 21 moves in the direction of the arrow a due to the gradual extension displacement of.

At the rapid falling portion of the drive pulse, the piezoelectric element 23 causes a rapid contraction displacement, but at this time, the lens holding frame 21 does not substantially move due to inertia, and the spring 2
4 slides on the guide shaft 22 by overcoming the frictional connection between the guide shaft 22 and the frictional joint Ma.

In the above-described configuration, theoretically, the mass of the object (here, the mass of the spring 24) constituting the friction coupling portion Ma is the mass of the moving body (here, the holding frame 2 including the lens L).
1 mass), the moving body can be driven at a higher speed. Therefore, the relationship between the ratio of the mass of the friction coupling portion Ma to the mass of the moving body and the driving speed of the moving body was examined by experiments.

FIG. 3 is a graph showing the relationship between the mass of the moving body and the frequency of the driving pulse for driving the piezoelectric element (hereinafter referred to as the driving frequency), and the ratio of the mass of the friction coupling portion to the mass of the moving body and the driving speed of the moving body. The experimental results of investigating the relationship with are shown. According to this experimental result, if the mass of the frictional coupling portion is equal to or less than 1/4 of the mass of the moving body, the theoretical maximum speed V1 is 1 /
It can be seen that it can be driven at two or more speeds.

Since the mass of the frictional joint cannot be reduced to zero, the driving speed on the Y axis at which the ratio of the mass of the frictional joint / the mass of the moving body is zero in FIG. 3 is a theoretical value.

FIG. 4 shows an experimental result of examining the relationship between the driving frequency and the driving speed. Here, FIG. 4A shows a case where the mass of the friction coupling portion is sufficiently light, and FIG. The heavy case is shown in (b). According to the experimental results, when the mass of the friction coupling portion is light (a), the peak value of the driving speed is at a high driving frequency, and the driving speed is also high. When the mass of the friction coupling portion is heavy (b), there is a peak value of the driving speed at a low driving frequency, and the driving speed is also low. That is, it can be seen that the drive frequency can be set higher and the drive speed can be increased as the mass of the friction coupling portion is reduced.

FIG. 5 shows an experimental result of examining the relationship between the ratio of the mass of the friction coupling portion to the mass of the piezoelectric element and the driving speed. The same piezoelectric element is used, and the driving frequency is set to an optimum value. Set. According to the experimental results, if the mass of the friction coupling portion is equal to or less than 3/2 of the mass of the piezoelectric element, the driving can be performed at half the theoretical maximum speed Vmax.

[0028]

Next, an embodiment in which the driving device of the present invention is applied to a moving stage will be described. 6 is an exploded perspective view showing an actuator suitable for application to a moving stage, and FIG. 7 is a perspective view showing an assembled state of the actuator.

Referring to FIG. 6 and FIG.
Are support blocks 51 and 52 fixed to a base of a moving stage (not shown), a guide shaft (guide member) 53, a piezoelectric element 54, a frictional force generating section 55, and a slider block (moving body).
56 and the like.

The guide shaft 53 has support blocks 51 and 5 fixed to a base of a moving stage (not shown) by screws or the like.
2 is fixedly supported by small screws 51a and 52a. One surface of the piezoelectric element 54 has a frictional force generating portion 5.
5 and the other surface is adhesively fixed to the slider block 56.

The slider block 56 is guided by the guide shaft 53 and is supported so as to be movable in the guide axis direction. The slider block 56 is designed to reduce the frictional force F1 generated between the slider block 56 and the guide shaft 53. It is preferable to support 56 with a guide shaft 53 via a rolling bearing or the like. Reference numeral 57 denotes a screw hole into which a connecting pin for connecting the slider block 56 and a table 64 described later is implanted.

The frictional force generating portion 55 is composed of a block portion 55a bonded and fixed to the piezoelectric element 54 and a holding portion 55b for holding the guide shaft 53 at a predetermined pressure. The holding portion 55b is frictionally connected to the guide shaft 53. , And constitute a friction coupling portion Ma. The frictional force F2 at the frictional coupling portion Ma is significantly larger than the frictional force F1 at the sliding portion Mb composed of the slider block 56 and the guide shaft 53 (F2>
> F1) is set. The frictional force generating section 55 is made as light as possible to reduce the mass ratio to the slider block (moving body) 56, thereby enabling high-speed driving.

With this configuration, when a saw-tooth wave driving pulse having a gentle rising portion and a rapid falling portion as shown in FIG. Gently expands and displaces in the thickness direction. At this time, the holding portion 55b of the frictional force generating portion 55 is frictionally coupled to the guide shaft 53 with the frictional force F2, so that the frictional force generating portion 55 moves with respect to the guide shaft 53. Instead, the slider block 56 is guided by the guide shaft 53 and moves in the direction of arrow a.

In the rapid falling portion of the drive pulse, the piezoelectric element 54 contracts rapidly in the thickness direction to cause displacement. At this time, the reaction force of the inertial force of the slider block 56 trying to stay at that position overcomes the frictional force F2 of the frictional coupling portion Ma and causes the frictional coupling portion Ma to slip, so that the frictional force generating portion 5
5 moves in the direction of arrow a with respect to the guide shaft 53, and the slider block 56 does not move.

By continuously applying the driving pulse to the piezoelectric element 54, the slider block 56 can be continuously moved in the direction of arrow a. In order to move the slider block in the opposite direction (the direction opposite to the arrow a), the waveform of the sawtooth drive pulse applied to the piezoelectric element 54 is changed so that the drive pulse includes a rapid rising portion and a gentle falling portion. Can be achieved by applying Further, the waveform of the drive pulse applied to the piezoelectric element 54 is not limited to a sawtooth wave pulse, and may be a waveform obtained by performing full-wave rectification of a sine wave AC waveform.

FIG. 8 is an exploded perspective view showing a moving stage 60 constituted by using the above-described actuator. In FIG. 8, reference numeral 61 denotes a base, 62 denotes a linear ball bearing provided on a side edge of the base 61, 64 denotes a table on which articles are placed, and a slide portion 63 which engages with the linear ball bearing 62 on the lower surface. Is provided. On the base 61, the support blocks 51 and 52 of the actuator 50 described above are fixed at the center thereof, and the actuator 50 is assembled and arranged.

Two linear bars provided on the side edge of the base 61
The bearing 62 is of a known type and is arranged in parallel, engages with two slide portions 63 arranged in parallel with the lower side edge of the table 64, and engages the table 64 with respect to the base 61.
Are supported so that they can be translated.

A hole 64 is formed in the center of the table 64 to engage with a connecting pin 68 implanted on the slider block 56 of the actuator 50. The hole 65 is used to move the table 64. It is elongated in the direction perpendicular to the direction, and engages with the connecting pin 68 without looseness in the moving direction of the table 64, and loosely engages with the connecting pin 68 in the direction perpendicular to the moving direction. The operating direction of the actuator 50 and the table 6 supported by the linear ball bearing 62
The configuration is such that even if there is an error in the movement direction of the table 4, the movement of the table 64 will not be hindered.

In this movement stage 60, a table 64
In order to detect the position, an MR sensor is provided. That is, the magnetized rod 69 is fixed to the base 61 and the table 64 is fixed.
The magnetoresistive element 70 is fixed at a position opposite to the magnetized rod 69 on the back surface of the magnetoresistive element 70. When the magnetoresistive element 70 moves on the magnetized rod 69 by the movement of the table 64, the magnetic resistance of the magnetoresistive element 70 The resistance is periodically changed according to the magnetic pole pitch, and the position and the moving distance of the table 64 are detected.

In the moving stage described above, the actuator used as a driving device has a structure that does not use an inertial body unlike a conventional actuator, and is therefore mounted on a moving table. Even when the mass differs depending on the object, it can always be driven at a high driving speed without being affected by the mass of the placed object.

[0041]

As described above, the driving device using the electromechanical transducer of the present invention does not use an inertial body unlike the conventional driving device, so that the ratio of the mass of the moving body to the mass of the inertial body is optimized. It is not necessary to keep the value, and the mass of the frictional force generating portion can be reduced with respect to the mass of the moving body, so that a high driving speed can be obtained.

Since the driving speed does not fluctuate depending on the mass of the moving body, a high driving speed is always maintained even when the mass varies depending on the object placed on the moving table such as the moving stage. It is possible to provide a driving device which can be maintained and is suitable as a driving device such as a moving stage.

[Brief description of the drawings]

FIG. 1 is a diagram schematically illustrating a conventional piezoelectric element driving device using an inertial body.

FIG. 2 is a diagram schematically illustrating a piezoelectric element driving device according to the present invention.

FIG. 3 is a diagram for explaining a relationship between a ratio of a friction coupling portion mass to a moving body mass and a driving speed of the moving body.

FIG. 4 is a diagram illustrating a relationship between a driving frequency and a driving speed of a moving object.

FIG. 5 is a view for explaining the relationship between the ratio of the mass of the moving body to the mass of the piezoelectric element and the driving speed of the moving body.

FIG. 6 is an exploded perspective view showing a configuration of an actuator according to the embodiment of the present invention.

FIG. 7 is a perspective view showing an assembled state of the actuator shown in FIG. 6;

FIG. 8 is an exploded perspective view showing the configuration of a moving stage using the actuator of FIG. 6;

FIG. 9 is a perspective view illustrating a lens driving mechanism using a conventional piezoelectric element driving device using an inertial body.

FIG. 10 is a diagram illustrating a waveform of a drive pulse applied to a piezoelectric element.

FIG. 11 is a view for explaining the relationship between the ratio of the mass of the inertial body to the mass of the moving body and the driving speed of the moving body.

[Explanation of symbols]

 11, 21 Lens holding frame 12, 22 Guide shaft 13, 23 Piezoelectric element 14 Inertial body 15, 24 Spring L lens 50 Actuator 51, 52 Support block 53 Guide shaft 54 Piezoelectric element 55 Friction force generating portion 55a Block portion 55b Nipping Part 60 Movement stage 64 Table

Claims (4)

[Claims] An electromechanical transducer, a moving body fixedly coupled to one end of the electromechanical transducer and moving with the electromechanical transducer, and a guide member for guiding the moving body in a predetermined direction; Friction coupled to the other end of the electromechanical transducer and frictionally coupled to the guide member, wherein the frictional coupling portion generates a frictional force greater than a frictional force generated between the moving body and the guide member. A drive device using an electromechanical transducer, comprising: a force generating member; and drive control means for supplying electric power for expanding and contracting the electromechanical transducer. 2. The mass of the moving body and the mass of the frictional force generating member are set in a relationship of (mass of the moving body) / 4 ≧ (mass of the frictional force generating member). A driving device using the electromechanical conversion element according to claim 1. 3. The mass of the electromechanical transducer and the mass of the frictional force generating member are set in a relationship of (mass of the electromechanical transducer) × 3/2 ≧ (mass of the frictional force generating member). A driving device using the electromechanical transducer according to claim 1. 4. The electromechanical conversion element according to claim 1, wherein the drive control means causes the electromechanical conversion element to expand and contract so that no slip occurs at a frictional connection between the guide member and the frictional force generating member. The driving device using the electromechanical transducer according to claim 1, wherein the driving device can move the moving body only by the amount of expansion and contraction.