JPH041598B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention uses a vibration wave motor that utilizes mechanical vibration waves generated by an electro-mechanical energy conversion element such as an electrostrictive element or a magnetostrictive element. It relates to devices that drive lenses and other things.

As already known from Japanese Patent Application Laid-open No. 52-29192, the vibration wave motor brings a fixed body and a moving body into frictional contact, and connects at least one of them to the electro-mechanical energy conversion element itself or Electricity
It is composed of an elastic vibrating body that includes a mechanical energy conversion element, and by applying high-frequency electrical energy above the audible frequency to the electro-mechanical energy conversion element, mechanical vibration energy is generated and the moving body is frictionally driven in one direction. It is something that makes you

Among such vibration wave motors, the present invention particularly uses a type of vibration wave motor that generates bending vibration on the frictional contact surface between a fixed body and a movable body, and uses the traveling vibration wave to frictionally drive the movable body. .

Conventionally, attempts have been made to apply vibration wave motors to lens drives, but the following problems have arisen. That is, in terms of lens drive, in addition to electric drive in which the lens is driven by the force of a vibration wave motor, manual drive in which the photographer drives the lens by his or her own power is strongly desired. However, in a vibration wave motor, a fixed body and a movable body come into strong frictional contact, and the driving force is transmitted through this frictional contact. Therefore, in order to move the moving body when it is not driven, a large force exceeding the frictional force is required. That is, when driving the lens manually, a torque greater than the friction torque is required, and in order to reduce the torque and improve operability, a clutch mechanism or the like is required. This complicates the structure and is disadvantageous in terms of cost.

An object of the present invention is to solve the above-mentioned problems and provide a drive device using a vibration wave motor that can reduce the driving load during manual operation and improve manual operability without complicating the structure. It is to provide.

In order to achieve this object, the present invention provides a vibration wave motor including a vibrating body and a plurality of electro-mechanical energy conversion elements, the electric-mechanical energy conversion elements being integrally coupled with the vibrating body, or Alternatively, the driven member is driven by contacting the vibrating body of the vibration wave motor, and the control circuit connects the pulse generation source, automatic manual mode switching means, and mode control circuit. The pulse generation source applies generated pulses to the electro-mechanical energy conversion element to vibrate the vibration wave motor, and the mode control circuit controls the generation pulse mode of the pulse generation source. The device operates in two modes: an automatic mode in which a traveling vibration wave is generated in the vibrating body and a manual mode in which a standing vibration wave is generated in the vibrating body, and the automatic manual mode switching means selects one of the modes. It is characterized by making the frictional contact between the vibrating body and the driven member in the manual mode into a dynamic friction state, thereby reducing the coefficient of friction and the contact area. do.

Before describing embodiments of the present invention, the driving principle of a vibration wave motor (also called a piezoelectric motor or an ultrasonic motor) will be explained with reference to FIG.

In Fig. 1, 1 is a moving body as a driven member pressurized by a force F, 2 is a fixed body as a vibrating body that vibrates elastically by an electrostrictive element, and the x-axis is set on the surface of the fixed body 2. , and the z-axis is its normal direction. When bending vibration is applied to the surface of the fixed body 2 by the electrostrictive element, a traveling vibration wave is generated and propagates on the surface of the fixed body 2. This traveling vibrational wave is a surface wave accompanied by longitudinal waves and transverse waves, and the motion of its mass point follows an elliptical orbit. Focusing on the mass point A, it is performing an elliptical motion with a longitudinal amplitude u and a lateral amplitude w, and if the traveling direction of the surface wave is the x-axis direction, the elliptical motion is counterclockwise. This surface wave has vertices A, A'...
, whose apex velocity is only the x component, and v
=2πfu (f is the frequency). Therefore, moving object 1
When the surface of the movable body 1 is brought into frictional contact with the surface of the fixed body 2, the surface of the movable body 1 contacts only the vertices A, A', . . . , so the movable body 1 is driven in the direction of arrow N by the frictional force.

The speed of the moving body 1 is proportional to the frequency f. Also,
Due to the frictional drive due to pressure contact, it depends not only on the longitudinal amplitude u but also on the transverse amplitude w. That is, the speed of the moving body 1 is proportional to the magnitude of the elliptical motion. Therefore, the speed of the moving body 1 is proportional to the voltage applied to the electrostrictive element.

FIG. 2 is an exploded view showing the basic configuration of the vibration wave motor used in the present invention. Hard rubber 1 is attached to the annular moving body 1 to facilitate frictional contact.
a is glued. Electrostrictive elements 3 a and 3 b forming two groups are bonded to the annular fixed body 2 . When the electrostrictive elements 3a and 3b operate independently,
The fixed body 2 is placed in a state where it resonates, that is, in a position where a standing vibration wave exists, and the standing vibration wavelength of the electrostrictive element 3a and the standing vibration wavelength of the electrostrictive element 3b are equal. , are arranged so that they are 90° out of phase (physical position shifted by 1 wavelength/4). The felt 4 absorbs vibrations on the surface of the fixed body 2 opposite to the frictional contact surface. The support body 5 supports the fixed body 2, the electrostrictive elements 3a and 3b, and the felt 4.

FIG. 3 is a diagram illustrating the generation of traveling vibration waves and standing vibration waves. For the sake of explanation, the electrostrictive elements 3a and 3b are not arranged as shown in FIG. 2 but are arranged alternately, but they satisfy the same conditions as above and are equivalent arrangements. The drive power supply 6 supplies a voltage of V=V _p sin ωt. A voltage V _p sin ₍ ωt ± /2) is applied. ± of the voltage V _p sin (ωt±π/2) is switched depending on the direction in which the moving body 1 is moved. 3A to 3F show the state of vibration waves when a voltage V _p sin (ωt-π/2) is applied. A shows a state in which a standing vibration wave 10 is generated only by the electrostrictive element 3a, and B shows a state in which a standing vibration wave 11 with a 90° phase delay is generated only by the electrostrictive element 3b. H~N are two electrostrictive elements 3
It shows a state in which traveling vibration waves 12 are generated by operating a and 3b simultaneously. C is time t=0+
2nπ/ω, D is time t=π/2ω+2nπ/ω, E is time t=π/ω+2nπ/ω, F is 3π/2ω+2nπ/
ω, the phase of the traveling vibration wave 12 is shown. The traveling vibration wave 12 travels to the right in FIG. 3, but any mass point on the frictional contact surface of the fixed body 2 performs an elliptical motion in a counterclockwise direction. Therefore, the moving body 1 moves to the left.

In the state in which the standing vibration waves 10 and 11 of A and B are generated, the mass points other than the nodes on the frictional contact surface of the fixed body 2 exhibit only transverse vibration, that is, vertical movement in FIG. 3.
Therefore, the frictional contact between the moving body 1 and the fixed body 2 is not a static friction state but a dynamic friction state,
The coefficient of friction becomes smaller and the contact area becomes smaller.
Therefore, when moving the movable body 1 manually, it can be moved with a small force.

FIG. 4 shows the structure of a zoom lens driving device according to an embodiment of the present invention. Components similar to those in FIG. 2 are designated by the same reference numerals.

At the rear end of the fixed barrel 13 of the lens barrel, a mounting member 14 such as a bayonet or screw mount for mounting on the camera is provided. Fixed body 13
A straight groove 13a is provided in the optical axis direction. The lens holding barrels 15 and 16 are fitted inside the fixed barrel 13, and hold a lens optical system 17 that performs a magnification change function and a correction function for aberrations accompanying the magnification change. Pins 15a, 16a are installed in each lens holding barrel 15, 16, and these pins 15a, 16a are inserted into the straight groove 13a.
It penetrates through and fits into cam grooves 18a and 18b of a cam cylinder 18 fitted on the outer periphery of the fixed cylinder 13. The lens holding cylinder 19 holds a focusing lens optical system 20,
A threaded portion 19a screwed onto the outer periphery of the lens holding barrel 15
has. The cylindrical flange 19b is connected to the distance adjustment ring 2.
It is fitted into a rectilinear groove 21a formed on the inner circumferential surface of the lens 1 parallel to the optical axis direction. A grip portion 21b is provided at the tip of the distance adjustment ring 21. The friction contact portion 21c of the distance adjustment ring 21 corresponds to the movable body 1 in FIG. 2, and is pressed against the fixed body 2 by a ring leaf spring 22. The base cylinder 23 is integrally fixed to the fixed body 13 with screws (not shown), and supports the fixed body 2, the electrostrictive elements 3a and 3b, and the felt 4.

An outer cylinder 24 is screwed to the base cylinder 23.
A first ring 25 and a second ring 26 for bearings are attached to the inside of the bearing. That is, the first ring 25 is pressed against the friction contact portion 21c of the distance adjustment ring 21 by the ring-shaped spring 22 via the bearing ball 27.
The second ring 26 is attached by being screwed into the inner circumferential surface of the outer cylinder 24, and a V-shaped circumferential groove is formed at the joint between the first ring 25 and the second ring 26. A bearing ball 28 is held between the groove and a substantially U-shaped circumferential groove formed on the outer peripheral surface of the distance adjustment ring 21. As a result, the distance adjustment ring 21
is rotatably attached to the outer cylinder 24, and
Rotatable frictional contact of the frictional contact portion 21c with the fixed body 2 is ensured.

The code plate 29 has comb-shaped electrodes,
The distance adjustment ring 2 is attached to the inner wall surface of the outer cylinder 24.
When the slider 30 fixed to the lens 1 slides on the comb-shaped electrode, the movement consists of a number of pulses corresponding to the amount of rotation of the distance adjustment ring 21, that is, the amount of movement of the focusing lens optical system 20. A quantity monitor signal is generated.
An electric manual changeover switch 31 is provided on the outer cylinder 24, and its contact piece 32 is mounted on the base cylinder 23. The operating pin 33 is attached to the cam cylinder 18,
The cam cylinder 18 is rotated by turning it around the optical axis from the outside of the base cylinder 23. When the cam cylinder 18 rotates, the cam grooves 18a and 18b engage the pins 15a and 16a.
Since the lenses are moved along the rectilinear groove 13a, the lens holding cylinders 15 and 16 move in the optical axis direction and perform a magnification change action and an aberration correction action.

FIG. 5 shows a circuit of one embodiment of the present invention. The autofocus light receiver 34 is connected to the distance measuring circuit 35 using, for example, a charge-coupled device. Distance measurement circuit 35
Output terminal A outputs a high-level drive signal or a low-level stop signal to the vibration wave motor, and output terminal B outputs a high-level near-side drive direction signal or a low-level infinity-side drive direction signal. A switching signal is inputted to the input terminal C from the electric manual switching circuit 36 via the inverter 37, and a movement amount monitor signal is inputted to the input terminal D from the monitor signal generation circuit 38 via the chattering absorption circuit 39.
The electric manual changeover circuit 36 is the electric manual changeover switch 3
1 and a resistor 40, the monitor signal generation circuit 3
8 consists of a code plate 29, a slider 30 and a resistor 41. The pulse generation circuit 42 consists of an oscillator 43, frequency dividers 44, 45 with a frequency division ratio of 1/2, and an inverter 46, and pulses with a 90° phase difference are transmitted between the frequency dividers 44, 45, and an inverter 46.
Output from 45. 47 is an OR gate, 48 is an AND gate, and 49 is an exclusive OR gate. The exclusive OR gate 49 assumes that the phase of the pulse of the frequency divider 45 is advanced by 90 degrees with respect to the pulse of the frequency divider 44 when the input from the output terminal B of the distance measuring circuit 35 is at a high level, and by 90 degrees when the input is at a low level. ° It is considered late.

The drive control circuit 50 is a circuit that controls the drive of the electrostrictive elements 3a and 3b, and includes two push-pull circuits 51 and 5 made up of transistors, resistors, and inverters.
2. It is composed of switching transistors 53, 54, etc. switching transistor 5
3 and 54 are connected to a power source via a resistor 55 and a lens drive power switch (not shown).

Next, the operation of the embodiment shown in FIGS. 4 and 5 will be explained. Lens drive power switch (not shown)
When turned on, the electric manual switching circuit 36, inverter 37, OR gate 47, and AND gate 4 are activated.
8. Exclusive OR gate 49, pulse generation circuit 4
2. Power is supplied to the drive control circuit 50, and the pulse generation circuit 42 starts operating.

When the electric manual changeover switch 31 is turned off and electric drive is selected, the electric manual changeover circuit 3
6 outputs a high level switching signal, AND gate 48 is opened. Further, this switching signal is inverted by the inverter 37, becomes low level, and is input to the input terminal C of the distance measuring circuit 35.

When the first stroke of a release button consisting of two strokes is pressed for photographing operation of the camera, a photometric calculation operation is started. The distance measuring circuit 35 determines that it is electrically driven by inputting a low-level switching signal to the input terminal C, starts automatic focusing operation, and sets the focusing range to a narrow width for automatic focusing. The light receiver 34 receives the reflected light from the subject, and the distance measuring circuit 35 uses the subject information from the light receiver 34 to detect a focusing error based on a known contrast detection method, shift detection method, etc., and calculates the amount of lens drive and Calculate the driving direction. The lens driving amount is preset in a counter (not shown) in the distance measuring circuit 35. A high level drive signal is output from the output terminal A, and if it is assumed that the subject is on the close side, a high level close side drive direction signal is output from the output terminal B. Therefore, the OR gate 47 and the AND gate 48 both output high level signals, and the switching transistors 53 and 54
Turn on. Therefore, push-pull circuit 5
1 and 52 are supplied with power. Pulse generation circuit 4
2 is in operation, and the pulse of the frequency divider 44 directly controls the push-pull circuit 52, so that the electrostrictive element 3
High frequency power is applied to b. The pulse of the frequency divider 45 is inverted by the exclusive OR gate 49 and has a phase lead of 90° with respect to the pulse of the frequency divider 44, and controls the push-pull circuit 51, so that the pulse is inverted in the electrostrictive element 3a. High frequency power with a 90° phase lead is given. As a result, a traveling vibration wave 12 is generated in the fixed body 2, and the distance adjustment ring 21 is rotated in the focusing direction. Along with this, the lens holding cylinder 19 rotates while being screwed together with the lens holding cylinder 15.
Move in the drawing direction and reach the focus area.

As the distance adjustment ring 21 rotates, the slider 30 slides on the code plate 29 and generates a movement amount monitor signal with a pulse number corresponding to the movement amount of the lens. This movement amount monitor signal is input to the input terminal D of the distance measuring circuit 35.
, and subtract the preset lens drive amount from the counter. When the counter value becomes zero,
A low level stop signal is output from the output terminal A, and the outputs of the OR gate 47 and the AND gate 48 are inverted to low level, so the switching transistors 53 and 54 are turned off, and the electrostrictive elements 3a,
3b is then disconnected from the power source, and the driving of the distance adjustment ring 21 is stopped. Here again, distance measurement is performed by the light receiver 34 and the distance measuring circuit 35, and if the focusing error is within the in-focus range, an in-focus display is performed. When the lens is not in the in-focus area, the lens is driven again in the same manner as described above.

When the subject is at infinity, the distance measuring circuit 3
Since the output terminal B of 5 outputs a low-level infinity side drive direction signal, the exclusive OR gate 49 passes the pulse of the frequency divider 45 as it is, and assumes that the pulse is delayed by 90 degrees in phase from the pulse of the frequency divider 44. do. Therefore, the electrostrictive elements 3a and 3b generate traveling vibration waves that travel in opposite directions, the distance adjustment ring 21 rotates in the opposite direction, and the lens holding cylinder 19 is moved in the retracting direction.

When the electric manual changeover switch 31 is turned on and manual drive is selected, the electric manual changeover circuit 3
6 outputs a low level switching signal, the output of the OR gate 47 becomes high level and turns on the switching transistor 54. On the other hand, the output of the AND gate 48 becomes low level, turning off the switching transistor 53. Therefore, high frequency power is not supplied to the electrostrictive element 3b, but only to the electrostrictive element 3a. Therefore, a standing vibration wave 10 is generated in the fixed body 2, and the friction torque between the fixed body 2 and the distance adjustment ring 21 is reduced. Therefore, by holding the grip portion 21b slightly exposed from the tip of the outer cylinder 24 and turning the distance adjustment ring 21, it will turn lightly with a small manual torque, and the lens holding cylinder 19 will be moved in the optical axis direction.

The distance measuring circuit 35 determines that manual drive is being performed by inputting a high-level switching signal to the input terminal C, sets the width of a wide focusing range for manual driving, and sets the focusing lens. When the optical system 20 reaches the in-focus area, in-focus display is performed.

According to this embodiment, the distance adjustment ring 21 can be moved lightly during manual focus adjustment, so manual operability can be improved. Additionally, the following advantages of vibration wave motors can be utilized in cameras.

(1) Since it does not have a winding, it is easy to manufacture and does not require much manpower.

(2) The amount of expensive materials used can be reduced.

(3) Dimensions are smaller and can be made into flat structures or elongated shapes.

(4) It can be configured as a low-speed motor and does not require a reduction mechanism.

(5) It has large starting torque and small moment of inertia.

2 to 5, the electrostrictive elements 3a and 3b correspond to the electro-mechanical energy conversion element of the present invention, the fixed body 2 corresponds to the vibrating body, and the movable body 1 or the distance adjustment ring 21 corresponds to the driven member. The pulse generation circuit 42 corresponds to a pulse generation source, the inverter 37, OR gate 47, AND gate 48, exclusive OR gate 49, and drive control circuit 50 correspond to a mode control circuit, and the electric manual switching circuit 36 corresponds to an automatic Corresponds to manual mode switching means. Further, 60 shown in FIG. 2 corresponds to the vibration wave motor of the present invention, and 70 shown in FIG. 5 corresponds to a control circuit.

In the illustrated embodiment, a plurality of electrostrictive elements 3a and 3b are used, but one electrostrictive element may be polarized into a plurality of elements. Further, the electrostrictive element may be provided on the friction contact portion 21c of the distance adjustment ring 21, or may be provided on both the fixed body 2 and the friction contact portion 21c. Furthermore, the fixed body 2 itself may be composed of an electrostrictive element. The optimal frequency of the vibration waves produced by the electrostrictive element is in the ultrasonic range.

Focus error detection is not limited to an optical method, but may also be an ultrasonic method.

The present invention is suitable not only for use in focusing drive of a lens, but also for manual operation of zoom lens drive, that is, power zoom drive.

As explained above, according to the present invention, the frictional contact between the vibrating body and the driven member in the manual mode is made into a dynamic friction state, and the friction coefficient is reduced and the contact area is reduced. It is possible to reduce the driving load during manual operation and improve manual operability without complication.

[Brief explanation of drawings]

Figure 1 is a diagram explaining the driving principle of the vibration wave motor, Figure 2 is an exploded view showing the basic configuration of the vibration wave motor used in the present invention, and Figure 3 is the progression in the vibration wave motor shown in Figure 2. FIG. 4 is a cross-sectional view showing an embodiment of the present invention, and FIG. 5 is a circuit diagram for explaining the generation of vibration waves and standing vibration waves. 1... Moving body (driven member), 2... Fixed body (vibrating body), 3a, 3b... Electrostrictive element (electrical-mechanical energy conversion element), 10, 11... Standing vibration wave, 12... ...Travelling vibration wave, 13...Fixed cylinder, 1
5, 16... Lens holding cylinder, 19... Lens holding cylinder, 20... Focusing lens optical system, 21... Distance adjustment ring (driven member), 23... Base cylinder, 24...
Outer cylinder, 31... Electric manual changeover switch, 32...
Contact piece, 34... Light receiver, 35... Distance measuring circuit, 36
...Electric manual switching circuit (automatic manual mode switching means), 37... Inverter, 42... Pulse generation circuit (pulse generation source), 44, 45... Frequency divider,
47...or gate, 48...and gate, 4
9... Exclusive OR gate, 50... Drive control circuit, 37 and 47-50... Mode control circuit, 5
1, 52... Push-pull circuit, 53, 54...
Switching transistor, 60... Vibration wave motor, 70... Control circuit.

Claims (1)

[Claims] 1. Vibration wave motor 60 and driven members 1, 21
and a control circuit 70, the vibration wave motor 60 having a vibrating body 2 and a plurality of electro-mechanical energy conversion elements 3a, 3b,
The electro-mechanical energy conversion elements 3a, 3b are integrally coupled with the vibrating body 2, or are also used as the vibrating body 2, and the driven members 1, 21 are in contact with the vibrating body 2 of the vibration wave motor 60. The control circuit 70 includes a pulse generation source 42, an automatic manual mode switching means 36, a mode control circuit 37,
47 to 50, the pulse generation source 42 converts the generated pulses into the electro-mechanical energy conversion elements 3a and 3b.
The mode control circuits 37, 47 to 50 control the pulse generation mode of the pulse generation source 42, and apply a traveling vibration wave to the vibrating body 2. It operates in two modes: an automatic mode for generating standing vibration waves and a manual mode for generating standing vibration waves in the vibrating body 2, and the automatic manual mode switching means 36 can selectively switch one of the modes. Drive device.