Displacement sensor for a rod

The displacement sensor (100) includes a rod (103) including a conical convex graduated magnetically anomalous region (105) and a magnetic sensor (110) located in close proximity to the concical convex graduated magnetically anomalous region (105). The magnetic sensor (110) generates a positional signal that is related to the position of the concical convex graduated magnetically anomalous region (105) in relation to the magnetic sensor (110).

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a displacement sensor, and more particularly, to a displacement sensor for a rod.

2. Statement of the Problem

A piston comprises a device that moves linearly within a bore in order to perform mechanical work, such as providing pressure to a fluid or to move a fluid. In addition, a piston can move in response to the introduction of a fluid into the bore or in response to removal of fluid from the bore. As a result, pistons are widely used to convert fluid movement into mechanical motion of the piston and to convert mechanical motion of the piston into fluid movement.

Pistons are widely used in industrial applications. Pistons are used to move fluids. Pistons are used in valves to control the flow of fluids, including liquids and gases. Because of these uses, it is often desirable to know an accurate and instantaneous displacement of a piston rod.

SUMMARY OF THE SOLUTION

A displacement sensor is provided according to an embodiment of the invention. The displacement sensor comprises a rod including a graduated magnetically anomalous region and a magnetic sensor located in close proximity to the graduated magnetically anomalous region. The magnetic sensor generates a positional signal that is related to the position of the graduated magnetically anomalous region in relation to the magnetic sensor.

A displacement sensor is provided according to an embodiment of the invention. The displacement sensor comprises a rod including a graduated magnetically anomalous region and a magnetic sensor located in close proximity to the graduated magnetically anomalous region. The magnetic sensor comprises a coupling member comprising two legs and a top end, two magnets affixed to bottom leg ends of the two legs of the coupling member, and a Hall Effect sensor affixed to the top end of the coupling member. The Hall Effect sensor is in magnetic communication with the two magnets. The magnetic sensor generates a positional signal that is related to the position of the graduated magnetically anomalous region in relation to the magnetic sensor.

A displacement sensor is provided according to an embodiment of the invention. The displacement sensor comprises a rod including a graduated magnetically anomalous insert and a magnetic sensor located in close proximity to the graduated magnetically anomalous insert. The magnetic sensor generates a positional signal that is related to the position of the graduated magnetically anomalous insert in relation to the magnetic sensor.

A displacement sensor is provided according to an embodiment of the invention. The displacement sensor comprises a substantially magnetic rod including a graduated bore portion and a magnetic sensor located in close proximity to the graduated bore portion. The magnetic sensor generates a positional signal that is related to the position of the graduated bore portion in relation to the magnetic sensor.

A displacement sensor is provided according to an embodiment of the invention. The displacement sensor comprises a substantially magnetic rod including a graduated magnetically anomalous region formed from the rod and a magnetic sensor located in close proximity to the graduated magnetically anomalous region. The magnetic sensor generates a positional signal that is related to the position of the graduated magnetically anomalous region in relation to the magnetic sensor.

ASPECTS OF THE INVENTION

In one embodiment of the displacement sensor, the graduated magnetically anomalous region is at least partially within the rod.

In another embodiment of the displacement sensor, the graduated magnetically anomalous region is substantially fully within the rod.

In yet another embodiment of the displacement sensor, the graduated magnetically anomalous region is substantially axially centered in the rod.

In yet another embodiment of the displacement sensor, the graduated magnetically anomalous region comprises a graduated magnetically responsive insert.

In yet another embodiment of the displacement sensor, the rod includes a hollow portion and the graduated magnetically anomalous region comprises a graduated magnetically responsive insert residing in the hollow portion.

In yet another embodiment of the displacement sensor, the rod is substantially magnetic and the graduated magnetically anomalous region comprises a graduated bore portion.

In yet another embodiment of the displacement sensor, the rod is substantially magnetic and the graduated magnetically anomalous region is formed from the rod.

In yet another embodiment of the displacement sensor, the magnetic sensor comprises a coupling member comprising two legs and a top end, two magnets affixed to bottom leg ends of the two legs of the coupling member, and a Hall Effect sensor affixed to the top end of the coupling member, wherein the Hall Effect sensor is in magnetic communication with the two magnets.

In yet another embodiment of the displacement sensor, the two magnets are substantially arranged along an arc corresponding to a rod surface.

In yet another embodiment of the displacement sensor, the two magnets comprise two substantially opposite magnets.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1shows a magnetic sensor110according to an embodiment of the invention. The magnetic sensor110is a component of a displacement sensor100(seeFIG. 2). The displacement sensor100is discussed below in the context of a piston rod. However, it should be understood that the displacement sensor100of any embodiment can be used with any manner of displaceable rod or member.

The magnetic sensor110comprises two coupling members111including two legs112aand112b. The two legs112aand112breceive two corresponding magnets114aand114b. Each leg112includes a top end120, wherein the Hall Effect sensor116is received between the two top ends120aand120b. The Hall Effect sensor116can be merely positioned between the two top ends120aand120b, or can be affixed, bonded, or clamped between the two top ends120aand120bin some manner. Alternatively, the coupling member111can comprise one piece that includes multiple legs112.

In this embodiment, the magnets114are substantially arranged along an arc (see dashed line). The arc corresponds to a piston rod surface (seeFIG. 2). In this manner, the full face area of a magnet114is placed in close proximity to the piston rod103and to the graduated magnetically anomalous region105. Interaction between a magnet114and the graduated magnetically anomalous region105is therefore improved.

In one embodiment, the two magnets114aand114bare substantially opposite in position (i.e., such as 180 degrees apart, for example) around the graduated magnetically anomalous region105. In this manner, the magnetic circuit can be optimally effective. However, it should be understood that where multiple magnets are employed, they can be positioned in any desired location or constellation around the graduated magnetically anomalous region105.

FIG. 2shows a piston displacement sensor100according to an embodiment of the invention. The piston displacement sensor100includes a graduated magnetically anomalous region105as part of a piston rod103and a magnetic sensor110in close proximity to the graduated magnetically anomalous region105(and in close proximity to the piston rod103). However, it should be understood that the displacement sensor100can be employed with any manner of moving rod103, and is not limited in application to a piston.

The magnetic sensor110does not need to contact the piston rod103. Instead, the magnetic sensor110maintains a working gap G between itself and the graduated magnetically anomalous region105(seeFIG. 9). In some embodiments, the working gap G changes in size as the piston rod103moves axially in relation to the magnetic sensor110. It should also be understood that in some embodiments a fixed gap is maintained between the magnetic sensor110and the piston rod103, independent of the working gap G.

The magnetic sensor110generates a positional signal that is related to the position of the graduated magnetically anomalous region105because the magnetic resistance is dependent on the position of the magnetic sensor110and the graduated magnetically anomalous region105. The positional signal is generated by a magnetic interaction between the magnetic sensor110and the graduated magnetically anomalous region105, as in the Hall Effect. The graduated magnetically anomalous region105in effect forms a magnetic circuit for the magnetic sensor110. The size of the working gap G controls the effectiveness of the magnetic circuit. Therefore, the magnetic flux received and measured by the magnetic sensor110can be decreased by increasing the working gap G. If the piston rod103is moved toward the left in the figure, then the magnetic sensor110will measure a lower level of magnetic flux. Conversely, as the piston rod103is moved toward the right in the figure, the working gap G will be reduced and the magnetic sensor110will measure a higher level of magnetic flux.

The graduated magnetically anomalous region105can comprise any material that responds to magnetic flux in some manner. The graduated magnetically anomalous region105can conduct or transmit the magnetic flux. For example, where the graduated magnetically anomalous region105has a high magnetic permeability, the graduated magnetically anomalous region105will conduct magnetic flux. As a result, the magnetic sensor110will receive and detect more magnetic flux. Alternatively, the graduated magnetically anomalous region105can possess a level of magnetism that is less than or greater than a magnetism of the surrounding piston rod103. Therefore, because the graduated magnetically anomalous region105is magnetically anomalous, the magnetic sensor110can detect a varying positional signal that enables determination of the position of the piston rod103.

The graduated magnetically anomalous region105in one embodiment comprises an insert that is cast into or otherwise embedded in the piston rod103(also see FIGS.4and6-8). Alternatively, the graduated magnetically anomalous region105can be an insert that is inserted into and resides in a hollow portion102. The graduated magnetically anomalous region105can comprise a solid insert, such as a magnetically responsive metal or metal compound or a magnetically responsive ceramic or ceramic compound. Alternatively, the graduated magnetically anomalous region105can comprise a hollow vessel filled with a magnetically responsive fluid. In another alternative, the graduated magnetically anomalous region105comprises a graduated bore portion105in the piston rod103(seeFIG. 3), wherein the bore or shaped region interacts with the magnetic sensor110. In yet another embodiment, the graduated magnetically anomalous region105comprises a graduated magnetically anomalous region105formed from the piston rod103(seeFIG. 5).

In one embodiment of the piston displacement sensor100, the graduated magnetically anomalous region105is at least partially within the piston rod103. In another embodiment, the graduated magnetically anomalous region105is substantially fully within the piston rod103. In yet another embodiment, the graduated magnetically anomalous region105is substantially axially centered in the piston rod103.

The graduated magnetically anomalous region105is graduated in some manner. In the embodiment shown, the graduated magnetically anomalous region105is substantially conical. However, other shapes can be employed (seeFIGS. 6-8). As a result, the magnetic sensor110can produce a positional signal that varies in relation to the graduated magnetically anomalous region105. When the magnetic sensor110is at a larger end of the graduated magnetically anomalous region105, in one embodiment the graduated magnetically anomalous region105will conduct more magnetic flux and therefore the positional signal will be increased. Conversely, when the magnetic sensor110is at a smaller end, the positional signal will be increased as more magnetic flux is conducted to the Hall Effect sensor116by the coupling member111.

One benefit of the invention is that an absolute position of the piston can be accurately determined from the positional signal. Because of the graduation in the graduated magnetically anomalous region105, the absolute position can be determined even when the piston is not moving or after a reset or loss of electrical power in an associated external controller or processor.

Another benefit of the invention is that the direction of motion of the piston can be accurately determined. The direction of motion can be determined from the signal level of the positional signal, wherein the signal level changes as the graduated size of the graduated magnetically anomalous region105increases or decreases.

Yet another benefit of the invention is that the velocity and acceleration of the piston can be provided. The velocity and acceleration can be determined from changes in the positional signal over time.

The magnetic sensor110includes a Hall Effect sensor116and an associated wiring harness117, a coupling member111comprising two legs, and two magnets114corresponding to the two legs. It should be understood that more than two legs and two magnets can be used. The entire magnetic sensor assembly110, and the graduated magnetically anomalous region105, can be enclosed in the interior of a piston or valve.

The coupling member111comprises a magnetically soft or magnetically conducting material. For example, the coupling member111can be formed of iron, steel, or a ferritic steel. However, other magnetically conducting materials can be employed. As a result, a portion of the magnetic flux generated by the one or more magnets114is conducted by the coupling member111to the Hall Effect sensor116. At the same time, the one or more magnets114will interact with the graduated magnetically anomalous region105if the magnetic sensor110is in close proximity. When the one or more magnets114are close to the graduated magnetically anomalous region105(i.e., when the working gap G is small), then a magnetic circuit is strong and the coupling member111will conduct a large amount of the magnetic flux from the one or more magnets114to the Hall Effect sensor116. When the one or more magnets114are far away (i.e., a large working gap G), then the graduated magnetically anomalous region105will conduct a much smaller amount of the magnetic flux from the one or more magnets114, wherein the amount of magnetism transferred by the coupling member111to the Hall Effect sensor116will be reduced. In this manner, the Hall Effect sensor116can produce a positional signal that is related to the position of the magnetically responsive insert in relation to the magnetic sensor110.

In this embodiment, the piston rod103includes a hollow portion102and the graduated magnetically anomalous region105comprises a graduated magnetically anomalous insert105. The graduated magnetically anomalous insert105is located in the hollow portion102. The hollow portion102can be of any needed size or shape. The graduated magnetically anomalous insert105in one embodiment is glued or bonded in the hollow portion102. Alternatively, the graduated magnetically anomalous insert105can be held in by a press or friction fit or can be blocked in by a plug or other sealing device (not shown). To this end, the graduated magnetically anomalous insert105can include a cylindrical portion107. The cylindrical portion107can provide a friction fit in the hollow portion102or can provide a region for bonding the graduated magnetically anomalous insert105in the hollow portion102.

In one embodiment, the magnetic sensor110can be embedded in a body130of a non-magnetically responsive material. The body130can comprise any magnetically non-conducting material, such as plastic, for example. The body130can be used to hold the components of the magnetic sensor110together as a unit. In addition, the body130can be used to mount or affix the magnetic sensor100to a nearby structure. In addition, the body130can be used to protect and/or seal the magnetic sensor110.

FIG. 3shows the piston rod103according to another embodiment of the invention. In this embodiment, the piston rod103is substantially magnetic. The piston rod103includes a straight bore portion104and a graduated bore portion105. The graduated bore portion105comprises a graduated region of reduced magnetivity. The graduated bore portion105therefore interacts with the magnetic sensor110as previously described in order to generate the positional signal. The positional signal is therefore related to the position of the graduated bore portion105in relation to the magnetic sensor110.

FIG. 4shows the piston rod103according to another embodiment of the invention. In this embodiment, the graduated magnetically anomalous region105is substantially axially embedded in the piston rod103. In this embodiment, the diameter of the piston rod is not uniform in an embedded region108. Instead, the diameter of the piston rod103is larger at one end of the embedded region108, wherein the piston rod103therefore has a substantially uniform cross-sectional area of piston rod material around the graduated magnetically anomalous region105. As a result, this embodiment does not suffer from reduced rod strength in the embedded region108.

FIG. 5shows the piston rod103according to another embodiment of the invention. In this embodiment, the piston rod103is substantially magnetic and includes a graduated magnetically anomalous region105formed in the piston rod103. The graduated magnetically anomalous region105in this embodiment can be formed in any manner, such as by casting or machining, for example. The graduated magnetically anomalous region105can include a diameter that is smaller than the normal diameter D of the piston rod103. The graduated magnetically anomalous region105can include a diameter that is larger than the normal diameter D of the piston rod103. In addition, the graduated magnetically anomalous region105can flare from a diameter that is smaller than the normal diameter D to a diameter that is larger than the normal diameter D, as is shown in the figure. This graduated magnetically anomalous region105interacts with the magnetic sensor110in order to generate the positional signal. The positional signal is therefore related to the position of the graduated magnetically anomalous region105in relation to the magnetic sensor110.

FIG. 6shows the piston rod103according to another embodiment of the invention. In this embodiment, the graduated magnetically anomalous region105comprises a wedge-shaped insert105. The wedge-shaped insert105can be substantially rectangular in outline or can comprise any graduated wedge shape. The wedge-shaped insert105can be partially embedded in the piston rod103, as shown, or can be completely embedded. Of course, the wedge shape of this figure (andFIGS. 7-8) will require that the piston rod103be constrained from rotating in order for the magnetic sensor110to function properly and effectively.

FIG. 7shows the piston rod103wherein the graduated magnetically anomalous insert105is partially embedded. As a result, a portion of the graduated magnetically anomalous insert105in this embodiment extends from the piston rod103.

FIG. 8shows the piston rod103according to another embodiment of the invention. In this embodiment, the graduated magnetically anomalous region105comprises a stepped insert105including multiple steps106. A step106can be of any desired shape or size. The stepped insert105can be completely embedded in the piston rod103, as shown, or can be partially embedded.

FIG. 9shows the piston displacement sensor100according to another embodiment of the invention. In this embodiment, the graduated magnetically anomalous region105comprises a curved conical shape. Consequently, the graduated magnetically anomalous region105comprises a substantially bulged or convex conical shape. The shape in this embodiment operates to substantially linearize the dependence of the magnetic field strength in the working air gap. As a result, the magnetic field at the Hall Effect sensor116does not fall off as rapidly as in a strictly straight-sided conical shape.