Ultrasonic motor and ultrasonic apparatus with ultrasonic motor

Abstract: In an ultrasonic motor having a periodically vibrating member vibrated periodically by the application of a high-frequency voltage and a moving body 11b moved by the periodic vibration of the periodically vibrating member, a node supporting/pressurising member 17, which supports a vibration node of the periodically vibrating member and presses the periodically vibrating member on the moving body 11b, or a fitted support member 22, which is fitted at the vibration node of the periodically vibrating member and increases the engagement strength with the periodically vibrating member, is provided, and further a guide member 24 for guiding the movement direction is preferably provided on the moving body 11b, and a movement regulating member 23 is preferably provided to regulate the movement direction of the moving body 11b together with the guide member 24.

Description: The present invention relates to an ultrasonic motor used for driving printers, paper feeders, machine tools, camera zoom mechanisms, and the like and, more particularly, to an ultrasonic motor of a type such that a periodically vibrating member is supported and pressurised. In recent years, an ultrasonic motor has been known in which a driving signal of a predetermined frequency is generated by a variable oscillator, and the driving signal is applied to a piezoelectric element via a power amplifier, by which travelling waves are generated on a vibrating body connected to the piezoelectric element to move a moving body touching the vibrating body with a predetermined pressure (for example, see Japanese Patent Publication No. Sho 62-92781). In particular, an ultrasonic drive unit using elongation vibration and bending vibration of a rectangular piezoelectric vibrating plate (dual-mode vibrator), which is capable of effecting linear movement, rotational movement, etc. of a moving body by combined displacement of vibration mode, is expected to be used for various applications. Fig. 7 shows an ultrasonic motor of a type using a rectangular vibrator. This motor is made up of a piezoelectric vibrating body 14 vibrated by the application of a high-frequency voltage, a moving body 11 pressed on the vibrating body 14, a support member 26 for supporting the vibration node of the vibrating body 14, and a pressurising member 33, which is pressed on both ends of the support member 26, for providing a pressurising force to press the moving body 11 on the vibrating body 14 (see Jpn. J. Appl. Phys. Vol. 31 (1992) Pt. 1, No. 9BP3079). With this unit, the moving body 11 is rotated by the combination of elongation vibration and bending vibration of the vibrating body 14. Fig. 8 also shows an ultrasonic motor of a type using a rectangular vibrator. This motor is made up of a vibrating body 14 consisting of multi-layer piezoelectric elements 14h and a vibrating portion 14i connected to the piezoelectric elements 14h, a cylindrical support member 26 locked to the vibration node of the vibrating body 14, protrusions 13 fixed on the lower side of the vibrating body 14, and a moving body 11 in contact with the protrusions 13 (see Jpn. J. Appl. Phys. Vol. 34 (1995) pp2756-2759). With this unit, the moving body 11 is moved linearly in a fixed direction by elliptical vibrations of the protrusions 13 produced by the combination of elongation vibration and bending vibration of the vibrating body 14. However, according to the aforementioned ultrasonic motor, because the pressurising member 33 is needed in addition to the support member 26, there exists technical problems in that the configuration of the unit is complicated, the whole of the unit is large in size, and loss of vibration is liable to occur for the small vibration body 14. Also, the aforementioned support member 26 is usually locked to the piezoelectric vibrating body 14 with a screw or pinning construction, so that the structural strength is not so high. Therefore, there arises a technical problem in that the pressurising force provided to the support member 26 cannot be increased. Further, the piezoelectric vibrating body 14 has a technical problem in that the moving direction of the moving body 11 is changed with respect to the target direction by a shift in assembling, non uniformity of contact surface between the vibrating body 14 and the moving body 11, and the like. Japan 06284752A discloses an ultrasonic motor comprising of a piezoelectric element which is fixed to a rectangular vibrator. The rectangular vibrator can be vibrated by the application of a high frequency voltage and the vibrator is urged towards a moving body by a support member in the form of a pair of leaf springs acting upon pins extending from the sides of the rectangular vibrator. DE 4440679A also discloses a pair of piezoelectric elements fixed to a vibrating body. The vibrating body is biased into engagement with a fixed body by means of a compression spring whose force acts through pins extending from the side faces of the vibrating body. Thereupon, the present invention was made to solve the above-mentioned technical problems, and accordingly an object thereof is to provide an ultrasonic motor in which the configuration of the unit is simplified and made compact, the support structure for the piezoelectric vibrating body is strengthened, and the change in moving direction of the moving body is prevented. It is an object of the present invention to provide an ultrasonic motor in which the configuration of the unit is simplified and made compact, since the periodically vibrating member is supported and pressurised by the node supporting/pressurising member. It is another object of the present invention to provide an ultrasonic motor where a sufficient frictional force is produced on the moving body, achieving stable movement, since the engagement strength with the periodically vibrating member is increased by the fitted support member, and a pressurising force greater than before is applied to the fitted support member. It is another object of the present invention to provide an ultrasonic motor where stable movement can be achieved against vibration deviation, since the periodically vibrating body is not displaced in any direction other than the regulating direction. It is a further object of the present invention to provide an ultrasonic motor where the unit configuration of the motor can be made compact and simplified, since the pressurising mechanism on the side of the periodically vibrating member is omitted. According to a first aspect of the present invention, there is provided an ultrasonic motor comprising: a periodically vibrating member being vibrated periodically by the application of a high-frequency voltage; a moving body being moved by the periodic vibration of said periodically vibrating member; and a node supporting/pressurising member in the form of a single member which supports a vibration node of said periodically vibrating member and which provides a pressing force to a surface of the vibrating member to urge said periodically vibrating member towards said moving body. Embodiments of the present invention will now be described, by way of example only and with reference to the accompanying drawings, in which: Figs. 1A and 1B are explanatory views showing a first embodiment of an ultrasonic drive unit according to the present invention; Fig. 2 is an explanatory view showing a modification of the embodiment shown in FIGS. 1A and 1B; Fig. 3 is an explanatory view showing a second embodiment of an ultrasonic drive unit according to the present invention; Fig. 4 is an explanatory view showing a modification of the embodiment shown in Fig. 3; Fig. 5 is an explanatory view showing a modification of the embodiment shown in Fig. 3; Fig. 6 is an explanatory view showing a third embodiment in which the ultrasonic drive unit shown in Figs. 1A and 1B are improved; Fig. 7 is an explanatory view showing a configuration of an ultrasonic drive unit relating to the prior art; Fig. 8 is an explanatory view showing a configuration of an ultrasonic drive unit relating to the prior art; and Fig. 9 is a block diagram showing an embodiment of an electronic apparatus with an ultrasonic motor in accordance with the present invention. As noted above, the first aspect of the present invention provides an ultrasonic motor having a periodically vibrating member vibrated periodically by the application of a high-frequency voltage and a moving body moved by the periodic vibration of the periodically vibrating member, comprising a node supporting/pressurising member which supports a vibration node of the periodically vibrating member and presses the periodically vibrating member on the moving body. The operation of the first aspect of the invention is such that the node supporting/pressurising member supports the vibration node of the periodically vibrating member and presses the periodically vibrating member to produce a frictional force between the periodically vibrating member and the moving body, so that a pressurising member need not be provided in addition to the node supporting/pressurising member. In this aspect of the invention, when the periodically vibrating member consists of a piezoelectric element only, the case where a vibrating body is connected to the piezoelectric element is included. Also, when the moving body is formed integrally with a driven object, the case where the moving body is formed as a separate member from a driven object is included. As noted above, the preferred embodiment of the first aspect of the present invention provides an ultrasonic motor having a periodically vibrating member vibrated periodically by the application of a high-frequency voltage and a moving body moved by the periodic vibration of the periodically vibrating member, comprising a fitted support member which is fitted at the vibration node of the periodically vibrating member and which increases the engagement strength with the periodically vibrating member. The operation of this embodiment of the invention is such that the engagement strength between the fitted support member and the periodically vibrating member is increased, and a large pressing force is applied to the fitted support member, so that a sufficient frictional force is produced between the moving body and the periodically vibrating member. Also, in the first aspect of the invention, from the viewpoint of stabilising the moving direction, it is preferable that a guide member for guiding the movement direction be provided on the moving body, whereas a movement regulating member be provided to regulate the movement direction of the moving body together with the guide member. As noted above, the present invention may also provide an ultrasonic motor having a periodically vibrating member vibrated periodically by the application of a high-frequency voltage and a friction providing member for moving the periodically vibrating member by providing a frictional force along with the periodic vibration, comprising a guide member for guiding the movement direction of the periodically vibrating member and a movement regulating member for regulating the movement direction of the periodically vibrating member together with the guide member. The operation of this embodiment of the invention is such that the periodically vibrating member can be moved precisely in the regulating direction by the guide member and the movement regulating member. As noted above, in a second aspect the present invention provides an ultrasonic motor having a periodically vibrating member vibrated periodically by the application of a high-frequency voltage, a moving body moved by the periodic vibration of the periodically vibrating member, and a node support member for supporting a vibration node of the periodically vibrating member, comprising a pressuring member for providing a pressing force for pressing the moving body on the periodically vibrating member to the moving body. The operation of the second aspect of the invention is such that the pressurising member provides a pressing force from the side of the moving body to press the moving body on the periodically vibrating member, so that a pressurising member need not be provided on the side of the periodically vibrating member. Embodiments of the present invention will now be described in detail with reference to Figs. 1 to 9. [Embodiment 1] Figs. 1A and 1B show embodiment 1 in which the first aspect of the invention is applied to an ultrasonic drive unit. This embodiment comprises: a vibrating body 14 serving as a periodically vibrating member of the present invention; protrusions 13 fixed to the lower part of the vibrating body 14; a rail 11a serving as a moving body of the present invention, which is in contact with the protrusions 13; rotating members 12, which are in contact with the lower surface of the rail 11a, for guiding the rail 11a; a spring member 17 serving as a node supporting/pressurising member of the present invention, which is in contact with the upper surface of the vibrating body 14; and rubber sheets 15, 16, and 18 disposed between the spring member 17 and the vibrating body 14 and between the spring member 17 and a fixed plate 19. The vibrating body 14 is formed in a rectangular plate or bar shape, and is, for example, made of a piezoelectric element subjected to a predetermined polarisation. Also, a vibrating body 14 of the type which has a vibrating portion in face contact with the piezoelectric element may be used. The spring member 17 has a V shape in cross section. The lower tip end of the V shape is pressed on a vibration node 14a on the vibrating body 14 via the rubber sheet 15. The upper tip ends of the V shape are in contact with the fixed plate 19 via the rubber sheets 16 and 18. Next, the operation of this ultrasonic drive unit will be described. The vibrating body 14 to which a high-frequency voltage is applied starts elongation vibration and bending vibration. The protrusions 13 fixed to the lower part of the vibrating body 14 come into contact with the rail 11a at a predetermined timing and move the rail 11a linearly in the horizontal direction. At this time, the spring member 17 supports the vibration node 14a to prevent the vibrating body 14 from moving, and also provides a pressurising force to the vibrating body 14 due to elastic deformation. Thus a sufficient frictional force is produced between the protrusion 13 and the rail 11a. Therefore, it is unnecessary to provide a member for pressurising the vibrating body 14 in addition to the spring member 17. As described above, according to this embodiment, the vibrating body 14 is supported and pressurised by one member, so that the pressuring member relating to the prior art is omitted, and the configuration of the unit is simplified and made compact. Fig. 2 shows an ultrasonic drive unit in accordance with a modification of embodiment 1. This modified embodiment has almost the same configuration as that of embodiment 1 except that there is provided a prismatic fastener 21 for fixing the vibrating body 14 by passing through the rubber sheet 15 and the spring member 17. According to this configuration, the spring member 17 securely supports the vibration node 14a of the vibrating body 14. Therefore, the support point of the vibrating body 14 is not changed from the vibration node 14a by the vibration of the vibrating body 14, and the vibration of the vibrating body 14 is stabilised. [Embodiment 2] Fig. 3 shows embodiment 2 in which the first aspect of the invention is applied to an ultrasonic drive unit. This embodiment comprises: a rectangular vibrating body 14 in contact with a moving body 11b; spring members 17a and 17b fixed at a vibration node 14a of the vibrating body 14; and fixed plates 19 for supporting the spring members 17a and 17b. Specifically, the spring members 17a, 17b are formed in a convexly curved plate shape with the portion where the spring member 17a, 17b is fixed to the vibrating body 14 being bent at an angle thereto as shown. Next, the operation of this embodiment will be described. The vibrating body 14 to which a high-frequency voltage is applied effects elongation vibration and bending vibration at a predetermined timing, and rotates the moving body 11b by the composite displacement thereof. At this time, like embodiment 1, the spring members 17a, 17b support the vibrating body 14, and also provide a pressing force to press the vibrating body 14 on the moving body 11b, so that a separate member used for pressurisation is not needed unlike the prior art. Figs. 4 and 5 show a modification of embodiment 2. A first mode of the modified embodiment has almost the same configuration as that of embodiment 2, as shown in Fig. 4, except that engagement grooves 14b and 14c are formed at both edges of the vibration node 14a of the vibrating body 14, and the end portions of the spring members 17b and 17a are engaged with the grooves 14b and 14c. respectively, by deflecting the spring members 17a and 17b. A second mode of the modified embodiment has almost the same configuration as that of embodiment 2, as shown in Fig. 5, except that engagement protrusions 14d and 14e are provided at both ends of the vibration node 14a of the vibrating body 14, and the spring members 17b and 17a are engaged with the sides of the engagement protrusions 14d and 14e opposite to the moving body 11b, respectively, by deflecting the spring members 17a and 17b. [Embodiment 3] Fig. 6 shows embodiment 3 in which the moving direction of the moving body in accordance with the first aspect of the invention is improved. This embodiment comprises: a vibrating body 14; protrusions 13 provided on the lower side of the vibrating body; a rail 11a in contact with the protrusions 13; a guide groove 11c serving as a guide member of the present invention, which is formed on the surface of the rail 11a; and movement regulating members 23 serving as movement regulating members of the present invention, which are provided integrally with the protrusions 13. According to this configuration, the movement regulating members 23 enter the guide groove 11c to regulate the moving direction of the rail 11a. Therefore, the rail 11a is not affected by vibration deviation of the vibrating body 14, so that stable movement is effected. [Embodiment 4] This embodiment is characterised in that a predetermined groove is provided in the direction of vibration mode displacement on a rectangular plate shaped vibrating body of dual vibration mode. According to this configuration, when the resonance frequencies of elongation vibration and bending vibration do not agree with each other, the resonance frequencies are made to agree by the predetermined groove. Therefore, the vibrating body need not be fabricated with tight accuracy to make the resonance frequencies agree with each other, so that the manufacturing process of the vibrating body can be simplified. [Embodiment 5] Fig. 9 is a block diagram for an embodiment of an electronic apparatus using the ultrasonic motor in accordance with the present invention. By using the ultrasonic motor described in the above embodiments, an electronic apparatus with an ultrasonic motor can be realised by providing a transmission mechanism 50 operating integrally with a moving body 11 of the ultrasonic motor and an output mechanism 51 operating based on the operation of the transmission mechanism 50. As the transmission mechanism 50, a transmission wheel such as gear and frictional wheel and the like are preferably used. As the output mechanism 51, preferably, a shutter driving mechanism and lens driving mechanism are used for a camera, a hand driving mechanism, calendar driving mechanism, etc. for an electronic clock, and a tool feed mechanism, workpiece feed mechanism, etc. for a machine tool. As the electronic apparatus with the ultrasonic motor in accordance with the present invention, electronic clocks, measuring instruments, cameras, printers, printing machines, machine tools, robots, transfer apparatuses, and the like are preferably realised. Further, if a configuration is employed in which an output shaft is installed to the moving body, and a power transmission mechanism is provided to transmit a torque from the output shaft, a driving mechanism for an ultrasonic motor can be realised.

Claims: An ultrasonic motor comprising: a periodically vibrating member (14) being vibrated periodically by the application of a high-frequency voltage; a moving body (11a) being moved by the periodic vibration of said periodically vibrating member (14); characterized by a node supporting/pressurising member (17) in the form of a single member which supports a vibration node of said periodically vibrating member (14) and which provides a pressing force to a surface of the vibrating member to urge said periodically vibrating member (14) towards said moving body (11a). An ultrasonic motor as claimed in claim 1, wherein a guide member (11c) for guiding the movement direction is provided on said moving body (11a), and a movement regulating member (23) is provided to regulate the movement direction of said moving body (11a) together with said guide member (11c). An electronic apparatus including an ultrasonic motor as claimed in claim 1 or claim 2, further comprising: a transmission mechanism (50) operating integrally with the moving body (11) of said ultrasonic motor; and an output mechanism (51) operating based on the operation of said transmission mechanism (50).

Inventors: IINO AKIHIRO, KASUGA MASAO, SUZUKI MAKOTO, IINO, AKIHIRO, KASUGA, MASAO, SUZUKI, MAKOTO
Applicants: SEIKO INSTR INC, SEIKO INSTRUMENTS INC.
Application year: 1998
Main classification: H01L41
IPC codes: H02N2, H01L41