JPH04191509A - Stroke detection device for cylinder device - Google Patents

Abstract

PURPOSE:To reduce noises effectively and improve reliability of a device by positioning an end of a magnetostrictive line housed in a fine and long tube at a longitudinally intermediate position of a driving coil. CONSTITUTION:An end 21A of an amolphous wire 21 is positioned at an intermediate part in a longitudinal direction of a driving coil 15. When a pulse current is applied to the driving coil 15, a generated line of magnetic force shows the highest density at the intermediate part in the longitudinal direction of the driving coil 15. Supersonic wave is effectively generated on the amolphous wire by magnetostrictive effect. The supersonic wave is propagated from one end of the amolphous wire 21 positioned at the intermediate position in a longitudinal direction of the driving coil 15, that is, the end 21A on the side of the driving coil 15 in the direction to a detection coil 17. When the supersonic wave passes a magnetized portion 21C of the amolphous wire 21, a detection signal is output from a detection coil 17 with certainty.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a stroke detection device for a cylinder device suitable for use in detecting, for example, the piston stroke of a cylinder device, and in particular, it relates to a stroke detection device for a cylinder device that utilizes magnetostrictive effects. The present invention relates to a stroke detection device for a cylinder device that improves detection performance.

[Prior Art] For example, when operating a cylinder device installed in a construction machine or the like by automatic control, a stroke detection device that detects the stroke of a piston is required.

Therefore, FIGS. 13 to 20 show stroke detection devices for cylinder devices according to the prior art.

In the figure, 1 indicates a tube constituting the main body of the cylinder device, and the tube 1 is made of, for example, CFRP or GFRP.
The inner cylinder 2 is formed into a cylindrical shape from a non-magnetic material such as reinforced plastic, aluminum, stainless steel, or ceramic, and the outer peripheral surface of the inner cylinder 2 is coated with a fiber material impregnated with resin until it reaches a predetermined thickness. It consists of an outer cylinder 3 formed by winding the outer cylinder 3, and between the outer cylinder 3 and the inner cylinder 2, an elongated tube 12, which will be described later, is connected to a drive coil 15 and a detection coil 17.
It is buried with. Here, the outer cylinder 3 is made of a filamentous fiber material 4 such as carbon fiber, glass fiber, aramid fiber, or ceramic fiber, and a resin material such as epoxy resin, polyester resin, or polyimide resin having thermosetting and adhesive properties. This is impregnated and cross-wound around the outer circumferential surface of the inner cylinder 2 at a predetermined winding angle O (see Fig. 19) using means such as filament winding, finished to the required thickness, and heat cured. is formed by.

5.6 shows a head cover and a rod cover that cover both ends of the tube 1, and the head cover 5 and the rod cover 6 are provided with oil-on-line thread combining and discharging boats 5A and 6A, and the supply and discharging boat 5A.

6A is designed to supply and discharge pressure oil from the outside into hydraulic chambers A and 13, which will be described later. 7,7. . . . indicates tie rods that extend in the axial direction between the head cover 5 and the rod cover 6 and fasten them to the tube 1, and each tie rod 7 is provided at a predetermined interval in the circumferential direction of the tube 1. and lock nuts 8, 8. ...
is screwed on.

Reference numeral 9 indicates a piston that is slidably inserted into the inner cylinder 2 of the tube 1, and the piston 9 is made of a non-magnetic material such as reinforced plastic or stainless steel, and a piston seal 9A is provided at the center of its outer circumference. is installed. The piston 9 defines two hydraulic chambers A and B within the tube 1, and is slid to the right as shown in FIG. 13 due to the differential pressure between the hydraulic chambers A and B. There is. 1
0 indicates a piston rod whose proximal end is fixed to the piston 9 and whose distal end protrudes outside the tube 1 through the rod cover 6, and a mounting eye IOA is attached to the protruding end of the piston rod 10 by means such as welding. It is fixed.

Reference numeral 11 denotes a ring-shaped magnet embedded in the outer circumferential surface of the piston 9. The magnet 11 is displaced along with the piston 9 inside the tube 1, and partially covers an amorphous ribbon 13 (described later) at a position corresponding to the magnet 11. Detection coil 1 which will be described later
7 generates a detection signal corresponding to the stroke position of the piston 9.

Reference numeral 12 indicates an elongated tube extending in the axial direction between the inner tube 2 and the outer tube 3 and provided within the tube 1. The elongated tube 12 is made of a resin material or the like and has an inner diameter of about 2 to 3 mm, for example. The tube 1 is formed so as to extend in a long and narrow straight line from one end of the tube 1 to the other end. Reference numeral 13 indicates an amorphous ribbon as a magnetostrictive wire housed in the elongated tube 12, and the amorphous ribbon 13 is formed into an elongated strip (ribbon shape) by a magnetostrictive material having a large magnetostrictive coefficient, such as an iron-based amorphous ferromagnetic alloy. The width dimension is about 2 mm, and the wall thickness is about 20 to 40 μm. The amorphous ribbon 13 extends from one end of the elongated tube 12 to the other end, and both ends 13A and 13B are covered with a vibration-proof material 1 such as sponge or cotton to prevent reflection of ultrasonic waves, etc., which will be described later.
4.14 at both ends of the elongated tube 12.

Reference numeral 15 indicates a drive coil located at one end of the elongated tube 12 and wound around the outer peripheral surface of the elongated tube 12 with a predetermined number of turns. It is connected to a power supply circuit 16, and the drive power supply circuit 16 applies a pulsed input current a shown in FIG. 16 to the drive coil 15 at a predetermined time t. The drive coil 15 changes the magnetic field of the amorphous ribbon 13 by applying an input current a, thereby causing the amorphous ribbon 13 to generate ultrasonic waves based on magnetostrictive vibrations. Then, this ultrasonic wave is transmitted from one end of the amorphous ribbon 13 to the other end, for example, at a frequency of 500
The sound propagates through the area 13 at a speed of about 0 to 6000m8.

Reference numeral 17 indicates a detection coil wound around the outer peripheral surface of the elongated tube 12 so as to extend over the entire stroke length of the piston 9, and the detection coil 17 extends from the drive coil 15 in the axial direction as shown in FIG. The elongated tube 12 is wound many times over the entire stroke length of the piston 9 from one end of the elongated tube 12 to the other end, and both ends thereof are connected to an external detection circuit 18 . Here, in the detection coil 17, when an input current a (see FIG. 16) is first applied to the drive coil 15, an induced electromotive force is generated as shown in FIG. 17 due to the magnetic field generated in the amorphous ribbon 13. The detection coil 17 then outputs this as a first detection signal to the detection circuit 18. Next, the ultrasonic wave based on the input current a propagates (passes) through the amorphous ribbon 13 to a position corresponding to the magnet 11 (then, the corresponding part of the amorphous ribbon 13 is partially magnetized by the magnet 11). Therefore, a reverse magnetostriction phenomenon occurs in this magnetized portion 13C, and an induced electromotive force is generated again in the detection coil 17, and the detection coil 17 outputs this as a second detection signal C to the detection circuit 18. .

Then, the detection circuit 18 detects the time 1+ between the detection signals S and C.
The relationship between (1+ <1) and the stroke position of the piston 9 is detected as a characteristic with high linearity as shown in Fig. 18, and the value of this time t1 is converted into a voltage value and output to the control device of the cylinder device, etc. do. In this case, time t1
For measurement, a triangular wave is generated simultaneously with the application of input current a,
This triangular wave may be held based on the peak of the detection signal C, or the time t1 may be successively measured using means such as a timer.

A stroke detection device for a cylinder device according to the prior art has the above-mentioned configuration, and a manufacturing method thereof will be described next.

First, an inner cylinder 2 made of a non-magnetic material such as reinforced plastic was finished with a predetermined accuracy (inner surface accuracy, outer surface accuracy, roundness, etc.), and an amorphous ribbon 13 was housed on the outer peripheral surface of the inner cylinder 2. A coil 15 driving the elongated tube 12,
The detection coil 17 is arranged in a wound state, extended in the axial direction of the inner cylinder 2, and fixed by adhesive or other means.

Then, as shown in FIG. 19, the filamentous fiber material 4 impregnated with resin is cross-wound around the outer peripheral surface of the inner cylinder 2 at a predetermined winding angle θ using means such as filament winding method, as shown in FIG. Finish to a certain thickness. In this case, the winding angle θ is set to a winding angle close to 0 degrees with respect to the central axis O-0, for example, θ=5 to 3.
By setting the angle to about 0 degrees, the bending strength can be increased.

After winding the filamentous fiber material 4 around the outer circumferential surface of the inner cylinder 2, they are placed in a curing furnace (not shown) and, for example,
By curing at a high temperature of about 20 degrees, the outer cylinder 3 is integrally formed on the outer peripheral side of the inner cylinder 2, and the desired tube 1 is obtained.

Next, the piston 9 and the like are inserted into the tube 1, and the head cover 5 and rod cover 6 are attached to both ends of the tube 1, and these are connected using tie rods 7 and the like as shown in FIG. Fix and assemble the cylinder device.

Then, both ends of the drive coil 15 and the detection coil 17 are pulled out from the head cover 5 side or the rod cover 6 side via lead wires, etc., and the drive power supply circuit 1
6 and the detection circuit 18 to complete a stroke detection device for a cylinder device.

(Then, the hydraulic chamber A of the tube 1,
When pressure oil is supplied and discharged into B, the piston 9 slides within the tube 1 due to the differential pressure between the hydraulic chambers A and B, and the rod 10
Activate the load etc. installed on the mounting eye IOA. When the input terminal a shown in FIG. 16 is applied from the drive power supply circuit 16 to the drive coil 15, an ultrasonic wave is generated due to the strain phenomenon of the amorphous ribbon 13 in the elongated tube 12, which travels through the ribbon 13 for a long time. It propagates in the horizontal direction.

At this time, an induced electromotive force is generated in the detection coil 17 wound around the ribbon 13 due to electromagnetic induction, and a first detection signal is output from the detection coil 17 to the detection circuit 18 (Fig. 17). reference). - On the other hand, at the position of the amorphous ribbon 13 corresponding to the magnet 11 of the piston 9, the ribbon 13 is partially magnetized by the magnet 11, so the ultrasonic waves propagating through the ribbon 13 cause the magnetization of the ribbon 13. When passing through the part 13C, an inverse magnetostriction phenomenon occurs in this part, and the next induced electromotive force is generated in the detection coil 17, and the second detection signal C is output from the detection coil 17 to the detection circuit 18. Ru. Then, the detection circuit 18
Based on the time t1 between the detection signals A and C, the stroke position of the piston 9 can be sequentially detected by obtaining the characteristics illustrated in FIG.

[Problems to be Solved by the Invention] However, in the above-mentioned prior art, as shown in FIG.
Since one end 13A of the amorphous ribbon 13 provided in the elongated tube 12 is made to protrude in the axial direction from the drive coil 15 and is positioned by the vibration isolating material 14, the following problems arise. That is, the lines of magnetic force generated by the drive coil 15 have the highest density at a position corresponding to the middle portion of the drive coil 15 in the length direction. Then, a pulsed current a is applied to the drive coil 15, and the ultrasonic waves generated by the amorphous ribbon 13 due to the magnetostrictive effect are generated as shown by the arrow in FIG. Both ends 13A, 13 of the amorphous ribbon 13 from the position where
B, that is, it propagates in two directions: the drive coil 15 side and the detection coil 17 side.

However, in order to detect the position of the piston 9, only the ultrasonic waves propagating toward the detection coil 17 side are necessary, and those in the opposite direction are reflected at the end 13A side of the amorphous ribbon 13 and become noise, causing the detection coil 17 It causes harmful effects such as interfering with the ultrasonic waves traveling in the side direction and weakening the signal.
For example, the detection coil 17 may output a signal containing noise n as shown in FIG. If this phenomenon is severe, the stroke detection device may distinguish between the first detection signal C, the second detection signal C, and the noise n, and may erroneously detect the stroke of the piston 9.

The present invention has been made in view of the problems of the prior art described above.
The present invention provides a stroke detection device for a cylinder device that can improve the ratio, increase detection accuracy, and improve stability.

[Means for Solving the Problems] The features of the configuration adopted by the present invention in order to solve the above-mentioned problems include a magnet provided on the piston, a magnet extending from one end of the tube to the other end, and a magnet extending from one end of the tube to the other. an elongated tube in which a magnetostrictive wire having a large magnetostrictive coefficient is accommodated; and a drive coil wound around the outer periphery of one end of the elongated tube to generate ultrasonic waves in the magnetostrictive wire by applying a pulsed input current. ,
When the ultrasonic wave passes through the position of the magnetostrictive wire that is wound around the outer periphery of the elongated tube in the length direction of the elongated tube separately from the drive coil and corresponds to the magnet, it is caused by an inverse magnetostriction phenomenon. and a detection coil that detects the generated induced electromotive force as a detection signal, and one end of the magnetostrictive wire housed in the elongated tube is positioned at a longitudinally intermediate portion of the drive coil.

Further, the detection coil detects an induced electromotive force due to an input terminal applied to a drive coil as a first detection signal, and also causes a reverse magnetostriction phenomenon when the ultrasonic wave passes through a position of a magnetostrictive wire corresponding to the magnet. The induced electromotive force generated by this may be detected as the second detection signal.

Two magnets may be provided spaced apart by a predetermined distance in the axial direction of the piston.

Furthermore, a plurality of the magnets are provided at predetermined distances in the axial direction of the piston and facing different directions, and the elongated tube, the drive coil, and the detection coil are arranged in the axial direction of the tube so as to face each of the magnets. Stretch it out,
A plurality of them may be provided in the tube.

Furthermore, at least two elongated tubes may be provided in the tube, and the positions of the drive coil and the detection coil wound around each of the elongated tubes may be reversed between at least one of the elongated tubes and the other. .

[Effect]

With the above configuration, the ultrasonic waves generated in the magnetostrictive wire by the drive coil propagate in one direction only toward the detection coil, thereby improving the S/N ratio.

[Example] Hereinafter, an example of the present invention will be described based on FIGS. 1 to 12. Note that the same components as those in the prior art described above are given the same reference numerals and their explanations will be omitted.

1 and 2 show a first embodiment of the invention.

In the figure, reference numeral 21 denotes an amorphous wire as a magnetostrictive wire housed in the elongated tube 12. The amorphous wire 21 is used in place of the amorphous ribbon 13 described in the prior art. Made of amorphous wire with a magnetostriction coefficient of 30 to 40X1
At around 0-6, the distortion caused by changes in the magnetic field is large;
Moreover, the strength is 300Kgf/rrl', and the sensing effect is strong.

Ends 2LA and 21B of the amorphous wire 21 on the drive coil 15 side and the detection coil 17 side are supported by vibration isolators 22 and 23, respectively, and one end 2LA is supported by the vibration isolator 22 so that the drive coil 15 It is positioned at the middle part in the length direction. Further, the vibration isolators 22 and 23 are formed in substantially the same manner as the vibration isolators 14 described in the prior art.

The stroke detection device for a cylinder device according to this embodiment is constructed as described above, and its basic operation is not particularly different from that of the prior art.

However, in this embodiment, since the end portion 21A of the amorphous wire 21 is positioned at the midpoint in the length direction of the drive coil 15, the lines of magnetic force generated by applying the pulsed current a to the drive coil 15 are The density is highest at the middle part of the drive coil 15 in the length direction, and ultrasonic waves can be effectively generated in the amorphous wire 21 due to the magnetostrictive effect. The light propagates in one direction from one end of the amorphous wire 21 positioned at the midpoint in the width direction, that is, the end 21A on the drive coil 15 side, toward the detection coil 17 side, passing through the magnetized portion 21C of the amorphous wire 21. At times, the detection signal C is reliably output from the detection coil 17.

Therefore, according to this embodiment, since the ultrasonic waves generated in the amorphous wire 21 from the drive coil 15 by the magnetostrictive effect can be effectively propagated in one direction, the generation of noise can be reliably prevented. As shown in Fig. 2, it is possible to avoid a situation where the first detection signal S and the second detection signal C cannot be distinguished, and these detection signals S and C can be reliably detected to determine the stroke of the cylinder device. Detection accuracy can be significantly improved.

In the first embodiment, the ring-shaped magnet 11 is embedded in the piston 9, but if the piston 9 is a cylinder device that does not rotate relative to the tube l, the magnet 11 is embedded in the piston 9. need not be formed into a ring shape; for example, a rod-shaped magnet 31 may be embedded in the piston 9 so as to face the elongated tube 12, etc., as in the first modification shown in FIG.

Further, the elongated tube 12 that accommodates the amorphous wire 21 does not need to extend linearly in the axial direction of the tube 1 (
For example, as in the second modification shown in FIG. 4, an elongated tube 32 is spirally wound around the outer peripheral surface of the inner cylinder 2, and the elongated tube 32 is extended from one end of the inner cylinder 2 to the other end. After stretching, this °
The outer cylinder 3 may be integrally formed by wrapping the fiber material 4 from above. In this case, the amorphous wire 21 is housed in the elongated carbon dioxide 32 in advance, and the drive coil 15 and the detection coil 17 are wound around the outer periphery of the elongated tube 32. It may also be formed of a resin material or the like. In the second modification shown in FIG. 4, by extending the elongated tube 32 in a spiral shape,
Since the effective length of the detection coil 17 can be significantly increased, even small strokes of the piston 9 can be reliably detected.
Stroke detection accuracy can be greatly improved.

Next, FIG. 5 and FIG. 6 show a second embodiment of the present invention, and in this embodiment, the same components as in the first embodiment are given the same reference numerals, and their explanations will be omitted. Assuming,
The feature of this embodiment is that a fixed magnet 41 is embedded at a predetermined position between the inner cylinder 2 and the outer cylinder 3, and is located around the detection coil 17 wound around the outer peripheral surface of the elongated tube 12. .

Here, to explain the case where the fixed magnet 41 is fixed at a position relatively close to the drive coil 15 side (see FIG. 1), as in the first embodiment, the detection coil 1
In addition to outputting the first detection signal b and the second detection signal C from 7, when the ultrasonic wave passes through the position of the fixed magnet 41, an inverse magnetostriction phenomenon occurs here as well, and an induced electromotive force is generated, and the third detection signal d is detected from the detection coil 17 as shown in FIG. The stroke 19- of the piston 9 can be detected more accurately by measuring the time t1 between the detection signals a and c based on the reference value, using the time t2 between the two as a reference value.

Thus, in this embodiment configured in this way, it is possible to obtain almost the same effects as in the first embodiment, but in particular, in this embodiment, since the fixed magnet 41 is provided, the external temperature and Even if the speed of sound changes due to a change in humidity or stress is applied to the amorphous wire 21 for some reason, and the times tl and t2 change,
By measuring time t with time t2 as a reference,
Can cancel the effects of changes in sound speed, etc.
Stroke detection accuracy can be maintained well.

Next, FIG. 7 and FIG. 8 show a third embodiment of the present invention, and in this embodiment, the same components as in the first embodiment are given the same reference numerals, and their explanations will be omitted. In addition, the feature of this embodiment is that instead of the magnet 11 used in the above embodiment,
Ring-shaped magnets 51 are provided at both ends of the piston 9 in the axial direction.
．． 52 were buried with a predetermined distance between them.

In this case, when the ultrasonic waves generated in the amorphous wire 21 pass through a position corresponding to the magnet 51, the first
As illustrated in FIG. 8, the second detection signal c1 is detected at time t, and when the ultrasonic wave passes through a position corresponding to the magnet 52, the second detection signal c, The third detection signal c2 is detected at time t3. Then, at this time t3, the magnet 51.
52. Therefore, by measuring time t1 using this time t3 as a reference value, the piston 9
It becomes possible to accurately detect the stroke of

Thus, even in this embodiment configured in this way, the time t
By measuring the time t1 using 3 as a reference value, it is possible to obtain substantially the same effects as in the second embodiment.

Next, FIGS. 9 and 10 show a fourth embodiment of the present invention, and in this embodiment, the same components as in the first embodiment are designated by the same reference numerals, and their explanations will be omitted. However, the feature of this embodiment is that instead of the ring-shaped magnets 51 and 52 used in the third embodiment, magnets 51 and 52 are arranged in opposite directions with a predetermined distance between them at both ends of the piston 9 in the axial direction. Bar-shaped magnets 61 and 62 are embedded in the magnet 6.
The elongated tube 63.63, the drive coil 64.64, and the detection coil 65.65 are connected to the tube 1 so as to face the tube 1.62.
The reason for this is that the tube is buried between the inner tube 2 and the outer tube 3 so as to extend in the axial direction.

Here, each elongated wire tube 63, each drive coil 64, and each detection coil 65 are formed in the same manner as the elongated tube 12 and detection coil 17 described in the prior art, and each elongated tube 63 has an amorphous wire 21 inside. It is accommodated. Further, both ends of each drive coil 64 are connected to an external drive power supply circuit 66.6.
6, each detection coil 65 is connected to an external detection circuit 67, 67 through a lead wire, etc., and each drive power supply circuit 66 applies the input terminal a shown in FIG. 16 to each drive coil 64. Ru. Each drive coil 64 and each detection coil 65 are arranged at the same position in the length direction of the tube 1, and one of the detection coils 65 is connected to the first detection coil 65 as shown in FIG. At time t4 from the signal b+ and the detection signal b1, a second detection signal c3 corresponding to the position of the magnet 61 is outputted to one of the detection circuits 67, and the other one outputs the second detection signal c3, which corresponds to the position of the magnet 61, as shown in FIG. 1 detection signal b2 and at time t5 from the detection signal b2,
The second detection signal c4 corresponding to the position of the magnet 62 is output to the other detection circuit 67. Thus, also in this embodiment configured in this manner, the time difference (t5) between the detection signals C31C4 from each detection coil 65 is By setting t<) as the reference value, it is possible to obtain almost the same effect as in the third embodiment, but in particular, in this embodiment, two detection coils 65 and the like are provided, and as shown in FIG. (a), (b)
Since the two sets of detection signals t)++C3 and b2, G4 shown in the figure are taken out, it is possible to reliably prevent the detection signals C3°G4 from interfering with each other. For example, even when the separation dimension ρ is made small, By determining the reference value from time 14.15, the stroke of the piston 9 can be detected more accurately.

Next, FIG. 11 and FIG. 12 show a fifth embodiment of the present invention, and in this embodiment, the same components as in the first embodiment are given the same reference numerals, and their explanation will be omitted. In other words, the features of this embodiment include elongated tubes 71, 71' and drive coils 72, 72 similar to the elongated tubes 63, drive coils 64, and detection coils 65 used in the fourth embodiment. 73' and the detection coils 73 and 73' are buried in the tube 1 with the combinations reversed with respect to each other.

Here, a drive coil 72 is wound around the outer periphery of one end of the elongated tube 71, and a predetermined distance from the drive coil 72 is detected over a predetermined length from one end of the elongated tube 71 to the other end. A coil 73 is wound. On the other hand, a drive coil 72' is wound around the outer periphery of the other end of the elongated tube 71', and is spaced a predetermined distance from the drive coil 72' by a predetermined length from the other end of the elongated tube 71' to one end. A detection coil 73' is wound throughout. The dimension between the drive coils 72 and 72' is a predetermined length that approximately corresponds to the length of the tube 1, and both ends of these are connected to external drive power supply circuits 74 and 74 via a wire or the like. ', and both ends of the detection coils 73, 73' are connected to external detection circuits 75, 75' via lead wires, etc., respectively.

(Therefore, even in this embodiment configured in this way, the first detection signals b3 and b4 and the second detection signals shown in FIGS. C
By detecting times s and 06 and measuring these times ts and t7, substantially the same effect as in the fourth embodiment can be obtained. Dimensions and time between drive coils 72 and 72' js, t7
Since there is a certain correspondence with the sum of (t6+:t7),
Using this time (ts + t7) as the reference value, time j6
．． The stroke of the piston 9 can be accurately detected by either f17. In this case, the drive coil 72
．． Dimensions between 72'℃. Then, the sound speed ■ is ■=ρo
/ (t6+t,), so
The stroke of the piston 9 can be detected with high precision at either time t6 or t7 by constantly calculating changes in the sound velocity (2) due to changes in temperature, humidity, stress, etc.

In each of the above embodiments, the elongated tube 12 (32, 63, 71° 71') housing the amorphous wire 21, the drive coil 15 (64, 72, 72'), and the detection coil 17 (65, 73, 73') ) etc., one or two sets of detection sensors are embedded in the tube l, but the present invention is not limited to this, and three or more sets of detection sensors are embedded in the tube l to improve detection accuracy. may be further improved. In this case, even if one set of detection sensors fails, the stroke of the piston 9 can be detected by other detection sensors, and reliability can be greatly improved.

Further, in each of the embodiments described above, the outer cylinder 3 of the tube 1 is formed using filament winding method or the like using the filamentous fiber material 4, but instead of this,
The outer cylinder 3 may be formed by a tape winding method using a tape-like fiber material, a hand lay-up method using a woven fiber material, or the like.

Furthermore, in each of the above embodiments, the first detection signal b(b, ,
b2. ) and the second detection signal c (c+, C3,
), the stroke of the piston 9 is detected based on the time t+ (t4, t5...), etc., but instead of this, it is possible to
The stroke of the piston 9 may be detected based on the detection signal C (C+, C3, . . . ) and the time.

Further, in each of the above embodiments, the elongated tube 12 (32°63.7
1.71'), but instead of this, a magnetostrictive wire such as an amorphous ribbon may be accommodated.

[Effects of the Invention] As detailed above, since one end of the magnetostrictive wire housed in the elongated tube is positioned at the midpoint in the longitudinal direction of the drive coil, the magnetostrictive wire is It is possible to propagate the ultrasonic waves generated by the It has various effects such as highly accurate detection and improved reliability.

[Brief explanation of the drawing]

1 and 2 show a first embodiment of the present invention, FIG. 1 is a principle diagram of a stroke detection device, FIG. 2 is a characteristic diagram of a detection signal, and FIG. 3 is a diagram of the first embodiment. FIG. 4 is an external view of the inner cylinder etc. showing a second modification; FIGS. 5 and 6 show a second embodiment; Fig. 5 is a vertical sectional view of the main part of the cylinder device, Fig. 6 is a characteristic line diagram of the detection signal, and Figs.
FIG. 7 is a vertical sectional view of the main part of the cylinder device, FIG. 8 is a characteristic line diagram of the detection signal, and FIG. 9 and FIGS. 1O (A) and (B) are the fourth embodiment. 9 is a vertical sectional view of the main part of the cylinder device, FIGS. 10(a) and 10(b) are characteristic diagrams of different detection signals, and FIGS. 11 and 12.
Figures (A) and (B) show the fifth embodiment, Figure 11 is a longitudinal sectional view of the main part of the cylinder device, Figures 12 (A) and (B) are characteristic curves of different detection signals, 13 to 20 show the prior art, FIG. 13 is an overall view of the cylinder device, FIG. 14 is a principle diagram of the stroke detection device, and FIG. 15 is a diagram of the principle of the stroke detection device.
The figure shows a cross-sectional view in the direction of arrow FIG. 19 is an explanatory diagram showing a state in which the fiber material is wound around the outer peripheral surface of the inner cylinder, and FIG. 20 is a characteristic diagram of the detection signal. 1...Tube, 2...Inner tube, 3...Outer tube, 9.
... Piston, lO ... Piston rod, 11, 31
, 51.52, 61.62... Magnet, 12, 3
2゜63.71.71'...Elongated tube, 15,64
, 72.72'... Drive coil, 17, 65, 73.
73'...Detection coil, 21...Amorphous wire (magnetostrictive wire), a-input terminal, b, b,, b2. ba,
b4...first detection signal, C, CI I 021 C
a, C4+ C5+ C6... second detection signal, t,
, t+, t2+ t:]+ t4. t5. t6.
'e7...time. ■ n 榔 ゆくらに & U 纂

Claims (5)

[Claims] (1) A cylinder device consisting of a tube made of a non-magnetic material, a piston slidably provided within the tube, and a rod having one end fixed to the piston and the other end protruding outside the tube. , a magnet provided on the piston, an elongated tube extending from one end of the tube to the other end and containing a magnetostrictive wire with a large magnetostriction coefficient therein, and an outer periphery of one end of the elongated tube. a drive coil that is wound and generates ultrasonic waves in the magnetostrictive wire by applying a pulsed input current; and a drive coil that extends along the length of the elongated tube separately from the drive coil, a detection coil that is wound around the magnet and detects the induced electromotive force generated by the reverse magnetostriction phenomenon as a detection signal when the ultrasonic wave passes through the position of the magnetostrictive wire corresponding to the magnet, and inside the elongated tube. A stroke detection device for a cylinder device, characterized in that one end of the magnetostrictive wire accommodated in the drive coil is positioned at a longitudinally intermediate portion of the drive coil. (2) The detection coil detects the induced electromotive force due to the input current applied to the drive coil as a first detection signal, and also detects inverse magnetostriction when the ultrasonic wave passes through the position of the magnetostrictive wire corresponding to the magnet. A stroke detection device for a cylinder device according to claim (1), wherein the induced electromotive force generated by the phenomenon is detected as the second detection signal. (3) A stroke detection device for a cylinder device according to claim (1), wherein two magnets are provided spaced apart by a predetermined distance in the axial direction of the piston. (4) A plurality of the magnets are provided at a predetermined distance in the axial direction of the piston and oriented in different directions, and the elongated tube, drive coil, and detection coil are arranged in the axial direction of the tube so as to face each magnet. A stroke detecting device for a cylinder device according to claim (1), wherein a plurality of stroke detecting devices are provided on the tube so as to be elongated. (5) At least two of the elongated tubes are provided in the tube, and the positions of the drive coil and the detection coil wound around each of the elongated tubes are reversed between at least one of the elongated tubes and the other. A stroke detection device for a cylinder device according to scope (1).