1. Technical Field
The invention relates to a motor, a robot hand, and a robot.
2. Related Art
As a motor that drives a driven body using vibration of a piezoelectric element, a motor is known that drives a driven body by causing a protrusion of a reinforcement plate of an actuator in which a rectangular flat plate-like piezoelectric element is laminated on the reinforcement plate having the protrusion integrally formed to abut on the driven body (JP-A-2010-233335). Ina motor having this piezoelectric actuator, an impelling unit is included for causing the protrusion provided in the reinforcement plate of the piezoelectric actuator to abut on the driven body, and frictional force between the protrusion of the reinforcement plate and the driven body, which is caused by the impelling force generated by the impelling unit transmits vibration of the protrusion of the reinforcement plate tracing a substantially elliptical trajectory to the driven body, thereby driving the driven body in a predetermined direction.
In JP-A-2010-233335 described above, in order for the impelling unit to impel the protrusion of the reinforcement plate against the rotational center of the driven body, spring members are disposed on both sides of the piezoelectric actuator including the reinforcement plate. However, since the protrusion of the reinforcement plate operates in a substantially elliptical trajectory, the reaction force on the protrusion of the reinforcement plate from the driven body by the impelling force is generated in a direction intersecting the direction of the impelling force toward the rotational center of the driven body. Due to the reaction force intersecting the direction of the impelling force, the operation of the protrusion of the reinforcement plate does not trace the desired elliptical trajectory. That is, there is a problem in that the reaction force becomes a cause of degradation of the efficiency in changing the vibration of the actuator into the driving force of the driven body.
An advantage of some aspects of the invention is that it provides a motor with good efficiency using an impelling unit that does not cause the reaction force of an actuator from a driven unit to impede conversion of vibration of the actuator into the driving force of the driven unit, a robot hand using the motor, and a robot.
This application example of the invention is directed to a motor including: a driven unit having a cylindrical rotation surface; an actuator including a vibrator plate having, on an end portion, a protrusion impelled against the rotation surface of the driven unit, and a piezoelectric body laminated on the vibrator plate; and an impelling unit impelling the actuator against the driven unit, wherein, assuming that the elliptical trajectory of the protrusion traced by vibration of the actuator that drives the driven unit is disposed to abut on the rotation surface, a contact point between the elliptical trajectory and the rotation surface is a contact point P, a point of action where an impelling force by the impelling unit is exerted on the actuator is a point of action Q, and a rotational center of the driven unit is a rotational center R, an angle θ1 between the impelling direction of the impelling unit and a direction connecting the rotational center R and the contact point P and an angle θ2 between the impelling direction of the impelling unit and a direction connecting the contact point P and the point of action Q satisfy the following relationship.
θ1<θ2
According to the above-described application example, by causing the angles θ1 and θ2 to have the above relationship, a component force of the reaction force exerted on the protrusion of the vibrator plate from the driven unit so as not to cause the protrusion of the vibrator plate to be directed to the rotational center of the driven unit is suppressed, so that the vibration of the excited actuator may be converted into the rotational force of the driven unit with a high efficiency.
This application example of the invention is directed to a robot hand including the motor according to the above-described application example.
The robot hand according to this application example has a high degree of freedom and thus can achieve a reduction in size and weight even though a large number of motors are included therein.
This application example of the invention is directed to a robot including the robot hand according to the above-described application example.
The robot hand according to this application example has a high degree of versatility and is able to perform an assembly operation or inspection on a complex electronic device.
The invention will be described with reference to the accompanying drawings, wherein like numbers reference like elements.
Hereinafter, exemplary embodiments of the invention will be described with reference to the drawings.
The actuator 30 is formed by bonding piezoelectric elements 32 and 33 made of rectangular piezoelectric bodies having electrodes formed therein with a vibrator plate 31 interposed therebetween. The piezoelectric elements 32 and 33 may use a material having piezoelectricity, for example, Lead Zirconate Titanate (PZT: Pb(Zr,Ti)O3), quartz crystal, or Lithium Niobate (LiNbO3). Particularly, PZT is appropriately used. The formed electrodes may be formed by depositing a conductive metal such as Au, Ti, or Ag and forming layers through sputtering or the like. The vibrator plate 31 has a protrusion 31a at the end portion, which is fixed to the support body 40 as the actuator 30, is impelled by the coil spring 60 against the driven body 20, and abuts on the driven body 20. In addition, the vibrator plate 31 is formed of stainless steel, nickel, a rubber metal, or the like, and due to workability, stainless steel is appropriately used. The actuator 30 is fixed to the support body 40 by screws 50 which are inserted through holes 31c of mounting portions 31b formed in the vibrator plate 31 for mounting to the support body 40 and are screwed into screw holes 40b of fixing portions 40a formed in the support body 40.
The driven body 20 has a cylindrical shape and is driven by the vibration of the actuator 30 as the protrusion 31a of the actuator 30 is impelled against and comes in contact with a cylindrical surface 20a due to the coil spring 60. In addition, as illustrated in
The support body 40 includes guide holes 40c, and guide pins 70 provided in the base 10 are inserted through the guide holes 40c such that the support body 40 is slidably fixed to the base 10. The shape of the guide hole 40c is a track shape in plan view in this embodiment so as to enable the support body 40 to slide in the impelling direction of the actuator 30, and is slightly greater than the outer diameter of the guide portion of the guide pin 70 in a direction intersecting the impelling direction of the actuator 30 so as to minimize the backlash amount in the direction intersecting the impelling direction of the actuator 30.
In addition, in the support body 40, the one end portions of the coil springs 60 as the impelling units are respectively fixed to two fixing portions 40a to which the actuator 30 is mounted. The other end portions of the coil springs 60 are mounted to spring mounting portions 11 provided on the base 10 so that the base body 40 is impelled in a direction of the driven body 20. In the support body 40, the mounting portion 31b of the vibrator plate 31 of the actuator 30 is placed on the fixing portion 40a of the support body 40, and the actuator 30 is fixed to the screw hole 40b provided in the fixing portion 40a by the screw 50. The protrusion 31a of the fixed actuator 30 is impelled against the driven body 20 by a predetermined force via the support body 40. In addition, the impelling unit is not limited to the coil spring 60, and for example, a leaf spring or an elastic rubber may also be used.
Next, the operation of the actuator 30 will be described with reference to
In addition, as illustrated in
The elliptical trajectories S1 and S2 of the protrusion 31a that are generated by the vibration of the actuator 30 described above are impelled against and come in contact with the driven body 20 due to the impelling force and thus drive the driven body 20 in the directions of illustrated arrows s1 and s2. The relationship among the elliptical trajectories S1 and S2, the driven body 20, the coil spring 60 as the impelling unit, and the support body 40 will be described with reference to
As illustrated in
Assuming that a straight line connecting the rotational center R of the driven body 20 and the contact point P is L1 and a straight line connecting the contact point P and the impelling point QR is L2, it is preferable that an angle θ1 between a straight line L3 passing through the contact point P in parallel to the illustrated impelling direction of an impelling force F by the coil spring 60 as the impelling unit, and the straight line L1 and an angle θ2 between the straight line L3 and the straight line L2 satisfy the following relationship.
θ1<θ2 (1)
f1>fR1
The difference between the component forces f1 and fR1 is exerted so that the impelling force F due to the coil spring 60 impels the protrusion 31a against the rotational center R of the driven body 20.
That is, from the relationship of the angles θ1 and θ2 shown in Expression (1), the component force fR1 of the impelling force generated by the reaction force FR that does not cause the protrusion 31a to be directed to the rotational center R is suppressed, and the vibration of the excited actuator 30 may be converted into rotational force of the driven body 20 with high efficiency.
θ1′>θ2 (2)
In addition, the angle θ1′ in
f1<fR1′
When the relationship of the angles θ1′ and θ2 shown in Expression (2) is satisfied, the component force fR1′ of the impelling force generated by the reaction force FR′ that does not cause the protrusion 31a to be directed to the rotational center R cannot be suppressed by the component force f1 of the impelling force F, and an efficiency in converting the vibration of the excited actuator 30 into the rotational force of f the driven body 20 is significantly damaged. In addition, even in the case of the elliptical trajectory S2 shown in
The above-described elliptical trajectories S1 and S2 may be measured by the following method. The motor 100 according to this embodiment is driven, reflected light of a laser beam K emitted toward the protrusion 31a in the direction shown in
While checking the elliptical trajectories S1 and S2 measured as such, by changing the dimensions of each of the piezoelectric elements 32 and 33 of the actuator 30, the driving voltage, the impelling force of the coil spring 60, the arrangement position of the actuator 30, the material of the piezoelectric elements 32 and 33, the material of the driven body 20, surface finish of the cylindrical surface 20a, and the like, the motor 100 that satisfies the conditions of Expression (1) is manufactured.
By the arrangements of the impelling unit as illustrated in
In addition, in a motor 120 illustrated in
The arm portion 2200 includes a first frame 2210, a second frame 2220, a third frame 2230, a fourth frame 2240, and a fifth frame 2250. The first frame 2210 is rotatably or bendably connected to the main body portion 2100 with a rotation bending shaft. The second frame 2220 is connected to the first and third frames 2210 and 2230 via a rotation bending shaft. The third frame 2230 is connected to the second and fourth frames 2220 and 2240 via a rotation bending shaft. The fourth frame 2240 is connected to the third and fifth frames 2230 and 2250 via a rotation bending shaft. The fifth frame 2250 is connected to the fourth frame 2240 via a rotation bending shaft. The arm portion 2200 is moved as the frames 2210 to 2250 are complexly rotated or bent about the corresponding rotation bending shafts under the control of the control unit.
To the side of the fifth frame 2250 of the arm portion 2200 opposite to the side where the fourth frame 2240 is provided, a robot hand connection portion 2300 is connected, and the robot hand 1000 is mounted to the robot hand connection portion 2300. The motor 100 that causes the robot hand 1000 to perform a rotation operation is embedded into the robot hand connection portion 2300, so that the robot hand 1000 can grasp an object. Using the robot hand 1000 which is small in size and weight, a robot which has a high degree of versatility and is able to perform an assembly operation, inspection, or the like on a complex electronic device may be provided.
The entire disclosure of Japanese Patent Application No. 2011-125103, filed Jun. 3, 2011 is expressly incorporated by reference herein.
Number | Date | Country | Kind |
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2011-125103 | Jun 2011 | JP | national |