Ultrasonic cutting element and ultrasonic treatment tool
Provided is an ultrasonic cutting element including a blade arm having a primary vibration plate and a blade portion fixed to one end of the primary vibration plate, a counter mass arm including one or more secondary vibration plates, a holding member to which vibration ends of the blade arm and the counter mass arm are respectively connected and which holds the blade arm and the counter mass arm in parallel, and a driving portion being a piezoelectric actuator that imparts ultrasonic vibrations to at least one of the primary vibration plate or the secondary vibration plate, in which the blade arm and the counter mass arm respectively bending-vibrate in a primary surface direction in a resonant mode in which the arms vibrate in mutually opposite phases as flexural vibrators.
1. An ultrasonic cutting element comprising:
a blade arm having a primary vibration plate and a blade portion fixed to one end of the primary vibration plate;
a counter mass arm including one or more secondary vibration plates;
a holding member to which a vibration end of the primary vibration plate and a vibration end of the secondary vibration plate are respectively connected and which holds the blade arm and the counter mass arm in parallel; and
a driving portion that imparts ultrasonic vibrations to at least one of the primary vibration plate or the secondary vibration plate,
wherein the driving portion is a piezoelectric actuator having a lower portion electrode, a piezoelectric film, and an upper portion electrode laminated in this order from a primary surface side on at least one of a primary surface of the primary vibration plate or a primary surface of the secondary vibration plate, and
the blade arm and the counter mass arm respectively bending-vibrate in a primary surface direction in a resonant mode in which the arms vibrate in mutually opposite phases as flexural vibrators,
wherein, in a case in which an axis extending toward a distal end of the blade portion from the vibration end of the primary vibration plate is considered as an x axis, a location of the vibration end is at x=0, a material density, a width, and a thickness of the blade arm are represented by ρ b , w b (x), and t b (x) respectively, and a material density, a width, and a thickness of the counter mass arm are represented by ρ cm , w cm (x), and t cm (x) respectively,
I
b
=
∫
0
Lb
ρ
b
·
w
b
(
x
)
·
t
b
(
x
)
·
u
(
x
)
·
dx
I
c
m
=
∫
0
Lcm
ρ
c
m
·
w
c
m
(
x
)
·
t
c
m
(
x
)
·
u
(
x
)
·
dx
u
(
x
)
=
x
L
b
I
ratio
=
I
b
I
c
m
(
I
b
≤
I
c
m
)
,
I
c
m
I
b
(
I
c
m
<
I
b
)
the blade arm and the counter mass arm satisfy I ratio ≥0.14.
2. The ultrasonic cutting element according to claim 1 , further comprising:
a flexible wire having one end connected to the holding member so as to guide the blade portion to a cutting subject.
3. The ultrasonic cutting element according to claim 1 ,
wherein the primary vibration plate, the secondary vibration plate, and the holding member are formed of a single plate.
4. The ultrasonic cutting element according to claim 1 ,
wherein the blade arm and the counter mass arm satisfy I ratio ≥0.2.
5. The ultrasonic cutting element according to claim 1 , further comprising:
a vibration detection portion that detects vibrations of the blade arm.
6. The ultrasonic cutting element according to claim 1 ,
wherein the counter mass arm includes a pressing portion that comes into contact with the subject, a pressure application portion that applies a pressure to the subject through the pressing portion, and a stress detection portion that detects a stress generated by the application of the pressure.
7. The ultrasonic cutting element according to claim 1 ,
wherein the piezoelectric film that is used in the driving portion is made of a perovskite-type oxide which is preferentially oriented in a tetragonal c axis and is represented by Pb(Zr y , Ti z , Nb 1-y-z )O 3 , 0<y<1, 0<z<1.
8. The ultrasonic cutting element according to claim 7 ,
wherein the primary vibration plate and the secondary vibration plate are made of a material having a greater thermal expansion coefficient than a thermal expansion coefficient of the piezoelectric film.
9. An ultrasonic treatment tool comprising:
the ultrasonic cutting element according to claim 1 ; and
a signal control portion that imparts a driving voltage signal in a resonant mode for generating bending vibrations to the blade arm and the counter mass arm between the upper portion electrode and the lower portion electrode of the driving portion.