JP6875966B2 - Displacement detector - Google Patents

Description

The present invention relates to a displacement detection device that detects a displacement amount of a member.

Patent Document 1 describes a magnet attached to a displacement member that displaces following the object to be measured, a magnetic sensor that is arranged so as to face the magnet, and a spring that urges the displacement member toward the object to be measured. Displacement detection device provided with the above is disclosed. In this displacement detection device, the position of the magnet changes according to the displacement of the object to be measured, and the direction and magnitude of the magnetic flux passing through the magnetic sensor changes as the position of the magnet changes. Therefore, the output value of the magnetic sensor The amount of displacement of the object to be measured can be specified based on.

Japanese Unexamined Patent Publication No. 2015-10876

In a displacement detection device such as the displacement detection device described in Patent Document 1, in which the displacement member is urged toward the object to be measured by a spring, the amount of compression of the spring becomes small when the displacement member protrudes, so that the displacement occurs. The force that presses the member against the object to be measured becomes smaller. If the force that presses the displacement member against the object to be measured becomes small in this way, the displacement member may not be able to follow the movement of the object to be measured.

On the other hand, when the displacement member is pushed in, the amount of compression of the spring becomes large, so that the force that pushes the displacement member against the object to be measured becomes large. If the force that presses the displacement member against the object to be measured becomes large in this way, the object to be measured may be hindered from freely moving toward the displacement member.

That is, in the displacement detection device having the above configuration, in order to cope with such a restriction, the amount of expansion and contraction of the spring, that is, the detection range of the displacement detection device is limited, and the force for pressing the displacement member against the object to be measured changes. The width needs to be reduced.

The present invention has been made in view of the above problems, and provides a displacement detection device capable of reducing the change width of the pressing force acting on the object to be measured without limiting the detection range of the displacement detection device. The purpose is to provide.

In the first invention, at least a part of the magnetic material is provided outside the range in which the magnet can be displaced in the displacement direction, and the displacement member has an attractive force that attracts the magnet and the magnetic material and an urging force of the urging member. It is characterized in that it is pressed against the displacement detection target member by the resultant force of and.

In the first invention, at least a part of the magnetic material is provided outside the range in which the magnet can be displaced in the displacement direction, and the attractive force attracting the magnet and the magnetic material and the urging force of the urging member are combined. The displacement member is pressed against the displacement detection target member. The attractive force generated between the magnetic material and the magnet acts in the direction in which the displacement member is pressed against the displacement detection target member or in the direction opposite to the direction in which the displacement member is pressed against the displacement detection target member. The range of change in the resultant force between the attractive force acting as a force and the urging force becomes small.

In the second invention, the attractive force attracting the magnetic material to the magnet acts on the displacement detection target member in the direction of pressing the displacement member against the displacement detection target member, and the attractive force attracting the magnet to the displacement detection target member. On the other hand, it is characterized by having at least one of a second magnetic material that acts in a direction opposite to the direction in which the displacement member is pressed.

In the third invention, the first magnetic material is provided on the support member between the magnet and the displacement detection target member, and the second magnetic material is on the support member on the side opposite to the displacement detection target member with respect to the magnet. It is characterized in that it is provided.

In the second and third inventions, the magnetic material is a first magnetic material provided on the support member between the magnet and the displacement detection target member, and the support member on the side opposite to the displacement detection target member with respect to the magnet. It has at least one of a second magnetic material provided. The attractive force generated between the magnet and the first magnetic body acts in the direction of pressing the displacement member against the displacement detection target member, and the attractive force generated between the magnet and the second magnetic body displaces the displacement member. Since it acts in the direction opposite to the direction of pressing against the member to be detected, the range of change in the resultant force between the attractive force acting as the pressing force and the urging force becomes small. Therefore, the displacement member can be made to follow the displacement detection target member, and it is possible to prevent the displacement detection target member from being hindered from moving toward the displacement detection device side.

A fourth aspect of the present invention is further provided with a magnetic shield that shields magnetism acting on the magnetic detection unit from the outside, and the magnetic material is formed integrally with the magnetic shield.

In the fourth invention, the magnetic material is formed integrally with the magnetic shield. Therefore, the number of parts can be reduced, and the manufacturing cost of the displacement detection device can be reduced.

According to the present invention, there is provided a displacement detection device capable of reducing the change width of a pressing force acting on a measurement object without limiting the detection range of the displacement detection device.

It is sectional drawing which shows the state which the compression amount of a spring is small in the displacement detection apparatus which concerns on embodiment of this invention. It is sectional drawing which shows the state which the compression amount of a spring is large in the displacement detection apparatus which concerns on embodiment of this invention. It is a graph which shows the relationship between the displacement amount of the displacement detection target member, and the pressing force acting on the displacement detection target member. It is sectional drawing which shows the modification of the displacement detection apparatus which concerns on embodiment of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

The displacement detection device 100 according to the embodiment of the present invention is attached to a valve device including a valve body such as a spool valve, and detects the displacement amount (stroke amount) of the valve body. Hereinafter, a case where the displacement detection device 100 is used as a displacement detection device for detecting the displacement of the spool valve 51 of the hydraulic valve device 50 will be described with reference to FIGS. 1 to 3.

The hydraulic valve device 50 includes a cylindrical sleeve 52 and a spool valve 51 arranged in the sleeve 52. In the hydraulic valve device 50, the spool valve 51 is displaced in the axial direction by supplying and discharging hydraulic oil to the oil chamber 53 facing the one end surface 51a of the spool valve 51 through the supply and discharge holes 52a provided in the sleeve 52. .. Then, the displacement of the spool valve 51 controls the opening and closing of a port (not shown) formed on the sleeve 52. As shown in FIG. 1, the displacement detection device 100 is attached to the end of the sleeve 52 so as to face one end surface 51a of the spool valve 51.

The displacement detection device 100 includes a rod member 22 as a displacement member that displaces following a spool valve 51 that is a displacement detection target member, a magnet 24 that is arranged on one end side of the rod member 22 and displaces with the rod member 22, and a rod. A casing 12 as a support member that reciprocally supports the member 22 in the displacement direction, a spring 27 as an urging member arranged in the casing 12 and urging the rod member 22 toward the spool valve 51, and a magnet 24. A magnetic detection unit 32 is provided on the casing 12 so as to face the magnet 24 in a direction orthogonal to the displacement direction of the magnet 24.

The casing 12 is a bottomed tubular member formed of a non-magnetic material such as brass, and is formed inside the cylindrical cylindrical portion 12a, the bottom portion 12b provided on one end side of the cylindrical portion 12a, and the cylindrical portion 12a. It has a housing portion 12c and a storage portion 12c. A part of the rod member 22 in which the magnet 24 is arranged together with the magnet 24 is accommodated in the accommodating portion 12c.

The cylindrical portion 12a is formed with a fixing hole 12e which is a non-penetrating stepped hole which is opened on the outer peripheral surface of the cylindrical portion 12a and is formed toward the accommodating portion 12c. The magnetic detection unit 32 is fixed in the fixing hole 12e.

Further, a support hole 12d through which the rod member 22 is inserted is formed in the bottom portion 12b. Bush 18s that slidably support the rod member 22 are provided in the support holes 12d at two positions separated in the axial direction. By providing bushes 18 for supporting the rod member 22 at two places, the axis of the rod member 22 cantilevered and supported by the casing 12 is tilted with respect to the support axis O which is the axis of the support hole 12d. It can be suppressed to some extent. The bush 18 may be provided at one place, in which case the axial length of the casing 12 can be shortened.

Further, in the bottom portion 12b, a plurality of communication holes 12f for communicating the accommodating portion 12c and the outside are formed around the support hole 12d. One end of the communication hole 12f that opens to the outside faces the oil chamber 53 of the hydraulic valve device 50, and the hydraulic oil in the oil chamber 53 flows into the accommodating portion 12c through the communication hole 12f. That is, the accommodating portion 12c is filled with hydraulic oil.

The rod member 22 is a base of a cylindrical shaft portion 22a slidably supported by a casing 12 via a bush 18, a hemispherical contact portion 22b formed at the tip of the shaft portion 22a, and a shaft portion 22a. It has a flange portion 22c formed at an end and extending radially outward of the shaft portion 22a.

Further, the flange portion 22c is provided with a columnar holding portion 22d extending on the opposite side of the shaft portion 22a coaxially with the shaft portion 22a. In terms of design, the rod member 22 is supported by the casing 12 so that the axis of the rod member 22 and the support axis O of the support hole 12d are arranged coaxially. That is, the axis of the rod member 22 coincides with the support axis O.

The rod member 22 is made of a non-magnetic material like the casing 12, but the spool valve 51 comes into contact with the contact portion 22b, so that the rod member 22 is preferably made of austenitic stainless steel or the like having a certain degree of hardness. ..

The magnet 24 is a permanent magnet formed in a cylindrical shape containing rare earth elements such as Nd and Sm, and is formed on the outer periphery of the holding portion 22d so that the N pole 24a and the S pole 24b are aligned in the axial direction of the holding portion 22d. Be placed. The magnet 24 has an insertion hole 24c through which the holding portion 22d is inserted, and a C-shaped retaining ring 26 is locked to the end of the holding portion 22d protruding from the insertion hole 24c so that the magnet 24 has a C-shaped retaining ring with respect to the holding portion 22d. It is fixed.

Further, a cushioning material 25 formed of an elastically deformable member is provided between the magnet 24 and the retaining ring 26. Therefore, when the magnet 24 is assembled to the holding portion 22d, the cushioning material 25 is deformed, and the magnet 24 is pressed against the flange portion 22c by the restoring force of the cushioning material 25. Therefore, the magnet 24 is fixed at a predetermined position with respect to the rod member 22 without having any play in the axial direction. Further, since the force acting on the magnet 24 during assembly is absorbed by the cushioning material 25, it is possible to prevent the magnet 24 from being damaged during assembly.

The magnet 24 is displaced along with the rod member 22 following the spool valve 51, and is displaced along the support axis O over the displacement range L shown as the displaceable range of the magnet 24 in FIGS. 1 and 2.

The lid member 14 is inserted and fixed to the open end of the accommodating portion 12c in a state where the magnet 24 and a part of the rod member 22 to which the magnet 24 is assembled are accommodated in the accommodating portion 12c. Like the casing 12, the lid member 14 is made of a non-magnetic material such as brass. A seal member (not shown) is provided between the lid member 14 and the accommodating portion 12c, and the seal member blocks communication between the inside and the outside of the accommodating portion 12c to prevent hydraulic oil from leaking to the outside.

As a fixing method of the lid member 14, a general fixing method such as press fitting or screwing is used. Further, the lid member 14 may be pressed and fixed to the casing 12 by assembling a member different from the lid member 14 to the casing 12.

The spring 27 is a coil spring made of a non-magnetic material such as austenitic stainless steel, and is assembled between the flange portion 22c and the lid member 14 in a compressed state. Therefore, the urging force of the spring 27 always acts in the direction of pressing the rod member 22 against the spool valve 51. When the displacement detection device 100 is not assembled to the hydraulic valve device 50, the rod member 22 is pressed by the urging force of the spring 27, and the flange portion 22c is in contact with the bottom portion 12b. Further, the position where the spring 27 is arranged is not limited to between the flange portion 22c and the lid member 14, and any urging force of the spring 27 acts in the direction of pressing the rod member 22 against the spool valve 51. It may be arranged in such a position.

The magnetic detector 32 includes magnetic sensors such as Hall elements and magnetoresistive elements (not shown) that output an output value according to a change in the magnetic field due to the displacement of the magnet 24, and an amplification circuit (not shown) that processes the output value of the magnetic sensor. It has a processing circuit of. The magnetic detection unit 32 outputs a detection value corresponding to the displacement amount of the rod member 22 calculated based on the output value of the magnetic sensor, that is, the displacement amount of the spool valve 51 in contact with the rod member 22.

The magnetic detection unit 32 is mounted on the substrate 34, and is assembled to the casing 12 by fixing the substrate 34 to the stepped portion of the fixing hole 12e formed in the cylindrical portion 12a.

With the magnetic detection unit 32 arranged in the fixing hole 12e, a cylindrical magnetic shield 16 is assembled on the outer circumference of the cylindrical portion 12a so as to cover the fixing hole 12e. The magnetic shield 16 is formed of a soft magnetic material having a small coercive force such as an iron alloy capable of shielding magnetism, and suppresses the influence of magnetism outside the displacement detection device 100 on the magnetic detection unit 32.

Further, a notch (not shown) is formed in the magnetic shield 16, and a lead wire (not shown) connecting a controller (not shown) that controls the operation of the spool valve 51 and the magnetic detection unit 32 is arranged through the notch.

Next, the detection of the displacement amount of the spool valve 51 by the displacement detection device 100 having the above configuration will be described.

The displacement of the spool valve 51 is transmitted to the displacement detection device 100 via the rod member 22 with which the spool valve 51 abuts.

In the displacement detection device 100, when the rod member 22 is displaced along the support axis O, the magnet 24 is also displaced, and the direction and magnitude of the magnetic flux passing through the magnetic detection unit 32 are changed. Then, the output value of the magnetic detector 32 changes according to the change in the direction and magnitude of the magnetic flux passing through the magnetic detector 32. Therefore, the displacement amount of the rod member 22, that is, the displacement amount of the spool valve 51 can be detected based on the output value of the magnetic detection unit 32.

Here, in the displacement detection device 100 having the above configuration, in order to stably detect the displacement amount of the spool valve 51, it is necessary to make the rod member 22 always follow the spool valve 51. For this purpose, in the state where the rod member 22 is most retracted from the casing 12, that is, when the amount of compression of the spring 27 is the smallest, the pressing force for pressing the rod member 22 against the spool valve 51 is set to a certain magnitude. That must be done.

However, if such a pressing force is to be secured by the urging force of the spring 27, the initial deflection amount of the spring 27 becomes large, and the deflection amount until the spring 27 reaches the close contact height, that is, the allowable displacement of the rod member 22. The amount is reduced, and the displacement detection range of the displacement detection device 100 is narrowed. Further, it is conceivable to increase the amount of deflection of the spring 27 in order to expand the displacement detection range, but if the amount of deflection is increased, the total length of the spring 27 becomes long, so that the displacement detection device 100 becomes large.

On the other hand, the urging force of the spring 27 gradually increases in proportion to the amount of the rod member 22 entering the casing 12. Therefore, if the urging force of the spring 27 is increased to some extent in the state where the rod member 22 is most retracted from the casing 12, the urging force of the spring 27 is further increased as the rod member 22 enters the casing 12. As described above, when the urging force of the spring 27 becomes large and the force of pressing the rod member 22 against the spool valve 51 becomes larger than necessary, the spool valve 51 freely moves toward the displacement detection device 100 side. There is a risk of hindering.

Further, in the displacement detection device 100, the accommodating portion 12c in which the flange portion 22c of the rod member 22 is accommodated is filled with hydraulic oil. Then, the hydraulic oil in the accommodating portion 12c flows through the gap between the flange portion 22c and the cylindrical portion 12a when the rod member 22 is displaced in the support axis O direction. The hydraulic oil receives a resistance force that acts in the direction opposite to the direction of movement. Therefore, when the pressing force for pressing the rod member 22 against the spool valve 51 becomes smaller as the rod member 22 moves in the direction of exiting from the casing 12, the rod member 22 is separated from the spool valve 51 due to the resistance force of the hydraulic oil. There is a risk that it will end up.

In this way, in order to stably detect the displacement amount of the spool valve 51, the pressing force that presses the rod member 22 against the spool valve 51 is larger than the size that the rod member 22 can always follow the spool valve 51. While increasing the size, it is necessary to limit the size so as not to hinder the movement of the spool valve 51. That is, in the displacement detection device 100 having the above configuration, when the amount of the rod member 22 leaving the casing 12 is relatively large, the pressing force is increased and the amount of the rod member 22 entering the casing 12 is relatively large. In the state, it is necessary to make the change width, which is the difference between the minimum value and the maximum value of the pressing force, as small as possible by reducing the pressing force.

Therefore, in order to reduce the change width of the pressing force, the displacement detection device 100 according to the present embodiment has a state in which the rod member 22 withdraws from the casing 12 in a relatively large amount or the rod member 22 enters the casing 12. Further provided are magnetic bodies 41 and 42 that attract the magnet 24 when the amount is relatively large.

The magnetic bodies 41 and 42 are members provided on the casing 12 and formed of a soft magnetic material such as an iron-based alloy like the magnetic shield 16, and have a displacement range in which the magnet 24 can be displaced in the displacement direction. At least a part thereof is provided on the outside of L. The magnetic bodies 41 and 42 are a first magnetic body 41 provided in the casing 12 between the magnet 24 and the spool valve 51, and a second magnetic body 41 provided in the casing 12 on the side opposite to the spool valve 51 with respect to the magnet 24. It has a body 42 and.

Specifically, the first magnetic body 41 is provided on the outer circumference of the cylindrical portion 12a on the bottom 12b side of the magnetic detection portion 32, and has a shape that is bent inward in the radial direction along the outer surface of the bottom portion 12b. Further, the second magnetic body 42 is provided on the outer circumference of the cylindrical portion 12a on the lid member 14 side of the magnetic detection portion 32, and has a shape that is bent inward in the radial direction toward the lid member 14.

As described above, at least a part of the first magnetic body 41 and the second magnetic body 42 is provided outside the displacement range L of the magnet 24 in the support axis O direction. The first magnetic body 41 and the second magnetic body 42 are not limited to the above shapes, and the cylindrical portion 12a is provided as long as at least a part of the first magnetic body 41 and the second magnetic body 42 is provided outside the displacement range L of the magnet 24 in the support axis O direction. It may be a simple tubular member formed along the above, or a simple annular member formed along the outer surface of the bottom portion 12b.

Further, the first magnetic body 41 and the second magnetic body 42 are integrally formed with the magnetic shield 16. By integrally forming the first magnetic body 41 and the second magnetic body 42 with the magnetic shield 16, the number of parts can be reduced, the management cost of parts, and the manufacturing cost of the displacement detection device 100 can be reduced. The first magnetic body 41 and the second magnetic body 42 may be formed of a member different from the magnetic shield 16. In this case, the first magnetic body 41 and the second magnetic body 42 may be formed of a hard magnetic material having a certain degree of coercive force within a range that does not affect the detection value of the magnetic detection unit 32 so much.

As described above, since the first magnetic body 41 and the second magnetic body 42 formed of the magnetic material are arranged outside the displacement range L of the magnet 24, the magnet 24 has the first magnetic force as shown in FIG. When the magnet 24 is displaced toward the body 41, an attractive force is generated in which the magnet 24 and the first magnetic body 41 attract each other, and this attractive force is generated in the direction in which the first magnetic body 41 attracts the magnet 24, that is, the magnet 24 attracts the magnet 24. It acts in the direction of pressing the attached rod member 22 against the spool valve 51.

On the other hand, as shown in FIG. 2, when the magnet 24 is displaced in the direction approaching the second magnetic body 42, an attractive force is generated in which the magnet 24 and the second magnetic body 42 attract each other, and this attractive force is the second. 2 The magnetic body 42 acts in the direction of attracting the magnet 24, that is, in the direction of pulling the rod member 22 to which the magnet 24 is attached away from the spool valve 51. In other words, the attractive force that attracts the magnet 24 and the second magnetic body 42 acts in the direction opposite to the direction in which the rod member 22 to which the magnet 24 is attached is pressed against the spool valve 51.

Subsequently, with reference to the graph of FIG. 3, changes in the urging force and the suction force with respect to the displacement amount of the rod member 22 will be described. In the graph of FIG. 3, the horizontal axis represents the displacement amount (stroke amount) of the rod member 22, and the vertical axis represents the magnitude of the pressing force such as the urging force or suction force that presses the rod member 22 against the spool valve 51. Is shown.

When the pressing force acting in the direction of pressing the rod member 22 against the spool valve 51 is on the positive side, the magnet 24, the first magnetic body 41, and the second magnetic body 42 are shown by the one-point chain line in the graph of FIG. When the rod member 22 is most retracted from the casing 12, the attractive force generated between the magnet 24 and the first magnetic body 41 becomes large, so that the maximum value (Fm1) is on the positive side. It becomes. Then, in the state where the rod member 22 has entered the casing 12 most, the attractive force that the magnet 24 and the second magnetic body 42 attract to each other becomes large, so that the maximum value (Fm2) is obtained on the minus side. Further, when the displacement amount of the rod member 22 is in the intermediate region, the attractive force generated between the magnet 24 and the first magnetic body 41 and the second magnetic body 42 becomes smaller and cancels out, so that the attractive force is canceled. Is zero.

On the other hand, the urging force of the spring 27 is the minimum when the rod member 22 is most retracted from the casing 12, that is, when the amount of compression of the spring 27 is the smallest, as shown by the broken line in the graph of FIG. The rod member 22 increases proportionally from the force (Fs1) toward the maximum urging force (Fs2) when the rod member 22 has entered the casing 12 most, that is, when the amount of compression of the spring 27 is the largest.

Here, the attractive force generated between the magnet 24 and the first magnetic body 41 and the second magnetic body 42 and the urging force of the spring 27 both act on the rod member 22. Therefore, these resultant forces act as a pressing force that presses the rod member 22 against the spool valve 51.

As shown by the solid line in the graph of FIG. 3, the resultant force of the attractive force generated between the magnet 24 and the first magnetic body 41 and the second magnetic body 42 and the urging force of the spring 27 is casing by the rod member 22. From the value of the resultant force of the suction force and the urging force (Fs1 + Fm1) in the state of most exiting from 12, to the value of the resultant force of the suction force and the urging force (Fs2-Fm2) in the state of the rod member 22 most entering the casing 12. It changes in a curve toward it.

As described above, in the displacement detection device 100, by providing the first magnetic body 41 and the second magnetic body 42, the resultant force acting as the pressing force is generated in the state where the rod member 22 withdraws from the casing 12 in a relatively large amount. In a state where the rod member 22 enters the casing 12 in a relatively large amount, the resultant force acting as a pressing force becomes small.

As is clear from the graph of FIG. 3, the change width (ΔFr), which is the difference between the minimum value and the maximum value of the resultant force between the suction force and the urging force, is the change width (Fs2) of the urging force of the spring 27. It is smaller than −Fs1). Further, the minimum value of the resultant force between the suction force and the urging force is larger than the minimum value of the urging force of the spring 27 alone, and the maximum value of the resultant force of the suction force and the urging force is the maximum value of the spring 27 alone. It is a small value compared to the maximum value of the urging force.

Therefore, by acting the resultant force of such characteristics as a pressing force, the rod member 22 can be surely followed with the spool valve 51, and the movement of the spool valve 51 toward the displacement detection device 100 side is hindered. It is possible to prevent this from happening. Further, when the rod member 22 moves in the direction of exiting from the casing 12, the resultant force acting as a pressing force is maintained at a predetermined magnitude or more, so that the rod member 22 is moved from the spool valve 51 by the resistance force of the hydraulic oil. It is also possible to prevent them from being separated.

By changing the characteristics of the attractive force generated between the magnet 24 and the first magnetic body 41 and the second magnetic body 42, the characteristics of the resultant force between the attractive force and the urging force can be changed to a flatter characteristic. It is possible. Specifically, for example, the rod member is changed by changing the thickness of the first magnetic body 41, the distance from the support axis O to the first magnetic body 41, and the like according to the distance from the displacement range L of the magnet 24. It is possible to change the characteristics of the attractive force in a state where the amount of the 22 leaving the casing 12 is relatively large. Further, by arranging the first magnetic body 41 and the second magnetic body 42 so as to face the magnet 24 in the support axis O direction, the rod member 22 is most retracted from the casing 12 and the rod member 22 is the casing 12. It is possible to increase the suction force in the state where it is most intruded.

According to the above embodiment, the following effects are obtained.

In the displacement detection device 100, the rod member 22 is pressed against the spool valve 51 by the resultant force of the attractive force of the magnet 24 and the first magnetic body 41 and the second magnetic body 42 attracting each other and the urging force of the spring 27. Be done. Here, the attractive force that attracts the magnet 24 and the first magnetic body 41 acts in the direction of pressing the rod member 22 against the spool valve 51, so that even if the urging force of the spring 27 becomes small, the pressing force remains. It is held at a predetermined size by the attractive force of the magnet 24 and the first magnetic body 41. On the other hand, the attractive force attracted by the magnet 24 and the second magnetic body 42 acts in the direction opposite to the direction in which the rod member 22 is pressed against the spool valve 51, so that even if the urging force of the spring 27 becomes large. The pressing force is limited to a predetermined size by the attractive force between the magnet 24 and the second magnetic body 42.

As described above, the change width (ΔFr), which is the difference between the minimum value and the maximum value of the resultant force between the suction force and the urging force, is smaller than the change width (Fs2-Fs1) of the urging force of the spring 27. Further, the minimum value of the resultant force between the suction force and the urging force is larger than the minimum value of the urging force of the spring 27 alone, and the maximum value of the resultant force of the suction force and the urging force is the maximum value of the spring 27 alone. It is a small value compared to the maximum value of the urging force.

Therefore, by acting the resultant force of such characteristics as a pressing force, the rod member 22 can be surely followed with the spool valve 51, and the movement of the spool valve 51 toward the displacement detection device 100 side is hindered. It is possible to prevent this from happening.

In the displacement detection device 100, the first magnetic body 41 provided in the casing 12 between the magnet 24 and the spool valve 51 and the second magnetic body 41 provided in the casing 12 on the side opposite to the spool valve 51 with respect to the magnet 24. Although two magnetic bodies, that is, a magnetic body 42, are provided, instead of this, only one of the first magnetic body 41 and the second magnetic body 42 may be provided. In this case as well, the change width of the resultant force can be made smaller than the change width of the urging force of the spring 27 alone.

Further, in the displacement detection device 100, in the cross-sectional view shown in FIG. 1, each of the magnetic bodies 41 and 42 provided on the outside of the casing 12 has a corner portion whose cross-sectional shape is substantially right-angled according to the outer shape of the casing 12. It is formed so as to have an L shape having. Instead, each of the magnetic bodies 41 and 42 may have a cross-sectional shape in which the corners are formed in a tapered or curved shape. Further, the magnetic bodies 41 and 42 may be formed so that the entire cross-sectional shape is arcuate or curved in the cross-sectional view shown in FIG.

Here, when the cross-sectional shape of each of the magnetic bodies 41 and 42 is arcuate or curved, the diameter of each of the magnetic bodies 41 and 42 is larger than that of the magnet 24 as compared with the case where the cross-sectional shape is L-shaped. The portion placed closer in the direction increases. In this way, when the magnetic bodies 41 and 42 are partially brought close to the magnet 24 in the radial direction, the characteristics of the attractive force that the magnet 24 and the magnetic bodies 41 and 42 attract to each other change. By changing the cross-sectional shapes of 41 and 42, for example, the attractive force gradually increases from the stage where the magnet 24 is slightly displaced toward the magnetic bodies 41 and 42, and the magnet 24 is substantially linear with respect to the displacement. It is also possible to have a characteristic that the suction force is increased. That is, by appropriately deforming the cross-sectional shape of each of the magnetic bodies 41 and 42, the resultant force of the attractive force generated between the magnet 24 and each of the magnetic bodies 41 and 42 and the urging force of the spring 27 is combined with the rod member 22. It is also possible to make it substantially constant regardless of the amount of displacement of. In this case, the outer shape of the casing 12 is preferably a shape that matches the shapes of the magnetic bodies 41 and 42.

Subsequently, a modified example of the displacement detection device 100 according to the embodiment of the present invention will be described with reference to FIG.

In the above embodiment, the first magnetic body 41 and the second magnetic body 42 are provided on the outer periphery of the casing 12. Instead, as shown in FIG. 4, the bottom portion 12g is formed of a member different from the cylindrical portion 12a, and the bottom portion 12g is formed of a soft magnetic material so as to function as a first magnetic material that attracts the magnet 24. Further, the lid member 15 may be formed of a soft magnetic material to function as a second magnetic material that attracts the magnet 24.

In this case as well, as in the above embodiment, the attractive force of the magnet 24 and the bottom portion 12g attracting each other acts in the direction of pressing the rod member 22 against the spool valve 51, so that the urging force of the spring 27 is reduced. The pressing force is maintained at a predetermined size by the attractive force between the magnet 24 and the bottom 12 g. On the other hand, the attractive force that attracts the magnet 24 and the lid member 15 acts in the direction opposite to the direction in which the rod member 22 is pressed against the spool valve 51, so that even if the urging force of the spring 27 becomes large, the pressing force is applied. Is limited to a predetermined size by the attractive force of the magnet 24 and the lid member 15. Further, since the bottom portion 12g and the lid member 15 are provided so as to face the magnet 24 in the support axis O direction, the rod member 22 is most retracted from the casing 12 and the rod member 22 is most inserted into the casing 12. A stable suction force can be obtained in this state.

The configuration, operation, and effect of the embodiment of the present invention configured as described above will be collectively described.

A rod member 22 that is displaced following the spool valve 51, a spring 27 that urges the rod member 22 toward the spool valve 51, and a magnet 24 that is arranged on one end side of the rod member 22 and is displaced together with the rod member 22. , A casing 12 that reciprocally supports the rod member 22 in the displacement direction, a magnetic detection unit 32 that is arranged on the casing 12 and detects a change in the magnetic field due to the displacement of the magnet 24, and a magnet 24 that is provided on the casing 12 and attracts the magnet 24. The magnetic bodies 41 and 42 are provided with matching magnetic bodies 41 and 42, the magnetic bodies 41 and 42 are provided with at least a part outside the displacement range L in which the magnet 24 can be displaced in the displacement direction, and the rod member 22 is the magnet 24 and the magnetic body. It is pressed against the spool valve 51 by the resultant force of the attractive force that attracts the 41 and 42 and the urging force of the spring 27.

In this configuration, at least a part of the magnetic bodies 41 and 42 is provided outside the displacement range L in which the magnet 24 can be displaced in the displacement direction, and the attractive force that attracts the magnet 24 and the magnetic bodies 41 and 42 and the spring 27 The rod member 22 is pressed against the spool valve 51 by the urging force of and the resultant force of.

The attractive force generated between the magnetic bodies 41 and 42 arranged outside the displacement range L in which the magnet 24 can be displaced and the magnet 24 is the direction in which the rod member 22 is pressed against the spool valve 51, or the rod. It acts in the direction opposite to the direction in which the member 22 is pressed against the spool valve 51. Therefore, the change width (ΔFr), which is the difference between the minimum value and the maximum value of the resultant force between the suction force and the urging force, is smaller than the change width (Fs2-Fs1) of the urging force of the spring 27. Therefore, by acting the resultant force of the suction force and the urging force as the pressing force, the rod member 22 is surely followed by the spool valve 51, and the movement of the spool valve 51 toward the displacement detection device 100 side is hindered. It is possible to prevent the displacement.

Further, in the magnetic bodies 41 and 42, the attractive force attracting the magnet 24 acts on the first magnetic body 41 in the direction of pressing the rod member 22 against the spool valve 51, and the attractive force attracting the magnet 24 is the spool. It has at least one of a second magnetic body 42 that acts in a direction opposite to the direction in which the rod member 22 is pressed against the valve 51.

Further, the first magnetic body 41 is provided in the casing 12 between the magnet 24 and the spool valve 51, and the second magnetic body 42 is provided in the casing 12 on the side opposite to the spool valve 51 with respect to the magnet 24. ..

In these configurations, the magnetic bodies 41 and 42 are attached to the first magnetic body 41 provided in the casing 12 between the magnet 24 and the spool valve 51, and to the casing 12 on the side opposite to the spool valve 51 with respect to the magnet 24. It has at least one of the second magnetic material 42 provided. That is, the attractive force generated between the magnet 24 and the magnetic bodies 41 and 42 is in the direction opposite to the direction in which the rod member 22 is pressed against the spool valve 51 and the direction in which the rod member 22 is pressed against the spool valve 51. , Acts on either one. Therefore, the change width (ΔFr), which is the difference between the minimum value and the maximum value of the resultant force between the suction force and the urging force, is smaller than the change width (Fs2-Fs1) of the urging force of the spring 27. Therefore, by acting the resultant force of the suction force and the urging force as the pressing force, the rod member 22 is surely followed by the spool valve 51, and the movement of the spool valve 51 toward the displacement detection device 100 side is hindered. It is possible to prevent the displacement.

Further, the casing 12 is further provided with a magnetic shield 16 that shields the magnetism acting on the magnetic detection unit 32 from the outside, and the magnetic bodies 41 and 42 are integrally formed with the magnetic shield 16.

In this configuration, the magnetic bodies 41 and 42 are integrally formed with the magnetic shield 16. By integrally forming the magnetic bodies 41 and 42 with the magnetic shield 16 in this way, the number of parts can be reduced, the management cost of parts, and the manufacturing cost of the displacement detection device 100 can be reduced.

Although the embodiments of the present invention have been described above, the above embodiments are only a part of the application examples of the present invention, and the technical scope of the present invention is limited to the specific configurations of the above embodiments. Absent.

100 ... displacement detection device, 12 ... casing (support member), 12 g ... bottom (magnetic material, first magnetic material), 15 ... lid member (magnetic material, second magnetic material), 16 ... magnetic shield, 22 ... rod member (displacement member), 24 ... magnet, 27 ... spring (biased member), 32 ... magnetic detector, 41 ... first magnetic material (Magnetic material), 42 ... Second magnetic material (Magnetic material), 50 ... Hydraulic valve device, 51 ... Spool valve (Displacement detection target member)

Claims (4)

Displacement members that displace following the displacement detection target member, and
An urging member that urges the displacement member toward the displacement detection target member, and
A magnet arranged on one end side of the displacement member and displaced together with the displacement member,
A support member that reciprocates the displacement member in the displacement direction,
A magnetic detector arranged on the support member and detecting a change in the magnetic field due to the displacement of the magnet.
A magnetic material provided on the support member and attracting the magnet is provided.
The magnetic material is provided with at least a part outside the range in which the magnet can be displaced in the displacement direction.
The displacement member is a displacement detection device characterized in that the displacement member is pressed against the displacement detection target member by the resultant force of the attractive force of the magnet and the magnetic body attracting each other and the urging force of the urging member. The magnetic material is
A first magnetic body in which an attractive force attracting the magnet acts in a direction of pressing the displacement member against the displacement detection target member.
Claim 1 is characterized in that the attractive force attracting the magnet has at least one of a second magnetic material that acts in a direction opposite to the direction in which the displacement member is pressed against the displacement detection target member. Displacement detection device according to. The first magnetic material is provided on the support member between the magnet and the displacement detection target member.
The displacement detection device according to claim 2, wherein the second magnetic material is provided on the support member on the side opposite to the displacement detection target member with respect to the magnet. Further provided on the support member is a magnetic shield that shields magnetism acting on the magnetic detection unit from the outside.
The displacement detection device according to any one of claims 1 to 3, wherein the magnetic material is integrally formed with the magnetic shield.

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