JPH03289373A - Linear motor and method of forming linear motor - Google Patents

Abstract

PURPOSE:To improve efficiency of movement by increasing movement of an inertial body made against a friction force to it when a voltage is applied to expand and contract an electrostrictive element. CONSTITUTION:When a pulse voltage (a) is applied to an electrostrictive element 3, a movable body 1 is moved in a direction shown by arrow A, by a pulling force which is greater than a friction force and obtained from a great force produced at the start of an expansion operation, and is stopped by a pulling force produced at the end of the expansion operation. Since at the following gradual shrinkage of the electrostrictive element 3, movement of the movable body 1 is stopped by a friction force, an inertia body 2 moves as being pulled by the movable body 1. Moreover, when a pulse b of a drive voltage signal s2 is input to an electrostrictive element 23, the movable body 1 is moved in a direction shown by arrow B, by a reverse effect.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a linear motor, and particularly to a linear motor using an electrostrictive element.

(Prior Art) FIG. 8 shows a principle diagram of this type of linear motor that has been proposed in the past.

In the figure, it is assumed that a movable body 21 having a mass m□ is placed on a mounting surface 24, and a suitable frictional force is generated between them and the movable body 21 is in a stationary state. The inertial body 22 with a mass m2 is attached to the movable body 21 via the electrostrictive element 23, but the mounting surface 2
4, an appropriate gap is provided so that no frictional force is generated.

In this state, when a sawtooth voltage pulse a of the oscillation voltage signal s2 shown in FIG. 8(b) is applied to the electrostrictive element 23, the electrostrictive element responds with rapid expansion in the directions of arrows A and B. Repeated slow contractions. At the start of this extension, the movable body 21 and the inertial body 22 receive an equal and large force C or less (referred to as a repulsive force) in the direction of separating them from each other, so the movable body 21 overcomes the frictional force and moves in the A direction. Furthermore, at the end of the extension, the movable body 21 and the inertial body 22 receive an equal force (hereinafter referred to as gravitational force) in the direction in which they approach each other, so the movement of the movable body 21 is stopped by this gravitational force and frictional force. on the other hand,
Since no particularly large force is generated when the electrostrictive element 23 contracts other than during these transient times, the inertial body 22, which is not subject to frictional force, is attracted to the movable body 21. Therefore, the movable body 21 moves in the direction A while the drive voltage signal S1 consisting of the sawtooth pulse a shown in FIG. 8(b) is applied.

Conversely, when the sawtooth voltage pulse b of the drive voltage signal S2 shown in FIG. 8(b) is applied to the electrostrictive element 23, the movable body 21 moves in the direction B due to an action opposite to the above-described action. Become.

Next, we will show the results of simulations of movement under various conditions, which will be described later.

In FIGS. 3 to 7, Po and P are movable bodies 21. Each displacement state of the inertial body 22 is shown.

xl, X2 is the movable body 21. Each displacement amount of the inertial body 22 is shown. Further, the directions of arrows A and H in each figure correspond to the directions of arrows A and H in FIG. shows.

Conditions in the case of FIG. 3 are shown below.

Mass of movable body 21 m, =0.006 kg movable body 2
1 dynamic friction force fv□ = 0.2 N Newton) Movable body 2
1 static friction force fs1==1.2・fv1N Mass of inertial body 22 m2=0. ool kg Dynamic friction force f of the inertial body 22
v2=0 Static friction force fs of inertial body 22, =0 Spring constant σ of electrostrictive element 23 =5.68X107N/m
Viscosity coefficient p of electrostrictive element 23 = 120 N's/m Displacement coefficient v of electrostrictive element 23 = 0.15 μm/V...
(1) Furthermore, the maximum peak value Vm and period T of the drive voltage signal s2 are set to Vm=3.5V and period T=30 μS, respectively.

In this case, since the frictional force of the movable body 21 is small, the movable body 21 continues to move for a predetermined period of time even after the pulse of the drive voltage signal s2 ends. This phenomenon is l! It is not preferable to control the position of the movable body 21 using the dynamic voltage signal S2. Therefore, in order to immediately stop the movement of the movable body 21 when the pulse of the drive voltage signal s2 ends, the arm support shaft 252, for example, as shown by the dotted line in FIG. 8(a),
Working arm 25□, roller 251. A possible method is to increase the frictional force of the movable body 21 by providing a friction applying means 25 such as a suction spring 254. This friction applying means 25 is
It acts to press the movable body 21 against the mounting surface 24 and contributes only to an increase in frictional force.

FIG. 4 shows the state of movement when the dynamic frictional force fv of the movable body 21 under the above conditions (1) is set to 6N using these methods.

In this case, when pulse a of drive voltage signal s2 is input,
Due to the large repulsive force generated when the electrostrictive element 23 starts to expand, the movable body 21 receives a force in the direction of arrow A that is greater than the frictional force and moves in the same direction. However, the amount of movement at this time is related to the ratio of the masses of the movable body 21 and the inertial body 22, and the smaller the ratio of the movable body 21, the greater the amount of movement due to the repulsive force at this time.

Then, the movement of the movable body 21 is stopped due to the attractive force generated at the end of the extension, and when the electrostrictive element 23 subsequently contracts, the movement is blocked by the frictional force, so that the inertial body 22
Move as if being drawn to. Thereafter, these movements are repeated every time the pulse a is generated, but in the figure, damped vibration is generated in the inertial body 22 at the time the pulse ends.

Note that when a pulse of the dynamic voltage signal s2 is input to the electrostrictive element 23, the movable body 21 moves in the direction of arrow B due to the opposite effect.

FIG. 5 shows how the inertial body 22 moves when an appropriate dynamic friction force, for example fv2=IN, is applied to suppress this damped vibration. By applying an appropriate frictional force to the inertial body 22 in this manner, excessive movement can be suppressed.

(Problem to be solved by the invention) When we define the one with a larger frictional force as a movable body and the one with a smaller frictional force as an inertial body, - the mass of the movable body is set larger than that of the inertial body within the shell. However, an object of the present invention is to provide a near motor that is more stable and has better moving efficiency than these general methods.

(Means for solving the problem) l) An electrostrictive element that expands and contracts according to an applied voltage, and a mass that is integrally attached to both ends of the electrostrictive element in the direction in which the electrostrictive element expands and contracts. By acting on the first and second inertia bodies having different mass and the first inertia body having a small mass,
and friction force increasing means for increasing the friction force generated on the first inertial body.

2) A method for forming a linear motor is such that in the direction of expansion and contraction of an electrostrictive element that expands and contracts in response to an applied voltage, a first inertia acting on one end of the electrostrictive element is replaced by a second inertia acting on the other end of the electrostrictive element.
Among the frictional forces generated as the electrostrictive element expands and contracts, the relationship between the frictional force f acting on the one end side and the frictional force f2 acting on the other end side is: Make sure that f2>f2≧0.

(Function) When a voltage is applied to the electrostrictive element to cause it to expand and contract, the first inertial body overcomes the frictional force and increases the amount of movement.

(Example) First, to explain the present invention in detail, the mass m0 of the movable body 21 in FIG. 8(a) is smaller than the mass of the inertial body 22, and the frictional force of the movable body 21 is equal to Let's assume a case where it is set larger.

According to the simulation, the state of each movement in this case is as shown in FIG. 6 under the following conditions.

Mass of movable body 21 m, = o, ool kg movable body 21
Dynamic frictional force fv□=6N in Newton) Static frictional force of movable body 21 fs□=1.2・fv1N Mass of inertial body 22 m2
=0.006 kg Dynamic frictional force fν2 of the inertial body 22 = 0 Static frictional force fs2 of the inertial body 22 = 0 (2) It is assumed that each characteristic of the electrostrictive element 23 is the same as the condition in (1) above.

In this case, although the pulse waveform of the drive voltage signal s2 applied to the electrostrictive element 23 and its peak value Vm are the same as in the case of FIG. 4, it can be seen that the amount of movement of the movable body 21 increases significantly. In this case, when the voltage of pulse a is applied to the electrostrictive element 23, the movable body 21 receives a force in the direction of arrow A that is greater than the frictional force due to the large repulsive force generated at the start of its extension, and moves in the same direction. The movement of the movable body 21 is then stopped due to the attractive force generated at the end of the extension. Then, when the electrostrictive element 23 gradually contracts, the movement of the movable body 21 is prevented by the frictional force, so that the inertial body 22 moves as if attracted to the movable body 21. still.

The amount of movement of the movable body 21 due to the repulsive force is related to the ratio of the masses of the movable body 21 and the inertial body 22, but because the ratio of the movable body 21 is set small, it is larger than in the case of FIG. 4. Become. Thereafter, these movements are repeated every time the pulse a of the opening voltage signal s2 is generated, but in this case, damped vibration has occurred in the inertial body 22 at the time the pulse a ends.

FIG. 7 shows the situation when an appropriate dynamic frictional force fν2=IN is applied to the inertial body 22 in order to suppress this damped vibration. By applying an appropriate frictional force to the inertial body 22 in this manner, excessive movement can be suppressed.

Note that when the electrostrictive element 23 receives the pulse b of the opening voltage signal s2, the movable body 21 moves in the direction of arrow B due to the opposite effect.

FIG. 1 is a block diagram showing an embodiment of the present invention based on the above explanation of the principle, with FIG. 1(a) being a top view and FIG. 1(b) being a front view.

In the figure, 1 and 2 indicate a movable body and an inertial body, respectively, and these are integrally coupled via an electrostrictive element 3 whose expansion and contraction direction is in the direction of the center line 1. Further, the inertial body 2 is formed to surround the movable body 1 so that its center of gravity substantially coincides with the center of gravity of the movable body 1. Further, a compressed spring 6 is suspended between the movable body 1 and the inertial body 2 in order to apply an appropriate pressing force to the electrostrictive element 3 in order to suit the usage conditions of the electrostrictive element 3. Furthermore, when the movable body 1 (filled part) formed as described above is placed on the mounting surface 11, the lower surface of the movable body 1 is in contact with the mounting surface 11, and the inertial body 2 is in contact with the mounting surface 11. and the mounting surface are spaced apart from each other.

On the other hand, the rotating arm 7 that presses the upper surface of the movable body is rotatably held at one end by a support 8 raised from the mounting surface 11, and rotatably holds a roller 7 at the other end. .

Further, the rotating arm 7 is biased in the direction of arrow C by a spring 9 stretched between the rotating arm 7 and the mounting surface.

The friction increasing means configured as described above increases the frictional force generated between the lower surface of the movable body 1 and the mounting surface 11, and its strength can be appropriately set by the tension of the spring 9.

In the near motor configured as above, the conditions are as follows: Mass of movable body 1, m, = 0. OOl kg Dynamic friction force of movable body 1 fv1 = 6N Newton) Static friction force of movable body 1 f
sx = 1-2・f vx N Mass of inertial body 2 m2
= 0.006 kg Dynamic frictional force fv2 of inertial body 2 = 0 Static frictional force fs2 of inertial body 2 = 0 Spring constant a of electrostrictive element 3 = 5.68xlO' No
Viscosity coefficient p of va electrostrictive element 3 = 12Of? s/++
+The displacement coefficient of the electrostrictive element 3 is set to -0.15 μm/V, and the maximum wave height value Vm shown in FIG. 5v,
By applying a sawtooth drive voltage signal s2 with a period T of 30 μS, the movable body 1. And each displacement amount of the inertial body 2 is,
The states are respectively indicated by Pyu and P in the figure.

Further, in order to suppress the effect explained in FIG. 5, that is, the extra damped vibration of the inertial body 2 after the pulse of the drive voltage signal S2 ends, a rubber 12 or the like is attached to the lower surface of the inertial body 2, or It may also be configured such that an appropriate dynamic frictional force fv2 can be obtained by directly bringing its lower surface into contact with the mounting surface.

FIG. 2 shows an example in which the linear motor of the present invention is applied to an azimuth adjustment device for a magnetic head of a magnetic recording and reproducing device.
Components common to those in FIG. 1 are designated by the same reference numerals and their explanations will be omitted.

The upper surface of the movable body 1'' in the figure is formed to form a predetermined inclination angle θ with respect to the mounting surface 11, and the rotary arm 7' has a rotary arm 7' that rotates when the movable body P is at the reference position. The magnetic head 14 is placed so that the gap is parallel to a vertical line m passing through the rotation axis of the movable arm 7''. Further, when the magnetic recording/reproducing apparatus is in operation, it is assumed that the magnetic tape 15 moves in the direction of arrow B with the magnetic tape 15 in m contact with the tape-contacting surface of the magnetic head 14. In the above configuration, by applying a predetermined drive voltage signal s2 to the electrostrictive element 3, the moving body 10 is
, B, the rotating arm 7' rotates and the azimuth of the magnetic head 14 can be adjusted.

However, in this case, the mass of the rotating arm 7' and the magnetic head 14 formed integrally therewith is affected, and the mass m of the movable body 1'' and the frictional force are substantially reduced depending on the direction of movement thereof. Although it is necessary to take this change into account, this effect can be ignored if the inclination angle O is sufficiently small.

Although one configuration example and one application example of the present invention have been shown above, it is clear that the present invention is not limited to these embodiments and can take various forms.

(Effects of the Invention) According to the present invention, a near motor is provided in which the amount of movement per t pulse of the drive voltage applied to the electrostrictive element is larger than that of the conventional one, and the movement stops immediately at the end of the pulse. Therefore, it is suitable for use in servo control and the like that require stable operation.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a linear motor according to an embodiment of the present invention, FIG. 2 is a block diagram of a linear motor according to another embodiment of the present invention, and FIGS. 3 to 7 are diagrams for explaining the present invention. FIG. 8 is a diagram showing a conventional example. 1... Movable body, 2... Inertial body, 3... Electrostrictive element,
6... Spring, 7... Rotating arm, 8... Support column, 9...
. . . Spring, standing . . . Moving body, 13 . . . Pulse wave voltage generating means, 14 . . . Magnetic head, 15 . . . Magnetic tape.

Claims (1)

[Scope of Claims] 1) An electrostrictive element that expands and contracts according to an applied voltage, and a first element that has a different mass and is integrally attached to both ends of the electrostrictive element in the direction in which the electrostrictive element expands and contracts. By acting on the second inertial body and the first inertial body having a small mass,
a linear motor comprising a frictional force increasing means for increasing the frictional force generated in the first inertial body. 2) The first inertia acting on one end of the electrostrictive element is set to be smaller than the second inertia acting on the other end in the direction of expansion and contraction of the electrostrictive element that expands and contracts in accordance with the applied voltage, and Among the frictional forces generated as the electrostrictive element expands and contracts,
A method for forming a linear motor, wherein the relationship between the frictional force f_1 acting on the one end side and the frictional force f_2 acting on the other end side is f_1>f_2≧0.