JP3312747B2 - Feed screw device with fail-safe mechanism - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates, for example relates to a feed screw apparatus for use in processing systems such as machine tools, in particular off
The present invention relates to a feed screw device with a fail-safe mechanism .

[0002]

2. Description of the Related Art At present, in the field of factory automation (FA), it is the biggest problem to completely unmann a production processing system for 24 hours. With the development of machine tools and the introduction of robots, labor savings have been remarkably progressing.

[0003] However, it is necessary for a worker who works on the site to deal with phenomena which are conditions assumed in advance, such as erroneous operation of a machine, programming error, unexpected tool damage, runaway due to noise, change in the surrounding environment, and the like. No effective means of security mechanisms have been developed yet. Therefore, many people are needed to monitor and maintain the line.

What is needed here is that "when a force equal to or greater than a preset value is applied, the evacuation operation is performed, the machine is stopped, and the entire system is operated on a safe side. The signal to move to "is a fail-safe function.

[0005] Such a function is called a "fail-safe mechanism" and has been studied, but it is a mechanism that is strongly desired but cannot be put to practical use with actual machine tools and the like.

As conventional fail-safe mechanisms, a mechanism combining a spring and a stopper, a structure combining two hydraulic cylinders, and a structure using a precision leaf spring are known.

However, complicated forces such as torque and axial force act on the feed screw device, and there is no fail-safe mechanism capable of specifically coping with these forces.

[0008] In particular, the fail-safe mechanism used in such a feed screw device is required to have high rigidity which does not displace up to a set load, to be able to perform an evacuation operation when the set load is exceeded, and to signal a start of the evacuation operation. In addition to this, the load to be set can be variably controlled, and a compact and easy-to-install structure is required.

[0009] The present invention has been made to solve the problems of the prior art described above, it is an object of double
Fail-safe, ideal for lead screw devices subjected to various forces
The purpose is to provide a mechanism to increase safety .

In addition, high rigidity is provided when the evacuation operation is not performed.
And the load can be variably controlled .

[0011]

[0012]

[0013]

According to the present invention, there is provided a feed screw shaft, a nut screwed to the feed screw shaft, a feed member attached to the nut, and a feed screw. A rotation driving means for rotating a screw shaft, wherein at a joint portion between the nut and the member to be fed , one of torque or axial force equal to or more than a set value.
Or when both act , the nut and the member to be fed
Is released, and the nut is connected to the torque or the shaft.
A fail-safe mechanism is provided for retracting in a direction to prevent an increase in force .

Further, the present invention is characterized in that setting force variable means for changing the setting force of the fail-safe mechanism is provided.

On the other hand, a detection signal is transmitted upon detecting a retreat operation.
The evacuation detecting means for performing the evacuation.

The fail-safe mechanism is a mechanism that performs a retreat operation with respect to both torque and axial force.

Further, the fail-safe mechanism is a mechanism that performs a retracting operation only with respect to the axial force.

Further, the fail-safe mechanism is a mechanism that performs a retracting operation only with respect to torque.

A fail-safe mechanism that performs a retreat operation for both torque and axial force includes two ring members joined to each other via a boundary surface orthogonal to the axial direction;
A fixed holding force is applied between the boundary surfaces by sucking or pressing the two ring members, and the ring member is fixed and held in the rotational direction by a static friction force corresponding to the fixed holding force, and the ring is fixed by the fixed holding force itself. Fixed holding means for fixedly holding the member in the axial direction, and when the torque is equal to or greater than a set static frictional force corresponding to a fixed holding force set in advance, a retreat operation for preventing an increase in torque by sliding the boundary surface. When the axial force becomes equal to or more than a fixed holding force set in advance, the shaft is separated from each other and a retreat operation for preventing an increase in the axial force is performed.

In addition, the fail-safe mechanism which retracts with respect to both the torque and the axial force has two ring members joined to each other via a boundary surface orthogonal to the rotation direction, and sucks or sucks the two ring members. The fixed holding force is applied between the boundary surfaces by pressing each other, the ring member is fixedly held in the axial direction by the static friction force corresponding to the fixed holding force, and the ring member is fixedly held in the rotating direction by the fixed holding force itself. When the axial force is equal to or greater than a set static friction force corresponding to a preset fixed holding force, the boundary surface slides in the axial direction to perform a retreat operation, and the torque is set to a predetermined fixed holding force. As described above, the evacuation operation is characterized by being separated from each other.

The fail-safe mechanism which retracts only with respect to the axial force has a detent mechanism which prevents relative rotation of the two ring members of the fail-safe mechanism of the seventh or eighth aspect and allows relative movement in the axial direction. It is characterized by that.

The detent mechanism is constituted by, for example, a ball spline mechanism.

The fail-safe mechanism which retracts only with respect to the torque is provided with an axial movement restricting means for permitting relative rotation of the two ring members of the fail-safe mechanism and preventing relative movement in the axial direction. It is characterized by having.

As the axial movement restricting means, for example, a rotary bearing such as an angular contact bearing is used.

Further, a concave portion into which the positioning ball fits is provided on the boundary surface of the ring member, and when a torque or an axial force exceeding a set value is applied, the positioning ball separates from the concave portion and rolls between the boundary surfaces to form a pair. Are characterized by relative rotation or relative movement in the axial direction.

As the fixed holding means, a magnet for magnetically attracting and holding between the boundary surfaces of the ring members is used.

When the magnet is an electromagnet, the set value changing means is constituted by a controller for controlling a current value applied to the electromagnet.

When the magnet is a permanent magnet, the set value changing means is configured to change the magnitude of the magnetic attraction force by changing the magnetic path passing between the two ring members.

The fixed holding means is constituted by a pressing means for pressing one of the two ring members while the other ring member is relatively fixed.

The pressing means may be, for example, one using an elastic force of an elastic member, one using an electromagnetic actuator using an electromagnetic force, one using an actuator using a fluid pressure cylinder such as pneumatic or hydraulic, a piezoelectric element or the like. Various actuators can be used, such as one using an actuator using an electrostrictive element, one using a thermal actuator using thermal expansion, and one using an actuator using a magnetostrictive element.

The fail-safe mechanism may be provided at a force acting portion between the nut and the member to be fed, or may be provided at a coupling portion connecting the rotary drive source and the feed screw shaft.

Further, the fail-safe system of the feed screw device includes a feed screw shaft, a nut screwed to the feed screw shaft, a member to be fed mounted on the nut, a rotation driving means for rotating the feed screw shaft. A drive control means for controlling the drive of the rotary drive means, and a fail-safe means for retracting in a direction for preventing an increase in the force when a force greater than a set value is applied to a force acting portion such as a torque or an axial force of a feed screw device. Mechanism and
An evacuation detection means for detecting the evacuation operation of the fail-safe mechanism, and the drive control means are controlled based on information detected by the evacuation detection means.

The control of the drive control means may be such that the rotary drive means is stopped urgently, or after further proceeding to stop the rotary drive means urgently, control is carried out so that the fail-safe mechanism automatically returns. It is effective.

[0034]

In the feed screw device with the fail-safe mechanism having the above-described structure, when the force acting on the force acting portion, such as the torque or the axial force, becomes greater than a preset force, the retracting mechanism moves in the force acting direction. To prevent an increase in force.

Further, by providing the set force varying means, it is possible to select an optimum set force according to the conditions of the member to be fed such as the type of the tool and the processing conditions.

Further, if the evacuation detecting means is provided, the fact that an overload has acted can be taken out as information.

If the retracting operation is performed in response to both the torque and the axial force, it is possible to cope with various complicated forces.

However, the fail-safe of the torque or the axial force may be selectively made to correspond only to the necessary force depending on the processing conditions and the like.

In particular, as a fail-safe mechanism, two ring members joined via a boundary surface orthogonal to the axial direction and a boundary surface orthogonal to the rotation direction, and are fixed and held to each other by a suction force or a pressing force. Is used, it is possible to make the apparatus compact, and it is possible to easily change the set force to be retracted only by changing the suction force and the pressing force between the ring members.

Further, if the spring member or the like is not used as the means for fixing and holding the two ring members by utilizing the attractive force of the magnet, high rigidity can be obtained.

[0041]

[0042]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the illustrated embodiments.

FIG. 1 shows a fail according to a first embodiment of the present invention.
4 shows a feed screw device with a safety mechanism .

The feed screw device 1 comprises a feed screw shaft 2 and
A nut 4 is attached to the feed screw shaft 2 via a number of balls 3, and a movable table 5 is attached to the nut 4 as a member to be fed. Feed screw shaft 2
Both ends of the feed screw shaft 2 are rotatably and axially fixed to the first and second bearing bases 6 and 7 via support bearings 8 and 8.
An end on the bearing base 6 side is operatively connected to a motor 10 as a rotation drive source via a coupling 9.

When the feed screw device 1 is driven, a force such as an axial force and a torque acts on the feed screw device 1. A fail-safe mechanism 20 is provided at the force acting portion. The torque is transmitted from the feed screw shaft 2 to the nut 4 and transmitted from the nut 4 to left and right guide members (not shown) supporting the movable table 5. The axial force is applied to the movable table 5 from the nut 4
Is transmitted to the bearing bases 6 and 7 through the feed screw shaft 2 through the shaft.

In the example of FIG. 1A, the fail-safe mechanism 2
0 is mounted between the nut 4 and the holder 11 of the movable table 5.

In the example shown in FIG. 1B, a fail-safe mechanism 20 is provided at the coupling portion.

The fail-safe mechanism 20 performs a retreat operation in a direction to prevent an increase in the force of the force acting portion when a force equal to or greater than a set value acts. The evacuation detecting means 12 for detecting the evacuation operation is provided, and the controller 13 urgently stops the motor 10 via the motor driver 14 based on the detection signal of the evacuation detecting means 12.

The fail-safe mechanism 20 includes a mechanism for performing a retreat operation corresponding to both the torque and the axial force, a mechanism for performing a retreat operation only for the axial force, and a mechanism for performing a retreat operation only for the torque. There are three embodiments.

FIGS. 2 and 3 show the fail-safe mechanism 2
The two basic forms 0 are described below, and these two basic forms will be described separately for each of the above three types of evacuation operations.

FIG. 2A shows the first basic form.
The fail-safe mechanism 20 has two ring members 21 and 22 joined to each other via boundary surfaces 21A and 22A orthogonal to the axial direction. And
The two ring members 21 and 22 are sucked or pressed by the fixed holding means 23 so that the boundary surface 21 is formed.
A fixed holding force is applied between A and 22A.

That is, the relative displacement of the ring members 21 and 22 in the rotation direction is regulated by the static friction force between the boundary surfaces 21A and 22A, and the relative displacement in the axial direction in the direction in which the boundary surfaces 21A and 22A are separated is fixedly held. Regulated by force itself,
It is fixed and held in the rotational direction and the axial direction between the ring members 21 and 22.

FIG. 2B shows the motion state of the two ring members 21 and 22 when the torque and the axial force are equal to or less than preset values. In this state, the ring members 21 and
2 are integrally rotated without being relatively displaced in the axial and rotational directions in the joined state.

FIG. 2C shows the retreat operation when the torque becomes equal to or more than the static friction torque between the set boundary surfaces. In this state, both ring members 21 and 22 slide between boundary surfaces 21A and 22A, and only ring member 21 on the input side idles while ring member 22 on the output side is stationary , that is, an increase in torque is prevented. Retreat operation in the direction .

FIG. 2D shows a state in which the axial force is larger than a preset fixed holding force. In this state, the boundary surfaces 21A and 22A of the ring members 21 and 22 are separated.

FIG. 2E shows a configuration in which the retract operation is performed only for the torque. This example is different from the basic configuration shown in FIG. 2A in that the ring members 21 and 22 are provided with axial displacement restricting means 24 such as a rotary bearing that prevents relative displacement in the axial direction and allows relative movement in the rotational direction. Is added. In this way, the movement in the axial direction is restricted, and the retreat operation can be performed only for the torque.

On the other hand, FIG. 2 (f) shows a configuration in which the retreat operation is performed only for the axial force. In this example, a detent means 25 is added to the basic configuration shown in FIG. 2 (a) to permit relative displacement of the ring members 21 and 22 in the axial direction and prevent relative movement in the rotational direction. It is. In this way, the relative displacement in the rotation direction is restricted, and the retreat operation can be performed only for the axial force.

FIG. 3A shows a second basic form. This fail-safe mechanism 20 includes two ring members 21 joined to each other via boundary surfaces 21B and 22B orthogonal to the rotation direction. , 22. For example, as shown in FIG.
2 are provided on each of the opposing surfaces, and the projections 21C and 22C are engaged with each other to form
The two ring members 21 and 22 are joined. Similar to the first basic configuration example, the two ring members 21 and 22 are provided with a fixed holding force between the boundary surfaces 21B and 22B by being attracted or pressed by the fixed holding means 23. That is, the ring members 21 and 22 are fixedly held in the axial direction by the static friction force corresponding to the fixed holding force of the boundary surfaces 21B and 22B, and the ring members 21 and 22 are fixed by the fixed holding force itself.
2 is fixedly held in the rotation direction.

FIG. 3C shows the motion state of the two ring members 21 and 22 when the torque and the axial force are equal to or less than preset values.

In this state, the ring members 21 and 22 rotate integrally without fixed relative displacement in the axial and rotational directions in a state of being integrally joined by a fixed holding force.

FIG. 3D shows a state in which the torque is equal to or higher than a fixed holding force set in advance. In this state,
The boundary surfaces 21B and 22B of the ring members 21 and 22 are separated from each other, and only the input side ring member 21 idles while the output side ring member 22 is stationary.

FIG. 3E shows a state in which the axial force has become equal to or greater than the static friction force corresponding to the fixed holding force set in advance. In this state, the boundary surface 21 of the ring members 21 and 22
The input side ring member 21 and the output side ring member 22 are separated from each other.

FIG. 3 (f) shows a configuration in which the retract operation is performed only for the torque. This example is different from the basic configuration shown in FIG. 3 (a) in that the ring members 21 and 22 are axially restricted by a rotational bearing or the like which prevents relative displacement in the axial direction and allows movement of the device in the rotational direction. 24 is added. In this way, the movement in the axial direction is restricted, and the retreat operation can be performed only for the torque.

On the other hand, FIG. 3 (g) shows a configuration in which the retreat operation is performed only for the axial force. In this example, a detent means 25 is added to the basic structure shown in FIG. 3 (a) to allow relative displacement of the ring members 21 and 22 in the axial direction and prevent relative movement in the rotational direction. It is. In this way, the relative displacement in the rotation direction is restricted, and the retreat operation can be performed only for the axial force. The example shown in FIG. 3 (a) can cope only with one-way torque acting in the direction of separating the boundary surfaces 21B and 22B, but a fail-safe mechanism corresponding to the torque in the opposite direction is arranged in series. This makes it possible to cope with the torque in both directions.

FIG. 4 (a) shows an example of a configuration in the case where torques in both directions are supported. In this case, the ring member located in the middle of the fail-safe mechanism arranged in series is constituted by one ring member 26, and the intermediate ring member 26
Are provided on both sides thereof, and have boundary surfaces 26B1 and 26B2 which are orthogonal to the rotational direction to be joined to the other ring members 21 and 22, respectively. The boundary surfaces 26B1 and 26B2 need to be set to the same phase.

FIG. 4B shows a state where a load equal to or greater than the set torque is applied when the torque rotates clockwise as viewed from the input member side.

In this state, the boundary surface 21B of the input side ring member 21 and the boundary surface 26B1 of the intermediate ring member 26 are separated from each other, the intermediate ring member 26 stands still, and the input side ring member 21 idles.

FIG. 4C shows a state where a load equal to or greater than the set torque is applied when the torque rotates counterclockwise as viewed from the input member side.

In this state, the boundary surface 22B of the output side ring member 22 is separated from the boundary surface 26B2 of the intermediate ring member 26, the output side ring member 22 is stationary, and the input side ring member 21 and the intermediate ring member 26 are separated. Is spinning integrally.

FIGS. 4D to 4F show modifications of the first and second basic forms of the above-described fail-safe mechanism.

In this modification, instead of fixing and holding the ring members 21 and 22 by the frictional force between the respective boundary surfaces, the boundary surfaces 21A and 22A of the ring members 21 and 22;
B, a fixing ball 27 is interposed between each of the boundary surfaces 21A,
22A; a hole 28 into which the 21B, 22B fits is provided, and the boundary surface 21A, 22A; 21B, 22B is fixedly held in a non-contact state with a resistance force that the fixing ball 27 gets over the edge of the hole 28. It is.

In other words, the fixing ball 27 is rotated by the ring member 2 until a predetermined load is applied in the rotation direction or the axial direction.
1 and 22 are held so as not to be relatively displaced,
Any structure may be used as long as the structure has a resistance to fix and hold the ring members 21 and 22 so that the ring members 21 and 22 are not relatively displaced in the rotational direction and the axial direction until a predetermined load is applied without using a ball.

[0073] Further, as shown in FIG. 4 (g), first, by combining the second basic form, the boundary surface 21 perpendicular to the axial direction
A, 22A and boundary surfaces 21B, 22 orthogonal to the rotation direction
B may be joined at two boundary surfaces 21A, 22A; 21B, 22B.

In the first and second basic forms, the boundary surface is perpendicular to the axial direction and the rotational direction is perpendicular. The other configuration is a tapered surface inclined at a predetermined angle with respect to the axial direction. You may make it shape.

FIG. 5 shows the fixed holding means 23 for fixedly holding the boundary between the ring members 21 and 22 and the set force varying means 29.
Examples of various configurations, are shown as an example the case of application to the first basic type shown in FIG.

FIG. 5A shows an example in which an electromagnet is used as the fixing and holding means 23 in the fail-safe mechanism of the first basic type. That is, the coil 30 is mounted with one ring member 21 as a core and the other ring member is used. The other ring member 22 as an armature is provided on the boundary surface 21A of the ring member 21 functioning as a core by allowing the member 22 to function as an armature and exciting the coil 30 by flowing a current.
Are magnetically attracted, and the ring members 21 and 22 are fixed by the magnetic attraction.

The structure of the ring member 21 to which the coil 30 is mounted is such that the center inner peripheral core portion 21 to which the coil 30 is mounted is
1 and an outer peripheral yoke portion 212 surrounding the outside of the coil 30
And an end face yoke 213 connecting the inner core 211 and the outer yoke 212. And
The inner peripheral core portion 211-the second ring member 22 as an armature-the outer peripheral core portion 212-the end face yoke portion 213-the inner peripheral core portion 211 constitute a closed magnetic path 31, and the inner peripheral core portion of the one ring member 21. The second ring member 22 is magnetically attracted by using the end surfaces of the 211 and the outer core 212 as a boundary surface 21A.

As described above, when an electromagnet is used as the fixed holding means 23, the fixed holding force, that is, the set load can be changed electrically by changing the current to the coil 30. Therefore, in this case, the fixed holding force varying means is constituted by the controller 32 for controlling the amount of current supplied to the coil 30.

FIG. 5B shows a structure in which a permanent magnet ring 33 is used as the fixed holding means 23 and the suction force is variable in combination with a transmission ring 34 as a setting force changing means. The case where it is applied to a mechanism is illustrated.

The permanent magnet ring 33 is mounted in an annular hole opened at the boundary surface 21A of the first ring member 21. As shown in FIG.
A plurality of magnet bodies 35 each having a magnetic pole as a pole are arranged at equal intervals in the circumferential direction, and the magnet bodies 35 of adjacent units are arranged so as to have the same polarity.

The transmission ring 34 is mounted between the permanent magnet ring 33 and the boundary surface 22A of the second ring member 22. The transmission ring 34 has magnetic units 36 made of iron or the like having the same length as the unit magnet 35 and arranged at the same pitch in the circumferential direction. The boundary between the adjacent magnetic units 36 is made of aluminum or the like. Are separated by a non-magnetic part 37. The transmission ring 34 and the permanent magnet ring 33 are relatively displaceable in the circumferential direction, and the position of the non-magnetic member 37 is set between the N pole and the S pole of the unit magnet 35 or the unit magnet 3
5, the magnetic flux amount can be controlled so that the magnetic flux from the N pole to the S pole of the unit magnet 35 passes through the second ring member 22 through the magnetic body portion 36 of the transmission ring 34. . Between the permanent magnet ring 33 and the transmission ring 34, a thin sliding member 38 of a non-magnetic material such as Teflon is provided.

As shown in FIG. 5C, when the non-magnetic member 37 is located at the boundary between the unit magnets 35 as shown in FIG. 5 (c), the unit magnet 35 and the magnetic member 36 of the transmission ring 34 become one. However, the magnetic flux does not reach the second ring member 22 and hardly any magnetic attraction is obtained.

On the other hand, as shown in FIG. 5D, when the non-magnetic member 37 is located at the center position of the unit magnet 35, the magnetic flux connecting the N pole and the S pole almost passes through the second ring member 22. ,
As shown in the graph of FIG. 5 (f), the maximum magnetic attraction f1 is obtained.

Further, as shown in FIG. 5E, when the non-magnetic member 37 is shifted from the center of the unit magnet 35, a part of the magnetic flux does not pass to the second ring member 22 and the N pole and the S The convergence between the poles causes the suction force f2 to be intermediate as shown in the graph of FIG.

The permanent magnet ring 33 and the transmission ring 34
The work of shifting the phase with may be performed manually,
It may be performed by a motor. Also, this permanent magnet ring 33
A combination of and a solenoid is also possible. In this case, it is possible to change the value of the set force by the amount of energization of the solenoid, or to facilitate the setting value setting operation.

FIGS. 6 (a) to 6 (c) show a type using an electromagnet as a fixing and holding means, and a second basic form of a fail-safe mechanism, particularly a fail-safe mechanism capable of coping with a torque in both directions as shown in FIG. The case where it applies is shown.

The coil 30 is mounted on the intermediate ring member 26, and the first and second ring members 21 and 22 on both sides are magnetically attracted by using the intermediate ring member 26 as an electromagnet. That is, the intermediate ring member 26 has an inner ring 261 and an outer ring 262 which are assembled concentrically at a predetermined interval, and a magnetic material is formed between the inner and outer rings 261 and 262 at the protrusions 26C1 and 26C2 which protrude left and right. The coil 30 is mounted between the inner and outer rings 261 and 262. In the magnetic field lines H, the inner ring 261 and the outer ring 262 form a closed circuit via the convex portions 21C and 22C of the left and right first and second ring members 21 and 22.
Magnetic attraction occurs between the boundary surfaces 21B, 26B1; 22B, 26B2 of the second ring members 21, 22 and the intermediate ring member 26. However, FIG. 3 without the intermediate ring member 26
Similarly, in the case of the basic type as shown in (a), the coil 30 may be mounted on the first or second ring member 21, 22.

[0088] The first to the left and right side surfaces of the intermediate ring member 26, the convex portion 21B of the second ring member 21, 22
A sliding member 264 with which B contacts slidably is provided. In the second basic form, the fixed holding
Instead of the above-described electromagnet as means, FIGS.
Similarly, the protrusions 26C1, 26C of the intermediate ring member 26
2 and the projections 21C of the first and second ring members 21 and 22;
Fixing ball 27 can be interposed between 22C
You. Further, similarly to FIG. 4 (g), the protrusions 26C1, 26C
The end faces of 2, 21C and 22C are brought into contact with the other
Friction can also be obtained.

FIG. 6 (d) shows an example of a configuration using a pressing means 40 for pressing the first and second ring members 21 and 22 together as a fixing means.

In the illustrated example, the rear surface of the second ring member 22 is pressed toward the first ring member 21. Second
In order to press the ring member 22 against the first ring member 21, the pressing means 40 is provided with an engagement seat 41 engaging with the first ring member 21.
The second ring member 22 is pressed against the first ring member 21 with the ring member 21 fixed.

As the pressing means 40, the elastic force of an elastic member 42 as shown in FIG. 6 (e) may be used.
As shown in FIG. 2, an actuator using a hydraulic cylinder 43 such as a hydraulic or pneumatic pressure may be used.Other actuators using an electromagnetic actuator using an electromagnetic force, actuators using a piezoelectric element or an electrostrictive element may be used. Those that use actuators, those that use actuators that use thermal expansion,
Such as those using actuators using magnetostrictive elements,
Various actuators can be used.

The configuration of the setting force varying means is as follows.
An appropriate means is selected according to each pressing means. For example, in the case of an elastic member, the fixed holding force can be changed by changing the amount of compression. In the case of a hydraulic cylinder, the fluid pressure may be controlled by a control valve. In this case, the current may be controlled. In the case of a piezoelectric element or an electrostrictive element, the applied voltage may be controlled.

As described above, the configuration of the fail-safe mechanism is the same as that of the first and second basic forms shown in FIGS. Various combinations are possible. Hereinafter, some specific examples will be described.

[First Specific Example] FIG. 7 shows a first specific example of a feed screw device with a fail-safe mechanism.

The first specific example is the same as the first embodiment.
Is mounted between the nut 4 as a force acting portion and the holder 11 of the movable table 5.

The fail-safe mechanism 20 has a first basic form shown in FIG.
1 and a second ring member 22 fixed to the holder of the movable table 5, and an electromagnet shown in FIG. 5A is used as a fixing force holding means.

The first ring member 21 is composed of an inner core 211 on which the coil 30 is mounted, and an outer yoke 212 mounted on the outer periphery of the coil 30. The part 212 is a bolt 214 on the end face side.
, And is integrally fixed to the nut 4 by a bolt 215 on a flange 4A provided at one end of the nut 4.

Then, the first and second ring members 21 and 22
The second ring member 22 is provided with evacuation detection means 12 such as a proximity switch for detecting whether or not the relative displacement has occurred.

FIG. 8 shows a system configuration when the fail-safe mechanism 20 is used.

That is, this control system is composed of the controller 1
The drive of the motor 10 is controlled via the motor driver 14 based on the drive signal from the controller 3.

Then, the detection signal detected by the evacuation detection means 12 is input to the controller 13, and based on the detection signal, an emergency stop signal for urgently stopping the driving of the motor 10 is output. You.

The coil 3 of the fail-safe mechanism 20
Fail-safe controller 1 that controls the amount of power to zero
The fixed holding force can be controlled by controlling the amount of current. The set force to be retracted varies depending on the type of tool, machining conditions, and the like, and is input from the controller 13 as needed. If various data such as the type of the tool is stored in the controller 13 in advance, the optimum fixed holding force can be automatically set only by inputting the type of the tool and the like.

FIG. 9 shows an operation state of the fail-safe mechanism of the feed screw device.

That is, when a load is applied, the feed screw shaft 2
, The torsional torque is transmitted to the nut 4 and the nut 4 and the holder 1 of the movable table 5 are rotated.
The torque is also transmitted to the fail-safe mechanism 20 mounted between the two. However, when the torque acting on the fail-safe mechanism 20 is smaller than the set static friction torque, as shown in FIG.
1 and 22 are integrally fixed and held in the axial direction and the rotational direction by the attraction force of the electromagnet.

In this embodiment, the rigidity is high and advantageous because the adhesive is fixed by the force of the electromagnet.

When the rotational torque of the feed screw shaft 2 increases and exceeds the static friction torque between the first and second ring members 21 and 22, as shown in FIG. The idling starts with the rotation of the shaft 2, and the movable table 5 does not move.

Then, the retreat detecting means 12 such as a proximity sensor detects the idle rotation of the nut 4 and outputs a signal. The signal is sent to the controller 13 to stop the motor 10 in an emergency, and to stop various operations related to the feeder in an emergency.
At the same time, the operation shifts to a return operation.

Since the screw feed mechanism of the feed screw shaft 2 and the nut 4 converts the rotational torque into an axial force, the torsional rotational torque of the nut 4 is much smaller than the rotational torque of the motor 10. The force that balances the torsional rotational torque of the nut 4 with the fixed holding force of the nut 4 and the holder 11 can be a small force. Therefore, the fail-safe mechanism 20
It is very effective to use the force in the rotational direction of the nut 4 and the fixed portion of the holder 11.

When the axial force in the direction in which the boundary surfaces 21A and 22A of the first and second ring members 21 and 22 are separated from each other becomes greater than the fixed holding force of the electromagnet, the first and second ring members 21 and 22 become the first and second ring members as shown in FIG. Boundary surfaces 21A, 22A of two ring members 21, 22
The gap is separated, the nut 4 idles, and the movable table 5 stops.

The evacuation detection means 12 such as a proximity sensor
As a result, a retreat operation is detected, and the controller 10 stops the motor 10 urgently and stops various operations as in the case where excessive torque is applied.

FIG. 10 shows a modification of the first embodiment of the fail-safe mechanism shown in FIG. 7. In this embodiment, a permanent magnet 22D is provided on the boundary surface 22A of the second ring member 22 in addition to the structure shown in FIG. And a configuration in which the permanent magnet 22D and the electromagnet are combined. Other configurations are exactly the same as those of the first specific example.

[Second Specific Example] FIG. 11 shows a second specific example of the fail-safe mechanism 20 corresponding only to the torque shown in FIG. 2 (e), and this second specific example is also shown in FIG. As shown in (1), an electromagnet is used as the fixing and holding means. In this example, similarly to the example shown in FIG. 7, the fail-safe mechanism 20 is mounted between the nut 4 and the holder 11, and the first ring member 21 on which the coil 30 is mounted is connected to the holder 11 of the movable table 5. It is provided in. On the other hand, a spring member 53 as a pressing means is mounted between the second ring member 22 joined to the first ring member 21 and the flange portion 4A provided on the outer periphery of the nut 4. The spring member 53 and the second ring member 22 are integrated. Interface 21 between first ring member 21 and second ring member 22
The fixed holding force between A and 22A is determined by the magnetic attraction force, and the spring member 53 is mounted in a compressed state, an expanded state or a free state. The first ring member 21 and the second ring member 22 are assembled via an angular contact bearing 50 as an axial displacement restricting means so as to prevent relative displacement in the axial direction and allow relative movement in the rotational direction. Have been.

FIG. 12 schematically shows the fail-safe mechanism of FIG. 11, and FIG.
The case where the torque acting on 0 is lower than the set value is shown. In this case, the first and second ring members 21 and 22 are in an integrally connected state, and the rotation of the feed screw shaft 2 is converted into the linear motion of the nut, and the movable table 5 moves.

FIG. 12B shows a case where the torque acting on the fail-safe mechanism 20 has exceeded a set value. In this case, the second ring member idles with the nut 4 and the movable table 5 stops. Will do.

FIG. 13 shows a modification of the second embodiment.

This modification is different from the first ring member 21 and the second ring member 21 in the first embodiment.
A screw mechanism for boosting is provided for separating the boundary surfaces 21A, 22A of the ring member 22 from each other, and the axial movement between the first ring member 21 and the nut 4 is restricted via the bearing 50 so as to be relatively rotatable. It is assembled.

That is, the second ring member 22 constitutes the boundary surface 22A facing the first ring member 21 and the boundary surface forming portion 22C on which the coil 30 is mounted, the inner periphery of the first ring member 21 and the nut. And an intermediate nut portion 22D mounted between the four outer peripheries.

The intermediate nut portion 2 of the second ring member 22
A screw groove 22D1 having a smaller lead than the screw provided on the screw shaft 2 is formed on the inner circumference of the 2D and the outer circumference of the nut 4, and a ball 22D2 is interposed between the screw grooves. The outer periphery of the intermediate nut portion 22D and the first ring member 21
A spline groove 22E1 is formed on the inner periphery, and a ball 22E2 is interposed between the spline grooves 22E1.
The axial movement of the intermediate nut portion 22D of the second ring member 22 is allowed to restrict the rotation.

When an excessive torque acts, the second torque
The interface between the interface 22C of the ring member 22 and the interface 21A, 22A of the first ring member 21 slips and idles, and the intermediate nut 22C rotates relative to the nut 4,
The intermediate nut portion 22C is sent out in a direction protruding from the nut 4, and the first ring 21 and the second ring member 22 are forcibly separated from each other. And the table stops.

In this embodiment, it is not necessary to provide a ball spline mechanism to prevent rotation, but a ball bush may be used. In other words, the intermediate nut portion 22D may be allowed to move in the axial direction. I just need.

[Third Specific Example] Next, a third specific example of the fail-safe mechanism corresponding to only the axial force shown in FIG. 14 and FIG. 2 (f) is shown. The electromagnet shown in a) was used.

Also in this example, the fail-safe mechanism 20 is mounted between the nut 4 and the holder 11, and the first ring member 21 on which the coil 30 is mounted is provided on the movable table 5 on the holder 11 side. The second ring member 22 to be joined to the first ring member 21 is constituted by a flange portion of the nut 4.

The first ring member 21 and the second ring member 22 are allowed to move relative to each other in the axial direction between the first ring member 21 and the second ring member 22 by the ball spline mechanism 51 serving as a detent means. In addition, the relative movement in the rotation direction is restricted. The ball spline mechanism 51 includes an outer peripheral surface of the nut 4 and the first ring member 21.
A large number of spline balls 53 are interposed between spline grooves 52 formed in the inner peripheral surface so as to face each other in the axial direction.

By applying the ball spline mechanism 51 in this manner, as shown in FIG. 15A, relative movement in the axial direction can be smoothly performed while maintaining high rigidity in the rotation direction.

Further, in this example, the nut 4 and the holder 1
1 between the first ring member 21 and the second ring member 22
A spring member 54 for urging the boundary surfaces 21A and 22A apart from each other is mounted, and the electromagnetic attraction force of the first ring member 21 is applied to oppose the spring force of the spring member 54.

In this way, as shown in FIG. 15 (b), when the axial force acting on the fail-safe mechanism 20 exceeds the set value, the boundary surfaces 21A and 22 are mechanically moved by the spring force.
A can be immediately separated.

[Fourth Specific Example] FIG. 16 shows a fourth specific example of the feed screw device with a fail-safe mechanism corresponding to only the axial force shown in FIG. 2 (f).

The fourth embodiment has basically the same construction as the third embodiment, and includes a permanent magnet ring 33 and a transmission ring 34 shown in FIG. 5B as fixing force holding means and setting force varying means. The only difference is the use of a combination configuration of.

The permanent magnet ring 33 and the transmission ring 34
Is exactly the same as the configuration shown in FIG. 5, and a description thereof will be omitted.

[Fifth Embodiment] FIG. 17 shows a fifth embodiment of the feed screw device with a fail-safe mechanism according to the present invention. The fifth specific example has a boundary surface orthogonal to the rotation direction as in FIG. 3 and a second example in which the first, second and intermediate ring members 21, 22, and 26 are combined as in FIG. This is a basic configuration, and each boundary surface 21B, 26B1; 22
B, and utilizes the electrodeposition magnet and the fixed holding means 26B2.

This embodiment corresponds to the retraction of only the torque, and has basically the same configuration as that of the second embodiment, except that the first and second ring members 21 and 22 are angular contact members as axial direction restricting means. It is rotatably connected via a bearing 50.

[Sixth Specific Example] FIG. 18 shows a sixth specific example of the fail-safe mechanism which performs the retracting operation only with respect to the torque. The fail-safe mechanism according to the sixth specific example is a modification of the first basic configuration shown in FIG. 4 and is provided with fixing balls 27 on the boundary surfaces 21A and 22A of the two ring members 21 and 22.
A hole 28 into which the first and second members are fitted is provided to prevent relative displacement in the rotation direction between the first and second members via the fixing ball 27.

In this specific example, a multi-stage spring 44 for pressing one of the first ring members 21 against the second ring member 22 is used as a fixed holding means for applying a fixed holding force. The multi-stage spring 44 is provided with the first ring member 21 and the nut 4
Is mounted in a compressed state between a flange 4A as a locking seat provided in the first ring member 21 and the first ring member 21.

On the other hand, an adjusting bolt 45 as a set force varying means is screwed into the flange 4A. The tip of the adjusting bolt 45 is engaged with the middle of the multi-stage spring 44 to adjust the screwing amount of the adjusting bolt 45. The pressing force can be adjusted with.

[Seventh Embodiment] FIG. 19 shows a seventh embodiment of the present invention.

The seventh specific example is used for a coupling portion, and is of a type in which a fixing ball 27 is interposed between boundary surfaces 21A and 22A of first and second ring members 21 and 22. First ring member 21 and second ring member 22
Are provided on the input side member 91 and the output side member 92 of the coupling 9, respectively. The second ring member 22 is formed integrally with the output side member 92.

On the other hand, the first ring member 21 is
1 is connected via a spline mechanism 93 so as to prevent relative movement in the rotation direction and to be relatively movable in the axial direction.

A seat sleeve 94 is attached to the second ring member 22 and extends to the outer peripheral side of the first ring member 21.
A multi-stage spring 44 is mounted in a compressed state between the locking seat 41 fixed to the free end side of the seat sleeve 94 and the first ring member 21.

Further, the locking seat 41 is attached to the seat sleeve 94 so as to be displaceable in the axial direction by an adjusting bolt 45, so that the compression amount of the multi-stage spring 44 can be adjusted.

The fixing ball 27 is held by a retainer 95. The retainer 95 is provided with a groove 96 extending in the radial direction, and the ball 27 moves along the groove 96. And the first and second ring members 2
A semi-circular tapered groove 97 that becomes shallower toward the outer peripheral side is formed around the hole 28 that holds each ball 27 on the boundary surfaces 21A and 22A between the first and second boundaries 21A and 22A.

The operation of the fail-safe mechanism is as follows.

When the torque exceeds the set value, the in-plane force acting on the ball 27 exceeds the value at which the ball 27 can pop out of the hole 28.

The ball 27 moves to the outer peripheral side along the tapered groove 97 of both boundary surfaces 21A and 22A. Then, the distance between the two boundary surfaces 21A and 22A increases, and the ball 27 starts to rotate on the outer circumference.

When the torque decreases, the taper groove 97
The ball 27 moves toward the center of the boundary surfaces 21A and 22A and returns to the original hole 28.

[Eighth Specific Example] FIG. 20 shows an example of a structure in which the force setting section of the fail-safe mechanism of FIG. 19 is in a stationary system.

That is, only the part of the stationary system different from FIG. 19 will be described.
2 and is rotatably supported via a bearing 98 in a separate structure. With such a configuration, the seat sleeve 94 is free in the rotational direction with respect to the coupling, and can be fixed to the stationary system. The amount can be adjusted.

[0147]

The present invention has the above-described structure and operation. When a torque or an axial force exceeding a predetermined value is applied from the outside, the fail-safe mechanism moves in the direction in which the force acts and prevents the force from increasing. In addition, it is possible to prevent breakage of each constituent member.

In particular, the face between the nut and the feed member
The fail-safe mechanism is provided by providing a re-safe mechanism.
The force acting on the surface is small.

[Brief description of the drawings]

FIG. 1 shows a feed screw device with a fail-safe mechanism according to the present invention, and FIG. 1 (a) is a schematic diagram showing a state in which a fail-safe mechanism is mounted between a nut and a nut holder of a table; FIG. 2B is a schematic configuration diagram showing a state in which the fail-safe mechanism is mounted on the coupling unit.

FIGS. 2A and 2B show a first basic form of the fail-safe mechanism. FIG. 2A is a basic configuration diagram, FIGS. 2B to 2D are operation explanatory diagrams, and FIG. FIG. 3F is a basic configuration diagram corresponding only to torque, and FIG. 4F is a basic configuration diagram corresponding only to axial force.

FIGS. 3A and 3B show a second basic form of the fail-safe mechanism. FIG. 3A is a basic configuration diagram, FIG. 3B is a schematic perspective view, and FIGS. FIG. 3 (f) is a basic configuration diagram only corresponding to torque, and FIG. 4 (g) is a basic configuration diagram only corresponding to axial force.

4 (a) is a diagram showing a basic configuration corresponding to both rotation directions of the second basic type of FIG. 3, FIGS. 4 (b) and 4 (c) are explanatory diagrams of the operation, and FIGS. (f) is a configuration diagram when a fixing ball is interposed between the boundary surfaces, and (g) is a configuration diagram when both a boundary surface perpendicular to the axial direction and a boundary surface perpendicular to the rotation direction are provided. is there.

FIG. 5A is a schematic configuration diagram when an electromagnet is used as fixed holding means, and FIG. 5B is a schematic configuration diagram when a permanent magnet with a variable attraction force is used as the fixed holding means. , The same figure
(c)-(e) are explanatory diagrams of the operation of the variable permanent magnet, and FIG. (f) is a characteristic diagram of the attraction force of the permanent magnet of FIG.

FIGS. 6 (a) to 6 (c) are schematic structural views when an electromagnet is used as a fixing and holding means of the fail-safe mechanism of FIG. 4 (a), and FIGS. FIG. 7 is a view showing various configuration examples of a fixing and holding means for fixing by pressing a button.

FIG. 7 is a sectional view showing a first specific example of a feed screw device with a fail-safe mechanism according to the present invention.

FIG. 8 is a configuration diagram of a fail-safe system of the feed screw device of FIG. 7;

9 (a) to 9 (c) are schematic sectional views showing the operation state of the fail-safe mechanism of the feed screw device of FIG.

FIG. 10 is a sectional view showing a modified example of the feed screw device with the fail-safe mechanism of FIG. 7;

FIG. 11 is a cross-sectional view showing a second specific example of the feed screw device with a fail-safe mechanism of the present invention.

12 (a) and 12 (b) are schematic sectional views showing the operation state of the fail-safe mechanism of the apparatus of FIG.

FIG. 13 (a) is a half sectional view showing a schematic configuration of a modification of the second specific example, and FIG. 13 (b) is an operation explanatory diagram of FIG. 13 (a).

FIG. 14 is a cross-sectional view showing a third specific example of the feed screw device with a fail-safe mechanism of the present invention.

15 (a) and 15 (b) are schematic sectional views showing the operation state of the fail-safe mechanism of the apparatus shown in FIG.

FIG. 16 is a sectional view showing a fourth specific example of a feed screw device with a fail-safe mechanism according to the present invention.

FIG. 17 is a sectional view showing a fifth specific example of the feed screw device with a fail-safe mechanism of the present invention.

FIG. 18 is a sectional view showing a sixth specific example of the feed screw device with a fail-safe mechanism of the present invention.

FIGS. 19A and 19B show a seventh embodiment of the feed screw device with a fail-safe mechanism of the present invention. FIG. 19A is a sectional view, and FIG. 19B is a sectional view of the vicinity of a ball between boundary surfaces. Enlarged sectional view,
FIG. 4C is an explanatory diagram for explaining a ball trajectory when the ball is operated.

FIG. 20 is a sectional view showing an eighth specific example of the feed screw device with a fail-safe mechanism of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Feed screw device 2 Feed screw 3 Ball 4 Nut 9 Coupling 10 Motor 11 Holder 12 Evacuation detection means 13 Controller 15 Fail safe controller 20 Fail safe mechanism 21 First ring member 22 Second ring member 23 Fixed holding means 24 Axial direction regulation Means 25 Anti-rotation means 26 Intermediate ring member 27 Fixing ball 28 Hole 29 Setting force varying means 30 Coil 31 Magnetic path 33 Permanent magnet ring 34 Transmission ring 35 Magnet unit 36 Magnetic material part 37 Non-magnetic material part 38 Sliding material Reference Signs List 40 Pressing means 41 Engagement seat 42 Elastic member 44 Multi-stage spring

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-195461 (JP, A) JP-A-62-24942 (JP, A) JP-A-4-19452 (JP, A) 4375 (JP, B2) Jiko 3-20607 (JP, Y2) Jiko 63-30215 (JP, Y2)

Claims (24)

(57) [Claims] 1. A feed screw device comprising: a feed screw shaft; a nut screwed to the feed screw shaft; a feed member attached to the nut; and rotation driving means for rotating the feed screw shaft. When one or both of a torque or an axial force equal to or greater than a set value is applied to a joint between the nut and the member to be fed ,
The joining between the nut and the member to be fed is released, and the
Direction in which the nut prevents the torque or the axial force from increasing
Fail-safe mechanism with feed screw and wherein in that a fail-safe mechanism for the operation of the saving. 2. One of the torque or the axial force or
That both settings are provided setting force variation means for varying
The feed screw device with a fail-safe mechanism according to claim 1, wherein: 3. A retracting operation detecting means for detecting a retracting operation of the nut and transmitting a detection signal .
The feed screw device with a fail-safe mechanism according to claim 1. Wherein said nut of said fail-safe mechanism
A saving operation for both the torque and the axial force
The feed screw device with a fail-safe mechanism according to any one of claims 1 to 3, wherein: Wherein said nut of said fail-safe mechanism
Characterized by the save operation for only the axial force
The feed screw device with a fail-safe mechanism according to claim 1 . Wherein said nut of said fail-safe mechanism
The evacuation operation is performed only for the torque .
A feed screw device with a fail-safe mechanism according to any one of claims 1 to 3 . Wherein said fail-safe mechanism includes two ring member via the boundary surfaces perpendicular to the axial direction are joined together, between the boundary surfaces by suction or mutually pressed against the two ring members given fixed holding force, with a static frictional force corresponding to the fixed holding force securing retaining the ring member in the rotation direction, fixed hold the re <br/> ring member in the axial direction by the fixed holding force itself Fixed holding means, and one of the two ring members is attached to the nut.
Is, the other is attached to the object to be feed member, at the set static or frictional force which the torque corresponding to the preset said fixed holding force, wherein the boundary surface is slipped
By releasing the joining of the two ring members,
Nut is the save operation in a direction to prevent an increase in the torque, the the axial force is set the more fixed retaining force in advance, the two ring members separated from each other by the nut
There can be a saving operation in a direction to prevent an increase of the axial force
The feed screw device with a fail-safe mechanism according to claim 4, characterized in that: Wherein said fail-safe mechanism includes two ring members which are bonded to each other through a boundary surface which is perpendicular to the direction of rotation, between the boundary surfaces by suction or mutually pressing the two ring members Give fixed holding force, front
With a static frictional force corresponding to the serial fixed holding force securing retaining the ring member in the axial direction, and fixing and holding means for fixedly holding said <br/> ring member in the rotational direction by the fixed holding force itself,
And one of the two ring members is attached to the nut.
Is, the other is attached to the object feeding member, wherein the axial force is set still higher frictional force corresponding to a preset the fixed holding force, the boundary surface of the two ring members sliding in the axial direction When the bond is released
Ri, the nut is the save operation in a direction to prevent an increase of the axial force, when the torque is set the more fixed retaining force in advance, and the two ring members are spaced apart from each other, said nut
5. The feed screw device with a fail-safe mechanism according to claim 4, wherein the retracting operation is performed in a direction in which the torque prevents the increase in the torque . Wherein said fail-safe mechanism according to claim characterized by having a detent mechanism that permits relative movement in the axial direction by preventing the relative rotation of the two ring members 7
Or a feed screw device with a fail-safe mechanism according to 8 . 10. The feed screw device with a fail-safe mechanism according to claim 9 , wherein said detent mechanism is a ball spline mechanism. Wherein said fail-safe mechanism, 請, characterized in that an axial movement restricting means for preventing relative axial movement and allows relative rotation of the two ring members
A feed screw device with a fail-safe mechanism according to claim 7 or 8 . 12. The method of claim 11, wherein axial movement restricting means and being a rotational bearing that is interposed between the ring member
The feed screw device with a fail-safe mechanism according to claim 11. 13. The feed screw device with a fail-safe mechanism according to claim 11, wherein said rotary bearing is an angular contact bearing. 14. A concave portion into which a positioning ball fits is provided on a boundary surface of said ring member, and when a torque or an axial force exceeding a set value acts thereon, said positioning ball comes off from said concave portion. The two ring members roll relative to each other or move axially relative to each other by rolling on the boundary surface .
A feed screw device with a fail-safe mechanism according to any one of claims 7 to 13 . 15. The fixed holding means to be a magnet for securing holding a boundary surface of the ring member by magnetic attraction
The feed screw device with a fail-safe mechanism according to any one of claims 7 to 11, wherein: 16. A feed screw device with a fail-safe mechanism according to claim 15, wherein said magnet is an electromagnet, and said set force changing means is a controller for controlling a current value applied to said electromagnet. 17. The magnet is a permanent magnet, according to claim, characterized in that the magnitude of the magnetic attraction force varied by varying the magnetic path passing between said two ring members 15
4. A feed screw device with a fail-safe mechanism according to item 1. 18. The fixed holding means having a pressing means for pressing the other of said ring member in a state in which the ring member is a relatively fixed one of the two ring members
The feed screw device with a fail-safe mechanism according to any one of claims 7 to 14, wherein: 19. A feed screw device with a fail-safe mechanism according to claim 18, wherein said pressing means uses an elastic force of an elastic member. 20. The feed screw device with a fail-safe mechanism according to claim 18, wherein said pressing means is an electromagnetic actuator utilizing an electromagnetic force. 21. The pressing means and wherein the air pressure, an actuator using a fluid pressure cylinder of the hydraulic or the like
The feed screw device with a fail-safe mechanism according to claim 18 . 22. The pressing means claims, characterized in that an actuator using a piezoelectric element or electrostrictive element
19. The feed screw device with a fail-safe mechanism according to 18 . 23. A feed screw device with a fail-safe mechanism according to claim 18, wherein said pressing means is a thermal actuator utilizing thermal expansion. 24. A feed screw device with a fail-safe mechanism according to claim 18, wherein said pressing means is an actuator using a magnetostrictive element.