JPH0290578A - Piezoelectric actuator - Google Patents

Abstract

PURPOSE:To prevent defects such as the occurrence of noises due to resonance, the uncertainty of a working quantity, and others by a method wherein a stroke piezoelectric element and a clamp piezoelectric element are driven by an alternate voltage whose frequency is other than integral multiple of the number of the natural vibration of a reciprocating working part of an actuator. CONSTITUTION:A clamp holding mechanism N makes spacers u and v slide pressing them outward by the function of springs j and q to clamp a plunger in a radial direction of the shaft with a wedge section when clamping members k and l are short in holding force due to the occurrence of gap caused by the wear of the inner circumferential pressing faces s of the clamping members k and l. And, the clamp holding mechanism N is constituted in such a manner that it decreases automatically in diameter by the abrasion loss of the clamping members k and l so as to keep a clamping force constant. That is, when a reciprocating working part increases in mass and a vibration system decreases in the number of natural vibration, there is much possibility that a piezoelectric element g resonates with the drive frequency of an actuator, but the resonance between a drive voltage and the vibration system is prevented from occurring, so that defects such as the occurrence of noises due to resonance, the uncertainty of a working quantity due to the irregularity of a stroke in quantity, and others can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Industrial Application Field The present invention relates to conventional technology used to operate various devices. Conventionally, as a form of piezoelectric actuator, a plunger that moves in an axial direction, Some devices are composed of a clamp that grips the plunger, a piezoelectric element that operates the clamp, and a stroke piezoelectric element that moves the plunger. is connected to
Therefore, due to slippage between the clamp and plunger,
If the clamp or plunger wears out (approximately 1 μm), the expansion/contraction stroke of the piezoelectric element for the clamp (several μm)
Because the clamping force was small, the clamping force was insufficient, causing performance deterioration.

Therefore, between the clamp piezoelectric element and the clamp member,
A piezoelectric actuator has been devised in which a wedge-shaped spacer biased by a spring is interposed to move the clamp member toward the plunger according to the amount of wear on the clamp member and maintain the initial pressing force.

(c) Problem to be solved by the invention However, in the part driven by the stroke piezoelectric element,
The addition of the wedge-shaped spacer increases the mass of the vibration system, and the presence of the spring lowers the natural frequency, which resonates with the frequency of the drive voltage, causing the stroke amount to be irregular and the amount of movement to be irregular. In addition, the plunger and the clamp member may be worn out, and the bond between the piezoelectric elements may be peeled off due to excessive acceleration.

Furthermore, noise was generated due to resonance.

(d) Means for Solving the Problems The present invention provides a piezoelectric device that includes a plunger that can move forward and backward in the axial direction within a casing, a piezoelectric element for stroke, and a piezoelectric clamping element that clamps the plunger via a clamp member. It is an object of the present invention to provide a piezoelectric actuator in which a stroke piezoelectric element and a clamping piezoelectric element are driven by an AC voltage having a frequency other than an integral multiple of the natural frequency of the reciprocating part of the actuator. 6 (e) Functions and Effects The configuration described above prevents resonance of the vibration system, thereby preventing noise generation and peeling of the piezoelectric element adhesive.

(f) Examples The present invention will be specifically described below based on examples shown in the attached drawings.

FIG. 1 shows the configuration of the piezoelectric actuator (8) according to this embodiment.

As shown in the figure, the actuator (^) is connected to the front and rear walls (a
)(b) A cylindrical actuator casing (
A plunger (d) is mounted concentrically within C) so as to be movable back and forth along the axis, and three piezoelectric elements (e) and (f) are mounted concentrically on the outer peripheral surface of the plunger (d).
It is constructed by arranging a piezoelectric element assembly (B) consisting of (g).

Furthermore, in the illustrated embodiment, the piezoelectric element (e) is supported on the left side of the holder (1), and the piezoelectric elements (f) and (g) are supported on the right side of the holder (H). Holder (11
) is fixed at its outer periphery to the end face of the front wall (a) with bolts (Ho).

The inner diameter part of the holder (H) is provided with a female screw part (h) in the axial direction, and the spaced screw part (h) has a clamp member (k) connected to the piezoelectric element for clamping (e). The base is screwed on. (i) is a male thread provided at the base of the clamp member (k), and (J) is a spring provided between the clamping piezoelectric element (e) and the holder (H).

In addition, a mounting bracket (m) is connected to the outside of the stroke piezoelectric element ((+) that is not fixed to the holder (11).
The inner diameter part of the mounting bracket (Ill) is provided with a female thread part (n) in the axial direction, and the spaced thread part (n) has a clamp member (,Q) connected to the piezoelectric element for clamping (f). The base is screwed on.

(p) is a male threaded portion provided at the base of the clamp member (1);
(q) is a spring provided between the clamping piezoelectric element (f) and the mounting bracket (1).

In addition, spacers (Ll) (V) having wedge portions (H) on the inner periphery of the piezoelectric elements for clamping (e) and (f) are provided.
A clamp member (
k) (j) is fitted into the inner circumference of the spacer (u)m.

As shown in FIG. 2, the clamp members (k) (, 11) connected to the clamping piezoelectric elements (e) and (f) have male screws (i) and (i) at the base, and the outer periphery of the other side. A part of the taper (") is formed on the inner periphery, while a pressing surface (") is formed on the inner periphery.
S) is provided. (1) is an appropriate number of slits provided on the pressing surface (S), and the tip is divided.

Further, as shown in FIG. 3, the spacer (uHv) interposed between the inner diameter parts of the clamping piezoelectric elements (e) and (f) has a base fitting hole (E) that is connected to the clamping member (k). (J)
While being fitted and supported by the intermediate shaft portion (F), the other end is divided by providing an appropriate number of slits (G).

Therefore, the clamp member (k) (jl) and the clamp.

A spacer (U) (V) with a tapered part formed in a wedge-shaped shape is interposed between the piezoelectric elements (e) and (f) for use,
Spacers (U) and (V) are biased by springs (j) and (q), and these force the clamping members (k) and
The same clamp member (k) (J) depending on the amount of wear of J)
moves toward the plunger (d) and constitutes a clamping force holding mechanism (N) that holds the initial pressing force.

The piezoelectric elements (e), (f), and (g) apply voltage to O.
It is configured to loosen in the radial direction when FF is applied.

That is, the piezoelectric element ((3) (f) reduces its inner diameter when energized, clamps the plunger (d) via the clamp member (kHz) and spacer (uHv), and when it is not energized. In this state, the inner diameter is expanded and the clamp of the plunger (d) is released.

On the other hand, when the piezoelectric element (g) is energized, the plunger (d)
The upper part of the plunger (d) is in a state of not extending in the axial direction, and in a non-energized state, the upper part of the plunger (d) is contracted, shortening its total length in the axial direction.

The plunger (d) then connects these three piezoelectric elements (
e) is a control device (the procedure for applying pressure to) (g) will be described later.
C), it can be moved in the axial direction.

The piezoelectric elements (e), (f), and (a) are cylindrical elements formed by laminating a large number of piezoelectric element pieces in the axial direction of the plunger (d), and electrodes are provided at both ends of the cylinder. By applying a voltage to both ends of this, the structure is configured such that it can be balanced.

Further, the plunger (d) is connected to the clamp member (k) (j
), it is desirable to use a material with a small linear expansion coefficient, high hardness, strength, creep resistance, and abrasion resistance, as well as high processing precision. Conceivable.

FIG. 4 shows the configuration of a control device (C) for controlling the piezoelectric actuator (A). As shown in FIG. 6, the control device (C) includes a microphone V7 processor (
It consists of an input/output interface (S), an input/output interface (S), and a memory (U) that stores the drive order program of the piezoelectric elements (e), (f), and (g).

Next, the movement of the plunger (d) by the actuator (^) having such a configuration will be explained with reference to FIGS. 5 to 7.

When a drive signal is input to the control device (C) from the actuator drive button (■°) shown in Fig. 4, the memory (j
According to the drive order program read from l), the fifth
As shown in the figure, a voltage is applied to the piezoelectric element (f) to contract it and clamp the plunger [d], and then the voltage is removed from the piezoelectric element (e) to expand the diameter of the plunger (
d) Release the clamp.

Next, as shown in FIG. 6, when the voltage application to the piezoelectric element (g) is released and the piezoelectric element (g) is contracted, the piezoelectric element (1) moves in the direction of the arrow, and along with this, the piezoelectric element (f) The plunger (d) clamped by also moves in the direction of the arrow.

Thereafter, as shown in FIG. 7, a voltage is applied to the piezoelectric element (e) to clamp the plunger (d), and then the voltage is removed from the piezoelectric element (e) to clamp the plunger (d).
d) Release the clamp. And the pressure element (q)
When a voltage is applied to the piezoelectric element (g), the piezoelectric element (g) moves in the direction of the arrow.

After that, by repeating the above operation, the plunger (
d) can be moved like an inchworm with a stroke on the μm order or sub-μm order, and various devices and machines can be operated precisely.

Also, the clamp holding a of the clamp member (kHJ)
[(N) is a clamp member (
k) (J!) When the inner pressing surface (S) of (J!) wears out and a gap is created, causing insufficient force to grip the plunger (d), the action of the springs (j) and (q) will cause the spacer [U] (
Slide it while pressing V) outward, and tighten it in the radial direction of the shaft using the wedge part. Then, the 7th clamp part (k) (N
) is configured to automatically reduce the wear amount and diameter to ensure a constant clamping force at all times, so reliable and accurate actuator operation can be expected.

In particular, because the clamp holding mechanism (N) is provided, the mass of the reciprocating part due to the stroke piezoelectric element (g) becomes large, and because the springs (j) and (q) are provided, the above-mentioned member However, in the present invention, the actuator is driven with a voltage at a frequency other than an integral multiple of the natural frequency of the vibration system. As a result, resonance between the drive voltage and the vibration system does not occur, and noise generation due to the above resonance, uncertainty in the amount of movement due to irregular stroke amount, wear of the plunger and clamp member, and excessive Problems such as peeling of piezoelectric element adhesion due to acceleration are prevented.

Next, a hot water mixing system incorporating the piezoelectric actuator of the present invention! (D) will be explained.

Figure 8 shows a hot water mixing device (0), in which a hot water supply pipe and a water supply pipe are connected to the inlets of the hot water side and water side flow rate regulating valves (ν1) (V2), respectively, and each valve (Vl) ( The outflow ports of V2) are arranged to face each other and communicate with each other, and the flow rate ratio and the sum of the flow rates of hot water and water supplied from the hot water supply pipe and the water supply pipe are
Adjust with the hot water side and water side flow rate adjustment valves (Vl) (V2),
The set temperature and flow rate are maintained.

The hot water side and water side flow rate regulating valves (Vl) (V2) have substantially the same configuration except that the fluids passing through them are different for hot water and hot water, and are configured as follows.

That is, an inflow pipe (2) (2) is formed on the negative side of the main body (1), an outflow pipe (3) is formed on the other side, and the outflow pipe (3) is formed at the intersection with the inflow pipe (2) (2). Extend into the inside of the open pipe (3
) are formed with main valve seats (4) (4) on the end faces of the same main valve seats (4).
) A diaphragm (5H5) is stretched over the upper end surface of the inflow pipe (2) (2) surrounding the outer periphery of (4), and the diaphragm (5H5) is
5) A pilot valve seat (6) (6) is provided in the center of (5), and an orifice (7) (7) is provided on the same periphery to connect the outflow pipe (3) and inflow pipe (2) (2), respectively. The upper part of the diaphragm (505) is connected to the actuator mounting base (8).
(8) to form pressure chambers (9) (9) between the base (8) (8) and the diaphragm (5H5).

The piezoelectric actuator (AI) (A2) described above is arranged on the top surface of the actuator mounting base (8) (8), and the plunger (A2) of the actuator (A1) (A2)
P) The main valve seat is activated by operating the diaphragm (5) (5) by the contact and separation of the valve body (11) (11) extending from (P) with the pilot valve seat (6) (6). (4)(
4) and the lower surface of the diaphragm (5) (5) are brought into contact with and separated from each other to open and close the hot water side and water side flow rate regulating valves (Vl) (V2).

Then, each actuator (AI) (A2) is operated based on the detected value of the temperature sensor (12) provided in the outflow pipe (3) to adjust the temperature of the mixed hot water discharged from the outflow pipe (3).
It is configured to control to a preset target temperature.

As mentioned above, the piezoelectric actuator (AI) (A2) attached to the hot water mixing device (0) has problems such as noise generation due to resonance, uncertainty in the amount of operation due to irregular stroke amount, and Since defects such as wear and peeling of the piezoelectric element adhesion due to excessive acceleration are prevented, the operation of the hot/water mixing device (0) is quiet and accurate, and durability is improved.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention, and FIG. 1 is a cross-sectional side view of a piezoelectric actuator according to the present invention, and FIGS.
The figure is a perspective view of the main parts of the present invention, FIG. 4 is an explanatory diagram of the configuration of the control device, FIGS. 5 to 7 are explanatory diagrams of the operating state of the actuator, and FIG. 8 is a cross-sectional side view of an automatic on-off valve equipped with an actuator. It is a diagram. A: Actuator B: Piezoelectric element assembly C: Control device base D: Automatic on-off valve a: Front wall b: Rear wall C: Actuator casing d Nib plunger e (f): Piezoelectric element for clamp g: Piezoelectric element for stroke k (,1!): Clamp member V (U) Ni spacer q (j) Ni spring

Claims (1)

[Claims] 1) A plunger that can move forward and backward in the axial direction within the casing;
In a piezoelectric actuator equipped with a stroke piezoelectric element and a clamping piezoelectric element that clamps a plunger via a clamp member, an AC voltage having a frequency other than an integral multiple of the natural frequency of the reciprocating part of the actuator, A piezoelectric actuator characterized by driving a stroke piezoelectric element and a clamp piezoelectric element.